28,525 research outputs found
model and Higgs mass in standard model calculated by Gaussian effective potential approach with a new regularization-renormalization method
Basing on new regularization-renormalization method, the
model used in standard model is studied both perturbatively and
nonperturbatively (by Gaussian effective potential). The invariant property of
two mass scales is stressed and the existence of a (Landau) pole is emphasized.
Then after coupling with the SU(2)U(1) gauge fields, the Higgs mass in
standard model (SM) can be calculated as 138GeV. The critical
temperature () for restoration of symmetry of Higgs field, the critical
energy scale (, the maximum energy scale under which the lower
excitation sector of the GEP is valid) and the maximum energy scale
(, at which the symmetry of the Higgs field is restored) in the
standard model are 476 GeV, GeV
and GeVv respectively.Comment: 12 pages, LaTex, no figur
A nonlocal eigenvalue problem and the stability of spikes for reaction-diffusion systems with fractional reaction rates
We consider a nonlocal eigenvalue problem which arises in the study of stability of spike solutions for reaction-diffusion systems with
fractional reaction rates such as the Sel'kov model, the
Gray-Scott system, the hypercycle Eigen and Schuster, angiogenesis, and the generalized Gierer-Meinhardt
system.
We give some sufficient and explicit conditions for stability
by studying the corresponding nonlocal eigenvalue problem in a new
range of parameters
Anisotropic determined up to 92 T and the signature of multi-band superconductivity in Ca(PtAs)((FePt)As) superconductor
The upper critical fields, (), of single crystals of the
superconductor
Ca(PtAs)((FePt)As)
( 0.246) are determined over a wide range of temperatures
down to = 1.42 K and magnetic fields of up to 92 T. The
measurements of anisotropic () curves are performed in pulsed
magnetic fields using radio-frequency contactless penetration depth
measurements for magnetic field applied both parallel and perpendicular to the
\textbf{ab}-plane. Whereas a clear upward curvature in
() along \textbf{H}\textbf{c} is
observed with decreasing temperature, the ()
along \textbf{H}\textbf{ab} shows a flattening at low temperatures.
The rapid increase of the () at low
temperatures suggests that the superconductivity can be described by two
dominating bands. The anisotropy parameter,
, is 7 close
to and decreases considerably to 1 with decreasing temperature,
showing rather weak anisotropy at low temperatures.Comment: 4pages, 3figures, accepted PRB Rapid Communicatio
A research protocol for developing a Point-Of-Care Key Evidence Tool 'POCKET': a checklist for multidimensional evidence reporting on point-of-care in vitro diagnostics.
INTRODUCTION: Point-of-care in vitro diagnostics (POC-IVD) are increasingly becoming widespread as an acceptable means of providing rapid diagnostic results to facilitate decision-making in many clinical pathways. Evidence in utility, usability and cost-effectiveness is currently provided in a fragmented and detached manner that is fraught with methodological challenges given the disruptive nature these tests have on the clinical pathway. The Point-of-care Key Evidence Tool (POCKET) checklist aims to provide an integrated evidence-based framework that incorporates all required evidence to guide the evaluation of POC-IVD to meet the needs of policy and decisionmakers in the National Health Service (NHS). METHODS AND ANALYSIS: A multimethod approach will be applied in order to develop the POCKET. A thorough literature review has formed the basis of a robust Delphi process and validation study. Semistructured interviews are being undertaken with POC-IVD stakeholders, including industry, regulators, commissioners, clinicians and patients to understand what evidence is required to facilitate decision-making. Emergent themes will be translated into a series of statements to form a survey questionnaire that aims to reach a consensus in each stakeholder group to what needs to be included in the tool. Results will be presented to a workshop to discuss the statements brought forward and the optimal format for the tool. Once assembled, the tool will be field-tested through case studies to ensure validity and usability and inform refinement, if required. The final version will be published online with a call for comments. Limitations include unpredictable sample representation, development of compromise position rather than consensus, and absence of blinding in validation exercise. ETHICS AND DISSEMINATION: The Imperial College Joint Research Compliance Office and the Imperial College Hospitals NHS Trust R&D department have approved the protocol. The checklist tool will be disseminated through a PhD thesis, a website, peer-reviewed publication, academic conferences and formal presentations
Large magnetic penetration depth and thermal fluctuations in a Ca(PtAs)[(FePt)As] (x=0.097) single crystal
We have measured the temperature dependence of the absolute value of the
magnetic penetration depth in a
Ca(PtAs)[(FePt)As] (x=0.097)
single crystal using a low-temperature magnetic force microscope (MFM). We
obtain (0)1000 nm via extrapolating the data to .
