First Stars. I. Evolution without mass loss

The first generation of stars was formed from primordial gas. Numerical simulations suggest that the first stars were predominantly very massive, with typical masses M > 100 Mo. These stars were responsible for the reionization of the universe, the initial enrichment of the intergalactic medium with heavy elements, and other cosmological consequences. In this work, we study the structure of Zero Age Main Sequence stars for a wide mass and metallicity range and the evolution of 100, 150, 200, 250 and 300 Mo galactic and pregalactic Pop III very massive stars without mass loss, with metallicity Z=10E-6 and 10E-9, respectively. Using a stellar evolution code, a system of 10 equations together with boundary conditions are solved simultaneously. For the change of chemical composition, which determines the evolution of a star, a diffusion treatment for convection and semiconvection is used. A set of 30 nuclear reactions are solved simultaneously with the stellar structure and evolution equations. Several results on the main sequence, and during the hydrogen and helium burning phases, are described. Low metallicity massive stars are hotter and more compact and luminous than their metal enriched counterparts. Due to their high temperatures, pregalactic stars activate sooner the triple alpha reaction self-producing their own heavy elements. Both galactic and pregalactic stars are radiation pressure dominated and evolve below the Eddington luminosity limit with short lifetimes. The physical characteristics of the first stars have an important influence in predictions of the ionizing photon yields from the first luminous objects; also they develop large convective cores with important helium core masses which are important for explosion calculations.Comment: 17 pages, 24 figures, 2 table

Aberration-corrected electron microscopy of nanoparticles

The early history of scanning transmission electron microscopy (STEM) is reviewed as a way to frame the technical issues that make aberration correction an essential upgrade for the study of nanoparticles using STEM. The principles of aberration correction are explained, and the use of aberration-corrected microscopy in the study of nanostructures is exemplified in order to remark the features and challenges in the use of this measuring techniqu

Rhizobium Promotes Non-Legumes Growth and Quality in Several Production Steps: Towards a Biofertilization of Edible Raw Vegetables Healthy for Humans

The biofertilization of crops with plant-growth-promoting microorganisms is currently considered as a healthy alternative to chemical fertilization. However, only microorganisms safe for humans can be used as biofertilizers, particularly in vegetables that are raw consumed, in order to avoid sanitary problems derived from the presence of pathogenic bacteria in the final products. In the present work we showed that Rhizobium strains colonize the roots of tomato and pepper plants promoting their growth in different production stages increasing yield and quality of seedlings and fruits. Our results confirmed those obtained in cereals and alimentary oil producing plants extending the number of non-legumes susceptible to be biofertilized with rhizobia to those whose fruits are raw consumed. This is a relevant conclusion since safety of rhizobia for human health has been demonstrated after several decades of legume inoculation ensuring that they are optimal bacteria for biofertilization

SHP-2 Promotes the Maturation of Oligodendrocyte Precursor Cells Through Akt and ERK1/2 Signaling In Vitro

Background: Oligodendrocyte precursor cells (OPCs) differentiate into oligodendrocytes (OLs), which are responsible for myelination. Myelin is essential for saltatory nerve conduction in the vertebrate nervous system. However, the molecular mechanisms of maturation and myelination by oligodendrocytes remain elusive. Methods and Findings: In the present study, we showed that maturation of oligodendrocytes was attenuated by sodium orthovanadate (a comprehensive inhibitor of tyrosine phosphatases) and PTPi IV (a specific inhibitor of SHP-2). It is also found that SHP-2 was persistently expressed during maturation process of OPCs. Down-regulation of endogenous SHP-2 led to impairment of oligodendrocytes maturation and this effect was triiodo-L-thyronine (T3) dependent. Furthermore, overexpression of SHP-2 was shown to promote maturation of oligodendrocytes. Finally, it has been identified that SHP-2 was involved in activation of Akt and extracellular-regulated kinases 1 and 2 (ERK1/2) induced by T3 in oligodendrocytes

