Key Processes (key + process)

Distribution by Scientific Domains
Distribution within Life Sciences


Selected Abstracts


Teaching and Learning with Therapists Who Work with Street Children and Their Families

FAMILY PROCESS, Issue 3 2010
JANINE ROBERTS ED.D.
Providing training for people working with some of the most marginalized families in Guatemala and Peru meant establishing credibility as a facilitator; entering organizations as a learner; cocreating training agendas; and working in a format that paralleled a strength-based, resilience focus in therapy. Strategies used for different phases of the work are detailed: multiple ways to gather information, shadowing staff, delivering topics on demand, and creating learning environments with a focus on families as teachers. Key processes included moving in and out of the role of facilitator and participant, entering into the trainings from different vantage points within the organizations, and designing activities with an eye to how they would impact work relationships of staff and clients. RESUMEN Brindar capacitación a personas que trabajan con algunas de las familias más marginadas de Guatemala y Perú implicó establecer credibilidad como facilitador; ingresar en organizaciones como alumno; co-crear agendas de capacitación y trabajar en un formato análogo a un enfoque basado en las virtudes y la resiliencia en terapia. Se detallan las estrategias utilizadas en las diferentes fases del trabajo: distintas maneras de reunir información, observación del personal, charlas a pedido, y creación de ambientes de aprendizaje haciendo hincapié en las familias como maestras. Los procesos clave consistieron en asumir y abandonar el rol de facilitador y participante, iniciar las capacitaciones desde diferentes posiciones de ventaja dentro de las organizaciones y diseñar actividades con miras a cómo repercutirían sobre las relaciones laborales del personal y los clientes. Palabras clave: capacitación colaborativa, niños que trabajan en la calle, terapia familiar en Latinoamérica [source]


Hyporheic and total transient storage in small, sand-bed streams

HYDROLOGICAL PROCESSES, Issue 12 2008
John M. Stofleth
Abstract Key processes in stream ecosystems are linked to hydraulic retention, which is the departure of stream flow from ideal ,plug flow', and reflects fluid movement through surface and hyporheic storage zones. Most existing information about hyporheic exchange is based on flume studies or field measurements in relatively steep streams with beds coarser than sand. Stream tracer studies may be used to quantify overall hydraulic retention, but disaggregation of surface and hyporheic retention remains difficult. A stream tracer approach was used to compute the rates at which stream water is exchanged with water in storage zones (total storage) in short reaches of two small, sand-bed streams under free and obstructed flow conditions. Tracer curves were fit to the one-dimensional transport with inflow storage model OTIS-P. Networks of piezometers were used to measure specific discharge between the stream and the groundwater. In the sand-bed streams studied, parameters describing total retention were in the upper 50% of data compiled from the literature, most of which represented streams with beds coarser than sand. However, hyporheic storage was an insignificant component of total hydraulic retention, representing only 0·01,0·49% of total exchange, and this fraction did not increase after installation of flow obstructions. Total retention did not vary systematically with bed material size, but increased 50,100% following flow obstruction. Removal of roughness elements, such as large wood and debris dams, is detrimental to processes dependent upon transient storage in small, sand-bed streams. Copyright © 2007 John Wiley & Sons, Ltd. [source]


Long-range transport of organic chemicals in the environment

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2009
Martin Scheringer
Abstract The long-range transport (LRT) of organic chemicals in the environment is reviewed, with particular focus on the role of environmental fate and transport models and the relationship between model results and field data. Results from generic multimedia box models, spatially resolved multimedia box models, and atmospheric transport models are highlighted, including conceptual investigations of cold-trap effect and global fractionation as well as results for particular chemicals, such as hexachlorocyclohexanes, DDT, polychlorinated biphenyls, perfluoroocctanoic acid, and polybrominated diphenyl ethers. Comparison of model results to field data shows that in many cases environmental fate models provide a good description of the distribution dynamics observed in the field, with deviations between measured and modeled concentrations around a factor of five. Sorption to atmospheric aerosols as a key process influencing the LRT of semivolatile organic chemicals (SOCs) is discussed, and the need for more measurements of the aerosol,air partitioning of SOCs and of the reactivity of particle-bound chemicals is pointed out. Key findings from field campaigns measuring legacy persistent organic pollutants (POPs) as well as new POPs are summarized. Finally, the relationship between science and politics in the field of POPs is addressed. Research into the LRT of organic chemicals has always occurred in interaction with political activities aiming to reduce the emissions of POPs. Since the late 1990s, the Stockholm Convention and the Aarhus Protocol on POPs have formed an important political context for research concerning POPs; the implementation of these international treaties creates a demand for ongoing research into the LRT of organic chemicals. [source]


Site-directed mutagenesis of selected residues at the active site of aryl-alcohol oxidase, an H2O2 -producing ligninolytic enzyme

