bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence against GABA Release from Glutamatergic Mossy Fiber Terminals in the Developing Hippocampus
Authors: Uchigashima Motokazu , Fukaya Masahiro , Watanabe Masahiko , Kamiya Haruyuki
Published: July 2007

Hippocampal mossy fibers of young rodents have been reported to corelease inhibitory neurotransmitter GABA in addition to excitatory transmitter glutamate. In this study, we aimed at re-evaluating this corelease hypothesis of both inhibitory and excitatory transmitters in the hippocampus. Electrophysiological examination revealed that, in juvenile mice and rats of the two to 3 weeks old, stimulation at the granule cell layer of the dentate gyrus elicited monosynaptic GABAergic IPSCs in CA3 neurons in the presence of ionotropic glutamate receptor (iGluR) blockers, only when rather strong stimuli were given. The group II mGluR agonist (2S,1′R,2′R,3′R)-2-(2,3-dicarboxycyclo-propyl)glycine (DCG-IV), which selectively suppresses transmission at the mossy fiber–CA3 synapse, abolished almost all postsynaptic responses elicited by the weak stimuli, whereas those by strong stimuli were inhibited only slightly. In addition, the minimal stimulation elicited GABAergic IPSCs in neonatal mice of the first postnatal week, whereas these responses are not sensitive to DCG-IV. Immunohistochemical examination revealed that mossy fiber terminals expressed GABA and the GABA-synthesizing enzyme GAD67, although the expression levels were much weaker than those in the inhibitory interneurons. Notably, the expression levels of the vesicular GABA transporter were much lower than those of GABA and GAD67, and almost below detection threshold. These results suggest that mossy fiber synapses are purely glutamatergic and apparent monosynaptic IPSCs so far reported are evoked by costimulation of inhibitory interneurons, at least in young mice and rats. Hippocampal mossy fiber terminals synthesize and store GABA, but have limited ability in vesicular release for GABA in the developing rodents.
Reliability and Heterogeneity of Calcium Signaling at Single Presynaptic Boutons of Cerebellar Granule Cells
Authors: Brenowitz Stephan D. , Regehr Wade G.
Published: July 2007

Activity-dependent elevation of calcium within presynaptic boutons regulates many aspects of synaptic transmission. Here, we examine presynaptic residual calcium (Cares) transients in individual presynaptic boutons of cerebellar granule cells at near-physiological temperatures using two-photon microscopy. Properties of Caresunder conditions of zero-added buffer were determined by measuring Carestransients while loading boutons to a steady-state indicator concentration. These experiments revealed that, in the absence of exogenous calcium buffers, a single action potential evokes transients of Caresthat vary widely in different boutons both in amplitude (400–900 nm) and time course (25–55 ms). Variation in calcium influx density, endogenous buffer capacity, and calcium extrusion density contribute to differences in Caresamong boutons. Heterogeneity in Careswithin different boutons suggests that plasticity can be regulated independently at different synapses arising from an individual granule cell. In a given bouton, Caressignals were highly reproducible from trial to trial and failures of calcium influx were not observed. We find that a factor contributing to this reliability is that an action potential opens a large number of calcium channels (20–125) in a bouton. Presynaptic calcium signals were also used to assess the ability of granule cell axons to convey somatically generated action potentials to distant synapses. In response to pairs of action potentials or trains, granule cell boutons showed a remarkable ability to respond reliably at frequencies up to 500 Hz. Thus, individual boutons appear specialized for reliable calcium signaling during bursts of high-frequency activation such as those that are observedin vivo.
Cocaine Experience Controls Bidirectional Synaptic Plasticity in the Nucleus Accumbens
Authors: Kourrich Saïd , Rothwell Patrick E. , Klug Jason R. , Thomas Mark J.
Published: July 2007

Plasticity of glutamatergic synapses is a fundamental mechanism through which experience changes neural function to impact future behavior. In animal models of addiction, glutamatergic signaling in the nucleus accumbens (NAc) exerts powerful control over drug-seeking behavior. However, little is known about whether, how or when experience with drugs may trigger synaptic plasticity in this key nucleus. Using whole-cell synaptic physiology in NAc brain slices, we demonstrate that a progression of bidirectional changes in glutamatergic synaptic strength occurs after repeatedin vivoexposure to cocaine. During a protracted drug-free period, NAc neurons from cocaine-experienced mice develop a robust potentiation of AMPAR-mediated synaptic transmission. However, a single re-exposure to cocaine during extended withdrawal becomes a potent stimulus for synaptic depression, abruptly reversing the initial potentiation. These enduring modifications in AMPAR-mediated responses and plasticity may provide a neural substrate for disrupted processing of drug-related stimuli in drug-experienced individuals.
Behavioral andIn VitroCorrelates of Compulsive-Like Food Seeking Induced by Operant Conditioning inAplysia
Authors: Nargeot Romuald , Petrissans Christine , Simmers John
Published: July 2007

