dc motion of ac driven sine-Gordon solitons

We investigate the dependence of dc soliton motion sustained by pure ac driving in the sine-Gordon model on various parameter problems, such as frequency, initial kink velocity or relative phase. We show by means of the collective coordinate formalism that ac driving induces a net dc velocity whose modulus and direction depend on the driving phase and on the kink initial velocity. Numerical simulations of the full sine-Gordon equation confirm the correctness and accuracy of this prediction. Nontrivial cases when dc soliton motion is transformed into oscillation as well as the effects of damping are analyzed. Our results generalize previous work on the undamped problem, and clarify a long standing issue about the existence and characteristics of this phenomenon in damped problems, whose possible appearance in other systems is also discussed.CICyT (Spain) grant MAT95-0325DGES (Spain) grant PB96-011

The role of gas infall in the evolution of disc galaxies

Spiral galaxies are thought to acquire their gas through a protracted infall phase resulting in the inside-out growth of their associated discs. For field spirals, this infall occurs in the lower density environments of the cosmic web. The overall infall rate, as well as the galactocentric radius at which this infall is incorporated into the star-forming disc, plays a pivotal role in shaping the characteristics observed today. Indeed, characterising the functional form of this spatio-temporal infall in-situ is exceedingly difficult, and one is forced to constrain these forms using the present day state of galaxies with model or simulation predictions. We present the infall rates used as input to a grid of chemical evolution models spanning the mass spectrum of discs observed today. We provide a systematic comparison with alternate analytical infall schemes in the literature, including a first comparison with cosmological simulations. Identifying the degeneracies associated with the adopted infall rate prescriptions in galaxy models is an important step in the development of a consistent picture of disc galaxy formation and evolution.Comment: 12 pages, 12 figures, MNRAS, accepte

Synthesis and biological activity of a new class of antitumor cyclopeptides based on the solomonamides

Solomonamides A (1) and B (2) are novel natural products recently isolated from the marine sponge Theonella swinhoei [1]. Preliminary structural studies revealed an unprecedented cyclic peptide type structure. Interestingly, solomonamide A exhibits anti-inflammatory activity, showing potent reduction (60%) of inflammation at a very low concentration of 100 µg/kg in animal models. However, the scarcity of these compounds from their natural sources has been a drawback for further pharmacological assays. In fact, the anti-inflammatory activity of solomonamide B was not evaluated due to the limited amounts. This difficulty to access large amounts of these compounds makes quite difficult to gain insight into their biological profiles and mechanism of action and justifies the chemical synthesis of this new class of cyclic peptides. As a consequence, the solomonamides have been the subject of several synthetic efforts [2] notably by the Reddy group who has recently reported the first total synthesis of solomonamide B based on a intramolecular Heck reaction, which led to a revision of the initially proposed structure for 2 [3].Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Antitumor and antiangiogenic potential of solomonamide synthesis intermediates

Es comunicación (formato panel) a congreso internacionalIn this work we developed a new synthetic strategy towards the solomonamides. a novel class of cyclopeptides of marine origin. The described synthetic approach utilized an olefin metathesis reaction to form the [15]-membered ring contained in these natural products. During the synthetic process, a diverse set of analogues was generated and we evaluated their potential antitumor activity in vitro. For this purpose we performed in vitro proliferation assays, determining the IC50 values of the compounds in a panel of tumor cell lines. In addition, we evaluated the possible antiangiogenic effects of these solomonamide analogues by using in vitro endothelial cell differentiation assays. Our results showed that the potential antitumor and antiangiogenic activity of the studied analogues depended on their chemical structure, suggesting that the presence of specific functional groups could be responsible of their biological activity. Further studies are needed to understand the basis of the observed activities in endothelial and tumor cells.Our experimental work is supported by grants BIO2014-56092-R (MINECO and FEDER) and P12-CTS-1507 (Andalusian Government and FEDER) and funds from group BIO-267 (Andalusian Government). The "CIBER de Enfermedades Raras" is an initiative from the ISCIII (Spain). This communicaction has the support of a travel grant "Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The role of gas infall in the evolution of disc galaxies

