The properties of the avalanche processes that develop on a dynamical lattice, the structure of links in which changes due to a specific characteristic of each lattice node, namely, its “activity,” ...which determines the probability of connection of a certain node with neighboring nodes in one step of lattice evolution. The statistics of the sizes of the avalanches appearing in the lattice system is studied as a function of the node activity and the link lifetime (the lifetime of the links formed in the system). It is analytically and numerically shows that the type of avalanche dynamics in the system changes as a function of these parameters. The following three regimes can take place in the system: (1) avalanches of any sizes, from small to catastrophic, can appear, which is reflected in the power-law behavior of the probability density function of the appearance of avalanches of certain sizes; (2) avalanches of a certain average size mainly appear in the system, and the probability density is close to that of a normal distribution; and (3) transient regime, where the probability density function of the appearance of avalanches of certain sizes is close to an exponential function. These results open up the possibilities of controlling the behavior of a complex system; in particular, they can be used to prevent catastrophic avalanches by changing the link lifetime and the average node activity.
Using the Geant4 software package, a numerical simulation of a neutron source of the time-offlight spectrometer GNEIS created on the basis of the SC-1000 synchrocyclotron with 1 GeV proton energy at ...the NRC Kurchatov Institute—PNPI (Gatchina) has been carried out. The influence of the structural features of the neutron source of the spectrometer on the spatial and energy distributions of neutrons has been studied. The intensity and spectral characteristics of the neutron flux in the range of 1–1000 MeV have been determined on the basis of the obtained information and detailed allowance for all elements of the neutron beam guide system. It is found that the best agreement between the experiment and calculation performed by means of Geant4 is observed when using the QGSP_INCLXX_HP model. In the neutron energy range of 1–200 MeV, the difference between the experimental and calculated shapes of the spectra is less than 25%.
The article presents a description of the ISNP/GNEIS testing facility with a neutron spectrum that reproduces the spectrum of atmospheric neutron radiation. The facility was developed at the ...Petersburg Nuclear Physics Institute (PNPI) of the National Research Center Kurchatov Institute in collaboration with the Institute of Space Device Engineering, a branch of JSC (Joint Stock Company) United Rocket and Space Corporation. The spallation neutron source of the facility is based on the 1-GeV SC-1000 proton synchrocyclotron at the PNPI. The internal neutron-production lead target produces 10-ns pulses of neutrons with a repetition rate of 45–50 Hz and an average neutron intensity of 3 × 10
14
n/s (in the 4σ solid angle). In the irradiation area located at a distance of 36 m from the neutron source, a high-quality collimated neutron beam with a broad energy spectrum of 1–1000 MeV and a neutron flux of 4 × 10
5
n/(cm
2
s) allows conducting accelerated single-event soft error testing of electronic components. In the course of the irradiation, the neutron energy spectrum and intensity and the spatial profile of the beam are controlled using a fission ionization chamber (beam monitor) and a position-sensitive multiwire proportional counter (beam profile meter). The data acquisition system of the ISNP/GNEIS facility utilizes 250 MS/s 12 bit CAEN waveform digitizers for the processing of signals from the monitor and profile meter by the neutron time-of-flight technique. In the report, parameters of the ISNP/GNEIS testing facility are discussed in comparison with analogous world-class facilities, as well as requirements and recommendations of the standards used in this field.
Dry spells and climatic hazards are responsible for maize output decline, sometimes to levels below potential yield levels. There is a pressing need to reduce the gap between actual and potential ...maize yield/ha, especially among farmers in semi-arid regions. This present study examines the potential role of supplemental irrigation and its differential impact on maize yield in the Eastern Cape Province of South Africa. In this study, maize yield data were generated from information recorded over a period of 20 years by farmers in Ntabankulu through cross-sectional interviews with 124 randomly-selected farming households. Maize yields for interviewed farmers were analysed for each of the experienced climatic hazards, for yield decline per ha and preferable adaptation strategies. Maize yield analyses show a maximum ceiling/attainable yield of 0.234 t/ha and average farm yield of 0.146 t/ha. Floods or hailstorms cause 75% decline in maize yield/ha and there was no significant difference between farmers practising irrigation and those practising dryland farming (P > 0.05). Low/no rains throughout the season; delay or low onset of rainfall and a rain-break for a week or more in a season results in 75%; 54% and 50.5% decline in maize yield/ha, respectively. On a scale of 1 to 10, farmers highly rank practicing supplementary irrigation (8.4) and change of planting date (7.8) as important adaptation strategies. Rescheduling planting date from the traditional planting times to earlier or later planting dates, assisted by use of weather reports and forecasting, to some extent curbs the impact of delays or slow onset of rainfall on yield. Supplemental irrigation is instrumental in reducing the impact of mid-season drought (rains break for a week) and light rainfall throughout the season. Analyses of actual yields and yield decline against each of the experienced climatic hazards provided insight into management possibilities to stabilize maize output.
