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Selected AbstractsWastewater treatment plants as a pathway for aquatic contamination by pharmaceuticals in the Ebro river basin (Northeast Spain)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2007Meritxell Gros Abstract The occurrence of 28 pharmaceuticals of major human consumption in Spain, including analgesics and anti-inflam-matories, lipid regulators, psychiatric drugs, antibiotics, antihistamines, and ,-blockers, was assessed along the Ebro river basin, one of the biggest irrigated lands in that country. Target compounds were simultaneously analyzed by off-line solid-phase extraction, followed by liquid chromatography-tandem mass spectrometry. The loads of detected pharmaceuticals and their removal rates were studied in seven wastewater treatment plants (WWTPs) located in the main cities along the basin. Total loads ranged from 2 to 5 and from 0.5 to 1.5 g/d/1,000 inhabitants in influent and effluent wastewaters, respectively. High removal rates (60,90%) were achieved mainly for analgesics and anti-inflammatories. The other groups showed lower rates, ranging from 20 to 60%, and in most cases, the antiepileptic carbamazepine, macrolide antibiotics, and trimethoprim were not eliminated at all. Finally, the contribution of WWTP effluents to the presence of pharmaceuticals in receiving river waters was surveyed. In receiving surface water, the most ubiquitous compounds were the analgesics and anti-inflammatories ibuprofen, diclofenac, and naproxen; the lipid regulators bezafibrate and gemfibrozil; the antibiotics erythromycin, azithromycin, sulfamethoxazole, trimethoprim, and less frequently, ofloxacin; the antiepileptic carbamazepine; the antihistamine ranitidine; and the ,-blockers atenolol and sotalol. Although levels found in WWTP effluents ranged from low ,g/L to high ng/L, pharmaceuticals in river waters occurred at levels at least one order of magnitude lower (low ng/L range) because of dilution effect. From the results obtained, it was proved that WWTP are hot spots of aquatic contamination concerning pharmaceuticals of human consumption. [source] Sediment transport in a highly regulated fluvial system during two consecutive floods (lower Ebro River, NE Iberian Peninsula)EARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2005Damia Vericat Abstract The transfer of sediment through a highly regulated large fluvial system (lower Ebro River) was analysed during two consecutive floods by means of sediment sampling. Suspended sediment and bedload transport were measured upstream and downstream of large reservoirs. The dams substantially altered flood timing, particularly the peaks, which were advanced downstream from the dams for flood control purposes. The suspended sediment yield upstream from the dams was 1 700 000 tonnes, which represented nearly 99 per cent of the total solid yield. The mean concentrations were close to 0·5 g l,1. The sediment yield downstream from the dams was an order of magnitude lower (173 000 tonnes), showing a mean concentration of 0·05 g l,1. The dams captured up to 95 per cent of the fine sediment carried in suspension in the river channel, preventing it from reaching the lowermost reaches of the river and the delta plain. Total bedload transport upstream from the dams was estimated to be about 25 000 tonnes, only 1·5 per cent of the total load. The median bedload rate was 100 gms,1. Below the dams, the river carried 178 000 tonnes, around 51 per cent of the total load, at a mean rate of 250 g ms,1. The results of sediment transport upstream and downstream from the large dams illustrate the magnitude of the sediment deficit in the lower Ebro River. The river mobilized a total of 350 000 tonnes in the downstream reaches, which were not replaced by sediment from upstream. Therefore, sediment was necessarily entrained from the riverbed and channel banks, causing a mean incision of 33 mm over the 27 km long study reach, altogether a significant step towards the long-term degradation of the lower Ebro River. Copyright © 2005 John Wiley & Sons, Ltd. [source] Service restoration method considering simultaneous disconnection of distributed generators by one-bank fault of distribution systemELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 8 2008Hirotaka Takano Abstract Distributed generators (DGs) such as fuel cells and solar cells are going to be installed in the demand side of distribution systems. The DGs can reduce distribution loss by appropriate allocation. However, there are several problems installing DGs such as service restoration of distribution system with DGs and so on. When one bank fault of distribution substation occurs in distribution system, since DGs are simultaneously disconnected from the system, it is not easy to restore isolated load by one bank switching in distribution substation. Therefore, a service restoration method to determine restoration configuration and restoration procedures (switching procedure from normal configuration to restoration configuration) taking into account simultaneous disconnection of DGs is needed. In this paper, the authors propose a computation method to determine the optimal restoration configuration and the restoration procedure considering simultaneous disconnection of DGs by one bank fault of distribution system. In the proposed algorithm, after all of the restoration configuration candidates are effectively enumerated under the operational constraints, the optimal configuration to restore the isolated load is selected among enumerated configuration candidates. After determining the optimal restoration configuration, the optimal restoration procedures are obtained by greedy algorithm. Numerical simulations are carried out for a real scale system model with 237 sectionalizing switches (configuration candidates are 2237) and 21 DGs (total output is 5250 kW which is 3% of total load) in order to examine the validity of the proposed algorithm. