Nanotube Theory

Effect of Twisting on Nanotube Electronic Structure




Effect of twisting on the properties of a metallic armchair (6,6) nanotube. Three twisted configurations are shown. Twisting is found to transform the metallic nanotube to a semiconducting one with a band-gap that varies with the twist angle as shown.



Effect of Bending on Nanotube Electronic Structure




Variation of the local density of states (LDOS) along the length of a (6,6) nanotube as a function of the bending angle.


Source:www.research.ibm.com/nanoscience/index/index.html



Nanotubes proved safe

But for the authors of [1] their results indicate that if carbon nanotubes reach the lungs, they are much more toxic than carbon black and can be more toxic than quartz. These studies have to be read with some caution because a study by the National Institute for Occupational Safety and Health (NIOSH) showed that none or only a small fraction of the nanotubes present in the air can be inhaled [2].

[1]Pulmonary Toxicity of Single-Wall Carbon Nanotubes in Mice 7 and 90 Days after Intratracheal Instillation. Toxicol Sci 2003, 77:126-134.

[2]Exposure to Carbon Nanotube Material: Aerosol Release During the Handling of Unrefined Single Walled Carbon Nanotube Material. J Toxicol Environ Health 2004, 67:87-107.





It is also important to note that specific particle surface area is probably a better indication for maximum tolerated exposure level than total mass. Inhaled nano-fibres (diameter smaller than 100 nm) also can enter the alveoli and their clearing would, in addition, depend on the length of the specific fibre.

A recent study [1] has provided, for the first time, morphological data showing that inhaled polystyrene particles are transported into the pulmonary capillary space, presumably by transcytosis........ In inhalation experiments with rats, using 13Clabelled particles, they found that nano-sized particles (25 nm) were present in several organs 24 hours after exposure. The most extraordinary finding was the discovery of particles in the central nervous system (CNS). The authors examined this phenomenon further and found that particles, after being taken up by the nerve cells, can be transported via nerves (in this experiment via the olfactory nerves) at a speed of 2.5 mm per hour [2].


[1]Evidence that exogenous substances can be phagocytized by alveolar epithelial cells and transported into blood capillaries. Cell Tissue Res 2003, 311:47-51.

[2]Extrapulmonary translocation of ultrafine carbon particle following whole-body inhalation exposure of rats. J Toxicol Environ Health A 2002, 65:1531-1543.

Analyzing the composition: Raman effect

NANOPLEX™ biomarker detection

These silica-coated, surface enhanced Raman scattering (SERS)-active metal nanoparticles allow robust, ultrasensitive, highly-multiplexed biomarker quantitation in any biological matrix, including whole blood.


http://www.oxonica.com/diagnostics/diagnostics_biodiagnostics.php

Raman scattering or the Raman effect is the inelastic scattering of a photon, discovered By Dr. Raman who received Noble in 1920 in recognition of its significance as a tool for analyzing the composition of liquids, gases, and solids.

When light is scattered from an atom or molecule, most photons are elastically scattered (Rayleigh scattering). The scattered photons have the same energy (frequency) and wavelength as the incident photons. However, a small fraction of the scattered light (approximately 1 in 10 million photons) is scattered by an excitation, with the scattered photons having a frequency different from, and usually lower than, the frequency of the incident photons. In a gas, Raman scattering can occur with a change in vibrational, rotational or electronic energy of a molecule. Chemists are concerned primarily with the vibrational Raman effect.

wikipedia.org

Glass-coated, analyte-tagged nanoparticles (GANs) are core-shell particles where a nanometer-scale Au or Ag core is functionalized with Raman active molecules and encapsulated in a glass shell. The glass shell provides the particle with mechanical and chemical stability. Specifically, the glass coating renders the particle amenable to use in many solvents without altering the Raman spectral response and makes agglomeration a nonfactor. The density and thickness of the glass shell are controllable through synthetic conditions; thus, the rate of diffusion through the silica network can be tuned and the metal cores kept sequestered from any exterior reaction. This will allow for the attachment of biomolecules to the glass shell without altering the Raman response. GANs can be identified by the Raman spectrum of the attached Raman tag, and two differently labeled samples are unambiguously identified. The scattering from the Raman tag is amplified through surface-enhanced Raman scattering. The narrow bandwidth (~20 cm-1) of the Raman peaks and fingerprint-like spectra will allow multiple Raman tags to be simultaneously evaluated with a single excitation source.


Mulvaney, 2003, A New Tagging System Based on Detection with Surface-Enhanced Raman Scattering;American Chemical Society





NANOPLEX™ No-wash Assay

NANOPLEX™ Direct is a homogeneous assay format rivalling conventional ELISAs while offering several advantages including

* Simple procedure using a one-step, no-wash assay format
* High sensitivity, on par with heterogeneous, amplified systems
* Leverages the performance of surface-enhanced Raman scattering (SERS)
* Near IR detection allows for data collection in whole blood, serum and plasma backgrounds
* Multiplexing capability of the technology allows for quantitation of multiple analytes in a single reaction
* Benchtop reader and proprietary software for data analysis






Procedure

The many different facets of risk

'Everything is poison, there is poison in everything. Only the dose makes a thing not a poison.'

arthritis-research.com/content/10/1/R20




The discovery of structural form

Algorithms for finding structure in data have become increasingly important both as tools for scientific data analysis and as models of human learning, yet they suffer from a critical limitation. Scientists discover qualitatively new forms of structure in observed data: For instance, Linnaeus recognized the hierarchical organization of biological species, and Mendeleev recognized the periodic structure of the chemical elements. Analogous insights play a pivotal role in cognitive development: Children discover that object category labels can be organized into hierarchies, friendship networks are organized into cliques, and comparative relations (e.g., “bigger than” or “better than”) respect a transitive order. Standard algorithms, however, can only learn structures of a single form that must be specified in advance: For instance, algorithms for hierarchical clustering create tree structures, whereas algorithms for dimensionality-reduction create low-dimensional spaces. Here, we present a computational model that learns structures of many different forms and that discovers which form is best for a given dataset. The model makes probabilistic inferences over a space of graph grammars representing trees, linear orders, multidimensional spaces, rings, dominance hierarchies, cliques, and other forms and successfully discovers the underlying structure of a variety of physical, biological, and social domains. Our approach brings structure learning methods closer to human abilities and may lead to a deeper computational understanding of cognitive development.


http://www.pnas.org/content/105/31/10687

Nano Delivery

The great potential of using nanodevices as delivery systems to specific targets in living organisms was first explored for medical uses. In plants, the same principles can be applied for a broad range of uses, in particular to tackle infections. Nanoparticles tagged to agrochemicals or other substances could reduce the damage to other plant tissues and the amount of chemicals released into the environment. To explore the benefits of applying nanotechnology to agriculture, the first stage is to work out the correct penetration and transport of the nanoparticles into plants................. The nanoparticles can be charged with different substances, introduced within the plants and, if necessary, concentrated into localized areas by using magnets. Also simple or more complex microscopical techniques can be used in localization studies.

Annals of Botany 101: 187–195, 2008, Oxford Journals; Nanoparticles as Smart Treatment-delivery Systems in Plants: Assessment of Different Techniques of Microscopy for their Visualization in Plant Tissues



The role of water ingress in tablet dissolution, and subsequent drug release, is usually inferred from the drug release profile and by models that make various assumptions concerning the geometry, water diffusion and the physical changes that occur.....There are numerous examples of the use of Magnetic Resonance Imaging (MRI) for pharmaceutical applications1 and, especially, hydration studies. Since the technique is non-invasive and non-destructive, it is possible to study the dissolution of one tablet without disturbing the process. However, its use is frequently constrained by the availability of MRI systems for long experiments, the high running costs (i.e. helium and nitrogen for superconducting magnets) and a requirement for expert users.

MRI provides information on the water, and lipid (where present), proton* density (M0) and mobility (by the spin-lattice and spin-spin relaxation times, T1, and T2) in up to three spatial dimensions. ‘Diagnostic’ or weighted images primarily use T1/T2
contrast to augment the signal intensity of various features, in addition to the usual proton density contrast, i.e. the variation of signal intensity according to water concentration. This enables segmentation of those features for quantifying thicknesses (1D), areas (2D) and volumes (3D), for example. For example, ‘T1 contrast’ can be altered by varying the repetition time (TR) of a spin echo imaging protocol3. T1 is the time constant for recovery of the magnetization, or signal, after a radio frequency pulse, therefore the inherent signal-to-noise of the image is increased by increasing TR. Unfortunately this proportionally lengthens the image scan time. However, different materials, or parts thereof, with different water-content and/or - mobility have different T1 recoveries so TR can be reduced to enhance the contrast between various features, which also serves to reduce the image scan time.

PharmaSense; Measurement of Water Ingress and Gel Layer Formation during Tablet Dissolution in a US Pharmacopeia 4 Flow Cell; www.oxford-instruments.com

Hydrogels represent an ideal class of polymeric material for various biomedical applications, including drug delivery, cell encapsulation and tissue engineering [1]. Thermosensitive hydrogels can be used as in situ forming implants.These biodegradable delivery systems are generally liquid formulations that form a semisolid or solid depot after injection into the desired tissue or organ. General advantages are localized or systemic prolonged drug delivery periods, drug dosage reduction along with reduction of undesirable side effects and reduced frequency of application.
Source: Non-invasive in vitro characterization of chitosan based in situ gelling O/W emulsions by 1H-NMR Relaxometry; www.oxford-instruments.com



A single oral dose of the formulation to mice could maintain sustained drug levels for 5–8 days in the plasma and for 9 days in the brain. There was a significant improvement in the pharmacokinetic parameters such as mean residence time and relative bioavailability as compared with free drugs. The pharmacodynamic parameters such as the ratio of area under the curve to minimum inhibitory concentration (AUC/MIC) and the time up to which MIC levels were maintained in plasma (TMIC) were also improved. In Mycobacterium tuberculosis H37Rv infected mice, five oral doses of the nanoparticle formulation administered every 10th day resulted in undetectable bacilli in the meninges, as assessed on the basis of cfu and histopathology.

