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1

Enhanced Angiogenesis for Tissue Regeneration using Human Stem Cells and Biodegradable Nanoparticulate Polymeric Vectors.  

National Technical Information Service (NTIS)

Mesenchymal stem cells (MSC) are progenitor cells which can differentiate down multiple lineages including bone. Ideally, scaffold for bone tissue engineering should exhibit biofunctionality of natural materials. In this regards, a novel polymeric biocomp...

D. Singh F. Yang J. J. Green S. Botatyrev S. Cho

2008-01-01

2

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

3

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

Microsoft Academic Search

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

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

2009-01-01

4

Polymeric vectors for ocular gene delivery  

PubMed Central

Gene therapy holds promise for the treatment of many inherited and acquired diseases of the eye. Successful ocular to targeted cells with minimal toxicity. A major gene therapy interventions depend on challenge is to overcome both intracellular and extracellular barriers associated with ocular gene delivery. Numerous viral and nonviral vectors were explored to improve transfection efficiency. Among nonviral delivery systems, polymeric vectors have gained significant attention in recent years owing to their nontoxic and non-immunogenic nature. Polyplexes or nanoparticles can be prepared by interaction of cationic polymers with DNA, which facilitate cellular uptake, endolysosomal escape and nuclear entry through active mechanisms. Chemical modification of these polymers allows for the generation of flexible delivery vectors with desirable properties. In this article several synthetic and natural polymeric systems utilized for ocular gene delivery are discussed.

Tamboli, Viral; Mishra, Gyan P; Mitra, Ashim K

2011-01-01

5

Multifunctional Nanoparticulate Polyelectrolyte Complexes  

Microsoft Academic Search

Water-soluble, biodegradable, polymeric, polyelectrolyte complex dispersions (PECs) have evolved because of the limitations,\\u000a in terms of toxicity, of the currently available systems. These aqueous nanoparticulate architectures offer a significant\\u000a advantage for products that may be used as drug delivery systems in humans. PECs are created by mixing oppositely charged\\u000a polyions. Their hydrodynamic diameter, surface charge, and polydispersity are highly dependent

Sean M. Hartig; Rachel R. Greene; Mikhail M. Dikov; Ales Prokop; Jeffrey M. Davidson

2007-01-01

6

Polymer vectors via controlled\\/living radical polymerization for gene delivery  

Microsoft Academic Search

The design of efficient gene delivery vectors is a challenging task in gene therapy. Recent progress in living\\/controlled radical polymerizations (LRPs), in particular atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization providing a means for the design and synthesis of new polymeric gene vectors with well-defined compositions, architectures and functionalities is reviewed here. Polymeric gene vectors

F. J. Xu; W. T. Yang

2011-01-01

7

Nanoparticulate systems for polynucleotide delivery  

PubMed Central

Nanotechnology has tremendously influenced gene therapy research in recent years. Nanometer-size systems have been extensively investigated for delivering genes at both local and systemic levels. These systems offer several advantages in terms of tissue penetrability, cellular uptake, systemic circulation, and cell targeting as compared to larger systems. They can protect the polynucleotide from a variety of degradative and destabilizing factors and enhance delivery efficiency to the cells. A variety of polymeric and non-polymeric nanoparticles have been investigated in an effort to maximize the delivery efficiency while minimizing the toxic effects. This article provides a review on the most commonly used nanoparticulate systems for gene delivery. We have discussed frequently used polymers, such as, polyethyleneimine, poly (lactide-co-glycolide), chitosan, as well as non-polymeric materials such as cationic lipids and metallic nanoparticles. The advantages and limitations of each system have been elaborated.

Basarkar, Ashwin; Singh, Jagdish

2007-01-01

8

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

2013-10-05

9

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

2008-03-01

10

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

11

Encapsulation of antioxidants in gastrointestinal-resistant nanoparticulate carriers.  

PubMed

Reactive oxygen species (ROS) are known to cause several human pathologies. For this reason, antioxidants have gained utmost importance because of their potential as prophylactic and therapeutic agents in many diseases. Examples of their application include their use in diabetic patients, as aging drugs, in cancer diseases, Parkinson's, Alzheimer's, autoimmune disorders, and also in inflammation. Antioxidants have limited absorption profiles, therefore low bioavailability and low concentrations at the target site. Efforts have been done towards loading antioxidant molecules in advanced nanoparticulate carriers, e.g., liposomes, polymeric nanoparticles, solid lipid nanoparticles, self-emulsifying drug delivery system. Examples of -successful achievements include the encapsulation of drugs and other active ingredients, e.g., coenzyme Q10, vitamin E and vitamin A, resveratrol and polyphenols, curcumin, lycopene, silymarin, and superoxide dismutase. This review focuses on the comprehensive analysis of using nanoparticulate carriers for loading these molecules for oral administration. PMID:23740112

Souto, Eliana B; Severino, Patrícia; Basso, Rafael; Santana, Maria Helena A

2013-01-01

12

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

13

Collection and characterization of airborne nanoparticulates  

SciTech Connect

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 >1000 individual particles, ranging in size from approximately 1 to 100 nm and (2) complex, branched clusters of amorphous, carbonaceous spherules (containing from 50 to >1000 spherules, which range in size from 10 to 40 nm in diameter) and carbon nanocrystal aggregates containing nanotubes and other polyhedra. Commercial nanoparticulate aggregates of TiO{sub 2} and Si{sub 3}N{sub 4} are also observed in the context of characterization standards and the nanotechnology potential for contributing to atmospheric pollutants.

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

2004-03-15

14

Expanded Bed Chromatography as a Tool for Nanoparticulate Separation: Kinetic Study and Adsorption of Protein Nanoparticles  

Microsoft Academic Search

Expanded bed adsorption was investigated together with its suitability for the practical recovery of nanoparticulate mimics\\u000a of products such as plasmid DNA and viruses as putative gene therapy vectors. The study assessed the binding of protein nanoparticles\\u000a fabricated from bovine serum albumin (BSA) with average size of 80 nm as a model system and viral size\\/charge mimic to the\\u000a streamline DEAE

Mohsen Jahanshahi; Melika Ebrahimpour

2009-01-01

15

vectors  

NSDL National Science Digital Library

The word vector comes from the Latin term vehere, to carry. In Biology, a vector is an agent which carries disease, such as a mosquito carrying infected blood from one patient to the next. In physics, a vector is a quantity which has both a magnitude and a direction associated with it. The most commonly used example of vectors in everyday life is velocity. When you drive your car, your speedometer tells you the speed of your car, but it doesn't tell you where you are going. The combination of both where you are going and how fast you are going there is your car's velocity.

Joiner, David; The Shodor Education Foundation, Inc.

16

Vectors  

NSDL National Science Digital Library

This web page 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

2006-07-16

17

Photosensitive liquid crystals with nanoparticulate internal structure  

NASA Astrophysics Data System (ADS)

Stabilization of thermodynamic relaxation of photoinduced cis isomers of azobenzene liquid-crystal molecules is observed in nanoparticulate networks. The phenomenon permits bistability of the phase state (anisotropic and isotropic) of the material and reversible all-optical switching between those states, resulting in strong changes in the light-scattering properties of the material. Recording of complex optical structures with high spatial resolution with the aid of laser beams of different wavelengths is demonstrated.

Tabiryan, N.; Grozhik, V.; Serak, S.

2002-11-01

18

Intratumoral Drug Delivery with Nanoparticulate Carriers  

PubMed Central

Stiff extracellular matrix, elevated interstitial fluid pressure, and the affinity for the tumor cells in the peripheral region of a solid tumor mass have long been recognized as significant barriers to diffusion of small-molecular-weight drugs and antibodies. However, their impacts on nanoparticle-based drug delivery have begun to receive due attention only recently. This article reviews biological features of many solid tumors that influence transport of drugs and nanoparticles and properties of nanoparticles relevant to their intratumoral transport, studied in various tumor models. We also discuss several experimental approaches employed to date for enhancement of intratumoral nanoparticle penetration. The impact of nanoparticle distribution on the effectiveness of chemotherapy remains to be investigated and should be considered in the design of new nanoparticulate drug carriers.

Holback, Hillary

2011-01-01

19

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

20

Nanoparticulate Alnico Thin Films with High Coercivity  

NASA Astrophysics Data System (ADS)

Alnico V (Fe--8% Al--14% Ni--24% Co--3% Cu) nanoparticulate thin films have been produced by dc magnetron sputtering. The films were sputtered on Si substrates for magnetic measurements and carbon-coated copper grids for TEM measurements. The as-deposited films have a fine grained microstructure with the bcc crystal structure. The as-made films were subjected to a full heat treatment which consists of heating the sample to 900 ^oC, then cooling it to 600 ^oC and finally annealing it at 600 ^oC for several hours. After the heat treatment, the thin films broke up into large nanoparticles (20-60 nm) surrounded by small nanoparticles (2 nm). Electron diffraction data showed that the annealed samples had an fcc structure. The maximum room temperature coercivity was found to be 2 kOe after 6h of annealing at 600 ^oC. The high coercivity could be due to strain that was induced during precipitation. The evolution of crystal structure and microstructure with annealing will be monitored and related to the observed magnetic properties.

Akdogan, Ozan; Hadjipanayis, George C.

2009-03-01

21

Resolution of two-way data from on-line Fouriertransform Raman spectroscopic monitoring of the anionic dispersion polymerization of styrene and 1,3-butadiene by parallel vector analysis (PVA) and window factor analysis (WFA)  

Microsoft Academic Search

On-line Fourier-transform Raman spectroscopic monitoring of the anionic dispersion polymerization of styrene and 1,3-butadiene has been implemented with a noninvasive optic fiber Raman probe. After suitable pretreatment of the Raman spectra obtained, the resulting two-way data are analyzed using two self-modeling curve resolution (SMCR) techniques, parallel vector analysis (PVA) proposed in the preceding paper, as well as window factor analysis

Jian-Hui Jiang; Yukihiro Ozaki; Michael Kleimann; Heinz W Siesler

2004-01-01

22

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

23

Freeze Drying: Potential for Powdered Nanoparticulate Product  

Microsoft Academic Search

Nanoparticles were prepared by using an emulsion solvent evaporation method. Further, the drying of an anti-cancer drug of proprietary nature (nanosized) was carried out by a freeze-drying technique to get a free-flowing powder. A systematic approach was developed to study the freeze-drying technique for polymeric nanoparticles. Initially, the freeze-thawing experiments were carried out with varying concentrations of cryoprotectants to screen

V. V. Patil; P. P. Dandekar; V. B. Patravale; B. N. Thorat

2010-01-01

24

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

25

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

Microsoft Academic Search

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

Michael J. Heller; Raj Krishnan; Avery Sonnenberg

2010-01-01

26

Monolithic precolumns as efficient tools for guiding the design of nanoparticulate drug-delivery formulations.  

PubMed

The development of nanomedicines for improved diagnosis and treatment of diseases is pushing current analytical methods to their limits. More efficient, quantitative high-throughput screening methods are needed to guide the optimization of promising nanoparticulate drug delivery formulations. In response to this need, we present herein a novel approach using monolithic separation media. The unique porosity of our capillary monolithic precolumns allows the direct injection and online removal of protamine-oligonucleotide nanoparticles ("proticles") without column clogging, thus avoiding the need for time-consuming off-line sample workup. Furthermore, ring-opening metathesis polymerization (ROMP)-derived monoliths show equivalent preconcentration efficiency for the target drug vasoactive intestinal peptide (VIP) as conventional particle-packed precolumns. The performance of the ROMP-derived monolithic precolumns was constant over at least 100 injections of crude proticle-containing and 300 injections of highly acidic samples. Applying a validated LC-MS/MS capillary monolithic column switching method, we demonstrate the rapid determination of both drug load and in vitro drug release kinetics of proticles within the critical first 2 h and investigate the stability of VIP-loaded proticles in aqueous storage medium intended for inhalation therapy. PMID:22861123

Gatschelhofer, Christina; Prasch, Agnes; Buchmeiser, Michael R; Zimmer, Andreas; Wernig, Karin; Griesbacher, Martin; Pieber, Thomas R; Sinner, Frank M

2012-08-22

27

Kinetic Analysis of Nanoparticulate Polyelectrolyte Complex Interactions with Endothelial Cells  

PubMed Central

A non-toxic, nanoparticulate polyelectrolyte complex (PEC) drug delivery system was formulated to maintain suitable physicochemical properties at physiological pH. Toxicity, binding, and internalization were evaluated in relevant microvascular endothelial cells. PEC were non-toxic, as indicated by cell proliferation studies and propidium iodide staining. Inhibitor studies revealed that PEC were bound, in part, via heparan sulfate proteoglycans and internalized through macropinocytosis. A novel, flow cytometric, Scatchard protocol was established and showed that PEC, in the absence of surface modification, bind cells non-specifically with positive cooperativity, as seen by graphical transformations.

Hartig, Sean M.; Greene, Rachel; Carlesso, Gianluca; Higginbotham, James N.; Khan, Wasif N.; Prokop, Ales; Davidson, Jeffrey M.

2007-01-01

28

Concepts and practices used to develop functional PLGA-based nanoparticulate systems  

PubMed Central

The functionality of bare polylactide-co-glycolide (PLGA) nanoparticles is limited to drug depot or drug solubilization in their hard cores. They have inherent weaknesses as a drug-delivery system. For instance, when administered intravenously, the nanoparticles undergo rapid clearance from systemic circulation before reaching the site of action. Furthermore, plain PLGA nanoparticles cannot distinguish between different cell types. Recent research shows that surface functionalization of nanoparticles and development of new nanoparticulate dosage forms help overcome these delivery challenges and improve in vivo performance. Immense research efforts have propelled the development of diverse functional PLGA-based nanoparticulate delivery systems. Representative examples include PEGylated micelles/nanoparticles (PEG, polyethylene glycol), polyplexes, polymersomes, core-shell–type lipid-PLGA hybrids, cell-PLGA hybrids, receptor-specific ligand-PLGA conjugates, and theranostics. Each PLGA-based nanoparticulate dosage form has specific features that distinguish it from other nanoparticulate systems. This review focuses on fundamental concepts and practices that are used in the development of various functional nanoparticulate dosage forms. We describe how the attributes of these functional nanoparticulate forms might contribute to achievement of desired therapeutic effects that are not attainable using conventional therapies. Functional PLGA-based nanoparticulate systems are expected to deliver chemotherapeutic, diagnostic, and imaging agents in a highly selective and effective manner.

Sah, Hongkee; Thoma, Laura A; Desu, Hari R; Sah, Edel; Wood, George C

2013-01-01

29

Photothermal analysis of individual nanoparticulate samples using micromechanical resonators.  

PubMed

The ability to detect and analyze single sample entities such as single nanoparticles, viruses, spores, or molecules is of fundamental interest. This can provide insight into the individual specific properties which may differ from the statistical sample average. Here we introduce resonant photothermal spectroscopy, a novel method that enables the analysis of individual nanoparticulate samples. Absorption of light by an individual sample placed on a microstring resonator results in local heating of the string, which is reflected in its resonance frequency. The working principle of the spectrometer is demonstrated by analyzing the optical absorption of different micro- and nanoparticles on a microstring. We present the measurement of a simple absorption spectrum of multiple polystyrene microparticles illuminated with an unfocused LED light source. Using a diode laser, single 170 nm polystyrene nanoparticles are detected. With the current setup, nanoparticulate samples with a mass of ~40 ag are detectable. By using nanostrings, visible and infrared photothermal spectroscopy in the subattogram mass regime is possible and single molecule detection is within reach. PMID:23799869

Larsen, Tom; Schmid, Silvan; Villanueva, Luis G; Boisen, Anja

2013-07-08

30

Electro- and nonlinear optics of liquid crystal materials with nanoparticulate internal structure  

NASA Astrophysics Data System (ADS)

The combination of liquid crystals (LCs) and reconfigurable nanoparticulate networks results in most versatile materials for controlling light beams. These material systems can be used for developing multi-functional reconfigurable photonics and opto-electronics components and spatial light modulators with ultimate light modulating capabilities. We review here our results in laser recording of one and two-dimensional diffraction gratings and gratings with variable pitch. Nonlinear optical properties of LC with nanoparticulate internal networks and diffraction gratings laser-recorded in these materials are discussed. Nanoparticulate networks are capable of stabilizing the thermodynamic relaxation of photoinduced cis-isomers of molecules in photosensitive azobenzene LCs used as host for the nanoparticulate network leading to bistability of the phase state (anisotropic and isotropic) of the material, and reversible all-optical switching between those states.

Tabiryan, Nelson; Grozhik, Vladimir; Nersisyan, Sarik; Serak, Svetlana

2003-11-01

31

The synthesis of metal nanoparticulate catalysts within functional microgel particles  

NASA Astrophysics Data System (ADS)

Electrostatically and sterically stabilized polymer microgel particles have been prepared containing either amino (poly(2-(diethylamino)ethyl methacrylate), PDEA) or carboxylic acid (poly(acrylic acid), PAA; poly(methacrylic acid), PMMA) functional groups. The PDEA, PAA and PMAA particles can be used for the incorporation of a large variety of metal nanoparticulate catalysts due to their functional amine and carboxylic acid groups; Pd, Ru and Ni nanoparticles have been synthesized. The more polar PAA microgels were designed as the nanocatalyst carrier system in aqueous reaction media while the less polar PMAA particles were prepared as the metal nanoparticle template for use in catalytic reactions that take place in organic solvents. The sterically and electrostatically stabilized microgel particles possess surface functional groups that can potentially interact with the microchannel walls of microfluidic catalytic reactors.

Kaliva, Maria; Pavlopoulou, Eleni; Christodoulakis, Konstantinos; Vamvakaki, Maria; Anastasiadis, Spiros H.

2012-02-01

32

Functionally Graded Dual-Nanoparticulate-Reinforced Aluminum Matrix Composite Materials  

NASA Astrophysics Data System (ADS)

Functionally graded carbon nanotubes (CNT) and nano Silicon carbide (nSiC) reinforced aluminum (Al) matrix composite materials were fully densified by a simple ball milling and hot-pressing processes. The nSiC was used as a physical mixing agent to increase dispersity of the CNT in the Al particles. It was observed that the CNT was better dispersed in the Al particles with a nSiC mixing agent compared to without it used. SEM micrograph showed that the interface of the each layers had very tightly adhesion without any serious pores and micro-cracks. This functionally graded dual-nanoparticulate-reinforced Al matrix composite by powder metallurgical approach could also be applied to comples matrix materials.

Kwon, Hansang; Lee, Gil-Geun; Leparoux, Marc; Kawasaki, Akira

2013-03-01

33

A TEM analysis of nanoparticulates in a Polar ice core  

SciTech Connect

This paper explores the prospect for analyzing nanoparticulates in age-dated ice cores representing times in antiquity to establish a historical reference for atmospheric particulate regimes. Analytical transmission electron microscope (TEM) techniques were utilized to observe representative ice-melt water drops dried down on carbon/formvar or similar coated grids. A 10,000-year-old Greenland ice core was melted, and representative water drops were transferred to coated grids in a clean room environment. Essentially, all particulates observed were aggregates and either crystalline or complex mixtures of nanocrystals. Especially notable was the observation of carbon nanotubes and related fullerene-like nanocrystal forms. These observations are similar with some aspects of contemporary airborne particulates including carbon nanotubes and complex nanocrystal aggregates.

Esquivel, E.V.; Murr, L.E

2004-03-15

34

Realization assessment of stabilizer with presonication on size-distribution of itraconazole nanoparticulate in wet-nanomilling  

Microsoft Academic Search

The paper investigates fabrication of itraconazole nanoparticulate in wet-nanomilling by appropriate alteration of the suspension properties and the milling parameters. By wet-nanomilling, stable nano-scale particulate can be prepared which have better physical properties. In this study, effects of adding stabilizer on nanoparticulate size and polydispersity index were performed during production of itraconazole nanoparticulate. In addition, the effect of pre-sonication followed

R. Radzuan; A. B. Abdul Majeed; T. Julianto; M. K. Hamzah; N. R. Hamzah; N. I. Bukhari

2009-01-01

35

An RGD-modified MRI-visible polymeric vector for targeted siRNA delivery to hepatocellular carcinoma in nude mice.  

PubMed

RNA interference (RNAi) has significant therapeutic promise for the genetic treatment of hepatocellular carcinoma (HCC). Targeted vectors are able to deliver small interfering RNA (siRNA) into HCC cells with high transfection efficiency and stability. The tripeptide arginine glycine aspartic acid (RGD)-modified non-viral vector, polyethylene glycol-grafted polyethylenimine functionalized with superparamagnetic iron oxide nanoparticles (RGD-PEG-g-PEI-SPION), was constructed as a magnetic resonance imaging (MRI)-visible nanocarrier for the delivery of Survivin siRNA targeting the human HCC cell line Bel-7402. The biophysical characterization of the RGD-PEG-g-PEI-SPION was performed. The RGD-modified complexes exhibited a higher transfection efficiency in transferring Survivin siRNA into Bel-7402 cells compared with a non-targeted delivery system, which resulted in more significant gene suppression at both the Survivin mRNA and protein expression levels. Then, the level of caspase-3 activation was significantly elevated, and a remarkable level of tumor cell apoptosis was induced. As a result, the tumor growth in the nude mice Bel-7402 hepatoma model was significantly inhibited. The targeting ability of the RGD-PEG-g-PEI-SPION was successfully imaged by MRI scans performed in vitro and in vivo. Our results strongly indicated that the RGD-PEG-g-PEI-SPION can potentially be used as a targeted non-viral vector for altering gene expression in the treatment of hepatocellular carcinoma and for detecting the tumor in vivo as an effective MRI probe. PMID:23922634

Wu, Chun; Gong, Faming; Pang, Pengfei; Shen, Min; Zhu, Kangshun; Cheng, Du; Liu, Zhihao; Shan, Hong

2013-06-07

36

An RGD-Modified MRI-Visible Polymeric Vector for Targeted siRNA Delivery to Hepatocellular Carcinoma in Nude Mice  

PubMed Central

RNA interference (RNAi) has significant therapeutic promise for the genetic treatment of hepatocellular carcinoma (HCC). Targeted vectors are able to deliver small interfering RNA (siRNA) into HCC cells with high transfection efficiency and stability. The tripeptide arginine glycine aspartic acid (RGD)-modified non-viral vector, polyethylene glycol-grafted polyethylenimine functionalized with superparamagnetic iron oxide nanoparticles (RGD-PEG-g-PEI-SPION), was constructed as a magnetic resonance imaging (MRI)-visible nanocarrier for the delivery of Survivin siRNA targeting the human HCC cell line Bel-7402. The biophysical characterization of the RGD-PEG-g-PEI-SPION was performed. The RGD-modified complexes exhibited a higher transfection efficiency in transferring Survivin siRNA into Bel-7402 cells compared with a non-targeted delivery system, which resulted in more significant gene suppression at both the Survivin mRNA and protein expression levels. Then, the level of caspase-3 activation was significantly elevated, and a remarkable level of tumor cell apoptosis was induced. As a result, the tumor growth in the nude mice Bel-7402 hepatoma model was significantly inhibited. The targeting ability of the RGD-PEG-g-PEI-SPION was successfully imaged by MRI scans performed in vitro and in vivo. Our results strongly indicated that the RGD-PEG-g-PEI-SPION can potentially be used as a targeted non-viral vector for altering gene expression in the treatment of hepatocellular carcinoma and for detecting the tumor in vivo as an effective MRI probe.

Shen, Min; Zhu, Kangshun; Cheng, Du; Liu, Zhihao; Shan, Hong

2013-01-01

37

Miniemulsion polymerization  

Microsoft Academic Search

Miniemulsions have some unique and desirable properties. They are far more robust to variations in the recipe or contaminant levels than conventional emulsions. Particle number was found to be less sensitive by at least an order of magnitude, to changes in initiator, water-phase retarder, and oil-phase inhibitor concentrations than macroemulsion polymerizations. This is because, unlike macroemulsion polymerization, there is no

F. J Schork; G. W Poehlein; S Wang; J Reimers; J Rodrigues; C Samer

1999-01-01

38

Nucleic Acids Bind to Nanoparticulate iron (II) Monosulphide in Aqueous Solutions  

NASA Astrophysics Data System (ADS)

In the hydrothermal FeS-world origin of life scenarios nucleic acids are suggested to bind to iron (II) monosulphide precipitated from the reaction between hydrothermal sulphidic vent solutions and iron-bearing oceanic water. In lower temperature systems, the first precipitate from this process is nanoparticulate, metastable FeSm with a mackinawite structure. Although the interactions between bulk crystalline iron sulphide minerals and nucleic acids have been reported, their reaction with nanoparticulate FeSm has not previously been investigated. We investigated the binding of different nucleic acids, and their constituents, to freshly precipitated, nanoparticulate FeSm. The degree to which the organic molecules interacted with FeSm is chromosomal DNA > RNA > oligomeric DNA > deoxadenosine monophosphate ? deoxyadenosine ? adenine. Although we found that FeSm does not fluoresce within the visible spectrum and there is no quantum confinement effect seen in the absorption, the mechanism of linkage of the FeSm to these biomolecules appears to be primarily electrostatic and similar to that found for the attachment of ZnS quantum dots. The results of a preliminary study of similar reactions with nanoparticulate CuS further supported the suggestion that the interaction mechanism was generic for nanoparticulate transition metal sulphides. In terms of the FeS-world hypothesis, the results of this study further support the idea that sulphide minerals precipitated at hydrothermal vents interact with biomolecules and could have assisted in the formation and polymerisation of nucleic acids.

Hatton, Bryan; Rickard, David

2008-06-01

39

Microstructures and nanostructures for environmental carbon nanotubes and nanoparticulate soots.  

PubMed

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 ( approximately 5 to 50 nm diameter) differentiate themselves from multiconcentric fullerenic nanoparticles and especially turbostratic BC and carbonaceous soot nanospherules ( approximately 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

2008-12-01

40

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.

Brito, Luis; Amiji, Mansoor

2007-01-01

41

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.

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

2013-01-01

42

Pharmaceutical development and regulatory considerations for nanoparticles and nanoparticulate drug delivery systems.  

PubMed

Pharmaceutical nanomaterials (NMs) encompass a wide variety of materials including drug nanoparticles (NPs), which can be amorphous or crystalline; or nanoparticulate drug delivery systems, such as micelles, microemulsions, liposomes, drug-polymer conjugates, and antibody-drug conjugates. These NMs are either transient or persistent-depending on whether the integrity of their structure and size is maintained until reaching the site of drug action. Examples of several approved drug products are included as pharmaceutical nanoparticulate systems along with a commentary on the current development issues and paradigms for various categories of NPs. This commentary discusses the preparation of nanoparticulate systems for commercial development, and the biopharmaceutical and pharmacokinetic advantages of these systems. A criterion of criticality is defined that incorporates the structure, in addition to size requirement of pharmaceutical NPs to identify systems that may require special development and regulatory considerations. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:3867-3882, 2013. PMID:24037829

Narang, Ajit S; Chang, Rong-Kun; Hussain, Munir A

2013-08-23

43

Combustion-derived nanoparticulate induces the adverse vascular effects of diesel exhaust inhalation  

PubMed Central

Aim Exposure to road traffic and air pollution may be a trigger of acute myocardial infarction, but the individual pollutants responsible for this effect have not been established. We assess the role of combustion-derived-nanoparticles in mediating the adverse cardiovascular effects of air pollution. Methods and results To determine the in vivo effects of inhalation of diesel exhaust components, 16 healthy volunteers were exposed to (i) dilute diesel exhaust, (ii) pure carbon nanoparticulate, (iii) filtered diesel exhaust, or (iv) filtered air, in a randomized double blind cross-over study. Following each exposure, forearm blood flow was measured during intra-brachial bradykinin, acetylcholine, sodium nitroprusside, and verapamil infusions. Compared with filtered air, inhalation of diesel exhaust increased systolic blood pressure (145 ± 4 vs. 133 ± 3 mmHg, P< 0.05) and attenuated vasodilatation to bradykinin (P= 0.005), acetylcholine (P= 0.008), and sodium nitroprusside (P< 0.001). Exposure to pure carbon nanoparticulate or filtered exhaust had no effect on endothelium-dependent or -independent vasodilatation. To determine the direct vascular effects of nanoparticulate, isolated rat aortic rings (n= 6–9 per group) were assessed in vitro by wire myography and exposed to diesel exhaust particulate, pure carbon nanoparticulate and vehicle. Compared with vehicle, diesel exhaust particulate (but not pure carbon nanoparticulate) attenuated both acetylcholine (P< 0.001) and sodium-nitroprusside (P= 0.019)-induced vasorelaxation. These effects were partially attributable to both soluble and insoluble components of the particulate. Conclusion Combustion-derived nanoparticulate appears to predominately mediate the adverse vascular effects of diesel exhaust inhalation. This provides a rationale for testing environmental health interventions targeted at reducing traffic-derived particulate emissions.

Mills, Nicholas L.; Miller, Mark R.; Lucking, Andrew J.; Beveridge, Jon; Flint, Laura; Boere, A. John F.; Fokkens, Paul H.; Boon, Nicholas A.; Sandstrom, Thomas; Blomberg, Anders; Duffin, Rodger; Donaldson, Ken; Hadoke, Patrick W.F.; Cassee, Flemming R.; Newby, David E.

2011-01-01

44

Design and assembly of solid-phases for the effective recovery of nanoparticulate bioproducts in fluidised bed contactors.  

PubMed

Practical recovery of nanoparticulate bioproducts from suspension feedstocks has been studied in batch, fixed bed and fluidised bed adsorptive contactors. The performance of five discrete configurations of adsorbent solid phase has been critically evaluated in the anion exchange recovery of mg quantities of BSA nanoparticles. These have served as surrogate size mimics of less easily sourced viral and plasmid gene therapy vectors, characterised by high value and a shortage of supply in quantities sufficient for research and development. Performance parameters of binding capacity, efficacy of washing, desorption efficiency and total cycle time were strongly influenced by the external and internal topographies of solid phases, together with the localised concentrations of interacting chemical ligands which modulate adsorption. In respect of a full operational recovery cycle, porous adsorbents developed for refined chromatographic fractionation of macromolecules, appear less suited overall than solid, nonporous particles, or solid particles coated with a shallow pellicle of active adsorbent material. Such findings have been confirmed in a detailed demonstration of the recovery of plasmid DNA (7.8 Kb) from chemical lysates of Escherichia coli. PMID:11787793

Zhang, Z; Burton, S; Williams, S; Thwaites, E; Lyddiatt, A

2001-01-01

45

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

46

Application of Size Exclusion Chromatography in the Development and Characterization of Nanoparticulate Drug Delivery Systems  

Microsoft Academic Search

The successful production of effective nanoparticulate drug delivery systems depends on maintaining the characteristics of the starting materials and the final formulation. Since compendial standards for traditional drug delivery systems do not always apply to nanosystems, analytical procedures for nanosized delivery systems must be established. This will ensure the quality of such products as they reach the marketplace. Size exclusion

Daniel P. Otto; Hermanus C. M. Vosloo; Melgardt M. de Villiers

2007-01-01

47

Microemulsion Polymerization  

Microsoft Academic Search

Polymerization in microemulsions is reviewed. The effects of internal microstructure (oil in water, water in oil, bicontinuous) on resulting polymer morphology and characteristics are described. Aspects controlling latex particle size and composite closed cell and open cell length scales are discussed. Formulation effects on polymer functionalization are outlined.

Florentina M. Pavel

2004-01-01

48

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

49

Low temperature NO 2 sensitivity of nano-particulate SnO 2 film for work function sensors  

Microsoft Academic Search

Work function based investigations of NO2 sensitivity of tin oxide (SnO2) nano-particulate films were carried out at low temperatures under different humidity conditions. A simple preparation technique was employed to obtain stoichiometric nano-particulate SnO2 films. The nano-particles size was determined by atomic force microscopy (AFM) and the work function measurements were done at 130°C by a computer controlled Kelvin probe

A. Karthigeyan; R. P. Gupta; K. Scharnagl; M. Burgmair; M. Zimmer; S. K. Sharma; I. Eisele

2001-01-01

50

Biokompatible Polymere  

NASA Astrophysics Data System (ADS)

Der klinische Einsatz von synthetischen Polymeren begann in den 60-er Jahren in Form von Einwegartikeln, wie beispielsweise Spritzen und Kathetern, vor allem aufgrund der Tatsache, dass Infektionen infolge nicht ausreichender Sterilität der wiederverwendbaren Artikel aus Glas und metallischen Werkstoffen durch den Einsatz von sterilen Einwegartikeln signifikant reduziert werden konnten [1]. Die Einführung der medizinischen Einwegartikel aus Polymeren erfolgte somit nicht nur aus ökonomischen, sondern auch aus hygienischen Gründen. Wegen der steigenden Anzahl synthetischer Polymere und dem zunehmenden Bedarf an ärztlicher Versorgung reicht die Anwendung von Polymeren in der Medizin von preisgünstigen Einwegartikeln, die nur kurzzeitig intrakorporal eingesetzt werden, bis hin zu Implantaten, welche über eine längere Zeit grossen Beanspruchungen im menschlichen Körper ausgesetzt sind. Die steigende Verbreitung von klinisch eingesetzten Polymeren ist auf ihre einfache und preisgünstige Verarbeitbarkeit in eine Vielzahl von Formen und Geometrien sowie auf ihr breites Eigenschaftsspektrum zurückzuführen. Polymere werden daher in fast allen medizinischen Bereichen eingesetzt.

Ha, Suk-Woo; Wintermantel, Erich; Maier, Gerhard

51

Osteogenic and antimicrobial nanoparticulate calcium phosphate and poly-(D,L-lactide-co-glycolide) powders for the treatment of osteomyelitis.  

PubMed

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

2013-04-13

52

Effective polymeric dispersants for vacuum, convection and freeze drying of drug nanosuspensions.  

PubMed

Drying nanosuspensions into redispersable powders is a critical issue in developing solid dosage forms of drug nanoparticles. The particle fusion and chain entanglement of polymeric steric stabilizers adsorbed onto the nanoparticle surface should be prevented to retain redispersibility after drying. Herein, we report that only a small amount of polymeric dispersants such as carrageenan, gelatin, and alginic acid between 0.5 and 3 wt.% in various drug nanosuspensions can provide sufficient redispersibility in vacuum, convection, and freeze drying. In vacuum and freeze drying of naproxen nanosuspensions, the addition of only 0.5 wt.% carrageenan resulted in the formation of redispersable nanoparticulate powders. The amounts of polymeric dispersants required for redispersibility was lowest for carrageenan and highest for gelatin. The specific interactions between the dispersants and steric stabilizers (or drugs), in addition to viscosity increase during drying, appeared to effectively prevent irreversible particle aggregation. PMID:20637852

Kim, Sujung; Lee, Jonghwi

2010-07-15

53

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

54

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

55

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

56

Mössbauer analysis of the phase distribution present in nanoparticulate Fe/SiO2 samples  

NASA Astrophysics Data System (ADS)

Results are presented on the phase distribution and magnetic properties of nanoparticulate Fe/SiO2 samples prepared by high-energy ball milling. From our data, we suggest that the elevated coercivities measured in the samples are linked to the coupling of the core of the particles (?-Fe) with a highly disordered phase present in their surface region and whose behavior exhibits some similarities with a spin-glass phase.

de Julián, C.; Alcázar, G. A. Pérez; Cebollada, F.; Montero, M. I.; González, J. M.; Marco, J. F.

