Context. Converging networks of interstellar filaments, that is hubs, have been recently linked to the formation of stellar clusters and massive stars. Understanding the relationship between the ...evolution of these systems and the formation of cores and stars inside them is at the heart of current star formation research. Aims. The goal is to study the kinematic and density structure of the SDC13 prototypical hub at high angular resolution to determine what drives its evolution and fragmentation. Methods. We have mapped SDC13, a ~1000 M⊙ infrared dark hub, in NH3(1,1) and NH3(2,2) emission lines, with both the Jansky Very Large Array and Green Bank Telescope. The high angular resolution achieved in the combined dataset allowed us to probe scales down to 0.07 pc. After fitting the ammonia lines, we computed the integrated intensities, centroid velocities and line widths, along with gas temperatures and H2 column densities. Results. The mass-per-unit-lengths of all four hub filaments are thermally super-critical, consistent with the presence of tens of gravitationally bound cores identified along them. These cores exhibit a regular separation of ~0.37 ± 0.16 pc suggesting gravitational instabilities running along these super-critical filaments are responsible for their fragmentation. The observed local increase of the dense gas velocity dispersion towards starless cores is believed to be a consequence of such fragmentation process. Using energy conservation arguments, we estimate that the gravitational to kinetic energy conversion efficiency in the SDC13 cores is ~35%. We see velocity gradient peaks towards ~63% of cores as expected during the early stages of filament fragmentation. Another clear observational signature is the presence of the most massive cores at the filaments’ junction, where the velocity dispersion is largest. We interpret this as the result of the hub morphology generating the largest acceleration gradients near the hub centre. Conclusions. We propose a scenario for the evolution of the SDC13 hub in which filaments first form as post-shock structures in a supersonic turbulent flow. As a result of the turbulent energy dissipation in the shock, the dense gas within the filaments is initially mostly sub-sonic. Then gravity takes over and starts shaping the evolution of the hub, both fragmenting filaments and pulling the gas towards the centre of the gravitational well. By doing so, gravitational energy is converted into kinetic energy in both local (cores) and global (hub centre) potential well minima. Furthermore, the generation of larger gravitational acceleration gradients at the filament junctions promotes the formation of more massive cores.
Benefits of immunosuppressive therapy in Crohn's disease have been demonstrated in controlled trials; however, it is unclear whether these drugs alter the longer-term natural history of this ...condition.
To assess changes in disease outcomes in a population-based cohort of patients diagnosed in Cardiff from 1986 to 2003. Case notes from Crohn's disease incidence studies in Cardiff were reviewed retrospectively for disease characteristics and follow-up information on drug therapy, and the need for surgery for Crohn's disease. The study population was divided into three groups by year of diagnosis (Group A=1986-1991, Group B=1992-1997 and Group C=1998-2003).
341 patients were included. Kaplan-Meier (KM) analysis showed increasing use of immunosuppressants over time. At 5 years after diagnosis this was 11% in Group A, 28% in Group B, and 45% in Group C (p=0.001) and the median time to start of thiopurines was 77, 21 and 11 months in Group A, B and C respectively. There was a significant reduction in long-term steroid use at 5 years post diagnosis: 45 (44%), 31 (31%) and 24 (19%) patients in Group A, B and C respectively (p=0.001). KM analysis showed a significant reduction in the cumulative probability of intestinal surgery: At 5 years this was 59% (Group A), 37% (Group B) and 25% (Group C) (p=0.001). In a multivariate Cox analysis, year of diagnosis, disease location, oral corticosteroids within 3 months of diagnosis and early thiopurine use (within the first year of diagnosis) were all independent factors affecting likelihood of intestinal surgery.
This population-based cohort shows marked changes in rates of surgery, and the reduction is independently associated with year of diagnosis, and associated temporally with increased and earlier thiopurine use.
Science and technologies based on terahertz frequency electromagnetic radiation (100 GHz-30 THz) have developed rapidly over the last 30 years. For most of the 20th Century, terahertz radiation, then ...referred to as sub-millimeter wave or far-infrared radiation, was mainly utilized by astronomers and some spectroscopists. Following the development of laser based terahertz time-domain spectroscopy in the 1980s and 1990s the field of THz science and technology expanded rapidly, to the extent that it now touches many areas from fundamental science to 'real world' applications. For example THz radiation is being used to optimize materials for new solar cells, and may also be a key technology for the next generation of airport security scanners. While the field was emerging it was possible to keep track of all new developments, however now the field has grown so much that it is increasingly difficult to follow the diverse range of new discoveries and applications that are appearing. At this point in time, when the field of THz science and technology is moving from an emerging to a more established and interdisciplinary field, it is apt to present a roadmap to help identify the breadth and future directions of the field. The aim of this roadmap is to present a snapshot of the present state of THz science and technology in 2017, and provide an opinion on the challenges and opportunities that the future holds. To be able to achieve this aim, we have invited a group of international experts to write 18 sections that cover most of the key areas of THz science and technology. We hope that The 2017 Roadmap on THz science and technology will prove to be a useful resource by providing a wide ranging introduction to the capabilities of THz radiation for those outside or just entering the field as well as providing perspective and breadth for those who are well established. We also feel that this review should serve as a useful guide for government and funding agencies.
