Constraining the Nature of the 18 min Periodic Radio Transient GLEAM-X J162759.5-523504.3 via Multiwavelength Observations and Magneto-thermal Simulations

We observed the periodic radio transient GLEAM-X J162759.5-523504.3 (GLEAM-X J1627) using the Chandra X-ray Observatory for about 30 ks on 2022 January 22–23, simultaneously with radio observations from the Murchison Widefield Array, MeerKAT, and the Australia Telescope Compact Array. Its radio emission and 18 min periodicity led the source to be tentatively interpreted as an extreme magnetar or a peculiar highly magnetic white dwarf. The source was not detected in the 0.3–8 keV energy range with a 3σ upper limit on the count rate of 3 × 10−4 counts s−1. No radio emission was detected during our X-ray observations either. Furthermore, we studied the field around GLEAM-X J1627 using archival European Southern Observatory and DECam Plane Survey data, as well as recent Southern African Large Telescope observations. Many sources are present close to the position of GLEAM-X J1627, but only two within the 2'' radio position uncertainty. Depending on the assumed spectral distribution, the upper limits converted to an X-ray luminosity of LX < 6.5 × 1029 erg s−1 for a blackbody with temperature kT = 0.3 keV, or LX < 9 × 1029 erg s−1 for a power law with photon index Γ = 2 (assuming a 1.3 kpc distance). Furthermore, we performed magneto-thermal simulations for neutron stars considering crust- and core-dominated field configurations. Based on our multiband limits, we conclude that (i) in the magnetar scenario, the X-ray upper limits suggest that GLEAM-X J1627 should be older than ∼1 Myr, unless it has a core-dominated magnetic field or has experienced fast cooling; (ii) in the white dwarf scenario, we can rule out most binary systems, a hot sub-dwarf, and a hot magnetic isolated white dwarf (T ≳ 10.000 K), while a cold isolated white dwarf is still compatible with our limits.N.R., F.C.Z., C.D., M.R., V.G., C.P., A.B., and E.P. are supported by the ERC Consolidator Grant "MAGNESIA" under grant agreement No. 817661, and National Spanish grant No. PGC2018-095512-BI00. F.C.Z., A.B., and V.G. are also supported by Juan de la Cierva Fellowships. C.D., M.R., and C.A.'s work has been carried out within the framework of the doctoral program in Physics of the Universitat Autónoma de Barcelona. N.H.W. is supported by an Australian Research Council Future Fellowship (project number FT190100231) funded by the Australian Government. D.d.M. acknowledges financial support from the Italian Space Agency (ASI) and National Institute for Astrophysics (INAF) under agreements ASI-INAF I/037/12/0 and ASI-INAF n.2017-14-H.0 and from INAF "Sostegno alla ricerca scientifica main streams dell'INAF," Presidential Decree 43/2018 and from INAF "SKA/CTA projects," Presidential Decree 70/2016. D.B. acknowledges support from the South African National Research Foundation. D.V. is supported by the ERC Starting Grant "IMAGINE" under grant agreement No. 948582. This work was also partially supported by the program Unidad de Excelencia Maria de Maetzu de Maeztu CEX2020-001058-M and by the PHAROS COST Action (grant No. CA16214)

CADASIL Affects Multiple Aspects of Cerebral Small Vessel Function on 7T-MRI

International audienceObjective: Cerebral small vessel diseases (cSVDs) are a major cause of stroke and dementia. We used cutting-edge 7T-MRI techniques in patients with Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL), to establish which aspects of cerebral small vessel function are affected by this monogenic form of cSVD. Methods: We recruited 23 CADASIL patients (age 51.1 AE 10.1 years, 52% women) and 13 age-and sex-matched controls (46.1 AE 12.6, 46% women). Small vessel function measures included: basal ganglia and centrum semiovale perforating artery blood flow velocity and pulsatility, vascular reactivity to a visual stimulus in the occipital cortex and reactivity to hypercapnia in the cortex, subcortical gray matter, white matter, and white matter hyperintensities. Results: Compared with controls, CADASIL patients showed lower blood flow velocity and higher pulsatility index within perforating arteries of the centrum semiovale (mean difference À 0.09 cm/s, p = 0.03 and 0.20, p = 0.009) and basal ganglia (mean difference À 0.98 cm/s, p = 0.003 and 0.17, p = 0.06). Small vessel reactivity to a short visual stimulus was decreased (blood-oxygen-level dependent [BOLD] mean difference À0.21%, p = 0.04) in patients, while reactivity to hypercapnia was preserved in the cortex, subcortical gray matter, and normal appearing white matter. Among patients, reactivity to hypercapnia was decreased in white matter hyperintensities compared to normal appearing white matter (BOLD mean difference À0.29%, p = 0.02). Interpretation: Multiple aspects of cerebral small vessel function on 7T-MRI were abnormal in CADASIL patients, indicative of increased arteriolar stiffness and regional abnormalities in reactivity, locally also in relation to white matter injury. These observations provide novel markers of cSVD for mechanistic and intervention studies

