bluuebunny/crossref_metadata_2025 huggingface dataset:
Discrete element method for modelling solid and particulate materials
Authors: Tavarez Federico A. , Plesha Michael E.
Published: October 2006

The discrete element method (DEM) is developed in this study as a general and robust technique for unified two‐dimensional modelling of the mechanical behaviour of solid and particulate materials, including the transition from solid phase to particulate phase. Inter‐element parameters (contact stiffnesses and failure criteria) are theoretically established as functions of element size and commonly accepted material parameters including Young's modulus, Poisson's ratio, ultimate tensile strength, and fracture toughness. A main feature of such an approach is that it promises to provide convergence with refinement of a DEM discretization. Regarding contact failure, an energy criterion based on the material's ultimate tensile strength and fracture toughness is developed to limit the maximum contact forces and inter‐element relative displacement. This paper also addresses the issue of numerical stability in DEM computations and provides a theoretical method for the determination of a stable time‐step. The method developed herein is validated by modelling several test problems having analytic solutions and results show that indeed convergence is obtained. Moreover, a very good agreement with the theoretical results is obtained in both elastic behaviour and fracture. An example application of the method to high‐speed penetration of a concrete beam is also given. Copyright © 2006 John Wiley & Sons, Ltd.
Overview and construction of meshfree basis functions: from moving least squares to entropy approximants
Authors: Sukumar N. , Wright R. W.
Published: October 2006

In this paper, an overview of the construction of meshfree basis functions is presented, with particular emphasis on moving least‐squares approximants, natural neighbour‐based polygonal interpolants, and entropy approximants. The use of information‐theoretic variational principles to derive approximation schemes is a recent development. In this setting, data approximation is viewed as an inductive inference problem, with the basis functions being synonymous with a discrete probability distribution and the polynomial reproducing conditions acting as the linear constraints. The maximization (minimization) of the Shannon–Jaynes entropy functional (relative entropy functional) is used to unify the construction of globally and locally supported convex approximation schemes. A JAVA applet is used to visualize the meshfree basis functions, and comparisons and links between different meshfree approximation schemes are presented. Copyright © 2006 John Wiley & Sons, Ltd.
Effect of organic additives on formation and structure of polyelectrolyte‐oppositely charged surfactant complexes
Authors: Zakharova J. A. , Otdelnova M. V. , Aliev I. I. , Motyakin M. V. , Wasserman A. M. , Zezin A. B. , Kabanov V. A.
Published: October 2006

Effect of butanol and Triton X‐100 on formation, supramolecular organization and local dynamics of poly(N‐ethyl‐4‐vinylpyridinium)‐dodecyl sulfate complexes have been studied by UV spectroscopy, high‐speed sedimentation, laser light scattering and electron spin resonance (ESR) spectroscopy. It was found that solubilization of butanol promotes aggregation of the complex species in solution and results in contraction of the region in which water‐soluble complexes are formed. On the contrary, highly aggregated complexes disaggregate up to molecularly dispersed state upon addition of Triton X‐100. It was found that under the experimental conditions neither butanol (up to 3 wt%) nor Triton X‐100 ([Triton X‐100]/[sodium dodecylsulfate] ≤ 1:1) cause destruction of the complexes. The results of ESR spin probe and spin label studies show that in both cases supramolecular realignments are accompanied by a slight increase of the local molecular mobility of surfactant ions in the complex micelles, segmental mobility of polyelectrolyte being unchanged. Copyright © 2006 John Wiley & Sons, Ltd.
Pilot evaluation of hypnosis for the treatment of hot flashes in breast cancer survivors
Authors: Elkins Gary , Marcus Joel , Stearns Vered , Hasan Rajab M.
Published: October 2006

This single arm, pilot study investigated the use of hypnosis to reduce hot flashes in 16 breast cancer survivors. Each patient provided baseline data and received 4 weekly sessions of hypnosis that followed a standardized transcript. Patients were also instructed in self‐hypnosis. Throughout the clinical care, patients completed daily diaries of the frequency and severity of their hot flashes. Patients also completed baseline and post‐treatment ratings of the degree to which hot flashes interfered with daily activities and quality of life. Results indicated a 59% decrease in total daily hot flashes and a 70% decrease in weekly hot flash scores from their baselines. There was also a significant decrease in the degree to which hot flashes interfered with daily activities for all measures including work, social activities, leisure activities, sleep, mood, concentration, relations with others, sexuality, enjoyment of life, and overall quality of life. This pilot study suggests that clinical hypnosis may be an effective non‐hormonal and non‐pharmacological treatment for hot flashes. A randomized, controlled clinical trial is planned to more definitively elucidate the efficacy and applicability of hypnosis for reducing hot flashes. Copyright © 2006 John Wiley & Sons, Ltd.
The n‐factor of nonsorted circles along a climate gradient in Arctic Alaska
Authors: Kade A. , Romanovsky V. E. , Walker D. A.
Published: October 2006