This large and pronounced anisotropy in this system are responsible
for large thermal fluctuations and the presence of a liquid vortex phase in
this low-temperature superconductor with critical temperature of 11 K,
consistent with the interpretation of the electrical transport data. The
superconducting parameters obtained from and coherence length
place this compound in the extreme type \MakeUppercase{\romannumeral 2} regime.
Meissner responses (via MFM) at different locations across the sample are
similar to each other, indicating good homogeneity of the superconducting state
on a sub-micron scale
Characterization of the ZFX family of transcription factors that bind downstream of the start site of CpG island promoters
Our study focuses on a family of ubiquitously expressed human C₂H₂ zinc finger proteins comprised of ZFX, ZFY and ZNF711. Although their protein structure suggests that ZFX, ZFY and ZNF711 are transcriptional regulators, the mechanisms by which they influence transcription have not yet been elucidated. We used CRISPR-mediated deletion to create bi-allelic knockouts of ZFX and/or ZNF711 in female HEK293T cells (which naturally lack ZFY). We found that loss of either ZFX or ZNF711 reduced cell growth and that the double knockout cells have major defects in proliferation. RNA-seq analysis revealed that thousands of genes showed altered expression in the double knockout clones, suggesting that these TFs are critical regulators of the transcriptome. To gain insight into how these TFs regulate transcription, we created mutant ZFX proteins and analyzed them for DNA binding and transactivation capability. We found that zinc fingers 11–13 are necessary and sufficient for DNA binding and, in combination with the N terminal region, constitute a functional transactivator. Our functional analyses of the ZFX family provides important new insights into transcriptional regulation in human cells by members of the large, but under-studied family of C₂H₂ zinc finger proteins
ASTROD and ASTROD I -- Overview and Progress
In this paper, we present an overview of ASTROD (Astrodynamical Space Test of
Relativity using Optical Devices) and ASTROD I mission concepts and studies.
The missions employ deep-space laser ranging using drag-free spacecraft to map
the gravitational field in the solar-system. The solar-system gravitational
field is determined by three factors: the dynamic distribution of matter in the
solar system; the dynamic distribution of matter outside the solar system
(galactic, cosmological, etc.) and gravitational waves propagating through the
solar system. Different relativistic theories of gravity make different
predictions of the solar-system gravitational field. Hence, precise
measurements of the solar-system gravitational field test all these. The tests
and observations include: (i) a precise determination of the relativistic
parameters beta and gamma with 3-5 orders of magnitude improvement over
previous measurements; (ii) a 1-2 order of magnitude improvement in the
measurement of G-dot; (iii) a precise determination of any anomalous, constant
acceleration Aa directed towards the Sun; (iv) a measurement of solar angular
momentum via the Lense-Thirring effect; (v) the detection of solar g-mode
oscillations via their changing gravity field, thus, providing a new eye to see
inside the Sun; (vi) precise determination of the planetary orbit elements and
masses; (viii) better determination of the orbits and masses of major
asteroids; (ix) detection and observation of gravitational waves from massive
black holes and galactic binary stars in the frequency range 0.05 mHz to 5 mHz;
and (x) exploring background gravitational-waves.Comment: 17 pages, 6 figures, presented to The Third International ASTROD
Symposium on Laser Astrodynamics, Space Test of Relativity and
Gravitational-Wave Astronomy, Beijing, July 14-16, 2006; International
Journal of Modern Physics D, in press (2008
Existence and Stability of a Spike in the Central Component for a Consumer Chain Model
