Showing papers by "University of the Witwatersrand published in 1999"
TL;DR: In this paper, the formal relationship between US Vanderbilt-type pseudopotentials and Blochl's projector augmented wave (PAW) method is derived and the Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional.
Abstract: The formal relationship between ultrasoft (US) Vanderbilt-type pseudopotentials and Bl\"ochl's projector augmented wave (PAW) method is derived. It is shown that the total energy functional for US pseudopotentials can be obtained by linearization of two terms in a slightly modified PAW total energy functional. The Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional. A simple way to implement the PAW method in existing plane-wave codes supporting US pseudopotentials is pointed out. In addition, critical tests are presented to compare the accuracy and efficiency of the PAW and the US pseudopotential method with relaxed core all electron methods. These tests include small molecules $({\mathrm{H}}_{2}{,\mathrm{}\mathrm{H}}_{2}{\mathrm{O},\mathrm{}\mathrm{Li}}_{2}{,\mathrm{}\mathrm{N}}_{2}{,\mathrm{}\mathrm{F}}_{2}{,\mathrm{}\mathrm{BF}}_{3}{,\mathrm{}\mathrm{SiF}}_{4})$ and several bulk systems (diamond, Si, V, Li, Ca, ${\mathrm{CaF}}_{2},$ Fe, Co, Ni). Particular attention is paid to the bulk properties and magnetic energies of Fe, Co, and Ni.
57,691 citations
TL;DR: The tetratricopeptide repeat motif may represent an ancient protein-protein interaction module that has been recruited by different proteins and adapted for specific functions.
Abstract: The tetratricopeptide repeat (TPR) motif is a protein-protein interaction module found in multiple copies in a number of functionally different proteins that facilitates specific interactions with a partner protein(s). Three-dimensional structural data have shown that a TPR motif contains two antiparallel alpha-helices such that tandem arrays of TPR motifs generate a right-handed helical structure with an amphipathic channel that might accommodate the complementary region of a target protein. Most TPR-containing proteins are associated with multiprotein complexes, and there is extensive evidence indicating that TPR motifs are important to the functioning of chaperone, cell-cycle, transcription, and protein transport complexes. The TPR motif may represent an ancient protein-protein interaction module that has been recruited by different proteins and adapted for specific functions. BioEssays 1999;21:932-939.
1,199 citations
TL;DR: The linear generalized equation described in this paper provides a further dimension to the prediction of lattice potential energies/enthalpies of ionic solids and can be utilized to predict and rationalize the thermochemistry in topical areas of synthetic inorganic chemistry as well as in emerging areas.
Abstract: The linear generalized equation described in this paper provides a further dimension to the prediction of lattice potential energies/enthalpies of ionic solids. First, it offers an alternative (and often more direct) approach to the well-established Kapustinskii equation (whose capabilities have also recently been extended by our recent provision of an extended set of thermochemical radii). Second, it makes possible the acquisition of lattice energy estimates for salts which, up until now, except for simple 1:1 salts, could not be considered because of lack of crystal structure data. We have generalized Bartlett's correlation for MX (1:1) salts, between the lattice enthalpy and the inverse cube root of the molecular (formula unit) volume, such as to render it applicable across an extended range of ionic salts for the estimation of lattice potential energies. When new salts are synthesized, acquisition of full crystal structure data is not always possible and powder data provides only minimal structural in...
583 citations
TL;DR: Although dispersal had the strongest effect on the predicted spread rate, it was showed that dispersal interacts strongly with plant life history, disturbance, and habitat loss in influencing the predicted rate of spread.
Abstract: Models of plant migration based on estimates of biological parameters severely underestimate the rate of spread when compared to empirical estimates of plant migration rates. This is disturbing, since an ability to predict migration and colonization rates is needed for predicting how native species will distribute themselves in response to habitat loss and climate change and how rapidly invasive species will spread. Part of the problem is the difficulty of formally including rare long‐distance dispersal events in spread models. In this article, we explore the process of making predictions about plant migration rates. In particular, we examine the links between data, statistical models, and ecological predictions. We fit mixtures of Weibull distributions to several dispersal data sets and show that statistical and biological criteria for selecting the most appropriate statistical model conflict. Fitting a two‐component mixture model to the same data increases the spread‐rate prediction by an aver...
