Dynamics of Line-Driven Winds from Disks in Cataclysmic Variables. I. Solution Topology and Wind Geometry

We analyze the dynamics of 2-D stationary, line-driven winds from accretion disks in cataclysmic variable stars. The driving force is that of line radiation pressure, in the formalism developed by Castor, Abbott & Klein for O stars. Our main assumption is that wind helical streamlines lie on straight cones. We find that the Euler equation for the disk wind has two eigenvalues, the mass loss rate and the flow tilt angle with the disk. Both are calculated self-consistently. The wind is characterized by two distinct regions, an outer wind launched beyond four white dwarf radii from the rotation axis, and an inner wind launched within this radius. The inner wind is very steep, up to 80 degrees with the disk plane, while the outer wind has a typical tilt of 60 degrees. In both cases the ray dispersion is small. We, therefore, confirm the bi-conical geometry of disk winds as suggested by observations and kinematical modeling. The wind collimation angle appears to be robust and depends only on the disk temperature stratification. The flow critical points lie high above the disk for the inner wind, but close to the disk photosphere for the outer wind. Comparison with existing kinematical and dynamical models is provided. Mass loss rates from the disk as well as wind velocity laws are discussed in a subsequent paper.Comment: 21 pages, 10 Postscript figures; available also from http://www.pa.uky.edu/~shlosman/publ.html. Astrophysical Journal, submitte

9286 Stars: An Agglomeration of Stellar Polarization Catalogs

This is a revision. The revisions are minor. The new version of the catalog should be used in preference to the old. The most serious error in the older version was that $\theta_diff$ was incorrect, being sometimes far too large, for Reiz and Franco entries; the correct values are all zero for that reference. We present an agglomeration of stellar polarization catalogs with results for 9286 stars. We have endeavored to eliminate errors, provide accurate (arcsecond) positions, sensibly weight multiple observations of the same star, and provide reasonable distances. This catalog is included as an ASCII file (catalog.txt) in the source of this submission.Comment: The most serious error in the older version was that $\theta_diff$ was incorrect, being sometimes far too large, for Reiz and Franco entries; the correct values are all zero for that reference. 11 pages, no figures. Accepted for Astronomical Journal. Catalog also available as an ASCII file by anonymous FTP from ftp://vermi.berkeley.edu/pub/polcat/p14.ou

A Possible Periodicity in the Radio Lightcurves of 3C454.3

During the period 1966.5 - 2006.2 the 15GHz and 8GHz lightcurves of 3C454.3 (z=0.859) show a qsasi-periodicity of ~12.8 yr (~6.9 yr in the rest frame of the source) with a double-bump structure. This periodic behaviour is interpreted in terms of a rotating double-jet model in which the two jets are created from the black holes in a binary system and rotate with the period of the orbital motion. The periodic variations in the radio fluxes of 3C454.3 are suggested to be mainly due to the lighthouse effects (or the variation in Doppler boosting) of the precessing jets which are caused by the orbital motion. In addition, variations in the mass-flow rates accreting onto the black holes may be also involved.Comment: 15 pages, 11 figure

Role of Pyocyanin and Extracellular DNA in Facilitating Pseudomonas aeruginosa Biofilm Formation

Pseudomonas aeruginosa is an opportunistic Gram‐negative bacterium that is primarily responsible for infections related to cystic fibrosis (CF) airways, burn wounds, urinary tract infections, surgery‐associated infections, and HIV‐related illness. Pyocyanin and extracellular DNA (eDNA) are the major factors dictating the progression of biofilm formation and infection. Pyocyanin is a potent virulence factor causing cell death in infected CF patients and is associated with high mortality. eDNA is a key player in P. aeruginosa biofilm formation and is also responsible for the high viscosity of CF sputum that blocks the respiratory airway passages. In this chapter, we summarize our recent findings on the role of pyocyanin in facilitating P. aeruginosa biofilm formation. Pyocyanin promotes eDNA release in P. aeruginosa by inducing cell lysis mediated via hydrogen peroxide (H2O2) production. Pyocyanin intercalates with the nitrogenous bases of DNA and creates structural perturbation on the double‐helix structure. Pyocyanin‐eDNA binding significantly influences P. aeruginosa cell surface hydrophobicity and influences the physicochemical interactions facilitating bacterial cell‐to‐cell interaction (aggregation) and ultimately facilitates robust biofilm formation. A pyocyanin knockout (ΔphzA‐G) mutant is shown to have significantly reduced eDNA release and biofilm formation in comparison to its wild‐type. To this end, we discover that antioxidant glutathione directly binds to pyocyanin and modulates pyocyanin structure and function, thus inhibiting pyocyanin‐eDNA binding and consequently hampering biofilm development

