A new type of polymeric heavy metal complexing precipitant used as fishery disinfectant and antiparasitic drug

NASA Astrophysics Data System (ADS)

Liu, Y. C.; Zhang, A. N.; Wang, X. B.; Xu, J.; Zeng, X. H.; Wang, H. M.

2017-08-01

This paper presents a technique to produce a new kind of fishery drug that is water emulsion suspending agent containing polymeric calcium-iron-dithiocarbamate with heavy metal complexing precipitate ability, good disinfection and auxiliary insecticidal efficacy. The product has good dispersion, high efficiency and low toxicity, as well as no pollution and no harmful residues. It not only can be used in the pond waters and ornamental waters, but also can meet the high requirements of the aquaculture waters. There is non-pollutant emission in the production, which is a green environment-friendly technique without three waste discharges. This technology belongs to the ecological and environmental protection.

Metal chelation dual-template epitope imprinting polymer via distillation-precipitation polymerization for recognition of porcine serum albumin.

PubMed

Qin, Ya-Ping; Wang, Hai-Yan; He, Xi-Wen; Li, Wen-You; Zhang, Yu-Kui

2018-08-01

A novel dual-template epitope imprinting polymer coated on magnetic carbon nanotubes (MCNTs@D-EMIP) was successfully prepared for specific recognition of porcine serum albumin (PSA) via dual-template epitope imprinting, metal chelation imprinting and distillation-precipitation polymerization (DPP). C-terminal peptides and N-terminal peptides of PSA were selected as templates simultaneously, and zinc acrylate and ethylene glycol dimethacrylate (EGDMA) were used as functional monomer and cross-linker, respectively. The epitope templates were immobilized by metal chelation and six-membered ring formed with zinc acrylate. Finally, MCNTs@D-EMIP was synthesized by DPP in only 30 min, which was much shorter than those of other polymerization methods. The prepared MCNTs@D-EMIP displayed specific recognition ability toward PSA and its adsorption amount and imprinting factor were 45.05 mg g -1 and 4.50, which were much higher than those of single template epitope imprinting polymers. Besides, high-performance liquid chromatography (HPLC) analysis of PSA in porcine blood serum real sample indicated that the specificity was not affected by other competitive proteins, which forcefully stated that the MCNTs@D-EMIP had potential to be applied in bio-separation area. In addition, the results of cross-reactivity experiment proved that this strategy had generality to prepare dual-template epitope imprinting polymer for recognition of target protein. In summary, this study provided an efficient protocol to recognize target protein in complex sample via dual-template epitope imprinting approach, metal chelation imprinting and distillation-precipitation polymerization. Copyright © 2018 Elsevier B.V. All rights reserved.

Protein precipitation behavior of condensed tannins from Lotus pedunculatus and Trifolium repens with different mean degrees of polymerization

USDA-ARS?s Scientific Manuscript database

The precipitation of bovine serum albumin (BSA), lysozyme (LYS), and alfalfa leaf protein (ALF) by two large- and two medium-sized condensed tannin (CT) fractions of similar flavan-3-ol subunit composition is described. CT fractions isolated from white clover flowers and big trefoil leaves exhibited...

Supercritical antisolvent co-precipitation of rifampicin and ethyl cellulose.

PubMed

Djerafi, Rania; Swanepoel, Andri; Crampon, Christelle; Kalombo, Lonji; Labuschagne, Philip; Badens, Elisabeth; Masmoudi, Yasmine

2017-05-01

Rifampicin-loaded submicron-sized particles were prepared through supercritical anti-solvent process using ethyl cellulose as polymeric encapsulating excipient. Ethyl acetate and a mixture of ethyl acetate/dimethyl sulfoxide (70/30 and 85/15) were used as solvents for both drug and polymeric excipient. When ethyl acetate was used, rifampicin was crystallized separately without being embedded within the ethyl cellulose matrix while by using the ethyl acetate/dimethyl sulfoxide mixture, reduced crystallinity of the active ingredient was observed and a simultaneous precipitation of ethyl cellulose and drug was achieved. The effect of solvent/CO 2 molar ratio and polymer/drug mass ratio on the co-precipitates morphology and drug loading was investigated. Using the solvent mixture, co-precipitates with particle sizes ranging between 190 and 230nm were obtained with drug loading and drug precipitation yield from respectively 8.5 to 38.5 and 42.4 to 77.2% when decreasing the ethyl cellulose/rifampicin ratio. Results show that the solvent nature and the initial drug concentrations affect morphology and drug precipitation yield of the formulations. In vitro dissolution studies revealed that the release profile of rifampicin was sustained when co-precipitation was carried out with the solvent mixture. It was demonstrated that the drug to polymer ratio influenced amorphous content of the SAS co-precipitates. Differential scanning calorimetry thermograms and infrared spectra revealed that there is neither interaction between rifampicin and the polymer nor degradation of rifampicin during co-precipitation. In addition, stability stress tests on SAS co-precipitates were carried out at 75% relative humidity and room temperature in order to evaluate their physical stability. SAS co-precipitates were X-ray amorphous and remained stable after 6months of storage. The SAS co-precipitation process using a mixture of ethyl acetate/dimethyl sulfoxide demonstrates that this strategy can be successful for controlling rifampicin delivery. Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of polymer coating morphology on microsensor response

NASA Astrophysics Data System (ADS)

Levit, Natalia; Pestov, Dmitry; Tepper, Gary C.

2004-03-01

Nanoscale polymeric coatings are used in a variety of sensor systems. The influence of polymer coating morphology on sensor response was investigated and it was determined that coating morphology plays a particularly important role in transducers based on optical or acoustic resonance such as surface acoustic wave (SAW) or surface plasmon resonance (SPR) devices. Nanoscale polymeric coatings were deposited onto a number of miniature devices using a "solvent-free" deposition technique known as Rapid Expansion of Supercritical Solutions (RESS). In RESS, the supercritical solvent goes into the vapor phase upon fast depressurization and separates from the polymer. Therefore, dry polymer particles are deposited from the gas phase. The average diameter of RESS precipitates is about two orders of magnitude smaller than the minimum droplet size achievable by the air-brush method. For rubbery polymers, such as PIB and PDMS, the nanoscale solute droplets produced by RESS agglomerate on the surface forming a highly-uniform continuous nanoscale film. For glassy and crstalline polymers, the RESS droplets produce uniform particulate coatings exhibiting high surface-to-volume ratio. The coating morphology can be changed by controlling the RESS processing conditions.

21 CFR 177.2250 - Filters, microporous polymeric.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Filters, microporous polymeric. 177.2250 Section... Repeated Use § 177.2250 Filters, microporous polymeric. Microporous polymeric filters identified in... liquid food. (a) Microporous polymeric filters consist of a suitably permeable, continuous, polymeric...

Preparation of monodisperse curcumin-imprinted polymer by precipitation polymerization and its application for the extraction of curcuminoids from Curcuma longa L.

PubMed

Kitabatake, Tomoko; Tabo, Hiromi; Matsunaga, Hisami; Haginaka, Jun

2013-08-01

A monodisperse molecularly imprinted polymer (MIP) for curcumin was first prepared by precipitation polymerization using methacrylamide (MAM) and 4-vinylpyridine as functional co-monomers, divinylbenzene as a crosslinker, and a mixture of acetonitrile and toluene as a porogen. The use of MAM as the co-monomer resulted in the formation of a monodisperse MIP and non-imprinted polymer (NIP). MIP and NIP, respectively, were monodispersed with a narrow particle size distribution (3.3 ± 0.09 and 3.5 ± 0.10 μm). In addition to shape recognition, hydrophobic and hydrogen-bonding interactions affected the retention and molecular-recognition of curcumin on the MIP. The MIP for curcumin could extract curcuminoids (curcumin, demethoxycurcumin, and bisdemethoxycurcumin) in Curcuma longa L.

2DCOS and PCMW2D analysis of FT-IR/ATR spectra measured at variable temperatures on-line to a polyurethane polymerization

NASA Astrophysics Data System (ADS)

Schuchardt, Patrick; Unger, Miriam; Siesler, Heinz W.

2018-01-01

In the present communication the potential of 2DCOS analysis and the spin-off technique perturbation-correlation moving window 2D (PCMW2D) analysis is illustrated with reference to spectroscopic changes observed in a data set recorded by in-line fiber-coupled FT-IR spectroscopy in the attenuated total reflection (ATR) mode during a polyurethane solution polymerization at different temperatures. In view of the chemical functionalities involved, hydrogen bonding plays an important role in this polymerization reaction. Based on the 2DCOS and PCMW2D analysis, the sequence of hydrogen bonding changes accompanying the progress of polymerization and precipitation of solid polymer can be determined. Complementary to the kinetic data derived from the original variable-temperature spectra in a previous publication the results provide a more detailed picture of the investigated solution polymerization.

A preliminary characterization of Aglianico (Vitis vinifera L. cv.) grape proanthocyanidins and evaluation of their reactivity towards salivary proteins.

PubMed

Rinaldi, A; Jourdes, M; Teissedre, P L; Moio, L

2014-12-01

The flavan-3-ol and proanthocyanidin composition of Aglianico seeds and skins were for the first time determined by HPLC-MS in comparison with the international grapes Merlot and Cabernet Sauvignon. Monomers [(+)-catechin C, (-)-epicatechin EC, (-)-epicatechin-3-O-gallate, ECG] and oligomers [B1, B2, B3, B4 dimers and trimer C1] were identified and quantified in grape extracts. In order to evaluate the reactivity towards salivary proteins of model wine solutions of seeds and skins monomeric/oligomeric and polymeric fractions, the Saliva Precipitation Index (SPI) was carried out. Fractions were also analyzed for their mean degree of polymerization (mDP), percentage of galloylation (%G) and of prodelphinidin (%P) by phloroglucinolysis. Aglianico was the most effective in precipitating proteins than Merlot and Cabernet Sauvignon, mainly for the high percentage of galloylation of grape fractions. The mDP and the percentage of ECG in terminal units resulted to significantly contribute to the precipitation of salivary proteins by grape proanthocyanidins. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dielectric loss property of strong acids doped polyaniline (PANi)

NASA Astrophysics Data System (ADS)

Amalia, Rianti; Hafizah, Mas Ayu Elita; Andreas, Manaf, Azwar

2018-04-01

In this study, strong acid doped polyaniline (PANi) has been successfully fabricated through the chemical oxidative polymerization process with various polymerization times. Nonconducting PANi resulting from the polymerization process at various polymerization times were then doped by a strong acid HClO4 to generate dielectric properties. Ammonium Persulfate (APS) as an initiator was used during Polymerization process to develop dark green precipitates which then called Emeraldine Base Polyaniline (PANi-EB). The PANi-EB was successively doped by strong acid HClO4 with dopant and PANi ratio 10:1 to enhance the electrical conductivity. The conductivity of doped PANi was evaluated by Four Point Probe. Results of evaluation showed that the conductivity values of HClO4 doped PANi were in the range 337-363 mS/cm. The dielectric properties of doped PANi were evaluated by Vector Network Analyzer (VNA) which suggested that an increase in the permittivity value in the conducting PANi. It is concluded that PANi could be a potential candidate for electromagnetic waves absorbing materials.

Novel, one-step synthesis of zwitterionic polymer nanoparticles via distillation-precipitation polymerization and its application for dye removal membrane.

PubMed

Ibrahim, G P Syed; Isloor, Arun M; Inamuddin; Asiri, Abdullah M; Ismail, Norafiqah; Ismail, Ahmed Fauzi; Ashraf, Ghulam Md

2017-11-21

In this work, poly(MBAAm-co-SBMA) zwitterionic polymer nanoparticles were synthesized in one-step via distillation-precipitation polymerization (DPP) and were characterized. [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA) as monomer and N, N'-methylene bis(acrylamide) (MBAAm) as cross-linker are used for the synthesis of nanoparticles. As  far as our knowledge, this is the first such report on the synthesis of poly(MBAAm-co-SBMA) nanoparticles via DPP. The newly synthesized nanoparticles were further employed for the surface modification of polysulfone (PSF) hollow fiber membranes for dye removal. The modified hollow fiber membrane exhibited the improved permeability (56 L/ m 2 h bar) and dye removal (>98% of Reactive Black 5 and >80.7% of Reactive orange 16) with the high permeation of salts. Therefore, the as-prepared membrane can have potential application in textile and industrial wastewater treatment.

Surface properties of poly(acrylonitrile) (PAN) precipitation polymerized in supercritical CO2 and the influence of the molecular weight.

PubMed

Shen, Qing; Gu, Qing-Feng; Hu, Jian-Feng; Teng, Xin-Rong; Zhu, Yun-Feng

2003-11-15

In this paper, the surface properties, e.g., the total surface free energy and the related Lifshitz-van der Waals and Lewis acid-base components, of polyacrylonitrile (PAN) precipitation polymerized in supercritical CO(2) have been characterized. Moreover, the influence of molecular weight varying has been also investigated. Results show that the surface properties of PAN resulting from supercritical CO(2) are different from those obtained by the conventional method. Of these data, one important finding is that the supercritical CO(2) PAN seems to decrease the surface free energy with the increased molecular weight. Based on previous recorded NMR spectra of this PAN and especially compared to commercial PAN, such phenomena are discussed and ascribed to an increase of the H-bonds and a reduction of the isotacticity in the supercritical CO(2) condition for PAN.

Experimental mixture design as a tool for the synthesis of antimicrobial selective molecularly imprinted monodisperse microbeads.

PubMed

Benito-Peña, Elena; Navarro-Villoslada, Fernando; Carrasco, Sergio; Jockusch, Steffen; Ottaviani, M Francesca; Moreno-Bondi, Maria C

2015-05-27

The effect of the cross-linker on the shape and size of molecular imprinted polymer (MIP) beads prepared by precipitation polymerization has been evaluated using a chemometric approach. Molecularly imprinted microspheres for the selective recognition of fluoroquinolone antimicrobials were prepared in a one-step precipitation polymerization procedure using enrofloxacin (ENR) as the template molecule, methacrylic acid as functional monomer, 2-hydroxyethyl methacrylate as hydrophilic comonomer, and acetonitrile as the porogen. The type and amount of cross-linker, namely ethylene glycol dimethacrylate, divinylbenzene or trimethylolpropane trimethacrylate, to obtain monodispersed MIP spherical beads in the micrometer range was optimized using a simplex lattice design. Particle size and morphology were assessed by scanning electron microscopy, dynamic light scattering, and nitrogen adsorption measurements. Electron paramagnetic resonance spectroscopy in conjunction with a nitroxide as spin probe revealed information about the microviscosity and polarity of the binding sites in imprinted and nonimprinted polymer beads.

Liquid-liquid two phase systems for the production of porous hydrogels and hydrogel microspheres for biomedical applications: A tutorial review

PubMed Central

Elbert, Donald L.

2010-01-01

Macroporous hydrogels may have direct applications in regenerative medicine as scaffolds to support tissue formation. Hydrogel microspheres may be used as drug delivery vehicles or as building blocks to assemble modular scaffolds. A variety of techniques exist to produce macroporous hydrogels and hydrogel microspheres. A subset of these relies on liquid-liquid two phase systems. Within this subset, vastly different types of polymerization processes are found. In this review, the history, terminology and classification of liquid-liquid two phase polymerization and crosslinking are described. Instructive examples of hydrogel microsphere and macroporous scaffold formation by precipitation/dispersion, emulsion and suspension polymerizations are used to illustrate the nature of these processes. The role of the kinetics of phase separation in determining the morphology of scaffolds and microspheres is also delineated. Brief descriptions of miniemulsion, microemulsion polymerization and ionotropic gelation are also included. PMID:20659596

Potentiality of a ceramic membrane reactor for the laccase-catalyzed removal of bisphenol A from secondary effluents.

PubMed

Arca-Ramos, A; Eibes, G; Feijoo, G; Lema, J M; Moreira, M T

2015-11-01

In this study, the removal of bisphenol A (BPA) by laccase in a continuous enzymatic membrane reactor (EMR) was investigated. The effects of key parameters, namely, type of laccase, pH, and enzyme activity, were initially evaluated. Once optimal conditions were determined, the continuous removal of the pollutant in an EMR was assessed in synthetic and real biologically treated wastewaters. The reactor configuration consisted of a stirred tank reactor coupled to a ceramic membrane, which prevented the sorption of the pollutant and allowed the recovery and recycling of laccase. Nearly complete removal of BPA was attained under both operation regimes with removal yields above 94.5 %. In experiments with real wastewater, the removal of BPA remained high while the presence of colloids and certain ions and the formation of precipitates on the membrane potentially affected enzyme stability and made necessary the periodic addition of laccase. Polymerization and degradation were observed as probable mechanisms of BPA transformation by laccase.

Bioactive Polymeric Nanoparticles for Periodontal Therapy

PubMed Central

Alfonso-Rodríguez, Camilo Andrés; Medina-Castillo, Antonio L.; Alaminos, Miguel; Toledano, Manuel

2016-01-01

Aims to design calcium and zinc-loaded bioactive and cytocompatible nanoparticles for the treatment of periodontal disease. Methods PolymP-nActive nanoparticles were zinc or calcium loaded. Biomimetic calcium phosphate precipitation on polymeric particles was assessed after 7 days immersion in simulated body fluid, by scanning electron microscopy attached to an energy dispersive analysis system. Amorphous mineral deposition was probed by X-ray diffraction. Cell viability analysis was performed using oral mucosa fibroblasts by: 1) quantifying the liberated deoxyribonucleic acid from dead cells, 2) detecting the amount of lactate dehydrogenase enzyme released by cells with damaged membranes, and 3) by examining the cytoplasmic esterase function and cell membranes integrity with a fluorescence-based method using the Live/Dead commercial kit. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests. Results Precipitation of calcium and phosphate on the nanoparticles surfaces was observed in calcium-loaded nanoparticles. Non-loaded nanoparticles were found to be non-toxic in all the assays, calcium and zinc-loaded particles presented a dose dependent but very low cytotoxic effect. Conclusions The ability of calcium-loaded nanoparticles to promote precipitation of calcium phosphate deposits, together with their observed non-toxicity may offer new strategies for periodontal disease treatment. PMID:27820866

A High-Performance Recycling Solution for Polystyrene Achieved by the Synthesis of Renewable Poly(thioether) Networks Derived from d-Limonene

PubMed Central

Nash, Landon D.; Rodriguez, Jennifer N.; Lonnecker, Alexander T.; Raymond, Jeffery E.; Wilson, Thomas S.; Wooley, Karen L.; Maitland, Duncan J.

2014-01-01

Nanocomposite polymers have been prepared using a new sustainable materials synthesis process in which d-Limonene functions simultaneously both as a solvent for recycling polystyrene (PS) waste and as a monomer that undergoes UV-catalyzed thiol-ene polymerization reactions with polythiol co-monomers to afford polymeric products comprised of precipitated PS phases dispersed throughout elastomeric poly(thioether) networks. These blended networks exhibit mechanical properties that greatly exceed those of either polystyrene or the poly(thioether) network homopolymers alone. PMID:24249666

A microtitre-based method for measuring the haem polymerization inhibitory activity (HPIA) of antimalarial drugs.

PubMed

Basilico, N; Pagani, E; Monti, D; Olliaro, P; Taramelli, D

1998-07-01

The malaria parasite metabolizes haemoglobin and detoxifies the resulting haem by polymerizing it to form haemozoin (malaria pigment). A polymer identical to haemozoin, beta-haematin, can be obtained in vitro from haematin at acidic pH. Quinoline-containing anti-malarials (e.g. chloroquine) inhibit the formation of either polymer. Haem polymerization is an essential and unique pharmacological target. To identify molecules with haem polymerization inhibitory activity (HPIA) and quantify their potency, we developed a simple, inexpensive, quantitative in-vitro spectrophotometric microassay of haem polymerization. The assay uses 96-well U-bottomed polystyrene microplates and requires 24 h and a microplate reader. The relative amounts of polymerized and unpolymerized haematin are determined, based on solubility in DMSO, by measuring absorbance at 405 nm in the presence of test compounds as compared with untreated controls. The final product (a solid precipitate of polymerized haematin) was validated using infrared spectroscopy and the assay proved reproducible; in this assay, activity could be partly predicted based on the compound's chemical structure. Both water-soluble and water-insoluble compounds can be quantified by this method. Although the throughput of this assay is lower than that of radiometric methods, the assay is easier to set up and cheaper, and avoids the problems related to radioactive waste disposal.

Production methodologies of polymeric and hydrogel particles for drug delivery applications.

PubMed

Lima, Ana Catarina; Sher, Praveen; Mano, João F

2012-02-01

Polymeric particles are ideal vehicles for controlled delivery applications due to their ability to encapsulate a variety of substances, namely low- and high-molecular mass therapeutics, antigens or DNA. Micro and nano scale spherical materials have been developed as carriers for therapies, using appropriated methodologies, in order to achieve a prolonged and controlled drug administration. This paper reviews the methodologies used for the production of polymeric micro/nanoparticles. Emulsions, phase separation, spray drying, ionic gelation, polyelectrolyte complexation and supercritical fluids precipitation are all widely used processes for polymeric micro/nanoencapsulation. This paper also discusses the recent developments and patents reported in this field. Other less conventional methodologies are also described, such as the use of superhydrophobic substrates to produce hydrogel and polymeric particulate biomaterials. Polymeric drug delivery systems have gained increased importance due to the need for improving the efficiency and versatility of existing therapies. This allows the development of innovative concepts that could create more efficient systems, which in turn may address many healthcare needs worldwide. The existing methods to produce polymeric release systems have some critical drawbacks, which compromise the efficiency of these techniques. Improvements and development of new methodologies could be achieved by using multidisciplinary approaches and tools taken from other subjects, including nanotechnologies, biomimetics, tissue engineering, polymer science or microfluidics.

Reactivity of polymeric proanthocyanidins toward salivary proteins and their contribution to young red wine astringency.

PubMed

Sun, Baoshan; de Sá, Marta; Leandro, Conceição; Caldeira, Ilda; Duarte, Filomena L; Spranger, Isabel

2013-01-30

Recent studies have indicated the presence of significant amount of highly polymerized and soluble proanthocyanidins in red wine and such compounds interacted readily with proteins, suggesting that they might be particularly astringent. Thus, the objective of this work was to verify the astringency of polymeric proanthocyanidins and their contribution to red wine astringency. The precipitation reactions of the purified oligomeric procyanidins (degree of polymerization ranging from 2 to 12-15) and polymeric procyanidins (degree of polymerization ranging from 12-15 to 32-34) with human salivary proteins were studied; salivary proteins composition changes before and after the reaction was verified by SDS-PAGE and procyanidins composition changes by spectrometric, direct HPLC and thiolysis-HPLC methods. The astringency intensity of these two procyanidin fractions was evaluated by a sensory analysis panel. For verifying the correlation between polymeric proanthocyanidins and young red wine astringency, the levels of total oligomeric and total polymeric proanthocyanidins and other phenolic composition in various young red wines were quantified and the astringency intensities of these wines were evaluated by a sensory panel. The results showed that polymeric proanthocyanidins had much higher reactivity toward human salivary proteins and higher astringency intensity than the oligomeric ones. Furthermore, young red wine astringency intensities were highly correlated to levels of polymeric proanthocyanidins, particularly at low concentration range (correlation coefficient r = 0.9840) but not significant correlated to total polyphenols (r = 0.2343) or other individual phenolic compounds (generally r < 0.3). These results indicate the important contribution of polymeric proanthocyanidins to red wine astringency and the levels of polymeric polyphenols in red wines may be used as an indicator for its astringency.

Nouvelles morphologies de fibres electrofilees de polymere thermosensible =

NASA Astrophysics Data System (ADS)

Sta, Marwa

Ce memoire presente une etude sur la possibilite d'obtenir des membranes a base de polymeres thermosensibles avec differentes morphologies pour des applications d'administration de medicaments. Ces membranes ont ete obtenues par electrofilage du Poly (N vinylcaprolactame) (PNVCL), un polymere thermosensible, soit seul ou en melange avec du Polycaprolactone (PCL), un polymere biodegradable. Les parametres de procede ainsi que les proprietes de la solution a electrofiler ont ete optimises dans le but de creer des fibres de PNVCL lisses, continues et sans perles. Des solutions du melange (PNVCL) / (PCL) ont ete ensuite preparees en suivant quatre methodes differentes de preparation. Ces methodes se basent sur l'emploi de solvants distincts, eau distillee et chloroforme, avec differentes concentrations de polymere, 42wt% et 30wt% respectivement. Ces solutions ont ete electrofilees en utilisant les parametres de procede qui correspondaient aux meilleures conditions pour l'electrofilage du PNVCL. Ensuite, le ketophofene, un medicament hydrophobe, a ete ajoute au PNVCL et au melange PNVCL/PCL avant l'electrofilage afin d'etudier la capacite des fibres de PNVCL et de melanges de retenir le medicament hydrophobe et a en faire sa liberation. Enfin, des fibres noyau-enveloppes ont ete obtenues par electrofilage coaxial, en utilisant une solution aqueuse du melange PNVCL/PCL (42 wt%) pour l'enveloppe et une solution aqueuse du PEG (30 wt%) pour le noyau. Les morphologies des membranes resultantes et de leurs fibres ont ete caracterisees par microscopie electronique a balayage (MEB). La temperature de solution critique inferieure (LCST) de ces fibres, qui est la temperature en dessous de laquelle le polymere est soluble dans l'eau et au-dessus duquel il precipite, a ete evaluee par calorimetrie differentielle a balayage (DSC). L'efficacite d'encapsulation (EE) et la liberation du medicament ont ete evaluees en utilisant la technique de spectrophotometrie UV-visible. Des coupes transversales des fibres du melange (PNVCL) / (PCL) et des fibres preparees par electrofilage coaxial ont ete caracterisees par microscopie electronique a balayage (MEB) a haute resolution dans le but de determiner la taille des particules de PCL a l'interieur des fibres et de visualiser la morphologie noyau/enveloppe des fibres resultantes. Une membrane a nanofibres lisses et continues a ete obtenue par l'optimisation de l'electrofilage de PNVCL. L'addition de PCL au melange a conduit a un controle de la LCST et de l'hydrophobicite de la membrane. Il a egalement ete demontre que la liberation de medicament hydrophobe peut etre controlee par la morphologie de ce melange PCL/PNVCL. Finalement, il a ete possible de fabriquer des fibres noyau-enveloppe par l'electrofilage coaxial de PNVCL.

Synthesis of thermo-responsive bovine hemoglobin imprinted nanoparticles by combining ionic liquid immobilization with aqueous precipitation polymerization.

PubMed

Wang, Yongmei; Yang, Chongchong; Sun, Yan; Qiu, Fengtao; Xiang, Yang; Fu, Guoqi

2018-02-01

Surface molecular imprinting over functionalized nanoparticles has proved to be an effective approach for construction of artificial nanomaterials for protein recognition. Herein, we report a strategy for synthesis of core-shell protein-imprinted nanoparticles by the functionalization of nano-cores with ionic liquids followed by aqueous precipitation polymerization to build thermo-responsive imprinted polymer nano-shells. The immobilized ionic liquids can form multiple interactions with the protein template. The polymerization process can produce thermo-reversible physical crosslinks, which are advantageous to enhancing imprinting and facilitating template removal. With bovine hemoglobin as a model template, the imprinted nanoparticles showed temperature-sensitivity in both dispersion behaviors and rebinding capacities. Compared with the ionic-liquid-modified core nanoparticles, the imprinted particles exhibited greatly increased selectivity and two orders of magnitude higher binding affinity for the template protein. The imprinted nanoparticles achieved relatively high imprinting factor up to 5.0 and specific rebinding capacity of 67.7 mg/g, respectively. These nanoparticles also demonstrated rapid rebinding kinetics and good reproducibility after five cycles of adsorption-regeneration. Therefore, the presented approach may be viable for the fabrication of high-performance protein-imprinted nanoparticles with temperature sensitivity. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New tooth enamel from brushite crystals

NASA Technical Reports Server (NTRS)

Rubin, B.; Childress, J. D.

1974-01-01

Appropriate nutrient gel solution could be used to precipitate brushite, which becomes hydroxyapatite, mineral found in bones and teeth. Gel can be made from sodium metasilicate and phosphoric acid, or gelatin, or other organic materials that polymerize in presence of acid to get gelantinous medium.

40 CFR 63.482 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... operation operated in a batch mode. Block polymer means a polymer where the polymerization is controlled... frequent block average values. Continuous unit operation means a unit operation operated in a continuous... (EPM) result from the polymerization of ethylene and propylene and contain a saturated chain of the...

40 CFR 63.482 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... operation operated in a batch mode. Block polymer means a polymer where the polymerization is controlled... frequent block average values. Continuous unit operation means a unit operation operated in a continuous... (EPM) result from the polymerization of ethylene and propylene and contain a saturated chain of the...

40 CFR 63.482 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... operation operated in a batch mode. Block polymer means a polymer where the polymerization is controlled... frequent block average values. Continuous unit operation means a unit operation operated in a continuous... (EPM) result from the polymerization of ethylene and propylene and contain a saturated chain of the...

Barium bioaccumulation by bacterial biofilms and implications for Ba cycling and use of Ba proxies.

PubMed

Martinez-Ruiz, Francisca; Jroundi, Fadwa; Paytan, Adina; Guerra-Tschuschke, Isabel; Abad, María Del Mar; González-Muñoz, María Teresa

2018-04-24

Ba proxies have been broadly used to reconstruct past oceanic export production. However, the precise mechanisms underlying barite precipitation in undersaturated seawater are not known. The link between bacterial production and particulate Ba in the ocean suggests that bacteria may play a role. Here we show that under experimental conditions marine bacterial biofilms, particularly extracellular polymeric substances (EPS), are capable of bioaccumulating Ba, providing adequate conditions for barite precipitation. An amorphous P-rich phase is formed at the initial stages of Ba bioaccumulation, which evolves into barite crystals. This supports that in high productivity regions where large amounts of organic matter are subjected to bacterial degradation, the abundant EPS would serve to bind the necessary Ba and form nucleation sites leading to barite precipitation. This also provides new insights into barite precipitation and opens an exciting field to explore the role of EPS in mineral precipitation in the ocean.

Porous Ag/P/C Composite Electrodes: A New Approach for Metal Air Batteries

DTIC Science & Technology

2012-02-29

polished prior to use. Pyrrole was purified prior to use. Tetrabutylammonium hexafluorophosphate was precipitated from tetrabutylammonium bromide and...electrodes (Figure 1). Pyrrole polymerizes oxidatively at +0.6 V. A semi-reversible reduction-oxidation couple appeared with the oxidative peak

The Chemistry Involved in the Preparation of a Paint Pigment: An Experiment for the Freshman Laboratory

ERIC Educational Resources Information Center

Daines, Terri L.; Morse, Karen W.

1976-01-01

Describes an experiment that demonstrates the following principles and reactions: amphoterism, oxidation-reduction, equilibrium dependence on pH, solubility, and polymerization. The experiment involves the oxidation of chromium and the precipitation of a chromate salt. (MLH)

Pyrogallol-imprinted polymers with methyl methacrylate via precipitation polymerization

NASA Astrophysics Data System (ADS)

Mehamod, Faizatul Shimal; Othman, Nor Amira; Bulat, Ku Halim Ku; Suah, Faiz Bukhari Mohd

2018-06-01

Molecular simulation techniques are important to study the understanding of chemical and physical properties of any material. Computational modeling is considered as time reducer in finding the best recipes for Molecularly-Imprinted Polymers (MIPs). In this study, Pyrogallol-imprinted polymers (PIP) and non-imprinted polymers (NIPs) were synthesized via precipitation polymerization using Pyrogallol (Py), methyl methacrylate (MMA), divinylbenzene (DVB) as template, functional monomer and cross-linker, respectively. The recipe was according to the results from computational techniques. The synthesized PIP and NIPs were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) and UV-visible spectroscopy (UV-vis). Studies on adsorption isotherm showed that PIP and NIPs follow Scatchard isotherm models. Sorption kinetic study found that PIP and NIPs follow pseudo-second order which indicates the rate-limiting step is the surface adsorption. The imprinting factor of PIP was determined by selectivity study and showed the value of k >1, which proved that PIP was selective toward Pyrogallol compared to NIP.

Preparation and characterization of erythromycin molecularly imprinted polymers based on distillation-precipitation polymerization.

PubMed

Liu, Jiang; Li, Le; Tang, Hui; Zhao, Feilang; Ye, Bang-Ce; Li, Yingchun; Yao, Jun

2015-09-01

Erythromycin-imprinted polymers with excellent recognition properties were prepared by an innovative strategy called distillation-precipitation polymerization. The interaction between erythromycin and methacrylic acid was studied by ultraviolet absorption spectroscopy, and the as-prepared materials were characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. Moreover, their binding performances were evaluated in detail by static, kinetic and selective sorption tests. It was found that the molecularly imprinted polymers afforded good morphology, monodispersity, and high adsorption capacity when the fraction of the monomers was 7 vol% in the whole reaction system, and the adsorption data for imprinted polymers correlated well with the Langmuir model. The maximum capacity of the imprinted and the non-imprinted polymers for adsorbing erythromycin is 44.03 and 19.95 mg/g, respectively. The kinetic studies revealed that the adsorption process fitted a pseudo-second-order kinetic model. Furthermore, the imprinted polymers display higher affinity toward erythromycin, compared with its analogue roxithromycin. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Matrine- and oxymatrine-imprinted monodisperse polymers prepared by precipitation polymerization and their applications for the selective extraction of matrine-type alkaloids from Sophora flavescens Aiton.

PubMed

Funaya, Noriko; Haginaka, Jun

2012-07-27

Matrine (MT)- and oxymatrine (OMT)-imprinted monodisperse polymers have been prepared by precipitation polymerization. The prepared molecularly imprinted polymers (MIPs) for MT and OMT, MIP(MT) and MIP(OMT), were monodispersed microspheres of 3.3 and 3.9 μm in diameter, respectively. Binding experiments and Scatchard analyses revealed that two classes of binding sites were formed on MIP(MT) and MIP(OMT). In addition to shape recognition, ionic and hydrophobic interactions seemed to affect the retention and recognition of MT and OMT on MIP(MT) and MIP(OMT), respectively, in low acetonitrile content, and ionic and hydrophilic interactions affected these properties in high acetonitrile content. MIP(MT) was used to selectively extract MT and sophocarpine (13,14-dehydromatrine) from Sophora flavescens root, while MIP(OMT) was used to extract OMT and oxysophocarpine (13,14-dehydrooxymatrine). Copyright © 2012 Elsevier B.V. All rights reserved.

Wash water solids removal system study

NASA Technical Reports Server (NTRS)

1974-01-01

During wash water purification, surfactants tend to precipitate and foul the RO membranes, causing water flux decline and loss of salt rejection. The use of 165 to 190 ppm ferric chloride and optionally 0.25 to 1.0 ppm polymeric flocculate precipitates 92 to 96 percent of the surfactant from an Olive Leaf Soap based wash water. Crossflow filtration and pressure filtration yield good soap rejection at high water flux rates. Post-treatment of the chemically pretreated and filtered wash water with activated charcoal removes the residual soap down to an undetectable level.

21 CFR 870.3650 - Pacemaker polymeric mesh bag.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870.3650 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric...

Cobalt-Mediated Radical Polymerization of Vinyl Acetate and Acrylonitrile in Supercritical Carbon Dioxide.

PubMed

Kermagoret, Anthony; Chau, Ngoc Do Quyen; Grignard, Bruno; Cordella, Daniela; Debuigne, Antoine; Jérôme, Christine; Detrembleur, Christophe

2016-03-01

Cobalt-mediated radical polymerization (CMRP) of vinyl acetate (VAc) is successfully achieved in supercritical carbon dioxide (scCO2). CMRP of VAc is conducted using an alkyl-cobalt(III) adduct that is soluble in scCO2. Kinetics studies coupled to visual observations of the polymerization medium highlight that the melt viscosity and PVAc molar mass (Mn) are key parameters that affect the CMRP in scCO2. It is noticed that CMRP is controlled for Mn up to 10 000 g mol(-1), but loss of control is progressively observed for higher molar masses when PVAc precipitates in the polymerization medium. Low molar mass PVAc macroinitiator, prepared by CMRP in scCO2, is then successfully used to initiate the acrylonitrile polymerization. PVAc-b-PAN block copolymer is collected as a free flowing powder at the end of the process although the dispersity of the copolymer increases with the reaction time. Although optimization is required to decrease the dispersity of the polymer formed, this CMRP process opens new perspectives for macromolecular engineering in scCO2 without the utilization of fluorinated comonomers or organic solvents. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Composite Materials for Maxillofacial Prostheses.

DTIC Science & Technology

1980-08-01

projected composite systems are elastomeric-shelled, liquid-filled * microcapsules . Experiments continued on the interfacial polymerization process with...filled microcapsules . Experiments continued on the interfacial polymerization process, with spherical, sealed, capsules achieved. Needs identified are...consists of liquid-filled, elastomeric-shelled microcapsules held together to form a deformable mass; this is to simulate the semi-liquid cellular structure

Complete genome sequence of Lysinibacillus sphaericus LMG 22257, a strain with ureolytic activity inducing calcium carbonate precipitation.

PubMed

Yan, Wenkai; Xiao, Xiang; Zhang, Yu

2017-03-20

Microbiologically induced calcium carbonate precipitation shows the potential for use in bioremediation and construction consolidation, but the efficiency of this process must be improved. Lysinibacillus sphaericus LMG 22257 is a gram-positive ureolytic strain that has recently been applied for consolidating construction by mediating calcium carbonate precipitation. The complete genome sequence of L. sphaericus LMG 22257 is 3,436,578 base pairs with a GC content of 38.99%. The urea degradation pathway and genes related to extracellular polymeric substance biosynthesis were also identified. The strain can tolerate high alkalinity (pH up to 10) and high urea concentration (up to 3M). These findings provide insights into the microbiologically induced carbonate precipitation and extend the application of the metabolic potential of L. sphaericus LMG 22257 for bioremediation. Copyright © 2017 Elsevier B.V. All rights reserved.

Precipitation Behaviors of TiN Inclusion in GCr15 Bearing Steel Billet

NASA Astrophysics Data System (ADS)

Tian, Qianren; Wang, Guocheng; Zhao, Yang; Li, Jing; Wang, Qi

2018-06-01

There are many types of non-metallic TiN-based inclusions observed in GCr15 bearing steel, including single-particle TiN, multi-particle polymerized TiN, and complex inclusions like TiN-MnS, TiN-MgO-MgAl2O4 (TiN-MgO-MA), and TiN-MgAl2O4-MnS (TiN-MA-MnS). Thermodynamic calculations suggest that single-particle TiN precipitates dominate the mushy zone of GCr15 bearing steel. Kinetic calculations regarding TiN growth suggest that the final size of the single-particle TiN ranges between 1 and 6 μm in the initial concentration range of [pct Ti] = 0.0060 to 0.0079 and [pct N] = 0.0049 to 0.0070, at 1620 to 1640 K and a local cooling rate of 0.5 to 10 K/s. The multi-particle polymerized TiN are formed by single TiN particles in three stages: single-particle TiN inclusions approach each other drawn by the cavity bridge force (CBF), local active angles consolidate, and neck region sintering occurs. Based on the thermodynamic calculations of TiN, MnS, and MgO precipitation, the formation behaviors of complex inclusions of TiN-MnS, TiN-MgO-MA, and TiN-MA-MnS were investigated.

Kinetics of waterborne fluoropolymers prepared by one-step semi-continuous emulsion polymerization of chlorotrifluoroethylene, vinyl acetate, butyl acrylate and Veova 10

NASA Astrophysics Data System (ADS)

Liu, H. Z.; Wang, M. H.; Wang, Z. F.; Bian, J. M.

2018-01-01

Due to using gaseous fluorine monomer with toxicity, waterborne fluoropolymers are synthesized by semi-continuous high-pressure emulsion polymerization method which differs from free-pressure emulsion polymerization. To dates, the research on preparing process and kinetics for high-pressure emulsion polymerization is reported relatively less, which hinders researchers from understanding of mechanisms for monomer-fluorinated emulsion polymerization. The paper also provides a new method by element auxiliary analysis to calculate kinetics parameters of high-pressure emulsion polymerization. Based on aforementioned consideration, waterborne fluoropolymers were prepared by copolymerization of chlorotrifluoroethylene (CTFE), vinyl acetate (VAc), butyl acrylate (BA) and vinyl ester of versatic acid (Veova 10) using potassium persulfate as initiator and mixed surfactants. The kinetics of emulsion polymerization of waterborne fluoropolymers was then investigated. Effects of emulsifier concentration, initiator concentration, and polymerization temperature on polymerization rate (Rp) were evaluated, and relationship was described as Rp∝[I]0.10 and Rp∝[E]0.12. The apparent activation energy was determined to be 33.61 kJ·mol-1. Moreover, the relative conversion rate of CTFE with the other monomers was observed, and results indicated that CTFE monomer more uniformly copolymerized with the other monomers. The resulting emulsion properties and pressure change in an autoclave were evaluated at different stirring rates. The initial reaction time, defined as the beginning time of dropwise addition, was determined by the change in solid content and particle size of emulsion.

Magnetism in (Semi)Conducting Macrocycles of pi conjugated Polymers

DTIC Science & Technology

2016-12-09

wise and avoiding a break in the continuity of the macrocycle. As a first criterion we tested the continuity of the electron orbitals over the...magnesium chloride) and post polymerization functionalization by a Sonogashira coupling reaction is required (scheme 2). Scheme 2: Synthetic...Sonogashira post - polymerization chain end functionalization and B isotopic model of the different population present in the final batch

Effect of flour polymeric proteins on dough thermal properties and breadmaking characteristics for hard red spring wheat genotypes

USDA-ARS?s Scientific Manuscript database

The aim of this research was to investigate the effect of variation of flour polymeric proteins on rheological properties of dough under continuous mixing and thermal treatment for hard red spring (HRS) wheat genotypes grown in North Dakota, USA. Flour polymeric proteins were analyzed by size exclus...

Embedded cluster metal-polymeric micro interface and process for producing the same

DOEpatents

Menezes, Marlon E.; Birnbaum, Howard K.; Robertson, Ian M.

2002-01-29

A micro interface between a polymeric layer and a metal layer includes isolated clusters of metal partially embedded in the polymeric layer. The exposed portion of the clusters is smaller than embedded portions, so that a cross section, taken parallel to the interface, of an exposed portion of an individual cluster is smaller than a cross section, taken parallel to the interface, of an embedded portion of the individual cluster. At least half, but not all of the height of a preferred spherical cluster is embedded. The metal layer is completed by a continuous layer of metal bonded to the exposed portions of the discontinuous clusters. The micro interface is formed by heating a polymeric layer to a temperature, near its glass transition temperature, sufficient to allow penetration of the layer by metal clusters, after isolated clusters have been deposited on the layer at lower temperatures. The layer is recooled after embedding, and a continuous metal layer is deposited upon the polymeric layer to bond with the discontinuous metal clusters.

Dental Composites with Calcium / Strontium Phosphates and Polylysine.

PubMed

Panpisut, Piyaphong; Liaqat, Saad; Zacharaki, Eleni; Xia, Wendy; Petridis, Haralampos; Young, Anne Margaret

2016-01-01

This study developed light cured dental composites with added monocalcium phosphate monohydrate (MCPM), tristrontium phosphate (TSrP) and antimicrobial polylysine (PLS). The aim was to produce composites that have enhanced water sorption induced expansion, can promote apatite precipitation and release polylysine. Experimental composite formulations consisted of light activated dimethacrylate monomers combined with 80 wt% powder. The powder phase contained a dental glass with and without PLS (2.5 wt%) and/or reactive phosphate fillers (15 wt% TSrP and 10 wt% MCPM). The commercial composite, Z250, was used as a control. Monomer conversion and calculated polymerization shrinkage were assessed using FTIR. Subsequent mass or volume changes in water versus simulated body fluid (SBF) were quantified using gravimetric studies. These were used, along with Raman and SEM, to assess apatite precipitation on the composite surface. PLS release was determined using UV spectroscopy. Furthermore, biaxial flexural strengths after 24 hours of SBF immersion were obtained. Monomer conversion of the composites decreased upon the addition of phosphate fillers (from 76 to 64%) but was always higher than that of Z250 (54%). Phosphate addition increased water sorption induced expansion from 2 to 4% helping to balance the calculated polymerization shrinkage of ~ 3.4%. Phosphate addition promoted apatite precipitation from SBF. Polylysine increased the apatite layer thickness from ~ 10 to 20 μm after 4 weeks. The novel composites showed a burst release of PLS (3.7%) followed by diffusion-controlled release irrespective of phosphate addition. PLS and phosphates decreased strength from 154 MPa on average by 17% and 18%, respectively. All formulations, however, had greater strength than the ISO 4049 requirement of > 80 MPa. The addition of MCPM with TSrP promoted hygroscopic expansion, and apatite formation. These properties are expected to help compensate polymerization shrinkage and help remineralize demineralized dentin. Polylysine can be released from the composites at early time. This may kill residual bacteria.

Bioremediation of phenolic compounds from water with plant root surface peroxidases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adler, P.R.; Arora, R.; El Ghaouth, A.

1994-09-01

Peroxidases have been shown to polymerize phenolic compounds, thereby removing them from solution by precipitation. Others have studied the role of root surface associated peroxidases as a defense against fungal root pathogens; however, their use in detoxification of organic pollutants in vivo at the root surface has not been studied. Two plant species, waterhyacinth [Eichhornia crassipes (C. Mart) Solms-Laub.] and tomato (Lycopersicon esculentum L.), were tested for both in vitro and in vivo peroxidase activity on the root surface. In vitro studies indicated that root surface peroxidase activities were 181 and 78 nmol tetraguaiacol formed min{sup -1} g{sup -1} rootmore » fresh wt., for tomato and waterhyacinth, respectively. Light microscope studies revealed that guaiacol was polymerized in vivo at the root surface. Although peroxidase was evenly distributed on tomato roots, it was distributed patchily on waterhyacinth roots. In vitro studies using gas chromatography-mass spectrometry (GC-MS) showed that the efficiency of peroxidase to polymerize phenols vary with phenolic compound. We suggest that plants may be utilized as a source of peroxidases for removal of phenolic compounds that are on the EPA priority pollutant list and that root surface peroxidases may minimize the absorption of phenolic compounds into plants by precipitating them at the root surface. In this study we have identified a new use for root-associated proteins in ecologically engineering plant systems for bioremediation of phenolic compounds in the soil and water environment. 25 refs., 2 figs., 2 tabs.« less

Measurement and Analysis of in vitro Actin Polymerization

PubMed Central

Doolittle, Lynda K.; Rosen, Michael K.; Padrick, Shae B.

2014-01-01

Summary The polymerization of actin underlies force generation in numerous cellular processes. While actin polymerization can occur spontaneously, cells maintain control over this important process by preventing actin filament nucleation and then allowing stimulated polymerization and elongation by several regulated factors. Actin polymerization, regulated nucleation and controlled elongation activities can be reconstituted in vitro, and used to probe the signaling cascades cells use to control when and where actin polymerization occurs. Introducing a pyrene fluorophore allows detection of filament formation by an increase in pyrene fluorescence. This method has been used for many years and continues to be broadly used, owing to its simplicity and flexibility. Here we describe how to perform and analyze these in vitro actin polymerization assays, with an emphasis on extracting useful descriptive parameters from kinetic data. PMID:23868594

Impact of the lateral boundary conditions resolution on dynamical downscaling of precipitation in mediterranean spain

NASA Astrophysics Data System (ADS)

Amengual, A.; Romero, R.; Homar, V.; Ramis, C.; Alonso, S.

2007-08-01

Studies using transparent, polymeric witness plates consisting of polydimethlysiloxane (PDMS) have been conducted to measure the output of exploding bridge wire (EBW) detonators and exploding foil initiators (EFI). Polymeric witness plates are utilized to alleviate particle response issues that arise in gaseous flow fields containing shock waves and to allow measurements of shock-induced material velocities to be made using particle image velocimetry (PIV). Quantitative comparisons of velocity profiles across the shock waves in air and in PDMS demonstrate the improved response achieved by the dynamic witness plate method. Schlieren photographs complement the analysis through direct visualization of detonator-induced shock waves in the witness plates.

Three-dimensional tracking solar energy concentrator and method for making same

NASA Technical Reports Server (NTRS)

Miller, C. G.; Pohl, J. G. (Inventor)

1977-01-01

A three dimensional tracking solar energy concentrator, consisting of a stretched aluminized polymeric membrane supported by a hoop, was presented. The system is sturdy enough to withstand expected windage forces and precipitation. It can provide the high temperature output needed by central station power plants for power production in the multi-megawatt range.

Biochemical separations by continuous-bed chromatography.

PubMed

Tisch, T L; Frost, R; Liao, J L; Lam, W K; Remy, A; Scheinpflug, E; Siebert, C; Song, H; Stapleton, A

1998-08-07

Innovations in column-packing media for biomolecule purification have progressed from large spherical, porous polysaccharide beads to advanced polymeric supports. Continuous-bed technology is a radical new technology for chromatography based on the polymerization of advanced monomers and ionomers directly in the chromatographic column. The polymer chains form aggregates which coalesce into a dense, homogeneous network of interconnected nodules consisting of microparticles with an average diameter of 3000 A. The voids or channels between the nodules are large enough to permit a high hydrodynamic flow. Due to the high cross-linking of the polymer matrix, the surface of each nodule is nonporous yet the polymeric microparticles provide a very large surface area for high binding capacity. This paper will demonstrate the properties and advantages of using a continuous bed support for high resolution biomolecule separations at high flow-rates without sacrificing capacity.

Thiol surface functionalization via continuous phase plasma polymerization of allyl mercaptan, with subsequent maleimide-linked conjugation of collagen.

PubMed

Stynes, Gil D; Gengenbach, Thomas R; Kiroff, George K; Morrison, Wayne A; Kirkland, Mark A

2017-07-01

Thiol groups can undergo a large variety of chemical reactions and are used in solution phase to conjugate many bioactive molecules. Previous research on solid substrates with continuous phase glow discharge polymerization of thiol-containing monomers may have been compromised by oxidation. Thiol surface functionalization via glow discharge polymerization has been reported as requiring pulsing. Herein, continuous phase glow discharge polymerization of allyl mercaptan (2-propene-1-thiol) was used to generate significant densities of thiol groups on a mixed macrodiol polyurethane and tantalum. Three general classes of chemistry are used to conjugate proteins to thiol groups, with maleimide linkers being used most commonly. Here the pH specificity of maleimide reactions was used effectively to conjugate surface-bound thiol groups to amine groups in collagen. XPS demonstrated surface-bound thiol groups without evidence of oxidation, along with the subsequent presence of maleimide and collagen. Glow discharge reactor parameters were optimized by testing the resistance of bound collagen to degradation by 8 M urea. The nature of the chemical bonding of collagen to surface thiol groups was effectively assessed by colorimetric assay (ELISA) of residual collagen after incubation in 8 M urea over 8 days and after incubation with keratinocytes over 15 days. The facile creation of useable solid-supported thiol groups via continuous phase glow discharge polymerization of allyl mercaptan opens a route for attaching a vast array of bioactive molecules. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1940-1948, 2017. © 2017 Wiley Periodicals, Inc.

Study of continuous precipitation of ADU for the implantation in the pilot installation at the Atomic Energy Institute, Brazil. Estudo de precipitacao continua de DUA para a implantacao na instalacao piloto CEQ-IEA (in Portuguese)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Araujo, Jose Adroalado de

1974-05-15

The paper deals with the ammonium diuranate continuous precipitation with a high chemical purity degree from uranyl nitrate solutions, using 1.2 and 2.4 ammonium hydroxide solutions and gaseous NH{sub 3} as a precipitating agent. The precipitations were carried out in a continuous procedure with one and two stages. The variables studied were the NH[sub 4}OH solutions concentration, ADU precipitation curve, the flow rate of reactants, the temperature of the precipitation, pH of the suspended ADU, and ammonium diuranate filtrability. The experimental work performed and the data obtained permitted the design of a chemical reactor for the continuous nuclear grade ADUmore » precipitation at the Chemical Engineering Department of the Atomic Energy Institute of Sao Paulo.« less

Biofilm exopolymers control microbialite formation at thermal springs discharging into the alkaline Pyramid Lake, Nevada, USA

NASA Astrophysics Data System (ADS)

Arp, Gernot; Thiel, Volker; Reimer, Andreas; Michaelis, Walter; Reitner, Joachim

1999-07-01

Calcium carbonate precipitation and microbialite formation at highly supersaturated mixing zones of thermal spring waters and alkaline lake water have been investigated at Pyramid Lake, Nevada. Without precipitation, pure mixing should lead to a nearly 100-fold supersaturation at 40°C. Physicochemical precipitation is modified or even inhibited by the properties of biofilms, dependent on the extent of biofilm development and the current precipitation rate. Mucus substances (extracellular polymeric substances, EPS, e.g., of cyanobacteria) serve as effective Ca 2+-buffers, thus preventing seed crystal nucleation even in a highly supersaturated macroenvironment. Carbonate is then preferentially precipitated in mucus-free areas such as empty diatom tests or voids. After the buffer capacity of the EPS is surpassed, precipitation is observed at the margins of mucus areas. Hydrocarbon biomarkers extracted from (1) a calcifying Phormidium-biofilm, (2) the stromatolitic carbonate below, and (3) a fossil `tufa' of the Pleistocene pinnacles, indicate that the cyanobacterial primary producers have been subject to significant temporal changes in their species distribution. Accordingly, the species composition of cyanobacterial biofilms does not appear to be relevant for the formation of microbial carbonates in Pyramid Lake. The results demonstrate the crucial influence of mucus substances on carbonate precipitation in highly supersaturated natural environments.

Structure of Fe(III) precipitates generated by Fe(0) electrocoagulation in the presence of groundwater ions

NASA Astrophysics Data System (ADS)

van Genuchten, C. M.; Pena, J.; Addy, S. E.; Gadgil, A. J.

2012-12-01

Electrocoagulation (EC) using Fe(0) electrodes is an inexpensive and efficient technology capable of removing a variety of contaminants from water supplies. Because of its ease of use and modest electricity and Fe(0) requirements, EC has potential as an arsenic-removal technology for rural South Asia, where millions drink groundwater contaminated by arsenic. In EC, a small external voltage applied to a sacrificial Fe(0) anode in contact with an electrolyte (e.g. pumped groundwater containing arsenic) promotes the oxidative dissolution of Fe ions, which polymerize and create reactive hydrous ferric oxides (HFO) in-situ with a high affinity for binding contaminants. The chemical composition of the electrolyte influences EC performance. For example, major inorganic ions present in groundwater (e.g. Ca, Mg, P, As(V), Si) alter the pathway by which FeO6 oligomers polymerize to form crystalline Fe (oxyhydr)oxide minerals. Because the precipitate structure largely determines properties that govern the efficiency of EC systems (e.g. precipitate reactivity and colloidal stability), it is essential to understand the individual and interdependent structural effects of common groundwater ions. In this work, we integrate Fe K-edge EXAFS spectroscopy with the Pair Distribution Function (PDF) technique to create a detailed description of EC precipitate structure as a function of electrolyte chemistry. EC precipitate samples were generated in a range of individual and combined concentrations of Ca, Mg, P, As(V), and Si, encompassing most of the typical levels found in natural groundwater. Combining complementary EXAFS and PDF techniques with batch uptake experiments and general chemical reasoning, we obtain structural representations of EC precipitates that are inaccessible with any single characterization technique. Our results indicate that the presence of As(V), P, and Si oxyanions promote the formation of nanoscale material bearing similar, but not identical, intermediate-ranged atomic pair correlations as 2-line ferrihydrite (2LFH), rather than lepidocrocite (Lp) which is generated in an NaCl electrolyte. However, when Ca or Mg is added to oxyanion electrolytes, Fe-Fe polymerization and particle size both tend to increase and a Lp-like material with characteristic Fe-O and Fe-Fe pair correlations is once again favored. The presence of either Ca or Mg also enhances the removal P, As(V), and to a lesser extent, Si per mass of Fe. The analysis from EXAFS and PDF spectra provide new insights into the polyhedral connectivity of nanoscale oxyanion-bearing HFO formed under a wide range of chemical conditions, improving predictions of EC performance in the field and allowing for knowledge-based improvements in the design of future EC systems. Our PDF data also show that the most disordered EC precipitate samples (formed at high oxyanion/Fe ratios) all share a similar "backbone" of 3-4 peaks beyond the first 4 Å, regardless of the oxyanion present during synthesis. Using 2LFH as a reference, we index all atomic pair correlations throughout the coherently scattering structure of our disordered samples.

Nanodevices from Nanocomponents: Memory Logic and Mechanical Nanodevices

DTIC Science & Technology

2009-05-11

microemulsion method at room temperature. The microemulsion system was made up of cyclohexane, NP-5, PbSe and dimethylamine. Typically, 10 ml...30 min after the microemulsion system was formed, 100 \\i\\ dimethylamine aqueous solution (40wt %) was introduced to initiate the polymerization...growth was completed after 24 h of stirring. The nanoparticles were destabilized from the microemulsion using acetone and precipitated by

High-Molecular Compounds (Selected Articles).

DTIC Science & Technology

1987-09-11

with methacrylamide (AMK), methacrylic acid (MAK) and ethylene-glycolmethacrylate (MEG), copolymer of methylmethacrylate (MMA) and MAK and...polymerization in medium of isopropyl or butyl alcohol with dinitrile of azoisobutyric acid (DAK). Samples for the tests re-precipitated from acetone... temperatu .-es T. T in films of PVTs process of thermal structuring occurs, as a result of which polymer changes into undissolved state. * REFERENCES

Bioreduction of U(VI)-Phthalate to a Polymeric U(IV)-Phthalate Colloid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vazquez, G.; Dodge, C; Francis, A

2009-01-01

Phthalic acid, a ubiquitous organic ligand, formed soluble mono- and biligand complexes with a uranyl ion that was then reduced to a U(IV)-phthalate by a Clostridium species under anaerobic conditions. We confirmed the reduction of the hexavalent uranium to the tetravalent oxidation state by UV-vis absorption and X-ray absorption near edge structure spectroscopy. Sequential micro- and ultrafiltration of the solution revealed that the bioreduced uranium was present as a colloid with particles between 0.03 and 0.45 {mu}m. Analysis with extended X-ray absorption fine structure revealed the association of the reduced uranium with the phthalic acid as a repeating biligand 1:2more » U(IV):phthalic acid polymer. This is the first report of the formation of a U(IV) complexed to two phthalic acid molecules in the form of a polymeric colloid. Although it was proposed that the bioreduction and the precipitation of uranium might be an invaluable strategy to immobilize uranium in contaminated environments, our results suggest that the organic ligands present there might hinder the precipitation of the bioreduced uranium under anaerobic conditions and, thereby, enhance its environmental mobility as uranium organic complexes or colloids.« less

Monodisperse, molecularly imprinted polymers for creatinine by modified precipitation polymerization and their applications to creatinine assays for human serum and urine.

