Current direction induced rectification effect on (integer) quantized Hall plateaus

Current polarization induced rectification of the quantized Hall plateaus (QHPs) is studied within a Hartree type mean field approximation for asymmetrically depleted samples. We first investigate the existence of the current carrying incompressible strips (ISs), by solving the self-consistent equations, and their influence on magneto-transport (MT) properties. Next, the widths of the ISs are examined in terms of the steepness of the confining potential profile considering gate defined Hall bars. The corresponding MT coefficients are calculated using a local Ohm's law for a large fixed current and are compared for symmetric and asymmetric depleted samples. We predict that, the extend of the QHPs strongly depend on the current polarization, in the out of linear response regime, when considering asymmetrically depleted samples. Our results, concerning the extend of the QHPs depending on the current polarization are in contrast to the ones of the conventional theories of the integer quantized Hall effect (IQHE). We propose certain experimental conditions to test our theoretical predictions at high mobility, narrow samples.Comment: 4 pages, 3 figures, submitted to Phys. Re

Ordinal Multi-modal Feature Selection for Survival Analysis of Early-Stage Renal Cancer

Existing studies have demonstrated that combining genomic data and histopathological images can better stratify cancer patients with distinct prognosis than using single biomarker, for different biomarkers may provide complementary information. However, these multi-modal data, most high-dimensional, may contain redundant features that will deteriorate the performance of the prognosis model, and therefore it has become a challenging problem to select the informative features for survival analysis from the redundant and heterogeneous feature groups. Existing feature selection methods assume that the survival information of one patient is independent to another, and thus miss the ordinal relationship among the survival time of different patients. To solve this issue, we make use of the important ordinal survival information among different patients and propose an ordinal sparse canonical correlation analysis (i.e., OSCCA) framework to simultaneously identify important image features and eigengenes for survival analysis. Specifically, we formulate our framework basing on sparse canonical correlation analysis model, which aims at finding the best linear projections so that the highest correlation between the selected image features and eigengenes can be achieved. In addition, we also add constrains to ensure that the ordinal survival information of different patients is preserved after projection. We evaluate the effectiveness of our method on an early-stage renal cell carcinoma dataset. Experimental results demonstrate that the selected features correlated strongly with survival, by which we can achieve better patient stratification than the comparing methods

Self-consistent Coulomb picture of an electron-electron bilayer system

In this work we implement the self-consistent Thomas-Fermi approach and a local conductivity model to an electron-electron bilayer system. The presence of an incompressible strip, originating from screening calculations at the top (or bottom) layer is considered as a source of an external potential fluctuation to the bottom (or top) layer. This essentially yields modifications to both screening properties and the magneto-transport quantities. The effect of the temperature, inter-layer distance and density mismatch on the density and the potential fluctuations are investigated. It is observed that the existence of the incompressible strips plays an important role simply due to their poor screening properties on both screening and the magneto-resistance (MR) properties. Here we also report and interpret the observed MR Hysteresis within our model.Comment: 12 pages, 12 figures, submitted to PR

Realistic modelling of quantum point contacts subject to high magnetic fields and with current bias at out of linear response regime

The electron and current density distributions in the close proximity of quantum point contacts (QPCs) are investigated. A three dimensional Poisson equation is solved self-consistently to obtain the electron density and potential profile in the absence of an external magnetic field for gate and etching defined devices. We observe the surface charges and their apparent effect on the confinement potential, when considering the (deeply) etched QPCs. In the presence of an external magnetic field, we investigate the formation of the incompressible strips and their influence on the current distribution both in the linear response and out of linear response regime. A spatial asymmetry of the current carrying incompressible strips, induced by the large source drain voltages, is reported for such devices in the non-linear regime.Comment: 16 Pages, 9 Figures, submitted to PR

Lymphangitis carcinomatosa as an unusual presentation of renal cell carcinoma: a case report