FEBS JOURNAL, Issue 21 2006
Patricia Ferreira
Aryl-alcohol oxidase provides H2O2 for lignin biodegradation, a key process for carbon recycling in land ecosystems that is also of great biotechnological interest. However, little is known of the structural determinants of the catalytic activity of this fungal flavoenzyme, which oxidizes a variety of polyunsaturated alcohols. Different alcohol substrates were docked on the aryl-alcohol oxidase molecular structure, and six amino acid residues surrounding the putative substrate-binding site were chosen for site-directed mutagenesis modification. Several Pleurotus eryngii aryl-alcohol oxidase variants were purified to homogeneity after heterologous expression in Emericella nidulans, and characterized in terms of their steady-state kinetic properties. Two histidine residues (His502 and His546) are strictly required for aryl-alcohol oxidase catalysis, as shown by the lack of activity of different variants. This fact, together with their location near the isoalloxazine ring of FAD, suggested a contribution to catalysis by alcohol activation, enabling its oxidation by flavin-adenine dinucleotide (FAD). The presence of two aromatic residues (at positions 92 and 501) is also required, as shown by the conserved activity of the Y92F and F501Y enzyme variants and the strongly impaired activity of Y92A and F501A. By contrast, a third aromatic residue (Tyr78) does not seem to be involved in catalysis. The kinetic and spectral properties of the Phe501 variants suggested that this residue could affect the FAD environment, modulating the catalytic rate of the enzyme. Finaly, L315 affects the enzyme kcat, although it is not located in the near vicinity of the cofactor. The present study provides the first evidence for the role of aryl-alcohol oxidase active site residues. [source]


Habitat selection as a source of inter-specific differences in recruitment of two diadromous fish species

FRESHWATER BIOLOGY, Issue 11 2008
ROBIN HALE
Summary 1For aquatic species with highly dispersive offspring, the addition of new individuals into an area (recruitment) is a key process in determining local population size so understanding the causes of recruitment variability is critical. While three general causative mechanisms have been identified (the supply of individuals, habitat selection and mortality), we have a limited understanding of how variation in each is generated, and the consequences this may have for the spatial and temporal distribution of recruits. 2We examined whether active habitat selection during settlement could be the cause of variability in populations of two diadromous fish species using a field survey and laboratory-based choice experiments. If larval behaviour is important, we predicted there would be inter-specific differences in abundance between sites during the survey, and that larvae would prefer water collected from sites with higher conspecific abundances during the experiments. 3During the field survey, significant differences were detected between two rivers (the Cumberland and Grey), with one species (Galaxias maculatus) found in higher abundances at one site (the Cumberland River) while comparable numbers of a closely related species (Galaxias brevipinnis) were caught at both sites. Laboratory choice experiments were conducted to determine whether larval preferences during settlement could be the cause of these differences. G. maculatus larvae showed a preference for freshwater over saltwater, indicating that the fish may be responding to reduced salinities around river mouths during settlement. The results of a second experiment were consistent with the notion that larval preferences could be the mechanism driving differences in the populations of the two rivers, with G. maculatus preferring water collected from the Cumberland River while G. brevipinnis did not prefer water from either river. 4These results demonstrate that active habitat selection may be important in establishing spatial patterns of larvae at settlement, and that multiple cues are likely to be involved. This study also demonstrates that the behaviours exhibited by individuals can strongly influence the structure and dynamics of populations of aquatic species with complex life cycles. [source]


Relationship between post-fire regeneration and leaf economics spectrum in Mediterranean woody species

FUNCTIONAL ECOLOGY, Issue 1 2009
S. Saura-Mas
Summary 1Recent work has identified global-scale relationships between key leaf traits (leaf economics spectrum). However, it is important to determine whether this approach can be applied at local scale with smaller subsets of species facing similar environments. Since fire is a key process in Mediterranean shrubland dynamics we analyze whether fire-related life-history traits influence the pattern of correlation between the leaf economic spectrum and leaf moisture traits. 2Using structural equation modelling and exploratory path analysis, we developed alternative models to test how interspecific leaf traits are related to the seasonal variation of water content (leaves and shoots) and to the type of post-fire regeneration of Mediterranean woody species. 3This study demonstrates that for these species seasonal variation in water content and fuel moisture would be better predicted by the presence or absence of a trait describing post-fire seedling establishment than by the leaf economic spectrum traits. However, leaf dry matter content (LDMC) is influenced by both the leaf economic spectrum and the post-fire regenerative type. 4Seeder species (those that recruit via seeds immediately after fire) present lower LDMC and higher relative seasonal variation of relative water content (RWCrsv) than non-seeders. We hypothesize that since seeder species mostly evolved under the Mediterranean climate, they developed a particular strategy of drought tolerance (without causing an effect to the relation between the volume occupied by cytoplasm relative to the volume occupied by cell walls), which is the cause of the observed relation between LDMC and RWCrsv. 5This study suggests that the leaves of Mediterranean woody species would follow the general leaf economics spectrum (Wright et al. 2004) but that specific selective forces, such as disturbance regime, acting at regional scale also play a relevant role to explain leaf traits related to water content. [source]


Responses of China's summer monsoon climate to snow anomaly over the Tibetan Plateau

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 6 2003
Prof. Y. F. Qian
Abstract The climatological features of the winter snow depth over the Tibetan Plateau and the summer precipitation in China are diagnosed using datasets obtained from 78 snow observation stations and 160 rainfall stations during 1957 to 1998. The climatic effects of the snow anomaly over the Tibetan Plateau on the regional summer monsoon climate in China are diagnosed and numerically simulated by use of a regional climate model (RegCM2). The singular value decomposition technique is adopted to diagnose the relationships between the previous winter and spring plateau snow depth anomalies and the spring and summer regional precipitation in China. It is found that the snow depth anomaly, especially in winter, is one of the factors influencing precipitation in China; however, it is perhaps not the only one, and even not the most important one. Nevertheless, it is proved that the winter snow anomaly over the Tibetan Plateau is relatively more important than that in spring for the regional precipitation in China. Results of numerical simulations show that the snow anomaly over the plateau has effects that are evident on China's summer monsoon climate. The increase of both snow cover and snow depth can delay the onset and weaken the intensity of the summer monsoon obviously, resulting in a decrease in precipitation in southern China and an increase in the Yangtze and Huaihe River basins. The influence of the winter snow depth is more substantial than that of both the winter snow cover and the spring snow depth. The mechanism of how the plateau snow anomaly influences the regional monsoon climate is briefly analysed. It is found that snow anomalies over the Tibetan Plateau change the soil moisture and the surface temperature through the snowmelt process at first, and subsequently alter heat, moisture and radiation fluxes from the surface to the atmosphere. Abnormal circulation conditions induced by changes of surface fluxes may affect the underlying surface properties in turn. Such a long-term interaction between the wetland and the atmosphere is the key process resulting in later climatic changes. Copyright © 2003 Royal Meteorological Society [source]


