Arbuscular mycorrhiza status of gold and uranium tailings and surrounding soils of South Africa's deep level gold mines. II. Infectivity

AbstractAn AMF infectivity study and spore viability assessment was performed on substrata obtained from gold and uranium mine tailings dumps (‘slimes dams’) in the North West and Free State provinces of South Africa. Three slimes dams in each region were categorized as recently vegetated (RV), old vegetated (OV) and never vegetated (NV), and dams then divided into five zones based on elevation above ground level, steepness and broad chemical differences. Rhizosphere samples were collected from two of three plant species common to all sites; Eragrostis curvula, Atriplex semibaccata and Cynodon dactylon, as well as from bare areas, in order to allow comparisons across all site categories because of the rarity of the grasses on the lower slope of NV dams. Infectivity was determined by the mean infection percentage method from a bioassay of the substrata using Eragrostis curvula cv Ermelo as a host plant. There was no difference in total infectivity between North West and Free State substrata, but within regions, there were differences in infectivity between rehabilitation ages, between zones, and between rhizosphere and bare areas. Toepaddock substrata and veld soil produced the highest total infection levels overall. On both dams and veld, total arbuscular levels differed between rhizosphere and bare substrata, and the percentage of arbuscules (max. 15.4%) and vesicles (max. 22.0%) as a proportion of total infection structures was low. A low correlation between infectivity and total spore numbers was also found. Spore numbers and the numbers of viable spores increased with zone down the slimes dams to the veld, and also differed within zones between rhizosphere and bare substrata with marked interactive effects. Substratum organic matter (SOM) levels differed between regions, and between zones within the North West region increasing with distance down the slopes to the veld, and were strongly correlated with total spore numbers. Substratum pH values and most AMF parameters were positively correlated in the order of RV>OV>NV dams, indicating that natural colonization of acidic NV sites by AMF is at very low rates, and that AMF colonizing RV slopes are not surviving the transition from RV to OV, with the associated increase in acidity, conductivity and decline in plant cover. Substratum conductivity differed between zones in both regions, with minor interaction between region and zone, and was negatively correlated with pH, AMF infectivity and total spore numbers. Our findings demonstrate that the ameliorant effects of liming and irrigation on substratum pH and conductivity are short-lived, but despite the physico-chemical constraints, a significant measurable AMF inoculum potential does exist on all substrata. Amelioration of tailings with organic matter and use of acid and salt-tolerant AMF would be expected to contribute to more persistent AMF communities and vegetation on gold and uranium slimes dams

String and M-theory Deformations of Manifolds with Special Holonomy

The R^4-type corrections to ten and eleven dimensional supergravity required by string and M-theory imply corrections to supersymmetric supergravity compactifications on manifolds of special holonomy, which deform the metric away from the original holonomy. Nevertheless, in many such cases, including Calabi-Yau compactifications of string theory and G_2-compactifications of M-theory, it has been shown that the deformation preserves supersymmetry because of associated corrections to the supersymmetry transformation rules, Here, we consider Spin(7) compactifications in string theory and M-theory, and a class of non-compact SU(5) backgrounds in M-theory. Supersymmetry survives in all these cases too, despite the fact that the original special holonomy is perturbed into general holonomy in each case.Comment: Improved discussion of SU(5) holonomy backgrounds. Other minor typos corrected. Latex with JHEP3.cls, 42 page

Contribution to study of Creole Cuban Pig breed

The Creole pig is the only authoctonous Cuban pig breed and, at present time, it is specially important for the economy of the country. This breed is mainly located in the oriental areas, generally linked to family farms using natural resources and agricultural by-products. This paper study its morphological (twelve continuous variables and seven zoometric index) characteristics on a random sample formed by 100 adult animals belonging to both sexes from several geographical localisations in the Granma provincia. Also we have studied four phanaeroptical variables using a sample formed by 620 animals. The pig shows a sub-concave front profile pig, with sublonginlineal proportions, backline ascendant, long croup and with coat colours generally black, some animals are hairless, while other are half-haired.El Cerdo Criollo Cubano, el único porcino autóctono de Cuba, es especialmente importante para la actual situación económica del país. Se localiza generalmente en la zona oriental del país, en explotaciones familiares aprovechando los recursos naturales y subproductos agrícolas. Se estudia la caracterización morfológica (doce variables morfológicas y siete índices zoométricos) de la población utilizando una muestra aleatoria formada por 100 animales de ambas sexos de diferentes localizaciones geográficas de la provincia de Granma. Además se aborda la caracterización faneróptica utilizando cuatro variables en una muestra de 620 ejemplares. Se trata de un cerdo de perfil craneal subcóncavo, de proporciones sublongilíneas, línea dorsolumbar ascendente, grupa larga y derribada, y de capas generalmente negras, con unos animales lampiños y otros entrepelados