We identify stellar structures in the PHANGS sample of 74 nearby galaxies and construct morphological masks of sub-galactic environments based on
Spitzer
3.6
μ
m images. At the simplest level, we ...distinguish five environments: centres, bars, spiral arms, interarm regions, and discs without strong spirals. Slightly more sophisticated masks include rings and lenses, which are publicly released but not explicitly used in this paper. We examine trends with environment in the molecular gas content, star formation rate, and depletion time using PHANGS–ALMA CO(2–1) intensity maps and tracers of star formation. The interarm regions and discs without strong spirals clearly dominate in area, whereas molecular gas and star formation are quite evenly distributed among the five basic environments. We reproduce the molecular Kennicutt–Schmidt relation with a slope compatible with unity within the uncertainties and without significant slope differences among environments. In contrast to what has been suggested by early studies, we find that bars are not always deserts devoid of gas and star formation, but instead they show large diversity. Similarly, spiral arms do not account for most of the gas and star formation in disc galaxies, and they do not have shorter depletion times than the interarm regions. Spiral arms accumulate gas and star formation, without systematically boosting the star formation efficiency. Centres harbour remarkably high surface densities and on average shorter depletion times than other environments. Centres of barred galaxies show higher surface densities and wider distributions compared to the outer disc; yet, depletion times are similar to unbarred galaxies, suggesting highly intermittent periods of star formation when bars episodically drive gas inflow, without enhancing the central star formation efficiency permanently. In conclusion, we provide quantitative evidence that stellar structures in galaxies strongly affect the organisation of molecular gas and star formation, but their impact on star formation efficiency is more subtle.
Aim
Lymph node (LN) metastases are present in up to 17% of early colorectal cancers (pT1). Identification of associated histopathological factors would enable counselling of patients regarding this ...risk.
Method
Pubmed and Embase were employed utilizing the terms ‘early colorectal cancer’, ‘lymph node metastasis’, ‘submucosal invasion’, ‘lymphovascular invasion’, ‘tumour budding’ and ‘histological differentiation’. Analysis was performed using REVIEW MANAGER 5.1.
Results
Twenty‐three cohort studies including 4510 patients were analysed. There was a significantly higher risk of LN metastasis with a depth of submucosal invasion > 1 mm than with lesser degrees of penetration (OR 3.87, 95% CI 1.50–10.00, P = 0.005). Lymphovascular invasion was significantly associated with LN metastasis (OR 4.81, 95% CI 3.14–7.37, P < 0.00001). Poorly differentiated tumours had a higher risk of LN metastasis compared with well or moderately differentiated tumours (OR 5.60, 95% CI 2.90–10.82, P < 0.00001). Tumour budding was found to be significantly associated with LN metastasis (OR 7.74, 95% CI 4.47–13.39, P < 0.001).
Conclusion
Meta‐analysis of the current literature demonstrates that in early colorectal cancer a depth of submucosal invasion by the primary tumour of > 1 mm, lymphovascular invasion, poor differentiation and tumour budding are significantly associated with LN metastasis.
Aims.
The complexity of star formation at the physical scale of molecular clouds is not yet fully understood. We investigate the mechanisms regulating the formation of stars in different environments ...within nearby star-forming galaxies from the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) sample.
Methods.
Integral field spectroscopic data and radio-interferometric observations of 18 galaxies were combined to explore the existence of the resolved star formation main sequence (Σ
stellar
versus Σ
SFR
), resolved Kennicutt–Schmidt relation (Σ
mol. gas
versus Σ
SFR
), and resolved molecular gas main sequence (Σ
stellar
versus Σ
mol. gas
), and we derived their slope and scatter at spatial resolutions from 100 pc to 1 kpc (under various assumptions).
Results.