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(8): 44,55, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10133 [source] Catchment-scale contribution of forest roads to stream exports of sediment, phosphorus and nitrogenHYDROLOGICAL PROCESSES, Issue 23 2007Gary J. Sheridan Abstract The relative contribution of forest roads to total catchment exports of suspended sediment, phosphorus, and nitrogen was estimated for a 13 451 ha forested catchment in southeastern Australia. Instrumentation was installed for 1 year to quantify total in-stream exports of suspended sediment, phosphorus, and nitrogen. In addition, a total of 101 road,stream crossings were mapped and characterized in detail within the catchment to identify the properties of the road section where the road network and the stream network intersect. Sediment and nutrient generation rates from different forest road types within the catchment were quantified using permanent instrumentation and rainfall simulation. Sediment and nutrient generation rates, mapped stream crossing information, traffic data and annual rainfall data were used to estimate annual loads of sediment, phosphorus, and nitrogen from each stream crossing in the catchment. The annual sum of these loads was compared with the measured total catchment exports to estimate the proportional contribution of loads from roads within the catchment. The results indicated that 3·15 ha of near-stream unsealed road surface with an average slope of 8·4% delivered an estimated 50 t of the 1142 t of total suspended sediment exported from the catchment, or about 4·4% of the total sediment load from the forest. Stream discharge over this period was 69 573 Ml. The unsealed road network delivered an estimated maximum of 22 kg of the 1244 kg of total phosphorus from the catchment, or less than 1·8% of the total load from the forest. The average sediment and phosphorous load per crossing was estimated at 0·5 t (standard deviation 1·0 t) and 0·22 kg (standard deviation 0·30 kg) respectively. The lower proportional contribution of total phosphorus resulted from a low ratio of total phosphorus to total suspended sediment for the road-derived sediment. The unsealed road network delivered approximately 33 kg of the 20 163 kg of total nitrogen, about 0·16% of the total load of nitrogen from the forest. The data indicate that, in this catchment, improvement of stream crossings would yield only small benefits in terms of net catchment exports of total suspended sediment and total phosphorus, and no benefit in terms of total nitrogen. These results are for a catchment with minimal road-related mass movement, and extrapolation of these findings to the broader forested estate requires further research. Copyright © 2007 John Wiley & Sons, Ltd. [source] An unconditionally convergent algorithm for the evaluation of the ultimate limit state of RC sections subject to axial force and biaxial bendingINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 8 2007G. Alfano Abstract We present a numerical procedure, based upon a tangent approach, for evaluating the ultimate limit state (ULS) of reinforced concrete (RC) sections subject to axial force and biaxial bending. The RC sections are assumed to be of arbitrary polygonal shape and degree of connection; furthermore, it is possible to keep fixed a given amount of the total load and to find the ULS associated only with the remaining part which can be increased by means of a load multiplier. The solution procedure adopts two nested iterative schemes which, in turn, update the current value of the tentative ultimate load and the associated strain parameters. In this second scheme an effective integration procedure is used for evaluating in closed form, as explicit functions of the position vectors of the vertices of the section, the domain integrals appearing in the definition of the tangent matrix and of the stress resultants. Under mild hypotheses, which are practically satisfied for all cases of engineering interest, the existence and uniqueness of the ULS load multiplier is ensured and the global convergence of the proposed solution algorithm to such value is proved. An extensive set of numerical tests, carried out for rectangular, L-shaped and multicell sections shows the effectiveness of the proposed solution procedure. Copyright © 2007 John Wiley & Sons, Ltd. [source] Contribution of the largest events to suspended sediment transport across the USALAND DEGRADATION AND DEVELOPMENT, Issue 2 2010J. C. Gonzalez-Hidalgo Abstract This work analyses the contribution of the largest events to suspended sediment transport on the continental scale. The