bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Modelling of a Single-Link Flexible Manipulator System: A Particle Swarm Optimisation Approach
Authors: Alam M. S. , Tokhi M. O.
Published: August 2007

This paper presents investigations into modelling of a single-link flexible manipulator system using the particle swarm optimisation (PSO) algorithm. PSO is a population-based search algorithm and is initialised with a population of random solutions, called particles. Basic PSO with best model can hardly provide suitable solutions in the case of real-world multimodal problems. In order to improve diversity in the population set and hence to improve the global searching capability a local version of PSO with time varying inertia and acceleration coefficients is proposed and used in this work. The effectiveness of the algorithm in modelling is validated and verified in terms of tracking, stability and the ability of the derived model in capturing a system's dynamics. The effect of swarm size on the convergence of the proposed PSO algorithm is also analysed. Time domain and frequency domain results of derived models clearly show the potential of the modelling technique and the proposed algorithm in solving such control problems.
Research on Active Absorption Using Piezoelectric Ceramic
Authors: Congyun Zhu , Zeqiang Zhao , Qibai Huang
Published: August 2007

Piezoelectric ceramic (PZT) is used as the main material of the transducer, energy exchanger, arrester etc. and used in a control system in sound and vibration because of its excellent mechanical and electrical coupling performance, based on which, in this paper, a new active absorption system is designed in which the piezoelectric ceramic is used as the absorption material. Two equal distance microphones are placed in the front of the piezoelectric ceramic in order to measure the incident plane wave. Then, a voltage is applied on the piezoelectric ceramic in order to make the reflected wave zero using the adaptive controlling. Finally, an experiment is carried out and a good absorption effect attained. The experimental results denote that the theory is correct and practical.
Sorption-Analytic, Microcalorimetric and ab Initio Study of Ion-Exchange Equilibria Involving Mg2+ and Ca2+ Cations on Clinoptilolite
Authors: Tarasevich Yuri I. , Polyakov Valeri E. , Krysenko Dmytro O. , Aksenenko Eugene V.
Published: August 2007

The exchange equilibrium between Mg2+ and Ca2+ ions and the corresponding microcalorimetric ion-exchange heats were studied on two clinoptilolite (Cli) samples. Using the experimental values of the ion-exchange constants (free energies) and heats (enthalpies), reliable estimates of the entropy were obtained for the direct (Mg2+-Ca2+-Cli) and inverse ion-exchange reactions. It was shown that the sign (negative or positive) of the ion-exchange free energy in the case under study was determined essentially by the entropy constituent of the ion-exchange process. The selectivity of clinoptilolite towards Ca2+ cations rather than to Mg2+ cations was demonstrated.

The ab initio calculations undertaken confirmed the experimental results and provided structural information concerning the localisation of ions in the crystalline environment. In particular, it was shown that the 10-membered structural clinoptilolite rings provide favourable positions for hydrated Ca2+ cations. The energy gain of the system arising from the Ca2+-Mg-Cli exchange was -E = 8.0–3.4 kJ/mol depending on the localisation sites for the Ca2+ cations; these values are in acceptable quantitative agreement with experimental data for the exchange enthalpy variation –ΔH = (7.3-8.4) kJ/(g equiv). Data were obtained for the energetics of interaction of Ca2+ and Mg2+ ions with water molecules located in the first and second hydration spheres.
Sorption of Noble Metals on Silica Gel Chemically Modified with N-(5-Mercapto-1,3,4-Thiadiazol-2-yl)-N'-Propylurea Groups
Authors: Trokhimchuk A.K. , Boychenko I.M. , Losev V.N.
Published: August 2007

Sorption processes of noble metals on silica gel surface with covalently grafted N-(5-mercapto-1,3,4-thiadiazol-2-yl)- N'-propylurea groups (MTS) were studied. It was found that sorption onto MTS may occur via complexation and/or anion-exchange mechanisms depending on the acidity of the solutions. It was shown that differences in the kinetics and temperature conditions for the sorption of platinum and gold can be used to separate micro-amounts of these metals in solution.
Synthesis and Adsorptive Constitutive Properties of MMS/MFI Materials Prepared on the Basis of Al-Aerosil
Authors: Khomenko K.M. , Zhukow G.I. , Gornikov J.I. , Leboda R. , Brei V.V.
Published: August 2007

A method for the one-stage bitemplate synthesis of mesoporous zeolite-containing materials based on Al-aerosil (Al-MZ) is proposed. The prepared materials were characterized by IR spectroscopy (FT-IR), X-ray diffraction (XRD) and nitrogen adsorption methods.
Effect of Copper Ions upon the Sorption of Amino Acids onto a Fumed Silica Surface
Authors: Vlasova Nataliya M. , Markitan Ol'ga V.
Published: August 2007

