4,636 research outputs found
Unified formalism for higher-order non-autonomous dynamical systems
This work is devoted to giving a geometric framework for describing
higher-order non-autonomous mechanical systems. The starting point is to extend
the Lagrangian-Hamiltonian unified formalism of Skinner and Rusk for these
kinds of systems, generalizing previous developments for higher-order
autonomous mechanical systems and first-order non-autonomous mechanical
systems. Then, we use this unified formulation to derive the standard
Lagrangian and Hamiltonian formalisms, including the Legendre-Ostrogradsky map
and the Euler-Lagrange and the Hamilton equations, both for regular and
singular systems. As applications of our model, two examples of regular and
singular physical systems are studied.Comment: 43 pp. We have corrected and clarified the statement of Propositions
2 and 3. A remark is added after Proposition
Hamilton-Jacobi theory in multisymplectic classical field theories
The geometric framework for the Hamilton-Jacobi theory developed in previous
works is extended for multisymplectic first-order classical field theories. The
Hamilton-Jacobi problem is stated for the Lagrangian and the Hamiltonian
formalisms of these theories as a particular case of a more general problem,
and the classical Hamilton-Jacobi equation for field theories is recovered from
this geometrical setting. Particular and complete solutions to these problems
are defined and characterized in several equivalent ways in both formalisms,
and the equivalence between them is proved. The use of distributions in jet
bundles that represent the solutions to the field equations is the fundamental
tool in this formulation. Some examples are analyzed and, in particular, the
Hamilton-Jacobi equation for non-autonomous mechanical systems is obtained as a
special case of our results.Comment: 44 p
Unified formalism for the generalized kth-order Hamilton-Jacobi problem
The geometric formulation of the Hamilton-Jacobi theory enables us to
generalize it to systems of higher-order ordinary differential equations. In
this work we introduce the unified Lagrangian-Hamiltonian formalism for the
geometric Hamilton-Jacobi theory on higher-order autonomous dynamical systems
described by regular Lagrangian functions.Comment: 9pp. Revised version: Minor corrections done. Second part of our
previous work arXiv:1309.2166. arXiv admin note: substantial text overlap
with arXiv:1309.216
El acoso psicológico en el trabajo o Mobbing: patología emergente
El objetivo de este artículo es resaltar la importancia del
acoso psicológico en el trabajo 'mobbing', es un problema
de salud pública considerado así por las Naciones Unidas
(ONU), tipificado por la Organización Internacional del
Trabajo (OIT) y es un delito en nuestro Código Penal
Español. La Directiva marco 89/391/CEE sobre salud y
seguridad en el trabajo, pretenden proteger la salud de los
trabajadores, constatando que había un 8 % de empleados de
la Unión Europea que sufrían acoso laboral o mobbing,
acordando trasponer a los ordenamientos internos medidas de
protección de la salud laboral e integridad de los trabajadores.
Analizaremos los perfiles más frecuentes tanto de la víctima
de l a coso como de l acosador. Así como, las graves
consecuencias del acoso o mobbing tanto a nivel psíquico,
como físico y social.The aim of this paper is to highlight the importance of
bullying in the workplace "mobbing" is a public health
problem considered so by the United Nations (UN), typified
by the International Labour Organization (OIT) and is a
crime in our Spanish Penal Code. The Framework Directive
89/391/EEC on health and safety at work, intended to protect
the health of workers, noting that there was an 8% of EU
employees who suffered harassment or mobbing, agreeing to
transpose into the domestic legal measures protection of
occupational health and integrity of workers. Frequently
examine the profiles of both the victim of harassment and the
harasser. And the serious consequences of mobbing both
psychic and physical and social
Sugar-based bicyclic monomers for aliphatic polyesters: a comparative appraisal of acetalized alditols and isosorbide
Three series of polyalkanoates (adipates, suberates and sebacates) were synthesized using as monomers three sugar-based bicyclic diols derived from D-glucose (Glux-diol and isosorbide) and D-mannose (Manx-diol). Polycondensations were conducted in the melt applying similar reaction conditions for all cases. The aim was to compare the three bicyclic diols regarding their suitability to render aliphatic polyesters with enhanced thermal and mechanical properties. The ensuing polyesters had molecular weights (Mw) in the 25,000–50,000 g mol-1 range with highest values being attained for Glux-diol. All the polyesters started to decompose above 300 °C and most of them did
