Čerenkov radiation and electromagnetic pulse produced by electron beams traversing a finite path in air

Coherent Čerenkov radiation has been investigated previously in the time domain for an infinite path. The present calculations for a finite path length show an effect analogous to diffraction (in the frequency domain) in which radiation fields appear both at Cerenkov angles and at other angles. The latter have previously been named electromagnetic pulse fields.Hydrodynamics Group, Los Alamos National Laboratory, For Fred R. Buskirk and the U.S. Naval Sea Systems Command.Approved for public release; distribution is unlimited

Ecological and life history correlates of changes in avian migration timing in response to climate change

Spring migration of birds in many parts of the world has advanced as the climate has become warmer. Variation in advancement among species has been proposed to correlate with geography and life history features, but individual studies have reported variable results, and general patterns have been elusive. In a quantitative review of data from 389 bird species sampled at 69 European and 23 North American localities, we evaluated associations between change in the timing of migration and life history (body size, molt, broodedness), ecology (habitat, diet, nest position), and geography. We confirmed that spring migration advanced: -0.214 d yr-1 (95% CI: -0.266, -0.162) for first-arriving individuals and -0.104 d yr-1 (-0.139, -0.071) for the median date of passage. The rate of change in autumn was more variable: 0.090 d yr-1 (0.002, 0.176) delay for median passage and 0.019 d yr-1 (-0.175, 0.204) delay for the date of last departure. The response during spring was weaker in the far north and in species that migrate long distances to the wintering area. Autumn migration became increasingly delayed in species that are large-bodied, molt before departure, and that feed on seeds, insects, or fruits. Variation among species, especially during autumn, was associated in part with constraints surrounding the timing of the postnuptial molt. The results suggest that ecological and life history features of species may influence their ability to respond to climate change

Analysis, Design and Fabrication of centimeter-wave Dielectric Fresnel Zone Plate Lens and reflector

Fresnel lens has a long history in optics. This concept at non-optical wavelengths is also applicable. In this paper we report design and fabrication of a half and quarter wave dielectric Fresnel lens made of Plexiglas, and a Fresnel reflector at 11.1 GHz frequency. We made two lenses and one reflector at same frequency and compare their gain and radiation pattern to simulated results. Some methods for better focusing action will be introduced

Gas volume contents within a container, smart volume instrument

A method for determining the volume of an incompressible gas in a system including incompressible substances in a zero-gravity environment. The method includes inducing a volumetric displacement within a container and measuring the resulting pressure change. From this data, the liquid level can be determined

Market Valuations in the New Economy: An Investigation of What Has Changed

We find mixed support for the hypothesis that a “New Economy” subperiod occurred in the late 1990s in which the relation between equity value and traditional financial variables differs from previous periods. We examine a regression model of equity value on financial variables over 25 years for a broad firm sample and for firm subsamples thought to be emblematic of the New Economy. We find the regression model\u27s explanatory power declined in the New Economy subperiod for all firm subsamples. However, for all subsamples, the regression model\u27s structure during the New Economy subperiod is not unusual compared to other subperiods

Nutrient contamination from non-point sources: Dissolved nitrate and ammonium in surface and subsurface waters at EKU Meadowbrook Farm, Madison County, Kentucky

Agricultural activities often contaminate watersheds with excess nutrients leading to poor water quality and eutrophication. We assayed dissolved nutrient levels in surface and subsurface waters of Eastern Kentucky University’s Meadowbrook Farm in order to assess levels of dissolved nutrients leaving its farmland and draining into the Muddy Creek watershed. The Farm raises both crops and livestock so that nutrient sources include fertilizer and manure. We sampled springs, runoff, and subsurface pipe drainage as well as Muddy Creek on six days from May to August 2016 under a variety of weather conditions. Using established, standard colorimetric methods, we measured nitrate (NO3-; cadmium reduction method) and ammonium (NH4+; sodium hypochlorate method) via spectrophotometry with a precision and accuracy of ~0.1 mg/L. Nitrate was the dominant dissolved nitrogen species whereas ammonium was often absent in water samples. Nitrate levels were typically \u3c2 mg/L N- N- NO3 with the largest values between 7.0 and 14.3 mg/L. Springs and some runoff samples had higher nitrate values. Ammonium generally ranged between 0.0 and 0.5 mg/L N- NH4 with concentration spikes between 2.0 and 4.3 mg/L, but from no consistent source. Dissolved nitrogen concentration values responded to rainfall. Generally, nitrate concentrations increased more than ammonium concentrations during wetter periods. Spring samples maintained higher nitrogen concentrations regardless of different rainfall conditions. Lastly, nitrate contamination was significantly lower than composite national values from streams draining agricultural lands, whereas ammonium was about equal to the median national average. Median nitrate concentration was ~1.8 mg/L N- NO3 compared to the national value of ~2.8 mg/L, whereas the value for pristine streams is 0.24 mg/L N- NO3 (Dubrovsky et al., 2010). Median ammonium values from both data sets are ~0.1 mg/L N- NH4; the national value from pristine streams is ~0.025 mg/L N

