Pattern Competition in the Photorefractive Semiconductors

We analytically study the photorefractive Gunn effect in n-GaAs subjected to two external laser beams which form a moving interference pattern (MIP) in the semiconductor. When the intensity of the spatially independent part of the MIP, denoted by $I_0$, is small, the system has a periodic domain train (PDT), consistent with the results of linear stability analysis. When $I_0$ is large, the space-charge field induced by the MIP will compete with the PDT and result in complex dynamics, including driven chaos via quasiperiodic route

Spatiotemporal symmetries in the disynaptic canal-neck projection

The vestibular system in almost all vertebrates, and in particular in humans, controls balance by employing a set of six semicircular canals, three in each inner ear, to detect angular accelerations of the head in three mutually orthogonal coordinate planes. Signals from the canals are transmitted to eight (groups of) neck motoneurons, which activate the eight corresponding muscle groups. These signals may be either excitatory or inhibitory, depending on the direction of head acceleration. McCollum and Boyle have observed that in the cat the relevant network of neurons possesses octahedral symmetry, a structure that they deduce from the known innervation patterns (connections) from canals to muscles. We rederive the octahedral symmetry from mathematical features of the probable network architecture, and model the movement of the head in response to the activation patterns of the muscles concerned. We assume that connections between neck muscles can be modeled by a “coupled cell network,” a system of coupled ODEs whose variables correspond to the eight muscles, and that this network also has octahedral symmetry. The network and its symmetries imply that these ODEs must be equivariant under a suitable action of the octahedral group. It is observed that muscle motoneurons form natural “push-pull pairs” in which, for given movements of the head, one neuron produces an excitatory signal, whereas the other produces an inhibitory signal. By incorporating this feature into the mathematics in a natural way, we are led to a model in which the octahedral group acts by signed permutations on muscle motoneurons. We show that with the appropriate group actions, there are six possible spatiotemporal patterns of time-periodic states that can arise by Hopf bifurcation from an equilibrium representing an immobile head. Here we use results of Ashwin and Podvigina. Counting conjugate states, whose physiological interpretations can have significantly different features, there are 15 patterns of periodic oscillation, not counting left-right reflections or time-reversals as being different. We interpret these patterns as motions of the head, and note that all six types of pattern appear to correspond to natural head motions

TO USE A TREE OR A FOREST IN BEHAVIORAL INTENTION

Cloud computing is a new technology that has been applied to education and has e nabled the development of cloud computing classrooms; however, student behavioral intentions toward cloud computing remain unclear. Most researchers have evaluated, integrated, or compared few (1 to 3) theories to examine user behavioral intentions and few have addressed additional theories or models. In this study, we test, compare, and unify six well -known theories, namely, service quality (SQ), self - efficacy (SE), the motivational model (MM), technology acceptance model (TAM), theory of reason action (TRA)/theory of planned behavior (TPB), and innovation diffusion theory (IDT) in the context of cloud computing classrooms. This empirical study was conducted using an online survey. The data collected from the samples (n=478) were analyzed using structural equation modeling. We independently analyzed each of the six theories, formulating a united model. The analysis yielded three valuable findings. First, comparing the explained variance and degree of freedom (df) difference, yielded the following ranking in explained variance: MM=TAM\u3eIDT\u3eTPB\u3eSE=SQ (equal =; superior to\u3e). Second, comparing the explained variance yielded the following ranking in explained variance: MM\u3eTAM\u3eIDT\u3eTPB\u3eSE=SQ. Third, based on the united model of six theories, some factors significantly affect behavioral intention and others do not. The implications of this study are critical for both researchers and practitioners

A study of pulse propagation of electromagnetic signals through the solar corona

Solar probe to measure radial variation of electron density in solar coron

Tunable Kondo effect in a single donor atom

The Kondo effect has been observed in a single gate-tunable atom. The measurement device consists of a single As dopant incorporated in a Silicon nanostructure. The atomic orbitals of the dopant are tunable by the gate electric field. When they are tuned such that the ground state of the atomic system becomes a (nearly) degenerate superposition of two of the Silicon valleys, an exotic and hitherto unobserved valley Kondo effect appears. Together with the regular spin Kondo, the tunable valley Kondo effect allows for reversible electrical control over the symmetry of the Kondo ground state from an SU(2)- to an SU(4) -configuration.Comment: 10 pages, 8 figure

On conditional skewness with applications to environmental data

The statistical literature contains many univariate and multivariate skewness measures that allow two datasets to be compared, some of which are defined in terms of quantile values. In most situations, the comparison between two random vectors focuses on univariate comparisons of conditional random variables truncated in quantiles; this kind of comparison is of particular interest in the environmental sciences. In this work, we describe a new approach to comparing skewness in terms of the univariate convex transform ordering proposed by van Zwet (Convex transformations of random variables. Mathematical Centre Tracts, Amsterdam, 1964), associated with skewness as well as concentration. The key to these comparisons is the underlying dependence structure of the random vectors. Below we describe graphical tools and use several examples to illustrate these comparisons.The research of Félix Belzunce, Julio Mulero and José María Ruíz is partially funded by the Ministerio de Economía y Competitividad (Spain) under Grant MTM2012-34023-FEDER. Alfonso Suárez-Llorens acknowledges support received from the Ministerio de Economía y Competitividad (Spain) under Grant MTM2014-57559-P

The Pro-Survival Oct4/Stat1/Mcl-1 Axis Is Associated with Poor Prognosis in Lung Adenocarcinoma Patients.

The embryonic stem cell marker Oct4 is expressed in several human cancers and is positively correlated with a poor outcome in cancer patients. However, its physiological role in cancer progression remains poorly understood. Tumor cells block apoptosis to escape cell death so that they can proliferate indefinitely, leading to ineffective therapy for cancer patients. In this study, we investigated whether Oct4 regulates the apoptosis pathway and contributes to poor prognosis in patients with lung adenocarcinoma. Our results revealed that Oct4 expression is correlated with Stat1 expression in lung adenocarcinoma patients and Oct4 is directly bound to the Stat1 promoter to transactivate Stat1 in lung adenocarcinoma cells. Expression of the Stat1 downstream gene Mcl-1 increased in Oct4-overexpressing cancer cells, while Stat1 knockdown in Oct4-overexpressing cancer cells sensitized them to cisplatin-induced apoptosis. Furthermore, Oct4 promoted Stat1 expression and tumor growth, whereas silencing of Stat1 reduced Oct4-induced tumor growth in human lung tumor xenograft models. Taken together, we demonstrate that Oct4 is a pro-survival factor by inducing Stat1 expression and that the Oct4/Stat1/Mcl-1 axis may be a potential therapeutic target for lung adenocarcinoma

Evidence for Factorization in Three-body B --> D(*) K- K0 Decays

Motivated by recent experimental results, we use a factorization approach to study the three-body B --> D(*) K- K0 decay modes. Two mechanisms are proposed for kaon pair production: current-produced (from vacuum) and transition (from B meson). The Bbar0 --> D(*)+ K- K0 decay is governed solely by the current-produced mechanism. As the kaon pair can be produced only by the vector current, the matrix element can be extracted from e+ e- --> K Kbar processes via isospin relations. The decay rates obtained this way are in good agreement with experiment. Both current-produced and transition processes contribute to B- --> D(*)0 K- K0 decays. By using QCD counting rules and the measured B- --> D(*)0 K- K0 decay rates, the measured decay spectra can be understood.Comment: 17 pages, 6 figure