ABSTRACT
The evolution of molecular clouds in galactic centres is thought to differ from that in galactic discs due to a significant influence of the external gravitational potential. We present a ...set of numerical simulations of molecular clouds orbiting on the 100-pc stream of the Central Molecular Zone (the central ${\sim }500\,{{\rm pc}}$ of the Galaxy) and characterize their morphological and kinematic evolution in response to the background potential and eccentric orbital motion. We find that the clouds are shaped by strong shear and torques, by tidal and geometric deformation, and by their passage through the orbital pericentre. Within our simulations, these mechanisms control cloud sizes, aspect ratios, position angles, filamentary structure, column densities, velocity dispersions, line-of-sight velocity gradients, spin angular momenta, and kinematic complexity. By comparing these predictions to observations of clouds on the Galactic Centre ‘dust ridge’, we find that our simulations naturally reproduce a broad range of key observed morphological and kinematic features, which can be explained in terms of well-understood physical mechanisms. We argue that the accretion of gas clouds on to the central regions of galaxies, where the rotation curve turns over and the tidal field is fully compressive, is accompanied by transformative dynamical changes to the clouds, leading to collapse and star formation. This can generate an evolutionary progression of cloud collapse with a common starting point, which either marks the time of accretion on to the tidally compressive region or of the most recent pericentre passage. Together, these processes may naturally produce the synchronized starbursts observed in numerous (extra)galactic nuclei.
We present new JVLA observations of the high-mass cluster-forming region W51A from 2 to 16 GHz with resolution θfwhm ≈ 0.3−0.5″. The data reveal a wealth of observational results: (1) Currently ...forming, very massive (proto-O) stars are traced by o - H2CO21,1−21,2 emission, suggesting that this line can be used efficiently as a massive protostar tracer; (2) there is a spatially distributed population of ≲mJy continuum sources, including hypercompact H ii regions and candidate colliding wind binaries, in and around the W51 proto-clusters; and (3) there are two clearly detected protoclusters, W51e and W51 IRS2, that are gas-rich but may have most of their mass in stars within their inner ≲0.05 pc. The majority of the bolometric luminosity in W51 most likely comes from a third population of OB stars between these clusters. The presence of a substantial population of exposed O-stars coincident with a population of still-forming massive stars, together with a direct measurement of the low mass loss rate via ionized gas outflow from W51 IRS2, implies that feedback is ineffective at halting star formation in massive protoclusters. Instead, feedback may shut off the large-scale accretion of diffuse gas onto the W51 protoclusters, implying that they are evolving toward a state of gas exhaustion rather than gas expulsion. Recent theoretical models predict gas exhaustion to be a necessary step in the formation of gravitationally bound stellar clusters, and our results provide an observational validation of this process.
Summary
This study aimed to determine the effect of fish oil on bone mineral density (BMD). There were no differences in the 2-year BMD measures between high and low dose groups after adjusting for ...baseline BMD. This randomized controlled trial did not demonstrate any efficacy of omega-3 fatty acids on bone loss in adults.
Introduction
The purpose of this study is to investigate whether supplementation with high dose omega-3 fish oil could have an impact on BMD.
Methods
In a multicentre, double-blind randomized controlled trial (RCT) (ACTRN 12607000415404), 202 Australian participants aged ≥40 with knee osteoarthritis (mean age, 61.0 ± 10.0 years; 49 % female) were randomized to receive either high dose (4.5 g eicosapentaenoic acid and docosahexaenoic acid daily) or low dose (0.45 g/day) omega-3 fish oil for 2 years. BMD was assessed at baseline and 2 years by dual energy X-ray absorptiometry.
Results
In subjects with baseline and 2-year assessments, mean standardized BMD at baseline for low or high dose group was 1198 ± 198 and 1157 ± 169 mg/cm
2
, respectively, for the lumbar spine and was 1035 ± 165 and 1017 ± 174 mg/cm
2
, respectively, for the femoral neck. There were no differences in the 2-year BMD measures between high and low dose groups after adjusting for baseline BMD in the complete case regression analyses (lumbar spine 3.7, 95 % confidence interval (CI) −7.9 to 15.3 mg/cm
2
and femoral neck −5.5, 95 % CI −14.9 to 3.9 mg/cm
2
). The findings did not change with additional adjustments of age, gender, study centre and uses of bone-related drugs during the study period as well as using the intention-to-treat analysis or limiting to older participants (≥55 years at the baseline) (all
P
≥ 0.25). Mild adverse events such as headache and gastrointestinal intolerance were common but did not occur more frequently in either group. There were no serious adverse events related to the intervention.
Conclusion
A 2-year supplementation with high-dose omega-3 fish oil did not alter bone loss among men and women with knee osteoarthritis.
