8,248 research outputs found
Stability of rotating states in a weakly-interacting Bose-Einstein condensate
We investigate the lowest state of a rotating, weakly-interacting
Bose-Einstein condensate trapped in a harmonic confining potential that is
driven by an infinitesimally asymmetric perturbation. Although in an
axially-symmetric confining potential the gas has an axially-symmetric
single-particle density distribution, we show that in the presence of the small
asymmetric perturbation its lowest state is the one given by the mean-field
approximation, which is a broken-symmetric state. We also estimate the rate of
relaxation of angular momentum when the gas is no longer driven by the
asymmetric perturbation and identify two regimes of "slow" and "fast"
relaxation. States of certain symmetry are found to be more robust.Comment: 6 pages, RevTe
Dimensions of Community Change: How the Community of Sudbury Responded to Industrial Exposures and Cleaned up its Environment
A city in northern Ontario, which has suffered more than a century of pollution from mining, went from being internationally notorious for its pollution to winning awards for its environmental restoration. The inquiry was into the levers of change that led from an awareness of environmental destruction to taking action. Semi-structured interviews were conducted with 60 people from the community, politicians, industry, miners, and academics. The theory-based analysis led to a community-change model that has helped identify the multiple layers of change required for the re-greening of the environment. With reference to the collective impact literature, this city-level case study found that the city has embraced change based upon agreement on an emerging vision, taking advantage of a confluence of timing and events, adopting evidence-based knowledge, building a sense of pride and place, and having a diffuse yet linked leadership. The Sudbury story is helpful for other industrial communities looking to achieve change
Immediate effects of diamond burr debridement in patients with spontaneous chronic corneal epithelial defects, light and electron microscopic evaluation
Analytical results for a trapped, weakly-interacting Bose-Einstein condensate under rotation
We examine the problem of a repulsive, weakly-interacting and harmonically
trapped Bose-Einstein condensate under rotation. We derive a simple analytic
expression for the energy incorporating the interactions when the angular
momentum per particle is between zero and one and find that the interaction
energy decreases linearly as a function of the angular momentum in agreement
with previous numerical and limiting analytical studies.Comment: 3 pages, RevTe
Weakly Interacting Bose-Einstein Condensates Under Rotation: Mean-field versus Exact Solutions
We consider a weakly-interacting, harmonically-trapped Bose-Einstein
condensed gas under rotation and investigate the connection between the
energies obtained from mean-field calculations and from exact diagonalizations
in a subspace of degenerate states. From the latter we derive an approximation
scheme valid in the thermodynamic limit of many particles. Mean-field results
are shown to emerge as the correct leading-order approximation to exact
calculations in the same subspace.Comment: 4 pages, RevTex, submitted to PR
Ovalbumin sensitization and challenge increases the number of lung cells possessing a mesenchymal stromal cell phenotype
Abstract Background Recent studies have indicated the presence of multipotent mesenchymal stromal cells (MSCs) in human lung diseases. Excess airway smooth muscle, myofibroblasts and activated fibroblasts have each been noted in asthma, suggesting that mesenchymal progenitor cells play a role in asthma pathogenesis. We therefore sought to determine whether MSCs are present in the lungs of ovalbumin (OVA)-sensitized and challenged mice, a model of allergic airways disease. Methods Balb/c mice were sensitized and challenged with PBS or OVA over a 25 day period. Flow cytometry as well as colony forming and differentiation potential were used to analyze the emergence of MSCs along with gene expression studies using immunochemical analyses, quantitative polymerase chain reaction (qPCR), and gene expression beadchips. Results A CD45-negative subset of cells expressed Stro-1, Sca-1, CD73 and CD105. Selection for these markers and negative selection against CD45 yielded a population of cells capable of adipogenic, osteogenic and chondrogenic differentiation. Lungs from OVA-treated mice demonstrated a greater average colony forming unit-fibroblast (CFU-F) than control mice. Sorted cells differed from unsorted lung adherent cells, exhibiting a pattern of gene expression nearly identical to bone marrow-derived sorted cells. Finally, cells isolated from the bronchoalveolar lavage of a human asthma patient showed identical patterns of cell surface markers and differentiation potential. Conclusions In summary, allergen sensitization and challenge is accompanied by an increase of MSCs resident in the lungs that may regulate inflammatory and fibrotic responses.http://deepblue.lib.umich.edu/bitstream/2027.42/78265/1/1465-9921-11-127.xmlhttp://deepblue.lib.umich.edu/bitstream/2027.42/78265/2/1465-9921-11-127.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78265/3/1465-9921-11-127-S1.DOCPeer Reviewe