analysis is based on the United States Geological Survey (USGS) Suspended Sediment and Ancillary database. Data were obtained from 1314 catchments, comprising more than 2,500,000 daily events. The total number of days in the dataset amounts to 10,000 years. Catchments are of different sizes and belong to distinct climatic environments; they are distributed for the analysis according to USA hydrological divisions (HDs). The main objective of the research is to examine the effect of the n -largest event on the total suspended sediment load over recorded periods, and to discuss different behaviour between HDs. To accomplish this, the daily events at each catchment are ranked by magnitude, and then the percentage represented by the n -largest event (e.g. 3-largest, 5-largest, 10-largest, 15-largest, 20-largest, 25-largest) is calculated from the total accumulated load. Results indicate that suspended sediment transported by the 25-largest events represents on average more than 50,per cent of the total load. The California HD, mostly under Mediterranean climatic conditions, accounts for the highest percentage of sediment transport across conterminous USA, whatever n -largest daily events are selected. There, the 3-largest events contribute, on average, 38,per cent of the total sediment load, the 10-largest events represent 61,per cent and the 25-largest events produce more than 76,per cent of the total sediment transport. Overall, the contribution of largest daily events seems not to depend on the climatic conditions in small catchments (<100,km2) and, in addition, the percentage of suspended sediment increases over all HDs, while, at the same time, the catchment size decreases. Finally, we discuss differences between catchments across the USA, according to climatic and historical (i.e. land use) factors. Copyright © 2009 John Wiley & Sons, Ltd. [source] A note on optimal pricing for finite capacity queueing systems with multiple customer classesNAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 5 2008Serhan Ziya Abstract This article investigates optimal static prices for a finite capacity queueing system serving customers from different classes. We first show that the original multi-class formulation in which the price for each class is a decision variable can be reformulated as a single dimensional problem with the total load as the decision variable. Using this alternative formulation, we prove an upper bound for the optimal arrival rates for a fairly large class of queueing systems and provide sufficient conditions that ensure the existence of a unique optimal arrival rate vector. We show that these conditions hold for M/M/1/m and M/G/s/s systems and prove structural results on the relationships between the optimal arrival rates and system capacity. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008 [source] Vertex disjoint routings of cycles over toriNETWORKS: AN INTERNATIONAL JOURNAL, Issue 3 2007Jean-Claude Bermond Abstract We study the problem of designing a survivable WDM network based on covering the communication requests with subnetworks that are protected independently from each other. We consider here the case when the physical network is T(n), a torus of size n by n, the subnetworks are cycles and the communication scheme is all-to-all or total exchange (where all pairs of vertices communicate). We will represent the communication requests by a logical graph: a complete graph for the scheme of all-to-all. This problem can be modeled as follows: find a cycle partition or covering of the request edges of K, such that for each cycle in the partition, its request edges can be routed in the physical network T(n) by a set of vertex disjoint paths (equivalently, the routings with the request cycle form an elementary cycle in T(n)). Let the load of an edge of the WDM network be the number of paths associated with the requests using the edge. The cost of the network depends on the total load (the cost of transmission) and the maximum load (the cost of equipment). To minimize these costs, we will search for an optimal (or quasi optimal) routing satisfying the following two conditions: (a) each request edge is routed by a shortest path over T(n), and (b) the load of each physical edge resulting from the routing of all cycles of S is uniform or quasi uniform. In this article, we find a covering or partition of the request edges of K into cycles with an associated optimal or quasi optimal routing such that either (1) the number of cycles of the covering is minimum, or (2) the cycles have size 3 or 4. © 2007 Wiley Periodicals, Inc. NETWORKS, Vol. 49(3), 217,225 2007 [source] Approximation algorithms for channel allocation problems in broadcast networksNETWORKS: AN INTERNATIONAL JOURNAL, Issue 4 2006Rajiv Gandhi Abstract We study two packing problems that arise in the area of dissemination-based information systems; a second theme is the study of distributed approximation algorithms. The problems considered have the property that the space occupied by a collection of objects together could be significantly less than the sum of the sizes of the individual objects. In the Channel Allocation Problem, there are requests that are subsets of topics. There are a fixed number of channels that can carry an arbitrary number of topics. All the