Evaluación de una población de Sorghastrum pellitum (Hack.) Parodi hasta su reintroducción en áreas medanosas

In natural areas, the changes produced by fence and selective grazing of cattle led to the loss of some species and increasing others. Sorghastrum pellitum (red grass), fodder pasture important, has been virtually eliminated or reduced to marginal areas due to livestock use. The aim of this study was to evaluate the behavior of this species from seed germination and during a year of plant development. In spring 400 plants were established in field and their development was evaluated in this growing season. The results indicate a high sensitivity of seedlings to low temperatures. Once seedling stage past, the plants showed a good development with growth even in periods of low rainfall.En áreas de pastizales naturales, las modificaciones producidas por el apotreramiento y el pastoreo selectivo del ganado vacuno indujeron a la pérdida de algunas especies y el incremento de otras. Sorghastrum pellitum (pasto colorado o pasto vaca), forrajera estival importante del pastizal sammófilo, ha sido prácticamente eliminada o reducida a áreas marginales debido al uso ganadero. El objetivo de este trabajo fue evaluar el comportamiento de esta especie desde la germinación de los cariopsis y durante la primera estación de crecimiento de las plantas, especialmente su tolerancia a heladas. Mediante experiencias en condiciones semicontroladas se pretendió predecir sus aptitudes para la reintroducción. En invernáculo se evaluó el poder germinativo de los cariopsis, la emergencia y el crecimiento inicial de las plántulas. En primavera se realizó el transplante de 400 individuos a campo y se evaluó su desarrollo durante el primer ciclo vegetativo. Los resultados obtenidos indican una gran sensibilidad de las plántulas a las bajas temperaturas. Superada la etapa de plántula se observó un buen desarrollo a campo con crecimiento aún en períodos de escasas precipitaciones

Estados de condición del sitio pastizal de gramíneas bajas de planicie presentes en el departamento Loventué La Pampa

It has been evaluating range condition in twenty areas of shortgrasslands in Loventué - La Pampa. The state Condition's identification was realized with the standing - crop's dates. Frequency, density, cover and height of principal’s species were taken. The following indices were used to classified the grassland's Condition: Very Good; Good, Fair, Poor and Very Poor.Se evaluó la condición de pastura en 20 áreas de pastizal de planicie en el Departamento Loventué, La Pampa. La identificación del estado de condición se realizó en función del peso de las especies por unidad de muestreo. Se hicieron además determinaciones de frecuencia, densidad, cobertura y altura de las especies más importantes. Para la determinación de la condición de las áreas, fueron usados los siguientes índices: Muy buena. Buena, Regular, Mala y Muy Mala

Persistencia de los cambios provocados por los fuegos controlados en diferentes estructuras del bosque de caldén (Prosopis caldenia Burk.)

Fire may be reintroducted as prescribed burns for different purposes, mainly to remove accumulated fuels and the risk of intense fires or as a tool of range management in order to improve the forage offer. The objective of this study was to assess the vegetation response to burning 6 and 12 months after precribed fires in two different caldén woodlands: open woodland (BA) associated with torage species, and closed forest (BD) with a poor proportion of forage species a) in the community b) in the seed bank. The effect of prescribed burn in this study had less impact on the vegetation structure of both communities than expected, in terms of reduction of non palatable woody species and increasing of forage species abundance. The vegetation response is principally influenced by ils structural and floristic characteristics.La reintroducción del fuego en forma de quema prescriptas puede tener diferentes finalidades. El uso más frecuente es para la reducción de fitomasa altamente combustible, disminuyendo de esta manera los riesgos de propagación de incendio o como herramienta para mantener o aumentar la producción forrajera de las áreas. El objetivo del presente trabajo es evaluar la respuesta de la vegetación a la acción de la quema controlada en los 6 y 12 meses posteriores a la misma en dos variantes de la comunidad de bosque de caldén: bosque abierto (BA) con presencia de especies forrajeras y bosque denso (BD) con baja proporción de especies forrajeras a) en la vegetación b) en el banco de semillas de gramíneas. El efecto del fuego controlado observado en este trabajo para ambas comunidades no tuvo la magnitud de cambio estructural que se esperaba en lo que respecta a aumento de forrajeras y disminución de especies no forrajeras y leñosas. La respuesta de la vegetación estuvo principalmente condicionada por las características estructurales y florísticas de la comunidad