577 citations
TL;DR: Missense mutations at nucleotides 1809 and 1812 in the basic core promoter were found in 80% of all sequences and may represent wild‐type sequence in Southern African isolates and play a role in hepatocarcinogenesis in black African carriers of the virus.
264 citations
TL;DR: Nigerian children with rickets have a low intake of calcium and have a better response to treatment with calcium alone or in combination with vitamin D than to treatmentWith vitamin D alone.
Abstract: Background Nutritional rickets remains prevalent in many tropical countries despite the fact that such countries have ample sunlight. Some postulate that a deficiency of dietary calcium, rather than vitamin D, is often responsible for rickets after infancy. Methods We enrolled 123 Nigerian children (median age, 46 months) with rickets in a randomized, double-blind, controlled trial of 24 weeks of treatment with vitamin D (600,000 U intramuscularly at enrollment and at 12 weeks), calcium (1000 mg daily), or a combination of vitamin D and calcium. We compared the calcium intake of the children at enrollment with that of control children without rickets who were matched for sex, age, and weight. We measured serum calcium and alkaline phosphatase and used a 10-point radiographic score to assess the response to treatment at 24 weeks. Results The daily dietary calcium intake was low in the children with rickets and the control children (median, 203 mg and 196 mg, respectively; P=0.64). Treatment produced a smal...
263 citations
TL;DR: In this article, the authors used rainfall data from stations in South Africa that have not involved site relocations, but which have not been tested for inhomogeneities resulting from changes in instrumentation, a method of testing for changes in the intensity of extreme events is adopted.
Abstract: Extreme rainfall events can have severe impacts on society, so possible long-term changes in the intensity of extreme events are of concern. Testing for long-term changes in the intensity of extreme events is complicated by data inhomogeneities resulting from site and instrumentation changes. Using rainfall data from stations in South Africa that have not involved site relocations, but which have not been tested for inhomogeneities resulting from changes in instrumentation, a method of testing for changes in the intensity of extreme events is adopted. Significant increases in the intensity of extreme rainfall events between 1931-1960 and 1961-1990 are identified over about 70% of the country. The intensity of the 10-year high rainfall events has increased by over 10% over large areas of the country, except in parts of the north-east, north-west and in the winter rainfall region of the south-west. Percentage increases in the intensity of high rainfall events are largest for the most extreme events. While some inhomogeneities remain in the data used, the observed changes in the intensity of extreme rainfall events over South Africa are thought to be at least partly real.
237 citations
TL;DR: The endotracheal tube of patients undergoing mechanical ventilation becomes colonized rapidly with micro-organisms commonly associated with nosocomial pneumonia, and which may represent a persistent source of organisms causing such infections.
Abstract: Endotracheal tube colonization in patients undergoing mechanical ventilation was investigated. In the first part of this prospective study, the airway access tube was examined for the presence of secretions, airway obstruction and bacterial colonization, in cases undergoing extubation or tube change. In the second part of the study, the sequence of oropharyngeal, gastric, respiratory tract and endotracheal tube colonization was investigated by sequential swabbing at each site twice daily for 5 days in consecutive noninfected patients. In the first part, it was noted that all airway access tubes of cases undergoing extubation had secretions lining the interior of the distal third of the tube which were shown on scanning electron microscopy to be a biofilm. Gram-negative micro-organisms were isolated from these secretions in all but three cases. In the second part, it was noted that the sequence of colonization in patients undergoing mechanical ventilation was the oropharynx (36 h), the stomach (3660 h), the lower respiratory tract (60-84 h), and thereafter the endotracheal tube (60-96 h). Nosocomial pneumonia occurred in 13 patients and in eight cases identical organisms were noted in lower respiratory tract secretions and in secretions lining the interior of the endotracheal tube. The endotracheal tube of patients undergoing mechanical ventilation becomes colonized rapidly with micro-organisms commonly associated with nosocomial pneumonia, and which may represent a persistent source of organisms causing such infections.
226 citations
TL;DR: Increased predation on adult roan due to a build-up in lion numbers, following the zebra and wildebeest influx, seemed to be the proximate cause of the initial sharp decline in the roan population.
216 citations
TL;DR: The finding of abundant viral antigens and particles in the skin of EHF patients suggests an epidemiologic role for contact transmission and should be useful for EHF surveillance and prevention.