Energy security and shifting modes of governance

The concept of energy security fits uneasily into contemporary security debates. It is neither a clearly traditional nor a fully ‘non-traditional’ security issue. There are also limits to the social constructedness of the concept. This article argues that, while it is important to identify the differing securitizations of energy, these must be contextualized within the material realities and the differing historical modes of governance of the political economy of resources. This is essential for understanding the differing meanings accorded to energy security, the shifting modes through which energy is governed, and the extent to which energy security concerns drive international politics. In this context, contemporary concerns over energy security have both material and ideological dimensions: anxiety over the dual shift of power from West to East and from resource-importing to resource-exporting countries; and concern over the normative weakening of the neo-liberal mode of energy governance

Milestones in the Observations of Cosmic Magnetic Fields

Magnetic fields are observed everywhere in the universe. In this review, we concentrate on the observational aspects of the magnetic fields of Galactic and extragalactic objects. Readers can follow the milestones in the observations of cosmic magnetic fields obtained from the most important tracers of magnetic fields, namely, the star-light polarization, the Zeeman effect, the rotation measures (RMs, hereafter) of extragalactic radio sources, the pulsar RMs, radio polarization observations, as well as the newly implemented sub-mm and mm polarization capabilities. (Another long paragraph is omitted due to the limited space here)Comment: Invited Review (ChJA&A); 32 pages. Sorry if your significant contributions in this area were not mentioned. Published pdf & ps files (with high quality figures) now availble at http://www.chjaa.org/2002_2_4.ht

IS element IS16 as a molecular screening tool to identify hospital-associated strains of Enterococcus faecium

<p>Abstract</p> <p>Background</p> <p>Hospital strains of <it>Enterococcus faecium </it>could be characterized and typed by various molecular methods (MLST, AFLP, MLVA) and allocated to a distinct clonal complex known as MLST CC17. However, these techniques are laborious, time-consuming and cost-intensive. Our aim was to identify hospital <it>E. faecium </it>strains and differentiate them from colonizing and animal variants by a simple, inexpensive and reliable PCR-based screening assay. We describe here performance and predictive value of a single PCR detecting the insertion element, IS<it>16</it>, to identify hospital <it>E. faecium </it>isolates within a collection of 260 strains of hospital, animal and human commensal origins.</p> <p>Methods</p> <p>Specific primers were selected amplifying a 547-bp fragment of IS<it>16</it>. Presence of IS<it>16 </it>was determined by PCR screenings among the 260 <it>E. faecium </it>isolates. Distribution of IS<it>16 </it>was compared with a prevalence of commonly used markers for hospital strains, <it>esp </it>and <it>hyl</it>_<it>Efm</it>. All isolates were typed by MLST and partly by PFGE. Location of IS<it>16 </it>was analysed by Southern hybridization of plasmid and chromosomal DNA.</p> <p>Results</p> <p>IS<it>16 </it>was exclusively distributed only among 155 invasive strains belonging to the clonal complex of hospital-associated strains ("CC17"; 28 MLST types) and various vancomycin resistance genotypes (<it>van</it>A/B/negative). The five invasive IS<it>16</it>-negative strains did not belong to the clonal complex of hospital-associated strains (CC17). IS<it>16 </it>was absent in all but three isolates from 100 livestock, food-associated and human commensal strains ("non-CC17"; 64 MLST types). The three IS<it>16</it>-positive human commensal isolates revealed MLST types belonging to the clonal complex of hospital-associated strains (CC17). The values predicting a hospital-associated strain ("CC17") deduced from presence and absence of IS<it>16 </it>was 100% and thus superior to screening for the presence of <it>esp </it>(66%) and/or <it>hyl</it>_{<it>Efm </it>}(46%). Southern hybridizations revealed chromosomal as well as plasmid localization of IS<it>16</it>.</p> <p>Conclusions</p> <p>This simple screening assay for insertion element IS<it>16 </it>is capable of differentiating hospital-associated from human commensal, livestock- and food-associated <it>E. faecium </it>strains and thus allows predicting the epidemic strengths or supposed pathogenic potential of a given <it>E. faecium </it>isolate identified within the nosocomial setting.</p

IS element IS16 as a molecular screening tool to identify hospital-associated strains of Enterococcus faecium

