Home About us Contact
|
Home About us Contact | ||
|
|
||
Bed.
Kinds of Bed. Selected AbstractsOutcomes of eating disorders: A systematic review of the literature,INTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 4 2007Nancy D. Berkman PhD Abstract Objective: The RTI International-University of North Carolina at Chapel Hill Evidence-based Practice Center systematically reviewed evidence on factors associated with outcomes among individuals with anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED) and whether outcomes differed by sociodemographic characteristics. Method: We searched electronic databases including MEDLINE and reviewed studies published from 1980 to September, 2005, in all languages against a priori inclusion/exclusion criteria and focused on eating, psychiatric or psychological, or biomarker outcomes. Results: At followup, individuals with AN were more likely than comparisons to be depressed, have Asperger's syndrome and autism spectrum disorders, and suffer from anxiety disorders including obsessive-compulsive disorders. Mortality risk was significantly higher than what would be expected in the population and the risk of suicide was particularly pronounced. The only consistent factor across studies relating to worse BN outcomes was depression. A substantial proportion of individuals continue to suffer from eating disorders over time but BN was not associated with increased mortality risk. Data were insufficient to draw conclusions concerning factors associated with BED outcomes. Across disorders, little to no data were available to compare results based on sociodemographic characteristics. Conclusion: The strength of the bodies of literature was moderate for factors associated with AN and BN outcomes and weak for BED. © 2007 by Wiley Periodicals, Inc. Int J Eat Disord 2007 [source] Long-term stability of eating disorder diagnosesINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue S3 2007Manfred M. Fichter MD Abstract Objective: Data on the stability of eating disorder (ED) diagnoses (DSM-IV) over 12 years are presented for a large sample (N = 311) of female eating disordered patients with anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED). Method: Assessments were made at the beginning of therapy and 2-, 6-, and 12-year follow-ups. Diagnoses were derived from the Structured Inventory for Anorexic and Bulimic Eating Disorders. Possible diagnostic outcome categories were AN, BN, BED, NOS, no ED, and deceased. Results: At all follow-ups, more patients changed from AN or BED to BN than vice versa. No diagnostic crossover from AN to BED or vice versa occurred. BED showed the greatest variability and AN had the greatest stability over time. While the long-term outcome of BN and BED is similar, AN had a considerably worse long-term outcome than either BN or BED. Conclusion: Of the ED diagnoses, AN was most stable and BED most variable. The considerable diagnostic flux between BN and BED and similarities in course and outcome of BN and BED point to common biological and psychological maintaining processes. AN and BED are nosologically quite distant. © 2007 by Wiley Periodicals, Inc. Int J Eat Disord 2007 [source] Evaluating binge eating disorder in children: Development of the children's binge eating disorder scale (C-BEDS)INTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 1 2007Jennifer R. Shapiro PhD Abstract Objective: Binge eating disorder (BED) may manifest itself differently in children than adults. Recently researchers have proposed provisional criteria for measuring BED in children. The purpose of this study was to develop a brief, simple, structured, interviewer-administered scale (C-BEDS) to measure BED in children according to the provisional criteria and to compare diagnostic results with SCID diagnoses. Method: A total of 55 children between the ages of 5 and 13 were interviewed with both the SCID and the C-BEDS. Results: There was a significant association between the two measures (p = .001). Both measures adequately identified children with binge eating behaviors. Conclusion: Both the provisional criteria and the C-BEDS may be developmentally appropriate for use with children, although the C-BEDS may be a better screening instrument as it quickly identified children with subsyndromal BED. If used by physicians and other health providers, this brief measure may assist with identifying early onset binge eating behaviors and avoiding the associated consequences, including adult BED, obesity, and other comorbidities. © 2006 by Wiley Periodicals, Inc. Int J Eat Disord 2006 [source] Laboratory studies of binge eating disorderINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue S1 2003B. Timothy Walsh Abstract Introduction Because of questions about the accuracy of reported food intake, and in order to study psychological and environmental factors which might affect eating, a number of investigators have examined the eating behavior of individuals with binge eating disorder (BED) under controlled conditions that permit food consumption to be measured. Methods Published studies that evaluated the eating behavior of individuals with BED in a laboratory were reviewed. Results In laboratory meals, individuals with BED consumed more kilocalories than individuals of similar weight who did not meet criteria for BED. These differences are observed consistently when subjects are asked to binge eat and when they are not. Conclusions In a laboratory setting, individuals with BED exhibit objectively abnormal eating behavior. These data support, but do not prove, the validity of BED as a diagnostic entity. © 2003 by Wiley Periodicals, Inc. Int J Eat Disord 34: S30,S38, 2003. [source] Self-harm and substance use in a community sample of Black and White women with binge eating disorder or bulimia nervosaINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 4 2002Faith-Anne Dohm Abstract Objective This