1999-08-01

57

Effect of voids and pressure on melting of nano-particulate and bulk aluminum  

Microsoft Academic Search

Molecular dynamics simulations are performed using isobaric–isoenthalpic (NPH) ensembles to study the effect of internal defects\\u000a in the form of voids on the melting of bulk and nano-particulate aluminum in the size range of 2–9 nm. The main objectives\\u000a are to determine the critical interfacial area required to overcome the free energy barrier for the thermodynamic phase transition,\\u000a and to explore

Puneesh Puri; Vigor Yang

2009-01-01

58

Preparation and characterization of silica nanoparticulate polyacrylonitrile composite and porous nanofibers  

NASA Astrophysics Data System (ADS)

In this study, polyacrylonitrile (PAN) composite nanofibers containing different amounts of silica nanoparticulates have been obtained via electrospinning. The surface morphology, thermal properties and crystal structure of PAN/silica nanofibers are characterized using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, wide-angle x-ray diffraction (WAXD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The results indicate that the addition of silica nanoparticulates affects the structure and properties of the nanofibers. In addition to PAN/silica composite nanofibers, porous PAN nanofibers have been prepared by selective removal of the silica component from PAN/silica composite nanofibers using hydrofluoric (HF) acid. ATR-FTIR and thermal gravimetric analysis (TGA) experiments validate the removal of silica nanoparticulates by HF acid, whereas SEM and TEM results reveal that the porous nanofibers obtained from composite fibers with higher silica contents exhibited more nonuniform surface morphology. The Brunauer-Emmett-Teller (BET) surface area of porous PAN nanofibers made from PAN/silica (5 wt%) composite precursors is higher than that of pure nonporous PAN nanofibers.

Ji, Liwen; Saquing, Carl; Khan, Saad A.; Zhang, Xiangwu

2008-02-01

59

Preparation and characterization of silica nanoparticulate-polyacrylonitrile composite and porous nanofibers.  

PubMed

In this study, polyacrylonitrile (PAN) composite nanofibers containing different amounts of silica nanoparticulates have been obtained via electrospinning. The surface morphology, thermal properties and crystal structure of PAN/silica nanofibers are characterized using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, wide-angle x-ray diffraction (WAXD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The results indicate that the addition of silica nanoparticulates affects the structure and properties of the nanofibers. In addition to PAN/silica composite nanofibers, porous PAN nanofibers have been prepared by selective removal of the silica component from PAN/silica composite nanofibers using hydrofluoric (HF) acid. ATR-FTIR and thermal gravimetric analysis (TGA) experiments validate the removal of silica nanoparticulates by HF acid, whereas SEM and TEM results reveal that the porous nanofibers obtained from composite fibers with higher silica contents exhibited more nonuniform surface morphology. The Brunauer-Emmett-Teller (BET) surface area of porous PAN nanofibers made from PAN/silica (5 wt%) composite precursors is higher than that of pure nonporous PAN nanofibers. PMID:21730729

Ji, Liwen; Saquing, Carl; Khan, Saad A; Zhang, Xiangwu

2008-02-01

60

Vector Addition  

NSDL National Science Digital Library

This 2D applet simulates vector addition geometrically. The user selects the angle and magnitude of two vectors, which are then added together by the applet. The resultant vector and the values of its magnitude and angle, as well as the values of the x and y components of all three vectors, are calculated and displayed.

Duffy, Andrew

2004-11-28

61

Vector Calculator  

NSDL National Science Digital Library

A simple Java applet enabling users to add two two-dimensional vectors. The user can choose the two vectors by clicking on a grid. The components, magnitude, and direction are immediately shown. Once the two vectors are chosen, a press of a button shows the vector sum, its components, its magnitude and its direction.

Gea-Banacloche

2009-08-10

62

Nanoparticulate Adjuvants and Delivery Systems for Allergen Immunotherapy  

PubMed Central

In the last decades, significant progress in research and clinics has been made to offer possible innovative therapeutics for the management of allergic diseases. However, current allergen immunotherapy shows limitations concerning the long-term efficacy and safety due to local side effects and risk of anaphylaxis. Thus, effective and safe vaccines with reduced dose of allergen have been developed using adjuvants. Nevertheless, the use of adjuvants still has several disadvantages, which limits its use in human vaccines. In this context, several novel adjuvants for allergen immunotherapy are currently being investigated and developed. Currently, nanoparticles-based allergen-delivery systems have received much interest as potential adjuvants for allergen immunotherapy. It has been demonstrated that the incorporation of allergens into a delivery system plays an important role in the efficacy of allergy vaccines. Several nanoparticles-based delivery systems have been described, including biodegradable and nondegradable polymeric carriers. Therefore, this paper provides an overview of the current adjuvants used for allergen immunotherapy. Furthermore, nanoparticles-based allergen-delivery systems are focused as a novel and promising strategy for allergy vaccines.

De Souza Reboucas, Juliana; Esparza, Irene; Ferrer, Marta; Sanz, Maria Luisa; Irache, Juan Manuel; Gamazo, Carlos

2012-01-01

63

Living anionic polymerization  

Microsoft Academic Search

For about 40 years living anionic polymerization has been the premier technique for the synthesis of model polymers of controlled architecture and narrow molecular weight distribution (MWD). Nowadays, despite the continuing development of new strategies for the synthesis of well-defined polymers and copolymers (e.g. group transfer polymerization, living radical polymerization, etc.), anionic polymerization continues to be the most reliable and

Kunlun Hong; David Uhrig; Jimmy W Mays

1999-01-01

64

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.

Integrated Teaching And Learning Program

65

Biogenic nanoparticulate UO 2: Synthesis, characterization, and factors affecting surface reactivity  

NASA Astrophysics Data System (ADS)

The surface reactivity of biogenic, nanoparticulate UO 2 with respect to sorption of aqueous Zn(II) and particle annealing is different from that of bulk uraninite because of the presence of surface-associated organic matter on the biogenic UO 2. Synthesis of biogenic UO 2 was accomplished by reduction of aqueous uranyl ions, UO22+ by Shewanella putrefaciens CN32, and the resulting nanoparticles were washed using one of two protocols: (1) to remove surface-associated organic matter and soluble uranyl species (NAUO2), or (2) to remove only soluble uranyl species (BIUO2). A suite of bulk and surface characterization techniques was used to examine bulk and biogenic, nanoparticulate UO 2 as a function of particle size and surface-associated organic matter. The N 2-BET surface areas of the two biogenic UO 2 samples following the washing procedures are 128.63 m 2 g -1 (NAUO2) and 92.56 m 2 g -1 (BIUO2), and the average particle sizes range from 5-10 nm based on TEM imaging. Electrophoretic mobility measurements indicate that the surface charge behavior of biogenic, nanoparticulate UO 2 (both NAUO2 and BIUO2) over the pH range 3-9 is the same as that of bulk. The U L III-edge EXAFS spectra for biogenic UO 2 (both NAUO2 and BIUO2) were best fit with half the number of second-shell uranium neighbors compared to bulk uraninite, and no oxygen neighbors were detected beyond the first shell around U(IV) in the biogenic UO 2. At pH 7, sorption of Zn(II) onto both bulk uraninite and biogenic, nanoparticulate UO 2 is independent of electrolyte concentration, suggesting that Zn(II) sorption complexes are dominantly inner-sphere. The maximum surface area-normalized Zn(II) sorption loadings for the three substrates were 3.00 ± 0.20 ?mol m -2 UO 2 (bulk uraninite), 2.34 ± 0.12 ?mol m -2 UO 2 (NAUO2), and 2.57 ± 0.10 ?mol m -2 UO 2 (BIUO2). Fits of Zn K-edge EXAFS spectra for biogenic, nanoparticulate UO 2 indicate that Zn(II) sorption is dependent on the washing protocol. Zn-U pair correlations were observed at 2.8 ± 0.1 Å for NAUO2 and bulk uraninite; however, they were not observed for sample BIUO2. The derived Zn-U distance, coupled with an average Zn-O distance of 2.09 ± 0.02 Å, indicates that Zn(O,OH) 6 sorbs as bidentate, edge-sharing complexes to UO 8 polyhedra at the surface of NAUO2 nanoparticles and bulk uraninite, which is consistent with a Pauling bond-valence analysis. The absence of Zn-U pair correlations in sample BIUO2 suggests that Zn(II) binds preferentially to the organic matter coating rather than the UO 2 surface. Surface-associated organic matter on the biogenic UO 2 particles also inhibited particle annealing at 90 °C under anaerobic conditions. These results suggest that surface-associated organic matter decreases the reactivity of biogenic, nanoparticulate UO 2 surfaces relative to aqueous Zn(II) and possibly other environmental contaminants.

Singer, David M.; Farges, François; Brown, Gordon E., Jr.

2009-06-01

66

Nanoparticulate cerium dioxide and cerium dioxide-titanium dioxide composite thin films on glass by aerosol assisted chemical vapour deposition  

NASA Astrophysics Data System (ADS)

Two series of composite thin films were deposited on glass by aerosol assisted chemical vapour deposition (AACVD)—nanoparticulate cerium dioxide and nanoparticulate cerium dioxide embedded in a titanium dioxide matrix. The films were analysed by a range of techniques including UV-visible absorption spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive analysis by X-rays. The AACVD prepared films showed the functional properties of photocatalysis and super-hydrophilicity. The CeO 2 nanoparticle thin films displaying photocatalysis and photo-induced hydrophilicity almost comparable to that of anatase titania.

Qureshi, Uzma; Dunnill, Charles W.; Parkin, Ivan P.

2009-11-01

67

Oral Nanoparticulate Atorvastatin Calcium is More Efficient and Safe in Comparison to Lipicure ® in Treating Hyperlipidemia  

Microsoft Academic Search

Atorvastatin calcium (AC) is a second-generation 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor approved for clinical\\u000a use as a lipid lowering agent. AC, the world’s best selling drug is associated with poor oral bioavailability and serious\\u000a adverse effects like rhabdomyolysis on chronic administration. A biodegradable nanoparticulate approach was introduced here\\u000a with a view to improving the efficacy and safety of AC. Poly lactide-co-glycolic acid

A. K. Meena; D. Venkat Ratnam; G. Chandraiah; D. D. Ankola; P. Rama Rao; M. N. V. Ravi Kumar

2008-01-01

68

Grafting of PMMA brushes on titania nanoparticulate surface via surface-initiated conventional radical and “controlled” radical polymerization (ATRP)  

Microsoft Academic Search

Stable dispersion of titania nanoparticles in organic solvents are obtained by grafting poly(methyl methacrylate) layer on\\u000a to the surface. Titania nanoparticles are synthesized through the hydrolysis of titanium (IV) isopropoxide. The average size\\u000a of the titania particles is found to be 15 ± 2 nm. The polymer layer was introduced onto the surface by immobilizing the initiating\\u000a moiety. Azo initiator moiety required for

G. K. Raghuraman; Jürgen Rühe; Raghavachari Dhamodharan

2008-01-01

69

Novel Nanoparticulate Gel Formulations of Steroids for the Treatment of Macular Edema  

PubMed Central

Purpose: This article describes the development and characterization of PLGA nanoparticles of dexamethasone (DEX), hydrocortisone acetate (HA), and prednisolone acetate (PA) suspended in thermosensitive gels indicated for the treatment of macular edema (ME). Methods: Nanoparticles were prepared by oil-in-water (O/W) emulsion and dialysis methods using PLGA 50:50 and PLGA 65:35. These particles were characterized for entrapment efficiency, size distribution, surface morphology, crystallinity, and in vitro release. Further, ex vivo permeation studies of DEX in suspension and nanoparticulate formulations were carried out across the rabbit sclera. Results: Entrapment efficiencies of DEX, HA, and PA were found to be lower with the dialysis method. O/W emulsion/solvent evaporation technique resulted in higher entrapment efficiencies, that is, 77.3%, 91.3%, 92.3% for DEX, HA, and PA, respectively. Release from nanoparticles suspended in thermosensitive gels followed zero-order kinetics with no apparent burst effect. Ex vivo permeability studies further confirmed sustained release of DEX from nanoparticles suspended in thermosensitive gels. Conclusions: These novel nanoparticulate systems containing particles suspended in thermosensitive gels may provide sustained retina/choroid delivery of steroids following episcleral administration.

2010-01-01

70

Natural and anthropogenic environmental nanoparticulates: Their microstructural characterization and respiratory health implications  

NASA Astrophysics Data System (ADS)

A wide range of environmental particulate matter (PM) both indoor and outdoor and consisting of natural and anthropogenic PM was collected by high volume air filters, electrostatic precipitation, and thermophoretic precipitation directly onto transmission electron microscope (TEM) coated grid platforms. These collected PM have been systematically characterized by TEM, energy-dispersive X-ray spectrometry (EDS) and scanning electron microscopy (SEM). In the El Paso, TX, USA/Juarez, Mexico metroplex 93% of outdoor PM 1 is crystalline while 40% of PM 1 is carbonaceous soot (including multiwall carbon nanotubes (MWCNTs) and multiconcentric fullerenes) PM. Multiply-replicated cytotoxicity ( in vitro) assays utilizing a human epithelial (lung model) cell line (A549) consistently demonstrated varying degrees of cell death for essentially all PM which was characterized as aggregates of nanoparticulates or primary nanoparticles. Cytokine release was detected for Fe 2O 3, chrysotile asbestos, BC, and MWCNT PM while reactive oxygen species (ROS) production has been detected for Fe 2O 3, asbestos, BC, and MWCNT aggregate PM as well as natural gas combustion PM. Nanoparticulate materials in the indoor and outdoor environments appear to be variously cytotoxic, especially carbonaceous nano-PM such as multiwall carbon nanotubes, black carbon, and soot nano-PM produced by natural gas combustion.

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

71

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.

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

2010-01-01

72

n-type perylene to fill voids in solution processed nanoparticulate zinc oxide thin films  

NASA Astrophysics Data System (ADS)

Using nanoparticle dispersions for printing of semiconductors would be the easiest way to evolve from classic printing technologies towards printed electronics. However, nanoparticular thin films are unfavorable in transistor applications due to two reasons: (i) The charge transport in the thin film or at its interfaces to the gate dielectric is disturbed by the voids between the nanoparticles. (ii) These layers are highly sensitive to surface adsorbates due to their high surface to volume ratio. Atmospheric surface adsorbates, e.g. on metal oxides are known to influence the electrical properties of the thin films. In order to overcome the disadvantages of the nanoparticulate thin film, this work targets both issues with a combined approach. By choosing a qualified surface adsorbate, the perturbing surface of the nanoparticles will be passivated. By using the surface adsorbate as a linker to an electron conducting organic molecule, the n-type organic will be eligible for filling the voids between the particles. We present the synthesis of a new pyrrolidone functionalized n-type perylene diimide and its application in hetero-layer nanoparticulate zinc oxide (ZnO) field-effect transistors.

Bubel, Simon; Ringk, Andreas; Strohriegl, Peter; Schmechel, Roland

2012-07-01

73

Design and assembly of solid-phases for the effective recovery of nanoparticulate bioproducts in fluidised bed contactors  

Microsoft Academic Search

Practical recovery of nanoparticulate bioproducts from suspension feedstocks has been studied in batch, fixed bed and fluidised bed adsorptive contactors. The performance of five discrete configurations of adsorbent solid phase has been critically evaluated in the anion exchange recovery of mg quantities of BSA nanoparticles. These have served as surrogate size mimics of less easily sourced viral and plasmid gene

Zhanren Zhang; Simon Burton; Sharon Williams; Eric Thwaites; Andrew Lyddiatt

2001-01-01

74

Nanoparticulate mackinawite formation; a stopped and continuous flow XANES and EXAFS investigation  

NASA Astrophysics Data System (ADS)

The sequestration of sulfur and iron within sedimentary iron sulfides, and ultimately as pyrite, is a major sink in global biogeochemical cycles of those elements and has impacts on global carbon and oxygen cycles. The formation of the metastable black iron (II) monosulfide mackinawite is a key process because mackinawite forms in aqueous solutions where the Fe(II) and S(-II) IAP exceeds mackinawite’s Ksp. Mackinawite is the first formed iron sulfide phase, a consequence of Ostwald’s step rule and is a reactant phase during the formation of thermodynamically stable sedimentary iron sulfide minerals such as pyrite. The reaction of dissolved Fe(II) and sulfide is extremely fast and reactions in the environmentally significant near-neutral pH range tend to completion in <1 second. We have combined stopped and continuous flow techniques with X-ray absorption spectroscopy to evaluate the products of the fast precipitation kinetics of mackinawite over millisecond timescales. EXAFS spectra and data collected during flow experiments were compared with those from a well characterised freeze-dried nanoparticulate mackinawite standard and with published data. Published work has used Rietveld crystal structure refinement to determine bond distances of 2.2558 and 2.5976Å for Fe-S and Fe-Fe respectively. In our experiments Fe K edge XANES is consistent with tetrahedrally coordinated Fe in the precipitated sulfide phase. EXAFS data show that local Fe-S and Fe-Fe coordination and interatomic distances (Fe-S = 2.24Å; Fe-Fe = 2.57Å) are consistent with those determined for the standard mackinawite and published data. The coordination and spacing are developed in the precipitated phase after <10ms reaction at pH5, and considerably faster in experiments at near neutral to alkaline pH. No evidence for phases structurally intermediate between hexaqua Fe(II) and precipitated mackinawite was observed. Aqueous FeS° cluster complexes previously identified as intermediates during mackinawite formation and iron sulfide mineral transformations did not contribute significantly to the EXAFS spectra collected. For environmental, geological and biogeochemical applications, the precipitation of the mineral mackinawite can be considered to proceed rapidly from aqueous Fe(II) and S(-II) ions to the nanoparticulate crystalline mineral. The materials labelled “disordered mackinawite”, or “amorphous FeS” phase which have been widely quoted in the iron sulfide literature do not form at any stage of the precipitation of mackinawite from aqueous solutions. Physical and chemical properties previously ascribed to an amorphous or disordered structure are a consequence of the nanoparticulate form of the first precipitated solid.

Butler, I. B.; Bell, A. M.; Charnock, J. M.; Rickard, D.; Vaughan, D. J.; Oldroyd, A.

2009-12-01

75

Tricritical Points in the Equilibrium Polymerization of Sulfur Solutions  

NASA Astrophysics Data System (ADS)

A dilute n-->0 vector model provides a useful description of equilibrium polymerization in a solvent. Such polymerization occurs in liquid sulfur solutions and leads to a lower critical solution point that is analogous to the tricritical point found in 3He-4He mixtures. In the mean-field approximation, the model is identical to an earlier theory of Scott. Nonclassical critical behavior can explain certain discrepancies between Scott's theory and experiment.

Wheeler, John C.; Pfeuty, Pierre

1981-05-01

76

Effects of SiC volume fraction and aluminum particulate size on interfacial reactions in SiC nanoparticulate reinforced aluminum matrix composites  

Microsoft Academic Search

The SiC nanoparticulate reinforced Al–3.0wt.% Mg composites were fabricated by combining pressureless infiltration with ball-milling and cold-pressing technology at 700°C for 2h. The effects of SiC nanoparticulate volume fractions (6%, 10% and 14%) and Al particulate sizes (38?m and 74?m) on interfacial reactions were investigated by SEM, TEM and X-ray diffraction. The results show that the MgO at the interface

Bowen Xiong; Zhifeng Xu; Qingsong Yan; Baiping Lu; Changchun Cai

77

Nanoparticulate platinum(II) anticancer drug: synthesis and characterization of amphiphilic cyclotriphosphazene-platinum(II) conjugates.  

PubMed

Novel cyclotriphosphazene-platinum(II) conjugates were prepared by hydrolysis and platination of the amphiphilic cyclotriphosphazenes grafted with equimolar hydrophilic methoxy-poly(ethylene glycol) (MPEG) and hydrophobic oligopeptide. These macromolecular conjugates were found to form stable nanoparticles with a mean diameter of approximately 90-200 nm depending on the hydrophobicity of the conjugated (diamine)platinum moieties. The nanoparticulate platinum(II) conjugates have shown temperature and concentration dependent particle sizes. However, the particle sizes of the conjugates were found to decrease to a certain size as the solution concentration was decreased but remained stable even at 10 microM, which is enough for systemic delivery by injection. The conjugates exhibited lower in vitro cytotoxicity than cisplatin but reasonably good activity against selected human tumor cell lines. PMID:17709142

Yu, Ji Young; Jun, Yong Joo; Jang, Soo Hyun; Lee, Hwa Jeong; Sohn, Youn Soo

2007-07-16

78

Cardiac oxidative damage in mice following exposure to nanoparticulate titanium dioxide.  

PubMed

Nanoparticulate titanium dioxide (nano-TiO2 ) is a widely used powerful nanoparticulate material with high stability, anticorrosion, and photocatalytic property. However, it is possible that during nano-TiO2 exposure, there may be negative effects on cardiovascular system in intoxicated mice. The present study was therefore undertaken to determine nano-TiO2 -induced oxidative stress and to determine whether nano-TiO2 intoxication alters the antioxidant system in the mouse heart exposed to 2.5, 5, and 10 mg/kg body weight nano-TiO2 for 90 consecutive days. The findings showed that long-term exposure to nano-TiO2 resulted in obvious titanium accumulation in heart, in turn led to sparse cardiac muscle fibers, inflammatory response, cell necrosis, and cardiac biochemical dysfunction. Nano-TiO2 exposure promoted remarkably reactive oxygen species production such as superoxide radicals, hydrogen peroxide, and increased malondialdehyde, carbonyl and 8-OHdG levels as degradation products of lipid, protein, and DNA peroxidation in heart. Furthermore, nano-TiO2 exposure attenuated the activities of antioxidative enzymes, such as superoxide dismutase, ascorbate peroxidase, glutathione reductase, glutathione-S-transferase, and levels of antioxidants including ascorbic acid, glutathione, and thiol in heart. Therefore, TiO2 NPs exposure may impair cardiovascular system in mice, and attention should be aroused on the application of nano-TiO2 and their potential long-term exposure effects especially on human beings. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A: 3238-3246, 2013. PMID:23553934

Sheng, Lei; Wang, Xiaochun; Sang, Xuezi; Ze, Yuguan; Zhao, Xiaoyang; Liu, Dong; Gui, Suxin; Sun, Qingqing; Cheng, Jie; Cheng, Zhe; Hu, Renping; Wang, Ling; Hong, Fashui

2013-04-02

79

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

Microsoft Academic Search

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

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

2007-01-01

80

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.

81

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

82

Vector Calculus  

NSDL National Science Digital Library

This is a series of lectures, authored by Chris Tisdell of the University of New South Wales, for MATH2111 "Higher Several Variable Calculus" and "Vector Calculus", which is a 2nd-year mathematics subject taught at UNSW, Sydney. This playlist provides a shapshot of some lectures presented in Session 1, 2009. These lectures focus on presenting vector calculus in an applied and engineering context, while maintaining mathematical rigour. Thus, this playlist may be useful to students of mathematics, but also to those of engineering, physics and the applied sciences. There is an emphasis on examples and also on proofs.

Tisdell, Chris

2010-12-16

83

Thermodynamics of Polymerization. I  

Microsoft Academic Search

I. THE CHILING TEMPERATURE CONCEPT A. Thermodynamic Approach The Gibbs free energy of a system at temperature T is defined as were H is the enthalpy and S the entropy of the system. The free energy change for any polymerization will be, therefore, When the polymer has a lower free energy than the initial monomer, a polymerization can occur spontaneously,

Hideo Sawada

1969-01-01

84

Molecularly imprinted polymeric membranes  

Microsoft Academic Search

Molecularly imprinted polymeric membranes have been emerged since 1990. Among various kinds of molecular imprinting studies, the application of molecular imprinting to membrane separation is still a novel investigation. In the present review paper, molecularly imprinted polymeric membranes are summarized and examined. The application of molecular imprinting to membrane separation shortly leads to high performance separation membranes.

Masakazu Yoshikawa

2001-01-01

85

The Polymerization Motor  

Microsoft Academic Search

Polymerization and depolymerization of actin filaments and microtubules are thought to generate force for movement in various kinds of cell motility, ranging from lamellipodial protrusion to chromosome segregation. This article reviews the thermodynamic and physical theories of how a nonequilibrium polymerization reac- tion can be used to transduce chemical energy into me- chanical energy, and summarizes the evidence suggesting that

Julie A. Theriot

2000-01-01

86

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

87

Stereocontrol in radical polymerization.  

PubMed

The stereospecific radical polymerization of vinyl esters, methacrylates, and alpha-substituted acrylates was studied. Fluoroalcohols, as a solvent, have remarkable effects on the stereoregularity of the radical polymerizations of vinyl acetate, vinyl pivalate, and vinyl benzoate, affording polymers rich in syndiotacticity, heterotacticity, and isotacticity, respectively. This method was successfully applied to the polymerization of methacrylates to give syndiotactic polymers. The steric repulsion between the entering monomer and the chain-end monomeric unit bound by the solvent through hydrogen bonding is important for the stereochemical control in these systems. Lewis acid catalysts, such as lanthanide trifluoromethanesulfonates and zinc salts, were also effective for the stereocontrol during the radical polymerization of methyl methacrylate, to reduce the syndiotacticity and alpha-(alkoxymethyl)acrylates to synthesize isotactic and syndiotactic polymers. Radical polymerization of the methacrylates bearing a bulky ester group, such as the triphenylmethyl methacrylate derivatives, gave highly isotactic polymers, as in the case of anionic polymerization. In addition, the control of one-handed helical conformation was attained in the radical polymerization of 1-phenyldibenzosuberyl methacrylate using chiral neomenthanethiol or cobalt(II) complexes as an additive. PMID:11893057

Habaue, S; Okamoto, Y

2001-01-01

88

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.

89

Double-coated poly (butylcynanoacrylate) nanoparticulate delivery systems for brain targeting of dalargin via oral administration.  

PubMed

The aim of this study is to evaluate oral administration of poly (butylcyanoacrylate) nanoparticulate delivery systems (PBCA-NDSs), double-coated with Tween 80 and poly (ethylene) glycol (PEG) 20000 for brain delivery of hexapeptide dalargin, an anti-nociceptive peptide that does not cross blood-brain barrier (BBB) by itself. Studies have proven the brain uptake of Tween 80 overcoated nanoparticles after intravenous administration, but studies for brain delivery of nanoparticles after oral administration had been limited due to reduced bioavailability of nanoparticles and extensive degradation of the peptide and/or nanoparticles by gastrointestinal enzymes. To address this problem, dalargin-loaded PBCA-NDS were successively double-coated with Tween 80 and PEG 20000 in varied concentrations of up to 2% each. Measurement of in vivo central anti-nociceptive effect of dalargin along with a dose response curve was obtained by the tail flick test following the oral administration of PBCA-NDSs to mice. Results from the tail flick test indicated that significant dalargin-induced analgesia was observed from PBCA-NDSs with double-coating of Tween and PEG in comparison with single-coating of either Tween or PEG. Hence, it could be concluded that surface coated PBCA-NDS can be used successfully for brain targeting of dalargin or other peptides administered orally. However, further studies are required to elucidate the exact transport mechanism of PBCA-NDSs from gastrointestinal tract to brain. PMID:15858853

Das, Debanjan; Lin, Senshang

2005-06-01

90

Effects of chronic nanoparticulate silver exposure to adult and juvenile sheepshead minnows (Cyprinodon variegatus).  

PubMed

The use of nanoparticulate silver (AgNP) is increasingly widespread and recently has been shown to have a plausible release route into aquatic environments. To date, relatively little research has examined the effects of AgNP on estuarine fish. The authors present data indicating that chronic exposure to low levels of AgNP induces significant adverse effects in both juvenile and adult sheepshead minnows (Cyprinodon variegarus; SHMs). Chronic exposure to low levels of AgNP produced significant increases in tissue burdens in both juvenile and adult SHMs, resulting in significant thickening of epithelia gill tissue and in dramatically altered gene expression profiles. The results do not appear to be attributable to the release of silver ions through particle dissolution. The alteration in gene expression was greatest in adult gonads, but no evidence of AgNP-related dysfunction was found at the tissue level. In contrast, the authors found a significant effect on gill morphology, but very little evidence of effect on gill transcription profiles. PMID:21994144

Griffitt, Robert J; Brown-Peterson, Nancy J; Savin, Daniel A; Manning, C Steve; Boube, Idrissa; Ryan, R A; Brouwer, Marius

2012-01-01

91

Kinetically Controlled Formation of a Novel Nanoparticulate ZnS with Mixed Cubic and Hexagonal Stacking  

SciTech Connect

Nanoparticulate ZnS with mixed cubic and hexagonal close packed stacking was synthesized by reaction of zinc acetate with thioacetamide in weakly acidic solutions. The influences of temperature, reaction time, amounts of reagents and solution pH on the nanoparticle size and phase constitution were investigated. Experimental results suggest that the stacking in the nano-ZnS is controlled primarily by the precipitation kinetics. Factors that slow the precipitation rate favor the growth of nanoparticles with mixed stacking, probably because the probabilities of forming wurtzite-like layers and sphalerite-like layers under these conditions are approximately equal. Under conditions of rapid precipitation, the growth of sphalerite is favored, probably due to the aggregation of molecular clusters with sphalerite-like structure. UV-vis spectroscopy reveals that twins and stacking faults in nano-ZnS result in an electronic structure that differs from those of nano-scale sphalerite and wurtzite. New vibrational modes present in IR spectra of the nano-ZnS with mixed stacking indicate that the materials have novel optical properties. Control of defect microstructure may allow use of nano-ZnS in new technological applications.

Zhang,H.; Chen, B.; Gilbert, B.; Banfield, J.

2006-01-01

92

Synthesis and characterization of nanoparticulate MnS within the pores of mesoporous silica  

SciTech Connect

Mesoporous silica was loaded with nanoparticulate MnS via a simple post-synthesis treatment. The mesoporous material that still contained surfactant was passivated to prevent MnS formation at the surface. The surfactant was extracted and a novel manganese ethylxanthate was used to impregnate the pore network. This precursor thermally decomposes to yield MnS particles that are smaller or equal to the pore size. The particles exhibit all three common polymorphs. The passivation treatment is most effective at lower loadings because at the highest loadings (SiO{sub 2}:MnS molar ratio of 6:1) large particles (>50 nm) form at the exterior of the mesoporous particles. The integrity of the mesoporous network is maintained through the preparation and high order is maintained. The MnS particles exhibit unexpected ferromagnetism at low temperatures. Strong luminescence of these samples is observed and this suggests that they may have a range of important application areas. - Graphical abstract: A novel manganese ethylxanthate precursor was used to impregnate the pore network of mesoporous silica and was decomposed to yield MnS particles smaller or equal to the pore size. The particles exhibit all three common polymorphs, demonstrate unexpected ferromagnetism at low temperatures and display a strong luminescence.

Barry, Louse; Copley, Mark [Department of Chemistry, University College Cork, Cork (Ireland); Holmes, Justin D. [Department of Chemistry, University College Cork, Cork (Ireland); Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2 (Ireland); Otway, David J. [Department of Chemistry, University College Cork, Cork (Ireland); Kazakova, Olga [National Physical Laboratory, Teddington (United Kingdom); Morris, Michael A. [Department of Chemistry, University College Cork, Cork (Ireland); Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2 (Ireland)], E-mail: m.morris@ucc.ie

2007-12-15

93

Anionic Polymerization of Isoprene.  

National Technical Information Service (NTIS)

The polymerization of isoprene with butyllithium in cyclohexane has been studied. The initiation reaction was found to be complex; plots of conversion of butyllithium against time are sigmoidal. The order with respect to the initiator was found to be betw...

D. J. Worsfold S. Bywater

1964-01-01

94

Nanoconfinement Effect on Polymerization  

NASA Astrophysics Data System (ADS)

Ring-opening metathesis polymerization of endo-dicyclopentadidene (DCPD) with second generation Grubbs catalyst is carried out under nanoscale constraint. Differential scanning calorimetry is used to study the polymerization reaction both in the bulk and in the nanopores of controlled pore glass as a function of heating rate; the Tg of the resulting reaction product is also determined. In 110 nm-diameter pores, DCPD undergoes incomplete polymerization followed by the reverse Diels-Alder reaction to form pentadiene. Decreasing the heating rate shifts both reactions towards lower temperatures but does not avert the side reaction. In the bulk unconfined case, the reverse Diels-Alder reaction only occurs in the absence of catalyst. The glass transition temperature of the nanoconfined polymerization product is 164 C, approximately 20 C higher than the polymer prepared under bulk conditions. Reaction kinetics in bulk and nanoconfined cases will also be discussed.

Vaddey, Maitri; Simon, Sindee

2011-03-01

95

Photocontrolled living polymerizations  

NASA Astrophysics Data System (ADS)

Living polymerizations involve the creation of polymer chains without significant irreversible chain transfer or chain termination. Such processes are widely used to access well-defined macromolecular materials with controlled architectures, such as block and star polymers. Although this concept was first realized for anionic polymerizations in the 1950s, many key recent advances have been made, most notably in the area of radical polymerization. Here, we report a living photopolymerization that involves photoexcited monomers. Exposure of metal-containing ferrocenophane monomers to Pyrex-filtered light from a mercury lamp (?>310 nm) or to bright sunlight in the presence of an anionic initiator leads to living polymerizations, in which the conversion and molecular weight of the resulting polymer can be controlled by the irradiation time. Photoirradiation selectively weakens the iron-cyclopentadienyl bond in the monomer, allowing the use of moderately basic and highly functional-group-tolerant initiators. The polymerization proceeds through attack of the initiator and propagating anion on the iron atom of the photoexcited monomer and, remarkably, the polymerization rate decreases with increasing temperature. Block copolymer formation is possible when the light source is alternately switched on and off in between sequential addition of different monomers, providing unprecedented, photocontrolled access to new types of functional polymers.

Tanabe, Makoto; Vandermeulen, Guido W. M.; Chan, Wing Yan; Cyr, Paul W.; Vanderark, Lawrence; Rider, David A.; Manners, Ian

2006-06-01

96

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

97

Inkjet-printed gold nanoparticulate patterns for surface finish in electronic package  

NASA Astrophysics Data System (ADS)

Gold (Au) pads for surface finish in electronic package were developed by the inkjet printing method. The Au ink for printing was prepared by Au nanoparticles (NPs) coated with capping molecules of dodecylamine (C12H25NH2). The microstructures of the inkjet-printed Au films were characterized after sintering in various gas flows. The film sintered in air showed that bonding between NPs was not enough for further grain growth due to the incomplete decomposition of the capping layer. The film sintered under nitrogen (N2) had NPs existing on the surface and the bottom which did not participate in sintering. When the film was sintered under N2-bubbled through formic acid (FA/N2), a large portion of the pores were observed to make a holey pancake-like structure of the film. The microstructures of the inkjet-printed Au film became denser with grain growth when Au NPs were sintered under mixed gas flows of FA/N2 and N2. The resistivity of film was 4.79 ?? cm, about twice the bulk value. Organic analysis showed that about 0.43% of residual organics was left in the film. Therefore, this Au film was chosen for solder ball shear test because the microstructure was denser compared to the films sintered under other gasses such as N2 or FA/N2 and less organic residue was found from organic analyses. Even though the film sintered under N2 showed the best electrical property (4.35 ?? cm), it was not adopted in the shear test because NPs remaining on the bottom of the film could lead to the poor adhesion between the film and substrate and show low shear strength. The shear force was 8.04 newton (N) on average and the strength was 64 MPa. This shear strength is good enough to substitute the inkjet-printed Au nanoparticulate film for electroplating in electronic package.

Jang, Seonhee; Cho, Hyejin; Kang, Seongkoo; Oh, Sungil; Kim, Donghoon

2011-11-01

98

Functional polymeric microspheres synthesized by radiation polymerization  

NASA Astrophysics Data System (ADS)

New functional microspheres consisting of diethylene glycol dimethacrylate (2G) and a methacryloyl monomer containing four amino acids, L-asparagynyl-L-alanyl-L-asparagynyl-L-proline methyl ester (MA-NANPOMe) were synthesized by radiation induced co-polymerization. These four amino acids were previously identified as a part of the immunodominant region of the circumsporozoite (CS) protein of Plasmodium falciparum. The use of this synthetic peptide as an antigen in immunoassay for malaria is promising: the microspheres exposed to the sera of malaria patients showed marked fluorescence, while the spheres contacted with sera of healthy donors showed no fluorescence.

Safranj, Agneza; Kano, Shigeyuki; Yoshida, Masaru; Omichi, Hideki; Katakai, Ryoichi; Suzuki, Mamoru

1995-08-01

99

Supramolecular polymeric hydrogels.  

