3,023 research outputs found
Survival of near-critical branching Brownian motion
Consider a system of particles performing branching Brownian motion with
negative drift and killed upon hitting zero.
Initially there is one particle at . Kesten showed that the process
survives with positive probability if and only if . Here we are
interested in the asymptotics as \eps\to 0 of the survival probability
. It is proved that if then for all , exists and is a
travelling wave solution of the Fisher-KPP equation. Furthermore, we obtain
sharp asymptotics of the survival probability when and .
The proofs rely on probabilistic methods developed by the authors in a previous
work. This completes earlier work by Harris, Harris and Kyprianou and confirms
predictions made by Derrida and Simon, which were obtained using nonrigorous
PDE methods
A Qualitative Evaluation of Advances in Emergency Department Opioid Use Disorder Care in Michigan
The United States opioid epidemic claims the lives of tens of thousands of Americans each year due to opioid overdose. Hospital emergency departments (EDs) have been essential in combatting the crisis by stabilizing patients who are experiencing an overdose and other symptoms of their opioid use disorders (OUD). Over time, EDs have also become more involved in providing other addiction treatment services, such as prescribing and administering medications for opioid use disorder (MOUD) and referring their patients to outpatient behavioral health care providers for follow-up treatment. Policymakers have been essential in driving EDs to expand the scope of their addiction medicine services and referrals by creating specialized programs that provide incentivizes to participating hospitals.The following report summarizes advances in opioid use disorder care within EDs in 19 hospitals across 8 health systems in Michigan. These hospitals participated in an initiative created by the Community Foundation for Southeast Michigan (CFSEM) in collaboration with the Michigan Opioid Partnership (MOP), a public-private collaborative with a mission to reduce opioid overdoses in Michigan by improving the access and quality of prevention, treatment, harm reduction, and recovery services. The initiative was supported by State Opioid Response grants from the Michigan Department of Health and Human Services. Vital Strategies, a global public health organization that helps governments strengthen public health, provided support, technical assistance, and resources to improve hospital coordination and designed the evaluation. Specifically, hospitals were provided funding by CFSEM to improve OUD care training, coordination, delivery, and quality in their EDs. Hospitals and health systems funded by CFSEM included the University of Michigan Health System (Michigan Medicine hospital), Trinity Health (Mercy Health Muskegon, Mercy Health St. Mary, St. Joseph Mercy - Ann Arbor, St. Joseph Mercy Chelsea, St. Joseph Mercy Livingston, St. Joseph Mercy Oakland), Henry Ford Health Systems (Henry Ford â Main, Henry Ford - Wynadotte/ Brownstown), Beaumont Health Systems (Beaumont - Royal Oak, Beaumont â Troy, Beaumont â Wayne), Ascension (Ascension St. John Hospital, Ascension Genesys Hospital), Munson Healthcare (Munson Medical Center - Traverse City, Sparrow Health System (Sparrow Hospital - Lansing), Spectrum Health (Spectrum Health Butterworth), War Memorial, and Hurley Medical Center. After receiving funding, hospitals created work plans related to improving opioid use disorder care in their EDs, including by increasing their number of employed X-waivered providers, integrating clinical tracking and support tools into electronic medical records, and connecting patients with behavioral health care providers in the community to establish treatment continuity (i.e., "warm handoffs"). Researchers with the Bloomberg Overdose Prevention Initiative at the Johns Hopkins Bloomberg School of Public Health evaluated hospital improvement in these areas using surveys and qualitative interviews with participants
The Morphologies of the Small Magellanic Cloud
We compare the distribution of stars of different spectral types, and hence
mean age, within the central SMC and find that the asymmetric structures are
almost exclusively composed of young main sequence stars. Because of the
relative lack of older stars in these features, and the extremely regular
distribution of red giant and clump stars in the SMC central body, we conclude
that tides alone are not responsible for the irregular appearance of the
central SMC. The dominant physical mechanism in determining the current-day
appearance of the SMC must be star formation triggered by a hydrodynamic
interaction between gaseous components. These results extend the results of