The sorption of some amino acids (Aa) onto a fumed silica surface in the presence of copper ions was studied over the pH range 4–8. The adsorption process was interpreted in terms of the surface complexation theory using the basic Stern model (BSM). Equilibrium parameters were determined using the GRFIT program package. Only basic amino acids such as arginine, lysine and ornithine were sorbed from individual aqueous solutions onto the silica surface. Their sorption was modelled in terms of outer-sphere surface complexes. All these amino acids were sorbed onto silica in the presence of copper ions. Modelling of the amino acid sorption was based on ternary surface complexes. This allowed us to simulate the experimental data at different molar ratios Cu2+:Aa (1:1 and 1:2) over the total pH range studied.
Surface Active Sites of Modified Zeolites and Zirconia in the Conversion of Nitrogen(I, II) Oxides
Authors: Orlyk Svetlana M. , Mironyuk Tatyana V. , Boichuk Tatyana M.
Published: August 2007

Samples of zirconia doped with transition metal (Cr, Co, Ce) oxides, and also rhodium-promoted and Fe-containing zeolites of different structural types, were studied by NH3-TPD and IR spectroscopy. The various samples were analyzed with respect to their catalytic performances in deNO x reactions, in particular the selective catalytic reduction of NO (N2O) using hydrocarbons as reducing agents (HC SCR). Bifunctional zeolite- and ZrO2-based catalysts exhibited high activity in the SCR of nitrogen(I, II) oxides to dinitrogen due to the combination of the surface redox and acidic properties exhibited by these materials.
Influence of Structural and Chemical Modification of Silica on its Surface Hydration
Authors: Turova A.A. , Gun'ko V.M. , Turov V.V. , Gorbik P.P.
Published: August 2007

It was shown that an unusual structural type of water, which is weakly associated and unfrozen up to 180 K and possessing a proton resonance chemical shift at 1.5 ppm, appears at the patch-wise hydrophilic/hydrophobic interfaces of adsorbents placed in non-polar or weak solvents. Such water can amount to 10 wt% in amount.
Characteristics of the Thermal Desorption and Conversion of Organic Templates in Micropores of Zeolite-like Phosphates
Authors: Yaremov Pavel S. , Shvets Oleksiy V. , Ilyin Vladimir G.
Published: August 2007

The characteristics of the dehydration, thermal desorption and thermal decomposition of organic templates in zeolite-like aluminophosphates and silica aluminophosphates of different structural types have been elucidated. The influence of the pore size and acidic centres on the composition of the thermal decomposition products, including the secondary syntheses of normal, cyclic and aromatic hydrocarbons, has been established. The possibility of dehydration, oligomerization, cyclization, cracking, aromatization and alkylation of hydrocarbons in zeolite-like phosphates has been shown.
A Study on the Cross-Entropy Method for Rare-Event Probability Estimation
Authors: Homem-de-Mello Tito
Published: August 2007

We discuss the problem of estimating probabilities of rare events in static simulation models using the recently proposed cross-entropy method, which is a type of importance-sampling technique in which the new distributions are successively calculated by minimizing the cross-entropy with respect to the ideal (but unattainable) zero-variance distribution. In our approach, by working on a functional space we are able to provide an efficient procedure without assuming any specific family of distributions. We then describe an implementable algorithm that incorporates the ideas described in the paper. Some convergence properties of the proposed method are established, and numerical experiments are presented to illustrate the efficacy of the algorithm.
Tariff Optimization in Networks
Authors: Bouhtou Mustapha , van Hoesel Stan , van der Kraaij Anton F. , Lutton Jean-Luc
Published: August 2007

We consider the problem of determining a set of optimal tariffs for an agent in the network, who owns a subset of all the arcs, and who receives revenue by setting the tariffs on the arcs he owns. Multiple rational clients are active in the network, who route their demands on the least expensive paths from source to destination. The cost of a path is determined by fixed costs and tariffs on the arcs of the path. We introduce a remodeling of the network, using shortest paths. We develop three algorithms based on this shortest-path graph model: a combinatorial branch-and-bound algorithm, a path-oriented mixed integer program, and a known-arc-oriented mixed integer program. Combined with reduction methods, this remodeling enables us to solve the problem to optimality, for quite large instances. We provide computational results for the methods developed and compare them with the results of the arc-oriented mixed integer programming formulation of the problem, applied to the original network.
On a Binary-Encoded ILP Coloring Formulation
Authors: Lee Jon , Margot François
Published: August 2007

We further develop the 0/1 ILP formulation of Lee for edge coloring where colors are encoded in binary. With respect to that formulation, our main contributions are (i) an efficient separation algorithm for general block inequalities, (ii) an efficient LP-based separation algorithm for stars (i.e., the all-different polytope), (iii) an introduction of matching inequalities, (iv) an introduction of switched path inequalities and their efficient separation, (v) a complete description for paths, and (vi) the promising computational results.
A Two-Stage Heuristic with Ejection Pools and Generalized Ejection Chains for the Vehicle Routing Problem with Time Windows
Authors: Lim Andrew , Zhang Xingwen
Published: August 2007

