13,061 research outputs found
Recommended from our members
Librarians use of Web 2.0 in UK Medical Schools: Outcomes of a national survey
Using the results of an Email survey, this paper reviews the use of Web 2.0 technologies by librarians working in UK Medical Schools. Web 2.0 has been hailed as an innovation for facilitation of two way communication on the net, and it is, therefore, timely to measure how effectively librarians are capturing this opportunity for increased student engagement. The social nature of Web 2.0 can be particularly appropriate for undergraduate medical students who fit their studies around the unsocial hours and geographical isolation of clinical placements. This paper will investigate library use of blogs, Facebook, and Twitter. Consideration will also be given as to whether they facilitate a more collabroative library service or if they leave undergraduate medical students swamped with yet more information to manage
A distributionally robust perspective on uncertainty quantification and chance constrained programming
The objective of uncertainty quantification is to certify that a given physical, engineering or economic system satisfies multiple safety conditions with high probability. A more ambitious goal is to actively influence the system so as to guarantee and maintain its safety, a scenario which can be modeled through a chance constrained program. In this paper we assume that the parameters of the system are governed by an ambiguous distribution that is only known to belong to an ambiguity set characterized through generalized moment bounds and structural properties such as symmetry, unimodality or independence patterns. We delineate the watershed between tractability and intractability in ambiguity-averse uncertainty quantification and chance constrained programming. Using tools from distributionally robust optimization, we derive explicit conic reformulations for tractable problem classes and suggest efficiently computable conservative approximations for intractable ones
Optimum pulse shapes for stimulated Raman adiabatic passage
Stimulated Raman adiabatic passage (STIRAP), driven with pulses of optimum
shape and delay has the potential of reaching fidelities high enough to make it
suitable for fault-tolerant quantum information processing. The optimum pulse
shapes are obtained upon reduction of STIRAP to effective two-state systems. We
use the Dykhne-Davis-Pechukas (DDP) method to minimize nonadiabatic transitions
and to maximize the fidelity of STIRAP. This results in a particular relation
between the pulse shapes of the two fields driving the Raman process. The
DDP-optimized version of STIRAP maintains its robustness against variations in
the pulse intensities and durations, the single-photon detuning and possible
losses from the intermediate state.Comment: 8 pages, 6 figures. submitted to Phys. Rev.
Electroweak Sudakov Corrections and the Top Quark Forward-Backward Asymmetry
The Standard Model (SM) prediction of the top quark forward backward
asymmetry is shown to be slightly enhanced by a correction factor of 1.05 due
to electroweak Sudakov (EWS) logarithms of the form (\alpha/sin^2 \theta_W)^n
log^{m< 2n} (s/M_{W,Z}^2). The EWS effect on the dijet and t \bar{t} invariant
mass spectra is significant, reducing the SM prediction by ~20, 10 %
respectively for the highest invariant masses measured at the LHC, and changing
the shape of the high-mass tail of the spectrum. These corrections
significantly affect measurements of the top quark invariant mass spectrum and
the search for an excess of events related to the top quark forward-backward
asymmetry.Comment: 5 pages, 2 figure
- …