Oral nanoparticle-based antituberculosis drug delivery to the brain in an experimental model; Journal of Antimicrobial Chemotherapy 2006 57
www.oxfordjournals.org



Drug delivery and penetration into neoplastic cells distant from tumor vessels is critical for the effectiveness of solid tumor chemotherapy. We hypothesized that 10- to 20-nm nanoassemblies of phospholipids containing doxorubicin would improve the drug's penetration, accumulation, and antitumor activity.

We have developed a novel PEG-PE–based nanocarrier of doxorubicin that increased cytotoxicity in vitro and enhanced antitumor activity in vivo with low systemic toxicity. This drug packaging technology may provide a new strategy for design of cancer therapies.

Encapsulation of doxorubicin in PEG-PE micelles increased its internalization by A549 cells into lysosomes and enhanced cytotoxicity. Drug-encapsulated doxorubicin was more effective in inhibiting tumor growth in the subcutaneous LLC tumor model (mean tumor volumes in mice treated with 5 mg/kg M-Dox = 1126 mm3 and in control mice = 3693 mm3, difference = 2567 mm3, 95% confidence interval [CI] = 2190 to 2943 mm3, P<.001) than free doxorubicin (mean tumor volumes in doxorubicin-treated mice = 3021 mm3 and in control mice = 3693 mm3, difference = 672 mm3, 95% CI = 296 to 1049 mm3, P = .0332, Wilcoxon signed rank test). M-Dox treatment prolonged survival in both mouse models and reduced metastases in the pulmonary model; it also reduced toxicity.

Improving Penetration in Tumors With Nanoassemblies of Phospholipids and Doxorubicin;http://jnci.oxfordjournals.org/cgi/content/abstract/99/13/1004


the treatment of solid tumors may be improved by controlling the pharmacologic properties of anticancer therapeutics. In 1906, Paul Ehrlich established the concept of drug delivery (2) by proposing a carrier that would "bring therapeutically active groups to the organ in question." The objective of drug delivery in the treatment of solid tumors is to increase the concentration of a therapeutic agent in the tumor while limiting systemic exposure (3–5). Increasing the concentration of drugs in the tumor relative to normal tissues results in improved tumor control and reduced toxic side effects. Numerous drug delivery technologies have been developed to accomplish this objective, including liposomes (6), micelles (7), antibody-directed enzyme–prodrug therapy (8), photodynamic therapy (9), affinity targeting (10), and macromolecular drug carriers (11,12).

Many of these drug delivery technologies, including the one described by Tang et al., take advantage of the unique pathophysiology of tumor vasculature. As early as the 1920s, researchers using a transparent chamber and injectable dye techniques found that, in contrast to normal tissue, tumors contain a high density of abnormal blood vessels that are dilated and poorly differentiated, with chaotic architecture and aberrant branching (13–16). Subsequently, various parameters of tumor vasculature were found to be impaired: for example, tumor blood vessels were observed to have a higher permeability than normal ones. These impaired functions contribute to the higher concentration of plasma proteins detected in tumor tissues than in normal tissues (17–26). This phenomenon was elucidated by Maeda and colleagues (27–29) and reviewed by Seymour (30), who described it as the enhanced permeability and retention effect, which is a combination of the increased permeability of tumor blood vessels and the decreased rate of clearance. The enhanced permeability of tumor vessels is due in part to larger pores in the tumor vasculature (~100–2000 nm) (31–33) compared with those of normal healthy continuous vasculature (2–6 nm) (34). The decreased rate of clearance is due to the lack of functional lymphatic vessels within a tumor, although there are indications that lymphatic vessels may exist in the periphery of a tumor (35–37). Even though retention and cellular uptake in a tumor may be improved with a targeting moiety specific for tumor receptors, all macromolecules, including targeted ones, preferentially accumulate in solid tumors after intravenous administration because their longer plasma half-life compared with small molecules provides a sustained driving force for their migration across the leaky tumor vasculature into the tumor mass.

Despite the constant development of new drug delivery vehicles that focus on increasing the overall accumulation of anticancer drugs within a tumor, the penetration of these drug carriers––a factor that is equally important in determining efficacy––has received much less attention. The penetration of drugs and/or drug carriers in a tumor can be operationally defined at different length scales as 1) penetration from the surface of the tumor boundary into the tumor center (i.e., whole tissue scale), 2) penetration across the tumor blood vessel (i.e., vascular permeability), 3) penetration away from the blood vessels through the extracellular matrix (analogous to the effective diffusion coefficient), and 4) penetration into the tumor cell itself (cellular uptake). Optimizing penetration in a tumor is important at length scales that are relevant to the mode of action of the drug. Hence, for chemotherapeutic drugs such as doxorubicin that normally have an intranuclear mode of action, optimization of penetration from the macroscale down to the intracellular site of action is critical, whereas for radionuclides, homogeneous penetration through the tumor mass without substantial tumor cell uptake may suffice to elicit a therapeutic effect. In terms of the determinants of penetration, properties of the drug or drug carrier, such as molecular size and binding affinity, as well as properties of the tissue, including extracellular matrix constituents and pore interconnectedness, are important factors that will affect penetration at all length scales (38–44). Increasing molecular size limits penetration across the blood vessel (40) and through the tumor tissue (41). Although Tang et al. (1) used doxorubicin encapsulated in a polyethylene glycol-phosphatidylethanolamine (PEG-PE) micelle with a diameter of 10–20 nm, which is larger than doxorubicin alone, they achieved sufficient tumor accumulation to elicit a therapeutic response that they claimed could be attributed to the improved penetration of doxorubicin within the tumor.

Tang et al. (1) used a multitude of analytic, in vitro, and in vivo techniques to raise many interesting questions and present some promising results. Most notably, cellular uptake of doxorubicin was improved when delivered with PEG-PE, and this increased uptake may have contributed to the lower IC50 observed for doxorubicin PEG-PE micelles. Furthermore, the doxorubicin encapsulated within PEG-PE micelles demonstrated a different intracellular distribution than the free drug, and, in the light of the lower IC50 compared with free doxorubicin, these data suggest that the encapsulated doxorubicin may well have a different mechanism of cytotoxicity (45,46), though the precise mechanism of both cellular uptake and cytotoxicity of doxorubicin PEG-PE micelles remains a mystery. These results are also intriguing because they are in stark contrast to other drug delivery systems, in which encapsulated or conjugate drugs are often less cytotoxic than free drug. Many drug delivery systems demonstrate impressive tumor targeting in vivo but fail to elicit tumor regression because the drug is less bioavailable than free drug once it is localized to the tumor due to the encapsulation or conjugation process.

.....In our view, several aspects of this study are puzzling and deserve further scrutiny: first, it is surprising that the ability of PEG-PE to form micelles that can encapsulate doxorubicin has not been previously explored, as claimed by the authors, and, if this claim is correct, the authors deserve credit for examining the interaction of an old drug with a well-known formulation agent to create a potent drug delivery system.


Toward a Systems Engineering Approach to Cancer Drug Delivery; http://jnci.oxfordjournals.org/cgi/content/full/99/13/983

Begbroke Science Park

The farm house


http://www.begbroke.ox.ac.uk/about/photo_gallery.php

So it is only if the object disturbs the wave that you will know it is there

So it is only if the object disturbs the wave that you will know it is there......


If light of wavelength ! is scattered by an object, then the information carried by that scattered light can tell us about the details of that object, but only down to a level of detail d, where

d = 0.5 ! [1]

This means that light of wavelength 5 00 nm, say, will carry no information about any feature of an object that is less than 25 0 nm in size.

…… electrons could be considered as waves, with their wavelength given by

! = h/(mv ) [2]

(h is the P lanck constant, and m and v the mass and velocity of the electron respectively). For electrons travelling at 7 5% the speed of light, this gives a wavelength shorter than that of X -rays. The experimental proof of this hypothesis resulted from experiments ………. demonstrated that periodic objects (crystals) give rise to diffraction patterns for which the distribution of diffraction spots is given by the Bragg equation

2d sin("/2) = n! [3 ]

where d is the repeat pattern spacing and n is an integer. (This same equation can be used to describe the distribution of light spots caused by the scattering of the laser by the grid of wires…...) If we know the light or X –ray or electron wavelength !, and we measure the angles #, then we can determine the spacing d.

Seeing Nanoworld;
http://outreach.materials.ox.ac.uk/LearningResources
/downloads/Seeing%20in%20the%20Nanoworld.pdf


Nanoparticles can display four unique advantages over macroelectrodes when used for electroanalysis: enhancement of mass transport, catalysis, high effective surface area and control over electrode microenvironment. Therefore, much work has been carried out into their formation, characterisation and employment for the detection
of many electroactive species.

Cost considerations are important when manufacturing an electrode for use in any real system. This can lead to expensive materials such as gold and platinum being avoided because of the cost incurred when using large amounts to create macroelectrodes. Nanoparticle modification of an inexpensive base material, however, can lead to a larger surface area-to-volume ratio for the expensive metal, lowering the cost of the electrode. The large effective surface area may also cause there to be a larger number of active sites and often a higher signal-to-noise ratio.

