3,816 research outputs found
Acceptable Vibrations on Green Concrete
This thesis contains the results of various green concrete samples subjected to different vibration intensities to determine how green concrete withstands against these vibration intensities. The green concrete was exposed to these vibrations at times before, during, and after the concrete had set. The concrete was also exposed to different timed durations while being subjected to the different vibration levels. Every batch of concrete mixed included a controlled (un-vibrated) set of cylinders and a vibrated set of cylinders. The compressive strength and the resistivity of these concrete cylinders were measured and compared to determine if there was any significant difference between the two sets. It was found that the vibrations subjected to the cylinders did not create a significant effect; given the vibrations levels and timed durations stay within the limits of this study
Venous Air Embolism Leading to Cardiac Arrest in an Infant with Cyanotic Congenital Heart Disease
Gas emboli, including venous and arterial, are a rare but important complication of pediatric cardiac surgery. They have the potential to have devastating consequences and require prompt recognition and treatment. We present a case of gas embolism occurring in the immediate postoperative period in an infant with cyanotic congenital heart disease after palliative cardiac surgery resulting in cardiopulmonary arrest. The embolism was diagnosed by visualization of air within the vessel creating an airlock and occluding pulmonary blood flow
The Role of Drag in the Energetics of Strongly Forced Exoplanet Atmospheres
In contrast to the Earth, where frictional heating is typically negligible,
we show that drag mechanisms could act as an important heat source in the
strongly-forced atmospheres of some exoplanets, with the potential to alter the
circulation. We modify the standard formalism of the atmospheric energy cycle
to explicitly track the loss of kinetic energy and the associated frictional
(re)heating, for application to exoplanets such as the asymmetrically heated
"hot Jupiters" and gas giants on highly eccentric orbits. We establish that an
understanding of the dominant drag mechanisms and their dependence on local
atmospheric conditions is critical for accurate modeling, not just in their
ability to limit wind speeds, but also because they could possibly change the
energetics of the circulation enough to alter the nature of the flow. We
discuss possible sources of drag and estimate the strength necessary to
significantly influence the atmospheric energetics. As we show, the frictional
heating depends on the magnitude of kinetic energy dissipation as well as its
spatial variation, so that the more localized a drag mechanism is, the weaker
it can be and still affect the circulation. We also use the derived formalism
to estimate the rate of numerical loss of kinetic energy in a few previously
published hot Jupiter models with and without magnetic drag and find it to be
surprisingly large, at 5-10% of the incident stellar irradiation.Comment: 25 pages, 3 figures, 1 table, ApJ accepted; minor revision
Virial Sequences for Thick Discs and Haloes: Flattening and Global Anisotropy
The virial theorem prescribes the ratio of the globally-averaged equatorial
to vertical velocity dispersion of a tracer population in spherical and
flattened dark haloes. This gives sequences of physical models in the plane of
global anisotropy and flattening. The tracer may have any density, though there
are particularly simple results for power-laws and exponentials. We prove the
flattening theorem: for a spheroidally stratified tracer density with axis
ratio q in a dark density potential with axis ratio g, the ratio of globally
averaged equatorial to vertical velocity dispersion depends only on q/g. As the
stellar halo density and velocity dispersion of the Milky Way are accessible to
observations, this provides a new method for measuring the flattening of the
dark matter. If the kinematics of the local halo subdwarfs are representative,
then the Milky Way's dark halo is oblate with a flattening in the potential of
g ~ 0.85, corresponding to a flattening in the dark matter density of ~ 0.7.
The fractional pressure excess for power-law populations is roughly
proportional to both the ellipticity and the fall-off exponent. Given the same
pressure excess, if the density profile of one stellar population declines more
quickly than that of another, then it must be rounder. This implies that the
dual halo structure claimed by Carollo et al. (2007) for the Galaxy, a flatter
inner halo and a rounder outer halo, is inconsistent with the virial theorem.
For the thick disc, we provide formulae for the virial sequences of
double-exponential discs in logarithmic and Navarro-Frenk-White (NFW) haloes.
