Past explosion and future threat: Exacerbation of red water disease (Schistosomiasis haematobium) in the Upper Region of Ghana

An historical reconstruction is offered which suggests that the hyperendemicity of red water or Schistosomiasis haematobium in Ghana's Upper Region may have been, in part, an inadvertent by-product of agricultural development, through the construction of a large number of agricultural dams in an endemic area some 20 years ago. No disease prevention measures were undertaken in conjunction with the building of the dams, and S. haematobium prevalence may have been tripled in consequence. Certainly river blindness and probably other water-related diseases were also affected. Cyclical labor migration disseminates schistosomiasis southwards from the hyperendemic zone to those transmission sites where suitable snail hosts are to be found. History may be about to repeat itself in 1981 – 1985 in that a new wave of construction of dams will commence in the region; again without the concurrent introduction of any measures for disease control. Integrated planning is needed to prevent disease exacerbation by agriculture.     

Depositional environments of some Pleistocene coastal terrace deposits,southwestern Oregon—case history of a progradational beach and dune sequence

Pleistocene coastal terrace deposits exposed in sea cliffs near Gold Beach, Oregon can be divided into four stratigraphic units: a basal gravelly unit and three overlying sandy units, each with mud beds, a paleosol, or the modern soil in its uppermost part. The gravelly unit consists of gravel and sand in its lower part, sand, in part pebbly or cobbly, in its middle part, and mud and sand in its upper part. Black sand and transported pieces of wood are common in the middle part of the unit, and wood is common in the mud. This unit is interpreted as a progradational deposit including environments ranging from lower forebeach at the base to backbeach flats and streams at the top.The main sandy parts of the sandy units are made up of a crossbedded sand facies, the dominant structure in which is medium-scale crossbedding, and an irregularly bedded sand facies, which is locally pebbly and is dominated by scour-and-fill structures. Deciding between shallow marine and eolian interpretations of the sandy units proved exceptionally difficult until modern analogues were found in the fine details of the internal structures. Largely on the basis of such structural details, the crossbedded sand facies is interpreted as the product of small eolian dunes, and the irregularly bedded sand facies is interpreted as deposits of interdune ephemeral streams, ephemeral ponds, and wet to dry subaerial flats. The mud beds and paleosols at the tops of the sandy units represent times of temporary stabilization of the dune field.     

Crustal development in the Kaapvaal craton, II. The Proterozoic

The relationship in time and space of the elements comprising the greenstone—granitie terrane in the eastern Transvaal and Swaziland is discussed. On the evidence derived from structural analysis, metamorphic style, geochemistry, and geophysics it is concluded that sialic crust (now represented by the Ancient Gneiss Complex in Swaziland) pre-dates the Swaziland Sequence. It is postulated that the sialic crust formed as a result of partial and total melting of hydrous basaltic lithosphere under tectonically metastable conditions. Limited sedimentation and volcanism in small basins on this early crust took place during periods of quiescence, following which deformation resulted in the tectonic interslicing of the early sialic crust and the sedimentary—volcanic sequences that were metamorphosed at high temperatures and low pressure (Abukuma-type), and included limited partial melting. The protocontinental crust so formed was distended along linear zones overlying sites of mantle upwelling. Rifting resulted from the distension and was accompanied by intense volcanism typical of greenstone belts. Following mantle withdrawal sagging was initiated in the linear zone leading to sedimentation that was initially of turbidite type. As greater stability was achieved, the style of sedimentation changed and cratonic-type, Moodies Group sediments were deposited. The cyclic nature of the volcanism and sedimentation is considered to be a response to, and a reflection of, the degree of distension and of the vertical adjustments along the bounding faults. Diapiric rise of tonalitic magma produced as a result of partial melting of the early sialic crust mixing with mantle material caused the deformation of the original linear geometry. Continued depression of the amphibolite facies of the sialic crust into the zone of partial melting gave rise to potassic granitic magma that spread at higher crustal levels at interfaces of low free energy to form hood-like sheets of granite flanking the original linear rift. It is concluded that the eastern Transvaal and Swaziland area attained a crustal thickness of ± 25 km prior to 3.0 b.y.     

Bald kelp: natural and harvesting-induced frond loss in the South African kelp Ecklonia maxima

Ecklonia maxima dominates kelp beds on the west coast of southern Africa, and is commercially and ecologically valuable. Some plants lose all their secondary blades (fronds), leaving only the gas-filled bulb and short primary blade at the top of the stipe. These ‘bald’ kelps may persist for months or longer, occupying substratum space but contributing little to productivity. We investigated natural causes of balding in five kelp beds in False Bay, South Africa, and the effect of simulated commercial frond-harvesting on loss of fronds. Densities of sporophytes with and without fronds were measured at the water surface during low tides. Generalised linear modelling analysis showed a significant relationship between balding and site (whether sheltered from or exposed to swell/wind), position in the kelp bed (shoreward or seaward) and total E. maxima density. We conclude that balding is caused mainly by drying of meristematic basal regions of fronds during emersion of kelp heads at low tide. After partial harvesting of fronds, kelp heads floated higher out of the water, but after 95 days frond loss was significantly higher only when fronds were cut too close to the primary blade, possibly because of damage to meristematic tissue. Nevertheless, increased emersion that results from frond-harvesting may increase desiccation and blade loss and we suggest caution in setting harvest limits for this kelp.     