.....It was found that addition of albumin to a preparation of gold nanoparticles led to better dispersion of the nanoparticles in a carbon paste electrode, which increased the sensitivity of the electrode to hydroquinone and dopamine because electron transfer was better promoted

The use of nanoparticles in electroanalysis: a review; http://www.chem.ox.ac.uk/commercialisation.html





MARTENSITIC AND MAGNETIC TRANSFORMATION


Martensitic and magnetic transformation behaviours in Heusler type NiMnIn and Ni-CoMnIn Metamognetic shape memory alloys. Metallurgical and Materials Transac-tions, 4/1/2007.

Martensitic and magnetic transformation behaviors of Ni^sub 50^MnIn, Ni^sub 45^Co^sub 5^MnIn, and Ni^sub 42.5^ Co^sub 7.5^MnIn Heusler alloys were investigated by differential scanning calorimetry (DSC), vibrating sample magnetometry (VSM), and transmission electron microscopy (TEM).

The Iron is known to undergo a pressure-induced phase transition from the ferromagnetic (FM) body-centered-cubic (bcc) alpha-phase to the nonmagnetic (NM) hexagonal-close-packed (hcp) epsilon-phase, with a large observed pressure hysteresis whose origin is still a matter of debate.

Johnson et al, Princeton Univ., Pub med, 2008, http://www.ncbi.nlm.nih.gov/pubmed/18345915



Iron is a Block D, Group 8, Period 4 element. The electronic configuration is [Ar] 3d6 4s2. In its elemental form iron's CAS number is 7439-89-6. The iron atom has a radius of 124.1.pm and it's Van der Waals radius is 200.pm.

American Elements; http://outreach.materials.ox.ac.uk/LearningResources/
Nanotechnology/nanotechnologyindex.php



Magnetism has been known to humans for millennia, and for millennia interpretations of the nature of this elusive force capable of moving inert bodies have been produced. G B Porta in his book Natural Magick in 1589 wrote iron is drawn by the Loadstone, as a bride after the bridegroom, to be embraced; and the iron is so desirous to join with it as her husband,… Magentism was understood as a soul of inert matter which transformed it into something like a living organism.
Molecular Nanomagnets, OUP, 2006

Rolls-Royce invests in Oxford spin-out

Oxford BioSignals Ltd, one of the University's spin-out companies, has announced that Rolls-Royce has made a strategic equity investment in the company. The partnership between Oxford BioSignals, a leader in the intelligent signal processing field, and the international aerospace company will provide a comprehensive foundation for Oxford Biosignals to achieve its goals.

In addition to a cash contribution of £3.2m, Rolls-Royce is making a commitment to significant future business with Oxford BioSignals, who will provide intelligent signalling processing products and solutions for engine condition monitoring technology.

Dr Chris Floyd, Business Development Director for Rolls-Royce, said: 'The technology provided by Oxford BioSignals enables us to analyse output from multiple sensors on an aircraft engine in an integrated way, rather than relying on several different instruments. This will allow us to detect trends in engine performance more effectively. Our investment in Oxford BioSignals also gives us an opportunity to capitalise on the value of this technology to other markets. All in all this is a very exciting development for the company.'

Oxford BioSignals has been developing and supplying innovative diagnostic monitoring solutions to the healthcare market since it was founded in May 2000. Over the last two years, it has expanded its activities to supply jet engine condition monitoring products to the Rolls-Royce aero engine business in the UK, Europe, US and Far East.

www.ox.ac.uk/media


Oxford BioSignals Ltd

www.oxford-biosignals.com

Oxford Biosignals technology provides intelligent data acquisition and advanced signal interpretation for complex signal monitoring across the Medical and Industrial sectors.

The generic technology is based on neural networks and intelligent algorithms and covers a range of applications including innovative sleep diagnostics systems, patient health monitoring software and Industrial applications spanning aero engines, railways, pipelines and energy.

The technology enables unique signal interpretation facilitating reduced costs, decision support and integrity monitoring. Specialist expertise includes high volume, real time, data acquisition techniques and system prognosis.

http://www.isis-innovation.com/spinout/oxbiosignals.html

Nano Particles

When nanoparticles are used as quantitation tags, either the particles themselves or a measurable parameter emanating from the particles (e.g. photons) are quantified. Encoded nanoparticles used as substrates rely on one or more identifiable characteristics to allow them to serve as encoded physical hosts for multiplexed bioassays. This is analogous to the positional encoding of assays on microarrays, but in solution. Nanoparticles that leverage signal transduction involve a change either in the location of nanoparticles relative to one another, or a perturbation in the biological system caused by the nanoparticle — both of which, in turn, lead to a change in a measurable signal. Functional nanoparticles exploit specific physical or chemical properties of nanoparticles to carry out novel functions, such as catalysis of a biological reaction. For certain particles and/or applications, these divisions can be blurred, but they nonetheless serve as a general classification method.


Penn et al, Nanoparticles for bioanalysis, sciencedirect.com, Volume 7, Issue 5, October 2003, Pages 609-615



To obtain lectins without tedious purification steps, a convenient method for a one-step purification of lectins using sugar-immobilized gold nano-particles (SGNPs)was developed. Proteins in crude extracts from plant materials were precipitated with 60% ammonium sulphate, and the precipitate was re-dissolved in a small volume of phosphate buffer. The resultant solution was then mixed with appropriate SGNPs under an optimized condition. After incubating overnight at 4°C, lectins in the mixture formed aggregate with SGNPs, which was visually detected and easily sedimented by centrifugation. The aggregate was dissolved by adding inhibitory sugars, which were identical to the non-reducing sugar moieties on the SGNPs. According to SDS–PAGE and MS of thus obtained proteins, it was found that SGNPs isolated lectins with a high purity. For example, a protein isolated from banana using Glc{alpha}-GNP ({alpha}-glucose-immobilized gold nano-particle) was identified as banana lectin by trypsin-digested peptide-MS finger printing method.


One-Step Purification of Lectins from Banana Pulp Using Sugar-Immobilized Gold Nano-Particles; the journal of Biochemistry; bj.oxfordjournals.org


Particles:

In chemistry:

• Colloidal particle, part of a one-phase system of two or more components

In physics:
• Subatomic particle, which may be either:
o Elementary particle, a particle of which larger particles are composed, also called a fundamental particle
o Composite particle, a bound state between several elementary particles
o Point particle, an idealized particle that does not have any volume
• See also list of particles


In other contexts:
• Particle (ecology), in marine and freshwater ecology, a small object
• Particulate matter, in the areas of atmospheric physics and air pollution
• Particle (nanotechnology), a small object that behaves as a whole unit in terms of its transport and properties
• Grammatical particle, in linguistics, a useful catch-all lacking a strict definition
• Particle system, in computer graphics, a technique to simulate certain fuzzy phenomena
• Particle (band), a 2000 jam band from Los Angeles, California


Source: wikipedia

Center of Excellence

Opening of Chemistry Research Laboratory

http://www.chem.ox.ac.uk/imagesofoxford/royalvisit/queens_tour/index.htm

Solids are of immense technological importance

Close-Packed Structures

The most efficient way to fill space with spheres?


Other materials can be considered to form in similar structures to metals

Buckminsterfullerene






ALL Compounds are Solids under suitable conditions of temperature and pressure. Many exist only as solids.

Solids (especially Crystals) are of immense technological importance, they have always been fascinating.

Mechanical Properties

# Metals/Alloys, e.g. Titanium for aircraft
# Cement/Concrete Ca3SiO5
# 'Ceramics', e.g. clays, BN, SiC
# Lubricants, e.g. Graphite, MoS2
# Abrasives, e.g. Diamond

Electrical Properties

* Metallic Conductors, e.g. Cu, Ag...
* Semiconductors, e.g. Si, GaAs
* Superconductors, e.g. Nb3Sn, YBa2Cu3O7
* Electrolytes, e.g. LiI in pacemaker batteries
* Piezoelectrics, e.g. a Quartz (SiO2) in watches


Magnetic Properties

* e.g. CrO2, Fe3O4 for recording technology


Optical Properties

* Pigments, e.g. TiO2 in paints
* Phosphors, e.g. Eu3+ in Y2O3 is red on TV
* Lasers, e.g. Cr3+ in Al2O3 is ruby
* Frequency-doubling of light, e.g. LiNbO3

Catalysts

* Zeolite ZSM-5 (an aluminosilicate)

o - Petroleum refining
o - methanol octane

Sensors

* Oxygen sensor, e.g. ZrO2/CaO solid solution



Some Basic Definitions

LATTICE = An infinite array of points in space, in which each point has identical surroundings to all others.

CRYSTAL STRUCTURE = The periodic arrangement of atoms in the crystal.

