Topological phases of a dimerized Fermi–Hubbard model for semiconductor nano-lattices

Motivated by recent advances in fabricating artificial lattices in semiconductors and their promise for quantum simulation of topological materials, we study the one-dimensional dimerized Fermi–Hubbard model. We show how the topological phases at half-filling can be characterized by a reduced Zak phase defined based on the reduced density matrix of each spin subsystem. Signatures of bulk–boundary correspondence are observed in the triplon excitation of the bulk and the edge states of uncoupled spins at the boundaries. At quarter-filling, we show that owing to the presence of the Hubbard interaction the system can undergo a transition to the topological ground state of the non-interacting Su–Schrieffer–Heeger model with the application of a moderate-strength external magnetic field. We propose a robust experimental realization with a chain of dopant atoms in silicon or gate-defined quantum dots in GaAs where the transition can be probed by measuring the tunneling current through the many-body state of the chain

Rydberg entangling gates in silicon

In this paper we propose a Rydberg entangling gate scheme which we demonstrate theoretically to have an order-of-magnitude improvement in fidelities and speed over existing cold atom protocols. It requires a large Rabi frequency compared to the interaction strength, which is difficult in cold atoms, but natural in donors in silicon, where it could help overcome the strenuous requirements on atomic precision donor placement and substantial gate tuning, which so far has hampered scaling. Furthermore, the gate operation would be ultrafast, on the order of picoseconds. We calculate multivalley van der Waals, induced electric dipole and total Rydberg interactions for several donor species using the finite-element method and show that they are important even for low-lying excited states. We show that Rydberg gate operation is possible within the lifetime of donor excited states with 99.9% fidelity for the creation of a Bell state in the presence of decoherence

Role of the Netrin-like Domain of Procollagen C-Proteinase Enhancer-1 in the Control of Metalloproteinase Activity

The netrin-like (NTR) domain is a feature of several extracellular proteins, most notably the N-terminal domain of tissue inhibitors of metalloproteinases (TIMPs), where it functions as a strong inhibitor of matrix metalloproteinases and some other members of the metzincin superfamily. The presence of a C-terminal NTR domain in procollagen C-proteinase enhancers (PCPEs), proteins that stimulate the activity of astacin-like tolloid proteinases, raises the possibility that this might also have inhibitory activity. Here we show that both long and short forms of the PCPE-1 NTR domain, the latter beginning at the N-terminal cysteine known to be critical for TIMP activity, show no inhibition, at micromolar concentrations, of several members of the metzincin superfamily, including matrix metalloproteinase-2, bone morphogenetic protein-1 (a tolloid proteinase), and different ADAMTS (a disintegrin and a metalloproteinase with thrombospondin motifs) proteinases from the adamalysin family. In contrast, we report that the NTR domain within PCPE-1 leads to superstimulation of bone morphogenetic protein-1 activity in the presence of heparin and heparan sulfate. These observations point to a new mechanism whereby binding to cell surface-associated or extracellular heparin-like sulfated glycosaminoglycans might provide a means to accelerate procollagen processing in specific cellular and extracellular microenvironments

Packing and Hausdorff measures of stable trees

In this paper we discuss Hausdorff and packing measures of random continuous trees called stable trees. Stable trees form a specific class of L\'evy trees (introduced by Le Gall and Le Jan in 1998) that contains Aldous's continuum random tree (1991) which corresponds to the Brownian case. We provide results for the whole stable trees and for their level sets that are the sets of points situated at a given distance from the root. We first show that there is no exact packing measure for levels sets. We also prove that non-Brownian stable trees and their level sets have no exact Hausdorff measure with regularly varying gauge function, which continues previous results from a joint work with J-F Le Gall (2006).Comment: 40 page

Anomalous magnetic structure and spin dynamics in magnetoelectric LiFePO4

We report significant details of the magnetic structure and spin dynamics of LiFePO4 obtained by single-crystal neutron scattering. Our results confirm a previously reported collinear rotation of the spins away from the principal b axis, and they determine that the rotation is toward the a axis. In addition, we find a significant spin-canting component along c. The possible causes of these components are discussed, and their significance for the magnetoelectric effect is analyzed. Inelastic neutron scattering along the three principal directions reveals a highly anisotropic hard plane consistent with earlier susceptibility measurements. Using a spin Hamiltonian, we show that the spin dimensionality is intermediate between XY- and Ising-like, with an easy b axis and a hard c axis. It is shown that both next-nearest neighbor exchange couplings in the bc plane are in competition with the strongest nearest neighbor coupling. ©2015 American Physical Society8

A numerical study on the evolution of portfolio rules

In this paper we test computationally the performance of CAPM in an evolutionary setting. In particular we study the stability of distribution of wealth in a financial market where some traders invest as prescribed by CAPM and others behave according to different portfolio rules. Our study is motivated by recent analytical results that show that, whenever a logarithmic utility maximiser enters the market, CAPM traders vanish in the long run. Our analysis provides further insights and extends these results. We simulate a sequence of trades in a financial market and: first, we address the issue of how long is the long run in different parametric settings; second, we study the effect of heterogeneous savings behaviour on asymptotic wealth shares. We find that CAPM is particularly “unfit” for highly risky environments

