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This paper analyses a series of high-quality continuous records from southeastern Africa to study the spatiotemporal patterning of Holocene hydroclimatic anomalies in the region. Results indicate dominant frequencies of variability at millennial time scales, and a series of anomalies broadly common to all records. Of particular interest, data from the southern Cape coast exhibit periods of wetter/drier conditions that are out of phase with the sites less than 150 km away in the adjacent interior, but in phase with sites in tropical regions over 1000 km to the northeast. To explain such spatial patterns and gradients, we propose that the Agulhas Current may be a critical vector by which tropical climatic signals are propagated along the littoral zone, exerting a dominant, highly localized influence on near-coastal environmental conditions. Limitations in the data available do not allow for a detailed examination of the climatic dynamics related to these phenomena, but this paper highlights a series of avenues for future research to clarify the spatial extent and stability of the patterns observed.
The study objective was to determine the prevalence of Staphylococcus aureus colonisation in the nares and oropharynx of healthy persons and identify any risk factors associated with such S. aureus colonisation. In total 263 participants (177 adults and 86 minors) comprising 95 families were enrolled in a year-long prospective cohort study from one urban and one rural county in eastern Iowa, USA, through local newspaper advertisements and email lists and through the Keokuk Rural Health Study. Potential risk factors including demographic factors, medical history, farming and healthcare exposure were assessed. Among the participants, 25.4% of adults and 36.1% minors carried S. aureus in their nares and 37.9% of adults carried it in their oropharynx. The overall prevalence was 44.1% among adults and 36.1% for minors. Having at least one positive environmental site for S. aureus in the family home was associated with colonisation (prevalence ratio: 1.34, 95% CI: 1.07–1.66). The sensitivity of the oropharyngeal cultures was greater than that of the nares cultures (86.1% compared with 58.2%, respectively). In conclusion, the nares and oropharynx are both important colonisation sites for healthy community members and the presence of S. aureus in the home environment is associated with an increased probability of colonisation.
DNA barcode analysis of specimens belonging to the genus Histeromerus Wesmael, 1838 (Hymenoptera: Braconidae) reveals the presence of two species in North America. One is identified as H. canadensis Ashmead, 1891, which is widely recorded in North America, while the other is H. mystacinus Wesmael, 1838, a species formerly known only from the western Palaearctic.
We report the results of Long Baseline Array observations made in 2001 of ten southern sources proposed by Mattox et al. as counterparts to EGRET >100 MeV gamma-ray sources. Source structures are compared with published data where available and possible superluminal motions identified in several cases. The associations are examined in the light of Fermi observations, indicating that the confirmed counterparts tend to have radio properties consistent with other identifications, including flat radio spectral index, high brightness temperature, greater radio variability, and higher core dominance.
We present results from a multiwavelength study of the blazar PKS 1954–388 at radio, UV, X-ray, and gamma-ray energies. A RadioAstron observation at 1.66 GHz in June 2012 resulted in the detection of interferometric fringes on baselines of 6.2 Earth-diameters. This suggests a source frame brightness temperature of greater than 2 × 1012 K, well in excess of both equipartition and inverse Compton limits and implying the existence of Doppler boosting in the core. An 8.4-GHz TANAMI VLBI image, made less than a month after the RadioAstron observations, is consistent with a previously reported superluminal motion for a jet component. Flux density monitoring with the Australia Telescope Compact Array confirms previous evidence for long-term variability that increases with observing frequency. A search for more rapid variability revealed no evidence for significant day-scale flux density variation. The ATCA light-curve reveals a strong radio flare beginning in late 2013, which peaks higher, and earlier, at higher frequencies. Comparison with the Fermi gamma-ray light-curve indicates this followed ~ 9 months after the start of a prolonged gamma-ray high-state—a radio lag comparable to that seen in other blazars. The multiwavelength data are combined to derive a Spectral Energy Distribution, which is fitted by a one-zone synchrotron-self-Compton (SSC) model with the addition of external Compton (EC) emission.
This chapter provides a perspective on vegetation changes (as a proxy for overall terrestrial ecosystem changes) within southern Africa’s summer and winter rainfall zones. While climate is a major determinant on southern African ecosystems, topography, geology and fire also play critical roles in ecosystem pattern and processes. Late Quaternary climate changes impacted on southern African ecosystems but did not result in wholesale migration of these biomes. Instead, the palaeoenvironmental record reveals that community dynamics within biomes or at their ecotonal boundaries changed as individual species were favoured or disadvantaged by changing conditions (e.g. climate, fire regimes and/or human impacts) over time.
