Search

NaMMT clay incorporated and maleic acid (MA) crosslinked polyvinyl alcohol (PVA)-chitisan (CS) interpenetrating network (IPN) type nanocomposite membranes were prepared for dehydration of acetone by pervaporation (PV). FTIR, XRD, SEM, UV spectroscopy, mechanical properties, contact angle measurement, and DTA-TGA were used to characterize these membranes. The effect of clay, CS, and MA on the flux and separation factor for water were statistically optimized by Box-Behnken design (BBD). Accordingly, the membrane prepared with 39.3 wt.% CS, 3 wt.% each of MA and NaMMT nanoclay showed a flux/separation factor of 0.176-0.733 kg/[m.sup.2]h/ 277-168 for the pervaporative dehydration of 99 wt.% acetone. Highlights * IPN nanocomposite membranes were prepared from PVA, CS, and nano clay. * Structure and properties of the IPNs were characterized. * Synthesis parameters were optimized by BBD. * Membranes showed high flux and water selectivity for acetone dehydration by PV. KEYWORDS acetone dehydration, box-Behnken design, chitosan, pervaporation, polyvinyl alcohol, sodium montmorillonite, 1 | INTRODUCTION Acetone is a volatile organic solvent extensively used in various chemical process industries such as paints, plastics, leather, explosive, and pharmaceuticals. A trace amount of water present [...]

The application of copolymer hydrogels based on acrylamide (AAm) and acrylic acid (AA) in sub-Saharan soils can increase the quantity of water retained by the soil and improve plant establishment and growth. The aim of this work was to synthesize and characterize a copolymer based on acrylamide and acrylic acid and to evaluate its swelling capacity with different physicochemical parameters. This study also aimed to investigate the effect of metallic cations on the swelling capacity of the copolymer and to assess the improvement in water retention in sandy soils. The copolymer material was prepared by free-radical polymerization in aqueous solution at a temperature of 60[degrees]C and characterized by Fourier transform infrared (FTIR) and x-ray diffraction (XRD), and its average molecular weight was estimated from intrinsic viscosity measurements. The swelling capacity was evaluated with different physicochemical parameters, and the effect of metallic cations on the swelling capacity was investigated. Water retention in two sandy soils was also evaluated. The copolymer material containing 50% AAm and 50% AA can retain more than 8100% of water. The swelling ratio increased with increasing temperature, with a maximum swelling ratio at 65[degrees]C. The presence of metallic cations reduced the maximum swelling ratio of the copolymer material as the cation concentration increased. The copolymer material at 1% in a composition with the soil showed an improvement in the water retention of 12.2% and 7.9% for soil A and 7.9% for soil B. Soil air volume is improved by 19% for both soils. This study shows that the copolymer material has a high swelling ratio and can improve water retention in sandy soils. The copolymer can be used in agriculture to protect and improve plant growth and yield. Highlights * Synthesis and characterization of a copolymer based on acrylamide and acrylic acid. * Evaluating the swelling capacity with different physicochemical parameters. * The application of this copolymer in sub-Saharan soils increases the quantity of water retained. * The copolymer is prepared by polymerization in aqueous solution and characterized by FTIR and XRD. * This study shows that the copolymer has a high swelling ratio and improves water retention. KEYWORDS hydrogel, poly(AAm-co-AA), soils, swelling, water retention, 1 | INTRODUCTION Hydrogels are networks of cross-linked polymers capable of absorbing and retaining large quantity of water. Their structures are heterogeneous in different orders of micromorphology. (1) Many methods [...]

Water is one of the most important, yet least understood, liquids in nature. Many anomalous properties of liquid water originate from its well-connected hydrogen bond network.sup.1, including unusually efficient vibrational energy redistribution and relaxation.sup.2. An accurate description of the ultrafast vibrational motion of water molecules is essential for understanding the nature of hydrogen bonds and many solution-phase chemical reactions. Most existing knowledge of vibrational relaxation in water is built upon ultrafast spectroscopy experiments.sup.2-7. However, these experiments cannot directly resolve the motion of the atomic positions and require difficult translation of spectral dynamics into hydrogen bond dynamics. Here, we measure the ultrafast structural response to the excitation of the OH stretching vibration in liquid water with femtosecond temporal and atomic spatial resolution using liquid ultrafast electron scattering. We observed a transient hydrogen bond contraction of roughly 0.04 Å on a timescale of 80 femtoseconds, followed by a thermalization on a timescale of approximately 1 picosecond. Molecular dynamics simulations reveal the need to treat the distribution of the shared proton in the hydrogen bond quantum mechanically to capture the structural dynamics on femtosecond timescales. Our experiment and simulations unveil the intermolecular character of the water vibration preceding the relaxation of the OH stretch. Liquid ultrafast electron scattering measures structural responses in liquid water with femtosecond temporal and atomic spatial resolution to reveal a transient hydrogen bond contraction then thermalization preceding relaxation of the OH stretch., Author(s): Jie Yang [sup.1] [sup.2] [sup.11] , Riccardo Dettori [sup.3] , J. Pedro F. Nunes [sup.4] , Nanna H. List [sup.1] [sup.2] [sup.5] , Elisa Biasin [sup.1] [sup.2] , Martin [...]

Insulating materials can in principle be made metallic by applying pressure. In the case of pure water, this is estimated.sup.1 to require a pressure of 48 megabar, which is beyond current experimental capabilities and may only exist in the interior of large planets or stars.sup.2-4. Indeed, recent estimates and experiments indicate that water at pressures accessible in the laboratory will at best be superionic with high protonic conductivity.sup.5, but not metallic with conductive electrons.sup.1. Here we show that a metallic water solution can be prepared by massive doping with electrons upon reacting water with alkali metals. Although analogous metallic solutions of liquid ammonia with high concentrations of solvated electrons have long been known and characterized.sup.6-9, the explosive interaction between alkali metals and water.sup.10,11 has so far only permitted the preparation of aqueous solutions with low, submetallic electron concentrations.sup.12-14. We found that the explosive behaviour of the water-alkali metal reaction can be suppressed by adsorbing water vapour at a low pressure of about 10.sup.-4 millibar onto liquid sodium-potassium alloy drops ejected into a vacuum chamber. This set-up leads to the formation of a transient gold-coloured layer of a metallic water solution covering the metal alloy drops. The metallic character of this layer, doped with around 5 × 10.sup.21 electrons per cubic centimetre, is confirmed using optical reflection and synchrotron X-ray photoelectron spectroscopies. Spectroscopic measurements confirm that when water is adsorbed on drops of an alkali alloy at low pressure a gold-coloured metallic layer forms as electrons rapidly move from the drop into the water., Author(s): Philip E. Mason [sup.1] , H. Christian Schewe [sup.1] [sup.2] , Tillmann Buttersack [sup.1] [sup.2] [sup.3] , Vojtech Kostal [sup.1] , Marco Vitek [sup.1] , Ryan S. McMullen [sup.3] [...]