Assessment of hypotheses about dispersal in a long-lived seabird using multistate capture,recapture models

JOURNAL OF ANIMAL ECOLOGY, Issue 4 2004
Emmanuelle Cam
Summary 1Dispersal contributes to spatio-temporal variation in population size and is a key process in studies of life history evolution and studies with conservation implications. However, dispersal is still one of the major gaps in our knowledge of ecological dynamics. The very large literature on metapopulation dynamics lacks empirical bases on dispersal and relevant behavioural parameters. We used multistate capture,recapture models (data from 1988 to 2001) to address hypotheses about movement probability and habitat selection within a system of two breeding colonies in Audouin's gulls (Larus audouinii), an endemic species breeding in the Mediterranean and considered as threatened. 2Movement probability varied over time, and differed greatly between the colonies. 3We did not find evidence of an influence of colony size or density of predators on movement probability. 4In dispersers, our results did not support the hypotheses that movement probability between year t and t+ 1 was influenced by mean breeding success in the colony of origin (i.e. an indicator of habitat quality) or the destination colony in year t or t+ 1, or by the ratio of breeding success in these colonies in year t or t + 1 (i.e. quality gradient). 5Overall, movement probability was higher from the smaller colony to the larger, and from the colony with lower breeding success in year t to the more productive one. This provides slight support for two nonexclusive hypotheses about habitat selection (conspecific attraction and conspecific success attraction). 6Movement probability from the smaller, less productive colony was very high in some years, suggesting that the dynamics of both colonies were strongly influenced by adult dispersal. However, in absolute numbers, more individuals moved from the larger, more productive colony to the smaller one. This suggests that the system may function as a source,sink system. 7Use of multistate models to re-assess local survival showed that survival was lower in the less productive colony with higher emigration probability. This may reflect genuine differences in mortality between colonies, or more probably differences in permanent emigration from the study area. [source]


Cell and molecular mechanisms of insulin-induced angiogenesis

JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 11-12 2009
Yan Liu
Abstract Angiogenesis, the development of new blood vessel from pre-existing vessels, is a key process in the formation of the granulation tissue during wound healing. The appropriate development of new blood vessels, along with their subsequent maturation and differentiation, establishes the foundation for functional wound neovasculature. We performed studies in vivo and used a variety of cellular and molecular approaches in vitro to show that insulin stimulates angiogenesis and to elucidate the signalling mechanisms by which this protein stimulates microvessel development. Mice skin injected with insulin shows longer vessels with more branches, along with increased numbers of associated ,-smooth muscle actin-expressing cells, suggesting the appropriate differentiation and maturation of the new vessels. We also found that insulin stimulates human microvascular endothelial cell migration and tube formation, and that these effects occur independently of VEGF/VEGFR signalling, but are dependent upon the insulin receptor itself. Downstream signalling pathways involve PI3K, Akt, sterol regulatory element-binding protein 1 (SREBP-1) and Rac1; inhibition of these pathways results in elimination of endothelial cell migration and tube formation and significantly decreases the development of microvessels. Our findings strongly suggest that insulin is a good candidate for the treatment of ischaemic wounds and other conditions in which blood vessel development is impaired. [source]


Nicotine inhibits human gingival fibroblast migration via modulation of Rac signalling pathways

JOURNAL OF CLINICAL PERIODONTOLOGY, Issue 12 2005
Yiyu Fang
Abstract Aim: Cigarette smoking is a risk factor in the development of periodontal diseases. In addition, a delayed healing process has been shown in smokers compared with non-smokers after periodontal treatment. Cell migration is a key process of wound healing and it is highly regulated by a variety of signalling pathways. The small G protein, Rac, is necessary for cell migration. Our aim was to determine if nicotine disrupted Rac and its downstream signalling proteins, p21-activated kinase 1/2 (PAK1/2), and p44/42 mitogen-activated protein kinase (MAPK) (extracellular regulated kinase 1/2). Material and Methods: Primary human fibroblasts from healthy gingival tissues were cultured and grown to confluence. Cells were serum starved for 24 h, and then treated with nicotine (0 or 0.5 ,M) prior to in vitro wounding. Cell migration was analysed in live cell assays following in vitro wounds. Rac activity, phosphorylation levels of PAK1/2, and p44/42 MAPK were assessed in cultures treated with or without nicotine after multiple wounds. Results: Nicotine decreased cell migration rates by 50% compared with controls. In addition, nicotine altered the activation patterns of Rac and PAK 1/2 and up-regulated p44/42 MAPK. Conclusion: Decreased cell migration in periodontal wounds exposed to nicotine may be mediated through the Rac and PAK1/2 signalling pathways. [source]


In situ determination of sulfate turnover in peatlands: A down-scaled push,pull tracer technique,

