The Strong Levinson Theorem for the Dirac Equation

We consider the Dirac equation in one space dimension in the presence of a symmetric potential well. We connect the scattering phase shifts at E=+m and E=-m to the number of states that have left the positive energy continuum or joined the negative energy continuum respectively as the potential is turned on from zero.Comment: Submitted to Physical Review Letter

Hydrologic Analysis of Two Headwater Lake Basins of Differing Lake pH in the West-central Adirondack Mountains of New York

Hydrologic analysis of two headwater lake basins in the Adirondack Mountains, New York, during 1980-81 indicates that the degree of neutralization of acid precipitation is controlled by the groundwater contribution to the lake. According to flow-duration analyses, daily mean outflow/unit area from the neutral lake (Panther Lake, pH 5-7) was more sustained and contained a higher percentage of groundwater than that of the acidic lake (Woods Lake, pH 4-5). Outflow recession rates and maximum base-flow rates, derived from individual recession curves, were 3.9 times and 1.5 times greater, respectively, in the neutral-lake basin than in the acidic-lake basin. Groundwater contribution to lake outflow was also calculated from a lake-water budget; the groundwater contribution to the neutral lake was about 10 times greater than that to the acidic lake. Thick sandy till forms the groundwater reservoir and the major recharge area in both basins but covers 8.5 times more area in the neutral-lake basin than in the acidic-lake basin. More groundwater storage within the neutral basin provides longer contact time with neutralizing minerals and more groundwater discharge. As a result, the neutral lake has relatively high pH and alkalinity, and more net cation transport. (USGS

Phytosterol Pygeum africanum regulates prostate cancer in vitro and in vivo

Background Prostate cancer is an important public health problem. It is an excellent candidate disease for chemo-prevention because prostate cancer is typically slow growing and is usually diagnosed in elderly males. Pygeum africanum (Prunus africana or Rosaceae) is an African prune (plum) tree found in tropical Africa. An extract from the bark of Pygeum africanum has been used in Europe as a prevention and treatment of prostate disorders including benign prostatic hypertrophy (BPH). More recently in the USA, the phytotherapeutic preparations of Pygeum africanum and Saw palmetto have been marketed for prostate health including prostate cancer prevention and treatment. Methods The anti-cancer potential of Pygeum africanum has been tested both in vitro (PC-3 and LNCaP cells) and in␣vivo (TRAMP mouse model). Results In tissue culture, ethanolic extracts (30%) of Pygeum africanum inhibited the growth of PC-3 and LNCaP cells; induced apoptosis and altered cell kinetics; down regulated ERα and PKC-α protein, and demonstrated good binding ability to both mouse uterine estrogen receptors and LNCaP human androgen receptors. TRAMP mice fed Pygeum africanum showed a significant reduction (P = 0.034) in prostate cancer incidence (35%) compared to casein fed mice (62.5%). Conclusion Pygeum africanum, which is widely used in Europe and USA for treatment of BPH, has a significant role in regulation of prostate cancer both in␣vitro and in␣vivo and therefore may be a useful supplement for people at high risk for developing prostate cancer

Spatial and temporal variation in population trends in a long-distance migratory bird

Over the past three decades, evidence has been growing that many Afro-Palaearctic migratory bird populations have suffered sustained and severe declines. As causes of these declines exist across both the breeding and non-breeding season, identifying potential drivers of population change is complex. In order to explore the roles of changes in regional and local environmental conditions on population change, we examine spatial and temporal variation in population trajectories of one of Europe’s most abundant Afro-Palaearctic summer migrants, the willow warbler, Phylloscopus trochilus. Britain and Ireland. We use national survey data from Britain and Ireland (BBS: BTO/RSPB/JNCC Breeding Bird Survey and CBS: BWI/NPWS/Heritage Council Countryside Breeding Survey) from 1994 to 2006 to model the spatial and temporal variation in willow warbler population trends. Across Britain and Ireland, population trends follow a gradient from sharp declines in the south and east of England to shallow declines and/or slight increases in parts of north and west England, across Scotland and Ireland. Decreasing the spatial scale of analysis reveals variation in both the rate and spatial extent of population change within central England and the majority of Scotland. The rates of population change also vary temporally; declines in the south of England are shallower now than at the start of the time series, whereas populations further north in Britain have undergone periods of increase and decline. These patterns suggest that regional-scale drivers, such as changing climatic conditions, and local-scale processes, such as habitat change, are interacting to produce spatially variable population trends. We discuss the potential mechanisms underlying these interactions and the challenges in addressing such changes at scales relevant to migratory species