topics of each request must be broadcast on some channel. The load on any channel is the number of topics that are broadcast on that channel; the objective is to minimize the maximum load on any channel. We present approximation algorithms for this problem, and also show that the problem is MAX-SNP hard. The second problem is the Edge Partitioning Problem addressed by Goldschmidt, Hochbaum, Levin, and Olinick (Networks, 41:13,23, 2003). Each channel here can deliver topics for at most k requests, and we aim to minimize the total load on all channels. We present an O(n1/3),approximation algorithm, and also show that the algorithm can be made fully distributed with the same approximation guarantee; we also generalize the (nondistributed) Edge Partitioning Problem of graphs to the case of hypergraphs. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 47(4), 225,236 2006 [source] On-farm management practices to minimise off-site movement of pesticides from furrow irrigationPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 10 2006Danielle P Oliver Abstract Off-site movement of pesticides from furrow-irrigated agriculture has been a concern in the Ord River Irrigation Area, Western Australia. This paper reports on the effectiveness of incorporation of pesticides by cultivator or power harrows before irrigating, and spraying pesticides only onto beds to minimise off-site transport. Incorporation of pesticides by power harrows prior to irrigation was found to be more effective in decreasing the off-site transport of a more strongly sorbed pesticide, endosulfan. The average load of total endosulfan (, + , + sulfate) decreased by 74% (P < 0.01) from 11.41 g ha,1 from the conventionally treated bays to 2.96 g ha,1 from the incorporated irrigation bays. The total average load of atrazine leaving the irrigation bays was decreased by 81% (P < 0.05) from 87.82 g ha,1 under the conventional practice of spraying the whole field to 16.95 g ha,1 by spraying the beds only. A reduction of 52% in total average load of metolachlor was observed following incorporation with power harrows, but this was not significant. Incorporation by cultivator or by power harrows decreased the total load of atrazine or metolachlor leaving the irrigation bays over the whole irrigation period, but these treatments were not shown to be statistically significant, which may have been due to the limited number of field replicates. Incorporation of strongly sorbed pesticides (e.g. endosulfan) prior to irrigation significantly decreased the off-site transport of these pesticides in a furrow irrigation system and may be a useful practice to minimise off-site transport of other similar pesticides. Minimising off-site transport of weakly sorbed pesticides (e.g. atrazine and metolachlor) from a furrow irrigation system is more difficult. The nature of furrow irrigation makes it highly conducive to pesticide transport, particularly of weakly sorbed pesticides, and further work is needed to develop strategies to minimise the movement of this group of pesticides to water bodies. Copyright © 2006 Society of Chemical Industry [source] Release from foliar and floral fungal pathogen species does not explain the geographic spread of naturalized North American plants in EuropeJOURNAL OF ECOLOGY, Issue 3 2009Mark Van Kleunen Summary 1During the last centuries many alien species have established and spread in new regions, where some of them cause large ecological and economic problems. As one of the main explanations of the spread of alien species, the enemy-release hypothesis is widely accepted and frequently serves as justification for biological control. 2We used a global fungus,plant host distribution data set for 140 North American plant species naturalized in Europe to test whether alien plants are generally released from foliar and floral pathogens, whether they are mainly released from pathogens that are rare in the native range, and whether geographic spread of the North American plant species in Europe is associated with release from fungal pathogens. 3We show that the 140 North American plant species naturalized in Europe were released from 58% of their foliar and floral fungal pathogen species. However, when we also consider fungal pathogens of the native North American host range that in Europe so far have only been reported on other plant species, the estimated release is reduced to 10.3%. Moreover, in Europe North American plants have mainly escaped their rare, pathogens, of which the impact is restricted to few populations. Most importantly and directly opposing the enemy-release hypothesis, geographic spread of the alien plants in Europe was negatively associated with their release from fungal pathogens. 4Synthesis. North American plants may have escaped particular fungal species that control them in their native range, but based on total loads of fungal species, release from foliar and floral fungal pathogens does not explain the geographic spread of North American plant species in Europe. To test whether enemy release is the major driver of plant invasiveness, we urgently require more studies comparing release of invasive and non-invasive alien species from enemies of different guilds, and studies that assess the actual impact of the enemies. [source] | |||||||||||||||||||