The vehicle routing problem with time windows (VRPTW) is an important problem in logistics. The problem is to serve a number of customers at minimum cost without violating the customers’ time-window constraints or the vehicle-capacity constraint. In this paper, we propose a two-stage algorithm for the VRPTW. The algorithm first minimizes the number of vehicles with an ejection pool to hold temporarily unserved customers, which enables the algorithm to go through the infeasible solution space. Then it minimizes the total travel distance using a multi-start iterated hill-climbing algorithm with classical and new operators including generalized ejection chains, which enable the algorithm to search a larger neighborhood. We applied the algorithm to Solomon’s 56 VRPTW instances and Gehring and Homberger’s 300 extended instances. The experimental results showed that the algorithm is effective and efficient in reducing the number of vehicles and is also very competitive in terms of distance minimization. The m-VRPTW is a variant of the VRPTW in which a limited number of vehicles is available. A feasible solution to m-VRPTW may contain some unserved customers due to the insufficiency of vehicles. The primary objective of m-VRPTW is to maximize the number of customers served. We extended our VRPTW algorithm to solve m-VRPTW and the experimental results showed consistently good performance of the algorithm when compared with other methods.
Efficient Computation of Overlapping Variance Estimators for Simulation
Authors: Alexopoulos Christos , Argon Nilay Tanık , Goldsman David , Steiger Natalie M. , Tokol Gamze , Wilson James R.
Published: August 2007

For a steady-state simulation output process, we formulate efficient algorithms to compute certain estimators of the process variance parameter (i.e., the sum of covariances at all lags), where the estimators are derived in principle from overlapping batches separately and then averaged over all such batches. The algorithms require order-of-sample-size work to evaluate overlapping versions of the area and Cramér–von Mises estimators arising in the method of standardized time series. Recently, Alexopoulos et al. showed that, compared with estimators based on nonoverlapping batches, the estimators based on overlapping batches achieve reduced variance while maintaining similar bias asymptotically as the batch size increases. We provide illustrative analytical and Monte Carlo results for M/M/1 queue waiting times and for a first-order autoregressive process. We also present evidence that the asymptotic distribution of each overlapping variance estimator can be closely approximated using an appropriately rescaled chi-squared random variable with matching mean and variance.
Computing with Domino-Parity Inequalities for the Traveling Salesman Problem (TSP)
Authors: Cook William , Espinoza Daniel G. , Goycoolea Marcos
Published: August 2007

We describe methods for implementing separation algorithms for domino-parity inequalities for the symmetric traveling salesman problem. These inequalities were introduced by Letchford (2000), who showed that the separation problem can be solved in polynomial time when the support graph of the LP solution is planar. In our study we deal with the problem of how to use this algorithm in the general (nonplanar) case, continuing the work of Boyd et al. (2001). Our implementation includes pruning methods to restrict the search for dominoes, a parallelization of the main domino-building step, heuristics to obtain planar-support graphs, a safe-shrinking routine, a random-walk heuristic to extract additional violated constraints, and a tightening procedure to modify existing inequalities as the LP solution changes. We report computational results showing the strength of the new routines, including the optimal solution of a 33,810-city instance from the TSPLIB.
Study of the ZDDP Antiwear Tribofilm Formed on the DLC Coating Using AFM and XPS Techniques
Authors: Haque T. , Morina A. , Neville A. , Kapadia R. , Arrowsmith S.
Published: August 2007

To meet the challenge of the increasing demand of fuel economy, in recent years low friction nonferrous coatings such as diamond-like carbon (DLC) coatings have become very popular for automotive tribo-components. The interaction of lubricant additives, which are designed for ferrous surfaces, with nonferrous coatings is an important issue for the automotive and lubricant industries. The aim of this paper is to establish a link between the evolution of antiwear zinc dialkyl dithiophosphate (ZDDP) tribofilm and the tribological performance of a DLC coating under boundary lubrication conditions. Experiments were performed in a pin-on-plate reciprocating tribotester to produce the tribofilm. Atomic force microscopy (AFM) was used to record high resolution topographical images of the ZDDP films while chemical analysis of the ZDDP tribofilms was performed using X-ray photoelectron spectroscopy (XPS). Results in this study show that the ZDDP tribofilm consists of short chain zinc pyrophosphate (Zn2P2O7) and zinc metaphosphate (ZnOP2O5), and it is formed along the raised portion of the initial marks of the DLC surface.
Interaction between Telencephalin and ERM Family Proteins Mediates Dendritic Filopodia Formation
Authors: Furutani Yutaka , Matsuno Hitomi , Kawasaki Miwa , Sasaki Takehiko , Mori Kensaku , Yoshihara Yoshihiro
Published: August 2007

Dendritic filopodia are long, thin, actin-rich, and dynamic protrusions that are thought to play a critical role as a precursor of spines during neural development. We reported previously that a telencephalon-specific cell adhesion molecule, telencephalin (TLCN) [intercellular adhesion molecule-5 (ICAM-5)], is highly expressed in dendritic filopodia, facilitates the filopodia formation, and slows spine maturation. Here we demonstrate that TLCN cytoplasmic region binds ERM (ezrin/radixin/moesin) family proteins that link membrane proteins to actin cytoskeleton. In cultured hippocampal neurons, phosphorylated active forms of ERM proteins are colocalized with TLCN in dendritic filopodia, whereas α-actinin, another binding partner of TLCN, is colocalized with TLCN at surface membranes of soma and dendritic shafts. Expression of constitutively active ezrin induces dendritic filopodia formation, whereas small interference RNA-mediated knockdown of ERM proteins decreases filopodia density and accelerates spine maturation. These results indicate the important role of TLCN–ERM interaction in the formation of dendritic filopodia, which leads to subsequent synaptogenesis and establishment of functional neural circuitry in the developing brain.
Processing of Abstract Ordinal Knowledge in the Horizontal Segment of the Intraparietal Sulcus
Authors: Fias Wim , Lammertyn Jan , Caessens Bernie , Orban Guy A.
Published: August 2007

