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Water Phase (water + phase)

Distribution by Scientific Domains

Life Sciences	37%
Chemistry	25%
Polymers and Materials Science	20%
Earth and Environmental Science	16%

Selected Abstracts

A Novel and Efficient System of a Visible-Light-Responsive Organic Photoelectrocatalyst Working in a Water Phase

CHEMPHYSCHEM, Issue 5 2004
Toshiyuki Abe Prof.
The best of both worlds: An organic bilayer, composed of a perylene derivative (PV) and a phthalocyanine (H2Pc), was found to be a novel example of a photoanode involving a catalytic oxidation in water (see graphic). Based on the action spectrum for photocurrent, it is noted that the widespread visible light absorption (<750 nm) by only the PV can efficiently induce the photoanodic current generation at the interface of H2Pc/water coupled with the hole-conducting character of H2Pc. [source]

Bioavailability and biodegradation of nonylphenol in sediment determined with chemical and bioanalysis,

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2008
Jasperien de Weert
Abstract The surfactant nonylphenol (NP) is an endocrine-disrupting compound that is widely spread throughout the environment. Although environmental risk assessments are based on total NP concentrations, only the bioavailable fraction posses an environmental risk. The present study describes the bioavailability and biodegradability of NP over time in contaminated river sediment of a tributary of the Ebro River in Spain. The bioavailable fraction was collected with Tenax TA® beads, and biodegradation was determined in aerobic batch experiments. The presence of NP was analyzed chemically using gas chromatography-mass spectrometry and indirectly as estrogenic potency using an in vitro reporter gene assay (ER, - luc assay). Of the total extractable NP in the sediment, 95% ± 1.5% (mean ± standard error) desorbed quickly into the water phase. By aerobic biodegradation, the total extractable NP concentration and the estrogenic activity were reduced by 97% ± 0.5% and 94% ± 2%, respectively. The easily biodegradable fraction equals the potential bioavailable fraction. Only 43 to 86% of the estrogenic activity in the total extractable fraction, as detected in the ER, - luc assay, could be explained by the present NP concentration. This indicates that other estrogenic compounds were present and that their bioavailability and aerobic degradation were similar to that of NP. Therefore, we propose to use NP as an indicator compound to monitor estrogenicity of this Ebro River sediment. To what extent this conclusion holds for other river sediments depends on the composition of the contaminants and/or the nature of these sediments and requires further testing. [source]

Benzidine transformation processes in natural sediments

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2006
Joel Harden
Abstract Aromatic amines, such as benzidine and 3,3,-dichlorobenzidine, are chemicals used in the pigment and dye processes. Release of these compounds into the environment is important because of their carcinogenic and toxic nature. In the present study, the sediment and water samples were collected from Lake Macatawa (Holland, MI, USA) and subsequently spiked with benzidine. The grain size distribution of the sediment samples investigated here ranged in composition from sandy to silty-clay sediment types. The sediment,water systems spiked with benzidine were incubated under anaerobic conditions at 4, 15, and 23°C for 211 d. Degradation of benzidine was observed over the time-course analysis of the sediment,water mixtures. Three possible metabolites (aniline, 2-ethyl-1-hexanol, and 1-amino-2-hexene) were observed during this investigation as a result of gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry. No metabolites were observed in autoclaved bottles, suggesting that the transformation of benzidine in the sediment,water mixtures was the result of microbial activity. From sediment,water distribution experiments, benzidine demonstrated higher sorption affinity for the different sediment phases than its degradation product, aniline. Therefore, microbially mediated transformation of benzidine to aniline is expected to yield a greater total concentration of the more mobile compound, aniline, in the water phase and a greater possibility for transport of aniline in the water phase. [source]

Effects of lambda-cyhalothrln in two ditch microcosm systems of different trophic status

