RESUMEN
Carbonaceous asteroids, such as (101955) Bennu, preserve material from the early Solar System, including volatile compounds and organic molecules. We report spacecraft imaging and spectral data collected during and after retrieval of a sample from Bennu's surface. The sampling event mobilized rocks and dust into a debris plume, excavating a 9-meter-long elliptical crater. This exposed material is darker, spectrally redder, and more abundant in fine particulates than the original surface. The bulk density of the displaced subsurface material was 500 to 700 kilograms per cubic meter, which is about half that of the whole asteroid. Particulates that landed on instrument optics spectrally resemble aqueously altered carbonaceous meteorites. The spacecraft stored 250 ± 101 grams of material, which will be delivered to Earth in 2023.
RESUMEN
Two of the instruments onboard the OSIRIS-REx spacecraft, the MapCam color imager and the OVIRS visible and infrared spectrometer, observed the surface of asteroid (101955) Bennu in partially overlapping wavelengths. Significant scientific advances have been enabled by using data from these two instruments in tandem, but a robust statistical understanding of their relationship is needed for future analyses to cross-compare their data as accurately and sensitively as possible. Here we present a cross-instrument comparison of data acquired by MapCam and OVIRS, including methods and results for all global and site-specific observation campaigns in which both instruments were active. In our analysis, we consider both the absolute radiometric offset and the relative (normalized) variation between the two instruments; we find that both depend strongly on the photometric and instrumental conditions during the observation. The two instruments have a large absolute offset (>15%) due to their independent radiometric calibrations. However, they are very consistent (relative offset as low as 1%) when each instrument's response is normalized at a single wavelength, particularly at low phase angles where shadows on Bennu's rough surface are minimized. We recommend using the global datasets acquired at 12:30 pm local solar time for cross-comparisons; data acquired at higher phase angles have larger uncertainties.
RESUMEN
Visible-wavelength color and reflectance provide information about the geologic history of planetary surfaces. Here we present multispectral images (0.44 to 0.89 micrometers) of near-Earth asteroid (101955) Bennu. The surface has variable colors overlain on a moderately blue global terrain. Two primary boulder types are distinguishable by their reflectance and texture. Space weathering of Bennu surface materials does not simply progress from red to blue (or vice versa). Instead, freshly exposed, redder surfaces initially brighten in the near-ultraviolet region (i.e., become bluer at shorter wavelengths), then brighten in the visible to near-infrared region, leading to Bennu's moderately blue average color. Craters indicate that the time scale of these color changes is ~105 years. We attribute the reflectance and color variation to a combination of primordial heterogeneity and varying exposure ages.
RESUMEN
Rock breakdown due to diurnal thermal cycling has been hypothesized to drive boulder degradation and regolith production on airless bodies. Numerous studies have invoked its importance in driving landscape evolution, yet morphological features produced by thermal fracture processes have never been definitively observed on an airless body, or any surface where other weathering mechanisms may be ruled out. The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission provides an opportunity to search for evidence of thermal breakdown and assess its significance on asteroid surfaces. Here we show boulder morphologies observed on Bennu that are consistent with terrestrial observations and models of fatigue-driven exfoliation and demonstrate how crack propagation via thermal stress can lead to their development. The rate and expression of this process will vary with asteroid composition and location, influencing how different bodies evolve and their apparent relative surface ages from space weathering and cratering records.
RESUMEN
The OSIRIS-REx Camera Suite (OCAMS) onboard the OSIRIS-REx spacecraft is used to study the shape and surface of the mission's target, asteroid (101955) Bennu, in support of the selection of a sampling site. We present calibration methods and results for the three OCAMS cameras-MapCam, PolyCam, and SamCam-using data from pre-flight and in-flight calibration campaigns. Pre-flight calibrations established a baseline for a variety of camera properties, including bias and dark behavior, flat fields, stray light, and radiometric calibration. In-flight activities updated these calibrations where possible, allowing us to confidently measure Bennu's surface. Accurate calibration is critical not only for establishing a global understanding of Bennu, but also for enabling analyses of potential sampling locations and for providing scientific context for the returned sample.