Three study sites were selected on zonal sites from north to south along a climate gradient in Arctic Alaska. Air and mineral soil surface temperatures of nonsorted circles and adjacent well‐vegetated tundra plots were monitored from September 2003 through September 2004, and the depths of vegetation, soil organic horizons and snow were measured. N‐factors, the ratio of ground‐surface temperature to air temperature, were determined for the summer and winter seasons. N‐factors and thaw depths were greater for relatively barren nonsorted circles than for adjacent well‐vegetated tundra. Along the climate gradient, the thickness of vegetation, soil organic layer and snow increased from north to south, while n‐factors and thaw depths decreased at bare circles from 1.43 ± 0.02 to 0.74 ± 0.01 and from 81.2 ± 1.4 cm to 59.5 ± 2.4 cm, respectively, and at the tundra from 0.99 ± 0.02 to 0.17 ± 0.01 and from 62.6 ± 1.4 cm to 21.0 ± 2.8 cm, respectively. Copyright © 2006 John Wiley & Sons, Ltd.
High resolution crystal structures of unliganded and liganded human liver ACBP reveal a new mode of binding for the acyl‐CoA ligand
Authors: Taskinen Jukka P. , van Aalten Daan M. , Knudsen Jens , Wierenga Rik K.
Published: October 2006

The acyl‐CoA binding protein (ACBP) is essential for the fatty acid metabolism, membrane structure, membrane fusion, and ceramide synthesis. Here high resolution crystal structures of human cytosolic liver ACBP, unliganded and liganded with a physiological ligand, myristoyl‐CoA are described. The binding of the acyl‐CoA molecule induces only few structural differences near the binding pocket. The crystal form of the liganded ACBP, which has two ACBP molecules in the asymmetric unit, shows that in human ACBP the same acyl‐CoA binding pocket is present as previously described for the bovine and Plasmodium falciparum ACBP and the mode of binding of the 3′‐phosphate‐AMP moiety is conserved. Unexpectedly, in one of the acyl‐CoA binding pockets the acyl moiety is bound in a reversed mode as compared with the bovine and P. falciparum structures. In this binding mode, the myristoyl‐CoA molecule is fully ordered and bound across the two ACBP molecules of the crystallographic asymmetric unit: the 3′‐phosphate‐AMP moiety is bound in the binding pocket of one ACBP molecule and the acyl chain is bound in the pocket of the other ACBP molecule. The remaining binding pocket cavities of these two ACBP molecules are filled by other ligand fragments. This novel binding mode shows that the acyl moiety can flip out of its classical binding pocket and bind elsewhere, suggesting a mechanism for the acyl‐CoA transfer between ACBP and the active site of a target enzyme. This mechanism is of possible relevance for the in vivo function of ACBP. Proteins 2007. © 2006 Wiley‐Liss, Inc.
A novel cross‐linked RNase A dimer with enhanced enzymatic properties
Authors: Simons Brigitte L. , Kaplan Harvey , Fournier Sylvie M. , Cyr Terry , Hefford Mary Alice
Published: October 2006

A new cross‐linked ribonuclease A (RNase A) dimer composed of monomeric units covalently linked by a single amide bond between the side‐chains of Lys66 and Glu9 is described. The dimer was prepared in the absence of water by incubating a lyophilized preparation of RNase, sealed under vacuum, in an oven at 85°C. It was determined that the in vacuo procedure does not induce any significant conformational changes to the overall structure of RNase A, yet the amide cross‐link has an increased acid lability, indicating that it is exposed and conformationally strained. Examination of X‐ray crystallographic structures indicates that Lys66 and Glu9 are not close enough for the in vacuo dimer to adopt any of the known domain‐swapped conformations. Therefore, the in vacuo RNase A dimer appears to be a novel dimeric structure. The in vacuo RNase A dimer also exhibits a twofold increase in activity over monomeric RNase A on a per monomer basis. This doubling of enzymatic activity was shown using dsRNA and ssRNA as substrates. In addition to this enhanced ability to degrade RNA, the dimer is not inhibited by the cellular ribonuclease inhibitor protein (cRI). Proteins 2007. © 2006 Wiley‐Liss, Inc.
Origin of functional diversity among tetrameric voltage‐gated channels
Authors: Anselmi Claudio , Carloni Paolo , Torre Vincent
Published: October 2006

The aim of the present work is to relate functional differences of voltage‐gated K+ (Kv), hyperpolarization‐activated cyclic nucleotide‐gated (HCN), and cyclic nucleotide gated (CNG) channels to differences in their amino acid sequences. By means of combined bioinformatic sequence analyses and homology modelling, we suggest that: (1) CNG channels are less voltage‐dependent than Kv channels since the charge of their voltage sensor, the S4 helix, is lower than that of Kv channels and because of the presence of a conserved proline in the S4–S5 linker, which is quite likely to uncouple S4 from S5 and S6. (2) In HCN channels, S4 features a higher net positive charge with respect to Kv channels and an extensive network of hydrophobic residues, which is quite likely to provide a tight coupling among S4 and the neighboring helices. We suggest insights on the gating of HCN channels and the reasons why they open with membrane hyperpolarization and with a significantly longer time constant with respect to other channels. Proteins 2007. © 2006 Wiley‐Liss, Inc.
Influence of the protein matrix on intramolecular histidine ligation in ferric and ferrous hexacoordinate hemoglobins
Authors: Halder Puspita , Trent James T. , Hargrove Mark S.
Published: October 2006