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2008
Tobias Goldhammer
Abstract Bacterial sulfate reduction (BSR) is a key process in anaerobic respiration in wetlands and may have considerable impacts on methane emissions. A method to determine sulfate production and consumption in situ is lacking to date. We applied a single-well, injection-withdrawal tracer test for the in situ determination of potential sulfate turnover in a northern temperate peatland. Piezometers were installed in three peat depth levels (20, 30, and 50,cm) during summer 2004, and three series of injection-withdrawal cycles were carried out over a period of several days. Turnover rates of sulfate, calculated from first-order-reaction constant k (,0.097 to 0.053 h,1) and pore-water sulfate concentrations (approx. 10 µmol L,1), ranged from ,1.3 to ,9.0 nmol cm,3 d,1 for reduction and from +0.7 to +25.4 nmol cm,2 d,1 for production, which occurred after infiltration of water following a heavy rainstorm. Analysis of stable isotopes in peat-water sulfate revealed slightly increasing ,34S values and decreasing sulfate concentrations indicating the presence of BSR. The calculated low sulfur-fractionation factors of <2, are in line with high sulfate-reduction rates during BSR. Routine application will require technical optimization, but the method seems a promising addition to common ex situ techniques, as the investigated soil is not structurally altered. The method can furthermore be applied at low expense even in remote locations. [source]


Methods for evaluating human impact on soil microorganisms based on their activity, biomass, and diversity in agricultural soils

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 3 2006
Rainer Georg Joergensen
Abstract The present review is focused on microbiological methods used in agricultural soils accustomed to human disturbance. Recent developments in soil biology are analyzed with the aim of highlighting gaps in knowledge, unsolved research questions, and controversial results. Activity rates (basal respiration, N mineralization) and biomass are used as overall indices for assessing microbial functions in soil and can be supplemented by biomass ratios (C : N, C : P, and C : S) and eco-physiological ratios (soil organic C : microbial-biomass C, qCO2, qNmin). The community structure can be characterized by functional groups of the soil microbial biomass such as fungi and bacteria, Gram-negative and Gram-positive bacteria, or by biotic diversity. Methodological aspects of soil microbial indices are assessed, such as sampling, pretreatment of samples, and conversion factors of data into biomass values. Microbial-biomass C (µg (g soil),1) can be estimated by multiplying total PLFA (nmol (g soil),1) by the FPLFA -factor of 5.8 and DNA (µg (g soil),1) by the FDNA -factor of 6.0. In addition, the turnover of the soil microbial biomass is appreciated as a key process for maintaining nutrient cycles in soil. Examples are briefly presented that show the direction of human impact on soil microorganisms by the methods evaluated. These examples are taken from research on organic farming, reduced tillage, de-intensification of land-use management, degradation of peatland, slurry application, salinization, heavy-metal contamination, lignite deposition, pesticide application, antibiotics, TNT, and genetically modified plants. [source]


Exploitation of the complex chemistry of hindered amine stabilizers in effective plastics stabilization,

JOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 3 2007
J. Pospí
Hindered amine stabilizers (HAS) remain a prominent class of stabilizers having a fortunate development with continuous interest in shaping the future properties of plastics: increase in polymer durability, application extension, reaching new effects. Commercial tests provided much information. Insufficient mechanistic interpretations of the complex effects of environmental factors (harshness of testing, penetration of radiation and oxygen, superposition of temperature, atmospheric impurities) and those of the microenvironment (morphology of the polymer matrix, physical relations of HAS,polymer, interference between HAS and other additives) are a drawback. Model experiments complement commercial studies and explain some phenomena. A careful transfer of information from model experiments must be done to avoid misinterpretation of mechanisms, particularly of the HAS regenerative cycle. A critical analysis of primary steps of the HAS activity mechanism in the polymer matrix based on HAS-related primary nitroxides, formation of their stationary concentration and concentration gradients influenced by polymer morphology, spatial competition between autoreactions, and oxidation of polymer-developed alkyl radicals and their scavenging by nitroxides (the key process of HAS efficiency) is outlined. Cyclic regeneration of nitroxides affected by the structure of the amino moiety in the HAS molecule, influence of acid environment, atmospheric ozone or singlet oxygen, cooperative mixtures of HAS with UV absorbers, combinations with additives increasing the thermal stabilization effect and improving color retention, assessment of the heat stabilization performance of HAS by proper testing, and influence of the molecular weight of HAS are mentioned together with examples of the chemical consumption of HAS in the final phases of their lifetime. lifetime. J. VINYL ADDIT. TECHNOL., 13:119,132, 2007. © 2007 Society of Plastics Engineers [source]


Electrolytic pickling of duplex stainless steel

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 8 2005
N. Ipek
Abstract Pickling of duplex stainless steels has proved to be much more difficult than that of standard austenitic grades. Electrolytic pre-pickling is shown to be a key process towards facilitating the pickling process for material annealed both in the production-line and in laboratory experiments. The mechanism for the neutral electrolytic process on duplex 2205 and austenitic 316 steels has been examined and the oxide scale found to become thinner as a function of electrolytic pickling time. Spallation or peeling of the oxide induced by gas evolution did not play a decisive role. A maximum of about 20% of the current supplied to the oxidised steel surface goes to dissolution reactions whereas about 80% of the current was consumed in oxygen gas production. This makes the current utilisation very poor, particularly against the background of reports that in indirect electrolytic pickling only about 30% of the total current, supplied to the process, actually goes into the strip. A parametric study was therefore carried out to determine whether adjustment of process variables could improve the current utilisation. [source]


Documenting Accountability: Environmental Impact Assessment in a Peruvian Mining Project

