169 research outputs found
Building a Model of Collaboration Between Historically Black and Historically White Universities
Despite increases over the last two decades in the number of degrees awarded to students from underrepresented groups in science, technology, engineering, and mathematics (STEM) disciplines, enhancing diversity in these disciplines remains a challenge. This article describes a strategic approach to this challengeβthe development of a collaborative partnership between two universities: the historically Black Elizabeth City State University and the historically White University of New Hampshire. The partnership, a type of learning organization built on three mutually agreed upon principles, strives to enhance opportunities for underrepresented students to pursue careers in the STEM disciplines. This article further describes six promising practices that framed the partnership, which resulted in the submission of nine proposals to federal agencies and the funding of four grants that led to the implementation, research, learning, and evaluation that followed
Solitonic approach to the dimerization problem in correlated one-dimensional systems
Using exact diagonalizations we consider self-consistently the lattice
distortions in odd Peierls-Hubbard and spin-Peierls periodic rings in the
adiabatic harmonic approximation. From the tails of the inherent spin soliton
the dimerization d_\infty of regular even rings is found by extrapolations to
infinite ring lengths. Considering a wide region of electron-electron onsite
interaction values U>0 compared with the band width 4t_0 at intermediately
strong electron-phonon interaction g, known relationships obtained by other
methods are reproduced and/or refined within one unified approach: such as the
maximum of d_\infty at U \simeq 3 t_0 for g \simeq 0.5 and its shift to zero
for g \to g_c \approx 0.7. The hyperbolic tangent shape of the spin soliton is
retained for any U and g <~ 0.6. In the spin-Peierls limit the d_\infty are
found to be in agreement with results of DMRG computations.Comment: 4 pages, 4 figures, Physical Review B, Rapid Communications, v. 56
(1997) accepte
Prospectus, January 10, 1969
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Chemical Cartography with APOGEE: Large-scale Mean Metallicity Maps of the Milky Way
We present Galactic mean metallicity maps derived from the first year of the
SDSS-III APOGEE experiment. Mean abundances in different zones of
Galactocentric radius (0 < R < 15 kpc) at a range of heights above the plane (0
< |z| < 3 kpc), are derived from a sample of nearly 20,000 stars with
unprecedented coverage, including stars in the Galactic mid-plane at large
distances. We also split the sample into subsamples of stars with low and
high-[{\alpha}/M] abundance ratios. We assess possible biases in deriving the
mean abundances, and find they are likely to be small except in the inner
regions of the Galaxy. A negative radial gradient exists over much of the
Galaxy; however, the gradient appears to flatten for R < 6 kpc, in particular
near the Galactic mid-plane and for low-[{\alpha}/M] stars. At R > 6 kpc, the
gradient flattens as one moves off of the plane, and is flatter at all heights
for high-[{\alpha}/M] stars than for low-[{\alpha}/M] stars. Alternatively,
these gradients can be described as vertical gradients that flatten at larger
Galactocentric radius; these vertical gradients are similar for both low and
high-[{\alpha}/M] populations. Stars with higher [{\alpha}/M] appear to have a
flatter radial gradient than stars with lower [{\alpha}/M]. This could suggest
that the metallicity gradient has grown steeper with time or, alternatively,
that gradients are washed out over time by migration of stars.Comment: 16 pages, 12 figures, submitted to A
Tracing chemical evolution over the extent of the Milky Way's Disk with APOGEE Red Clump Stars
We employ the first two years of data from the near-infrared, high-resolution
SDSS-III/APOGEE spectroscopic survey to investigate the distribution of
metallicity and alpha-element abundances of stars over a large part of the
Milky Way disk. Using a sample of ~10,000 kinematically-unbiased red-clump
stars with ~5% distance accuracy as tracers, the [alpha/Fe] vs. [Fe/H]
distribution of this sample exhibits a bimodality in [alpha/Fe] at intermediate
metallicities, -0.9<[Fe/H]<-0.2, but at higher metallicities ([Fe/H]=+0.2) the
two sequences smoothly merge. We investigate the effects of the APOGEE
selection function and volume filling fraction and find that these have little
qualitative impact on the alpha-element abundance patterns. The described
abundance pattern is found throughout the range 5<R<11 kpc and 0<|Z|<2 kpc
across the Galaxy. The [alpha/Fe] trend of the high-alpha sequence is
surprisingly constant throughout the Galaxy, with little variation from region
to region (~10%). Using simple galactic chemical evolution models we derive an
average star formation efficiency (SFE) in the high-alpha sequence of ~4.5E-10
1/yr, which is quite close to the nearly-constant value found in
molecular-gas-dominated regions of nearby spirals. This result suggests that
the early evolution of the Milky Way disk was characterized by stars that
shared a similar star formation history and were formed in a well-mixed,
