The True Incidence of Magnetism among Field White Dwarfs

We study the incidence of magnetism in white dwarfs from three large and well-observed samples of hot, cool, and nearby white dwarfs in order to test whether the fraction of magnetic degenerates is biased, and whether it varies with effective temperature, cooling age, or distance. The magnetic fraction is considerably higher for the cool sample of Bergeron, Ruiz, and Leggett, and the Holberg, Oswalt, and Sion sample of local white dwarfs that it is for the generally-hotter white dwarfs of the Palomar Green Survey. We show that the mean mass of magnetic white dwarfs in this survey is 0.93 solar masses or more, so there may be a strong bias against their selection in the magnitude-limited Palomar Green Survey. We argue that this bias is not as important in the samples of cool and nearby white dwarfs. However, this bias may not account for all of the difference in the magnetic fractions of these samples. It is not clear that the magnetic white dwarfs in the cool and local samples are drawn from the same population as the hotter PG stars. In particular, two or threee of the cool sample are low-mass white dwarfs in unresolved binary systems. Moreover, there is a suggestion from the local sample that the fractional incidence may increase with decreasing temperature, luminosity, and/or cooling age. Overall, the true incidence of magnetism at the level of 2 megagauss or greater is at least 10%, and could be higher. Limited studies capable of detecting lower field strengths down to 10 kilogauss suggest by implication that the total fraction may be substantially higher than 10%.Comment: 16 pages, 2 figures, Astronomical Journal in press -- Jan 2003 issu

The Formation Rate, Mass and Luminosity Functions of DA White Dwarfs from the Palomar Green Survey

Spectrophotometric observations at high signal-to-noise ratio were obtained of a complete sample of 347 DA white dwarfs from the Palomar Green (PG) Survey. Fits of observed Balmer lines to synthetic spectra calculated from pure-hydrogen model atmospheres were used to obtain robust values of Teff, log g, masses, radii, and cooling ages. The luminosity function of the sample, weighted by 1/Vmax, was obtained and compared with other determinations. The mass distribution of the white dwarfs is derived, after important corrections for the radii of the white dwarfs in this magnitude-limited survey and for the cooling time scales. The formation rate of DA white dwarfs from the PG is estimated to be 0.6x10^(-12) pc^(-3) yr^(-1). Comparison with predictions from a theoretical study of the white dwarf formation rate for single stars indicates that >80% of the high mass component requires a different origin, presumably mergers of lower mass double degenerate stars. In order to estimate the recent formation rate of all white dwarfs in the local Galactic disk, corrections for incompleteness of the PG, addition of the DB-DO white dwarfs, and allowance for stars hidden by luminous binary companions had to be applied to enhance the rate. An overall formation rate of white dwarfs recently in the local Galactic disk of 1.15+/-0.25x10^(-12) pc^(-3) yr^(-1) is obtained. Two recent studies of samples of nearby Galactic planetary nebulae lead to estimates around twice as high. Difficulties in reconciling these determinations are discussed.Comment: 73 pages, 18 figures, accepted for publication in the ApJ Supplemen

Towards Better Integrators for Dissipative Particle Dynamics Simulations

Coarse-grained models that preserve hydrodynamics provide a natural approach to study collective properties of soft-matter systems. Here, we demonstrate that commonly used integration schemes in dissipative particle dynamics give rise to pronounced artifacts in physical quantities such as the compressibility and the diffusion coefficient. We assess the quality of these integration schemes, including variants based on a recently suggested self-consistent approach, and examine their relative performance. Implications of integrator-induced effects are discussed.Comment: 4 pages, 3 figures, 2 tables, accepted for publication in Phys. Rev. E (Rapid Communication), tentative publication issue: 01 Dec 200

Cognitive Sparing during the Administration of Whole Brain Radiotherapy and Prophylactic Cranial Irradiation: Current Concepts and Approaches