Intra-specific niche partitioning in Antarctic fur seals, Arctocephalus gazella

Competition for resources within a population can lead to niche partitioning between sexes, throughout ontogeny and among individuals, allowing con-specifics to co-exist. We aimed to quantify such partitioning in Antarctic fur seals, Arctocephalus gazella, breeding at South Georgia, which hosts ~95% of the world’s population. Whiskers were collected from 20 adult males and 20 adult females and stable isotope ratios were quantified every 5 mm along the length of each whisker. Nitrogen isotope ratios (δ15N) were used as proxies for trophic position and carbon isotope ratios (δ13C) indicated foraging habitat. Sexual segregation was evident: δ13C values were significantly lower in males than females, indicating males spent more time foraging south of the Polar Front in maritime Antarctica. In males δ13C values declined with age, suggesting males spent more time foraging south throughout ontogeny. In females δ13C values revealed two main foraging strategies: 70% of females spent most time foraging south of the Polar Front and had similar δ15N values to males, while 30% of females spent most time foraging north of the Polar Front and had significantly higher δ15N values. This niche partitioning may relax competition and ultimately elevate population carrying capacity with implications for ecology, evolution and conservation

Metapopulation dynamics of roseate terns: Sources, sinks and implications for conservation management decisions

Habitat management to restore or create breeding sites may allow metapopulations to increase in size and reduce the risk of demographic stochasticity or disasters causing metapopulation extinction. However, if newly restored or created sites are of low quality, they may act as sinks that draw individuals away from better quality sites to the detriment of metapopulation size. Following intensive conservation effort, the metapopulation of roseate tern (Sterna dougallii) in NW Europe is recovering from a large crash in numbers, but most former colonies remain unoccupied and hence are potential targets for restoration. To inform conservation efforts, we studied the dynamics of this metapopulation with a multistate integrated population model to assess each of the three main colonies for important demographic contributors to population growth rate, source/sink status and possible density dependence. All three study colonies are managed for roseate terns (and other tern species) in similar ways, but the demographic processes vary considerably between colonies. The largest colony is a source involved in almost all dispersal, and its growth is determined by survival rates and productivity. Productivity and juvenile apparent survival at the largest colony appear to be density-dependent. Although the mechanisms are unclear, this may provide an increasing impetus for emigration of recruits to other colonies in future. The smallest of the three colonies is a sink, relying on immigration for its growth. Simulation models suggest the metapopulation would be c. 10% larger in the absence of dispersal to the sink colony. This work indicates that, due to variable site quality, aims to enhance both distribution and size of metapopulations may be mutually exclusive. In this case, before future attempts to encourage recolonisation of former sites, assessments of site suitability should be undertaken, focusing on food availability and isolation from predators to maximise the likelihood of attaining levels of productivity and survival that avoid creation of a sink population to the detriment of the overall metapopulation size

Stable isotope values in South American fur seal pup whiskers as proxies of year-round maternal foraging ecology

Natural selection should favour strategies that maximise reproductive success. Females may use different resources during progressive stages of reproduction according to energetic demands, behavioural constraints and prey availability. We used South American fur seal, Arctocephalus australis australis, pup whisker isotope values as proxies for maternal diet and habitat use to determine how resource use (1) changes throughout pup development from in utero growth to mid-end of lactation and (2) how it differs among individuals. The longest whisker was cut from 5 male and 5 female fur seal pups (of approximately 8 months of age) at Bird Island, Falkland Islands, in 2018, and δ15N values and δ13C values were analysed every 5 mm along the length of each whisker. Patterns in δ13C values indicated that mothers used different habitats during the annual cycle, likely coinciding with seasonal shifts in prey availability or distribution. The individual specialisation index based on δ13C values was 0.34, indicating that adult females used different habitats, which could reduce intra-specific competition and ultimately enhance pup growth and survival. An increase in δ15N values occurred along every pup whisker from pup birth to mid-end of lactation, which likely reflected trophic enrichment related to suckling and fasting by pups, overriding the maternal isotopic signature. Pup whisker stable isotopes are useful proxies of maternal foraging ecology. However, physiological processes complicate interpretations by altering δ15N values. Interpreting these values therefore requires additional knowledge of the species’ ecology and physiology

Low Momentum Scattering in the Dirac Equation

It is shown that the amplitude for reflection of a Dirac particle with arbitrarily low momentum incident on a potential of finite range is -1 and hence the transmission coefficient T=0 in general. If however the potential supports a half-bound state at k=0 this result does not hold. In the case of an asymmetric potential the transmission coefficient T will be non-zero whilst for a symmetric potential T=1.Comment: 12 pages; revised to include additional references; to be published in J Phys

Ohio Northern Alumnus - July, 1927

https://digitalcommons.onu.edu/alumni_mag/1001/thumbnail.jp

Gravitational quasinormal modes for Anti-de Sitter black holes

Quasinormal mode spectra for gravitational perturbations of black holes in four dimensional de Sitter and anti-de Sitter space are investigated. The anti-de Sitter case is relevant to the ADS-CFT correspondence in superstring theory. The ADS-CFT correspondence suggests a prefered set of boundary conditions.Comment: 12 pages, 6 figures in ReVTe