Growth of calcium-aluminum-rich inclusions by coagulation and fragmentation in a turbulent protoplanetary disk: observations and modelisation

Whereas it is generally accepted that calcium-aluminum-rich inclusions (CAIs) from chondritic meteorites formed in a hot environment in the solar protoplanetary disk, the conditions of their formation remain debated. Recent laboratory studies of CAIs have provided new kind of data: their size distributions. We show that size distributions of CAIs measured in laboratory from sections of carbonaceous chondrites have a power law size distribution with cumulative size exponent between -1.7 and -1.9, which translates into cumulative size exponent between -2.5 and -2.8 after correction for sectioning. To explain these observations, numerical simulations were run to explore the growth of CAIs from micrometer to centimeter sizes, in a hot and turbulent protoplanetary disk through the competition of coagulation and fragmentation. We show that the size distributions obtained in growth simulations are in agreement with CAIs size distributions in meteorites. We explain the CAI sharp cut-off of their size distribution at centimeter sizes as the direct result from the famous fragmentation barrier, provided that CAI fragment for impact velocities larger than 10 m/s. The growth/destruction timescales of millimeter- and centimeter-sized CAIs is inversely proportional to the local dust/gas ratio and is about 10 years at 1300 K and up to 104 years at 1670K. This implies that the most refractory CAIs are expected to be smaller in size owing to their long growth timescale compared to less refractory CAIs. Conversely, the least refractory CAIs could have been recycled many times during the CAI production era which may have profound consequences for their radiometric age.Comment: Accepted in Icaru

The most primitive CM chondrites, Asuka 12085, 12169, and 12236, of subtypes 3.0–2.8: Their characteristic features and classification

CM chondrites (CMs) are the most abundant group of carbonaceous chondrites. CMs experienced varying degrees of secondary aqueous alteration and heating that modified or destroyed their primitive features. We have studied three chondrites, Asuka (A) 12085, A 12169, and A 12236. Their modal compositions, chondrule size distributions, and bulk composition indicate that they are CMs. However, the common occurrence of melilite in CAIs and glass in chondrules, abundant Fe–Ni metal, the absence of tochilinite-cronstedtite intergrowths, and almost no phyllosilicates, all suggest that these chondrites, especially A 12169, experienced only minimal aqueous alteration. The textures and compositions of metal and sulfides, the lack of ferroan rims on AOA olivines, the compositional distribution of ferroan olivine, and the Raman spectra of their matrices, indicate that these chondrites experienced neither significant heating nor dehydration. These chondrites, especially A 12169, are the most primitive CMs so far reported. The degree of the alteration increases from A 12169, through A 12236, to A 12085. We propose the criteria for subtypes of 3.0–2.8 for CMs. A 12169, A 12236, and A 12085 are classified as subtype 3.0, 2.9, and 2.8, respectively. The oxygen isotopic composition of the Asuka CMs is consistent with these samples having experienced only a limited degree of aqueous alteration. The CM and CO groups are probably not derived from a single heterogeneous parent body. These chondrites are also of particular significance in view of the imminent return of sample material from the asteroids Ryugu and Bennu

Characterising the CI and CI-like carbonaceous chondrites using thermogravimetric analysis and infrared spectroscopy

