Molecular properties of interfaces relevant for clathrate hydrate agglomeration

Clathrate hydrates of natural gases show promise for energy in regions traditionally poor of fossil fuels, suggest the possibility of mitigating the atmospheric impact of hydrocarbon consumption via CO 2 sequestration, could advance high-tech applications to address global challenges, including the water-energy nexus, and can lead to significant economic loss and potential safety hazards when they form in oil and gas pipelines. This focused review is motivated by several recent contributions, which demonstrate how atomistic and coarse-grained simulations have become a useful tool. The examples provided suggest the time is right to take advantage of the enhanced understanding provided by simulations, to couple them with experiments that could help design new chemicals for managing hydrate formation in pipelines, for designing chemical processes and additives to advance high-tech applications such as water desalination and natural gas storage, and perhaps also for the production of methane from geological hydrate deposits with simultaneous carbon dioxide sequestration

Impact and cost-effectiveness of hepatitis B virus prophylaxis in pregnancy: a dynamic simulation modelling study

BACKGROUND: In 2020, WHO recommended the addition of peripartum antiviral prophylaxis (PAP) to hepatitis B birth dose vaccination (HepB-BD) and hepatitis B infant vaccination (HepB3) to reduce mother-to-child transmission of hepatitis B virus (HBV) infection in pregnant women who have a marker of high infectivity (ie, HBV DNA ≥200 000 international units per mL or HBeAg-positive). We aimed to evaluate the impact and cost-effectiveness of this recommendation and of a theoretical simplified strategy whereby PAP is given to all pregnant women who are HBsAg-positive without risk stratification. METHODS: This modelling study used a dynamic simulation model of the HBV epidemic in 110 countries in all WHO regions, structured by age, sex, and country. We assessed three strategies of scaling up PAP for pregnant women: PAP for those with high viral load (PAP-VL); PAP for those who are HBeAg-positive (PAP-HBeAg); and PAP for all pregnant women who are HBsAg-positive (PAP-universal), in comparison with neonatal vaccination alone (HepB-BD). We investigated how different diagnostic and antiviral drug costs affected the cost-effectiveness of the strategies evaluated. Using a health-care provider perspective, we calculated incremental cost-effectiveness ratios in cost (US$) per disability-adjusted life-year (DALY) averted in each country's population and compared these with country-specific cost-effectiveness thresholds. We also calculated new neonatal infections averted for each of the strategies. FINDINGS: Adding PAP-VL to HepB-BD could avert around 1·1 million (95% uncertainty interval 1·0 million-1·2 million) new neonatal infections by 2030 and around 3·2 million (95% uncertainty interval 3·0 million-3·4 million) new neonatal infections and approximately 8·8 million (7·8 million-9·7 million) DALYs by 2100 across all the countries modelled. This strategy would probably be cost-effective up to 2100 in 28 (26%) of 106 countries analysed (which included some of the countries that have the greatest HBV burden) if costs are as currently expected to be, and in 74 (70%) countries if diagnostic and monitoring costs were lowered (by about 60-75%). The relative cost-effectiveness of PAP-VL and PAP-HBeAg was finely balanced and depended on the respective diagnostic and monitoring costs. The PAP-universal strategy could be more cost-effective than either of these strategies in most countries, but the use of antiviral treatment could be five times as high than with PAP-VL. INTERPRETATION: PAP can provide substantial health benefits, and, although the current approach might already be cost-effective in some high-burden settings, decreased diagnostic costs would probably be needed for PAP to be cost-effective in most countries. Therefore, careful consideration needs to be given about how such a strategy is implemented, and securing reduced costs for diagnostics should be a priority. The theoretical strategy of offering PAP to all women who are HBsAg-positive (eg, if diagnostic tests to identify mothers at risk of transmission are not available) could be a cost-effective alternative, depending on prevailing costs of diagnostics and antiviral therapy. FUNDING: UK Medical Research Council, UK National Institute for Health and Care Research, and the Vaccine Impact Modelling Consortium

