644 research outputs found

    Conservation equations and physical models for hypersonic air flows in thermal and chemical nonequilibrium

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    The conservation equations for simulating hypersonic flows in thermal and chemical nonequilibrium and details of the associated physical models are presented. These details include the curve fits used for defining thermodynamic properties of the 11 species air model, curve fits for collision cross sections, expressions for transport properties, the chemical kinetics models, and the vibrational and electronic energy relaxation models. The expressions are formulated in the context of either a two or three temperature model. Greater emphasis is placed on the two temperature model in which it is assumed that the translational and rotational energy models are in equilibrium at the translational temperature, T, and the vibrational, electronic, and electron translational energy modes are in equilibrium at the vibrational temperature, T sub v. The eigenvalues and eigenvectors associated with the Jacobian of the flux vector are also presented in order to accommodate the upwind based numerical solutions of the complete equation set

    An intracardiac electrogram model to bridge virtual hearts and implantable cardiac devices

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    Virtual heart models have been proposed to enhance the safety of implantable cardiac devices through closed loop validation. To communicate with a virtual heart, devices have been driven by cardiac signals at specific sites. As a result, only the action potentials of these sites are sensed. However, the real device implanted in the heart will sense a complex combination of near and far-field extracellular potential signals. Therefore many device functions, such as blanking periods and refractory periods, are designed to handle these unexpected signals. To represent these signals, we develop an intracardiac electrogram (IEGM) model as an interface between the virtual heart and the device. The model can capture not only the local excitation but also far-field signals and pacing afterpotentials. Moreover, the sensing controller can specify unipolar or bipolar electrogram (EGM) sensing configurations and introduce various oversensing and undersensing modes. The simulation results show that the model is able to reproduce clinically observed sensing problems, which significantly extends the capabilities of the virtual heart model in the context of device validation

    A Spontaneous Fatp4/Scl27a4 Splice Site Mutation in a New Murine Model for Congenital Ichthyosis

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    Congenital ichthyoses are life-threatening conditions in humans. We describe here the identification and molecular characterization of a novel recessive mutation in mice that results in newborn lethality with severe congenital lamellar ichthyosis. Mutant newborns have a taut, shiny, non-expandable epidermis that resembles cornified manifestations of autosomal-recessive congenital ichthyosis in humans. The skin is stretched so tightly that the newborn mice are immobilized. The genetic defect was mapped to a region near the proximal end of chromosome 2 by SNP analysis, suggesting Fatp4/Slc27a4 as a candidate gene. FATP4 mutations in humans cause ichthyosis prematurity syndrome (IPS), and mutations of Fatp4 in mice have previously been found to cause a phenotype that resembles human congenital ichthyoses. Characterization of the Fatp4 cDNA revealed a fusion of exon 8 to exon 10, with deletion of exon 9. Genomic sequencing identified an A to T mutation in the splice donor sequence at the 3′-end of exon 9. Loss of exon 9 results in a frame shift mutation upstream from the conserved very long-chain acyl-CoA synthase (VLACS) domain. Histological studies revealed that the mutant mice have defects in keratinocyte differentiation, along with hyperproliferation of the stratum basale of the epidermis, a hyperkeratotic stratum corneum, and reduced numbers of secondary hair follicles. Since Fatp4 protein is present primarily at the stratum granulosum and the stratum spinosum, the hyperproliferation and the alterations in hair follicle induction suggest that very long chain fatty acids, in addition to being required for normal cornification, may influence signals from the stratum corneum to the basal cells that help to orchestrate normal skin differentiation

    Brucella abortus Infection of Placental Trophoblasts Triggers Endoplasmic Reticulum Stress-Mediated Cell Death and Fetal Loss via Type IV Secretion System-Dependent Activation of CHOP.

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    Subversion of endoplasmic reticulum (ER) function is a feature shared by multiple intracellular bacteria and viruses, and in many cases this disruption of cellular function activates pathways of the unfolded protein response (UPR). In the case of infection with Brucella abortus, the etiologic agent of brucellosis, the unfolded protein response in the infected placenta contributes to placentitis and abortion, leading to pathogen transmission. Here we show that B. abortus infection of pregnant mice led to death of infected placental trophoblasts in a manner that depended on the VirB type IV secretion system (T4SS) and its effector VceC. The trophoblast death program required the ER stress-induced transcription factor CHOP. While NOD1/NOD2 expression in macrophages contributed to ER stress-induced inflammation, these receptors did not play a role in trophoblast death. Both placentitis and abortion were independent of apoptosis-associated Speck-like protein containing a caspase activation and recruitment domain (ASC). These studies show that B. abortus uses its T4SS to induce cell-type-specific responses to ER stress in trophoblasts that trigger placental inflammation and abortion. Our results suggest further that in B. abortus the T4SS and its effectors are under selection as bacterial transmission factors.IMPORTANCE Brucella abortus infects the placenta of pregnant cows, where it replicates to high levels and triggers abortion of the calf. The aborted material is highly infectious and transmits infection to both cows and humans, but very little is known about how B. abortus causes abortion. By studying this infection in pregnant mice, we discovered that B. abortus kills trophoblasts, which are important cells for maintaining pregnancy. This killing required an injected bacterial protein (VceC) that triggered an endoplasmic reticulum (ER) stress response in the trophoblast. By inhibiting ER stress or infecting mice that lack CHOP, a protein induced by ER stress, we could prevent death of trophoblasts, reduce inflammation, and increase the viability of the pups. Our results suggest that B. abortus injects VceC into placental trophoblasts to promote its transmission by abortion

