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A second-order class-D audio amplifier
Class-D audio amplifiers are particularly efficient, and this efficiency has led to their ubiquity in a wide range of modern electronic appliances. Their output takes the form of a high-frequency square wave whose duty cycle (ratio of on-time to off-time) is modulated at low frequency according to the audio signal. A mathematical model is developed here for a second-order class-D amplifier design (i.e., containing one second-order integrator) with negative feedback. We derive exact expressions for the dominant distortion terms, corresponding to a general audio input signal, and confirm these predictions with simulations. We also show how the observed phenomenon of “pulse skipping” arises from an instability of the analytical solution upon which the distortion calculations are based, and we provide predictions of the circumstances under which pulse skipping will take place, based on a stability analysis. These predictions are confirmed by simulations
Precise-Spike-Driven synaptic plasticity: Learning hetero-association of spatiotemporal spike patterns
10.1371/journal.pone.0078318PLoS ONE811-POLN
Highly Efficient Midinfrared On-Chip Electrical Generation of Graphene Plasmons by Inelastic Electron Tunneling Excitation
Inelastic electron tunneling provides a low-energy pathway for the excitation
of surface plasmons and light emission. We theoretically investigate tunnel
junctions based on metals and graphene. We show that graphene is potentially a
highly efficient material for tunneling excitation of plasmons because of its
narrow plasmon linewidths, strong emission, and large tunability in the
midinfrared wavelength regime. Compared to gold and silver, the enhancement can
be up to 10 times for similar wavelengths and up to 5 orders at their
respective plasmon operating wavelengths. Tunneling excitation of graphene
plasmons promises an efficient technology for on-chip electrical generation and
manipulation of plasmons for graphene-based optoelectronics and nanophotonic
integrated circuits.Comment: 12 pages, 7 figure
Photon-number-solving Decoy State Quantum Key Distribution
In this paper, a photon-number-resolving decoy state quantum key distribution
scheme is presented based on recent experimental advancements. A new upper
bound on the fraction of counts caused by multiphoton pulses is given. This
upper bound is independent of intensity of the decoy source, so that both the
signal pulses and the decoy pulses can be used to generate the raw key after
verified the security of the communication. This upper bound is also the lower
bound on the fraction of counts caused by multiphoton pulses as long as faint
coherent sources and high lossy channels are used. We show that Eve's coherent
multiphoton pulse (CMP) attack is more efficient than symmetric individual (SI)
attack when quantum bit error rate is small, so that CMP attack should be
considered to ensure the security of the final key. finally, optimal intensity
of laser source is presented which provides 23.9 km increase in the
transmission distance. 03.67.DdComment: This is a detailed and extended version of quant-ph/0504221. In this
paper, a detailed discussion of photon-number-resolving QKD scheme is
presented. Moreover, the detailed discussion of coherent multiphoton pulse
attack (CMP) is presented. 2 figures and some discussions are added. A
detailed cauculation of the "new" upper bound 'is presente
Toxicological evaluation of precocene II isolated from Ageratum conyzoides L. (Asteraceae) in Sprague Dawley rats
Precocene II (6,7-dimethoxy-2,2-dimethyl-2-chromene) was the main constituent isolated from Ageratum
conyzoides L. and reportedly possessed antifungal activity. The study investigated the isolation,
purification and toxicological effects of precocene II from A. conyzoides in Sprague Dawley rats.
Precocene II was isolated from the petroleum ether fraction of the plant and the structure was
determined by 1H-,13C-,DEPT-NMR and MS spectral techniques. Three groups of eight rats per group
were used for the study. While groups B and C were respectively administered with 25 and 50 mg/kg of
precocene II in 0.25% CMC-Na for 11 days by gastric intubation, group A was administered with 0.25%
CMC-Na and served as the control group. After the last treatment, animals were fasted overnight and on
the 12th day, they were injected intravenously with 0.2 ml/kg body weight of phenobarbital. Animals
were subsequently dissected from the abdominal region; blood was collected from the pulmonary vein
into EDTA anti-coagulated and non anti-coagulated tubes. The liver, kidney and spleen tissues were
extracted into separate bottles for histopathological examinations. Results from hematological study
indicated that the white blood cell (WBC), red blood cell (RBC), plateletcrit (PCT) and mean corpuscular hemoglobin count (MCHC) were significantly higher across the treated groups. Biochemical result showed that serum glucose level was significantly reduced in the treated groups. No apparent damage was noticed in the liver, kidney and spleen tissues. The result therefore suggests that precocene II
possesses hypoglycemic property and could alter some hematopoietic elements but was not toxic to the liver, kidney and spleen tissues
Evolution and maintenance of cooperation via inheritance of spatial neighbourhood
published_or_final_versio
Duration of untreated bipolar disorder: A multicenter study
Little is known about the demographic and clinical differences between short and long duration of untreated bipolar disorder (DUB) in Chinese patients. This study examined the demographic and clinical features of short (≤2 years) and long DUB (\u3e2 years) in China. A consecutively recruited sample of 555 patients with bipolar disorder (BD) was examined in 7 psychiatric hospitals and general hospital psychiatric units across China. Patients’ demographic and clinical characteristics were collected using a standardized protocol and data collection procedure. The mean DUB was 3.2 ± 6.0 years; long DUB accounted for 31.0% of the sample. Multivariate analyses revealed that longer duration of illness, diagnosis of BD type II, and earlier misdiagnosis of BD for major depressive disorder or schizophrenia were independently associated with long DUB. The mean DUB in Chinese BD patients was shorter than the reported figures from Western countries. The long-term impact of DUB on the outcome of BD is warranted
DeepTrace: Learning to Optimize Contact Tracing in Epidemic Networks with Graph Neural Networks
The goal of digital contact tracing is to diminish the spread of an epidemic
or pandemic by detecting and mitigating public health emergencies using digital
technologies. Since the start of the COVID- pandemic, a wide variety of
mobile digital apps have been deployed to identify people exposed to the
SARS-CoV-2 coronavirus and to stop onward transmission. Tracing sources of
spreading (i.e., backward contact tracing), as has been used in Japan and
Australia, has proven crucial as going backwards can pick up infections that
might otherwise be missed at superspreading events. How should robust backward
contact tracing automated by mobile computing and network analytics be
designed? In this paper, we formulate the forward and backward contact tracing
problem for epidemic source inference as maximum-likelihood (ML) estimation
subject to subgraph sampling. Besides its restricted case (inspired by the
seminal work of Zaman and Shah in 2011) when the full infection topology is
known, the general problem is more challenging due to its sheer combinatorial
complexity, problem scale and the fact that the full infection topology is
rarely accurately known. We propose a Graph Neural Network (GNN) framework,
named DeepTrace, to compute the ML estimator by leveraging the likelihood
structure to configure the training set with topological features of smaller
epidemic networks as training sets. We demonstrate that the performance of our
GNN approach improves over prior heuristics in the literature and serves as a
basis to design robust contact tracing analytics to combat pandemics
Insights into the molecular mechanism of RGL2-mediated inhibition of seed germination in Arabidopsis thaliana
10.1186/1471-2229-12-179BMC Plant Biology12
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