539 research outputs found
Sensitive Observations of Radio Recombination Lines in Orion and W51: The Data and Detection of Systematic Recombination Line Blueshifts Proportional to Impact Broadening
Sensitive spectral observations made in two frequency bands near 6.0 and 17.6
GHz are described for Orion and W51. Using frequency switching we were able to
achieve a dynamic range in excess of 10,000 without fitting sinusoidal or
polynomial baselines. This enabled us to detect lines as weak as T\Delta n$ as
high as 25 have been detected in Orion. In the Orion data, where the lines are
stronger, we have also detected a systematic shift in the line center
frequencies proportional to linewidth that cannot be explained by normal
optical depth effects.Comment: 22 pages, 13 figures. Accepted for publication in Astrophysics and
Space Scienc
Epidemiology and outcomes of Clostridium difficile infection in allogeneic hematopoietic cell and lung transplant recipients
BackgroundClostridium difficile infection (CDI) is a common complication of lung and allogeneic hematopoietic cell (HCT) transplant, but the epidemiology and outcomes of CDI after transplant are poorly described.MethodsWe performed a prospective, multicenter study of CDI within 365 days post‐allogeneic HCT or lung transplantation. Data were collected via patient interviews and medical chart review. Participants were followed weekly in the 12 weeks post‐transplant and while hospitalized and contacted monthly up to 18 months post‐transplantation.ResultsSix sites participated in the study with 614 total participants; 4 enrolled allogeneic HCT (385 participants) and 5 enrolled lung transplant recipients (229 participants). One hundred and fifty CDI cases occurred within 1 year of transplantation; the incidence among lung transplant recipients was 13.1% and among allogeneic HCTs was 31.2%. Median time to CDI was significantly shorter among allogeneic HCT than lung transplant recipients (27 days vs 90 days; P = .037). CDI was associated with significantly higher mortality from 31 to 180 days post‐index date among the allogeneic HCT recipients (Hazard ratio [HR] = 1.80; P = .007). There was a trend towards increased mortality among lung transplant recipients from 120 to 180 days post‐index date (HR = 4.7, P = .09).ConclusionsThe epidemiology and outcomes of CDI vary by transplant population; surveillance for CDI should continue beyond the immediate post‐transplant period.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143790/1/tid12855_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/143790/2/tid12855.pd
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Transpacific Transport of Ozone Pollution and the Effect of Recent Asian Emission Increases on Air Quality in North America: An Integrated Analysis Using Satellite, Aircraft, Ozonesonde, and Surface Observations
We use an ensemble of aircraft, satellite, sonde, and surface observations for April–May 2006 (NASA/INTEX-B aircraft campaign) to better understand the mechanisms for transpacific ozone pollution and its implications for North American air quality. The observations are interpreted with a global 3-D chemical transport model (GEOS-Chem). OMI NO2 satellite observations constrain Asian anthropogenic NOx emissions and indicate a factor of 2 increase from 2000 to 2006 in China. Satellite observations of CO from AIRS and TES indicate two major events of Asian transpacific pollution during INTEX-B. Correlation between TES CO and ozone observations shows evidence for transpacific ozone pollution. The semi-permanent Pacific High and Aleutian Low cause splitting of transpacific pollution plumes over the Northeast Pacific. The northern branch circulates around the Aleutian Low and has little impact on North America. The southern branch circulates around the Pacific High and some of that air impacts western North America. Both aircraft measurements and model results show sustained ozone production driven by peroxyacetylnitrate (PAN) decomposition in the southern branch, roughly doubling the transpacific influence from ozone produced in the Asian boundary layer. Model simulation of ozone observations at Mt. Bachelor Observatory in Oregon (2.7 km altitude) indicates a mean Asian ozone pollution contribution of 9±3 ppbv to the mean observed concentration of 54 ppbv, reflecting mostly an enhancement in background ozone rather than episodic Asian plumes. Asian pollution enhanced surface ozone concentrations by 5–7 ppbv over western North America in spring 2006. The 2000–2006 rise in Asian anthropogenic emissions increased this influence by 1–2 ppbv.Earth and Planetary SciencesEngineering and Applied Science
Using microphone arrays to investigate microhabitat selection by declining breeding birds
Understanding the microhabitat preferences of animals can help managers to develop better conservation and recovery strategies but this is challenging. Traditional methods are limited by cost, accuracy and human resources. In this study, we investigated avian microhabitat preferences using microphone arrays that are capable of accurately locating vocalizing birds. Our objective was to identify the microhabitat associations of two common species in steep population decline, the Boreal Chickadee Poecile hudsonicus and the Cape May Warbler Setophaga tigrina. We deployed 68 eight‐channel arrays at random locations in Labrador, Canada, during the 2016 avian breeding season. We returned in 2017 to the 18 array locations where the target species had been detected the previous year and characterized the microhabitat at the exact locations where they had been detected. We also characterized the microhabitat at randomly determined control locations. Results show that Boreal Chickadees select trees with greater diameter‐at‐breast‐height that are surrounded by greater stem density. We did not find evidence that Cape May Warblers exhibit microhabitat selection during song production. The study shows that microphone arrays are an effective tool for identifying preferred microhabitat that could be incorporated into future conservation or recovery strategies
Leptonic and Semileptonic Decays of Charm and Bottom Hadrons
We review the experimental measurements and theoretical descriptions of
leptonic and semileptonic decays of particles containing a single heavy quark,
either charm or bottom. Measurements of bottom semileptonic decays are used to
determine the magnitudes of two fundamental parameters of the standard model,
the Cabibbo-Kobayashi-Maskawa matrix elements and . These
parameters are connected with the physics of quark flavor and mass, and they
have important implications for the breakdown of CP symmetry. To extract
precise values of and from measurements, however,
requires a good understanding of the decay dynamics. Measurements of both charm
and bottom decay distributions provide information on the interactions
governing these processes. The underlying weak transition in each case is
relatively simple, but the strong interactions that bind the quarks into
hadrons introduce complications. We also discuss new theoretical approaches,
especially heavy-quark effective theory and lattice QCD, which are providing
insights and predictions now being tested by experiment. An international
effort at many laboratories will rapidly advance knowledge of this physics
during the next decade.Comment: This review article will be published in Reviews of Modern Physics in
the fall, 1995. This file contains only the abstract and the table of
contents. The full 168-page document including 47 figures is available at
http://charm.physics.ucsb.edu/papers/slrevtex.p
Measurement of the B-Meson Inclusive Semileptonic Branching Fraction and Electron-Energy Moments
We report a new measurement of the B-meson semileptonic decay momentum
spectrum that has been made with a sample of 9.4/fb of electron-positron
annihilation data collected with the CLEO II detector at the Y(4S) resonance.
