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Terms modified by Temporary Selected AbstractsShare Repurchase Offers and Liquidity: An Examination of Temporary and Permanent EffectsFINANCIAL MANAGEMENT, Issue 2 2008Nandkumar Nayar Open-market repurchase programs do not allow for precise estimates of share buy-back intensity to measure liquidity effects. To circumvent the uncertainty surrounding the quantity and timing of shares truly acquired in repurchase programs and to measure their long-term impact, we examine Dutch auctions and fixed-price tender offers. We investigate both the temporary and permanent liquidity effects of share repurchase programs and find that the improvement in liquidity is transitory and limited to the tender period when the firm's offer to repurchase shares is outstanding. Improvements in liquidity over longer intervals appear to be the result of an overall price improvement and a reduction in volatility rather than the result of structural change in market dynamics. [source] Bioaccessibility studies of ferro-chromium alloy particles for a simulated inhalation scenario: A comparative study with the pure metals and stainless steelINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 3 2010Klara Midander Abstract The European product safety legislation, REACH, requires that companies that manufacture, import, or use chemicals demonstrate safe use and high level of protection of their products placed on the market from a human health and environmental perspective. This process involves detailed assessment of potential hazards for various toxicity endpoints induced by the use of chemicals with a minimum use of animal testing. Such an assessment requires thorough understanding of relevant exposure scenarios including material characteristics and intrinsic properties and how, for instance, physical and chemical properties change from the manufacturing phase, throughout use, to final disposal. Temporary or permanent adverse health effects induced by particles depend either on their shape or physical characteristics, and/or on chemical interactions with the particle surface upon human exposure. Potential adverse effects caused by the exposure of metal particles through the gastrointestinal system, the pulmonary system, or the skin, and their subsequent potential for particle dissolution and metal release in contact with biological media, show significant gaps of knowledge. In vitro bioaccessibility testing at conditions of relevance for different exposure scenarios, combined with the generation of a detailed understanding of intrinsic material properties and surface characteristics, are in this context a useful approach to address aspects of relevance for accurate risk and hazard assessment of chemicals, including metals and alloys and to avoid the use of in vivo testing. Alloys are essential engineering materials in all kinds of applications in society, but their potential adverse effects on human health and the environment are very seldom assessed. Alloys are treated in REACH as mixtures of their constituent elements, an approach highly inappropriate because intrinsic properties of alloys generally are totally different compared with their pure metal components. A large research effort was therefore conducted to generate quantitative bioaccessibility data for particles of ferro-chromium alloys compared with particles of the pure metals and stainless steel exposed at in vitro conditions in synthetic biological media of relevance for particle inhalation and ingestion. All results are presented combining bioaccessibility data with aspects of particle characteristics, surface composition, and barrier properties of surface oxides. Iron and chromium were the main elements released from ferro-chromium alloys upon exposure in synthetic biological media. Both elements revealed time-dependent release processes. One week exposures resulted in very small released particle fractions being less than 0.3% of the particle mass at acidic conditions and less than 0.001% in near pH-neutral media. The extent of Fe released from ferro-chromium alloy particles was significantly lower compared with particles of pure Fe, whereas Cr was released to a very low and similar extent as from particles of pure Cr and stainless steel. Low release rates are a result of a surface oxide with passive properties predominantly composed of chromium(III)-rich oxides and silica and, to a lesser extent, of iron(II,III)oxides. Neither the relative bulk alloy composition nor the surface composition can be used to predict or assess the extent of metals released in different synthetic biological media. Ferro-chromium alloys cannot be assessed from the behavior of their pure metal constituents. Integr Environ Assess Manag 2010;6:441,455. © 2009 SETAC [source] A Bayesian Approach to Real Options: The Case of Distinguishing between Temporary and Permanent ShocksTHE JOURNAL OF FINANCE, Issue 5 2010STEVEN R. GRENADIER ABSTRACT Traditional real options models demonstrate the importance of the "option to wait" due to uncertainty over future shocks to project cash flows. However, there is often another important source of uncertainty: uncertainty over the permanence of past shocks. Adding Bayesian uncertainty over the permanence of past shocks augments the traditional option to wait with an additional "option to learn." The implied investment behavior differs significantly from that in standard models. For example, investment may occur at a time of stable or decreasing cash flows, respond sluggishly to cash flow shocks, and depend on the timing of project cash flows. [source] Robotic Replacement of the Descending Aorta in Human CadaverARTIFICIAL ORGANS, Issue 9 2006Norihiko Ishikawa Abstract:, Robot-assisted