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2005
Ivo Roessink
Abstract The fate and effects of the pyrethroid insecticide lambda-cyhalothrin were compared in mesotrophic (macrophyte-dominated) and eutrophic (phytoplankton-dominated) ditch microcosms (,0.5 m3). Lambda-cyhalothrin was applied three times at one-week intervals at concentrations of 10, 25, 50, 100, and 250 ng/L. The rate of dissipation of lambda-cyhalothrin in the water column of the two types of test systems was similar. After 1 d, only 30% of the amount applied remained in the water phase. Initial, direct effects were observed primarily on arthropod taxa. The most sensitive species was the phantom midge (Chaoborus obscuripes). Threshold levels for slight and transient direct toxic effects were similar (10 ng/L) between types of test systems. At treatment levels of 25 ng/L and higher, apparent population and community responses occurred. At treatments of 100 and 250 ng/L, the rate of recovery of the macroinvertebrate community was lower in the macrophyte-dominated systems, primarily because of a prolonged decline of the amphipod Gammarus pulex. This species occurred at high densities only in the macrophyte-dominated enclosures. Indirect effects (e.g., increase of rotifers and microcrustaceans) were more pronounced in the plankton-dominated test systems, particularly at treatment levels of 25 ng/L and higher. [source]

Modeling pentachlorophenol bioavailability and bioaccumulation by the freshwater fingernail clam Sphaerium corneum using artificial particles and humic acids

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2001
Noemi R. Verrengia Guerrero
Abstract The uptake of anthropogenic chemicals by benthic bivalves may occur through the water phase and also by the ingestion of particles from both the suspended matter and bottom sediments. Many chemicals sorb to sediments and, subsequently, are released in the digestive tract of animals. The assessment of sediment-bound chemicals has been difficult because of the complexity of the association between these chemicals and natural particles. To simplify this complexity, we previously devised a test system using artificial particles with known chemical structures. In the present work, we improved this experimental design by adding humic materials as a source of organic matter. Bioassays were conducted by exposing the fingernail clam Sphaerium corneum to sublethal levels of pentachlorophenol (PCP) in the presence or absence of the artificial particles, treated with or without a commercial preparation of humic acids. The results showed that the bioavailability and bioaccumulation could be explained on the basis of the interactions of PCP with the active groups and/or the backbone of the resins, both in systems with or without humic acids. This model may constitute a useful approach to modeling and predicting the uptake and accumulation of chemicals bound to natural sediments. [source]

Effect of degree of fluid saturation on transport coefficients in disturbed soils

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2004
A. Tuli
Summary To improve the predictive capability of transport models in soils we need experimental data that improve their understanding of properties at the scale of pores, including the effect of degree of fluid saturation. All transport occurs in the same soil pore space, so that one may intuitively expect a link between the different transport coefficients and key geometrical characteristics of the pores such as tortuosity and connectivity, and pore-size distribution. To understand the combined effects of pore geometry and pore-size distribution better, we measured the effect of degree of water saturation on hydraulic conductivity and bulk soil electrical conductivity, and of degree of air saturation on air conductivity and gaseous diffusion for a fine sand and a sandy loam soil. To all measured data were fitted a general transport model that includes both pore geometry and pore-size distribution parameters. The results show that both pore geometry and pore-size distribution determine the functional relations between degree of saturation, hydraulic conductivity and air conductivity. The control of pore size on convective transport is more for soils with a wider pore-size distribution. However, the relative contribution of pore-size distribution is much larger for the unsaturated hydraulic conductivity than for gaseous phase transport. For the other transport coefficients, their saturation dependency could be described solely by the pore-geometry term. The contribution of the latter to transport was much larger for transport in the air phase than in the water phase, supporting the view that connectivity dominates gaseous transport. Although the relation between effective fluid saturation and all four relative transport coefficients for the sand could be described by a single functional relation, the presence of a universal relationship between fluid saturation and transport for all soils is doubtful. [source]

Habitat selection and diel distribution of the crustacean zooplankton from a shallow Mediterranean lake during the turbid and clear water phases