PubMed

Miura, Chitose; Funaya, Noriko; Matsunaga, Hisami; Haginaka, Jun

2013-11-01

Molecularly imprinted polymers (MIPs) for creatinine were prepared by modified precipitation polymerization using methacrylic acid as a functional monomer and divinylbenzene as a crosslinker. The prepared MIPs were monodispersed with a narrow particle size distribution. Binding experiments and Scatchard analyses revealed that two classes of binding sites, high- and low-affinity sites, were formed on the MIPs. The retention and molecular-recognition properties of the MIPs were evaluated by hydrophilic interaction chromatography using a mixture of ammonium acetate buffer and acetonitrile as a mobile phase. With an increase of acetonitrile content, the retention factor of creatinine was increased on the MIP. In addition to shape recognition, hydrophilic interactions seemed to enhance the recognition of creatinine on the MIP. The MIPs' molecular-recognition ability was specific for creatinine; the structurally related compounds such as hydantoin, 1-methylhydantoin, 2-pyrrolidone, N-hydroxysuccinimide and creatine were not recognized. Furthermore, the creatinine concentrations in human serum and urine were successfully determined by direct injection of the deproteinized serum and diluted urine samples onto the MIP. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis of core-shell molecularly imprinted polymer microspheres by precipitation polymerization for the inline molecularly imprinted solid-phase extraction of thiabendazole from citrus fruits and orange juice samples.

PubMed

Barahona, Francisco; Turiel, Esther; Cormack, Peter A G; Martín-Esteban, Antonio

2011-01-01

In this work, the synthesis of molecularly imprinted polymer microspheres with narrow particle size distributions and core-shell morphology by a two-step precipitation polymerization procedure is described. Polydivinylbenzene (poly DVB-80) core particles were used as seed particles in the production of molecularly imprinted polymer shells by copolymerization of divinylbenzene-80 with methacrylic acid in the presence of thiabendazole (TBZ) and an appropriate porogen. Thereafter, polymer particles were packed into refillable stainless steel HPLC columns used in the development of an inline molecularly imprinted SPE method for the determination of TBZ in citrus fruits and orange juice samples. Under optimized chromatographic conditions, recoveries of TBZ within the range 81.1-106.4%, depending upon the sample, were obtained, with RSDs lower than 10%. This novel method permits the unequivocal determination of TBZ in the samples under study, according to the maximum residue levels allowed within Europe, in less than 20 min and without any need for a clean-up step in the analytical protocol. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of a calcium phosphate co-precipitate/poly(lactide-co-glycolide) DNA delivery system: release kinetics and cellular transfection studies.

PubMed

Kofron, Michelle D; Laurencin, Cato T

2004-06-01

One of the most common non-viral methods for the introduction of foreign deoxyribonucleic acid (DNA) into cultured cells is calcium phosphate co-precipitate transfection. This technique involves the encapsulation of DNA within a calcium phosphate co-precipitate, particulate addition to in vitro cell culture, endocytosis of the co-precipitate, and exogenous DNA expression by the transfected cell. In this study, we fabricated a novel non-viral gene transfer system by adsorbing DNA, encapsulated in calcium phosphate (DNA/Ca-P) co-precipitates, to biodegradable two- and three-dimensional poly(lactide-co-glycolide) matrices (2D-DNA/Ca-P/PLAGA, 3D-DNA/Ca-P/PLAGA). Co-precipitate release studies demonstrated an initial burst release over the first 48 h. By day 7, approximately 96% of the initially adsorbed DNA/Ca-P co-precipitate had been released. This was followed by low levels of co-precipitate release for 42 days. Polymerase chain reaction was used to demonstrate the ability of the released DNA containing co-precipitates to transfect SaOS-2 cells cultured in vitro on the 3D-DNA/Ca-P/PLAGA matrix and maintenance of the structural integrity of the exogenous DNA. In summary, a promising system for the incorporation and controlled delivery of exogenous genes encapsulated within a calcium phosphate co-precipitate from biodegradable polymeric matrices has been developed and may have applicability to the delivery of therapeutic genes and the transfection of other cell types.

DISPERSION POLYMERIZATION OF 2-HYDROXYETHYL METHACRYLATE IN SUPERCRITICAL CARBON DIOXIDE. (R826115)

EPA Science Inventory

Herein we report a successful dispersion polymerization of 2-hydroxyethyl methacrylate (HEMA) in a carbon dioxide continuous phase with a block copolymer consisting of polystyrene and poly(1,1-dihydroperfluorooctyl acrylate) as a stabilizer. Poly(2-hydroxyethyl methacrylate) was ...

Synthetic vascular graft fabrication by a precipitation-flotation method.

PubMed

Kowligi, R R; von Maltzahn, W W; Eberhart, R C

1988-01-01

The authors report a new technique for fabricating synthetic vascular grafts. It involves spraying a polymer solution (generated by mixing polymer solution and nitrogen gas in a spray nozzle) onto the surface of a flowing nonsolvent liquid (water): polymer fibers form during precipitation of the spray drops as they travel on the water surface, until picked up by a partially submerged rotating mandrel. Depending on process conditions, these fibers may aggregate to form a continuous layer or remain separated until they are picked up. A number of independent process variables allow control of characteristics of the conduits: gas and polymer solution feed rates, nozzle traverse speed, nonsolvent (water) flow rate, spray-mandrel spacing, and mandrel rpm. The SEM reveals that the graft wall consists of numerous fused polymeric fibers arrayed in both the circumferential and axial directions. The inner surface resembles a mesh of closely spaced fused fibers. The conduits have walls with interconnected pores (water permeabilities between 0.05 to 7.0 ml/min-cm2); nonporous surfaces also can be made. Tensile stress of the grafts at failure (in radial direction) varied between 0.05 to 2.3 MPa, whereas elongation at break ranged between 150 to 600%, depending on the porosity and fabrication conditions. A major advantage of this technique is its ability to produce grafts of a wide variety of fiber sizes and fusion characteristics in an inexpensive, safe, and reliable fashion.

Form and stability of aluminum hydroxide complexes in dilute solution

USGS Publications Warehouse

Hem, John David; Roberson, Charles Elmer

1967-01-01

Laboratory studies of solutions 4.53 x 10 -4 to 4.5 x 10 -5 molal (12.2-1.2 ppm) in aluminum, in 0.01 molal sodium perchlorate, were conducted to obtain information as to the probable behavior of aluminum in natural water. When the solutions were brought to pH 7.5-9.5 and allowed to stand for 24 hours, a precipitate was obtained which was virtually amorphous as shown by X-rays, and which had a solubility equivalent to that of boehmite. This precipitate had a hydrolysis constant (*Ks4) of 1.93 x 10 -13a. When solutions were allowed to stead at this pH range for 10 days, their precipitates gave the X-ray pattern of bayerite (*Ks4 = 1.11 > (10- 4). These hydrolysis constants were obtained at 25?C. and corrected to zero ionic strength and are in close agreement with other published values. The predominant dissolved form in this pH range is Al(OH) -4. Below neutral pH (7.0) the dissolved aluminum species consist of octahedral units in which each aluminum ion is surrounded by six water molecules or hydroxide ions. Single units such as Al(OH2)6 + 3 and AlOH(OH2)5+2 are most abundant below pH 5.0, and where the molar ratio (r) of combined hydroxide to total dissolved aluminum is low. When r is greater than 1.0, polymerization of the octahedral units occurs. When r is between 2.0 and 3.0, solutions aged for 10 days or more contained colloidal particles between 0.10 and 0.45 ? in diameter. Particles whose diameters were greater than 0.10 ? were identified by X-ray diffraction as gibbsite. Particles smaller than 0.10 ? were also present and were shown by means of the electron microscope to have a hexagonal crystal pattern. Structured material consisting of sheets of coalesced six-membered rings of aluminum ions held together by double OH bridges has a distinctive kinetic behavior. This property was used to determine amounts of polymerized material in solutions having r between 1.0 and 3.0 after aging times ranging from a few hours to more than 4 months. Aging increased the size and orderliness of the polymeric aggregates and was accompanied by a decrease in the pH of the solution. The kinetic experiments and stoichiometric data for solutions aged for long periods provided a means of determining activities of polymerized aluminum. From these values the solubility product for microcrystalline gibbsite was determined to be 2.24 x 10 -3, and its free energy of formation, -? 272.3 0.4 kcal per mole. Where polymerization was observed, the process did not stop with small polynuclear complexes containing a few aluminum ions, but proceeded with aging until macromolecules or colloidal-sized particles were formed.

cis,cis-Muconic acid: separation and catalysis to bio-adipic acid for nylon-6,6 polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vardon, Derek R.; Rorrer, Nicholas A.; Salvachúa, Davinia

cis,cis-Muconic acid is a polyunsaturated dicarboxylic acid that can be produced renewably via the biological conversion of sugars and lignin-derived aromatic compounds. Subsequently, muconic acid can be catalytically converted to adipic acid -- the most commercially significant dicarboxylic acid manufactured from petroleum. Nylon-6,6 is the major industrial application for adipic acid, consuming 85% of market demand; however, high purity adipic acid (99.8%) is required for polymer synthesis. As such, process technologies are needed to effectively separate and catalytically transform biologically derived muconic acid to adipic acid in high purity over stable catalytic materials. To that end, this study: (1) demonstratesmore » bioreactor production of muconate at 34.5 g L-1 in an engineered strain of Pseudomonas putida KT2440, (2) examines the staged recovery of muconic acid from culture media, (3) screens platinum group metals (e.g., Pd, Pt, Rh, Ru) for activity and leaching stability on activated carbon (AC) and silica supports, (4) evaluates the time-on-stream performance of Rh/AC in a trickle bed reactor, and (5) demonstrates the polymerization of bio-adipic acid to nylon-6,6. Separation experiments confirmed AC effectively removed broth color compounds, but subsequent pH/temperature shift crystallization resulted in significant levels of Na, P, K, S and N in the crystallized product. Ethanol dissolution of muconic acid precipitated bulk salts, achieving a purity of 99.8%. Batch catalysis screening reactions determined that Rh and Pd were both highly active compared to Pt and Ru, but Pd leached significantly (1-9%) from both AC and silica supports. Testing of Rh/AC in a continuous trickle bed reactor for 100 h confirmed stable performance after 24 h, although organic adsorption resulted in reduced steady-state activity. Lastly, polymerization of bio-adipic acid with hexamethyldiamine produced nylon-6,6 with comparable properties to its petrochemical counterpart, thereby demonstrating a path towards bio-based nylon production via muconic acid.« less

Mass Transfer Study of Chlorine Dioxide Gas Through Polymeric Packaging Materials

USDA-ARS?s Scientific Manuscript database

A continuous system for measuring the mass transfer of gaseous chlorine dioxide (ClO2), a strong oxidizing agent and used in food and pharmaceutical packaging, through 10 different types of polymeric packaging material was developed utilizing electrochemical sensor as a detector. Permeability, diff...

Novel synthesis and characterization of a collagen-based biopolymer initiated by hydroxyapatite nanoparticles.

PubMed

Bhuiyan, D; Jablonsky, M J; Kolesov, I; Middleton, J; Wick, T M; Tannenbaum, R

2015-03-01

In this study, we developed a novel synthesis method to create a complex collagen-based biopolymer that promises to possess the necessary material properties for a bone graft substitute. The synthesis was carried out in several steps. In the first step, a ring-opening polymerization reaction initiated by hydroxyapatite nanoparticles was used to polymerize d,l-lactide and glycolide monomers to form poly(lactide-co-glycolide) co-polymer. In the second step, the polymerization product was coupled with succinic anhydride, and subsequently was reacted with N-hydroxysuccinimide in the presence of dicyclohexylcarbodiimide as the cross-linking agent, in order to activate the co-polymer for collagen attachment. In the third and final step, the activated co-polymer was attached to calf skin collagen type I, in hydrochloric acid/phosphate buffer solution and the precipitated co-polymer with attached collagen was isolated. The synthesis was monitored by proton nuclear magnetic resonance, infrared and Raman spectroscopies, and the products after each step were characterized by thermal and mechanical analysis. Calculations of the relative amounts of the various components, coupled with initial dynamic mechanical analysis testing of the resulting biopolymer, afforded a preliminary assessment of the structure of the complex biomaterial formed by this novel polymerization process. Copyright © 2015. Published by Elsevier Ltd.

Cellulose biogenesis: Polymerization and crystallization are coupled processes in Acetobacter xylinum.

PubMed

Benziman, M; Haigler, C H; Brown, R M; White, A R; Cooper, K M

1980-11-01

Calcofluor White ST, stilbene derivative used commerically as an optical brightener for cellulose, increased the rate of glucose polymerization into cellulose by resting cells of the gram-negative bacterium Acetobacter xylinum. This bacterium normally produces a ribbon of cellulose that is a composite of crystalline microfibrils. In concentrations above 0.1 mM, Calcofluor disrupts the assembly of crystalline cellulose I microfibrils and their integration into a composite ribbon by stoichiometric binding to glucose residues of newly polymerized glucan chains. Under these conditions, the rate of glucose polymerization increases up to 4 times the control rate, whereas oxygen uptake increases only 10-15%. These observed effects are readily reversible. If free Calcofluor is washed away or depleted below the threshold value by binding to cellulose as polymerization continues, ribbon production and the normal rate of polymerization resume. It is concluded that polymerization and crystallization are cell-directed, coupled processes and that the rate of crystallization determines the rate of polymerization. It is suggested that coupling must be maintained for biogenesis of crystalline cellulose I.

Iron Polymerization and Arsenic Removal During In-Situ Iron Electrocoagulation in Synthetic Bangladeshi Groundwater

NASA Astrophysics Data System (ADS)

van Genuchten, C. M.; Pena, J.; Addy, S.; Gadgil, A.

2010-12-01

Millions of people worldwide are exposed to arsenic-contamination in groundwater drinking supplies. The majority of affected people live in rural Bangladesh. Electrocoagulation (EC) using iron electrodes is a promising arsenic removal strategy that is based on the generation of iron precipitates with a high affinity for arsenic through the electrochemical dissolution of a sacrificial iron anode. Many studies of iron hydrolysis in the presence of co-occurring ions in groundwater such as PO43-, SiO44-, and AsO43- suggest that these ions influence the polymerization and formation of iron oxide phases. However, the combined impact of these ions on precipitates generated by EC is not well understood. X-ray absorption spectroscopy (XAS) was used to examine EC precipitates generated in synthetic Bangladeshi groundwater (SBGW). The iron oxide structure and arsenic binding geometry were investigated as a function of EC operating conditions. As and Fe k-edge spectra were similar between samples regardless of the large range of current density (0.02, 1.1, 5.0, 100 mA/cm2) used during sample generation. This result suggests that current density does not play a large role in the formation EC precipitates in SBGW. Shell-by-shell fits of Fe K-edge data revealed the presence of a single Fe-Fe interatomic distance at approximately 3.06 Å. The absence of longer ranged Fe-Fe correlations suggests that EC precipitates consist of nano-scale chains (polymers) of FeO6 octahedra sharing equatorial edges. Shell-by-shell fits of As K-edge spectra show arsenic bound in primarily bidentate, binuclear corner sharing complexes. In this coordination geometry, arsenic prevents the formation of FeO6 corner-sharing linkages, which are necessary for 3-dimensional crystal growth. The individual and combined effects of other anions, such as PO43- and SiO44- present in SBGW are currently being investigated to determine the role of these ions in stunting crystal growth. The results provided by this study are useful in explaining the large adsorption capacity of EC precipitates. This study will also lead to better predictions of arsenic removal efficiency during EC and a better understanding of the long-term stability of arsenic-laden EC sludge.

Antimicrobial fabric adsorbed iodine produced by radiation-induced graft polymerization

NASA Astrophysics Data System (ADS)

Aoki, Shoji; Fujiwara, Kunio; Sugo, Takanobu; Suzuki, Koichi

2013-03-01

Antimicrobial fabric was synthesized by radiation-induced graft polymerization of N-vinyl pyrrolidone onto polyolefine nonwoven fabric and subsequent adsorption of iodine. In response of the huge request for the antimicrobial material applied to face masks for swine flu in 2009, operation procedure of continuous radiation-induced graft polymerization apparatus was improved. The improved grafting production per week increased 3.8 times compared to the production by former operation procedure. Shipped antimicrobial fabric had reached 130,000 m2 from June until December, 2009.

Effects of organic solutes on chemical reactions of aluminum

USGS Publications Warehouse

Lind, Carol J.; Hem, John David

1975-01-01

Concentrations of organic matter in the general range of 1-10 milligrams per litre organic carbon are common in natural water, and many naturally occurrin7 organic compounds form aluminum complexes. The aluminum concentrations in near-neutral pH solutions may be 10-100 times higher than the values predicted from solubility data if formation of such organic complexes is ignored. The processes of polymerization of aluminum hydroxide and precipitation of gibbsite are inhibited by the presence of the organic flavone compound quercetin in concentrations as low as 10 x -5.3 mole per litre. Quercetin forms a complex, with a probable molar ratio of 1:2 aluminum to quercetin, that has a formation constant (f12) of about 10 12. A complex with a higher aluminum-quercetin ratio also was observed, but this material tends to evolve into a compound of low solubility that removes aluminum from solution. In the presence of both dissolved aluminum and aqueous silica, low concentrations of quercetin improved the yield of crystallized kaolinite and halloysite. Small amounts of well-shaped kaolinite and halloysite crystals were identified by electron microscopy in solutions with pH's in the range 6.5-8.5 after 155 days aging in one experimer t and 481 days aging in a repeated experiment. The bulk of the precipitated material was amorphous to X-rays, and crystalline material was too small a proportion of the total to give identifiable X-ray diffraction peaks. The precipitates had aluminum-silicon ratios near 1, and their solubility corresponded to that found by Hem, Roberson, Lind, and Polzer (1973) for similar aluminosilicate precipitated in the absence of organic solutes. The improved yield of crystalline material obtained in the presence of quercetin probably is the result of the influence of the organic compound on the aluminum hydroxide polymerization process. Natural water containing color imparted by organic material tends to be higher in aluminum than would be predicted by pH, silica concentrations, and solubility data for inorganic aluminum species.

Monodisperse microbeads of hypercrosslinked polystyrene for liquid and supercritical fluid chromatography

NASA Astrophysics Data System (ADS)

Tsyurupa, M. P.; Blinnikova, Z. K.; Il'in, M. M.; Davankov, V. A.; Parenago, O. O.; Pokrovskii, O. I.; Usovich, O. I.

2015-11-01

Monodisperse styrene-divinylbenzene (1 wt %) copolymer microbeads are obtained via the elaborate method of high-productivity precipitation polymerization. The crosslinking of this copolymer with chloromethyl methyl ether in the presence of Friedel-Crafts catalyst yields porous hypercrosslinked polymers with degrees of crosslinking that range from 200 to 500%. Microbead sorbents are shown to be suited for selective stationary phases for high-performance liquid chromatography and supercritical fluid chromatography.

Sea buckthorn (Hippophae rhamnoides) proanthocyanidins inhibit in vitro enzymatic hydrolysis of protein.

PubMed

Arimboor, Ranjith; Arumughan, C

2011-08-01

Interactions of phenolics with other food constituents and digestive enzymes are likely to have interference with the digestion and bioavailability of food and phenolics. In this study the effect of sea buckthorn proanthocyanidins on in vitro digestion of protein was evaluated. Optimization of the extraction conditions showed that maximum recovery of sea buckthorn proanthocyanidins was obtained with acidified acetone; water mixture (60% to 70%, v/v). Crude proanthocyanidin extracts thus prepared were purified using sephadex gel column chromatography and their average degree of polymerization and the effects on enzymatic hydrolysis of bovine serum albumin as influenced by their protein precipitation capacities were studied. Average degree of polymerization of proanthocyanidins in berry pulp, kernel, seed coat, and leaves was 7.4, 5.6, 8.2, and 10.6, respectively. The EC50 values for the protein precipitation by the PA of berry pulp, kernel seed coat, and leaves were 44.2, 44.1, 65.8, and 39.8 μg, respectively. Relative enzymatic hydrolysis of the protein-proanthocyanidin complexes was 44.1% to 60.3% for pepsin and 57.5% to 67.7% for trypsin. Interactions of sea buckthorn proanthocyanidins with food proteins and digestive enzymes might alter the protein digestibility and phenolic bioavailabilty. © 2011 Institute of Food Technologists®

Acid-Labile Amphiphilic PEO-b-PPO-b-PEO Copolymers: Degradable Poloxamer Analogs.

PubMed

Worm, Matthias; Kang, Biao; Dingels, Carsten; Wurm, Frederik R; Frey, Holger

2016-05-01

Poly ((ethylene oxide)-b-(propylene oxide)-b-(ethylene oxide)) triblock copolymers commonly known as poloxamers or Pluronics constitute an important class of nonionic, biocompatible surfactants. Here, a method is reported to incorporate two acid-labile acetal moieties in the backbone of poloxamers to generate acid-cleavable nonionic surfactants. Poly(propylene oxide) is functionalized by means of an acetate-protected vinyl ether to introduce acetal units. Three cleavable PEO-PPO-PEO triblock copolymers (Mn,total = 6600, 8000, 9150 g·mol(-1) ; Mn,PEO = 2200, 3600, 4750 g·mol(-1) ) have been synthesized using anionic ring-opening polymerization. The amphiphilic copolymers exhibit narrow molecular weight distributions (Ð = 1.06-1.08). Surface tension measurements reveal surface-active behavior in aqueous solution comparable to established noncleavable poloxamers. Complete hydrolysis of the labile junctions after acidic treatment is verified by size exclusion chromatography. The block copolymers have been employed as surfactants in a miniemulsion polymerization to generate polystyrene (PS) nanoparticles with mean diameters of ≈200 nm and narrow size distribution, as determined by dynamic light scattering and scanning electron microscopy. Acid-triggered precipitation facilitates removal of surfactant fragments from the nanoparticles, which simplifies purification and enables nanoparticle precipitation "on demand." © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of HNTs@PEDOT composites via in situ chemical oxidative polymerization and their application in electrode materials

NASA Astrophysics Data System (ADS)

Wang, Fang; Zhang, Xianhong; Ma, Yuhong; Yang, Wantai

2018-01-01

The hybrid composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and halloysite nanotubes (HNTs) was synthesized by a two-step process. First, poly(sodium styrene sulfonate) (PSSNa) was grafted onto HNTs via surface initiated atom transfer radical polymerization. Then with the HNTs-g-PSS as a template and the grafted PSS chains as the counterion dopant, PEDOT was precipitated onto the template via in situ oxidization polymerization of EDOT to form HNTs@PEDOT hybrid composites. The conductivity of HNTs@PEDOT can reach up to 9.35 S/cm with the content of 40% HNTs-g-PSS, which increased almost 78 times than that of pure PEDOT (about 0.12 S/cm) prepared at the similar condition. Further treated with p-toluenesulfonic acid (TsOH) as external dopant, the conductivity of HNTs@PEDOT increased to 24.3 S/cm. The electrochemical properties of the composites were investigated with cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy with three-electrode cell configuration. The results showed that the capacitance of HNTs@PEDOT composite increased 55% than that of pure PEDOT.

Conjugated Polymers Via Direct Arylation Polymerization in Continuous Flow: Minimizing the Cost and Batch-to-Batch Variations for High-Throughput Energy Conversion.

PubMed

Gobalasingham, Nemal S; Carlé, Jon E; Krebs, Frederik C; Thompson, Barry C; Bundgaard, Eva; Helgesen, Martin

2017-11-01

Continuous flow methods are utilized in conjunction with direct arylation polymerization (DArP) for the scaled synthesis of the roll-to-roll compatible polymer, poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(4,7-di(thiophen-2-yl)-benzo[c][1,2,5]thiadiazole)] (PPDTBT). PPDTBT is based on simple, inexpensive, and scalable monomers using thienyl-flanked benzothiadiazole as the acceptor, which is the first β-unprotected substrate to be used in continuous flow via DArP, enabling critical evaluation of the suitability of this emerging synthetic method for minimizing defects and for the scaled synthesis of high-performance materials. To demonstrate the usefulness of the method, DArP-prepared PPDTBT via continuous flow synthesis is employed for the preparation of indium tin oxide (ITO)-free and flexible roll-coated solar cells to achieve a power conversion efficiency of 3.5% for 1 cm 2 devices, which is comparable to the performance of PPDTBT polymerized through Stille cross coupling. These efforts demonstrate the distinct advantages of the continuous flow protocol with DArP avoiding use of toxic tin chemicals, reducing the associated costs of polymer upscaling, and minimizing batch-to-batch variations for high-quality material. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of branched polymers under continuous-flow microprocess: an improvement of the control of macromolecular architectures.

PubMed

Bally, Florence; Serra, Christophe A; Brochon, Cyril; Hadziioannou, Georges

2011-11-15

Polymerization reactions can benefit from continuous-flow microprocess in terms of kinetics control, reactants mixing or simply efficiency when high-throughput screening experiments are carried out. In this work, we perform for the first time the synthesis of branched macromolecular architecture through a controlled/'living' polymerization technique, in tubular microreactor. Just by tuning process parameters, such as flow rates of the reactants, we manage to generate a library of polymers with various macromolecular characteristics. Compared to conventional batch process, polymerization kinetics shows a faster initiation step and more interestingly an improved branching efficiency. Due to reduced diffusion pathway, a characteristic of microsystems, it is thus possible to reach branched polymers exhibiting a denser architecture, and potentially a higher functionality for later applications. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Continuous, linearly intermixed fiber tows and composite molded article thereform

NASA Technical Reports Server (NTRS)

McMahon, Paul E. (Inventor); Chung, Tai-Shung (Inventor); Ying, Lincoln (Inventor)

2000-01-01

The instant invention involves a process used in preparing fibrous tows which may be formed into polymeric plastic composites. The process involves the steps of (a) forming a carbon fiber tow; (b) forming a thermoplastic polymeric fiber tow; (c) intermixing the two tows; and (d) withdrawing the intermixed tow for further use.

Performance intensification of Prague wastewater treatment plant.

PubMed

Novák, L; Havrlíková, D

2004-01-01

Prague wastewater treatment plant was intensified during 1994--1997 by construction of new regeneration tank and four new secondary settling tanks. Nevertheless, more stringent effluent limits and operational problems gave rise to necessity for further intensification and optimisation of plant performance. This paper describes principal operational problems of the plant and shows solutions and achieved results that have lead to plant performance stabilisation. The following items are discussed: low nitrification capacity, nitrification bioaugmentation, activated sludge bulking, insufficient sludge disposal capacity, chemical precipitation of raw wastewater, simultaneous precipitation, sludge chlorination, installation of denitrification zones, sludge rising in secondary settling tanks due to denitrification, dosage of cationic polymeric organic flocculant to secondary settling tanks, thermophilic operation of digestors, surplus activated sludge pre-thickening, mathematical modelling.

Property evolution during vitrification of dimethacrylate photopolymer networks

PubMed Central

Abu-Elenain, Dalia; Lewis, Steven H.; Stansbury, Jeffrey W.

2013-01-01

Objectives This study seeks to correlate the interrelated properties of conversion, shrinkage, modulus and stress as dimethacrylate networks transition from rubbery to glassy states during photopolymerization. Methods An unfilled BisGMA/TEGDMA resin was photocured for various irradiation intervals (7–600 s) to provide controlled levels of immediate conversion, which was monitored continuously for 10 min. Fiber optic near-infrared spectroscopy permitted coupling of real-time conversion measurement with dynamic polymerization shrinkage (linometer), modulus (dynamic mechanical analyzer) and stress (tensometer) development profiles. Results The varied irradiation conditions produced final conversion ranging from 6 % to more than 60 %. Post-irradiation conversion (dark cure) was quite limited when photopolymerization was interrupted either at very low or very high levels of conversion while significant dark cure contributions were possible for photocuring reactions suspended within the post-gel, rubbery regime. Analysis of conversion-based property evolution during and subsequent to photocuring demonstrated that the shrinkage rate increased significantly at about 40 % conversion followed by late-stage suppression in the conversion-dependent shrinkage rate that begins at about 45–50 % conversion. The gradual vitrification process over this conversion range is evident based on the broad but well-defined inflection in the modulus versus conversion data. As limiting conversion is approached, modulus and, to a somewhat lesser extent, stress rise precipitously as a result of vitrification with the stress profile showing little if any late-stage suppression as seen with shrinkage. Significance Near the limiting conversion for this model resin, the volumetric polymerization shrinkage rate slows while an exponential rise in modulus promotes the vitrification process that appears to largely dictate stress development. PMID:24080378

Effect of alkaline precipitation on Cr species of Cr(III)-bearing complexes typically used in the tannery industry.

PubMed

Wang, Dandan; Ye, Yuxuan; Liu, Hui; Ma, Hongrui; Zhang, Weiming

2018-02-01

Various organic compounds extensively used in the leather industry could influence the performance of alkaline precipitation with Cr(III). This study focused on two typical Cr(III)-bearing complexes (Cr(III)-collagen and Cr(III)-citrate) ubiquitous in tannery effluent yet with distinct treatment efficiencies, as Cr(III) was much more difficult to remove in the Cr(III)-citrate solution. Comprehensive analytical methods were employed to explore the intrinsic mechanism. It was found that a lower removal efficiency towards Cr(III) was significantly associated with higher oligomers. The molecular size of the Cr(III)-citrate complex continued to increase with rising pH, making it larger overall than Cr(III)-collagen species. The growing oligomer moiety of dissolved Cr(III)-complex species could persist in the stronger basic pH range, leading to the large amount of residual Cr(III) in the Cr(III)-citrate system. Combining this result with potentiometric titration and X-ray photoelectron spectroscopy data, it was believed that the polymeric species other than monomers facilitated resisting the attack from hydroxide ions, and the postulated Cr(III)-citrate species towards higher oligomers were discovered. Beyond that, both charge neutralization and sweeping effects were presented among the gradually emerging flocs in the Cr(III)-collagen system together with the electric double layer compression effect derived from salinity, thus resulting in a larger floc size and higher Cr(III) removal efficiency in saline solutions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Centrifugal precipitation chromatography

PubMed Central

Ito, Yoichiro; Lin, Qi

2009-01-01

Centrifugal precipitation chromatography separates analytes according their solubility in ammonium sulfate (AS) solution and other precipitants. The separation column is made from a pair of long spiral channels partitioned with a semipermeable membrane. In a typical separation, concentrated ammonium sulfate is eluted through one channel while water is eluted through the other channel in the opposite direction. The countercurrent process forms an exponential AS concentration gradient through the water channel. Consequently, protein samples injected into the water channel is subjected to a steadily increasing AS concentration and at the critical AS concentration they are precipitated and deposited in the channel bed by the centrifugal force. Then the chromatographic separation is started by gradually reducing the AS concentration in the AS channel which lowers the AS gradient concentration in the water channel. This results in dissolution of deposited proteins which are again precipitated at an advanced critical point as they move through the channel. Consequently, proteins repeat precipitation and dissolution through a long channel and finally eluted out from the column in the order of their solubility in the AS solution. The present method has been successfully applied to a number of analytes including human serum proteins, recombinant ketosteroid isomerase, carotenoid cleavage enzymes, plasmid DNA, polysaccharide, polymerized pigments, PEG-protein conjugates, etc. The method is capable to single out the target species of proteins by affinity ligand or immunoaffinity separation. PMID:19541553

Interactions between manganese oxides and multiple-ringed aromatic compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whelan, G.; Sims, R.C.

1992-08-01

Objective is to determine whether Mn reductive dissolution can oxidize multiple-ringed aromatics, such as PAHs, in an oxic environment Research indicated that certain PAHs (eg, dihydrodiols and diones that form free-radical intermediates) are susceptible to oxidation and polymerization. Over 14 days, 83, 76, 54, 70, and 20% of the Mn was reduced by 2,3-, 1,3-, and 1,4-naphthalenediol, quinizarin, and 1,4-naphthoquinone, respectively. 100, 100, and 65% of the first three PAHs were oxidized, respectively. Aromatics with diol functional groups were more easily oxidized than those with only dione groups. Relatively insoluble compounds like quinizarin can be oxidized; insoluble ''humic-like'' material precipitated,more » indicating a polymerization-humification process. Results suggest that electron transfer/organic release from the oxide surface is the rate-limiting step.« less

Interactions between manganese oxides and multiple-ringed aromatic compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whelan, G.; Sims, R.C.

1992-08-01

Objective is to determine whether Mn reductive dissolution can oxidize multiple-ringed aromatics, such as PAHs, in an oxic environment? Research indicated that certain PAHs (eg, dihydrodiols and diones that form free-radical intermediates) are susceptible to oxidation and polymerization. Over 14 days, 83, 76, 54, 70, and 20% of the Mn was reduced by 2,3-, 1,3-, and 1,4-naphthalenediol, quinizarin, and 1,4-naphthoquinone, respectively. 100, 100, and 65% of the first three PAHs were oxidized, respectively. Aromatics with diol functional groups were more easily oxidized than those with only dione groups. Relatively insoluble compounds like quinizarin can be oxidized; insoluble ``humic-like`` material precipitated,more » indicating a polymerization-humification process. Results suggest that electron transfer/organic release from the oxide surface is the rate-limiting step.« less

Continuous Precipitation of Ceria Nanoparticles from a Continuous Flow Micromixer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tseng, Chih Heng; Paul, Brian; Chang, Chih-hung

2013-01-01

Cerium oxide nanoparticles were continuously precipitated from a solution of cerium(III) nitrate and ammonium hydroxide using a micro-scale T-mixer. Findings show that the method of mixing is important in the ceria precipitation process. In batch mixing and deposition, disintegration and agglomeration dominates the deposited film. In T-mixing and deposition, more uniform nanorod particles are attainable. In addition, it was found that the micromixing approach reduced the exposure of the Ce(OH)3 precipates to oxygen, yielding hydroxide precipates in place of CeO2 precipitates. Advantages of the micro-scale T-mixing approach include shorter mixing times, better control of nanoparticle shape and less agglomeration.

Formation of Silica-Lysozyme Composites Through Co-Precipitation and Adsorption

NASA Astrophysics Data System (ADS)

van den Heuvel, Daniela B.; Stawski, Tomasz M.; Tobler, Dominique J.; Wirth, Richard; Peacock, Caroline L.; Benning, Liane G.

2018-04-01

Interactions between silica and proteins are crucial for the formation of biosilica and the production of novel functional hybrid materials for a range of industrial applications. The proteins control both precipitation pathway and the properties of the resulting silica-organic composites. Here we present data on the formation of silica-lysozyme composites through two different synthesis approaches (co-precipitation vs. adsorption) and show that the chemical and structural properties of these composites, when analyzed using a combination of synchrotron-based scattering (total scattering and SAXS), spectroscopic, electron microscopy and potentiometric methods vary dramatically. We document that while lysozyme was not incorporated into nor did its presence alter the molecular structure of silica, it strongly enhanced the aggregation of silica particles due to electrostatic and potentially hydrophobic interactions, leading to the formation of composites with characteristics differing from pure silica. The differences increased with increasing lysozyme content for both synthesis approaches. Yet, the absolute changes differ substantially between the two sets of composites, as lysozyme did not just affect aggregation during co-precipitation but also particle growth and likely polymerization during co-precipitation. Our results improve the fundamental understanding of how organic macromolecules interact with dissolved and nanoparticulate silica and how these interactions control the formation pathway of silica-organic composites from sodium silicate solutions, a widely available and cheap starting material.

Design of a Small-Scale Multi-Inlet Vortex Mixer for Scalable Nanoparticle Production and Application to the Encapsulation of Biologics by Inverse Flash NanoPrecipitation.

PubMed

Markwalter, Chester E; Prud'homme, Robert K

2018-05-14

Flash NanoPrecipitation (FNP) is a scalable approach to generate polymeric nanoparticles using rapid micromixing in specially-designed geometries such as a confined impinging jets (CIJ) mixer or a Multi-Inlet Vortex Mixer (MIVM). A major limitation of formulation screening using the MIVM is that a single run requires tens of milligrams of the therapeutic. To overcome this, we have developed a scaled-down version of the MIVM, requiring as little as 0.2 mg of therapeutic, for formulation screening. The redesigned mixer can then be attached to pumps for scale-up of the identified formulation. It was shown that Reynolds Number allowed accurate scaling between the two MIVM designs. The utility of the small-scale MIVM for formulation development was demonstrated through the encapsulation of a number of hydrophilic macromolecules using inverse Flash NanoPrecipitation with target loadings as high as 50% by mass. Copyright © 2018. Published by Elsevier Inc.

The role of extracellular DNA in uranium precipitation and biomineralisation.

PubMed

Hufton, Joseph; Harding, John H; Romero-González, Maria E

2016-10-26

Bacterial extra polymeric substances (EPS) have been associated with the extracellular precipitation of uranium. Here we report findings on the biomineralisation of uranium, with extracellular DNA (eDNA) used as a model biomolecule representative of EPS. The complexation and precipitation of eDNA with uranium were investigated as a function of pH, ionic strength and varying concentrations of reactants. The role of phosphate moieties in the biomineralisation mechanism was studied by enzymatically releasing phosphate (ePO 4 ) from eDNA compared to abiotic phosphate (aPO 4 ). The eDNA-uranium precipitates and uranium minerals obtained were characterised by Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FT-IR) spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-Ray analysis (SEM-EDX), X-Ray Powder Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS). ATR-FT-IR showed that at pH 5, the eDNA-uranium precipitation mechanism was predominantly mediated by interactions with phosphate moieties from eDNA. At pH 2, the uranium interactions with eDNA occur mainly through phosphate. The solubility equilibrium was dependent on pH with the formation of precipitate reduced as the pH increased. The XRD data confirmed the formation of a uranium phosphate precipitate when synthesised using ePO 4 . XPS and SEM-EDX studies showed the incorporation of carbon and nitrogen groups from the enzymatic orthophosphate hydrolysis on the obtained precipitated. These results suggested that the removal of uranium from solution occurs via two mechanisms: complexation by eDNA molecules and precipitation of a uranium phosphate mineral of the type (UO 2 HPO 4 )·xH 2 O by enzymatic orthophosphate hydrolysis. This demonstrated that eDNA from bacterial EPS is a key contributor to uranium biomineralisation.

Improved water resistance of SrAl2O4: Eu2+, Dy3+ phosphor directly achieved in a water-containing medium

NASA Astrophysics Data System (ADS)

Qi, Tonggang; Xia, Haofu; Zhang, Zhanhui; Kong, Shijin; Peng, Weikang; Zhao, Qi; Huang, Zhiliang

2017-03-01

In this paper, a heterogeneous precipitation method utilizing urea hydrolysis was adopted to coat a SiO2 layer on the surface of SrAl2O4:Eu2+, Dy3+ long persistence phosphors. To avoid phosphor hydrolysis in a water-containing coating medium, the hydrolysis and polymerization reactions of tetraethyl orthosilicate (TEOS) were concerned and carried out. The crystal phases, surface morphologies, hydrolysis stability and water resistance on afterglow properties of coated phosphors were investigated. Scanning electron microscopy, energy dispersive spectrum analysis, transmission electron microscope and Fourier transform infrared spectrum results confirmed that a continuous, uniform and compact SiO2 coating layer was successfully obtained on the phosphors surface. A theoretical coating amount of 5% or higher was found to be good for hydrolysis stability. Photoluminescence results revealed the coated phosphors showed much better water resistance on afterglow properties than the uncoated phosphor. We also discussed and proposed the hydrolysis restriction mechanism of SrAl2O4:Eu2+, Dy3+ in the water-containing coating medium.

Synthesis of metronidazole-imprinted molecularly imprinted polymers by distillation precipitation polymerization and their use as a solid-phase adsorbent and chromatographic filler.

PubMed

Liu, Jiang; Zhang, Lu; Li Han Song, Le; Liu, Yuan; Tang, Hui; Li, Yingchun

2015-04-01

Metronidazole-imprinted polymers with superior recognition properties were prepared by a novel strategy called distillation-precipitation polymerization. The as-obtained polymers were characterized by Fourier-transform infrared spectroscopy, laser particle size determination and scanning electron microscopy, and their binding performances were evaluated in detail by static, kinetic and dynamic rebinding tests, and Scatchard analysis. The results showed that when the fraction of the monomers was 5 vol% in the whole reaction system, the prepared polymers afforded good morphology, monodispersity, and high adsorption capacity and excellent selectivity to the target molecule, metronidazole. The optimal binding performance is 12.41 mg/g for metronidazole just before leakage occurred and 38.51 mg/g at saturation in dynamic rebinding tests. Metronidazole-imprinted polymers were further applied as packing agents in solid-phase extraction and as chromatographic filler, both of which served for the detection of metronidazole in fish tissue. The results illustrated the recoveries of spiked samples ranged from 82.97 to 87.83% by using molecularly imprinted solid-phase extraction combined with a C18 commercial column and 93.7 to 101.2% by directly using the polymer-packed chromatographic column. The relative standard deviation of both methods was less than 6%. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of monodisperse molecularly imprinted microspheres with multi-recognition ability via precipitation polymerization for the selective extraction of cyromazine, melamine, triamterene and trimethoprim.

PubMed

Wang, Xian-Hua; Xie, Li-Fu; Dong, Qian; Liu, Hao-Long; Huang, Yan-Ping; Liu, Zhao-Sheng

2015-12-15

Through precipitation polymerization, three monodisperse molecularly imprinted polymers (MIPs) containing imprints of 2,4-diamino-6-methyl-1,3,5-triazine (DM), cyromazine (CY) or trimethoprim (TM), were synthesized using methacrylic acid as functional monomer, divinylbenzene as cross-linker, and a mixture of acetonitrile-toluene (90/10, v/v) as porogen. The morphology and selectivity of the MIPs were characterized and compared systematically. The MIPs had the best specific binding in pure acetonitrile, and the data of adsorption experiment were fitted well with Langmuir and Freundlich model. In addition, DM-MIPs showed the excellent binding and multi-recognition capability for CY, melamine (ME), triamterene (TA) and TM, and the binding capacity were 7.18, 7.56, 5.66 and 5.45μmol/g, respectively. Due to the pseudo template and the ability of multi-recognition, DM-MIPs as sorbent material could avoid the effect of template leakage on quantitative analysis. Therefore, DM-MIPs were used as a solid-phase extraction material to enrich ME, CY, TA and TM from different bio-matrix samples for high performance liquid chromatography analysis. Under the optimized conditions, the recoveries of three spiked levels in different bio-matrix samples were ranged from 80.9% to 91.5% with RSD≤4.2 (n=3). Copyright © 2015 Elsevier B.V. All rights reserved.

Improving Tensile and Compressive Properties of an Extruded AZ91 Rod by the Combined Use of Torsion Deformation and Aging Treatment

PubMed Central

Song, Bo; Wang, Chunpeng; Guo, Ning; Pan, Hucheng; Xin, Renlong

2017-01-01

In this study, AZ91 magnesium alloy rods were used to investigate the effects of torsion deformation on microstructure and subsequent aging behavior. Extruded AZ91 rod has a uniform microstructure and typical fiber texture. Torsion deformation can generate a gradient microstructure on the cross-section of the rod. After torsion, from the center to the edge in the cross-section of the rod, both stored dislocations and area fraction of {10-12} twins gradually increase, and the basal pole of the texture tends to rotate in the ED direction. Direct aging usually generates coarse discontinuous precipitates and fine continuous precipitates simultaneously. Both twin structures and dislocations via torsion deformation can be effective microstructures for the nucleation of continuous precipitates during subsequent aging. Thus, aging after torsion can promote continuous precipitation and generate gradient precipitation characteristics. Both aging treatment and torsion deformation can reduce yield asymmetry, and torsion deformation enhances the aging hardening effect by promoting continuous precipitation. Therefore, combined use of torsion deformation and aging treatment can effectively enhance the yield strength and almost eliminate the yield asymmetry of the present extruded AZ91 rod. Finally, the relevant mechanisms are discussed. PMID:28772638

Absence of first-order unbinding transitions of fluid and polymerized membranes

NASA Technical Reports Server (NTRS)

Grotehans, Stefan; Lipowsky, Reinhard

1990-01-01

Unbinding transitions of fluid and polymerized membranes are studied by renormalization-group (RG) methods. Two different RG schemes are used and found to give rather consistent results. The fixed-point structure of both RG's exhibits a complex behavior as a function of the decay exponent tau for the fluctuation-induced interaction of the membranes. For tau greater than tau(S2) interacting membranes can undergo first-order transitions even in the strong-fluctuation regime. These estimates for tau(S2) imply, however, that both fluid and polymerized membranes unbind in a continuous way in the absence of lateral tension.

In-situ Frequency Dependent Dielectric Sensing of Cure

NASA Technical Reports Server (NTRS)

Kranbuehl, David E.

1996-01-01

With the expanding use of polymeric materials as composite matrices, adhesives, coatings and films, the need to develop low cost, automated fabrication processes to produce consistently high quality parts is critical. Essential to the development of reliable, automated, intelligent processing is the ability to continuously monitor the changing state of the polymeric resin in-situ in the fabrication tool. This final report discusses work done on developing dielectric sensing to monitor polymeric material cure and which provides a fundamental understanding of the underlying science for the use of frequency dependent dielectri sensors to monitor the cure process.

Highly efficient reversible addition-fragmentation chain-transfer polymerization in ethanol/water via flow chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Piaoran; Cao, Peng -Fei; Su, Zhe

Here, utilization of a flow reactor under high pressure allows highly efficient polymer synthesis via reversible addition–fragmentation chain-transfer (RAFT) polymerization in an aqueous system. Compared with the batch reaction, the flow reactor allows the RAFT polymerization to be performed in a high-efficiency manner at the same temperature. The adjustable pressure of the system allows further elevation of the reaction temperature and hence faster polymerization. Other reaction parameters, such as flow rate and initiator concentration, were also well studied to tune the monomer conversion and the molar mass dispersity (Ð) of the obtained polymers. Gel permeation chromatography, nuclear magnetic resonance (NMR),more » and Fourier transform infrared spectroscopies (FTIR) were utilized to monitor the polymerization process. With the initiator concentration of 0.15 mmol L –1, polymerization of poly(ethylene glycol) methyl ethermethacrylate with monomer conversion of 52% at 100 °C under 73 bar can be achieved within 40 min with narrow molar mass dispersity (D) Ð (<1.25). The strategy developed here provides a method to produce well-defined polymers via RAFT polymerization with high efficiency in a continuous manner.« less

In vivo non-invasive optical imaging of temperature-sensitive co-polymeric nanohydrogel

NASA Astrophysics Data System (ADS)

Chen, Haiyan; Zhang, Jian; Qian, Zhiyu; Liu, Fei; Chen, Xinyang; Hu, Yuzhu; Gu, Yueqing

2008-05-01

Assessment of hyperthermia in pathological tissue is a promising strategy for earlier diagnosis of malignant tumors. In this study, temperature-sensitive co-polymeric nanohydrogel poly(N-isopropylacrylamide-co-acrylic acid) (PNIPA-co-AA) was successfully synthesized by the precipitation polymerization method. The diameters of nanohydrogels were controlled to be less than 100 nm. Also the lower critical solution temperature (LCST, 40 °C) was manipulated above physiological temperature after integration of near-infrared (NIR) organic dye (heptamethine cyanine dye, HMCD) within its interior cores. NIR laser light (765 nm), together with sensitive charge coupled device (CCD) cameras, were designed to construct an NIR imaging system. The dynamic behaviors of PNIPA-co-AA-HMCD composites in denuded mice with or without local hyperthermia treatment were real-time monitored by an NIR imager. The results showed that the PNIPA-co-AA-HMCD composites accumulated in the leg treated with local heating and diffused much slower than that in the other leg without heating. The results demonstrated that the temperature-responsive PNIPA-co-AA-HMCD composites combining with an NIR imaging system could be an effective temperature mapping technique, which provides a promising prospect for earlier tumor diagnosis and thermally related therapeutic assessment.

Apparatus for consolidating a pre-impregnated, filament-reinforced polymeric prepreg material

NASA Technical Reports Server (NTRS)

Sandusky, Donald A. (Inventor)

1995-01-01

An apparatus and method were developed for providing a uniform, consolidated, unidirectional, continuous, fiber-reinforced polymeric material. The apparatus comprises a supply means, a forming means, a shaping means, and a take-up means. The forming means further comprises a pre-melting chamber and a stationary bar assembly. The shaping means is a loaded cooled nip-roller apparatus. Forming takes place by heating a polymeric prepreg material to a temperature where the polymer becomes viscous and applying pressure gradients at separate locations along the prepreg material. Upon exiting the forming means, the polymeric prepreg material is malleable, consolidated, and flattened. Shaping takes place by passing the malleable, consolidated, flattened prepreg material through a shaped, matched groove in a loaded, cooled nip-roller apparatus to provide the final solid product.

[Application of continuous mixing technology in ethanol precipitation process of Salvia miltiorrhiza by using micromixer].

PubMed

Gong, Xing-Chu; Shen, Ji-Chen; Qu, Hai-Bin

2016-12-01

Continuous pharmaceutical manufacturing is one of the development directions in international pharmaceutical technology. In this study, a continuous mixing technology of ethanol and concentrated extract in the ethanol precipitation of Salvia miltiorrhiza was realized by using a membrane dispersion method. The effects of ethanol flowrate, concentrated extract flowrate, and flowrate ratio on ethanol precipitation results were investigated. With the increase of the flowrates of ethanol and concentrated extract, retention rate of active phenolic acids components was increased, and the total solid removal rate was decreased. The purity of active components in supernatants was mainly affected by the ratio of ethanol flowrate and concentrated extract flowrate. The mixing efficiency of adding ethanol under continuous flow mixing mode in this study was comparable to that of industrial ethanol precipitation. Continuous adding ethanol by using a membrane dispersion mixer is a promising technology with many advantages such as easy enlargement, large production per unit volume, and easy control. Copyright© by the Chinese Pharmaceutical Association.

Downstream processing from melt granulation towards tablets: In-depth analysis of a continuous twin-screw melt granulation process using polymeric binders.

PubMed

Grymonpré, W; Verstraete, G; Vanhoorne, V; Remon, J P; De Beer, T; Vervaet, C

2018-03-01

The concept of twin-screw melt granulation (TSMG) has steadily (re)-gained interest in pharmaceutical formulation development as an intermediate step during tablet manufacturing. However, to be considered as a viable processing option for solid oral dosage forms there is a need to understand all critical sources of variability which could affect this granulation technique. The purpose of this study was to provide an in-depth analysis of the continuous TSMG process in order to expose the critical process parameters (CPP) and elucidate the impact of process and formulation parameters on the critical quality attributes (CQA) of granules and tablets during continuous TSMG. A first part of the study dealt with the screening of various amorphous polymers as binder for producing high-dosed melt granules of two model drug (i.e. acetaminophen and hydrochlorothiazide). The second part of this study described a quality-by-design (QbD) approach for melt granulation of hydrochlorothiazide in order to thoroughly evaluate TSMG, milling and tableting stage of the continuous TSMG line. Using amorphous polymeric binders resulted in melt granules with high milling efficiency due to their brittle behaviour without producing excessive amounts of fines, providing high granule yields with low friability. Therefore, it makes them extremely suitable for further downstream processing. One of the most important CPP during TSMG with polymeric binders was the granulation-torque, which - in case of polymers with high T g - increased during longer granulation runs to critical levels endangering the continuous process flow. However, by optimizing both screw speed and throughput or changing to polymeric binders with lower T g it was possible to significantly reduce this risk. This research paper highlighted that TSMG must be considered as a viable option during formulation development of solid oral dosage forms based on the robustness of the CQA of both melt granules and tablets. Copyright © 2017 Elsevier B.V. All rights reserved.

System to continuously produce carbon fiber via microwave assisted plasma processing

DOEpatents

White, Terry L [Knoxville, TN; Paulauskas, Felix L [Knoxville, TN; Bigelow, Timothy S [Knoxville, TN

2010-11-02

A system to continuously produce fully carbonized or graphitized carbon fibers using microwave-assisted plasma (MAP) processing comprises an elongated chamber in which a microwave plasma is excited in a selected gas atmosphere. Fiber is drawn continuously through the chamber, entering and exiting through openings designed to minimize in-leakage of air. There is a gradient of microwave power within the chamber with generally higher power near where the fiber exits and lower power near where the fiber enters. Polyacrylonitrile (PAN), pitch, or any other suitable organic/polymeric precursor fibers can be used as a feedstock for the inventive system. Oxidized or partially oxidized PAN or pitch or other polymeric fiber precursors are run continuously through a MAP reactor in an inert, non-oxidizing atmosphere to heat the fibers, drive off the unwanted elements such as oxygen, nitrogen, and hydrogen, and produce carbon or graphite fibers faster than conventionally produced carbon fibers.

Towards Well-Defined Polysilylenes and Polyphosphazenes

DTIC Science & Technology

1992-05-25

distribution), non - controlled degrees of polymerization and unknown end cyclopentasilanes 2 8 . The anionic intermediates have been observed groups. Some... control in polysilanes will be presented: ring-opening polymerization, and polymer modications.. Block and graft copolymers based on polysilanes will be...34sticks" to the surface of alkali metal and continues to grow to high possible to prepare polymers with controlled molecular weight, with low m"m

Climate Influences the Content and Chemical Composition of Foliar Tannins in Green and Senesced Tissues of Quercus rubra

PubMed Central

Top, Sara M.; Preston, Caroline M.; Dukes, Jeffrey S.; Tharayil, Nishanth

2017-01-01

Environmental stresses not only influence production of plant metabolites but could also modify their resorption during leaf senescence. The production-resorption dynamics of polyphenolic tannins, a class of defense compound whose ecological role extends beyond tissue senescence, could amplify the influence of climate on ecosystem processes. We studied the quantity, chemical composition, and tissue-association of tannins in green and freshly-senesced leaves of Quercus rubra exposed to different temperature (Warming and No Warming) and precipitation treatments (Dry, Ambient, Wet) at the Boston-Area Climate Experiment (BACE) in Massachusetts, USA. Climate influenced not only the quantity of tannins, but also their molecular composition and cell-wall associations. Irrespective of climatic treatments, tannin composition in Q. rubra was dominated by condensed tannins (CTs, proanthocyanidins). When exposed to Dry and Ambient*Warm conditions, Q. rubra produced higher quantities of tannins that were less polymerized. In contrast, under favorable conditions (Wet), tannins were produced in lower quantities, but the CTs were more polymerized. Further, even as the overall tissue tannin content declined, the content of hydrolysable tannins (HTs) increased under Wet treatments. The molecular composition of tannins influenced their content in senesced litter. Compared to the green leaves, the content of HTs decreased in senesced leaves across treatments, whereas the CT content was similar between green and senesced leaves in Wet treatments that produced more polymerized tannins. The content of total tannins in senesced leaves was higher in Warming treatments under both dry and ambient precipitation treatments. Our results suggest that, though climate directly influenced the production of tannins in green tissues (and similar patterns were observed in the senesced tissue), the influence of climate on tannin content of senesced tissue was partly mediated by the effect on the chemical composition of tannins. These different climatic impacts on leaves over the course of a growing season may alter forest dynamics, not only in decomposition and nutrient cycling dynamics, but also in herbivory dynamics. PMID:28559896

Property evolution during vitrification of dimethacrylate photopolymer networks.

PubMed

Abu-elenain, Dalia A; Lewis, Steven H; Stansbury, Jeffrey W

2013-11-01

This study seeks to correlate the interrelated properties of conversion, shrinkage, modulus and stress as dimethacrylate networks transition from rubbery to glassy states during photopolymerization. An unfilled BisGMA/TEGDMA resin was photocured for various irradiation intervals (7-600 s) to provide controlled levels of immediate conversion, which was monitored continuously for 10 min. Fiber optic near-infrared spectroscopy permitted coupling of real-time conversion measurement with dynamic polymerization shrinkage (linometer), modulus (dynamic mechanical analyzer) and stress (tensometer) development profiles. The varied irradiation conditions produced final conversion ranging from 6% to more than 60%. Post-irradiation conversion (dark cure) was quite limited when photopolymerization was interrupted either at very low or very high levels of conversion while significant dark cure contributions were possible for photocuring reactions suspended within the post-gel, rubbery regime. Analysis of conversion-based property evolution during and subsequent to photocuring demonstrated that the shrinkage rate increased significantly at about 40% conversion followed by late-stage suppression in the conversion-dependent shrinkage rate that begins at about 45-50% conversion. The gradual vitrification process over this conversion range is evident based on the broad but well-defined inflection in the modulus versus conversion data. As limiting conversion is approached, modulus and, to a somewhat lesser extent, stress rise precipitously as a result of vitrification with the stress profile showing little if any late-stage suppression as seen with shrinkage. Near the limiting conversion for this model resin, the volumetric polymerization shrinkage rate slows while an exponential rise in modulus promotes the vitrification process that appears to largely dictate stress development. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Water-Free Proton-Conducting Membranes for Fuel Cells

NASA Technical Reports Server (NTRS)

Narayanan, Sekharipuram; Yen, Shiao-Pin

2007-01-01

Poly-4-vinylpyridinebisulfate (P4VPBS) is a polymeric salt that has shown promise as a water-free proton-conducting material (solid electrolyte) suitable for use in membrane/electrode assemblies in fuel cells. Heretofore, proton-conducting membranes in fuel cells have been made from perfluorinated ionomers that cannot conduct protons in the absence of water and, consequently, cannot function at temperatures >100 C. In addition, the stability of perfluorinated ionomers at temperatures >100 C is questionable. However, the performances of fuel cells of the power systems of which they are parts could be improved if operating temperatures could be raised above 140 C. What is needed to make this possible is a solid-electrolyte material, such as P4VPBS, that can be cast into membranes and that both retains proton conductivity and remains stable in the desired higher operating temperature range. A family of solid-electrolyte materials different from P4VPBS was described in Anhydrous Proton-Conducting Membranes for Fuel Cells (NPO-30493), NASA Tech Briefs, Vol. 29, No. 8 (August 2005), page 48. Those materials notably include polymeric quaternized amine salts. If molecules of such a polymeric salt could be endowed with flexible chain structures, it would be possible to overcome the deficiencies of simple organic amine salts that must melt before being able to conduct protons. However, no polymeric quaternized amine salts have yet shown to be useful in this respect. The present solid electrolyte is made by quaternizing the linear polymer poly- 4-vinylpyridine (P4VP) to obtain P4VPBS. It is important to start with P4VP having a molecular weight of 160,000 daltons because P4VPBS made from lower-molecular-weight P4VP yields brittle membranes. In an experimental synthesis, P4VP was dissolved in methanol and then reacted with an excess of sulfuric acid to precipitate P4VPBS. The precipitate was recovered, washed several times with methanol to remove traces of acid, and dried to a white granular solid. In another synthesis, nanoparticles of silica rich with surface hydroxyl groups were added to P4VP in methanol solution, which was then reacted with excess sulfuric acid to precipitate granules of a composite that most probably had the composition (P4VPBS)-SiO2-SiO(HSO4)2. The granular P4VPBS produced in the first-mentioned synthesis was dissolved in water to make a glue-like, turbid solution; the granular P4VPBS/silica composite produced in the second-mentioned synthesis was mixed with water to make a turbid, glue-like suspension. The proportions of polymer salt to water in such preparations can be varied; it was found that approximately equal parts of water and polymer salt yield a solution or suspension amenable to further processing.