replacement of the thoracic aorta was performed in a human cadaver. Temporary shunt bypass was established by inserting a left axillary artery catheter and directing it through the aortic arch toward the right femoral artery through the abdominal aorta. The technique utilized the da Vinci surgical system inserted through the 4-cm supramammary working port and two additional thoracoscopic ports. The working port allowed the introduction of an endoscope, endoscopic instruments, and artificial graft and suture materials. The aorta was dissected using the robotic instruments and was clamped with two transthoracic clamps. After transaction of the aorta, a 20-mm polytetrafluoroethylene graft was cut and an end-to-end anastomosis was then performed with running 3-0 Prolene sutures with robotic instruments. The robotic system provides superior optics and allows for enhanced dexterity. Minimally invasive robotic replacement of the descending aorta is an effective procedure and may add benefits for both surgeon and patients. [source] Sentinel lymph node biopsy as guidance for central neck dissection in patients with papillary thyroid carcinomaCANCER, Issue 7 2008Jong-Lyel Roh MD Abstract BACKGROUND. Occult lymph node metastasis of papillary thyroid carcinoma (PTC) can be detected by sentinel lymph node (SLN) biopsy, but studies in larger patient cohorts undergoing complete central neck dissection may be required to assess the diagnostic accuracy of SLN. Therefore, the authors prospectively assessed the usefulness of SLN biopsy for the detection of central lymph node metastasis in patients with differentiated PTC who had no suspicious cervical lymphadenopathy. METHODS. After peritumoral injection of methylene blue, SLN biopsy was performed in 50 patients with newly diagnosed PTC who had no palpable or ultrasound (US)-detected lymph node involvement. After SLN biopsy, all patients underwent total thyroidectomy and central neck dissection. The diagnostic accuracy of intraoperative SLN sampling was calculated by comparison with the final pathologic diagnosis. RESULTS. SLNs were identified in 46 of 50 patients (92%); of these, 14 SLNs were positive and 32 SLNs were negative on intraoperative frozen sections. One patient had a positive SLN in the jugular region and subsequently underwent modified radical neck dissection. Final pathologic examination revealed that 18 patients (36%), including 4 who had negative SLNs, had central lymph node metastasis. Thus, the sensitivity, specificity, accuracy, and positive and negative predictive values of SLN biopsy were 77.8%, 100%, 92%, 100%, and 88.9%, respectively. Temporary and permanent hypocalcemia developed in 19 patients and 1 patient, respectively. There were no direct complications of SLN sampling. CONCLUSIONS. SLN biopsy in patients with PTC without gross clinical or US lymph node involvement was able to detect occult metastasis with high accuracy and may have the potential to select patients who require central neck dissection. Cancer 2008. © 2008 American Cancer Society. [source] They don't want to be temporaries: similarities between temps and core workersJOURNAL OF ORGANIZATIONAL BEHAVIOR, Issue 8 2007Maria José Chambel This study investigated the impact of employment status (temporary/regular) on the employee,organization relationship in samples from two firms employing both temps (n,=,234) and regular or core (n,=,204) workers. Temps and regular workers held similar beliefs regarding the nature of their employment relationship. However, among those temps for whom temporary work was their preferred status, the employment relationship was less socioemotional and more economic than was the case for other workers. When these temps preferred regular employment, their relationships were high socioemotional and low economic, comparable with that of core workers. A employee,organization relationship high on socioemotional terms was positively related to satisfaction with the organization, an attitude which in turn mediated the relationship between employment relationship and employees' performance and civic virtue behaviors (behaviors as assessed by their supervisors). Copyright © 2007 John Wiley & Sons, Ltd. [source] The co-evolution of functional and numerical flexibility: do technology and networking matter?NEW TECHNOLOGY, WORK AND EMPLOYMENT, Issue 3 2007Irini Voudouris This study explores the relationship between functional and numerical flexibility and the moderating effects of information and communication technology use and networking by investigating the relative predictive power of two approaches: contingency and configuration. The direction of the relationship between the two modes of flexibility depends on the type of flexible staffing arrangement used. Contractors and temporaries are shown to serve different aims and to have different opportunities for evolution. [source] p -Phenylenediamine sensitization is more prevalent in central and southern European patch test centres than in Scandinavian: results from a multicentre studyCONTACT DERMATITIS, Issue 6 2009Jacob Pontoppidan Thyssen Background:, Positive patch test reactions to p -phenylenediamine (PPD) are common. PPD is used in oxidative hair dyes and is also present in dark henna temporary ,tattoos'. Cross-sensitization to other contact allergens may occur. Because subjects sensitized to PPD are at risk of clinically severe reactions upon hair dyeing, there is a need for ,current' prevalence data on PPD sensitization. Objectives:, To compare PPD patch test results from dermatitis patients tested between 2003 and 2007 in 10 European patch test centres and to analyse the causes and determine relevance of positive PPD patch test reactions. Materials:, Patch testing was