665 research outputs found
Impact of the first COVID-19 pandemic wave on the Scottish Multiple Sclerosis Register population
On the flow-level stability of data networks without congestion control: the case of linear networks and upstream trees
In this paper, flow models of networks without congestion control are
considered. Users generate data transfers according to some Poisson processes
and transmit corresponding packet at a fixed rate equal to their access rate
until the entire document is received at the destination; some erasure codes
are used to make the transmission robust to packet losses. We study the
stability of the stochastic process representing the number of active flows in
two particular cases: linear networks and upstream trees. For the case of
linear networks, we notably use fluid limits and an interesting phenomenon of
"time scale separation" occurs. Bounds on the stability region of linear
networks are given. For the case of upstream trees, underlying monotonic
properties are used. Finally, the asymptotic stability of those processes is
analyzed when the access rate of the users decreases to 0. An appropriate
scaling is introduced and used to prove that the stability region of those
networks is asymptotically maximized
Neurodevelopmental and Perinatal Correlates of Simple Brain Metrics in Very Preterm Infants
OBJECTIVE: To explore perinatal correlates of 3 simple measures of brain size, known as metrics, in very preterm infants at term-equivalent age and their relationship to 2-year neurodevelopmental outcomes.DESIGN: Prospective cohort study of preterm infants born at a gestational age of less than 30 weeks or a weight of less than 1250 g between April 1, 2001, and December 31, 2003, and followed up at 2 years of corrected age. SETTING: The Royal Women\u27s Hospital and the magnetic resonance imaging unit at the Royal Children\u27s Hospital. PATIENTS: Two hundred thirty-six preterm infants. INTERVENTIONS: Brain metrics--biparietal, bifrontal, and transverse cerebellar diameters--on magnetic resonance imaging for preterm infants at term-equivalent age and neurodevelopmental assessments at 2 years of corrected age. MAIN OUTCOME MEASURES: Mental Development Index and the Psychomotor Development Index of the Bayley Scales of Infant Development-Revised. RESULTS: Higher birth weight z score, shorter duration of assisted ventilation, and postmenstrual age at magnetic resonance imaging were independently associated with increases in the 3 brain metrics, and male sex was associated with larger bifrontal and biparietal diameters. Only the biparietal diameter was predictive of cognitive and motor indices after adjustment for perinatal variables and social risk. CONCLUSION: This study provides further evidence of altered brain growth in preterm infants, relating to growth restriction and severity of illness, that in turn relate to neurodevelopmental outcome
A Novel Quantitative Simple Brain Metric Using MR Imaging for Preterm Infants
BACKGROUND AND PURPOSE: The application of volumetric techniques to preterm infants has revealed brain volume reductions. Such quantitative data are not available in routine neonatal radiologic care. The objective of this study was to develop simple brain metrics to compare brain size in preterm and term infants and to correlate these metrics with brain volumes from volumetric MR imaging techniques.MATERIALS AND METHODS: MR images from 189 preterm infants <30 weeks’ gestational age or <1250 g birthweight scanned at term-equivalent age and 36 term infants were studied. Fifteen tissue and fluid measures were systematically evaluated on 4 selected sections. The results were correlated with total brain, gray matter, white matter, and CSF volumes. RESULTS: The mean bifrontal, biparietal, and transverse cerebellar diameters were reduced (−11.6%, 95% confidence interval [CI], −13.8% to −9.3%; −12%, 95% CI, −14% to −9.8%; and −8.7%, 95% CI, −10.5% to −7% respectively) and the mean left ventricle diameter was increased (+22.3%, 95% CI, 2.9%–41.6%) in preterm infants (P < .01). Strong correlations were found between the bifrontal and biparietal measures with total brain tissue volume, whereas the size of the ventricles and the interhemispheric measure correlated with CSF volume. Intraobserver reliability was high (intraclass correlation coefficients [ICC], >0.7), where interobserver agreement was acceptable for tissue measures (ICC, >0.6) but lower for fluid measures (ICC, <0.4) CONCLUSIONS: Simple brain metrics at term-equivalent age showed smaller brain diameters and increased ventricle size in preterm infants compared with full-term infants. These measures represent a reliable and easily applicable method to quantify brain growth and assess brain atrophy in this at-risk population
Revisiting the Local Scaling Hypothesis in Stably Stratified Atmospheric Boundary Layer Turbulence: an Integration of Field and Laboratory Measurements with Large-eddy Simulations
The `local scaling' hypothesis, first introduced by Nieuwstadt two decades
ago, describes the turbulence structure of stable boundary layers in a very
succinct way and is an integral part of numerous local closure-based numerical
weather prediction models. However, the validity of this hypothesis under very
stable conditions is a subject of on-going debate. In this work, we attempt to
address this controversial issue by performing extensive analyses of turbulence
data from several field campaigns, wind-tunnel experiments and large-eddy
simulations. Wide range of stabilities, diverse field conditions and a
comprehensive set of turbulence statistics make this study distinct
The Fueling and Evolution of AGN: Internal and External Triggers
In this chapter, I review the fueling and evolution of active galactic nuclei
(AGN) under the influence of internal and external triggers, namely intrinsic
properties of host galaxies (morphological or Hubble type, color, presence of
bars and other non-axisymmetric features, etc) and external factors such as
environment and interactions. The most daunting challenge in fueling AGN is
arguably the angular momentum problem as even matter located at a radius of a
few hundred pc must lose more than 99.99 % of its specific angular momentum
before it is fit for consumption by a BH. I review mass accretion rates,
angular momentum requirements, the effectiveness of different fueling
mechanisms, and the growth and mass density of black BHs at different epochs. I
discuss connections between the nuclear and larger-scale properties of AGN,
both locally and at intermediate redshifts, outlining some recent results from
the GEMS and GOODS HST surveys.Comment: Invited Review Chapter to appear in LNP Volume on "AGN Physics on All
Scales", Chapter 6, in press. 40 pages, 12 figures. Typo in Eq 5 correcte
Formation and Evolution of Supermassive Black Holes
The correlation between the mass of supermassive black holes in galaxy nuclei
and the mass of the galaxy spheroids or bulges (or more precisely their central
velocity dispersion), suggests a common formation scenario for galaxies and
their central black holes. The growth of bulges and black holes can commonly
proceed through external gas accretion or hierarchical mergers, and are both
related to starbursts. Internal dynamical processes control and regulate the
rate of mass accretion. Self-regulation and feedback are the key of the
correlation. It is possible that the growth of one component, either BH or
bulge, takes over, breaking the correlation, as in Narrow Line Seyfert 1
objects. The formation of supermassive black holes can begin early in the
universe, from the collapse of Population III, and then through gas accretion.