Whole brain radiotherapy (WBRT) for the palliation of metastases, or as prophylaxis to prevent intracranial metastases, can be associated with subacute and late decline in memory and other cognitive functions. Moreover, these changes are often increased in both frequency and severity when cranial irradiation is combined with the use of systemic or intrathecal chemotherapy. Approaches to preventing or reducing this toxicity include the use of stereotactic radiosurgery (SRS) instead of WBRT; dose reduction for PCI; exclusion of the limbic circuit, hippocampal formation, and/or neural stem cell regions of the brain during radiotherapy; avoidance of intrathecal and/or systemic chemotherapy during radiotherapy; the use of high-dose, systemic chemotherapy in lieu of WBRT. This review discusses these concepts in detail as well as providing both neuroanatomic and radiobiologic background relevant to these issues

Copper(II)-bis(thiosemicarbazonato) complexes as anti-chlamydial agents

Lipophilic copper (Cu)-containing complexes have shown promising antibacterial activity against a range of bacterial pathogens. To examine the susceptibility of the intracellular human pathogen Chlamydia trachomatis to copper complexes containing bis(thiosemicarbazone) ligands [Cu(btsc)], we tested the in vitro effect of CuII-diacetyl- and CuII-glyoxal-bis[N(4)-methylthiosemicarbazonato] (Cu(atsm) and Cu(gtsm), respectively) on C. trachomatis. Cu(atsm) and to a greater extent, Cu(gtsm), prevented the formation of infectious chlamydial progeny. Impacts on host cell viability and respiration were also observed in addition to the Chlamydia impacts. This work suggests that copper-based complexes may represent a new lead approach for future development of new therapeutics against chlamydial infections, although host cell impacts need to be fully explored

Ebolavirus diagnosis made simple, comparable and faster than molecular detection methods: preparing for the future

Background The 2014/2015 Ebolavirus outbreak resulted in more than 28,000 cases and 11,323 reported deaths, as of March 2016. Domestic transmission of the Guinea strain associated with the outbreak occurred mainly in six African countries, and international transmission was reported in four countries. Outbreak management was limited by the inability to rapidly diagnose infected cases. A further fifteen countries in Africa are predicted to be at risk of Ebolavirus outbreaks in the future as a consequence of climate change and urbanization. Early detection of cases and reduction of transmission rates is critical to prevent and manage future severe outbreaks. We designed a rapid assay for detection of Ebolavirus using recombinase polymerase amplification, a rapid isothermal amplification technology that can be combined with portable lateral flow detection technology. The developed rapid assay operates in 30 min and was comparable with real-time TaqMan™ PCR. Methods Designed, screened, selected and optimized oligonucleotides using the NP coding region from Ebola Zaire virus (Guinea strain). We determined the analytical sensitivity of our Ebola rapid molecular test by testing selected primers and probe with tenfold serial dilutions (1.34 × 1010− 1.34 × 101 copies/μL) of cloned NP gene from Mayinga strain of Zaire ebolavirus in pCAGGS vector, and serially diluted cultured Ebolavirus as established by real-time TaqMan™ PCR that was performed using ABI7500 in Fast Mode. We tested extracted and reverse transcribed RNA from cultured Zaire ebolavirus strains – Mayinga, Gueckedou C05, Gueckedou C07, Makona, Kissidougou and Kiwit. We determined the analytical specificity of our assay with related viruses: Marburg, Ebola Reston and Ebola Sudan. We further tested for Dengue virus 1–4, Plasmodium falciparum and West Nile Virus (Kunjin strain). Results The assay had a detection limit of 134 copies per μL of plasmid containing the NP gene of Ebolavirus Mayinga, and cultured Ebolavirus and was highly specific for the Zaire ebolavirus species, including the Guinea strain responsible for the 2014/2015 outbreak. The assay did not detect related viruses like Marburg, Reston, or Sudan viruses, and other pathogens likely to be isolated from clinical samples. Conclusions Our assay could be suitable for implementation in district and primary health laboratories, as only a heating block and centrifuge is required for operation. The technique could provide a pathway for rapid screening of patients and animals for improved management of outbreaks

Risk of SARS-CoV-2 Transmission During Flexible Laryngoscopy: A Systematic Review.

