213 research outputs found

    Coagulation of small grains in disks: the influence of residual infall and initial small-grain content

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    Turbulent coagulation in protoplanetary disks is known to operate on timescale far shorter than the lifetime of the disk. In the absence of mechanisms that replenish the small dust grain population, protoplanetary disks would rapidly lose their continuum opacity-bearing dust. This is inconsistent with infrared observations of disks around T Tauri stars and Herbig Ae/Be stars, which are usually optically thick at visual wavelengths and show signatures of small (a<~ 3um) grains. A plausible replenishing mechanism of small grains is collisional fragmentation or erosion of large dust aggregates, which model calculations predict to play an important role in protoplanetary disks. If optically thick disks are to be seen as proof for ongoing fragmentation or erosion, then alternative explanations for the existence of optically thick disks must be studied carefully. In this study we explore two scenarios. First, we study the effect of residual, low-level infall of matter onto the disk surface. We find that infall rates as low as 10^{-11} Msun/yr can, in principle, replenish the small grain population to a level that keeps the disk marginally optically thick. However, it remains to be seen if the assumption of such inflow is realistic for star+disk systems at the age of several Myrs, at which winds and jets are expected to have removed any residual envelope. In summary, fragmentation or erosion still appear to be the most promising processes to explain the abundant presence of small grains in old disks.Comment: 10 pages, 4 figures, A&A in pres

    The MRI Sepsis Score: An Innovative Tool for the Evaluation of Septic Peritonitis in Mice Using 7-Tesla Small Animal MRI

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    Background: Magnetic resonance imaging (MRI) techniques are rarely used in the context of abdominal sepsis and in sepsis research. This study investigates the impact of MRI for monitoring septic peritonitis in an animal model (colon ascendens stent-induced peritonitis, CASP). The CASP model closely mimics that of human disease and is highly standardized. The most frequently employed readout parameter in mouse CASP studies is prolonged or decreased rate of survival. Monitoring the progression of peritonitis via MRI could provide a helpful tool in the evaluation of severity. The use of alternative readout systems could very well reduce the number of research animals. Perspectively, clinical improvement after certain treatment could be classified. Methods: This study describes for the first time MRI findings following the induction of septic peritonitis in mice using the CASP model. Two sublethal groups of mice with septic peritonitis were investigated. Each had received one of two differing stent diameters in order to control the leakage of feces into the abdominal cavity. Each mouse served as its own control. Imaging and analyses were performed blinded. Gut diameters, stomach volume, abdominal organ wall diameters, and volume of the adrenal glands were measured. Serum corticosterone levels were detected using ELISA. Serum IL-6, TNF-α, IL-1ÎČ, and IL-10 levels were screened by cytometric bead array. Statistical analysis was performed using the Mann-Whitney U test for nonparametric probes and the Kruskal-Wallis and t tests. Results: Using a 7-tesla MRI scanner 24 and 48 h after induction of septic peritonitis, interenteric fluid, organ swelling of spleen and adrenal glands, as well as dilatation of the stomach were compared to nonseptic conditions. Swelling of adrenal glands resulted in an increased serum corticosterone level. In addition, the wall of the intestine bowel was thickened. Based upon these findings, an MRI score (MRI sepsis score, MSS) for abdominal sepsis in mice was established. Reduced stent sizes led to reduced severity of the abdominal sepsis, which could be reproduced in the MSS, which is described here for the first time. Conclusions: Intraabdominal variations during septic peritonitis are detectable by MRI techniques. MRI methods should become a more important tool for the evaluation of abdominal peritonitis. MSS could provide an interesting tool for the evaluation of therapeutic strategies

    The MRI Sepsis Score: An Innovative Tool for the Evaluation of Septic Peritonitis in Mice Using 7-Tesla Small Animal MRI

