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1

Development of a polymeric nanoparticulate delivery system for indocyanine green  

NASA Astrophysics Data System (ADS)

Purpose. The objective of this project was to develop an intravenously administrable poly(dl-lactic-co-glycolic acid) (PLGA) nanoparticulate delivery system for Indocyanine Green (ICG), to enhance the potential for ICG use in tumor imaging and therapy. Methods. For this purpose PLGA nanoparticles entrapping ICG were engineered by spontaneous emulsification solvent diffusion method. ICG entrapment in nanoparticles was determined and physicochemical characterization of nanoparticles was performed. The stability of ICG in nanoparticles formulation under various conditions was determined. The intracellular uptake of ICG in nanoparticles by B16-F10 and C-33A cancer cell lines was studied in comparison with the free ICG solution. Anti-proliferation studies against cancer cells were performed to prove the photodynamic activity of ICG in nanoparticles. Biodistribution of ICG when delivered through nanoparticles and solution were evaluated in mice after tail vein injection. Results. PLGA nanoparticles with a mean diameter of 350 nm and 74% ICG entrapment were obtained. The nanoparticles were nearly spherical in shape with zeta potential of -16 mV. The nanoparticles formulation provided overall stability to ICG with degradation half-lives of 2.5--3.5 days as compared to 10--20 hr of free ICG solutions. The intracellular uptake of ICG through nanoparticles was directly proportional to time and extracellular nanoparticle concentration. The intracellular uptake of ICG was enhanced about 100-fold by nanoparticles formulation as compared to the free ICG solution. Nanoparticles formulation showed significant photodynamic effect at nano-molar ICG concentrations and very low light dose (fluence: 0.22 W/cm2 and energy density: 1.1 J/cm2). In-vivo, the blood circulation-time and retention-time of ICG in various organs was enhanced 2--5 times by nanoparticles formulation as compared to the free ICG solution. Conclusions. A PLGA nanoparticlute delivery system was developed for ICG, which demonstrated its capability in enhancing the potential of ICG use in tumor diagnosis and anticancer therapy.

Saxena, Vishal

2

Transport of polymeric nanoparticulate drug delivery systems in the proximity of silica and sand.  

PubMed

The contamination of the environment with traditional therapeutics due to metabolic excretion, improper disposal, and industrial waste has been well-recognized. However, knowledge of the environmental distribution and fate of emerging classes of nanomedicine is scarce. This work investigates the effect of surface chemistry of polymeric nanoparticulate drug delivery systems (PNDDS) on their adsorption dynamics and transport in the vicinity of environmentally relevant surfaces for a concentration comparable with hospital and pharmaceutical manufacturing effluents. To this end, five different types of paclitaxel-based nanomedicine having different polymer stabilizers were employed. Their transport behavior was characterized via quartz crystal microbalance, sand column, spectrofluorometry, and dynamic light scattering techniques. PNDDS having positive zeta-potential displayed strong adsorption onto silica surfaces and no mobility in porous media of quartz sand, even in the presence of humic acid. The mobility of negatively charged PNDDS strongly depended on the amount and type of salt present in the aqueous media: Without any salt, such PNDDS demonstrated no adsorption on silica surfaces and high levels of mobility in sand columns. The presence of CaCl2 and CaSO4, even at low ionic strengths (i.e. 10 mM), induced PNDDS adsorption on silica surfaces and strongly limited the mobility of such PNDSS in sand columns. PMID:25695909

Chen, I-Cheng; Zhang, Ming; Teipel, Blake; de Araujo, Isa Silveira; Yegin, Yagmur; Akbulut, Mustafa

2015-03-17

3

Effect of adsorbed extracellular polymeric substances (EPS) on colloidal mobility of nanoparticulate iron oxides  

NASA Astrophysics Data System (ADS)

Solubility and transport of nutrients and pollutants is affected by the presence of colloidal nanoparticles (CNP) which may act as mobile geosorbents. In soils and aquifers, pure and organically modified Fe- and Mn-oxy-hydroxides are of particular importance due to their ubiquitous presence and also due to their progressive use for environmental cleanup. Stability and aggregation behavior control the mobility of CNP and depend on pH, ionic strength, and the presence of monovalent or divalent anions. In natural environments, however, iron oxides are usually covered by organic matter. Such coverage will completely change the colloidal surface properties and impose additional control on the colloidal mobility. Important sources for natural organic coatings are extracellular polymeric substances (EPS), i.e., complex mixtures of biopolymers consisting of polysaccharides and proteins and variable amounts of lipids and nucleic acids. The objective of our study was to quantify the effect of EPS coatings on the colloidal stability, mobility and reactivity of hematite by column experiments. Columns (10 cm × 5 cm) were filled with glass beads (0.25 mm ø) as porous medium and operated in sterile closed flow conditions. Nanoparticulate hematite was coated to different degrees by extracellular polymeric substances (EPS) extracted from, liquid cultures of Bacillus subtillis. The pH was kept constant at 7. The hematite particles exhibited increasing colloidal stability with increasing amounts of EPS. Critical colloidal concentration (CCC) of the particles increased from 95 mM NaCl for uncoated particles to 250 mM NaCl for coated particles. EPS coated hematite did not react with the porous medium and stayed mobile while the uncoated hematite was immobile due to adsorption to the glass beads. Also colloidally unstable hematite particles did not show any mobility. Thus the organic coatings enhanced the colloidal stability, which consecutively increased the mobility of the particles. Also, the reactivity of these particles to the porous medium is reduced due to the masking of the reactive hematite surface sites with EPS. EPS coated CNP may define the major part of mobile material in natural environments like soils, sediments and aquifers.

Pradip Narvekar, Sneha; Totsche, Kai Uwe

2013-04-01

4

Development and characterization of polymeric nanoparticulate delivery system for hydrophillic drug: Gemcitabine  

NASA Astrophysics Data System (ADS)

Gemcitabine is a nucleoside analogue, used in various carcinomas such as non small cell lung cancer, pancreatic cancer, ovarian cancer and breast cancer. The major setbacks to the conventional therapy with gemcitabine include its short half-life and highly hydrophilic nature. The objectives of this investigation were to develop and evaluate the physiochemical properties, drug loading and entrapment efficiency, in vitro release, cytotoxicity, and cellular uptake of polymeric nano-particulate formulations containing gemcitabine hydrochloride. The study also entailed development and validation of a high performance liquid chromatography (HPLC) method for the analysis of gemcitabine hydrochloride. A reverse phase HPLC method using a C18 Luna column was developed and validated. Alginate and Poly lactide co glycolide/Poly-epsilon-caprolactone (PLGA:PCL 80:20) nanoparticles were prepared by multiple emulsion-solvent evaporation methodology. An aqueous solution of low viscosity alginate containing gemcitabine was emulsified into 10% solution of dioctyl-sulfosuccinate in dichloro methane (DCM) by sonication. The primary emulsion was then emulsified in 0.5% (w/v) aqueous solution of polyvinyl alcohol (PVA). Calcium chloride solution (60% w/v) was used to cause cross linking of the polymer. For PLGA:PCL system, the polymer mix was dissolved in dichloromethane (DCM) and an aqueous gemcitabine (with and without sodium chloride) was emulsified under ultrasonic conditions (12-watts; 1-min). This primary emulsion was further emulsified in 2% (w/v) PVA under ultrasonic conditions (24-watts; 3-min) to prepare a multiple-emulsion (w/o/w). In both cases DCM, the organic solvent was evaporated (20- hours, magnetic-stirrer) prior to ultracentrifugation (10000-rpm for PLGA:PCL; 25000-rpm for alginate). The pellet obtained was washed thrice with de-ionized water to remove PVA and any free drug and re-centrifuged. The particles were re-suspended in de-ionized water and then lyophilized to obtain the dried powdered delivery formulation. Particle size and surface charge of the nano-particles were measured using zeta-sizer. The surface morphology and microstructure were evaluated by scanning electron microscopy The drug loading and entrapment efficiencies were evaluated by a HPLC method (Luna C18 column (4.6 X 250 mm), 95/5 (v/v) 0.04M ammonium acetate/acetonitrile mobile phase (pH 5.5), 1.0 ml/min flow rate and 268 nm UV detection). Differential scanning calorimetry (DSC) was used to determine the physical state of gemcitabine in the nanoparticles. The cytotoxicity in pancreatic cancer cells (BxPC-3) was evaluated by MTT assay. The cellular uptake of gemcitabine solution and gemcitabine loaded alginate nano-particle suspension in BxPC-3 cells was determined for 15, 30 and 60 minutes. The particle-size and surface-charge was 564.7+/-56.5nm and -25.65+/-1.94mV for PLGA:PCL and 210.6+/-6.90nm and -33.21+/-1.63mV for alginate. Both the nano-particles were distinctly spherical and non-porous. The drug load was 5.14% for PLGA:PCL and 6.87% for alginate-particles, and the practical entrapment efficiency was found to be 54.1 % and 22.4% respectively. However, in case of PLGA:PCL particles, a two-fold increase in the entrapment efficiency was observed with the addition of sodium-chloride. The absence of endothermic melting peak of the drug in the DSC thermogram was an indication of the non-crystalline state of gemcitabine in the nanoparticles. In addition, there was no cytotoxicity associated with nanoparticle concentrations at-or-below 5 mg/mL. The uptake of nano-particles was around 4 times higher than the solution with treatment for 15 minutes and increased to almost 7 times following treatment for 60 minutes. Gemcitabine hydrochloride could be successfully formulated into a sustained release nano-particulate formulation using calcium cross-linked alginate and dioctyl sulfo succinate system. The nano-particulate delivery system exhibited better cytotoxic activity and also significantly enhanced the accumulation of the drug in BxPC-3 cell monolayers.

Khurana, Jatin

5

Enhanced oral bioavailability of fenofibrate using polymeric nanoparticulated systems: physicochemical characterization and in vivo investigation  

PubMed Central

Background The intention of this research was to prepare and compare various solubility-enhancing nanoparticulated systems in order to select a nanoparticulated formulation with the most improved oral bioavailability of poorly water-soluble fenofibrate. Methods The most appropriate excipients for different nanoparticulated preparations were selected by determining the drug solubility in 1% (w/v) aqueous solutions of each carrier. The polyvinylpyrrolidone (PVP) nanospheres, hydroxypropyl-?-cyclodextrin (HP-?-CD) nanocorpuscles, and gelatin nanocapsules were formulated as fenofibrate/PVP/sodium lauryl sulfate (SLS), fenofibrate/HP-?-CD, and fenofibrate/gelatin at the optimized weight ratios of 2.5:4.5:1, 1:4, and 1:8, respectively. The three solid-state products were achieved using the solvent-evaporation method through the spray-drying technique. The physicochemical characterization of these nanoparticles was accomplished by powder X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Their physicochemical properties, aqueous solubility, dissolution rate, and pharmacokinetics in rats were investigated in comparison with the drug powder. Results Among the tested carriers, PVP, HP-?-CD, gelatin, and SLS showed better solubility and were selected as the most appropriate constituents for various nanoparticulated systems. All of the formulations significantly improved the aqueous solubility, dissolution rate, and oral bioavailability of fenofibrate compared to the drug powder. The drug was present in the amorphous form in HP-?-CD nanocorpuscles; however, in other formulations, it existed in the crystalline state with a reduced intensity. The aqueous solubility and dissolution rates of the nanoparticles (after 30 minutes) were not significantly different from one another. Among the nanoparticulated systems tested in this study, the initial dissolution rates (up to 10 minutes) were higher with the PVP nanospheres and HP-?-CD nanocorpuscles; however, neither of them resulted in the highest oral bioavailability. Irrespective of relatively retarded dissolution rate, gelatin nanocapsules showed the highest apparent aqueous solubility and furnished the most improved oral bioavailability of the drug (~5.5-fold), owing to better wetting and diminution in crystallinity. Conclusion Fenofibrate-loaded gelatin nanocapsules prepared using the solvent-evaporation method through the spray-drying technique could be a potential oral pharmaceutical product for administering the poorly water-soluble fenofibrate with an enhanced bioavailability. PMID:25784807

Yousaf, Abid Mehmood; Kim, Dong Wuk; Oh, Yu-Kyoung; Yong, Chul Soon; Kim, Jong Oh; Choi, Han-Gon

2015-01-01

6

The n-->0 vector model and equilibrium polymerization  

NASA Astrophysics Data System (ADS)

Equilibrium polymerization of a monomer to long-chain polymers can be usefully described by the n-->0 limit of the n-vector model of magnetism in a small magnetic field. In the molecular-field approximation, the n-->0 vector model becomes identical to the earlier Tobolsky-Eisenberg theory of equilibrium polymerization. An error in an earlier analysis of the n-->0 vector model is corrected and the consequences for polymerization and polymer solutions are discussed. A curiosity of the n-->0 vector model-that its free energy does not everywhere satisfy the usual convexity requirements of thermodynamic stability-is also discussed. In an appendix the n-->0 limit of the cubic discrete n-vector model (Hillhorst model) is also shown to be equivalent in mean field to the Tobolsky-Eisenberg theory of equilibrium polymerization.

Wheeler, John C.; Pfeuty, Pierre

1981-08-01

7

Doxorubicin loaded Polymeric Nanoparticulate Delivery System to overcome drug resistance in osteosarcoma  

PubMed Central

Background Drug resistance is a primary hindrance for the efficiency of chemotherapy against osteosarcoma. Although chemotherapy has improved the prognosis of osteosarcoma patients dramatically after introduction of neo-adjuvant therapy in the early 1980's, the outcome has since reached plateau at approximately 70% for 5 year survival. The remaining 30% of the patients eventually develop resistance to multiple types of chemotherapy. In order to overcome both the dose-limiting side effects of conventional chemotherapeutic agents and the therapeutic failure incurred from multidrug resistant (MDR) tumor cells, we explored the possibility of loading doxorubicin onto biocompatible, lipid-modified dextran-based polymeric nanoparticles and evaluated the efficacy. Methods Doxorubicin was loaded onto a lipid-modified dextran based polymeric nano-system. The effect of various concentrations of doxorubicin alone or nanoparticle loaded doxorubicin on KHOS, KHOSR2, U-2OS, and U-2OSR2 cells was analyzed. Effects on drug retention, immunofluorescence, Pgp expression, and induction of apoptosis were also analyzed. Results Dextran nanoparticles loaded with doxorubicin had a curative effect on multidrug resistant osteosarcoma cell lines by increasing the amount of drug accumulation in the nucleus via Pgp independent pathway. Nanoparticles loaded with doxorubicin also showed increased apoptosis in osteosarcoma cells as compared with doxorubicin alone. Conclusion Lipid-modified dextran nanoparticles loaded with doxorubicin showed pronounced anti-proliferative effects against osteosarcoma cell lines. These findings may lead to new treatment options for MDR osteosarcoma. PMID:19917123

2009-01-01

8

Hybrid polymeric hydrogels for ocular drug delivery: nanoparticulate systems from copolymers of acrylic acid-functionalized chitosan and N-isopropylacrylamide or 2-hydroxyethyl methacrylate  

NASA Astrophysics Data System (ADS)

Nanoparticulate hybrid polymeric hydrogels (10-70 nm) have been obtained via the radical-induced co-polymerization of acrylic acid-functionalized chitosan with either N-isopropylacrylamide or 2-hydroxyethyl methacrylate, and the materials have been investigated for their ability to act as controlled release vehicles in ophthalmic drug delivery. Studies on the effects of network structure upon swelling properties, adhesiveness to substrates that mimic mucosal surfaces and biodegradability, coupled with in vitro drug release investigations employing ophthalmic drugs with differing aqueous solubilities, have identified nanoparticle compositions for each of the candidate drug molecules. The hybrid nanoparticles combine the temperature sensitivity of N-isopropylacrylamide or the good swelling characteristics of 2-hydroxyethyl methacrylate with the susceptibility of chitosan to lysozyme-induced biodegradation.

Barbu, Eugen; Verestiuc, Liliana; Iancu, Mihaela; Jatariu, Anca; Lungu, Adriana; Tsibouklis, John

2009-06-01

9

Development of acetazolamide-loaded, pH-triggered polymeric nanoparticulate in situ gel for sustained ocular delivery: in vitro. ex vivo evaluation and pharmacodynamic study.  

PubMed

The objective of research was to develop a novel pH-triggered polymeric nanoparticulate in situ gel (NP-ISG) for ophthalmic delivery of acetazolamide (ACZ) to enhance the conjunctival permeation and precorneal residence time of the formulation by overcoming the limitations of protective ocular barriers. Nanoparticles (NP1--NP12) were developed by nanoprecipitation method and evaluated for pharmacotechnical characteristics including transmission electron microscopy. The optimized formulation, NP10 was dispersed in carbopol 934?P to form nanoparticulate in situ gels (NP-ISG1--NP-ISG5). NP-ISG5 was selected as optimized formulation on the basis of gelation ability and residence time. Ex vivo transcorneal permeation study exhibited significantly higher ACZ permeation from NP-ISG5 (74.50?±?2.20?mg/cm(2)) and NP10 (93.5?±?2.25?mg/cm(2)) than eye drops (20.08?±?3.12?mg/cm(2)) and ACZ suspension (16.03?±?2.14). Modified Draize test with zero score indicated nonirritant property of NP-ISG5. Corneal toxicity study revealed no visual signs of tissue damage. Further, NP-ISG5 when tested for hypotensive effect on intraocular pressure (IOP) in rabbits revealed that NP-ISG5 caused significant decrease in IOP (p?

Singh, Jyotsana; Chhabra, Gulshan; Pathak, Kamla

2014-09-01

10

Transfection of Rat Pancreatic Islet Tissue by Polymeric Gene Vectors  

PubMed Central

Abstract Background In vitro genetic modification has been regarded as one option to improve the viability and functionality of pancreatic islets when used for transplantation in patients with diabetes, either as naked islets or in a type of bioartificial pancreas. In this approach, vector safety and poor transfection efficiency are major concerns. Methods In this study, the influence of in vitro transfection conditions on polyplexes constructed of polyethyleneimine (PEI) and plasmid DNA (pDNA) on the transfection efficiency was investigated by varying the transfection medium, the pDNA dose, and the amines of polycation/phosphates of pDNA (N/P) ratio. Results Ca2+-containing Krebs-Ringer-HEPES medium was more effective than RPMI 1640 medium by increasing transfection efficiency (2.5-fold). An increase in pDNA dose slightly reduced the transfection efficiency but had minimal influence on islet loss. However, the N/P ratio had a large effect on islet viability and transfection efficiency. For example, the PEI/pDNA ratio at N/P?=?10 caused greater islet loss (56% vs. 28%) and 30-fold less transfection efficiency than at N/P?=?5. Even under a set of best conditions selected from this study, mostly a fraction of cells located in the peripheral regions of an islet were transfected, and the viability and insulin secretion from the treated islets were not altered. However, it was found that the extent of apoptosis was noticeably higher (?16%) than in untreated islets (?2%). Conclusions These results suggest that the gene delivery efficacy to isolated islets can be improved by manipulating the transfection conditions. Polymeric vectors will broaden the options for islet transfection, which is currently limited to viral vectors. PMID:19580358

Kang, Han Chang

2009-01-01

11

Rare-earth-incorporated polymeric vector for enhanced gene delivery.  

PubMed

Cationic polymer PEI-CyD is doped with Nd by plasma technology to produce the gene vector: Nd@PEI-CyD. Luciferase expression and EGFP transfection experiments performed in vitro reveal that Nd@PEI-CyD has significantly higher transfection efficiency than lipofectamine 2000 and PEI-CyD and the mechanism is studied and proposed. The rare-earth element, Nd, stimulates the energy metabolism of cells, enhances cell uptake of complexes/pDNA, and regulates the cellular pathways. These special features suggest a new strategy involving metal-incorporated non-viral gene vectors. PMID:24103650

Wang, Qiwen; Jin, Weihong; Wu, Guosong; Zhao, Ying; Jin, Xue; Hu, Xiurong; Zhou, Jun; Tang, Guping; Chu, Paul K

2014-01-01

12

Nano-particulate coating on cotton fabric through DBD  

NASA Astrophysics Data System (ADS)

Plasma polymerization of fluorocarbon was processed through dielectric barrier discharge (DBD). A thin hydrophobic film packed with nano-particulate structure was obtained on cotton fabric surface. The contact angle of the water and 1-bromonaphthalene on coated cotton fabric was 133° and 124° separately. The surface morphology of the coating was observed through SEM (Scanning Electronic Microscope). It was found that cotton fabric surface was tightly adhered to a thin film packed by nano-particles from 10nm to 200nm. This process showed potential applications in continuous coating of textiles with functional nano-particulate polymers, but without changing their softness performance.

Guo, Ying; Zhang, Jing; Xu, Jinzhou; Zhou, Rongming; Yu, Jianyong

2008-02-01

13

Advances in polymeric and inorganic vectors for nonviral nucleic acid delivery  

PubMed Central

Nonviral systems for nucleic acid delivery offer a host of potential advantages compared with viruses, including reduced toxicity and immunogenicity, increased ease of production and less stringent vector size limitations, but remain far less efficient than their viral counterparts. In this article we review recent advances in the delivery of nucleic acids using polymeric and inorganic vectors. We discuss the wide range of materials being designed and evaluated for these purposes while considering the physical requirements and barriers to entry that these agents face and reviewing recent novel approaches towards improving delivery with respect to each of these barriers. Furthermore, we provide a brief overview of past and ongoing nonviral gene therapy clinical trials. We conclude with a discussion of multifunctional nucleic acid carriers and future directions. PMID:22826857

Sunshine, Joel C; Bishop, Corey J; Green, Jordan J

2014-01-01

14

Redesign of downstream processing techniques for nanoparticulate bioproducts  

Microsoft Academic Search

There has been much interest generated in the recov- ery of nanoparticulate (nanoparticle) bioproducts (Second generation of biotechnological products) such as plasmid DNA and viruses as putative gene therapy vectors, macromolecular assemblies as drug delivery vehicles and virus-like particles as vaccine compo- nents. Such product must be manufactured in advanced stages of purity, material definition and sophisticated formulation to rival

Mohsen Jahanshahi

2004-01-01

15

Design and development of oral nanoparticulated insulin in multiple emulsion.  

PubMed

The present research aimed at developing an injection-free nanoparticulated formulation in multiple emulsion form, for oral delivery of insulin, which otherwise undergoes degradation in the gastric environment if administered orally. Insulin-polymeric nanoparticles were prepared using layer by layer (LbL) adsorption method and incorporated into an emulsion to form a nanoparticulated multiple emulsion. Using 0.6 M sodium chloride, the insulin nanoaggregates of 300-400 nm size were obtained about a yield of 94%. The characteristics of a representative nanoparticle were as follows: particle size - 391.9±0.41 nm, polydispersity index -0.425, zeta potential- +20.6 mv, encapsulation efficiency- 86.7±1.42% and percentage entrapment efficiency of the insulin-polymeric nanoparticles in the inner aqueous phase of emulsion was 84.6%. The FT-IR analysis confirms that there were no drug interactions with the polymers. Stability analysis carried out for 3 months at 8-40 °C, showed only minor changes at the end period. The release kinetics of the nanoparticulated multiple emulsion at pH 7.4 followed first order kinetics and obeyed the Fickian law. However, at pH 2.0 the release kinetics from nanoparticulated multiple emulsion followed zero order kinetics without obeying to the Fickian law. In conclusion, our data demonstrate that the nanoparticulated multiple emulsion formulation has good release characteristics and imparted a tolerable protection for insulin at different pH conditions, which may be exploited for oral administration. PMID:24730439

Siddhartha, T Venkata; Senthil, V; Kishan, Ilindra Sai; Khatwal, Rizwan Basha; Madhunapantula, SubbaRao V

2014-01-01

16

Collection and characterization of airborne nanoparticulates  

Microsoft Academic Search

This paper describes the use of a thermal precipitation device to collect representative, airborne nanoparticulates on transmission electron microscope (TEM) grid supports and their characterization using a bright field (BF)–dark field (DF)–selected area electron diffraction (SAED)–energy dispersive spectrometry (EDS) analysis protocol. Two airborne nanoparticulate regimes are illustrated and compared: (1) general nanoparticulates, composed of nanocrystalline aggregates containing from 2 to

J. J. Bang; L. E. Murr; E. V Esquivel

2004-01-01

17

Polymeric nanoparticles: potent vectors for vaccine delivery targeting cancer and infectious diseases.  

PubMed

Nanocarriers with various compositions and biological properties have been extensively applied for in vitro/in vivo drug and gene delivery. The family of nanocarriers includes polymeric nanoparticles, lipid-based carriers (liposomes/micelles), dendrimers, carbon nanotubes, and gold nanoparticles (nanoshells/nanocages). Among different delivery systems, polymeric carriers have several properties such as: easy to synthesize, inexpensive, biocompatible, biodegradable, non-immunogenic, non-toxic, and water soluble. In addition, cationic polymers seem to produce more stable complexes led to a more protection during cellular trafficking than cationic lipids. Nanoparticles often show significant adjuvant effects in vaccine delivery since they may be easily taken up by antigen presenting cells (APCs). Natural polymers such as polysaccharides and synthetic polymers have demonstrated great potential to form vaccine nanoparticles. The development of new adjuvants or delivery systems for DNA and protein immunization is an expanding research field. This review describes polymeric carriers especially PLGA, chitosan, and PEI as vaccine delivery systems. PMID:24128651

Bolhassani, Azam; Javanzad, Shabnam; Saleh, Tayebeh; Hashemi, Mehrdad; Aghasadeghi, Mohammad Reza; Sadat, Seyed Mehdi

2014-01-01

18

Biological effects of nanoparticulate materials  

Microsoft Academic Search

A range of morphologically nanoparticulate materials including Ag, NiO, TiO2, multiwall carbon nanotubes, and chrysotile asbestos have been characterized by transmission electron microscopy. All but the TiO2 (anatase and rutile) were observed to exhibit some cytotoxicity at concentrations of 5 ?g\\/ml for a murine macrophage cell line as a respiratory response model. Silver exhibits interesting systemic differences for animal and

K. F. Soto; A. Carrasco; T. G. Powell; L. E. Murr; K. M. Garza

2006-01-01

19

Nanoparticulate drug delivery platforms for advancing bone infection therapies  

PubMed Central

Introduction The ongoing surge of resistance of bacterial pathogens to antibiotic therapies and the consistently aging median member of the human race signal an impending increase in the incidence of chronic bone infection. Nanotechnological platforms for local and sustained delivery of therapeutics hold the greatest potential for providing minimally invasive and maximally regenerative therapies for this rare but persistent condition. Areas covered Shortcomings of the clinically available treatment options, including poly(methyl methacrylate) beads and calcium sulfate cements, are discussed and their transcending using calcium-phosphate/polymeric nanoparticulate composites is foreseen. Bone is a composite wherein the weakness of each component alone is compensated for by the strength of its complement and an ideal bone substitute should be fundamentally the same. Expert opinion Discrepancy between in vitro and in vivo bioactivity assessments is highlighted, alongside the inherent imperfectness of the former. Challenges entailing the cross-disciplinary nature of engineering a new generation of drug delivery vehicles are delineated and it is concluded that the future for the nanoparticulate therapeutic carriers belongs to multifunctional, synergistic and theranostic composites capable of simultaneously targeting, monitoring and treating internal organismic disturbances in a smart, feedback fashion and in direct response to the demands of the local environment. PMID:25109804

Uskokovi?, Vuk; Desai, Tejal A

2015-01-01

20

Toxicological characteristics of nanoparticulate anatase titanium dioxide in mice  

Microsoft Academic Search

In an effort to examine liver injury, immune response, and other physiological effects in mice caused by intragastric administration of nanoparticulate anatase titanium dioxide (5nm), we assessed T lymphocytes, B lymphocyte and NK lymphocyte counts, hematological indices, biochemical parameters of liver functions, and histopathological changes in nanoparticulate titanium dioxide -treated mice. Indeed, mice treated with higher dose nanoparticulate titanium dioxide

Yanmei Duan; Jie Liu; Linglan Ma; Na Li; Huiting Liu; Jue Wang; Lei Zheng; Chao Liu; Xuefeng Wang; Xiaoyang Zhao; Jingying Yan; Sisi Wang; Han Wang; Xueguang Zhang; Fashui Hong

2010-01-01

21

In Vitro Dissolution Testing Strategies for Nanoparticulate Drug Delivery Systems: Recent Developments and Challenges  

PubMed Central

Nanoparticulate systems have emerged as prevalent drug delivery systems over the past few decades. These delivery systems (such as liposomes, emulsions, nanocrystals, and polymeric nanocarriers) have been extensively used to improve bioavailability, prolong pharmacological effects, achieve targeted drug delivery, as well as reduce side effects. Considering that any unanticipated change in product performance of such systems may result in toxicity and/or change in vivo efficacy, it is essential to develop suitable in vitro dissolution/release testing methods to ensure product quality and performance, and to assist in product development. The present review provides an overview of the current in vitro dissolution/release testing methods such as dialysis, sample and separate, as well as continuous flow methods. Challenges and future directions in the development of standardized and biorelevant in vitro dissolution/release testing methods for novel nanoparticulate systems are discussed. PMID:24069580

Shen, Jie; Burgess, Diane J.

2013-01-01

22

Multimodal nanoparticulate bioimaging contrast agents.  

PubMed

A wide variety of bioimaging techniques (e.g., ultrasound, computed X-ray tomography, magnetic resonance imaging (MRI), and positron emission tomography) are commonly employed for clinical diagnostics and scientific research. While all of these methods use a characteristic "energy-matter" interaction to provide specific details about biological processes, each modality differs from another in terms of spatial and temporal resolution, anatomical and molecular details, imaging depth, as well as the desirable material properties of contrast agents needed for augmented imaging. On many occasions, it is advantageous to apply multiple complimentary imaging modalities for faster and more accurate prognosis. Since most imaging modalities employ exogenous contrast agents to improve the signal-to-noise ratio, the development and use of multimodal contrast agents is considered to be highly advantageous for obtaining improved imagery from sought-after imaging modalities. Multimodal contrast agents offer improvements in patient care, and at the same time can reduce costs and enhance safety by limiting the number of contrast agent administrations required for imaging purposes. Herein, we describe the synthesis and characterization of nanoparticulate-based multimodal contrast agent for noninvasive bioimaging using MRI, optical, and photoacoustic tomography (PAT)-imaging modalities. The synthesis of these agents is described using microemulsions, which enable facile integration of the desired diversity of contrast agents and material components into a single entity. PMID:20217589

Sharma, Parvesh; Singh, Amit; Brown, Scott C; Bengtsson, Niclas; Walter, Glenn A; Grobmyer, Stephen R; Iwakuma, Nobutaka; Santra, Swadeshmukul; Scott, Edward W; Moudgil, Brij M

2010-01-01

23

Vectors  

NSDL National Science Digital Library

This web page, authored and curated by David P. Stern, introduces vectors as an extension of numbers having both magnitude and direction. The initial motivation is to describe velocity but the material includes a general discussion of vector algebra and an application to forces for the inclined plane. The page contains links to a related lesson plan and further opportunities to explore vectors. This is part of the extensive web site "From Stargazers to Starships", that uses space exploration and space science to introduce topics in physics and astronomy. Translations in Spanish and French are available.

Stern, David P. (David Peter), 1931-

24

Blazed vector grating liquid crystal cells with photocrosslinkable polymeric alignment films fabricated by one-step polarizer rotation method  

NASA Astrophysics Data System (ADS)

Blazed vector grating liquid crystal (LC) cells, in which the directors of low-molar-mass LCs are antisymmetrically distributed, were fabricated by one-step exposure of an empty glass cell inner-coated with a photocrosslinkable polymer LC (PCLC) to UV light. By adopting a LC cell structure, twisted nematic (TN) and homogeneous (HOMO) alignments were obtained in the blazed vector grating LC cells. Moreover, the diffraction efficiency of the blazed vector grating LC cells was greatly improved by increasing the thickness of the device in comparison with that of a blazed vector grating with a thin film structure obtained in our previous study. In addition, the diffraction efficiency and polarization states of ±1st-order diffracted beams from the resultant blazed vector grating LC cells were controlled by designing a blazed pattern in the alignment films, and these diffraction properties were well explained on the basis of Jones calculus and the elastic continuum theory of nematic LCs.

Kawai, Kotaro; Kuzuwata, Mitsuru; Sasaki, Tomoyuki; Noda, Kohei; Kawatsuki, Nobuhiro; Ono, Hiroshi

2014-12-01

25

Inactivation of harmful tumour-associated proteolysis by nanoparticulate system.  

PubMed

The primary aim in cancer therapy is to deliver anti-cancer drugs to their specific molecular targets in the tumour. Here we present a system composed of poly(d,l-lactide-co-glycolide) nanoparticles, cytokeratin specific monoclonal antibody and cystatin, a potent protease inhibitor, that can neutralize the excessive proteolytic activity associated with the invasive and metastatic potential of breast tumour cells. The antibody provides specific targeting of the delivery system to invasive breast epithelial cells and, additionally, prevents the generation of plasmin, a central extracellular protease involved in malignant progression. Polymeric nanoparticles rapidly enter the targeted cells and release the inhibitor cargo within the endosomes/lysosomes. The inhibitor is capable to inactivate lysosomal cysteine proteases, in particular cathepsin B, which is involved in the degradation of extracellular matrix inside the tumour cells. Our approach, which combines nanoparticulate delivery system with the inhibitory potential against extracellular and intracellular proteases, may improve the efficacy of therapy in patients with breast tumours compared to the application of individual protease inhibitors. PMID:19422896

Kos, Janko; Obermajer, Natasa; Doljak, Bojan; Kocbek, Petra; Kristl, Julijana

2009-11-01

26

Rate-programming of nano-particulate delivery systems for smart bioactive scaffolds in tissue engineering  

NASA Astrophysics Data System (ADS)

Development of smart bioactive scaffolds is of importance in tissue engineering, where cell proliferation, differentiation and migration within scaffolds can be regulated by the interactions between cells and scaffold through the use of growth factors (GFs) and extra cellular matrix peptides. One challenge in this area is to spatiotemporally control the dose, sequence and profile of release of GFs so as to regulate cellular fates during tissue regeneration. This challenge would be addressed by rate-programming of nano-particulate delivery systems, where the release of GFs via polymeric nanoparticles is controlled by means of the methods of, such as externally-controlled and physicochemically/architecturally-modulated so as to mimic the profile of physiological GFs. Identifying and understanding such factors as the desired release profiles, mechanisms of release, physicochemical characteristics of polymeric nanoparticles, and externally-triggering stimuli are essential for designing and optimizing such delivery systems. This review surveys the recent studies on the desired release profiles of GFs in various tissue engineering applications, elucidates the major release mechanisms and critical factors affecting release profiles, and overviews the role played by the mathematical models for optimizing nano-particulate delivery systems. Potentials of stimuli responsive nanoparticles for spatiotemporal control of GF release are also presented, along with the recent advances in strategies for spatiotemporal control of GF delivery within tissue engineered scaffolds. The recommendation for the future studies to overcome challenges for developing sophisticated particulate delivery systems in tissue engineering is discussed prior to the presentation of conclusions drawn from this paper.

Izadifar, Mohammad; Haddadi, Azita; Chen, Xiongbiao; Kelly, Michael E.

2015-01-01

27

Nanoformulation of poly(ethylene glycol) polymerized organic insect repellent by PIT emulsification method and its application for Japanese encephalitis vector control.  

PubMed

The utilization of increased dosage of insect repellents to overcome mosquito resistance has raised environmental concerns globally. In accord to this, we have formulated an efficacious, water-dispersive, nanometric formulation of a poor water-soluble insect repellent, diethylphenylacetamide (DEPA) by poly(ethylene glycol) (PEG) polymerization followed by PIT emulsification method. The critical micelle concentration of PEG in the spontaneously emulsified conventional DEPA droplets was determined, based on the droplets physical stability. Subjecting them to PIT emulsification yielded monodispersed polymeric nanomicelles of DEPA (Nano DEPA) with hydrodynamic mean diameter of 153.74nm. The high-resolution scanning and transmission electron microscopic studies revealed the characteristic core-shell structure of micelle. The comparative efficacy of Bulk DEPA and Nano DEPA was evaluated by larvicidal and WHO cone bioassay against the Japanese encephalitis vector Culex tritaeniorhynchus. The median lethal concentrations (48h) for 3rd instars C. tritaeniorhynchus larvae were found to be 0.416mg/L for Bulk DEPA and 0.052mg/L for Nano DEPA, respectively. The median knockdown concentrations (60min) for the two to three-day-old, sucrose-fed, female adult mosquitoes were 5.372% (v/v) and 3.471% (v/v) for Bulk and Nano DEPA, respectively. Further investigation by histopathological and biochemical studies propound that Nano DEPA exerted better bioefficacy as comparative to its bulk form even at minimal exposure concentrations. Hence, Nano DEPA will serve as an effective alternate in controlling the vector expansion with reduced dosage. PMID:25766922

Balaji, A P B; Mishra, Prabhakar; Suresh Kumar, R S; Mukherjee, Amitava; Chandrasekaran, Natarajan

2015-04-01

28

Extracellular stability of nanoparticulate drug carriers  

PubMed Central

Nanoparticulate (NP) drug carrier systems are attractive vehicles for selective drug delivery to solid tumors. Ideally, NPs should evade clearance by the reticuloendothelial system while maintaining the ability to interact with tumor cells and facilitate cellular uptake. Great effort has been made to fulfill these design criteria, yielding various types of functionalized NPs. Another important consideration in NP design is the physical and functional stability during circulation, which, if ignored, can significantly undermine the promise of intelligently designed NP drug carriers. This commentary reviews several NP examples with stability issues and their consequences, ending in a discussion of experimental methods for reliable prediction of NP stability. PMID:24214175

Liu, Karen C.; Yeo, Yoon

2014-01-01

29

Drug-Initiated Ring-Opening Polymerization of OCarboxyanhydrides for the Preparation of Anticancer Drug-  

E-print Network

Drug-Initiated Ring-Opening Polymerization of OCarboxyanhydrides for the Preparation of Anticancer Drug- Poly(Ocarboxyanhydride) Nanoconjugates Qian Yin, Rong Tong,, Yunxiang Xu, Kwanghyun Baek of polymer-drug conjugates for nanoparticulate drug delivery: hydroxyl-containing drug (e.g., camptothecin

Cheng, Jianjun

30

Nanoparticulate-catalyzed oxygen transfer processes  

DOEpatents

Nanoparticulates of oxygen transfer materials that are oxides of rare earth metals, combinations of rare earth metals, and combinations of transition metals and rare earth metals are used as catalysts in a variety of processes. Unexpectedly large thermal efficiencies are achieved relative to micron sized particulates. Processes that use these catalysts are exemplified in a multistage reactor. The exemplified reactor cracks C6 to C20 hydrocarbons, desulfurizes the hydrocarbon stream and reforms the hydrocarbons in the stream to produce hydrogen. In a first reactor stage the steam and hydrocarbon are passed through particulate mixed rare earth metal oxide to crack larger hydrocarbon molecules. In a second stage, the steam and hydrocarbon are passed through particulate material that desulfurizes the hydrocarbon. In a third stage, the hydrocarbon and steam are passed through a heated, mixed transition metal/rare earth metal oxide to reform the lower hydrocarbons and thereby produce hydrogen. Stages can be alone or combined. Parallel reactors can provide continuous reactant flow. Each of the processes can be carried out individually.

Hunt, Andrew T. (Atlanta, GA); Breitkopf, Richard C. (Dunwoody, GA)

2009-12-01

31

Occupational health risk to nanoparticulate exposure.  

PubMed

The evolution of nanotechnology from laboratory research to full-scale production has led to the need to understand the health risk to workers in that industry from the dispersion of nanoparticles escaping from various aspects of the production process. Risk is a function of both the hazard imposed by a compound or material and the expected exposure level. Therefore, research to evaluate proper exposure assessment methods specific to nanoparticles in a workplace atmosphere, as well as research on the toxicological properties of nanoparticles, has been conducted to better understand methods for protecting the health of workers in this burgeoning industry. From an assessment standpoint, researchers are evaluating both the accuracy and validity of currently available instruments and the merits of each of the three metrics – mass, surface area, and count – as indicators of exposure that provide the most relevant indication of worker health risk. Likewise, toxicologists are employing both in vitro and in vivo methods to understand the potential hazard to workers who may inhale aerosolized nanoparticles. This review provides an overview of current research efforts in nanoparticle exposure assessment and toxicology with an emphasis on how information from both fields of study combine to provide guidance to minimize the health risk posed by nanoparticulate exposure in the workplace. PMID:24592427

O'Shaughnessy, Patrick T

2013-01-01

32

Comparative cytotoxicity assessments of some manufactured and anthropogenic nanoparticulate materials  

NASA Astrophysics Data System (ADS)

Due to increasing diversity of newly engineered nanoparticles, it is important to consider the hazards of these materials. Very little is known regarding the potential toxicity of relatively new nanomaterials. However, beginning with several historical accounts of nanomaterials applications---chrysotile asbestos and silver---it was assumed that these examples would provide some awareness and guidelines for future nanomaterial and nanotechnology applications, especially health effects. In this study in vitro assays were performed on a murine alveolar macrophage cell line (RAW 264.7), human alveolar macrophage cell line (THB-1), and human epithelial lung cell line (A549) to assess the comparative cytotoxicity of a wide range of manufactured (Ag, TiO2, Fe2O3, Al2O3, ZrO2, black carbon, two different types of multiwall structures and chrysotile asbestos as the toxicity standard) and anthropogenic nanoparticulates. There are several parameters of nanoparticulates that are considered to trigger an inflammatory response (particularly respiratory) or cause toxicity. These parameters include: particle size, shape, specific surface area, transition metals in particulates, and organic compounds. Therefore, a wide variety of manufactured and anthropogenic nanoparticulates having different morphologies, sizes, specific surface area and chemistries as noted were tested. To determine the nanoparticulates' size and morphology, they were characterized by transmission electron microscopy, where it was observed that the commercial multiwall carbon nanotube aggregate had an identical morphology to chrysotile asbestos and combustion-formed carbon nanotubes, i.e.; those that form from natural gas combustion. Light optical microscopy was used to determine cell morphology upon exposure to nanoparticulates as an indication of cell death. Also, the polycyclic aromatic hydrocarbon (PAH) content of the collected nanoparticulates was analyzed and correlated with cytotoxic responses. For toxicity evaluation, cytokine production, mitochondrial function (MTT assay), reactive oxygen species generation (ROS), were assessed after 48 and 336 hours under control and exposed conditions. A simple, direct-contact assay was developed to evaluate the toxicity of anthropogenic particulate matter (PM), without removing it from high volume filter collections and exposing collected PM by direct contact with the human epithelial (A549) cells in culture. The cell viability data revealed that the manufactured nanomaterials exhibit cytotoxic response for the murine alveolar and human macrophage cell line, but in particular to the human epithelial cell line. Assay results for the direct-contact of filter-collected carbonaceous nanoparticulate, showed toxicity for all PM, but with various natural gas combustion PM being the most toxic. Light optical microscopy examination of affected human epithelial cells confirmed quantitative results. These nanoparticulate soots also produced the most reactive oxygen species (ROS) on the A549 cell culture as well as along with the Fe2O3, MWCNT-N, and black carbon (BC). Comparison of polycyclic aromatic hydrocarbon (PAH) content and concentration for the carbonaceous PM showed no PAH correlation with relative cell viability after 48 h. In addition, there was no correlation of cytotoxic response with specific surface area in the manufactured nanoparticulate materials. In conclusion, the manufactured as well as the anthropogenic nanomaterials were observed to generate large amounts of ROS and cytokines. This study suggests that the mechanism of toxicity is likely due to the generation of reactive oxygen species (ROS). Also, the comparative assessments presented, should be viewed as a precaution when considering the inhalation of the corresponding nanoparticulate materials in concentrations approaching those identified to be dangerous for recognized pathogens such as silica, black carbon, and asbestos. Humans should avoid breathing these nanoparticulate materials, although there are anthropogenic nanoparticulate materials such as MWCNT agg

Soto, Karla Fabiola

33

Multistrain influenza protection induced by a nanoparticulate mucosal immunotherapeutic  

Microsoft Academic Search

All commercial influenza vaccines elicit antibody responses that protect against seasonal infection, but this approach is limited by the need for annual vaccine reformulation that precludes efficient responses against epidemic and pandemic disease. In this study we describe a novel vaccination approach in which a nanoparticulate, liposome-based agent containing short, highly conserved influenza-derived peptides is delivered to the respiratory tract

W Tai; L Roberts; A Seryshev; J M Gubatan; C S Bland; R Zabriskie; S Kulkarni; L Soong; I Mbawuike; B Gilbert; F Kheradmand; D B Corry

2011-01-01

34

Polymeric microspheres  

DOEpatents

The invention features core-shell microsphere compositions, hollow polymeric microspheres, and methods for making the microspheres. The microspheres are characterized as having a polymeric shell with consistent shell thickness.

Walt, David R.; Mandal, Tarun K.; Fleming, Michael S.

2004-04-13

35

Nanoparticulate magnetite thin films as electrode materials for the fabrication of electrochemical capacitors  

Microsoft Academic Search

Magnetite nanoparticles in stable colloidal suspension were prepared by the co-precipitation method. Nanoparticulate magnetite\\u000a thin films on supporting stainless steel plates were prepared by drop-coating followed by heat treatment under controlled\\u000a conditions. The effects of calcination temperature and atmosphere on the microstructure and electrochemical properties of\\u000a nanoparticulate magnetite thin films were investigated. Nanoparticulate magnetite thin films prepared under optimized conditions

Suh Cem Pang; Wai Hwa Khoh; Suk Fun Chin

2010-01-01

36

Highly Conductive Nanoparticulate Films Achieved at Low Sintering Temperatures  

NASA Astrophysics Data System (ADS)

Nanoparticulate Ag films have been produced by the laser ablation of microparticle aerosol (LAMA) deposition process. LAMA enables the production of thick, nanoparticulate films that are free of organics and offers the ability to control the degree of agglomeration and initial film density. The films were subsequently annealed at a range of temperatures from 100°C to 250°C to densify the films and increase conductivity. We show that, by reducing the degree of agglomeration in the films, sintering of LAMA-produced films occurs at low temperatures and results in near fully dense Ag films that exhibit an order of magnitude higher conductivity when compared to thick films produced by other techniques that are sintered at similar temperatures. Good agreement is observed between experiments and a sintering model that suggests that surface diffusion is dominant at temperatures below 150°C, and a combination of surface and grain boundary diffusion are responsible for sintering at slightly higher temperatures.

Nahar, Manuj; Keto, John W.; Becker, Michael F.; Kovar, Desiderio

2015-02-01

37

Solid-state chemical synthesis of nanoparticulate zirconia  

Microsoft Academic Search

Mechanically activated reaction of anhydrous chloride precursors with Li2O has been used to synthesise ultrafine powders of ZrO2, Mg–PSZ, and Y–TZP. In each case, milling of the reactant mixtures resulted in a combination of amorphisation and overall microstructural refinement. Chemical reaction, with the consequent formation of nanoparticulate zirconia and LiCl, only occurred during subsequent low temperature heat treatment. The mechanism

A. C Dodd; P. G McCormick

2001-01-01

38

Détection et caractérisation optiques d'une nanoparticule métallique isolée  

NASA Astrophysics Data System (ADS)

La détection optique d'une nanoparticule métallique unique par une nouvelle technique de microscopie par modulation spatiale est décrite. Dans le cas d'un nano-objet de métal noble, la mesure quantitative de son spectre d'absorption au voisinage de la résonance plasmon de surface et sa comparaison précise à un modèle théorique permettent une identification optique complète de l'objet étudié: taille, forme et orientation sur la surface sont déterminées.

Del Fatti, N.; Muskens, O.; Vallée, F.; Huntzinger, J. R.; Billaud, P.; Broyer, M.

2006-10-01

39

DEVELOPMENT OF FUNCTIONAL NANOPARTICULATE MATERIALS: Examination of the Functional and Structural Properties of Nanoparticulate Metal Complexes Prepared by Precipitation with Compressed Antisolvent Technology  

E-print Network

. The research described in this dissertation involves the development of nanomaterials that interact with NO. Molecule-based nanoparticulate metal complexes were prepared using precipitation with compressed antisolvent technology. Microscopy and powder x...

Nguyen, Joseph G.

2008-01-01

40

Equilibrium Polymerization as a Critical Phenomenon  

NASA Astrophysics Data System (ADS)

Equilibrium polymerization can be described by the n-->0 limit of the n-vector model of magnetism in a small magnetic field. Nonclassical critical effects are predicted. The earlier theory of Tobolsky and Eisenberg is a mean-field approximation to the present theory. An application is made to the polymerization in sulfur.

Wheeler, John C.; Kennedy, Stephen J.; Pfeuty, Pierre

1980-12-01

41

ZnO Nanorod-TiO2-Nanoparticulate Electrode for Dye-Sensitized Solar Cells  

NASA Astrophysics Data System (ADS)

Highly dense ZnO nanorods were synthesized on TiO2-nanoparticulate coated fluorine-doped tin oxide (FTO) substrates by the chemical vapor deposition method for dye-sensitized solar cells (DSSCs). The uniformly grown ZnO nanorod layer has a thickness of ˜4 ?m on the TiO2-nanoparticulate layer with a wurtzite structures as confirmed by the X-ray diffraction pattern. The DSSC fabricated with a ZnO nanorod/TiO2-nanoparticulate electrode had an overall light-to-electricity conversion efficiency ? of 3.7% with a short-circuit current density JSC of 8.12 mA/cm2, open-circuit voltage VOC of 0.76 V, and fill factor \\mathit{FF} of 0.59, whereas ZnO nanowire/TiO2-nanoparticulate-electrode-based DSSCs exhibited a low ? of 1.1% with JSC of 2.14 mA/cm2 and slightly high VOC of 0.79 V. It is expected that the enhanced photovoltaic performance of the ZnO nanorod/TiO2-nanoparticulate electrode can be attributed to high dye loading and high light harvesting through large surface areas of ZnO nanorods incorporated with TiO2-nanoparticulate as compared with the ZnO nanowire/TiO2-nanoparticulate electrode.

Akhtar, M. Shaheer; Hyung, Jung-Hwan; Kim, Tae-Hong; Yang, O-Bong; Lee, Sang-Kwon

2009-12-01

42

ZnO Nanorod-TiO2-Nanoparticulate Electrode for Dye-Sensitized Solar Cells  

NASA Astrophysics Data System (ADS)

Highly dense ZnO nanorods were synthesized on TiO2-nanoparticulate coated fluorine-doped tin oxide (FTO) substrates by the chemical vapor deposition method for dye-sensitized solar cells (DSSCs). The uniformly grown ZnO nanorod layer has a thickness of ˜4 µm on the TiO2-nanoparticulate layer with a wurtzite structures as confirmed by the X-ray diffraction pattern. The DSSC fabricated with a ZnO nanorod/TiO2-nanoparticulate electrode had an overall light-to-electricity conversion efficiency ? of 3.7% with a short-circuit current density JSC of 8.12 mA/cm2, open-circuit voltage VOC of 0.76 V, and fill factor FF of 0.59, whereas ZnO nanowire/TiO2-nanoparticulate-electrode-based DSSCs exhibited a low ? of 1.1% with JSC of 2.14 mA/cm2 and slightly high VOC of 0.79 V. It is expected that the enhanced photovoltaic performance of the ZnO nanorod/TiO2-nanoparticulate electrode can be attributed to high dye loading and high light harvesting through large surface areas of ZnO nanorods incorporated with TiO2-nanoparticulate as compared with the ZnO nanowire/TiO2-nanoparticulate electrode.

Shaheer Akhtar, M.; Hyung, Jung-Hwan; Kim, Tae-Hong; Yang, O.-Bong; Lee, Sang-Kwon

2009-12-01

43

ZnO Nanorod-TiO2-Nanoparticulate Electrode for Dye-Sensitized Solar Cells  

Microsoft Academic Search

Highly dense ZnO nanorods were synthesized on TiO2-nanoparticulate coated fluorine-doped tin oxide (FTO) substrates by the chemical vapor deposition method for dye-sensitized solar cells (DSSCs). The uniformly grown ZnO nanorod layer has a thickness of ˜4 mum on the TiO2-nanoparticulate layer with a wurtzite structures as confirmed by the X-ray diffraction pattern. The DSSC fabricated with a ZnO nanorod\\/TiO2-nanoparticulate electrode

M. Shaheer Akhtar; Jung-Hwan Hyung; Tae-Hong Kim; O-Bong Yang; Sang-Kwon Lee

2009-01-01

44

Polymeric nanoparticles  

PubMed Central

Nanocarriers with various compositions and biological properties have been extensively applied for in vitro/in vivo drug and gene delivery. The family of nanocarriers includes polymeric nanoparticles, lipid-based carriers (liposomes/micelles), dendrimers, carbon nanotubes, and gold nanoparticles (nanoshells/nanocages). Among different delivery systems, polymeric carriers have several properties such as: easy to synthesize, inexpensive, biocompatible, biodegradable, non-immunogenic, non-toxic, and water soluble. In addition, cationic polymers seem to produce more stable complexes led to a more protection during cellular trafficking than cationic lipids. Nanoparticles often show significant adjuvant effects in vaccine delivery since they may be easily taken up by antigen presenting cells (APCs). Natural polymers such as polysaccharides and synthetic polymers have demonstrated great potential to form vaccine nanoparticles. The development of new adjuvants or delivery systems for DNA and protein immunization is an expanding research field. This review describes polymeric carriers especially PLGA, chitosan, and PEI as vaccine delivery systems. PMID:24128651

Bolhassani, Azam; Javanzad, Shabnam; Saleh, Tayebeh; Hashemi, Mehrdad; Aghasadeghi, Mohammad Reza; Sadat, Seyed Mehdi

2014-01-01

45

Pharmaceutical Properties of Nanoparticulate Formulation Composed of TPGS and PLGA for Controlled Delivery of Anticancer Drug  

E-print Network

A suitable management of the pharmaceutical property is needed and helpful to design a desired nanoparticulate delivery system, which includes the carrier nature, particle size and size distribution, morphology, surfactant ...

