Environmental Inspection Proclivity and State Manufacturing Growth: The US Experience from the 1990s

In this paper we construct a ranking of states based on their proclivity to inspect facilities for environmental compliance. Our measure utilizes state-level inspections data supplied by the US Environmental Protection Agency. After developing our ranking, we use it to predict state-level growth in manufacturing establishments. In doing so, we find support for the notion that enforcement intensity adversely impacts such growth. Our results offer insight into why existing studies that examine the impact of environmental regulation on location and growth produce inconsistent results.Monitoring and Enforcement, Environmental Regulations, Business Formation Growth

WORKMEN\u27S COMPENSATION ACTS-AMENDMENTS CHANGING PERIOD FOR ADDITIONAL COMPENSATION DUE TO AGGRAVATION OF INJURY

The typical workmen\u27s compensation act provides both for an award to compensate the employee for his original injury and for subsequent awards to compensate him for aggravation of the injury occurring after the original award. The time during which the original award may be opened to allow additional compensation for subsequent aggravation may not be expressly limited, or opening may be limited to a stated time after the original injury or the last payment of the original award. By amendment, the legislature may either lengthen or shorten this period for opening. Whether such amendment applies to a claim for compensation for aggravation when the original injury occurred before the effective date of the amendment is the problem with which the present comment is concerned. If what the courts say is taken to be controlling, the cases seem to be in irreconcilable conflict upon almost every point. However, the decisions themselves fall into a surprisingly uniform pattern

Spatial separation in a thermal mixture of ultracold 174^{174}Yb and 87^{87}Rb atoms

We report on the observation of unusually strong interactions in a thermal mixture of ultracold atoms which cause a significant modification of the spatial distribution. A mixture of $^{87}$Rb and $^{174}$Yb with a temperature of a few $\mu$K is prepared in a hybrid trap consisting of a bichromatic optical potential superimposed on a magnetic trap. For suitable trap parameters and temperatures, a spatial separation of the two species is observed. We infer that the separation is driven by a large interaction strength between $^{174}$Yb and $^{87}$Rb accompanied by a large three-body recombination rate. Based on this assumption we have developed a diffusion model which reproduces our observations

Singular electrostatic energy of nanoparticle clusters

The binding of clusters of metal nanoparticles is partly electrostatic. We address difficulties in calculating the electrostatic energy when high charging energies limit the total charge to a single quantum, entailing unequal potentials on the particles. We show that the energy at small separation $h$ has a strong logarithmic dependence on $h$. We give a general law for the strength of this logarithmic correction in terms of a) the energy at contact ignoring the charge quantization effects and b) an adjacency matrix specifying which spheres of the cluster are in contact and which is charged. We verify the theory by comparing the predicted energies for a tetrahedral cluster with an explicit numerical calculation.Comment: 17 pages, 3 figures. Submitted to Phys Rev

Effects of Stocking Density on Steer Performance and Carcass Characteristics in Bedded Hoop Barns