It can be described by associating with each lattice point a group of atoms called the MOTIF (BASIS)




http://www.chem.ox.ac.uk/icl/heyes/introtosolids/sumsch.html

Liposomes and Other Lipid-based Nanoparticles

Liposomal Gene Delivery

Negatively charged, or classical, liposomes have been used to deliver encapsulated drugs for some time and have also been used as vehicles for gene transfer into cells in culture. Problems with the efficiency of nucleic acid encapsulation, coupled with a requirement to separate the DNA-liposome complexes from "ghost" vesi-cles has lead to the development of positively charged liposomes. Cationic lipids are able to interact sponta-neously with negatively charged DNA to form clusters of aggregated vesicles along the nucleic acid. At a critical liposome density the DNA is condensed and becomes encapsulated within a lipid bilayer, although there is also some evidence that cationic liposomes do not actually encapsulate the DNA, but instead bind along the surface of the DNA, maintaining its original size and shape.
Cationic liposomes are also able to interact with negatively charged cell membranes more readily than classi-cal liposomes. Fusion between cationic vesicles and cell surfaces might result in delivery of the DNA directly across the plasma membrane. This process bypasses the endosomal-lysosomal route which leads to degra-dation of anionic liposome formulations. Cationic liposomes can be formed from a variety of cationic lipids, and they usually incorporate a neutral lipid such as DOPE (dioleoylphosphatidyl-ethanolamine) into the for-mulation in order to facilitate membrane fusion. A variety of cationic lipids have been developed to interact with DNA, but perhaps the best known are DOTAP (N-1(-(2,3-dioleoyloxy)propyl)-N,N,N-trimethylammoniumethyl sulphate) and DOTMA (N-(1-(2,3-dioleoyloxy)propyl)-N,N,N-trimethylammonium chloride). These are commercially available lipids that are sold as in vitro transfecting agents, with the latter sold as Lipofectin.
There have been several studies on the in vivo, systemic use of liposome/DNA complexes. The factors con-trolling the transfection efficiency of liposome/DNA complexes following intravenous administration are still poorly understood. Complexes formed between the cationic lipid DOTMA and DNA are rapidly cleared from the bloodstream and were found to be widely distributed in the body and expression was detected mainly in the lungs but also in the liver, spleen, heart and kidneys. Similar results were found when DOTAP-based liposomes were used and it was found that the main factors controlling transfection efficiency were the struc-ture of the cationic lipid and the ratio of the cationic lipid to DNA. The type of helper lipid used was also im-portant as the addition of DOPE was found to reduce the in vivo transfection efficiency of DOTAP/DNA com-plexes.

The transfection efficiency of liposome/DNA complexes in vivo has been shown to be relatively low, especially when compared to viral vectors. One study has suggested that the in vivo transfection efficiency of adenovi-ruses is around 200 times greater than that observed with liposomes. One explanation for the relatively poor transfection efficiency of liposome/DNA complexes is that they are susceptible to disruption by serum pro-teins. A variety of proteins are known to bind to liposomes in vitro and in vivo and may membrane destabili-sation. There are now serious efforts being made to develop liposomal vectors that are resistant to serum disruption. Novel cationic lipids are also being developed to try to improve the transfection efficiency of lipo-some/DNA complexes. Targeting of the liposomes to specific cell types has also been investigated as a means of improving the transfection efficiency.

There have been several clinical trials of liposome/DNA complexes, although almost all of these have been involved in the treatment of cystic fibrosis. Most protocols involve the use of DC-chol/DOPE liposomes di-rectly instilled onto the nasal epithelium of CF patients. The effect of gene expression on CFTR function was determined and the presence of the gene in the target cells was determined by PCR (polymerase chain reac-tion) and Southern blot analysis.
Initial clinical studies found no evidence of any safety problems with the use of liposome/DNA complexes. This is surprising as it is well documented that the liposome/DNA complexes used in clinical trials are directly cytotoxic in vitro. Furthermore, studies in mice and macaques have demonstrated that exposure to high doses or to repeat doses of liposome/DNA complexes results in histopathology and gross lung pathology, suggesting that these vectors may not be as clinically safe as previously thought.

http://www.gene-delivery.ox.ac.uk/Gene%20Therapy/Vectors/Synthetic%20Vectors/Liposomes/Liposomal%20Gene%20Delivery.htm



Liposome


Recent developments in nanotechnology have provided researchers with new tools for cancer imaging and treatment. This technology has enabled the development of nanoscale devices that can be conjugated with several functional molecules simultaneously, including tumor-specific ligands, antibodies, anticancer drugs, and imaging probes. Since these nanodevices are 100 to 1,000-fold smaller than cancer cells, they can be easily transferred through leaky blood vessels and interact with targeted tumor-specific proteins both on the surface of and inside cancer cells. Therefore, their application as cancer cell-specific delivery vehicles will be a significant addition to the currently available armory for cancer therapeutics and
imaging. Nanoparticles can consist of a number of materials, including polymers, metals, and ceramics. Based on their manufacturing methods and materials used, these particles can adopt diverse shapes and sizes with distinct properties. Many types of nanoparticles are under various stages of development as drug delivery systems, including liposomes and other lipid-based carriers (such as lipid emulsions and lipid-drug complexes), polymer-drug conjugates, polymer microspheres, micelles, and various ligand-targeted products (such as immunoconjugates).

Liposomes are self-assembling, spherical, closed colloidal structures composed of lipid bilayers that surround a central aqueous space. Liposomes are the most studied formulation of nanoparticle for drug delivery (Table 1). Several types of anticancer
drugs have been developed as lipid-based systems by using a variety of preparation methods. Liposomal formulations have shown an ability to improve the pharmacokinetics and pharmacodynamics of associated drugs.

Second Generation Liposomal Drugs....Surface-modified liposomes (Stealth) have hydrophilic carbohydrates or polymers, which usually are lipid derivatives of polyethylene glycol (PEG) grafted to the liposome surface. While this surface modification has solved the problem of fast clearance from the circulation, yielding liposomes with a significantly increased half-life in the blood, the challenge remains to attain preferential accumulation of liposomes in tumor tissues. One strategy to achieve tumor-specific targeting is to conjugate a targeting moiety on the outer surface of the lipid bilayer of the liposome that selectively delivers drug to the desired site of action............

2008;58:97–110; Application of Nanotechnology in Cancer Therapy and Imaging; American Cancer Society, Inc., 2008

Superior physiological performance through mild ketosis

During periods of stress, elevated catecholamines, steroids and cytokines increase the metabolism of stored fat in the body. The increase in circulating free fatty acids causes insulin resistance, decreases skeletal and cardiac muscular efficiency and may decrease metabolic fuel for the brain, which cannot metabolize fat, but can metabolize ketones. Ketone bodies contain more recoverable metabolic energy than fatty acids and yield 28% more energy on combustion than glucose. We are testing whether the negative effects of elevated free fatty acids can be overcome by mild ketosis. In collaboration with the National Institutes of Health in the US, we created a diet containing ketone bodies, which caused mild ketosis. We tested the metabolic mechanism underlying the effects of the ketone body diet during extreme exercise, with and without ketosis. Endurance and cognitive function, tested using treadmill exercise and a maze test, respectively, were found to be increased by the ketosis. We propose to further test the ketone diet before during and after 5 days of intense training, in a double-blind placebo-controlled cross-over trial. Exercise testing, cognitive function and skeletal and cardiac muscle energetics will be followed using psychological testing and non-invasive MRI of brain and muscle during exercise. Should subjects on the ketone body diet have greater metabolic efficiency, and therefore greater endurance and cognitive function, during extreme exercise and psychological stress than those on a normal diet, the diet could be used by athletes and to treat metabolic diseases, such as obesity, Alzheimer’s and Parkinson’s diseases.

Kieran Clarke: www.physiol.ox.ac.uk/Research_Groups/Cardiac_Metabolism/




Oxford BioSignals' are designed to automate the monitoring process for complex multiple signal systems. Visensia, a diagnosis technology, provides life-saving medical insight by analyzing five patient vital signs – heart rate, respiration rate, body temperature, oxygen saturation and blood pressure - and fuses this data into a measurable index. The first early warning system for patients created, which is used in Radcliff Hospital at Oxford, takes the vital sign information that is currently monitored such as heart rate, respiration rate and oxygen levels and defines them in a special way. It uses advance special software to look for small changes in several vital signs rather than a big change in just one vital sign. This can give doctors and nurses extra time to respond to an unwell patient. …….The technology has just been introduced on the A380, that’s the Airbus super jumbo, and that will be the first commercial airliner that will use the technology. Rolls Royce had first used the technology but this will be the first time this new generation of monitoring technology has been used on a commercial basis. http://www.oxford-biosignals.com/

Oxford Thinking

Through the centuries, Oxford’s great minds have changed and bettered the world through their discoveries, innovations and insights.

The Rt Hon Lord Chris Patten, Chancellor

Leaving a bequest to Oxford

A bequest is the only donation that just about anyone can make. It is often the greatest donation that anyone does make. A gift in your Will to support the Collegiate University can make a lasting contribution for generations to come, whether it endows scholarships or bursaries for gifted students, helps fund academic posts or provides new facilities and resources.

www.campaign.ox.ac.uk

University researchers tackle the end of the world

Will the human species survive the 21st century? What are the biggest threats to global civilization and human well-being? Are we addressing the right risks? These questions will be examined at a unique conference hosted by Oxford University’s Future of Humanity Institute, part of the Philosophy Faculty, from 17 to 20 July 2008.

www.ox.ac.uk/media


(1)The Oxford Invention

The Oxford Invention is a design protocol for inserting filled molecules of Buckminsterfullerene ("Buckyballs") into carbon, and other types of, nanotube. The Buckyballs are themselves filled with molecules that have either an electronic or structural property which can be used to represent the quantum bit (Qubit) of information, and which can be associated with other adjacent Qubits. The improved stability of the system now allows several thousand operations to be executed before quantum interference occurs ("decoherence").


(2)THE OXFORD INVENTION
A multiwalled carbon-nanotube (MWCNT)-based ammonia sensing method has been developed by scientists at Oxford University. Figure A shows how intercalation can lead to exfoliation of graphite, whilst Figure B shows the how intercalation does not occur with bamboo MWCNTs; hence electron transfer occurs at edge plane sites. X-Ray diffraction measurements (Figure C) over time further show that the bamboo MWCNT structure is not affected by intercalation. Experimental results show that MWCNTs provide excellent quantitative voltammetric response to the oxidation of NH3 allowing useful electrochemical measurements to be made.


