3,713 research outputs found
Inflationary Hubble Parameter from the Gravitational Wave Spectrum in the General Slow-roll Approximation
Improved general slow-roll formulae giving the primordial gravitational wave
spectrum are derived in the present work. Also the first and second order
general slow-roll inverse formulae giving the Hubble parameter in terms of
the gravitational wave spectrum are derived. Moreover, the general slow-roll
consistency condition relating the scalar and tensor spectra is obtained
Breaking scale invariance from a singular inflaton potential
In this paper we break the scale invariance of the primordial power spectrum
of curvature perturbations of inflation. Introducing a singular behaviour due
to spontaneous symmetry breaking in the inflaton potential, we obtain fully
analytic expressions of scale dependent oscillation and a modulation in power
on small scale in the primordial spectrum. And we give the associated cosmic
microwave background and matter power spectra which we can observe now and
discuss the signature of the scale dependence. We also address the possibility
of whether some inflationary model with featured potential might mimic the
predictions of the scale invariant power spectrum. We present some examples
which illustrate such degeneracies.Comment: 20 pages, 9 figures; Discussion expanded and references added;
Miscellaneous typos correcte
Strange meson-nucleon states in the quark potential model
The quark potential model and resonating group method are used to investigate
the bound states and/or resonances. The model potential consists of
the t-channel and s-channel one-gluon exchange potentials and the confining
potential with incorporating the QCD renormalization correction and the
spin-orbital suppression effect in it. It was shown in our previous work that
by considering the color octet contribution, use of this model to investigate
the low energy elastic scattering leads to the results which are in pretty
good agreement with the experimental data. In this paper, the same model and
method are employed to calculate the masses of the bound systems.
For this purpose, the resonating group equation is transformed into a standard
Schr\"odinger equation in which a nonlocal effective interaction
potential is included. Solving the Schr\"odinger equation by the variational
method, we are able to reproduce the masses of some currently concerned
states and get a view that these states possibly exist as
molecular states. For the system, the same calculation gives no support to
the existence of the resonance which was announced
recently.Comment: 15 pages, 4 figure
The variation of relative magnetic helicity around major flares
We have investigated the variation of magnetic helicity over a span of
several days around the times of 11 X-class flares which occurred in seven
active regions (NOAA 9672, 10030, 10314, 10486, 10564, 10696, and 10720) using
the magnetograms taken by the Michelson Doppler Imager (MDI) on board the Solar
and Heliospheric Observatory (SOHO). As a major result we found that each of
these major flares was preceded by a significant helicity accumulation over a
long period (0.5 to a few days). Another finding is that the helicity
accumulates at a nearly constant rate and then becomes nearly constant before
the flares. This led us to distinguish the helicity variation into two phases:
a phase of monotonically increasing helicity and the following phase of
relatively constant helicity. As expected, the amount of helicity accumulated
shows a modest correlation with time-integrated soft X-ray flux during flares.
However, the average helicity change rate in the first phase shows even
stronger correlation with the time-integrated soft X-ray flux. We discuss the
physical implications of this result and the possibility that this
characteristic helicity variation pattern can be used as an early warning sign
for solar eruptions
Formation, Manipulation, and Elasticity Measurement of a Nanometric Column of Water Molecules
Nanometer-sized columns of condensed water molecules are created by an
atomic-resolution force microscope operated in ambient conditions. Unusual
stepwise decrease of the force gradient associated with the thin water bridge
in the tip-substrate gap is observed during its stretch, exhibiting regularity
in step heights (~0.5 N/m) and plateau lengths (~1 nm). Such "quantized"
elasticity is indicative of the atomic-scale stick-slip at the tip-water
interface. A thermodynamic-instability-induced rupture of the water meniscus
(5-nm long and 2.6-nm wide) is also found. This work opens a high-resolution
study of the structure and the interface dynamics of a nanometric aqueous
column.Comment: 4 pages, 3 figure
Quenched Charmed Meson Spectra using Tadpole Improved Quark Action on Anisotropic Lattices
Charmed meson charmonium spectra are studied with improved quark actions on
anisotropic lattices. We measured the pseudo-scalar and vector meson dispersion
relations for 4 lowest lattice momentum modes with quark mass values ranging
from the strange quark to charm quark with 3 different values of gauge coupling
and 4 different values of bare speed of light . With the bare
speed of light parameter tuned in a mass-dependent way, we study the mass
spectra of , , ,
, and mesons.