<p>Abstract</p> <p>Introduction</p> <p>Renal cell carcinoma is a common adult malignancy that can present incidentally or with a multitude of clinical symptoms and signs. Metastatic spread is frequent, occurring via haematogenous and lymphatic routes, although it does not typically present with lymphangitis carcinomatosa.</p> <p>Case presentation</p> <p>We describe a patient who presented with cough and increasing dyspnoea. Initial chest x-ray and computed tomography were consistent with lymphangitis carcinomatosa that proved secondary to underlying renal cell carcinoma.</p> <p>Conclusion</p> <p>Lymphangitis carcinomatosa occurs with many different primary tumours and can rarely be the presenting feature of renal cell carcinoma. Underlying renal cell carcinoma should be considered in the differential diagnosis of lymphangitis carcinomatosa and excluded with subsequent investigations.</p

Northern Bering Sea tip jets

Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 39 (2012): L08807, doi:10.1029/2012GL051537.Low-level regions of high wind speed known as tip jets have been identified near Cape Farewell, Greenland's southernmost point. These wind systems contribute to this area being the windiest location on the ocean's surface and play an important role in the regional weather and climate. Here we present the first analysis of the wind systems that make the Siberian coast of the northern Bering Sea the windiest location in the North Pacific Ocean during the boreal winter. In particular we show that tips jets characterized by enhanced northeasterly winds occur in the vicinity of the two prominent headlands along the coast, Cape Navarin and Cape Olyutorsky. The advance of sea ice in the region is shown to impact the frequency and location of the high speed winds in the vicinity of these two capes. Furthermore, we show that these jets are associated with the interaction of extra-tropical cyclones with the high topography of the Koryak Mountain range, situated just inland of the capes. The windstress imparted to the ocean via the tip jets is argued to help drive the formation of dense water in winter in the northern Bering Sea, thus playing an important role in the regional oceanic circulation.GWKM was supported by the Natural Science and Engineering Research Council of Canada. RSP was funded by grant NA08OAR43200895 from the National Oceanic and Atmospheric Administration.2012-10-2

Spike-Train Responses of a Pair of Hodgkin-Huxley Neurons with Time-Delayed Couplings

Model calculations have been performed on the spike-train response of a pair of Hodgkin-Huxley (HH) neurons coupled by recurrent excitatory-excitatory couplings with time delay. The coupled, excitable HH neurons are assumed to receive the two kinds of spike-train inputs: the transient input consisting of $M$ impulses for the finite duration ($M$: integer) and the sequential input with the constant interspike interval (ISI). The distribution of the output ISI $T_{\rm o}$ shows a rich of variety depending on the coupling strength and the time delay. The comparison is made between the dependence of the output ISI for the transient inputs and that for the sequential inputs.Comment: 19 pages, 4 figure

Dynamical mean-field theory of spiking neuron ensembles: response to a single spike with independent noises

Dynamics of an ensemble of $N$-unit FitzHugh-Nagumo (FN) neurons subject to white noises has been studied by using a semi-analytical dynamical mean-field (DMF) theory in which the original $2 N$-dimensional {\it stochastic} differential equations are replaced by 8-dimensional {\it deterministic} differential equations expressed in terms of moments of local and global variables. Our DMF theory, which assumes weak noises and the Gaussian distribution of state variables, goes beyond weak couplings among constituent neurons. By using the expression for the firing probability due to an applied single spike, we have discussed effects of noises, synaptic couplings and the size of the ensemble on the spike timing precision, which is shown to be improved by increasing the size of the neuron ensemble, even when there are no couplings among neurons. When the coupling is introduced, neurons in ensembles respond to an input spike with a partial synchronization. DMF theory is extended to a large cluster which can be divided into multiple sub-clusters according to their functions. A model calculation has shown that when the noise intensity is moderate, the spike propagation with a fairly precise timing is possible among noisy sub-clusters with feed-forward couplings, as in the synfire chain. Results calculated by our DMF theory are nicely compared to those obtained by direct simulations. A comparison of DMF theory with the conventional moment method is also discussed.Comment: 29 pages, 2 figures; augmented the text and added Appendice