An \emph{ab initio} method for locating characteristic potential energy minima of liquids

It is possible in principle to probe the many--atom potential surface using density functional theory (DFT). This will allow us to apply DFT to the Hamiltonian formulation of atomic motion in monatomic liquids [\textit{Phys. Rev. E} {\bf 56}, 4179 (1997)]. For a monatomic system, analysis of the potential surface is facilitated by the random and symmetric classification of potential energy valleys. Since the random valleys are numerically dominant and uniform in their macroscopic potential properties, only a few quenches are necessary to establish these properties. Here we describe an efficient technique for doing this. Quenches are done from easily generated "stochastic" configurations, in which the nuclei are distributed uniformly within a constraint limiting the closeness of approach. For metallic Na with atomic pair potential interactions, it is shown that quenches from stochastic configurations and quenches from equilibrium liquid Molecular Dynamics (MD) configurations produce statistically identical distributions of the structural potential energy. Again for metallic Na, it is shown that DFT quenches from stochastic configurations provide the parameters which calibrate the Hamiltonian. A statistical mechanical analysis shows how the underlying potential properties can be extracted from the distributions found in quenches from stochastic configurations

On a fourth order nonlinear Helmholtz equation

In this paper, we study the mixed dispersion fourth order nonlinear Helmholtz equation $\Delta^2 u -\beta \Delta u + \alpha u= \Gamma|u|^{p-2} u$ in $\mathbb R^N$ for positive, bounded and $\mathbb Z^N$-periodic functions $\Gamma$. Using the dual method of Evequoz and Weth, we find solutions to this equation and establish some of their qualitative properties

Tritonia nilsodhneri marcus Ev., 1983 (Gastropoda, heterobranchia, tritoniidae): First records for the adriatic sea and new data on ecology and distribution of mediterranean populations

The nudibranch Tritonia nilsodhneri, usually feeding on a variety of gorgoniacean species, is known from different localities of the eastern Atlantic Ocean and the Mediterranean Sea. Knowledge of the host preferences of the Mediterranean populations is still scarce. Few records of this nudibranch have been reported from the eastern Mediterranean basin. With this report, the occurrence of T. nilsodhneri within the Mediterranean basin is extended to the Adriatic Sea. Furthermore, the list of the host species associated to the Mediterranean populations for feeding habits is increased from two up to five. Mediterranean specimens of T. nilsodhneri were observed for the first time feeding and spawning on Leptogorgia sarmentosa, Eunicella cavolini and E. labiata. Finally, these last two Gorgoniidae species are also reported here as a new host species for T. nilsodhneri

Microwave-assisted vacuum synthesis of tio2 nanocrystalline powders in one-pot, one-step procedure

A new method for fast and simple synthesis of crystalline TiO2 nanoparticles with photocat-alytic activity was developed by carrying out a classic sol–gel reaction directly under vacuum. The use of microwaves for fast heating of the reaction medium further reduces synthesis times. When the solvent is completely removed by vacuum, the product is obtained in the form of a powder that can be easily redispersed in water to yield a stable nanoparticle suspension, exhibiting a comparable photocatalytic activity with respect to a commercial product. The present methodology can, therefore, be considered a process intensification procedure for the production of nanotitania

Testing the nature of S0 galaxies using planetary nebula kinematics in NGC 1023

We investigate the manner in which lenticular galaxies are formed by studying their stellar kinematics: an S0 formed from a fading spiral galaxy should display similar cold outer disc kinematics to its progenitor, while an S0 formed in a minor merger should be more dominated by random motions. In a pilot study to attempt to distinguish between these scenarios, we have measured the planetary nebula (PN) kinematics of the nearby S0 system NGC 1023. Using the Planetary Nebula Spectrograph, we have detected and measured the line-of-sight velocities of 204 candidate PNe in the field of this galaxy. Out to intermediate radii, the system displays the kinematics of a normal rotationally-supported disc system. After correction of its rotational velocities for asymmetric drift, the galaxy lies just below the spiral galaxy Tully-Fisher relation, as one would expect for a fading system. However, at larger radii the kinematics undergo a gradual but major transition to random motion with little rotation. This transition does not seem to reflect a change in the viewing geometry or the presence of a distinct halo component, since the number counts of PNe follow the same simple exponential decline as the stellar continuum with the same projected disc ellipticity out to large radii. The galaxy's small companion, NGC 1023A, does not seem to be large enough to have caused the observed modification either. This combination of properties would seem to indicate a complex evolutionary history in either the transition to form an S0 or in the past life of the spiral galaxy from which the S0 formed. More data sets of this type from both spirals and S0s are needed in order to definitively determine the relationship between these types of system.Comment: Accepted for publication in MNRAS. Version with full resolution figure 1 can be found at http://www.nottingham.ac.uk/~ppzmrm/N1023_PNS.accepted.pd

Examining the role of individual movement in promoting coexistence in a spatially explicit prisoner's dilemma

