Schwinger's Propagator Is Only A Green's Function

Schwinger used an analytic continuation of the effective action to correctly compute the particle production rate per unit volume for QED in a uniform electric field. However, if one simply evaluates the one loop expectation value of the current operator using his propagator, the result is zero! We analyze this curious fact from the context of a canonical formalism of operators and states. The explanation turns out to be that Schwinger's propagator is not actually the expectation value of the time-ordered product of field operators in the presence of a time-independent state, although it is of course a Green's function. We compute the true propagator in the presence of a state which is empty at $x_+ = 0$ where $x_+ \equiv (x^0+x^3)/\sqrt{2}$ is the lightcone evolution parameter. Our result can be generalized to electric fields which depend arbitrarily on $x_+$.Comment: 18 pages, LaTeX 2 epsilo

Proposed Pilot Plant for Production of Sintered Beryllium Oxide from Berylore

Beryllium metal and beryllium oxide have attracted considerable attention as possible nuclear reactor materials on account of their low neutron absorption cross section and low atomic weight and the consequent moderating properties, i.e., ability to reduce the velocity of fast neutron to thermal level. The inert nature and high melting point of beryllium oxide make it suitable for high temperature gas cooled nuclear reactors. There is some doubt about its stability under extended Irradiation by fast neutrons. However, beryll- ium oxide holds promise as a future power reactor mate-rial. The cost of nuclear grade beryllium oxide sintered shapes tends to be high on account of the great degree of purity required and the initial high cost.of the ore

Oxidation of Hydrazine, Phenylhydrazine & Substituted henylhydrazines by Thallium (III) - Substituent Effects & Mechanism

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CO J = 2 - 1 Emission from Evolved Stars in the Galactic Bulge

We observe a sample of 8 evolved stars in the Galactic Bulge in the CO J = 2 - 1 line using the Submillimeter Array (SMA) with angular resolution of 1 - 4 arcseconds. These stars have been detected previously at infrared wavelengths, and several of them have OH maser emission. We detect CO J = 2 - 1 emission from three of the sources in the sample: OH 359.943 +0.260, [SLO2003] A12, and [SLO2003] A51. We do not detect the remaining 5 stars in the sample because of heavy contamination from the galactic foreground CO emission. Combining CO data with observations at infrared wavelengths constraining dust mass loss from these stars, we determine the gas-to-dust ratios of the Galactic Bulge stars for which CO emission is detected. For OH 359.943 +0.260, we determine a gas mass-loss rate of 7.9 (+/- 2.2) x 10^-5 M_Sun/year and a gas-to-dust ratio of 310 (+/- 89). For [SLO2003] A12, we find a gas mass-loss rate of 5.4 (+/- 2.8) x 10^-5 M_Sun/year and a gas-to-dust ratio of 220 (+/- 110). For [SLO2003] A51, we find a gas mass-loss rate of 3.4 (+/- 3.0) x 10^-5 M_Sun/year and a gas-to-dust ratio of 160 (+/- 140), reflecting the low quality of our tentative detection of the CO J = 2 - 1 emission from A51. We find the CO J = 2 - 1 detections of OH/IR stars in the Galactic Bulge require lower average CO J = 2 - 1 backgrounds.Comment: 40 pages, 16 figures, appeared in the 1 March 2013 issue of the Astrophysical Journa

Evaluation of correction of kyphotic deformity in dorso-lumbar spinal injuries by posterior stabilization with pedicular screw rod fixation

Background: Acute injury to dorso-lumbar spine is the second most frequent site after cervical spine in adults. The injury, although not associated with high mortality, causes severe morbidity. The management of the traumatic dorso-lumbar spine injuries has improved considerably in the last few years. The objective of the study was to evaluate correction of kyphotic deformity in dorso-lumbar spinal injuries by posterior stabilization with pedicular screw rod fixation.Methods: The study includes 52 patients with dorso-lumbar spinal injuries with or without neurological deficit treated between 2006 and 2014. Pre and postoperative kyphosis was measured by Cobb’s method on plain radiographs. Pre and postoperative neurological status was evaluated based on Frankel’s classification. All un-stable dorso-lumbar spine injuries where two or more columns are involved on X-ray and CT scan were included in the present study.Results: Majority of the patients were in the age group of 20-30 years (38.5%) followed by 31-40 years (30.8%). Males were more than females. The most common mode of injury was road traffic injury in 71.2% of the cases. The most common level of injury was at L1 in 28.8% of the cases followed by at level D12 in 25% of the cases. In all the groups the mean kyphosis angle is reduced significantly. Overall the improvement rate was 94.2% and failure rate was only 5.8%.Conclusions: In conclusion the posterior reduction and internal fixation is a useful procedure in the treatment of the acute injuries of the dorsolumbar spine.