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Chlorine
Kinds of Chlorine Terms modified by Chlorine Selected AbstractsEFFECTIVENESS OF CHLORINE AND NISIN-EDTA TREATMENTS OF WHOLE MELONS AND FRESH-CUT PIECES FOR REDUCING NATIVE MICROFLORA AND EXTENDING SHELF-LIFE,JOURNAL OF FOOD SAFETY, Issue 4 2002DIKE O. UKUKU ABSTRACT Efficacy of nisin-EDTA treatments as a sanitizing treatment for reducing native microflora of whole melons and extending shelf-life of fresh-cut pieces was compared to chlorine treatments. Whole cantaloupe and honeydew melons were washed with water, nisin (10 ,g/mL)-EDTA (0.02 M), or 200 ppm chlorine for 5 min at , 20C before fresh-cut preparation and storage at 5C for 15 days with periodic microbiological sampling. In addition, some fresh-cut pieces were washed with 10 ,g/mL nisin-EDTA or 50 ppm chlorine for 1 min before storage. Changes in appearance, odor, overall acceptability and the shelf-life of the minimally processed fresh-cut melons were investigated. Preliminary studies indicated that water washes, EDTA (0.002 to 0.2 M) or nisin (5 to 10 ,g/mL) were not effective in reducing the microflora of whole melon when used individually. Nisin-EDTA and chlorine treatments were significantly (P < 0.05) more effective in reducing native microflora than water washes. Nisin-EDTA treatments were significantly (P < 0.05) more effective than chlorine in reducing populations of yeast and mold and Pseudomonas spp. on whole melon surfaces but were not as effective as chlorine treatments for reducing aerobic mesophilic bacteria, lactic acid bacteria and total gram-negative bacteria. Microbial contaminants on fresh-cut pieces washed with 50 ppm chlorine or nisin-EDTA were further reduced. However, microbial populations increased throughout refrigerated storage irrespective of treatments. Odor, appearance, and overall acceptability ratings for cantaloupe and honeydew fresh-cut pieces treated with nisin-EDTA or chlorine were not significantly (P > 0.05) different from each other throughout the storage period (15 to 21 days). However, both treatments led to significantly (P < 0.05) improved ratings compared to the controls for the fresh-cut pieces at 9 to 12 days of storage and thereafter. The results of this study suggest that treatments with nisin-EDTA before and after fresh-cut processing would improve the quality and extend the shelf-life of fresh-cut melon. [source] Reaction with N,N -Diethyl- p -phenylenediamine: A Procedure for the Sensitive Square-Wave Voltammetric Detection of ChlorineELECTROANALYSIS, Issue 8 2003Hugo Seymour Abstract The reaction of chlorine and N,N -diethyl- p -phenylenediamine has been studied as a means of generating an analytical voltammetric signal of much improved sensitivity and selectivity for the detection of the former than is possible via direct electrolysis. A reaction mechanism is suggested whereby the chlorine attacks the primary amine of DEPD to form the N -chlorinated product that shows a much enhanced signal under conditions of square-wave voltammetry than does chlorine itself. The analytical parameters were found to vary with concentration of DEPD and a linear range from 17 to 495,,M was achievable with a corresponding limit of detection of 6.8,,M [source] Simultaneous Determination of Fluorine, Chlorine, Bromine and Iodine in Six Geochemical Reference Materials Using Pyrohydrolysis, Ion Chromatography and Inductively Coupled Plasma-Mass SpectrometryGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 4 2009Hélène Balcone-Boissard halogènes; pyrohydrolyse; chromatographie ionique; spectrométrie de masse couplée à une source de plasma induit; matériaux géologiques de référence Concentrations of halogens (fluorine, chlorine, bromine and iodine) were determined in six geochemical reference materials (BHVO-2, GS-N, JG-1, JR-1, JB-1b, JB-2). Halogens were first extracted from powdered samples using a pyrohydrolysis technique, then hydrolysis solutions were analysed by ion chromatography for F and Cl and inductively coupled plasma-mass spectrometry for Br and I. The detection limits in solutions were 100 ,g l,1 for both F and Cl and 10 ng l,1 for Br and I. Considering the extraction procedure, performed on a maximum of 500 mg of sample and producing 100 ml of pyrohydrolysis solution, detection limits in rock samples were 20 mg kg,1 for F and Cl and 2 ,g kg,1 for Br and I. The mean analytical errors on the studied composition ranges were estimated at 10 mg kg,1 for F and Cl, 100 ,g kg,1 for Br and 25 ,g kg,1 for I. The concentration values, based on repeated (generally > 10) sample analysis, were in good agreement generally with published values and narrowed the mean dispersion around mean values. Large dispersions are discussed in terms of samples heterogeneity and contaminations during sample preparation. Basaltic RMs were found to be more suitable for studies of halogen compositions than differentiated rock material, especially granites , the powders of which were heterogeneous in halogens at the 500 mg level. Les concentrations en halogènes (fluor, chlore, brome et iode) on été déterminées dans 6 matériaux géologiques de référence (BHVO-2, GS-N, JG-1, JR-1, JB-1b, JB-2), distribués par le GSJ, l'USGS et le CRPG. Les halogènes étaient d'abord extraits des échantillons, disponibles sous forme de poudre, par pyrohydrolyse. F et Cl sont ensuite analysés par chromatographie ionique, Br et I par spectrométrie de masse