1,469 research outputs found
Classical Cepheids: Yet another version of the Baade-Becker-Wesselink method
We propose a new version of the Baade--Becker--Wesselink technique, which
allows one to independently determine the colour excess and the intrinsic
colour of a radially pulsating star, in addition to its radius, luminosity, and
distance. It is considered to be a generalization of the Balona approach. The
method also allows the function F(CI) = BC + 10 log (Teff) for the class of
pulsating stars considered to be calibrated. We apply this technique to a
number of classical Cepheids with very accurate light and radial-velocity
curves and with bona fide membership in open clusters (SZ Tau, CF Cas, U Sgr,
DL Cas, GY Sge), and find the results to agree well with the reddening
estimates of the host open clusters. The new technique can also be applied to
other pulsating variables, e.g. RR Lyrae and RV Tauri.Comment: 6 pages, 2 figures, 1 table; Submitted to Astrophysical Bulletin,
201
Measuring the Reduced Shear
Neglecting the second order corrections in weak lensing measurements can lead
to a few percent uncertainties on cosmic shears, and becomes more important for
cluster lensing mass reconstructions. Existing methods which claim to measure
the reduced shears are not necessarily accurate to the second order when a
point spread function (PSF) is present. We show that the method of Zhang (2008)
exactly measures the reduced shears at the second order level in the presence
of PSF. A simple theorem is provided for further confirming our calculation,
and for judging the accuracy of any shear measurement method at the second
order based on its properties at the first order. The method of Zhang (2008) is
well defined mathematically. It does not require assumptions on the
morphologies of galaxies and the PSF. To reach a sub-percent level accuracy,
the CCD pixel size is required to be not larger than 1/3 of the Full Width at
Half Maximum (FWHM) of the PSF. Using a large ensemble (> 10^7) of mock
galaxies of unrestricted morphologies, we find that contaminations to the shear
signals from the noise of background photons can be removed in a well defined
way because they are not correlated with the source shapes. The residual shear
measurement errors due to background noise are consistent with zero at the
sub-percent level even when the amplitude of such noise reaches about 1/10 of
the source flux within the half-light radius of the source. This limit can in
principle be extended further with a larger galaxy ensemble in our simulations.
On the other hand, the source Poisson noise remains to be a cause of systematic
errors. For a sub-percent level accuracy, our method requires the amplitude of
the source Poisson noise to be less than 1/80 ~ 1/100 of the source flux within
the half-light radius of the source, corresponding to collecting roughly 10^4
source photons.Comment: 18 pages, 3 figures, 4 tables, minor changes from the previous
versio
Associations of dietary protein intake with fat free mass and grip strength: cross-sectional study in 146,816 UK Biobank participants
Adequate dietary protein intake is important for the maintenance of fat-free mass (FFM) and muscle strength: optimal requirements remain unknown. The aim of the current study was to explore the associations of protein intake with FFM and grip strength. We used baseline data from the UK Biobank (146,816 participants aged 40-69 years with data collected 2007-2010 across the UK) to examine the associations of protein intake with FFM and grip strength. Protein intake was positively associated with FFM (men 5.1% [95% CI: 5.0; 5.2] and women 7.7% [95% CI: 7.7; 7.8]) and grip strength (men 0.076 kg/kg [95% CI: 0.074; 0.078] and women 0.074 kg/kg [95% CI: 0.073; 0.076]) per 0.5 grams per kg body mass per day (g/kg/day) increment in protein intake. FFM and grip strength were higher with higher intakes across the full range of intakes, i.e. highest in those reporting consuming > 2.0 g/grams per kg/day independently of socio-demographics, other dietary measures, physical activity and comorbidities. FFM and grip strength were lower with age, but this association did not differ by protein intake categories (P > 0.05). Current recommendation for all adults (40-69 years) for protein intake (0.8 grams per kg body mass per day) may need to be increased to optimise FFM and grip strength
Two-loop corrections to the Isgur-Wise function in QCD sum rules
We complete the QCD sum rule analysis of the Isgur Wise form factor
at next-to-leading order in renormalization-group improved
perturbation theory. To this end, the exact result for the two-loop corrections
to the perturbative contribution is derived using the heavy quark effective
theory. Several techniques for the evaluation of two-loop integrals involving
two different types of heavy quark propagators are discussed in detail, among
them the methods of integration by parts and differential equations. The
order- corrections to the Isgur-Wise function turn out to be small
and well under control. At large recoil, they tend to decrease the form factor
by .Comment: 24 pages (REVTEX), 2 figures available upon request, SLAC-PUB-599
Implications of the Top Quark Mass Measurement for the CKM Parameters, and CP Asymmetries
Motivated by the recent determination of the top quark mass by the CDF
collaboration, \mt =174 \pm 10 ^{+13}_{-12} GeV, we review and update the
constraints on the parameters of the quark flavour mixing matrix in
the standard model. In performing our fits, we use inputs from the measurements
of the following quantities: (i) \abseps, the CP-violating parameter in
decays, (ii) \delmd, the mass difference due to the \bdbdbar\ mixing, (iii)
the matrix elements \absvcb and \absvub, and (iv) -hadron lifetimes. We
find that the allowed region of the unitarity triangle is very large, mostly
due to theoretical uncertainties. (This emphasizes the importance of
measurements of CP-violating rate asymmetries in the system.) Nevertheless,
the present data do somewhat restrict the allowed values of the coupling
constant product and the renormalization-scale
invariant bag constant . With the updated CKM matrix we present the
currently-allowed range of the ratio , as well as
the standard model predictions for the \bsbsbar\ mixing parameter \xs and the
quantities , and , which characterize
the CP-asymmetries in -decays. The ALEPH collaboration has recently reported
a significant improvement on the lower limit on the \bs-\bsb mass
difference, (95\% C.L.). This has interesting
consequences for the CKM parameters which are also worked out.
