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Planck constraints on the scale dependence of isotropic cosmic birefringence
No full textThe rotation of the linear polarisation plane of photons during propagation, also known as cosmic birefringence, is a powerful probe of parity-violating extensions of standard electromagnetism. Using Planck legacy data, we confirm previous estimates of the isotropic birefringence angle, finding β ≃ 0.30±0.05 [deg] at 68% CL, not including the systematic error from the instrumental polarisation angle. If this is a genuine signal, it could be explained by theories of Chern-Simons-type coupled to electromagnetism, which could lead to a harmonic scale-dependent birefringence signal, if the hypothesis of an ultra-light (pseudo) scalar field does not hold. To investigate these models, we pursue two complementary approaches: first, we fit the birefringence angle estimated at different multipoles, βℓ, with a power-law model and second, we perform a non-parametric Bayesian reconstruction of it. Both methods yield results consistent with a non-vanishing constant birefringence angle. The first method shows no significant dependence on the harmonic scale (up to 1.8σ CL), while the second method demonstrates that a constant model is favored by Bayesian evidence. This conclusion is robust across all four published Planck CMB solutions. Finally, we forecast that upcoming CMB observations by Simons Observatory, LiteBIRD and a wishful CMB-Stage 4 experiment could reduce current uncertainties by a factor of approximately
Search for Higgs boson decays into a pair of pseudoscalar particles in the γγτhadτhad final state using pp collisions at s = 13 TeV with the ATLAS detector
No full textA search for exotic decays of the 125 GeV Higgs boson into a pair of new spin-0 particles, H → aa, where one decays into a photon pair and the other into a τ-lepton pair, is presented. Hadronic decays of the τ-leptons are considered and reconstructed using a dedicated tagger for collimated τ-lepton pairs. The search uses 140 fb−1 of proton-proton collision data at a centre-of-mass energy of s = 13 TeV recorded between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider. The search is performed in the mass range of the a boson between 10 GeV and 60 GeV. No significant excess of events is observed above the Standard Model background expectation. Model-independent upper limits at 95% confidence level are set on the branching ratio of the Higgs boson to the γγττ final state, B(H → aa → γγττ), ranging from 0.2% to 2%, depending on the a-boson mass hypothesis
Spatial modelling of the hydrogeological connection between groundwater-dependent ecosystems and aquifers in the Kruger National Park, South Africa.
No full textAn improved understanding of the hydrogeological connection between aquifers and groundwater-dependent ecosystems (GDEs) is essential for an improved assessment and management of groundwater resources. In the Kruger National Park (KNP), which is also a prime conservation area of South Africa, groundwater plays the vital role of sustaining ecosystem functioning. Conducting hydrogeological assessments in this area will help to provide a robust methodological framework and a strategic tool for understanding groundwater flow and the influence of geology on groundwater occurrence and consequently the groundwater dependent ecosystems. This study therefore sought to assess the onnectivity
between groundwater-dependent ecosystems and groundwater in the Kruger National Park, South Africa. Two specific objectives were set mainly focussing on the characterisation of the aquifers within the KNP and secondly the delineation of GDEs in the KNP using freely accessible remote sensing data coupled with cloud computing approaches. To achieve the objectives of the study, the first step was to develop an understanding of the aquifers in the area. This was accomplished by utilizing pre-existing pumping test data to estimate the hydraulic parameters of the aquifers, as well as constructing geological cross- sections and analyzing borehole lithological core logs to identify preferential groundwater flow paths. Groundwater recharge was estimated using the cumulative rainfall departure and rainfall infiltration breakthrough methods. The analysis of the pumping test data showed that transmissivity ranged from 0.5 m2 d
-1 to 11.2 m2 d -1 , while storativity ranged from 1.28 × 10-6 to 4.38 × 10-4 . These results reveal that most of the selected boreholes have low transmissivity and storativity, as well as slightly high transmissivity for a few boreholes
drilled into the hard granite/gneiss rock. This suggested a porous but low permeability weathered aquifer, which agrees with the observed borehole lithological logs. Groundwater recharge received in the area ranged between 20.55 Mm3
a -1 and 29.4 Mm3 a -1. . The results further showed that groundwater mainly occurs/stored in joints, fractures, faults, zones of weathering and structures such as dyke intrusions. The site-specific conceptual model of the southern part of the KNP showed the aquifer mostly fractures to various extents. The area mostly consists of weathered rock material. GDEs were delineated using the weighted overlay tool. The thematic output layer was spatially classified into four classes: poor, fair, good and excellent according to the likelihood of GDE occurrence in the area. The results showed that only 2.39% of the total area is characterized by excellent likelihood of GDEs occurring. Most II of these areas are around rivers and areas on gentle slopes. The findings of this study demonstrate the effectiveness of incorporating hydrogeological study in understanding the relationship between GDEs and groundwater. The study therefore underscores the relevance of hydrogeological analysis for improved conceptualization of GDEs, rather than relying on surface indicators which do not consider connectivity between underlying aquifers and potential GDE