performed using PPD (1% free base in petrolatum from Trolab (Almirall Hermal GmbH, Reinbeck, Germany) or Chemotechnique (Malmö, Sweden), equivalent to 0.090 mg/cm2 in the TRUE® test from MEKOS Laboratories AS). Statistical analysis was performed using the chi-squared test. Results:, The weighted average prevalence was 4.6% among 21 515 patients. PPD sensitization occurred more often in centres located in Central and Southern Europe than in Scandinavian centres (odds ratio = 2.40; 95% confidence interval = 2.07,2.78). The overall proportion of positive patch test reactions to PPD that were registered as being of either current or ,past' relevance was high (weighted average 53.6% and 20.3%, respectively). Consumer hair dyeing was the most prominent cause of PPD sensitization (weighted average 41.8%). Furthermore, occupational hair dye exposure (10.6%) and cross-sensitization to textile dyes (12.6%) were frequently reported. Conclusions:, PPD sensitization caused by exposure to hair dyes is frequent and remains a present problem for patients visiting contact dermatitis clinics, especially in patch test centres located in Central and Southern Europe. [source] ANTISOCIAL BEHAVIOR AND YOUTH GANG MEMBERSHIP: SELECTION AND SOCIALIZATIONCRIMINOLOGY, Issue 1 2004RACHEL A. GORDON We examine whether gang membership is associated with higher levels of delinquency because boys predisposed to delinquent activity are more likely than others to join. We use 10 years of longitudinal data from 858 participants of the Pittsburgh Youth Study to identify periods before, during and after gang membership. We build on prior research by controlling for ages and calendar time, by better accounting for gang memberships that occurred before the study began, and by using fixed effects statistical models. We find more evidence than has been found in prior studies that boys who join gangs are more delinquent before entering the gang than those who do not join. Even with such selective differences, however, we replicate research showing that drug selling, drug use, violent behaviors and vandalism of property increase significantly when a youth joins a gang. The delinquency of peers appears to be one mechanism of socialization. These findings are clearest in youth self-reports, but are also evident in reports from parents and teachers on boys' behavior and delinquency. Once we adjust for time trends, we find that the increase in delinquency is temporary, that delinquency falls to pre-gang levels when boys leave gangs. [source] Side Effects and Complications of Fractional Laser Photothermolysis: Experience with 961 TreatmentsDERMATOLOGIC SURGERY, Issue 3 2008EMMY M. GRABER MD BACKGROUND A novel 1,550-nm erbium-doped laser (Fraxel, Reliant Technologies Inc.) has been shown to be effective in the treatment of photodamaged skin and scars with minimal postoperative recovery; however, studies evaluating its side effects and complication rates have been limited. PURPOSE The purpose was to determine the frequency and range of side effects and complications associated with fractional photothermolysis treatment. METHODS A retrospective evaluation of 961 successive 1,550-nm erbium-doped laser treatments in patients of various skin phototypes (I,V) was conducted in a single center. Side effects and complications of treatment, including time of onset and duration, were identified and tabulated. Patient demographics and laser parameters were also assessed. RESULTS Seventy-three treatments (7.6%) resulted in development of complications. The most frequent complications were acneiform eruptions (1.87%) and herpes simplex virus outbreaks (1.77%). Side effects and complications were equally distributed across different ages, skin types, body locations, laser parameters, and underlying skin conditions, except for postinflammatory hyperpigmentation, which occurred with increased frequency in patients with darker skin phototypes. CONCLUSIONS Fractional laser skin treatment is associated with a relatively low complication rate. Side effects and complications observed in this study were temporary and did not result in long-term or significantly severe sequelae (e.g., scarring). [source] Self-Limited Adverse Reaction to Human-Derived Collagen Injectable ProductDERMATOLOGIC SURGERY, Issue 10 2000Brent R. Moody MD Background. Soft tissue augmentation is a common and safe cosmetic and reconstructive procedure. Objective. We describe a temporary and self-limited adverse reaction to Dermalogen. Methods. Clinical and histologic evaluation following an adverse reaction noted at a Dermalogen skin test site. Results. Our patient was found to have a foreign body reaction to Dermalogen. Conclusion. Dermalogen, a form of acellular human collagen, may induce a foreign body reaction. [source] Effects of implementation of psychiatric guidelines on provider performance and patient outcome: systematic reviewACTA PSYCHIATRICA SCANDINAVICA, Issue 6 2007S. Weinmann Objective:, To identify evidence from comparative studies on the effects of psychiatric guideline implementation on provider performance and patient outcome. Effects of different implementation strategies were reviewed. Method:, Articles published between 1966 and March 2006 were searched through electronic databases and hand search. A systematic review of comparative studies of structured implementation of specific psychiatric guidelines was performed. Rates of guideline adherence, provider performance data, illness detection and diagnostic accuracy rates were extracted in addition to patient relevant outcome data. Results:, Eighteen studies (nine randomized-controlled trials, six non-randomized-controlled studies and three quasiexperimental before-and-after studies) were identified. Effects