PubMed

The supramolecular crosslinking of polymer chains in water by specific, directional and dynamic non-covalent interactions has led to the development of novel supramolecular polymeric hydrogels. These aqueous polymeric networks constitute an interesting class of soft materials exhibiting attractive properties such as stimuli-responsiveness and self-healing arising from their dynamic behaviour and that are crucial for a wide variety of emerging applications. We present here a critical review summarising the formation of dynamic polymeric networks through specific non-covalent interactions, with a particular emphasis on those systems based on host-guest complex formation, as well as the characterisation of their physical characteristics. Aqueous supramolecular chemistry has unlocked a versatile toolbox for the design and fine-tuning of the material properties of these hydrogels (264 references). PMID:22890548

Appel, Eric A; del Barrio, Jesús; Loh, Xian Jun; Scherman, Oren A

2012-08-13

100

Vector Addition Model  

NSDL National Science Digital Library

The Vector Addition model allows the user to practice vector addition of two vectors in two dimensions. You are given the magnitude and direction of the two vectors, and your goal is to fill in the nine values in the table (showing the x-component, y-component, and length) of the two vectors, and the resultant vector that is the sum of the first two vectors. The Vector Addition was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_bu_vector_addition.jar file will run the program if Java is installed.

Duffy, Andrew

2010-04-25

101

Elastic Energy Driven Polymerization  

PubMed Central

We present a molecular system where polymerization is controlled externally by tuning the elastic energy of the monomers. The elastic energy, provided by a DNA molecular spring, destabilizes the monomer state through a process analogous to domain swapping. This energy can be large (of ?10 kT) and thus drive polymerization at relatively low monomer concentrations. The monomer-dimer equilibrium provides a measurement of the elastic energy of the monomer, which in this construction appears limited by kink formation in the DNA molecular spring, in accord with previous theoretical and experimental investigations of the elasticity of sharply bent DNA.

Wang, Andrew; Zocchi, Giovanni

2009-01-01

102

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.

103

Electrodeposited nanoporous versus nanoparticulate ZnO films of similar roughness for dye-sensitized solar cell applications.  

PubMed

We present a comparative study of two different ZnO porous film morphologies for dye-sensitized solar cell (DSSC) fabrications. Nanoparticulate ZnO was prepared by the doctor-blade technique starting from a paste containing ZnO nanoparticles. Nanoporous ZnO films were grown by a soft template-assisted electrochemical growth technique. The film thicknesses were adjusted at similar roughness of about 300 in order to permit a worthy comparison. The effects on the cell performances of sensitization by dyes belonging to three different families, namely, xanthene (eosin Y) and indoline (D102, D131, D149 and D205) organic dyes as well as a ruthenium polypyridine complex (N719), have been investigated. The mesoporous electrodeposited matrix exhibits significant morphological changes upon the photoanode preparation, especially upon the dye sensitization, that yield to a dramatic change of the inner layer morphology and increase in the layer internal specific surface area. In the case of indoline dyes, better efficiencies were found with the electrodeposited ZnO porous matrixes compared to the nanoparticulate ones, in spite of significantly shorter electron lifetimes measured by impedance spectroscopy. The observation is interpreted in terms of much shorter transfer time in the oxide in the case of the electrodeposited ZnO films. Among the tested dyes, the D149 and D205 indoline organic dyes with a strong acceptor group were found the most efficient with the best cell over 4.6% of overall conversion efficiency. PMID:21082820

Guerin, V M; Magne, C; Pauporté, Th; Le Bahers, T; Rathousky, J

2010-11-17

104

Ozone-initiated histidine polymerization  

Microsoft Academic Search

The ozone-initiated histidine polymerization is found by spectroscopic methods. The structural characteristics of a polymer, as well as the kinetics and conditions of its formation are defined. The reaction scheme of the histidine polymerization is proposed.

L. K. Gerasimova; B. A. Tatarinov; N. N. Khovratovich; V. P. Khrapovitsky

1985-01-01

105

Smart Polymeric Materials  

Microsoft Academic Search

Smart polymeric materials respond with a considerable change in their properties to small changes in their environment. Environmental stimuli include temperature, pH, chemicals, and light. “Smart” stimuli-sensitive materials can be either synthetic or natural. This review discusses the application of smart materials as tools to solve biological problems such as bioseparation, drug delivery, biosensor design, tissue engineering, protein folding, and

Ipsita Roy; Munishwar Nath Gupta

2003-01-01

106

Polymerized Asphalt Emulsion.  

National Technical Information Service (NTIS)

It has been claimed that polymerized asphalt emulsion has outstanding characteristics of elasticity, adhesion, and cohesion which allows its use in seal coats in high speed, high volume roads, such as interstate highways. Another use would be on a lower c...

S. Q. Kidd

1990-01-01

107

RADIATION POLYMERIZATION DOSIMETRY  

Microsoft Academic Search

Quantitative studies of the high energy radiation photo sensitivity of ; certain liquid monomer-polymers have indicated a possible solution to the problem ; of high level dosimetry. Investigations of the relation between absorbed dose ; and factors which influence sensitivity have led to the development of a ; dependable system of radiation polymerization dosimetry. Changes in the ; composition of

F. E. Hoecker; I. W. Watkins; J. T. Han

1958-01-01

108

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

109

Flame retardant polymeric materials  

SciTech Connect

The flame retardation of polyolefins is the focus of this volume. Methods for reduction of smoke and experimental evaluation of flammability parameters for polymeric materials are discussed. The flammability evaluation methods for textiles and the use of mass spectrometry for analysis of polymers and their degradation products are also presented.

Lewin, M.; Atlas, S.M.; Pearce, E.M.

1982-01-01

110

Biodegradable Long-Circulating Polymeric Nanospheres  

Microsoft Academic Search

Injectable nanoparticulate carriers have important potential applications such as site-specific drug delivery or medical imaging. Conventional carriers, however, cannot generally be used because they are eliminated by the reticulo-endothelial system within seconds or minutes after intravenous injection. To address these limitations, monodisperse biodegradable nanospheres were developed from amphiphilic copolymers composed of two biocompatible blocks. The nanospheres exhibited dramatically increased blood

Ruxandra Gref; Yoshiharu Minamitake; Maria Teresa Peracchia; Vladimir Trubetskoy; Vladimir Torchilin; Robert Langer

1994-01-01

111

Sustained delivery and expression of DNA encapsulated in polymeric nanoparticles  

Microsoft Academic Search

Sustained release polymeric gene delivery systems offer increased resistance to nuclease degradation, increased amounts of plasmid DNA (pDNA) uptake, and the possibility of control in dosing and sustained duration of pDNA administration. Furthermore, such a system lacks the inherent problems associated with viral vectors. Biodegradable and biocompatible poly(DL-lactide-co-glycolide) polymer was used to enacapsulate pDNA (alkaline phosphatase, AP, a reporter gene)

H Cohen; R J Levy; J Gao; I Fishbein; V Kousaev; S Sosnowski; S Slomkowski; G Golomb

2000-01-01

112

[Molecular/polymeric magnetism  

SciTech Connect

New materials were synthesized to test the generality of magnetism in molecular/polymeric systems. The first room temperature molecular based magnet V(TCNE)[sub x][center dot]y(solvent) (1) is disclosed. The ferromagnetic and related transitions were studied in decamethylferrocenium tetracyanoethanide (TCNE), (1), and related materials. Our and others' models were tested for ferromagnetic and antiferromagnetic exchange between local sites; models for control of [Tc] were also tested.

Not Available

1993-01-01

113

Surface polymerization agents  

SciTech Connect

This is the final report of a 1-year, Laboratory-Directed R&D project at LANL. A joint technical demonstration was proposed between US Army Missile Command (Redstone Arsenal) and LANL. Objective was to demonstrate that an unmanned vehicle or missile could be used as a platform to deliver a surface polymerization agent in such a manner as to obstruct the filters of an air-breathing mechanism, resulting in operational failure.

Taylor, C.; Wilkerson, C.

1996-12-01

114

[Polymeric sorbents for hemoperfusion].  

PubMed

Applications of various sorbents and ion-exchange resins to hemoperfusion are reviewed. With respect to the type of processes accompanying removal of toxines from blood, the fillings of hemoperfusion columns are classified into the group of: sorbents, iono-sorbents and ion-exchangers, immunoadsorbents. Possibilities of improving hemocompatibility of polymeric materials used in hemoperfusion columns by a sorptive or covalent covering their surfaces with natural materials-heparin and/or albumin are discussed. PMID:2682576

Trochimczuk, A; Kolarz, B N

1989-01-01

115

Development of a nanoparticulate formulation of retinoic acid that suppresses Th17 cells and upregulates regulatory T cells  

PubMed Central

Retinoic acid (RA) is a small molecule capable of shunting developing T cells away from the Th17 lineage and towards the Treg phenotype, making it a potentially useful therapeutic for autoimmune and inflammatory diseases. However, therapy can be complicated by systemic toxicity and unpredictable bioavailability, making a targeted drug delivery vehicle for local therapy desirable. A promising approach is the use of nanoparticles, which have been demonstrated to increase potency and decrease toxicity of therapies in a variety of disease models including Th17 mediated diseases. Nanoparticles can also be targeted to specific cell types via surface modification, further increasing the potential specificity of this approach. We therefore constructed a nanoparticulate drug delivery platform from poly(lactic-co-glycolic acid) (PLGA) capable of encapsulating and releasing RA. Here we report the fabrication, characterization, and in vitro bioactivity of this platform. We demonstrate that RA containing PLGA nanoparticles suppress IL-17 production and ROR-?(t) expression in T cells polarized towards the Th17 phenotype in vitro with similar potency to that of free drug. Furthermore, we show that these particles enhance TGF-? dependent Foxp3 expression and IL-10 production of T cells in vitro with similar potency to free RA. Finally, we demonstrate that T cells polarized towards the Th17 phenotype in the presence of free and nanoparticulate RA have similarly suppressed ability to induce IL-6 production by fibroblasts. Our findings demonstrate the feasibility of RA delivery via biodegradable nanoparticles and represent an exciting technology for the treatment of autoimmune and inflammatory diseases.

Jeanbart, Laura; Nowyhed, Heba; Abraham, Clara; Craft, Joe

2010-01-01

116

POLYMERIZATION OF MONOMERIC TO POLYMERIC VESICLES. CHARACTERIZATION AND APPLICATIONS  

Microsoft Academic Search

The first reports on the polymerization of monomeric vesicles to their polymerized counterparts [1–18] appeared in the literature in the early 1980s. The primary goal of this early work was to stabilize the relatively unstable monomeric vesicles in order to stimulate the function of biological membranes. Triggered by these at-tempts and the prospects for utilization of polymerized vesicles as energy

Constantinos N. Paleos

1990-01-01

117

A nanoparticulate drug-delivery system for rivastigmine: physico-chemical and in vitro biological characterization.  

PubMed

The preparation and characterization of surface-PEGylated polymeric nanoparticles are described. These systems were obtained by UV irradiation of PHM and PHM-PEG(2000) as an inverse microemulsion, using an aqueous solution of the PHM/PHM-PEG(2000) copolymer mixture as the internal phase and triacetin saturated with water as the external phase, and characterized by dimensional analysis, zeta-potential measurements and XPS. in vitro biological tests demonstrated their cell compatibility and their ability to escape from phagocytosis. Rivastigmine was encapsulated into the nanoparticle structure and drug-release profiles from loaded samples were investigated in PBS at pH = 7.4 and human plasma. PMID:18041108

Craparo, Emanuela Fabiola; Pitarresi, Giovanna; Bondì, Maria Luisa; Casaletto, Maria Pia; Licciardi, Mariano; Giammona, Gaetano

2008-03-10

118

Models for actin polymerization motors  

Microsoft Academic Search

Actin polymerization drives cell membrane protrusions and the propulsion of intracellular pathogens. The molecular mechanisms\\u000a driving actin polymerization are not yet fully understood. Various mathematical models have been proposed to explain how cells\\u000a convert chemical energy released upon actin polymerization into a pushing force on a surface. These models have attempted\\u000a to explain puzzling properties of actin-based motility, including persistent

Richard B. Dickinson

2009-01-01

119

Vector-valued wavelets and vector filter banks  

Microsoft Academic Search

In this paper, we introduce vector-valued multiresolution analysis and vector-valued wavelets for vector-valued signal spaces. We construct vector-valued wavelets by using paraunitary vector filter bank theory. In particular, we construct vector-valued Meyer wavelets that are band-limited. We classify and construct vector-valued wavelets with sampling property. As an application of vector-valued wavelets, multiwavelets can be constructed from vector-valued wavelets. We show

Xiang-Gen Xia; B. W. Suter

1996-01-01

120

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

121

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

122

Antimicrobial polymeric surfaces  

US Patent & Trademark Office Database

Bactericidal compositions are disclosed that comprise a polymeric compound immobilized on a material. Medical devices are also disclosed which comprise such a bactericidal composition. Methods are disclosed for covalently derivatizing the surfaces of common materials with an antibacterial polycation, e.g., poly(vinyl-N-pyridinium bromide); the first step of the methods involves coating the surface with a nanolayer of silica. Various commercial synthetic polymers derivatized in this manner are bactericidal, i.e., they kill on contact up to 99% of deposited Gram-positive and Gram-negative bacteria, whether deposited through air or water.

Tiller; Joerg C. (Cambridge, MA); Liao; Chun-Jen (Taipei, TW); Lewis; Kim (Newton, MA); Klibanov; Alexander M. (Newton, MA)

2006-12-19

123

Vector Addition Patterns Model  

NSDL National Science Digital Library

The Vector Addition Patterns model illustrates the tail-to-tip method of adding vectors. The table at the bottom shows the components and lengths of the vectors. You can also rotate the vectors and trace out some interesting patterns. The Vector Addition Patterns model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_bu_vector_addition_patterns.jar file will run the program if Java is installed.

Duffy, Andrew

2010-05-02

124

Preparation of magnetic polymeric composite nanoparticles by seeded emulsion polymerization  

Microsoft Academic Search

Seeded emulsion polymerization was used to prepare magnetic polymeric composite nanoparticles (MPCNPs) with the aim to successfully encapsulate magnetite particles and to improve particle size distribution (PSD). Microscopical morphology and number-average diameter of hydrophilic magnetite particles (HMPs), magnetic seed latex nanoparticles (MSLNPs) and MPCNPs were observed and analyzed by transmission electron microscope (TEM). Weight-average diameter and PSD of MSLNPs and

Shulai Lu; Rongjun Qu; Jacqueline Forcada

2009-01-01

125

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

126

Vector Components Model  

NSDL National Science Digital Library

The Vector Components model allows the user to split a vector into its components, and practice finding the magnitude and direction of a vector if you know the components. In the "Find components" mode, you are given the magnitude and direction of the vector, and your goal is to find the x-component and the y-component of the vector. In the "Find magnitude and direction" mode, you are given the two components, and you need to find the magnitude and direction of the vector. The Vector Components was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_bu_vector_components.jar file will run the program if Java is installed.

Duffy, Andrew

2010-04-27

127

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

2012-07-02

128

Biocompatible Initiators for Lactide Polymerization  

Microsoft Academic Search

The review summarizes recent developments in the preparation and use of new initiators for the ring opening polymerization of lactide. The review compares different classes of initiator including metal complexes, classed according to their group in the periodic table, and carbon?based initiators\\/organocatalysts. Emphasis is placed on the polymerization kinetics and the control exhibited by the different types of initiators. Where

Rachel H. Platel; Linda M. Hodgson; Charlotte K. Williams

2008-01-01

129

Two Photon Polymerization of Ormosils  

Microsoft Academic Search

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

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

2010-01-01

130

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

131

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

132

Asymptotic Code Vector Density in Topographic Vector Quantizers.  

National Technical Information Service (NTIS)

A noise robust vector quantizer model is used to derive expressions for the asymptotic code vector density in various types of topographic vector quantizers. A topographic vector quantizer is not identical to a standard (i.e., Kohonen) topographic mapping...

S. P. Luttrell

1990-01-01

133

Macro motion vector quantization  

NASA Astrophysics Data System (ADS)

A new algorithm is developed for reducing the bit rate required for motion vectors. This algorithm is a generalization of block matching motion estimation in which the search region is represented as a codebook of motion vectors. The new algorithm, called macro motion vector quantization (MMVQ), generalized our earlier MVQ by coding a group of motion vectors. The codebook is a set of macro motion vectors which represent the block locations of the small neighboring blocks in the previous frame. We develop an interative design algorithm for the codebook. Our experiments show that the variances of displaced frame differences (DFDs) are reduced significantly compared to block matching algorithm (BMA) with the macroblock size.

Lee, Yoon Y.; Woods, John W.

1995-04-01

134

Preparation of magnetic polymeric particles via inverse microemulsion polymerization process  

NASA Astrophysics Data System (ADS)

Hydrophilic submicron magnetic polymeric particles were prepared using inverse microemulsion polymerization process. Firstly, the magnetic properties of iron oxide nanoparticles elaborated were examined using X-ray diffraction and magnetization analysis of the chemical structure and the magnetic properties, respectively. The results obtained using stoichiometric precipitation of FeCl2 and FeCl3 revealed the magnetite iron oxide properties. Secondly, various magnetic polymeric latexes were prepared by investigating the effect of surfactant (AOT) concentration, the amount of cross-linker (MBA), the initiator nature and the microemulsion elaboration methodology. The colloidal characterization of the final magnetic polymeric latexes revealed to be submicronic in size, spherical in morphology, containing 5-23wt% iron oxide and superparamagnetic in character.

Deng, Y.; Wang, L.; Yang, W.; Fu, S.; Elaïssari, A.

2003-02-01

135

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

136

Index Sets and Vectorization  

SciTech Connect

Vectorization is data parallelism (SIMD, SIMT, etc.) - extension of ISA enabling the same instruction to be performed on multiple data items simultaeously. Many/most CPUs support vectorization in some form. Vectorization is difficult to enable, but can yield large efficiency gains. Extra programmer effort is required because: (1) not all algorithms can be vectorized (regular algorithm structure and fine-grain parallelism must be used); (2) most CPUs have data alignment restrictions for load/store operations (obey or risk incorrect code); (3) special directives are often needed to enable vectorization; and (4) vector instructions are architecture-specific. Vectorization is the best way to optimize for power and performance due to reduced clock cycles. When data is organized properly, a vector load instruction (i.e. movaps) can replace 'normal' load instructions (i.e. movsd). Vector operations can potentially have a smaller footprint in the instruction cache when fewer instructions need to be executed. Hybrid index sets insulate users from architecture specific details. We have applied hybrid index sets to achieve optimal vectorization. We can extend this concept to handle other programming models.

Keasler, J A

2012-03-27

137

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

138

Lubricants and Polymeric Additives Therefor.  

National Technical Information Service (NTIS)

A polyhydroxy-carboxylate detergent copolymer with increased anti-sludging properties for internal combustion engine lubricating oils is the polymerization product of acrylic or alkacrylic acids and dihydroxy alkanes. Alkyl methacrylates having from 12 to...

H. F. Richards S. A. Herbert R. J. Moore

1965-01-01

139

Effectiveness of polymerization of a prosthetic composite using three polymerization systems  

Microsoft Academic Search

Statement of problem. Although properties of laboratory-polymerized composite materials are influenced by the type of polymerizing unit, little information is available regarding the comparison between use of a high-intensity light source and application of secondary heat treatment. Purpose. This study examined properties of a prosthetic veneering composite polymerized with 3 polymerizing systems to evaluate the effects of varying polymerization modes

Naomi Tanoue; Hideo Matsumura; Mitsuru Atsuta

1999-01-01

140

Application of living free radical polymerization for nucleic acid delivery.  

PubMed

Therapeutic gene delivery can alter protein function either through the replacement of nonfunctional genes to restore cellular health or through RNA interference (RNAi) to mask mutated and harmful genes. Researchers have investigated a range of nucleic acid-based therapeutics as potential treatments for hereditary, acquired, and infectious diseases. Candidate drugs include plasmids that induce gene expression and small, interfering RNAs (siRNAs) that silence target genes. Because of their self-assembly with nucleic acids into virus-sized nanoparticles and high transfection efficiency in vitro, cationic polymers have been extensively studied for nucleic acid delivery applications, but toxicity and particle stability have limited the clinical applications of these systems. The advent of living free radical polymerization has improved the quality, control, and reproducibility of these synthesized materials. This process yields well-defined, narrowly disperse materials with designed architectures and molecular weights. As a result, researchers can study the effects of polymer architecture and molecular weight on transfection efficiency and cytotoxicity, which will improve the design of next-generation vectors. In this Account, we review findings from structure-function studies that have elucidated key design motifs necessary for the development of effective nucleic acid vectors. Researchers have used robust methods such as atom transfer radical polymerization (ATRP), reverse addition-fragmentation chain transfer polymerization (RAFT), and ring-opening metastasis polymerization (ROMP) to engineer materials that enhance extracellular stability and cellular specificity and decrease toxicity. In addition, we discuss polymers that are biodegradable, form supramolecular structures, target specific cells, or facilitate endosomal release. Finally, we describe promising materials with a range of in vivo applications from pulmonary gene delivery to DNA vaccines. PMID:22242774

Chu, David S H; Schellinger, Joan G; Shi, Julie; Convertine, Anthony J; Stayton, Patrick S; Pun, Suzie H

2012-01-13

141

Some novel polymeric nanocomposites.  

PubMed

The nanocomposites described here all involve polymers and were chosen because they are already of commercial importance, show some promise of becoming so, or simply seem interesting. The field is so broad that some topics are mentioned only very briefly, and there is considerable emphasis on the polysiloxane nanocomposites studied by the author's research group. Some are typically prepared using techniques very similar to those used in the new sol-gel approach to ceramics, with either the polymer or the ceramic being the continuous phase. Other dispersed phases include particles responsive to an applied magnetic field, intercalated or exfoliated platelets obtained from clays, mica, or graphite, silsesquioxane nanocages, nanotubes, dual fillers, porous particles, spherical and ellipsoidal polymeric particles, and nanocatalysts. Also described are some typical studies involving theory or simulations on such particle reinforcement. Experiments on ceramics modified by dispersed polymers are equally interesting, but there is less relevant theory. Many of the fields mentioned have become so vast that the approach taken here is simply to describe general approaches and characteristics of the composites, list some specific examples, and provide leading references (with some emphasis on studies that are relatively recent or in the nature of reviews). PMID:17176026

Mark, James E

2006-12-01

142

Polymeric passive laser shutters  

NASA Astrophysics Data System (ADS)

Passive laser shutters are designed to control laser pulse duration by the regulation of the Q-factor through the use of substances which change in transparency upon exposure to light. The present paper outlines the development of such a shutter composed of a radiation-resistant modified polymethyl methacrylic matrix which may be filled with different clear dyes. Experiments performed using a nickel dithiobenzyl complex as the dye are presented which show the optical density of the dye in the clear state to be proportional to the initial optical density of the shutter, and the ratio of these optical densities to depend on the purity of the materials and the extent of decay of the dye during polymerization. The feasibility of the polymer shutter in a small laser was demonstrated in experiments with a garnet laser, where no degradation was observed after 100,000 pulses, a neodymium glass laser operating for over 10,000 pulses, and a ruby laser. Potential applications of the modified polymethyl methacrylate material in other laser system components are also noted.

Gromov, D. A.; Diumaev, K. M.; Manenkov, A. A.; Masliukov, A. P.; Matiushin, G. A.; Nechitailo, V. S.; Prokhorov, A. M.

1982-10-01

143

VAX vector architecture  

Microsoft Academic Search

The VAX architecture has been extended to include an integrated, register-based vector processor. This extension allows both high-end and low-end implementations and can be supported with only small changes by VAX\\/VMS and VAX\\/ULTRIX operating systems. The extension is effectively exploited by the new vectorizing capabilities of VAX Fortran. Features of the VAX vector architecture and the design decisions which make

Dileep Bhandarkar; Richard Brunner

1990-01-01

144

VAX vector architecture  

Microsoft Academic Search

The VAX Architecture has been extended to include an integrated, register-based vector processor. This extension allows both high-end and low-end implementations and can be supported with only small changes by VAX\\/VMS and VAX\\/ULTRIX operating systems. The extension is effectively exploited by the new vectorizing capabilities of VAX FORTRAN. Features of the VAX Vector Architecture and the design decisions which make

Dileep Bhandarkar; Richard Brunner

1990-01-01

145

Society for Vector Ecology  

NSDL National Science Digital Library

Formed in 1968, the Society for Vector Ecology (SOVE) is dedicated to studying "all aspects of the biology, ecology, and control of arthropod vectors and the interrelationships between the vectors and the disease agents they transmit." Comprised of researchers and operational and extension personnel around the globe, SOVE tracks and studies the biological organisms that transmit diseases. The SOVE Website contains information related to the Society (e.g., mission, history), its publications (journal, newsletter -- both .pdf format), and professional opportunities (conferences, employment). Several dozen links to additional vector ecology resources are provided.

2002-01-01

146

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.

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

147

Polarimetric vector diffraction tomography  

Microsoft Academic Search

Scalar linearized inverse scattering has recently found a unified treatment within the framework of diffraction tomography in either frequency or angular diversity. The linear inverse scattering theory can be extended to electromagnetic vector fields to include complete polarization information. Its essential feature is the formulation of a vector Porter-Bojarski integral equation to be inverted by dyadic algebra. Algorithms are discussed

Michael Brandfass; K. J. Langenberg; A. Fritsch

1994-01-01

148

Retroviruses as vectors.  

PubMed

Recombinant retroviruses have long been used to deliver heterologous genes to mammalian cells. Convenient packaging cell lines and vector plasmids have been distributed widely and 'home-made' retroviral vectors have now become a useful research tool in many laboratories. Compared to more traditional methods of gene transfer, retroviral vectors are extraordinarily efficient gene delivery vehicles which cause no detectable harm as they enter their target cells. In the nucleus the retroviral necleic acid becomes integrated into chromosomal DNA, ensuring its long-term persistence and stable transmission to all future progeny of the transduced cell. Up to 8 kilobases of foreign gene sequence can be packaged in a retroviral vector and this is more than enough for most gene therapy applications. Retroviral vectors can also be manufactured in large quantities to meet very stringent safety specifications. They have therefore been selected as the vectors of choice in 80% of the clinical gene therapy trials that have been approved to date. So far there have been no reported short- or long-term toxicity problems associated with their use in human gene therapy trials, now dating back to 1989. However, despite this impressive record, there is still great scope (and need) for the development of new, improved retroviral vectors and packaging systems to fuel further advances in the field of human gene therapy. In the following discussion, existing retroviral vectors are reviewed and current areas of technological development are emphasised. PMID:7767638

Vile, R G; Russell, S J

1995-01-01

149

New Support Vector Algorithms  

Microsoft Academic Search

We propose a new class of support vector algorithms for regression and classification. In these algorithms, a parameter ? lets one effectively control the number of support vectors. While this can be useful in its own right, the parameterization has the additional benefit of enabling us to eliminate one of the other free parameters of the algorithm: the accuracy parameter

Bernhard Schölkopf; Alex J. Smola; Robert C. Williamson; Peter L. Bartlett

2000-01-01

150

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.

151

Insect vector transmission assays.  

PubMed

Phytoplasmas are transmitted in a persistent propagative manner by phloem-feeding vectors belonging to the order Hemiptera, suborder Homoptera. Following acquisition from the infected source plant, there is a latent period before the vector can transmit, so transmission assays consist of three basic steps: acquisition, latency, and inoculation. More than 90 vector species (plant-, leafhoppers, and psyllids) have been discovered so far but many others are still undiscovered, and their role in spreading economically important crop diseases is neglected. Therefore, screening for vectors is an essential step in developing rational control strategies targeted against the actual vectors for phytoplasma-associated diseases. The mere detection of a phytoplasma in an insect does not imply that the insect is a vector; a transmission assay is required to provide conclusive evidence. Transmission experiments can be carried out using insects from phytoplasma-free laboratory colonies or field-collections. Moreover, transmission assays can be performed by feeding vectors on an artificial diet through Parafilm(®), after which phytoplasmas can be detected in the sucrose feeding medium by PCR. Transmission trials involve the use of different techniques according to the biology of the different vector species; planthoppers, leafhoppers, and psyllids. PMID:22987407

Bosco, Domenico; Tedeschi, Rosemarie

2013-01-01

152

The neurotoxicity of gene vectors and its amelioration by packaging with collagen hollow spheres.  

PubMed

Over the last twenty years there have been several reports on the use of nonviral vectors to facilitate gene transfer in the mammalian brain. Whilst a large emphasis has been placed on vector transfection efficiency, the study of the adverse effects upon the brain, caused by the vectors themselves, remains completely overshadowed. To this end, a study was undertaken to study the tissue response to three commercially available transfection agents in the brain of adult Sprague Dawley rats. The response to these transfection agents was compared to adeno-associated viral vector (AAV), PBS and naked DNA. Furthermore, the use of a collagen hollow sphere (CHS) sustained delivery system was analysed for its ability to reduce striatal toxicity of the most predominantly studied polymer vector, polyethyleneimine (PEI). The size of the gross tissue loss at the injection site was analysed after immunohistochemical staining and was used as an indication of acute toxicity. Polymeric vectors showed similar levels of acute brain toxicity as seen with AAV, and CHS were able to significantly reduce the toxicity of the PEI vector. In addition; the host response to the vectors was measured in terms of reactive astrocytes and microglial cell recruitment. To understand whether this gross tissue loss was caused by the direct toxicity of the vectors themselves an in vitro study on primary astrocytes was conducted. All vectors reduced the viability of the cells which is brought about by direct necrosis and apoptosis. The CHS delivery system reduced cell necrosis in the early stages of post administration. In conclusion, whilst polymeric gene vectors cause acute necrosis, administration in the brain causes adverse effects no worse than that of an AAV vector. Furthermore, packaging the PEI vector with CHS reduces surface charge and direct toxicity without elevating the host response. PMID:23245921

Newland, Ben; Moloney, Teresa C; Fontana, Gianluca; Browne, Shane; Abu-Rub, Mohammad T; Dowd, Eilís; Pandit, Abhay S

2012-12-13

153

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

154

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

155

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

156

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

157

Chemoprevention of pancreatic cancer using solid-lipid nanoparticulate delivery of a novel aspirin, curcumin and sulforaphane drug combination regimen  

PubMed Central

Pancreatic cancer is the fourth largest cause of cancer deaths in the Unites States and the prognosis is grim with <5% survival chances upon diagnosis. The objective of this study was to assess the combined chemopreventive effect of solid lipid nanoparticle (SLN) encapsulated drugs aspirin (ASP), curcumin (CUR) and free sulforaphane (SFN) for the chemoprevention of pancreatic cancer. Experiments were carried out (1) to evaluate the feasibility of encapsulation of these chemopreventive agents within solid lipid systems and (2) to measure the synergistic effects of a combination of ASP with CUR in SLNs mixed with free SFN against cell proliferation and apoptosis in pancreatic cancer cells, MIA PaCa-2 and Panc-1. The SLNs were prepared using a modified solvent evaporation technique and were characterized for particle sizing, encapsulation efficiency and drug release. ASP and CUR SLNs were formulated within the particle size range of 150–250 nm and were found to have an encapsulation efficiency of 85 and 69%, respectively. Sustained release of drugs over a 96 h period from SLNs was observed. The SLNs were stable over a 3-month storage period at room temperature. Cell viability studies demonstrated that combinations of low doses of ASP SLN (25 ?M), CUR SLN (2.5 ?M) and free SFN (5 ?M) significantly reduced cell viability by 43.6 and 48.49% in MIAPaca-2 and Panc-1 cell lines, respectively. Furthermore, increased apoptosis of 61.3 and 60.37% was found in MIA Paca-2 and Panc-1 cell lines, respectively, in comparison to the individual doses administered. Synergistic effects were demonstrated using MTS and apoptosis assays. Thus, this study successfully demonstrated the feasibility of using a solid lipid nanoparticulate system for the first time to deliver this novel combination chemoprevention regimen, providing valuable evidence for the usability of nanotechnology-based drug regimens towards pancreatic cancer chemoprevention.

SUTARIA, DHRUVITKUMAR; GRANDHI, BALAGANGADHAR KARTHIK; THAKKAR, ARVIND; WANG, JEFFREY; PRABHU, SUNIL

2012-01-01

158

Hazard and risk assessment of a nanoparticulate cerium oxide-based diesel fuel additive - a case study.  

PubMed

Envirox is a scientifically and commercially proven diesel fuel combustion catalyst based on nanoparticulate cerium oxide and has been demonstrated to reduce fuel consumption, greenhouse gas emissions (CO(2)), and particulate emissions when added to diesel at levels of 5 mg/L. Studies have confirmed the adverse effects of particulates on respiratory and cardiac health, and while the use of Envirox contributes to a reduction in the particulate content in the air, it is necessary to demonstrate that the addition of Envirox does not alter the intrinsic toxicity of particles emitted in the exhaust. The purpose of this study was to evaluate the safety in use of Envirox by addressing the classical risk paradigm. Hazard assessment has been addressed by examining a range of in vitro cell and cell-free endpoints to assess the toxicity of cerium oxide nanoparticles as well as particulates emitted from engines using Envirox. Exposure assessment has taken data from modeling studies and from airborne monitoring sites in London and Newcastle adjacent to routes where vehicles using Envirox passed. Data have demonstrated that for the exposure levels measured, the estimated internal dose for a referential human in a chronic exposure situation is much lower than the no-observed-effect level (NOEL) in the in vitro toxicity studies. Exposure to nano-size cerium oxide as a result of the addition of Envirox to diesel fuel at the current levels of exposure in ambient air is therefore unlikely to lead to pulmonary oxidative stress and inflammation, which are the precursors for respiratory and cardiac health problems. PMID:18444008

Park, Barry; Donaldson, Kenneth; Duffin, Rodger; Tran, Lang; Kelly, Frank; Mudway, Ian; Morin, Jean-Paul; Guest, Robert; Jenkinson, Peter; Samaras, Zissis; Giannouli, Myrsini; Kouridis, Haris; Martin, Patricia

2008-04-01

159

A Novel Nanoparticulate Formulation of Arsenic Trioxide with Enhanced Therapeutic Efficacy in a Murine Model of Breast Cancer  

PubMed Central

Purpose The clinical success of arsenic trioxide (As2O3) in hematological malignancies has not been replicated in solid tumors due to poor pharmacokinetics and dose-limiting toxicity. We have developed a novel nanoparticulate formulation of As2O3 encapsulated in liposomal vesicles or “nanobins” [(NB(Ni,As)] to overcome these hurdles. We postulated that nanobin encapsulation of As2O3 would improve its therapeutic index against clinically aggressive solid tumors, such as triple negative breast carcinomas. Experimental Design The cytotoxicity of NB(Ni,As), the empty nanobin, and free As2O3 was evaluated against a panel of human breast cancer cell lines. The plasma pharmacokinetics of NB(Ni,As) and free As2O3 were compared in rats to measure drug exposure. In addition, the antitumor activity of these agents was evaluated in an orthotopic model of human triple negative breast cancer. Results The NB(Ni,As) agent was much less cytotoxic in vitro against a panel of human breast cancer cell lines than free As2O3. In contrast, NB(Ni,As) dramatically potentiated the therapeutic efficacy of As2O3 in vivo in an orthotopic model of triple negative breast cancer. Reduced plasma clearance, enhanced tumor uptake, and induction of tumor cell apoptosis were observed for NB(Ni,As). Conclusions Nanobin encapsulation of As2O3 improves the pharmacokinetics and antitumor efficacy of this cytotoxic agent in vivo. Our findings demonstrate the therapeutic potential of this nanoscale agent and provide a foundation for future clinical studies in breast cancer and other solid tumors.

Ahn, Richard W.; Chen, Feng; Chen, Haimei; Stern, Stephan T.; Clogston, Jeffrey D.; Patri, Anil K.; Raja, Meera R.; Swindell, Elden P.; Parimi, Vamsi; Cryns, Vincent L.; O'Halloran, Thomas V.

2010-01-01

160

Stereospecific olefin polymerization catalysts  

DOEpatents

A metallocene catalyst system for the polymerization of .alpha.-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula ##STR1## wherein: R.sup.1, R.sup.2, and R.sup.3 are independently selected from the group consisting of hydrogen, C.sub.1 to C.sub.10 alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C.sub.1 to C.sub.10 alkyls as a substituent, C.sub.6 to C.sub.15 aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R.sup.8).sub.3 where R.sup.8 is selected from the group consisting of C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; R.sup.4 and R.sup.6 are substituents both having van der Waals radii larger than the van der Waals radii of groups R.sup.1 and R.sup.3 ; R.sup.5 is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E.sup.1, E.sup.2 are independently selected from the group consisting of Si(R.sup.9).sub.2, Si(R.sup.9).sub.2 --Si(R.sup.9).sub.2, Ge(R.sup.9).sub.2, Sn(R.sup.9).sub.2, C(R.sup.9).sub.2, C(R.sup.9).sub.2 --C(R.sup.9).sub.2, where R.sup.9 is C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; and the ligand may have C.sub.S or C.sub.1 -symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from .alpha.-olefin monomers.

