Zitterbewegung in External Magnetic Field: Classic versus Quantum Approach

We investigate variations of the Zitterbewegung frequency of electron due to an external static and uniform magnetic field employing the expectation value quantum approach, and compare our results with the classical model of spinning particles. We demonstrate that these two so far compatible approaches are not in agreement in the presence of an external uniform static magnetic field, in which the classical approach breaks the usual symmetry of free particles and antiparticles states, i.e. it leads to CP violation. Hence, regarding the Zitterbewegung frequency of electron, the classical approach in the presence of an external magnetic field is unlikely to correctly describe the spin of electron, while the quantum approach does, as expected. We also show that the results obtained via the expectation value are in close agreement with the quantum approach of the Heisenberg picture derived in the literature. However, the method we use is capable of being compared with the classical approach regarding the spin aspects. The classical interpretation of spin produced by the altered Zitterbewegung frequency, in the presence of an external magnetic field, are discussed.Comment: 16 pages, no figure

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

A SIMULATION STUDY OF A REFLECTOR CONTROL SYSTEM FOR A HETEROGENEOUS BOILING REACTOR

The feasibility of using a reflector control system for a heterogeneous boiling reactor through use of analog simulatlon tecbeiques was examined. The reactor kinetics, reactivity, and steam generation were simulated electronically while the hydraulic portion of the reflector system was represented by a full- scale physical mock-up. The two portions of the system were coupled together, and an attempt was made to achieve a stable, nonoscillating system. Various configurations of hydraulic coupling between the reflector tank and surge tank were used to produce the desired representation of the frictional forces in the system. A system of baffle plates in the coupling produced the desired damping. With the stable system, the effect of steam-load-demand changes for various values of incremental moderator worth was examined. These studies showed that a reflector control system for this type of reactor is feasible. (auth

SIMULATION OF VARIOUS ACCIDENT CONSIDERATIONS FOR A MERCHANT-SHIP PRESSURIZED-WATER REACTOR

A study was conducted on the safety aspects of foreseeable accident types in connection with the Nuclear Merchant Ship Reactor program. Four accidents have been selected for analysis by analog simulation techniques: continuous rod withdrawal, startup, loss of coolant flow, and cold-water insertion. The simulation of the reactor only was required for these situations because the effects of the accidents would be completed in less than one primary- coolant loop time. The external control system was ignored, and only the effects of the negative reactivity cocfficients were considered in the natural shutdown of the plant. Three phases of operation were considered in these analyses: operation with no safety system, high-flux scram, and period scram. The programs involved the variations of the scram parameters and the reactor temperature coefficients over the range of possible values for this reactor power plant. Results indicate that the inherent stabliity of the reactor system is sufficient to attenuate the power excursions resulting from the first three accidents. In the coldwater accident, if the difference in loop temperatures is on the order of 300 deg F, scram is necessary to limit the power excursion. (auth

\u3ci\u3ePlasmodium falciparum\u3c/i\u3e circumsporozoite vaccine immunogenicity and efficacy trial with natural challenge quantitation in an area of endemic human malaria of Kenya

It has been hypothesized that antibody induced by Plasmodium falciparum circumsporozoite protein vaccine would be effective against endemic human malaria. In a malaria endemic region of Kenya, 76 volunteers, in 38 pairs sleeping adjacently, were immunized with subunit circumsporozoite protein Asn-Ala-Asn-Pro tetrapeptide repeatpseudomonas toxin A, or hepatitis B vaccine. After quinine and doxcycycline, volunteers were followed for illness daily, parasitemia weekly, antibody, T-lymphocyte responses, and treated if indicated. Anopheles mosquitoes resting in houses were collected, and tested for P. falciparum antigen, or dissected for sporozoites and tested for blood meal ABO type and P. falciparum antigen. Vaccine was safe, with side-eflects similar in both groups, and immunogenic, engendering IgG antibody as high as 600 µg ml-1, but did not increase the proportion of volunteers with T-lymphocyte responses. Estimation of P. falciparum challenge averaged 0.194 potentially infective Anopheles bites/volunteer/day. Mosquito blood meals showed no difference in biting intensity between vaccine and control groups. Both groups had similar malaria-free survival curves, cumulative positive blood slides, cumulative parasites mm- 3, and numbers of parasites mm- 3 on first positive blood slide, during three post-vaccination observation periods. Every volunteer had P. falciparum parastiemia at least once. Vaccinees had 82% and controls 89% incidences of symptomatic parasitemia (P=0.514, efficacy 9%, statistical power 95% probability of eficacy ~50%). Vaccine-induced anti-sporozoite antibody was not protective in this study. Within designed statistical precisions the present study is in agreement with efficacy studies in Colombia, Venezuela and Tanzania