Dinámica de un arbustal de jarilla (Larrea divaricata cav.) luego de un incendio en el Parque Nacional Lihue Calel, La Pampa

The values of green biomass (Bv) measured in a grassland were associated with index values of normalized difference vegetation index (NDVI) from satellite data in three relict natural grassland on stream Chucul, from his beginning site 1 (32° 49'21, 0`` S and 64° 24 `07.0 `` W) until its demise in plain area: site 3 (33° 06` 25.5 `` S and 63° 32 `49.1 `` W). Under the hypothesis of correspondence of Bv and data obtained by images, the aim of this work is to determine the relationship between measured field data and satellite data in natural grasslands. Seasonally during the 2009-2011 cycle were sampled at random with 10 replicates of 0.25 m2 recording floristic list. To determine Bv in each plot the biomass was cut and separated in green and dry compartments and dryed to constant weight. For digital analysis bands 3 and 4 of Landsat 5 TM image (Path 228 Row 083) were used for each site close to the sampling date. The highest values of green biomass were determined for site 3, in December 2011: 189.6 g/m2 and in March for sites 1 and 2: 105.74 and 115.22 g/m2. Among all the observed values of biomass and NDVI estimated the correlation coefficient was highest at site 3 (R = 0.50). The results of the work for site 3 validate the hypothesis and indicats of the aptitude of digital images for study the status and changes in vegetation.En los ecosistemas semiáridos, las comunidades vegetales han evolucionado en presencia de fuegos frecuentes. Eso hace que muchas especies, hayan desarrollado mecanismos que les permiten tolerar su acción. En el Parque Nacional Lihué Calel, La Pampa, Argentina, a fines del año 2003, se produjo un incendio, que modificó la composición y estructura de las comunidades de arbustales de jarilla (Larrea spp.), presentes en las áreas afectadas. El objetivo de este estudio fue evaluar la dinámica post incendio de distintas áreas afectadas según la quema haya sido intensa y leve. Se trabajó además con un control no quemado. Los estudios fueron realizados al año (2005) y a los 4 años de producidos el incendio (2008). Se realizaron evaluaciones de abundancia-cobertura de vegetación (N=12). Además, se tomaron muestras compuestas de suelo al azar (N=16) para determinar carbono orgánico total, materia orgánica y textura. Por efecto del incendio, se produjeron modificaciones estructurales en la comunidad. En las áreas más intensamente quemadas se produjo un reemplazo de la jarilla por especies espinosas. En cuanto a las características del suelo, donde la intensidad del incendio fue leve, las variables edáficas no tuvieron cambios. En las áreas de quema intensa se observó un incremento de la fracción arena, además de cambios florísticos significativos

Prácticas de riesgo para transmisión de VIH en estudiantes de medicina de Latinoamérica y el Caribe, 2017

El objetivo del trabajo fue determinar las prácticas de riesgo para transmisión de VIH en estudiantes de medicina de Latinoamérica y el Caribe durante los meses de Enero a Febrero de 2017. Se realizó un estudio observacional, descriptivo de corte transversal, con muestreo no probabilístico por conveniencia en estudiantes de medicina de Latinoamérica y el Caribe, desde enero a febrero de 2017. Se escogió a estudiantes de medicina del primer al séptimo año de la carrera. Se procedió a la publicación en redes sociales del cuestionario electrónico mediante Google Doc©. Los resultados se expresan en tablas de frecuencias. Fueron incluidos 638 estudiantes de medicina, teniendo el 67,08% (428) una edad comprendida entre 20 a 24 años. Del total de encuestados el 56,02% ha practicado sexo anal, 88,65% ha practicado sexo oral, y 57,06% sexo vaginal en los últimos 6 meses. El 24,43% de los encuestados nunca ha utilizado condón durante sus relaciones sexuales. El 3,49% han pagado alguna vez por sexo, 27,57% ha ingerido alcohol durante las relaciones sexuales y 4,36% ha mantenido relaciones sexuales con usuarios de drogas intravenosas mientras que 63,88% nunca se ha hecho una prueba rápida para VIH. Las prácticas de riesgos más frecuentes fueron la baja utilización de condón durante la última relación sexual, la utilización de alcohol durante la relación sexual y la baja realización de prueba para VIH