study evaluated rates of self-harm and substance use in women with either bulimia nervosa (BN) or binge eating disorder (BED) and assessed whether differences in self-harm and substance use are related to sexual or physical abuse. Method Alcohol abuse, self-harm, and use or abuse of various illicit drugs were evaluated in a sample of 53 women with BN and 162 women with BED. Results Self-harm and substance use generally did not differentiate BED and BN cases, but rates of self-harm and substance use were elevated among women with a history of sexual or physical abuse relative to women without such a history. Discussion Elevated rates of self-harm and substance use may not be related uniquely to BN diagnostic status, but may be related to a characteristic shared by women with BN and BED, such as a history of sexual or physical abuse. © 2002 by Wiley Periodicals, Inc. Int J Eat Disord 32: 389,400, 2002. [source] The role of the ,-adrenergic receptor in the leg vasoconstrictor response to orthostatic stressACTA PHYSIOLOGICA, Issue 3 2009M. Kooijman Abstract Aim:, The prompt increase in peripheral vascular resistance, mediated by sympathetic ,-adrenergic stimulation, is believed to be the key event in blood pressure control during postural stress. However, despite the absence of central sympathetic control of the leg vasculature, postural leg vasoconstriction is preserved in spinal cord-injured individuals (SCI). This study aimed at assessing the contribution of both central and local sympathetically induced ,-adrenergic leg vasoconstriction to head-up tilt (HUT) by including healthy individuals and SCI, who lack central sympathetic baroreflex control over the leg vascular bed. Methods:, In 10 controls and nine SCI the femoral artery was cannulated for drug infusion. Upper leg blood flow (LBF) was measured bilaterally using venous occlusion strain gauge plethysmography before and during 30° HUT throughout intra-arterial infusion of saline or the non-selective ,-adrenergic receptor antagonist phentolamine respectively. Additionally, in six controls the leg vascular response to the cold pressor test was assessed during continued infusion of phentolamine, in order to confirm complete ,-adrenergic blockade by phentolamine. Results:, During infusion of phentolamine HUT still caused vasoconstriction in both groups: leg vascular resistance (mean arterial pressure/LBF) increased by 10 ± 2 AU (compared with 12 ± 2 AU during saline infusion), and 13 ± 3 AU (compared with 7 ± 3 AU during saline infusion) in controls and SCI respectively. Conclusion:, Effective ,-adrenergic blockade did not reduce HUT-induced vasoconstriction, regardless of intact baroreflex control of the leg vasculature. Apparently, redundant mechanisms compensate for the absence of sympathetic ,-adrenoceptor leg vasoconstriction in response to postural stress. [source] In Vivo Perfusion of Human Skin Substitutes With Microvessels Formed by Adult Circulating Endothelial Progenitor CellsDERMATOLOGIC SURGERY, Issue 2 2008ELAINE F. KUNG MD BACKGROUND At present, tissue-engineered human skin substitutes (HSSs) mainly function as temporary bioactive dressings due to inadequate perfusion. Failure to form functional vascular networks within the initial posttransplantation period compromises cell survival of the graft and its long-term viability in the wound bed. OBJECTIVES Our goal was to demonstrate that adult circulating endothelial progenitor cells (EPCs) seeded onto HSS can form functional microvessels capable of graft neovascularization and perfusion. MATERIALS AND METHODS Adult peripheral blood mononuclear cells (PBMCs) underwent CD34 selection and endothelial cell (EC) culture conditions. After in vitro expansion, flow cytometry verified EC phenotype before their incorporation into HSS. After 2 weeks in vivo, immunohistochemical analysis, immunofluorescent microscopy, and microfil polymer perfusion were performed. RESULTS CD34+ PBMCs differentiated into EPC demonstrating characteristic EC morphology and expression of CD31, Tie-2, and E-selectin after TNF,-induction. Numerous human CD31 and Ulex europaeus agglutinin-1 (UEA-1) microvessels within the engineered grafts (HSS/EPCs) inosculated with recipient murine circulation. Limitation of murine CD31 immunoreactivity to HSS margins showed angiogenesis was attributable to human EPC at 2 weeks posttransplantation. Delivery of intravenous rhodamine-conjugated UEA-1 and microfil polymer to HSS/EPCs demonstrated enhanced perfusion by functional microvessels compared to HSS control without EPCs. CONCLUSION We successfully engineered functional microvessels in HSS by incorporating adult circulating EPCs. This autologous EC source can form vascular conduits enabling perfusion and survival of human bioengineered tissues. [source] Vegetation and topographic controls on sediment deposition and storage on gully beds in a degraded mountain areaEARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2009Armando Molina Abstract Active gully systems developed on highly weathered or loose parent material are an important source of runoff and sediment production in degraded areas. However, a decrease of land pressure may lead to a return of a partial vegetation cover, whereby gully beds are preferred recolonization spots. Although the current knowledge on the role of vegetation on reducing sediment production on slopes is well developed, few studies exist on the significance of restoring sediment transport pathways on the total sediment budget of degraded mountainous catchments. This study in the Ecuadorian Andes evaluates the potential of vegetation to stabilize active gully systems by trapping and retaining eroded sediment in the gully bed, and analyses the significance of vegetation restoration in the gully bed in reducing sediment export from degraded catchments. Field measurements on 138 gully segments located in 13 ephemeral steep gullies with different ground