couplée à une source de plasma induit. Les limites de détection sont de 100 ,g l,1 pour F et Cl, et de 10 ng l,1 pour Br et I, respectivement. L'extraction des halogènes était réalisée sur 500 mg de poudre de roche, produisant 100 ml de solution d'extraction. Ainsi, pour les échantillons de roche, les limites de détection étaient de 20 mg kg,1 pour F et Cl, et 2 ,g kg,1 pour Br et I. L'erreur analytique moyenne sur la gamme de concentration étudiée est estimée à 10 mg kg,1 pour F et Cl, 100 ,g kg,1 pour Br et 25 ,g kg,1 pour I. Les valeurs de concentrations données, obtenues par l'analyse répétée (> 10) du même échantillon étaient en accord avec les valeurs reportées dans la littérature. Elles présentent en général une plus faible dispersion autour de la valeur moyenne. Dans le cas d'une importante dispersion des résultats, celle-ci est discutée en terme d'hétérogénéité de l'échantillon analysé et de contamination durant la préparation du matériel de référence. Les échantillons de référence de composition basaltique se révèlent être plus appropriés pour étudier les compositions en halogènes que les matériaux correspondant à des roches différenciées, en particulier des granites dont la distribution en halogènes apparaît hétérogène dans les poudres à l'échelle d'un aliquot de 500 mg. [source] INFLUENCE OF WASHING TREATMENT ON NATIVE MICROFLORA AND ESCHERICHIA COLI POPULATION OF INOCULATED CANTALOUPESJOURNAL OF FOOD SAFETY, Issue 1 2001DIKE O. UKUKU ABSTRACT The influence of chlorine or hydrogen peroxide treatment on populations of Escherichia coli 25922 on the external surface of inoculated cantaloupe was investigated. Surface treatment with 70% EtOH, followed by immersion in 108 CFU/mL E. coli inoculum deposited an average of 4.4 log10CFU/cm2 cell population on the cantaloupe surface. The efficncy of washing inoculated cantaloupe was dependent on storage interval between inoculation and treatment. Dipping the cantaloupes in solutions containing 1000 mg/L chlorine or 5% peroxide for 5 min, within 24 h of inoculation, caused a 2 log10 CFU/cm2 reduction of the indigenous surface microflora and a 3,4.0 log10 CFU/cm2 reduction in E. coli. The efficacy was less when the interval between inoculation and treatment exceeded 24 h. Chlorine appeared in be a better antimicrobial agent than hydrogen peroxide against F. coli ATCC 25922 inoculated on cantaloupe surfaces while hydrogen peroxide was better in reducing surface microflora of cantaloupe. [source] Acidified Sodium Chlorite as an Alternative to Chlorine for Elimination of Salmonella on Alfalfa SeedsJOURNAL OF FOOD SCIENCE, Issue 4 2009C.-H. Liao ABSTRACT:, The health and environmental hazard associated with the use of chlorine for food processing has been documented previously. This study was conducted to determine if acidified sodium chlorite (ASC) could be used to replace calcium hypochlorite (Ca[OCl]2) for disinfection of alfalfa seeds. Contaminated seeds containing approximately 1.5 × 107 CFU/g of Salmonella were treated with ASC or Ca(OCl)2 at different concentrations and for different periods of time. Results showed that the efficacy of ASC and Ca(OCl)2 for elimination of Salmonella on contaminated seeds could be improved greatly by extending the treatment time from the traditional 15 to 45 min. Treatment of seeds with 800 ppm of ASC for 45 min reduced the number of Salmonella by 3.9 log units, approximately 1.2 log units higher than that treated with 20000 ppm of Ca(OCl)2. Treatment of seeds with a lower concentration (100 to 400 ppm) of ASC for 45 min reduced the number of Salmonella by 1.3 to 2.2 log units. Soaking alfalfa seeds in 800 ppm of ASC for 45 min did not affect seed germination. However, soaking seeds in 20000 ppm of Ca(OCl)2 for 45 min reduced seed germination by 20%. Unlike Ca(OCl)2, antimicrobial efficiency of ASC was not affected by pre-exposure to alfalfa seeds. Data presented also showed that Salmonella on newly inoculated seeds that had been stored at 4 °C for less than 7 d were more sensitive to sanitizer treatment than those on seeds that had been stored for 4 wk or longer. [source] Geneses of High Chlorine and Silver,Lead,Zinc,Mineralized Granitoids in Tsushima, JapanRESOURCE GEOLOGY, Issue 3 2000Shunso ISHIHARA 7037. (5) They are high in Cl and S, which occur in fluid inclusions and as pyrrhotite>pyrite, respectively. Two genetic models are considered for the source of the unique granitoid magmas: the continental crust or the upper mantle fertilized with Si, K and 18O. The latter may be the case for the Tsushima granitoids, because of the low initial Sr ratio. The age of the granitoids (16 Ma) indicates the magmatism related to the opening of the Sea of Japan. It is suggested that both basaltic and granitic magmas were generated in the continental lithosphere under an extensional tectonic setting; the two magmas could have been partly mingled. The mingled magma was originally an oxidized type, but reduced during the emplacement by repeated inflow of S and C-bearing gases from the pelitic wall rocks. Because of the reduction, SO3 sulfur is almost nil in the rock-forming apatite, and most of sulfur remained in fluid phase of the magma as reduced species. Cl content was high in the original magma and concentrated in the fluid phase of the residual system which dissolved silver, lead and zinc metals. Such a fluid migrated into the Taishu fracture systems, as the magma crystallized, and formed the