The anterior intraparietal sulcus, and more specifically its horizontal segment (hIPS), is known to play a crucial role in the cognitive representation of numerical quantity. Whether the involvement of hIPS is restricted to the processing of numerical information or generalizes to non-numerical ordinal dimensions remains an open question. Using functional magnetic resonance imaging during comparison tasks, we demonstrate that the hIPS is equally responsive to numbers and letters, indicating that hIPS is also involved in the representation and processing of non-numerical ordinal series. This extends the numerical processing function of IPS into the realm of abstract knowledge processing.
Protein Kinase C Regulates Local Synthesis and Secretion of a Neuropeptide Required for Activity-Dependent Long-Term Synaptic Plasticity
Authors: Hu Jiang-Yuan , Chen Yang , Schacher Samuel
Published: August 2007

Long-term facilitation (LTF) of sensory neuron synapses inAplysiais produced by either nonassociative or associative stimuli. Nonassociative LTF can be produced by five spaced applications of serotonin (5-HT) and requires a phosphoinosotide 3-kinase (PI3K)-dependent and rapamycin-sensitive increase in the local synthesis of the sensory neuron neuropeptide sensorin and a protein kinase A (PKA)-dependent increase in the secretion of the newly synthesized sensorin. We report here that associative LTF produced by a single pairing of a brief tetanus with one application of 5-HT requires a rapid protein kinase C (PKC)-dependent and rapamycin-sensitive increase in local sensorin synthesis. This rapid increase in sensorin synthesis does not require PI3K activity or the presence of the sensory neuron cell body but does require the presence of the motor neuron. The secretion of newly synthesized sensorin by 2 h after stimulation requires both PKA and PKC activities to produce associative LTF because incubation with exogenous anti-sensorin antibody or the kinase inhibitors after tetanus plus 5-HT blocked LTF. The secreted sensorin leads to phosphorylation and translocation of p42/44 mitogen-activated protein kinase (MAPK) into the nuclei of the sensory neurons. Thus, different stimuli activating different signaling pathways converge by regulating the synthesis and release of a neuropeptide to produce long-term synaptic plasticity.
Timing and Location of Synaptic Inputs Determine Modes of Subthreshold Integration in Striatal Medium Spiny Neurons
Authors: Carter Adam G. , Soler-Llavina Gilberto J. , Sabatini Bernardo L.
Published: August 2007

Medium spiny neurons (MSNs) are the principal cells of the striatum and perform a central role in sensorimotor processing. MSNs must integrate many excitatory inputs located across their dendrites to fire action potentials and enable striatal function. However, the dependence of synaptic responses on the temporal and spatial distribution of these inputs remains unknown. Here, we use whole-cell recordings, two-photon microscopy, and two-photon glutamate uncaging to examine subthreshold synaptic integration in MSNs from acute rat brain slices. We find that synaptic responses can summate sublinearly, linearly, or supralinearly depending on the spatiotemporal pattern of activity. Repetitive activity at single inputs leads to sublinear summation, reflecting long-lived AMPA receptor desensitization. In contrast, asynchronous activity at multiple inputs generates linear summation, with synapses on neighboring spines functioning independently. Finally, synchronous activity at multiple inputs triggers supralinear summation at depolarized potentials, reflecting activation of NMDA receptors and L-type calcium channels. Thus, the properties of subthreshold integration in MSNs are determined by the distribution of synaptic inputs and the differential activation of multiple postsynaptic conductances.
A New Mutation in PlantALSConfers Resistance to Five Classes of ALS-Inhibiting Herbicides
Authors: Whaley Cory M. , Wilson Henry P. , Westwood James H.
Published: August 2007

Experiments were conducted to evaluate a biotype of smooth pigweed that had survived applications of sulfonylurea (SU) and imidazolinone (IMI) herbicides in a single season. The source field had a history of repeated acetolactate synthase (ALS)-inhibiting herbicide use over several years. Whole-plant response experiments evaluated the resistant (R11) biotype and an ALS-inhibitor susceptible (S) smooth pigweed biotype to herbicides from the SU, IMI, pyrimidinylthiobenzoate (PTB), and triazolopyrimidine sulfonanilide (TP) chemical families. The R11 biotype exhibited 60- to 3,200-fold resistance to all four ALS-Inhibiting herbicide chemistries compared with the S biotype. Nucleotide sequence comparison ofALSgenes from R11 and S biotypes revealed a single nucleotide difference that resulted in R11 having an amino acid substitution of aspartate to glutamate at position 376, as numbered relative to the protein sequence of mouseearcress. This is the first report of an amino acid substitution at this position of anALSgene isolated from a field-selected weed biotype. To verify the role of this mutation in herbicide resistance, theALSgene was cloned and expressed inArabidopsis. TransgenicArabidopsisexpressing thisALSgene exhibited resistance to SU, IMI, PTB, TP, and sulfonylaminocarbonyltriazolinone ALS-Inhibiting herbicide classes.
Triggers of Self-Induced Vomiting in Bulimic Disorders: The Roles of Core Beliefs and Imagery
Authors: Hinrichsen Hendrik , Morrison Tamara , Waller Glenn , Schmidt Ulrike
Published: August 2007

