Cosmological constraints for a two brane-world system with single equation of state

We present the study of two 3-brane system embedded in a 5-dimensional space-time in which the fifth dimension is compactified on a $S^{1}/Z_{2}$ orbifold. Assuming isotropic, homogeneous, and static branes, it can be shown that the dynamics of one brane is dominated by the other one when the metric coefficients have a particular form. We study the resulting cosmologies when one brane is dominated by a given single-fluid component.Comment: This work was presented at the VIII Taller of the DGFM, Tuxtla Gutierrez, Chiapas, Mexico noviembre 22-26, 201

An equation of state for purely kinetic k-essence inspired by cosmic topological defects

We investigate the physical properties of a purely kinetic k-essence model with an equation of state motivated in superconducting membranes. We compute the equation of state parameter $w$ and discuss its physical evolution via a nonlinear equation of state. Using the adiabatic speed of sound and energy density, we restrict the range of parameters of the model in order to have an acceptable physical behavior. Furthermore, we analyze the evolution of the luminosity distance $d_{L}$ with redshift $z$ by comparing (normalizing) it with the $\Lambda$CDM model. Since the equation of state parameter is $z$-dependent the evolution of the luminosity distance is also analyzed using the Alcock-Paczy\'{n}ski test.Comment: 19 pages, 13 figures, typos corrected and references adde

Two-brane system in a vacuum bulk with a single equation of state

We study the cosmology of a two-brane model in a five-dimensional spacetime, where the extra spatial coordinate is compactifed on an orbifold. Additionally, we consider the existence on each brane of matter fields that evolve in time. Solving the Einstein equations in a vacuum bulk, we can show how the matter fields in both branes are connected and they do not evolve independentlyComment: This work was presented at the IX Taller de la Division de Gravitacion y Fisica Matematica, Colima 201

Mixed spatially varying L2L^2-BV regularization of inverse ill-posed problems

Several generalizations of the traditional Tikhonov-Phillips regularization method have been proposed during the last two decades. Many of these generalizations are based upon inducing stability throughout the use of different penalizers which allow the capturing of diverse properties of the exact solution (e.g. edges, discontinuities, borders, etc.). However, in some problems in which it is known that the regularity of the exact solution is heterogeneous and/or anisotropic, it is reasonable to think that a much better option could be the simultaneous use of two or more penalizers of different nature. Such is the case, for instance, in some image restoration problems in which preservation of edges, borders or discontinuities is an important matter. In this work we present some results on the simultaneous use of penalizers of $L^2$ and of bounded variation (BV) type. For particular cases, existence and uniqueness results are proved. Open problems are discussed and results to signal restoration problems are presented.Comment: 18 pages, 12 figure

Advanced nozzle and engine components test facility

A test facility for conducting scaled advanced nozzle and engine component research is described. The CE-22 test facility, located in the Engine Research Building of the NASA Lewis Research Center, contains many systems for the economical testing of advanced scale-model nozzles and engine components. The combustion air and altitude exhaust systems are described. Combustion air can be supplied to a model up to 40 psig for primary air flow, and 40, 125, and 450 psig for secondary air flow. Altitude exhaust can be simulated up to 48,000 ft, or the exhaust can be atmospheric. Descriptions of the multiaxis thrust stand, a color schlieren flow visualization system used for qualitative flow analysis, a labyrinth flow measurement system, a data acquisition system, and auxiliary systems are discussed. Model recommended design information and temperature and pressure instrumentation recommendations are included

