A constant of quantum motion in two dimensions in crossed magnetic and electric fields

We consider the quantum dynamics of a single particle in the plane under the influence of a constant perpendicular magnetic and a crossed electric potential field. For a class of smooth and small potentials we construct a non-trivial invariant of motion. Do to so we proof that the Hamiltonian is unitarily equivalent to an effective Hamiltonian which commutes with the observable of kinetic energy.Comment: 18 pages, 2 figures; the title was changed and several typos corrected; to appear in J. Phys. A: Math. Theor. 43 (2010

Effects of Herding on Rangeland Use Efficiency in Kenya

Within each foraging itinerary, herders can intervene in the forage selection process, encouraging herds to use highly palatable and less palatable rangeland resources. Such a herding strategy could prevent rangeland degradation and increase livestock productivity. The objectives of this study were to examine forage availability and identify factors influencing stocking rates around night resting places on a ranch in Laikipia County, Kenya. Forage availability was measured along six regularly spaced transects around night resting places corralling one herd of camels, one mixed herd of goats and sheep, and two herds of cattle, with biomass sampling points at 50-, 150-, 250-, and 350-meter distance from the night resting places. Every four days, herbaceous biomass was collected at each sampling point and classified into monocotyledonous plants, dicotyledonous plants, and litter. Pooled samples of biomass were analyzed for their nutrient content. Activities of herders and herds were monitored. Stocking rates were calculated for the sampling points using georeferenced data of foraging itineraries recorded in 20-second intervals, area densities of herds measured by a hand-held global positioning system receiver, and live weights of all animals determined monthly. Except for the herd of camels, the distance to the night resting places had no effect on stocking rates. Not forage nutritive value, but palatability of dominant species on sampling points mainly influenced stocking rates, and thus forage availability. All livestock species sought patches dominated by Cynodon dactylon, possibly being overgrazed. Patches dominated by either Andropogon contortus or Themeda triandra were underused, as indicated by biomass accumulation. Thus, the efforts of the hired herders in this study did not lead to the desired herding effects. Therefore, motivating herders to design foraging itineraries utilizing diverse vegetation patches intentionally is crucial to an efficient use of rangeland resources, while meeting the nutritional requirements of animals

An axisymmetric time-domain spectral-element method for full-wave simulations: Application to ocean acoustics

The numerical simulation of acoustic waves in complex 3D media is a key topic in many branches of science, from exploration geophysics to non-destructive testing and medical imaging. With the drastic increase in computing capabilities this field has dramatically grown in the last twenty years. However many 3D computations, especially at high frequency and/or long range, are still far beyond current reach and force researchers to resort to approximations, for example by working in 2D (plane strain) or by using a paraxial approximation. This article presents and validates a numerical technique based on an axisymmetric formulation of a spectral finite-element method in the time domain for heterogeneous fluid-solid media. Taking advantage of axisymmetry enables the study of relevant 3D configurations at a very moderate computational cost. The axisymmetric spectral-element formulation is first introduced, and validation tests are then performed. A typical application of interest in ocean acoustics showing upslope propagation above a dipping viscoelastic ocean bottom is then presented. The method correctly models backscattered waves and explains the transmission losses discrepancies pointed out in Jensen et al. (2007). Finally, a realistic application to a double seamount problem is considered.Comment: Added a reference, and fixed a typo (cylindrical versus spherical

Wild olive seed weevil, Anchonocranus oleae Marshall (Coleoptera: Curculionidae), in cultivated olives in South Africa

Wild olive seed weevil, Anchonocranus oleae Marshall, larvae as well as oviposition and feeding damage were recorded in cultivated olives during a recent study on olive seed wasps in South Africa. Prematurely dropped fruit and fruit picked at harvest in two orchards near Stellenbosch and Agter- Paarl were examined regularly for olive seed wasp infestation over three seasons. In addition, olives were collected over a wider area of the olive growing regions of the Western Cape province for a survey to determine olive seed wasp distribution. DNA barcoding confirmed the identity of weevil larvae in kernels as A. oleae. The number of A. oleae larvae found in olive seeds and the number of olives with weevil oviposition or feeding damage were low. The presence of larvae and weevil damage in two orchards in the survey with no wild olive trees in close proximity suggest that the weevil could breed and persist in cultivated olive orchards. Currently A. oleae is not of economic concern, but if infested olives are discarded at harvest and left in orchards, the weevils could complete their development in the kernels and numbers could increase to damaging levels