Mu, L.

46

Spleen injury and apoptotic pathway in mice caused by titanium dioxide nanoparticules  

Microsoft Academic Search

Nanoparticulate titanium dioxide (TiO2) has been demonstrated to decrease immunity of mice, but very little is known about the injury of spleen involved immunomodulation and its molecular mechanism. In order to understand the spleen injury induced by intraperitoneal injection of TiO2 nanoparticules (NPs) for consecutive 45 days, the spleen pathological changes, apoptosis, the expression levels of the apoptotic genes and

Na Li; Yanmei Duan; Mengmeng Hong; Lei Zheng; Min Fei; Xiaoyang Zhao; Jue Wang; Yaling Cui; Huiting Liu; Jingwei Cai; Songjie Gong; Han Wang; Fashui Hong

2010-01-01

47

Chain Reaction Polymerization.  

ERIC Educational Resources Information Center

The salient features and importance of chain-reaction polymerization are discussed, including such topics as the thermodynamics of polymerization, free-radical polymerization kinetics, radical polymerization processes, copolymers, and free-radical chain, anionic, cationic, coordination, and ring-opening polymerizations. (JN)

McGrath, James E.

1981-01-01

48

Microstructures and Nanostructures for Environmental Carbon Nanotubes and Nanoparticulate Soots  

PubMed Central

This paper examines the microstructures and nanostructures for natural (mined) chrysotile asbestos nanotubes (Mg3 Si2O5 (OH)4) in comparison with commercial multiwall carbon nanotubes (MWCNTs), utilizing scanning and transmission electron microscopy (SEM and TEM). Black carbon (BC) and a variety of specific soot particulate (aggregate) microstructures and nanostructures are also examined comparatively by SEM and TEM. A range of MWCNTs collected in the environment (both indoor and outdoor) are also examined and shown to be similar to some commercial MWCNTs but to exhibit a diversity of microstructures and nanostructures, including aggregation with other multiconcentric fullerenic nanoparticles. MWCNTs formed in the environment nucleate from special hemispherical graphene “caps” and there is evidence for preferential or energetically favorable chiralities, tube growth, and closing. The multiconcentric graphene tubes (?5 to 50 nm diameter) differentiate themselves from multiconcentric fullerenic nanoparticles and especially turbostratic BC and carbonaceous soot nanospherules (?8 to 80 nm diameter) because the latter are composed of curved graphene fragments intermixed or intercalated with polycyclic aromatic hydrocarbon (PAH) isomers of varying molecular weights and mass concentrations; depending upon combustion conditions and sources. The functionalizing of these nanostructures and photoxidation and related photothermal phenomena, as these may influence the cytotoxicities of these nanoparticulate aggregates, will also be discussed in the context of nanostructures and nanostructure phenomena, and implications for respiratory health. PMID:19151426

Murr, L. E.

2008-01-01

49

Nanoparticulate carriers (NPC) for oral pharmaceutics and nutraceutics.  

PubMed

The introduction of nanoparticulate carriers (NPC) in the pharmaceutic and nutraceutic fields has changed the definitions of disease management and treatment, diagnosis, as well as the supply food chain in the agri-food sector. NPC composed of synthetic polymers, proteins or polysaccharides gather interesting properties to be used for oral administration of pharmaceutics and nutraceutics. Oral administration remains the most convenient way of delivering drugs (e.g. peptides, proteins and nucleic acids) since these suffer similar metabolic pathways as food supply. Recent advances in biotechnology have produced highly potent new molecules however with low oral bioavailability. A suitable and promising approach to overcome their sensitivity to chemical and enzymatic hydrolysis as well as the poor cellular uptake, would be their entrapment within suitable gastrointestinal (GI) resistant NPC. Increasing attention has been paid to the potential use of NPC for peptides, proteins, antioxidants (carotenoids, omega fatty acids, coenzyme Q10), vitamins, probiotics, for oral administration. This review focuses on the most important materials to produce NPC for oral administration, and the most recent achievements in the production techniques and bioactives successfully delivered by these means. PMID:20225647

Lopes, C M; Martins-Lopes, P; Souto, E B

2010-02-01

50

Nanoparticulate carriers for the treatment of coronary restenosis  

PubMed Central

The current treatment for coronary restenosis following balloon angioplasty involves the use of a mechanical or a drug-eluting stent. Despite the high usage of commercially-available drug-eluting stents in the cardiac field, there are a number of limitations. This review will present the background of restenosis, go briefly into the molecular and cellular mechanisms of restenosis, the use of mechanical stents in coronary restenosis, and will provide an overview of the drugs and genes tested to treat restenosis. The primary focus of this article is to present a comprehensive overview on the use of nanoparticulate delivery systems in the treatment of restenosis both in-vitro and in-vivo. Nanocarriers have been tested in a variety of animal models and in human clinical trials with favorable results. Polymer-based nanoparticles, liposomes, and micelles will be discussed, in addition to the findings presented in the field of cardiovascular drug targeting. Nanocarrier-based delivery presents a viable alternative to the current stent based therapies. PMID:17722543

Brito, Luis; Amiji, Mansoor

2007-01-01

51

Structurally inhomogeneous nanoparticulate catalysts in cobalt-catalyzed carbon nanotube growth  

SciTech Connect

The structure of nanoparticulate catalysts involved in cobalt-catalyzed chemical vapor deposition growth of carbon nanotubes (CNTs) was investigated by in situ environmental transmission electron microscopy (ETEM). In contrast to previous studies, the analyses of ETEM images showed that the nanoparticulate catalysts were structurally inhomogeneous during CNT growth in the source gas of acetylene at a rate of pressure increase of about 3?Pa/h and at 550?°C. The lattice fringes observed in the nanoparticulate catalysts can be accounted for by not a single crystalline structure but by several possible pairs of structures including pure Co and cobalt carbides. The inhomogeneous structures were unstable with time. The possible origin of the inhomogeneous structures is discussed.

Kohigashi, Y. [The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Department of Physics, Graduate School of Science, Osaka University, 1-1 Machikane-yama, Toyonaka, Osaka 560-0043 (Japan); Yoshida, H.; Takeda, S., E-mail: takeda@sanken.osaka-u.ac.jp [The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Homma, Y. [Department of Physics, Tokyo University of Science, Shinjuku, Tokyo 162-8601 (Japan)

2014-08-18

52

Chemical components, pharmacological properties, and nanoparticulate delivery systems of Brucea javanica  

PubMed Central

Brucea javanica has demonstrated a variety of antitumoral, antimalarial, and anti- inflammatory properties. As a Chinese herbal medicine, Brucea javanica is mainly used in the treatment of lung and gastrointestinal cancers. Pharmacological research has identified the main antitumor components are tetracyclic triterpene quassinoids. However, most of these active components have poor water solubility and low bioavailability, which greatly limit their clinical application. Nanoparticulate delivery systems are urgently needed to improve the bioavailability of Brucea javanica. This paper mainly focuses on the chemical components in Brucea javanica and its pharmacological properties and nanoparticulate formulations, in an attempt to encourage further research on its active components and nanoparticulate drug delivery systems to expand its clinical applications. It is expected to improve the level of pharmaceutical research and provide a strong scientific foundation for further study on the medicinal properties of this plant. PMID:23319860

Chen, Meiwan; Chen, Ruie; Wang, Shengpeng; Tan, Wen; Hu, Yangyang; Peng, Xinsheng; Wang, Yitao

2013-01-01

53

Interaction Between Nanoparticulate Anatase TiO 2 and Lactate Dehydrogenase  

Microsoft Academic Search

In order to study the mechanisms underlying the effects of TiO2 nanoparticles on lactate dehydrogenase (LDH, EC1.1.1.27), Institute of Cancer Research region mice were injected with nanoparticulate\\u000a anatase TiO2 (5 nm) of various doses into the abdominal cavity daily for 14 days. We then examined LDH activity in vivo and in vitro and\\u000a direct evident for interaction between nanoparticulate anatase TiO2 and

Yanmei Duan; Na Li; Chao Liu; Huiting Liu; Yaling Cui; Han Wang; Fashui Hong

2010-01-01

54

Structure evolution of nanoparticulate Fe2O3  

NASA Astrophysics Data System (ADS)

The atomic structure and properties of nanoparticulate Fe2O3 are characterized starting from its smallest Fe2O3 building unit through (Fe2O3)n clusters to nanometer-sized Fe2O3 particles. This is achieved by combining global structure optimizations at the density functional theory level, molecular dynamics simulations by employing tailored, ab initio parameterized interatomic potential functions and experiments. With the exception of nearly tetrahedral, adamantane-like (Fe2O3)2 small (Fe2O3)n clusters assume compact, virtually amorphous structures with little or no symmetry. For n = 2-5 (Fe2O3)n clusters consist mainly of two- and three-membered Fe-O rings. Starting from n = 5 they increasingly assume tetrahedral shape with the adamantane-like (Fe2O3)2 unit as the main building block. However, the small energy differences between different isomers of the same cluster-size make precise structural assignment for larger (Fe2O3)n clusters difficult. The tetrahedral morphology persists for Fe2O3 nanoparticles with up to 3 nm in diameter. Simulated crystallization of larger nanoparticles with diameters of about 5 nm demonstrates pronounced melting point depression and leads to formation of ?-Fe2O3 single crystals with hexagonal morphology. This finding is in excellent agreement with the results obtained for Fe2O3 nanopowders generated by laser vaporization and provides the first direct indication that ?-Fe2O3 may be thermodynamically the most stable phase in this size regime.The atomic structure and properties of nanoparticulate Fe2O3 are characterized starting from its smallest Fe2O3 building unit through (Fe2O3)n clusters to nanometer-sized Fe2O3 particles. This is achieved by combining global structure optimizations at the density functional theory level, molecular dynamics simulations by employing tailored, ab initio parameterized interatomic potential functions and experiments. With the exception of nearly tetrahedral, adamantane-like (Fe2O3)2 small (Fe2O3)n clusters assume compact, virtually amorphous structures with little or no symmetry. For n = 2-5 (Fe2O3)n clusters consist mainly of two- and three-membered Fe-O rings. Starting from n = 5 they increasingly assume tetrahedral shape with the adamantane-like (Fe2O3)2 unit as the main building block. However, the small energy differences between different isomers of the same cluster-size make precise structural assignment for larger (Fe2O3)n clusters difficult. The tetrahedral morphology persists for Fe2O3 nanoparticles with up to 3 nm in diameter. Simulated crystallization of larger nanoparticles with diameters of about 5 nm demonstrates pronounced melting point depression and leads to formation of ?-Fe2O3 single crystals with hexagonal morphology. This finding is in excellent agreement with the results obtained for Fe2O3 nanopowders generated by laser vaporization and provides the first direct indication that ?-Fe2O3 may be thermodynamically the most stable phase in this size regime. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06989g

Erlebach, Andreas; Kurland, Heinz-Dieter; Grabow, Janet; Müller, Frank A.; Sierka, Marek

2015-02-01

55

Methylation of Mercury by Bacteria Exposed to Dissolved, Nanoparticulate, and Microparticulate Mercuric Sulfides  

E-print Network

Methylation of Mercury by Bacteria Exposed to Dissolved, Nanoparticulate, and Microparticulate in the environment is partly controlled by the bioavailability of inorganic divalent mercury (Hg(II)) to anaerobic matter to form chemical species that include organic-coated mercury sulfide nanoparticles as reaction

56

Nanoparticulate Iron Oxide Minerals in Soils and Sediments: Unique Properties and Contaminant Scavenging Mechanisms  

Microsoft Academic Search

Nanoparticulate goethite, akaganeite, hematite, ferrihydrite and schwertmannite are important constituents of soils, sediments and mine drainage outflows. These minerals have high sorption capacities for metal and anionic contaminants such as arsenic, chromium, lead, mercury and selenium. Contaminant sequestration is accomplished mainly by surface complexation, but aggregation of particles may encapsulate sorbed surface species into the multigrain interior interfaces, with significant

Glenn A. Waychunas; Christopher S. Kim; Jillian F. Banfield

2005-01-01

57

X-ray phase computed tomography for nanoparticulated imaging probes and therapeutics: preliminary feasibility study  

NASA Astrophysics Data System (ADS)

With the scientific progress in cancer biology, pharmacology and biomedical engineering, the nano-biotechnology based imaging probes and therapeutical agents (namely probes/agents) - a form of theranostics - are among the strategic solutions bearing the hope for the cure of cancer. The key feature distinguishing the nanoparticulated probes/agents from their conventional counterparts is their targeting capability. A large surface-to-volume ratio in nanoparticulated probes/agents enables the accommodation of multiple targeting, imaging and therapeutic components to cope with the intra- and inter-tumor heterogeneity. Most nanoparticulated probes/agents are synthesized with low atomic number materials and thus their x-ray attenuation are very similar to biological tissues. However, their microscopic structures are very different, which may result in significant differences in their refractive properties. Recently, the investigation in the x-ray grating-based differential phase contrast (DPC) CT has demonstrated its advantages in differentiating low-atomic materials over the conventional attenuation-based CT. We believe that a synergy of x-ray grating-based DPC CT and nanoparticulated imaging probes and therapeutic agents may play a significant role in extensive preclinical and clinical applications, or even become a modality for molecular imaging. Hence, we propose to image the refractive property of nanoparticulated imaging probes and therapeutical agents using x-ray grating-based DPC CT. In this work, we conduct a preliminary feasibility study with a focus to characterize the contrast-to-noise ratio (CNR) and contrast-detail behavior of the x-ray grating-based DPC CT. The obtained data may be instructive to the architecture design and performance optimization of the x-ray grating-based DPC CT for imaging biomarker-targeted imaging probes and therapeutic agents, and even informative to the translation of preclinical research in theranostics into clinical applications.

Tang, Xiangyang; Yang, Yi; Tang, Shaojie

2011-03-01

58

Polymerization of perfluorobutadiene  

NASA Technical Reports Server (NTRS)

Diisopropyl peroxydicarbonate dissolved in liquid perfluorobutadiene is conducted in a sealed vessel at the autogenous pressure of polymerization. Reaction temperature, ratio of catalyst to monomer, and amount of agitation determine degree of polymerization and product yield.

Newman, J.; Toy, M. S.

1970-01-01

59

Particle-Level Modeling of the Charge-Discharge Behavior of Nanoparticulate Phase-Separating Li-Ion Battery Electrodes  

E-print Network

In nanoparticulate phase-separating electrodes, phase separation inside the particles can be hindered during their charge/discharge cycles even when a thermodynamic driving force for phase separation exists. In such cases, ...

Orvananos, Bernardo

60

Anticancer Polymeric Nanomedicines  

Microsoft Academic Search

Polymers play important roles in the design of delivery nanocarriers for cancer therapies. Polymeric nanocarriers with anticancer drugs conjugated or encapsulated, also known as polymeric nanomedicines, form a variety of different architectures including polymer?drug conjugates, micelles, nanospheres, nanogels, vesicles, and dendrimers. This review focuses on the current state of the preclinical and clinical investigations of polymer?drug conjugates and polymeric micelles.

Rong Tong; Jianjun Cheng

2007-01-01

61

Polymerization Reactor Engineering.  

ERIC Educational Resources Information Center

Describes a polymerization reactor engineering course offered at Michigan Technological University which focuses on the design and operation of industrial polymerization reactors to achieve a desired degree of polymerization and molecular weight distribution. Provides a list of the course topics and assigned readings. (TW)

Skaates, J. Michael

1987-01-01

62

Oxidative stress in the brain of mice caused by translocated nanoparticulate TiO 2 delivered to the abdominal cavity  

Microsoft Academic Search

In order to study the mechanisms underlying the effects of TiO2 nanoparticles on the brain, ICR mice were injected with nanoparticulate anatase TiO2 (5nm) of various doses into the abdominal cavity daily for 14 days. We then examined the coefficient of the brain, the brain pathological changes and oxidative stress-mediated responses, and the accumulation of nanoparticulate anatase TiO2 and levels

Linglan Ma; Jie Liu; Na Li; Jue Wang; Yanmei Duan; Jinying Yan; Huiting Liu; Han Wang; Fashui Hong

2010-01-01

63

A Novel Method for Preparing Ordered SnO 2\\/TiO 2 Alternate Nanoparticulate Films  

Microsoft Academic Search

A novel method using LB films as precursors to prepare pure inorganic ordered film with periodic structure was developed. Surfactant-stabilized SnO2 nanoparticulate organosols and TiO2 nanoparticulate organosols were prepared and used as spreading solutions. Using LB technique, the good film-forming ability of the surfactant-stabilized SnO2 nanoparticles and TiO2 nanoparticles was confirmed by the determination of the ?–A isotherms. The surfactant-stabilized

Lixin Cao; Haibao Wan; Lihua Huo; Shiquan Xi

2001-01-01

64

P38-Nrf-2 Signaling Pathway of Oxidative Stress in Mice Caused by Nanoparticulate TiO 2  

Microsoft Academic Search

Some recent studies have been previously suggested that nanoparticulate titanium dioxide (TiO2) damaged liver function and decreased immunity of mice, but the spleen injury and its oxidative stress mechanism are still\\u000a unclear. To understand the spleen injury induced by intragastric administration of nanoparticulate anatase TiO2 for consecutive 30 days, the spleen pathological changes, the oxidative stress, and p38 and c-Jun N-terminal

Jue Wang; Na Li; Lei Zheng; Sisi Wang; Ying Wang; Xiaoyang Zhao; Yanmei Duan; Yaling Cui; Min Zhou; Jingwei Cai; Songjie Gong; Han Wang; Fashui Hong

2011-01-01

65

Cationic additives in nanosystems activate cytotoxicity and inflammatory response of human neutrophils: lipid nanoparticles versus polymeric nanoparticles  

PubMed Central

This report compares the effect of lipid and polymeric nanoparticles upon human neutrophils in the presence of cationic surfactants. Nanostructured lipid carriers and poly(lactic-co-glycolic) acid nanoparticles were manufactured as lipid and polymeric systems, respectively. Some cytotoxic and proinflammatory mediators such as lactate dehydrogenase (LDH), elastase, O2•?, and intracellular Ca2+ were examined. The nanoparticles showed a size of 170–225 nm. Incorporation of cetyltrimethylammonium bromide or soyaethyl morpholinium ethosulfate, the cationic surfactant, converted zeta potential from a negative to a positive charge. Nanoparticles without cationic surfactants revealed a negligible change on immune and inflammatory responses. Cationic surfactants in both nanoparticulate and free forms induced cell death and the release of mediators. Lipid nanoparticles generally demonstrated a greater response compared to polymeric nanoparticles. The neutrophil morphology observed by electron microscopy confirmed this trend. Cetyltrimethylammonium bromide as the coating material showed more significant activation of neutrophils than soyaethyl morpholinium ethosulfate. Confocal microscope imaging displayed a limited internalization of nanoparticles into neutrophils. It is proposed that cationic nanoparticles interact with the cell membrane, triggering membrane disruption and the following Ca2+ influx. The elevation of intracellular Ca2+ induces degranulation and oxidative stress. The consequence of these effects is cytotoxicity and cell death. Caution should be taken when selecting feasible nanoparticulate formulations and cationic additives for consideration of applicability and toxicity. PMID:25609950

Hwang, Tsong-Long; Aljuffali, Ibrahim A; Lin, Chwan-Fwu; Chang, Yuan-Ting; Fang, Jia-You

2015-01-01

66

High-resolution patterned nanoparticulate Ag electrodes toward all printed organic thin film transistors  

Microsoft Academic Search

High-resolution patterned nanoparticulate Ag electrode arrays and all printed organic thin film transistors (OTFTs) were demonstrated using a simple dip-casting and a photoresist-free, non-relief-pattern lithographic process. An octadecyltrichlorosilane self-assembled monolayer was deposited to provide low surface energy and patterned by deep ultraviolet light, resulting in reproducible periodic arrays of patterned hydrophilic domains separated from hydrophobic surroundings. Using a simple dip-casting

Sung Kyu Park; Yong-Hoon Kim; Jeong-In Han

2009-01-01

67

Seeded growth of robust SERS-active 2D Au@Ag nanoparticulate films  

SciTech Connect

We demonstrate herein a novel and versatile solution-based methodology for fabricating self-organized two-dimensional (2D) Au nanoparticle arrays on glass using in situ nucleation at an aminosilane monolayer followed by seeded, electroless growth; subsequent deposition of Ag produced Au{at}Ag core-shell nanoparticulate films which proved highly promising as surface-enhanced Raman scattering (SERS) platforms.

Baker, Gary A [ORNL; Dai, Sheng [ORNL; Hagaman, Edward {Ed} W [ORNL; Mahurin, Shannon Mark [ORNL; Zhu, Haoguo [ORNL; Bao, Lili [Oak Ridge National Laboratory (ORNL)

2008-01-01

68

Nanoparticulate TiO 2-stearate alternating multilayers deposited through the LB method  

Microsoft Academic Search

Stable nanoparticulate TiO2-stearate (TiO2-St) monolayers can be obtained by using TiO2 (anatase-type) hydrosol as the subphase. The area extrapolated to ?= 0 is 0.25 nm2 per hydrocarbon chain of the monolayer. The “collapse” pressure is about 50 mN m?1. The monolayer can be transferred onto a solid substrate perfectly under certain pressure. The surface of the even-layer (odd-layer) of the

Linsong Li; Yongmei Chen; Shihai Kan; Xintong Zhang; Xiaogang Peng; Mingdeng Liu; Tiejin Li

1996-01-01

69

Effect of Particle Size on the Photocatalytic Activity of Nanoparticulate Zinc Oxide  

Microsoft Academic Search

In this study, a three-stage process consisting of mechanical milling, heat treatment, and washing has been used to manufacture\\u000a nanoparticulate ZnO powders with a controlled particle size and minimal agglomeration. By varying the temperature of the post-milling\\u000a heat treatment, it was possible to control the average particle size over the range of 28–57 nm. The photocatalytic activity\\u000a of these powders was

A. C. Dodd; A. J. McKinley; M. Saunders; T. Tsuzuki

2006-01-01

70

Scanning tunneling microscopy\\/spectroscopy of titanium dioxide nanoparticulate film on Au( 1 1 1 ) surface  

Microsoft Academic Search

Scanning tunneling microscopy (STM)\\/scanning tunneling spectroscopy (STS) of titanium dioxide nanoparticulate film on Au(111) surface is carried out yielding topography, I–V, dI\\/dV versus V and normalized dI\\/dV versus V. Isolated nanoparticles were found to exhibit semiconducting behavior with a band gap which varies from 1 to >3.0eV depending on the nature of substrate\\/nanoparticle\\/tip junction formation. Increase in the particulate density

Suwarna Datar; P. Madhu Kumar; Murali Sastry; C. V Dharmadhikari

2004-01-01

71

Hyper-Rayleigh scattering (HRS) spectroscopy applied to nanoparticulate TiO 2  

Microsoft Academic Search

We have probed the photophysics of nanoparticulate TiO2 using hyper-Rayleigh scattering (HRS) spectroscopy. We find that despite its Wurtzite structure, the anatase particles we prepared are only weakly hyperpolarizable, which suggests that second harmonic generation may couple transitions which are: (a) only weakly allowed, i.e. indirect; or (b) associated with states, probably surface states, of low density. Addition of a

M. R. V. Sahyun

2002-01-01

72

Nanoparticulate-induced toxicity and related mechanism in vitro and in vivo  

Microsoft Academic Search

In urban areas, the quantity of exhaust particles from vehicle emissions is tremendous and has been regarded as the main contributor\\u000a to particulate matter (PM) pollution. Recently, the nano-sized PM on public health has begun to raise the attention. The increased\\u000a toxicity of nanoparticulate can be largely explained by their small size, high airborne concentration, extensive surface area\\u000a and high

Hye Won Kim; Eun-Kyung Ahn; Bo Keun Jee; Hyoung-Kyu Yoon; Kweon Haeng Lee; Young Lim

2009-01-01

73

Water-based nanoparticulate solar cells using a diketopyrrolopyrrole donor polymer.  

PubMed

Organic photovoltaic devices with either bulk heterojunction (BHJ) or nanoparticulate (NP) active layers have been prepared from a 1?:?2 blend of (poly{3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-naphthalene}) (PDPP-TNT) and the fullerene acceptor, ([6,6]-phenyl C71-butyric acid methyl ester) (PC70BM). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) have been used to investigate the morphology of the active layers of the two approaches. Mild thermal treatment of the NP film is required to promote initial joining of the NPs in order for the devices to function, however the NP structure is retained. Consequently, whereas gross phase segregation of the active layer occurs in the BHJ device spin cast from chloroform, the nanoparticulate approach retains control of the material domain sizes on the length scale of exciton diffusion in the materials. As a result, NP devices are found to generate more than twice the current density of BHJ devices and have a substantially greater overall efficiency. The use of aqueous nanoparticulate dispersions offers a promising approach to control the donor acceptor morphology on the nanoscale with the benefit of environmentally-friendly, solution-based fabrication. PMID:24382591

Vaughan, Ben; Williams, Evan L; Holmes, Natalie P; Sonar, Prashant; Dodabalapur, Ananth; Dastoor, Paul C; Belcher, Warwick J

2014-02-14

74

Making Polymeric Microspheres  

NASA Technical Reports Server (NTRS)

Combination of advanced techniques yields uniform particles for biomedical applications. Process combines ink-jet and irradiation/freeze-polymerization techniques to make polymeric microspheres of uniform size in diameters from 100 to 400 micrometer. Microspheres used in chromatography, cell sorting, cell labeling, and manufacture of pharmaceutical materials.

Rhim, Won-Kyu; Hyson, Michael T.; Chung, Sang-Kun; Colvin, Michael S.; Chang, Manchium

1989-01-01

75

Step-Growth Polymerization.  

ERIC Educational Resources Information Center

Following a comparison of chain-growth and step-growth polymerization, focuses on the latter process by describing requirements for high molecular weight, step-growth polymerization kinetics, synthesis and molecular weight distribution of some linear step-growth polymers, and three-dimensional network step-growth polymers. (JN)

Stille, J. K.

1981-01-01

76

Halley's polymeric organic molecules  

SciTech Connect

The detection of polymeric organic compounds in the mass spectrum of Comet Halley obtained with the Positive Ion Cluster Composition analyzer on Giotto are examined. It is found that, in addition to polyoxymethylene, other polymers and complex molecules may exist in the comet. It is suggested that polymerized hydrogen cyanide may be a source for the observed CN and NH2 jets. 31 refs.

Huebner, W.F.; Boice, D.C.; Korth, A.

1989-01-01

77

Halley's polymeric organic molecules  

NASA Technical Reports Server (NTRS)

The detection of polymeric organic compounds in the mass spectrum of Comet Halley obtained with the Positive Ion Cluster Composition analyzer on Giotto are examined. It is found that, in addition to polyoxymethylene, other polymers and complex molecules may exist in the comet. It is suggested that polymerized hydrogen cyanide may be a source for the observed CN and NH2 jets.

Huebner, W. F.; Boice, D. C.; Korth, A.

1989-01-01

78

Ferroportin mediates the intestinal absorption of iron from a nanoparticulate ferritin core mimetic in mice  

PubMed Central

The ferritin core is composed of fine nanoparticulate Fe3+ oxohydroxide, and we have developed a synthetic mimetic, nanoparticulate Fe3+ polyoxohydroxide (nanoFe3+). The aim of this study was to determine how dietary iron derived in this fashion is absorbed in the duodenum. Following a 4 wk run-in on an Fe-deficient diet, mice with intestinal-specific disruption of the Fpn-1 gene (Fpn-KO), or littermate wild-type (WT) controls, were supplemented with Fe2+ sulfate (FeSO4), nanoFe3+, or no added Fe for a further 4 wk. A control group was Fe sufficient throughout. Direct intestinal absorption of nanoFe3+ was investigated using isolated duodenal loops. Our data show that FeSO4 and nanoFe3+ are equally bioavailable in WT mice, and at wk 8 the mean ± sem hemoglobin increase was 18 ± 7 g/L in the FeSO4 group and 30 ± 5 g/L in the nanoFe3+ group. Oral iron failed to be utilized by Fpn-KO mice and was retained in enterocytes, irrespective of the iron source. In summary, although nanoFe3+ is taken up directly by the duodenum its homeostasis is under the normal regulatory control of dietary iron absorption, namely via ferroportin-dependent efflux from enterocytes, and thus offers potential as a novel oral iron supplement.—Aslam, M. F., Frazer, D. M., Faria, N., Bruggraber, S. F. A., Wilkins, S. J., Mirciov, C., Powell, J. J., Anderson, G. J., Pereira, D. I. A. Ferroportin mediates the intestinal absorption of iron from a nanoparticulate ferritin core mimetic in mice. PMID:24776745

Aslam, Mohamad F.; Frazer, David M.; Faria, Nuno; Bruggraber, Sylvaine F. A.; Wilkins, Sarah J.; Mirciov, Cornel; Powell, Jonathan J.; Anderson, Greg J.; Pereira, Dora I. A.

2014-01-01

79

Structure and electrical properties of nanoparticulate tungsten oxide prepared by microwave plasma synthesis  

NASA Astrophysics Data System (ADS)

Nanoparticulate WO3 films were prepared using microwave plasma synthesis and studied with respect to the electrical conductivity in dependence of ambient conditions. The WO3 films with a monoclinic structure were made from cluster-assembled nanoparticles (diameter 3 nm) by means of dispersion and spin-coating. Above 100 °C a thermally activated decrease of the electrical resistance due to oxygen vacancy donors is found. A reversible increase of the electrical resistance R due to oxygen uptake is observed. The decrease of R in response to reducing H2S in the ppm range is studied in dependence of temperature and pre-annealing conditions.

Sagmeister, M.; Postl, M.; Brossmann, U.; List, E. J. W.; Klug, A.; Letofsky-Papst, I.; Szabó, D. V.; Würschum, R.

2011-08-01

80

Extreme enhancement and reduction of the dielectric response of polymer nanoparticulate composites via interphasial charges  

NASA Astrophysics Data System (ADS)

An analytical solution is constructed for the homogenized (i.e., macroscopic) dielectric response of particulate composites comprising a random distribution of particles bonded to a matrix material through interphases of finite size that contain space charges. By accounting for interphasial charges, the solution is able to describe and explain both the extreme enhancement and the reduction of the dielectric response typically exhibited by emerging polymer nanoparticulate composites. More generally, the solution reveals that judicious manipulation of interphasial charges provides a promising path forward for the design of materials with exceptional dielectric properties.

Lopez-Pamies, Oscar; Goudarzi, Taha; Meddeb, Amira B.; Ounaies, Zoubeida

2014-06-01

81

Preparation and Organized Assembly of Nanoparticulate TiO 2–Stearate Alternating Langmuir–Blodgett Films  

Microsoft Academic Search

Nanoparticulate TiO2–stearate Langmuir–Blodgett-type monolayers and multilayers were directly obtained by using TiO2hydrosol as the subphase. The surface pressure-versus-surface area isotherms showed that the monolayer could be compressed to a mean molecular area of 0.25 nm2. The monolayer was transferred onto a CaF2or Si substrate at a dipping speed of 18 cm\\/min and surface pressure of 25 mN\\/m. It exhibited Y-type

Lin Song Li; Zheng Hui; Yongmei Chen; Xin Tong Zhang; Xiaogang Peng; Zhongfan Liu; Tie Jin Li

1997-01-01

82

Imbibition dynamics of nano-particulate ink-jet drops on micro-porous media  

E-print Network

-jet deposition of colloidal fluids on to absorbing surfaces such as micro-porous coated papers. As an ink drop strikes a surface with significant velocity, its subsequent deformation and radial expansion are initially driven by the impact inertia, and later... Imbibition dynamics of nano-particulate ink-jet drops on micro-porous media Hsiao, W.-K., Hoath, S. D., Martin, G. D., Hutchings, I. M., Chilton, N. B. and Jones, S., Proc Nanotech 2011 Conference, Boston, June 2011. Imbibition dynamics...

Hsiao, W.-K.; Hoath, S.D.; Martin, G.D.; Hutchings, I.M.; Chilton, N.B.; Jones, S.

83

Multiphase Polymeric Materials  

NSDL National Science Digital Library

Developed by a group of PhD students at the University of Southern Mississippi, the Multiphase Polymeric Materials Website presents both general information about composites and current research on multiphase polymeric materials, including information about blends, coatings, and nanocomposites. As the newest addition to Macrogalleria (described in the March 31, 1999 Scout Report for Science & Engineering), the Multiphase Polymeric Materials Website includes information on Composites in General, Composites, Characterization and Analysis, and Application. Most useful to researchers, the Application section introduces the relationship between polymer composites and component level electronics with examples such as PCB Construction, Encapsulation of Integrated Circuits, and Non-Conductive Adhesives.

84

Thermally Polymerized Rylene Nanoparticles  

E-print Network

Rylene dyes functionalized with varying numbers of phenyl trifluorovinyl ether (TFVE) moieties were subjected to a thermal emulsion polymerization to yield shape-persistent, water-soluble chromophore nanoparticles. Perylene ...

Andrew, Trisha Lionel

85

Rapid detection of cancer related DNA nanoparticulate biomarkers and nanoparticles in whole blood  

NASA Astrophysics Data System (ADS)

The ability to rapidly detect cell free circulating (cfc) DNA, cfc-RNA, exosomes and other nanoparticulate disease biomarkers as well as drug delivery nanoparticles directly in blood is a major challenge for nanomedicine. We now show that microarray and new high voltage dielectrophoretic (DEP) devices can be used to rapidly isolate and detect cfc-DNA nanoparticulates and nanoparticles directly from whole blood and other high conductance samples (plasma, serum, urine, etc.). At DEP frequencies of 5kHz-10kHz both fluorescent-stained high molecular weight (hmw) DNA, cfc-DNA and fluorescent nanoparticles separate from the blood and become highly concentrated at specific DEP highfield regions over the microelectrodes, while blood cells move to the DEP low field-regions. The blood cells can then be removed by a simple fluidic wash while the DNA and nanoparticles remain highly concentrated. The hmw-DNA could be detected at a level of <260ng/ml and the nanoparticles at <9.5 x 109 particles/ml, detection levels that are well within the range for viable clinical diagnostics and drug nanoparticle monitoring. Disease specific cfc-DNA materials could also be detected directly in blood from patients with Chronic Lymphocytic Leukemia (CLL) and confirmed by PCR genotyping analysis.

Heller, Michael J.; Krishnan, Raj; Sonnenberg, Avery

2010-08-01

86

Electric relaxation processes in chemodynamics of aqueous metal complexes: from simple ligands to soft nanoparticulate complexants.  

PubMed

The chemodynamics of metal complexes with nanoparticulate complexants can differ significantly from that for simple ligands. The spatial confinement of charged sites and binding sites to the nanoparticulate body impacts on the time scales of various steps in the overall complex formation process. The greater the charge carried by the nanoparticle, the longer it takes to set up the counterion distribution equilibrium with the medium. A z+ metal ion (z > 1) in a 1:1 background electrolyte will accumulate in the counterionic atmosphere around negatively charged simple ions, as well as within/around the body of a soft nanoparticle with negative structural charge. The rate of accumulation is often governed by diffusion and proceeds until Boltzmann partition equilibrium between the charged entity and the ions in the medium is attained. The electrostatic accumulation proceeds simultaneously with outer-sphere and inner-sphere complex formation. The rate of the eventual inner-sphere complex formation is generally controlled by the rate constant of dehydration of the metal ion, k(w). For common transition metal ions with moderate to fast dehydration rates, e.g., Cu(2+), Pb(2+), and Cd(2+), it is shown that the ionic equilibration with the medium may be the slower step and thus rate-limiting in their overall complexation with nanoparticles. PMID:22126743

van Leeuwen, Herman P; Buffle, Jacques; Town, Raewyn M

2012-01-10

87

Nanoparticulate Transport of Oximes over an In Vitro Blood-Brain Barrier Model  

PubMed Central

Background Due to the use of organophosphates (OP) as pesticides and the availability of OP-type nerve agents, an effective medical treatment for OP poisonings is still a challenging problem. The acute toxicity of an OP poisoning is mainly due to the inhibition of acetylcholinesterase (AChE) in the peripheral and central nervous systems (CNS). This results in an increase in the synaptic concentration of the neurotransmitter acetylcholine, overstimulation of cholinergic receptors and disorder of numerous body functions up to death. The standard treatment of OP poisoning includes a combination of a muscarinic antagonist and an AChE reactivator (oxime). However, these oximes can not cross the blood-brain barrier (BBB) sufficiently. Therefore, new strategies are needed to transport oximes over the BBB. Methodology/Principal Findings In this study, we combined different oximes (obidoxime dichloride and two different HI 6 salts, HI 6 dichloride monohydrate and HI 6 dimethanesulfonate) with human serum albumin nanoparticles and could show an oxime transport over an in vitro BBB model. In general, the nanoparticulate transported oximes achieved a better reactivation of OP-inhibited AChE than free oximes. Conclusions/Significance With these nanoparticles, for the first time, a tool exists that could enable a transport of oximes over the BBB. This is very important for survival after severe OP intoxication. Therefore, these nanoparticulate formulations are promising formulations for the treatment of the peripheral and the CNS after OP poisoning. PMID:21151975

Wagner, Sylvia; Kufleitner, Jürgen; Zensi, Anja; Dadparvar, Miriam; Wien, Sascha; Bungert, Judith; Vogel, Tikva; Worek, Franz; Kreuter, Jörg; von Briesen, Hagen

2010-01-01

88

In vitro and in vivo equivalence testing of nanoparticulate intravenous formulations.  

PubMed

The topic of bioequivalence evaluation of nanoparticulate intravenous formulations is one that has been intensely debated in recent times since the release of the specific recommendations by many regulatory authorities worldwide. Product specific bioequivalence guidelines for many of the nanoparticulate systems where therapeutic molecules are directly coupled (human albumin bound paclitaxel nanosuspension), functionalized (iron- carbohydrate preparations) or entrapped/coated to a carrier (doxorubicin liposomal formulations), have been approved by the drug regulatory agencies. These current regulatory procedures include complete characterization of the generic formulation in terms of its physicochemical characteristics, pharmacokinetics disposition and/or non clinical testing with respect to the reference formulation. The concept of in vitro equivalency is emerging as a valuable tool in these guidances as generic product differing in in vitro parameters can result in a different biopharmaceutical profile with respect to pharmacokinetics and biodistribution. Furthermore, in case of systems with entrapped drug, classical pharmacokinetic parameters alone may only ensure the equivalent clearance of test and reference product from systemic circulation but may fail to detect the extent to which the nanoparticles are taken up by different target organs and, consequently, the safety and efficacy effects. Hence, additional tissue distribution study in preclinical study models has reflected in recent guidances. Understanding and interpretation of these regulatory requirements thus presents most critical component of a generic product development cycle. This article reviews these current regulatory procedures with special emphasis on in vitro population bioequivalence (POP BE) and preclinical testing of generic formulations. PMID:24203084

Pathak, S M; Ruby, P K; Aggarwal, D

2014-04-01

89

Fabrication of an inkjet-printed seed pattern with silver nanoparticulate ink on a textured silicon solar cell wafer  

NASA Astrophysics Data System (ADS)

In this study, the possibility of using inkjet printing in the fabrication of a conductive seed pattern on a textured silicon solar wafer is investigated. Firstly, solar cell wafers were coated with a hydrophobic solution. It was found that the surface texture of a solar cell wafer causes a slight increase in the contact angle of silver nanoparticulate ink by 7.5° due to a weak Cassie-Baxter wetting state. After selective laser ablation of the hydrophobic coating and the SiNx layer in preparation for the surface energy-patterned finger electrode regions, silver nanoparticulate ink was deposited with a piezo drop-on-demand inkjet print head. Because the threshold laser fluence for the ablation of the hydrophobic coating is lower than that for the SiNx layer, the effective width of a surface energy-patterned finger electrode region with the Gaussian laser beam profile was found to be wider than the actual width of the SiNx-ablated region. Although this initially results in a widened deposition of silver nanoparticulate ink, the subsequent drying of silver nanoparticulate ink is found to cause a reduction of line width of around 6% to 14%. Therefore, the final line width of the seed pattern is the outcome of two opposing phenomena. The physical and electrical characteristics of the seed pattern are as narrow as 58.5 ± 1.2 µm, as thick as 1.81 µm on average and as conductive as 2.72 µ? cm.

Shin, Dong-Youn

2010-12-01

90

Vector Voyage!  

NSDL National Science Digital Library

In this activity, students will use vector analysis to understand the concept of dead reckoning. Students will use vectors to plot their course based on a time and speed. They will then correct the positions with vectors representing winds and currents.

Jeff White

2004-01-01

91

Osteogenic and Antimicrobial Nanoparticulate Calcium Phosphate and Poly-(D, L-Lactide-co-Glycolide) Powders for the Treatment of Osteomyelitis  

PubMed Central

Development of a material for simultaneous sustained and localized delivery of antibiotics and induction of spontaneous regeneration of hard tissues affected by osteomyelitis stands for an important clinical need. In this work, a comparative analysis of the bacterial and osteoblastic cell response to two different nanoparticulate carriers of clindamycin, an antibiotic commonly prescribed in the treatment of bone infection, one composed of calcium phosphate and the other comprising poly-(D,L-lactide-co-glycolide)-coated calcium phosphate, was carried out. Three different non-cytotoxic phases of calcium phosphate, exhibiting dissolution and drug release profiles in the range of one week to two months to one year, respectively, were included in the analysis: monetite, amorphous calcium phosphate and hydroxyapatite. Spherical morphologies and narrow size distribution of both types of nanopowders were confirmed in transmission and scanning electron microscopic analyses. The antibiotic-containing powders exhibited sustained drug release contingent upon the degradation rate of the carrier. Assessment of the antibacterial performance of the antibiotic-encapsulated powders against Staphylococcus aureus, the most common pathogen isolated from infected bone, yielded satisfactory results both in broths and on blood agar plates for all the analyzed powders. In contrast, no cytotoxic behavior was detected upon the incubation of the antibiotic powders with the osteoblastic MC3T3-E1 cell line for up to three weeks. The cells were shown to engage in a close contact with the antibiotic-containing particles, irrespective of their internal or surface phase composition, polymeric or mineral. At the same time, both types of particles upregulated the expression of osteogenic markers osteocalcin, osteopontin, Runx2 and protocollagen type I, suggesting their ability to promote osteogenesis and enhance remineralization of the infected site in addition to eliminating the bacterial source of infection. PMID:23706222

Uskokovi?, Vuk; Hoover, Charles; Vukomanovi?, Marija; Uskokovi?, Dragan P.; Desai, Tejal A.

2013-01-01

92

Encapsulation by Miniemulsion Polymerization  

NASA Astrophysics Data System (ADS)

The miniemulsion technique offers the possibility for the encapsulation of different materials, ranging from liquid to solid, from organic to inorganic, and from molecularly dissolved to aggregated species into polymeric nanoparticles or nanocapsules. Using this technique, a wide variety of novel functional nanomaterials can be generated. This review focuses on the preparation of functional nanostructures by encapsulating organic or inorganic material in polymeric nanoparticles. The examples demonstrate the possibilities to protect the encapsulated material as dyes, pigments, fragrances, photo-initiators, drugs, magnetite, or even DNA, use them as marker systems (dyes, magnetite), or create nanoparticles with completely new properties.

Landfester, Katharina; Weiss, Clemens K.

93

Net methylation of mercury in estuarine sediment microcosms amended with dissolved, nanoparticulate, and microparticulate mercuric sulfides.  

PubMed

The production of methylmercury (MeHg) by anaerobic microorganisms depends in part on the speciation and bioavailability of inorganic mercury to these organisms. Our previous work with pure cultures of methylating bacteria has demonstrated that the methylation potential of mercury decreased during the aging of mercuric sulfides (from dissolved to nanoparticulate and microcrystalline HgS). The objective of this study was to understand the relationship between mercury sulfide speciation and methylation potential in experiments that more closely simulate the complexity of sediment settings. The study involved sediment slurry microcosms that represented a spectrum of salinities in an estuary and were each amended with different forms of mercuric sulfides: dissolved Hg and sulfide, nanoparticulate HgS (3-4 nm in diameter), and microparticulate HgS (>500 nm). The results indicated that net MeHg production was influenced by both the activity of sulfate-reducing microorganisms (roughly represented by the rate of sulfate loss) and the bioavailability of mercury. In the presence of abundant sulfate and carbon sources (supporting relatively high microbial activity), net MeHg production in the slurries amended with dissolved Hg was greater than in slurries amended with nano-HgS, similar to previous experiments with pure bacterial cultures. In microcosms with minimal microbial activity (indicated by low rates of sulfate loss), the addition of either dissolved Hg or nano-HgS resulted in similar amounts of net MeHg production. For all slurries receiving micro-HgS, MeHg production did not exceed abiotic controls. In slurries amended with dissolved and nano-HgS, mercury was mainly partitioned to bulk-scale mineral particles and colloids, indicating that Hg bioavailability was not simply related to dissolved Hg concentration or speciation. Overall, the results suggest that models for mercury methylation potential in the environment will need to balance the relative contributions of mercury speciation and activity of methylating microorganisms. PMID:25007388

Zhang, Tong; Kucharzyk, Katarzyna H; Kim, Bojeong; Deshusses, Marc A; Hsu-Kim, Heileen

2014-08-19

94

Plasma Polymerization on Metals  

Microsoft Academic Search

An ellipsometric technique is described for accurately measuring the film thickness of plasma-polymerized polymers on metallic substrates. The index of refraction n and absorption index Kof the plasma polymer film can also be studied by ellipsometry. Films of plasma polystyrene and polyepichlorohydrin were deposited on evaporated aluminum substrates and their thickness and optical constants determined. Plasma polystyrene films from 20

P. J. Dynes; D. H. Kaelble

1976-01-01

95

Protein specific polymeric immunomicrospheres  

NASA Technical Reports Server (NTRS)

Small, round, bio-compatible microspheres capable of covalently bonding proteins and having a uniform diameter below about 3500 A are prepared by substantially instantaneously initiating polymerization of an aqueous emulsion containing no more than 35% total monomer including an acrylic monomer substituted with a covalently bondable group such as hydroxyl, amino or carboxyl and a minor amount of a cross-linking agent.

Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Dreyer, William J. (Inventor)

1980-01-01

96

Variable Effect during Polymerization  

ERIC Educational Resources Information Center

An experiment performing the polymerization of 3-methylthiophene(P-3MT) onto the conditions for the selective electrode to determine the catechol by using cyclic voltammetry was performed. The P-3MT formed under optimized conditions improved electrochemical reversibility, selectivity and reproducibility for the detection of the catechol.

Lunsford, S. K.

2005-01-01

97

Vector quantization  

Microsoft Academic Search

A vector quantizer is a system for mapping a sequence of continuous or discrete vectors into a digital sequence suitable for communication over or storage in a digital channel. The goal of such a system is data compression: to reduce the bit rate so as to minimize communication channel capacity or digital storage memory requirements while maintaining the necessary fidelity

Robert M. Gray

1984-01-01

98

Active radar guides missile to its target: receptor-based targeted treatment of hepatocellular carcinoma by nanoparticulate systems.  

PubMed

Patients with hepatocellular carcinoma (HCC) usually present at advanced stages and do not benefit from surgical resection, so drug therapy should deserve a prominent place in unresectable HCC treatment. But chemotherapy agents, such as doxorubicin, cisplatin, and paclitaxel, frequently encounter important problems such as low specificity and non-selective biodistribution. Recently, the development of nanotechnology led to significant breakthroughs to overcome these problems. Decorating the surfaces of nanoparticulate-based drug carriers with homing devices has demonstrated its potential in concentrating chemotherapy agents specifically to HCC cells. In this paper, we reviewed the current status of active targeting strategies for nanoparticulate systems based on various receptors such as asialoglycoprotein receptor, transferrin receptor, epidermal growth factor receptor, folate receptor, integrin, and CD44, which are abundantly expressed on the surfaces of hepatocytes or liver cancer cells. Furthermore, we pointed out their merits and defects and provided theoretical references for further research. PMID:25424700

Yan, Jing-Jun; Liao, Jia-Zhi; Lin, Ju-Sheng; He, Xing-Xing

2015-01-01

99

Improved surface photovoltaic response of nanoparticulate TiO 2-pyridine derivative monolayer\\/n-Si(111) assembly  

Microsoft Academic Search

Nanoparticulate TiO2-pyridine derivative monolayer\\/n-Si(111) assembly was fabricated by Langmuir-Blodgett (LB) technique from 4-[4?-N,N-(didodecylamino) stryll pyridium (PII), and its photovoltaic conversion properties were investigated by surface photovoltage spectroscopy. Sensitization effect of PII molecule as well as TiO2 nanoparticle on n-Si(111) is observed, and the photovoltaic response of this assembly is about 20 times as high as that of n-Si(111).

J.-H. Yang; W.-S. Yang; X.-D. Chai; Y.-M. Chen; L.-S. Li; Y.-A. Cao; Y.-B. Bai; D.-J. Wang; T.-J. Li

1997-01-01

100

RuO 2-wired high-rate nanoparticulate TiO 2 (anatase): Suppression of particle growth using silica  

Microsoft Academic Search

To enhance the high-rate capability (up to 120C, 20A\\/g) of nanoparticulate TiO2 (anatase) formed by thermal treatment of protonated TiO2 nanotubes, we used two types of additives: RuO2 as an electron-conductive material [Y.-G. Guo, Y.-S. Hu, W. Sigle, J. Maier, Adv. Mater. 19 (2007) 2087] and silica as a suppressant of particle growth during heat treatment. We show systematically that

B. Erjavec; R. Dominko; P. Umek; S. Sturm; S. Pejovnik; M. Gaberscek; J. Jamnik

2008-01-01

101

Laser-induced enhancement of the surface hardness of nanoparticulate TiO 2 self-cleaning layer  

Microsoft Academic Search

We here report that the abrasion resistance of nanoparticulate TiO2 self-cleaning layers can be highly enhanced without a considerable loss of photocatalytic capability. TiO2 coating layers solution-deposited onto the glass substrate were irradiated by a pulsed ultraviolet (UV) laser at 355nm, which modified the surface morphologies via laser-induced local melting of TiO2 nanoparticles. The surface hardness, measured by pencil scratch

Jonghyun Kim; Jinsoo Kim; Myeongkyu Lee

2010-01-01

102

Vector Fields  

NSDL National Science Digital Library

Vector fields are vectors which change from point to point. A standard example is the velocity of moving air, in other words, wind. For instance, the current wind pattern in the San Francisco area can be found at . This site has a 2-dimensional representation; careful reading of the webpage will tell you at what elevation the wind is shown. How would you represent a vector field in 3 dimensions? What features are important? Some simple examples are shown. Each can be rotated by clicking and dragging with the mouse. Explore!

Dray, Tevian

2006-01-01

103

Cloning vector  

DOEpatents

A vector comprising a filamentous phage sequence containing a first copy of filamentous phage gene X and other sequences necessary for the phage to propagate is disclosed. The vector also contains a second copy of filamentous phage gene X downstream from a promoter capable of promoting transcription in a bacterial host. In a preferred form of the present invention, the filamentous phage is M13 and the vector additionally includes a restriction endonuclease site located in such a manner as to substantially inactivate the second gene X when a DNA sequence is inserted into the restriction site.

Guilfoyle, Richard A. (Madison, WI); Smith, Lloyd M. (Madison, WI)

1994-01-01

104

Cloning vector  

DOEpatents

A vector comprising a filamentous phage sequence containing a first copy of filamentous phage gene X and other sequences necessary for the phage to propagate is disclosed. The vector also contains a second copy of filamentous phage gene X downstream from a promoter capable of promoting transcription in a bacterial host. In a preferred form of the present invention, the filamentous phage is M13 and the vector additionally includes a restriction endonuclease site located in such a manner as to substantially inactivate the second gene X when a DNA sequence is inserted into the restriction site. 2 figures.

Guilfoyle, R.A.; Smith, L.M.

1994-12-27

105

Rheologie des Polymeres Charges  

NASA Astrophysics Data System (ADS)

Une etude des proprietes rheologiques en ecoulement oscillatoire et en ecoulement transitoire a ete realisee sur des suspensions de particules spheriques dans des solutions de polymere d'une part et dans des polymeres a l'etat fondu d'autre part. Une attention particuliere a ete portee sur l'influence des parametres suivants sur les proprietes en ecoulement de ces fluides complexes: nature du fluide suspendant, fraction volumique en particule, temperature. Apres analyse des resultats, de nouveaux modeles empiriques ont ete proposes afin de predire l'allure des courbes d'ecoulement de ces suspensions en cisaillement oscillatoire. Enfin, certaines analogies entre les proprietes visqueuses et viscoelastiques des suspensions dans les deux milieux mentionnes precedemment ont ete discutees.

Lepez, Olivier

106

Modeling oscillatory microtubule polymerization  

NASA Astrophysics Data System (ADS)

Polymerization of microtubules is ubiquitous in biological cells and under certain conditions it becomes oscillatory in time. Here, simple reaction models are analyzed that capture such oscillations as well as the length distribution of microtubules. We assume reaction conditions that are stationary over many oscillation periods, and it is a Hopf bifurcation that leads to a persistent oscillatory microtubule polymerization in these models. Analytical expressions are derived for the threshold of the bifurcation and the oscillation frequency in terms of reaction rates, and typical trends of their parameter dependence are presented. Both, a catastrophe rate that depends on the density of guanosine triphosphate liganded tubulin dimers and a delay reaction, such as the depolymerization of shrinking microtubules or the decay of oligomers, support oscillations. For a tubulin dimer concentration below the threshold, oscillatory microtubule polymerization occurs transiently on the route to a stationary state, as shown by numerical solutions of the model equations. Close to threshold, a so-called amplitude equation is derived and it is shown that the bifurcation to microtubule oscillations is supercritical.

Hammele, Martin; Zimmermann, Walter

2003-02-01

107

Developments in polymerization lamps.  