A reliable understanding of radiolysis processes in supercritical water (SCW) cooled reactors is required to ensure optimal water chemistry control. In this perspective, Monte Carlo track chemistry simulations of the radiolysis of pure, deaerated SCW at 400 [degrees]C by 2 MeV mono-energetic neutrons were carried out as a function of water density between 0.15 and 0.6 g/[cm.sup.3]. The yields of hydronium ions ([H.sup.3][O.sup.+]) formed at early time were obtained based on the G values calculated for the first three generated recoil protons. Combining our calculated G([H.sup.3][O.sup.+]) values with a cylindrical track model allowed us to estimate the concentrations of [H.sup.3][O.sup.+] and the corresponding pH values. An abrupt, transient, and highly acidic pH response ('acid spikes') was observed at early times around the 'native' fast neutron and recoil proton trajectories. This intra-track acidity was found to be strongest at times of less than a few tens to a hundred of picoseconds, depending on the value of the density considered (pH ~ 1). At longer times, the pH gradually increased for all densities, finally reaching a constant value corresponding to the non-radiolytic, pre-irradiation concentration of [H.sup.3][O.sup.+], due to the autoprotolysis of water. Interestingly, the lower the density of the water, the longer the time required to reach this constant value. Because many in-core processes in nuclear reactors critically depend on the pH, the present work raises the question whether such highly acidic pH fluctuations, though local and transitory, could promote or contribute to corrosion and degradation of materials under proposed SCW-cooled reactor operating conditions. Key words: supercritical water (SCW), fast neutron and recoil protons, radiolysis, acid spike, Monte Carlo track chemistry simulations, generation IV SCW-cooled reactor. Il importe d'avoir une comprehension fiable des processus de radiolyse qui ont cours dans les reacteurs refroidis a l'eau supercritique afin d'assurer un controle optimal de la chimie de l'eau. Dans cette optique, nous avons effectue des simulations Monte Carlo de la trajectoire des particules pour decrire la radiolyse a 400 [degrees]C de l'eau supercritique pure, desaeree, par des neutrons monoenergetiques de 2 MeV en fonction de la densite de l'eau dont les valeurs sont comprises entre 0,15 et 0,6 g/[cm.sup.3]. Les rendements d'ions hydronium ([H.sup.3][O.sup.+]) formes dans les premiers instants ont ete obtenus a l'aide des valeurs G calculees pour les trois premiers protons de recul generes. En integrant nos valeurs calculees de G([H.sup.3][O.sup.+]) a un modele de trajectoires cylindriques, nous avons ete en mesure d'estimer les concentrations de [H.sup.3][O.sup.+] et les valeurs de pH correspondantes. Nous avons observe une reponse caracterisee par une variation breve et abrupte du pH vers des valeurs tres basses ([much less than] pics d'acidite [much greater than]) aux premiers instants de la trajectoire des neutrons rapides/protons de recul. Cette acidite intratrajectorielle s'est revelee etre la plus forte a des instants correspondant a moins de quelques dizaines a une centaine de picosecondes, selon la valeur de densite consideree (pH ~ 1). A des temps plus longs, le pH augmentait graduellement a toutes les valeurs de densite, pour finalement atteindre une valeur constante correspondant a la concentration de [H.sup.3][O.sup.+] non radiolytique prevalant avant l'irradiation, en raison de l'autoprotolyse de l'eau. Fait interessant, plus la densite de l'eau est faible, plus le temps necessaire pour atteindre cette valeur constante est long. Comme de nombreux processus au coeur des reacteurs nucleaires dependent dans une large mesure du pH, les presents travaux soulevent la question a savoir si de telles fluctuations de pH fortement acide, bien qu'elles soient localisees et transitoires, pourraient favoriser la corrosion et la degradation des materiaux dans les conditions proposees de fonctionnement d'un reacteur refroidi a l'eau supercritique. [Traduit par la Redaction] Mots-cles : eau supercritique, radiolyse par neutrons rapides/protons de recul, pic d'acidite, simulations Monte Carlo de la trajectoire des particules, reacteur de [4.sup.e] generation refroidi a l'eau supercritique., Introduction Supercritical water (SCW) (i.e., water at temperatures and pressures above its thermodynamic critical point in the P-V-T diagram; for light water, [H.sub.2]O: [T.sub.c] = 373.95 [degrees]C, P.sub.c] = 22.06 [...]

Polyurethane (PU) is an emerging resin matrix for fiber reinforced polymer (FRP) composites. In the present article, effects of immersion in water or alkaline solution on water uptake and thermomechanical properties of a PU were investigated. A traditional epoxy resin matrix was investigated for comparison. As found, unlike the epoxy (hydrolysis occurred in case of alkaline solution), water and alkaline solution immersion showed a similar effect for the PU resin. For both immersion, the water uptake of the PU system reached the equilibrium content of 2.5%-2.7%, in accordance with the Fick's law. Glass transition temperature ([T.sub.g]) of the PU decreased rapidly after the first month of immersion and then leveled off. Both immersion for a short term (e.g., 1 month of immersion) led to an obvious decrease in the tensile strength, while long-term immersion brought in obvious recovery. Remarkable increase in the elongation at break (up to 16.6%) due to immersion was found. The higher the immersion temperatures, the less the degradation of the tensile strength. The variations of the thermalmechanical properties were attributed to the waterinduced plasticization and the postcuring-induced increase of the crosslinkage. Compared with the common epoxy system, the PU system showed better resistance to the immersion. POLYM. ENG. SCI., 58:2276-2287, 2018., INTRODUCTIONSince the 1930s, polyurethane (PU) resins (PUs) with a particular function group, -NHCOO-, have been widely used as coatings [1], foams [2], rubbers [3], shape-memory polymers [4], insulation materials [5], [...]

Processing of a high glass transition ([T.sub.g]) polymer such as polyethersulfone (PES; [T.sub.g] = 225[degrees]C) poses a challenge as it requires high processing temperatures or sometimes toxic solvents. In this work, we report of a facile process using superheated water (s[h.sub.[H.sub.2]]O) and supercritical carbon dioxide (scC[O.sub.2]) co-media. PES solids were foamed in the scC[O.sub.2]/sh[H.sub.2]O co-media or scC[O.sub.2] alone in a batch process at different temperatures. The scC[O.sub.2]/sh[H.sub.2]O produced a synergistic effect and achieved PES foams even at processing temperatures as low as 85[degrees]C below the nominal [T.sub.g]; whereas, scC[O.sub.2] alone required higher processing temperatures. Moreover, the scC[O.sub.2]/sh[H.sub.2]O comedia produced highly porous PES foams that were at least 23% higher in porosity than what was obtained using scC[O.sub.2] alone. In addition, the scC[O.sub.2]/sh[H.sub.2]O produced open cell foams at some processing conditions; whereas, scC[O.sub.2] produced closed cell morphologies. Since both C[O.sub.2] and [H.sub.2]O are innocuous, this approach has potential for use in the preparation of ultrafiltration membranes, which currently require the use of toxic solvents for their fabrication by way of the phase inversion process. Moreover, the use of scC[O.sub.2]/sh[H.sub.2]O is a cost-effective approach for the processing of high [T.sub.g] polymers at significantly lower temperatures., INTRODUCTION Polyethersulfone (PES), by virtue of its high mechanical strength (Young's modulus >2.5 GPa), chemical stability and thermal stability, is notable for a number of high performance and load bearing [...]

Ammonia is vital to society, but its manufacture is energy intensive, has a large carbon footprint and requires high initial capital outlays. An intriguing reaction now suggests that energy-efficient alternatives are possible. Coordination-induced bond weakening enables nitrogen fixation., Author(s): Máté J. Bezdek, Paul J. Chirik Author Affiliations: A fresh approach to synthesizing ammonia from air and water Global food production requires ammonia-based fertilizers. The industrial transformation of atmospheric [...]

