Switching Boundary Conditions in the Many-Body Diffusion Algorithm

In this paper we show how the transposition, the basic operation of the permutation group, can be taken into account in a diffusion process of identical particles. Whereas in an earlier approach the method was applied to systems in which the potential is invariant under interchanging the Cartesian components of the particle coordinates, this condition on the potential is avoided here. In general, the potential introduces a switching of the boundary conditions of the walkers. These transitions modelled by a continuous-time Markov chain generate sample paths for the propagator as a Feynman-Kac functional. A few examples, including harmonic fermions with an anharmonic interaction, and the ground-state energy of ortho-helium are studied to elucidate the theoretical discussion and to illustrate the feasibility of a sign-problem-free implementation scheme for the recently developed many-body diffusion approach.Comment: 16 pages REVTEX + 6 postscript figures, submitted to Phys. Rev. E on Jan. 27, 199

Desulfo-glucosinolate sulfotransferases isolated from several Arabidopsis thaliana ecotypes differ in their sequence and enzyme kinetics

The goal was to investigate whether the diverse glucosinolate (Gl) profiles described for different Arabidopsis thaliana (L.) Heynh. ecotypes are at least partially shaped by the kinetic properties of sulfotransferases (SOTs) (EC 2.8.2.-) catalyzing the final step in Gl core structure biosynthesis. This study focuses on only one of the three SOTs that contribute to Gl biosynthesis. Homologues of AtSOT18 proteins were characterized, which was inspired by earlier findings on SOTs from ecotypes Col-0 and C24 differing in two amino acids (aa) and specific enzyme activities. Could there be a correlation of AtSOT18 enzyme activities and differences in Gl profiles between the ecotypes? SOT18 sequences from eight Arabidopsis ecotypes with highly diverse Gl patterns differed in two aa at various positions in the protein sequence. The SOT18 sequence from Col-0 showed the highest similarity to the largest number of other sequences in the alignment. The small differences in the primary sequence lead to important structural changes in secondary and tertiary structure that might be the key of different kinetic activities towards a broad range of substrates. All recombinant AtSOT18 proteins showed low substrate specificity with an indolic Gl, while the specificity for aliphatic substrates varied. There is no correlation in the kinetic behavior with the major ds-Gl contents or with the ratio of C-3/C-4 ds-Gl in the respective ecotype. Therefore, is it unlikely that ds-Gl AtSOT18 proteins play a major role in shaping the Gl profile in Arabidopsis

Limitations in the use of IR spectra for the determination of hydrogen concentration in a-Si: H films

Infra-red (IR) spectroscopy has been used to monitor hydrogen concentrations in hydrogenated amorphous silicon thin films. Wagging and. stretching modes were used with appropriate correction factors for film thickness and proportionality constants to convert between integrated absorption and hydrogen concentration. Two different types of IR spectra were observed even though in other respects the films appeared to be identical. The values of hydrogen concentration were calculated from wagging and stretching modes. These values are in agreement for one type of IR spectrum but are not the same for the other type. Possible reasons for observed differences are presented as well as a suggestion for an improved procedure which can give more reliable values of the hydrogen concentration

Using Microsoft HoloLens to improve memory recall in anatomy and physiology: A pilot study to examine the efficacy of using augmented reality in education

This paper explores the use of augmented reality (AR) to improve memory recall and learning experiences in human anatomy and physiology. In particular, the opportunity to assess new computer technologies to improve learning environments may allow for an improvement in self-efficacy and a reduction in test anxiety. Twenty-two undergraduates participated in one of two study groups, the Microsoft HoloLens group (HLNS) or the traditional projector-based Microsoft Power Point group (PPT). Each group completed a five-minute, three-subject anatomy identification and brain physiology memory test. After a three-minute time delay, participants completed a fill-in-the-blank anatomy identification test and brain physiology question test, followed by questionnaires for systems self-efficacy and test anxiety. Results indicated the PPT group significantly outperformed the HLNS group in the brain lobe identification portion of the exam and had reported higher mean test anxiety scores (though not high enough to be considered unhealthy levels). However, the HLNS group showed a significantly higher preference to the learning experience compared to the PPT group based on the systems self-efficacy questionnaire. This pilot study demonstrates an opportunity for the HLNS to use used in learning environments to improve the psychological aspects of studying and test taking

Distributed Symmetry Breaking in Hypergraphs

Fundamental local symmetry breaking problems such as Maximal Independent Set (MIS) and coloring have been recognized as important by the community, and studied extensively in (standard) graphs. In particular, fast (i.e., logarithmic run time) randomized algorithms are well-established for MIS and $\Delta +1$-coloring in both the LOCAL and CONGEST distributed computing models. On the other hand, comparatively much less is known on the complexity of distributed symmetry breaking in {\em hypergraphs}. In particular, a key question is whether a fast (randomized) algorithm for MIS exists for hypergraphs. In this paper, we study the distributed complexity of symmetry breaking in hypergraphs by presenting distributed randomized algorithms for a variety of fundamental problems under a natural distributed computing model for hypergraphs. We first show that MIS in hypergraphs (of arbitrary dimension) can be solved in $O(\log^2 n)$ rounds ($n$ is the number of nodes of the hypergraph) in the LOCAL model. We then present a key result of this paper --- an $O(\Delta^{\epsilon}\text{polylog}(n))$-round hypergraph MIS algorithm in the CONGEST model where $\Delta$ is the maximum node degree of the hypergraph and $\epsilon > 0$ is any arbitrarily small constant. To demonstrate the usefulness of hypergraph MIS, we present applications of our hypergraph algorithm to solving problems in (standard) graphs. In particular, the hypergraph MIS yields fast distributed algorithms for the {\em balanced minimal dominating set} problem (left open in Harris et al. [ICALP 2013]) and the {\em minimal connected dominating set problem}. We also present distributed algorithms for coloring, maximal matching, and maximal clique in hypergraphs.Comment: Changes from the previous version: More references adde

A law of large numbers approximation for Markov population processes with countably many types

When modelling metapopulation dynamics, the influence of a single patch on the metapopulation depends on the number of individuals in the patch. Since the population size has no natural upper limit, this leads to systems in which there are countably infinitely many possible types of individual. Analogous considerations apply in the transmission of parasitic diseases. In this paper, we prove a law of large numbers for rather general systems of this kind, together with a rather sharp bound on the rate of convergence in an appropriately chosen weighted $\ell_1$ norm.Comment: revised version in response to referee comments, 34 page

Bipolaron Binding in Quantum Wires

A theory of bipolaron states in quantum wires with a parabolic potential well is developed applying the Feynman variational principle. The basic parameters of the bipolaron ground state (the binding energy, the number of phonons in the bipolaron cloud, the effective mass, and the bipolaron radius) are studied as a function of sizes of the potential well. Two cases are considered in detail: a cylindrical quantum wire and a planar quantum wire. Analytical expressions for the bipolaron parameters are obtained at large and small sizes of the quantum well. It is shown that at $R\gg 1$ [where $R$ means the radius (halfwidth) of a cylindrical (planar) quantum wire, expressed in Feynman units], the influence of confinement on the bipolaron binding energy is described by the function $\sim 1/R^{2}$ for both cases, while at small sizes this influence is different in each case. In quantum wires, the bipolaron binding energy $W(R)$ increases logarithmically with decreasing radius. The shapes and the sizes of a nanostructure, which are favorable for observation of stable bipolaron states, are determined.Comment: 17 pages, 6 figures, E-mail addresses: [email protected]; [email protected]