We show that in order to avoid a breakdown of general covariance at the quantum level the total flux in each outgoing partial wave of a quantum field in a black hole background must be equal to that of a (1 + 1) dimensional blackbody at the Hawking temperature.PACS numbers: 04.62.+v, 04.70.Dy, Introduction.-Hawking radiation from black holes is one of the most striking effects that is known, or at least widely agreed, to arise from the combination of quantum mechanics and general relativity. Hawking radiation originates upon quantization of matter in a background spacetime that contains an event horizon-for example, a black hole. One finds that the occupation number spectrum of quantum field modes in the vacuum state is that of a blackbody at a fixed temperature given by the surface gravity of the horizon. The literature contains several derivations of Hawking radiation, each with strengths and weaknesses. Hawking's original derivation [1, 2] is very direct and physical, but it relies on hypothetical properties of modes that undergo extreme blue shifts, and specifically assumes that their interactions with matter can be ignored. Derivations based on Euclidean quantum gravity are quick and elegant, but the formalism lacks a secure microscopic foundation [3]. Derivations based on string theory have a logically consistent foundation, but they only apply to special solutions in unrealistic worldmodels, and they do not explain the simplicity and generality of the results inferred from the other methods [4,5]. In all these approaches, the Hawking radiation appears as a rather special and isolated phenomenon. Here we discuss another approach, which ties its existence to the cancellation of gravitational anomalies.

We calculate the contribution of graviton exchange to the running of gauge couplings at lowest nontrivial order in perturbation theory. Including this contribution in a theory that features coupling constant unification does not upset this unification, but rather shifts the unification scale. When extrapolated formally, the gravitational correction renders all gauge couplings asymptotically free.PACS numbers: 12.10. Kt, 11.10.Hi The straightforward framework for quantum gravitygeneral relativity quantized for small fluctuations around flat space-is a famously nonrenormalizable quantum field theory [1,2,3,4]. Nevertheless, this framework is appropriate for describing interactions at energies and momenta below the Planck scale M P ≡ c/G Newton ≈ 1.4×10 19 GeV/c 2 when treated as an effective low-energy theory. Indeed, if one makes subtractions to normalize physical couplings at an energy scale E 0 well below M P in such a way as to enforce the Einstein-Hilbert action of general relativity at the classical level with minimal couplings and a vanishing (or very small) cosmological term, then quantum corrections to this classical action at scale E will occur with coefficients containing positive powers of (E − E 0 )/M P , a small number. That procedure is the implicit foundation for practical use of classical general relativity as a model of nature despite the existence of quantum mechanics. It therefore underlies an enormous range of successful physical and astrophysical applications. Only the classical theory really comes into play in those applications, because the quantum corrections are quantitatively small. Thus, the conceptual framework of effective field theory provides a sophisticated rationalization for proceeding naively in applying the classical theory.Still, as Donoghue has emphasized [5], calculating corrections to the classical theory is a problem of methodological interest. Moreover, quantitative considerations concerning interactions at ultra-high energy scales, perhaps approaching the Planck scale, are important in assessing the possibility of gauge theory coupling unification [6,7]. Also, the size of gravitational corrections, in comparison to the leading classical term, give an objective indication for the characteristic scale for the onset of quantum gravity phenomenology. With these motivations, we consider here the one-loop (that is, first nontrivial order in perturbation theory) gravitational correction to running of gauge theory couplings.

We explore the method of Robinson and Wilczek for deriving the Hawking temperature of a black hole. In this method, the Hawking radiation restores general covariance in an effective theory of near-horizon physics which otherwise exhibits a gravitational anomaly at the quantum level. The method has been shown to work for broad classes of black holes in arbitrary spacetime dimensions.These include static black holes, accreting or evaporating black holes, charged black holes, rotating black holes, and even black rings. In the cases of charged and rotating black holes, the expected super-radiant current is also reproduced. * This essay received an "Honorable Mention" in the 2007 Essay Competition of the Gravity Research Foundation.

Basic science biomechanical study.

The most common orthopedic injuries in professional surfers involve the knee, ankle, shoulder, hip, and back. Surfers' rear extremities were preferentially injured which is the extremity responsible for power and torque. Shoulder injuries increased the probability of an operative intervention. Last, overuse injuries (femoral-acetabular impingement, rotator cuffs) occurred in the older surf population compared with more acute injuries (ankle sprains/fractures, anterior cruciate ligament tears) which is also consistent with time to surgery.

Level III.

The utilization of autologous and allogeneic transfusions in total joint arthroplasties was to characterize patients who may benefit from giving preoperative blood donations. We conducted a retrospective chart review of 525 patients to document preoperative hematocrit, estimated blood loss, length of stay, transfusions, and medical comorbidities. Results of our review showed that total hip arthroplasty revision (THA-R) had the highest prevalence of transfusions (60%) followed by total hip arthroplasty (THA, 53%), total knee arthroplasty-revision (TKA-R, 33%), and total knee arthroplasty (TKA, 23%). There was significant waste of autologous donations: 92% of TKA patients, 64% of THA, and 33% of THA-R patients wasted on average 1.527, 1.321, and 1.5 autologous units, respectively. Pre-operative hematocrit was the strongest predictor of future transfusion need across all procedures, and primary THA had additional predictors in age and gender.

As biomedical technology improves, we should continue to see changes to implant design and manufacturing. Having an understanding of the history and evolution of these implants will provide us with context in which to guide future implant design and clinical use. This review article provides a comprehensive overview of the evolution of early shoulder stabilization techniques and implants to the modern implants being used today.