Scattering of sound by atmospheric turbulence predictions in a refractive shadow zone

According to ray theory, regions exist in an upward refracting atmosphere where no sound should be present. Experiments show, however, that appreciable sound levels penetrate these so-called shadow zones. Two mechanisms contribute to sound in the shadow zone: diffraction and turbulent scattering of sound. Diffractive effects can be pronounced at lower frequencies but are small at high frequencies. In the short wavelength limit, then, scattering due to turbulence should be the predominant mechanism involved in producing the sound levels measured in shadow zones. No existing analytical method includes turbulence effects in the prediction of sound pressure levels in upward refractive shadow zones. In order to obtain quantitative average sound pressure level predictions, a numerical simulation of the effect of atmospheric turbulence on sound propagation is performed. The simulation is based on scattering from randomly distributed scattering centers ('turbules'). Sound pressure levels are computed for many realizations of a turbulent atmosphere. Predictions from the numerical simulation are compared with existing theories and experimental data

Chronology of Lead Pollution Contained in Banded Coral Skeletons

Lead concentrations relative to calcium within dated subsamples of hermatypic (reef-building) coral skeletons from St. Croix, US Virgin Islands, record ambient pollution levels. Concentrations within a coral from a polluted reef (395 ng g-1) average five-fold higher than within a coral from a pristine site (87 ng g-1). The lead chronologies of both corals show a significant increase in concentration towards the present during the past 26 yr (1954–1980). The increase in lead concentration in the coral from the pristine site is suggested to represent the increase in lead availability from global pollution. Coral skeletons offer the probability of development into tools for longterm chemical recorders of levels of lead and possibly other metals or compounds in seawater

The effects of entry on incumbent innovation and productivity

How does firm entry affect innovation incentives in incumbent firms? Microdata suggest that there is heterogeneity across industries. Specifically, incumbent productivity growth and patenting is positively correlated with lagged greenfield foreign firm entry in technologically advanced industries, but not in laggard industries. In this paper we provide evidence that these correlations arise from a causal effect predicted by Schumpeterian growth theory—the threat of technologically advanced entry spurs innovation incentives in sectors close to the technology frontier, where successful innovation allows incumbents to survive the threat, but discourages innovation in laggard sectors, where the threat reduces incumbents' expected rents from innovating. We find that the empirical patterns hold using rich micro panel data for the United Kingdom. We control for the endogeneity of entry by exploiting major European and U.K. policy reforms, and allow for endogeneity of additional factors. We complement the analysis for foreign entry with evidence for domestic entry and entry through imports

Strategic Considerations in Invention and Innovation: The Case of Natural Resources

Strategic considerations may induce a resource importing country to invent a substitute earlier than it intends to put it to use. There are also circumstances in which it would wish to delay an invention date even if it could obtain it at an earlier date at no extra cost. Similar paradoxical results obtain if resource cartels behave strategically. Setting prices high may be a way of deterring invention. If those engaged in R and D are not resource users, and the cartel has access to similar R and D technology, it will pre-empt rivals. This may not be the case if resource users can also engage in R and D

Distribution of radioactive jackrabbit pellets in the vicinity of the B-C CRIBS, 200 East Area, U.S.A.E.C. Hanford Reservation

During 1972 and 1973 a study was conducted in the B-C Cribs, 200 East Area, to learn the extent to which jackrabbits (Lepus californicus) and their predators had dispersed buried radioactive wastes in their fecal pellets and scats. The specific objective was to gather sufficient data on the pattern of dispersal so that statistically valid sampling strategies could be developed in future programs, depending upon management planning objectives for the area. A secondary objective was to relate these data with parameters, such as topography, wind direction, vegetation types, animal behavior, that might help explain the pattern of dispersal. In 1972, 2625 circular sampling sites were surveyed along 30 transects radiating out 2.4 to 3.2 km from the B-C Cribs. Radioactive contaminated feces, urine, soil and vegetation were distributed in all directions from the cribs, but the area to the south and southwest was more densely and uniformly contaminated. Of the ultimate sampling units surveyed, 278 or 10.6% had activity in excess o f 10,000 counts per minute (cprn) measured with a Geiger-Mueller counter. Of these 278 circular areas, 179 or 64% were found within 0.5 km of the cribs, 23.4% were between 0.5 and 1.0 km, and the remaining 12.2% were further than 1 km from the central point. Although most droppings with a count rate greater than 20,000 cpm were found within 400 meters of the crib, pellets registering in excess of 100,000 cprn were found up to 1.6 km from the cribs. The pellets appeared to be distributed into the prevailing wind directions and contrary to the immediate contours: the only correlation seemed to be with increased vegetation density to the south and southwest, vegetation that is prime jackrabbit habitat. In May-June, 1973, 48 additional transects were run: 7 were parallel to lines established in the B-C Crib Area during 1972; 18 radiated from an abandoned gun battery site 3.2 km east of the cribs; and 23 were run from power lines 5 km south to southwest of the cribs back towards the source of contamination. No contaminated jackrabbit pellets were found at these distances, but one contaminated coyote scat was found near the gun battery site. During 1972 and 1973 field crews walked 106.7 km along 78 radii and recorded observations on 6671 ultimate sampling units of approximately 1.4 m{sup 2}