(3)THE OXFORD INVENTION

Oxford researchers hypothesised that the activity of a particular protein previously thought to be unrelated to cancer may play a direct role in the regulation of tumour cell proliferation and progression. Subsequent investigation of levels of expression of the protein in human tumour samples using immunohistochemical staining confirmed that, compared with normal tissues, the protein is expressed excessively in tissues from patients with lung, breast, head and neck cancers as well as lymphomas.

http://www.isis-innovation.com/licensing







CARBON NANOTUBE BASED AMMONIA SENSOR - Isis Project No 2861

Introduction

Isis Innovation, the technology transfer company of the University of Oxford, releases a new method for sensing ammonia aimed at industrial applications.
Marketing Opportunity

Ammonia (NH3) is a noxious and toxic gas. Determination of NH3 concentration is important in monitoring industrial processes and also in the water industry for ensuring that effluent meets regulations. Semi-conductor based sensors are widely used, but are known to become less effective over time. Electrochemical sensors have also been used, however such systems have experienced premature failure from analyte or solvent intercalation of the graphite-based electrodes. Clearly a more robust electrochemical sensor, capable of accurate measurement of NH3 concentration in industrial environments, would be highly desirable.

http://www.isis-innovation.com/licensing/2861.html







....Scientists have many tools for studying the size, shape, and surface properties of particulates outside of the physiological environment; however, it is difficult to measure many of these same properties in situ without perturbing the environment, leading to spurious findings. Characterizing nanoparticle systems in situ can be further complicated by an organism's active clearance, defense, and/or immune responses. As toxicologists begin to examine nanomaterials in a systematic fashion, there is consensus that a series of guidelines or recommended practices is necessary for basic characterization of nanomaterials. These recommended practices should be developed jointly by physical scientists skilled in nano characterization and biological scientists experienced in toxicology research.

Power et al, Research Strategies for Safety Evaluation of Nanomaterials, Oxford Journals; Toxicological Sciences 2006 90(2):296-303; doi:10.1093/toxsci/kfj099






How often people had conversations with others of differing political viewpoints.

One logical conjecture would be to expect this form of political behavior to be much like any other. In other words, it would be disproportionately the province of well-educated, high-income populations. Indeed, the frequency of general political discussion tracks closely with these characteristics of high socioeconomic status. But the correlates of cross-cutting conversation are strikingly different. there are clear patterns of difference with respect to race, income, and education, but they are not in the usual directions. Nonwhites are significantly more likely to engage in cross-cutting political conversation than whites. And as income increases, the frequency of disagreeable conversations declines. Exposure to disagreement is highest among those who have completed less than a high school degree and lowest among those who have attended graduate school.

http://www.fhi.ox.ac.uk/index.html





Acetylcholine to enhance attention

According to research published in this week's issue of Nature, a nervous system chemical called acetylcholine is vital for our brain cells to pay attention to a demanding task.

"For the first time we have been able to precisely identify the mechanism by which the brain implements a state of attention and increases awareness for important tasks," says Professor Alex Thiele from Newcastle University, who led the research.

Attention is essential for perception, awareness, learning and memory. This research is important because it increases understanding of how our brains work and also has potential use in the development of treatments for neurological conditions linked to awareness and attention, including Alzheimer's disease and attention-deficit hyperactivity disorder.

In the study, which was part-funded by the Wellcome Trust, Professor Thiele and colleagues used a primate model to explore the role in attention of acetylcholine - a naturally occurring chemical involved in signal transmission in the nervous system.

Researchers applied small amounts of acetylcholine to animals before they took part in an exercise demanding high attention. The receptors and nerve cells in the animals' brains showed greater activity associated with attention, and the animals showed an increased awareness of the task. Blocking specific acetylcholine receptors reversed this process and reduced attention.

source: www.wellcome.ac.uk//News/News-archive/Browse-by-date/2008/News/WTX049857.html




Drug receptors and nanomedicine

G-coupled receptors are neurologically located and are involved in most sensory and brain functions. As such they are the major focus of drug research. However, this activity is hampered by the lack of receptors on which to work, details about their structure since we do not have any ligand-activated GPCR structures yet, and the lack of details of how they are activated at the molecular level. By focusing on one GPCR, which is uniquely expressed in E. coli and available purified and functionally competent, we are in a position to develop generic technology which will be applicable to other GPCRs, when they become available. In particular, a novel development of a detection methods involving surface plasmon resonance, has been developed within the IRC, and this is now suitable for high throughput screening of ligands for this and other similar GPCRs. Also, single GPCR molecules have been visualized by electron microscopy, and fluorescently labeled GPCR has been produced for single molecul interaction studies at the nanoscale. To gain insight into the activation mechanism, solid state NMR detection of the natural activating hormones is being carried out, yielding conformational information at sub-nm resolution and dynamics at the nanosecond level.

http://www.bionanotechnology.ox.ac.uk/
index.php?option=com_content&task=view&id=53&Itemid=78




Bioinformatics Links Directory
A complete list of all links listed in Nucleic Acids Research 2008 Web Server issue can be accessed online at http://bioinfomatics.ca/links_directory/narweb2008/. The 2008 update of the Bioinformatics Links Directory, which includes the Web Server list and summaries, is also available online at the Nucleic Acids Research website, http://nar.oxfordjournals.org/.

Oxford measurements

“there is probably a little more ozone at the seaside than inland” says Dr. Dobson. “but I doubt if what you can smell there is ozone. Seaweed has a similar smell. What you get on the ground is diffusing down from the upper air and formed by ultra violet light from the sun. it would have to be about 100 times the normal amount at ground level before you could smell it. A ground level you only get a few parts in 100m.”
The Oxford Times, feb 8, 1957



The second international conference on atmospheric ozone was held at Oxford in 1936 (the first had been in 1929 in Paris). In the following year Dobson moved into his new house, 'Watch Hill' at Shotover on the outskirts of Oxford. His laboratory there was a substantial brick building with two workrooms, one large and one small, with provision to make zenith sky observations, and a well equipped workshop. A wooden hut was built near by and was used ..... as the office for collating and plotting the data sent in by the network of spectrophotometers.

Work on atmospheric pollution
In the early 1930s Dobson became concerned with the study of atmospheric pollution, and from 1934 to 1950 served as Chairman of the Atmospheric Pollution Committee of the Department of Scientific and Industrial Research Under his guidance reliable methods were developed for the measurement of smoke, deposited matter and sulphur dioxide, and a detailed survey was conducted in Leicester from 1937 to 1939.


http://www.atm.ox.ac.uk/user/barnett/ozoneconference/dobson.htm


The comparative anatomy of risk regulation regimes
....Sets out two key dimensions for analysing risk regulation regimes. The first dimension relates to the three constituent components of a risk regulation regime that are common to any control system—i.e. ways of gathering information, ways of setting standards, goals or targets and ways of changing behaviour and enforcement to meet the standards or targets. The second dimension relates both to the context of risk regulation regimes—i.e. the character of the risks being tackled, public attitudes towards risks and the configuration of related organized interests— and the content of regimes—i.e. their size, structure, and style. Analysis of risk regulation regimes along these two dimensions provides an essential starting point for compartive analysis, picks up fine-grained distinctions between regimes and identifies regime features that are central to a range of debates about risk regulation.

Christopher Hood et al, The Government of Risk; www.oxfordscholarship.com




....... The first of twin revelations to hit Bramwell was a timely spark that Thatcher was right, “state planning was bound to fail” (2). The second occurred while she stayed on a small farm (a rite of passage for some) where Bramwell “learned of the unquantifiable pleasures, and through knowing the ex-farmers, something of the unique quality of faces untouched by television expressions, or modesty, unselfconsciousness and worth – virtu.” (3) This farm experience was a “constant inspiration”, regurgitated in each book. Had she not met the ex-farmers she “would not have recognized what it was that so many ecologists were trying to preserve.” (4) Because reviewers complained her treatment of the rural couple was condescendingly High Tory, she atoned in her next book acknowledging the lives of such people consisted of dirty low-paying toil. She then takes flight again over England’s verdant countryside naming several species of trees from the farm concluding she: “is not without sympathy for ecological values” having “retained a gut feeling about the value of the rural life and the countryside”. To this she later adds, “I live in the country still, because I am happier there.” (5)

Her books are polemical. The second volume begins: “Perhaps unusually for an academic book, I have tried, deliberately, to include my own views in the analysis.” And later:

“I refer in passing in this work to the harmony and beauty of nature. I have taken this as a given....I have not formally addressed or endorsed the reality of the claim that rural life is in some way morally superior. I have however felt it throughout as an underlying argument, hard to prove, not academically acceptable, yet presiding within the assumptions of our culture...Paeans of praise for the yeoman spirit fall easily into cliché, and while such people were in evidence, it is hardly necessary to delineate their virtues in detail; it was a common presumption of the culture at the time, and like all such presumptions, it was not – it did not have to be – articulated convincingly.” (6)


http://www.ecofascism.com/review11.html

The star of the month

The Dengue Virus Genome
Dengue virus is a small virus that carries a single strand of RNA as its genome. The genome encodes only ten proteins. Three of these are structural proteins that form the coat of the virus and deliver the RNA to target cells, and seven of them are nonstructural proteins that orchestrate the production of new viruses once the virus gets inside the cell. The outermost structural protein, termed the envelope protein, is shown here from PDB entry 1k4r. The virus is enveloped with a lipid membrane, and 180 identical copies of the envelope protein are attached to the surface of the membrane by a short transmembrane segment. The job of the envelope protein is to attach to a cell surface and begin the process of infection.