POLAR: POLITICAL AND LEGAL ANTHROPOLOGY REVIEW, Issue 2 2009
Fabiana Li
Over the past two decades, practices of accountability have acquired a new presence in neoliberal governance and resource extraction in Peru. In the context of mining activity, accountability generally refers to public mechanisms of evaluation and record-keeping through which citizens can make corporations and governments answerable to them. However, I argue that these practices often prioritize mining interests by enabling corporations to define and ultimately enforce standards of performance. This article focuses on a key process in the making of social and environmental accountability in mining projects: Environmental Impact Assessment (EIA). I show that the form of the documents produced for the EIA (i.e., their required components, as established in legal frameworks) and the process of making them public (participatory meetings and public forums) can take precedence over their content. I examine two aspects of the EIA that make this possible. First, the risks that are identified in the EIA are those that a company deems to be technically manageable based on the solutions and interventions that it has to offer. Second, the participatory process of the EIA creates collaborative relationships among state agents, corporations, NGOs, and communities that strengthen the EIA's claims of accountability while circumscribing the spaces for opposition to a proposed project. [source]


Significance of CD 105 expression for tumour angiogenesis and prognosis in endometrial carcinomas

APMIS, Issue 11 2003
HELGA B. SALVESEN
Angiogenesis is a key process in tumour growth and metastasis, and Factor-VIII microvascular density has been found to influence prognosis among endometrial carcinoma patients. The CD105/endoglin antibody has been reported to preferentially bind to activated endothelial cells in tissues participating in angiogenesis, and we therefore wanted to compare the prognostic significance of CD105/endoglin to that of Factor-VIII. In a population-based endometrial carcinoma study with long (median 11.5 years) and complete patient follow-up, mean intratumour microvascular density (MVD) assessed using CD105/endoglin was investigated and compared with previous data for MVD assessed using Factor-VIII. MVD by CD105/endoglin was significantly correlated with MVD by Factor-VIII (p=0.001). However, tumours within the two groups defined by the upper and lower quartiles for CD105/endoglin-MVD were both significantly more often metastatic (FIGO-stage III/IV; p=0.03), with high tumour cell proliferation by Ki67 (p=0.007) and with reduced survival (p=0.036) as compared with the intermediate groups. In Cox regression analysis, CD105/endoglin-MVD showed independent prognostic influence when analysed together with patient age, FIGO stage, histologic subtype, histologic grade and Factor-VIII-MVD, while the latter lost its prognostic impact when CD105/endoglin was included. In the subgroup with high MVD, there was a tendency towards improved response to radiation therapy. In conclusion, CD105/endoglin-MVD is significantly associated with FIGO stage, tumour proliferation and prognosis in endometrial carcinoma, indicating that this is a better angiogenic marker in these tumours. [source]


Evaluation of macrofaunal effects on leaf litter breakdown rates in aquatic and terrestrial habitats

AUSTRAL ECOLOGY, Issue 6 2006
AUGUSTO C. DE A. RIBAS
Abstract Decomposition of the organic matter is a key process in the functioning of aquatic and terrestrial ecosystems, although different factors influence processing rates between and within these habitats. Most patterns were described for temperate regions, with fewer studies in tropical, warmer sites. In this study, we carried out a factorial experiment to compare processing rates of mixed species of leaf litter between terrestrial and aquatic habitats at a tropical site, using ,ne and coarse mesh cages to allow or prevent colonization by macroinvertebrates. The experiment was followed for 10 weeks, and loss of leaf litter mass through time was evaluated using exponential models. We found no interaction between habitat and mesh size and leaf litter breakdown rates did not differ between ,ne and coarse mesh cages, suggesting that macroinvertebrates do not influence leaf litter decomposition in either habitat at our studied site. Leaf breakdown rates were faster in aquatic than in terrestrial habitats and the magnitude of these differences were comparable to studies in temperate regions, suggesting that equivalent factors can influence between-habitat differences detected in our study. [source]


Local Variation in Shredder Distribution can Explain their Oversight in Tropical Streams

BIOTROPICA, Issue 5 2009
Regina Camacho
ABSTRACT Stream shredders play an important role in the breakdown of allochthonous leaf litter,a well-known, key process in temperate headwater streams. In contrast, it has been suggested that litter breakdown in tropical streams is driven by microorganisms, shredders being scarce or absent. We propose that shredders have been overlooked in some tropical streams for two reasons: (1) assuming that tropical shredders belong to the same taxa as temperate ones, without determining the diet of tropical litter fauna; and (2) the small spatial scale of most tropical stream studies, which do not account for intra- and inter-site comparisons. We explored shredder abundance and species richness in six streams in each of two tropical regions, the Australian wet tropics (AWT) and Panama (PAN), finding 734 individuals of 12 shredder species in AWT and 391 individuals of 16 species in PAN. Shredder species richness was positively related to altitude in AWT, but not in PAN. Shredder contribution to total leaf breakdown in the field was 24±3 SE percent in AWT and negligible in PAN, but this was probably due to the unsuccessful colonization of experimental cages by PAN shredders. In the laboratory, shredder contribution to total leaf breakdown was higher than in the field (35%±2 SE in AWT and 64%±3 SE in PAN) and varied with leaf decomposability. Our results support earlier indications that shredders are not scarce or functionally unimportant in the tropics, and suggest that their contribution to litter processing should be determined along altitudinal gradients. [source]


Trafficking of Leishmania donovani promastigotes in non-lytic compartments in neutrophils enables the subsequent transfer of parasites to macrophages