Present in most organisms, hexacoordinate hemoglobins (hxHbs) are proteins that have evolved the capacity for reversible bis‐histidyl heme coordination. The heme prosthetic group enables diverse protein functionality, such as electron transfer, redox reactions, ligand transport, and enzymatic catalysis. The reactivity of heme is greatly effected by the coordination and noncovalent chemical environment imposed by its connate protein. Of considerable interest is how the hxHb globin fold achieves reversible intramolecular coordination while still enabling high‐affinity binding of oxygen, nitric oxide, and other small ligands. Here we explore this question by examining the role of the protein matrix on coordination behavior in a group of hxHbs from animals, plants, and bacteria, including human neuroglobin and cytoglobin, a nonsymbiotic hemoglobin from rice, and a truncated hemoglobin from the cyanobacterium Synechocystis. This is done with a set of experiments measuring the reduction potentials of each wild‐type hxHb and its corresponding mutant protein where the reversibly bound histidine (the distal His) has been replaced with a noncoordinating side chain. These reduction potentials, coupled with studies of the mutant proteins saturated with exogenous imidazole, enable us to assess the effects of the protein matrices on histidine coordination. Our results show significant variation among the hxHbs, demonstrating flexibility in the globin moiety's ability to regulate reversible coordination. This regulation is particularly evident in the plant nonsymbiotic hemoglobins, where ferric state histidine coordination affinity is substantially lowered by the protein matrix. Proteins 2007. © 2006 Wiley‐Liss, Inc.
In‐line flame arresters to prevent flashback of thermal combustion units
Authors: Heidermann Thomas , Davies Michael
Published: October 2006

Thermal combustion units in chemical, pharmaceutical, and petrochemical plants use burner systems for thermal waste disposal to reduce emissions. The advantage of premixed burner units is related primarily to greater stability of flame, the reduction of NOx emissions, and control and technical reasons. Unfortunately, the production of premixed flames requires the highly flammable fuel and oxidant gases to be mixed in confined chambers before they are burned. To form the flame, the mixed gases must pass through the burner exit ports where combustion takes place. Under certain conditions, the flame can burn back through the burner exit ports and ignite the potentially explosive gas–air mixture in the piping system. Of course, burner system designers have the expertise to design suitable burners that prevent flashback by flow‐control measures.

Flame arresters can be used as a secondary measure to increase plant safety. Flame arresters are autonomous safety devices that protect workers, environment, and plant against deflagration and detonation caused by flashback from a combustion process while allowing vapor flow.

To maximize the effectiveness of flame arresters, attention should be given to proper selection, application, and maintenance of the device. For this, it is most important to know under which conditions the arrester was tested and have the capability to decide which test standard is the most effective for the specific application.

This article focuses on the application of in‐line deflagration vs. in‐line detonation arresters and provides design criteria based on live field testing on when to use which arrester type. © 2006 American Institute of Chemical Engineers Process Saf Prog, 2007
A real‐life example of choosing an inherently safer process option
Authors: Study Karen
Published: October 2006

Although choosing an inherently safer alternative may seem straightforward, sometimes what seems to be the most obvious alternative may not provide the best risk reduction. The process designer must maintain a broad perspective to be able to recognize all potential hazards when evaluating design options. All aspects of operation such as start‐up, shutdown, utility failure, as well as normal operation should be considered. Choosing the inherently safer option is best accomplished early in the option selection phase of a project. However, recycle back to the option selection phase may be needed if an option is not thoroughly evaluated early in the process. This report reviews a project to supply ammonia to a catalytic reactor. During the course of the project, an “inherently safer” alternative was selected and later discarded because of issues uncovered during the detail design phase. The final option chosen will be compared to (1) the original design and (2) the initial “inherently safer” alternative. The final option was inherently safer than both the original design and the initial “inherently safer” alternative, even though the design team initially believed that it would not be. © 2006 American Institute of Chemical Engineers Process Saf Prog, 2006
Structural study on the crystallization behavior of Sb3Te2 alloy for phase change memory
Authors: Sun Chang Woo , Lee Jeong Yong , Youm Minsoo , Kim Yong Tae
Published: October 2006

The atomic crystal structure of the Sb3Te2 binary alloy has been investigated with high‐resolution transmission electron microscopy (HR‐TEM) and fast Fourier transform patterns. As a result, there is inconsistency between the previous theoretical model and the experimental result. But, from the calculations of lattice parameters and the number of layers in the unit cell, it is found that the Sb3Te2 alloy can be crystallized into the Sb2Te structure with P$ \bar 3 $m1 space group and the difference between stacking sequences of the Sb3Te2 and the Sb2Te structures has been discussed with the proposed atomic arrangement model of unit cells. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ab initio computational modeling on the tautomerism of monochalcogenocarboxylic acids CH3C(O)XH (X = S, Se, and Te) in the polar and aprotic solution
Authors: Li Qiang‐Gen , Liang Guo‐Ming , Wang Xin , Chu San‐Yan , Ren Yi
Published: October 2006