vegetation cover indicate that gully bed vegetation is the most important factor in promoting short-term (1,15 years) sediment deposition and gully stabilization. In well-vegetated gully systems ( , 30% of ground vegetation cover), 0.035 m3 m,1 of sediment is deposited yearly in the gully bed. Almost 50 per cent of the observed variance in sediment deposition volumes can be explained by the mean ground vegetation cover of the gully bed. The presence of vegetation in gully beds gives rise to the formation of vegetated buffer zones, which enhance short-term sediment trapping even in active gully systems in mountainous environments. Vegetation buffer zones are shown to modify the connectivity of sediment fluxes, as they reduce the transport efficiency of gully systems. First calculations on data on sediment deposition patterns in our study area show that gully bed deposition in response to gully bed revegetation can represent more than 25 per cent of the volume of sediment generated within the catchment. Our findings indicate that relatively small changes in landscape connectivity have the potential to create strong (positive) feedback loops between erosion and vegetation dynamics. Copyright © 2009 John Wiley & Sons, Ltd. [source] Long-term landscape evolution: linking tectonics and surface processesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 3 2007Paul Bishop Abstract Research in landscape evolution over millions to tens of millions of years slowed considerably in the mid-20th century, when Davisian and other approaches to geomorphology were replaced by functional, morphometric and ultimately process-based approaches. Hack's scheme of dynamic equilibrium in landscape evolution was perhaps the major theoretical contribution to long-term landscape evolution between the 1950s and about 1990, but it essentially ,looked back' to Davis for its springboard to a viewpoint contrary to that of Davis, as did less widely known schemes, such as Crickmay's hypothesis of unequal activity. Since about 1990, the field of long-term landscape evolution has blossomed again, stimulated by the plate tectonics revolution and its re-forging of the link between tectonics and topography, and by the development of numerical models that explore the links between tectonic processes and surface processes. This numerical modelling of landscape evolution has been built around formulation of bedrock river processes and slope processes, and has mostly focused on high-elevation passive continental margins and convergent zones; these models now routinely include flexural and denudational isostasy. Major breakthroughs in analytical and geochronological techniques have been of profound relevance to all of the above. Low-temperature thermochronology, and in particular apatite fission track analysis and (U,Th)/He analysis in apatite, have enabled rates of rock uplift and denudational exhumation from relatively shallow crustal depths (up to about 4 km) to be determined directly from, in effect, rock hand specimens. In a few situations, (U,Th)/He analysis has been used to determine the antiquity of major, long-wavelength topography. Cosmogenic isotope analysis has enabled the determination of the ,ages' of bedrock and sedimentary surfaces, and/or the rates of denudation of these surfaces. These latter advances represent in some ways a ,holy grail' in geomorphology in that they enable determination of ,dates and rates' of geomorphological processes directly from rock surfaces. The increasing availability of analytical techniques such as cosmogenic isotope analysis should mean that much larger data sets become possible and lead to more sophisticated analyses, such as probability density functions (PDFs) of cosmogenic ages and even of cosmogenic isotope concentrations (CICs). PDFs of isotope concentrations must be a function of catchment area geomorphology (including tectonics) and it is at least theoretically possible to infer aspects of source area geomorphology and geomorphological processes from PDFs of CICs in sediments (,detrital CICs'). Thus it may be possible to use PDFs of detrital CICs in basin sediments as a tool to infer aspects of the sediments' source area geomorphology and tectonics, complementing the standard sedimentological textural and compositional approaches to such issues. One of the most stimulating of recent conceptual advances has followed the considerations of the relationships between tectonics, climate and surface processes and especially the recognition of the importance of denudational isostasy in driving rock uplift (i.e. in driving tectonics and crustal processes). Attention has been focused very directly on surface processes and on the ways in which they may ,drive' rock uplift and thus even influence sub-surface crustal conditions, such as pressure and temperature. Consequently, the broader geoscience communities are looking to geomorphologists to provide more detailed information on rates and processes of bedrock channel incision, as well as on catchment responses to such bedrock channel processes. More sophisticated numerical models of processes in bedrock channels and on their flanking hillslopes are required. In current numerical models of long-term evolution of hillslopes and interfluves, for example, the simple dependency on slope of both the fluvial and hillslope components of these models means that a Davisian-type of landscape evolution characterized by slope lowering is inevitably ,confirmed' by the models. In numerical modelling, the next advances will require better parameterized algorithms for hillslope processes, and more sophisticated formulations of bedrock channel incision processes, incorporating, for example, the effects of sediment shielding of the bed. Such increasing sophistication must be matched by careful assessment and testing of model outputs using pre-established criteria and tests. Confirmation by these more sophisticated