279 research outputs found
Spin in the path integral: anti-commuting versus commuting variables
We discuss the equivalence between the path integral representations of spin
dynamics for anti-commuting (Grassmann) and commuting variables and establish a
bosonization dictionary for both generators of spin and single fermion
operators. The content of this construction in terms of the representations of
the spin algebra is discussed in the path integral setting. Finally it is shown
how a `free field realization' (Dyson mapping) can be constructed in the path
integral.Comment: 9 pages, Late
On the Determination of and from Hadronic Two Body Decays
{}From Class I decays : B^o \ra \pi^+ ( \rho^+ ) + D^- ( {D^*}^- ), we
determine , and from Class III decays : B^+ \ra \pi^+ ( \rho^+ ) +
\ol{D}^o ( {\ol{D}^*}^o ), we determine an allowed domain in the plane. We find that within one standard deviation errors, the allowed band
of from Class I decays is at least three standard deviations removed from
the allowed domain from Class III decays.If we expand the
experimental errors to two standard deviations we do find a small intersection
between the band and the allowed domain. The results
usually quoted in the literature lie in this intersection. We suggest : (1) an
independent measurement of the branching ratio for the Class III decay, B^+
\ra \rho^+ \ol{D}^o , (2) a high-statistics measurement of the branching ratio
of the Class I decay, B \ra \ol{D} ( \ol{D}^* ) + D_s ( D_s^* ) in both
charged states, and (3) a measurement of the longitudinal polarization fraction
in the Class III decay B^+ \ra \rho^+ {\ol{D}^*}^o to shed more light on the
questions involved .Comment: 9pages(Latex)+4 figures(PS file appended), PAR/LPTHE/94-2
Comparison of stimulation patterns for FES-cycling using measures of oxygen cost and stimulation cost
<b>Aim</b><p></p>
The energy efficiency of FES-cycling in spinal cord injured subjects is very much lower than that of normal cycling, and efficiency is dependent upon the parameters of muscle stimulation. We investigated measures which can be used to evaluate the effect on cycling performance of changes in stimulation parameters, and which might therefore be used to optimise them. We aimed to determine whether oxygen cost and stimulation cost measurements are sensitive enough to allow discrimination between the efficacy of different activation ranges for stimulation of each muscle group during constant-power cycling. <p></p>
<b>Methods</b><p></p>
We employed a custom FES-cycling ergometer system, with accurate control of cadence and stimulated exercise workrate. Two sets of muscle activation angles (âstimulation patternsâ), denoted âP1â and âP2â, were applied repeatedly (eight times each) during constant-power cycling, in a repeated measures design with a single paraplegic subject. Pulmonary oxygen uptake was measured in real time and used to determine the oxygen cost of the exercise. A new measure of stimulation cost of the exercise is proposed, which represents the total rate of stimulation charge applied to the stimulated muscle groups during cycling. A number of energy-efficiency measures were also estimated. <p></p>
<b>Results</b><p></p>
Average oxygen cost and stimulation cost of P1 were found to be significantly lower than those for P2 (paired <i>t</i>-test, <i>p</i> < 0.05): oxygen costs were 0.56 ± 0.03 l min<sup>â1</sup> and 0.61 ± 0.04 l min<sup>â1</sup>(mean ± S.D.), respectively; stimulation costs were 74.91 ± 12.15 mC min<sup>â1</sup> and 100.30 ± 14.78 mC min<sup>â1</sup> (mean ± S.D.), respectively. Correspondingly, all efficiency estimates for P1 were greater than those for P2. <p></p>
<b>Conclusion</b><p></p>
Oxygen cost and stimulation cost measures both allow discrimination between the efficacy of different muscle activation patterns during constant-power FES-cycling. However, stimulation cost is more easily determined in real time, and responds more rapidly and with greatly improved signal-to-noise properties than the ventilatory oxygen uptake measurements required for estimation of oxygen cost. These measures may find utility in the adjustment of stimulation patterns for achievement of optimal cycling performance. <p></p>
Noise and Measurement Efficiency of a Partially Coherent Mesoscopic Detector
We study the noise properties and efficiency of a mesoscopic resonant-level
conductor which is used as a quantum detector, in the regime where transport
through the level is only partially phase coherent. We contrast models in which
detector incoherence arises from escape to a voltage probe, versus those in
which it arises from a random time-dependent potential. Particular attention is
paid to the back-action charge noise of the system. While the average detector
current is similar in all models, we find that its noise properties and
measurement efficiency are sensitive both to the degree of coherence and to the
nature of the dephasing source. Detector incoherence prevents quantum limited
detection, except in the non-generic case where the source of dephasing is not
associated with extra unobserved information. This latter case can be realized
in a version of the voltage probe model.Comment: 15 pages, 5 figures; revised dicussion of voltage probe model
Development of a Momentum Determined Electron Beam in the 1 -45 GeV Range
A beam line for electrons with energies in the range of 1 to 45 GeV, low
contamination of hadrons and muons and high intensity up to 10^6 per
accelerator spill at 27 GeV was setup at U70 accelerator in Protvino, Russia. A
beam tagging system based on drift chambers with 160 micron resolution was able
to measure relative electron beam momentum precisely. The resolution sigma_p p
was 0.13% at 45 GeV where multiple scattering is negligible. This test beam
setup provided the possibility to study properties of lead tungstate crystals
(PbWO_4) for the BTeV experiment at Fermilab.Comment: 12 pages, 8 figures; work done by the BTeV Electromagnetic
Calorimeter grou
Understanding variation in ambulance service non-conveyance rates: a mixed methods study
Background
In England in 2015/16, ambulance services responded to nearly 11 million calls. Ambulance Quality Indicators show that half of the patients receiving a response by telephone or face to face were not conveyed to an emergency department. A total of 11% of patients received telephone advice only. A total of 38% of patients were sent an ambulance but were not conveyed to an emergency department. For the 10 large ambulance services in England, rates of calls ending in telephone advice varied between 5% and 17%. Rates of patients who were sent an ambulance but not conveyed to an emergency department varied between 23% and 51%. Overall non-conveyance rates varied between 40% and 68%.
