The sulfur biogeochemical cycle plays a key role in regulating Earth’s surface redox through diverse abiotic and biological reactions that have distinctive stable isotopic fractionations. As such, ...variations in the sulfur isotopic composition (δ34S) of sedimentary sulfate and sulfide phases over Earth history can be used to infer substantive changes to the Earth’s surface environment, including the rise of atmospheric oxygen. Such inferences assume that individual δ34S records reflect temporal changes in the global sulfur cycle; this assumption may be well grounded for sulfate-bearing minerals but is less well established for pyrite-based records. Here, we investigate alternative controls on the sedimentary sulfur isotopic composition of marine pyrite by examining a 300-m drill core of Mediterranean sediments deposited over the past 500,000 y and spanning the last five glacial–interglacial periods. Because this interval is far shorter than the residence time of marine sulfate, any change in the sulfur isotopic record preserved in pyrite (δ34Spyr) necessarily corresponds to local environmental changes. The stratigraphic variations (>76‰) in the isotopic data reported here are among the largest ever observed in pyrite, and are in phase with glacial–interglacial sea level and temperature changes. In this case, the dominant control appears to be glacial–interglacial variations in sedimentation rates. These results suggest that there exist important but previously overlooked depositional controls on sedimentary sulfur isotope records, especially associated with intervals of substantial sea level change. This work provides an important perspective on the origin of variability in such records and suggests meaningful paleoenvironmental information can be derived from pyrite δ34S records.
•Addressing the open question on high ClO4 content and high ClO4/Cl ratio found on Mars.•In situ sensing of free radicals generated by electrostatic discharge (ESD) in a Mars chamber.•Detection of ...NaClO3, NaClO4, and Na2CO3 formed in NaCl through redox plasma chemistry.•Evidences of 1000 times oxidation power of ESD-electron over UVC-photon in the experimental setting.•Scaling to Mars conditions suggests an important contribution of plasma chemistry occurred in Martian dust events in perchlorate formation.
We report experimental evidences to support a new formation mechanism, multiphase redox plasma chemistry, for perchlorate on Mars observed during the Phoenix mission, whose high concentrations and high ClO4/Cl ratio cannot be fully interpreted by photochemistry. This chemical reaction occurs between Cl-bearing minerals on the Mars surface and free radicals generated by electrostatic discharge (ESD) during Mars dust events (dust storms, dust devils, and grain saltation).
We conducted simulated ESD experiments in a Mars chamber with pure CO2, CO2 + H2O(g), and Mars Simulate Gas Mixture at Martian atmospheric pressure. We directly observed (1) the instantaneous generation of atmospheric free radicals CO+2, CO+, OI, HIII, HII, OH, ArI, N2, and N+2 in normal glow discharge (NGD), detected by in situ plasma emission spectroscopy, and O3 by UV and Mid-IR spectroscopy; (2) the fast transformation of NaCl to NaClO3 and NaClO4 detected by laser Raman spectroscopy, with oxychlorine enrichment at the sample surfaces confirmed by ion chromatography. Through two sets of experimental comparison, we found that the oxidation power of ESD-electron is three orders of magnitude higher than that of UVC-photon. We scaled our experimental results to the modeled ESD in Mars dust events and Mars surface UV radiation level, and concluded that plasma chemistry occurred during Mars dust events can be an additional important formation mechanism for the large amounts of perchlorates observed during various missions to Mars.
This paper critically considers the conceptualization of the ‘region’ in regional economic development. It utilizes the Durban Aerotropolis in KwaZulu-Natal, South Africa as a case of reference ...through which the conceptualization and underpinnings of ‘region’ associated with economic development are understood. This exercise is prompted by the nomenclatural shifts in local government from local economic development to regional economic development which is causing shifts in approaches to the implementation of economic development projects. The findings presented in this paper show that in the conceptualisation of the region in the instance of the Durban Aerotropolis, understanding the function, form and scale of a regional economic development project becomes pertinent to the social construction of the region with consequences for the project focus and implementation. In the discussion, function is examined as the purpose of a regional economic development project, form refers to the kind of economic development mechanism or strategy which could assist in fulfilling that purpose and scale speaks to the extent, reach and magnitude of the project, without which the implications are challenging practical enactment or implementation of regional economic development projects. The social constructions of region outlined in this paper thereby attest to the multiplicity of definitions which are typically based on the context in which the concept is being used and thus shows the ‘region’ inherent in regional economic development as produced through, and for, an assemblage of economic activity in space. From this we understand the region in regional economic development to be a social construct which presents itself as an assemblage of economic activity in space. Although we understand regions as spatially contingent, the theoretical and empirical conceptualisation of regions within regional economic development planning, policy–making and practice must draw on the specifics of contextuality to ensure its utility to economic development.