Observations of the physical behaviour (motions) of the valence (frontier) electrons in the iconic benchmark hydride molecules C[H.sub.4], N[H.sub.3], and [H.sub.2]O are used to provide a direct experimental evaluation of hybridization and of the localized and delocalized orbital models of molecular electronic structure, after more than 80 years since the initial proposals of these theoretical concepts. Our previously published experimental measurements of valence (frontier) electron momentum probability distributions, made by electron momentum spectroscopy (EMS), are compared with those calculated using the localized molecular orbital (LMO) model and a range of hybrid orbital models, as well as with the delocalized canonical molecular orbital (CMO) and density functional theory Kohn-Sham orbital (KSO) models. In all cases, the electron momentum probability distributions calculated with LMOs and localized hybrid orbital type models are inconsistent with the experimental observations. In contrast, those calculated with the delocalized CMOs and KSOs are in very good agreement with the experimental measurements. These findings are of importance in those research applications such as reactivity, drug and novel material design, and also in molecular electronics, where the shapes and orientations of particular valence (frontier) orbital electron density probability distributions (and not the total electron densities) are considered to be key determining factors. These findings and their implications are also of pedagogical significance in chemistry and molecular physics. Key words: hybrid orbitals, localized and delocalized orbitals, calculated and experimental valence electron probability distributions. Par observation du comportement physique (mouvements) des electrons de valence (frontieres) dans les emblematiques molecules d'hydrure types, C[H.sub.4], N[H.sub.3] et [H.sub.2]O, nous avons realise une evaluation experimentale directe de l'hybridation et des modeles d'orbitales localisees et delocalisees de la structure electronique moleculaire, plus de 80 ans apres les premiers enonces de ces concepts theoriques. Nous avons compare nos mesures experimentales des distributions probabilistes du moment des electrons de valence (frontieres), que nous avons publiees anterieurement etrealisees par spectroscopie de moment electronique (EMS, electron momentum spectroscopy), aux valeurs que nous avons calculees a l'aide du modele d'orbitales moleculaires localisees (LMO, localized molecular orbital) et d'un ensemble de modeles d'orbitales hybrides, en plus de les comparer a celles obtenues par le modele d'orbitales moleculaires canoniques (CMO, canonical molecular orbital) delocalisees et par le modele d'orbitales de Kohn-Sham (KSO, Kohn-Sham orbital) en theorie de la fonctionnelle de la densite. Dans tous les cas, les distributions probabilistes du moment electronique calculees a l'aide des modeles de type LMO et d'orbitales hybrides localisees ne concordent pas avec les observations experimentales. Par contre, celles qui ont ete calculees a l'aide des modeles de type CMO delocalisees et KSO concordent tres bien avec les valeurs experimentales. Ces resultats sont importants dans le contexte d'applications de la recherche telles que la conception de medicaments et de nouveaux materiaux basee sur la reactivite, et aussi dans le domaine de l'electronique moleculaire, ou les formes et les orientations des distributions probabilistes de la densite de certaines orbitales d'electrons de valence (frontieres)--et non de la densite electronique totale--sont considerees comme des facteurs determinants. En outre, ces resultats et leurs implications representent une valeur pedagogique en chimie et en physique moleculaire. [Traduit par la Redaction] Mots-cles : orbitales hybrides, orbitales localisees et delocalisees, valeurs theorique et experimentale de la distribution probabiliste des electrons de valence., Introduction Adequate visual and theoretical orbital models of molecular electronic structure are essential for obtaining a better understanding of fundamental phenomena in research applications such as molecular design and predictions [...]

A rapid test method was developed for the determination of hydrogen sulfide and sulfides in waters using a potassium chloride-impregnated test paper with color intensity evaluation of the formed CdS zone by colorimetry and diffuse reflectance spectroscopy. The determination conditions, viz. acidity, gas preexraction time, air pumping rate, and working concentration range (0.005-0.16 mg of [H.sub.2]S/L), were optimized. The procedure proposed is easy-to-perform, and the time of single determination is 20 min; in addition, the procedure is cost effective, sensitive, selective, does not require expensive equipment and expertise of executor, and is not inferior in accuracy to photometric methods. The procedure was tested on real water samples. The concentration hydrogen sulfide in the Don and Temernik rivers in Rostov-on- Don is not higher than the maximum permissible concentration (MPC). Keywords: hydrogen sulfide, sulfides, rapid test methods, colorimetry, diffuse reflectance spectroscopy, test paper, Hydrogen sulfide and sulfides are toxic and hazardous to human health. The anthropogenic pollution of hydrosphere by these substances is usually associated with the disposal of waste waters, in which [...]

A procedure is developed for the determination of several amines in drinking and natural waters by capillary electrophoresis with isotachophoretic on-line preconcentration without sample preparation. A background electrolyte based on acridine as an absorbing ion is proposed for analysis with isotachophoretic on-line preconcentration and indirect photometric detection. The sample was injected in the hydrodynamic mode. The procedure was tested on drinking and natural water samples. The accuracy of data obtained was confirmed by the added--found method. The analytical range was from 0.25 to 5 mg/L. The time of one analysis was 5-6 min. Keywords: capillary electrophoresis, self-induced isotachophoresis, amines, In recent years, the determination of organic amines in aqueous media, including drinking, natural, and waste waters, attract great attention [1-4]. Such methods as gas chromatography, reverse-phase liquid and ion [...]

A new version of the chronoamperometric method, adapted to the determination of the oxidative (oxidant) activity of a medium on an example of chlorinated water, was proposed. The supporting solution contained [K.sub.4] Fe[(CN).sub.6]. By its oxidation with oxidants present in the sample, [K.sub.3] Fe[(CN).sub.6] formed; its reduction current served as an analytical signal. The current of [K.sub.3] Fe[(CN).sub.6] reduction was recorded at a potential of 0 V, selected from the cyclic voltammogram of the [K.sub.3] Fe[(CN).sub.6]/[K.sub.4] Fe[(CN).sub.6] system in the range where the oxidized form of the reagent was reduced and the reduced form was stable. A gold electrode was the measuring electrode. The possibility of using a stable solution of [K.sub.3] Fe[(CN).sub.6] as a component of a standard addition and as a solution for plotting a calibration curve was demonstrated. The limit of detection of the amount of dissolved chlorine and products of its interaction with water is 8 x 10-6 M. The data obtained by the proposed procedure and by the iodometric methods correlate well with each other (r = 0.93-0.95). The proposed version of the chronoamperometric method can be used to monitor the amount of dissolved chlorine and products of its interaction with water in water supply systems, pools, and disinfecting solutions and to determine other water-soluble oxidants. Keywords: chronoamperometry, oxidative (oxidant) activity, potassium hexacyanoferrate(III), potassium hexacyanoferrate(II), chlorine, potable water DOI: 10.1134/S1061934817080056, Monitoring of the integral oxidative (oxidant) activity (OA) of water, which is determined by the total content of molecular and radical oxidants, is very important, because drinking water is one [...]

It is often claimed that the form of a water crystal can be changed by human intent although there are few scientific studies that have tested this claim. In 2006, several researchers published the first scientific report which shows positive results for the claim. Recently, the authors have also considered this issue. Unexpectedly, they found two serious weak points in the conventional test procedure for water crystal formation. One of the points relates to the use of judgement, and the other relates to sample size. These points did not seem easy to find, and the authors were concerned that many researchers may fall into the trap laid by these points. In the present paper, the authors discuss these methodological problems of conventional tests, and indicate that photographs of water crystals are not independent parameters and that the numbers of water bottles used are too few to conclude something statistically. Keywords: water crystal formation, morphological, intent, psi Il est souvent affirme que la formation d'un cristal d'eau peut etre modifiee par l'intention humaine bien que peu d'etudes scientifiques ont mis a l'epreuve certe affirmation. En 2006, plusieurs chercheurs ont publie le premier compie rendu scientifique qui montrait des resultats positifs en faveur de certe affirmation. Recemment, les auteurs ont egalement etudie certe question. De facon inattendue, ils ont decouvert deux faiblesses methodologiques graves dans la procedure conventionnelle de test de la formation de cristal d'eau. L'une de ces faiblesses est relative a l'utilisation d'un jugement, l'autre a la taille d'echantillon. Ces points ne sont pas faciles a detecter, et les auteurs craignent que d'autres chercheurs puissent tomber dans les memes chausses-trapes. Dans cet article, les auteurs discutent ces problemes methodologiques des tests conventionnels, et indiquent que les photographies de cristaux d'eau ne sont pas des parametres independants et que le nombre de bouteilles d'eau utilise est trop faible pour permettre de conclure sur le plan statistique. Haufig wird behauptet, die Form eines Wasserkristalls liesse sich absichtlich durch Menschen beeinflussen, obwohl es nur wenige wissenschaftliche Studien gibt, die diese Behauptung uberpriift haben. 2006 haben mehrere Forscher die erste wissenschaftliche Arbeit dazu veroffentlicht, die positive Ergebnisse erbrachte. Die Autoren haben sich kurzlich uber dieses Thema nochmals Gedanken gemacht. Sie stiessen dabei wider Erwarten auf zwei gravierende Schwachstellen beim konventionellen Testverfahren zur Wasserkristallbildung. Einer der Punkte betrifft die Art der Einschatzung, der andere die Grosse der Stichprobe. Diese Punkte waren nicht leicht zu erschliessen, und die Verfasser befurchten, dass viele Forscher durch diese Punkte in die Irre gefuhrt werden konnten. In der vorliegenden Arbeit diskutieren die Autoren diese methodologischen Probleme der konventionellen Tests und weisen darauf hin, dass die Fotografien der Wasserkristalle nicht unabhangig voneinander sind und dass die Anzahl der verwendeten Wasserflaschen zu gering ist, um statistische Schlussfolgerungen zu ziehen. Se afirma a menudo que la intencion humana puede cambiar la forma de un cristal de agua aunque pocos estudios cientificos han puesto a prueba esta afirmacion. En 2006, varios investigadores publicaron el primer informe cientifico que apoyo la hipotesis. Recientemente, los autores de este trabajo tambien consideraron esta cuestion. Inesperadamente, encontraron dos vulnerabilidades serias en el procedimiento convencional para evaluar la formacion de cristal de agua. Uno de los problemas se refiere a la evaluacion y el otro al tamano de la muestra. Estos puntos no son faciles de detectar y los autores consideran que muchos investigadores pueden dejarse enganar por estos puntos. En este trabajo, los autores discuten estos problemas metodologicos de las pruebas convencionales e indican que las fotografias de los cristales de agua no son parametros independientes y que se usaron demasiadas pocas botellas de agua para concluir algo estadisticamente., DISCUSSION SUR LA METHODOLOGIE DE LA FORMATION DE CRISTAL D'EAU COMME SYSTEME DE DETECTION DU PSI DISKUSSION ZUR METHODOLOGIE DER WASSERKRISTALLBILDUNG ZUM PSI-NACHWEIS UNA DISCUSION SOBRE LA METODOLOGIA DE LA [...]

