The Structure and Stability of Selected, 2-D Self-Gravitating Systems.

Models of radially and vertically extended self-gravitating disks orbiting around a central point mass are relevant to the dynamics of astrophysical systems and are thought to be common in many galaxies. The gravity driven instabilities in these accretion disks are now believed to be a possible mechanism for star formation via disk fragmentation (Shu, Adams, & Lizano 1987, Adams, Rudin & Shu 1989; Christodoulou 1995). We quantify these regions of instability using a simple toroidal model of an accretion disk. We choose the two-dimensional axisymmetric, incompressible slender disks to examine and map out these principal modes of gravity driven instabilities. Through stability analyses and numerical simulations we have found that only the gravity driven intermediate modes (see Goodman and Narayan 1988) are important in all self-gravitating accretion disks with small or moderate axis ratios. The P-mode instability found by Papalaizou and Pringle (1983) is unlikely to play a role in the dynamics of realistic disk systems. Next, we extend the existing numerical methods for constructing equilibrium structures to include nonaxisymmetric systems. We have developed a new computational technique to obtain two-dimensional, nonaxisymmetric, compressible systems with nontrivial internal motions. We have constructed two types of two-dimensional configurations: infinite cylinders and infinitesimally thin disks. The infinite cylinders have been primarily restricted to elliptic-like boundaries but the disks have exhibited much more flexibility in their geometries. At smaller axis ratios, they become dumbbells or loosely coupled binaries. The topology and dynamics of the flow is governed by the presence of vortices and stagnation points. In our simulation it is shown that there are equilibrium configurations that can only exist in the presence of internal differential motions and not in uniformly rotating models. This indicates that in general, the equilibrium structures of these nonaxisymmetric configurations are dependent not just on the constant frame rotation but perhaps even more importantly on the internal differential fluid motion. This is especially important when we construct nonaxisymmetric models with high T/$\vert$W$\vert,$ where T and W are the kinetic and the gravitational potential energy respectively. In these systems, most of the contribution to T/$\vert$W$\vert$ comes from internal rotation

The feasibility of subirrigation systems on claypan soils in the Midwest

This was a study to evaluate the suitability of subirrigation along with alternative soil and water trujlnagement practices on claypan soil. Crop yields on these soils are usually low because of limited water management for crop production. Several years of crops, soil and weather data collected on a claypan soil in Illinois were used to study performance of subirrigation and conventional irrigation on these soils. Various drain spacings and depth combinations for both good and poor· quality surface drainage were simulated. Results indicated that optimum drain spacing for subirrigation on these soils would be 6 m under good surface drainage, and a weir setting depth of 35 cm on a 5-year recurrence interval basis. However, such a close drain spacing may not be economically feasible.U.S. Geological SurveyU.S. Department of the InteriorOpe

Farmers’ perceptions towards production of Ojinegra lamb meat, an autochthonous sheep breed