Davisian-type numerical models of slope lowering under conditions of tectonic stability (no active rock uplift), and of constant slope angle and steady-state landscape under conditions of ongoing rock uplift, will indicate that the Davis and Hack models are not mutually exclusive. A Hack-type model (or a variant of it, incorporating slope adjustment to rock strength rather than to regolith strength) will apply to active settings where there is sufficient stream power and/or sediment flux for channels to incise at the rate of rock uplift. Post-orogenic settings of decreased (or zero) active rock uplift would be characterized by a Davisian scheme of declining slope angles and non-steady-state (or transient) landscapes. Such post-orogenic landscapes deserve much more attention than they have received of late, not least because the intriguing questions they pose about the preservation of ancient landscapes were hinted at in passing in the 1960s and have recently re-surfaced. As we begin to ask again some of the grand questions that lay at the heart of geomorphology in its earliest days, large-scale geomorphology is on the threshold of another ,golden' era to match that of the first half of the 20th century, when cyclical approaches underpinned virtually all geomorphological work. Copyright © 2007 John Wiley & Sons, Ltd. [source] Development of the saltation system under controlled environmental conditionsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2002Samantha ArnoldArticle first published online: 24 JUN 200 Abstract The transport of sand by the wind occurs predominantly by the process of saltation. Following the entrainment of sand by an above threshold wind, the saltation system is regulated by the mutual interaction of the atmospheric boundary-layer, the sand cloud and the sand bed. Despite existing data on the spatial and temporal development of the sand transport system, very little is known about the development of the saltation system towards equilibrium. Results are presented from wind-tunnel experiments that were designed to address the simultaneous spatial and temporal development of the saltation system, with and without artificial sand feed. The development of the saltation system was monitored over a streamwise length of 8 m during a period of 3600 s. Mass flux data were measured simultaneously at 1 m intervals by the downwind deployment of seven Aarhus sand traps. Wind velocity data were collected throughout the experiments. The downwind spatial development of the saltation system is manifested by an overshoot in mass flux and friction velocity prior to declining towards a quasi-equilibrium. Mass flux overshoots at approximately 4 m downwind, in remarkable agreement with existing data of a comparable scale. Friction velocity overshoots at approximately 6 m downwind, a result not previously witnessed in saltation studies. The overshoot of mass flux prior to the overshoot in friction velocity is a spatial manifestation of the time lag between the entrainment of grains and the deceleration of the wind by the grains in transport. Temporally, the development of the saltation system is controlled by the availability of entrainable grains from the sand bed. Through time the saltation system develops from a transport-limited to a supply-limited system. The depletion of the sand bed through time limits the appropriateness of the assumption of ,equilibrium' for the universal prediction of mass flux. Copyright © 2002 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 PolandEARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2002Jolanta, 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] Crust strength: a wind tunnel study of the effect of impact by saltating particles on cohesive soil surfacesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2001M. A. Rice Abstract A wind tunnel study examined the effect of distributions of saltating particles on sediment surfaces which were characterized by distributions of their tensile strength. The sediments consisted of varying proportions of large sand-sized particles with a fine particle cement. The energies of the impacting particles and the surface strengths were compared with the mass of material lost from the surface. It is important to consider distributions of parameters rather than mean values only, since abrasion and erosion may occur from surfaces not predicted from average strength and saltation velocities. At the impact velocities used in this study (mean velocity 4·4 m s,1, with standard deviation of 0·51), surfaces containing less than 12 per cent fine material were easily eroded, but insignificant erosion occurred when the fine particle content exceeded 60 per cent. Small amounts of cementing material were easily ruptured, allowing the large sand grains to be moved (largely in creep) by the bombarding particles. A significant amount of energy was lost to the bed. As the percentage of fine material increased, the surface became more difficult to break up and less energy was lost to the bed. The probability that erosion will occur for known energy distributions of impacting particles and surface strength can be calculated and the mass loss increases exponentially with a decrease in the percentage of fine cementing particles. Copyright © 2001 John Wiley & Sons, Ltd. [source] An experimental study on the ripple,dune transitionEARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2001André 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] Contrast Echocardiography: Clinical UtilityECHOCARDIOGRAPHY, Issue 2000Gerald Maurer M.D. This article reviews the advances made by the echocardiography contrast agents from their first appearance in the early 1970s with homemade preparations up to the new generation of transpul-monary contrast agents made of small microbubbles capable of transversing the lung's capillary bed. The great progress in contrast agent development has