CELLULAR MICROBIOLOGY, Issue 1 2008
Pascale Gueirard
Summary Inoculation of Leishmania (L.) spp. promastigotes in the dermis of mammals by blood-feeding sand flies can be accompanied by the rapid recruitment of neutrophils, inflammatory monocytes and dendritic cells. Despite the presence of these lytic leucocytes, parasitism is efficiently established. We show here that Leishmania donovani promastigotes are targeted to two different compartments in neutrophils. The compartments harbouring either damaged or non-damaged parasites were characterized at the electron microscopy (EM) level using the glucose 6-phosphatase cytochemistry and endosome,phagosome fusion assays. One involves the contribution of lysosomes leading to the formation of highly lytic compartments where parasites are rapidly degraded. The other is lysosome-independent and involves the contribution of a compartment displaying some features of the endoplasmic reticulum (ER) where parasites are protected from degradation. Using genetically modified parasites, we show that the promastigote surface lipophosphoglycan (LPG) is required to inhibit lysosome fusion and maintain parasites in neutrophil compartments displaying ER features. L. donovani -harbouring neutrophils that eventually enter apoptosis can be phagocytosed by macrophages enabling the stealth entry of parasites into their final replicative host cells. Thus, the ability of L. donovani to avoid trafficking into lysosomes-derived compartments in short-lived neutrophils constitutes a key process for the subsequent establishment of long-term parasitism. [source]


The role of taurine in diabetes and the development of diabetic complications

DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 5 2001
Svend Høime Hansen
Abstract The ubiquitously found ,-amino acid taurine has several physiological functions, e.g. in bile acid formation, as an osmolyte by cell volume regulation, in the heart, in the retina, in the formation of N -chlorotaurine by reaction with hypochlorous acid in leucocytes, and possibly for intracellular scavenging of carbonyl groups. Some animals, such as the cat and the C57BL/6 mouse, have disturbances in taurine homeostasis. The C57BL/6 mouse strain is widely used in diabetic and atherosclerotic animal models. In diabetes, the high extracellular levels of glucose disturb the cellular osmoregulation and sorbitol is formed intracellularly due to the intracellular polyol pathway, which is suspected to be one of the key processes in the development of diabetic late complications and associated cellular dysfunctions. Intracellular accumulation of sorbitol is most likely to cause depletion of other intracellular compounds including osmolytes such as myo -inositol and taurine. When considering the clinical complications in diabetes, several links can be established between altered taurine metabolism and the development of cellular dysfunctions in diabetes which cause the clinical complications observed in diabetes, e.g. retinopathy, neuropathy, nephropathy, cardiomyopathy, platelet aggregation, endothelial dysfunction and atherosclerosis. Possible therapeutic perspectives could be a supplementation with taurine and other osmolytes and low-molecular compounds, perhaps in a combinational therapy with aldose reductase inhibitors. Copyright © 2001 John Wiley & Sons, Ltd. [source]


Analysis of GaInAsP laser diodes degraded by light absorption at an active layer of the facet

ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 2 2010
Hiroyuki Ichikawa
Abstract Electrostatic discharge-induced degradation is one of the serious reliability problems of GaInAsP/InP laser diodes. The authors have conducted an analysis of electrostatic discharge-induced degradation, and have elucidated the principal degradation mechanism. The main cause of degradation is heating by light absorption at the active layer of the facet. This phenomenon is similar to the catastrophic optical damage that occurs in GaAs-based high-power laser diodes. The problem has become more serious with the recent tendency to high power demand. Therefore, technology to suppress against degradation is extremely important. Focusing on facet coating, which is one of the key processes to suppress facet degradation, we demonstrated that facet degradation can be successfully suppressed by inserting an ultrathin aluminum layer between the semiconductor and the dielectric coaling films. This effect is caused by a reduction of surface recombination. This degradation suppression technology has the potential to be applied not only to GaInAsP/InP laser diodes, but to any InP-based laser diodes. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(2): 32,38, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10196 [source]


The behaviour of soil process models of ammonia volatilization at contrasting spatial scales

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2008
R. Corstanje
Summary Process models are commonly used in soil science to obtain predictions at a spatial scale that is different from the scale at which the model was developed, or the scale at which information on model inputs is available. When this happens, the model and its inputs require aggregation or disaggregation to the application scale, and this is a complex problem. Furthermore, the validity of the aggregated model predictions depends on whether the model describes the key processes that determine the process outcome at the target scale. Different models may therefore be required at different spatial scales. In this paper we develop a diagnostic framework which allows us to judge whether a model is appropriate for use at one or more spatial scales both with respect to the prediction of variations at those scale and in the requirement for disaggregation of the inputs. We show that spatially nested analysis of the covariance of predictions with measured process outcomes is an efficient way to do this. This is applied to models of the processes that lead to ammonia volatilization from soil after the application of urea. We identify the component correlations at different scales of a nested scheme as the diagnostic with which to evaluate model behaviour. These correlations show how well the model emulates components of spatial variation of the target process at the scales of the sampling scheme. Aggregate correlations were identified as the most pertinent to evaluate models for prediction at particular scales since they measure how well aggregated predictions at some scale correlate with aggregated values of the measured outcome. There are two circumstances under which models are used to make predictions. In the first case only the model is used to predict, and the most useful diagnostic is the concordance aggregate correlation. In the second case model predictions are assimilated with observations which should correct bias in the prediction, and errors in the variance; the aggregate correlations would be the most suitable diagnostic. [source]


