96 research outputs found
Evolución de la eficiencia y productividad empleando DEA para una empresa de servicios financieros
El presente trabajo representa la profundización del análisis de eficiencia aplicado a una importante empresa de Servicios Financieros de la ciudad de Córdoba, comparativo con los resultados provistos por el Tablero de Comando (BSC) con que trabaja internamente la institución. Aquella etapa previa, junto con el trabajo realizado con sus autoridades, resultó determinante al momento de seleccionar las variables con las que hemos trabajado.El objetivo de la etapa presentada a continuación es analizar si las variaciones en la eficiencia de las sucursales de la empresa bajo estudio consideradas, se deben a una mejora (desmejora) en el uso de los recursos asignados a las mismas, a un cambio técnico en los procesos que le permiten generar los servicios brindados, o a una combinación de ambos, y si tal combinación se traduce o no en un cambio en su productividad. Para ello, utilizamos el Índice de Malmquist orientado a las entradas, bajo el supuesto de retornos constantes a escala, de acuerdo al enfoque propuesto por Färe et al.(1994) y Lovell (2003), sobre la base de los trabajos previos de Malmquist (1953) y Caves et al. (1982).https://rdu.unc.edu.ar/handle/11086/4528Fil: Cortaberria, Sofía C. Universidad Nacional de Córdoba. Facultad de Ciencias Económicas; Argentina.Fil: Racagni, Josefina. Universidad Nacional de Córdoba. Facultad de Ciencias Económicas; Argentina.Fil: Guevel, Hernán Pablo. Universidad Nacional de Córdoba. Facultad de Ciencias Económicas; Argentina.Otras Economía y Negocio
SPE-44 Implements Sperm Cell Fate
The sperm/oocyte decision in the hermaphrodite germline of Caenorhabditis elegans provides a powerful model for the characterization of stem cell fate specification and differentiation. The germline sex determination program that governs gamete fate has been well studied, but direct mediators of cell-type-specific transcription are largely unknown. We report the identification of spe-44 as a critical regulator of sperm gene expression. Deletion of spe-44 causes sperm-specific defects in cytokinesis, cell cycle progression, and organelle assembly resulting in sterility. Expression of spe-44 correlates precisely with spermatogenesis and is regulated by the germline sex determination pathway. spe-44 is required for the appropriate expression of several hundred sperm-enriched genes. The SPE-44 protein is restricted to the sperm-producing germline, where it localizes to the autosomes (which contain sperm genes) but is excluded from the transcriptionally silent X chromosome (which does not). The orthologous gene in other Caenorhabditis species is similarly expressed in a sex-biased manner, and the protein likewise exhibits autosome-specific localization in developing sperm, strongly suggestive of an evolutionarily conserved role in sperm gene expression. Our analysis represents the first identification of a transcriptional regulator whose primary function is the control of gamete-type-specific transcription in this system
Population health intervention research: what is the place for pilot studies?
BACKGROUND: An international workshop on population health intervention research (PHIR) was organized to foster exchanges between experts from different disciplines and different fields. AIMS: This paper aims to summarize the discussions around one of the issues addressed: the place or role of pilot studies in PHIR. Pilot studies are well-established in biomedical research, but the situation is more ambiguous for PHIR, in which a pilot study could refer to different purposes. METHODS: The workshop included formal presentations of participants and moderated discussions. An oral synthesis was carried out by a rapporteur to validate by expert consensus the key points of the discussion and the recommendations. All discussions have been recorded and fully transcribed. DISCUSSION: PHIR generally addresses complex interventions. Thus, numerous tasks may be required to inform the intervention and test different aspects of its design and implementation. While in clinical research the pilot study mainly concerns the preparation of the trial, in PHIR the pilot study focuses on the preparation of both the intervention and the trial. In particular, pilot studies in PHIR could be used for viability evaluation and theory development. RECOMMENDATION FROM THE WORKSHOP PARTICIPANTS: The following recommendations were generated by consensus from the workshop discussions: i) terms need to be clarified for PHIR; ii) reporting and publication should be standardized and transparency should be promoted; iii) the objectives and research questions should drive the methods used and be clearly stated; iv) a pilot study is generally needed for complex intervention evaluation and for research-designed programs; and v) for field-designed programs, it is important to integrate evaluability assessments as pilot studies. CONCLUSION: Pilot studies play an important role in intervention development and evaluation. In particular, they contribute to a better understanding of the mechanisms of intervention and the conditions of its applicability and transferability. Pilot studies could therefore facilitate evidence-based decisions about design and conduct of main studies aimed to generate evidence to inform public health policy
Properties of Rubble-Pile Asteroid (101955) Bennu from OSIRIS-REx Imaging and Thermal Analysis
Establishing the abundance and physical properties of regolith and boulders on asteroids is crucial for understanding the formation and degradation mechanisms at work on their surfaces. Using images and thermal data from NASA's Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft, we show that asteroid (101955) Bennu's surface is globally rough, dense with boulders, and low in albedo. The number of boulders is surprising given Bennu's moderate thermal inertia, suggesting that simple models linking thermal inertia to particle size do not adequately capture the complexity relating these properties. At the same time, we find evidence for a wide range of particle sizes with distinct albedo characteristics. Our findings imply that ages of Bennu's surface particles span from the disruption of the asteroid's parent body (boulders) to recent in situ production (micrometre-scale particles)
Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.
Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability
Energetic eruptions leading to a peculiar hydrogen-rich explosion of a massive star
Every supernova so far observed has been considered to be the terminal explosion of a star. Moreover, all supernovae with absorption lines in their spectra show those lines decreasing in velocity over time, as the ejecta expand and thin, revealing slower-moving material that was previously hidden. In addition, every supernova that exhibits the absorption lines of hydrogen has one main light-curve peak, or a plateau in luminosity, lasting approximately 100 days before declining1. Here we report observations of iPTF14hls, an event that has spectra identical to a hydrogen-rich core-collapse supernova, but characteristics that differ extensively from those of known supernovae. The light curve has at least five peaks and remains bright for more than 600 days; the absorption lines show little to no decrease in velocity; and the radius of the line-forming region is more than an order of magnitude bigger than the radius of the photosphere derived from the continuum emission. These characteristics are consistent with a shell of several tens of solar masses ejected by the progenitor star at supernova-level energies a few hundred days before a terminal explosion. Another possible eruption was recorded at the same position in 1954. Multiple energetic pre-supernova eruptions are expected to occur in stars of 95 to 130 solar masses, which experience the pulsational pair instability2,3,4,5. That model, however, does not account for the continued presence of hydrogen, or the energetics observed here. Another mechanism for the violent ejection of mass in massive stars may be required
Evidence for widespread hydrated minerals on asteroid (101955) Bennu
Early spectral data from the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission reveal evidence for abundant hydrated minerals on the surface of near-Earth asteroid (101955) Bennu in the form of a near-infrared absorption near 2.7 µm and thermal infrared spectral features that are most similar to those of aqueously altered CM-type carbonaceous chondrites. We observe these spectral features across the surface of Bennu, and there is no evidence of substantial rotational variability at the spatial scales of tens to hundreds of metres observed to date. In the visible and near-infrared (0.4 to 2.4 µm) Bennu’s spectrum appears featureless and with a blue (negative) slope, confirming previous ground-based observations. Bennu may represent a class of objects that could have brought volatiles and organic chemistry to Earth
The dynamic geophysical environment of (101955) Bennu based on OSIRIS-REx measurements
The top-shaped morphology characteristic of asteroid (101955) Bennu, often found among fast-spinning asteroids and binary asteroid primaries, may have contributed substantially to binary asteroid formation. Yet a detailed geophysical analysis of this morphology for a fast-spinning asteroid has not been possible prior to the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. Combining the measured Bennu mass and shape obtained during the Preliminary Survey phase of the OSIRIS-REx mission, we find a notable transition in Bennu’s surface slopes within its rotational Roche lobe, defined as the region where material is energetically trapped to the surface. As the intersection of the rotational Roche lobe with Bennu’s surface has been most recently migrating towards its equator (given Bennu’s increasing spin rate), we infer that Bennu’s surface slopes have been changing across its surface within the last million years. We also find evidence for substantial density heterogeneity within this body, suggesting that its interior is a mixture of voids and boulders. The presence of such heterogeneity and Bennu’s top shape are consistent with spin-induced failure at some point in its past, although the manner of its failure cannot yet be determined. Future measurements by the OSIRIS-REx spacecraft will provide insight into and may resolve questions regarding the formation and evolution of Bennu’s top-shape morphology and its link to the formation of binary asteroids
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