PubMed

Polymerization shrinkage of composite resins and the consequent stress generated at the composite-tooth interface continue to pose a serious clinical challenge. The development of high-intensity halogen lamps and the advent of curing units providing higher energy performance, such as laser lamps, plasma arc units, and, most recently, light-emitting diode (LED) curing units, have revolutionized polymerization lamp use and brought major changes in light-application techniques. A comprehensive review of the literature yielded the following conclusions: (1) the most reliable curing unit for any type of composite resin is the high-density halogen lamp, fitted with a programming device to enable both pulse-delay and soft-start techniques; (2) if any other type of curing unit is used, information must be available on the compatibility of the unit with the composite materials to be used; (3) polymerization lamp manufacturers need to focus on the ongoing development of LED technology; (4) further research is required to identify the most reliable light-application techniques. PMID:18560645

Jiménez-Planas, Amparo; Martín, Juan; Abalos, Camilo; Llamas, Rafael

2008-02-01

108

Equivalent Vectors  

ERIC Educational Resources Information Center

The cross-product is a mathematical operation that is performed between two 3-dimensional vectors. The result is a vector that is orthogonal or perpendicular to both of them. Learning about this for the first time while taking Calculus-III, the class was taught that if AxB = AxC, it does not necessarily follow that B = C. This seemed baffling. The…

Levine, Robert

2004-01-01

109

Structure-Based Rational Design of Prodrugs To Enable Their Combination with Polymeric Nanoparticle Delivery Platforms for Enhanced Antitumor Efficacy**  

PubMed Central

Drug-loaded nanoparticles (NPs) are of particular interest for efficient cancer therapy due to their improved drug delivery and therapeutic index in various types of cancer. However, the encapsulation of many chemotherapeutics into delivery NPs is often hampered by their unfavorable physicochemical properties. Here, we employed a drug reform strategy to construct a small library of SN-38 (7-ethyl-10-hydroxycamptothecin)-derived prodrugs, in which the phenolate group was modified with a variety of hydrophobic moieties. This esterification fine-tuned the polarity of the SN-38 molecule and enhanced the lipophilicity of the formed prodrugs, thereby inducing their self-assembly into biodegradable poly(ethylene glycol)-block-poly(d,l-lactic acid) (PEG-PLA) nanoparticulate structures. Our strategy combining the rational engineering of prodrugs with the pre-eminent features of conventionally used polymeric materials should open new avenues for designing more potent drug delivery systems as a therapeutic modality. PMID:25196427

Wang, Hangxiang; Xie, Haiyang; Wu, Jiaping; Wei, Xuyong; Zhou, Lin; Xu, Xiao; Zheng, Shusen

2014-01-01

110

Structure-based rational design of prodrugs to enable their combination with polymeric nanoparticle delivery platforms for enhanced antitumor efficacy.  

PubMed

Drug-loaded nanoparticles (NPs) are of particular interest for efficient cancer therapy due to their improved drug delivery and therapeutic index in various types of cancer. However, the encapsulation of many chemotherapeutics into delivery NPs is often hampered by their unfavorable physicochemical properties. Here, we employed a drug reform strategy to construct a small library of SN-38 (7-ethyl-10-hydroxycamptothecin)-derived prodrugs, in which the phenolate group was modified with a variety of hydrophobic moieties. This esterification fine-tuned the polarity of the SN-38 molecule and enhanced the lipophilicity of the formed prodrugs, thereby inducing their self-assembly into biodegradable poly(ethylene glycol)-block-poly(d,l-lactic acid) (PEG-PLA) nanoparticulate structures. Our strategy combining the rational engineering of prodrugs with the pre-eminent features of conventionally used polymeric materials should open new avenues for designing more potent drug delivery systems as a therapeutic modality. PMID:25196427

Wang, Hangxiang; Xie, Haiyang; Wu, Jiaping; Wei, Xuyong; Zhou, Lin; Xu, Xiao; Zheng, Shusen

2014-10-20

111

Reciprocal Vectors  

NASA Astrophysics Data System (ADS)

Reciprocal vectors and barycentric coordinates are well-established concepts in various scientific fields, where lattices and grids are essential, e.g., in solid state physics, crystallography, in the numerical analysis of partial differential equations using finite elements, and also in computer graphics and visualisation. In preparation of the Cluster mission, Chanteur [1998] in Chapter 14 of ISSI SR-001 adopted reciprocal vectors to construct estimators for spatial derivatives from four-point measurements, to perform error analysis, and to write down the spatial aliasing condition for four-point wave analysis techniques in a very transparent form. Reciprocal vectors also entered the study on the ac- curacy of plasma moment derivatives, described in Chapter 17 of ISSI SR-001 [Vogt and Paschmann, 1998]. As will be shown below, by using the least squares approach presented in Chapter 12 of ISSI SR-001 [Harvey, 1998], reciprocal vectors are a convenient means in discontinuity analysis to express boundary parameters in terms of crossing times. This chapter is intended to provide a conceptual introduction to reciprocal vectors, and to emphasise their importance for the analysis of data from the Cluster spacecraft mission. It is organised as follows: The crossing times approach to boundary analysis is presented in Section 4.2 as a way to motivate the use of reciprocal vectors; some of their most important properties are briefly addressed in Section 4.3; then Section 4.4 deals with various aspects of the spatial gradient reconstruction problem; magnetic curvature estimation is reviewed in Section 4.5, while Section 4.6 contains a discussion on the errors of boundary analysis and curvature estimation. Finally, in Section 4.7 we suggest a way to generalise the reciprocal vector concept to cases where the number of spacecraft, N, is not four.

Vogt, Joachim; Paschmann, Gotz; Chanteur, Gérard

112

Polymerization Evaluation by Spectrophotometric Measurements.  

ERIC Educational Resources Information Center

Discusses polymerization evaluation by spectrophotometric measurements by considering: (1) association degrees and molar absorptivities; (2) association degrees and equilibrium constants; and (3) absorbance and equilibrium constants. (JN)

Dunach, Jaume

1985-01-01

113

Living olefin polymerization processes  

DOEpatents

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Schrock, Richard R.; Baumann, Robert

2003-08-26

114

Living olefin polymerization processes  

DOEpatents

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Schrock, Richard R.; Bauman, Robert

2006-11-14

115

Living olefin polymerization processes  

DOEpatents

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Schrock, R.R.; Baumann, R.

1999-03-30

116

Living olefin polymerization processes  

DOEpatents

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Schrock, Richard R. (Winchester, MA); Baumann, Robert (Cambridge, MA)

1999-01-01

117

Bimorphic polymeric photomechanical actuator  

NASA Technical Reports Server (NTRS)

A bimorphic polymeric photomechanical actuator, in one embodiment using polyvinylidene fluoride (PVDF) as a photosensitive body, transmitting light over fiber optic cables, and controlling the shape and pulse duration of the light pulse to control movement of the actuator. Multiple light beams are utilized to generate different ranges of motion for the actuator from a single photomechanical body and alternative designs use multiple light beams and multiple photomechanical bodies to provide controlled movement. Actuator movement using one or more ranges of motion is utilized to control motion to position an actuating element in three dimensional space.

Sarkisov, Sergey S. (Inventor); Curley, Michael J. (Inventor); Adamovsky, Grigory (Inventor); Sarkisov, Jr., Sergey S. (Inventor); Fields, Aisha B. (Inventor)

2006-01-01

118

Navigational Vectors  

NSDL National Science Digital Library

This is a high school instructional unit that features nine lessons relating to vectors. Students build understanding of vector properties as they learn airplane navigation. Problem-based learning activities include reading real-time weather maps, tracking airplanes flying in U.S. skies, calculating vector components, analyzing effects of wind velocity, and completing training segments similar to a private pilot certification program. Participants have access to help from experts at the Polaris Career Center. Comprehensive teacher guides, student guides, reference materials, and assessments are included. This resource was developed by the Center for Innovation in Science and Engineering Education (CIESE). Participation is cost-free; additional options are available for registered users.

2008-12-10

119

The nanoparticulation by octaarginine-modified liposome improves ?-galactosylceramide-mediated antitumor therapy via systemic administration.  

PubMed

Alpha-galactosylceramide (?GC), a lipid antigen present on CD1d molecules, is predicted to have clinical applications as a new class of adjuvant, because ?GC strongly activates natural killer T (NKT) cells which produce large amounts of IFN-?. Here, we incorporated ?GC into stearylated octaarginine-modified liposomes (R8-Lip), our original delivery system developed for vaccines, and investigated the effect of nanoparticulation. Unexpectedly, the systemic administered R8-Lip incorporating ?GC (?GC/R8-Lip) failed to improve the immune responses mediated by ?GC compared with soluble ?GC in vivo, although ?GC/R8-Lip drastically enhanced ?GC presentation on CD1d in antigen presenting cells in vitro. Thus, we optimized the ?GC/R8-Lip in vivo to overcome this inverse correlation. In optimization in vivo, we found that size control of liposome and R8-modification were critical for enhancing the production of IFN-?. The optimization led to the accumulation of ?GC/R8-Lip in the spleen and a positive therapeutic effect against highly malignant B16 melanoma cells. The optimized ?GC/R8-Lip also enhanced ?GC presentation on CD1d in antigen presenting cells and resulted in an expansion in the population of NKT cells. Herein, we show that R8-Lip is a potent delivery system, and size control and R8-modification in liposomal construction are promising techniques for achieving systemic ?GC therapy. PMID:23860186

Nakamura, Takashi; Yamazaki, Daiki; Yamauchi, Jun; Harashima, Hideyoshi

2013-10-28

120

Why extreme dilutions reach non-zero asymptotes: a nanoparticulate hypothesis based on froth flotation.  

PubMed

Extreme dilutions, especially homeopathic remedies of 30c, 200c, and higher potencies, are prepared by a process of serial dilution of 1:100 per step. As a result, dilution factors of 10(60), 10(400), or even greater are achieved. Therefore, both the presence of any active ingredient and the therapeutic efficacy of these medicines have been contentious because the existence of even traces of the starting raw materials in them is inconceivable. However, physicochemical studies of these solutions have unequivocally established the presence of the starting raw materials in nanoparticulate form even in these extreme (super-Avogadro, >10(23)) dilutions. In this article, we propose and validate a hypothesis to explain how nanoparticles are retained even at such enormous dilution levels. We show that once the bulk concentration is below a threshold level of a few nanograms/milliliter (ng/mL), at the end of each dilution step, all of the nanoparticles levitate to the surface and are accommodated as a monolayer at the top. This dominant population at the air-liquid interface is preserved and carried to the subsequent step, thereby forming an asymptotic concentration. Thus, all dilutions are only apparent and not real in terms of the concentrations of the starting raw materials. PMID:23083226

Chikramane, Prashant S; Kalita, Dhrubajyoti; Suresh, Akkihebbal K; Kane, Shantaram G; Bellare, Jayesh R

2012-11-13

121

Developing micro-/nanoparticulate drug delivery systems using “design of experiments”  

PubMed Central

Of late, micro and nanoparticluate drug delivery systems have been gaining immense importance primarily attributed to their improved drug release controlling and targeting efficiencies. Also, the small particle size and desirable surface charge associated with these delivery systems render them suitable for specific applications like lymphatic uptake, pulmonary uptake, tumor targeting, brain targeting, etc. For decades, micro and nanoparticulate systems have been prepared by the conventional “trial and error” approach of changing One Variable at a Time (OVAT). Using this methodology, the solution of a specific problematic formulation characteristic can certainly be achieved, but attainment of the true optimal composition is never guaranteed. Thus, the present manuscript provides an updated account of the systematic approach “Design of Experiments (DoE)” as applicable to formulation development of microparticles and nanostructured systems. Besides providing a bird's eye view of the various experimental designs and optimization techniques employed for DoE optimization of such systems, the present manuscript also presents a copilation of the major micro/nano-structuctred systems optimized through DoE till date. In a nutshell, the article will act both as a ready reckoner of DoE optimization of micro/nano drug delivery systems and a catalyst in providing an impetus to young pharmaceutical “nano & micro” researchers to venture into the rewarding field of systematic DoE optimization. PMID:23071925

Singh, Bhupinder; Bhatowa, Rahul; Tripathi, Chandra Bhushan; Kapil, Rishi

2011-01-01

122

Osteogenesis on nanoparticulate mineralized collagen scaffolds via autogenous activation of the canonical BMP receptor signaling pathway.  

PubMed

Skeletal regenerative medicine frequently incorporates deliverable growth factors to stimulate osteogenesis. However, the cost and side effects secondary to supraphysiologic dosages of growth factors warrant investigation of alternative methods of stimulating osteogenesis for clinical utilization. In this work, we describe growth factor independent osteogenic induction of human mesenchymal stem cells (hMSCs) on a novel nanoparticulate mineralized collagen glycosaminoglycan scaffold (MC-GAG). hMSCs demonstrated elevated osteogenic gene expression and mineralization on MC-GAG with minimal to no effect upon addition of BMP-2 when compared to non-mineralized scaffolds (Col-GAG). To investigate the intracellular pathways responsible for the increase in osteogenesis, we examined the canonical and non-canonical pathways downstream from BMP receptor activation. Constitutive Smad1/5 phosphorylation with nuclear translocation occurred on MC-GAG independent of BMP-2, whereas Smad1/5 phosphorylation depended on BMP-2 stimulation on Col-GAG. When non-canonical BMPR signaling molecules were examined, ERK1/2 phosphorylation was found to be decreased in MC-GAG but elevated in Col-GAG. No differences in Smad2/3 or p38 activation were detected. Collectively, these results demonstrated that MC-GAG scaffolds induce osteogenesis without exogenous BMP-2 addition via endogenous activation of the canonical BMP receptor signaling pathway. PMID:25736501

Ren, Xiaoyan; Bischoff, David; Weisgerber, Daniel W; Lewis, Michael S; Tu, Victor; Yamaguchi, Dean T; Miller, Timothy A; Harley, Brendan A C; Lee, Justine C

2015-05-01

123

Ice sheets as a significant source of highly reactive nanoparticulate iron to the oceans.  

PubMed

The Greenland and Antarctic Ice Sheets cover ~ 10% of global land surface, but are rarely considered as active components of the global iron cycle. The ocean waters around both ice sheets harbour highly productive coastal ecosystems, many of which are iron limited. Measurements of iron concentrations in subglacial runoff from a large Greenland Ice Sheet catchment reveal the potential for globally significant export of labile iron fractions to the near-coastal euphotic zone. We estimate that the flux of bioavailable iron associated with glacial runoff is 0.40-2.54 Tg per year in Greenland and 0.06-0.17 Tg per year in Antarctica. Iron fluxes are dominated by a highly reactive and potentially bioavailable nanoparticulate suspended sediment fraction, similar to that identified in Antarctic icebergs. Estimates of labile iron fluxes in meltwater are comparable with aeolian dust fluxes to the oceans surrounding Greenland and Antarctica, and are similarly expected to increase in a warming climate with enhanced melting. PMID:24845560

Hawkings, Jon R; Wadham, Jemma L; Tranter, Martyn; Raiswell, Rob; Benning, Liane G; Statham, Peter J; Tedstone, Andrew; Nienow, Peter; Lee, Katherine; Telling, Jon

2014-01-01

124

Vector carpets  

SciTech Connect

Previous papers have described a general method for visualizing vector fields that involves drawing many small ``glyphs`` to represent the field. This paper shows how to improve the speed of the algorithm by utilizing hardware support for line drawing and extends the technique from regular to unstructured grids. The new approach can be used to visualize vector fields at arbitrary surfaces within regular and unstructured grids. Applications of the algorithm include interactive visualization of transient electromagnetic fields and visualization of velocity fields in fluid flow problems.

Dovey, D.

1995-03-22

125

Organometallic Polymeric Conductors  

NASA Technical Reports Server (NTRS)

For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductivity with long-term environmental stability, good processability, and good mechanical properties. Recently, other investigators have reported hybrid films made from an electrically conductive polymer combined with insulating polymers. In all of these instances, the films were prepared by infiltrating an insulating polymer with a precursor for a conductive polymer (either polypyrrole or polythiophene), and oxidatively polymerizing the precursor in situ. The resulting composite films have good electrical conductivity, while overcoming the brittleness inherent in most conductive polymers. The highest conductivities reported (approximately 4/Scm) were achieved with polythiophene in a polystyrene host polymer. The best films using a polyamide as base polymer were four orders of magnitude less conductive than the polystyrene films. The authors suggested that this was because polyimides were unable to swell sufficiently for infiltration of monomer as in the polystyrene. It was not clear, however, if the different conductivities obtained were merely the result of differing oxidation conditions. Oxidation time, temperature and oxidant concentration varied widely among the studies.

1997-01-01

126

In Vitro Analysis of Nanoparticulate Hydroxyapatite/Chitosan Composites as Potential Drug Delivery Platforms for the Sustained Release of Antibiotics in the Treatment of Osteomyelitis  

PubMed Central

Nanoparticulate composites of hydroxyapatite (HAp) and chitosan were synthesized by ultrasound-assisted sequential precipitation and characterized for their microstructure at the atomic scale, surface charge, drug release properties, and combined antibacterial and osteogenic response. Crystallinity of HAp nanoparticles was reduced because of the interference of the surface layers of chitosan with the dissolution/reprecipitation-mediated recrystallization mechanism that conditions the transition from the as-precipitated amorphous calcium phosphate phase to the most thermodynamically stable one—HAp. Embedment of 5–10 nm sized, narrowly dispersed HAp nanoparticles within the polymeric matrix mitigated the burst release of the small molecule model drug, fluorescein, bound to HAp by physisorption, and promoted sustained-release kinetics throughout the 3 weeks of release time. The addition of chitosan to the particulate drug carrier formulation, however, reduced the antibacterial efficacy against S aureus. Excellent cell spreading and proliferation of osteoblastic MC3T3-E1 cells evidenced on microscopic conglomerates of HAp nanoparticles in vitro also markedly diminished on HAp/chitosan composites. Mitochondrial dehydrogenase activity exhibited normal values only for HAp/chitosan particle concentrations of up to 2 mg/cm2 and significantly dropped, by about 50%, at higher particle concentrations (4 and 8 mg/cm2). The gene expression of osteocalcin, a mineralization inductor, and the transcription factor Runx2 was downregulated in cells incubated in the presence of 3 mg/cm2 HAp/chitosan composite particles, whereas the expression of osteopontin, a potent mineralization inhibitor, was upregulated, further demonstrating the partially unfavorable osteoblastic cell response to the given particles. The peak in the expression of osteogenic markers paralleling the osteoblastic differentiation was also delayed most for the cell population incubated with HAp/chitosan particles. Overall, the positive effect of chitosan coating on the drug elution profile of HAp nanoparticles as carriers for the controlled delivery of antibiotics in the treatment of osteomyelitis was compensated for by the lower bacteriostatic efficiency and the comparatively unviable cell response to the composite material, especially at higher dosages. PMID:24382825

USKOKOVI?, VUK; DESAI, TEJAL A.

2014-01-01

127

Coating of plasma polymerized film  

NASA Technical Reports Server (NTRS)

Plasma polymerized thin film coating and the use of other coatings is suggested for passivation film, thin film used for conducting light, and solid body lubrication film of dielectrics of ultra insulators for electrical conduction, electron accessories, etc. The special features of flow discharge development and the polymerized film growth mechanism are discussed.

Morita, S.; Ishibashi, S.

1980-01-01

128

Polymeric coatings using electronic excitation  

NASA Technical Reports Server (NTRS)

Process has been developed for glow discharge polymerization which is accomplished in inert atmosphere by using vacuum chamber. Polymeric coating, in this type of environment, produces high molecular weight coating polymers that have good stability and are resistant to abrasions and solvents.

Lee, S. M.

1972-01-01

129

Pipeline vectorization  

Microsoft Academic Search

This paper presents pipeline vectorization, amethod for synthesizing hardware pipelines based on softwarevectorizing compilers. The method improves eciencyand ease of development of hardware designs, particularlyfor users with little electronics design experience. We proposeseveral loop transformations to customize pipelinesto meet hardware resource constraints, while maximizingavailable parallelism. For run-time recongurable systems,we apply hardware specialization to increase...

Markus Weinhardt; Wayne Luk

2001-01-01

130

Room temperature ferromagnetism in Eu-doped ZnO nanoparticulate powders prepared by combustion reaction method  

NASA Astrophysics Data System (ADS)

Nanoparticulate powders of Eu-doped ZnO with 1.0, 1.5, 2.0 and 3.0 at% Eu were synthesized by combustion reaction method using zinc nitrate, europium nitrate and urea as fuel without subsequent heat treatments. X-ray diffraction patterns (XRD) of all samples showed broad peaks consistent with the ZnO wurtzite structure. The absence of extra reflections in the diffraction patterns ensures the phase purity, except for x=0.03 that exhibits small reflection corresponding to Eu2O3 phase. The average crystallite size determined from the most prominent (1 0 1) peak of the diffraction using Scherrer's equation was in good agreement with those determined by transmission electron microscopy (TEM); being ~26 nm. The magnetic properties measurements were performed using a vibrating sample magnetometer (VSM) in magnetic fields up to 2.0 kOe at room temperature. The hysteresis loops, typical of magnetic behaviors, indicating that the presence of an ordered magnetic structure can exist in the Eu-doped ZnO wurtzite structure at room temperature. The room temperature ferromagnetism behavior increases with the Eu3+ doping concentration. All samples exhibited the same Curie temperature (TC) around ~726 K, except for x=0.01; TC~643 K. High resolution transmission electron microscopy (HRTEM) images revealed defects/strain in the lattice and grain boundaries of Eu-doped ZnO nanoparticulate powders. The origin of room temperature ferromagnetism in Eu-doped ZnO nanoparticulate powders was discussed in terms of these defects, which increase with the Eu3+ doping concentration.

Franco, A.; Pessoni, H. V. S.; Soares, M. P.

2014-04-01

131

Cytotoxic Responses and Potential Respiratory Health Effects of Carbon and Carbonaceous Nanoparticulates in the Paso del Norte Airshed Environment  

PubMed Central

We have utilized a range of manufactured or commercial nanoparticulate materials, including surrogate carbon nano-PM along with combustion-generated carbonaceous (soot) nano-PM characteristic of environmental nano-PM (both indoor and outdoor) to investigate and compare their cytotoxic response in vitro with an immortalized human epithelial (lung model) cell line (A549). These have included nano-Ag, Al2O3, TiO2, Fe2O3, ZrO2, Si3N4, chrysotile asbestos, BC, 2 types of MWCNT-aggregate PM (MWCNT-R and MWCNT-N), and high-volume glass fiber collected soots: candle, wood, diesel (truck), tire, and 3-types of natural gas kitchen burner-generated soots: yellow (fuel-rich) flame, low-flow blue flame, and normal flow blue flame soot PM. These carbonaceous nano-PM species can be found in either the indoor and outdoor environments or microenvironments. Two-day and two-week in-vitro cultures of A549 showed cell death (or decreased cell viability) for all nanoparticulate materials, but especially significant for all but the TiO2 and candle, wood, and diesel PM. The natural gas kitchen burner combustion PM cell death response was characteristic of BC and MWCNT PM. There was no correlation with total PAH content of the soot PM. Cytokine release (IL-6, IL-8) was detected for the Ag, Fe2 O3, asbestos, BC and the MWCNT PM. Reactive oxygen species (ROS) production was also detected for Ag, Fe2 O3, ZrO2, asbestos, BC, and the MWCNT aggregate PM, as well as the natural gas kitchen burner combustion PM. TEM, FESEM, and optical microscopy examination of these nanomaterials illustrate the wide range in PM morphologies and crystallinities as well as cell morphologies. Taken together, these results illustrate proinflammatory and related respiratory health issues in relation to environmental nanoparticulates. PMID:18441401

Soto, K. F.; Murr, L. E.; Garza, K. M.

2008-01-01

132

Cytotoxic responses and potential respiratory health effects of carbon and carbonaceous nanoparticulates in the Paso del Norte airshed environment.  

PubMed

We have utilized a range of manufactured or commercial nanoparticulate materials, including surrogate carbon nano-PM along with combustion-generated carbonaceous (soot) nano-PM characteristic of environmental nano- PM (both indoor and outdoor) to investigate and compare their cytotoxic response in vitro with an immortalized human epithelial (lung model) cell line (A549). These have included nano-Ag, Al2O3, TiO2, Fe2O3, ZrO2, Si3N4, chrysotile asbestos, BC, 2 types of MWCNT-aggregate PM (MWCNT-R and MWCNT-N), and high-volume glass fiber collected soots: candle, wood, diesel (truck), tire, and 3-types of natural gas kitchen burner-generated soots: yellow (fuel-rich) flame, low-flow blue flame, and normal flow blue flame soot PM. These carbonaceous nano-PM species can be found in either the indoor and outdoor environments or microenvironments. Two-day and two-week in-vitro cultures of A549 showed cell death (or decreased cell viability) for all nanoparticulate materials, but especially significant for all but the TiO2 and candle, wood, and diesel PM. The natural gas kitchen burner combustion PM cell death response was characteristic of BC and MWCNT PM. There was no correlation with total PAH content of the soot PM. Cytokine release (IL-6, IL-8) was detected for the Ag, Fe2 O3, asbestos, BC and the MWCNT PM. Reactive oxygen species (ROS) production was also detected for Ag, Fe2 O3, ZrO2, asbestos, BC, and the MWCNT aggregate PM, as well as the natural gas kitchen burner combustion PM. TEM, FESEM, and optical microscopy examination of these nanomaterials illustrate the wide range in PM morphologies and crystallinities as well as cell morphologies. Taken together, these results illustrate proinflammatory and related respiratory health issues in relation to environmental nanoparticulates. PMID:18441401

Soto, K F; Murr, L E; Garza, K M

2008-03-01

133

Recovery of visible-light photocatalytic efficiency of N-doped TiO 2 nanoparticulate films  

Microsoft Academic Search

Bare TiO2 and N-doped TiO2 nanoparticulate films in anatase phase were prepared on glass substrates by laser ablation of titanium target in O2, N2\\/O2 and NH3\\/N2\\/O2 atmospheres, respectively. The nitrogen dopant concentration increased notably when a small amount of NH3 was added into the N2\\/O2 mixture. The film prepared in NH3\\/N2\\/O2 exhibited enhanced photoabsorption and photocatalytic ability in the visible-light

Lan Mi; Peng Xu; Hong Shen; Pei-Nan Wang

2008-01-01

134

Autogenic reactions for preparing carbon-encapsulated, nanoparticulate TiO 2 electrodes for lithium-ion batteries  

Microsoft Academic Search

We report an anhydrous, autogenic technique for synthesizing electronically interconnected, carbon-encapsulated, nanoparticulate anatase anode materials (TiO2–C) for lithium-ion batteries. The TiO2–C nanoparticles provide a reversible capacity of ?200mAhg?1, which exceeds the theoretical capacity of the commercially attractive spinel anode, Li4Ti5O12 (175mAhg?1) and is competitive with the capacity reported for other TiO2 products. The processing method is extremely versatile and has

Vilas G. Pol; Sun-Ho Kang; Jose M. Calderon-Moreno; Christopher S. Johnson; Michael M. Thackeray

2010-01-01

135

Nanospray technology for an in situ gelling nanoparticulate powder as a wound dressing.  

PubMed

In the current study the feasibility of the novel nano spray drying technique for the production of stable nanoparticulate dry powder, able to gel when administered locally on a wound, is explored. Gentamicin sulphate (GS) was loaded into alginate/pectin nanoparticles as highly soluble (hygroscopic) model drug with wide range antibacterial agent for wound dressing. The influence of process variables, mainly spray mesh size and feed concentration, on particle size and morphology, powder wound fluid uptake ability and gelling rate, as well as hydrogel water vapour transmission at wound site were studied. Particles morphology was spherical with few exceptions as slightly corrugated particles when the larger nozzle was used. Production of spherical nanoparticles (d50 ? 350 nm) in good yield (82-92%) required 4 ?m spray mesh whereas 7 ?m mesh produced larger wrinkled particles. Nano spray-dried particles showed high encapsulation efficiency (? 80%), good flowability, high fluid uptake, fast gel formation (15 min) and proper adhesiveness to fill the wound site and to remove easily the formulation after use. Moreover, moisture transmission of the in situ formed hydrogel was between 95 and 90 g/m(2)/h, an optimum range to avoid wound dehydration or occlusion phenomena. Release of the encapsulated GS, monitored as permeation rate using Franz cells in simulated wound fluid (SWF) was related to particle size and gelling rate. Sustained permeation profiles were obtained achieving total permeation of the drug between 3 and 6 days. However, all nano spray-dried formulations presented a burst effect, suitable to prevent infection spreading at the beginning of the therapy. Antimicrobial tests against Staphylococcus aureus and Pseudomonas aeruginosa showed stronger and prolonged antimicrobial effect of the nanoparticles compared to pure GS both shortly after administration and over time (till 12 days). PMID:24979533

De Cicco, Felicetta; Porta, Amalia; Sansone, Francesca; Aquino, Rita P; Del Gaudio, Pasquale

2014-10-01

136

Microparticulated and nanoparticulated zirconium oxide added to calcium silicate cement: Evaluation of physicochemical and biological properties.  

PubMed

The physicochemical and biological properties of calcium silicate-based cement (CS) associated to microparticulated (micro) or nanoparticulated (nano) zirconium oxide (ZrO2 ) were compared with CS and bismuth oxide (BO) with CS. The pH, release of calcium ions, radiopacity, setting time, and compression strength of the materials were evaluated. The tissue reaction promoted by these materials in the subcutaneous was also investigated by morphological, immunohistochemical, and quantitative analyses. For this purpose, polyethylene tubes filled with materials were implanted into rat subcutaneous. After 7, 15, 30, and 60 days, the tubes surrounded by capsules were fixed and embedded in paraffin. In the H&E-stained sections, the number of inflammatory cells (ICs) in the capsule was obtained. Moreover, detection of interleukin-6 (IL-6) by immunohistochemistry and number of IL-6 immunolabeled cells were carried out. von Kossa method was also performed. The differences among the groups were subjected to Tukey test (p???0.05). The solutions containing the materials presented an alkaline pH and released calcium ions. The addition of radiopacifiers increased setting time and radiopacity of CS. A higher compressive strength in the CS?+?ZrO2 (micro and nano) was found compared with CS?+?BO. The number of IC and IL-6 positive cells in the materials with ZrO2 was significantly reduced in comparison with CS?+?BO. von Kossa-positive structures were observed adjacent to implanted materials. The ZrO2 associated to the CS provides satisfactory physicochemical properties and better biological response than BO. Thus, ZrO2 may be a good alternative for use as radiopacifying agent in substitution to BO. PMID:24497271

Silva, Guilherme F; Bosso, Roberta; Ferino, Rafael V; Tanomaru-Filho, Mário; Bernardi, Maria I B; Guerreiro-Tanomaru, Juliane M; Cerri, Paulo S

2014-12-01

137

Methylation of mercury by bacteria exposed to dissolved, nanoparticulate, and microparticulate mercuric sulfides.  

PubMed

The production of the neurotoxic methylmercury in the environment is partly controlled by the bioavailability of inorganic divalent mercury (Hg(II)) to anaerobic bacteria that methylate Hg(II). In sediment porewater, Hg(II) associates with sulfides and natural organic matter to form chemical species that include organic-coated mercury sulfide nanoparticles as reaction intermediates of heterogeneous mineral precipitation. Here, we exposed two strains of sulfate-reducing bacteria to three forms of inorganic mercury: dissolved Hg and sulfide, nanoparticulate HgS, and microparticulate HgS. The bacteria cultures exposed to HgS nanoparticles methylated mercury at a rate slower than cultures exposed to dissolved forms of mercury. However, net methylmercury production in cultures exposed to nanoparticles was 6 times greater than in cultures treated with microscale particles, even when normalized to specific surface area. Furthermore, the methylation potential of HgS nanoparticles decreased with storage time of the nanoparticles in their original stock solution. In bacteria cultures amended with nano-HgS from a 16 h-old nanoparticle stock, 6-10% of total mercury was converted to methylmercury after one day. In contrast, 2-4% was methylated in cultures amended with nano-HgS that was aged for 3 days or 1 week. The methylation of mercury derived from nanoparticles (in contrast to the larger particles) would not be predicted by equilibrium speciation of mercury in the aqueous phase (<0.2 ?m) and was possibly caused by the disordered structure of nanoparticles that facilitated release of chemically labile mercury species immediately adjacent to cell surfaces. Our results add new dimensions to the mechanistic understanding of mercury methylation potential by demonstrating that bioavailability is related to the geochemical intermediates of rate-limited mercury sulfide precipitation reactions. These findings could help explain observations that the "aging" of mercury in sediments reduces its methylation potential and provide a basis for assessing and remediating methylmercury hotspots in the environment. PMID:22145980

Zhang, Tong; Kim, Bojeong; Levard, Clément; Reinsch, Brian C; Lowry, Gregory V; Deshusses, Marc A; Hsu-Kim, Heileen

2012-07-01

138

Production of monodisperse, polymeric microspheres  

NASA Technical Reports Server (NTRS)

Very small, individual polymeric microspheres with very precise size and a wide variation in monomer type and properties are produced by deploying a precisely formed liquid monomer droplet, suitably an acrylic compound such as hydroxyethyl methacrylate into a containerless environment. The droplet which assumes a spheroid shape is subjected to polymerizing radiation such as ultraviolet or gamma radiation as it travels through the environment. Polymeric microspheres having precise diameters varying no more than plus or minus 5 percent from an average size are recovered. Many types of fillers including magnetic fillers may be dispersed in the liquid droplet.

Rembaum, Alan (Inventor); Rhim, Won-Kyu (Inventor); Hyson, Michael T. (Inventor); Chang, Manchium (Inventor)

1990-01-01

139

High temperature structural, polymeric foams from high internal emulsion polymerization  

SciTech Connect

In 1982, a high internal phase emulsion (HIPE) polymerization process to manufacture microcellular, polymeric foam systems was patented by Unilever. This patent discloses a polymerization process that occurs in a water-in-oil emulsion in which the water represents at least 76% of the emulsion by volume. The oil phase consists of vinyl monomers such as styrene and acrylates that are crosslinked by divinyl monomers during polymerization. After polymerization and drying to remove the water phase, the result is a crosslinked polymer foam with an open cell microstructure that is homogeneous throughout in terms of morphology, density, and mechanical properties. Since 1982, numerous patents have examined various HIPE polymerized foam processing techniques and applications that include absorbents for body fluids, cleaning materials, and ion exchange systems. All the published HIPE polymerized foams have concentrated on materials for low temperature applications. Copolymerization of styrene with maleic anhydride and N-substituted maleimides to produce heat resistant thermoplastics has been studied extensively. These investigations have shown that styrene will free radically copolymerize with N-substituted maleimides to create an alternating thermoplastic copolymer with a Tg of approximately 200{degrees}C. However, there are many difficulties in attempting the maleimide styrene copolymerization in a HIPE such as lower polymerization temperatures, maleimide solubility difficulties in both styrene and water, and difficulty obtaining a stable HIPE with a styrene/maleimide oil phase. This work describes the preparation of copolymer foams from N-ethylmaleimide and Bis(3-ethyl-5-methyl-4-maleimide-phenyl)methane with styrene based monomers and crosslinking agents.

Hoisington, M.A.; Duke, J.R.; Apen, P.G.

1996-02-01

140

Was Mineral Surface Complexity and Toxicity an Impetus for Evolution of Microbial Extracellular Polymeric Substances?  

NASA Astrophysics Data System (ADS)

Modern ecological niches are teeming with an astonishing diversity of microbial life closely associated with mineral surfaces, highlighting the remarkable success of microorganisms in conquering the challenges and capitalizing on the benefits presented by the mineral-water interface. Such community-living is enabled by an extracellular, polymeric, biofilm matrix developed at cell surfaces. Despite the energetic penalties, biofilm formation capability likely evolved on early Earth because of crucial cell survival functions, of which recognized roles include facilitating cell-attachment at mineral surfaces, intercellular signaling and lateral gene transfer, protection from dessication in tidal pools, and screening toxic UV light and toxic soluble metals. Cell-attachment to mineral surfaces was likely critical for cell survival and function, but the potential toxicity of mineral surfaces towards cells and the complexities of the mineral-water-cell interface in promoting biofilm formation, have not been fully appreciated. We examined the effects of nanoparticulate oxides (amorphous SiO2, anatase ?-TiO2, and ?-Al2O3) on EPS- and biofilm-producing wild-type strains and their isogenic knock-out mutants which are defective in EPS-producing ability. In detail, we used Gram-negative wild-type Pseudomonas aeruginosa PAO1 and its EPS knock-out mutant ?-psl, and the Gram-positive wild-type Bacillus subtilis NCIB3610 and its EPS-knock-out mutant yhxB?. We conducted bacterial growth experiments in the presence of each oxide in order to determine the viability of each cell type relative to oxide-free controls. The amount of EPS generated in the presence of oxides was also quantified and qualitatively analyzed by fluorescent stains. The results indicated a previously unrecognized role for microbial extracellular polymeric substances (EPS) in shielding both Gram-negative and Gram-positive cells against the toxic effects of mineral surfaces. This role is distinct from the protection provided against toxic soluble metals. Furthermore, we found that mineral toxicity is specific to the surface chemistry and particle size of the mineral, and that EPS protect against this mineral-specific toxicity via different mechanisms. Most intriguingly, we determined that EPS production is mineral-induced. By addressing the mechanistic detailed interactions at the mineral-water-cell interface, we provide insight to the potential impact of nanoparticulate mineral surfaces in promoting increased complexity of cell surfaces, including EPS and biofilm formation, on early Earth.

Sahai, N.; Xu, J.; Zhu, C.; Campbell, J.; Hickey, W.; Zhang, N.

2011-12-01

141

Highly transparent and conductive Al-doped ZnO nanoparticulate thin films using direct write processing  

NASA Astrophysics Data System (ADS)

Solution processable Al-doped ZnO (AZO) thin films are attractive candidates for low cost transparent electrodes. We demonstrate here an optimized nanoparticulate ink for the fabrication of AZO thin films using scalable, low-cost direct write processing (ultrasonic spray deposition) in air at atmospheric pressure. The thin films were made via thermal processing of as-deposited films. AZO films deposited using the proposed nanoparticulate ink with further reducing in vacuum and rf plasma of forming gas exhibited optical transparency greater than 95% across the visible spectrum, and electrical resistivity of 0.5 ? cm and it drops down to 7.0 × 10-2 ? cm after illuminating with UV light, which is comparable to commercially available tin doped indium oxide colloidal coatings. Various structural analyses were performed to investigate the influence of ink chemistry, deposition parameters, and annealing temperatures on the structural, optical, and electrical characteristics of the spray deposited AZO thin films. Optical micrographs confirmed the presence of surface defects and cracks using the AZO NPs ink without any additives. After adding N-(2-Aminoethyl)-3-aminopropylmethyldimethoxy silane to the ink, AZO films exhibited an optical transparency which was virtually identical to that of the plain glass substrate.

Vunnam, S.; Ankireddy, K.; Kellar, J.; Cross, W.

2014-05-01

142

Polymerization of anionic wormlike micelles.  

PubMed

Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles. PMID:16430253

Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

2006-01-31

143

Anisotropy adjustment and thickness of thin layer doped by nanoparticules magnetic for the realization of phase matching between fundamental modes in monomode waveguides  

Microsoft Academic Search

Recently, research has been concentrated on the study of the magnetic nanoparticules for their use in the design of magneto-optical devices. The magneto-optical waveguides for example exploit the Faraday effect to obtain a rotation of polarization TE and TM independent of the propagation direction. In this work, we study isolating component whose operating principle is based on the minimization of

M. R. Lebbal; T. Boumaza; M. Bouchemat; A. Hocini; F. Hobar; A. Benghalia; J. J. Rosseau; F. Royer

2008-01-01

144

Polymeric waveguides for optical backplanes  

Microsoft Academic Search

Organic polymeric materials offer great promise for the creation of optical guided-wave structures. We have developed a number of new polymeric compositions which can be used to fabricate optical waveguide circuitry characterized by low loss and high thermal stability (up to 75 years at 120 degree(s)C for 840 nm wavelength). This technology makes possible the fabrication of complex point-to-point optical

Lawrence W. Shacklette; K. M. Stengel; L. Eldada; C. Xu; James T. Yardley

1995-01-01

145

Design and evaluation of a novel nanoparticulate-based formulation encapsulating a HIP complex of lysozyme  

PubMed Central

Formulation development of protein therapeutics using polymeric nanoparticles has found very little success in recent years. Major formulation challenges include rapid denaturation, susceptibility to lose bioactivity in presence of organic solvents and poor encapsulation in polymeric matrix. In the present study, we have prepared hydrophobic ion pairing (HIP) complex of lysozyme, a model protein, using dextran sulfate (DS) as a complexing polymer. We have optimized the process of formation and dissociation of HIP complex between lysozyme and DS. The effect of HIP complexation on enzymatic activity of lysozyme was also studied. Nanoparticles were prepared and characterized using spontaneous emulsion solvent diffusion method. Furthermore, we have also investigated release of lysozyme from nanoparticles along with its enzymatic activity. Results of this study indicate that nanoparticles can sustain the release of lysozyme without compromising its enzymatic activity. HIP complexation using a polymer may also be employed to formulate sustained release dosage forms of other macromolecules with enhanced encapsulation efficiency. PMID:23137392

Gaudana, Ripal; Gokulgandhi, Mitan; Khurana, Varun; Kwatra, Deep; Mitra, Ashim K.

2015-01-01

146

Direct polymerization of proteins.  

PubMed

We report the synthesis of active polymers of superfolder green fluorescent protein (sfGFP) in one step using Click chemistry. Up to six copies of the non-natural amino acids (nnAAs) p-azido-l-phenylalanine (pAzF) or p-propargyloxy-l-phenylalanine (pPaF) were site-specifically inserted into sfGFP by cell-free protein synthesis (CFPS). sfGFP containing two or three copies of these nnAAs were coupled by copper-catalyzed azide-alkyne cycloaddition to synthesize linear or branched protein polymers, respectively. The protein polymers retained ?63% of their specific activity (i.e., fluorescence) after coupling. Polymerization of a concentrated solution of triply substituted sfGFP resulted in fluorescent macromolecular particles. Our method can be generalized to synthesize polymers of a protein or copolymers of any two or more proteins, and the conjugation sites can be determined exactly by standard genetic manipulation. Polymers of proteins and small molecules can also be created with this technology to make a new class of scaffolds or biomaterials. PMID:24200191

Albayrak, Cem; Swartz, James R

2014-06-20

147

Kinetics of silica polymerization  

SciTech Connect

The polymerization of silicic acid in geothermal brine-like aqueous solutions to produce amorphous silica in colloidal form has been studied experimentally and theoretically. A large amount of high quality experimental data has been generated over the temperature rang 23 to 100{sup 0}C. Wide ranges of dissolved silica concentration, pH, and sodium chloride concentration were covered. The catalytic effects of fluoride and the reaction inhibiting effects of aluminum and boron were studied also. Two basic processes have been separately studied: the formation of new colloidal particles by the homogeneous nucleation process and the deposition of dissolved silica on pre-existing colloidal particles. A rigorous theory of the formation of colloidal particles of amorphous silica by homogeneous nucleation was developed. This theory employs the Lothe-Pound formalism, and is embodied in the computer code SILNUC which quantitatively models the homogeneous nucleation and growth of colloidal silica particles in more than enough detail for practical application. The theory and code were extensively used in planning the experimental work and analyzing the data produced. The code is now complete and running in its final form. It is capable of reproducing most of the experimental results to within experimental error. It is also capable of extrapolation to experimentally inaccessible conditions, i.e., high temperatures, rapidly varying temperature and pH, etc.

Weres, O.; Yee, A.; Tsao, L.

1980-05-01

148

Nanoparticulate flurbiprofen reduces amyloid-?42 generation in an in vitro blood–brain barrier model  

PubMed Central

Introduction The amyloid-?42 (A?42) peptide plays a crucial role in the pathogenesis of Alzheimer’s disease (AD), the most common neurodegenerative disorder affecting the elderly. Over the past years, several approaches and compounds developed for the treatment of AD have failed in clinical studies, likely in part due to their low penetration of the blood–brain barrier (BBB). Since nanotechnology-based strategies offer new possibilities for the delivery of drugs to the brain, this technique is studied intensively for the treatment of AD and other neurological disorders. Methods The A?42 lowering drug flurbiprofen was embedded in polylactide (PLA) nanoparticles by emulsification-diffusion technique and their potential as drug carriers in an in vitro BBB model was examined. First, the cytotoxic potential of the PLA-flurbiprofen nanoparticles on endothelial cells and the cellular binding and uptake by endothelial cells was studied. Furthermore, the biological activity of the nanoparticulate flurbiprofen on ?-secretase modulation as well as its in vitro release was examined. Furthermore, the protein corona of the nanoparticles was studied as well as their ability to transport flurbiprofen across an in vitro BBB model. Results PLA-flurbiprofen nanoparticles were endocytosed by endothelial cells and neither affected the vitality nor barrier function of the endothelial cell monolayer. The exposure of the PLA-flurbiprofen nanoparticles to human plasma occurred in a rapid protein corona formation, resulting in their decoration with bioactive proteins, including apolipoprotein E. Furthermore, luminally administered PLA-flurbiprofen nanoparticles in contrast to free flurbiprofen were able to modulate ?-secretase activity by selectively decreasing A?42 levels in the abluminal compartment of the BBB model. Conclusions In this study, we were able to show that flurbiprofen can be transported by PLA nanoparticles across an in vitro BBB model and most importantly, the transported flurbiprofen modulated ?-secretase activity by selectively decreasing A?42 levels. These results demonstrate that the modification of drugs via embedding in nanoparticles is a promising tool to facilitate drug delivery to the brain, which enables future development for the treatment of neurodegenerative disorders like AD. PMID:24280275

2013-01-01

149

Particulate Emissions from the Combustion of Diesel Fuel with a Fuel-Borne Nanoparticulate Cerium Catalyst  

NASA Astrophysics Data System (ADS)

To address the adverse impacts on health and climate from the use of diesel-fueled vehicles, a number of technological solutions have been developed for reducing diesel soot emissions and to improve fuel economy. One such solution is the use fuel-borne metal oxide catalysts. Of current interest are commercially-available fuel additives consisting of nanoparticulate cerium oxide (CeO2). In response to the possible use of CeO2-containing fuels in on-road vehicles in the U.S., the Environmental Protection Agency is conducting research to address the potential toxicity and environmental effects of particulate CeO2 emitted with diesel soot. In this study, emissions from a diesel-fueled electric generator were size-segregated on polished silicon wafers in a nanoparticle cascade impactor. The diesel fuel contained 10 ppm Ce by weight in the form of crystalline CeO2 nanoparticles 4 nm to 7.5 nm in size. Primary CeO2 nanoparticles were observed in the diesel emissions as well as CeO2 aggregates encompassing a broad range of sizes up to at least 200 nm. We report the characterization of individual particles from the size-resolved samples with focused ion-beam scanning electron microscopy and energy-dispersive x-ray spectroscopy. Results show a dependency between the impactor size range and CeO2 agglomeration state: in the larger size fractions of the impactor (e.g., 560 nm to 1000 nm) CeO2 nanoparticles were predominantly attached to soot particles. In the smaller size fractions of the impactor (e.g., 100 nm to 320 nm), CeO2 aggregates tended to be larger and unattached to soot. The result is important because the deposition of CeO2 nanoparticles attached to soot particles in the lung or on environmental surfaces such as plant tissue will likely present different consequences than the deposition of unagglomerated CeO2 particles. Disclaimer The U.S. Environmental Protection Agency through its Office of Research and Development funded and collaborated in the research described here under Interagency Agreement DW-13-92339401 to National Institute of Standards and Technology. It has been subjected to Agency review and approved for publication.

Conny, J. M.; Willis, R. D.; Weinstein, J. P.; Krantz, T.; King, C.

2013-12-01

150

Polymeric materials in Space  

NASA Astrophysics Data System (ADS)

Paper of short review type. It is the continuation of and addition to previous review papers "V. E. Skurat. Polymers in Space. In: Encyclopedia of aerospace engineering, vol. 4, Wiley and sons, 2010; Ibid., 2012 (on line)". Following topics are considered: (1) Destruction of polymers by solar radiation with various wavelengths in different spectral regions (visible-UV, vacuum UV (VUV), deep UV, soft and hard X-rays) are discussed. In difference with common polymer photochemistry induced by UV radiation, directions of various routs of polymer phototransformations and their relative yields are greatly dependent on wavelength of light (photon energy) during illuminations in VUV, deep UV and X-ray regions. During last twenty years, intensive spacecraft investigations of solar spectrum show great periodic and spontaneous variations of radiation intensities in short-wavelengths regions - up to one - two decimal orders of magnitude for X-rays. As a result, during solar flares the absorbed dose on the polymer surfaces from X-rays can be compared with absorbed dose from VUV radiation. (2) Some new approaches to predictions of reaction efficiencies of fast orbital atomic oxygen in their interaction with polymeric materials are considered. (3) Some aspects of photocatalitic destruction of polymers in vacuum conditions by full-spectrum solar radiation are discussed. This process can take place in enamels containing semiconducting particles (TiO2, ZnO) as pigments. (4) Contamination of spacecraft surfaces from intrinsic outer atmosphere play important role not only from the point of view of deterioration of optical and thermophysical properties. Layers of SiO2 contaminations with nanometer thicknesses can greatly diminish mass losses from perfluorinated polymers under VUV irradiation.

Skurat, Vladimir

151

Polymeric materials for neovascularization  

NASA Astrophysics Data System (ADS)

Revascularization therapies have emerged as a promising strategy to treat various acute and chronic wounds, cardiovascular diseases, and tissue defects. It is common to either administer proangiogenic growth factors, such as vascular endothelial growth factor (VEGF), or transplant cells that endogenously express multiple proangiogenic factors. Additionally, these strategies utilize a wide variety of polymeric systems, including hydrogels and biodegradable plastics, to deliver proangiogenic factors in a sophisticated manner to maintain a sustained proangiogenic environment. Despite some impressive results in rebuilding vascular networks, it is still a challenging task to engineer mature and functional neovessels in target tissues, because of the increasing complexities involved with neovascularization applications. To resolve these challenges, this work aims to design a wide variety of proangiogenic biomaterial systems with tunable properties used for neovascularization therapies. This thesis describes the design of several biomaterial systems used for the delivery of proangiogenic factors in neovascularization therapies, including: an electrospun/electrosprayed biodegradable plastic patch used for directional blood vessel growth (Chapter 2), an alginate-g-pyrrole hydrogel system that biochemically stimulates cellular endogenous proangiogenic factor expression (Chapter 3), an enzyme-catalyzed alginate-g-pyrrole hydrogel system for VEGF delivery (Chapter 4), an enzyme-activated alginate-g-pyrrole hydrogel system with systematically controllable electrical and mechanical properties (Chapter 5), and an alginate-g-pyrrole hydrogel that enables the decoupled control of electrical conductivity and mechanical rigidity and is use to electrically stimulate cellular endogenous proangiogenic factor expression (Chapter 6). Overall, the biomaterial systems developed in this thesis will be broadly useful for improving the quality of a wide array of molecular and cellular based revascularization therapies.

DeVolder, Ross John

152

Preparation and characterization of a polymeric (PLGA) nanoparticulate drug delivery system with simultaneous incorporation of chemotherapeutic and thermo-optical agents.  

PubMed

The objective of this study was to develop biodegradable poly(DL-lactide-co-glycolic acid) (PLGA) nanoparticles simultaneously loaded with indocyanine green (ICG) and doxorubicin (DOX). The modified oil in water single emulsion solvent evaporation method was used. To enhance the incorporation of both agents and control particle size, four independent processing parameters including amount of polymer, initial ICG content, initial DOX content, and concentration of poly-vinyl alcohol (PVA) were investigated. The ICG and DOX entrapment in nanoparticles as well as the nanoparticle size were determined. The nanoparticles produced by standardized formulation were in the range of 171+/-2 nm (n=3) with low polydispersity index (0.040+/-0.014, n=3). The entrapment efficiency was determined by spectrofluorometer measurements. The efficiency was 44.4+/-1.6% for ICG and 74.3+/-1.9% for DOX. Drug loading was 0.015+/-0.001%, w/w, for ICG and 0.022+/-0.001%, w/w, for DOX (n=3). The release pattern was biphasic. ICG and DOX loaded-nanoparticle preparation was standardized based on the following parameters: PLGA concentration, PVA concentration and initial drug content. PMID:19775872

Manchanda, Romila; Fernandez-Fernandez, Alicia; Nagesetti, Abhignyan; McGoron, Anthony J

2010-01-01

153

Femtosecond Laser Processing by Using Patterned Vector Optical Fields  

PubMed Central

We present and demonstrate an approach for femtosecond laser processing by using patterned vector optical fields (PVOFs) composed of multiple individual vector optical fields. The PVOFs can be flexibly engineered due to the diversity of individual vector optical fields in spatial arrangement and distribution of states of polarization, and it is easily created with the aid of a spatial light modulator. The focused PVOFs will certainly result in various interference patterns, which are then used to fabricate multi-microholes with various patterns on silicon. The present approach can be expanded to fabricate three-dimensional microstructures based on two-photon polymerization. PMID:23884360

Lou, Kai; Qian, Sheng-Xia; Ren, Zhi-Cheng; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian

2013-01-01

154

A novel approach for the intravenous delivery of leuprolide using core-cross-linked polymeric micelles.  