Cytogenetic analysis of three species of Pseudacteon (Diptera, Phoridae) parasitoids of the fire ants using standard and molecular techniques

Pseudacteon flies, parasitoids of worker ants, are being intensively studied as potentially effective agents in the biological control of the invasive pest fire ant genus Solenopsis (Hymenoptera: Formicidae). This is the first attempt to describe the karyotype of P. curvatus Borgmeier, P. nocens Borgmeier and P. tricuspis Borgmeier. The three species possess 2n = 6; chromosomes I and II were metacentric in the three species, but chromosome pair III was subtelocentric in P. curvatus and P. tricuspis, and telocentric in P. nocens. All three species possess a C positive band in chromosome II, lack C positive heterochromatin on chromosome I, and are mostly differentiated with respect to chromosome III. P. curvatus and P. tricuspis possess a C positive band, but at different locations, whereas this band is absent in P. nocens. Heterochromatic bands are neither AT nor GC rich as revealed by fluorescent banding. In situ hybridization with an 18S rDNA probe revealed a signal on chromosome II in a similar location to the C positive band in the three species. The apparent lack of morphologically distinct sex chromosomes is consistent with proposals of environmental sex determination in the genus. Small differences detected in chromosome length and morphology suggests that chromosomes have been highly conserved during the evolutionary radiation of Pseudacteon. Possible mechanisms of karyotype evolution in the three species are suggested

Morphological and Physicochemical Characterization of Agglomerates of Titanium Dioxide Nanoparticles in Cell Culture Media

Titanium dioxide nanoparticles (TiO2 NP) are possible carcinogenic materials (2B-IARC) and their toxicity depends on shape, size, and electrical charge of primary NP and on the system formed by NP media. The aim of this work was to characterize agglomerates of three TiO2 NP by evaluating their morphometry, stability, and zeta potential (ζ) in liquid media and their changes with time. Sizes of agglomerates by dynamic light scattering (DLS) resulted to be 10–50 times larger than those obtained by digital image analysis (DIA) given the charged zone around particles. Fractal dimension (FD) was highest for agglomerates of spheres and belts in F12K, and in E171 in FBS media. E171 and belts increased FD with time. At time zero, using water as dispersant FD was larger for agglomerates of spheres than for of E171. Belts suspended in water had the smallest values of circularity (Ci) which was approximately unchanged with time. All dispersions had ζ values around −30 mV at physiological pH (7.4) and dispersions of NP in water and FBS showed maximum stability (Turbiscan Lab analysis). Results help in understanding the complex NP geometry-size-stability relationships when performing in vivo and in vitro environmental-toxicity works and help in supporting decisions on the usage of TiO2 NP

LSST: from Science Drivers to Reference Design and Anticipated Data Products

(Abridged) We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a wide-field ground-based system sited at Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg$^2$ field of view, and a 3.2 Gigapixel camera. The standard observing sequence will consist of pairs of 15-second exposures in a given field, with two such visits in each pointing in a given night. With these repeats, the LSST system is capable of imaging about 10,000 square degrees of sky in a single filter in three nights. The typical 5$\sigma$ point-source depth in a single visit in $r$ will be $\sim 24.5$ (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be contained within 30,000 deg$^2$ with $\delta<+34.5^\circ$, and will be imaged multiple times in six bands, $ugrizy$, covering the wavelength range 320--1050 nm. About 90\% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 deg$^2$ region about 800 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to $r\sim27.5$. The remaining 10\% of the observing time will be allocated to projects such as a Very Deep and Fast time domain survey. The goal is to make LSST data products, including a relational database of about 32 trillion observations of 40 billion objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures available from https://www.lsst.org/overvie

Clinical prediction models for mortality in patients with covid-19: external validation and individual participant data meta-analysis