RESUMEN
Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.
RESUMEN
During its approach to asteroid (101955) Bennu, NASA's Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft surveyed Bennu's immediate environment, photometric properties, and rotation state. Discovery of a dusty environment, a natural satellite, or unexpected asteroid characteristics would have had consequences for the mission's safety and observation strategy. Here we show that spacecraft observations during this period were highly sensitive to satellites (sub-meter scale) but reveal none, although later navigational images indicate that further investigation is needed. We constrain average dust production in September 2018 from Bennu's surface to an upper limit of 150 g s-1 averaged over 34 min. Bennu's disk-integrated photometric phase function validates measurements from the pre-encounter astronomical campaign. We demonstrate that Bennu's rotation rate is accelerating continuously at 3.63 ± 0.52 × 10-6 degrees day-2, likely due to the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, with evolutionary implications.
RESUMEN
NASA'S Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer (OSIRIS-REx) spacecraft recently arrived at the near-Earth asteroid (101955) Bennu, a primitive body that represents the objects that may have brought prebiotic molecules and volatiles such as water to Earth1. Bennu is a low-albedo B-type asteroid2 that has been linked to organic-rich hydrated carbonaceous chondrites3. Such meteorites are altered by ejection from their parent body and contaminated by atmospheric entry and terrestrial microbes. Therefore, the primary mission objective is to return a sample of Bennu to Earth that is pristine-that is, not affected by these processes4. The OSIRIS-REx spacecraft carries a sophisticated suite of instruments to characterize Bennu's global properties, support the selection of a sampling site and document that site at a sub-centimetre scale5-11. Here we consider early OSIRIS-REx observations of Bennu to understand how the asteroid's properties compare to pre-encounter expectations and to assess the prospects for sample return. The bulk composition of Bennu appears to be hydrated and volatile-rich, as expected. However, in contrast to pre-encounter modelling of Bennu's thermal inertia12 and radar polarization ratios13-which indicated a generally smooth surface covered by centimetre-scale particles-resolved imaging reveals an unexpected surficial diversity. The albedo, texture, particle size and roughness are beyond the spacecraft design specifications. On the basis of our pre-encounter knowledge, we developed a sampling strategy to target 50-metre-diameter patches of loose regolith with grain sizes smaller than two centimetres4. We observe only a small number of apparently hazard-free regions, of the order of 5 to 20 metres in extent, the sampling of which poses a substantial challenge to mission success.
Asunto(s)
Medio Ambiente Extraterrestre/química , Planetas Menores , Vuelo Espacial , Exobiología , Origen de la Vida , Vuelo Espacial/instrumentación , Propiedades de SuperficieRESUMEN
In the Southern hemisphere, Réunion Island acts as a sentinel for infections preferentially occurring during the austral winter that are likely to reach the Northern hemisphere a few months later. We relate the main features concerning patients that were admitted during years 2009 and 2010 in our intensive care unit with an A(H1N1)v2009 infection, mainly for acute respiratory distress. Demographic, clinical, and biological data as well as given medications and outcome were prospectively collected among all PCR-confirmed influenza-infected patients. In 2009 and 2010, 25 patients met the criteria. Patients' median age was 40.4 (±17.4) years. Most of them (22/25) had comorbidities such as: chronic diseases, overweight, obesity, pregnancy, and Down syndrome. Maximum bed-occupation rate was 10 days per million inhabitants. Main diagnosis for ICU admission was virus-related pneumonia. Twenty-two out of 25 patients needed mechanical ventilation, some required rescue therapies such as extracorporeal membranous oxygenation (ECMO) or hi-frequency oscillation ventilation (HFOV), both only available in few French hospitals. Within the study period, 12 patients died (48%) mainly of multi-organ failure. Through 2009 and 2010 autumn and winter periods, for several weeks, the A(H1N1)v2009 virus infection resulted in a significant increase of workload in Réunion Island ICUs. In 2010, the failure of the mass immunization campaign, particularly among the at-risk groups, led to severe cases of A(H1N1)v2009 infections, particularly among patients with comorbidities. Our data may contribute toward better management of influenza virus pandemics in the future.
