333 research outputs found
Formation and Dissociation of Hydrate Plugs in a Water in Oil Emulsion
4 pagesIn this paper, we present experimental results of the formation and dissociation of methane hydrate plugs in a semi-batch reactor. The plugs are done from water in heptane emulsion (water content from 30 %). The experimental results shows that the formation rate and dissociation rate are controlled by the heat transfer at the wall of the reactor. An unexpected behaviour is observed as the temperature decreases under the 0°C temperature during dissociation and seems to form ice which slows down the dissociation rate
Safety of Endoscopic Retrograde Cholangiopancreatography (ERCP) in Pregnancy: A Systematic Review and Meta-Analysis
Background/Aims: Endoscopic retrograde cholangiopancreatography (ERCP) is a technically challenging procedure rarely associated with severe postprocedure complications. Hormonal changes during pregnancy promote cholelithiasis, but there are limited clinical data available on the outcomes of ERCP in pregnant women. ERCP techniques without irradiation were recently introduced as potential alternative. We performed a systematic review and meta-analysis to assess the safety of ERCP in pregnancy and to compare outcomes of radiation versus nonradiation ERCP. Materials and Methods: A systematic search of PubMed, Medline/Ovid, Web of Science, and Google Scholar through April 18th, 2018 using PRISMA and MOOSE guidelines identified 27 studies reporting the outcomes of ERCP in pregnancy. Random effects pooled event rate and 95% confidence intervals (CIs) were estimated. Heterogeneity was measured by I2, and meta-regression analysis was conducted. Adverse outcomes were divided into fetal, maternal pregnancy-related, and maternal nonpregnancy-related. Results: In all, 27 studies reporting on 1,307 pregnant patients who underwent ERCP were identified. Median age was 27.1 years. All results were statistically significant (P...) (See full abstract in article)
Herschel Observations Of The Galactic H Ii Region Rcw 79
Triggered star formation around H II regions could be an important process. The Galactic H II region RCW79 is a prototypical object for triggered highâmass star formation. Aims. We aim to obtain a census of the young stellar population observed at the edges of the H II region and to determine the properties of the young sources in order to characterize the star formation processes that take place at the edges of this ionized region. Methods. We take advantage of Herschel data from the surveys HOBYS, `` Evolution of Interstellar Dust\u27\u27, and HiâGal to extract compact sources. We use the algorithm getsources. We complement the Herschel data with archival 2MASS, Spitzer, and WISE data to determine the physical parameters of the sources (e. g., envelope mass, dust temperature, and luminosity) by fitting the spectral energy distribution. Results. We created the dust temperature and column density maps along with the column density probability distribution function (PDF) for the entire RCW79 region. We obtained a sample of 50 compact sources in this region, 96% of which are situated in the ionizationâcompressed layer of cold and dense gas that is characterized by the column density PDF with a doubleâpeaked lognormal distribution. The 50 sources have sizes of similar to 0.1â0.4 pc with a typical value of similar to 0 : 2 pc, temperatures of similar to 11â26 K, envelope masses of similar to 6 760 Mâcircle dot, densities of similar to 0.1 44 +/â 10(5) cm(3), and luminosities of similar to 19â12712 Lâcircle dot. The sources are classified into 16 class 0, 19 intermediate, and 15 class I objects. Their distribution follows the evolutionary tracks in the diagram of bolometric luminosity versus envelope mass (LâbolâMâenv) well. A mass threshold of 140 M fi, determined from the LâbolâMâenv diagram, yields 12 candidate massive dense cores that may form highâmass stars. The core formation efficiency (CFE) for the 8 massive condensations shows an increasing trend of the CFE with density. This suggests that the denser the condensation, the higher the fraction of its mass transformation into dense cores, as previously observed in other highâmass starâforming regions
High-mass Starless Clumps in the inner Galactic Plane: the Sample and Dust Properties
We report a sample of 463 high-mass starless clump (HMSC) candidates within
and . This sample has been singled out from
10861 ATLASGAL clumps. All of these sources are not associated with any known
star-forming activities collected in SIMBAD and young stellar objects
identified using color-based criteria. We also make sure that the HMSC
candidates have neither point sources at 24 and 70 \micron~nor strong extended
emission at 24 m. Most of the identified HMSCs are infrared (
m) dark and some are even dark at 70 m. Their distribution shows
crowding in Galactic spiral arms and toward the Galactic center and some
well-known star-forming complexes. Many HMSCs are associated with large-scale
filaments. Some basic parameters were attained from column density and dust
temperature maps constructed via fitting far-infrared and submillimeter
continuum data to modified blackbodies. The HMSC candidates have sizes, masses,
and densities similar to clumps associated with Class II methanol masers and
HII regions, suggesting they will evolve into star-forming clumps. More than
90% of the HMSC candidates have densities above some proposed thresholds for
forming high-mass stars. With dust temperatures and luminosity-to-mass ratios
significantly lower than that for star-forming sources, the HMSC candidates are
externally heated and genuinely at very early stages of high-mass star
formation. Twenty sources with equivalent radius pc and
mass surface density g cm could be possible high-mass
starless cores. Further investigations toward these HMSCs would undoubtedly
shed light on comprehensively understanding the birth of high-mass stars.Comment: 16 pages, 15 figures, and 5 tables. Accepted for publication in ApJS.
