Search results for "periodic"
showing 10 items of 769 documents
3,4-trans-4-Aryl-3-(1-pyridinio)-1,2,3,4-tetrahydropyridine-6-thiolates—new group of potential cardiotonic drugs
2005
Abstract 3,4- trans -4-Aryl-3-(1-pyridinio)-1,2,3,4-tetrahydropyridine-6-thiolates 6 – 11 were prepared by a Michael reaction of N -acetonylpyridinium chloride with 3-aryl-2-cyanothioacrylamides or by a one-pot three-carbon condensation of N -acetonylpyridinium chloride, aromatic aldehyde and 2-cyanothioacetamide, and their cardiotonic properties were studied. 3,4- trans -5-cyano-2-hydroxy-2-methyl-4-(3-nitrophenyl)-3-(1-pyridinio)-1,2,3,4-tetrahydropyridine-6-thiolate 8 was considered as a lead compound in this series since it in vitro experiments (spontaneously beating rat atria) showed a cardiotonic activity similar to that of milrinone 2 , however compound 8 induced activity at lover co…
Características y visibilidad de las revistas españolas de ciencias de la salud en bases de datos
2015
Se describen las características de 207 revistas españolas de ciencias de la salud activas en 2014 y su visibilidad en seis bases de datos biomédicas y multidisciplinares. Scopus e Ibecs son las bases de datos que mayor número de revistas cubren, y Medline y WoS las que menos. La disciplina mejor representada es medicina, seguida de psicología, enfermería y farmacia. Se observa la práctica ausencia de revistas editadas exclusivamente en papel, la existencia de revistas publicadas en inglés, el aumento de versiones bilingües español-inglés y el acceso gratuito a los contenidos. El artículo incorpora el censo de revistas, que puede servir de referencia para los investigadores para selecciona…
Periodic Solutions of the Second Order Quadratic Rational Difference Equation $$x_{n+1}=\frac{\alpha }{(1+x_n)x_{n-1}} $$ x n + 1 = α ( 1 + x n ) x n…
2016
The aim of this article is to investigate the periodic nature of solutions of a rational difference equation $$x_{n+1}=\frac{\alpha }{(1+x_n)x_{n-1}}. {(*)} $$ We explore Open Problem 3.3 given in Amleh et al. (Int J Differ Equ 3(1):1–35, 2008, [2]) that requires to determine all periodic solutions of the equation (*). We conclude that for the equation (*) there are no periodic solution with prime period 3 and 4. Period 7 is first period for which exists nonnegative parameter \(\alpha \) and nonnegative initial conditions.
Wedge filling and interface delocalization in finite Ising lattices with antisymmetric surface fields
2003
Theoretical predictions by Parry et al. for wetting phenomena in a wedge geometry are tested by Monte Carlo simulations. Simple cubic $L\ifmmode\times\else\texttimes\fi{}L\ifmmode\times\else\texttimes\fi{}{L}_{y}$ Ising lattices with nearest neighbor ferromagnetic exchange and four free $L\ifmmode\times\else\texttimes\fi{}{L}_{y}$ surfaces, at which antisymmetric surface fields $\ifmmode\pm\else\textpm\fi{}{H}_{s}$ act, are studied for a wide range of linear dimensions $(4l~Ll~320,30l~{L}_{y}l~1000),$ in an attempt to clarify finite size effects on the wedge filling transition in this ``double-wedge'' geometry. Interpreting the Ising model as a lattice gas, the problem is equivalent to a li…
Variations on a Theorem of Fine & Wilf
2001
In 1965, Fine & Wilf proved the following theorem: if (fn)n≥0 and (gn)n≥0 are periodic sequences of real numbers, of periods h and k respectively, and fn = gn for 0 ≤ n ≤ h+k-gcd(h, k), then fn = gn for all n ≥ 0. Furthermore, the constant h + k - gcd(h, k) is best possible. In this paper we consider some variations on this theorem. In particular, we study the case where fn ≤ gn instead of fn = gn. We also obtain a generalization to more than two periods.
Periodic Orbits in the Isosceles Three-Body Problem
1991
The Saturn’s satellites Janus and Epimetheus are the first known bodies in the Solar System that has horseshoe orbits in a frame that rotates with uniform angular velocity. Both satellites have similar masses and orbital elements when they are far from one another. Moreover, their orbits are nearly symmetric. In fact, in the past, they have been identify as a unique satellite and afterwards, some mathematical theories about their orbits has been necessaries to understand why they do not collide. In particular, the interest in planar three-body problem with two small masses has increased6. We assume that the two small masses have similar symmetric initial conditions. The aim of this paper is…
4-(3-Hydroxy-4-methoxyphenyl)-3-(3,4,5-trimethoxyphenyl)-2,5-dihydro-1H-pyrrole-2,5-dione
2005
The title compound, C20H19NO7, crystallizes in the space group Pna21. X-ray analysis shows the compound has the desired 3′-hydroxy and 4′-methoxy substitution pattern, as in the natural template combretastatin A-4.
Dynamics of two competing species in the presence of Lévy noise sources
2010
We consider a Lotka-Volterra system of two competing species subject to multiplicative alpha-stable Lévy noise. The interaction parameter between the species is a random process which obeys a stochastic differential equation with a generalized bistable potential in the presence both of a periodic driving term and an additive alpha-stable Lévy noise. We study the species dynamics, which is characterized by two different regimes, exclusion of one species and coexistence of both. We find quasi-periodic oscillations and stochastic resonance phenomenon in the dynamics of the competing species, analysing the role of the Lévy noise sources.
Invariance of electrophilicity of independent fragments. Application to intramolecular diels-alder reactions
2010
Abstract We herein demonstrate that the global electrophilicity may be distributed into fragments within a single molecule by using an empirical partitioning scheme of the electronic chemical potential framed on the chemical potential inequality principle. Group electrophilicity for several fragments may thereby be defined. Their values show a remarkable stability, independent of the chemical environment they are attached to. The model is applied to asses the chemical reactivity of a series of fragments involved in intramolecular Diels–Alder reactions.
Continuing Education in the Health Sciences in Spain
2008
<div class="ftSection"><span class="ftInlineSubsectionTitle">Background:</span><p>Employers have long been concerned about the professional qualifications of their employees. Decision makers in the health sciences are no exception, particularly now that they are seriously considering the improvement and full accreditation of continuing education as part of the planned European convergence.</p></div><div class="ftSection"><span class="ftInlineSubsectionTitle">Method:</span><p>Medical and nursing professionals were questioned about their views on continuing education, suitable content of possible programs, and implementation, in comp…