Asunto(s)
Epidemias , Subtipo H1N1 del Virus de la Influenza A , Gripe Humana/epidemiología , Adolescente , Adulto , Anciano , Antivirales/uso terapéutico , Terapia Combinada , Comorbilidad , Susceptibilidad a Enfermedades , Femenino , Humanos , Subtipo H1N1 del Virus de la Influenza A/genética , Subtipo H1N1 del Virus de la Influenza A/aislamiento & purificación , Gripe Humana/complicaciones , Gripe Humana/terapia , Gripe Humana/virología , Unidades de Cuidados Intensivos/estadística & datos numéricos , Masculino , Persona de Mediana Edad , Insuficiencia Multiorgánica/etiología , Insuficiencia Multiorgánica/mortalidad , Admisión del Paciente/estadística & datos numéricos , Reacción en Cadena de la Polimerasa , Embarazo , Complicaciones Infecciosas del Embarazo/epidemiología , Complicaciones Infecciosas del Embarazo/virología , Estudios Prospectivos , Respiración Artificial , Síndrome de Dificultad Respiratoria/epidemiología , Síndrome de Dificultad Respiratoria/etiología , Reunión/epidemiología , Adulto JovenRESUMEN
A 19-year-old patient admitted in an oncology unit for an autograft (Hodgkin disease), developed on day 20 a fatal acute respiratory failure and multiple organ failure due to an infection of the A(H1N1)v2009 virus, which was acquired in the hospital, despite partial preventive measures. At that time, the specific vaccine was not available in Réunion. We discuss the nosocomial origin of the infection. Following the epidemic wave, the vaccination rate of the general population and the hospital employees remains very low.
Asunto(s)
Infección Hospitalaria/virología , Subtipo H1N1 del Virus de la Influenza A , Gripe Humana/virología , Infecciones por Acinetobacter/complicaciones , Acinetobacter baumannii , Antiinfecciosos/uso terapéutico , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Bacteriemia/complicaciones , Transfusión de Componentes Sanguíneos , Infección Hospitalaria/complicaciones , Infección Hospitalaria/tratamiento farmacológico , Infección Hospitalaria/terapia , Epidemias , Oxigenación por Membrana Extracorpórea , Resultado Fatal , Femenino , Enfermedad de Hodgkin/complicaciones , Enfermedad de Hodgkin/tratamiento farmacológico , Humanos , Huésped Inmunocomprometido , Gripe Humana/complicaciones , Gripe Humana/tratamiento farmacológico , Gripe Humana/epidemiología , Gripe Humana/terapia , Insuficiencia Multiorgánica/etiología , Respiración Artificial , Síndrome de Dificultad Respiratoria/etiología , Reunión/epidemiología , Infecciones Estafilocócicas/complicaciones , Acondicionamiento Pretrasplante/efectos adversos , Adulto JovenRESUMEN
AIM OF THE STUDY: The antibiotic resistance of enterobacteriacae knows a worldwide worrying evolution with an increase of the extended spectrum betalactamases (ESBL) that spread into the community. Few publications describe this problem in the Indian Ocean area. The aim of this study is first to identify in Félix Guyon Hospital (Reunion Island) the emergent antibiotics resistance for enterobacteriaceae between 1997/1998 and 2006/2007 periods, at second, to update the prophylactic and therapeutic measures for handling the risk linked to multiresistant enterobacteriaceae in our hospital and third, to assess the risk in Reunion Island and especially at the community level. METHODS: The antibiotic susceptibility of 7814 enterobacteriaceae strains collected among patients, during 1997/1998 and 2006/2007 periods, were analysed as well as the consumption of the third generation cephalosporins, imipenem and fluoroquinolones. RESULTS: Within a span of time of 10 years, an important increase (+57 %) of the resistance prevalence of enterobacteriaceae is observed. The resistance by the ESBL production mechanism is predominant especially for Enterobacter cloacae and Escherichia coli. An important use of broad spectrum antibiotics is correlated with this resistance evolution. CONCLUSION: The emergence of ESBL-producing enterobacteriaceae in our hospital is impairing both therapeutic and health care. It requires a much better control of antibiotics prescriptions and therefore, an important multidisciplinary implication. A proof molecular analysis would allow to evaluate the risk more precisely, especially at the community level.