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    Background: Magnetic resonance imaging (MRI) techniques are rarely used in the context of abdominal sepsis and in sepsis research. This study investigates the impact of MRI for monitoring septic peritonitis in an animal model (colon ascendens stent-induced peritonitis, CASP). The CASP model closely mimics that of human disease and is highly standardized. The most frequently employed readout parameter in mouse CASP studies is prolonged or decreased rate of survival. Monitoring the progression of peritonitis via MRI could provide a helpful tool in the evaluation of severity. The use of alternative readout systems could very well reduce the number of research animals. Perspectively, clinical improvement after certain treatment could be classified. Methods: This study describes for the first time MRI findings following the induction of septic peritonitis in mice using the CASP model. Two sublethal groups of mice with septic peritonitis were investigated. Each had received one of two differing stent diameters in order to control the leakage of feces into the abdominal cavity. Each mouse served as its own control. Imaging and analyses were performed blinded. Gut diameters, stomach volume, abdominal organ wall diameters, and volume of the adrenal glands were measured. Serum corticosterone levels were detected using ELISA. Serum IL-6, TNF-α, IL-1ÎČ, and IL-10 levels were screened by cytometric bead array. Statistical analysis was performed using the Mann-Whitney U test for nonparametric probes and the Kruskal-Wallis and t tests. Results: Using a 7-tesla MRI scanner 24 and 48 h after induction of septic peritonitis, interenteric fluid, organ swelling of spleen and adrenal glands, as well as dilatation of the stomach were compared to nonseptic conditions. Swelling of adrenal glands resulted in an increased serum corticosterone level. In addition, the wall of the intestine bowel was thickened. Based upon these findings, an MRI score (MRI sepsis score, MSS) for abdominal sepsis in mice was established. Reduced stent sizes led to reduced severity of the abdominal sepsis, which could be reproduced in the MSS, which is described here for the first time. Conclusions: Intraabdominal variations during septic peritonitis are detectable by MRI techniques. MRI methods should become a more important tool for the evaluation of abdominal peritonitis. MSS could provide an interesting tool for the evaluation of therapeutic strategies

    Water emission in NGC1333-IRAS4: The physical structure of the envelope

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    We report ISO-LWS far infrared observations of CO, water and oxygen lines towards the protobinary system IRAS4 in the NGC1333 cloud. We detected several water, OH, CO rotational lines, and two [OI] and [CII] fine structure lines. Given the relatively poor spectral and spatial resolution of these observations, assessing the origin of the observed emission is not straightforward. In this paper, we focus on the water line emission and explore the hypothesis that it originates in the envelopes that surround the two protostars, IRAS4 A and B, thanks to an accurate model. The model reproduces quite well the observed water line fluxes, predicting a density profile, mass accretion rate, central mass, and water abundance profile in agreement with previous works. We hence conclude that the emission from the envelopes is a viable explanation for the observed water emission, although we cannot totally rule out the alternative that the observed water emission originates in the outflow

    Protein profiling in hepatocellular carcinoma by label-free quantitative proteomics in two west african populations

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    Background: Hepatocellular Carcinoma is the third most common cause of cancer related death worldwide, often diagnosed by measuring serum AFP; a poor performance stand-alone biomarker. With the aim of improving on this, our study focuses on plasma proteins identified by Mass Spectrometry in order to investigate and validate differences seen in the respective proteomes of controls and subjects with LC and HCC. Methods: Mass Spectrometry analysis using liquid chromatography electro spray ionization quadrupole time-of-flight was conducted on 339 subjects using a pooled expression profiling approach. ELISA assays were performed on four significantly differentially expressed proteins to validate their expression profiles in subjects from the Gambia and a pilot group from Nigeria. Results from this were collated for statistical multiplexing using logistic regression analysis. Results: Twenty-six proteins were identified as differentially expressed between the three subject groups. Direct measurements of four; hemopexin, alpha-1-antitrypsin, apolipoprotein A1 and complement component 3 confirmed their change in abundance in LC and HCC versus control patients. These trends were independently replicated in the pilot validation subjects from Nigeria. The statistical multiplexing of these proteins demonstrated performance comparable to or greater than ALT in identifying liver cirrhosis or carcinogenesis. This exercise also proposed preliminary cut offs with achievable sensitivity, specificity and AUC statistics greater than reported AFP averages. Conclusions: The validated changes of expression in these proteins have the potential for development into highperformance tests usable in the diagnosis and or monitoring of HCC and LC patients. The identification of sustained expression trends strengthens the suggestion of these four proteins as worthy candidates for further investigation in the context of liver disease. The statistical combinations also provide a novel inroad of analyses able to propose definitive cutoffs and combinations for evaluation of performance
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