Self-compensation in phosphorus-doped CdTe

We investigate the self-compensation mechanism in phosphorus-doped CdTe. The formation energies, charge transition levels, and defects states of several P-related point defects susceptible to cause self-compensation are addressed by first-principles calculations. Moreover, we assess the in uence of the spin-orbit coupling and supercell-size effects on the stability of AX centers donors, which are believed to be responsible for most of the self-compensation. We report an improved result for the lowest-energy configuration of the P interstitial (P$_\text{i}$) and find that the self-compensation mechanism is not due to the formation of AX centers. Under Te-rich growth conditions, (P$_\text{i}$) exhibits a formation energy lower than the substitutional acceptor (P$_\text{Te}$) when the Fermi level is near the valence band, acting as compensating donor. While, for Cd-rich growth conditions, our results suggest that p-type doping is limited by the formation of (P$_\text{Te}$-V$_\text{Te}$) complexes.Comment: 5 page

Self-compensation in chlorine-doped CdTe

Indexación: ScopuDefect energetics, charge transition levels, and electronic band structures of several Cl-related complexes in CdTe are studied using density-functional theory calculations. We investigate substitutional chlorine (ClTe and ClCd) and complexes formed by ClTe with the cadmium vacancy (ClTe-VCd and 2ClTe-VCd) and the TeCd antisite (ClTe-TeCd). Our calculations show that none of the complexes studied induce deep levels in the CdTe band gap. Moreover, we find that ClTe-VCd and ClTe are the most stable Cl-related centers in n-type and p-type CdTe, under Te-rich growth conditions, showing shallow donor and acceptor properties, respectively. This result suggests that the experimentally-observed Fermi level pinning near midgap would be originated in self-compensation. We also find that the formation of the ClTe-TeCd complex passivates the deep level associated to the Te antisite in neutral charge state. © 2019, The Author(s).https://www-nature-com.recursosbiblioteca.unab.cl/articles/s41598-019-45625-

Techno-Typological Analysis of Lithic Tools from Ipilla 2 an Early Archaic Site in the Andes of Arica, Chile

El estudio de la tecnología lítica en los Andes se inició con la identificación tipológica de puntas de proyectil para definir secuencias cronológico-culturales de sociedades de cazadores recolectores. Análisis tecno-tipológicos como el que se presenta en este trabajo, tratan de mostrar que las morfologías de instrumentos líticos no son estáticas pues varían de acuerdo a su uso, mantenimiento y reciclaje. En este estudio, exploramos y caracterizamos la variabilidad morfológica del instrumental lítico del sitio Ipilla 2, un campamento abierto del Arcaico Temprano (9.670-9.541 cal. a.p.), ubicado en los Andes de Arica (3.400 msm), norte de Chile. Los resultados sugieren que los instrumentos fueron intensamente mantenidos para extender su vida útil, lo que alteró los diseños originales. Otro proceso tecnológico incluyó la manufactura secuencial de distintos filos en un mismo instrumento. Estos resultados aportan a la comprensión de los modos de vida de las sociedades de cazadores recolectores andinos y muestran que, metodológicamente, las formas tipológicas deben considerarse desde una perspectiva dinámica para convertirse en una herramienta analítica más eficaz.The study of lithic technology in the Andes began with the classification of projectile point typologies to define chronological and cultural sequences of hunter-gatherer societies. Techno-typological analysis such as the onepresented here, try to show that lithic morphologies are not static as they vary in relation to their use, maintenance and recycling. In this study we explore and characterize the technological and typological variability of stone tools from Ipilla 2, an Early Archaic open-air camp (9,670-9,541 cal. BP) located in the Andes of Arica (3,400 m asl), northern Chile. The results show that tools were intensely maintained to extend their use-life, which transformed their original designs. Another technological process included the sequential manufacture of different edges in the same instrument. These results contribute to understanding the lifestyles of Andean hunter-gatherer societies and show that methodologically, lithic typologies must be considered from a dynamic perspective to become a more effective analytic tool.Fil: Herrera, Katherine A.. Universidad de Tarapacá; ChileFil: Ugalde, Paula C.. Centro de Investigaciones del Hombre en el Desierto; ChileFil: Osorio, Daniela. Centro de Investigaciones del Hombre en el Desierto; ChileFil: Capriles Flores, Jose Mariano. Universidad de Tarapacá; ChileFil: Hocsman, Salomón. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Estudios Sociales. Universidad Nacional de Tucumán. Instituto Superior de Estudios Sociales; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Arqueología y Museo; ArgentinaFil: Santoro Vargas, Calogero Mauricio. Centro de Investigaciones del Hombre en el Desierto; Chile. Universidad de Tarapacá; Chil