Estimation of coronary artery hyperemic blood flow based on arterial lumen volume using angiographic images

The purpose of this study is to develop a method to estimate the hyperemic blood flow in a coronary artery using the sum of the distal lumen volumes in a swine animal model. The limitations of visually assessing coronary artery disease are well known. These limitations are particularly important in intermediate coronary lesions where it is difficult to determine whether a particular lesion is the cause of ischemia. Therefore, a functional measure of stenosis severity is needed using angiographic image data. Coronary arteriography was performed in 10 swine (Yorkshire, 25–35 kg) after power injection of contrast material into the left main coronary artery. A densitometry technique was used to quantify regional flow and lumen volume in vivo after inducing hyperemia. Additionally, 3 swine hearts were casted and imaged post-mortem using cone-beam CT to obtain the lumen volume and the arterial length of corresponding coronary arteries. Using densitometry, the results showed that the stem hyperemic flow (Q) and the associated crown lumen volume (V) were related by Q = 159.08 V3/4 (r = 0.98, SEE = 10.59 ml/min). The stem hyperemic flow and the associated crown length (L) using cone-beam CT were related by Q = 2.89 L (r = 0.99, SEE = 8.72 ml/min). These results indicate that measured arterial branch lengths or lumen volumes can potentially be used to predict the expected hyperemic flow in an arterial tree. This, in conjunction with measured hyperemic flow in the presence of a stenosis, could be used to predict fractional flow reserve based entirely on angiographic data

Transfer Functions for Protein Signal Transduction: Application to a Model of Striatal Neural Plasticity

We present a novel formulation for biochemical reaction networks in the context of signal transduction. The model consists of input-output transfer functions, which are derived from differential equations, using stable equilibria. We select a set of 'source' species, which receive input signals. Signals are transmitted to all other species in the system (the 'target' species) with a specific delay and transmission strength. The delay is computed as the maximal reaction time until a stable equilibrium for the target species is reached, in the context of all other reactions in the system. The transmission strength is the concentration change of the target species. The computed input-output transfer functions can be stored in a matrix, fitted with parameters, and recalled to build discrete dynamical models. By separating reaction time and concentration we can greatly simplify the model, circumventing typical problems of complex dynamical systems. The transfer function transformation can be applied to mass-action kinetic models of signal transduction. The paper shows that this approach yields significant insight, while remaining an executable dynamical model for signal transduction. In particular we can deconstruct the complex system into local transfer functions between individual species. As an example, we examine modularity and signal integration using a published model of striatal neural plasticity. The modules that emerge correspond to a known biological distinction between calcium-dependent and cAMP-dependent pathways. We also found that overall interconnectedness depends on the magnitude of input, with high connectivity at low input and less connectivity at moderate to high input. This general result, which directly follows from the properties of individual transfer functions, contradicts notions of ubiquitous complexity by showing input-dependent signal transmission inactivation.Comment: 13 pages, 5 tables, 15 figure

Specific Y14 domains mediate its nucleo-cytoplasmic shuttling and association with spliced mRNA

Pre-mRNA splicing deposits multi-protein complexes, termed exon junction complexes (EJCs), on mRNAs near exon-exon junctions. The core of EJC consists of four proteins, eIF4AIII, MLN51, Y14 and Magoh. Y14 is a nuclear protein that can shuttle between the nucleus and the cytoplasm, and binds specifically to Magoh. Here we delineate a Y14 nuclear localization signal that also confers its nuclear export, which we name YNS. We further identified a 12-amino-acid peptide near Y14's carboxyl terminus that is required for its association with spliced mRNAs, as well as for Magoh binding. Furthermore, the Y14 mutants, which are deficient in binding to Magoh, could still be localized to the nucleus, suggesting the existence of both the nuclear import pathway and function for Y14 unaccompanied by Magoh

Proximity to Sports Facilities and Sports Participation for Adolescents in Germany

Objectives - To assess the relationship between proximity to specific sports facilities and participation in the corresponding sports activities for adolescents in Germany. Methods - A sample of 1,768 adolescents aged 11–17 years old and living in 161 German communities was examined. Distances to the nearest sports facilities were calculated as an indicator of proximity to sports facilities using Geographic Information Systems (GIS). Participation in specific leisure-time sports activities in sports clubs was assessed using a self-report questionnaire and individual-level socio-demographic variables were derived from a parent questionnaire. Community-level socio-demographics as covariates were selected from the INKAR database, in particular from indicators and maps on land development. Logistic regression analyses were conducted to examine associations between proximity to the nearest sports facilities and participation in the corresponding sports activities. Results - The logisitic regression analyses showed that girls residing longer distances from the nearest gym were less likely to engage in indoor sports activities; a significant interaction between distances to gyms and level of urbanization was identified. Decomposition of the interaction term showed that for adolescent girls living in rural areas participation in indoor sports activities was positively associated with gym proximity. Proximity to tennis courts and indoor pools was not associated with participation in tennis or water sports, respectively. Conclusions - Improved proximity to gyms is likely to be more important for female adolescents living in rural areas