Bercaw, John E. (Pasadena, CA); Herzog, Timothy A. (Pasadena, CA)

1998-01-01

161

Stereospecific olefin polymerization catalysts  

DOEpatents

A metallocene catalyst system is described for the polymerization of {alpha}-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula shown wherein: R{sup 1}, R{sup 2}, and R{sup 3} are independently selected from the group consisting of hydrogen, C{sub 1} to C{sub 10} alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C{sub 1} to C{sub 10} alkyls as a substituent, C{sub 6} to C{sub 15} aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R{sup 8}){sub 3} where R{sup 8} is selected from the group consisting of C{sub 1} to C{sub 10} alkyl, C{sub 6} to C{sub 15} aryl or C{sub 3} to C{sub 10} cycloalkyl; R{sup 4} and R{sup 6} are substituents both having van der Waals radii larger than the van der Waals radii of groups R{sup 1} and R{sup 3}; R{sup 5} is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E{sup 1}, E{sup 2} are independently selected from the group consisting of Si(R{sup 9}){sub 2}, Si(R{sup 9}){sub 2}--Si(R{sup 9}){sub 2}, Ge(R{sup 9}){sub 2}, Sn(R{sup 9}){sub 2}, C(R{sup 9}){sub 2}, C(R{sup 9}){sub 2}--C(R{sup 9}){sub 2}, where R{sup 9} is C{sub 1} to C{sub 10} alkyl, C{sub 6} to C{sub 15} aryl or C{sub 3} to C{sub 10} cycloalkyl; and the ligand may have C{sub S} or C{sub 1}-symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from {alpha}-olefin monomers.

Bercaw, J.E.; Herzog, T.A.

1998-01-13

162

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

163

1-(3'-amino)propylsilatrane derivatives as covalent surface linkers to nanoparticulate metal oxide films for use in photoelectrochemical cells  

NASA Astrophysics Data System (ADS)

A triethanolamine-protected silane, 1-(3'-amino)propylsilatrane, was incorporated into the structure of porphyrin- and ruthenium-based dyes and used to link them to transparent semiconductor nanoparticulate metal oxide films. Silatrane reacts with the metal oxide to form strong, covalent silyl ether bonds. In this study, silatrane-functionalized dyes and analogous carboxylate-functionalized dyes were used as visible light sensitizers for porous nanoparticulate SnO2 photoanodes. The performance of the dyes was compared in photoelectrochemical cells incorporating either non-regenerative or regenerative redox components. The non-regenerative cell used NADH (?-nicotinamide adenine dinucleotide) as a sacrificial electron donor and Hg2SO4/Hg as a sacrificial cathode, whereas the regenerative cell used the iodide/triiodide redox couple. Experiments showed that the silyl ether bonding gave the electrodes increased stability toward sensitizer desorption compared to carboxylate surface linkages. Porphyrin-silatrane dyes also demonstrated similar or better performance than their carboxylate analogs in photoelectrochemical cells. The improvement correlates with the results from transient absorbance spectroscopy, which show that the longer linker on the silatrane porphyrins slows charge recombination between oxidized porphyrin and the electrode surface. The improved photoelectrochemical cell efficiency and stability of the silatrane-based dyes compared to carboxylates demonstrate that silatranes are promising agents for bonding organic molecules to metal oxide surfaces.

Brennan, Bradley J.; Keirstead, Amy E.; Liddell, Paul A.; Vail, Sean A.; Moore, Thomas A.; Moore, Ana L.; Gust, Devens

2009-12-01

164

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

165

Hydrocarbon Polymeric Binder for Advanced Solid Propellant.  

National Technical Information Service (NTIS)

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 ...

J. E. Potts

1972-01-01

166

From Living Carbocationic to Living Radical Polymerization.  

National Technical Information Service (NTIS)

'Living' carbocationic polymerization is compared to 'living' radical process. Similarities and differences are discussed. 'Living' radical polymerization of vinyl acetate and methyl methacrylate to provide polymers with controlled molecular weights and n...

K. Matyjaszewski

1994-01-01

167

Understanding Vector Fields.  

ERIC Educational Resources Information Center

|Presented are activities that help students understand the idea of a vector field. Included are definitions, flow lines, tangential and normal components along curves, flux and work, field conservation, and differential equations. (KR)|

Curjel, C. R.

1990-01-01

168

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.

169

LTR-Vectors.  

National Technical Information Service (NTIS)

The patent application describes the production of vectors composed of portions of retrovirus, particularly of Moloney sarcoma virus DNA including the 'LTR' sequence which can activate genes and additional viral sequences which can 'rescue' these genes in...

G. F. Vande Woude W. L. McClements M. K. Oskarsson D. G. Blair

1981-01-01

170

Vector Mesons at HERA  

SciTech Connect

The rich experimental landscape of exclusive vector meson production at the high energy electron-proton collider HERA is reviewed, with emphasis on the transition from soft to hard diffraction and perturbative QCD interpretations.

Favart, L

2009-03-23

171

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

172

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

173

Poynting-vector filter  

SciTech Connect

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

174

Optics for vector scanning  

Microsoft Academic Search

Vector scanning of laser beams is critical to the success of stereolithography, laser marking, CAD-output-to-microfilm and many other industrial applications. The design of a vector scan lens system can assume many different configurations. This paper will discuss pre-objective, and post-objective alternatives for two and three axis scanning. Various parameters required for system specification are reviewed and the basic configuration of

Jonathan S. Ehrmann

1991-01-01

175

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

2009-11-16

176

A top-down approach for construction of hybrid polymer-virus gene delivery vectors.  

PubMed

Safe and efficient delivery of therapeutic nucleic acids remains the primary hurdle for human gene therapy. While many researchers have attempted to re-engineer viruses to be suited for gene delivery, others have sought to develop non-viral alternatives. We have developed a complementary approach in which viral and synthetic components are combined to form hybrid nanoparticulate vectors. In particular, we complexed non-infectious retrovirus-like particles lacking a viral envelope protein, from Moloney murine leukemia virus (M-VLP) or human immunodeficiency virus (H-VLP), with poly-L-lysine (PLL) or polyethylenimine (PEI) over a range of polymer/VLP ratios. At appropriate stoichiometry (75-250 microg polymer/10(6) VLP), the polymers replace the function of the viral envelope protein and interact with the target cell membrane, initiate cellular uptake and facilitate escape from endocytic vesicles. The viral particle, once in the cytosol, efficiently completes its normal infection process including integration of viral genes with the host genome as demonstrated by long-term (at least 5 weeks) transgene expression. In addition, hybrid vectors comprising H-VLP were shown to be capable of infecting non-dividing cells. PMID:20117154

Ramsey, Joshua D; Vu, Halong N; Pack, Daniel W

2010-01-31

177

Polymeric media for tritium fixation  

Microsoft Academic Search

The synthesis and leach testing of several polymeric media for tritium ; fixation are presented. Tritiated bakelite, poly(acrylonitrile) and polystyrene ; successfully fixed tritium. Tritium leach rates at the tracer level appear to be ; negligible. Advantages and disadvantages of the processes are discussed, and ; further bench-scale investigations underway are reported. Rough cost estimates ; are presented for the

J. A. Franz; L. L. Burger

1975-01-01

178

Ballistic Resistance of Polymeric Materials  

Microsoft Academic Search

Ballistic-resistant body armor has been credited with saving more than 2,500 lives, but new materials are constantly being developed, and there currently exists no method for evaluating armor over time to ensure the continued effectiveness of the protection. We report on progress towards development of a standard test method for reliability of the active polymeric materials that comprise them.

Chad Snyder

2005-01-01

179

Ballistic Resistance of Polymeric Materials  

NASA Astrophysics Data System (ADS)

Ballistic-resistant body armor has been credited with saving more than 2,500 lives, but new materials are constantly being developed, and there currently exists no method for evaluating armor over time to ensure the continued effectiveness of the protection. We report on progress towards development of a standard test method for reliability of the active polymeric materials that comprise them.

Snyder, Chad

2005-03-01

180

POLYMERIC INTERFACES FOR STACK MONITORING  

EPA Science Inventory

Research has been performed on the use of polymeric interfaces for in situ continuous stack monitoring of gaseous pollutants. Permeabilities of candidate interface materials to SO2 were measured at temperatures from ambient to 200C, and the results were used to design interfaces ...

181

Actin Polymerization and ATP Hydrolysis  

NASA Astrophysics Data System (ADS)

F-actin is the major component of muscle thin filaments and, more generally, of the microfilaments of the dynamic, multifunctional cytoskeletal systems of nonmuscle eukaryotic cells. Polymeric F-actin is formed by reversible noncovalent self-association of monomeric G-actin. To understand the dynamics of microfilament systems in cells, the dynamics of polymerization of pure actin must be understood. The following model has emerged from recent work. During the polymerization process, adenosine 5'-triphosphate (ATP) that is bound to G-actin is hydrolyzed to adenosine 5'-diphosphate (ADP) that is bound to F-actin. The hydrolysis reaction occurs on the F-actin subsequent to the polymerization reaction in two steps: cleavage of ATP followed by the slower release of inorganic phosphate (Pi). As a result, at high rates of filament growth a transient cap of ATP-actin subunits exists at the ends of elongating filaments, and at steady state a stabilizing cap of ADP \\cdot Pi-actin subunits exists at the barbed ends of filaments. Cleavage of ATP results in a highly stable filament with bound ADP \\cdot Pi, and release of Pi destabilizes the filament. Thus these two steps of the hydrolytic reaction provide potential mechanisms for regulating the monomer-polymer transition.

Korn, Edward D.; Carlier, Marie-France; Pantaloni, Dominique

1987-10-01

182

Fire Retardance of Polymeric Materials  

Microsoft Academic Search

The flammability characteristics of natural and synthetic polymeric materials is of broad interest with particular aspects including intumescent coatings, fibers and fabrics, reinforced plastics, elastomers, cellular plastics, and ablative materials. Rapid expansion of plastics in wearing apparel, draperies, carpeting, automotive and aircraft components, and in allied consumer industries, makes it imperative that a better understanding of the flammability characteristics of

Irving N. Einhorn

1971-01-01

183

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

184

Anionic polymerization of fluorinated vinyl monomers  

Microsoft Academic Search

Several fluorinated vinyl monomers, which were believed to be difficult to homopolymerize under common radical polymerization, were polymerized under anionic conditions. They include hexafluoro-1,3-butadiene, ?,??-trifluorostyrene, ?-trifluoromethylacrylates, and ?-trifluoromethylstyrene which are key monomers whose behavior toward polymerization is unclear and these vinyl monomers have to be investigated individually to complete the overall picture. This knowledge will allow us aalso to yield

T. Narita

1999-01-01

185

Conformation of Adsorbed Polymeric Chain. II  

Microsoft Academic Search

By developing the theoretical treatment of an isolated polymeric chain at an interface, which is based on a three-dimensional random walk on a simple cubic lattice, the average number of segments in the tail of a polymeric chain k¯0 and the average number of trains per polymeric chain m¯ are calculated in the limit in which the chain length n

Kinsi Motomura; Ryohei Matuura

1969-01-01

186

VectorBase: a data resource for invertebrate vector genomics  

Microsoft Academic Search

VectorBase (http:\\/\\/www.vectorbase.org) is an NIAID-funded Bioinformatic Resource Center focused on invertebrate vectors of human patho- gens. VectorBase annotates and curates vector genomes providing a web accessible integrated resource for the research community. Currently, VectorBase contains genome information for three mosquito species: Aedes aegypti, Anopheles gam- biae and Culex quinquefasciatus, a body louse Pediculus humanus and a tick species Ixodes scapularis.

Daniel Lawson; Peter Arensburger; Peter Atkinson; Nora J. Besansky; Robert V. Bruggner; Ryan Butler; Kathryn S. Campbell; George K. Christophides; Scott Christley; Emmanuel Dialynas; Martin Hammond; Catherine A. Hill; Nathan Konopinski; Neil F. Lobo; Robert M. Maccallum; Gregory R. Madey; Karine Megy; Jason Meyer; Seth Redmond; David W. Severson; Eric O. Stinson; Pantelis Topalis; Ewan Birney; William M. Gelbart; Fotis C. Kafatos; Christos Louis; Frank H. Collins

2009-01-01

187

Synthesis of Powdered Polymeric Microparticles by Using Supercritical Carbon Dioxide as the Polymerizing Medium  

Microsoft Academic Search

Polystyrene microparticles were synthesized by emulsion polymerization in supercritical carbon dioxide (sc-CO2) using (polydimethylsiloxane) (PDMS) as a surfactant\\/stabilizer and azobisisobutyronitrile (AIBN) as initiator. The emulsion polymerization was carried out by varying pressures within the range 13.79–17.93 MPa. At the end of polymerization, powdered polymeric micoparticles were collected by depressurizing CO2. The powdered polymeric microparticles were characterized by SEM, GPC, DSC and

Isha R. Kamrupi; Swapan K. Dolui

2010-01-01

188

Visualizing Nonlinear Vector Field Topology  

Microsoft Academic Search

Abstract| We present our results on the visualization of non-linear vector eld topology. The underlying mathemat- ics is done in Cliord algebra, a system describing geometry by extending the usual vector space by a multiplication of vectors. We started with the observation that all known algorithms for vector eld topology are based on piecewise linear or bilinear approximation and that

Gerik Scheuermann; Heinz Krüger; Martin Menzel; Alyn P. Rockwood

1998-01-01

189

Interactions of vector solitons  

NASA Astrophysics Data System (ADS)

In this paper, we study the interaction of two widely separated vector solitons in the nonintegrable coupled nonlinear Schrödinger (NLS) equations. Using a modification of Karpman-Solov'ev perturbation method, we derive dynamical equations for the evolution of both solitons' internal parameters. We show that these dynamical equations allow fixed points that correspond to stationary two-vector-soliton bound states if these solitons have the same phase in one component (same sign) and ?-phase difference in the other component (opposite sign). However, linear stability analysis indicates that these bound states are always unstable due to a phase-related unstable eigenvalue. We also investigate vector-soliton interactions and show that, in contrast to soliton interactions in the single NLS equation, vector solitons repel or attract each other depending not only on their relative phases but also on their initial position separation. Lastly, interaction of an arbitrary number of vector solitons is also studied in brief. All our analytical results are supported by direct numerical simulations.

Yang, Jianke

2001-08-01

190

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

2012-02-27

191

Vector WIMP miracle  

NASA Astrophysics Data System (ADS)

Weakly interacting massive particle (WIMP) is well known to be a good candidate for dark matter, and it is also predicted by many new physics models beyond the standard model at the TeV scale. We found that, if the WIMP is a vector particle (spin-one particle) which is associated with some gauge symmetry broken at the TeV scale, the Higgs mass is often predicted to be 120-125 GeV, which is very consistent with the result of Higgs searches recently reported by ATLAS and CMS Collaborations at the Large Hadron Collider experiment. In this Letter, we consider the vector WIMP using a non-linear sigma model in order to confirm this result as general as possible in a bottom-up approach. Near-future prospects to detect the vector WIMP at both direct and indirect detection experiments of dark matter are also discussed.

Abe, Tomohiro; Kakizaki, Mitsuru; Matsumoto, Shigeki; Seto, Osamu

2012-07-01

192

Urban malaria vector biology.  

PubMed

One of the main reasons for the set-back in the urban malaria control programme is the peculiar biobehaviour of the principal urban malaria vector Anopheles stephensi. Certain relevant facts such as incrimination as the vector of malaria, sibling or biological species, resting habitat, manlanding behaviour, seasonal prevalence, blood meal analysis, longevity, parity status, daily survival and mortality rates of adults, breeding habitats and vertical distribution of larvae of An. stephensi have been discussed. Determination of density of the vector using various parameters and their relation to malaria endemicity in an urban situation have been reviewed. An. stephensi has become resistant to DDT, HCH, malathion and propoxur in many places in India. Hence for control source reduction, use of predators such as fish and biolarvicides such as Bacillus thuringiensis var israelensis H14 and B. sphaericus, personal protection, i.e., use of appropriate clothing, bed nets, indigenous repellents, etc., information, education and communication (IEC) are to be stressed. PMID:9291684

Hati, A K

1997-08-01

193

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.

Andrew, Trisha L.; Swager, Timothy M.

2011-01-01

194

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

195

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

196

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

197

Electrochemical polymerization of pyrrole derivatives  

SciTech Connect

Electrochemical copolymerization of pyrrole and 3-(6-ferrocenyl-6-hydroxyhexyl)pyrrole (P-Fc) yields a ferrocene functionalized polypyrrole with a controlled amount of ferrocene functionalization. Similarly, copolymers of pyrrole and 3-(4-(2,5- dimethoxyphenyl)butyl)pyrrole (P-MP) can be made by electrochemical polymerization and converted to the copolymers containing pH dependent electroactive hydroquinone moieties. 16 refs., 6 figs.

Inagaki, T.; Hunter, M.; Yang, X.Q.; Skotheim, T.A.; Lee, H.S.; Okamoto, Y.

1988-01-01

198

Polymeric membranes for lipase immobilization  

Microsoft Academic Search

Lipase triacylglycerol acylhydrolase, (E.C. 3.1.1.3) is an enzyme that is fully active on aggregated substrates and practically\\u000a inactive on monodisperse systems. A lipase immobilized on polymeric membranes has been applied for sunflower oil hydrolysis.\\u000a The influence of membrane properties on enzyme activity is studied. Membranes made of poly(vinyl chloride), collagen, cellulose\\u000a acetate and polytetrafluoroethylene were used for adsorption of lipase.

Magdalena Rucka; Bo?ena Turkiewicz; Janusz S. ?uk

1990-01-01

199

DC plasma polymerization of hexamethyldisiloxane  

Microsoft Academic Search

Hexamethyldisiloxane (HMDS) was polymerized onto metallic and insulating substrates in a parallel-plate DC reactor. The limits\\u000a of the DC reactor with respect to pressure and power were determined for deposition of PP-HMDS films. In all conditions ranging\\u000a from 5 Pa\\/0.3 W to 100 Pa\\/50 W, solid films were deposited. No powders or oily films were obtained under any condition in

W. J. van Ooij; S. Eufinger; Sheyu Guo

1997-01-01

200

Polymeric nanocomposites as photonic sensors  

NASA Astrophysics Data System (ADS)

Hydrogel-coated refractive nanoparticles can self-assemble to form perfect colloidal crystalline array (CCA), which can act as a photonic sensor in visible and near-infrared region triggered by temperature. The aim of this study was to tune the lattice parameters of these CCAs made of poly-(N-isopropylacrylamide) coated silica nanoparticles and hence their sensor properties by varying various factors. The synthetic scheme of this work involves surface modification of silica nanoparticles followed by radical polymerization to obtain polymeric nanocomposites. Photon correlation spectroscopy (PCS) was used to measure the particle size of these nanocomposites with temperature variation and a sharp decrease from 1094.8 nm to 506.8 nm at the LCST (lower critical solution temperature) region was observed, which can be attributed to volume-phase transition. Atomic Force Microscopy (AFM) images complemented these results. Reflectance measurements were performed to obtain the position of photonic stop-bands as a function of temperature as well as core particle size, which can be explained with the help of Bragg's diffraction equation. With temperature increase the stop band shifted towards lower wavelength due to hydrogel collapse at elevated temperature, whereas the core particle size was directly proportional to the position of the stop band. In conclusion, self-assembly was proven to be a very simple and cost-effective approach for making photonic sensors made of polymeric nanocomposites and their sensor properties can be effectively tuned by varying certain factors.

Dey, Tania

2010-06-01

201

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

202

Enhanced electron extraction from template-free 3D nanoparticulate transparent conducting oxide (TCO) electrodes for dye-sensitized solar cells.  

PubMed

The semiconducting metal oxide-based photoanodes in the most efficient dye-sensitized solar cells (DSSCs) desires a low doping level to promote charge separation, which, however, limits the subsequent electron extraction in the slow diffusion regime. These conflicts are mitigated in a new photoanode design that decouples the charge separation and extraction functions. A three-dimensional highly doped fluorinated SnO(2) (FTO) nanoparticulate film serves as conductive core for low-resistance and drift-assisted charge extraction while a thin, low-doped conformal TiO(2) shell maintains a large resistance to recombination (and therefore long charge lifetime). EIS reveals that the electron transit time is reduced by orders of magnitude, whereas the recombination resistance remains in the range of traditional nanoparticle TiO(2) photoelectrodes. PMID:22834639

Yang, Zhenzhen; Gao, Shanmin; Li, Tao; Liu, Fa-Qian; Ren, Yang; Xu, Tao

2012-08-03

203

Traffic of poly(lactic acid) nanoparticulate vaccine vehicle from intestinal mucus to sub-epithelial immune competent cells  

Microsoft Academic Search

Mucosal immunization is designed to induce strong immune responses at portal of pathogen entry. Unfortunately, mechanisms underlying the fate of the vaccine vector co-administered with antigens are still partially uncovered and limit further development of mucosal vaccines. Hence, poly(lactic acid) (PLA) nanoparticles being a versatile vaccine vehicle, we have analyzed the fate of these PLA nanoparticles during their uptake at

Charlotte Primard; Nicolas Rochereau; Elsa Luciani; Christian Genin; Thierry Delair; Stéphane Paul; Bernard Verrier

2010-01-01

204

Vectorized cluster search  

NASA Astrophysics Data System (ADS)

Contrary to conventional wisdom, the construction of clusters on a lattice can easily be vectorized, namely over each ``generation'' in a breadth first search. This applies directly to e.g. the single cluster variant of the Swendsen-Wang algorithm. On a Cray-YMP, total CPU time was reduced by a factor 3.5 - 7 in actual applications.

Evertz, H. G.

205

Reversing Motion Vector Fields  

Microsoft Academic Search

We examine the problem of estimating a reverse motionvector field from a given forward motion vector fieldand its motion-compensated residual. This problem haspractical importance when providing reverse-play functionalityin compressed video environments, where video data isstored, processed, and transported in compressed form. Wepresent a family of algorithms that trade off motion vectoraccuracy for computational efficiency. Experimental resultsdemonstrate the performance of these...

Susie J. Wee

1998-01-01

206

Kerneltron: support vector \\  

Microsoft Academic Search

Detection of complex objects in streaming video poses two fundamental challenges: training from sparse data with proper generalization across variations in the object class and the environment; and the computational power required of the trained classifier running real-time. The Kerneltron supports the generalization performance of a support vector machine (SVM) and offers the bandwidth and efficiency of a massively parallel

R. Genov; G. Cauwenberghs

2003-01-01

207

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

208

Killing vectors and anisotropy  

NASA Astrophysics Data System (ADS)

We consider an action that can generate fluids with three unequal stresses for metrics with a spacelike Killing vector. The parameters in the action are directly related to the stress anisotropies. The field equations following from the action are applied to an anisotropic cosmological expansion and an extension of the Gott-Hiscock cosmic string.

Krisch, J. P.; Glass, E. N.

2009-08-01

209

Support vector machines  

Microsoft Academic Search

My first exposure to Support Vector Machines came this spring when heard Sue Dumais present impressive results on text categorization using this analysis technique. This issue's collection of essays should help familiarize our readers with this interesting new racehorse in the Machine Learning stable. Bernhard Scholkopf, in an introductory overview, points out that a particular advantage of SVMs over other

M. A. Hearst; S. T. Dumais; E. Osman; J. Platt; B. Scholkopf

1998-01-01

210

Killing vectors and anisotropy  

SciTech Connect

We consider an action that can generate fluids with three unequal stresses for metrics with a spacelike Killing vector. The parameters in the action are directly related to the stress anisotropies. The field equations following from the action are applied to an anisotropic cosmological expansion and an extension of the Gott-Hiscock cosmic string.

Krisch, J. P.; Glass, E. N. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2009-08-15

211

Singular Vectors' Subtle Secrets  

ERIC Educational Resources Information Center

|Social scientists use adjacency tables to discover influence networks within and among groups. Building on work by Moler and Morrison, we use ordered pairs from the components of the first and second singular vectors of adjacency matrices as tools to distinguish these groups and to identify particularly strong or weak individuals.|

James, David; Lachance, Michael; Remski, Joan

2011-01-01

212

Fluidic thrust vector control  

Microsoft Academic Search

The design and testing of a fluidic control nozzle for tactical missile thrust vector control (TVC) are discussed. Attention is given to a nozzle with a circular cross section up to the point of flow separation, two control ports that alternately open and close, and a nozzle extension downstream of the control ports being a two-dimensional rectangular slot. Design of

V. E. Haloulakos

1982-01-01

213

Raman scattering in non-polymerized and photo-polymerized C60 films at 5 K  

NASA Astrophysics Data System (ADS)

The Raman spectra of non-polymerized and photo-polymerized fullerene films of various polymerization degrees were studied at 5 K in the 250-1590 cm-1 range. It was found that the Raman spectra of non-polymerized film display splitting of the lines corresponding to Ag and Hg vibrational modes of free C60 molecule which is induced by the crystal field of the low-temperature phase. The Raman spectra of photo-polymerized films at low temperatures exhibit pronounced lines corresponding to Ag(2) vibrations of monomers, dimers and linear chains. Based on the analysis of the spectra of photo-polymerized films of various polymerization degrees (~45, ~85, and ~95%), the spectrum evolution in the region of molecular modes of fullerene was studied vs. polymerization degree. It was found that in the films with high polymerization degree (~85 and ~95%), the linear polymer chains dominate while in the film with lower polymerization degree (~45%) the dimers are dominant. An increase of polymerization degree entails a significant frequency increase (~2.8 cm-1) of Ag(2) mode of the fullerene monomer induced by changes in its environment upon the transition from non-polymerized to photo-polymerized films. Such a shift was not observed for the lines corresponding to the fullerene photopolymer.

Peschanskii, A. V.; Glamazda, A. Yu.; Fomin, V. I.; Karachevtsev, V. A.

2012-09-01

214

Vector-Tensor and Vector-Vector Decay Amplitude Analysis of B0??K*0  

NASA Astrophysics Data System (ADS)

We perform an amplitude analysis of the decays B0??K2*(1430)0, ?K*(892)0, and ?(K?)S-wave0 with a sample of about 384×106 BB¯ pairs recorded with the BABAR detector. The fractions of longitudinal polarization fL of the vector-tensor and vector-vector decay modes are measured to be 0.853-0.069+0.061±0.036 and 0.506±0.040±0.015, respectively. Overall, twelve parameters are measured for the vector-vector decay and seven parameters for the vector-tensor decay, including the branching fractions and parameters sensitive to CP violation.

Aubert, B.; Bona, M.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Tisserand, V.; Zghiche, A.; Grauges, E.; Palano, A.; Chen, J. C.; Qi, N. D.; Rong, G.; Wang, P.; Zhu, Y. S.; Eigen, G.; Ofte, I.; Stugu, B.; Abrams, G. S.; Battaglia, M.; Brown, D. N.; Button-Shafer, J.; Cahn, R. N.; Charles, E.; Gill, M. S.; Groysman, Y.; Jacobsen, R. G.; Kadyk, J. A.; Kerth, L. T.; Kolomensky, Yu. G.; Kukartsev, G.; Pegna, D. Lopes; Lynch, G.; Mir, L. M.; Orimoto, T. J.; Pripstein, M.; Roe, N. A.; Ronan, M. T.; Wenzel, W. A.; Sanchez, P. Del Amo; Barrett, M.; Ford, K. E.; Harrison, T. J.; Hart, A. J.; Hawkes, C. M.; Watson, A. T.; Held, T.; Koch, H.; Lewandowski, B.; Pelizaeus, M.; Peters, K.; Schroeder, T.; Steinke, M.; Boyd, J. T.; Burke, J. P.; Cottingham, W. N.; Walker, D.; Asgeirsson, D. J.; Cuhadar-Donszelmann, T.; Fulsom, B. G.; Hearty, C.; Knecht, N. S.; Mattison, T. S.; McKenna, J. A.; Khan, A.; Kyberd, P.; Saleem, M.; Sherwood, D. J.; Teodorescu, L.; Blinov, V. E.; Bukin, A. D.; Druzhinin, V. P.; Golubev, V. B.; Onuchin, A. P.; Serednyakov, S. I.; Skovpen, Yu. I.; Solodov, E. P.; Todyshev, K. Yu; Best, D. S.; Bondioli, M.; Bruinsma, M.; Chao, M.; Curry, S.; Eschrich, I.; Kirkby, D.; Lankford, A. J.; Lund, P.; Mandelkern, M.; Roethel, W.; Stoker, D. P.; Abachi, S.; Buchanan, C.; Foulkes, S. D.; Gary, J. W.; Long, O.; Shen, B. C.; Wang, K.; Zhang, L.; Hadavand, H. K.; Hill, E. J.; Paar, H. P.; Rahatlou, S.; Sharma, V.; Berryhill, J. W.; Campagnari, C.; Cunha, A.; Dahmes, B.; Hong, T. M.; Kovalskyi, D.; Richman, J. D.; Beck, T. W.; Eisner, A. M.; Flacco, C. J.; Heusch, C. A.; Kroseberg, J.; Lockman, W. S.; Nesom, G.; Schalk, T.; Schumm, B. A.; Seiden, A.; Spradlin, P.; Williams, D. C.; Wilson, M. G.; Albert, J.; Chen, E.; Cheng, C. H.; Dvoretskii, A.; Fang, F.; Hitlin, D. G.; Narsky, I.; Piatenko, T.; Porter, F. C.; Mancinelli, G.; Meadows, B. T.; Mishra, K.; Sokoloff, M. D.; Blanc, F.; Bloom, P. C.; Chen, S.; Ford, W. T.; Hirschauer, J. F.; Kreisel, A.; Nagel, M.; Nauenberg, U.; Olivas, A.; Ruddick, W. O.; Smith, J. G.; Ulmer, K. A.; Wagner, S. R.; Zhang, J.; Chen, A.; Eckhart, E. A.; Soffer, A.; Toki, W. H.; Wilson, R. J.; Winklmeier, F.; Zeng, Q.; Altenburg, D. D.; Feltresi, E.; Hauke, A.; Jasper, H.; Merkel, J.; Petzold, A.; Spaan, B.; Brandt, T.; Klose, V.; Lacker, H. M.; Mader, W. F.; Nogowski, R.; Schubert, J.; Schubert, K. R.; Schwierz, R.; Sundermann, J. E.; Volk, A.; Bernard, D.; Bonneaud, G. R.; Latour, E.; Thiebaux, Ch.; Verderi, M.; Clark, P. J.; Gradl, W.; Muheim, F.; Playfer, S.; Robertson, A. I.; Xie, Y.; Andreotti, M.; Bettoni, D.; Bozzi, C.; Calabrese, R.; Cibinetto, G.; Luppi, E.; Negrini, M.; Petrella, A.; Piemontese, L.; Prencipe, E.; Anulli, F.; Baldini-Ferroli, R.; Calcaterra, A.; de Sangro, R.; Finocchiaro, G.; Pacetti, S.; Patteri, P.; Peruzzi, I. M.; Piccolo, M.; Rama, M.; Zallo, A.; Buzzo, A.; Contri, R.; Vetere, M. Lo; Macri, M. M.; Monge, M. R.; Passaggio, S.; Patrignani, C.; Robutti, E.; Santroni, A.; Tosi, S.; Brandenburg, G.; Chaisanguanthum, K. S.; Lee, C. L.; Morii, M.; Wu, J.; Dubitzky, R. S.; Marks, J.; Schenk, S.; Uwer, U.; Bard, D. J.; Bhimji, W.; Bowerman, D. A.; Dauncey, P. D.; Egede, U.; Flack, R. L.; Nash, J. A.; Nikolich, M. B.; Vazquez, W. Panduro; Behera, P. K.; Chai, X.; Charles, M. J.; Mallik, U.; Meyer, N. T.; Ziegler, V.; Cochran, J.; Crawley, H. B.; Dong, L.; Eyges, V.; Meyer, W. T.; Prell, S.; Rosenberg, E. I.; Rubin, A. E.; Gao, Y.; Gritsan, A. V.; Guo, Z. J.; Denig, A. G.; Fritsch, M.; Schott, G.; Arnaud, N.; Davier, M.; Grosdidier, G.; Höcker, A.; Lepeltier, V.; Diberder, F. Le; Lutz, A. M.; Oyanguren, A.; Pruvot, S.; Rodier, S.; Roudeau, P.; Schune, M. H.; Serrano, J.; Stocchi, A.; Wang, W. F.; Wormser, G.; Lange, D. J.; Wright, D. M.; Chavez, C. A.; Forster, I. J.; Fry, J. R.; Gabathuler, E.; Gamet, R.; George, K. A.; Hutchcroft, D. E.; Payne, D. J.; Schofield, K. C.; Touramanis, C.; Bevan, A. J.; Clarke, C. K.; Lodovico, F. Di; Menges, W.; Sacco, R.; Cowan, G.; Flaecher, H. U.; Hopkins, D. A.; Jackson, P. S.; McMahon, T. R.; Salvatore, F.; Wren, A. C.; Brown, D. N.; Davis, C. L.; Allison, J.; Barlow, N. R.; Barlow, R. J.; Chia, Y. M.; Edgar, C. L.; Lafferty, G. D.; Naisbit, M. T.; Williams, J. C.; Yi, J. I.; Chen, C.; Hulsbergen, W. D.; Jawahery, A.; Lae, C. K.; Roberts, D. A.; Simi, G.; Blaylock, G.; Dallapiccola, C.; Hertzbach, S. S.; Li, X.; Moore, T. B.; Saremi, S.; Staengle, H.; Cowan, R.; Sciolla, G.; Sekula, S. J.; Spitznagel, M.; Taylor, F.; Yamamoto, R. K.; Kim, H.; McLachlin, S. E.; Patel, P.. M.; Robertson, S. H.; Lazzaro, A.; Lombardo, V.; Palombo, F.; Bauer, J. M.; Cremaldi, L.; Eschenburg, V.; Godang, R.; Kroeger, R.; Sanders, D. A.; Summers, D. J.; Zhao, H. W.; Brunet, S.; Côté, D.; Simard, M.; Taras, P.

2007-02-01

215

Novel temperature-sensitive crosslinked polymeric nanocapsules  

Microsoft Academic Search

Novel temperature-sensitive polymeric nanocapsules crosslinked via amide groups were prepared by the surface-initiated atom transfer radical polymerization (SI-ATRP) technique based on the widely used sacrificial SiO2 nanoparticle templates. In the strategy developed, the silica templates were removed by being etched with HF to obtain the crosslinked polymeric nanocapsules after the poly(methyl acrylate) (PMA) chains grafted on the SiO2 templates were

Bin Mu; Peng Liu

2010-01-01

216

Effect of External Field for Polypyrrole Polymerization  

Microsoft Academic Search

Summary form only given. Polypyrrole(PPy) is one of the most stables conducting polymers due to its high thermostability and life stability. In general, it has been known that PPy films can be synthesize by anodic electropolymerization, oxidative chemical polymerization and plasma enhanced polymerization. We have synthesized polypyrrole(PPy) nanofilms using vapor-phase oxidative polymerization process in a vacuum chamber under ultraviolet (UV)

Jaehong Park; Jaeseong Lee; Whikun Yi

2006-01-01

217

(Meth)Acrylate Vinyl Ester Hybrid Polymerizations  

PubMed Central

In this study vinyl ester monomers were synthesized by an amine catalyzed Michael addition reaction between a multifunctional thiol and the acrylate double bond of vinyl acrylate. The copolymerization behavior of both methacrylate/vinyl ester and acrylate/vinyl ester systems was studied with near-infrared spectroscopy. In acrylate/vinyl ester systems, the acrylate groups polymerize faster than the vinyl ester groups resulting in an overall conversion of 80% for acrylate double bonds in the acrylate/vinyl ester system relative to only 50% in the bulk acrylate system. In the methacrylate/vinyl ester systems, the difference in reactivity is even more pronounced resulting in two distinguishable polymerization regimes, one dominated by methacrylate polymerization and a second dominated by vinyl ester polymerization. A faster polymerization rate and higher overall conversion of the methacrylate double bonds is thus achieved relative to polymerization of the pure methacrylate system. The methacrylate conversion in the methacrylate/vinyl ester system is near 100% compared to only ~60% in the pure methacrylate system. Utilizing hydrophilic vinyl ester and hydrophobic methacrylate monomers, polymerization-induced phase separation is observed. The phase separated domain size is on the order of ~1 ?m under the polymerization conditions. The phase separated domains become larger and more distinct with slower polymerization and correspondingly increased time for diffusion.

