Browsing by Author "Hill K"

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    An Isolated Stellar-mass Black Hole Detected through Astrometric Microlensing
    (IOP Publishing on behalf of the American Astronomical Society, 2022-07-06) Sahu KC; Anderson J; Casertano S; Bond HE; Udalski A; Dominik M; Calamida A; Bellini A; Brown TM; Rejkuba M; Bajaj V; Kains N; Ferguson HC; Fryer CL; Yock P; Mróz P; Kozłowski S; Pietrukowicz P; Poleski R; Skowron J; Soszyński I; Szymański MK; Ulaczyk K; Wyrzykowski Ł; Barry RK; Bennett DP; Bond IA; Hirao Y; Silva SI; Kondo I; Koshimoto N; Ranc C; Rattenbury NJ; Sumi T; Suzuki D; Tristram PJ; Vandorou A; Beaulieu J-P; Marquette J-B; Cole A; Fouqué P; Hill K; Dieters S; Coutures C; Dominis-Prester D; Bennett C; Bachelet E; Menzies J; Albrow M; Pollard K; Gould A; Yee JC; Allen W; Almeida LA; Christie G; Drummond J; Gal-Yam A; Gorbikov E; Jablonski F; Lee C-U; Maoz D; Manulis I; McCormick J; Natusch T; Pogge RW; Shvartzvald Y; Jørgensen UG; Alsubai KA; Andersen MI; Bozza V; Novati SC; Burgdorf M; Hinse TC; Hundertmark M; Husser T-O; Kerins E; Longa-Peña P; Mancini L; Penny M; Rahvar S; Ricci D; Sajadian S; Skottfelt J; Snodgrass C; Southworth J; Tregloan-Reed J; Wambsganss J; Wertz O; Tsapras Y; Street RA; Bramich DM; Horne K; Steele IA
    We report the first unambiguous detection and mass measurement of an isolated stellar-mass black hole (BH). We used the Hubble Space Telescope (HST) to carry out precise astrometry of the source star of the long-duration (t E ≃ 270 days), high-magnification microlensing event MOA-2011-BLG-191/OGLE-2011-BLG-0462 (hereafter designated as MOA-11-191/OGLE-11-462), in the direction of the Galactic bulge. HST imaging, conducted at eight epochs over an interval of 6 yr, reveals a clear relativistic astrometric deflection of the background star's apparent position. Ground-based photometry of MOA-11-191/OGLE-11-462 shows a parallactic signature of the effect of Earth's motion on the microlensing light curve. Combining the HST astrometry with the ground-based light curve and the derived parallax, we obtain a lens mass of 7.1 ± 1.3 M ⊙ and a distance of 1.58 ± 0.18 kpc. We show that the lens emits no detectable light, which, along with having a mass higher than is possible for a white dwarf or neutron star, confirms its BH nature. Our analysis also provides an absolute proper motion for the BH. The proper motion is offset from the mean motion of Galactic disk stars at similar distances by an amount corresponding to a transverse space velocity of �1/445 km s-1, suggesting that the BH received a "natal kick"from its supernova explosion. Previous mass determinations for stellar-mass BHs have come from radial velocity measurements of Galactic X-ray binaries and from gravitational radiation emitted by merging BHs in binary systems in external galaxies. Our mass measurement is the first for an isolated stellar-mass BH using any technique.
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    Handlers' Expectations and Perceived Compatibility regarding the Partnership with Their First Guide Dogs
    (MDPI (Basel, Switzerland), 2021-09-22) Lloyd J; Budge C; Stafford K; Hill K; Cogger N; Cobb M
    The main function of a guide dog is as a mobility aid, but they can also fulfill psychosocial roles as companions, social facilitators, and objects/providers of affection. This study examined the outcome of 50 peoples' (handlers) partnerships with their first guide dog. Overall compatibility and the fulfilment of the handlers' expectations regarding mobility and social factors related to guide dog usage were measured, and relationships between putative risk factors and the outcome of matching success were identified. The findings demonstrate that the dogs are generally exceeding expectations. The high average ratings of compatibility were notable, particularly with respect to the emotional compatibility between handler and dog. Comparing responses of those who felt the handler-dog pairing was a good match with those who felt it was a mismatch revealed it was the working aspects of the relationship that differentiated the two groups. However, the many aspects of life with a guide dog, beyond the complexities of the working relationship, suggest that a more nuanced compatibility measure accommodating both positive and negative aspects of the relationship could assist with matching, training and follow up of the handler-dog team to maximize success.
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    Surveying cytotoxic chemotherapy use in small animal cancer treatment: insights into use and influencing factors in New Zealand
    (Taylor and Francis Group on behalf of the New Zealand Veterinary Association, 2025-07-20) Northover S; Hill K; Cogger N; Isaksen K
    Aim: To determine how frequently cytotoxic chemotherapy is administered in small animal practice to treat cancer and the reasons why clinics and clinicians do or do not offer and administer chemotherapy in New Zealand. Methods: A cross-sectional study involving veterinarians working in small and mixed animal practice was performed using an online questionnaire distributed via social media and email. The survey included closed and open-ended questions on respondent demographics, frequency of chemotherapy administration, medications used, cancers treated, and factors influencing administration. Fisher's exact tests were used to assess associations between variables, and content analysis was applied to open-ended responses. Results: Completed questionnaires were returned by 164 veterinarians working in New Zealand during the study period. Of the 164 respondents, 131 (80%) stated that they would probably or definitely discuss cytotoxic chemotherapy with clients as a potential treatment option for small animals with cancer. Within the 12-months preceding July 2023, 56 (34%) respondents had personally administered chemotherapy and 96 (58.5%) worked at clinics where it was administered: 5 (3%) administered it weekly, 6 (4%) at least monthly, 21 (12.8%) every 1–6 months, and 22 (13.4%) every 6–12 months. The most common reason given for administering chemotherapy was to provide comprehensive care to the patient. Improving quality and quantity of life was frequently reported. The most common reason for not administering chemotherapy was referral of cases externally for treatment. Excluding referral, respondents stated they do not administer chemotherapy because of insufficient knowledge regarding chemotherapy and the medications used, or insufficient training in how to handle and administer cytotoxic medications. Of the veterinarians that do not currently perform chemotherapy, 40% and 42% would consider performing it if they had additional education in oncology and chemotherapy, and in the handling and administration of cytotoxic medications, respectively. Conclusion: Cytotoxic chemotherapy is frequently discussed as a treatment option by veterinarians in New Zealand but is currently administered by a smaller proportion. Decisions to use chemotherapy are guided by quality-of-life considerations and adherence to standards of care, while limited knowledge and training hinders its use by other clinicians. Clinical relevance: Chemotherapy is administered less frequently in New Zealand than in the UK. Continuing education and the development of resources that further clinicians' knowledge regarding oncology, chemotherapy, and safe drug handling and administration are needed to support wider adoption in clinical practice.