Computational modeling by an ab initio molecular orbital method (HF and MP2) with the 6‐311+G(d,p) and 6‐311++G(2df,2pd) basis sets on the tautomerism of three monochalcogenocarboxylic acids CH3C(O)XH (X = S, Se, and Te) in the polar and aprotic solution tetrahydrofuran (THF) was undertaken using the combined supramolecular/continuum method, in which CH3OCH3 was considered as a realistic model for THF in the supermolecule. Our calculations showed that the tautomerism involving CH3OCH3 not only gives the preference of the enol form CH3C(X)OH (X = S, Se, and Te) in the tautomeric equilibrium, but also significantly lowers the tautomeric barriers by >34 kJ/mol in THF solution. These results support the experiments of Kato and coworkers, in contrast with earlier Delaere et al.'s theoretical prediction for the tautomeric barrier of thioformic acid HC(O)SH…O(CH3)2, in which the barrier is increased by ∼6 kJ/mol relative to reactants complex because of the constraint in locating the tautomeric transition structure. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Characterization of compounds in the Chinese herbal drug Mu‐Dan‐Pi by liquid chromatography coupled to electrospray ionization mass spectrometry
Authors: Xu Shun‐jun , Yang Liu , Zeng Xing , Zhang Mian , Wang Zheng‐tao
Published: October 2006

Cortex Moutan is a well‐known traditional Chinese medicine derived from Paeonia suffruticosa ANDREWS. However, root cortices of P. delavayi and P. decomposita also are used under the name of this drug in some regions such as Yunnan and Sichuan Provinces, respectively. In order to make a comparison of their chemical constituents, the compounds of the three Paeonia species were analyzed by high‐performance liquid chromatography‐diode array detection/electrospray ionization and quadrupole‐time‐of‐flight tandem mass spectrometry (HPLC‐DAD/ESI‐MS2). A total of 50 compounds were observed in the 50% (v/v) methanolic extracts, including 17 monoterpenes, 14 galloyl glucoses, 10 acetophenones, 5 phenolic acids, 3 flavonoids and 1 triterpene. These chemical constituents were separated on a C18 column and identified or tentatively characterized based on UV spectra and MS fragmentation behavior. The chemical compositions of the three Paeonia species were found to have many differences. Paeonol was the predominant constituent of P. suffruticosa and P. decomposita, while P. delavayi contained albiflorin and more galloyl glucoses than the other two Paeonia species. Most of these identified compounds have been reported from P. delavayi and P. decomposita for the first time. The ESI‐MS fragmentation behavior of monoterpene glycosides, acetophenones and galloyl glucoses was also investigated successively, and appropriate characteristic pathways were proposed. The large differences in chemical compounds among the three Paeonia species strongly encouraged further comparison of the bioactivities of these three species. Copyright © 2006 John Wiley & Sons, Ltd.
Selective detection of homocysteine by laser desorption/ionization mass spectrometry
Authors: Su Chih‐Lin , Tseng Wei‐Lung
Published: October 2006

This article describes the use of 2,3‐naphthalenedicarboxaldehyde (NDA) as a selective probe for the determination of homocysteine (HCys) via fluorescence measurement and laser desorption/ionization mass spectrometry (LDI‐MS). The derivatives of three aminothiols–HCys, glutathione (GSH), and γ‐glutamylcysteine (γ‐Glu‐Cys)–with NDA under alkaline conditions possess different fluorescence emission characteristics, which allow us to identify them from amines, amino acids, and thiols. By selecting appropriate pH and excitation wavelengths, the limits of detection (LODs) at a signal‐to‐noise ratio of 3 were 5.2, 1.4 and 16 nM for HCys, GSH and γ‐Glu‐Cys, respectively. Additionally, strong UV absorption of the NDA‐HCys derivative was further observed at 331 nm; it could be directly detected by LDI‐MS with a 337‐nm nitrogen laser. Selective detection of HCys has been achieved by conducting the LDI‐MS of the NDA‐HCys derivative, which was found at m/z 406.9. The lowest detectable concentration of the NDA‐HCys derivative in this approach was 500 nM. Quantitative determination of HCys in urine samples was accomplished by LDI‐MS. Also, a calibration curve was created from plasma samples spiked with standard HCys (20–100 µM). The experimental results suggest that our proposed methods have great potential in clinical diagnosis and metabolomics application. Copyright © 2006 John Wiley & Sons, Ltd.
Compensation voltage shifting in high‐field asymmetric waveform ion mobility spectrometry‐mass spectrometry
Authors: Kolakowski Beata M. , McCooeye Margaret A. , Mester Zoltan
Published: October 2006

The separation and ion focusing properties of High‐Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) depend on desolvated ions entering the device, leading to a compound‐specific, reproducible compensation voltage (CV) for each ion. This study shows that the conditions identified for stable spray and satisfactory ion desolvation in normal electrospray ionization mass spectrometry (ESI‐MS) operation might significantly differ from those required for FAIMS‐MS. In a typical setup with high‐flow electrospray conditions, ions could be incompletely desolvated, resulting in the formation of unidentified clusters with differing behavior in a FAIMS environment. This causes compound‐specific shifts of as much as 10 V in CV values when the mobile phase composition and/or flow rate are varied. The shifts diminish and finally disappear when the flow rate of methanol, used as mobile phase, is reduced to 40 µL/min and that of acetonitrile to 20 µL/min. The reproducibility of the observed CV was determined by scanning the CV while infusing a five‐component mixture into a 400 µL/min flow of methanol or 50:50 acetonitrile/water. The relative standard deviation (RSD) for these multiple scans ranged from 0.7% to 6%. Therefore, under a constant set of experimental parameters, the CV does not shift appreciably. These observations have an impact on method development strategies. High flow rates can be used with the FAIMS device, since the CV values are reproducible, but it is likely that clusters are forming. Therefore, CV scans should be performed under conditions which mimic the chromatographic elution or flow injection analysis conditions, including matrix composition, to minimize errors in CV determination. An alternative approach is to determine the liquid flow rate at which the CV becomes compound‐specific and to split the mobile phase stream accordingly. These experimental results may be specific to the setup used for this study and may not be directly applicable to other instrument FAIMS devices. Copyright © 2006 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.
Quantification of small molecule organic acids from Mycobacterium tuberculosis culture supernatant using ion exclusion liquid chromatography/mass spectrometry
Authors: Goodwin Michael B. , Boshoff Helena I. , Barry Clifton E. , Dowd Cynthia S.
Published: October 2006