Lee, TaiYeon; Cramer, Neil; Hoyle, Charles; Stansbury, Jeffrey

2009-01-01

218

Lentiviral and Retroviral Vector Systems  

Microsoft Academic Search

Retroviruses have been widely used as gene transfer vectors, and in fact represent the vector system used in the majority\\u000a of clinical gene therapy trials for cancer to date. In an ex vivo setting, conventional replication-defective oncoretrovirus\\u000a vectors can reliably and efficiently achieve permanent gene transfer which is selective for dividing cells; however, successful\\u000a application of these vectors in vivo

Renata Stripecke; Noriyuki Kasahara

219

Effect of polymerization under pressure on indirect tensile mechanical properties of light-polymerized composites  

Microsoft Academic Search

Statement of Problem. Flaws developed during polymerization of restorative materials cause a decrease in mechanical properties. Purpose. The aim of this study was to determine the effect of polymerization under pressure on the indirect tensile mechanical properties (stiffness and diametral tensile strength) of several light-polymerized composites. Material and Methods. Five light-polymerized composites were tested: Brilliant, Z100, TPH Spectrum, Prodigy, and

Tamar Brosh; Nechama Ferstand; Harold Cardash; Haim Baharav

2002-01-01

220

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

221

Light scattering in polymeric lightguides  

NASA Astrophysics Data System (ADS)

The scattering properties of polymeric optical fibers (POF) are studied to elucidate the light-energy loss mechanism. Methods for measuring light scattering with a different degree of averaging along the POF length are described. The possibility of quantitatively estimating the sizes of scattering inhomogeneities on the basis of experimentally obtained relationships between the scattering index and the wavelength is demonstrated. The obtained sizes of the scattering inhomogeneities for a POF with a polystyrene core are in the range of 30-200 nm. This agrees well with data obtained during structural investigations of the same samples using electron microscopy.

Mariukov, M. A.

1988-05-01

222

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.

Curtiss, C F; Bird, R B

1996-01-01

223

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

224

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

225

Polymeric microcapsules for synthetic applications.  

PubMed

For decades scientists have been working on closed systems for transportation, catalysis and protection, which are inspired by natural cells. Only recently polymer based systems have emerged for these systems, since they are more robust, give protection from the environment and give a more stable membrane. Various methods have been developed to prepare polymer based capsules. They can be made by self-assembly, templating, in situ polymerization or precipitation. Their application has been explored in various areas e.g. drug delivery, diagnostics, sensors and nano reactors. Considering the output in this field has substantially grown, more developments can be expected from this latter application. PMID:18655033

Lensen, Dennis; Vriezema, Dennis M; van Hest, Jan C M

2008-11-10

226

Simplified representation of vector fields  

Microsoft Academic Search

Vector field visualization remains a difficult task. Although many local and global visualization methods for vector fields such as flow data exist, they usually require extensive user experience on setting the visualization parameters in order to produce images communicating the desired insight. We present a visualization method that produces simplified but suggestive images of the vector field automatically, based on

Alexandru Telea; Jarke J. van Wijk

1999-01-01

227

Tomographic reconstruction of vector fields  

Microsoft Academic Search

The application of tomography to the reconstruction of vector fields is considered. Two different types of interaction between the radiation used for measurement and the investigated vector fields are discussed. A complete reconstruction of a vector field can only be obtained if measurements based on both types of interaction are available. Otherwise, only curl-free or source-free components of the field

Hans Braun; Axel Hauck

1991-01-01

228

Scientific computing on vector computers  

Microsoft Academic Search

The goal of this volume is to gradually guide from usual base of general purpose computer knowledge to the highly specialized knowledge necessary for the efficient use of vector computers. The basic rules for the selection of optimal data structures and algorithms for vector computers are presented. The properties of the hardware and software of the following vector computers are

Schonaver

1987-01-01

229

Proven-prompt vector normalizer  

Microsoft Academic Search

The cosine of the angle between two vectors is a frequency needed quantity in computer graphics algorithms. Provided the vectors are normalized, it can easily be computed by evaluating their dot product. However, this requires the essential problem of rapidly normalizing a vector, which includes three divisions and one square root operation, to be solved. The authors describe a single-chip

Guenter Knittel

1993-01-01

230

Successive refinement lattice vector quantization  

Microsoft Academic Search

Lattice vector quantization (LVQ) solves the complexity problem of LBG based vector quantizers, yielding very general codebooks. However, a single stage LVQ, when applied to high resolution quantization of a vector, may result in very large and unwieldy indices, making it unsuitable for applications requiring successive refinement. The goal of this work is to develop a unified framework for progressive

Debargha Mukherjee; Sanjit K. Mitra

2002-01-01

231

Biocompatibility of biomaterials: hemocompatibility, immunocompatiblity and biocompatibility of solid polymeric materials and soluble targetable polymeric carriers  

Microsoft Academic Search

The biocompatibility and immunocompatibility of polymeric materials is of fundamental importance for their possible therapeutic uses. Aspects of biocompatibility of solid polymeric materials and soluble polymeric materials differ. Solid materials are used in polymer implants, as membranes in kidney dialysis and cardiopulmonary bypass, for polymer coating of other materials to increase their biocompatibility, for encapsulation of cells producing hormones and

Blanka ?íhová

1996-01-01

232

Fluidic thrust vector control  

NASA Astrophysics Data System (ADS)

The design and testing of a fluidic control nozzle for tactical missile thrust vector control (TVC) are discussed. Attention is given to a nozzle with a circular cross section up to the point of flow separation, two control ports that alternately open and close, and a nozzle extension downstream of the control ports being a two-dimensional rectangular slot. Design of the TVC system involved characterizing the flow and the sensitivity parameters, the dynamic response, and the performance of hot-gas firings. The test firings verified the feasibility of a nozzle that could withstand 5000 F, the use of thrust vector angles of over 20 deg. A dynamic model test demonstrated a repeatable performance with pressures up to 2000 psia, driving frequencies up to 50 Hz, and a response of 10-15 msec. Adjustment of the chamber pressures permitted equivalent performance using with different heat ratios during cold dynamic tests with CH4.

Haloulakos, V. E.

233

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.

2008-10-23

234

Maximally symmetric vector propagator  

SciTech Connect

We derive the propagator for a massive vector field on a de Sitter background of arbitrary dimension. This propagator is de Sitter invariant and possesses the proper flat space-time and massless limits. Moreover, the retarded Green's function inferred from it produces the correct classical response to a test source. Our result is expressed in a tensor basis which is convenient for performing quantum-field-theory computations using dimensional regularization.

Tsamis, N. C.; Woodard, R. P. [Department of Physics, University of Crete, GR-710 03 Heraklion (Greece); Department of Physics, University of Florida, Gainesville, Florida 32611 (United States)

2007-05-15

235

Programming stem cells for therapeutic angiogenesis using biodegradable polymeric nanoparticles.  

PubMed

Controlled vascular growth is critical for successful tissue regeneration and wound healing, as well as for treating ischemic diseases such as stroke, heart attack or peripheral arterial diseases. Direct delivery of angiogenic growth factors has the potential to stimulate new blood vessel growth, but is often associated with limitations such as lack of targeting and short half-life in vivo. Gene therapy offers an alternative approach by delivering genes encoding angiogenic factors, but often requires using virus, and is limited by safety concerns. Here we describe a recently developed strategy for stimulating vascular growth by programming stem cells to overexpress angiogenic factors in situ using biodegradable polymeric nanoparticles. Specifically our strategy utilized stem cells as delivery vehicles by taking advantage of their ability to migrate toward ischemic tissues in vivo. Using the optimized polymeric vectors, adipose-derived stem cells were modified to overexpress an angiogenic gene encoding vascular endothelial growth factor (VEGF). We described the processes for polymer synthesis, nanoparticle formation, transfecting stem cells in vitro, as well as methods for validating the efficacy of VEGF-expressing stem cells for promoting angiogenesis in a murine hindlimb ischemia model. PMID:24121540

Keeney, Michael; Deveza, Lorenzo; Yang, Fan

2013-09-27

236

21 CFR 870.3650 - Pacemaker polymeric mesh bag.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Pacemaker polymeric mesh bag. 870.3650 ...Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted...

2013-04-01

237

40 CFR 721.10299 - Polymeric MDI based polyurethanes (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Polymeric MDI based polyurethanes (generic). 721.10299 Section...721.10299 Polymeric MDI based polyurethanes (generic). (a) Chemical substance...identified generically as polymeric MDI based polyurethanes (PMNs P-00-2,...

2013-07-01

238

Polymers with Very Low Polydispersities from Atom Transfer Radical Polymerization.  

National Technical Information Service (NTIS)

A new radical polymerization process yields well-defined polymers that normally could only be obtained through anionic polymerizations. Atom transfer radical polymerizations (ATRP) of styrene were conducted with several solubilizing ligands for the copper...

T. E. Patten J. Xia T. Abernathy K. Matyjaszewski

1996-01-01

239

Flame Retardancy of Cellular Polymeric Materials  

Microsoft Academic Search

The combustion behavior of cellular polymeric materials is reviewed. The correlations between the structure and thermophysical properties of cellular polymers are discussed. The tests for potential fire hazard of cellular polymeric materials are reviewed. The approaches to flame retardancy of rigid foams based on reactive polyfunctional olygomers (phenolformaldehyde and urea formaldehyde ones, polyurethane) are demonstrated.

R. M. Aseeva; G. E. Zaikov

1996-01-01

240

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

241

Electrohydrodynamic atomization for biodegradable polymeric particle production  

Microsoft Academic Search

Electrohydrodynamic atomization (EHDA) has many applications such as electrospray ionization in mass spectroscopy, electrospray deposition of thin films, pharmaceutical productions, and polymeric particle fabrications for drug encapsulation. In the present study, EHDA was employed to produce biodegradable polymeric micro- and nanoparticles. The effects of processing parameters such as polymer concentration, flow rate, surfactants, organic salt, and setup configurations on the

Jingwei Xie; Liang Kuang Lim; Yiyong Phua; Jinsong Hua; Chi-Hwa Wang

2006-01-01

242

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.

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

2013-01-01

243

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

244

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

245

Engineering atom transfer radical polymerization: Catalyst technology  

Microsoft Academic Search

Atom transfer radical polymerization (ATRP) is a controlled\\/living radical polymerization process developed a decade ago that allows the synthesis of tailored macromolecules. It has been widely used in the laboratory for polymer synthesis since, but significant use is yet to be made of it at an industrial scale for polymer production. This is due to the low activity of the

Santiago Faucher

2007-01-01

246

Silanized polymeric nanoparticles for DNA isolation.  

PubMed

The aim of this study is to prepare silanized polymeric nanoparticles for DNA isolation. Polymeric p(HEMA)-IMEO-PBA nanoparticles around 85.7nm diameter, was obtained by surfactant free emulsion polymerization for DNA isolation. Synthesized nanoparticles for characterization studies were realized scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Zeta-size. Surface area, average particle size and size distribution were also performed. The surface area of synthesized silanized polymeric nanoparticles was 2460m(2)/g. Synthesized polymeric nanoparticles were silanized with 3-(2-imidazoline-1-yl)propyl (triethoxysilane) (IMEO). After that, phenylboronic acid (PBA) which is DNA specific ligand were covalently binded to silanized polymeric nanoparticles. The amount of DNA adsorbed onto the p(HEMA)-IMEO-PBA nanoparticles first increased and then reached a saturation value at around 14.0mg/mL of DNA concentration. The maximum adsorption was 672.41mg/g silanized polymeric nanoparticles in the optimum adsorption medium. The maximum DNA adsorption was achieved at 4°C. The overall recovery of DNA was calculated as 95%. In repetitive adsorption-desorption circles, it is observed not being important decrease in DNA adsorption capacities. The results were shown that silanized polymeric nanoparticles can be a good alternative for DNA isolation. PMID:24094151

Türkcan, Ceren; Akgöl, Sinan; Denizli, Adil

2013-05-22

247

Insight into Organometallic-Mediated Radical Polymerization  

Microsoft Academic Search

This review focuses on an emerging class of controlled radical polymerization named Organometallic-Mediated Radical Polymerization (OMRP). The latter is based on the temporary deactivation of the growing radical species by a transition metal complex and the reversible formation of a carbon-metal covalent bond. Initially developed with cobalt complexes, OMRP has extended to several metals today. As highlighted here, the choice

Marie Hurtgen; Christophe Detrembleur; Christine Jerome; Antoine Debuigne

2011-01-01

248

Materials science: Nanoscale control of chain polymerization  

Microsoft Academic Search

Polymer industries depend on the spontaneous polymerization of molecules into chains in response to an appropriate trigger. We have succeeded in inducing and guiding chain polymerization over tiny distances, initiating and terminating linear propagation at any chosen point to a spatial precision of about 1 nm by using the probe tip of a scanning tunnelling microscope. Being able to exert

Yuji Okawa; Masakazu Aono

2001-01-01

249

Radical Polymerization Yielding Polymers with Mw/Mn<1.05 by Homogeneous Atom Transfer Radical Polymerization.  

National Technical Information Service (NTIS)

We have found that radical polymerization processes can yield well-defined polymers that heretofore could only be obtained through anionic polymerizations. Specifically, ATRP employing ligands that solubilize the copper halides in the polymerization mediu...

T. E. Patten J. Xia T. Abernathy K. Matyjaszewski

1996-01-01

250

Twenty-Fourth Asilomar Conference on Polymeric Materials.  

National Technical Information Service (NTIS)

The 2001 Asilomar Conference on Polymeric Materials emphasized nanostructured polymeric systems. The conference included such topics as multi functional dendrimers, nanoscale processing and fabrication, periodically modulated nanocomposites, nanoparticles...

E. Baer

2001-01-01

251

Warm vector inflation  

NASA Astrophysics Data System (ADS)

In this Letter we introduce the "warm vector inflation" scenario. In warm inflation scenario radiation is produced during the inflation epoch and reheating is avoided. Slow-roll and perturbation parameters of this model are presented. We develop our model using intermediate inflation model. In this case, the model is compatible with observational data. We also study the model using another exact cosmological solution, named logamediate scenario. We present slow-roll and Hubble parameters, power spectrum and tensor-scalar ratio in terms of inflaton. The model is compatible with WMAP7 and Planck observational data.

Setare, M. R.; Kamali, V.

2013-10-01

252

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

253

HIV-1-Based Lentiviral Vectors.  

PubMed

Numerous viral vectors have been developed for the delivery of transgenes to specific target cells. For persistent transgene expression, vectors based on retroviruses are attractive delivery vehicles because of their ability to stably integrate their DNA into the host cell genome. Initially, vectors based on simple retroviruses were the vector of choice for such applications. However, these vectors can only transduce actively dividing cells. Therefore, much interest has turned to retroviral vectors based on the lentivirus genus because of their ability to transduce both dividing and non-dividing cells. The best characterized lentiviral vectors are derived from the human immunodeficiency virus type 1 (HIV-1). This chapter describes the basic features of the HIV-1 replication cycle and the many improvements reported for the lentiviral vector systems to increase the safety and efficiency. We also provide practical information on the production of HIV-1 derived lentiviral vectors, the cell transduction protocol and a method to determine the transduction titers of a lentiviral vector. PMID:24158830

Liu, Ying Poi; Berkhout, Ben

2014-01-01

254

Polycyclic Vector scheduling vs. Chaining on 1Port Vector supercomputers  

Microsoft Academic Search

This paper studies the impact of chaining and several instruction scheduling schemes on one-memory-port vector supercomputers, illustrated by the Cray-1 and Cray-2. The lack of instruction chaining in the Cray-2 vector processor requires a different instruction scheduling scheme from that of the Cray-1. Situations are characterized in which simple vector scheduling can generate optimal code, which fully utilizes at least

Ju-ho Tang; Edward S. Davidson; Johau Tong

1988-01-01

255

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

256

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

257

Optics for vector scanning  

NASA Astrophysics Data System (ADS)

Vector scanning of laser beams is critical to the success of stereolithography, laser marking, CAD-output-to-microfilm and many other industrial applications. The design of a vector scan lens system can assume many different configurations. This paper will discuss pre-objective, and post-objective alternatives for two and three axis scanning. Various parameters required for system specification are reviewed and the basic configuration of the two axis scan head is presented. The pre-objective scan f-theta lens, its scan distortion, telecentric options, and single origin scan systems are described. Fixed focus and dynamic focus post-objective systems are presented discussing the relative merits of each approach and noting the limitations of each design solution. Data presented describe limiting field sizes for fixed focus systems, and limiting f-numbers for thin lens systems. Thin lens design equations for three post-objective configurations are presented with suggested optimization techniques for overall system layout. Examples of pre-objective and post-objective scan lens systems as well as pre- configured systems are presented.

Ehrmann, Jonathan S.

1991-02-01

258

Eliminating malaria vectors.  

PubMed

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

Killeen, Gerry F; Seyoum, Aklilu; Sikaala, Chadwick; Zomboko, Amri S; Gimnig, John E; Govella, Nicodem J; White, Michael T

2013-06-07

259

3-D Vector Field Simulation  

NSDL National Science Digital Library

This simulation illustrates a wide range of 3D vector fields, including spherical, radial, and linear. The fields can be displayed as vectors, particle trajectories, equipotentials, and other options. The number of particles, vectors, or streamlines, and the field strength are adjustable. Directions and source code are also included. This is an extension of a 3D Electric and Magnetic Field viewer from the same author.

Falstad, Paul

2004-07-13

260

Student Preconceptions about Vector Kinematics  

NSDL National Science Digital Library

This article describes a study focused on examining student (15- to 17-year-old students possess just before taking their first physics course) preconceptions about vector characteristics that physics teachers consider so obvious that they are not discussed in class. So consideration of these characteristics is crucial to effective instruction. The author uses seven vector characteristics and three tasks to interview students and then presents the most common student preconceptions regarding each of the implicit vector characteristics.

Aguirre, Jose

2006-12-06

261

Method for forming polymerized microfluidic devices  

DOEpatents

Methods for making a microfluidic device according to embodiments of the present invention include defining.about.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.; Hatch, Anson V.; Wang, Ying-Chih; Singh, Anup K.; Renzi, Ronald F.; Claudnic, Mark R.

2013-03-12

262

Method for forming polymerized microfluidic devices  

SciTech Connect

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

263

Execution of vector operations for Intel 860  

SciTech Connect

When designing a portable setup compiler from the C[] language, the compiler setup problem is solved for various SIMD computers. A vector and vector operations are defined in C[]. A map of vector operations is trivial for computers with vector registers. Some problems appear when mapping them to computers without vector registers. It is shown how to effectively perform vector operations for the 1860 microcomputer as an example of one without vector registers.

Khaletskii, D.A.

1995-03-01

264

The “parallel vectors” operator: a vector field visualization primitive  

Microsoft Academic Search

In this paper we propose an elementary operation on a pair of vector fields as a building block for defining and computing global line-type features of vector or scalar fields. While usual feature definitions often are procedural and therefore implicit, our operator allows precise mathematical definitions. It can serve as a basis for comparing feature definitions and for reuse of

Ronald Peikert; Martin Roth

1999-01-01

265

Properties of an indirect composite material polymerized with two different laboratory polymerizing systems.  

PubMed

The purpose of the current study was to evaluate the performance of two laboratory light polymerization systems used to polymerize an indirect composite (Sinfony). A two-step polymerization system (Visio-Alfa and Beta) and a halogen-metal halide unit (Twinkle MIII) were assessed. The composite was polymerized either with the Visio units or with the MIII unit for different exposure periods. Knoop hardness, water sorption, and solubility in water of the composite polymerized with the following modes were determined: Visio, 15 minutes; MIII, 30, 60, 90, 120, and 180 seconds. Extension of light exposure time to the MIII unit improved the hardness of the composite from 30.5 (30 s) to 40.7 (180 s), whereas hardness obtained with the Visio units resulted in 24.8 (15 minutes). Water sorption and solubility of the composite were greater when it was polymerized with the Visio units than with the MIII unit. PMID:16279727

Satsukawa, Hidetada; Koizumi, Hiroyasu; Tanoue, Naomi; Nemoto, Mika; Ogino, Tomohisa; Matsumura, Hideo

2005-09-01

266

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

PubMed

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

2013-09-17

267

Nanoparticulated heat-stable (STa) and heat-labile B subunit (LTB) recombinant toxin improves vaccine protection against enterotoxigenic Escherichia coli challenge in mouse.  

PubMed

Enterotoxigenic Escherichia coli (ETEC) remains a major cause of diarrheic disease in developing areas, for which there is no effective vaccine available. In this study, we genetically engineered a recombinant heat-stable enterotoxin (STa) coupled to the subunit B of heat-labile enterotoxin (LTB). This fusion protein, STa-LTB, possesses a single amino acid substitution at position 14 of STa. Our data demonstrates that the enterotoxicity of STa in STa-LTB was dramatically reduced. A gelatin nanovaccine candidate was prepared using the purified STa-LTB fusion protein characterized with an entrapment efficiency of 84.88 ± 6.37% and smooth spheres size ranges of 80-200 nm. Antigen-specific antibody responses against STa-LTB and STa in the sera and the intestinal mucus respectively were used to test the immunogenicity of the nanovaccine. This vaccine was further screened in mice by its ability to elicit neutralizing antibodies against STa and protect animals from the challenge with ETEC in mice. The STa-LTB nanoparticles delivered demonstrated a capacity to induce significantly higher and long-lasting antibody responses and increased immune protection against ETEC challenge relative to the control STa-LTB vaccine absorbed in conventional aluminum hydrate salt (p < 0.01). These results warrant the further studies of the development of a novel nanoparticulate vaccine as a broad-spectrum vaccine against ETEC infection. PMID:23040995

Deng, Guangcun; Zeng, Jin; Jian, Minjie; Liu, Wenmiao; Zhang, Zhong; Liu, Xiaoming; Wang, Yujiong

2012-10-05

268

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

PubMed

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 TiO(2) 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 its efficiency can be greatly enhanced by welding the interface with a laser. TiO(2) films formed on the TCO-coated glass substrate were irradiated with a pulsed ultraviolet laser beam at 355 nm; this transmits through the TCO and glass but is strongly absorbed by TiO(2). Electron microscopy analysis and impedance measurements showed that a thin continuous TiO(2) layer is formed at the interface as a result of the local melting of TiO(2) nanoparticles and this layer completely bridges the gap between the two electrodes, improving the current flow with a reduced contact resistance. We were able to improve the efficiency by 35-65% with this process. DSSCs fabricated using a homemade TiO(2) paste revealed an efficiency improvement from eta = 3.3% to 5.4%, and an increase from 8.2% to 11.2% was achieved with the TiO(2) electrodes made from a commercial paste. PMID:20671364

Kim, Jinsoo; Kim, Jonghyun; Lee, Myeongkyu

2010-07-30

269

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

NASA Astrophysics Data System (ADS)

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 its efficiency can be greatly enhanced by welding the interface with a laser. TiO2 films formed on the TCO-coated glass substrate were irradiated with a pulsed ultraviolet laser beam at 355 nm this transmits through the TCO and glass but is strongly absorbed by TiO2. Electron microscopy analysis and impedance measurements showed that a thin continuous TiO2 layer is formed at the interface as a result of the local melting of TiO2 nanoparticles and this layer completely bridges the gap between the two electrodes, improving the current flow with a reduced contact resistance. We were able to improve the efficiency by 35-65% with this process. DSSCs fabricated using a homemade TiO2 paste revealed an efficiency improvement from ? = 3.3% to 5.4%, and an increase from 8.2% to 11.2% was achieved with the TiO2 electrodes made from a commercial paste.

Kim, Jinsoo; Kim, Jonghyun; Lee, Myeongkyu

2010-08-01

270

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.

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

2013-01-01

271

Polymeric Materials Science in the Microgravity Environment.  

National Technical Information Service (NTIS)

The microgravity environment presents some interesting possibilities for the study of polymer science. Properties of polymeric materials depend heavily on their processing history and environment. Thus, there seem to be some potentially interesting and us...

D. R. Coulter

1989-01-01

272

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

273

Characterizing polymeric methylene diphenyl diisocyanate reactions ...  

Treesearch

Title: Characterizing polymeric methylene diphenyl diisocyanate reactions with wood. ... adhesion, plant cell walls, loblolly pine, chemical reactions, nanotechnology, ... This article was written and prepared by U.S. Government employees on ...

274

Homogeneous Anionic Polymerization of Unsaturated Monomers.  

National Technical Information Service (NTIS)

This review discusses the polymerization of unsaturated monomers by carbanionic mechanisms. Particular emphasis is placed on the synthesis possibilities of these systems, i.e., monodisperse polymers, block copolymers, and polymers reactive end-groups.

M. Morton L. J. Fetters

1967-01-01

275

Layered Polymeric Optical Systems Using Continuous Coextrusion.  

National Technical Information Service (NTIS)

Polymers are receiving considerable attention as components in novel optical systems because of the tailored functionality, ease of manufacturing, and relatively low cost. The processing of layered polymeric systems by coextrusion is a method to produce f...

H. Song J. Lott J. Zhou K. Singer Y. Wu

2009-01-01

276

Radiation-induced polymerization of 3-octylthiophene  

NASA Astrophysics Data System (ADS)

In order to develop a new synthetic method and to study mechanism of oxidative polymerization of conducting polymers, polymerization of 3-octylthiophene in several organic solvents by ?-irradiation was examined. Polymers bimodal distribution with molecular weights at 500-1000 and 2000-3000 were generated by the irradiation of chloroform solutions. The values of monomer conversion (G(-M)) decreased from 445 to 10 with doses from 0.99 kGy to 594 kGy. The large G(-M) values and dose dependence of G(-M) cannot be explained with widely accepted mechanism for electrochemical polymerization or chemical oxidative polymerization. Another mechanism, which proceeds through chain reactions, is proposed. This mechanism explains the large G(-M) and the dependence on the dose.

Ishigaki, Akihiro; Koizumi, Hitoshi

2012-07-01

277

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

278

Hydroxy Butyric Acids: Properties and Polymerization.  

National Technical Information Service (NTIS)

Hydroxybutyric acids and their lactones are discussed. Their properties, polymerization methods and polymers are reviewed. Special interest is in poly (Beta-hydroxybutyrate), because it is a naturally occuring, optically active, highly crystalline and bio...

J. Ahlgren

1991-01-01

279

Twentieth Asilomar Conference on Polymeric Materials.  

National Technical Information Service (NTIS)

The 1997 Asilomar Conference on Polymeric Materials focused on electroactive polymer systems. New directions were probed for use of such materials in power sources. The implications in biological integration of such systems were also explored. An attempt ...

E. Baer

1997-01-01

280

EPR study of Frontally Polymerized Multifunctional Acrylates  

NASA Astrophysics Data System (ADS)

Electron Paramagnetic Resonance(EPR) study of frontally polymerized Trimethylopropane Trimethacrylate(TMPTMA), Trimethylopropane Triacrylate(TMPTA), 1,6-Hexanidiol Diacrylate(HDODA) and Pentaerythritol Tetracrylate(PETA) was done to determine the absolute radical concentration. Higher radical concentrations were found in the frontally polymerized samples compared to the bulk polymerized samples for TMTPMA and PETA. The concentration of radicals was highest in TMPTMA frontal sample at 8.74 X 10-3 moles/kg. The lowest measureable concentration was in the HDODA bulk samples at 0.0266 X 10-3 moles/kg. For all frontally polymerized samples high radical concentrations were observed at the point of initiation after which the signal intensity decreased to steady state within a few centimeters down the front. An exponential growth in the radical signal was observed in the mixture of TMPTMA and TMPTA when the concentration of the TMPTMA was increased.

Dahal, Ashutosh; Regmi, Aayush; Thoma, Anna; Valencia, Alecia; Viner, Veronika; Cueto, Rafael; Blane Baker, D.; Pojman, John; Bunton, Patrick

2011-03-01

281

Vectors for cancer gene therapy  

Microsoft Academic Search

Many viral and non-viral vector systems have now been developed for gene therapy applications. In this article, the pros and cons of these vector systems are discussed in relation to the different cancer gene therapy strategies. The protocols used in cancer gene therapy can be broadly divided into six categories including gene transfer to explanted cells for use as cell-based

J. Zhang; S. J. Russell

1996-01-01

282

Divergence-Based Vector Quantization  

Microsoft Academic Search

Supervised and unsupervised vector quantization methods for classification and clustering traditionally use dissimilarities, frequently taken as Euclidean distances. In this article, we investigate the applicability of divergences instead, focusing on online learning. We deduce the mathematical fundamentals for its utilization in gradient-based online vector quantization algorithms. It bears on the generalized derivatives of the divergences known as Fréchet derivatives in

Thomas Villmann; Sven Haase

2011-01-01

283

Construction of vector field hierarchies  

Microsoft Academic Search

We present a method for the hierarchical representation of vector fields. Our approach is based on iterative refinement using clustering and principal component analysis. The input to our algorithm is a discrete set of points with associated vectors. The algorithm generates a top-down segmentation of the discrete field by splitting clusters of points. We measure the error of the various

Bjoern Heckel; Gunther H. Weber; Bernd Hamann; Kenneth I. Joy

1999-01-01

284

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

285

Vector filtering for color imaging  

Microsoft Academic Search

Vector processing operations use essential spectral and spatial information to remove noise and localize microarray spots. The proposed fully automated vector technique can be easily implemented in either hardware or software; and incorporated in any existing microarray image analysis and gene expression tool.

Rastislav Lukac; Bogdan Smolka; Karl Martin; Konstantinos N. Plataniotis; Anastasios N. Venetsanopoulos

2005-01-01

286

Vectorized Monte Carlo Photon Transport.  

National Technical Information Service (NTIS)

The results of current research in the development of a CRAY algorithm for time-dependent Monte Carlo photon radiation transport is presented. The method that has been developed is a fully vectorized particle-vector scheme. This technique tracks groups of...

F. W. Bobrowicz J. E. Lynch K. J. Fisher J. E. Tabor

1983-01-01

287

The Physics Classroom: Vector Addition  

NSDL National Science Digital Library

This student tutorial provides practice in the basics of vector addition. The author provides free-body diagrams and animations to guide users through the Pythagorean method and the tip-to-tail method of adding vectors. SEE RELATED ITEMS for related Java simulations that supplement this tutorial.

Henderson, Tom

2011-01-10

288

Collapse of the state vector  

NASA Astrophysics Data System (ADS)

Modifications of quantum mechanics are considered, in which the state vector of any system, large or small, undergoes a stochastic evolution. The general class of theories is described, in which the probability distribution of the state vector collapses to a sum of ? functions, one for each possible final state, with coefficients given by the Born rule.

Weinberg, Steven

2012-06-01

289

Rechargeable Antibacterial and Antifungal Polymeric Silver Sulfadiazines  

Microsoft Academic Search

Poly(methyl methacrylate) (PMMA)-based rechargeable antibacterial and antifungal polymeric silver sulfadiazines were prepared by copolymerizing acryloyl sulfadiazine with methyl methacrylate and sequentially treating the copolymers with dilute silver nitrate aqueous solutions. The chemical structures of the samples were characterized by FT-IR, 1H-NMR, XPS, and TGA analyses. On contact, the PMMA-based polymeric silver sulfadiazines provided 100% inactivation of 108—109 CFU\\/mL of Escherichia

Zhengbing Cao; Xinbo Sun; Yuyu Sun; Hao Fong

2009-01-01

290

Living polymers and mechanisms of anionic polymerization  

Microsoft Academic Search

Following a short introduction and a brief discussion of thermodynamics of propagation, the kinetics and mechanisms of anionic\\u000a polymerization are reviewed. The systems involving living polymers, a term introduced by this writer, are discussed in greater\\u000a detail because the existence of various ionic species participating in polymerization was clearly revealed by their studies.\\u000a Indeed, a large part of this review

Michael Szwarc

291

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

292

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

293

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.

Larson, Nate; Ghandehari, Hamidreza

2012-01-01

294

Viral vectors for malaria vaccine development  

Microsoft Academic Search

A workshop on viral vectors for malaria vaccine development, organized by the PATH Malaria Vaccine Initiative, was held in Bethesda, MD on October 20, 2005. Recent advancements in viral-vectored malaria vaccine development and emerging vector technologies were presented and discussed. Classic viral vectors such as poxvirus, adenovirus and alphavirus vectors have been successfully used to deliver malaria antigens. Some of

Shengqiang Li; Emily Locke; Joseph Bruder; David Clarke; Denise L. Doolan; Menzo J. E. Havenga; Adrian V. S. Hill; Peter Liljestrom; Thomas P. Monath; Hussein Y. Naim; Christian Ockenhouse; De-chu C. Tang; Kent R. Van Kampen; Jean-Francois Viret; Fidel Zavala; Filip Dubovsky

2007-01-01

295

Equilibrium polymerization of cyclic carbonate oligomers  

NASA Astrophysics Data System (ADS)

A model of the polymerization of ring oligomers of bisphenol A polycarbonate (BPA-PC) is used to investigate the influence of dimensionality (2D or 3D), density and temperature on the size distribution of the polymer chains. The polymerization step is catalyzed by a single active particle, conserves the number and type of the chemical bonds, and occurs without a significant gain in either potential energy or configurational entropy. Monte Carlo and molecular dynamics simulations show that polymerization of cyclic oligomers occurs readily at high density and is driven by the entropy associated with the distribution of interparticle bonds. Polymerization competes at lower densities with long range diffusion, which favors small molecular species, and is prevented if the system is sufficiently dilute. Polymerization occurs in 2D via a weakly first order transition as a function of density and is characterized by low hysteresis and large fluctuations in the size of polymer chains. Polymerization occurs more readily in 3D than in 2D, and is favored by increasing temperature, as expected for an entropy-driven process.

Ballone, P.; Jones, R. O.

2001-08-01

296

Cosmological perturbations from vector inflation  

SciTech Connect

We analyze the behavior of linear perturbations in vector inflation. In contrast to scalar field inflation, the linearized theory with vector fields contains couplings between scalar, vector, and tensor modes. The perturbations decouple only in the ultraviolet limit, which allows us to carry out the canonical quantization. Superhorizon perturbations can be approximately analyzed due to suppressed mixing between different modes in the small field models. We find that the vector perturbations of the metric decay exponentially, but the scalar and tensor modes could remain weakly coupled throughout the evolution. As a result, vector inflation can produce significant correlations of the scalar and tensor modes in the CMB. For realistic models the effect is rather small, but not negligible.

Golovnev, Alexey; Vanchurin, Vitaly [Arnold-Sommerfeld-Center for Theoretical Physics, Department fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Theresienstrasse 37, D-80333, Munich (Germany)

2009-05-15

297

A neural support vector machine.  

PubMed

Support vector machines are state-of-the-art pattern recognition algorithms that are well founded in optimization and generalization theory but not obviously applicable to the brain. This paper presents Bio-SVM, a biologically feasible support vector machine. An unstable associative memory oscillates between support vectors and interacts with a feed-forward classification pathway. Kernel neurons blend support vectors and sensory input. Downstream temporal integration generates the classification. Instant learning of surprising events and off-line tuning of support vector weights trains the system. Emotion-based learning, forgetting trivia, sleep and brain oscillations are phenomena that agree with the Bio-SVM model. A mapping to the olfactory system is suggested. PMID:20092978

Jändel, Magnus

2010-01-11

298

New ring-opening polymerizations for copolymers having controlled microstructures  

Microsoft Academic Search

Various prestructured cyclic monomers were synthesized and polymerized to construct the copolymers of controlled mer sequence. Vinylcyclopropanes with substituents –CN, –CO2R and –C6H5 were prepared and radically ring-opening polymerized in 1,5-fashion to obtain high molecular weight polymers. Anionic polymerization of these monomers gave 3,5-polymers with vinyl pendent group. 2-Phenyl-3-vinyloxirane polymerized radically by C–C scission. These polymerization behaviors of 3-membered ring

I Cho

2000-01-01

299

Traffic of poly(lactic acid) nanoparticulate vaccine vehicle from intestinal mucus to sub-epithelial immune competent cells.  

