Studies on Arsenic Release and its Mitigation from Tailings Dam Using Nanomagnetite Particles

Knowledge of the geochemistry of As in tailings material after beneficiation of gold-bearing sulphidic ores is necessary to comprehend the nature, stability and mobilization of As into the geo-environment and its subsequent mitigation during storage. In this study, XRD combined with reflected light microscopy and SEM-EDX were employed to carry out studies on the min-eralogical composition of As in a tailings material. Arsenic-rich solutions were generated from the tailings material using de-ionised water to ascertain As mobilisation. The remediation kinetics of the soluble As was carried out using nanomagnetite (Fe3O4). The XRD and SEM- EDX analyses showed that the major source of As in the tailings material is arsenopyrite (FeAsS). The study further confirmed that the residual As mineral in the tailings material is capable of decomposing during storage and can be subsequently mobilised into the geo-environment. It was established that nanomagnetite can efficiently re-move As from tailings leachates; preferably at pH between 6 and 7 and Langmuir isotherm best described the sorption process while the Gibbs free energy of the sorption was found to be -12.1026 KJ/mol. Thus, nanomagnetite can be used to mitigate arsenic foot-prints from tailings dam

Balancing socio-Economic and Academic Needs: A case of Higher Education Graduate Students.

The need to pursue higher degrees to meet job demands, while at the same time working for social obligations, can be quite challenging. This is especially so when such students have to pay their tuition privately. This paper is based on the findings of a study done among students on masters programs in higher education at Makerere University in 2008. It reports some of the challenges graduate students face as they struggle to attain higher degree qualifications needed in order to secure better jobs, gain promotion, or toretain their jobs at their current places of work. Specifically, it reports some of the risks students take while looking for additional funds to pay university fees; while at the same time sustaining families and other social economic obligations. A lot of study time is lost in various activities students engage in to realize the needed funds, a fact that could have adverse effects on the quality of their study performance

Micromagnetic simulations of sweep-rate dependent coercivity in perpendicular recording media

The results of micromagnetic simulations are presented which examine the impact of thermal fluctuations on sweep rate dependent coercivities of both single-layer and exchange-coupled-composite (ECC) perpendicular magnetic recording media. M-H loops are calculated at four temperatures and sweep rates spanning five decades with fields applied normal to the plane and at 45 degrees. The impact of interactions between grains is evaluated. The results indicate a significantly weaker sweep-rate dependence for ECC media suggesting more robustness to long-term thermal effects. Fitting the modeled results to Sharrock-like scaling proposed by Feng and Visscher [J. Appl. Phys. 95, 7043 (2004)] is successful only in the case of single-layer media with the field normal to the plane.Comment: 7 pages, 14 figure

Point Mutations in Centromeric Histone Induce Post-zygotic Incompatibility and Uniparental Inheritance.

The centromeric histone 3 variant (CENH3, aka CENP-A) is essential for the segregation of sister chromatids during mitosis and meiosis. To better define CENH3 functional constraints, we complemented a null allele in Arabidopsis with a variety of mutant alleles, each inducing a single amino acid change in conserved residues of the histone fold domain. Many of these transgenic missense lines displayed wild-type growth and fertility on self-pollination, but exhibited frequent post-zygotic death and uniparental inheritance when crossed with wild-type plants. The failure of centromeres marked by these missense mutation in the histone fold domain of CENH3 reproduces the genome elimination syndromes described with chimeric CENH3 and CENH3 from diverged species. Additionally, evidence that a single point mutation is sufficient to generate a haploid inducer provide a simple one-step method for the identification of non-transgenic haploid inducers in existing mutagenized collections of crop species. As proof of the extreme simplicity of this approach to create haploid-inducing lines, we performed an in silico search for previously identified point mutations in CENH3 and identified an Arabidopsis line carrying the A86V substitution within the histone fold domain. This A87V non-transgenic line, while fully fertile on self-pollination, produced postzygotic death and uniparental haploids when crossed to wild type

Low-temperature formation of polycyclic aromatic hydrocarbons in Titan’s atmosphere

The detection of benzene in Titan’s atmosphere led to the emergence of polycyclic aromatic hydrocarbons (PAHs) as potential nucleation agents triggering the growth of Titan’s orange-brownish haze layers. However, the fundamental mechanisms leading to the formation of PAHs in Titan’s low-temperature atmosphere have remained elusive. We provide persuasive evidence through laboratory experiments and computations that prototype PAHs like anthracene and phenanthrene (C14H10) are synthesized via barrierless reactions involving naphthyl radicals (C10H7•) with vinylacetylene (CH2=CH–C≡CH) in low-temperature environments. These elementary reactions are rapid, have no entrance barriers, and synthesize anthracene and phenanthrene via van der Waals complexes and submerged barriers. This facile route to anthracene and phenanthrene—potential building blocks to complex PAHs and aerosols in Titan—signifies a critical shift in the perception that PAHs can only be formed under high-temperature conditions, providing a detailed understanding of the chemistry of Titan’s atmosphere by untangling elementary reactions on the most fundamental level

