5,800 research outputs found
Theory of plasmon decay in dense plasmas and warm dense matter
The decay of the Langmuir waves in dense plasmas is not accurately predicted
by the prevalent Landau damping theory. A dielectric function theory is
introduced, predicting much higher damping than the Landau damping theory. This
strong damping is in better agreement with the experimentally observed data in
metals. It is shown that the strong plasmon decay leads to the existence of a
parameter regime where the backward Raman scattering is unstable while the
forward Raman scattering is stable. This regime may be used to create intense
x-ray pulses, by means of the the backward Raman compression. The optimal pulse
duration and intensity is estimated
Initialization by measurement of a two-qubit superconducting circuit
We demonstrate initialization by joint measurement of two transmon qubits in
3D circuit quantum electrodynamics. Homodyne detection of cavity transmission
is enhanced by Josephson parametric amplification to discriminate the two-qubit
ground state from single-qubit excitations non-destructively and with 98.1%
fidelity. Measurement and postselection of a steady-state mixture with 4.7%
residual excitation per qubit achieve 98.8% fidelity to the ground state, thus
outperforming passive initialization.Comment: 5 pages, 4 figures, and Supplementary Information (7 figures, 1
table
PERLAKSANAAN DAN KEBERKESANAN KAEDAH LATTICE DALAM PENGAJARAN KEMAHIRAN MATEMATIK: SATU KAJIAN KES DI SEKOLAH RENDAH
Dalam pendidikan matematik, penguasaan pendaraban nombor merupakan salah satu kemahiran penting untuk matapelajaran matematik di sekolah rendah. Seandainya murid-murid tidak dapat menguasai kemahiran ini pada peringkat awal pembelajaran matematik, mereka bakal menghadapi pelbagai masalah dan cabaran dalam penguasaan kemahiran seterusnya yang memerlukan kemahiran pendaraban sebagai asas. Oleh yang demikian, satu kajian telah dijalankan untuk menilai sejauh manakah keberkesanan perlaksanaan kaedah Lattice dalam membantu meningkatkan kemahiran asas pendaraban, yang melibatkan pendaraban nombor dua dan tiga digit. Rekabentuk kajian yang digunakan ialah kajian kuasi-experimental yang melibatkan sampel murid sebanyak 15 orang murid darjah empat di Sekolah Jenis Kebangsaan Cina Chung Cheng, Batu Pahat, Johor. Ujian Pra dan Pos telah dilakukan bagi membandingkan tahap pencapaian sampel kajian sebelum dan selepas rawatan menerusi empat sesi intervensi. Secara keseluruhannya, hasil kajian telah mendapati peningkatan purata skor sebanyak 42.67 peratus selepas rawatan dengan penggunaan kaedah Lattice. Kesimpulannya, kaedah Lattice merupakan kaedah yang berkesan dalam meningkatkan pemahaman dan kemahiran responden dalam topik pendaraban
TOPICAL REVIEW: Slow light in semiconductor heterostructures
This paper presents an overview of slow light in semiconductor heterostructures. The focus of this paper is to provide a unified framework to summarize and compare various physical mechanisms of slow light proposed and demonstrated in the past few years. We expand and generalize the discussions on fundamental limitation of slow light and the delay–bandwidth product trade-off to include gain systems and other mechanisms such as injection locking. We derive the maximum fractional delay and compare the differences between material dispersion and waveguide dispersion based devices. The delay–bandwidth product is proportional to the square root of the device length for a material dispersion based device but has a linear relationship for a waveguide dispersion based device. Possible scenarios to overcome the delay–bandwidth product limitation are discussed. The prospects of slow light in various applications are also investigated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58125/2/d7_5_R01.pd
Remarks on Renormalization of Black Hole Entropy
We elaborate the renormalization process of entropy of a nonextremal and an
extremal Reissner-Nordstr\"{o}m black hole by using the Pauli-Villars
regularization method, in which the regulator fields obey either the
Bose-Einstein or Fermi-Dirac distribution depending on their spin-statistics.
The black hole entropy involves only two renormalization constants. We also
discuss the entropy and temperature of the extremal black hole.Comment: 14 pages, revtex, no figure
Association between actigraphy-derived physical activity and cognitive performance in patients with schizophrenia
An association between low levels of physical activity and impaired cognitive performance in schizophrenia has been proposed, but most studies have relied on self-report measures of activity. This study examined the association between actigraphy-derived physical activity and cognitive performance adjusting for multiple covariates in patients with schizophrenia.
Patients with schizophrenia (n = 199) were recruited from chronic psychiatric wards, and 60 age-, sex- and body mass index-matched comparison participants were recruited from the staff of two hospitals and universities. Physical activity was assessed objectively for 7 days using an ActiGraph. Cognitive performance was assessed with the Cognitrone test from the Vienna Test System and the Grooved Pegboard Test. Demographic variables, metabolic parameters, positive and negative symptoms, duration of illness and hospitalization, and medication use were included as covariates. Pearson correlations and multivariable linear regressions were conducted to examine the associations between physical activity levels and cognitive performance.
Patients with schizophrenia were less physically active and had poorer performance on attention/concentration and speed of processing than the comparison group. Patients with schizophrenia who spent more time in light physical activity showed better performance on attention/concentration (β = 0.198, p = 0.020) and speed of processing (β= −0.169, p = 0.048) tasks than those who were less active. Cognitive performance was also associated with moderate-vigorous physical activity, but the effect was no longer significant once light physical activity had been taken into account.
This study provides evidence for a positive association between objectively measured light physical activity and cognitive performance in people with schizophrenia, after adjustment for multiple confounders
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