709 research outputs found
Embarking as Captain of the Ship for the Curriculum Committee
This commentary examines the curriculum chairâs responsibilities and discusses considerations when assuming this role, using a captain of the ship metaphor. From knowing the crew to managing a diverse set of responsibilities, the path to becoming an effective chair is challenging and each captainâs stripe must be earned. Advice is provided to assist with understanding the curriculum and governance processes, as well as the chairâs various roles and professional development. The need for both leadership and management is also emphasized
Scaling anomalies in the coarsening dynamics of fractal viscous fingering patterns
We analyze a recent experiment of Sharon \textit{et al.} (2003) on the
coarsening, due to surface tension, of fractal viscous fingering patterns
(FVFPs) grown in a radial Hele-Shaw cell. We argue that an unforced Hele-Shaw
model, a natural model for that experiment, belongs to the same universality
class as model B of phase ordering. Two series of numerical simulations with
model B are performed, with the FVFPs grown in the experiment, and with
Diffusion Limited Aggregates, as the initial conditions. We observed
Lifshitz-Slyozov scaling at intermediate distances and very slow
convergence to this scaling at small distances. Dynamic scale invariance breaks
down at large distances.Comment: 4 pages, 4 eps figures; to appear in Phys. Rev.
Layer-by-Layer Assembled Nanowire Networks Enable Graph Theoretical Design of Multifunctional Coatings
Multifunctional coatings are central for information, biomedical,
transportation and energy technologies. These coatings must possess
hard-to-attain properties and be scalable, adaptable, and sustainable, which
makes layer-by-layer assembly (LBL) of nanomaterials uniquely suitable for
these technologies. What remains largely unexplored is that LBL enables
computational methodologies for structural design of these composites.
Utilizing silver nanowires (NWs), we develop and validate a graph theoretical
(GT) description of their LBL composites. GT successfully describes the
multilayer structure with nonrandom disorder and enables simultaneous rapid
assessment of several properties of electrical conductivity, electromagnetic
transparency, and anisotropy. GT models for property assessment can be rapidly
validated due to (1) quasi-2D confinement of NWs and (2) accurate microscopy
data for stochastic organization of the NW networks. We finally show that
spray-assisted LBL offers direct translation of the GT-based design of
composite coatings to additive, scalable manufacturing of drone wings with
straightforward extensions to other technologies
Prevention of Catheter-Related Blood Stream Infection: Back to Basics?
Background: Central venous catheter (CVC)-related infections are a substantial problem in the intensive care unit (ICU). Our infection control team initiated the routine use of antiseptic-coated (chlorhexidine-silver sulfadiazine; Chx-SS) CVCs in our adult ICUs to reduce catheter-associated (CA) and catheter-related (CR) blood stream infection (BSI) as we implemented other educational and best practice standardization strategies. Prior randomized studies documented that the use of Chx-SS catheters reduces microbial colonization of the catheter compared with an uncoated standard (Std) CVC but does not reduce CR-BSI. We therefore implemented the routine use of uncoated Std CVCs in our surgical ICU (SICU) and examined the impact of this change. Hypothesis: The use of uncoated Std CVCs does not increase CR-BSI rate in an SICU. Methods: Prospective evaluation of universal use of uncoated Std CVCs, implemented November 2007 in the SICU. The incidences of CA-BSI and CR-BSI were compared during November 2006-October 2007 (universal use of Chx-SS CVCs) and November 2007-October 2008 (universal use of Std CVCs) by t-test. The definitions of the U.S. Centers for Disease Control and Prevention were used for CA-BSI and CR-BSI. Patient data were collected via a dedicated Acute Physiology and Chronic Health Evaluation (APACHE) III coordinator for the SICU. Results: Annual use of CVCs increased significantly in the last six years, from 3,543 (2001) to 5,799 (2006) total days. The APACHE III scores on day 1 increased from a mean of 54.4 in 2004 to 55.6 in 2008 (p = 0.0010; 95% confidence interval [CI] 1.29-5.13). The mean age of the patients was unchanged over this period, ranging from 58.2 to 59.6 years. The Chx-SS catheters were implemented in the SICU in 2002. Data regarding the specific incidence of CR-BSI were collected beginning at the end of 2005, with mandatory catheter tip cultures when CVCs were removed. Little difference was identified in the incidence of BSI between the interval with universal Chx-SS use and that with Std CVC use. (Total BSI 0.7 vs. 0.8 per 1,000 catheter days; CA-BSI 0.5 vs. 0.8 per 1,000 catheter days; CR-BSI 0.2 vs. 0 per 1,000 catheter days.) No difference was seen in the causative pathogens of CA-BSI or CR-BSI. Conclusion: Eliminating the universal use of Chx-SS-coated CVCs in an SICU with a low background incidence of CR-BSIs did not result in an increase in the rate of CR-BSIs. This study documents the greater importance of adherence to standardization of the processes of care related to CVC placement than of coated CVC use in the reduction of CR-BSI.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90456/1/sur-2E2009-2E082.pd
The supernova rate in local galaxy clusters
We report a measurement of the supernova (SN) rates (Ia and core-collapse) in
galaxy clusters based on the 136 SNe of the sample described in Cappellaro et
al. (1999) and Mannucci et al. (2005).