on provider performance or patient outcome were moderate and temporary in most cases. Studies with positive outcomes used complex multifaceted interventions or specific psychological methods to implement guidelines. Conclusion:, There is insufficient high-quality evidence to draw firm conclusions on the effects of implementation of specific psychiatric guidelines. [source] Housing anxiety and multiple geographies in post-tsunami Sri LankaDISASTERS, Issue 4 2009Camillo Boano Tsunami intervention has been an extraordinary and unprecedented relief and recovery operation. This article underlines the complexities posed by shelter and housing intervention in post-tsunami Sri Lanka, revealing a pragmatic, reductionist approach to shelter and housing reconstruction in a contested and fragmented environment. Competition, housing anxiety and buffer zone implementation have resulted in compulsory villagisation inland, stirring feelings of discrimination and tension, and becoming major obstacles to equitable rebuilding of houses and livelihoods. A new tsunami geography has been imposed on an already vulnerable conflict-based geography, in which shelter has been conceived as a mono-dimensional artefact. An analysis of the process and outcomes of temporary and permanent post-tsunami housing programmes yields information about the extent to which shelter policies and programmes serve not only physical needs but ,higher order' objectives for a comprehensive and sustainable recovery plan. [source] Temporary self-expanding metallic stents and pneumatic dilation for the treatment of achalasia: a prospective study with a long-term follow-upDISEASES OF THE ESOPHAGUS, Issue 5 2010Y.-D. Li SUMMARY The present study compares the efficacy of a self-expanding metallic stent (SEMS, diameter of 30 mm) and pneumatic dilation for the long-term clinical treatment of achalasia. A total of 155 patients diagnosed with achalasia were allocated for pneumatic dilation (n= 80, group A) or a temporary, 30-mm diameter SEMS (n= 75, group B). The SEMSs were placed under fluoroscopic guidance and removed by gastroscopy 4,5 days after placement. Data on clinical symptoms, complications, and long-term clinical outcomes were collected, and follow-up observations were performed at 6 months and at 1, 3,5, 5,8, 8,10, and >10 years, postoperatively. Pneumatic dilation and stent placement were technically successful in all of the patients. There were no significant differences in technique success, 30-day mortality, or complications between the two groups. The clinical remission rate in group A was significantly lower than that in group B at 1, 1,3, 3,5, 5,8 and, >10 years (P < 0.05), while the cumulative clinical failure rate in group A (66%, 53/80) was higher than that in group B (92%, 6/75). The mean primary patency in group B was significantly longer than that in group A (4.2 vs 2.1 years, respectively; P < 0.001). A temporary, 30-mm diameter SEMS was associated with a better long-term clinical efficacy in the treatment of patients with achalasia as compared with treatment with pneumatic dilation. [source] Integrating species life-history traits and patterns of deforestation in amphibian conservation planningDIVERSITY AND DISTRIBUTIONS, Issue 1 2010C. G. Becker Abstract Aim, To identify priority areas for amphibian conservation in southeastern Brazil, by integrating species life-history traits and patterns of deforestation. Location, State of São Paulo, Brazil. Methods, We used the software Marxan to evaluate different scenarios of amphibian conservation planning. Our approach differs from previous methods by explicitly including two different landscape metrics; habitat split for species with aquatic larvae, and habitat loss for species with terrestrial development. We evaluated the effect of habitat requirements by classifying species breeding habitats in five categories (flowing water, still water permanent, still water temporary, bromeliad or bamboo, and terrestrial). We performed analyses using two scales, grid cells and watersheds and also considered nature preserves as protected areas. Results, We found contrasting patterns of deforestation between coastal and inland regions. Seventy-six grid cells and 14 watersheds are capable of representing each species at least once. When accounting for grid cells already protected in state and national parks and considering species habitat requirements we found 16 high-priority grid cells for species with one or two reproductive habitats, and only one cell representing species with four habitat requirements. Key areas for the conservation of species breeding in flowing and permanent still waters are concentrated in southern state, while those for amphibians breeding in temporary ponds are concentrated in central to eastern zones. Eastern highland zones are key areas for preserving species breeding terrestrially by direct or indirect development. Species breeding in bromeliads and bamboos are already well represented in protected areas. Main conclusions, Our results emphasize the need to integrate information on landscape configuration and species life-history traits to produce more ecologically relevant conservation strategies. [source] Hydrologic and geomorphic effects of temporary ice-dammed lake formation during jökulhlaupsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2003Matthew J. Roberts Abstract Glacial outburst ,oods (jökulhlaups) occur frequently in glaciated environments, and the resultant ,ooding causes geomorphic change and, in some instances, damage to local infrastructure. During some jökulhlaups, ,oodwater is stored temporarily in ice-marginal locations. In July 1999, a linearly rising jökulhlaup burst from Sólheimajökull, Iceland. During this remarkable