14,233 research outputs found
Soft Spin Wave Near nu=1: Evidence for a Magnetic Instability in Skyrmion Systems
The ground state of the two dimensional electron gas near =1 is
investigated by inelastic light scattering measurements carried down to very
low temperatures. Away from =1, the ferromagnetic spin wave collapses and
a new low-energy spin wave emerges below the Zeeman gap. The emergent spin wave
shows soft behavior as its energy increases with temperature and reaches the
Zeeman energy for temperatures above 2 K. The observed softening indicates an
instability of the two dimensional electron gas towards a magnetic order that
breaks spin rotational symmetry. We discuss our findings in light of the
possible existence of a Skyrme crystal.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let
On fuzzy BCC-ideals over a t-norm
Using a t-norm T, the notion of T-fuzzy BCC-ideals of BCC-algebras is introduced, and some of their properties are investigated.
Connections between different types of fuzzy BCC-ideals induced by
t-norms are described
A key to room-temperature ferromagnetism in Fe-doped ZnO: Cu
Successful synthesis of room-temperature ferromagnetic semiconductors,
ZnFeO, is reported. The essential ingredient in achieving
room-temperature ferromagnetism in bulk ZnFeO was found to be
additional Cu doping. A transition temperature as high as 550 K was obtained in
ZnFeCuO; the saturation magnetization at room
temperature reached a value of per Fe. Large
magnetoresistance was also observed below K.Comment: 11 pages, 4 figures; to appear in Appl. Phys. Let
Precision spectroscopy and density-dependent frequency shifts in ultracold Sr
By varying the density of an ultracold Sr sample from cm
to cm, we make the first definitive measurement of the
density-related frequency shift and linewidth broadening of the -
optical clock transition in an alkaline earth system. In addition, we
report the most accurate measurement to date of the Sr
optical clock transition frequency. Including a detailed analysis of systematic
errors, the frequency is () Hz.Comment: 4 pages, 4 figures, 1 table. submitte
Acute Hypercapnia/Ischemia Alters the Esterification of Arachidonic Acid and Docosahexaenoic Acid Epoxide Metabolites in Rat Brain Neutral Lipids.
In the brain, approximately 90% of oxylipins are esterified to lipids. However, the significance of this esterification process is not known. In the present study, we (1) validated an aminopropyl solid phase extraction (SPE) method for separating esterified lipids using 100 and 500 mg columns and (2) applied the method to quantify the distribution of esterified oxylipins within phospholipids (PL) and neutral lipids (NL) (i.e. triacylglycerol and cholesteryl ester) in rats subjected to head-focused microwave fixation (controls) or CO2 -induced hypercapnia/ischemia. We hypothesized that oxylipin esterification into these lipid pools will be altered following CO2 -induced hypercapnia/ischemia. Lipids were extracted from control (n = 8) and CO2 -asphyxiated (n = 8) rat brains and separated on aminopropyl cartridges to yield PL and NL. The separated lipid fractions were hydrolyzed, purified with hydrophobic-lipophilic-balanced SPE columns, and analyzed with ultra-high-pressure liquid chromatography coupled to tandem mass spectrometry. Method validation showed that the 500 mg (vs 100 mg) aminopropyl columns yielded acceptable separation and recovery of esterified fatty acid epoxides but not other oxylipins. Two epoxides of arachidonic acid (ARA) were significantly increased, and three epoxides of docosahexaenoic acid (DHA) were significantly decreased in brain NL of CO2 -asphyxiated rats compared to controls subjected to head-focused microwave fixation. PL-bound fatty acid epoxides were highly variable and did not differ significantly between the groups. This study demonstrates that hypercapnia/ischemia alters the concentration of ARA and DHA epoxides within NL, reflecting an active turnover process regulating brain fatty acid epoxide concentrations
Hawking radiation from the Schwarzschild black hole with a global monopole via gravitational anomaly
Hawking flux from the Schwarzschild black hole with a global monopole is
obtained by using Robinson and Wilczek's method. Adopting a dimension reduction
technique, the effective quantum field in the (3+1)--dimensional global
monopole background can be described by an infinite collection of the
(1+1)--dimensional massless fields if neglecting the ingoing modes near the
horizon, where the gravitational anomaly can be cancelled by the
(1+1)--dimensional black body radiation at the Hawking temperature.Comment: 4 pages, no figure, 3nd revsion with one reference adde
Netons: Vibrations of Complex Networks
We consider atoms interacting each other through the topological structure of
a complex network and investigate lattice vibrations of the system, the quanta
of which we call {\em netons} for convenience. The density of neton levels,
obtained numerically, reveals that unlike a local regular lattice, the system
develops a gap of a finite width, manifesting extreme rigidity of the network
structure at low energies. Two different network models, the small-world
network and the scale-free network, are compared: The characteristic structure
of the former is described by an additional peak in the level density whereas a
power-law tail is observed in the latter, indicating excitability of netons at
arbitrarily high energies. The gap width is also found to vanish in the
small-world network when the connection range .Comment: 9 pages, 6 figures, to appear in JP
Tune-In: Training Under Negative Environments with Interference for Attention Networks Simulating Cocktail Party Effect
We study the cocktail party problem and propose a novel attention network
called Tune-In, abbreviated for training under negative environments with
interference. It firstly learns two separate spaces of speaker-knowledge and
speech-stimuli based on a shared feature space, where a new block structure is
designed as the building block for all spaces, and then cooperatively solves
different tasks. Between the two spaces, information is cast towards each other
via a novel cross- and dual-attention mechanism, mimicking the bottom-up and
top-down processes of a human's cocktail party effect. It turns out that
substantially discriminative and generalizable speaker representations can be
learnt in severely interfered conditions via our self-supervised training. The
experimental results verify this seeming paradox. The learnt speaker embedding
has superior discriminative power than a standard speaker verification method;
meanwhile, Tune-In achieves remarkably better speech separation performances in
terms of SI-SNRi and SDRi consistently in all test modes, and especially at
lower memory and computational consumption, than state-of-the-art benchmark
systems.Comment: Accepted in AAAI 202
Sandglasset: A Light Multi-Granularity Self-attentive Network For Time-Domain Speech Separation
One of the leading single-channel speech separation (SS) models is based on a
TasNet with a dual-path segmentation technique, where the size of each segment
remains unchanged throughout all layers. In contrast, our key finding is that
multi-granularity features are essential for enhancing contextual modeling and
computational efficiency. We introduce a self-attentive network with a novel
sandglass-shape, namely Sandglasset, which advances the state-of-the-art (SOTA)
SS performance at significantly smaller model size and computational cost.
Forward along each block inside Sandglasset, the temporal granularity of the
features gradually becomes coarser until reaching half of the network blocks,
and then successively turns finer towards the raw signal level. We also unfold
that residual connections between features with the same granularity are
critical for preserving information after passing through the bottleneck layer.
Experiments show our Sandglasset with only 2.3M parameters has achieved the
best results on two benchmark SS datasets -- WSJ0-2mix and WSJ0-3mix, where the
SI-SNRi scores have been improved by absolute 0.8 dB and 2.4 dB, respectively,
comparing to the prior SOTA results.Comment: Accepted in ICASSP 202
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