Polymeric Biomaterials: Diverse Functions Enabled by Advances in Macromolecular Chemistry

PubMed Central

Liang, Yingkai; Li, Linqing; Scott, Rebecca A.; Kiick, Kristi L.

2017-01-01

Biomaterials have been extensively used to leverage beneficial outcomes in various therapeutic applications, such as providing spatial and temporal control over the release of therapeutic agents in drug delivery as well as engineering functional tissues and promoting the healing process in tissue engineering and regenerative medicine. This perspective presents important milestones in the development of polymeric biomaterials with defined structures and properties. Contemporary studies of biomaterial design have been reviewed with focus on constructing materials with controlled structure, dynamic functionality, and biological complexity. Examples of these polymeric biomaterials enabled by advanced synthetic methodologies, dynamic chemistry/assembly strategies, and modulated cell-material interactions have been highlighted. As the field of polymeric biomaterials continues to evolve with increased sophistication, current challenges and future directions for the design and translation of these materials are also summarized. PMID:29151616

Microbial bio-mineralization processes in hydrothermal travertine: the case study of two active travertine systems (Tuscany, Italy).

NASA Astrophysics Data System (ADS)

Barilaro, Federica; Bontognali, Tomaso R. R.; Mc Kenzie, Judith A.; Vasconcelos, Crisogono

2015-04-01

Modern hydrothermal travertine deposits, occurring today at Bagni San Filippo (Radicofani Basin) and at Bagni di Saturnia (Albegna Valley) in Tuscany, Central Italy, have been investigated with the main purpose to improve the understanding of the processes that control calcium carbonate precipitation in hydrothermal-spring settings. Present-day thermal activity at Bagni di Saturnia is characterized by a 37.5°C thermal spring with a rate of about 800 l/s, with a pH of ca. 6.4. Thermal water discharges at Bagni San Filippo reach a rate of 20 litres per second at a maximum temperature of 50°C and a pH of ca. 7. The springs expel water enriched in H2S-CO2-SO42- and HCO3- and divalent cations (Ca and Mg). In the studied areas, travertine precipitation occurs in association with living microbial mats and biofilms, composed of a heterogeneous community of green algae, filamentous cyanobacteria and other types of prokaryotes, anoxygenic photosynthetic bacteria and heterotrophic heat-tolerant bacteria, with a variable amount of extracellular polymeric substances (EPS). Nine categories of fabric types, dominantly calcite and aragonite in composition, showing a wide range of macro- and micro-porosity, have been identified. High magnification analysis of dendritic and laminated boundstone, crystalline crust cementstone, raft boundstone, coated bubble boundstone, micrite mudstone and coated reed boundstone fabric types, suggests that precipitation occurs in association with organic matter. Diatoms, cyanobacteria filaments and other bacteria are then associated with the EPS and often appear totally or partially entombed (passively or actively) in it. Organic extracellular polymeric substances (EPS) and often the external surface of cyanobacterial sheaths are the location where the calcite minerals nucleate and grow. Precipitation begins with organomineral nano-globules consisting of nanometre-size, from sub-spherical to globular-like, raised structures (5 to 80 nm diameter). The nano-globules, that represent the first stage of precipitation, coalesce and organize in rods. The assemblage of these rods gives rise to triangular-like morphologies that, gradually, evolve to form well developed calcite crystals, substituting/replacing the organic matter. The presence of EPS, microbs, and calcite mineral phase suggest that biological activity and degradation of organic matter may play a fundamental role in the travertine formation. Acicular crystals of aragonite, nucleated also on organic compound and characterized by the lack of nano-globules, surround the calcite crystals aggregates. The precipitation of aragonite may suggest a change in micro-environmental conditions that involve a predominantly abiotic mechanism of precipitation. Gypsum crystals were mainly individuated in the upper zone of microbial mats and filamentous organic structures connected to the crystals have been observed. A biologically induced process is also claimed for the identified framboidal pyrite related to possible sulphate reducing bacteria. These observations suggest that biological activities are crucial in travertine precipitation. Travertine precipitation is not only related to abiotic parameters of calcium equilibrium, such us physicochemical carbon dioxid degassing and elevated temperature of the hydrothermal water. This study 1) demonstrates that organomineralization processes are not only exclusive of marine carbonate and tufa and 2) confirms the importance of micro- and nano-scale investigation to discriminate between biotic versus abiotic origin of the precipitates.

Selective sequential precipitation of dissolved metals in mine drainage from coal mine

NASA Astrophysics Data System (ADS)

Yim, Giljae; Bok, Songmin; Ji, Sangwoo; Oh, Chamteut; Cheong, Youngwook; Han, Youngsoo; Ahn, Joosung

2017-04-01

In abandoned mines in Korea, a large amount of mine drainage continues to flow out and spread pollution. In purification of the mine drainage a massive amount of sludge is generated as waste. Since this metal sludge contains high Fe, Al and Mn oxides, developing the treatment method to recover homogeneous individual metal with high purity may beneficial to recycle waste metals as useful resources and reduce the amount of sludge production. In this regard, we established a dissolved metals selective precipitation process to treat Waryong Industry's mine drainage. The process that selectively precipitates metals dissolved in mine drainage is a continuous Fe-buffer-Al process, and each process consists of the neutralization tank, the coagulation tank, and the settling tank. Based on this process, this study verified the operational applicability of the Fe and Al selective precipitation. Our previous study revealed that high-purity Fe and Al precipitates could be recovered at a flow rate of 1.5 ton/day, while the lower purity was achieved when the rate was increased to about 3 ton/day due to the difficulty in reagent dosage control. In the current study was conducted to increase the capacity of the system to recover Fe and Al as high-purity precipitates at a flow rate of 10 ton/day with the ensured continuous operations by introducing an automatic reagent injection system. The previous study had a difficulty in controlling the pH and operating system continuously due to the manually controlled reagent injection system. To upgrade this and ensure the optimal pH in a stable way, a continuous reagent injection system was installed. The result of operation of the 10 ton/day system confirmed that the scaled-up process could maintain the stable recovery rates and purities of precipitates on site.

1995 Annual Report and Five Year (1995-1999) Strategic Investment Plan

DTIC Science & Technology

1996-08-01

fouling release hull coatings exploiting the low surface energy of surface oriented perfluorinated alkyl compounds . This project is a continuation...would not be able to adhere to it. The lowest surface free energies can be created by adsorbed monolayers of closely packed perfluorinated compounds ...embedding such molecules into the surface of polymeric matrices, and by binding the perfluorinated compounds into a polymeric backbone to create comb type

Synthesis and characterization of novel polyacid-stabilized latexes.

PubMed

Yang, Pengcheng; Armes, S P

2012-09-18

A series of novel polyacid macromonomers based on 2-hydroxypropyl methacrylate (HPMA) were prepared by atom transfer radical polymerization (ATRP) via a two-step route. First, a range of well-defined PHPMA homopolymer precursors were synthesized by ATRP using a tertiary amine-functionalized initiator, 2-(dimethylamino)ethyl-2-bromoisobutyrylamide, and a CuCl/2, 2'-bipyridine (bpy) catalyst in alcoholic media at 50 °C. ATRP polymerizations were relatively slow and poorly controlled in pure isopropanol (IPA), especially when targeting higher degrees of polymerization (DP > 30). Improved control was achieved by addition of water: low polydispersity (M(w)/M(n) < 1.25) PHPMA homopolymers of DP = 30, 40, 50, 60, or 70 were successfully prepared using a 9:1 w/w % IPA/water mixture at 50 °C. These PHPMA homopolymer precursors were then derivatized to produce the corresponding poly(2-(succinyloxy)propyl methacrylate) (PSPMA) macromonomers by quaternizing the tertiary amine end-group with excess 4-vinylbenzyl chloride, followed by esterification of the pendent hydroxyl groups using excess succinic anhydride at 20 °C. These polyacid macromonomers were evaluated as reactive steric stabilizers for polystyrene latex synthesis under either aqueous emulsion polymerization or alcoholic dispersion polymerization conditions. Near-monodisperse polystyrene latexes were obtained via aqueous emulsion polymerization using 10 wt % PSPMA macromonomer (with respect to styrene monomer) with various initiators as evidenced by scanning electron microscopy, disk centrifuge photosedimentometry and light scattering studies. PSPMA macromomer concentrations as low as 1.0 wt % also produced near-monodisperse latexes, suggesting that these PSPMA macromonomers are highly effective stabilizers. Alcoholic dispersion polymerization of styrene conducted in various ethanol/water mixtures with 10 wt % PSPMA(50) macromonomer produced relatively large near-monodisperse latexes. Increasing the water content in such formulations led to smaller latexes, as expected. Control experiments conducted with 10 wt % PSPMA(50) homopolymer produced relatively large polydisperse latexes via emulsion polymerization and only macroscopic precipitates via alcoholic dispersion polymerization. Thus the terminal styrene group on the macromonomer chains is essential for the formation of well-defined latexes. FT-IR spectroscopy indicated that these latexes contained PSPMA macromonomer, whereas (1)H NMR spectroscopy studies of dissolved latexes allowed stabilizer contents to be determined. Aqueous electrophoresis and X-ray photoelectron spectroscopy studies confirmed that the PSPMA macromonomer chains were located at the latex surface, as expected. Finally, these polyacid-stabilized polystyrene latexes exhibited excellent freeze-thaw stability and remained colloidally stable in the presence of electrolyte.

Rates of manganese oxidation in aqueous systems

USGS Publications Warehouse

Hem, J.D.

1981-01-01

The rate of crystal growth of Mn3O4 (hausmannite) and ??MnOOH (feitknechtite) in aerated aqueous manganous perchlorate systems, near 0.01 M in total manganese, was determined at pH levels ranging from 7.00 to 9.00 and at temperatures from 0.5 to 37.4??C. The process is autocatalytic, but becomes psuedo first-order in dissolved Mn2+ activity when the amount of precipitate surface is large compared to the amount of unreacted manganese. Reaction rates determined by titrations using an automated pH-stat were fitted to an equation for precipitate growth. The rates are proportional to surface area of oxide and degree of supersaturation with respect to Mn2+. The oxide obtained at the higher temperature was Mn3O4, but at 0.5?? C only ??MnOOH was formed. At intermediate temperatures, mixtures of these solids were formed. The rate of precipitation of hausmannite is strongly influenced by temperature, and that of feitknechtite much less so. The difference in activation energy may be related to differences in crystal structure of the oxides and the geometry of polymeric hydroxy ion precursors. ?? 1981.

Protein Binding and Astringent Taste of a Polymeric Procyanidin, 1,2,3,4,6-Penta-O-galloyl-β-D-glucopyranose, Castalagin and Grandinin

PubMed Central

Hofmann, Thomas; Glabasnia, Arne; Schwarz, Bernd; Wisman, Kimberly N.; Gangwer, Kelly A.; Hagerman, Ann E.

2008-01-01

The objective of the present investigation was to examine oral astringency and protein binding activity of four structurally well-defined tannins, namely procyanidin (epicatechin16(4→8)catechin), pentagalloyl glucose (1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose), castalagin, and grandinin, representing the three main structural categories of tannins, the proanthocyanidins, the gallotannins, and the ellagitannins. Astringency threshold and dose response were determined by the half-tongue test using a trained human panel. Protein binding stoichiometry and relative affinity were determined using radioiodinated bovine serum albumin in precipitation or competitive binding assays. Procyanidin and pentagalloyl glucose were perceived as highly astringent compounds and had relatively steep dose response curves but castalagin and grandinin had a lower mass threshold for detection. In vitro, procyanidin was the most effective protein precipitating agent, and grandinin the least. Increasing the temperature increased protein precipitation by the hydrolysable tannins, especially grandinin. All four polyphenols had higher relative affinity for proline-rich proteins than for bovine serum albumin. PMID:17147439

Do biofilms and clays alter the chemistry and fabric of a hyper-alklaine, saline, non-marine carbonate precipitate?

NASA Astrophysics Data System (ADS)

Rogerson, Michael; Saunders, Paul; Mercedes-Martin, Ramon; Brasier, Alex; Pedley, Martyn

2015-04-01

Non-marine carbonates comprise a hugely diverse family of deposits, which reflect a constellation of forcing factors from local hydraulics to regional climatology. However, the two dominant controls on precipitation are solution chemistry and benthic microbial biogeochemistry. Here, we present a unifying concept for understanding how these controls influence deposit characteristics, and re-emphasise the importance of biofilms. It is generally accepted that biofilms play an important part in the precipitation of authigenic minerals in a wide variety of settings. In carbonate settings, biofilms are recognised to increase the amount of calcite precipitation and alter the geometry and coarse scale petrography of the precipitate. They determine at what water marginal water chemistries calcite starts to precipitate and microbialites give way to chemical limestones. Biofilms also interact with ambient water, controlling chemical accumulation transport. New evidence, drawn from unique experimental approaches, is demonstrating that biofilm influence extends to control of calcite trace element composition, and crystal scale fabric. Under tightly controlled temperature and chemical conditions, fully replicated experiments show that Mg incorporation into tufa carbonate defies the expected thermodynamic control. However, there is a pronounced influence on (Mg/Ca)calcite from precipitation rate, so that rapidly forming precipitates develop with very low magnesium content indicating kinetic control on fractionation. Calcite precipitation rate in these experiments is controlled by biofilm growth rate and reflects kinetic fractionation arises from the electrochemical activity of extracellular organic acids. These effects are therefore likely to occur wherever these molecules occur, including stromatolites, soil and lake carbonates and (via colloidal organic acids) speleothems. The presence of Extracellular polymeric substances (EPS), even without the presence of cells, also alters precipitation style. Spherular and shrubby calcite growths are well known from the geological record, but their environmental significance is not clear. Sterile, microcosm experiments have shown that these forms occur in saline, hyperalkaline settings ' but only in the presence of organic acid molecules in solution. The presence of inorganic materials (hydrated magnesium clays) does not impact on precipitate morphology, and reduces the precipitation rate of calcite.

Molecularly imprinted polymer for glutathione by modified precipitation polymerization and its application to determination of glutathione in supplements.

PubMed

Nakamura, Yukari; Masumoto, Shizuka; Matsunaga, Hisami; Haginaka, Jun

2017-09-10

Molecularly imprinted polymers (MIP) particles for glutathione (GSH) with a narrow particle size distribution were prepared by modified precipitation polymerization using methacrylic acid as a functional monomer, divinylbenzene as a crosslinker and water as a co-solvent. The particle diameters of the MIP and non-imprinted polymer (NIP) prepared under the optimum conditions were 3.81±0.95 (average±standard deviation) and 3.39±1.22μm, respectively. The retention and molecular-recognition properties of the prepared MIP were evaluated using a mixture of acetonitrile and water as a mobile phase in hydrophilic interaction chromatography. With an increase of acetonitrile content, the retention factor of GSH was increased on the MIP. In addition to shape recognition, hydrophilic interactions seem to work for the recognition of GSH on the MIP. The MIP had a specific molecular-recognition ability for GSH, while glutathione disulfide, l-Glu, l-Cys, Gly-Gly and l-Cys-Gly could not be retained or recognized on the MIP. The effect of column temperature revealed that the separation of GSH on the MIP was entropically driven. Binding experiments and Scatchard analyses revealed that one binding sites were formed on both the MIP and NIP, while the MIP gave higher affinity and capacity for GSH than the NIP. Furthermore, the MIP was successfully applied for determination of GSH in the supplements. Copyright © 2016 Elsevier B.V. All rights reserved.

Monitoring precipitation chemistry on the Monongahela National Forest

Treesearch

John B. Currier; Gerald M. Aubertin

1976-01-01

Personnel from the Monongahela National Forest and the Northeastern Forest Experiment Station are collaborating in forest-wide monitoring of precipitation chemistry. Present monitoring facilities consist of one continuous precipitation collector/pH recorder and 12 precipitation collectors. Samples collected in these facilities are picked up and analyzed biweekly for...

Negatively charged polysulfone membranes with hydrophilicity and antifouling properties based on in situ cross-linked polymerization.

PubMed

Zhu, Lijing; Song, Haiming; Zhang, Dawei; Wang, Gang; Zeng, Zhixiang; Xue, Qunji

2017-07-15

Polysulfone (PSf) membrane has been widely used in water separation and purification, although, membrane fouling is still a serious problem limiting its potential. We aim to improve the antifouling of PSf membranes via a very simple and efficient method. In this work, antifouling PSf membranes were fabricated via in situ cross-linked polymerization coupled with non-solvent induced phase separation. In brief, acrylic acid (AA) and vinyltriethoxysilane (VTEOS) were copolymerized in PSf solution, then directly casted into membranes without purification. With the increase of monomers concentration, the morphology of the as-cast membranes changed from a finger-like morphology to a fully sponge-like structure due to the increased viscosity and decreased precipitation rate of the polymer solutions. Meanwhile, the hydrophilicity and electronegativity of modified membranes were highly improved leading to inhibited protein adsorption and improved antifouling property. Furthermore, in order to further find out the different roles player by AA and VTESO, the modified membrane without VTEOS was prepared and characterized. The results indicated that AA is more effective in the membrane hydrophilicity improvement, VTEOS is more crucial to improve membrane stability. This work provides valuable guidance for fabricating PSf membranes with hydrophilicity and antifouling property via in situ cross-linked polymerization. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of aqueous Si/Mg ratio and pH on the nucleation and growth of sepiolite at 25 °C

NASA Astrophysics Data System (ADS)

Baldermann, Andre; Mavromatis, Vasileios; Frick, Paula M.; Dietzel, Martin

2018-04-01

Sepiolite [Mg4Si6O15(OH)2·6H2O] is a trioctahedral 2:1 Mg-silicate that has been often used to reconstruct the evolution of sedimentary environments and facies in the geological record. To date, however, the reaction paths underlying sepiolite formation are poorly constrained and most of the existing models are based on empirical observations. In order to shed light on the mechanisms controlling the formation of this mineral phase, in the present study, sepiolite was precipitated at 25 ± 1 °C from modified seawater and MgCl2 solutions undersaturated with respect to brucite and amorphous silica. Although a suite of hydrous Mg-silicates, such as kerolite, saponite, stevensite and talc, were oversaturated in the solutions at a higher level relative to sepiolite at any time of reaction, poorly crystallized, aluminous sepiolite was the only precipitate after 91 days. The precipitated sepiolite [Mg3.4-3.8Al0.1-0.4)∑3.8-3.9(Si5.9-6.0Al0-0.1)O15(OH)2·nH2O] shares a number of structural and chemical similarities with natural sepiolite, such as a fibrous crystal shape and an atomic Si/(Si + Mg+Al) ratio of ∼0.61. The proposed reaction path for the formation of sepiolite is based on the temporal evolution of the chemical compositions of the experimental solution and solids: (i) Nucleation and growth of Al-sepiolite occurred during the first 8 days of the experimental runs via condensation and polymerization of Sisbnd OH tetrahedra onto Mg-Al-O-OH template sheets at a precipitation rate of ∼2.19 ± 0.01 × 10-10 mol s-1. (ii) At decreasing pH and in the absence of [Al]aq this intermediate phase transformed into aluminous sepiolite at a slower crystal growth rate of ∼1.08 ± 0.02 × 10-12 mol s-1. This finding explains the high abundances of sepiolite in highly alkaline, evaporitic, lacustrine and soil environments, where the growth rates of sepiolite are considered faster (10-11 to 10-10 mol s-1, Brady, 1992). We propose that (i) low rates of Mg2+ ion dehydration and silica condensation and polymerization at the surface of the initial precipitate, (ii) the formation of MgS 040 aquo-complexes and (iii) the reduced sorption rates of [Si]aq and [Mg]aq at the active growth sites on sepiolite surfaces at pH ≤ 8.3 retard the precipitation of sepiolite in marine-diagenetic environments.

Various aspects of ultrasound assisted emulsion polymerization process.

PubMed

Korkut, Ibrahim; Bayramoglu, Mahmut

2014-07-01

In this paper, the effects of ultrasonic (US) power, pulse ratio, probe area and recipe composition were investigated on two process responses namely, monomer (methyl methacrylate, MMA) conversion and electrical energy consumption per mass of product polymer (PMMA). Pulsed mode US is more suitable than continuous mode US for emulsion polymerization. The probe (tip) area has little effect on the yield of polymerization when comparing 19 and 13 mm probes, 13 mm probe performing slightly better for high conversion levels. Meanwhile, large probe area is beneficial for high conversion efficiency of electric energy to US energy as well as for high radical generation yield per energy consumed. The conversion increased slightly and electrical energy consumption decreased substantially by using a recipe with high SDS and monomer concentrations. Conclusions presented in this paper may be useful for scale-up of US assisted emulsion polymerization. Copyright © 2014 Elsevier B.V. All rights reserved.

Clays as possible catalysts for peptide formation in the prebiotic era

NASA Technical Reports Server (NTRS)

Paecht-Horowitz, M.

1976-01-01

From the point of view of prebiotic synthesis, clays might have performed functions of concentration, catalysis, and protection of molecules. The degrees of polymerization obtained, when amino acid adenylates are added to montmorillonite suspensions in water, are much higher than those obtained by polymerization in the absence of such a clay. In addition, they are of a discrete spectrum, usually multiples of 6 or 7, and reach values of up to 40 mers. In the absence of clay a continuous spectrum of degrees of polymerization is obtained, and usually up to 4-6 mers only. Copolymerization in the absence of clays yields mostly random copolymers, in their presence mostly block copolymers are obtained. Optical density measurements show that after adsorption has taken place on the clay, stacking of its layers occurs. Polymerization starts only after these stacked layers have been formed

21 CFR 178.3740 - Plasticizers in polymeric substances.

Code of Federal Regulations, 2012 CFR

2012-04-01

... (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: ADJUVANTS, PRODUCTION AIDS, AND... type of food and under the conditions of time and temperature characterizing the conditions of its... that contain more than 8 percent of alcohol) at temperatures not to exceed room temperature. The...

21 CFR 178.3740 - Plasticizers in polymeric substances.

Code of Federal Regulations, 2010 CFR

2010-04-01

... (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: ADJUVANTS, PRODUCTION AIDS, AND... type of food and under the conditions of time and temperature characterizing the conditions of its... that contain more than 8 percent of alcohol) at temperatures not to exceed room temperature. The...

21 CFR 178.3740 - Plasticizers in polymeric substances.

Code of Federal Regulations, 2013 CFR

2013-04-01

... (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: ADJUVANTS, PRODUCTION AIDS, AND... type of food and under the conditions of time and temperature characterizing the conditions of its... that contain more than 8 percent of alcohol) at temperatures not to exceed room temperature. The...

21 CFR 178.3740 - Plasticizers in polymeric substances.

Code of Federal Regulations, 2011 CFR

2011-04-01

... (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: ADJUVANTS, PRODUCTION AIDS, AND... type of food and under the conditions of time and temperature characterizing the conditions of its... that contain more than 8 percent of alcohol) at temperatures not to exceed room temperature. The...

Deposition of functionalized polymer layers in surface plasmon resonance immunosensors by in-situ polymerization in the evanescent wave field.

PubMed

Chegel, Vladimir; Whitcombe, Michael J; Turner, Nicholas W; Piletsky, Sergey A

2009-01-01

Traditionally, the integration of sensing gel layers in surface plasmon resonance (SPR) is achieved via "bulk" methods, such as precipitation, spin-coating or in-situ polymerization onto the total surface of the sensor chip, combined with covalent attachment of the antibody or receptor to the gel surface. This is wasteful in terms of materials as the sensing only occurs at the point of resonance interrogated by the laser. By isolating the sensing materials (antibodies, enzymes, aptamers, polymers, MIPs, etc.) to this exact spot a more efficient use of these recognition elements will be achieved. Here we present a method for the in-situ formation of polymers, using the energy of the evanescent wave field on the surface of an SPR device, specifically localized at the point of interrogation. Using the photo-initiator couple of methylene blue (sensitizing dye) and sodium p-toluenesulfinate (reducing agent) we polymerized a mixture of N,N-methylene-bis-acrylamide and methacrylic acid in water at the focal point of SPR. No polymerization was seen in solution or at any other sites on the sensor surface. Varying parameters such as monomer concentration and exposure time allowed precise control over the polymer thickness (from 20-200 nm). Standard coupling with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide was used for the immobilization of protein G which was used to bind IgG in a typical biosensor format. This model system demonstrated the characteristic performance for this type of immunosensor, validating our deposition method.

Highly temperature responsive core-shell magnetic particles: synthesis, characterization and colloidal properties.

PubMed

Rahman, Md Mahbubor; Chehimi, Mohamed M; Fessi, Hatem; Elaissari, Abdelhamid

2011-08-15

Temperature responsive magnetic polymer submicron particles were prepared by two step seed emulsion polymerization process. First, magnetic seed polymer particles were obtained by emulsion polymerization of styrene using potassium persulfate (KPS) as an initiator and divinylbenzne (DVB) as a cross-linker in the presence of oil-in-water magnetic emulsion (organic ferrofluid droplets). Thereafter, DVB cross-linked magnetic polymer particles were used as seed in the precipitation polymerization of N-isopropylacrylamide (NIPAM) to induce thermosensitive PNIPAM shell onto the hydrophobic polymer surface of the cross-linked magnetic polymer particles. To impart cationic functional groups in the thermosensitive PNIPAM backbone, the functional monomer aminoethylmethacrylate hydrochloride (AEMH) was used to polymerize with NIPAM while N,N'-methylenebisacrylamide (MBA) and 2, 2'-azobis (2-methylpropionamidine) dihydrochloride (V-50) were used as a cross-linker and as an initiator respectively. The effect of seed to monomer (w/w) ratio along with seed nature on the final particle morphology was investigated. Dynamic light scattering (DLS) results demonstrated particles swelling at below volume phase transition temperature (VPTT) and deswelling above the VPTT. The perfect core (magnetic) shell (polymer) structure of the particles prepared was confirmed by Transmission Electron Microscopy (TEM). The chemical composition of the particles were determined by thermogravimetric analysis (TGA). The effect of temperature, pH, ionic strength on the colloidal properties such as size and zeta potential of the micron sized thermo-sensitive magnetic particles were also studied. In addition, a short mechanistic discussion on the formation of core-shell morphology of magnetic polymer particles has also been discussed. Copyright © 2011 Elsevier Inc. All rights reserved.

Tunable, Quantitative Fenton-RAFT Polymerization via Metered Reagent Addition.

PubMed

Nothling, Mitchell D; McKenzie, Thomas G; Reyhani, Amin; Qiao, Greg G

2018-05-10

A continuous supply of radical species is a key requirement for activating chain growth and accessing quantitative monomer conversions in reversible addition-fragmentation chain transfer (RAFT) polymerization. In Fenton-RAFT, activation is provided by hydroxyl radicals, whose indiscriminate reactivity and short-lived nature poses a challenge to accessing extended polymerization times and quantitative monomer conversions. Here, an alternative Fenton-RAFT procedure is presented, whereby radical generation can be finely controlled via metered dosing of a component of the Fenton redox reaction (H 2 O 2 ) using an external pumping system. By limiting the instantaneous flux of radicals and ensuring sustained radical generation over tunable time periods, metered reagent addition reduces unwanted radical "wasting" reactions and provides access to consistent quantitative monomer conversions with high chain-end fidelity. Fine tuning of radical concentration during polymerization is achieved simply via adjustment of reagent dose rate, offering significant potential for automation. This modular strategy holds promise for extending traditional RAFT initiation toward more tightly regulated radical concentration profiles and affords excellent prospects for the automation of Fenton-RAFT polymerization. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modeling of lipase catalyzed ring-opening polymerization of epsilon-caprolactone.

PubMed

Sivalingam, G; Madras, Giridhar

2004-01-01

Enzymatic ring-opening polymerization of epsilon-caprolactone by various lipases was investigated in toluene at various temperatures. The determination of molecular weight and structural identification was carried out with gel permeation chromatography and proton NMR, respectively. Among the various lipases employed, an immobilized lipase from Candida antartica B (Novozym 435) showed the highest catalytic activity. The polymerization of epsilon-caprolactone by Novozym 435 showed an optimal temperature of 65 degrees C and an optimum toluene content of 50/50 v/v of toluene and epsilon-caprolactone. As lipases can degrade polyesters, a maximum in the molecular weight with time was obtained due to the competition of ring opening polymerization and degradation by specific chain end scission. The optimum temperature, toluene content, and the variation of molecular weight with time are consistent with earlier observations. A comprehensive model based on continuous distribution kinetics was developed to model these phenomena. The model accounts for simultaneous polymerization, degradation and enzyme deactivation and provides a technique to determine the rate coefficients for these processes. The dependence of these rate coefficients with temperature and monomer concentration is also discussed.

Preparation of anti-CD4 monoclonal antibody-conjugated magnetic poly(glycidyl methacrylate) particles and their application on CD4+ lymphocyte separation.

PubMed

Pimpha, Nuttaporn; Chaleawlert-umpon, Saowaluk; Chruewkamlow, Nuttapol; Kasinrerk, Watchara

2011-03-15

Novel immunomagnetic particles have been prepared for separation of CD4(+) lymphocytes. The magnetic nanoparticles with a diameter of approximately 5-6 nm were first synthesized by co-precipitation from ferrous and ferric iron solutions and subsequently encapsulated with poly(glycidyl methacrylate) (PGMA) by precipitation polymerization. Monoclonal antibody specific to CD4 molecules expressed on CD4(+) lymphocytes was conjugated to the surface of magnetic PGMA particles through covalent bonding between epoxide functional groups on the particle surface and primary amine groups of the antibodies. The generated immunomagnetic particles have successfully separated CD4(+) lymphocytes from whole blood with over 95% purity. The results indicated that these particles can be employed for cell separation and provide a strong potential to be applied in various biomedical applications including diagnosis, and monitoring of human diseases. Copyright © 2010 Elsevier B.V. All rights reserved.

Block copolymers for biomimetic composites

NASA Astrophysics Data System (ADS)

Calvert, Paul D.; Oner, Mualla; Burdon, Jeremy; Rieke, Peter C.; Farmer, Kelly

1993-07-01

Mineralized biological tissues can be regarded as composites where a fine reinforcement is laid down in a very controlled fashion within a tough polymeric matrix. Such materials include bone, antler, tooth enamel, mollusc shell, and crustacean shell. We have been exploring ways of forming similar structures by synthetic routes involving precipitation of reinforcing particles directly into a polymeric matrix. Part of this biomimetic approach requires polymer matrices which can exert a high degree of control over the mineralization process. Polymer gels have been formed from cross-linked methacrylates with various types of functionality within the gel. By incorporating calcium binding groups we have been producing gels which lead to preferential mineralization of the gel when it is incubated in a supersaturated solution of calcium oxalate or calcium carbonate. Similarly we have been incorporating silane groups within the gel in order to promote the deposition of silica in a gel body when it is immersed in a metastable solution of partly hydrolysed silicon alkoxides.

Exogenous acetaldehyde as a tool for modulating wine color and astringency during fermentation.

PubMed

Sheridan, Marlena K; Elias, Ryan J

2015-06-15

Wine tannins undergo modifications during fermentation and storage that can decrease their perceived astringency and increase color stability. Acetaldehyde acts as a bridging compound to form modified tannins and polymeric pigments that are less likely to form tannin-protein complexes than unmodified tannins. Red wines are often treated with oxygen in order to yield acetaldehyde, however this approach can lead to unintended consequences due to the generation of reactive oxygen species. The present study employs exogenous acetaldehyde at relatively low and high treatment concentrations during fermentation to encourage tannin modification without promoting potentially deleterious oxidation reactions. The high acetaldehyde treatment significantly increased polymeric pigments in the wine without increasing concentrations of free and sulfite-bound acetaldehyde. Protein-tannin precipitation was also significantly decreased with the addition of exogenous acetaldehyde. These results indicate a possible treatment of wines early in their production to increase color stability and lower astringency of finished wines. Copyright © 2015 Elsevier Ltd. All rights reserved.

Designing Drug Conjugates Based on Sugar Decorated V-Shape and Star Polymethacrylates: Influence of Composition and Architecture of Polymeric Carrier.

PubMed

Mielańczyk, Anna; Neugebauer, Dorota

2015-12-16

Amphiphilic ethylenediamine (EDA)-functionalized V-shape and star copolymers with centrally placed methyl-α,D-glucopyranoside were designed as nanocarriers. Anticancer doxorubicin (DOX) was conjugated in water via amine groups in copolymers to form ketimine linkers. Variations of arm length and number (40-65 units per arm and 2 vs 3 vs 4 arms), DOX feed amount, and conjugation site content (50-160 units of EDA groups), as responsible for efficiency of drug attachment (10-60 units of conjugated DOX) and its release at various pH (5.0 vs 7.4), were studied to demonstrate potential for drug delivery. Size of conjugate particles (10-195 nm) formed in aqueous solution was strongly dependent on the polymer composition and topology. The broad range of drug amounts (25-95%) were detected by the precipitation method, showing pH sensitivity by some polymeric conjugates with faster DOX release in acidic conditions.

Polymeric phase change nanocomposite (PMMA/Fe:ZnO) for electronic packaging application

NASA Astrophysics Data System (ADS)

Maji, Pranabi; Choudhary, Ram Bilash; Majhi, Malati

2018-01-01

This paper reported the effect of Fe-doped ZnO (Fe:ZnO) nanoparticles on the structural, morphological, thermal, optical and dielectric properties of PMMA matrix. Fe-doped ZnO nanoparticle was synthesized by co-precipitation method, after its surface modification incorporated into the PMMA matrix by free radical polymerization method. The phase analysis and crystal structure were investigated by XRD and FTIR technique. These studies confirmed the chemical structure of the PMMA/Fe:ZnO nanocomposite. FESEM image showed the pyramidal shape and high porosity of PMMA/Fe:ZnO nanocomposite. Thermal analysis of the sample was carried out by thermo-gravimetric analyzer. PMMA/Fe:ZnO nanocomposite was found to have better thermal stability compared to pure one. Broadband dielectric spectroscopic technique was used to investigate the transition of electrical properties of Fe-doped ZnO nanoparticle reinforced PMMA matrix in temperature range 313-373 K. The results elucidated a phase transition from glassy to rubbery state at 344 K.

Synthesis of molecular imprinting polymers for extraction of gallic acid from urine.

PubMed

Bhawani, Showkat Ahmad; Sen, Tham Soon; Ibrahim, Mohammad Nasir Mohammad

2018-02-21

The molecularly imprinted polymers for gallic acid were synthesized by precipitation polymerization. During the process of synthesis a non-covalent approach was used for the interaction of template and monomer. In the polymerization process, gallic acid was used as a template, acrylic acid as a functional monomer, ethylene glycol dimethacrylate as a cross-linker and 2,2'-azobisisobutyronitrile as an initiator and acetonitrile as a solvent. The synthesized imprinted and non-imprinted polymer particles were characterized by using Fourier-transform infrared spectroscopy and scanning electron microscopy. The rebinding efficiency of synthesized polymer particles was evaluated by batch binding assay. The highly selective imprinted polymer for gallic acid was MIPI1 with a composition (molar ratio) of 1:4:20, template: monomer: cross-linker, respectively. The MIPI1 showed highest binding efficiency (79.50%) as compared to other imprinted and non-imprinted polymers. The highly selective imprinted polymers have successfully extracted about 80% of gallic acid from spiked urine sample.

The Synthesis of Carborane-Oxetane Monomers and their Polymerization

DTIC Science & Technology

1988-07-11

polyether glycol was liter demonstrated.’ During this time, " modified cationic polymerization technique was developef’, which allowed the synthesis of...Migration of these chemicals in the propellant grain is a continuous and serious problem. We proposed that a urethane curable polyether glycol with a...Br CH3 g 3 Cl CH3 This scheme has the advantage that the leaving group is not on the oxetane. Oxetane is a neopentyl type system which is typically

Radiation-induced polymerization of glass forming systems. VI. Polymerization rate at higher conversion in binary systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaetsu, I.; Ito, A.; Hayashi, K.

1973-08-01

The effect of temperature and composition on the inflection point in the time-conversion curve and the saturated conversion was investigated in the gamma -radio-induced radical polymerization of binary systems consisting of a glass- forming monomer and a solvent. In the polymerization of completely homogeneous systems such as glycidyl methacrylate (GMA) -triacetin and hydroxyethyl methacrylate (HEMA) --propylene glycol systems, the time-conversion curve has an inflection point at polymerization temperatures between T/sub vm/(T/sub v/ of monomer system) and T/sub vp/ (T/sub v/ of polymer system). Such conversions at the inflection point changed monotonically between 0 and 100% in this temperature range. T/submore » v/ was found to be 30 to 50 deg C higher than T/sub g/ (glass transition temperature) and a monotonic function of composition (monomer -- polymer -- solvent). The acceleration effect continued to 100% conversion above T/sub vp/, and no acceleration effect was observed below T/sub vm/. The saturated conversion in homogeneous systems changed monotonically between 0 and 100% for polymerization temperatures between T/sub gm/ (T/sub g/ of monomer system) and T/sub gp/(T of polymer system). T/sub g/ was also a monotonic function of composition. No saturation in conversion was observed above T/sub gp/ , and no polymerization occurred below T/sub gm/. In the polymerization of completely heterogeneous systems such as HEMA-dioctyl phthalate, no acceleration effect was observed at any temperature and composition. The saturated conversion was 100% sbove T/sub g/ of pure HEMA, and no polymerization occurred below this temperature in this system. (auth)« less

Improving Global Precipitation Product Access at the GES DISC

NASA Technical Reports Server (NTRS)

Liu, Z.; Vollmer, B.; Savtchenko, A.; Ostrenga, D.; DeShong, B.; Fang, F.; Albayrak, R,; Sherman, E.; Greene, M.; Li, A.;

CONTINUOUS PRECIPITATION METHOD FOR CONVERSION OF URANYL NITRATE TO URANIUM HEXAFLUORIDE

DOEpatents

Reinhart, G.M.; Collopy, T.J.

1962-11-13

A continuous precipitation process is given for converting a uranyl nitrate solution to uranium tetrafluoride. A stream of the uranyl nitrate solution and a stream of an aqueous ammonium hydroxide solution are continuously introduced into an agitated reaction zone maintained at a pH of 5.0 to 6.5. Flow rates are adjusted to provide a mean residence time of the resulting slurry in the reaction zone of at least 30 minutes. After a startup period of two hours the precipitate is recovered from the effluent stream by filtration and is converted to uranium tetrafluoride by reduction to uranium dioxide with hydrogen and reaction of the uranium dioxide with anhydrous hydrogen fluoride. (AEC)

A new method to measure the polymerization shrinkage kinetics of light cured composites.

PubMed

Lee, I B; Cho, B H; Son, H H; Um, C M

2005-04-01

This study was undertaken to develop a new measurement method to determine the initial dynamic volumetric shrinkage of composite resins during polymerization, and to investigate the effect of curing light intensity on the polymerization shrinkage kinetics. The instrument was basically an electromagnetic balance that was constructed with a force transducer using a position sensitive photo detector (PSPD) and a negative feedback servo amplifier. The volumetric change of composites during polymerization was detected continuously as a buoyancy change in distilled water by means of the Archimedes' principle. Using this new instrument, the dynamic patterns of the polymerization shrinkage of seven commercial composite resins were measured. The polymerization shrinkage of the composites was 1.92 approximately 4.05 volume %. The shrinkage of a packable composite was the lowest, and that of a flowable composite was the highest. The maximum rate of polymerization shrinkage increased with increasing light intensity but the peak shrinkage rate time decreased with increasing light intensity. A strong positive relationship was observed between the square root of the light intensity and the maximum shrinkage rate. The shrinkage rate per unit time, dVol%/dt, showed that the instrument can be a valuable research method for investigating the polymerization reaction kinetics. This new shrinkage-measuring instrument has some advantages that it was insensitive to temperature changes and could measure the dynamic volumetric shrinkage in real time without complicated processes. Therefore, it can be used to characterize the shrinkage kinetics in a wide range of commercial and experimental visible-light-cure materials in relation to their composition and chemistry.

Decreased insulin sensitivity due to continuous nutrient administration in neonatal pigs

USDA-ARS?s Scientific Manuscript database

Chronic TPN compared to intermittent formula feeding has been shown to induce hepatic insulin resistance and steatosis in neonatal pigs. We hypothesized that the route of feeding (IV vs. enteral) rather than the nature of the diet (elemental vs polymeric) or the feeding regimen (continuous vs interm...

Polymeric Precipitation Inhibitors Promote Fenofibrate Supersaturation and Enhance Drug Absorption from a Type IV Lipid-Based Formulation.

PubMed

Suys, Estelle J A; Chalmers, David K; Pouton, Colin W; Porter, Christopher J H

2018-06-04

The ability of lipid-based formulations (LBFs) to increase the solubilization, and prolong the supersaturation, of poorly water-soluble drugs (PWSDs) in the gastrointestinal (GI) fluids has generated significant interest in the past decade. One mechanism to enhance the utility of LBFs is to prolong supersaturation via the addition of polymers that inhibit drug precipitation (polymeric precipitation inhibitors or PPIs) to the formulation. In this work, we have evaluated the performance of a range of PPIs and have identified PPIs that are sufficiently soluble in LBF to allow the construction of single phase formulations. An in vitro model was first employed to assess drug (fenofibrate) solubilization and supersaturation on LBF dispersion and digestion. An in vitro-in situ model was subsequently employed to simultaneously evaluate the impact of PPI enhanced drug supersaturation on drug absorption in rats. The stabilizing effect of the polymers was polymer specific and most pronounced at higher drug loads. Polymers that were soluble in LBF allowed simple processing as single phase formulations, while formulations containing more hydrophilic polymers required polymer suspension in the formulation. The lipid-soluble polymers Eudragit (EU) RL100 and poly(propylene glycol) bis(2-aminopropyl ether) (PPGAE) and the water-soluble polymer hydroxypropylmethyl cellulose (HPMC) E4M were identified as the most effective PPIs in delaying fenofibrate precipitation in vitro. An in vitro model of lipid digestion was subsequently coupled directly to an in situ single pass intestinal perfusion assay to evaluate the influence of PPIs on fenofibrate absorption from LBFs in vivo. This coupled model allowed for real-time evaluation of the impact of supersaturation stabilization on absorptive drug flux and provided better discrimination between the different PPIs and formulations. In the presence of the in situ absorption sink, increased fenofibrate supersaturation resulted in increased drug exposure, and a good correlation was found between the degree of in vitro supersaturation and in vivo drug exposure. An improved in vitro-in vivo correlation was apparent when comparing the same formulation under different supersaturation conditions. These observations directly exemplify the potential utility of PPIs in promoting drug absorption from LBF, via stabilization of supersaturation, and further confirm that relatively brief periods of supersaturation may be sufficient to promote drug absorption, at least for highly permeable drugs such as fenofibrate.

Apparatus and method for stabilization or oxidation of polymeric materials

DOEpatents

Paulauskas, Felix L [Knoxville, TN; Sherman, Daniel M [Knoxville, TN

2010-01-19

An apparatus for treating polymeric materials comprises a treatment chamber adapted to maintain a selected atmosphere at a selected temperature; a means for supporting the polymeric material within the chamber; and, a source of ozone-containing gas, which decomposes at the selected temperature yielding at least one reactive oxidative species whereby the polymer is stabilized and cross linked through exposure to the oxidative species in the chamber at the selected temperature. The ozone may be generated by a plasma discharge or by various chemical processes. The apparatus may be configured for either batch-type or continuous-type processing. The apparatus and method are especially useful for preparing polymer fibers, particularly PAN fibers, for later carbonization treatments as well as to make flame-retardant fabrics.

Chemical characterization of selected LDEF polymeric materials

NASA Technical Reports Server (NTRS)

Young, Philip R.; Slemp, Wayne S.

1991-01-01

Chemical characterization of selected polymeric materials which received exposure on the Long Duration Exposure Facility (LDEF) is reported. The specimens examined include silvered fluorinated ethylene propylene Teflon thermal blanket material, polysulfone, epoxy, polyimide matrix resin/graphite fiber reinforced composites, and several high performance polymer films. These specimens came from numerous LDEF locations, and thus received different environmental exposures. The results to date show no significant change at the molecular level in the polymer that survived exposure. Scanning electron and scanning tunneling microscopes show resin loss and a texturing of some specimens which resulted in a change in optical properties. The potential effect of a silicon-containing molecular contamination on these materials is addressed. The possibility of continued post-exposure degradation of some polymeric films is also proposed.

Characterizing precipitate evolution of an Al–Zn–Mg–Cu-based commercial alloy during artificial aging and non-isothermal heat treatments by in situ electrical resistivity monitoring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Fulin; Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L7; Zurob, Hatem S., E-mail: zurobh@mcmaster.ca

In situ electrical resistivity monitoring technique was employed to continuously evaluate the precipitate evolution of an Al–Zn–Mg–Cu-based commercial alloy during typical artificial aging treatments. The effects of artificial aging on the precipitates stability during non-isothermal heat treatments were also explored. Conventional hardness test, transmission electron microscopy and differential scanning calorimetry were also adopted to verify the electrical resistivity results. The results indicated that both the precipitation process and its timely rate could be followed by the monitored electrical resistivity during artificial aging treatments. The electrical resistivity results gave overall information on continuous precipitation and dissolution processes, especially under high heatingmore » rates. Samples artificial aging heat treated at 120 °C for 24 h followed by aging at 150 °C for 24 h presented more stable state and coarser precipitates than the samples only artificial aging heat treated at 120 °C for 24 h or triple artificial aging heat treated at 120 °C/24 h + 195 °C/15 min + 120 °/24 h. While the incoherent η precipitates in the samples artificial aging heat treated at 120 °C for 24 h followed by aging at 150 °C for 24 h were more easiness to coarsening and dissolve during non-isothermal heat treatments as well. - Highlights: • In situ electrical resistivity monitoring technique was employed on an Al-Zn-Mg-Cu alloy. • The precipitate evolution during typical artificial aging treatments was studied. • The precipitate stability during non-isothermal heat treatments was explored. • The electrical resistivity wonderfully monitored continuous precipitation and dissolution. • The alloy submitted to a T7 treatment presents a more stable state during heating due to incoherent η precipitates.« less

Sorption and precipitation of Mn2+ by viable and autoclaved Shewanella putrefaciens: Effect of contact time

NASA Astrophysics Data System (ADS)

Chubar, Natalia; Visser, Tom; Avramut, Cristina; de Waard, Helen

2013-01-01

The sorption of Mn(II) by viable and inactivated cells of Shewanella putrefaciens, a non-pathogenic, facultative anaerobic, gram-negative bacterium characterised as a Mn(IV) and Fe(III) reducer, was studied under aerobic conditions, as a function of pH, bacterial density and metal loading. During a short contact time (3-24 h), the adsorptive behaviour of live and dead bacteria toward Mn(II) was sufficiently similar, an observation that was reflected in the studies on adsorption kinetics at various metal loadings, effects of pH, bacteria density, isotherms and drifting of pH during adsorption. Continuing the experiment for an additional 2-30 days demonstrated that the Mn(II) sorption by suspensions of viable and autoclaved cells differed significantly from one another. The sorption to dead cells was characterised by a rapid equilibration and was described by an isotherm. In contrast, the sorption (uptake) to live bacteria exhibited a complex time-dependent uptake. This uptake began as adsorption and ion exchange processes followed by bioprecipitation, and it was accompanied by the formation of polymeric sugars (EPS) and the release of dissolved organic substances. FTIR, EXAFS/XANES and XPS demonstrated that manganese(II) phosphate was the main precipitate formed in 125 ml batches, which is the first evidence of the ability of microbes to synthesise manganese phosphates. XPS and XANES spectra did not detect Mn(II) oxidation. Although the release of protein-like compounds by the viable bacteria increased in the presence of Mn2+ (and, by contrast, the release of carbohydrates did not change), electrochemical analyses did not indicate any aqueous complexation of Mn(II) by the organic ligands.

Non-ureolytic calcium carbonate precipitation by Lysinibacillus sp. YS11 isolated from the rhizosphere of Miscanthus sacchariflorus.

PubMed

Lee, Yun Suk; Kim, Hyun Jung; Park, Woojun

2017-06-01

Although microbially induced calcium carbonate precipitation (MICP) through ureolysis has been widely studied in environmental engineering fields, urea utilization might cause environmental problems as a result of ammonia and nitrate production. In this study, many non-ureolytic calcium carbonate-precipitating bacteria that induced an alkaline environment were isolated from the rhizosphere of Miscanthus sacchariflorus near an artificial stream and their ability to precipitate calcium carbonate minerals with the absence of urea was investigated. MICP was observed using a phase-contrast microscope and ion-selective electrode. Only Lysinibacillus sp. YS11 showed MICP in aerobic conditions. Energy dispersive X-ray spectrometry and X-ray diffraction confirmed the presence of calcium carbonate. Field emission scanning electron microscopy analysis indicated the formation of morphologically distinct minerals around cells under these conditions. Monitoring of bacterial growth, pH changes, and Ca 2+ concentrations under aerobic, hypoxia, and anaerobic conditions suggested that strain YS11 could induce alkaline conditions up to a pH of 8.9 and utilize 95% of free Ca 2+ only under aerobic conditions. Unusual Ca 2+ binding and its release from cells were observed under hypoxia conditions. Biofilm and extracellular polymeric substances (EPS) formation were enhanced during MICP. Strain YS11 has resistance at high pH and in high salt concentrations, as well as its spore-forming ability, which supports its potential application for self-healing concrete.

Synergistic effect of PLGA nanoparticles and submicron triglyceride droplets in enhancing the intestinal solubilisation of a lipophilic weak base.

PubMed

Joyce, Paul; Prestidge, Clive A

2018-06-15

A novel hybrid microparticulate system composed of poly(lactic-co-glycolic) acid (PLGA) nanoparticles and submicron medium-chain triglyceride (MCT) droplets was fabricated to overcome the pH-dependent solubility and precipitation challenges associated with a model poorly water-soluble weak base, cinnarizine (CIN). Molecular CIN was confined within both the lipid and polymer phase of PLGA-lipid hybrid (PLH) and PLGA-lipid-mannitol hybrid (PLMH) particles, which offered significant biopharmaceutical advantages in comparison to the unformulated drug, submicron MCT droplets and PLGA nanoparticles. This was highlighted by a substantial reduction in the pH-induced precipitation during in vitro gastrointestinal two-step dissolution studies. A >2.5-fold solubilisation enhancement was observed for the composite particles during simulated intestinal conditions, compared to pure CIN. Furthermore, the drug solubilisation capacity during in vitro intestinal digesting conditions was ~2-2.5 times greater for PLMH particles compared to the precursor emulsion droplets and PLGA nanoparticles. The observations from this study indicate that a synergy exists between the degradation products of PLGA nanoparticles and lipid droplets, whereby the dual-phase release and dissolution mechanism of the hybrid particles aids in prolonging pH-provoked precipitation. Subsequently, the ability for PLGA polymers and oligomers to act as polymeric precipitation inhibitors has been highlighted for the first time. Copyright © 2018 Elsevier B.V. All rights reserved.

Rates of manganese oxidation in aqueous systems

NASA Astrophysics Data System (ADS)

Hem, John D.

1981-08-01

The rate of crystal growth of Mn 3O 4 (hausmannite) and βMnOOH (feitknechtite) in aerated aqueous manganous perchlorate systems, near 0.01 M in total manganese, was determined at pH levels ranging from 7.00 to 9.00 and at temperatures from 0.5 to 37.4°C. The process is autocatalytic, but becomes psuedo first-order in dissolved Mn 2+ activity when the amount of precipitate surface is large compared to the amount of unreacted manganese. Reaction rates determined by titrations using an automated pH-stat were fitted to an equation for precipitate growth. The rates are proportional to surface area of oxide and degree of supersaturation with respect to Mn 2+. The oxide obtained at the higher temperature was Mn 3O 4, but at 0.5° C only βMnOOH was formed. At intermediate temperatures, mixtures of these solids were formed. The rate of precipitation of hausmannite is strongly influenced by temperature, and that of feitknechtite much less so. The difference in activation energy may be related to differences in crystal structure of the oxides and the geometry of polymeric hydroxy ion precursors.

Trends in the precipitation and crystallization behavior of supersaturated aqueous solutions of poorly water-soluble drugs assessed using synchrotron radiation.

PubMed

Raina, Shweta A; Van Eerdenbrugh, Bernard; Alonzo, David E; Mo, Huaping; Zhang, Geoff G Z; Gao, Yi; Taylor, Lynne S

2015-06-01

Amorphous materials are high-energy solids that can potentially enhance the bioavailability of poorly soluble compounds. A major impediment to their widespread use as a formulation platform is the tendency of amorphous materials to crystallize. The aim of this study was to evaluate the relative crystallization tendency of six structural analogues belonging to the dihydropyridine class, in an aqueous environment in the absence and presence of polymers, using wide-angle X-ray scattering synchrotron radiation and polarized light microscopy. The crystallization behavior of precipitates generated from supersaturated solutions of the active pharmaceutical ingredients was found to be highly variable ranging from immediate to several hours in the absence of polymers. Polymers with intermediate hydrophilicity/hydrophobicity were found to substantially delay crystallization, whereas strongly hydrophilic or hydrophobic polymers were largely ineffective. Nuclear magnetic resonance spectroscopy experiments supported the supposition that polymers need to have affinity for both the drug-rich precipitate and the aqueous phase in order to be effective crystallization inhibitors. This study highlights the variability in the crystallization tendency of different compounds and provides insight into the mechanism of inhibition by polymeric additives. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szcześ, Aleksandra, E-mail: aszczes@poczta.umcs.lublin.pl; Czemierska, Magdalena; Jarosz-Wilkołazka, Anna

Extracellular polymeric substance (EPS) extracted from Rhodococcus opacus bacterial strain was used as a matrix for calcium carbonate precipitation using the vapour diffusion method. The total exopolymer and water-soluble exopolymer fraction of different concentrations were spread on the mica surface by the spin-coating method. The obtained layers were characterized using the atomic force microscopy measurement and XPS analysis. The effects of polymer concentration, initial pH of calcium chloride solution and precipitation time on the obtained crystals properties were investigated. Raman spectroscopy and scanning electron microscopy were used to characterize the precipitated minerals. It was found that the type of precipitatedmore » CaCO{sub 3} polymorph and the crystal size depend on the kind of EPS fraction. The obtained results indicates that the water soluble fraction favours vaterite dissolution and calcite growth, whereas the total EPS stabilizes vaterite and this effect is stronger at basic pH. It seems to be due to different contents of the functional group of EPS fractions. - Highlights: • CaCO{sub 3} crystal size and polymorph can be controlled by EPS substance obtained from R. opacus. • The water soluble fraction favours vaterite dissolution and calcite growth. • The total EPS stabilizes vaterite. • This effect is stronger at basic pH.« less

Molecularly imprinted polymer for caffeic acid by precipitation polymerization and its application to extraction of caffeic acid and chlorogenic acid from Eucommia ulmodies leaves.

PubMed

Miura, Chitose; Matsunaga, Hisami; Haginaka, Jun

2016-08-05

Molecularly imprinted polymers (MIPs) for caffeic acid (CA) were prepared using 4-vinylpyridine and methacrylamide (MAM) as functional monomers, divinylbenzene as a crosslinker and acetonitrile-toluene (3:1, v/v) as a porogen by precipitation polymerization. The use of MAM as the co-monomer resulted in the formation of microsphere MIPs and non-imprinted polymers (NIPs) with ca. 3- and 5-μm particle diameters, respectively. Binding experiments and Scatchard analyses revealed that the binding capacity and affinity of the MIP to CA are higher than those of the NIP. The retention and molecular-recognition properties of the prepared MIPs were evaluated using water-acetonitrile and sodium phosphate buffer-acetonitrile as mobile phases in hydrophilic interaction chromatography (HILIC) and reversed-phase chromatography, respectively. In HILIC mode, the MIP showed higher molecular-recognition ability for CA than in reversed-phase mode. In addition to shape recognition, hydrophilic interactions seem to work for the recognition of CA on the MIP in HILIC mode, while hydrogen bonding and hydrophobic interactions seem to work for the recognition of CA in reversed-phase mode. The MIP had a specific molecular-recognition ability for CA in HILIC mode, while other structurally related compounds, such as chlorogenic acid （CGA), gallic acid, protocatechuic acid and vanillic acid, could not be recognized by the MIP. Furthermore, the MIP was successfully applied for extraction of CA and CGA in the leaves of Eucommia ulmodies in HILIC mode. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis of a new magnetic-MIP for the selective detection of 1-chloro-2,4-dinitrobenzene, a highly allergenic compound.

PubMed

Uzuriaga-Sánchez, Rosario Josefina; Wong, Ademar; Khan, Sabir; Pividori, Maria I; Picasso, Gino; Sotomayor, Maria D P T

2017-05-01

Molecularly imprinted polymers (MIPs) in combination with magnetic nanoparticles, in a core@shell format, were studied for selective detection of 1-chloro-2,4-dinitrobenzene (CDNB), a powerful allergenic substance. Magnetic nanoparticles were prepared by the co-precipitation method and mixed with oleic acid (OA). This material was then encapsulated in three types of hydrophobic polymeric matrix, poly-(MA-co-EDGMA), poly-(AA-co-EDGMA), and poly-(1-VN-co-EDGMA), by the mini-emulsion method. These matrices were used due to their ability to interact specifically with the functional groups of the analyte. Finally, the MIP-CDNB was obtained on the magnetic-hydrophobic surfaces using precipitation polymerization in the presence of the analyte. XRD diffraction patterns suggested the presence of magnetite in the composite and SEM analysis revealed a nanoparticle size between 10 and 18nm. Under the optimized adsorption conditions, the magnetic-MIP material showed a higher adsorption capacity (5.1mgg -1 ) than its non-magnetic counterpart (4.2mgg -1 ). In tests of the selectivity of the magnetic-MIP towards CDNB, α-values of 2.5 and 10.4, respectively, were obtained for dichlorophenol and o-nitrophenol, two structurally similar compounds, and no adsorption was observed for any other non-analogous analyte. The magnetic-MIP and magnetic-NIP were applied using water enriched with 0.5mgL -1 of CDNB, achieving recovery values of 83.8(±0.8)% and 66(±1)%, respectively, revealing the suitability of the material for detection of CDNB. Copyright © 2016 Elsevier B.V. All rights reserved.

Magnetic mesoporous molecularly imprinted polymers based on surface precipitation polymerization for selective enrichment of triclosan and triclocarban.

