Boyle's law and gravitational instability

We have re-examined the classical problem of the macroscopic equation of state for a hydrostatic isothermal self-gravitating gas cloud bounded by an external medium at constant pressure. We have obtained analytical conditions for its equilibrium and stability without imposing any specific shape and symmetry to the cloud density distribution. The equilibrium condition can be stated in the form of an upper limit to the cloud mass; this is found to be inversely proportional to the power 3/2 of a form factor \mu characterizing the shape of the cloud. In this respect, the spherical solution, associated with the maximum value of the form factor, \mu = 1, turns out to correspond to the shape that is most difficult to realize. Surprisingly, the condition that defines the onset of the Bonnor instability (or gravothermal catastrophe) can be cast in the form of an upper limit to the density contrast within the cloud that is independent of the cloud shape. We have then carried out a similar analysis in the two-dimensional case of infinite cylinders, without assuming axisymmetry. The results obtained in this paper generalize well-known results available for spherical or axisymmetric cylindrical isothermal clouds that have had wide astrophysical applications, especially in the study of the interstellar medium.Comment: 9 pages, 2 figures, to appear in A&

Simulating the formation and evolution of galaxies: Multi-phase description of the interstellar medium, star formation, and energy feedback

We present a multi-phase representation of the ISM in NB-TSPH simulations of galaxy formation and evolution with particular attention to the case of early-type galaxies. Cold gas clouds are described by the so-called sticky particles algorithm. They can freely move throughout the hot ISM medium; stars form within these clouds and the mass exchange among the three baryonic phases (hot gas, cold clouds, stars) is governed by radiative and Compton cooling and energy feedback by supernova (SN) explosions, stellar winds, and UV radiation. We also consider thermal conduction, cloud-cloud collisions, and chemical enrichment. Our model agrees with and improves upon previous studies on the same subject. The results for the star formation rate are very promising and agree with recent observational data on early-type galaxies. These models lend further support to the revised monolithic scheme of galaxy formation, which has recently been also strengthened by high redshift data leading to the so-called downsizing and top-down scenarios.Comment: 17 pages, 17 figure

Triplets of supermassive black holes: Astrophysics, Gravitational Waves and Detection

Supermassive black holes (SMBHs) found in the centers of many galaxies have been recognized to play a fundamental active role in the cosmological structure formation process. In hierarchical formation scenarios, SMBHs are expected to form binaries following the merger of their host galaxies. If these binaries do not coalesce before the merger with a third galaxy, the formation of a black hole triple system is possible. Numerical simulations of the dynamics of triples within galaxy cores exhibit phases of very high eccentricity (as high as $e \sim 0.99$). During these phases, intense bursts of gravitational radiation can be emitted at orbital periapsis. This produces a gravitational wave signal at frequencies substantially higher than the orbital frequency. The likelihood of detection of these bursts with pulsar timing and the Laser Interferometer Space Antenna ({\it LISA}) is estimated using several population models of SMBHs with masses $\gtrsim 10^7 {\rm M_\odot}$. Assuming a fraction of binaries $\ge 0.1$ in triple system, we find that few to few dozens of these bursts will produce residuals $>1$ ns, within the sensitivity range of forthcoming pulsar timing arrays (PTAs). However, most of such bursts will be washed out in the underlying confusion noise produced by all the other 'standard' SMBH binaries emitting in the same frequency window. A detailed data analysis study would be required to assess resolvability of such sources. Implementing a basic resolvability criterion, we find that the chance of catching a resolvable burst at a one nanosecond precision level is 2-50%, depending on the adopted SMBH evolution model. On the other hand, the probability of detecting bursts produced by massive binaries (masses \gtrsim 10^7\msun) with {\it LISA} is negligible.Comment: Accepted for publication by MNRAS, minor change