PubMed

Therapeutic peptides are highly attractive drugs for the treatment of various diseases. However, their poor pharmacokinetics due to rapid renal elimination limits their clinical applications. In this study, a model hormone peptide, leuprolide, was covalently linked to core-cross-linked polymeric micelles (CCL-PMs) via two different hydrolysable ester linkages, thereby yielding a nanoparticulate system with tuneable drug release kinetics. The ester linkage that provided the slowest peptide release kinetics was selected for in vivo evaluation. Compared to the soluble peptide, the leuprolide-entrapped CCL-PMs showed a prolonged circulation half-life (14.4h) following a single intravenous injection in healthy rats and the released leuprolide was detected in blood for 3days. In addition, the area under the plasma concentration-time curve (AUC) value was >100-fold higher for leuprolide-entrapped CCL-PMs than for soluble leuprolide. Importantly, the released peptide remained biologically active as demonstrated by increased and long-lasting plasma testosterone levels. This study shows that covalent linkage of peptides to CCL-PMs via hydrolytically sensitive ester bonds is a promising approach to achieving sustained systemic levels of peptides after intravenous administration. PMID:25583642

Hu, Qizhi; van Gaal, Ethlinn V B; Brundel, Paul; Ippel, Hans; Hackeng, Tilman; Rijcken, Cristianne J F; Storm, Gert; Hennink, Wim E; Prakash, Jai

2015-05-10

155

On-demand photoinitiated polymerization  

DOEpatents

Compositions and methods for adjustable lenses are provided. In some embodiments, the lenses contain a lens matrix material, a masking compound, and a prepolymer. The lens matrix material provides structure to the lens. The masking compound is capable of blocking polymerization or crosslinking of the prepolymer, until photoisomerization of the compound is triggered, and the compound is converted from a first isomer to a second isomer having a different absorption profile. The prepolymer is a composition that can undergo a polymerization or crosslinking reaction upon photoinitiation to alter one or more of the properties of the lenses.

Boydston, Andrew J; Grubbs, Robert H; Daeffler, Chris; Momcilovic, Nebojsa

2013-12-10

156

Polymeric materials for theranostic applications.  

PubMed

Nanotechnology has continuously contributed to the fast development of diagnostic and therapeutic agents. Theranostic nanomedicine has encompassed the ongoing efforts on concurrent molecular imaging of biomarkers, delivery of therapeutic agents, and monitoring of therapy response. Among these formulations, polymer-based theranostic agents hold great promise for the construction of multifunctional agents for translational medicine. In this article, we reviewed the state-of-the-art polymeric nanoparticles, from preparation to application, as potential theranostic agents for diagnosis and therapy. We summarized several major polymer formulas, including polymeric conjugate complexes, nanospheres, micelles, and dendrimers for integrated molecular imaging and therapeutic applications. PMID:23765400

Wang, Zhe; Niu, Gang; Chen, Xiaoyuan

2014-06-01

157

Absence of systemic toxicity in mouse model towards BaTiO3 nanoparticulate based eluate treatment.  

PubMed

One of the existing issues in implant failure of orthopedic biomaterials is the toxicity induced by the fine particles released during long term use in vivo, leading to acute inflammatory response. In developing a new class of piezobiocomposite to mimic the integrated electrical and mechanical properties of bone, bone-mimicking physical properties as well as in vitro cytocompatibility properties have been achieved with spark plasma sintered hydroxyapatite (HA)-barium titanate (BaTiO3) composites. However, the presence of BaTiO3 remains a concern towards the potential toxicity effect. To address this issue, present work reports the first result to conclusively confirm the non-toxic effect of HA-BaTiO3 piezobiocomposite nanoparticulates, in vivo. Twenty BALB/c mice were intra-articularly injected at their right knee joints with different concentrations of HA-BaTiO3 composite of up to 25 mg/ml. The histopathological examination confirmed the absence of any trace of injected particles or any sign of inflammatory reaction in the vital organs, such as heart, spleen, kidney and liver at 7 days post-exposure period. Rather, the injected nanoparticulates were found to be agglomerated in the vicinity of the knee joint, surrounded by macrophages. Importantly, the absence of any systemic toxicity response in any of the vital organs in the treated mouse model, other than a mild local response at the site of delivery, was recorded. The serum biochemical analyses using proinflammatory cytokines (TNF-? and IL-1?) also complimented to the non-immunogenic response to injected particulates. Altogether, the absence of any inflammatory/adverse reaction will open up myriad of opportunities for BaTiO3 based piezoelectric implantable devices in biomedical applications. PMID:25655497

Dubey, Ashutosh Kumar; Thrivikraman, Greeshma; Basu, Bikramjit

2015-02-01

158

Vectors: Tip to Tail  

NSDL National Science Digital Library

In this lesson students will learn the characteristics and appropriate use of vectors. They will find the magnitude and direction of vectors, they will add and subtract vectors and use an interactive website to practice what they have learned.

Sharon Linamen

2012-07-23

159

Photochemical transformations of anthraquinone in polymeric alcohols  

NASA Astrophysics Data System (ADS)

It is established that the photolysis of anthraquinone in both aerated and deoxygenated polymeric alcohols is not accompanied by reduction with the formation of anthrahydroquinone; as a result, an adduct of hydroxyanthracene and polymeric alcohol is formed.

Tsaplev, Yu. B.

2012-12-01

160

A MECHANICAL STRAIN SENSOR FOR POLYMERIC MATERIALS  

E-print Network

A MECHANICAL STRAIN SENSOR FOR POLYMERIC MATERIALS AND PHOTOPHYSICAL INVESTIGATIONS OF LARGE ...................................................................................................... 1 1.2 Basic theory of fluorescence ...................................................................................................... 17 A MECHANICAL STRAIN SENSOR FOR POLYMERIC MATERIALS ....... 21 3.1 Introduction

161

Thermally Stable, Piezoelectric and Pyroelectric Polymeric Substrates  

NASA Technical Reports Server (NTRS)

A thermally stable, piezoelectric and pyroelectric polymeric substrate was prepared. This thermally stable, piezoelectric and pyroelectric polymeric substrate may be used to prepare electromechanical transducers, thermomechanical transducers, accelerometers. acoustic sensors, infrared sensors, pressure sensors, vibration sensors, impact sensors, in-situ temperature sensors, in-situ stress/strain sensors, micro actuators, switches, adjustable fresnel lenses, speakers, tactile sensors. weather sensors, micro positioners, ultrasonic devices, power generators, tunable reflectors, microphones, and hydrophones. The process for preparing these polymeric substrates includes: providing a polymeric substrate having a softening temperature greater than 1000 C; depositing a metal electrode material onto the polymer film; attaching a plurality of electrical leads to the metal electrode coated polymeric substrate; heating the metal electrode coated polymeric substrate in a low dielectric medium; applying a voltage to the heated metal electrode coated polymeric substrate to induce polarization; and cooling the polarized metal electrode coated polymeric electrode while maintaining a constant voltage.

Simpson, Joycely O. (Inventor); St.Clair, Terry L. (Inventor)

1999-01-01

162

Dynamics of nanoparticules detected at 1 AU by S/WAVES onboard STEREO spacecraft  

NASA Astrophysics Data System (ADS)

In order to interpret in detail the S/WAVES data on the interplanetary nanodust discovered by STEREO at 1 AU [Meyer-Vernet et al., 2009], we study the dynamics of nanoparticles in the inner interplanetary medium as well as the distribution of their velocities and directions of arrival, with a model based on [Czechowski and Mann, 2012]. We deduce the charges released by their impacts on the STEREO spacecraft at 1 AU and their dependence on the position of the spacecraft on their orbits. The model studies nanoparticles of size equal or smaller than about 70 nm, assumed to be created via collisional fragmentation of dust grains of larger size moving on keplerian orbits, and sublimation of dust, meteoroids and comets. The nanoparticles are released near the Sun with initial velocities close to keplerian, and mainly subjected to the Lorentz force calculated with a simple solar wind model. A part of the nanoparticles is accelerated to high speeds of the order of 300 km/s, thereby providing impact charges between 10(-14) and 10(-11) Cb [Belheouane, 2014] which enable them to be detected by S/WAVES, whereas another part is trapped within about 0.2 AU from the Sun. We discuss how the fluxes and direction of arrival at 1 AU are expected to change in function of the solar cycle. These results enable us to interpret in detail the STEREO/WAVES observations [Zaslavsky et al., 2012]; [Pantellini et al., 2013]; [Le Chat et al., 2013]. Belheouane, S. (2014). Nanoparticules dans le vent solaire, observations spatiales et theorie. PhD thesis, Pierre and Marie Curie University UPMC. Czechowski, A. and Mann, I. (2012). Nanodust Dynamics in Interplanetary Space, chapter Nanodust Dynamics in Interplanetary Space. Springer Berlin Heidelberg. Le Chat, G., Zaslavsky, A., Meyer-Vernet, N., Issautier, K., Belheouane, S., Pantellini, F., Maksimovic, M., Zouganelis, I., Bale, S., and Kasper, J. (2013). Interplanetary Nanodust Detection by the Solar Terrestrial Relations Observatory/WAVES Low Frequency Receiver. Solar Physics, 286(2):549-559. Meyer-Vernet, N., Maksimovic, M., Czechowski, A., Mann, I., Zouganelis, I., Goetz, K., Kaiser, M., Cyr, O. S., Bougeret, J.-L., and Bale, S. (2009). Dust Detection by the Wave Instrument on STEREO : Nanoparticles Picked up by the Solar Wind? Solar Phys, 256:463-474. Pantellini, F., Le Chat, G., Belheouane, S., Meyer-Vernet, N., and Zaslavsky, A. (2013). On the detection of nano dust using spacecraft based boom antennas. Solar Wind 13: Proceedings of the Thirteenth International Solar Wind Conference, 1539:414-417. Zaslavsky, A., Meyer-Vernet, N., Mann, I., Czechowski, A., Issautier, K., Le Chat, G., Pantellini, F., Goetz, K., Maksimovic, M., Bale, S. D., and Kasper, J. K. (2012). Interplanetary dust detection by radio antennas: Mass calibration and fluxes measured by STEREO/WAVES. J. Geophys. Res., 117.

Belheouane, Soraya; Issautier, Karine; Meyer-Vernet, Nicole; Le Chat, Gaétan; Czechowski, Andrzej; Zaslavsky, Arnaud; Zouganelis, Yannis; Mann, Ingrid

163

Title of Thesis: COMPARING MICROWAVE INDUCED POLYMERIZATION TO THERMAL INDUCED POLYMERIZATION OF THE  

E-print Network

POLYMERIZATION OF THE RESIN BISPHENOL A-GLYCIDYL METHACRYLATE. Degree candidate: Thomas J. Miller Degree and year by microwave energy and polymerization induced by thermal energy of the resin bisphenol A-glycidyl methacrylate INDUCED POLYMERIZATION TO THERMAL INDUCED POLYMERIZATION OF THE RESIN BISPHENOL A- GLYCIDYL METHACRYLATE

Anlage, Steven

164

Nonlinear optical and conductive polymeric material  

DOEpatents

A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl[sub 5] or W(CO)[sub 6]/hv.

Barton, T.J.; Ijadi-Maghsoodi, S.; Pang, Y.

1992-05-19

165

Nonlinear optical and conductive polymeric material  

DOEpatents

A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl.sub.5 or W(CO).sub.6 /hv.

Barton, Thomas J. (Ames, IA); Ijadi-Maghsoodi, Sina (Ames, IA); Pang, Yi (Ames, IA)

1993-10-19

166

Nonlinear optical and conductive polymeric material  

DOEpatents

A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl.sub.5 or W(CO).sub.6 /hv.

Barton, Thomas J. (Ames, IA); Ijadi-Maghsoodi, Sina (Ames, IA); Pang, Yi (Ames, IA)

1992-05-19

167

Nonlinear optical and conductive polymeric material  

DOEpatents

A polymeric material is described which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl[sub 5] or W(CO)[sub 6].

Barton, T.J.; Ijadi-Maghsooodi, S; Yi Pang.

1993-10-19

168

Synthesis of polymeric microparticles for water purification  

Microsoft Academic Search

In the present study, highly crosslinked poly(styrene\\/meta-diisopropylbenzene) P(St\\/mDIB) microparticles were prepared employing both an emulsifier-free emulsion polymerization and a single-step swelling polymerization process. The effect of the crosslinker concentration on the particle size and morphology was examined experimentally. Polystyrene microparticles were also prepared by emulsion polymerization in the presence of ?-cyclodextrin, P(St\\/?-CD). The ability of the synthesized polymeric microparticles to

Olga Kammona; Elpiniki Dini; Costas Kiparissides; Rosa Allabashi

2008-01-01

169

Sleeving nanocelluloses by admicellar polymerization.  

PubMed

This investigation reports the first application of admicellar polymerization to cellulose nanofibers in the form of bacterial cellulose, microfibrillated cellulose, and cellulose nanowhiskers using styrene and ethyl acrylate. The success of this physical sleeving was assessed by SEM, FTIR, and contact angle measurements, providing an original and simple approach to the modification of cellulose nanofibers in their pristine aqueous environment. PMID:23921337

Trovatti, Eliane; Ferreira, Adriane de Medeiros; Carvalho, Antonio José Felix; Ribeiro, Sidney José Lima; Gandini, Alessandro

2013-10-15

170

Outdoor HV composite polymeric insulators  

Microsoft Academic Search

HV composite polymeric insulators are being accepted increasingly for use in outdoor installations by the traditionally cautious electric power utilities worldwide. They currently represent ~60 to 70% of newly installed HV insulators in North America. The tremendous growth in the applications of non-ceramic composite insulators is due to their advantages over the traditional ceramic and glass insulators. These include light

R. Hackam

1999-01-01

171

Supramolecular polymerization: Living it up  

NASA Astrophysics Data System (ADS)

Protein fibril formation is involved in many human diseases and thus has been mechanistically elucidated in the context of understanding -- and in turn treating -- them. This biological phenomenon has now also inspired the design of a supramolecular system that undergoes living polymerization.

Würthner, Frank

2014-03-01

172

Low vibration polymeric composite engine  

NASA Astrophysics Data System (ADS)

An internal combustion engine is constructed with metallic parts in its regions which are subjected to high stress (temperature, pressure) during combustion and polymeric materials in its regions which are subjected to relatively lower stresses. The integrated construction helps realize increased power densities and reductions on engine noise without compromising engine performance. V-configuration Diesel engines particularly benefit from this construction.

Guimond, David P.; Muench, Rolf K.

1994-12-01

173

Polymerization-induced phase separation  

Microsoft Academic Search

A molecular dynamics simulation is performed to study the kinetics of microphase separation in a polymer-dispersed-liquid-crystal forming process. An equimolar mixture of monomers and liquid crystal molecules are thermalized in a well mixed state. The monomers are then polymerized at the same temperature. The end product is a spanning gel with liquid crystal molecules aggregating in droplets here and there.

J. C. Lee

1999-01-01

174

The Viscosity of Polymeric Fluids.  

ERIC Educational Resources Information Center

To illustrate the behavior of polymeric fluids and in what respects they differ from Newtonian liquids, an experiment was developed to account for the shear-rate dependence of non-Newtonian fluids. Background information, procedures, and results are provided for the experiment. Useful in transport processes, fluid mechanics, or physical chemistry…

Perrin, J. E.; Martin, G. C.

1983-01-01

175

Single-crystalline polymeric nitrogen  

Microsoft Academic Search

The authors synthesized polymeric nitrogen at pressures above 110 GPa with laser heating above 2000 K. To prove its cubic gauche (cg) structure, the authors have grown single crystals which produced strong reflections at large diffraction angles. The authors found nine peaks in the 2Theta=35° range with a special diamond anvil cell. All of the peaks agree with the cg-N

M. I. Eremets; A. G. Gavriliuk; I. A. Trojan

2007-01-01

176

Single-crystalline polymeric nitrogen  

Microsoft Academic Search

The authors synthesized polymeric nitrogen at pressures above 110 GPa with laser heating above 2000 K. To prove its cubic gauche (cg) structure, the authors have grown single crystals which produced strong reflections at large diffraction angles. The authors found nine peaks in the 2&THgr;=35° range with a special diamond anvil cell. All of the peaks agree with the cg-N

M. I. Eremets; A. G. Gavriliuk; I. A. Trojan

2007-01-01

177

Synthesis, morphology and antifungal activity of nano-particulated amphotericin-B, ketoconazole and thymoquinone against Candida albicans yeasts and Candida biofilm.  

PubMed

In the current study, nano-particulated drugs-Amphotericin-B, Ketoconazole and Thymoquinone (an active ingredient of Nigella sativa)-were prepared using the ball milling technique, and their particle sizes were examined by transmission electron microscopy (TEM) and using a particle size analyzer. The grain sizes of the prepared compounds were found in between 5 to 20 nm, and exhibited quasi-spherical morphology. The antifungal activity of each nano-particulated drug was investigated in vitro against Candida albicans yeasts and Candida biofilm, and compared with their micro-structured conventional forms. Nano-sized drugs were found to be two to four times more effective in disinfecting both the Candida yeasts and Candida biofilm. The study is a first of its kind as nano-forms of drugs have not been studied against Candida and Candida biofilm before. Further investigations are required for the determination of the clinical significance of the nano-formulation of antifungal substances. PMID:25560257

Randhawa, Mohammad A; Gondal, Mohammed A; Al-Zahrani, Al-Hosain J; Rashid, Siddique G; Ali, Ashraf

2015-01-01

178

Versatile and efficient targeting using a single nanoparticulate platform: application to cancer and Alzheimer's disease.  

PubMed

A versatile and efficient functionalization strategy for polymeric nanoparticles (NPs) has been reported and successfully applied to PEGylated, biodegradable poly(alkyl cyanoacrylate) (PACA) nanocarriers. The relevance of this platform was demonstrated in both the fields of cancer and Alzheimer's disease (AD). Prepared by copper-catalyzed azide-alkyne cycloaddition (CuAAC) and subsequent self-assembly in aqueous solution of amphiphilic copolymers, the resulting functionalized polymeric NPs exhibited requisite characteristics for drug delivery purposes: (i) a biodegradable core made of poly(alkyl cyanoacrylate), (ii) a hydrophilic poly(ethylene glycol) (PEG) outer shell leading to colloidal stabilization, (iii) fluorescent properties provided by the covalent linkage of a rhodamine B-based dye to the polymer backbone, and (iv) surface functionalization with biologically active ligands that enabled specific targeting. The construction method is very versatile and was illustrated by the coupling of a small library of ligands (e.g., biotin, curcumin derivatives, and antibody), resulting in high affinity toward (i) murine lung carcinoma (M109) and human breast cancer (MCF7) cell lines, even in a coculture environment with healthy cells and (ii) the ?-amyloid peptide 1-42 (A?(1-42)), believed to be the most representative and toxic species in AD, both under its monomeric and fibrillar forms. In the case of AD, the ligand-functionalized NPs exhibited higher affinity toward A?(1-42) species comparatively to other kinds of colloidal systems and led to significant aggregation inhibition and toxicity rescue of A?(1-42) at low molar ratios. PMID:22725248

Le Droumaguet, Benjamin; Nicolas, Julien; Brambilla, Davide; Mura, Simona; Maksimenko, Andrei; De Kimpe, Line; Salvati, Elisa; Zona, Cristiano; Airoldi, Cristina; Canovi, Mara; Gobbi, Marco; Magali, Noiray; La Ferla, Barbara; Nicotra, Francesco; Scheper, Wiep; Flores, Orfeu; Masserini, Massimo; Andrieux, Karine; Couvreur, Patrick

2012-07-24

179

Preparation of well-crystallized Pd 20Te 7 alloy nanoparticulate catalysts with uniform structure and composition in liquid-phase  

Microsoft Academic Search

The synthesis system of uniform and well-crystallized alloy nanoparticulate catalysts has been studied based on the calculation of pH dependent metal complex concentrations in an aqueous solution. Results of both the prediction based on calculation and EXAFS analysis clearly demonstrated that [Pd2+(EDTA)] and Te-citric acid complex species were generated independently in the solution. Since the formations of metal complexes are

Hideyuki Takahashi; Norikazu Konishi; Hironobu Ohno; Kazunari Takahashi; Yuichiro Koike; Kiyotaka Asakura; Atsushi Muramatsu

2011-01-01

180

Effects of particle dispersion on photocatalysis probed by the effect of platinum on dichloroacetic acid oxidation by P25 and nanoparticulate rutile  

Microsoft Academic Search

Oxidation of dichloracetic acid (DCA) by two titanium dioxide catalysts (P25 and a nanoparticulate rutile (NR)) was measured at pH 3 and the results compared with parallel measurements on the same TiO2s modified by deposition of platinum.Although the platinum loading corresponded to less than one platinum crystallite for each TiO2 crystal, platinization significantly increased photocatalytic activity – 30-fold in the

Terry A. Egerton; John A. Mattinson

2010-01-01

181

Laser welding of nanoparticulate TiO2 and transparent conducting oxide electrodes for highly efficient dye-sensitized solar cell  

Microsoft Academic Search

Poor interfacial contact is often encountered in nanoparticulate film-based devices. The dye-sensitized solar cell (DSSC) is a representative case in which a nanoporous TiO2 electrode needs to be prepared on the transparent conducting oxide (TCO)-coated glass substrate. In this study, we demonstrate that the inter-electrode contact resistance accounts for a considerable portion of the total resistance of a DSSC and

Jinsoo Kim; Jonghyun Kim; Myeongkyu Lee

2010-01-01

182

Systematic Modulation of Quantum (Electron) Tunneling Behavior by Atomic Layer Deposition on Nanoparticulate SnO2 and TiO2  

E-print Network

on Nanoparticulate SnO2 and TiO2 Photoanodes Chaiya Prasittichai,,§, Jason R. Avila,, Omar K. Farha,*, and Joseph T, Illinois 60439, United States *S Supporting Information ABSTRACT: Ultrathin films of TiO2, ZrO2, and Al2O3 were conformally created on SnO2 and TiO2 photo- electrodes via atomic layer deposition (ALD

183

Electronic properties of the interface between p-CuI and anatase-phase n-TiO2 single crystal and nanoparticulate surfaces: A photoemission study  

Microsoft Academic Search

We present a study of the growth of the p-type inorganic semiconductor CuI on n-type TiO2 anatase single crystal (101) surfaces and on nanoparticulate anatase surfaces using synchrotron radiation photoemission spectroscopy. Core level photoemission data obtained using synchrotron radiation reveal that both the substrate (TiO2) and the overlayer (CuI) core levels shift to a lower binding energy to different degrees

A. R. Kumarasinghe; W. R. Flavell; A. G. Thomas; A. K. Mallick; D. Tsoutsou; C. Chatwin; S. Rayner; P. Kirkham; S. Warren; S. Patel; P. Christian; P. O'Brien; M. Grätzel; R. Hengerer

2007-01-01

184

Toxicity of nanoparticulate and bulk ZnO, Al 2O 3 and TiO 2 to the nematode Caenorhabditis elegans  

Microsoft Academic Search

Limited information is available on the environmental behavior and associated potential risk of manufactured oxide nanoparticles (NPs). In this research, toxicity of nanoparticulate and bulk ZnO, Al2O3 and TiO2 were examined to the nematode Caenorhabditis elegans with Escherichia coli as a food source. Parallel experiments with dissolved metal ions from NPs were also conducted. The 24-h median lethal concentration (LC50)

Huanhua Wang; Robert L. Wick; Baoshan Xing

2009-01-01

185

Anisotropy adjustment and thickness of thin layer doped by nanoparticules magnetic for the realization of phase matching between fundamental modes in monomode waveguides  

NASA Astrophysics Data System (ADS)

Recently, research has been concentrated on the study of the magnetic nanoparticules for their use in the design of magneto-optical devices. The magneto-optical waveguides for example exploit the Faraday effect to obtain a rotation of polarization TE and TM independent of the propagation direction. In this work, we study isolating component whose operating principle is based on the minimization of the phase mismatch between TE and TM fundamental propagation modes. It appeared promising to use as a guiding film the thin layers doped by magnetic nanoparticules ?-Fe2O3 in order to carry out an adequate phase mismatch. This last can be adjusted by permanent linear birefringence resulting from the application of an external magnetic field during the gelation of the solution which constitutes the guiding film. Many studies were undertaken primarily to minimize the birefringence between TE and TM modes, for that this work represents a new potential means to reach the phase matching by acting on the anisotropy and the thin layer thickness. This condition can be realized in the waveguides with SiO2/TiO2 guiding thin layer doped by nanoparticules of maghemite ?-Fe2O3. The simulations carried out by the FMM method and MATLAB allowed to deduce the conditions to decrease the phase mismatch and increase the conversion ratio of TE/TM modes in order to ameliorate the isolation.

Lebbal, M. R.; Boumaza, T.; Bouchemat, M.; Hocini, A.; Hobar, F.; Benghalia, A.; Rosseau, J. J.; Royer, F.

2008-05-01

186

Rotations with Rodrigues' Vector  

ERIC Educational Resources Information Center

The rotational dynamics was studied from the point of view of Rodrigues' vector. This vector is defined here by its connection with other forms of parametrization of the rotation matrix. The rotation matrix was expressed in terms of this vector. The angular velocity was computed using the components of Rodrigues' vector as coordinates. It appears…

Pina, E.

2011-01-01

187

Vector-Borne Diseases  

NSDL National Science Digital Library

This online encyclopedia article discusses vector-borne diseases. It defines vectors as the transmitters of disease-causing organisms that carry the pathogens from one host to another. The article reviews the biological range of vectors, the transmission and types of vector-borne diseases, patterns of occurrence and existing control measures.

Harvey Artsob

188

Polymeric nanocapsules via miniemulsion polymerization using redox initiation  

Microsoft Academic Search

The effect of using a redox initiation system (hydrogen peroxide and ascorbic acid), on the morphology of the nanoparticles formed in methyl methacrylate miniemulsion polymerization reactions with lecithin as surfactant and using high amounts of miglyol 812 or castor oil as costabilizer is compared to the use of a conventional organic phase initiator (2,2?-azo-bis-isobutironitrile). It was observed that with miglyol

Ana Paula Romio; Neusa Bernardy; Elenara Lemos Senna; Pedro H. H. Araújo; Claudia Sayer

2009-01-01

189

Vector Interpolative Logic  

E-print Network

Abstract: Vector interpolative logic (I-logic) is a consistent generalization of vector classical logic, so that the components of analyzed I-logic vectors have values from the real interval [0, 1]. All laws of classical logic and as a consequence, vector classical logic too, are preserved in the vector I- logic. This result is not possible in the frame of conventional fuzzy and/or MV- logic approaches.

Dragan Radojevi?; Zvonko Mari?

190

Vector Lane Threading  

Microsoft Academic Search

Multi-lane vector processors achieve excellent computa- tional throughput for programs with high data-level paral- lelism (DLP). However, application phases without signif- icant DLP are unable to fully utilize the datapaths in the vector lanes. In this paper, we propose vector lane thread- ing (VLT), an architectural enhancement that allows idle vector lanes to run short-vector or scalar threads. VLT- enhanced

Suzanne Rivoire; Rebecca Schultz; Tomofumi Okuda; Christos Kozyrakis

2006-01-01

191

A Multithreaded Vector Coprocessor  

Microsoft Academic Search

A multithreaded vector co-processor design is described. It is intended to be placed with its private vector memory, on an expansion board, linked to the scalar processor and its cache-based memory hierarchy. The vector co-processor can run up to 8 vector tasks (threads) in parallel. Vector registers can be accessed either as independent sets of scalar values or as array

Bernard Goossens

1997-01-01

192

Metal containing polymeric functional microspheres  

NASA Technical Reports Server (NTRS)

Polymeric functional microspheres containing metal or metal compounds are formed by addition polymerization of a covalently bondable olefinic monomer such as hydroxyethylmethacrylate in the presence of finely divided metal or metal oxide particles, such as iron, gold, platinum or magnetite, which are embedded in the resulting microspheres. The microspheres can be covalently bonded to chemotherapeutic agents, antibodies, or other proteins providing a means for labeling or separating labeled cells. Labeled cells or microspheres can be concentrated at a specific body location such as in the vicinity of a malignant tumor by applying a magnetic field to the location and then introducing the magnetically attractable microspheres or cells into the circulatory system of the subject. Labeled cells can be separated from a cell mixture by applying a predetermined magnetic field to a tube in which the mixture is flowing. After collection of the labeled cells, the magnetic field is discontinued and the labeled sub-cell population recovered.

Yen, Shiao-Ping S. (Inventor); Rembaum, Alan (Inventor); Molday, Robert S. (Inventor)

1979-01-01

193

Polymeric cationic substituted acrylamide surfactants  

SciTech Connect

A new composition of matter comprises a copolymer of a surface active quaternary ammonium monomer salt and from 50 to 97% by wt of acrylamide. The new copolymers can have molecular weights substantially greater than 10,000 and still remain water soluble and surface active. Copolymers are prepared by polymerization techniques known in the art. The quaternary ammonium monomer is dispersed under inert atmosphere in aqueous solution which may additionally contain dissolved therein a low molecular weight alcohol such as ethanol, isopropanol, and the like. Acidic polymerization initiator such as the azo initiators, organic peroxides, or redox initiators such as the sulfite- persulfate system is then added in an amount calculated to yield a polymer product of desired molecular weight. (14 claims.

Nieh, E.C.Y.

1983-11-15

194

Thermally-Polymerized Rylene Nanoparticles  

PubMed Central

Rylene dyes functionalized with varying numbers of phenyl trifluorovinylether (TFVE) moieties were subjected to a thermal emulsion polymerization to yield shape-persistent, water-soluble chromophore nanoparticles. Perylene and terrylene diimide derivatives containing either two or four phenyl TFVE functional groups were synthesized and subjected to thermal emulsion polymerization in tetraglyme. Dynamic light scattering measurements indicated that particles with sizes ranging from 70 – 100 nm were obtained in tetraglyme, depending on monomer concentration. The photophysical properties of individual monomers were preserved in the nanoemulsions and emission colors could be tuned between yellow, orange, red, and deep red. The nanoparticles were found to retain their shape upon dissolution into water and the resulting water suspensions displayed moderate to high fluorescence quantum yield. PMID:21731112

Andrew, Trisha L.; Swager, Timothy M.

2011-01-01

195

Thermally-Polymerized Rylene Nanoparticles.  

PubMed

Rylene dyes functionalized with varying numbers of phenyl trifluorovinylether (TFVE) moieties were subjected to a thermal emulsion polymerization to yield shape-persistent, water-soluble chromophore nanoparticles. Perylene and terrylene diimide derivatives containing either two or four phenyl TFVE functional groups were synthesized and subjected to thermal emulsion polymerization in tetraglyme. Dynamic light scattering measurements indicated that particles with sizes ranging from 70 - 100 nm were obtained in tetraglyme, depending on monomer concentration. The photophysical properties of individual monomers were preserved in the nanoemulsions and emission colors could be tuned between yellow, orange, red, and deep red. The nanoparticles were found to retain their shape upon dissolution into water and the resulting water suspensions displayed moderate to high fluorescence quantum yield. PMID:21731112

Andrew, Trisha L; Swager, Timothy M

2011-04-12

196

Analyses of spacecraft polymeric materials  

NASA Technical Reports Server (NTRS)

Partial analytical characterizations are made by four different techniques of three polymeric materials used in conjunction with the Space Telescope for samples flown on mission STS-8. The polymers were Tedlar, Kapton H, and Kapton F. The surfaces of the three polymers were attacked and oxidized by atomic oxygen, and fluorine is lost from the surface of Kapton F, largely due to displacement by atomic oxygen.

Worley, S. D.; Fromhold, A. T.; Daneshvar, K.; Whitaker, A. F.; Little, S. A.

1986-01-01

197

Radiation-hardened polymeric films  

DOEpatents

The radiation-induced conductivity of polymeric dielectrics with low electronic mobility is reduced by doping with electron donor or electron acceptor compounds at a level of 10/sup 15/ to 10/sup 21/ molecules of dopant/cm/sup 3/. Polyesters, polyolefins, perfluoropolyolefins, vinyl polymers, vinylidene polymers, polycarbonates, polysulfones and polyimides can benefit from such a treatment. Usable dopants include 2,4,7-trinitro-9-fluorenone, tetracyanethylene, 7,7,8,8-tetracyanoquinodimethane, m-dinitrobenzene, 2-isopropylcarbazole, and triphenylamine.

Arnold, C. Jr.; Hughes, R.C.; Kepler, R.G.; Kurtz, S.R.

1984-07-16

198

Macrokinetic characteristics of isobutylene polymerization  

SciTech Connect

This paper describes a method of obtaining oligo and polyisobutylene with a molecular mass of 112-50,000: the cationic polymerization of isobutylene carried out in the presence of AlCl/sub 3/, in an environment of hydrocarbons (butanes, etc.) or chlorinated hydrocarbons (ethyl chloride, methyl chloride, etc.) at a temperature of 173-353 K/sub 3/ and in mixer-reactors of complicated design with a volume of 1.5-30 m.

Minsker, K.S.; Berlin, A.A.; Enikolopyan, N.S.; Prochukhan, Y.A.; Svinkov, A.G.

1986-08-01

199

Radiation-hardened polymeric films  

DOEpatents

The radiation-induced conductivity of polymeric dielectrics with low electronic mobility is reduced by doping with electron donor or electron acceptor compounds at a level of 10.sup.15 to 10.sup.21 molecules of dopant/cm.sup.3. Polyesters, polyolefins, perfluoropolyolefins, vinyl polymers, vinylidene polymers, polycarbonates, polysulfones and polyimides can benefit from such a treatment. Usable dopants include 2,4,7-trinitro-9-fluorenone, tetracyanethylene, 7,7,8,8-tetracyanoquinodimethane, m-dinitrobenzene, 2-isopropylcarbazole, and triphenylamine.

Arnold, Jr., Charles (Albuquerque, NM); Hughes, Robert C. (Albuquerque, NM); Kepler, R. Glen (Albuquerque, NM); Kurtz, Steven R. (Albuquerque, NM)

1986-01-01

200

Polymeric nanoparticles for molecular imaging.  

PubMed

Conventional imaging technologies (X-ray computed tomography, magnetic resonance, and optical) depend on contrast agents to visualize a target site or organ of interest. The imaging agents currently used in clinics for diagnosis suffer from disadvantages including poor target specificity and in vivo instability. Consequently, delivery of low concentrations of contrast agents to region of interest affects image quality. Therefore, it is important to selectively deliver high payload of contrast agent to obtain clinically useful images. Nanoparticles offer multifunctional capabilities to transport high concentrations of imaging probes selectively to diseased site inside the body. Polymeric nanoparticles, incorporated with contrast agents, have shown significant benefits in molecular imaging applications. These materials possess the ability to encapsulate different contrast agents within a single matrix enabling multimodal imaging possibilities. The materials can be surface conjugated to target-specific biomolecules for controlling the navigation under in vivo conditions. The versatility of this class of nanomaterials makes them an attractive platform for developing highly sensitive molecular imaging agents. The research community's progress in the area of synthesis of polymeric nanomaterials and their in vivo imaging applications has been noteworthy, but it is still in the pioneer stage of development. The challenges ahead should focus on the design and fabrication of these materials including burst release of contrasts agents, solubility, and stability issues of polymeric nanomaterials. PMID:24616442

Srikar, R; Upendran, Anandhi; Kannan, Raghuraman

2014-01-01

201

Two Photon Polymerization of Ormosils  

NASA Astrophysics Data System (ADS)

In this work, 3D structures of hybrid polymers—ORMOSILS (organically modified silicates) were produced via Two Photon Polymerization (2PP) of hybrid methacrylates based on silane derivates. Synthetic routes have been used to obtain series of hybrid monomers, their structure and purity being checked by NMR Spectroscopy and Fourier Transform Infrared Spectroscopy. Two photon polymerization method (a relatively new technology which allows fast micro and nano processing of three-dimensional structures with application in medical devices, tissue scaffolds, photonic crystals etc) was used for monomers processing. As laser a Ti: Sapphire laser was used, with 200 fs pulse duration and 2 kHz repetition rate, emitting at 775 nm. A parametric study on the influence of the processing parameters (laser fluence, laser scanning velocity, photo initiator) on the written structures was carried out. The as prepared polymeric scaffolds were tested in mesenchymal stem cells and fibroblasts cell cultures, with the aim of further obtaining bone and dermal grafts. Cells morphology, proliferation, adhesion and alignment were analyzed for different experimental conditions.

Matei, A.; Zamfirescu, M.; Jipa, F.; Luculescu, C.; Dinescu, M.; Buruiana, E. C.; Buruiana, T.; Sima, L. E.; Petrescu, S. M.

2010-10-01

202

Ring-Expansion Metathesis Polymerization  

PubMed Central

Ring-expansion metathesis polymerization (REMP) mediated by recently developed cyclic Ru catalysts has been studied in detail with a focus on the polymer products obtained under varied reaction conditions and catalyst architectures. Depending upon the nature of the catalyst structure, two distinct molecular weight evolutions were observed. Polymerization conducted with catalysts bearing 6-carbon tethers displayed rapid polymer molecular weight growth which reached a maximum value at ca 70% monomer conversion, resembling chain-growth polymerization mechanism. In contrast, 5-carbon tethered catalysts lead to molecular weight growth that resembled a step-growth mechanism with a steep increase occurring only after 95% monomer conversion. The underlying reason for these mechanistic differences appeared to be ready release of 5-carbon tethered catalysts from growing polymer rings, which competed significantly with propagation. Owing to reversible chain transfer and the lack of end groups in REMP, the final molecular weights of cyclic polymers was controlled by thermodynamic equilibria. Large ring sizes in the range of 60 - 120 kDa were observed at equilibrium for polycyclooctene and polycyclododecatriene, which were found to be independent of catalyst structure and initial monomer/catalyst ratio. While 6-carbon tethered catalysts slowly incorporated into the formed cyclic polymer, the incorporation of 5-carbon tethered catalysts was minimal, as revealed by ICP-MS. Further polymer analysis was conducted using melt-state magic-angle spinning 13C NMR spectroscopy of both linear and cyclic polymers, which revealed little or no chain ends for the latter topology. PMID:19199611

Xia, Yan; Boydston, Andrew J.; Yao, Yefeng; Kornfield, Julia A.; Gorodetskaya, Irina A.; Spiess, Hans W.; Grubbs, Robert H.

2009-01-01

203

Novel pentablock copolymer-based nanoparticulate systems for sustained protein delivery.  

PubMed

The design, synthesis, and application of novel biodegradable and biocompatible pentablock (PB) copolymers, i.e., polyglycolic acid-polycaprolactone-polyethylene glycol-polycaprolactone-polyglycolic acid (PGA-PCL-PEG-PCL-PGA) and polylactic acid-polycaprolactone-polyethylene glycol-polycaprolactone-polylactic acid (PLA-PCL-PEG-PCL-PLA) for sustained protein delivery, are reported. The PB copolymers can be engineered to generate sustained delivery of protein therapeutics to the posterior segment of the eye. PB copolymers with different block arrangements and molecular weights were synthesized by ring-opening polymerization and characterized by proton nuclear magnetic resonance ((1)H-NMR), gel permeation chromatography (GPC), and X-ray diffraction (XRD) spectroscopy. Immunoglobulin G (IgG) was selected as a model protein due to its structural similarity to bevacizumab. The influence of polymer molecular weight, composition, and isomerism on formulation parameters such as entrapment efficiency, drug loading, and in vitro release profile was delineated. Crystallinity and molecular weight of copolymers exhibited a substantial effect on formulation parameters. A secondary structure of released IgG was confirmed by circular dichroism (CD) spectroscopy. In vitro cytotoxicity, cell viability, and biocompatibility studies performed on human retinal pigment epithelial cells (ARPE-19) and/or macrophage cell line (RAW 264.7) demonstrated PB copolymers to be excellent biomaterials. Novel PB polymers may be the answer to the unmet need of a sustained release protein formulation. PMID:25319053

Patel, Sulabh P; Vaishya, Ravi; Pal, Dhananjay; Mitra, Ashim K

2015-04-01

204

Ring-expansion metathesis polymerization: catalyst-dependent polymerization profiles.  

PubMed

Ring-expansion metathesis polymerization (REMP) mediated by recently developed cyclic Ru catalysts has been studied in detail with a focus on the polymer products obtained under varied reaction conditions and catalyst architectures. Depending upon the nature of the catalyst structure, two distinct molecular weight evolutions were observed. Polymerization conducted with catalysts bearing six-carbon tethers displayed rapid polymer molecular weight growth which reached a maximum value at ca. 70% monomer conversion, resembling a chain-growth polymerization mechanism. In contrast, five-carbon-tethered catalysts led to molecular weight growth that resembled a step-growth mechanism with a steep increase occurring only after 95% monomer conversion. The underlying reason for these mechanistic differences appeared to be ready release of five-carbon-tethered catalysts from growing polymer rings, which competed significantly with propagation. Owing to reversible chain transfer and the lack of end groups in REMP, the final molecular weights of cyclic polymers was controlled by thermodynamic equilibria. Large ring sizes in the range of 60-120 kDa were observed at equilibrium for polycyclooctene and polycyclododecatriene, which were found to be independent of catalyst structure and initial monomer/catalyst ratio. While six-carbon-tethered catalysts were slowly incorporated into the formed cyclic polymer, the incorporation of five-carbon-tethered catalysts was minimal, as revealed by ICP-MS. Further polymer analysis was conducted using melt-state magic-angle spinning (13)C NMR spectroscopy of both linear and cyclic polymers, which revealed little or no chain ends for the latter topology. PMID:19199611

Xia, Yan; Boydston, Andrew J; Yao, Yefeng; Kornfield, Julia A; Gorodetskaya, Irina A; Spiess, Hans W; Grubbs, Robert H

2009-02-25

205

Effect of mixing on polymerization of styrene  

E-print Network

on Polymerization of Styrene. (August 1977) Michael Norris Treybig, B. S, , Texas Tech University Chairman of Advisory Committee: Dr. R. G. Anthony Styrene was polymerized in a 50 ml bench scale constant flow stirred tank reactor (CFSTR). The polymerization... degrees of mixing in the reactor. To simulate the performance of the laboratory reactor and to determine the effect of mixing on the molecular weight distribution (MWD), mathematical models were developed based on the concepts of micromixing and total...

Treybig, Michael Norris

1977-01-01

206

Self-Initiation in Cationic Polymerization  

Microsoft Academic Search

A critical examination of polymerization, dimerization, and isomerization experiments carried out under carefully controlled (anhydrous) conditions leads to the conclusion that polymerization, etc. may proceed in purest monomer\\/Friedel-Crafts halide systems in the absence of coinitiators. Thus the well-entrenched view that Friedel-Crafts halides always require coinitiator (protogenic impurities) for initiation of cationic polymerizations has to be modified. It is postulated that

J. P. Kennedy

1972-01-01

207

Fluoropolymer materials and architectures prepared by controlled radical polymerizations  

Microsoft Academic Search

This review initially summarizes the mechanisms, merits and limitations of the three controlled radical polymerizations: nitroxide mediated polymerization (NMP), atom transfer radical polymerization (ATRP) or metal catalyzed living radical polymerization, and reversible addition–fragmentation chain transfer (RAFT) polymerization. This is followed by two parts, one dealing with homo- and copolymerizations of fluorinated methacrylates and acrylates, and a second where fluorinated styrenes,

Natanya M. L. Hansen; Katja Jankova; Søren Hvilsted

2007-01-01

208

Anti-biofouling polymer-decorated lutetium-based nanoparticulate contrast agents for in vivo high-resolution trimodal imaging.  

PubMed

Nanomaterials have gained considerable attention and interest in the development of novel and high-resolution contrast agents for medical diagnosis and prognosis in clinic. A classical urea-based homogeneous precipitation route that combines the merits of in situ thermal decomposition and surface modification is introduced to construct polyethylene glycol molecule (PEG)-decorated hybrid lutetium oxide nanoparticles (PEG-UCNPs). By utilizing the admirable optical and magnetic properties of the yielded PEG-UCNPs, in vivo up-conversion luminescence and T1 -enhanced magnetic resonance imaging of small animals are conducted, revealing obvious signals after subcutaneous and intravenous injection, respectively. Due to the strong X-ray absorption and high atomic number of lanthanide elements, X-ray computed-tomography imaging based on PEG-UCNPs is then designed and carried out, achieving excellent imaging outcome in animal experiments. This is the first example of the usage of hybrid lutetium oxide nanoparticles as effective nanoprobes. Furthermore, biodistribution, clearance route, as well as long-term toxicity are investigated in detail after intravenous injection in a murine model, indicating the overall safety of PEG-UCNPs. Compared with previous lanthanide fluorides, our nanoprobes exhibit more advantages, such as facile construction process and nearly total excretion from the animal body within a month. Taken together, these results promise the use of PEG-UCNPs as a safe and efficient nanoparticulate contrast agent for potential application in multimodal imaging. PMID:24610806

Liu, Zhen; Dong, Kai; Liu, Jianhua; Han, Xueli; Ren, Jinsong; Qu, Xiaogang

2014-06-25

209

Physicochemical characterization and toxicological evaluation of plant-based anionic polymers and their nanoparticulated system for ocular delivery.  

PubMed

The water-soluble fractions of mucilages and gum from the seeds of fenugreek, isphagula and mango bark exudate were isolated, purified and characterized using X-ray diffraction (XRD) spectrometry, Fourier transform infrared spectroscopy (FT-IR), maldi/GC-MS, elemental analysis, 1D ((1)H and (13)C) and 2D (HMQC, COSY) nuclear magnetic resonance spectroscopy (NMR). The fenugreek mucilage was identified to be a galactomannan chain consisting of 4 units of galactose attached to the backbone of 6 mannose units in 1:1.5 ratio. The isphagula mucilage was identified to be an arabinoxylan polysaccharide chain consisting of 4 units of arabinofuranose attached to the backbone of 9 xylopyrannose units in 1:3 ratio. The mango gum showed the presence of amylose, ?-arabinofuranosyl and ?-galactopyranosyl, respectively. The characterized mucilages and gum were individually formulated into nanoparticulate system using their complementarily charged polymer chitosan. The particles were observed to be spherical in shape in the range of 61.5-90 nm having zetapotential between 31 and 34 mV and PDI of 0.097-0.241. The prepared nanoparticles were observed to be nonirritant and nontoxic in vitro and in vivo upto 2000 ?g/ml. Therefore, these mucilages and gum can be the alternatives of anionic polymers for the ocular drug delivery system. PMID:23952497

Pathak, Deepa; Kumar, Prashant; Kuppusamy, Gowthamarajan; Gupta, Ankur; Kamble, Bhagyashree; Wadhwani, Ashish

2014-12-01

210

Revisiting the Fundamentals in the Design and Control of Nanoparticulate Colloids in the Frame of Soft Chemistry1  

PubMed Central

This review presents thoughts on some of the fundamental features of conceptual models applied in the design of fine particles in the frames of colloid and soft chemistry. A special emphasis is placed on the limitations of these models, an acknowledgment of which is vital in improving their intricacy and effectiveness in predicting the outcomes of the corresponding experimental settings. Thermodynamics of self-assembly phenomena illustrated on the examples of protein assembly and micellization is analyzed in relation to the previously elaborated thesis that each self-assembly in reality presents a co-assembly, since it implies a mutual reorganization of the assembling system and its immediate environment. Parameters used in the design of fine particles by precipitation are discussed while referring to solubility product, various measures of supersaturation levels, induction time, nucleation and crystal growth rates, interfacial energies, and the Ostwald–Lussac law of phases. Again, the main drawbacks and inadequacies of using the aforementioned parameters in tailoring the materials properties in a soft and colloidal chemical setting were particularly emphasized. The basic and practical limitations of zeta-potential analyses, routinely used to stabilize colloidal dispersions and initiate specific interactions between soft chemical entities, were also outlined. The final section of the paper reiterates the unavoidable presence of practical qualitative models in the design and control of nanoparticulate colloids, which is supported by the overwhelming complexity of quantitative relationships that govern the processes of their formation and assembly. PMID:24490052

Uskokovi?, Vuk

2013-01-01

211

Fe isotope exchange between Fe(II) aq and nanoparticulate mackinawite (FeS m) during nanoparticle growth  

NASA Astrophysics Data System (ADS)

We detail the results of an experimental study on the kinetics of Fe isotope exchange between aqueous Fe(II) aq and nanoparticulate mackinawite (FeS m) at 25 °C and 2 °C over a one month period. The rate of isotopic exchange decreases synchronously with the growth of FeS m nanoparticles. 100% isotopic exchange between bulk FeS m and the solution is never reached and the extent of isotope exchange asymptotes to a maximum of ~ 75%. We demonstrate that particle growth driven by Ostwald ripening would produce much faster isotopic exchange than observed and would be limited by the extent of dissolution-recrystallisation. We show that Fe isotope exchange kinetics are consistent with i) FeS m nanoparticles that have a core-shell structure, in which Fe isotope mobility is restricted to exchange between the surface shell and the solution and ii) a nanoparticle growth via an aggregation-growth mechanism. We argue that because of the structure of FeS m nanoparticles, the approach to isotopic equilibrium is kinetically restricted at low temperatures. FeS m is a reactive component in diagenetic pyrite forming systems since FeS m dissolves and reacts to form pyrite. Isotopic mobility and potential equilibration between FeS m and Fe(II) aq thus have direct implications for the ultimate Fe isotope signature recorded in sedimentary pyrite.

Guilbaud, Romain; Butler, Ian B.; Ellam, Rob M.; Rickard, David

2010-11-01

212

Malaria Vector Species  

NSDL National Science Digital Library

A sub-page of the extremely informative VectorBase. This is a worldwide listing of malaria vectors divided into 12 geographic regions following the 1957 classic The Epidemiology and Control of Malaria by MacDonald.

0000-00-00

213

Understanding Singular Vectors  

ERIC Educational Resources Information Center

matrix yields a surprisingly simple, heuristical approximation to its singular vectors. There are correspondingly good approximations to the singular values. Such rules of thumb provide an intuitive interpretation of the singular vectors that helps explain why the SVD is so…

James, David; Botteron, Cynthia

2013-01-01

214

Energy elastic effects and the concept of temperature in flowing polymeric liquids  

Microsoft Academic Search

The incorporation of energy elastic effects in the modeling of flowing polymeric liquids is discussed. Since conformational\\u000a energetic effects are determined by structural features much smaller than the end-to-end vector of the polymer chains, commonly\\u000a employed single conformation tensor models are insufficient to describe energy elastic effects. The need for a local structural\\u000a variable is substantiated by studying a microscopic

Markus Hütter; Clarisse Luap; Hans Christian Öttinger

2009-01-01

215

Vector Piezoresponse Force Microscopy  

Microsoft Academic Search

A novel approach for nanoscale imaging and characterization of the orientation dependence of electromechanical properties---vector piezoresponse force microscopy (Vector PFM)---is described. The relationship between local electromechanical response, polarization, piezoelectric constants, and crystallographic orientation is analyzed in detail. The image formation mechanism in vector PFM is discussed. Conditions for complete three-dimensional (3D) reconstruction of the electromechanical response vector and evaluation of

Sergei V. Kalinin; Brian J. Rodriguez; Stephen Jesse; Junsoo Shin; Arthur P. Baddorf; Pradyumna Gupta; Himanshu Jain; David B. Williams; Alexei Gruverman

2006-01-01

216

Method of forming metallic coatings on polymeric substrates and of forming graded polymeric coatings or films  

SciTech Connect

The invention described herein relates to methods of forming graded polymeric coatings or films on a desired substrate and of forming metallic coatings on polymeric or other nonmetallic substrates. In particular, it relates to methods of forming such coatings or films by sorption and/or diffusion of metals into coatings or films of polymeric material deposited by conventional techniques on a desired substrate.

Liepins, R.

1981-03-11

217

Does topology drive fiber polymerization?  

PubMed

We have developed new procedures to examine the early steps in fibrin polymerization. First, we isolated fibrinogen monomers from plasma fibrinogen by gel filtration. Polymerization of fibrinogen monomers differed from that of plasma fibrinogen. The formation of protofibrils was slower and the transformation of protofibrils to fibers faster for the fibrinogen monomers. Second, we used formaldehyde to terminate the polymerization reactions. The formaldehyde-fixed products obtained at each time point were examined by dynamic light scattering and transmission electron microscopy (TEM). The data showed the formaldehyde-fixed products were stable and representative of the reaction intermediates. TEM images showed monomers, short oligomers, protofibrils, and thin fibers. The amount and length of these species varied with time. Short oligomers were less than 5% of the molecules at all times. Third, we developed models that recapitulate the TEM images. Fibrin monomer models were assembled into protofibrils, and protofibrils were assembled into two-strand fibers using Chimera software. Monomers were based on fibrinogen crystal structures, and the end-to-end interactions between monomers were based on D-dimer crystal structures. Protofibrils assembled from S-shaped monomers through asymmetric D:D interactions were ordered helical structures. Fibers were modeled by duplicating a protofibril and rotating the duplicate 120° around its long axis. No specific interactions were presumed. The two protofibrils simply twisted around one another to form a fiber. This model suggests that the conformation of the protofibril per se promotes the assembly into fibers. These findings introduce a novel mechanism for fibrin assembly that may be relevant to other biopolymers. PMID:25419972

Huang, Lihong; Hsiao, Joe Ping-Lin; Powierza, Camilla; Taylor, Russell M; Lord, Susan T

2014-12-16

218

Redox Reactions in Polymeric Systems  

NASA Astrophysics Data System (ADS)

Reduction-Oxidization (redox) reactions performed in polymeric environments resulted in the reversible formation of stable silver nanoparticle and two reductive radicals. The reversible formation of stable silver nanoparticles in polyvinyl alcohol (PVA) and polyacrylic acid (PAA) crosslinked polymer films containing silver ions was achieved by electrochemical methods for potential applications in electrochromic devices. Cyclic voltammetry and galvanostatic methods were used to reversibly generate silver particles while the particle formation and decay optical absorption spectra were used to evaluate reversibility, relative particle size and minimum cycle speeds. Mechanisms for the formation and decay of particles are discussed with electron microscopy data determining actual size of generated silver particles. Light activated polymeric radicals produced from sulfonated polyether ether ketone (SPEEK) with PVA or SPEEK with sodium formate solutions were generated using 350 nm photons. The mechanism of radical generation is discussed for potential application for dehalogenating a well known environmental hazard carbon tetrachloride (CCl4). The reaction of the generated radicals with CCl4 was followed by ion selective electrode specific for chlorine allowing for the attainment of kinetic data and reaction mechanisms. The degradation of CCl4 was observed in both SPEEK/PVA and SPEEK/formate solutions but the kinetic data revealed SPEEK/formate to be more efficient. The success of SPEEK radicals in dechlorinating CCl4 lead to the investigation of polymeric blends, films and solution of SPEEK and polyamines for the generation of SPEEK radicals with a higher redox potential. SPEEK/polyamine radicals were generated by exposing polymer blends to 350 nm photons. Optical and electron spin resonance (ESR) spectra confirmed the generation of the anionic radical with a higher reducing potential. Kinetic data was obtained for selected system by following the formation and decay of the optical and ESR signatures. The reactions leading to the generation of highly reductive radicals is discussed.

