8,434 research outputs found
Cavity optoelectromechanical regenerative amplification
Cavity optoelectromechanical regenerative amplification is demonstrated. An
optical cavity enhances mechanical transduction, allowing sensitive measurement
even for heavy oscillators. A 27.3 MHz mechanical mode of a microtoroid was
linewidth narrowed to 6.6\pm1.4 mHz, 30 times smaller than previously achieved
with radiation pressure driving in such a system. These results may have
applications in areas such as ultrasensitive optomechanical mass spectroscopy
Effects of metallic spacer in layered superconducting Sr2(MgTi)O3FeAs
The highly two-dimensional superconducting system
Sr2(MgTi)O3FeAs, recently synthesized in the range of 0.2 < y <
0.5, shows an Mg concentration-dependent . Reducing the Mg concentration
from y=0.5 leads to a sudden increase in , with a maximum ~40 K at
y=0.2. Using first principles calculations, the unsynthesized stoichiometric
y=0 and the substoichiometric y=0.5 compounds have been investigated. For the
50% Mg-doped phase (y=0.5), Sr2(MgTi)O3 layers are completely
insulating spacers between FeAs layers, leading to the fermiology such as that
found for other Fe pnictides. At y=0, representing a phase with metallic
Sr2TiO3 layers, the -centered Fe-derived Fermi surfaces (FSs)
considerably shrink or disappear. Instead, three -centered Ti FSs
appear, and in particular two of them have similar size, like in MgB2.
Interestingly, FSs have very low Fermi velocity in large fractions: the lowest
being 0.6 cm/s. Furthermore, our fixed spin moment calculations
suggest the possibility of magnetic ordering, with magnetic Ti and nearly
nonmagnetic Fe ions. These results indicate a crucial role of
Sr2(MgTi)O3 layers in this superconductivity.Comment: 7 pages; Proceedings of ICSM-201
Interferometric detection of mode splitting for whispering gallery mode biosensors
Sensors based on whispering gallery mode resonators can detect single
nanoparticles and even single molecules. Particles attaching to the resonator
induce a doublet in the transmission spectrum which provides a self-referenced
detection signal. However, in practice this spectral feature is often obscured
by the width of the resonance line which hides the doublet structure. This
happens particularly in liquid environments that reduce the effective Q factor
of the resonator. In this paper we demonstrate an interferometric set-up that
allows the direct detection of the hidden doublet and thus provides a pathway
for developing practical sensor applications.Comment: 9 page
Effect of LSVT on Lexical Tone in Speakers with Parkinson's Disease
Lee Silverman Voice Treatment (LSVT) has well-documented treatment efficacy for individuals with hypokinetic dysarthria associated with Parkinson's disease (PD). Positive changes have been noted after treatment not only for vocal loudness but also for many other speech dimensions, including intonation (monotonicity). There have been few studies investigating the effect of LSVT on lexical tone which, like intonation, is controlled by variations in fundamental frequency. This study involved 12 Cantonese speakers with idiopathic PD who were enrolled in a standard LVST treatment protocol. Speech data were collected 3-4 days before treatment and 1 day after treatment. A wide variety of perceptual and acoustic variables were analyzed. The results showed significant improvements in loudness and intonation after treatment, but no significant changes in lexical tone. These results have theoretical implications for the relationship between tone and intonation and for models of the physiological control of fundamental frequency
A Toxicological Study of HangAmDan-B in Mice
AbstractThe aim of the study was to define the toxicity of HangAmDan-B (HAD-B) in mice over the short and long term. HAD-B was studied in 1-week single and 5-week repeated oral dose toxicity tests on male Imprinting Control Region mice. Doses used in 1 week single oral dose toxicity tests were 0, 0.2, 1, 5, and 25 g/kg/day and those of repeated toxicity test were 0, 0.04, 0.2, 1, and 2 g/kg/day. Blood and urine samples were assayed and their morphology observed. Numerical data were compared using Mann-Whitney U test and analysis of variance. Significantly decreased red blood cell levels in mice from S2-HAD-B, S3-HAD-B, S4-HAD-B, and S5-HAD-B groups