Trajectory-dependent energy loss for swift He atoms axially scattered off a silver surface

Angle- and energy-loss- resolved distributions of helium atoms grazingly scattered from a Ag(110) surface along low indexed crystallographic directions are investigated considering impact energies in the few keV range. Final projectile distributions are evaluated within a semi-classical formalism that includes dissipative effects due to electron-hole excitations through a friction force. For mono-energetic beams impinging along the $[1\bar{1}0]$, $[1\bar{1}2]$ and $[1\bar{1}0]$ directions, the model predicts the presence of multiple peak structures in energy-loss spectra. Such structures provide detailed information about the trajectory-dependent energy loss. However, when the experimental dispersion of the incident beam is taken into account, these energy-loss peaks are completely washed out, giving rise to a smooth energy-loss distribution, in fairly good agreement with available experimental data

Activation of the Plasmodium egress effector subtilisin-like protease 1 is mediated by plasmepsin X destruction of the prodomain

Following each round of replication, daughter merozoites of the malaria parasite Plasmodium falciparum escape (egress) from the infected host red blood cell (RBC) by rupturing the parasitophorous vacuole membrane (PVM) and the RBC membrane (RBCM). A proteolytic cascade orchestrated by a parasite serine protease, subtilisin-like protease 1 (SUB1), regulates the membrane breakdown. SUB1 activation involves primary autoprocessing of the 82-kDa zymogen to a 54-kDa (p54) intermediate that remains bound to its inhibitory propiece (p31) postcleavage. A second processing step converts p54 to the terminal 47-kDa (p47) form of SUB1. Although the aspartic protease plasmepsin X (PM X) has been implicated in the activation of SUB1, the mechanism remains unknown. Here, we show that upon knockdown of PM X, the inhibitory p31-p54 complex of SUB1 accumulates in the parasites. Using recombinant PM X and SUB1, we show that PM X can directly cleave both p31 and p54. We have mapped the cleavage sites on recombinant p31. Furthermore, we demonstrate that the conversion of p54 to p47 can be effected by cleavage at either SUB1 or PM X cleavage sites that are adjacent to one another. Importantly, once the p31 is removed, p54 is fully functional inside the parasites, suggesting that the conversion to p47 is dispensable for SUB1 activity. Relief of propiece inhibition via a heterologous protease is a novel mechanism for subtilisin activation

Sistema georreferenciado de indicadores de calidad de suelos para los llanos orientales de colombia estudio de caso: municipio de puerto lópez, meta

Geosoil permite almacenar, consultar e interpretar información tanto del suelo como de su entorno biofísico a diferentes escalas: parcela, finca, comunidad, municipio, departamento, región, país. Opera a partir de una base de datos relacional elaborada en ACCES 2000, compuesta por una serie de tablas principales estructuradas con información a diferentes niveles jerárquicos que permiten la caracterización de las propiedades del suelo. Los elementos morfológicos y analíticos del suelo se combinan para conformar indicadores de calidad mediante un sistema de calificación que permite visualizar el grado y el número de limitaciones que podría tener un suelo para ser utilizado en agricultura. Además, posee módulos en los cuales el usuario puede: (a) adicionar o consultar características espaciales y de atributos del suelo; (b) visualizar la interpretación de los indicadores de calidad, agrupados en rangos de limitación (c) determinar la aptitud general del suelo para un cultivo específico mediante la comparación entre oferta (suelo) vs. demanda (requerimientos del cultivo); (d) calcular necesidades de fertilización; (e) generar reportes de la variabilidad en profundidad de algunas características, para uno o más suelos; (f) cartografiar los resultados mediante un link con el SIG MapMaker y (g) visualizar mapas de variabilidad espacial y/o temporal (isolíneas) de la variable utilizada como indicador. ABSTRACT The System Georeferenced of soil quality indicators for the savannas of Colombia. Geosoil allows to as much store, to consult and to process data of the soil as of his biophysics surroundings on different scales: parcel, property, community, municipality, department, region, and country. It operates from a relational database elaborated in ACCES 2000, composed by a series of structured main tables with information at different hierarchic levels that they allow the characterization of the properties of the soil. The morphologic and analytical elements of the ground are combined to conform indicators of quality by means of a qualification system that allows visualizing the degree and the number of limitations that could have a soil to be used in agriculture. In addition, it has modules in which the user can: (a) to add or to consult space characteristics and of attributes of the soil; (b) to visualize the interpretation of the quality indicators, grouped in limitation ranks; (c) to determine the general aptitude of the soil for a specific culture by means of the comparison between supply (soil) versus demands (requirements of the culture); (d) to calculate the fertilization necessities (e) to generate reports of the variability in depth of some characteristics, for one or more soil; (f) to map the results by means of a link with the MapMaker GIS (g) to visualize maps of space and/or temporary variability (isolines) of the variable used like indicator. Key words: indicators, soil quality, Geographical Information Systems, soil database, land degradation and land evaluation, savannas

Participatory impact pathways analysis : A practical application of program theory in research-for-development

The Challenge Program on Water and Food pursues food security and poverty alleviation through the efforts of some 50 research-for-development projects. These involve almost 200 organizations working in nine river basins around the world. An approach was developed to enhance the developmental impact of the program through better impact assessment, to provide a framework for monitoring and evaluation, to permit stakeholders to derive strategic and programmatic lessons for future initiatives, and to provide information that can be used to inform public awareness efforts. The approach makes explicit a project's program theory by describing its impact pathways in terms of a logic model and network maps. A narrative combines the logic model and the network maps into a single explanatory account and adds to overall plausibility by explaining the steps in the logic model and the key risks and assumptions. Participatory Impact Pathways Analysis is based on concepts related to program theory drawn from the fields of evaluation, organizational learning, and social network analysis

Light-Induced Metastable Magnetic Texture Uncovered by in situ Lorentz Microscopy

Magnetic topological defects, such as vortices and Skyrmions, can be stabilized as equilibrium structures in nanoscale geometries and by tailored intrinsic magnetic interactions. Here, employing rapid quench conditions, we report the observation of a light-induced metastable magnetic texture, which consists of a dense nanoscale network of vortices and antivortices. Our results demonstrate the emergence of ordering mechanisms in quenched optically driven systems, which may give a general access to novel magnetic structures on nanometer length scales