Abstract: Laboratory diagnosis of Ebola hemorrhagic fever (EHF) is currently performed by virus isolation and serology and can be done only in a few high-containment laboratories worldwide. In 1995, during the EHF outbreak in the Democratic Republic of Congo, the possibility of using immunohistochemistry (IHC) testing of formalin-fixed postmortem skin specimens was investigated as an alternative diagnostic method for EHF. Fourteen of 19 cases of suspected EHF met the surveillance definition for EHF and were positive by IHC. IHC, serologic, and virus isolation results were concordant for all EHF and non-EHF cases. IHC and electron microscopic examination showed that endothelial cells, mononuclear phagocytes, and hepatocytes are main targets of infection, and IHC showed an association of cellular damage with viral infection. The finding of abundant viral antigens and particles in the skin of EHF patients suggests an epidemiologic role for contact transmission. IHC testing of formalin-fixed skin specimens is a safe, sensitive, and specific method for laboratory diagnosis of EHF and should be useful for EHF surveillance and prevention.
214 citations
TL;DR: In this article, the structural properties of hard oxides were investigated using ab initio electronic structure calculations and structural properties compared with the soft monoclinic baddeyelite phase.
Abstract: The potentially hard oxides ${\mathrm{ZrO}}_{2}$ and ${\mathrm{HfO}}_{2}$ are investigated using ab initio electronic structure calculations and structural properties of the lowest phases compared. In general there are strong similarities between some phases apart from the softer monoclinic baddeyelite phase, which in ${\mathrm{HfO}}_{2}$ is the lowest energy phase with a bulk modulus almost twice that of ${\mathrm{ZrO}}_{2}.$ Other differences relate to the formation of the first orthorhombic phase, especially the inter-relation between $\mathrm{Pbc}21$ and $\mathrm{Pbca}$ structures. The bulk moduli of the high-pressure, cotunnite-type phases are in good agreement with experimental results. The present calculations confirm that these phases are highly incompressible and are thus good candidates for hard materials.
TL;DR: In this article, high-resolution stable isotope variations and growth structure analyses of the last three millennia of a 6600-year stalagmite record at Cold Air Cave, Makapansgat Valley, South Africa, are presented.
Abstract: High-resolution stable isotope variations and growth structure analyses of the last three millennia of a 6600-year stalagmite record at Cold Air Cave, Makapansgat Valley, South Africa, are presented. Growth layers, which are measurable over the last 250 years, are shown to be annual. The correlation between the width of growth layers and precipitation is strongly positive. Changes inδ18O andδ13C are positively correlated and inversely correlated to changes in the colour of the growth layers in the stalagmite. Variations in colour are directly correlated with mean annual temperature. Dark colouration is the product of increased temperature and mobilization of organic matter from the soil, and is associated with wetter summers and enhanced growth of C4 grasses. Darker colouring and enrichedδ18O andδ13C reflect a warmer, wetter environment, whereas lighter colouring and depleted isotopic values are indicative of cooler, drier conditions. The dominant episode in the 3000-year record is the cool, dry 500-year ...
TL;DR: The young men and women in this study, who were free of medication or sleep complaints, perceived their sleep inaccurately when compared to objective polysomnographic recordings.
TL;DR: The popliteal entrapment syndrome is more prevalent than has formerly been appreciated and surgical correction is advised in all cases of types I, II, III, and IV entrapments at the time of diagnosis to avoid occlusion as a result of continued arterial wall degeneration.
TL;DR: In this article, the fundamental principles of water drop corona as an aging mechanism for nonceramic insulators are presented, and it is demonstrated that water drops in the shed and sheath regions enhance the electric field and may cause corona which can play an important role in long-term performance.
Abstract: The fundamental principles of water drop corona as an aging mechanism for nonceramic insulators are presented. It is demonstrated that water drops in the sheath regions enhance the electric field and may cause corona which can play an important role in long-term performance. Electric field enhancement caused by water drops in different locations on the shed and sheath are demonstrated by means of electric field calculations and small scale experiments. The threshold magnitude of the surface electric field for corona from water drops is presented for two silicone rubber surfaces having different hydrophobic properties. The effect of water drop corona activity on the properties of the surface material is shown using small scale aging experiments.
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TL;DR: In this paper, the authors used multiple variance-ratio and auto-regressive fractionally integrated moving-average tests and new data (U.S. dollar-based national equity indexes for the 1987?1997 period) to clarify these results.