AEFB gratefully acknowledges the support of an EPSRC CASE PhD studentship.The emergence of cooperation is a major conundrum of evolutionary biology. To unravel this evolutionary riddle, several models have been developed within the theoretical framework of spatial game theory, focussing on the interactions between two general classes of player, "cooperators" and "defectors". Generally, explicit movement in the spatial domain is not considered in these models, with strategies moving via imitation or through colonisation of neighbouring sites. We present here a spatially explicit stochastic individual-based model in which pure cooperators and defectors undergo random motion via diffusion and also chemotaxis guided by the gradient of a semiochemical. Individual movement rules are derived from an underlying system of reaction-diffusion-taxis partial differential equations which describes the dynamics of the local number of individuals and the concentration of the semiochemical. Local interactions are governed by the payoff matrix of the classical prisoner's dilemma, and accumulated payoffs are translated into offspring. We investigate the cases of both synchronous and non-synchronous generations. Focussing on an ecological scenario where defectors are parasitic on cooperators, we find that random motion and semiochemical sensing bring about self-generated patterns in which resident cooperators and parasitic defectors can coexist in proportions that fluctuate about non-zero values. Remarkably, coexistence emerges as a genuine consequence of the natural tendency of cooperators to aggregate into clusters, without the need for them to find physical shelter or outrun the parasitic defectors. This provides further evidence that spatial clustering enhances the benefits of mutual cooperation and plays a crucial role in preserving cooperative behaviours.PostprintPeer reviewe

Dark-Matter Content of Early-Type Galaxies with Planetary Nebulae

We examine the dark matter properties of nearby early-type galaxies using planetary nebulae (PNe) as mass probes. We have designed a specialised instrument, the Planetary Nebula Spectrograph (PN.S) operating at the William Herschel telescope, with the purpose of measuring PN velocities with best efficiency. The primary scientific objective of this custom-built instrument is the study of the PN kinematics in 12 ordinary round galaxies. Preliminary results showing a dearth of dark matter in ordinary galaxies (Romanowsky et al. 2003) are now confirmed by the first complete PN.S datasets. On the other hand early-type galaxies with a "regular" dark matter content are starting to be observed among the brighter PN.S target sample, thus confirming a correlation between the global dark-to-luminous mass virial ratio (f_DM=M_DM/M_star) and the galaxy luminosity and mass.Comment: 5 pages, 2 figures. To appear in the proceedings of the IAU Symposium 244 "Dark Galaxies and Lost Baryons", Cardiff 25-29 June 2007, eds. J.I. Davies & M.J. Disne

Adjoint bi-continuous semigroups and semigroups on the space of measures

For a given bi-continuous semigroup T on a Banach space X we define its adjoint on an appropriate closed subspace X^o of the norm dual X'. Under some abstract conditions this adjoint semigroup is again bi-continuous with respect to the weak topology (X^o,X). An application is the following: For K a Polish space we consider operator semigroups on the space C(K) of bounded, continuous functions (endowed with the compact-open topology) and on the space M(K) of bounded Baire measures (endowed with the weak*-topology). We show that bi-continuous semigroups on M(K) are precisely those that are adjoints of a bi-continuous semigroups on C(K). We also prove that the class of bi-continuous semigroups on C(K) with respect to the compact-open topology coincides with the class of equicontinuous semigroups with respect to the strict topology. In general, if K is not Polish space this is not the case

Algoritmos de derivación y confirmación diagnóstica de citología cervical atípica: desafíos para la actualización

Indexación: ScieloEl Programa Nacional de Pesquisa y Control del Cáncer Cervicouterino de Chile ha contribuido al descenso sostenido de la mortalidad por cáncer de cuello uterino. Para la reducción de esta mortalidad ha sido fundamental la citología exfoliativa del cérvix, la que no está exenta de resultados inciertos. En este sentido, los frotis clasificados como atípicos se consideran ambiguos por la presencia de anomalías celulares de difícil determinación, lo que se traduce en un diagnóstico de probabilidad incierta. En la literatura nacional como internacional, se manifiesta un notorio interés por unificar la nomenclatura citológica cervical y los algoritmos de derivación y confirmación diagnóstica, para el manejo clínico de las mujeres con anomalías citológicas cervicales y lesiones precursoras de cáncer cervicouterino. Por lo anterior, se considera relevante los estudios que proporcionen evidencia clínica epidemiológica actualizada, que permitan optimizar el cumplimiento del Programa Nacional de Cáncer Cervicouterino, conducentes al logro de los Objetivos Sanitarios del período 2011-2020.The National Research and Control of Cervical Cancer in Chile had contributed to the sustained decline in mortality from cervical cancer. The exfoliative cytology of the cervix has been to reduce this mortality, which is not without uncertain results. The smears classified as atypical are considered ambiguous by the presence of cellular abnormalities difficult to determine, resulting in a diagnosis of uncertain probability. The literature, both nationally and internationally, is widespread interest to unify the nomenclature cervical cytology and the support of the derivation algorithms for the clinical management of women with cytologic abnormalities cervical and cervical cancer precursor lesions. Therefore, it is relevant to perform studies the provide updated epidemiological clinical evidence, to optimize the performance of the National Program for the achievement of health objectives for the period 2011-2020.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-75262012000400015&nrm=is

Resistenza a fatica dell’acciaio 1.5%Cr-0.2%Mo-0.2%C sinterizzato e sottoposto a nitrurazione in plasma: effetto della frazione di sezione utile resistente

In questo lavoro è stata studiata la resistenza a fatica per flessione alternata di un acciaio sinterizzatocontenente 1.5%Cr, 0.2%Mo e 0.2%C nitrurato in plasma. Il materiale è stato prodotto variando la pressione dicompattazione e la temperatura di sinterizzazione per ottenere diversi valori della frazione di sezione utileresistente. L’indurimento superficiale e lo stato di tensione residua di compressione nello strato di diffusionepromuovono la nucleazione della cricca di fatica negli strati sub superficiali rendendo il comportamento afatica meno sensibile alla porosità superficiale (tendenzialmente maggiore rispetto alla porosità media) efortemente dipendente dalla frazione di sezione utile resistente