Have cryptocurrencies arrived in the system of fiat currencies? An appraisal based on monetary policy uncertainty
No full textThis paper examines the relationship between Bitcoin and other cryptocurrencies and monetary policy uncertainty (MPU). Bitcoin was introduced in 2008 as a decentralized digital currency, free from government control, to offer an alternative to traditional fiat currencies. Given its independence from central banks and, thus, monetary policies, Bitcoin is often considered a hedge against economic instability and uncertain monetary environments. Understanding if and how Bitcoin and other cryptocurrencies react to monetary policy uncertainty allows us to evaluate how integrated cryptocurrencies are into the fiat currency monetary system. To this end, this study empirically investigates the predictive power of MPU regarding cryptocurrency prices and volatility. It shows that by and large, the returns and the volatility of cryptocurrencies are independent from MPU which indicates that cryptocurrencies are still special and not a part of the fiat system
Zeolite-y-loaded chitosan nanoparticles as endodontic antimicrobial agent: an in vitro study
No full textObjectives The objectives were to synthesize a bioactive nanocomposite as an endodontic antimicrobial agent by loading previously synthesized electrosprayed chitosan nanoparticles (Ch-Np) into Zeolite-Y as a carrier and compare its antimicrobial activity against two endodontic pathogens using the agar diffusion test. Additionally, the effect of tissue inhibitors (dentin powder and serum albumin) on the antimicrobial activity of the Ch-Np-Zeolite nanocomposite was studied. Finally, the possible cytotoxicity of the novel nanocomposite against Balb/c 3T3 mouse fibroblast cells was evaluated. Materials and Methods A concentration of 3% (w/v) electrosprayed Ch-Np was mixed with Zeolite-Y in a concentration of 53.3 (w/v) and characterized using high-resolution scanning electron microscopy (HR-SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis. The antimicrobial activity was evaluated against Streptococcus mutans and Enterococcus faecalis using the agar diffusion test, and the time-kill test was performed using the broth microdilution technique in the presence of tissue inhibitors. The cytotoxicity was evaluated against 3T3 mouse fibroblast cells using the standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Statistical Analysis The difference between the antimicrobial activity of Ch-Np-Zeolite nanocomposite against S. mutans and E. faecalis was analyzed using the Mann-Whitney's U test. The effect of tissue inhibitors on the antimicrobial activity of Ch-Np-Zeolite nanocomposite was analyzed by comparing the mean of log colony-forming unit per milliliter over time. For the cytotoxicity assay, a statistically significant difference between each group and their control was made using a t -test with a probability value of p ≤ 0.05, considered a significant difference. Results HR-SEM of the dried paste-like mixture Ch-Np-Zeolite revealed the typical crystal habit of the supporting zeolite, and EDS analysis confirmed that the zeolite parent material retained its elemental composition after loading with Ch-Np. The antimicrobial activity of Ch-Np-Zeolite was demonstrated by the mean diameter inhibition zones of 9.57 and 7.85 mm for S. mutans and E. faecalis, respectively. Streptococcus mutans and E. faecalis were completely eradicated in the presence of tissue inhibitors. The Ch-Np-Zeolite nanocomposite significantly promoted the growth of 3T3 fibroblast cells (p < 0.05), supporting its lack of cytotoxicity. Conclusion Zeolite-Y-loaded Ch-Np nanocomposite shows promising antimicrobial activity while maintaining its biocompatibility even in the presence of tissue inhibitors
Strategic business movements? the migration of online romance fraudsters from Nigeria to Ghana
No full textThis study used an emic approach to examine the dynamics of online romance fraud, focusing on the migration of offenders from Nigeria to Ghana. We collected data through qualitative methods, such as semi-structured interviews and focus group discussions. Ghanaian police officers and Nigerian law enforcement officers were consulted for their perspectives. Thematic analysis revealed key findings, including the migration patterns of Nigerian offenders to Ghana and the institutionalisation of scamming enterprises. These findings shed light on the transnational and structural factors driving online romance fraud in West Africa, highlighting both its global reach and the local mechanisms sustaining these criminal networks. This research contributes to a deeper understanding of regional and international cybercrime dynamics, offering valuable insights to inform policy and law enforcement strategies
Feeding hope: Zimbabwean migrants in South Africa and the evolving landscape of cross-border remittances
No full textCross-border food remittances contribute to household food security in the receiving countries in the Global South. This paper draws on recent research on Zimbabwean cross-border food remittances from South Africa to Zimbabwe to explore the impact on food security back home. This is achieved by examining food remittance flows from South Africa through digital channels and informal land corridors using cross-border transporters. The paper discusses both the recent widespread use of digital and mobile technology-based pathways and other traditional channels to remit food back home to Zimbabwe and the factors that have contributed to the shift. The study is based on a desktop methodology that involves an in-depth analysis of peer-reviewed journal articles and reports on food remittances by Zimbabwean migrants based in South Africa. The findings reveal complex and interesting insights into past and current cross-border food flows. First, the food remitting channels are diverse and include hybrid food remitting processes. Second, cross-border food remittances impact local food systems, although households with family members in the diaspora generally enjoy improved food and nutrition security. The paper also examines the impact of the shift to digital food transfers on households, cross-border food transfers, and local food producers, particularly in terms of accessibility, affordability, and nutritional diversity