Motivated behaviors comprise appetitive actions whose occurrence results partly from an internally driven incentive to act. Such impulsive behavior can also be regulated by external rewarding stimuli that, through learning processes, can lead to accelerated and seemingly automatic, compulsive-like recurrences of the rewarded act. Here, we explored such behavioral plasticity inAplysiaby analyzing how appetitive reward stimulation in a form of operant conditioning can modify a goal-directed component of the animal's food-seeking behavior. In naive animals, protraction/retraction cycles of the tongue-like radula are expressed sporadically with highly variable interbite intervals. In contrast, animals that were previously given a food-reward stimulus in association with each spontaneous radula bite now expressed movement cycles with an elevated frequency and a stereotyped rhythmic organization. This rate increase and regularization, which was retained for several hours after training, depended on both the reward quality and its contingency because accelerated, stereotyped biting was not induced in animals that had previously received a less-palatable food stimulus or had been subjected to nonassociative reward stimulation. Neuronal correlates of these learning-induced changes were also expressed in the radula motor pattern-generating circuitry of isolated buccal ganglia. In suchin vitropreparations, moreover, manipulation of the burst frequency of the bilateral motor pattern-initiating B63 interneurons indicated that the regularization of radula motor pattern generation in contingently trained animals occurred separately from an increase in cycle rate, thereby suggesting independent processes of network plasticity. These data therefore suggest that operant conditioning can induce compulsive-like actions inAplysiafeeding behavior and provide a substrate for a cellular analysis of the underlying mechanisms.
Residual Effects from Fish Wheel Capture and Handling of Yukon River Fall Chum Salmon
Authors: Bromaghin Jeffrey F. , Underwood Tevis J. , Hander Raymond F.
Published: July 2007

Since 1996, U.S. Fish and Wildlife Service biologists have annually used fish wheels to capture migrating adult fall chum salmon Oncorhynchus keta in the main-stem Yukon River, Alaska, and estimated their abundance via mark–recapture methods. In each year of the study, the mark rate of captured fish at a site near Rampart has been substantially greater than rates observed at numerous locations upriver of that site. The factors most likely to cause the observed reduction in the mark rate are violations of mark–recapture model assumptions or the mortality of marked fish between the Rampart site and upriver locations. Results of studies conducted through 2000 were most consistent with the hypothesis of mortality. We investigate potential explanatory factors for the apparent reduction in mark rates at upriver locations using data collected during additional studies from 2001 to 2003. Results document that holding fish in submerged pens at the marking site negatively affects their ability to migrate for at least some time. No evidence of tag loss or spatial segregation within the mark–recapture study area was observed. A conclusion that some aspect of the capture and handling of fish elevates their mortality upriver of the mark–recapture study area seems well founded. However, holding of fish does not solely explain the reduction in mark rates at upriver locations, and other contributing factors remain unidentified. Researchers using fish wheels should be aware that the gear may be more harmful to fish than was previously thought and may bias estimators of some parameters such as abundance or migration speed.
Design of a Compound Inclined Screen Trap for Anadromous Salmonid Smolts
Authors: Dexter Daniel J. , Schliep Donald V.
Published: July 2007

In the late 1980s, Minnesota Department of Natural Resources fish managers became compelled to address the decline of wild steelhead Oncorhynchus mykiss in Lake Superior. Requisite to the development of stock–recruitment models, permanent smolt traps were designed and constructed on two Lake Superior tributaries. The design was engineered to function in a broad range of discharges with complete structural integrity, to keep itself free of debris, and to sample a large portion of the emigrating salmonid population. The first of these traps was built on the French River (discharge, from 3 to >1,840 ft3/s (cfs)) and began operation in 1994. After several years of very successful operation a second trap was built on the Knife River (discharge, from 5 to >9,000 cfs) that began operation in 1997. These structures employ fixed stainless steel dewatering screens permanently fixed at opposed compound inclines on each side of a channel that carries water to a catch–retention box, which is also fixed and above the level of the stream. Fish falling onto the screen are directed by gravity to the center channel, where they travel with the flowing water to the catch box. A stainless steel, overshot, rotating drum screen in the catch box has effectively retained fish with low mortality while expelling water-borne debris. Both traps have operated continuously during open-water periods since 1997 to sample emigrating salmonid smolts (primarily wild steelhead). Smolt capture efficiency has been estimated to be 94% with the French River trap and 85% with the Knife River trap. Fish managers may wish to examine and consider this design as a possibility for addressing their smolt monitoring needs.
Yellow Perch in South Dakota: Population Variability and Predicted Effects of Creel Limit Reductions and Minimum Length Limits
Authors: Isermann Daniel A. , Willis David W. , Blackwell Brian G. , Lucchesi David O.
Published: July 2007

