ANTHROPOLOGY & EDUCATION QUARTERLY, Issue 2 2001
Mary Bushnell
Educational reformers and social observers call for increasing community in our schools and neighborhoods. In that discourse, community appears as a catch phrase that has become meaningless in its ubiquity. Through an ethnographic study of a small elementary school in which community is regularly invoked, the author identifies community's negative as well as beneficial aspects and discusses the implications for schools. [source]

Effects of vegetation on channel morphodynamics: results and insights from laboratory experiments

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2010
Michal Tal
Abstract A series of laboratory experiments demonstrates that riparian vegetation can cause a braided channel to self-organize to, and maintain, a dynamic, single-thread channel. The initial condition for the experiments was steady-state braiding in non-cohesive sand under uniform discharge. From here, an experiment consisted of repeated cycles alternating a short duration high flow with a long duration low flow, and uniform dispersal of alfalfa seeds over the bed at the end of each high flow. Plants established on freshly deposited bars and areas of braidplain that were unoccupied during low flow. The presence of the plants had the effect of progressively focusing the high flow so that a single dominant channel developed. The single-thread channel self-adjusted to carry the high flow. Vegetation also slowed the rate of bank erosion. Matching of deposition along the point bar with erosion along the outer bend enabled the channel to develop sinuosity and migrate laterally while suppressing channel splitting and the creation of new channel width. The experimental channels spontaneously reproduced many of the mechanisms by which natural meandering channels migrate and maintain a single dominant channel, in particular bend growth and channel cutoff. In contrast with the braided system, where channel switching is a nearly continuous process, vegetation maintained a coherent channel until wholesale diversion of flow via cutoff and/or avulsion occurred, by which point the previous channel tended to be highly unfavorable for flow. Thus vegetation discouraged the coexistence of multiple channels. Varying discharge was key to allowing expression of feedbacks between the plants and the flow and promoting the transition from braiding to a single-thread channel that was then dynamically maintained. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Meltwater discharge through the subglacial bed and its land-forming consequences from numerical experiments in the Polish lowland during the last glaciation

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2009
Jan A. Piotrowski
Abstract Numerical experiments suggest that the last glaciation severely affected the upper lithosphere groundwater system in NW Poland: primarily its flow pattern, velocities and fluxes. We have simulated subglacial groundwater flow in two and three spatial dimensions using finite difference codes for steady-state and transient conditions. The results show how profoundly the ice sheet modifies groundwater pressure heads beneath and some distance beyond the ice margin. All model runs show water discharge at the ice forefield driven by ice-sheet-thickness-modulated, down-ice-decreasing hydraulic heads. In relation to non-glacial times, the transient 3D model shows significant changes in the groundwater flow directions in a regionally extensive aquifer ca. 90 m below the ice,bed interface and up to 40 km in front of the glacier. Comparison with empirical data suggests that, depending on the model run, only between 5 and 24% of the meltwater formed at the ice sole drained through the bed as groundwater. This is consistent with field observations documenting abundant occurrence of tunnel valleys, indicating that the remaining portion of basal meltwater was evacuated through a channelized subglacial drainage system. Groundwater flow simulation suggests that in areas of very low hydraulic conductivity and adverse subglacial slopes water ponding at the ice sole was likely. In these areas the relief shows distinct palaeo-ice lobes, indicating fast ice flow, possibly triggered by the undrained water at the ice,bed interface. Owing to the abundance of low-permeability strata in the bed, the simulated groundwater flow depth is less than ca. 200 m. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Macro-scale bed roughness of the siple coast ice streams in West Antarctica

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2004
Martin J. Siegert
Abstract Subglacial bed conditions are key to understanding ice stream behaviour and evolution, with bed roughness re,ecting substrate composition and ,ow resistance. Here we present an analysis of bed roughness in the Siple Coast region of West Antarctica from airborne radio-echo sounding data. The ice streams are associated generally with low bed roughness values, which decrease downstream. The bed of the slow-,owing Ice Stream C (,10 000 km2) is also characterized by being smooth at all scales (wavelengths ranging from 5 km to in excess of 40 km). Furthermore, the bed is smooth either side of Ice Stream C. This suggests the location of the ice stream is controlled by internal ice sheet dynamics rather than by bed morphology. If the ice stream were encouraged to migrate laterally, when active, there would be little resistance offered by the subglacial morphology. Other inter-ice stream regions are rough, however, indicating a subglacial topographic in,uence on ice stream position. Bed roughness increases up-,ow of ice streams, which, unless the bed is modi,ed, may limit the inland migration of these systems. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Bedload transport resistance in rough open-channel flows

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2004
Peng Gao
Abstract During bedload movement by saltation, streamwise momentum is transferred from the ,ow to the saltating grains. When the grains collide with other grains on the bed or in the ,ow, streamwise momentum is reduced, and there is a decrease in streamwise ,ow velocity and an increase in ,ow resistance, herein termed bedload transport resistance fbt. Based on experiments in two ,umes with ,xed and mobile plane beds and previously published data, an equation is developed that may be used to predict fbt for both capacity and non-capacity ,ows. The variables in this equation are identi,ed by dimensional analysis and the coef,cients are determined by non-linear regression. This equation applies to rough turbulent open-channel ,ows, where the relative submergence is between 1 and 20 and the entire sediment load moves by saltation. An investigation of the relative magnitudes of fbt and grain resistance fc suggests that where dimensionless shear stress , is less than 1 and saltation is the dominant mode of bedload transport, fbt/fc increases with , but never exceeds 1. Copyright © 2004 John Wiley & Sons, Ltd. [source]

