44,822 research outputs found
Look right! A retrospective study of pedestrian accidents involving overseas visitors to London
Introduction: Research within the European Union has shown international visitors to have a higher injury mortality than residents. Traffic accidents are the leading cause of injury-related death among overseas visitors and evidence suggests overseas visitors are at a greater risk of being involved in road traffic accidents than the resident population. Little information looks specifically at pedestrian injuries to overseas visitors. Pedestrian deaths account for 21% of all UK road deaths.
Methods: A retrospective database review of London helicopter emergency medical service (HEMS) missions was undertaken to examine the number and type of missions to overseas visitors, specifically examining pedestrian incidents.
Results: Of 121 missions to overseas visitors, 74 (61%) involved the visitor as a pedestrian struck by a vehicle. Thirty-five pedestrians (47%) were struck by a bus and 20 by a car (27%). Fourteen patients (19%) had an initial Glasgow coma scale score of 3–8, suggesting severe head injury and half of all patients required prehospital intubation (38/74, 51%). Mortality was 16% (12/74%) and 62 patients (84%) survived to hospital discharge. Of 39 patients admitted to the Royal London Hospital, the average injury severity score (ISS%) was 23.0 (ISS >15 denotes severe trauma) with a mean inpatient stay of 17.9 days.
Conclusion: During the 7-year period studied, 61% of HEMS missions to overseas visitors involved a pedestrian being struck by a vehicle, compared with 16% of missions to UK residents. For HEMS missions, serious trauma to pedestrians is disproportionally more common among the visitor population to London
Quarkonium spin structure in lattice NRQCD
Numerical simulations of the quarkonium spin splittings are done in the
framework of lattice nonrelativistic quantum chromodynamics (NRQCD). At leading
order in the velocity expansion the spin splittings are of , where
is the renormalized quark mass and is the mean squared quark
velocity. A systematic analysis is done of all next-to-leading order
corrections. This includes the addition of relativistic
interactions, and the removal of discretization errors in the
leading-order interactions. Simulations are done for both S- and P-wave mesons,
with a variety of heavy quark actions and over a wide range of lattice
spacings. Two prescriptions for the tadpole improvement of the action are also
studied in detail: one using the measured value of the average plaquette, the
other using the mean link measured in Landau gauge. Next-to-leading order
interactions result in a very large reduction in the charmonium splittings,
down by about 60% from their values at leading order. There are further
indications that the velocity expansion may be poorly convergent for
charmonium. Prelimary results show a small correction to the hyperfine
splitting in the Upsilon system.Comment: 16 pages, REVTEX v3.1, 5 postscript figures include
Tadpole renormalization and relativistic corrections in lattice NRQCD
We make a comparison of two tadpole renormalization schemes in the context of
the quarkonium hyperfine splittings in lattice NRQCD. Improved gauge-field and
NRQCD actions are analyzed using the mean-link in Landau gauge, and
using the fourth root of the average plaquette . Simulations are done
for , , and systems. The hyperfine splittings are
computed both at leading and at next-to-leading order in the relativistic
expansion. Results are obtained at lattice spacings in the range of about
0.14~fm to 0.38~fm. A number of features emerge, all of which favor tadpole
renormalization using . This includes much better scaling behavior of
the hyperfine splittings in the three quarkonium systems when is
used. We also find that relativistic corrections to the spin splittings are
smaller when is used, particularly for the and
systems. We also see signs of a breakdown in the NRQCD expansion when the bare
quark mass falls below about one in lattice units. Simulations with
also appear to be better behaved in this context: the bare quark masses turn
out to be larger when is used, compared to when is used on
lattices with comparable spacings. These results also demonstrate the need to
go beyond tree-level tadpole improvement for precision simulations.Comment: 14 pages, 7 figures (minor changes to some phraseology and
references
D to K and D to pi semileptonic form factors from Lattice QCD
We present a very high statistics study of D and D_s semileptonic decay form
factors on the lattice. We work with MILC N_f=2+1 lattices and use the Highly
Improved Staggered Quark action (HISQ) for both the charm and the strange and
light valence quarks. We use both scalar and vector currents to determine the
form factors f_0(q^2) and f_+(q^2) for a range of D and D_s semileptonic
decays, including D to pi and D to K. By using a phased boundary condition we
are able to tune accurately to q^2=0 and explore the whole q^2 range allowed by
kinematics. We can thus compare the shape in q^2 to that from experiment and
extract the CKM matrix element |V_cs|. We show that the form factors are
insensitive to the spectator quark: D to K and D_s to eta_s form factors are
essentially the same, which is also true for D to pi and D_s to K within 5%.
This has important implications when considering the corresponding B/B_s
processes.Comment: To appear in the proceedings of The 5th International Workshop on
Charm Physics (Charm 2012
V_cs from D_s to {\phi}l{\nu} semileptonic decay and full lattice QCD
We determine the complete set of axial and vector form factors for the Ds to
{\phi}l{\nu} decay from full lattice QCD for the first time. The valence quarks
are implemented using the Highly Improved Staggered Quark action and we
normalise the appropriate axial and vector currents fully nonperturbatively.
The q^2 and angular distributions we obtain for the differential rate agree
well with those from the BaBar experiment and, from the total branching
fraction, we obtain Vcs = 1.017(63), in good agreement with that from D to
Kl{\nu} semileptonic decay. We also find the mass and decay constant of the
{\phi} meson in good agreement with experiment, showing that its decay to
K{\bar{K}} (which we do not include here) has at most a small effect. We
include an Appendix on nonperturbative renormalisation of the complete set of
staggered vector and axial vector bilinears needed for this calculation.Comment: 19 pages, 13 figure
Precision Charmonium Spectroscopy From Lattice QCD
We present results for Charmonium spectroscopy using Non-Relativistic QCD
(NRQCD). For the NRQCD action the leading order spin-dependent and next to
leading order spin-independent interactions have been included with
tadpole-improved coefficients. We use multi-exponential fits to multiple
correlation functions to extract ground and excited states. Splittings
between the lowest , and states are given and we have accurate
values for the state hyperfine splitting and the fine structure.
Agreement with experiment is good - the remaining systematic errors are
discussed.Comment: 23 pages uuencoded latex file. Contains figures in late
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