There are good matches to the observational data on the flattening and
anisotropy of the thick disc if the thin disc is exponential with a short
scalelength ~ 2.6 kpc and normalisation of 56 solar masses per square parsec,
together with a logarithmic dark halo.Comment: MNRAS, submitted, 13 pages, 7 figures, small changes to made to
correspond to final accepted versio
Faculty Artist Recital: Tim Hurtz, Oboe; Russell Bedford, Bassoon; Harold Gray, Piano; Arthur Lewis, Viola; Bedford Watkins, Harpsichord; October 17, 1974
Centennial East Recital HallThursday EveningOctober 17, 19748:15 p.m
The association between neurodegeneration and local complement activation in the thalamus to progressive multiple sclerosis outcome
The extent of grey matter demyelination and neurodegeneration in the progressive multiple sclerosis (PMS) brains at post‐mortem associates with more severe disease. Regional tissue atrophy, especially affecting the cortical and deep grey matter, including the thalamus, is prognostic for poor outcomes. Microglial and complement activation are important in the pathogenesis and contribute to damaging processes that underlie tissue atrophy in PMS. We investigated the extent of pathology and innate immune activation in the thalamus in comparison to cortical grey and white matter in blocks from 21 cases of PMS and 10 matched controls. Using a digital pathology workflow, we show that the thalamus is invariably affected by demyelination and had a far higher proportion of active inflammatory lesions than forebrain cortical tissue blocks from the same cases. Lesions were larger and more frequent in the medial nuclei near the ventricular margin, whilst neuronal loss was greatest in the lateral thalamic nuclei. The extent of thalamic neuron loss was not associated with thalamic demyelination but correlated with the burden of white matter pathology in other forebrain areas (Spearman r = 0.79, p < 0.0001). Only thalamic neuronal loss, and not that seen in other forebrain cortical areas, correlated with disease duration (Spearman r = −0.58, p = 0.009) and age of death (Spearman r = −0.47, p = 0.045). Immunoreactivity for the complement pattern recognition molecule C1q, and products of complement activation (C4d, Bb and C3b) were elevated in thalamic lesions with an active inflammatory pathology. Complement regulatory protein, C1 inhibitor, was unchanged in expression. We conclude that active inflammatory demyelination, neuronal loss and local complement synthesis and activation in the thalamus, are important to the pathological and clinical disease outcomes of PMS
Liberation-focused Community Outreach: A Qualitative Exploration of Peer Group Supervision during Disaster Response
While it is clear that community outreach and disaster response must include cultural and social justice competence, there is a dearth of knowledge regarding the process by which this can occur. Guided by liberation psychology, this qualitative study examined the peer group supervision process of psychologists and counselors providing outreach to Haitian communities in Florida after the 2010 earthquake in Haiti. The findings suggest that peer supervision generated a cyclical process in which the practitioners focused on both content and process themes that were salient to the community outreach. During supervision, practitioners used content information on the community\u27s culture, strengths, and sociopolitical issues to conceptualize the community\u27s experiences and needs. This content informed the outreach process, including the practitioners’ roles and the ways in which they connected and developed respectful relationships with the community. Ongoing peer supervision appeared to facilitate a liberation-focused community outreach and increase consciousness among the practitioners
Atmospheric circulation of hot Jupiters: insensitivity to initial conditions
The ongoing characterization of hot Jupiters has motivated a variety of
circulation models of their atmospheres. Such models must be integrated
starting from an assumed initial state, which is typically taken to be a
wind-free, rest state. Here, we investigate the sensitivity of hot-Jupiter
atmospheric circulation models to initial conditions. We consider two classes
of models--shallow-water models, which have proven successful at illuminating
the dynamical mechanisms at play on these planets, and full three-dimensional
models similar to those being explored in the literature. Models are
initialized with zonal jets, and we explore a variety of different initial jet
profiles. We demonstrate that, in both classes of models, the final,
equilibrated state is independent of initial condition--as long as frictional
drag near the bottom of the domain and/or interaction with a specified
planetary interior are included so that the atmosphere can adjust angular
momentum over time relative to the interior. When such mechanisms are included,
otherwise identical models initialized with vastly different initial conditions
all converge to the same statistical steady state. In some cases, the models
exhibit modest time variability; this variability results in random
fluctuations about the statistical steady state, but we emphasize that, even in
these cases, the statistical steady state itself does not depend on initial
conditions. Although the outcome of hot-Jupiter circulation models depend on
details of the radiative forcing and frictional drag, aspects of which remain
uncertain, we conclude that the specification of initial conditions is not a
source of uncertainty, at least over the parameter range explored in most
current models.Comment: Revised version; accepted and published. 16 pages, 16 figure
Complement activation and increased anaphylatoxin receptor expression are associated with cortical grey matter lesions and the compartmentalised inflammatory response of multiple sclerosis
Background: The extent of cortical pathology is an important determinant of multiple sclerosis (MS) severity. Cortical demyelination and neurodegeneration are related to inflammation of the overlying leptomeninges, a more inflammatory CSF milieu and with parenchymal microglia and astroglia activation. These are all components of the compartmentalised inflammatory response. Compartmentalised inflammation is a feature of progressive MS, which is not targeted by disease modifying therapies. Complement is differentially expressed in the MS CSF and complement, and complement receptors, are associated with demyelination and neurodegeneration. Methods: To better understand if complement activation in the leptomeninges is associated with underlying cortical demyelination, inflammation, and microglial activation, we performed a neuropathological study of progressive MS (n = 22, 14 females), neuroinflammatory (n = 8), and non-neurological disease controls (n = 10). We then quantified the relative extent of demyelination, connective tissue inflammation, complement, and complement receptor positive microglia/macrophages. Results: Complement was elevated at the leptomeninges, subpial, and within and around vessels of the cortical grey matter. The extent of complement C1q immunoreactivity correlated with connective tissue infiltrates, whilst activation products C4d, Bb, and C3b associated with grey matter demyelination, and C3a receptor 1+ and C5a receptor 1+ microglia/macrophages closely apposed C3b labelled cells. The density of C3a receptor 1+ and C5a receptor 1+ cells was increased at the expanding edge of subpial and leukocortical lesions. C5a receptor 1+ cells expressed TNFα, iNOS and contained puncta immunoreactive for proteolipid protein, neurofilament and synaptophysin, suggesting their involvement in grey matter lesion expansion. Interpretation: The presence of products of complement activation at the brain surfaces, their association with the extent of underlying pathology and increased complement anaphylatoxin receptor positive microglia/macrophages at expanding cortical grey matter lesions, could represent a target to modify compartmentalised inflammation and cortical demyelination
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