South Africa is susceptible to droughts. However, little documentation exists on drought occurrence in South Africa at national, provincial and municipal administrative boundaries. This study ...profiles hydrological drought in OR Tambo District Municipality from 1998 to 2018, computing frequency, severity and intensity in order to show areas of high vulnerability. Data used were obtained from South African Weather Services. Standardised precipitation index (SPI) was calculated using the Meteorological Drought Monitor (MDM) software. Results showed a wide variation in monthly precipitation throughout the year. Coastal areas receive higher rainfall than inland municipalities. The study revealed that Nyandeni experienced the highest drought frequency of 62%, Mhlontlo (58%), King Sabatha Dalindyebo Municipality (57%), Ngquza Hill (55%) and Port St Johns Municipality showing the least at 52%. Hydrological drought severity frequency and duration varied between seven days and nine weeks. Drought intensity class exposed the annual average intensity for the five local municipalities represented as follows: KSDM (–0.71), PSJM (–0.99), Ngquza Hill (–0.81), Nyandeni (–0.71) and Mhlontlo (–0.62). The longest drought duration across OR Tambo was experienced in 2014 with durations varying from 3 to 11 weeks across the municipalities. OR Tambo District Municipality is susceptible to hydrological droughts and the extent varies across local municipalities. Results could be used for both adaptation planning and mitigating the impacts of future droughts. In addition, they could assist in guiding allocation of drought relief resources in ways that prioritise drought prone and vulnerable municipality.
Source-sink theory has contributed to our understanding of the function of protected areas, particularly due to their role as population sources. Marine reserves are a preferred management tool for ...the conservation of natural populations, creating areas of good quality habitat and thus improving population connectivity by enhancing larval supply and recruitment among shores. Despite recent advances in the study of protected areas in the context of the source-sink theory, rigorous and empirical testing of marine reserves as metapopulation sources for the adjacent areas remain largely unexplored. We investigated the role of marine reserves as population sources, whether there was spill-over beyond the reserve boundaries and if so, whether spill-over was directional. We measured percentage cover and recruitment of mussels (
Perna perna
) at two reserves and two comparably sized exploited control areas on the south-east coast of South Africa where unprotected populations are severely affected by artisanal exploitation. Adult abundances were enhanced within reserves, but decreased towards their edges. We predicted that recruitment would mirror adult abundances and show directionality, with northern shores having greater recruitment following the prevalent northward flow of near-shore currents. There were, however, no correlations between adult abundances and recruitment for any months or shores, and no clear spatial patterns in recruitment (i.e. similar patterns occurred at reserves and controls). The results emphasise that, while reserves may act as important refuges by protecting adult abundances, their influence on promoting recovery of near-by exploited shores through larval spill-over may be overestimated.
The rising prevalence of the failure of fast-growing cities’ waste authorities to account for solid waste service function and provide effective solid waste systems poses serious environmental ...hazards and health risks. Household solid waste mismanagement in Mthatha, a fast-growing city in South Africa with a rapid population increase, is emerging as a major environmental hazard. An effective solid waste audit system could reduce the extent of this problem. This study aimed at categorising and quantifying household solid waste generation and determining the drivers of waste generation and mismanagement that have the potential to increase risk and/or vulnerability to household solid waste-related environmental hazards. Stratified random sampling was used to select 248 sample households and to categorise them according to upgraded high-density informal residential settlements (64), high-density formal residential settlements (62), middle-density residential settlements (61) and low-density residential settlements (61). The results revealed that the waste generation rate increased one moves from informal settlements (1.84 bags of waste per household per week) to low-density, low socioeconomic statuses (2.26 bags), middle-density settlements (2.39 bags) and low-density residential settlements (2.84 bags). Food waste was the most commonly generated type of waste for more than 50% of the respondents. Approximately 89% of the most common types of waste reported across all settlements had the potential to be recycled, reused or composted. Only four factors emerged as significant determinants (p < 0.05) of the volume of solid waste generated per household per week: household socio-economic status, household size, knowledge of waste management and household participation in waste separation. Results on drivers of household solid waste generation and variations across residential settlements could be utilised when designing growing cities’ waste management plans, with the objective of reducing the volume of solid waste sent to landfill sites, illegal dumping and open burning of waste, thus reducing the associated negative impacts that mismanaged waste poses to the environment. Enforcing waste separation at the household level could promote reuse and recycling, which in turn would reduce waste volumes.