We present high-resolution radio observations of the second Galactic superluminal radio source GRO1655-40, which was detected as an X-ray transient on 1994 July 27. Our radio radio images reveal two components moving away from each other at an angular speed of 65±5 mas/day, corresponding to superluminal motion (υ/c = 1.4 ± 0.4) at the estimated distance of 3–5 kpc. The 12-day delay between the X-ray and radio outbursts suggests that the ejection of material at relativistic speeds occurs during a stable phase of accretion onto a black hole, which follows an unstable phase with a high accretion rate. A complete description and discussion of these observations can be found in Tingay et al 1995 (Nature, 374, pp 141–143).
PKS 1934–638 is an archetypal GPS source, peaking at 1.4 GHz and exhibits almost no flux density variability. VLBI images at frequencies of .843, 2.3, 4.8, & 8.4 were made with the southern hemisphere VLBI array and they reveal that the source is a 42 mas compact double. There is no detectable change in separation over the last 20 years, yielding an upper limit of ~ 0.03c ± 0.2c on any expansion velocity. The spectral shapes of the two components are remarkably similar, despite indications of finer structure on longer baselines. Magnetic field calculations indicate fields of a few mGauss and the results are consistent with equipartition.
Boiling is the most common method of household water treatment in developing countries; however, it is not always effectively practised. We conducted a randomized controlled trial among 210 households to assess the effectiveness of water pasteurization and safe-storage interventions in reducing Escherichia coli contamination of household drinking water in a water-boiling population in rural Peru. Households were randomized to receive either a safe-storage container or a safe-storage container plus water pasteurization indicator or to a control group. During a 13-week follow-up period, households that received a safe-storage container and water pasteurization indicator did not have a significantly different prevalence of stored drinking-water contamination relative to the control group [prevalence ratio (PR) 1·18, 95% confidence interval (CI) 0·92–1·52]. Similarly, receipt of a safe-storage container alone had no effect on prevalence of contamination (PR 1·02, 95% CI 0·79–1·31). Although use of water pasteurization indicators and locally available storage containers did not increase the safety of household drinking water in this study, future research could illuminate factors that facilitate the effective use of these interventions to improve water quality and reduce the risk of waterborne disease in populations that boil drinking water.
Significant gaps in immunity to polio, measles, and rubella may exist in adults in Cambodia and threaten vaccine-preventable disease (VPD) elimination and control goals, despite high childhood vaccination coverage. We conducted a nationwide serological survey during November–December 2012 of 2154 women aged 15–39 years to assess immunity to polio, measles, and rubella and to estimate congenital rubella syndrome (CRS) incidence. Measles and rubella antibodies were detected by IgG ELISA and polio antibodies by microneutralization testing. Age-structured catalytic models were fitted to rubella serological data to predict CRS cases. Overall, 29·8% of women lacked immunity to at least one poliovirus (PV); seroprevalence to PV1, PV2 and PV3 was 85·9%, 93·4% and 83·3%, respectively. Rubella and measles antibody seroprevalence was 73·3% and 95·9%, respectively. In the 15–19 years age group, 48·2% [95% confidence interval (CI) 42·4–54·1] were susceptible to either PV1 or PV3, and 40·3% (95% CI 33·0–47·5) to rubella virus. Based on rubella antibody seroprevalence, we estimate that >600 infants are born with CRS in Cambodia annually. Significant numbers of Cambodian women are still susceptible to polio and rubella, especially those aged 15–19 years, emphasizing the need to include adults in VPD surveillance and a potential role for vaccination strategies targeted at adults.
Cameroon has experienced recurrent cholera epidemics with high mortality rates. In September 2009, epidemic cholera was detected in the Far North region of Cameroon and the reported case-fatality rate was 12%. We conducted village-, healthcare facility- and community-level surveys to investigate reasons for excess cholera mortality. Results of this investigation suggest that cholera patients who died were less likely to seek care, receive rehydration therapy and antibiotics at a healthcare facility, and tended to live further from healthcare facilities. Furthermore, use of oral rehydration salts at home was very low in both decedents and survivors. Despite the many challenges inherent to delivering care in Cameroon, practical measures could be taken to reduce cholera mortality in this region, including the timely provision of treatment supplies, training of healthcare workers, establishment of rehydration centres, and promotion of household water treatment and enhanced handwashing with soap.