We collected annual gill-net samples of yellow perch Perca flavescens in six South Dakota lakes over 4–5 years. We also simulated the effects of reductions in daily creel limits for yellow perch (i.e., from 25 fish/angler to 5, 10, or 15 fish/angler) and use of minimum total length limits (229 and 254 mm). Population indices varied widely among lakes and among years within lakes to the extent that indices from any individual year were largely uninformative. Creel surveys indicated that few anglers typically achieved a daily creel limit of 25 yellow perch. Except in Waubay Lake, lowering the creel limit from 25 to 5 fish/angler would be necessary to achieve harvest reductions of 25% or more within most of the fisheries we examined. Minimum length limits were projected to improve size and age structure, but harvest reductions often exceeded 50% and yield declined or only slightly increased (by ≤13%). Yellow perch in these lakes had achieved much of their full growth potential by the time they reached 229 and 254 mm. Consequently, although length limits were predicted to increase age and size structures, asymptotic growth prevented yellow perch from attaining substantially larger sizes. Length limits were predicted to be most beneficial when fishing mortality represented most of the total mortality in each population and when growth occurred at median or fast rates. A 229-mm length limit was predicted to improve size and age structures with less-severe reductions in harvest or yield than a 254-mm limit. Population dynamics and the harvest-oriented nature of yellow perch anglers may dictate that yield maximization is still a reasonable management goal for many South Dakota yellow perch fisheries. Increasing the number of yellow perch that attain 229 mm is possible for certain fisheries if angler harvest represents the dominant source of mortality.
Design of large‐area OLED displays utilizing seamless tiled components
Authors: Aston Mark
Published: July 2007

Abstract— In recent years, the majority of R&D for large‐area displays has been to serve the production of large monolithic substrate technology such as plasma‐display panels (PDPs) and TFT‐LCD. While the pursuit of large displays for domestic and light‐industrial use benefits from the production of these high‐quality high‐pixel‐count technologies, there is still a need to produce displays in formats other than 4:3 or 16:9 and on a larger scale than currently available in single‐substrate displays. The options that exist for producing tiled displays from emerging technologies is examined and a practical technique for creating large‐area (1.8 × 1.2 m and larger) monochrome or color displays from tiling smaller units is discussed. This presents a cost‐effective approach for arranging small tiles to create a much larger screen and offers a simple way to address the market gap between large monolithic displays and small conventional LED video‐wall displays, in the size range of 1–10‐mm pixels for advertising and industrial use. By examining the requirements for pixel size and pitch against the range of viewing distances commonly associated with the target markets for these displays, it will be shown that complex manufacturing is not always required.
An active‐matrix organic light‐emitting‐diode pixel circuit for the compensation of I × R voltage drop in power line
Authors: Jung Sang‐Hoon , Lee Hong‐Koo , Ahn Tae‐Joon , Kim Chang‐Yeon , Kim Chang‐Dong , Chung In‐Jae
Published: July 2007

Abstract— A new voltage‐driving active‐matrix organic light‐emitting diode (AMOLED) pixel circuit is proposed to improve the display image‐quality of AMOLED displays. Because OLEDs are current‐driven devices, the I × R voltage drop in the power lines is evitable. Accordingly, the I × R voltage‐drop compensation scheme should be included in the pixel‐driving method when a voltage‐compensation method is used. The proposed pixel was designed for the compensation of an I × R voltage drop in the power lines as well as for the compensation of the threshold‐voltage non‐uniformity of low‐temperature polycrystalline‐silicon thin‐film transistors (LTPS TFTs). In order to verify the compensation ability of the proposed pixel, SPICE simulation was performed and compared with those of other conventional pixels. When the Vss voltage varies from 0 to 1 V, the drain current of the proposed pixel decreased by under 1% while that of conventional Vth compensation methods without Vss compensation decreased by over 60%. 2.2‐in. QCIF+ full‐color AMOLED displays, which employ the proposed pixel, have been also developed. It was verified by comparison of the display image quality with a conventional panel that our proposed panel successfully overcame the voltage‐drop problems in the power lines.
Wide‐angle film diffuser
Authors: Lu Zhijian Z. J. , Lee James W. , Kim Jong Man
Published: July 2007

Abstract— A unique roll‐to‐roll mass‐producible high‐transmission wide‐angle diffuser (WAD™) film for use in LCD backlights is reported. WAD™ diffuser films include optical structures that efficiently manage forward light scattering and significantly reduces backward light scattering. WAD™ technology facilitates backlights with significantly higher brightness and thinner backlight profiles.
Fast phase modulation using dual‐frequency nematic liquid crystals
Authors: Barnik Mikhail I. , Palto Serguei P.
Published: July 2007

Abstract— Experimental study and numerical simulations of optical phase modulators based on nematic liquid crystals characterized by frequency sign inversion of the dielectric anisotropy has been performed. The received results point out an extreme role of back‐flow effects and electro‐hydrodynamic instability, which make restrictions for creating high‐speed phase modulators with large switchable values of phase retardation. It is shown by numerical simulations that the hydrodynamic destabilization can be suppressed by decreasing the ratio of Leslie coefficients |α2/α4,5|.
Visual gamma measurement and methods to compare gamma models
Authors: Besuijen Jacobus
Published: July 2007