FRESHWATER BIOLOGY, Issue 3 2007
BRUNO B. CASTRO
Summary 1. The fish fauna of many shallow Mediterranean Lakes is dominated by small-bodied exotic omnivores, with potential implications for fish,zooplankton interactions still largely unknown. Here we studied diel variation in the vertical and horizontal distribution of the crustacean plankton in Lake Vela, a shallow polymictic and eutrophic lake. Diel sampling was carried out on three consecutive days along a horizontal transect, including an open-water station and a macrophyte (Nymphaea alba) bed. Since transparency is a key determinant of the predation risk posed by fish, the zooplankton sampling campaigns were conducted in both the turbid (autumn) and clear water (spring) phases. 2. In the turbid phase, most taxa were homogeneously distributed along the vertical and horizontal axes in the three consecutive days. The only exception was for copepod nauplii, which showed vertical heterogeneity, possibly as a response to invertebrate predators. 3. In the clear water phase, most zooplankton taxa displayed habitat selection. Vertically, the general response consisted of a daily vertical migration (DVM), despite the limited depth (1.6 m). Horizontally, zooplankters showed an overall preference for the pelagic zone, independent of the time of the day. Such evidence is contrary to the postulated role of macrophytes as an anti-predator refuge for the zooplankton. 4. These vertical (DVM) and horizontal (macrophyte-avoidance) patterns were particularly conspicuous for large Daphnia, suggesting that predation risk from size-selective predators (fish) was the main factor behind the spatial heterogeneity of zooplankton in the spring. Thus, the difference in the zooplankton spatial distribution pattern and habitat selection among seasons (turbid and clear water phases) seems to be mediated the predation risk from fish, which is directly related to water transparency. 5. The zooplankton in Lake Vela have anti-predator behaviour that minimises predation from fish. We hypothesise that, due to the distinct fish community of shallow Mediterranean lakes, aquatic macrophytes may not provide adequate refuge to zooplankters, as seen in northern temperate lakes. [source]

Fabrication of Microbeads with a Controllable Hollow Interior and Porous Wall Using a Capillary Fluidic Device

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2009
Sung-Wook Choi
Abstract Poly(D,L -lactide-co-glycolide) (PLGA) microbeads with a hollow interior and porous wall are prepared using a simple fluidic device fabricated with PVC tubes, glass capillaries, and a needle. Using the fluidic device with three flow channels, uniform water-in-oil-in-water (W-O-W) emulsions with a single inner water droplet can be achieved with controllable dimensions by varying the flow rate of each phase. The resultant W-O-W emulsions evolve into PLGA microbeads with a hollow interior and porous wall after the organic solvent in the middle oil phase evaporates. Two approaches are employed for developing a porous structure in the wall: emulsion templating and fast solvent evaporation. For emulsion templating, a homogenized, water-in-oil (W/O) emulsion is introduced as the middle phase instead of the pure oil phase. Low-molecular-weight fluorescein isothiocyanate (FITC) and high-molecular-weight fluorescein isothiocyanate,dextran conjugate (FITC,DEX) is added to the inner water phase to elucidate both the pore size and their interconnectivity in the wall of the microbeads. From optical fluorescence microscopy and scanning electron microscopy images, it is confirmed that the emulsion-templated microbeads (W-W/O-W) have larger and better interconnected pores than the W-O-W microbeads. These microstructured microbeads can potentially be employed for cell encapsulation and tissue engineering, as well as protection of active agents. [source]

