Cosmological black holes and the direction of time

Macroscopic irreversible processes emerge from fundamental physical laws of reversible character. The source of the local irreversibility seems to be not in the laws themselves but in the initial and boundary conditions of the equations that represent the laws. In this work we propose that the screening of currents by black hole event horizons determines, locally, a preferred direction for the flux of electromagnetic energy. We study the growth of black hole event horizons due to the cosmological expansion and accretion of cosmic microwave background radiation, for different cosmological models. We propose generalized McVittie co-moving metrics and integrate the rate of accretion of cosmic microwave background radiation onto a supermassive black hole over cosmic time. We find that for flat, open, and closed Friedmann cosmological models, the ratio of the total area of the black hole event horizons with respect to the area of a radial co-moving space-like hypersurface always increases. Since accretion of cosmic radiation sets an absolute lower limit to the total matter accreted by black holes, this implies that the causal past and future are not mirror symmetric for any spacetime event. The asymmetry causes a net Poynting flux in the global future direction; the latter is in turn related to the ever increasing thermodynamic entropy. Thus, we expose a connection between four different "time arrows": cosmological, electromagnetic, gravitational, and thermodynamic.Comment: 13 pages, 2 figures in Foundations of Science (2017

Regulation of brain endothelial barrier function by microRNAs in health and neuroinflammation

Brain endothelial cells constitute the major cellular element of the highly specialized blood–brain barrier (BBB) and thereby contribute to CNS homeostasis by restricting entry of circulating leukocytes and blood-borne molecules into the CNS. Therefore, compromised function of brain endothelial cells has serious consequences for BBB integrity. This has been associated with early events in the pathogenesis of several disorders that affect the CNS, such as multiple sclerosis, HIV-associated neurologic disorder, and stroke. Recent studies demonstrate that brain endothelial microRNAs play critical roles in the regulation of BBB function under normal and neuroinflammatory conditions. This review will focus on emerging evidence that indicates that brain endothelial microRNAs regulate barrier function and orchestrate various phases of the neuroinflammatory response, including endothelial activation in response to cytokines as well as restoration of inflamed endothelium into a quiescent state. In particular, we discuss novel microRNA regulatory mechanisms and their contribution to cellular interactions at the neurovascular unit that influence the overall function of the BBB in health and during neuroinflammatio

The perceived role of bullying bystanders in Mexican secondary school settings

Bystanders play an important role in school bullying dynamics, having the power to provide or withhold the social rewards bullies seek. Bystander support is also beneficial for bullying victims, who experience less social and mental health problems if they have defenders. Even though bystanders generally disapprove of bullying, they rarely intervene in bullying incidents. Research suggests that two factors closely related to bystander intervention in bullying are moral disengagement and self-efficacy. Cultural influences and gender may also play a part in bullying and bystander dynamics. The main aim of this study was to explore Mexican secondary school students’ perceptions of their role in bullying situations. The study focused on gender differences in these perceptions, students' levels of self-efficacy, students’ use of moral disengagement dynamics, and student receptivity to material that encourages prosocial bystander behaviour. A questionnaire was developed to gauge students’ views on these topics, and administered to a sample of 186 secondary school students. Focus groups were also conducted to gain insight on group understandings and norms. A six-session workshop was designed and implemented to expose students to material on prosocial bystander behaviour. Results suggested that most students feel empathy towards bullying victims and acknowledge that they have the power to make a difference. However, participants are reluctant to put ideas into action for fear of bully retaliation and the belief that they cannot rely on support from other peers and school staff. This sense of powerlessness seems to have a cultural component to it, and is more common in male students. Other gender differences were observed: females displayed higher self-efficacy to help and lower moral disengagement levels. Research on cultural influences on bullying and bystander behaviour worldwide is needed, as well as further research on the implications, obstacles and opportunities of gender differences in this regard. Studies on what bystanders need to feel safe when helping bullying victims would also be a valuable resource for anti-bullying intervention efforts

AE Aurigae: first detection of non-thermal X-ray emission from a bow shock produced by a runaway star

Runaway stars produce shocks when passing through interstellar medium at supersonic velocities. Bow shocks have been detected in the mid-infrared for several high-mass runaway stars and in radio waves for one star. Theoretical models predict the production of high-energy photons by non-thermal radiative processes in a number sufficiently large to be detected in X-rays. To date, no stellar bow shock has been detected at such energies. We present the first detection of X-ray emission from a bow shock produced by a runaway star. The star is AE Aur, which was likely expelled from its birthplace by the encounter of two massive binary systems and now is passing through the dense nebula IC 405. The X-ray emission from the bow shock is detected at 30" to the northeast of the star, coinciding with an enhancement in the density of the nebula. From the analysis of the observed X-ray spectrum of the source and our theoretical emission model, we confirm that the X-ray emission is produced mainly by inverse Compton upscattering of infrared photons from dust in the shock front.Comment: Accepted for publication in the Astrophysical Journal with number ApJ, 757, L6. Four figure

Cellular immune responses in amniotic fluid of women with preterm labor and intraâ amniotic infection or intraâ amniotic inflammation