turbulent, and molecular-dominated ISM with a gas consumption timescale (1/SFE)
of ~2 Gyr. Finally, while the two alpha-element sequences in the inner Galaxy
can be explained by a single chemical evolutionary track this cannot hold in
the outer Galaxy, requiring instead a mix of two or more populations with
distinct enrichment histories.Comment: 18 pages, 17 figures. Accepted for publication in Ap
Telomere disruption results in non-random formation of de novo dicentric chromosomes involving acrocentric human chromosomes
Copyright: Β© 2010 Stimpson et al.Genome rearrangement often produces chromosomes with two centromeres (dicentrics) that are inherently unstable because of bridge formation and breakage during cell division. However, mammalian dicentrics, and particularly those in humans, can be quite stable, usually because one centromere is functionally silenced. Molecular mechanisms of centromere inactivation are poorly understood since there are few systems to experimentally create dicentric human chromosomes. Here, we describe a human cell culture model that enriches for de novo dicentrics. We demonstrate that transient disruption of human telomere structure non-randomly produces dicentric fusions involving acrocentric chromosomes. The induced dicentrics vary in structure near fusion breakpoints and like naturally-occurring dicentrics, exhibit various inter-centromeric distances. Many functional dicentrics persist for months after formation. Even those with distantly spaced centromeres remain functionally dicentric for 20 cell generations. Other dicentrics within the population reflect centromere inactivation. In some cases, centromere inactivation occurs by an apparently epigenetic mechanism. In other dicentrics, the size of the alpha-satellite DNA array associated with CENP-A is reduced compared to the same array before dicentric formation. Extrachromosomal fragments that contained CENP-A often appear in the same cells as dicentrics. Some of these fragments are derived from the same alpha-satellite DNA array as inactivated centromeres. Our results indicate that dicentric human chromosomes undergo alternative fates after formation. Many retain two active centromeres and are stable through multiple cell divisions. Others undergo centromere inactivation. This event occurs within a broad temporal window and can involve deletion of chromatin that marks the locus as a site for CENP-A maintenance/replenishment.This work was supported by the Tumorzentrum Heidelberg/Mannheim grant (D.10026941)and by March of Dimes Research Foundation grant #1-FY06-377 and NIH R01 GM069514
Influenza, Winter Olympiad, 2002
Prospective surveillance for influenza was performed during the 2002 Salt Lake City Winter Olympics. Oseltamivir was administered to patients with influenzalike illness and confirmed influenza, while their close contacts were given oseltamivir prophylactically. Influenza A/B was diagnosed in 36 of 188 patients, including 13 athletes. Prompt management limited the spread of this outbreak
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Candidate glutamatergic and dopaminergic pathway gene variants do not influence Huntingtonβs disease motor onset
Huntingtonβs disease (HD) is a neurodegenerative disorder characterized by motor, cognitive, and behavioral disturbances. It is caused by the expansion of the HTT CAG repeat, which is the major determinant of age at onset (AO) of motor symptoms. Aberrant function of N-methyl-D-aspartate receptors and/or overexposure to dopamine has been suggested to cause significant neurotoxicity, contributing to HD pathogenesis. We used genetic association analysis in 1,628 HD patients to evaluate candidate polymorphisms in N-methyl-D-aspartate receptor subtype genes (GRIN2A rs4998386 and rs2650427, and GRIN2B rs1806201) and functional polymorphisms in genes in the dopamine pathway (DAT1 3β² UTR 40-bp variable number tandem repeat (VNTR), DRD4 exon 3 48-bp VNTR, DRD2 rs1800497, and COMT rs4608) as potential modifiers of the disease process. None of the seven polymorphisms tested was found to be associated with significant modification of motor AO, either in a dominant or additive model, after adjusting for ancestry. The results of this candidate-genetic study therefore do not provide strong evidence to support a modulatory role for these variations within glutamatergic and dopaminergic genes in the AO of HD motor manifestations
Medication adherence: A call for action
Poor adherence to efficacious cardiovascular related medications has led to considerable morbidity, mortality, and avoidable health care costs. This paper provides results of a recent think tank meeting in which various stakeholder groups representing key experts from consumers, community health providers, the academic community, decision-making government officials (FDA, NIH, etc), and industry scientists met to evaluate the current status of medication adherence and provide recommendations for improving outcomes. Below, we review the magnitude of the problem of medication adherence, prevalence, impact, and cost. We then summarize proven effective approaches and conclude with a discussion of recommendations to address this growing and significant public health issue of medication non adherence
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