Layered Software Architecture for Nanosatellites

Layered software architecture has been used to increase code portability and reduce development times during the Systems Development Life Cycle (SDLC). The main objective of the EMIDSS-4 project is to develop a reliable and scalable hardware and software layered architecture for data acquisition in nanosatellites. An iterative hardware/software co-design approach was employed, transitioning from an FPGA architecture to an NXP-based microcontroller. The results demonstrate that the new architecture provides continuous and adaptable data acquisition capabilities, enhancing the long-term viability of the project. In conclusion, this study contributes to the field of space exploration and lays the foundation for future research in nanosatellites.ITESO, A. C

Hierarchical Shape Construction and Complexity for Slidable Polyominoes under Uniform External Forces

Advances in technology have given us the ability to create and manipulate robots for numerous applications at the molecular scale. At this size, fabrication tool limitations motivate the use of simple robots. The individual control of these simple objects can be infeasible. We investigate a model of robot motion planning, based on global external signals, known as the tilt model. Given a board and initial placement of polyominoes, the board may be tilted in any of the 4 cardinal directions, causing all slidable polyominoes to move maximally in the specified direction until blocked. We propose a new hierarchy of shapes and design a single configuration that is strongly universal for any w × h bounded shape within this hierarchy (it can be reconfigured to construct any w × h bounded shape in the hierarchy). This class of shapes constitutes the most general set of buildable shapes in the literature, with most previous work consisting of just the first-level of our hierarchy. We accompany this result with a O(n4 log n)-time algorithm for deciding if a given hole-free shape is a member of the hierarchy. For our second result, we resolve a long-standing open problem within the field: We show that deciding if a given position may be covered by a tile for a given initial board configuration is PSPACEcomplete, even when all movable pieces are 1 × 1 tiles with no glues. We achieve this result by a reduction from Non-deterministic Constraint Logic for a one-player unbounded game

Evolution of substrate specificity in a retained enzyme driven by gene loss.

The connection between gene loss and the functional adaptation of retained proteins is still poorly understood. We apply phylogenomics and metabolic modeling to detect bacterial species that are evolving by gene loss, with the finding that Actinomycetaceae genomes from human cavities are undergoing sizable reductions, including loss of L-histidine and L-tryptophan biosynthesis. We observe that the dual-substrate phosphoribosyl isomerase A or priA gene, at which these pathways converge, appears to coevolve with the occurrence of trp and his genes. Characterization of a dozen PriA homologs shows that these enzymes adapt from bifunctionality in the largest genomes, to a monofunctional, yet not necessarily specialized, inefficient form in genomes undergoing reduction. These functional changes are accomplished via mutations, which result from relaxation of purifying selection, in residues structurally mapped after sequence and X-ray structural analyses. Our results show how gene loss can drive the evolution of substrate specificity from retained enzymes

Contested Futures: Envisioning “Personalized,” “Stratified,” and “Precision” Medicine

In recent years, discourses around “personalized,” “stratified,” and “precision” medicine have proliferated. These concepts broadly refer to the translational potential carried by new data-intensive biomedical research modes. Each describes expectations about the future of medicine and healthcare that data-intensive innovation promises to bring forth. The definitions and uses of the concepts are, however, plural, contested and characterized by diverse ideas about the kinds of futures that are desired and desirable. In this paper, we unpack key disputes around the “personalized,” “stratified,” and “precision” terms, and map the epistemic, political and economic contexts that structure them as well as the different roles attributed to patients and citizens in competing future imaginaries. We show the ethical and value baggage embedded within the promises that are manufactured through terminological choices and argue that the context and future-oriented nature of these choices helps to understanding how data-intensive biomedical innovations are made socially meaningful