OBJECTIVE: To externally validate various prognostic models and scoring rules for predicting short term mortality in patients admitted to hospital for covid-19. DESIGN: Two stage individual participant data meta-analysis. SETTING: Secondary and tertiary care. PARTICIPANTS: 46 914 patients across 18 countries, admitted to a hospital with polymerase chain reaction confirmed covid-19 from November 2019 to April 2021. DATA SOURCES: Multiple (clustered) cohorts in Brazil, Belgium, China, Czech Republic, Egypt, France, Iran, Israel, Italy, Mexico, Netherlands, Portugal, Russia, Saudi Arabia, Spain, Sweden, United Kingdom, and United States previously identified by a living systematic review of covid-19 prediction models published in The BMJ, and through PROSPERO, reference checking, and expert knowledge. MODEL SELECTION AND ELIGIBILITY CRITERIA: Prognostic models identified by the living systematic review and through contacting experts. A priori models were excluded that had a high risk of bias in the participant domain of PROBAST (prediction model study risk of bias assessment tool) or for which the applicability was deemed poor. METHODS: Eight prognostic models with diverse predictors were identified and validated. A two stage individual participant data meta-analysis was performed of the estimated model concordance (C) statistic, calibration slope, calibration-in-the-large, and observed to expected ratio (O:E) across the included clusters. MAIN OUTCOME MEASURES: 30 day mortality or in-hospital mortality. RESULTS: Datasets included 27 clusters from 18 different countries and contained data on 46 914patients. The pooled estimates ranged from 0.67 to 0.80 (C statistic), 0.22 to 1.22 (calibration slope), and 0.18 to 2.59 (O:E ratio) and were prone to substantial between study heterogeneity. The 4C Mortality Score by Knight et al (pooled C statistic 0.80, 95% confidence interval 0.75 to 0.84, 95% prediction interval 0.72 to 0.86) and clinical model by Wang et al (0.77, 0.73 to 0.80, 0.63 to 0.87) had the highest discriminative ability. On average, 29% fewer deaths were observed than predicted by the 4C Mortality Score (pooled O:E 0.71, 95% confidence interval 0.45 to 1.11, 95% prediction interval 0.21 to 2.39), 35% fewer than predicted by the Wang clinical model (0.65, 0.52 to 0.82, 0.23 to 1.89), and 4% fewer than predicted by Xie et al's model (0.96, 0.59 to 1.55, 0.21 to 4.28). CONCLUSION: The prognostic value of the included models varied greatly between the data sources. Although the Knight 4C Mortality Score and Wang clinical model appeared most promising, recalibration (intercept and slope updates) is needed before implementation in routine care

Nuclear Reprogramming: Kinetics of Cell Cycle and Metabolic Progression as Determinants of Success

Establishment of totipotency after somatic cell nuclear transfer (NT) requires not only reprogramming of gene expression, but also conversion of the cell cycle from quiescence to the precisely timed sequence of embryonic cleavage. Inadequate adaptation of the somatic nucleus to the embryonic cell cycle regime may lay the foundation for NT embryo failure and their reported lower cell counts. We combined bright field and fluorescence imaging of histone H2b-GFP expressing mouse embryos, to record cell divisions up to the blastocyst stage. This allowed us to quantitatively analyze cleavage kinetics of cloned embryos and revealed an extended and inconstant duration of the second and third cell cycles compared to fertilized controls generated by intracytoplasmic sperm injection (ICSI). Compared to fertilized embryos, slow and fast cleaving NT embryos presented similar rates of errors in M phase, but were considerably less tolerant to mitotic errors and underwent cleavage arrest. Although NT embryos vary substantially in their speed of cell cycle progression, transcriptome analysis did not detect systematic differences between fast and slow NT embryos. Profiling of amino acid turnover during pre-implantation development revealed that NT embryos consume lower amounts of amino acids, in particular arginine, than fertilized embryos until morula stage. An increased arginine supplementation enhanced development to blastocyst and increased embryo cell numbers. We conclude that a cell cycle delay, which is independent of pluripotency marker reactivation, and metabolic restraints reduce cell counts of NT embryos and impede their development