Preemption, Leapfrogging, and Competition in Patent Races

This paper investigates when patent races will be characterized by vigorous competition and when they will degenerate into a monopoly. Under some conditions, a firm with an arbitrarily small headstart can preempt its rivals. Such 'e-preemption' is shown to depend on whether a firm that is behind in the patent race, as measured by the expected time remaining until discovery, can't 'leapfrog' the competition and become the new leader. An example of an R and D game with random discovery illustrates how e-preemption can occur when leapfrogging is impossible. A multi-stage R and D process allows leapfrogging and thus permits competition. A similar conclusion emerges in a model of a deterministic patent race with imperfect monitoring of rival firms' R and D investment activities

Vasopeptidase inhibition attenuates the progression of renal injury in subtotal nephrectomized rats

Vasopeptidase inhibition attenuates the progression of renal injury in subtotal nephrectomized rats.BackgroundVasopeptidase inhibitors are a new class of cardiovascular compounds that inhibit both angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP). The aim of the present study was to explore the effects of omapatrilat, a vasopeptidase inhibitor, on renal function and pathology in subtotally nephrectomized (STNx) rats.MethodsSTNx rats were randomized to four groups and treated for 12 weeks: no treatment (N = 14); omapatrilat at a low dose of 10 mg/kg (L, N = 12) and at a high dose of 40 mg/kg (H, N = 10); or an ACE inhibitor, fosinopril, at a dose of 10 mg/kg (N = 12). Sham-operated rats were used as control animals (N = 12).ResultsElevated blood pressure in STNx rats (174 ± 9mm Hg) was reduced by omapatrilat in a dose-dependent manner (L, 121 ± 3mm Hg; H, 110 ± 3mm Hg) and by fosinopril (149 ± 5mm Hg). Proteinuria in STNx rats (246 ± 73 mg/day) was reduced by treatment with fosinopril (88 ± 21 mg/day) and was normalized by treatment with omapatrilat (L, 30 ± 4 mg/day; H, 20 ± 2 mg/day vs. control 25 ± 1 mg/day). Decreased glomerular filtration rates, elevated plasma urea and creatinine and glomerulosclerosis, and tubulointerstitial fibrosis were ameliorated by omapatrilat and fosinopril to a similar degree. Compared with fosinopril, omapatrilat treatment was associated with increased plasma renin activity and decreased renal ACE and NEP binding in a dose-dependent manner.ConclusionThese findings suggest that vasopeptidase inhibition may provide a useful strategy for the treatment of progressive renal disease

Obesity-Induced Colorectal Cancer Is Driven by Caloric Silencing of the Guanylin-GUCY2C Paracrine Signaling Axis.

Obesity is a well-known risk factor for colorectal cancer but precisely how it influences risks of malignancy remains unclear. During colon cancer development in humans or animals, attenuation of the colonic cell surface receptor guanylyl cyclase C (GUCY2C) that occurs due to loss of its paracrine hormone ligand guanylin contributes universally to malignant progression. In this study, we explored a link between obesity and GUCY2C silencing in colorectal cancer. Using genetically engineered mice on different diets, we found that diet-induced obesity caused a loss of guanylin expression in the colon with subsequent GUCY2C silencing, epithelial dysfunction, and tumorigenesis. Mechanistic investigations revealed that obesity reversibly silenced guanylin expression through calorie-dependent induction of endoplasmic reticulum stress and the unfolded protein response in intestinal epithelial cells. In transgenic mice, enforcing specific expression of guanylin in intestinal epithelial cells restored GUCY2C signaling, eliminating intestinal tumors associated with a high calorie diet. Our findings show how caloric suppression of the guanylin-GUCY2C signaling axis links obesity to negation of a universal tumor suppressor pathway in colorectal cancer, suggesting an opportunity to prevent colorectal cancer in obese patients through hormone replacement with the FDA-approved oral GUCY2C ligand linaclotide

The Path to Eliminating Raccoon Rabies in the Eastern US-Obstacles and Opportunities in Urban-Suburban Landscapes

Rabies in terrestrial wildlife poses a significant public and animal health threat. Oral rabies vaccination (ORV) targeting specific vector species has proven effective in eliminating certain rabies variants in Europe and Canada. The goal of eliminating the raccoon rabies variant (RRV) in the US is achievable through an integrated ORV program at the landscape scale. Current wildlife rabies management in the US includes extensive air and ground ORV programs in 16 eastern states coordinated by Wildlife Services (WS)’ National Rabies Management Program. More than 10 million vaccine-baits are distributed annually targeting raccoons (Procyon lotor) and striped skunks (Mephitis mephitis) with the long-term goal of eliminating RRV. Achieving vaccine-induced herd immunity in target species in developed landscapes has proven challenging due to abundant anthropogenic food sources, higher wildlife densities, decreased home ranges, habitat fragmentation, and non-target bait competition. Effectively managing RRV in the urban-suburban landscape requires greater understanding of meso-carnivore ecology in these landscapes and critical analyses of current baiting strategies. Preliminary results from urban-suburban studies demonstrate fewer potential ORV bait encounters for target species than expected, lower seroconversion rates compared to rural habitats and patchy bait distribution patterns. New technologies including the use of Point of Interest GPS units to document ground bait distribution in combination with research conducted by WS including ORV field trials, urban density studies, and raccoon, skunk, and opossum (Didelphis virginiana) ecology have provided valuable insight to overcome the obstacles of urban rabies management and make eliminating RRV a reality