The impact of sudden commencements on ground magnetic field variability: Immediate and delayed consequences

We examine how Sudden Commencements (SCs) and Storm Sudden Commencements (SSCs) influence the occurrence of high rates of change of the magnetic field (R) as a function of geomagnetic latitude. These rapid, high amplitude variations in the ground-level geomagnetic field pose a significant risk to ground infrastructure, such as power networks, as the drivers of geomagnetically induced currents. We find that rates of change of ∼ 30 nT min−1 at near-equatorial stations are up to 700 times more likely in an SC than in any random interval. This factor decreases with geomagnetic latitude such that rates of change around 30 nT min−1 are only up to 10 times more likely by 65°. At equatorial latitudes we find that 25% of all R in excess of 50 nT min−1 occurs during SCs. This percentage also decreases with geomagnetic latitude, reaching ≤ 1% by 55°. However, the time period from the SC to three days afterwards accounts for ≥ 90% of geomagnetic field fluctuations over 50 nT min−1, up to ∼ 60° latitude. Above 60°, other phenomena such as isolated substorms account for the majority of large R. Furthermore, the elevated rates of change observed during and after SCs are solely due to those classified as SSCs. These results show that SSCs are the predominant risk events for large R at mid and low latitudes, but that the risk from the SC itself decreases with latitude

The Approach to Ergodicity in Monte Carlo Simulations

The approach to the ergodic limit in Monte Carlo simulations is studied using both analytic and numerical methods. With the help of a stochastic model, a metric is defined that enables the examination of a simulation in both the ergodic and non-ergodic regimes. In the non-ergodic regime, the model implies how the simulation is expected to approach ergodic behavior analytically, and the analytically inferred decay law of the metric allows the monitoring of the onset of ergodic behavior. The metric is related to previously defined measures developed for molecular dynamics simulations, and the metric enables the comparison of the relative efficiencies of different Monte Carlo schemes. Applications to Lennard-Jones 13-particle clusters are shown to match the model for Metropolis, J-walking and parallel tempering based approaches. The relative efficiencies of these three Monte Carlo approaches are compared, and the decay law is shown to be useful in determining needed high temperature parameters in parallel tempering and J-walking studies of atomic clusters.Comment: 17 Pages, 7 Figure

Enhanced Fusion-Evaporation Cross Sections in Neutron-Rich 132^{132}Sn on 64^{64}Ni

Evaporation residue cross sections have been measured with neutron-rich radioactive $^{132}$Sn beams on $^{64}$Ni in the vicinity of the Coulomb barrier. The average beam intensity was $2\times 10^{4}$ particles per second and the smallest cross section measured was less than 5 mb. Large subbarrier fusion enhancement was observed. Coupled-channels calculations taking into account inelastic excitation and neutron transfer underpredict the measured cross sections below the barrier.Comment: 4 pages including 1 table and 3 figure

Evaluating Interaction of Cord Blood Hematopoietic Stem/Progenitor Cells with Functionally Integrated Three-Dimensional Microenvironments