A Deadly Switch
In the infectious form of the virus, the envelope protein lays flat on the surface of the virus, forming a smooth coat with icosahedral symmetry. However, when the virus is carried into the cell and into lysozomes, the acidic environment causes the protein to snap into a different shape, assembling into trimeric spike, as shown at the bottom from PDB entry 1ok8. Several hydrophobic amino acids at the tip of this spike, colored bright red here, insert into the lysozomal membrane and cause the virus membrane to fuse with lysozome. This releases the RNA into the cell and infection starts. The hemagglutinin protein on the surface of influenza virus plays a similar role, but the two proteins use entirely different mechanisms to perform a similar task.

PDB (Protein Data Bank): http://www.pdb.org/pdb/home/home.do


MENOPAUSE

……..The reality of human reproduction in developing countries is, of course, far from intended goals, as is most visibly illustrated by the escalating HIV/AIDS epidemic.

Programmatically, the RH approach calls for an expansion of the scope (in terms of health problems addressed) of reproductive health services, including, but not limited to, family planning. It also entails broadening the constituencies to which reproduc-tive health services are addressed to include not only women in the childbearing age but also those from adolescence to post-menopause.

http://www.gprg.org/pubs/workingpapers/pdfs/gprg-wps-005.pdf

There are no simple treatments for established osteoporosis. Treatment is therefore aimed at the time of rapid bone loss during the menopause. HRT based on oestrogen, alone or in combination with proges-terone, has been shown to retard, stop or even reverse bone loss after the menopause. HRT is recom-mended for a maximum of 10 years. That leaves a treatment gap of about 15 years between stopping HRT and the age at which fractures become common.

http://www.jr2.ox.ac.uk/bandolier/painres/download/Bando003.pdf



... Furthermore, in developing countries, women at later age are more vulnerable to mental health problems - that is as their traditional roles fades out they loose their purpose of life, since their only productive identity vanishes by the order of nature.

Risk Society

.....Whether or not the controversial idea of a ‘risk society’ is theoretically coherent or accurate as a historical generalization is much debated, but there has undoubtedly been an avalanche of discussion and literature on risk, hazard, and blame in recent times, and that phenomenon needs some explanation. As well as a ‘risk society’, we are also said to live in a ‘regulatory state’. The idea of the ‘regulatory state’ is that a new institutional and policy style has emerged, in which government's role as regulator advances while its role as a direct employer or property-owner may decline through privatization and bureaucratic downsizing. The two ideas of ‘risk society’ and ‘regulatory state’ could, indeed, be linked in so far as risk and safety is often held to be one of the major drivers of contemporary regulatory growth, for example in the development of EU regulation (see Royal Society 1992). In turn, development of risk regulation is interpreted by many to reflect broader political and cultural change. Building on a ‘grid-group’ analysis of culture that highlights a dynamic of conflict among four fundamentally different sets of beliefs and attitudes, risk is seen as a political weapon used by a society poised between the cultures of individualism and egalitarianism, to blame those who wield power in the state and big corporations for what happens to the rest of us. From this perspective the increased salience of risk and regulation reflects a cultural shift away from ‘hierarchist’ world-views over matters of trust and blame.

Christopher Hood (All Souls College, Oxford), 2003, The Government of Risk:Understanding Risk Regulation Regimes; OUP



"What then is a legislature for? Parliament has multiple roles: to sustain the executive; to scrutinise executive actions; to represent territory; to represent shades of opinion. As before, these objectives are not wholly compatible, and writers with one conception of parliament may deny that a role that according to another conception is central is legitimate at all."

Evidence to the Commission on Electoral Systems
By Iain McLean, Professor of Politics, Oxford University





Selection Bias Modelling

Selection arises in non-randomized studies when individuals self-select into or are non-randomly allocated to a particular group. Selection creates statistical problems when it is based on unobserved individual characteristics. Moreover, selection on the basis of unobserved individual characteristics is very common. Examples include students with high unobserved ability being the most likely to go to university and workers with high unobserved productivity having relatively high probabilities of participating in the labour market. Failure to account for selection leads to biased estimates of the causal effects of explanatory variables on the outcome of interest. Indeed, the estimated effect of education on wages is biased upwards if no account is taken of the higher average ability of individuals with more education.

http://springschool.politics.ox.ac.uk/courses/selection_bias.asp

The Philip Ball's Freedom to Think

Hobbes became convinced that this must be the axiom he was seeking. Constant motion was the natural state of all things - including people. All human sensations and emotions, he concluded, were the result of motion. From this basic principle Hobbes would work upwards to a theory of society.

What, precisely, does Hobbes mean by this assumption? It is, to modern eyes, a cold and soulless (not to mention an obscure) description of human nature. He pictured a person as a sophisticated mechanism acted upon by external forces. This machine consists of not only the body with its nerves, muscles and sense organs, but also the mind with its imagination, memory and reason. The mind is purely a kind of calculating machine - a computer, if you will. Such machines were popular in the seventeenth century: the Scottish mathematician John Napier (1550-1617) devised one, as did the French philosopher and mathematician Blaise Pascal (1623-62). They were mechanical devices for adding and subtracting numbers; and this, said Hobbes, is all the mind does too:

When a man Reasoneth, hee does nothing else but conceive a summe totall, from Addition of parcels; or conceive a Remainder, from Subtraction of one summe from another . . . For REASON . . . is nothing but Reckoning.

The body, meanwhile, is merely a system of jointed limbs moved by the strings and pulleys of muscles and nerves. Man is an automaton.

Indeed, Hobbes held that the ingenious mechanical automata created by some inventors of the era were truly possessed of a kind of primitive life. To him there was nothing mysterious or upsetting about such an idea. Others were less sanguine: the Spanish Inquisition imprisoned some makers of automata on the grounds that they were dabbling in witchcraft and black magic.

What impelled Hobbes's mechanical people into action was not just external stimuli relayed to the brain by the apparatus of the senses. They were imbued also with an inner compulsion to remain in motion. For what is death but immobility, and which person did not seek to avoid death? 'Every man . . .', said Hobbes, 'shuns . . . death, and this he doth, by a certain impulsion of nature, no less than that whereby a stone moves downward.'

Mankind's volitions, therefore, are divided by Hobbes into 'appetites' and 'aversions': the desire to seek ways of continuing this motion and to avoid things that obstruct them. Some appetites are innate, such as hunger; others are learnt through experience. To decide on a course of action, we weigh up the relevant appetites and aversions and act accordingly.

What Hobbes means by 'motion' is a little vague, for he clearly does not intend to imply that we are forever seeking to run around at full pelt. Motion is rather a kind of liberty - a freedom to move at will. Those things that impede liberty impede motion. Even if a man sits still, the mechanism of his mind may be in furious motion: the freedom to think is an innate desire too.

What room is there in this mechanical description for free will? According to Hobbes, there is none - he was a strict determinist. Humans are puppets whose strings are pulled by the forces at play in the world. Yet Hobbes saw nothing intolerable in this bleak picture. After all, he believed that he had arrived at this basic, indisputable postulate about human nature by introspection - by considering his own nature. The first puppet he saw was himself:

whosoever looketh into himself, and considereth what he doth, when he does think, opine, reason, hope, feare, &c, and upon what grounds; he shall thereby read and know, what are the thoughts, and Passions of all other men, upon the like occasions.


Critical Mass: How One Thing Leads to Another

by Philip Ball

Winner of Aventis Prize, the world's most prestigious Science book award

Carbon Nanotubes

Oxford Materials Outreach

Carbon Nanotubes are Single-Walled, Double Walled and Multi-Walled black nano scale cylindrical tubes of graphitic carbon with numerous applications. Carbon Nanotubes are the stiffest and strongest known fibers and have unique electrical properties. Applications for AE Carbon Nanotubes� include in flat screen displays, scanning probe microscopes in brushes for commercial electric motors, and in sensing devices and because of their strength in numerous aerospace and automotive uses, in body armor and tear-resistant cloth fibers and textiles and stronger and lighter sports equipment . Carbon nanotubes can behave like a conductive metallic or semiconductor depending on their structure, which is useful for nanoscale electronic devices and in electrically conductive films in coatings, plastics, nanowire, nanofiber and in certain bioscience applications.

Source://outreach.materials.ox.ac.uk/LearningResources/Nanotechnology/nanotechnologyindex.php



BUCKY BALLS

The most well-known crystal structure of carbon is diamond, which can be described as (cubic F)*(C-C). That is, it has the same Bravais lattice as Au (cubic F), but the motif is a pair of C atoms instead of one Au atom. Carbon crystallises in
several other forms Ð one is graphite, in the form of sheets of C atoms arranged in a hexagonal array, with these sheets held together by weak (Van der Waals) forces. If we take a sheet of graphite, it can be rolled into a tube and joined, with no discontinuities. These carbon nanotubes were first discovered by Iijima in the electron microscope in 1991. They are very strong, and so can be used as strengthening fibres within composites; and they can be used as containers inside which thin crystal wires can be grown, with properties which are different to the bulk, or within which individual molecules can be packed. If a piece with 60 carbon atoms is cut from a single graphite sheet, it can be bent into a football shaped molecule, C60, known as a bucky ball (after the architect Buckminster Fuller who
had previously built large structures with this shape). Indeed the bucky ball is small enough to pack inside a nanotube (see Figure 9), and an atom is small enough to place inside a bucky ball. So individual atoms can be held inside bucky balls, which in turn are packed within a nanotube. Scientists are investigating whether
this structure might be the basis for the next generation of (quantum) computers.


