Two new pulsating low-mass pre-white dwarfs or SX Phenix stars?*

Context. The discovery of pulsations in low-mass stars opens an opportunity for probing their interiors and to determine their evolution, by employing the tools of asteroseismology. Aims. We aim to analyze high-speed photometry of SDSSJ145847.02$+$070754.46 and SDSSJ173001.94$+$070600.25 and discover brightness variabilities. In order to locate these stars in the $T_{\rm eff} - \log g$ diagram we fit optical spectra (SDSS) with synthetic non-magnetic spectra derived from model atmospheres. Methods. To carry out this study, we used the photometric data obtained by us for these stars with the 2.15m telescope at CASLEO, Argentina. We analyzed their light curves and we apply the Discrete Fourier Transform to determine the pulsation frequencies. Finally, we compare both stars in the $T_{\rm eff} - \log g$ diagram, with known two pre-white dwarfs, seven pulsating pre-ELM white dwarf stars, $\delta$ Scuti and SX Phe stars. Results. We report the discovery of pulsations in SDSSJ145847.02$+$070754.46 and SDSSJ173001.94$+$070600.25. We determine their effective temperature and surface gravity to be $T_{\rm eff}$ = 7 972 $\pm$ 200 K, $\log g$ = 4.25 $\pm$ 0.5 and $T_{\rm eff}$ = 7 925 $\pm$ 200 K, $\log g$ = 4.25 $\pm$ 0.5, respectively. With these parameters these new pulsating low-mass stars can be identified with either ELM white dwarfs (with ~ 0.17 Mo) or more massive SX Phe stars. We identified pulsation periods of 3 278.7 and 1 633.9 s for SDSSJ145847.02$+$070754.46 and a pulsation period of 3 367.1 s for SDSSJ173001.94$+$070600.25. These two new objects together with those of Maxted et al. (2013, 2014) indicate the possible existence of a new instability domain towards the late stages of evolution of low-mass white dwarf stars, although their identification with SX Phe stars cannot be discarded.Comment: 5 pages, 5 figures, 1 table, accepted for publication in A&A

Long Range Dynamics Related to Magnetic Impurity in the 2D Heisenberg Antiferromagnet

We consider a magnetic impurity in the two-dimensional Heisenberg antifferomagnet with long range antiferromagnetic order. At low temperature the impurity magnetic susceptibility has a Curie term ($\propto 1/T$) and a logarithmic correction ($\propto \ln(T)$). We calculate the correction and derive related Ward identity for the impurity-spin-wave vertex.Comment: 5 pages, 6 figure

Nuevas estrellas pre enanas blancas pulsantes de masa extremadamente baja descubiertas en el CASLEO

The Extremely Low Mass white dwarfs (ELM, M 0.18--0.20 M) could arise after the loss of large amount of mass suffered by a red giant star in a binary system. The low mass white dwarfs have become an important source of study because some of them are pulsating stars. The latter is an unprecedented opportunity to know their interior and the evolutionary channels leading to their origin, by employing asteroseismology. In this paper, we present photometric analysis of data obtained in the CASLEO (Complejo Astronómico El Leoncito) about four new pulsating stars, that according to their surface gravities and effective temperatures, would be pre-ELM white dwarf stars. With this discovery, the number of pulsating pre-ELM white dwarf stars known would increase to six members.Fil: Corti, Mariela Alejandra. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; ArgentinaFil: Kanaan, Antonio. Universidade Federal de Santa Catarina; BrasilFil: Corsico, Alejandro Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; ArgentinaFil: Kepler, S. O.. Universidade Federal do Rio Grande do Sul; BrasilFil: Althaus, Leandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; ArgentinaFil: Koester, D.. Universität Kiel; AlemaniaFil: Sánchez Arias, Julieta Paz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; Argentin