PubMed

Mucosal immunization is designed to induce strong immune responses at portal of pathogen entry. Unfortunately, mechanisms underlying the fate of the vaccine vector co-administered with antigens are still partially uncovered and limit further development of mucosal vaccines. Hence, poly(lactic acid) (PLA) nanoparticles being a versatile vaccine vehicle, we have analyzed the fate of these PLA nanoparticles during their uptake at intestinal mucosal sites, both in vivo and ex vivo, to decipher the mechanisms involved during this process. We first designed specific fluorescent PLA nanoparticles exhibiting strong colloidal stability after encapsulation of either 6-coumarin or CellTrace BODIPY before monitoring their transport through mucosa in the mouse ligated ileal loop model. The journey of the particles appears to follow a three-step process. Most particles are first entrapped in the mucus. Then, crossing of the epithelial barrier takes place exclusively through M-cells, leading to an accumulation in Peyer's patches (PP). Lastly, we noticed specific interaction of these PLA nanoparticles with underlying B cells and dendritic cells (DCs) of PP. Furthermore, we could document that DCs engulfing some nanoparticles could exhibit a TLR8+ specific expression. Specific targeting of these two cell types strongly supports the use of PLA nanoparticles as a vaccine delivery system for oral use. Indeed, following oral gavage of mice with PLA nanoparticles, we were able to observe the same biodistribution patterns, indicating that these nanoparticles specifically reach immune target required for oral immunization. PMID:20471085

Primard, Charlotte; Rochereau, Nicolas; Luciani, Elsa; Genin, Christian; Delair, Thierry; Paul, Stéphane; Verrier, Bernard

2010-05-14

300

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

301

Controlled Architecture Polymers by Anionic Polymerization  

NASA Astrophysics Data System (ADS)

Anionic polymerization is the most important synthetic tool to produce model polymers and copolymers with complex macromolecular architectures. High vacuum techniques1 have to be used in order to avoid premature living chain termination or linking agent destruction. These techniques are very demanding in glass blowing practice, time consuming and usually lead to the synthesis of a few grams of model polymers. Nevertheless, these Â"limitationsÂ" are a small price to pay given the potential of anionic polymerization to generate true model polymeric materials. By using anionic polymerization and controlled chlorosilane chemistry a variety of macromolecular architectures have been created2. A few examples are the miktoarm stars ( AnB, AnBn), the á,ù-branched polymers ( AnBAn), and the comb-shaped polymers (A-g-B1or2) where A, B are polymeric chains with different molecular weight or chemistry and n, m: 2-8. Recent advances in anionic polymerization methodology led to the synthesis of well-defined cyclic co- and terpolymers3,4, as well as dendritic polymers5, multicomponent multiblock polymers6 and polymeric materials having as building blocks macromonomers7. References 1. N. Hadjichristidis, H. Iatrou, S. Pispas, M. Pitsikalis, J. Polym. Sci., Part A : Polym. Chem. 38, 3211 (2000). 2. N. Hadjichristidis, M. Pitsikalis, S. Pispas, H. Iatrou, Chem. Rev. 101, 3747 (2001). 3. H. Iatrou, N. Hadjichristidis, G. Meier H. Frielinghaus, and M. Monkenbusch, Macromolecules 35 5426 (2002) 4. D. Pantazis, D. Schulz, N. Hadjichristidis, J. Polym. Sci., Part A : Polym.Chem. 40, 1476 (2002) 5. I. Chalari, and N. Hadjichristidis, J. Polym. Sci., Part A: Polym. Chem. 40, 1519 (2002) 6. K. Takahashi, H. Hasegawa, T. Hashimoto, V. Bellas, H. Iatrou, N. Hadjichristidis, Macromolecules 35, 4859 (2002) 7. D. Pantazis, I. Chalari, N. Hadjichristidis, Macromolecules, submitted

Hadjichristidis, Nikos

2003-03-01

302

Applying Data Mapping Techniques to Vector DSPs  

Microsoft Academic Search

Vector digital signal processors (DSPs) offer a good performance to power consumption ratio. Therefore, they are suitable\\u000a for mobile devices in software defined radio applications. These vector DSPs require input algorithms with vector operations.\\u000a The performance of vectorized algorithms to a great extent depends on the distribution of data on vector elements. Traditional\\u000a algorithms for vectorization focus on the extraction

Peter Westermann; Ludwig Schwoerer; Andre Kaufmann

2009-01-01

303

Motion vector quantization for video coding.  

PubMed

A new algorithm is developed for the vector quantization of motion vectors. This algorithm, called motion vector quantization (MVQ), simultaneously estimates and vector quantizes the motion vectors by reinterpreting the block matching algorithm as a type of vector quantization. An iterative design algorithm, based on this concept, is developed. In addition to reducing rate for fixed length encoding, the algorithm also reduces the computation considerably. We include coding simulation results on the Flower Garden sequence. PMID:18289987

Lee, Y Y; Woods, J W

1995-01-01

304

Colliders and brane vector phenomenology  

SciTech Connect

Brane world oscillations manifest themselves as massive vector gauge fields. Their coupling to the standard model is deduced using the method of nonlinear realizations of the spontaneously broken higher dimensional space-time symmetries. Brane vectors are stable and weakly interacting and therefore escape particle detectors unnoticed. LEP and Tevatron data on the production of a single photon in conjunction with missing energy are used to delineate experimentally excluded regions of brane vector parameter space. The additional region of parameter space accessible to the LHC as well as a future lepton linear collider is also determined by means of this process.

Clark, T. E.; Love, S. T.; Xiong, C.; Nitta, Muneto; Veldhuis, T. ter [Department of Physics, Purdue University, West Lafayette, Indiana 47907-2036 (United States); Department of Physics, Keio University, Hiyoshi, Yokohoma, Kanagawa, 223-8521 (Japan); Department of Physics and Astronomy, Macalester College, Saint Paul, Minnesota 55105-1899 (United States)

2008-12-01

305

Insecticide resistance and vector control.  

PubMed

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. We describe the mechanisms of insecticide resistance, as well as specific instances of resistance emergence worldwide, and discuss prospects for resistance management and priorities for detection and surveillance. PMID:19785227

Brogdon, William G; McAllister, Janet C

2004-01-01

306

Baculovirus as a vaccine vector  

PubMed Central

Baculovirus is extensively utilized as an excellent tool for production of recombinant protein in insect cells. Baculovirus infects insects in nature and is non-pathogenic to humans. In addition to insect cells, baculovirus is capable of transducing a broad range of animal cells. Due to its biosafety, large cloning capacity, low cytotoxicity, and non-replication nature in the transduced cells as well as the ease of manipulation and production, baculovirus has been utilized as RNA interference mediators, gene delivery vectors, and vaccine vectors for a wide variety of applications. This article focuses on the utilization of baculoviruses as vaccine vectors to prepare antigen or subunit vaccines.

Lu, Hsin-Yu; Chen, Yi-Hsuan; Liu, Hung-Jen

2012-01-01

307

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.

Brown, Jeremy

2009-04-01

308

Design, development, and demonstration of a fully LabVIEW controlled in situ electrochemical Fourier transform infrared setup combined with a wall-jet electrode to investigate the electrochemical interface of nanoparticulate electrocatalysts under reaction conditions.  

PubMed

We present a detailed description of the construction of an in situ electrochemical ATR-FTIR setup combined with a wall-jet electrode to investigate the electrocatalytic properties of nanoparticulate catalysts in situ under controlled mass transport conditions. The presented setup allows the electrochemical interface to be probed in combination with the simultaneous determination of reaction rates. At the same time, the high level of automation allows it to be used as a standard tool in electrocatalysis research. The performance of the setup was demonstrated by probing the oxygen reduction reaction on a platinum black catalyst in sulfuric electrolyte. PMID:23902087

Nesselberger, Markus; Ashton, Sean J; Wiberg, Gustav K H; Arenz, Matthias

2013-07-01

309

A model for treating avian aspergillosis: serum and lung tissue kinetics for Japanese quail (Coturnix japonica) following single and multiple aerosol exposures of a nanoparticulate itraconazole suspension.  

PubMed

Abstract Aspergillosis is frequently reported in parrots, falcons and other birds held in captivity. Inhalation is the main route of infection for Aspergillus fumigatus, resulting in both acute and chronic disease conditions. Itraconazole (ITRA) is an antifungal commonly used in birds, but administration requires repeated oral dosing and the safety margin is narrow. We describe lung tissue and serum pharmacokinetics of a nanoparticulate ITRA suspension administered to Japanese quail by aerosol exposure. Aerosolized ITRA (1 and 10% suspension) administered over 30 min did not induce adverse clinical reactions in quail upon single or 5-day repeated doses. High lung concentrations, well above the inhibitory levels for A. fumigatus, of 4.14 ± 0.19 ?g/g and 27.5 ± 4.58 ?g/g (mean ± SEM, n = 3), were achieved following single-dose inhalation of 1% and 10% suspension, respectively. Upon multiple dose administration of 10% suspension, mean lung concentrations reached 104.9 ± 10.1 ?g/g. Drug clearance from the lungs was slow with terminal half-lives of 19.7 h and 35.8 h following inhalation of 1% and 10% suspension, respectively. Data suggest that lung clearance is solubility driven. Lung concentrations of hydroxy-itraconazole reached 1-2% of the ITRA lung tissue concentration indicating metabolism in lung tissue. Steady, but low, serum concentrations of ITRA could be measured after multiple dose administration, reaching less than 0.1% of the lung tissue concentration. This formulation may represent a novel, easy to administer treatment modality for fungal lung infection, preventing high systemic exposure. It may also be useful as metaphylaxis to prevent the outbreak of aspergillosis in colonized animals. PMID:23815436

Rundfeldt, Chris; Wyska, El?bieta; Steckel, Hartwig; Witkowski, Andrzej; Je?ewska-Witkowska, Gra?yna; Wla?, Piotr

2013-07-02

310

Electrohydrodynamic atomization for biodegradable polymeric particle production.  

PubMed

Electrohydrodynamic atomization (EHDA) has many applications such as electrospray ionization in mass spectroscopy, electrospray deposition of thin films, pharmaceutical productions, and polymeric particle fabrications for drug encapsulation. In the present study, EHDA was employed to produce biodegradable polymeric micro- and nanoparticles. The effects of processing parameters such as polymer concentration, flow rate, surfactants, organic salt, and setup configurations on the size and morphology of polymeric particles were investigated systematically. By changing the various processing parameters, controllable particle shape and size can be achieved. PLGA nanoparticles with size of around 250 nm can be obtained by using organic salts to increase the conductivity of the spraying solution even at a relatively high flow rate. A higher flow rate has the advantage of producing a stable cone spray and can be easily reproduced. Solid and porous particles can be fabricated using different experimental setups to control the organic solvent evaporation rate. Also, paclitaxel, a model antineoplastic drug, was encapsulated in polymeric particles which can be employed for controlled release applications. In short, EHDA is a promising technique to fabricate polymeric micro- or nanoparticles which can be used in drug delivery systems. PMID:16842810

Xie, Jingwei; Lim, Liang Kuang; Phua, Yiyong; Hua, Jinsong; Wang, Chi-Hwa

2006-06-29

311

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

Mogilner, A; Oster, G

1996-01-01

312

Kinematics Problem: Acceleration with Vectors  

NSDL National Science Digital Library

Physicists use arrows to represent many things in diagrams (position is in meters and time is in seconds). The learner is to identify the vector quantity that is being represented by the arrow in the simulation.

Christian, Wolfgang; Belloni, Mario

2006-01-20

313

Scalable production of adenovirus vectors.  

PubMed

Recombinant adenoviruses (AdV) are highly efficient at gene transfer for a broad spectrum of cell types and species. They became one of the vectors of choice for gene delivery and expression of foreign proteins in gene therapy and vaccination purposes. To meet the need of significant amounts of adenoviral vectors for preclinical and possibly clinical uses, scalable and reproducible production processes are required.In this chapter, we review processes used for scalable production of two types of first generation (E1-deleted) adenoviral vectors (Human and Canine) using stirred tank bioreactors. The production of adenovirus vectors using either suspension (HEK 293) or anchorage-dependent cells (MDCK-E1) are described to exemplify scalable production processes with different cell-culture types. The downstream processes will be covered in the next chapter. PMID:24132486

Silva, Ana Carina; Fernandes, Paulo; Sousa, Marcos F Q; Alves, Paula M

2014-01-01

314

Hyperphysics-Basic Vector Operations  

NSDL National Science Digital Library

This page is interactive resource allowing the teacher to choose among topics related to vector operations. The subjects are organized in flow charts that make it easy to move from one topic to a related item. Vector resolution, addition, and product are covered in-depth, with conceptual support in practical applications such as torque, work, and magnetic force. This item is part of a larger collection under continuing development by Dr. Rod Nave, Georgia State University.

Nave, Carl R.

2010-08-17

315

Discrete multiscale vector field decomposition  

Microsoft Academic Search

While 2D and 3D vector fields are ubiquitous in computational sciences, their use in graphics is often limited to regular grids, where computations are easily handled through finite-difference methods. In this paper, we propose a set of simple and accurate tools for the analysis of 3D discrete vector fields on arbitrary tetrahedral grids. We introduce a variational, multiscale decomposition of

Yiying Tong; Santiago V. Lombeyda; Anil N. Hirani; Mathieu Desbrun

2003-01-01

316

Entropy-constrained vector quantization  

Microsoft Academic Search

An iterative descent algorithm based on a Lagrangian formulation for designing vector quantizers having minimum distortion subject to an entropy constraint is discussed. These entropy-constrained vector quantizers (ECVQs) can be used in tandem with variable-rate noiseless coding systems to provide locally optimal variable-rate block source coding with respect to a fidelity criterion. Experiments on sampled speech and on synthetic sources

PHILIP A. CHOU; TOM LOOKABAUGH; ROBERT M. GRAY

1989-01-01

317

Simplified Support Vector Decision Rules  

Microsoft Academic Search

A Support Vector Machine (SVM) is a universal learning machine whose decision surfaceis parameterized by a set of support vectors and by a set of corresponding weights.An SVM is also characterized by a kernel function. Choice of the kernel determines whether the resulting SVM is a polynomial classifier, a two-layer neural network, a radialbasis function machine, or some otherlearning machine.SVMs

Christopher J. C. Burges

1996-01-01

318

Vectors: Ghosts in the Machine  

Microsoft Academic Search

\\u000a You may not know it, but there’s an unseen world of invisible forces at work in your games called vectors. They’re what make\\u000a your objects move and detect collisions, and they help you create simulations of real-world physical objects. Vectors are\\u000a like the atoms and molecules of the game universe—everything is dependent on them, but they’re very hard to see

Rex Spuy

319

Development of nonhuman adenoviruses as vaccine vectors  

PubMed Central

Human adenoviral (HAd) vectors have demonstrated great potential as vaccine vectors. Preclinical and clinical studies have demonstrated the feasibility of vector design, robust antigen expression and protective immunity using this system. However, clinical use of adenoviral vectors for vaccine purposes is anticipated to be limited by vector immunity that is either preexisting or develops rapidly following the first inoculation with adenoviral vectors. Vector immunity inactivates the vector particles and rapidly removes the transduced cells, thereby limiting the duration of transgene expression. Due to strong vector immunity, subsequent use of the same vector is usually less efficient. In order to circumvent this limitation, nonhuman adenoviral vectors have been proposed as alternative vectors. In addition to eluding HAd immunity, these vectors possess most of the attractive features of HAd vectors. Several replication-competent or replication-defective nonhuman adenoviral vectors have been developed and investigated for their potential as vaccine delivery vectors. Here, we review recent advances in the design and characterization of various nonhuman adenoviral vectors, and discuss their potential applications for human and animal vaccination.

Bangari, Dinesh S.; Mittal, Suresh K.

2006-01-01

320

Axisymmetric Coanda-assisted vectoring  

NASA Astrophysics Data System (ADS)

An experimental demonstration of a jet vectoring technique used in our novel spray method called Coanda-assisted Spray Manipulation (CSM) is presented. CSM makes use of the Coanda effect on axisymmetric geometries through the interaction of two jets: a primary jet and a control jet. The primary jet has larger volume flow rate but generally a smaller momentum flux than the control jet. The primary jet flows through the center of a rounded collar. The control jet is parallel to the primary and is adjacent to the convex collar. The Reynolds number range for the primary jet at the exit plane was between 20,000 and 80,000. The flow was in the incompressible Mach number range (Mach < 0.3). The control jet attaches to the convex wall and vectors according to known Coanda effect principles, entraining and vectoring the primary jet, resulting in controllable r - ? directional spraying. Several annular control slots and collar radii were tested over a range of momentum flux ratios to determine the effects of these variables on the vectored jet angle and spreading. Two and Three-component Particle Image Velocimetry systems were used to determine the vectoring angle and the profile of the combined jet in each experiment. The experiments show that the control slot and expansion radius, along with the momentum ratios of the two jets predominantly affected the vectoring angle and profile of the combined jets.

Allen, Dustin; Smith, Barton L.

2009-01-01

321

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

322

Nanoencapsulation of quercetin via miniemulsion polymerization.  

PubMed

The nanoencapsulation of quercetin, a strong antioxidant and radical scavenger, via methyl methacrylate miniemulsion polymerization, using miglyol 812 as costabilizer and lecithin as surfactant was studied and the effect of the monomer/co-stabilizer ratio and different types of initiator, 2,2'azobisisobutyronitrile (AIBN) and redox pair composed of hydrogen peroxide and ascorbic acid, was investigated. Reactions conducted in the presence of quercetin showed lower polymerization rates, indicating that the presence of quercetin inhibits (redox pair) and/or retards (AIBN) the polymerization reaction. The increment of the concentration of ascorbic acid in the reactions initiated by a redox pair resulted in a considerable increase of the reaction rate without influencing other properties as average particle diameter, due to the fact that ascorbic acid acts as a reducing agent minimizing the oxidation of quercetin. Higher quercetin recovery was obtained for nanocapsules when compared with nanospheres. PMID:20738073

Bernardy, Neusa; Romio, Ana Paula; Barcelos, Erika I; Dal Pizzol, Carine; Dora, Cristina L; Lemos-Senna, Elenara; Araujo, Pedro H H; Sayer, Claudia

2010-04-01

323

The photorefractive effect in polymeric systems  

NASA Astrophysics Data System (ADS)

The review concerns the photorefractive effect in polymeric systems, which involves the creation, upon a primary photochemical reaction, of a phase grating shifted in space relative to the fringe pattern. The interaction of interfering laser beams accompanied by energy transfer from one beam to the other as well as salient features of the refractive index modulation in polymeric systems with low and high glass transition temperatures are considered. Particular attention is given to the photorefractive polymers with high glass transition temperatures containing nanocrystalline J-aggregates of cyanine dyes, which are characterised by high third-order nonlinear electric susceptibilities and induce modulation of the refractive index due to the Kerr electrooptic effect. The prospects for application of polymeric photorefractive materials are outlined.

Vannikov, Anatolii V.; Grishina, Antonina D.

2003-06-01

324

Layered polymeric optical systems using continuous coextrusion  

NASA Astrophysics Data System (ADS)

Polymers are receiving considerable attention as components in novel optical systems because of the tailored functionality, ease of manufacturing, and relatively low cost. The processing of layered polymeric systems by coextrusion is a method to produce films comprising hundreds to thousands of alternating layers in a single, one-step roll-to-roll process. Several layered polymer optical systems have been fabricated by coextrusion, including gradient refractive index lenses, tunable refractive index elastomers, photonic crystals, and mechanically tunable photonic crystals. Layered polymeric optical systems made by coextrusion can also incorporate active components such as photoreactive additives for multilayered patterning and laser dyes for all-polymer laser systems. Coextrusion is a process which allows for the flexible design of polymeric optical systems using layers with thickness spanning the nanoscale to the microscale.

Song, Hyunmin; Singer, Kenneth; Wu, Yeheng; Zhou, Juefei; Lott, Joe; Andrews, James; Hiltner, Anne; Baer, Eric; Weder, Christoph; Bunch, Robert; Lepkowicz, Richard; Beadie, Guy

2009-08-01

325

VectorBase: a home for invertebrate vectors of human pathogens  

Microsoft Academic Search

VectorBase (http:\\/\\/www.vectorbase.org\\/) is a web- accessible data repository for information about invertebrate vectors of human pathogens. VectorBase annotates and maintains vector genomes providing an integrated resource for the research community. Currently, VectorBase contains genome information for two organisms: Anopheles gambiae, a vector for the Plasmodium protozoan agent causing malaria, and Aedes aegypti, a vector for the flaviviral agents causing Yellow

Daniel Lawson; Peter Arensburger; Peter Atkinson; Nora J. Besansky; Robert V. Bruggner; Ryan Butler; Kathryn S. Campbell; George K. Christophides; Scott Christley; Emmanuel Dialynas; David Emmert; Martin Hammond; Catherine A. Hill; Ryan C. Kennedy; Neil F. Lobo; M. Robert Maccallum; Gregory R. Madey; Karine Megy; Seth Redmond; Susan Russo; David W. Severson; Eric O. Stinson; Pantelis Topalis; Evgeni M. Zdobnov; Ewan Birney; William M. Gelbart; Fotis C. Kafatos; Christos Louis; Frank H. Collins

2007-01-01

326

Producing ORMOSIL scaffolds by femtosecond laser polymerization  

NASA Astrophysics Data System (ADS)

Structures with different geometries and sizes were built via direct femtosecond laser writing, starting from new organic/inorganic hybrid monomers based on hybrid methacrylate containing triethoxysilane, in addition to urethane and urea groups. Multifunctional oligomer of urethane dimethacrylate type was chosen as comonomer in polymerization experiments because dimethacrylates give rise to the formation of a polymer network, having a number of favorable properties including biocompatibility and surface nanostructuring. Free standing polymeric structures were designed and created in order to be tested in fibroblast cells culture. Investigations of the cellular adhesion, proliferation, and viability of L929 mouse fibroblasts on free-standing laser processed scaffolds were performed for different scaffold designs.

Matei, A.; Zamfirescu, M.; Radu, C.; Buruiana, E. C.; Buruiana, T.; Mustaciosu, C.; Petcu, I.; Radu, M.; Dinescu, M.

2012-07-01

327

PEG based hyperbranched polymeric hollow nanospheres  

NASA Astrophysics Data System (ADS)

The synthesis of a new PEG based hyperbranched copolymer of poly(ethylene glycol) methyl ether methacrylate-co-ethylene glycol dimethacrylate (PEGMEMA-co-EGDMA) was achieved via a one-step in situ deactivation enhanced atom transfer radical polymerization (DE-ATRP). Then, hollow PEG based nanospheres were fabricated from this polymer using a solvent evaporation method and post-stabilisation strategy. Furthermore, the analysis using a cellular metabolic activity assay proved that the copolymer did not affect cellular metabolism, indicating that this PEG based polymeric nanosphere has potential for use in drug delivery applications.

Cao, Hongliang; Dong, Yixiao; O'Rorke, Suzanne; Wang, Wenxin; Pandit, Abhay

2011-02-01

328

Development of new catalysts for living polymerizations: From interesting reaction mechanisms to new polymeric materials  

NASA Astrophysics Data System (ADS)

Synthetic polymers have revolutionized the modern world. The synthesis of these new materials has relied heavily on the development of new catalytic methods. Remarkable advances have been reported over the past twenty years concerning development of homogeneous olefin polymerization catalysts. Single-site catalysts are now available that are unparalleled in all of polymer chemistry concerning the detailed control of macromolecular stereochemistry. Despite years of fervent research, very few catalytic systems are available for living/controlled polymerization of olefins. While various methods for living anionic, cationic, and radical-based polymerizations have been exploited for the synthesis of complex polymer architectures, the lack of methodology concerning olefin polymerization has limited the development of new polyolefin-based materials. As part of an ongoing effort in the development of new methods for controlled polymerization reactions, a catalyst for the highly stereospecific and living polymerization of propylene was discovered. The complex, a titanium chloride bearing two perfluorinated phenoxyimine ligands, was originally designed for isospecific propylene polymerization. However, the activated catalyst gave highly syndiotactic polypropylene with a narrow molecular weight distribution. The living nature of the polymerization was demonstrated by the synthesis of a series of new ethylene/propylene block copolymers. Mechanistic studies, including a new propagation-based approach, determined that this unexpected microstructure was the result of chain-end control enhanced by an unusual secondary monomer insertion. This mechanism was exploited for the synthesis of vinyl-functional polyolefins, and these polymers were transformed to a series of functional polymers through chemical modification. Although polyolefins are currently indispensable materials, the search for degradable polymeric materials derived from renewable resources is critical for sustainability. Poly(lactic acid)s are among the most promising candidates due to their excellent mechanical properties, renewable agricultural feedstocks, and biodegradability. These materials are readily synthesized by the ring-opening polymerization of lactide using various metal-based catalysts. Along these lines, new classes of zinc and cadmium-based compounds were developed for lactide polymerization. These new complexes display interesting stereocontrol in the polymerization, giving partially tactic polymers through chain-end control mechanisms. In particular, two types of cadmium catalysts display opposite selectivity, hinting at the existence different mechanisms in these closely related classes of compounds.

Hustad, Phillip Dene

329

Gradient algorithms for designing predictive vector quantizers  

Microsoft Academic Search

A predictive vector quantizer (PVQ) is a vector extension of a predictive quantizer. It consists of two parts: a conventional memoryless vector quantizer (VQ) and a vector predictor. Two gradient algorithms for designing a PVQ are developed in this paper: the steepest descent (SD) algorithm and the stochastic gradient (SG) algorithm. Both have the property of improving the quantizer and

PAO-CHI CHANG; ROBERT M. GRAY

1986-01-01

330

Visualizing Non-Linear Vector Field Topology  

Microsoft Academic Search

We present our results on the visualization of non-linear vector eld topology. The underlying mathemat- ics is done in Cliord algebra, a system describing geometry by extending the usual vector space by a multiplication of vectors. We started with the observation that all known algorithms for vector eld topology are based on piecewise linear or bilinear approximation and that these

Gerik Scheuermann; Heinz Kr; Martin Menzel; Alyn P. Rockwood

331

Replicative retroviral vectors for cancer gene therapy  

Microsoft Academic Search

Poor efficiency of gene transfer into cancer cells constitutes the major bottleneck of current cancer gene therapy. We reasoned that because tumors are masses of rapidly dividing cells, they would be most efficiently transduced with vector systems allowing transgene propagation. We thus designed two replicative retrovirus-derived vector systems: one inherently replicative vector, and one defective vector propagated by a helper

Sounkary K Solly; Stephane Trajcevski; Charlotte Frisén; Georg W Holzer; Elisabeth Nelson; Béatrice Clerc; Evelyn Abordo-Adesida; Maria Castro; Pedro Lowenstein; David Klatzmann

2003-01-01

332

21 CFR 872.6070 - Ultraviolet activator for polymerization.  

Code of Federal Regulations, 2010 CFR

... Ultraviolet activator for polymerization. 872.6070 Section 872.6070 Food and Drugs FOOD AND DRUG ADMINISTRATION... DENTAL DEVICES Miscellaneous Devices § 872.6070 Ultraviolet activator for polymerization....

2010-04-01

333

21 CFR 872.6070 - Ultraviolet activator for polymerization.  

Code of Federal Regulations, 2010 CFR

... Ultraviolet activator for polymerization. 872.6070 Section 872.6070 Food and Drugs FOOD AND DRUG ADMINISTRATION... DENTAL DEVICES Miscellaneous Devices § 872.6070 Ultraviolet activator for polymerization....

2009-04-01

334

Equivalent performance in different helical resonator plasma polymerization coater platforms.  

National Technical Information Service (NTIS)

Plasma polymerization is used in fabricating target mandrels for implosion experiments on the NOVA laser. As part of effort to translate the theoretical aspects of plasma polymerization fundamentals into practical improvements in a production oriented env...

R. M. Brusasco

1993-01-01

335

Polymerization and Halogen Scrambling Behavior of Phenyl-Substituted Cyclotriphosphazenes.  

National Technical Information Service (NTIS)

A new series of poly(organophosphazenes) with phenyl groups bonded to the skeleton has been prepared by the polymerization of phenylhalogen cyclotriphosphazenes. In addition, evidence about the mechanism of chlorophosphazene polymerization has been obtain...

H. R. Allcock M. S. Connolly

1984-01-01

336

Molecular Imprinting of Polymeric Core-Shell Nanoparticles.  

National Technical Information Service (NTIS)

In order to evaluate the compatibility of structured nanoparticles produced by aqueous emulsion polymerization with the non-covalent imprinting procedure, a number of imprinted polymeric nanoparticles have been synthesized by seeded emulsion polymerizatio...

N. P. Moral A. G. Mayes

2002-01-01

337

Fabrication and manipulation of polymeric magnetic particles with magnetorheological fluid  

NASA Astrophysics Data System (ADS)

Polymeric magnetic microparticles have been created using a microfluidic device via ultraviolet (UV) polymerization of double emulsions, resulting in cores of magnetorheological (MR) fluids surrounded by polymeric shells. We demonstrate that the resultant particles can be manipulated magnetically to achieve triggered rupture of the capsules. This illustrates the great potential of our capsules for triggered release of active ingredients encapsulated in the polymeric magnetic microparticles.

Rodríguez-López, Jaime; Shum, Ho Cheung; Elvira, Luis; Montero de Espinosa, Francisco; Weitz, David A.

2013-01-01

338

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

339

Vector finite elements for electromagnetic field computation  

Microsoft Academic Search

A novel structure for the finite-element analysis of vector fields is presented. This structure uses the affine transformation to represent vectors and vector operations over triangular domains. Two-dimensional high-order vector elements are derived that are consistent with Whitney forms. One-form elements preserve the continuity of the tangential components of a vector field across element boundaries, while two-form elements preserve the

Zoltan J. Cendes

1991-01-01

340

Vector quantization and learning vector quantization for radar target classification  

NASA Astrophysics Data System (ADS)

Radar target classification performance is greatly dependent on how the classifier represents the strongly angle dependent radar target signatures. This paper compares the performance of classifiers that represent radar target signatures using vector quantization (VQ) and learning vector quantization (LVQ). The classifier performance is evaluated with a set of high resolution millimeter-wave radar data from four ground vehicles (Camaro, van, pickup, and bulldozer). LVQ explicitly includes classification performance in its data representation criterion, whereas VQ only makes use of a distortion measure such as mean square distance. The classifier that uses LVQ to represent the radar data has a much higher probability of correct classification than VQ.

Stewart, Clayton V.; Lu, Yi-Chuan; Larson, Victor J.

1993-10-01

341

Vector control in developed countries  

PubMed Central

The recent rapid growth of California's population, leading to competition for space between residential, industrial and agricultural interests, the development of its water resources and increasing water pollution provide the basic ingredients of its present vector problems. Within the past half-century, the original mosquito habitats provided by nature have gradually given place to even more numerous and productive habitats of man-made character. At the same time, emphasis in mosquito control has shifted from physical to chemical, with the more recent extension to biological approaches as well. The growing domestic fly problem, continuing despite the virtual disappearance of the horse, is attributable to an increasing amount of organic by-products, stemming from growing communities, expanding industries and changing agriculture. The programme for the control of disease vectors and pest insects and animals directs its major effort to the following broad areas: (1) water management (including land preparation), (2) solid organic wastes management (emphasizing utilization), (3) community management (including design, layout, and storage practices of buildings and grounds), and (4) recreational area management (related to wildlife management). It is apparent that vector control can often employ economics as an ally in securing its objectives. Effective organization of the environment to produce maximum economic benefits to industry, agriculture, and the community results generally in conditions unfavourable to the survival of vector and noxious animal species. Hence, vector prevention or suppression is preferable to control as a programme objective.

Peters, Richard F.

1963-01-01

342

Photo-induced polymerization of polyaniline  

Microsoft Academic Search

A straightforward route to prepare polyaniline is presented in which photons and metallic ions replace conventional oxidants to promote polymerization of aniline monomer. The photopolymerization methods yield a composite material that has been characterized by its UV, visible and Raman spectroscopic analysis and by scanning electron microscopy and X-ray microanalysis as well. Intriguing forms of silver wires embedded in polyaniline

R. A. de Barros; W. M. de Azevedo; F. M. de Aguiar

2003-01-01

343

Transition metal catalysts for controlled radical polymerization  

Microsoft Academic Search

The discovery, in the mid 1990s, that certain cobalt, ruthenium and copper complexes could effectively control the radical polymerization of a number of polar olefins, allowing for the facile synthesis of complex macromolecular architectures, fostered an intense search for increasingly better performing catalysts. As a consequence, several metal complexes were designed and tested. This article presents an organized and detailed

Fabio di Lena; Krzysztof Matyjaszewski

2010-01-01

344

UV polymerization of hydrodynamically shaped fibers.  

PubMed

Most natural and man-made fibers have circular cross-sections; thus the properties of materials composed of non-circular fibers are largely unexplored. We demonstrate the technology for fabricating fibers with predetermined cross-sectional shape. Passive hydrodynamic focusing and UV polymerization of a shaped acrylate stream produced metre-long fibers for structural and mechanical characterization. PMID:21246152

Thangawng, Abel L; Howell, Peter B; Spillmann, Christopher M; Naciri, Jawad; Ligler, Frances S

2011-01-19

345

Band Structure of Polymeric Sulfur Nitride.  

National Technical Information Service (NTIS)

Using the Extended Huckel Method, a band structure calculation of polymeric sulfur nitride based on X-ray crystallographic data has been carried out. The results of the calculation suggest that the metallic properties of (SN)x arise from the accidental ov...

A. A. Bright P. Soven

1975-01-01

346

Molecular/polymeric magnetism. Progress report.  

National Technical Information Service (NTIS)

New materials were synthesized to test the generality of magnetism in molecular/polymeric systems. The first room temperature molecular based magnet V(TCNE)(sub x)(center dot)y(solvent) (1) is disclosed. The ferromagnetic and related transitions were stud...

1993-01-01

347

Biodegradable polymeric nanoparticles as drug delivery devices  

Microsoft Academic Search

This review presents the most outstanding contributions in the field of biodegradable polymeric nanoparticles used as drug delivery systems. Methods of preparation, drug loading and drug release are covered. The most important findings on surface modification methods as well as surface characterization are covered from 1990 through mid-2000.

Kumaresh S Soppimath; Tejraj M Aminabhavi; Anandrao R Kulkarni; Walter E Rudzinski

2001-01-01

348

Anionic Polymerization of Butadiene and Styrene.  

National Technical Information Service (NTIS)

A kinetic study was made of the polymerization of butadiene and styrene in an aliphatic hydrocarbon solvent with the use of butyllithium as an initiator. It is shown that the anomalous behavior in the initiation reaction exhibited by isoprene under these ...

A. F. Johnson D. J. Worsfold

1964-01-01

349

The Mechanism and kinetics of plasma polymerization  

Microsoft Academic Search

The discussion presented in this review has shown that plasma polymerization is a complex process involving a large number of both homogeneous and heterogeneous reactions. While the details of the overall polymer deposition mechanism are not yet understood fully, certain features have been elucidated. Thus, the available experimental evidence suggests that free radicals are the primary species propagating chain growth,

Alexis T. Bell

350

Automatic ultrasonic monitoring of vinyl chloride polymerization  

Microsoft Academic Search

An automatic method and apparatus for continuous monitoring of vinyl chloride suspension polymerization was developed and built, which enables a parallel measurements of attenuation changes and velocity of ultrasonic propagation in frequency range from hundreds of kHz to units of MHz and in dynamic range greater than 60 dB. The results of automatic measurements were compared and tested by previous

Petr Sladky; Ludvik Parma; Josef Zdrazil

1982-01-01

351

Oligonucleotide and Long Polymeric DNA Encoding  

Microsoft Academic Search

This report summarizes the work done at Lawrence Livermore National Laboratory for the Oligonucleotide and Long Polymeric DNA Encoding project, part of the Microelectronic Bioprocesses Program at DARPA. The goal of the project was to develop a process by which long (circa 10,000 base-pair) synthetic DNA molecules could be synthesized in a timely and economic manner. During construction of the

E Miller; R P Mariella Jr; A T Christian; S N Gardner; J M Williams

2003-01-01

352

Fingerprinting the thermal history of polymeric materials  

SciTech Connect

Knowledge of temperatures experienced by a polymeric material in storage or in the field helps predict the useful life or remaining service life of the parent component. This report describes a nondestructive test procedure to characterize the maximum temperature and time-at-temperature of semicrystalline polymers commonly used in electrical cable insulations and as parts of other components.