Black, James R., II

2011-12-01

219

Vector Microprocessors Krste Asanovic  

E-print Network

Vector Microprocessors by Krste Asanovi´c B.A. (University of Cambridge) 1987 A dissertation 1998 #12;Vector Microprocessors Copyright 1998 by Krste Asanovi´c #12;1 Abstract Vector Microprocessors microprocessor imple- mentations targeting a much broader range of applications. I present the design

Asanoviæ, Krste

220

Support vector domain description  

Microsoft Academic Search

This paper shows the use of a data domain description method, inspired by the support vector machine by Vapnik, called the support vector domain description (SVDD). This data description can be used for novelty or outlier de- tection. A spherically shaped decision boundary around a set of objects is constructed by a set of support vectors describing the sphere boundary.

David M. J. Tax; Robert P. W. Duin

1999-01-01

221

Nonviral Vector Systems  

Microsoft Academic Search

Gene therapy requires efficient vectors for delivering therapeutic genes. Advances in developments of nonviral vectors have\\u000a been established for improving the efficiency of gene delivery. This chapter describes different nonviral methods as well\\u000a as their applications. Some new directions in developing nonviral vectors are also discussed.

Pui-yan Lee; Leaf Huang

222

Rhotrix Vector Spaces  

ERIC Educational Resources Information Center

By rhotrix we understand an object that lies in some way between (n x n)-dimensional matrices and (2n - 1) x (2n - 1)-dimensional matrices. Representation of vectors in rhotrices is different from the representation of vectors in matrices. A number of vector spaces in matrices and their properties are known. On the other hand, little seems to be…

Aminu, Abdulhadi

2010-01-01

223

Electrically controlled polymeric gel actuators  

DOEpatents

Electrically controlled polymeric gel actuators or synthetic muscles are described capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots. 11 figures.

Adolf, D.B.; Shahinpoor, M.; Segalman, D.J.; Witkowski, W.R.

1993-10-05

224

Template polymerization of nucleotide analogues  

NASA Technical Reports Server (NTRS)

Recent work on the template-directed reactions of the natural D-nucleotides has made it clear that l-nucleotides and nucleotide-like derivatives of other sugars would strongly inhibit the formation of long oligonucleotides. Consequently, attention is focusing on molecules simpler than nucleotides that might have acted as monomers of an information transfer system. We have begun a general exploration of the template directed reactions of diverse peptide analogues. I will present work by Dr. Taifeng Wu on oxidative oligomerization of phosphorothioates and of Dr. Mary Tohidi on the cyclic polymerization of nucleoside and related cyclic pyrophosphates.

Orgel, L. E.

1991-01-01

225

Electrically controlled polymeric gel actuators  

DOEpatents

Electrically controlled polymeric gel actuators or synthetic muscles capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots.

Adolf, Douglas B. (Albuquerque, NM); Shahinpoor, Mohsen (Albuquerque, NM); Segalman, Daniel J. (Albuquerque, NM); Witkowski, Walter R. (Albuquerque, NM)

1993-01-01

226

Marketing NASA Langley Polymeric Materials  

NASA Technical Reports Server (NTRS)

A marketing tool was created to expand the knowledge of LaRC developed polymeric materials, in order to facilitate the technology transfer process and increase technology commercialization awareness among a non-technical audience. The created brochure features four materials, LaRC-CP, LaRC-RP46, LaRC-SI, and LaRC-IA, and highlights their competitive strengths in potential commercial applications. Excellent opportunities exist in the $40 million per year microelectronics market and the $6 billion adhesives market. It is hoped that the created brochure will generate inquiries regarding the use of the above materials in markets such as these.

Flynn, Diane M.

1995-01-01

227

Multicomponent diffusion in polymeric liquids.  

PubMed Central

It is shown how the phase-space kinetic theory of polymeric liquid mixtures leads to a set of extended Maxwell-Stefan equations describing multicomponent diffusion. This expression reduces to standard results for dilute solutions and for undiluted polymers. The polymer molecules are modeled as flexible bead-spring structures. To obtain the Maxwell-Stefan equations, the usual expression for the hydrodynamic drag force on a bead, used in previous kinetic theories, must be replaced by a new expression that accounts explicitly for bead-bead interactions between different molecules. PMID:11607693

Curtiss, C F; Bird, R B

1996-01-01

228

Ionene modified small polymeric beads  

NASA Technical Reports Server (NTRS)

Linear ionene polyquaternary cationic polymeric segments are bonded by means of the Menshutkin reaction (quaternization) to biocompatible, extremely small, porous particles containing halide or tertiary amine sites which are centers for attachment of the segments. The modified beads in the form of emulsions or suspensions offer a large, positively-charged surface area capable of irreversibly binding polyanions such as heparin, DNA, RNA or bile acids to remove them from solution or of reversibly binding monoanions such as penicillin, pesticides, sex attractants and the like for slow release from the suspension.

Rembaum, Alan (Inventor)

1977-01-01

229

Polymerization  

NSDL National Science Digital Library

In this activity, by the Concord Consortium's Molecular Literacy project, students "explore both polymers and copolymers." Upon completion of this activity students should be able to compare linear, branched, and cross-linked polymers; connect the density of polymers with differences in their structure; and connect polymer structures with their reversibility, and consider the importance for recycling." The activity itself is a java-based interactive resource built upon the free, open source Molecular Workbench software. In the activity, students are allowed to explore at their own pace in a digital environment full of demonstrations, illustrations, and models they can manipulate. In addition to the activity, visitors will find an overview of the activity, a test and rubric, central concepts, and their correlation to AAAS standards.

230

Rotations with Rodrigues' vector  

NASA Astrophysics Data System (ADS)

The rotational dynamics was studied from the point of view of Rodrigues' vector. This vector is defined here by its connection with other forms of parametrization of the rotation matrix. The rotation matrix was expressed in terms of this vector. The angular velocity was computed using the components of Rodrigues' vector as coordinates. It appears to be a fundamental matrix that is used to express the components of the angular velocity, the rotation matrix and the angular momentum vector. The Hamiltonian formalism of rotational dynamics in terms of this vector uses the same matrix. The quantization of the rotational dynamics is performed with simple rules if one uses Rodrigues' vector and similar formal expressions for the quantum operators that mimic the Hamiltonian classical dynamics.

Piña, E.

2011-09-01

231

Combustion-Generated Nanoparticulates in the El Paso, TX, USA / Juarez, Mexico Metroplex: Their Comparative Characterization and Potential for Adverse Health Effects  

PubMed Central

In this paper we report on the collection of fine (PM1) and ultrafine (PM0.1), or nanoparticulate, carbonaceous materials using thermophoretic precipitation onto silicon monoxide/formvar-coated 3 mm grids which were examined in the transmission electron microscope (TEM). We characterize and compare diesel particulate matter (DPM), tire particulate matter (TPM), wood burning particulate matter, and other soot (or black carbons (BC)) along with carbon nanotube and related fullerene nanoparticle aggregates in the outdoor air, as well as carbon nanotube aggregates in the indoor air; and with reference to specific gas combustion sources. These TEM investigations include detailed microstructural and microdiffraction observations and comparisons as they relate to the aggregate morphologies as well as their component (primary) nanoparticles. We have also conducted both clinical surveys regarding asthma incidence and the use of gas cooking stoves as well as random surveys by zip code throughout the city of El Paso. In addition, we report on short term (2 day) and longer term (2 week) in vitro assays for black carbon and a commercial multiwall carbon nanotube aggregate sample using a murine macrophage cell line, which demonstrate significant cytotoxicity; comparable to a chrysotile asbestos nanoparticulate reference. The multi-wall carbon nanotube aggregate material is identical to those collected in the indoor and outdoor air, and may serve as a surrogate. Taken together with the plethora of toxic responses reported for DPM, these findings prompt concerns for airborne carbonaceous nanoparticulates in general. The implications of these preliminary findings and their potential health effects, as well as directions for related studies addressing these complex issues, will also be examined. PMID:16823077

Murr, L. E.; Soto, K. F.; Garza, K. M.; Guerrero, P. A.; Martinez, F.; Esquivel, E. V.; Ramirez, D. A.; Shi, Y.; Bang, J. J.; Venzor, J.

2006-01-01

232

Spring-loaded polymeric gel actuators  

DOEpatents

Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications. 5 figs.

Shahinpoor, M.

1995-02-14

233

Photoinitiating Monomers in Free Radical Polymerization  

Microsoft Academic Search

of Paper The photopolymerization of Vinyl acrylate (VA) has been investigated with respect to the self-initiating efficiency. VA initiated polymerization of conventional acrylates exhibit fast rates of polymerization and high degrees of conversion are obtained. Herein we report a comprehensive real time infrared (RTIR) investigation of the reaction kinetics of the homo- and copolymerization of VA with various comonomers in

E. S. Jönsson; T. Y. Lee; K. Viswanathan; C. E. Hoyle; T. M. Roper; C. A. Guymon; C. Nason; I. V. Khudyakov

234

Modeling of Emulsion Polymerization of Vinyl Chloride  

Microsoft Academic Search

A survey of the principles of emulsion polymerization modeling of vinyl chloride is presented. Experimental results and model equations for particle nucleation, particle coalescence, and particle growth are discussed. A mechanism for particle coalescence in the course of polymerization is proposed based on the assumption that radical desorption from a particle is the rate-determining step for coalescence. Equations for the

Klaus Tauer; Gerhard Reinisch; Herbert Gajewski; Ingolf Müller

1991-01-01

235

Spring-loaded polymeric gel actuators  

DOEpatents

Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications.

Shahinpoor, Mohsen (Albuquerque, NM)

1995-01-01

236

Escalation of polymerization in a thermal gradient  

PubMed Central

For the emergence of early life, the formation of biopolymers such as RNA is essential. However, the addition of nucleotide monomers to existing oligonucleotides requires millimolar concentrations. Even in such optimistic settings, no polymerization of RNA longer than about 20 bases could be demonstrated. How then could self-replicating ribozymes appear, for which recent experiments suggest a minimal length of 200 nt? Here, we demonstrate a mechanism to bridge this gap: the escalated polymerization of nucleotides by a spatially confined thermal gradient. The gradient accumulates monomers by thermophoresis and convection while retaining longer polymers exponentially better. Polymerization and accumulation become mutually self-enhancing and result in a hyperexponential escalation of polymer length. We describe this escalation theoretically under the conservative assumption of reversible polymerization. Taking into account the separately measured thermophoretic properties of RNA, we extrapolate the results for primordial RNA polymerization inside a temperature gradient in pores or fissures of rocks. With a dilute, nanomolar concentration of monomers the model predicts that a pore length of 5 cm and a temperature difference of 10 K suffice to polymerize 200-mers of RNA in micromolar concentrations. The probability to generate these long RNAs is raised by a factor of >10600 compared with polymerization in a physical equilibrium. We experimentally validate the theory with the reversible polymerization of DNA blocks in a laser-driven thermal trap. The results confirm that a thermal gradient can significantly enlarge the available sequence space for the emergence of catalytically active polymers. PMID:23630280

Mast, Christof B.; Schink, Severin; Gerland, Ulrich; Braun, Dieter

2013-01-01

237

New developments of polymeric dental composites  

Microsoft Academic Search

The currently used commercial restorative composites contain a mixture of various cross-linking dimethacrylates, glass- and\\/or silicon dioxide fillers, and a photoinitiator system. They are cured by irradiation with visible light. New developments of polymeric composites for restorative filling materials are mainly focused on the reduction of polymerization shrinkage, and improvement of biocompatibility, wear resistance and processing properties. This can be

Norbert Moszner; Ulrich Salz

2001-01-01

238

Volumetric polymerization shrinkage of contemporary composite resins.  

PubMed

The polymerization shrinkage of composite resins may affect negatively the clinical outcome of the restoration. Extensive research has been carried out to develop new formulations of composite resins in order to provide good handling characteristics and some dimensional stability during polymerization. The purpose of this study was to analyze, in vitro, the magnitude of the volumetric polymerization shrinkage of 7 contemporary composite resins (Definite, Suprafill, SureFil, Filtek Z250, Fill Magic, Alert, and Solitaire) to determine whether there are differences among these materials. The tests were conducted with precision of 0.1 mg. The volumetric shrinkage was measured by hydrostatic weighing before and after polymerization and calculated by known mathematical equations. One-way ANOVA (á = 0.05) was used to determine statistically significant differences in volumetric shrinkage among the tested composite resins. Suprafill (1.87+/-0.01) and Definite (1.89+/-0.01) shrank significantly less than the other composite resins. SureFil (2.01+/-0.06), Filtek Z250 (1.99+/-0.03), and Fill Magic (2.02+/-0.02) presented intermediate levels of polymerization shrinkage. Alert and Solitaire presented the highest degree of polymerization shrinkage. Knowing the polymerization shrinkage rates of the commercially available composite resins, the dentist would be able to choose between using composite resins with lower polymerization shrinkage rates or adopting technical or operational procedures to minimize the adverse effects deriving from resin contraction during light-activation. PMID:19089177

Nagem Filho, Halim; Nagem, Haline Drumond; Francisconi, Paulo Afonso Silveira; Franco, Eduardo Batista; Mondelli, Rafael Francisco Lia; Coutinho, Kennedy Queiroz

2007-10-01

239

Polymeric Additives For Graphite/Epoxy Composites  

NASA Technical Reports Server (NTRS)

Report describes experimental studies of properties of several graphite/epoxy composites containing polymeric additives as flexibilizing or toughening agents. Emphasizes effects of brominated polymeric additives (BPA's) with or without carboxy-terminated butadiene acrylonitrile rubber. Reviews effects of individual and combined additives on fracture toughnesses, environmental stabilities, hot/wet strengths, thermomechanical behaviors, and other mechanical properties of composites.

Kourtides, D. A.; Nir, Z.

1990-01-01

240

Adsorption and photoactivity of tetra(4-carboxyphenyl)porphyrin (TCPP) on nanoparticulate TiO{sub 2}  

SciTech Connect

Tetra(4-carboxyphenyl)porphyrin (TCPP) adsorbs strongly onto nanoparticulate TiO{sub 2} and serves as an efficient photosensitizer for solar-energy conversion by TCPP-sensitized TiO{sub 2} electrodes. Nanoparticulate TiO{sub 2} electrodes were prepared from Degussa P25 TiO{sub 2} powder in the standard manner for a Graetzel cell. Adsorption studies of TCPP onto these sintered TiO{sub 2} electrodes gave a saturation surface coverage of 47 {micro}mol/g. Adsorption studies of TCPP onto colloidal dispersions of Degussa P25 in ethanol gave a saturation surface coverage of 77 {micro}mol/g. The difference between the saturation coverages is attributed to the reduction of the available surface area in the TiO{sub 2} films after sintering, from 55 m{sup 2}/g as a free colloid to about 34 m{sup 2}/g as a sintered electrode. The nature of the binding of TCPP onto the TiO{sub 2} electrodes was investigated using X-ray photoelectron spectroscopy (XPS) and Resonance Raman Spectroscopy (RRS). In the XPS spectra of TiO{sub 2} with adsorbed TCPP, the O (1s) and Ti (2p{sub 3/2}) peaks of TiO{sub 2} were shifted to a higher binding energy value, by about 0.3 eV, and the O (1s) and N (1s) peaks of TCPP were shifted to a higher binding energy, by about 0.7 eV. Upon adsorption of TCPP, one of the Ti (2p{sub 3/2}) peaks of TiO{sub 2} disappeared, suggesting complexation and removal of surface states. The RRS results indicated that for cases in which TCPP was adsorbed onto TiO{sub 2} films from ethanolic solutions of about 1 {micro}M concentration, the porphyrin spectrum showed distinctive interactions with the surface, but for cases in which it was adsorbed from higher concentrations, the RRS spectra were similar to spectra of TCPP powder, indicating the dominance of porphyrin-porphyrin interactions. The authors conclude that lateral interactions between adsorbed TCPP are significant upon adsorption from all but the lowest (micromolar) initial concentrations. Photovoltaic cells with TCPP-sensitized TiO{sub 2} electrodes gave good solar-energy conversion efficiencies. At light simulating one sun (AM 1.5), a cell sensitized by TCPP gives a short-circuit photocurrent of about 6 mA/cm{sup 2} and an open-circuit photopotential of 485 mV. The incident photon-to-current conversion efficiency was 55% at the Soret peak and 25--45% at the Q-band peaks; the cells have a fill factor of 60--70% and an overall energy conversion efficiency of about 3%.

Cherian, S.; Wamser, C.C.

2000-04-20

241

Generation of Oxidants From the Reaction of Nanoparticulate Zero-Valent Iron and Oxygen for the use in Contaminant Remediation  

NASA Astrophysics Data System (ADS)

The reaction of zero-valent iron (ZVI) with oxygen can lead to the formation of oxidants, which may be used to transform recalcitrant contaminants including non-polar organics and certain metals. Nanoparticulate iron might provide a practical mechanism of remediating oxygen-containing groundwater and contaminated soil. To gain insight into the reaction mechanism and to quantify the yield of oxidants, experiments were performed with model organic compounds in the presence of nanoparticulate zero-valent iron and oxygen. At pH values below 5, ZVI nanoparticles were oxidized within 30 minutes with a stoichiometry of approximately two Fe0 oxidized per O2 consumed. Using the oxidation of methanol and ethanol to formaldehyde and acetaldehyde, respectively, we found that less than 2% of the consumed oxygen was converted to reactive oxidants under acidic conditions. The yield of aldehydes increased with pH up to pH 7, with maximum oxidant yields of around 5% relative to the mass of ZVI added. The increase of aldehyde yield with pH was attributable to changes in the processes responsible for oxidant production. At pH values below 5, the corrosion of ZVI by oxygen produces hydrogen peroxide, which subsequently reacts with ferrous iron [Fe(II)] via the Fenton reaction. At higher pH values, the aldehydes are produced when Fe(II), the initial product of ZVI oxidation, reacts with oxygen. The decrease in oxidant yield at pH values above 7 may be attributable to precipitation of Fe(II). The oxidation of benzoic acid and 2-propanol to para-hydroxybenzoic acid and acetone, respectively, followed a very different trend compared to the primary alcohols. In both cases, the highest product yields (approximately 2% with respect to ZVI added) were observed at pH 3. Yields decreased with increasing pH, with no oxidized product detected at neutral pH. These results suggest that two different oxidants may be produced by the system: hydroxyl radical (OH-·) at acidic pH and a more selective oxidant such as the ferryl ion [Fe(IV)] at neutral pH. This provides insight into the type of compounds that may be oxidized using the zero-valent iron and oxygen system. The addition of certain compounds such as oxalate and polyoxometalate (POM) may improve contaminant remediation efficiencies by enhancing oxidant yields. The introduction of 1 mM oxalate improved the formaldehyde yield by approximately 20% at neutral pH. Oxalate accelerates the Fenton reaction and limits the passivation of the ZVI surface by increasing iron solubility. The presence of excess POM greatly enhanced the yield of formaldehyde, with maximum yields of 60 and 35% with respect to ZVI added at pH 2 and 7, respectively. The mechanism of POM enhancement is a function of solution pH. At acidic pH, POM acts an electron shuttle by directly transferring electrons from ZVI to oxygen to increase the hydrogen peroxide production. At neutral pH, POM may act by forming soluble iron-complexes and preventing the build-up of an iron oxide layer on the ZVI surface.

Keenan, C. R.; Lee, C.; Sedlak, D. L.

2007-12-01

242

Formulation, stability and pharmacokinetics of sugar-based salmon calcitonin-loaded nanoporous/nanoparticulate microparticles (NPMPs) for inhalation.  

PubMed

A challenge exists to produce dry powder inhaler (DPI) formulations with appropriate formulation stability, biological activity and suitable physicochemical and aerosolisation characteristics that provide a viable alternative to parenteral formulations. The present study aimed to produce sugar-based nanoporous/nanoparticulate microparticles (NPMPs) loaded with a therapeutic peptide - salmon calcitonin (sCT). The physicochemical properties of the powders and their suitability for pulmonary delivery of sCT were determined. Production of powders composed of sCT loaded into raffinose or trehalose with or without hydroxypropyl-?-cyclodextrin was carried out using a laboratory scale spray dryer. Spray dried microparticles were spherical, porous and of small geometric size (?2?m). Aerodynamic assessment showed that the fine particle fraction (FPF) less than 5?m ranged from 45 to 86%, depending on the formulation. The mass median aerodynamic diameter (MMAD) varied between 1.9 and 4.7?m. Compared to unprocessed sCT, sCT:raffinose composite systems presented a bioactivity of approximately 100% and sCT:trehalose composite systems between 70-90% after spray drying. Storage stability studies demonstrated composite systems with raffinose to be more stable than those containing trehalose. These sugar-based salmon calcitonin-loaded NPMPs retain reasonable sCT bioactivity and have micromeritic and physicochemical properties which indicate their suitability for pulmonary delivery. Formulations presented a similar pharmacokinetic profile to sCT solution. Hence the advantage of a dry powder formulation is its non-invasive delivery route and ease of administration of the sCT. PMID:25660067

Amaro, Maria Inês; Tewes, Frederic; Gobbo, Oliviero; Tajber, Lidia; Corrigan, Owen I; Ehrhardt, Carsten; Healy, Anne Marie

2015-04-10

243

Exchange bias beyond the superparamagnetic blocking temperature of the antiferromagnet in a Ni-NiO nanoparticulate system  

SciTech Connect

We report magnetic and exchange bias studies on Ni-NiO nanoparticulate systems synthesized by a two-step process, namely, chemical reduction of a Ni salt followed by air annealing of the dried precipitate in the temperature range 400–550?°C. Size of Ni and NiO crystallites as estimated from X–ray diffraction line broadening ranges between 10.5–13.5?nm and 2.3–4?nm, respectively. The magneto-thermal plots (M-T) of these bi-magnetic samples show a well developed peak in the vicinity of 130?K. This has been identified as the superparamagnetic blocking temperature “T{sub B}” of NiO. Interestingly, all samples exhibit exchange bias even above their respective NiO blocking temperatures, right up to 300?K, the maximum temperature of measurement. This is in contrast to previous reports since exchange bias requires the antiferromagnetic NiO to have a stable direction of its moment in order to pin the ferromagnet (Ni) magnetization, whereas such stability is unlikely above T{sub B} since the NiO is superparamagnetic, its moment flipping under thermal activation. Our observation is elucidated by taking into account the core-shell morphology of the Ni-NiO nanoparticles whereby clustering of some of these nanoparticles connects their NiO shells to form extended continuous regions of NiO, which because of their large size remain blocked at T?>?T{sub B}, with thermally stable spins capable of pinning the Ni cores and giving rise to exchange bias. The investigated samples may thus be envisaged as being constituted of both isolated core-shell Ni-NiO nanoparticles as well as clustered ones, with T{sub B} denoting the blocking temperature of the NiO shell of the isolated particles.

Roy, Aparna, E-mail: aparna.roy@ua.pt, E-mail: aparnaroy15@gmail.com; Ferreira, J. M. F. [Department of Materials and Ceramics Engineering and CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); De Toro, J. A.; Muniz, P.; Riveiro, J. M. [Departamento de Fisica Aplicada, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain); Amaral, V. S. [Department of Physics and CICECO, University of Aveiro, 3810-193 Aveiro (Portugal)

2014-02-21

244

High pinning performance of YBa2Cu3O7?x films added with Y2O3 nanoparticulate defects  

NASA Astrophysics Data System (ADS)

We report the epitaxial growth and superconducting properties of Y2O3-added YBa2Cu3Ox (YBCO) films grown on SrTiO3-buffered MgO substrates by pulsed-laser deposition using surface-modified YBCO targets. Areas of Y2O3 sectors on the YBCO target were increased to 5.44% and 9.22% of the total YBCO pellet in order to find a correlation between the Y2O3 content, morphology, and the pinning properties of YBCO + Y2O3 mixed films. The maximum global pinning forces, FP, at 77 K were 14.3 GN m?3 and 1.15 GN m?3 for the Y2O3 5.44A% and 9.22A%, respectively. The 5.44A% Y2O3-added sample presents a very high value of pinning force at 77 K, approaching the value obtained in YBCO films with added BaZrO3 nanorods, but with less depression in the superconducting critical temperature, Tc. In accordance with scanning transmission electron microscopy (STEM) observations, both films present nanoparticulate Y2O3 dispersed in a YBCO matrix where Y2Ba4Cu8O16 (Y248) intergrowths were also observed. Consistent with the strong pinning theory, the size and distribution of randomly dispersed Y2O3 particles are optimal for the flux pinning of a 5.44A% Y2O3-YBCO film, while in the case of a 9.22A% film, the YBCO matrix is degraded by jam-packed Y248 intergrowth, which leads to a comparatively poor pinning performance. We further used the single-vortex dynamics model to account for vortex pinning in the samples. The 5.44A% Y2O3-YBCO film result shows good agreement with the model fit up to 4 T of the applied magnetic field.

Mele, Paolo; Guzman, Roger; Gazquez, Jaume; Puig, Teresa; Obradors, Xavier; Saini, Shrikant; Yoshida, Yutaka; Mukaida, Masashi; Ichinose, Ataru; Matsumoto, Kaname; Idries Adam, Malik

2015-02-01

245

Nanoparticulate TiO2 Protection of Midgut Damage in the Silkworm (Bombyx mori) Following Phoxim Exposure.  

PubMed

Bombyx mori (B. mori) is often subjected to phoxim poisoning in China due to phoxim exposure, which leads to a decrease in silk production. Nanoparticulate (NP) titanium dioxide (nano-TiO2) has been shown to attenuate damages in B. mori caused by phoxim exposure. However, little is known about the molecular mechanisms of midgut injury due to organophosphorus insecticide exposure and its repair by nano-TiO2 pretreatment. In this study, phoxim exposure for 36 h led to significant decreases in body weight and survival and increased oxidative stress and midgut injury. Pretreatment with nano-TiO2 attenuated the phoxim-induced midgut injury, increased body weight and survival, and decreased oxidative stress in the midgut of B. mori. Digital gene-expression data showed that exposure to phoxim results in significant changes in the expression of 254 genes in the phoxim-exposed midgut and 303 genes in phoxim + nano-TiO2-exposed midgut. Specifically, phoxim exposure led to upregulation of Tpx, ?-amylase, trypsin, and glycoside hydrolase genes involved in digestion and absorption. Phoxim exposure also led to the downregulation of Cyp450 and Cyp4C1 genes involved in an antioxidant capacity. In contrast, a combination of both phoxim and nano-TiO2 treatment significantly decreased the change in ?-amylase, trypsin, and glycoside hydrolases (GHs), which are involved in digestion and absorption. These results indicated that Tpx, ?-amylase, trypsin, GHs, Cyp450, and Cyp4C1 may be potential biomarkers of midgut toxicity caused by phoxim exposure and the attenuation of these toxic impacts by nano-TiO2. PMID:25552327

Wang, Ling; Su, Mingyu; Zhao, Xiaoyang; Hong, Jie; Yu, Xiaohong; Xu, Bingqing; Sheng, Lei; Liu, Dong; Shen, Weide; Li, Bing; Hong, Fashui

2015-04-01

246

Chemodynamics of soft nanoparticulate complexes: Cu(II) and Ni(II) complexes with fulvic acids and aquatic humic acids.  

PubMed

The dynamics of metal complexation by small humic substances (fulvic acid and aquatic humic acid, collectively denoted as “fulvic-like substance”, FS) are explored within the framework of concepts recently developed for soft nanoparticulate complexants. From a comprehensive collection of published equilibrium and dissociation rate constants for CuFS and NiFS complexes, the association rate constant, ka, is determined as a function of the degree of complexing site occupation, ?. From this large data set, it is shown for the first time that ka is independent of ?. This result has important consequences for finding the nature of the rate limiting step in the association process. The influence of electric effects on the rate of the association process is described, namely (i) the accelerating effect of the negatively charged electrostatic field of FS on the diffusion of metal ions toward it, and (ii) the extent to which metal ions electrostatically accumulate in the counterionic atmosphere of FS. These processes are discussed qualitatively in relation to the derived values of ka. For slowly dehydrating metal ions such as Ni(H2O)6 2+ (dehydration rate constant, kw), ka is expected to derive straight from kw. In contrast, for rapidly dehydrating metal ions such as Cu(H2O)6 2+, transport limitations and electric effects involved in the formation of the precursor outer-sphere associate appear to be important overall rate-limiting factors. This is of great significance for understanding the chemodynamics of humic complexes in the sense that inner-sphere complex formation would not always be the (sole) rate limiting step. PMID:22934531

Town, Raewyn M; van Leeuwen, Herman P; Buffle, Jacques

2012-10-01

247

FIV vector systems.  

PubMed

Why is feline immunodeficiency virus (FIV) such an appealing candidate for gene therapy vector development? Phylogenetic analysis suggests FIV is only distantly related to the primate lentiviruses, and despite repeated exposure, neither seroconversion nor other detectable evidence of human infection occurs. FIV naturally infects diverse Felidae worldwide, including the domestic cat. Here, the disease progression parallels the immunodeficiency caused by HIV, and for that reason, FIV and the cat provide an excellent model for anti-virals and AIDS vaccine research. Simple genome organization also facilitates vector development and analysis: FIV has only three accessory/regulatory proteins. To overcome FIV's cat-specific tropism, feline vectors are equipped with hybrid LTRs, since the FIV LTR shows low activity in human cells. Recombinant FIV vectors generate titers comparable to other lentiviral systems, are capable of incorporating heterologous envelopes and efficiently transduce dividing and nondividing cells in the presence and absence of the accessory proteins in vitro. Compared to HIV vectors, FIV vector development is still in its infancy, but initial in vivo data in various species and tissues indicate long-term gene expression at therapeutic levels, and thus FIV vectors hold great promise. Future efficacy studies in animal models and primates will determine the FIV vectors' suitability for gene therapy. The design of recombinant FIV vectors incorporates safety features described for primate lentiviral vectors with the benefit that biosafety testing of FIV vectors can occur in the natural host. Currently, FIV vectors are generated in a transient fashion, but the availability of a stable producer system amenable to better characterization and scale-up will considerably increase the potential for use of FIV vectors in the clinic. PMID:12465464

Sauter, S L; Gasmi, M

2001-11-01

248

Oxidation-responsive polymeric vesicles  

NASA Astrophysics Data System (ADS)

Vesicles formed in water by synthetic macro-amphiphiles have attracted much attention as nanocontainers having properties that extend the physical and chemical limits of liposomes. We sought to develop ABA block copolymeric amphiphiles that self-assemble into unilamellar vesicles that can be further oxidatively destabilized. We selected poly(ethylene glycol) (PEG) as the hydrophilic A blocks, owing to its resistance to protein adsorption and low toxicity. As hydrophobic B blocks, we selected poly(propylene sulphide) (PPS), owing to its extreme hydrophobicity, its low glass-transition temperature, and most importantly its oxidative conversion from a hydrophobe to a hydrophile, poly(propylene sulphoxide) and ultimately poly(propylene sulphone). This is the first example of the use of oxidative conversions to destabilize such carriers. This new class of oxidation-responsive polymeric vesicles may find applications as nanocontainers in drug delivery, biosensing and biodetection.

Napoli, Alessandro; Valentini, Massimiliano; Tirelli, Nicola; Müller, Martin; Hubbell, Jeffrey A.

2004-03-01

249

Oxidation-responsive polymeric vesicles.  

PubMed

Vesicles formed in water by synthetic macro-amphiphiles have attracted much attention as nanocontainers having properties that extend the physical and chemical limits of liposomes. We sought to develop ABA block copolymeric amphiphiles that self-assemble into unilamellar vesicles that can be further oxidatively destabilized. We selected poly(ethylene glycol) (PEG) as the hydrophilic A blocks, owing to its resistance to protein adsorption and low toxicity. As hydrophobic B blocks, we selected poly(propylene sulphide) (PPS), owing to its extreme hydrophobicity, its low glass-transition temperature, and most importantly its oxidative conversion from a hydrophobe to a hydrophile, poly(propylene sulphoxide) and ultimately poly(propylene sulphone). This is the first example of the use of oxidative conversions to destabilize such carriers. This new class of oxidation-responsive polymeric vesicles may find applications as nanocontainers in drug delivery, biosensing and biodetection. PMID:14991021

Napoli, Alessandro; Valentini, Massimiliano; Tirelli, Nicola; Müller, Martin; Hubbell, Jeffrey A

2004-03-01

250

Molecular and polymeric ceramic precursors  

SciTech Connect

The development of new methods for the production of complex materials is one of the most important problems in modern solid state chemistry and materials science. This project is attempting to apply the synthetic principles which have evolved in inorganic and organometallic chemistry to the production of technologically important non-oxide ceramics, such as boron nitride, boron carbide and metal borides. Recent work has now resulted in the production of new polymer systems, including poly(B-vinylborazine), polyvinylpentaborane and polyborazylene, that have proven to be high yield precursors to boron-based ceramic materials. Current work is now directed toward the synthesis of new types of molecular and polymeric boron-containing species and an exploration of the solid state properties of the ceramics that have been produced in these studies.

Sneddon, L.G.

1992-06-01

251

Molecular and polymeric ceramic precursors  

SciTech Connect

The development of new methods for the production of complex materials is one of the most important problems in modern solid state chemistry and materials science. This project is attempting to apply the synthetic principles which have evolved inorganic and organometallic chemistry to the production of technologically important non-oxide ceramics, such as boron nitride, boron carbide and metal borides. Our recent work has now resulted in the production of new polymer systems, including poly(B-vinylborazine), polyvinylpentaborane and polyborazylene, that have proven to be high yield precursors to boron-based ceramic materials. Current work is now directed toward the synthesis of new types of molecular and polymeric boron-containing species and on exploration of the solid state properties of the ceramics that have been produced in these studies.

Sneddon, L.G.

1991-08-01

252

Hemocompatibility of Polymeric Nanostructured Surfaces  

PubMed Central

Tissue integration is an important property when inducing transplant tolerance, however, the hemocompatibility of the biomaterial surface also plays an important role in the ultimate success of the implant. Therefore, in order to induce transplant tolerance, it is critical to understand the interaction of blood components with the material surfaces. In this study, we have investigated the adsorption of key blood serum proteins, in vitro adhesion and activation of platelets and clotting kinetics of whole blood on flat polycaprolactone (PCL) surfaces, nanowire (NW) surfaces and nanofiber (NF) surfaces. Previous studies have shown that polymeric nanostructured surfaces improve cell adhesion, proliferation and viability; however it is unclear how these polymeric nanostructured surfaces interact with the blood and its components. Protein adsorption results indicate that while there were no significant differences in total albumin adsorption on PCL, NW and NF surfaces, NW surfaces had higher total fibrinogen and immunoglobulin-G adsorption compared to NF and PCL surfaces. In contrast, NF surfaces had higher surface FIB and IgG adsorption compared to PCL and NW surfaces. Platelet adhesion and viability studies show more adhesion and clustering of platelets on the NF surfaces as compared to PCL and NW surfaces. Platelet activation studies reveal that NW surfaces have the highest percentage of unactivated platelets, whereas NF surfaces have the highest percentage of fully activated platelets. Whole blood clotting results indicate that NW surfaces maintain an increased amount of free hemoglobin during the clotting process compared to PCL and NF surface, indicating less clotting and slower rate of clotting on their surfaces. PMID:23848447

Leszczak, Victoria; Smith, Barbara S.; Popat, Ketul C.

2013-01-01

253

Branchless vectorized median filtering  

Microsoft Academic Search

Median filtering is an important tool in signal or image processing. Based on the vector capabilities of modern hardware, which allows for vectorized min, max and mask operations, we provide a median algorithm of complexity O(NM) that is both branchless and vectorized. In contrast to conventional fast median filters, whose run-time is data-dependent and that can operate only on scalar

M. Kachelriess

2009-01-01

254

ESR studies of semicontinuous emulsion polymerization  

SciTech Connect

Electron spin resonance (ESR) is used in the detection and quantification of propagating radicals during a semicontinuous emulsion polymerization. The propagating radical concentration is crucial for the determination of kinetic parameters of the emulsion polymerization process. A flow reactor was built which involves a closed-loop flow system that circulates latex from the polymerization reactor through the ESR cavity for free-radical measurements and back to the reactor. With the continuous measurement of the radical concentrations during a polymerization of methyl methacrylate (MMA), {bar n} (average number of radicals per particle) and k{sub p} (propagating rate constant), are measured throughout the entire polymerization. For the polymerization of the MMA system studied, the authors observed a gradual increased in n and decrease in k{sub p} during the run, suggesting a diffusionally controlled process and that the polymerization is not occurring homogeneously throughout the polymer particles. In the glassy pMMA matrix, radicals can be {open_quotes}trapped{close_quotes} within a minimum volume and remain unterminated.

Lau, W.; Westmoreland, D.G. [Rohm and Haas Co., Spring House, PA (United States)

1993-12-31

255

Vectorized Monte Carlo  

SciTech Connect

Examination of the global algorithms and local kernels of conventional general-purpose Monte Carlo codes shows that multigroup Monte Carlo methods have sufficient structure to permit efficient vectorization. A structured multigroup Monte Carlo algorithm for vector computers is developed in which many particle events are treated at once on a cell-by-cell basis. Vectorization of kernels for tracking and variance reduction is described, and a new method for discrete sampling is developed to facilitate the vectorization of collision analysis. To demonstrate the potential of the new method, a vectorized Monte Carlo code for multigroup radiation transport analysis was developed. This code incorporates many features of conventional general-purpose production codes, including general geometry, splitting and Russian roulette, survival biasing, variance estimation via batching, a number of cutoffs, and generalized tallies of collision, tracklength, and surface crossing estimators with response functions. Predictions of vectorized performance characteristics for the CYBER-205 were made using emulated coding and a dynamic model of vector instruction timing. Computation rates were examined for a variety of test problems to determine sensitivities to batch size and vector lengths. Significant speedups are predicted for even a few hundred particles per batch, and asymptotic speedups by about 40 over equivalent Amdahl 470V/8 scalar codes arepredicted for a few thousand particles per batch. The principal conclusion is that vectorization of a general-purpose multigroup Monte Carlo code is well worth the significant effort required for stylized coding and major algorithmic changes.

Brown, F.B.

1981-01-01

256

Photosensitization of nanoparticulate TiO2 using a Re(I)-polypyridyl complex: studies on interfacial electron transfer in the ultrafast time domain.  

PubMed

We have synthesized a new photoactive rhenium(i)-complex having a pendant catechol functionality [Re(CO)(3)Cl(L)] (1) (L is 4-[2-(4'-methyl-2,2'-bipyridinyl-4-yl)vinyl]benzene-1,2-diol) for studying the dynamics of the interfacial electron transfer between nanoparticulate TiO(2) and the photoexcited states of this Re(i)-complex using femtosecond transient absorption spectroscopy. Our steady state absorption studies revealed that complex 1 can bind strongly to TiO(2) surfaces through the catechol functionality with the formation of a charge transfer (CT) complex, which has been confirmed by the appearance of a new red-shifted CT band. The longer wavelength absorption band for 1, bound to TiO(2) through the proposed catecholate functionality, could also be explained based on the DFT calculations. Dynamics of the interfacial electron transfer between 1 and TiO(2) nanoparticles was investigated by studying kinetics at various wavelengths in the visible and near infrared regions. Electron injection into the conduction band of the nanoparticulate TiO(2) was confirmed by detection of the conduction band electron in TiO(2) ([e(-)](TiO(2)(CB))) and the cation radical of the adsorbed dye (1?(+)) in real time as monitored by transient absorption spectroscopy. A single exponential and pulse-width limited (<100 fs) electron injection was observed. Back electron transfer dynamics was determined by monitoring the decay kinetics of 1?(+) and . PMID:22549294

Kar, Prasenjit; Banerjee, Tanmay; Verma, Sandeep; Sen, Anik; Das, Amitava; Ganguly, Bishwajit; Ghosh, Hirendra N

2012-06-14

257

Method for forming polymerized microfluidic devices  

DOEpatents

Methods for making a micofluidic device according to embodiments of the present invention include defining a cavity. Polymer precursor solution is positioned in the cavity, and exposed to light to begin the polymerization process and define a microchannel. In some embodiments, after the polymerization process is partially complete, a solvent rinse is performed, or fresh polymer precursor introduced into the microchannel. This may promote removal of unpolymerized material from the microchannel and enable smaller feature sizes. The polymer precursor solution may contain an iniferter. Polymerized features therefore may be capped with the iniferter, which is photoactive. The iniferter may aid later binding of a polyacrylamide gel to the microchannel surface.

Sommer, Gregory J. (Livermore, CA); Hatch, Anson V. (Tracy, CA); Wang, Ying-Chih (Pleasanton, CA); Singh, Anup K. (Danville, CA); Renzi, Ronald F. (Tracy, CA); Claudnic, Mark R. (Livermore, CA)

2011-11-01

258

Hyperbranched polysiloxysilane nanoparticles for nonviral gene delivery vectors and nanoprobes  

NASA Astrophysics Data System (ADS)

We report an approach to produce predefined surface charge tunable gene delivery vectors using siloxysilsane-based polymer for gene delivery studies. To obtain nonviral vectors, new series of hyperbranched polysiloxysilane (HBPS) were synthesized, and the end groups in polymer structures have modified with hydrophilic molecules; in other words, carboxylic acid and quaternary ammonium groups were employed into terminal structures to give the amphiphilicity. The novelty of these amphiphilic HBPS polymers lies in the fact that nanoparticles with different zeta potential (surface charge density) can be easily tailored and functionalized. These polymeric nanoparticles which containing various chemical groups on the surface indicated altered surface charge distributions (from -40 to +64mV). Finally, the use of these nanoparticles as efficient gene delivery vectors was demonstrated by means of in vitro transfection study using ?- galactosidase plasmid and pEGFP-N1 plasmid, and the most efficient combination was obtained using HBPS-CN30:70.

Kim, Won Jin; Bonoiu, Adela C.; Lee, Kwang-Sup; Hayakawa, Teruaki; Xia, Cheng; Kakimoto, Masa-aki; Pudavar, Haridas E.; Prasad, Paras N.

2009-08-01

259

Fabrication and manipulation of polymeric magnetic particles with magnetorheological fluid  

E-print Network

Fabrication and manipulation of polymeric magnetic particles with magnetorheological fluid Jaime: Magnetorheological fluid Microfluidic Polymeric particle a b s t r a c t Polymeric magnetic microparticles have been in cores of magnetorheological (MR) fluids surrounded by polymeric shells. We demonstrate

260

Design of new pigment dispersants by controlled radical polymerization  

Microsoft Academic Search

Polymeric pigment dispersants are essential for the formulation of high solids and waterborne coatings. New technologies for controlled polymerization play an important role for the development of improved pigment dispersants. In the last years, big progress has been made especially on nitroxide-mediated controlled free radical polymerization, as well as on atom transfer radical polymerization (ATRP). Both techniques overcome limitations of

Clemens Auschra; Ernst Eckstein; Andreas Mühlebach; Marie-Odile Zink; François Rime

2002-01-01

261

Polymerization in emulsion microdroplet reactors  

NASA Astrophysics Data System (ADS)

The goal of this research project is to utilize emulsion droplets as chemical reactors for execution of complex polymerization chemistries to develop unique and functional particle materials. Emulsions are dispersions of immiscible fluids where one fluid usually exists in the form of drops. Not surprisingly, if a liquid-to-solid chemical reaction proceeds to completion within these drops, the resultant solid particles will possess the shape and relative size distribution of the drops. The two immiscible liquid phases required for emulsion polymerization provide unique and complex chemical and physical environments suitable for the engineering of novel materials. The development of novel non-ionic fluorosurfactants allows fluorocarbon oils to be used as the continuous phase in a water-free emulsion. Such emulsions enable the encapsulation of almost any hydrocarbon compound in droplets that may be used as separate compartments for water-sensitive syntheses. Here, we exemplify the promise of this approach by suspension polymerization of polyurethanes (PU), in which the liquid precursor is emulsified into droplets that are then converted 1:1 into polymer particles. The stability of the droplets against coalescence upon removal of the continuous phase by evaporation confirms the formation of solid PU particles. These results prove that the water-free environment of fluorocarbon based emulsions enables high conversion. We produce monodisperse, cross-linked, and fluorescently labeled PU-latexes with controllable mesh size through microfluidic emulsification in a simple one-step process. A novel method for the fabrication of monodisperse mesoporous silica particles is presented. It is based on the formation of well-defined equally sized emulsion droplets using a microfluidic approach. The droplets contain the silica precursor/surfactant solution and are suspended in hexadecane as the continuous oil phase. The solvent is then expelled from the droplets, leading to concentration and micellization of the surfactant. At the same time, the silica solidifies around the surfactant structures, forming equally sized mesoporous particles. The procedure can be tuned to produce well-separated particles or alternatively particles that are linked together. The latter allows us to create 2D or 3D structures with hierarchical porosity. Oil, water, and surfactant liquid mixtures exhibit very complex phase behavior. Depending on the conditions, such mixtures give rise to highly organized structures. A proper selection of the type and concentration of surfactants determines the structuring at the nanoscale level. In this work, we show that hierarchically bimodal nanoporous structures can be obtained by templating silica microparticles with a specially designed surfactant micelle/microemulsion mixture. Tuning the phase state by adjusting the surfactant composition and concentration allows for the controlled design of a system where microemulsion droplets coexist with smaller surfactant micellar structures. The microemulsion droplet and micellar dimensions determine the two types of pore sizes (single nanometers and tens of nanometers). We also demonstrate the fabrication of carbon and carbon/platinum replicas of the silica microspheres using a "lost-wax" approach. Such particles have great potential for the design of electrocatalysts for fuel cells, chromatography separations, and other applications. It was determined that slight variations in microemulsion mixture components (electrolyte concentration, wt% of surfactants, oil to sol ratio, etc.) produces strikingly different pore morphologies and particle surface areas. Control over the size and structure of the smaller micelle-templated pores was made possible by varying the length of the hydrocarbon block within the trimethyl ammonium bromide surfactant and characterized using X-ray diffraction. The effect of emulsion aging was studied by synthesizing particles at progressive time levels from a sample emulsion. It was discovered surface pore size increases after just a few hours, with

Carroll, Nick J.

262

Support Vector Data Description  

Microsoft Academic Search

Data domain description concerns the characterization of a data set. A good description covers all target data but includes no superfluous space. The boundary of a dataset can be used to detect novel data or outliers. We will present the Support Vector Data Description (SVDD) which is inspired by the Support Vector Classifier. It obtains a spherically shaped boundary around

David M. J. Tax; Robert P. W. Duin

2004-01-01

263

Exploring acceleration through vectors  

NSDL National Science Digital Library

This in class worksheet is designed to get students to think about and manipulate different accelerations in their head. Students work together with written descriptions of velocity and acceleration and draw the vectors in part one, and then turn that around in part two where they write descriptions of a car's motion based on the vector pictures they are given.

264

Hydrocarbon polymeric binder for advanced solid propellant  

NASA Technical Reports Server (NTRS)

A series of DEAB initiated isoprene polymerizations were run in the 5-gallon stirred autoclave reactor. Polymerization run parameters such as initiator concentration and feed rate were correlated with the molecular weight to provide a basis for molecular weight control in future runs. Synthetic methods were developed for the preparation of n-1,3-alkadienes. By these methods, 1,3-nonadiene was polymerized using DEAB initiator to give an ester-telechelic polynonadiene. This was subsequently hydrogenated with copper chromite catalyst to give a hydroxyl terminated saturated liquid hydrocarbon prepolymer having greatly improved viscosity characteristics and a Tg 18 degrees lower than that of the hydrogenated polyisoprenes. The hydroxyl-telechelic saturated polymers prepared by the hydrogenolysis of ester-telechelic polyisoprene were reached with diisocyanates under conditions favoring linear chain extension gel permeation chromatography was used to monitor this condensation polymerization. Fractions having molecular weights above one million were produced.

Potts, J. E. (editor)

1972-01-01

265

Hydrogel polymerization in microgravity for contact lenses  

NASA Astrophysics Data System (ADS)

Contact lenses become widely used for vision correction. The modern contact lenses made of polymer materials have to satisfy a number of requirements: biocompatibility and non-toxicity, low elastic module, high oxygen permeability, good wettability, mechanical strength and stable shape. To following all these requirements, special polymer compositions and polymerization techniques are in development. One of the unique technology is based on polymerization process in microgravity. The synthesis of the polymer structures proceeds in low concentration solution and Earth gravity has a great influence on the polymerization kinetics and final properties of the gel. The microgravity conditions give a possibility to get a regular polymer network with specific macromolecular structure. The experiments on board of space station and theoretical models of the polymerization processes are considered for contact lenses application.

Shcherbakova, Oksana; Kostarev, Konstantin; Kondyurin, Alexey

266

PERMEABILITY OF POLYMERIC MEMBRANE LINING MATERIALS  

EPA Science Inventory

Permeabilities to three gases (carbon dioxide, methane, and nitrogen), water vapor, and five solvents (methanol, acetone, cyclohexane, xylene, and chloroform) are reported for a broad range of commercial polymeric membranes. Gas and water vapor transmission (WVT) data were determ...

267

Physicochemically functional ultrathin films by interfacial polymerization  

DOEpatents

Interfacially-polymerized ultrathin films containing physicochemically functional groups are disclosed, both with and without supports. Various applications are disclsoed, including membrane electrodes, selective membranes and sorbents, biocompatible materials, targeted drug delivery, and narrow band optical absorbers.

Lonsdale, Harold K. (Bend, OR); Babcock, Walter C. (Bend, OR); Friensen, Dwayne T. (Bend, OR); Smith, Kelly L. (Bend, OR); Johnson, Bruce M. (Bend, OR); Wamser, Carl C. (West Linn, OR)

1990-01-01

268

Reverse-osmosis membranes by plasma polymerization  

NASA Technical Reports Server (NTRS)

Thin allyl amine polymer films were developed using plasma polymerization. Resulting dry composite membranes effectively reject sodium chloride during reverse osmosis. Films are 98% sodium chloride rejective, and 46% urea rejective.

Hollahan, J. R.; Wydeven, T.

1972-01-01

269

Design strategies for fluorescent biodegradable polymeric biomaterials  

E-print Network

Design strategies for fluorescent biodegradable polymeric biomaterials Yi Zhangab and Jian Yang biomaterials: biodegradable fluorescent polymers. Researchers have made significant efforts in developing versatile fluorescent biomaterials due to their promising applications in biological/biomedical labeling

Yang, Jian

270

Aging of polymeric composites : a literature review  

E-print Network

Due to their increased use in today's society, an extensive survey was undertaken in this report to condense what's been, thus far, discovered as to the effects of aging on polymeric composites. Special emphasis was placed ...

Treviño-Garrido, Margie N

2013-01-01

271

Physicochemically functional ultrathin films by interfacial polymerization  

DOEpatents

Interfacially-polymerized ultrathin films containing physicochemically functional groups are disclosed, both with and without supports. Various applications are disclosed, including membrane electrodes, selective membranes and sorbents, biocompatible materials, targeted drug delivery, and narrow band optical absorbers. 3 figs.

Lonsdale, H.K.; Babcock, W.C.; Friensen, D.T.; Smith, K.L.; Johnson, B.M.; Wamser, C.C.

1990-08-14

272

Polymerization as a Model Chain Reaction  

ERIC Educational Resources Information Center

Describes the features of the free radical, anionic, and cationic mechanisms of chain addition polymerization. Indicates that the nature of chain reactions can be best taught through the study of macromolecules. (CC)

Morton, Maurice

1973-01-01

273

Thermo-optically active polymeric photonic components  

Microsoft Academic Search

We report on a variety of thermo-optically active polymeric components including tunable Bragg grating filters, tunable arrayed waveguide gratings, digital optical switches with low power consumption and high isolation, and variable optical attenuators with wide dynamic range

Louay Eldada; Robert Norwood; Robert Blomquist; Lawrence W. Shacklette; Michael J. McFarland

2000-01-01

274

Vector generator scan converter  

DOEpatents

High printing speeds for graphics data are achieved with a laser printer by transmitting compressed graphics data from a main processor over an I/O channel to a vector generator scan converter which reconstructs a full graphics image for input to the laser printer through a raster data input port. The vector generator scan converter includes a microprocessor with associated microcode memory containing a microcode instruction set, a working memory for storing compressed data, vector generator hardware for drawing a full graphic image from vector parameters calculated by the microprocessor, image buffer memory for storing the reconstructed graphics image and an output scanner for reading the graphics image data and inputting the data to the printer. The vector generator scan converter eliminates the bottleneck created by the I/O channel for transmitting graphics data from the main processor to the laser printer, and increases printer speed up to thirty fold. 7 figs.

Moore, J.M.; Leighton, J.F.

1988-02-05

275

Acoustic vector solitons.  

PubMed

A theory of an acoustic vector soliton of self-induced transparency is constructed. By using the perturbative reduction method the magnetic Bloch equations and the equation of motion for the displacement field for the small area pulse are reduced to a system of two coupled nonlinear Schrödinger equations. The shape of an acoustic vector soliton with the sum and difference of the frequencies is presented. Explicit analytical expressions for the parameters of an acoustic vector soliton are obtained as well as simulations of an acoustic vector soliton presented with realistic parameters which can be reached in experiments. It is shown that the vector soliton in the special case can be reduced to the breather solution, and these nonlinear waves have different profiles. PMID:23005248

Adamashvili, G T

2012-06-01

276

Vector theories in cosmology  

SciTech Connect

This article provides a general study of the Hamiltonian stability and the hyperbolicity of vector field models involving both a general function of the Faraday tensor and its dual, f(F{sup 2},FF-tilde), as well as a Proca potential for the vector field, V(A{sup 2}). In particular it is demonstrated that theories involving only f(F{sup 2}) do not satisfy the hyperbolicity conditions. It is then shown that in this class of models, the cosmological dynamics always dilutes the vector field. In the case of a nonminimal coupling to gravity, it is established that theories involving Rf(A{sup 2}) or Rf(F{sup 2}) are generically pathologic. To finish, we exhibit a model where the vector field is not diluted during the cosmological evolution, because of a nonminimal vector field-curvature coupling which maintains second-order field equations. The relevance of such models for cosmology is discussed.