A simulation of the hydrothermal response to the Chesapeake Bay bolide impact

GEOFLUIDS (ELECTRONIC), Issue 3 2005
W. E. SANFORD
Abstract Groundwater more saline than seawater has been discovered in the tsunami breccia of the Chesapeake Bay Impact Crater. One hypothesis for the origin of this brine is that it may be a liquid residual following steam separation in a hydrothermal system that evolved following the impact. Initial scoping calculations have demonstrated that it is feasible such a residual brine could have remained in the crater for the 35 million years since impact. Numerical simulations have been conducted using the code HYDROTHERM to test whether or not conditions were suitable in the millennia following the impact for the development of a steam phase in the hydrothermal system. Hydraulic and thermal parameters were estimated for the bedrock underlying the crater and the tsunami breccia that fills the crater. Simulations at three different breccia permeabilities suggest that the type of hydrothermal system that might have developed would have been very sensitive to the permeability. A relatively low breccia permeability (1 × 10,16 m2) results in a system partitioned into a shallow water phase and a deeper superheated steam phase. A moderate breccia permeability (1 × 10,15 m2) results in a system with regionally extensive multiphase conditions. A relatively high breccia permeability (1 × 10,14 m2) results in a system dominated by warm-water convection cells. The permeability of the crater breccia could have had any of these values at given depths and times during the hydrothermal system evolution as the sediments compacted. The simulations were not able to take into account transient permeability conditions, or equations of state that account for the salt content of seawater. Results suggest, however, that it is likely that steam conditions existed at some time in the system following impact, providing additional evidence that is consistent with a hydrothermal origin for the crater brine. [source]

Gas breakthrough experiments on fine-grained sedimentary rocks

GEOFLUIDS (ELECTRONIC), Issue 1 2002
A. Hildenbrand
Abstract The capillary sealing efficiency of fine-grained sedimentary rocks has been investigated by gas breakthrough experiments on fully water saturated claystones and siltstones (Boom Clay from Belgium, Opalinus Clay from Switzerland and Tertiary mudstone from offshore Norway) of different lithological compositions. Sand contents of the samples were consistently below 12%, major clay minerals were illite and smectite. Porosities determined by mercury injection lay between 10 and 30% while specific surface areas determined by nitrogen adsorption (BET method) ranged from 20 to 48 m2 g , 1. Total organic carbon contents were below 2%. Prior to the gas breakthrough experiments the absolute (single phase) permeability (kabs) of the samples was determined by steady state flow tests with water or NaCl brine. The kabs values ranged between 3 and 550 nDarcy (3 × 10,21 and 5.5 × 10,19 m2). The maximum effective permeability to the gas-phase (keff) measured after gas breakthrough on initially water-saturated samples extended from 0.01 nDarcy (1 × 10,23 m2) up to 1100 nDarcy (1.1 × 10,18 m2). The residual differential pressures after re-imbibition of the water phase, referred to as the ,minimum capillary displacement pressures' (Pd), ranged from 0.06 to 6.7 MPa. During the re-imbibition process the effective permeability to the gas phase decreases with decreasing differential pressure. The recorded permeability/pressure data were used to derive the pore size distribution (mostly between 8 and 60 nm) and the transport porosity of the conducting pore system (10 -5,10 -2%). Correlations could be established between (i) absolute permeability coefficients and the maximum effective permeability coefficients and (ii) effective or absolute permeability coefficients and capillary sealing efficiency. No correlation was found between the capillary displacement pressures determined from gas breakthrough experiments and those derived theoretically by mercury injection. [source]

Assessment of bismuth thiols and conventional disinfectants on drinking water biofilms

JOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2003
F. Codony
Abstract Aims: Biofilms in water distribution systems represent a far more significant reservoir of micro-organisms than the water phase. Biofilms are (i) resistant to disinfectants, (ii) nuclei for microbial regrowth, (iii) a refuge for pathogens, (iv) accompanied by taste and odour problems, and (v) corrode surfaces. The effects of the current strategies for disinfection of drinking water systems in large buildings (chlorination, copper and silver ionization, and hyper-heating) were compared with a new generation of bismuth thiol (BT) biocides. Methods and Results: Multispecies biofilms were treated with 0·8 mg l,1 of free chlorine, 400 and 40 ,g l,1 of copper and silver ions, respectively, at 55 and 70°C, and bismuth-2,3-dimercaptopropanol (BisBAL). Furthermore, the effect of combined heat and BisBAL on planktonic cell viability was examined in monoculture using Escherichia coli suspensions. Inactivation rates for BisBAL were similar to copper,silver ions, where the effects were slower than for free chlorine or temperature. The BisBAL effect on E. coli monocultures was augmented greatly by increasing temperatures. Conclusions: Like copper,silver ions, BTs show more persistent residual effects than chlorine and hyper-heating in water systems. BT efficiency increased with temperature. Like copper,silver ions, BT action is relatively slow. Significance and Impact of the Study: BT presents a new approach to containing water biofilms. BT action is not as rapid, but is more thorough than chlorine, and less caustic. BTs may also be more efficacious in hot water systems. At sub-minimum inhibition concentration levels, BTs uniquely inhibit bacterial exopolysaccharide, thereby retarding biofilm formation. Thus, the combination of bactericidal and residual effects may prevent slime build-up in hot water systems. [source]