The organic composition of the feed sludge to six laboratory-scale anaerobic digesters was adjusted by substituting a proportion of the primary sludge for glucose or propionic acid solution. ...Substitution with glucose caused an increase in the microbial extracellular polymer (ECP) content of the digested sludge, which altered the particle size distribution of the sludge and made the sludge more difficult to dewater. Substitution with propionic acid gave similar results to the control. The relationship between the digested sludge extracted ECP yield and sludge filtrability determined using the capillary suction time test was significant at the
P=0.01 level. The level of ECP for optimum sludge dewaterability was calculated as 17.2
mg
g
−1 SS. The protein and carbohydrate composition of the extracted polymer did not appear to affect the sludge dewaterability. Results present will allow predictions to be made into the effect that changes in the influent sewage composition has on essential downstream processes.
Microbial sulfur cycling in marine sediments often occurs in environments characterized by transient chemical gradients that affect both the availability of nutrients and the activity of microbes. ...High turnover rates of intermediate valence sulfur compounds and the intermittent availability of oxygen in these systems greatly impact the activity of sulfur-oxidizing micro-organisms in particular. In this study, the thiosulfate-oxidizing hydrothermal vent bacterium Thiomicrospira thermophila strain EPR85 was grown in continuous culture at a range of dissolved oxygen concentrations (0.04-1.9 mM) and high pressure (5-10 MPa) in medium buffered at pH 8. Thiosulfate oxidation under these conditions produced tetrathionate, sulfate, and elemental sulfur, in contrast to previous closed-system experiments at ambient pressure during which thiosulfate was quantitatively oxidized to sulfate. The maximum observed specific growth rate at 5 MPa pressure under unlimited O
was 0.25 hr
. This is comparable to the μ
(0.28 hr
) observed at low pH (<6) at ambient pressure when T. thermophila produces the same mix of sulfur species. The half-saturation constant for O
(
) estimated from this study was 0.2 mM (at a cell density of 10
cells/ml) and was robust at all pressures tested (0.4-10 MPa), consistent with piezotolerant behavior of this strain. The cell-specific
was determined to be 1.5 pmol O
/cell. The concentrations of products formed were correlated with oxygen availability, with tetrathionate production in excess of sulfate production at all pressure conditions tested. This study provides evidence for transient sulfur storage during times when substrate concentration exceeds cell-specific
and subsequent consumption when oxygen dropped below that threshold. These results may be common among sulfur oxidizers in a variety of environments (e.g., deep marine sediments to photosynthetic microbial mats).
Microbial sulfur cycling in marine sediments often occurs in environments characterized by transient chemical gradients that affect both the availability of nutrients and the activity of microbes. ...High turnover rates of intermediate valence sulfur compounds and the intermittent availability of oxygen in these systems greatly impact the activity of sulfur‐oxidizing micro‐organisms in particular. In this study, the thiosulfate‐oxidizing hydrothermal vent bacterium Thiomicrospira thermophila strain EPR85 was grown in continuous culture at a range of dissolved oxygen concentrations (0.04–1.9 mM) and high pressure (5–10 MPa) in medium buffered at pH 8. Thiosulfate oxidation under these conditions produced tetrathionate, sulfate, and elemental sulfur, in contrast to previous closed‐system experiments at ambient pressure during which thiosulfate was quantitatively oxidized to sulfate. The maximum observed specific growth rate at 5 MPa pressure under unlimited O2 was 0.25 hr−1. This is comparable to the μmax (0.28 hr−1) observed at low pH (<6) at ambient pressure when T. thermophila produces the same mix of sulfur species. The half‐saturation constant for O2 (KO2) estimated from this study was 0.2 mM (at a cell density of 105 cells/ml) and was robust at all pressures tested (0.4–10 MPa), consistent with piezotolerant behavior of this strain. The cell‐specific KO2 was determined to be 1.5 pmol O2/cell. The concentrations of products formed were correlated with oxygen availability, with tetrathionate production in excess of sulfate production at all pressure conditions tested. This study provides evidence for transient sulfur storage during times when substrate concentration exceeds cell‐specific KO2 and subsequent consumption when oxygen dropped below that threshold. These results may be common among sulfur oxidizers in a variety of environments (e.g., deep marine sediments to photosynthetic microbial mats).