Hepatic artery aneurysm repair: a case report

<p>Abstract</p> <p>Introduction</p> <p>Hepatic artery aneurysms remain a clinically significant entity. Their incidence continues to rise slowly and mortality from spontaneous rupture is high. Repair is recommended in those aneurysms greater than 2 cm in diameter. It is not surprising that vascular comorbidities, such as ischaemic heart disease, are common in surgical patients, particularly those with arterial aneurysms such as these. The decision of when to operate on patients who require urgent surgery despite having recently suffered an acute coronary syndrome remains somewhat of a grey and controversial area. We discuss the role of delayed surgery and postoperative followup of this vascular problem.</p> <p>Case presentation</p> <p>A 58-year-old man was admitted with a 5.5 cm hepatic artery aneurysm. The aneurysm was asymptomatic and was an incidental finding as a result of an abdominal computed tomography scan to investigate an episode of haemoptysis (Figure <figr fid="F1">1</figr>). Three weeks prior to admission, the patient had suffered a large inferior myocardial infarction and was treated by thrombolysis and primary coronary angioplasty. Angiographic assessment revealed a large aneurysm of the common hepatic artery involving the origins of the hepatic, gastroduodenal, left and right gastric arteries and the splenic artery (Figures <figr fid="F2">2</figr> and <figr fid="F3">3</figr>). Endovascular treatment was not considered feasible and immediate surgery was too high-risk in the early post-infarction period. Therefore, surgery was delayed for 3 months when aneurysm repair with reconstruction of the hepatic artery was successfully performed. Graft patency was confirmed with the aid of an abdominal arterial duplex. Plasma levels of conventional liver function enzymes and of alpha-glutathione-<it>S</it>-transferase were within normal limits. This was used to assess the extent of any hepatocellular damage perioperatively. The patient made a good recovery and was well at his routine outpatient check-ups.</p> <p>Conclusion</p> <p>There is no significant difference in cardiac risk in patients who have undergone vascular surgery within 6 months of a myocardial infarction compared with those who have had the operation in the 6 to12 month time frame. Use of alpha-glutathione-<it>S</it>-transferase gives an indication of the immediate state of hepatic function and should be used in addition to traditional liver function tests to monitor hepatic function postoperatively.</p

ALMA unveils rings and gaps in the protoplanetary system HD 169142: signatures of two giant protoplanets

The protoplanetary system HD 169142 is one of the few cases where a potential candidate protoplanet has recently been detected by direct imaging in the near-infrared. To study the interaction between the protoplanet and the disk itself, observations of the gas and dust surface density structure are needed. This paper reports new ALMA observations of the dust continuum at 1.3 mm, 12CO, 13CO, and C18O J = 2−1 emission from the system HD 169142 (which is observed almost face-on) at an angular resolution of ∼0.3"×0.2′′ (∼35 × 20 au). The dust continuum emission reveals a double-ring structure with an inner ring between 0.17"−0.28" (∼20−35 au) and an outer ring between 0.48−0.64 (∼56−83 au). The size and position of the inner ring is in good agreement with previous polarimetric observations in the near-infrared and is consistent with dust trapping by a massive planet. No dust emission is detected inside the inner dust cavity (R μm size). Using the thermo-chemical disk code dali, we modeled the continuum and the CO isotopolog emission to quantitatively measure the gas and dust surface densities. The resulting gas surface density is reduced by a factor of ∼30−40 inward of the dust gap. The gas and dust distribution indicate that two giant planets shape the disk structure through dynamical clearing (dust cavity and gap) and dust trapping (double-ring dust distribution)

Are women residency supervisors obligated to nurture?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73923/1/j.1365-2929.2006.02635.x.pd

An inherited complex organic molecule reservoir in a warm planet-hosting disk

Quantifying the composition of the material in protoplanetary disks is essential to determining the potential for exoplanetary systems to produce and support habitable environments. When considering potential habitability, complex organic molecules are relevant, key among which is methanol (CH3OH). Methanol primarily forms at low temperatures via the hydrogenation of CO ice on the surface of icy dust grains and is a necessary basis for the formation of more complex species such as amino acids and proteins. We report the detection of CH3OH in a disk around a young, luminous A-type star, HD 100546. This disk is warm and therefore does not host an abundant reservoir of CO ice. We argue that the CH3OH cannot form in situ, and hence that this disk has probably inherited complex-organic-molecule-rich ice from an earlier cold dark cloud phase. This is strong evidence that at least some interstellar organic material survives the disk-formation process and can then be incorporated into forming planets, moons and comets. Therefore, crucial pre-biotic chemical evolution already takes place in dark star-forming clouds

The cometary composition of a protoplanetary disk as revealed by complex cyanides