The influence of plant cover and land use on slope,channel decoupling in a foothill catchment: a case study from the Carpathian Foothills, southern Poland

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2002
Jolanta, chowicz
Abstract This paper examines the influence of plant cover and land use on slope,channel decoupling in the Stara Rzeka Stream catchment (22·4 km2) and its subcatchment Dworski Potok Stream (0·3 km2). The Stara Rzeka catchment is situated in the marginal part of the Carpathian Foothills and is characterized by a relief of low and medium hills. The catchment is used for agriculture but unlike other foothill catchments, it has a relatively extensive unfragmented area of forests (41·3 per cent). Grasslands and pastures (13·8 per cent) are mainly along the broad and flat valley floor. In the cultivated area (38·5 per cent) of the northern low hill part of the catchment, the fields are long, narrow and separated by boundary strips. They stretch from the hilltops to the valley bottom and are traditionally ploughed along the slopes. The research into slope wash was carried out at six sites downslope (August 1989 to October 1990) and on experimental plots (1989,1991). Transport of suspended matter was determined in the channels of the Stara Rzeka and Dworski Potok Streams (1987,1991). The results show that transport and export of the material on the slopes depend on the morphology of the slope and on the agricultural use of the area. The mosaic of fields which are used differently makes the soil wash process very intensive only if the slopes are ploughed and unprotected by a dense cover of vegetation. The material displaced is mostly accumulated at the foot of the slopes or at the bottom of the valley. Footslope areas and flat valley bottoms covered with grass function as a barrier separating the slope and the river bed. These features generally negate the transfer of slope-originated material to the bed of the stream. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Controls on englacial sediment deposition during the November 1996 jökulhlaup, Skei,arárjökull, Iceland

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2001
Matthew J. Roberts
Abstract This paper presents sedimentary evidence for rapid englacial debris entrainment during jökulhlaups. Previous studies of jökulhlaup sedimentology have focused predominantly on proglacial impact, rather than depositional processes within glaciers. However, observations of supraglacial floodwater outbursts suggest that englacial sediment emplacement is possible during jökulhlaups. The November 1996 jökulhlaup from Skei,arárjökull, Iceland presented one of the first opportunities to examine englacial flood deposits in relation to former supraglacial outlets. Using observations from Skei,arárjökull, this paper identifies and explains controls on the deposition of englacial flood sediments and presents a qualitative model for englacial jökulhlaup deposition. Englacial jökulhlaup deposits were contained within complex networks of upglacier-dipping fractures. Simultaneous englacial deposition of fines and boulder-sized sediment demonstrates that englacial fracture discharge had a high transport capacity. Fracture geometry was an important control on the architecture of englacial jökulhlaup deposits. The occurrence of pervasively frozen flood deposits within Skei,arárjökull is attributed to freeze-on by glaciohydraulic supercooling. Floodwater, flowing subglacially or through upglacier-dipping fractures, would have supercooled as it was raised to the surface faster than its pressure-melting point could increase as glaciostatic pressure decreased. Evidence for floodwater contact with the glacier bed is supported by the ubiquitous occurrence of sheared diamict rip-ups and intra-clasts of basal ice within jökulhlaup fractures, deposited englacially some 200,350 m above the bed of Skei,arárjökull. Evidence for fluidal supercooled sediment accretion is apparent within stratified sands, deposited englacially at exceptionally high angles of rest in the absence of post-depositional disturbance. Such primary sediment structures cannot be explained unless sediment is progressively accreted to opposing fracture walls. Ice retreat from areas of former supraglacial outbursts revealed distinct ridges characterized by localized upwellings of sediment-rich floodwater. These deposits are an important addition to current models of englacial sedimentation and demonstrate the potential for post-jökulhlaup landform development. Copyright © 2001 John Wiley & Sons, Ltd. [source]

An experimental study on the ripple,dune transition

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2001
André Robert
Abstract Flume experiments were conducted on different bed stages across the ripple,dune transition. As flow velocity increases, an initially flat bed surface (made of fairly uniform sandy material) is gradually transformed into a two-dimensional rippled bed. With further increase in velocity, two-dimensional ripples are replaced by irregular, linguoid ripples. As the average velocity necessary for the ripple,dune transition to occur is imposed on the bed surface, these non-equilibrium linguoid ripples are further transformed into larger, two-dimensional dunes. For each of these stages across the transition, a concrete mould of the bed was created and the flow structure above each fixed bed surface investigated. An acoustic Doppler velocimeter was used to study the flow characteristics above each bed surface. Detailed profiles were used along a transect located in the middle of the channel. Results are presented in the form of spatially averaged profiles of various flow characteristics and of contour maps of flow fields (section view). They clearly illustrate some important distinctions in the flow structure above the different bedform types associated with different stages during the transition. Turbulence intensity and Reynolds stresses gradually increase throughout the transition. Two-dimensional ripples present a fairly uniform spatial distribution of turbulent flow characteristics above the bed. Linguoid ripples induce three-dimensional turbulence structure at greater heights above the bed surface and turbulence intensity tends to increase steadily with height above bed surface in the wake region. A very significant increase in turbulence intensity and momentum exchange occurs during the transition from linguoid ripples to dunes. The turbulent flow field properties above dunes are highly dependent on the position along and above the bed surface and these fields present a very high degree of spatial variability (when compared with the rippled beds). Further investigations under natural conditions emphasizing sediment transport mechanisms and rates during the transition should represent the next step of analysis, together with an emphasis on quadrant analysis. Copyright © 2001 John Wiley & Sons, Ltd. [source]