Primeras curvas de luz de estrellas variables ZZ Ceti observadas en el CASLEO

Las estrellas enanas blancas DA variables, o ZZ Ceti, constituyen la familia de enanas blancas pulsantes más numerosa. A partir del advenimiento del Sloan Digital Sky Survey (SDSS) el número de objetos conocidos de esta clase se elevó a 160. Estas estrellas poseen atmósferas ricas en Hidrógeno y se localizan en un rango de temperaturas efectivas entre 10500 y 12300 K. La astrosismología de enanas blancas permite extraer información acerca de la estructura interna y las propiedades globales de estos objetos compactos y antiguos. Esta técnica consiste básicamente en la comparación de los peréodos de pulsación observados con períodos calculados a partir de modelos teóricos representativos. En este trabajo presentamos las primeras curvas de luz resultantes de datos fotométricos de estrellas enanas blancas candidatas a ser variables ZZ Ceti, obtenidos con el telescopio de 2.15 m del CASLEO. Se incluyen también, nuevos peréodos de pulsación y parámetros físicos derivados para las enanas blancas pulsantes ya conocidas: BPM37093, L19-2 y PG1159-035, entre otras.DA white dwarf stars, ZZ Ceti, are the most numerous class among the pulsating white dwarfs. These stars have atmospheres dominated by hydrogen, and effective temperatures between 10500 and 12300 K. Because of the periodic variations of their luminosity, we can use asteroseismology to study the inner structure and the global properties of these compact and old objects. These techniques basically consists on the comparison between the observed pulsation periods and theoretical periods computed from representative models. In this work we present the first light curves and Fourier transforms of the ZZ Ceti stars WD162813+122452 y BPM37093, obtained with the 2,15 m telescope at CASLEO. Observational data and physical parameters derived for some ZZ Ceti observed candidates are also included.Fil: Corti, Mariela A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto Argentino de Radioastronomia (i); Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Romero, Alejandra D.. Universidade Federal do Rio Grande do Sul; BrasilFil: Kanaan, Antonio. Universidade Federal Da Santa Catarina; BrasilFil: Kepler, S. O.. Universidade Federal do Rio Grande do Sul; BrasilFil: Costa, J. E.. Centro de Previsao de Tempo e Estudos Climaticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Córsico, Alejandro H.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Astrofísica de La Plata; Argentina; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Althaus, Leandro G.. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Astrofísica de La Plata; Argentina; Argentin

Two new pulsating low-mass pre-white dwarfs or SX Phoenicis stars?

Context. The discovery of pulsations in low-mass stars opens an opportunity to probe their interiors and determine their evolution by employing the tools of asteroseismology. Aims. We aim to analyse high-speed photometry of SDSS J145847.02+070754.46 and SDSS J173001.94+070600.25 and discover brightness variabilities. In order to locate these stars in the Teff - log g diagram, we fit optical spectra (SDSS) with synthetic non-magnetic spectra derived from model atmospheres. Methods. To carry out this study, we used the photometric data we obtained for these stars with the 2.15 m telescope at CASLEO, Argentina. We analysed their light curves and applied the discrete Fourier transform (FT) to determine the pulsation frequencies. Finally, we compare both stars in the Teff - log g diagram, with two known pre-white dwarfs and seven pulsating pre-ELM white dwarf stars, δ Scuti, and SX Phe stars Results. We report the discovery of pulsations in SDSS J145847.02+070754.46 and SDSS J173001.94+070600.25. We determine their effective temperature and surface gravity to be Teff = 7972 ± 200 K, log g = 4.25 ± 0.5 and Teff = 7925 ± 200 K, log g = 4.25 ± 0.5, respectively. With these parameters, these new pulsating low-mass stars can be identified with either ELM white dwarfs (with ∼0.17 MO) or more massive SX Phe stars. We identified pulsation periods of 3278.7 and 1633.9 s for SDSS J145847.02+070754.46 and a pulsation period of 3367.1 s for SDSS J173001.94+070600.25. These two new objects, together with those of Maxted et al. (2013, 2014), indicate the possible existence of a new instability domain towards the late stages of evolution of low-mass white dwarf stars, although their identification with SX Phe stars cannot be discarded.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí

Pathogen dependent effects of high amounts of oxytocin on the bloodmilk barrier integrity during mastitis in dairy cows.

The reduction of antibiotic use in food producing animals becomes increasingly important. Therefore, suitable alternatives for mastitis treatment in dairy cows have to be considered. Oxytocin (OT) induces milk ejection and hence supports milk removal from infected mammary quarters. Beyond udder emptying, the injection of very high dosages of OT causes increased somatic cell counts (SCC) in milk and enables the transfer of immunoglobulins (Ig) from blood into milk through a reduced blood-milk barrier integrity. The aim of the present study was to investigate pathogen-specific changes of SCC, the blood derived milk components lactate dehydrogenase (LDH), serum albumin (SA), and IgG in milk of cows suffering from mastitis caused by different pathogens treated with two intravenous injections of high dosages of OT (100 IU). Milk samples from 184 dairy cows from different farms were collected on day 1 (day of clinical examination and mastitis diagnosis) and on days 2, 3, 14, and 28. Bacteriological examination (day 1) identified involved pathogens. Cows were randomly assigned to treatment (OT injections on days 1 and 2) or control group (no OT). Independently of the assigned experimental group, cows received the common therapy protocol of the veterinary practice after sample collection if the general condition was affected. Milk SCC, LDH, SA, and IgG changed specifically depending on involved pathogens. Highest values of all three parameters were measured in mastitis caused by Streptococcus uberis. Changes were less pronounced with other Streptococci spp., Staphylococci spp. or Corynebacterium bovis. Oxytocin treatment did not affect any of the studied parameters independent of the involved pathogen. Only in quarters infected with Staphylococci other than Staphylococcus aureus a decreased SCC and increased IgG concentrations in quarters, where no pathogens were detected, were observed. Thus, high dosage OT administration is obviously not suitable as a stand-alone mastitis treatment in dairy cows