PubMed

Wang, Xuemei; Huang, Pengfei; Ma, Xiaomin; Du, Xinzhen; Lu, Xiaoquan

2018-02-16

Novel magnetic mesoporous molecularly imprinted polymers (MMIPs) were prepared based on surface precipitation polymerization using Triclosan (TCS) as template and methacrylic acid as functional monomer. The synthesized MMIPs-TCS were applied to the adsorbent of magnetic solid-phase extraction (MSPE) coupled with HPLC for the enrichment and determination of TCS. The MMIPs-TCS were characterized by fourier-transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N 2 adsorption-desorption transmission, and vibrating sample magnetometry. Under the optimum condition, the MMIPs-TCS-MSPE-HPLC method shows low limits of detection (LODs) (0.20-0.90 μg L -1 ) and limits of quantification detection (LOQs) (0.66-2.97 μg L -1 ), wide linear ranges from 10.0 to 1000 μg L -1 for each compound with exception of 2,4,6-TCP from 20.0 to 1000 μg L -1 , and acceptable reproducibility (relative standard deviation, RSD <6.6% for intra-day, RSD <8.1% for inter-day). The satisfactory recoveries were in the range of 89.5%-108.4% with good RSDs less than 8.0% at the three spiked levels of 20, 50 and 80 μg L -1 . Moreover, the adsorption experiments show the MMIPs-TCS possess rapid binding affinity, excellent magnetic response, specific selectivity and high adsorption capacity toward TCS with a maximum adsorption capacity of 1955.8 μg g -1 . Copyright © 2018 Elsevier B.V. All rights reserved.

Mechanisms of Precipitation of Different Generations of Gamma-Prime Precipitates During Continuous Cooling of a Nickel Base Superalloy (PREPRINT)

DTIC Science & Technology

2012-08-01

processed through the powder metallurgy route and develops a polycrystalline microstructure consisting of γ grains with nanoscale γ’ precipitates...on the cooling rate employed. Faster cooling rates, such as those encountered during water quenching the alloy from the high temperature single γ...and the first generation γ’ precipitates. Subsequently on quenching to a lower temperature a second generation of γ’ precipitates are formed that are

Economics of recombinant antibody production processes at various scales: Industry-standard compared to continuous precipitation.

PubMed

Hammerschmidt, Nikolaus; Tscheliessnig, Anne; Sommer, Ralf; Helk, Bernhard; Jungbauer, Alois

2014-06-01

Standard industry processes for recombinant antibody production employ protein A affinity chromatography in combination with other chromatography steps and ultra-/diafiltration. This study compares a generic antibody production process with a recently developed purification process based on a series of selective precipitation steps. The new process makes two of the usual three chromatographic steps obsolete and can be performed in a continuous fashion. Cost of Goods (CoGs) analyses were done for: (i) a generic chromatography-based antibody standard purification; (ii) the continuous precipitation-based purification process coupled to a continuous perfusion production system; and (iii) a hybrid process, coupling the continuous purification process to an upstream batch process. The results of this economic analysis show that the precipitation-based process offers cost reductions at all stages of the life cycle of a therapeutic antibody, (i.e. clinical phase I, II and III, as well as full commercial production). The savings in clinical phase production are largely attributed to the fact that expensive chromatographic resins are omitted. These economic analyses will help to determine the strategies that are best suited for small-scale production in parallel fashion, which is of importance for antibody production in non-privileged countries and for personalized medicine. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Copper, gold, and silver decorated magnetic core-polymeric shell nanostructures for destruction of pathogenic bacteria

NASA Astrophysics Data System (ADS)

Padervand, Mohsen; Karanji, Ahmad Kiani; Elahifard, Mohammad Reza

2017-05-01

Fe3O4 magnetic nanoparticles (MNPs) were prepared by co-precipitation method. The nanoparticles were silica coated using TEOS, and then modified by the polymeric layers of polypropylene glycol (PPG) and polyethylene glycol (PEG). Finally, the core-shell samples were decorated with Ag, Au, and Cu nanoparticles. The products were characterized by vibrating sample magnetometry (VSM), TGA, SEM, XRD, and FTIR methods. The antibacterial activity of the prepared samples was evaluated in inactivation of E. coli and S. aureus microorganisms, representing the Gram-negative and Gram-positive species, respectively. The effect of solid dosage, bacteria concentration and type of polymeric modifier on the antibacterial activity was investigated. TEM images of the bacteria were recorded after the treatment time and according to the observed changes in the cell wall, the mechanism of antibacterial action was discussed. The prepared nanostructures showed high antibacterial activity against both Gram-negative and Gram-positive bacteria. This was due to the leaching of metal ions which subsequently led to the lysis of bacteria. A theoretical investigation was also done by studying the interaction of loaded metals with the nucleotide components of the microorganism DNA, and the obtained results were used to explain the experimental data. Finally, based on the observed inactivation curves, we explain the antibacterial behavior of the prepared nanostructures mathematically.

Synthesis and characterization of inorganic materials precipitated into polymeric and novel liquid crystalline systems

NASA Astrophysics Data System (ADS)

Lubeck, Christopher Ryan

The use of nanostructured, hybrid materials possesses great future potential. Many examples of nanostructured materials exist within nature, such as animal bone, animal teeth, and seashells. This research, inspired by nature, strove to mimic salient properties of natural materials, utilizing methods observed within nature to produce materials. Further, this research increased the functionality of the templates from "mere" template to functional participant. Different chemical methods to produce hybrid materials were employed within this research to achieve these goals. First, electro-osmosis was utilized to drive ions into a polymeric matrix to form hybrid inorganic polymer material, creating a material inspired by naturally occurring bone or seashell in which the inorganic component provides strength and the polymeric material decreases the brittleness of the combined hybrid material. Second, self-assembled amphiphiles, forming higher ordered structures, acted as a template for inorganic cadmium sulfide. Electronically active molecules based on ethylene oxide and aniline segments were synthesized to create interaction between the templating material and the resulting inorganic cadmium sulfide. The templating process utilized self-assembly to create the inorganic structure through the interaction of the amphiphiles with water. The use of self-assembly is itself inspired by nature. Self-assembled structures are observed within living cells as cell walls and cell membranes are created through hydrophilic and hydrophobic interactions. Finally, the mesostructured inorganic cadmium sulfide was itself utilized as a template to form mesostructured copper sulfide.

Molecularly imprinted polymers coated on multi-walled carbon nanotubes through a simple indirect method for the determination of 2,4-dichlorophenoxyacetic acid in environmental water

NASA Astrophysics Data System (ADS)

Yang, Weijie; Jiao, Feipeng; Zhou, Lei; Chen, Xiaoqing; Jiang, Xinyu

2013-11-01

A new and facile method was presented to graft molecularly imprinted polymers (MIPs) on carbon nanotubes (CNTs) for 2,4-dichlorophenoxyacetic acid (2,4-D) analysis. In brief, CNTs were firstly coated with a layer of vinyl group modified silica, followed by a common precipitation polymerization with 2,4-D as the template, ethylene glycol dimethacrylate (EGDMA) as the crosslinker and 2,2-azobisisobutyronitrile (AIBN) as the initiator. The imprinted effects obtained by using different monomers were investigated, and the results showed that acrylamide (AM) and styrene as mixed monomers was the best choice. This functionalized material was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetry (TG), which demonstrated a successful polymerization reaction on CNTs with MIPs grafting ratio of about 80%. The results of static adsorption experiments indicated the imprinted material possessed fast kinetics and good selectivity for 2,4-D molecules. A corresponding analytical method was developed and demonstrated to be applicable for the determination of 2,4-D in environmental water. The recoveries were in the range from 74.6% to 81.2% with relative standard deviation below 7.0%. To be emphasized, the method for MIPs coating proposed herein also provides a significant reference for other radical polymerization reactions based on CNTs.

Oligopeptides and copeptides of homochiral sequence, via beta-sheets, from mixtures of racemic alpha-amino acids, in a one-pot reaction in water; relevance to biochirogenesis.

PubMed

Illos, Roni A; Bisogno, Fabricio R; Clodic, Gilles; Bolbach, Gerard; Weissbuch, Isabelle; Lahav, Meir

2008-07-09

As part of our studies on the biochirogenesis of peptides of homochiral sequence during early evolution, the formation of oligopeptides composed of 14-24 residues of the same handedness in the polymerization of dl-leucine (Leu), dl-phenylalanine (Phe), and dl-valine (Val) in aqueous solutions, by activation with N, N'-carbonyldiimidazole and then initiation with a primary amine, in a one-pot reaction, was demonstrated by MALDI-TOF MS using deuterium enantio-labeled alpha-amino acids. The formation of long isotactic peptides is rationalized by the following steps occurring in tandem: (i) creation of a library of short diasteroisomeric oligopeptides containing isotactic peptides in excess in comparison to a binomial kinetics, as a result of an asymmetric induction exerted by the N-terminal residue of a given handedness; (ii) precipitation of the less soluble racemic isotactic penta- and hexapeptides in the form of beta-sheets that are delineated by homochiral rims; (iii) regio-enantiospecific chain elongation occurring heterogeneously at the beta-sheets/solution interface. Polymerization of l-Leu with l-isoleucine (Ile) or l-Phe with l- (1) N-Me-histidine yielded mixtures of copeptides containing both residues. In contrast, in the polymerization of the corresponding mixtures of l- + d-alpha-amino acids, the long oligopeptides were composed mainly from oligo- l-Leu and oligo- d-Ile in the first system and oligo- d-Phe in the second. Furthermore, in the polymerization of mixtures of hydrophobic racemic alpha-amino acids dl-Leu, dl-Val, and dl-Phe and with added racemic dl-alanine and dl-tyrosine, copeptides of homochiral sequences are most dominantly represented. Possible routes for a spontaneous "mirror-symmetry breaking" process of the racemic mixtures of homochiral peptides are presented.

Can Polyphosphate Biochemistry Affect Biological Apatite Saturation?

NASA Astrophysics Data System (ADS)

Omelon, S. J.; Matsuura, N.; Gorelikov, I.; Wynnyckyj, C.; Grynpas, M. D.

2010-12-01

Phosphorus (P) is an important and limiting element for life. One strategy for storing ortho phosphates (Pi) is polymerization. Polymerized Pi's (polyphosphates: (PO3-)n: polyPs) serve as a Pi bank, as well as a catiion chelator, energy source, & regulator of responses to stresses in the stationary phase of culture growth and development1. PolyP biochemistry has been investigated in yeasts, bacteria & plants2. Bigeochemical cycling of P includes the condensation of Pi into pyro (P2O7-4), & polyPs, & the release of Pi from these compounds by the hydrolytic degradation of Pi from phosphomonoester bonds. Alkaline phosphatase (ALP) is one of the predominate enzymes for regenerating Pi in aquatic systems3, & it cleaves Pi from polyPs. ALP is also the enzyme associated with apatite biomineralization in vertebrates4. PolyP was proposed to be the ALP substrate in bone mineralization5. Where calcium ions are plentiful in many aquatic environments, there is no requirement for aquatic life to generate Ca-stores. However, terrestrial vertebrates benefit from a bioavailable Ca-store such as apatite. The Pi storage strategy of polymerizing PO4-3 into polyPs dovetails well with Ca-banking, as polyPs sequester Ca, forming a neutral calcium polyphosphate (Ca-polyP: (Ca(PO3)2)n) complex. This neutral complex represents a high total [Ca+2] & [PO4-3], without the threat of inadvertent apatite precipitation, as the free [Ca+2] & [PO4-3], and therefore apatite saturation, are zero. Recent identification of polyP in regions of bone resorption & calcifying cartilage5 suggests that vertebrates may use polyP chemistry to bank Ca+2 and PO4-3. In vitro experiments with nanoparticulate Ca-polyP & ALP were undertaken to determine if carbonated apatite could precipitate from 1M Ca-polyP in Pi-free “physiological fluid” (0.1 M NaCl, 2 mM Ca+2, 0.8 mM Mg+2, pH ~8.0 ±0.5, 37 °C), as this is estimated to generate the [Ca+2] & [PO4-3] required to form the apatite content of bone tissue (estimated to be 1 g apatite/mL). Carbonates (as NaHCO3 or CaCO3) were used to buffer the protons produced upon polyP hydrolytic degradation to Pi, releasing Ca+2, increasing apatite saturation for precipitation. Initial Ca:P ratios (by EDS) was <1, indicative of Ca-polyP. After incubation, Ca:P ratios were >1, suggesting the formation of Ca-PO4 minerals. XRD results identified Na-Ca- carbonate phases, & hydroxyapatite & carbonated apatite, & residual carbonate reagent. Further optimization of this biological apatite precipitation system will be presented. 1 Kornberg, A., Ann Rev Biochem 1999 (68) 89 2 Kulaev IS, Vagabov VM, Kulakovskaya TV (2004) The Biochemistry of Inorganic Polyphosphates. Chichester, England, John Wiley & Sons, Ltd. 3 Blake, R. E., O’Neil, J.R., and Surov, A. Am J Sci 2005 (305) 596 4 Heersche, J. N. M. et al. (1990) Bone Regulatory Factors; Plenum Press: New York 5 Omelon et al., PLoS ONE 2009 4(5), e5634

Assessment of CLIGEN precipitation and storm pattern generation under four precipitation depth categories in China

USDA-ARS?s Scientific Manuscript database

CLIGEN (CLImate GENerator) is a widely used stochastic weather generator to simulate continuous daily precipitation and storm pattern information for hydrological and soil erosion models. Although CLIGEN has been tested in several regions in the world, thoroughly assessment before applying it to Chi...

40 CFR 434.63 - Effluent limitations for precipitation events.

Code of Federal Regulations, 2012 CFR

2012-07-01

... events. 434.63 Section 434.63 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... precipitation events. (a)(1) The alternate limitations specified in paragraph (a)(2) of this section apply with... than or equal to the 10-year, 24-hour precipitation event (or snowmelt of equivalent volume) may comply...

40 CFR 434.63 - Effluent limitations for precipitation events.

Code of Federal Regulations, 2014 CFR

2014-07-01

... events. 434.63 Section 434.63 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... precipitation events. (a)(1) The alternate limitations specified in paragraph (a)(2) of this section apply with... than or equal to the 10-year, 24-hour precipitation event (or snowmelt of equivalent volume) may comply...

40 CFR 434.63 - Effluent limitations for precipitation events.

Code of Federal Regulations, 2013 CFR

2013-07-01

... events. 434.63 Section 434.63 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... precipitation events. (a)(1) The alternate limitations specified in paragraph (a)(2) of this section apply with... than or equal to the 10-year, 24-hour precipitation event (or snowmelt of equivalent volume) may comply...

Apparatus and method for oxidation and stabilization of polymeric materials

DOEpatents

Paulauskas, Felix L [Knoxville, TN; White, Terry L [Knoxville, TN; Sherman, Daniel M [Knoxville, TN

2009-05-19

An apparatus for treating polymeric materials comprises a treatment chamber adapted to maintain a selected atmosphere; a means for supporting the polymeric material within the chamber; and, a source of plasma-derived gas containing at least one reactive oxidative species whereby the polymer is stabilized and cross linked through exposure to the oxidative species in the chamber at a selected temperature. The polymer may be directly exposed to the plasma, or alternatively, the plasma may be established in a separate volume from which the reactive species may be extracted and introduced into the vicinity of the polymer. The apparatus may be configured for either batch-type or continuous-type processing. The apparatus and method are especially useful for preparing polymer fibers, particularly PAN fibers, for later carbonization treatments.

Apparatus and method for oxidation and stabilization of polymeric materials

DOEpatents

Paulauskas, Felix L [Knoxville, TN; White, Terry L [Knoxville, TN; Sherman, Daniel M [Knoxville, TN

2010-08-31

An apparatus for treating polymeric materials comprises a treatment chamber adapted to maintain a selected atmosphere; a means for supporting the polymeric material within the chamber; and, a source of plasma-derived gas containing at least one reactive oxidative species whereby the polymer is stabilized and cross linked through exposure to the oxidative species in the chamber at a selected temperature. The polymer may be directly exposed to the plasma, or alternatively, the plasma may be established in a separate volume from which the reactive species may be extracted and introduced into the vicinity of the polymer. The apparatus may be configured for either batch-type or continuous-type processing. The apparatus and method are especially useful for preparing polymer fibers, particularly PAN fibers, for later carbonization treatments.

Mechanical Properties of Organized Microcomposites Fabricated by Interference Lithography

NASA Astrophysics Data System (ADS)

Singamaneni, Srikanth; Chang, Sehoon; Jang, Ji-Hyun; Davis, Whitney; Thomas, Edwin; Tsukruk, Vladimir

2009-03-01

We demonstrate that organized, porous, polymer microstructures with continuous open nanoscale pores and sub-micron spacings obtained via interference lithography can be successfully utilized in a highly non-traditional field of ordered microcomposites. Organized microcomposite structures are fabricated by employing two independent strategies, namely, capillary infiltration and in situ polymerization of the rubbery component into the porous glassy microframes. The mechanical properties and ultimate fracture behavior of the single and bicomponent microframes are investigated at different length scales. The ordered single and bi-component microstructures with high degree of control over the microscopic organization of the polymeric phases result in excellent mechanical properties. Combining hard and soft polymer components provides multifunctional materials and coatings with synergetic properties and is frequently utilized for design of advanced polymeric composites.

Mechanical property characterization of polymeric composites reinforced by continuous microfibers

NASA Astrophysics Data System (ADS)

Zubayar, Ali

Innumerable experimental works have been conducted to study the effect of polymerization on the potential properties of the composites. Experimental techniques are employed to understand the effects of various fibers, their volume fractions and matrix properties in polymer composites. However, these experiments require fabrication of various composites which are time consuming and cost prohibitive. Advances in computational micromechanics allow us to study the various polymer based composites by using finite element simulations. The mechanical properties of continuous fiber composite strands are directional. In traditional continuous fiber laminated composites, all fibers lie in the same plane. This provides very desirable increases in the in-plane mechanical properties, but little in the transverse mechanical properties. The effect of different fiber/matrix combinations with various orientations is also available. Overall mechanical properties of different micro continuous fiber reinforced composites with orthogonal geometry are still unavailable in the contemporary research field. In this research, the mechanical properties of advanced polymeric composite reinforced by continuous micro fiber will be characterized based on analytical investigation and FE computational modeling. Initially, we have chosen IM7/PEEK, Carbon Fiber/Nylon 6, and Carbon Fiber/Epoxy as three different case study materials for analysis. To obtain the equivalent properties of the micro-hetero structures, a concept of micro-scale representative volume elements (RVEs) is introduced. Five types of micro scale RVEs (3 square and 2 hexagonal) containing a continuous micro fiber in the polymer matrix were designed. Uniaxial tensile, lateral expansion and transverse shear tests on each RVE were designed and conducted by the finite element computer modeling software ANSYS. The formulae based on elasticity theory were derived for extracting the equivalent mechanical properties (Young's moduli, shear moduli, and Poisson's ratios) from the numerical solutions of the RVEs undergone these three load tests. Validation of the obtained micro-scale mechanical properties will be performed using rule of mixture (ROM), 1st, and 2nd order of the mathematical model and experimental data.

Integrated continuous dissolution, refolding and tag removal of fusion proteins from inclusion bodies in a tubular reactor.

PubMed

Pan, Siqi; Zelger, Monika; Jungbauer, Alois; Hahn, Rainer

2014-09-20

An integrated continuous tubular reactor system was developed for processing an autoprotease expressed as inclusion bodies. The inclusion bodies were suspended and fed into the tubular reactor system for continuous dissolving, refolding and precipitation. During refolding, the dissolved autoprotease cleaves itself, separating the fusion tag from the target peptide. Subsequently, the cleaved fusion tag and any uncleaved autoprotease were precipitated out in the precipitation step. The processed exiting solution results in the purified soluble target peptide. Refolding and precipitation yields performed in the tubular reactor were similar to batch reactor and process was stable for at least 20 h. The authenticity of purified peptide was also verified by mass spectroscopy. Productivity (in mg/l/h and mg/h) calculated in the tubular process was twice and 1.5 times of the batch process, respectively. Although it is more complex to setup a tubular than a batch reactor, it offers faster mixing, higher productivity and better integration to other bioprocessing steps. With increasing interest of integrated continuous biomanufacturing, the use of tubular reactors in industrial settings offers clear advantages. Copyright © 2014 Elsevier B.V. All rights reserved.

Amphiphilic Soft Janus Particles as Interfacial Stabilizers

NASA Astrophysics Data System (ADS)

Wang, Wenda; Niu, Sunny; Sosa, Chris; Prud'Homme, Robert; Priestley, Rodney; Priestley Polymer Group Team; Prud'homme Research Group Team

Janus particles, which incorporate two or more ``faces'' with different chemical functionality, have attracted great attention in scientific research. Amphiphilic Janus particles have two faces with distinctly different hydrophobicity. This can be thought of as colloidal surfactants. Theoretical studies on the stabilization of emulsions using Janus particles have confirmed higher efficiency. Herein we synthesize the narrow distributed amphiphilic polymeric Janus particles via Precipitation-Induced Self-Assembly (PISA). The efficiency of the amphiphilic Janus particles are tested on different oil/water systems. Biocompatible polymers can also be used on this strategy and may potentially have wide application for food emulsion, cosmetics and personal products.

Optimum Orientation of the Atmospheric River (AR) for Extreme Storms in Feather, Yuba, and American River Watersheds in the Pacific Coast of the US

NASA Astrophysics Data System (ADS)

Ohara, N.; Kavvas, M. L.; Anderson, M.; Chen, Z. Q.; Ishida, K.

2016-12-01

This study investigated physical maximum precipitation rates for the next generation of flood management strategies under evolving climate conditions using a regional atmospheric model. The model experiments using a non-hydrostatic atmospheric models, MM5, revealed the precipitation mechanism affected by topography and non-linear dynamics of the atmosphere in the Pacific Coast of the US during the Atmospheric River (AR) events. Significant historical storm events were identified based on the continuous weather simulations for the Feather, Yuba, and American river watersheds in California. For these historical storms, the basin precipitations were maximized by setting fully saturated atmospheric layers at the boundary of the outer nesting domain. It was found that maximizing the atmospheric moisture supply at the model boundary does not always increase the precipitation in Feather and Yuba River basins. The pattern of the precipitation increase and decrease by the maximization suggested the rain shadow effect of the Coast Range causing this unexpected precipitation reduction by the moisture maximization. The ground precipitation seems to be controlled by the AR orientation to the topography as well as the precipitable water. Finally, the steady-state precipitation experiments were performed to find an optimum AR orientation to yield the most significant continuous precipitation rate in the Feather, Yuba, and American River basins. This physically-based numerical experiment can potentially incorporate the climate change effects, explicitly.

A precipitation collector and automated pH-monitoring system

Treesearch

Gerald M. Aubertin; Benjamin C. Thorner; John Campbell

1976-01-01

A sensitive precipitation collector and automated pH-monitoring system are described. This system provides for continuous monitoring and recording of the pH of precipitation. Discrete or composite rainwater samples are manually obtainable for chemical analyses. The system can easily be adapted to accommodate a flow-through specific conductance probe and monitoring...

Surface Chemical Studies on Pyrite in the Presence of Polysaccharide-Based Flotation Depressants.

PubMed

Rath; Subramanian; Pradeep

2000-09-01

The interaction of dextrin and guar gum with pyrite has been investigated through adsorption, flotation, and electrokinetic measurements. The adsorption densities of the polysaccharides onto pyrite reveal a region of higher adsorption density in the pH range 7.5-11, with a maximum around pH 10 for both polymers. The isotherms exhibit Langmuirian behavior. The adsorption density of guar gum onto pyrite is higher than that of dextrin. Electrokinetic measurements indicate a decrease in the electrophoretic mobility values in proportion to the concentration of the polymer added. Co-precipitation tests confirm polymer-ferric species interaction in the bulk solution, especially in the pH range 5.5-8.5. The pH range for higher adsorption, significant co-precipitation, and appreciable depression of pyrite encompass each other. XPS and FTIR spectroscopic studies provide evidence in support of chemical interaction between hydroxylated pyrite and the hydroxyl groups of the polymeric depressants. Copyright 2000 Academic Press.

Isolation of beta-mannanase from Cocos nucifera Linn haustorium and its application in the depolymerization of beta-(1,4)-linked D-mannans.

PubMed

Soumya, Rema S; Abraham, Emilia T

2010-05-01

Beta-mannanase was extracted from coconut (Cocos nucifera Linn) haustorium and purified through ammonium sulfate precipitation and sepharose 6B-lectin affinity chromatography. Coconut beta-mannanase is an acidic protein with a pI of 3.75. The molecular mass of coconut beta-mannanase (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) was found to be 44 kDa and was confirmed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The optimum temperature and pH for enzyme activity was 70 degrees C and 5.2. The enzyme was used for the preparation of neutraceutical dietary supplement from galactomannans of guar gum and tender coconut kernel having a beta-(1,4)-linked D-mannose backbone. Depolymerized guar gum has 92% of oligosaccharides with a degree of polymerization of 3 and 7. Tender coconut kernel has a degree of polymerization of 9-39 oligosaccharides along with disaccharides and trisaccharides. Hence this mannanase will be useful to depolymerize beta-(1,4)-linked D-mannose polysaccharides from most plant sources to produce prebiotics in a cost-effective technique.

Newly designed silver coated-magnetic, monodisperse polymeric microbeads as SERS substrate for low-level detection of amoxicillin

NASA Astrophysics Data System (ADS)

Kibar, Güneş; Topal, Ahmet Emin; Dana, Aykutlu; Tuncel, Ali

2016-09-01

We report the preparation of silver-coated magnetic polymethacrylate core-shell nanoparticles for use in surface-enhanced Raman scattering based drug detection. Monodisperse porous poly (mono-2-(methacryloyloxy)ethyl succinate-co-glycerol dimethacrylate), poly (MMES-co-GDMA) microbeads of ca. 5 μm diameter were first synthesized through a multistage microsuspension polymerization technique to serve as a carboxyl-bearing core region. Microspheres were subsequently magnetized by the co-precipitation of ferric ions, aminated through the surface hydroxyl groups and decorated with Au nanoparticles via electrostatic attraction. An Ag shell was then formed on top of the Au layer through a seed-mediated growth process, resulting in micron-sized monodisperse microbeads that exhibit Raman enhancement effects due to the roughness of the Ag surface layer. The core-shell microspheres were used as a new substrate for the detection of amoxicillin at trace concentrations up to 10-8 M by SERS. The proposed SERS platform can be evaluated as a useful tool for the follow-up amoxicillin pollution and low-level detection of amoxicillin in aqueous media.

Polymerization amplified SPR-DNA assay on noncovalently functionalized graphene.

PubMed

Yuan, Pei-Xin; Deng, Sheng-Yuan; Yao, Chuan-Guang; Wan, Ying; Cosnier, Serge; Shan, Dan

2017-03-15

A highly efficient surface plasmon resonance (SPR)-based DNA assay was developed, by employing noncovalently functionalized graphene nanosheets as a substrate, and enzymatic catalysis-induced polymerization as mass relay. The objective of this strategy was manifold: first of all, to sensitize the overall SPR output by in situ optimized electrogeneration of graphene thin-film, which was characterized by atomic force microscopic topography; secondly, to regulate the self-assembly and orientation of biotinylated capture probes on nickel-chelated nitrilotriacetic acid (NTA) scaffolds, that anchored onto graphene-supported pyrenyl derivatives; and lastly, to synergize the signal amplification via real-time conversion of the additive aniline into polyaniline precipitation by horseradish peroxidase-tagged reporters. With this setup, a precise and replicable DNA sensing platform for specific targets was achieved with a detection limit down to femtomolar, thus demonstrating a beneficial exploration and exploitation of two-dimensional nanomaterials as unique SPR infrastructure. The possibility of such ″bottom-up″ architecture mounted with ″top-down″ weight reactor would be most likely extensible and adaptable to protein determinations. Copyright © 2016 Elsevier B.V. All rights reserved.

In-situ complex with by-product HCl and release chloride ions to dissolve aramid.

PubMed

Dai, Yu; Cheng, Zheng; Yuan, Yihao; Meng, Chenbo; Qin, Jiaqiang; Liu, Xiangyang

2018-06-20

Because of the strong hydrogen-bond interaction among macromolecular chains, addition of chloride salts is generally needed to offer Cl- ions for dissolution of aromatic polyamides. In this paper, poly-(benzimidazole-terephthalamide) which complexed with by-product HCl during polymerization (PABI-HCl) was prepared and imidazole compound as cosolvent was added into dimethylacetamide (DMAc) to dissolve PABI-HCl. Due to stronger affinity to protons, imidazole compound could in-situ complex with HCl of PABI-HCl and form imidazolium hydrochloride. Then imidazolium hydrochloride would ionize and produce much free Cl- ions which acted as stronger hydrogen-bond acceptor to disrupt interaction among macromolecular chains. As a result, solubility of PABI-HCl in DMAc was improved significantly in existence of small amount of imidazole compound. Moreover, DMAc-imidazole mixture was utlized for synthesis of different kinds of aramids and no precipitation was observed with progress of the reaction. So the mixture was suitable to be utlized as solvent for polymerization of aramid. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface chemistry of ferrihydrite: Part 1. EXAFS studies of the geometry of coprecipitated and adsorbed arsenate

USGS Publications Warehouse

Waychunas, G.A.; Rea, B.A.; Fuller, C.C.; Davis, J.A.

1993-01-01

EXAFS spectra were collected on both the As and Fe K-edges from samples of two-line ferrihydrite with adsorbed (ADS) and coprecipitated (CPT) arsenate prepared over a range of conditions and arsenate surface coverages. Spectra also were collected for arsenate adsorbed on the surfaces of three FeOOH crystalline polymorphs, ?? (goethite), ?? (akaganeite), and ?? (lepidocrocite), and as a free ion in aqueous: solution. Analyses of the As EXAFS show clear evidence for inner sphere bidentate (bridging) arsenate complexes on the ferrihydrite surface and on the surfaces of the crystalline FeOOH polymorphs. The bridging arsenate is attached to adjacent apices of edge-sharing Fe oxyhydroxyl octahedra. The arsenic-iron distance at the interface (3.28 ??0.01 A ??) is close to that expected for this geometry on the FeOOH polymorph surfaces, but is slightly shorter on the ferrihydrite surfaces (3.25 ?? 0.02 A ??). Mono-dentate arsenate linkages (3.60 ?? 0.03 A ??) also occur on the ferrihydrite, but are not generally observed on the crystalline FeOOH polymorphs. The proportion of monodentate bonds appears largest for adsorption samples with the smallest As Fe molar ratio. In all cases the arsenate tetrahedral complex is relatively undistorted with As-O bonds of 1.66 ?? 0.01 A ??. Precipitation of arsenate or scorodite-like phases was not observed for any samples, all of which were prepared at a pH value of 8. The Fe EXAFS results confirm that the Fe-Fe correlations in the ferrihydrite are progressively disrupted in the CPT samples as the As Fe ratio is increased. Coherent crystallite size is probably no more than 10 A?? in diameter and no Fe oxyhydroxyl octahedra corner-sharing linkages (as would be present in FeOOH polymorphs) are observed at the largest As Fe ratios. Comparison of the number and type of Fe-Fe neighbors with the topological constraints imposed by the arsenate saturation limit in the CPT samples (about 0.7 As Fe) indicates ferrihydrite units consisting mainly of Fe oxyhydroxyl octahedra arranged in short dioctahedral chains with minimal interchain linking by octahedra corners. This is consistent with an enlarged surface area and a larger proportion of sites for bidentate arsenate bonding in CPT samples as compared to the ADS samples, which saturate with arsenate at lower As Fe ratios. The latter samples have larger crystallite sizes and a definite proportion of ferric octahedra sharing corners. The ratio of corner-sharing to edge-sharing Fe oxyhydroxyl octahedra in the ADS samples, and CPT samples with small As loadings, is very similar to what would be present in very small particles of goethite or akaganeite. The difference in the polymeric structure of ADS and CPT samples at higher As Fe ratios is due to strong arsenate bidentate adsorption that poisons the surface of particles of ferrihydrite precipitated in the presence of substantial arsenate, limiting their normal crystallization, and preventing further Fe-O-Fe polymerization. If the arsenate is applied after precipitation much less adsorption occurs since polymerization has already progressed. In both ADS and CPT samples, Fe-O-Fe polymerization increases with age, though at different rates for each type of sample. ?? 1993.

Isothermal Time-Temperature-Precipitation Diagram for an Aluminum Alloy 6005A by In Situ DSC Experiments

PubMed Central

Milkereit, Benjamin; Giersberg, Lydia; Kessler, Olaf; Schick, Christoph

2014-01-01

Time-temperature-precipitation (TTP) diagrams deliver important material data, such as temperature and time ranges critical for precipitation during the quenching step of the age hardening procedure. Although the quenching step is continuous, isothermal TTP diagrams are often applied. Together with a so-called Quench Factor Analysis, they can be used to describe very different cooling paths. Typically, these diagrams are constructed based on mechanical properties or microstructures after an interrupted quenching, i.e., ex situ analyses. In recent years, an in situ calorimetric method to record continuous cooling precipitation diagrams of aluminum alloys has been developed to the application level by our group. This method has now been transferred to isothermal experiments, in which the whole heat treatment cycle was performed in a differential scanning calorimeter. The Al-Mg-Si-wrought alloy 6005A was investigated. Solution annealing at 540 °C and overcritical quenching to several temperatures between 450 °C and 250 °C were followed by isothermal soaking. Based on the heat flow curves during isothermal soaking, TTP diagrams were determined. An appropriate evaluation method has been developed. It was found that three different precipitation reactions in characteristic temperature intervals exist. Some of the low temperature reactions are not accessible in continuous cooling experiments and require isothermal studies. PMID:28788587

Isothermal Time-Temperature-Precipitation Diagram for an Aluminum Alloy 6005A by In Situ DSC Experiments.

PubMed

Milkereit, Benjamin; Giersberg, Lydia; Kessler, Olaf; Schick, Christoph

2014-03-28

Time-temperature-precipitation (TTP) diagrams deliver important material data, such as temperature and time ranges critical for precipitation during the quenching step of the age hardening procedure. Although the quenching step is continuous, isothermal TTP diagrams are often applied. Together with a so-called Quench Factor Analysis, they can be used to describe very different cooling paths. Typically, these diagrams are constructed based on mechanical properties or microstructures after an interrupted quenching, i.e ., ex situ analyses. In recent years, an in situ calorimetric method to record continuous cooling precipitation diagrams of aluminum alloys has been developed to the application level by our group. This method has now been transferred to isothermal experiments, in which the whole heat treatment cycle was performed in a differential scanning calorimeter. The Al-Mg-Si-wrought alloy 6005A was investigated. Solution annealing at 540 °C and overcritical quenching to several temperatures between 450 °C and 250 °C were followed by isothermal soaking. Based on the heat flow curves during isothermal soaking, TTP diagrams were determined. An appropriate evaluation method has been developed. It was found that three different precipitation reactions in characteristic temperature intervals exist. Some of the low temperature reactions are not accessible in continuous cooling experiments and require isothermal studies.

Nanoporous polymeric nanofibers based on selectively etched PS-b-PDMS block copolymers.

PubMed

Demirel, Gokcen B; Buyukserin, Fatih; Morris, Michael A; Demirel, Gokhan

2012-01-01

One-dimensional nanoporous polymeric nanofibers have been fabricated within an anodic aluminum oxide (AAO) membrane by a facile approach based on selective etching of poly(dimethylsiloxane) (PDMS) domains in polystyrene-block-poly(dimethylsiloxane) (PS-b-PDMS) block copolymers that had been formed within the AAO template. It was observed that prior to etching, the well-ordered PS-b-PDMS nanofibers are solid and do not have any porosity. The postetched PS nanofibers, on the other hand, had a highly porous structure having about 20-50 nm pore size. The nanoporous polymeric fibers were also employed as a drug carrier for the native, continuous, and pulsatile drug release using Rhodamine B (RB) as a model drug. These studies showed that enhanced drug release and tunable drug dosage can be achieved by using ultrasound irradiation. © 2011 American Chemical Society

Peptide-directed self-assembly of functionalized polymeric nanoparticles. Part II: effects of nanoparticle composition on assembly behavior and multiple drug loading ability.

PubMed

Xiang, Xu; Ding, Xiaochu; Moser, Trevor; Gao, Qi; Shokuhfar, Tolou; Heiden, Patricia A

2015-04-01

Peptide-functionalized polymeric nanoparticles were designed and self-assembled into continuous nanoparticle fibers and three-dimensional scaffolds via ionic complementary peptide interaction. Different nanoparticle compositions can be designed to be appropriate for each desired drug, so that the release of each drug is individually controlled and the simultaneous sustainable release of multiple drugs is achieved in a single scaffold. A self-assembled scaffold membrane was incubated with NIH3T3 fibroblast cells in a culture dish that demonstrated non-toxicity and non-inhibition on cell proliferation. This type of nanoparticle scaffold combines the advantages of peptide self-assembly and the versatility of polymeric nanoparticle controlled release systems for tissue engineering. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

RAFT polymerization and some of its applications.

PubMed

Moad, Graeme; Rizzardo, Ezio; Thang, San H

2013-08-01

Reversible addition-fragmentation chain transfer (RAFT) is one of the most robust and versatile methods for controlling radical polymerization. With appropriate selection of the RAFT agent for the monomers and reaction conditions, it is applicable to the majority of monomers subject to radical polymerization. The process can be used in the synthesis of well-defined homo-, gradient, diblock, triblock, and star polymers and more complex architectures, which include microgels and polymer brushes. In this Focus Review we describe how the development of RAFT and RAFT application has been facilitated by the adoption of continuous flow techniques using tubular reactors and through the use of high-throughput methodology. Applications described include the use of RAFT in the preparation of polymers for optoelectronics, block copolymer therapeutics, and star polymer rheology control agents. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

M23C6 carbides and Cr2N nitrides in aged duplex stainless steel: A SEM, TEM and FIB tomography investigation.

PubMed

Maetz, J-Y; Douillard, T; Cazottes, S; Verdu, C; Kléber, X

2016-05-01

The precipitation evolution during ageing of a 2101 lean duplex stainless steel was investigated, revealing that the precipitate type and morphology depends on the nature of the grain boundary. Triangular M23C6 carbides precipitate only at γ/δ interfaces and rod-like Cr2N nitrides precipitate at both γ/δ and δ/δ interfaces. After 15min of ageing, the M23C6 size no longer evolves, whereas that of the Cr2N continues to evolve. For Cr2N, the morphology is maintained at γ/δ interfaces, whereas percolation occurs to form a continuous layer at δ/δ interfaces. By combining 2D and 3D characterisation at the nanoscale using transmission electron microscopy (TEM) and focused ion beam (FIB) tomography, a complete description of the precipitation evolution was obtained, including the composition, crystallographic structure, orientation relationship with the matrix phases, location, morphology, size and volume fraction. Copyright © 2016 Elsevier Ltd. All rights reserved.

Self-assembly of resins and asphaltenes facilitates asphaltene dissolution by an organic acid.

PubMed

Hashmi, Sara M; Firoozabadi, Abbas

2013-03-15

Asphaltene precipitation occurs in petroleum fluids under certain unfavorable conditions, but can be controlled by tuning composition. Aromatic solvents in large quantities can prevent precipitation entirely and can dissolve already precipitated asphaltenes. Some polymeric surfactants can dissolve asphaltenes when added at much lower concentrations than required by aromatic solvents. Other dispersants can truncate asphaltene precipitation at the sub-micron length scale, creating stable colloidal asphaltene dispersants. One particular asphaltene dispersant, dodecylbenzene sulfonic acid (DBSA), can do both, namely: (1) stabilize asphaltene colloids and (2) dissolve asphaltenes to the molecular scale. Acid-base interactions are responsible for the efficiency of DBSA in dissolving asphaltenes compared to aromatic solvents. However, many details remain to be quantified regarding the action of DBSA on asphaltenes, including the effect of petroleum fluid composition. For instance, resins, naturally amphiphilic components of petroleum fluids, can associate with asphaltenes, but it is unknown whether they cooperate or compete with DBSA. Similarly, the presence of metals is known to hinder asphaltene dissolution by DBSA, but its effect on colloidal asphaltene stabilization has yet to be considered. We introduce the concepts of cooperativity and competition between petroleum fluid components and DBSA in stabilizing and dissolving asphaltenes. Notably, we find that resins cooperatively interact with DBSA in dissolving asphaltenes. We use UV-vis spectroscopy to investigate the interactions responsible for the phase transitions between unstable suspensions, stable suspensions, and molecular solutions of asphaltenes. Copyright © 2012 Elsevier Inc. All rights reserved.

Different arsenate and phosphate incorporation effects on the nucleation and growth of iron(III) (Hydr)oxides on quartz.

PubMed

Neil, Chelsea W; Lee, Byeongdu; Jun, Young-Shin

2014-10-21

Iron(III) (hydr)oxides play an important role in the geochemical cycling of contaminants in natural and engineered aquatic systems. The ability of iron(III) (hydr)oxides to immobilize contaminants can be related to whether the precipitates form heterogeneously (e.g., at mineral surfaces) or homogeneously in solution. Utilizing grazing incidence small-angle X-ray scattering (GISAXS), we studied heterogeneous iron(III) (hydr)oxide nucleation and growth on quartz substrates for systems containing arsenate and phosphate anions. For the iron(III) only system, the radius of gyration (Rg) of heterogeneously formed precipitates grew from 1.5 to 2.5 (± 1.0) nm within 1 h. For the system containing 10(-5) M arsenate, Rg grew from 3.6 to 6.1 (± 0.5) nm, and for the system containing 10(-5) M phosphate, Rg grew from 2.0 to 4.0 (± 0.2) nm. While the systems containing these oxyanions had more growth, the system containing only iron(III) had the most nucleation events on substrates. Ex situ analyses of homogeneously and heterogeneously formed precipitates indicated that precipitates in the arsenate system had the highest water content and that oxyanions may bridge iron(III) hydroxide polymeric embryos to form a structure similar to ferric arsenate or ferric phosphate. These new findings are important because differences in nucleation and growth rates and particle sizes will impact the number of available reactive sites and the reactivity of newly formed particles toward aqueous contaminants.

Bacterially mediated mineralization of vaterite

NASA Astrophysics Data System (ADS)

Rodriguez-Navarro, Carlos; Jimenez-Lopez, Concepcion; Rodriguez-Navarro, Alejandro; Gonzalez-Muñoz, Maria Teresa; Rodriguez-Gallego, Manuel

2007-03-01

Myxococcus xanthus, a common soil bacterium, plays an active role in the formation of spheroidal vaterite. Bacterial production of CO 2 and NH 3 and the transformation of the NH 3 to NH4+ and OH -, thus increasing solution pH and carbonate alkalinity, set the physicochemical conditions (high supersaturation) leading to vaterite precipitation in the microenvironment around cells, and directly onto the surface of bacterial cells. In the latter case, fossilization of bacteria occurs. Vaterite crystals formed by aggregation of oriented nanocrystals with c-axis normal to the bacterial cell-wall, or to the core of the spherulite when bacteria were not encapsulated. While preferred orientation of vaterite c-axis appears to be determined by electrostatic affinity (ionotropic effect) between vaterite crystal (0001) planes and the negatively charged functional groups of organic molecules on the bacterium cell-wall or on extracellular polymeric substances (EPS), analysis of the changes in the culture medium chemistry as well as high resolution transmission electron microscopy (HRTEM) observations point to polymorph selection by physicochemical (kinetic) factors (high supersaturation) and stabilization by organics, both connected with bacterial activity. The latter is in agreement with inorganic precipitation of vaterite induced by NH 3 and CO 2 addition in the protein-rich sterile culture medium. Our results as well as recent studies on vaterite precipitation in the presence of different types of bacteria suggest that bacterially mediated vaterite precipitation is not strain-specific, and could be more common than previously thought.

A monitor for continuous measurement of temperature, pH, and conductance of wet precipitation: Preliminary results from the Adirondack Mountains, New York

USGS Publications Warehouse

Johnsson, P.A.; Reddy, M.M.

1990-01-01

This report describes a continuous wet-only precipitation monitor designed by the U.S. Geological Survey to record variations in rainfall temperature, pH, and specific conductance at 1-min intervals over the course of storms. Initial sampling in the Adirondack Mountains showed that rainfall acidity varied over the course of summer storms, with low initial pH values increasing as storm intensity increased.This report describes a continuous wet-only precipitation monitor designed by the U.S. Geological Survey to record variations in rainfall temperature, pH, and specific conductance at 1-min intervals over the course of storms. Initial sampling in the Adirondack Mountains showed that rainfall acidity varied over the course of summer storms, with low initial pH values increasing as storm intensity increased.

Encapsulation of albumin in self-assembled layer-by-layer microcapsules: comparison of co-precipitation and adsorption techniques.

PubMed

Labala, Suman; Mandapalli, Praveen Kumar; Bhatnagar, Shubhmita; Venuganti, Venkata Vamsi Krishna

2015-01-01

The objective of this study is to prepare and characterize polymeric self-assembled layer-by-layer microcapsules (LbL-MC) to deliver a model protein, bovine serum albumin (BSA). The aim is to compare the BSA encapsulation in LbL-MC using co-precipitation and adsorption methods. In co-precipitation method, BSA was co-precipitated with growing calcium carbonate particles to form a core template. Later, poly(styrene sulfonate) and poly(allylamine hydrochloride) were sequentially adsorbed onto the CaCO3 templates. In adsorption method, preformed LbL-MC were incubated with BSA and encapsulation efficiency is optimized for pH and salt concentration. Free and BSA-encapsulated LbL-MC were characterized using Zetasizer, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy and differential scanning calorimeter. Later, in vitro release studies were performed using dialysis membrane method at pH 4, 7.4 and 9. Results from Zetasizer and SEM showed free LbL-MC with an average size and zeta-potential of 2.0 ± 0.6 μm and 8.1 ± 1.9 mV, respectively. Zeta-potential of BSA-loaded LbL-MC was (-)7.4 ± 0.7 mV and (-)5.7 ± 1.0 mV for co-precipitation and adsorption methods, respectively. In adsorption method, BSA encapsulation in LbL-MC was found to be greater at pH 6.0 and 0.2 M NaCl. Co-precipitation method provided four-fold greater encapsulation efficiency (%) of BSA in LbL-MC compared with adsorption method. At pH 4, the BSA release from LbL-MC was extended up to 120 h. Polyacrylamide gel electrophoresis showed that BSA encapsulated in LBL-MC through co-precipitation is stable toward trypsin treatment. In conclusion, co-precipitation method provided greater encapsulation of BSA in LbL-MC. Furthermore, LbL-MC can be developed as carriers for pH-controlled protein delivery.

Reducing the heterogeneity of xylan through processing.

PubMed

Zhang, Wei; Johnson, Amanda M; Barone, Justin R; Renneckar, Scott

2016-10-05

Glycerol thermal processing (GTP) of hardwood biomass at temperatures between 200 and 240°C facilitated stepwise biopolymer fractionation, while limiting significant degradation of the major hemicellulose, glucuronoxylan, into water-extractable oligosaccharides. After GTP pretreatment and sequential water and organic solvent extraction, up to 80% of the initial xylan remained in the pretreated biomass. The majority of the xylan from GTP pretreated and water/solvent extracted biomass was removed using a mild alkali extraction and the composition was compared to xylan directly isolated from untreated hardwood. The precipitated xylan from the neutralized alkaline filtrate was isolated as a water insoluble xylan portion (WIX). The residual xylan dissolved in the neutralized filtrate was precipitated in cold methanol and recovered as the water soluble xylan portion (WSX). Results showed that xylan in WIX was in a polymeric form with a number average degree of polymerization (DP) over 100, whereas the WSX had a much lower average DP of 27 (ca) and contained more substitution. As the processing severity increased during GTP pretreatment, the proportion of WIX increased and the purity of the xylan within the WIX sample reached 84% based on compositional analysis. FT-IR analysis of WIX revealed that xylan isolated after GTP contained peaks related to a reduced carbonyl signal compared to the control. Furthermore, crude WSX contained less xylan with more lignin contamination at severe GTP conditions. The recovery of the xylan in two portions facilitated a preferential purification strategy resulting in WIX with an extremely narrow polydispersity index between 1.1 and 1.25, dependent upon the GTP severity. This study provided insight into fractionating higher molecular weight xylan that may serve value-added applications such as healthcare materials and advanced packaging. Copyright © 2016 Elsevier Ltd. All rights reserved.

Lignin-solubilizing ability of actinomycetes isolated from termite (Termitidae) gut.

PubMed Central

Pasti, M B; Pometto, A L; Nuti, M P; Crawford, D L

1990-01-01

The lignocellulose-degrading abilities of 11 novel actinomycete strains isolated from termite gut were determined and compared with that of the well-characterized actinomycete, Streptomyces viridosporus T7A. Lignocellulose bioconversion was followed by (i) monitoring the degradation of [14C]lignin- and [14C]cellulose-labeled phloem of Abies concolor to 14CO2 and 14C-labeled water-soluble products, (ii) determining lignocellulose, lignin, and carbohydrate losses resulting from growth on a lignocellulose substrate prepared from corn stalks (Zea mays), and (iii) quantifying production of a water-soluble lignin degradation intermediate (acid-precipitable polymeric lignin). The actinomycetes were all Streptomyces strains and could be placed into three groups, including a group of five strains that appear superior to S. viridosporus T7A in lignocellulose-degrading ability, three strains of approximately equal ability, and three strains of lesser ability. Strain A2 was clearly the superior and most effective lignocellulose decomposer of those tested. Of the assays used, total lignocellulose weight loss was most useful in determining overall bioconversion ability but not in identifying the best lignin-solubilizing strains. A screening procedure based on 14CO2 evolution from [14C-lignin]lignocellulose combined with measurement of acid-precipitable polymeric lignin yield was the most effective in identifying lignin-solubilizing strains. For the termite gut strains, the pH of the medium showed no increase after 3 weeks of growth on lignocellulose. This is markedly different from the pattern observed with S. viridosporus T7A, which raises the medium pH considerably. Production of extracellular peroxidases by the 11 strains and S. viridosporus T7A was followed for 5 days in liquid cultures.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2167628

Imprinted nanospheres based on precipitation polymerization for the simultaneous extraction of six urinary benzene metabolites from urine followed by injector port silylation and gas chromatography-tandem mass spectrometric analysis.

PubMed

Chauhan, Abhishek; Bhatia, Tejasvi; Gupta, Manoj Kumar; Pandey, Pathya; Pandey, Vivek; Saxena, Prem Narain; Mudiam, Mohana Krishna Reddy

2015-09-15

In the present communication, uniformly sized molecularly imprinted polymer (MIP) as nanospheres were synthesized based on precipitation polymerization using dual-template imprinting approach and used it as sorbent for solid phase extraction of six urinary benzene metabolites (UBMs). This approach in combination with injector port silylation (IPS) has been used for the quantitative determination of these UBMs by gas chromatography-tandem mass spectrometry. The MIP was synthesized by using t,t-muconic acid (t,t-MA) and 1,2,4-trihydroxybenzene (THB) as templates, methacrylic acid (MAA) as a monomer, ethyleneglycoldimethacrylate (EGDMA) as crosslinker, acetonitrile and dimethylsulphoxide as a porogen and azobisisobutyronitrile (AIBN) as an initiator. The factors affecting the performance of polymer and IPS were investigated and optimized for the simultaneous determination of UBMs in urine. Binding study of imprinted and non-imprinted polymer (NIP) shows that, MIP possesses higher affinity in comparison to NIP for these analytes. Under the optimum conditions, the method developed was found to be linear with regression coefficients falls in the range of 0.9721-0.9988 for all the analyzed metabolites. The percent recovery of the metabolites analyzed in urine was found to be in the range of 76-89%, while the limit of detection and limit of quantification were found to be in the range of 0.9-9.1ngmL(-1) and 2.8-27ngmL(-1) respectively. The validated method was successfully applied to the real urine samples collected from different groups (kitchen workers, smokers and petroleum workers) and found that the developed method has been promising applications in the routine analysis of urine samples of benzene exposed population. Copyright © 2015 Elsevier B.V. All rights reserved.

Composition and molecular scale structure of nanophases formed by precipitation of biotite weathering products

NASA Astrophysics Data System (ADS)

Tamrat, Wuhib Zewde; Rose, Jérôme; Grauby, Olivier; Doelsch, Emmanuel; Levard, Clément; Chaurand, Perrine; Basile-Doelsch, Isabelle

2018-05-01

Because of their large surface area and reactivity, nanometric-size soil mineral phases have a high potential for soil organic matter stabilization, contaminant sorption or soil aggregation. In the literature, Fe and Al phases have been the main targets of batch-synthesized nanomineral studies while nano-aluminosilicates (Al and Si phases) have been mainly studied in Andic soils. In the present work, we synthesized secondary nanophases of Fe, Al and Si. To simulate a system as close as possible to soil conditions, we conducted laboratory simulations of the processes of (1) biotite alteration in acidic conditions producing a Al Si Fe Mg K leachate solution and (2) the following neoformation of secondary nanophases by titrating the leachate solution to pH 4.2, 5 and 7. The morphology of the nanophases, their size, crystallinity and chemistry were characterized by TEM-EDX on single particles and their local atomic structure by EXAFS (Extended X-ray Absorption Fine Structure) at the Fe absorption K-edge. The main nanophases formed were amorphous particles 10-60 nm in size whose composition (dominated by Fe and Si) was strongly controlled by the pH conditions at the end of the titration. At pH 4.2 and pH 7, the structure of the nanophases was dominated by the polymerization of Fe, which was hindered by Al, Si, Mg and K. Conversely, at pH 5, the polymerization of Fe was counteracted by precipitation of high amounts of Si. The synthetized nanophases were estimated to be rather analogous to nanophases formed in natural biotite-bearing soils. Because of their small size and potential high surface reactivity, the adsorption capacities of these nanophases with respect to the OM should be revisited in the framework of soil C storage.

Crystallization control for remediation of an FetO-rich CaO-SiO2-Al2O3-MgO EAF waste slag.

PubMed

Jung, Sung Suk; Sohn, Il

2014-01-01

In this work, the crystallization behavior of synthesized FetO-rich electric arc furnace (EAF) waste slags with a basicity range of 0.7 to 1.08 was investigated. Crystal growth in the melts was observed in situ using a confocal laser scanning microscope, and a delayed crystallization for higher-basicity samples was observed in the continuous cooling transformation and time temperature transformation diagrams. This result is likely due to the polymerization of the melt structure as a result of the increased number of network-forming FeO4 and AlO4 units, as suggested by Raman analysis. The complex incorporation of Al and Fe ions in the form of AlO4 and FeO4 tetrahedral units dominant in the melt structure at a higher basicity constrained the precipitation of a magnetic, nonstoichiometric, and Fe-rich MgAlFeO4 primary phase. The growth of this spinel phase caused a clear compositional separation from amorphous phase during isothermal cooling at 1473 K leading to a clear separation between the primary and amorphous phases, allowing an efficient magnetic separation of Fe compounds from the slag for effective remediation and recycling of synthesized EAF waste slags for use in higher value-added ordinary Portland cement.

Microbially induced and microbially catalysed precipitation: two different carbonate factories

NASA Astrophysics Data System (ADS)

Meister, Patrick

2016-04-01

The landmark paper by Schlager (2003) has revealed three types of benthic carbonate production referred to as "carbonate factories", operative at different locations at different times in Earth history. The tropical or T-factory comprises the classical platforms and fringing reefs and is dominated by carbonate precipitation by autotrophic calcifying metazoans ("biotically controlled" precipitation). The cool or C-factory is also biotically controlled but via heterotrophic, calcifying metazoans in cold and deep waters at the continental margins. A further type is the mud-mound or M-factory, where carbonate precipitation is supported by microorganisms but not controlled by a specific enzymatic pathway ("biotically induced" precipitation). How exactly the microbes influence precipitation is still poorly understood. Based on recent experimental and field studies, the microbial influence on modern mud mound and microbialite growth includes two fundamentally different processes: (1) Metabolic activity of microbes may increase the saturation state with respect to a particular mineral phase, thereby indirectly driving the precipitation of the mineral phase: microbially induced precipitation. (2) In a situation, where a solution is already supersaturated but precipitation of the mineral is inhibited by a kinetic barrier, microbes may act as a catalyser, i.e. they lower the kinetic barrier: microbially catalysed precipitation. Such a catalytic effect can occur e.g. via secreted polymeric substances or specific chemical groups on the cell surface, at which the minerals nucleate or which facilitate mechanistically the bonding of new ions to the mineral surface. Based on these latest developments in microbialite formation, I propose to extend the scheme of benthic carbonate factories of Schlager et al. (2003) by introducing an additional branch distinguishing microbially induced from microbially catalysed precipitation. Although both mechanisms could be operative in a M-factory, and it is difficult to distinguish their products, their cause is very different. A Mi-factory ("i" for induced) is predominant under low carbonate saturation in normal seawater; a Mc-factory ("c" for catalysed) is operative in higher-alkalinity waters. The latter conditions may not only occur in shallow seas restricted from open sea water but may also have occurred in the aftermath of catastrophic events (e.g. P/T boundary) or during the Precambrian, before the onset of metazoan calcifiers. Thus, adding the additional distinction between microbially induced and microbially catalysed precipitation would allow the application of Schlager's concept of benthic carbonate factories beyond the Phanerozoic and probably over the entire Earth history.

Grafting of molecularly imprinted polymer to porous polyethylene filtration membranes by plasma polymerization.

PubMed

Cowieson, D; Piletska, E; Moczko, E; Piletsky, S

2013-08-01

An application of plasma-induced grafting of polyethylene membranes with a thin layer of molecularly imprinted polymer (MIP) was presented. High-density polyethylene (HDPE) membranes, "Vyon," were used as a substrate for plasma grafting modification. The herbicide atrazine, one of the most popular targets of the molecular imprinting, was chosen as a template. The parameters of the plasma treatment were optimized in order to achieve a good balance between polymerization and ablation processes. Modified HDPE membranes were characterized, and the presence of the grafted polymeric layer was confirmed based on the observed weight gain, pore size measurements, and infrared spectrometry. Since there was no significant change in the porosity of the modified membranes, it was assumed that only a thin layer of the polymer was introduced on the surface. The experiments on the re-binding of the template atrazine to the membranes modified with MIP and blank polymers were performed. HDPE membranes which were grafted with polymer using continuous plasma polymerization demonstrated the best result which was expressed in an imprinted factor equal to 3, suggesting that molecular imprinting was successfully achieved.

Stress reduction in phase-separated, cross-linked networks: influence of phase structure and kinetics of reaction

PubMed Central

Szczepanski, Caroline R.; Stansbury, Jeffrey W.

