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Andrew J Alexander - One of the best experts on this subject based on the ideXlab platform.
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pulsed laser induced nucleation of Sodium Chlorate at high energy densities
Crystal Growth & Design, 2019Co-Authors: Eleanor R Barber, Nina L H Kinney, Andrew J AlexanderAbstract:We report on a study of laser-induced nucleation (LIN) of Sodium Chlorate in supersaturated aqueous solutions using focused nanosecond laser pulses at high energy densities (420 kJ cm–2). On irradiation with a single laser pulse, optical breakdown was observed in the form of a luminous plasma, and numerous microbubbles were produced. On the basis of the observations, we estimate the energy threshold for optical breakdown in the solutions to be 70 J cm–2. Remarkably, even at high energy densities, single laser pulses produced on average only one or two crystals. The mean number of crystals obtained was 1.5 (532 nm) and 1.8 (1064 nm) per sample (3 cm3). The effect of left circularly polarized (LCP) and right circularly polarized (RCP) light on the nucleation of dextrorotatory (d) versus levorotatory (l) enantiomorphs of cubic (phase I) Sodium Chlorate crystals was investigated. No significant correlation between the helicity of circular polarization and the chirality of enantiomorph was observed. The result...
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chiral hide and seek retention of enantiomorphism in laser induced nucleation of molten Sodium Chlorate
Journal of Chemical Physics, 2011Co-Authors: Martin R Ward, Gary W Copeland, Andrew J AlexanderAbstract:We report the observation of non-photochemical laser-induced nucleation (NPLIN) of Sodium Chlorate from its melt using nanosecond pulses of light at 1064 nm. The fraction of samples that nucleate is shown to depend linearly on the peak power density of the laser pulses. Remarkably, we observe that most samples are nucleated by the laser back into the enantiomorph (dextrorotatory or levorotatory) of the solid prior to melting. We do not observe a significant dependence on polarization of the light, and we put forward symmetry arguments that rule out an optical Kerr effect mechanism. Our observations of retention of chirality can be explained by decomposition of small amounts of the Sodium Chlorate to form Sodium chloride, which provide cavities for retention of clusters of Sodium Chlorate even 18 °C above the melting point. These clusters remain sub-critical on cooling, but can be activated by NPLIN via an isotropic polarizability mechanism. We have developed a heterogeneous model of NPLIN in cavities, which reproduces the experimental data using simple physical data available for Sodium Chlorate.
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enantiomorphic symmetry breaking in crystallization of molten Sodium Chlorate
Chemical Communications, 2010Co-Authors: Martin R Ward, Gary W Copeland, Andrew J AlexanderAbstract:Enantiomorphic symmetry breaking of stirred samples of molten Sodium Chlorate is demonstrated, revealing the unexpected involvement of an achiral solid phase. The results should stimulate future computational models of nucleation, including symmetry breaking, and have implications for mechanisms that invoke enantiomorphism in natural minerals to explain biohomochirality.
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crystallization of Sodium Chlorate with d glucose co solute is not enantioselective
Crystal Growth & Design, 2008Co-Authors: Andrew J AlexanderAbstract:New evidence is presented that crystallization of Sodium Chlorate in the presence of the chiral co-solute d-glucose does not bias the growth of levorotatory crystals over dextrorotatory. The weighted mean percentage of d-NaClO3 was found to be Wd = 50.4 ± 1.4, compared to previous experiments of Kipping and Pope showing Wd = 31.7 ± 0.9 [J. Chem. Soc. Trans. 1898, 73, 606]. Possible explanations for the discrepancy between the historical results and the present work are discussed. The present work casts doubt on a result that has been accepted for over a century, concerning the ability of a chiral molecule to influence asymmetric crystallization, which has been used to promote theories on the possible origins of biological homochirality.
Riaz Mahmood - One of the best experts on this subject based on the ideXlab platform.
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Acute renal toxicity of Sodium Chlorate: Redox imbalance, enhanced DNA damage, metabolic alterations and inhibition of brush border membrane enzymes in rats
Environmental Toxicology, 2018Co-Authors: Hussain Arif, Aijaz Ahmed Khan, Riaz MahmoodAbstract:Sodium Chlorate (NaClO3 ) is widely used in paper and pulp industries and as a non-selective herbicide. Humans can be exposed to NaClO3 through contaminated drinking water due to its improper and unchecked usage in industries and as herbicide. NaClO3 is also present as a major stable by-product in drinking water that has been disinfected with chlorine dioxide. In this study, we have investigated the effect of a single acute oral dose of NaClO3 on rat kidney. Adult male Wistar rats were divided into one control and four NaClO3 treated groups that were orally given different doses of NaClO3 and euthanized 24 hr after the treatment. Oral administration of NaClO3 resulted in increased hydrogen peroxide levels, lipid, and protein oxidation while thiol and glutathione content and activities of brush border membrane enzymes were decreased in kidney in a NaClO3 dose-dependent manner. Significant alterations in the activities of enzymes involved in carbohydrate metabolism and antioxidant defense were also observed. Administration of NaClO3 induced DNA fragmentation and increased DNA-protein cross-linking. Histological studies showed marked damage in kidney from NaClO3 treated animals. These results strongly suggest that NaClO3 induces nephrotoxicity via redox imbalance that results in DNA and membrane damage, metabolic alterations and brush border membrane enzyme dysfunction.