Early-type cluster galaxies show a type Ia SN rate (0.066 SNuM) similar to
that obtained by Sharon et al. (2007) and more than 3 times larger than that in
field early-type galaxies (0.019 SNuM). This difference has a 98% statistical
confidence level. We examine many possible observational biases which could
affect the rate determination, and conclude that none of them is likely to
significantly alter the results. We investigate how the rate is related to
several properties of the parent galaxies, and find that cluster membership,
morphology and radio power all affect the SN rate, while galaxy mass has no
measurable effect. The increased rate may be due to galaxy interactions in
clusters, inducing either the formation of young stars or a different evolution
of the progenitor binary systems.
We present the first measurement of the core-collapse SN rate in cluster
late-type galaxies, which turns out to be comparable to the rate in field
galaxies. This suggests that no large systematic difference in the initial mass
function exists between the two environments.Comment: MNRAS, revised version after referee's comment
MIBG avidity correlates with clinical features, tumor biology, and outcomes in neuroblastoma: A report from the Childrenâs Oncology Group
BackgroundPrior studies suggest that neuroblastomas that do not accumulate metaiodobenzylguanidine (MIBG) on diagnostic imaging (MIBG nonâavid) may have more favorable features compared with MIBG avid tumors. We compared clinical features, biologic features, and clinical outcomes between patients with MIBG nonavid and MIBG avid neuroblastoma.ProcedurePatients had metastatic highâ or intermediateârisk neuroblastoma and were treated on Childrenâs Oncology Group protocols A3973 or A3961. Comparisons of clinical and biologic features according to MIBG avidity were made with chiâsquared or Fisher exact tests. Eventâfree (EFS) and overall (OS) survival compared using logârank tests and modeled using Cox models.ResultsThirty of 343 patients (8.7%) had MIBG nonavid disease. Patients with nonavid tumors were less likely to have adrenal primary tumors (34.5 vs. 57.2%; P = 0.019), bone metastases (36.7 vs. 61.7%; P = 0.008), or positive urine catecholamines (66.7 vs. 91.0%; P < 0.001) compared with patients with MIBG avid tumors. Nonavid tumors were more likely to be MYCN amplified (53.8 vs. 32.6%; P = 0.030) and had lower norepinephrine transporter expression. Patients with MIBG nonavid disease had a 5âyear EFS of 50.0% compared with 38.7% for patients with MIBG avid disease (P = 0.028). On multivariate testing in highârisk patients, MIBG avidity was the sole adverse prognostic factor for EFS identified (hazard ratio 1.77; 95% confidence interval 1.04â2.99; P = 0.034).ConclusionsPatients with MIBG nonavid neuroblastoma have lower rates of adrenal primary tumors, bone metastasis, and catecholamine secretion. Despite being more likely to have MYCNâamplified tumors, these patients have superior outcomes compared with patients with MIBG avid disease.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138438/1/pbc26545_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138438/2/pbc26545.pd
Foldable structures made of hydrogel bilayers
We discuss self-folding of a thin sheet by using patterned hydrogel bilayers, which act as hinges connecting flat faces. Folding is actuated by heterogeneous swelling due to different crosslinking densities of the polymer network in the two layers. Our analysis is based on a dimensionally reduced plate model, obtained by applying a recently developed theory [1], which provides us with an explicit connection between (three-dimensional) material properties and the curvatures induced at the hinges. This connection offers a recipe for the fabrication and design of the bilayers, by providing the values of the cross-linking density of each layer that need to be imprinted during polymerization in order to produce a desired folded shape upon swelling
Clec16a is critical for autolysosome function and Purkinje cell survival
CLEC16A is in a locus genetically linked to autoimmune diseases including multiple sclerosis, but the function of this gene in the nervous system is unknown. Here we show that two mouse strains carrying independent Clec16a mutations developed neurodegenerative disease characterized by motor impairments and loss of Purkinje cells. Neurons from Clec16a-mutant mice exhibited increased expression of the autophagy substrate p62, accumulation of abnormal intra-axonal membranous structures bearing the autophagy protein LC3, and abnormal Golgi morphology. Multiple aspects of endocytosis, lysosome and Golgi function were normal in Clec16a-deficient murine embryonic fibroblasts and HeLa cells. However, these cells displayed abnormal bulk autophagy despite unimpaired autophagosome formation. Cultured Clec16a-deficient cells exhibited a striking accumulation of LC3 and LAMP-1 positive autolysosomes containing undigested cytoplasmic contents. Therefore Clec16a, an autophagy protein that is critical for autolysosome function and clearance, is required for Purkinje cell survival
Blood Lead Levels Among Pregnant Women: Historical Versus Contemporaneous Exposures
Blood lead among pregnant women, even at modest levels, may impair offspring cognitive development. We examine whether blood lead levels (BLLs) result from current versus historic exposures, among a cohort of pregnant women. Cumulative logit models were used to characterize the relationship between maternal risk factors and higher BLLs. Maternal blood lead levels more likely result from lead remobilization from historic versus contemporaneous exposures. Even if all lead sources were abated immediately, women and their fetuses would experience lead exposure for decades. This work emphasizes the importance of addressing sources of environmental lead exposure in the United States and internationally
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