Evidence of Klein tunneling in graphene p-n junctions

Transport through potential barriers in graphene is investigated using a set of metallic gates capacitively coupled to graphene to modulate the potential landscape. When a gate-induced potential step is steep enough, disorder becomes less important and the resistance across the step is in quantitative agreement with predictions of Klein tunneling of Dirac fermions up to a small correction. We also perform magnetoresistance measurements at low magnetic fields and compare them to recent predictions.Comment: Major changes made: 1) Taking into account properly the contribution of the resistance of monopolar junctions to the odd part of the resistance. To better present the results we use a fitting parameter for the amplitude of screening in graphene. 2) Wrong data for the diffusive model in figures 3, 9 and 10 was plotted in former version. 3) Figure 5 moved to EPAP

Cost effective flat plate photovoltaic modules using light trapping

Work in optical trapping in 'thick films' is described to form a design guide for photovoltaic engineers. A thick optical film can trap light by diffusive reflection and total internal reflection. Light can be propagated reasonably long distances compared with layer thicknesses by this technique. This makes it possible to conduct light from inter-cell and intra-cell areas now not used in photovoltaic modules onto active cell areas

On charged impurity structures in liquid helium

The thermoluminescence spectra of impurity-helium condensates (IHC) submerged in superfluid helium have been observed for the first time. Thermoluminescence of impurity-helium condensates submerged in superfluid helium is explained by neutralization reactions occurring in impurity nanoclusters. Optical spectra of excited products of neutralization reactions between nitrogen cations and thermoactivated electrons were rather different from the spectra observed at higher temperatures, when the luminescence due to nitrogen atom recombination dominates. New results on current detection during the IHC destruction are presented. Two different mechanisms of nanocluster charging are proposed to describe the phenomena observed during preparation and warmup of IHC samples in bulk superfluid helium, and destruction of IHC samples out of liquid helium

EVASION OF MORTGAGE MORATORIA BY PROSECUTION OF PERSONAL REMEDIES

For reasons political, social and economic which have never been fully analyzed, the moratory legislation of the last five years has shown special favor to the debtor whose obligation is secured by mortgage of land, and this legislation is faintly echoed in moratory decisions which have no direct statutory foundation. Granted that contracts have sometimes received similar treatment, that banks and insurance companies have also enjoyed indulgence, and that the new chapters of the Bankruptcy Act extend asylum to all and sundry, yet the mortgage is so far favored that the word moratorium brings to mind this case before all others

Modeling canopy-induced turbulence in the Earth system: a unified parameterization of turbulent exchange within plant canopies and the roughness sublayer (CLM-ml v0)

Land surface models used in climate models neglect the roughness sublayer and parameterize within-canopy turbulence in an ad hoc manner. We implemented a roughness sublayer turbulence parameterization in a multilayer canopy model (CLM-ml v0) to test if this theory provides a tractable parameterization extending from the ground through the canopy and the roughness sublayer. We compared the canopy model with the Community Land Model (CLM4.5) at seven forest, two grassland, and three cropland AmeriFlux sites over a range of canopy heights, leaf area indexes, and climates. CLM4.5 has pronounced biases during summer months at forest sites in midday latent heat flux, sensible heat flux, gross primary production, nighttime friction velocity, and the radiative temperature diurnal range. The new canopy model reduces these biases by introducing new physics. Advances in modeling stomatal conductance and canopy physiology beyond what is in CLM4.5 substantially improve model performance at the forest sites. The signature of the roughness sublayer is most evident in nighttime friction velocity and the diurnal cycle of radiative temperature, but is also seen in sensible heat flux. Within-canopy temperature profiles are markedly different compared with profiles obtained using Monin–Obukhov similarity theory, and the roughness sublayer produces cooler daytime and warmer nighttime temperatures. The herbaceous sites also show model improvements, but the improvements are related less systematically to the roughness sublayer parameterization in these canopies. The multilayer canopy with the roughness sublayer turbulence improves simulations compared with CLM4.5 while also advancing the theoretical basis for surface flux parameterizations