Kinetic behaviour of the adsorption and photocatalytic degradation of salicylic acid in aqueous TiO2 microsphere suspension

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2004
XZ Li
Abstract A new photocatalyst, named TiO2 microspheres, prepared by a sol-spraying-calcination method, can freely suspend with air bubbling in its aqueous suspension and easily settle down from a water phase under gravity. The experimental results demonstrated that TiO2 microspheres had better adsorption capacity than conventional TiO2 powders, due to large surface area, large pore volume, and also a porous structure. The photocatalytic activity of TiO2 microspheres in aqueous suspension was evaluated using salicylic acid (SA) as a model substrate. It was found that the Langmuir,Hinshelwood model in its integral form described the kinetics of SA photocatalytic degradation in the TiO2 microsphere suspensions better than its simplified form as a first-order reaction model, since the significant substrate adsorption on the catalysts was not negligible. The kinetics of SA photocatalytic degradation with different initial concentrations and pH was further investigated. The experiments demonstrated that the change of pH could significantly affect the adsorption of SA in the TiO2 microsphere suspensions. The effects of substrate adsorption rate and photoreaction rate on the overall performance of photocatalytic degradation is also discussed on the basis of experimental data. Copyright © 2004 Society of Chemical Industry [source]

Preparation of polymer-supported polyethylene glycol and phase-transfer catalytic activity in benzoate synthesis

AICHE JOURNAL, Issue 3 2010
Baojiao Gao
Abstract The crosslinked polymeric microspheres (GMA/MMA) of glycyl methacrylate (GMA) and methyl methacrylate (MMA) were prepared by suspension polymerization. Polyethylene glycol (PEG) was grafted on GMA/MMA microsphers via the ring-opening reaction of the epoxy groups on the surfaces of GMA/MMA microspheres, forming a polymer-supported triphase catalyst, PEG-GMA/MMA. The Phase-transfer catalytic activity of PEG-GMA/MMA microspheres was evaluated using the esterification reaction of n -chlorobutane in organic phase and benzoic acid in water phase as a model system. The effects of various factors on the phase transfer catalysis reaction of liquid,solid,liquid were investigated. The experimental results show that the PEG-GMA/MMA microspheres are an effective and stable triphase catalyst for the esterification reaction carried out between oil phase and water phase. The polarity of the organic solvent, the ratio of oil phase volume to water phase volume and the density of the grafted PEG on PEG-GMA/MMA microspheres affect the reaction rate greatly. For this investigated system, the solvent with high polarity is appropriate, an adequate volume ratio of oil phase to water phase is 2:1, and the optimal PEG density on the polymeric microspheres is 15 g/100 g. Triphase catalysts offer many advantages associated with heterogeneous catalysts such as easy separation from the reaction mixture and reusability. The activity of PEG-GMA/MMA microspheres is not nearly decreased after reusing of 10 recycles. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

A preliminary approach to modeling gas hydrate/ice deposition from dissolved water in a liquid condensate system

AICHE JOURNAL, Issue 7 2009
Joseph W. Nicholas
Abstract Gas hydrate/ice deposition from a dissolved water phase in a liquid condensate system was modeled using a mass and energy balance. The same modeling parameters were used to model three flow loop experiments (1.89 and 2.83 L/min flow rate deposition tests and a 1.89 L/min dissociation test) with acceptable accuracy. Relative changes in both temperature and pressure drop were modeled using an ice deposit with a 67% void fraction. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Synthesis of hollow crosslinked miktoarm polymer using miniemulsion as templates