Use of bedded hoop barns for feeding cattle has grown in part due to increased regulations regarding open feedlot runoff. In 2010, ISU estimated almost 700 hoop barns in Iowa used for beef cattle and more than 80% were used for cattle feeding. Work in Iowa also has documented that cattle confined in a bedded hoop barn perform similarly to cattle fed in an open feedlot with shelter. The work was done with a stocking density of 50 sq ft per steer in the bedded hoop barn. A hoop barn is a more expensive facility system compared with open lot configurations. Fixed costs per steer (facilities) are partially determined by stocking density. The objective of this study was to determine the effects of increased stocking density on performance and carcass characteristics of steers fed in bedded hoop and bedded open front facilities. The trials were conducted in 2008 to 2011 at the ISU Armstrong Research Farm, Lewis, IA. The hoop barn was stocked with 40, 45 and 50 head per pen resulting in 50, 45 and 40 sq ft per steer, respectively. There was one stocking density per housing type per trial. The diet fed was 45.0% dry corn, 14.8% ground hay, 36.8% modified distillers grains and 3.4% supplement on an as-fed basis. The total diet was approximately 69% dry matter. Cattle growth rate (ADG), feed intake (DMI), feed efficiency (F/G) and mean mud score did not differ based on stocking density (P\u3e0.05). However, the cattle given more square feet numerically had greater feed intake and were more efficient (about 4-5%) than the more densely stocked cattle. This study may not have had enough replications to detect statistically significant differences. Also the mean carcass characteristics (fat cover, rib eye area, marbling score, quality grade and yield grade) did not differ by stocking density (P\u3e0.05). When comparing seasons only, steers fed in summer tended to have heavier market liveweight, heavier carcass weight, required less feed per liveweight and less marbling compared with steers fed in winter (P≤0.10). Also, the summer-fed steers grew faster and gained more liveweight than the winter-fed steers (P\u3c0.005). These results suggest that this study may not have reached the maximum stocking density for feeding beef cattle in a bedded hoop barn. In other words, market cattle can probably be stocked at less square footage per steer than the 40 sq ft per steer used in this study. Observations of farmers with hoop barns suggest that 37 or 35 sq ft per steer may be feasible. Several factors may affect stocking density including genetics or frame size of the cattle and may interact with season. Also, it should be noted that as the density of cattle increases, more management is required, i.e., more bedding, more bunk space, more waterer space and observing individual cattle for health issues becomes more difficult

Geometric origin of excess low-frequency vibrational modes in amorphous solids

Glasses have a large excess of low-frequency vibrational modes in comparison with crystalline solids. We show that such a feature is a necessary consequence of the geometry generic to weakly connected solids. In particular, we analyze the density of states of a recently simulated system, comprised of weakly compressed spheres at zero temperature. We account for the observed a) constancy of the density of modes with frequency, b) appearance of a low-frequency cutoff, and c) power-law increase of this cutoff with compression. We predict a length scale below which vibrations are very different from those of a continuous elastic body.Comment: 4 pages, 2 figures. Argument rewritten, identical result

Different Scenarios for Critical Glassy Dynamics

We study the role of different terms in the $N$-body potential of glass forming systems on the critical dynamics near the glass transition. Using a simplified spin model with quenched disorder, where the different terms of the real $N$-body potential are mapped into multi-spin interactions, we identified three possible scenarios. For each scenario we introduce a ``minimal'' model representative of the critical glassy dynamics near, both above and below, the critical transition lin e. For each ``minimal'' model we discuss the low temperature equilibrium dynamics.Comment: Completely revised version, 8 pages, 5 figures, typeset using EURO-LaTeX, Europhysics Letters (in press

Low Temperature Physics

Contains research objectives and reports on one research project

Nutrient Retention Performance of a Crushed Limestone Floor Surface in a Bedded Hoop Barn with Confined Beef Cattle

Bedded confinement systems with partial concrete floors are increasingly being adopted by beef cattle feeders. The objective of this study was to determine the extent that manure nutrients moved into the soil below the geotextile fabric and packed limestone screenings floor of a bedded hoop barn used for beef cattle feeding at the ISU Armstrong Research and Demonstration Farm. Soil samples were taken (shallow and deep) before construction in 2004 and in 2008 after 7 groups of cattle were fed. Although single samples before and after animal feeding cannot provide conclusive evidence of moisture or nutrient migration, comparison of the sample results confirm a trend consistent with slow migration of manure nutrients into the soil profile. Phosphorus, calcium and magnesium did not show consistent or major trends with time. Organic matter showed a consistent increasing trend in both shallow and deep samples. Shallow sampling showed a marked increase only in nitrate-nitrogen, from 1.51 ppm to 11.47 ppm. These results are consistent with measurable, but very slow migration of moisture and nutrients into the soil profile. Additional soil tests over time and performance of an infiltration ring study may give more conclusive answers in the future