Abstract— The correct estimation of the gamma exponent describing the tone‐reproduction curve of a display is an important step in color management. Several methods for visual gamma estimation have been proposed. In this study, the theoretical merits and practical problems of a number of these methods are discussed and compared, and improvements are suggested. A new method to compare gamma models with different numbers of parameters is introduced. In an experiment, spatial and temporal brightness‐matching methods were tested with 32 untrained subjects working on a CRT and an LCD with different resolutions under office and low‐illumination conditions. Illumination had no effect on gamma estimations. Subjects had great difficulties with spatial brightness matching at low resolutions. Temporal and spatial visual brightness matching for untrained subjects showed a larger gamma than photometric fits.
Support Vector Machine (SVM) based compression artifact‐reduction technique
Authors: Biswas Mainak , Kumar Sanjeev , Nguyen T. Q. , Balram Nikhil
Published: July 2007

Abstract—A compression artifact‐reduction algorithm based on support vector regression is proposed. The algorithm belongs to a broad family of standard reconstruction methods, but a standardization model is determined from a set of training samples of original images and the corresponding noise‐corrupted version. As opposed to artifact‐reduction methods specific to each type of compression artifact (e.g., blocking, ringing,etc.), we treat such artifacts as a manifestation of the same problem, which is the quantization of DCT coefficients. In the testing step, the algorithm tries to undo the effect of quantization by using the relationship between the original and artifact‐corrupted image, determined during the training step. Experimental results exhibit significant reduction in all types of compression artifacts.
Water resources and environmental management: issues, challenges, opportunities and options
Authors: Loucks D.P.
Published: July 2007

Managing water in an integrated and sustainable manner is currently challenging water resource managers throughout the world. It requires professionals from many disciplines working together with impacted stakeholders in crafting a strategy that is economically efficient, ecologically sound, and acceptable to all who are impacted by how this resource is managed over space and time. Such strategies can not be formed from the top down. However those at the top levels of government must be involved in facilitating a bottom–up, public participatory process of helping all those who are impacted by how water is allocated and managed achieve a shared vision of how their water resource system functions. This shared vision should include the economical, ecological and social impacts of alternative management policies, and the tradeoffs among conflicting multiple purposes for which water serves and among all economic, environmental and social objectives for which water can achieve. Appropriate technology is continually being developed that helps us manage water better, but it appears the real constraints to more effective management are often institutional or social. This paper attempts to outline some of the current water resources and environmental management issues and concerns, and suggests some ways of addressing them.
Objectives and achievements of the European water supply and sanitation technology platform (WSSTP): a review
Authors: Wilderer P.A. , d'Arras D.
Published: July 2007

The European Water Supply and Sanitation Technology Platform (WSSTP) is an industry driven organisation aiming to strengthen the potential for technological innovation and the competitiveness of the European Water Industry. In response to global challenges and regional demands a strategy has been proposed to ensure safe, secure and sustainable water and sanitation services for the benefit of industry, the society and the environment. Integrated Water Resources Management is used as a guiding principle. Water supply, wastewater treatment (sanitation), river basin management and concerns of regulators, financing institutions and the civil society are the key elements of a system to be sustainably managed. Decision makers of the private and the public sector are to understand that investment in research, technology development and implementation of innovation is an important element in the process of securing economic prosperity, social stability and functioning of the ecological systems which we as human beings are a part of. A hierarchic, practice oriented structure is proposed to organize and govern research and technology development in Europe. Research will be organized within the framework of thematically designed pilot programmes containing a distinct number of implementation cases to execute close-to-reality research.
Sustainable management of urban water resources in China
Authors: Qian Y.
Published: July 2007

Due to the rapid development of economy, China has been facing severe water shortage and water pollution problems. This paper discusses three strategies developed for the urban water resource management in China, which is essential for the sustainable development of its economy. These strategies include setting high priority for demand control and water conservation, controlling pollution from the sources and increasing investment for wastewater treatment; and developing untraditional water resources, such as rainwater harvesting, wastewater reclamation, seawater utilization, etc. It is hoped that these strategies may not only solve the water shortage and water pollution problems at low capital and operational costs, but also meet the present and future needs on water resources in China.
Urban water supply management in Shanghai
Authors: Liu S.Q.
Published: July 2007

Shanghai is the largest city in China with fast growth of population and economics during the last two decades. Management of water resource and water supply systems is one of the most important strategies for its sustainable urban development. In order to meet the increasing requirements of water demand, studies on policies and technologies for water resources development and water supply management have been implemented in the last few years. New water resource projects, water saving policies and water quality improvement have been adopted and played important roles for Shanghai's long-term rapid development.
River restoration: paradigms, paradoxes and the urban dimension
Authors: Clifford N.J.
Published: July 2007