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Sodium Chlorate induces dna damage and dna protein cross linking in rat intestine a dose dependent study
Chemosphere, 2017Co-Authors: Shaikh Nisar Ali, Hussain Arif, Fariheen Aisha Ansari, Riaz MahmoodAbstract:Sodium Chlorate (NaClO3) is widely used in paper and pulp industries and as a non-selective herbicide. It is also a major by-product generated upon disinfection of drinking water by chlorine dioxide. In this study, we have investigated the genotoxicity of NaClO3 on the small intestine of rats. Adult male rats were divided into 5 groups: one control and four NaClO3 treated groups. The NaClO3 treated groups were given a single acute oral dose of NaClO3 (100, 250, 500 and 750 mg/kg body weight) and sacrificed 24 h later. Administration of NaClO3 caused significant DNA damage in a dose dependent manner in the rat intestine. This was evident from the comet assay which showed DNA strand breaks and was further confirmed by agarose gel electrophoresis and release of free nucleotides. Increased DNA protein cross-linking in NaClO3 administered groups showed formation of a critical lesion which hampers activities of proteins/enzymes involved in DNA repair, transcription and replication. Thus, oral administration of NaClO3 induces DNA damage in the rat intestine, probably through Chlorate induced production of reactive oxygen species.
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Sodium Chlorate a major water disinfection byproduct alters brush border membrane enzymes carbohydrate metabolism and impairs antioxidant system of wistar rat intestine
Environmental Toxicology, 2017Co-Authors: Shaikh Nisar Ali, Aijaz Ahmed Khan, Fariheen Aisha Ansari, Riaz MahmoodAbstract:Sodium Chlorate (NaClO3 ) is a widely used nonselective herbicide. It is also generated as a by-product during disinfection of drinking water by chlorine dioxide. The purpose of this study was to evaluate the effect of NaClO3 on rat intestine. Adult male rats were randomly divided into five groups: control and remaining four groups were administered orally different doses of NaClO3 and sacrificed 24 h after the treatment. The administration of NaClO3 produced acute oxidative stress in the intestine, which manifested in the form of markedly enhanced malondialdehyde levels and carbonyl content and lowered total sulfhydryl groups and glutathione levels. The activities of several brush border membrane (BBM) enzymes were greatly reduced as compared to control. There were alterations in the activities of various enzymes of carbohydrate metabolism and those involved in maintaining the antioxidant defense system. Histological studies support the biochemical results showing NaClO3 dose-dependent increase in tissue damage. Thus, the present study shows that oral administration of NaClO3 decreases the activities of BBM enzymes, induces oxidative stress, alters metabolic pathways, and impairs the antioxidant system of rat intestine. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1607-1616, 2017.
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Sodium Chlorate a herbicide and major water disinfectant byproduct generates reactive oxygen species and induces oxidative damage in human erythrocytes
Environmental Science and Pollution Research, 2017Co-Authors: Shaikh Nisar Ali, Mir Kaisar Ahmad, Riaz MahmoodAbstract:Sodium Chlorate (NaClO3) is a widely used non-selective herbicide. It is also generated as a byproduct during disinfection of drinking water by chlorine dioxide. In the present work, the effects of NaClO3 on human erythrocytes were studied under in vitro conditions. Incubation of erythrocytes with different concentrations of NaClO3 at 37 °C for 90 min resulted in significant hemolysis. Cell lysates were prepared from NaClO3-treated and untreated (control) erythrocytes and assayed for various biochemical parameters. Methemoglobin levels were significantly increased and methemoglobin reductase activity was reduced upon NaClO3 treatment. There was a significant increase in protein oxidation and lipid peroxidation with a decrease in reduced glutathione and total sulfhydryl content. This suggests the induction of oxidative stress in erythrocytes upon exposure to NaClO3. The occurrence of oxidative stress was confirmed by significantly increased generation of reactive oxygen species and lowered antioxidant response of the cells. NaClO3 treatment also increased nitric oxide levels showing induction of nitrosative stress. The activities of major antioxidant and membrane-bound and metabolic enzymes were significantly altered upon incubation of erythrocytes with NaClO3. The erythrocytes became more osmotically fragile while electron microscopic images showed gross morphological alterations in NaClO3-treated cells. These results show that NaClO3 induces oxidative stress in human erythrocytes, which results in extensive membrane damage and lowers the antioxidant response.