Spaces of Utopia and Dystopia: Landscaping the Contemporary City

GEOGRAFISKA ANNALER SERIES B: HUMAN GEOGRAPHY, Issue 3-4 2002
Gordon MacLeod
Some of the most recent literature within urban studies gives the distinct impression that the contemporary city now constitutes an intensely uneven patchwork of utopian and dystopian spaces that are, to all intents and purposes, physically proximate but institutionally estranged. For instance, so,called edge cities (Garreau, 1991) have been heralded as a new Eden for the information age. Meanwhile tenderly manicured urban villages, gated estates and fashionably gentrified inner,city enclaves are all being furiously marketed as idyllic landscapes to ensure a variety of lifestyle fantasies. Such lifestyles are offered additional expression beyond the home, as renaissance sites in many downtowns afford city stakeholders the pleasurable freedoms one might ordinarily associate with urban civic life. None,the,less, strict assurances are given about how these privatized domiciliary and commercialized ,public' spaces are suitably excluded from the real and imagined threats of another fiercely hostile, dystopian environment ,out there'. This is captured in a number of (largely US) perspectives which warn of a ,fortified' or ,revanchist' urban landscape, characterized by mounting social and political unrest and pockmarked with marginal interstices: derelict industrial sites, concentrated hyperghettos, and peripheral shanty towns where the poor and the homeless are increasingly shunted. Our paper offers a review of some key debates in urban geography, planning and urban politics in order to examine this patchwork,quilt urbanism, In doing so, it seeks to uncover some of the key processes through which contemporary urban landscapes of utopia and dystopia come to exist in the way they do. [source]


Systemverhalten und Prozessoptimierung beim Erddruckschild

GEOMECHANICS AND TUNNELLING, Issue 3 2008
Ulrich Maidl Dr.-Ing.
Eine konsequente Analyse der Prozessdaten kann die Sicherheit, aber auch die Effektivität des Ressourceneinsatzes beim hoch technisierten Schildvortrieb erheblich steigern. Präventive Maßnahmen zur Prozessoptimierung können durch die zeitnahe Analyse des Systemverhaltens während des Bauablaufs rechtzeitig eingeleitet werden. Eine Analyse des Systemverhaltens wird durch die Aufspaltung des Bauablaufs in Teilprozesse und die Definition der Schlüsselprozesse möglich. Im folgenden Artikel wird am Beispiel des Erddruckschilds aufgezeigt, wie beim heutigen Stand der Technik Prozesse realitätsnah simuliert und während der Ausführung unter Einsatz der vorhandenen Mess- und Datenerfassungstechnik analysiert werden können. System Behaviour and Process Optimization at EPB Shield A consistent analysis of the process parameters in highly mechanised shield tunnelling, not only increases the safety, but it also improves the efficiency of the resources in action. The real time analysis of the system's behaviour allows to timely carry out preventive measures during the construction process with the aim of optimizing the construction process. The analysis of the system's behaviour is possible by splitting the construction sequence in a series of partial processes and by defining the key processes. The present paper represents an EPB shield study case, which shows how the present state of the art allows simulating processes realistically during construction, by applying existing monitoring and data registration technology. [source]


Keeping your globally mobile employees healthy, safe, and secure

GLOBAL BUSINESS AND ORGANIZATIONAL EXCELLENCE, Issue 1 2009
Myles Druckman
Companies are sending higher numbers of older employees to difficult or dangerous locations, which increases the chances of a medical event where healthcare services are least available. Business travelers and international assignees and their employers need to adequately assess and prepare for such possibilities. The author describes five key processes that will help companies perform duty of care and minimize risks to the employee and company alike; the elements of a best-practice international preassignment health program to ensure assignees are fit for work in locations with high medical risk; and the five responsibilities of globally mobile employees for protecting their health and getting medical help if they need it. © 2009 Wiley Periodicals, Inc. [source]


Changes in grassland ecosystem function due to extreme rainfall events: implications for responses to climate change

GLOBAL CHANGE BIOLOGY, Issue 7 2008
PHILIP A. FAY
Abstract Climate change is causing measurable changes in rainfall patterns, and will likely cause increases in extreme rainfall events, with uncertain implications for key processes in ecosystem function and carbon cycling. We examined how variation in rainfall total quantity (Q), the interval between rainfall events (I), and individual event size (SE) affected soil water content (SWC) and three aspects of ecosystem function: leaf photosynthetic carbon gain (), aboveground net primary productivity (ANPP), and soil respiration (). We utilized rainout shelter-covered mesocosms (2.6 m3) containing assemblages of tallgrass prairie grasses and forbs. These were hand watered with 16 I×Q treatment combinations, using event sizes from 4 to 53 mm. Increasing Q by 250% (400,1000 mm yr,1) increased mean soil moisture and all three processes as expected, but only by 20,55% (P,0.004), suggesting diminishing returns in ecosystem function as Q increased. Increasing I (from 3 to 15 days between rainfall inputs) caused both positive () and negative () changes in ecosystem processes (20,70%, P,0.01), within and across levels of Q, indicating that I strongly influenced the effects of Q, and shifted the system towards increased net carbon uptake. Variation in SE at shorter I produced greater response in soil moisture and ecosystem processes than did variation in SE at longer I, suggesting greater stability in ecosystem function at longer I and a priming effect at shorter I. Significant differences in ANPP and between treatments differing in I and Q but sharing the same SE showed that the prevailing pattern of rainfall influenced the responses to a given event size. Grassland ecosystem responses to extreme rainfall patterns expected with climate change are, therefore, likely to be variable, depending on how I, Q, and SE combine, but will likely result in changes in ecosystem carbon cycling. [source]


Comparing and evaluating process-based ecosystem model predictions of carbon and water fluxes in major European forest biomes

