The effects of a background potential in star cluster evolution: a delay in the relaxation time-scale and runaway collision processes

Runaway stellar collisions in dense star clusters are invoked to explain the presence of very massive stars or blue stragglers in the center of those systems. This process has also been explored for the first star clusters in the Universe and shown to yield stars that may collapse at some points into an intermediate mass black hole. Although the early evolution of star clusters requires the explicit modeling of the gas out of which the stars form, these calculations would be extremely time-consuming and often the effects of the gas can be accurately treated by including a background potential to account for the extra gravitational force. We apply this approximation to model the early evolution of the first dense star clusters formed in the Universe by performing $N$-body simulations, our goal is to understand how the additional gravitational force affects the growth of a very massive star through stellar mergers in the central parts of the star cluster. Our results show that the background potential increases the velocities of the stars, causing an overall delay in the evolution of the clusters and in the runaway growth of a massive star at the center. The population of binary stars is lower due to the increased kinetic energy of the stars, initially reducing the number of stellar collisions, and we show that relaxation processes are also affected. Despite these effects, the external potential enhances the mass of the merger product by a factor $\sim$2 if the collisions are maintained for long times.Comment: 16 pages. Accepted for publication in Astronomy and Astrophysic

A systematic review of the quality of life of carers of children with cleft lip and/or plate

Caring for an infant or child requires a significant amount of time, energy and resources; this burden is further increased when the infant or child has a chronic condition or disability. Prior research has demonstrated that caregiving for a child with special needs impacts upon parents or carers mental health, well-being and quality of life. This article systematically reviews the literature pertaining to the impact of caring for a child with cleft lip and /or palate upon parental quality of life. A search of four databases was conducted with a number of key terms; the titles, abstracts and finally the whole article were read and assessed for relevance. Only articles written in English were included in the review. The results yielded four relevant articles; that displayed inconsistent results. The results of these articles are reviewed. It was evident that the construct of quality of life was narrowly operationalised in all four articles either being assessed as health-related quality of life or as the impact upon the family. Further all four studies emanated from the same country. The limitations are discussed with recommendations made for future research endeavours

UK Libraries\u27 Wildcat Histories: Preserving Student Activist Social Media Content

In this presentation, we describe the current web archiving program at the University of Kentucky Libraries; provide an overview of the Wildcat Histories activist student organization social media preservation project, funded by Project STAND; discuss the technical aspects of the Wildcat Histories project; and the project\u27s current status and lessons learned

Preservation Perseverance: Archiving Social Media Content, A University of Kentucky/Latino Student Union Collaboration

The voices of activist student leaders and organizations are crucial to preserve, whether it be in a formal archives or as part of an archiving process undertaken by individuals and groups to preserve their legacies. Increasingly, these voices are found in social media and other online and web platforms that are difficult to preserve. Wildcat Histories is a year-long, grant-funded collaboration between the University of Kentucky Libraries and the University of Kentucky Latino Student Union (LSU) to research the best technologies for (as of July 2023) and then carry out the preservation of activist student organization social media content. The authors present an overview and current status of and next steps for the project, including examples of preserved LSU social media platforms. They then describe the current technical aspects and communication and outreach activities of the project. They end with reflection questions for others considering taking on similar projects

Fronto-striatal cognitive deficits at different stages of Parkinson's disease

Groups of patients with idiopathic Parkinson's disease, either medicated or unmedicated, were compared with matched groups of normal controls on a computerized battery previously shown to be sensitive to frontal lobe dysfunction, including tests of planning, spatial working memory and attentional set-shifting. In a series of problems based on the 'Tower of London' test, medicated patients with Parkinson's disease were shown to be impaired in the amount of time spent thinking about (planning) the solution to each problem. Additionally, an impairment in terms of the accuracy of the solution produced on this test was only evident in those patients with more severe clinical symptoms and was accompanied by deficits in an associated test of spatial short-term memory. Medicated patients with both mild and severe clinical symptoms were also impaired on a related test of spatial working memory. In contrast, a group of patients who were unmedicated and 'early in the course' of the disease were unimpaired in all three of these tests. However, all three Parkinson's disease groups were impaired in the test of attentional set-shifting ability, although unimpaired in a test of pattern recognition which is insensitive to frontal lobe damage. These data are compared with those previously published from a group of young neurosurgical patients with localized excisions of the frontal lobes and are discussed in terms of the specific nature of the cognitive deficit at different stages of Parkinson's disease

