Landauer formula without Landauer's assumptions

The Landauer formula for dissipationless conductance lies at the heart of modern electronic transport, yet it remains without a clear microscopic basis. We analyse the Landauer formula microscopically and give a straightforward quantum kinetic derivation for open systems. Some important experimental implications follow. These lie beyond the Landauer result as popularly received

Anomalies in one-dimensional electron transport: Quantum point contacts and wires

Over the last several decades, interest in quasi-one dimensional charge transport has progressed from the seminal discoveries of Landauer quantization of conductance as a function of carrier density, to significant finer-scale phenomena. Those include: (i) fractional conductance, or '0.7 anomaly'; (ii) zero-bias anomaly; (iii) Rashba-effect anomalies; and (iv) apparent violation of the Landauer upper bound on conductance. In this work we present a very short summary of the first three items. The last anomaly, which remained theoretically unexamined until recently, is discussed in detail with emphasis on novel low-dimensional physics

Low genetic diversity and absence of population differentiation of hilsa (Tenualosa ilisha) revealed by mitochondrial DNA cytochrome b region in Ganga and Hooghly rivers

We investigated the mtDNA cytochrome b based genetic structure of anadromous clupeid hilsa, Tenualosa ilisha, from the rivers Ganga and Hooghly. Six different haplotypes were observed, in sample size of 240, with a single dominant haplotype present in both rivers. Analysis of molecular variance (AMOVA) of Ganga and Hooghly populations does not suggest existence of population structuring in hilsa. AMOVA conducted on the whole population from Ganga and Hooghly suggested existence of a single population, migrating to Ganga and Hooghly rivers through the estuaries for spawning and breeding.Keywords: Hilsa, Tenualosa ilisha, Ganga, Hooghly, Bay of Bengal, West Bengal, India, mtDNA cytochrome bAfrican Journal of Biotechnology Vol. 12(22), pp. 3383-338

Surrogate regression modelling for fast seismogram generation and detection of microseismic events in heterogeneous velocity models

This is the author accepted manuscript. The final version is available from Oxford University Press (OUP) via the DOI in this record.Given a 3D heterogeneous velocity model with a few million voxels, fast generation of accurate seismic responses at specified receiver positions from known microseismic event locations is a well-known challenge in geophysics, since it typically involves numerical solution of the computationally expensive elastic wave equation. Thousands of such forward simulations are often a routine requirement for parameter estimation of microseimsic events via a suitable source inversion process. Parameter estimation based on forward modelling is often advantageous over a direct regression-based inversion approach when there are unknown number of parameters to be estimated and the seismic data has complicated noise characteristics which may not always allow a stable and unique solution in a direct inversion process. In this paper, starting from Graphics Processing Unit (GPU) based synthetic simulations of a few thousand forward seismic shots due to microseismic events via pseudo-spectral solution of elastic wave equation, we develop a step-by-step process to generate a surrogate regression modelling framework, using machine learning techniques that can produce accurate seismograms at specified receiver locations. The trained surrogate models can then be used as a high-speed meta-model/emulator or proxy for the original full elastic wave propagator to generate seismic responses for other microseismic event locations also. The accuracies of the surrogate models have been evaluated using two independent sets of training and testing Latin hypercube (LH) quasi-random samples, drawn from a heterogeneous marine velocity model. The predicted seismograms have been used thereafter to calculate batch likelihood functions, with specified noise characteristics. Finally, the trained models on 23 receivers placed at the sea-bed in a marine velocity model are used to determine the maximum likelihood estimate (MLE) of the event locations which can in future be used in a Bayesian analysis for microseismic event detection.This work has been supported by the Shell Projects and Technology. The Wilkes high performance GPU computing service at the University of Cambridge has been used in this work

Impact of Induction Therapy on Clinical Outcomes of Kidney Transplant Recipients: A Single-Centre Cohort Study