David J Nisbet - One of the best experts on this subject based on the ideXlab platform.
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reduction of e coli o157 h7 populations in sheep by supplementation of an experimental Sodium Chlorate product
Small Ruminant Research, 2003Co-Authors: T S Edrington, Robin C Anderson, Todd R Callaway, Kenneth J Genovese, Y S Jung, J L Mcreynolds, K M Bischoff, David J NisbetAbstract:Ruminant animals are naturally infected with the pathogen Escherichia coli O157:H7, annually responsible for numerous meat recalls, foodborne illnesses and deaths. E. coli are equipped with the enzyme nitrate reductase, which not only enables this bacteria to respire anaerobically, but also converts Chlorate to the toxic metabolite chlorite. This enzyme system is particular to only a few intestinal bacteria, therefore the vast majority are not affected by Chlorate. Sodium Chlorate has been shown to effectively decrease foodborne pathogens in several livestock species, including ruminants. However, because infection and proliferation of E. coli occurs primarily in the lower intestine, there is interest in “by-passing” the rumen, thereby, delivering Chlorate directly to the largest population of pathogens. The objective of the current study was to evaluate the ability of an experimental Sodium Chlorate product (ECP II), designed to by-pass the rumen, in reducing fecal shedding and gut concentrations of E. coli O157:H7. Twenty crossbred mature ewes were adapted to a high grain ration and experimentally inoculated with E. coli O157:H7. Thirty-six hours following inoculation, sheep received in their feed one of the following ECP treatments: (1) control (CON), no Chlorate; (2) 1X (LOW); (3) 2X (MED); and (4) 4X (HIGH) where X=1.1 g Chlorate ion equivalents/kg BW (five sheep per treatment). Fecal samples were collected every 12 h following inoculation and 24 h following the feeding of Chlorate, all animals were euthanized and tissue samples and their respective contents collected from the rumen, cecum and rectum. The MED and HIGH Chlorate treatments significantly reduced fecal shedding of E. coli O157:H7 compared to the CON treatment [1.53, 1.11, and 3.89 CFU/g feces (log10), respectively]. Ruminal contents were similar among treatments, while Chlorate tended to decrease (P=0.08) and reduced (P<0.05) E. coli O157:H7 populations in the cecum and rectum, respectively. Populations of generic E. coli in the cecal contents were numerically lower (P=0.11) in the LOW treatment and tended to decrease (P=0.06) in the MED and HIGH Chlorate treatments, respectively. Fermentation profiles through the gastrointestinal tract were unaffected as indicated by slight, but not significant, changes in volatile fatty acids (VFA) profiles in sheep fed Chlorate. Results from this study indicate that this experimental Chlorate product, administered in the feed, was effective in reducing E. coli O157:H7 from the lower gut of sheep as evidenced by the lower cecal and rectal but not ruminal concentrations. Feeding Chlorate may be an effective method to decrease E. coli O157:H7 populations in ruminant animals prior to slaughter.
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Sodium Chlorate supplementation reduces e coli o157 h7 populations in cattle
Journal of Animal Science, 2002Co-Authors: Todd R Callaway, Robin C Anderson, Timothy J Anderson, Kenneth J Genovese, L F Kubena, T L Poole, J A Byrd, David J NisbetAbstract:Cattle are a natural reservoir of the food-borne pathogen Escherichia coli 0157:H7. Therefore, strategies that reduce E. coli 0157:H7 prior to slaughter will reduce human exposures to this virulent pathogen. When bacteria that can anaerobically respire on nitrate (e.g., E. coli) are exposed to Chlorate, they die because the intracellular enzyme nitrate reductase converts nitrate to nitrite, but also co-metabolically reduces Chlorate to cytotoxic chlorite. Because Chlorate is bactericidal only against nitrate reductase-positive bacteria, it has been suggested that Chlorate supplementation be used as a strategy to reduce E. coli 0157:H7 populations in cattle prior to harvest. Cattle (n = 8) were fed a feedlot-style high-grain diet experimentally infected with three strains of E. coli O157:H7. Cattle were given access to drinking water supplemented with 2.5 mM KNO 3 and 100 mM NaCl (controls; n = 4) or 2.5 mM KNO 3 and 100 mM NaClO 3 (Chlorate-treated; n = 4). Sodium Chlorate treatment for 24 h reduced the population of all E. coli 0157:H7 strains approximately two logs (10 4 to 10 2 ) in the rumen and three logs (10 6 to 10 3 ) in the feces. Chlorate treatment reduced total coliforms and generic E. coli from 10 6 to 10 4 in the rumen and by two logs throughout the rest of the gastrointestinal tract (ileum, cecum, colon, and rectum). Chlorate treatment reduced E. coli O157:H7 counts throughout the intestinal tract but did not alter total culturable anaerobic bacterial counts or the ruminal fermentation pattern. Therefore, it appears that Chlorate supplementation is a viable potential strategy to reduce E. coli O157:H7 populations in cattle prior to harvest.