silver,lead,zinc deposits. [source] ChemInform Abstract: A Facile Synthesis of 5(6)-(Chloromethyl)benzimidazoles: Replacement of a Sulfonic Acid Functionality by Chlorine.CHEMINFORM, Issue 29 2008Bela Pete Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Internal Delivery of Soft Chlorine and Bromine Atoms: Stereoselective Synthesis of (E)-,-Halogenovinyl(aryl)-,3 -iodanes Through Domino ,3 -Iodanation,1,4-Halogen Shift,Fluorination of Alkynes.CHEMINFORM, Issue 51 2007Masahito Ochiai Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Relative ortho-Directing Power of Fluorine, Chlorine and Methoxy Group for the Metalation Reaction in the Diazine Series.CHEMINFORM, Issue 12 2004Diazines. Abstract For Abstract see ChemInform Abstract in Full Text. [source] Intramolecular Carbolithiation Promoted by a DTBB-Catalyzed Chlorine,Lithium Exchange.CHEMINFORM, Issue 8 2004Miguel Yus Abstract For Abstract see ChemInform Abstract in Full Text. [source] Use of a Fluorous Bridge for Diffusion Controlled Uptake of Molecular Chlorine in Chlorine Addition to Alkenes.CHEMINFORM, Issue 6 2004Jernej Iskra Abstract For Abstract see ChemInform Abstract in Full Text. [source] Electrochemical Determination of a Free Chlorine Residual Using Cathodic Potential-Step ChronocoulometryELECTROANALYSIS, Issue 8 2005Shin-ya Kishioka Abstract The cathodic reaction of chlorine residual (CR) combined with anodic pre-electrolysis enables the quantification of CR as a gaseous chlorine. Potential-step chronocoulometry was successfully applied to extend the CR detection range. [source] Reaction with N,N -Diethyl- p -phenylenediamine: A Procedure for the Sensitive Square-Wave Voltammetric Detection of ChlorineELECTROANALYSIS, Issue 8 2003Hugo Seymour Abstract The reaction of chlorine and N,N -diethyl- p -phenylenediamine has been studied as a means of generating an analytical voltammetric signal of much improved sensitivity and selectivity for the detection of the former than is possible via direct electrolysis. A reaction mechanism is suggested whereby the chlorine attacks the primary amine of DEPD to form the N -chlorinated product that shows a much enhanced signal under conditions of square-wave voltammetry than does chlorine itself. The analytical parameters were found to vary with concentration of DEPD and a linear range from 17 to 495,,M was achievable with a corresponding limit of detection of 6.8,,M [source] Possible role of reactive chlorine in microbial antagonism and organic matter chlorination in terrestrial environmentsENVIRONMENTAL MICROBIOLOGY, Issue 6 2009Per Bengtson Summary Several studies have demonstrated that extensive formation of organically bound chlorine occurs both in soil and in decaying plant material. Previous studies suggest that enzymatic formation of reactive chlorine outside cells is a major source. However, the ecological role of microbial-induced extracellular chlorination processes remains unclear. In the present paper, we assess whether or not the literature supports the hypothesis that extracellular chlorination is involved in direct antagonism against competitors for the same resources. Our review shows that it is by no means rare that biotic processes create conditions that render biocidal concentrations of reactive chlorine compounds, which suggest that extracellular production of reactive chlorine may have an important role in antagonistic microbial interactions. To test the validity, we searched the UniprotPK database for microorganisms that are known to produce haloperoxidases. It appeared that many of the identified haloperoxidases from terrestrial environments are originating from organisms that are associated with living plants or decomposing plant material. The results of the in silico screening were supported by various field and laboratory studies on natural chlorination. Hence, the ability to produce reactive chlorine seems to be especially common in environments that are known for antibiotic-mediated competition for resources (interference competition). Yet, the ability to produce haloperoxidases is also recorded, for example, for plant endosymbionts and parasites, and there is little or no empirical evidence that suggests that these organisms are antagonistic. [source] Aquatic photochemistry of chlorinated triclosan derivatives: Potential source of polychlorodibenzo- P -dioxins,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2009Jeffrey M. Buth Abstract Triclosan (TCS; 5-chloro-2-(2,4-dichlorophenoxy)phenol), a common antimicrobial agent, may react with residual chlorine in tap water during transport to wastewater treatment plants or during chlorine disinfection of wastewater, generating chlorinated TCS derivatives (CTDs): 4,5-dichloro-2-(2,4-dichlorophenoxy)phenol (4-Cl-TCS), 5,6-dichloro-2-(2,4-dichlorophenoxy)phenol (6-C1-TCS), and 4,5,6-trichloro-2-(2,4-dichlorophenoxy)phenol (4,6-Cl-TCS). The photochemistry of CTDs was investigated due to the potential formation of polychlorodibenzo- p -dioxin (PCDD) photoproducts. Photolysis rates were highly dependent upon CTD speciation, because the phenolate species degraded 44 to 586 times faster than the phenol forms. Photolysis quantum yield values for TCS, 4-Cl-TCS, 6-Cl-TCS, and 4,6-Cl-TCS of 0.39, 0.07, 0.29, and 0.05, respectively, were determined for the phenolate species. Photolyses performed in Mississippi River and Lake Josephine (USA) waters gave similar quantum yields as buffered, pure water at the same pH, indicating that indirect photolysis processes involving photosensitization of dissolved organic matter are not competitive with direct photolysis. The photochemical conversion of the three CTDs to PCDDs under solar irradiation was confirmed in natural and buffered, pure water at yields of 0.5 to 2.5%. The CTD-derived PCDDs possess higher toxicities than 2,8-dichlorodibenzo- p -dioxin, a previously identified photoproduct of TCS, due to their higher chlorine substitution in the lateral positions. The load of TCS- and CTD-derived PCDDs to United States surface waters is estimated to be between 46 and 92 g toxicity equivalent units per year. Other identified photoproducts of each CTD were 2,4-dichlorophenol and reductive dechlorination products. [source] Persistent or not persistent?ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2009Polychlorinated biphenyls are readily depurated by grizzly bears (Ursus arctos horribilis) Abstract Major pharmacokinetic processes influencing polychlorinated biphenyl (PCB) accumulation in mammals include uptake, biotransformation, respiration, and excretion. We characterized some of the factors underlying PCB accumulation/loss by evaluating PCB concentrations and patterns in pre- and posthibernation grizzly bears (Ursus arctos horribilis) and their prey. The PCB congeners with vicinal meta - and para -chlorine unsubstituted hydrogen positions consistently showed loss both before and during hibernation, supporting the idea of a dominant role for biotransformation. Retention of all other studied congeners relative to that of PCB 194 varied widely (from <1 to 100%) and was highly correlated with log octanol--water partition coefficient (p < 0.0001). A lack of loss for most of these other congeners during hibernation supports the notion that excretion (e.g., fecal or urinary) or lack of uptake during the feeding season underlies their lack of accumulation, because hibernating bears do not eat or excrete. We estimate that grizzly bears retain less than 10% of total PCBs taken up from their diet. Our results suggest that for grizzly bears, depuration of PCBs via biotransformation is important (explaining ,40% of loss), but that nonbiotransformation processes, such as excretion, may be more important (explaining ,60% of loss). These findings, together with the approximately 91% loss of the persistent PCB 153 congener relative to PCB 194 in grizzly bears, raise important questions about how one defines persistence of PCBs in wildlife and may have bearing on the interpretation of food-web biomagnification studies. [source] Altered reproduction in fish exposed to pulp and paper mill effluents: Roles of individual compounds and mill operating conditionsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2008L. Mark Hewitt Abstract For the last 20 years, studies conducted in North America, Scandinavia, and New Zealand have shown that pulp and paper mill effluents affect fish reproduction. Despite the level of effort applied, few leads are available regarding the factors responsible. Effluents affect reproduction in multiple fish species, as evidenced by decreased gonad size, decreased circulating and gonadal production of reproductive steroids, altered expression of secondary sex characteristics, and decreased egg production. Several studies also have shown that effluent constituents are capable of accumulating in fish and binding to sex steroid receptors/binding proteins. Studies aimed at isolating biologically active substances within the pulping and papermaking process have provided clues about their source, and work has progressed in identifying opportunities for in-mill treatment technologies. Following comparisons of manufacturing processes and fish responses before and after process changes, it can be concluded that effluent from all types of mill processes are capable of affecting fish reproduction and that any improvements could not be attributed to a specific process modification (because mills normally performed multiple modifications simultaneously). Improved reproductive performance in fish generally was associated with reduced use of molecular chlorine, improved condensate handling, and liquor spill control. Effluent biotreatment has been effective in reducing some effects, but biotreated effluents also have shown no difference or an exacerbation of effects. The role of biotreatment in relation to effects on fish reproduction remains unclear and needs to be resolved. [source] Synthesis of 1,3-Diphospha-2,3-dihydro-1H -phenalenesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2010Arkadii Tarasevych Abstract The reaction of 1,8-dilithionaphthalene (1) with methylenebis[(dialkylamino)chlorophosphanes] [R2N(Cl)PCH2P(Cl)NR2; R = Me (2a), Et (2b)] leads to the formation of new heterocyclic compounds, 1,3-diphospha-2,3-dihydro-1H -phenalenes 3a,b as a mixture of cis and trans isomers. DFT calculations indicate that the cis isomers are thermodynamically more stable by about 1,3 kcal/mol than the trans isomers. Compounds 3a,b can be converted into dithio the derivatives 5a,b and the borane complexes 6a,b, which were characterized by NMR spectroscopy and investigated by X-ray diffraction analysis. The dialkylamino groups in 3 can be substituted by chlorine to give the chlorophosphane 7. [source] Small molecule , -amyloid inhibitors that stabilize protofibrillar structures in vitro improve cognition and pathology in