To determine the chemical oxygen demand (COD) of water by oxithermography, we studied a high-temperature reactor with two inputs of the gas flow. Such a design allowed the creation of an internal circuit of the oxygen--inert gas (argon) binary flow in the reactor for the oxidation of organic substances and the determination of COD by the decrease in the concentration of oxygen in the binary mixture. The optimum operation parameters of the instrument, affecting the analytical characteristics of the method, were determined. The detection limit for a water sample of the volume 10 [micro]L was 3.4 mg O/L. It was shown that the oxithermograph and the proposed procedure can be used for the determination of COD in drinking and natural waters of Bryansk oblast. The approach developed has an advantage, consisting in the reagentless rapid determination of the COD of waters without preliminary sample preparation. Keywords: oxithermography, determination of chemical oxygen demand, high-temperature oxidation, high-temperature solid electrolyte cells, optimum conditions, A considerable number of analytical problems require the determination of integral characteristics of a test sample. This is most often needed in the study of complex natural samples. For example, [...]

Deamination of adenine is one of several forms of premutagenic lesions occurring in DNA. In the present study, mechanisms for the deamination reaction of adenine with [OH.sup.-]/n[H.sub.2]O(n = 0,1,2,3)and 3[H.sub.2]O were investigated. HF/6-31G(d), B3LYP/6-31G(d), MP2/6-31G(d), and B3LYP/6-31+G(d) levels of theory were employed to search for and optimize all geometries. Energies were calculated at the G3MP2B3 and CBS-QB3 levels of theory. The effect of solvent (water) was computed using the polarizable continuum model (PCM). Intrinsic reaction coordinate (IRC) calculations were performed for all transition states. Five pathways were investigated for the deamination reaction of adenine with [OH.sup.-]/n[H.sub.2]O and 3[H.sub.2]O. The first four pathways (A-D) are initiated by deprotonation at the amino group of adenine by [OH.sup.-], while pathway E is initiated by tautomerization of adenine. For all pathways the next two steps involve formation of a tetrahedral intermediate followed by dissociation to products via a 1,3-proton shift. Deamination with a single [OH.sup.-] has a high activation barrier (190 kJ [mol.sup.-1] using the G3MP2B3 level) for the rate-determining step. The addition of one water molecule reduces this barrier by 68 kJ [mol.sup.-1] at the G3MP2B3 level. Adding additional water molecules decreases the overall activation energy of the reaction, but the effect becomes smaller with each additional water molecule. The most plausible mechanism is pathway E, the deamination reaction of adenine with 3[H.sub.2]O, with an overall G3MP2B3 activation energy of 139 and 137 kJ [mol.sup.-1] for the gas phase and PCM, respectively. This barrier is lower than that for the deamination with [OH.sup.-]/3[H.sup.2]O by 6 and 2kJ [mol.sup.-1] for the gas phase and PCM, respectively. Keywords: deamination, adenine, 1,3-proton shift, optimized structures, deprotonation. Resume : La desamination de l'adenine est une des multiples formes prises par les lesions premutagenes pouvant se produire dans l'ADN. Dans le present travail, on a etudie les mecanismes de la reaction de desamination de l'adenine avec du [OH.sup.-]/n[H.sup.2]O (n = 0, 1, 2 et 3) et 3[H.sup.2]O. Dans la recherche et l'optimisation de toutes les geometries, on a fait appel a des calculs aux niveaux HF/3-31G(d), B3LYP/6-31G(d), MP2/6-31G(d) et B3LYP/6-31+G(d) de la theorie. Les energies ont ete calculees aux niveaux G3MP2B3 et CBS-QB3 de la theorie. On a calcule l'effet du solvant (eau) en utilisant le modele du continuum polarisable (MCP). On a effectue des calculs de coordonnees reactionnelles intrinseques (CRI) pour tous les etats de transition. On a examine cinq voies reactionnelles pour la reaction de desamination de l'adenine avec [OH.sup.-]/n[H.sub.2]Oet3[H.sup.2]O. Les quatre premieres voies (A- D) sont initiees par la deprotonation du groupe amino de l'adenine par le [OH.sup.-], alors que la voie E est initiee par une tautomerisation de l'adenine. Pour l'ensemble des cinq voies reactionnelles, les deux etapes suivantes impliquent la formation d'un intermediaire tetraedrique, suivie par la dissociation en produits par le biais d'un deplacement 1,3 de proton. Sur la base des calculs au niveau G3MP2B3 la barriere d'activation de l'etape cinetiquement determinante de la desamination avec un seul [OH.sup.-] est elevee, a 190 kJ [mol.sup.-1]. L'addition d'une molecule d'eau reduit cette barriere par 68 kJ [mol.sup.-1] (au niveau G3MP2B3). L'addition de molecules d'eau supplementaires diminue l'energie d'activation totale de la reaction, mais l'effet diminue avec l'addition de chaque molecule d'eau additionnelle. Le mecanisme le plus plausible est la voie E, la reaction de desamination de l'adenine avec 3[H.sub.2]O, avec une energie d'activation globale au niveau G3MP2B3 de 139 et de 137 kJ [mol.sup.-1] respectivement pour la phase gazeuse et le modele du continuum polarisable (MCP). La barriere est inferieure a celle pour la desamination avec [OH.sup.-]/3[H.sub.2]O par 6 et 2kJ [mol.sup.-1] respectivement pour la phase gazeuse et le MCP. [Traduit par la Redaction] Mots-cles: desamination, adenine, deplacement 1,3 de proton, structure optimisee, deprotonation., Introduction Extensive knowledge and understanding of genetic material and its physicochemical properties is one of the natural goals of science. One of the essential components of genetic material is adenine [...]

Poly (acrylonitrile-co-methyl acrylate) copolymer designated as PANMA was used for making pervaporation membrane. This membrane was used for separation of acetic acid-water mixtures over the concentration range of 80-99.5 wt% acetic acid in water. Interaction parameters based on Flory-Huggins lattice model and engaged species induced clustering (ENSIC) model was used to explain swelling of the membranes. Coupling in sorption was explained in terms of activity coefficient of water and acid in feed and membrane using Flory-Huggins model and also by interpolating ENSIC parameters. Flow coupling in pervaporation was also determined from phenomenological deviation coefficients. Intrinsic membrane properties like partial permeability and membrane selectivity of the solvents were also determined. Diffusion coefficient and plasticization coefficient of the solvents were obtained using a modified solution-diffusion model. The copolymer membrane showed high flux and water selectivity for highly concentrated acid. Thus, at 30[degress]C temperature 1-20 wt% water in feed was concentrated to 82-84 wt% water in permeate and for 0.95 wt% water in feed, the membrane showed thickness normalized flux and water selectivity of 1.71 kg [m.sup.(-2)] [h.sup.(-1)] mμ and 409, respectively. POLYM. ENG. SCI., 53:1073-1084, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION In chemical industries acetic acid is considered as one of the most important organic intermediates (1). Highly pure acetic acid is required for production of many important chemicals like [...]

