Quantum Entanglement in the S=1/2 Spin Ladder with Ring Exchange

In this paper we study the concurrence and the block-block entanglement in the $S=1/2$ spin ladder with four-spin ring exchange by the exact diagonalization method of finite cluster of spins. The relationship between the global phase diagram and the ground-state entanglement is investigated. It is shown that the block-block entanglement of different block size and geometry manifests richer information of the system. We find that the extremal point of the two-site block-block entanglement on the rung locates a transition point exactly due to SU(4) symmetry at this point. The scaling behavior of the block-block entanglement is discussed. Our results suggest that the block-block entanglement can be used as a convenient marker of quantum phase transition in some complex spin systems.Comment: 5 pages, 7 figure

Hippocampal Neuronal Polarity Specified by Spatially Localized mPar3/mPar6 and PI 3-Kinase Activity

AbstractHow a neuron becomes polarized remains an outstanding question. Here, we report that selection of the future axon among neurites of a cultured hippocampal neuron requires the activity of growth factor receptor tyrosine kinase, phosphatidylinositol 3-kinase (PI 3-kinase), as well as atypical protein kinase C (aPKC). The PI 3-kinase activity, highly localized to the tip of the newly specified axon of stage 3 neurons, is essential for the proper subcellular localization of mPar3, the mammalian homolog of C. elegans polarity protein Par3. Polarized distribution of not only mPar3 but also mPar6 is important for axon formation; ectopic expression of mPar6 or mPar3, or just the N terminus of mPar3, leaves neurons with no axon specified. Thus, neuronal polarity is likely to be controlled by the mPar3/mPar6/aPKC complex and the PI 3-kinase signaling pathway, both serving evolutionarily conserved roles in specifying cell polarity

An Open Receptor-Binding Cavity of Hemagglutinin-Esterase-Fusion Glycoprotein from Newly-Identified Influenza D Virus: Basis for Its Broad Cell Tropism.

Influenza viruses cause seasonal flu each year and pandemics or epidemic sporadically, posing a major threat to public health. Recently, a new influenza D virus (IDV) was isolated from pigs and cattle. Here, we reveal that the IDV utilizes 9-O-acetylated sialic acids as its receptor for virus entry. Then, we determined the crystal structures of hemagglutinin-esterase-fusion glycoprotein (HEF) of IDV both in its free form and in complex with the receptor and enzymatic substrate analogs. The IDV HEF shows an extremely similar structural fold as the human-infecting influenza C virus (ICV) HEF. However, IDV HEF has an open receptor-binding cavity to accommodate diverse extended glycan moieties. This structural difference provides an explanation for the phenomenon that the IDV has a broad cell tropism. As IDV HEF is structurally and functionally similar to ICV HEF, our findings highlight the potential threat of the virus to public health

2,2,2-Trifluoro­ethyl 4-methyl­benzene­sulfonate

In the crystal structure of the title compound, C9H9F3O3S, inter­molecular C—H⋯O hydrogen bonds link the mol­ecules along the c-axis direction. Also present are slipped π–π stacking inter­actions between phenyl­ene rings, with perpendicular inter­planar distances of 3.55 (2) Å and centroid–centroid distances of 3.851 (2) Å

Methyl 2-amino-5-chloro­benzoate

The title compound, C8H8ClNO2, is almost planar, with an r.m.s. deviation of 0.0410 Å from the plane through the non-hydrogen atoms. In the crystal structure, inter­molecular N—H⋯O hydrogen bonds link the mol­ecules into chains along the b axis. An intra­molecular N—H⋯O hydrogen bond results in the formation of a six-membered ring

Inside-Out Radial Migration Facilitates Lineage-Dependent Neocortical Microcircuit Assembly

SummaryNeocortical excitatory neurons migrate radially along the glial fibers of mother radial glial progenitors (RGPs) in a birth-date-dependent inside-out manner. However, the precise functional significance of this well-established orderly neuronal migration remains largely unclear. Here, we show that strong electrical synapses selectively form between RGPs and their newborn progeny and between sister excitatory neurons in ontogenetic radial clones at the embryonic stage. Interestingly, the preferential electrical coupling between sister excitatory neurons, but not that between RGP and newborn progeny, is eliminated in mice lacking REELIN or upon clonal depletion of DISABLED-1, which compromises the inside-out radial neuronal migration pattern in the developing neocortex. Moreover, increased levels of Ephrin-A ligand or receptor that laterally disperse sister excitatory neurons also disrupt preferential electrical coupling between radially aligned sister excitatory neurons. These results suggest that RGP-guided inside-out radial neuronal migration facilitates the initial assembly of lineage-dependent precise columnar microcircuits in the neocortex

Dynamical response of fractional-order nonlinear system with combined parametric and forcing excitation

A dynamical analysis of a Mathieu-van der Pol-Duffing nonlinear system with fractional-order derivative under combined parametric and forcing excitation is studied in this paper. The approximate analytical solution is researched for 1/2 sub harmonic resonance coupled with primary parametric resonance based on the improved averaging approach. The steady-state periodic solution including its stability condition is established. The equivalent linear stiffness coefficient (ELDC) and equivalent linear damping coefficient (ELSC) for this nonlinear fractional-order oscillator are defined. Then, the numerical simulations are presented in three typical cases by iterative algorithms. The time history, phase portrait, FFT spectrum and Poincare maps are shown to explain the system response. Some different responses, such as quasi-periodic, multi-periodic and single periodic behaviors are observed and investigated. The results of comparisons between the numerical solutions and the approximate analytical solutions in three typical cases show the correctness of the analytical solutions. The influences of the fractional-order parameters on the system dynamical response are researched based on the ELDC and ELSC. Through analysis, it could be found that the increase of the fractional-order coefficient would result in the rightward and downward movements of the amplitude-frequency curves. The increase of the fractional-order coefficient will also move the bifurcation point rightwards and will make the existing range of steady-state solution larger. It could also be found that the ELSC will become larger and ELDC smaller when the fractional order is closer to zero, so that the decrease of the fractional order would make the response amplitude larger. At last, the detailed conclusions are summarized, which is beneficial to design and control this kind of fractional-order nonlinear system