8,792 research outputs found
Energy Gaps and Kohn Anomalies in Elemental Superconductors
The momentum and temperature dependence of the lifetimes of acoustic phonons
in the elemental superconductors Pb and Nb was determined by resonant spin-echo
spectroscopy with neutrons. In both elements, the superconducting energy gap
extracted from these measurements was found to converge with sharp anomalies
originating from Fermi-surface nesting (Kohn anomalies) at low temperatures.
The results indicate electron many-body correlations beyond the standard
theoretical framework for conventional superconductivity. A possible mechanism
is the interplay between superconductivity and spin- or charge-density-wave
fluctuations, which may induce dynamical nesting of the Fermi surface
Constraints on nuclear matter parameters of an Effective Chiral Model
Within an effective non-linear chiral model, we evaluate nuclear matter
parameters exploiting the uncertainties in the nuclear saturation properties.
The model is sternly constrained with minimal free parameters, which display
the interlink between nuclear incompressibility (), the nucleon effective
mass (), the pion decay constant () and the meson
mass (). The best fit among the various parameter set is then
extracted and employed to study the resulting Equation of state (EOS). Further,
we also discuss the consequences of imposing constraints on nuclear EOS from
Heavy-Ion collision and other phenomenological model predictions.Comment: 10 pages, 8 figure
Collapse to Black Holes in Brans-Dicke Theory: I. Horizon Boundary Conditions for Dynamical Spacetimes
We present a new numerical code that evolves a spherically symmetric
configuration of collisionless matter in the Brans-Dicke theory of gravitation.
In this theory the spacetime is dynamical even in spherical symmetry, where it
can contain gravitational radiation. Our code is capable of accurately tracking
collapse to a black hole in a dynamical spacetime arbitrarily far into the
future, without encountering either coordinate pathologies or spacetime
singularities. This is accomplished by truncating the spacetime at a spherical
surface inside the apparent horizon, and subsequently solving the evolution and
constraint equations only in the exterior region. We use our code to address a
number of long-standing theoretical questions about collapse to black holes in
Brans-Dicke theory.Comment: 46 pages including figures, uuencoded gz-compressed postscript,
Submitted to Phys Rev
The Essence of Transpersonal Psychology Contemporary Views
The authors compiled 80 chronologically ordered passages from the contemporary psychology
literature that address the essence of transpersonal psychology. A thematic analysis of
these passages revealed that the two most frequent categories, occurring 53 (66.2%) and 49
(61.2%) times respectively, were: (a) Going beyond or transcending the individual, ego, self,
the personal, personality, or personal identity; existence of a deeper, true, or authentic Self;
and (b) Spirituality, psychospiritual, psychospiritual development, the spiritual, spirit. Other,
less frequent, themes included: special states of consciousness; interconnectivity/unity; going
beyond other schools of psychology; emphasis on a scientific approach; mysticism; full range
of consciousness; greater potential; inclusion of non-Western psychologies; meditation; and
existence of a wider reality
Encoded Hydrogel Microparticles for Sensitive and Multiplex microRNA Detection Directly from Raw Cell Lysates
In recent years, microRNAs (miRNAs) have emerged as promising diagnostic markers because of their unique dysregulation patterns under various disease conditions and high stability in biological fluids. However, current methods of analyzing miRNA levels typically require RNA isolation, which is cumbersome and time-consuming. To achieve high-throughput and accurate miRNA profiling, this study eliminates the need for purification steps by detecting miRNA directly from raw cellular lysate using nonfouling polyethylene glycol microparticles. In contrast to recent studies on direct miRNA measurements from cell lysate, our hydrogel-based system provides high-confidence quantification with robust performance. The lysis buffer for the assay was optimized to maximize reaction and labeling efficiency, and this assay has a low limit of detection (<1000 cells) without target amplification. Additionally, the capability for multiplexing was demonstrated through analyzing the levels of three endogenous miRNAs in 3T3 cell lysate. This versatile platform holds great potential for rapid and reliable direct miRNA quantification in complex media, and can be further extended to single-cell analysis by exploiting the flexibility and scalability of our system.National Cancer Institute (U.S.) (Grant 5R21CA177393-02
Gravitational Radiation Instability in Hot Young Neutron Stars
We show that gravitational radiation drives an instability in hot young
rapidly rotating neutron stars. This instability occurs primarily in the l=2
r-mode and will carry away most of the angular momentum of a rapidly rotating
star by gravitational radiation. On the timescale needed to cool a young
neutron star to about T=10^9 K (about one year) this instability can reduce the
rotation rate of a rapidly rotating star to about 0.076\Omega_K, where \Omega_K
is the Keplerian angular velocity where mass shedding occurs. In older colder
neutron stars this instability is suppressed by viscous effects, allowing older
stars to be spun up by accretion to larger angular velocities.Comment: 4 Pages, 2 Figure
Neutron scattering study of soft phonons and diffuse scattering in insulating LaSrCuO
Soft phonons and diffuse scattering in insulating LaSrCuO
() have been studied by the neutron scattering technique. The X-point
phonon softens from high temperature towards the structural transition
temperature K, and the Z-point phonon softens again below 200 K.