a mouse model of Alzheimer's diseaseEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2010Cheryl A. Hawkes Abstract ,-Amyloid (A,) peptides are thought to play a major role in the pathogenesis of Alzheimer's disease. Compounds that disrupt the kinetic pathways of A, aggregation may be useful in elucidating the role of oligomeric, protofibrillar and fibrillar A, in the etiology of the disease. We have previously reported that scyllo -inositol inhibits A,42 fibril formation but the mechanism(s) by which this occurs has not been investigated in detail. Using a series of scyllo -inositol derivatives in which one or two hydroxyl groups were replaced with hydrogen, chlorine or methoxy substituents, we examined the role of hydrogen bonding and hydrophobicity in the structure,function relationship of scyllo -inositol,A, binding. We report here that all scyllo -inositol derivatives demonstrated reduced effectiveness in preventing A,42 fibrillization compared with scyllo -inositol, suggesting that scyllo -inositol interacts with A,42 via key hydrogen bonds that are formed by all hydroxyl groups. Increasing the hydrophobicity of scyllo -inositol by the addition of two methoxy groups (1,4-di- O -methyl- scyllo -inositol) produced a derivative that stabilized A,42 protofibrils in vitro. Prophylactic administration of 1,4-di- O -methyl- scyllo -inositol to TgCRND8 mice attenuated spatial memory impairments and significantly decreased cerebral amyloid pathology. These results suggest that A, aggregation can be targeted at multiple points along the kinetic pathway for the improvement of Alzheimer's disease-like pathology. [source] Theoretical Description of Substituent Effects in Electrophilic Aromatic Substitution ReactionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 35 2008Tobias Schwabe Abstract The ability of the current Kohn,Sham density functional theory (DFT) to compute the change of the proton affinity (PA) of phenol derivatives due to substitution is investigated. These systems can be used as models to predict reactivities in electrophilic aromatic substitution reactions. The complexity of the problem is increased systematically by introducing successively up to four substituents in five typical cases (methyl, cyano, fluorine, chlorine, and bromine). Our investigation can be regarded as representative for an important class of problems consistently encountered in the DFT modeling of organic reactions. High-level theoretical reference data from CCSD(T) and SCS-MP2 wave-function calculations are presented, and the PAs are compared to those obtained by a series of density functionals (DFs). It is shown that not all DFs are capable of quantitatively reproducing the substituent effects. These can be simply linear in the number of substituents or show more complicated patterns. Especially for halogens, some DFs even fail completely. In these cases, linearly increasing errors with the number of groups are observed. Reliable results are obtained with hybrid DFs or the even more accurate double-hybrid DF approach. The errors are attributed to the common self-interaction (over-delocalization) error in part of the DFs. Comparison with Hartree,Fock results shows that a reliable account of electron correlation is necessary to compute the PA of unsaturated and highly substituted molecules with chemical accuracy.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Iodinated Indole Alkaloids From Plakortis simplex , New Plakohypaphorines and an Evaluation of Their Antihistamine ActivityEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2004Francesca Borrelli Abstract Three new iodinated tryptophan derivatives, plakohypaphorines D,F (4,6), have been isolated from the Caribbean sponge Plakortis simplex. Their structures have been determined by applying spectroscopic methods and microwave-assisted selective dehalogenation. Compound 5 is the first naturally occurring triiodinated indole, while compound 6 is a unique metabolite because it possesses both chlorine and iodine atoms on the indole nucleus. We have evaluated the antihistamine activity of the whole series of plakohypaphorines A,F, but only the diiodinated analogues proved to be active: they display a specific antagonism of the noncompetitive type. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Magnetically Controllable Silver Nanocomposite with Multifunctional Phosphotriazine Matrix and High Antimicrobial ActivityADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Panagiotis Dallas Abstract A recently developed multi-functional phosphotriazine-based polymer is used as a matrix for embedding ,-Fe2O3 nanoparticles as well as a suitable chemical template for surface modification with silver nanoparticles. For the primary magnetic modification, maghemite nanoparticles are surface modified with oleic acid in order to render them organophilic and to prevent the aggregation of the nanoparticles. This aggregation could occur as the polymer synthesis, based on reaction of phosphonitrilic chlorine and 1,4-phenylenediamine, takes place in toluene. The surface active amine units of the polymer structure enable the reduction of silver cations to silver nanoparticles, which are well attached and finely dispersed on its surface. The developed nanocomposite represents one of the few magnetically controllable antibacterial agents based on silver nanoparticles. Magnetic measurements reveal the completely suppressed interactions