<p>Abstract</p> <p>Background</p> <p>Hospital strains of <it>Enterococcus faecium </it>could be characterized and typed by various molecular methods (MLST, AFLP, MLVA) and allocated to a distinct clonal complex known as MLST CC17. However, these techniques are laborious, time-consuming and cost-intensive. Our aim was to identify hospital <it>E. faecium </it>strains and differentiate them from colonizing and animal variants by a simple, inexpensive and reliable PCR-based screening assay. We describe here performance and predictive value of a single PCR detecting the insertion element, IS<it>16</it>, to identify hospital <it>E. faecium </it>isolates within a collection of 260 strains of hospital, animal and human commensal origins.</p> <p>Methods</p> <p>Specific primers were selected amplifying a 547-bp fragment of IS<it>16</it>. Presence of IS<it>16 </it>was determined by PCR screenings among the 260 <it>E. faecium </it>isolates. Distribution of IS<it>16 </it>was compared with a prevalence of commonly used markers for hospital strains, <it>esp </it>and <it>hyl</it>_<it>Efm</it>. All isolates were typed by MLST and partly by PFGE. Location of IS<it>16 </it>was analysed by Southern hybridization of plasmid and chromosomal DNA.</p> <p>Results</p> <p>IS<it>16 </it>was exclusively distributed only among 155 invasive strains belonging to the clonal complex of hospital-associated strains ("CC17"; 28 MLST types) and various vancomycin resistance genotypes (<it>van</it>A/B/negative). The five invasive IS<it>16</it>-negative strains did not belong to the clonal complex of hospital-associated strains (CC17). IS<it>16 </it>was absent in all but three isolates from 100 livestock, food-associated and human commensal strains ("non-CC17"; 64 MLST types). The three IS<it>16</it>-positive human commensal isolates revealed MLST types belonging to the clonal complex of hospital-associated strains (CC17). The values predicting a hospital-associated strain ("CC17") deduced from presence and absence of IS<it>16 </it>was 100% and thus superior to screening for the presence of <it>esp </it>(66%) and/or <it>hyl</it>_{<it>Efm </it>}(46%). Southern hybridizations revealed chromosomal as well as plasmid localization of IS<it>16</it>.</p> <p>Conclusions</p> <p>This simple screening assay for insertion element IS<it>16 </it>is capable of differentiating hospital-associated from human commensal, livestock- and food-associated <it>E. faecium </it>strains and thus allows predicting the epidemic strengths or supposed pathogenic potential of a given <it>E. faecium </it>isolate identified within the nosocomial setting.</p

An investigation of the impact of data breach severity on the readability of mandatory data breach notification letters: evidence from U.S. firms

The aim of this article is to investigate the impact of data breach severity on the readability of mandatory data breach notification letters. Using a content analysis approach to determine data breach severity attributes (measured by the total number of breached records, type of data accessed, the source of the data breach, and how the data were used), in conjunction with readability measures (reading complexity, numerical intensity, length of letter, word size, and unique words), 512 data breach incidents from 281 U.S. firms across the 2012–2015 period were examined. The results indicate that data breach severity has a positive impact on reading complexity, length of letter, word size, and unique words, and a negative impact on numerical terms. Interpreting the results collectively through the lens of impression management, it can be inferred that business managers may be attempting to obfuscate bad news associated with high data breach severity incidents by manipulating syntactical features of the data breach notification letters in a way that makes the message difficult for individuals to comprehend. The study contributes to the information studies and impression management behavior literatures by analyzing linguistic cues in notifications following a data breach incident

Supercurrent anomalies in 4d SCFTs

We use holographic renormalization of minimal \mathcalN=2 gauged supergravity in order to derive the general form of the quantum Ward identities for 3d \mathcalN=2 and 4d \mathcalN=1 superconformal theories on general curved backgrounds, including an arbitrary fermionic source for the supercurrent. The Ward identities for 4d \mathcalN=1 theories contain both bosonic and fermionic global anomalies, which we determine explicitly up to quadratic order in the supercurrent source. The Ward identities we derive apply to any superconformal theory, independently of whether it admits a holographic dual, except for the specific values of the $a$ and $c$ anomaly coefficients, which are equal due to our starting point of a two-derivative bulk supergravity theory. In the case of 4d \mathcalN=1 superconformal theories, we show that the fermionic anomalies lead to an anomalous transformation of the supercurrent under rigid supersymmetry on backgrounds admitting Killing spinors, even if all anomalies are numerically zero on such backgrounds. The anomalous transformation of the supercurrent under rigid supersymmetry leads to an obstruction to the $Q$-exactness of the stress tensor in supersymmetric vacua, and may have implications for the applicability of localization techniques. We use this obstruction to the $Q$-exactness of the stress tensor in order to resolve a number of apparent paradoxes relating to the supersymmetric Casimir energy, the BPS condition for supsersymmetric vacua, and the compatibility of holographic renormalization with supersymmetry, that were presented in the literature