The purpose of this study was to evaluate long-term efficacy of immunosuppressive drugs based on the type of induction therapy given to kidney transplant recipients, and determine the occurrence of graft dysfunctions or rejections. We compared the safety and efficacy of anti-thymocyte globulin (ATG) and basiliximab (BAS) in high-risk patients and analyzed the cumulative incidence of immediate, slow, and delayed graft function in kidney transplant recipients to determine their initial short-term graft function. Evaluation of the long-term efficacy after 3 years post-transplantation by assessment of patients and graft survival, incidence of infections, and risks of rejection were the primary endpoints. Patients with stable graft survival were observed more with ATG (85%) than BAS (70%); in contrast, graft dysfunctions, graft nephrectomy, rejection episodes, and patient deaths were more prevalent with BAS than ATG, with statistically significant differences in long-term graft functioning. Patient survival at 3 years in ATG group was 90.4%, compared to 88% in BAS group, and graft survival was 90.4% in the ATG group and 81.3% in the BAS group (P < 0.001). The use of both induction therapies resulted in good patient and graft survival outcomes than placebo, and the results showed that there was a significant difference in both patient and graft survival after 3 years between induction of ATG and BAS, suggesting that ATG can be safer, effective, and preferable drug over BAS for high-risk recipients

Evidence for a fractional quantum Hall state with anisotropic longitudinal transport

At high magnetic fields, where the Fermi level lies in the N=0 lowest Landau level (LL), a clean two-dimensional electron system (2DES) exhibits numerous incompressible liquid phases which display the fractional quantized Hall effect (FQHE) (Das Sarma and Pinczuk, 1997). These liquid phases do not break rotational symmetry, exhibiting resistivities which are isotropic in the plane. In contrast, at lower fields, when the Fermi level lies in the $N\ge2$ third and several higher LLs, the 2DES displays a distinctly different class of collective states. In particular, near half filling of these high LLs the 2DES exhibits a strongly anisotropic longitudinal resistance at low temperatures (Lilly et al., 1999; Du et al., 1999). These "stripe" phases, which do not exhibit the quantized Hall effect, resemble nematic liquid crystals, possessing broken rotational symmetry and orientational order (Koulakov et al., 1996; Fogler et al., 1996; Moessner and Chalker, 1996; Fradkin and Kivelson, 1999; Fradkin et al, 2010). Here we report a surprising new observation: An electronic configuration in the N=1 second LL whose resistivity tensor simultaneously displays a robust fractionally quantized Hall plateau and a strongly anisotropic longitudinal resistance resembling that of the stripe phases.Comment: Nature Physics, (2011

Wigner Crystallization in a Quasi-3D Electronic System

When a strong magnetic field is applied perpendicularly (along z) to a sheet confining electrons to two dimensions (x-y), highly correlated states emerge as a result of the interplay between electron-electron interactions, confinement and disorder. These so-called fractional quantum Hall (FQH) liquids form a series of states which ultimately give way to a periodic electron solid that crystallizes at high magnetic fields. This quantum phase of electrons has been identified previously as a disorder-pinned two-dimensional Wigner crystal with broken translational symmetry in the x-y plane. Here, we report our discovery of a new insulating quantum phase of electrons when a very high magnetic field, up to 45T, is applied in a geometry parallel (y-direction) to the two-dimensional electron sheet. Our data point towards this new quantum phase being an electron solid in a "quasi-3D" configuration induced by orbital coupling with the parallel field

Conditionally-live attenuated SIV upregulates global T effector memory cell frequency under replication permissive conditions.

Background: Live attenuated SIV induces potent protection against superinfection with virulent virus; however the mechanism of this vaccine effect is poorly understood. Such knowledge is important for the development of clinically acceptable vaccine modalities against HIV. Results: Using a novel, doxycycline dependent, replication-competent live-attenuated SIVmac239Δnef (SIVrtTAΔnef), we show that under replication-permissive conditions SIV-rtTAΔnef is fully viable. Twelve rhesus macaques were infected with a peak plasma vRNA on average two log10 lower than in 6 macaques infected with unconditionally replication-competent SIVΔnef. Consistent with the attenuated phenotype of the viruses the majority of animals displayed low or undetectable levels of viraemia by 42-84 days after infection. Next, comparison of circulating T cells before and after chronic infection with parental SIVΔnef revealed a profound global polarisation toward CD28-CCR7- T-effector memory 2 (TEM2) cells within CD95+CD4+ and CD95+CD8+ populations. Critically, a similar effect was seen in the CD95+ CD4+ population and to somewhat lesser extent in the CD95+ CD8+ population of SIV-rtTAΔnef chronically infected macaques that were maintained on doxycycline, but was not seen in animals from which doxycycline had been withdrawn. The proportions of gut-homing T-central memory (TCM) and TEM defined by the expression of α4β7 and CD95 and differential expression of CD28 were increased in CD4 and CD8 cells under replication competent conditions and gut-homing CD4 TCM were also significantly increased under non-permissive conditions. TEM2 polarisation was seen in the small intestines of animals under replication permissive conditions but the effect was less pronounced than in the circulation. Intracellular cytokine staining of circulating SIV-specific T cells for IL-2, IFN-γ, TNF-α and IL-17 showed that the extent of polyfunctionality in CD4 and CD8 T cells was associated with replication permissivity; however, signature patterns of cytokine combinations were not distinguishable between groups of macaques. Conclusion: Taken together our results show that the global T memory cell compartment is profoundly skewed towards a mature effector phenotype by attenuated SIV. Results with the replication-conditional mutant suggest that maintenance of this effect, that may be important in vaccine design, might require persistence of replicating virus