kept pace with the progress made by echocar-diographic equipment, thus making the study of myocardial perfusion in the clinical settings a near-future reality. This article also discusses the medical need that myocardial contrast echo has the potential to satisfy. [source] Role of the charge in continuous beds in the chiral separation of hydroxy acids by ligand-exchange capillary electrochromatographyELECTROPHORESIS, Issue 17 2003Oliver Lecnik Abstract This paper deals with the chiral separation of hydroxy acids using diallyl-dimethylammonium chloride as a positive charge-providing agent in the continuous bed. The chiral continuous bed was prepared by in situ copolymerization of monomers, including an L -4-hydroxyproline derivative as a chiral selector. This phase was applied to the chiral separation of hydroxy monocarboxylic acids and hydroxy dicarboxylic acids, respectively. The influence of both the selector concentration and the charge-providing agent on retention and separation was investigated. [source] Validation of a tool to safely triage selected patients with chest pain to unmonitored bedsEMERGENCY MEDICINE AUSTRALASIA, Issue 4 2002Ronald V Sultana Abstract Objective: To externally validate a chest pain protocol that triages low risk patients with chest pain to an unmonitored bed. Methods: Retrospective study of all patients admitted from the emergency department of a tertiary referral public teaching hospital with an admission diagnosis of ,unstable angina' or suspected ischemic chest pain. Data was collected on adverse outcomes and analysed on the basis of intention-to-treat according to the chest pain protocol. Results: There were no life-threatening arrhythmias, cardiac arrests or deaths within the first 72 h of admission in the group assigned to an unmonitored bed by the chest pain protocol ([0/244]; 0.0%: 95% confidence interval 0.0,1.5%). Four patients had an uncomplicated myocardial infarction, two patients had recurrent ischemic chest pain and one patient developed acute pulmonary oedema ([7/244]; 2.9%: 95% confidence interval 1.2,5.8%). Conclusion: This retrospective study externally validated the chest pain protocol. Care in a monitored bed would not have altered outcomes for patients triaged to an unmonitored bed by the chest pain protocol. Compared to current guidelines, application of the chest pain protocol could increase the availability of monitored beds. [source] Biofilm Growth and Bed Fluidization in a Fluidized Bed Reactor Packed with Support Materials of Low Density,ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 2 2004R.A. Saucedo-Terán Abstract Support materials of low-density for fluidized bed reactors provide several operational advantages, including lower energy requirements and proper biofilm growth balance. The aim of this investigation was to study the extent of biofilm growth and bed fluidization in an experimental reactor, using polyester resin (,pr,=,1220,kg/m3) and vitrified expanded perlite (,vep,=,1710,kg/m3) as alternative support materials to conventional silica sand. A noteworthy amount of biofilm was observed to be attached to both support materials from the very beginning of the bioreactor operation. Nevertheless, there were significant variations in biofilm growth and activity over the course of the experimental trials. For both perlite and polyester beds, the highest biofilm mass and the highest total number of mesophilic bacteria were observed between the 7th and the 10th day, showing a steady state trend at the end of the experimental runs. The chemical oxygen demand (COD) removal levels were concomitant with biofilm mass and total mesophilic bacteria changes, although the polyester bed efficiency was slightly higher than that for the perlite bed. As expected, the polyester bed was fluidized at a lower re-circulation flow compared to the perlite bed. Reactor back-washing was not required for these support materials since biomass excess was adequately separated by means of a special internal device. The efficiencies of removal of organic matter achieved were acceptable (up to 78,%) despite the low volume of the support material (25,%) and the low hydraulic retention time (30,min). [source] On the ignition of fuel beds by firebrands,,FIRE AND MATERIALS, Issue 1 2006Samuel L. Manzello Abstract An experimental apparatus has been built to investigate the ignition of fuel beds as a result of impact with burning firebrands. The apparatus allowed the ignition and deposition of both single and multiple firebrands onto the target fuel bed. The moisture content of the fuel beds used was varied, and the fuels considered were pine needle beds, shredded paper beds and crevices constructed of cedar shingles. Firebrands were simulated by machining wood (Pinus ponderosa) into small disks of uniform geometry and the size of the disks was varied. Firebrand simulation was necessary because it is difficult to capture and characterize firebrands from an actual burning object. The firebrand ignition apparatus was installed into the fire emulator/detector evaluator to investigate the influence of an air flow on the ignition propensity of fuel beds. The results of this study are presented and compared with relevant studies in the literature. Published in 2005 by John Wiley & Sons, Ltd. [source] A comparison of the relative contributions of temporal and spatial variation in the density of drifting invertebrates in a Dorset (U.K.) chalk streamFRESHWATER BIOLOGY, Issue 8 2008MARTIN W. NEALE Summary 1. Invertebrate drift is commonly investigated in streams, with the majority of studies focussed on temporal (typically diel) variation. In comparison, few studies have investigated spatial variation in drift and there is little consensus among them. We tested the hypothesis that spatial variation in invertebrate drift is as important as temporal variation. 