Light-cone coordinates based at a geodesic world line

Continuing work initiated in an earlier publication [Phys. Rev. D 69, 084007 (2004)], we construct a system of light-cone coordinates based at a geodesic world line of an arbitrary curved spacetime. The construction involves (i) an advanced-time or a retarded-time coordinate that labels past or future light cones centered on the world line, (ii) a radial coordinate that is an affine parameter on the null generators of these light cones, and (iii) angular coordinates that are constant on each generator. The spacetime metric is calculated in the light-cone coordinates, and it is expressed as an expansion in powers of the radial coordinate in terms of the irreducible components of the Riemann tensor evaluated on the world line. The formalism is illustrated in two simple applications, the first involving a comoving world line of a spatially-flat cosmology, the other featuring an observer placed on the axis of symmetry of Melvin's magnetic universe.Comment: 11 pages, 1 figur

Health Behaviors Among College Students: The Influence of Future Time Perspective and Basic Psychological Need Satisfaction

Health behavior change may prevent many fatal diseases, and may be influenced by social and motivational constructs. We assessed the interaction effect of future time perspective and basic psychological need fulfillment on positive and negative health behaviors. Future time perspective was associated with more positive, and less negative, health behaviors. Need fulfillment was associated with only positive health behaviors. In moderation analyses, individuals reporting both high need fulfillment and future perspective reported greater positive health behaviors, and were especially unlikely to smoke. Enhancing future-mindedness and supporting need satisfaction in interventions targeting modifiable health behaviors is encouraged

Solution of the Bohr hamiltonian for soft triaxial nuclei

The Bohr-Mottelson model is solved for a generic soft triaxial nucleus, separating the Bohr hamiltonian exactly and using a number of different model-potentials: a displaced harmonic oscillator in $\gamma$, which is solved with an approximated algebraic technique, and Coulomb/Kratzer, harmonic/Davidson and infinite square well potentials in $\beta$, which are solved exactly. In each case we derive analytic expressions for the eigenenergies which are then used to calculate energy spectra. Here we study the chain of osmium isotopes and we compare our results with experimental information and previous calculations.Comment: 13 pages, 9 figure

Emperical Tests of Acceptance Sampling Plans

Acceptance sampling is a quality control procedure applied as an alternative to 100% inspection. A random sample of items is drawn from a lot to determine the fraction of items which have a required quality characteristic. Both the number of items to be inspected and the criterion for determining conformance of the lot to the requirement are given by an appropriate sampling plan with specified risks of Type I and Type II sampling errors. In this paper, we present the results of empirical tests of the accuracy of selected sampling plans reported in the literature. These plans are for measureable quality characteristics which are known have either binomial, exponential, normal, gamma, Weibull, inverse Gaussian, or Poisson distributions. In the main, results support the accepted wisdom that variables acceptance plans are superior to attributes (binomial) acceptance plans, in the sense that these provide comparable protection against risks at reduced sampling cost. For the Gaussian and Weibull plans, however, there are ranges of the shape parameters for which the required sample sizes are in fact larger than the corresponding attributes plans, dramatically so for instances of large skew. Tests further confirm that the published inverse-Gaussian (IG) plan is flawed, as reported by White and Johnson (2011)

A supersymmetric model of gamma ray bursts

We propose a model for gamma ray bursts in which a star subject to a high level of fermion degeneracy undergoes a phase transition to a supersymmetric state. The burst is initiated by the transition of fermion pairs to sfermion pairs which, uninhibited by the Pauli exclusion principle, can drop to the ground state of minimum momentum through photon emission. The jet structure is attributed to the Bose statistics of sfermions whereby subsequent sfermion pairs are preferentially emitted into the same state (sfermion amplification by stimulated emission). Bremsstrahlung gamma rays tend to preserve the directional information of the sfermion momenta and are themselves enhanced by stimulated emission.Comment: published versio

Probabilistic Requirements (Partial) Verification Methods Best Practices Improvement. Variables Acceptance Sampling Calculators: Empirical Testing

The NASA Engineering and Safety Center was requested to improve on the Best Practices document produced for the NESC assessment, Verification of Probabilistic Requirements for the Constellation Program, by giving a recommended procedure for using acceptance sampling by variables techniques as an alternative to the potentially resource-intensive acceptance sampling by attributes method given in the document. In this paper, the results of empirical tests intended to assess the accuracy of acceptance sampling plan calculators implemented for six variable distributions are presented

Probabilistic Requirements (Partial) Verification Methods Best Practices Improvement. Variables Acceptance Sampling Calculators: Derivations and Verification of Plans

The NASA Engineering and Safety Center was requested to improve on the Best Practices document produced for the NESC assessment, Verification of Probabilistic Requirements for the Constellation Program, by giving a recommended procedure for using acceptance sampling by variables techniques. This recommended procedure would be used as an alternative to the potentially resource-intensive acceptance sampling by attributes method given in the document. This document contains the outcome of the assessment

Stress in Swine

Stress appears to be increasing in swine and its toll ranges from death of animals to undesirable meat characteristics. The authors review the problem and list some preventive measures you can take

A study of Feshbach resonances and the unitary limit in a model of strongly correlated nucleons

A model of strongly interacting and correlated hadrons is developed. The interaction used contains a long range attraction and short range repulsive hard core. Using this interaction and various limiting situations of it, a study of the effect of bound states and Feshbach resonances is given. The limiting situations are a pure square well interaction, a delta-shell potential and a pure hard core potential. The limit of a pure hard core potential are compared with results for a spinless Bose and Fermi gas. The limit of many partial waves for a pure hard core interaction is also considered and result in expressions involving the hard core volume. This feature arises from a scaling relation similar to that for hard sphere scattering with diffractive corrections. The role of underlying isospin symmetries associated with the strong interaction of protons and neutrons in this two component model is investigated. Properties are studied with varying proton fraction. An analytic expression for the Beth Uhlenbeck continuum integral is developed which closely approximates exact results based on the potential model considered. An analysis of features associated with a unitary limit is given. In the unitary limit of very large scattering length, the ratio of effective range to thermal wavelength appears as a limiting scale. Thermodynamic quantities such as the entropy and compressibility are also developed. The effective range corrections to the entropy vary as the cube of this ratio for low temperatures and are therefore considerably reduced compared to the corrections to the interaction energy which varies linearly with this ratio. Effective range corrections to the compressibility are also linear in the ratio.Comment: 39 pages, 15 figures, 2 table