1,990 research outputs found
The Non-Perturbative Contribution to the Free Energy of Hot SU(N) Gauge Theory
The non-perturbative input necessary for the determination of the part of the weak coupling expansion of the free energy density for
SU(2) and SU(3) gauge theories is estimated. Although the perturbative
information completing the contribution to this order is missing, we give
arguments that the magnetic fluctuations are dominated by screened elementary
magnetic gluons.Comment: Talk presented at LATTICE96(finite temperature) 3 pages Latex2e, 3 ps
figures, 14 k
Screening Masses and Improvement in Pure SU(2) Lattice Gauge Theory at High Temperatures
From the long-distance behaviour of gluon and Polyakov loop correlation
functions we extract masses resp. energies in the electric and magnetic
sectors. We discuss their dependence on the temperature and on the momentum as
well as the relevance of an improvement of the lattice discretization of the
action.Comment: Talk presented at LATTICE97 (Finite Temperature and Density) by J.
Rank, 3 pages, LaTeX File, espcrc2.sty Style File and 2 eps figures include
Observations of the J = 10 manifold of the pure rotational band of phosphine on Saturn
Saturn was observed in the vicinity of the J = 10 manifold of the pure rotational band of phosphine on 1984 July 10 and 12 from NASA's Kuiper Airborne Observatory with the facility far-infrared cooled grating spectrometer. On each night observations of the full disk plus rings were made at 4 to 6 discrete wavelengths which selectively sampled the manifold and the adjacent continuum. The previously reported detection of this manifold is confirmed. After subtraction of the flux due to the rings, the data are compared with disk-averaged models of Saturn. It is found that PH3 must be strongly depleted above the thermal inversion (approx. 70 mbar). The best fitting models consistent with other observational constaints indicate that PH3 is significantly depleted at even deeper atmospheric levels ( or = 500 mbar), implying an eddy diffusion coefficient for Saturn of 10 to the 4 cm sq/sec
Counselling to include tailored use of combined oral contraception in clinical practice: an evaluation
BACKGROUND: Combined oral contraception (COC, 'the pill') remains the most prescribed method of contraception in the UK. Although a variety of regimens for taking monophasic COC are held to be clinically safe, women are not routinely counselled about these choices and there is a lack of evidence on how to provide this information to women. AIM: To assess the usefulness and feasibility of including tailored use of monophasic COC within routine COC counselling in a sexual and reproductive health (SRH) service using a structured format. METHOD: Using a structured format, healthcare professionals (HCPs) counselled new and established COC users attending an SRH service about standard and tailored ways of taking the pill. Questionnaires were used to survey both the HCPs and patients immediately after the initial consultation, and then the patients again 8 weeks later. RESULTS: Nearly all patients (98%, n=95) felt it was helpful to be informed of the different ways of using monophasic COC by the HCP, without giving too much information at one time (96%, n=108). The HCPs were confident of their COC counselling (99%, n=110) and did not think the consultations took significantly longer (88%, n=98). CONCLUSION: This study demonstrates that information on different pill taking regimens is useful and acceptable to patients, and can improve contraceptive pill user choice. It is also feasible for HCPs to perform COC counselling to include tailored pill use during routine consultations in a clinical setting
Infrared spectra of WC10 planetary nebulae nuclei
The 5.2 to 8.0 micron spectra are presented for two planetary nebulae nuclei Hen1044 (He2-113) and CPD-56 8032. The unidentified infrared (UIR) emission bands at 6.2 microns, 6.9 microns, 7.7 microns are present in the spectra of Hen1044 and in CPD-56 8032, and the 8.6 micron band is present in the long wavelength shoulder of the 7.7 micron band in the spectrum of CPD-56 8032. The 8 to 13 micron spectra of these two stars by Aitken et. al. clearly show the presence of the 8.6 micron band in He2-113 while weakly resolving this feature in the spectra of CPD-56 8032. In their spectra the 11.3 micron band is also clearly detected in both objects. The 6.2 micron and 7.7 micron bands are characteristic of the infrared active C-C stretching modes in polycyclic aromatic hydrocarbons (PAHs); the 3.3 micron, 8.6 micron, and 11.3 micron bands are respectively assigned to the in-plane stretching mode, the in-plane bending mode, and the out-of-plane bending mode of the aromatic CH bond. The weak 6.9 micron emission feature is attributed to the UIR spectrum by Bregman et. al. The IRAS LRS spectra of He2-113 (IRAS 14562-5406) and CPD-56 8032 (IRAS 17047-5650) are presented. Cohen et. al. identify the broad plateau from 11.3 to 13.0 microns in the spectrum of He2-113 with increased hydrogenation of PAHs. This broad plateau is not seen in the LRS spectrum of CPD-56 8032. Also, He2-113 has greater infrared excess emission in the 17-22 micron region than does CPD-56 8032