Recent evidence has suggested a specific role for core beliefs in the triggering of bulimic behaviors. However, less is known about the role of imagery in this link despite its role in other disorders. The present study aimed to investigate the potential roles of core beliefs and imagery in triggering self-induced vomiting. Thirty bulimic women took part in a semistructured interview focusing on their mental processes prior to vomiting and completed a self-report measure of core beliefs. The results showed that prior to vomiting, a clinically significant proportion of bulimic patients reported thoughts relating to defectiveness/shame, failure, and social isolation core beliefs and associated feelings of shame and anxiety. Most patients perceived these feelings as triggers to their vomiting. A large number of bulimic patients also reported experiencing visual images prior to vomiting, and those images tended to be recurrent and linked to adverse life experiences. Overall, the findings suggest that defectiveness/shame, failure, and social isolation core beliefs and recurrent negative images (linked to adverse life experiences) may play important roles in the triggering of self-induced vomiting in bulimic disorders.
Development of a Measure of Egodystonicity
Authors: Purdon Christine , Cripps Emily , Faull Matthew , Joseph Stephen , Rowa Karen
Published: August 2007

The term egodystonicity is a distinguishing feature of obsessional thoughts (American Psychiatric Association, 2000) but has not been consistently nor comprehensively defined. These two studies present the development and initial validation of the Ego-Dystonicity Questionnaire (EDQ). A definition of the term egodystonicity was developed, drawing from existing definitions and theoretical models of obsessive-compulsive disorder (OCD). An item pool was developed and refined through initial testing, the product of which was a 37-item self-report measure. Respondents identify a specific type of thought (e.g., their most upsetting obsession, most upsetting worry) and then answer each item with respect to that thought. In study 1, two nonclinical samples (N = 278) and one sample of individuals with OCD (N = 17) were administered the EDQ along with self-report measures of mood, personality, OCD symptoms, and appraisal of obsessional thoughts. A principal components analysis of the nonclinical sample yielded four factors. Scales based on these factors had acceptable internal reliability. The EDQ distinguished between obsessional thoughts and common worries, and individuals in the clinical sample had higher scores than the nonclinical sample. The EDQ showed low to moderate correlations with OCD symptoms, mood, and appraisal of obsessions but was not associated with personality traits such as neuroticism. In study 2, individuals with OCD (N = 28) completed the EDQ in reference to their most or least upsetting obsession. As predicted, egodystonicity varied according to obsession type. These data indicate that the EDQ is a valid measure with potential for use in understanding and treating obsessional problems.
The Menace Within: Obsessions and the Self
Authors: Aardema Frederick , O’Connor Kieron
Published: August 2007

The current article attempts to provide a theoretical account of obsessions about blasphemy, sexuality, and aggression from an inference-based perspective. It is argued that self-evaluative and self-representational dimensions in obsessions need to be taken into account to allow for the misrepresentation of mental states. A persuasive narrative containing rhetorical devices informs the misrepresentation of mental states and gives credibility to the obsession. These narrative devices seem to originate from a distrust of the self where the person overinvests in a sense of self-as-could-be rather than a sense of self-as-is, which consequently gives rise to a discordance between the person and the obsession (i.e., egodystonicity). The article concludes with some theoretical and clinical implications for cognitive models of obsessive-compulsive disorder.
Fate of atrazine in a grassed phytoremediation system
Authors: Henderson Keri L. , Belden Jason B. , Coats Joel R.
Published: August 2007

Atrazine is a well-known contaminant of surface waters and has been implicated in point-source pollution at agrochemical dealerships in the Midwest. Although the fate of atrazine has been well documented in soil and water, little is known about the fate of this contaminant and its metabolites within a grassed system. In the present study, [U-ring-14C]atrazine was added to soil in closed systems to determine the fate of the parent compound and its metabolites in soil, including degradation and movement into plants and air. Soil was treated with 25 mg/kg [14C]labeled atrazine and allowed to age for 5 d. Four systems then were amended with a mixture of prairie grasses, and the remaining four chambers were maintained as unvegetated controls. Dissipation and distribution of parent compound and metabolites were recorded for 21 d. Plant uptake of [14C]residue was less than 0.5% of applied radioactivity. Approximately 2% of total applied [14C]atrazine was mineralized to [14C]CO2, with no differences between vegetated and unvegetated systems. Mass balance recoveries were 76% for grassed systems and 77.5% for unvegetated controls. Approximately 40% of applied radioactivity remained bound to the soil following extraction. The most prevalent extractable compound detected in the soil was the parent, atrazine; major metabolites in soil were deethylatrazine (DEA) and didealkylatrazine (DDA). Leaf tissue contained concentrations of atrazine and key metabolites, i.e., DEA, DDA, and deisopropylatrazine (DIA), above those allowed in forage grasses by the U.S. Environmental Protection Agency; another key metabolite, hydroxyatrazine, was the most prevalent compound identified in both leaf and root tissue.
Laboratory culturing and selection for increased resistance to cadmium reduce genetic variation in the least killifish,Heterandria formosa
Authors: Athrey N.R. Giridhar , Leberg Paul L. , Klerks Paul L.
Published: August 2007