NOTE: this is a revised and updated version of our previous paper.Comment: LaTeX, 27 pages, 16 uuencoded figures (enclosed), CERN-TH.7398/94,
UdeM-GPP-TH-94-0
Regulation of murine airway surface liquid volume by CFTR and Ca2+-activated Cl- conductances
Two Cl- conductances have been described in the apical membrane of both human and murine proximal airway epithelia that are thought to play predominant roles in airway hydration: (1) CFTR, which is cAMP regulated and (2) the Ca2+-activated Cl- conductance (CaCC) whose molecular identity is uncertain. In addition to second messenger regulation, cross talk between these two channels may also exist and, whereas CFTR is absent or defective in cystic fibrosis (CF) airways, CaCC is preserved, and may even be up-regulated. Increased CaCC activity in CF airways is controversial. Hence, we have investigated the effects of CFTR on CaCC activity and have also assessed the relative contributions of these two conductances to airway surface liquid (ASL) height (volume) in murine tracheal epithelia. We find that CaCC is up-regulated in intact murine CF tracheal epithelia, which leads to an increase in UTP-mediated Cl-/volume secretion. This up-regulation is dependent on cell polarity and is lost in nonpolarized epithelia. We find no role for an increased electrical driving force in CaCC up-regulation but do find an increased Ca2+ signal in response to mucosal nucleotides that may contribute to the increased Cl-/volume secretion seen in intact epithelia. CFTR plays a critical role in maintaining ASL height under basal conditions and accordingly, ASL height is reduced in CF epithelia. In contrast, CaCC does not appear to significantly affect basal ASL height, but does appear to be important in regulating ASL height in response to released agonists (e.g., mucosal nucleotides). We conclude that both CaCC and the Ca2+ signal are increased in CF airway epithelia, and that they contribute to acute but not basal regulation of ASL height
Heavy quark mass determination from the quarkonium ground state energy: a pole mass approach
The heavy quark pole mass in perturbation theory suffers from a renormalon
caused, inherent uncertainty of . This fundamental
difficulty of determining the pole mass to an accuracy better than the inherent
uncertainty can be overcome by direct resummation of the first infrared
renormalon. We show how a properly defined pole mass as well as the mass for the top and bottom quarks can be determined accurately from the
quarkonium ground state energy.Comment: 16 pages; published versio
Identifying New Sources of Resistance to Brown Stem Rot in Soybean
Brown stem rot (BSR), caused by the fungus Phialophora gregata f. sp. sojae (Allington & D.W. Chamberlain) W. Gams (syn. Cadophora gregata), causes yield losses up to 38%. Three dominant BSR-resistant genes have been identified: Rbs1, Rbs2, and Rbs3. Additional BSR resistance loci will complement breeding efforts by expanding the soybean [Glycine max (L.) Merr.] genetic base. The objective of this research was to determine if PI 594637, PI 594638B, PI 594650A, and PI 594858B contained novel BSR resistance genes. The accessions were crossed to three genotypes with known BSR resistance genes and populations were developed for allelism studies. A minimum of 60 F2:3 families tracing to individual F2 plants in each population were used, and six seeds from each F2:3 family were tested. Resistant and susceptible controls and parents were also included. The BSR symptoms were assessed under growth chamber conditions 5 wk after inoculation by measuring foliar and stem severities and recovery of P. gregata from stem sections. Allelism tests of F2:3 plants from crosses of PI 594638B, PI 594858B, and PI 594650A with the resistant sources fit a 15:1 ratio, indicating that the resistant gene possessed by each of the PIs was nonallelic to Rbs1, Rbs2, and Rbs3. The three PIs contain at least one novel BSR resistance gene and have the potential to serve as donors to elite germplasm, increasing stability of host resistance to P. gregata. Allelism tests of PI 594637 segregated in a 3:1 ratio and no significant difference was found between PI 594637 and the susceptible controls, indicating that PI 594637 is susceptible to BSR
Applying a basic development needs approach for sustainable and integrated community development in less-developed areas: Report of ongoing Iranian experience
Introduction: Despite considerable achievements in the provision of basic developmental facilities in terms of drinking water, access to primary healthcare services, high-quality and nutritious food, social services, and proper housing facilities, there are many rural and slum communities in Iran where these essential needs remain unfulfilled. Lack of equity is prominent, as large differences exist in underprivileged provinces. New policies developed in the past two decades have resulted in substantial achievements in meeting population needs and reducing the socio-economic gap; nevertheless, poverty levels, unemployment due to a large increase in the birth rate in the early 1980s, and lack of community participation are matters yet to be addressed. To overcome these deficiencies, a basic development needs approach was adopted to promote the concept of community self-help and self-reliance through intersectoral collaboration, creating an environment where people could take an active part in the development process, with the Iranian government providing the necessary support to achieve the desired level of development. Description of the project: Following firm commitment from the Iranian government and technical support from the World Health Organization Regional Office, basic development needs was assigned a high priority in health and health-related sectors, reflected in the third National Masterplan (2001-2005). A comprehensive intersectoral plan was designed, and pilot projects were commenced in three villages. Each village elected a representative, and committee clusters were formed to run and monitor projects identified by a process of local needs assessment and priority assignment. In each region, a variety of needs were elicited from these assessments, which were actively supported by local authorities. Lesson learned: A basic development needs approach was found to be a reliable discipline to improve community participation, needs-led resource allocation and intersectoral co-operation in community development, particularly in underprivileged areas. Iran's initial experience of basic development needs has gained widespread public support but will require periodical evaluation as it is introduced into other rural and urban regions across the country. © 2004 The Royal Institute of Public Health. Published by Elsevier Ltd. All rights reserved
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