On Vertically Global, Horizontally Local Models for Astrophysical Disks

Disks with a barotropic equilibrium structure, for which the pressure is only a function of the density, rotate on cylinders in the presence of a gravitational potential, so that the angular frequency of such a disk is independent of height. Such disks with barotropic equilibria can be approximately modeled using the shearing box framework, representing a small disk volume with height-independent angular frequency. If the disk is in baroclinic equilibrium, the angular frequency does generally depend on height, and it is thus necessary to go beyond the standard shearing box approach. In this paper, we show that given a global disk model, it is possible to develop approximate models that are local in horizontal planes without an expansion in height with shearing-periodic boundary conditions. We refer to the resulting framework as the vertically global shearing box (VGSB). These models can be non-axisymmetric for globally barotropic equilibria but should be axisymmetric for globally baroclinic equilibria. We provide explicit equations for this VGSB which can be implemented in standard magnetohydrodynamic codes by generalizing the shearing-periodic boundary conditions to allow for a height-dependent angular frequency and shear rate. We also discuss the limitations that result from the radial approximations that are needed in order to impose height-dependent shearing periodic boundary conditions. We illustrate the potential of this framework by studying a vertical shear instability and examining the modes associated with the magnetorotational instability.Comment: 24 pages, 8 figures, updated to match published versio

Modified bubble level senses pitch and roll angles over wide range

Bubble level sensor with fiber-optic field flattener is simple, rugged, small, and impervious to temperature and vibration effects. Pitch angles from -15 deg to +40 deg and roll angles of +30 deg are determined within 0.5 deg

Computational methods for internal flows with emphasis on turbomachinery

Current computational methods for analyzing flows in turbomachinery and other related internal propulsion components are presented. The methods are divided into two classes. The inviscid methods deal specifically with turbomachinery applications. Viscous methods, deal with generalized duct flows as well as flows in turbomachinery passages. Inviscid methods are categorized into the potential, stream function, and Euler aproaches. Viscous methods are treated in terms of parabolic, partially parabolic, and elliptic procedures. Various grids used in association with these procedures are also discussed

Finding an identity and meeting a standard : connecting the conflicting in teacher induction

This article has the apparently contradictory aims of describing a discourse of new teachers that is at odds with the policy-derived competence-based discourse of the professional standard for teachers, but of also seeking to find some points of connection that may help start a dialogue between policy and research. The experience of new teachers is conceptualized as personal stories of identity formation with a clear emotional-relational dimension and a sense of self and intrinsic purpose in which others, especially colleagues and children, are central - themes not visible in the standard. The empirical context is that of new teachers in Scotland but the argument is supported through a wider literature that extends beyond the traditional limits of teacher education, drawing on, for example, notions of self-identity, pure relationship and ontological security in the work of Giddens. Whether a more constructive dialogue can begin depends partly on the extent to which the formal standard can be expected to capture the complex, personal nature of the beginner's experience, and partly on the possibility of research identifying particular areas of competence, such as understanding difference, that connect in some way to the standard

An Investigation of the Informed Consent Being Rendered Under PL 94-142 on Behalf of Handicapped Children in Foster Care

Submitted to the Department of Special Education and to the Faculty of the Graduate School of the University of Kansas in partial fulfullment of the requirements for the degree of Doctor of Philosophy.The purpose of this investigation was to examine the level of accuracy and agreement of social worker and foster parent representatives of handicapped foster children with respect to their understanding of eight Local Education Agency (LEA) Team special education decisions. The accuracy and agreement of these representatives were examined under four quasi-experimental conditions of representative involvement: when both, neither, or either of the two representatives had been involved in the foster children's last IEP staffing. Subjects consisted of 96 sets of social workers and foster parents in two states, Kansas and Massachusetts. Procedures consisted of conducting face-to-face interviews with subjects in order to obtain their responses regarding the eight LEA Team decisions of: (a) classification, (b) e l i g i b i l i t y , (c) program placement, (d) IEP goals, (e) IEP objectives, (f) responsibility for service delivery, (g) frequency of service delivery, (h) duration of service delivery. Three sets of survey instruments were developed and field tested for this study. Recordings of subject responses were obtained and scored for accuracy and agreement of the two sets of representatives. The foster care representatives 1 responses were compared to those of a control group of natural parent subjects who were matched according to the LEA of the handicapped children under Condition 4, both representatives involved in the last IEP staffing. Results showed significant disagreement between social worker and foster parent on five LEA Team decisions under the four conditions of representative involvement. Six significant results were obtained with respect to social worker and foster parent accuracy under the four conditions. Comparisons between the foster care representatives and the natural parent representatives revealed significant differences between the two groups in terms of the magnitude of their accuracy and their agreement across the eight LEA Team decisions. The investigator concluded that the special education representation of the handicapped foster children examined in this study lacked the consistency in agreement and accuracy that is necessary for informed consent to be rendered on their behalf

Escherichia coli of sequence type 3835 carrying blaNDM-1, blaCTX-M-15, blaCMY-42 and blaSHV-12