IntroductionThe primary purpose of this study is to evaluate the relative effectiveness of 2 of the best developed and most promising forms of therapy for problem gambling, namely face-to-face ...motivational interviewing (MI) combined with a self-instruction booklet (W) and follow-up telephone booster sessions (B; MI+W+B) and face-to-face cognitive–behavioural therapy (CBT).Methods and analysisThis project is a single-blind pragmatic randomised clinical trial of 2 interventions, with and without the addition of relapse-prevention text messages. Trial assessments take place pretreatment, at 3 and 12 months. A total of 300 participants will be recruited through a community treatment agency that provides services across New Zealand and randomised to up to 10 face-to-face sessions of CBT or 1 face-to-face session of MI+W+up to 5 B. Participants will also be randomised to 9 months of postcare text messaging. Eligibility criteria include a self-perception of having a current gambling problem and a willingness to participate in all components of the study (eg, read workbook). The statistical analysis will use an intent-to-treat approach. Primary outcome measures are days spent gambling and amount of money spent per day gambling in the prior month. Secondary outcome measures include problem gambling severity, gambling urges, gambling cognitions, mood, alcohol, drug use, tobacco, psychological distress, quality of life, health status and direct and indirect costs associated with treatment.Ethics and disseminationThe research methods to be used in this study have been approved by the Ministry of Health, Health and Disability Ethics Committees (HDEC) 15/CEN/99. The investigators will provide annual reports to the HDEC and report any adverse events to this committee. Amendments will also be submitted to this committee. The results of this trial will be submitted for publication in peer-reviewed journals and as a report to the funding body. Additionally, the results will be presented at national and international conferences.Trial registration numberACTRN12615000637549.
Background
Recent evidence has suggested an association between postoperative non‐steroidal anti‐inflammatory drugs (NSAIDs) and increased operation‐specific complications. This study aimed to ...determine the safety profile following gastrointestinal surgery across a multicentre setting in the UK.
Methods
This multicentre study was carried out during a 2‐week interval in September–October 2013. Consecutive adults undergoing elective or emergency gastrointestinal resection were included. The study was powered to detect a 10 per cent increase in major complications (grade III–V according to the Dindo–Clavien classification). The effect of administration of NSAIDs on the day of surgery or the following 2 days was risk‐adjusted using propensity score matching and multivariable logistic regression to produce adjusted odds ratios (ORs). The type of NSAID and the dose were registered.
Results
Across 109 centres, early postoperative NSAIDs were administered to 242 (16·1 per cent) of 1503 patients. Complications occurred in 981 patients (65·3 per cent), which were major in 257 (17·1 per cent) and minor (Dindo–Clavien grade I–II) in 724 (48·2 per cent). Propensity score matching created well balanced groups. Treatment with NSAIDs was associated with a reduction in overall complications (OR 0·72, 95 per cent confidence interval 0·52 to 0·99; P = 0·041). This effect predominately comprised a reduction in minor complications with high‐dose NSAIDs (OR 0·57, 0·39 to 0·89; P = 0·009).
Conclusion
Early use of NSAIDs is associated with a reduction in postoperative adverse events following major gastrointestinal surgery.
Some non‐steroidal anti‐inflammatory drugs may be beneficial
Increasing evidence indicates that combined mechanical and oral antibiotic bowel preparation reduces the infectious complications of colorectal surgery. Anecdotal evidence suggests the combination is ...rarely used in the UK and Europe.
To establish colorectal surgeons' current use and awareness of the benefits of such bowel preparation, and to identify decision-making influences surrounding preoperative bowel preparation.
An electronic survey was emailed to all members of the Association of Coloproctology of Great Britain and Ireland, and promoted via Twitter.
A total of 495 respondents completed the survey: 413 (83.2%) UK, 39 (7.9%) other European, 43 (8.7%) non-European. Respondents used oral antibiotics for 12–20% of cases. Mechanical bowel preparation (MBP), phosphate enema, and no preparation, respectively, ranged between 9 and 80%. Combined MBP and oral antibiotic bowel preparation ranged between 5.5 and 18.6%.
Fifty-three percent (260/495) agreed that combined mechanical and oral antibiotic bowel preparation reduces surgical site infection; 32% (157/495) agreed that the combination reduces risk of anastomotic leak.
Kappa statistics between 0.06 and 0.27 indicate considerable incongruity between surgeons' awareness of the literature, and day-to-day practice.
Twenty-four percent (96/495) believed MBP to be incompatible with enhanced recovery after surgery (ERAS); 41% (204/495) believed that MBP delays return to normal intestinal function.