In recent years, the production of cotton in Australia has been limited by the availability of irrigation water. To overcome this problem, poorer quality ([Na.sup.+]-rich) irrigation sources have been used in some situations, despite the effects elevated levels of [Na.sup.+] may have on soil physical and chemical properties. This paper reports on changes in the surface-connected structural form attributes of two Vertosols from eastern Australia (one Red Vertosol, one Black Vertosol) after treatment with a range of different water-quality solutions. Intact soil columns from each of the Vertosols were irrigated through six wet-dry cycles using one of six treatment solutions with varying [Na.sup.+] concentrations. Replicate columns for each treatment of each soil were analysed post-irrigation for selected chemical attributes. A second set of replicate columns was impregnated with a fluorescent resin post-irrigation, horizontally sectioned, and photographed under ultraviolet light. Image analysis was carried out on the section photographs to yield quantitative estimates of porosity (P), surface area ([S.sub.v]), solid and pore star lengths ([l.sub.s.sup.*] and [l.sub.p.sup.*]), and solid and pore genus ([g.sub.s] and [1.sub.gp]). Generally, the soil treated with the low-[Na.sup.+] solution had the most desirable structural form attributes (larger P, [S.sub.v], and [g.sub.p] and smaller [l.sub.s.sup.*] and [g.sub.s]), while the soil treated with the high-[Na.sup.+] solution had the least desirable structural attributes. The structural attributes and chemical properties of the Red Vertosol changed more markedly with water quality than did those of the Black Vertosol. The difference in response to water quality between these two soils is presumed to be related to the clay mineral suites and the exchange capacity of these soils; the Black Vertosol contains appreciably more smectite and has a much larger effective cation exchange capacity than the Red Vertosol. Additional keywords: exchangeable sodium percentage, stability, mineralogy, morphology., Introduction During the last decade the availability of water in eastern Australia for irrigated crops, including cotton (Gossypium hirsutum), has been severely curtailed by limited rainfall and reduced water allocations. [...]

The copper(I) iodide/1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)piperazine (CuI-L2) system catalyzed the cross-coupling reactions between aryl halides and aqueous ammonia in water to produce primary aromatic amines in good yields. The protocol was simple and efficient, avoiding the need for inert atmosphere, additional base, or other additives. Key words: copper, catalysis, cross coupling, water chemistry, aqueous ammonia, primary arylamine. Le systeme iodure de cuivre(I)/1,4-bis(2-hydroxy-3,5-di-ieri-butylbenzyl)piperazine (CuI-L2) catalyse les reactions de couplages croisees entre les halogenures d'aryles et une solution aqueuse d'ammoniaque pour conduire a la formation d'amines aromatiques primaires avec de bons rendements. Le protocole est simple et efficace, il ne necessite pas d'atmosphere inerte, de base additionnelle ou d'autres additifs. Mots-cles : cuivre, catalyse, couplage croise, chimie dans l'eau, solution aqueuse d'ammoniaque, arylamine primaire., Introduction Ammonia is an attractive source of nitrogen in organic synthesis owing to its great abundance and low cost. (1) In recent years, the palladium- or copper-catalyzed coupling of aryl [...]

Silica-filled polydimethylsiloxane (PDMS) composite membranes are prepared on a polytetrafluoroethylene support structure. The structure and the performance of the membranes are characterized by scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetry. The pervaporation process for acetic/water separation is performed within the PDMS membranes. The vulcanization temperature was found to have a great influence on the separation performance of the membrane. The addition of silica can significantly improve the pervaporation flux and enhance the thermal stability of the membrane. With an increase in the feed temperature, selectivity decreases and permeation flux increases. Performed with a pure PDMS membrane vulcanized at 30°C, the separation factor at first will increase, then decrease when the feed flow rate was increased from 14 to 38 L * [h.sup.-1]. The maximum separation factor is achieved when the feed flow rate is 26 L * [h.sup.-1]. POLYM. ENG. SCI., 51:819-825, 2011. [C]2011 Society of Plastics Engineers, INTRODUCTION Membrane pervaporation is one of the more promising candidates for low-cost separation processes, especially for mixtures of close volatility or for mixtures with thermal or chemical sensitivity (1). Membrane [...]

Because solar energy is available in large excess relative to current rates of energy consumption, effective conversion of this renewable yet intermittent resource into a transportable and dispatchable chemical fuel may ensure the goal of a sustainable energy future. However, low conversion efficiencies, particularly with C[O.sub.2] reduction, as well as utilization of precious materials have limited the practical generation of solar fuels. By using a solar cavity-receiver ==reactor, we combined the oxygen uptake and release capacity of cerium oxide and facile catalysis at elevated temperatures to thermochemically dissociate C[O.sub.2] and [H.sub.2]O, yielding CO and [H.sub.2], respectively. Stable and rapid generation of fuel was demonstrated over 500 cycles. Solar-to-fuel efficiencies of 0.7 to 0.8% were achieved and shown to be largely limited by the system scale and design rather than by chemistry. 10.1126/science.1197834

A novel chromatographic separation method is introduced which employs water (saturated with [CO.sub.2]) as a stationary phase and [CO.sub.2] (saturated with water) as a mobile phase. Since water and [CO.sub.2] have little miscibility, conditions can be attained that create a stationary phase of water lining the inside of an uncoated stainless steel capillary. Because altering temperature and pressure can change both the density of the mobile phase and the polarity of the stationary phase, these experimental parameters offer good flexibility for optimizing separations and allow for different gradient programmed separation options. Further, since this method is free of organic stationary and mobile phase components, it is environmentally compatible and allows the use of universal flame ionization detection. This system offers very good sample capacity, peak symmetry, and retention time reproducibility (~1% RSD run-to-run, ~4% RSD day-to-day). Analytes such as alcohols, carboxylic acids, phenols, and tocopherols are employed to investigate this relatively inexpensive and robust method. As an application, the system is used to quantify ethanol in alcoholic beverages and biofuel and to analyze caffeine levels in drinks. In all cases, quantitative results are obtained with quick throughput times and often little need for sample preparation. 10.1021/ac1018793

Driven by the urgent demand of detecting trace amounts of pentschlorophenol (PCP) in contaminative water, a label-free immunosensor with ultra sensitivity and high selectivity was constructed based on a hybrid [CdSe.sub.x][Te.sub.1-x] (0 [less than or equal to] x [less than or equal to] 1) nanocrystal (NCs)-modified Ti[O.sub.2] nanotube (NT) arrays for the first time. The [CdSe.sub.x][Te.sub.1-x] NCs were photoelectrodeposited on inner and outer space of the Ti[O.sub.2] NTs, leading to high photoelectrical conversion efficiency in the visible region. PCP antibodies are covalently conjugated on the Ti[O.sub.2] NTs due to the large surface area and good biocompatibility. Since the photocurrent is highly dependent on the Ti[O.sub.2] surface properties, the specific interaction between PCP and the antibodies results in a sensitive change in the photocurrent, with a limit of detection (LOD) of 1 pM. High sensor-to-sensor reproducibility is achieved. The sensor was applied for the direct analysis of river water samples. 10.1021/ac101798t

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2010.06.008 Byline: Carine Julcour Lebigue (a), Caroline Andriantsiferana (a), N'Guessan Krou (a), Catherine Ayral (a), Elham Mohamed (a), Anne-Marie Wilhelm (a), Henri Delmas (a), Laurence Le Coq (b), Claire Gerente (b), Karl M. Smith (c), Suangusa Pullket (c), Geoffrey D. Fowler (c), Nigel J.D. Graham (c) Abstract: This paper describes a preliminary evaluation of the performance of carbonaceous materials prepared from sewage sludges (SBCMs) in a hybrid water treatment process based on adsorption and catalytic wet air oxidation; phenol was used as the model pollutant. Three different sewage sludges were treated by either carbonisation or steam activation, and the physico-chemical properties of the resultant carbonaceous materials (e.g. hardness, BET surface area, ash and elemental content, surface chemistry) were evaluated and compared with a commercial reference activated carbon (PICA F22). The adsorption capacity for phenol of the SBCMs was greater than suggested by their BET surface area, but less than F22; a steam activated, dewatered raw sludge (SA_DRAW) had the greatest adsorption capacity of the SBCMs in the investigated range of concentrations ( Author Affiliation: (a) Universite de Toulouse, Laboratoire de Genie Chimique, UMR CNRS 5503, 4, allee Emile Monso, BP 84234, 31432 Toulouse Cedex 4, France (b) GEPEA UMR 6144, Ecole des Mines de Nantes, 4 rue Alfred Kastler, 44307 Nantes Cedex 3, France (c) Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK Article History: Received 31 January 2010; Revised 16 May 2010; Accepted 11 June 2010