Asunto(s)
Infección Hospitalaria/microbiología , Farmacorresistencia Bacteriana Múltiple/genética , Infecciones por Enterobacteriaceae/microbiología , Enterobacteriaceae/efectos de los fármacos , Resistencia betalactámica/genética , beta-Lactamasas/aislamiento & purificación , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Resistencia a las Cefalosporinas/genética , Cefalosporinasa/genética , Cefalosporinasa/metabolismo , Infección Hospitalaria/epidemiología , Utilización de Medicamentos , Enterobacteriaceae/enzimología , Enterobacteriaceae/genética , Enterobacteriaceae/aislamiento & purificación , Infecciones por Enterobacteriaceae/epidemiología , Fluoroquinolonas/farmacología , Fluoroquinolonas/uso terapéutico , Humanos , Imipenem/farmacología , Imipenem/uso terapéutico , Estudios Retrospectivos , Reunión/epidemiología , Especificidad por Sustrato , beta-Lactamasas/genéticaRESUMEN
Although fire blight, caused by the bacterium Erwinia amylovora, is one of the most destructive diseases of apple (Malus x domestica) worldwide, no major, qualitative gene for resistance to this disease has been identified to date in apple. We conducted a quantitative trait locus (QTL) analysis in two F(1) progenies derived from crosses between the cultivars Fiesta and either Discovery or Prima. Both progenies were inoculated in the greenhouse with the same strain of E. amylovora, and the length of necrosis was scored 7 days and 14 days after inoculation. Additive QTLs were identified using the MAPQTL: software, and digenic epistatic interactions, which are an indication of putative epistatic QTLs, were detected by two-way analyses of variance. A major QTL explaining 34.3--46.6% of the phenotypic variation was identified on linkage group (LG) 7 of Fiesta in both progenies at the same genetic position. Four minor QTLs were also identified on LGs 3, 12 and 13. In addition, several significant digenic interactions were identified in both progenies. These results confirm the complex polygenic nature of resistance to fire blight in the progenies studied and also reveal the existence of a major QTL on LG7 that is stable in two distinct genetic backgrounds. This QTL could be a valuable target in marker-assisted selection to obtain new, fire blight-resistant apple cultivars and forms a starting point for discovering the function of the genes underlying such QTLs involved in fire blight control.
Asunto(s)
Erwinia amylovora , Inmunidad Innata/genética , Malus/genética , Enfermedades de las Plantas/microbiología , Sitios de Carácter Cuantitativo , Análisis de Varianza , Mapeo Cromosómico , Cruzamientos Genéticos , Epistasis Genética , Enfermedades de las Plantas/genéticaAsunto(s)
Enfermedades Renales Poliquísticas/epidemiología , Adulto , Factores de Edad , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Hipertensión Renal/etiología , Fallo Renal Crónico/etiología , Masculino , Persona de Mediana Edad , Enfermedades Renales Poliquísticas/complicaciones , Enfermedades Renales Poliquísticas/genética , Factores SexualesRESUMEN
The statistical analysis of morphometric data collected from biopsies of human superficial peroneal nerve is complicated by the heterogeneity of the population of myelinated fibres. In order to make separate statistical analyses of the subpopulations of large and small fibres we have developed a computer program (written in PASCAL) for their automatic separation. The method is based on a dynamic centres clustering algorithm and was applied to the multifactorial space defined by the principal component analysis of the morphometric variables: axonal diameter, myelin sheath thickness, circularity index and g-ratio. The classification technique was applied to measurements obtained from 5 control nerves, and to simulated data, and in each case it gave consistent Gaussian subpopulations with no need for the introduction of supplementary variables.