Habitat structure: a fundamental concept and framework for urban soil ecology

Habitat structure is defined as the composition and arrangement of physical matter at a location. Although habitat structure is the physical template underlying ecological patterns and processes, the concept is relatively unappreciated and underdeveloped in ecology. However, it provides a fundamental concept for urban ecology because human activities in urban ecosystems are often targeted toward management of habitat structure. In addition, the concept emphasizes the fine-scale, on-the-ground perspective needed in the study of urban soil ecology. To illustrate this, urban soil ecology research is summarized from the perspective of habitat structure effects. Among the key conclusions emerging from the literature review are: (1) habitat structure provides a unifying theme for multivariate research about urban soil ecology; (2) heterogeneous urban habitat structures influence soil ecological variables in different ways; (3) more research is needed to understand relationships among sociological variables, habitat structure patterns and urban soil ecology. To stimulate urban soil ecology research, a conceptual framework is presented to show the direct and indirect relationships among habitat structure and ecological variables. Because habitat structure serves as a physical link between sociocultural and ecological systems, it can be used as a focus for interdisciplinary and applied research (e.g., pest management) about the multiple, interactive effects of urbanization on the ecology of soils

The Society for Immunotherapy of Cancer consensus statement on immunotherapy for the treatment of squamous cell carcinoma of the head and neck (HNSCC).

Head and neck cancers, including those of the lip and oral cavity, nasal cavity, paranasal sinuses, oropharynx, larynx and nasopharynx represent nearly 700,000 new cases and 380,000 deaths worldwide per annum, and account for over 10,000 annual deaths in the United States alone. Improvement in outcomes are needed for patients with recurrent and or metastatic squamous cell carcinoma of the head and neck (HNSCC). In 2016, the US Food and Drug Administration (FDA) granted the first immunotherapeutic approvals - the anti-PD-1 immune checkpoint inhibitors nivolumab and pembrolizumab - for the treatment of patients with recurrent squamous cell carcinoma of the head and neck (HNSCC) that is refractory to platinum-based regimens. The European Commission followed in 2017 with approval of nivolumab for treatment of the same patient population, and shortly thereafter with approval of pembrolizumab monotherapy for the treatment of recurrent or metastatic HNSCC in adults whose tumors express PD-L1 with a ≥ 50% tumor proportion score and have progressed on or after platinum-containing chemotherapy. Then in 2019, the FDA granted approval for PD-1 inhibition as first-line treatment for patients with metastatic or unresectable, recurrent HNSCC, approving pembrolizumab in combination with platinum and fluorouracil for all patients with HNSCC and pembrolizumab as a single agent for patients with HNSCC whose tumors express a PD-L1 combined positive score ≥ 1. These approvals marked the first new therapies for these patients since 2006, as well as the first immunotherapeutic approvals in this disease. In light of the introduction of these novel therapies for the treatment of patients with head and neck cancer, The Society for Immunotherapy of Cancer (SITC) formed an expert committee tasked with generating consensus recommendations for emerging immunotherapies, including appropriate patient selection, therapy sequence, response monitoring, adverse event management, and biomarker testing. These consensus guidelines serve as a foundation to assist clinicians\u27 understanding of the role of immunotherapies in this disease setting, and to standardize utilization across the field for patient benefit. Due to country-specific variances in approvals, availability and regulations regarding the discussed agents, this panel focused solely on FDA-approved drugs for the treatment of patients in the U.S

