644 research outputs found
Corner reflectors and Quantum-Non-Demolition Measurements in gravitational wave antennae
We propose Fabry-Perot cavity with corner reflectors instead of spherical
mirrors to reduce the contribution of thermoelastic noise in the coating which
is relatively large for spherical mirrors and which prevents the sensitivity
better than Standard Quantum Limit (SQL) from being achieved in laser
gravitational wave antenna. We demonstrate that thermo-refractive noise in
corner reflector (CR) is substantially smaller than SQL. We show that the
distortion of main mode of cavity with CR caused by tilt and displacement of
one reflector is smaller than for cavity with spherical mirrors. We also
consider the distortion caused by small nonperpendicularity of corner facets
and by optical inhomogeneity of fused silica which is proposed as a material
for corner reflectors.Comment: 12 pages, LaTex, 7 figure
Preparation of facilities for fundamental research with ultracold neutrons at PNPI
The WWR-M reactor of PNPI offers a unique opportunity to prepare a source for
ultracold neutrons (UCN) in an environment of high neutron flux (about 3*10^12
n/cm^2/s) at still acceptable radiation heat release (about 4*10^-3 W/g). It
can be realized within the reactor thermal column situated close to the reactor
core. With its large diameter of 1 m, this channel allows to install a 15 cm
thick bismuth shielding, a graphite premoderator (300 dm^3 at 20 K), and a
superfluid helium converter (35 dm^3). At a temperature of 1.2 K it is possible
to remove the heat release power of about 20 W. Using the 4pi flux of cold
neutrons within the reactor column can bring more than a factor 100 of cold
neutron flux incident on the superfluid helium with respect to the present cold
neutron beam conditions at the ILL reactor. The storage lifetime for UCN in
superfluid He at 1.2 K is about 30 s, which is sufficient when feeding
experiments requiring a similar filling time. The calculated density of UCN
with energy between 50 neV and 250 neV in an experimental volume of 40 liters
is about 10^4 n/cm^3. Technical solutions for realization of the project are
discussed.Comment: 10 pages, more detail
Transverse phase-locking in fully frustrated Josephson junction arrays: a new type of fractional giant steps
We study, analytically and numerically, phase locking of driven vortex
lattices in fully-frustrated Josephson junction arrays at zero temperature. We
consider the case when an ac current is applied {\it perpendicular} to a dc
current. We observe phase locking, steps in the current-voltage
characteristics, with a dependence on external ac-drive amplitude and frequency
qualitatively different from the Shapiro steps, observed when the ac and dc
currents are applied in parallel. Further, the critical current increases with
increasing transverse ac-drive amplitude, while it decreases for longitudinal
ac-drive. The critical current and the phase-locked current step width,
increase quadratically with (small) amplitudes of the ac-drive. For larger
amplitudes of the transverse ac-signal, we find windows where the critical
current is hysteretic, and windows where phase locking is suppressed due to
dynamical instabilities. We characterize the dynamical states around the
phase-locking interference condition in the curve with voltage noise,
Lyapunov exponents and Poincar\'e sections. We find that zero temperature
phase-locking behavior in large fully frustrated arrays is well described by an
effective four plaquette model.Comment: 12 pages, 11 figure
Effect of lurbinectedin on the QTc interval in patients with advanced solid tumors: an exposure–response analysis
Purpose: This study assessed the effect of lurbinectedin, a highly selective inhibitor of oncogenic transcription, on the change from baseline in Fridericia’s corrected QT interval (¿QTcF) and electrocardiography (ECG) morphological patterns, and lurbinectedin concentration–¿QTcF (C-¿QTcF) relationship, in patients with advanced solid tumors. Methods: Patients with QTcF = 500 ms, QRS < 110 ms, PR < 200 ms, and normal cardiac conduction and function received lurbinectedin 3.2 mg/m2 as a 1-h intravenous infusion every 3 weeks. ECGs were collected in triplicate via 12-lead digital recorder in treatment cycle 1 and 2 and analyzed centrally. ECG collection time-matched blood samples were drawn to measure lurbinectedin plasma concentration. No effect on QTc interval was concluded if the upper bound (UB) of the least square (LS) mean two-sided 90% confidence intervals (CI) for ¿QTcF at each time point was < 20 ms. C-¿QTcF was explored using linear mixed-effects analysis. Results: A total of 1707 ECGs were collected from 39 patients (females, 22; median age, 56 years). The largest UB of the 90% CI of ¿QTcF was 9.6 ms, thus lower than the more conservative 10 ms threshold established at the ICH E14 guideline for QT studies in healthy volunteers. C-¿QTcF was better fit by an effect compartment model, and the 90% CI of predicted ¿QTcF at Cmax was 7.81 ms, also below the 10 ms threshold of clinical concern. Conclusions: ECG parameters and C-¿QTcF modelling in this prospective study indicate that lurbinectedin was not associated with a clinically relevant effect on cardiac repolarization
Observing the First Stars and Black Holes
The high sensitivity of JWST will open a new window on the end of the
cosmological dark ages. Small stellar clusters, with a stellar mass of several
10^6 M_sun, and low-mass black holes (BHs), with a mass of several 10^5 M_sun
should be directly detectable out to redshift z=10, and individual supernovae
(SNe) and gamma ray burst (GRB) afterglows are bright enough to be visible
beyond this redshift. Dense primordial gas, in the process of collapsing from
large scales to form protogalaxies, may also be possible to image through
diffuse recombination line emission, possibly even before stars or BHs are
formed. In this article, I discuss the key physical processes that are expected
to have determined the sizes of the first star-clusters and black holes, and
the prospect of studying these objects by direct detections with JWST and with
other instruments. The direct light emitted by the very first stellar clusters
and intermediate-mass black holes at z>10 will likely fall below JWST's
detection threshold. However, JWST could reveal a decline at the faint-end of
the high-redshift luminosity function, and thereby shed light on radiative and
other feedback effects that operate at these early epochs. JWST will also have
the sensitivity to detect individual SNe from beyond z=10. In a dedicated
survey lasting for several weeks, thousands of SNe could be detected at z>6,
with a redshift distribution extending to the formation of the very first stars
at z>15. Using these SNe as tracers may be the only method to map out the
earliest stages of the cosmic star-formation history. Finally, we point out
that studying the earliest objects at high redshift will also offer a new
window on the primordial power spectrum, on 100 times smaller scales than
probed by current large-scale structure data.Comment: Invited contribution to "Astrophysics in the Next Decade: JWST and
Concurrent Facilities", Astrophysics & Space Science Library, Eds. H.