Electrons from primary semileptonic decays and secondary charm decays were
separated by using charge and angular correlations in Y(4S) events with a
high-momentum lepton and an additional electron. We determined the semileptonic
branching fraction to be (10.91 +- 0.09 +- 0.24)% from the normalization of the
electron-energy spectrum. We also measured the moments of the electron energy
spectrum with minimum energies from 0.6 GeV to 1.5 GeV.Comment: 36 pages postscript, als available through
http://w4.lns.cornell.edu/public/CLNS/, Submitted to PRD (back-to-back with
preceding preprint hep-ex/0403052
Enhanced GII.4 human norovirus infection in gnotobiotic pigs transplanted with a human gut microbiota
The role of commensal microbiota in enteric viral infections has been explored extensively, but the interaction between human gut microbiota (HGM) and human norovirus (HuNoV) is poorly understood. In this study, we established an HGM-Transplanted gnotobiotic (Gn) pig model of HuNoV infection and disease, using an infant stool as HGM transplant and a HuNoV GII.4/2006b strain for virus inoculation. Compared to germ-free Gn pigs, HuNoV inoculation in HGMT Gn pigs resulted in increased HuNoV shedding, characterized by significantly higher shedding titres on post inoculation day (PID) 3, 4, 6, 8 and 9, and significantly longer mean duration of virus shedding. In addition, virus titres were significantly higher in duodenum and distal ileum of HGMT Gn pigs on PID10, while comparable and transient HuNoV viremia was detected in both groups. 16S rRNA gene sequencing demonstrated that HuNoV infection dramatically altered intestinal microbiota in HGMT Gn pigs at the phylum (Proteobacteria, Firmicutes and Bacteroidetes) and genus (Enterococcus, Bifidobacterium, Clostridium, Ruminococcus, Anaerococcus, Bacteroides and Lactobacillus) levels. In summary, enhanced GII.4 HuNoV infection was observed in the presence of HGM, and host microbiota was susceptible to disruption upon HuNoV infection
Study of the B^0 Semileptonic Decay Spectrum at the Upsilon(4S) Resonance
We have made a first measurement of the lepton momentum spectrum in a sample
of events enriched in neutral B's through a partial reconstruction of B0 -->
D*- l+ nu. This spectrum, measured with 2.38 fb**-1 of data collected at the
Upsilon(4S) resonance by the CLEO II detector, is compared directly to the
inclusive lepton spectrum from all Upsilon(4S) events in the same data set.
These two spectra are consistent with having the same shape above 1.5 GeV/c.
From the two spectra and two other CLEO measurements, we obtain the B0 and B+
semileptonic branching fractions, b0 and b+, their ratio, and the production
ratio f+-/f00 of B+ and B0 pairs at the Upsilon(4S). We report b+/b0=0.950
(+0.117-0.080) +- 0.091, b0 = (10.78 +- 0.60 +- 0.69)%, and b+ = (10.25 +- 0.57
+- 0.65)%. b+/b0 is equivalent to the ratio of charged to neutral B lifetimes,
tau+/tau0.Comment: 14 page, postscript file also available at
http://w4.lns.cornell.edu/public/CLN
Measurement of the Mass Splittings between the States
We present new measurements of photon energies and branching fractions for
the radiative transitions: Upsilon(2S)->gamma+chi_b(J=0,1,2). The masses of the
chi_b states are determined from the measured radiative photon energies. The
ratio of mass splittings between the chi_b substates,
r==(M[J=2]-M[J=1])/(M[J=1]-M[J=0]) with M the chi_b mass, provides information
on the nature of the bbbar confining potential. We find
r(1P)=0.54+/-0.02+/-0.02. This value is in conflict with the previous world
average, but more consistent with the theoretical expectation that r(1P)<r(2P);
i.e., that this mass splittings ratio is smaller for the chi_b(1P) triplet than
for the chi_b(2P) triplet.Comment: 11 page postscript file, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
Radiative Decay Modes of the Meson
Using data recorded by the CLEO-II detector at CESR we have searched for four
radiative decay modes of the meson: ,
, , and . We
obtain 90% CL upper limits on the branching ratios of these modes of , , and
respectively.Comment: 15 page postscript file, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
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