Objective
To explain variation in non-conveyance rates between ambulance services.
Design
A sequential mixed methods study with five work packages.
Setting
Ten of the 11 ambulance services serving >â99% of the population of England.
Methods
(1) A qualitative interview study of managers and paramedics from each ambulance service, as well as ambulance commissioners (totalling 49 interviews undertaken in 2015). (2) An analysis of 1 month of routine data from each ambulance service (November 2014). (3) A qualitative study in three ambulance services with different published rates of calls ending in telephone advice (120 hours of observation and 20 interviews undertaken in 2016). (4) An analysis of routine data from one ambulance service linked to emergency department attendance, hospital admission and mortality data (6 months of 2013). (5) A substudy of non-conveyance for people calling 999 with breathing problems.
Results
Interviewees in the qualitative study identified factors that they perceived to affect non-conveyance rates. Where possible, these perceptions were tested using routine data. Some variation in non-conveyance rates between ambulance services was likely to be due to differences in the way rates were calculated by individual services, particularly in relation to telephone advice. Rates for the number of patients sent an ambulance but not conveyed to an emergency department were associated with patient-level factors: age, sex, deprivation, time of call, reason for call, urgency level and skill level of attending crew. However, variation between ambulance services remained after adjustment for patient-level factors. Variation was explained by ambulance service-level factors after adjustment for patient-level factors: the percentage of calls attended by advanced paramedics [odds ratio 1.05, 95% confidence interval (CI) 1.04 to 1.07], the perception of ambulance service staff and commissioners that advanced paramedics were established and valued within the workforce of an ambulance service (odds ratio 1.84, 95% CI 1.45 to 2.33), and the perception of ambulance service staff and commissioners that senior management was risk averse regarding non-conveyance within an ambulance service (odds ratio 0.78, 95% CI 0.63 to 0.98).
Limitations
Routine data from ambulance services are complex and not consistently collected or analysed by ambulance services, thus limiting the utility of comparative analyses.
Conclusions
Variation in non-conveyance rates between ambulance services in England could be reduced by addressing variation in the types of paramedics attending calls, variation in how advanced paramedics are used and variation in perceptions of the risk associated with non-conveyance within ambulance service management. Linking routine ambulance data with emergency department attendance, hospital admission and mortality data for all ambulance services in the UK would allow comparison of the safety and appropriateness of their different non-conveyance rates.
Funding
The National Institute for Health Research Health Services and Delivery Research programme
Comparison of Radiation Damage in Lead Tungstate Crystals under Pion and Gamma Irradiation
Studies of the radiation hardness of lead tungstate crystals produced by the
Bogoroditsk Techno-Chemical Plant in Russia and the Shanghai Institute of
Ceramics in China have been carried out at IHEP, Protvino. The crystals were
irradiated by a 40-GeV pion beam. After full recovery, the same crystals were
irradiated using a -ray source. The dose rate profiles along
the crystal length were observed to be quite similar. We compare the effects of
the two types of radiation on the crystals light output.Comment: 10 pages, 8 figures, Latex 2e, 28.04.04 - minor grammatical change
Correlation of Beam Electron and LED Signal Losses under Irradiation and Long-term Recovery of Lead Tungstate Crystals
Radiation damage in lead tungstate crystals reduces their transparency. The
calibration that relates the amount of light detected in such crystals to
incident energy of photons or electrons is of paramount importance to
maintaining the energy resolution the detection system. We report on tests of
lead tungstate crystals, read out by photomultiplier tubes, exposed to
irradiation by monoenergetic electron or pion beams. The beam electrons
themselves were used to measure the scintillation light output, and a blue
light emitting diode (LED) was used to track variations of crystals
transparency. We report on the correlation of the LED measurement with
radiation damage by the beams and also show that it can accurately monitor the
crystals recovery from such damage.Comment: 9 pages, 6 figures, LaTeX2
LED Monitoring System for the BTeV Lead Tungstate Crystal Calorimeter Prototype
We report on the performance of a monitoring system for a prototype
calorimeter for the BTeV experiment that uses Lead Tungstate crystals coupled
with photomultiplier tubes. The tests were carried out at the 70 GeV
accelerator complex at Protvino, Russia.Comment: 12 pages, 8 figures, LaTeX2e, revised versio
Design and performance of LED calibration system prototype for the lead tungstate crystal calorimeter
A highly stable monitoring system based on blue and red light emitting diodes
coupled to a distribution network comprised of optical fibers has been
developed for an electromagnetic calorimeter that uses lead tungstate crystals
readout with photomultiplier tubes. We report of the system prototype design
and on the results of laboratory tests. Stability better than 0.1% (r.m.s.) has
been achieved during one week of prototype operation.Comment: 10 pages, 6 figures, LaTeX2
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