event, subglacial ,oodwater pooled transiently in two relict ice-dammed lake basins, before draining suddenly back into Sólheimajökull. The signi,cance of such rapid formation and attendant drainage of temporary ice-dammed lakes during jökulhlaups has not been addressed. Consequently, this paper: (i) assesses the hydrologic and geomorphic effects of temporary ice-dammed lake formation caused by lake-basin ,retro-,lling'; and (ii) discusses the impact and signi,cance of transient retro-,lling under jökulhlaup conditions. Pre- and post-,ood ,eldwork at Sólheimajökull enabled the impact and signi,cance of lake-basin retro-,lling to be assessed. Field evidence demonstrates that the July 1999 jökulhlaup had an unusually rapid rise to peak discharge, resulting in subglacial ,oodwater being purged to ice-marginal locations. The propensity for temporary retro-,lling was controlled by rapid expulsion of ,oodwater from Sólheimajökull, coincident with locations suitable for ,oodwater storage. Floodwater inundated both ice-marginal lake basins, permitting signi,cant volumes of sediment deposition. Coarse-grained deltas prograding from the ice margin and boulders perched on scoured bedrock provide geomorphic records of sudden retro-,lling. The depositional characteristics of lake-basin deposits at Sólheimajökull are similar to jökulhlaup sediments documented in proglacial settings elsewhere; however, their depositional setting and association with ice-marginal landforms is distinctive. Findings suggest that temporary ice-dammed lake formation and drainage has the capacity to alter the shape of the ,ood hydrograph, especially if drainage of a temporary lake is superimposed on the original jökulhlaup. Deposits associated with lake-basin retro-,lling have a long-term preservation potential that could help to identify temporary ice-dammed lake formation in modern and ancient glacial environments. Copyright © 2003 John Wiley & Sons, Ltd. [source] How do paedomorphic newts cope with lake drying?ECOGRAPHY, Issue 4 2003Mathieu Denoël Paedomorphosis, in which adult individuals retain larval traits, is widespread in newts and salamanders. Most evolutionary models predict the maintenance of this life-history trait in favourable aquatic habitats surrounded by hostile terrestrial environments. Nevertheless, numerous ponds inhabited by paedomorphic individuals are unpredictable and temporary. In an experimental framework, I showed that paedomorphic newts were able to metamorphose and thus survive in the absence of water. However, the mere decrease of water level or the life space do not seem to induce metamorphosis in paedomorphs. On the contrary, drying up induces almost all individuals to move on land and after that to colonize other aquatic sites located nearby. Such terrestrial migrations allow survival in drying conditions without metamorphosis as long as the distances of terrestrial migration are short. These results are consistent with the presence of paedomorphs in drying ponds and are in favor of classic optimality models predicting metamorphosis in unfavorable environments. [source] PROMOTING INNOVATION IN THE ELECTRICITY INDUSTRYECONOMIC AFFAIRS, Issue 2 2010L. Lynne Kiesling Smart metering can bring significant benefits to electricity markets by allowing customers to reduce demand or increase supply when generation capacity is temporarily scarce. To reap the full efficiency and environmental benefits of this technology, regulators must allow price volatility and free entry into the market. The efficiency gains are enormous as both demand and supply will be affected by both temporary and longer-lasting price changes. Experiments have shown the value of this approach. [source] Cyclical Clusters in Global Circuits: Overlapping Spaces in Furniture Trade FairsECONOMIC GEOGRAPHY, Issue 4 2008Dominic Power abstract This article contributes to an understanding of temporary or event-based economic phenomena in economic and industrial geography by drawing on research conducted on the furniture and interior design industry. It argues that trade fairs should be seen not simply as temporary industry gatherings, but as central, though temporary, spaces for knowledge and market processes that symbolize microcosms of the industry they represent and function as effective marketplaces. It suggests that these temporary events should be viewed not as isolated from one another, but as arranged together in an almost continual global circuit. In this sense, trade fairs are less temporary clusters than they are cyclical clusters; they are complexes of overlapping spaces that are scheduled and arranged in such a way that spaces can be reproduced, reenacted, and renewed over time. Although actual fairs are short-lived events, their presence in the business cycle has lasting consequences for the organization of markets and industries and for the firms of which they are comprised. [source] Share Repurchase Offers and Liquidity: An Examination of Temporary and Permanent EffectsFINANCIAL MANAGEMENT, Issue 2 2008Nandkumar Nayar Open-market repurchase programs do not allow for precise estimates of share buy-back intensity to measure liquidity effects. To circumvent the uncertainty surrounding the quantity and timing of shares truly acquired in repurchase programs and to measure their long-term impact, we examine Dutch auctions and fixed-price tender offers. We investigate both the temporary and permanent liquidity effects of share repurchase programs and find that the improvement in liquidity is transitory and limited to the tender period when the firm's offer to repurchase shares is outstanding. Improvements in liquidity over longer intervals appear to be the result of an overall price improvement and a reduction in