2014-01-01

A mechanism for polymerization shrinkage and stress reduction was developed for heterogeneous networks formed via ambient, photo-initiated polymerization-induced phase separation (PIPS). The material system used consists of a bulk homopolymer matrix of triethylene glycol dimethacrylate (TEGDMA) modified with one of three non-reactive, linear prepolymers (poly-methyl, ethyl and butyl methacrylate). At higher prepolymer loading levels (10–20 wt%) an enhanced reduction in both shrinkage and polymerization stress is observed. The onset of gelation in these materials is delayed to a higher degree of methacrylate conversion (~15–25%), providing more time for phase structure evolution by thermodynamically driven monomer diffusion between immiscible phases prior to network macro-gelation. The resulting phase structure was probed by introducing a fluorescently tagged prepolymer into the matrix. The phase structure evolves from a dispersion of prepolymer at low loading levels to a fully co-continuous heterogeneous network at higher loadings. The bulk modulus in phase separated networks is equivalent or greater than that of poly(TEGDMA), despite a reduced polymerization rate and cross-link density in the prepolymer-rich domains. PMID:25418999

Melamine-formaldehyde aerogels

DOEpatents

Pekala, Richard W.

1992-01-01

Organic aerogels that are transparent and essentially colorless are prepa from the aqueous, sol-gel polymerization of melamine with formaldehyde. The melamine-formaldehyde (MF) aerogels have low densities, high surface areas, continuous porsity, ultrafine cell/pore sizes, and optical clarity.

Bacterially induced mineralization of calcium carbonate: the role of exopolysaccharides and capsular polysaccharides.

PubMed

Ercole, Claudia; Cacchio, Paola; Botta, Anna Lucia; Centi, Valeria; Lepidi, Aldo

2007-02-01

Bacterially induced carbonate mineralization has been proposed as a new method for the restoration of limestones in historic buildings and monuments. We describe here the formation of calcite crystals by extracellular polymeric substances isolated from Bacillus firmus and Bacillus sphaericus. We isolated bacterial outer structures (glycocalix and parietal polymers), such as exopolysaccharides (EPS) and capsular polysaccharides (CPS) and checked for their influence on calcite precipitation. CPS and EPS extracted from both B. firmus and B. sphaericus were able to mediate CaCO3 precipitation in vitro. X-ray microanalysis showed that in all cases the formed crystals were calcite. Scanning electron microscopy showed that the shape of the crystals depended on the fractions utilized. These results suggest the possibility that biochemical composition of CPS or EPS influences the resulting morphology of CaCO3. There were no precipitates in the blank samples. CPS and EPS comprised of proteins and glycoproteins. Positive alcian blue staining also reveals acidic polysaccharides in CPS and EPS fractions. Proteins with molecular masses of 25-40 kDa and 70 kDa in the CPS fraction were highly expressed in the presence of calcium oxalate. This high level of synthesis could be related to the binding of calcium ions and carbonate deposition.

A micro-reactor for preparing uniform molecularly imprinted polymer beads.

PubMed

Zourob, Mohammed; Mohr, Stephan; Mayes, Andrew G; Macaskill, Alexandra; Pérez-Moral, Natalia; Fielden, Peter R; Goddard, Nicholas J

2006-02-01

In this study, uniform spherical molecularly imprinted polymer beads were prepared via controlled suspension polymerization in a spiral-shaped microchannel using mineral oil and perfluorocarbon liquid as continuous phases. Monodisperse droplets containing the monomers, template, initiator, and porogenic solvent were introduced into the microchannel, and particles of uniform size were produced by subsequent UV polymerization, quickly and without wasting polymer materials. The droplet/particle size was varied by changing the flow conditions in the microfluidic device. The diameter of the resulting products typically had a coefficient of variation (CV) below 2%. The specific binding sites that were created during the imprinting process were analysed via radioligand binding analysis. The molecularly imprinted microspheres produced in the liquid perfluorocarbon continuous phase had a higher binding capacity compared with the particles produced in the mineral oil continuous phase, though it should be noted that the aim of this study was not to optimize or maximize imprinting performance, but rather to demonstrate broad applicability and compatibility with known MIP production methods. The successful imprinting against a model compound using two very different continuous phases (one requiring a surfactant to stabilize the droplets the other not) demonstrates the generality of this current simple approach.

Molecularly Imprinted Polymers: Novel Discovery for Drug Delivery.

PubMed

Dhanashree, Surve; Priyanka, Mohite; Manisha, Karpe; Vilasrao, Kadam

2016-01-01

Molecularly imprinted polymers (MIP) are novel carriers synthesized by imprinting of a template over a polymer. This paper presents the recent application of MIP for diagnostic and therapeutic drug delivery. MIP owing to their 3D polymeric structures and due to bond formation with the template serves as a reservoir of active causing stimuli sensitive, enantioselective, targetted and/or controlled release. The review elaborates about key factors for optimization of MIP, controlled release by MIP for various administration routes various forms like patches, contact lenses, nanowires along with illustrations. To overcome the limitation of organic solvent usage causing increased cost, water compatible MIP and use of supercritical fluid technology for molecular imprinting were developed. Novel methods for developing water compatible MIP like pickering emulsion polymerization, co-precipitation method, cyclodextrin imprinting, surface grafting, controlled/living radical chain polymerization methods are described with illustration in this review. Various protein imprinting methods like bulk, epitope and surface imprinting are described along with illustrations. Further, application of MIP in microdevices as biomimetic sensing element for personalized therapy is elaborated. Although development and application of MIP in drug delivery is still at its infancy, constant efforts of researchers will lead to a novel intelligent drug delivery with commercial value. Efforts should be directed in developing solid oral dosage forms consisting of MIP for therapeutic protein and peptide delivery and targeted release of potent drugs addressing life threatening disease like cancer. Amalgamation of bio-engineering and pharmaceutical techniques can make these future prospects into reality.

Kinetic of antigent-antibody reactions with scattering method

NASA Astrophysics Data System (ADS)

Bilyi, Olexander I.; Kiselyov, Yevgen M.; Novikov, Volodymyr P.

2001-07-01

The immune reactions of interaction antigen-antibody represent specific effect of an antigene with an antibody, which outcome are the complex immune aggregates forming precipitate in case of a soluble antigene, or agglutinate in case of a corpuscular antigene. Immunological methods which uses in the quality of carrier protein latex's polymeric microspheresis, gained name and method latex agglutination. Polymeric microspheresis have the array of advantages before biological carries, which consist in the opportunity of the variation of attributes surface and size microspheresis in the broad band of meanings with the preservation of narrow distribution particles behind measurements, the putting of functional groups, necessary for bunch with ligand on stage their synthesis, in ragidity at storage. The quantitative evaluation of parameters of a response of interaction antigen-antibody in immunology is possible by optical methods on a measurement of a modification of intensity of a light stream of a solution in an outcome of a course of a reaction. Concentration of immune complexes determine both on slacking a taking place stream of light, and on a modification of intensity of a stream of light scattering suspended particles in a solution. The process light scattering by colloidal aggregates are formed from suspension microspheresis with adsorbed on their surface protein is described. In report the physics principle of registration immune reaction by light scattering methods is concerned. The results of the effectiveness latex's preparation created on basis of the polymeric carries is described.

Novel PLA modification of organic microcontainers based on ring opening polymerization: synthesis, characterization, biocompatibility and drug loading/release properties.

PubMed

Efthimiadou, E K; Tziveleka, L-A; Bilalis, P; Kordas, G

2012-05-30

In the current study, poly lactic acid (PLA) modified hollow crosslinked poly(hydroxyethyl methacrylate) (PHEMA) microspheres have been prepared, in order to obtain a stimulus-responsive, biocompatible carrier with sustained drug release properties. The synthetical process consisted of the preparation of poly(methacrylic acid)@poly(hydroxyethyl methacrylate-co-N,N'-methylene bis(acrylamide)) microspheres by a two stage distillation-precipitation polymerization technique using 2,2'-azobisisobutyronitrile as initiator. Following core removal, a PLA coating of the microspheres was formed, after ring opening polymerization of DL-lactide, attributing the initiator's role to the active hydroxyl groups of PHEMA. The anticancer drug daunorubicin (DNR) was selected for the study of loading and release behavior of the coated microspheres. The loading capacity of the PLA modified microspheres was found to be four times higher than that of the parent ones (16% compared to 4%). This coated microspherical carrier exhibited a moderate pH responsive drug release behavior due to the pH dependent water uptake of PHEMA, and PLA hydrolysis. The in vitro cytotoxicity of both the parent and the DNR-loaded or empty modified hollow microspheres has been also examined on MCF-7 breast cancer cells. The results showed that although the empty microspheres were moderately cytotoxic, the DNR-loaded microspheres had more potent anti-tumor effect than the free drug. Therefore, the prepared coated microspheres are interesting drug delivery systems. Copyright © 2012 Elsevier B.V. All rights reserved.

Colloidal Covalent Organic Frameworks

PubMed Central

2017-01-01

Covalent organic frameworks (COFs) are two- or three-dimensional (2D or 3D) polymer networks with designed topology and chemical functionality, permanent porosity, and high surface areas. These features are potentially useful for a broad range of applications, including catalysis, optoelectronics, and energy storage devices. But current COF syntheses offer poor control over the material’s morphology and final form, generally providing insoluble and unprocessable microcrystalline powder aggregates. COF polymerizations are often performed under conditions in which the monomers are only partially soluble in the reaction solvent, and this heterogeneity has hindered understanding of their polymerization or crystallization processes. Here we report homogeneous polymerization conditions for boronate ester-linked, 2D COFs that inhibit crystallite precipitation, resulting in stable colloidal suspensions of 2D COF nanoparticles. The hexagonal, layered structures of the colloids are confirmed by small-angle and wide-angle X-ray scattering, and kinetic characterization provides insight into the growth process. The colloid size is modulated by solvent conditions, and the technique is demonstrated for four 2D boronate ester-linked COFs. The diameter of individual COF nanoparticles in solution is monitored and quantified during COF growth and stabilization at elevated temperature using in situ variable-temperature liquid cell transmission electron microscopy imaging, a new characterization technique that complements conventional bulk scattering techniques. Solution casting of the colloids yields a free-standing transparent COF film with retained crystallinity and porosity, as well as preferential crystallite orientation. Collectively this structural control provides new opportunities for understanding COF formation and designing morphologies for device applications. PMID:28149954

Oligo(ethylene glycol)-sidechain microgels prepared in absence of cross-linking agent: Polymerization, characterization and variation of particle deformability.

PubMed

Welsch, Nicole; Lyon, L Andrew

2017-01-01

We present a systematic study of self-cross-linked microgels formed by precipitation polymerization of oligo ethylene glycol methacrylates. The cross-linking density of these microgels and, thus, the network flexibility can be easily tuned through the modulation of the reaction temperature during polymerization. Microgels prepared in absence of any difunctional monomer, i.e. cross-linker, show enhanced deformability and particle spreading on solid surfaces as compared to microgels cross-linked with varying amounts of poly(ethylene glycol diacrylate) (PEG-DA) in addition to self-crosslinking. Particles prepared at low reaction temperatures exhibit the highest degree of spreading due to the lightly cross-linked and flexible polymer network. Moreover, AFM force spectroscopy studies suggest that cross-linker-free microgels constitute of a more homogeneous polymer network than PEG-DA cross-linked particles and have elastic moduli at the particle apex that are ~5 times smaller than the moduli of 5 mol-% PEG-DA cross-linked microgels. Resistive pulse sensing experiments demonstrate that microgels prepared at 75 and 80°C without PEG-DA are able to deform significantly to pass through nanopores that are smaller than the microgel size. Additionally, we found that polymer network flexibility of microgels is a useful tool to control the formation of particle dewetting patterns. This offers a promising new avenue for build-up of 2D self-assembled particle structures with patterned chemical and mechanical properties.

Oligo(ethylene glycol)-sidechain microgels prepared in absence of cross-linking agent: Polymerization, characterization and variation of particle deformability

PubMed Central

Lyon, L. Andrew

2017-01-01

We present a systematic study of self-cross-linked microgels formed by precipitation polymerization of oligo ethylene glycol methacrylates. The cross-linking density of these microgels and, thus, the network flexibility can be easily tuned through the modulation of the reaction temperature during polymerization. Microgels prepared in absence of any difunctional monomer, i.e. cross-linker, show enhanced deformability and particle spreading on solid surfaces as compared to microgels cross-linked with varying amounts of poly(ethylene glycol diacrylate) (PEG-DA) in addition to self-crosslinking. Particles prepared at low reaction temperatures exhibit the highest degree of spreading due to the lightly cross-linked and flexible polymer network. Moreover, AFM force spectroscopy studies suggest that cross-linker-free microgels constitute of a more homogeneous polymer network than PEG-DA cross-linked particles and have elastic moduli at the particle apex that are ~5 times smaller than the moduli of 5 mol-% PEG-DA cross-linked microgels. Resistive pulse sensing experiments demonstrate that microgels prepared at 75 and 80°C without PEG-DA are able to deform significantly to pass through nanopores that are smaller than the microgel size. Additionally, we found that polymer network flexibility of microgels is a useful tool to control the formation of particle dewetting patterns. This offers a promising new avenue for build-up of 2D self-assembled particle structures with patterned chemical and mechanical properties. PMID:28719648

Chapter 7: Precipitation Change in the United States

NASA Technical Reports Server (NTRS)

Easterling, D. R.; Kunkel, K. E.; Arnold, J. R.; Knutson, T.; LeGrande, A. N.; Leung, L. R.; Vose, R. S.; Waliser, D. E.; Wehner, M. F.

2017-01-01

Annual precipitation has decreased in much of the West, Southwest, and Southeast and increased in most of the Northern and Southern Plains, Midwest, and Northeast. A national average increase of 4% in annual precipitation since 1901 is mostly a result of large increases in the fall season. Heavy precipitation events in most parts of the United States have increased in both intensity and frequency since 1901. There are important regional differences in trends, with the largest increases occurring in the northeastern United States. In particular, mesoscale convective systems (organized clusters of thunderstorms)-the main mechanism for warm season precipitation in the central part of the United States-have increased in occurrence and precipitation amounts since 1979. The frequency and intensity of heavy precipitation events are projected to continue to increase over the 21st century (high confidence). Mesoscale convective systems in the central United States are expected to continue to increase in number and intensity in the future. There are, however, important regional and seasonal differences in projected changes in total precipitation: the northern United States, including Alaska, is projected to receive more precipitation in the winter and spring, and parts of the southwestern United States are projected to receive less precipitation in the winter and spring. Northern Hemisphere spring snow cover extent, North America maximum snow depth, snow water equivalent in the western United States, and extreme snowfall years in the southern and western United States have all declined, while extreme snowfall years in parts of the northern United States have increased. Projections indicate large declines in snowpack in the western United States and shifts to more precipitation falling as rain than snow in the cold season in many parts of the central and eastern United States.

Stabilization of enzymatically polymerized phenolic chemicals in a model soil organic matter-free geomaterial.

PubMed

Palomo, Mónica; Bhandari, Alok

2012-01-01

A variety of remediation methods, including contaminant transformation by peroxidase-mediated oxidative polymerization, have been proposed to manage soils and groundwater contaminated with chlorinated phenols. Phenol stabilization has been successfully observed during cross polymerization between phenolic polymers and soil organic matter (SOM) for soils with SOM >3%. This study evaluates peroxidase-mediated transformation and removal of 2,4-dichlorophenol (DCP) from an aqueous phase in contact with a natural geomaterial modified to contain negligible (<0.3%) SOM. The results are compared with those for soils with higher SOM. The SOM-free sorbent was generated by removing SOM using a NaOCl oxidation. When horseradish peroxidase (HRP) was used to induce polymerization of DCP, the soil-water phase distribution relationship (PDR) of DCP polymerization products (DPP) was complete within 1 d and PDRs did not significantly change over the 28 d of study. The conversion of DCP to DPP was close to 95% efficient. Extractable solute consisted entirely of DPP with 5% or less of unreacted DCP. The aqueous extractability of DPP from SOM-free geomaterial decreased at longer contact times and at smaller residual aqueous concentrations of DPP. DCP stabilization appeared to have resulted from a combination of sorption, precipitation, and ligand exchange between oligomeric products and the exposed mineral surfaces. Modification of the mineral surface through coverage with DPP enhanced the time-dependent retention of the oligomers. DPP stabilization in SOM-free geomaterial was comparable with that reported in the literature with soil containing SOM contents >1%. Results from this study suggest that the effectiveness of HRP-mediated stabilization of phenolic compounds not only depends on the cross-coupling with SOM, but also on the modification of the surface of the sorbent that can augment affinity with oligomers and enhance stabilization. Coverage of the mineral surface by phenolic oligomers may be analogous to SOM that can potentially sorb other xenobiotics. HRP- mediated reactions can be used to stabilize DCP associated with low SOM mineral soils or aquifer media, thereby restricting the transport of phenolic contaminants in the soil environment. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Multi-scale fluctuation analysis of precipitation in Beijing by Extreme-point Symmetric Mode Decomposition

NASA Astrophysics Data System (ADS)

Li, Jiqing; Duan, Zhipeng; Huang, Jing

2018-06-01

With the aggravation of the global climate change, the shortage of water resources in China is becoming more and more serious. Using reasonable methods to study changes in precipitation is very important for planning and management of water resources. Based on the time series of precipitation in Beijing from 1951 to 2015, the multi-scale features of precipitation are analyzed by the Extreme-point Symmetric Mode Decomposition (ESMD) method to forecast the precipitation shift. The results show that the precipitation series have periodic changes of 2.6, 4.3, 14 and 21.7 years, and the variance contribution rate of each modal component shows that the inter-annual variation dominates the precipitation in Beijing. It is predicted that precipitation in Beijing will continue to decrease in the near future.

Shear Driven Synthesis of Polymeric Micro- and Nanomaterials

NASA Astrophysics Data System (ADS)

Tian, Tian

Polymeric micro- and nanomaterials play a significant role in various current and emerging technologies. A liquid shear based method was developed to fabricate a wide range of polymeric materials, which include fibers, sheets, ribbons, rods and spheres in a scalable, cost-effective and simple way. During the process, droplet shearing, droplet deformation, droplet breaking up and polymer precipitation occur simultaneously. The size and morphology of the resultant structures are determined by the dominating process which is further controlled by the experimental parameters including polymer concentration, polymer molecular weight and antisolvent concentration. Among all of these structures, nanofibers have attracted the latest research interest due to the unique properties. Current leading fiber production approaches in the market possess certain drawbacks. For example, the throughput of electrospinning is limited to around 2.5 kg/hr and the diameter of fiber produced by wet spinning cannot be below micrometer while melt spinning is only applicable to melt-processable polymers. The breakthrough of our liquid shear driven technique for fiber synthesis is that it produces fibers with diameter from 200 nm to several micrometers from a wide range of liquid- processable polymers with high commercial yield (up to 12 kg/hr). Thus in Chapter 2, the optimum parameters range for fiber formation is established and the effects of those parameters on fiber size are investigated. In the original liquid shear method, medium with high viscosity is needed to exert strong shear stress on the droplet and to stretch the droplets to long strand. However, the viscous medium complicates the post sample washing procedure and introduces the potential slippery danger in the working area. Thus a non-viscous medium shearing method is developed in Chapter 3 and it is the first time proposed that the synthesis of PLA or PS nanofibers can be completed in the aqueous ethanol medium. Colloid science usually categorizes emulsion as oil in water (O/W) and water in oil (W/O) dispersions. Oil in oil emulsion can also be formulated from the immiscible organic liquid pairs. Using the phase separation in the PS-cyclohexane system, the emulsion are formed under continuous shearing while the continuous phase is solvent-rich and the disperse phase is polymer-rich. By shearing the emulsions, the fibers sizes are reduced around 10X due to the smaller initial polymer droplet size. The fiber sizes are further reduced to 100 nm which enhances the competitive advantages of liquid shear technique. Controlled drug release combines the advantages of increased therapeutic efficacy, reduced toxicity and lower administration frequency. By dispersing model drugs in the spinning polymer solution, these drugs are successfully encapsulated inside the biodegradable matrix and the encapsulation efficiency is modulated by polymer concentration and fiber size while the release profile of the drug is determined by the degradation rate of the polymer matrix.

Discontinuous precipitation at the deformation band in copper alloy

NASA Astrophysics Data System (ADS)

Han, Seung Zeon; Ahn, Jee Hyuk; You, Young Soo; Lee, Jehyun; Goto, Masahiro; Kim, Kwangho; Kim, Sangshik

2018-01-01

The Cu-Ni-Si alloy is known as a precipitation hardening alloy, where the Ni2Si intermetallic compound is precipitated in the matrix during aging. There are two types of precipitation of Ni2Si: continuous and discontinuous cellular. The discontinuous cellular precipitation is generally initiated at interfaces especially grain boundaries in the matrix. To observe the grain boundary effect on the discontinuous precipitation, a large-grained Cu-Ni-Si-Ti alloy was intentionally fabricated by unidirectional solidification and plastically deformed by groove rolling. While discontinuous cellular precipitation has been generally known to occur only at the high angled grain boundaries in the alloys, we found that it was also generated inside the grains, at the deformation bands formed by plastic deformation.

Changes in chemical processes in soils caused by acid precipitation

Treesearch

Stephen A. Norton

1976-01-01

The acidification of precipitation is an accomplished fact. The only question that remains is whether the present trend of acidification is to continue into the future, and if so, to what degree. A related question is, are the consequences of acid precipitation reversible and to what extent, or over what time period? Research conducted over the last twenty years has...

Hydrogen ion input to the Hubbard Brook Experimental Forest, New Hampshire, during the last decade

Treesearch

Gene E. Likens; F. Herbert Bormann; John S. Eaton; Robert S. Pierce; Noye M. Johnson

1976-01-01

Being downwind of eastern and midwestern industrial centers, the Hubbard Brook Experimental Forest offers a prime location to monitor long-term trends in atmospheric chemistry. Continuous measurements of precipitation chemistry during the last 10 years provide a measure of recent changes in precipitation inputs of hydrogen ion. The weighted average pH of precipitation...

Melamine-formaldehyde aerogels

DOEpatents

Pekala, R.W.

1992-01-14

Organic aerogels that are transparent and essentially colorless are prepared from the aqueous, sol-gel polymerization of melamine with formaldehyde. The melamine-formaldehyde (MF) aerogels have low densities, high surface areas, continuous porosity, ultrafine cell/pore sizes, and optical clarity. 3 figs.

Synthesis of high capacity cathodes for lithium-ion batteries by morphology-tailored hydroxide co-precipitation

NASA Astrophysics Data System (ADS)

Wang, Dapeng; Belharouak, Ilias; Ortega, Luis H.; Zhang, Xiaofeng; Xu, Rui; Zhou, Dehua; Zhou, Guangwen; Amine, Khalil

2015-01-01

Nickel manganese hydroxide co-precipitation inside a continuous stirred tank reactor was studied with sodium hydroxide and ammonium hydroxide as the precipitation agents. The ammonium hydroxide concentration had an effect on the primary and secondary particle evolution. The two-step precipitation mechanism proposed earlier was experimentally confirmed. In cell tests, Li- and Mn-rich composite cathode materials based on the hydroxide precursors demonstrated good electrochemical performance in terms of cycle life over a wide range of lithium content.

Low-shrink composite resins: a review of their history, strategies for managing shrinkage, and clinical significance.

PubMed

Pitel, Mark L

2013-09-01

Despite numerous advances in composite resin technology over the course of many decades, shrinkage behavior and the resultant stresses inherent to direct placed composite restorations continue to challenge clinicians. This overview of composite resins includes a review of their history and development along with a discussion of strategies for reducing polymerization shrinkage. An assessment of the clinical significance of these materials is also provided, including a discussion of the differences between polymerization shrinkage and stress, incremental layering versus bulk placement, and the emergence of lower shrinkage stress monomer chemistry.

Prebiotic thermal polymerization of crystals of amino acids via the diketopiperazine reaction.

PubMed

Mosqueira, F G; Ramos-Bernal, S; Negrón-Mendoza, A

2008-01-01

In this work, we continue our studies on the thermal prebiotic oligomerization of amino acids. The next step is to consider all four types of electromagnetic interactions that our model may admit. In addition, only the polymerization of amino acids via the formation of diketopiperazine, which arises from the cyclodehydration of two amino acids, will be considered. By assuming that only one residue group of two will predominate in the diketopiperazine molecule, it is possible to reduce the three-body problem to a simpler situation with the two objects that we have already solved.

Graft polymerization of wood sawdust and peat with ethylene carbonate. A novel method for the preparation of supports with enhanced mechanical properties to be used in biofiltration of organic vapors.

PubMed

Hernández-Meléndez, O; Peydecastaing, J; Bárzana, E; Vaca-Garcia, C; Hernández-Luna, M; Borredon, M E

2009-01-01

The graft polymerization reaction between ethylene carbonate (EC) and scots pine sawdust (SPS) or peat moss (PM) offers a solvent-free approach to the simple and inexpensive aliphatic derivatization of these lignocellulosic fibers. This reaction was studied with liquid or vapor EC phases in three different reactor configurations: batch stirred (BSR), semi-continuous stirred (SSR) and continuous tubular in the gas phase (CVTR). The use of a vapor phase allowed a satisfactory grafting yield and minimal production of non-grafted polyol by-products. The crosslinking agent 4,4'-methylenebis(phenylisocyanate) (MDI) achieved superior characteristics to form shaped tablets resistant to water disaggregation, a high water retention capacity and high compression strength, characteristics that conventional organic supports like PM or PM-polyurethane foam mixtures used in biofiltration of waste gases do not completely possess.

Hot spring deposits on a cliff face: A case study from Jifei, Yunnan Province, China

NASA Astrophysics Data System (ADS)

Jones, Brian; Peng, Xiaotong

2014-04-01

A cliff face in the Jifei karst area, southwest China, is covered by a spectacular succession of precipitates that formed from the hot spring water that once flowed down its surface. This layered succession is formed of aragonite layers that are formed largely of “fountain dendrites”, calcite layers that are formed mostly of “cone dendrites”, and microlaminated layers that contain numerous microbes and extracellular polymeric substances (EPS). Many of the aragonite crystals are hollow due to preferential dissolution of their cores. The calcite cone dendrites are commonly covered with biofilms, reticulate Si-Mg coatings, and other precipitates. The microbial layers include dodecahedral calcite crystals and accessory minerals that include opal-A, amorphous Si-Mg coatings, trona, barite, potassium sulfate crystals, mirabillite, and gaylussite. Interpretation of the δ18O(calcite) and δ18O(aragonite) indicates precipitation from water with a temperature of 54 to 66 °C. The active hot spring at the top of the cliff presently ejects water at a temperature of 65 °C. Layers, 1 mm to 6 cm thick, record temporal changes in the fluids from which the precipitates formed. This succession is not, however, formed of recurring cycles that can be linked to diurnal or seasonal changes in the local climate. Indeed, it appears that the climatic contrast between the wet season and the dry season had little impact on precipitation from the spring waters that flowed down the cliff face. Integration of currently available evidence suggests that the primary driving force was aperiodic changes in the CO2 content of the spring waters because that seems to be the prime control on the saturation levels that underpinned precipitation of the calcite and aragonite as well as the dissolution of the aragonite. Such variations in the CO2 content of the spring water were probably due to changes that took place in the subterranean plumbing system of the spring.

The importance of hot drought in providing more useful, and higher confidence, projections of future climatic, hydrologic, and ecosystem impacts.

NASA Astrophysics Data System (ADS)

Overpeck, J. T.; Udall, B. H.

2017-12-01

Often cited as a general guide to future climatic change, "the wet get wetter, and the dry get drier" is a misleading way to look towards the future for many regions of the globe, just as the simple use of multi-model ensemble projections of temperature and precipitation change averaged over many years can also be quite misleading for real-world planning and decision-making. Factors that support these assertions are multi-fold. First, we know with high confidence that warming will continue as long as greenhouse gas emissions continue. Second, continued warming will act to make droughts more frequent, longer and more severe in many regions. Even in the absence of precipitation declines, increases in evaporation and evapotranspiration, among other things, will drive regional drying. It is misleading to suggest to decision-makers that although the future may see an increase in drought risk, a projected increase in mean precipitation will counter-balance the increased drought risk. This counter-balancing will be absent during periods of precipitation-dominated drought. Moreover, projections of precipitation change are usually associated with much less confidence than projections of warming. For example, in places like the headwaters of the Colorado and Rio Grande Rivers, or East Africa, many models suggest we should be seeing an increase in precipitation, when in fact we are only seeing significant warming. Moreover, paleoclimatic evidence suggests that state-of-the-art Earth System Models may underestimate the risk of future multi-decadal droughts, even though these droughts have occurred in many regions during the last 2000 years. This reality suggests that even in regions that do see modest increases in mean precipitation, there will likely be periods in the future characterized by decades of below 20th century mean precipitation coupled with unprecedented warmth. Hot drought may be a much more widespread and serious threat than widely recognized.

Membrane separation of ionic liquid solutions

DOEpatents

Campos, Daniel; Feiring, Andrew Edward; Majumdar, Sudipto; Nemser, Stuart

2015-09-01

A membrane separation process using a highly fluorinated polymer membrane that selectively permeates water of an aqueous ionic liquid solution to provide dry ionic liquid. Preferably the polymer is a polymer that includes polymerized perfluoro-2,2-dimethyl-1,3-dioxole (PDD). The process is also capable of removing small molecular compounds such as organic solvents that can be present in the solution. This membrane separation process is suitable for drying the aqueous ionic liquid byproduct from precipitating solutions of biomass dissolved in ionic liquid, and is thus instrumental to providing usable lignocellulosic products for energy consumption and other industrial uses in an environmentally benign manner.

Synthesis and self-assembly of amphiphilic polymeric microparticles.

PubMed

Dendukuri, Dhananjay; Hatton, T Alan; Doyle, Patrick S

2007-04-10

We report the synthesis and self-assembly of amphiphilic, nonspherical, polymeric microparticles. Wedge-shaped particles bearing segregated hydrophilic and hydrophobic sections were synthesized in a microfludic channel by polymerizing across laminar coflowing streams of hydrophilic and hydrophobic polymers using continuous flow lithography (CFL). Particle monodispersity was characterized by measuring both the size of the particles formed and the extent of amphiphilicity. The coefficient of variation (COV) was found to be less than 2.5% in all measured dimensions. Particle structure was further characterized by measuring the curvature of the interface between the sections and the extent of cross-linking using FTIR spectroscopy. The amphiphilic particles were allowed to self-assemble in water or at water-oil interfaces. In water, the geometry of the particles enabled the formation of micelle-like structures, while in emulsions, the particles migrated to the oil-water interface and oriented themselves to minimize their surface energy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

In order to develop the conditions for preparing polymers with different molecular masses, the authors continued their investigation of TMSP (1-(trimethylsilyl)-1-propyne) polymerization catalyzed by TaCl{sub 5} and TaCl{sub 5}/BuLi at various ratios of VTMS (regulator of molecular mass of the polymer) : catalyst. They also studied the effect of the structure of silahydrocarbon on the process of TMSP polymerization. To this end, they carried out polymerization of TMSP in the presence of additives of vinylphenyldimethylsilane and vinylallyldimethylsilane. The conditions of experiments and the results obtained are shown. The method for controlling the molecular mass of PTMSP makes it possible tomore » prepare PTMSP suitable for manufacture of both flat membranes and hollow fibers. The paper also describes the experimental study of PTMSP gas permeability, gas sorption in PTMSP, and a computer program for the prediction of all gas permeability parameters of polymers.« less

Nanocellular foam with solid flame retardant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Liang; Kelly-Rowley, Anne M.; Bunker, Shana P.

Prepare nanofoam by (a) providing an aqueous solution of a flame retardant dissolved in an aqueous solvent, wherein the flame retardant is a solid at 23.degree. C. and 101 kiloPascals pressure when in neat form; (b) providing a fluid polymer composition selected from a solution of polymer dissolved in a water-miscible solvent or a latex of polymer particles in a continuous aqueous phase; (c) mixing the aqueous solution of flame retardant with the fluid polymer composition to form a mixture; (d) removing water and, if present, solvent from the mixture to produce a polymeric composition having less than 74 weight-percentmore » flame retardant based on total polymeric composition weight; (e) compound the polymeric composition with a matrix polymer to form a matrix polymer composition; and (f) foam the matrix polymer composition into nanofoam having a porosity of at least 60 percent.« less

Optimizing Glassy Polymer Network Morphology for Nano-particle Dispersion, Stabilization and Performance

DTIC Science & Technology

2016-10-03

dissolution, toughener dissolution and controlled chain-extension reactions in the continuous reactor high temperature “hot-zone” to advance conversion...rheology and tack. 2. Simultaneous MWCNT dispersion and stabilization in the continuous reactor low temperature “cold-zone” leading to an increased...Weight and Low Dispersity Polyacrylonitrile by Low Temperature RAFT Polymerization, Moskowitz, Jeremy, Abel, Brooks, McCormick, Charles, Wiggins

Continuous and simultaneous measurements of precipitation and vapor isotopes over two monsoon seasons during 2016-2017 in Singapore

NASA Astrophysics Data System (ADS)

Jackisch, D.; He, S.; Ong, M. R.; Goodkin, N.

2017-12-01

Water isotopes are important tracers of climate dynamics and their measurement can provide valuable insights into the relationship between isotopes and atmospheric parameters and overall convective activities. While most studies provide data on daily or even monthly time scales, high-temporal in-situ stable isotope measurements are scarce, especially in the tropics. In this study, we presented δ18O and δ2H values in precipitation and vapor continuously and simultaneously measured using laser spectroscopy in Singapore during the 2016/2017 Northeast (NE) Asian monsoon and 2017 Southwest (SW) Asian monsoon. We found that δ-values of precipitation and vapor exhibit quite different patterns during individual events, although there is a significant correlation between the δ-values of precipitation and of vapor. δ-values in precipitation during individual precipitation events show a distinct V-shape pattern, with the lowest isotope values observed in the middle of the event. However, isotopes in water vapor mostly show an L-shape and are characterized by a gradual decrease with the onset of rainfall. The difference in δ-values of precipitation and vapor is generally constant during the early stage of the events but gradually increases near the end. It is likely that vapor and precipitation are closer to equilibrium at the early stage of a rain event, but diverge at the later stages. This divergence can be largely attributed to the evaporation of raindrops. We notice a frequent drop in d-excess of precipitation, whereas d-excess in vapor increases. In addition, a significant correlation exists between outgoing longwave radiation (OLR) and isotopes in both precipitation and vapor, suggesting an influence of regional convective activity.

Polymerization of Building Blocks of Life on Europa and Other Icy Moons.

PubMed

Kimura, Jun; Kitadai, Norio

2015-06-01

The outer Solar System may provide a potential habitat for extraterrestrial life. Remote sensing data from the Galileo spacecraft suggest that the jovian icy moons--Europa, Ganymede, and possibly Callisto--may harbor liquid water oceans underneath their icy crusts. Although compositional information required for the discussion of habitability is limited because of significantly restricted observation data, organic molecules are ubiquitous in the Universe. Recently, in situ spacecraft measurements and experiments suggest that amino acids can be formed abiotically on interstellar ices and comets. These amino acids could be continuously delivered by meteorite or comet impacts to icy moons. Here, we show that polymerization of organic monomers, in particular amino acids and nucleotides, could proceed spontaneously in the cold environment of icy moons, in particular the jovian icy moon Europa as a typical example, based on thermodynamic calculations, though kinetics of formation are not addressed. Observed surface temperature on Europa is 120 and 80 K in the equatorial region and polar region, respectively. At such low temperatures, Gibbs energies of polymerization become negative, and the estimated thermal structure of the icy crust should contain a shallow region (i.e., at a depth of only a few kilometers) favorable for polymerization. Investigation of the possibility of organic monomer polymerization on icy moons could provide good constraints on the origin and early evolution of extraterrestrial life.

Structural and surface functionality changes in reticulated vitreous carbon produced from poly(furfuryl alcohol) with sodium hydroxide additions

NASA Astrophysics Data System (ADS)

Oishi, Silvia Sizuka; Botelho, Edson Cocchieri; Rezende, Mirabel Cerqueira; Ferreira, Neidenêi Gomes

2017-02-01

The use of sodium hydroxide to neutralize the acid catalyst increases the storage life of poly(furfuryl alcohol) (PFA) resin avoiding its continuous polymerization. In this work, a concentrated sodium hydroxide solution (NaOH) was added directly to the PFA resin in order to minimize the production of wastes generated when PFA is washed with diluted basic solution. Thus, different amounts of this concentrated basic solution were added to the resin up to reaching pH values of around 3, 5, 7, and 9. From these four types of modified PFA two sample sets of reticulated vitreous carbon (RVC) were processed and heat treated at two different temperatures (1000 and 1700 °C). A correlation among cross-link density of PFA and RVC morphology, structural ordering and surface functionalities was systematically studied using Fourier transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy techniques. The PFA neutralization (pH 7) led to its higher polymerization degree, promoting a crystallinity decrease on RVC treated at 1000 °C as well as its highest percentages of carboxylic groups on surface. A NaOH excess (pH 9) substantially increased the RVC oxygen content, but its crystallinity remained similar to those for samples from pH 3 and 5 treated at 1000 °C, probably due to the reduced presence of carboxylic group and the lower polymerization degree of its cured resin. Samples with pH 3 and 5 heat treated at 1000 and 1700 °C can be considered the most ordered which indicated that small quantities of NaOH may be advantageous to minimize continuous polymerization of PFA resin increasing its storage life and improving RVC microstructure.

Water resources data, North Carolina, water year 2004. Volume 2: Ground-water records

USGS Publications Warehouse

Howe, S.S.; Breton, P.L.; Chapman, M.J.

2005-01-01

Water-resources data for the 2004 water year for North Carolina consist of records of stage, discharge, water quality for streams; stage and contents for lakes and reservoirs; precipitation; and ground-water levels and water quality of ground water. Volume 1 contains discharge records for 217 gaging stations; stage and contents for 58 lakes and reservoirs; stage only records for 22 gaging stations; elevations for 9 stations; water quality for 39 gaging stations and 5 miscellaneous sites, and continuous water quality for 35 sites; and continuous precipitation at 127 sites. Volume 2 contains ground-water-level data from 161 observation wells, ground-water-quality data from 38 wells, continuous water quality for 7 sites and continuous precipitation at 7 sites. Additional water data were collected at 51 sites not involved in the systematic data-collection program, and are published as miscellaneous measurements in Volume 1. The collection of water-resources data in North Carolina is a part of the National Water-Data System operated by the U.S. Geological Survey in cooperation with State, municipal, and Federal agencies.

Reverse osmosis brine for phosphorus recovery from source separated urine.

PubMed

Tian, Xiujun; Wang, Guotian; Guan, Detian; Li, Jiuyi; Wang, Aimin; Li, Jin; Yu, Zhe; Chen, Yong; Zhang, Zhongguo

2016-12-01

Phosphorus (P) recovery from waste streams has recently been recognized as a key step in the sustainable supply of this indispensable and non-renewable resource. The feasibility of using brine from a reverse osmosis (RO) membrane unit treating cooling water as a precipitant for P recovery from source separated urine was evaluated in the present study. P removal efficiency, process parameters and precipitate properties were investigated in batch and continuous flow experiments. More than 90% of P removal was obtained from both undiluted fresh and hydrolyzed urines by mixing with RO brine (1:1, v/v) at a pH over 9.0. Around 2.58 and 1.24 Kg of precipitates could be recovered from 1 m 3 hydrolyzed and fresh urine, respectively, and the precipitated solids contain 8.1-19.0% of P, 10.3-15.2% of Ca, 3.7-5.0% of Mg and 0.1-3.5% of ammonium nitrogen. Satisfactory P removal performance was also achieved in a continuous flow precipitation reactor with a hydraulic retention time of 3-6 h. RO brine could be considered as urinal and toilet flush water despite of a marginally higher precipitation tendency than tap water. This study provides a widely available, low - cost and efficient precipitant for P recovery in urban areas, which will make P recovery from urine more economically attractive. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impact of Fe(III)-OM complexes and Fe(III) polymerization on SOM pools reactivity under different land uses

NASA Astrophysics Data System (ADS)

Giannetta, B.; Plaza, C.; Zaccone, C.; Siebecker, M. G.; Rovira, P.; Vischetti, C.; Sparks, D. L.

2017-12-01

Soil organic matter (SOM) protection and long-term accumulation are controlled by adsorption to mineral surfaces in different ways, depending on its molecular structure and pedo-climatic conditions. Iron (Fe) oxides are known to be key regulators of the soil carbon (C) cycle, and Fe speciation in soils is highly dependent on environmental conditions and chemical interactions with SOM. However, the molecular structure and hydrolysis of Fe species formed in association with SOM is still poorly described. We hypothesize the existence of two pools of Fe which interact with SOM: mononuclear Fe(III)-SOM complexes and precipitated Fe(III) hydroxides. To verify our hypothesis, we investigated the interactions between Fe(III) and physically isolated soil fractions by means of batch experiments at pH 7. Specifically, we examined the fine silt plus clay (FSi+C) fraction, obtained by ultrasonic dispersion and wet sieving. The soil samples spanned several land uses, including coniferous forest (CFS), grassland (GS), technosols (TS) and agricultural (AS) soils. Solid phase products and supernatants were analyzed for C and Fe content. X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis were also performed. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to assess the main C functional groups involved in C complexation and desorption experiments. Preliminary linear combination fitting (LCF) of Fe K-edge extended X-ray absorption fine structure (EXAFS) spectra suggested the formation of ferrihydrite-like polymeric Fe(III) oxides in reacted CFS and GS samples, with higher C and Fe concentration. Conversely, mononuclear Fe(III) OM complexes dominated the speciation for TS and AS samples, characterized by lower C and Fe concentration, inhibiting the hydrolysis and polymerization of Fe (III). This approach will help revealing the mechanisms by which SOM pools can control Fe(III) speciation, and will elucidate how both Fe(III)-OM complexes and Fe(III) polymerization can affect SOM reactivity and, consequently, its mean residence time in different ecosystems.

Effect of Various Retrogression Regimes on Aging Behavior and Precipitates Characterization of a High Zn-Containing Al-Zn-Mg-Cu Alloy

NASA Astrophysics Data System (ADS)

Wen, Kai; Xiong, Baiqing; Zhang, Yongan; Li, Zhihui; Li, Xiwu; Huang, Shuhui; Yan, Lizhen; Yan, Hongwei; Liu, Hongwei

2018-03-01

In the present work, the influence of various retrogression treatments on hardness, electrical conductivity and mechanical properties of a high Zn-containing Al-Zn-Mg-Cu alloy is investigated and several retrogression regimes subjected to a same strength level are proposed. The precipitates are qualitatively investigated by means of transmission electron microscopy (TEM) and high-resolution transmission electron microscopy techniques. Based on the matrix precipitate observations, the distributions of precipitate size and nearest inter-precipitate distance are extracted from bright-field TEM images projected along <110>Al orientation with the aid of an imaging analysis and an arithmetic method. The results show that GP zones and η' precipitates are the major precipitates and the precipitate size and its distribution range continuously enlarge with the retrogression regime expands to an extent of high temperature. The nearest inter-precipitate distance ranges obtained are quite the same and the average distance of nearest inter-precipitates show a slight increase. The influence of precipitates on mechanical properties is discussed through the interaction relationship between precipitates and dislocations.

Effect of Various Retrogression Regimes on Aging Behavior and Precipitates Characterization of a High Zn-Containing Al-Zn-Mg-Cu Alloy

NASA Astrophysics Data System (ADS)

Wen, Kai; Xiong, Baiqing; Zhang, Yongan; Li, Zhihui; Li, Xiwu; Huang, Shuhui; Yan, Lizhen; Yan, Hongwei; Liu, Hongwei

2018-05-01

In the present work, the influence of various retrogression treatments on hardness, electrical conductivity and mechanical properties of a high Zn-containing Al-Zn-Mg-Cu alloy is investigated and several retrogression regimes subjected to a same strength level are proposed. The precipitates are qualitatively investigated by means of transmission electron microscopy (TEM) and high-resolution transmission electron microscopy techniques. Based on the matrix precipitate observations, the distributions of precipitate size and nearest inter-precipitate distance are extracted from bright-field TEM images projected along <110>Al orientation with the aid of an imaging analysis and an arithmetic method. The results show that GP zones and η' precipitates are the major precipitates and the precipitate size and its distribution range continuously enlarge with the retrogression regime expands to an extent of high temperature. The nearest inter-precipitate distance ranges obtained are quite the same and the average distance of nearest inter-precipitates show a slight increase. The influence of precipitates on mechanical properties is discussed through the interaction relationship between precipitates and dislocations.

The evolution of Carbon isotopes in calcite in the presence of cyanobacteria

NASA Astrophysics Data System (ADS)

Grimm, Christian; Mavromatis, Vasileios; Pokrovsky, Oleg S.; Oelkers, Eric H.

2016-04-01

Stable isotopic compositions in carbonates are widely used as indicators of environmental conditions prevailing during mineral formation. This reconstruction is substantially based on the assumption that there is no change in the mineral composition over geological time. However, recent experimental studies have shown that carbon and magnesium isotopes in hydrous Mg-carbonates undergo continuous re-equilibration with the ambient solution even after mineral precipitation stopped ([1] and [2], respectively). To verify whether this holds true for anhydrous Ca-bearing carbonates which readily form at earth's surface environments, a series of batch system calcite precipitation experiments were performed in the presence of actively growing cyanobacteria Synechococcus sp. The bacteria were grown at ambient temperature in a BG11 culture medium (SIGMA C3061) and continuous stirring, air-bubbling and illumination. Calcite precipitation was initiated by the addition of 8.5mM CaCl2 and 0-50 mM NaHCO3 or NaHCO3-Na2CO3 mixtures. The presence of cyanobacteria is on one hand promoting CaCO3 formation due to increasing pH resulting from photosynthesis. On the other hand, actively growing cyanobacteria drastically change carbon isotope signature of the aqueous fluid phase by preferably incorporating the lighter 12C isotope into biomass [1]. This study explores the effect of continuously changing carbon isotope compositions in dissolved inorganic carbon (DIC) on precipitated calcite which is in chemical equilibrium with the ambient fluid phase. [1] Mavromatis et al. (2015). The continuous re-equilibration of carbon isotope compositions of hydrous Mg-carbonates in the presence of cyanobacteria. Chem. Geol. 404, 41-51 [2] Mavromatis et al. (2012). Magnesium isotope fractionation during hydrous magnesium carbonate precipitation with and without cyanobacteria. Geochim. Cosmochim. Acta 76, 161-174

Trends in snowfall versus rainfall in the Western United States--Revisited

NASA Astrophysics Data System (ADS)

Dettinger, M. D.; Knowles, N.; Cayan, D. R.

2015-12-01

Knowles et al. (J. Climate, 2006) documented long-term (1949-2004) trends in precipitation form, with a smaller fraction of precipitation falling, in recent decades, on days with reported snow compared to days when no snow was reported (and when precipitation was presumably rain). This precipitation-amount-corrected trend was found at three-quarters of 261 cooperative weather stations across the region. The trends correlated with corresponding trends towards warmer winter air temperatures at the weather stations involved. An update of those analyses through the more recent period indicates that the overall swing towards less precipitation fraction occurring on snowy days has continued through the intervening years, with 21st Century rain/snow fractions remaining significantly higher than historical norms at most stations. The same data have also been used to develop site-specific statistical relations between precipitation form (snowy-day precipitation vs purely rainy day) and air temperatures by logistical regressions at over 200 stations across the West, to determine whether the general temperature trends mentioned above have, in fact, been large enough to explain the trending precipitation forms. That is, were the warming trends detected across the West large enough to actually raise temperatures above the local snow-rain thresholds at most stations? The regression relations show that the temperature at which half of the wet days have been snowy historically varies, from station to station, across a range from -2ºC to +4ºC. Thus at some stations winter storm temperatures would have to rise above about -2ºC to markedly impact precipitation forms, while at other stations, temperature had to rise above +4ºC. Nonetheless, observed temperature trends since 1950 have been sufficient to explain the observed regional precipitation-form trends. The fitted precipitation form-temperature relations also provide a basis for estimating precipitation forms in hydrological models and in climate-change projections across the region, allowing—for example—more geographically informed projections of precipitation-form changes under future climates. On the whole, though, the expected relations between warming trends and precipitation-form trends found by Knowles et al. (2006) continue to hold.

Factors controlling stream water nitrate and phosphor loads during precipitation events

NASA Astrophysics Data System (ADS)

Rozemeijer, J. C.; van der Velde, Y.; van Geer, F. G.; de Rooij, G. H.; Broers, H. P.; Bierkens, M. F. P.

2009-04-01

Pollution of surface waters in densely populated areas with intensive land use is a serious threat to their ecological, industrial and recreational utilization. European and national manure policies and several regional and local pilot projects aim at reducing pollution loads to surface waters. For the evaluation of measures, water authorities and environmental research institutes are putting a lot of effort into monitoring surface water quality. Fro regional surface water quality monitoring, the measurement locations are usually situated in the downstream part of the catchment to represent a larger area. The monitoring frequency is usually low (e.g. monthly), due to the high costs for sampling and analysis. As a consequence, human induced trends in nutrient loads and concentrations in these monitoring data are often concealed by the large variability of surface water quality caused by meteorological variations. Because natural surface water quality variability is poorly understood, large uncertainties occur in the estimates of (trends in) nutrient loads or average concentrations. This study aims at uncertainty reduction in the estimates of mean concentrations and loads of N and P from regional monitoring data. For this purpose, we related continuous N and P records of stream water to variations in precipitation, discharge, groundwater level and tube drain discharge. A specially designed multi scale experimental setup was installed in an agricultural lowland catchment in The Netherlands. At the catchment outlet, continuous measurements of water quality and discharge were performed from July 2007-January 2009. At an experimental field within the catchment continuous measurements of precipitation, groundwater levels and tube drain discharges were collected. 20 significant rainfall events with a variety of antecedent conditions, durations and intensities were selected for analysis. Singular and multiple regression analysis was used to identify relations between the continuous N and P records and characteristics of the dynamics of discharge, precipitation, groundwater level and tube drain discharge. From this study, we conclude that generally available and easy to measure explanatory data (such as continuous records of discharge, precipitation and groundwater level) can reduce uncertainty in estimations of N and P loads and mean concentrations. However, for capturing the observed short load pulses of P, continuous or discharge proportional sampling is needed.

Sustainable Hypersaline Microbial Fuel Cells: Inexpensive Recyclable Polymer Supports for Carbon Nanotube Conductive Paint Anodes.

PubMed

Grattieri, Matteo; Shivel, Nelson D; Sifat, Iram; Bestetti, Massimiliano; Minteer, Shelley D

2017-05-09

Microbial fuel cells are an emerging technology for wastewater treatment, but to be commercially viable and sustainable, the electrode materials must be inexpensive, recyclable, and reliable. In this study, recyclable polymeric supports were explored for the development of anode electrodes to be applied in single-chamber microbial fuel cells operated in field under hypersaline conditions. The support was covered with a carbon nanotube (CNT) based conductive paint, and biofilms were able to colonize the electrodes. The single-chamber microbial fuel cells with Pt-free cathodes delivered a reproducible power output after 15 days of operation to achieve 12±1 mW m -2 at a current density of 69±7 mA m -2 . The decrease of the performance in long-term experiments was mostly related to inorganic precipitates on the cathode electrode and did not affect the performance of the anode, as shown by experiments in which the cathode was replaced and the fuel cell performance was regenerated. The results of these studies show the feasibility of polymeric supports coated with CNT-based paint for microbial fuel cell applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of hollow spherical calcium phosphate nanoparticles using polymeric nanotemplates

NASA Astrophysics Data System (ADS)

Tjandra, Wiliana; Ravi, Palaniswamy; Yao, Jia; Tam, Kam C.

2006-12-01

Poly(methylmethacrylate)-block-poly(methacrylic acid) (PMMA-b-PMAA) copolymer was synthesized by an atom transfer radical polymerization (ATRP) technique. The block copolymer was employed as a template for the controlled precipitation of calcium phosphate from aqueous solution at different pH values. A Ca2+ ion selective electrode was used to study the interactions between Ca2+ ions and the polymer, which indicated a possible weak interaction between Ca2+ and un-ionized MAA segments at pH~4.0 in addition to electrostatic interaction between Ca2+ and ionized MAA segments at higher pH. An interesting structure representing that of a superstructure consisting of hybrid nano-filaments was observed by the transmission electron microscope at pH~4.0. The filaments originated from a core of similar size to primary polymer aggregates, suggesting that cooperative interactions at a local level between dissolving calcium phosphate clusters and disassembling polymer segments are responsible for the secondary growth process. A hollow spherical morphology was obtained at pH~7.0 and 9.0. Such calcium phosphate/polymer monohybrids with complex morphologies are interesting and might be useful as novel drug delivery carriers, ceramics precursors, reinforcing fillers or biomedical implants.

Antibiofilm effect of poly(vinyl alcohol-co-ethylene) (PVA-co-PE) halamine film against Listeria innocua and Escherichia coli O157:H7.

PubMed

Cossu, Andrea; Si, Yang; Sun, Gang; Nitin, Nitin

2017-08-11

Bacterial biofilm formation is linked to several infections and foodborne disease outbreaks. To address this challenge, there is an unmet need to develop rechargeable antimicrobial materials that can provide continuous sanitation of contact surfaces especially in the food industry. This study was aimed at evaluating a novel rechargeable antimicrobial polymer formed using PVA-co-PE with halamine functionality to prevent biofilm formation with repeated exposure to high loads of bacteria and organic content and also aid in inactivation of pre-formed biofilms upon contact with this novel material. Antibiofilm activity of this rechargeable antimicrobial material was evaluated using a combination of fluorescence and scanning electron microscopies and biofilm metabolic activity analyses. The results based on imaging and metabolic activity measurements demonstrated that halamine functionalized polymer films significantly reduced L. innocua and E. coli O157:H7 biofilms formation. This novel polymeric material maintained its antibiofilm activity with repeated cycles of extended exposure to high levels of bacterial load. These polymeric films were recharged using bleach and cleaned using mechanical sonication after each cycle of extended incubation with bacteria. Halamine functionalized polymeric material also exhibited significant antibacterial activity against pre-formed biofilms on a model surface. In summary, results demonstrate potential of this antimicrobial material to provide continuous sanitation surfaces and applications for inactivating pre-formed biofilms without extensive use of resources including water and heat. This polymeric material may be used as a replacement for existing polymeric materials or used as a coating on diverse materials. IMPORTANCE Conventional sanitizers can have limited efficacy in inactivating biofilms in areas with limited accessibility and buildup of organic biomass. Furthermore, none of the current approaches provide continuous sanitation of surfaces. There is a significant unmet need to develop and validate materials that can prevent biofilm formation as well as inactivate pre-formed biofilms. In this study the efficacy of a copolymer film containing N-halamine against the biofilms of L. innocua and E. coli O157:H7 was evaluated. The polymer film showed a strong biofilm inhibitory activity against pre-grown biofilm or prevented the growth of a new biofilm. The polymer film also maintained its anti-biofilm activity revealed after multiple cycles of exposure to high titer of bacterial load with recharging of the polymer film using bleach at intermediate steps between the cycles. Overall, the results demonstrate potential of a novel antimicrobial material to inhibit and treat biofilms in food industry applications. Copyright © 2017 American Society for Microbiology.

Antibiofilm Effect of Poly(Vinyl Alcohol-co-Ethylene) Halamine Film against Listeria innocua and Escherichia coli O157:H7

PubMed Central

Cossu, Andrea; Si, Yang; Sun, Gang

2017-01-01

ABSTRACT Bacterial biofilm formation is linked to several infections and foodborne disease outbreaks. To address this challenge, there is an unmet need to develop rechargeable antimicrobial materials that can provide continuous sanitation of contact surfaces, especially in the food industry. This study was aimed at evaluating a novel rechargeable antimicrobial polymer formed using poly(vinyl alcohol-co-ethylene) (PVA-co-PE) with halamine functionality to prevent biofilm formation with repeated exposure to high loads of bacteria and organic content and also to aid in inactivation of preformed biofilms upon contact with this novel material. The antibiofilm activity of this rechargeable antimicrobial material was evaluated using a combination of fluorescence and scanning electron microscopy techniques and biofilm metabolic activity analyses. The results determined on the basis of imaging and metabolic activity measurements demonstrated that halamine-functionalized polymer films significantly reduced Listeria innocua and Escherichia coli O157:H7 biofilm formation. This novel polymeric material maintained its antibiofilm activity with repeated cycles of extended exposure to high levels of bacterial load. These polymeric films were recharged using bleach and cleaned using mechanical sonication after each cycle of extended incubation with bacteria. Halamine-functionalized polymeric material also exhibited significant antibacterial activity against preformed biofilms on a model surface. In summary, our results demonstrate the potential of this antimicrobial material to provide continuous sanitation of surfaces and applications for inactivating preformed biofilms without extensive use of resources, including water and heat. This polymeric material may be used as a replacement for existing polymeric materials or as a coating on diverse materials. IMPORTANCE Conventional sanitizers can have limited efficacy in inactivating biofilms in areas with limited accessibility and buildup of organic biomass. Furthermore, none of the current approaches provide continuous sanitation of surfaces. There is a significant unmet need to develop and validate materials that can prevent biofilm formation as well as inactivate preformed biofilms. In this study, the efficacy of a copolymer film containing N-halamine against biofilms of L. innocua and E. coli O157:H7 was evaluated. The polymer film showed strong inhibitory activity against pregrown biofilm or prevented the growth of a new biofilm. The polymer film also maintained its antibiofilm activity after multiple cycles of exposure to high titers of bacterial load with recharging of the polymer film using bleach at intermediate steps between the cycles. Overall, the results demonstrate the potential of a novel antimicrobial material to inhibit and treat biofilms in food industry applications. PMID:28802271

Impacts of global warming of 1.5 °C and 2.0 °C on precipitation patterns in China by regional climate model (COSMO-CLM)

NASA Astrophysics Data System (ADS)

Sun, Hemin; Wang, Anqian; Zhai, Jianqing; Huang, Jinlong; Wang, Yanjun; Wen, Shanshan; Zeng, Xiaofan; Su, Buda

2018-05-01

Regional precipitation patterns may change in a warmer climate, thereby increasing flood and drought risks. In this paper, annual, annual maximum, intense, heavy, moderate, light, and trace precipitation are employed as indicators to assess changes in precipitation patterns under two scenarios in which the global mean temperature increases by 1.5 °C and 2.0 °C relative to pre-industrial levels using the regional climate model COSMO-CLM (CCLM). The results show that annual precipitation in China will be approximately 2.5% higher under 1.5 °C warming relative to the present-day baseline (1980-2009), although it will decrease by approximately 4.0% under an additional 0.5 °C increase in global mean temperature. This trend is spatially consistent for regions with annual precipitation of 400-800 mm, which has experienced a drying trend during the past half century; thus, limiting global warming to 1.5 °C may mitigate these drying conditions. The annual maximum precipitation continues to increase from present day levels to the 2.0 °C warming scenario. Relative to the baseline period, the frequency of trace and light precipitation days exhibits a negative trend, while that of moderate, heavy, and intense precipitation days has a positive trend under the 1.5 °C warming scenario. For the 2.0 °C warming world, the frequency of days is projected to decrease for all precipitation categories, although the intensity of intense precipitation increases. Spatially, a decrease in the number of precipitation days is expected to continue in central and northern China, where a drying trend has persisted over the past half century. Southeastern China, which already suffers greatly from flooding, is expected to face more heavy and intense precipitation with an additional 0.5 °C increase in global mean temperature. Meanwhile, the intensity of intense precipitation is expected to increase in northern China, and the contribution of light and moderate precipitation to the annual precipitation is expected to decrease in southeastern China. Therefore, flood risk in northern China and drought risk in southern China should draw more attention for a global air temperature increase from 1.5 °C to 2.0 °C.