Some 5-13 micrometer airborne observations of Comet Wilson 1986l: Preliminary results
Comet Wilson was observed from the Kuiper Airborne Observatory approximately 23.6 and 25.7 Apr. 1987, UT (approx. 3 to 5 days after perihelion) using the NASA-Ames Faint Object Grating Spectrometer. Spectrophotometric data were observed with a 21 inch aperture between 5 and 13 micrometer and with a spectral resolution of 50 to 100. Spectra of the inner coma and nucleus reveal a fairly smooth continuum with little evidence of silicate emission. The 5 to 8 micrometer color temperature of the comet was 300 + or - 15 K, approx. 15 percent higher than the equilibrium blackbody temperature. All three spectra of the nucleus show a new emission feature at approx. 12.25 micrometer approx. two channels (.22 micrometer) wide. Visual and photographic observations made during the time of these observations showed a broad faint, possible two component tail. No outburst activity was observed
The Gluon Propagator at High Temperature
We study the gluon propagator in Landau gauge in the deconfined phase of
gauge theory. From the long-distance behaviour of correlation functions
of temporal and spatial components of the gauge fields we extract electric
() and magnetic () screening masses. For temperatures larger than
twice we find no additional temperature dependence in , while
drops with increasing temperature. The decrease is consistent with
the expected behaviour, . We find
and .Comment: 11 pages, TEX-file, 5 PS-figur
Infrared receivers for low background astronomy: Incoherent detectors and coherent devices from one micrometer to one millimeter
The status of incoherent detectors and coherent receivers over the infrared wavelength range from one micrometer to one millimeter is described. General principles of infrared receivers are included, and photon detectors, bolometers, coherent receivers, and important supporting technologies are discussed, with emphasis on their suitability for low background astronomical applications. Broad recommendations are presented and specific opportunities are identified for development of improved devices
Gauge Boson Masses in the 3-d, SU(2) Gauge-Higgs Model
We study gauge boson propagators in the symmetric and symmetry broken phases
of the 3-d, gauge-Higgs model. Correlation functions for the gauge
fields are calculated in Landau gauge. They are found to decay exponentially at
large distances leading to a non-vanishing mass for the gauge bosons. We find
that the W-boson screening mass drops in the symmetry broken phase when
approaching the critical temperature. In the symmetric phase the screening mass
stays small and is independent of the scalar--gauge coupling (the hopping
parameter). Numerical results coincide with corresponding calculations
performed for the pure gauge theory. We find in this phase
which is consistent with analytic calculations based on gap equations. This is,
however, significantly smaller than masses extracted from gauge invariant
vector boson correlation functions. As internal consistency check we also have
calculated correlation functions for gauge invariant operators leading to
scalar and vector boson masses. Finite lattice size effects have been
systematically analyzed on lattices of size with and
.Comment: 20 pages, LaTeX2e File, 8 Postscript figure
Comparative Analysis of Tandem Repeats from Hundreds of Species Reveals Unique Insights into Centromere Evolution
Centromeres are essential for chromosome segregation, yet their DNA sequences
evolve rapidly. In most animals and plants that have been studied, centromeres
contain megabase-scale arrays of tandem repeats. Despite their importance, very
little is known about the degree to which centromere tandem repeats share
common properties between different species across different phyla. We used
bioinformatic methods to identify high-copy tandem repeats from 282 species
using publicly available genomic sequence and our own data. The assumption that
the most abundant tandem repeat is the centromere DNA was true for most species
whose centromeres have been previously characterized, suggesting this is a
general property of genomes. Our methods are compatible with all current
sequencing technologies. Long Pacific Biosciences sequence reads allowed us to
find tandem repeat monomers up to 1,419 bp. High-copy centromere tandem repeats
were found in almost all animal and plant genomes, but repeat monomers were
highly variable in sequence composition and in length. Furthermore,
phylogenetic analysis of sequence homology showed little evidence of sequence
conservation beyond ~50 million years of divergence. We find that despite an
overall lack of sequence conservation, centromere tandem repeats from diverse
species showed similar modes of evolution, including the appearance of higher
order repeat structures in which several polymorphic monomers make up a larger
repeating unit. While centromere position in most eukaryotes is epigenetically
determined, our results indicate that tandem repeats are highly prevalent at
centromeres of both animals and plants. This suggests a functional role for
such repeats, perhaps in promoting concerted evolution of centromere DNA across
chromosomes
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