206 research outputs found
Postoperative nausea and vomiting following orthognathic surgery
The purpose of this study was to assess the incidence and risk factors associated with postoperative nausea (PON) and vomiting (POV) after orthognathic surgery. A review of the clinical records of consecutively enrolled subjects (2008–2012) at a single academic institution was conducted between 9/2013 and 3/2014. Data on the occurrence of PON and POV and potential patient-related, intraoperative, and postoperative explanatory factors were extracted from the medical records. Logistic models were used for the presence/absence of postoperative nausea and vomiting separately. Data from 204 subjects were analyzed: 63% were female, 72% Caucasian, and the median age was 19 years. Thirty-three percent had a mandibular osteotomy alone, 27% a maxillary osteotomy alone, and 40% had bimaxillary osteotomies. Sixty-seven percent experienced PON and 27% experienced POV. The most important risk factors for PON in this series were female gender, increased intravenous fluids, and the use of nitrous oxide, and for POV were race, additional procedures, and morphine administration. The incidence of PON and POV following orthognathic surgery in the current cohort of patients, after the introduction of the updated 2007 consensus guidelines for the management of postoperative nausea and vomiting, has not decreased substantially from that reported in 2003–2004
Palaeontology, the biogeohistory of Victoria
The broad-scale distribution of fossils within Victoria is controlled by general global patterns in the biological evolution of life on Earth, the local development and environmental evolution of habitats, and the occurrence of geological processes conducive to the preservation of fossil floras and faunas. Early Palaeozoic fossils are mostly marine in origin because of the predominance of marine sedimentary rocks in Victoria and because life on land was not significant during most of this time interval. Middle Palaeozoic sequences have both terrestrial and marine fossil records. Within Victoria, marine rocks are only very minor components of strata deposited during the late Palaeozoic, so that few marine fossils are known from this time period. A similar situation existed during most of the Mesozoic except towards the end of this era when marine conditions began to prevail in the Bass Strait region. During long intervals in the Cainozoic, large areas of Victoria were flooded by shallow-marine seas, particularly in the southern basins of Bass Strait, as well as in the northwest of the State (Murray Basin). Cainozoic sediments contain an extraordinary range of animal and plant fossils. During the Quaternary, the landscape of Victoria became, and continues to be, dominated by continental environments including, at times, extensive freshwater lake systems. Fossil floras and faunas from sediments deposited in these lake systems and from other continental sediments, as well as from Quaternary sediments deposited in marginal marine environments, collectively record a history of rapid fluctuations in climate and sea level.<br /
Quantification of selection bias in studies of risk factors for birth defects among livebirths
Background: Risk factors for birth defects are frequently investigated using data limited to liveborn infants. By conditioning on survival, results of such studies may be distorted by selection bias, also described as “livebirth bias.” However, the implications of livebirth bias on risk estimation remain poorly understood. Objectives: We sought to quantify livebirth bias and to investigate the conditions under which it arose. Methods: We used data on 3994 birth defects cases and 11 829 controls enrolled in the National Birth Defects Prevention Study to compare odds ratio (OR) estimates of the relationship between three established risk factors (antiepileptic drug use, smoking, and multifetal pregnancy) and four birth defects (anencephaly, spina bifida, omphalocele, and cleft palate) when restricted to livebirths as compared to among livebirths, stillbirths, and elective terminations. Exposures and birth defects represented varying strengths of association with livebirth; all controls were liveborn. We performed a quantitative bias analysis to evaluate the sensitivity of our results to excluding terminated and stillborn controls. Results: Cases ranged from 33% liveborn (anencephaly) to 99% (cleft palate). Smoking and multifetal pregnancy were associated with livebirth among anencephaly (crude OR [cOR] 0.61 and cOR 3.15, respectively) and omphalocele cases (cOR 2.22 and cOR 5.22, respectively). For analyses of the association between exposures and birth defects, restricting to livebirths produced negligible differences in estimates except for anencephaly and multifetal pregnancy, which was twofold higher among livebirths (adjusted OR [aOR] 4.93) as among all pregnancy outcomes (aOR 2.44). Within tested scenarios, bias analyses suggested that results were not sensitive to the restriction to liveborn controls. Conclusions: Selection bias was generally limited except for high mortality defects in the context of exposures strongly associated with livebirth. Findings indicate that substantial livebirth bias is unlikely to affect studies of risk factors for most birth defects