FITS images for the far-IR to sub-mm data, H2 column density and dust
temperature maps of all the HMSC candidates are available at https:
//yuanjinghua.github.io/hmscs.html. Codes used for this work are publicly
available from https://github.com/yuanjinghua/HMSCs_ca
Interactions of the Infrared bubble N4 with the surroundings
The physical mechanisms that induce the transformation of a certain mass of
gas in new stars are far from being well understood. Infrared bubbles
associated with HII regions have been considered to be good samples of
investigating triggered star formation. In this paper we report on the
investigation of the dust properties of the infrared bubble N4 around the HII
region G11.898+0.747, analyzing its interaction with its surroundings and star
formation histories therein, with the aim of determining the possibility of
star formation triggered by the expansion of the bubble. Using Herschel PACS
and SPIRE images with a wide wavelength coverage, we reveal the dust properties
over the entire bubble. Meanwhile, we are able to identify six dust clumps
surrounding the bubble, with a mean size of 0.50 pc, temperature of about 22 K,
mean column density of 1.7 cm, mean volume density of
about 4.4 cm, and a mean mass of 320 . In
addition, from PAH emission seen at 8 m, free-free emission detected at 20
cm and a probability density function in special regions, we could identify
clear signatures of the influence of the HII region on the surroundings. There
are hints of star formation, though further investigation is required to
demonstrate that N4 is the triggering source.Comment: Accepted by ApJ (16 pages, 11 figures, 9 tables
Maize meal fortification is associated with improved vitamin A and iron status in adolescents and reduced childhood anaemia in a food aid-dependent refugee population
Abstract Objective To assess changes in the Fe and vitamin A status of the population of Nangweshi refugee camp associated with the introduction of maize meal fortification. Design Pre- and post-intervention study using a longitudinal cohort. Setting Nangweshi refugee camp, Zambia. Subjects Two hundred and twelve adolescents (10-19 years), 157 children (6-59 months) and 118 women (20-49 years) were selected at random by household survey in July 2003 and followed up after 12 months. Results Maize grain was milled and fortified in two custom-designed mills installed at a central location in the camp and a daily ration of 400 g per person was distributed twice monthly to households as part of the routine food aid ration. During the intervention period mean Hb increased in children (0·87 g/dl; P < 0·001) and adolescents (0·24 g/dl; P = 0·043) but did not increase in women. Anaemia decreased in children by 23·4 % (P < 0·001) but there was no significant change in adolescents or women. Serum transferrin receptor (log10-transformed) decreased by â0·082 ÎŒg/ml (P = 0·036) indicating an improvement in the Fe status of adolescents but there was no significant decrease in the prevalence of deficiency (â8·5 %; P = 0·079). In adolescents, serum retinol increased by 0·16 ÎŒmol/l (P < 0·001) and vitamin A deficiency decreased by 26·1 % (P < 0·001). Conclusions The introduction of fortified maize meal led to a decrease in anaemia in children and a decrease in vitamin A deficiency in adolescents. Centralised, camp-level milling and fortification of maize meal is a feasible and pertinent intervention in food aid operation
Fecal Microbiota Transplantation in Decompensated Cirrhosis: A Systematic Review on Safety and Efficacy
