5,299 research outputs found
Traveling wave solutions for wave equations with two exponential nonlinearities
We use a simple method that leads to the integrals involved in obtaining the
traveling wave solutions of wave equations with one and two exponential
nonlinearities. When the constant term in the integrand is zero, implicit
solutions in terms of hypergeometric functions are obtained while when that
term is nonzero all the basic traveling wave solutions of Liouville, Tzitzeica
and their variants, as well as sine/sinh-Gordon equations with important
applications in the phenomenology of nonlinear physics and dynamical systems
are found through a detailed study of the corresponding elliptic equationsComment: 9 pages, 7 figures, 42 references, version matching the published
articl
Systematic evaluation of software product line architectures
The architecture of a software product line is one of its most important artifacts as it represents an abstraction of the products that can be generated. It is crucial to evaluate the quality attributes of a product line architecture in order to: increase the productivity of the product line process and the quality of the products; provide a means to understand the potential behavior of the products and, consequently, decrease their time to market; and, improve the handling of the product line variability. The evaluation of product line architecture can serve as a basis to analyze the managerial and economical values of a product line for software managers and architects. Most of the current research on the evaluation of product line architecture does not take into account metrics directly obtained from UML models and their variabilities; the metrics used instead are difficult to be applied in general and to be used for quantitative analysis. This paper presents a Systematic Evaluation Method for UML-based Software Product Line Architecture, the SystEM-PLA. SystEM-PLA differs from current research as it provides stakeholders with a means to: (i) estimate and analyze potential products; (ii) use predefined basic UML-based metrics to compose quality attribute metrics; (iii) perform feasibility and trade-off analysis of a product line architecture with respect to its quality attributes; and, (iv) make the evaluation of product line architecture more flexible. An example using the SEI’s Arcade Game Maker (AGM) product line is presented as a proof of concept, illustrating SystEM-PLA activities. Metrics for complexity and extensibility quality attributes are defined and used to
perform a trade-off analysis
Traveling Wave Solutions for Wave Equations with Exponential Nonlinearities
We use a simple method which leads to the quadrature involved in obtaining the traveling wave solutions of wave equations with one and two exponential nonlinearities. When the constant term in the integrand is zero, implicit solutions in terms of hypergeometric functions are obtained while when that term is nonzero we give all the basic traveling wave solutions based on a detailed study of the corresponding elliptic equations of several well-known particular cases with important applications in physics
Transcriptomic analysis of the hepatic response to stress in the red cusk-eel (Genypterus chilensis): Insights into lipid metabolism, oxidative stress and liver steatosis
Indexación: Scopus.Teleosts exhibit a broad divergence in their adaptive response to stress, depending on the magnitude, duration, and frequency of stressors and the species receiving the stimulus. We have previously reported that the red cusk-eel (Genypterus chilensis), an important marine farmed fish, shows a physiological response to stress that results in increased skeletal muscle atrophy mediated by over-expression of components of the ubiquitin proteasome and autophagy-lysosomal systems. To better understand the systemic effects of stress on the red cusk-eel metabolism, the present study assessed the transcriptomic hepatic response to repetitive handling-stress. Using high-Throughput RNA-seq, 259 up-regulated transcripts were found, mostly associated with angiogenesis, gluconeogenesis, and triacylglyceride catabolism. Conversely, 293 transcripts were down-regulated, associated to cholesterol biosynthesis, PPARα signaling, fatty acid biosynthesis, and glycolysis. This gene signature was concordant with hepatic metabolite levels and hepatic oxidative damage. Moreover, the increased plasmatic levels of AST (aspartate aminotransferase), ALT (alanine aminotransferase) and AP (alkaline phosphatase), as well as liver histology suggest stress-induced liver steatosis. This study offers an integrative molecular and biochemical analysis of the hepatic response to handling-stress, and reveals unknown aspects of lipid metabolism in a non-model teleost.http://journals.plos.org/plosone/article?id=10.1371/journal.pone.017644
Colección de especies vegetales de la provincia de Morona Santiago con potencial uso medicinal: aislamiento y caracterización quÃmica y biológica
Computational Simulations of a Mach 0.745 Transonic Truss-Braced Wing Design
A joint effort between the NASA Ames and Langley Research Centers was undertaken to analyze the Mach 0.745 variant of the Boeing Transonic Truss-Braced Wing (TTBW) Design. Two different flow solvers, LAVA and USM3D, were used to predict the TTBW flight performance. Sensitivity studies related to mesh resolution and numerical schemes were conducted to define best practices for this type of geometry and flow regime. Validation efforts compared the numerical simulation results of various modeling methods against experimental data taken from the NASA Ames 11-foot Unitary Wind Tunnel experimental data. The fidelity of the computational representation of the wind tunnel experiment, such as utilizing a porous wall boundary condition to model the ventilated test section, was varied to examine how different tunnel effects influence CFD predictions. LAVA and USM3D results both show an approximate 0.5 angle of attack shift from experimental lift curve data. This drove an investigation that revealed that the trailing edge of the experimental model was rounded in comparison to the CAD model, due to manufacturing tolerances, which had not been accounted for in the initial simulations of the experiment. Simulating the TTBW with an approximation of this rounded trailing-edge reduces error by approximately 60%. An accurate representation of the tested TTBW geometry, ideally including any wing twists and deflections experienced during the test under various loading conditions, will be necessary for proper validation of the CFD
Use of faeces as an alternative to inoculum of buffalo rumen contents in the in vitro gas production technique.