Quantitative analysis of cellular small molecule organic acids of intermediary metabolism can provide critical insight into bacterial metabolic pathways. The concentration of these metabolites in culture supernatant varies at different growth stages or under particular environmental conditions reflecting both the energy and the biosynthetic needs, yielding metabolic information about the microorganism. The method described here utilizes ion exclusion chromatography with formic acid, coupled with a mass‐selective detector using selective ion monitoring with negative mode electrospray ionization (SIM ES−), to detect and quantify several small organic acids in culture supernatants. The µM limits of quantitation (LOQs) were found to be 5.5 ± 0.9 for pyruvate, 7.0 ± 0.4 for malate, 2.5 ± 0.5 for succinate, 12.7 ± 0.8 for lactate, and 6.6 ± 0.2 for fumarate. The method was used to detect and quantify these acids in the culture supernatants from Mycobacterium tuberculosis. Supernatant samples were spiked with stable‐isotope‐labeled internal standards, and the organic acids were quantified by isotope ratiometry. Published in 2006 by John Wiley & Sons, Ltd.
Sizing a trial to alter the trajectory of health behaviours: methods, parameter estimates, and their application
Authors: Murray David M. , Blitstein Jonathan L. , Hannan Peter J. , Baker William L. , Lytle Leslie A.
Published: October 2006

Group‐randomized trials often involve repeat observations on the same participants. When there are no more than two observations from each participant, standard mixed‐model regression methods for a pretest–posttest design can be used. When there are more than two observations from each participant, random coefficients models may be useful. This paper describes the random coefficients analysis appropriate to data from an extended nested cohort design and presents the methods for power analysis and sample size calculations based on that analysis. We provide estimates for the parameters required for those calculations for a number of adolescent health behaviours. We also show how the estimates can be used to plan a future trial. Copyright © 2006 John Wiley & Sons, Ltd.
A direct INT‐dehydrogenase assay (DIDHA) for assessing chemical toxicity
Authors: Bitton G. , Khafif T. , Chataigner N. , Bastide J. , Coste C. M.
Published: October 2006

A direct INT‐dehydrogenase assay (DIDHA) was developed to measure chemical toxicity as well as toxicant interactions. This test consists of measuring quickly and directly the dehydrogenase activity (i.e., INT reduction) with the aid of a double beam spectrophotometer, thus avoiding formazan extraction and centrifugation steps. The assay was used to determine the toxicity of heavy metals, phenol, α‐naphtol, and herbicides (Barban, propanil, swep, BIPC, and CIPC). It was also useful in demonstrating the protective effect of clays and humic acids with regard to herbicide toxicity as well as antagonistic and synergistic interactions among toxicants.
Comparison of respiration and luminescent tests in bacterial toxicity assessment
Authors: Reteuna C. , Vasseur P. , Cabridenc R. , Lepailleur H.
Published: October 2006

The toxicity assessment of chemicals on complex microbial communities are generally preferred to toxic tests conducted with pure cultures of bacteria. The purpose of this study is to compare the “Respiration” test studying metabolic criteria of mix bacterial populations and the “Microtox” test using lyophilized cultures of luminescent bacteria. The inhibition of oxygen consumption was compared with the inhibition of the bioluminescence of Photobacterium phosphoreum.

In the first part of this study, the methodology of the “Respiration” test and the “Microtox” test was improved to optimize their performance in toxicity assessment.

In the second part, toxicity of an organic chemical, the 3,5‐Dichlorophenol, and an inorganic chemical, copper sulfate, was evaluated with the two tests. Results were compared and characteristics of the testing methods are discussed according to their sensitivity, reproducibility, representativity and ease of execution.

The repeatability study for the “Respiration” test and the “Microtox” test gives variation coefficients less than 15% and 10% respectively. The variation coefficients concerning the reproducibility study are found to be 15% or 18% for the “Respiration” test, 5% or 28% for the “Microtox” test, depending on the tested toxicant. These two toxicity tests are easy to perform. But the “Microtox” test offers the advantage of being more sensitive and much faster. On the other hand, the “Respiration” test which was conducted on a microbial community is probably more representative of microflora in rivers.
Effect of suspended solids concentration and filament type on the toxicity of chlorine and hydrogen peroxide to bulking activated sludge
Authors: Chang‐Womkim  , Koopman Ben , Bitton Gabriel
Published: October 2006