2. The density of drifting invertebrates in a chalk stream was sampled using an array of nets arranged to determine vertical, lateral and longitudinal variation. Samples were collected at dawn, during the day, at dusk and by night, on four separate monthly occasions. Insecta and Crustacea were analysed separately to identify the effect of differing life history strategies. The density of drifting debris was also recorded, to act as a null model. 3. Time of day and vertical position together explained the majority of the variance in invertebrate drift (79% for Insecta and 97% for Crustacea), with drift densities higher at dusk and night, and nearer the stream bed. Independently, time of day (38%, Insecta; 52%, Crustacea) and vertical position (41%, Insecta; 45%, Crustacea) explained a similar amount of the observed variance. Month explained some of the variance in insect drift (9%) but none for Crustacea. 4. Variation in the density of drifting debris showed little in common with invertebrate drift. There was little variation associated with time of day and only 27% of the observed variation in debris could be explained by the factors investigated here, with month explaining the largest proportion (20%). We suggest the difference in drifting debris and invertebrates provides further evidence for a strong behavioural component in invertebrate drift. 5. Spatial variation in invertebrate drift can be of the same order of magnitude as the much-described diel temporal variation. The extent of this spatial variation poses problems when attempting to quantify invertebrate drift and we recommend that spatial replication should be incorporated into drift studies. [source] Habitat selection and diel distribution of the crustacean zooplankton from a shallow Mediterranean lake during the turbid and clear water phasesFRESHWATER BIOLOGY, Issue 3 2007BRUNO B. CASTRO Summary 1. The fish fauna of many shallow Mediterranean Lakes is dominated by small-bodied exotic omnivores, with potential implications for fish,zooplankton interactions still largely unknown. Here we studied diel variation in the vertical and horizontal distribution of the crustacean plankton in Lake Vela, a shallow polymictic and eutrophic lake. Diel sampling was carried out on three consecutive days along a horizontal transect, including an open-water station and a macrophyte (Nymphaea alba) bed. Since transparency is a key determinant of the predation risk posed by fish, the zooplankton sampling campaigns were conducted in both the turbid (autumn) and clear water (spring) phases. 2. In the turbid phase, most taxa were homogeneously distributed along the vertical and horizontal axes in the three consecutive days. The only exception was for copepod nauplii, which showed vertical heterogeneity, possibly as a response to invertebrate predators. 3. In the clear water phase, most zooplankton taxa displayed habitat selection. Vertically, the general response consisted of a daily vertical migration (DVM), despite the limited depth (1.6 m). Horizontally, zooplankters showed an overall preference for the pelagic zone, independent of the time of the day. Such evidence is contrary to the postulated role of macrophytes as an anti-predator refuge for the zooplankton. 4. These vertical (DVM) and horizontal (macrophyte-avoidance) patterns were particularly conspicuous for large Daphnia, suggesting that predation risk from size-selective predators (fish) was the main factor behind the spatial heterogeneity of zooplankton in the spring. Thus, the difference in the zooplankton spatial distribution pattern and habitat selection among seasons (turbid and clear water phases) seems to be mediated the predation risk from fish, which is directly related to water transparency. 5. The zooplankton in Lake Vela have anti-predator behaviour that minimises predation from fish. We hypothesise that, due to the distinct fish community of shallow Mediterranean lakes, aquatic macrophytes may not provide adequate refuge to zooplankters, as seen in northern temperate lakes. [source] Structural patterns in coarse gravelriver beds: typology, survey and assessment of the roles of grain size and river regimeGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 1 2002Lea Wittenberg The concept of river-bed stability as indexed by the occurrence of stable bed forms was examined in humid-temperate perennial streams and in Mediterranean ephemeral streams. The study examined the structural patterns of bed forms and their spatial distribution between temperate-humid and Mediterranean streams. Study sites in Northumberland, UK, and Mt. Carmel, Israel, were selected for their morphometric similarity, despite the contrast in climate, vegetation and hydrological regime. Fieldwork was based on a large number of Wolman grain size distributions and structure measurements along cross-sections at seven sites; Differences in mean grain size of bed structures were estimated using the general linear model (GLM) procedure and Duncan's multiple range test. Based on field evidence, river-bed configurations were divided into structural categories, according to the depositional setting of each measured particle on the river bed. Statistical analysis confirmed former qualitative descriptions of small-scale bed forms. The study identified spatial segregation in bed form distribution. In general, 30,40%of the bed material in the surveyed perennial streams was clustered, in contrast to approximately 10%in the ephemeral counterparts. The sorting index revealed higher values for the perennial streams, namely 2.39,3.59 compared with 1.73,2.07 for the ephemeral counterparts. It is suggested that the degree of sediment sorting and the proportion of clusters are strongly related. Sediment sorting, sediment supply and the hydrological regime explain the mechanism of cluster formation. It is assumed that climate shifts or human interference within river basins might affect the regional characteristic flood hydrograph, and consequently