Over the last two decades, in Spain there has been a growing interest in recovering and maintaining autochthonous livestock breeds. This has partly occurred because these breeds are considered essential to coping with changing socio-economic and environmental conditions. The aim of the present work is to analyze the perceptions of the farmers toward the production lamb meat from an autochthonous livestock breed in Spain. In addition, were explored the interrelationships between these perceptions and characteristics of farms as well as the farmers’ objectives. The information used was obtained from a sample of 34 lamb meat producers of an autochthone sheep breed originally from northeastern Spain. The statistical analysis performed was descriptive analysis, factor analysis and cluster analysis. The results show that breeders greatly value the positive effects of sheep breeding on rural development, which generate employment in disadvantaged areas. The cluster analysis reveals the existence of two groups of farmers with different perceptions. Moreover, results indicate that the positive perceptions of producers toward autochthonous breeds are closely related to the farmers’ objectives. Hence, public and private organization initiatives that seek to promote the development of a particular breed should account for livestock farm heterogeneity. En las dos últimas décadas se ha producido en España un creciente interés por recuperar y mantener razas de ganado autóctonas, en parte por considerarse esenciales en la adaptación a condiciones socio-económicas y ambientales cambiantes. El objetivo del trabajo es analizar las percepciones de un grupo de productores hacia la carne de cordero de una raza autóctona, relacionándolas con diferentes objetivos de los ganaderos y con características de sus explotaciones. La información empleada en el estudio se obtuvo a partir de entrevistas personales dirigidas a una muestra de 34 productores de ovino de la raza autóctona originaria del noreste de España. El análisis estadístico consistió en análisis descriptivo, factorial y cluster. Los resultados indican que los ganaderos valoran mucho el efecto positivo de la explotación de la raza sobre el desarrollo rural y la generación de empleo en zonas desfavorecidas. La segmentación realizada muestra la existencia de dos grupos de productores con percepciones diferentes hacia la raza. Además las percepciones positivas de los ganaderos hacia la raza autóctona, están muy relacionadas con los objetivos perseguidos por los ganaderos en su explotación. Es por ello que cualquier medida tomada por organizaciones públicas ó privadas que pretenda la promoción y fomento de una raza, debería tener en cuenta la heterogeneidad de las explotaciones

Comparison of Best Management Practice Adoption Between Virginia\u27s Chesapeake Bay Basin and Southern Rivers Watersheds

Producers in two regions of Virginia (Chesapeake Bay basin and Southern Rivers region) were surveyed to compare farming practices and agricultural best management practice (BMP) adoption. Objectives were to assess farming operations and determine the extent of cost-share and non-cost-share BMP implementation and gain insight into the impact of selected socioeconomic factors on the BMP adoption. Although farming characteristics and producer attitudes toward pollution and water quality were similar, BMP implementation differed between the two regions. Differences in BMP implementation may be due to a more focused, longer-term NPS pollution control educational effort in the Bay basin

Evaluation of laparoscopic-assisted anorectoplasty for the management of intermediate and high anorectal malformations in boys: Mansoura experience

Introduction: Laparoscopic-assisted anorectoplasty (LAARP) has been gaining great popularity for management of imperforate anus. This study aims to evaluate the use of this technique for high and intermediate anorectal malformations in boys.Patients and methods: From December 2012 to December 2016, we performed LAARP on 20 boys, all of which were colostomized at birth. Findings regarding the patients’ age at operation, type of anomaly, associated morbidities, sacral ratios, operative time, intraoperative complications, hospital stay, immediate/long-term postoperative complications, and reoperations were noted. Postoperatively, we evaluated the patients using barium enema, an ascending and voiding cystourethrogram, pelvic MRI, and a functional continence evaluation questionnaire.Results: A total of 11 patients presented with rectourethral bulbar fistula (RBF), seven with rectourethral prostatic fistula (RPF), one with rectovesical fistula, and one with no fistula. Mean sacral ratio was 0.82 ± 0.19. Mean age at time of LAARP was 236 ± 77 days. Mean operative time was 152 ± 32 min. Our most common intraoperative complication was peritoneal contamination (20%). Incidence of rectal mucosal prolapse was 40%. Barium enema revealed a mean rectoanal angle of 107 ± 13°. Ascending and voiding cystourethrogram revealed a residual urethral diverticulum in seven cases, six of which had RBFs. Mean MRI placement score obtained was 0.76± 0.51 denoting excellent rectal position.Conclusion: Usage of LAARP to manage high and intermediate anorectal malformations in boys is feasible, allowing accurate rectal placement within the muscle complex and with good postoperative functional results. Residual urethral diverticulum occurred more frequently in patients with RBF. Incidence of mucosal prolapse is high after LAARP and should be avoided.Keywords: laparoscopic-assisted anorectoplasty, anorectal malformations, residual urethral diverticulum post LAAR

How to Authenticate a Device? Formal Authentication Models for M2M Communications Defending against Ghost Compromising Attack