Populations exposed to environmental contaminants can undergo intense selection pressures, which in turn can lead to a loss of genetic variation. We assessed this loss of genetic variation in the least killifish Heterandria formosa for laboratory populations that had undergone eight generations of selection for an increased resistance to cadmium. Using microsatellite markers, we compared genetic variation between three selection and three control laboratory populations and between these laboratory populations and the source population. Heterozygosity was lower in each selection population than it was in its paired control population, with this difference being statistically significant in two of the three comparisons. This is evidence that adaptation to environmental contaminants can result in an overall loss of genetic variation. Furthermore, the laboratory populations had much lower heterozygosity than did the source population. The latter loss of genetic variation, probably a result of random drift, did not prevent the laboratory populations from showing a strong response to the selection for cadmium resistance. The loss of genetic variation resulting from maintaining populations in the laboratory demonstrates that it is important to maintain a large population size for such populations and that the potential for loss of genetic variation in laboratory populations is taken into consideration in ecotoxicology when extrapolating from laboratory to natural populations.
An algal toxicity database of organic toxicants derived by a closed-system technique
Authors: Tsai Kuo-Pei , Chen Chung-Yuan
Published: August 2007

The current study presents the toxicity data of 90 organic compounds with various modes of actions to Pseudokirchneriella subcapitata. The assessment was conducted using a closed-system technique, and a biomass-type end point based on the cell density was employed. The above toxicity data were compared with test results from ciliate (Tetrahymena pyriformis), water flea (Daphnia magna), fish (Pimephales promelas), and luminescent bacteria (Photobacterium phosphoreum). Satisfactory correlation relationships between toxicity data from algae and other aquatic organisms were found (r2 = 0.66-0.82). Pseudokirchneriella subcapitata revealed considerably higher sensitivity to organic toxicants compared with other organisms. Benzenes, aldehydes, and alkanes also were highly selective to the test alga. In addition, the results show that conventional algal batch tests tend to underestimate the toxicity of organic compounds, except in the case of 4-chlorophenol. Toxicity observed from the closed-system test is approximately 2- to 380-fold higher than that estimated by conventional batch tests. Such a phenomenon can be found in nearly all organic compounds, regardless of the chemical's Henry's law constant. In the risk assessment of chemicals, following the European Union's practice, approximately 30% (7 of 23) of the cases may result in a more strict classification when the batch test is replaced by the closed-system test. More effort therefore is needed to revise the algal toxicity database using the closed-system test method.
Chemical reactivation and aging kinetics of organophosphorus-inhibited cholinesterases from two earthworm species
Authors: Rodríguez-Castellanos Laura , Sanchez-Hernandez Juan C.
Published: August 2007

An in vitro study was conducted to evaluate the ability of pyridine-2-aldoxime methochloride (2-PAM) to recover organophosphorus (OP)-inhibited cholinesterase (ChE) activity of two earthworm species (Eisenia fetida and Lumbricus terrestris). After inhibition of ChE activity by OP pesticides, an alkyl group may be released from the OP-ChE complex. This reaction is termed aging, and the esterase cannot be reactivated either spontaneously or by the action of reactivating agents, such as 2-PAM. We also examined the aging kinetics of OP-inhibited ChE activity to evaluate the suitability of 2-PAM reactivation methodology for field monitoring. A 2-PAM concentration of 5 × 10−4 M was enough to reactivate the OP-inhibited ChE activity after 60 min of incubation at 25°C. Chemical reactivation kinetics followed an exponential rise to a maximum of 70 to 80% of normal enzyme activity when ChEs were inhibited with methyl paraoxon or dichlorvos and up to 60% for the chlorpyrifos-inhibited ChE of E. fetida. The aging rates (ka) of the inhibited ChEs were strongly affected by the OP type, and these rates decreased for both earthworm species in the following order: Methyl paraoxon (ka = 0.023–0.033/h) > dichlorvos (ka = 0.008–0.009/h) > chlorpyrifos oxon (ka = 0.003–0.006/h). In particular, chlorpyrifos-inhibited ChE activity of L. terrestris aged slowly (median aging time, 190 h), which means that chemical reactivation of esterase activity with 2-PAM seems feasible one week after exposure to OP pesticides. We conclude that reactivation of earthworm ChE activity by treatment with 2-PAM is a complementary and specific methodology for assessing exposure to OP pesticides.
Cultivar and Seeding Rate Effects on the Competitive Ability of Spring Cereals Grown under Organic Production in Northern Canada
Authors: Mason H. , Navabi A. , Frick B. , O'Donovan J. , Spaner D.
Published: August 2007