alter the sedimentary character of the river bed. In the case where river bed stability is reduced owing to changes in cluster bed form distribution, rivers that normally do not yield a significant amount of sediment might be subject to notable sedimentation problems. [source] Ruptured pseudoaneurysm of the internal maxillary artery complicating CT-guided fine-needle aspiration in an irradiated, surgical bedHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 12 2007John C. Oh BA Abstract Background. CT-guided fine-needle aspiration (FNA) is a safe procedure, but major complications can occur rarely. Pseudoaneurysm rupture in the head and neck region following CT-guided FNA is an emergency that can result in life-threatening hemorrhage. This case emphasizes the salient risk factors for pseudoaneurysm formation and rupture in the head and neck region following CT-guided FNA. Methods. A patient was seen with oral and facial hemorrhage as a result of a ruptured pseudoaneurysm 11 weeks following CT-guided FNA in a previously irradiated surgical bed. Results. The patient was treated with coil embolization in and around the pseudoaneurysm and discharged without any further complications. Conclusions. Although CT-guided FNA is a safe and effective procedure, some patients may be at increased risk for rare but major complications. Caution should be used in proceeding with CT-guided FNA in an irradiated surgical bed of the head and neck. © 2007 Wiley Periodicals, Inc. Head Neck, 2007 [source] Surgical margin determination in head and neck oncology: Current clinical practice.HEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 11 2005Neck Society Member Survey, The results of an International American Head Abstract Background. Our aim was to investigate the ways in which surgeons who perform head and neck ablative procedures on a regular basis define margins, how they use frozen sections to evaluate margins, and the effect of chemoradiation on determining tumor margins. Methods. A custom-designed questionnaire was mailed to members of the American Head and Neck Society asking members how they evaluate and define tumor margins. Results. Of 1500 surveys mailed, 476 completed surveys were received. The most common response for distance of a clear pathologic margin was >5 mm on microscopic evaluation. A margin containing carcinoma in situ was considered a positive margin by most, but most did not consider a margin containing dysplasia a positive margin. When initial frozen section margins are positive for tumor and further resection results in negative frozen section margins, 90% consider the patient's margin negative. Most surgeons sample the frozen section from the surgical bed rather than from the main specimen. Nearly half use wider margins when resecting tumors treated with neoadjuvant therapy. When resecting recurrent or residual tumors treated with previous chemoradiation therapy, most resect to the pretreatment margin. Conclusions. No uniform criteria to define a clear surgical margin exist among practicing head and neck surgeons. Most head and neck surgeons consider margins clear if resection completed after an initial positive frozen section margin reveals negative margins, but this view is not shared by all. Most surgeons take frozen sections from the surgical bed; however, error may occur when identifying the positive margin within the surgical bed. The definition of a clear tumor margin after chemoradiation is unclear. These questions could be addressed in a multicenter prospective trial. © 2005 Wiley Periodicals, Inc. Head Neck27: XXX,XXX, 2005 [source] Reflections on Retelling a Renaissance MurderHISTORY AND THEORY, Issue 4 2002Thomas V. Cohen This mischievously artful essay plays out on several levels; think of them as storeys of an imaginary castle much like the real, solid, central Italian one it explores and expounds. On its own ground floor, the essay recounts a gruesome murder, a noble husband's midnight revenge upon his wife and upon her bastard lover, his own half,brother, in her castle chamber, in bed. In sex. Of course. The murder itself is pure Renaissance, quintessential Boccaccio or Bandello, but the aftermath, in fort and village, is more singular, more ethnographically delightful, as castle and village trace a ceremonious passage from frozen limbo to fluid grief and storytelling, finally set in motion by the arrival of the dead wife's brother. Meanwhile, one flight up, the essay retells my own investigation of the real castle's geometry, as I clambered through rooms, peered out windows, prowled the roof, and scanned blueprints seeking the places of the plotters' plots. In an expository attic, I lodge reflections on my teaching stratagems, as I led a first,year seminar into detection's crafts and exposition's ploys. All the while, on its rooftop, this essay dances among fantastical chimneys and turrets of high theory and literary practice, musing on the patent irony of artful artifice, which evokes both the irony and the pathos of scholars' cool histories about hot deeds and feelings. Art suggests we authors had best hide ourselves, unlike normal essayists, so as not to spoil the show. But, I posit, our self,effacement is so conspicuous that it proclaims our presence, as in fact it should, and, by so doing, trumpets the necessary tensions of our artifice and craft. Thus artfulness itself nicely both proclaims and celebrates the bittersweet frustrations of historians' and readers' quest for knowledge and, especially, for experience of a lost past. [source] Transient deformation of a poroelastic channel bedINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2002P.C. Hsieh Abstract The coupled transient response of a poroelastic bed form due to stream flow and non-linear water waves is investigated numerically. The theory of potential flow is applied to channel flow while Biot's theory of poroelasticity (J. Appl. Phys. 