River restoration is an increasingly common feature of river and environmental management, and may be characterized by one of several ‘restoration paradigms’. These paradigms reflect the key drivers for restoration efforts, and the scientific expertise used to underpin intervention options. At present, however, success rates for restoration schemes are low, and concerns are growing that conventional approaches to river restoration may be fundamentally flawed. Particular issues arise in the case of urban environments, where the case for restoration intervention may otherwise be strongest. In this review, the restoration paradigms are introduced, and the requirement for increased multi-disciplinary perspectives and more comprehensive appraisal processes is outlined. Characteristics of urban rivers are also described. Some paradoxes arising from misclassification and inappropriate conceptualization of these highly fragmented systems are presented, which offer grounds for more optimistic assessments of likely restoration success.
Going with the flow: global warming and the challenge of sustaining river ecosystems in monsoonal Asia
Authors: Dudgeon D.
Published: July 2007

River ecosystems in monsoonal Asia are experiencing human impacts to the detriment of the rich biodiversity they support. Threats include hydrologic alteration, pollution, habitat destruction, overexploitation, and invasive exotic species. Global warming will cause further changes to river ecosystems, and may act synergistically with other threat factors. Significant upward or northward range adjustments by the freshwater biota will be necessary to cope with rising temperatures, but there will be significant constraints upon dispersal ability and availability of suitable habitat for many organisms. Global warming will exacerbate existing impacts of hydrologic alteration because of the adaptive human responses that will be engendered by changes in climate and runoff, particularly dams constructed for hydropower generation, flood protection, water storage, and irrigation. The consequences of further hydrologic alteration and habitat fragmentation will be profound, since almost all ecological processes, material transfers and life-cycle events in the rivers of monsoonal Asia are mediated or controlled by flow. Thus a change in the timing or amounts of flow changes everything. Collaborative research to determine the environmental allocation of water flow needed to maintain ecosystem integrity and sustain biodiversity in the human-dominated rivers of monsoonal Asia should be a priority for ecologists, engineers and water-resource managers.
Epilithic diatom as a biological indicator for the assessment of water quality in the East River
Authors: Fan K.W. , Fok L. , Lee J.H.W. , Chen F.
Published: July 2007

A group research project has been initiated to develop an integrated river management strategy and assessment criteria for the East River in Guangdong province. Four field surveys were conducted in 2004 to study the geomorphologic, hydrologic and environmental features of the basin. Epilithic diatom and water samples were collected from four sites in the upper and lower reaches of the river. A total of 23 diatom genera were identified from the study sites during the two sampling periods. The diatom genus Nitzschia represented the most pollutant dependent epilithic diatoms, comprising over 38% of the overall diatom population in the polluted sites. The correlation between water quality and the Shannon diversity index (H), generic index (GI), trophic diatom index (TDI) and diatom assemblage index to organic pollution (DAIpo) was investigated in this study. The results suggested that epilithic diatom might be used as a biological indicator for the environmental health assessment of the East River.
Use of P-17 and NOX specific primer sets for assimilable organic carbon (AOC) measurements
Authors: Zhang T. , Qin X.L. , Fang H.H.P.
Published: July 2007

In this study, two primer sets were at first designed specific to P-17 and NOX, the two bacterial species used for measurements of assimilable organic carbon (AOC) in water, based on their respective 16S rDNA sequences. These two primer sets were then used to measure the AOC content in 41 water samples by quantitative real time polymerase chain reaction (qRT-PCR). Results showed that P-17 and NOX cell numbers quantified by qRT-PCR using the designed primer sets were consistently higher (about 40.8% for P-17 and 54.8% for NOX measurements) than those by the traditional but time-consuming plate culture method. This proposed method not only saves the 5 days needed for plate culture, but also may detect AOC at concentrations as low as 0.3 μg-acetate-C/l and 0.6 μg-oxalate-C/l, which are lower than those measured by the plate culture and other methods. Using this new method, the water from the tap and a local reservoir were found containing 122 μg/l and 194 μg/l AOC, respectively, accounting for 5.7% and 7.8% of TOC.
Lab-on-a-chip devices for microbial monitoring and detection in water
Authors: Liu W.-T. , Lay C.
Published: July 2007

According to the World Health Organization, diarrhoea is one of the four main diseases caused by environmental exposure and represents the most common water related disease. In developing countries, the access to safe drinking water is still utopian. Moreover, water is not an endless resource anymore; therefore alternative water supplies need to be investigated. Since water is becoming a worldwide issue, there is an increasing effort to ensure its quality and safety through the development of rapid and effective system of diagnostic which could be applied even in remote places in poor countries. The possibility to diagnose on site and in real time an infectious agent is one of the most challenging goals in lab-on-a-chip technologies. This review describes and discusses the potentialities of microfluidic technology in this new emerging field.
A statistical approach to downscaling of sub-daily extreme rainfall processes for climate-related impact studies in urban areas
Authors: Nguyen V.-T.-V. , Nguyen T.-D. , Cung A.
Published: July 2007

