1,581 research outputs found
Bright Source of Cold Ions for Surface-Electrode Traps
We produce large numbers of low-energy ions by photoionization of
laser-cooled atoms inside a surface-electrode-based Paul trap. The
isotope-selective trap loading rate of Yb ions/s exceeds
that attained by photoionization (electron impact ionization) of an atomic beam
by four (six) orders of magnitude. Traps as shallow as 0.13 eV are easily
loaded with this technique. The ions are confined in the same spatial region as
the laser-cooled atoms, which will allow the experimental investigation of
interactions between cold ions and cold atoms or Bose-Einstein condensates.Comment: Paper submitted to PRL for review on 2/1/0
Symmetry-breaking and chaos in electron transport in semiconductor superlattices
We study the motion of electrons in a single miniband of a semiconductor
superlattice driven by THz electric field polarized along the growth direction.
We work in the semiclassical balance-equation model, including different
elastic and inelastic scattering rates, and incorporating the self-consistent
electric field generated by electron motion. We explore regions of complex
dynamics, which can include chaotic behaviour and symmetry-breaking. We
estimate the magnitudes of dc current and dc voltage that spontaneously appear
in regions of broken-symmetry for parameters characteristic of modern
semiconductor superlattices. This work complements PRL 80(1998)2669 [
cond-mat/9709026 ].Comment: 4 pages, 3 figures, RevTEX, EPS
New Salamanders (Caudata: Plethodontidae) From Guatemala, with Miscellaneous Notes on Known Species
New salamanders in the genera Bolitoglossa and Dendrotriton are described from the highlands of Guatemala. These species are distinguished from their congeners by morphology and molecular differences, including elements of color pattern. These new species of salamanders were collected over the last 30 years, and for many of them the localities of some of these new species are now badly degradedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111063/1/MP200.pd
Clustering in surgical trials : database of intracluster correlations
PMID: 22217216 [PubMed - indexed for MEDLINE] PMCID: PMC3311136 Free PMC ArticlePeer reviewedPublisher PD
Rapid range expansion in the Great Plains narrow-mouthed toad (Gastrophryne olivacea) and a revised taxonomy for North American microhylids
We investigated genetic variation within the Great Plains narrow-mouthed toad, Gastrophryne olivacea, across its geographic range in the United States and Mexico. An analysis of mitochondrial DNA (mtDNA) from 105 frogs revealed remarkably low levels of genetic diversity in individuals inhabiting the central United States and northern Mexico. We found that this widespread matrilineal lineage is divergent (ca. 2% in mtDNA) from haplotypes that originate from the western United States and western coast of Mexico. Using a dataset that included all five species of Gastrophryne and both species of the closely related genus Hypopachus, we investigated the phylogenetic placement of G. olivacea. This analysis recovered strong support that G. olivacea, the tropically distributed G. elegans, and the temperately distributed G. carolinensisconstitute a monophyletic assemblage. However, the placement of G. pictiventris and G. usta render Gastrophryne paraphyletic with respect to Hypopachus. To complement our mitochondrial analysis, we examined a small fragment of nuclear DNA and recovered consistent patterns. In light of our findings we recommend (1) the resurrection of the nomen G. mazatlanensis Taylor (1943) for the disjunct western clade of G. olivaceaand (2) the tentative placement of G. pictiventris and G. usta in Hypopachus. To explore possible scenarios leading to low levels of genetic diversity in G. olivacea, we used mismatch distributions and Bayesian Skyline plots to examine historic population expansion and demography. Collectively these analyses suggest that G. olivacea rapidly expanded in effective population size and geographic range during the late Pleistocene or early Holocene. This hypothesis is consistent with fossil data from northern localities and contemporary observations that suggest ongoing northern expansion. Given our findings, we suspect that the rapid range expansion of G. olivacea may have been facilitated by ecological associations with open habitats and seasonal water bodies
Spacetime Supersymmetry in a nontrivial NS-NS Superstring Background
In this paper we consider superstring propagation in a nontrivial NS-NS
background. We deform the world sheet stress tensor and supercurrent with an
infinitesimal B_{\mu\nu} field. We construct the gauge-covariant super-Poincare
generators in this background and show that the B_{\mu\nu} field spontaneously
breaks spacetime supersymmetry. We find that the gauge-covariant spacetime
momenta cease to commute with each other and with the spacetime supercharges.
We construct a set of "magnetic" super-Poincare generators that are conserved
for constant field strength H_{\mu\nu\lambda}, and show that these generators
obey a "magnetic" extension of the ordinary supersymmetry algebra.Comment: 13 pages, Latex. Published versio
CRISPR Knockout of the HuR Gene Causes a Xenograft Lethal Phenotype.
Pancreatic ductal adenocarcinoma (PDA) is the third leading cause of cancer-related deaths in the United States, whereas colorectal cancer is the third most common cancer. The RNA-binding protein HuR (ELAVL1) supports a pro-oncogenic network in gastrointestinal (GI) cancer cells through enhanced HuR expression. Using a publically available database, HuR expression levels were determined to be increased in primary PDA and colorectal cancer tumor cohorts as compared with normal pancreas and colon tissues, respectively. CRISPR/Cas9 technology was successfully used to delete the HuR gene in both PDA (MIA PaCa-2 and Hs 766T) and colorectal cancer (HCT116) cell lines. HuR deficiency has a mild phenotype
A case-controlled study of relativesâ complaints concerning patients who died in hospital: the role of treatment escalation / limitation planning
Objectives
To independently assess quality of care among patients who died in hospital and whose next-of-kin submitted a letter of complaint and make comparisons with matched controls. To identify whether use of a treatment escalation limitation plan (TELP) during the terminal illness was a relevant background factor.
Design
The study was an investigator-blinded retrospective case-note review of 42 complaints cases and 72 controls matched for age, sex, ward location and time of death.
Setting
The acute medical and surgical wards of three District General Hospitals administered by NHS Lanarkshire, Scotland.
Participants
None.
Intervention
None.
Outcome measures
Quality of care: Clinical âproblemsâ, non-beneficial interventions (NBIs) and harms were evaluated using the Structured Judgment Review Method. Complaints were categorized using the Healthcare Complaints Analysis Tool.
Results
The event frequencies and rate ratios for clinical âproblemsâ, NBIs and harms were consistently higher in complaint cases compared to controls. The difference was only significant for NBIs (P = 0.05). TELPs were used less frequently in complaint cases compared to controls (23.8 versus 47.2%, P = 0.013). The relationship between TELP use and the three key clinical outcomes was nonsignificant.
Conclusions
Care delivered to patients at end-of-life whose next-of-kin submitted a complaint was poorer overall than among control patients when assessed independently by blinded reviewers. Regular use of a TELP in acute clinical settings has the potential to influence complaints relating to end-of-life care, but this requires further prospective study
Targeting the Endothelin A Receptor in IgA Nephropathy
Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide and carries a substantial risk of kidney failure. New agency-approved therapies, either specifically for IgAN or for chronic kidney disease (CKD) in general, hold out hope for mitigating renal deterioration in patients with IgAN. The latest addition to this therapeutic armamentarium targets the endothelin-A receptor (ETAR). Activation of ETAR on multiple renal cell types elicits a host of pathophysiological effects, including vasoconstriction, cell proliferation, inflammation, apoptosis, and fibrosis. Blockade of ETAR is renoprotective in experimental models of IgAN and reduces proteinuria in patients with IgAN. This review discusses the evidence supporting the use of ETAR blockade in IgAN as well as addressing the potential role for this class of agents among the current and emerging therapies for treating this disorder.</p
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