In Machine-to-Machine (M2M) communications, authentication of a device is of upmost importance for applications of Internet of Things. As traditional authentication schemes always assume the presence of a person, most authentication technologies cannot be applied in machine-centric M2M context. In this paper, we make the first attempt to formally model the authentication in M2M. We first model four attacking adversaries that can formulate all possible attacks in M2M, which are channel eavesdropping attack, credential compromise attack, function compromise attack, and ghost compromise attack. Next, we propose four models to tackle those corresponding adversaries, namely, credential-based model, machine-metrics-based model, reference-based model, and witness-based model. We also illustrate several concrete attacking methods and authentication approaches. We proof the authentication security for all proposed models and compare them for clarity. Our models present soundness and completeness in terms of authentication security, which can guide the design and analysis of concrete authentication protocols. Particularly, we construct a uniform authentication framework for M2M context and point out all possible authentication mechanisms in M2M

Characterization of surface proteins of Cronobacter muytjensii using monoclonal antibodies and MALDI-TOF Mass spectrometry

<p>Abstract</p> <p>Background</p> <p><it>Cronobacter </it>spp. is a newly emerging pathogen that causes meningitis in infants and other diseases in elderly and immunocompromised individuals. This study was undertaken to investigate surface antigenic determinants in <it>Cronobacter </it>spp. using monoclonal antibodies (MAbs) and MALDI-TOF Mass spectrometry.</p> <p>Results</p> <p>Spleenocytes from mice that were immunized with heat-killed (20 min, 80°C) <it>Cronobacter </it>cells were fused with SP2 myeloma cells. Five desirable MAbs (A1, B5, 2C2, C5 and A4) were selected. MAbs A1, B5, 2C2 and C5 were of IgG2a isotype while A4 was an IgM. Specificity of the MAbs was determined by using immunoblotting with outer membrane protein preparations (OMPs) extracted from 12 <it>Cronobacter </it>and 6 non-<it>Cronobacter </it>bacteria. All MAbs recognized proteins with molecular weight ranging between 36 and 49 kDa except for one isolate (44) in which no OMPs were detected. In addition, MAbs recognized two bands (38-41 kDa) in four of the non-<it>Cronobacter </it>bacteria. Most of the proteins recognized by the MAbs were identified by MALDI-TOF peptide sequencing and appeared to be heterogeneous with the identities of some of them are still unknown. All MAbs recognized the same epitope as determined by an additive Index ELISA with their epitopes appeared to be conformational rather than sequential. Further, none of the MAbs recognized purified LPS from <it>Cronobacter </it>spp. Specificity of the MAbs toward OMPs was further confirmed by transmission electron microscopy.</p> <p>Conclusions</p> <p>Results obtained in this study highlight the immunological cross-reactivity among <it>Cronobacter </it>OMPs and their <it>Enterobacteriaceae </it>counterparts. Nevertheless, the identity of the identified proteins appeared to be different as inferred from the MALDI-TOF sequencing and identification.</p

Deuteron-Proton Elastic Scattering at Intermediate Energies

The deuteron-proton elastic scattering has been studied in the multiple scattering expansion formalism. The essential attention has been given to such relativistic problem as a deuteron wave function in a moving frame and transformation of spin states due to Wigner rotation. Parameterization of the nucleon-nucleon $t$-matrix has been used to take the off-energy shell effects into account. The vector, $A_y,$ and tensor, $A_{yy}$, analyzing powers of the deuteron have been calculated at two deuteron kinetic energies: 395 MeV and 1200 MeV. The obtained results are compared with the experimental data

Boosted three-dimensional black-hole evolutions with singularity excision

Binary black hole interactions provide potentially the strongest source of gravitational radiation for detectors currently under development. We present some results from the Binary Black Hole Grand Challenge Alliance three- dimensional Cauchy evolution module. These constitute essential steps towards modeling such interactions and predicting gravitational radiation waveforms. We report on single black hole evolutions and the first successful demonstration of a black hole moving freely through a three-dimensional computational grid via a Cauchy evolution: a hole moving ~6M at 0.1c during a total evolution of duration ~60M