not display perceivable crystallinity. On the contrary, they had glass transition temperatures much higher than usually found in homologous polyesters made of alkanediols, and showed a stress– strain behavior consistent with their Tg values. Glux-diol was particularly effective in increasing the Tg and to render therefore polyesters with high elastic modulus and considerable mechanical
strength.Peer ReviewedPostprint (published version
Triblock copolyesters derived from lactic acid and glucose: synthesis, nanoparticle formation and simulation
ABA triblock copolyesters were synthesized by ring-opening polymerization (ROP) of l-lactide in solution initiated by a telechelic d-glucose-based polyester macroinitiator. The macroinitiator with a number-average molecular weight about 2500 g mol-1 was synthesized by non-stoichiometric polycondensation in the melt of 2,4:3,5-di-O-methylene-d-glucitol and dimethyl succinate. Two triblock copolyesters of Mn ranging between ~6000 and ~9000 g mol-1, and differing in the length of the polylactide blocks were prepared. These copolyesters started to decompose when heated at ~220 °C and degraded slowly upon aqueous incubation under physiological conditions. They did not display any perceivable crystallinity and showed a single glass transition temperature (Tg) around 60 °C with the higher value corresponding to the larger content in glucitol units. The copolyesters were able to form nanoparticles with average diameters of ~100–130 nm and satisfactory dispersity. The effect of the block lengths on size, ¿-potential values and physical stability of the nanoparticles was evaluated. A molecular dynamics simulation study allowed modelling the two-phase structure of the nanoparticles and evidenced the preference of the glucose-based block to be peripherally located.Peer ReviewedPostprint (author's final draft
Lagrangian submanifolds and dynamics on Lie affgebroids
We introduce the notion of a symplectic Lie affgebroid and their Lagrangian
submanifolds in order to describe the Lagrangian (Hamiltonian) dynamics on a
Lie affgebroid in terms of this type of structures. Several examples are
discussed.Comment: 50 pages. Several sections update
Paciente autista en el ámbito odontológico: autoagresiones versus maltrato infantil
El paciente autista representa un reto en el ámbito odontológico. Las características propias de este trastorno les confieren
un apartado especial en el terreno del maltrato infantil. Saber hacer un diagnóstico diferencial entre lesiones autoinfringidas por el propio individuo o lesiones producidas por otra persona será el campo de batalla del odontólogo. Pero no solo el maltrato se refiere a la acción, también cobra especial relevancia la omisión o la negligencia tanto de personas como de instituciones que no velan por los derechos de estas personas.The autistic patient represents a challenge in the dental field. The characteristics of this disorder gives them a special
section in the field of child abuse. Knowing differential diagnosis between self inflicted injury by the individual or injuries caused by
another person will be the battlefield of the dentist. But not only abuse refers to the action, also has special relevance omission or
negligence of both people and institutions that do not ensure the rights of these people
Evolución de la producción y comercio mundial de Frutas en el Mundo
El análisis del consumo de fruta en el mundo obliga a estudiar su
producción y comercialización. Asia es el continente que produce de forma
creciente casi el 50% de la fruta mundial, importando y exportando volúmenes
similares, como consecuencia de un creciente consumo interno de fruta. América
produce un 21,4% de la fruta mundial, sin embargo exporta el 25% de su
producción, lo que refleja un reducido consumo interno, agravado en países pobres
donde el porcentaje de exportación supera el 70% de su producción. Europa
aporta el 16% de la producción mundial, exportando una cuarta parte, pero
importa más de la mitad de la fruta mundial, procedente de África y América. El
aumento del consumo interno, los atractivos precios de los productos importados,
las importaciones de contra estación y los canales de distribución fuertemente
establecidos, son causas que están provocando un nuevo orden económico mundial,
que puede que cambie la tendencia actual del comercio de frutas.Esta investigación ha sido financiada por el proyecto “Plan estratégico del sector agroalimentario de la Región de Murcia”, financiado por
la Consejería de Agricultura y Medio Ambiente de la Región de Murcia
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