volatility rather than the result of structural change in market dynamics. [source] Market Reaction to Changes in the S&P SmallCap 600 IndexFINANCIAL REVIEW, Issue 3 2006S. Gowri Shankar G12; G14 Abstract Firms added to (deleted from) the S&P 600 index experience a significant price increase (decrease) at announcement. Firms that newly enter (exit) the S&P universe experience a larger price increase (decrease) than firms that move between S&P indexes. Trading volumes are higher after the announcement and institutional ownership increases (decreases) following index additions (deletions). However, the price and volume effects are temporary and are fully reversed within 60 days, in contrast to the permanent effects reported for S&P 500 changes. Our results support the temporary price-pressure hypothesis and are similar to results reported for Russell 2000 index changes. [source] Subtle top-down control of a freshwater meiofaunal assemblage by juvenile fishFRESHWATER BIOLOGY, Issue 9 2010GERARD DINEEN Summary 1. Top-down control of prey assemblages by fish predators has been clearly demonstrated in lakes (for zooplankton prey) and rivers (for macroinvertebrate prey). Fish predation can have a significant impact on the body size of prey assemblages; often large-bodied prey are reduced in abundance, and indirect facilitation of small-bodied prey occurs potentially initiating a trophic cascade. 2. Benthic communities in aquatic ecosystems also include a numerous and functionally important meiofaunal-sized component, but in freshwaters the impact of fish predation on meiofaunal assemblages is unknown. We used a laboratory microcosm study to explore the impact of juvenile fish predation on the abundance and size structure of a riverine meiofaunal assemblage. 3. The presence of fish in our microcosms had no significant effect on overall meiofaunal (temporary and permanent) abundance. However, for the Copepoda, we found the first evidence of top-down control of freshwater meiofaunal assemblages; in microcosms with juvenile fish, the abundance of large-bodied Copepoda was significantly reduced, whereas small-bodied Copepoda were significantly more abundant suggesting indirect facilitation. 4. We conclude that predation by juvenile fish can alter the structure of freshwater meiofaunal assemblages, although we do not yet know whether these relatively subtle changes are overwhelmed by large-scale events such as flow disturbances. [source] Effects of drying regime on microbial colonization and shredder preference in seasonal woodland wetlandsFRESHWATER BIOLOGY, Issue 3 2008MARTYN D. INKLEY Summary 1. Energy budgets of wetlands in temperate deciduous forests are dominated by terrestrially derived leaf litter that decays under different drying conditions depending on autumn precipitation. We compared decay rates and microbial colonization of maple leaves under different inundation schedules in a field experiment, and then conducted a laboratory study on shredder preference. In the field, litter bags either remained submerged (permanent), were moved to a dried part of the basin once and then returned (semi-permanent), or were alternated between wet and dry conditions for 8 weeks (temporary). 2. There was no difference in decay rates among treatments, but leaves incubated under permanent and semi-permanent conditions had higher fungal and bacterial biomass, and lower C : N ratios than those incubated under alternating drying and wetting conditions. 3. To determine the effects of these differences in litter nutritional quality on shredder preference, we conducted a laboratory preference test with larvae of leaf-shredding caddisflies that inhabit the wetland. Caddisflies spent twice as much time foraging on permanent and semi-permanent litter than on litter incubated under temporary conditions. 4. There is considerable variation among previous studies in how basin drying affects litter breakdown in wetlands, and no previous information on shredder preference. We found that frequent drying in a shallow wetland reduces the nutritional quality of leaf litter (lower microbial biomass and nitrogen content), and therefore preference by invertebrate shredders. These results suggest that inter-annual shifts in drying regime should alter detritus processing rates, and hence the mobilization of the energy and nutrients in leaf litter to the wetland food web. [source] The potential role of waterbirds in dispersing invertebrates and plants in arid AustraliaFRESHWATER BIOLOGY, Issue 2 2008A. J. GREEN Summary 1. The role of waterbirds as vectors of plants and invertebrates within and between arid-zone wetlands is poorly understood. We present the first detailed study of passive dispersal by nomadic birds in Australasia. We investigated the numbers and types of invertebrate and plant propagules within freshly collected faecal samples as well as their viability. We compared dispersal among Grey Teal (Anas gracilis), Eurasian Coot (Fulica atra) and Black Swan (Cygnus atratus) in the Macquarie Marshes, a complex of temporary to semi-permanent wetlands in New South Wales. 2. When faecal samples (n = 60) were inundated in the laboratory and monitored over 3 weeks, ciliates (75% of samples), nematodes (22%), ostracods (13%) and rotifers (5%) were recorded, with higher taxon richness in coot samples. Faecal samples (n = 71) were also sieved to quantify intact propagules, and ostracod eggs (70% of samples), large branchiopod eggs (31%) and bryozoan statoblasts (31%) were the most abundant invertebrates. Diaspores of 19 plant taxa were recorded, 14 of which were germinated in the laboratory or shown to be viable at the end of germination trials. The abundance and diversity of invertebrate propagules was highest in coot samples, whereas the abundance and diversity of diaspores was highest in teal samples. 