ProblemPreterm birth is commonly preceded by preterm labor, a syndrome that is causally linked to both intraâ amniotic infection and intraâ amniotic inflammation. However, the stereotypical cellular immune responses in these two clinical conditions are poorly understood.Method of studyAmniotic fluid samples (n = 26) were collected from women diagnosed with preterm labor and intraâ amniotic infection (amniotic fluid ILâ 6 concentrations â ¥2.6 ng/mL and culturable microorganisms, n = 10) or intraâ amniotic inflammation (amniotic fluid ILâ 6 concentrations â ¥2.6 ng/mL without culturable microorganisms, n = 16). Flow cytometry was performed to evaluate the phenotype and number of amniotic fluid leukocytes. Amniotic fluid concentrations of classical proâ inflammatory cytokines, type 1 and type 2 cytokines, and Tâ cell chemokines were determined using immunoassays.ResultsWomen with spontaneous preterm labor and intraâ amniotic infection had (a) a greater number of total leukocytes, including neutrophils and monocytes/macrophages, in amniotic fluid; (b) a higher number of total T cells and CD4+ T cells, but not CD8+ T cells or B cells, in amniotic fluid; and (c) increased amniotic fluid concentrations of ILâ 6, ILâ 1β, and ILâ 10, compared to those with intraâ amniotic inflammation. However, no differences in amniotic fluid concentrations of Tâ cell cytokines and chemokines were observed between these two clinical conditions.ConclusionThe cellular immune responses observed in women with preterm labor and intraâ amniotic infection are more severe than in those with intraâ amniotic inflammation, and neutrophils, monocytes/macrophages, and CD4+ T cells are the main immune cells responding to microorganisms that invade the amniotic cavity. These findings provide insights into the intraâ amniotic immune mechanisms underlying the human syndrome of preterm labor.The relative distribution of innate and adaptive immune cell subsets in amniotic fluid of women with preterm labor and intraâ amniotic inflammation. Flow cytometry analysis is shown as a tâ SNE plot.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151891/1/aji13171_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151891/2/aji13171.pd

Efficacy of atmospheric pressure dielectric barrier discharge for inactivating airborne pathogens

Atmospheric pressure plasmas have gained attention in recent years for several environmental applications. This technology could potentially be used to deactivate airborne microorganisms, surface-bound microorganisms, and biofilms. In this work, the authors explore the efficacy of the atmospheric pressure dielectric barrier discharge (DBD) to inactivate airborne Staphylococcus epidermidis and Aspergillus niger that are opportunistic pathogens associated with nosocomial infections. This technology uses air as the source of gas and does not require any process gas such as helium, argon, nitrogen, or hydrogen. The effect of DBD was studied on aerosolized S. epidermidis and aerosolized A. niger spores via scanning electron microscopy (SEM). The morphology observed on the SEM micrographs showed deformations in the cellular structure of both microor- ganisms. Cell structure damage upon interaction with the DBD suggests leakage of vital cellular materials, which is a key mechanism for microbial inactivation. The chemical structure of the cell surface of S. epidermidis was also analyzed by near edge x-ray absorption fine structure spectros- copy before and after DBD exposure. Results from surface analysis revealed that reactive oxygen species from the DBD discharge contributed to alterations on the chemistry of the cell membrane/ cell wall of S. epidermidis

Interpretation Misunderstandings about Elementary Quantum Mechanics

Quantum Mechanics is a fundamental physical theory about atomic-scale processes. It was built between 1920 and 1940 by the most distinguished physicists of that time. The accordance between the predictions of the theory and experimental results is remarkable. The physical interpretation of its mathematical constructs, however, raised unprecedented controversies. Ontological, semantic, and epistemic vagueness abound in the orthodox interpretations and have resulted in serious misunderstandings that are often repeated in textbooks and elsewhere. In this work, we identify, criticize, and clarify the most spread ones

An X-ray study of the SNR G344.7-0.1 and the central object CXOU J170357.8-414302

Aims. We report results of an X-ray study of the supernova remnant (SNR) G344.7-0.1 and the point-like X-ray source located at the geometrical center of the SNR radio structure. Methods. The morphology and spectral properties of the remnant and the central X-ray point-like source were studied using data from the XMM-Newton and Chandra satellites. Archival radio data and infrared Spitzer observations at 8 and 24 $\mu$m were used to compare and study its multi-band properties at different wavelengths. Results. The XMM-Newton and Chandra observations reveal that the overall X-ray emission of G344.7-0.1 is extended and correlates very well with regions of bright radio and infrared emission. The X-ray spectrum is dominated by prominent atomic emission lines. These characteristics suggest that the X-ray emission originated in a thin thermal plasma, whose radiation is represented well by a plane-parallel shock plasma model (PSHOCK). Our study favors the scenario in which G344.7-0.1 is a 6 x 10^3 year old SNR expanding in a medium with a high density gradient and is most likely encountering a molecular cloud on the western side. In addition, we report the discovery of a soft point-like X-ray source located at the geometrical center of the radio SNR structure. The object presents some characteristics of the so-called compact central objects (CCO). However, its neutral hydrogen absorption column (N_{H}) is inconsistent with that of the SNR. Coincident with the position of the source, we found infrared and optical objects with typical early-K star characteristics. The X-ray source may be a foreground star or the CCO associated with the SNR. If this latter possibility were confirmed, the point-like source would be the farthest CCO detected so far and the eighth member of the new population of isolated and weakly magnetized neutron stars.Comment: 9 pages, 8 figures, accepted for publication in Astronomy and Astrophysics. Higher resolution figures can be seen on A&