Wash Solution Bath Life Extension for the Space Shuttle Rocket Motor Aqueous Cleaning System

NASA Technical Reports Server (NTRS)

Saunders, Chad; Evans, Kurt; Sagers, Neil

1999-01-01

A spray-in-air aqueous cleaning system, which replaced 1,1,1 trichloroethane (TCA) vapor degreasing, is used for critical cleaning of Space Shuttle Redesigned Solid Rocket Motor (RSRM) metal parts. Small-scale testing demonstrated that the alkaline-based wash solution possesses adequate soil loading and cleaning properties. However, full-scale testing exhibited unexpected depletion of some primary components of the wash solution. Specifically, there was a significant decrease in the concentration of sodium metasilicate which forced change-out of the wash solution after eight days. Extension of wash solution bath life was necessary to ease the burden of frequent change-out on manufacturing. A laboratory study supports a depletion mechanism that is initiated by the hydrolysis of sodium tripolyphosphate (STPP) lowering the pH of the solution. The decrease in pH causes polymerization and subsequent precipitation of sodium metasilicate (SM). Further investigation showed that maintaining the pH was the key to preventing the precipitation of the sodium metasilicate. Implementation to the full scale operation demonstrated that periodic additions of potassium hydroxide (KOH) extended the useful bath life to more than four months.

Cryogelation of molecularly imprinted nanoparticles: a macroporous structure as affinity chromatography column for removal of β-blockers from complex samples.

PubMed

Hajizadeh, Solmaz; Xu, Changgang; Kirsebom, Harald; Ye, Lei; Mattiasson, Bo

2013-01-25

In this work, a new macroporous molecularly imprinted cryogel (MIP composite cryogel) was synthesized by glutaraldehyde cross-linking reaction of poly(vinyl alcohol) (PVA) particles and amino-modified molecularly imprinted core-shell nanoparticles. The MIP core-shell nanoparticles were prepared using propranolol as a template by one-pot precipitation polymerization with sequential monomer addition. The characteristics of the MIP composite cryogel were studied by scanning electron microscopy (SEM) and texture analyzer. The macroporous structure of the composite (with the pore size varying from a few micrometers to 100 μm) enabled high mass transfer of particulate-containing fluids. In a solid phase extraction (SPE) process, the efficiency and selectivity of the MIP composite cryogel were investigated, where the cryogel was used as an affinity matrix to remove propranolol from aqueous solution as well as from complex plasma sample without prior protein precipitation. The MIP composite cryogel maintained high selectivity and stability and could be used repeatedly after regeneration. Copyright © 2012 Elsevier B.V. All rights reserved.

Exploring biotic vs. abiotic controls on syngenetic carbonate and clay mineral precipitation

NASA Astrophysics Data System (ADS)

Nascimento, Gabriela S.; McKenzie, Judith A.; Martinez Ruiz, Francisca; Bontognali, Tomaso R. R.; Vasconcelos, Crisogono

2016-04-01

A possible syngenetic relationship between carbonate and clay mineral precipitation has been reported for sedimentary rocks deposited in both lacustrine and marine sedimentary environments throughout the geological record. In particular, the mineral dolomite is often found associated with Mg-rich clays, such as stevensite. It is notable that this carbonate/clay association has been recorded in numerous samples taken from modern dolomite precipitating environments; for example, the Coorong lakes, South Australia, coastal sabkhas, Abu Dhabi, UAE and coastal hypersaline lagoons (Lagoa Vermelha and Brejo do Espinho) east of Rio de Janeiro, Brazil. An HRTEM study of samples from these three locations indicates a possible physical/chemical association between the Ca-dolomite and Mg-rich clays, demonstrating a probable co-precipitation. To test this hypothesis, we have conducted a series of biotic and abiotic laboratory experiments. If this syngenesis actually occurs in nature, what, if any, are the biogeochemical processes controlling these precipitation reactions? Our experiments were designed to determine the extent of the biotic versus abiotic component influencing the mineral precipitation and, in the case of a biotic influence, to understand the mechanism through which microorganisms might mediate the formation of clay minerals. The experiments were carried out in the Geomicrobiology Laboratory of ETH Zürich using cultures of living microbes and artificial organic compounds that simulate functional groups present in natural biofilms formed under both aerobic and anaerobic conditions. In addition, pure inorganic experiments were designed to understand possible physico-chemical conditions for diagenetic processes that could induce dissolution of Mg-carbonates and precipitation of Mg-rich clays. Our results show a remarkable biotic influence during the formation of clay minerals. Specifically, extracellular polymeric substances (EPS), released by microbes in their surrounding environments, appear to play a key role in the mineralization process, by binding and concentrating silica and by stabilizing cations in specific co-ordination positions. This step may be essential for the initial nucleation of the clay mineral. Also, the conditions of the biotic experiments probably helped to lower kinetic barriers and promote the reactions, which apparently remained kinetically constrained in the abiotic experiments. These initial experimental results provide information to understand the syngenetic relationship between dolomite and Mg-rich clay precipitation and furnish additional information to help reconstruct paleoenviromental conditions for similar deposits found in the geological record.

Fluid Dynamic Characterization of a Polymeric Heart Valve Prototype (Poli-Valve) tested under Continuous and Pulsatile Flow Conditions

PubMed Central

De Gaetano, Francesco; Serrani, Marta; Bagnoli, Paola; Brubert, Jacob; Stasiak, Joanna; Moggridge, Geoff D.; Costantino, Maria Laura

2016-01-01

Introduction Only mechanical and biological heart valve prostheses are currently commercially available. The former show longer durability but require anticoagulant therapy, the latter display better fluid dynamic behaviour but do not have adequate durability. New Polymeric Heart Valves (PHVs) could potentially combine the haemodynamic properties of biological valves with the durability of mechanical valves. This work presents a hydrodynamic evaluation of two groups of newly developed supra-annular tri-leaflet prosthetic heart valves made from styrenic block copolymers (SBC): Poli-Valves. Methods Two types of Poli-Valves made of SBC differing in polystyrene fraction content were tested under continuous and pulsatile flow conditions as prescribed by ISO 5840 Standard. An ad - hoc designed pulse duplicator allowed the valve prototypes to be tested at different flow rates and frequencies. Pressure and flow were recorded; pressure drops, effective orifice area (EOA), and regurgitant volume were computed to assess the valve’s behaviour. Results Both types Poli-Valves met the minimum requirements in terms of regurgitation and EOA as specified by ISO 5840 Standard. Results were compared with five mechanical heart valves (MHVs) and five tissue heart valves (THVs), currently available on the market. Conclusion Based on these results, polymeric heart valves based on styrenic block copolymers, as Poli-Valves are, can be considered as promising alternative for heart valve replacement in near future. PMID:26689146

Progressive biogeochemical transformation of placer gold particles drives compositional changes in associated biofilm communities.

PubMed

Rea, Maria Angelica; Standish, Christopher D; Shuster, Jeremiah; Bissett, Andrew; Reith, Frank

2018-05-03

Biofilms on placer gold (Au)-particle surfaces drive Au solubilization and re-concentration thereby progressively transforming the particles. Gold solubilization induces Au-toxicity; however, Au-detoxifying community members ameliorates Au-toxicity by precipitating soluble Au to metallic Au. We hypothesize that Au-dissolution and re-concentration (precipitation) places selective pressures on associated microbial communities, leading to compositional changes and subsequent Au-particle transformation. We analyzed Au-particles from eight United Kingdom sites using next generation sequencing, electron microscopy and micro-analyses. Gold particles contained biofilms composed of prokaryotic cells and extracellular polymeric substances intermixed with (bio)minerals. Across all sites communities were dominated by Proteobacteria (689, 97% Operational Taxonomic Units, 59.3% of total reads), with β-Proteobacteria being the most abundant. A wide range of Au-morphotypes including nanoparticles, micro-crystals, sheet-like Au and secondary rims, indicated that dissolution and re-precipitation occurred, and from this transformation indices were calculated. Multivariate statistical analyses showed a significant relationship between the extent of Au-particle transformation and biofilm community composition, with putative metal-resistant Au-cycling taxa linked to progressive Au transformation. These included the genera Pseudomonas, Leptothrix and Acinetobacter. Additionally, putative exoelectrogenic genera Rhodoferax and Geobacter were highly abundant. In conclusion, biogeochemical Au-cycling and Au-particle transformation occurred at all sites and exerted a strong influence on biofilm community composition.

Modulation of calcium carbonate precipitation by exopolysaccharide in Bacillus sp. JH7.

PubMed

Kim, Hyun Jung; Shin, Bora; Lee, Yun Suk; Park, Woojun

2017-08-01

Extracellular polymeric substance (EPS) is proposed to facilitate calcium ion supersaturation through its nucleation effect during the microbially induced calcium carbonate precipitation (MICP) process. However, the supersaturation effect of Ca 2+ via EPS in MICP has not been clearly demonstrated. Enhanced exopolysaccharide production of the alkali- and halotolerant MICP-capable bacteria, Bacillus sp. JH7, was achieved through glycerol addition. This was demonstrated by measuring cellular precipitation and Congo red binding. Interestingly, field emission scanning electron microscopy and energy-dispersive X-ray spectrometry analysis demonstrated that there was no MICP under glycerol-amended conditions. Although glycerol promoted exopolysaccharide capture of Ca 2+ ions, Ca 2+ embedded onto EPS did not participate in MICP formation. The pH was reduced in glycerol-added media, which led us to analyze high acetate production under our test conditions. Purified glycerol-induced exopolysaccharide showed a higher capacity of Ca 2+ capture than the control. Quantitative RT-PCR analysis showed that three genes involved in exopolysaccharide production were highly upregulated by glycerol. The amounts of three detected monosaccharides (arabinose, glucose, and mannose) were altered by glycerol. Cell hydrophobicity measurements indicated that glycerol could confer more hydrophilic characteristics to cells, which might enhance Ca 2+ binding onto EPS. Unexpectedly, our data demonstrated, for the first time, that glycerol could promote exopolysaccharide and acetate production under our test condition, which could inhibit MICP by reducing the availability of free Ca 2+ .

Model compounds of iron gall inks - a Mössbauer study

NASA Astrophysics Data System (ADS)

Lerf, A.; Wagner, F. E.

2016-12-01

Ferrogallic inks were used for at least two millennia before they became obsolete in the 20th century. The chemistry of such inks is, however, still largely unclear. Today it is of particular interest for the conservation of old manuscripts. 57Fe Mössbauer spectra of the ink on historical documents showed the presence of Fe(II) oxalate and of Fe(III) sites presumably representing iron oxihydroxides. To obtain more information on the behaviour of ink on paper we have performed Mössbauer studies at 300 and 4.2 K on iron gall inks prepared from FeSO4ṡ7H2O and tannin. These inks were either written on paper or isolated as a precipitate by centrifugation. In the dried precipitate there is still a strong contribution of the FeSO4ṡ7H2O which is absent in the same ink written on paper, for which a broad ferrous component with a quadrupole splitting (QS) of about 2.5 mm/s was found. The dominant Fe(III) site present in all inks on paper with QS ≈ 0.82 mm/s is not Fe(III) gallate and different from the precipitates. We propose that nanoparticulate oxidic clusters or molecular composites covered by a shell of polymerized oxidation products of the phenols are formed on the paper.

Maintenance of the secondary structure of horse cytochrome c during the conversion process of monomers to oligomers by addition of ethanol.

PubMed

Hirota, Shun; Ueda, Mariko; Hayashi, Yugo; Nagao, Satoshi; Kamikubo, Hironari; Kataoka, Mikio

2012-12-01

We have previously shown that polymerization of cytochrome c (cyt c) occurs by successively domain swapping its C-terminal α-helix in the presence of ethanol. However, the factors that govern the conversion process of monomers to domain-swapped oligomers remain unknown. We found that oligomeric cyt c is produced in the presence of ethanol and the oligomers precipitate due to low solubility. The optical absorption spectra revealed that in the presence of 30-40% ethanol, the Met-heme coordination in cyt c is dissociated. However, according to circular dichroism and small-angle X-ray scattering measurements, the α-helical structure of cyt c is maintained in solution with a little perturbation and the radius of gyration increases slightly but without dissociation of the C-terminal α-helix from the rest of the protein by the addition of ethanol. Solid-state nuclear magnetic resonance spectra showed that oligomeric cyt c in the precipitate also retains most of its α-helical structure. In the transmission electron microscopic image of the precipitate obtained by the addition of ethanol to cyt c, spherical particles with diameters of about 3 nm were detected. These results indicate that oligomeric cyt c forms through a state with the Met80 region locally unfolded, while maintaining the secondary structure, possibly an open monomer.

Calcite biomineralization by bacterial isolates from the recently discovered pristine karstic herrenberg cave.

PubMed

Rusznyák, Anna; Akob, Denise M; Nietzsche, Sándor; Eusterhues, Karin; Totsche, Kai Uwe; Neu, Thomas R; Frosch, Torsten; Popp, Jürgen; Keiner, Robert; Geletneky, Jörn; Katzschmann, Lutz; Schulze, Ernst-Detlef; Küsel, Kirsten

2012-02-01

Karstic caves represent one of the most important subterranean carbon storages on Earth and provide windows into the subsurface. The recent discovery of the Herrenberg Cave, Germany, gave us the opportunity to investigate the diversity and potential role of bacteria in carbonate mineral formation. Calcite was the only mineral observed by Raman spectroscopy to precipitate as stalactites from seepage water. Bacterial cells were found on the surface and interior of stalactites by confocal laser scanning microscopy. Proteobacteria dominated the microbial communities inhabiting stalactites, representing more than 70% of total 16S rRNA gene clones. Proteobacteria formed 22 to 34% of the detected communities in fluvial sediments, and a large fraction of these bacteria were also metabolically active. A total of 9 isolates, belonging to the genera Arthrobacter, Flavobacterium, Pseudomonas, Rhodococcus, Serratia, and Stenotrophomonas, grew on alkaline carbonate-precipitating medium. Two cultures with the most intense precipitate formation, Arthrobacter sulfonivorans and Rhodococcus globerulus, grew as aggregates, produced extracellular polymeric substances (EPS), and formed mixtures of calcite, vaterite, and monohydrocalcite. R. globerulus formed idiomorphous crystals with rhombohedral morphology, whereas A. sulfonivorans formed xenomorphous globular crystals, evidence for taxon-specific crystal morphologies. The results of this study highlighted the importance of combining various techniques in order to understand the geomicrobiology of karstic caves, but further studies are needed to determine whether the mineralogical biosignatures found in nutrient-rich media can also be found in oligotrophic caves.

Patterns of methane-related carbonate formation in the black sea

NASA Astrophysics Data System (ADS)

Reitner, J.; Peckmann, J.; Reimer, A.; Thiel, V.

2003-04-01

Methane seeps on the northwestern Black Sea shelf were investigated during the GHOSTDABS expedition in 2001. Seep areas close to the Dniepr Canyon are sites of intense carbonate formation. In anoxic waters, at depths between 200 and 400 m, we found three different modes of seepage-induced carbonate precipitation. The most spectacular type comprises up to 4 m high Ca-carbonate towers flushed by methane gas (type 1). These buildups are constructed of cm to dm-scale calcified hollow spheres which are made and later surrounded by microbial mats. At the base of these microbial mats the spheres are stabilized by a continuous rim of carbonate cement. At a later stage, the fragile spheres are entirely cemented by fibrous aragonite and Mg calcite. The towers harbour a highly diverse microbial community, which are, at least in part, based on the anaerobic oxidation of methane (AOM). A second variety of methane-derived carbonates was observed in the vicinity of the large carbonate towers and consists of lenticular concretions growing within the sediment (type 2). The concretions are up to several decimeters in size and consist of Mg calcite crystal aggregates that progressively fuse together, thereby incorporating ambient sedimentary matter. Associated biofilms surrounding the concretions clearly show AOM related populations but exhibit a different community structure and a smaller microbial diversity than type 1 carbonates. Type 3 encompasses background sediments irregularly cemented with microcrystalline Mg-calcite (automicrite). These precipitates may show very thin internal biofilms, and are further characterized by small, “birds eye”-type cavities. These cavities appear to arise from ascending gas bubbles, and are partly cemented by granular to blocky Mg calcites. The internal surfaces are frequently coated by thin biofilms resembling those found associated with type 2 concretions. All studied Ca-carbonates have low d13C values (-25 to -35 permille vs. PDB) and show a strong autofluorescence due to inclusions of intracrystalline organic matter. We assume that an increase in carbonate alkalinity due to AOM triggers carbonate precipitation on organic matrices provided by extracellular polymeric substances (EPS). Electron microscopic evidence also suggests that the internal alignment of sugar-rich EPS molecules may control the spatial arrangement of the calcification fabrics observed. EPS remains were extracted from the methane carbonates and the function was tested by in vitro calcification/inhibition experiments.

Polymer recycling: potential application of radiation technology

NASA Astrophysics Data System (ADS)

Burillo, Guillermina; Clough, Roger L.; Czvikovszky, Tibor; Guven, Olgun; Le Moel, Alain; Liu, Weiwei; Singh, Ajit; Yang, Jingtian; Zaharescu, Traian

2002-04-01

Management of solid waste is an important problem, which is becoming progressively worse as a byproduct of continuing economic growth and development. Polymeric materials (plastics and rubbers) comprise a steadily increasing proportion of the municipal and industrial waste going into landfill. Development of technologies for reducing polymeric waste, which are acceptable from the environmental standpoint, and which are cost-effective, has proven to be a difficult challenge due to complexities inherent in the reuse of polymers. Establishing optimal processes for the reuse/recycling of polymeric materials thus remains a worldwide challenge as we enter the new century. Due to the ability of ionizing radiation to alter the structure and properties of bulk polymeric materials, and the fact that it is applicable to essentially all polymer types, irradiation holds promise for impacting the polymer waste problem. The three main possibilities for use of radiation in this application are: (1) enhancing the mechanical properties and performance of recovered materials or material blends, principally through crosslinking, or through surface modification of different phases being combined; (2) treatment causing or enhancing the decomposition of polymers, particularly through chain scission, leading to recovery of either low molecular weight mixtures, or powders, for use as chemical feedstocks or additives; (3) production of advanced polymeric materials designed for environmental compatibility. This paper provides an overview of the polymer recycling problem, describes the major technological obstacles to the implementation of recycling technologies, and outlines some of the approaches being taken. A review of radiation-based recycling research is then provided, followed by a discussion of future directions where irradiation may be relevant to the problems currently inhibiting the widespread recycling of polymeric materials.

Ozonation of Canadian Athabasca asphaltene

NASA Astrophysics Data System (ADS)

Cha, Zhixiong

Application of ozonation in the petrochemical industry for heavy hydrocarbon upgrading has not been sufficiently explored. Among heavy hydrocarbons, asphaltenes are the heaviest and the most difficult fractions for analysis and treatment. Therefore, ozonation of asphaltenes presents an interesting application in the petrochemical industry. Commercial application of ozonation in the petrochemical industry has three obstacles: availability of an ozone-resistant and environmentally friendly solvent, the precipitation of ozonation intermediates during reaction, and recovery of the solvent and separation of the ozonation products. Preliminary ozonation of Athabasca oil sands asphaltene in nonparticipating solvents encountered serious precipitation of the ozonation intermediates. The precipitated intermediates could be polymeric ozonides and intermolecular ozonides or polymeric peroxides. Because the inhomogeneous reaction medium caused low ozone efficiency, various participating solvents such as methanol and acetic acid were added to form more soluble hydroperoxides. The mass balance results showed that on average, one asphaltene molecule reacted with 12 ozone molecules through the electrophilic reaction and the subsequent decomposition of ozonation intermediates generated acetone extractable products. GC/MS analysis of these compounds indicated that the free radical reactions could be important for generation of volatile products. The extensively ozonated asphaltene in the presence of participating solvents were refluxed with methanol to generate more volatile products. GC/MS analysis of the methanol-esterified ozonation products indicated that most volatile products were aliphatic carboxylic acid esters generated through cleavage of substituents. Reaction kinetics study showed that asphaltene ozonation was initially a diffusion rate-controlled reaction and later developed to a chemical reaction rate-controlled reaction after depletion of the reactive aromatic sites. Two new solvent systems, a self-sustaining ozonation system and a cyclohexane/acetone/water or a cyclohexane/acetone/methanol system, were studied to overcome the drawback of using halogenated solvents. The self-sustaining ozonation process employed the final ozonation products as the reaction solvent. Compared to the self-sustaining ozonation, the cyclohexane solvent system showed higher ozone efficiency; however, it required dynamic adjustment of the solvent system during ozonation. An extensively ozonated asphaltene's weight would be doubled. Distillation of the products separated about 45% volatile products having biodiesel-style chemical structures. Compared to distillation, more than 90% of the ozonation products were extractable by acetone. The remaining acetone-insoluble part was further classified by dichloromethane and other solvents of different polarities. The separated ozonation products were good fuel additives or materials for other products.

Endothelial delivery of antioxidant enzymes loaded into non-polymeric magnetic nanoparticles

PubMed Central

Chorny, Michael; Hood, Elizabeth; Levy, Robert J.; Muzykantov, Vladimir R.

2010-01-01

Antioxidant enzymes have shown promise as a therapy for pathological conditions involving increased production of reactive oxygen species (ROS). However the efficiency of their use for combating oxidative stress is dependent on the ability to achieve therapeutically adequate levels of active enzymes at the site of ROS-mediated injury. Thus, the implementation of antioxidant enzyme therapy requires a strategy enabling both guided delivery to the target site and effective protection of the protein in its active form. To address these requirements we developed magnetically responsive nanoparticles (MNP) formed by precipitation of calcium oleate in the presence of magnetite-based ferrofluid (controlled aggregation/precipitation) as a carrier for magnetically guided delivery of therapeutic proteins. We hypothesized that antioxidant enzymes, catalase and superoxide dismutase, can be protected from proteolytic inactivation by encapsulation in MNP. We also hypothesized that catalase-loaded MNP applied with a high-gradient magnetic field can rescue endothelial cells from hydrogen peroxide toxicity in culture. To test these hypotheses, a family of enzyme-loaded MNP formulations were prepared and characterized with respect to their magnetic properties, enzyme entrapment yields and protection capacity. SOD- and catalase-loaded MNP were formed with average sizes ranging from 300 to 400 nm, and a protein loading efficiency of 20–33%. MNP were strongly magnetically responsive (magnetic moment at saturation of 14.3 emu/g) in the absence of magnetic remanence, and exhibited a protracted release of their cargo protein in plasma. Catalase stably associated with MNP was protected from proteolysis and retained 20% of its initial enzymatic activity after 24 hr of exposure to pronase. Under magnetic guidance catalase-loaded MNP were rapidly taken up by cultured endothelial cells providing increased resistance to oxidative stress (62±12% cells rescued from hydrogen peroxide induced cell death vs. 10±4% under non-magnetic conditions). We conclude that non-polymeric MNP formed using the controlled aggregation/precipitation strategy are a promising carrier for targeted antioxidant enzyme therapy, and in combination with magnetic guidance can be applied to protect endothelial cells from oxidative stress mediated damage. This protective effect of magnetically targeted MNP impregnated with antioxidant enzymes can be highly relevant for the treatment of cardiovascular disease and should be further investigated in animal models. PMID:20483366

Endothelial delivery of antioxidant enzymes loaded into non-polymeric magnetic nanoparticles.

PubMed

Chorny, Michael; Hood, Elizabeth; Levy, Robert J; Muzykantov, Vladimir R

2010-08-17

Antioxidant enzymes have shown promise as a therapy for pathological conditions involving increased production of reactive oxygen species (ROS). However the efficiency of their use for combating oxidative stress is dependent on the ability to achieve therapeutically adequate levels of active enzymes at the site of ROS-mediated injury. Thus, the implementation of antioxidant enzyme therapy requires a strategy enabling both guided delivery to the target site and effective protection of the protein in its active form. To address these requirements we developed magnetically responsive nanoparticles (MNP) formed by precipitation of calcium oleate in the presence of magnetite-based ferrofluid (controlled aggregation/precipitation) as a carrier for magnetically guided delivery of therapeutic proteins. We hypothesized that antioxidant enzymes, catalase and superoxide dismutase (SOD), can be protected from proteolytic inactivation by encapsulation in MNP. We also hypothesized that catalase-loaded MNP applied with a high-gradient magnetic field can rescue endothelial cells from hydrogen peroxide toxicity in culture. To test these hypotheses, a family of enzyme-loaded MNP formulations were prepared and characterized with respect to their magnetic properties, enzyme entrapment yields and protection capacity. SOD- and catalase-loaded MNP were formed with average sizes ranging from 300 to 400 nm, and a protein loading efficiency of 20-33%. MNP were strongly magnetically responsive (magnetic moment at saturation of 14.3 emu/g) in the absence of magnetic remanence, and exhibited a protracted release of their cargo protein in plasma. Catalase stably associated with MNP was protected from proteolysis and retained 20% of its initial enzymatic activity after 24h of exposure to pronase. Under magnetic guidance catalase-loaded MNP were rapidly taken up by cultured endothelial cells providing increased resistance to oxidative stress (62+/-12% cells rescued from hydrogen peroxide induced cell death vs. 10+/-4% under non-magnetic conditions). We conclude that non-polymeric MNP formed using the controlled aggregation/precipitation strategy are a promising carrier for targeted antioxidant enzyme therapy, and in combination with magnetic guidance can be applied to protect endothelial cells from oxidative stress mediated damage. This protective effect of magnetically targeted MNP impregnated with antioxidant enzymes can be highly relevant for the treatment of cardiovascular disease and should be further investigated in animal models. Copyright 2010 Elsevier B.V. All rights reserved.

Variability of precipitation in Poland under climate change

NASA Astrophysics Data System (ADS)

Szwed, Małgorzata

2018-02-01

The surface warming has been widespread over the entire globe. Central Europe, including Poland, is not an exception. Global temperature increases are accompanied by changes in other climatic variables. Climate change in Poland manifests itself also as change in annual sums of precipitation. They have been slightly growing but, what is more important, seasonal and monthly distributions of precipitation have been also changing. The most visible increases have been observed during colder half-year, especially in March. A decreasing contribution of summer precipitation total (June-August) to the annual total is observed. Climate projections for Poland predict further warming and continuation of already observed changes in the quantity of precipitation as well as its spatial and seasonal distribution.

Exploring New Pathways in Precipitation Assimilation

NASA Technical Reports Server (NTRS)

Hou, Arthur; Zhang, Sara Q.

2004-01-01

Precipitation assimilation poses a special challenge in that the forward model for rain in a global forecast system is based on parameterized physics, which can have large systematic errors that must be rectified to use precipitation data effectively within a standard statistical analysis framework. We examine some key issues in precipitation assimilation and describe several exploratory studies in assimilating rainfall and latent heating information in NASA's global data assimilation systems using the forecast model as a weak constraint. We present results from two research activities. The first is the assimilation of surface rainfall data using a time-continuous variational assimilation based on a column model of the full moist physics. The second is the assimilation of convective and stratiform latent heating retrievals from microwave sensors using a variational technique with physical parameters in the moist physics schemes as a control variable. We will show the impact of assimilating these data on analyses and forecasts. Among the lessons learned are (1) that the time-continuous application of moisture/temperature tendency corrections to mitigate model deficiencies offers an effective strategy for assimilating precipitation information, and (2) that the model prognostic variables must be allowed to directly respond to an improved rain and latent heating field within an analysis cycle to reap the full benefit of assimilating precipitation information. of microwave radiances versus retrieval information in raining areas, and initial efforts in developing ensemble techniques such as Kalman filter/smoother for precipitation assimilation. Looking to the future, we discuss new research directions including the assimilation

Molten tin reprocessing of spent nuclear fuel elements. [Patent application; continuous process

DOEpatents

Heckman, R.A.

1980-12-19

A method and apparatus for reprocessing spent nuclear fuel is described. Within a containment vessel, a solid plug of tin and nitride precipitates supports a circulating bath of liquid tin therein. Spent nuclear fuel is immersed in the liquid tin under an atmosphere of nitrogen, resulting in the formation of nitride precipitates. The layer of liquid tin and nitride precipitates which interfaces the plug is solidified and integrated with the plug. Part of the plug is melted, removing nitride precipitates from the containment vessel, while a portion of the plug remains solidified to support te liquid tin and nitride precipitates remaining in the containment vessel. The process is practiced numerous times until substantially all of the precipitated nitrides are removed from the containment vessel.

Sampling problems: The small scale structure of precipitation

NASA Technical Reports Server (NTRS)

Crane, R. K.

1981-01-01

The quantitative measurement of precipitation characteristics for any area on the surface of the Earth is not an easy task. Precipitation is rather variable in both space and time, and the distribution of surface rainfall data given location typically is substantially skewed. There are a number of precipitation process at work in the atmosphere, and few of them are well understood. The formal theory on sampling and estimating precipitation appears considerably deficient. Little systematic attention is given to nonsampling errors that always arise in utilizing any measurement system. Although the precipitation measurement problem is an old one, it continues to be one that is in need of systematic and careful attention. A brief history of the presently competing measurement technologies should aid us in understanding the problem inherent in this measurement task.

Method for production of hydrocarbons from hydrates

DOEpatents

McGuire, Patrick L.

1984-01-01

A method of recovering natural gas entrapped in frozen subsurface gas hydrate formations in arctic regions. A hot supersaturated solution of CaCl.sub.2 or CaBr.sub.2, or a mixture thereof, is pumped under pressure down a wellbore and into a subsurface hydrate formation so as to hydrostatically fracture the formation. The CaCl.sub.2 /CaBr.sub.2 solution dissolves the solid hydrates and thereby releases the gas entrapped therein. Additionally, the solution contains a polymeric viscosifier, which operates to maintain in suspension finely divided crystalline CaCl.sub.2 /CaBr.sub.2 that precipitates from the supersaturated solution as it is cooled during injection into the formation.

Detection of Inulin, a Prebiotic Polysaccharide, in Maple Syrup.

PubMed

Sun, Jiadong; Ma, Hang; Seeram, Navindra P; Rowley, David C

2016-09-28

Maple syrup is a widely consumed plant-derived natural sweetener produced by concentrating xylem sap collected from certain maple (Acer) species. During thermal evaporation of water, natural phytochemical components are concentrated in maple syrup. The polymeric components from maple syrup were isolated by ethanol precipitation, dialysis, and anion exchange chromatography and structurally characterized by glycosyl composition analysis, glycosyl linkage analysis, and nuclear magnetic resonance spectroscopy. Among the maple syrup polysaccharides, one neutral polysaccharide was characterized as inulin with a broad molecular weight distribution, representing the first isolation of this prebiotic carbohydrate from a xylem sap. In addition, two acidic polysaccharides with structural similarity were identified as arabinogalactans derived from rhamnogalacturonan type I pectic polysaccharides.

Impact of low-pressure glow-discharge-pulsed plasma polymerization on properties of polyaniline thin films

NASA Astrophysics Data System (ADS)

Jatratkar, Aviraj A.; Yadav, Jyotiprakash B.; Deshmukh, R. R.; Barshilia, Harish C.; Puri, Vijaya; Puri, R. K.

2016-12-01

This study reports on polyaniline thin films deposited on a glass substrate using a low-pressure glow-discharge-pulsed plasma polymerization method. The polyaniline thin film obtained by pulsed plasma polymerization has been successfully demonstrated as an optical waveguide with a transmission loss of 3.93 dB cm-1, and has the potential to be employed in integrated optics. An attempt has been made to investigate the effect of plasma OFF-time on the structural, optical as well as surface properties of polyaniline thin film. The plasma ON-time has been kept constant and the plasma OFF-time has been varied throughout the work. The plasma OFF-time strongly influenced the properties of the polyaniline thin film, and a nanostructured and compact surface was revealed in the morphological studies. The plasma OFF-time was found to enhance film thickness, roughness, refractive index and optical transmission loss, whereas it reduced the optical band gap of the polyaniline thin films. Retention in the aromatic structure was confirmed by FTIR results. Optical studies revealed a π-π* electronic transition at about 317 nm as well as the formation of a branched structure. As compared with continuous wave plasma, pulsed plasma polymerization shows better properties. Pulsed plasma polymerization reduced the roughness of the film from 1.2 nm to 0.42 nm and the optical transmission loss from 6.56 dB cm-1 to 3.39 dB cm-1.

Polymerization of Building Blocks of Life on Europa and Other Icy Moons

PubMed Central

Kitadai, Norio

2015-01-01

Abstract The outer Solar System may provide a potential habitat for extraterrestrial life. Remote sensing data from the Galileo spacecraft suggest that the jovian icy moons—Europa, Ganymede, and possibly Callisto—may harbor liquid water oceans underneath their icy crusts. Although compositional information required for the discussion of habitability is limited because of significantly restricted observation data, organic molecules are ubiquitous in the Universe. Recently, in situ spacecraft measurements and experiments suggest that amino acids can be formed abiotically on interstellar ices and comets. These amino acids could be continuously delivered by meteorite or comet impacts to icy moons. Here, we show that polymerization of organic monomers, in particular amino acids and nucleotides, could proceed spontaneously in the cold environment of icy moons, in particular the jovian icy moon Europa as a typical example, based on thermodynamic calculations, though kinetics of formation are not addressed. Observed surface temperature on Europa is 120 and 80 K in the equatorial region and polar region, respectively. At such low temperatures, Gibbs energies of polymerization become negative, and the estimated thermal structure of the icy crust should contain a shallow region (i.e., at a depth of only a few kilometers) favorable for polymerization. Investigation of the possibility of organic monomer polymerization on icy moons could provide good constraints on the origin and early evolution of extraterrestrial life. Key Words: Planetary science—Europa—Planetary habitability and biosignatures—Extraterrestrial life—Extraterrestrial organic compounds. Astrobiology 15, 430–441. PMID:26060981

Precipitation data considerations for evaluating subdaily changes in rainless periods due to climate change

USDA-ARS?s Scientific Manuscript database

Quantifying magnitudes and frequencies of rainless times between storms (TBS), or storm occurrence, is required for generating continuous sequences of precipitation for modeling inputs to small watershed models for conservation studies. Two parameters characterize TBS, minimum TBS (MTBS) and averag...

Increasing influence of air temperature on upper Colorado River streamflow

USGS Publications Warehouse

Woodhouse, Connie A.; Pederson, Gregory T.; Morino, Kiyomi; McAfee, Stephanie A.; McCabe, Gregory J.

2016-01-01

This empirical study examines the influence of precipitation, temperature, and antecedent soil moisture on upper Colorado River basin (UCRB) water year streamflow over the past century. While cool season precipitation explains most of the variability in annual flows, temperature appears to be highly influential under certain conditions, with the role of antecedent fall soil moisture less clear. In both wet and dry years, when flow is substantially different than expected given precipitation, these factors can modulate the dominant precipitation influence on streamflow. Different combinations of temperature, precipitation, and soil moisture can result in flow deficits of similar magnitude, but recent droughts have been amplified by warmer temperatures that exacerbate the effects of relatively modest precipitation deficits. Since 1988, a marked increase in the frequency of warm years with lower flows than expected, given precipitation, suggests continued warming temperatures will be an increasingly important influence in reducing future UCRB water supplies.

Estimating Global Precipitation for Science and Application

NASA Technical Reports Server (NTRS)

Huffman, George J.

2013-01-01

Over the past two decades there has been vigorous development in the satellite assets and the algorithms necessary to estimate precipitation around the globe. In particular the highly successful joint NASAJAXA Tropical Rainfall Measuring Mission (TRMM) and the upcoming Global Precipitation Measurement (GPM) mission, also joint between NASA and JAXA, have driven these issues. At the same time, the long-running Global Precipitation Climatology Project (GPCP) continues to extend a stable, climate-oriented view of global precipitation. This talk will provide an overview of these projects and the wider international community of precipitation datasets, sketch plans for next-generation products, and provide some examples of the best use for the different products. One key lesson learned is that different data sets are needed to address the variety of issues that need precipitation data, including detailed 3-D views of hurricanes, flash flood forecasting, drought analysis, and global change.

Durability of a continuous strand mat polymeric composite for automotive structural applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Corum, J.M.; McCoy, H.E. Jr.; Ruggles, M.B.

1995-12-31

A key unanswered question that must be addressed before polymeric composites will be widely used in automotive structural components is their durability. Major durability issues are the effects of cyclic loadings, creep, automotive environments, and low-energy impacts on dimensional stability, strength, and stiffness. The U.S. Department of Energy is sponsoring a project at Oak Ridge National Laboratory to address these issues and to develop, in cooperation with the Automotive Composites Consortium, experimentally based, durability driven, design guidelines. The initial reference material is an isocyanurate reinforced with a continuous strand, swirl glass mat. This paper describes the basic deformation and failuremore » behavior of the reference material, and it presents test results illustrating the property degradations caused by loading, time, and environmental effects. The importance of characterizing and understanding damage and how it leads to failure is also discussed. The results presented are from the initial phases of an ongoing project. The ongoing effort and plans are briefly described.« less

Antiretroviral Drugs-Loaded Nanoparticles Fabricated by Dispersion Polymerization with Potential for HIV/AIDS Treatment

PubMed Central

Ogunwuyi, Oluwaseun; Kumari, Namita; Smith, Kahli A.; Bolshakov, Oleg; Adesina, Simeon; Gugssa, Ayele; Anderson, Winston A.; Nekhai, Sergei; Akala, Emmanuel O.

2016-01-01

Highly active antiretroviral (ARV) therapy (HAART) for chronic suppression of HIV replication has revolutionized the treatment of HIV/AIDS. HAART is no panacea; treatments must be maintained for life. Although great progress has been made in ARV therapy, HIV continues to replicate in anatomical and intracellular sites where ARV drugs have restricted access. Nanotechnology has been considered a platform to circumvent some of the challenges in HIV/AIDS treatment. Dispersion polymerization was used to fabricate two types (PMM and ECA) of polymeric nanoparticles, and each was successfully loaded with four ARV drugs (zidovudine, lamivudine, nevirapine, and raltegravir), followed by physicochemical characterization: scanning electron microscope, particle size, zeta potential, drug loading, and in vitro availability. These nanoparticles efficiently inhibited HIV-1 infection in CEM T cells and peripheral blood mononuclear cells; they hold promise for the treatment of HIV/AIDS. The ARV-loaded nanoparticles with polyethylene glycol on the corona may facilitate tethering ligands for targeting specific receptors expressed on the cells of HIV reservoirs. PMID:27013886

Plasma Surface Modification of Polyaramid Fibers for Protective Clothing

NASA Astrophysics Data System (ADS)

Widodo, Mohamad

2011-12-01

The purpose of this research was to develop a novel process that would achieve biocidal properties on Kevlar fabric via atmospheric pressure plasma jet (APPJ) induced-graft polymerization of monomers. In the course of the study, experiments were carried out to understand plasma-monomer-substrate interactions, particularly, how each of the main parameters in the plasma processing affects the formation of surface radicals and eventually the degree of graft polymerization of monomers. The study also served to explore the possibility of developing plasma-initiated and plasma-controlled graft polymerization for continuous operation. In this regards, three methods of processing were studied, which included two-step plasma graft-polymerization with immersion, two-step and one-step plasma graft-polymerization with pad-dry. In general, plasma treatment did not cause visible damage to the surface of Kevlar fibers, except for the appearance of tiny globules distributed almost uniformly indicating a minor effect of plasma treatment to the surface morphology of the polymer. From the examination of SEM images, however, it was found that a very localized surface etching seemed to have taken place, especially at high RF power (800 W) and long time of exposure (60 s), even in plasma downstream mode of operation. It was suggested that a small amount of charged particles might have escaped and reached the substrate surface. High density of surface radicals, which is the prerequisite for high graft density and high antimicrobial activity, was achieved by the combination of high RF power and short exposure time or low RF power and long time of exposure. This was a clear indication that the formation of surface radicals is a function of amount of the dissipated energy, which also explained the two-factor interaction between the two process parameters. XPS results showed that hydrolysis of the anilide bond of PPTA chains took place to some extent on the surface of Kevlar, leading to the formation carboxylic and phenyl amine groups, which may provide additional active sites for grafting by way of hydrogen abstraction from the latter. Further analysis of XPS data, however, showed that macroradicals and active sites of grafting were formed at least at one of the carbon atoms in the aromatic ring. A reduction of microbial activity up to 3-log reduction was achieved by plasma treated Kevlar grafted by either diallyl diammonium chloride (DADMAC) or 3- ((trimethoxysilyl)-propyl) dimethylammonium chloride (TMS), with the latter being the one with better performance. It was found that high antimicrobial activity was obtained by the combination of high RF power, short time of exposure, and low concentration of monomer. Of the three processing methods studied, the one with immersion method produced higher graft yield. However, one-step plasma graft-polymerization with pad-dry method has proven itself more interesting due to its potential for an open continuous process. This research has been successful in producing effective antimicrobial properties on Kevlar fabric by plasma-initiated and plasma-controlled graft polymerization, which is unprecedented. The design of experiments showed that better results with higher order of log reduction can be obtained by process optimization, e.g. by using response surface methods. It would also be very beneficial to continue the research for the development of plasma graft-polymerization process with more rigorous design, which involves the use of crosslinker and antimicrobial monomers with different chemistry. A study that involves the development of a robust design for processes that perform consistently as intended under a wide range of user's conditions and yet produce high-level performance with high reliability would also be advantageous. The major implication of the findings from this research for the finishing of Kevlar is that a wide array of different surface functionalities may become more readily available now than ever. Plasma technology has made surface chemistry functionalization of Kevlar more straightforward and easier to perform, which opens new avenues for achieving functional and multifunctional Kevlar fabrics using a fast, more economic and environmentally friendly continuous process for niche market such as military applications and protective clothing for emergency responders.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abrao, Alcidio.; Araujo, Jose Adroaldo de; Franca Junior, J.M.

This paper describes a technique for the production of nuclear grade ammonium diuranate (ADU) using uranyl sulfate solutions obtained as eluate from the ion exchange (strong cationic resin) purification of uranium, by precipitation with NH{sub 3} gas. The precipitation of ADU by direct introduction of NH{sub 3} gas into acid uranyl sulfate solution has as consequence a high coprecipitation of sulfate ion, reaching ratios as high as 10 to 14% SO{sub 4}/ADU. To overcome this serious inconvenience, the reverse order of addition of reagents was studied, the ADU precipitation being done in such a way that the pH of themore » mixture was kept higher than 6 during the whole precipitation. This modification, in conjunction with the adjustment of other precipitation parameters, like temperature, precipitation time, aging time, concentration of uranium in uranyl sulfate and pH, allowed a sucessful precipitation of ADU with low sulfate content. The technique was applied at pilot plant scale, using batch and continuous precipitation, in both cases the obtained ADU was low in sulfate.« less

Evaluating PRISM precipitation grid data as possible surrogates for station data at four sites in Oklahoma

USDA-ARS?s Scientific Manuscript database

The development of climate-sensitive decision support for agriculture or water resource management requires long time series of monthly precipitation for specific locations. Archived station data for many locations is available, but time continuity, quality, and spatial coverage of station data rem...

40 CFR 434.63 - Effluent limitations for precipitation events.

Code of Federal Regulations, 2011 CFR

2011-07-01

... events. 434.63 Section 434.63 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... events. (a)(1) The alternate limitations specified in paragraph (a)(2) of this section apply with respect... than or equal to the 10-year, 24-hour precipitation event (or snowmelt of equivalent volume) may comply...

The Dependence of Portevin-Le Châtelier Effect on the γ' Precipitates in a Wrought Ni-Base Superalloy

NASA Astrophysics Data System (ADS)

Wang, Xinguang; Han, Guoming; Cui, Chuanyong; Guan, Shuai; Jin, Tao; Sun, Xiaofeng; Hu, Zhuangqi

2016-12-01

The dependence of Portevin-Le Châtelier (PLC) effect on the γ' precipitates of the Nimonic 263 alloy in different microstructural conditions has been studied by analyzing the parameters of the tensile curves and the deformation mechanisms. It is shown that the γ' precipitates with different sizes, edge-to-edge interprecipitate distance, and areal number density are obtained by altering the aging time. It is demonstrated that when the mean size of the γ' precipitates is less than 28 nm (aging less than 25 hours), the deformation mechanisms are dominated by APB-coupled a/2<101> dislocations shearing the small γ' precipitates and the slip bands continuously cutting the γ and γ' phases. When the γ' size is between 28 and 45 nm (aging time between 25 and 50 hours), the deformation mechanism is controlled by the APB-coupled a/2<101> dislocations shearing the small γ' precipitates, the a/6<112> Shockley partial dislocation continuously shearing the γ and γ' phases combined with matrix dislocations by-passing the γ' precipitates; If the γ' size over 45 nm (aging time more than 50 hours), Orowan by-passing becomes the main deformation mechanism. Moreover, with increasing the aging time, the critical plastic strain for the onset of the PLC effect increases and reaches a maximum after aging for 50 hours, and then gradually decreases. At last, the dependence of critical plastic strain on the deformation mechanisms is well explained by the elementary incremental strain (γ). The precipitation process of the γ' phase can directly influence the PLC effect by changing the interactions among solutes atoms, mobile dislocations, and forest dislocations.

Advances in polymeric systems for tissue engineering and biomedical applications.

PubMed

Ravichandran, Rajeswari; Sundarrajan, Subramanian; Venugopal, Jayarama Reddy; Mukherjee, Shayanti; Ramakrishna, Seeram

2012-03-01

The characteristics of tissue engineered scaffolds are major concerns in the quest to fabricate ideal scaffolds for tissue engineering applications. The polymer scaffolds employed for tissue engineering applications should possess multifunctional properties such as biocompatibility, biodegradability and favorable mechanical properties as it comes in direct contact with the body fluids in vivo. Additionally, the polymer system should also possess biomimetic architecture and should support stem cell adhesion, proliferation and differentiation. As the progress in polymer technology continues, polymeric biomaterials have taken characteristics more closely related to that desired for tissue engineering and clinical needs. Stimuli responsive polymers also termed as smart biomaterials respond to stimuli such as pH, temperature, enzyme, antigen, glucose and electrical stimuli that are inherently present in living systems. This review highlights the exciting advancements in these polymeric systems that relate to biological and tissue engineering applications. Additionally, several aspects of technology namely scaffold fabrication methods and surface modifications to confer biological functionality to the polymers have also been discussed. The ultimate objective is to emphasize on these underutilized adaptive behaviors of the polymers so that novel applications and new generations of smart polymeric materials can be realized for biomedical and tissue engineering applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pyrolytic carbon membranes containing silica: morphological approach on gas transport behavior

NASA Astrophysics Data System (ADS)

Park, Ho Bum; Lee, Sun Yong; Lee, Young Moo

2005-04-01

Pyrolytic carbon membrane containing silica (C-SiO 2) is a new-class material for gas separation, and in the present work we will deal with it in view of the morphological changes arising from the difference in the molecular structure of the polymeric precursors. The silica embedded carbon membranes were fabricated by a predetermined pyrolysis step using imide-siloxane copolymers (PISs) that was synthesized from benzophenone tetracarboxylic dianhydrides (BTDA), 4,4'-oxydianiline (ODA), and amine-terminated polydimethylsiloxane (PDMS). To induce different morphologies at the same chemical composition, the copolymers were prepared using one-step (preferentially a random segmented copolymer) sand two-step polymerization (a block segmented copolymer) methods. The polymeric precursors and their pyrolytic C-SiO 2 membranes were analyzed using thermal analysis, atomic force microscopy, and transmission electron microscopy, etc. It was found that the C-SiO 2 membrane derived from the random PIS copolymer showed a micro-structure containing small well-dispersed silica domains, whereas the C-SiO 2 membrane from the block PIS copolymer exhibited a micro-structure containing large silica domains in the continuous carbon matrix. Eventually, the gas transport through these C-SiO 2 membranes was significantly affected by the morphological changes of the polymeric precursors.

Diatomaceous earth as a protective vehicle for bacteria applied for self-healing concrete.

PubMed

Wang, J Y; Belie, N De; Verstraete, W

2012-04-01

Crack repair is crucial since cracks are the main cause for the decreased service life of concrete structures. An original and promising way to repair cracks is to pre-incorporate healing agents inside the concrete matrix to heal cracks the moment they appear. Thus, the concrete obtains self-healing properties. The goal of our research is to apply bacterially precipitated CaCO₃ to heal cracks in concrete since the microbial calcium carbonate is more compatible with the concrete matrix and more environmentally friendly relative to the normally used polymeric materials. Diatomaceous earth (DE) was used in this study to protect bacteria from the high-pH environment of concrete. The experimental results showed that DE had a very good protective effect for bacteria. DE immobilized bacteria had much higher ureolytic activity (12-17 g/l urea was decomposed within 3 days) than that of un-immobilized bacteria (less than 1 g/l urea was decomposed within the same time span) in cement slurry. The optimal concentration of DE for immobilization was 60% (w/v, weight of DE/volume of bacterial suspension). Self-healing in cracked specimens was visualized under light microscopy. The images showed that cracks with a width ranging from 0.15 to 0.17 mm in the specimens containing DE immobilized bacteria were completely filled by the precipitation. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were used to characterize the precipitation around the crack wall, which was confirmed to be calcium carbonate. The result from a capillary water absorption test showed that the specimens with DE immobilized bacteria had the lowest water absorption (30% of the reference ones), which indicated that the precipitation inside the cracks increased the water penetration resistance of the cracked specimens.

Mineral Carbonation Employing Ultramafic Mine Waste

NASA Astrophysics Data System (ADS)

Southam, G.; McCutcheon, J.; Power, I. M.; Harrison, A. L.; Wilson, S. A.; Dipple, G. M.

2014-12-01

Carbonate minerals are an important, stable carbon sink being investigated as a strategy to sequester CO2 produced by human activity. A natural playa (Atlin, BC, CAN) that has demonstrated the ability to microbially-accelerate hydromagnesite formation was used as an experimental model. Growth of microbial mats from Atlin, in a 10 m long flow-through bioreactor catalysed hydromagnesite precipitation under 'natural' conditions. To enhance mineral carbonation, chrysotile from the Clinton Creek Asbestos Mine (YT, CAN) was used as a target substrate for sulphuric acid leaching, releasing as much as 94% of the magnesium into solution via chemical weathering. This magnesium-rich 'feedstock' was used to examine the ability of the microbialites to enhance carbonate mineral precipitation using only atmospheric CO2 as the carbon source. The phototrophic consortium catalysed the precipitation of platy hydromagnesite [Mg5(CO3)4(OH)2·4H2O] accompanied by magnesite [MgCO3], aragonite [CaCO3], and minor dypingite [Mg5(CO3)4(OH)2·5H2O]. Scanning Electron Microscopy-Energy Dispersive Spectroscopy indicated that cell exteriors and extracellular polymeric substances (EPS) served as nucleation sites for carbonate precipitation. In many cases, entire cyanobacteria filaments were entombed in magnesium carbonate coatings, which appeared to contain a framework of EPS. Cell coatings were composed of small crystals, which intuitively resulted from rapid crystal nucleation. Excess nutrient addition generated eutrophic conditions in the bioreactor, resulting in the growth of a pellicle that sealed the bioreactor contents from the atmosphere. The resulting anaerobic conditions induced fermentation and subsequent acid generation, which in turn caused a drop in pH to circumneutral values and a reduction in carbonate precipitation. Monitoring of the water chemistry conditions indicated that a high pH (> 9.4), and relatively high concentrations of magnesium (> 3000 ppm), compared with the natural wetland (up to 1000 ppm), and dissolved inorganic carbon (> 20 mM C) were ideal for carbonate precipitation. Under optimum nutrient and magnesium inputs, a mass balance calculation using water chemistry data and hydromagnesite as the sole mineral product resulted in a carbon sequestration rate of 61 t C/ha/year.

Mechanisms Related to Different Generations of gamma’ Precipitation During Continuous Cooling of a Nickel Base Superalloy

DTIC Science & Technology

2012-04-01

strongly depen- dent on the cooling rate employed. Faster cooling rates, such as those encountered during water quenching the alloy from the high temperature...precipitates. Subsequently on quenching to a lower temperature a second generation of c0 precipitates are formed that are considerably smaller in size and...annealing after rapid quenching of the alloy from the high temperature single c phase field. Therefore, typically these studies have focused on amonomodal

Precipitated withdrawal from nicotine reduces reinforcing effects of a visual stimulus for rats.

PubMed

Weaver, Matthew T; Sweitzer, Maggie; Coddington, Sarah; Sheppard, Jaimee; Verdecchia, Nicole; Caggiula, Anthony R; Sved, Alan F; Donny, Eric C

2012-07-01

Research has identified at least two positive reinforcement-related effects of nicotine: (a) primary reinforcement and (b) enhancement of reinforcement from concurrently available stimuli. Prior examples of the reinforcement-enhancing effects with rats showed that repeated, intermittent nicotine exposure increased responding for non-nicotine reinforcers, and this effect remained robust over several weeks. However, the effects of continuous nicotine exposure on responding for a non-nicotine reinforcer are unknown, as are the effects of abruptly withdrawing continuous nicotine on behavior maintained by the same reinforcer. Lever pressing for a visual reinforcer under a fixed ratio schedule was assessed while rats were maintained on a chronic, continuous infusion of nicotine (3.16 mg/kg/day; osmotic minipump). The effects of precipitated withdrawal on responding, following 16 days of continuous nicotine exposure, were assessed by pre-session subcutaneous injections of mecamylamine (1.0 mg/kg). Continuous nicotine initially increased active responding for the visual reinforcer; however, continued exposure resulted in an attenuation of this effect. Precipitated withdrawal from nicotine resulted in a significant decline in active responding. The initial increase in responding for the visual reinforcer with chronic nicotine exposure is consistent with prior research showing that intermittent exposure to nicotine acts as a reinforcement enhancer. However, the attenuation of this enhancement following prolonged nicotine exposure is in contrast with the persistent effects previously reported. Finally, the decrease in visual reinforcers below control levels (nicotine-naive animals) following nicotine withdrawal highlights a potential for affective withdrawal, which may serve as a motive for continued nicotine use.

Synthesis, characterization, and application of novel Zn(II)-ionic imprinted polymer for preconcentration of Zn(II) ions from aqueous solution

NASA Astrophysics Data System (ADS)

Wirawan, T.; Supriyanto, G.; Soegianto, A.

2018-04-01

Preparation of a new Zn2+ ion-imprinted polymer (Zn-IIP) is presented in this report. The Zn-IIP are prepared by precipitation polymerization using 8-hydroxyquinoline (8HQ) as a ligand, methacrylic acid (MAA) as functional monomer, and ethylene glycol dimethacrylate (EGDMA) as a cross-linker has been prepared. The benzoyl peroxide and ethanol/acetonitrile (2:1) mixture were used as initiator and porogen, respectively. Precipitation polymerization was carried out by heating in a water bath at 60°C for 8 hours. After polymerization, cavities in the polymer particles corresponding to the Zn2+ ions were created by leaching the polymer with 2 mol L-1 HNO3. The polymer was washed with aquabidest and dried in an oven at the temperature of 60°C for 24 hours. The Zn-IIP was characterized by Fourier Transform Infrared Spectrophotometry (FT-IR) and Scanning Electron Microscopy (SEM). The synthesized Zn-IIP was used as a new adsorbent for solid phase extraction (SPE) of Zn(II) prior to Flame Atomic Absorption Spectrometry (FAAS) determination. The experimental parameters for SPE, such as pH of the sample, loading rate, and elution volume, have been optimized. The effect of pH of the sample on the extraction of analyte was studied in batch mode. The effects of loading rate and elution volume on the extraction of analyte were studied in dynamic mode by loading of the sample through IIP-SPE cartridge containing 100 mg of the synthesized Zn-IIP. The imprinted polymer (Zn-IIP) have bands at 3433.06 cm-1 (O-H), 1508.23 cm-1 (C=N aromatics), 1284.5 cm-1 (C-N aromatics), 1056.9 cm-1 (C-O phenol), 1724.24 cm-1 (C=O), and 1639.38 cm-1 (conjugated C=O with C=C). The Scanning Electron Microscopy (SEM) images of IIP and IIP show that the IIP is seen to have more cavities than NIP. The optimum pH for quantitative Zn(II) retention was 5.5, and the elution was completed with 2 mL of 1.0 mol L-1 nitric acid. The optimum loading rate was 0.5 mL min-1. The recovery of Zn(II) from solution samples after its SPE extraction on IIP with 50-fold theoretical preconcentration was 94.60-104.50%. The LOD and LOQ with 50-fold theoretical preconcentration obtained were 0.0073 mg L-1 and 0.0244 mg L-1, respectively.

Application of Pulse Spark Discharges for Scale Prevention and Continuous Filtration Methods in Coal-Fired Power Plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, Young; Fridman, Alexander

2012-06-30

The overall objective of the present work was to develop a new scale-prevention technology by continuously precipitating and removing dissolved mineral ions (such as calcium and magnesium) in cooling water while the COC could be doubled from the present standard value of 3.5. The hypothesis of the present study was that if we could successfully precipitate and remove the excess calcium ions in cooling water, we could prevent condenser-tube fouling and at the same time double the COC. The approach in the study was to utilize pulse spark discharges directly in water to precipitate dissolved mineral ions in recirculating coolingmore » water into relatively large suspended particles, which could be removed by a self-cleaning filter. The present study began with a basic scientific research to better understand the mechanism of pulse spark discharges in water and conducted a series of validation experiments using hard water in a laboratory cooling tower. Task 1 of the present work was to demonstrate if the spark discharge could precipitate the mineral ions in water. Task 2 was to demonstrate if the selfcleaning filter could continuously remove these precipitated calcium particles such that the blowdown could be eliminated or significantly reduced. Task 3 was to demonstrate if the scale could be prevented or minimized at condenser tubes with a COC of 8 or (almost) zero blowdown. In Task 1, we successfully completed the validation study that confirmed the precipitation of dissolved calcium ions in cooling water with the supporting data of calcium hardness over time as measured by a calcium ion probe. In Task 2, we confirmed through experimental tests that the self-cleaning filter could continuously remove precipitated calcium particles in a simulated laboratory cooling tower such that the blowdown could be eliminated or significantly reduced. In addition, chemical water analysis data were obtained which were used to confirm the COC calculation. In Task 3, we conducted a series of heat transfer fouling tests using a condenser heat exchanger in the laboratory cooling tower, from which we confirmed that the plasma water treatment technology could prevent or significantly mitigate mineral foulings in condenser tubes when compared with the no-treatment case. With the completion of the present work, a cooling water treatment technology using pulse spark discharges is currently ready for field-validation tests. The plasma water treatment technology is a true mechanical water softener with almost no maintenance, which continuously converts hard water to soft water spending a relatively small amount of energy. Such a mechanical water softener could find wide-spread applications to solve hard water problems both in industry and at home.« less

Nanoparticle Control of Void Formation and Expansion in Polymeric and Composite Systems

DTIC Science & Technology

2007-02-01

facilities of GloCal Network Corporation, a Delaware legal entity with facilities in Seattle, Washington. The team succeeded at performing work in the State of...Delaware and Washington concurrently. After December 1, 2006, Professor Seferis and his team will continue the research, exclusively through GloCal

Toward Ultrasonic Tunable Ultra-Damping Metamaterials

DTIC Science & Technology

2014-03-06

difference is ascribed to the reported presence of a nonmagnetic dead layer around ferrite MNPs and to the silicon-rich shell that is visible on TEM images...spheres deformation. Then, the polymerization of the continuous phase somehow “ freezes ” the structure and the removal of the dispersed phase creates

Continuous nutrient administration decreases insulin sensitivity in neonatal pigs

USDA-ARS?s Scientific Manuscript database

We previously showed that chronic TPN compared to intermittent feeding of a formula results in hepatic insulin resistance and steatosis in neonatal pigs. We hypothesized that the route of feeding (IV vs enteral) rather than the nature of the diet (elemental vs polymeric) or the feeding regimen (cont...