The Z-point phonon softening persists to low temperature, in contrast to the
behavior observed in the superconducting compound, in which the
Z-point phonon hardens below . The diffuse scattering associated with the
structural phase transition at 410 K appears at commensurate positions. These
results highlight interesting differences between superconducting and
insulating samples.Comment: 5 pages, 5 figure
Structural instability associated with the tilting of CuO6 octahedra in La2-xSrxCuO4
Comprehensive inelastic neutron-scattering measurements were performed to
study the soft optical phonons in La2-xSrxCuO4 at x=0.10, 0.12 and 0.18. We
found at x=0.18 that the softening of Z-point phonon, suggesting incipient
structural transition from the low-temperature orthorhombic (LTO) to
low-temperature tetragonal (LTT) phase, breaks at Tc, which is consistent with
the previous report by Lee et al. for the optimally doped x=0.15 sample. As for
x=0.10 and 0.12, on the other hand, the softening continues even below Tc. It
is thus clarified that the breaking of soft phonon is characteristic of
La2-xSrxCuO4 in the optimally and overdoped regions. In the course of studying
the soft phonons, we discovered that a central peak remains above the LTO to
high-temperature tetragonal (HTT) phase transition at Ts1 and splits into
incommensurate components along the (1 1 0)HTT direction at higher
temperatures. This is a common feature for both x=0.12 and 0.18 and their
temperature dependences of the splitting 2d can be scaled by using a
renormalized temperature T/Ts1. In the high temperature limit, d saturates
around d ~ 0.12 r.l.u., which value is close to the splitting of incommensurate
magnetic signals. This implies that the incipient lattice modulation starts
appearing at very high temperature. Details of this modulation and its
relations with other properties are, however, not yet clarified.Comment: 7 pages, 5 eps figure
Serum levels of matrix metalloproteinases-2 and-9 and their tissue inhibitors in inflammatory neuromuscular disorders
We monitored serum levels of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) before and during intravenously applied immunoglobulin (IVIG) therapy in 33 patients with chronic immune-mediated neuropathies and myopathies and 15 controls. Baseline MMP-2 and TIMP-2 serum levels were lower and MMP-9 and TIMP-1 serum levels higher in all patients compared to age-matched controls. Eight days after IVIG treatment, MMP-2, TIMP-2, and TIMP-1 serum levels increased, while MMP-9 serum levels decreased, indicating tissue repair. After 60 days, MMP-9 levels increased, MMP-2 approached normal levels, while TIMP-1 and TIMP-2 serum levels were below day 8 levels, indicating relapsing tissue damage. Comparing the MMP/TIMP results with the clinical courses, IVIG treatment tended to change MMP/TIMP levels in a way that paralleled clinical improvement and relapse. In sum, during a distinct time period, IVIG therapy seems to be able to modulate VIMP-mediated tissue repair. Copyright (c) 2006 S. Karger AG, Basel
Scaling of the conductance distribution near the Anderson transition
The single parameter scaling hypothesis is the foundation of our
understanding of the Anderson transition. However, the conductance of a
disordered system is a fluctuating quantity which does not obey a one parameter
scaling law. It is essential to investigate the scaling of the full conductance
distribution to establish the scaling hypothesis. We present a clear cut
numerical demonstration that the conductance distribution indeed obeys one
parameter scaling near the Anderson transition
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