3. One Australian Pelican (Pelecanus conspicillatus) sample was obtained and found to contain more taxa and far more propagules than any sample from other waterbirds, suggesting that piscivorous birds might have an important role in the indirect dispersal of propagules ingested by fish. 4. Our results support a role for birds in explaining the distributions of cosmopolitan plant genera such as Lemna, Typha, Myriophyllum and Nitella. The alien plants Ranunculus sceleratus, Medicago polymorpha and Polygonum arenastrum were recorded, demonstrating the potential role of waterfowl in the spread of exotic species. As the frequency and duration of flooding of arid-zone wetlands decreases owing to human activities, the importance of waterbirds in facilitating recolonisation of temporary wetlands is likely to increase. [source] Foraging tactics in alternative heterochronic salamander morphs: trophic quality of ponds matters more than water permanencyFRESHWATER BIOLOGY, Issue 9 2007MATHIEU DENOEL Summary 1. In lentic freshwater habitats, the composition of animal assemblages shifts along a gradient from temporary to permanent basins. When habitats with different degrees of permanence are at the scale of the home range of species, they constitute alternatives in terms of energy acquisition through feeding. 2. In this context, previous studies showed an advantage of metamorphic over paedomorphic tiger salamanders (Ambystoma tigrinum) in temporary ponds which are only available to metamorphs. The aim of this study was to establish whether salamanders obtain similar benefits in ponds that do not differ in water permanence and whether salamanders shifted from detrimental to advantageous ponds. To this end, we determined the feeding habits, body condition and movement patterns of the two morphs in a complex of four permanent and four temporary ponds. 3. Consistent with previous studies, metamorphs consumed higher-quality diets than paedomorphs in term of energy intake. However, these differences occurred because metamorphs consumed fairy shrimp in a single temporary pond. Individual movement patterns confirmed that most of the metamorphs used different aquatic habitats both within and between years and that most of them moved from permanent ponds for breeding towards the most profitable temporary pond in terms of foraging. 4. These results indicate that habitat selection by salamanders is optimal in term of energy intake in metamorphs that use high quality ponds independently of hydroperiod. It seems that both spatial and temporal variation can influence the relative foraging success of each morph. [source] Life history and production of Agapetus quadratus (Trichoptera: Glossosomatidae) in a temporary, spring-fed streamFRESHWATER BIOLOGY, Issue 6 2005MARUXA ÁLVAREZ Summary 1. The life history and trophic basis of production of the caddisfly grazer Agapetus quadratus were studied in the torrent Gorg Blau, a spring-fed stream on the island of Majorca that dries annually during summer. 2. Quantitative random samples were taken every 2,3 weeks during an annual surficial flow period, from November 2000 to mid-July 2001. Instars of field-collected larvae were determined by measurements of head width and pronotum length, and the sex of all pupae was determined to study sexual dimorphism and sex ratio. 3. Stage-frequency histograms suggested a trivoltine population, with an average cohort time of 4 months. Larval development was asynchronous, with continuous growth and overlapping generations. Recruitment peaks were identified in mid-November, early March and late June, indicative of winter, spring and summer generations. On average, females were larger than males and the mean sex ratio was 2 : 3 (females : males). Population densities and biomasses derived from the field data were used to calculate production and turnover rate. 4. Annual production of A. quadratus in the torrent Gorg Blau (4.80 g dry mass m,2 year,1) was the highest ever reported for the genus, being comparable with that estimated for some insects with rapid development and multiple cohorts. 5. Estimates of production of A. quadratus were combined with foregut content analysis to estimate the fraction of total production derived from the principal food sources: algae and organic detritus. Algae supported a major proportion of the production of this grazer. 6. The low density of predators characteristic of many temporary streams, and the small amplitudes in discharge and temperature during most of the wet period that characterise the spring habitats might allow high levels of grazer production in this particular Mediterranean stream. [source] The importance of meiofauna to lotic ecosystem functioningFRESHWATER BIOLOGY, Issue 1 2000Christine C. Hakenkamp Summary 1Although meiofauna occur in large numbers in many streams, almost nothing is known about their functional role. 2In other systems, meiofauna influence microbial and organic matter dynamics through consumption and bioturbation. Given that these are important processes in streams, meiofauna have the potential to influence lotic function by changing the quality and availability of organic matter as well as the number and biotic activity of benthic microbes. Selective feeding by meiofauna has the potential to alter the availability of nutrients and organic carbon. 3Meiofauna generally contribute only a small amount to metazoan production and biomass in streams, although exceptions occur. Within a stream, the relative importance of meiofauna may reflect whether the temporary or permanent meiofauna dominate the meiobenthos as well as the season when samples are collected. 