The general relativistic infinite plane

Uniform fields are one of the simplest and most pedagogically useful examples in introductory courses on electrostatics or Newtonian gravity. In general relativity there have been several proposals as to what constitutes a uniform field. In this article we examine two metrics that can be considered the general relativistic version of the infinite plane with finite mass per unit area. The first metric is the 4D version of the 5D "brane" world models which are the starting point for many current research papers. The second case is the cosmological domain wall metric. We examine to what extent these different metrics match or deviate from our Newtonian intuition about the gravitational field of an infinite plane. These solutions provide the beginning student in general relativity both computational practice and conceptual insight into Einstein's field equations. In addition they do this by introducing the student to material that is at the forefront of current research.Comment: Accepted for publication in the American Journal of Physic

Wind Effects on Near- and Midfield Mixing in Tidally Pulsed River Plumes

River plumes transport and mix land-based tracers into the ocean. In tidally pulsed river plumes, wind effects have long been considered negligible in modulating interfacial mixing in the energetic nearfield region. This research tests the influence of variable, realistic winds on mixing in the interior plume. A numerical model of the Merrimack River plume-shelf system is utilized, with an application of the salinity variance approach employed to identify spatial and temporal variation in advection, straining, and dissipation (mixing) of vertical salinity variance (stratification). Results indicate that moderate wind stresses (∼0.5 Pa) with a northward component countering the downcoast rotation of the plume are most effective at decreasing stratification in the domain relative to other wind conditions. Northward winds advect plume and ambient shelf stratification offshore, allowing shelf water salinity to increase in the nearshore, which strengthens the density gradient at the plume base. Straining in the plume increases with winds enhancing offshore-directed surface velocities, leading to increased shear at the plume base. Increased straining and larger density gradients at the plume base enhance variance dissipation in the near- and midfield plume, and dissipation remains enhanced if the shelf is clear of residual stratification. The smaller spatial and temporal scales of the Merrimack plume allow the mechanisms to occur at tidal time scales in direct response to instantaneous winds. This is the first study to show tidal time scale wind-induced straining and advection as controlling factors on near- and midfield mixing rates in river plumes under realistic winds

RELACIÓN ENTRE EL RENDIMIENTO ACADÉMICO DE LOS INGRESANTES Y EL ABANDONO DE LOS ESTUDIOS UNIVERSITARIOS: COMPARACIÓN ENTRE CARRERAS DE INGENIERÍA Y ECONOMICAS

La preocupación por orientar adecuadamente los recursos que se afectan a los programas de apoyo a los estudiantes de primer año de las carreras, nos llevó a trabajar intentando generar un modelo que sea capaz de determinar, anticipadamente, que estudiantes se encontrarían en situación de abandonar sus estudios. En una primera aplicación del modelo, se analizó la correlación entre el rendimiento académico y el abandono para diez cohortes de ingresantes, de las dos carreras de Ingeniería que ofrece la Universidad Nacional de Luján, observándose una significativa correlación entre el rendimiento académico del estudiante en el primer cuatrimestre y el abandono de los estudios durante el segundo, tercero y cuarto cuatrimestre. En este trabajo, presentamos los resultados que se alcanzaron al aplicar el mismo modelo a las diez cohortes, equivalentes, de estudiantes de las dos carreras del campo de las Ciencias Económicas que se ofrecen en la misma Institución: Licenciatura en Administración y Licenciatura en Comercio Internacional. Las principales conclusiones a las que arribamos es que el modelo se valida positivamente al cambiar el origen disciplinar de las carreras en las que se aplica. Por otra parte, existe mayor correlación entre el rendimiento académico en el primer cuatrimestre y el momento en que se abandonan los estudios para los estudiantes de carreras de Ciencias Económicas que la observada en los de Ingeniería. Se repite el fenómeno observado para las carreras de Ingeniería, de disminuir la correlación entre el rendimiento académico y el abandono para la cohorte 2002. También se detecta una diferencia significativa respecto de la moda para la cantidad de asignaturas aprobadas durante el primer cuatrimestre para las cuatro carreras

Soil Application Effects of Metarhizium anisopliae on Japanese Beetle (Coleoptera: Scarabaeidae) Behavior and Survival in Turfgrass Microcosms

The effect of mycelial and conidial formulations of the insect pathogenic fungi, M. anisopliae, on the survival and behavior Japanese beetle, Popillia japonica Newman, larvae and ovipositing adults in turfgrass-soil microcosms was explored. Changes in Japanese beetle grub feeding site selection on sod roots, movement patterns, and survival in Metarhizium anisopliae inoculated soil were examined in greenhouse studies and through the use of radiographic analysis in the laboratory. Our studies indicate that the application of mycelial particles in soil affected the behavior of both larval and adult Japanese beetles. Japanese beetle grubs avoided soil that contained high concentrations of pathogen for up to 20 d after application. Conversely, the incorporation of mycelial particles increased oviposition in both choice and no choice studies. Our findings on scarab response to inundative applications of M. anisopliae mycelium may help explain some of the inconsistency in results that often occur when fungal pathogens are used to control insects in the fiel

Sexual Selection: Do Flies Lie with Asymmetric Legs?