Asunto(s)
Técnicas Citológicas , Fibras Nerviosas Mielínicas/citología , Neurología/métodos , Neuronas/clasificación , Nervio Peroneo/citología , Algoritmos , Humanos , Programas InformáticosRESUMEN
In morphometric studies of peripheral nerves, the statistical analysis of such data as axon diameters is complicated by the presence of multimodal distributions. Nerve fiber diameters, for example, cannot be analyzed by classical parametric tests, and such descriptive statistics as mean or variance lose much of their usefulness. The recent development of stochastic catastrophe models offers a new parametric tool with which to describe multimodal distributions. This paper describes our development of a PASCAL computer program that permitted the modelling, comparison and segmentation of multimodal distributions. The method is based on a description of the multimodal frequency distributions by probability density functions of the canonical exponential family.
Asunto(s)
Axones/ultraestructura , Nervios Periféricos/ultraestructura , Humanos , Pierna/inervación , Microcomputadores , Microscopía Electrónica , Modelos Biológicos , Programas Informáticos , Procesos EstocásticosRESUMEN
A follow-up study over 12 years was conducted among 556 men aged 30 to 54 in 1960 and working at that time in factories around Paris (France). Various occupational exposures were recorded at the time of the 1960 survey after a technical study of each workplace. The annual rate of decline of FEV1 during 12 years was estimated for each subject from the measurements in 1960 and 1972. This rate (the FEV1 slope) was related independently of FEV1 level (which reflects the loss since the beginning of adult life) and of smoking habits to occupational exposure to dust, gases, and heat. FEV1 slope was significantly related to inhalation of mineral dust (even in the absence of silica) as well as to grain dust, and the slope was steeper with increased intensity of exposure to dust. Analysis of job changes showed that among heavily exposed subjects, those who changed jobs had a less steep slope than those who did not. Our results support the hypothesis of a causal role of exposure to dust in the development of chronic airflow obstruction and of a benefit when exposure to dust ceases. Exposure to dust, gas, and heat usually occurred together so data on gas and heat were analysed after taking account of exposure to dust. The influence of heat on FEV1 decline showed a clear trend. Results suggest that exposure to gases associated with exposure to dust or heat or both had a deleterious effect. After adjusting for age, smoking, and FEV1 level (ASLA) the following average slopes were obtained: 44 ml/a (for exposure to none or to only a slight amount of dust, or to gases alone), 51 ml/a (heat), 53 ml/a (noticeable dust), 55 ml/a (noticeable dust and heat), 60 ml/a (noticeable dust, heat, and high concentration of gases). Independently of the occupational exposures, ASLA FEV1 slopes among manual workers were related to skill, being 44 ml/a for skilled and 51 ml/a for unskilled men. Independently of social class and occupational exposures recorded, there were differences in FEV1 slopes by factory, suggesting that one should not rely on using one factory as the control of studies of occupational exposure to another.
Asunto(s)
Pulmón/fisiopatología , Enfermedades Profesionales/etiología , Industria Química , Estudios de Seguimiento , Industria de Procesamiento de Alimentos , Volumen Espiratorio Forzado , Humanos , Masculino , Metalurgia , Paris , Respiración , FumarRESUMEN
Various models predicting VC and FEV1 from age and height have been compared by both theoretical and practical approaches on several subgroups of a working population examined in 1960 and 1972. The models in which spirographic values are proportional to the cube of the height give a significantly worse fit of the data. All the other models give similar predicted values in practical terms, but cutoff points depend on the distributions of VC and FEV1 given age and height. Results show that these distributions are closer to a normal than to a lognormal distribution. The use of reference values and classical cutoffs is then discussed. Rather than using a single cutoff point, a more quantitative way is proposed to describe the subjects' functional status, for example by situating him in the percentile of the reference population. In screening, cutoff points cannot be choosen without specifying first the decision considered and the population concerned.