............in diamond, each carbon atom is at the centre of a tetrahedron of four other carbon atoms, and this arrangement is exceedingly strong. And this tetrahedron of atoms survives, with some distortion, into the amorphous state of carbon. Adjacent connected tetrahedra can rotate about their common bond, and this random rotation, when repeated for all bonds, results in the amorphous structure. During this rotation, the first nearest distance, and the second nearest distance of the tetrahedron are retained, and appear in the distribution function of the amorphous state, but the third nearest neighbour distance is not retained and does not appear.

Wavws of the future; outreach.materials.ox.ac.uk





Nanomaterials are often classified in the literature based on dimensionality. Crucial to this classification is the concept of confinement, which may be roughly interpreted as a restriction in the ability of electrons to move in one or more spatial dimensions. 0D nanomaterials, such as quantum dots and metal nanoparticles, are confined in all three dimensions. 1D nanomaterials are confined in two directions and extended in only one: electrons flow almost exclusively along this extended dimension. Examples of one-dimensional nanomaterials are nanotubes and nanowires. Finally, 2D nanomaterials, which are confined in one dimension and extended in two, include thin films, surfaces, and interfaces. Interestingly, material structures currently used as elementary semiconductor devices fall under this category.

Nanomaterials can also be divided into inorganic and organic classes.

The term inorganic nanomaterials describes nanostructures in which carbon is
not present and combined with some other element. Four types of inorganic nanostructures are fullerenes and carbon nanotubes, nanowires, semiconductor nanocrystals, and nanoparticles.

.......Further, nanotubes have a current carrying capacity of one billion amps per square centimeter while copper wires burn out at one million amps per square centimeter. They also have more than 20 times the tensile strength of high-steel alloys, but are lighter than aluminum. Finally, it is estimated that nanotubes can transmit nearly twice as much heat as pure diamond and are likely to remain stable in higher temperatures than metal wires.

Miller, John C. Handbook of Nanotechnology : Business, Policy, and Intellectual Property Law, John Wiley & Sons, 2004. p 17




Since the re-discovery of carbon nanotubes (CNTs) in 1991 , they have become widely exploited in electroanalysis. CNTs are assigned into two classes: single walled (SWCNTs) and multi-wall carbon nanotubes (MWCNTs). The former consist of a single graphite sheet rolled flawless producing a tube diameter of 1-2 nm while the latter comprise several concentric tubes fitted one inside the other. There are a number of morphological variations of the latter including “hollow-tube”, “herringbone” or “bamboo-like”MWCNTs.

http://compton.chem.ox.ac.uk/news/2006/poster%20Xiaobo.pdf


Particle surface and biocompatibility Reports on the surface properties of nanoparticles, both physical and chemical, stress that nanoparticles differ from bulk materials. Their properties depend heavily on the particle size. Therefore, nanoparticles are not merely small crystals but an intermediate state of matter placed between bulk and molecular material. Independently of the particle size, two parameters play dominant role. The charges carried by the particle in contact with the cell membranes and the chemical reactivity of the particle.

Nanoparticles – known and unknown health risks, Journal Nanobiotechnology.com; Oxford Journals, 2004




One-dimensional nanoscale materials - SiC

Silicon carbide (SiC) is a material of great technological interest for devices designed to operate at high temperatures, high power, high frequency, and in harsh environments. SiC with the fibrous structure is a potential candidate as a reinforcement material for ceramic as a result of its weavability, high tensile strength and high Young's modulus. SiC has displayed the unique optical property that the photoluminescence emission is in the blue range at room temperature when the scale decreases to nanometre

p-SiC nanorods have been synthesized by the reaction of SiO and carbon
nano-capsules. It was found that the synthesis conditions, i.e. the composition ratio of SiO to carbon nano-capsules in weight and the reaction temperature, are very important for the synthesis of SiC nanorods.

The most interesting phenomenon is that a SiC nanorod with one kind of axis direction can grow on other SiC nanorod with the another kind of axis direction!

Oxford Journals: The microstructural analysis of SiC nanorods by high-resolution electron microscopy


Non-metalic Materials: ceramic nanocomposites

....Recent work in Oxford has shown that very small volume fractions (e.g. 1-2%) of nanophase additions can have dramatic effects on the properties of structural ceramics, and research elsewhere gives reason to believe that this might also be the case with functional ceramics. Furthermore, some of these effects might be synergistic in that they could improve both the mechanical and the functional properties of the material.
Oxford Materials
http://www.materials.ox.ac.uk/uploads/file/research/RIP2005.pdf



Bionanotechnology and carbon nanotubes: protein-functionalisation and biosensing


Small molecules, such as O2, NO2, and NH3, as well as larger protein molecules and DNA can adsorb onto carbon nanotubes (CNTs). The presence of such molecules can change the electrical properties of CNTs. In this project we are investigating the sensing behaviour in nitrogen-doped CNTs (which have been predicted to be metallic) when they are functionalized with metalloproteins. We have shown that proteins
including, cytochrome c, ferredoxin, ferritin and azurin can be adsorbed onto nitrogen-doped nanotubes and imaged using Atomic Force Microscopy (AFM). These functionalised CNTs are integrated into circuits and I-V curves are being
measured.


Dr. S. Contera*, H. Hamnett*, N. Toledo*, K. Voïtchovsky *, Dr. M. de Planque*, Dr. N. Grobert, Professor J. F. Ryan*(*Bionanotechnology IRC, Physics Department, University of Oxford), Oxford Materials


One-dimensional crystal growth inside single-wall carbon nanotubes

Crystals of various salts and metals grown within single-wall carbon nanotubes are effectively 1-D wires, with a range of interesting physical properties which arise from their unique configurations, We are exploring ways of growing these structures, which are characterised by HREM, EDX and EELS. Their physical properties are also under investigation.

OXFORD MATERIALS; Professor A.I. Kirkland, Dr. J. Sloan, Dr. J.L. Hutchison, Professor M.L.H. Green*; (*Inorganic Chemistry Laboratory) (Funded by EPSRC, Leverhulme Trust and The Royal Society).


Cell Division: Mitosis

....One of the most important concepts in biology is that the properties of individual cells are determined by the chromosomes that they inherit. A key observation leading to this notion was that cell division is preceded by the meristemic division of its nucleus, namely the condensation of its chromosomes from interphase chromatin, the splitting of chromosomes into a pair of closely apposed sister chromatids, and their subsequent disjunction to opposite poles of the cell prior to its division, a process known as mitosis. We now know that the hereditary material of chromosomes is DNA and that each chromosome contains a single immensely long molecule that is usually replicated many hours before cells actually enter mitosis. What has remained mysterious until recently is what holds sister DNAs together. It has long been suspected but never proven that this “sister chromatid cohesion” has a crucial role in ensuring that microtubules pull sister DNAs in opposite directions. Equally mysterious has been the trigger for what is arguably the most dramatic and one of the most highly regulated events in the life of a eukaryotic cell, the sudden disjunction of sister chromatids at the metaphase to anaphase transition.

Prof Kim Nasmyth, The mechanism by which chromosomal DNA molecules are held together: entrapment within cohesin rings?
http://www.bioch.ox.ac.uk/aspsite/research/brochure/Nasmyth/









The NC-AFM is a unique atomic tool and has the following characteristics: (i) true atomic resolution; (ii) ability to map atomic force three-dimensionally (so-called atomic force spectroscopy); (iii) ability to observe even insulators; and (iv)
ability to measure mechanical responses, such as elastic deformation. In addition, high-performance NC-AFMs, such as our home-built version, have a vertical resolution of ~0.001 nm (= 1 pm) and a lateral resolution of ~0.01 nm (= 10 pm).
As a result, NC-AFM can be used to observe weakly bounded molecules using an attractive force weak enough so that the attractive force between the tip and the individual molecule does not exceed the threshold needed to move a weakly adsorbed molecule. Further, it can be used to observe a very small lateral shift of an individual Si dimer, i.e. a small strain, adjacent to a missing Si dimer defect, due to stress around the missing Si dimer defect.

Atom-selective imaging and mechanical atom manipulation using the non-contact atomic force microscope; Journal of Electron Microscopy, 2004






The AFM-tip induced oxidation process is based on negatively biasing the tip with respect to the substrate under ambient conditions, which can be either a semiconductor or a metal. The substrate locally oxidizes upon moving the tip in contact mode across the surface. The oxidant for the chemical reaction is provided by OH- ions in the water droplet that is formed between the tip and the sample. Thus, the lateral resolution of the AFM oxidation process depends strongly on the humidity in the air.
sorce: http://www.research.ibm.com/nanoscience/afm_oxidation.html




AFM: From Cellular imaging to molecular manipulation
...Using a sharp tip attached at the end of a soft cantilever as a probe, the atomic force microscope (AFM) explores the surface topography of biological samples bathed in physiological solutions. In the last few years, the AFM has gained popularity among biologists. This has been obtained through the improvement of the equipment and imaging techniques as well as through the development of new non-imaging applications. Biological imaging has to face a main difficulty that is the softness and the dynamics of most biological materials. Progress in understanding the AFM tip-biological samples interactions provided spectacular results in different biological fields. (Pubmed 2003 Jan;19(1):92-9)

Carbon nanotubes additional power for AFM technique
......Among many scanning probe microscopies, atomic force microscopy (AFM) is a useful technique to analyse the structure of biological materials because of its applicability to non-conductors in physiological conditions with high resolution. However, the resolution has been limited to an inherent property of the technique; tip effect associated with a large radius of the scanning probe. To overcome this problem, we developed a carbon nanotube probe by attaching a carbon nanotube to a conventional scanning probe under a well-controlled process. Because of the constant and small radius of the tip (2.5–10 nm) and the high aspect ratio (1 : 100) of the carbon nanotube, the lateral resolution has been much improved judging from the apparent widths of DNA and nucleosomes. The carbon nanotube probes also possessed a higher durability than the conventional probes. We further evaluated the quality of carbon nanotube probes by three parameters to find out the best condition for AFM imaging: the angle to the tip axis; the length; and the tight fixation to the conventional tip. These carbon nanotube probes, with high vertical resolution, enabled us to clearly visualize the subunit organization of multi-subunit proteins and to propose structural models for proliferating cell nuclear antigen and replication factor C.