A micropillar-integrated smart microfluidic device for specific capture and sorting of cells

ELECTROPHORESIS, Issue 24 2007
Yan-Jun Liu
Abstract An integrated smart microfluidic device consisting of nickel micropillars, microvalves, and microchannels was developed for specific capture and sorting of cells. A regular hexagonal array of nickel micropillars was integrated on the bottom of a microchannel by standard photolithography, which can generate strong induced magnetic field gradients under an external magnetic field to efficiently trap superparamagnetic beads (SPMBs) in a flowing stream, forming a bed with sufficient magnetic beads as a capture zone. Fluids could be manipulated by programmed controlling the integrated air-pressure-actuated microvalves, based on which in situ bio-functionalization of SPMBs trapped in the capture zone was realized by covalent attachment of specific proteins directly to their surface on the integrated microfluidic device. In this case, only small volumes of protein solutions (62.5,nL in the capture zone; 375,nL in total volume needed to fill the device from inlet A to the intersection of outlet channels F and G) can meet the need for protein! The newly designed microfluidic device reduced greatly chemical and biological reagent consumption and simplified drastically tedious manual handling. Based on the specific interaction between wheat germ agglutinin (WGA) and N -acetylglucosamine on the cell membrane, A549 cancer cells were effectively captured and sorted on the microfluidic device. Capture efficiency ranged from 62 to 74%. The integrated microfluidic device provides a reliable technique for cell sorting. [source]

Separation of proteins in a multicompartment electrolyzer with chambers defined by a bed of gel beads

ELECTROPHORESIS, Issue 4 2003
Marina Cretich
Abstract Multicompartment electrolyzers (MEs) with isoelectric membranes were introduced in 1989 for purifying proteins in an electric field. At the basis of ME technology there are membranes consisting of cross-linked copolymers of acrylamide and acrylamido monomers bearing protolytic groups. The technology employed for casting the membranes is an extension of the isoelectric focusing in immobilized pH gradient technique for which specific acrylamido monomers, known with the trade name of Immobiline, have been developed. However, the use of continuous membranes presents several disadvantages. Due to the mechanical characteristics of polyacrylamide, the gel must physically adhere onto a rigid support, which prevents it from collapsing. The support must have a highly porous structure in order to be permeable to proteins. The mechanical fragility of the membranes is one of the main problems that hinders the industrial scale application of ME separators. In order to overcome this problem, we propose to substitute the continuous membranes with a bed of gel beads of identical comonomer composition, obtained by an inverse emulsion polymerization process. [source]

The role of macroinvertebrates and fish in regulating the provision by macrophytes of refugia for zooplankton in a warm temperate shallow lake

FRESHWATER BIOLOGY, Issue 10 2010
MARÍA de los ÁNGELES GONZÁLEZ SAGRARIO
Summary 1.,The zooplankton often undergoes diel horizontal migration (DHM) from the open water to the littoral of shallow lakes, thus avoiding predators in the former. This behaviour has functional impacts within the lake, as it enhances zooplankton survival, increases their control of phytoplankton and tends to stabilise the clear water state. However, most of the evidence supporting this migration pattern comes from cold north temperate lakes, and more evidence from tropical and subtropical areas, as well as from southern temperate areas, is needed. 2.,We conducted a field study of the diel horizontal and vertical migration of zooplankton, and the horizontal distribution of potential predatory macroinvertebrates and fish, over two consecutive days in the summer in a temperate lake in the southern hemisphere. We took zooplankton samples at two depths, at three sampling stations (inside beds of aquatic macrophytes, at their edge and in open water) along three transects running from the centre of a bed of Ceratophyllum demersum to open water. At each sampling station, we also took samples of macroinvertebrates and fish and measured physical and chemical environmental variables. 3.,Zooplankton (pelagic cladocerans, calanoid copepods and rotifers) avoided the shore, probably because of the greater risk from predators there. Larger and more vulnerable cladocerans, such as Diaphanosoma brachyurum and Moina micrura, were two to four times more abundant in open water than at the edge of or inside beds of macrophytes, respectively, by both day and night. Less vulnerable zooplankton [i.e. of medium body size (Ceriodaphnia dubia) or with the ability to swim fast (calanoid copepods)] were distributed evenly between open water and the edge of the plant beds. Small zooplankton, Bosmina huaronensis and pelagic rotifers, showed an even distribution among the three sampling stations. Accordingly, no DHM of zooplankton occurred, although larger organisms migrated vertically inside C. demersum stands. 4.,Macrophytes contained high densities of predatory macroinvertebrates and fish. The predator assemblage, composed of large-bodied macroinvertebrates (including odonates and shrimps) and small littoral fish, was permanently associated with submerged macrophytes. None of these groups moved outside the plant beds or changed their population structure (fish) over the diel cycle. 5.,Submerged macrophyte beds do not represent a refuge for zooplankton in lakes where predators are numerous among the plants, implying a weaker top-down control of phytoplankton biomass by zooplankton and, consequently, a more turbid lake. The effectiveness of macrophytes as a refuge for zooplankton depends on the associated assemblage of predatory macroinvertebrates and fish among the plants. [source]