Organically managed production systems often experience greater weed pressure than their conventional counterparts, potentially causing yield losses and increased weed seed build‐up. The use of competitive crop cultivars and the cultural practice of increasing seeding rates may moderate such production constraints. Field trials were conducted at two organically managed locations in Alberta, Canada for 2 yr to determine the effect of competition with tame oat (Avena sativa L.), cultivar, and crop seeding rate (300 and 600 seeds m−2) on the competitive ability and agronomic performance of Canadian spring wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). Cultivars were selected based on their differing heights, tillering capacities, and times to maturity. Simulated weed competition from tame oat reduced grain yield by an average of 27%. Barley cultivars were generally more competitive than wheat cultivars. Height and early maturity were more closely associated with weed suppression and yield maintenance than tillering capacity. The modern semidwarf CDC Go was the highest yielding wheat cultivar, but was a poor weed suppressor. Doubling the seeding rate increased grain yield and weed suppression. This effect was not cultivar specific, which implies that doubling the seeding rate may be a generally effective method of overcoming yield losses and weed seed build‐up associated with increased weed populations under organic production.
Drought Resistance in the Race Durango Dry Bean Landraces and Cultivars
Authors: Singh Shree P.
Published: August 2007

Increasing water deficit or drought is a problem for dry bean (Phaseolus vulgaris L.) production in the western USA. Identification of drought‐resistant cultivars is crucial for sustainable production in the region. The objectives of this study were to (i) measure the effects of drought on seed yield, seed weight, and days to maturity; (ii) determine correlation among the three traits in drought‐stressed (DS) and nonstressed (NS) environments; and (iii) identify drought‐resistant dry bean landraces and cultivars. Three landraces and 17 cultivars of race Durango were evaluated in DS and NS environments. Drought intensity index ranged from 0.32 to 0.88. There was a mean reduction in yield of 60% due to drought stress. Also, seed weight was reduced by 14% and maturity was reduced by 4 d in DS. Yield, seed weight, and maturity in NS and DS were positively correlated, and so were seed weight and maturity in NS and DS. But, the DS yield was negatively correlated with seed weight in both DS and NS. The ability to detect yield differences among 20 genotypes decreased with increasing drought stress. Cultivars Viva, NW 63, UI 239, and Common Red Mexican landrace had high yield in both DS and NS and below average reduction in yield due to DS, thus, exhibiting drought resistance. Buster, UI 126, and UI 465 were most susceptible. The frequency and timing of irrigation for the four drought‐resistant genotypes should be determined and breeding, genetics, and physiology research intensified to maximize yield and water use efficiency in the western USA, which is facing increasing water shortage.
Rotational Effects in Oklahoma Peanut Production: Prospects for Peanut Rotations in the Post‐Quota Era
Authors: Godsey Chad B. , Vitale Jeffrey , Damicone John P. , Sholar James R. , Nickels Jerald , Baker Jerry
Published: August 2007

The Farm Security and Rural Investment Act of 2002 greatly impacted the southwest (SW) peanut (Arachis hypogaea) growing region. Due to decreased market prices, peanut has lost favor in crop rotations to other crops such as cotton (Gossypium hirsutum L.). Before 2002, a 12‐yr peanut rotation study was conducted in Oklahoma to investigate the agronomic benefits and economics of rotating peanut with corn (Zea mays L.), cotton, and grain sorghum [Sorghum bicolor (L.) Moench]. Eight rotations were evaluated in 2‐ and 3‐yr intervals. Incidence of disease, yield, and economic profit were evaluated each year. Twelve years of data indicated rotating peanut every third year with either corn or cotton increased peanut pod yield by 520 and 490 kg ha−1, respectively, compared with the continuous peanut rotation. Two‐year rotations of peanut with corn, cotton, or sorghum performed no better than the peanut monoculture. Economic analysis indicates that, even with the removal of the peanut quota system in 2000 and a 50% reduction in peanut prices, the peanut monoculture would still remain the most profitable choice for farmers, generating economic returns of $411 ha−1, but would not be recommended due to increase in disease pressure. Recent increases in cotton yield indicate that a peanut‐cotton rotation is the best rotation for southwest producers.
Performance of Peanut and Cotton in a Bahiagrass Cropping System
Authors: Katsvairo Tawainga W. , Wright David L. , Marois James J. , Hartzog Dallas L. , Balkcom Kris B. , Wiatrak Pawel P. , Rich Jimmy R.
Published: August 2007

Yields for peanut (Arachis hypogaea L.) and cotton (Gossypium hirsutum L.) have reached a plateau in the southeastern USA (SE). This, coupled with environmental concerns and increased production costs, prompt the need to find alternatives to the limited peanut/cotton rotation currently used. Bahiagrass (Paspalum notatum Fluegge) was introduced to the current peanut/cotton cropping system to evaluate its effect on peanut and cotton performance. Our objectives were to compare crop yields in a conventional rotation of cotton‐cotton‐peanut vs. a bahiagrass–bahiagrass–peanut–cotton rotation under irrigated and nonirrigated conditions. Field studies were conducted in Quincy, FL, on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults) from 2000 to 2004. During 2–3 yr of the study, peanut yields were 900 kg ha−1 greater (averaged across irrigation treatments) following 2 yr of bahiagrass compared with following 2 yr of cotton under both irrigated and nonirrigated conditions. Root biomass was greater for cotton in the bahiagrass rotation compared with cotton in the conventional rotation. The greater root biomass, however, resulted in rank growth and cotton in the bahiagrass rotation yielded the same as cotton in the conventional rotation. It appears potential exists for greater cotton yield in the bahiagrass rotation once effective management practices have been identified.
Common Waterhemp Growth and Fecundity as Influenced by Emergence Date and Competing Crop
Authors: Uscanga‐Mortera E. , Clay S. A. , Forcella F. , Gunsolus J.
Published: August 2007