A novel technique of spectroscopic imaging using a near-infrared (NIR) laser sheet beam was developed for visualization of liquid water in a proton-exchange membrane (PEM) sandwiched between two opaque electrodes set in a polymer electrolyte fuel cell (PEFC). In-plane two-dimensional distribution of water in the thin membrane was clearly visualized during the fuel cell operation. Under the condition of fuel feeding into the PEFC without humidification, water was generated by the fuel cell reaction in the whole electrode area. In contrast, under the condition of fuel feeding with humidification, the PEM got wet in the vicinity of a gas flow field locally. 10.1021/ac101525z

In atomic force spectroscopic studies of the elastomeric protein ubiquitin, the [beta]-strands 1-5 serve as the force clamp. Simulations show how the rupture force in the force-induced unfolding depends on the kinetics of water molecule insertion into positions where they can eventually form hydrogen bonding bridges with the backbone hydrogen bonds in the force-clamp region. The intrusion of water into this region is slowed down by the hydrophobic shielding effect of carbonaceous groups on the surface residues of [beta]-strands 1-5, which thereby regulates water insertion prior to hydrogen bond breakage. The experiments show that the unfolding of the mechanically stressed protein is nonexponential due to static disorder. Our simulations show that different numbers and/ or locations of bridging water molecules give rise to a long-lived distribution of transition states and static disorder. We find that slowing down the translational (not rotational) motions of the water molecules by increasing the mass of their oxygen atoms, which leaves the force field and thereby the equilibrium structure of the solvent unchanged, increases the average rupture force; however, the early stages of the force versus time behavior are very similar for our 'normal' and fictitious 'heavy' water models. Finally, we construct six mutant systems to regulate the hydrophobic shielding effect of the surface residues in the force-clamp region. The mutations in the two termini of [beta]-sheets 1-5 are found to determine a preference for different unfolding pathways and change mutant's average rupture force. molecular dynamics simulation | single molecule spectroscopy | unfolding kinetics doi/ 10.1073/pnas.1013159107

Dynamic ion speciation using DMT (Donnan membrane technique) requires insight into the physicochemical characteristics of diffusion in charged membranes (tortuosity, local diffusion coefficients) as well as ion accumulation. The latter can be precluded by studying the diffusion of neutral species, such as boric acid, B[(OH).sub.3.sup.0](aq), arsenite, As[(OH).sub.3.sup.0](aq), or water. In this study, the diffusion rate of B[(OH).sub.3.sup.0] has been evaluated as a function of the concentration, pH, and ionic strength. The rate is linearly dependent on the concentration of solely the neutral species, without a significant contribution of negatively charged species such as B[(OH).sub.4.sup.-], present at high pH. A striking finding is the very strong effect (factor of ~10) of the type of cation ([K.sup.+], [Na.sup.+], [Ca.sup.2+], [Mg.sup.2+], [Al.sup.3+], and [H.sup.+]) on the diffusion coefficient of B[(OH).sub.3.sup.0] and also As[(OH).sub.3.sup.0]. The decrease of the diffusion coefficient can be rationalized as an enhancement of the mean viscosity of the confined solution in the membrane. The diffusion coefficients can be described by a semiempirical relationship, linking the mean viscosity of the confined solute of the membrane to the viscosity of the free solution. In proton-saturated membranes, as used in fuel cells, viscosity is relatively more enhanced; i.e., a stronger water network is formed. Extraordinarily, our B[(OH).sub.3]-calibrated model (in [HNO.sub.3]) correctly predicts the reported diffusion coefficient of water ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]), measured with [sup.1]H NMR and quasi-elastic neutron scattering in [H.sup.+]-Nation membranes. Upon drying these membranes, the local hydronium, H[([H.sub.2]O).sub.n.sup.+], concentration and corresponding viscosity increase, resulting in a severe reduction of the diffusion coefficient ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] [approximately equal to] 5-50 times), in agreement with the model. The present study has a second goal, i.e., development of the methodology for measuring the free concentration of neutral species in solution. Our data suggest that the free concentration can be measured with DMT in natural systems if one accounts for the variation in the cation composition of the membrane and corresponding viscosity/diffusion coefficient. 10.1021/ac1009436

This paper reports the first detections of an antidepressant, lamotrigine, and its major metabolite (2-N-glucuronide), in environmental water samples using a new chlorine mass-filter technique with accurate mass and high resolution. A quantitative method is described using solid phase extraction (SPE) followed by liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOF-MS) for the simultaneous analysis of both compounds in aqueous samples, including drinking water, groundwater, surface water, and wastewater collected from sewage treatment plants. The recoveries of the analytes ranged from 75 to 99%, depending on the type of water extracted. The method detection limits were 1 and 5 ng/L for lamotrigine and its metabolite, respectively. The method was validated with more than a hundred aqueous samples analyzed and lamotrigine and its 2-N-glucuronide metabolite were mostly detected in both wastewater and surface water impacted sites at mean concentrations of 488 and 209 ng/L, respectively. Lamotrigine was detected in 94% of all the wastewater samples analyzed. Two detections for lamotrigine occurred in drinking water. To our knowledge, this is the first report of water samples containing lamotrigine, a relatively new drug used for the treatment of epilepsy3, and type I bipolar syndrome. It is also the first report of a glucuronide of an antidepressant surviving wastewater treatment plant operations and becoming a ground and surface water contaminant. 10.1021/ac1014645

Two time-division-multiplexed (TDM) sources based on fiber Bragg gratings were applied to monitor gas temperature, [H.sub.2]O mole fraction, and C[H.sub.4] mole fraction using line-of-sight absorption spectroscopy in a practical high-pressure gas turbine combustor test article. Collectively, the two sources cycle through 14 wavelengths in the 1329-1667 nm range every 33 [micro]s. Although it is based on absorption spectroscopy, this sensing technology is fundamentally different from typical diode-laser-based absorption sensors and has many advantages. Specifically, the TDM lasers allow efficient, flexible acquisition of discrete-wavelength information over a wide spectral range at very high speeds (typically 30 kHz) and thereby provide a multiplicity of precise data at high speeds. For the present gas turbine application, the TDM source wavelengths were chosen using simulated temperature-difference spectra. This approach is used to select TDM wavelengths that are near the optimum values for precise temperature and species-concentration measurements. The application of TDM lasers for other measurements in high-pressure, turbulent reacting flows and for two-dimensional tomographic reconstruction of the temperature and species-concentration fields is also forecast. OCIS codes: 300.1030, 120.1740, 120.6780.