The results extrapolated to the continuum limit are compared with the
experiment and qualitative agreement is found.Comment: 8 pages, 2 figures, latex fil
Essential nonlinearities in hearing
Our hearing organ, the cochlea, evidently poises itself at a Hopf bifurcation
to maximize tuning and amplification. We show that in this condition several
effects are expected to be generic: compression of the dynamic range,
infinitely shrap tuning at zero input, and generation of combination tones.
These effects are "essentially" nonlinear in that they become more marked the
smaller the forcing: there is no audible sound soft enough not to evoke them.
All the well-documented nonlinear aspects of hearing therefore appear to be
consequences of the same underlying mechanism.Comment: 4 pages, 3 figure
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Smartphone-based pathogen diagnosis in urinary sepsis patients.
BackgroundThere is an urgent need for rapid, sensitive, and affordable diagnostics for microbial infections at the point-of-care. Although a number of innovative systems have been reported that transform mobile phones into potential diagnostic tools, the translational challenge to clinical diagnostics remains a significant hurdle to overcome.MethodsA smartphone-based real-time loop-mediated isothermal amplification (smaRT-LAMP) system was developed for pathogen ID in urinary sepsis patients. The free, custom-built mobile phone app allows the phone to serve as a stand-alone device for quantitative diagnostics, allowing the determination of genome copy-number of bacterial pathogens in real time.FindingsA head-to-head comparative bacterial analysis of urine from sepsis patients revealed that the performance of smaRT-LAMP matched that of clinical diagnostics at the admitting hospital in a fraction of the time (~1 h vs. 18-28 h). Among patients with bacteremic complications of their urinary sepsis, pathogen ID from the urine matched that from the blood - potentially allowing pathogen diagnosis shortly after hospital admission. Additionally, smaRT-LAMP did not exhibit false positives in sepsis patients with clinically negative urine cultures.InterpretationThe smaRT-LAMP system is effective against diverse Gram-negative and -positive pathogens and biological specimens, costs less than $100 US to fabricate (in addition to the smartphone), and is configurable for the simultaneous detection of multiple pathogens. SmaRT-LAMP thus offers the potential to deliver rapid diagnosis and treatment of urinary tract infections and urinary sepsis with a simple test that can be performed at low cost at the point-of-care. FUND: National Institutes of Health, Chan-Zuckerberg Biohub, Bill and Melinda Gates Foundation
Statistical Mechanics of Dilute Batch Minority Games with Random External Information
We study the dynamics and statics of a dilute batch minority game with random
external information. We focus on the case in which the number of connections
per agent is infinite in the thermodynamic limit. The dynamical scenario of
ergodicity breaking in this model is different from the phase transition in the
standard minority game and is characterised by the onset of long-term memory at
finite integrated response. We demonstrate that finite memory appears at the
AT-line obtained from the corresponding replica calculation, and compare the
behaviour of the dilute model with the minority game with market impact
correction, which is known to exhibit similar features.Comment: 22 pages, 6 figures, text modified, references updated and added,
figure added, typos correcte
QCD sum rules for the pseudoscalar decay constants - To constrain the strange quark mass
We study the higher order corrections of quark masses to the
Gell-MannOakesRenner (GOR) relation by constructing QCD sum rules
exclusively for pseudoscalar mesons from the axial-vector correlation function,
. To project out
the pseudoscalar meson contributions, we apply to this
correlation function and construct sum rules for the decay constants of
pseudoscalar mesons, and . The OPE is proportional to
quark masses due to PCAC. To leading order in quark mass, each sum rule
reproduces the corresponding GOR relation. For kaon and , the deviation
from the GOR relation due to higher orders in quark mass is found to be
substantial. But the deviation gives better agreements with the phenomenology.
Our sum rule provides a sensitive relation between and , which
stringently constrain the value for . To reproduce the experimental value
for , is found to be 186 MeV at 1 GeV scale. The sum
rule also supports this finding.Comment: 14 pages including 3 figures. slightly revised. Accepted for
publication in Physical Review
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