Abstract: The few existing studies on equity price dynamics and market efficiency for Latin American emerging equity markets show conflicting results. This study uses multiple variance-ratio and auto-regressive fractionally integrated moving-average tests and new data (U.S. dollar-based national equity indexes for the 1987?1997 period) to clarify these results. Documented evidence shows that equity prices in major Latin American emerging equity markets--Argentina, Brazil, Chile and Mexico?follow a random walk, and that they are, generally, weak-form efficient. In sum, therefore, the evidence suggests that international investors in these markets cannot use historical information to design systematically profitable trading schemes because future long-term returns are not dependent on past returns.
TL;DR: In this article, an objectives hierarchy has been developed to service management's institutional hierarchy, with value based statements of strategic intent which have been tested against public opinion, and the objectives hierarchy gives Kruger Park management a mandate to maintain biodiversity in all its natural facets and fluxes.
Abstract: Summary
1. In trying to operationalize the notion of sustainable ecosystem health, ecologists have focused on identifying sets of indicators which can be used to assess river condition relative to some normative, undegraded condition. Recognition and description of this normative state has proved elusive, particularly in highly variable semiarid ecosystems. Without an operational definition of the desired system condition that reflects both scientific rigour and broader societal value systems, rivers are unlikely to be managed effectively.
2. Managing river health should not be confused with measuring it. Many monitoring or assessment programs become ends in themselves instead of being the means to achieving specific management goals. The absence of a test of the results of monitoring further introduces the risk of management by observation and ‘pseudo-fact’. Health ‘endpoints’ provide a scientific description of management goals, while ‘values’ provide a societal perspective. Together they complement the use of indicators and provide the basis for a strategic rather than reactive approach to management.
3. The integration of value systems, endpoints and indicators of ecosystem health or ecosystem integrity forms the cornerstone of a consultative management process for the rivers of the Kruger National Park.
4. An objectives hierarchy has been developed to service management’s institutional hierarchy. ‘Vision’ and objectives serve upper levels of management with value based statements of strategic intent which have been tested against public opinion. Goals provide managers on the ground with specific ecological endpoints termed ‘thresholds of probable concern’ (TPCs). TPCs are described by a range of spatially and temporally bounded indicators of the system’s response to the main potential agents of change.
5. TPCs represent statements or hypotheses of the limits of acceptable change in ecosystem structure, function and composition. They thereby provide an inductive and strategic approach to adaptive management in a data poor situation. Integrated monitoring, research and modelling track criteria relative to TPCs and question whether management action, or recalibration of the TPC, is needed. TPCs thus provide direction for management but their validity and appropriateness are frequently challenged and adaptively modified.
6. The objectives hierarchy gives Kruger Park management a mandate to ‘maintain biodiversity in all its natural facets and fluxes’. Alluviation, as a consequence of increased sediment supply and decreased sediment transport capacity, is a major threat to the biodiversity of the bedrock-controlled rivers which flow through the park. Thus, for example, TPCs for geomorphic diversity reflect permissible ranges of change in bedrock character of the physical template. They are measured as change in the proportion of different geomorphic units in identified representative reaches. TPCs for riparian vegetation are measured as change in population structure of selected species within the representative reaches. They reflect a likely range of biotic responses to change in the physical template. A specific set of indicators, reflecting response to the major agents of change, therefore provides a parsimonious program for assessing ecosystem condition relative to explicit goals and a clearly defined management process.
TL;DR: The white working classes in the pre-First World War British Empire were not composed of ‘nationally discrete entities, but were bound together into an Imperial working class by flows of population which traversed the world as discussed by the authors.
Abstract: The white working classes in the pre-First World War British Empire were not composed of ‘nationally’ discrete entities, but were bound together into an Imperial working class by flows of population which traversed the world. The labour movements based on this imperial working class produced and disseminated a common ideology of White Labourism. In this ideology, the element of the critique of exploitation and the element of racism were inextricably intermingled. The paper seeks to identify a few of the many ‘vectors’ along which white labourist ideology moved around the world. The paper ends with a discussion of the British labour movement response to the 1914 deportations of South African white labour leaders, which seeks to demonstrate how integral to that movement the conceptions of White Labourism had become.
TL;DR: Observed mutations in Smad2 and Smad4 genes demonstrate that TGF-β pathway is altered in hepatocellular carcinoma.