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2009
De'an Xiong
Abstract Hollow crosslinked polymers (HCPs) were synthesized using arm first method via atom transfer radical polymerization. The polymerization process was performed in miniemulsion system, in which the macroinitiator, PEG-Br, was in the water phase, whereas the vinyl-monomer, 4-vinylpyridine (4VP), and the crosslinker, DVB, were in the butanone phase. TEM images and light scattering characterization showed that the resultant polymer contained a hollow space, and the volume of the hollow space could be adjusted by changing the ratio of water to butanone. Also, hollow crosslinked Miktoarm polymers (HCMPs) were synthesized through this method when two different macroinitiators, PEG-Br and PNIPAM-Br, were used to coinitiate the polymerization of the vinyl-monomer, 4VP and DVB. The 1H NMR spectra showed that the hollow polymers contained both PEG arms and PNIPAM arms. The hollow morphologies of the resultant Miktoarm polymers were the same as the HCPs. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1651,1660, 2009 [source]

Latices of poly(fluoroalkyl mathacrylate)- b -poly(butyl methacrylate) copolymers prepared via reversible addition,fragmentation chain transfer polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2007
Xiaodong Zhou
Abstract Poly(fluoroalkyl mathacrylate)- block -poly(butyl methacrylate) diblock copolymer latices were synthesized by a two-step process. In the first step, a homopolymer end-capped with a dithiobenzoyl group [poly(fluoroalkyl mathacrylate) (PFAMA) or poly(butyl methacrylate) (PBMA)] was prepared in bulk via reversible addition,fragmentation chain transfer (RAFT) polymerization with 2-cyanoprop-2-yl dithiobenzoate as a RAFT agent. In the second step, the homopolymer chain-transfer agent (macro-CTA) was dissolved in the second monomer, mixed with a water phase containing a surfactant, and then ultrasonicated to form a miniemulsion. Subsequently, the RAFT-mediated miniemulsion polymerization of the second monomer (butyl methacrylate or fluoroalkyl mathacrylate) was carried out in the presence of the first block macro-CTA. The influence of the polymerization sequence of the two kinds of monomers on the colloidal stability and molecular weight distribution was investigated. Gel permeation chromatography analyses and particle size results indicated that using the PFAMA macro-CTA as the first block was better than using the PBMA RAFT agent with respect to the colloidal stability and the narrow molecular weight distribution of the F-copolymer latices. The F-copolymers were characterized with 1H NMR, 19F NMR, and Fourier transform infrared spectroscopy. Comparing the contact angle of a water droplet on a thin film formed by the fluorinated copolymer with that of PBMA, we found that for the diblock copolymers containing a fluorinated block, the surface energy decreased greatly, and the hydrophobicity increased. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 471,484, 2007 [source]

Interfacial living radical copolymerization of oil- and water-soluble comonomers to form composite polymer capsules

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2006
Mir Mukkaram Ali
Abstract The suspension copolymerization of methyl methacrylate with hydroxy-functional poly(ethylene glycol) monomethacrylate (PEGMA) by atom transfer radical polymerization (ATRP) yielded soluble, controlled-molecular-weight amphiphilic copolymers (weight-average molecular weight/number-average molecular weight <1.3). Despite extensive partitioning of PEGMA into the water phase, copolymers containing up to 24 mol % PEGMA were formed in the oil phase, from comonomer feeds containing 30 mol % PEGMA. Conversions by suspension polymerization were comparable to those obtained by solution polymerization, at over 70%. Suspension copolymers with high PEGMA contents contained high-molecular-weight polymer formed by uncontrolled polymerization, unless poly(vinyl pyrrolidone) was added to displace the growing polymer from the interface. The addition of diethylene glycol dimethacrylate gave capsules at 17 mol % PEGMA with ATRP, whereas conventional free-radical polymerization required 24 mol % PEGMA to form capsules. The lower PEGMA level required for capsule formation with ATRP was attributed to the lower rates of propagation and crosslinking and to improved incorporation of PEGMA into the final gels. Suspension ATRP with 24 mol % PEGMA in the feed gave two-layer capsule walls consisting of an inner layer visible by transmission electron microscopy and an outer layer visible by both transmission electron microscopy and environmental scanning electron microscopy, which indicated a compositional gradient across the capsule wall. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 156,171, 2006 [source]