Background and Aims: Due to increasing knowledge of the âgutâliver axisâ, there has been growing interest regarding the use of fecal microbiota transplant in the management of chronic liver disease. There are limited data available and current guidelines are mostly based on expert opinions. We aim to perform the first systematic review investigating safety and efficacy of fecal microbiota transplant particularly among high-risk decompensated cirrhosis patient populations. Methods: Literature search was performed using variations of the keywords âfecal microbiota transplantâ and âcirrhosisâ on PubMed/Medline from inception to 3 October 2021. The resulting 116 articles were independently screened by two authors. In total, 5 qualifying studies, including 2 randomized control trials and 3 retrospective case series, were found to meet established eligibility criteria and have adequate quality of evidence to be included in this review. Results: Of the total 58 qualifying patients, there were 2 deaths post fecal microbiota transplant, 1 of which could not rule out being related (1.7%). Among the remaining 56 participants, 8 serious adverse events were reported, of which 2 could not rule out being related (3.6%). The success rate of fecal microbiota transplantation in treating recurrent Clostridioides difficile infection among patients with decompensated cirrhosis was 77.8%. The success rate when used as investigational treatment for hepatic encephalopathy was 86.7%, with multiple studies reporting clinically significant improvement in encephalopathy testing scores. Conclusions: We found a marginally higher rate of deaths and serious adverse events from fecal microbiota transplant in our patient population compared with the average immunocompetent population, where it was previously found to have 0 deaths and SAE rate of 2.83%. The efficacy when used for recurrent C.difficile infection was 77.8% and 87% in the decompensated cirrhotic and general populations, respectively. Studies on efficacy in novel treatment of hepatic encephalopathy have been promising. This study concludes that fecal microbiota transplant use in decompensated cirrhosis patients should be used with caution and preferably be limited to research purposes until better data are available
Recycling in the management of solid waste : a study of the governance of Hong Kong's EcoPark
published_or_final_versionPolitics and Public AdministrationMasterMaster of Public Administratio
Intraluminal Endovascular Coil Migration: A Rare Complication Post-Embolization of the Gastroduodenal Artery for a Previously Bleeding Duodenal Ulcer
Transarterial angiographic embolization is a highly effective, safe treatment for non-variceal upper gastrointestinal bleeding refractory to endoscopic intervention. However, intraluminal coil migration is a possible complication. Coil migration, while usually a self-limiting process, can lead to significant rebleeding. In our case, a patient presented with a life-threatening duodenal ulcer hemorrhage, likely precipitated by intraluminal endovascular coil migration after a recent gastro-duodenal artery embolization. He was successfully managed without endoscopic coil removal and had no additional gastrointestinal bleeding. It is important for endoscopists to be aware of this complication and weigh the risks and benefits of coil removal
Mucosal antibodies to the C terminus of toxin A prevent colonization of Clostridium difficile
Mucosal immunity is considered important for protection against Clostridium difficile infection (CDI). We show that in hamsters immunized with Bacillus subtilis spores expressing a carboxy-terminal segment (TcdA26-39) of C. difficile toxin A, no colonization occurs in protected animals when challenged with C. difficile strain 630. In contrast, animals immunized with toxoids showed no protection and remained fully colonized. Along with neutralizing toxins, antibodies to TcdA26-39 (but not to toxoids), whether raised to the recombinant protein or to TcdA26-39 expressed on the B. subtilis spore surface, cross-react with a number of seemingly unrelated proteins expressed on the vegetative cell surface or spore coat of C. difficile. These include two dehydrogenases, AdhE1 and LdhA, as well as the CdeC protein that is present on the spore. Anti-TcdA26-39 mucosal antibodies obtained following immunization with recombinant B. subtilis spores were able to reduce the adhesion of C. difficile to mucus-producing intestinal cells. This cross-reaction is intriguing yet important since it illustrates the importance of mucosal immunity for complete protection against CDI
- âŠ