Nonequilibrium Singlet-Triplet Kondo Effect in Carbon Nanotubes

The Kondo-effect is a many-body phenomenon arising due to conduction electrons scattering off a localized spin. Coherent spin-flip scattering off such a quantum impurity correlates the conduction electrons and at low temperature this leads to a zero-bias conductance anomaly. This has become a common signature in bias-spectroscopy of single-electron transistors, observed in GaAs quantum dots as well as in various single-molecule transistors. While the zero-bias Kondo effect is well established it remains uncertain to what extent Kondo correlations persist in non-equilibrium situations where inelastic processes induce decoherence. Here we report on a pronounced conductance peak observed at finite bias-voltage in a carbon nanotube quantum dot in the spin singlet ground state. We explain this finite-bias conductance anomaly by a nonequilibrium Kondo-effect involving excitations into a spin triplet state. Excellent agreement between calculated and measured nonlinear conductance is obtained, thus strongly supporting the correlated nature of this nonequilibrium resonance.Comment: 21 pages, 5 figure

Validation of standard operating procedures in a multicenter retrospective study to identify-omics biomarkers for chronic low back pain

Chronic low back pain (CLBP) is one of the most common medical conditions, ranking as the greatest contributor to global disability and accounting for huge societal costs based on the Global Burden of Disease 2010 study. Large genetic and -omics studies provide a promising avenue for the screening, development and validation of biomarkers useful for personalized diagnosis and treatment (precision medicine). Multicentre studies are needed for such an effort, and a standardized and homogeneous approach is vital for recruitment of large numbers of participants among different centres (clinical and laboratories) to obtain robust and reproducible results. To date, no validated standard operating procedures (SOPs) for genetic/-omics studies in chronic pain have been developed. In this study, we validated an SOP model that will be used in the multicentre (5 centres) retrospective “PainOmics” study, funded by the European Community in the 7th Framework Programme, which aims to develop new biomarkers for CLBP through three different -omics approaches: genomics, glycomics and activomics. The SOPs describe the specific procedures for (1) blood collection, (2) sample processing and storage, (3) shipping details and (4) cross-check testing and validation before assays that all the centres involved in the study have to follow. Multivariate analysis revealed the absolute specificity and homogeneity of the samples collected by the five centres for all genetics, glycomics and activomics analyses. The SOPs used in our multicenter study have been validated. Hence, they could represent an innovative tool for the correct management and collection of reliable samples in other large-omics-based multicenter studies

Parallel chemistry acceleration algorithm with ISAT table-size control in the application of gaseous detonation

In order to improve the computational efficiency of a parallel ISAT (in situ adaptive tabulation)-based chemistry acceleration algorithm in the computations of transient, chemically reacting flows, a control strategy is proposed to maintain the sizes of the data tables in the ISAT computations. The table-size control strategy is then combined with a parallel algorithm to simulate two-dimensional gaseous detonation wave propagation. In the computation of 2H2 + O2 detonation, two sets of tests are conducted to identify the size control strategy. In the first set, the maximum total table size (Mtot) summed over all sub-zones is fixed, while the maximum size of the table on each sub-zone (Msin) is varied. In the second set, a fixed Msin is used for all the tables on the sub-zones while Mtot is varied. A maximum speedup ratio of 4.29 is found in the former tests, while 5.52 is found in the latter. Two parameters, σf and p, are proposed to analyze the load balance and synchronization among table operations in the parallel ISAT computations in the above tests. It is found that both load balance and synchronization have clear influences on the speedup ratio. A parameter pM is defined, and a strategy to choose the optimal maximum table sizes (both Mtot and Msin) based on pM is proposed and is verified to be universal in the computations of both 2H2 + O2 detonation and C2H4 + 3O2 detonation. Finally, the parallel acceleration algorithm enhanced with table-size control is shown to be highly accurate for the detonations in both fuels

Ultra-violet radiation is responsible for the differences in global epidemiology of chickenpox and the evolution of varicella-zoster virus as man migrated out of Africa

<p>Abstract</p> <p>Background</p> <p>Of the eight human herpes viruses, varicella-zoster virus, which causes chickenpox and zoster, has a unique epidemiology. Primary infection is much less common in children in the tropics compared with temperate areas. This results in increased adult susceptibility causing outbreaks, for example in health-care workers migrating from tropical to temperate countries. The recent demonstration that there are different genotypes of varicella-zoster virus and their geographic segregation into tropical and temperate areas suggests a distinct, yet previously unconsidered climatic factor may be responsible for both the clinical and molecular epidemiological features of this virus infection.</p> <p>Presentation of the hypothesis</p> <p>Unlike other human herpes viruses, varicella-zoster virus does not require intimate contact for infection to occur indicating that transmission may be interrupted by a geographically restricted climatic factor. The factor with the largest difference between tropical and temperate zones is ultra-violet radiation. This could reduce the infectiousness of chickenpox cases by inactivating virus in vesicles, before or after rupture. This would explain decreased transmissibility in the tropics and why the peak chickenpox incidence in temperate zones occurs during winter and spring, when ultra-violet radiation is at its lowest. The evolution of geographically restricted genotypes is also explained by ultra-violet radiation driving natural selection of different virus genotypes with varying degrees of resistance to inactivation, tropical genotypes being the most resistant. Consequently, temperate viruses should be more sensitive to its effects. This is supported by the observation that temperate genotypes are found in the tropics only in specific circumstances, namely where ultra-violet radiation has either been excluded or significantly reduced in intensity.</p> <p>Testing the Hypothesis</p> <p>The hypothesis is testable by exposing different virus genotypes to ultra-violet radiation and quantifying virus survival by plaque forming units or quantitative mRNA RT-PCR.</p> <p>Implications of the hypothesis</p> <p>The ancestral varicella-zoster virus, most probably a tropical genotype, co-migrated with man as he left Africa approximately 200,000 years ago. For this virus to have lost the selective advantage of resistance to ultra-violet radiation, the hypothesis would predict that the temperate, ultra-violet sensitive virus should have acquired another selective advantage as an evolutionary trade-off. One obvious advantage could be an increased reactivation rate as zoster to set up more rounds of chickenpox transmission. If this were so, the mechanism responsible for resistance to ultra-violet radiation might also be involved in reactivation and latency. This could then provide the first insight into a genetic correlate of the survival strategy of this virus.</p

How does study quality affect the results of a diagnostic meta-analysis?

