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Tropical forest regions in equatorial Africa are threatened with degradation, deforestation and biodiversity loss as a result of land-cover change. We investigated historical land-cover dynamics in unprotected forested areas of the Littoral Region in south-western Cameroon during 1975–2017, to detect changes that may influence this important biodiversity and wildlife area. Processed Landsat imagery was used to map and monitor changes in land use and land cover. From 1975 to 2017 the area of high-value forest landscapes decreased by c. 420,000 ha, and increasing forest fragmentation caused a decline of c. 12% in the largest patch index. Conversely, disturbed vegetation, cleared areas and urban areas all expanded in extent, by 32% (c. 400,000 ha), 5.6% (c. 26,800 ha) and 6.6% (c. 78,631 ha), respectively. The greatest increase was in the area converted to oil palm plantations (c. 26,893 ha), followed by logging and land clearing (c. 34,838 ha), all of which were the major factors driving deforestation in the study area. Our findings highlight the increasing threats facing the wider Littoral Region, which includes Mount Nlonako and Ebo Forest, both of which are critical areas for regional conservation and the latter a proposed National Park and the only sizable area of intact forest in the region. Intact forest in the Littoral Region, and in particular at Ebo, merits urgent protection.
Indigenous women and children experience some of the most profound health disparities globally. These disparities are grounded in historical and contemporary trauma secondary to colonial atrocities perpetuated by settler society. The health disparities that exist for chronic diseases may have their origins in early-life exposures that Indigenous women and children face. Mechanistically, there is evidence that these adverse exposures epigenetically modify genes associated with cardiometabolic disease risk. Interventions designed to support a resilient pregnancy and first 1000 days of life should abrogate disparities in early-life socioeconomic status. Breastfeeding, prenatal care and early child education are key targets for governments and health care providers to start addressing current health disparities in cardiometabolic diseases among Indigenous youth. Programmes grounded in cultural safety and co-developed with communities have successfully reduced health disparities. More works of this kind are needed to reduce inequities in cardiometabolic diseases among Indigenous women and children worldwide.
A small fraction of Tidal Disruption Events (TDE) produce relativistic jets, evidenced by their non-thermal X-ray spectra and transient radio emission. Here we present milliarcsecond-resolution imaging results on TDE J1644+5734 with the European VLBI Network (EVN). These provide a strong astrometric constraint on the average apparent jet velocity βapp < 0.27, that constrains the intrinsic jet velocity for a given viewing angle.
During 1990 we surveyed the southern sky using a multi-beam receiver at frequencies of 4850 and 843 MHz. The half-power beamwidths were 4 and 25 arcmin respectively. The finished surveys cover the declination range between +10 and −90 degrees declination, essentially complete in right ascension, an area of 7.30 steradians. Preliminary analysis of the 4850 MHz data indicates that we will achieve a five sigma flux density limit of about 30 mJy. We estimate that we will find between 80 000 and 90 000 new sources above this limit. This is a revised version of the paper presented at the Regional Meeting by the first four authors; the surveys now have been completed.
The Molonglo Observatory Synthesis Telescope (MOST), which at present images a fully synthesised 70′ field in 12 h, is being converted to enable observing modes which extend the field size to 160′. The new observing modes will allow the MOST to survey completely the sky south of δ = −30° to a (5σ) sensitivity limit of about 5 mJy. The result will be a catalogue of over 400,000 radio sources with a spatial density of less than 1 source per 100 beam areas, providing the foundation for a number of novel astronomical and cosmological investigations. The conversion involves construction of 352 low-noise HEMT preamplifiers, 88 digitally controlled UHF quad phase shifters, 88 mixers and IF sections, a new communication and control system, and several other new sub-systems. The project has been funded and developments are well advanced.
Non-typhoidal Salmonella are an important but poorly characterized cause of paediatric diarrhoea in developing countries. We conducted a hospital-based case-control study in children aged <5 years in Ho Chi Minh City to define the epidemiology and examine risk factors associated with Salmonella diarrhoeal infections. From 1419 diarrhoea cases and 571 controls enrolled between 2009 and 2010, 77 (5·4%) diarrhoea cases were stool culture-positive for non-typhoidal Salmonella. Salmonella patients were more likely to be younger than controls (median age 10 and 12 months, respectively) [odds ratio (OR) 0·97; 95% confidence interval (CI) 0·94–0·99], to report a recent diarrhoeal contact (8·1% cases, 1·8% controls; OR 5·98, 95% CI 1·8–20·4) and to live in a household with >2 children (cases 20·8%, controls 10·2%; OR 2·32, 95% CI 1·2–4·7). Our findings indicate that Salmonella are an important cause of paediatric gastroenteritis in this setting and we suggest that transmission may occur through direct human contact in the home.