This paper discusses recent improvements achieved in the growth of epitaxial layers of GaAs and AlGaAs using the liquid arsine substitute tertiarybutylarsine (TBA) and metal alkyls. The high purity TBA now available yields undoped GaAs with residual donor/acceptor concentrations in the low 1014 cm−3 range. Under optimized growth conditiorp the layers are either n-type and have 77*K mobilities up to 85,000 cm2 //Vs or they are compensated or p-type. For aluminum gallium arsenide, layers grown with TBA have properties similar to arsine-grown material as demonstrated by low temperature photoluminescence (PL). The PL efficiencies and line widths of the TBA-grown AlGaAs samples are comparable to those prepared with arsine.
Catalytic combustion is an emerging technology in which fuels can be combusted homogeneously supported by a catalyst. The catalyst allows non-flammable mixtures of fuel and air to be oxidized with the resulting heat generated used to initiate thermal or homogeneous combustion. With the proper catalysts the fuel can be combusted with efficiencies so high that unburned CO or HC emissions are less than 10 ppm. Furthermore, because the fuel-air mixtures are relatively lean compared to conventional processes the adiabatic temperatures are below that required for the formation of NOx i.e. > 1500°C. The success of this technology would eliminate the need for expensive after-treatment of emissions from gas fired power plants and boilers.
This is a very demanding application, especially for natural gas fueled combustors, since the catalyst will have to initiate reaction between 400 and 500°C, at linear velocities exceeding 50 ft/sec, and retain its activity after experiencing temperatures up to 1400°C. Furthermore, the monolithic ceramic or metallic support upon which the catalyst is deposited must also retain structural integrity after experiencing high temperatures and severe thermal shock.
This paper will describe the fundamental concepts of this new technology, the major technical problems being addressed and the progress being made.
Carbon dioxide is an attractive organic solvent in today's chemical process environment in that it is non-flammable, inexpensive, and exhibits low toxicity. Further, materials solubilized in carbon dioxide are easily and completely recovered/concentrated from solution via a simple pressure quench. Despite these favorable properties, CO2 is non-polar, and as such is a very poor solvent for materials such as conventional metal chelating agents, thus blocking application of carbon dioxide in metal extraction/recovery. Consequently, we are exploring the molecular design of materials which are highly CO2-philic, that is, they exhibit solubilities in carbon dioxide which are significantly greater than alkanes with the same number of main-chain atoms. By functionalizing chelating moieties with CO2-philic oligomers, we have generated materials which both effectively extract metals from solid matrices and which dissolve in carbon dioxide in significant quantities.
The dissolution of a drug delivery system consisting of gentamicin sulfate in a hydrophobic polyanhydride matrix has been examined. The in vitro release of gentamicin is a function of the composition of the dissolution medium, with slower release in pH 7.4 buffer than in unbuffered water. This is consistent with an anion exchange taking place under conditions in which carboxylate polymer chain-ends form a poorly soluble salt with gentamicin, and sulfate is released into solution. Results of additional experiments probing this model are digeussed.
Environmental and safety issues are becoming increasingly critical for the selection of materials and their processing techniques. While the choice of “green” materials is important from the perspective of disposal of spent or used products, the choice of environmentally sound processes is important to cut down manufacturing waste and limit the use of toxic solvents and solids. Some examples from the electronics and the aerospace industry are described.
Using High Resolution Electron Microscopy, we have investigated the structure/function relationships of the Nd2O3/MgO and MgO/Nd2O3 catalyst systems which are active in the oxidative coupling of methane. In both cases catalytic performance was found to depend critically on the morphology of Nd2O3. We demonstrate that high selectivities are associated with a thin disordered film of neodymia on the MgO surface for the Nd2O3/MgO system whilst for the reverse catalyst, the dominant morphology is a highly disordered cubic form of Nd2O3.
The US semiconductor industry uses 5–7 thousand pounds of arsine annually. Fifty to eighty percent of the arsine used becomes a waste product, which requires abatement. Traditional methods of abatement are reviewed with an emphasis on dry chemical scrubbing. A variety of dry chemical scrubbing materials were evaluated for arsine capacity, using activated carbon as the baseline for comparison. A proprietary mixed oxide composition, employing copper oxide as the active ingredient was identified as having high capacity and efficiency. Disposal and possible reclamation options are discussed.