The active black holes can then play a significant role in the re-ionization of
the universe. The nuclear activity is now frequently invoked as a feedback to
star formation in galaxies, and even more spectacularly in cooling flows. The
growth of SMBH is certainly there self-regulated. SMBHs perturb their local
environment, and the mergers of binary SMBHs help to heat and destroy central
stellar cusps. The interpretation of the X-ray background yields important
constraints on the history of AGN activity and obscuration, and the census of
AGN at low and at high redshifts reveals the downsizing effect, already
observed for star formation. History appears quite different for bright QSO and
low-luminosity AGN: the first grow rapidly at high z, and their number density
decreases then sharply, while the density of low-luminosity objects peaks more
recently, and then decreases smoothly.Comment: 31 pages, 13 figures, review paper for Astrophysics Update
Destruction of chemical warfare surrogates using a portable atmospheric pressure plasma jet
Today’s reality is connected with mitigation of threats from the new chemical and biological warfare agents. A novel investigation of cold plasmas in contact with liquids presented in this paper demonstrated that the chemically reactive environment produced by atmospheric pressure plasma jet (APPJ) is potentially capable of rapid destruction of chemical warfare agents in a broad spectrum. The decontamination of three different chemical warfare agent surrogates dissolved in liquid is investigated by using an easily transportable APPJ. The jet is powered by a kHz signal source connected to a low-voltage DC source and with He as working gas. The detailed investigation of electrical properties is performed for various plasmas at different distances from the sample. The measurements of plasma properties in situ are supported by the optical spectrometry measurements, whereas the high performance liquid chromatography measurements before and after the treatment of aqueous solutions of Malathion, Fenitrothion and Dimethyl Methylphosphonate. These solutions are used to evaluate destruction and its efficiency for specific neural agent simulants. The particular removal rates are found to be from 56% up to 96% during 10 min treatment. The data obtained provide basis to evaluate APPJ’s efficiency at different operating conditions. The presented results are promising and could be improved with different operating conditions and optimization of the decontamination process
X-ray Survey Results on Active Galaxy Physics and Evolution
This "pedagogical" review describes the key Chandra and XMM-Newton
extragalactic surveys to date and details some of their implications for AGN
physics and evolution. We additionally highlight two topics of current
widespread interest: (1) X-ray constraints on the AGN content of luminous
submillimeter galaxies, and (2) the demography and physics of high-redshift (z
> 4) AGN as revealed by X-ray observations. Finally, we discuss prospects for
future X-ray surveys with Chandra, XMM-Newton, and upcoming missions.Comment: 26 pages, in Physics of Active Galactic Nuclei at All Scales, eds.
Alloin D., Johnson R., Lira P. (Springer-Verlag, Berlin), version with all
figures at http://www.astro.psu.edu/users/niel/papers/papers.htm
What's wrong with John? A randomised controlled trial of Mental Health First Aid (MHFA) training with nursing students
BACKGROUND: The prevalence of mental health problems have been found to be higher among university students compared to their non-student peers. Nursing students in particular face a range of additional stressors which may impact their undergraduate performance and their careers. Mental Health First Aid (MHFA) aims to increase mental health literacy and to reduce stigma and may positively impact on the student population. This paper describes a MHFA randomised controlled trial targeting nursing students at a large Australian university. This study aimed to measure the impact of the MHFA course on mental health literacy, mental health first aid intentions, confidence in helping someone with a mental health problem and stigmatising attitudes including social distance. METHODS: Participants were first year nursing students (n = 181) randomly allocated to the intervention (n = 92) or control (n = 89) group. Intervention group participants received the standardised MHFA course for nursing students. Online self-report questionnaires were completed at three time intervals: baseline (one week prior to the intervention: T1) (n = 140), post intervention (T2) (n = 120), and two months post intervention (T3) (n = 109). Measures included demographics, mental health knowledge, recognition of depression, confidence in helping, mental health first aid intentions and stigmatising attitudes including social distance. Repeated measures ANOVA was computed to measure if the impact of time (T1, T2, T3) and group (intervention and control) on the outcome variables. RESULTS: There was a significant improvement among intervention compared to control group participants across the three time periods for knowledge scores (p < 0.001), confidence in helping (p < 0.001), mental health first aid intentions (p < 0.001), total personal stigma (p < 0.05), personal dangerous/unpredictable stigma (p < 0.05) and social distance (p < 0.05) scores. CONCLUSION: MHFA is useful training to embed in university courses and has the potential to enhance mental health literacy and reduce stigmatising attitudes and social distance. While this course has particular salience for nursing and other health science students, there are broader benefits to the general university population that should be considered and opportunities accordingly explored for all students to complete the course. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ACTRN12614000861651 . Retrospectively registered 11 August 2014
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