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
Search for single top quarks in the tau+jets channel using 4.8 fb of collision data
We present the first direct search for single top quark production using tau
leptons. The search is based on 4.8 fb of integrated luminosity
collected in collisions at =1.96 TeV with the D0 detector
at the Fermilab Tevatron Collider. We select events with a final state
including an isolated tau lepton, missing transverse energy, two or three jets,
one or two of them tagged. We use a multivariate technique to discriminate
signal from background. The number of events observed in data in this final
state is consistent with the signal plus background expectation. We set in the
tau+jets channel an upper limit on the single top quark cross section of
\TauLimObs pb at the 95% C.L. This measurement allows a gain of 4% in expected
sensitivity for the observation of single top production when combining it with
electron+jets and muon+jets channels already published by the D0 collaboration
with 2.3 fb of data. We measure a combined cross section of
\SuperCombineXSall pb, which is the most precise measurement to date.Comment: 12 pages, 5 figure
b-Jet Identification in the D0 Experiment
Algorithms distinguishing jets originating from b quarks from other jet
flavors are important tools in the physics program of the D0 experiment at the
Fermilab Tevatron p-pbar collider. This article describes the methods that have
been used to identify b-quark jets, exploiting in particular the long lifetimes
of b-flavored hadrons, and the calibration of the performance of these
algorithms based on collider data.Comment: submitted to Nuclear Instruments and Methods in Physics Research
Search for pair production of the scalar top quark in the electron-muon final state
We report the result of a search for the pair production of the lightest
supersymmetric partner of the top quark () in
collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron
collider corresponding to an integrated luminosity of 5.4 fb. The scalar
top quarks are assumed to decay into a quark, a charged lepton, and a
scalar neutrino (), and the search is performed in the electron
plus muon final state. No significant excess of events above the standard model
prediction is detected, and improved exclusion limits at the 95% C.L. are set
in the the (,) mass plane
Measurement of the dijet invariant mass cross section in proton anti-proton collisions at sqrt{s} = 1.96 TeV
The inclusive dijet production double differential cross section as a
function of the dijet invariant mass and of the largest absolute rapidity of
the two jets with the largest transverse momentum in an event is measured in
proton anti-proton collisions at sqrt{s} = 1.96 TeV using 0.7 fb^{-1}
integrated luminosity collected with the D0 detector at the Fermilab Tevatron
Collider. The measurement is performed in six rapidity regions up to a maximum
rapidity of 2.4. Next-to-leading order perturbative QCD predictions are found
to be in agreement with the data.Comment: Published in Phys. Lett. B, 693, (2010), 531-538, 8 pages, 2 figures,
6 table
Measurement of Z/gamma*+jet+X angular distributions in ppbar collisions at sqrt{s}=1.96 TeV
We present the first measurements at a hadron collider of differential cross
sections for Z+jet+X production in delta phi(Z, jet), |delta y(Z, jet)| and
|y_boost(Z, jet)|. Vector boson production in association with jets is an
excellent probe of QCD and constitutes the main background to many small cross
section processes, such as associated Higgs production. These measurements are
crucial tests of the predictions of perturbative QCD and current event
generators, which have varied success in describing the data. Using these
measurements as inputs in tuning event generators will increase the
experimental sensitivity to rare signals.Comment: Published in Physics Letters B 682 (2010), pp. 370-380. 15 pages, 6
figure
Search for the standard model Higgs boson in tau final states
We present a search for the standard model Higgs boson using hadronically
decaying tau leptons, in 1 inverse femtobarn of data collected with the D0
detector at the Fermilab Tevatron ppbar collider. We select two final states:
tau plus missing transverse energy and b jets, and tau+ tau- plus jets. These
final states are sensitive to a combination of associated W/Z boson plus Higgs
boson, vector boson fusion and gluon-gluon fusion production processes. The
observed ratio of the combined limit on the Higgs production cross section at
the 95% C.L. to the standard model expectation is 29 for a Higgs boson mass of
115 GeV.Comment: publication versio
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