Restoration of Lake Geneva: Expected versus observed responses of phytoplankton to decreases in phosphorus

LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 2 2002
Orlane Anneville
Abstract Long-term phytoplankton responses in Lake Geneva to a decline in phosphorus (P) loading are examined in terms of summer (July,September) biomass and community structure. With the rapid development of human activity on its banks and within its catchment area in the 1960s, this large subalpine hydrosystem shifted from oligotrophy to eutrophy within approximately one decade. Measures to reduce P loading were initiated successfully in the mid-1970s, when total P concentrations in the winter overturn altered from 90 ,g/L in 1980 to 40 ,g/L in 1998. Until the 1990s, algal descriptors improved as expected (biomass decline, reappearance of diatom species, increased contribution of nanoplankton). Then, paradoxically, and in contrast to the reappearance of oligotrophic species, summer algal biomass began to increase. Pre-summer (period prior to the beginning of the clear water phase) dissolved inorganic phosphorus concentrations and summer phytoplankton composition presented similar interannual trends. However, the succession of phytoplankton structure during the reoligotrophication phase differed greatly from that during the eutrophication period, and a recent abnormal upward trend in algal densities is mainly the result of the development of large species that formerly were only common from late September until November. This community change, mainly triggered by filamentous (Mougeotia gracillima, Tribonema) or motile forms (Dinobryon sociale, Cryptophycea), seems to have been induced by the earlier and greater deepening of the P-depleted layer. In addition to milder summers, this massive development of larger forms seems to be favoured by four of their biological features: tolerance to warm temperatures, tolerance to low-light intensity (might exploit deeper layers where P is not yet limiting), shapes not only providing a large surface to volume ratio or motility (adaptation to low-nutrient concentrations), but increasing resistance to zooplankton grazing. This paradoxical trend, perhaps reinforced by the decline on roach Rutilus rutilus abundance (an opportunistic planktivore), is likely to remain until the P-depleted zone is extended below the layers that can be frequently resupplied in nutrients by hydrodynamic processes. [source]

A facile approach to surface graft vinyl acetate onto polyolefin articles

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2004
Lin Tan
Abstract A facile and environment friendly approach was developed to graft vinyl acetate (VAc) onto plastic articles in an aqueous solution using tert -butyl alcohol (TBA) as a compatiblizer and benzoyl peroxide (BPO) as an initiator. In a novel setup, excessive monomer suspended in a water phase, VAc could be conveniently grafted on the model substrate of low-density polyethylene (LDPE) film and the graft percentage (GP) could be developed up to 7.3%. Reaction temperature could increase GP significantly, while adding monomer over a critical volume did not influence GP. By adding some paradioxybenzene, i.e. 0.06,0.08% in VAc phase, homopolymer PVAc could be avoided practically, while graft polymerization proceeded favorably in aqueous solutions. It was proved by attenuated total reflection-infrared (ATR-IR) spectroscopy that grafted VAc was located mainly at the surface of the LDPE film and hydrophilic nature of both grafted and alcoholyzed films were improved via contact angle measurements. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Charge generation during filling of insulated tanks

PROCESS SAFETY PROGRESS, Issue 3 2002
Migvia Vidal
This research involves charge generation measurements for various flammable fluids during filling of insulated tanks and relating static charging with flow rate and physicochemical parameters, especially changes in electrical conductivity. The objective is to correlate static charge measured inside baffled metal and polyethylene tanks as a function of impeller, Reynolds number, and the electrical conductivity of both the hydrocarbon and the dispersed water phase for a variety of flammable liquids. A product of the research is a correlation for polyethylene and other plastic insulated tanks for transfers of low conductivity liquid fuels. Also, a universal (dimensionless) correlation that relates the charging data to the colloidal nature of the mixture will be developed for static charge generation during impeller mixing of light hydrocarbons containing various concentrations of water in cylindrical tanks. The correlation of electrostatic data from this research will help make it possible to control electrostatic charges, and, as a result, greatly improve safety of operations involving flammable fluids in industry. [source]