The adaptive character and possible course of evolution—following permanent byssal attachment—of the heteromyarian form in the Bivalvia is considered in relation to the eulamellibranch Dreissenacea and the filibranch Mytilacea. In both it assumes the extreme condition of ventral (anterior) flattening representing a high degree of adaptation for epifaunal life. The presence of a shell shelf in the umbonal regions of Dreissena and Septifer is associated with the greatest degree of ventral flattening; it permits retention of the anterior adductor and its attachment to parallel surfaces. Enlargement of the posterior regions of the visceropedal mass and the posterior territory of the mantle/shell involves formation of an elongated opisthodetic ligament. That of the Dreissenacea, here initially described, is of unique complication. In primitive infaunal isomyarians an organ of locomotion through soft substrates, in these heteromyarians the foot becomes essentially concerned with byssal attachment with which much the greatest part of the small anterior and large posterior retractors becomes exclusively concerned. Although strikingly similar to the Mytilacea, the Dreissenacea which now inhabit slowly moving or still, silt-laden freshwaters would seem most probably to have evolved under very different marine conditions prior to their relatively recent migration into freshwaters.
This Summary for Policymakers presents key findings from the Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX). The SREX approaches the topic by assessing the scientific literature on issues that range from the relationship between climate change and extreme weather and climate events (‘climate extremes’) to the implications of these events for society and sustainable development. The assessment concerns the interaction of climatic, environmental, and human factors that can lead to impacts and disasters, options for managing the risks posed by impacts and disasters, and the important role that non-climatic factors play in determining impacts. Box SPM.1 defines concepts central to the SREX.
The character and severity of impacts from climate extremes depend not only on the extremes themselves but also on exposure and vulnerability. In this report, adverse impacts are considered disasters when they produce widespread damage and cause severe alterations in the normal functioning of communities or societies. Climate extremes, exposure, and vulnerability are influenced by a wide range of factors, including anthropogenic climate change, natural climate variability, and socioeconomic development (Figure SPM.1). Disaster risk management and adaptation to climate change focus on reducing exposure and vulnerability and increasing resilience to the potential adverse impacts of climate extremes, even though risks cannot fully be eliminated (Figure SPM.2). Although mitigation of climate change is not the focus of this report, adaptation and mitigation can complement each other and together can significantly reduce the risks of climate change. [SYR AR4, 5.3]
This paper considers the evolution of the concept that the local distribution of animals in the sea is largely determined by the habitat preferences and behaviour of the animals themselves. Examples are mainly taken from studies on invertebrate animals. Nineteenth-century investigations on the behavioural responses of micro-organisms to such variables as light, salinity and oxygen, stimulated analogus investigations on the behaviour of marine invertebrates. From 1920 onwards, various lines of research have developed, notably on the settlement of marine larvae, but also on habitat selection by adult planktonic and benthic invertebrates, and on host finding by parasites and commensals.
Attention has been drawn to the relevance of genetic studies on behaviour, and to the significance of investigations on terrestrial animals. A synoptic view of habitat selection has been advanced in which animals respond to a complex of interacting stimuli from their physical, chemical and biological environment.
Simple models have been presented which consider the influence of dilution of the preferred habitat by less preferred alternatives, alteration of the rate of change of a habitat, the relation between habitat preferences and lethal limits, and the colonisation of new habitats.
InAs/AlGaAs quantum dot infrared photodetectors based on bound-to-bound intraband transitions in undoped InAs quantum dots are reported. AlGaAs blocking layers were employed to achieve low dark current. The photoresponse peaked at 6.2 μm. At 77 K and –0.7 V bias the responsivity was 14 mA/W and the detectivtiy, D*, was 1010 cmHz1/2/W.
We investigated the electrical characteristics of the MOSCAP structures with W/WNx/poly Si1−xGex gates stack using C-V and I-V. The low frequency C-V measurements demonstrated that the flat band voltage of the W/WNx /poly Si0.4Ge0.6 stack was lower than that of W/ WNx /poly Si0.2Ge0.8 stack by 0.3V, and showed less gate-poly-depletion-effect than that of W/ WNx /poly- Si0.2Ge0.8 gates due to the increase of dopant activation rate with the increase of Ge content in the poly Si1−xGex films. As Ge content in poly Si1−xGex increased, the leakage current level increased a little due to the increase of direct tunneling and QBD became higher due to the lower boron penetration.
Nanocomposites of PMR-15 polyimide and a diamine modified silicate were prepared by addition of the silicate to the PMR-15 resin. The orientation of the ion exchange diamine within the silicate gallery was determined by x-ray diffraction and found to depend on the clay cation exchange capacity. The oligomer melt viscosity exhibited a dependence on the orientation of the diamine in the silicate interlayer, and in some cases, on the length of the diamine. A correlation was observed between the oligomer melt viscosity and the crosslinking enthalpy, where nanocomposites with an increased melt viscosity exhibited a decrease in enthalpy on crosslinking. After crosslinking, those nanocomposites with a high melt viscosity had poorer thermal oxidative stability compared to the less viscous systems. The melt viscosity was tailored by co-exchange of an aromatic diamine and an aliphatic amine into the silicate. Nanocomposites prepared with this silicate exhibited an increase in thermal oxidative stability compared to the neat resin.