The CI and CI-like chondrites provide a record of aqueous alteration in the early solar system. However, the CI-like chondrites differ in having also experienced a late stage period of thermal metamorphism. In order to constrain the nature and extent of the aqueous and thermal alteration, we have investigated the bulk mineralogy and abundance of H2O in the CI and CI-like chondrites using thermogravimetric analysis and infrared spectroscopy. The CI chondrites Ivuna and Orgueil show significant mass loss (28.5–31.8 wt.%) upon heating to 1000 °C due to dehydration and dehydroxylation of abundant phyllosilicates and Fe-(oxy)hydroxides and the decomposition of Fe-sulphides, carbonates and organics. Infrared spectra for Ivuna and Orgueil have a prominent 3-μm feature due to bound −OH/H2O in phyllosilicates and Fe-(oxy)hydroxides and only a minor 11-μm feature from anhydrous silicates. These characteristics are consistent with previous studies indicating that the CI chondrites underwent near-complete aqueous alteration. Similarities in the total abundance of H2O and 3 μm/11 μm ratio suggest that there is no difference in the relative degree of hydration experienced by Ivuna and Orgueil. In contrast, the CI-like chondrites Y-82162 and Y-980115 show lower mass loss (13.8–18.8 wt.%) and contain >50 % less H2O than the CI chondrites. The 3-μm feature is almost absent from spectra of Y-82162 and Y-980115 but the 11-μm feature is intense. The CI-like chondrites experienced thermal metamorphism at temperatures >500 °C that initially caused dehydration and dehydroxylation of phyllosilicates before partial recrystallization back into anhydrous silicates. The surfaces of many C-type asteroids were probably heated through impact metamorphism and/or solar radiation, so thermally altered carbonaceous chondrites are likely good analogues for samples that will be returned by the Hayabusa-2 and OSIRIS-REx missions

LAYERED TEXTURE IN THE CH/CB ISHEYEVO CHONDRITE.

77th Annual Meeting of the Meteoritical-Society, Casablanca, MOROCCO, SEP 08-13, 2014International audienc

Radiative heating of carbonaceous near-Earth objects as a cause of thermal metamorphism for CK chondrites

International audienc

Hospital costs of renal transplant management.

International audienceRenal transplantation is considered to be a cost-effective therapy, but hospital medical costs are not accurately known. The aim of this work was to evaluate the costs of hospital stay for renal transplantation. This retrospective study included all patients who underwent renal transplantation between January 1, 2004, and December 31, 2005, in our University hospital. The incurred costs were determined using our center's analytical accounting (AA). The mean local cost was then compared with the median national cost of hospitalization for renal transplantation, based on a sample of participating centers contributing to the National Cost Scale (NCS) per homogenous diagnosis-related group (DRG). These mean costs were weighed against the financing obtained by national rates of the case-mix based payment system (termed T2A). Data were collected from 77 patients. Their mean length of stay was 19.4 days. AA determined the cost of management to be euro14,100 per patient. National economic approaches were significantly higher: euro16,389 for NCS and euro17,369 for national rates. Thus, the specific DRG rate (case mix index) of renal transplantation covers the expenses incurred by our center. These results are rather interesting; however, it is unlike those obtained for the management of other diseases such as acute myeloid leukemia, where T2A underestimates the actual cost by 2-4 times. Last, the hospital budget and T2A must be considered as a whole. The fact that DRGs with favorable and unfavorable pricing balance out should be taken into account

Incidence and risk factors of anemia in patients with early breast cancer treated by adjuvant chemotherapy.

International audienceBACKGROUND: The study's objective was to assess the predictive factors of anemia induced by chemotherapy in early breast cancer patients. PATIENTS AND METHODS: Patients treated by adjuvant or neo-adjuvant anthracyclin-based regimens with or without taxanes between 1998 and 2006 in a French university hospital were studied. Chemotherapy included. Anemia was defined as a hemoglobin (Hb) concentration lower than 12 g/dL. Multivariate analysis by logistic regression was used to search for baseline risk factors linked to the occurrence of anemia. RESULTS: Among 378 patients, anemia was observed in 64% of cases. The occurrence of anemia was significantly related to 6 risk factors: exposure to taxanes (HR 11.5, 95% CI, 2.5-52.6), high dose of anthracyclin (epirubicin 100 mg/m²)(HR 4.3; 95% CI, 2.8-8), Hb at baseline 60 (HR 2.5; 95% CI, 1.4-5) years old (HR 2.5; 95% CI, 1.4-5) and Body Mass Index (BMI) ≤ 25 kg/m² (HR 1.7; 95% CI, 1.0-2.8). CONCLUSION: Taking into account the following factors: type of chemotherapy, BMI, age, Hb at baseline should allow a better identification of patients at risk of anemia