Phillips, P.J.

1992-09-01

353

Radiation sterilization of polymeric implant materials  

SciTech Connect

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 polymer chains under the influence of high-energy radiation, must be considered. It is essential to indicate whether polymeric implants are used in short-term (acute) or long-term (chronic) applications. Relatively small changes in their physicochemical, mechanical, and biological properties may be tolerable in the short term, whereas similar changes may lead to catastrophic failures in long-term applications. Therefore, polymeric implants which are to be sterilized by high-energy irradiation should be carefully evaluated for long-term property changes which may be induced by the radiation.

Bruck, S.D.; Mueller, E.P.

1988-08-01

354

Hot-embossed polymeric optical waveguides  

NASA Astrophysics Data System (ADS)

Polymer waveguides have attracted a great deal of attention for their potential applications as optical components in optical communications, optical interconnections and optical sensors because they are easy to manufacture at a low temperature, and they have a low processing cost. Hot embossing is powerful and effective tools to produce a large volume of waveguides and structure high-precision micro/nano patterns of thin polymer films using a stamp for optical applications. In this work, fabrication techniques of hot embossed polymeric optical waveguides for parallel optical interconnection module, multi-channel variable optical attenuator and optical printed circuit boards are demonstrated. The single- and multi-mode waveguides are produced by core filling and UV curing processes. New approaches to fabricating single-mode polymeric waveguides with the high thermal stability in thermosetting polymers and two-dimensional multi-mode polymeric waveguides for high-density parallel optical interconnections as well as a simultaneous fabrication of single-mode polymeric waveguides with micro pedestals for passive fiber alignment are also reported.

Choi, Choon-Gi; Kim, Jin-Tae; Han, Sang-Pil; Ahn, Seung-Ho

2004-10-01

355

Nanofibers And Related Structures Formed By Polymerization  

NASA Astrophysics Data System (ADS)

Nanofibers of cyanoacrylate were obtained by polymerization from the monomer vapor at a temperature near room temperature. The nanofibers had diameters ranging from 20 nm to 100 nm and lengths of up to several millimeters. Water molecules present on the substrate initiated the living anionic polymerization. As growth continued, the living ends were carried on the tip of each growing nanofiber. These nanofibers formed on glass, metal, plastic, electrospun nanofibers of other polymers, and other surfaces. Some fibers were tapered, some were branched, and some were bent. The number of fibers was varied by controlling the exposure of the substrate to water vapor. Under different conditions the monomer vapor was collected as droplets along electrospun nanofibers, or as droplets at the points where two electrospun nanofibers crossed. The addition of the initiator caused the droplets to polymerize, forming permanent beads on the fibers, and strong mechanical connections at the cross points. This phenomenon provides new ways to construct nanofiber structures engineered on nanometer scales. For example, filters constructed from an open structure of fibers can be coated with nanofibers polymerized from a vapor of nanometer scale droplets flowing through the structure, to improve the capture of molecules or particles.

Doiphode, S. V.

2005-03-01

356

A capacitively coupled polymeric internal antenna  

Microsoft Academic Search

A capacitively-coupled polymeric internal antenna is introduced for Bluetooth or GPS applications. Such an antenna can be easily fabricated on a flexible film substrate and attached to the inside surface of the plastic housing of a portable wireless device, such as a PDA. The proposed antenna saves critical space on the printed circuit board (PCB) and eliminates the need for

Khan M. Z. Shams; M. Ali

2004-01-01

357

Crumpling and buckling transitions in polymerized membranes  

Microsoft Academic Search

We consider polymerized non-self-avoiding membranes fluctuating under constrained boundary conditions. Such constraints prevent the membranes from being crumpled at high temperature and introduce a tension. Upon lowering the temperature this tension reduces, and vanishes at a transition temperature below which the membrane assumes a buckled state. Buckling transition points, depending on boundary conditions, arrange on a line which terminates at

E. Guitter; F. David; S. Leibler; L. Peliti

1988-01-01

358

Limiting Conversion Phenomenon in Hybrid Miniemulsion Polymerization  

Microsoft Academic Search

A phenomenon seemingly unique to hybrid miniemulsion polymerization was observed where monomer conversion would either plateau at a limiting value or quickly switch to a dramatically lesser rate. This phenomenon has been attributed to a combination of three factors. The first factor is the degree to which the monomer and resinous component are compatible. Second is the resultant particle morphology

John G. Tsavalas; Yingwu Luo; Laila Hudda; F. Joseph Schork

2003-01-01

359

Admicellar Polymerization of Polystyrene on Natural Rubber Particles  

Microsoft Academic Search

Admicellar polymerization is a reaction for coating a thin-film of polymer on a surface. The process consists of the polymerization of the adsolubilized monomer in the hydrophobic regions of the surfactant bilayers that adsorbed on the substrate surface. In this research, the admicellar polymerization of polystyrene was carried out using micron to submicron size natural rubber particles as substrates. Cetyl

Rathanawan Magaraphan; Vijitra Srinarang

2009-01-01

360

Polymeric derivatives of plant growth regulators: synthesis and properties  

Microsoft Academic Search

The polymeric formulations of plant growth regulators (PGRs) are high molecular weight systems in which the PGR unit is attached to the polymeric chain by a hydrolysable chemical bond. These polymeric derivatives (esters, ethers, or else) of PGRs are characterised by the ability to release the active compound (PGR) from their solutions (mainly aqueous) in certain conditions. The release of

Aristidis M. Tsatsakis; Michail I. Shtilman

1994-01-01

361

21 CFR 178.3740 - Plasticizers in polymeric substances.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Plasticizers in polymeric substances. 178.3740...and Production Aids § 178.3740 Plasticizers in polymeric substances. Subject...of this section may be safely used as plasticizers in polymeric substances used...

2009-04-01

362

21 CFR 178.3740 - Plasticizers in polymeric substances.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2009-04-01 true Plasticizers in polymeric substances. 178.3740...and Production Aids § 178.3740 Plasticizers in polymeric substances. Subject...of this section may be safely used as plasticizers in polymeric substances used...

2010-01-01

363

Recent advance in living anionic polymerization of functionalized styrene derivatives  

Microsoft Academic Search

This review covers recent advance of living anionic polymerization of styrene derivatives with functional groups. Although there have so far been reported several successful systems of living anionic polymerization of functionalized styrene derivatives, most useful functional groups are not amenable to the conditions of living anionic polymerization of styrene. Therefore, we herein present two generalized strategies to be able to

Akira Hirao; Surapich Loykulnant; Takashi Ishizone

2002-01-01

364

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

365

Synthesis of monodisperse functional polymeric microspheres for immunoassay  

Microsoft Academic Search

Methods for the synthesis of functional polymeric suspensions with narrow particle size distribution are analysed. Attention is concentrated on the conditions of the preparation of polymeric microspheres with aldehyde, carboxyl, epoxy, or amino groups on the surface, which possess a set of properties enabling their use for biochemical studies. Methods of modification of functional groups of the polymeric suspensions that

Nikolai I Prokopov; Inessa A Gritskova; Vladimir R Cherkasov; Anatolii E Chalykh

1996-01-01

366

Living\\/controlled radical polymerizations in dispersed phase systems  

Microsoft Academic Search

Living\\/controlled radical polymerization provides a route to synthesizing materials with designed microstructure and narrow molecular weight distributions. A variety of living radical systems have been developed in recent years, and are based on either reversible termination (SFRP, ATRP) or reversible transfer mechanisms (RAFT, degenerative transfer). Application of living radical polymerization to heterogeneous systems such as emulsion and miniemulsion polymerization may

Michael F. Cunningham

2002-01-01

367

Effect of capping protein on the kinetics of actin polymerization  

Microsoft Academic Search

Acanthamoeba capping protein increased the rate of actin polymerization from monomers with and without calcium. In the absence of calcium, capping protein also increased the critical concentration for polymerization. Various models were evaluated for their ability to predict the effect of capping protein on kinetic curves for actin polymerization under conditions where the critical concentration was not changed. Several models,

John A. Cooper; Thomas D. Pollard

1985-01-01

368

POLYMERIZATION OF VINYL CHLORIDE UNDER EFFECT OF $gamma$RADIATION  

Microsoft Academic Search

Experiments were conducted on the polymerization of technical vinyl ; chloride under the effect of gamma radiation at with an activity of 18,000 g-; equiv Ra was used as the source. Ths polymerization kinetics was shown to obey ; the general laws governing free radical polymerization. There is a considerable ; induction period, because the initial radicals react with inhibiting

L. D. Bubis; V. L. Karpov; Yu. M. Malinskii; D. M. Yanovskii

1962-01-01

369

ON Co⁶° GAMMA RAY-INITIATED EMULSION POLYMERIZATION  

Microsoft Academic Search

A study was made of the Co⁶° gamma -ray-initiated polymerization ; of methyl methacrylate and styrene; conversion rates were measured by a ; dilatometric method. The dependence of polymerization rate on monomer ; concentration and radiation intensity was determined for each monomer. It is ; shown that the emulsion polymerization of methyl methacrylate can be described by ; accepted theories

G. J. K. Acres; F. L. Dalton

1963-01-01

370

RADIATION-INDUCED POLYMERIZATION OF FORMALDEHYDE IN LIQUID STATE  

Microsoft Academic Search

Monomeric formaldehyde is rapidly polymerized by ionizing radiation, ; especially in the liquid state, and gives the polyoxymethylene of high molecular ; weight. The reaction rate itself is large but considerably different in bulk and ; solution systems. There is no linear relation between the polymerization rate ; and monomer concentration. This paper confirms these facts for solution ; polymerization

S. Nakashio; K. Takahashi; M. Kondo

1963-01-01

371

Studies in Polymerization. XVII. The Initiation of Vinyl Polymerization by Tetrakis (Triphenyl Phosphite) Nickel (0)  

Microsoft Academic Search

It has been found that tetrakis (triphenyl phosphite) nickel (0), in the presence of a suitable organic halide, is a very active initiator of free-radical polymerization. This paper describes a detailed kinetic study of the initiation of the polymerization of methyl methacrylate at 25 ^circC by the system Ni{P(OPh)_3}_4 + CCl_4, together with some observations on the systems in which

C. H. Bamford; K. Hargreaves

1967-01-01

372

Control of methyl methacrylate radical polymerization via Enhanced Spin Capturing Polymerization (ESCP)  

Microsoft Academic Search

The nitrone mediated polymerization of methyl methacrylate (MMA) via the enhanced (termination) spin capturing polymerization (ESCP) process is made possible via the addition of small amounts of styrene (between 5 and 10 vol.%) to the reaction mixture. Efficient control over the molecular weight between 7000 and 57,000 g mol?1 (at 60 °C) yields macromolecules that feature a mid-chain alkoxyamine functionality and are rich

Lin Zang; Edgar H. H. Wong; Christopher Barner-Kowollik; Thomas Junkers

2010-01-01

373

Organic\\/inorganic hybrid composites prepared by polymerization compounding and controlled free radical polymerization  

Microsoft Academic Search

A new method to produce highly filled and well dispersed polymer solid composites using controlled free radical polymerization has been developed. Grafting of polymers onto ultrafine silica was done in bulk polymerization at 120°C in presence of N-tert-butyl-1-diethylphosphono2,2-dimethyl propyl nitroxide (DEPN) as a nitroxide stable free radical. Optimum conditions for tert-butyl hydroperoxide grafting onto fumed silica were first determined. The

A Kasseh; A Ait-Kadi; B Riedl; J. F Pierson

2003-01-01

374

Manipulation of SV40 Vectors.  

PubMed

ABSTACT: SV40 is a small simian virus that has been extensively used as a viral vector in mammalian cells (1-4). The viral genome is a double-stranded supercoiled DNA molecule of 5243 bp (Fig. 1A) that is packaged into a capsid containing the viral structural proteins VP1,VP2, and VP3. SV40 induces a lytic infection cycle in permissive cells. The first step in the replication cycle is synthesis of early mRNA. This is followed by DNA replication and expression of late mRNAs that encode the structural proteins. New virus particles are formed, and the infection ultimately kills the cells. Fig. 1. Schematic diagrams of the genome of SV40 and the SV40 expression vectors p14, pBABY, and pSVEpR4. The detailed maps and constructions of these vectors have been described elsewhere (8,(11,(12). PMID:21416355

Hammurskjöld, M L

1991-01-01

375

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.

376

Polymerization and phase separation studies in liquids  

NASA Astrophysics Data System (ADS)

In technology, a thermosetting polymer's electrical, thermal and mechanical properties are modified by incorporating an elastomer phase in its matrix. This is achieved by phase separation of the dissolved elastomer during the course of polymerization until the liquid vitrifies. The phase separation mechanism and nature of interface formed determine the negative effect of phase separation on polymerization and the transition of mass-controlled kinetics to diffusion-controlled kinetics. This thesis provides an experimental study of polymerization, phase separation and vitrification processes by using real time measurements of dielectric relaxation, calorimetric changes, elastic constants and thermal conductivity of diepoxide-amine mixtures with and without the phase separating amine-terminated butadiene acrylonitrile elastomer. The results are discussed in general terms of mutual slowing of molecular diffusion and polymerization, and of the development of diffused interfaces between regions of elastomer and polymer matrix, that form as a result of, (i) high degree of spatial heterogeneity in the intermingled regions of non-stoichiometric amounts of polymer and elastomer, (ii) high degree of compatibility between the elastomer and polymer matrix and (iii) large size of the elastomer and polymer molecules. The consequence of molecular diffusional constraints and manifestation of spatial heterogeneity is confirmed by the appearance of Johari-Goldstein relaxation which acts as the precursor for the significantly broadened alpha-relaxation and higher values of dielectric permittivity in the frequency range of 1 kHz and greater. Spatial heterogeneity in the intermingled regions of non-stoichiometric amounts of polymer and elastomer is also confirmed by calorimetry studies. With increasing diffusional limitation, the total heat of polymerization varies from values obtained for stoichiometric amounts of reactants with no change in calorimetric peak temperature. Furthermore, the relaxation region of reversible heat capacity broadens. Diffusional constraints are also confirmed by the corresponding broadening of measured thermal conductivity values. Part of the thesis has been published in papers listed in Chapter I.

Venkateshan, Karthik

377

[Spin polymerization of DNA/RNA nucleotides].  

PubMed

The Car-Parrinello molecular dynamics (CPMD) has been used to study the ion-radical (IR) polymerization (triplet (T) and singlet (S/TO) states) of adenine mononucleotides upon interaction with Mg2+(H2O)2-ATP(4-). It has been found that the IR polymerization occurs only upon Mg2+(H2O)2-ATP(4-) excitation into a T state (the Franck-Condon or femtosecond laser excitation); it naturally occurs in the dark with DNA polymerase or another Mg-holoenzyme upon interaction of Mg with two Asp residues. The IR path affects only the HO-C3' group of ribose, leaving the HO-C2' group inactive. The IR polymerization starts with the homolytic removal of the hydrogen atom from the HO-C3' group and its transfer onto the hydroxyl radical *OH, a product of the ATP cleavage, which yields a water molecule. A further progress of the reaction involves interaction between two ion-radicals *AMP. The reaction is sensitive to the recombination of *OH and *AMP. It is mostly suppressed by the appearance of identically directed electron spins on both radicals (the radical pair in the T-state) in the vicinity of the HO-C3' group and not suppressed in the vicinity of the HO-C2' group (the spins in the radical pair are oppositely directed, the radical pair in the To state), making the latter inert on the IR polymerization, but allowing it to be active in the ionic (hydrolytic) polymerization. PMID:21542349

Tulub, A A

378

Modular Approach to Physics: Vector Addition Practice - Three Vectors  

NSDL National Science Digital Library

This item is a Java simulation that allows users to interactively practice the addition of three vectors using the tip-to-tail method. This item is part of a larger collection of simulation based physics models sponsored by the MAP project (Modular Approach to Physics).

2008-12-17

379

Target-triggered polymerization for biosensing.  

PubMed

Because of the potential applications of biosensors in clinical diagnosis, biomedical research, environmental analysis, and food quality control, researchers are very interested in developing sensitive, selective, rapid, reliable, and low-cost versions of these devices. A classic biosensor directly transduces ligand-target binding events into a measurable physical readout. Because of the limited detection sensitivity and selectivity in earlier biosensors, researchers have developed a number of sensing/signal amplification strategies. Through the use of nanostructured or long chain polymeric materials to increase the upload of signal tags for amplification of the signal readout associated with the ligand-target binding events, researchers have achieved high sensitivity and exceptional selectivity. Very recently, target-triggered polymerization-assisted signal amplification strategies have been exploited as a new biosensing mechanism with many attractive features. This strategy couples a small initiator molecule to the DNA/protein detection probe prior to DNA hybridization or DNA/protein and protein/protein binding events. After ligand-target binding, the in-situ polymerization reaction is triggered. As a result, tens to hundreds of small monomer signal reporter molecules assemble into long chain polymers at the location where the initiator molecule was attached. The resulting polymer materials changed the optical and electrochemical properties at this location, which make the signal easily distinguishable from the background. The assay time ranged from minutes to hours and was determined by the degree of amplification needed. In this Account, we summarize a series of electrochemical and optical biosensors that employ target-triggered polymerization. We focus on the use of atom transfer radical polymerization (ATRP), as well as activator generated electron transfer for atom transfer radical polymerization (AGET ATRP) for in-situ formation of polymer materials for optically or electrochemically transducing DNA hybridization and protein-target binding. ATRP and AGET ATRP can tolerate a wide range of functional monomers. They also allow for the preparation of well-controlled polymers with narrow molecular weight distribution, which was predetermined by the concentration ratio of the consumed monomer to the introduced initiator. Because the reaction initiator can be attached to a variety of detection probes through well-established cross-linking reactions, this technique could be expanded as a universal strategy for the sensitive detection of DNA and proteins. We see enormous potential for this new sensing technology in the development of portable DNA/protein sensors for point-of-need applications. PMID:22780874

Wu, Yafeng; Wei, Wei; Liu, Songqin

2012-07-10

380

Video Compression using Vector Quantization.  

National Technical Information Service (NTIS)

This report presents some results and findings of our work on very-low-bit-rate video compression systems using vector quantization (VQ). We have identified multiscale segmentation and variable-rate coding as two important concepts whose effective use can...

M. Venkatraman H. Kwon N. M. Nasrabadi

1998-01-01

381

Voice conversion through vector quantization  

Microsoft Academic Search

The authors propose a new voice conversion technique through vector quantization and spectrum mapping. The basic idea of this technique is to make mapping codebooks which represent the correspondence between different speakers' codebooks. The mapping codebooks for spectrum parameters, power values and pitch frequencies are separately generated using training utterances. This technique makes it possible to precisely control voice individuality.

Masanobu ABE; Satoshi NAKAMURA; Kiyohiro SHIKANO; Hisao KUWABARA

1988-01-01

382

Constructing monocrystalline covalent organic networks by polymerization  

NASA Astrophysics Data System (ADS)

An emerging strategy for making ordered materials is modular construction, which connects preformed molecular subunits to neighbours through interactions of properly selected reactive sites. This strategy has yielded remarkable materials, including metal-organic frameworks joined by coordinative bonds, supramolecular networks linked by strong non-covalent interactions, and covalent organic frameworks in which atoms of carbon and other light elements are bonded covalently. However, the strategy has not yet produced covalently bonded organic materials in the form of large single crystals. Here we show that such materials can result from reversible self-addition polymerizations of suitably designed monomers. In particular, monomers with four tetrahedrally oriented nitroso groups polymerize to form diamondoid azodioxy networks that can be fully characterized by single-crystal X-ray diffraction. This work forges a strong new link between polymer science and supramolecular chemistry by showing how predictably ordered covalent or non-covalent structures can both be built using a single modular strategy.

Beaudoin, Daniel; Maris, Thierry; Wuest, James D.

2013-10-01

383

Living anionic polymerization using a microfluidic reactor  

SciTech Connect

Living anionic polymerizations were conducted within aluminum-polyimide microfluidic devices. Polymerizations of styrene in cyclohexane were carried out at various conditions, including elevated temperature (60 °C) and high monomer concentration (42%, by volume). The reactions were safely maintained at a controlled temperature at all points in the reactor. Conducting these reactions in a batch reactor results in uncontrolled heat generation with potentially dangerous rises in pressure. Moreover, the microfluidic nature of these devices allows for flexible 2D designing of the flow channel. Four flow designs were examined (straight, periodically pinched, obtuse zigzag, and acute zigzag channels). The ability to use the channel pattern to increase the level of mixing throughout the reactor was evaluated. When moderately high molecular mass polymers with increased viscosity were made, the patterned channels produced polymers with narrower PDI, indicating that passive mixing arising from the channel design is improving the reaction conditions.

Iida, Kazunori; Chastek, Thomas Q.; Beers, Kathryn L.; Cavicchi, Kevin A.; Chun, Jaehun; Fasolka, Michael J.

2009-02-01

384

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

385

Calixarene-based supramolecular polymerization in solution.  

PubMed

Calixarenes are one kind of phenol-formaldehyde cyclic oligomers, discovered from the Bakelite process. Their intrinsic characteristics, including the unique structural scaffold, facile modification and adjustable inclusion property, show pronounced potential for supramolecular polymerization. In this tutorial review, we summarize the current stage of fabrication of calixarene-based supramolecular polymers. Three types of calixarene-based supramolecular polymers are, respectively, illustrated according to the different activities of calixarenes: (1) calixarene-based supramolecular polycaps, (2) supramolecular polymers with polymeric calixarene scaffolds where the cavities remain unexploited; (3) supramolecular polymers formed by the host-guest interactions offered by calixarene cavities. Furthermore, the stimuli-responsiveness and functions of calixarene-based supramolecular polymers are illustrated, which endow them with a broad range of potential applications as smart, self-healing materials and delivery carriers. PMID:22617955

Guo, Dong-Sheng; Liu, Yu

2012-05-22

386

Polymeric multilayer capsules in drug delivery.  

PubMed

Recent advances in medicine and biotechnology have prompted the need to develop nanoengineered delivery systems that can encapsulate a wide variety of novel therapeutics such as proteins, chemotherapeutics, and nucleic acids. Moreover, these delivery systems should be "intelligent", such that they can deliver their payload at a well-defined time, place, or after a specific stimulus. Polymeric multilayer capsules, made by layer-by-layer (LbL) coating of a sacrificial template followed by dissolution of the template, allow the design of microcapsules in aqueous conditions by using simple building blocks and assembly procedures, and provide a previously unmet control over the functionality of the microcapsules. Polymeric multilayer capsules have recently received increased interest from the life science community, and many interesting systems have appeared in the literature with biodegradable components and biospecific functionalities. In this Review we give an overview of the recent breakthroughs in their application for drug delivery. PMID:20645362

De Cock, Liesbeth J; De Koker, Stefaan; De Geest, Bruno G; Grooten, Johan; Vervaet, Chris; Remon, Jean Paul; Sukhorukov, Gleb B; Antipina, Maria N

2010-09-17

387

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.

Vilos, C.; Velasquez, L. A.

2012-01-01

388

Low-Energy Polymeric Phases of Alanates  

NASA Astrophysics Data System (ADS)

Low-energy structures of alanates are currently known to be described by patterns of isolated, nearly ideal tetrahedral [AlH4] anions and metal cations. We discover that the novel polymeric motif recently proposed for LiAlH4 plays a dominant role in a series of alanates, including LiAlH4, NaAlH4, KAlH4, Mg(AlH4)2, Ca(AlH4)2 and Sr(AlH4)2. In particular, most of the low-energy structures discovered for the whole series are characterized by networks of corner-sharing [AlH6] octahedra, forming wires and/or planes throughout the materials. Finally, for Mg(AlH4)2 and Sr(AlH4)2, we identify two polymeric phases to be lowest in energy at low temperatures.

Tran, Huan; Amsler, Maximilian; Marques, Miguel; Botti, Silvana; Willand, Alexander; Goedecker, Stefan

2013-03-01

389

Low-energy polymeric phases of alanates.  

PubMed

Low-energy structures of alanates are currently known to be described by patterns of isolated, nearly ideal tetrahedral [AlH4] anions and metal cations. We discover that the novel polymeric motif recently proposed for LiAlH4 plays a dominant role in a series of alanates, including LiAlH4, NaAlH4, KAlH4, Mg(AlH4)2, Ca(AlH4)2, and Sr(AlH4)2. In particular, most of the low-energy structures discovered for the whole series are characterized by networks of corner-sharing [AlH6] octahedra, forming wires and/or planes throughout the materials. Finally, for Mg(AlH4)2 and Sr(AlH4)2, we identify two polymeric phases to be lowest in energy at low temperatures. PMID:23581335

Huan, Tran Doan; Amsler, Maximilian; Marques, Miguel A L; Botti, Silvana; Willand, Alexander; Goedecker, Stefan

2013-03-25

390

Low-Energy Polymeric Phases of Alanates  

NASA Astrophysics Data System (ADS)

Low-energy structures of alanates are currently known to be described by patterns of isolated, nearly ideal tetrahedral [AlH4] anions and metal cations. We discover that the novel polymeric motif recently proposed for LiAlH4 plays a dominant role in a series of alanates, including LiAlH4, NaAlH4, KAlH4, Mg(AlH4)2, Ca(AlH4)2, and Sr(AlH4)2. In particular, most of the low-energy structures discovered for the whole series are characterized by networks of corner-sharing [AlH6] octahedra, forming wires and/or planes throughout the materials. Finally, for Mg(AlH4)2 and Sr(AlH4)2, we identify two polymeric phases to be lowest in energy at low temperatures.

Huan, Tran Doan; Amsler, Maximilian; Marques, Miguel A. L.; Botti, Silvana; Willand, Alexander; Goedecker, Stefan

2013-03-01

391

Constructing monocrystalline covalent organic networks by polymerization.  

PubMed

An emerging strategy for making ordered materials is modular construction, which connects preformed molecular subunits to neighbours through interactions of properly selected reactive sites. This strategy has yielded remarkable materials, including metal-organic frameworks joined by coordinative bonds, supramolecular networks linked by strong non-covalent interactions, and covalent organic frameworks in which atoms of carbon and other light elements are bonded covalently. However, the strategy has not yet produced covalently bonded organic materials in the form of large single crystals. Here we show that such materials can result from reversible self-addition polymerizations of suitably designed monomers. In particular, monomers with four tetrahedrally oriented nitroso groups polymerize to form diamondoid azodioxy networks that can be fully characterized by single-crystal X-ray diffraction. This work forges a strong new link between polymer science and supramolecular chemistry by showing how predictably ordered covalent or non-covalent structures can both be built using a single modular strategy. PMID:24056338

Beaudoin, Daniel; Maris, Thierry; Wuest, James D

2013-08-25

392

Lignins as Components of Polymeric Composite Materials  

NASA Astrophysics Data System (ADS)

The results of studies of natural, native, and technical lignins are surveyed. Data are presented on the structures and physicochemical properties of various technical lignins (hydrolytic, sulphite, and sulphate lignins), which constitute the waste of the cellulose-paper and hydrolytic industries. Considerable attention is devoted to the examination of the properties of lignins which are responsible for their employment for the reinforcement of elastomers and the modification of plastics. The methods of utilisation and rational employment of technical lignins in the plastics industry as active ingredients of polymeric composite materials are examined. The importance of sulphate lignins as the most active from the standpoint of structure and properties in relation to the polymer matrix for the creation of highly filled lignin-containing polymeric materials — lignoplastics of the type of poprolin — is specially emphasised. The bibliography includes 160 references.

Lyubeshkina, E. G.

1983-07-01

393

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

394

Superparamagnetic Latex via Inverse Emulsion Polymerization  

Microsoft Academic Search

The structure-directing nature of block copolymers, combined with the “miniemulsion” polymerization process, facilitate synthesis of superparamagnetic latex loaded with nanometric magnetic iron oxide. A “double-hydrophilic” diblock copolymer (polyethylene oxide block-co-polymethacrylic acid), present during the precipitation of magnetic iron oxide, directs nucleation, controls growth, and sterically stabilizes the resulting 5 nm superparamagnetic iron oxide. After drying, the coated particles spontaneously repeptize

Klaus Wormuth

2001-01-01

395

Folate receptor targeted biodegradable polymeric doxorubicin micelles  

Microsoft Academic Search

Biodegradable polymeric micelles, self-assembled from a di-block copolymer of poly(d,l-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG), were prepared to achieve folate receptor targeted delivery of doxorubicin (DOX). In the di-block copolymer structure of PLGA–b-PEG, DOX was chemically conjugated to a terminal end of PLGA to produce DOX–PLGA–mPEG, and folate was separately conjugated to a terminal end of PEG to produce

Hyuk Sang Yoo; Tae Gwan Park

2004-01-01

396

The polymerization shrinkage of composite resins.  

PubMed

The majority of methods used for the determination of volumetric polymerization shrinkage rely on mercury as the immersion medium. With current concern for industrial hygiene, the water-filled dilatometer may have advantages. The purpose of this study was to adapt this method for external-energy-cured materials. Six materials were investigated: Aurafill, Silar, Concise, Heliomolar, P-30, and Occlusin. Measurements were taken over one hour, and results ranged from 0.9 to 2.24 volume percent. PMID:2606268

Rees, J S; Jacobsen, P H

1989-01-01

397

Unexpected and unusual failures of polymeric materials  

Microsoft Academic Search

Polymeric products are produced with the expectation that they will process satisfactorily and perform as intended without failure. Yet polymers do fail sometimes. The failures are often completely unexpected or unusual and the causes may not be easy to determine. This paper brings together such failures under five categories:1.In production or processing of polymers.2.Assembly of polymers into products.3.Unauthorized or unexpected

Myer Ezrin; Gary Lavigne

2007-01-01

398

[Molecular/polymeric magnetism]. Progress report  

SciTech Connect

New materials were synthesized to test the generality of magnetism in molecular/polymeric systems. The first room temperature molecular based magnet V(TCNE){sub x}{center_dot}y(solvent) (1) is disclosed. The ferromagnetic and related transitions were studied in decamethylferrocenium tetracyanoethanide (TCNE), (1), and related materials. Our and others` models were tested for ferromagnetic and antiferromagnetic exchange between local sites; models for control of {Tc} were also tested.

Not Available

1993-03-01

399

Thermal Characterization of Polymeric Plaster Composites  

Microsoft Academic Search

Plaster composites have been developed by the authors, aiming the manufacture of plasterboards and other building materials\\u000a with enhanced properties. Polymeric plaster composites,obtained from hydration of commercial plaster of Paris with aqueous\\u000a solutions of a commercial polyester, were characterized by thermogravimetry (TG) and differential thermal analysis (DTA).\\u000a A method using derivative thermogravimetry (DTG) was developed to determine the polymer content

J. Dweck; B. F. Andrade; E. E. C. Monteiro; R. Fischer

2002-01-01

400

Biologically responsive polymeric nanoparticles for drug delivery.  

PubMed

Responsive nanoparticles that release their drug cargo in accordance with a change in pH or oxidative stress are of significant clinical interest as this approach offers the opportunity to link drug delivery to a specific location or disease state. This research news article reviews the current state of this field by examining a series of published articles that highlight the novelty and benefits of using responsive polymeric particles to achieve functionally-targeted drug delivery. PMID:22988558

Colson, Yolonda L; Grinstaff, Mark W

2012-07-24

401

Crumpling and buckling transitions in polymerized membranes  

NASA Astrophysics Data System (ADS)

We consider polymerized non-self-avoiding membranes fluctuating under constrained boundary conditions. Such constraints prevent the membranes from being crumpled at high temperature and introduce a tension. Upon lowering the temperature this tension reduces, and vanishes at a transition temperature below which the membrane assumes a buckled state. Buckling transition points, depending on boundary conditions, arrange on a line which terminates at the crumpling transition. We study the critical properties of these transitions by various field-theoretical techniques.

Guitter, E.; David, F.; Leibler, S.; Peliti, L.

1988-12-01

402

Polymeric foam behavior under dynamic compressive loading  

Microsoft Academic Search

Polymeric foams are commonly used in many impact-absorbing applications and thermal-acoustic insulated devices. To improve their mechanical performances, these structures have to be modeled. Constitutive equations (for their macroscopic behavior) have to be identified and then determined by appropriate tests.Tests were carried out on polypropylene foams under high strain rate compression. In this work, the material behaviour has been determined

P. Viot; F. Beani; J.-L. Lataillade

2005-01-01

403

INHIBITING THE POLYMERIZATION OF NUCLEAR COOLANTS  

DOEpatents

>The formation of new reactor coolants which contain an additive tbat suppresses polymerization of the primary dissoclation free radical products of the pyrolytic and radiation decomposition of the organic coolants is described. The coolants consist of polyphenyls and condensed ring compounds having from two to about four carbon rings and from 0.1 to 5% of a powdered metal hydride chosen from the group consisting of the group IIA and IVA dispersed in the hydrocarbon.

Colichman, E.L.

1959-10-20

404

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

405

Polymeric Composites Containing Alumina Trihydrate and Silica  

Microsoft Academic Search

Unsaturated polyester resin based on poly [1,2-propylene-maleate-phthalate] was used with styrene monomer (35% by weight) as a binder and alumina trihydrate (ATH) (Al2O3.3H2O) or silica ((SiO2), to produce polymeric composites. The effect of type and concentration of the two fillers on the physical, chemical, mechanical, thermal and electrical properties of the crosslinked (styrenated) polyester (SP) and its composites have been

S. H. Mansour

2000-01-01

406

Vector meson-vector meson interaction and dynamically generated resonances  

SciTech Connect

Using the local hidden gauge formalism for the vector meson-vector meson interaction within a unitary approach we find that 11 states get dynamically generated. Five of them are associated to the f{sub 0}(1370), f{sub 0}(1710), f{sub 2}(1270), f{sub 2}'(1525), and K{sub 2}*(1430) resonances, by comparing the mass, width, and decay pattern of these states with those of their experimental counterparts. At the same time we predict six other states with the quantum numbers of h{sub 1}, a{sub 0}, b{sub 1}, a{sub 2}, K{sub 0}*, and K{sub 1} which could be tested by future experiments.

Oset, E.; Geng, L. S.; Molina, R.; Nicmorus, D. [Departamento de Fisica Teorica and IFIC, Universidad de Valencia-CSIC, E-46071 Valencia (Spain)

2010-08-05

407

Polymerization shrinkage of dental composite resins.  

PubMed

Aesthetic materials have always been a priority for the restoration of anterior teeth; increasingly, they have also gained prominence in the restoration of posterior teeth. This has been due to their advantages as an alternative to amalgam. Their drawbacks however, can include poor marginal adaptation, postoperative sensitivity and cuspal movement. These are particularly associated with the polymerization shrinkage accompanying the placement of composite resins. Consequently, a variety of methods have been used for determining the polymerization shrinkage. These range from dilatometer methods, specific gravity methods and deflecting disc systems to optical methods. In this work a unique method for the qualitative analysis of polymerization shrinkage was undertaken. This method utilized a miniature transducer and provided details of the shrinkage from within the material. The results indicated movement of material towards the initiating light, followed by a return movement away from it. The study was expanded to incorporate clinical aspects, whereby the composite resin was in direct contact with dental tissue, as in a restoration. Tests were performed with surface-treated cavity moulds, as in restoration placement, and without surface treatment. Results indicated that the shrinkage was highly dependent upon the region under investigation, as well as on the state of the surface. PMID:11521760

Ensaff, H; O'Doherty, D M; Jacobsen, P H

2001-01-01

408

Homogeneous catalysts for stereoregular olefin polymerization  

DOEpatents

The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C.sub.5 R'.sub.4-x R*.sub.x) A (C.sub.5 R".sub.4-y R"'.sub.y) M Q.sub.p, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R', R", R"', and R* represent substituted and unsubstituted alkyl groups having 1-30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3.ltoreq.p.ltoreq.o. Related complexes may be prepared by alkylation of the corresponding dichorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form "cation-like" species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other .alpha.-olefin polymerization can be effected with very high efficiency and isospecificity.