桐柏碰撞造山带及其邻区变形特征与构造格局

桐柏碰撞造山带及其邻区可以划分为九个大地构造单元,自北向南分别是:华北克拉通南缘岩石构造单元——宽坪岩群、具弧后盆地性质的二郎坪岩石构造单元、具岛弧性质的秦岭杂岩单元、龟山岩组和南湾岩组构成的俯冲前缘楔构造带、构造混杂岩带、桐柏北部高压岩片单元、桐柏核部杂岩单元、桐柏南部高压岩片单元以及随州构造变形带。根据详细的构造解析以及新的地质年代学资料,本文将中生代以来的构造变形划分为五幕,前两幕变形主要发育在构造混杂岩带以南的各个岩石构造单元中,之后的三幕变形则波及整个研究区。第一幕变形的时间约为255～238Ma,以发育区域上透入性的片理及北西西向的拉伸线理为主,并导致了高压岩片早期自西向东的挤出。第二幕变形的时间约为230～215Ma,以自北向南的逆冲推覆构造为主,使得高压岩片进一步垂向抬升。第三幕变形应早于下侏罗统,以近北西西向的宽缓褶皱为主要特征,该幕变形期间桐柏核部杂岩及其两侧高压岩片单元发生同步的抬升。第四幕变形大致发生在140～130Ma之间,主要表现为桐柏核部杂岩两侧走滑型韧性剪切带的活动,桐柏核部杂岩表现出向东的挤出。第五幕变形发生在120～80Ma,表现为北西向及北东向的脆性断裂活动,并切割以上所有构造形迹。桐柏高压岩片的抬升剥露受多幕变形控制,呈阶段性的抬升。     

Optimal water depth management on river-fed National Wildlife Refuges in a changing climate

The prairie pothole region (PPR) in the north-central United States and south-central Canada constitutes the most important waterfowl breeding area in North America. Projected long-term changes in precipitation and temperature may alter the drivers of waterfowl abundance: wetland availability and emergent vegetation cover. Previous studies have focused on isolated wetland dynamics, but the implications of changing precipitation on managed, river-fed wetlands have not been addressed. Using a structured decision making (SDM) approach, we derived optimal water management actions for 20 years at four river-fed National Wildlife Refuges (NWRs) in North and South Dakota under contrasting increasing/decreasing (+/?0.4 %/year) inflow scenarios derived from empirical trends. Refuge pool depth is manipulated by control structures. Optimal management involves setting control structure heights that have the highest probability of providing a desired mix of waterfowl habitat, given refuge capacities and inflows. We found optimal seasonal control structure heights for each refuge were essentially the same under increasing and decreasing inflow trends of 0.4 %/year over the next 20 years. Results suggest managed pools in the NWRs receive large inflows relative to their capacities. Hence, water availability does not constrain management; pool bathymetry and management tactics can be greater constraints on attaining management objectives than climate-mediated inflow. We present time-dependent optimal seasonal control structure heights for each refuge, which are resilient to the non-stationary precipitation scenarios we examined. Managers can use this information to provide a desired mixture of wildlife habitats, and to re-assess management objectives in reserves where pool bathymetry prevents attaining the currently stated objectives.     

Canada-France-Hawaii Telescope's “redeye” infrared camera system: Array performance

The Canada-France-Hawaii Telescope (CFHT) has recently commissioned two facility infrared cameras for astronomical observations in the 1.0 to 2.5 micron region. These cameras use NICMOS3 256×256 pixel arrays fabricated from Hg:Cd:Te. We report here on array performance and discuss two unique features of these arrays, namely corner glow and residual images. We have developed techniques for reducing corner glow and a method of clearing residual image charge. We discuss our techniques and their side effects.     

The relation of conducting polymer actuator material properties to performance

Materials used in many branches of engineering are of low molecular weight and not flexible. As we develop more sophisticated engineering devices one can look to nature for inspiration and advocate the use of high molecular weight flexible materials. Conducting polymer actuators will soon be used in applications where traditional low molecular weight actuator systems are incapable of mimicking the functionality provided by nature's muscle. To incorporate conducting polymer actuators into engineering systems it is of high importance to not only model and predict the behavior of these actuators but also understand the connection of material properties to performance. In this paper, the importance of fundamental actuation mechanisms and the fundamental material properties of conducting polymer muscles such as ionic diffusion rate, electrochemical operating window, strain to charge ratio, ratio of charge carried by positive versus negative ions, and salt draining are discussed and their effect on performance is demonstrated. The relevance of engineered geometry to the performance of conducting polymer muscles is also shown. Our understanding of what limits the performance of existing conducting polymers actuators provides directions for the improvement of the next generation of conducting polymer actuators.     

Relative sea‐level observations in western Scotland since the Last Glacial Maximum for testing models of glacial isostatic land movements and ice‐sheet reconstructions

Observations of relative sea‐level change and local deglaciation in western Scotland provide critical constraints for modelling glacio‐isostatic rebound in northern Britain over the last 18 000 years. The longest records come from Skye, Arisaig and Knapdale with a shorter, Holocene, record from Kintail. Biostratigraphic (diatom, pollen, dinoflagellate, foraminifera and thecamoebian), lithological and radiocarbon analyses provide age and elevation parameters for each sea‐level index point. All four sites reveal relative sea‐level change that is highly non‐monotonic in time as the local vertical component of glacio‐isostatic rebound and eustasy (or global meltwater influx) dominate at different periods. Copyright © 2006 John Wiley & Sons, Ltd.