Incidence of debris discs around FGK stars in the solar neighbourhood
Debris discs are a consequence of the planet formation process and constitute
the fingerprints of planetesimal systems. Their solar system's counterparts are
the asteroid and Edgeworth-Kuiper belts. The aim of this paper is to provide
robust numbers for the incidence of debris discs around FGK stars in the solar
neighbourhood. The full sample of 177 FGK stars with d<20 pc proposed for the
DUNES survey is presented. Herschel/PACS observations at 100 and 160 micron
complemented with data at 70 micron, and at 250, 350 and 500 micron SPIRE
photometry, were obtained. The 123 objects observed by the DUNES collaboration
were presented in a previous paper. The remaining 54 stars, shared with the
DEBRIS consortium and observed by them, and the combined full sample are
studied in this paper. The incidence of debris discs per spectral type is
analysed and put into context together with other parameters of the sample,
like metallicity, rotation and activity, and age.
The subsample of 105 stars with d<15 pc containing 23 F, 33 G and 49 K stars,
is complete for F stars, almost complete for G stars and contains a substantial
number of K stars to draw solid conclusions on objects of this spectral type.
The incidence rates of debris discs per spectral type 0.26 (6 objects with
excesses out of 23 F stars), 0.21 (7 out of 33 G stars) and 0.20 (10 out of 49
K stars), the fraction for all three spectral types together being 0.22 (23 out
of 105 stars). Uncertainties corresponding to a 95% confidence level are given
in the text for all these numbers. The medians of the upper limits of
L_dust/L_* for each spectral type are 7.8E-7 (F), 1.4E-6 (G) and 2.2E-6 (K);
the lowest values being around 4.0E-7. The incidence of debris discs is similar
for active (young) and inactive (old) stars. The fractional luminosity tends to
drop with increasing age, as expected from collisional erosion of the debris
belts.Comment: 31 pages, 15 figures, 10 tables, 2 appendice
Quasienergy spectrum and tunneling current in ac-driven triple quantum dot shuttles
The dynamics of electrons in ac driven double quantum dots have been
extensively analyzed by means of Floquet theory. In these systems, coherent
destruction of tunneling has been shown to occur for certain ac field
parameters. In the present work we analyze, by means of Floquet theory, the
electron dynamics of a triple quantum dot in series attached to electric
contacts, where the central dot position oscillates. In particular, we analyze
the quasienergy spectrum of this ac driven nanoelectromechanical system, as a
function of the intensity and frequency of the ac field and of external dc
voltages. For strong driving fields, we derive, by means of perturbation
theory, analytical expressions for the quasienergies of the driven oscillator
system. From this analysis we discuss the conditions for coherent destruction
of tunneling (CDT) to occur as a function of detuning and field parameters. For
zero detuning, and from the invariance of the Floquet Hamiltonian under a
generalized parity transformation, we find analytical expressions describing
the symmetry properties of the Fourier components of the Floquet states under
such transformation. By using these expressions, we show that in the vicinity
of the CDT condition, the quasienergy spectrum exhibits exact crossings which
can be characterized by the parity properties of the corresponding
eigenvectors
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