population studies (cf. Gardiner and Hatzidimitriou) inward in radius and also
confirm the suggestion of the spheroidal nature of the central SMC based on
kinematic arguments (Dopita et al; Hardy, Suntzeff & Azzopardi). Finally, we
find no evidence in the underlying older stellar population for a ``bar'' or
``outer arm'', again supporting our classification of the central SMC as a
spheroidal body with highly irregular recent star formation.Comment: 8 pages, accepted for publication in ApJ Letters (higher quality
figures available at http://ngala.as.arizona.edu/dennis/mcsurvey.html
Recommended from our members
Cholera and ABO Blood Group: Understanding an Ancient Association
Quantifying the Drivers of Star Formation on Galactic Scales. I. The Small Magellanic Cloud
We use the star formation history of the Small Magellanic Cloud (SMC) to
place quantitative limits on the effect of tidal interactions and gas infall on
the star formation and chemical enrichment history of the SMC. The coincident
timing of two recent (< 4 Gyr) increases in the star formation rate and
SMC/Milky Way(MW) pericenter passages suggests that global star formation in
the SMC is driven at least in part by tidal forces due to the MW. The Large
Magellanic Cloud (LMC) is the other potential driver of star formation, but is
only near the SMC during the most recent burst. The poorly constrained LMC-SMC
orbit is our principal uncertainty. To explore the correspondence between
bursts and MW pericenter passages further, we model star formation in the SMC
using a combination of continuous and tidally-triggered star formation. The
behavior of the tidally-triggered mode is a strong inverse function of the
SMC-MW separation (preferred behavior ~ r^-5, resulting in a factor of ~100
difference in the rate of tidally-triggered star formation at pericenter and
apocenter). Despite the success of these closed-box evolutionary models in
reproducing the recent SMC star formation history and current chemical
abundance, they have some systematic shortcomings that are remedied by
postulating that a sizable infall event (~ 50% of the total gas mass) occured
about 4 Gyr ago. Regardless of whether this infall event is included, the
fraction of stars in the SMC that formed via a tidally triggered mode is > 10%
and could be as large as 70%.Comment: Accepted for publication in Ap
On the Spatial Distribution of Stellar Populations in the Large Magellanic Cloud
We measure the angular correlation function of stars in a region of the Large
Magellanic Cloud (LMC) that spans 2 degrees by 1.5 degrees. We find that the
correlation functions of stellar populations are represented well by
exponential functions of the angular separation for separations between 2 and
40 arcmin (corresponding to ~ 30 pc and 550 pc for an LMC distance of 50 kpc).
The inner boundary is set by the presence of distinct, highly correlated
structures, which are the more familiar stellar clusters, and the outer
boundary is set by the observed region's size and the presence of two principal
centers of star formation within the region. We also find that the
normalization and scale length of the correlation function changes
systematically with the mean age of the stellar population. The existence of
positive correlation at large separations (~300 pc), even in the youngest
population, argues for large-scale hierarchical structure in current star
formation. The evolution of the angular correlation toward lower normalizations
and longer scale lengths with stellar age argues for the dispersion of stars
with time. We show that a simple, stochastic, self-propagating star formation
model is qualitatively consistent with this behavior of the correlation
function.Comment: 30 pages, 13 Figures. Scheduled for publication in AJ in June 199
Analysis of the Human Mucosal Response to Cholera Reveals Sustained Activation of Innate Immune Signaling Pathways
To better understand the innate immune response to Vibrio cholerae infection, we tracked gene expression in the duodenal mucosa of 11 Bangladeshi adults with cholera, using biopsy specimens obtained immediately after rehydration and 30 and 180 days later. We identified differentially expressed genes and performed an analysis to predict differentially regulated pathways and upstream regulators. During acute cholera, there was a broad increase in the expression of genes associated with innate immunity, including activation of the NF-kappaB, mitogen-activated protein kinase (MAPK), and Toll-like receptor (TLR)-mediated signaling pathways, which, unexpectedly, persisted even 30 days after infection. Focusing on early differences in gene expression, we identified 37 genes that were differentially expressed on days 2 and 30 across the 11 participants. These genes included