1962; 33(4):1482) is adopted to deal with the deformable porous bed. A boundary-fitted co-ordinate system is used to calculate the variation in the bed form. The result of a simple periodic wave form over a soft poroelastic bed agrees well with the analytical solution of Hsieh et al. (J. Eng. Mech., ASCE 2000; 126(10):1064). However, due to the rapidly damping second dilatational wave inside the soft poroelastic bed, the solution for transient bed form near the interface is not easy to compute accurately. In order to overcome this difficulty, a simplified numerical model based on the boundary layer correction concept proposed by Hsieh et al. (2000) is established, which neglects Darcy's terms. The transient deformation of an irregular poroelastic bed that includes a trench and a downward step at the channel bed is simulated successfully. Copyright © 2002 John Wiley & Sons, Ltd. [source] Dynamic response of soft poroelastic bed to linear water waves,a boundary layer correction approachINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 7 2001Ping-Cheng Hsieh Abstract According to Chen et al. (Journal of Engineering Mechanics, ASCE 1997; 123(10):1041,1049.) a boundary layer exists within the porous bed and near the homogeneous-water/porous-bed interface when oscillatory water waves propagate over a soft poroelastic bed. This boundary layer makes the evaluation of the second kind of longitudinal wave inside the soft poroelastic bed very inaccurate. In this study, the boundary layer correction approach for the poroelastic bed is applied to the boundary value problem of linear oscillatory water waves propagating over a soft poroelastic bed. After the analyses of length scale and order of magnitude of physical variables are done, a perturbation expansion for the boundary layer correction approach based on two small parameters is proposed and solved. The solutions are carried out for the first and third kind of waves throughout the entire domain. The second kind of wave which disappears outside the boundary layer is solved systematically inside the boundary layer. The results are compared with the linear wave solutions of Huang and Song (Journal of Engineering Mechanics, ASCE 1993; 119:1003,1020.) to confirm the validity. Moreover, a simplified boundary layer correction formulation which is expected to be very useful in numerical computation is also proposed. Copyright © 2001 John Wiley & Sons, Ltd. [source] An eigenvector-based linear reconstruction scheme for the shallow-water equations on two-dimensional unstructured meshesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 1 2007Sandra Soares Frazăo Abstract This paper presents a new approach to MUSCL reconstruction for solving the shallow-water equations on two-dimensional unstructured meshes. The approach takes advantage of the particular structure of the shallow-water equations. Indeed, their hyperbolic nature allows the flow variables to be expressed as a linear combination of the eigenvectors of the system. The particularity of the shallow-water equations is that the coefficients of this combination only depend upon the water depth. Reconstructing only the water depth with second-order accuracy and using only a first-order reconstruction for the flow velocity proves to be as accurate as the classical MUSCL approach. The method also appears to be more robust in cases with very strong depth gradients such as the propagation of a wave on a dry bed. Since only one reconstruction is needed (against three reconstructions in the MUSCL approach) the EVR method is shown to be 1.4,5 times as fast as the classical MUSCL scheme, depending on the computational application. Copyright © 2006 John Wiley & Sons, Ltd. [source] Mathematical modelling of hydrogen storage in a LaNi5 hydride bedINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2003Yuksel Kaplan Abstract This paper presents a numerical investigation of hydrogen storage in a metal hydrid bed. For this purpose, a two-dimensional mathematical model which considers complex heat and mass transfer and fluid flow during the hydriding process is accomplished in this study. The coupled differential equations are solved with numerical method based on integrations of governing equation over finite control volumes. The driving force for fluid flow is considered to be pressure difference due to the temperature distribution in the system. It is found that fluid flow enhances the local hydriding rate in the system by driving the hot fluid to the colder regions. The numerical results were found to agree satisfactorily with the experimental data available in the literature. Copyright © 2003 John Wiley & Sons, Ltd. [source] Gasification of char particles in packed beds: analysis and resultsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2001S. 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] Theoretical performance analysis of the multi-stage gas,solid fluidized bed air preheaterINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2001Sang Il Park Abstract The multi-stage fluidized bed can be used to preheat the combustion air by recovering the waste heat from the exhaust gas from industrial furnaces. The dilute-phase fluidized bed may be formed to exclude the excessive pressure drop across the multi-stage fluidized bed. But, in this case, the solid particles do not reach to the thermal equilibrium due to relatively short residence time in each layer of fluidized bed. In this study, a theoretical analysis on the dilute phase multistage fluidized bed heat exchanger was performed. A parameter related to the degree of thermal equilibrium between gas and solid particles at the dilute-phase fluidized beds was derived. Using this parameter, a relatively simple expression was obtained for the thermal efficiencies of the multi-stage fluidized bed heat exchanger and air preheater. Copyright © 2001 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||