Unveiling the white dwarf in J191213.72−441045.1 through ultraviolet observations

J191213.72−441045.1 is a binary system composed of a white dwarf and an M-dwarf in a 4.03-hour orbit. It shows emission in radio, optical, and X-ray, all modulated at the white dwarf spin period of 5.3 min, as well as various orbital sideband frequencies. Like in the prototype of the class of radio-pulsing white dwarfs, AR Scorpii, the observed pulsed emission seems to be driven by the binary interaction. In this work, we present an analysis of far-ultraviolet spectra obtained with the Cosmic Origins Spectrograph at the Hubble Space Telescope, in which we directly detect the white dwarf in J191213.72−441045.1. We find that the white dwarf has a temperature of Teff = 11485 ± 90 K and mass of 0.59 ± 0.05 M⊙. We place a tentative upper limit on the magnetic field of ≈50 MG. If the white dwarf is in thermal equilibrium, its physical parameters would imply that crystallisation has not started in the core of the white dwarf. Alternatively, the effective temperature could have been affected by compressional heating, indicating a past phase of accretion. The relatively low upper limit to the magnetic field and potential lack of crystallisation that could generate a strong field pose challenges to pulsar-like models for the system and give preference to propeller models with a low magnetic field. We also develop a geometric model of the binary interaction which explains many salient features of the system

Zooming in on cerebral small vessel function in small vessel diseases with 7T MRI: Rationale and design of the “ZOOM@SVDs” study

Background: Cerebral small vessel diseases (SVDs) are a major cause of stroke and dementia. Yet, specific treatment strategies are lacking in part because of a limited understanding of the underlying disease processes. There is therefore an urgent need to study SVDs at their core, the small vessels themselves. Objective: This paper presents the rationale and design of the ZOOM@SVDs study, which aims to establish measures of cerebral small vessel dysfunction on 7T MRI as novel disease markers of SVDs. Methods: ZOOM@SVDs is a prospective observational cohort study with two years follow-up. ZOOM@SVDs recruits participants with Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL, N = 20), sporadic SVDs (N = 60), and healthy controls (N = 40). Participants undergo 7T brain MRI to assess different aspects of small vessel function including small vessel reactivity, cerebral perforating artery flow, and pulsatility. Extensive work-up at baseline and follow-up further includes clinical and neuropsychological assessment as well as 3T brain MRI to assess conventional SVD imaging markers. Measures of small vessel dysfunction are compared between patients and controls, and related to the severity of clinical and conventional MRI manifestations of SVDs. Discussion: ZOOM@SVDs will deliver novel markers of cerebral small vessel function in patients with monogenic and sporadic forms of SVDs, and establish their relation with disease burden and progression. These small vessel markers can support etiological studies in SVDs and may serve as surrogate outcome measures in future clinical trials to show target engagement of drugs directed at the small vessels

Do large South African acquisitions result in post-acquisition improvements in cash flow returns?

The purpose of this study is to evaluate whether South African acquisitions result in success, with success measured as post-acquisition improvements in cash flow returns. The reason for this approach is the view that a firm's intrinsic value is coupled to its long-term cash-generating ability. Post-acquisition change in cash flow returns for large acquisitions made by JSE-listed firms over the period 1995 - 2009 were analysed. Cash flow returns were measured as free cash flow to the firm over capital employed. This measurement of cash flow return is neutral to the firm's financing decision and capital structure, thus facilitating a comparison between different firms. Changes in annual cash flow returns were measured over the period covering five years preceding and five years following completion of acquisitions. The cash flow returns of the acquiring firms were compared to benchmark returns of firms in the same sector which did not undertake major acquisitions. The study found in 22 of 24 tests that the benchmarked post-acquisition cash flow returns and EBITDA returns were not significantly different in relation to the benchmarked pre-acquisition returns. However, in two tests which adjusted for operating leases and used total returns over the pre-acquisition and post-acquisition periods, it was found that the difference in returns were significant. The sample of eleven firms is relatively small and any inferences about South African acquisitions in general should therefore be approached with care. The divergence in results between the individual firms within the sample, as well as the outlined sensitivities of observed results lend further support for this cautionary approach. Despite the limited number of acquisitions that occurred over the period, this study should contribute towards a better understanding of the overall value proposition of large South African acquisitions, as well as provide impetus for related future research