among maghemite nanoparticles because of their perfect surface coating with an organic surfactant and fine dispersion inside the polymer matrix. This magnetic nanocomposite exhibits a high antibacterial and antifungal activity as proven by tests with nine bacterial strains and four candida (yeast genus) species. For the majority of the tested species, the minimum-inhibition concentrations are below 100,mg,L,1, which is comparable to their equivalent minimum-inhibition concentrations in colloidal silver systems. [source] Molar group contributions to the heat of combustion,FIRE AND MATERIALS, Issue 3 2002Richard N. Walters Experimental results for the gross heat of combustion of over 140 commercial and developmental polymers and small molecules of known chemical structure were used to derive additive molar group contributions to the heat of combustion. The materials examined contained carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, chlorine, fluorine and silicon in linear, branched and cyclic structures. Values for the molar group contributions were summed and divided by the molecular weight of the molecule or polymer repeat unit to yield the gross heat of combustion as determined by oxygen bomb calorimetry. This new method provides an accurate single step method for calculating the heat of combustion. The average relative error of the calculated gross heats of combustion is 2.8%. Published in 2002 by John Wiley & Sons, Ltd. [source] Formation processes at the Ohalo II submerged prehistoric campsite, Israel, inferred from soil micromorphology and magnetic susceptibility studiesGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 4 2003Alexander Tsatskin Soil-geomorphic analysis coupled with micromorphology, SEM/EDS, magnetic susceptibility, and conventional sedimentological studies allowed us to reconstruct the site formation history and validate the archaeologically observed variability of human activities in the prehistoric camp of Ohalo II (19.5 ka B.P.), Sea of Galilee, Israel. The cultural layers rest upon the Late Pleistocene Lake Lisan deposits that accumulated under conditions of changing water supply and increasing rate of sedimentation from deep-water varvelike deposits to basalt-derived, near-shore sandy lacustrine deposits. Intermittent occupation is recorded in some localities, indicating short-term inundation episodes, which led to partial truncation and deformation of the sediments, primarily in the eastern lakeward part of the site. On the elevated, landward positions, incipient soils with strongly bioturbated profiles formed. Micromorphology demonstrates that intentional flooring was applied within the remains of brush huts, where millimeter-sized, horizontally organized burnt and unheated vegetal tissues were likely to have been placed upon the compacted ground. In fireplaces, the cultural deposits in thin sections are composed of strongly mixed, abundant wood charcoal, ashes, and fishbone remains. Post-depositional alterations were controlled by intermittent inundation of the site and salinization, which induced gypsum and pyrite deposition, primarily along decayed roots, and eventual pyrite oxidation. Accumulation of sodium and chlorine in the post-occupation deposits is likely to have occurred because of discharge of saline groundwater. Although only suggestive at this stage of research, the conclusions drawn from magnetic susceptibility parameters of archaeologically related deposits at Ohalo II fit well with the micromorphological reconstructions and provide new information on the Late Pleistocene evolution of the Lake Lisan/Sea of Galilee fluctuating system. © 2003 Wiley Periodicals, Inc. [source] Br/Cl signature of hydrothermal fluids: liquid,vapour fractionation of bromine revisitedGEOFLUIDS (ELECTRONIC), Issue 2 2006A. LIEBSCHER Abstract Br/Cl ratios of hydrothermal fluids are widely used as geochemical tracers in marine hydrothermal systems to prove fluid phase separation processes. However, previous results of the liquid,vapour fractionation of bromine are ambiguous. Here we report new experimental results of the liquid,vapour fractionation of bromine in the system H2O,NaCl,NaBr at 380,450°C and 22.9,41.7 MPa. Our data indicate that bromine is generally more enriched than chlorine in the liquid phase. Calculated exchange coefficients KD(Br-Cl)liquid-vapour for the reaction Brvapour + Clliquid = Brliquid + Clvapour are between 0.94 ± 0.08 and 1.66 ± 0.14 within the investigated P,T range. They correlate positively with DClliquid-vapour and suggest increasing bromine,chlorine fractionation with increasing opening of the liquid,vapour solvus, i.e. increasing distance to the critical curve in the H2O,NaCl system. An empirical fit of the form KD(Br-Cl)liquid-vapour = a*ln[b*(DClliquid-vapour,1) + e1/a] yields a = 0.349 and b = 1.697. Based on this empirical fit and the well-constrained phase relations in the H2O,NaCl system we calculated the effect of fluid phase separation on the Br/Cl signature of a hydrothermal fluid with initial seawater composition for closed and open adiabatic ascents along the 4.5 and 4.8 J g,1 K,1 isentropes. The calculations indicate that fluid phase separation can significantly alter the Br/Cl ratio in hydrothermal fluids. The predicted Br/Cl evolutions are in accord with the Br/Cl signatures in low-salinity vent fluids from the 9 to 10°N East Pacific Rise. [source] Simultaneous Determination of