Biallelic variants in KARS1 are associated with neurodevelopmental disorders and hearing loss recapitulated by the knockout zebrafish

Purpose: Pathogenic variants in Lysyl-tRNA synthetase 1 (KARS1) have increasingly been recognized as a cause of early-onset complex neurological phenotypes. To advance the timely diagnosis of KARS1-related disorders, we sought to delineate its phenotype and generate a disease model to understand its function in vivo. Methods: Through international collaboration, we identified 22 affected individuals from 16 unrelated families harboring biallelic likely pathogenic or pathogenic in KARS1 variants. Sequencing approaches ranged from disease-specific panels to genome sequencing. We generated loss-of-function alleles in zebrafish. Results: We identify ten new and four known biallelic missense variants in KARS1 presenting with a moderate-to-severe developmental delay, progressive neurological and neurosensory abnormalities, and variable white matter involvement. We describe novel KARS1-associated signs such as autism, hyperactive behavior, pontine hypoplasia, and cerebellar atrophy with prevalent vermian involvement. Loss of kars1 leads to upregulation of p53, tissue-specific apoptosis, and downregulation of neurodevelopmental related genes, recapitulating key tissue-specific disease phenotypes of patients. Inhibition of p53 rescued several defects of kars1−/− knockouts. Conclusion: Our work delineates the clinical spectrum associated with KARS1 defects and provides a novel animal model for KARS1-related human diseases revealing p53 signaling components as potential therapeutic targets

Robot Nurse for Patient's Lifting

This document reports the development of a Robot Nurse for Patient’s Lifting or Robot Enfermera para Carga de Pacientes (RECPA). This robot is designed for hospital use and is capable of assisting nursing personnel during the mobilization of patients. In the same way, it has a multimodal social interface that allows human-robot interaction in different modalities. The robot aims to be a support tool for nursing personnel, avoiding physical risks in their work environment. We target mainly to avoid back injuries, the most common work injury in nursing.The project was developed during 2017 and 2018 in collaboration with multiple partners (Hoiho, Fusmat, Mirai, Korella and Libersalus) under an agile project management method (SCRUM). The design and development have been supported by an in-depth analysis of the international and national robot markets. Similarly, a collection of qualitative and quantitative observations of hospital requirement and regulations was done. As a consequence, a high-resolution robot prototype is proposed to lift weight up to 70Kg.This report describes the technical advances of the project with a multidisciplinary approach; interaction design, multimodal interfaces, mechatronics, and social and service robotics for healthcare. Three main sections describe the multiple modules that conform the robot: the mechatronics section, the interface section and the product design. Each of these sections describes the design and development of 18 modules for user's control, positing of the robot and lifting weight. Initial sections describe the market study, definition of the needs, design proposals and early prototypes. Later chapters describe the construction of the robot, the development of the designs, redesign process, and modifications due to the limitations in equipment and manufacturing.RECPA presents several novelties in the successful integration of mechatronic devices and multimodal interactive technologies for the control of this service robot aiming health industry. For instance, RECPA lifts 70Kg that represents an improvement over other robotic systems. Also, RECPA can be operated using a multimodal interface (eye movement, gestures, touch screen and joystick) that requires a minimal user's training. Additionally, the social interface facilitates user’s interaction. However, the project also was constrained by intrinsic Mexican conditions such as access to imported materials and equipment, specialized experience professionals, and corporative culture for the coordination of complex projects. Tests of the final prototype show that the RECPA robot is capable of lifting a static punctual load of 70 kg when the robot does not move. On-site load tests damaged the robot; hence, various repairs of the prototype were required. Future work of this project implies a) Testing with human patients (partnership with a health institution is required), b) Registration intellectual property and c) Research and development to build a prototype suitable to pass international regulations (FCC and FDA) among others. These improvements require further financial investments and the application of strict security protocols supervised by an external biomedical consultancy. The present results and prototype can be considered satisfactory according to time and financial setup. In the near future, Libersalus SA de CV aims to achieve the final goal of lifting a patient using RECPA, with the support of new investments and similar partnerships