Implications of formula feeding to reduce HIV transmission

Background. The risk of vertical transmission of HIV during breast-feeding has prompted renewed interest in the role of supplementary feeding during childhood. However, it is also known that supplementary feeding is an important vector of disease transmission. The aim of this study was to investigate the level of microbial contamination present in bottle feeds given to infants living in Mangaung, South Africa. Methods. The study followed a cross-sectional design. Two hundred randomly selected households were visited and caregivers of bottle-feeding infants in the selected area were requested to provide a sample of the infants\' bottle feed. Nutritional and microbial content of each bottle feed were measured. Bottle feeds were classified as unfit for human consumption if they had a standard plate count greater than 50 000 organisms per millilitre feed, or a total coliform count greater than 10 coliform organisms per millilitre. Findings. A total of 84.5% of all the bottle feeds were classified as unfit for human consumption. There was no major difference in nutritional quality of the fit and unfit feeds. The infants receiving unfit bottle feeds were younger than those receiving fit bottle feeds (11.1 ± 6.9 months compared with 14.0 ± 7.6 months, respectively; p = 0.010) and also weighed less. Interpretation. This finding underlines the need to address the content of feeding literacy programmes. Bottle-feeding in Mangaung is currently not a safe alternative to breast-feeding and should therefore not be promoted. Southern African Journal of HIV Medicine Vol. 5 (3) 2004: 38-4

An investigation of risky sexual behaviours, basic HIV knowledge and intention to use condoms among a sample of men who have sex with men in a student community