Insourcing Health Care Innovation

Many health care professionals find it irritating when management gurus recommend solving health care\u27s problems with approaches they would “copy and paste” from unrelated industries — a former chief executive of a manufacturing company claims that the same simple lessons that enabled him to transform his own industry can improve value in health care, or a business-school professor offers an eight-point leadership plan that she\u27s translated into health care as easily as if she\u27d translated it into French. Many people who work in health care value outside perspectives and are open to new approaches — and yet bristle at facile recommendations emerging from these translations

Varietal effects on methane intensity of paddy fields under different irrigation management

Alternate wetting and drying irrigation (AWD) has been shown to decrease water use and trace gas emissions from paddy fields. Whereas genotypic water use shows little variation, it has been shown that rice varieties differ in the magnitude of their methane emissions. Management and variety-related emission factors have been proposed for modelling the impact of paddy production on climate change; however, the magnitude of a potential reduction in greenhouse gas emissions by changing varieties has not yet been fully assessed. AWD has been shown to affect genotypic yields and high-yielding varieties suffer the greatest loss when grown under AWD. The highest yielding varieties may not have the highest methane emissions; thus, a potential yield loss could be compensated by a larger reduction in methane emissions. However, AWD can only be implemented under full control of irrigation water, leaving the rainy seasons with little scope to reduce methane emissions from paddy fields. Employing low-emitting varieties during the rainy season may be an option to reduce methane emissions but may compromise farmers’ income if such varieties perform less well than the current standard. Methane emissions and rice yields were determined in field trials over two consecutive winter/spring seasons with continuously flooded and AWD irrigation treatments for 20 lowland rice varieties in the Mekong Delta of Vietnam. Based on the results, this paper investigates the magnitude of methane savings through varietal choice for both AWD and continuous flooding in relation to genotypic yields and explores potential options for compensating farmers’ mitigation efforts

CFTR gene variant for patients with congenital absence of vas deferens [3]

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Mitogenomics of the Olive Seed Weevil, Anchonocranus oleae Marshall and Implications for Its Phylogenetic Position in Curculionidae

Anchonocranus oleae Marshall (Coleoptera: Curculionidae) is a seed-feeding weevil native to southern Africa; its larvae are known to develop in the fruits of the African Wild Olive and, more rarely, cultivated olives. The species has been mainly found in the Western Cape province of South Africa, but it has remained in relative obscurity because it does not seem to represent a current threat to commercial olive production. As part of an ongoing effort to produce baseline genetic data for olive-associated entomofauna in South Africa, we generated reference DNA barcodes for A. oleae collected from wild and cultivated olives and sequenced its mitogenome for assessment of the phylogenetic position of the species in the family Curculionidae. The mitochondrial phylogeny estimate indicated that A. oleae shares a common ancestor with Elaidobius (tribe Derelomini), but a definite and close relationship to this tribe and the precise tribal placement of A. oleae in the subfamily Curculioninae could not be inferred due to the lack of representative mitogenomes of other relevant curculionine tribes and genera. This study will assist future work on the DNA-based species identification, genetic diversity, and phylogenetic position of the genus Anchonocranus and related taxa

Dynamic effect of phase conjugation on wave localization

We investigate what would happen to the time dependence of a pulse reflected by a disordered single-mode waveguide, if it is closed at one end not by an ordinary mirror but by a phase-conjugating mirror. We find that the waveguide acts like a virtual cavity with resonance frequency equal to the working frequency omega_0 of the phase-conjugating mirror. The decay in time of the average power spectrum of the reflected pulse is delayed for frequencies near omega_0. In the presence of localization the resonance width is tau_s^{-1}exp(-L/l), with L the length of the waveguide, l the mean free path, and tau_s the scattering time. Inside this frequency range the decay of the average power spectrum is delayed up to times t simeq tau_s exp(L/l).Comment: 10 pages including 2 figure