Development of superconducting YBa2Cu3O(x) wires with low resistance electrical contacts

Materials exhibiting superconductivity above liquid nitrogen temperatures (77 K) will enable new applications of this phenomena. One of the first commercial applications of this technology will be superconducting magnets for medical imaging. However, a large number of aerospace applications of the high temperature superconducting materials have also been identified. These include magnetic suspension and balance of models in wind tunnels and resistanceless leads to anemometers. The development of superconducting wires fabricated from the ceramic materials is critical for these applications. The progress in application of a patented fiber process developed by Clemson University for the fabrication of superconducting wires is reviewed. The effect of particle size and heat treatment on the quality of materials is discussed. Recent advances made at Christopher Newport College in the development of micro-ohm resistance electrical contacts which are capable of carrying the highest reported direct current to this material is presented

Acute military psychiatric casualties from the war in Iraq

Background: The view that most military personnel evacuated from war zones are suffering from combat stress reactions, or are otherwise traumatised by the horrors of war, has an impact on all aspects of military psychiatry. Aims: To delineate the reasons for psychiatric aeromedical evacuation from Iraq from the start of build-up of UK forces in January 2003 until the end of October that year, 6 months after the end of formal hostilities. Method: A retrospective study was conducted of field and in-patient psychiatric assessments of 116 military personnel evacuated to the UK military psychiatric in-patient facility in Catterick Garrison. Results: Evacuees were mainly non-combatants (69%). A significant proportion were in reserve service (21%) and had a history of contact with mental health services (37%). Only 3% had a combat stress reaction. In over 85% of cases evacuation was for low mood attributed to separation from friends or family, or difficulties adjusting to the environment. Conclusions: These findings have implications especially for screening for suitability for deployment, and for understanding any longer-term mental health problems arising in veterans from Iraq

On the rate of black hole binary mergers in galactic nuclei due to dynamical hardening

We assess the contribution of dynamical hardening by direct three-body scattering interactions to the rate of stellar-mass black hole binary (BHB) mergers in galactic nuclei. We derive an analytic model for the single-binary encounter rate in a nucleus with spherical and disk components hosting a super-massive black hole (SMBH). We determine the total number of encounters $N_{\rm GW}$ needed to harden a BHB to the point that inspiral due to gravitational wave emission occurs before the next three-body scattering event. This is done independently for both the spherical and disk components. Using a Monte Carlo approach, we refine our calculations for $N_{\rm GW}$ to include gravitational wave emission between scattering events. For astrophysically plausible models we find that typically $N_{\rm GW} \lesssim$ 10. We find two separate regimes for the efficient dynamical hardening of BHBs: (1) spherical star clusters with high central densities, low velocity dispersions and no significant Keplerian component; and (2) migration traps in disks around SMBHs lacking any significant spherical stellar component in the vicinity of the migration trap, which is expected due to effective orbital inclination reduction of any spherical population by the disk. We also find a weak correlation between the ratio of the second-order velocity moment to velocity dispersion in galactic nuclei and the rate of BHB mergers, where this ratio is a proxy for the ratio between the rotation- and dispersion-supported components. Because disks enforce planar interactions that are efficient in hardening BHBs, particularly in migration traps, they have high merger rates that can contribute significantly to the rate of BHB mergers detected by the advanced Laser Interferometer Gravitational-Wave Observatory.Comment: 13 pages, 9 figures, accepted for publication in MNRA