This paper presents a spatial-temporal downscaling approach to describe the linkage between large-scale climate variables for daily scale to annual maximum (AM) precipitations for daily and sub-daily scales at a local site. More specifically, the proposed approach is based on a combination of a spatial downscaling method to link large-scale climate variables as provided by General Circulation Model (GCM) simulations with daily extreme precipitations at a local site and a temporal downscaling procedure to describe the relationships between daily extreme precipitations with sub-daily extreme precipitations using the scaling General Extreme Value (GEV) distribution. The feasibility of the proposed downscaling method has been tested based on climate simulation outputs from two GCMs under the A2 scenario (HadCM3A2 and CGCM2A2) and using available AM precipitation data for durations ranging from 5 minutes to 1 day at 15 raingage stations in Quebec (Canada) for the 1961–1990 period. Results of this numerical application has indicated that it is feasible to link large-scale climate predictors for daily scale given by GCM simulation outputs with daily and sub-daily AM precipitations at a local site. Furthermore, it was found that AM precipitations at a local site downscaled from the HadCM3A2 displayed a small change in the future, while those values estimated from the CGCM2A2 indicated a large increasing trend for future periods.
Health aspects of freshwater cyanobacterial toxins
Authors: Shaw G. , Lam P.K.S.
Published: July 2007

Cyanobacterial (blue-green algal) toxins are known to cause poisoning in humans, livestock and wild animals. Based on their toxic mechanisms, cyanobacterial toxins are generally categorized as neurotoxins, hepatotoxins or cytotoxins. The acute oral toxicities of these toxins vary substantially, with the saxitoxins being the most toxic having an LD50 of 60 μg/kg. By comparison, the acute oral LD50 for microcystin LR (the most toxic congener) and cylindrospermopsin are approximately 5,000 to 10,000 μg/kg and 6,000 μg/kg over 5 days, respectively. There are well known adverse health issues of cyanobacterial toxin poisonings. The most serious health consequences have occurred in Brazil with the reported deaths of people from gastrointestinal symptoms associated with exposure to microcystins and cylindrospermopsin. Increased number of symptoms has also been reported via exposure to cyanobacterial toxins through water-based recreational activities. Toxins may also be present in drinking water and thus guideline values are necessary to protect the health of the population. Guideline values are available for microcystins but not for saxitoxins, cylindrospermopsin or deoxycylindrospermopsin. Considerable research is being undertaken currently on more fully understanding the mechanisms of toxicity of cylindrospermopsin to enable relevant guidelines to be established.
Characterization of dissolved organic matter and disinfection characteristics of source water from the Pearl River
Authors: Zhao Z.Y. , Gu J.D. , Li H.B.
Published: July 2007

Source water samples were collected from Guangzhou segment of Pearl River and filtered through Amicon® YC-05, YM-1, YM-3, YM-10, YM-30, YM-100 and ZM-500 membranes sequentially after pre-treatment. The apparent molecular weights of the 8 fractions were calibrated using high-performance size exclusion chromatograph (HPSEC) and they ranged from 0.36 to 182.6 kDa. These fractionated isolates and the raw water were disinfected by chlorine or chlorine dioxide to determine their disinfection characteristics. Results showed that apparent molecular weight of the main dissolved organic matter (DOM) in the RO isolate of water sample was less than 360 Da and this part of the DOM was mainly from anthropogenic activities and contamination of wastewater. RO fraction was the controlling factor for the raw water disinfection process according to the THMs concentrations detected. Disinfection by chlorine dioxide produced less THMs that by chlorine.
Integrated water resources management: lost on the road from ambition to realisation?
Authors: Jeffrey P. , Gearey M.
Published: July 2007

The recognition that water plays a central role in industrial, agricultural, economic, social and cultural development has, over the past half century, led to the development of strategic management approaches based on the concept of integrated water resources management (IWRM). This paper assesses the extent to which IWRM theory has been converted into practice and identifies existing “research gaps”. We set out our arguments as a critique of IWRM; describing its basic tenets, exploring its value as a conceptual tool, considering its scientific pedigree, questioning its novelty as a resource management paradigm, and suggesting ways of translating the theory into more widespread practice. Finally, we argue that whilst models in their broadest sense can make a significant contribution to IWRM research and practice, a revised assessment of the source of their value is required.
Spatio-temporal statistical models for river monitoring networks
Authors: Clement L. , Thas O. , Vanrolleghem P.A. , Ottoy J.P.
Published: July 2007

