6,816 research outputs found
750 GeV Resonance in the Gauged -Extended MSSM
Recently the ATLAS and CMS collaborations at the LHC announced their
observation of a potential 750 GeV di-photon resonance, after analyzing the
TeV LHC data. This observation has significant implications for
low-energy supersymmetry. Beyond the MSSM and the NMSSM, we study the
MSSM-extensions with an extra gauge symmetry. The anomaly cancellation
and the spontaneous breaking of the non-decoupled generically require
introducing vector-like supermultiplets (both colored and color-neutral ones)
and singlet supermultiplets, respectively. We illustrate that the potential 750
GeV resonance () can be accommodated in various mechanisms, as a
singlet-like scalar or pseudoscalar. Three benchmark scenarios are presented:
(1) vector-like quarks (VLQ) mediated ; (2) scalar
VLQ mediated ; (3) heavy scalar (pseudo-scalar)
associated production . Additionally, we notice
that the -mediated vector boson fusion production and -associated
production , if yielding a signal rate of the observed level,
might have been excluded by the searches for via Drell-Yan process at the
LHC.Comment: v3, figure update with corresponding modification in discussion,
version accepted by PL
Space-Time Phononic Crystals with Anomalous Topological Edge States
It is well known that an interface created by two topologically distinct
structures could host nontrivial edge states that are immune to defects. In
this letter, we introduce a one-dimensional space-time phononic crystal and
study the associated anomalous topological edge states. A space-decoupled time
modulation is assumed. While preserving the key topological feature of the
system, such a modulation also duplicates the edge state mode across the
spectrum, both inside and outside the band gap. It is shown that, in contrast
to conventional topological edge states which are excited by frequencies in the
Bragg regime, the time-modulation-induced frequency conversion can be leveraged
to access topological edge states at a deep subwavelength scale where the
entire phononic crystal size is merely 1/5.1 of the wavelength. This remarkable
feature could open a new route for designing miniature devices that are based
on topological physics
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Postsynaptic protein organization revealed by electron microscopy.
Neuronal synapses are key devices for transmitting and processing information in the nervous system. Synaptic plasticity, generally regarded as the cellular basis of learning and memory, involves changes of subcellular structures that take place at the nanoscale. High-resolution imaging methods, especially electron microscopy (EM), have allowed for quantitative analysis of such nanoscale structures in different types of synapses. In particular, the semi-ordered organization of neurotransmitter receptors and their interacting scaffolds in the postsynaptic density have been characterized for both excitatory and inhibitory synapses by studies using various EM techniques such as immuno-EM, electron tomography of high-pressure freezing and freeze-substituted samples, and cryo electron tomography. These techniques, in combination with new correlative approaches, will further facilitate our understanding of the molecular organization underlying diverse functions of neuronal synapses
Accumulation of Dense Core Vesicles in Hippocampal Synapses Following Chronic Inactivity.
The morphology and function of neuronal synapses are regulated by neural activity, as manifested in activity-dependent synapse maturation and various forms of synaptic plasticity. Here we employed cryo-electron tomography (cryo-ET) to visualize synaptic ultrastructure in cultured hippocampal neurons and investigated changes in subcellular features in response to chronic inactivity, a paradigm often used for the induction of homeostatic synaptic plasticity. We observed a more than 2-fold increase in the mean number of dense core vesicles (DCVs) in the presynaptic compartment of excitatory synapses and an almost 20-fold increase in the number of DCVs in the presynaptic compartment of inhibitory synapses after 2 days treatment with the voltage-gated sodium channel blocker tetrodotoxin (TTX). Short-term treatment with TTX and the N-methyl-D-aspartate receptor (NMDAR) antagonist amino-5-phosphonovaleric acid (AP5) caused a 3-fold increase in the number of DCVs within 100 nm of the active zone area in excitatory synapses but had no significant effects on the overall number of DCVs. In contrast, there were very few DCVs in the postsynaptic compartments of both synapse types under all conditions. These results are consistent with a role for presynaptic DCVs in activity-dependent synapse maturation. We speculate that these accumulated DCVs can be released upon reactivation and may contribute to homeostatic metaplasticity
Evaluation of a wave-vector-frequency-domain method for nonlinear wave propagation
A wave-vector-frequency-domain method is presented to describe one-directional forward or backward acoustic wave propagation in a nonlinear homogeneous medium. Starting from a frequency-domain representation of the second-order nonlinear acoustic wave equation, an implicit solution for
the nonlinear term is proposed by employing the Green’s function. Its approximation, which is more suitable for numerical implementation, is used. An error study is carried out to test the efficiency of the model by comparing the results with the Fubini solution. It is shown that the error grows as the propagation distance and step-size increase. However, for the specific case tested, even at a step size as large as one wavelength, sufficient accuracy for plane-wave propagation is observed. A two-dimensional steered transducer problem is explored to verify the nonlinear acoustic field directional independence
of the model. A three-dimensional single-element transducer problem is solved to verify the forward model by comparing it with an existing nonlinear wave propagation code. Finally, backward-projection behavior is examined. The sound field over a plane in an absorptive medium is backward
projected to the source and compared with the initial field, where good agreement is observed
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