We study a three-component consumer chain model which is based on Schnakenberg type kinetics. In this model there is one consumer feeding on the producer and a second consumer feeding on the first consumer. This means that the first consumer (central component) plays a hybrid role: it acts both as consumer and producer. The model is an extension of the Schnakenberg model suggested in \cite{gm,schn1} for which there is only one producer and one consumer. It is assumed that both the producer and second consumer diffuse much faster than the central component. We construct single spike solutions on an interval for which the profile of the first consumer is that of a spike. The profiles of the producer and the second consumer only vary on a much larger spatial scale due to faster diffusion of these components. It is shown that there exist two different single spike solutions if the feed rates are small enough: a large-amplitude and a small-amplitude spike. We study the stability properties of these solutions in terms of the system parameters. We use a rigorous analysis for the linearized operator around single spike solutions based on nonlocal eigenvalue problems. The following result is established: If the time-relaxation constants for both producer and second consumer vanish, the large-amplitude spike solution is stable and the small-amplitude spike solution is unstable. We also derive results on the stability of solutions when these two time-relaxation constants are small. We show a new effect: if the time-relaxation constant of the second consumer is very small, the large-amplitude spike solution becomes unstable. To the best of our knowledge this phenomenon has not been observed before for the stability of spike patterns. It seems that this behavior is not possible for two-component reaction-diffusion systems but that at least three components are required. Our main motivation to study this system is mathematical since the novel interaction of a spike in the central component with two other components results in new types of conditions for the existence and stability of a spike. This model is realistic if several assumptions are made: (i) cooperation of consumers is prevalent in the system, (ii) the producer and the second consumer diffuse much faster than the first consumer, and (iii) there is practically an unlimited pool of producer. The first assumption has been proven to be correct in many types of consumer groups or populations, the second assumption occurs if the central component has a much smaller mobility than the other two, the third assumption is realistic if the consumers do not feel the impact of the limited amount of producer due to its large quantity. This chain model plays a role in population biology, where consumer and producer are often called predator and prey. This system can also be used as a model for a sequence of irreversible autocatalytic reactions in a container which is in contact with a well-stirred reservoir
Numerical simulation of time delay interferometry for eLISA/NGO
eLISA/NGO is a new gravitational wave detection proposal with arm length of
10^6 km and one interferometer down-scaled from LISA. Just like LISA and
ASTROD-GW, in order to attain the requisite sensitivity for eLISA/NGO, laser
frequency noise must be suppressed to below the secondary noises such as the
optical path noise, acceleration noise etc. In previous papers, we have
performed the numerical simulation of the time delay interferometry (TDI) for
LISA and ASTROD-GW with one arm dysfunctional by using the CGC 2.7 ephemeris.
The results are well below their respective limits which the laser frequency
noise is required to be suppressed. In this paper, we follow the same procedure
to simulate the time delay interferometry numerically. To do this, we work out
a set of 1000-day optimized mission orbits of the eLISA/NGO spacecraft starting
at January 1st, 2021 using the CGC 2.7 ephemeris framework. We then use the
numerical method to calculate the residual optical path differences in the
second-generation TDI solutions as in our previous papers. The maximum path
length difference, for all configurations calculated, is below 13 mm (43 ps).
It is well below the limit which the laser frequency noise is required to be
suppressed for eLISA/NGO. We compare and discuss the resulting differences due
to the different arm lengths for various mission proposals -- eLISA/NGO, an
NGO-LISA-type mission with a nominal arm length of 2 x 10^6 km, LISA and
ASTROD-GW.Comment: 17 pages, 13 figures, 3 tables, minor changes in description to match
the accepted version of Classical and Quantum Gravity. arXiv admin note: text
overlap with arXiv:1102.496
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