Abstract: TGF-beta is a negative regulator of liver growth. Smad family of genes, as mediators of TGF-beta pathway, are candidate tumor suppressor genes in hepatocellular carcinoma (HCC). We studied 35 HCC and non-tumour liver tissues for possible mutations in Smad2 and Smad4 genes. Three tumours displayed somatic mutations; two in Smad4 (Asp332Gly and Cys401Arg) and one in Smad2 (Gln407Arg) genes. All three mutations were A:T --> G:C transitions suspected to result from oxidative stress as observed in mitochondrial DNA. These observation demonstrate that TGF-beta pathway is altered in hepatocellular carcinoma.
TL;DR: Analysis of the dependence of the rate ofLeaching on the concentration of ferric ions and on the pH, together with results obtained from electrochemical measurements, provided clear evidence that the higher rate of leaching with bacteria is due to the bacteria increasing the pH at the surface of the pyrite.
Abstract: In spite of the environmental and commercial interests in the bacterial leaching of pyrite, two central questions have not been answered after more than 35 years of research: does Thiobacillus ferrooxidans enhance the rate of leaching above that achieved by ferric sulfate solutions under the same conditions, and if so, how do the bacteria affect such an enhancement? Experimental conditions of previous studies were such that the concentrations of ferric and ferrous ions changed substantially throughout the course of the experiments. This has made it difficult to interpret the data obtained from these previous works. The aim of this work was to answer these two questions by employing an experimental apparatus designed to maintain the concentrations in solution at a constant value. This was achieved by using the constant redox potential apparatus described previously (P. I. Harvey, and F. K. Crundwell, Appl. Environ. Microbiol. 63:2586‐2592, 1997; T. A. Fowler, and F. K. Crundwell, Appl. Environ. Microbiol. 64:3570‐3575, 1998). Experiments were conducted in both the presence and absence of T. ferrooxidans, maintaining the same conditions in solution. The rate of dissolution of pyrite with bacteria was higher than that without bacteria at the same concentrations of ferrous and ferric ions in solution. Analysis of the dependence of the rate of leaching on the concentration of ferric ions and on the pH, together with results obtained from electrochemical measurements, provided clear evidence that the higher rate of leaching with bacteria is due to the bacteria increasing the pH at the surface of the pyrite. The oxidation of pyrite (FeS2) in the presence of Thiobacillus ferrooxidans is a significant factor in the formation of acid mine drainage, an environmental problem of considerable concern (7). However, T. ferrooxidans is used in commercial processes to extract gold from pyrite and arsenopyrite. The processing plant at Sansu, Ghana, treats more than 960 tons of pyrite concentrate per day with bacteria, while other processing plants have been commissioned in Australia, Brazil, and South Africa (5). The mechanisms of bacterial interaction with pyrite are the subject of much debate and controversy, despite the commercial and environmental interests in the process. It is well known that pyrite is dissolved by ferric ions, forming ferrous ions, and that T. ferrooxidans catalyzes the oxidation of ferrous ions to regenerate the ferric ions. This set of reactions is as follows (24):
TL;DR: It was concluded that the foods analyzed in this study were of acceptable quality and safety and the presence of selected foodborne pathogens in the food samples as well as the existence of nonpathogenic E. coli 1 (in food and water samples) was investigated.
TL;DR: The Namaqualand metamorphic complex is a well-exposed, INTRODUCTION Mesoproterozoic, low-pressure, amphibolite-granulite-facies terrane flanking the Archaean Kaapvaal Craton of southern Africa as discussed by the authors.
Abstract: The Namaqualand Metamorphic Complex is a well-exposed, INTRODUCTION Mesoproterozoic, low-pressure, amphibolite–granulite-facies terrane flanking the Archaean Kaapvaal Craton of southern Africa. Previous isotopic dating in the region suggests an ~150 my period of prograde granulite-facies metamorphism and episodic granite emplacement The mid-crustal granulite-facies problem in the mid-crust. In contrast, thermal modelling suggests that Granulite-facies terranes are rocks of the Earth’s lower suband superjacent magmatic accretion should not have exceeded and middle crust that equilibrated at high pressures (P ) 30 my in duration. This enigma is resolved by precise U–Pb zircon and temperatures (T ). Their petrology and geoSHRIMP dating of the major orthogneissic units of the region. chronology commonly preserve both prograde and retroThese data point to Kibaran crustal growth at 1220–1170 Ma, grade characteristics. Because these terranes reflect a which occurred on the margins of a Palaeoproterozoic (2000–1800 number of different crustal and tectonic processes, their Ma) continental nucleus. A later, distinct, orogenic episode, here origin is important in understanding the nature of contermed the Namaquan (time equivalent of the Grenvillian), involved tinental growth and crustal evolution. crustal thickening and magmatism at 1060–1030 Ma and was Granulite-facies rocks typically reflect P–T conditions responsible for, and coeval with, the peak of metamorphism. Lowof 6–9 kbar and 750–850°C and comprise anhydrous P granulite-facies metamorphism resulted from advective heating mineral assemblages that point to conditions of reduced and crustal thickening by magmatic accretion over a 30 my interval. water activity (Harley, 1989). In the lower crust some granulite-facies rocks are thought to be residues of partial melting that has moved melt and volatiles to higher crustal levels. Alternatively, granulite-facies rocks may form where mutually soluble CO2–H2O-rich fluids stream upwards through the crust, causing local reduction in volatile content and accompanying mineral phase changes along the fluid flow paths (Harley, 1989). In the
TL;DR: Olanzapine appears to be at least as effective as lithium in the treatment of mania and did not differ from lithium in terms of treatment emergent extrapyramidal side-effects as measured by the Simpson-Angus Scale.