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effect of oral Sodium Chlorate administration on escherichia coli o157 h7 in the gut of experimentally infected pigs
International Journal of Food Microbiology, 2001Co-Authors: Robin C Anderson, Todd R Callaway, Sandra A Buckley, Timothy J Anderson, Kenneth J Genovese, Cynthia L Sheffield, David J NisbetAbstract:Abstract Strategies are sought to reduce pathogenic Escherichia coli concentrations in food animals. Because E. coli possess respiratory nitrate reductase activity, which also reduces Chlorate to cytotoxic chlorite, we tested and found that oral Sodium Chlorate administration reduced gut concentrations of E. coli O157:H7 in experimentally infected pigs and wildtype E. coli concentrations in nonchallenged pigs. Mean±S.E. concentrations (log10 CFU/g) of E. coli O157:H7 in ileal, cecal, colonic and rectal contents from placebo-treated pigs were 4.03±0.66, 3.82±0.24, 4.42±0.25 and 4.03±0.16, respectively. In contrast, E. coli O157:H7 concentrations were reduced (P
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effect of Sodium Chlorate on salmonella typhimurium concentrations in the weaned pig gut
Journal of Food Protection, 2001Co-Authors: Robin C Anderson, Todd R Callaway, Sandra A Buckley, Kenneth J Genovese, L F Kubena, R B Harvey, David J NisbetAbstract:Salmonella cause economic losses to the swine industry due to disease and compromised food safety. Since the gut is a major reservoir for Salmonella, strategies are sought to reduce their concentration in pigs immediately before processing. Respiratory nitrate reductase activity possessed by Salmonella also catalyzes the intracellular reduction of Chlorate (an analog of nitrate) to chlorite, which is lethal to the microbe. Since most gastrointestinal anaerobes lack respiratory nitrate reductase, we conducted a study to determine if Chlorate may selectively kill Salmonella within the pig gut. Weaned pigs orally infected with 8 x 10(7) CFU of a novobiocin- and nalidixic acid-resistant strain of Salmonella Typhimurium were treated 8 and 16 h later via oral gavage (10 ml) with 0 or 100 mM Sodium Chlorate. Pigs were euthanized at 8-h intervals after receiving the last treatment. Samples collected by necropsy were cultured qualitatively and quantitatively for Salmonella and for most probable numbers of total culturable anaerobes. A significant (P < 0.05) Chlorate treatment effect was observed on cecal concentrations of Salmonella, with the largest reductions occurring 16 h after receiving the last Chlorate treatment. An observed treatment by time after treatment interaction suggests the Chlorate effect was concentration dependent. Chlorate treatment may provide a means to reduce foodborne pathogens immediately before harvest.
Kevin J Roberts - One of the best experts on this subject based on the ideXlab platform.
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characterization of the structural environment of dithionate ions associated with their role in the crystal habit modification of Sodium Chlorate
Crystal Growth & Design, 2018Co-Authors: Zhipeng Lan, Guilherme A Calligaris, Alan S De Menezes, Adenilson Dos O Santos, Xiaojun Lai, L P Cardoso, Kevin J RobertsAbstract:Sodium Chlorate (NaClO3) crystals change from a cuboid to a tetrahedron of {111} morphology when crystallized in the presence of Sodium dithionate (Na2S2O6) impurity. Polarized extended X-ray absorption fine structure at the S K-edge, used to probe the local structure around this impurity with respect to its orientation within the bulk crystal lattice, reveals that the S–S bond of the S2O62– ions is closely aligned along the / lattice direction. High resolution diffraction studies using X-ray multiple diffraction reveal growth-induced anisotropy in the doped crystals associated with subtle lattice distortions in the symmetry-independent {111} and {111} growth sectors. The data are consistent with a mechanistic model involving the creation of lattice vacancies and the substitution of one of the SO3 anionic groups of the dopant ion for a host ClO3 ion when incorporated at the {111} growth interface with the other SO3 group substituting for one or more anionic sites in the succeeding gr...