Taking Be proud! Be responsible! to the Suburbs: A Replication Study

CONTEXT: An important phase of HIV prevention research is replicating successful interventions with different groups and in different settings. METHODS: Be Proud! Be Responsible!, a successful intervention originally targeting black urban males and carried out in nonschool settings, was presented in health classes at urban and suburban schools with diverse student bodies. A group-randomized intervention study, which included 1,357 ninth and 10th graders from 10 paired schools in a Midwestern metropolitan area, was conducted in 2000-2002. Half the schools received the intervention, and half received a general health promotion program. Students\u27 reports of their sexual behavior and selected cognitive mediators were analyzed immediately following the programs and four and 12 months later. RESULTS: Compared with students who received the control curriculum, students exposed to the intervention reported significantly greater knowledge of HIV, other STDs and condoms; greater confidence in their ability to control sexual impulses, to use condoms and to negotiate the use of condoms; and stronger intentions to use condoms. Stratified analyses revealed that the strongest intervention impacts were on knowledge and efficacy among males and students attending suburban schools. The intervention had no impact on sexual initiation, frequency of intercourse or condom use. CONCLUSIONS: Schools are a logical and viable setting for the dissemination and acquisition of information about HIV, including prevention strategies. However, the behavioral impact of an intervention may not be easily transferable when the program is taught outside a carefully controlled, nonschool setting

Control of star formation by supersonic turbulence

Understanding the formation of stars in galaxies is central to much of modern astrophysics. For several decades it has been thought that stellar birth is primarily controlled by the interplay between gravity and magnetostatic support, modulated by ambipolar diffusion. Recently, however, both observational and numerical work has begun to suggest that support by supersonic turbulence rather than magnetic fields controls star formation. In this review we outline a new theory of star formation relying on the control by turbulence. We demonstrate that although supersonic turbulence can provide global support, it nevertheless produces density enhancements that allow local collapse. Inefficient, isolated star formation is a hallmark of turbulent support, while efficient, clustered star formation occurs in its absence. The consequences of this theory are then explored for both local star formation and galactic scale star formation. (ABSTRACT ABBREVIATED)Comment: Invited review for "Reviews of Modern Physics", 87 pages including 28 figures, in pres

An exploration of the implementation of open disclosure of adverse events in the UK : a scoping review and qualitative exploration

Background: In 2009 the UK National Patient Safety Agency relaunched its Being Open framework to facilitate the open disclosure of adverse events to patients in the NHS. The implementation of the framework has been, and remains, challenging in practice. Aim: The aim of this work was to both critically evaluate and extend the current evidence base relating to open disclosure, with a view to supporting the implementation of a policy of open disclosure of adverse events in the NHS. Methods: This work was conducted in three phases. The first phase comprised two focused systematic literature reviews, one summarising empirical research on the effectiveness of interventions to enhance open disclosure, and a second, broader scoping review, looking at reports of current opinion and practice and wider knowledge. The second phase involved primary qualitative research with the objective of generating new knowledge about UK-based stakeholders' views on their role in and experiences of open disclosure. Stakeholder interviews were analysed using the framework approach. The third phase synthesised the findings from the first two phases to inform and develop a set of short pragmatic suggestions for NHS trust management, to facilitate the implementation and evaluation of open disclosure. Results: A total of 610 papers met the inclusion criteria for the broad review. A large body of literature discussed open disclosure from a number of related, but sometimes conflicted, perspectives. Evidential gaps persist and current practice is based largely on expert consensus rather than evidence. There appears to be a tension between the existing pragmatic guidance and the more in-depth critiques of what being consistent and transparent in health care really means. Eleven papers met the inclusion criteria for the more focused review. There was little evidence for the effectiveness of disclosure alone on organisational or individual outcomes or of interventions to promote and support open disclosure. Interviews with stakeholders identified strong support for the basic principle of being honest with patients or relatives when someone was seriously harmed by health care. In practice however, the issues are complex and there is confusion about a number of issues relating to disclosure policies in the UK. The interviews generated insights into the difficulties perceived within health care at individual and institutional levels, in relation to fully implementing the Being Open guidance. Conclusions: There are several clear strategies that the NHS could learn from to implement and sustain a policy of openness. Literature reviews and stakeholder accounts both identified the potential benefits of a culture that was generally more open (not just retrospectively open about serious harm). Future work could usefully evaluate the impact of disclosure on legal challenges within the NHS, best practice in models of support and training for open disclosure, embedding disclosure conversations in critical incident analysis and disclosure of less serious events