Observing the Sunyaev-Zel'dovich Effect Closer to Home

Hot gas trapped in a dark matter halo will produce a decrement in the surface brightness of the microwave background, the Sunyaev-Zel'dovich (SZ) effect. While massive clusters produce the strongest central SZ decrements, we point out that a local galaxy halo, specifically the halo of M31, may be one of the brightest integrated SZ sources in the sky. For various realistic gas distributions consistent with current X-ray limits, we show that the integrated SZ decrement from M31 will be comparable to decrements already detected in more distant sources, provided its halo contains an appreciable quantity of hot gas. A measurement of this decrement would provide direct information on the mass, spatial distribution and thermodynamic state of hot gas in a low-mass halo, and could place important constraints on current models of galaxy formation. Detecting such an extended (~ 10 degree), low-amplitude signal will be challenging, but should be possible with all-sky SZ maps from satellite missions such as the Wilkinson Microwave Anisotropy Probe or the Planck Surveyor.Comment: 5 pages, 3 figures; submitted to MNRA

Could human challenge studies for COVID-19 vaccines be justified in South Africa?

Although human challenge studies (HCSs) have been widely employed in vaccine development for malaria, dengue, typhoid and cholera, the role of this research design in COVID-19 remains controversial. While the potential social value of HCSs in the context of a pandemic is clear, bioethicists are divided on the ethics, given that effective treatment for COVID-19 has eluded us to date. While compelling ethics arguments have been offered on both sides of the debate, scientific and regulatory complexities may not have been fully appreciated. Furthermore, accelerated development of efficacious vaccine candidates in traditional clinical trials has diluted some of the arguments in favour of HCSs. In low- and middle-income country settings, including South Africa, the need for robust patient care conditions for the conduct of HCSs, coupled with considerations such as perceptions of risk, consent processes, remuneration, vaccine hesitancy, fear of exploitation and access to vaccines, makes HCSs challenging to justify

Medicinal plants with cholinesterase inhibitory activity: A Review

Alzheimer’s disease (AD), a common neurodegenerative disease, is characterized by low levels in the brain of the neurotransmitter, acetylcholine (ACh). Clinical treatment of this disease is palliative and relies mostly on enhancing cholinergic function by stimulation of cholinergic receptors or prolonging the availability of ACh released into the neuronal synaptic cleft by use of agents which restore or improve the levels of acetylcholine. Inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), enzymes which breakdown acetylcholine, are considered as a promising strategy for the treatment of AD. A potential source of AChE and BChE inhibitors is provided by the abundance of plants in nature, and natural products continue to provide useful drugs and templates for the development of other compounds. The present work constitutes a review of the literature on 123 species of medicinal plants that have been tested for AChE inhibitory activity and 42 plant species which have been tested for BChE inhibitory activity. The plant species listed are potential cholinesterase inhibitors and may aid researchers in their study of natural products which may be useful in the treatment of AD.Key words: Alzheimer’s disease, acetylcholine, acetylcholinesterase, butyrylcholinesterase and medicinal plants

Isolation and quarantine in South Africa during COVID-19: Draconian measures or proportional response?

In the midst of an unprecedented public health crisis, extraordinary containment measures must be implemented. These include both isolation and quarantine, either on a voluntary basis or enforced. In the transition from voluntary to mandatory isolation, conflicts arise at the intersection of ethics, human rights and the law. The Siracusa Principles adopted by the United Nations Economic and Social Council in 1985 and enshrined in international human rights legislation and guidelines specify conditions under which civil liberties may be infringed. In order for isolation processes in South Africa to claim legitimacy, it is important that these principles as well as national laws and constitutional rights are embedded in state action

Partition distribution of selected organochlorine pesticides in water, sediment pore water and surface sediment from uMngeni River, KwaZulu-Natal, South Africa

