Melting behavior of large disordered sodium clusters

The melting-like transition in disordered sodium clusters Na_N, with N=92 and 142 is studied by using a first-principles constant-energy molecular dynamics simulation method. Na_142, whose atoms are distributed in two (surface and inner) main shells with different radial distances to the center of mass of the cluster, melts in two steps: the first one, at approx. 130 K, is characterized by a high intrashell mobility of the atoms, and the second, homogeneous melting, at approx. 270 K, involves diffusive motion of all the atoms across the whole cluster volume (both intrashell and intershell displacements are allowed). On the contrary, the melting of Na_92 proceeds gradually over a very wide temperature interval, without any abrupt step visible in the thermal or structural melting indicators. The occurrence of well defined steps in the melting transition is then shown to be related to the existence of a distribution of the atoms in shells. Thereby we propose a necessary condition for a cluster to be considered rigorously amorphouslike (totally disordered), namely that there are no space regions of the cluster where the local value of the atomic density is considerably reduced. Na_92 is the only cluster from the two considered that verifies this condition, so its thermal behavior can be considered as representative of that expected for amorphous clusters. Na_142, on the other hand, has a discernible atomic shell structure and should be considered instead as just partially disordered. The thermal behavior of these two clusters is also compared to that of icosahedral (totally ordered) sodium clusters of the same sizes.Comment: LaTeX file. 7 pages with 12 picture

Qué papel juega el hongo Phytophthora cinnamomi en el desarrollo de la regeneración natural y repoblaciones de encina y alcornoque

Se presentan los resultados resumidos de tres trabajos realizados para conocer el papel que juega el hongo Phytophthora cinnamomi en el desarrollo de plántulas de encina (Quercus ilex) y alcornoque (Quercus suber). Se realizaron dos prospecciones para detectar la presencia de P.cinnamomi en focos de seca en dehesas de encina y alcornoque de Extremadura en 1991-1992 y 1999-2000. El porcentaje de focos en los que se detectó la presencia de P. cinnamomi ha permanecido relativamente estable entre las dos prospecciones. También se determinó la tasa de crecimiento relativo para nueve aislados de P. cinnamomi a diferentes temperaturas, observando una elevada variabilidad tanto en la temperatura óptima de crecimiento como en el valor de la propia tasa diaria de crecimiento máxima. También se estudió la emergencia y supervivencia de plántulas de encina y alcornoque procedentes de dos dehesas ecológicamente diferentes, cultivadas en condiciones controladas en suelos de estas dehesas infectados naturalmente con P. cinnamomi y en estos mismos suelos previamente desinfectados en autoclave. Un factor limitante en los procesos de regeneración natural y en las repoblaciones por siembra directa de encinas y alcornoque puede ser su alta susceptibilidad a las infecciones por P. cinnamomi.Por último, se estudió durante dos años consecutivos, la supervivencia de las plantas de encina de una repoblación sobre un suelo naturalmente infectado con P. cinnamomi en la provincia de Badajoz (SO de España). Los resultados obtenidos se discuten teniendo en cuenta el déficit hídrico, los daños por P. cinnamomi, la competencia con otras especies y las posibles medidas sanitarias que amortigüen los daños en las repoblaciones con encinas._______________________________Three different studies were performed with the aim to determine the role of Phytophthora cinnamomi in the early development of seedlings of holm oak (Quercus ilex) and cork oak (Quercus suber). Two surveys, for the presence of Phytophthora cinnamomi in declining holm oak and cork oak stands in Extremadura (SW Spain) were performed in 1991-1992 and 1999-2000. The percentage of decline foci where P. cinnamomi is envolved has remained relatively stable in the lapse of time between the two surveys. Growth rates were determined for 9 P. cinnamomi isolates. Considerable variation in optimum growth temperatures and in daily growth rates occurred among isolates. The emergence and survival of pregerminated holm oak and cork oak acorns from two ecologically different dehesas (Mediterranean open woodlands) were studied in two soils from these stands naturally infected with P. cinnamomi, and in the same soils previously sterilized in the autoclave. The demonstrated high susceptibility of holm and cork oak young seedlings to P. cinnamomi could be a limiting factor in mediterranean opend woodlands (dehesas) not only in natural regenerationprocesses but also when reforestation by direct sowing is implemented. Finally, the viability of 1 year old holm oak seedlings in a soil naturally infected with P. cinnamomi was studied during two consecutive years in a plot located in SW Spain. Results obtained are discussed in the framework of seasonal water deficit, P. cinnamomi damage, weed competition and sanitation thechniques to be used in declined holm oak stands in Spain

Comparative Genomics of Peroxisome Biogenesis Proteins:Making Sense of the PEX Proteins

PEX genes encode proteins involved in peroxisome biogenesis and proliferation. Using a comparative genomics approach, we clarify the evolutionary relationships between the 37 known PEX proteins in a representative set of eukaryotes, including all common model organisms, pathogenic unicellular eukaryotes and human. A large number of previously unknown PEX orthologs were identified. We analyzed all PEX proteins, their conservation and domain architecture and defined the core set of PEX proteins that is required to make a peroxisome. The molecular processes in peroxisome biogenesis in different organisms were put into context, showing that peroxisomes are not static organelles in eukaryotic evolution. Organisms that lack peroxisomes still contain a few PEX proteins, which probably play a role in alternative processes. Finally, the relationships between PEX proteins of two large families, the Pex11 and Pex23 families, were analyzed, thereby contributing to the understanding of their complicated and sometimes incorrect nomenclature. We provide an exhaustive overview of this important eukaryotic organelle

Vesicle fusion as a target process for the action of sphingosine and its derived drugs