....the carbon nanotube probes high durability are proved advantagous, after scanning for 3 h with the scan rate of 3 Hz, the carbon nanotube still stayed in good condition. In contrast, conventional probes received serious damage after scanning under the same conditions. This high durability of the carbon nanotube probe probably results from high flexibility of the carbon nanotube and its tight fixation by amorphous carbon deposition.

This success in the application of carbon nanotube probes provides the current AFM technology with an additional power for the analyses of the detailed structure of biological materials and the relationship between the structure and function of proteins.


Oxfordjournals.org: Atomic force microscopy with carbon nanotube probe resolves the subunit organization of protein complexes


Carbon nanotubes have attracted much attention for medical applications, especially their use as nanocontainers for targeted drug and gene delivery. Medical applications include the use of carbon nanotubes for targeted drug and gene delivery, for which issues relating to the acceptance and containment of drugs or genes are not properly understood.The Quarterly Journal of Mechanics and Applied Mathematics 2007 60(2):231-253; doi:10.1093/qjmam/hbm005


Materials scientists performed chemical reactions inside tiny tubes of carbon atoms
known as nanotubes. Essentially, these are sheets of graphite an atom thick that are folded back on themselves to form cylinders. They were used to force molecules into long straight chains. The work has made it into the Guinness Book of World Records. The nano-sized test tubes are so tiny that around 300 billion would fit on to a full stop.

David Britz, Oxford University Dept of Materials, BBC News


While benefits of nanotechnology are widely publicised, the discussion of the potential effects of their widespread use in the consumer and industrial products are just beginning to emerge [7,8]. Both pioneers of nanotechnology [9] and its opponents [10] are finding it extremelyhard to argue their case as there is limited information available to support one side or the other. It has been shown that nanomaterials can enter the human body through several ports. Accidental or involuntary contact during production or use is most likely to happen via the lungs from where a rapid translocation through the blood stream is possible to other vital organs [11]. On the cellular level an ability to act as a gene vector has been demonstrated for nanoparticles [12]. Carbon black nanoparticles have been implicated in interfering with cell signalling [13]. There is work that demonstrates uses of DNA for the size separation of carbon nanotubes [14]. The DNA strand just wraps around it if the tube diameter is right. While excellent for the separation purposes it raises some concerns over the consequences of carbon nanotubes entering the human body.

Nanoparticles – known and unknown health risk! Nanobitechnology Journal,
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK


Making measurements as close to the biological action point
......How best to approach nanomaterial characterization include using proper sampling and measurement techniques, forming multidisciplinary teams, and making measurements as close to the biological action point as possible…… Determination of the primary size distribution of a sample requires a well-dispersed system and measurement of enough particles to achieve statistical reliability. For a monodisperse system, the latter requirement is relatively easy to meet. However, as polydispersity increases, it becomes necessary to measure a progressively larger number of particles to accurately portray the size distribution. For nanoscale particles in an aqueous environment, an ensemble method of measurement such as centrifugal sedimentation or laser or dynamic light scattering is normally preferred, but this may not be practical or the system may be difficult to maintain in a dispersed state. For dry as-received powders, dynamic mobility analysis can be used for dispersed material or BET surface area can provide an estimated average size based on a nonporous spherical model. The latter method has the added advantage of providing a direct measurement of specific surface area (SSA) and micro- or meso-porosity, both of which are key properties of interest.

Microscopy is one of the most powerful techniques and is often relied upon exclusively to provide valuable information regarding size, shape, and morphology. For nanoparticles, electron microscopy is normally required to capture images with the necessary resolution and is currently the only technique that provides reliable information regarding shape at this scale. However, the microscopist should ensure that enough particles are examined to provide a statistically valid representation of the full size or shape distribution. This can be very difficult and time consuming, and may require the image analysis of literally thousands of individual particles. There are many commercial automated image analysis systems and computer software packages that are used for this purpose.

Powers et al, Research Strategies for Safety Evaluation of Nanomaterials, 2006
http://toxsci.oxfordjournals.org/cgi/reprint/kfj099v1




...............Boundaries of condensed homogeneous phases (liquids and some solids) in the nano-scale present, continua, but only with two dimensions; in the third dimension their characteristics change. Such boundaries may be defined as bonded surface continua. Besides a surface tension force, all characteristics of nanolayers at boundaries of condensed phases are different from their bulk properties (e.g., density, viscosity, heat, and mass transfer rates) in the surface toward bulk direction.


Scales, Macro, Micro, Nano, Atto; http://www.chemlibnetbase.com/books/4877/DK3254ch1.pdf




THE EFFECT DOSE

Because of their small size and large specific surface area (SA), insoluble nanoparticles are almost not affected by the gravitational force and are generally formulated in stable suspensions or sols. This raises, however, a potential difficulty in in vitro assay systems in which cells adhering to the bottom of a culture vessel may not be exposed to the majority of nanoparticles in suspension.
..............We found, in all cell lines and for all end points, that the cellular response was determined by the total mass/number/Surface Area of particles as well as their concentration. Practically, for a given volume of dispersion, both parameters are of course intimately interdependent. We conclude that the nominal dose remains the most appropriate metric for in vitro toxicity testing of insoluble SNP dispersed in aqueous medium. This observation has important bearings on the experimental design and the interpretation of in vitro toxicological studies with nanoparticles.

Nominal and Effective Dosimetry of Silica Nanoparticles in Cytotoxicity Assays; Oxford Journals; Toxicological Sciences 2008 104(1):155-162; doi:10.1093/toxsci/kfn072







Particles in general and nanoparticles specifically, diffuse, settle, and agglomerate in cell culture media as a function of systemic and particle properties: media density and viscosity and particle size, shape, charge and density, for example. Cellular dose then is also a function of these factors as they determine the rate of transport of nanoparticles to cells in culture.............We conclude that simple surrogates of dose can cause significant misinterpretation of response and uptake data for nanoparticles in vitro. Incorporating particokinetics and principles of dosimetry would significantly improve the basis for nanoparticle toxicity assessment, increasing the predictive power and scalability of such assays.

Teegardin J., Particokinetics In Vitro: Dosimetry Considerations for In Vitro Nanoparticle Toxicity Assessments; Toxicological Sciences 2007 95(2):300-312; doi:10.1093/toxsci/kfl165


Nanotechnology has enabled the development of nanoscale devices that can be conjugated with several functional molecules simultaneously, including tumor-specific ligands, antibodies, anticancer drugs, and imaging probes. Since these
nanodevices are 100 to 1,000-fold smaller than cancer cells, they can be easily transferred through leaky blood vessels and interact with targeted tumor-specific proteins both on the surface of and inside cancer cells. Therefore, their application as cancer cell-specific delivery vehicles will be a significant addition to the currently available armory for cancer therapeutics and imaging. (CA Cancer J Clin 2008;58:97–110.); American Cancer Society, Inc., 2008.


Selenium (Se) is an essential trace element with a narrow margin between beneficial and toxic effects. As a promising chemopreventive agent, its use requires consumption over the long term, so the toxicity of Se is always a crucial concern. Based on clinical findings and recent studies in selenoprotein gene-modified mice, it is likely that the antioxidant function of one or more selenoproteins is responsible for the chemopreventive effect of Se. Furthermore, upregulation of phase 2 enzymes by Se has been implicated as a possible chemopreventive mechanism at supranutritional dietary levels. Se-methylselenocysteine (SeMSC), a naturally occurring organic Se product, is considered as one of the most effective chemopreventive selenocompounds. The present study revealed that, as compared with SeMSC, elemental Se at nano size (Nano-Se) possessed equal efficacy in increasing the activities of glutathione peroxidase, thioredoxin reductase, and glutathione S-transferase, but had much lower toxicity as indicated by median lethal dose, acute liver injury, survival rate, and short-term toxicity. Our results suggest that Nano-Se can serve as a potential chemopreventive agent with reduced risk of Se toxicity.

Elemental Selenium at Nano Size (Nano-Se) as a Potential Chemopreventive Agent with Reduced Risk of Selenium Toxicity; Oxford Journals; 2007



Relation between peak structures of loss functions of single double-walled carbon nanotubes and interband transition energies

Electron energy-loss spectra of single double-walled carbon nanotubes (DWCNTs) were compared with calculated joint density of states (jDOSs) obtained by a simple tight-binding (STB) and an extended tight-binding (ETB) method. From the comparisons, interband transition energies of ETB calculations show better agreement with peak positions of the experimental spectra than those of STB results. From a further comparison among calculated jDOS, real and imaginary parts of a dielectric function and a loss function Im[–1/{varepsilon}], it was confirmed that the peak energies in a spectrum of single DWCNTs are almost equal to those of the optical absorption spectrum {varepsilon}.

Physical properties of carbon nanotubes (CNTs) depend on diameters and chiralities of the CNTs.

Electron energy-loss spectroscopy (EELS) studies on multi-walled WS2 tubes [4] and few-walled CNTs [5] have been reported. It was shown that peak positions of the spectra for the thinner nanotubes were similar to those of optical absorption spectra.

Journal of Electron Microscopy 2008 57(4):129-132; doi:10.1093/jmicro/dfn012