Developing a strategic action plan for reducing the burden of stroke in Africa: report of the first African Stroke Leaders' Summit
No full textIntroduction: Stroke is a leading cause of adult neurologic disability, cognitive decline, and death worldwide, and particularly in Africa. Stroke research in Africa has exposed challenges militating against the translation of research evidence into practice and policy. The evidence-based, context-sensitive multilevel strategies required to surmount these challenges are presented in this report on the first African Stroke Leaders' Summit (ASLS) organized to tackle the burden of stroke in Africa. Methods: The Africa–UK Stroke Partnership (AUKSP) Project had a Steering Committee (SC) and four theme-based Working Groups (WGs): stroke services, stroke training/capacity building, research and stroke advocacy, each with defined terms of reference. These groups generated 20 priorities (five per thematic area) during breakout sessions at the first ASLS which were further refined into four topmost priorities (one per thematic area) at the general consensus session. Results: The topmost priorities included promoting the development of acute stroke services (stroke services), strengthening population-based stroke education focusing on prevention and symptom recognition (stroke training), research on hypertension control to reduce stroke risk (stroke research), and developing national stroke action plans (advocacy). Conclusion: Sustained reduction of stroke burden in Africa requires the adaptation of best practices to the African context, building the capacity of African stroke care professionals and using available resources with political support. Improving stroke literacy in African communities is a complementary strategy to reinforce healthy lifestyle choices and improve screening and detection of hypertension and other modifiable stroke risk factors
Mapping MAPP: jazz pedagogies & praxes of freedom
No full textDuring its active years, the community arts organisation Musical Action for People’s Power (hereafter MAPP) functioned in a multitude of ways, as a: concert organiser; provider of sound (systems); co-participant in workshops and solidarity events with other community or youth groups and trade unions; but mainly as an “educational body”, which in 1989, semi-formally transitioned into a school for music education, renaming itself Musical Action for People’s Progress. As a pedagogic site, MAPP produced an education through arts practice which undid, in its methodology and practice, apartheid’s segregationist education policies and was deeply embedded in the mass democratic movement and other circuits of comradely organisation(s). Despite its active role, it has no presence in academic literature, its archive of different mediums is sparse, and its impact is not fully understood. This research project maps the network of pedagogies, people, places, and politics of MAPP in an effort to analyse the conditions which led to its formation, the people who contributed to MAPP’s cultural work, and the everyday events and changes during its eight years of activity. In particular, the project asks whether the practices and pedagogies of MAPP through jazz inform a philosophy of art-making as a practice of freedom. It does so through archival and historiographic methodologies based on critical practices of cartography, black study, jazz pedagogy, and DJ scholarship
Dynamical models of galaxies observed in Hı line emission with MeerKAT
No full textThe dynamics of galaxies play a crucial role in understanding the evolution of these cosmic structures. In this work, we use neutral atomic hydrogen (Hı) emission line observations to generate 3D dynamical models of two galaxies, ESO 418- G 006 and WISEA J033235.23- 275532.8. These two galaxies form part of the Looking At the Distant Universe with the MeerKAT Array (LADUMA) survey. The first Hı interferometric observations of these extragalactic systems are constituted by this survey. Due to the exquisite nature of MeerKAT data, dynamical models of these galaxies are constructed at ˜1000 resolution, with these models used to gain insights into di↵erent evolutionary aspects of these galaxies. Using the dynamical model and resulting rotation curve of ESO 418- G 006, the first mass model of this galaxy is constructed to constrain the radial distribution properties of its dark matter content. This analysis reveals that a declining rotation curve most accurately represents the kinematics of ESO 418- G 006. Using the resulting mass model, the dark matter halo of this galaxy is parameterized using both the spherical pseudoisothermal (ISO) and NFW halo models. From this parameterization, the dark matter halo of ESO 418- G 006 is found to be best described by a halo consisting of a constantdensity inner core, with a core radius Rc = 3.79 ± 0.73 kpc and a core density ⇢0 = 0.083 ± 0.026 Mpc3. Due to the interesting morphology of the second galaxy that this work focuses on, WISEA J033235.23-275532.8, di↵erent 3D dynamical models of this galaxy are constructed, incorporating a warped Hı disk and a flat Hı disk respectively. This is undertaken to identify the model that can best describe the overall kinematics of this galaxy. Through a rigorous comparison of these models, we find that those incorporating a flat Hı disk do suciently well in resembling the data of WISEA J033235.23-275532.8. The resulting rotation curve of WISEA J033235.23-275532.8, generated from the bestfound flat Hı disk model, is found to mainly exhibit the typical shape associated with disk galaxies, but also exhibits a kinematic anomaly