Aryl hydrocarbon receptor nuclear translocator (ARNT) gene as a positional and functional candidate for type 2 diabetes and prediabetic intermediate traits: Mutation detection, case-control studies, and gene expression analysis

<p>Abstract</p> <p>Background</p> <p>ARNT, a member of the basic helix-loop-helix family of transcription factors, is located on human chromosome 1q21–q24, a region which showed well replicated linkage to type 2 diabetes. We hypothesized that common polymorphisms in the <it>ARNT </it>gene might increase the susceptibility to type 2 diabetes through impaired glucose-stimulated insulin secretion.</p> <p>Methods</p> <p>We selected 9 single nucleotide polymorphisms to tag common variation across the <it>ARNT </it>gene. Additionally we searched for novel variants in functional coding domains in European American and African American samples. Case-control studies were performed in 191 European American individuals with type 2 diabetes and 187 nondiabetic European American control individuals, and in 372 African American individuals with type 2 diabetes and 194 African American control individuals. Metabolic effects of <it>ARNT </it>variants were examined in 122 members of 26 European American families from Utah and in 225 unrelated individuals from Arkansas. Gene expression was tested in 8 sibling pairs discordant for type 2 diabetes.</p> <p>Results</p> <p>No nonsynonymous variants or novel polymorphisms were identified. No SNP was associated with type 2 diabetes in either African Americans or European Americans, but among nondiabetic European American individuals, <it>ARNT </it>SNPs rs188970 and rs11204735 were associated with acute insulin response (AIR_g; p =< 0.005). SNP rs2134688 interacted with body mass index to alter β-cell compensation to insulin resistance (disposition index; p = 0.004). No significant difference in <it>ARNT </it>mRNA levels was observed in transformed lymphocytes from sibling pairs discordant for type 2 diabetes.</p> <p>Conclusion</p> <p>Common <it>ARNT </it>variants are unlikely to explain the linkage signal on chromosome 1q, but may alter insulin secretion in nondiabetic subjects. Our studies cannot exclude a role for rare variants or variants of small (< 1.6) effect size.</p

Thermal quenches in N=2* plasmas

We exploit gauge/gravity duality to study `thermal quenches' in a plasma of the strongly coupled N=2* gauge theory. Specifically, we consider the response of an initial thermal equilibrium state of the theory under variations of the bosonic or fermionic mass, to leading order in m/T<<1. When the masses are made to vary in time, novel new counterterms must be introduced to renormalize the boundary theory. We consider transitions the conformal super-Yang-Mills theory to the mass deformed gauge theory and also the reverse transitions. By construction, these transitions are controlled by a characteristic time scale \calt and we show how the response of the system depends on the ratio of this time scale to the thermal time scale 1/T. The response shows interesting scaling behaviour both in the limit of fast quenches with T\calt<<1 and slow quenches with T\calt>>1. In the limit that T\calt\to\infty, we observe the expected adiabatic response. For fast quenches, the relaxation to the final equilibrium is controlled by the lowest quasinormal mode of the bulk scalar dual to the quenched operator. For slow quenches, the system relaxes with a (nearly) adiabatic response that is governed entirely by the late time profile of the mass. We describe new renormalization scheme ambiguities in defining gauge invariant observables for the theory with time dependant couplings.Comment: 78 pages, 17 figure