Health Risk of Obesity in Native American Adolescents
Recent reports demonstrate the need to improve methods for identifying obesity among adolescent minority populations, especially among Native American adolescents. Our study examined several anthropometric measures to see which one was the best indicator of obesity for Native American adolescents. We compared our data with that provided by the Centers for Disease Control and Prevention (CDC), and the National Health and Nutrition Examination Surveys (NHANESIII). We examined which measures diï¬ered signiï¬cantly from the NHANESIII, and which were most eï¬ective for measuring obesity in Native American adolescents. Our study population represented a cross-sectional, epidemiological population (N=183) of Native American students (ages 14-18) from diverse tribal backgrounds at an urban residential high school. We obtained baseline anthropometric measurements of height, weight, waist, triceps skin-fold, and calf skin-fold measures from the Native American students and compared this information with reference data to assess weight classiï¬cation by body mass indices for our population. Under the conditions of our study, we found the calf skin-fold measure to be the best indicator of normal weight in male Native American adolescents, and the triceps skin-fold measure to be the best indicator of obesity in male Native American adolescents. The assessment of health risk by anthropometric measures we obtained appears appropriate for predicting obesity and developing eï¬ective interventions for Native American adolescents in general. Correlations between anthropometric measures and obesity in our study population may prove of signiï¬cant interest for monitoring obesity prevention initiatives for Native American adolescents
Vortex stabilization in a small rotating asymmetric Bose-Einstein condensate
We use a variational method to investigate the ground-state phase diagram of
a small, asymmetric Bose-Einstein condensate with respect to the dimensionless
interparticle interaction strength and the applied external rotation
speed . For a given , the transition lines between no-vortex
and vortex states are shifted toward higher relative to those for the
symmetric case. We also find a re-entrant behavior, where the number of vortex
cores can decrease for large . In addition, stabilizing a vortex in a
rotating asymmetric trap requires a minimum interaction strength. For a given
asymmetry, the evolution of the variational parameters with increasing
shows two different types of transitions (sharp or continuous), depending on
the strength of the interaction. We also investigate transitions to states with
higher vorticity; the corresponding angular momentum increases continuously as
a function of
Species delimitation in lemurs: multiple genetic loci reveal low levels of species diversity in the genus Cheirogaleus
<p>Abstract</p> <p>Background</p> <p>Species are viewed as the fundamental unit in most subdisciplines of biology. To conservationists this unit represents the currency for global biodiversity assessments. Even though Madagascar belongs to one of the top eight biodiversity hotspots of the world, the taxonomy of its charismatic lemuriform primates is not stable. Within the last 25 years, the number of described lemur species has more than doubled, with many newly described species identified among the nocturnal and small-bodied cheirogaleids. Here, we characterize the diversity of the dwarf lemurs (genus <it>Cheirogaleus</it>) and assess the status of the seven described species, based on phylogenetic and population genetic analysis of mtDNA (<it>cytb </it>+ <it>cox2</it>) and three nuclear markers (<it>adora3</it>, <it>fiba </it>and <it>vWF</it>).</p> <p>Results</p> <p>This study identified three distinct evolutionary lineages within the genus <it>Cheirogaleus</it>. Population genetic cluster analyses revealed a further layer of population divergence with six distinct genotypic clusters.</p> <p>Conclusion</p> <p>Based on the general metapopulation lineage concept and multiple concordant data sets, we identify three exclusive groups of dwarf lemur populations that correspond to three of the seven named species: <it>C. major</it>, <it>C. medius </it>and <it>C. crossleyi</it>. These three species were found to be genealogically exclusive in both mtDNA and nDNA loci and are morphologically distinguishable. The molecular and morphometric data indicate that <it>C. adipicaudatus </it>and <it>C. ravus </it>are synonymous with <it>C. medius </it>and <it>C. major</it>, respectively. <it>Cheirogaleus sibreei </it>falls into the <it>C. medius </it>mtDNA clade, but in morphological analyses the membership is not clearly resolved. We do not have sufficient data to assess the status of <it>C. minusculus</it>. Although additional patterns of population differentiation are evident, there are no clear subdivisions that would warrant additional specific status. We propose that ecological and more geographic data should be collected to confirm these results.</p
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