Thesis (MA)--Stellenbosch University, 2012.ENGLISH ABSTRACT: The primary objective of the study was to determine the level of self-reported sexual risk behaviour of student men who have sex with men at a South African higher educational institution. The secondary objective was to determine the level of Human Immunodefiency Virus (HIV) knowledge among student men who have sex with men, and lastly to determine the extent to which the theory of planned behaviour is applicable in explaining intentions to use condoms. A sample of fifty student men who have sex with men were recruited to take part in an online baseline and follow-up survey, three months apart. Many of the student men who have sex with men reported sexual behaviour, which may place them at risk of contracting HIV. More than fifty percent (56%) had used alcohol or drugs during sexual intercourse in the past. Six percent (6.1%) reported having been forced to have sexual intercourse against their will. While 8% had experienced abuse and violence on campus, 22% had experienced abuse only and another 6% reported having experienced some form of violence due to their sexual preference. Most participants (70%) reported having used condoms almost always or always when engaging in penetrative sexual behaviours, but 30% had used condoms inconsistently or not at all in the past. The sample of student MSM scored high on a questionnaire of basic HIV knowledge, with a mean score of 14.57 (80.94%). The present study questions the applicability of the theory of planned behaviour in understanding and predicting intention to use condoms among a sample of student men who have sex with men attending a South African higher education institution. Only two of the major theoretical variables, namely attitude and perceived group norms, could significantly predict intention to use condoms. Attitudes regarding condom use were found to have an inverse The primary objective of the study was to determine the level of self-reported sexual risk behaviour of student men who have sex with men at a South African higher educational institution. The secondary objective was to determine the level of Human Immunodefiency Virus (HIV) knowledge among student men who have sex with men, and lastly to determine the extent to which the theory of planned behaviour is applicable in explaining intentions to use condoms. A sample of fifty student men who have sex with men were recruited to take part in an online baseline and follow-up survey, three months apart. Many of the student men who have sex with men reported sexual behaviour, which may place them at risk of contracting HIV. More than fifty percent (56%) had used alcohol or drugs during sexual intercourse in the past. Six percent (6.1%) reported having been forced to have sexual intercourse against their will. While 8% had experienced abuse and violence on campus, 22% had experienced abuse only and another 6% reported having experienced some form of violence due to their sexual preference. Most participants (70%) reported having used condoms almost always or always when engaging in penetrative sexual behaviours, but 30% had used condoms inconsistently or not at all in the past. The sample of student MSM scored high on a questionnaire of basic HIV knowledge, with a mean score of 14.57 (80.94%). The present study questions the applicability of the theory of planned behaviour in understanding and predicting intention to use condoms among a sample of student men who have sex with men attending a South African higher education institution. Only two of the major theoretical variables, namely attitude and perceived group norms, could significantly predict intention to use condoms. Attitudes regarding condom use were found to have an inversrelationship with intention to use condoms. The results from the hierarchical multiple regression analyses revealed that the linear combination of the theory of planned behaviour variables could significantly account for 68% of the variance in intention to use condoms when the predictors were considered together. Interventions that seek to lessen HIV risk behaviour among student men who have sex with men should endeavour to incorporate elements which should aim to augment perceived subjective norms regarding condom use. The findings advocate for additional research to be undertaken on the applicability of the theory of planned behaviour in informing health communication and sexual health interventions that aim to reduce HIV transmission risk among student men who have sex with men at higher educational institutions.AFRIKAANSE OPSOMMING: Die primêre doel van die studie was om die vlak van self-gerapporteerde seksuele risiko gedrag van studentemans wat seks beoefen met mans (MSM) by 'n Suid-Afrikaanse hoër onderwysinstelling te bepaal. Die sekondêre doel was om die vlak van kennis oor die Menslike Immuniteitsgebreksvirus (MIV) onder studente MSM te bepaal, en laastens om die mate waarin die teorie van beplande gedrag toepaslik is om die voorneme om kondoom gebruik te verduidelik. ʼn Steekproef van vyftig studente MSM was gewerf om aan ʼn aanlyn basislynopname en opvolgopname deel te neem. Talle van die studente MSM het seksuele gedrag gerapporteer wat die mans blootstel aan die risiko om MIV op te doen. Meer as vyftig persent (56%) het in die verlede alkohol of dwelms gebruik tydens seksuele omgang. Ses persent (6,1%) het gerapporteer dat hulle al gedwing is om seksuele omgang teen hul wil te hê. Terwyl agt persent mishandeling en geweld op kampus ervaar het, het 22% slegs misbruik ervaar en nog 6% het een of ander vorm van geweld ervaar as gevolg van hul seksuele voorkeur. Die meeste deelnemers (70%) het gerapporteer dat hulle tydens penetratiewe seks byna altyd kondome gebruik, maar 30% het óf glad nie, óf ongereeld in die verlede kondome gebruik. Die studente MSM wat aan die steekproef deelgeneem het, het hoë tellings behaal in ‘n vraelys oor basiese MIV-feite, met ' ʼn gemiddelde telling van 14.57 (80.94%). Die huidige studie bevraagteken die toepasbaarheid van die teorie van beplande gedrag om die voorneme om kondome te gebruik onder ’n steekproef van studente MSM aan ’n Suid-Afrikaanse hoër onderwysinstelling te verstaan en te voorspel. Slegs twee van die belangrikste teoretiese veranderlikes, naamlik houding en subjektiewe groepnorme, kon beduidend die voorneme voorspel om kondome te gebruik. Houding oor kondoom gebruik het ʼn omgekeerde verwantskap met die voorneme om kondome te gebruik voorspel. Die resultate van die hiërargiese meervoudige regressie-ontleding het aangedui dat, wanneer die voorspellers saam oorweeg word, die lineêre kombinasie van die teorie van beplande gedrag veranderlikes betekenisvol tot 68% van die variansie in die voorneme om kondome te gebruik kan verklaar. Ingrypings wat daarop gemik is om MIV-risiko gedrag onder studente MSM te verminder, behoort elemente in te sluit wat streef daarna om waarneembare subjektiewe norme rakende kondoomgebruik aan te vul. Die bevindinge wys dat addisionele navorsing oor die gebruik van die teorie van beplande gedrag in gesondheidskommunikasie en seksuelegesondheid intervensies wat daarop gemik is om die risiko van MIV-oordrag tussen studente MSM by inrigtings vir hoër onderwys te verminder nodig is