Abstract: Neuroleptics are of established efficacy in mania. Controlled data on the use of olanzapine in mania is however, absent. In this study, 30 patients meeting DSM-IV criteria for mania were randomly allocated to receive either olanzapine or lithium in a 4 week double-blind randomized controlled design. There were no significant outcome differences between the two groups on any of the primary outcome measures, the Brief Psychiatric Rating Scale (lithium 28.2; olanzapine 28.0; P = 0.44); Clinical Global Impression (CGI) improvement scale (lithium 2.75, olanzapine 2.36; P = 0.163) or the Mania Scale (lithium 13.2, olanzapine 10.2; P = 0.315). Olanzapine was however, significantly superior to lithium on the CGI-severity scale at week 4 (lithium 2.83, olanzapine 2.29; P = 0.025). Olanzapine did not differ from lithium in terms of treatment emergent extrapyramidal side-effects as measured by the Simpson-Angus Scale. Olanzapine appears to be at least as effective as lithium in the treatment of mania.
TL;DR: The core promoter (CP) of hepatitis B virus plays a central role in HBV replication and morphogenesis, directing the transcription of both species of 3.5 kb mRNA: pregenomic (pg) RNA and precore (pre‐C) mRNA.
Abstract: The core promoter (CP) of hepatitis B virus (HBV) plays a central role in HBV replication and morphogenesis, directing the transcription of both species of 3.5 kb mRNA: pregenomic (pg) RNA and precore (pre-C) mRNA. The CP overlaps the 3' end of the X open-reading frame (ORF) and the 5' end of the pre-C/C ORF. The major functional elements of the CP are the upper regulatory region (URR) and the basic core promoter (BCP). The BCP is sufficient for accurate initiation of both pre-C mRNA and pgRNA transcription. It contains four AT-rich regions and the initiators for pre-C mRNA and pgRNA transcription. The upstream regulatory region consists of the negative regulatory element and the core upstream regulatory sequence. Co-operative interaction of various liver-enriched and ubiquitous transcription factors is necessary for liver-specific expression from the CP. These factors bind to the CP. Sequence conservation within the CP is crucial for maintaining active viral replication, and variation may contribute to the persistence of HBV within the host, leading to chronic infection and, ultimately, hepatocarcinogenesis. The most frequently described mutations within this region are an A to T transversion at position 1762 together with a G to A transition at position 1764. This double mutant is accompanied by a reduced level of hepatitis B e antigen (HBeAg) expression. Deletions, insertions and duplications occur within the CP.
TL;DR: To determine the effectiveness and safety of misoprostol administered vaginally or orally for third trimester cervical ripening or induction of labour, the best available evidence is provided.
TL;DR: The analysis of the data shows that diffusion through the product layer does not limit the rate of dissolution when bacteria are present, which suggests that the action of T. ferrooxidans in oxidizing the sulfur formed on the particle surface is to remove the barrier to diffusion by ferrous ions.