Observations of comets and asteroids show that the Solar Nebula that spawned our planetary system was rich in water and organic molecules. Bombardment brought these organics to the young Earth's surface, seeding its early chemistry. Unlike asteroids, comets preserve a nearly pristine record of the Solar Nebula composition. The presence of cyanides in comets, including 0.01% of methyl cyanide (CH3CN) with respect to water, is of special interest because of the importance of C-N bonds for abiotic amino acid synthesis. Comet-like compositions of simple and complex volatiles are found in protostars, and can be readily explained by a combination of gas-phase chemistry to form e.g. HCN and an active ice-phase chemistry on grain surfaces that advances complexity[3]. Simple volatiles, including water and HCN, have been detected previously in Solar Nebula analogues - protoplanetary disks around young stars - indicating that they survive disk formation or are reformed in situ. It has been hitherto unclear whether the same holds for more complex organic molecules outside of the Solar Nebula, since recent observations show a dramatic change in the chemistry at the boundary between nascent envelopes and young disks due to accretion shocks[8]. Here we report the detection of CH3CN (and HCN and HC3N) in the protoplanetary disk around the young star MWC 480. We find abundance ratios of these N-bearing organics in the gas-phase similar to comets, which suggests an even higher relative abundance of complex cyanides in the disk ice. This implies that complex organics accompany simpler volatiles in protoplanetary disks, and that the rich organic chemistry of the Solar Nebula was not unique.Comment: Definitive version of the manuscript is published in Nature, 520, 7546, 198, 2015. This is the author's versio

Probing midplane CO abundance and gas temperature with DCO+ in the protoplanetary disk around HD 169142

Context. Physical and chemical processes in protoplanetary disks affect the disk structure and the midplane environment within which planets form. The simple deuterated molecular cation DCO+ has been proposed to act as a tracer of the disk midplane conditions. Aims. This work aims to understand which midplane conditions are probed by the DCO+ emission in the disk around the Herbig Ae star HD 169142. We explore the sensitivity of the DCO+ formation pathways to gas temperature and CO abundance. Methods. The DCO+ J = 3−2 transition was observed with Atacama Large Millimeter/submillimeter Array at a spatial resolution of ~0.3′′ (35 AU at 117 pc). We modeled the DCO+ emission in HD 169142 with a physical disk structure adapted from the literature, and employed a simple deuterium chemical network to investigate the formation of DCO+ through the cold deuterium fractionation pathway via H2D+. Parameterized models are used to modify the gas temperature and CO abundance structure of the disk midplane to test their effect on DCO+ production. Contributions from the warm deuterium fractionation pathway via CH2D+ are approximated using a constant abundance in the intermediate disk layers. Results. The DCO+ line is detected in the HD 169142 disk with a total integrated line flux of 730 ± 73 mJy km s−1. The radial intensity profile reveals a warm, inner component of the DCO+ emission at radii ≲30 AU and a broad, ring-like structure from ~50–230 AU with a peak at 100 AU just beyond the edge of the millimeter grain distribution. Parameterized models show that alterations to the midplane gas temperature and CO abundance are both needed to recover the observed DCO+ radial intensity profile. The alterations are relative to the fiducial physical structure of the literature model constrained by dust and CO observations. The best-fit model contains a shadowed, cold midplane in the region z∕r 120 AU. The warm deuterium fractionation pathway is implemented as a constant DCO+ abundance of 2.0 × 10−12 between 30–70 K and contributes >85% to the DCO+ emission at r < 83 AU in the best-fit model. Conclusions. The DCO+ emission probes a reservoir of cold material in the HD 169142 outer disk that is not probed by the millimeter continuum, the spectral energy distribution, nor the emission from the 12 CO, 13 CO, or C18O J = 2−1 lines. The DCO+ emission is a sensitive probe of gas temperature and CO abundance near the disk midplane and provides information about the outer disk beyond the millimeter continuum distribution that is largely absent in abundant gaseous tracers such as CO isotopologues

One way or another? Criminal investigators' beliefs regarding the disclosure of evidence in interviews with suspects in England and Wales

The research base concerning interviews with suspects remains to be comprehensively developed. For example, the extant literature provides differing views regarding how best to undertake the important interview task of disclosing evidence. In the current study, using a self-report questionnaire, 224 investigators based in England and Wales were asked as to their own preferred methods. Most respondents advocated a gradual method of disclosing evidence, stating that this approach would better reveal inconsistencies and obtain a complete version of events (similar to the reasoning of those who preferred disclosing evidence later). Those who advocated revealing evidence early stated this approach would more likely elicit confessions. Several respondents would not commit to one single method, arguing that their chosen strategy was contextually dependent. The study’s findings suggest that it remains arguable as to whether there is one best approach to evidence disclosure and/or whether particular circumstances should influence interviewing strategies