A global data set of soil particle size properties

A standardized global data set of soil horizon thicknesses and textures (particle size distributions) was compiled. This data set will be used by the improved ground hydrology parameterization designed for the Goddard Institute for Space Studies General Circulation Model (GISS GCM) Model 3. The data set specifies the top and bottom depths and the percent abundance of sand, silt, and clay of individual soil horizons in each of the 106 soil types cataloged for nine continental divisions. When combined with the World Soil Data File, the result is a global data set of variations in physical properties throughout the soil profile. These properties are important in the determination of water storage in individual soil horizons and exchange of water with the lower atmosphere. The incorporation of this data set into the GISS GCM should improve model performance by including more realistic variability in land-surface properties

Rheology and Contact Lifetime Distribution in Dense Granular Flows

We study the rheology and distribution of interparticle contact lifetimes for gravity-driven, dense granular flows of non-cohesive particles down an inclined plane using large-scale, three dimensional, granular dynamics simulations. Rather than observing a large number of long-lived contacts as might be expected for dense flows, brief binary collisions predominate. In the hard particle limit, the rheology conforms to Bagnold scaling, where the shear stress is quadratic in the strain rate. As the particles are made softer, however, we find significant deviations from Bagnold rheology; the material flows more like a viscous fluid. We attribute this change in the collective rheology of the material to subtle changes in the contact lifetime distribution involving the increasing lifetime and number of the long-lived contacts in the softer particle systems.Comment: 4 page

Plug flow and the breakdown of Bagnold scaling in cohesive granular flows

Cohesive granular media flowing down an inclined plane are studied by discrete element simulations. Previous work on cohesionless granular media demonstrated that within the steady flow regime where gravitational energy is balanced by dissipation arising from intergrain forces, the velocity profile in the flow direction scales with depth in a manner consistent with the predictions of Bagnold. Here we demonstrate that this Bagnold scaling does not hold for the analogous steady-flows in cohesive granular media. We develop a generalization of the Bagnold constitutive relation to account for our observation and speculate as to the underlying physical mechanisms responsible for the different constitutive laws for cohesive and noncohesive granular media.Comment: 8 pages, 10 figure

Firearms, Youth Homicide, and Public Health

Homicide is seven times as common among U.S. non-Hispanic Black as among non-Hispanic White youth ages 15 to 24 years. In 83% of these youth homicides, the murder weapon is a firearm. Yet, for more than a decade, the national public health position on youth violence has been largely silent about the role of firearms, and tools used by public health professionals to reduce harm from other potential hazards have been unusable where guns are concerned. This deprives already underserved populations from the full benefits public health agencies might be able to deliver. In part, political prohibitions against research about direct measures of firearm control and the absence of valid public health surveillance are responsible. More refined epidemiologic theories as well as traditional public health methods are needed if the U.S. aims to reduce disparate Black-White youth homicide rates

The Long Duration Exposure Facility (LDEF) photographic survey special publication

During the construction, integration, launch, retrieval and deintegration of the Long Duration Exposure Facility (LDEF), photographic surveys were made. Approximately 10,000 photographs were taken during the various phases of the LDEF project. These surveys are of technical and scientific importance because they revealed the pre and post flight conditions of the experiment trays as well as the spacecraft. Visual inspection of the photographs reveal valuable data such as space environment's effects and the earth atmosphere's effects post-retrieval. Careful files and records have been kept of these photographs. Each photograph has a Kennedy Space Center photo number or a Johnson Spaceflight Center photo number as well as a Langley Research Center photo number. The tray number, row number, and experiment number are also noted. Out of the 10,000 photographs taken, approximately 700 selected photographs were chosen for publication in a NASA Special Publication (SP) because they reveal the effects of space exposure to the viewer. These photographs will give researchers and spacecraft designers visual images of the effects of the space environment on specific materials, systems and spacecraft in general. One can visually see the degradation of thermal blankets, meteoroid craters, outgassing discoloration, atomic oxygen erosion, etc

Photographic Survey of the LDEF Mission

This publication documents a selected number of pre-flight, in-flight, and postflight photographs of the LDEF and experiments. Changes in condition of the experiments caused by space exposure are discussed. Accompanying this black and white publication it a CD-ROM that contains the color version of the photographs as well as the text

Headache and Acute Illness in Children

Thirty-seven children with headaches who were seen in a walk-in clinic were matched to 37 headache-free controls. Thirty percent of the headache group and 11% of the headache-free control group had a body temperature above 38°C (p < 0.05). Nonrhythmic pain was more commonly associated with fever than was rhythmic pain (p < 0.05). Of 34 headache subjects who completed questionnaires, those with more intense headaches reported a greater number of headache-exacerbating factors (p < 0.01).Bilateral headaches were more painful than unilateral headaches, and in two thirds of the subjects, the intensity of pain paralleled the course of the underlying illness. A family history of migraine was more common in the headache group as compared to the headache-free control group (p < 0.05). Headaches associated with acute illnesses may be a precursor to later migraine. (J Child Neurol 1987;2:22-27)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68022/2/10.1177_088307388700200104.pd

The Diversity of Concentrated Prescribing Behavior: An Application to Antipsychotics

Physicians prescribing drugs for patients with schizophrenia and related conditions are remarkably concentrated in their choice among antipsychotic drugs. In 2007 the single antipsychotic drug prescribed by a physician accounted for 66% of all antipsychotic prescriptions written by that physician. Which particular branded antipsychotic was the prescriber's "favorite" varied widely across physicians, i.e. physician prescribing concentration patterns are diverse. Building on Frank and Zeckhauser's [2007] characterization of physician treatments varying from "custom made" to "ready-to-wear", we construct a model of physician learning that generates a number of hypotheses. Using 2007 annual antipsychotic prescribing behavior on 17,652 physicians from IMS Health, we evaluate these predictions empirically. While physician prescribing behavior is generally quite concentrated, prescribers having greater volumes, those with training in psychiatry, male prescribers, and those not approaching retirement age tend to have less concentrated prescribing patterns.