Nutrient contamination from non-point sources: Dissolved nitrate and ammonium in surface and subsurface waters at EKU Meadowbrook Farm, Madison County, Kentucky

Agricultural activities often contaminate watersheds with excess nutrients leading to poor water quality and eutrophication. We assayed dissolved nutrient levels in surface and subsurface waters of Eastern Kentucky University’s Meadowbrook Farm in order to assess levels of dissolved nutrients leaving its farmland and draining into the Muddy Creek watershed. The Farm raises both crops and livestock so that nutrient sources include fertilizer and manure. We sampled springs, runoff, and subsurface pipe drainage as well as Muddy Creek on six days from May to August 2016 under a variety of weather conditions. Using established, standard colorimetric methods, we measured nitrate (NO3-; cadmium reduction method) and ammonium (NH4+; sodium hypochlorate method) via spectrophotometry with a precision and accuracy of ~0.1 mg/L. Nitrate was the dominant dissolved nitrogen species whereas ammonium was often absent in water samples. Nitrate levels were typically \u3c2 mg/L N- N- NO3 with the largest values between 7.0 and 14.3 mg/L. Springs and some runoff samples had higher nitrate values. Ammonium generally ranged between 0.0 and 0.5 mg/L N- NH4 with concentration spikes between 2.0 and 4.3 mg/L, but from no consistent source. Dissolved nitrogen concentration values responded to rainfall. Generally, nitrate concentrations increased more than ammonium concentrations during wetter periods. Spring samples maintained higher nitrogen concentrations regardless of different rainfall conditions. Lastly, nitrate contamination was significantly lower than composite national values from streams draining agricultural lands, whereas ammonium was about equal to the median national average. Median nitrate concentration was ~1.8 mg/L N- NO3 compared to the national value of ~2.8 mg/L, whereas the value for pristine streams is 0.24 mg/L N- NO3 (Dubrovsky et al., 2010). Median ammonium values from both data sets are ~0.1 mg/L N- NH4; the national value from pristine streams is ~0.025 mg/L N

Nutrient contamination from non-point sources: Dissolved phosphate in surface and subsurface waters at EKU Meadowbrook Farm, Madison County, Kentucky

Farms are non-point sources for nutrient contaminants that drain into watersheds and contribute to eutrophication and other environmental problems. Eastern Kentucky University’s Meadowbrook Farm raises both crops and livestock, causing dissolved phosphorus in the form of orthophosphate (PO43-) from fertilizer and animal manure to enter surface and subsurface waters, eventually flowing into Muddy Creek, a tributary of the Kentucky River. We sampled surface water, springs, and water from French drains that emanate from the farm, and also sampled Muddy Creek waters from May through August 2016. Typically, 1 to 2 days after sampling, we colorimetrically measured dissolved orthophosphate concentration using the established ascorbic acid method and a UV-VIS spectrophotometer with general accuracy and precision of ~0.1 mg/L, or ppm. Phosphate values measured from the farm are less than those measured nationally from agricultural lands. The median value of orthophosphate from Farm waters was 0.02 mg/L P-PO4, but nationally the level is ~0.1 mg/L P-PO4; pristine water display 0.010 mg/L P-PO4. Phosphate concentrations are also low when compared to nitrate usually ranging from 0 to 0.2 mg/L P-PO4 with higher concentrations of 0.5 to 2.7 mg/L P-PO4 occurring sporadically. With minor exceptions, we saw little difference in phosphate concentration between different sample sources whether spring water, water from subsurface drains, surface waters flowing over the Farm, or Muddy Creek waters. However, one sub-watershed draining the Farm had increased levels of phosphate on 24 May (2.7 mg/L P-PO4). Overall patterns of phosphate concentration were similar whether sampling during periods with little or no rainfall, or periods following rain events. An exception occurred on 24 June, when overland waters of the same sub-watershed mentioned above had a value of 0.5 mg/L, immediately following a significant rain event