This article explores importance of SMEs in a given economy. It will also show us the reason why SMEs should be given full concentration and also to provide for the existing SMEs and encouraging more ...to start up.The contribution of the Small and Medium Enterprises (SMEs) to the Local Economic Development (LED) of a nation is well recognized. In developing countries, the contribution of SMEs towards employment generation is significant because they:• Nurture entrepreneurship.• Since small businesses employs the citizens of the country, it helps to reduce risks (reduce crime rates).• Support the building up of systemic productive capacities and the creation of resilient economic systems, through linkages between small and large enterprises.• Tend to use more labour intensive production processes than large enterprises, boosting employment and leading to more equitable income distribution• Provide livelihood opportunities through simple, value adding processing activities in agriculturally based economies;
Hydrothermal experiments were conducted to evaluate the kinetics of H₂₍ₐq₎ oxidation in the homogeneous H₂–O₂–H₂O system at conditions reflecting subsurface/near-seafloor hydrothermal environments ...(55–250°C and 242–497bar). The kinetics of the water-forming reaction that controls the fundamental equilibrium between dissolved H₂₍ₐq₎ and O₂₍ₐq₎, are expected to impose significant constraints on the redox gradients that develop when mixing occurs between oxygenated seawater and high-temperature anoxic vent fluid at near-seafloor conditions. Experimental data indicate that, indeed, the kinetics of H₂₍ₐq₎–O₂₍ₐq₎ equilibrium become slower with decreasing temperature, allowing excess H₂₍ₐq₎ to remain in solution. Sluggish reaction rates of H₂₍ₐq₎ oxidation suggest that active microbial populations in near-seafloor and subsurface environments could potentially utilize both H₂₍ₐq₎ and O₂₍ₐq₎, even at temperatures lower than 40°C due to H₂₍ₐq₎ persistence in the seawater/vent fluid mixtures. For these H₂–O₂ disequilibrium conditions, redox gradients along the seawater/hydrothermal fluid mixing interface are not sharp and microbially-mediated H₂₍ₐq₎ oxidation coupled with a lack of other electron acceptors (e.g. nitrate) could provide an important energy source available at low-temperature diffuse flow vent sites. More importantly, when H₂₍ₐq₎–O₂₍ₐq₎ disequilibrium conditions apply, formation of metastable hydrogen peroxide is observed. The yield of H₂O₂₍ₐq₎ synthesis appears to be enhanced under conditions of elevated H₂₍ₐq₎/O₂₍ₐq₎ molar ratios that correspond to abundant H₂₍ₐq₎ concentrations. Formation of metastable H₂O₂ is expected to affect the distribution of dissolved organic carbon (DOC) owing to the existence of an additional strong oxidizing agent. Oxidation of magnetite and/or Fe⁺⁺ by hydrogen peroxide could also induce formation of metastable hydroxyl radicals (•OH) through Fenton-type reactions, further broadening the implications of hydrogen peroxide in hydrothermal environments.
Small Medium and Micro Enterprises (SMMEs) play an important role in the economy of many countries. The Small Medium and Micro Enterprises (SMMEs) sector is a major contributor to technical ...innovation and new product developments, in terms of employment, economic development.The creation and expansion of new SMMEs helps to produce a high volume of new jobs. Entrepreneurs have high expectations and are often found among new and innovative and technology-based firms, but in order for them to play a major role in economic growth and development, it is also necessary that there is a real supply of fresh innovations and processes to renew businesses.Many eminent scholars have written about the challenges that SMMEs face worldwide. Some scholars have decided to look into these problems based on different sectors. Basically the researcher has looked at external forces that small businesses face while considering all small businesses registered with the Business Support Centre (BSC), Pietermaritzburg, South Africa. These external factors are basically not controllable by a single business. SMME’s are said to be a lifeline of many nations and thereby attention must be drawn to them starting from micro businesses to small and medium enterprises. Entrepreneurial activity helps to reduce both employment and underemployment.After reviewing an extensive range of literature on the development and enhancement of SMMEs, it was evident that most research has considered businesses based on a certain list that they have acquired from the Chamber of Commerce of different countries and provinces, some have considered walking within a certain location in order to access data etc.The researcher decided to base the research on an organisation that has some SMMEs registered with them. The researcher has looked into these individual organisations and also their mother company called Business Support Centre (BSC), Pietermaritzburg in KwaZulu Natal Province in South Africa. This will enable the researcher to have direct contact with all the registered small businesses with BSC and also the management of BSC and it will enable the researcher to access adequate information on the problems these small businesses face externally.
A diimidazolium salt incorporating a secondary amine moiety has been used to prepare a palladium(II) di-N-heterocyclic carbene amino complex that can be deprotonated with NaH to give the first ...example of a transition metal NHC-amide.
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