Common waterhemp (Amarathus rudis Sauer) is a frequent weed in glyphosate‐resistant (GR) crops in the midwestern USA due, in part, to the delayed emergence of its seedlings. Variable waterhemp emergence was simulated by transplanting seedlings into both corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] and bare plot areas at differing crop growth stages during two growing seasons in western Minnesota. Growth and fecundity were measured. As expected, late planted weeds produced little dry matter and few seeds, and competition from corn or soybean reduced waterhemp dry weight and fecundity by ≥ 90% compared with isolated plants. Interestingly, common waterhemp was affected differently by crop and transplanting date. Common waterhemp grown with corn was always shaded by the crop canopy but produced seeds even when transplanted as late as the V10 growth stage. In soybean, weeds transplanted before the V4 growth stage were taller than soybean and produced more seeds than those transplanted into corn at a comparable growth stage; however, those transplanted after V5 produced no seeds. Consequently, control of late‐emerging common waterhemp plants in soybean may not be needed, whereas control of late‐emerging plants in corn may be justified because of relatively high levels of seed production.
Raising awareness on water and climate related risks - an overview
Authors: van Woerkum C.
Published: August 2007

Climate change is not an easy subject from the perspective of communications studies: it is widely regarded as a most important issue, but its global scope and the lack of consensus on its consequences can make it hard to encompass. This article aims to structure the field and set out the domains of communicative action that are involved, as well identify the actors involved and their role in the overall debate. The different modalities of communication and the dynamics in the use of media in the present time are considered, before discussion of some basic issues with regard to communication, such as the meaning of (scientific) information versus more emotional cues, the opportunities for action that can be offered to citizens/consumers, and the issue of trust in responsible agencies.
Transboundary flood management in the Rhine basin: challenges for improved cooperation
Authors: Becker G. , Aerts J. , Huitema D.
Published: August 2007

An appropriate institutional set up is essential for efficient transboundary flood management in the Rhine basin, particularly in view of future uncertainties like climate change. Flood management factors are identified based on a historical comparison in the Netherlands and Germany. They include differences in the perception of the problem and how to solve it; in the understanding of key items and how to address them; in administrative responsibilities and the political will to act. Suggestions are made to improve cooperation, in particular to generate a common problem perception and problem analysis, to develop a common vision for future flood strategies and to create a network of discussion platforms to promote social learning and to prepare, decide and implement flood management issues.
When climate change is a fact! Adaptive strategies for drinking water production in a changing natural environment
Authors: Meuleman A.F.M. , Cirkel G. , Zwolsman G.J.J.
Published: August 2007

Climate change increases water system dynamics through temperature changes, changes in precipitation patterns, evaporation, and water quality and water storage in ice packs. Water system dependent economical stakeholders, such as drinking water companies in the Netherlands, have to cope with consequences of climate change, e.g. floods and water shortages in river systems, upcoming of brackish ground water, salt water intrusion, increasing peak demands and microbiological activity due to temperature rise. In the past decades, however, both water systems and drinking water production have become more and more inflexible; water systems have been heavily regulated aiming at maximum security and economic functions and the drinking water supply in the Netherlands has grown into an inflexible, but cheap and reliable, system. At a water catchment scale, flexibility and adaptation are solutions to overcome climate change related consequences. Flexible adaptive strategies for drinking water production comprise new sources for drinking water production, application of storage concepts in the short term, and a redesign of large centralized systems, including flexible treatment plants, in the long term. Transition to flexible concepts will take decades because investment depreciation periods of assets are long. These strategies must be based on thorough knowledge of current assets to seize opportunities for change.
The closed city as a strategy to reduce vulnerability of urban areas for climate change
Authors: de Graaf R.E. , van de Giesen N.C. , van de Ven F.H.M.
Published: August 2007

Urbanization, land subsidence and sea level rise will increase vulnerability to droughts in the urbanized low-lying areas in the western part of the Netherlands. In this paper a possibility is explored to decrease vulnerability of urban areas by implementing an alternative water supply option. A four component vulnerability framework is presented that includes threshold capacity, coping capacity, recovery capacity and adaptive capacity. By using the vulnerability framework it is elaborated that current water supply strategies in the Netherlands mainly focus on increasing threshold capacity by constructing improved water storage and delivery infrastructure. A complete vulnerability decreasing strategy requires measures that include all four components. Adaptive capacity can be developed by starting experiments with new modes of water supply. A concept which is symbolically called ‘the closed city’ uses local urban rainfall as the only source of water supply. The ‘closed city’ can decrease the water dependence of urban areas on (1) the surrounding rural areas that are diminishing in size and that are increasingly under strain and (2) river water resources that will probably be less constant and reliable as a result of climate change.