The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Co-limitation towards lower latitudes shapes global forest diversity gradients

The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers

Global phylogeography and ancient evolution of the widespread human gut virus crAssphage

Microbiomes are vast communities of microorganisms and viruses that populate all natural ecosystems. Viruses have been considered to be the most variable component of microbiomes, as supported by virome surveys and examples of high genomic mosaicism. However, recent evidence suggests that the human gut virome is remarkably stable compared with that of other environments. Here, we investigate the origin, evolution and epidemiology of crAssphage, a widespread human gut virus. Through a global collaboration, we obtained DNA sequences of crAssphage from more than one-third of the world’s countries and showed that the phylogeography of crAssphage is locally clustered within countries, cities and individuals. We also found fully colinear crAssphage-like genomes in both Old-World and New-World primates, suggesting that the association of crAssphage with primates may be millions of years old. Finally, by exploiting a large cohort of more than 1,000 individuals, we tested whether crAssphage is associated with bacterial taxonomic groups of the gut microbiome, diverse human health parameters and a wide range of dietary factors. We identified strong correlations with different clades of bacteria that are related to Bacteroidetes and weak associations with several diet categories, but no significant association with health or disease. We conclude that crAssphage is a benign cosmopolitan virus that may have coevolved with the human lineage and is an integral part of the normal human gut virome

Deposición y caracterización de recubrimientos de Nitruro de Boro producidos por pulverización catódica

Boron nitride (BN) is an important technological material with thermal, electrical, and mechanical properties that approach those of diamond. BN may be formed in three main crystalline forms: cubic (c-BN), wurtzite (w-BN), and hexagonal (h-BN). c-BN is the most attractive BN structure due to an unique set of properties. Three factors are common to all successful PVD c-BN experiments: bombardment of the growing film by energetic ions (generally 100-500 eV). an elevated substrate temperature (300-400 °C optimum), and the achievement of the correct film stoichiometry. In this work the literature was reviewed on the physical vapour deposition and characterization of c-BN thin films, placing special emphasis on the substrate bias (d.c. or r.f.) as a dominant effect on the c-BN content onto films. BN thin films were prepared using d.c and r.f. negative substrate bias. Threshold bias for formation of c-BN phase was identified for both cases. Films were characterized by Fourier Transformed Infrared Spectroscopy (FTIR) used for phase identification. Atomic Force Microscope (AFM) and Scaning Electronic Microscope (SEM) for morphological structural characterization. Characterization of thin films obtained is according to layer structural models proposed in the literature.El nitruro de boro (BN) es un material de gran importancia tecnológica, con propiedades térmicas, eléctricas y mecánicas que se aproximan a las del diamante. El nitruro de boro se puede formar principalmente en tres estructuras cristalinas: cúbico (c-BN). wurtzite (w-BN) y hexagonal (h-BN). El c-BN es la estructura más interesante, debido a su conjunto único de propiedades. Tres parámetros son comunes a todos los experimentos PVD para la producción exitosa de c-BN: Bombardeo de la película en crecimiento con iones energéticos (generalmente 100-500eV), elevada temperatura del substrato (300-400°C) y la correcta estequiometria en la película. En este trabajo se revisó la literatura de deposición física de vapor y caracterización de películas delgadas de c-BN, poniendo especial énfasis en el voltaje de polarización del substrato (d.c. y r.f.) como efecto dominante en el contenido de c-BN dentro de la película. Se prepararon películas delgadas de BN usando voltaje de polarización del substrato d.c. y r.f. Se identificó el voltaje crítico para la formación de la fase c-BN en ambos casos. Las películas se caracterizaron por medio de espectroscopia de Infrarrojo con Transformada de Fourier (FTIR), usada para la identificación de fase, Microscopia de Fuerza Atómica (AFM) y Microscopia Electrónica de Barrido (SEM) para la caracterización morfológica. La caracterización de las películas obtenidas este de acuerdo con el modelo estructural de capas propuesto en la literatura

Renal compromise in HIV/AIDS in patients attended at a chilean children hospital Compromiso renal e infección por VIH/SIDA en pacientes atendidos en un hospital pediátrico chileno

The aim of this study was to determine the frequency of renal abnormalities in HIV positive children hospitalized in one pediatric hospital in Chile. Method: a cross sectional study was performed during April 2007. Results: A total of 18 patients were evaluated, ten male and eight female ranging in age from 4 to 19 years. The average age at the time of HIV diagnosis and nephrologic evaluations were 2,69 and 10,7 years respectively. All patients had acquired HIV infection by vertical transmission. Urine samples of two children had microalbuminuria; two had monosymptomatic hematuria, and ten had ¿squamous? cells. Hypercalciuria was detected in one patient, renal lithiasis in another and two patients had abnormal renal ultrasonography. All 19 patients had normal blood pressures. Overall 7 patients (39%) had a renal abnormality. Conclusions: The relatively high incidence of renal abnormalities in our series support the need for a nation-wide screening program to assess the incidence of re

Hemolytic-uremic syndrome in Chile: clinical features, evolution and prognostic factors

Background: Hemolytic-uremic syndrome (HUS) is characterized by acute renal failure, microangiopathic hemolytic anemia and thrombocytopenia. Aim: To describe the characteristics of patients with the diagnosis of HUS in Chile, and to identify the most reliable early predictors of morbidity and mortality. Material and methods: The clinical records of patients with HUS aged less than 15 years, attended between January 1990 and December 2003 in 15 hospitals, were reviewed. Demographic, clinical, biochemical, hematological parameters, morbidity and mortality were analyzed. Results: A cohort of 587 patients aged 2 to 8 years, 48% males, was analyzed. Ninety two percent had diarrhea. At the moment of diagnosis, anuria was observed in 39% of the patients, hypertension in 45% and seizures in 17%. Forty two percent required renal replacement therapy (RRT) and peritoneal dialysis was used in the majority of cases (78%). The most frequently isolated etiological agent was Escherichia coli. Mortality rate was 2.9% in the acute phase of the disease and there was a positive correlation between mortality and anuria, seizures, white blood cell count (WCC) >20.000/mm3 and requirements of renal replacement therapy (p <0.05). Twelve percent of patients evolved to chronic renal failure and the risk factors during the acute phase were the need for renal replacement therapy, anuria, WCC >20.000/mm3, seizures and hypertension. Conclusions: The present study emphasizes important clinical and epidemiological aspects of HUS in a Chilean pediatric population