The energy distribution of electrons in radio jets

Black-hole and neutron-star X-ray binaries exhibit compact radio jets, when they are in the so called quiescent, hard, or hard intermediate states. The radio spectrum in these states is flat to slightly inverted. It is widely accepted that the energy distribution of the electrons, in the rest frame of the jet, is a power law with index p. A power-law energy distribution of the electrons in the jet is sufficient to explain the flat to slightly inverted spectrum emitted by the jet from radio to near infrared wavelengths, but is it necessary? Contrary to what our thinking was decades ago, now we know that the jets originate in the hot inner flow around black holes and neutron stars. Thus, we have investigated the spectrum that is emitted by a thermal jet with kT in the range 100-250 keV. We have computed the emitted spectrum from radio to near infrared using either a thermal distribution of electrons or a power-law one. We have found that parabolic jets with a thermal distribution of electrons give inverted spectra with alpha in the range 0-0.4, while jets with a power-law distribution of electrons give inverted spectra with alpha in the range 0-0.2. The rest of the parameters are kept the same in the two cases. The break frequency, which marks the transition from optically thick to optically thin synchrotron emission, is comparable for the two electron energy distributions. Our conclusion is that, contrary to common belief, it is not necessary to invoke a power-law energy distribution of the electrons in a jet to explain its flat to slightly inverted radio spectrum. A relativistic Maxwellian produces similar spectra. Thus, the widely invoked corona around black holes in X-ray binaries may actually be the jet.Comment: 4 pages, 2 figures, accepted by A&A Letter

City Diplomacy: Towards More Strategic Networking? Learning with WHO Healthy Cities

Cities are increasingly capturing the attention of major international actors and now regularly feature in multilateral processes. Yet while there are many studies on networking among cities, there have been few studies of 'city networks' as formal and institutionalized governance structures facilitating city-to-city and city-to-other actors cooperation, or 'city diplomacy'. Institutionalized networks of cities, while not new, are becoming a growing presence on the international scene, almost omnipresent and perhaps even too common. Might it be time for a 'Darwinian' selection between city networking options? Diving deeper into this networked challenge, this essay focuses on the effects this networked diplomacy and overlap it might have on cities. Drawing on a research collaboration between the UCL City Leadership Laboratory at University College London and the World Health Organization's Healthy Cities Network and both a global dataset of city networks as well as qualitative focus group data, we consider the growth of these governance structures, their strengths, but also the weaknesses associated with their rapid growth, and how cities can engage with this networked landscape more strategically. In short, we argue that the potential of city networks must go hand-in-hand with more integrative and strategic thinking at both local and international levels

Progressive Fracture of Laminated Fiber-Reinforced Composite Stiffened Plate Under Pressure

S-Glass/epoxy laminated fiber-reinforced composite stiffened plate structure with laminate configuration (0/90)5 was simulated to investigate damage and fracture progression, under uniform pressure. For comparison reasons a simple plate was examined, in addition with the stiffened plate. An integrated computer code was used for the simulation. The damage initiation began with matrix failure in tension, continuous with damage and/or fracture progression as a result of additional matrix failure and fiber fracture and followed by additional interply delamination. Fracture through the thickness began when the damage accumulation was 90%. After that stage, the cracks propagate rapidly and the structures collapse. The collapse load for the simple plate is 21.57 MPa (3120 psi) and for the stiffened plate 25.24 MPa (3660 psi)

A surveillance system to assess the need for updating systematic reviews.