Esposito-Farese, Gilles; Pitrou, Cyril; Uzan, Jean-Philippe [GRECO, Institut d'Astrophysique de Paris, UMR 7095-CNRS, Universite Pierre et Marie Curie-Paris 6, 98bis boulevard Arago, F-75014 Paris (France); Institute of Cosmology and Gravitation, Dennis Sciama Building, Burnaby Road, Portsmouth, PO1 3FX (United Kingdom); GRECO, Institut d'Astrophysique de Paris, UMR 7095-CNRS, Universite Pierre et Marie Curie-Paris 6, 98bis boulevard Arago, F-75014 Paris (France) and Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, Cape Town (South Africa)

2010-03-15

277

Vector generator scan converter  

DOEpatents

High printing speeds for graphics data are achieved with a laser printer by transmitting compressed graphics data from a main processor over an I/O (input/output) channel to a vector generator scan converter which reconstructs a full graphics image for input to the laser printer through a raster data input port. The vector generator scan converter includes a microprocessor with associated microcode memory containing a microcode instruction set, a working memory for storing compressed data, vector generator hardward for drawing a full graphic image from vector parameters calculated by the microprocessor, image buffer memory for storing the reconstructed graphics image and an output scanner for reading the graphics image data and inputting the data to the printer. The vector generator scan converter eliminates the bottleneck created by the I/O channel for transmitting graphics data from the main processor to the laser printer, and increases printer speed up to thirty fold.

Moore, James M. (Livermore, CA); Leighton, James F. (Livermore, CA)

1990-01-01

278

Intracellular trafficking of nonviral vectors  

Microsoft Academic Search

Nonviral vectors continue to be attractive alternatives to viruses due to their low toxicity and immunogenicity, lack of pathogenicity, and ease of pharmacologic production. However, nonviral vectors also continue to suffer from relatively low levels of gene transfer compared to viruses, thus the drive to improve these vectors continues. Many studies on vector–cell interactions have reported that nonviral vectors bind

L K Medina-Kauwe; J Xie; S Hamm-Alvarez

2005-01-01

279

Radiation sterilization of polymeric implant materials  

Microsoft Academic Search

High-energy irradiation sterilization of medical devices and implants composed of polymeric biomaterials that are in contact with tissue and\\/or blood, may adversely affect their long-term mechanical and\\/or biological performance (tissue and\\/or blood compatibility). Since many polymeric implants may contain trace quantities of catalysts and\\/or other additives, the effect of high-energy radiation on these additives, and possible synergistic effects with the

Stephen D. Bruck; Edward P. Mueller

1988-01-01

280

Polymeric micelles: authoritative aspects for drug delivery  

Microsoft Academic Search

The generation of supramolecular architectures with well-defined structures and functionalities is recently garnering attraction. Self-assemblage of amphiphilic polymers leads to the formation of polymeric micelles that demonstrate unique set of characteristics such as excellent biocompatibility, low toxicity, enhanced blood circulation time, and solubilization of poorly water-soluble drugs. In this article, we provide an up-to-date review on important aspects of polymeric

Sushant S. Kulthe; Yogesh M. Choudhari; Nazma N. Inamdar; Vishnukant Mourya

2012-01-01

281

Post polymerization cure shape memory polymers  

DOEpatents

This invention relates to chemical polymer compositions, methods of synthesis, and fabrication methods for devices regarding polymers capable of displaying shape memory behavior (SMPs) and which can first be polymerized to a linear or branched polymeric structure, having thermoplastic properties, subsequently processed into a device through processes typical of polymer melts, solutions, and dispersions and then crossed linked to a shape memory thermoset polymer retaining the processed shape.

Wilson, Thomas S; Hearon, Michael Keith; Bearinger, Jane P

2014-11-11

282

Next-generation polymeric photonic devices  

Microsoft Academic Search

A versatile polymeric waveguide technology is proposed for low-cost high-performance photonic devices that address the needs of both the telecom and the datacom industries. We have developed advanced organic polymeric materials that can be readily made into both multimode and single-mode optical waveguide structures of controlled numerical aperture and geometry. These materials are formed from highly-crosslinked acrylate monomers with specific

Louay A. Eldada; Lawrence W. Shacklette; Robert A. Norwood; James T. Yardley

1997-01-01

283

Biaxially oriented film on flexible polymeric substrate  

DOEpatents

A flexible polymer-based template having a biaxially oriented film grown on the surface of a polymeric substrate. The template having the biaxially oriented film can be used for further epitaxial growth of films of interest for applications such as photovoltaic cells, light emitting diodes, and the like. Methods of forming such a flexible template and providing the polymeric substrate with a biaxially oriented film deposited thereon are also described.

Finkikoglu, Alp T. (Los Alamos, NM); Matias, Vladimir (Santa Fe, NM)

2009-10-13

284

Containerless polymeric microsphere production for biomedical applications  

NASA Technical Reports Server (NTRS)

A containerless method that produces highly uniform microspheres (greater than 50 microns in diameter) from many materials has been developed for biomedical applications. A piezoelectrically vibrated drop generator forms uniform (monodisperse) monomer droplets that are either electrostatistically levitated and polymerized using UV irradiation, or free-radical polymerized. Spheres of 2-hydroxyethyl methacrylate polymer have been produced with diameters of 155 microns + or - 1.57 percent.

Rhim, W. K.; Hyson, M. T.; Chung, S. K.; Colvin, M.; Chang, M.

1987-01-01

285

Polymeric waveguide Fabry Perot resonators  

NASA Astrophysics Data System (ADS)

Optical microcavities are used in variety of applications ranging from sensors to lasers and signal routing in high volume communication networks. Achieving a high quality factor (Q) is necessary for achieving the higher sensitivity in sensing applications and for narrow linewidth light emission in most lasing applications. In this work, we propose a new way for achieving a higher quality factor in thin film, Fabry-Perot polymeric optical resonators. We show that lateral photon confinement in a vertical Fabry-Perot microcavities can be achieved by optical writing of a refractive index profile utilizing our UV-sensitive polymer. This method can improve the quality factor by one or more orders of magnitudes. In order to demonstrate this improvement, the device has been fabricated. The fabricated device consists of two dielectric Bragg reflectors with a layer of 100 ?m thick polymer layer between them. The polymer is a thiol-ene/methacrylate photopolymer whose optical index can be modified utilizing standard photo-lithography processes. The refractive index of this polymer can be modified utilizing standard photo-lithography processes. The measured finesse of the fabricated device was 692 and the quality factor was 55000. The achieved finesse combined with the flexible polymer layer allows this device to be used as an ultrasound detector in optical micromachined ultrasound transducers (OMUT).

Tadayon, Mohammad Amin; Baylor, Martha-Elizabeth; Ashkenazi, Shai

2014-03-01

286

Polymeric conjugates for drug delivery  

PubMed Central

The field of polymer therapeutics has evolved over the past decade and has resulted in the development of polymer-drug conjugates with a wide variety of architectures and chemical properties. Whereas traditional non-degradable polymeric carriers such as poly(ethylene glycol) (PEG) and N-(2-hydroxypropyl methacrylamide) (HPMA) copolymers have been translated to use in the clinic, functionalized polymer-drug conjugates are increasingly being utilized to obtain biodegradable, stimuli-sensitive, and targeted systems in an attempt to further enhance localized drug delivery and ease of elimination. In addition, the study of conjugates bearing both therapeutic and diagnostic agents has resulted in multifunctional carriers with the potential to both “see and treat” patients. In this paper, the rational design of polymer-drug conjugates will be discussed followed by a review of different classes of conjugates currently under investigation. The design and chemistry used for the synthesis of various conjugates will be presented with additional comments on their potential applications and current developmental status. PMID:22707853

Larson, Nate; Ghandehari, Hamidreza

2012-01-01

287

Quadratic exponential vectors  

SciTech Connect

We give a necessary and sufficient condition for the existence of a quadratic exponential vector with test function in L{sup 2}(R{sup d}) intersection L{sup {infinity}}(R{sup d}). We prove the linear independence and totality, in the quadratic Fock space, of these vectors. Using a technique different from the one used by Accardi et al. [Quantum Probability and Infinite Dimensional Analysis, Vol. 25, p. 262, (2009)], we also extend, to a more general class of test functions, the explicit form of the scalar product between two such vectors.

Accardi, Luigi; Dhahri, Ameur [Volterra Center, University of Roma Tor Vergata, Via Columbia 2, 00133 Roma (Italy)

2009-12-15

288

Occurrence and behaviour of dissolved, nano-particulate and micro-particulate iron in waste waters and treatment systems: new insights from electrochemical analysis.  

PubMed

Cyclic-, Differential Pulse- and Steady-state Microdisc Voltammetry (CV, DPV, SMV) techniques have been used to quantify the occurrence and fate of dissolved Fe(ii)/Fe(iii), nano-particulate and micro-particulate iron over a 12 month period in a series of net-acidic and net-alkaline coal mine drainages and passive treatment systems. Total iron in the mine waters is typically 10-100 mg L(-1), with values up to 2100 mg L(-1). Between 30 and 80% of the total iron occurs as solid phase, of which 20 to 80% is nano-particulate. Nano-particulate iron comprises 20 to 70% of the nominally "dissolved" (i.e. <0.45 ?m) iron. Since coagulation and sedimentation are the only processes required to remove solid phase iron, these data have important implications for the generation or consumption of acidity during water treatment. In most waters, the majority of truly dissolved iron occurs as Fe(ii) (average 64 ± 22%). Activities of Fe(ii) do not correlate with pH and geochemical modelling shows that no Fe(ii) mineral is supersaturated. Removal of Fe(ii) must proceed via oxidation and hydrolysis. Except in waters with pH < 4.4, activities of Fe(iii) are strongly and negatively correlated with pH. Geochemical modelling suggests that the activity of Fe(iii) is controlled by the solubility of hydrous ferric oxides and oxyhydroxysulfates, supported by scanning and transmission electron microscopic analysis of solids. Nevertheless, the waters are generally supersaturated with respect to ferrihydrite and schwertmannite, and are not at redox equilibrium, indicating the key role of oxidation and hydrolysis kinetics on water treatment. Typically 70-100% of iron is retained in the treatment systems. Oxidation, hydrolysis, precipitation, coagulation and sedimentation occur in all treatment systems and - independent of water chemistry and the type of treatment system - hydroxides and oxyhydroxysulfates are the main iron sinks. The electrochemical data thus reveal the rationale for incomplete iron retention in individual systems and can thus inform future design criteria. The successful application of this low cost and rapid electrochemical method demonstrates its significant potential for real-time, on-site monitoring of iron-enriched waters and may in future substitute traditional analytical methods. PMID:22370608

Matthies, R; Aplin, A C; Horrocks, B R; Mudashiru, L K

2012-04-01

289

Promotion of Atom Transfer Radical Polymerization and Ring-Opening Metathesis Polymerization in Ionic Liquids  

Microsoft Academic Search

In the last decade, there has been an increasing interest in using ionic liquids as solvents for chemical reactions and polymerizations. This interest is stimulated not only by their nonvolatility (green solvents) but also by their special properties, which often affect the course of a reaction or polymerization and the properties of products. Recent developments in ionic liquids as solvents

Meiran Xie; Huijing Han; Liang Ding; Jiaxin Shi

2009-01-01

290

Chemical oxidative polymerization of aminodiphenylamines.  

PubMed

The course of oxidation of 4-aminodiphenylamine with ammonium peroxydisulfate in an acidic aqueous ethanol solution as well as the properties of the oxidation products were compared with those of 2-aminodiphenylamine. Semiconducting oligomers of 4-aminodiphenylamine and nonconducting oligomers of 2-aminodiphenylamine of weight-average molecular weights 3700 and 1900, respectively, were prepared by using an oxidant to monomer molar ratio of 1.25. When this ratio was changed from 0.5 to 2.5, the highest conductivity of oxidation products of 4-aminodiphenylamine, 2.5 x 10 (-4) S cm (-1), was reached at the molar ratio [oxidant]/[monomer] = 1.5. The mechanism of the oxidative polymerization of aminodiphenylamines has been theoretically studied by the AM1 and MNDO-PM3 semiempirical quantum chemical methods combined with the MM2 molecular mechanics force-field method and conductor-like screening model of solvation. Molecular orbital calculations revealed the prevalence of N prim-C10 coupling reaction of 4-aminodiphenylamine, while N prim-C5 is the main coupling mode between 2-aminodiphenylamine units. FTIR and Raman spectroscopic studies confirm the prevalent formation of linear N prim-C10 coupled oligomers of 4-aminodiphenylamine and suggest branching and formation of phenazine structural units in the oligomers of 2-aminodiphenylamine. The results are discussed with respect to the oxidation of aniline with ammonium peroxydisulfate, leading to polyaniline, in which 4-aminodiphenylamine is the major dimer and 2-aminodiphenylamine is the most important dimeric intermediate byproduct. PMID:18489148

Ciri?-Marjanovi?, Gordana; Trchová, Miroslava; Konyushenko, Elena N; Holler, Petr; Stejskal, Jaroslav

2008-06-12

291

Targeted adenoviral vectors  

NASA Astrophysics Data System (ADS)

The practical implementation of gene therapy in the clinical setting mandates gene delivery vehicles, or vectors, capable of efficient gene delivery selectively to the target disease cells. The utility of adenoviral vectors for gene therapy is restricted by their dependence on the native adenoviral primary cellular receptor for cell entry. Therefore, a number of strategies have been developed to allow CAR-independent infection of specific cell types, including the use of bispecific conjugates and genetic modifications to the adenoviral capsid proteins, in particular the fibre protein. These targeted adenoviral vectors have demonstrated efficient gene transfer in vitro , correlating with a therapeutic benefit in preclinical animal models. Such vectors are predicted to possess enhanced efficacy in human clinical studies, although anatomical barriers to their use must be circumvented.

Douglas, Joanne T.

292

Light Vector Mesons  

E-print Network

This article reviews the current status of experimental results obtained in the measurement of light vector mesons produced in proton-proton and heavy ion collisions at different energies. The review is focused on two phenomena related to the light vector mesons; the modification of the spectral shape in search of Chiral symmetry restoration and suppression of the meson production in heavy ion collisions. The experimental results show that the spectral shape of light vector mesons are modified compared to the parameters measured in vacuum. The nature and the magnitude of the modification depends on the energy density of the media in which they are produced. The suppression patterns of light vector mesons are different from the measurements of other mesons and baryons. The mechanisms responsible for the suppression of the mesons are not yet understood. Systematic comparison of existing experimental results points to the missing data which may help to resolve the problem.

Alexander Milov

2008-12-21

293

Poynting-vector filter  

DOEpatents

A determination is made of frequency components associated with a particular bearing or location resulting from sources emitting electromagnetic-wave energy for which a Poynting-Vector can be defined. The broadband frequency components associated with a specific direction or location of interest are isolated from other components in the power spectrum that are not associated with the direction or location of interest. The collection of pointing vectors can be used to characterize the source.

Carrigan, Charles R. (Tracy, CA)

2011-08-02

294

Vectorized Finite State Automata  

Microsoft Academic Search

. We present a technique of finite state parsingbased on vectorization and describe the application of thistechnique to a well-known problem of natural language processing,that of extracting relational information from Englishtext. We define Vectorized Finite State Automata, the theoreticalmodel behind the applied system, and discuss theirsignificance.0 IntroductionOne of the persistent problems in building finite automata onthe large scale required by

András Kornai

295

Relative Velocity and Vectors  

NSDL National Science Digital Library

This activity is designed to enhance student comprehension of air and wind velocity, through the use of real time flight data. Students will read about relative velocity, complete a work sheet on vectors, and then gather and analyze real world data. All of the materials, including links to sites for data collection, are provided in this learning object. After completing the activity, students will be able to define relative velocity, add and subtract vectors, and determine aircraft speed using raw data.

Weaver, David

296

Combustion Synthesis of Nanoparticulate LiMgxMn1-xPO4 (x=0, 0.1, 0.2) Carbon Composites  

SciTech Connect

A combustion synthesis technique was used to prepare nanoparticulate LiMgxMn1-xPO4 (x=0, 0.1,0.2)/carbon composites. Powders consisted of carbon-coated particles about 30 nm in diameter, which were partly agglomerated into larger secondary particles. The utilization of the active materials in lithium cells depended most strongly upon the post-treatment and the Mg content, and was not influenced by the amount of carbon. Best results were achieved with a hydrothermally treated LiMg0.2Mn0.8PO4/C composite, which exhibited close to 50percent utilization of the theoretical capacity at a C/2 discharge rate.

Doeff, Marca M; Chen, Jiajun; Conry, Thomas E.; Wang, Ruigang; Wilcox, James; Aumentado, Albert

2009-12-14

297

Structural basis of reverse nucleotide polymerization  

PubMed Central

Nucleotide polymerization proceeds in the forward (5?-3?) direction. This tenet of the central dogma of molecular biology is found in diverse processes including transcription, reverse transcription, DNA replication, and even in lagging strand synthesis where reverse polymerization (3?-5?) would present a “simpler” solution. Interestingly, reverse (3?-5?) nucleotide addition is catalyzed by the tRNA maturation enzyme tRNAHis guanylyltransferase, a structural homolog of canonical forward polymerases. We present a Candida albicans tRNAHis guanylyltransferase-tRNAHis complex structure that reveals the structural basis of reverse polymerization. The directionality of nucleotide polymerization is determined by the orientation of approach of the nucleotide substrate. The tRNA substrate enters the enzyme’s active site from the opposite direction (180° flip) compared with similar nucleotide substrates of canonical 5?-3? polymerases, and the finger domains are on opposing sides of the core palm domain. Structural, biochemical, and phylogenetic data indicate that reverse polymerization appeared early in evolution and resembles a mirror image of the forward process. PMID:24324136

Nakamura, Akiyoshi; Nemoto, Taiki; Heinemann, Ilka U.; Yamashita, Keitaro; Sonoda, Tomoyo; Komoda, Keisuke; Tanaka, Isao; Söll, Dieter; Yao, Min

2013-01-01

298

Cell motility driven by actin polymerization.  

PubMed Central

Certain kinds of cellular movements are apparently driven by actin polymerization. Examples include the lamellipodia of spreading and migrating embryonic cells, and the bacterium Listeria monocytogenes, that propels itself through its host's cytoplasm by constructing behind it a polymerized tail of cross-linked actin filaments. Peskin et al. (1993) formulated a model to explain how a polymerizing filament could rectify the Brownian motion of an object so as to produce unidirectional force (Peskin, C., G. Odell, and G. Oster. 1993. Cellular motions and thermal fluctuations: the Brownian ratchet. Biophys. J. 65:316-324). Their "Brownian ratchet" model assumed that the filament was stiff and that thermal fluctuations affected only the "load," i.e., the object being pushed. However, under many conditions of biological interest, the thermal fluctuations of the load are insufficient to produce the observed motions. Here we shall show that the thermal motions of the polymerizing filaments can produce a directed force. This "elastic Brownian ratchet" can explain quantitatively the propulsion of Listeria and the protrusive mechanics of lamellipodia. The model also explains how the polymerization process nucleates the orthogonal structure of the actin network in lamellipodia. Images FIGURE 1 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE C.1 PMID:8968574

Mogilner, A; Oster, G

1996-01-01

299

SiO2 Nanoparticule-induced size-dependent genotoxicity - an in vitro study using sister chromatid exchange, micronucleus and comet assay.  

PubMed

Abstract Fine particles with a characteristic size smaller than 100?nm (i.e. nanoparticlesspread out in nowadays life. Silicon or Si, is one of the most abundant chemical elements found on the Earth. Its oxide forms, such as silicate (SiO4) and silicon dioxide, also known as silica (SiO2), are the main constituents of sand and quartz contributing to 90% of the Earth's crust. In this work, three genotoxicity systems "sister chromatid exchange, cytokinesis block micronucleus test and single cell gel electrophoresis (comet) assay" were employed to provide further insight into the cytotoxic and mutagenic/genotoxic potential of SiO2 nanoparticules (particle size 6?nm, 20?nm, 50?nm) in cultured peripheral blood lymphocytes as in vitro. It was observed that there is a significant decrease in Mitotic index (MI), Cytokinesis block proliferation index (CBPI), proliferation index (PRI) values expressed as Cell Kinetic parameters compared with negative control (p?nanoparticules is dependent to particule size. PMID:24960636

Battal, Dilek; Celik, Ayla; Güler, Gizem; Akta?, Ayça; Yildirimcan, Saadet; Ocakoglu, Kasim; Cömeleko?lu, Ulkü

2014-06-24

300

Fire-Retardant Polymeric Additives  

NASA Technical Reports Server (NTRS)

Polyhydroxyamide (PHA) and polymethoxyamide (PMeOA) are fire-retardant (FR) thermoplastic polymers and have been found to be useful as an additive for imparting fire retardant properties to other compatible, thermoplastic polymers (including some elastomers). Examples of compatible flammable polymers include nylons, polyesters, and acrylics. Unlike most prior additives, PHA and PMeOA do not appreciably degrade the mechanical properties of the matrix polymer; indeed, in some cases, mechanical properties are enhanced. Also, unlike some prior additives, PHA and PMeOA do not decompose into large amounts of corrosive or toxic compounds during combustion and can be processed at elevated temperatures. PMeOA derivative formulations were synthesized and used as an FR additive in the fabrication of polyamide (PA) and polystyrene (PS) composites with notable reduction (>30 percent for PS) in peak heat release rates compared to the neat polymer as measured by a Cone Calorimeter (ASTM E1354). Synergistic effects were noted with nanosilica composites. These nanosilica composites had more than 50-percent reduction in peak heat release rates. In a typical application, a flammable thermoplastic, thermoplastic blend, or elastomer that one seeks to render flame-retardant is first dry-mixed with PHA or PMeOA or derivative thereof. The proportion of PHA or PMeOA or derivative in the mixture is typically chosen to lie between 1 and 20 weight percent. The dry blend can then be melt-extruded. The extruded polymer blend can further be extruded and/or molded into fibers, pipes, or any other of a variety of objects that may be required to be fire-retardant. The physical and chemical mechanisms which impart flame retardancy of the additive include inhibiting free-radical oxidation in the vapor phase, preventing vaporization of fuel (the polymer), and cooling through the formation of chemical bonds in either the vapor or the condensed phase. Under thermal stress, the cyclic hydroxyl/ methoxy component forms polybenzoxazole (PBO) in a reaction that absorbs heat from its surroundings. PBO under thermal stress cross-links, forming a protective char layer, which thermally insulates the polymer. Thus, the formation of the char layer further assists to extinguish the fire by preventing vaporization of the polymeric fuel.

Williams, Martha K.; Smith, Trent M.

2011-01-01

301

Mixing in polymeric microfluidic devices.  

SciTech Connect

This SAND report describes progress made during a Sandia National Laboratories sponsored graduate fellowship. The fellowship was funded through an LDRD proposal. The goal of this project is development and characterization of mixing strategies for polymeric microfluidic devices. The mixing strategies under investigation include electroosmotic flow focusing, hydrodynamic focusing, physical constrictions and porous polymer monoliths. For electroosmotic flow focusing, simulations were performed to determine the effect of electroosmotic flow in a microchannel with heterogeneous surface potential. The heterogeneous surface potential caused recirculations to form within the microchannel. These recirculations could then be used to restrict two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the mixing region surface potential to the average channel surface potential was made large in magnitude and negative in sign, and when the ratio of the characteristic convection time to the characteristic diffusion time was minimized. Based on these results, experiments were performed to evaluate the manipulation of surface potential using living-radical photopolymerization. The material chosen to manipulate typically exhibits a negative surface potential. Using living-radical surface grafting, a positive surface potential was produced using 2-(Dimethylamino)ethyl methacrylate and a neutral surface was produced using a poly(ethylene glycol) surface graft. Simulations investigating hydrodynamic focusing were also performed. For this technique, mixing is enhanced by using a tertiary fluid stream to constrict the two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the tertiary flow stream flow-rate to the mixing streams flow-rate was maximized. Also, like the electroosmotic focusing mixer, mixing was also maximized when the ratio of the characteristic convection time to the characteristic diffusion time was minimized. Physical constrictions were investigated through simulations. The results show that the maximum mixing occurs when the height of the mixing region is minimized. Finally, experiments were performed to determine the effectiveness of using porous polymer monoliths to enhance mixing. The porous polymer monoliths were constructed using a monomer/salt paste. Two salt crystal size ranges were used; 75 to 106 microns and 53 to 180 microns. Mixing in the porous polymer monoliths fabricated with the 75 to 106 micron salt crystal size range was six times higher than a channel without a monolith. Mixing in the monolith fabricated with the 53 to 180 micron salt crystal size range was nine times higher.

Schunk, Peter Randall; Sun, Amy Cha-Tien; Davis, Robert H. (University of Colorado at Boulder, Boulder, CO); Brotherton, Christopher M. (University of Colorado at Boulder, Boulder, CO)

2006-04-01

302

Molecular Probe Fluorescence Monitoring of Polymerization  

NASA Technical Reports Server (NTRS)

This project investigated the feasibility of using fluorescence spectroscopy to determine viscosity of polymer/monomer in support of Transient Interfacial Phenomena in Miscible Polymer Systems (TIPMPS). This project will attempt to measure gradient induced flow at a miscible interface during and / or after in-flight polymerization of dodecyl acrylate (lauryl acrylate). Concentration and temperature gradients will be intentionally introduced during polymerization and the resultant fluid flow determined by Particle Imaging Velocimetry (PIV). This report describes an investigation of the feasibility of using fluorescence of a probe molecule to monitor viscosity and/or concentration during and after polymerization. The probe used was pyrene which has been shown to be sensitive to its local environment in methyl methacrylate.

Bunton, Patrick

2002-01-01

303

Universal metastability of sickle hemoglobin polymerization  

NASA Astrophysics Data System (ADS)

Sickle hemoglobin (HbS) is a natural mutation of the normal hemoglobin (HbA) found in the red blood cells of human body. Polymerization of HbS occurs when the concentration of deoxyHbS exceeds a well-defined solubility, which is the underlying cause of the Sickle Cell Disease. It has long been assumed that thermodynamic equilibrium is reached when polymerization comes to an end. However, in this thesis we demonstrate that in confined volume as well as in bulk solution, HbS polymerization terminates prematurely, leaving the solution in a metastable state. A newly developed Reservoir method as well as modulated excitation method were adopted for the study. This discovery of universal metastability gives us new insights into understanding the mechanism of sickle cell disease.

Weng, Weijun

304

Drug-initiated ring-opening polymerization of O-carboxyanhydrides for the preparation of anticancer drug-poly(O-carboxyanhydride) nanoconjugates.  

PubMed

We report a novel synthetic strategy of polymer-drug conjugates for nanoparticulate drug delivery: hydroxyl-containing drug (e.g., camptothecin, paclitaxel, doxorubicin and docetaxel) can initiate controlled polymerization of phenyl O-carboxyanhydride (Phe-OCA) to afford drug-poly(Phe-OCA) conjugated nanoparticles, termed drug-PheLA nanoconjugates (NCs). Our new NCs have well-controlled physicochemical properties, including high drug loading, quantitative drug loading efficiency, controlled particle size with narrow particle size distribution, and sustained drug release profile over days without "burst" release effect as observed in conventional polymer/drug encapsulates. Compared with polylactide NCs, the PheLA NCs have increased noncovalent hydrophobic interchain interactions and thereby result in remarkable stability in human serum with negligible particle aggregation. Such distinctive properties can reduce the premature disassembly of NCs upon dilution in the bloodstream and prolong NCs' in vivo circulation with the enhancement of intratumoral accumulation of NCs, which has a bearing on therapeutic effectiveness. PMID:23445497

Yin, Qian; Tong, Rong; Xu, Yunxiang; Baek, Kwanghyun; Dobrucki, Lawrence W; Fan, Timothy M; Cheng, Jianjun

2013-03-11

305

Polymeric matrix materials for infrared metamaterials  

DOEpatents

A polymeric matrix material exhibits low loss at optical frequencies and facilitates the fabrication of all-dielectric metamaterials. The low-loss polymeric matrix material can be synthesized by providing an unsaturated polymer, comprising double or triple bonds; partially hydrogenating the unsaturated polymer; depositing a film of the partially hydrogenated polymer and a crosslinker on a substrate; and photopatterning the film by exposing the film to ultraviolet light through a patterning mask, thereby cross-linking at least some of the remaining unsaturated groups of the partially hydrogenated polymer in the exposed portions.

Dirk, Shawn M; Rasberry, Roger D; Rahimian, Kamyar

2014-04-22

306

Mycobacteriophage vector systems.  

PubMed

Successful application of molecular genetic approaches to the study of mycobacteria necessitates the introduction of recombinant DNA molecules into mycobacterial cells. Efficient methods of introducing DNA into Mycobacterium smegmatis protoplasts have been developed, and the construction of mycobacteriophage recombinant DNA vectors has been initiated. Novel Escherichia coli-Mycobacterium shuttle vectors, termed shuttle phasmids, have been constructed. These vectors were constructed by inserting E. coli cosmids into nonessential regions of mycobacteriophage DNAs. Shuttle phasmids are multifunctional vectors that replicate in E. coli as plasmids and replicate in mycobacteria as phage. The presence of the bacteriophage lambda cos sequences permits the use of the lambda in vitro packaging system for efficient cloning of additional genes into these vectors. Temperate shuttle phasmids have been constructed that can infect and lyse mycobacterial cells or lysogenize mycobacterial cells to stably integrate and express cloned DNA into mycobacterial genomes. Shuttle phasmids can be transduced into a wide variety of mycobacterial species and thus should permit the development of molecular genetic systems for the mycobacteria. PMID:2652256

Jacobs, W R; Snapper, S B; Tuckman, M; Bloom, B R

1989-01-01

307

Method of Making Thermally Stable, Piezoelectric and Proelectric Polymeric Substrates  

NASA Technical Reports Server (NTRS)

A thermally stable, piezoelectric and pyroelectric polymeric substrate was prepared. This thermally stable, piezoelectric and pyroelectric polymeric substrate may be used to prepare electromechanical transducers, thermomechanical transducers, accelerometers, acoustic sensors, infrared sensors, pressure sensors, vibration sensors, impact sensors. in-situ temperature sensors, in-situ stress/strain sensors, micro actuators, switches, adjustable fresnel lenses, speakers, tactile sensors, weather sensors, micro positioners, ultrasonic devices, power generators, tunable reflectors, microphones, and hydrophones. The process for preparing these polymeric substrates includes: providing a polymeric substrate having a softening temperature greater than 100 C; depositing a metal electrode material onto the polymer film; attaching a plurality of electrical leads to the metal electrode coated polymeric substrate; heating the metal electrode coated polymeric substrate in a low dielectric medium: applying a voltage to the heated metal electrode coated polymeric substrate to induce polarization; and cooling the polarized metal electrode coated polymeric electrode while maintaining a constant voltage.

Simpson, Joycelyn O. (Inventor); St.Clair, Terry L. (Inventor)

1999-01-01

308

Polymerization Initiated at the Sidewalls of Carbon Nanotubes  

NASA Technical Reports Server (NTRS)

A process has been developed for growing polymer chains via anionic, cationic, or radical polymerization from the side walls of functionalized carbon nanotubes, which will facilitate greater dispersion in polymer matrices, and will greatly enhance reinforcement ability in polymeric material.

Tour, James M.; Hudson, Jared L.

2011-01-01

309

ORIGINAL CONTRIBUTION Dynamic rheology studies of in situ polymerization process  

E-print Network

ORIGINAL CONTRIBUTION Dynamic rheology studies of in situ polymerization process of polyacrylamide­cellulose small-amplitude oscillatory shear experiments for in situ polymerization process of polyacrylamide­cellulose hydrogels. Keywords Polyacrylamide . Cellulose nanocrystals . Nanocomposite hydrogels . Dynamic rheology

310

21 CFR 870.3650 - Pacemaker polymeric mesh bag.  

Code of Federal Regulations, 2014 CFR

...ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is...

2014-04-01

311

21 CFR 870.3650 - Pacemaker polymeric mesh bag.  

Code of Federal Regulations, 2010 CFR

...ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is...

2010-04-01

312

Polymeric matrices for DNA sequencing by capillary electrophoresis  

E-print Network

Polymeric matrices for DNA sequencing by capillary electrophoresis We review the wide range of polymeric materials that have been employed for DNA sequencing separations by capillary electrophoresis-linked polymer networks. Keywords: DNA sequencing / Capillary electrophoresis / Polymer solutions / Matrices

Barron, Annelise E.

313

Polymeric nanoparticles for co-delivery of synthetic long peptide antigen and poly IC as therapeutic cancer vaccine formulation.  

PubMed

The aim of the current study was to develop a cancer vaccine formulation for treatment of human papillomavirus (HPV)-induced malignancies. Synthetic long peptides (SLPs) derived from HPV16 E6 and E7 oncoproteins have been used for therapeutic vaccination in clinical trials with promising results. In preclinical and clinical studies adjuvants based on mineral oils (such as incomplete Freund's adjuvant (IFA) and Montanide) are used to create a sustained release depot at the injection site. While the depot effect of mineral oils is important for induction of robust immune responses, their administration is accompanied with severe adverse and long lasting side effects. In order to develop an alternative for IFA family of adjuvants, polymeric nanoparticles (NPs) based on hydrophilic polyester (poly(d,l lactic-co-hydroxymethyl glycolic acid) (pLHMGA)) were prepared. These NPs were loaded with a synthetic long peptide (SLP) derived from HPV16 E7 oncoprotein and a toll like receptor 3 (TLR3) ligand (poly IC) by double emulsion solvent evaporation technique. The therapeutic efficacy of the nanoparticulate formulations was compared to that of HPV SLP+poly IC formulated in IFA. Encapsulation of HPV SLP antigen in NPs substantially enhanced the population of HPV-specific CD8+ T cells when combined with poly IC either co-encapsulated with the antigen or in its soluble form. The therapeutic efficacy of NPs containing poly IC in tumor eradication was equivalent to that of the IFA formulation. Importantly, administration of pLHMGA nanoparticles was not associated with adverse effects and therefore these biodegradable nanoparticles are excellent substitutes for IFA in cancer vaccines. PMID:25660830

Rahimian, Sima; Fransen, Marieke F; Kleinovink, Jan Willem; Christensen, Jonatan Riis; Amidi, Maryam; Hennink, Wim E; Ossendorp, Ferry

2015-04-10

314

CCMR: Carbon Nanotube Polymer Hybrids: Polymerization of Functionalized Carbon Nanotubes  

NSDL National Science Digital Library

This project was to functionalize carbon nanotubes, and polymerize from their surfaces to increase solubility, decrease bundling, and form polymer-nanotube hybrid materials. Single wall carbon nanotubes (SWNT) were the main focus of this project. Functionalization was accomplished by attaching nitroxide-mediated radical polymerization (NMP) initiator molecules to SWNT. Both covalent and non-covalent attachment methods were used for initiator attachment. Polymerization of styrene was used to test polymerizations off SWNT. Nitroxide exchange reactions were also explored.

Peterson, Joseph

2004-08-17

315

Bunyavirus-Vector Interactions  

PubMed Central

The Bunyaviridae family is comprised of more than 350 viruses, of which many within the Hantavirus, Orthobunyavirus, Nairovirus, Tospovirus, and Phlebovirus genera are significant human or agricultural pathogens. The viruses within the Orthobunyavirus, Nairovirus, and Phlebovirus genera are transmitted by hematophagous arthropods, such as mosquitoes, midges, flies, and ticks, and their associated arthropods not only serve as vectors but also as virus reservoirs in many cases. This review presents an overview of several important emerging or re-emerging bunyaviruses and describes what is known about bunyavirus-vector interactions based on epidemiological, ultrastructural, and genetic studies of members of this virus family. PMID:25402172

Horne, Kate McElroy; Vanlandingham, Dana L.

2014-01-01

316

Self-healing polymeric materials: A review of recent developments  

Microsoft Academic Search

The development and characterization of self-healing synthetic polymeric materials have been inspired by biological systems in which damage triggers an autonomic healing response. This is an emerging and fascinating area of research that could significantly extend the working life and safety of the polymeric components for a broad range of applications. An overview of various self-healing concepts for polymeric materials

Dong Yang Wu; Sam Meure; David Solomon

2008-01-01

317

Interfacial activity of a novel family of polymeric surfactants  

Microsoft Academic Search

A novel series of polymeric surfactants based on carboxy methyl cellulose and alkyl poly(etheroxy) acrylate were synthesized by ultrasonic irradiation. These polymeric surfactants have exhibit excellent surface activity due to their unique structure. The influences of salt, alcohol and alkali on the interfacial activity of these polymeric surfactants were studied by interfacial tensiometery, dynamic laser scattering (DLS), UV spectroscope and

Ya Cao; Huilin Li

2002-01-01

318

Photophysics of all- trans-retinoic acid (ATRA) chemisorbed to nanoparticulate TiO 2: Evidence for TiO 2* to ATRA energy transfer and reverse electron transfer sensitisation  

Microsoft Academic Search

The photophysics of all-trans-retinoic acid (ATRA) in methanol solution and of the system comprising ATRA chemisorbed to nanoparticulate TiO2 have been examined in methanol solution and in aqueous dispersion (pH = 7), respectively. We found evidence for two closely spaced singlet excited states of ATRA, tentatively assigned as n??* and ???*, with the former primarily responsible for ATRA fluorescence. The

M. R. V. Sahyun; N. Serpone

1998-01-01

319

TRANSITION METAL CATALYSIS IN CONTROLLED RADICAL POLYMERIZATION: ATOM TRANSFER RADICAL POLYMERIZATION. (R826735)  

EPA Science Inventory

Novel and diversified macromolecular structures, which include polymers with designed topologies (top), compostions (middle), and functionalities (bottom), can be prepared by atom transfer radical polymerization processes. These polymers can be synthesized from a large variety of...

320

Switchable Adhesion from Bicomponent Polymeric Brushes  

Microsoft Academic Search

We investigated the adhesive and wetting properties of bicomponent polymeric brushes made from end functionalized hydrophilic and hydrophobic polymer chains. The molecular organization of the mixed brush could be varied reversibly by exposure to selective solvents for the two polymers. Adhesive properties were tested by debonding a flat ended probe from soft pressure-sensitive-adhesives (hydrophobic & hydrophilic) and wetting properties were

Haris Retsos; Ganna Gorodyska; Costantino Creton

2005-01-01

321

Polymeric Micellar Delivery Systems in Oncology  

Microsoft Academic Search

The purpose of drug delivery systems in cancer chemotherapy is to achieve selective delivery of anti-cancer agents to cancer tissue at an effective concentrations for the appropriate dur- ation of time, so that we may be able to reduce the adverse effects of a drug and simul- taneously enhance the anti-tumor effect. Polymeric micelles were expected to increase the accumulation

Yasuhiro Matsumura

2008-01-01

322

Non-traditional plasticization of polymeric films.  

PubMed

The objective of this study was to investigate the influence of methylparaben, ibuprofen, chlorpheniramine maleate and theophylline on the thermal and mechanical properties of polymeric films of Eudragit RS 30 D. The effects of methylparaben and ibuprofen in the film coating on the rate of drug release from Eudragit RS 30 D coated beads were also studied. The physical and mechanical properties of the cast films and coated beads were investigated using thermal analysis, tensile testing, X-ray diffraction analysis and dissolution testing. The results demonstrated that the glass transition temperature of the Eudragit RS 30 D decreased with increasing levels of methylparaben, ibuprofen and chlorpheniramine maleate in the film. Theophylline exerted no influence on the thermal properties of the polymer. The higher levels of the ibuprofen and methylparaben incorporated into the film resulted in a decrease in the tensile strength of the film. The decrease in Young's modulus of Eudragit RS 30 D coated beads was attributed to an increase in the flexibility of the polymeric films when the level of methylparaben or ibuprofen in the polymeric dispersion was increased. The dissolution data demonstrated that the rate of release of the ibuprofen from coated beads was decreased by increasing the amount of ibuprofen and methylparaben in the polymeric film coating. PMID:10205601

Wu, C; McGinity, J W

1999-01-15

323

Polymeric biomaterials for tissue and organ regeneration  

Microsoft Academic Search

This paper reviews recent work involving polymeric biomaterials used for skin, cartilage, bone, vascular, nerve and liver regeneration. Skin trauma involves damage to the epidermal, dermal and\\/or subdermal tissues. Epithelial, dermal and full-thickness replacements are considered. Cartilage research is mainly focused on replacing hyaline cartilage. Researchers investigate both nondegradable polymers, which must provide mechanical stability, and degradable polymers, which must

B. L Seal; T. C Otero; A Panitch

2001-01-01

324

Thermostatistics of the Polymeric Ideal Gas  

E-print Network

In this paper, we formulate statistical mechanics of the polymerized systems in the semiclassical regime. On the corresponding polymeric symplectic manifold, we set up a noncanonical coordinate system in which all of the polymeric effects are summarized in the density of states. Since we show that the polymeric effects only change the number of microstates of a statistical system, working in this coordinate is quite reasonable from the statistical point of view. The results show that the number of microstates decreases due to existence of an upper bound for the momentum of the test particles in the polymer framework. We obtain a corresponding canonical partition function by means of the deformed density of states. By using the partition function, we study thermodynamics of the ideal gas in the polymer framework and show that our results are in good agreement with those that arise from the full quantum consideration at high temperature, and they coincide with their usual counterpart in the limit of low temperature.

M. A. Gorji; K. Nozari; B. Vakili

2014-08-20

325

REMENDABLE POLYMERIC MATERIALS USING REVERSIBLE COVALENT BONDS  

Microsoft Academic Search

Materials that can recover mechanical properties following failure offer increased safety and service life. Moreover, successful development of such systems would reduce factors of safety required in design thus reducing weight. Inspiration for remendable materials comes from nature where the ability to heal is a characteristic of living organisms and a prime example of autonomy. The development of self-healing polymeric

Giuseppe R. Palmese; Amy M. Peterson; Robert E. Jensen

326

Polymer microcantilevers fabricated via multiphoton absorption polymerization  

E-print Network

Polymer microcantilevers fabricated via multiphoton absorption polymerization Z. Bayindir, Y. Sun polymer cantilevers. Atomic force microscopy has been used to characterize the mechanical properties orders of magnitude smaller than would be predicted from the properties of the bulk polymer.6 If correct

Teich, Malvin C.

327

Modular and Dynamic Functionalization of Polymeric Scaffolds  

Microsoft Academic Search

The design and synthesis of multifunctionalized, architecturally controlled polymers is a prerequisite for a variety of future applications of polymeric materials. On the basis of Nature's use of self-assembly in the creation of biomaterials, this Account describes concepts that were developed over the past 5 years that utilize noncovalent interactions such as hydrogen bonding, ionic interactions, electrostatic interactions, metal coordination,

Clinton R. South; Caroline Burd; Marcus Weck

2007-01-01

328

Microstructures fabricated by laser-induced polymerization  

Microsoft Academic Search

The application of laser technology has shown great advantages in the fast growing area where electronic and mechanical components are combined to form miniature structures. Use of laser-induced polymerization (LIP) in making microstructures has drawn increasing attention. A focused laser beam can be guided directly to write three-dimensional patterns. The advantages are high cure speed, constant intensity along the curing

Xinming Huang; Robert O. Warrington; Craig R. Friedrich

1998-01-01

329

Polymeric components for telecom and datacom  

NASA Astrophysics Data System (ADS)

Polymeric optical waveguide components offer attractive properties for applications in optical telecom and datacom systems. These are high speed for electro-optic modulators, low power dissipation for thermo-optic (digital) switches and low-cost for all active and passive components. We report on active and passive components realized by utilizing polymer-specific attractive techniques such as planarizing spincoating, low-temperature reflowing and direct photodefinition. Examples are multimode photodefined passive polymeric waveguides for optical interconnect applications; photodefined monomode polymeric waveguides loaded with rare-earth doped nanoparticles for planar waveguide amplifiers and with non-linear chromophores for electro-optic modulators. We will show that polymer waveguide technology allows vertical stacking of electro-optic microringresonators with their port waveguides to realize high-speed modulators. By reflowing the reactive-ion-etched microring we could reduce the scattering by wall roughness considerably. Thermo-optic polymeric microringresonators combine the high thermo-optic coefficient and low thermal conductivity of polymers with the small size of the microring. It will be shown that this yields a broad wavelength tuning range at low power dissipation.

Diemeer, Mart; Dekker, Ronald; Hilderink, Lucie; Leinse, Arne; Balakrishnan, Muralidharan; Faccini, Mirko; Driessen, Alfred

2005-09-01

330

Impregnated metal-polymeric functional beads  

NASA Technical Reports Server (NTRS)

Amine containing polymeric microspheres such as polyvinyl pyridine are complexed with metal salts or acids containing metals such as gold, platinum or iron. After reduction with sodium borohydride, the salt is reduced to finely divided free metal or metal oxides, useful as catalysts. Microspheres containing covalent bonding sites can be used for labeling or separating proteins.

Rembaum, Alan (Inventor); Volksen, Willi (Inventor)

1978-01-01

331

Impregnated metal-polymeric functional beads  

NASA Technical Reports Server (NTRS)

Amine containing polymeric microspheres such as polyvinyl pyridine are complexed with metal salts or acids containing metals such as gold, platinum or iron. After reduction with sodium borohydride, the salt is reduced to finely divided free metal or metal oxides, useful as catalysts. Microspheres containing covalent bonding sites can be used for labeling or separating proteins.

Rembaum, Alan (Inventor); Volksen, Willi (Inventor)

1980-01-01

332

Polymeric components for all-optical networks  

Microsoft Academic Search

All-optical networks that exhibit high speed, high capacity, scalability, configurability, and transparency are becoming a reality through the exploitation of the unique properties of fiber and integrated optics. An advanced polymeric waveguide technology was developed for affordable passive and active integrated optical elements that address the needs of these networks. We engineered high-performance organic polymers that can be readily made

Louay A. Eldada; Karl W. Beeson; Deepti Pant; Robert Blomquist; Lawrence W. Shacklette; Michael J. McFarland

2000-01-01

333

Polymeric Electrolytic Hygrometer For Harsh Environments  

NASA Technical Reports Server (NTRS)

Design of polymeric electrolytic hygrometer improved to meet need for reliable measurements of relative humidity in harsh environments of pulpmills and papermills. Redesigned sensor head features shorter, more-rigidly-held sensing element, less vulnerable than previous version to swell and loss of electrical contact. Useful for control of batch dryers in food and pharmaceutical industries.

Lawson, Daniel D.; Shakkottai, Parthasarathy; Venkateshan, Shakkottai P.

1989-01-01

334

Free heme and sickle hemoglobin polymerization  

NASA Astrophysics Data System (ADS)

This work investigates further the mechanism of one of the most interesting of the protein self-assembly systems---the polymerization of sickle hemoglobin and the role of free heme in it. Polymerization of sickle hemoglobin is the primary event in the pathology of a chronic hemolytic condition called sickle cell anemia with complex pathogenesis, unexplained variability and symptomatic treatment. Auto-oxidation develops in hemoglobin solutions exposed to room temperature and causes release of ferriheme. The composition of such solutions is investigated by mass spectrometry. Heme dimers whose amount corresponds to the initial amounts of heme released from the protein are followed. Differences in the dimer peak height are established for hemoglobin variants A, S and C and depending on the exposure duration. The effects of free heme on polymerization kinetics are studied. Growth rates and two characteristic parameters of nucleation are measured for stored Hb S. After dialysis of polymerizing solutions, no spherulites are detected at moderately high supersaturation and prolonged exposure times. The addition of 0.16-0.26 mM amounts of heme to dialyzed solutions leads to restoration of polymerization. The measured kinetic parameters have higher values compared to the ones before dialysis. The amount of heme in non-dialyzed aged solution is characterized using spectrophotometry. Three methods are used: difference in absorbance of dialyzed and non-dialyzed solutions, characteristic absorbance of heme-albumin complex and absorbance of non-dialyzed solutions with added potassium cyanide. The various approaches suggest the presence of 0.12 to 0.18 mM of free ferriheme in such solutions. Open questions are whether the same amounts of free heme are present in vivo and whether the same mechanism operates intracellulary. If the answer to those questions is positive, then removal of free heme from erythrocytes can influence their readiness to sickle.

Uzunova, Veselina V.

335

Polymerization by classical and frustrated Lewis pairs.  

PubMed

Main-group classical and frustrated Lewis pairs (CLPs and FLPs) comprising strong Lewis acids (LAs) and strong Lewis bases (LBs) are highly active for polymerization of conjugated polar alkenes, affording typically high molecular weight polymers with relatively narrow molecular weight distributions. Especially effective systems are the Lewis pairs (LPs) consisting of the strong LA Al(C6F5)3 and strong LBs, such as achiral phosphines and chiral chelating diphosphines, N-heterocyclic carbenes, and phosphazene superbases, for polymerization of methacrylates and acrylamides as well as renewable ?-methylene-?-butyrolactones. Chain initiation involves cooperative addition of LPs to the monomer to generate zwitterionic active species, and chain propagation proceeds via a bimetallic, activated-monomer addition mechanism. Transition metal nucleophile/electrophile pairs comprising neutral metallocene bis(ester enolate)s and strong LAs E(C6F5)3 (E = Al, B) generate two drastically different polymerization systems, depending on the LA. With E = Al, catalyst activation and chain initiating events lead to dually active ion-pairs, thereby effecting ion-pairing polymerization that affords polymers with unique stereo-multiblock microstructures. With E = B, on the other hand, the FLP-induced catalyst activation generates metallacyclic cations paired with the hydridoborate anion [HB(C6F5)3](-); uniquely, such ion-pairs effect catalytic polymerization of conjugated polar alkenes by an H-shuttling mechanism, with the cation catalyzing chain growth and the anion promoting chain transfer by shuttling the hydride between the cation and anion centers through the neutral borane. PMID:23097029

Chen, Eugene Y-X

2013-01-01

336

Vector Meson Dominance  

E-print Network

Historically vector-meson physics arose along two different paths to be reviewed in Sections 1 and 2. In Section 3, the phenomenological consequences will be discussed with an emphasis on those aspects of the subject matter relevant in present-day discussions on deep inelastic scattering in the diffraction region of low values of the Bjorken variable.

Dieter Schildknecht

2005-11-08

337

Vectors Point Toward Pisa  

ERIC Educational Resources Information Center

The author shows that the set of all sequences in which each term is the sum of the two previous terms forms a vector space of dimension two. He uses this result to obtain the formula for the Fibonacci sequence and applies the same technique to other linear recursive relations. (MM)

Dean, Richard A.

1971-01-01

338

Fuzzy support vector machines  

Microsoft Academic Search

A support vector machine (SVM) learns the decision surface from two distinct classes of the input points. In many applications, each input point may not be fully assigned to one of these two classes. In this paper, we apply a fuzzy membership to each input point and reformulate the SVMs such that different input points can make different contributions to

Chun-Fu Lin; Sheng-De Wang

2002-01-01

339

Vectorizing Cartoon Animations  

Microsoft Academic Search

We present a system for vectorizing 2D raster format cartoon animations. The output animations are visually flicker free, smaller in file size, and easy to edit. We identify decorative lines separately from colored regions. We use an accurate and semantically meaningful image decomposition algorithm, supporting an arbitrary color model for each region. To ensure temporal coherence in the output, we

Song-hai Zhang; Tao Chen; Yi-fei Zhang; Shi-min Hu; Ralph R. Martin

2009-01-01

340

Vector potential methods  

NASA Technical Reports Server (NTRS)

Vector potential and related methods, for the simulation of both inviscid and viscous flows over aerodynamic configurations, are briefly reviewed. The advantages and disadvantages of several formulations are discussed and alternate strategies are recommended. Scalar potential, modified potential, alternate formulations of Euler equations, least-squares formulation, variational principles, iterative techniques and related methods, and viscous flow simulation are discussed.

Hafez, M.

1989-01-01

341

Support vector machines  

NASA Technical Reports Server (NTRS)

Support Vector Machines (SVMs) are a type of supervised learning algorith,, other examples of which are Artificial Neural Networks (ANNs), Decision Trees, and Naive Bayesian Classifiers. Supervised learning algorithms are used to classify objects labled by a 'supervisor' - typically a human 'expert.'.

Garay, Michael J.; Mazzoni, Dominic; Davies, Roger; Wagstaff, Kiri

2004-01-01

342

Vector Analysis on Fractals  

E-print Network

Post-Critically Finite fractals are self-similar structures with the boundary ... form on a vector space F of real valued functions on X, and E(u) = 0 if and ..... zero seminorm elements and completing. ... Magnetic Schrödinger operators. Classically.

Daniel J. Kelleher

2014-08-31

343

Vector Autoregressions and Reality  

Microsoft Academic Search

This article questions the statistical significance of variance decompositions and impulse response functions for unrestricted vector autoregressions. It suggests that previous authors have failed to provide confidence intervals for variance decompositions and impulse response functions. Two methods of computing such confidence intervals are developed: first, using a normal approximation; second, using bootstrapped resampling. An example from Sims's work is used

David E. Runkle

1987-01-01

344

Automatic, continuous online monitoring of polymerization reactions (ACOMP): Progress in characterization of polymers and polymerization reactions  

NASA Astrophysics Data System (ADS)

An original method is presented as an efficient technique for characterizing polymers, and understanding the kinetics of the polymerization reactions. The Automatic Continuous Online Monitoring of Polymerization Reactions (ACOMP) method developed at Tulane University involves following one or more characteristics of a polymerization reaction: monomer conversion, different molecular weight averages, intrinsic viscosity, etc. By performing an automatic withdrawal and dilution of the polymer solution to create a small stream which flows through a detector train, including light scattering, viscometer, refractive index, Ultraviolet/Visible detectors, a continuum of data points can be obtained, allowing powerful analysis methods to be developed. The goal of this work is to expand ACOMP to new polymerization reactions, such as free radical copolymerization, controlled radical polymerization, inverse emulsion polymerization, both to achieve a complete physical characterization of the polymers synthesized and a better understanding of the reaction mechanisms. For each of the reactions ACOMP brings significant innovations in the analysis of the kinetics. Other new methods, such as Automatic Continuous Mixing (ACM) and Simultaneous Multiple Sample Light Scattering (SMSLS) are also used, as well as traditional multi-detector Size Exclusion Chromatography (SEC). As an immediate consequence it is hoped that the information on reaction kinetics and mechanisms offer a better fundamental knowledge, control and ability to optimize reactions. At the industrial scale, online monitoring should allow a more efficient use of resources, energy, reactor and personnel time as well as a higher product quality.

