7,019 research outputs found
Parton distribution function dependence of benchmark Standard Model total cross sections at the 7 TeV LHC
We compare predictions for the W, Z, gg->H and t-tbar total cross sections at
the Large Hadron Collider (LHC), for a centre-of-mass energy of 7 TeV, using
the most recent publicly available next-to-leading order and
next-to-next-to-leading order parton distribution functions (PDFs) from all PDF
fitting groups. In particular, we focus on the dependence on the different
values of the strong coupling, alpha_S(M_Z^2), used by each group. We also
perform a comparison of the relevant quark-antiquark and gluon-gluon luminosity
functions. We make some comments on the recent PDF4LHC recommendations.
Finally, we discuss the comparison of data and theory for W and Z cross
sections at the LHC.Comment: 40 pages, 18 figures. v2: version published in JHE
Distribution of GPs in Scotland by age, gender and deprivation
General practice in the UK is widely reported to be in crisis, with particular concerns about recruitment and retention of family doctors. This study assessed the distribution of GPs in Scotland by age, gender and deprivation, using routinely available data. We found that there are more GPs (and fewer patients per GP) in the least deprived deciles than there are in the most deprived deciles. Furthermore, there are a higher proportion of older GPs in the most deprived deciles. There are also important gender differences in the distribution of GPs. We discuss the implications of these findings for policymakers and practitioners
Study of Monte Carlo approach to experimental uncertainty propagation with MSTW 2008 PDFs
We investigate the Monte Carlo approach to propagation of experimental
uncertainties within the context of the established "MSTW 2008" global analysis
of parton distribution functions (PDFs) of the proton at next-to-leading order
in the strong coupling. We show that the Monte Carlo approach using replicas of
the original data gives PDF uncertainties in good agreement with the usual
Hessian approach using the standard Delta(chi^2) = 1 criterion, then we explore
potential parameterisation bias by increasing the number of free parameters,
concluding that any parameterisation bias is likely to be small, with the
exception of the valence-quark distributions at low momentum fractions x. We
motivate the need for a larger tolerance, Delta(chi^2) > 1, by making fits to
restricted data sets and idealised consistent or inconsistent pseudodata.
Instead of using data replicas, we alternatively produce PDF sets randomly
distributed according to the covariance matrix of fit parameters including
appropriate tolerance values, then we demonstrate a simpler method to produce
an arbitrary number of random predictions on-the-fly from the existing
eigenvector PDF sets. Finally, as a simple example application, we use Bayesian
reweighting to study the effect of recent LHC data on the lepton charge
asymmetry from W boson decays.Comment: 37 pages, 17 figures. v2: version published in JHEP. Supplementary
material at http://mstwpdf.hepforge.org/random
Life science experiments during parabolic flight: The McGill experience
Over the past twelve years, members of the Aerospace Medical Research Unit of McGill University have carried out a wide variety of tests and experiments in the weightless condition created by parabolic flight. This paper discusses the pros and cons of that environment for the life scientist, and uses examples from the McGill program of the types of activities which can be carried out in a transport aircraft such as the NASA KC-135
Unintegrated parton distributions and electroweak boson production at hadron colliders
We describe the use of doubly-unintegrated parton distributions in
hadron-hadron collisions, using the (z,k_t)-factorisation prescription where
the transverse momentum of the incoming parton is generated in the last
evolution step. We apply this formalism to calculate the transverse momentum
(P_T) distributions of produced W and Z bosons and compare the predictions to
Tevatron Run 1 data. We find that the observed P_T distributions can be
generated almost entirely by the leading order q_1 q_2 -> W,Z subprocesses,
using known and universal doubly-unintegrated quark distributions. We also
calculate the P_T distribution of the Standard Model Higgs boson at the LHC,
where the dominant production mechanism is by gluon-gluon fusion.Comment: 20 pages, 8 figures. Version to appear in Phys. Rev. D; correction to
Higgs P_T distribution made in Erratu
Treatment needs and skill mix workforce requirements for prosthodontic care: a comparison of estimates using normative and sociodental approaches.
The traditional measure for assessing dental treatment needs and workforce requirements based solely on normative need (NN) has major shortcomings. The sociodental approach (SDA) to assess needs overcomes some of the shortcomings as it combines normative and subjective needs assessments and also incorporates behavioural propensity (Sheiham and Tsakos 2007). The objective of this study was to estimate and compare prosthodontic treatment needs and workforce requirements, using the normative and the sociodental approaches for different skill mix models
Treatment needs and skill mix workforce requirements for prosthodontic care: a comparison of estimates using normative and sociodental approaches.
The traditional measure for assessing dental treatment needs and workforce requirements based solely on normative need (NN) has major shortcomings. The sociodental approach (SDA) to assess needs overcomes some of the shortcomings as it combines normative and subjective needs assessments and also incorporates behavioural propensity (Sheiham and Tsakos 2007). The objective of this study was to estimate and compare prosthodontic treatment needs and workforce requirements, using the normative and the sociodental approaches for different skill mix models
Enhanced recovery after surgery
Enhanced Recovery or Fast Track Recovery after Surgery protocols (ERAS) have significantly changed perioperative care following colorectal surgery and are promoted as reducing the stress response to surgery.
The present systematic review aimed to examine the impact on the magnitude of the systemic inflammatory response (SIR) for each ERAS component following colorectal surgery using objective markers such as C-reactive protein (CRP) and interleukin-6 (IL-6).
A literature search was performed of the US National Library of Medicine (MEDLINE), EMBASE, PubMed, and the Cochrane Database of Systematic Reviews using appropriate keywords and subject headings to February 2015.
Included studies had to assess the impact of the selected ERAS component on the SIR using either CRP or IL-6.
Nineteen studies, including 1898 patients, were included. Fourteen studies (1246 patients) examined the impact of laparoscopic surgery on the postoperative markers of SIR. Ten of these studies (1040 patients) reported that laparoscopic surgery reduced postoperative CRP. One study (53 patients) reported reduced postoperative CRP using opioid-minimising analgesia. One study (142 patients) reported no change in postoperative CRP following preoperative carbohydrate loading. Two studies (108 patients) reported conflicting results with respect to the impact of goal-directed fluid therapy on postoperative IL-6. No studies examined the effect of other ERAS components, including mechanical bowel preparation, antibiotic prophylaxis, thromboprophylaxis, and avoidance of nasogastric tubes and peritoneal drains on markers of the postoperative SIR following colorectal surgery.
The present systematic review shows that, with the exception of laparoscopic surgery, objective evidence of the effect of individual components of ERAS protocols in reducing the stress response following colorectal surgery is limited
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CCH <i>N</i> = 4-3 emission from dense interstellar clouds
The authors have searched for N = 4 - 3 rotational line emission from the ethynyl radical CCH, at 349 GHz toward a number of galactic molecular clouds. They have detected emission from ten giant molecular clouds and have derived CCH column densities on the order of 1014 - 1015cm-2. They find that CCH emission arises from dense gas, n(H2) ~ 104 - 105cm-3, but not from very dense material, n(H2) > 106cm-3, nor from hot gas such as the "hot core" region in Orion
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