When introducing new wastewater treatment plants (WWTP), investors and policy makers often want to know if there indeed is a beneficial effect of the installation of a WWTP on the river water quality. Such an effect can be established in time as well as in space. Since both temporal and spatial components affect the output of a monitoring network, their dependence structure has to be modelled. River water quality data typically come from a river monitoring network for which the spatial dependence structure is unidirectional. Thus the traditional spatio-temporal models are not appropriate, as they cannot take advantage of this directional information. In this paper, a state-space model is presented in which the spatial dependence of the state variable is represented by a directed acyclic graph, and the temporal dependence by a first-order autoregressive process. The state-space model is extended with a linear model for the mean to estimate the effect of the activation of a WWTP on the dissolved oxygen concentration downstream.
Strategic analysis for sustainable urban river aquatic environment using the system dynamic approach
Authors: Lee M.T. , Chang Y.C.
Published: July 2007

A sustainable aquatic environment, which relates to the issues of pollution mitigation and ecological restoration, is one of the important indicators of the vitality and prosperity of a city. Traditionally, resort to engineering efforts is always the first priority in dealing with such problems. Nevertheless, treated as an integrated system, the nature of the problem should involve many aspects including economic, ecological, environmental, and engineering factors. Meanwhile, the special feature of the time-dependent state has also made such a system a dynamic and complex problem. The current research has employed the concepts of integrated assessment trying to aggregate related studies and tackling the problem as a complete system. With the aid of the system dynamic modeling tool, which is capable of dealing with dynamic and complex problems, the simulation model was formulated following the macrostructure of system behavior. Various strategies for improving the sustainability of the aquatic environment in Love River, Kaohsiung, Taiwan have been evaluated. The decision makers are therefore allowed to choose more effective strategies based on the integrated perspectives.
Evaluation of BASINS/WinHSPF applicability for pollutant loading estimation for a Korean watershed
Authors: Jeon J.H. , Yoon C.G. , Ham J.H. , Jung K.W.
Published: July 2007

Applicability of a widely accepted watershed-based water quality assessment tool (BASINS) and its associated watershed model (WinHSPF) was evaluated on the Seamangeum watershed in Korea. The study site is the largest polder project area in Korea and its environmental quality has been debated for the last five years. BASINS was found to be a convenient and powerful tool for assessment of watershed characteristics, and provided various tools to delineate the watershed into land segments and river reaches, reclassify land use, and parameterize for WinHSPF simulation. Calibration results were satisfactory showing model efficiency over 0.80 for stream flow, temperature, and dissolved oxygen simulation, and model output for water quality constituents also reasonably matched the observed data. It was demonstrated that calibration with dry-day data for a relatively long period might be adequate to simulate hydrologic characteristics and water quality of the watershed with WinHSPF, and using parameters generated with BASINS for nonpoint source pollution simulation is suggested when enough wet-day monitoring data are not available. The unit-area load of biochemical oxygen demand, total nitrogen, and total phosphorus was 27.8, 48.2, and 4.3 kg/ha/yr, respectively. These values are within the expected range but on the high side of the reported values, which implies that effective control measures are required to protect water quality of the downstream reservoir. Overall, BASINS/WinHSPF was applicable and found to be a powerful tool in pollutant loading estimation from the watershed, and its use in Korea is recommended.
Application of uncertainty and sensitivity analysis in river basin management
Authors: Xu Y. , Mynett A.E.
Published: July 2007

Considering uncertainty in the decision-making process in river basin management is important because uncertainty is regarded as one of the main obstacles to sound decision-making. In case of high uncertainty, the risks of making a wrong decision could be quite high, which may have severe consequences. This paper applies a screening sensitivity analysis method, the Morris method, to investigate the propagation of uncertainty from factors in a flood damage model into the model outputs and explores the importance of factors based on the sensitivity analysis. Uncertainty reduction in the most influential factors identified by the Morris method is proposed as a means to reduce the uncertainty in model outputs. In this way the risks of making a wrong decision could be reduced. The results in this paper show that the Morris method is an efficient approach to help reduce the uncertainty in model outputs.
An uncertainty analysis of the flood-stage upstream from a bridge
Authors: Sowiński M.
Published: July 2007

The paper begins with the formulation of the problem in the form of a general performance function. Next the Latin hypercube sampling (LHS) technique – a modified version of the Monte Carlo method is briefly described. The essential uncertainty analysis of the flood-stage upstream from a bridge starts with a description of the hydraulic model. This model concept is based on the HEC-RAS model developed for subcritical flow under a bridge without piers in which the energy equation is applied. The next section contains the characteristic of the basic variables including a specification of their statistics (means and variances). Next the problem of correlated variables is discussed and assumptions concerning correlation among basic variables are formulated. The analysis of results is based on LHS ranking lists obtained from the computer package UNCSAM. Results fot two examples are given: one for independent and the other for correlated variables.
Towards a synthesis of data-based and theory-based models of environmental systems
Authors: Lin Z. , Beck M.B.
Published: July 2007