Redefining the histopathologic profile of acute aortic syndromes: Clinical and prognostic implications

Objectives: The study objectives were to describe the aortic histopathologic substrates in patients with type A surgically treated acute aortic syndromes, to provide clinico-pathological correlations, and to identify the possible prognostic role of histology. Methods: We assessed the aortic wall degenerative or inflammatory alterations of 158 patients according to the histopathologic consensus documents. Moreover, we correlated these histologic patterns with the patients' clinical data and long-term follow-up for mortality, major aorta-related events, and nonaorta-related events (including cardiovascular ones). Results: We identified 2 histopathologic patterns: 122 patients (77%) with degenerative alterations and 36 patients (23%) with mixed degenerative-atherosclerotic lesions. Patients with mixed alterations were older (mean 69.6 \ub1 8.7 years vs 62.2 \ub1 12.4 years, P = .001) and more hypercholesterolemic (33.3% vs 13.9%, P = .017). The degenerative subgroup showed more intralamellar-mucoid extracellular matrix accumulation (86% vs 66.7%, P = .017) and a lower prevalence of translamellar collagen increase (9.8% vs 50%, P < .001). Patients with mixed degenerative-atherosclerotic abnormalities more frequently had long-term nonaorta-related events compared with those with degenerative abnormalities alone (P = .046); no differences were found between the groups with respect to mortality, major aorta-related events, and cardiovascular nonaorta-related events. Conclusions: Although degenerative lesions of the medial layer were present in all specimens, substantial atherosclerosis coexisted in approximately one quarter of cases. Patients with mixed degenerative-atherosclerotic abnormalities had a coherent clinical risk profile, a clinical presentation frequently mimicking acute coronary syndrome, and a higher incidence of nonaorta-related events during follow-up. Histopathologic characterization may improve the long-term prognostic stratification of patients after surgical treatment. \ua9 2018 The American Association for Thoracic Surger

Exceptionally potent human monoclonal antibodies are effective for prophylaxis and therapy of tetanus in mice

Human monoclonal antibodies were used here to study the mechanism of neuron intoxication by tetanus neurotoxin and to evaluate them as a safe preventive and therapeutic substitute of hyperimmune sera for tetanus in mice. By screening memory B cells of immune donors, we selected two monoclonal antibodies specific for tetanus neurotoxin with exceptionally high neutralizing activities, which were extensively characterized both structurally and functionally. We found that these antibodies interfere with the binding and translocation of the neurotoxin into neurons by interacting with two epitopes, whose definition pinpoints crucial events in the cellular pathogenesis of tetanus. This information explains the unprecedented neutralization ability of these antibodies, which were found to be exceptionally potent in preventing experimental tetanus when injected in mice long before the neurotoxin. Moreover, their Fab derivatives neutralized tetanus neurotoxin in post-exposure experiments, suggesting their potential therapeutic use via intrathecal injection. As such, these human monoclonal antibodies, as well as their Fab derivatives, meet all requirements for being considered for prophylaxis and therapy of human tetanus and are ready for clinical trials

Liquid Limits: The Glass Transition and Liquid-Gas Spinodal Boundaries of Metastable Liquids

The liquid-gas spinodal and the glass transition define ultimate boundaries beyond which substances cannot exist as (stable or metastable) liquids. The relation between these limits is analyzed {\it via} computer simulations of a model liquid. The results obtained indicate that the liquid - gas spinodal and the glass transition lines intersect at a finite temperature, implying a glass - gas mechanical instability locus at low temperatures. The glass transition lines obtained by thermodynamic and dynamic criteria agree very well with each other.Comment: 5 pages, 4 figures, to appear in Phys. Rev. Let