were observed in single oral dose toxicity tests. Hemoglobin, hematocrit, and mean cell hemoglobin values in mice from the S4-HAD-B and S5-HAD-B groups were also significantly decreased. No mortalities or significant differences in all factors were observed during the dosing period of the repeated dose toxicity test. Administering 2 g/kg/day of HAD-B in mice over a 5-week period showed no significant hematological changes. However, risk of anemia with more than 5 g/kg/ day administration of HAD-B was found. In general, HAD-B appears to be safe and nontoxic, and a no observed adverse effect level in mice was established at 2 g/kg/ day. This data serves as satisfactory preclinical evidence for the safety of HAD-B should a future clinical trial for HAD-B be launched. Further studies are required to confirm these safety results and to carry out a safety trial in humans
Heisenberg-picture approach to the exact quantum motion of a time-dependent forced harmonic oscillator
In the Heisenberg picture, the generalized invariant and exact quantum
motions are found for a time-dependent forced harmonic oscillator. We find the
eigenstate and the coherent state of the invariant and show that the
dispersions of these quantum states do not depend on the external force. Our
formalism is applied to several interesting cases.Comment: 15 pages, two eps files, to appear in Phys. Rev. A 53 (6) (1996
Born Effective Charges and Infrared Response of LiBC
Calculations of the zone center optical mode frequencies (including LO-TO
splitting), Born effective charges Z for each atom,
dielectric constants and , and the dielectric
response in the infrared, using density functional linear response theory, are
reported. Calculated Raman modes are in excellent agreement with experimental
values (170 cm and 1170 cm), while it will require better
experimental data to clarify the infrared active mode frequencies. The Born
effective charges Z (i) have surprisingly different values
for B and C, and (ii) show considerable anisotropy. Relationships between the
effective charges and LO-TO splitting are discussed, and the predicted
reflectivity in the range 0 -- 1400 cm is presented. These results hold
possible implications for Li removal in LiBC, and C substition for B in
MgB.Comment: 6 pages, 3 figure
Constraints on the R-parity- and Lepton-Flavor-Violating Couplings from B0 Decats to Two Charged Leptons
We derive the upper bounds on certain products of R-parity- and
lepton-flavor-violating couplings from the decays of the neutral meson into
two charged leptons. These modes of decays can constrain the product
combinations of the couplings with one or more heavy generation indices. We
find that most of these bounds are stronger than the previous ones.Comment: Table is changed; version to appear in Phys. Rev.
The nature and role of trap states in a dendrimer-based organic field-effect transistor explosive sensor
We report the fabrication and charge transport characterization of carbazole dendrimer-based organic field-effect transistors (OFETs) for the sensing of explosive vapors. After exposure to para-nitrotoluene (pNT) vapor, the OFET channel carrier mobility decreases due to trapping induced by the absorbed pNT. The influence of trap states on transport in devices before and after exposure to pNT vapor has been determined using temperature-dependent measurements of the field-effect mobility. These data clearly show that the absorption of pNT vapor into the dendrimer active layer results in the formation of additional trap states. Such states inhibit charge transport by decreasing the density of conducting states. (C) 2013 AIP Publishing LLC
Study protocol for a randomised controlled trial of invasive versus conservative management of primary spontaneous pneumothorax
INTRODUCTION: Current management of primary spontaneous pneumothorax (PSP) is variable, with little evidence from randomised controlled trials to guide treatment. Guidelines emphasise intervention in many patients, which involves chest drain insertion, hospital admission and occasionally surgery. However, there is evidence that conservative management may be effective and safe, and it may also reduce the risk of recurrence. Significant questions remain regarding the optimal initial approach to the management of PSP
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