Toxic inhibition of three communities of filamentous microorganisms by chlorine and hydrogen peroxide was investigated in relation to the total suspended solids concentration of bulking acitvated sludges. The filament communities studied were dominated by type 1701, Sphaerotilus natans, and the combination of type 021N and Thiothrix spp., respectively. Activity of filamentous and gross biomass was assessed separately using the malachite green‐INT (MINT) test. The effectiveness of toxicants was characterized in terms of the concentration required to inhibit 50% of microbial dehydrogenase activity (IC50). IC50s were found to be proportional to total suspended solids concentration. Values for filamentous biomass were generally lower than those for gross biomass. Relative sensitivity (ratio of gross IC50 to filamentous IC50) did not vary significantly over the practical range of total suspended solids concentraton. This parameter was unaffected by the nature of the toxicant in S. natans and type 021N/Thiothrix dominated sludges, but was toxicant specific in type 1701 dominated sludge. Overall, S. natans and type 1701 were the least sensitive of the filament types studied. Bulking caused by these organisms has been successfully cured by toxicant addition in numerous past instances. It is therefore expected that type 021N, Thiothrix, and most other types of filamentous bulking can also be controlled by this technique.
ATP‐TOX system—a new, rapid, sensitive bacterial toxicity screening system based on the determination of ATP
Authors: Xu Hao , Wuhan  , Hubei  , Dutka B. J.
Published: October 2006

A new toxicity screening test, based on the inhibition of bacterial growth and luciferase activity by toxicants was developed. In the ATP‐TOX System, chemical toxicity was found to be time‐dependent and increased with increasing exposure time up to 5 hours. Three organisms were evaluated in this study: E. coli K‐12 PQ37, Pseudomonas fluorescens and Salmonella typhimurium. E. coli K‐12 PQ37 was found to be the most sensitive organism. It was also shown that P. fluorescens was more sensitive to toxicants when grown in minimal medium than in nutrient broth, suggesting that nutrients may have a protective effect on the bacterium. In comparative studies using selected toxic chemicals the ATP‐TOX System was found to be more sensitive than the Spirillum volutans test and comparable to the Microtox test. Toxicant activity in sediment samples was found to be time dependent and increased with increasing exposure time in both ATP‐TOX (E. coli) System and Microtox. The ATP‐TOX System is complementary to the Microtox test as it also provides indications of low grade toxicant activity which is only manifested in actively growing cells over several life cycles. Thus, the ATP‐TOX System appears to be an ideal screening test for sediment toxicity. The data indicate that the ATP‐TOX System is sensitive, rapid, reproducible, economical and has great potential in applied studies.
The effects and removal of chromium in chlamydomonas sp.
Authors: Ayoub George M. , Sayigh Bassim A.
Published: October 2006

The effect of chromium addition on the green alga Chlamydomonas sp. was investigated. Experiments were conducted by culturing pure stock cultures of the algae in a synthetically prepared culture medium simulating wastewater. Doses of chromium with different concentrations were added in shock and continuous forms. The effect of these doses on the growth of the algae was evaluated by carrying out algal cell counts. Possible removal of chromium by algal accumulation of the chromium was also evaluated by measuring residual chromium concentrations in the effluent. The results indicated that Chlamydomanas sp. could tolerate shock chromium doses of up to 0.2 mg. ℓ−1 and continous doses of up to 0.25 mg. ℓ−1 and can adapt to the presence of chromium in the medium. However, possible morphological changes could be induced in the cell. Furthermore, Chlamydomonas sp. was found to remove about 20% of the chromium found in the reactor.
Photobacterium phosphoreum toxicity bioassay. II. Toxicity data compilation
Authors: Kaiser Klaus L. E. , Ribo Juan M.
Published: October 2006

This review of Photobacterium phosphoreum toxicity bioassay, commonly known as the Microtox tests, consists of two parts. This second part (Toxicity Data Compilation) is a listing of all published and certain unpublished Microtox toxicity data for single organic compounds, including some salts and organometallic compounds. This listing consists of three tables: the first provides the reference source, toxicity value(s), chemical formula, name, the Chemical Abstracts Service (CAS) and Registry of Toxic Effects of Chemical Substances (RTECS) accession numbers, and molecular weight of each compound. At present, this table contains approximately 500 entries, which are ordered by the compounds' molecular formula. Two additional tables, ordered accordingly, are intended to provide quick access through cross‐references with the CAS and RTECS numbers, respectively.
Enzyme biosynthesis versus enzyme activity as a basis for microbial toxicity testing
Authors: Dutton R. J. , Bitton G. , Koopman B.
Published: October 2006

A toxicity assay based on inhibition of β‐galactosidase biosynthesis was compared to a similar assay based on inhibition of β‐galactosidase activity. In both tests, Escherichia coli grown in a minimal medium was exposed to isopropyl‐β‐thiogalactoside to induce β‐galactosidase biosynthesis. The induction step preceded contact of cells with the toxicant in the enzyme activity assay, whereas in the enzyme biosynthesis test, the inducer was added following contact of cells with the toxicant. Relative sensitivity was judged on the basis of responses to the heavy metals Hg2+, Cu2+, and Cd2+, and the organics 3,4‐dichlorophenol, formaldehyde, Hydrothol, phenol, sodium dodecyl sulphate, and toluene. Comparison of these results to the IC50s achieved with other microbial systems, Daphnia bioassay, and fish bioassay indicates that the enzyme activity test was moderately sensitive to heavy metals but was insensitive to organic toxicants. The test based on inhibition of enzyme biosynthesis was sensitive to both heavy metals and toxic organics.
RK mutatest variations for rapid independent determination of toxicity and mutagenicity
Authors: Hayes Sidney
Published: October 2006

