711 research outputs found
Nuclear radiation analysis
A study program of radiation shielding against the deleterious effects of nuclear radiation on man and equipment is reported. The methods used to analyze the radiation environment from bremsstrahlung photons are discussed along with the methods employed by transport code users. The theory and numerical methods used to solve transport of neutrons and gammas are described, and the neutron and cosmic fluxes that would be present on the gamma-ray telescope were analyzed
Neighbors' income, public goods, and wellâbeing
How does neighbors' income affect individual wellâbeing? Our analysis is based on rich U.S. local data from the Behavioral Risk Factor Surveillance System, which contains information on where respondents live and their selfâreported wellâbeing. We find that the effect of neighbors' income on individuals' selfâreported wellâbeing varies with the size of the neighborhood included. In smaller areas such as ZIP codes, we find a positive relationship between median income and individuals' life satisfaction, whereas it is the opposite at the county, MSA, and state levels. We provide evidence that local public goods and local area characteristics such as unemployment, criminality, and poverty rates drive the association between satisfaction and neighbors' income at the ZIP code level. The neighbors' income effects are mainly concentrated among poorer individuals and are as large as one quarter of the effect of own income on selfâreported wellâbeing
Propensity to consent to data linkage: experimental evidence on the role of three survey design features in a UK longitudinal panel
When performing data linkage, survey respondents need to provide their informed consent. Since not all respondents agree to this request, the linked data-set will have fewer observations than the survey data-set alone and bias may be introduced. By focusing on the role that survey design features play in gaining respondentsâ consent, this paper provides an innovative contribution to the studies in this field. Analysing experimental data collected in a nationally representative household panel survey of the British population, we find that interview features such as question format (dependent/independent questions) and placement of the consent question within the questionnaire have an impact on consent rates
Measurement of the Cross Section Asymmetry of the Reaction gp-->pi0p in the Resonance Energy Region Eg = 0.5 - 1.1 GeV
The cross section asymmetry Sigma has been measured for the photoproduction
of pi0-mesons off protons, using polarized photons in the energy range Eg = 0.5
- 1.1 GeV. The CM angular coverage is Theta = 85 - 125 deg with energy and
angle steps of 25 MeV and 5 deg, respectively. The obtained Sigma data, which
cover the second and third resonance regions, are compared with existing
experimental data and recent phenomenological analyses. The influence of these
measurements on such analyses is also considered
The influence of Ga-irradiation on the transport properties of mesoscopic conducting thin films
We studied the influence of 30keV Ga-ions -- commonly used in focused ion
beam (FIB) devices -- on the transport properties of thin crystalline graphite
flake, LaCaMnO and Co thin films. The changes of the
electrical resistance were measured in-situ during irradiation and also the
temperature and magnetic field dependence before and after irradiation. Our
results show that the transport properties of these materials strongly change
at Ga fluences much below those used for patterning and ion beam induced
deposition (IBID), limiting seriously the use of FIB when the intrinsic
properties of the materials of interest are of importance. We present a method
that can be used to protect the sample as well as to produce selectively
irradiation-induced changes.Comment: 14 pages, 11 figures, will be published in Nanotechnology 201
Linking PIAAC Data to Individual Administrative Data: Insights from a German Pilot Project
Linking survey data to administrative data offers researchers many opportunities. In particular, it enables them to enrich survey data with additional information without increasing the burden on respondents. German PIAAC data on individual skills, for example, can be combined with administrative data on individual employment histories. However, as the linkage of survey data with administrative data records requires the consent of respondents, there may be bias in the linked dataset if only a subsample of respondents - for example, high-educated individuals - give their consent. The present chapter provides an overview of the pilot project about linking the German PIAAC data with individual administrative data. In a first step, we illustrate characteristics of the linkable datasets and describe the linkage process and its methodological challenges. In a second step, we provide an illustrative example of the use of the linked data and investigate how the skills assessed in PIAAC are associated with the linkage decision
Continental weathering and recovery from ocean nutrient stress during the Early Triassic Biotic Crisis
Following the latest Permian extinction âŒ252 million years ago, normal marine and terrestrial
ecosystems did not recover for another 5-9 million years. The driver(s) for the Early Triassic
biotic crisis, marked by high atmospheric CO2 concentration, extreme ocean warming, and
marine anoxia, remains unclear. Here we constrain the timing of authigenic K-bearing mineral
formation extracted from supergene weathering profiles of NW-Pangea by Argon geochronology,
to demonstrate that an accelerated hydrological cycle causing intense chemical
alteration of the continents occurred between âŒ254 and 248 Ma, and continued throughout
the Triassic period. We show that enhanced ocean nutrient supply from this intense continental
weathering did not trigger increased ocean productivity during the Early Triassic
biotic crisis, due to strong thermal ocean stratification off NW Pangea. Nitrogen isotope
constraints suggest, instead, that full recovery from ocean nutrient stress, despite some brief
amelioration âŒ1.5 million years after the latest Permian extinction, did not commence until
climate cooling revitalized the global upwelling systems and ocean mixing âŒ10 million years
after the mass extinction
Compensatory Evolution in RNA Secondary Structures Increases Substitution Rate Variation among Sites
There is growing evidence that interactions between biological molecules (e.g., RNAâRNA, proteinâprotein, RNAâprotein) place limits on the rate and trajectory of molecular evolution. Here, by extending Kimura's model of compensatory evolution at interacting sites, we show that the ratio of transition to transversion substitutions (Îș) at interacting sites should be equal to the square of the ratio at independent sites. Because transition mutations generally occur at a higher rate than transversions, the model predicts that Îș should be higher at interacting sites than at independent sites. We tested this prediction in 10 RNA secondary structures by comparing phylogenetically derived estimates of Îș in paired sites within stems (Îșp) and unpaired sites within loops (Îșu). Eight of the 10 structures showed an excellent match to the quantitative predictions of the model, and 9 of the 10 structures matched the qualitative prediction Îșp > Îșu. Only the Rev response element from the human immunovirus (HIV) genome showed the reverse pattern, with Îșp < Îșu. Although a variety of evolutionary forces could produce quantitative deviations from the model predictions, the reversal in magnitude of Îșp and Îșu could be achieved only by violating the model assumption that the underlying transition (or transversion) mutation rates were identical in paired and unpaired regions of the molecule. We explore the ability of the APOBEC3 enzymes, host defense mechanisms against retroviruses, which induce transition mutations preferentially in single-stranded regions of the HIV genome, to explain this exception to the rule. Taken as a whole, our findings suggest that Îș may have utility as a simple diagnostic to evaluate proposed secondary structures
Precise Measurement of Sigma Beam Asymmetry for Positive Pion Photoproduction on the Proton from 800 to 1500 Mev
The Sigma beam asymmetry for positive pion photoproduction on the proton has
been measured over an angular range of 40-170 deg at photon energies from 0.8
to 1.5 GeV. The resulting data set includes 237 accurate points, 136 of these
belonging to an almost unexplored domain above 1.05 GeV. Data of such high
precision provide severe constraints for partial wave analyses. The influence
of this experiment on the GW multipole analysis is demonstrated. Significant
changes are found in multipoles connected to the S31(1620) and P13(1720)
resonances. Comparisons using the MAID analysis are also presented.Comment: 11 pages, 4 eps figures. to be published in Physics Letters
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