Stochastic Gravity: Theory and Applications

Whereas semiclassical gravity is based on the semiclassical Einstein equation with sources given by the expectation value of the stress-energy tensor of quantum fields, stochastic semiclassical gravity is based on the Einstein-Langevin equation, which has in addition sources due to the noise kernel. In the first part, we describe the fundamentals of this new theory via two approaches: the axiomatic and the functional. In the second part, we describe three applications of stochastic gravity theory. First, we consider metric perturbations in a Minkowski spacetime, compute the two-point correlation functions of these perturbations and prove that Minkowski spacetime is a stable solution of semiclassical gravity. Second, we discuss structure formation from the stochastic gravity viewpoint. Third, we discuss the backreaction of Hawking radiation in the gravitational background of a black hole and describe the metric fluctuations near the event horizon of an evaporating black holeComment: 100 pages, no figures; an update of the 2003 review in Living Reviews in Relativity gr-qc/0307032 ; it includes new sections on the Validity of Semiclassical Gravity, the Stability of Minkowski Spacetime, and the Metric Fluctuations of an Evaporating Black Hol

Significant Reduction of Antibiotic Use in the Community after a Nationwide Campaign in France, 2002–2007

Didier Guillemot and colleagues describe the evaluation of a nationwide programme in France aimed at decreasing unnecessary outpatient prescriptions for antibiotics. The campaign was successful, particularly in reducing prescriptions for children

ICAR: endoscopic skull‐base surgery

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Desire for Antibiotics and Antibiotic Prescribing for Adults with Upper Respiratory Tract Infections

OBJECTIVE: Prior studies have shown that 60% to 75% of adults with upper respiratory tract infections want antibiotics. More recent research indicates declines in antibiotic prescribing for upper respiratory tract infections. To investigate whether there has been a comparable decrease in patients’ desire for antibiotics, we measured the proportion of adults with upper respiratory tract infections who wanted antibiotics in the winter of 2001–2002. We also sought to identify factors independently associated with wanting antibiotics and antibiotic prescribing. DESIGN: Prospective survey of adults with upper respiratory tract infections prior to visiting an acute care clinic from November 2001 to February 2002. MEASUREMENTS AND MAIN RESULTS: Thirty-nine percent of 310 patients wanted antibiotics. Many patients wanted relief from symptoms (43%) or pain (24%) and many patients expected to receive a diagnosis (49%) or reassurance during the visit (13%). In multivariable modeling, independent predictors of wanting antibiotics were prior antibiotic use (odds ratio [OR], 2.4; 95% confidence interval [CI], 1.3 to 4.7) and current smoking (OR, 3.1; 95% CI, 1.3 to 7.3). Physicians prescribed antibiotics to 46% of patients who wanted antibiotics and 29% of patients who did not want antibiotics (P= .01). In multivariable modeling, wanting antibiotics was an independent predictor of antibiotic prescribing (OR, 2.1; 95% CI, 1.1 to 4.4). CONCLUSIONS: Only 39% of adults seeking care for upper respiratory tract infections wanted antibiotics, less than in previous studies. In continuing efforts to break the cycle of inappropriate antibiotic use, physicians should not assume that most patients with upper respiratory tract infections want antibiotics

Multidisciplinary Cancer Conferences: Exploring Obstacles and Facilitators to Their Implementation

A study of the implementation in Canada of multidisciplinary cancer conferences—which can facilitate diagnosis and treatment discussions and optimize patient management—using grounded theory methodology

Quantitative Analysis of GPR Signals: Transmitted Wavelet, Amplitude Decay, and Sampling-Related Amplitude Distortions

3noWe study the importance of accurately recording signal amplitudes for the quantitative analysis of GPR data sets. Specifically, we measure the peak amplitudes of signals emitted by GPR antennas with different central frequencies and study their amplitude decay with distance, in order to extrapolate the peak amplitude of the wavelet initially transmitted by each antenna. The purpose is to compare the reference and reflected amplitudes in order to accurately estimate the subsurface EM impedance contrasts. Moreover, we study how sampling-related amplitude distortions can affect the quantitative analysis, and subsequently the resulting subsurface models, even in the absence of aliasing effects. The well-known Nyquist–Shannon theorem gives practical lower limits for the sampling rate in order to preserve the spectral content of a digitized signal; however, we show that it does not prevent possible amplitude distortions. In particular, we demonstrate that significant and unrecoverable loss of amplitude information occurs even at sampling rates well above the Nyquist– Shannon threshold. Interpolation may theoretically reduce such amplitude distortions; however, its accuracy would depend on the implemented algorithm and it is not verifiable in real data sets, since the actual amplitude information is limited to the sampled values. Moreover, re-sampling the interpolated signal simply reintroduces the initial problem, when a new sampling rate is selected. Our analysis suggests that, in order to limit the maximum peak amplitude error within 5%, the sampling rate selected during data acquisition must be at least 12 times the signal central frequency, which is higher than the commonly adopted standards.reservedmixedDossi, M.; Forte, Emanuele; Pipan, M.Dossi, M.; Forte, Emanuele; Pipan, M