Partitioning and Characterization of Tyrosine-Tagged Green Fluorescent Proteins in Aqueous Two-Phase Systems

BIOTECHNOLOGY PROGRESS, Issue 3 2004
Sara Fexby
The green fluorescent protein GFPuv has been genetically engineered to investigate the influence of N-terminal tyrosine extensions in aqueous two-phase systems. Fusions in the N-terminus affected the protein expression, and tags containing three tyrosines and prolines influenced the expression favorably. This effect is probably due to changes in mRNA stability, because the amounts of corresponding mRNAs correlated with the amounts of GFPuv proteins. The partitioning was investigated in two different aqueous two-phase systems, a two-polymer system composed of EO30PO70/dextran and a PEG/salt system with potassium phosphate. Partitioning in the PEG/salt system generally was more favorable than in the EO30PO70/dextran system. Tags with three tyrosines resulted in higher partitioning toward the EO30PO70- and PEG-rich phases, respectively. The effect of adding proline residues to the tag was also investigated, and the partitioning effect of the tag was enhanced when prolines were included in the tags with three tyrosines. The best tyrosine tag, Y3P2, increased the partition coefficient 5 times in the PEG/salt system. Thermoseparation of the EO30PO70 phase allowed recovery of 83% Y3P2-GFPuv protein in a water phase. [source]

Water Accessibility to the Binding Cleft as a Major Switching Factor from Entropy-Driven to Enthalpy-Driven Binding of an Alkyl Group by Synthetic Receptors

CHEMISTRY - AN ASIAN JOURNAL, Issue 5 2010
Sayaka Matsumoto
Abstract Free energy, enthalpy, and entropy changes in the binding of alkyl pyridines to water-soluble zinc porphyrin receptors with varying accessibility of water to the binding cleft were determined to explain why the driving force of hydrophobic effects is enthalpic in some occasions and entropic in others. Zinc porphyrins bearing four alkyl pillars with terminal solubilizing poly(oxyethylene) (POE) chains of molecular weight of 750 (1), with eight alkyl pillars with terminal solubilizing POE chains of molecular weight of 350 (3), and with eight alkyl pillars with POE of molecular weight of 750 (4) had a binding cleft with decreasing water accessibility in this order as revealed by binding selectivity of imidazole/pyridine. Although all these porphyrins showed that the free energy of binding (,,Go) increases linearly as the alkyl group of the guest is lengthened (,,Go per CH2 was 2.6, 2.8, and 2.6,kJ,mol,1 for 1, 3, and 4, respectively), the origin of the free energy gain was much different. Receptor 1 with the most hydrophilic binding site bound the alkyl group by an enthalpic driving force (4-pentylpyridine favored over 4-methylpyridine by ,,Ho=,16.4,kJ,mol,1), while receptor 4 with the most hydrophobic binding site by an entropic driving force (4-pentylpyridine favored over 4-methylpyridine by ,,So=39.6,J,K,1,mol,1). Receptor 3 showed intermediate behavior: both enthalpic and entropic terms drove the binding of the alkyl group with the enthalpic driving force being dominant. The binding site of the four-pillared receptor (1) is open and accessible to water molecules, and is more hydrophilic than that of the eight-pillared receptor (4). We propose that the alkyl chains of 1 are exposed to water to produce a room to accommodate the guest to result in enthalpy-driven hydrophobic binding, whereas 4 can accommodate the guest without such structural changes to lead to entropy-driven hydrophobic binding. Therefore, accessibility of water or exposure of the binding site to the water phase switches the driving force of hydrophobic effects from an entropic force to an enthalpic force. [source]