SummaryA newly described species of empidid or ‘dance fly’ shows a bizarre polymorphism in their forelegs, which presumably serve as a mating lure. This trait may have evolved by frequency-dependent deceptive male signalling

Imprints of Nuclear Symmetry Energy on Properties of Neutron Stars

Significant progress has been made in recent years in constraining the density dependence of nuclear symmetry energy using terrestrial nuclear laboratory data. Around and below the nuclear matter saturation density, the experimental constraints start to merge in a relatively narrow region. At supra-saturation densities, there are, however, still large uncertainties. After summarizing the latest experimental constraints on the density dependence of nuclear symmetry energy, we highlight a few recent studies examining imprints of nuclear symmetry energy on the binding energy, energy release during hadron-quark phase transitions as well as the $w$-mode frequency and damping time of gravitational wave emission of neutron stars.Comment: 10 pages. Invited talk given in the Nuclear Astrophysics session of INPC2010, July 4-9, 2010, Vancouver, Canada; Journal of Physics: Conference Series (2011

Frequent Undetected Ward-Based Methicillin-Resistant Staphylococcus aureus Transmission Linked to Patient Sharing Between Hospitals.

Background: Recent evidence suggests that hospital transmission of methicillin-resistant Staphylococcus aureus (MRSA) is uncommon in UK centers that have implemented sustained infection control programs. We investigated whether a healthcare-network analysis could shed light on transmission paths currently sustaining MRSA levels in UK hospitals. Methods: A cross-sectional observational study was performed in 2 National Health Service hospital groups and a general district hospital in Southeast London. All MRSA patients identified at inpatient, outpatient, and community settings between 1 November 2011 and 29 February 2012 were included. We identified genetically defined MRSA transmission clusters in individual hospitals and across the healthcare network, and examined genetic differentiation of sequence type (ST) 22 MRSA isolates within and between hospitals and inpatient or outpatient and community settings, as informed by average and median pairwise single-nucleotide polymorphisms (SNPs) and SNP-based proportions of nearly identical isolates. Results: Two hundred forty-eight of 610 (40.7%) MRSA patients were linked in 90 transmission clusters, of which 27 spanned multiple hospitals. Analysis of a large 32 patient ST22-MRSA cluster showed that 26 of 32 patients (81.3%) had multiple contacts with one another during ward stays at any hospital. No residential, outpatient, or significant community healthcare contacts were identified. Genetic differentiation between ST22 MRSA inpatient isolates from different hospitals was less than between inpatient isolates from the same hospitals (P ≤ .01). Conclusions: There is evidence of frequent ward-based transmission of MRSA brought about by frequent patient admissions to multiple hospitals. Limiting in-ward transmission requires sharing of MRSA status data between hospitals

Meaning in hoarding: perspectives of people who hoard on clutter, culture, and agency

Hoarding has become increasingly prominent in clinical practice and popular culture in recent years, giving rise to extensive research and commentary. Critical responses in the social sciences have criticised the cultural assumptions built in to the construct of ‘hoarding disorder’ and expressed fears that it may generate stigma outweighing its benefits; however, few of these studies have engaged directly with ‘hoarders’ themselves. This paper reports on in-depth, semi-structured interviews with ten individuals living in England, who received assessment and intervention for hoarding from Social Services. Their narratives drew on the cultural repertoire of values and discourses around waste and worth, the mediation of sociality and relationships through material objects, physical constraints on keeping order, and the role played by mental health. Analysing these perspectives anthropologically shows how dominant models of hoarding, such as the DSM-5 paradigm, potentially lend themselves to reductionist understandings that efface the meaning ‘hoarding’ may have and thereby deny agency to the person labelled as ‘hoarder’. More culturally informed analysis, by contrast, affords insights into the complex landscape of value, waste, social critique, emotion, interpersonal relationships and practical difficulties that may underlie hoarding cases, and points the way to more person-centred practice and analysis

Law in social work education: reviewing the evidence on teaching, learning and assessment

This paper presents the findings from a systemic review of knowledge relating to current practice in the teaching, learning and assessment of law in social work education. The research comprised an internationally conducted systematic review of the literature, together with a survey of current education practice in the four countries of the UK. Two consultation events sought the views of a range of stakeholders, including the perspectives of service users and carers. Set in the context of debates about the relationship between law and social work practice, this paper identifies the common themes emerging from the review and offers an analysis of key findings, together with priorities for future directions in education practice

The Century Survey Galactic Halo Project III: A Complete 4300 deg^2 Survey of Blue Horizontal Branch Stars in the Metal-Weak Thick Disk and Inner Halo

We present a complete spectroscopic survey of 2414 2MASS-selected blue horizontal branch (BHB) candidates selected over 4300 deg^2 of the sky. We identify 655 BHB stars in this non-kinematically selected sample. We calculate the luminosity function of field BHB stars and find evidence for very few hot BHB stars in the field. The BHB stars located at a distance from the Galactic plane |Z|<4 kpc trace what is clearly a metal-weak thick disk population, with a mean metallicity of [Fe/H]= -1.7, a rotation velocity gradient of dv_{rot}/d|Z|= -28+-3.4 km/s in the region |Z|<6 kpc, and a density scale height of h_Z= 1.26+-0.1 kpc. The BHB stars located at 5<|Z|<9 kpc are a predominantly inner-halo population, with a mean metallicity of [Fe/H]= -2.0 and a mean Galactic rotation of -4+-31 km/s. We infer the density of halo and thick disk BHB stars is 104+-37 kpc^-3 near the Sun, and the relative normalization of halo to thick-disk BHB stars is 4+-1% near the Sun.Comment: 12 pages in emulateapj format, accepted for publication in February A