The RK mutatest is a recently developed, forward, short‐term, bacterial genetic test system for quantitation of mutagenic activity and toxicity. Rapid quantitative, semi‐quantitative, and qualitative variations of the standard RK mutatest protocol were developed and tested using reference genotoxic agents. Several of the reported mutatest modifications considerably reduced assay time, and would be useful for a quick first‐stage evaluation of the biological damaging effect of environmental substances.
Toxicity assessment of the antiparasitic ivermectin
Authors: Rodrigues M. A. La R. , Mattei Rita
Published: October 2006

The citotoxicity of ivermectin, a streptomycete‐derived macrocyclic lactone active against a wide variety of nematode and arthropod parasites, was evaluated in pig kidney cells IB‐RS‐2. The cells were cultured in the presence of different levels of ivermectin for 72 h. The cell count decreased as ivermectin concentration in the medium was increased from 0 to 20 †g/mL, and this decrease was time and dose dependent; at 40 †g/mL cell death occurred within 24 h. Ivermectin (20 †g/mL) decreased protein synthesis and glucose utilization. These effects became progressively less between 48 and 72 h when compared to untreated cells.
Fecal coliforms as indicators in tropical waters: A review
Authors: Hazen Terry C.
Published: October 2006

Nowhere is the importance of accurate determination of recent human fecal contamination greater than in the tropics. The diversity of waterborne diseases and their severity is greatest in tropical environments. Since most of the countries in tropical climates are underdeveloped, with large populations that are undernourished, ill‐housed, with poor medical services, waterborne diseases may have a much greater effect on public health in the tropics than in temperate areas. Universally, tropical areas accept water maximum contaminant levels developed by temperate nations, despite the obvious differences in tropical climates. High densities of total and fecal coliform bacteria have been detected in pristine streams and in groundwater samples collected from many tropical parts of the world, even in epiphytic vegetation 10 m above ground in the rain forest of Puerto Rico. Nucleic acid (DNA) analyses of Escherichia coli from pristine tropical environs has indicated that they are identical to clinical isolates of E. coli. Many tropical source waters have been shown to have enteric pathogens in the complete absence of coliforms. Diffusion chamber studies with E. coli at several tropical sites reveal that this bacterium can survive indefinitely in most freshwaters in Puerto Rico. An evaluation of methods for the enumeration of fecal coliforms showed that currently used media have poor reliability as a result of large numbers of false positive and false negative results when applied to tropical water samples. Total and fecal coliform bacteria are not reliable indicators of recent biological contamination of waters in tropical areas. Fecal streptococci and coliphages in tropical waters violate the same underlying assumptions of indicator assays as the coliforms. Anaerobic bacteria like Bifidobacterium spp. and Clostridium perfringens show some promise in terms of survival, but not in ease of enumeration and media specificity. The best course at present lies in using current techniques for direct enumeration of pathogens by fluorescent staining and nucleic acid analysis, and developing tropical maximum contaminant levels for certain resistant pathogens in tropical waters.
Detection and recovery of Legionella in water
Authors: Barbaree J. M. , Morrill W. E. , Fields B. S. , Martin W. T. , Sanden G. N.
Published: October 2006

Methods used to detect Legionella include direct fluorescent antibody stain, genetic probe, and culturing. Culturing is preferred for detecting Legionella pneumophila (Lp) in water; however, recovery rates are affected by treatment of water samples. Experiments with water‐containing Lp showed that (a) a water storage temperature of 4°C results in a slower decline in numbers of Lp as compared with 25, 35, and 45°C; (b) a water sample containing Lp and nonlegionellae microflora is appropriate for quality control of selective media used to isolate Legionella from environmental water specimens; and (c) acid treatment and concentration of water by filtration are effective techniques for isolating Lp from environmental water samples, but they do not yield 100% recovery of Lp cells.
Coliphage association with coliform indicators: A case study in Chile
Authors: Castillo Gabriela , Thiers R. , Dutka B. J. , El‐Shaarawi A. H.
Published: October 2006

This paper summarizes the results obtained from an International Development Research Centre (IDRC), Ottawa, Canada, funded study to evaluate the potential of using coliphage as an indicator of water quality. Raw water sample data indicated that the A‐1 test combined with the coliphage test would make an excellent screening program for health hazards in these waters. The superiority of the Presence/Absence test for detecting microbial health hazards in potable water was readily shown, while the H2S paper strip technique was found to be equally efficient for testing potable waters as traditional coliform water quality indicators.
Southeast Asian experiences with the coliphage test
Authors: Suan Sim Tiow , Chuen Ho Yueh , Sivaborvorn Komol
Published: October 2006

The increasing demand for potable water in Southeast Asia warrants the need for a simple, rapid, and economical water quality test that can be used by unskilled personnel to monitor potential fecal contamination of drinking water supplies. The coliphage test is expected to fulfill this need since many advantages can be attributed to this test.

