Forward-backward asymmetry of top quark in unparticle physics

The updated CDF measurement of the forward-backward asymmetry (FBA) in the top quark production p{bar p} -> t{bar t} at Tevatron (with the CMS energy 1.96 TeV) shows a deviation of 2*sigma from the value predicted by the Standard QCD Model. We present calculation of this quantity in the scenario where colored unparticle physics contributes to the s-channel of the process, and obtain the regions in the plane of the unparticle parameters lambda and dU which give the values of the FBA and of the total t{bar t} production cross section compatible with the present measurements.Comment: 15 pages, 5 figures; various typos corrected, fig.3 has higher resolution, Ref.[16](2nd entry) is new; version to appear in Phys.Lett.

Detection of Biomolecular Binding Through Enhancement of Localized Surface Plasmon Resonance (LSPR) by Gold Nanoparticles

To amplify the difference in localized surface plasmon resonance (LSPR) spectra of gold nano-islands due to intermolecular binding events, gold nanoparticles were used. LSPR-based optical biosensors consisting of gold nano-islands were readily made on glass substrates using evaporation and heat treatment. Streptavidin (STA) and biotinylated bovine serum albumin (Bio-BSA) were chosen as the model receptor and the model analyte, respectively, to demonstrate the effectiveness of this detection method. Using this model system, we were able to enhance the sensitivity in monitoring the binding of Bio-BSA to gold nano-island surfaces functionalized with STA through the addition of gold nanoparticle-STA conjugates. In addition, SU-8 well chips with gold nano-island surfaces were fabricated through a conventional UV patterning method and were then utilized for image detection using the attenuated total reflection mode. These results suggest that the gold nano-island well chip may have the potential to be used for multiple and simultaneous detection of various bio-substances

Signal Amplification by Enzymatic Reaction in an Immunosensor Based on Localized Surface Plasmon Resonance (LSPR)

An enzymatic reaction was employed as a means to enhance the sensitivity of an immunosensor based on localized surface plasmon resonance (LSPR). The reaction occurs after intermolecular binding between an antigen and an antibody on gold nano-island (NI) surfaces. For LSPR sensing, the gold NI surface was fabricated on glass substrates using vacuum evaporation and heat treatment. The interferon-γ (IFN-γ) capture antibody was immobilized on the gold NIs, followed by binding of IFN-γ to the antibody. Subsequently, a biotinylated antibody and a horseradish peroxidase (HRP) conjugated with avidin were simultaneously introduced. A solution of 4-chloro-1-naphthol (4-CN) was then used for precipitation; precipitation was the result of the enzymatic reaction catalyzed the HRP on gold NIs. The LSPR spectra were obtained after each binding process. Using this method, the enzyme-catalyzed precipitation reaction on the gold NI surface was found to effectively amplify the change in the signal of the LSPR immunosensor after intermolecular binding

Silicon resonant microcantilevers for absolute pressure measurement

This work is focused on the developing of silicon resonant microcantilevers for the measurement of the absolute pressure. The microcantilevers have been fabricated with a two-mask bulk micromachining process. The variation in resonance response of microcantilevers was investigated as a function of pressure 10−1-105 Pa, both in terms of resonance frequency and quality factor. A theoretical description of the resonating microstructure is given according to different molecular and viscous regimes. Also a brief discussion on the different quality factors contributions is presented. Theoretical and experimental data show a very satisfying agreement. The microstructure behavior demonstrates a certain sensitivity over a six decade range and the potential evolution of an absolute pressure sensor working in the same rang

Diesel Engine Exhaust Initiates a Sequence of Pulmonary and Cardiovascular Effects in Rats

This study was designed to determine the sequence of events leading to cardiopulmonary effects following acute inhalation of diesel engine exhaust in rats. Rats were exposed for 2 h to diesel engine exhaust (1.9 mg/m3), and biological parameters related to antioxidant defense, inflammation, and procoagulation were examined after 4, 18, 24, 48, and 72 h. This in vivo inhalation study showed a pulmonary anti-oxidant response (an increased activity of the anti-oxidant enzymes glutathione peroxidase and superoxide dismutase and an increase in heme oxygenase-1 protein, heme oxygenase activity, and uric acid) which precedes the inflammatory response (an increase in IL-6 and TNF-α). In addition, increased plasma thrombogenicity and immediate anti-oxidant defense gene expression in aorta tissue shortly after the exposure might suggest direct translocation of diesel engine exhaust components to the vasculature but mediation by other pathways cannot be ruled out. This study therefore shows that different stages in oxidative stress are not only affected by dose increments but are also time dependent

