4,380 research outputs found
Berry Phase Effects on Electronic Properties
Ever since its discovery, the Berry phase has permeated through all branches
of physics. Over the last three decades, it was gradually realized that the
Berry phase of the electronic wave function can have a profound effect on
material properties and is responsible for a spectrum of phenomena, such as
ferroelectricity, orbital magnetism, various (quantum/anomalous/spin) Hall
effects, and quantum charge pumping. This progress is summarized in a
pedagogical manner in this review. We start with a brief summary of necessary
background, followed by a detailed discussion of the Berry phase effect in a
variety of solid state applications. A common thread of the review is the
semiclassical formulation of electron dynamics, which is a versatile tool in
the study of electron dynamics in the presence of electromagnetic fields and
more general perturbations. Finally, we demonstrate a re-quantization method
that converts a semiclassical theory to an effective quantum theory. It is
clear that the Berry phase should be added as a basic ingredient to our
understanding of basic material properties.Comment: 48 pages, 16 figures, submitted to RM
Longitudinal Optogenetic Motor Mapping Revealed Structural and Functional Impairments and Enhanced Corticorubral Projection after Contusive Spinal Cord Injury in Mice
Current evaluation of impairment and repair after spinal cord injury (SCI) is largely dependent on behavioral assessment and histological analysis of injured tissue and pathways. Here, we evaluated whether transcranial optogenetic mapping of motor cortex could reflect longitudinal structural and functional damage and recovery after SCI. In Thy1-Channelrhodopsin2 transgenic mice, repeated motor mappings were made by recording optogenetically evoked electromyograms (EMGs) of a hindlimb at baseline and 1 day and 2, 4, and 6 weeks after mild, moderate, and severe spinal cord contusion. Injuries caused initial decreases in EMG amplitude, losses of motor map, and subsequent partial recoveries, all of which corresponded to injury severity. Reductions in map size were positively correlated with motor performance, as measured by Basso Mouse Scale, rota-rod, and grid walk tests, at different time points, as well as with lesion area at spinal cord epicenter at 6 weeks post-SCI. Retrograde tracing with Fluoro-Gold showed decreased numbers of cortico- and rubrospinal neurons, with the latter being negatively correlated with motor map size. Combined retro- and anterograde tracing and immunostaining revealed more neurons activated in red nucleus by cortical stimulation and enhanced corticorubral axons and synapses in red nucleus after SCI. Electrophysiological recordings showed lower threshold and higher amplitude of corticorubral synaptic response after SCI. We conclude that transcranial optogenetic motor mapping is sensitive and efficient for longitudinal evaluation of impairment and plasticity of SCI, and that spinal cord contusion induces stronger anatomical and functional corticorubral connection that may contribute to spontaneous recovery of motor function
A Novel Joint Angle-Range-Velocity Estimation Method for MIMO-OFDM ISAC Systems
Integrated sensing and communications (ISAC) is emerging as a key technique
for next-generation wireless systems. In order to expedite the practical
implementation of ISAC within pervasive mobile networks, it is essential to
equip widely-deployed base stations with radar sensing capabilities. Thus, the
utilization of standardized multiple-input multiple-output (MIMO) orthogonal
frequency division multiplexing (OFDM) hardware architectures and waveforms
becomes pivotal for realizing seamless integration of effective communication
and sensing functionalities. In this paper, we introduce a novel joint
angle-range-velocity estimation algorithm for the MIMO-OFDM ISAC system. This
approach exclusively depends on conventional MIMO-OFDM communication waveforms,
which are widely adopted in wireless communications. Specifically, the
angle-range-velocity information of potential targets is jointly extracted by
utilizing all the received echo signals within a coherent processing interval
(CPI). Therefore, the proposed joint estimation algorithm can achieve larger
processing gains and higher resolution by fully exploiting echo signals and
jointly estimating the angle-range-velocity information. Theoretical analysis
for maximum unambiguous range, resolution, and processing gains are provided to
verify the advantages of the proposed joint estimation algorithm. Finally,
extensive numerical experiments are presented to demonstrate that the proposed
joint estimation approach can achieve significantly lower
root-mean-square-error (RMSE) of angle/range/velocity estimation for both
single-target and multi-target scenarios.Comment: 13 pages, 8 figures, submitted to IEEE Tran
Geography and similarity of regional cuisines in China
Food occupies a central position in every culture and it is therefore of
great interest to understand the evolution of food culture. The advent of the
World Wide Web and online recipe repositories has begun to provide
unprecedented opportunities for data-driven, quantitative study of food
culture. Here we harness an online database documenting recipes from various
Chinese regional cuisines and investigate the similarity of regional cuisines
in terms of geography and climate. We found that the geographical proximity,
rather than climate proximity is a crucial factor that determines the
similarity of regional cuisines. We develop a model of regional cuisine
evolution that provides helpful clues to understand the evolution of cuisines
and cultures.Comment: 13 pages, 11 figures and 2 table
Sharp One-Parameter Mean Bounds for Yang Mean
We prove that the double inequality Jα(a,b)<U(a,b)<Jβ(a,b) holds for all a,b>0 with a≠b if and only if α≤2/(π-2)=0.8187⋯ and β≥3/2, where U(a,b)=(a-b)/[2arctan((a-b)/2ab)], and Jp(a,b)=p(ap+1-bp+1)/[(p+1)(ap-bp)] (p≠0,-1), J0(a,b)=(a-b)/(loga-logb), and J-1(a,b)=ab(loga-logb)/(a-b) are the Yang and pth one-parameter means of a and b, respectively
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