This paper reports on three-dimensional synchrotron radiation/Fourier transform-infrared microspectroscopy (SR/FT-IRM) imaging studies of water inclusions at the buried interface of solid-contact-ion-selective electrodes (SC-ISEs). It is our intention to describe a nondestructive method that may be used in surface studies of the buried interfaces of materials, especially multilayers of polymers. Herein, we demonstrate the power of SR/FT-IRM for studying water inclusions at the buried interfaces of SCISEs. A poly(methyl methacrylate)--poly(decyl methacyrlate) [PMMA--PDMA] copolymer revealed the presence of micrometer sized inclusions of water at the gold/ membrane interface, while a coupling of a hydrophobic solid contact of poly(3-octylthiopheue 2,5-diyl) (POT) prevented the accumulation of water at the buried interface. A similar study with a poly (3,4-ethylenedioxythiophene)/poly (styrenesulfonate) [PEDOT/PSS] solid contact also revealed an absence of distinct micrometer-sized pools of water; however, there were signs of absorption of water accompanied by swelling of the PEDOT/PSS underlayer, and these membrane zones are enriched with respect to water. 10.1021/ac101009n

The oxygen decay coefficient is a key parameter used to predict the distribution of oxygen concentrations spatially and temporally in a waste rock pile. The present study proposes a new equation to calculate the oxygen decay coefficient based on the oxidation rate (sulfate release rate) of the waste rock, dry density, and equivalent porosity for oxygen transport. The equation gave oxygen decay coefficients that were of the same order of magnitude as those obtained from a semianalytic solution to the modified Fick's law with an oxygen consumption term. Values were in the range of 3.74 x [10.sup.-8] [s.sup.-1] for air dry waste rock and 3.99 x [10.sup.-7] [s.sup.-1] for moist waste rock. The effect of water addition frequency on the oxidation rate and the oxygen decay coefficient was investigated through four column experiments with various flushing rates and a laboratory case simulating actual precipitation at a specific site. The results indicated that the oxygen decay coefficient was dependent on not only the oxidation rate but also on the physical characteristics of the waste rock, such as porosity and dry density. The flushing rate had a significant influence on the oxidation rate of the waste rock and the calculated oxygen decay coefficient. The oxidation rate of the waste rock decreased from 1.19 x [10.sup.-6] to 5.32 x [10.sup.-7] [s.sup.-1] with an increase in flushing intervals from 1 week to 4 weeks. When the drying period was longer than 3 weeks, the oxidation rate decreased very slowly with an increase in drying period for the tested waste rock. DOI: 10.1061/(ASCE)EE.1943-7870.0000213 CE Database subject headings: Laboratory tests; Oxidation; Coefficients; Sulfates; Water content; Oxygen demand; Waste management; Rocks. Author keywords: Laboratory tests; Oxidation; Oxygen decay coefficient; Sulfate; Water content.

Modified by ethylenediaminetetraacetic acid (EDTA) salts and unmodified bagasse fibers were tested for the removal of total dissolved solids (TDSs) from cooling tower water. Parameters such as hydrogen ion concentration (pH), particle size of bagasse fibers, and the concentrations of adsorbent and adsorbate were studied to optimize the conditions to be applied on a commercial scale for the decontamination of effluents of cooling tower water. The optimum pH for TDS removal was between 6 and 6.5. The efficiency of TDS removal increased when the size of fiber particles decreased (100 [micro]m) and when the concentration of EDTA salt increased to reach 78 mg/g of modified bagasse fibers. The adsorption parameters were determined using both Langmuir and Freundlich isotherms. The preferential mechanisms for the retention of TDSs are a complexation process between the TDSs and chemical functions present on the surface of fibers, and the chelation process with the EDTA attached to the fibers. The results obtained could be valuable for application to cooling tower water treatment and for the softening of hard drinking water. DOI: 10.1061/(ASCE)EE.1943-7870.0000195 CE Database subject headings: Salt; Fibers; Cooling towers; Cooling water; Water treatment. Author keywords: EDTA salt; Modified bagasse fiber; Cooling tower water; Hard water; TDS removal.

Membrane-extraction ion mobility spectrometry (ME-IMS) has been developed for in situ sampling and analysis of trace chlorinated hydrocarbons in water in a single procedure. The sampling is configured so that aqueous contaminants permeate through a spiral hollow poly(dimethylsiloxane) (PDMS) membrane and are carded away by a vapor flow through the membrane tube. The extracted analyte flows into an atmospheric-pressure chemical-ionization (APCI) chamber and is analyzed in a specially made IMS analyzer. The PDMS membrane was found to effectively extract chlorinated hydrocarbon solvents from the liquid phase to vapor. The specialized IMS analyzer has measured resolutions of R = 33 and 41, respectively, for negative-and positive-modes and is capable of detecting aqueous tetrachloroethylene (PCE) and trichloroethylene (ICE) as low as 80 and 74 [micro]g/L in the negative ion mode, respectively. The time-dependent characteristics of sampling and detection of TCE are both experimentally and theoretically studied for various concentrations, membrane lengths, and flow rates. These characteristics demonstrate that membrane-extraction IMS is feasible for the continuous monitoring of chlorinated hydrocarbons in water. 10.1021/ac100162d

Sulfur-induced polioencephalomalacia (sPEM), a neurological disorder affecting ruminants, is associated with consumption of diets with increased S (high-S). High-S water is commonly found in many western states and is a major source of dietary S for grazing cattle. Consumption of high-S water has been associated with sPEM and decreased performance. Identification of a feed supplement that would counteract the negative effects of high-S water would decrease the incidence of sPEM and prevent performance reductions in regions with problematic water sources. The objectives of this study were to 1) determine the effects of administering high-S drinking water to forage-fed feedlot steers on health and performance, and 2) determine the effectiveness of clinoptilolite, a clay mineral with increased cation-exchange capacity, in negating the effects of high-S drinking water. Yearling steers (n = 96; 318.2 [+ or -] 2.1 kg of BW) were randomly assigned to 1 of 4 treatments for a 77-d trial period: control with low-S water (566 mg of S[O.sub.4]/L), high-S water (3,651 mg of S[O.sub.4]/L), or high-S water plus clinoptilolite supplemented at 2.5 or 5.0% of the diet DM. Feed and water consumption were measured daily, and all steers were weighed on d -2, -1, 29, 53, 76, and 77. Plasma samples were collected on d 0, 58, and 77, and liver samples on d 0 and 77. There was a greater (P [less than or equal to] 0.046) frequency of sPEM in high-S steers than control steers, but no differences among high-S treatment groups. In total, 12 cases of sPEM were confirmed by the presence of cortical lesions in steers consuming high-S water. Daily DMI (P = 0.002) and daily water intake (P = 0.001) were less in high-S water steers than control steers. No differences (P [greater than or equal to] 0.546) in ADG or G:F were observed. Plasma Cu decreased (P = 0.029) to a greater magnitude in high-S water steers than the control steers over the 77-d trial period. Mineral analyses of hepatic tissue from randomly selected healthy steers from each treatment group (n = 10 per treatment) showed an interaction (P [less than or equal to] 0.034) of sample time and treatment for Cu, Se, and Zn concentrations. These results suggest that clinoptilolite does not negate the effects of high-S water, and administration of high-S water decreases herd health through an increased incidence of sPEM and reduced nutritional status. Key words: clinoptilolite, polioencephalomalacia, steer, sulfur, water doi: 10.2527/jas.2009-2343

The Athabasca oil sands in Canada are a less conventional source of oil which have seen rapid development. There are concerns about the environmental impact, with particular respect to components in oil sands process water which may enter the aquatic ecosystem. Naphthenic acids have been previously targeted for study, due to their implications in toxicity toward aquatic wildlife, but it is believed that other components, too, contribute toward the potential toxicity of the oil sands process water. When mass spectrometry is used, it is necessary to use instrumentation with a high resolving power and mass accuracy when studying complex mixtures, but the technique has previously been hindered by the range of compounds that have been accessible via common ionization techniques, such as electrospray ionization. The research described here applied Fourier transform ion cyclotron resonance mass spectrometry in conjunction with electrospray ionization and atmospheric pressure photoionization, in both positive-ion and negative-ion modes, to the characterization of oil sands process water for the first time. The results highlight the need for broader characterization when investigating toxic components within oil sands process water. 10.1021/ac100103y