Abstract: Organochlorine pesticides (OCPs) were analysed in surface water, pore water and surface sediment samples collected from the uMngeni River, which is one of the largest rivers in the province of KwaZulu-Natal, South Africa. Liquid-liquid extraction was used to extract the analytes from water and pore water samples and soxhlet extraction was used to extract sediment samples with subsequent florisil clean-up and gas chromatography-mass spectrometry (GC-MS) analysis. Twelve selected OCPs were analysed and their total concentrations were found to range from 8.04–21.06 ng/mL, 36.06–188.43 ng/mL and 148.17–554.73 ng/g in unfiltered surface water, unfiltered pore water and surface sediment (dry weight (dw)), respectively. The results indicated that the concentrations of these selected pesticides were far higher in sediment (72%) than in pore water (25%) and water (3%). The most polluted sites were Northern Wastewater Treatment influent (NWTI) for water (Σ12OCP = 19.41 ± 1.43 ng/mL) and Northern Wastewater Treatment effluent (NWTE) for pore water (Σ12 OCP = 166.23 ± 7.16 ng/mL) and sediment (Σ12 OCP = 495.21 ± 32.38 ng/g). The most abundant individual OCPs and their average concentrations in general in the river were p,p′-DDE in unfiltered water (1.62 ±0.22 ng/mL) and unfiltered sediment pore water (17.09 ±7.96 ng/mL), and endrin in surface sediment (55.57 ± 19.01 ng/g, dw)

Constraints on isocurvature models from the WMAP first-year data

We investigate the constraints imposed by the first-year WMAP CMB data extended to higher multipole by data from ACBAR, BOOMERANG, CBI and the VSA and by the LSS data from the 2dF galaxy redshift survey on the possible amplitude of primordial isocurvature modes. A flat universe with CDM and Lambda is assumed, and the baryon, CDM (CI), and neutrino density (NID) and velocity (NIV) isocurvature modes are considered. Constraints on the allowed isocurvature contributions are established from the data for various combinations of the adiabatic mode and one, two, and three isocurvature modes, with intermode cross-correlations allowed. Since baryon and CDM isocurvature are observationally virtually indistinguishable, these modes are not considered separately. We find that when just a single isocurvature mode is added, the present data allows an isocurvature fraction as large as 13+-6, 7+-4, and 13+-7 percent for adiabatic plus the CI, NID, and NIV modes, respectively. When two isocurvature modes plus the adiabatic mode and cross-correlations are allowed, these percentages rise to 47+-16, 34+-12, and 44+-12 for the combinations CI+NID, CI+NIV, and NID+NIV, respectively. Finally, when all three isocurvature modes and cross-correlations are allowed, the admissible isocurvature fraction rises to 57+-9 per cent. The sensitivity of the results to the choice of prior probability distribution is examined.Comment: 20 pages, 24 figures. Submitted to PR

The initial conditions of the universe: how much isocurvature is allowed?

We investigate the constraints imposed by the current data on correlated mixtures of adiabatic and non-adiabatic primordial perturbations. We discover subtle flat directions in parameter space that tolerate large (~60%) contributions of non-adiabatic fluctuations. In particular, larger values of the baryon density and a spectral tilt are allowed. The cancellations in the degenerate directions are explored and the role of priors elucidated.Comment: 4 pages, 4 figures. Submitted to PR

Molecular detection of carbapenemase-producing genes in referral Enterobacteriaceae in South Africa: A short report

Molecular confirmation of carbapenemase-producing Enterobacteriaceae (CPE) was introduced in South Africa (SA) at the end of 2011. We report on the detection of these resistance genes based on referral isolates. Enterobacteriaceae with non-susceptibility to any of the carbapenems according to defined criteria for antimicrobial susceptibility testing results were sent to a reference laboratory. A proportion of isolates had limited demographic, epidemiological and clinical data available. Organism identification was reconfirmed using reference laboratory methods, and the presence of carbapenemases was confirmed with a real-time polymerase chain reaction. We analysed 1 503 significant isolates received for confirmation from the National Health Laboratory Service and some private laboratories during 2012 - 2015 and confirmed one or more carbapenemase-producing genes in 68% of isolates, the most common organism being Klebsiella pneumoniae (60%). The most common carbapenemase genes were blaNDM, followed by blaOXA-48 and its variants. BlaOXA-48 and its variants demonstrated non-susceptibility to ertapenem in 89% of the isolates when analysed by the phenotypic method, and to ceftazidime in 34%. Overall, the detection rate for carbapenemases in K. pneumoniae blood isolates in the public sector was 1.9% during the 4-year period. This report indicates the presence of CPE in SA, and it is important for all healthcare workers to be aware of this major public health threat so that infection prevention and control measures can be implemented to prevent the spread of CPE in healthcare facilities