Spiral galaxies are thought to acquire their gas through a protracted infall phase resulting in the inside-out growth of their associated discs. For field spirals, this infall occurs in the lower density environments of the cosmic web. The overall infall rate, as well as the galactocentric radius at which this infall is incorporated into the star-forming disc, plays a pivotal role in shaping the characteristics observed today. Indeed, characterising the functional form of this spatio-temporal infall in-situ is exceedingly difficult, and one is forced to constrain these forms using the present day state of galaxies with model or simulation predictions. We present the infall rates used as input to a grid of chemical evolution models spanning the mass spectrum of discs observed today. We provide a systematic comparison with alternate analytical infall schemes in the literature, including a first comparison with cosmological simulations. Identifying the degeneracies associated with the adopted infall rate prescriptions in galaxy models is an important step in the development of a consistent picture of disc galaxy formation and evolution

Interactions and star formation activity in Wolf-Rayet galaxies

We present the main results of the PhD Thesis carried out by L\'opez-S\'anchez (2006), in which a detailed morphological, photometrical and spectroscopical analysis of a sample of 20 Wolf-Rayet (WR) galaxies was realized. The main aims are the study of the star formation and O and WR stellar populations in these galaxies and the role that interactions between low surface companion objects have in the triggering of the bursts. We analyze the morphology, stellar populations, physical conditions, chemical abundances and kinematics of the ionized gas, as well as the star-formation activity of each system.Comment: 16 pages, 15 figure

Control difuso de la tasa de transferencia de extremo a extremo en protocolos de transporte de Internet

La dinámica del tráfico de extremo a extremo en Internet es un problema complejo para el cual los modelos disponibles son, en el mejor de los casos incompletos. Esta comunicación describe nuevos mecanismos para regulación de la tasa de transferencia de extremo a extremo en la capa de transporte por medio de sistemas difusos. Se describen una generalización basada en lógica difusa de los mecanismos de control de flujo y congestión de TCP (Transport Control Protocol), el diseño de un regulador difuso basado en mecanismo de ventana para TCP, así como la metodología de diseño empleada para simular e implementar de manera experimental el sistema. Se resume un estudio comparativo del regulador difuso presentado frente a los mecanismos tradicionales. El regulador difuso resulta útil como enfoque de modelado y proporciona significativas mejoras de prestaciones respecto a un conjunto de criterios.Ministerio de Educación y Ciencia TEC2005-04359/MICJunta de Amdalucía TIC2006-63

Dense circum-nuclear molecular gas in starburst galaxies

We present results from a study of the dense circum-nuclear molecular gas of starburst galaxies. The study aims to investigate the interplay between starbursts, active galactic nuclei and molecular gas. We characterise the dense gas traced by HCN, HCO$^{+}$ and HNC and examine its kinematics in the circum-nuclear regions of nine starburst galaxies observed with the Australia Telescope Compact Array. We detect HCN (1$-$0) and HCO$^{+}$ (1$-$0) in seven of the nine galaxies and HNC (1$-$0) in four. Approximately 7 arcsec resolution maps of the circum-nuclear molecular gas are presented. The velocity integrated intensity ratios, HCO$^{+}$ (1$-$0)/HCN (1$-$0) and HNC (1$-$0)/HCN (1$-$0), are calculated. Using these integrated intensity ratios and spatial intensity ratio maps we identify photon dominated regions (PDRs) in NGC 1097, NGC 1365 and NGC 1808. We find no galaxy which shows the PDR signature in only one part of the observed nuclear region. We also observe unusually strong HNC emission in NGC 5236, but it is not strong enough to be consistent with X-ray dominated region (XDR) chemistry. Rotation curves are derived for five of the galaxies and dynamical mass estimates of the inner regions of three of the galaxies are made.Comment: Accepted for publication in MNRAS, 22 December 2015. Main manuscript is 13 pages, containing 3 figures. Also has 4 appendices of 13 pages total containing numerous figures and details of calculation