3,246 research outputs found
New treatments: Costs, benefits and decision-making procedures
One hallmark of modern medicine is the ever-rising cost of providing life-saving or life-extending treatments. Advances in medical care and the ability to improve the duration and quality of life, combined with the expectations of both doctors and patients that all new modalities of treatment developed will be implemented in everyday practice, are the major reasons for modern medicineâs becoming so expensive. In these circumstances resource allocation decisions need to be made and appropriate priority-setting processes developed. This challenge faces all societies but most agonisingly middle income countries like South Africa where the expectations of physicians and patients are geared to the best that can be achieved in any country â even the wealthiest. Expensive, new or established standard treatments that may benefit patients may be considered in at least two categories. The first is when each individual patient will be a direct beneficiary. This applies, for example, when a pacemaker or orthopaedic prosthesis is installed, when an organ such as a kidney, heart or liver is transplanted, or when chronic renal dialysis is initiated. While such treatments have some mortality and a measure of sub-optimal results, good outcomes are the rul
Correlation of ERTS multispectral imagery with suspended matter and chlorophyll in lower Chesapeake Bay
The feasibility of using multispectral satellite imagery to monitor the characteristics of estuarine waters is being investigated. Preliminary comparisons of MSS imagery with suspended matter concentrations, particle counts, chlorophyll, transmittance and bathymetry have been made. Some visual correlation of radiance with particulates and chlorophyll has been established. Effects of bathymetry are present, and their relation to transmittance and radiance is being investigated. Greatest detail in suspended matter is revealed by MSS band 5. Near-surface suspended sediment load and chlorophyll can be observed in bands 6 and 7. Images received to date have partially defined extent and location of high suspensate concentrations. Net quantity of suspended matter in the lower Bay has been decreasing since the inception of the study, and represents the diminution of turbid flood waters carried into the Bay in late September, 1972. The results so far point to the utility of MSS imagery in monitoring estuarine water character for the assessment of siltation, productivity, and water types
Helicity-selective phase-matching and quasi-phase matching of circularly polarized high-order harmonics: Towards chiral attosecond pulses
Phase matching of circularly polarized high-order harmonics driven by counter-rotating bi-chromatic lasers was recently predicted theoretically and demonstrated experimentally. In that work, phase matching was analyzed by assuming that the total energy, spin angular momentum and linear momentum of the photons participating in the process are conserved. Here we propose a new perspective on phase matching of circularly polarized high harmonics. We derive an extended phase matching condition by requiring a new propagation matching condition between the classical vectorial bi-chromatic laser pump and harmonics fields. This allows us to include the influence of the laser pulse envelopes on phase matching. We find that the helicity dependent phase matching facilitates generation of high harmonics beams with a high degree of chirality. Indeed, we present an experimentally measured chiral spectrum that can support a train of attosecond pulses with a high degree of circular polarization. Moreover, while the degree of circularity of the most intense pulse approaches unity, all other pulses exhibit reduced circularity. This feature suggests the possibility of using a train of attosecond pulses as an isolated attosecond probe for chiral-sensitive experiments
Correlation of chlorophyll, suspended matter, and related parameters of waters in the lower Chesapeake Bay area to LANDSAT-1 imagery
The author has identified the following significant results. An effort to relate water parameters of the lower Chesapeake Bay area to multispectral scanner images of LANDSAT 1 has shown that some spectral bands can be correlated to water parameters, and has demonstrated the feasibility of synoptic mapping of estuaries by satellite. Bands 5 and 6 were shown to be useful for monitoring total particles. Band 5 showed high correlation with suspended sediment concentration. Attenuation coefficients monitored continuously by ship along three baselines were cross correlated with radiance values on three days. Improved correlations resulted when tidal conditions were taken into consideration. A contouring program was developed to display sediment variation in the lower Chesapeake Bay from the MSS bands
Master Integrals for the 2-loop QCD virtual corrections to the Forward-Backward Asymmetry
We present the Master Integrals needed for the calculation of the two-loop
QCD corrections to the forward-backward asymmetry of a quark-antiquark pair
produced in electron-positron annihilation events. The abelian diagrams
entering in the evaluation of the vector form factors were calculated in a
previous paper. We consider here the non-abelian diagrams and the diagrams
entering in the computation of the axial form factors, for arbitrary space-like
momentum transfer Q^2 and finite heavy quark mass m. Both the UV and IR
divergences are regularized in the continuous D-dimensional scheme. The Master
Integrals are Laurent-expanded around D=4 and evaluated by the differential
equation method; the coefficients of the expansions are expressed as
1-dimensional harmonic polylogarithms of maximum weight 4.Comment: 38 pages, 6 figures, typos corrected, version accepted by Nucl. Phys.