Comparison of the abilities of redtop (Agrostis alba L.) and zoysiagrass (Zoysia japonica Steud.) to purify liquid animal waste

GRASSLAND SCIENCE, Issue 1 2006
Naoko Takada-Oikawa
Abstract The animal waste treatment facility of Azabu University utilizes cultivation beds where liquid animal waste is purified by filtration through soil and vegetation. The beds are presently covered with zoysiagrass (Zoysia japonica Steud.), which thrives in warm weather. However, the purification activities of this grass decrease during winter dormancy. To improve purification activity between autumn and early spring, we introduced redtop (Agrostis alba L.), which thrives in cool conditions, into an experimental bed and compared the purification efficiency with that of zoysiagrass. Drainage purified through the bed of redtop showed significantly lower values of turbidity, chemical oxygen demand, total phosphorus and ammonium-nitrogen concentrations, and significantly higher nitrate-nitrogen concentrations than that through zoysiagrass during the late vegetative stage when redtop had the highest biomass. This suggested vigorous nitrification activity of rhizosphere under aerobic conditions afforded by redtop. The high purification efficiency of redtop appeared to be associated with better essential salts absorption and improved physicochemical properties of soil supporting its growth. The results showed that the purification efficiency of redtop is higher than that of zoysiagrass under seasonal low temperatures. [source]

Is central neck dissection necessary for the treatment of lateral cervical nodal recurrence of papillary thyroid carcinoma?

HEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 10 2007
Jong-Lyel Roh MD
Abstract Background: Although the pattern of cervical lymph node metastases from papillary thyroid carcinoma (PTC) has been described, little is known about the pattern of lateral cervical nodal recurrence. The aim of this study was to establish the optimal strategy for neck dissection in patients who underwent reoperation for lateral cervical recurrence of PTC. Methods: We reviewed the records of 22 patients who underwent neck dissection for lateral nodal recurrence of thyroid cancer between 2002 and 2004. Eight patients had thyroid remnants or recurrent tumors in the bed and 6 had undergone lateral neck dissection prior to referral. Patients underwent comprehensive dissection of the posterolateral and ipsilateral (n = 10) or bilateral (n = 12) central neck. The pattern of nodal recurrence and postoperative morbidity were analyzed. Results: All patients had lateral compartment involvement, 91% at mid-lower, 45% at upper, and 18% at posterior sites. Central nodes were involved in 86% of patients: 82% at ipsilateral paratracheal, 32% at pretracheal, 27% at superior mediastinal, and 2 patients at contralateral sites. Skip lateral recurrence with no positive central nodes was rarely observed (14%). Postoperative vocal cord palsy (n = 1) and hypoparathyroidism (n = 5) developed only in patients undergoing bilateral central compartment dissection. Conclusions: The inclusion of comprehensive ipsilateral central and lateral neck dissection in the reoperation for patients with lateral neck recurrence of PTC is an optimal surgical strategy. © 2007 Wiley Periodicals, Inc. Head Neck, 2007 [source]

Enhancement of heat transfer in hydrogen storage tank with hydrogen absorbing alloy (optimum fin layout)

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2008
Yuichi Mitsutake
Abstract Optimization of the fin layout in a metal hydride (MH) bed has been sought to enhance poor heat transmission in a hydrogen storage tank, and to obtain a maximum hydrogen absorption rate with a smaller volume of fins. Two different fin configurations, radial and circular fins, in a vertical cylindrical reactor vessel were tested with a La-Ni-based AB5 type hydrogen storage alloy. A two-dimensional transient heat conduction analysis, coupled with predicted temperature and concentration of absorbed hydrogen in the bed for the exothermic hydride reaction, was used to evaluate enhancement of the hydrogen absorption time. The estimated temperature and concentration agreed within 6 K and 8.5%, respectively, with our experimental results. The effect of thickness and the spacing and shape of fins on the hydrogen absorption time were analytically evaluated, so that the optimum range of the each fin layout was obtained by the trade off between absorption time and reduction in the MH volume due to the volume occupied by fins. The hydrogen absorption time for the recommended layout of circular fins was reduced to approximately one-third of that without fins. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(3): 165,183, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20195 [source]

Sediment infiltration traps: their use to monitor salmonid spawning habitat in headwater tributaries of the Cascapédia River, Québec