Continuous administration of an elemental diet induces insulin resistance in neonatal pigs

USDA-ARS?s Scientific Manuscript database

We previously showed that total parenteral nutrition (TPN) compared to intermittent enteral feeding of a milk-based formula induces insulin resistance and hepatic steatosis in neonatal pigs. We hypothesized that intravenous (IV) feeding rather than the nature of the diet (elemental vs polymeric) or ...

Composite Materials for Maxillofacial Prostheses.

DTIC Science & Technology

1981-08-01

necessary and Identify byv block number) MAXILLOFACIAL PROSTHESES; PROSTHETIC MATERIALS: MICROCAPSULES : SOFT FILLERS; ELASTOMER COMPOSITES 2,. ABSTRACT...used as fillers in the fabrication of maxillofacial prostheses. The projected systems are elastomeric-shelled, liquid-filled microcapsules . Improvements...elastomeric-shelled, liquid-filled microcapsules . Experiments continued on the interfacial polymerization process, with spherical, sealed, capsules

Synthesis of 1D Fe₃O₄/P(MBAAm-co-MAA) nanochains as stabilizers for Ag nanoparticles and templates for hollow mesoporous structure, and their applications in catalytic reaction and drug delivery.

PubMed

Zhang, Wei; Si, Xiaowei; Liu, Bin; Bian, Guomin; Qi, Yonglin; Yang, Xinlin; Li, Chenxi

2015-10-15

One-dimensional (1D) magnetic Fe3O4/P(MBAAm-co-MAA) nanochains were prepared by distillation-precipitation polymerization of MBAAm and MAA in the presence of Fe3O4 nanoparticles as building blocks under a magnetic heating stirrer, which played two critical roles: serving as magnetic field to induce the self-assembly of Fe3O4 nanoparticles into 1D nanochains and providing thermal energy to induce the polymerization of MAA and MBAAm on the surface of the Fe3O4 nanoparticles. The thickness of the P(MBAAm-co-MAA) layer can be easily tuned by adjusting the successive polymerization steps. The polymer layer that contained carboxyl groups was used as stabilizers for loading Ag nanoparticles and the reaction locus for deposition of outer silica layer via a sol-gel method in presence of C18TMS as the pore directing agent for tri-layer nanochains. The corresponding hollow mesoporous silica nanochains with movable maghemite cores (γ-Fe2O3@mSiO2) were produced after removal of the polymer mid-layer and the alkyl groups of the pore directing agent via calcination of the tri-layer nanochains at high temperature. The Fe3O4/P(MBAAm-co-MAA)/Ag nanochains exhibited a highly catalytic efficiency and well reusable property toward the reduction of nitrophenol. Furthermore, the γ-Fe2O3@mSiO2 nanochains possessed hollow mesoporous structure and high specific surface area (197.2 m(2) g(-1)) were used as a drug carrier, which displayed a controlled release property. Copyright © 2015 Elsevier Inc. All rights reserved.

Structure-Composition-Property Relationships in Polymeric Amorphous Calcium Phosphate-Based Dental Composites †

PubMed Central

O’Donnell, Justin N.R.; Schumacher, Gary E.; Antonucci, Joseph M.; Skrtic, Drago

2009-01-01

Our studies of amorphous calcium phosphate (ACP)-based materials over the last decade have yielded bioactive polymeric composites capable of protecting teeth from demineralization or even regenerating lost tooth mineral. The anti-cariogenic/re-mineralizing potential of these ACP composites originates from their propensity, when exposed to the oral environment, to release in a sustained manner sufficient levels of mineral-forming calcium and phosphate ions to promote formation of stable apatitic tooth mineral. However, the less than optimal ACP filler/resin matrix cohesion, excessive polymerization shrinkage and water sorption of these experimental materials can adversely affect their physicochemical and mechanical properties, and, ultimately, limit their lifespan. This study demonstrates the effects of chemical structure and composition of the methacrylate monomers used to form the matrix phase of composites on degree of vinyl conversion (DVC) and water sorption of both copolymers and composites and the release of mineral ions from the composites. Modification of ACP surface via introducing cations and/or polymers ab initio during filler synthesis failed to yield mechanically improved composites. However, moderate improvement in composite’s mechanical stability without compromising its remineralization potential was achieved by silanization and/or milling of ACP filler. Using ethoxylated bisphenol A dimethacrylate or urethane dimethacrylate as base monomers and adding moderate amounts of hydrophilic 2-hydroxyethyl methacrylate or its isomer ethyl-α-hydroxymethacrylate appears to be a promising route to maximize the remineralizing ability of the filler while maintaining high DVC. Exploration of the structure/composition/property relationships of ACP fillers and polymer matrices is complex but essential for achieving a better understanding of the fundamental mechanisms that govern dissolution/re-precipitation of bioactive ACP fillers, and, ultimately, the suitability of the composites for clinical evaluation. PMID:21966588

Surface-Atmosphere Moisture Interactions in the Frozen Ground Regions of Eurasia.

PubMed

Ford, Trent W; Frauenfeld, Oliver W

2016-01-18

Climate models simulate an intensifying Arctic hydrologic cycle in response to climatic warming, however the role of surface-atmosphere interactions from degrading frozen ground is unclear in these projections. Using Modern-Era Retrospective Analysis for Research and Applications (MERRA) data in high-latitude Eurasia, we examine long-term variability in surface-atmosphere coupling as represented by the statistical relationship between surface evaporative fraction (EF) and afternoon precipitation. Changes in EF, precipitation, and their statistical association are then related to underlying permafrost type and snow cover. Results indicate significant positive trends in July EF in the Central Siberian Plateau, corresponding to significant increases in afternoon precipitation. The positive trends are only significant over continuous permafrost, with non-significant or negative EF and precipitation trends over isolated, sporadic, and discontinuous permafrost areas. Concurrently, increasing EF and subsequent precipitation are found to coincide with significant trends in May and June snowmelt, which potentially provides the moisture source for the observed enhanced latent heating and moisture recycling in the region. As climate change causes continuous permafrost to transition to discontinuous, discontinuous to sporadic, sporadic to isolated, and isolated permafrost disappears, this will also alter patterns of atmospheric convection, moisture recycling, and hence the hydrologic cycle in high-latitude land areas.

Precipitation Strengthening by Induction Treatment in High Strength Low Carbon Microalloyed Hot-Rolled Plates

NASA Astrophysics Data System (ADS)

Larzabal, G.; Isasti, N.; Rodriguez-Ibabe, J. M.; Uranga, P.

2018-03-01

The use of microalloyed steels in the production of thick plates is expanding due to the possibility of achieving attractive combinations of strength and toughness. As market requirements for high strength plates are increasing and new applications require reduced weight and innovative designs, novel approaches to attaining cost-effective grades are being developed. The mechanism of precipitation strengthening has been widely used in thin strip products, since the optimization of the coiling strategy offers interesting combinations in terms of final properties and microalloying additions. Precipitation strengthening in thick plates, however, is less widespread due to the limitation of interphase precipitation during continuous cooling after hot rolling. With the main objective of exploring the limits of this strengthening mechanism, laboratory thermomechanical simulations that reproduced plate hot rolling mill conditions were performed using low carbon steels microalloyed with Nb, NbMo, and TiMo additions. After continuous cooling to room temperature, a set of heat treatments using fast heating rates were applied simulating the conditions of induction heat treatments. An important increase of both yield and tensile strengths was measured after induction treatment without any important impairment in toughness properties. A significant precipitation hardening is observed in Mo-containing grades under specific heat treatment parameters.

Dissolution and Precipitation Behaviour during Continuous Heating of Al–Mg–Si Alloys in a Wide Range of Heating Rates

PubMed Central

Osten, Julia; Milkereit, Benjamin; Schick, Christoph; Kessler, Olaf

2015-01-01

In the present study, the dissolution and precipitation behaviour of four different aluminium alloys (EN AW-6005A, EN AW-6082, EN AW-6016, and EN AW-6181) in four different initial heat treatment conditions (T4, T6, overaged, and soft annealed) was investigated during heating in a wide dynamic range. Differential scanning calorimetry (DSC) was used to record heating curves between 20 and 600 °C. Heating rates were studied from 0.01 K/s to 5 K/s. We paid particular attention to control baseline stability, generating flat baselines and allowing accurate quantitative evaluation of the resulting DSC curves. As the heating rate increases, the individual dissolution and precipitation reactions shift to higher temperatures. The reactions during heating are significantly superimposed and partially run simultaneously. In addition, precipitation and dissolution reactions are increasingly suppressed as the heating rate increases, whereby exothermic precipitation reactions are suppressed earlier than endothermic dissolution reactions. Integrating the heating curves allowed the enthalpy levels of the different initial microstructural conditions to be quantified. Referring to time–temperature–austenitisation diagrams for steels, continuous heating dissolution diagrams for aluminium alloys were constructed to summarise the results in graphical form. These diagrams may support process optimisation in heat treatment shops.

A novel sequential process for remediating rare-earth wastewater.

PubMed

Cui, Mingcan; Jang, Min; Kang, Kyounglim; Kim, Dukmin; Snyder, Shane A; Khim, Jeehyeong

2016-02-01

A novel and economic sequential process consisting of precipitation, adsorption, and oxidation was developed to remediate actual rare-earth (RE) wastewater containing various toxic pollutants, including radioactive species. In the precipitation step, porous air stones (PAS) containing waste oyster shell (WOS), PASWOS, was prepared and used to precipitate most heavy metals with >97% removal efficiencies. The SEM-EDS analysis revealed that PAS plays a key role in preventing the surface coating of precipitants on the surface of WOS and in releasing the dissolved species of WOS successively. For the adsorption step, a polyurethane (PU) impregnated by coal mine drainage sludge (CMDS), PUCMDS, was synthesized and applied to deplete fluoride (F), arsenic (As), uranium (U), and thorium (Th) that remained after precipitation. The continuous-mode sequential process using PAS(WOS), PU(CMDS), and ozone (O3) had 99.9-100% removal efficiencies of heavy metals, 99.3-99.9% of F and As, 95.8-99.4% of U and Th, and 92.4% of COD(Cr) for 100 days. The sequential process can treat RE wastewater economically and effectively without stirred-tank reactors, pH controller, continuous injection of chemicals, and significant sludge generation, as well as the quality of the outlet met the EPA recommended limits. Copyright © 2015 Elsevier Ltd. All rights reserved.

Cross-Regional Assessment Of Coupling And Variability In Precipitation-Runoff Relationships

NASA Astrophysics Data System (ADS)

Carey, S. K.; Tetzlaff, D.; Soulsby, C.; Buttle, J. M.; Laudon, H.; McDonnell, J. J.; McGuire, K. J.; Seibert, J.; Shanley, J. B.

2011-12-01

The higher mid-latitudes of the northern hemisphere are particularly sensitive to change due to the important role the zero-degree isotherm plays in the phase of precipitation and intermediate storage as snow. An international inter-catchment comparison program North-Watch seeks to improve our understanding of the sensitivity of northern catchments to change by examining their hydrological and biogeochemical variability and response. The catchments are located in Sweden (Krycklan), Scotland (Mharcaidh, Girnock and Strontian), the United States (Sleepers River, Hubbard Brook and HJ Andrews) and Canada (Catamaran, Dorset and Wolf Creek). For this study, 8 catchments with 10 continuous years of daily precipitation and runoff data were selected to assess the seasonal coupling of rainfall and runoff and the memory effect of runoff events on the hydrograph at different time scales. To assess the coupling and synchroneity of precipitation, continuous wavelet transforms and wavelet coherence were used. Wavelet spectra identified the relative importance of both annual versus seasonal flows while wavelet coherence was applied to identify over different time scales along the 10-year window how well precipitation and runoff were coupled. For example, while on a given day, precipitation may be closely coupled to runoff, a wet year may not necessarily be a high runoff year in catchments with large storage. Assessing different averaging periods in the variation of daily flows highlights the importance of seasonality in runoff response and the relative influence of rain versus snowmelt on flow magnitude and variability. Wet catchments with limited seasonal precipitation variability (Strontian, Girnock) have precipitation signals more closely coupled with runoff, whereas dryer catchments dominated by snow (Wolf Creek, Krycklan) have strongly coupling only during freshet. Most catchments with highly seasonal precipitation show strong intermittent coupling during their wet season. At longer time scales, some catchments do not exhibit coupling in their input-output relations, which is related to catchment storage.

An NMR relaxometry and gravimetric study of gelatin-free aqueous polyacrylamide dosimeters

NASA Astrophysics Data System (ADS)

Babic, Steven; Schreiner, L. John

2006-09-01

In conformal radiation therapy, a high dose of radiation is given to a target volume to increase the probability of cure, and care is taken to minimize the dose to surrounding healthy tissue. The techniques used to achieve this are very complicated and the precise verification of the resulting three-dimensional (3D) dose distribution is required. Polyacrylamide gelatin (PAG) dosimeters with magnetic resonance imaging and optical computed tomography scanning provide the required 3D dosimetry with high spatial resolution. Many basic studies have characterized these chemical dosimeters that polymerize under irradiation. However, the investigation of the fundamental properties of the radiation-induced polymerization in PAG dosimeters is complicated by the presence of the background gelatin matrix. In this work, a gelatin-free model system for the study of the basic radiation-induced polymerization in PAG dosimeters has been developed. Experiments were performed on gelatin-free dosimeters, named aqueous polyacrylamide (APA) dosimeters, containing equal amounts of acrylamide and N,N'-methylene-bisacrylamide. The APA dosimeters were prepared with four different total monomer concentrations (2, 4, 6 and 8% by weight). Nuclear magnetic resonance (NMR) spin-spin and spin-lattice proton relaxation measurements at 20 MHz, and gravimetric analyses performed on all four dosimeters, show a continuous degree of polymerization over the dose range of 0-25 Gy. The developed NMR model explains the relationship observed between the relaxation data and the amount of crosslinked polymer formed at each dose. This model can be extended with gelatin relaxation data to provide a fundamental understanding of radiation-induced polymerization in the conventional PAG dosimeters.

An NMR relaxometry and gravimetric study of gelatin-free aqueous polyacrylamide dosimeters.

PubMed

Babic, Steven; Schreiner, L John

2006-09-07

In conformal radiation therapy, a high dose of radiation is given to a target volume to increase the probability of cure, and care is taken to minimize the dose to surrounding healthy tissue. The techniques used to achieve this are very complicated and the precise verification of the resulting three-dimensional (3D) dose distribution is required. Polyacrylamide gelatin (PAG) dosimeters with magnetic resonance imaging and optical computed tomography scanning provide the required 3D dosimetry with high spatial resolution. Many basic studies have characterized these chemical dosimeters that polymerize under irradiation. However, the investigation of the fundamental properties of the radiation-induced polymerization in PAG dosimeters is complicated by the presence of the background gelatin matrix. In this work, a gelatin-free model system for the study of the basic radiation-induced polymerization in PAG dosimeters has been developed. Experiments were performed on gelatin-free dosimeters, named aqueous polyacrylamide (APA) dosimeters, containing equal amounts of acrylamide and N,N'-methylene-bisacrylamide. The APA dosimeters were prepared with four different total monomer concentrations (2, 4, 6 and 8% by weight). Nuclear magnetic resonance (NMR) spin-spin and spin-lattice proton relaxation measurements at 20 MHz, and gravimetric analyses performed on all four dosimeters, show a continuous degree of polymerization over the dose range of 0-25 Gy. The developed NMR model explains the relationship observed between the relaxation data and the amount of crosslinked polymer formed at each dose. This model can be extended with gelatin relaxation data to provide a fundamental understanding of radiation-induced polymerization in the conventional PAG dosimeters.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, Samuel, E-mail: S.J.Clark@warwick.ac.uk; Janik, Vit, E-mail: V.Janik@warwick.ac.uk; Rijkenberg, Arjan, E-mail: arjan.rijkenberg@tatasteel.com

In-situ characterization techniques have been applied to elucidate the influence of γ/α transformation upon the extent of interphase precipitation in a low-carbon, vanadium-HSLA steel. Electron Back-scattered diffraction analyses of the γ/α orientation relationship with continuous cooling at 2 and 10 K/s suggest that the proportion of ferrite likely to hold interphase precipitation varies little with cooling rate. However, TEM analyses show that the interphase precipitation refines with increasing cooling rate in this cooling range. With cooling rates in excess of 20 K/s, interphase precipitation is increasingly suppressed due to the increasingly diffusional-displacive nature of the Widmanstätten γ/α transformation that ismore » activated. The present study illustrates that the extent and dimensions of interphase precipitation can be controlled through controlled cooling. - Highlights: • In-situ characterization of γ/α transformation • EBSD characterization of γ/α transformation orientation relationship • Extent of interphase precipitation can be controlled through controlled cooling.« less

An integrated precipitation and ion-exchange chromatography process for antibody manufacturing: Process development strategy and continuous chromatography exploration.

PubMed

Großhans, Steffen; Wang, Gang; Fischer, Christian; Hubbuch, Jürgen

2018-01-19

In the past decades, research was carried out to find cost-efficient alternatives to Protein A chromatography as a capture step in monoclonal antibody (mAb) purification processes. In this work, polyethylene glycol (PEG) precipitation has shown promising results in the case of mAb yield and purity. Especially with respect to continuous processing, PEG precipitation has many advantages, like low cost of goods, simple setup, easy scalability, and the option to handle perfusion reactors. Nevertheless, replacing Protein A has the disadvantage of renouncing a platform unit operation as well. Furthermore, PEG precipitation is not capable of reducing high molecular weight impurities (HMW) like aggregates or DNA. To overcome these challenges, an integrated process strategy combining PEG precipitation with cation-exchange chromatography (CEX) for purification of a mAb is presented. This work discusses the process strategy as well as the associated fast, easy, and material-saving process development platform. These were implemented through the combination of high-throughput methods with empirical and mechanistic modeling. The strategy allows the development of a common batch process. Additionally, it is feasible to develop a continuous process. In the presented case study, a mAb provided from cell culture fluid (HCCF) was purified. The precipitation and resolubilization conditions as well as the chromatography method were optimized, and the mutual influence of all steps was investigated. A mAb yield of over 95.0% and a host cell protein (HCP) reduction of over 99.0% could be shown. At the same time, the aggregate level was reduced from 3.12% to 1.20% and the DNA level was reduced by five orders of magnitude. Furthermore, the mAb was concentrated three times to a final concentration of 11.9mg/mL. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Microstructural Evolution and the Precipitation Behavior in X90 Linepipe Steel During Isothermal Processing

NASA Astrophysics Data System (ADS)

Tian, Y.; Wang, H. T.; Wang, Z. D.; Misra, R. D. K.; Wang, G. D.

2018-03-01

Thermomechanical controlled processing of 560-MPa (X90) linepipe steel was simulated in the laboratory using a thermomechanical simulator to study the microstructural evolution and precipitation behavior during isothermal holding. The results indicated that martensite was obtained when the steels were isothermally held for 5 s at 700 °C. Subsequently, granular bainite and acicular ferrite transformation occurred with increased holding time. Different amount of polygonal ferrite formed after isothermally holding for 600-3600 s. Pearlite nucleated after isothermally holding for 3600 s. Precipitation occurred after isothermal holding for 5 s and continuous precipitation occurred at grain boundaries after isothermally holding for 600 s. After isothermally holding for 3600 s, large Nb/Ti carbide precipitated. The presence of MX-type precipitates was confirmed by diffraction pattern. The interphase precipitation (IP) occurred between 5 and 30 s. Maximum hardness was obtained after isothermally holding for 600 s when IP occurred and rapidly decreased to a low value, mainly because polygonal ferrite dominated the microstructure after isothermally holding for 3600 s.

Microstructural characterization and strengthening behavior of nanometer sized carbides in Ti–Mo microalloyed steels during continuous cooling process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Chih-Yuan, E-mail: chen6563@gmail.com; Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan; Yang, Jer-Ren, E-mail: jryang@ntu.edu.tw

Nanometer-sized carbides that precipitated in a Ti–Mo bearing steel after interrupted continuous cooling in a temperature range of 620–700 °C with or without hot deformation were investigated by field-emission-gun transmission electron microscopy. The nanometer-sized carbides were identified as randomly homogeneous precipitation carbides and interphase precipitation carbides coexisting in the ferrite matrix. It is found that this dual precipitation morphology of carbides in the steel leads to the non-uniform mechanical properties of individual ferrite grains. Vickers hardness data mainly revealed that, in the specimens cooled at a rate of 0.5 °C/s without hot deformation, the range of Vickers hardness distribution wasmore » 230–340 HV 0.1 when cooling was interrupted at 680 °C, and 220–360 HV 0.1 when cooling was interrupted at 650 °C. For the specimens cooled at a rate of 0.5 °C/s with hot deformation, the range of Vickers hardness distribution was 290–360 HV 0.1 when cooling was interrupted at 680 °C, and 280–340 HV 0.1 when cooling was interrupted at 650 °C. Therefore, a narrower range of hardness distribution occurred in the specimens that underwent hot deformation and were then cooled with a lower interrupted cooling temperature. The uniform precipitation status in each ferrite grain can lead to ferrite grains with a narrower Vickers hardness distribution. On the other hand, interrupted cooling produced a maximum Vickers hardness of 320–330 HV 0.1 for the hot deformed specimens and 290–310 HV 0.1 for the non-deformed specimens with cooling interrupted in the temperature range of 660–670 °C. The maximum Vickers hardness obtained in such a temperature range can be ascribed to the full precipitation of the microalloying elements in the supersaturated ferrite matrix with a tiny size (~ 4–7 nm). - Highlight: • The interrupted continuous cooling temperatures were 620 °C to 700 °C. • Precipitation carbides with dual dispersed morphology coexisted in the matrix. • Heavy hot deformation narrowed the range of hardness distribution. • Full precipitation of nano-sized carbides achieved maximum hardening.« less

Mars Science Laboratory relative humidity observations: Initial results.

PubMed

Harri, A-M; Genzer, M; Kemppinen, O; Gomez-Elvira, J; Haberle, R; Polkko, J; Savijärvi, H; Rennó, N; Rodriguez-Manfredi, J A; Schmidt, W; Richardson, M; Siili, T; Paton, M; Torre-Juarez, M De La; Mäkinen, T; Newman, C; Rafkin, S; Mischna, M; Merikallio, S; Haukka, H; Martin-Torres, J; Komu, M; Zorzano, M-P; Peinado, V; Vazquez, L; Urqui, R

2014-09-01

The Mars Science Laboratory (MSL) made a successful landing at Gale crater early August 2012. MSL has an environmental instrument package called the Rover Environmental Monitoring Station (REMS) as a part of its scientific payload. REMS comprises instrumentation for the observation of atmospheric pressure, temperature of the air, ground temperature, wind speed and direction, relative humidity (REMS-H), and UV measurements. We concentrate on describing the REMS-H measurement performance and initial observations during the first 100 MSL sols as well as constraining the REMS-H results by comparing them with earlier observations and modeling results. The REMS-H device is based on polymeric capacitive humidity sensors developed by Vaisala Inc., and it makes use of transducer electronics section placed in the vicinity of the three humidity sensor heads. The humidity device is mounted on the REMS boom providing ventilation with the ambient atmosphere through a filter protecting the device from airborne dust. The final relative humidity results appear to be convincing and are aligned with earlier indirect observations of the total atmospheric precipitable water content. The water mixing ratio in the atmospheric surface layer appears to vary between 30 and 75 ppm. When assuming uniform mixing, the precipitable water content of the atmosphere is ranging from a few to six precipitable micrometers. Atmospheric water mixing ratio at Gale crater varies from 30 to 140 ppmMSL relative humidity observation provides good dataHighest detected relative humidity reading during first MSL 100 sols is RH75.

Ion chromatographic methods for the detection of starch hydrolysis products in ruminal digesta.

PubMed

Barsuhn, K; Kotarski, S F

1991-06-21

Dionex high-performance ion chromatographic methods were evaluated for separation and quantitation of plant sugars and starch digestion products in the ruminal digesta of cattle. Mono- and disaccharides were eluted from a Dionex CarboPac PA1 column with sodium hydroxide used isocratically or as a pH gradient. Maltooligosaccharides which had a degree of polymerization (DP) less than 30 glucose residues were eluted in 60 min by a sodium hydroxide eluent containing a sodium acetate gradient. Carbohydrates were detected amperometrically. Responses were linear (r2 greater than 0.99) for glucose, disaccharides and maltooligosaccharides (DP less than 8). Precipitation and solid-phase extraction methods were evaluated for clean-up of samples of feedstuffs, ruminal contents, and bacterial culture fluids. Perchloric acid precipitation hydrolyzed sucrose but did not affect recoveries of cellobiose, isomaltose or maltose. Ethanol in concentrations of 79 and 86% precipitated maltooligosaccharides having chain lengths larger than 14 and 9 glucose residues, respectively. Maltooligosaccharide recoveries from solid-phase extraction columns varied with maltooligosaccharide size and column packing. Recoveries were greater than 94% for short chains (DP less than 6) eluted from phenyl-substituted columns and variable for all oligosaccharides eluted from C18 columns. Applications of these methods are presented and include: (1) detection of sugars in ruminant feed, (2) monitoring changes in ruminal sugars after feeding and (3) monitoring changes in extracellular sugars and oligosaccharides in the culture fluids of the ruminal bacterium, Bacteroides ruminicola.

Calcite Biomineralization by Bacterial Isolates from the Recently Discovered Pristine Karstic Herrenberg Cave

PubMed Central

Rusznyák, Anna; Akob, Denise M.; Nietzsche, Sándor; Eusterhues, Karin; Totsche, Kai Uwe; Neu, Thomas R.; Frosch, Torsten; Popp, Jürgen; Keiner, Robert; Geletneky, Jörn; Katzschmann, Lutz; Schulze, Ernst-Detlef

2012-01-01

Karstic caves represent one of the most important subterranean carbon storages on Earth and provide windows into the subsurface. The recent discovery of the Herrenberg Cave, Germany, gave us the opportunity to investigate the diversity and potential role of bacteria in carbonate mineral formation. Calcite was the only mineral observed by Raman spectroscopy to precipitate as stalactites from seepage water. Bacterial cells were found on the surface and interior of stalactites by confocal laser scanning microscopy. Proteobacteria dominated the microbial communities inhabiting stalactites, representing more than 70% of total 16S rRNA gene clones. Proteobacteria formed 22 to 34% of the detected communities in fluvial sediments, and a large fraction of these bacteria were also metabolically active. A total of 9 isolates, belonging to the genera Arthrobacter, Flavobacterium, Pseudomonas, Rhodococcus, Serratia, and Stenotrophomonas, grew on alkaline carbonate-precipitating medium. Two cultures with the most intense precipitate formation, Arthrobacter sulfonivorans and Rhodococcus globerulus, grew as aggregates, produced extracellular polymeric substances (EPS), and formed mixtures of calcite, vaterite, and monohydrocalcite. R. globerulus formed idiomorphous crystals with rhombohedral morphology, whereas A. sulfonivorans formed xenomorphous globular crystals, evidence for taxon-specific crystal morphologies. The results of this study highlighted the importance of combining various techniques in order to understand the geomicrobiology of karstic caves, but further studies are needed to determine whether the mineralogical biosignatures found in nutrient-rich media can also be found in oligotrophic caves. PMID:22179248

Mars Science Laboratory relative humidity observations: Initial results

PubMed Central

Harri, A-M; Genzer, M; Kemppinen, O; Gomez-Elvira, J; Haberle, R; Polkko, J; Savijärvi, H; Rennó, N; Rodriguez-Manfredi, JA; Schmidt, W; Richardson, M; Siili, T; Paton, M; Torre-Juarez, M De La; Mäkinen, T; Newman, C; Rafkin, S; Mischna, M; Merikallio, S; Haukka, H; Martin-Torres, J; Komu, M; Zorzano, M-P; Peinado, V; Vazquez, L; Urqui, R

2014-01-01

The Mars Science Laboratory (MSL) made a successful landing at Gale crater early August 2012. MSL has an environmental instrument package called the Rover Environmental Monitoring Station (REMS) as a part of its scientific payload. REMS comprises instrumentation for the observation of atmospheric pressure, temperature of the air, ground temperature, wind speed and direction, relative humidity (REMS-H), and UV measurements. We concentrate on describing the REMS-H measurement performance and initial observations during the first 100 MSL sols as well as constraining the REMS-H results by comparing them with earlier observations and modeling results. The REMS-H device is based on polymeric capacitive humidity sensors developed by Vaisala Inc., and it makes use of transducer electronics section placed in the vicinity of the three humidity sensor heads. The humidity device is mounted on the REMS boom providing ventilation with the ambient atmosphere through a filter protecting the device from airborne dust. The final relative humidity results appear to be convincing and are aligned with earlier indirect observations of the total atmospheric precipitable water content. The water mixing ratio in the atmospheric surface layer appears to vary between 30 and 75 ppm. When assuming uniform mixing, the precipitable water content of the atmosphere is ranging from a few to six precipitable micrometers. Key Points Atmospheric water mixing ratio at Gale crater varies from 30 to 140 ppm MSL relative humidity observation provides good data Highest detected relative humidity reading during first MSL 100 sols is RH75% PMID:26213667

Interpretation and modelling of fission product Ba and Mo releases from fuel

NASA Astrophysics Data System (ADS)

Brillant, G.

2010-02-01

The release mechanisms of two fission products (namely barium and molybdenum) in severe accident conditions are studied using the VERCORS experimental observations. Barium is observed to be mostly released under reducing conditions while molybdenum release is most observed under oxidizing conditions. As well, the volatility of some precipitates in fuel is evaluated by thermodynamic equilibrium calculations. The polymeric species (MoO 3) n are calculated to largely contribute to molybdenum partial pressure and barium volatility is greatly enhanced if the gas atmosphere is reducing. Analytical models of fission product release from fuel are proposed for barium and molybdenum. Finally, these models have been integrated in the ASTEC/ELSA code and validation calculations have been performed on several experimental tests.

Synthetic Strategies in the Preparation of Polymer/Inorganic Hybrid Nanoparticles

PubMed Central

Hood, Matthew A.; Mari, Margherita; Muñoz-Espí, Rafael

2014-01-01

This article reviews the recent advances and challenges in the preparation of polymer/inorganic hybrid nanoparticles. We mainly focus on synthetic strategies, basing our classification on whether the inorganic and the polymer components have been formed in situ or ex situ, of the hybrid material. Accordingly, four types of strategies are identified and described, referring to recent examples: (i) ex situ formation of the components and subsequent attachment or integration, either by covalent or noncovalent bonding; (ii) in situ polymerization in the presence of ex situ formed inorganic nanoparticles; (iii) in situ precipitation of the inorganic components on or in polymer structures; and (iv) strategies in which both polymer and inorganic component are simultaneously formed in situ. PMID:28788665

Chemical modification of magnetite nanoparticles and preparation of acrylic-base magnetic nanocomposite particles via miniemulsion polymerization

NASA Astrophysics Data System (ADS)

Mahdieh, Athar; Mahdavian, Ali Reza; Salehi-Mobarakeh, Hamid

2017-03-01

Nowadays, magnetic nanocomposite particles have attracted many interests because of their versatile applications. A new method for chemical modification of Fe3O4 nanoparticles with polymerizable groups is presented here. After synthesis of Fe3O4 nanoparticles by co-precipitation method, they were modified sequentially with 3-aminopropyl triethoxysilane (APTES), acryloyl chloride (AC) and benzoyl chloride (BC) and all were characterized by FTIR, XRD, SEM and TGA analyses. Then the modified magnetite nanoparticles with unsaturated acrylic groups were copolymerized with methyl methacrylate (MMA), butyl acrylate (BA) and acrylic acid (AA) through miniemulsion polymerization. Although several reports exist on preparation of magnetite-base polymer particles, but the efficiency of magnetite encapsulationwith reasonable content and obtaining final stable latexes with limited aggregation ofFe3O4 are still important issues. These were considered here by controlling reaction parameters. Hence, a seriesofmagneticnanocomposites latex particlescontaining different amounts of Fe3O4 nanoparticles (0-10 wt%) were prepared with core-shell morphology and diameter below 200 nm and were characterized by FT-IR, DSC and TGA analyses. Their morphology and size distribution were studied by SEM, TEM and DLS analyses too. Magnetic properties of all products were also measuredby VSM analysis and the results revealed almost superparamagnetic properties for the obtained nanocomposite particles.

Synergistically enhanced selective intracellular uptake of anticancer drug carrier comprising folic acid-conjugated hydrogels containing magnetite nanoparticles

NASA Astrophysics Data System (ADS)

Kim, Haneul; Jo, Ara; Baek, Seulgi; Lim, Daeun; Park, Soon-Yong; Cho, Soo Kyung; Chung, Jin Woong; Yoon, Jinhwan

2017-01-01

Targeted drug delivery has long been extensively researched since drug delivery and release at the diseased site with minimum dosage realizes the effective therapy without adverse side effects. In this work, to achieve enhanced intracellular uptake of anticancer drug carriers for efficient chemo-therapy, we have designed targeted multifunctional anticancer drug carrier hydrogels. Temperature-responsive poly(N-isopropylacrylamide) (PNIPAm) hydrogel core containing superparamagnetic magnetite nanoparticles (MNP) were prepared using precipitation polymerization, and further polymerized with amine-functionalized copolymer shell to facilitate the conjugation of targeting ligand. Then, folic acid, specific targeting ligand for cervical cancer cell line (HeLa), was conjugated on the hydrogel surface, yielding the ligand conjugated hybrid hydrogels. We revealed that enhanced intracellular uptake by HeLa cells in vitro was enabled by both magnetic attraction and receptor-mediated endocytosis, which were contributed by MNP and folic acid, respectively. Furthermore, site-specific uptake of the developed carrier was confirmed by incubating with several other cell lines. Based on synergistically enhanced intracellular uptake, efficient cytotoxicity and apoptotic activity of HeLa cells incubated with anticancer drug loaded hybrid hydrogels were successfully achieved. The developed dual-targeted hybrid hydrogels are expected to provide a platform for the next generation intelligent drug delivery systems.

Application of molecular imprinted polymer nanoparticles as a selective solid phase extraction for preconcentration and trace determination of 2,4-dichlorophenoxyacetic acid in the human urine and different water samples.

PubMed

Omidi, Fariborz; Behbahani, Mohammad; Sadeghi Abandansari, Hamid; Sedighi, Alireza; Shahtaheri, Seyed Jamaleddin

2014-01-01

A molecular-imprinted polymer nanoparticles (MIP-NP) for the selective preconcentration of 2,4-dichlorophenoxyacetic acid (2,4-D) is described. It was obtained by precipitation polymerization from methacrylic acid (the functional monomer), ethylene glycol dimethacrylate (the cross-linker), 2,2'-azobisisobutyronitrile (the initiator) and 2,4-D (the template molecule) in acetonitrile solution. The MIP-NPs were characterized by thermogravimetric analysis, and by scanning electron microscopy. Imprinted 2,4-D molecules were removed from the polymeric structure using acetic acid in methanol (15:85 v/v %) as the eluting solvent. The sorption and desorption process occur within 10 min and 15 min, respectively. The maximum sorbent capacity of the molecular imprinted polymer is 89.2 mg g(-1). The relative standard deviation and limit of detection for water samples by introduced selective solid phase extraction were 4.2% and 1.25 μg L(-1), and these data for urine samples were 4.7% and 1.80 μg L(-1), respectively. The method was applied to the determination of 2,4-D in the urine and different water samples.

Effect of leaching residual methyl methacrylate concentrations on in vitro cytotoxicity of heat polymerized denture base acrylic resin processed with different polymerization cycles

PubMed Central

BURAL, Canan; AKTAŞ, Esin; DENIZ, Günnur; ÜNLÜÇERÇI, Yeşim; BAYRAKTAR, Gülsen

2011-01-01

Objectives Residual methyl methacrylate (MMA) may leach from the acrylic resin denture bases and have adverse effects on the oral mucosa. This in vitro study evaluated and correlated the effect of the leaching residual MMA concentrations ([MMA]r) on in vitro cytotoxicity of L-929 fibroblasts. Material and Methods A total of 144 heat-polymerized acrylic resin specimens were fabricated using 4 different polymerization cycles: (1) at 74ºC for 9 h, (2) at 74ºC for 9 h and terminal boiling (at 100ºC) for 30 min, (3) at 74ºC for 9 h and terminal boiling for 3 h, (4) at 74ºC for 30 min and terminal boiling for 30 min. Specimens were eluted in a complete cell culture medium at 37ºC for 1, 2, 5 and 7 days. [MMA]r in eluates was measured using high-performance liquid chromatography. In vitro cytotoxicity of eluates on L-929 fibroblasts was evaluated by means of cell proliferation using a tetrazolium salt XTT (sodium 3´-[1-phenyl-aminocarbonyl)-3,4-tetrazolium]bis(4-methoxy-6-nitro)benzenesulphonic acid) assay. Differences in [MMA]r of eluates and cell proliferation values between polymerization cycles were statistically analyzed by Kruskal-Wallis, Friedman and Dunn's multiple comparison tests. The correlation between [MMA]r of eluates and cell proliferation was analyzed by Pearson's correlation test (p<0.05). Results [MMA]r was significantly (p≤0.001) higher in eluates of specimens polymerized with cycle without terminal boiling after elution of 1 and 2 days. Cell proliferation values for all cycles were significantly (p<0.01) lower in eluates of 1 day than those of 2 days. The correlation between [MMA]r and cell proliferation values was negative after all elution periods, showing significance (p<0.05) for elution of 1 and 2 days. MMA continued to leach from acrylic resin throughout 7 days and leaching concentrations markedly reduced after elution of 1 and 2 days. Conclusion Due to reduction of leaching residual MMA concentrations, use of terminal boiling in the polymerization process for at least 30 min and water storage of the heat-polymerized denture bases for at least 1 to 2 days before denture delivery is clinically recommended for minimizing the residual MMA and possible cytotoxic effects. PMID:21956586

Systematic recover of long high-resolution rainfall time series recorded by pluviographs during the 20th century.

NASA Astrophysics Data System (ADS)

Delitala, Alessandro M. S.; Deidda, Roberto; Mascaro, Giuseppe; Piga, Enrico; Querzoli, Giorgio

2010-05-01

During most of the 20th century, precipitation has been continuously measured by means of the so-called "pluviographs", i.e. rain gauges including a mechanical apparatus for continuously recording the depth of water from precipitation on specific strip charts, usually on a weekly basis. The signal recorded on such strips was visually examined by trained personnel on a regular basis, in order to extract the daily precipitation totals and the maximum precipitation intensities over short periods (from a few minutes to hours). The rest of the high-resolution information contained in the signal was usually not extracted, except for specific cases. A systematic recovering of the entire information at high temporal resolution contained in these precipitation signals would provide a fundamental database to improve the characterization of historical rainfall climatology during the previous century. The Department of Land Engineering of the University of Cagliari has recently developed and tested an automatic software, based on image analysis techniques, which is able to acquire the scanned images of the pluviograph strip charts, to automatically digitise the signal and to produce a digital database of continuous precipitation records at the highest possible temporal resolution, i.e. 5 to 10 minutes. Along with that, a significant amount of daily precipitation totals from the late 19th and the 20th century, either elaborated from pluviograph strip charts or simply derived from bucket rain gauges, still exists in paper form, but it has never been digitalized. Within a project partly-funded by the Operational Programme of the European Union "Italia-Francia Marittimo", the Regional Environmental Protection Agency of Sardinia and the University of Cagliari will recover both the high-resolution rainfall signals and the older time series of daily totals recorded by a large number of pluviographs belonging to the historical monitoring networks of the island of Sardinia. Such data will then be used to construct the high-resolution climatology of precipitation over Sardinia, both assuming stationary climate and slowly varying climate. Specific attention will be devoted to a set of critical hydrological basins, often affected by intense precipitation and flash floods. All information will then be made available to researchers, regional officers, technicians (e.g. hydraulic engineers) and the greater public interested into such information. The present poster describes the general scope of the E.U. project and the specific activities in the field of climatology of Sardinia rainfall that will be conducted as well as the expected results. A section will be dedicated to show how the pluviograph strips are automatically digitized.

Continuous microfluidic assembly of biodegradable poly(beta-amino ester)/DNA nanoparticles for enhanced gene delivery.

PubMed

Wilson, David R; Mosenia, Arman; Suprenant, Mark P; Upadhya, Rahul; Routkevitch, Denis; Meyer, Randall A; Quinones-Hinojosa, Alfredo; Green, Jordan J

2017-06-01

Translation of biomaterial-based nanoparticle formulations to the clinic faces significant challenges including efficacy, safety, consistency and scale-up of manufacturing, and stability during long-term storage. Continuous microfluidic fabrication of polymeric nanoparticles has the potential to alleviate the challenges associated with manufacture, while offering a scalable solution for clinical level production. Poly(beta-amino esters) (PBAE)s are a class of biodegradable cationic polymers that self-assemble with anionic plasmid DNA to form polyplex nanoparticles that have been shown to be effective for transfecting cancer cells specifically in vitro and in vivo. Here, we demonstrate the use of a microfluidic device for the continuous and scalable production of PBAE/DNA nanoparticles followed by lyophilization and long term storage that results in improved in vitro efficacy in multiple cancer cell lines compared to nanoparticles produced by bulk mixing as well as in comparison to widely used commercially available transfection reagents polyethylenimine and Lipofectamine® 2000. We further characterized the nanoparticles using nanoparticle tracking analysis (NTA) to show that microfluidic mixing resulted in fewer DNA-free polymeric nanoparticles compared to those produced by bulk mixing. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1813-1825, 2017. © 2017 Wiley Periodicals, Inc.

Continuous treatment of N-Methyl-p-nitro aniline (MNA) in an Upflow Anaerobic Sludge Blanket (UASB) bioreactor

PubMed Central

Olivares, Christopher I.; Wang, Junqin; Silva Luna, Carlos D.; Field, Jim A.; Abrell, Leif; Sierra-Alvarez, Reyes

2017-01-01

N-methyl-p-nitroaniline (MNA) is an ingredient of insensitive munitions (IM) compounds that serves as a plasticizer and helps reduce unwanted detonations. As its use becomes widespread, MNA waste streams will be generated, necessitating viable treatment options. We studied MNA biodegradation and its inhibition potential to, a representative anaerobic microbial population in wastewater treatment, methanogens. Anaerobic biodegradation and toxicity assays were performed and an up-flow anaerobic sludge blanket reactor (UASB) was operated to test continuous degradation of MNA. MNA was transformed almost stoichiometrically to N-methyl-p-phenylenediamine (MPD). MPD was not mineralized, however, it was readily autoxidized and polymerized extensively upon aeration at pH = 9. In the UASB reactor, MNA was fully degraded up to a loading rate of 297.5 μM MNA d-1). Regarding toxicity, MNA was very inhibitory to acetoclastic methanogens (IC50 = 103 μM) whereas MPD was much less toxic, causing only 13.9% inhibition at the highest concentration tested (1025 μM). The results taken as a whole indicate that anaerobic sludge can transform MNA to MPD continuously, and that the transformation decreases the cytotoxicity of the parent pollutant. MPD can be removed through extensive polymerization. These insights could help define efficient treatment options for waste streams polluted with MNA. PMID:26454121

Polymerization kinetics of wheat gluten upon thermosetting. A mechanistic model.

PubMed

Domenek, Sandra; Morel, Marie-Hélène; Bonicel, Joëlle; Guilbert, Stéphane

2002-10-09

Size exclusion high-performance liquid chromatography analysis was carried out on wheat gluten-glycerol blends subjected to different heat treatments. The elution profiles were analyzed in order to follow the solubility loss of protein fractions with specific molecular size. Owing to the known biochemical changes involved during the heat denaturation of gluten, a mechanistic mathematical model was developed, which divided the protein denaturation into two distinct reaction steps: (i) reversible change in protein conformation and (ii) protein precipitation through disulfide bonding between initially SDS-soluble and SDS-insoluble reaction partners. Activation energies of gluten unfolding, refolding, and precipitation were calculated with the Arrhenius law to 53.9 kJ x mol(-1), 29.5 kJ x mol(-1), and 172 kJ x mol(-1), respectively. The rate of protein solubility loss decreased as the cross-linking reaction proceeded, which may be attributed to the formation of a three-dimensional network progressively hindering the reaction. The enhanced susceptibility to aggregation of large molecules was assigned to a risen reaction probability due to their higher number of cysteine residues and to the increased percentage of unfolded and thereby activated proteins as complete protein refolding seemed to be an anticooperative process.

Design and Synthesis of Network-Forming Triblock Copolymers Using Tapered Block Interfaces

PubMed Central

Kuan, Wei-Fan; Roy, Raghunath; Rong, Lixia; Hsiao, Benjamin S.; Epps, Thomas H.

2012-01-01

We report a strategy for generating novel dual-tapered poly(isoprene-b-isoprene/styrene-b-styrene-b-styrene/methyl methacrylate-b-methyl methacrylate) [P(I-IS-S-SM-M)] triblock copolymers that combines anionic polymerization, atom transfer radical polymerization (ATRP), and Huisgen 1,3-dipolar cycloaddition click chemistry. The tapered interfaces between blocks were synthesized via a semi-batch feed using programmable syringe pumps. This strategy allows us to manipulate the transition region between copolymer blocks in triblock copolymers providing control over the interfacial interactions in our nanoscale phase-separated materials independent of molecular weight and block constituents. Additionally, we show the ability to retain a desirous and complex multiply-continuous network structure (alternating gyroid) in our dual-tapered triblock material. PMID:23066522

Low resolution radar digital interface. [with data recorder for precipitation measurements

NASA Technical Reports Server (NTRS)

1973-01-01

This document describes the design and operation of a low resolution radar data recording system for precipitation measurements. This system records a full azimuth scan on seven track magnetic tapes every five minutes. It is designed to operate on a continuous basis with operator intervention required only for changing tape reels and calibration.

Precipitation from Space: Advancing Earth System Science

NASA Technical Reports Server (NTRS)

Kucera, Paul A.; Ebert, Elizabeth E.; Turk, F. Joseph; Levizzani, Vicenzo; Kirschbaum, Dalia; Tapiador, Francisco J.; Loew, Alexander; Borsche, M.

2012-01-01

Of the three primary sources of spatially contiguous precipitation observations (surface networks, ground-based radar, and satellite-based radar/radiometers), only the last is a viable source over ocean and much of the Earth's land. As recently as 15 years ago, users needing quantitative detail of precipitation on anything under a monthly time scale relied upon products derived from geostationary satellite thermal infrared (IR) indices. The Special Sensor Microwave Imager (SSMI) passive microwave (PMW) imagers originated in 1987 and continue today with the SSMI sounder (SSMIS) sensor. The fortunate longevity of the joint National Aeronautics and Space Administration (NASA) and Japan Aerospace Exploration Agency (JAXA) Tropical Rainfall Measuring Mission (TRMM) is providing the environmental science community a nearly unbroken data record (as of April 2012, over 14 years) of tropical and sub-tropical precipitation processes. TRMM was originally conceived in the mid-1980s as a climate mission with relatively modest goals, including monthly averaged precipitation. TRMM data were quickly exploited for model data assimilation and, beginning in 1999 with the availability of near real time data, for tropical cyclone warnings. To overcome the intermittently spaced revisit from these and other low Earth-orbiting satellites, many methods to merge PMW-based precipitation data and geostationary satellite observations have been developed, such as the TRMM Multisatellite Precipitation Product and the Climate Prediction Center (CPC) morphing method (CMORPH. The purpose of this article is not to provide a survey or assessment of these and other satellite-based precipitation datasets, which are well summarized in several recent articles. Rather, the intent is to demonstrate how the availability and continuity of satellite-based precipitation data records is transforming the ways that scientific and societal issues related to precipitation are addressed, in ways that would not be otherwise possible. These developments have taken place in parallel with the growth of an increasingly interconnected scientific environment. Scientists from different disciplines can easily interact with each other via information and materials they encounter online, and collaborate remotely without ever meeting each other in person. Likewise, these precipitation datasets are quickly and easily available via various data portals and are widely used. Within the framework of the NASA/JAXA Global Precipitation Measurement (GPM mission, these applications will become increasingly interconnected. We emphasize that precipitation observations by themselves provide an incomplete picture of the state of the atmosphere. For example, it is unlikely that a richer understanding of the global water cycle will be possible by standalone missions and algorithms, but must also involve some component of data, where model analyses of the physical state are constrained alongside multiple observations (e.g., precipitation, evaporation, radiation). The next section provides examples extracted from the many applications that use various high-resolution precipitation products. The final section summarizes the future system for global precipitation processing.

Corrosion performance of 7075 alloy under laser heat treatment

NASA Astrophysics Data System (ADS)

Liu, Tong; Su, Ruiming; Qu, Yingdong; Li, Rongde

2018-05-01

Microstructure, exfoliation corrosion (EXCO), intergranular corrosion (IGC) and potentidynamic polarization test of the 7075 aluminum alloy after retrogression and re-aging (RRA) treatment, and laser retrogression and re-aging (LRRA), respectively, were studied by using scanning electron microscope, and transmission electron microscope (TEM). The results show that after pre-aging, laser treatment (650 W, 2 mm s‑1) and re-aging a lot of matrix precipitates of alloy were precipitated again. The semi-continuous grain boundary precipitates and the wider precipitate-free zones (PFZ) improve the corrosion resistance of the alloy. The corrosion properties of the alloy after LRRA (650 W, 2 mm s‑1) treatment are better than that after RRA treatment.

Highly Efficient and Facile Photocatalytic Recycling System Suitable for ICAR ATRP of Hydrophilic Monomers.

PubMed

Jiang, Xiaowu; Zhang, Lifen; Cheng, Zhenping; Zhu, Xiulin

2016-08-01

Photoinduced initiators for continuous activator regeneration atom transfer radical polymerization (ATRP) of hydrophilic monomers in heptane/ethanol latent-biphasic system for copper catalyst separation and recycling have been realized for the first time at room temperature with different wavelengths of visible light LED (green, blue, purple, and white LED) as external stimulus, using 2-bromophenylacetate as the ATRP initiator and camphorquinone/triethylamine as the photoinitiator. In this system, hybrid catalyst complex (HCc) is synthesized as a novel nonpolar catalyst, which is preferentially dissolved in heptane. The hydrophilic polymers obtained catalyzed by HCc in heptane/ethanol mixture solvent show typical "living" features, for example, the values of Mn,GPC increase linearly with monomer conversion up to quantitative level (>96%) and the molecular weight distributions were kept narrow (Mw /Mn < 1.20) throughout the polymerization process. It should be noted that the excellent controllability of this novel polymerization system can be achieved even after 5 catalyst recycling experiments under LED irradiation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct dry transfer of CVD graphene to an optical substrate by in situ photo-polymerization

NASA Astrophysics Data System (ADS)

Kessler, Felipe; Muñoz, Pablo A. R.; Phelan, Ciaran; Romani, Eric C.; Larrudé, Dunieskys R. G.; Freire, Fernando L.; Thoroh de Souza, Eunézio A.; de Matos, Christiano J. S.; Fechine, Guilhermino J. M.

2018-05-01

Here, we report on a method that allows graphene produced by chemical vapor deposition (CVD) to be directly transferred to an optically transparent photo resin, by in situ photo-polymerization of the latter, with high efficiency and low contamination. Two photocurable resins, A and B, with different viscosities but essentially the same chemical structure, were used. Raman spectroscopy and surface energy results show that large continuous areas of graphene were transferred with minimal defects to the lower viscosity resin (B), due to the better contact between the resin and graphene. As a proof-of-principle optical experiment, graphene on the polymeric substrate was subjected to high-intensity femtosecond infrared pulses and third-harmonic generation was observed with no noticeable degradation of the sample. A sheet third-order susceptibility χ (3) = 0.71 ×10-28m3V-2 was obtained, matching that of graphene on a glass substrate. These results indicate the suitability of the proposed transfer method, and of the photo resin, for the production of nonlinear photonic components and devices.

Composite plasma polymerized sulfonated polystyrene membrane for PEMFC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nath, Bhabesh Kumar; Khan, Aziz; Chutia, Joyanti, E-mail: jchutiaiasst@gmail.com

2015-10-15

Highlights: • Methyl methane sulfonate (MMS) is used as the sulfonating agent. • The proton conductivity of the membrane is found to be 0.141 S cm{sup −1}. • Power density of fuel cell with styrene/MMS membrane is 0.5 W cm{sup −2}. • The membrane exhibits thermal stability up to 140 °C. - Abstract: This work presents the introduction of an organic compound methyl methane sulfonate (MMS) for the first time in fabrication of polystyrene based proton exchange membrane (PEM) by plasma polymerization process. The membrane is fabricated by co-polymerizing styrene and MMS in capacitively coupled continuous RF plasma. The chemicalmore » composition of the plasma polymerized polymer membrane is investigated using Fourier Transform Infrared Spectroscopy which reveals the formation of composite structure of styrene and MMS. The surface morphology studied using AFM and SEM depicts the effect of higher partial pressure of MMS on surface topography of the membrane. The proton transport property of the membrane studied using electrochemical impedance spectroscopy shows the achievement of maximum proton conductivity of 0.141 S cm{sup −1} which is comparable to Nafion 117 membrane. Fuel cell performance test of the synthesized membrane shows a maximum power density of 500 mW cm{sup −2} and current density of 0.62 A cm{sup −2} at 0.6 V.« less

Surface morphology control of cross-linked polymer particles via dispersion polymerization.

PubMed

Peng, Bo; Imhof, Arnout

2015-05-14

Cross-linked polymer colloids (poly(methyl methacrylate) and polystyrene) with diverse shapes were prepared in polar solvents (ethanol, methanol and water) via dispersion polymerization, in which a linear addition of the cross-linker was used during reaction. Apart from spherical particles we found dented spheres or particles covered with nodules, or a combination of both. A comprehensive investigation was carried out, mainly concentrating on the effect of the experimental conditions (e.g., the addition start time and total addition time, cross-linker density and the solvency of the solvents) on particle morphologies. Consequently, we suggest a number of effective ways for the synthesis of regular (spherical) colloidal particles through maintaining a relatively low concentration of the cross-linker during the entire reaction, or forcing the co-polymerization (of monomer and cross-linker) locus to the continuous medium, or using a high quality or quantity of the stabilizer. Moreover, the size of the particles was also precisely manipulated by varying the polarity of the solvents, the concentration of the cross-linker, and the amount and average molecular weight of the stabilizer. In addition, the formation of the heavily dented particles with a very rough surface prepared under a pure or oxygen-'contaminated' nitrogen environment was monitored over time. The results accumulated in this article are of use for a better understanding of the mechanism of the polymerization and control over the structure and property of polymer particles.

Recycling WEEE: Polymer characterization and pyrolysis study for waste of crystalline silicon photovoltaic modules.

PubMed

Dias, Pablo; Javimczik, Selene; Benevit, Mariana; Veit, Hugo

2017-02-01

Photovoltaic (PV) modules contain both valuable and hazardous materials, which makes its recycling meaningful economically and environmentally. In general, the recycling of PV modules starts with the removal of the polymeric ethylene-vinyl acetate (EVA) resin using pyrolysis, which assists in the recovery of materials such as silicon, copper and silver. The pyrolysis implementation, however, needs improvement given its importance. In this study, the polymers in the PV modules were characterized by Fourier transform infrared spectroscopy (FTIR) and the removal of the EVA resin using pyrolysis has been studied and optimized. The results revealed that 30min pyrolysis at 500°C removes >99% of the polymers present in photovoltaic modules. Moreover, the behavior of different particle size milled modules during the pyrolysis process was evaluated. It is shown that polymeric materials tend to remain at a larger particle size and thus, this fraction has the greatest mass loss during pyrolysis. A thermo gravimetric analysis (TGA) performed in all polymeric matter revealed the optimum pyrolysis temperature is around 500°C. Temperatures above 500°C continue to degrade matter, but mass loss rate is 6.25 times smaller. This study demonstrates the use of pyrolysis can remove >99% of the polymeric matter from PV modules, which assists the recycling of this hazardous waste and avoids its disposal. Copyright © 2016 Elsevier Ltd. All rights reserved.

Polymeric micellar pH-sensitive drug delivery system for doxorubicin.

PubMed

Hrubý, Martin; Konák, Cestmír; Ulbrich, Karel

2005-03-02

A novel polymeric micellar pH-sensitive system for delivery of doxorubicin (DOX) is described. Polymeric micelles were prepared by self-assembly of amphiphilic diblock copolymers in aqueous solutions. The copolymers consist of a biocompatible hydrophilic poly(ethylene oxide) (PEO) block and a hydrophobic block containing covalently bound anthracycline antibiotic DOX. The starting block copolymers poly(ethylene oxide)-block-poly(allyl glycidyl ether) (PEO-PAGE) with a very narrow molecular weight distribution (Mw/Mn ca. 1.05) were prepared by anionic ring opening polymerization using sodium salt of poly(ethylene oxide) monomethyl ether as macroinitiator and allyl glycidyl ether as functional monomer. The copolymers were covalently modified via reactive double bonds by the addition of methyl sulfanylacetate. The resulting ester subsequently reacted with hydrazine hydrate yielding polymer hydrazide. The hydrazide was coupled with DOX yielding pH-sensitive hydrazone bonds between the drug and carrier. The resulting conjugate containing ca. 3 wt.% DOX forms micelles with Rh(a)=104 nm in phosphate-buffered saline. After incubation in buffers at 37 degrees C DOX was released faster at pH 5.0 (close to pH in endosomes; 43% DOX released within 24 h) than at pH 7.4 (pH of blood plasma; 16% DOX released within 24 h). Cleavage of hydrazone bonds between DOX and carrier continues even after plateau in the DOX release from micelles incubated in aqueous solutions is reached.