    Super-diffusive Transport Processes in Porous Media

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    The basic assumption of models for the transport of contaminants through soil is that the movements of solute particles are characterized by the Brownian motion. However, the complexity of pore space in natural porous media makes the hypothesis of Brownian motion far too restrictive in some situations. Therefore, alternative models have been proposed. One of the models, many times encountered in hydrology, is based in fractional differential equations, which is a one-dimensional fractional advection diffusion equation where the usual second-order derivative gives place to a fractional derivative of order α, with 1 < α ≤ 2. When a fractional derivative replaces the second-order derivative in a diffusion or dispersion model, it leads to anomalous diffusion, also called super-diffusion. We derive analytical solutions for the fractional advection diffusion equation with different initial and boundary conditions. Additionally, we analyze how the fractional parameter α affects the behavior of the solutions

    Detection of Japanese Encephalitis Virus in Vector Mosquitoes in a Non-endemic Area, India

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    Japanese Encephalitis (JE) is a serious growing public health problem in India, gradually engulfing new areas. In north India, eastern districts of Uttar Pradesh had been highly endemic for JE since 1978. JE outbreak was reported to have jumped over 800 km distance from its earlier most endemic area (eastern parts of north India) to a location (Karnal) in the Haryana state of western parts of north India, during the year 1990, which never reported JE earlier.1 Later, the disease gradually spread to its adjoining districts in the state. First time, from western Uttar Pradesh, 7 cases and 4 deaths due to suspected JE were reported in 2003 from Saharanpur district. In the subsequent year, 13 deaths due to suspected viral encephalitis were reported from 26th September to 23rd October, 2004 from one village namely Khekra, from Baghpat district of Uttar Pradesh which is about 128 km west of Saharanpur. A serosurvey carried out on 24th and 25th October, 2004 among the family members of dead persons revealed hemagglutination inhibition (HI) antibodies against JE and West Nile (WN) virus. Further, an outbreak of suspected JE was reported from Saharanpur district in 2005, with 212 cases and 157 deaths. This caused matter of great concern to extend further studies in Baghpat where prevalence of flavivirus infection was already recorded in the locality. For monitoring of arbovirus activities in an area, detection of virus in human sera is cumbersome, difficult and also not desirable. Therefore, as an alternative approach, detection of virus antigen in mosquitoes by antigen capture enzyme linked immunosorbent assay (ELISA) has provided a reliable tool to comprehend the types of virus circulating in nature.2 Detecting arbovirus in mosquitos forms an important part of vector surveillance and may at times also serve as an early warning signal for outbreaks, if however linked with phonological and epidemiological studies. Vector infection and abundance were found to be good indicators of JE occurrence in surveillance studies conducted in South India.3 An attempt was thus made to detect the presence of JE virus (JEV) antigen in vector mosquitoes by ELISA method from the encephalitis-affected area of Baghpat district and to provide evidence of circulating of Japanese Encephalitis virus (JEV) in natural animal-mosquito cycle

    Editorial: The shadowlands of (geo)science communication in academia – definitions, problems, and possible solutions

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    Science communication is an important part of research, including in the geosciences, as it can (1) benefit both society and science and (2) make science more publicly accountable. However, much of this work takes place in “shadowlands” that are neither fully seen nor understood. These shadowlands are spaces, aspects, and practices of science communication that are not clearly defined and may be harmful with respect to the science being communicated or for the science communicators themselves. With the increasing expectation in academia that researchers should participate in science communication, there is a need to address some of the major issues that lurk in these shadowlands. Here, the editorial team of Geoscience Communication seeks to shine a light on the shadowlands of geoscience communication by geoscientists in academia and suggest some solutions and examples of effective practice. The issues broadly fall under three categories: (1) harmful or unclear objectives, (2) poor quality and lack of rigor, and (3) exploitation of science communicators working within academia. Ameliorating these problems will require the following action: (1) clarifying objectives and audiences, (2) adequately training science communicators, and (3) giving science communication equivalent recognition to other professional activities. In this editorial, our aim is to cultivate a more transparent and responsible landscape for geoscience communication – a transformation that will ultimately benefit the progress of science; the welfare of scientists; and, more broadly, society at large

    Quantifying the Relationship Between Atmospheric River Origin Conditions and Landfall Temperature

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    The temperature of landfalling atmospheric rivers (ARs) has direct implications for regional water resources. Compared to cool ARs, warm ARs can result in more surface runoff and flooding, less water availability via low snow accumulations and enhanced snowmelt, and greater challenges for storm forecasting and reservoir operations. Based on case studies, ARs with subtropical origin locations and warm origin conditions are assumed to be associated with warmer landfall temperatures—though, to date, this has not yet been demonstrated systematically. We analyze North Pacific ARs that made landfall along the West Coast of North America from 1980 to 2017. We find that ARs originating over the subtropical Pacific Ocean near Hawaii (“Pineapple Express”-type ARs) are indeed 1.5°C warmer and 2&nbsp;kg/m2 moister in winter than ARs originating elsewhere. We extend this analysis for the full study population of ARs by quantifying AR origin conditions, including the spatial distribution of origin temperature, moisture content, and integrated vapor transport (IVT). We use fixed effects multivariate regression to quantify the relative influence of the origin conditions on landfall temperature. Our regression models show that AR origins with lower latitudes, longer AR lifetimes, and stronger IVT are associated with warmer landfall temperatures and that ARs that start warm generally stay warm. We also find that the phase of the El Niño/Southern Oscillation does not exhibit a consistent relationship with AR landfall temperature. Overall, our results partially affirm—yet&nbsp;also complicate—common assumptions about the role of different origin conditions in landfalling AR temperature
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