406 research outputs found
Fire Blight of Pears and Apples
This fact sheet describes fire blight, a bacterial disease of concern to apple and pear growers, and how it can be managed
North American Genetic Counselors\u27 Approach to Collecting and Using Ancestry in Clinical Practice
Current guidelines from the National Society of Genetic Counselors (NSGC) recommend that patients\u27 ancestry be obtained when taking a family history. However, no study has explored how consistently genetic counselors obtain or utilize this information. The goals of this study included assessing how genetic counselors collect their patients\u27 ancestry, what factors influence this decision, and how they view the utility of this information. Genetic counselors working in a direct patient care setting in the US or Canada were recruited to participate in an anonymous survey via an NSGC email blast. Most participants (n = 115) obtain information about their patients\u27 ancestry (96.5%), with the most common methods being directly asking the patient (91%) and utilizing intake forms (43.2%). Of participants who ask about ancestry directly, 50.5% always ask about the presence of Ashkenazi Jewish ancestry and 70.3% always ask about additional ancestries, suggesting that for most genetic counselors’ collection of ancestry is standard practice. However, the clinical utility of ancestry information is highly variable, with the impact on genetic testing choice being particularly low. A slight majority of participants support a reevaluation of current ancestry guidelines (51.3%), with many participants suggesting that the varying utility of ancestry in different clinical indications/specialties should be incorporated into guidelines. Despite being standard practice for most genetic counselors, no unified approach or standard for how ancestral information should be used in genetic counseling practice was identified
Neutral theory of chemical reaction networks
To what extent do the characteristic features of a chemical reaction network
reflect its purpose and function? In general, one argues that correlations
between specific features and specific functions are key to understanding a
complex structure. However, specific features may sometimes be neutral and
uncorrelated with any system-specific purpose, function or causal chain. Such
neutral features are caused by chance and randomness. Here we compare two
classes of chemical networks: one that has been subjected to biological
evolution (the chemical reaction network of metabolism in living cells) and one
that has not (the atmospheric planetary chemical reaction networks). Their
degree distributions are shown to share the very same neutral
system-independent features. The shape of the broad distributions is to a large
extent controlled by a single parameter, the network size. From this
perspective, there is little difference between atmospheric and metabolic
networks; they are just different sizes of the same random assembling network.
In other words, the shape of the degree distribution is a neutral
characteristic feature and has no functional or evolutionary implications in
itself; it is not a matter of life and death.Comment: 13 pages, 8 figure
Species Abundance Patterns in Complex Evolutionary Dynamics
An analytic theory of species abundance patterns (SAPs) in biological
networks is presented. The theory is based on multispecies replicator dynamics
equivalent to the Lotka-Volterra equation, with diverse interspecies
interactions. Various SAPs observed in nature are derived from a single
parameter. The abundance distribution is formed like a widely observed
left-skewed lognormal distribution. As the model has a general form, the result
can be applied to similar patterns in other complex biological networks, e.g.
gene expression.Comment: 4 pages, 3 figures. Physical Review Letters, in pres
Efektywne wykorzystanie nowych technologii na lekcjach
książka wydana przez Centrum Edukacji Obywatelskiej, tłumaczenie Patrycja Schmyd
Calibrating and testing tissue equivalent proportional counters with 37Ar
A method for testing and calibrating tissue equivalent proportional counters with37Ar is described.37Ar is produced by exposure of argon in its normal isotope composition to thermal neutrons. It is shown that - up to volume ratios of 0.01 of argon to the tissue equivalent gas - there is no appreciable effect of the argon admixture on the function of the proportional counter. Conventional calibration methods with characteristic x-rays or with -particles require modifications of the detectors, and they test only small sub-volumes in the counters. In contrast, argon permits calibrations and tests of the resolution that are representative for the entire counter volume and that do not require changes in detector construction. The method is equally applicable to multi-element proportional counters; it is here exemplified by its application to a long cylindrical counter of simplified design that is part of such a multi-element configuration
Electromagnetic Cascades and Cascade Nucleosynthesis in the Early Universe
We describe a calculation of electromagnetic cascading in radiation and
matter in the early universe initiated by the decay of massive particles or by
some other process. We have used a combination of Monte Carlo and numerical
techniques which enables us to use exact cross sections, where known, for all
the relevant processes. In cascades initiated after the epoch of big bang
nucleosynthesis -rays in the cascades will photodisintegrate He,
producing He and deuterium. Using the observed He and deuterium
abundances we are able to place constraints on the cascade energy deposition as
a function of cosmic time. In the case of the decay of massive primordial
particles, we place limits on the density of massive primordial particles as a
function of their mean decay time, and on the expected intensity of decay
neutrinos.Comment: compressed and uuencoded postscript. We now include a comparison with
previous work of the photon spectrum in the cascade and the limits we
calculate for the density of massive particles. The method of calculation of
photon spectra at low energies has been improved. Most figures are revised.
Our conclusions are substantially unchange
Electron-based crystalline undulator
We discuss the features of a crystalline undulator of the novel type based on
the effect of a planar channeling of ultra-relativistic electrons in a
periodically bent crystals. It is demonstrated that an electron-based undulator
is feasible in the tens of GeV range of the beam energies, which is noticeably
higher than the energy interval allowed in a positron-based undulator.
Numerical analysis of the main parameters of the undulator as well as the
characteristics of the emitted undulator radiation is carried out for 20 and 50
GeV electrons channeling in diamond and silicon crystals along the (111)
crystallographic planes.Comment: 16 pages, 8 figures, Latex, IOP styl
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