ESTIMATING INVESTMENT RIGIDITY WITHIN A THRESHOLD REGRESSION FRAMEWORK: THE CASE OF U.S. HOG PRODUCTION SECTOR

As the U.S. hog production sector becomes ever more specialized, the importance of capital inputs has heightened. Given that it is costly to adjust the capital stock and that the associated adjustment cost function may exhibit cost asymmetries between investment and disinvestment, profit-maximizing producers may find themselves trapped in a situation where it is neither profitable investing nor worthwhile disinvesting. This article addresses two issues related to the employment of quasi-fixed input in the U.S. hog production sector: does an inaction or sluggish regime exist in the demand for quasi-fixed input, and, if so, to what extent has this impeded adjustment in quasi-fixed input stock and, hence, hog output supply toward the long-term equilibrium levels? The conceptual framework is based on the work by Abel and Eberly and allows for the existence of an inaction/sluggish regime, alongside an investment regime and a disinvestment regime. Quarterly data from 1976 through 1999 are used to estimate the three-regime investment demand equation, treating breeding sows as the quasi-fixed input. The threshold estimation procedure recently advanced by Hansen is adopted. To provide a linkage between breeding herd investment and hog output supply, a hog supply equation, specified in part as a function of lagged breeding stock, is estimated by a least squares procedure. The dynamic recursive system of investment demand and hog supply is used to simulate the effects on breeding stock and hog supply of changes in the magnitude of investment rigidities. The econometric results strongly support the three-regime breeding herd investment model. More than 10 percent of the observations fall into the sluggish regime, indicating that this regime has occurred sufficiently often to warrant attention. The estimated rate of adjustment toward the long-run equilibrium breeding stock is 2.7 percent per quarter. The existence of a linkage between lagged breeding stock and hog supply is confirmed. Thus, the results suggest that it is important to account for investment rigidity when estimating breeding herd demand and hog supply. Simulation results indicate that the effects on breeding stock and hog supply of continued specialization in the hog production sector may not be as significant as what the hog production sector has experienced in the past decades. More importantly the simulations suggest that the impact of increasing investment rigidity is rather modest, about 3 percent at most and, thus, no policy intervention appears to be needed. However, the econometric results clearly indicate that estimates will be biased if investment rigidity is not explicitly accounted for when estimating breeding herd demand and hog supply.Livestock Production/Industries,

Nonlinear Criterion for the Stability of Molecular Clouds

Dynamically significant magnetic fields are routinely observed in molecular clouds, with mass-to-flux ratio lambda = (2 pi sqrt{G}) (Sigma/B) ~ 1 (here Sigma is the total column density and B is the field strength). It is widely believed that ``subcritical'' clouds with lambda < 1 cannot collapse, based on virial arguments by Mestel and Spitzer and a linear stability analysis by Nakano and Nakamura. Here we confirm, using high resolution numerical models that begin with a strongly supersonic velocity dispersion, that this criterion is a fully nonlinear stability condition. All the high-resolution models with lambda <= 0.95 form ``Spitzer sheets'' but collapse no further. All models with lambda >= 1.02 collapse to the maximum numerically resolvable density. We also investigate other factors determining the collapse time for supercritical models. We show that there is a strong stochastic element in the collapse time: models that differ only in details of their initial conditions can have collapse times that vary by as much as a factor of 3. The collapse time cannot be determined from just the velocity dispersion; it depends also on its distribution. Finally, we discuss the astrophysical implications of our results.Comment: 11 pages, 5 figure

Disseminated cutaneous gout: a rare manifestation of a common disease

Disseminated cutaneous gout is a rare atypical cutaneous manifestation of gout in which widespread dermal and subcutaneous tophi develop at extra-articular body sites. Given the lack of joint involvement that is typically a feature in tophaceous gout, the diagnosis may not be initially suspected. We present the case of a 50-year-old Hispanic man with poorly controlled gout who was evaluated for several years of firm papulonodules over the trunk and upper and lower extremities, sparing the joints; histopathology confirmed, the diagnosis of disseminated cutaneous gout. Per our literature review, disseminated cutaneous gout presents with polymorphous papules and nodules that can mimic other, more common cutaneous diseases. There is a preponderance of cases in males, Asians, and patients with longstanding gout. The lower extremities are involved in nearly all reports. Uric acid-lowering therapy with allopurinol has been reported to decrease the size and number of lesions in a minority of treated patients

Gen Z’s Fitness Concepts and Ways to be Fit: Insights to Strengthen Students’ Learning Experiences in Tertiary Physical Education

Being dubbed as digital natives born and raised in the highly industrial era, generation z students differ from previous generations. A recent study revealed an increasing number of dropped-out students in physical education classes in one of the leading State Universities in the Philippines. Several reasons have been revealed, and one of those is the current tertiary physical education curriculum content. Hence, this study aimed to determine the fitness concepts and ways to stay fit of generation Z students and utilize in enhancing the curriculum content and improve the students’ learning experiences in tertiary physical education. Using the descriptive phenomenology research design, 95 research participants took part in focus group discussions, in-depth interviews, and unobtrusive participant observations. The findings of this inquiry indicated three (3) reasons why generation Z students still perceive physical education as an essential course in schools (gadget addiction; early childhood diseases; and stress release) and six (6) ways to stay healthy (exercise and physical activities; balanced diet; enough sleep/rest; self-discipline; and use of technology to promote fitness). The findings and conclusions served as critical components in strengthening the tertiary physical education curriculum to tailor the learning experiences to generation Z students' concepts, ways, and preferences