Using the quantum probability ranking principle to rank interdependent documents

A known limitation of the Probability Ranking Principle (PRP) is that it does not cater for dependence between documents. Recently, the Quantum Probability Ranking Principle (QPRP) has been proposed, which implicitly captures dependencies between documents through “quantum interference”. This paper explores whether this new ranking principle leads to improved performance for subtopic retrieval, where novelty and diversity is required. In a thorough empirical investigation, models based on the PRP, as well as other recently proposed ranking strategies for subtopic retrieval (i.e. Maximal Marginal Relevance (MMR) and Portfolio Theory(PT)), are compared against the QPRP. On the given task, it is shown that the QPRP outperforms these other ranking strategies. And unlike MMR and PT, one of the main advantages of the QPRP is that no parameter estimation/tuning is required; making the QPRP both simple and effective. This research demonstrates that the application of quantum theory to problems within information retrieval can lead to significant improvements

Melanophore migration and survival during zebrafish adult pigment stripe development require the immunoglobulin superfamily adhesion molecule Igsf11.

The zebrafish adult pigment pattern has emerged as a useful model for understanding the development and evolution of adult form as well as pattern-forming mechanisms more generally. In this species, a series of horizontal melanophore stripes arises during the larval-to-adult transformation, but the genetic and cellular bases for stripe formation remain largely unknown. Here, we show that the seurat mutant phenotype, consisting of an irregular spotted pattern, arises from lesions in the gene encoding Immunoglobulin superfamily member 11 (Igsf11). We find that Igsf11 is expressed by melanophores and their precursors, and we demonstrate by cell transplantation and genetic rescue that igsf11 functions autonomously to this lineage in promoting adult stripe development. Further analyses of cell behaviors in vitro, in vivo, and in explant cultures ex vivo demonstrate that Igsf11 mediates adhesive interactions and that mutants for igsf11 exhibit defects in both the migration and survival of melanophores and their precursors. These findings identify the first in vivo requirements for igsf11 as well as the first instance of an immunoglobulin superfamily member functioning in pigment cell development and patterning. Our results provide new insights into adult pigment pattern morphogenesis and how cellular interactions mediate pattern formation

The use of liver histopathology, lipid peroxidation and acetylcholinesterase assays as biomarkers of contaminant-induced stress in the Cape stumpnose, Rhabdosargus holubi (Teleostei: Sparidae), from selected South African estuaries

Three biomarkers of contaminant-induced stress (liver histopathology, the lipid peroxidation (LPx) assay and the acetylcholinesterase (AChE) assay) were adapted for application to the estuarine-dependent marine fish Rhabdosargus holubi (Steindachner, 1881). Specimens of R. holubi were collected using a seine net from 3 temporarily open/closed estuaries in the Eastern Cape, South Africa, each impacted by different anthropogenic activities. The East Kleinemonde estuary has a housing settlement on the banks in the lower reaches and some agriculture in its catchment. The Old Woman’s estuary has a golf course adjacent to its lower and middle reaches and is crossed by a national road in its upper reaches. The Mtana estuary is virtually pristine, with limited cattle grazing occurring along the banks of the estuary and some subsistence agriculture in the catchment. According to the biomarker results from this study, R. holubi from the East Kleinemonde were in good health, as reflected by low LPx and high AChE levels. The liver histopathology did, however, suggest possible previous exposure to stress (increased melanomacrophage centres, increased perivascular connective tissue and severe vacuolation). Overall, liver histopathology results did not differ significantly between estuaries. Fish from the Old Womans recorded significantly inhibited AChE and increased LPx, while fish from the Mtana exhibited significantly increased LPx only, suggesting possible exposure to anticholinesterase contaminants in the former estuary and some form of oxidative stress in the latter. Although water samples were collected from each of the 3 estuaries and analysed for polychlorinated biphenyls, organochlorines, organophosphorous pesticides and pyrethroids, none of these chemicals were detected. Aspesticide residues in water are highly variable, both temporally and spatially, future studies should focus on measuring tissue burdens of organisms in order to identify the contaminant stressor. This study has shown that while chemical analyses of water provide a ‘snap-shot’ of water quality at the time of sampling, biomonitoring can integrate past exposures to stress and is thus useful for identifying potential situations of concern that require further detailed investigation.Keywords: biomonitoring, pollution, estuaries, AChE, LPx, histopatholog