Fluorine, Chlorine, Bromine and Iodine in Six Geochemical Reference Materials Using Pyrohydrolysis, Ion Chromatography and Inductively Coupled Plasma-Mass SpectrometryGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 4 2009Hélène Balcone-Boissard halogènes; pyrohydrolyse; chromatographie ionique; spectrométrie de masse couplée à une source de plasma induit; matériaux géologiques de référence Concentrations of halogens (fluorine, chlorine, bromine and iodine) were determined in six geochemical reference materials (BHVO-2, GS-N, JG-1, JR-1, JB-1b, JB-2). Halogens were first extracted from powdered samples using a pyrohydrolysis technique, then hydrolysis solutions were analysed by ion chromatography for F and Cl and inductively coupled plasma-mass spectrometry for Br and I. The detection limits in solutions were 100 ,g l,1 for both F and Cl and 10 ng l,1 for Br and I. Considering the extraction procedure, performed on a maximum of 500 mg of sample and producing 100 ml of pyrohydrolysis solution, detection limits in rock samples were 20 mg kg,1 for F and Cl and 2 ,g kg,1 for Br and I. The mean analytical errors on the studied composition ranges were estimated at 10 mg kg,1 for F and Cl, 100 ,g kg,1 for Br and 25 ,g kg,1 for I. The concentration values, based on repeated (generally > 10) sample analysis, were in good agreement generally with published values and narrowed the mean dispersion around mean values. Large dispersions are discussed in terms of samples heterogeneity and contaminations during sample preparation. Basaltic RMs were found to be more suitable for studies of halogen compositions than differentiated rock material, especially granites , the powders of which were heterogeneous in halogens at the 500 mg level. Les concentrations en halogènes (fluor, chlore, brome et iode) on été déterminées dans 6 matériaux géologiques de référence (BHVO-2, GS-N, JG-1, JR-1, JB-1b, JB-2), distribués par le GSJ, l'USGS et le CRPG. Les halogènes étaient d'abord extraits des échantillons, disponibles sous forme de poudre, par pyrohydrolyse. F et Cl sont ensuite analysés par chromatographie ionique, Br et I par spectrométrie de masse couplée à une source de plasma induit. Les limites de détection sont de 100 ,g l,1 pour F et Cl, et de 10 ng l,1 pour Br et I, respectivement. L'extraction des halogènes était réalisée sur 500 mg de poudre de roche, produisant 100 ml de solution d'extraction. Ainsi, pour les échantillons de roche, les limites de détection étaient de 20 mg kg,1 pour F et Cl, et 2 ,g kg,1 pour Br et I. L'erreur analytique moyenne sur la gamme de concentration étudiée est estimée à 10 mg kg,1 pour F et Cl, 100 ,g kg,1 pour Br et 25 ,g kg,1 pour I. Les valeurs de concentrations données, obtenues par l'analyse répétée (> 10) du même échantillon étaient en accord avec les valeurs reportées dans la littérature. Elles présentent en général une plus faible dispersion autour de la valeur moyenne. Dans le cas d'une importante dispersion des résultats, celle-ci est discutée en terme d'hétérogénéité de l'échantillon analysé et de contamination durant la préparation du matériel de référence. Les échantillons de référence de composition basaltique se révèlent être plus appropriés pour étudier les compositions en halogènes que les matériaux correspondant à des roches différenciées, en particulier des granites dont la distribution en halogènes apparaît hétérogène dans les poudres à l'échelle d'un aliquot de 500 mg. [source] Effect of Well Disinfection on Arsenic in Ground WaterGROUND WATER MONITORING & REMEDIATION, Issue 2 2008Madeline Gotkowitz Domestic water wells are routinely subjected to in situ chemical disinfection treatments to control nuisance or pathogenic bacteria. Most treatments are chlorine based and presumably cause strongly oxidizing conditions in the wellbore. Water resource managers in Wisconsin were concerned that such treatments might facilitate release of arsenic from sulfide minerals disseminated within a confined sandstone aquifer. To test this hypothesis, a well was subjected to four disinfection treatments over 9 months time. The first treatment consisted of routine pumping of the well without chemical disinfection; three subsequent treatments included chlorine disinfection and pumping. Pretreatment arsenic concentrations in well water ranged from 7.4 to 18 ,g/L. Elevated arsenic concentrations up to 57 ,g/L in the chemical treatment solutions purged from the well are attributed to the disintegration or dissolution of biofilms or scale. Following each of the four treatments, arsenic concentrations decreased to less than 10 ,g/L during a period of pumping. Arsenic concentrations generally returned to pretreatment levels under stagnant, nonpumping conditions imposed following each treatment. Populations of iron-oxidizing, heterotrophic, and sulfate-reducing bacteria decreased following chemical treatments but were never fully eradicated from the well. Strongly oxidizing conditions were induced by the chlorine-based disinfections, but the treatments did not result in sustained increases in well water arsenic. Results suggest that disruption of biofilm and mineral deposits in the well and the water distribution system in tandem with chlorine disinfection can improve water quality in this setting. [source] Retention of chloride in soil and cycling of organic matter-bound chlorineHYDROLOGICAL PROCESSES, Issue 11 2005G. Öberg Abstract Chloride (Clinorg) is generally