GLOBAL CHANGE BIOLOGY, Issue 12 2005
Pablo Morales
Abstract Process-based models can be classified into: (a) terrestrial biogeochemical models (TBMs), which simulate fluxes of carbon, water and nitrogen coupled within terrestrial ecosystems, and (b) dynamic global vegetation models (DGVMs), which further couple these processes interactively with changes in slow ecosystem processes depending on resource competition, establishment, growth and mortality of different vegetation types. In this study, four models , RHESSys, GOTILWA+, LPJ-GUESS and ORCHIDEE , representing both modelling approaches were compared and evaluated against benchmarks provided by eddy-covariance measurements of carbon and water fluxes at 15 forest sites within the EUROFLUX project. Overall, model-measurement agreement varied greatly among sites. Both modelling approaches have somewhat different strengths, but there was no model among those tested that universally performed well on the two variables evaluated. Small biases and errors suggest that ORCHIDEE and GOTILWA+ performed better in simulating carbon fluxes while LPJ-GUESS and RHESSys did a better job in simulating water fluxes. In general, the models can be considered as useful tools for studies of climate change impacts on carbon and water cycling in forests. However, the various sources of variation among models simulations and between models simulations and observed data described in this study place some constraints on the results and to some extent reduce their reliability. For example, at most sites in the Mediterranean region all models generally performed poorly most likely because of problems in the representation of water stress effects on both carbon uptake by photosynthesis and carbon release by heterotrophic respiration (Rh). The use of flux data as a means of assessing key processes in models of this type is an important approach to improving model performance. Our results show that the models have value but that further model development is necessary with regard to the representation of the some of the key ecosystem processes. [source]


Synovial mast cells: role in acute and chronic arthritis

IMMUNOLOGICAL REVIEWS, Issue 1 2007
Peter A. Nigrovic
Summary:, Mast cells reside in the normal synovium and increase strikingly in number in rheumatoid arthritis and other joint diseases. Given the broad spectrum of activity of this lineage, it has for decades been considered probable that mast cells are involved in the pathophysiology of synovitis. Recent work in murine arthritis has substantiated this suspicion, showing that mast cells can contribute importantly to the initiation of inflammatory arthritis. However, the role of the greatly expanded population of synovial mast cells in established arthritis remains unknown. Here we review the current understanding of mast cell function in acute arthritis and consider the potentially important influence of this cell on key processes within the chronically inflamed synovium, including leukocyte recruitment and activation, fibroblast proliferation, angiogenesis, matrix remodeling, and injury to collagen and bone. We also consider recent evidence supporting an immunomodulatory or anti-inflammatory role for mast cells as well as pharmacologic approaches to the mast cell as a therapeutic target in inflammatory arthritis. [source]


MicroRNA in the immune system, microRNA as an immune system

IMMUNOLOGY, Issue 3 2009
Li-Fan Lu
Summary The advent of microRNA has potentially uncovered a new level of complexity to be considered for every biological process. Through the modulation of transcription and translation, microRNA alter the basal state of cells and the outcome of stimulatory events. The exact effect of the microRNA network and individual microRNA on cellular processes is only just starting to be dissected. In the immune system, microRNA appear to have a key role in the early differentiation and effector differentiation of B cells. In T cells, microRNA have been shown to be key regulators of the lineage induction pathways, and to have a strong role in the induction, function and maintenance of the regulatory T-cell lineage. MicroRNA are also important for regulating the differentiation of dendritic cells and macrophages via toll-like receptors, with responsibilities in suppressing effector function before activation and enhancing function after stimulation. In addition to regulating key processes in the immune system, microRNA may also represent an archaic immune system themselves. Small interfering RNA of viral origin has been shown to function as an intracellular mediator in the suppression of viral infection in eukaryotes as diverse as plants, insects, nematodes and fungi, and there is growing evidence that endogenous mammalian microRNA can have similar impacts. In this article we speculate that the anti-viral function of microRNA drove the expression of different subsets of microRNA in different cellular lineages, which may have, in turn, led to the myriad of roles microRNA play in lineage differentiation and stability. [source]


Animal use replacement, reduction, and refinement: Development of an integrated testing strategy for bioconcentration of chemicals in fish,

INTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 1 2007
Watze de Wolf
Abstract When addressing the use of fish for the environmental safety of chemicals and effluents, there are many opportunities for applying the principles of the 3Rs: Reduce, Refine, and Replace. The current environmental regulatory testing strategy for bioconcentration and secondary poisoning has been reviewed, and alternative approaches that provide useful information are described. Several approaches can be used to reduce the number of fish used in the Organization for Economic Cooperation and Development (OECD) Test Guideline 305, including alternative in vivo test methods such as the dietary accumulation test and the static exposure approach. The best replacement approach would seem to use read-across, chemical grouping, and quantitative structure-activity relationships with an assessment of the key processes in bioconcentration: Adsorption, distribution, metabolism, and excretion. Biomimetic extraction has particular usefulness in addressing bioavailable chemicals and is in some circumstances capable of predicting uptake. Use of alternative organisms such as invertebrates should also be considered. A single cut-off value for molecular weight and size beyond which no absorption will take place cannot be identified. Recommendations for their use in bioaccumulative (B) categorization schemes are provided. Assessment of biotransformation with in vitro assays and in silico approaches holds significant promise. Further research is needed to identify their variability and confidence limits and the ways to use this as a basis to estimate bioconcentration factors. A tiered bioconcentration testing strategy has been developed taking account of the alternatives discussed. [source]