Current on an Infinitely Long Cylindrical Antenna

The infinitely long circular cylindrical antenna driven at some cross section by a localized electromotive force, V, circumscribing the cylinder in a peripheral band is considered. The asymptotic expression for the current at large distances from the driving e.m.f. is derived using the saddle point method. It is shown that the amplitude of this current is proportional to the reciprocal of the logarithm of axial distance from the driving e.m.f

Decoherence of Quantum-Enhanced Timing Accuracy

Quantum enhancement of optical pulse timing accuracy is investigated in the Heisenberg picture. Effects of optical loss, group-velocity dispersion, and Kerr nonlinearity on the position and momentum of an optical pulse are studied via Heisenberg equations of motion. Using the developed formalism, the impact of decoherence by optical loss on the use of adiabatic soliton control for beating the timing standard quantum limit [Tsang, Phys. Rev. Lett. 97, 023902 (2006)] is analyzed theoretically and numerically. The analysis shows that an appreciable enhancement can be achieved using current technology, despite an increase in timing jitter mainly due to the Gordon-Haus effect. The decoherence effect of optical loss on the transmission of quantum-enhanced timing information is also studied, in order to identify situations in which the enhancement is able to survive.Comment: 12 pages, 4 figures, submitte

Relationships Between Net Primary Production, Water Transparency, Chlorophyll A, and Total Phosphorus in Oak Lake, Brookings County, South Dakota

Lake trophic state is of primary concern for water resource managers and is used as a measure of water quality and classification for beneficial uses. Secchi transparency, total phosphorus and chlorophyll a are surrogate measurements used in the calculation of trophic state indices (TSI) which classify waters as oligotrophic, mesotrophic, eutrophic or hypereutrophic. Yet the relationships between these surrogate measurements and direct measures of lake productivity vary regionally and may be influenced by external factors such as non-algal turbidity. Prairie pothole basins, common throughout eastern South Dakota and southwestern Minnesota, are shallow glacial lakes subject to frequent winds and sediment resuspension. Light-dark oxygen bottle methodology was employed to evaluate vertical planktonic production within an eastern South Dakota pothole basin. Secchi transparency, total phosphorus and planktonic chlorophyll a were also measured from each of three basin sites at biweekly intervals throughout the 2012 growing season. Secchi transparencies ranged between 0.13 and 0.25 meters, corresponding to an average TSISD value of 84.4 (hypereutrophy). Total phosphorus concentrations ranged between 178 and 858 ug/L, corresponding to an average TSITP of 86.7 (hypereutrophy). Chlorophyll a values corresponded to an average TSIChla value of 69.4 (transitional between eutrophy and hypereutrophy) and vertical production profiles yielded areal net primary productivity values averaging 288.3 mg C∙m-2∙d-1 (mesotrophy). Our results support the hypothesis that resuspended non-algal turbidity, not planktonic production, decreases water transparency and reduces potential net primary production. Chlorophyll a TSI values corresponded most closely with measurements of planktonic production and better represented the trophic state of this basin

Growing Season Productivity and Trophic Classification of Oak Lake, Brookings County, South Dakota

Changes in lake trophic state present concerns to water resource managers interested in maintaining water quality to support assigned beneficial uses. Contemporary methods of classifying lakes involve the use of surrogate indicators of production. However, some of these measurements are sensitive to wind induced resuspension of sediments, leading to inflated indications of basin production. This source of error is common to many shallow glacial lakes in eastern South Dakota and southwestern Minnesota. The objectives of this effort were to (1) estimate and define the trend in seasonal water column net and gross primary production and community respiration within a shallow pothole basin, (2) compare the mean net primary productivity values among three sub-basin sites and (3) evaluate trophic state classification using surrogate measures against actual production measurements. Water production as measured at three basin sites in Oak Lake, South Dakota, was evaluated using the light/dark bottle method once every two weeks throughout the 2010 growing season. Mean net primary productivity was 741 mg C•m-2•d-1and ranged from 35 to 1,462 mg C•m-2•d-1. Estimated to the light compensation depth, Oak Lake mean net primary production would lead to a eutrophic classification for this basin but would range between mesotrophic and hypereutrophic throughout the growing season. Trophic State Index values, derived from Secchi depth, ranged between 65 and 83, with a mean of 75, leading to an index classification of eutrophic or hypereutrophic. Secchi transparency explained 82% of the variation in net primary production while chlorophyll a explained only 17%. We concluded that Secchi transparency is an adequate surrogate for planktonic production despite consistently overestimating actual production levels within this basin

Dynamics of relativistic solitons

Relativistic solitons are self-trapped, finite size, electromagnetic waves of relativistic intensity that propagate without diffraction spreading. They have been predicted theoretically within the relativistic fluid approximation, and have been observed in multi-dimensional particle in cell simulations of laser pulse interaction with the plasma. Solitons were observed in the laser irradiated plasmas with the proton imaging technique as well. This paper reviews many theoretical results on relativistic solitons in electron-ion plasmas.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

A global risk assessment of primates under climate and land use/cover scenarios

Primates are facing an impending extinction crisis, driven by extensive habitat loss, land use change, and hunting. Climate change is an additional threat, which alone or in combination with other drivers, may severely impact those taxa unable to track suitable environmental conditions. Here, we investigate the extent of climate and land use/cover (LUC) change-related risks for primates. We employed an analytical approach to objectively select a subset of climate scenarios, for which we then calculated changes in climatic and LUC conditions for 2050 across primate ranges (N=426 species) under a best- and a worst-case scenario. Generalised linear models were used to examine whether these changes varied according to region, conservation status, range extent, and dominant habitat. Finally, we reclassified primate ranges based on different magnitudes of maximum temperature change, and quantified the proportion of ranges overall and of primate hotspots in particular that are likely to be exposed to extreme temperature increases. We found that, under the worst-case scenario, 74% of Neotropical forest-dwelling primates are likely to be exposed to maximum temperature increases up to 7°C. In contrast, 38% of Malagasy savanna primates will experience less pronounced warming of up to 3.5°C. About one quarter of Asian and African primates will face up to 50% crop expansion within their range. Primary land (undisturbed habitat) is expected to disappear across species’ ranges, whereas secondary land (disturbed habitat) will increase by up to 98%. With 86% of primate ranges likely to be exposed to maximum temperature increases >3°C, primate hotspots in the Neotropics are expected to be particularly vulnerable. Our study highlights the fundamental exposure risk of a large percentage of primate ranges to predicted climate and LUC changes. Importantly, our findings underscore the urgency with which climate change mitigation measures need to be implemented to avert primate extinctions on an unprecedented scale

P53 is active in murine stem cells and alters the transcriptome in a manner that is reminiscent of mutant p53

Since it was found that p53 is highly expressed in murine embryonic stem cells, it remained a mystery whether p53 is active in this cell type. We show that a significant part of p53 is localised in the nucleus of murine embryonic stem cells and that the majority of this nuclear p53 is bound to DNA. According to its nuclear localisation, we show that p53 alters the transcriptional program of stem cells. Nevertheless, the anti-proliferative activity of p53 is compromised in stem cells, and this control is due, at least in part, to the high amount of MdmX that is present in embryonic stem cells and bound to p53. Instead of the anti-proliferative activity that p53 has in differentiated cells, p53 controls transcription of pro-proliferative genes in embryonic stem cells including c-myc and c-jun. The impeded anti-proliferative activity of p53 and the induction of certain proto-oncogenes by p53 in murine embryonic stem cells can explain why stem cells proliferate efficiently despite having high levels of p53