Skin lesion classification from dermoscopic images using deep learning techniques

The recent emergence of deep learning methods for medical image analysis has enabled the development of intelligent medical imaging-based diagnosis systems that can assist the human expert in making better decisions about a patient’s health. In this paper we focus on the problem of skin lesion classification, particularly early melanoma detection, and present a deep-learning based approach to solve the problem of classifying a dermoscopic image containing a skin lesion as malignant or benign. The proposed solution is built around the VGGNet convolutional neural network architecture and uses the transfer learning paradigm. Experimental results are encouraging: on the ISIC Archive dataset, the proposed method achieves a sensitivity value of 78.66%, which is significantly higher than the current state of the art on that dataset.Postprint (author's final draft

Spin filtering in nanowire directional coupler

The spin transport characteristics of a nanowire directional electronic coupler have been evaluated theoretically via a transfer matrix approach. The application of a gate field in the region of mixing allows for control of spin current through the different leads of the coupler via the Rashba spin-orbit interaction. The combination of spin-orbit interaction and applied gate voltages on different legs of the coupler give rise to a controllable modulation of the spin polarization. Both structural factors and field strength tuning lead to a rich phenomenology that could be exploited in spintronic devices.Comment: 9 pages, 4 figure

Protocol-based verification of message-passing parallel programs

© 2015 ACM.We present ParTypes, a type-based methodology for the verification of Message Passing Interface (MPI) programs written in the C programming language. The aim is to statically verify programs against protocol specifications, enforcing properties such as fidelity and absence of deadlocks. We develop a protocol language based on a dependent type system for message-passing parallel programs, which includes various communication operators, such as point-to-point messages, broadcast, reduce, array scatter and gather. For the verification of a program against a given protocol, the protocol is first translated into a representation read by VCC, a software verifier for C. We successfully verified several MPI programs in a running time that is independent of the number of processes or other input parameters. This contrasts with alternative techniques, notably model checking and runtime verification, that suffer from the state-explosion problem or that otherwise depend on parameters to the program itself. We experimentally evaluated our approach against state-of-the-art tools for MPI to conclude that our approach offers a scalable solution

Economic and cultural determinants of elite attitudes toward redistribution

Previous studies have posited that elites are willing to advance the redistribution of income and social goods when the negative effects of inequality, such as crime and conflict, threaten their own interests. Although elites acknowledge these negative effects, their support for redistributive policies remains low throughout the Global South. We address this paradox using a multi-method research design. Drawing on 56 in-depth interviews with Brazilian political and economic elites, we document how, when discussing the negative effects of inequality, interviewees consistently characterized the poor as ignorant, irrational and politically incompetent. We use these findings to theorize about the negative impact of such perceptions of the poor on elite support for redistribution. We then test this relationship using survey data gathered from random samples of political and economic elites in Brazil, South Africa and Uruguay (N = 544). We find the relationship to be robust

Poloidal-toroidal decomposition in a finite cylinder. II. Discretization, regularization and validation

The Navier-Stokes equations in a finite cylinder are written in terms of poloidal and toroidal potentials in order to impose incompressibility. Regularity of the solutions is ensured in several ways: First, the potentials are represented using a spectral basis which is analytic at the cylindrical axis. Second, the non-physical discontinuous boundary conditions at the cylindrical corners are smoothed using a polynomial approximation to a steep exponential profile. Third, the nonlinear term is evaluated in such a way as to eliminate singularities. The resulting pseudo-spectral code is tested using exact polynomial solutions and the spectral convergence of the coefficients is demonstrated. Our solutions are shown to agree with exact polynomial solutions and with previous axisymmetric calculations of vortex breakdown and of nonaxisymmetric calculations of onset of helical spirals. Parallelization by azimuthal wavenumber is shown to be highly effective

Conductive and convective heat transfer in fluid flows between differentially heated and rotating cylinders

The flow of fluid confined between a heated rotating cylinder and a cooled stationary cylinder is a canonical experiment for the study of heat transfer in engineering. The theoretical treatment of this system is greatly simplified if the cylinders are assumed to be of infinite length or periodic in the axial direction, in which cases heat transfer occurs only through conduction as in a solid. We here investigate numerically heat transfer and the onset of turbulence in such flows by using both periodic and no-slip boundary conditions in the axial direction. We obtain a simple linear criterion that determines whether the infinite-cylinder assumption can be employed. The curvature of the cylinders enters this linear relationship through the slope and additive constant. For a given length-to-gap aspect ratio there is a critical Rayleigh number beyond which the laminar flow in the finite system is convective and so the behaviour is entirely different from the periodic case. The criterion does not depend on the Prandtl number and appears quite robust with respect to the Reynolds number. In particular, it continues to work reasonably in the turbulent regime.Comment: 25 pages, 9 figure

Molecular dynamics simulation of the regrowth of nanometric multigate Si devices

We use molecular dynamics (MD) simulation techniques to study the regrowth of nanometric multigate Si devices, such as fins and nanowires, surrounded by free surfaces and interfaces with amorphous material. Our results indicate that atoms in amorphous regions close to lateral free surfaces or interfaces rearrange at a slower rate compared to those in bulk due to the discontinuity of the lateral crystalline template. Consequently, the recrystallization front which advances faster in the device center than at the interfaces adopts new orientations. Regrowth then proceeds depending on the particular orientation of the new amorphous/crystal interfaces. In the particular case of (110) oriented fins, the new amorphous/crystal interfaces are aligned along the (111) direction, which produces frequent twining during further regrowth. Based on our simulation results, we propose alternatives to overcome this defected recrystallization in multigate structures: device orientation along (100) to prevent the formation of limiting {111} I amorphous/crystal interfaces and presence of a crystalline seed along the device body to favor regrowth perpendicular to the lateral surfaces/interfaces rather than parallel to them. (C) 2012 American Institute of Physics. [doi :10.1063/1.3679126