We have studied the effects of nitridation on the leakage current of thin (7-8 nm) gate or tunnel oxides. A polarity dependence of the tunneling current has been found this behavior is related to the presence of a thin silicon oxynitride layer at the SiO2/Si-substrate interface. The oxynitride layer lowers the tunneling current when electrons are injected from the interface where the oxynitride is located (substrate injection). The current flowing across the oxide when electrons are injected from the opposite interface (gate injection) is not influenced by the oxynitride. The increase of nitrogen concentration leads to a decrease of the tunneling current for substrate electron injection.
Material interaction during integration of tungsten gate stack for 1 Gb DRAM was investigated by Transition Electron Microscopy (TEM), X-ray Diffraction analysis (XRD) and Auger Electron Spectroscopy (AES). During selective side-wall oxidation tungsten gate conductor undergoes a structural transformation. The transformation results in the reduction of tungsten crystal lattice spacing, re-crystallization of tungsten and/or growth of grains. During a highly selective oxidation process, a relatively small but noticeable amount of oxygen was incorporated into the tungsten layer. The incorporation of oxygen is attributed to the formation of a stable WO x (x<2) composite.
Microcrystalline inclusions in hydrogenated and fluorinated amorphous silicongermanium alloys, α-Si, Ge:H, F, were studied. Microcrystals grown during RF or DC glow discharge deposition from SiF4, GeF4 and H2 consist of either pure Si or Ge. Microcrystals produced by thermal annealing of initially amorphous alloys are either microcrystalline Ge or microcrystalline Si-Ge alloys depending on the annealing temperature. Values for the grain size were calculated from X-ray diffraction (XRD) and Raman spectra. The grain size of the “grown” microcrystal ranges from 8 to 60 nm. These grown grains exhibit preferential orientation of the (220) planes parallel to the substrate surface. Microcrystals produced by high-temperature anneal are randomly oriented. Scanning electron micrographs of as-grown samples show protruding platelets several 100 nm long and several 10 nm wide. Fractured cross sections exhibit columnar structure.
We study the interface between un-alloyed a-Si:H,F and an a-Si0.4,Ge0.6:H,F alloy using superlattice structures. From infrared spectroscopy we estimate a width of 8 A for the excess hydrogen layer, and X-ray diffraction data give us a width of 2Å contributing to the width of the diffraction peak. Vibrational Raman scattering data show that the ratios of the number of Si-Si, Ge-Ge and Si-Ge bonds is not altered by changing the number of interfaces. This fact allows us to establish an upper limit for the interface width of 3 atomic layers, i.e. one layer in each partner plus an intermediate layer.
a-Si and μc-Si were grown from SiF4 with H2 dilution in a DC glow discharge. The crystallinity of films deposited over a range of substrate temperatures and SiF4/H2 flow ratios was studied by Raman spectroscopy and the boundary between microcrystalline and amorphous Si was determined. We find that μc-Si can be grown from SiF4 with less H2 dilution than from SiH4. In the SiF4/H2 system, the etching by of F atoms appears responsible for μc-growth; H atoms play an important role in balancing growth and etching reactions.
We present a detailed study of the growth of a-Si:H,F from SiF4 and H4. The growth surface appears to have a high density of surface states. These surface states can be thermally relaxed by keeping the films at growth temperature after the termination of growth, suggesting that the states were created during film growth. When frozen in, the surface state density is found to depend on the conditions during film growth. The density is related to the sharpness of the valence band tail as measured by the Urbach Energy. We believe that a reaction on the growth surface resulting in fluorine elimination creates these surface states and also affects the formation of the Si-network.
A suitable choice of an electrode material is important for an acceptable electrical contact to a high-permittivity dielectric, such as PLZT. A material which does not form a low-permittivity oxide is necessary, since these dielectrics generally require high temperature deposition or annealing in an oxidizing environment. Platinum, which is one of the few metals that satisfy this requirement, has been widely employed for contacting PLZT. However, for integrated circuit applications, an adhesion layer must be superposed between Pt and the substrate, and Ti is used frequently. Therefore, we have investigated the Pt/Ti combination to determine its suitability as an electrode for contacting PLZT. Using x-ray diffraction, Rutherford backscattering spectrometry, Auger electron microscopy, and scanning electron microscope techniques, interdiffusion of Pt/Ti bilayers has been investigated. Pt/Ti films with or without PLZT overlay were annealed in either O2 or N2 ambients or in N2 followed by O2. Annealing temperatures varied from 500 to 800 °C. It was observed that the anneal ambient has a marked effect on the interdiffusion processes, the reaction products, the morphology of the structures, and the crystallization of PLZT.