A two-pronged approach to interpreting field data through the use of models is presented. This approach builds upon both data- and theory-based models and their associated methods of system identification. It seeks to overcome their respective limitations: that theory-based models are not unambiguously identifiable from the observations, while a well identified data-based model may not be capable of a satisfactory theoretical interpretation. The purpose of the approach is thereby to gain a deeper understanding of complex environmental systems. Recursive methods of time-series analysis are used to identify the data-based models and the modified recursive prediction error algorithm is employed for parameter estimation of the theory-based models. The results of these identification exercises for the two classes of models can be compared in terms of the macro-parameters of the studied system's time constant and steady-state gain. Two case studies are presented to illustrate the overall performance of the two-pronged approach. It is found that: (1) more is to be gained through the joint application of the two classes of models than the exclusive use of either; (2) to some extent, identifying the structure and estimating the parameters of one type of model can be improved by recourse to the corresponding results for the other; and (3) reconciliation of the results from identifying the two classes of model in the parameter space has significant advantages over the more familiar process of evaluating a model's performance in the terms of its (observed) state space features.
Probabilistic evaluation of ammonia toxicity in Milwaukee's Outer Harbor
Authors: Melching C.S. , Novotny V. , Schilling J.B.
Published: July 2007

Water-quality models that are simple yet sound and reliable and that correspond to water-quality criteria that include magnitude, frequency, and duration components are needed. Monte Carlo models are developed on the basis of available flow and water-quality data and a deterministic water-quality model appropriate for the problem at hand and the data available. Monte Carlo models yield time series and probability distributions of constituents of interest in conformance with water-quality criteria. The application of a Monte Carlo model to the probabilistic evaluation of ammonia toxicity in Milwaukee's Outer Harbor is presented here. Under typical operating conditions for the Jones Island Wastewater Treatment Plant, ammonia toxicity was found to not be a problem for the Outer Harbor. The Monte Carlo model then was used to determine effluent limits that would meet the ammonia toxicity criteria.
Parameter sensitivity analysis for activated sludge models No. 1 and 3 combined with one-dimensional settling model
Authors: Kim J.R. , Ko J.H. , Lee J.J. , Kim S.H. , Park T.J. , Kim C.W. , Woo H.J.
Published: July 2007

The aim of this study was to suggest a sensitivity analysis technique that can reliably predict effluent quality and minimize calibration efforts without being seriously affected by influent composition and parameter uncertainty in the activated sludge models No. 1 (ASM1) and No. 3 (ASM3) with a settling model. The parameter sensitivities for ASM1 and ASM3 were analyzed by three techniques such as SVM-Slope, RVM-SlopeMA, and RVM-AreaCRF. The settling model parameters were also considered. The selected highly sensitive parameters were estimated with a genetic algorithm, and the simulation results were compared as ΔEQ. For ASM1, the SVM-Slope technique proved to be an acceptable approach because it identified consistent sensitive parameter sets and presented smaller ΔEQ under every tested condition. For ASM3, no technique identified consistently sensitive parameters under different conditions. This phenomenon was regarded as the reflection of the high sensitivity of the ASM3 parameters. But it should be noted that the SVM-Slope technique presented reliable ΔEQ under every influent condition. Moreover, it was the simplest and easiest methodology for coding and quantification among those tested. Therefore, it was concluded that the SVM-Slope technique could be a reasonable approach for both ASM1 and ASM3.
Practical approach to parameter estimation for ASM3+bio-P module applied to five-stage step-feed EBPR process
Authors: Lee S.H. , Ko J.H. , Poo K.M. , Lee T.H. , Woo H.J. , Kim C.W.
Published: July 2007

Various parameter optimization approaches to a five-stage step-feed EBPR process modeled using the ASM3+bio-P module were examined. Five stoichiometric (YSTO,NO, YH,O2, YH,NO, YPAO,O2, YPO4) and seven kinetic parameters (kSTO, ηNO, bH, μmax,PAO, qPHA, qPP, μmax,A) were estimated. The optimization approaches could be classified based on the data sources (batch experiments or CSTR operation data) and the number of target variables used in calculating the objective function. Optimized parameter values obtained by each approach were validated with CSTR operation data that were not used for parameter optimization. The results showed that the parameter optimization only with batch experimental results could not be directly applied to CSTR operation data. ASM3+bio-P module parameters could be finely optimized only with CSTR operation data when sufficient target variables for objective function calculation were applied. When the number of target variables was increased, prediction performance was significantly improved. Once optimized, the model was able to predict the characteristic features of the five-stage step-feed process; namely, a high PAO yield, fast PAO growth, fast XPP storage, slow XSTO and XPHA storage.
Stability analysis of a wastewater treatment plantwith saturated control
Authors: Grognard F. , Bernard O.
Published: July 2007

This paper presents a saturated proportional controller that achieves depollution of wastewater in a continuous anaerobic digester. This goal is reached by defining a region of the state-space where the depollution is achieved and forcing attractivity and invariance of this region. The control variable is the dilution rate and the controlled variable is a linear combination (Sλ) of the substrates concentrations, that could be the chemical oxygen demand or the biological oxygen demand, depending on the value of λ. No measurement of the substrates concentrations in the input flow is required: the only necessary measurement is Sλ.