HYDROLOGICAL PROCESSES, Issue 20 2005
André E. Zimmermann
Abstract Sediment infiltration can clog salmon nests and reduce egg survival. As a countermeasure, environmental managers often deploy infiltration traps to monitor sediment infiltration. Traps provide a repeatable means of measuring infiltration and enable comparisons to be made between sites. Results from infiltration rates measured with traps have also been used to estimate infilling rates into salmon nests. Application of these data is questionable, as the composition of the bed and the amount of fine sediment within the bed is known to affect infiltration rates. Thus, infiltration rates measured with infiltration traps may differ from the infiltration rates occurring in redd and riffle gravels. To examine how relationships between sediment infiltration rates varied between four watersheds, we continuously monitored suspended sediment transport, shear stress and infiltration rates at four sites over 5 months. We also compared infiltration rates measured with infiltration traps with changes in the hydraulic conductivity and subsurface grain size distribution of adjacent artificially constructed salmon nests and natural riffle gravels. Among the four watersheds, clear differences in sediment infiltration rates were observed. The differences correlated with the subsurface silt content but no strong relationship existed between land-use or basin physiography/geology. Despite observing an average of 30 kg m,2 of sediment finer than 2 mm being deposited in the infiltration traps during the study, no change in redd or riffle substrate was observed. If the deposition rates measured with the traps reflect the processes in redds, enough sediment would have been deposited to inhibit egg emergence. However, no reduction in egg survival to the eyed stage was observed. In summary, our results show that infiltration traps with clean gravels can be used to detect intersite differences in sediment transport regimes. Extrapolations of sediment infiltration rates measured with such collectors to estimate infiltration rates in redds or riffles is, however, flawed. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Suspended sediment concentration and the ripple,dune transition

HYDROLOGICAL PROCESSES, Issue 17 2004
Robert J. Schindler
Abstract Flume experiments were conducted in order to monitor changes in flow turbulence intensity and suspended sediment concentration at seven stages across the ripple,dune transition and at three different positions above the bed surface. Three-dimensional velocity measurements were obtained using an acoustic Doppler velocimeter (ADV). Suspended sediment concentration (SSC) was monitored indirectly using ADV signal amplitude. Although limited to time-averaged parameters, the analysis reveals that SSC varies significantly with stage across the transition and with sampling height. The statistical analysis also reveals an apparent uniformity of suspended sediment concentration with height above the bed in the lower half of the flow depth at the critical stage in the transition from ripples to dunes. This is also the stage at which turbulence intensity is maximized. Statistically significant correlations were also observed between suspended sediment concentrations and root-mean-square values of vertical velocity fluctuations. These correlations reflect the various levels of shear-layer activity and the distinct turbulent flow regions across the transition. Conversely, time-averaged values of Reynolds shear stress exhibit a very weak relationship with suspended sediment concentrations. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Geochemical weathering at the bed of Haut Glacier d'Arolla, Switzerland,a new model

HYDROLOGICAL PROCESSES, Issue 5 2002
M. Tranter
Waters were sampled from 17 boreholes at Haut Glacier d'Arolla during the 1993 and 1994 ablation seasons. Three types of concentrated subglacial water were identified, based on the relative proportions of Ca2+, HCO3, and SO42, to Si. Type A waters are the most solute rich and have the lowest relative proportion of Si. They are believed to form in hydrologically inefficient areas of a distributed drainage system. Most solute is obtained from coupled sulphide oxidation and carbonate dissolution (SO,CD). It is possible that there is a subglacial source of O2, perhaps from gas bubbles released during regelation, because the high SO42, levels found (up to 1200 µeq/L) are greater than could be achieved if sulphides are oxidized by oxygen in saturated water at 0 °C (c.414 µeq/L). A more likely alternative is that sulphide is oxidized by Fe3+ in anoxic environments. If this is the case, exchange reactions involving FeIII and FeII from silicates are possible. These have the potential to generate relatively high concentrations of HCO3, with respect to SO42,. Formation of secondary weathering products, such as clays, may explain the low Si concentrations of Type A waters. Type B waters were the most frequently sampled subglacial water. They are believed to be representative of waters flowing in more efficient parts of a distributed drainage system. Residence time and reaction kinetics help determine the solute composition of these waters. The initial water,rock reactions are carbonate and silicate hydrolysis, and there is exchange of divalent cations from solution for monovalent cations held on surface exchange sites. Hydrolysis is followed by SO,CD. The SO42, concentrations usually are <414 µeq/L, although some range up to 580 µeq/L, which suggests that elements of the distributed drainage system may become anoxic. Type C waters were the most dilute, yet they were very turbid. Their chemical composition is characterized by low SO42, : HCO3, ratios and high pH. Type C waters were usually artefacts of the borehole chemical weathering environment. True Type C waters are believed to flow through sulphide-poor basal debris, particularly in the channel marginal zone. The composition of bulk runoff was most similar to diluted Type B waters at high discharge, and was similar to a mixture of Type B and C waters at lower discharge. These observations suggest that some supraglacial meltwaters input to the bed are stored temporarily in the channel marginal zone during rising discharge and are released during declining flow. Little of the subglacial chemical weathering we infer is associated with the sequestration of atmospheric CO2. The progression of reactions is from carbonate and silicate hydrolysis, through sulphide oxidation by first oxygen and then FeIII, which drives further carbonate and silicate weathering. A crude estimate of the ratio of carbonate to silicate weathering following hydrolysis is 4 : 1. We speculate that microbial oxidation of organic carbon also may occur. Both sulphide oxidation and microbial oxidation of organic carbon are likely to drive the bed towards suboxic conditions. Hence, we believe that subglacial chemical weathering does not sequester significant quantities of atmospheric CO2 and that one of the key controls on the rate and magnitude of solute acquisition is microbial activity, which catalyses the reduction of FeIII and the oxidation of FeS2. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Cradling in the prevention of excessive crying and colic symptoms in infants