Dynamique de dégradation des forêts galeries et comblement du cours d’eau Agbado dans le département des Collines au Bénin

La présente étude évalue l’impact de la dégradation des galeries forestières sur le comblement de la rivière Agbado dans le département des Collines au Bénin. Elle a conduit à la description succincte des changements d’occupation des terres pendant la période d’étude et a révélé une tendance à la hausse des espaces anthropisés au détriment des zones forestières. Ainsi, les galeries forestières ont connu un taux de régression annuel de 0,87% et de conversion de 82,44%. La quantité de charges solides, le poids spécifique de la vase, la superficie moyenne des sous-bassins de très faible pente, le taux de dénudation et l’indice d’agressivité climatique ont permis d’estimer la vitesse de comblement. L’indice d’agressivité climatique varie entre 25 et 150 et rend compte de la forte capacité érosive du climat dans le bassin. Les sédiments en suspension mesurés pendant la période d’août à septembre 2011 varient de 0,05 g/l à 0,26 g/l et permettent d’affirmer que l’érosion hydrique est l’un des facteurs responsables des matières en suspension dans le cours d’eau. Le taux de dénudation annuel calculé à partir du flux volumétrique est de 9,9 t/km2/an occasionnant un comblement de 1,1 mm/an du lit du cours d’eau.Mots clés : Bassin versant, érosion, sédimentation, ressources en eau

The role of politics in the life of a conservation incentive: An analysis of agri-environment schemes in Hungary

State-financed financial incentives are an increasingly popular tool for conservation on private lands. From policy and conservation perspectives, questions remain around the sustainability and longevity of behavioural changes associated with undertaking conservation work in exchange for payment. Further under-examined factors include inquiry into the role of the state as regulating agency, primary negotiator and enforcer, and how its politics and street-level relations influence participation. During 2015–6 a unique opportunity arose to investigate these issues as the Hungarian government unexpectedly cancelled its national agri-environmental programme to farmers. Through agricultural land use data, interviews and surveys (n = 260), we analysed the consequences of the cancellation of cash payments on i) land use change, ii) farmers' maintenance of conservation activities and iii) farmers' relations with conservation actors. We demonstrate that withdrawal of conservation payments resulted in farmers cropping more intensively, with consequences for conservation agencies' relationships with farmers. Many farmers maintained a number of individual conservation rules despite not receiving payment. Measures associated with highest financial burdens and least apparent benefits were most likely to be broken, and several socio-ecological factors, including land use type (grassland or arable), farm size, and additional legal obligations (other subsidies and land leases) influenced farmers who desisted with specific conservation rules. Adherence arose from technological lock-in, perceived surveillance by state agencies, fear of retrospective sanction, and intention to re-apply. The Hungarian context underscores the relevance of accounting for the ways in which multi-level politics influence farmer-public agency relations in the day-to-day management of conservation incentive schemes

Maternal Age, Paternal Age and Effective Fecundability in Rural Bangladesh

Effective fecundability is defined as the monthly probability for a conception that leads to a livebirth. One method of assessing effective fecundability is by examining lengths of first birth intervals. Using demographic records of marriage and birth, we examine the effects of maternal age, paternal age, mother’s education, and religion on effective fecundability in a rural region of Bangladesh. Data came from a prospective demographic and health survey conducted in Matlab thana by the International Centre for Diarrhoeal Disease Research, Bangladesh. Marriage and birth records from 1975 to 1982 were used to generate first birth intervals. A parametric hazards model of fecundability was used to simultaneously estimate primary sterility, effective fecundability as well as effects of fixed and time varying covariates on effective fecundability. Marriage records were matched for 10,255 pairs of partners, including exact times to birth and observations right censored by death, divorce, migration, or the end of record-keeping. The age range at marriage for wives was 12 and 25 years. The prevalence of primary sterility was 5.1% (± 2.6% SE). The estimate of effective fecundability was 0.053 (±0.002). The most parsimonious model showed reduced fecundability for women under 16 years and highest fecundability from 17 to 19 years, relative to the reference age group (20 to 25) years. Fecundability was significantly higher for father’s age 25 to 29 years relative to other ages. Religion and mother’s education were not associated with fecundability. The results suggest that Bangladeshi women have a higher prevalence of sterility and lower effective fecundability compared to other samples in developing settings

An action principle for the quantization of parametric theories and nonlinear quantum cosmology

By parametrizing the action integral for the standard Schrodinger equation we present a derivation of the recently proposed method for quantizing a parametrized theory. The reformulation suggests a natural extension from conventional to nonlinear quantum mechanics. This generalization enables a unitary description of the quantum evolution for a broad class of constrained Hamiltonian systems with a nonlinear kinematic structure. In particular, the new theory is applicable to the quantization of cosmological models where a chosen gravitational degree of freedom acts as geometric time. This is demonstrated explicitly using three cosmological models: the Friedmann universe with a massless scalar field and Bianchi type I and IX models. Based on these investigations, the prospect of further developing the proposed quantization scheme in the context of quantum gravity is discussed.Comment: 14 page