the endosomal Toll-like receptor gene TLR8, which was expressed in lamina propria cells. Underscoring a potential role for endosomal TLR-mediated signaling in vivo, our pathway analysis found that interferon regulatory factor 7 and beta 1 and alpha 2 interferons were among the top upstream regulators activated during cholera. Among the innate immune effectors, we found that the gene for DUOX2, an NADPH oxidase involved in the maintenance of intestinal homeostasis, was upregulated in intestinal epithelial cells during cholera. Notably, the observed increases in DUOX2 and TLR8 expression were also modeled in vitro when Caco-2 or THP-1 cells, respectively, were stimulated with live V. cholerae but not with heat-killed organisms or cholera toxin alone. These previously unidentified features of the innate immune response to V. cholerae extend our understanding of the mucosal immune signaling pathways and effectors activated in vivo following cholera
Analysis of the Human Mucosal Response to Cholera Reveals Sustained Activation of Innate Immune Signaling Pathways
To better understand the innate immune response to Vibrio cholerae infection, we tracked gene expression in the duodenal mucosa of 11 Bangladeshi adults with cholera, using biopsy specimens obtained immediately after rehydration and 30 and 180 days later. We identified differentially expressed genes and performed an analysis to predict differentially regulated pathways and upstream regulators. During acute cholera, there was a broad increase in the expression of genes associated with innate immunity, including activation of the NF-kappaB, mitogen-activated protein kinase (MAPK), and Toll-like receptor (TLR)-mediated signaling pathways, which, unexpectedly, persisted even 30 days after infection. Focusing on early differences in gene expression, we identified 37 genes that were differentially expressed on days 2 and 30 across the 11 participants. These genes included the endosomal Toll-like receptor gene TLR8, which was expressed in lamina propria cells. Underscoring a potential role for endosomal TLR-mediated signaling in vivo, our pathway analysis found that interferon regulatory factor 7 and beta 1 and alpha 2 interferons were among the top upstream regulators activated during cholera. Among the innate immune effectors, we found that the gene for DUOX2, an NADPH oxidase involved in the maintenance of intestinal homeostasis, was upregulated in intestinal epithelial cells during cholera. Notably, the observed increases in DUOX2 and TLR8 expression were also modeled in vitro when Caco-2 or THP-1 cells, respectively, were stimulated with live V. cholerae but not with heat-killed organisms or cholera toxin alone. These previously unidentified features of the innate immune response to V. cholerae extend our understanding of the mucosal immune signaling pathways and effectors activated in vivo following cholera
The Nature of the Density Clump in the Fornax Dwarf Spheroidal Galaxy
We have imaged the recently discovered stellar overdensity located
approximately one core radius from the center of the Fornax dwarf spheroidal
galaxy using the Magellan Clay 6.5m telescope with the Magellan Instant Camera
(MagIC). Superb seeing conditions allowed us to probe the stellar populations
of this overdensity and of a control field within Fornax to a limiting
magnitude of R=26. The color-magnitude diagram of the overdensity field is
virtually identical to that of the control field with the exception of the
presence of a population arising from a very short (less than 300 Myr in
duration) burst of star formation 1.4 Gyr ago. Coleman et al. have argued that
this overdensity might be related to a shell structure in Fornax that was
created when Fornax captured a smaller galaxy. Our results are consistent with
this model, but we argue that the metallicity of this young component favors a
scenario in which the gas was part of Fornax itself.Comment: 24 pages including 8 figures and 3 tables. Accepted by Astronomical
Journa
Effects of Youth Tobacco Access and Possession Policy Interventions on Heavy Adolescent Smokers
This study evaluated the effects of tobacco PUP (Purchase, Use and Possession) laws on tobacco use patterns among students in twenty-four towns, which were randomly assigned into an experimental and a control group. The experimental group involved both PUP law enforcement and reducing minorsâ access to commercial sources of tobacco, and the condition for the control group involved only efforts to reduce minorsâ access to commercial sources of tobacco. The present study found that adolescents in the control group had a significantly greater increase in the percentage of youth who smoked 20 or more cigarettes per day when compared to the experimental group
- âŠ