IMPORTANCE: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reportedly infected otolaryngologists disproportionately in the early parts of the coronavirus disease 2019 pandemic. Recommendations from national and international health organizations suggest minimizing the use of flexible laryngoscopy as a result. OBJECTIVE: To review evidence on the risks of aerosolization and transmission of SARS-CoV-2 from patients to health care personnel during endoscopy of the upper aerodigestive tract. EVIDENCE REVIEW: A comprehensive review of literature was performed on April 19, 2020, using the PubMed/MEDLINE (1966-April 2020), Embase (1975-April 2020), and Web of Science (1900-April 2020) databases. All English-language primary research studies were included if they assessed the transmission of SARS-CoV-2 or SARS-CoV-1 during procedures in the upper aerodigestive tract. The primary outcome measure was disease transmission among health care workers. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used for accuracy of reporting. FINDINGS: The queries for SARS-CoV-2 and SARS-CoV-1 identified 6 articles for systematic review. No studies included in this review provided data for SARS-CoV-2 transmission during flexible laryngoscopy. A total of 204 of 1264 health care workers (16.1%) had procedure-specific infections of SARS-CoV-1 or SARS-CoV-2. Among those, 53 of 221 (24.0%) were exposed during intubation, 1 of 15 (6.7%) during bronchoscopy, and 1 of 1 (100%) during endoscopy-assisted intubation. CONCLUSIONS AND RELEVANCE: A substantial lack of research precludes formal conclusions about the safety of flexible laryngoscopy and transmission of SARS-CoV-2 from patients to health care workers. The use of appropriate precautionary measures and personal protective equipment appears to reduce the risk of transmission. Given the uncertainty in transmission and the known benefits of safety precautions, upper airway endoscopy may be reasonable to perform if precautionary steps are taken

Electronic Spectroscopy of Chloro(terpyridine)platinum(II)

The electronic spectrum of [Pt(tpy)Cl]^+ (tpy = 2,2':6',2"-terpyridine) is influenced dramatically by intermolecular stacking interactions in solution and in the solid state. The crystal structure of [Pt(tpy)Cl]ClO_4 (monoclinic, P2_1/c (No. 14); a = 7.085(2), b = 17.064(5), c = 26.905(8) Å; β = 90.0(1) °; Z = 8) consists of discrete Pt_2 units (Pt-Pt = 3.269(1) Å) arranged along an infinite tpy-π stack (spacing ~ 3.35 Å). Variable-temperature and concentration studies of the absorption and emission spectra of [Pt(tpy)Cl]^+ suggest that similar metal-metal and ligand-ligand interactions persist in the solution phase. The high concentration, low-temperature emission spectrum (5:5:1 ethanol:methanol:DMF) reveals a 740-nm band indicative of M-M oligomerization, a 650-nm band attributable to tpy π-π interactions, and a 470-nm band characteristic of mononuclear [Pt(tpy)Cl]^+ π-π* emission. Concentration-dependent absorption spectra were fit to a "two-dimer" model, yielding equilibrium constants for the formation of Pt-Pt-, and tpy-tpy-bound dimers of 1.3(1) x 10^3 and 1.0(1) x 10^3 M^(-1), respectively, in 0.1 M aqueous NaCl. The low temperature solid-state luminescence of [Pt(tpy)Cl]^+ is assigned to a ^3(MMLCT) (MMLCT = metal-metal-to-ligand charge transfer) transition. The energy of this band is highly dependent on the counterion (PF_6^-, ClO_4^- , C1^-, CF_3SO_3^-), in line with the different colors of these various salts. In contrast, the room-temperature solid-state emission spectra are more difficult to interpret. While the red perchlorate salt exhibits a relatively narrow emission band at 725 nm (red-shifted from the 77-K maximum at 695 nm), consistent with a 3(MMLCT) transition, the orange (Cl^-, ClO_4^-, CF_3SO_3^-) and yellow (PF6^-) salts have extremely broad room-temperature emission bands that all appear at nearly the same energy (λ_(max) ~ 640 nm). We assign this luminescence to an eximeric intraligand transition resulting from π- π interactions and propose that the temperature dependent emissions from the orange and yellow solid materials originate from multiple electronic states

