2,712 research outputs found
Field-induced magnetic ordering in the Haldane system PbNi2V2O8
The Haldane system PbNi2V2O8 was investigated by the temperature dependent
magnetization M(T) measurements at fields higher than H_c, with H_c the
critical fields necessary to close the Haldane gap. It is revealed that M(T)
for H > H_c exhibits a cusp-like minimum at T_{min}, below which M(T) increases
with decreasing T having a convex curve. These features have been observed for
both and , with c-axis being parallel to the chain.
These data indicate the occurrence of field-induced magnetic ordering around
T_{min}. Phase boundaries for and do not cross each
other, consistent with the theoretical calculation for negative single-ion
anisotropy D.Comment: 3 figures, submitted to Phys. Rev.
Final-state read-out of exciton qubits by observing resonantly excited photoluminescence in quantum dots
We report on a new approach to detect excitonic qubits in semiconductor
quantum dots by observing spontaneous emissions from the relevant qubit level.
The ground state of excitons is resonantly excited by picosecond optical
pulses. Emissions from the same state are temporally resolved with picosecond
time resolution. To capture weak emissions, we greatly suppress the elastic
scattering of excitation beams, by applying obliquely incident geometry to the
micro photoluminescence set-up. Rabi oscillations of the ground-state excitons
appear to be involved in the dependence of emission intensity on excitation
amplitude.Comment: 4 pages, 4 figures, to appear in Appl. Phys. Let
Single crystal MgB2 with anisotropic superconducting properties
The discovery of superconductor in magnesium diboride MgB2 with high Tc (39
K) has raised some challenging issues; whether this new superconductor
resembles a high temperature cuprate superconductor(HTS) or a low temperature
metallic superconductor; which superconducting mechanism, a phonon- mediated
BCS or a hole superconducting mechanism or other new exotic mechanism may
account for this superconductivity; and how about its future for applications.
In order to clarify the above questions, experiments using the single crystal
sample are urgently required. Here we have first succeeded in obtaining the
single crystal of this new MgB2 superconductivity, and performed its electrical
resistance and magnetization measurements. Their experiments show that the
electronic and magnetic properties depend on the crystallographic direction.
Our results indicate that the single crystal MgB2 superconductor shows
anisotropic superconducting properties and thus can provide scientific basis
for the research of its superconducting mechanism and its applications.Comment: 7 pages pdf fil
Tachycardia-induced myocardial ischemia and diastolic dysfunction potentiate secretion of ANP, not BNP, in hypertrophic cardiomyopathy
Kido, S; Hasebe, N; Ishii, Y; Kikuchi, K, AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 290(3), H1064-H1070, 2006. "Copyright 2006 by the American Physical Society."
publisherThe aim of this study was to investigate what factor determines tachycardia-induced secretion of atrial and brain natriuretic peptides (ANP and BNP, respectively) in patients with hypertrophic cardiomyopathy (HCM). HCM patients with normal left ventricular (LV) systolic function and intact coronary artery (n = 22) underwent rapid atrial pacing test. The cardiac secretion of ANP and BNP and the lactate extraction ratio (LER) were evaluated by using blood samples from the coronary sinus and aorta. LV end-diastolic pressure (LVEDP) and the time constant of LV relaxation of tau were measured by a catheter-tip transducer. These parameters were compared with normal controls (n = 8). HCM patients were divided into obstructive (HOCM) and nonobstructive (HNCM) groups. The cardiac secretion of ANP was significantly increased by rapid pacing in HOCM from 384 ± 101 to 1,268 ± 334 pg/ml (P < 0.05); however, it was not significant in control and HNCM groups. In contrast, the cardiac secretion of BNP was fairly constant and rather significantly decreased in HCM (P < 0.01). The cardiac ANP secretion was significantly correlated with changes in LER (r = –0.57, P < 0.01) and tau (r = 0.73, P < 0.001) in HCM patients. Tachycardia potentiates the cardiac secretion of ANP, not BNP, in patients with HCM, particularly when it induces myocardial ischemia and LV diastolic dysfunction
Dynamical Casimir effect for TE and TM modes in a resonant cavity bisected by a plasma sheet
Parametric photon creation via the dynamical Casimir effect (DCE) is
evaluated numerically, in a three-dimensional rectangular resonant cavity
bisected by a semiconductor diaphragm (SD), which is irradiated by a pulsed
laser with frequency of GHz order. The aim of this paper is to determine some
of the optimum conditions required to detect DCE photons relevant to a novel
experimental detection system. We expand upon the thin plasma sheet model
[Crocce et al., Phys. Rev. A 70 033811 (2004)] to estimate the number of
photons for both TE and TM modes at any given SD position. Numerical
calculations are performed considering up to 51 inter-mode couplings by varying
the SD location, driving period and laser power without any perturbations. It
is found that the number of photons created for TE modes strongly depends on SD
position, where the strongest enhancement occurs at the midpoint (not near the
cavity wall); while TM modes have weak dependence on SD position. Another
important finding is the fact that significant photon production for TM
modes still takes place at the midpoint even for a low laser power of 0.01
micro J/pulse, although the number of TE photons decreases almost
proportionately with laser power. We also find a relatively wide tuning range
for both TE and TM modes that is correlated with the frequency variation of the
instantaneous mode functions caused by the interaction between the cavity
photons and conduction electrons in the SD excited by a pulsed laser.Comment: 9 pages, 8 figure files; version 2, minor grammatical changes and two
references added; version 4 agrees with version in Phys. Rev. A; DOI no.
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