Abstract: This paper reports the results of leaching experiments conducted with and without Thiobacillus ferrooxidans at the same conditions in solution. The extent of leaching of ZnS with bacteria is significantly higher than that without bacteria at high concentrations of ferrous ions. A porous layer of elemental sulfur is present on the surfaces of the chemically leached particles, while no sulfur is present on the surfaces of the bacterially leached particles. The analysis of the data using the shrinking-core model shows that the chemical leaching of ZnS is limited by the diffusion of ferrous ions through the sulfur product layer at high concentrations of ferrous ions. The analysis of the data shows that diffusion through the product layer does not limit the rate of dissolution when bacteria are present. This suggests that the action of T. ferrooxidans in oxidizing the sulfur formed on the particle surface is to remove the barrier to diffusion by ferrous ions.
TL;DR: Validation of VA findings demonstrate that the cause of death profile derived from VA can be used with confidence for planning purposes, including the high death rates from kwashiorkor and violence, emerging AIDS and pulmonary tuberculosis, and circulatory deaths in the middle‐aged and young elderly.
Abstract: Information on cause of death is essential for rational public health planning, yet mortality data in South Africa is limited. In the Agincourt subdistrict, verbal autopsies (VA) have been used to determine cause of death. A VA is conducted on all deaths recorded during annual demographic and health surveillance. Trained lay fieldworkers interview a close caregiver to elicit signs and symptoms of the terminal illness. Each questionnaire is reviewed by three medical practitioners blind to each other's assessment, who assign a 'probable cause of death' where possible. Of 1001 deaths of adults and children identified between 1992 and 1995, 932 VAs were completed. The profile of deaths reflects a mixed picture: the 'unfinished agenda' of communicable disease and malnutrition (diarrhoea and kwashiorkor predominantly) are responsible for over half of deaths in under-fives, accidents are prominent in the 5-14 age-group, while the 'emerging agenda' of violence and chronic degenerative disease (particularly circulatory disease) is pronounced among the middle-aged and elderly. This profile shows the social and demographic transition to be well underway within a rural, underdeveloped population. Validation of VA findings demonstrate that the cause of death profile derived from VA can be used with confidence for planning purposes. Findings of note include the high death rates from kwashiorkor and violence, emerging AIDS and pulmonary tuberculosis, and circulatory deaths in the middle-aged and young elderly. A deeper understanding of the causal factors underlying these critical health problems is needed to strengthen policy and better target interventions.
TL;DR: Basic laboratory and clinicoepidemiologic investigations over the past two decades have learned much about the molecular biological basis of yersinia, witnessed an evolving epidemiology of transmission and drug resistance capabilities, categorized the remarkable array of clinical manifestations caused by its human disease-causing species.
Abstract: The nature of a microorganism may be so fascinating and intellectually appealing that individuals are drawn to try and unravel the mysteries of its microbial past, present and future. Such would seem to be the case with the charismatic yersiniae as described by Bottone [1, 2]. Basic laboratory and clinicoepidemiologic investigations over the past two decades have sought to unravel the keys to the pathogenesis of these prototypic invasive and immunogenic pathogens. We have learned much about the molecular biological basis of yersinia, witnessed an evolving epidemiology of transmission and drug resistance capabilities, categorized the remarkable array of clinical manifestations caused by its human disease-causing species, and compared the historical contribution of yersiniae to the misery and suffering of mankind to the present-day scourges, tuberculosis and acquired immunodeficiency syndrome (AIDS).
TL;DR: In this article, it is shown that the wave function of one state changes sign but not the other, if the exceptional point is encircled in the complex plane, and an experimental setup is suggested where this peculiar phase change could be observed.
Abstract: Avoided level crossings are associated with exceptional points which are the singularities of the spectrum and eigenfunctions, when considered as functions of a complex coupling parameter. It is shown that the wave function of one state changes sign but not the other, if the exceptional point is encircled in the complex plane. An experimental setup is suggested where this peculiar phase change could be observed.
TL;DR: In this article, a survey of the properties of silicone rubber for outdoor insulation is presented and the methods of assessing these properties are discussed and this is followed by a detailed survey of what is known of aging recovery mechanisms.
Abstract: This paper surveys the properties which give silicone rubber its distinctive and highly desirable performance characteristics for use as outdoor insulation. The methods of assessing these properties arediscussed and this is followed byadetailedsurveyof whatis knownof agingaud recovery mechanisms. Corona is identified as the principle electrical aging agent and evidence is presented for irreversible loss of polymer as a result of aging. However, the surface recov. ery mechanisms are robust and, provided there is an adequate resting period, the hydrophobic properties recover, This supports the view, from service experience, that there is no substantial evidence to show that normal aging, unless it results in the exposure of the glass fiber core, detracts from the performance of insulators.