considered to be a hydrologically and chemically inert substance. Past research suggests that Clinorg participates in a complex biogeochemical cycle involving the formation of organically bound chlorine (Clorg). The present study examines whether Clorg cycling is sufficiently extensive as to influence the geochemical cycling of Clinorg. Undisturbed soil cores were collected in a coniferous forest soil in SE Sweden. The cores were stored in climate chambers for three months, irrigated with artificial rain, and the leachate was collected and analysed. The water balance of the lysimeters could be well described, and we found that 20,50% of the chlorine leached from the lysimeters was organically bound and that the amounts lost did not decrease with time. This strongly suggests that a substantial amount of Clorg forms in topsoil, and that subsequent leaching to deeper layers causes a considerable withdrawal of Clinorg. The concentration of both organic carbon and Clorg in the leachate was considerably higher than concentrations observed in the runoff in the actual catchment, suggesting that organic matter precipitates or is mineralized on its way through the soil. Copyright © 2005 John Wiley & Sons, Ltd. [source] Cleaning effectiveness of root canal irrigation with electrochemically activated anolyte and catholyte solutions: a pilot studyINTERNATIONAL ENDODONTIC JOURNAL, Issue 6 2000A. M. Solovyeva Abstract Aim The aim of this study was to evaluate the potential of electrochemically activated (ECA) anolyte and catholyte solutions to clean root canals during conventional root canal preparation. Methodology Twenty extracted single-rooted human mature permanent teeth were allocated randomly into four groups of five teeth. The pulp chambers were accessed and the canals prepared by hand with conventional stainless steel endodontic instruments using a double-flared technique. One or other of the following irrigants was used during preparation: distilled water, 3% NaOCl, anolyte neutral cathodic (ANC) (300 mg L,1 of active chlorine), and a combination of anolyte neutral cathodic (ANC) (300 mg L,1 of active chlorine) and catholyte. The teeth were split longitudinally and the canal walls examined for debris and smear layer by scanning electron microscopy. SEM photomicrographs were taken separately in the coronal, middle and apical parts of canal at magnification of ×800 to evaluate the debridement of extra-cellular matrix and at a magnification of ×2500 to evaluate the presence of smear layer. Results Irrigation with distilled water did not remove debris in the apical part of canals and left a continuous and firm smear layer overlying compressed low-mineralized predentine. All chemically active irrigants demonstrated improved cleaning potential compared to distilled water. The quality of loose debris elimination was similar for NaOCl and the anolyte ANC solution. The combination of anolyte ANC and catholyte resulted in improved cleaning, particularly in the apical third of canals. The evaluation of smear layer demonstrated that none of the irrigants were effective in its total removal; however, chemically active irrigants affected its surface and thickness. Compared to NaOCl, the ECA solutions left a thinner smear layer with a smoother and more even surface. NaOCl enhanced the opening of tubules predominantly in the coronal and middle thirds of canals, whereas combination of ANC and catholyte resulted in more numerous open dentine tubules throughout the whole length of canals. Conclusions Irrigation with electrochemically activated solutions cleaned root canal walls and may be an alternative to NaOCl in conventional root canal treatment. Further investigation of ECA solutions for root canal irrigation is warranted. [source] The role of chlorine atoms and hydroxyl radicals in the formation of PCDDs from the oxidative pyrolysis of 2,4,6-trichlorophenolINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 2 2010Lavrent Khachatryan A 132-step gas-phase reaction kinetic model has been combined with a four-step surface model for the formation of 1,3,6,8-tetrachlorodibenzo- p -dioxin (1,3,6,8-TCDD) from the oxidation of 2,4,6-trichlorophenol (2,4,6-TCP) in the presence of hexane. The revised model is based on a simpler model previously published in the literature and modified by adding Cl-releasing and the surface submodels, recalculating polynomial functions for thermodynamic parameters, and updating gas-phase submodels for (i) 1,3,6,8-TCDD formation, (ii) hydrogen oxidation, and (iii) hexane oxidation. The roles of the potential chain carriers, OH and Cl, in the formation of 1,3,6,8-TCDD were specifically addressed. In spite of the reported high reactivity of Cl, it was found that OH:Cl , 1, and OH is the dominant chain carrier from the apparent onset of purely gas-phase reactions at 750 K to 99% conversion of 2,4,6-TCP and hexane at 1075 K. This suggests that oxidation reactions are always dominant in realistic combustion systems, even where there are high concentrations of chlorine and relatively rich burning conditions. The update of the three gas-phase submodels as well as incorporation of Cl-releasing and the surface submodels resulted in improved agreement between calculated and experimental yields of 1,3,6,8-TCDD yields at temperatures as low as 800 K. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 90,97, 2010 [source] | |||||||||||||||||||||||||||||||||||||||||||||||||