Few UK and European colorectal surgeons use mechanical and oral antibiotic bowel preparation, despite evidence of its efficacy in reducing infectious complications. The influence of ERAS pathways and UK and European guidelines may explain this. In contradiction to the UK and Europe, North American guidelines recommend incorporating combined mechanical and oral antibiotic bowel preparation into ERAS programmes. This study suggests that future UK and European guidelines incorporate combined mechanical and oral antibiotic bowel preparation into the ERAS pathway.
Skeletal muscle fibers typically undergo modifications in their mitochondrial content, concomitant with alterations in oxidative metabolism that occur during the development of muscle fiber and in ...response to physiological stimuli. We examined how cold acclimation affects the mitochondrial properties of two fish skeletal muscle fiber types and how the regulators of mitochondrial content differed between tissues. After 2 mo of acclimation to either 4 or 18 degrees C, mitochondrial enzyme activities in both red and white muscle were higher in cold-acclimated fish. No significant differences were detected between acclimation temperatures in the abundance of steady-state mitochondrial mRNA (cytochrome-c oxidase 1, subunit 6 of F0F1-ATPase), rRNA (16S), or DNA copy number. Steady-state mRNA for nuclear-encoded respiratory (adenine nucleotide translocase 1) and glycolytic genes showed high interindividual variability, particularly in the cold-acclimated fish. Although mitochondrial enzymes were 10-fold different between the two muscle types, mitochondrial DNA copy number differed only 4-fold. The relative abundance of mitochondrial mRNA and nuclear mRNA in red and white muscle reflected the differences in copy number of their respective genes. These data suggest that the response to physiological stimuli and determination of tissue-specific mitochondrial properties likely result from the regulation of nuclear-encoded genes.
ABSTRACT
We use hydrodynamical simulations to study the Milky Way’s central molecular zone (CMZ). The simulations include a non-equilibrium chemical network, the gas self-gravity, star formation, and ...supernova feedback. We resolve the structure of the interstellar medium at sub-parsec resolution while also capturing the interaction between the CMZ and the bar-driven large-scale flow out to $R\sim 5\, {\rm kpc}$. Our main findings are as follows: (1) The distinction between inner (R ≲ 120 pc) and outer (120 ≲ R ≲ 450 pc) CMZ that is sometimes proposed in the literature is unnecessary. Instead, the CMZ is best described as single structure, namely a star-forming ring with outer radius R ≃ 200 pc which includes the 1.3° complex and which is directly interacting with the dust lanes that mediate the bar-driven inflow. (2) This accretion can induce a significant tilt of the CMZ out of the plane. A tilted CMZ might provide an alternative explanation to the ∞-shaped structure identified in Herschel data by Molinari et al. (3) The bar in our simulation efficiently drives an inflow from the Galactic disc (R ≃ 3 kpc) down to the CMZ (R ≃ 200 pc) of the order of $1\rm \, M_\odot \, yr^{-1}$, consistent with observational determinations. (4) Supernova feedback can drive an inflow from the CMZ inwards towards the circumnuclear disc of the order of ${\sim}0.03\, \rm M_\odot \, yr^{-1}$. (5) We give a new interpretation for the 3D placement of the 20 and 50 km s−1 clouds, according to which they are close (R ≲ 30 pc) to the Galactic Centre, but are also connected to the larger scale streams at R ≳ 100 pc.
ABSTRACT
The Milky Way’s Central Molecular Zone (CMZ) has emerged in recent years as a unique laboratory for the study of star formation. Here we use the simulations presented in Tress et al. to ...investigate star formation in the CMZ. These simulations resolve the structure of the interstellar medium at sub-parsec resolution while also including the large-scale flow in which the CMZ is embedded. Our main findings are as follows. (1) While most of the star formation happens in the CMZ ring at $R\gtrsim 100 \, {\rm pc}$, a significant amount also occurs closer to Sgr A* at $R \lesssim 10\, {\rm pc}$. (2) Most of the star formation in the CMZ happens downstream of the apocentres, consistent with the ‘pearls-on-a-string’ scenario, and in contrast to the notion that an absolute evolutionary timeline of star formation is triggered by pericentre passage. (3) Within the time-scale of our simulations (∼100 Myr), the depletion time of the CMZ is constant within a factor of ∼2. This suggests that variations in the star formation rate are primarily driven by variations in the mass of the CMZ, caused, for example, by active galactic nuclei (AGN) feedback or externally induced changes in the bar-driven inflow rate, and not by variations in the depletion time. (4) We study the trajectories of newly born stars in our simulations. We find several examples that have age and 3D velocity compatible with those of the Arches and Quintuplet clusters. Our simulations suggest that these prominent clusters originated near the collision sites where the bar-driven inflow accretes on to the CMZ, at symmetrical locations with respect to the Galactic Centre, and that they have already decoupled from the gas in which they were born.
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