Background: The use of systematic literature review to inform evidence based practice in diagnostics is rapidly expanding. Although the primary diagnostic literature is extensive, studies are often of low methodological quality or poorly reported. There has been no rigorously evaluated, evidence based tool to assess the methodological quality of diagnostic studies. The primary objective of this study was to determine the extent to which variations in the quality of primary studies impact the results of a diagnostic meta-analysis and whether this differs with diagnostic test type. A secondary objective was to contribute to the evaluation of QUADAS, an evidence-based tool for the assessment of quality in diagnostic accuracy studies. Methods: This study was conducted as part of large systematic review of tests used in the diagnosis and further investigation of urinary tract infection (UTI) in children. All studies included in this review were assessed using QUADAS, an evidence-based tool for the assessment of quality in systematic reviews of diagnostic accuracy studies. The impact of individual components of QUADAS on a summary measure of diagnostic accuracy was investigated using regression analysis. The review divided the diagnosis and further investigation of UTI into the following three clinical stages: diagnosis of UTI, localisation of infection, and further investigation of the UTI. Each stage used different types of diagnostic test, which were considered to involve different quality concerns. Results: Many of the studies included in our review were poorly reported. The proportion of QUADAS items fulfilled was similar for studies in different sections of the review. However, as might be expected, the individual items fulfilled differed between the three clinical stages. Regression analysis found that different items showed a strong association with test performance for the different tests evaluated. These differences were observed both within and between the three clinical stages assessed by the review. The results of regression analyses were also affected by whether or not a weighting (by sample size) was applied. Our analysis was severely limited by the completeness of reporting and the differences between the index tests evaluated and the reference standards used to confirm diagnoses in the primary studies. Few tests were evaluated by sufficient studies to allow meaningful use of meta-analytic pooling and investigation of heterogeneity. This meant that further analysis to investigate heterogeneity could only be undertaken using a subset of studies, and that the findings are open to various interpretations. Conclusion: Further work is needed to investigate the influence of methodological quality on the results of diagnostic meta-analyses. Large data sets of well-reported primary studies are needed to address this question. Without significant improvements in the completeness of reporting of primary studies, progress in this area will be limited

The Spin Structure of the Nucleon

We present an overview of recent experimental and theoretical advances in our understanding of the spin structure of protons and neutrons.Comment: 84 pages, 29 figure

Improving Cancer Classification Accuracy Using Gene Pairs

Recent studies suggest that the deregulation of pathways, rather than individual genes, may be critical in triggering carcinogenesis. The pathway deregulation is often caused by the simultaneous deregulation of more than one gene in the pathway. This suggests that robust gene pair combinations may exploit the underlying bio-molecular reactions that are relevant to the pathway deregulation and thus they could provide better biomarkers for cancer, as compared to individual genes. In order to validate this hypothesis, in this paper, we used gene pair combinations, called doublets, as input to the cancer classification algorithms, instead of the original expression values, and we showed that the classification accuracy was consistently improved across different datasets and classification algorithms. We validated the proposed approach using nine cancer datasets and five classification algorithms including Prediction Analysis for Microarrays (PAM), C4.5 Decision Trees (DT), Naive Bayesian (NB), Support Vector Machine (SVM), and k-Nearest Neighbor (k-NN)

Limits on WWZ and WW\gamma couplings from p\bar{p}\to e\nu jj X events at \sqrt{s} = 1.8 TeV

We present limits on anomalous WWZ and WW-gamma couplings from a search for WW and WZ production in p-bar p collisions at sqrt(s)=1.8 TeV. We use p-bar p -> e-nu jjX events recorded with the D0 detector at the Fermilab Tevatron Collider during the 1992-1995 run. The data sample corresponds to an integrated luminosity of 96.0+-5.1 pb^(-1). Assuming identical WWZ and WW-gamma coupling parameters, the 95% CL limits on the CP-conserving couplings are -0.33<lambda<0.36 (Delta-kappa=0) and -0.43<Delta-kappa<0.59 (lambda=0), for a form factor scale Lambda = 2.0 TeV. Limits based on other assumptions are also presented.Comment: 11 pages, 2 figures, 2 table

Search for New Physics in e mu X Data at D0 Using Sleuth: A Quasi-Model-Independent Search Strategy for New Physics

We present a quasi-model-independent search for the physics responsible for electroweak symmetry breaking. We define final states to be studied, and construct a rule that identifies a set of relevant variables for any particular final state. A new algorithm ("Sleuth") searches for regions of excess in those variables and quantifies the significance of any detected excess. After demonstrating the sensitivity of the method, we apply it to the semi-inclusive channel e mu X collected in 108 pb^-1 of ppbar collisions at sqrt(s) = 1.8 TeV at the D0 experiment during 1992-1996 at the Fermilab Tevatron. We find no evidence of new high p_T physics in this sample.Comment: 23 pages, 12 figures. Submitted to Physical Review