New Delhi metallo-β-lactamase (NDM) represents a serious challenge for treatment and public health. A carbapenem-resistant Escherichia coli clinical strain WCHEC13-8 was subjected to antimicrobial susceptibility tests, whole genome sequencing and conjugation experiments. It was resistant to imipenem (MIC, >256 μg/ml) and meropenem (MIC, 128 μg/ml) and belonged to ST3835. blaNDM-1 was the only carbapenemase gene detected. Strain WCHEC13-8 also had a plasmid-borne AmpC gene (blaCMY-42) and two extended-spectrum β-lactamase genes (blaCTX-M-15 and blaSHV-12). blaNDM-1 and blaSHV-12 were carried by a 54-kb IncX3 self-transmissible plasmid, which is identical to plasmid pNDM-HF727 from Enterobacter cloacae. blaCMY-42 was carried by a 64-kb IncI1 plasmid and blaCTX-M-15 was located on a 141-kb plasmid with multiple F replicons (replicon type: F36:A4:B1). blaCMY-42 was in a complicated context and the mobilisation of blaCMY-42 was due to the transposition of IS Ecp1 by misidentifying its right-end boundary. Genetic context of blaNDM-1 in strain WCHEC13-8 was closely related to those on IncX3 plasmids in various Enterobacteriaceae species in China. In conclusion, a multidrug-resistant ST3835 E. coli clinical strain carrying blaNDM-1, blaCTX-M-15, blaCMY-42 and blaSHV-12 was identified. IncX3 plasmids may be making a significant contribution to the dissemination of blaNDM among Enterobacteriaceae in China

Increased human pathogenic potential of Escherichia coli from polymicrobial urinary tract infections in comparison to isolates from monomicrobial culture samples

The current diagnostic standard procedure outlined by the Health Protection Agency for urinary tract infections (UTIs) in clinical laboratories does not report bacteria isolated from samples containing three or more different bacterial species. As a result many UTIs go unreported and untreated, particularly in elderly patients, where polymicrobial UTI samples are especially prevalent. This study reports the presence of the major uropathogenic species in mixed culture urine samples from elderly patients, and of resistance to front-line antibiotics, with potentially increased levels of resistance to ciprofloxacin and trimethoprim. Most importantly, the study highlights that Escherichia coli present in polymicrobial UTI samples are statistically more invasive (P<0.001) in in vitro epithelial cell infection assays than those isolated from monomicrobial culture samples. In summary, the results of this study suggest that the current diagnostic standard procedure for polymicrobial UTI samples needs to be reassessed, and that E. coli present in polymicrobial UTI samples may pose an increased risk to human health

Time-dependent transonic flow solutions for axial turbomachinery

Three-dimensional unsteady transonic flow through an axial turbomachine stage is described in terms of a pair of two-dimensional formulations pertaining to orthogonal surfaces, namely, a blade-to-blade surface and a hub-to-casing surface. The resulting systems of nonlinear, inviscid, compressible equations of motion are solved by an explicit finite-difference technique. The blade-to-blade program includes the periodic interaction between rotor and stator blade rows. Treatment of the boundary conditions and of the blade slipstream motion by a characteristic type procedure is discussed in detail. Harmonic analysis of the acoustic far field produced by the blade row interaction, including an arbitrary initial transient, is outlined. Results from the blade-to-blade program are compared with experimental measurements of the rotating pressure field at the tip of a high-speed fan. The hub-to-casing program determines circumferentially averaged flow properties on a meridional plane. Blade row interactions are neglected in this formulation, but the force distributions over the entire blade surface for both the rotor and stator are obtained. Results from the hub-to-casing program are compared with a relaxation method solution for a subsonic rotor. Results are also presented for a quiet fan stage which includes transonic flow in both the rotor and stator and a normal shock in the stator

Short Circuits in Thermally Ionized Plasmas: A Mechanism for Intermittent Heating of Protoplanetary Disks

Many astrophysical systems of interest, including protoplanetary accretion disks, are made of turbu- lent magnetized gas with near solar metallicity. Thermal ionization of alkali metals in such gas exceeds non-thermal ionization when temperatures climb above roughly 1000 K. As a result, the conductiv- ity, proportional to the ionization fraction, gains a strong, positive dependence on temperature. In this paper, we demonstrate that this relation between the temperature and the conductivity triggers an exponential instability that acts similarly to an electrical short, where the increased conductivity concentrates the current and locally increases the Ohmic heating. This contrasts with the resistiv- ity increase expected in an ideal magnetic reconnection region. The instability acts to focus narrow current sheets into even narrower sheets with far higher currents and temparatures. We lay out the basic principles of this behavior in this paper using protoplanetary disks as our example host system, motivated by observations of chondritic meteorites and their ancestors, dust grains in protoplanetary disks, that reveal the existence of strong, frequent heating events that this instability could explain.Comment: 9 pages, 6 figures, 1 table Accepted, Ap