The fusion of membranes is a central part of the physiological processes involving the intracellular transport and maturation of vesicles and the final release of their contents, such as neurotransmitters and hormones, by exocytosis. Traditionally, in this process, proteins, such SNAREs have been considered the essential components of the fusion molecular machinery, while lipids have been seen as merely structural elements. Nevertheless, sphingosine, an intracellular signalling lipid, greatly increases the release of neurotransmitters in neuronal and neuroendocrine cells, affecting the exocytotic fusion mode through the direct interaction with SNAREs. Moreover, recent studies suggest that FTY-720 (Fingolimod), a sphingosine structural analogue used in the treatment of multiple sclerosis, simulates sphingosine in the promotion of exocytosis. Furthermore, this drug also induces the intracellular fusion of organelles such as dense vesicles and mitochondria causing cell death in neuroendocrine cells. Therefore, the effect of sphingosine and synthetic derivatives on the heterologous and homologous fusion of organelles can be considered as a new mechanism of action of sphingolipids influencing important physiological processes, which could underlie therapeutic uses of sphingosine derived lipids in the treatment of neurodegenerative disorders and cancers of neuronal origin such neuroblastoma

Relationship between the offlap-break location of Holocene prograding wedges on wave climate in southeastern Iberian Peninsula

Wave climate exerts a significant influence on the development of Holocene sedimentary prograding wedges. This is demonstrated by the fact that near-bed orbital velocities between 0.10 and 0.14 m/s (threshold for resuspension) occur in the vicinity of the infralittoral prograding wedges (IPW) offlap-breaks during storm-weather conditions, but during medium wave energy conditions in the case of prodeltaic wedges

The role of late Quaternary tectonic activity and sea-level changes on sedimentary processes interaction in the Gulf of Cadiz upper and middle continental slope (SW Iberia)

A morphological and seismic-stratigraphic analysis of the Gulf of Cadiz area near the Strait of Gibraltar is presented in this work, focused on the sedimentary evolution of the upper and proximal middle-continental slope since the Mid-Pleistocene. Based on the analysis of seismic reflection profiles and swath bathymetry data, this work analyses the close influence of the activity of buried and outcropping diapiric ridges and late Quaternary sea-level changes on the evolution of contouritic features related to the Mediterranean Outflow Water (MOW) and Eastern North Atlantic Central Water (ENACW), gravitational features and fluid-escape structures. The stratigraphic architecture reveals that, under active diapiric deformation, the upper slope plastered drift grew during low sea-level stages, when sediment supply was high and the ENACW swept the upper slope, contrasting with the present-day highstand situation dominated by northwest-trending MOW flow. The south-estward ENACW flow forced asymmetry and lateral migration of gullies incised in the plastered drift. Two evolutionary stages have been established: 1) After the Mid Pleistocene, activity of diapirs with a NE trend determined the location of the deepest depressions which were infilled by plastered contouritic drifts; 2) Between Late Quaternary and present, a drastic change of buried diapirs growth pattern and orientation to a NW trend enhanced slope-derived gravitational processes affecting the bottom current dynamics. Adjustments to tectonic changes led to a phase of plastered drift growth on the upper slope during which depocenters varied their distribution and orientation. In a long-term the structural control on sedimentation shows a northwestward displacement of deformation, resulting in an overall extension of the contourite depositional system to the NW. In a short-term, sea-level changes favored drift deposition, gullies incision and the strengthening of water masses. This work evidences the importance of tectonic deformation in sedimentation at recent time scales, and the twodirectional interplay between recent tectonic activity and bottom current dynamics.Versión del edito

Opinions and Practices of Lung Cancer Screening by Physician Specialty

BACKGROUND In response to the National Lung Screening Trial, numerous professional organizations published guidelines recommending annual lung cancer screening with low-dose computed tomography (LDCT) for high-risk patients. Prior studies found that physician attitudes and knowledge about lung cancer screening directly impacts the number of screening exams ordered.METHODS In 2015, we surveyed 34 pulmonologists and 186 primary care providers (PCPs) to evaluate opinions and practices of lung cancer screening in a large academic medical center. We compared PCP and pulmonologist responses using t-tests and χ2 tests.RESULTS The overall survey response rate was 40% (39% for PCPs and 50% for pulmonologists). Pulmonologists were more likely than PCPs to report lung cancer screening as beneficial for patients (88.2% versus 37.7%, P < .0001) and as being cost-effective (47.1% versus 14.3%, P = .02). More pulmonologists (76%) reported ordering a LDCT for screening in the past 12 months compared to PCPs (41%, P = .012). Pulmonologists and PCPs reported similar barriers to referring patients for lung cancer screening, including patient costs (82.4% versus 77.8%), potential for emotional harm (58.8% versus 58.3%), high false positive rate (47.1% versus 69.4%), and likelihood for medical complications (47.1% versus 59.7%).LIMITATIONS Our results are generalizable to academic medical centers and responses may be susceptible to recall bias, non-response bias, and social desirability bias.CONCLUSION We found significant differences in opinions and practices between PCPs and pulmonologists regarding lung cancer screening referrals and perceived benefits. As lung cancer screening continues to emerge in clinical practice, it is important to understand these differences across provider specialty to ensure screening is implemented and offered to patients appropriately

Shapes of the 192,190^{192,190}Pb ground states from beta decay studies using the total absorption technique

The beta decay of $^{192,190}$Pb has been studied using the total absorption technique at the ISOLDE(CERN) facility. The beta-decay strength deduced from the measurements, combined with QRPA theoretical calculations, allow us to infer that the ground states of the $^{192,190}$Pb isotopes are spherical. These results represent the first application of the shape determination method using the total absorption technique for heavy nuclei and in a region where there is considerable interest in nuclear shapes and shape effects