32,946 research outputs found

    Cosmic microwave background constraints on coupled dark matter

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    We study CMB constraints on a model with a cosmological constant and a fraction of dark matter non-minimally coupled to a massless scalar field. In this scenario, there is an extra gravity-like fifth force which can affect the evolution of the Universe enough to have a discernible effect on measurements of cosmological parameters. Using Planck and WMAP polarisation data, we find that up to half of the dark matter can be coupled. The coupling can also be several times larger than in models with a single species of cold dark matter coupled to a quintessence scalar field, as the scalar field does not play the role of dark energy and is therefore less constrained by the data.Comment: 5 pages, 4 figure

    Why are Immigrants' Incarceration Rates so Low? Evidence on Selective Immigration, Deterrence, and Deportation

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    The perception that immigration adversely affects crime rates led to legislation in the 1990s that particularly increased punishment of criminal aliens. In fact, immigrants have much lower institutionalization (incarceration) rates than the native born - on the order of one-fifth the rate of natives. More recently arrived immigrants have the lowest relative incarceration rates, and this difference increased from 1980 to 2000. We examine whether the improvement in immigrants' relative incarceration rates over the last three decades is linked to increased deportation, immigrant self-selection, or deterrence. Our evidence suggests that deportation does not drive the results. Rather, the process of migration selects individuals who either have lower criminal propensities or are more responsive to deterrent effects than the average native. Immigrants who were already in the country reduced their relative institutionalization probability over the decades; and the newly arrived immigrants in the 1980s and 1990s seem to be particularly unlikely to be involved in criminal activity, consistent with increasingly positive selection along this dimension.

    The Company You Keep: The Effects of Family and Neighborhood on Disadvantaged Youths

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    We examine the effects of family background variables and neighborhood peers on the behaviors of inner-city youths in a tight labor market using data from the 1989 NBER survey of youths living in low-income Boston neighborhoods. We find that family adult behaviors are strongly related to analogous youth behaviors. The links between the behavior of older family members and youths are important for criminal activity, drug and alcohol use, childbearing out of wedlock, schooling, and church attendance. We also find that the behaviors of neighborhood peers appear to substantially affect youth behaviors in a manner suggestive of contagion models of neighborhood effects. Residence in a neighborhood in which a large proportion of other youths are involved in crime is associated with a substantial increase in an individual's probability of the being involved in crime. Significant neighborhood peer effects are also apparent for drug and alcohol use, church attendance, and the propensity of youths to be out of school and out of work. Our results indicate that family and peer influences both operate in manner such that "like begets like."

    Transforming squeezed light into a large amplitude coherent state superposition

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    A quantum superposition of two coherent states of light with small amplitude can be obtained by subtracting a photon from a squeezed vacuum state. In experiments this preparation can be made conditioned on the detection of a photon in the field from a squeezed light source. We propose and analyze an extended measurement strategy which allows generation of high fidelity coherent state superpositions with larger amplitude.Comment: 6 pages, 4 figures, v2: published versio

    Validation and determination of a reference interval for Canine HbA1c using an immunoturbidimetric assay

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    Background: Hemoglobin A1c (HbA1c) provides a reliable measure of glycemic control over 2–3 months in human diabetes mellitus. In dogs, presence of HbA1c has been demonstrated, but there are no validated commercial assays. Objective: The purpose of the study was to validate a commercially available automated immunoturbidimetric assay for canine HbA1c and determine an RI in a hospital population. Methods: The specificity of the assay was assessed by inducing glycosylation in vitro using isolated canine hemoglobin, repeatability by measuring canine samples 5 times in succession, long term inter-assay imprecision by measuring supplied control materials, stability using samples stored at 4°C over 5 days and −20°C over 8 weeks, linearity by mixing samples of known HbA1c in differing proportions, and the effect of anticoagulants with paired samples. An RI was determined using EDTA-anticoagulated blood samples from 60 nondiabetic hospitalized animals of various ages and breeds. Hemoglobin A1c was also measured in 10 diabetic dogs. Results: The concentration of HbA1c increased proportionally with glucose concentration in vitro. For repeat measurements, the CV was 4.08% (range 1.16–6.10%). Samples were stable for 5 days at 4°C. The assay was linear within the assessed range. Heparin- and EDTA-anticoagulated blood provided comparable results. The RI for HbA1c was 9–18.5 mmol/mol. There was no apparent effect of age or breed on HbA1c. In diabetic dogs, HbA1c ranged from 14 to 48 mmol/mol. Conclusions: The assay provides a reliable method for canine HbA1c measurement with good analytic performance
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