Alb, Alina M.

345

Insect Vectors of Human Pathogens  

NSDL National Science Digital Library

Four orders of insects (Hemiptera, Phthiraptera, Diptera, and Siphonaptera) are covered detailing vector species along with their pathogens of human importance. Links to pathogens as well as vectors are highlighted (some of these are CDC, and WHO).

0000-00-00

346

A vector asymmetrical NNV equation  

NASA Astrophysics Data System (ADS)

A vector asymmetrical Nizhnik-Novikov-Veselov (NNV) equation is proposed based on its bilinear form. Soliton solutions expressed by Pfaffians are obtained. Bilinear Bäcklund transformation and the corresponding Lax pair for the vector ANNV equation are derived.

Yu, Guo-Fu; Tam, Hon-Wah

2008-08-01

347

Mechanisms of Drug Diffusion from Polymeric Devices.  

NASA Astrophysics Data System (ADS)

A detailed mechanistic study of drug diffusion and the factors which influence drug diffusion through polymeric controlled release systems was undertaken to understand drug diffusion through hydrophilic and hydrophobic polymeric systems. The effect of improved aqueous solubility of the salt form (ionizable form) of selected drugs on diffusion through hydrophilic and hydrophobic polymeric membranes was compared to diffusion of the less soluble (unionizable form) of the drugs. Model drugs chosen for these studies were prednisolone, prednisolone phosphate sodium (prednisolone phosphoric acid disodium salt), pilocarpine, pilocarpine hydrochloride, sulfacetamide and sodium sulfacetamide. The hydrophilic polymers were hydrogels of hydroxyethylmethacrylate (PHEMA) and hydrophobic polymers were copolyether-urethane -urea (Biomer) and polydimethylsiloxane (PDMS). Salt forms of the drugs permeated faster than the free forms through the hydrophilic polymers because of higher aqueous solubility. The free forms of the drugs had higher diffusion rates than the salt forms due to increased solubility in the hydrophobic polymers. Drug solubility in polymers and the water fraction of the polymeric membrane were determined to be the primary factors in diffusion through polymeric membranes. Drug aqueous solubility was of secondary importance. Two controlled release systems were then designed to further study drug release. The Biomer and copolymers of polystyrene and PHEMA were chosen as the polymers for the fabrication of the devices. These copolymers incorporated the favorable attributes of hydrophobic and hydrophilic homopolymers into single polymers. Prednisolone was used as a model drug for these studies. The effects of initial drug load, drug loading solvents and the drug polymer interactions on drug release from the devices were then studied. The drug release from these devices increased as the initial drug load increased. Drug loading solvents had a marked effect on drug release. Different solvents can swell or dissolve either or all segments of polymers. Therefore, the release rates of the drug can be controlled by selectively loading into either selected or both segments of the copolymers. The study of physical and chemical drug-polymer interactions and polymer morphology provided additional understanding of drug release mechanisms from these polymeric devices.

Sharma, Kuldeepak

1987-09-01

348

Vectors from A to B  

NSDL National Science Digital Library

This is an activity about vectors and velocity. It outlines the addition and subtraction of vectors, and introduces the application of trigonometry to describing vectors. The resource is designed to support student analysis of THEMIS (Time History of Events and Macroscale Interactions during Substorms) Magnetometer line-plot data. Learners will complete worksheets consisting of problem sets that allow them to work with vector data in magnetic fields. This is activity 15 from Exploring Magnetism: Earth's Magnetic Personality.

349

Some experiences with Krylov vectors and Lanczos vectors  

NASA Technical Reports Server (NTRS)

This paper illustrates the use of Krylov vectors and Lanczos vectors for reduced-order modeling in structural dynamics and for control of flexible structures. Krylov vectors and Lanczos vectors are defined and illustrated, and several applications that have been under study at The University of Texas at Austin are reviewed: model reduction for undamped structural dynamics systems, component mode synthesis using Krylov vectors, model reduction of damped structural dynamics systems, and one-sided and two-sided unsymmetric block-Lanczos model-reduction algorithms.

Craig, Roy R., Jr.; Su, Tzu-Jeng; Kim, Hyoung M.

1993-01-01

350

Kinematics of vector fields  

E-print Network

Different (not only by sign) affine connections are introduced for contravariant and covariant tensor fields over a differentiable manifold by means of a non-canonical contraction operator, defining the notion dual bases and commuting with the covariant and with the Lie-differential operator. Classification of the linear transports on the basis of the connections between the connections is given. Notion of relative velocity and relative acceleration for vector fields are determined. By means of these kinematic characteristics several other types of notions as shear velocity, shear acceleration, rotation velocity, rotation acceleration, expansion velocity and expansion acceleration are introduced and on their basis auto-parallel and non-isotropic (non-null) vector fields are classified.

S. Manoff

2000-03-02

351

Insecticide Resistance and Vector Control  

Microsoft Academic Search

Insecticide resistance has been a problem in all insect groups that serve as vectors of emerging diseases. Although mechanisms by which insecticides become less effective are similar across all vector taxa, each resistance problem is potentially unique and may involve a complex pattern of resistance foci. The main defense against resistance is close surveillance of the susceptibility of vector populations.

William G. Brogdon; Janet C. McAllister

1998-01-01

352

Statistical analysis of cointegration vectors  

Microsoft Academic Search

We consider a nonstationary vector autoregressive process which is integrated of order 1, and generated by i.i.d. Gaussian errors. We then derive the maximum likelihood estimator of the space of cointegration vectors and the likelihood ratio test of the hypothesis that it has a given number of dimensions. Further we test linear hypotheses about the cointegration vectors. The asymptotic distribution

Soren Johansen

1988-01-01

353

Support Vector Machine(SVM)  

E-print Network

Support Vector Machine(SVM) Jinlong Wu Outline Some Classification Problems From The Real World Techniques Support Vector Machine(SVM) Jinlong Wu Department of Scientific and Engineering Computing, School of Mathematical Scineces, PKU 2007. 6.1 1 / 37 #12;Support Vector Machine(SVM) Jinlong Wu Outline Some

Li, Tiejun

354

Multiple Cause Vector Quantization  

E-print Network

We propose a model that can learn parts-based representations of highdimensional data. Our key assumption is that the dimensions of the data can be separated into several disjoint subsets, or factors, which take on values independently of each other. We assume each factor has a small number of discrete states, and model it using a vector quantizer. The selected states of each factor represent the multiple causes of the input.

David A. Ross; Richard S. Zemel

2003-01-01

355

Durability of Polymeric Glazing and Absorber Materials  

SciTech Connect

The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes. The objective of this task is to quantify lifetimes through measurement of the optical and mechanical stability of candidate polymeric glazing and absorber materials. Polycarbonate sheet glazings, as proposed by two industry partners, have been tested for resistance to UV radiation with three complementary methods. Incorporation of a specific 2-mil thick UV-absorbing screening layer results in glazing lifetimes of at least 15 years; improved screens promise even longer lifetimes. Proposed absorber materials were tested for creep and embrittlement under high temperature, and appear adequate for planned ICS absorbers.

Jorgensen, G.; Terwilliger, K.; Bingham, C.; Milbourne, M.

2005-01-01

356

Polymeric Quantization and Black Hole Thermodynamics  

E-print Network

Polymer quantization is a non-standard representation of the quantum mechanics that inspired by loop quantum gravity. To study the associated statistical mechanics, one needs to find microstates' energies which are eigenvalues of the Hamiltonian operator in the polymer framework. But, this is not an easy task at all since the Hamiltonian takes a nonlinear form in polymer picture. In this paper, we introduce a semiclassical method in which it is not necessary to solve the eigenvalue problem. Instead, we work with the classical Hamiltonian function and the deformed density of states in the polymeric phase space. Implementing this method, we obtain the canonical partition function for the polymerized systems and we show that our results are in good agreement with those arising from full quantum considerations. Using the partition function, we study the thermodynamics of quantum Schwarzschild black hole and we obtain corrections to the Bekenstein-Hawking entropy due to loop quantum gravity effects.

M. A. Gorji; Kourosh Nozari; B. Vakili

2014-05-18

357

Therapeutic Strategies Based on Polymeric Microparticles  

PubMed Central

The development of the field of materials science, the ability to perform multidisciplinary scientific work, and the need for novel administration technologies that maximize therapeutic effects and minimize adverse reactions to readily available drugs have led to the development of delivery systems based on microencapsulation, which has taken one step closer to the target of personalized medicine. Drug delivery systems based on polymeric microparticles are generating a strong impact on preclinical and clinical drug development and have reached a broad development in different fields supporting a critical role in the near future of medical practice. This paper presents the foundations of polymeric microparticles based on their formulation, mechanisms of drug release and some of their innovative therapeutic strategies to board multiple diseases. PMID:22665988

Vilos, C.; Velasquez, L. A.

2012-01-01

358

Charge-transfer magnetoelectrics of polymeric multiferroics.  

PubMed

The renaissance of multiferroics has yielded a deeper understanding of magneto-electric coupling of inorganic single-phase multiferroics and composites. Here, we report charge-transfer polymeric multiferroics, which exhibit external field-controlled magnetic, ferroelectric, and microwave response, as well as magneto-dielectric coupling. The charge-transfer-controlled ferroic properties result from the magnetic field-tunable triplet exciton which has been validated by the dynamic polaron-bipolaron transition model. In addition, the temperature-dependent dielectric discontinuity and electric-field-dependent polarization confirms room temperature ferroelectricity of crystalline charge-transfer polymeric multiferroics due to the triplet exciton, which allows the tunability of polarization by the photoexcitation. PMID:24654686

Qin, Wei; Jasion, Daniel; Chen, Xiaomin; Wuttig, Manfred; Ren, Shenqiang

2014-04-22

359

Therapeutic strategies based on polymeric microparticles.  

PubMed

The development of the field of materials science, the ability to perform multidisciplinary scientific work, and the need for novel administration technologies that maximize therapeutic effects and minimize adverse reactions to readily available drugs have led to the development of delivery systems based on microencapsulation, which has taken one step closer to the target of personalized medicine. Drug delivery systems based on polymeric microparticles are generating a strong impact on preclinical and clinical drug development and have reached a broad development in different fields supporting a critical role in the near future of medical practice. This paper presents the foundations of polymeric microparticles based on their formulation, mechanisms of drug release and some of their innovative therapeutic strategies to board multiple diseases. PMID:22665988

Vilos, C; Velasquez, L A

2012-01-01

360

Cooperative polymerization of one-patch colloids  

SciTech Connect

We numerically investigate cooperative polymerization in an off-lattice model based on a pairwise additive potential using particles with a single attractive patch that covers 30% of the colloid surface. Upon cooling, these particles self-assemble into small clusters which, below a density-dependent temperature, spontaneously reorganize into long straight tubes. We evaluate the partition functions of clusters of all sizes to provide an accurate description of the chemical reaction constants governing this process. Our calculations show that, for intermediate sizes, the partition functions retain contributions from two different structures, differing in both energy and entropy. We illustrate the microscopic mechanism behind the complex polymerization process in this system and provide a detailed evaluation of its thermodynamics.

Vissers, Teun; Smallenburg, Frank; Munaò, Gianmarco; Preisler, Zden?k; Sciortino, Francesco [Sapienza, Università di Roma, Piazzale Aldo Moro 2, 00185, Roma (Italy)] [Sapienza, Università di Roma, Piazzale Aldo Moro 2, 00185, Roma (Italy)

2014-04-14

361

Bimetallic complexes and polymerization catalysts therefrom  

DOEpatents

Group 3-6 or Lanthanide metal complexes possessing two metal centers, catalysts derived therefrom by combining the same with strong Lewis acids, Bronsted acid salts, salts containing a cationic oxidizing agent or subjected to bulk electrolysis in the presence of compatible, inert non-coordinating anions and the use of such catalysts for polymerizing olefins, diolefins and/or acetylenically unsaturated monomers are disclosed.

Patton, Jasson T. (Midland, MI); Marks, Tobin J. (Evanston, IL); Li, Liting (Evanston, IL)

2000-11-28

362

Experiment: Micro Dispersive Suspension Polymerization of MMA.  

E-print Network

Experiment: Micro Dispersive Suspension Polymerization of MMA. Procedures: 1. Prepare PVA solution of PDMS(50~90cst, MW=4000~6000) in a 20ml-vial c. Put 35ml of purified MMA in the 125ml-flask d. Put 15ml of hexane in the 20ml-vial e. Dissolve the LPO and PDMS f. Pour the PDMS-hexane solution into the LPO-MMA

Choi, Kyu Yong

363

Polymeric assemblies for sensitive colorimetric assays  

DOEpatents

The presently claimed invention relates to polymeric assemblies which visibly change color in the presence of analyte. In particular, the presently claimed invention relates to liposomes comprising a plurality of lipid monomers, which comprises a polymerizable group, a hydrophilic head group and a hydrophobic tail group, and one or more ligands. Overall carbon chain length, and polymerizable group positioning on the monomer influence color change sensitivity to analyte concentrations.

Charych, Deborah (Albany, CA)

2000-01-01

364

Terahertz Quality Control of Polymeric Products  

NASA Astrophysics Data System (ADS)

We report on experiments that evaluate the potential of terahertz (THz) time-domain spectroscopy (TDS) for quality control of polymeric compounds. We investigate specimens out of a polyethylene compound with silver-coated titanium dioxide nanospheres and a glass-fiber reinforced epoxy composite. We further examine an industrial polymer product produced by injection molding. Our data demonstrates that THz imaging is a powerful tool for contactless quality control in the polymer industry.

Rutz, Frank; Koch, Martin; Khare, Shilpa; Moneke, Martin; Richter, Heike; Ewert, Uwe

2006-04-01

365

X-ray microscopy of polymeric materials  

SciTech Connect

The authors describe how the scanning transmission x-ray microscope at Brookhaven National Laboratory can be used to investigate the bulk characteristics of polymeric materials with chemical sensitivity at a spatial resolution of about 50 nm. They present examples ranging from unoriented multiphase polymers to highly oriented Kevlar fibers. In the case of oriented samples, a dichroism technique is used to determine the orientation of specific chemical bonds. Extension of the technique to investigate surfaces of thick samples is discussed.

Ade, H.; Smith, A.P. [North Carolina State Univ., Raleigh, NC (United States). Dept. of Physics; Hsiao, B.; Cieslinski, R. [DuPont, Wilmington, DE (United States). Experimental Station; Mitchell, G. [Dow Chemical, Midland, MI (United States). Analytical Science Lab.; Rightor, E. [Dow Chemical, Freeport, TX (United States). Texas Polymer Center

1995-09-01

366

Biologically produced acid precipitable polymeric lignin  

DOEpatents

A water soluble, acid precipitable polymeric degraded lignin (APPL), having a molecular weight of at least 12,000 daltons, and comprising, by percentage of total weight, at least three times the number of phenolic hydroxyl groups and carboxylic acid groups present in native lignin. The APPL may be modified by chemical oxidation and reduction to increase its phenolic hydroxyl content and reduce the number of its antioxidant inhibitory side chains, thereby improving antioxidant properties.

Crawford, Don L. (Moscow, ID); Pometto, III, Anthony L. (Moscow, ID)

1984-01-01

367

Performance of selected polymeric materials on LDEF  

NASA Technical Reports Server (NTRS)

The NASA Long Duration Exposure Facility (LDEF) provided a unique environmental exposure of a wide variety of materials for potential advanced spacecraft application. This paper examines the molecular level response of selected polymeric materials which flew onboard this vehicle. Polymers include epolyimide, polysulfone, and polystyrene film and polyimide, polysulfone, and epoxy matrix resin/graphite fiber reinforced composites. Several promising experimental films were also studied. Most specimens received 5.8 years of low Earth orbital (LEO) exposure on LDEF. Several samples received on 10 months of exposure. Chemical characterization techniques included ultraviolet-visible and infrared spectroscopy, thermal analysis, x-ray photoelectron spectroscopy, and selected solution property measurements. Results suggest that many molecular level effects present during the first 10 months of exposure were not present after 5.8 years of exposure for specimens on or near Row 9. Increased AO fluence near the end of the mission likely eroded away much environmentally induced surface phenomena. The objective of this work is to provide fundamental information for use in improving the performance of polymeric materials for LEO application. A secondary objective is to gain an appreciation for the constraints and limitations of results from LDEF polymeric materials experiments.

Young, Philip R.; Slemp, Wayne S.; Stein, Bland A.

1993-01-01

368

Polymerization initated at sidewalls of carbon nanotubes  

NASA Technical Reports Server (NTRS)

The present invention is directed to aryl halide (such as aryl bromide) functionalized carbon nanotubes that can be utilized in anionic polymerization processes to form polymer-carbon nanotube materials with improved dispersion ability in polymer matrices. In this process the aryl halide is reacted with an alkyllithium species or is reacted with a metal to replace the aryl-bromine bond with an aryl-lithium or aryl-metal bond, respectively. It has further been discovered that other functionalized carbon nanotubes, after deprotonation with a deprotonation agent, can similarly be utilized in anionic polymerization processes to form polymer-carbon nanotube materials. Additionally or alternatively, a ring opening polymerization process can be performed. The resultant materials can be used by themselves due to their enhanced strength and reinforcement ability when compared to their unbound polymer analogs. Additionally, these materials can also be blended with pre-formed polymers to establish compatibility and enhanced dispersion of nanotubes in otherwise hard to disperse matrices resulting in significantly improved material properties. The resultant polymer-carbon nanotube materials can also be used in drug delivery processes due to their improved dispersion ability and biodegradability, and can also be used for scaffolding to promote cellular growth of tissue.

Tour, James M. (Inventor); Hudson, Jared L. (Inventor); Krishnamoorti, Ramanan (Inventor); Yurekli, Koray (Inventor); Mitchell, Cynthia A. (Inventor)

2011-01-01

369

Vector representation of tourmaline compositions  

NASA Technical Reports Server (NTRS)

The vector method for representing mineral compositions of amphibole and mica groups is applied to the tourmaline group. Consideration is given to the methods for drawing the relevant vector diagrams, relating the exchange vectors to one another, and contouring the diagrams for constant values of Na, Ca, Li, Fe, Mg, Al, Si, and OH. The method is used to depict a wide range of possible tourmaline end-member compositions and solid solutions, starting from a single point. In addition to vector depictions of multicomponent natural tourmalines, vectors are presented for simpler systems such as (Na,Al)-tourmalines, alkali-free tourmalines, and elbaites.

Burt, Donald M.

1989-01-01

370

Vector ecology of equine piroplasmosis.  

PubMed

Equine piroplasmosis is a disease of Equidae, including horses, donkeys, mules, and zebras, caused by either of two protozoan parasites, Theileria equi or Babesia caballi. These parasites are biologically transmitted between hosts via tick vectors, and although they have inherent differences they are categorized together because they cause similar pathology and have similar morphologies, life cycles, and vector relationships. To complete their life cycle, these parasites must undergo a complex series of developmental events, including sexual-stage development in their tick vectors. Consequently, ticks are the definitive hosts as well as vectors for these parasites, and the vector relationship is restricted to a few competent tick species. Because the vector relationship is critical to the epidemiology of these parasites, we highlight current knowledge of the vector ecology of these tick-borne equine pathogens, emphasizing tick transmissibility and potential control strategies to prevent their spread. PMID:25564746

Scoles, Glen A; Ueti, Massaro W

2015-01-01

371

Initial in vitro screening approach to investigate the potential health and environmental hazards of Envirox™ – a nanoparticulate cerium oxide diesel fuel additive  

PubMed Central

Nanotechnology is the new industrial revolution of the 21st Century as the various processes lead to radical improvements in medicine, manufacturing, energy production, land remediation, information technology and many other everyday products and applications. With this revolution however, there are undoubted concerns for health, safety and the environment which arise from the unique nature of materials and processes at the nanometre scale. The in vitro assays used in the screening strategy are all validated, internationally accepted protocols and provide a useful indication of potential toxicity of a chemical as a result of effects on various toxicological endpoints such as local site of contact (dermal) irritation, general cytotoxicity and mutagenicity. The initial in vitro screening strategy described in this paper to investigate the potential health implications, if any, which may arise following exposure to one specific application of nanoparticulate cerium oxide used as a diesel fuel borne catalyst, reflects a precautionary approach and the results will inform judgement on how best to proceed to ensure safe use. PMID:18053256

Park, Barry; Martin, Patricia; Harris, Chris; Guest, Robert; Whittingham, Andrew; Jenkinson, Peter; Handley, John

2007-01-01

372

Design, characterization, and aerosolization of organic solution advanced spray-dried moxifloxacin and ofloxacin dipalmitoylphosphatidylcholine (DPPC) microparticulate/nanoparticulate powders for pulmonary inhalation aerosol delivery  

PubMed Central

The aim of this study was to design and develop respirable antibiotics moxifloxacin (MOXI) hydrochloride and ofloxacin (OFLX) microparticles and nanoparticles, and multifunctional antibiotics particles with or without lung surfactant 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) for targeted dry powder inhalation delivery as a pulmonary nanomedicine. Particles were rationally designed and produced by advanced spray-drying particle engineering from an organic solution in closed mode (no water) from dilute solution. Scanning electron microscopy indicated that these particles had both optimal particle morphology and surface morphology, and the particle size distributions were suitable for pulmonary delivery. Comprehensive and systematic physicochemical characterization and in vitro aerosol dispersion performance revealed significant differences between these two fluoroquinolone antibiotics following spray drying as drug aerosols and as cospray-dried antibiotic drug: DPPC aerosols. Fourier transform infrared spectroscopy and confocal Raman microspectroscopy were employed to probe composition and interactions in the solid state. Spray-dried MOXI was rendered noncrystalline (amorphous) following organic solution advanced spray drying. This was in contrast to spray-dried OFLX, which retained partial crystallinity, as did OFLX:DPPC powders at certain compositions. Aerosol dispersion performance was conducted using inertial impaction with a dry powder inhaler device approved for human use. The present study demonstrates that the use of DPPC offers improved aerosol delivery of MOXI as cospray-dried microparticulate/nanoparticulate powders, whereas residual partial crystallinity influenced aerosol dispersion of OFLX and most of the compositions of OFLX:DPPC inhalation powders. PMID:24092972

Duan, Jinghua; Vogt, Frederick G; Li, Xiaojian; Hayes, Don; Mansour, Heidi M

2013-01-01

373

Initial in vitro screening approach to investigate the potential health and environmental hazards of Enviroxtrade mark - a nanoparticulate cerium oxide diesel fuel additive.  

PubMed

Nanotechnology is the new industrial revolution of the 21st Century as the various processes lead to radical improvements in medicine, manufacturing, energy production, land remediation, information technology and many other everyday products and applications. With this revolution however, there are undoubted concerns for health, safety and the environment which arise from the unique nature of materials and processes at the nanometre scale.The in vitro assays used in the screening strategy are all validated, internationally accepted protocols and provide a useful indication of potential toxicity of a chemical as a result of effects on various toxicological endpoints such as local site of contact (dermal) irritation, general cytotoxicity and mutagenicity.The initial in vitro screening strategy described in this paper to investigate the potential health implications, if any, which may arise following exposure to one specific application of nanoparticulate cerium oxide used as a diesel fuel borne catalyst, reflects a precautionary approach and the results will inform judgement on how best to proceed to ensure safe use. PMID:18053256

Park, Barry; Martin, Patricia; Harris, Chris; Guest, Robert; Whittingham, Andrew; Jenkinson, Peter; Handley, John

2007-01-01

374

Design, Characterization, and Aerosol Dispersion Performance Modeling of Advanced Spray-Dried Microparticulate/Nanoparticulate Mannitol Powders for Targeted Pulmonary Delivery as Dry Powder Inhalers  

PubMed Central

Abstract Background: The purpose was to design and characterize inhalable microparticulate/nanoparticulate dry powders of mannitol with essential particle properties for targeted dry powder delivery for cystic fibrosis mucolytic treatment by dilute organic solution spray drying, and, in addition, to tailor and correlate aerosol dispersion performance delivered as dry powder inhalers based on spray-drying conditions and solid-state physicochemical properties. Methods: Organic solution advanced spray drying from dilute solution followed by comprehensive solid-state physicochemical characterization and in vitro dry powder aerosolization were used. Results: The particle size distribution of the spray-dried (SD) powders was narrow, unimodal, and in the range of ?500?nm to 2.0??m. The particles possessed spherical particle morphology, relatively smooth surface morphology, low water content and vapor sorption (crystallization occurred at exposure above 65% relative humidity), and retention of crystallinity by polymorphic interconversion. The emitted dose, fine particle fraction (FPF), and respirable fraction (RF) were all relatively high. The mass median aerodynamic diameters were below 4??m for all SD mannitol aerosols. Conclusion: The in vitro aerosol deposition stage patterns could be tailored based on spray-drying pump rate. Positive linear correlation was observed between both FPF and RF values with spray-drying pump rates. The interplay between various spray-drying conditions, particle physicochemical properties, and aerosol dispersion performance was observed and examined, which enabled tailoring and modeling of high aerosol deposition patterns. PMID:24502451

Li, Xiaojian; Vogt, Frederick G.; Hayes, Don

2014-01-01

375

Polyoxometalate-Enhanced Oxidation of Organic Compounds by Nanoparticulate Zero-Valent Iron and Ferrous Ion in the Presence of Oxygen  

PubMed Central

In the presence of oxygen, organic compounds can be oxidized by zero-valent iron or dissolved Fe(II). However, this process is not a very effective means of degrading contaminants because the yields of oxidants are usually low (i.e., typically less than 5% of the iron added is converted into oxidants capable of transforming organic compounds). The addition of polyoxometalate (POM) greatly increases the yield of oxidants in both systems. The mechanism of POM enhancement depends on solution pH. Under acidic conditions, POM-mediates the electron transfer from nanoparticulate zero-valent iron (nZVI) or Fe(II) to oxygen, increasing the production of hydrogen peroxide, which is subsequently converted to hydroxyl radical through the Fenton reaction. At neutral pH values, iron forms a complex with POM, preventing iron precipitation on the nZVI surface and in bulk solution. At pH 7, the yield of oxidant approaches the theoretical maximum in the nZVI/O2 and the Fe(II)/O2 systems when POM is present, suggesting that coordination of iron by POM alters the mechanism of the Fenton reaction by converting the active oxidant from ferryl ion to hydroxyl radical. Comparable enhancements in oxidant yields are also observed when nZVI or Fe(II) are exposed to oxygen in the presence of silica-immobilized POM. PMID:18678027

Lee, Changha; Keenan, Christina R.; Sedlak, David L.

2008-01-01

376

Nanoparticulate Mn3O4/VGCF composite conversion-anode material with extraordinarily high capacity and excellent rate capability for lithium ion batteries.  

PubMed

In this work, highly conductive vapor grown carbon fiber (VGCF) was applied as an electrically conductive agent for facile synthesis of a nanoparticulate Mn3O4/VGCF composite material. This material exhibits super high specific capacity and excellent rate capability as a conversion-anode for lithium ion batteries. Rate performance test result demonstrates that at the discharge/charge current density of 0.2 A g(-1) a reversible capacity of ca. 950 mAh g(-1) is delivered, and when the current rate is increased to a high current density of 5 A g(-1), a reversible capacity of ca. 390 mAh g(-1) is retained. Cyclic performance examination conducted at the current density of 0.5 A g(-1) reveals that in the initial 20 cycles the reversible capacity decreases gradually from 855 to 747 mAh g(-1). However, since then, it increases gradually with cycle number increasing, and after 200 cycles an extraordinarily high reversible capacity of 1391 mAh g(-1) is achieved. PMID:25247688

Ma, Feng; Yuan, Anbao; Xu, Jiaqiang

2014-10-22

377

Polymeric micelles as drug carriers: their lights and shadows.  

PubMed

In this review, polymeric micelles as drug-targeting carriers are concisely explained. In the first introduction part, I describe a brief history of polymer micelle's research for drug targeting, and then I explain this review's focus. Since most other review articles concerning polymeric micelle carriers explain only what was achieved in the polymeric micelle's research, I describe this review by focusing on what was not done. In the second part, I take up three characteristics of polymeric micelle carriers by comparing their advantages and disadvantages, what was done and what was not done in the past studies, and what is easily achieved and what is difficult to be achieved with polymeric micelles. In the last part, I discuss three common problems of nano-sized drug carrier systems including polymeric micelles, and then I add a few comments on these problems. PMID:25012065

Yokoyama, Masayuki

2014-08-01

378

Measurement and Analysis of in vitro Actin Polymerization  

PubMed Central

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

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

2014-01-01

379

Progesterone withdrawal stimulates mammary gland tubulin polymerization in pregnant rats.  

PubMed

The size of the polymerized tubulin pool in mammary glands of late pregnant rats increased 2.4-fold 24 h after bilateral ovariectomy using a [3H]colchicine binding assay for tubulin. The total (free plus polymerized) tubulin concentration was not altered. Stimulation of tubulin polymerization as well as the induced rise in lactose content were both completely inhibited in rats that had been fitted with progesterone implants at the time of surgery. The increase in polymerized tubulin was not blocked by 17 beta-estradiol implants, although this treatment did partially inhibit the rise in tissue lactose following ovariectomy. The results indicate that increased polymerization during induced lactogenesis reflects a shift of free tubulin into the polymerized pool and that this shift is related to the withdrawal of progesterone. PMID:2986954

Loizzi, R F

1985-06-01

380

Vector potential photoelectron microscopy  

SciTech Connect

A new class of electron microscope has been developed for the chemical microanalysis of a wide range of real world samples using photoelectron spectroscopy. Highly structured, three-dimensional samples, such as fiber mats and fracture surfaces can be imaged, as well as insulators and magnetic materials. The new microscope uses the vector potential field from a solenoid magnet as a spatial reference for imaging. A prototype instrument has demonstrated imaging of uncoated silk, magnetic steel wool, and micron-sized single strand tungsten wires.

Browning, R. [R. Browning Consultants, 14 John Street, Shoreham, New York 11786 (United States)

2011-10-15

381

Vectoring: Steering a Plane  

NSDL National Science Digital Library

In this two part activity, learners work in pairs or individually to discover how vectoring the thrust from a jet engine affects movement of an airplane. In part one, learners construct an F-15 ACTIVE model with a balloon engine. In part two, learners conduct a series of experiments by changing the angle of the straw to control the direction of the thrust. This activity emphasizes the scientific method including prediction, observation, data collection, and analysis. This lesson plan includes background information, an extension and a sample worksheet.

2011-08-20

382

Vector potential photoelectron microscopy  

NASA Astrophysics Data System (ADS)

A new class of electron microscope has been developed for the chemical microanalysis of a wide range of real world samples using photoelectron spectroscopy. Highly structured, three-dimensional samples, such as fiber mats and fracture surfaces can be imaged, as well as insulators and magnetic materials. The new microscope uses the vector potential field from a solenoid magnet as a spatial reference for imaging. A prototype instrument has demonstrated imaging of uncoated silk, magnetic steel wool, and micron-sized single strand tungsten wires.

Browning, R.

2011-10-01

383

Aerodynamics of thrust vectoring  

NASA Technical Reports Server (NTRS)

Thrust vectoring as a means to enhance maneuverability and aerodynamic performane of a tactical aircraft is discussed. This concept usually involves the installation of a multifunction nozzle. With the nozzle, the engine thrust can be changed in direction without changing the attitude of the aircraft. Change in the direction of thrust induces a significant change in the aerodynamic forces on the aircraft. Therefore, this device can be used for lift-augmenting as well as stability and control purposes. When the thrust is deflected in the longitudinal direction, the lift force and the pitching stability can be manipulated, while the yawing stability can be controlled by directing the thrust in the lateral direction.

Tseng, J. B.; Lan, C. Edward

1989-01-01

384

Eliminating malaria vectors  

PubMed Central

Malaria vectors which predominantly feed indoors upon humans have been locally eliminated from several settings with insecticide treated nets (ITNs), indoor residual spraying or larval source management. Recent dramatic declines of An. gambiae in east Africa with imperfect ITN coverage suggest mosquito populations can rapidly collapse when forced below realistically achievable, non-zero thresholds of density and supporting resource availability. Here we explain why insecticide-based mosquito elimination strategies are feasible, desirable and can be extended to a wider variety of species by expanding the vector control arsenal to cover a broader spectrum of the resources they need to survive. The greatest advantage of eliminating mosquitoes, rather than merely controlling them, is that this precludes local selection for behavioural or physiological resistance traits. The greatest challenges are therefore to achieve high biological coverage of targeted resources rapidly enough to prevent local emergence of resistance and to then continually exclude, monitor for and respond to re-invasion from external populations. PMID:23758937

2013-01-01

385

Microemulsion polymerization of styrene initiated with gamma ray  

NASA Astrophysics Data System (ADS)

The styrene microemulsion with high monomer content was stabilized with a specially designed emulsifier with a branch in lipophilic head. In order to keep the microemulsion stable during polymerization, the microemulsion was initiated with gamma ray at room temperature. It was observed that there was an apparent plateau of polymerization rate during polymerization. It was the number of growing polymer particles instead of the total polymer particles being kept constant during the plateau. The polymerization kinetics showed some similarity to that in styrene microemulsion stabilized with SDS and n-pentanol.

Mangling, Xu; Xuewu, Ge; Zhicheng, Zhang; Zhichao, Wu; Manwei, Zhang

1997-04-01

386

Online observation of emulsion polymerization by fluorescence technique  

NASA Astrophysics Data System (ADS)

An online observation of local polarity via fluorescence spectroscopy was used to study the formation and growth of polymer particles during an emulsifier-free heterogeneous polymerization. The reaction mixture consisted of styrene dispersed in water and the polymerization was initiated by a macro-initiator (hydrolyzed propene-maleic acid copolymer with t-butyl perester groups). Pyrenyl probes were attached to the backbone of the initiator to analyze the heterogeneous reaction. The experimental results allow a clear distinction of different time regions during the heterogeneous polymerization. Information about the heating period, the latex formation, the particle growth and the final stage of the polymerization process (gel point) were obtained.

Rudschuck, S.; Adams, J.; Fuhrmann, J.

1999-05-01

387

Free Radical Polymerization of Styrene: A Radiotracer Experiment  

ERIC Educational Resources Information Center

Describes an experiment designed to acquaint the chemistry student with polymerization reactions, vacuum techniques, liquid scintillation counting, gas-liquid chromatography, and the handling of radioactive materials. (MLH)

Mazza, R. J.

1975-01-01

388

Assessing Long-term Reliability of Polymeric Housing Materials  

NASA Astrophysics Data System (ADS)

Application of polymeric materials for housing of outdoor insulators is expected to rapidly increase in the near future. However, the lifetime and the aging deterioration, owing to environmental conditions, are concerned. To understand the long-term reliability of the insulation performance of polymeric materials, the salt fog tests were performed on the polymeric insulators made of ethylene vinyl acetate (EVA) and silicone rubber (SiR). The hydrophobicity was also evaluated. The samples which 11 years have passed since the installation were taken away from an actual distribution system in the region where pollution condition was comparatively severe. The results indicated that the polymeric insulators had enough insulation performance.

Miyake, Takuma; Arata, Yoshihiro; Sakoda, Tatsuya; Otsubo, Masahisa; Sonoda, Yasufumi; Yamaguchi, Hiroshi

389

Biochemical Functionalization of Polymeric Cell Substrata Can Alter Mechanical Compliance  

E-print Network

of polymer multilayer films of nanoscale thickness, functionalized with RGD through different processing compliance of polymeric substrata such as weak polyelectrolyte multilayers (PEMs), increasingly utilized

Van Vliet, Krystyn J.

390

Microfluidic approaches to the synthesis of complex polymeric particles  

E-print Network

The synthesis of micron-sized polymeric particles with precise control over shape, monodispersity and chemistry is a technologically important objective. Varied applications including medical diagnostics. designer fabrics ...

Dendukuri, Dhananjay, 1978-

2007-01-01

391

Uptake of Nitroaromatic Compounds by Polymeric Tubing  

SciTech Connect

The type of polymeric material used in the manufacturing of tubing determines its strength, elasticity, and durability. Tubing made of polymeric material is commonly used for analytical work because it is readily available, inexpensive and can be relatively inert. Polymeric tubing is used in many sampling applications for explosive compounds. A major concern is the uptake of the explosive compounds into or onto the tubing during sampling. Because of the reactive nature of explosives, it is important that as little of the detectable explosive as possible is lost by tubing uptake. It is also important that nothing leaches out of the tubing to interfere with the detection of explosives. High Performance Liquid Chromatography (HPLC) is commonly used for the analysis of trace levels of explosive compounds in the range of parts per billion (ppb) to parts per million (ppm). This study attempts to determine which types of polymers are most conducive to sampling applications where large volumes of dilute explosive solutions are collected through a length of tubing for analysis. This was determined by analyzing the amount of explosive lost from solution per cm{sup 2} of tubing in solution. It was determined that tubing made of polyethylene, teflon, polypropylene, or KYNAR{reg_sign} is recommended for dilute trinitrotoluene (TNT) solution analyses. Tubing made of polypropylene, PHARMED{reg_sign}, KYNAR{reg_sign}, or polyethylene is recommended for analyses involving dilute explosive solutions of RDX. Tubing made from polyurethane, TYGON{reg_sign}, nylon, vinyl, gum rubber, or reinforced PVC are not recommended because they leach contaminants into solution that may interfere with HPLC analysis of explosive peaks.

BOUNKEUA, VIENGNGEUN; RODACY, PHILIP J.

2001-04-01

392

Targeting intracellular compartments by magnetic polymeric nanoparticles.  

PubMed

Superparamagnetic iron oxide nanoparticles (SPIONs) show a great promise for a wide specter of bioapplications, due to their characteristic magnetic properties exhibited only in the presence of magnetic field. Their advantages in the fields of magnetic drug targeting and imaging are well established and their safety is assumed, since iron oxide nanoparticles have already been approved for in vivo application, however, according to many literature reports the bare metal oxide nanoparticles may cause toxic effects on treated cells. Therefore, it is reasonable to prevent the direct interactions between metal oxide core and surrounding environment. In the current research ricinoleic acid coated maghemite nanoparticles were successfully synthesized, characterized and incorporated in the polymeric matrix, resulting in nanosized magnetic polymeric particles. The carrier system was shown to exhibit superparamagnetic properties and was therefore responsive towards external magnetic field. Bioevaluation using T47-D breast cancer cells confirmed internalization of magnetic polymeric nanoparticles (MNPs) and their intracellular localization in various subcellular compartments, depending on presence/absence of external magnetic field. However, the number of internalized MNPs observed by fluorescent and transmission electron microscopy was relatively low, making such way of targeting effective only for delivery of highly potent drugs. The scanning electron microscopy of treated cells revealed that MNPs influenced the cell adhesion, when external magnetic field was applied, and that treatment resulted in damaged apical plasma membrane right after exposure to the magnetic carrier. On the other hand, MNPs showed only reversibly reduced cellular metabolic activity in concentrations up to 200 ?g/ml and, in the tested concentration the cell cycle distribution was within the normal range, indicating safety of the established magnetic carrier system for the treated cells. PMID:23603023

Kocbek, Petra; Kralj, Slavko; Kreft, Mateja Erdani; Kristl, Julijana

2013-09-27

393

Light-Driven Polymeric Bimorph Actuators  

NASA Technical Reports Server (NTRS)

Light-driven polymeric bimorph actuators are being developed as alternatives to prior electrically and optically driven actuators in advanced, highly miniaturized devices and systems exemplified by microelectromechanical systems (MEMS), micro-electro-optical-mechanical systems (MEOMS), and sensor and actuator arrays in smart structures. These light-driven polymeric bimorph actuators are intended to satisfy a need for actuators that (1) in comparison with the prior actuators, are simpler and less power-hungry; (2) can be driven by low-power visible or mid-infrared light delivered through conventional optic fibers; and (3) are suitable for integration with optical sensors and multiple actuators of the same or different type. The immediate predecessors of the present light-driven polymeric bimorph actuators are bimorph actuators that exploit a photorestrictive effect in lead lanthanum zirconate titanate (PLZT) ceramics. The disadvantages of the PLZT-based actuators are that (1) it is difficult to shape the PLZT ceramics, which are hard and brittle; (2) for actuation, it is necessary to use ultraviolet light (wavelengths < 380 nm), which must be generated by use of high-power, high-pressure arc lamps or lasers; (3) it is difficult to deliver sufficient ultraviolet light through conventional optical fibers because of significant losses in the fibers; (4) the response times of the PLZT actuators are of the order of several seconds unacceptably long for typical applications; and (5) the maximum mechanical displacements of the PLZT-based actuators are limited to those characterized by low strains beyond which PLZT ceramics disintegrate because of their brittleness. The basic element of a light-driven bimorph actuator of the present developmental type is a cantilever beam comprising two layers, at least one of which is a polymer that exhibits a photomechanical effect (see figure). The dominant mechanism of the photomechanical effect is a photothermal one: absorption of light energy causes heating, which, in turn, causes thermal expansion.

Adamovsky, Gregory; Sarkisov, Sergey S.; Curley, Michael J.

2009-01-01

394

Living Carbocationic Polymerization. XXIII. Analysis of Slow Initiation in Living Isobutylene Polymerization  

Microsoft Academic Search

The aim of this research was to develop a quantitative treatment of the consequences of relatively slow initiation on Mn and N (the number of molecules formed, Wp\\/Mn, where Wp=weight of polymer formed) in living carbocationic polymerizations, particularly for the case of the incremental monomer addition (IMA) technique. This has been achieved by analysis of the effect of initiator efficiency

M. Zsuga; J. P. Kennedy; T. Kelen

1989-01-01

395

Thio-amide functionalized polymers via polymerization or post-polymerization modification  

NASA Astrophysics Data System (ADS)

Decreasing supplies of fresh water and increasing population necessitates development of advanced water cleaning technologies, which would facilitate the removal of water pollutants. Amongst the worst of such contaminants are heavy metals and cyanides, infamous for their high toxicity. To assist the water purification processes, we aim to synthesize functionalized macromolecules that would contribute in the decontamination processes by scavenging detrimental chemicals. Epitomizing this role thio-amide unit features remarkable chemical flexibility that facilitates reversible catch-release of the ions, where the behavior controlled by subtle red-ox changes in the environment. Chemical tunability of the thio-amide moiety enables synthesis of thio-amide based monomers and post-polymerization modification agents. Two distinct synthetic pathways, polymerization and post-polymerization modification, have been exploited, leading to functional thioamide-based macromolecules: thioamide-monomers were copolymerized with N-isopropylacrylamide and post-polymerization modifications of poly(dimethylaminoethyl methacrylate) and poly(propargyl methacrylate) were accomplished via quarternization and "click" reactions, respectively.

Ozcam, Ali; Henke, Adam; Stibingerova, Iva; Srogl, Jiri; Genzer, Jan

2011-03-01

396

Polymerization of formic acid under high pressure  

SciTech Connect

We report Raman, infrared, and x-ray diffraction (XRD) measurements, along with ab initio calculations on formic acid (FA) under pressure up to 50 GPa. We find an infinite chain Pna2{sub 1} structure to be a high-pressure phase at room temperature. Our data indicate the symmetrization and a partially covalent character of the intrachain hydrogen bonds above approximately 20 GPa. Raman spectra and XRD patterns indicate a loss of long-range order at pressures above 40 GPa, with a large hysteresis upon decompression. We attribute this behavior to a three-dimensional polymerization of FA.

Goncharov, A.F.; Manaa, M.R.; Zaug, J.M.; Gee, R.H.; Fried, L.E.; Montgomery, W.B. (UCB); (LLNL)

2010-07-19

397

Space environmental effects on polymeric materials  

NASA Technical Reports Server (NTRS)

Polymer-matrix composites have considerable potential for use in the construction of orbiting structures such as the space station and space antennas because of their light weight, high strength, and low thermal expansion. However, they can suffer surface erosion by interaction with atomic oxygen in low-Earth orbit and degradation and/or embrittlement by electrons and ultraviolet radiation especially in geosynchronous orbit. Thus, a study of the effect of these environmental hazards on polymeric materials is an important step in the assessment of such materials for future use in space.

Kiefer, Richard L.; Orwoll, Robert A.

1988-01-01

398

Heat flux concentration through polymeric thermal lenses  

NASA Astrophysics Data System (ADS)

A significant contributor to energy inefficiency is the generation as well as the uneven dissipation of heat. Practical methods to adeptly channel heat flux (Q) would then have widespread applications to improved energy utilization and thermal energy management. It would be beneficial to engineer lens-like composite materials (graded in terms of length or thermal conductivity) with augmented attributes for heat control. Here, we propose and demonstrate polymeric composite based Q focusing lenses, architected through geometrical considerations. We indicate a five-fold enhancement of the Q, at the level of ˜2500 W/m2, enabled through such thermal lenses.

Kapadia, R. S.; Bandaru, P. R.

2014-12-01

399

Functional Lactide Monomers: Methodology and Polymerization  

PubMed Central

Side-chain functionalized lactide analogues have been synthesized from commercially available amino acids and polymerized using stannous octoate as a catalyst. The synthetic strategy presented allows for the incorporation of any protected amino acid for the preparation of functionalized diastereomerically pure lactide monomers. The resulting functionalized cyclic monomers can be homopolymerized, and copolymerized with lactides, then quantitatively deprotected forming new functional poly(lactide)-based materials. This strategy allows for the introduction of functional groups along a poly(lactide) (PLA) backbone that after deprotection can be viewed as chemical handles for further functionalization of PLA, yielding improved biomaterials for a variety of applications. PMID:16768392

Gerhardt, Warren W.; Noga, David E.; Hardcastle, Kenneth I.; García, Andrés J.; M. Collard, David; Weck, Marcus

2008-01-01

400

Vapor Deposited Polymeric-Organic Composite Films  

NASA Astrophysics Data System (ADS)

Over the past few years, polymeric films have played an important role in advanced IC technologies and optoelectronics. In depositing these polymeric films with tailorable and desired properties, vapor deposition techniques have potential advantages over spin-on techniques. This thesis explores the vapor deposition of polymeric-organic composite films, and investigates the resulted Nm's composition, structure and electro-optic (EO) effect. The source materials chosen are the newly commercialized polymer, Teflon AF ^circler, and the highly nonlinear organic chromophore, N,N-dimethyl aminonitrostilbene (DANS). We developed a novel two-step deposition process to fabricate smooth and uniform Teflon AF films using a physical vapor deposition technique. These films are found to be chemically equivalent to the spin-on films and source material. The films are always amorphous, but their morphology depends greatly on the deposition conditions. We successfully co-deposited Teflon AF-DANS polymeric -organic composite films with large EO effects, which, to our knowledge, is the first to be reported for a vapor deposited composite EO film. A mathematical procedure to determine the composition of the composite films using x-ray photoelectron spectroscopy (XPS) was developed, and the compositions, structures, and electro-optic effects of the composite films were investigated. We find that Teflon AF-DANS composite films remain amorphous and there is no interaction between Teflon AF and DANS components when the DANS density is below 10%. The films behave as a pure guest-host system with the DANS molecules dispersed in a Teflon AF matrix, the increase of electro-optic effects following a DANS composition increase. At DANS concentrations of 10%, the EO coefficient reaches its maximum value of about 2.4 pm/V, which is close to that predicted by theory. The decrease and disappearance of EO effects in the films with high DANS density are believed to be caused by an anti -pair effect and phase separation since the DANS anti-pairs and DANS crystallites have no contribution to EO effect. The anti-pair effect can begin to manifest at concentration of 10% DANS due to the dipole-dipole interaction among highly polar DANS molecules, and phase separation is found in films containing more than 25% DANS.

Ma, Xinfa

1995-11-01

401

Studies of molecular properties of polymeric materials  

NASA Technical Reports Server (NTRS)

Aerospace environment effects (high energy electrons, thermal cycling, atomic oxygen, and aircraft fluids) on polymeric and composite materials considered for structural use in spacecraft and advanced aircraft are examined. These materials include Mylar, Ultem, and Kapton. In addition to providing information on the behavior of the materials, attempts are made to relate the measurements to the molecular processes occurring in the material. A summary and overview of the technical aspects are given along with a list of the papers that resulted from the studies. The actual papers are included in the appendices and a glossary of technical terms and definitions is included in the front matter.

Harries, W. L.; Long, Sheila Ann T.; Long, Edward R., Jr.

1990-01-01

402

Phase transformations in pressure polymerized C 60  

NASA Astrophysics Data System (ADS)

Differential Scanning Calorimetry and infra-red spectroscopy have been used to study the depolymerization of the two pressure polymerized phases of C 60, i.e., rhombohedral (R) and orthorhombic (O) into monomeric C 60 at p=1 atm. The depolymerization enthalpies obtained were 10.3 ± 0.5 and 20.1 ± 0.6 kJ/mol for R-, O-phases, respectively. The R-phase, prepared at 1025-1050 K and 6 GPa ('magnetic carbon') demonstrated the depolymerization behaviour, similar to the typical R-phase. Part of the p- T-phase diagram of C 60 was sketched in, using experimental and literature data.

Korobov, M. V.; Senyavin, V. M.; Bogachev, A. G.; Stukalin, E. B.; Davydov, V. A.; Kashevarova, L. S.; Rakhmanina, A. V.; Agafonov, V.; Szwarc, A.

2003-11-01

403

Durability of Polymeric Glazing and Absorber Materials  

SciTech Connect

The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes. We have begun evaluation of several new UV-screened polycarbonate sheet glazing constructions. This has involved interactions with several major polymer industry companies to obtain improved candidate samples. Proposed absorber materials were tested for UV resistance, and appear adequate for unglazed ICS absorbers.

Jorgensen, G.; Terwilliger, K.; Bingham, C.; Lindquist, C.; Milbourne, M.

2005-11-01

404

DIPLOMA THESIS VECTOR ANTENNA FOR  

E-print Network

Polarization 10 3 Design Considerations for the Vector Antenna 11 3.1 Vector Antenna 11 3.2 Determining.5 Antenna Loss Resistance 14 3.6 Determining the Operation Frequency for the Vector Antenna 16 3.7 Design.1 Mechanical Considerations for Design 19 4.2 The Cover of the Antenna 19 4.3 The material for the Antennas 20

405

Solar imaging vector magnetograph  

NASA Technical Reports Server (NTRS)

This report describes an instrument which has been constructed at the University of Hawaii to make observations of the magnetic field in solar active regions. Detailed knowledge of active region magnetic structures is crucial to understanding many solar phenomena, because the magnetic field both defines the morphology of structures seen in the solar atmosphere and is the apparent energy source for solar flares. The new vector magnetograph was conceived in response to a perceived discrepancy between the capabilities of X ray imaging telescopes to be operating during the current solar maximum and those of existing magnetographs. There were no space-based magnetographs planned for this period; the existing ground-based instruments variously suffered from lack of sensitivity, poor time resolution, inadequate spatial resolution or unreliable sites. Yet the studies of flares and their relationship to the solar corona planned for the 1991-1994 maximum absolutely required high quality vector magnetic field measurements. By 'vector' measurements we mean that the observation attempts to deduce the complete strength and direction of the field at the measurement site, rather than just the line of sight component as obtained by a traditional longitudinal magnetograph. Knowledge of the vector field permits one to calculate photospheric electric currents, which might play a part in heating the corona, and to calculate energy stored in coronal magnetic fields as the result of such currents. Information about the strength and direction of magnetic fields in the solar atmosphere can be obtained in a number of ways, but quantitative data is best obtained by observing Zeeman-effect polarization in solar spectral lines. The technique requires measuring the complete state of polarization at one or more wavelengths within a magnetically sensitive line of the solar spectrum. This measurement must be done for each independent spatial point for which one wants magnetic field data. All the measurements need to be done in a time short compared to the time scale for changes of the solar features being observed. Were it possible, one would want to record all the needed data simultaneously, since temporal variation of atmospheric seeing degrades both the image and the polarization sensitivity. Since the measurements must span four dimensions, two spatial plus polarization and wavelength, we had some freedom to design the instrument to favor some dimensions over others in terms of simultaneity. Our earlier instrument, the Haleakala Stokes Polarimeter, records a range of wavelengths spanning two spectral lines in each reading, but requires two seconds to determine the polarization state and obtains spatial information only by assembling a long sequence of measurements at single locations on the sun. The new instrument sacrifices spectral detail and accuracy in favor of greatly improved imaging characteristics. The scientific goals for this instrument were to measure surface magnetic fields with enough accuracy to permit calculations of photospheric currents, but with a field of view covering an entire typical active region, high spatial resolution, and a fast enough temporal cadence for detecting flare-associated changes in magnetic structures.

Canfield, Richard C.

1993-01-01

406

40 CFR 721.10568 - Diethanolamine salt of polymeric acid (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Diethanolamine salt of polymeric acid (generic). 721...Substances § 721.10568 Diethanolamine salt of polymeric acid (generic). (a...identified generically as diethanolamine salt of polymeric acid (PMN...

2013-07-01

407

Novel solid redox polymerization electrodes; Electrochemical properties  

SciTech Connect

In this paper the generic redox reaction of a class of linear sulfur-containing redox polymerization electrodes is described by (SRS){sub n} + n (2e{sup {minus}}) {r reversible} n (SRS), the polymer electrode which can be progressively depolymerized, leading ultimately to monomeric anions, as the sulfur-sulfur bridges between the organic R groups are cleaved during discharge and then the monomer anions can be subsequently reoxidized back to the original polymer during charge. This is the first time the process of electrodepolmerization-electropolymerization has been exploited for energy storage, establishing a broad class of chemically flexible, low equivalent weight, and inexpensive electrodes for advanced batteries. Electrochemical investigation of a diverse group of novel solid redox polymerization electrodes indicates that these materials are excellent candidates for all-solid-state, thin-film, energy-storage systems. some of the advantages offered by the batteries based on these materials include high energy density and rate capability, extensive utilization of positive electrode capacity, ease of fabrication, low cost, and superior reliability, and safety.