LACCASE Is Necessary and Nonredundant with PEROXIDASE for Lignin Polymerization during Vascular Development in Arabidopsis[C][W

PubMed Central

Zhao, Qiao; Nakashima, Jin; Chen, Fang; Yin, Yanbin; Fu, Chunxiang; Yun, Jianfei; Shao, Hui; Wang, Xiaoqiang; Wang, Zeng-Yu; Dixon, Richard A.

2013-01-01

The evolution of lignin biosynthesis was critical in the transition of plants from an aquatic to an upright terrestrial lifestyle. Lignin is assembled by oxidative polymerization of two major monomers, coniferyl alcohol and sinapyl alcohol. Although two recently discovered laccases, LAC4 and LAC17, have been shown to play a role in lignin polymerization in Arabidopsis thaliana, disruption of both genes only leads to a relatively small change in lignin content and only under continuous illumination. Simultaneous disruption of LAC11 along with LAC4 and LAC17 causes severe plant growth arrest, narrower root diameter, indehiscent anthers, and vascular development arrest with lack of lignification. Genome-wide transcript analysis revealed that all the putative lignin peroxidase genes are expressed at normal levels or even higher in the laccase triple mutant, suggesting that lignin laccase activity is necessary and nonredundant with peroxidase activity for monolignol polymerization during plant vascular development. Interestingly, even though lignin deposition in roots is almost completely abolished in the lac11 lac4 lac17 triple mutant, the Casparian strip, which is lignified through the activity of peroxidase, is still functional. Phylogenetic analysis revealed that lignin laccase genes have no orthologs in lower plant species, suggesting that the monolignol laccase genes diverged after the evolution of seed plants. PMID:24143805

21 CFR 700.14 - Use of vinyl chloride as an ingredient, including propellant of cosmetic aerosol products.

Code of Federal Regulations, 2010 CFR

2010-04-01

..., DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) COSMETICS GENERAL Requirements for Specific Cosmetic... inhaled at high concentrations. Studies also demonstrate carcinogenic effects in animals as a result of..., including liver cancer, in workers engaged in the polymerization of vinyl chloride. It is the view of the...

40 CFR 63.11395 - What are the standards and compliance requirements for existing sources?

Code of Federal Regulations, 2013 CFR

2013-07-01

... routine and long-term maintenance) and continuous monitoring system. (4) A list of operating parameters... polymerization process equipment and monomer recovery process equipment and convey the collected gas stream.... (2) 0.05 lb/hr of AN from the control device for monomer recovery process equipment. (3) If you do...

40 CFR 63.11395 - What are the standards and compliance requirements for existing sources?

Code of Federal Regulations, 2012 CFR

2012-07-01

... routine and long-term maintenance) and continuous monitoring system. (4) A list of operating parameters... polymerization process equipment and monomer recovery process equipment and convey the collected gas stream.... (2) 0.05 lb/hr of AN from the control device for monomer recovery process equipment. (3) If you do...

40 CFR 63.11395 - What are the standards and compliance requirements for existing sources?

Code of Federal Regulations, 2014 CFR

2014-07-01

... routine and long-term maintenance) and continuous monitoring system. (4) A list of operating parameters... polymerization process equipment and monomer recovery process equipment and convey the collected gas stream.... (2) 0.05 lb/hr of AN from the control device for monomer recovery process equipment. (3) If you do...

40 CFR 60.741 - Definitions, symbols, and cross-reference tables.

Code of Federal Regulations, 2010 CFR

2010-07-01

... prepolymers to a supporting web other than paper, plastic film, metallic foil, or metal coil. Substrate means... (i) entering the emission control device, in dry standard cubic meters per hour when Method 18 or 25... coats a continuous web to produce a substrate with a polymeric coating. Should the coating process not...

Effects of Bovine Polymerized Hemoglobin in Coagulation in Controlled Hemorrhagic Shock in Swine

DTIC Science & Technology

2005-01-01

continuous blood pressure monitoring. A pulmonary artery catheter was also inserted. To mimic soft tissue injury, the rectus abdominus muscle was crushed in...volume by catheter withdrawal of blood over 15 min (;1.7 mL/kg/min). Time 0 designated initiation of the rectus abdominus crush and concomitant hemorrhage

On the Coupling between Recrystallization and Precipitation Following Hot Deformation in a γ-γ' Nickel-Based Superalloy

NASA Astrophysics Data System (ADS)

Seret, Anthony; Moussa, Charbel; Bernacki, Marc; Bozzolo, Nathalie

2018-06-01

Postdynamic recrystallization and γ' precipitation during cooling from γ' supersolvus temperature after hot compression were studied in the AD730 (AD730 is a trademark of Aubert et Duval Company in Paris, France) γ-γ' nickel-based superalloy. Emphasis was on not only both phenomena as distinct mechanisms but also on their mutual influence in terms of physical mechanisms. The growth of γ' precipitates is hastened in the unrecrystallized grains compared to the recrystallized ones. This could possibly be attributed to the higher dislocation content acting as high-diffusivity paths. Postdynamic recrystallization is not prevented by Smith-Zener pinning of the recrystallization front by the γ' precipitates. Instead, the recrystallization front dissolves γ' precipitates, which then reprecipitate discontinuously or continuously and coherently with the surrounding γ matrix in the recrystallized grains.

Modification of linear prepolymers to tailor heterogeneous network formation through photo-initiated Polymerization-Induced Phase Separation

PubMed Central

Szczepanski, Caroline R.; Stansbury, Jeffrey W.

2015-01-01

Polymerization-induced phase separation (PIPS) was studied in ambient photopolymerizations of triethylene glycol dimethacrylate (TEGDMA) modified by poly(methyl methacrylate) (PMMA). The molecular weight of PMMA and the rate of network formation (through incident UV-irradiation) were varied to influence both the promotion of phase separation through increases in overall free energy, as well as the extent to which phase development occurs during polymerization through diffusion prior to network gelation. The overall free energy of the polymerizing system increases with PMMA molecular weight, such that PIPS is promoted thermodynamically at low loading levels (5 wt%) of a higher molecular weight PMMA (120 kDa), while a higher loading level (20 wt%) is needed to induce PIPS with lower PMMA molecular weight (11 kDa), and phase separation was not promoted at any loading level tested of the lowest molecular weight PMMA (1 kDa). Due to these differences in overall free energy, systems modified by PMMA (11 kDa) underwent phase separation via Nucleation and Growth, and systems modified by PMMA (120 kDa), followed the Spinodal Decomposition mechanism. Despite differences in phase structure, all materials form a continuous phase rich in TEGDMA homopolymer. At high irradiation intensity (Io=20mW/cm2), the rate of network formation prohibited significant phase separation, even when thermodynamically preferred. A staged curing approach, which utilizes low intensity irradiation (Io=300µW/cm2) for the first ~50% of reaction to allow phase separation via diffusion, followed by a high intensity flood-cure to achieve a high degree of conversion, was employed to form phase-separated networks with reduced polymerization stress yet equivalent final conversion and modulus. PMID:26190865

Implications of a decrease in the precipitation area for the past and the future

NASA Astrophysics Data System (ADS)

Benestad, Rasmus E.

2018-04-01

The total area with 24 hrs precipitation has shrunk by 7% between 50°S–50°N over the period 1998–2016, according to the satellite-based Tropical Rain Measurement Mission data. A decrease in the daily precipitation area is an indication of profound changes in the hydrological cycle, where the global rate of precipitation is balanced by the global rate of evaporation. This decrease was accompanied by increases in total precipitation, evaporation, and wet-day mean precipitation. If these trends are real, then they suggest increased drought frequencies and more intense rainfall. Satellite records, however, may be inhomogeneous because they are synthesised from a number of individual missions with improved technology over time. A linear dependency was also found between the global mean temperature and the 50°S–50°N daily precipitation area with a slope value of ‑17 × 106 km 2/°C. This dependency was used with climate model simulations to make future projections which suggested a continued decrease that will strengthen in the future. The precipitation area evolves differently when the precipitation is accumulated over short and long time scales, however, and there has been a slight increase in the monthly precipitation area while the daily precipitation area decreased. An increase on monthly scale may indicate more pronounced variations in the rainfall patterns due to migrating rain-producing phenomena.

Detailed Analysis of Indian Summer Monsoon Rainfall Processes with Modern/High-Quality Satellite Observations

NASA Technical Reports Server (NTRS)

Smith, Eric A.; Kuo, Kwo-Sen; Mehta, Amita V.; Yang, Song

2007-01-01

We examine, in detail, Indian Summer Monsoon rainfall processes using modernhigh quality satellite precipitation measurements. The focus here is on measurements derived from three NASA cloud and precipitation satellite missionslinstruments (TRMM/PR&TMI, AQUNAMSRE, and CLOUDSATICPR), and a fourth TRMM Project-generated multi-satellite precipitation measurement dataset (viz., TRMM standard algorithm 3b42) -- all from a period beginning in 1998 up to the present. It is emphasized that the 3b42 algorithm blends passive microwave (PMW) radiometer-based precipitation estimates from LEO satellites with infi-ared (IR) precipitation estimates from a world network of CEO satellites (representing -15% of the complete space-time coverage) All of these observations are first cross-calibrated to precipitation estimates taken from standard TRMM combined PR-TMI algorithm 2b31, and second adjusted at the large scale based on monthly-averaged rain-gage measurements. The blended approach takes advantage of direct estimates of precipitation from the PMW radiometerequipped LEO satellites -- but which suffer fi-om sampling limitations -- in combination with less accurate IR estimates from the optical-infrared imaging cameras on GEO satellites -- but which provide continuous diurnal sampling. The advantages of the current technologies are evident in the continuity and coverage properties inherent to the resultant precipitation datasets that have been an outgrowth of these stable measuring and retrieval technologies. There is a wealth of information contained in the current satellite measurements of precipitation regarding the salient precipitation properties of the Indian Summer Monsoon. Using different datasets obtained from the measuring systems noted above, we have analyzed the observations cast in the form of: (1) spatially distributed means and variances over the hierarchy of relevant time scales (hourly I diurnally, daily, monthly, seasonally I intra-seasonally, and inter-annually), (2) time series at these different time scales taken as area-averages over the hierarchy of relevant space scales (Indian sub-Division, Indian sub-continent, and Circumambient Indian Ocean), (3) principal autocorrelation and cross-correlation structures over various monsoon space-time domains, (4) diurnally modulated amplitude-phase properties of rain rates over different monsoon space-time domains, (5) foremost rain rate probability distributions intrinsic to monsoon precipitation, and (6) behavior of extreme events including occurrences of flood and drought episodes throughout the course of inter-annual monsoon processes.

A Guide for Developing Standard Operating Job Procedures for the Tertiary Chemical Treatment - Lime Precipitation Process Wastewater Treatment Facility. SOJP No. 6.

ERIC Educational Resources Information Center

Petrasek, Al, Jr.

This guide describes the standard operating job procedures for the tertiary chemical treatment - lime precipitation process of wastewater treatment plants. Step-by-step instructions are given for pre-start up, start-up, continuous operation, and shut-down procedures. In addition, some theoretical material is presented along with some relevant…

Snowmelt runoff and water yield along elevation and temperature gradients in California's southern Sierra Nevada

Treesearch

Carolyn T. Hunsaker; Thomas W. Whitaker; Roger C. Bales

2012-01-01

Differences in hydrologic response across the rain-snow transition in the southern Sierra Nevada were studied in eight headwater catchments – the Kings River Experimental Watersheds – using continuous precipitation, snowpack, and streamflow measurements. The annual runoff ratio (discharge divided by precipitation) increased about 0.1 per 300 m of mean catchment...

A combination of electro-enzymatic catalysis and electrocoagulation for the removal of endocrine disrupting chemicals from water.

PubMed

Zhao, He; Zhang, Di; Du, Penghui; Li, Haitao; Liu, Chenming; Li, Yuping; Cao, Hongbin; Crittenden, John C; Huang, Qingguo

2015-10-30

We in this study investigated a novel electrochemical approach combining electro-enzyme and electrocoagulation to precipitate bisphenol A (BPA) from water containing humic acid (HA). Horseradish peroxidase was immobilized on the graphite felt of Ti electrode as HRP-GF/Ti cathode, with aluminum plate anode establishing a pair of working electrodes. BPA was 100% removed and the reduction of total organic carbon (TOC) reached 95.1% after 20-min sequencing treatment with the current density of 2.3 mA/cm(2). Real wastewater (TOC=28.76 mg/L, BPA=4.1 μg/L) also can achieve 94% BPA removal and 52% TOC reduction after sequencing treatment. Additionally, coupled electro-system with continuous flow only required energy of 0.016 kWh/m(3) to achieve simultaneous 90% BPA and 85% TOC removal. As indicated in the time-of-flight mass spectrometry and FTIR spectra, the electro-enzymatic process not only oxidized BPA into dimer and BPA-3,4-quinone, but also greatly altered the chemical and structural features of HA, where hydrophilic moieties (phenolic and alcohols) transformed into hydrophobic forms (ethers, quinone and aliphatic). These polymerized products were effectively separated from aquous solution during anodic electrocoagulation, leading to significant removal of BPA and TOC. Thus, the coupled process may provide a faster and less energy strategy to control certain emerging contaminants in water/wastewater treatment. Copyright © 2015 Elsevier B.V. All rights reserved.

A Semiempirical Model for Sigma-Phase Precipitation in Duplex and Superduplex Stainless Steels

NASA Astrophysics Data System (ADS)

Ferro, P.; Bonollo, F.

2012-04-01

Sigma phase is known to reduce the mechanical properties and corrosion resistance of duplex and superduplex stainless steels. Therefore, heat treatments and welding must be carefully performed so as to avoid the appearance of such a detrimental phase, and clearly, models suitable to faithfully predict σ-phase precipitation are very useful tools. Most fully analytical models are based on thermodynamic calculations whose agreement with experimental results is not always good, so that such models should be used for qualitative purposes only. Alternatively, it is possible to exploit semiempirical models, where time-temperature-transformation (TTT) diagrams are empirically determined for a given alloy and the continuous-cooling-transformation (CCT) diagram is calculated from the TTT diagram. In this work, a semiempirical model for σ-phase precipitation in duplex and superduplex stainless steels, under both isothermal and unisothermal conditions, is proposed. Model parameters are calculated from empirical data and CCT diagrams are obtained by means of the additivity rule, whereas experimental measurements for model validation are taken from the literature. This model gives a satisfactory estimation of σ-phase precipitates during both isothermal aging and the continuous cooling process.

InSAR constraints on soil moisture evolution after the March 2015 extreme precipitation event in Chile.

PubMed

Scott, C P; Lohman, R B; Jordan, T E

2017-07-07

Constraints on soil moisture can guide agricultural practices, act as input into weather, flooding and climate models and inform water resource policies. Space-based interferometric synthetic aperture radar (InSAR) observations provide near-global coverage, even in the presence of clouds, of proxies for soil moisture derived from the amplitude and phase content of radar imagery. We describe results from a 1.5 year-long InSAR time series spanning the March, 2015 extreme precipitation event in the hyperarid Atacama desert of Chile, constraining the immediate increase in soil moisture and drying out over the following months, as well as the response to a later, smaller precipitation event. The inferred temporal evolution of soil moisture is remarkably consistent between independent, overlapping SAR tracks covering a region ~100 km in extent. The unusually large rain event, combined with the extensive spatial and temporal coverage of the SAR dataset, present an unprecedented opportunity to image the time-evolution of soil characteristics over different surface types. Constraints on the timescale of shallow water storage after precipitation events are increasingly valuable as global water resources continue to be stretched to their limits and communities continue to develop in flood-prone areas.

Precipitation-snowmelt timing and snowmelt augmentation of large peak flow events, western Cascades, Oregon

NASA Astrophysics Data System (ADS)

Jennings, Keith; Jones, Julia A.

2015-09-01

This study tested multiple hydrologic mechanisms to explain snowpack dynamics in extreme rain-on-snow floods, which occur widely in the temperate and polar regions. We examined 26, 10 day large storm events over the period 1992-2012 in the H.J. Andrews Experimental Forest in western Oregon, using statistical analyses (regression, ANOVA, and wavelet coherence) of hourly snowmelt lysimeter, air and dewpoint temperature, wind speed, precipitation, and discharge data. All events involved snowpack outflow, but only seven events had continuous net snowpack outflow, including three of the five top-ranked peak discharge events. Peak discharge was not related to precipitation rate, but it was related to the 10 day sum of precipitation and net snowpack outflow, indicating an increased flood response to continuously melting snowpacks. The two largest peak discharge events in the study had significant wavelet coherence at multiple time scales over several days; a distribution of phase differences between precipitation and net snowpack outflow at the 12-32 h time scale with a sharp peak at π/2 radians; and strongly correlated snowpack outflow among lysimeters representing 42% of basin area. The recipe for an extreme rain-on-snow event includes persistent, slow melt within the snowpack, which appears to produce a near-saturated zone within the snowpack throughout the landscape, such that the snowpack may transmit pressure waves of precipitation directly to streams, and this process is synchronized across the landscape. Further work is needed to understand the internal dynamics of a melting snowpack throughout a snow-covered landscape and its contribution to extreme rain-on-snow floods.

40 CFR 60.471 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

.... Electrostatic precipitator (ESP) means an air pollution control device in which solid or liquid particulates in... suface. High velocity air filter (HVAF) means an air pollution control filtration device for the removal... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) STANDARDS OF...

40 CFR 60.471 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

.... Electrostatic precipitator (ESP) means an air pollution control device in which solid or liquid particulates in... suface. High velocity air filter (HVAF) means an air pollution control filtration device for the removal... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) STANDARDS OF...

40 CFR 60.471 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

.... Electrostatic precipitator (ESP) means an air pollution control device in which solid or liquid particulates in... suface. High velocity air filter (HVAF) means an air pollution control filtration device for the removal... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) STANDARDS OF...

40 CFR 60.471 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

.... Electrostatic precipitator (ESP) means an air pollution control device in which solid or liquid particulates in... suface. High velocity air filter (HVAF) means an air pollution control filtration device for the removal... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) STANDARDS OF...

40 CFR 60.471 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

.... Electrostatic precipitator (ESP) means an air pollution control device in which solid or liquid particulates in... suface. High velocity air filter (HVAF) means an air pollution control filtration device for the removal... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) STANDARDS OF...

The Impacts of Atmospheric Rivers on California's Extreme Precipitation

NASA Astrophysics Data System (ADS)

Asgari Lamjiri, M.; Dettinger, M. D.; Ralph, M.

2017-12-01

Atmospheric rivers (ARs) are long, narrow corridors of enhanced water vapor transport that are typically associated with extratropical cyclones. ARs can be beneficial and replenish water resources, be hazardous and cause damaging floods, or have a combination of hazardous and beneficial impacts. Thus, understanding hydrologic impacts of ARs can help to improve water reservoir management and enhance flood risk mitigation, especially in California where there is extremely large year-to-year variability in annual precipitation accumulations. At the continental scale, gridded hourly precipitation observations are used in this study to identify unique characteristics of precipitation events impacting the US west coast compared to other regions in the US; precipitation events are defined here as continuous periods of precipitation with at least 5 mm of accumulated precipitation. It is shown that on average, the US west coast receives the largest precipitation totals across the US; these extreme precipitation events are largely associated with the most persistent ARs. Within California, hourly precipitation observations from 200 sites are being analyzed to better understand distinct categories of ARs that dictate extreme precipitation in different regions of California. It is found that, on average, the north coast, northern Sierra, and the Transverse Ranges experience the largest precipitation events; north coast and northern Sierra precipitation events tend to be longer, whereas the Transverse Ranges generally experience higher maximum and event-averaged intensities. ARs contribute significantly to extreme precipitation events in all regions of California, particularly the north coast, northern Sierra, and the Transverse Ranges. ARs associated with extreme precipitation events across California are significantly more persistent and have higher integrated vapor transport intensities than those associated with non-extreme events. Composites of characteristics of ARs which yield extreme precipitation events in different regions of California are studied to categorize the most impactful ARs in each region.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilcox, Kevin R.; Shi, Zheng; Gherardi, Laureano A.

Climatic changes are altering Earth's hydrological cycle, resulting in altered precipitation amounts, increased interannual variability of precipitation, and more frequent extreme precipitation events. These trends will likely continue into the future, having substantial impacts on net primary productivity (NPP) and associated ecosystem services such as food production and carbon sequestration. Frequently, experimental manipulations of precipitation have linked altered precipitation regimes to changes in NPP. Yet, findings have been diverse and substantial uncertainty still surrounds generalities describing patterns of ecosystem sensitivity to altered precipitation. Additionally, we do not know whether previously observed correlations between NPP and precipitation remain accurate when precipitationmore » changes become extreme. We synthesized results from 83 case studies of experimental precipitation manipulations in grasslands worldwide. Here, we used meta-analytical techniques to search for generalities and asymmetries of aboveground NPP (ANPP) and belowground NPP (BNPP) responses to both the direction and magnitude of precipitation change. Sensitivity (i.e., productivity response standardized by the amount of precipitation change) of BNPP was similar under precipitation additions and reductions, but ANPP was more sensitive to precipitation additions than reductions; this was especially evident in drier ecosystems. Additionally, overall relationships between the magnitude of productivity responses and the magnitude of precipitation change were saturating in form. The saturating form of this relationship was likely driven by ANPP responses to very extreme precipitation increases, although there were limited studies imposing extreme precipitation change, and there was considerable variation among experiments. Finally, this highlights the importance of incorporating gradients of manipulations, ranging from extreme drought to extreme precipitation increases into future climate change experiments. Additionally, policy and land management decisions related to global change scenarios should consider how ANPP and BNPP responses may differ, and that ecosystem responses to extreme events might not be predicted from relationships found under moderate environmental changes.« less

Process intensification for the production of hydroxyapatite nanoparticles

NASA Astrophysics Data System (ADS)

Castro, Filipa Juliana Fernandes

Precipitation processes are widely used in chemical industry for the production of particulate solids. In these processes, the chemical and physical nature of synthesized particles is of key importance. The traditional stirred tank batch reactors are affected by non-uniform mixing of reactants, often resulting in broad particle size distribution. The main objective of this thesis was to apply meso and microreactors for the synthesis of hydroxyapatite (HAp) nanoparticles under near-physiological conditions of pH and temperature, in order to overcome the limitations associated with stirred tank batch reactors. Meso and microreactors offer unique features in comparison with conventional chemical reactors. Their high surface-to-volume ratio enables enhanced heat and mass transfer, as well as rapid and efficient mixing. In addition to low consumption of reagents, meso and microreactors are usually operated in continuous flow, making them attractive tools for high throughput experimentation. Precipitation of HAp was first studied in a stirred tank batch reactor, mixing being assured by a novel metal stirrer. HAp was synthetized by mixing diluted aqueous solutions of calcium hydroxide and orthophosphoric acid at 37 °C. After process optimization, a suspension of HAp nanoparticles with pH close to 7 was obtained for a mixing molar ratio Ca/P=1.33. The precipitation process was characterized by three stages: precipitation of amorphous calcium phosphate, transformation of amorphous calcium phosphate into HAp and growth of HAp crystals. The reaction system was further characterized based on equilibrium equations. The resolution of the system, which was possible with the knowledge of three process variables (temperature, pH and calcium concentration), allowed identifying and quantifying all the chemical species present in solution. The proposed model was validated by comparing the experimental and theoretical conductivity. Precipitation of HAp was then investigated in a meso oscillatory flow reactor (meso-OFR). The mesoreactor was first operated batchwise in a vertical tube and experiments were performed under the same conditions of temperature, reactants concentration and power density applied in the stirred tank batch reactor. Despite hydrodynamic conditions being not directly comparable, it was possible to assess the effectiveness of both reactors in terms of mixing and quality of the precipitated particles. The experimental results show the advantages of the meso-OFR over the stirred tank due to the production, about four times faster, of smaller and more uniform HAp nanoparticles. Afterwards, continuous-flow precipitation of HAp was carried out in one meso-OFR and in a series of eight meso-OFRs. Experiments were carried out using fixed frequency (f) and amplitude (x0), varying only the residence time. HAp nanoparticles were successfully obtained in both systems, mean particle size and aggregation degree of the prepared HAp particles decreasing with decreasing residence time. In the present work continuous-flow precipitation of HAp was also investigated in two ultrasonic microreactors. Initially, the process was carried out in a tubular microreactor immersed in an ultrasonic bath, where single-phase (laminar) and gas-liquid flow experiments were both performed. Continuous-flow precipitation of HAp in single-phase flow was then done in a Teflon microreactor with integrated piezoelectric actuator. Rod-like shape HAp nanoparticles were yielded in both reactors under near-physiological conditions of pH and temperature. Further, particles showed improved characteristics, namely in terms of size, shape, particle aggregation and crystallinity. In summary, scale-down of the HAp precipitation process has resulted in the formation of HAp nanoparticles with improved characteristics when compared with HAp particles prepared in a stirred tank batch reactor. Therefore, we believe that the work developed can be a useful contribution to the development of a platform for the continuous production of high quality HAp nanoparticles.

The Global Distribution of Precipitation and Clouds. Chapter 2.4

NASA Technical Reports Server (NTRS)

Shepherd, J. Marshall; Adler, Robert; Huffman, George; Rossow, William; Ritter, Michael; Curtis, Scott

2004-01-01

The water cycle is the key circuit moving water through the Earth's system. This large system, powered by energy from the sun, is a continuous exchange of moisture between the oceans, the atmosphere, and the land. Precipitation (including rain, snow, sleet, freezing rain, and hail), is the primary mechanism for transporting water from the atmosphere back to the Earth's surface and is the key physical process that links aspects of climate, weather, and the global water cycle. Global precipitation and associate cloud processes are critical for understanding the water cycle balance on a global scale and interactions with the Earth's climate system. However, unlike measurement of less dynamic and more homogenous meteorological fields such as pressure or even temperature, accurate assessment of global precipitation is particularly challenging due to its highly stochastic and rapidly changing nature. It is not uncommon to observe a broad spectrum of precipitation rates and distributions over very localized time scales. Furthermore, precipitating systems generally exhibit nonhomogeneous spatial distributions of rain rates over local to global domains.

Hydrogeology, geochemistry, and quality of water of The Basin and Oak Spring areas of the Chisos Mountains, Big Bend National Park, Texas

USGS Publications Warehouse

Baker, E.T.; Buszka, P.M.

1993-01-01

Water-chemistry data, hydrochemical facies, and isotopic data also indicate that water from Oak Spring originates principally from precipitation onto the land surface of the Oak Spring area. Tritium data indicate that Oak Spring water is "modern," with an average age of recharge less than 14 years. The flow rates recorded almost continuously at Oak Spring beginning in December 1986 show a close relation between precipitation and discharge. The highest recorded spring flow of 167 gallons per minute in December 1986 is attributed to record high precipitation in the area during 1986. The lowest recorded flow of 22.4 gallons per minute, in December 1989, followed a period of 20 out of 26 months of below-normal precipitation. Flow at Oak Spring typically lags behind precipitation by about 1 month. This fairly rapid response indicates the spring is fed by a shallow aquifer having good permeability and effective recharge areas with the ability to absorb precipitation rapidly.

An Ultra-high Resolution Synthetic Precipitation Data for Ungauged Sites

NASA Astrophysics Data System (ADS)

Kim, Hong-Joong; Choi, Kyung-Min; Oh, Jai-Ho

2018-05-01

Despite the enormous damage caused by record heavy rainfall, the amount of precipitation in areas without observation points cannot be known precisely. One way to overcome these difficulties is to estimate meteorological data at ungauged sites. In this study, we have used observation data over Seoul city to calculate high-resolution (250-meter resolution) synthetic precipitation over a 10-year (2005-2014) period. Furthermore, three cases are analyzed by evaluating the rainfall intensity and performing statistical analysis over the 10-year period. In the case where the typhoon "Meari" passed to the west coast during 28-30 June 2011, the Pearson correlation coefficient was 0.93 for seven validation points, which implies that the temporal correlation between the observed precipitation and synthetic precipitation was very good. It can be confirmed that the time series of observation and synthetic precipitation in the period almost completely matches the observed rainfall. On June 28-29, 2011, the estimation of 10 to 30 mm h-1 of continuous strong precipitation was correct. In addition, it is shown that the synthetic precipitation closely follows the observed precipitation for all three cases. Statistical analysis of 10 years of data reveals a very high correlation coefficient between synthetic precipitation and observed rainfall (0.86). Thus, synthetic precipitation data show good agreement with the observations. Therefore, the 250-m resolution synthetic precipitation amount calculated in this study is useful as basic data in weather applications, such as urban flood detection.

Rocket investigations of electron precipitation and VLF waves in the Antarctic upper atmosphere

NASA Technical Reports Server (NTRS)

Sheldon, W. R.; Benbrook, J. R.; Bering, E. A.

1988-01-01

The results of two Antarctic rocket campaigns, primarily initiated to investigate electron precipitation stimulated by signals from the Siple-Station ground-based VLF transmitter, are presented. While the primary objective of the campaigns was not achieved, the Siple VLF transmitter facilitated a study of the wave environment in the ionosphere. Standing wave patterns in the ionosphere were observed for the first time by detectors flown aboard the Nike-Tomahawk rockets; the same detectors monitored a continuous signal from the transmitter through the neutral atmosphere and into the ionosphere, providing unique data for comparison with theoretical studies of wave propagation. The measurements of penetrating electron precipitation were interpreted in terms of a model of energetic electron precipitation from the trapped radiational belts.

Continuous Real-time Measurements of δ-values of Precipitation during Rain Events: Insights into Tropical Convection

NASA Astrophysics Data System (ADS)

He, S.; Goodkin, N.; Jackisch, D.; Ong, M. R.

2017-12-01

Studying how the tropical convection affects stable isotopes in precipitation can help us understand the evolution of the precipitation isotopes over time and improve the interpretation of paleoclimate records in the tropical region. We have been continuously monitoring δ-values of precipitation during rain events in Singapore for the past three years (2014-2017) using a diffusion sampler-cavity ring-down spectrometer (DS-CRDS) system. This period of time spans the most recent El Niño and La Niña, and thus affords us the opportunity to use our ultra-high temporal resolutsion data to examine the El Niño-Southern Oscillation (ENSO) impact on the precipitation isotopes during convection and the intra-annual variability in the region. δ-values of precipitation could change significantly during a single event, and mainly exhibits "V" (or "U" ) shape or "W" shape patterns. The mesoscale subsidence and rain re-evaporation are two processes that largely shape the isotopes of precipitation during events. Time series of the initial, highest and lowest δ-values of individual events, and absolute change in δ-values during these events show clear evolution over time. Events with low δ-values occurred less frequently in 2015 than the other years. Likewise, the frequency of events with larger magnitude change in δ-values and low initial values are also lower in 2015. The events with low averaged δ-values usually have very low initial δ-values, and are closely associated with organized regional convection, indicating that the convective activities in the upwind area can significantly influence the δ-values of precipitation. All these observations suggest lower intensity and frequency of regional organized convection in 2015. The ENSO event in 2015 was likely responsible for these changes. During an ENSO event, convection over the central and eastern Pacific is strengthened while that of the western Pacific and Southeast Asia is supressed, resulting in a weakened monsoon in the region. Therefore, we believe that ENSO can not only impact the regional convection, but also drive the intra-annual variability in δ-values of precipitation in the area.

Exploring the effects of climatic variables on monthly precipitation variation using a continuous wavelet-based multiscale entropy approach.

PubMed

Roushangar, Kiyoumars; Alizadeh, Farhad; Adamowski, Jan

2018-08-01

Understanding precipitation on a regional basis is an important component of water resources planning and management. The present study outlines a methodology based on continuous wavelet transform (CWT) and multiscale entropy (CWME), combined with self-organizing map (SOM) and k-means clustering techniques, to measure and analyze the complexity of precipitation. Historical monthly precipitation data from 1960 to 2010 at 31 rain gauges across Iran were preprocessed by CWT. The multi-resolution CWT approach segregated the major features of the original precipitation series by unfolding the structure of the time series which was often ambiguous. The entropy concept was then applied to components obtained from CWT to measure dispersion, uncertainty, disorder, and diversification of subcomponents. Based on different validity indices, k-means clustering captured homogenous areas more accurately, and additional analysis was performed based on the outcome of this approach. The 31 rain gauges in this study were clustered into 6 groups, each one having a unique CWME pattern across different time scales. The results of clustering showed that hydrologic similarity (multiscale variation of precipitation) was not based on geographic contiguity. According to the pattern of entropy across the scales, each cluster was assigned an entropy signature that provided an estimation of the entropy pattern of precipitation data in each cluster. Based on the pattern of mean CWME for each cluster, a characteristic signature was assigned, which provided an estimation of the CWME of a cluster across scales of 1-2, 3-8, and 9-13 months relative to other stations. The validity of the homogeneous clusters demonstrated the usefulness of the proposed approach to regionalize precipitation. Further analysis based on wavelet coherence (WTC) was performed by selecting central rain gauges in each cluster and analyzing against temperature, wind, Multivariate ENSO index (MEI), and East Atlantic (EA) and North Atlantic Oscillation (NAO), indeces. The results revealed that all climatic features except NAO influenced precipitation in Iran during the 1960-2010 period. Copyright © 2018 Elsevier Inc. All rights reserved.

Final report for DOE Grant No. DE-SC0006609 - Persistence of Microbially Facilitated Calcite Precipitation as an in situ Treatment for Strontium-90

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Robert W.; Fujita, Yoshiko; Hubbard, Susan S.

2013-11-15

Subsurface radionuclide and metal contaminants throughout the U.S. Department of Energy (DOE) complex pose one of DOE's greatest challenges for long-term stewardship. One promising stabilization mechanism for divalent ions, such as the short-lived radionuclide 90Sr, is co-precipitation in calcite. We have previously found that nutrient addition can stimulate microbial ureolytic activity, that this activity accelerates calcite precipitation and co-precipitation of Sr, and that higher calcite precipitation rates can result in increased Sr partitioning. We have conducted integrated field, laboratory, and computational research to evaluate the relationships between ureolysis and calcite precipitation rates and trace metal partitioning under environmentally relevant conditions,more » and investigated the coupling between flow/flux manipulations and precipitate distribution. A field experimental campaign conducted at the Integrated Field Research Challenge (IFRC) site located at Rifle, CO was based on a continuous recirculation design; water extracted from a down-gradient well was amended with urea and molasses (a carbon and electron donor) and re-injected into an up-gradient well. The goal of the recirculation design and simultaneous injection of urea and molasses was to uniformly accelerate the hydrolysis of urea and calcite precipitation over the entire inter-wellbore zone. The urea-molasses recirculation phase lasted, with brief interruptions for geophysical surveys, for 12 days and was followed by long-term monitoring which continued for 13 months. A post experiment core located within the inter-wellbore zone was collected on day 321 and characterized with respect to cation exchange capacity, mineral carbonate content, urease activity, ureC gene abundance, extractable ammonium (a urea hydrolysis product) content, and the 13C isotopic composition of solid carbonates. It was also subjected to selective extractions for strontium and uranium. Result of the core characterization suggest that urea hydrolysis occurred primarily within the upper portion of the inter-wellbore zone and that strontium was mobilized from cation exchange sites and subsequently co-precipitated with new calcium carbonate.« less

Asymmetric responses of primary productivity to precipitation extremes: A synthesis of grassland precipitation manipulation experiments.

PubMed

Wilcox, Kevin R; Shi, Zheng; Gherardi, Laureano A; Lemoine, Nathan P; Koerner, Sally E; Hoover, David L; Bork, Edward; Byrne, Kerry M; Cahill, James; Collins, Scott L; Evans, Sarah; Gilgen, Anna K; Holub, Petr; Jiang, Lifen; Knapp, Alan K; LeCain, Daniel; Liang, Junyi; Garcia-Palacios, Pablo; Peñuelas, Josep; Pockman, William T; Smith, Melinda D; Sun, Shanghua; White, Shannon R; Yahdjian, Laura; Zhu, Kai; Luo, Yiqi

2017-10-01

Climatic changes are altering Earth's hydrological cycle, resulting in altered precipitation amounts, increased interannual variability of precipitation, and more frequent extreme precipitation events. These trends will likely continue into the future, having substantial impacts on net primary productivity (NPP) and associated ecosystem services such as food production and carbon sequestration. Frequently, experimental manipulations of precipitation have linked altered precipitation regimes to changes in NPP. Yet, findings have been diverse and substantial uncertainty still surrounds generalities describing patterns of ecosystem sensitivity to altered precipitation. Additionally, we do not know whether previously observed correlations between NPP and precipitation remain accurate when precipitation changes become extreme. We synthesized results from 83 case studies of experimental precipitation manipulations in grasslands worldwide. We used meta-analytical techniques to search for generalities and asymmetries of aboveground NPP (ANPP) and belowground NPP (BNPP) responses to both the direction and magnitude of precipitation change. Sensitivity (i.e., productivity response standardized by the amount of precipitation change) of BNPP was similar under precipitation additions and reductions, but ANPP was more sensitive to precipitation additions than reductions; this was especially evident in drier ecosystems. Additionally, overall relationships between the magnitude of productivity responses and the magnitude of precipitation change were saturating in form. The saturating form of this relationship was likely driven by ANPP responses to very extreme precipitation increases, although there were limited studies imposing extreme precipitation change, and there was considerable variation among experiments. This highlights the importance of incorporating gradients of manipulations, ranging from extreme drought to extreme precipitation increases into future climate change experiments. Additionally, policy and land management decisions related to global change scenarios should consider how ANPP and BNPP responses may differ, and that ecosystem responses to extreme events might not be predicted from relationships found under moderate environmental changes. © 2017 John Wiley & Sons Ltd.

21 CFR 175.320 - Resinous and polymeric coatings for polyolefin films.

Code of Federal Regulations, 2012 CFR

2012-04-01

... coating is applied as a continuous film over one or both sides of a base film produced from one or more of the basic olefin polymers complying with § 177.1520 of this chapter. The base polyolefin film may... as are provided: List of substances Limitations (i) Resins and polymers: Acrylic acid polymer and its...

21 CFR 175.320 - Resinous and polymeric coatings for polyolefin films.

Code of Federal Regulations, 2013 CFR

2013-04-01

... coating is applied as a continuous film over one or both sides of a base film produced from one or more of the basic olefin polymers complying with § 177.1520 of this chapter. The base polyolefin film may... as are provided: List of substances Limitations (i) Resins and polymers: Acrylic acid polymer and its...

Specially Treated Aramid Fiber Stabilized Gel-Emulsions: Preparation of Porous Polymeric Monoliths and Highly Efficient Removing of Airborne HCHO.

PubMed

Liu, Jianfei; Chen, Xiangli; Wang, Pei; Fu, Xuwei; Liu, Kaiqiang; Fang, Yu

2017-08-01

Porous polymeric monoliths with densities as low as ≈0.060 g cm -3 are prepared in a gel-emulsion template way, of which the stabilizer employed is a newly discovered acidified aramid fiber that is so efficient that 0.05% (w/v, accounts for continuous phase) is enough to gel the system. The porous monoliths as obtained can be dried at ambient conditions, avoiding energy-consuming processes. Importantly, the monoliths show selective adsorption to HCHO, and the corresponding adsorption capacity (M6) is ≈2700 mg g -1 , the best result that is reported until now. More importantly, the monoliths can be reused after drying. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Roles of additives and surface control in slurry atomization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, S.C.

1992-06-01

As reported in the quarterly report of March of 1992, the relative viscosity of a Newtonian Coal Water Slurry (CWS) in the presence of an anionic polymeric dispersant is an order of magnitude higher than the prediction of the well established Krieger-Dougherty Equation which describes the relative viscosity of a non-aggregated Newtonian suspension as a function of particle volume fraction. Note that the anionic dispersant is used in such a quantity that the resulting interparticle electrostatic repulsion counter-balances the interparticle van der Waals attraction. Investigation continues to determine the mechanisms of such excess energy dissipation under shear. New experimental resultsmore » are presented in this report to verify the role of the anionic polymeric dispersant in such excess energy dissipation of CWS.« less

[Roles of additives and surface control in slurry atomization]. Quarterly report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, S.C.

1992-06-01

As reported in the quarterly report of March of 1992, the relative viscosity of a Newtonian Coal Water Slurry (CWS) in the presence of an anionic polymeric dispersant is an order of magnitude higher than the prediction of the well established Krieger-Dougherty Equation which describes the relative viscosity of a non-aggregated Newtonian suspension as a function of particle volume fraction. Note that the anionic dispersant is used in such a quantity that the resulting interparticle electrostatic repulsion counter-balances the interparticle van der Waals attraction. Investigation continues to determine the mechanisms of such excess energy dissipation under shear. New experimental resultsmore » are presented in this report to verify the role of the anionic polymeric dispersant in such excess energy dissipation of CWS.« less

Three-dimensional Macroscopic Scaffolds With a Gradient in Stiffness for Functional Regeneration of Interfacial Tissues

PubMed Central

Singh, Milind; Dormer, Nathan; Salash, Jean R.; Christian, Jordan M.; Moore, David S.; Berkland, Cory; Detamore, Michael S.

2010-01-01

A novel approach has been demonstrated to construct biocompatible, macroporous 3-D tissue engineering scaffolds containing a continuous macroscopic gradient in composition that yields a stiffness gradient along the axis of the scaffold. Polymeric microspheres, made of poly(d,l-lactic-co-glycolic acid) (PLGA), and composite microspheres encapsulating a higher stiffness nano-phase material (PLGA encapsulating CaCO3 or TiO2 nanoparticles) were used for the construction of microsphere-based scaffolds. Using controlled infusion of polymeric and composite microspheres, gradient scaffolds displaying an anisotropic macroscopic distribution of CaCO3/TiO2 were fabricated via an ethanol sintering technique. The controllable mechanical characteristics and biocompatible nature of these scaffolds warrants further investigation for interfacial tissue engineering applications. PMID:20336753

A parallel algorithm for step- and chain-growth polymerization in molecular dynamics.

PubMed

de Buyl, Pierre; Nies, Erik

2015-04-07

Classical Molecular Dynamics (MD) simulations provide insight into the properties of many soft-matter systems. In some situations, it is interesting to model the creation of chemical bonds, a process that is not part of the MD framework. In this context, we propose a parallel algorithm for step- and chain-growth polymerization that is based on a generic reaction scheme, works at a given intrinsic rate and produces continuous trajectories. We present an implementation in the ESPResSo++ simulation software and compare it with the corresponding feature in LAMMPS. For chain growth, our results are compared to the existing simulation literature. For step growth, a rate equation is proposed for the evolution of the crosslinker population that compares well to the simulations for low crosslinker functionality or for short times.

A parallel algorithm for step- and chain-growth polymerization in molecular dynamics

NASA Astrophysics Data System (ADS)

de Buyl, Pierre; Nies, Erik

2015-04-01

Classical Molecular Dynamics (MD) simulations provide insight into the properties of many soft-matter systems. In some situations, it is interesting to model the creation of chemical bonds, a process that is not part of the MD framework. In this context, we propose a parallel algorithm for step- and chain-growth polymerization that is based on a generic reaction scheme, works at a given intrinsic rate and produces continuous trajectories. We present an implementation in the ESPResSo++ simulation software and compare it with the corresponding feature in LAMMPS. For chain growth, our results are compared to the existing simulation literature. For step growth, a rate equation is proposed for the evolution of the crosslinker population that compares well to the simulations for low crosslinker functionality or for short times.

Organocatalyzed Photocontrolled Radical Polymerization of Semifluorinated (Meth)acrylates Driven by Visible Light.

PubMed

Gong, Honghong; Zhao, Yucheng; Shen, Xianwang; Lin, Jun; Chen, Mao

2018-01-02

Fluorinated polymers are important materials that are widely used in many areas. Herein, we report the development of a metal-free photocontrolled radical polymerization of semifluorinated (meth)acrylates with a new visible-light-absorbing organocatalyst. This method enabled the production of a variety of semifluorinated polymers with narrow molar-weight distributions from semifluorinated trithiocarbonates or perfluoroalkyl iodides. The high performance of "ON/OFF" control and chain-extension experiments further demonstrate the utility and reliability of this method. Furthermore, to streamline the preparation of semifluorinated polymers, a scalable continuous-flow approach has been developed. Given the broad interest in fluorinated materials and photopolymerization, we expect that this method will facilitate the development of advanced materials with unique properties. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polymerization and photochromism of ammonium molybdate in porous glass

NASA Astrophysics Data System (ADS)

Pak, V. N.; Borisov, A. N.

2016-08-01

Modification of porous glass (PG) plates is carried out by impregnation with aqueous solutions of ammonium molybdate (NH4)2MoO4 with subsequent removal of water at 120°C. A long-wavelength shift of absorption spectra upon accumulation of the salt in PG indicates polymerization of MoO 4 2- anions at low concentrations of the encapsulated salt. Photochromism manifests itself as the anionic forms in PG become larger. UV irradiation of the modified plates causes enhancement of continuous absorption in the visible range. The proposed mechanism of photoreduction of the polianions in PG involves the removal of oxygen atoms from the bridging-Mo-O-Mo-bonds and stabilization of the colored forms by means of conjugation of the electrons released from the 4 d-levels of pentavalent molybdenum.

Land surface water cycles observed with satellite sensors

NASA Technical Reports Server (NTRS)

Nghiem, Son V.; Njoku, E. G.; Brakenridge, G. R.; Kim, Y.

2005-01-01

Acceleration of the global water cycle may lead to increased global precipitation, faster evaporation and a consequent exacerbation of hydrologic extreme. In the U.S. national assessment of the potential consequences of climate variability and change, two GCMs (CGCM1 and HadCM2) show a large increase in precipitation in the future over the southwestern U.S. particularly during winter (Felzer and Heard, 1999). Increased precipitation potentially has important impacts on agricultural and water use in the southeast U.S. (Hatch et al., 1999) and in the central Great Plains (Nielsen, 1997). A hurricane model predicts a 40% precipitation increase for severe hurricanes affecting southeastern Florida, which provokes substantially greater flooding that could negate most of the benefits of present water-management practices in this basin (Gutowski et al., 1994). Thus, it is important to observe the hydroclimate on a continuous longterm basis to address the question of increased precipitation in the enhanced water cycle.

Connecting Urbanization to Precipitation: the case of Mexico City

NASA Astrophysics Data System (ADS)

Georgescu, Matei

2017-04-01

Considerable evidence exists illustrating the influence of urban environments on precipitation. We revisit this theme of significant interest to a broad spectrum of disciplines ranging from urban planning to engineering to urban numerical modeling and climate, by detailing the simulated effect of Mexico City's built environment on regional precipitation. Utilizing the Weather Research and Forecasting (WRF) system to determine spatiotemporal changes in near-surface air temperature, precipitation, and boundary layer conditions induced by the modern-day urban landscape relative to presettlement conditions, I mechanistically link the built environment-induced increase in air temperature to simulated increases in rainfall during the evening hours. This simulated increase in precipitation is in agreement with historical observations documenting observed rainfall increase. These results have important implications for understanding the meteorological conditions leading to the widespread and recurrent urban flooding that continues to plague the Mexico City Metropolitan Area.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsigabu Gebrehiwet; James R. Henriksen; Luanjing Guo

Multi-component mineral precipitation in porous, subsurface environments is challenging to simulate or engineer when in situ reactant mixing is controlled by diffusion. In contrast to well-mixed systems, the conditions that favor mineral precipitation in porous media are distributed along chemical gradients, which evolve spatially due to concurrent mineral precipitation and modification of solute transport in the media. The resulting physical and chemical characteristics of a mixing/precipitation zone are a consequence of coupling between transport and chemical processes, and the distinctive properties of individual chemical systems. We examined the spatial distribution of precipitates formed in “double diffusion” columns for two chemicalmore » systems, calcium carbonate and calcium phosphate. Polyacrylamide hydrogel was used as a low permeability, high porosity medium to maximize diffusive mixing and minimize pressure- and density-driven flow between reactant solutions. In the calcium phosphate system, multiple, visually dense and narrow bands of precipitates were observed that were reminiscent of previously reported Liesegang patterns. In the calcium carbonate system, wider precipitation zones characterized by more sparse distributions of precipitates and a more open channel structure were observed. In both cases, formation of precipitates inhibited, but did not necessarily eliminate, continued transport and mixing of the reactants. A reactive transport model with fully implicit coupling between diffusion, chemical speciation and precipitation kinetics, but where explicit details of nucleation processes were neglected, was able to qualitatively simulate properties of the precipitation zones. The results help to illustrate how changes in the physical properties of a precipitation zone depend on coupling between diffusion-controlled reactant mixing and chemistry-specific details of precipitation kinetics.« less

Strontium Co-precipitation During Biomineralization of Calcite in Porous Media Using Differing Treatment Strategies

NASA Astrophysics Data System (ADS)

Lauchnor, E. G.; Schultz, L.; Mitchell, A.; Cunningham, A. B.; Gerlach, R.

2013-12-01

The process of ureolytically-induced calcium carbonate mineralization has been shown in laboratory studies to be effective in co-precipitation of heavy metals and radionuclides. During this process, the microbially catalyzed hydrolysis of urea increases alkalinity and pH, thus promoting CaCO3 precipitation in the presence of dissolved calcium. One proposed application of biomineralization includes the remediation of radionuclides such as strontium, which can be co-precipitated in situ within calcite. Strontium is of concern at several US DOE sites where it is a radioactive product of uranium fission and groundwater contaminant. Our research focuses on promoting attached bacteria, or biofilms, in subsurface environments where they serve as immobilized catalysts in biomineralization and can aide in co-precipitation of some contaminants. In this work, flat plate reactors with 1 mm etched flow channels designed to mimic a porous medium environment were used. Reactors were inoculated with the model ureolytic bacterium Sporosarcina pasteurii and addition of urea, calcium and strontium containing fluid was performed to induce biomineralization. Continuous flow and stopped-flow injection strategies were investigated to evaluate differences in strontium co-precipitation efficiency. During stopped-flow experiments, injection of cementation fluid containing urea, Ca2+ and Sr2+ was alternated with growth nutrients for stimulation of microbial activity. Control parameters such as urea and calcium concentration and injection flow rate are currently being varied to optimize rate and efficiency of strontium co-precipitation. Ureolytically induced calcite precipitation and strontium incorporation in the calcite was verified by chemical and mineralogical analyses, including X-ray diffraction and ICP-MS. Strontium co-precipitation efficiency was similar under different injection strategies. Alternating calcium-containing fluid with growth nutrients allowed for continued viability of the ureolytic biofilms and also insured that bacterially-induced mineralization was still occurring after 60 days of operation. Batch rate experiments demonstrated the effective use of alternative sources of substrates for biomineralization, which are economical for use in field-scale remediation. Fertilizer has been shown to be an effective urea source and several economical carbon and nutrient sources such as molasses and whey are being evaluated for stimulating ureolytic microorganisms. This research demonstrates on a bench scale the use of different injection strategies to control precipitation of calcium carbonate, as well as the feasibility of strontium co-precipitation in porous media. The ongoing optimization of strontium co-precipitation will lead to additional work on potential remediation of other heavy metal groundwater contaminants.

Removal of carbamazepine and clofibric acid from water using double templates-molecularly imprinted polymers.

PubMed

Dai, Chao-meng; Zhang, Juan; Zhang, Ya-lei; Zhou, Xue-fei; Duan, Yan-ping; Liu, Shu-guang

2013-08-01

A novel double templates-molecularly imprinted polymer (MIP) was prepared by precipitation polymerization using carbamazepine (CBZ) and clofibric acid (CA) as the double templates molecular and 2-vinylpyridine as functional monomer. The equilibrium data of MIP was well described by the Freundlich isotherm model. Two kinetic models were adopted to describe the experimental data, and the pseudo second-order model well-described adsorption of CBZ and CA on the MIP. Adsorption experimental results showed that the MIP had good selectivity and adsorption capacity for CBZ and CA in the presence of competitive compounds compared with non-imprinted polymer, commercial powdered activated carbon, and C18 adsorbents. The feasibility of removing CBZ and CA from water by the MIP was demonstrated using tap water, lake water, and river water.

In vitro genotoxicity and cytotoxicity of polydopamine-coated magnetic nanostructures.

PubMed

Woźniak, Anna; Walawender, Magdalena; Tempka, Dominika; Coy, Emerson; Załęski, Karol; Grześkowiak, Bartosz F; Mrówczyński, Radosław

2017-10-01

Synthesis of magnetic nanoparticles and magnetic nanoclusters was performed by the co-precipitation method or solvothermal synthesis, respectively, followed by oxidative polymerization of dopamine, resulting in a polydopamine (PDA) shell. The nanomaterials obtained were described using TEM, FTIR and magnetic measurements. For the first time, cyto- and genotoxicity studies of polydopamine-coated nanostructures were performed on cancer and normal cell lines, providing in-depth insight into the toxicity of such materials. The tests conducted, e.g. ROS, apoptosis and DNA double-break of the nanomaterials obtained revealed the low toxicity of these structures. Thus, these results prove the biocompatibility and low genotoxicity of these materials and provide new data on the toxicity of PDA-coated materials, which is of great importance for their biomedical application. Copyright © 2017 Elsevier Ltd. All rights reserved.

On the origin of fiber calcite crystals in moonmilk deposits.

PubMed

Cañaveras, Juan Carlos; Cuezva, Soledad; Sanchez-Moral, Sergio; Lario, Javier; Laiz, Leonila; Gonzalez, Juan Miguel; Saiz-Jimenez, Cesareo

2006-01-01

In this study, we show that moonmilk subaerial speleothems in Altamira Cave (Spain) consist of a network of fiber calcite crystals and active microbial structures. In Altamira moonmilks, the study of the typology and distribution of fiber crystals, extracellular polymeric substances, and microorganisms allowed us to define the initial stages of fiber crystal formation in recent samples as well as the variations in the microstructural arrangement in more evolved stages. Thus, we have been able to show the existence of a relationship among the different types of fiber crystals and their origins. This allowed us to outline a model that illustrates the different stages of formation of the moonmilk, developed on different substrata, concluding that microbes influence physicochemical precipitation, resulting in a variety of fiber crystal morphologies and sizes.

Novel cationic supersaturable nanomicellar systems of raloxifene hydrochloride with enhanced biopharmaceutical attributes.

PubMed

Jain, Atul; Kaur, Rajpreet; Beg, Sarwar; Kushwah, Varun; Jain, Sanyog; Singh, Bhupinder

2018-06-01

The work describes systematic development of nanomicellar cationic supersaturable self-nanoemulsifying drug delivery systems (CS-SNEDDS) for augmenting oral biopharmaceutical performance of raloxifene hydrochloride. Plain SNEDDS formulation containing Capryol 90, Cremophor RH 40, and Transcutol HP was optimized using D-optimal mixture design. SNEDDS were characterized for emulsification time, globule size, in vitro drug release, and ex vivo permeation. The CS-SNEDDS formulation was prepared from the optimized SNEDDS by adding oleylamine as the cationic charge inducer and HPMC as the polymeric precipitation inhibitor. Evaluation of CS-SNEDDS was carried out through in vitro cell line studies on Caco-2 and MCF-7 cells, in situ perfusion, and in vivo pharmacokinetic studies, which indicated significant improvement in biopharmaceutical attributes of the drug from CS-SNEDDS over plain drug.

Mechanisms of iron-silica aqueous interaction and the genesis of Precambrian iron formation

NASA Astrophysics Data System (ADS)

Chemtob, S. M.; Catalano, J. G.; Moynier, F.; Pringle, E. A.

2015-12-01

Iron formations (IFs), Fe- and Si-rich chemical sediments common in Precambrian successions, preserve key information about the compositional, biological, and oxidative evolution of the Precambrian ocean. Stable Si isotopes (δ30Si) of IF have been used to infer paleo-oceanic composition, and secular variations in δ30Si may reflect ancient biogeochemical cycles. The δ30Si of primary Fe-Si precipitates that formed IF depends not only on the δ30Si of aqueous silica but also on the precipitation mechanism. Multiple formation mechanisms for these primary precipitates are plausible. Aqueous Si may have adsorbed on newly precipitated iron oxyhydroxide surfaces; alternatively, Fe and Si may have coprecipitated as a single phase. Here we explore variations in the Si isotope fractionation factor (ɛ) with Fe-Si aqueous interaction mechanism (adsorption vs. coprecipitation). In adsorption experiments, sodium silicate solutions (pH 8.1, 125-2000 µM Si) were reacted with iron oxide particles (hematite, ferrihydrite, goethite, and magnetite) for 24 to 72 hours. Resultant solutions had δ30Si between 0 and +6‰. Calculated ɛ varied significantly with oxide mineralogy and morphology. For ferrihydrite, ɛ = -1.7‰; for hematite, ɛ = -2 to -5‰, depending on particle morphology. Apparent ɛ decreased upon surface site saturation, implying a smaller isotope effect for polymeric Si adsorption than monomeric adsorption. In coprecipitation experiments, solutions of Na-silicate and Fe(II) chloride (0.4-10 mM) were prepared anaerobically, then air-oxidized for 3 days to induce precipitation. At low Si concentrations, magnetite formed; near silica saturation, lepidocrocite and ferrihydrite formed. The Si isotope fractionation factor for coprecipitation was within the range of ɛ observed for adsorption (ɛ = -2.3 ± 1.0‰). These results indicate that the mechanism of Fe-Si interaction affects ɛ, presumably due to varying silicate coordination environments. These isotopic analyses will be paired with Si K-edge and Fe K-edge X-ray absorption spectra of the solids to illustrate how Si bonding environment affects ɛ. Effective reconstruction of paleo-oceanic δ30Si may require additional constraints on the relative importance of Si adsorption and Fe-Si coprecipitation in the production of IF primary precipitates.

The twenty-first century Colorado River hot drought and implications for the future

NASA Astrophysics Data System (ADS)

Udall, Bradley; Overpeck, Jonathan

2017-03-01

Between 2000 and 2014, annual Colorado River flows averaged 19% below the 1906-1999 average, the worst 15-year drought on record. At least one-sixth to one-half (average at one-third) of this loss is due to unprecedented temperatures (0.9°C above the 1906-1999 average), confirming model-based analysis that continued warming will likely further reduce flows. Whereas it is virtually certain that warming will continue with additional emissions of greenhouse gases to the atmosphere, there has been no observed trend toward greater precipitation in the Colorado Basin, nor are climate models in agreement that there should be a trend. Moreover, there is a significant risk of decadal and multidecadal drought in the coming century, indicating that any increase in mean precipitation will likely be offset during periods of prolonged drought. Recently published estimates of Colorado River flow sensitivity to temperature combined with a large number of recent climate model-based temperature projections indicate that continued business-as-usual warming will drive temperature-induced declines in river flow, conservatively -20% by midcentury and -35% by end-century, with support for losses exceeding -30% at midcentury and -55% at end-century. Precipitation increases may moderate these declines somewhat, but to date no such increases are evident and there is no model agreement on future precipitation changes. These results, combined with the increasing likelihood of prolonged drought in the river basin, suggest that future climate change impacts on the Colorado River flows will be much more serious than currently assumed, especially if substantial reductions in greenhouse gas emissions do not occur.