Thronson, A. Tielens, M. Stiavelli, Springer: Dordrecht (2008
Comparative Study of Multifragmentation of Gold Nuclei Induced by Relativistic Protons, He, and C
Multiple emission of intermediate-mass fragments has been studied for the
collisions of p, He and C on Au with the setup FASA. The mean
IMF multiplicities (for the events with at least one IMF) are saturating at the
value of for the incident energies above 6 GeV. The observed IMF
multiplicities cannot be described in a two-stage scenario, a fast cascade
followed by a statistical multifragmentation. Agreement with the measured IMF
multiplicities is obtained by introducing an intermediate phase and modifying
empirically the excitation energies and masses of the remnants.
The angular distributions and energy spectra from the p-induced collisions
are in agreement with the scenario of ``thermal'' multifragmentation of a hot
and diluted target spectator. In the case of C+Au(22.4 GeV) and
He(14.6 GeV)+Au collisions, deviations from a pure thermal break-up are
seen in the energy spectra of the emitted fragments, which are harder than
those both from model calculations and from the measured ones for p-induced
collisions. This difference is attributed to a collective flow.Comment: 33 pages 15 figures, accepted in Nucl. Phys.
Transverse Phase Locking for Vortex Motion in Square and Triangular Pinning Arrays
We analyze transverse phase locking for vortex motion in a superconductor
with a longitudinal DC drive and a transverse AC drive. For both square and
triangular arrays we observe a variety of fractional phase locking steps in the
velocity versus DC drive which correspond to stable vortex orbits. The locking
steps are more pronounced for the triangular arrays which is due to the fact
that the vortex motion has a periodic transverse velocity component even for
zero transverse AC drive. All the steps increase monotonically in width with AC
amplitude. We confirm that the width of some fractional steps in the square
arrays scales as the square of the AC driving amplitude. In addition we
demonstrate scaling in the velocity versus applied DC driving curves at
depinning and on the main step, similar to that seen for phase locking in
charge-density wave systems. The phase locking steps are most prominent for
commensurate vortex fillings where the interstitial vortices form symmetrical
ground states. For increasing temperature, the fractional steps are washed out
very quickly, while the main step gains a linear component and disappears at
melting. For triangular pinning arrays we again observe transverse phase
locking, with the main and several of the fractional step widths scaling
linearly with AC amplitude.Comment: 10 pages, 14 postscript figure
Bottom Production
We review the prospects for bottom production physics at the LHC.Comment: 74 pages, Latex, 71 figures, to appear in the Report of the ``1999
CERN Workshop on SM physics (and more) at the LHC'', P. Nason, G. Ridolfi, O.
Schneider G.F. Tartarelli, P. Vikas (conveners
Charged BTZ-like Black Holes in Higher Dimensions
Motivated by many worthwhile paper about (2 + 1)-dimensional BTZ black holes,
we generalize them to to (n + 1)-dimensional solutions, so called BTZ-like
solutions. We show that the electric field of BTZ-like solutions is the same as
(2 + 1)-dimensional BTZ black holes, and also their lapse functions are
approximately the same, too. By these similarities, it is also interesting to
investigate the geometric and thermodynamics properties of the BTZ-like
solutions. We find that, depending on the metric parameters, the BTZ-like
solutions may be interpreted as black hole solutions with inner (Cauchy) and
outer (event) horizons, an extreme black hole or naked singularity. Then, we
calculate thermodynamics quantities and conserved quantities, and show that
they satisfy the first law of thermodynamics. Finally, we perform a stability
analysis in the canonical ensemble and show that the BTZ-like solutions are
stable in the whole phase space.Comment: 5 pages, two column format, one figur
Evidence for a narrow dip structure at 1.9 GeV/c in diffractive photoproduction
A narrow dip structure has been observed at 1.9 GeV/c in a study of
diffractive photoproduction of the final state performed by the
Fermilab experiment E687.Comment: The data of Figure 6 can be obtained by downloading the raw data file
e687_6pi.txt. v5 (2nov2018): added Fig. 7, the 6 pion energy distribution as
requested by a reade
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