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Characterization of the Structural Environment of Dithionate Ions Associated with Their Role in the Crystal Habit Modification of Sodium Chlorate
2018Co-Authors: Zhipeng Lan, Guilherme A Calligaris, Alan S De Menezes, Adenilson Dos O Santos, Xiaojun Lai, L P Cardoso, Kevin J RobertsAbstract:Sodium Chlorate (NaClO3) crystals change from a cuboid to a tetrahedron of {1̅1̅1̅} morphology when crystallized in the presence of Sodium dithionate (Na2S2O6) impurity. Polarized extended X-ray absorption fine structure at the S K-edge, used to probe the local structure around this impurity with respect to its orientation within the bulk crystal lattice, reveals that the S–S bond of the S2O62– ions is closely aligned along the / lattice direction. High resolution diffraction studies using X-ray multiple diffraction reveal growth-induced anisotropy in the doped crystals associated with subtle lattice distortions in the symmetry-independent {1̅1̅1̅} and {111} growth sectors. The data are consistent with a mechanistic model involving the creation of lattice vacancies and the substitution of one of the SO3 anionic groups of the dopant ion for a host ClO3 ion when incorporated at the {1̅1̅1̅} growth interface with the other SO3 group substituting for one or more anionic sites in the succeeding growth layer depending on the degree of impurity concentration within the crystallization solution. This mechanism is also fully consistent with the formation of twinning at higher impurity concentrations previously reported by Lan et al. Cryst. Growth & Des. 2014, 14, 6084–6092
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X-ray Topographic and Polarized Optical Microscopy Studies of Inversion Twinning in Sodium Chlorate Single Crystals Grown in the Presence of Sodium Dithionate Impurities
Crystal Growth & Design, 2014Co-Authors: Kevin J Roberts, H. KlapperAbstract:Sodium Chlorate (NaClO3) crystallizes in the enantiomorphic space group P213 which allows two chiral structural configurations (l and d forms). These crystals can form growth twins when the solution contains impurity ions of dithionate with the mole ratio 1:1000 (dithionate/Chlorate) or higher. The impurity modifies the crystal habit from a cube-like morphology to one dominated by the minor {111} tetrahedral form. An X-ray topography study and the experimental observation of crystal growth reveal that the twinning phenomenon is consistent either as a result of the surface nucleation of a tetrahedral crystal of the morphologically opposite chirality on an existing tetrahedral habit face or by twinning at the nucleation stage and subsequent growth as two intergrown tetrahedral crystals. Polarized optical microscopy reveals that the optical activities of the twinned crystals observed are inversed with respect to each other. This is consistent with a merohedral mirror twinning system following twin law of m(0...
Martin R Ward - One of the best experts on this subject based on the ideXlab platform.
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chiral hide and seek retention of enantiomorphism in laser induced nucleation of molten Sodium Chlorate
Journal of Chemical Physics, 2011Co-Authors: Martin R Ward, Gary W Copeland, Andrew J AlexanderAbstract:We report the observation of non-photochemical laser-induced nucleation (NPLIN) of Sodium Chlorate from its melt using nanosecond pulses of light at 1064 nm. The fraction of samples that nucleate is shown to depend linearly on the peak power density of the laser pulses. Remarkably, we observe that most samples are nucleated by the laser back into the enantiomorph (dextrorotatory or levorotatory) of the solid prior to melting. We do not observe a significant dependence on polarization of the light, and we put forward symmetry arguments that rule out an optical Kerr effect mechanism. Our observations of retention of chirality can be explained by decomposition of small amounts of the Sodium Chlorate to form Sodium chloride, which provide cavities for retention of clusters of Sodium Chlorate even 18 °C above the melting point. These clusters remain sub-critical on cooling, but can be activated by NPLIN via an isotropic polarizability mechanism. We have developed a heterogeneous model of NPLIN in cavities, which reproduces the experimental data using simple physical data available for Sodium Chlorate.
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enantiomorphic symmetry breaking in crystallization of molten Sodium Chlorate
Chemical Communications, 2010Co-Authors: Martin R Ward, Gary W Copeland, Andrew J AlexanderAbstract:Enantiomorphic symmetry breaking of stirred samples of molten Sodium Chlorate is demonstrated, revealing the unexpected involvement of an achiral solid phase. The results should stimulate future computational models of nucleation, including symmetry breaking, and have implications for mechanisms that invoke enantiomorphism in natural minerals to explain biohomochirality.