Electroweak Fermion-loop Contributions to the Muon Anomalous Magnetic Moment
The two-loop electroweak corrections to the anomalous magnetic moment of the
muon, generated by fermionic loops, are calculated. An interesting role of the
top quark in the anomaly cancellation is observed. New corrections, including
terms of order , are computed and a class of diagrams
previously thought to vanish are found to be important. The total fermionic
correction is which decreases the electroweak
effects on , predicted from one-loop calculations, by 12\%. We give an
updated theoretical prediction for of the muon.Comment: Corrected versio
Flexible structure control laboratory development and technology demonstration
An experimental structure is described which was constructed to demonstrate and validate recent emerging technologies in the active control and identification of large flexible space structures. The configuration consists of a large, 20 foot diameter antenna-like flexible structure in the horizontal plane with a gimballed central hub, a flexible feed-boom assembly hanging from the hub, and 12 flexible ribs radiating outward. Fourteen electrodynamic force actuators mounted to the hub and to the individual ribs provide the means to excite the structure and exert control forces. Thirty permanently mounted sensors, including optical encoders and analog induction devices provide measurements of structural response at widely distributed points. An experimental remote optical sensor provides sixteen additional sensing channels. A computer samples the sensors, computes the control updates and sends commands to the actuators in real time, while simultaneously displaying selected outputs on a graphics terminal and saving them in memory. Several control experiments were conducted thus far and are documented. These include implementation of distributed parameter system control, model reference adaptive control, and static shape control. These experiments have demonstrated the successful implementation of state-of-the-art control approaches using actual hardware
In Pursuit of New Physics with B_s Decays
The presence of a sizeable CP-violating phase in B_s^0-B_s^0-bar mixing would
be an unambiguous signal of physics beyond the Standard Model. We analyse
various possibilities to detect such a new phase considering both tagged and
untagged decays. The effects of a sizeable width difference Delta Gamma between
the B_s mass eigenstates, on which the untagged analyses rely, are included in
all formulae. A novel method to find this phase from simple measurements of
lifetimes and branching ratios in untagged decays is proposed. This method does
not involve two-exponential fits, which require much larger statistics. For the
tagged decays, an outstanding role is played by the observables of the
time-dependent angular distribution of the B_s -> J/psi [-> l^+ l^-] \phi [->
K^+K^-] decay products. We list the formulae needed for the angular analysis in
the presence of both a new CP-violating phase and a sizeable Delta Gamma, and
propose methods to remove a remaining discrete ambiguity in the new phase. This
phase can therefore be determined in an unambiguous way.Comment: minor changes, lattice prediction of Delta Gamma updated, appears in
PR
First order radiative corrections to Bhabha scattering in dimensions
The luminosity measurement at the projected International Linear
Collider ILC is planned to be performed with forward Bhabha scattering with an
accuracy of the order of . A theoretical prediction of the
differential cross-section has to include one-loop weak corrections, with
leading higher order terms, and the complete two-loop QED corrections. Here, we
present the weak part and the virtual one-loop photonic corrections. For the
photonic corrections, the expansions in are derived with
inclusion of the terms of order in order to match the two-loop
accuracy. For the photonic box master integral in dimensions we compare
several different methods of evaluation.Comment: 35 pages, 3 figures, 2 tables, uses feynmp.sty, references update
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