Missing Momentum Reconstruction and Spin Measurements at Hadron Colliders

We study methods for reconstructing the momenta of invisible particles in cascade decay chains at hadron colliders. We focus on scenarios, such as SUSY and UED, in which new physics particles are pair produced. Their subsequent decays lead to two decay chains ending with neutral stable particles escaping detection. Assuming that the masses of the decaying particles are already measured, we obtain the momenta by imposing the mass-shell constraints. Using this information, we develop techniques of determining spins of particles in theories beyond the standard model. Unlike the methods relying on Lorentz invariant variables, this method can be used to determine the spin of the particle which initiates the decay chain. We present two complementary ways of applying our method by using more inclusive variables relying on kinematic information from one decay chain, as well as constructing correlation variables based on the kinematics of both decay chains in the same event.Comment: Version to appear in JHE

Computational approaches to understanding the self-assembly of peptide-based nanostructures

The interest in the self-assembly of peptide-based systems has grown significantly over the past 10–15 years, as more and more applications are shown to benefit from the useful properties of the amino acid based monomers. With the desire to apply the principals of self-assembly to systems within new application areas, there has been an increasing emphasis in understanding the governing forces involved in the self-assembly process, and using this understanding to predict the behaviour of, and design, new materials. To this end, computational approaches have played an increasingly important role over the past decade in helping to decode how small changes in the primary structure can lead to significantly different nanostructures with new function. In this review, a brief survey of the different computational approaches employed in this quest for understanding are provided, along with representative examples of the types of questions that can be answered with each of the different approaches

A new view of electrochemistry at highly oriented pyrolytic graphite

Major new insights on electrochemical processes at graphite electrodes are reported, following extensive investigations of two of the most studied redox couples, Fe(CN)64–/3– and Ru(NH3)63+/2+. Experiments have been carried out on five different grades of highly oriented pyrolytic graphite (HOPG) that vary in step-edge height and surface coverage. Significantly, the same electrochemical characteristic is observed on all surfaces, independent of surface quality: initial cyclic voltammetry (CV) is close to reversible on freshly cleaved surfaces (>400 measurements for Fe(CN)64–/3– and >100 for Ru(NH3)63+/2+), in marked contrast to previous studies that have found very slow electron transfer (ET) kinetics, with an interpretation that ET only occurs at step edges. Significantly, high spatial resolution electrochemical imaging with scanning electrochemical cell microscopy, on the highest quality mechanically cleaved HOPG, demonstrates definitively that the pristine basal surface supports fast ET, and that ET is not confined to step edges. However, the history of the HOPG surface strongly influences the electrochemical behavior. Thus, Fe(CN)64–/3– shows markedly diminished ET kinetics with either extended exposure of the HOPG surface to the ambient environment or repeated CV measurements. In situ atomic force microscopy (AFM) reveals that the deterioration in apparent ET kinetics is coupled with the deposition of material on the HOPG electrode, while conducting-AFM highlights that, after cleaving, the local surface conductivity of HOPG deteriorates significantly with time. These observations and new insights are not only important for graphite, but have significant implications for electrochemistry at related carbon materials such as graphene and carbon nanotubes

Electrochemical oxidation of dihydronicotinamide adenine dinucleotide (NADH) : Comparison of highly oriented pyrolytic graphite (HOPG) and polycrystalline boron-doped diamond (pBDD) electrodes

The electro-oxidation of nicotinamide adenine dinucleotide (NADH) is studied at bare surfaces of highly oriented pyrolytic graphite (HOPG) and semi-metallic polycrystalline boron-doped diamond (pBDD). A comparison of these two carbon electrode materials is interesting because they possess broadly similar densities of electronic states that are much lower than most metal electrodes, but graphite has carbon sp2-hybridization, while in diamond the carbon is sp3-hybridised, with resulting major differences in bulk structure and surface termination. Using cyclic voltammetry (CV), it is shown that NADH oxidation is facile at HOPG surfaces but the reaction products tend to strongly adsorb, which causes rapid deactivation of the electrode activity. This is an important factor that needs to be taken into account when assessing HOPG and its intrinsic activity. It is also shown that NADH itself adsorbs at HOPG, a fact that has not been recognized previously, but has implications for understanding the mechanism of the electro-oxidation process. Although pBDD was found to be less susceptible to surface fouling, pBDD is not immune to deterioration of the electrode response, and the reaction showed more sluggish kinetics on this electrode. Scanning electrochemical cell microscopy (SECCM) highlights a significant voltammetric variation in electroactivity between different crystal surface facets that are presented to solution with a pBDD electrode. The electroactivity of different grains correlates with the local dopant level, as visualized by field emission-scanning electron microscopy. SECCM measurements further prove that the basal plane of HOPG has high activity towards NADH electro-oxidation. These new insights on NADH voltammetry are useful for the design of optimal carbon-based electrodes for NADH electroanalysis