In order to evaluate the use of the coliphage test, an intensive study to correlate the results of the coliphage test with three other water quality tests—viz., conventional five‐tube most probable number (MPN) fermentation test, the A1 broth five‐tube MPN test, and the membrane filtration test—was carried out. At least 1000 water samples were examined over a 20‐month period. Results of the tests showed that there is a consistent relationship between coliphages and fecal coliforms in river water, pond water, well water and rainwater, in that coliphages are frequently found when fecal coliforms are detected. On the other hand, correlation analyses have also showed that in water sources that are shallow and turbid due to residual sediments, correlation between coliphages and fecal coliforms was less significant. Further analyses have also indicated that the factors that most affected the coliphage tests were turbidity, pH, and dissolved oxygen. In the process of evaluating the coliphage procedure, it was found that the test can be performed at ambient temperatures and results can be obtained after 6–8 h of incubation.
Removal of cyanobacterial toxins in water treatment processes: Laboratory and pilot‐scale experiments
Authors: Keijola A. M. , Himberg K. , Esala A. L. , Sivonen K. , Hiis‐Virta L.
Published: October 2006

The effectiveness of various drinking water treatment processes has been tested in laboratory and pilot scale experiments using neurotoxic and hepatotoxic cyanobacterial blooms and laboratory‐grown algal cultures as test material. The species involved belonged to the genera Microcystis, Oscillatoria, and Anabaena. Microcystis and Oscillatoria hepatotoxins were analyzed by high performance liquid chromatography. The Anabaena neurotoxin, anatoxin‐a, was determined using gas chromatography/mass spectrometry techniques. Toxicity was tested and verified by mouse bioassay. The laboratory study, made with freeze‐dried cyanobacteria, showed that toxins were not removed by conventional flocculation treatment procedures. The simultaneous addition of a small amount of powdered activated carbon with the flocculation chemical did not improve the removal of hepatotoxins significantly. Substantial reduction of toxins was achieved by granulated activated carbon filtration and by ozonization. Pilot plant studies supported the laboratory findings. Results of the slow sand filtration experiments suggested some removal of toxins.
Annual variation and reliability of fecal indicators in a polluted river
Authors: Niemi R. M. , Niemi J. S.
Published: October 2006

Fecal indicators were enumerated over a period of one year in the river Vantaanjoki discharging to the Gulf of Finland. The river was divided into three zones, one affected by nonpoint loading, another receiving treated domestic sewage, and the lower reach with no substantial further loading. The reliability of routine enumeration methods for thermotolerant coliforms and fecal streptococci was tested by isolating strains for confirmation.

Fecal indicators showed wide spatial and temporal variation: the concentrations and numbers were low in summer, higher in winter under the ice cover, and highest during the periods of high discharge in spring and autumn.

Of the 931 thermotolerant coliforms isolated, 74% were identified as Escherichia coli by the API 20 E identification system. A total of 3441 strains were tested for gas and indole production at 44.5°C. Of these, 73% were gas positive and 89% indole positive. Of the 3567 fecal streptococci, 67% were confirmed as catalase negative and esculin positive on bile esculin azide agar at 44.5°C. The proportion of confirmed fecal indicators varied both in different reaches of the river and seasonally. The enumeration of fecal streptococci was in some cases unreliable.

Correlations between different fecal indicators and between fecal indicators and chemical water quality variables were calculated within seasons. Correlation coefficients varied with season but showed good overall compatibility.
Toxicity of a trivalent organic arsenic compound, dimethylarsinous glutathione in a rat liver cell line (TRL 1215)
Authors: Sakurai T , Kojima C , Kobayashi Y , Hirano S , Sakurai M H , Waalkes M P , Himeno S
Published: October 2006

Background and purpose:

Although inorganic arsenite (AsIII) is toxic in humans, it has recently emerged as an effective chemotherapeutic agent for acute promyelocytic leukemia (APL). In humans and most animals, AsIII is enzymatically methylated in the liver to weakly toxic dimethylarsinic acid (DMAsV) that is a major pentavalent methylarsenic metabolite. Recent reports have indicated that trivalent methylarsenicals are produced through methylation of AsIII and participate in arsenic poisoning. Trivalent methylarsenicals may be generated as arsenical–glutathione conjugates, such as dimethylarsinous glutathione (DMAsIIIG), during the methylation process. However, less information is available on the cytotoxicity of DMAsIIIG.

Experimental approach:

We synthesized and purified DMAsIIIG using high performance TLC (HPTLC) methods and measured its cytotoxicity in rat liver cell line (TRL 1215 cells).

Key results:

DMAsIIIG was highly cytotoxic in TRL 1215 cells with a LC50 of 160 nM. We also found that DMAsIIIG molecule itself was not transported efficiently into the cells and was not cytotoxic; however it readily became strongly cytotoxic by dissociating into trivalent dimethylarsenicals and glutathione (GSH). The addition of GSH in micromolar physiological concentrations prevented the breakdown of DMAsIIIG, and the DMAsIIIG‐induced cytotoxicity. Physiological concentrations of normal human serum (HS), human serum albumin (HSA), and human red blood cells (HRBC) also reduced both the cytotoxicity and cellular arsenic uptake induced by exposure to DMAsIIIG.

Conclusions and implications:

These findings suggest that the significant cytotoxicity induced by DMAsIIIG may not be seen in healthy humans, even if DMAsIIIG is formed in the body from AsIII.

British Journal of Pharmacology (2006) 149, 888–897. doi:10.1038/sj.bjp.0706899