The economic impact of periprosthetic infection in total hip arthroplasty

© 2020 Canadian Medical Association. All rights reserved. Background: Periprosthetic joint infection (PJI) is the third leading cause of total hip arthroplasty (THA) failure. Although controversial, 2-stage revision remains the gold standard treatment for PJI in most situations. To date, there have been few studies describing the economic impact of PJI in today\u27s health care environment. The purpose of the current study was to obtain an accurate estimate of the institutional cost associated with the management of PJI in THA and to assess the economic burden of PJI compared with primary uncomplicated THA. Methods: We conducted a review of primary THA cases and 2-stage revision THA for PJI at our institution. Patients were matched for age and body mass index. All costs associated with each procedure were recorded. Descriptive statistics were used to summarize the collected data. Mean costs, length of stay, clinic visits and readmission rates associated with the 2 cohorts were compared. Results: Fifty consecutive cases of revision THA were matched with 50 cases of uncomplicated primary THA between 2006 and 2014. Compared with the primary THA cohort, PJI was associated with a significant increase in mean length of hospital stay (26.5 v. 2.0 d, p \u3c 0.001), mean number of clinic visits (9.2 v. 3.8, p \u3c 0.001), number of readmissions (12 v. 1, p \u3c 0.001) and average overall cost (Can$38 107 v. Can$6764, t = 8.3, p \u3c 0.001). Conclusion: Treatment of PJI is a tremendous economic burden. Our data suggest a 5-fold increase in hospital expenditure in the management of PJI compared with primary uncomplicated THA

Genome sequence of Desulfitobacterium hafniense DCB-2, a Gram-positive anaerobe capable of dehalogenation and metal reduction

<p>Abstract</p> <p>Background</p> <p>The genome of the Gram-positive, metal-reducing, dehalorespiring <it>Desulfitobacterium hafniense </it>DCB-2 was sequenced in order to gain insights into its metabolic capacities, adaptive physiology, and regulatory machineries, and to compare with that of <it>Desulfitobacterium hafniense </it>Y51, the phylogenetically closest strain among the species with a sequenced genome.</p> <p>Results</p> <p>The genome of <it>Desulfitobacterium hafniense </it>DCB-2 is composed of a 5,279,134-bp circular chromosome with 5,042 predicted genes. Genome content and parallel physiological studies support the cell's ability to fix N₂and CO₂, form spores and biofilms, reduce metals, and use a variety of electron acceptors in respiration, including halogenated organic compounds. The genome contained seven reductive dehalogenase genes and four nitrogenase gene homologs but lacked the Nar respiratory nitrate reductase system. The <it>D. hafniense </it>DCB-2 genome contained genes for 43 RNA polymerase sigma factors including 27 sigma-24 subunits, 59 two-component signal transduction systems, and about 730 transporter proteins. In addition, it contained genes for 53 molybdopterin-binding oxidoreductases, 19 flavoprotein paralogs of the fumarate reductase, and many other FAD/FMN-binding oxidoreductases, proving the cell's versatility in both adaptive and reductive capacities. Together with the ability to form spores, the presence of the CO₂-fixing Wood-Ljungdahl pathway and the genes associated with oxygen tolerance add flexibility to the cell's options for survival under stress.</p> <p>Conclusions</p> <p><it>D. hafniense </it>DCB-2's genome contains genes consistent with its abilities for dehalogenation, metal reduction, N₂and CO₂fixation, anaerobic respiration, oxygen tolerance, spore formation, and biofilm formation which make this organism a potential candidate for bioremediation at contaminated sites.</p