INFANT MENTAL HEALTH JOURNAL, Issue 3 2005
Elina Hyödynmaa
To evaluate lying in a cradle in the prevention of excessive infant crying or colic symptoms, and to investigate potential protective or risk factors for the phenomenon, 220 newborns were randomized to sleep either in a bed or cot (control group, N = 108) or in a cradle (cradle group, N = 112). During three months, the parents filled in diaries on the sleeping place most used and the amount of crying of their infants. Three infants in the cradle group and one control fulfilled the criteria of colic. The percentages of extremely weepy infants (25.7% vs 24.4 %) and the intensity of crying did not differ between the groups. Medication for colic symptoms was used equally frequently in both groups. A high educational (OR 3.18, 95% CI 1.01; 10.04) and socioeconomic (OR 3.76, 95% CI 1.34; 10.52) level of the family and having a sibling with a history of colic (OR 6.46, 95% CI 1.17; 35.73) were predictors for the infant being weepy. Absence of nursing problems and having no sibling with a history of colic seemed to be related with a low amount of crying. Excessive infant crying was less common in families with unemployed fathers compared to those in which the father had an occupation (p = 0.018). Cradling seems not to prevent excessive crying or colic symptoms in infants. Breast-feeding guidance during rooming-in period and presence of father or another adult supporter at home might be preventive means against excessive crying. [source]

Finite element modelling of free-surface flows with non-hydrostatic pressure and k,, turbulence model

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2005
C. Leupi
Abstract Validation of 3D finite element model for free-surface flow is conducted using a high quality and high spatial resolution data set. The commonly numerical models with the conventional hydrostatic pressure still remain the most widely used approach for the solution of practical engineering problems. However, when a 3D description of the velocity field is required, it is useful to resort to a more accurate model in which the hydrostatic assumption is removed. The present research finds its motivation in the increasing need for efficient management of geophysical flows such as estuaries (multiphase fluid flow) or natural rivers with the presence of short waves and/or strong bathymetry gradient, and/or strong channel curvature. A numerical solution is based on the unsteady Reynolds-averaged Navier,Stokes equations on the unstructured grid. The eddy viscosity is calculated from the efficient k,, turbulence model. The model uses implicit fractional step time stepping, and the characteristics method is used to compute the convection terms in the multi-layers system (suitable for the vertical stratified fluid flow), in which the vertical grid is located at predefined heights and the number of elements in the water column depends on water depth. The bottommost and topmost elements of variable height allow a faithful representation of the bed and the time-varying free-surface, respectively. The model is applied to the 3D open channel flows of various complexity, for which experimental data are available for comparison. Computations with and without non-hydrostatic are compared for the same trench to test the validity of the conventional hydrostatic pressure assumption. Good agreement is found between numerical computations and experiments. Copyright © 2005 John Wiley & Sons, Ltd. [source]

A Room Temperature Ionic Liquid (RTIL)-Mediated, Non-Hydrolytic Sol,Gel Methodology to Prepare Molecularly Imprinted, Silica-Based Hybrid Monoliths for Chiral Separation,

ADVANCED MATERIALS, Issue 24 2006
H.-F. Wang
Silica-based hybrid molecularly imprinted polymer (MIP) monoliths with good chiral recognition ability are synthesized (see figure) using a novel method, a room temperature ionic liquid (RTIL)-mediated, non-hydrolytic sol,gel technique. The approach avoids the cracking and shrinking of the bed during drying, which is commonly associated with conventional sol,gel processing, overcomes the shortcomings associated with conventional organic-polymer-based MIP matrices, and offers improved selectivity. [source]

Effect of pressure and temperature on cluster and particle heat transfer in a pressurized circulating fluidized bed

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 14 2001
B. V. Reddy
Abstract The present work reports the influence of pressure and bed temperature on particle-to-wall heat transfer in a pressurized circulating fluidized bed (PCFB). The particle convection heat transfer plays a dominant role in determining the bed-to-wall heat transfer coefficient. So far, no information is reported on the effect of pressure and bed temperature on particle-to-wall heat transfer in a PCFB in the published literature. The present investigation reports some information in this direction. The effect of system pressure and bed temperature are investigated to study their influence on cluster and particle heat transfer. The particle convection heat transfer coefficient increases with system pressure and bed temperature due to higher cluster thermal conductivity. The increase in particle concentration (suspension density) results in greater cluster solid fraction and also the particle concentration near the wall is enhanced. This results in higher cluster and particle convection heat transfer between the bed and the wall. Higher particle convection heat transfer coefficient results in enhanced heat transfer between the bed and the wall. The results will also help to understand the bed-to-wall heat transfer mechanism in a better way in a PCFB. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Gasification of char particles in packed beds: analysis and results