BackgroundSystematic reviews (SRs) can become outdated as new evidence emerges over time. Organizations that produce SRs need a surveillance method to determine when reviews are likely to require updating. This report describes the development and initial results of a surveillance system to assess SRs produced by the Agency for Healthcare Research and Quality (AHRQ) Evidence-based Practice Center (EPC) Program.MethodsTwenty-four SRs were assessed using existing methods that incorporate limited literature searches, expert opinion, and quantitative methods for the presence of signals triggering the need for updating. The system was designed to begin surveillance six months after the release of the original review, and then ceforth every six months for any review not classified as being a high priority for updating. The outcome of each round of surveillance was a classification of the SR as being low, medium or high priority for updating.ResultsTwenty-four SRs underwent surveillance at least once, and ten underwent surveillance a second time during the 18 months of the program. Two SRs were classified as high, five as medium, and 17 as low priority for updating. The time lapse between the searches conducted for the original reports and the updated searches (search time lapse - STL) ranged from 11 months to 62 months: The STL for the high priority reports were 29 months and 54 months; those for medium priority reports ranged from 19 to 62 months; and those for low priority reports ranged from 11 to 33 months. Neither the STL nor the number of new relevant articles was perfectly associated with a signal for updating. Challenges of implementing the surveillance system included determining what constituted the actual conclusions of an SR that required assessing; and sometimes poor response rates of experts.ConclusionIn this system of regular surveillance of 24 systematic reviews on a variety of clinical interventions produced by a leading organization, about 70% of reviews were determined to have a low priority for updating. Evidence suggests that the time period for surveillance is yearly rather than the six months used in this project

Learning Max-CSPs via Active Constraint Acquisition

Constraint acquisition can assist non-expert users to model their problems as constraint networks. In active constraint acquisition, this is achieved through an interaction between the learner, who posts examples, and the user who classifies them as solutions or not. Although there has been recent progress in active constraint acquisition, the focus has only been on learning satisfaction problems with hard constraints. In this paper, we deal with the problem of learning soft constraints in optimization problems via active constraint acquisition, specifically in the context of the Max-CSP. Towards this, we first introduce a new type of queries in the context of constraint acquisition, namely partial preference queries, and then we present a novel algorithm for learning soft constraints in Max-CSPs, using such queries. We also give some experimental results

The health of the public: What has gone wrong?

COVID-19, a new pandemic, has swept the world. How could this have happened? In theory the world should have been prepared, armed as it has been since 2005 with a new set of International Health Regulations with universal commitment by WHO Member States. Yet disaster has struck. The authors of this paper consider that fundamental rethinking is needed, with a new review of the post-World War 2 international system for global governance for health. Whilst WHO and its present and future actions will be scrutinized, the organization is fundamentally made up of 194 Member States, which must share the responsibility for ensuring better global health protection in the future. It is clear the world needs a more effective WHO, but it also needs countries to support and develop their public health infrastructure to face today’s more complex health challenges, which can only grow in scope and complexity over coming years. The paper proposes several key steps to achieve these goals

Health 2020 – achieving health and development in today’s Europe

Health and well-being are universal human goals that are currently considered to be vital human rights; major components of equitable human, economic and social development; and a resource for everyday life. These goals are increasingly seen as central to human development and security. Health is no longer seen as simply items of consumption to be financed but is considered an asset that needs to be nurtured and equitably improved and also as a positive concept, emphasizing social and personal resources as well as physical capacity

Constraint Modelling with LLMs Using In-Context Learning

Constraint Programming (CP) allows for the modelling and solving of a wide range of combinatorial problems. However, modelling such problems using constraints over decision variables still requires significant expertise, both in conceptual thinking and syntactic use of modelling languages. In this work, we explore the potential of using pre-trained Large Language Models (LLMs) as coding assistants, to transform textual problem descriptions into concrete and executable CP specifications. We present different transformation pipelines with explicit intermediate representations, and we investigate the potential benefit of various retrieval-augmented example selection strategies for in-context learning. We evaluate our approach on 2 datasets from the literature, namely NL4Opt (optimisation) and Logic Grid Puzzles (satisfaction), and a heterogeneous set of exercises from a CP course. The results show that pre-trained LLMs have promising potential for initialising the modelling process, with retrieval-augmented in-context learning significantly enhancing their modelling capabilities

Health promotion and health systems: some unfinished business

n/