As the terminal step in photosystem II, and a potential half-reaction for artificial photosynthesis, water oxidation (2[H.sub.2]O [right arrow] [O.sub.2] + 4[e.sup.-] + 4[H.sup.+]) is key, but it imposes a significant mechanistic challenge with requirements for both 4[e.sup.-]/4[H.sup.+] loss and O--O bond formation. Significant progress in water oxidation catalysis has been achieved recently by use of single-site Ru metal complex catalysts such as [[Ru(Mebimpy)(bpy)(O[H.sub.2])].sup.2+] [Mebimpy = 2,6bis(1-methylbenzimidazol-2-yl)-pyridine; bpy = 2,2'-bipyridine]. When oxidized from [Ru.sup.ll]O[H.sub.2+] to [Ru.sup.V] = [O.sup.3+], these complexes undergo O--O bond formation by O-atom attack on a [H.sub.2]O molecule, which is often the rate-limiting step. Microscopic details of O--O bond formation have been explored by quantum mechanical/molecular mechanical (QM/MM) simulations the results of which provide detailed insight into mechanism and a strategy for enhancing catalytic rates. It utilizes added bases as proton acceptors and concerted atom-proton transfer (APT) with O-atom transfer to the O atom of a water molecule in concert with proton transfer to the base (B). Base catalyzed APT reactivity in water oxidation is observed both in solution and on the surfaces of oxide electrodes derivatized by attached phosphonated metal complex catalysts. These results have important implications for catalytic, electrocatalytic, and photoelectrocatalytic water oxidation. water split | O--O coupling | base effect | isotope effect doi/ 10.1073/pnas.1001132107

The experimental technique of tracer pulse chromatography was used to simultaneously measure the uptake of eluent components by a [C.sub.18]-bonded reversed-phase liquid chromatography (RPLC) packing and the retention factors for a series of test analytes over the full range of eluent composition for methanol and acetonitrile with water. The primary objective of the research was to determine whether or not the uptake of eluent components immobilized as part of the stationary phase would influence the retention of analyte standards. Both acetonitrile and methanol were absorbed in or adsorbed on the [C.sub.18]-bonded phase with the maximum amount of acetonitrile sorbed being about four times that of methanol. The thermodynamic void volume of the column and the excess sorption isotherms of acetonitrile, methanol, and water in binary aqueous/organic mixtures were determined directly from the tracer pulse experiments. The absolute sorption isotherms of the eluent components were indirectly estimated by a combination of techniques. Regression analysis of the nonstationary inflection point of the excess isotherms provided an estimate of the volume of eluent sorbed by the stationary phase but only over a limited eluent composition range. In order to expand the applicable composition range, several commonly used 'unretained' probe solutes were tested to determine the accuracy of the assumption that the retention volumes of these solutes provided a viable measure of the kinetic void volume (mobile-phase volume) of the column. The difference between the thermodynamic and kinetic void volumes provided an estimate of the absolute volume of eluent present in the stationary phase. The experimental results showed that some solutes, viz., water and thiourea, did provide an accurate measure of the mobile-phase volume but only over a limited range of eluent composition. Using deuterated water as the unretained dead time marker for water-rich eluents combined with the regression results from excess isotherm data, the absolute volume of eluent sorbed by the stationary phase could be estimated over the full range of eluent composition. The effect of this uptake of eluent on the retention of the test solutes appeared to be minimal for this particular set of test analytes. 10.1021/ac100148b

To understand the behavior of concrete material in ambient water, a series of triaxial compressive tests of concrete cylindrical specimens ([phi] 100 x 200 mm) was conducted on a large scale triaxial machine. The acting pattern of water, confining pressure, loading strain rate, and moisture content were chosen as test parameters. The water acting patterns on concrete were directly divided into mechanical loading and real water loading according to whether the specimens were directly exposed to water or not. The confining pressure ranged from 0-8 MPa and the strain rate included [10.sup.-5]/s, [10.sup.-3]/s, and [10.sup.-2]/s. By testing dry and saturated specimens, the effect of moisture on concrete strength was also examined. The test results indicated that the compressive strengths of both dry and saturated concrete increase obviously with the confining pressure under mechanical confining pressure. However, the effect on the strengthened dry concrete specimens is more significant. The strength of dry concrete under real water loading decreased remarkably, even less than its uniaxial strength, whereas the compressive strength of the saturated concrete specimen under real water loading is close to its uniaxial compressive strength. The strength of concrete increases with strain rate, and this phenomenon becomes more apparent under water loading. DOI: 10.1061/(ASCE)0733-9399(2010)136:3(379) CE Database subject headings: Concrete; Saturation; Strength; Compression; Pore pressure; Strain rates. Author keywords: Concrete; Saturation; Strength, triaxial compression; Water loading; Pore pressure; Strain rate.

Three experimental techniques, laser flash photolysis, redox catalysis, and stopped-flow, were used to investigate the variation of the oxidation rate constant of phenol in neat water with the driving force offered by a series of electron acceptors. Taking into account a result previously obtained with a low--driving force electron acceptor thus allowed scanning more than half an electron-volt driving force range. Variation of the rate constant with pH showed the transition between a direct phenol oxidation reaction at low pH, where the rate constant does not vary with pH, and a stepwise reaction involving the prior deprotonation of phenol by OH-, characterized by a unity-slope variation. Analyses of the direct oxidation kinetics, based on its variation with the driving force and on the determination of H/D isotope effects, ruled out a stepwise mechanism in which electron transfer is followed by the deprotonation of the initial cation radical at the benefit of a pathway in which proton and electron are transferred concertedly. Derivation of the characteristics of counterdiffusion in termolecular reactions allowed showing that the concerted process is under activation control. It is characterized by a remarkably small reorganization energy, in line with the electrochemical counterpart of the reaction, underpinning the very peculiar behavior of water as proton acceptor when it is used as the solvent. photochemistry | proton-coupled electron transfer | water as proton acceptor doi/10.1073/pnas.0914693107

A major roadblock to the vitrification of cells is the requirement of high concentrations of cryoprotectant (CPA) chemicals and the damage caused by prolonged exposure of cells to these high concentrations above the glass transition temperature. These effects are minimized with controlled CPA loading. Certain organic oils, such as soybean oil, are made of triacylglycerols and are capable of dissolving small amounts of water, a property which is enhanced significantly as temperature is increased. This phenomenon was exploited here to accomplish temperature-controlled concentration of glycerol in single water droplets dispersed in the organic phase. Emulsions of aqueous solutions of glycerol in soybean oil were made and subjected to a temperature increase of 10 [degrees]C from room temperature. Upon increasing temperature, water dissolved into the oil, rendering the 15-20 [micro]m droplets concentrated an average of 3.6 times and 2.6 times for 1 and 2 M starting concentrations, respectively, with the oil-insoluble glycerol in 90-110 s. This phenomenon could be used to dynamically concentrate CPAs within cell-containing droplets which may then be vitrified before being exposed to high temperatures for fatally long times. 10.1021/ac9022742

Surface-enhanced Raman scattering (SERS) spectra were collected continuously during cyclic voltammetric measurements on silver electrodes in alkaline aqueous solution at room temperature. Three water librational modes as well as the bending mode peak were observed in cathodic potential range. The 2D-COS analysis of spectra collected in LiOH and KOH solutions showed that the librational bands appear prior to the bending band on the cathodic scan, while in CsOH solution the potential dependence of these bands was identical. A comparison of librational band frequencies revealed that the water molecules around [C.sup.s+] cations arranged on the electrode surface were poorly hydrogen bonded in contrast to [Li.sup.+] and [K.sup.+]. The water bending band of spectra collected in LiOH solution was found to be the convolution of two contributions, consistent with a two state model of water arranged on an electrode surface. 10.1021/ac902299u

A new analytical approach to determine the speciation of hydrophobic organic analytes is presented. The freely dissolved concentration in a sample is controlled by passive dosing from silicone (poly(dimethylsiioxane)), and the total sample concentration at equilibrium is measured. The free fraction is determined as the ratio between measured concentrations in pure water and sample. [sup.14]Clabeled fluoranthene served as model analyte, and total sample concentrations were easily measured by liquid scintillation counting. The method was applied to surface water, stormwater runoff, and wastewater. In the untreated wastewater, 61% of the fluoranthene was bound to suspended solids, 28% was associated to dissolved organic matter, and 11% was freely dissolved, while in treated wastewater, the speciation was 16% bound to suspended solids, 4% bound to dissolved organic matter, and 80% freely dissolved. The free fraction in roof runoff (85%) and surface water (91%) was markedly higher than in runoff from paved areas, which ranged from 27 to 36%. A log [K.sub.DOC] value of 5.26 was determined for Aldrich humic acid, which agrees well with reported values obtained by fluorescence quenching and solid phase microextraction (SPME). This analytical approach combines simplicity with high precision, and it does not require any phase separation steps. 10.1021/ac902378w