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2001
S. Dasappa
Abstract In this paper a packed bed of char particles is considered for experimental study and analysis. The packed char bed is modelled by extending the single-particle analysis (Dasappa et al., 1994a, Chem. Eng. Sci.49,2:223,232. Dasappa et al., 1994b, Twenty-fifth Symposium (International) on Combustion, pp. 1619,1628. Dasappa et al., 1998, Twenty-seventh Symposium (International) on Combustion, pp. 1335,1342.). All the reactions related to gasification are introduced into the reaction system as in Dasappa et al. (1998). The propagation of the reaction front into the packed char bed against the air stream is modelled. The results are compared with the experimental data on a model quartz reactor using charcoal. Experimental data of propagation of the reaction front through the packed bed from the present study and of Groeneveld's charcoal gasifier are used for comparison. Using the analysis of Dosanjh et al. 1987 (Combust. Flame68:131,142), it is shown that heat loss dominates the heat generation at the quench condition. It is also shown that increasing the oxygen fraction in air has resulted in flame front to propagate into the char bed. The critical air mass flux for peak propagation rate in a bed of char is found to be 0.1 kg m,2 s. Copyright © 2001 John Wiley & Sons, Ltd. [source]

The Arade 1 Shipwreck: Preliminary Results of the 2004 and 2005 Field Seasons

INTERNATIONAL JOURNAL OF NAUTICAL ARCHAEOLOGY, Issue 2 2008
Vanessa Loureiro
Lost after partial destruction by dredging in 1970, Arade 1 was a priority for the Centro Nacional de Arqueologia Náutica e Subaquática (CNANS). The upper part of the hull, lying over a 7-m-long area of the bed of the Arade river, was fully observed and recorded during the first two seasons (2001 and 2002) and dismantled in a third phase (2003). The 2004 and 2005 seasons aimed at the excavation, full recording and dismantling of the lower hull, briefly observed at the end of 2002. This second, detached, portion of the hull, was buried in the sediment and corresponds to midships. © 2008 The Authors [source]

Structure and Functioning of the "Egg Bank" of a Fairy Shrimp in a Temporary Pool: Chirocephalus ruffoi from Pollino National Park (Southern Italy) as a Case Study

INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 1 2004
Graziella Mura
Abstract To investigate their distribution and total numbers, resting eggs of the anostracan Chirocephalus ruffoi were collected from the bed of a temporary pool in southern Italy. Samples were taken at 0.5 m intervals along six transects oriented at 30° from each other, by means of a cylindrical core sampler. The horizontal distribution of intact resting eggs was extremely patchy, with cyst number per core ranging from 191 to 1,400 (CV = 32.7%), corresponding to a mean of between 0.8 and 4.3 cysts cm,3. Differences observed were related to core position and transect orientation, total cyst numbers being markedly higher in the leeward area of the pool compared to the windward area. Marked variation was also evident in vertical distribution, a significant, though weak correlation was recorded between egg density and sediment depth. Cyst-bank size (± 95% confidence limits) of the pool bed, estimated from the mean cyst number cm,3 obtained for the 6 transects, ranged between 1.0 × 108 and 1.3 × 108 cysts. Hatching in the laboratory was very erratic. Despite significant differences in hatching, the observed variation was unrelated to most of the variables considered (position within sections, cores and transects, pre-incubation treatment) and was explained only by initial sediment conditions (moist/dry). In none of the experimental conditions tested was synchronous hatching obtained. Possible causal factors (mixing of the bottom sediments by cattle, egg age, storage conditions, differential exposure to environmental cues as well as variability in hatching response even at clutch level) are discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Weight Change and Lower Body Disability in Older Mexican Americans

JOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 10 2005
Soham Al Snih MD
Objectives: To examine the association between 2-year weight change and onset of lower body disability over time in older Mexican Americans. Design: Data were from the Hispanic Established Population for the Epidemiological Study of the Elderly (1993,2001). Weight change was examined by comparing baseline weight to weight at 2-year follow-up. Incidence of lower body disability was studied from the end of this period through an additional 5 years. Setting: Five southwestern states: Texas, New Mexico, Colorado, Arizona, and California. Participants: One thousand seven hundred thirty-seven noninstitutionalized Mexican-American men and women aged 65 and older who reported no limitation in activities of daily living (ADLs) and were able to perform the walk test at 2-year follow-up. Measurements: In-home interviews assessed sociodemographic factors, self-reported physician diagnoses of medical conditions (arthritis, diabetes mellitus, heart attack, stroke, hip fracture, and cancer), self-reported ADLs, depressive symptoms, and number of hospitalizations. Cognitive function, handgrip muscle strength, and body mass index (BMI) were obtained. The outcomes were any limitation of lower body ADL (walking across a small room, bathing, transferring from a bed to a chair, and using the toilet) and limitation on the walk test over subsequent 5-year follow-up period. General Estimation Equation (GEE) was used to estimate lower body disability over time. Results: Weight change of 5% or more occurred in 42.3% of the participants; 21.7% lost weight, 20.6% gained weight, and 57.7% had stable weight. Using GEE analysis, with stable weight as the reference, weight loss of 5% or more was associated with greater risk of any lower body ADL limitation (odds ratio (OR)=1.43, 95% confidence interval (CI)=1.06,1.95) and walking limitation (OR=1.35, 95% CI=1.03,1.76) after controlling for sociodemographic variables and BMI at baseline. Weight gain of 5% or more was associated with greater risk of any lower body ADL limitation (OR=1.39, 95% CI=1.02,1.89), after controlling for sociodemographic variables and BMI at baseline. When medical conditions, handgrip muscle strength, high depressive symptomatology, cognitive function, and hospitalization were added to the equation, the relationship between 2-year weight change (>5% loss or >5% gain) and lower body disability decreased. Conclusion: Health conditions and muscle strength partially mediate the association between weight loss or gain and future loss of ability to walk and independently perform ADLs. [source]