Liu, M. (Ceramatec, Inc., Salt Lake City, UT (United States)); Visco, S.J.; De Jonghe, L.C. (Lawrence Berkeley Lab., CA (United States). Materials and Chemical Sciences Div.)

1991-07-01

408

Functionalized nanoparticle interactions with polymeric membranes  

PubMed Central

A series of experiments was performed to measure the retention of a class of functionalized nanoparticles (NPs) onporous (microfiltration and ultrafiltration) membranes. The findings impact engineered water and wastewater treatment using membrane technology, characterization and analytical schemes for NP detection, and the use of NPs in waste treatment scenarios. The NPs studied were composed of silver, titanium dioxide, and gold; had organic coatings to yield either positive or negative surface charge; and were between 2 and 10 nm in diameter. NP solutions were applied to polymeric membranes composed of different materials and pore sizes (ranging from ~2 nm [3 kDa molecular weight cutoff] to 0.2 ?m). Greater than 99% rejection was observed of positively charged NPs by negatively charged membranes even though pore diameters were up to 20 times the NP diameter; thus, sorption caused rejection. Negatively charged NPs were less well rejected, but behavior was dependant not only on surface functionality but on NP core material (Ag, TiO2, or Au). NP rejection depended more upon NP properties than membrane properties; all of the negatively charged polymeric membranes behaved similarly. The NP-membrane interaction behavior fell into four categories, which are defined and described here. PMID:22177020

Ladner, D.A.; Steele, M.; Weir, A.; Hristovski, K.; Westerhoff, P.

2011-01-01

409

Crystallization of calcium sulfate on polymeric surfaces.  

PubMed

Surface crystallization of calcium sulfate dihydrate (gypsum) on a series of polymeric surfaces was studied using a quartz microbalance system. Polyelectrolyte multilayer films (positively and negatively charged surfaces) were formed on the quartz crystal microbalance (QCM) sensors utilizing a layer-by-layer spin-assembly method. The kinetics of gypsum surface crystallization was quantified in terms of the evolution of gypsum mineral scale on the different surfaces. For comparison mineral scaling was also evaluated on silica and polyamide surfaces. For surfaces of the same charge polarity (+/-), the mass density of gypsum scale was lower (PSSpolymeric surfaces via alteration of surface both surface topography and chemistry. In this regards, an expanded systematic study is needed in order to quantitatively clarify the interplay between the above two factors in controlling surface crystallization. PMID:21316694

Lin, Nancy H; Shih, Wen-Yi; Lyster, Eric; Cohen, Yoram

2011-04-15

410

Predicting Polymeric Crystal Structures by Evolutionary Algorithms  

E-print Network

The recently developed evolutionary algorithm USPEX proved to be a tool that enables accurate and reliable prediction of structures for a given chemical composition. Here we extend this method to predict the crystal structure of polymers by performing constrained evolutionary search, where each monomeric unit is treated as one or several building blocks with fixed connectivity. This greatly reduces the search space and allows the initial structure generation with different sequences and packings using these blocks. The new constrained evolutionary algorithm is successfully tested and validated on a diverse range of experimentally known polymers, namely polyethylene (PE), polyacetylene (PA), poly(glycolic acid) (PGA), poly(vinyl chloride) (PVC), poly(oxymethylene) (POM), poly(phenylene oxide) (PPO), and poly (p-phenylene sulfide) (PPS). By fixing the orientation of polymeric chains, this method can be further extended to predict all polymorphs of poly(vinylidene fluoride) (PVDF), and the complex linear polymer crystals, such as nylon-6 and cellulose. The excellent agreement between predicted crystal structures and experimentally known structures assures a major role of this approach in the efficient design of the future polymeric materials.

Qiang Zhu; Vinit Sharma; Artem R Oganov; Rampi Ramprasad

2014-06-05

411

Macrocyclic and polymeric oxaziridine-derivatives.  

PubMed

Macrocyclic and polymeric imines 5,5' and 6,6' are obtained in excellent yields by template-free polycondensation of 1,6-bis(4-formylbenzoyloxy)hexane (1) with commercially available 4,4'-methylene-bis(cyclohexylamine) (2) and with bis(2-amino-2-methylprop-1-yl)adipate dihydrochloride (4), respectively. The degree of macrocyclization during imine synthesis strongly depends on the diamine. Matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) mass spectrometry analysis and gel permeation chromatography (GPC) measurements show that (2) leads to more macrocyclic adducts than (4). The subsequent meta-chloroperoxybenzoic acid oxidation of polyimines 5,5' and 6,6' ($ \\bar M_{\\rm n} $ = 1650-11 200 g mol(-1) , $ \\bar M_{\\rm w} $ = 3800-27 350 g mol(-1) ) yields the corresponding polyoxaziridines 7,7' and 8,8' consisting of macrocyclic and linear polymeric structures ($ \\bar M_{\\rm n} $ = 1750-8050 g mol(-1) , $ \\bar M_{\\rm w} $ = 3250-15 800 g mol(-1) ). The synthesized polyoxaziridines are relatively stable and storable at room temperature. PMID:23307394

Dickmeis, Marcus; Cinar, Hakan; Ritter, Helmut

2013-02-12

412

Progress towards the synthesis of polymeric nitrogen  

SciTech Connect

Current conventional energetic compounds rely on strong covalent bonds within individual molecules for energy storage. A new class of energetic compounds has been recently proposed that entirely replaces weak van der Waals interactions with strong covalent bonds arranged in a continuous, uniform network, thus tremendously enhancing the energy per volume. In particular, recent theoretical calculations have suggested that a phosphorus-like or polymeric form of nitrogen may exist metastably at atmospheric pressure as a hard, insulating solid with an enhanced energy per unit volume. It is predicted that the polymeric phase of nitrogen should be stable at high pressure. And therefore the megabar diamond anvil cell might provide the ideal vehicle for carrying out proof-of-existence experiments. currently, the authors are bringing to bear technologies for achieving multimegabar pressures and temperatures of several thousand K. These conditions are necessary to rearrange the bonds of strongly covalent systems into highly energetic configurations. There is no doubt that the transformations will show strong hysteresis making the initial synthesis difficult, but for these very same reasons, these new compounds potentially will be metastable at ambient conditions in their energetic state. They discuss their results and progress to date, indicating that they are well on their way to understanding the high pressure equation-of-state of sold N{sub 2}.

Lorenzana, H.E.; McMahan, A.K.; Yoo, C.S.; Barbee, T.W. III

1994-06-01

413

Space environmental effects on polymeric materials  

NASA Technical Reports Server (NTRS)

Two of the major environmental hazards in the Geosynchronous Earth Orbit (GEO) are energetic charged particles and ultraviolet radiation. The charged particles, electrons and protons, range in energy from 0.1 to 4 MeV and each have a flux of 10 to the 8th sq cm/sec. Over a 30 year lifetime, materials in the GEO will have an absorbed dose from this radiation of 10 to the 10th rads. The ultraviolet radiation comes uninhibited from the sun with an irradiance of 1.4 kw/sq m. Radiation is known to initiate chain sission and crosslinking in polymeric materials, both of which affect their structural properties. The 30-year dose level from the combined radiation in the GEO exceeds the threshold for measurable damage in most polymer systems studied. Of further concern is possible synergistic effects from the simultaneous irradiation with charged particles and ultraviolet radiation. Most studies on radiation effects on polymeric materials use either electrons or ultraviolet radiation alone, or in a sequential combination.

Kiefer, Richard L.; Orwoll, Robert A.

1988-01-01

414

Strong liquid-crystalline polymeric compositions  

DOEpatents

Strong liquid-crystalline polymeric (LCP) compositions of matter are described. LCP backbones are combined with liquid crystalline (LC) side chains in a manner which maximizes molecular ordering through interdigitation of the side chains, thereby yielding materials which are predicted to have superior mechanical properties over existing LCPs. The theoretical design of LCPs having such characteristics includes consideration of the spacing distance between side chains along the backbone, the need for rigid sections in the backbone and in the side chains, the degree of polymerization, the length of the side chains, the regularity of the spacing of the side chains along the backbone, the interdigitation of side chains in sub-molecular strips, the packing of the side chains on one or two sides of the backbone to which they are attached, the symmetry of the side chains, the points of attachment of the side chains to the backbone, the flexibility and size of the chemical group connecting each side chain to the backbone, the effect of semiflexible sections in the backbone and the side chains, and the choice of types of dipolar and/or hydrogen bonding forces in the backbones and the side chains for easy alignment. 27 figures.

Dowell, F.

1993-12-07

415

Strong liquid-crystalline polymeric compositions  

DOEpatents

Strong liquid-crystalline polymeric (LCP) compositions of matter. LCP backbones are combined with liquid crystalline (LC) side chains in a manner which maximizes molecular ordering through interdigitation of the side chains, thereby yielding materials which are predicted to have superior mechanical properties over existing LCPs. The theoretical design of LCPs having such characteristics includes consideration of the spacing distance between side chains along the backbone, the need for rigid sections in the backbone and in the side chains, the degree of polymerization, the length of the side chains, the regularity of the spacing of the side chains along the backbone, the interdigitation of side chains in sub-molecular strips, the packing of the side chains on one or two sides of the backbone to which they are attached, the symmetry of the side chains, the points of attachment of the side chains to the backbone, the flexibility and size of the chemical group connecting each side chain to the backbone, the effect of semiflexible sections in the backbone and the side chains, and the choice of types of dipolar and/or hydrogen bonding forces in the backbones and the side chains for easy alignment.

Dowell, Flonnie (Los Alamos, NM)

1993-01-01

416

Polymerization of nitrogen in sodium azide  

NASA Astrophysics Data System (ADS)

The high-pressure behavior of nitrogen in NaN3 was studied to 160 GPa at 120-3300 K using Raman spectroscopy, electrical conductivity, laser heating, and shear deformation methods. Nitrogen in sodium azide is in a molecularlike form; azide ions N3- are straight chains of three atoms linked with covalent bonds and weakly interact with each other. By application of high pressures we strongly increased interaction between ions. We found that at pressures above 19 GPa a new phase appeared, indicating a strong coupling between the azide ions. Another transformation occurs at about 50 GPa, accompanied by the appearance of new Raman peaks and a darkening of the sample. With increasing pressure, the sample becomes completely opaque above 120 GPa, and the azide molecular vibron disappears, evidencing completion of the transformation to a nonmolecular nitrogen state with amorphouslike structure which crystallizes after laser heating up to 3300 K. Laser heating and the application of shear stress accelerates the transformation and causes the transformations to occur at lower pressures. These changes can be interpreted in terms of a transformation of the azide ions to larger nitrogen clusters and then polymeric nitrogen net. The polymeric forms can be preserved on decompression in the diamond anvil cell but transform back to the starting azide and other new phases under ambient conditions.

Eremets, M. I.; Popov, M. Yu.; Trojan, I. A.; Denisov, V. N.; Boehler, R.; Hemley, R. J.

2004-06-01

417

Predicting polymeric crystal structures by evolutionary algorithms  

NASA Astrophysics Data System (ADS)

The recently developed evolutionary algorithm USPEX proved to be a tool that enables accurate and reliable prediction of structures. Here we extend this method to predict the crystal structure of polymers by constrained evolutionary search, where each monomeric unit is treated as a building block with fixed connectivity. This greatly reduces the search space and allows the initial structure generation with different sequences and packings of these blocks. The new constrained evolutionary algorithm is successfully tested and validated on a diverse range of experimentally known polymers, namely, polyethylene, polyacetylene, poly(glycolic acid), poly(vinyl chloride), poly(oxymethylene), poly(phenylene oxide), and poly (p-phenylene sulfide). By fixing the orientation of polymeric chains, this method can be further extended to predict the structures of complex linear polymers, such as all polymorphs of poly(vinylidene fluoride), nylon-6 and cellulose. The excellent agreement between predicted crystal structures and experimentally known structures assures a major role of this approach in the efficient design of the future polymeric materials.

Zhu, Qiang; Sharma, Vinit; Oganov, Artem R.; Ramprasad, Ramamurthy

2014-10-01

418

Novel silicon and tin alloy nano-particulate materials via spark erosion for high performance and high capacity anodes in lithium ion batteries  

NASA Astrophysics Data System (ADS)

The advent and popularity of portable electronics, as well as the need to reduce carbon-based fuel dependence for environmental and economic reasons, has led to the search for higher energy density portable power storage methods. Lithium ion batteries offer the highest energy density of any portable energy storage technology, but their potential is limited by the currently used materials. Theoretical capacities of silicon (3580 mAh/g) and tin (990 mAh/g) are significantly higher than existing graphitic anodes (372 mAh/g). However, silicon and tin must be scaled down to the nano-level to mitigate the pulverization from drastic volume changes in the anode structure during lithium ion insertion/extraction. The available synthesis techniques for silicon and tin nano-particles are complicated and scale-up is costly. A unique one-step process for synthesizing Si-Sn alloy and Sn nano-particles via spark plasma erosion has been developed to achieve the ideal nano-particulate size and carbon coating architecture. Spark erosion produces crystalline and amorphous spherical nano-particles, averaging 5-500nm in diameter. Several tin and silicon alloys have been spark eroded and thoroughly characterized using SEM, TEM, EDS, XPS, Auger spectroscopy, NMR spectroscopy and TGA. The resulting nano-particles show improved performance as anodes over commercialized materials. In particular, pure sparked Sn particles show stable reversible capacity at ˜460 mAh/g with >99.5% coulombic efficiency for over 100 cycles. These particles are drop-in ready for existing commercial anode processing techniques and by only adding 10% of the sparked Sn particles the total current cell capacity will increase by ˜13%.

White, Emma Marie Hamilton

419

Choose your models wisely: how different murine bone marrow-derived dendritic cell protocols influence the success of nanoparticulate vaccines in vitro.  

PubMed

Dendritic cell (DC)-based cancer vaccination has shown great potential in cancer immunotherapy. As a result, novel nanoparticles aiming to load DCs with tumor antigens are being developed and evaluated in vitro. For this, murine bone marrow-derived DCs (BM-DCs) are most commonly used as model DCs. However, many different protocols exist to generate these cells. Therefore, we investigated to what extent different BM-DC culture protocols impact on the immunobiology of the cells, as well as their response to particulate antigens. We evaluated 4 different BM-DC protocols with 2 main variables: bovine serum and cytokine combinations. Our results show distinct differences in yield, phenotypical maturation status and the production of immune stimulatory and immune suppressive cytokines by the different BM-DCs. Importantly, we demonstrate that the antigen-loading of these different BM-DCs via transfection with mRNA lipoplexes results in large differences in transfection efficiency as well as in the capacity of mRNA-transfected BM-DCs to stimulate antigen-specific T cells. Thus, it is clear that the BM-DC model can have significant confounding effects on the evaluation of novel nanoparticulate vaccines. To take this into account when testing novel particulate antigen-delivery systems in BM-DC models, we propose to (1) perform a thorough immunological characterization of the BM-DCs and to (2) not only judge a particle's potential for cancer vaccination based on transfection efficiency, but also to include an evaluation of functional end-points such as T cell activation. PMID:24960224

Dewitte, Heleen; Verbeke, Rein; Breckpot, Karine; Vandenbroucke, Roosmarijn E; Libert, Claude; De Smedt, Stefaan C; Lentacker, Ine

2014-12-10

420

Organic-coated nanoparticulate zero valent iron for remediation of chemical oxygen demand (COD) and dissolved metals from tropical landfill leachate.  

PubMed

The use of nanoparticulate zero valent iron (NZVI) in the treatment of inorganic contaminants in landfill leachate and polluted plumes has been the subject of many studies, especially in temperate, developed countries. However, NZVI's potential for reduction of chemical oxygen demand (COD) and treatment of metal ion mixtures has not been explored in detail. We investigated the efficiency of NZVI synthesized in the presence of starch, mercaptoacetic, mercaptosuccinic, or mercaptopropenoic acid for the reduction of COD, nutrients, and metal ions from landfill leachate in tropical Sri Lanka. Synthesized NZVI were characterized with X-ray diffraction (XRD), transmission electron microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), thermal gravimetric analysis, Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller. Of the samples tested, Starch-NZVI (S-NZVI) and mercaptoacetic-NZVI (MA-NZVI) performed well for treatment both COD and metal mixture. The removal percentages for COD, nitrate-nitrogen, and phosphate from S-NZVI were 50, 88, and 99 %, respectively. Heavy metal removal was higher in S-NZVI (>95 %) than others. MA-NZVI, its oxidation products, and functional groups of its coating showed the maximum removal amounts for both Cu (56.27 mg g(-1)) and Zn (28.38 mg g(-1)). All mercapto-NZVI showed well-stabilized nature under FTIR and XRD investigations. Therefore, we suggest mercapto acids as better agents to enhance the air stability for NZVI since chemically bonded thiol and carbonyl groups actively participation for stabilization process. PMID:24535668

Wijesekara, S S R M D H R; Basnayake, B F A; Vithanage, Meththika

2014-06-01

421

Polymeric micelles – a new generation of colloidal drug carriers  

Microsoft Academic Search

Polymeric micelles have recently emerged as a novel promising colloidal carrier for the targeting of poorly water soluble and amphiphilic drugs. Polymeric micelles are considerably more stable than surfactant micelles and can solubilize substantial amounts of hydrophobic compounds in their inner core. Due to their hydrophilic shell and small size they sometimes exhibit prolonged circulation times in vivo and can

Marie-Christine Jones; Jean-Christophe Leroux

1999-01-01

422

Polymeric Micelles - The Future of Oral Drug Delivery  

Microsoft Academic Search

This work examines current advancements in polymeric micelles as a method for oral delivery of poorly water-soluble drugs. The oral route presents several barriers to drug delivery that the chosen vesicle must overcome. Polymeric micelles have several physical properties, including molecular weight and copolymer block composition, which can be tailored to alter the vesicle structure and overcome these barriers. Examination

Isaac Godfroy

423

Polymerization kinetics in three-dimensional direct laser writing.  

PubMed

By in-situ measuring the scattered light during microstructure formation, the polymerization kinetics of three-dimensional direct laser writing are investigated in detail. Oxygen quenching, oxygen diffusion, and inhibitor depletion are shown to have substantial impact on the kinetic behavior. For typical photoresists based on multifunctional acrylates, the polymerization occurs in less than a millisecond. PMID:25146724

Mueller, Jonathan B; Fischer, Joachim; Mayer, Frederik; Kadic, Muamer; Wegener, Martin

2014-10-01

424

PERMEABILITY OF POLYMERIC MEMBRANE LINING MATERIALS FOR WASTE MANAGEMENT FACILITIES  

EPA Science Inventory

The paper discusses the types of materials used in the manufacture of polymeric liners for waste management and the permeability of such liners. It also presents experimental permeability results for a range of commercial polymeric membranes to gases, water vapor, and solvent vap...

425

Polymerization and surface modification by low pressure plasma technique  

NASA Astrophysics Data System (ADS)

A durable water repellent, stain resistant or flame retardant character can be conferred to polyacrylonitrile (PAN) textiles by using the plasma induced graft polymerization technique. The monomers used are perfluoroalkylacrylate, (meth)acrylate phosphates, and phosphonates which are well known to be effective for the waterproofing and the fireproofing of polymeric substrates, respectively.

Tsafack, M.-J.; Hochart, F.; Levalois-Grützmacher, J.

2004-06-01

426

Developments of rare earth metal catalysts for olefin polymerization  

Microsoft Academic Search

This review article describes recent developments in rare earth metal complexes as polymerization catalysts, focusing on the polymerization of ethylene and ?-olefins. Most of this kind of catalysts had been based on metallocene type complexes, and their catalytic behaviors are surveyed. Advanced series of half-metallocene and non-Cp type catalyst systems are also summarized.

Yuushou Nakayama; Hajime Yasuda

2004-01-01

427

Polymerization Simulator for Introductory Polymer and Material Science Courses  

ERIC Educational Resources Information Center

This work describes how molecular simulation of polymerization reactions can be used to enrich introductory polymer or material science courses to give students a deeper understanding of free-radical chain and stepwise growth polymerization reactions. These simulations have proven to be effective media for instruction that do not require material…

Chirdon, William M.

2010-01-01

428

Measurement of linear polymerization contraction using digital laser interferometry.  

PubMed

Polymerization shrinkage is an unavoidable consequence of resin composite photopolymerization and is one of the most important factors in determining the clinical quality and durability of composite filling. Many different methods of measuring polymerization shrinkage are described in the literature. Digital laser interferometry is a method that enables direct observation of polymerization shrinkage in real time. This study used the digital holographic interferometry method to measure the linear polymerization contraction of composite materials: Tetric Ceram (Vivadent), Spectrum TPH (Dentsply) and Valux Plus (3M Dental Products) polymerized with three different curing modes of the Elipar Trilight (ESPE) halogen curing unit. The highest polymerization contraction was recorded by "standard mode" (ETS) (1.24 +/- 2.66% lin), and the lowest by "medium mode" (ETM) (0.40 +/- 0.41% lin) during 40 second illumination. The "exponentional mode" (ETE) showed the highest expansion during the first 10 seconds of illumination. Curing units with initial low intensity enable better inner adaptation of composite material, preventing the detachment of material from dentin during polymerization and avoiding the negative consequences of polymerization shrinkage. PMID:15986955

Knezevic, Alena; Demoli, Nazif; Tarle, Zrinka; Meniga, Andrej; Sutalo, Jozo; Pichler, Goran

2005-01-01

429

Aquacultural Engineering 19 (1999) 163178 Phosphate binding polymeric hydrogels for  

E-print Network

Aquacultural Engineering 19 (1999) 163­178 Phosphate binding polymeric hydrogels for aquaculture in the aquaculture industry. In this study, novel phosphate binding crosslinked poly(allylamine), PAA · HCl, polymeric hydrogel materials were developed, which efficiently bind phosphate anions in aquaculture

Rubloff, Gary W.

430

Polypropylene carbon nanotube composites by in situ polymerization  

Microsoft Academic Search

The preparation of isotactic polypropylene nanocomposites filled with crude, purified and oxidized multi-walled carbon nanotubes (MWCNTs) was accomplished by polymerization of propylene with a metallocene\\/methylaluminoxane (MAO) catalyst and in situ coating. A good interfacial adhesion between the matrix and the filler is crucial for the successful preparation of nanocomposites; therefore, the polymerizations were performed with a new in situ coating

Andreas Funck; Walter Kaminsky

2007-01-01

431

Conduction mechanism in plasma polymerized lemongrass oil films  

Microsoft Academic Search

The electrical characteristics of radiofrequency plasma polymerized lemongrass oil is discussed in this paper. In plasma polymerized lemongrass oil film, Schottky conduction is observed and we found that the Schottky barrier height depends on the applied field, the field direction and the electrodes used.

D. Sakthi Kumar; M. G. Krishna Pillai

1999-01-01

432

Micropatterned composite membranes of polymerized and fluid lipid bilayers.  

PubMed

Micropatterned composite membranes of polymerized and fluid lipid bilayers were constructed on solid substrates. Lithographic photopolymerization of a diacetylene-containing phospholipid, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DiynePC), and subsequent removal of nonreacted monomers by a detergent solution (0.1 M sodium dodecyl sulfate (SDS)) yielded a patterned polymeric bilayer matrix on the substrate. Fluid lipid bilayers of phosphatidylcholine from egg yolk (egg-PC) were incorporated into the lipid-free wells surrounded by the polymeric bilayers through the process of fusion and reorganization of suspended small unilamellar vesicles. Spatial distribution of the fluid bilayers in the patterned bilayer depended on the degree of photopolymerization that in turn could be modulated by varying the applied UV irradiation dose. The polymeric bilayer domains blocked lateral diffusion of the fluid lipid bilayers and confined them in the defined areas (corrals), if the polymerization was conducted with a sufficiently large UV dose. On the other hand, lipid molecules of the fluid bilayers penetrated into the polymeric bilayer domains, if the UV dose was relatively small. A direct correlation was observed between the applied UV dose and the lateral diffusion coefficient of fluorescent marker molecules in the fluid bilayers embedded within the polymeric bilayer domains. Artificial control of lateral diffusion by polymeric bilayers may lead to the creation of complex and versatile biomimetic model membrane arrays. PMID:15323525

Morigaki, Kenichi; Kiyosue, Kazuyuki; Taguchi, Takahisa

2004-08-31

433

Appendix A: The Names of Polymers and Polymeric  

E-print Network

Appendix A: The Names of Polymers and Polymeric Materials Every newcomer to the study of polymers AND POLYMERIC MATERIALS common to all members of the class. For example 203 epoxy polyamide polyester carboxymethylcellulose CN cellulose nitrate celluloid, nitrate CPE chlorinated polyethylene

Hall, Christopher

434

Incorporation of polymeric nanoparticles into solid dosage forms  

Microsoft Academic Search

Besides parenteral delivery, polymeric nanoparticles have been used for oral drug delivery. In this study, model polymeric nanoparticles (aqueous colloidal polymer dispersions: Eudragit® RL 30D, L 30D, NE 30D, or Aquacoat®) with different physicochemical properties were incorporated into various solid dosage forms (granules, tablets, pellets or films). The compatibility of the nanoparticles with commonly used tabletting excipients and the redispersibility

Christoph Schmidt; Roland Bodmeier

1999-01-01

435

Nano Polymeric Carrier Fabrication Technologies for Advanced Antitumor Therapy  

PubMed Central

Comparing with the traditional therapeutic methods, newly developed cancer therapy based on the nanoparticulates attracted extensively interest due to its unique advantages. However, there are still some drawbacks such as the unfavorable in vivo performance for nanomedicine and undesirable tumor escape from the immunotherapy. While as we know that the in vivo performance strongly depended on the nanocarrier structural properties, thus, the big gap between in vitro and in vivo can be overcome by nanocarrier's structural tailoring by fine chemical design and microstructural tuning. In addition, this fine nanocarrier's engineering can also provide practical solution to solve the problems in traditional cancer immunotherapy. In this paper, we review the latest development in nanomedicine, cancer therapy, and nanoimmunotherapy. We then give an explanation why fine nanocanrrie's engineering with special focus on the unique pathology of tumor microenvironments and properties of immunocells can obviously promote the in vivo performance and improve the therapeutic index of nanoimmunotherapy. PMID:24369011

Li, Wei; Zhao, Mengxin; Ke, Changhong; Zhang, Ge; Zhang, Li; Li, Huafei; Zhang, Fulei; Sun, Yun; Dai, Jianxin; Wang, Hao; Guo, Yajun

2013-01-01

436

Vector reconstruction from firing rates  

Microsoft Academic Search

In a number of systems including wind detection in the cricket, visual motion perception and coding of arm movement direction in the monkey and place cell response to position in the rat hippocampus, firing rates in a population of tuned neurons are correlated with a vector quantity. We examine and compare several methods that allow the coded vector to be

Emilio Salinas; L. F. Abbott

1994-01-01

437

Vectors on the Basketball Court  

ERIC Educational Resources Information Center

An Idea Bank published in the April/May 2009 issue of "The Science Teacher" describes an experiential physics lesson on vectors and vector addition (Brown 2009). Like its football predecessor, the basketball-based investigation presented in this Idea Bank addresses National Science Education Standards Content B, Physical Science, 9-12 (NRC 1996)…

Bergman, Daniel

2010-01-01

438

Self-Organized and Cu-Coordinated Surface Linear Polymerization  

PubMed Central

We demonstrate a controllable surface-coordinated linear polymerization of long-chain poly(phenylacetylenyl)s that are self-organized into a “circuit-board” pattern on a Cu(100) surface. Scanning tunneling microscopy/spectroscopy (STM/S) corroborated by ab initio calculations, reveals the atomistic details of the molecular structure, and provides a clear signature of electronic and vibrational properties of the poly(phenylacetylene)s chains. Notably, the polymerization reaction is confined epitaxially to the copper lattice, despite a large strain along the polymerized chain that subsequently renders it metallic. Polymerization and depolymerization reactions can be controlled locally at the nanoscale by using a charged metal tip. This control demonstrates the possibility of precisely accessing and controlling conjugated chain-growth polymerization at low temperature. This finding may lead to the bottom-up design and realization of sophisticated architectures for molecular nano-devices. PMID:23811605

Li, Qing; Owens, Jonathan R.; Han, Chengbo; Sumpter, Bobby G.; Lu, Wenchang; Bernholc, Jerzy; Meunier, V.; Maksymovych, Peter; Fuentes-Cabrera, Miguel; Pan, Minghu

2013-01-01

439

Strain gauge method for measuring polymerization contraction of composite restoratives.  

PubMed

Post-gel polymerization contraction of composite restoratives produces a volumetric change in phase with the development of a modulus of elasticity and distributes contractile stresses through the resin hard tissue interface into the tooth. A new method for monitoring the polymerization contraction of composite restoratives utilizes electrical resistance strain gauges. The strain gauge system was calibrated with dial gauge measurements of the bulk expansion of gypsum products. Three composite types (microfilled, hybrid and posterior) were evaluated for polymerization exotherm, contraction during curing, and contraction for various shades. A 60-s curing time was used. The posterior composite (P-50) demonstrated the lowest exotherm and polymerization contraction. The contraction for Silux Plus dark grey was significantly lower than all other shades of all materials. The strain gauge method appears to be well suited for real-time measurement of the curing process and provides a means for studying the kinetics of polymerization. PMID:1839631

Sakaguchi, R L; Sasik, C T; Bunczak, M A; Douglas, W H

1991-10-01

440

Octonionic Reformulation of Vector Analysis  

E-print Network

According to celebrated Hurwitz theorem, there exists four division algebras consisting of R (real numbers), C (complex numbers), H (quaternions) and O (octonions). Keeping in view the utility of octonion variable we have tried to extend the three dimensional vector analysis to seven dimensional one. Starting with the scalar and vector product in seven dimensions, we have redefined the gradient, divergence and curl in seven dimension. It is shown that the identity n(n-1)(n-3)(n-7)=0 is satisfied only for 0, 1, 3 and 7 dimensional vectors. We have tried to write all the vector inequalities and formulas in terms of seven dimensions and it is shown that same formulas loose their meaning in seven dimensions due to non-associativity of octonions. The vector formulas are retained only if we put certain restrictions on octonions and split octonions.

Bhupendra C. S. Chauhan; P. S. Bisht; O. P. S. Negi

2010-11-17

441

Choosing a Viral Vector System Janet Douglas  

E-print Network

#12;Retroviral vector design Delete packaging signal Maintain packaging signal #12;The Problem viral vectors are "designed" to infect all cell types...tropism of virus = tropism of vector · Some for AAV (small packaging size) #12;#12;Recombinant Viral Vector Systems · Vector has characteristics

Chapman, Michael S.

442

Formation of monodisperse PMMA particles by radiation-induced dispersion polymerization—I. Synthesis and polymerization kinetics  

NASA Astrophysics Data System (ADS)

Highly monodisperse poly(methyl methacrylate) microparticles were directly prepared by radiation-induced dispersion polymerization at room temperature in aqueous alcohol media using poly( N-vinylpyrrolidone) as a steric stabilizer. Monomer conversion was studied dilatometrically and polymer molecular weight was determined viscometrically. The gel effect was evident from the increase of the molecular weight with conversion and also from the percentage conversion vs. time curves. The influences of dose rate, monomer concentration, stabilizer content, medium polarity, polymerization temperature on the polymerization rate and the molecular weight of polymer have been examined. It was found that the overall activation energy for the rate of polymerization is 18.44 kJ/mol (10-25°C). Based on the experimental results, the polymerization mechanisms were discussed.

Ye, Qiang; Ge, Xuewu; Zhang, Zhicheng

2003-01-01

443

Semismooth support vector machines.  

SciTech Connect

The linear support vector machine can be posed as a quadratic program in a variety of ways. In this paper, we look at a formulation using the two-norm for the misclassification error that leads to a positive definite quadratic program with a single equality constraint when the Wolfe dual is taken. The quadratic term is a small rank update to a positive definite matrix. We reformulate the optimality conditions as a semismooth system of equations using the Fischer-Burmeister function and apply a damped Newton method to solve the resulting problem. The algorithm is shown to converge from any starting point with a Q-quadratic rate of convergence. At each iteration, we use the Sherman-Morrison-Woodbury update formula to solve a single linear system of equations. Significant computational savings are realized as the inactive variables are identified and exploited during the solution process. Results for a 60 million variable problem are presented, demonstrating the effectiveness of the proposed method on a personal computer.

Ferris, M. C.; Munson, T. S.; Mathematics and Computer Science; Univ. of Wisconsin

2004-09-01

444

Kinetic simulation of living carbocationic polymerizations. II. Simulation of living isobutylene polymerization using a mechanistic model  

Microsoft Academic Search

This paper discusses the kinetic simulation of TiCl4––coinitiated living carbocationic isobutylene (IB) polymerizations governed by dormant-active equilibria, using a mechanistic model. Two kinetic models were constructed from the same underlying mechanism: one using a commercial simulation software package (Predici®), and the other using the method of moments. Parameter estimation from experimental batch reactor data with Predici yielded a rate constant

Judit E. Puskas; Sohel Shaikh; Kevin Z. Yao; Kim B. McAuley; Gabor Kaszas

2005-01-01

445

Polymerization of Formic Acid under High Pressure  

SciTech Connect

We report combined Raman, infrared (IR) and x-ray diffraction (XRD) measurements, along with ab initio calculations on formic acid under pressure up to 50 GPa. Contrary to the report of Allan and Clark (PRL 82, 3464 (1999)), we find an infinite chain low-temperature Pna2{sub 1} structure consisting of trans molecules to be a high-pressure phase at room temperature. Our data indicate the symmetrization and a partially covalent character of the intra-chain hydrogen bonds above approximately 20 GPa. Raman spectra and XRD patterns indicate a loss of the long-range order at pressures above 40 GPa with a large hysteresis at decompression. We attribute this behavior to a three-dimensional polymerization of formic acid.

Goncharov, A F; Manaa, M R; Zaug, J M; Fried, L E; Montgomery, W B

2004-08-23

446

Solid polymeric electrolytes for lithium batteries  

DOEpatents

Novel conductive polyanionic polymers and methods for their preparion are provided. The polyanionic polymers comprise repeating units of weakly-coordinating anionic groups chemically linked to polymer chains. The polymer chains in turn comprise repeating spacer groups. Spacer groups can be chosen to be of length and structure to impart desired electrochemical and physical properties to the polymers. Preferred embodiments are prepared from precursor polymers comprising the Lewis acid borate tri-coordinated to a selected ligand and repeating spacer groups to form repeating polymer chain units. These precursor polymers are reacted with a chosen Lewis base to form a polyanionic polymer comprising weakly coordinating anionic groups spaced at chosen intervals along the polymer chain. The polyanionic polymers exhibit high conductivity and physical properties which make them suitable as solid polymeric electrolytes in lithium batteries, especially secondary lithium batteries.

Angell, Charles A.; Xu, Wu; Sun, Xiaoguang

2006-03-14

447

Elastic, Conductive, Polymeric Hydrogels and Sponges  

PubMed Central

As a result of inherent rigidity of the conjugated macromolecular chains resulted from the delocalized ?-electron system along the polymer backbone, it has been a huge challenge to make conducting polymer hydrogels elastic by far. Herein elastic and conductive polypyrrole hydrogels with only conducting polymer as the continuous phase have been simply synthesized in the indispensable conditions of 1) mixed solvent, 2) deficient oxidant, and 3) monthly secondary growth. The elastic mechanism and oxidative polymerization mechanism on the resulting PPy hydrogels have been discussed. The resulting hydrogels show some novel properties, e.g., shape memory elasticity, fast functionalization with various guest objects, and fast removal of organic infectants from aqueous solutions, all of which cannot be observed from traditional non-elastic conducting polymer counterparts. What's more, light-weight, elastic, and conductive organic sponges with excellent stress-sensing behavior have been successfully achieved via using the resulting polypyrrole hydrogels as precursors. PMID:25052015

Lu, Yun; He, Weina; Cao, Tai; Guo, Haitao; Zhang, Yongyi; Li, Qingwen; Shao, Ziqiang; Cui, Yulin; Zhang, Xuetong

2014-01-01

448

Analytical SFE applied to polymeric materials  

SciTech Connect

Polymeric materials afford unique challenges for analytical supercritical fluid extraction. Oligomeric components, monomers, anti-oxidants, finishes, residual solvents and processing additives are some of the analytes of interest. In addition to their marginal solubility in 100% CO{sub 2}, the extraction analyte is many times diffusion limited rather than enthalpically driven which means that exhaustive extractions from polymer matrices may be slow. The presentation will draw upon our experiences in the (a) fractionation of high density polyethylene with supercritical propane-modified CO{sub 2}, (b) coupling of SFE and Fourier Transform Infrared Spectrometry (FT-IR) for analysis of finishes from polyester, nylon, aramid, and polyurethane, and (c) removal of low molecular weight oligomers and additives from polyamides and polystyrene and their identification by on-line supercritical fluid chromatography/FT-IR.

Taylor, L.T. [Virginia Tech, Blacksburg, VA (United States)

1995-12-31

449

Space environmental effects on polymeric materials  

NASA Technical Reports Server (NTRS)

Polymeric materials that may be exposed on spacecraft to the hostile environment beyond Earth's atmosphere were subjected to atomic oxygen, electron bombardment, and ultraviolet radiation in terrestrial experiments. Evidence is presented for the utility of an inexpensive asher for determining the relative susceptibility of organic polymers to atomic oxygen. Kapton, Ultem, P1700 polysulfone, and m-CBB/BIS-A (a specially formulated polymer prepared at NASA Langley) all eroded at high rates, just as was observed in shuttle experiments. Films of Ultem, P1700 polysulfone, and m-CBB/BIS-A were irradiated with 85 keV electrons. The UV/VIS absorbance of Ultem was found to decay with time after irradiation, indicating free radical decay. The tensile properties of Ultem began to change only after it had been exposed to 100 Mrads. The effects of dose rate, temperature, and simultaneous vs. sequential electron and UV irradiation were also studied.

Kiefer, Richard L.; Orwoll, Robert A.

1987-01-01

450

Fluorination of silicone rubber by plasma polymerization  

NASA Astrophysics Data System (ADS)

Plasma polymerized fluorocarbon (PPFC) films were deposited onto various silicone rubber substrates, including O-rings, to decrease oil uptake. Depositions were performed using a radio frequency (rf)-powered plasma reactor and various fluorocarbon monomers, such as C2F6, C2F 5H, C3F6, and 1H,1H,2H-perfluoro-1-dodecene. PPFC films which were most promising for inhibiting oil uptake were deposited with 1H,1H,2H-perfluoro-1-dodecene, and were composed predominantly of perfluoromethylene (CF2) species. These films displayed low critical surface energies (as low as 2.7 mJ/m2), and high contact angles with oil (84°), which were correlated with the amount of CF2 species present in the film. For the films with the highest degree of CF2 (up to 67%), CF2 chains may have been oriented slightly perpendicular to the substrate and terminated by CF3 species. Adhesion of the PPFC films directly to silicone rubber was found to be poor. However, when a plasma polymerized hydrocarbon interlayer was deposited on the silicone rubber prior to the fluorocarbon films, adhesion was excellent. O-rings coated with multilayer fluorocarbon films showed 2.6% oil uptake after soaking in oil for 100 hrs at 100°C. Due to variability in data, and the low quality of the industrial grade silicone rubber, the oil uptake mechanism was determined to be from oil flowing through flaws in the film due to defects within the substrate, not from generalized diffusion through the film. This mechanism was confirmed using higher quality silicone rubber, which showed little or no oil diffusion. Therefore, this film may perform well as an oil-repelling barrier when deposited on a high quality silicone rubber.

Fielding, Jennifer Chase

451

Chikungunya Virus–Vector Interactions  

PubMed Central

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes chikungunya fever, a severe, debilitating disease that often produces chronic arthralgia. Since 2004, CHIKV has emerged in Africa, Indian Ocean islands, Asia, Europe, and the Americas, causing millions of human infections. Central to understanding CHIKV emergence is knowledge of the natural ecology of transmission and vector infection dynamics. This review presents current understanding of CHIKV infection dynamics in mosquito vectors and its relationship to human disease emergence. The following topics are reviewed: CHIKV infection and vector life history traits including transmission cycles, genetic origins, distribution, emergence and spread, dispersal, vector competence, vector immunity and microbial interactions, and co-infection by CHIKV and other arboviruses. The genetics of vector susceptibility and host range changes, population heterogeneity and selection for the fittest viral genomes, dual host cycling and its impact on CHIKV adaptation, viral bottlenecks and intrahost diversity, and adaptive constraints on CHIKV evolution are also discussed. The potential for CHIKV re-emergence and expansion into new areas and prospects for prevention via vector control are also briefly reviewed. PMID:25421891

Coffey, Lark L.; Failloux, Anna-Bella; Weaver, Scott C.

2014-01-01

452

Enhancing poxvirus vectors vaccine immunogenicity.  

PubMed

Attenuated recombinant poxvirus vectors expressing heterologous antigens from pathogens are currently at various stages in clinical trials with the aim to establish their efficacy. This is because these vectors have shown excellent safety profiles, significant immunogenicity against foreign expressed antigens and are able to induce protective immune responses. In view of the limited efficacy triggered by some poxvirus strains used in clinical trials (i.e, ALVAC in the RV144 phase III clinical trial for HIV), and of the restrictive replication capacity of the highly attenuated vectors like MVA and NYVAC, there is a consensus that further improvements of these vectors should be pursuit. In this review we considered several strategies that are currently being implemented, as well as new approaches, to improve the immunogenicity of the poxvirus vectors. This includes heterologous prime/boost protocols, use of co-stimulatory molecules, deletion of viral immunomodulatory genes still present in the poxvirus genome, enhancing virus promoter strength, enhancing vector replication capacity, optimizing expression of foreign heterologous sequences, and the combined use of adjuvants. An optimized poxvirus vector triggering long-lasting immunity with a high protective efficacy against a selective disease should be sought. PMID:25424927

García-Arriaza, Juan; Esteban, Mariano

2014-01-01

453

Emerging Vector-Borne Diseases – Incidence through Vectors  

PubMed Central

Vector-borne diseases use to be a major public health concern only in tropical and subtropical areas, but today they are an emerging threat for the continental and developed countries also. Nowadays, in intercontinental countries, there is a struggle with emerging diseases, which have found their way to appear through vectors. Vector-borne zoonotic diseases occur when vectors, animal hosts, climate conditions, pathogens, and susceptible human population exist at the same time, at the same place. Global climate change is predicted to lead to an increase in vector-borne infectious diseases and disease outbreaks. It could affect the range and population of pathogens, host and vectors, transmission season, etc. Reliable surveillance for diseases that are most likely to emerge is required. Canine vector-borne diseases represent a complex group of diseases including anaplasmosis, babesiosis, bartonellosis, borreliosis, dirofilariosis, ehrlichiosis, and leishmaniosis. Some of these diseases cause serious clinical symptoms in dogs and some of them have a zoonotic potential with an effect to public health. It is expected from veterinarians in coordination with medical doctors to play a fundamental role at primarily prevention and then treatment of vector-borne diseases in dogs. The One Health concept has to be integrated into the struggle against emerging diseases. During a 4-year period, from 2009 to 2013, a total number of 551 dog samples were analyzed for vector-borne diseases (borreliosis, babesiosis, ehrlichiosis, anaplasmosis, dirofilariosis, and leishmaniasis) in routine laboratory work. The analysis was done by serological tests – ELISA for borreliosis, dirofilariosis, and leishmaniasis, modified Knott test for dirofilariosis, and blood smear for babesiosis, ehrlichiosis, and anaplasmosis. This number of samples represented 75% of total number of samples that were sent for analysis for different diseases in dogs. Annually, on average more then half of the samples brought to the laboratory to analysis for different infectious diseases are analyzed for vector-borne diseases. In the region of Vojvodina (northern part of Serbia), the following vector-borne infectious diseases have been found in dogs so far borreliosis, babesiosis, dirofilariosis, leishmaniasis, and anaplasmosis. PMID:25520951

Savi?, Sara; Vidi?, Branka; Grgi?, Zivoslav; Potkonjak, Aleksandar; Spasojevic, Ljubica

2014-01-01

454

Inflation with Massive Vector Fields  

E-print Network

We investigate the coupling between the inflaton and massive vector fields. All renormalizable couplings with shift symmetry of the inflaton are considered. The massive vector can be decomposed into a scalar mode and a divergence-free vector mode. We show that the former naturally interacts with the inflaton and the latter decouples at tree level. The model in general predicts $f_{NL}^\\mathrm{equil} = \\mathcal{O}(1)$, while in some regions of the parameter space large non-Gaussianity can arise.

Liu, Junyu; Zhou, Siyi

2015-01-01

455

Idea Bank: Vector, Vector--That's Our Cry!  

NSDL National Science Digital Library

There are all kinds of computer-based software programs and websites available to help students understand and manipulate vector quantities. But if you have the time and want to do something different, this Idea Bank describes an easy, low-tech, and fun activity for teaching the "head-to-tail" method of combining vectors and the difference between "distance" and "displacement." All you need for this activity are scissors, some envelopes, metersticks, and a football field.

Jeremy Brown

2009-04-01

456

Polymerizer Temperature Cascade Control System Based on Generalized Predictive Control  

NASA Astrophysics Data System (ADS)

The polymerize process is the first stage in PAN-based carbon fiber production, and its temperature control affects directly the quality and yield of the last products. It has the serious time delay character if polymerizer temperature is controlled by the mixture of the hot water and the cold one, and the polymerization process will release a lot of heat. All these make it is very complex to control the polymerizer temperature. The paper analyzes polymerizing technology firstly, then provides design and realization methods of polymerizer temperature cascade control based on generalized predictive control (GPC), and the system is realized through the control layer and the monitoring layer. The former realizes the model identification and the recursive computation in the generalized predictive control, and sends the results to the latter, and the latter realizes PID with dead-zone control of the mixed water temperature control using the results of the main regulator. The practice shows that the polymerize temperature cascade system runs well and has evident effect with effective control.

Yanfei, Ye; Bailin, Wang; Mingheng, Shao; Yongqi, Zhang

457

Are Bred Vectors The Same As Lyapunov Vectors?  

NASA Astrophysics Data System (ADS)

Regional loss of predictability is an indication of the instability of the underlying flow, where small errors in the initial conditions (or imperfections in the model) grow to large amplitudes in finite times. The stability properties of evolving flows have been studied using Lyapunov vectors (e.g., Alligood et al, 1996, Ott, 1993, Kalnay, 2002), singular vectors (e.g., Lorenz, 1965, Farrell, 1988, Molteni and Palmer, 1993), and, more recently, with bred vectors (e.g., Szunyogh et al, 1997, Cai et al, 2001). Bred vectors (BVs) are, by construction, closely related to Lyapunov vectors (LVs). In fact, after an infinitely long breeding time, and with the use of infinitesimal ampli- tudes, bred vectors are identical to leading Lyapunov vectors. In practical applications, however, bred vectors are different from Lyapunov vectors in two important ways: a) bred vectors are never globally orthogonalized and are intrinsically local in space and time, and b) they are finite-amplitude, finite-time vectors. These two differences are very significant in a dynamical system whose size is very large. For example, the at- mosphere is large enough to have "room" for several synoptic scale instabilities (e.g., storms) to develop independently in different regions (say, North America and Aus- tralia), and it is complex enough to have several different possible types of instabilities (such as barotropic, baroclinic, convective, and even Brownian motion). Bred vectors share some of their properties with leading LVs (Corazza et al, 2001a, 2001b, Toth and Kalnay, 1993, 1997, Cai et al, 2001). For example, 1) Bred vectors are independent of the norm used to define the size of the perturba- tion. Corazza et al. (2001) showed that bred vectors obtained using a potential enstro- phy norm were indistinguishable from bred vectors obtained using a streamfunction squared norm, in contrast with singular vectors. 2) Bred vectors are independent of the length of the rescaling period as long as the perturbations remain approximately linear (for example, for atmospheric models the interval for rescaling could be varied between a single time step and 1 day without affecting qualitatively the characteristics of the bred vectors. However, the finite-amplitude, finite-time, and lack of orthogonalization of the BVs introduces important differences with LVs: 1) In regions that undergo strong instabilities, the bred vectors tend to be locally domi- 1 nated by simple, low-dimensional structures. Patil et al (2001) showed that the BV-dim (appendix) gives a good estimate of the number of dominant directions (shapes) of the local k bred vectors. For example, if half of them are aligned in one direction, and half in a different direction, the BV-dim is about two. If the majority of the bred vectors are aligned predominantly in one direction and only a few are aligned in a second direction, then the BV-dim is between 1 and 2. Patil et al., (2001) showed that the regions with low dimensionality cover about 20% of the atmosphere. They also found that these low-dimensionality regions have a very well defined vertical structure, and a typical lifetime of 3-7 days. The low dimensionality identifies regions where the in- stability of the basic flow has manifested itself in a low number of preferred directions of perturbation growth. 2) Using a Quasi-Geostrophic simulation system of data assimilation developed by Morss (1999), Corazza et al (2001a, b) found that bred vectors have structures that closely resemble the background (short forecasts used as first guess) errors, which in turn dominate the local analysis errors. This is especially true in regions of low dimensionality, which is not surprising if these are unstable regions where errors grow in preferred shapes. 3) The number of bred vectors needed to represent the unstable subspace in the QG system is small (about 6-10). This was shown by computing the local BV-dim as a function of the number of independent bred vectors. Convergence in the local dimen- sion starts to occur at about 6 BVs, and is essentially

Kalnay, E.; Corazza, M.; Cai, M.

458

Plasma polymerized allylamine coated quartz particles for humic acid removal.  

PubMed

Allylamine plasma polymerization has been used to modify the surface of quartz particles for humic acid removal via an inductively coupled rotating barrel plasma reactor. Plasma polymerized allylamine (ppAA) films were deposited at a power of 25 W, allylamine flow rate of 4.4 sccm and polymerization times of 5-60 min. The influence of polymerization time on surface chemistry was investigated via X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectrometry (ToF-SIMS) and electrokinetic analysis. Acid orange 7 adsorption/desorption quantified the number of surface amine groups. Humic acid removal via ppAA quartz particles was examined by varying pH, removal time, humic acid concentration, and particle mass. Increasing the polymerization time increased the concentration of amine groups on the ppAA quartz surface, thus also increasing the isoelectric point. ToF-SIMS demonstrated uniform distribution of amine groups across the particle surface. Greatest humic acid removal was observed at pH 5 due to electrostatic attraction. At higher pH values, for longer polymerization times, humic acid removal was also observed due to hydrogen bonding. Increasing the initial humic acid concentration increased the mass of humic acid removed, with longer polymerization times exhibiting the greatest increases. Plasma polymerization using a rotating plasma reactor has shown to be a successful method for modifying quartz particles for the removal of humic acid. Further development of the plasma polymerization process and investigation of additional contaminants will aid in the development of a low cost water treatment system. PMID:22633110

Jarvis, Karyn L; Majewski, Peter

2012-08-15

459

The polymerization of acetyl-CoA carboxylase.  

PubMed

Citrate, an allosteric activator of acetyl-CoA carboxylase, induces polymerization of an inactive protomeric form of the enzyme into an active filamentous form composed of 10-20 protomers. The light-scattering properties of the carboxylase were used to study the kinetics of its polymerization and depolymerization. From stopped flow kinetic studies, we have established that polymerization is a second order process, with a second order rate constant of 597,000 M-1 s-1. There appear to be two steps which limit polymerization of the inactive carboxylase protomer: 1) a rapid citrate-induced conformational change which is independent of enzyme concentration and leads to an active protomeric form of the enzyme (Beaty, N. B., and Lane, M. D. (1983) J. Biol. Chem. 258, 13043-13050, preceding paper) and 2) the dimerization of the active protomer, which constitutes the first step of polymerization and is enzyme concentration-dependent. Dimerization is the rate-limiting step of acetyl-CoA carboxylase polymerization. Depolymerization of fully polymerized acetyl-CoA carboxylase is caused by malonyl-CoA, ATP X Mg, and Mg2+. Both malonyl-CoA and ATP X Mg (and HCO-3) compete with citrate in the maintenance of a given state of the protomer-polymer equilibrium apparently by carboxylating the enzyme to form enzyme-biotin-CO-2 which destablizes the polymeric form. Free citrate is the species responsible for polymerizing the enzyme and Mg2+ causes depolymerization of the enzyme by lowering the concentration of free citrate. PMID:6138356

Beaty, N B; Lane, M D

1983-11-10

460

Intrinsic embedded sensors for polymeric mechatronics: flexure and force sensing.  

PubMed

While polymeric fabrication processes, including recent advances in additive manufacturing, have revolutionized manufacturing, little work has been done on effective sensing elements compatible with and embedded within polymeric structures. In this paper, we describe the development and evaluation of two important sensing modalities for embedding in polymeric mechatronic and robotic mechanisms: multi-axis flexure joint angle sensing utilizing IR phototransistors, and a small (12 mm), three-axis force sensing via embedded silicon strain gages with similar performance characteristics as an equally sized metal element based sensor. PMID:24573310

Jentoft, Leif P; Dollar, Aaron M; Wagner, Christopher R; Howe, Robert D

2014-01-01

461

Preparation of acrylate IPN copolymer latexes by radiation emulsion polymerization  

NASA Astrophysics Data System (ADS)

Radiation-induced and chemical initiation are compared in the initiation of acrylate emulsion copolymer latexes. The particle diameter, distribution and microstructure are influenced by emulsifier concentration, radiation dose and temperature. The results show that the emulsion particle diameter of radiation polymerization is smaller and better distributed in comparison to using chemical polymerization. In addition, interlude polymer net (IPN) core-shell copolymer latexes are observed by transmission electron microscope (TEM). The bounding face of core-shell acrylate copolymmer texes of radiation polymerization is clearer. The morphology of acrylate IPN copolymer latexes is further investigated.

Wu, Minghong; Zhou, Ruimin; Ma, Zue-Teh; Bao, Borong; Lei, Jianqiu

1997-03-01