All three relations were recovered at the highest spatial resolution (100 pc). Furthermore, significant variations in these scaling relations were observed across different galactic environments. The exclusion of non-detections has a systematic impact on the inferred slope as a function of the spatial scale. Finally, the scatter of the Σ
mol. gas + stellar
versus Σ
SFR
correlation is smaller than that of the resolved star formation main sequence, but higher than that found for the resolved Kennicutt–Schmidt relation.
Conclusions.
The resolved molecular gas main sequence has the tightest relation at a spatial scale of 100 pc (scatter of 0.34 dex), followed by the resolved Kennicutt–Schmidt relation (0.41 dex) and then the resolved star formation main sequence (0.51 dex). This is consistent with expectations from the timescales involved in the evolutionary cycle of molecular clouds. Surprisingly, the resolved Kennicutt–Schmidt relation shows the least variation across galaxies and environments, suggesting a tight link between molecular gas and subsequent star formation. The scatter of the three relations decreases at lower spatial resolutions, with the resolved Kennicutt–Schmidt relation being the tightest (0.27 dex) at a spatial scale of 1 kpc. Variation in the slope of the resolved star formation main sequence among galaxies is partially due to different detection fractions of Σ
SFR
with respect to Σ
stellar
.
A likely important feature of the poorly understood aerosol‐cloud interactions over the Southern Ocean (SO) is the dominant role of sea spray aerosol, versus terrestrial aerosol. Ice nucleating ...particles (INPs), or particles required for heterogeneous ice nucleation, present over the SO have not been studied in several decades. In this study, boundary layer aerosol properties and immersion freezing INP number concentrations (nINPs) were measured during a ship campaign that occurred south of Australia (down to 53°S) in March–April 2016. Ocean surface chlorophyll a concentrations ranged from 0.11 to 1.77 mg/m3, and nINPs were a factor of 100 lower than historical surveys, ranging from 0.38 to 4.6 m−3 at −20 °C. The INP population included organic heat‐stable material, with contributions from heat‐labile material. Lower INP source potentials of SO seawater samples compared to Arctic seawater were consistent with lower ice nucleating site densities in this study compared to north Atlantic air masses.
Plain Language Summary
The Southern Ocean is known for a prevalence of clouds that contain both liquid and ice, which are one of the most poorly understood cloud regimes in the climate system. A large gap in understanding important processes in these clouds is a lack of knowledge regarding particles (e.g., sea spray) required for forming ice crystals, termed ice nucleating particles. In a ship‐based monthlong field study, several instruments were deployed in efforts to characterize the ice nucleating particles present over the Southern Ocean for the first time in over four decades. Abundances of ice nucleating particles throughout the voyage were extremely low compared to other ocean regions, and concentrations were 2 orders of magnitude lower than the most recent survey conducted in the 1970s. We report that the ocean‐derived ice nucleating particles observed in this study were organic in nature, supporting a hypothesized link between ice nucleating particles and organic particles associated with phytoplankton blooms. The data from this study provide a desperately needed benchmark for constraining the number of ice crystals that may form in the remote and poorly understood clouds occurring over the Southern Ocean.
Key Points
Number concentrations of ice nucleating particles over the Southern Ocean in March 2016 were a factor of 100 lower than historical surveys
The ice nucleating particle source strength of Southern Ocean seawater was lower than previous measurements in northern hemisphere seawater
Ice nucleation site densities were lower over the Southern Ocean compared to measurements of pristine air masses from other ocean basins
As many as two of every three major surgery patients are malnourished preoperatively - a diagnosis rarely made and treated even less frequently. Unfortunately, perioperative malnutrition is perhaps ...the least often identified surgical risk factor and is among the most treatable to improve outcomes.
Two important perioperative nutrition guidelines were published recently. Both emphasize nutrition assessment as an essential component of preoperative screening. The recently published perioperative nutrition screen (PONS) readily identifies patients at malnutrition risk, allowing for preoperative nutritional optimization. The use of computerized tomography scan and ultrasound lean body mass (LBM) evaluation to identify sarcopenia associated with surgical risk and guide nutrition intervention is garnering further support. Preoperative nutrition optimization in malnourished patients, use of immunonutrition in all major surgery, avoidance of preoperative fasting, inclusion of postoperative high-protein nutritional supplements, and early postoperative oral intake have all recently been shown to improve outcomes and should be utilized.
The recent publication of new surgical nutrition guidelines, the PONS score, and use of LBM assessments will allow better identification and earlier intervention on perioperative malnutrition. It is essential that in the future no patient undergoes elective surgery without nutrition screening and nutrition intervention when malnutrition risk is identified.
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