Deaths Between Bedrails and Air Pressure Mattresses

JOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 6 2002
Steven H. Miles MD
OBJECTIVES: To describe how patients die by becoming trapped between therapeutic air pressure mattresses and bed rails. DESIGN: A retrospective review of all voluntary reports deaths in beds with air mattresses that can be found in the Food and Drug Administration's on-line databases of adverse medical events that cover 1994 to 2001. SETTING: Death reports come from manufacturers, medical staff, and coroners and describe deaths in hospitals, nursing homes, and home care, although type of care site is often not given. MEASUREMENTS: Event descriptions were reviewed to determine how the person became entrapped in the rail and how responsibility for the event was allocated. RESULTS: There were 35 deaths involving many product lines. Twenty-one deaths involved overlay air mattresses placed on top of a regular mattress. Thirteen patients died in beds with built-in air mattresses. Compression of the mattress allowed an off-center person to slide against the rail where reexpansion of the mattress kept the person compressed against the rail. Two patterns were seen. In one, the mattress bunched up behind a person who was lying on the side of the bed, pushing the neck against a bedrail. In the second type, a patient died after sliding off the bed and having the neck or chest compressed between the rail and bed. Manufacturers attributed the deaths to poor clinical decision-making or inadequate monitoring. CONCLUSIONS: Lethal asphyxiation in beds with air pressure mattresses is a variant of bedrail-mattress entrapment that requires redesign by bed manufacturers and risk awareness by clinicians. [source]

Cohesive-driven particle circulation in the solids conveying zone of a single-screw extruder

ADVANCES IN POLYMER TECHNOLOGY, Issue 2 2008
Michael R. Thompson
Abstract Aspects of heat transfer within the solids conveying zone of a single-screw extruder were studied by using a specially constructed drum testing apparatus. Experiments were conducted with linear low-density polyethylene, polystyrene (PS), and polypropylene (PP) samples by examining their transient temperature profile while the heated drum was stationary or moving. In accordance with classic solids conveying theory, the granular beds of PP and PS remained as plugs while the drum rotated. In such cases, the dominant modes of heat transfer for these systems are conduction through the contact area of a particle and conduction through the interstitial gas. An exception to this behavior was found with PE, in which the bed temperature increased more rapidly while the drum rotated. Visual observations of the bed showed that the particles circulated in the presence of shear and that this complex flow pattern increased in velocity as the drum temperature approached the onset temperature for melting the PE material. With strong correlation between the rate of circulation and the temperature rise in the bed, the movement of particles was assumed to act in a convective heat transfer mode bringing about more uniform heating of the polymer. The circulation phenomenon was attributed to dominant adhesive forces at the particle,drum interface overcoming the cohesive strength of the bulk. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:74,88, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20121 [source]

Water absorption properties of phosphate glass fiber-reinforced poly-,-caprolactone composites for craniofacial bone repair

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008
Levent Onal
Abstract The moisture uptake of polymers and composites has increasing significance where these materials are specified for invasive, long-term medical applications. Here we analyze mass gain and the ensuing degradation mechanisms in phosphate glass fiber reinforced poly-,-caprolactone laminates. Specimens were manufactured using in situ polymerization of ,-caprolactone around a bed of phosphate glass fibers. The latter were sized with 3-aminopropyltriethoxysilane to control the rate of modulus degradation. Fiber content was the main variable in the study, and it was found that the moisture diffusion coefficient increased significantly with increasing fiber volume fraction. Diffusion, plasticization, and leaching of constituents appear to be the dominant aspects of the process over these short-term tests. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source]

Quality of cardiopulmonary resuscitation on manikins: on the floor and in the bed

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2009
H. JÄNTTI
Background: In general, in-hospital resuscitation is performed in a bed and out-of-hospital resuscitation on the floor. The surface under the patient may affect the cardiopulmonary resuscitation (CPR) quality; therefore, we evaluated CPR quality (the percentage of chest compressions of correct depth) and rescuer's fatigue (the mean compression depth minute by minute) when CPR is performed on a manikin on the floor or in the bed. Methods: Forty-four simulated cardiac arrest scenarios of 10 min were treated by intensive care unit (ICU) nurses in pairs using a 30 : 2 chest compression-to-ventilation ratio. The rescuer who performed the compressions was changed every 2 min. CPR was randomly performed either on the floor or in the bed without a backboard; in both settings, participants kneeled beside the manikin. Results: A total number of 1060 chest compressions, 44% with correct depth, were performed on the floor; 1068 chest compressions were performed in the bed, and 58% of these were the correct depth. These differences were not significant between groups. The mean compression depth during the scenario was 44.9±6.2 mm (mean±SD) on the floor and 43.0±5.9 mm in the bed (P=0.3). The mean chest compression depth decreased over time on both surfaces (P<0.001), indicating rescuer fatigue, but this change was not different between the groups (P=0.305). Conclusions: ICU nurses perform chest compression as effectively on the floor as in the bed. The mean chest compression depth decreases over time, but the surface had no significant effect. [source]