Despite advances in ex vivo expansion of cord blood-derived hematopoietic stem/progenitor cells (CB-HSPC), challenges still remain regarding the ability to obtain, from a single unit, sufficient numbers of cells to treat an adolescent or adult patient. We and others have shown that CB-HSPC can be expanded ex vivo in two-dimensional (2D) cultures, but the absolute percentage of the more primitive stem cells decreases with time. During development, the fetal liver is the main site of HSPC expansion. Therefore, here we investigated, in vitro, the outcome of interactions of primitive HSPC with surrogate fetal liver environments. We compared bioengineered liver constructs made from a natural three-dimensional-liver-extracellular-matrix (3D-ECM) seeded with hepatoblasts, fetal liver-derived (LvSt), or bone marrow-derived stromal cells, to their respective 2D culture counterparts. We showed that the inclusion of cellular components within the 3D-ECM scaffolds was necessary for maintenance of HSPC viability in culture, and that irrespective of the microenvironment used, the 3D-ECM structures led to the maintenance of a more primitive subpopulation of HSPC, as determined by flow cytometry and colony forming assays. In addition, we showed that the timing and extent of expansion depends upon the biological component used, with LvSt providing the optimal balance between preservation of primitive CB HSPC and cellular differentiation. Stem Cells Translational Medicine 2018;7:271–282

The Role of Depressive Symptomatology in Peri- and Post-Menopause

Objectives: There is evidence that menopausal symptoms manifested at peri-menopause occur less fre- quently when compared to the symptoms experienced at post-menopause. The aim of this study was to investigate this and to test the hypothesis that depressive symptomatology mediates the relationship between menopausal stage and symptom frequency. Methods: This cross-sectional study included 213 women (M age = 52 years), of whom 125 were peri- and 88 post-menopausal. Measures comprised the Center for Epidemiologic Studies-Depression scale (CES-D) and the Women’s Health Questionnaire (WHQ) vasomotor symptoms and somatic symptoms subscales. Results: Multiple mediated regression analyses provided evidence that somatic symptoms and vasomotor symptoms were less frequent at post- compared to peri-menopause, and that these differences were mediated by depressive symptomatology. Multivariate effect sizes ranged from small to moderate, and univariate effect sizes were uniformly small with wide confidence intervals. Conclusions: The frequency of vasomotor and somatic symptoms appears to increase with depressed affect. The management of symptoms could include interventions of a psychotherapeutic nature, which may offset this effect, particularly in women for whom depressive symptoms are a feature of the climac- teric syndrome. The extent to which depression and the climacteric syndrome may be causally related to one another remains unclear and longitudinal research should further examine the mechanisms of this association

A New Composite Restorative Based on a Hydrophobic Matrix

A hydrophobic restorative composite based on a fluorocarbon analog of an alkyl methacrylate and a bisphenol adduct was formulated into a one-paste system, which polymerized in the presence of blue light. Physical, mechanical, and water-related properties were determined. High contact angles and low water sorption were shown by the experimental composite. Capillary penetration of oral fluids around restorations, therefore, could be prevented in the presence of this highly hydrophobic surface. The physical and mechanical properties of the experimental composite were either comparable to or somewhat less favorable than commercial Bis-GMA composites.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67042/2/10.1177_00220345790580100401.pd

Mechanistic Insights into β-Lactamase-Catalysed Carbapenem Degradation Through Product Characterisation

β-Lactamases are a major threat to the clinical use of carbapenems, which are often antibiotics of last resort. Despite this, the reaction outcomes and mechanisms by which β-lactamases degrade carbapenems are still not fully understood. The carbapenem bicyclic core consists of a β-lactam ring fused to a pyrroline ring. Following β-lactamase-mediated opening of the β-lactam, the pyrroline may interconvert between an enamine (2-pyrroline) form and two epimeric imine (1-pyrroline) forms; previous crystallographic and spectroscopic studies have reported all three of these forms in the contexts of hydrolysis by different β-lactamases. As we show by NMR spectroscopy, the serine β-lactamases (KPC-2, SFC-1, CMY-10, OXA-23, and OXA-48) and metallo-β-lactamases (NDM-1, VIM-1, BcII, CphA, and L1) tested all degrade carbapenems to preferentially give the Δ2 (enamine) and/or (R)-Δ1 (imine) products. Rapid non-enzymatic tautomerisation of the Δ2 product to the (R)-Δ1 product prevents assignment of the nascent enzymatic product by NMR. The observed stereoselectivity implies that carbapenemases control the form of their pyrroline ring intermediate(s)/product(s), thereby preventing pyrroline tautomerisation from inhibiting catalysis.FWN – Publicaties zonder aanstelling Universiteit Leide