► Larval export of mussels and associated fauna from marine reserves was tested. ► Harvesting outside reserves led to replacement of mussels by coralline algal turf. ► There was no effect of distance ...away from a reserve on mussels or associated fauna. ► Reserves protected adult stocks of mussels but there was no export of mussel larvae. ► Reserves provided larval export of non-targeted associated species.
Populations of organisms that create habitat can often be fragmented throughout landscapes by anthropogenic disturbances such as harvesting and loss or change to the identity of such bioengineers may lead to large changes in biodiversity. Using the fauna associated with a bioengineer, the intertidal mussel
Perna perna, we tested hypotheses about the relative importance of larval export from protected populations in marine reserves. Harvesting led to the replacement of
P. perna and the domination of shores outside reserves by turf-forming coralline algae, mostly
Corallina spp. We determined whether the diverse fauna recruiting onto artificial units of habitat placed within mussel beds differed between reserves and non-reserve areas or whether shores outside reserves, and open to harvesting, received recruits through larval export from reserves. Furthermore, we determined whether this was affected by the distance away from reserves and whether colonisation was achieved by movement of adults from surrounding biogenic habitats or via the plankton. Overall, we found no effect of increasing distance away from a reserve on the cover of adult mussels or associated fauna. We found strong effects of the presence of marine reserves on abundances of molluscs and polychaetes but not crustaceans. There were greater densities of molluscs in sites with a reserve (i.e. inside reserves, and up to 5
km outside reserve boundaries), but more polychaetes in exploited sites. For molluscs, this pattern was driven by gastropods rather than bivalves. Furthermore, although reserves had greater cover of adult mussels than non-reserve areas, recruitment of mussels was not greater inside or near to reserves. Our study illustrates the effectiveness of these reserves in protecting stocks of adult mussels, and although there was no evidence that reserves provided export of the larvae of mussels (the target species), they did provide larval export of non-targeted associated species. By protecting a harvested bioengineer and through export of the larvae of its associated fauna, these reserves fulfil some, but not all the conservation aims of a marine protected area.
Abstract
The world faces problems such as improper waste disposal that have spread to include disposal near water bodies. It is getting difficult to find fresh water everywhere. Given that surface ...sources provide around one-third of the world's drinking water needs, their contamination exacerbates the issue. This paper aims at evaluating the impacts of solid waste on water quality along the Mthatha River. During the rainy and dry seasons of 2021, Hanna probe instruments were used to assess the physicochemical quality of water before and after identified illegal dump sites. To compare the measured mean values of water quality parameters data were analysed using ANOVA in SPSS version 22. In terms of temperature, dissolved oxygen, pH, nitrite, conductivity, and Escherichia coli, the water quality in the sampling points after the illegal dump sites revealed deterioration, which was more severe in the rainy season and moderate in the dry season. The study's findings suggest that illegal dump sites along water bodies negatively impact the water quality. Diverse research on water pollution shows that declining water quality endangers aquatic species and is unsafe for human consumption. This paper recommends strengthening of laws against improper waste handling, and frequent waste collection to prevent contamination of water bodies.
Water shortages are a chronic and severe problem in South Africa. Allocation of this limited water resources, environmental quality, and policies for sustainable water use are issues of increasing ...concern that require accurate and timely information to evolve strategies for dynamic natural resources management. Specifically, this paper is aimed to assist the planning, restoring and to rationally allocate the water resources in any river basin in resolving the current water stresses in many parts of South Africa, by using integrated knowledge from simulation and integrated river basin management approach. The developed system dynamic (SD) allocation system was used to investigates the extent to which the framework is ‘sustainable’ in the medium and long terms in evaluating existing and future water allocation among conflicting users at Mkomazi River Basin (MRB), KwaZulu-Natal Province, South Africa The invented SD framework confirms agricultural water use as the highest demand when compared with other users. The optimal sustainability performance index (0.25) of the system at 70% dependable flow shows an integrated scenario that combines rainfall variation with improved irrigation water use efficiency as a suitable framework plan. The study uses integrated knowledge from simulation and integrated river basin management approach as a feasible method to assist the planning, restoring and to rationally allocate the water resources in any river basin with similar attributes to the study area in resolving the current water stresses in many parts of the country. Water resources managers would find these tools beneficial in understanding the complex nature of water resources allocation and in determining priorities area which required prompt attention and intervention.
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