Silver niobate is a conventional perovskite oxide compound, known to exhibit a rich polymorphism. Although often classified as antiferroelectric, its low-temperature structure remains unclear. Here, first-principles calculations reveal a previously overlooked and unusual rhombohedral ferroelectric phase with R3 symmetry that emerges as the thermodynamic ground state despite its close energetic competition among previously proposed structures. Remarkably, this phase is structurally chiral, with chirality emerging improperly from the coupling between polarization and in-phase rotations of the oxygen octahedra along [111], producing a ferri-chiral state with incomplete cancellation of local chiral motifs. As a consequence, the phase exhibits significant natural optical activity comparable to that of quartz. Although energetically favored, its experimental observation may be hindered by kinetic limitations, potentially contributing to the ongoing controversy surrounding the low-temperature structure of silver niobate.
Per- and polyfluoroalkyl substances (PFASs) are synthetic chemicals widely used in industrial applications and consumer products due to their thermal stability and resistance to degradation. These properties also contribute to their environmental persistence and potential adverse health effects. Despite increasing global concern regarding PFAS exposure, biomonitoring data from African populations remain limited. This study investigated the serum concentrations of perfluorooctanoic acid (PFOA), perfluorooctanesulfonate (PFOS), and perfluorobutane sulfonate (PFBS), and their association with diabetes mellitus (DM) in a mixed-ancestry population from Bellville South, Cape Town, South Africa. Serum samples (n = 179) were analysed using liquid chromatography–tandem mass spectrometry (LC–MS-8030), and statistical analyses were performed using STATISTICA 13.5 software. All three PFASs were detected in 100% of samples, with PFOA exhibiting the highest mean concentration (9.43 ± 13.16 ng/mL), followed by PFBS and PFOS. PFAS concentrations were generally higher in females than in males, with significantly elevated PFOA levels observed among women (p = 0.0116). No statistically significant associations were identified between PFAS concentrations and glycemic status, obesity, or related metabolic indicators (p > 0.05). However, PFOS showed a modest positive correlation with HbA1c in females, suggesting potential gender-specific interactions. These findings confirm measurable PFAS exposure in the South African population and highlight the need for larger longitudinal studies implications.
The study examined the response of Lake Baringo's water levels to hydro-meteorological forcings and estimated lake water budget components. Hydroclimatic and lake water level data were obtained from satellite and ground stations in addition to in situ sampling. Data were analysed for long-term (1970-1995) and short-term (2008-2021) periods. Results of a water balance model indicated the river inflows contributed 74% and 71% to the lake storage during the 1970-1995 and 2008-2021 periods, respectively, while precipitation contributed 26% and 29% during the same periods. Of the water losses, evaporation contributed the most (64-79%) compared to water abstractions from tributaries (32-15%), and underground seepage (7-6%) over the long-term range (1970 to 2021). Sensitivity analysis showed lake levels to be highly responsive to hydro-meteorological variables. We recommend continuous monitoring of the water balance components, and integrated watershed management actions that sustain surface inflows into the lake.
Environmental noise pollution is an underestimated problem, despite its proven effects on public health in rapidly urbanizing cities, particularly in sub-Saharan Africa, where empirical data remains limited. This study aims to analyze the spatial and temporal variability of environmental noise pollution in Bukavu, Democratic Republic of the Congo (DRC), a city characterized by rapid population growth, a high concentration of schools, and a high intensity of urban activity. Noise levels (LAeq) were measured using an SPL-25 sound level meter at 17 specific sites, categorized based on three land use types, including commercial, residential and schools, spanning the wet and dry seasons, during the daytime (07:00–18:00). Descriptive statistical analyses and seasonal comparisons were carried out, supplemented by spatial interpolation (IDW) to map the distribution of noise. Average noise levels in the wet season (67.83 ± 9.36 dB(A)) and the dry season (66.81 ± 8.55 dB(A)) were above the World Health Organization's daytime noise threshold. Maximum recorded levels reached 114.0 dB(A) in commercial areas and 111.3 dB(A) in school zones, exposing schoolchildren to worrying levels of noise pollution. Spatial analysis using GIS revealed a heterogeneous distribution of noise (30.8-114 dB(A)) with hotspots along the roads of Bukavu. Noise levels were high during the day and in the evening, with noise peaks more noticeable in the morning and evening at sites with heavy traffic. These findings underscore the need to incorporate noise management into urban planning and environmental health policies to reduce urban population exposure.
The relationship between land and violent conflict in Africa has long been a focal point for scholarly inquiry and development policy. According to an influential neo-Malthusian narrative, violent land conflicts erupt when land scarcity, population pressure, and state failure combine. In this paper we join a growing corpus of researchers arguing that the links between violent conflict and land scarcity are not linear, but embedded in complex and entangled social, economic and political processes. Using an extended case-study approach we explore land disputes in the Panzi neighbourhood of Bukavu, which is situated in the conflict-affected eastern part of the Democratic Republic of Congo and appears to embody a neo-Malthusian crisis. We present three main findings.First, we demonstrate how large-scale violent conflict can create opportunities for new actors to reconfigure the political order, generating struggles and negotiations over public authority and land rights among a multitude of more or less self-proclaimed public authorities and land claimants.Second, we show that although armed conflict reconfigures the links between public authority and land rights, it does not radically change how land is governed, or how people gain and hold on to property. Both before and after major political ruptures, people gain land rights through daily negotiations with competing public authorities.Third, we show that these struggles and negotiations do not take place on a level playing field. Rather, well-connected and wealthy actors with access to military power tend to fare better in such contests.Based on our research, we conclude that land scarcity functions as a contextual amplifier, rather than a direct cause of violent conflict. However, more research and conceptual work is needed to better understand this link.