4We suggest stream conditions (small sediment grain size, restricted interstitial flow) under which meiofauna have the greatest likelihood of influencing stream ecosystem function. 5Important areas for future research include addressing whether meiofauna feed selectively, whether meiofauna are links or sinks for carbon in streams, and whether bioturbation by meiofauna influences stream ecosystem processes in a predictable manner. [source] Transgenerational plasticity for sexual reproduction and diapause in the life cycle of monogonont rotifers: intraclonal, intraspecific and interspecific variation in the response to crowdingFUNCTIONAL ECOLOGY, Issue 3 2004T. SCHRÖDER Summary 1In monogonont rotifers parthenogenetic reproduction allows population growth, and mictic (sexual) reproduction leads to the production of diapausing eggs. When amictic females are exposed to a mixis stimulus, they produce mictic daughters, whose eggs develop into males or, if fertilized, into diapausing eggs. Experiments showed that mictic offspring production is initiated by crowding in females of Brachionus angularis Gosse 1851, Epiphanes senta (O.F. Müller 1773) and Rhinoglena frontalis Ehrenberg 1853, just as it is in Brachionus calyciflorus Pallas 1766 and B. plicatilis Müller 1786. 2In B. calyciflorus, B. angularis, E. senta and R. frontalis, the propensity of amictic females to respond to crowding by producing mictic female offspring is low in the stem female hatching from a diapausing egg, but then increases after some generations. In many cases, only few mictic offspring are produced by crowded females of the second to the fifth generation, but the maximal response occurs only in later generations. Delayed sexual reproduction in early generations from the resting egg may be advantageous, because it first favours rapid population growth and later on maximizes resting egg production. However, it may be disadvantageous, if unpredictable environmental variation causes a population decline when sexual reproduction is still suppressed. 3The extent to which sexual reproduction is delayed varies among and within species. When strains from populations in temporary and permanent habitats were compared, sexual reproduction was significantly delayed in strains from temporary habitats in all species, whereas in B. calyciflorus and R. frontalis mixis was not significantly delayed in strains from permanent habitats. In E. senta mixis was significantly delayed in clones from both habitat types. 4Within all strains there was significant variation among clones in the propensity to produce mictic offspring, the extent to which sexual reproduction was delayed in the first generations after the stem female hatched, or both. [source] Resolving the enigma of early coastal settlement in the Hawaiian Islands: The stratigraphic sequence of the Wainiha Beach Site in Kaua'iGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 2 2004Mike T. Carson Archaeological excavation has documented stratified cultural deposits at the Wainiha Beach Site in Kaua'i (Hawaiian Islands), beginning with the occupation of a residential structure dated around A.D. 1030,1400. After about A.D. 1400, the excavated area contains abundant evidence of widespread repeated temporary activities ending in the post-Contact era (post-A.D. 1778). The presence of an early permanent residence followed by a later period of temporary activities opposes conventional understanding of a trend from temporary to permanent occupation in similar sites in the Hawaiian Islands. The complete stratigraphic sequence is disclosed here, with reference to formation processes and depositional context of eight major strata documented in a controlled excavation 0.95 m deep. Various human activities (such as digging pits, trampling, etc.) and periodic natural high-energy events (such as tsunami) appear to have altered the upper portions of underlying deposits. Large sections of the earliest human occupation layer were obliterated, and successive episodes of short-lived activities created numerous inconsistencies in the stratigraphy. These results have important implications for interpreting the cultural sequence not only at Wainiha but also at other rather enigmatic beach sites in the Hawaiian Islands and elsewhere. © 2004 Wiley Periodicals, Inc. [source] Clusters, Power and Place: Inequality and Local Growth in Time,SpaceGEOGRAFISKA ANNALER SERIES B: HUMAN GEOGRAPHY, Issue 2 2002Harald Bathelt The argument of this paper is that a deeper appreciation of the nature of the power relationships between firms and the circuits of power that bind them together is key to understanding how clusters function , including how they might emerge and how they might decline. We begin to develop a conceptualization that allows us to generate a deeper understanding of the processes that enable the production and reproduction of enterprise clusters under some combinations of circumstances but not others. The sections of the paper explore: (1) concepts of power and circuits of power including their spatialities; (2) the temporarily stabilized relationships which occur in clusters of economic activity; (3) the openness and permeability of clusters as a way of understanding conditions that foster cluster growth; (4) a tentative integration of concepts. From this reading of the concepts of clustering and power we draw the conclusion that clusters are, at any particular point in time, temporary and transient conjunctures of interfirm relationships. They depend on specific circumstances in ,time,space' and, because of their very transience and specificity, those conditions might be very difficult if not impossible to create through the blunt instruments of policy. 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