Marks, Tobin J. (Evanston, IL); Eisen, Moris S. (Evanston, IL); Giardello, Michael A. (Skokie, IL)

1995-01-01

409

Homogeneous catalysts for stereoregular olefin polymerization  

DOEpatents

The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C.sub.5 R'.sub.4-x R*.sub.x) A (C.sub.5 R".sub.4-y R'".sub.y) M Q.sub.p, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R', R", R'", and R* represent substituted and unsubstituted alkyl groups having 1-30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3.ltoreq.p.ltoreq.o. Related complexes may be prepared by alkylation of the corresponding dichorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form "cation-like" species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other .alpha.-olefin polymerization can be effected with very high efficiency and isospecificity.

Marks, Tobin J. (Evanston, IL); Eisen, Moris S. (Evanston, IL); Giardello, Michael A. (Skokie, IL)

1994-01-01

410

Surface-initiated polymerization of superhydrophobic polymethylene.  

PubMed

We report a new surface-initiated polymerization strategy that yields superhydrophobic polymethylene (PM) films from initially smooth substrates of gold and silicon. The films are prepared by assembling a vinyl-terminated self-assembled monolayer, followed by exposure of the surface to a 0.1 M solution of borane, and polymerizing from the borane sites upon exposure to a solution of diazomethane at -17 degrees C. Surface-initiated polymethylenation (SIPM) presents rapid growth in relation to other surface-initiated reactions, producing PM films thicker than 500 nm after 2 min of reaction and 3 microm after 24 h of reaction. AFM and SEM images show the presence of micro- and nanoscale features that enable the entrapment of air when exposed to water. Consistent with this result, these films exhibit advancing water contact angles greater than 160 degrees, dramatically different than 103 degrees measured for smooth PM films, and hysteresis values ranging from 2 degrees to 40 degrees, depending on the substrate and polymerization time. The superhydrophobic character of the films results in the entrapment of air at the polymer/solution interface to provide remarkable resistances greater than 10(10) Omega x cm(2) against the transport of aqueous redox probes and cause the film to behave as a "perfect" capacitor. PMID:20359210

Tuberquia, Juan C; Nizamidin, Nabijan; Harl, Robert R; Albert, Jake; Hunter, Jason; Rogers, Bridget R; Jennings, G Kane

2010-04-28

411

The presence of ?' chain impairs fibrin polymerization  

PubMed Central

Introduction A fraction of fibrinogen molecules contain an alternatively spliced variant chain called ?’. Plasma levels of this variant have been associated with both myocardial infarction and venous thrombosis. Because clot structure has been associated with cardiovascular risk, we examined the effect of ?’ chain on clot structure. Materials and Methods We expressed three fibrinogen variants in Chinese hamster ovary (CHO) cells: ?/? homodimer, ?/?’ heterodimer, and ?’/?’ homodimer. We observed thrombin-catalyzed fibrinopeptide release by HPLC, fibrin polymerization by turbidity, and clot structure by scanning electron microscopy. We characterized post-translational modifications by mass spectrometry. Results Fibrinopeptide A was released at the same rate for all three fibrinogens, while fibrinopeptide B was released faster from the ?’/?’ homodimer. The rise in turbidity was slower and final absorbance was lower during polymerization of ?’-containing fibrinogens than for ?/? fibrinogen. Micrographs showed that ?’/?’ fibrin clots are composed of very thin fibers, while the diameter of ?/?’ fibers is similar to ?/? fibers. Further, the fiber networks formed from ?’-containing samples were non-uniform. Mass spectrometry showed heterogeneous addition of N-glycans and tyrosine sulfation in the ?’ chain. Conclusions The presence of ?’ chains slows lateral aggregation and alters fibrin structure. We suggest these changes are likely due to charge-charge repulsion, such that polymerization of the ?’/?’ homodimer is more impaired than the heterodimer since these repulsions are partially offset by incorporation of ? chains in the ?/?’ heterodimer.

Gersh, Kathryn C.; Nagaswami, Chandrasekaran; Weisel, John W.; Lord, Susan T.

2009-01-01

412

Template Polymerization using a controlled reaction scheme  

NASA Astrophysics Data System (ADS)

We employ a Monte Carlo simulation scheme based on the bond fluctuation model to simulate template polymerization via controlled scheme (i.e., termination and chain transfer reactions are neglected) involving co-polymerization of free monomers and monomers bound to a planar template with equidistant sites occupied by bound monomers. A new macromolecule is initiated in bulk by activation of an initiator; any monomer (free or bound) that is within the reaction distance (nearest neighbors) of the initiator can be incorporated into the growing chain. As the chain propagates, it adds new monomers to the macromolecule. Those monomers can either be bulk (i.e. free) monomers or those that are placed on the predefined template. We analyze the effect of the number and the density of monomers bound on the substrate on the composition and monomer distribution in the resultant co-polymers. Our results reveal that a greater number of bound monomers on the planar template promotes polymerization of most/all of the bound monomers to form an array attached to the template. In addition, there exists an optimum density of spacing of bound monomers on the template, at which the likelihood of the bound monomers getting incorporated in the growing chains is maximum. This is in contrast to our earlier findings for linear templates, where a higher density of spacing favors the incorporation of bound monomers in the growing chains.

Datta, Preeta; Genzer, Jan

2013-03-01

413

Template polymerization using a controlled reaction scheme  

NASA Astrophysics Data System (ADS)

We employ a Monte Carlo simulation scheme based on the bond fluctuation model to simulate template polymerization via controlled scheme (i.e., termination and chain transfer reactions are neglected) involving co-polymerization of free monomers and monomers bound to a template that consists of four linear substrates with equispaced sites occupied by bound monomers. A new macromolecule is initiated by activation of an initiator; any monomer (free or bound) that is within the reaction distance (nearest neighbors) of the initiator can be incorporated into the chain. As the chain propagates, it adds new monomers to the macromolecule. Those monomers can either be bulk (i.e. free) monomers or those that are placed on the predefined template. We analyze the effect of the number of spacing of the bound monomers on the composition and monomer distribution in the resultant co-polymer. Our results reveal that the larger the total number of bound monomers in the system and the more dense spacing, the greater is the likelihood of those getting incorporated in the growing chains. In addition, a greater number of bound monomers on the linear template promotes polymerization of most/all of the bound monomers to form a linear array attached to the template.

Genzer, Jan; Datta, Preeta

2012-02-01

414

In situ forming polymeric drug delivery systems.  

PubMed

In situ forming polymeric formulations are drug delivery systems that are in sol form before administration in the body, but once administered, undergo gelation in situ, to form a gel. The formation of gels depends on factors like temperature modulation, pH change, presence of ions and ultra violet irradiation, from which the drug gets released in a sustained and controlled manner. Various polymers that are used for the formulation of in situ gels include gellan gum, alginic acid, xyloglucan, pectin, chitosan, poly(DL-lactic acid), poly(DL-lactide-co-glycolide) and poly-caprolactone. The choice of solvents like water, dimethylsulphoxide, N-methyl pyrrolidone, triacetin and 2-pyrrolidone for these formulations depends on the solubility of polymer used. Mainly in situ gels are administered by oral, ocular, rectal, vaginal, injectable and intraperitoneal routes. The in situ gel forming polymeric formulations offer several advantages like sustained and prolonged action in comparison to conventional drug delivery systems. The article presents a detailed review of these types of polymeric systems, their evaluation, advancements and their commercial formulations. From a manufacturing point of view, the production of such devices is less complex and thus lowers the investment and manufacturing cost. PMID:20490289

Madan, M; Bajaj, A; Lewis, S; Udupa, N; Baig, J A

2009-05-01

415

Radical Nature of Cu-Catalyzed Controlled Radical Polymerizations (Atom Transfer Radical Polymerization).  

PubMed

Copper-catalyzed atom transfer radical polymerization (ATRP) is one of the most robust and precise techniques for controlling radical polymerization. The very good control of molecular weights, polydispersities, functionalities, chain composition, and topologies unusual for radical systems combined with the application of transition metals as catalysts requires more detailed mechanistic studies and proof of the radical nature of active species. The following results are in agreement with the radical nature of ATRP: reverse ATRP, chemoselectivities similar to those for conventional radical polymerization (effect of additives and inhibitors/scavengers, reactivity ratios, transfer coefficients), regioselectivities similar to those for conventional radical polymerization (low proportion of head-to-head units and expected structure of both tail and head end groups), stereoselectivities (tacticities) similar to that in conventional radical polymerization, EPR detection of X-Mtn+1 species resulting from the persistent radical effect, and confirmation of the termination by doubling molecular weights as well as cross-linking with multifunctional initiators and inimers. In addition, it seems that, in most ATRP systems, the contribution of degenerative transfer and reversible formation of organometallic intermediates is small and a halogen atom is transferred in the concerted process rather than in a two-step process with the involvement of radical anions. PMID:9680403

Matyjaszewski

1998-07-28

416

Symbolic Vector Analysis in Plasma Physics.  

National Technical Information Service (NTIS)

Many problems in plasma physics involve substantial amounts of analytical vector calculation. The complexity usually originates from both the vector operations themselves and the choice of underlying coordinate system. A computer algebra package for symbo...

H. Qin W. M. Tang G. Rewoldt

1997-01-01

417

Symbolic Vector Analysis in Plasma Physics  

SciTech Connect

Many problems in plasma physics involve substantial amounts of analytical vector calculation. The complexity usually originates from both the vector operations themselves and the choice of underlying coordinate system. A computer algebra package for symbolic vector analysis in general coordinate systems, GeneralVectorAnalysis (GVA), is developed using Mathematica. The modern viewpoint for 3D vector calculus, differential forms on 3-manifolds, is adopted to unify and systematize the vector calculus operations in general coordinate systems. This package will benefit physicists and applied mathematicians in their research where complicated vector analysis is required. It will not only save a huge amount of human brain-power and dramatically improve accuracy, but this package will also be an intelligent tool to assist researchers in finding the right approaches to their problems. Several applications of this symbolic vector analysis package to plasma physics are also given.

Qin, H.; Rewoldt, G.; Tang, W.M.

1997-10-01

418

Symbolic Vector Analysis in Plasma Physics  

SciTech Connect

Many problems in plasma physics involve substantial amounts of analytical vector calculation. The complexity usually originates from both the vector operations themselves and the choice of underlying coordinate system. A computer algebra package for symbolic vector analysis in general coordinate systems, General Vector Analysis (GVA), is developed using Mathematica. The modern viewpoint for 3D vector calculus, differential forms on 3-manifolds, is adopted to unify and systematize the vector calculus operations in general coordinate systems. This package will benefit physicists and applied mathematicians in their research where complicated vector analysis is required. It will not only save a huge amount of human brain-power and dramatically improve accuracy, but this package will also be an intelligent tool to assist researchers in finding the right approaches to their problems. Several applications of this symbolic vector analysis package to plasma physics are also given.

Qin, H.; Tang, W.M.; Rewoldt, G.

1997-10-09

419

The vector knowledge of beginning physics students  

NSDL National Science Digital Library

A study involving about 300 university engineering students probed their understanding of vectors. After mathematics and physics courses in high school and a semester of college calculus, only one-third indicated familiarity with finding magnitudes or recognizing vector components.

Knight, Randall D.

2005-10-26

420

Visualization Tool for Engineering Vector Analysis.  

National Technical Information Service (NTIS)

A prototype computer tool was designed to support an interactive, visual approach to the learning of vector analysis. The objective was to construct a prototype environment in which vectors, scalars and points could be entered, manipulated and observed in...

B. L. Miranda

1995-01-01

421

Present status of vectorized Monte Carlo  

SciTech Connect

Monte Carlo applications have traditionally been limited by the large amounts of computer time required to produce acceptably small statistical uncertainties, so the immediate benefit of vectorization is an increase in either the number of jobs completed or the number of particles processed per job, typically by one order of magnitude or more. This results directly in improved engineering design analyses, since Monte Carlo methods are used as standards for correcting more approximate methods. The relatively small number of vectorized programs is a consequence of the newness of vectorized Monte Carlo, the difficulties of nonportability, and the very large development effort required to rewrite or restructure Monte Carlo codes for vectorization. Based on the successful efforts to date, it may be concluded that Monte Carlo vectorization will spread to increasing numbers of codes and applications. The possibility of multitasking provides even further motivation for vectorizing Monte Carlo, since the step from vector to multitasked vector is relatively straightforward.

Brown, F.B.

1987-01-01

422

Lentiviral Vectors for Immune Cells Targeting  

PubMed Central

Lentiviral vectors are efficient gene delivery vehicles suitable for delivering long-term transgene expression in various cell types. Engineering lentiviral vectors to have the capacity to transduce specific cell types is of great interest to advance the translation of lentiviral vectors towards the clinic. Here we provide an overview of innovative approaches to target lentiviral vectors to cells of the immune system. In this overview we distinguish between two types of lentiviral vector targeting strategies: 1) targeting of the vectors to specific cells by lentiviral vector surface modifications, and 2) targeting at the level of transgene transcription by insertion of tissue-specific promoters to drive transgene expression. It is clear that each strategy is of enormous value but ultimately combining these approaches may help reduce the effects of off-target expression and improve the efficiency and saftey of lentiviral vectors for gene therapy.

Froelich, Steven; Tai, April; Wang, Pin

2009-01-01

423

Idea Bank: Vectors on the Basketball Court  

NSDL National Science Digital Library

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 I

Bergman, Daniel

2010-03-01

424

Imaging vector fields using Line Integral Convolution.  

National Technical Information Service (NTIS)

Imaging vector fields has applications in science, art, image processing and special effects. An effective new approach is to use linear and curvilinear filtering techniques to locally blur textures along a vector field. This approach builds on several pr...

B. Cabral L. C. Leedom

1993-01-01

425

Vectors and vector-borne diseases of horses.  

PubMed

Most diseases of horses with zoonotic importance are transmitted by arthropods. The vectors belong to two very distantly related groups, the chelicerate Ixodidae (Acari = ticks) and the hexapod Diptera (true flies). Almost all relevant species are predestined for transmitting pathogens by their blood-sucking habits. Especially species of Diptera, one of the megadiverse orders of holometabolan insects (ca. 150.000 spp.), affect the health status and performance of horses during the grazing period in summer. The severity of pathological effect depends on the pathogen, but also on the group of vectors and the intensity of the infection or infestation. Dipteran species but also blood-sucking representatives of Acari (Ixodidae) can damage their hosts by sucking blood, causing myiasis, allergy, paralysis and intoxication, and also transmit various bacterial, viral, parasitic, spirochetal and rickettsial diseases to animals and also humans. The aim of this review was to provide extensive information on the infectious diseases transmitted by members of the two arthropod lineages (Ixodidae, Diptera) and a systematic overview of the vectors. For each taxon, usually on the ordinal, family, and genus level a short characterisation is given, allowing non-entomologists easy identification. Additionally, the biology of the relevant species (or genera) is outlined briefly. PMID:23054414

Onmaz, A C; Beutel, R G; Schneeberg, K; Pavaloiu, A N; Komarek, A; van den Hoven, R

2012-09-30

426

Benchmarking the IBM 3090 with Vector Facility  

SciTech Connect

The IBM 3090 with Vector Facility is an extremely interesting machine because it combines very good scaler performance with enhanced vector and multitasking performance. For many IBM installations with a large scientific workload, the 3090/vector/MTF combination may be an ideal means of increasing throughput at minimum cost. However, neither the vector nor multitasking capabilities are sufficiently developed to make the 3090 competitive with our current worker machines for our large-scale scientific codes.

Brickner, R.G.; Wasserman, H.J.; Hayes, A.H.; Moore, J.W.

1986-01-01

427

VEST: Abstract Vector Calculus Simplication in Mathematics.  

National Technical Information Service (NTIS)

We present a new package, VEST (Vector Einstein Summation Tools), that performs abstract vector calculus computations in Mathematica. Through the use of index notation, VEST is able to reduce scalar and vector expressions of a very general type using a sy...

H. Qin J. Burby J. Squire

2013-01-01

428

Applications of Vector Fields to Image Processing  

Microsoft Academic Search

We use rotational and curvature properties of vector fields to identify critical features of an image. Using vector analysis and dif-ferential geometry, we establish the properties needed, and then use these properties in three ways. First, our results make it theoretically possible to identify extremal edges of an intensity function f(x, y) of two variables by considering the gradient vector

Raul Machuca; Keith Phillips

1983-01-01

429

Detecting boundaries in a vector field  

Microsoft Academic Search

A vector gradient approach is proposed to detect boundaries in multidimensional data with multiple attributes (a vector field). It is used to extend a gradient edge detector to color images. The statistical effects of noise on the distribution of the amplitudes and directions of the vector gradient are characterized. The noise behavior of the L 2 norm of the scalar

H.-C. Lee; D. R. Cok

1991-01-01

430

A vector algorithm for lattice gas hydrodynamics  

SciTech Connect

A code implementing a cellular automaton for simulating fluid flows is presented in the style of Fortran 8X. Major data structures and the boundary characteristics are represented by bit vectors, resulting in efficient use of memory. Use of vector-length, bitwise operations yields significant speedup. The code is equally applicable to other vector supercomputers that support the full range of boolean operations.

Lim, H.A.; Riccardi, G.; Bauer, C.M.; Sharma, S. (Supercomputer Computations Research Institute, Florida State Univ., Tallahassee, FL (US))

1989-01-01

431

Vector quantization based on Gaussian mixture models  

Microsoft Academic Search

We model the underlying probability density function of vectors in a database as a Gaussian mixture (GM) model. The model is employed for high rate vector quantization analysis and for design of vector quantizers. It is shown that the high rate formulas accurately predict the performance of model-based quantizers. We propose a novel method for optimizing GM model parameters for

P. Hedelin; J. Skoglund

2000-01-01

432

Regularization of Vector Fields by Surgery.  

National Technical Information Service (NTIS)

Regularization is a common procedure in the study of differential equations. The usual method is to multiply the vector field by a suitably chosen positive scalar function which vanishes on the set of singularities of the vector field. The new vector fiel...

R. Easton

1970-01-01

433

PhET Simulation: Vector Addition  

NSDL National Science Digital Library

This applet allows user to learn how to add vectors. Users may drag vectors onto a graph, changing their length and angle, and calculate their sum. The magnitude, angle, and components of each vector can be displayed in several formats. Teaching ideas and activities are included. This is part of a larger collection developed by the Physics Education Technology project (PhET).

2008-07-13

434

Problems with the Method of Correlated Vectors  

ERIC Educational Resources Information Center

The method of correlated vectors has been used widely to identify variables that are associated with general intelligence (g). Briefly, this method involves finding the correlation between the vector of intelligence subtests' g-loadings and the vector of those subtests' correlations with the variable in question. We describe two major problems…

Ashton, M.C.; Lee, K.

2005-01-01

435

Inverse scattering with sparse Bayesian vector regression  

Microsoft Academic Search

A Bayesian formulation is employed to develop a sparse vector regression model. The model is used to characterize the connection between measured vector scattered-field data x and the underlying target responsible for these fields, characterized by the parameter vector t. The scattering data x may be measured at multiple positions and\\/or at multiple frequencies. The statistical model is trained using

Yijun Yu; Balaji Krishnapuram; Lawrence Carin

2004-01-01

436

Effect of Coflow on Counterflow Thrust Vectoring  

Microsoft Academic Search

A unique, fluidic-based thrust vectoring technique known as CounterFlow Thrust Vector Control (CFTVC) has been investigated at the Fluid Mechanics Research Laboratory (FMRL) over the past few years. These studies have demonstrated that CFTVC is a simple, robust and efficient method for thrust vectoring of supersonic jets of various geometries. In an effort to better evaluate the system performance under

F. S. Alvi; A. Krothapalli; P. J. Strykowski

1997-01-01

437

Feedback control for counterflow thrust vectoring  

Microsoft Academic Search

Thrust vector control is used to increase the maneuverability of aircraft. In current aircraft it is implemented using movable control surfaces such as vanes and flaps. Counterflow thrust vectoring (CFTV) is a fluidic approach to thrust vectoring that has the potential to improve on the conventional approaches by reducing weight and increasing the reaction speed. Open loop implementation of CFTV

Emmanuel G. Collins; Yanan Zhao; F. Alvi; M. I. Alidu; P. J. Strykowski

2004-01-01

438

Single-layer white-light polymeric luminescent film by plasma polymerization for light emitting diodes  

NASA Astrophysics Data System (ADS)

Efficient white polymeric light-emitting diodes (PLED) were fabricated with a single active layer consisted of three-dimentional crosslinking ?-conjugated system by plasma polymerization from conjugated monomers. As indicated by the FTIR, XPS UV-vis and PL spectra, the plasma polymer chains were constructed by various chromophores including naphthalene, phenyl, polyene and alkyl groups. Upon optical excitation, the light emission was characterized with a broad peak (FMHW ˜ 100 nm) located at 430 nm. In a PLED device, however, the energy transfer by Foster processes (FRET) between multiple host-guest pairs give rise to white emission located in CIE coordinates of (0.3439, 0.3369). This result illustrated the feasibility of large area contour coating of single-layer white-light luminescent polymers for LEDs by simple plasma polymerization methods. This work is supported by National Science Council of Taiwan.

Chang, Chun-Chih; Chang, Yi-Hsing; Chen, Ying-Chu; Chang-Mou Yang, Arnold; Hwang, Kuo-Chu

2006-03-01

439

Viral vectors for vaccine applications  

PubMed Central

Traditional approach of inactivated or live-attenuated vaccine immunization has resulted in impressive success in the reduction and control of infectious disease outbreaks. However, many pathogens remain less amenable to deal with the traditional vaccine strategies, and more appropriate vaccine strategy is in need. Recent discoveries that led to increased understanding of viral molecular biology and genetics has rendered the used of viruses as vaccine platforms and as potential anti-cancer agents. Due to their ability to effectively induce both humoral and cell-mediated immune responses, viral vectors are deemed as an attractive alternative to the traditional platforms to deliver vaccine antigens as well as to specifically target and kill tumor cells. With potential targets ranging from cancers to a vast number of infectious diseases, the benefits resulting from successful application of viral vectors to prevent and treat human diseases can be immense.

Choi, Youngjoo

2013-01-01

440

A Novel Algorithm Base on How to Use the Least Vectors to Another Vector  

Microsoft Academic Search

A novel algorithm, which can be used to resolve the problem that how to use the least vectors in vector space, expresses the known vector, was proposed in this paper. Compared with MP (matching pursuit) algorithm, the new algorithm has less errors and more exactly than MP algorithm of the lower dimension. By this novel algorithm, the vectors was cut

Tian Ya-fei; Wang Zheng-rong; Guo Ai-ping

2009-01-01

441

Status of the standard vector-axial-vector model for nuclear beta decay  

Microsoft Academic Search

The complete set of experimental results on correlations in nuclear beta decay is analyzed in terms of the general Hamiltonian including scalar, vector, axial vector, and tensor interactions with an arbitrary degree of parity violation. It is concluded that the standard vector minus axial-vector model with maximal parity violation (left-handed lepton current) is compatible with the data and rigorous limits

A. I. Boothroyd; J. Markey; P. Vogel

1984-01-01

442

GAPS IN SUPPORT VECTOR OPTIMIZATION  

SciTech Connect

We show that the stopping criteria used in many support vector machine (SVM) algorithms working on the dual can be interpreted as primal optimality bounds which in turn are known to be important for the statistical analysis of SVMs. To this end we revisit the duality theory underlying the derivation of the dual and show that in many interesting cases primal optimality bounds are the same as known dual optimality bounds.

STEINWART, INGO [Los Alamos National Laboratory; HUSH, DON [Los Alamos National Laboratory; SCOVEL, CLINT [Los Alamos National Laboratory; LIST, NICOLAS [Los Alamos National Laboratory

2007-01-29

443

Multichannel vector sum phase shifter.  

PubMed

A novel multichannel vector sum phase shifter that is suitable for phased array antenna applications is demonstrated. Each channel is implemented using a distinct optical wavelength. Selective control of each channel is performed using an acousto-optic polarization coupler. The concept is successfully demonstrated for two individually controlled channels. For each channel, a continuously variable frequency linear phase shift is demonstrated between DC and 7 GHz, with the phasing range exceeding 100 degrees. PMID:16570403

Bui, Lam Anh; Ghorbani, Kamran; Mitchell, Arnan

2006-03-01

444

2-D Vector Field Simulation  

NSDL National Science Digital Library

The applet simulates various vector fields, including spherical, radial, and constant plane. It is a generalized version of an electrostatic field simulation by the same author. The field strength and number of particles simulated are adjustable. Divergence, curl, and potential can be color-coded. Grid lines, potential lines, or streamlines can be displayed. Directions, specific links to the subject and source code are also included.

Falstad, Paul

2004-07-23

445

Ellipse Support Vector Data Description  

Microsoft Academic Search

This paper presents a novel Boundary-based approach in one-class classification that is inspired by support vector data description\\u000a (SVDD). The SVDD is a popular kernel method which tries to fit a hypersphere around the target objects and of course more\\u000a precise boundary is relied on selecting proper parameters for the kernel functions. Even with a flexible Gaussian kernel function,\\u000a the

Mohammad GhasemiGol; Reza Monsefi; Hadi Sadoghi Yazdi

446

Vector Spaces in Primary School  

Microsoft Academic Search

This article describes a simple and relatively inexpensive teaching situation designed to introduce 11?12#fr1\\/2> year?olds informally to some fundamental concepts of two?dimensional vector space. The ‘game’ situation in which the structure is embedded results from attempts to provide an approach which is at once interesting to children and acceptable to their teachers.In five graded steps the children build up a

Gerard Beggan

1973-01-01

447

Polymers with Very Low Polydispersities from Atom Transfer Radical Polymerization  

NASA Astrophysics Data System (ADS)

A radical polymerization process that yields well-defined polymers normally obtained only through anionic polymerizations is reported. Atom transfer radical polymerizations of styrene were conducted with several solubilizing ligands for the copper(I) halides: 4,4'-di-tert-butyl, 4,4'-di-n-heptyl, and 4,4'-di-(5-nonyl)-2,2'-dipyridyl. The resulting polymerizations have all of the characteristics of a living polymerization and displayed linear semilogarithmic kinetic plots, a linear correlation between the number-average molecular weight and the monomer conversion, and low polydispersities (ratio of the weight-average to number-average molecular weights of 1.04 to 1.05). Similar results were obtained for the polymerization of acrylates.

Patten, Timothy E.; Xia, Jianhui; Abernathy, Teresa; Matyjaszewski, Krzysztof

1996-05-01

448

Nanoparticulate material delivery to plants  

Microsoft Academic Search

The successful application of various nanoplatforms in medicine under in vitro conditions has generated some interest in agri-nanotechnology. This technology holds the promise of controlled release of agrochemicals and site targeted delivery of various macromolecules needed for improved plant disease resistance, efficient nutrient utilization and enhanced plant growth. Processes such as nanoencapsulation show the benefit of more efficient use and

Remya Nair; Saino Hanna Varghese; Baiju G. Nair; T. Maekawa; Y. Yoshida; D. Sakthi Kumar

2010-01-01

449

Elementary processes at nanoparticulate photocatalysts  

NASA Astrophysics Data System (ADS)

The paper is a mini review on the authors own work related to laser induced processes at metal nanoparticle/oxidic support systems. A number of aspects will be addressed ranging from the nano particle size dependence on the efficiency of the photochemical process, the influence of low coordination sites of the nano particles and dynamical processes such as energy transfer between adsorbates, light induced particle changes or spill over processes. The paper reviews nano and femtosecond laser experiments as well as quantum state resolved experiments. Results will be compared to typical findings from simple oxidic supports and metal single crystals. This review may be of interest for future photocatalyst development for applications such as solar fuel synthesis and related problems.

Al-Shamery, K.; Al-Shemmary, A.; Buchwald, R.; Hoogestraat, D.; Kampling, M.; Nickut, P.; Wille, A.

2010-05-01

450

Aggregate breakdown of nanoparticulate titania  

NASA Astrophysics Data System (ADS)

Six nanosized titanium dioxide powders synthesized from a sulfate process were investigated. The targeted end-use of this powder was for a de-NOx catalyst honeycomb monolith. Alteration of synthesis parameters had resulted principally in differences in soluble ion level and specific surface area of the powders. The goal of this investigation was to understand the role of synthesis parameters in the aggregation behavior of these powders. Investigation via scanning electron microscopy of the powders revealed three different aggregation iterations at specific length scales. Secondary and higher order aggregate strength was investigated via oscillatory stress rheometry as a means of simulating shear conditions encountered during extrusion. G' and G'' were measured as a function of the applied oscillatory stress. Oscillatory rheometry indicated a strong variation as a function of the sulfate level of the particles in the viscoelastic yield strengths. Powder yield stresses ranged from 3.0 Pa to 24.0 Pa of oscillatory stress. Compaction curves to 750 MPa found strong similarities in extrapolated yield point of stage I and II compaction for each of the powders (at approximately 500 MPa) suggesting that the variation in sulfate was greatest above the primary aggregate level. Scanning electron microscopy of samples at different states of shear in oscillatory rheometry confirmed the variation in the linear elastic region and the viscous flow regime. A technique of this investigation was to approach aggregation via a novel perspective: aggregates are distinguished as being loose open structures that are highly disordered and stochastic in nature. The methodology used was to investigate the shear stresses required to rupture the various aggregation stages encountered and investigate the attempt to realign the now free-flowing constituents comprising the aggregate into a denser configuration. Mercury porosimetry was utilized to measure the pore size of the compact resulting from compaction via dry pressing and tape casting secondary scale aggregates. Mercury porosimetry of tapes cast at 0.85 and 9.09 cm/sec exhibited pore sizes ranging from 200-500 nm suggesting packing of intact micron-sized primary aggregates. Porosimetry further showed that this peak was absent in pressed pellets corroborating arguments of ruptured primary aggregates during compaction to 750 MPa.

Venugopal, Navin

451

Gaussian statistics for palaeomagnetic vectors  

USGS Publications Warehouse

With the aim of treating the statistics of palaeomagnetic directions and intensities jointly and consistently, we represent the mean and the variance of palaeomagnetic vectors, at a particular site and of a particular polarity, by a probability density function in a Cartesian three-space of orthogonal magnetic-field components consisting of a single (unimoda) non-zero mean, spherically-symmetrical (isotropic) Gaussian function. For palaeomagnetic data of mixed polarities, we consider a bimodal distribution consisting of a pair of such symmetrical Gaussian functions, with equal, but opposite, means and equal variances. For both the Gaussian and bi-Gaussian distributions, and in the spherical three-space of intensity, inclination, and declination, we obtain analytical expressions for the marginal density functions, the cumulative distributions, and the expected values and variances for each spherical coordinate (including the angle with respect to the axis of symmetry of the distributions). The mathematical expressions for the intensity and off-axis angle are closed-form and especially manageable, with the intensity distribution being Rayleigh-Rician. In the limit of small relative vectorial dispersion, the Gaussian (bi-Gaussian) directional distribution approaches a Fisher (Bingham) distribution and the intensity distribution approaches a normal distribution. In the opposite limit of large relative vectorial dispersion, the directional distributions approach a spherically-uniform distribution and the intensity distribution approaches a Maxwell distribution. We quantify biases in estimating the properties of the vector field resulting from the use of simple arithmetic averages, such as estimates of the intensity or the inclination of the mean vector, or the variances of these quantities. With the statistical framework developed here and using the maximum-likelihood method, which gives unbiased estimates in the limit of large data numbers, we demonstrate how to formulate the inverse problem, and how to estimate the mean and variance of the magnetic vector field, even when the data consist of mixed combinations of directions and intensities. We examine palaeomagnetic secular-variation data from Hawaii and Re??union, and although these two sites are on almost opposite latitudes, we find significant differences in the mean vector and differences in the local vectorial variances, with the Hawaiian data being particularly anisotropic. These observations are inconsistent with a description of the mean field as being a simple geocentric axial dipole and with secular variation being statistically symmetrical with respect to reflection through the equatorial plane. Finally, our analysis of palaeomagnetic acquisition data from the 1960 Kilauea flow in Hawaii and the Holocene Xitle flow in Mexico, is consistent with the widely held suspicion that directional data are more accurate than intensity data.

Love, J. J.; Constable, C. G.

2003-01-01

452

Torse forming vector fields and exterior concurrent vector fields on Riemannian manifolds and applications  

NASA Astrophysics Data System (ADS)

We interrelate the concept of a torse forming vector field and the concepts of exterior concurrent and quasi-exterior concurrent vector fields. Different second order properties of a torse forming vector field T are studied, as for instance it is proved that any torse forming is a quasi-exterior concurrent vector field. We obtain a necessary and sufficient condition for a torse forming vector field to be 2-exterior concurrent. In this case a foliation is given.

Mihai, Adela; Mihai, Ion

2013-11-01

453

Near-infrared emissive BODIPY polymeric and copolymeric dyes  

Microsoft Academic Search

Novel near-Infrared emissive BODIPY polymeric dyes (polymers A and B) were prepared by Sonogashira cross-coupling reaction of 2,6-diiodo BODIPY dyes bearing one and two styryl groups at 3,5 positions (5, 6) with 2,6-diethynyl BODIPY dye, respectively. These polymeric dyes (A and B) display absorption maxima at 697 and 738 nm, and emission maxima at 715 and 760 nm, respectively. These polymeric dyes

Venkat R. Donuru; Shilei Zhu; Sarah Green; Haiying Liu

2010-01-01

454

Metal-free anionic polymerization of n-butyl acrylate  

Microsoft Academic Search

Results on the metal-free anionic polymerization of n-butyl acrylate (BA) are presented. BA was polymerized in tetrahydrofuran, using tetrabutylammonium 2-nitropropanate as initiator. With very pure initiator, the polymerization started without inhibition periods, which may be caused by transfer reactions between the precursor molecule 2-nitropropane in the synthesis of the initiator and growing chains. Even the addition of 2-nitropropane or of

Dirk Broska; Andreas Fieberg; Friedhelm Bandermann

1998-01-01

455

Nanostructured functional materials prepared by atom transfer radical polymerization  

Microsoft Academic Search

Atom transfer radical polymerization (ATRP) is the most extensively studied controlled\\/living radical polymerization (CRP) method, with the interest originating primarily in its simplicity and broad applicability, and in the ability to prepare previously inaccessible well-defined nanostructured polymeric materials. This review illustrates the range of well-defined advanced functional materials that can be prepared by ATRP. We detail the precise synthesis of

Krzysztof Matyjaszewski; Nicolay V. Tsarevsky

2009-01-01

456

Macromolecular architectures by living and controlled\\/living polymerizations  

Microsoft Academic Search

The discovery of living anionic polymerization by Szwarc 50 years ago opened the way to the synthesis of model polymers. This ground-breaking discovery inspired many researchers to develop controlled\\/living routes for a plethora of monomers including those not compatible with anionic polymerization. These methods and their combinations serve as an arsenal for the synthesis of well-defined polymeric materials with predetermined

Nikos Hadjichristidis; Hermis Iatrou; Marinos Pitsikalis; Jimmy Mays

2006-01-01

457

Solution polymerization behavior of acrylonitrile by moderate temperature azoinitiator  

Microsoft Academic Search

Acrylonitrile (AN) was solution-polymerized in dimethyl sulfoxide (DMSO) and tertiary butyl alcohol (TBA) at 30, 40 and 50°C using a moderate temperature initiator, 2,2?-azobis(2,4,-dimethylvaleronitrile) (ADMVN); the effects of type and amount of solvent, polymerization temperature, and initiator concentration were investigated. On the whole, the experimental results corresponded to predictions. Moderate polymerization temperature using ADMVN proved to be successful in obtaining

Won Seok Lyoo; Han Do Ghim; Won Sik Yoon; Jinwon Lee; Hyun Seok Lee; Byung Chul Ji

1999-01-01

458

Polymerization of 1,3Dienes with Functional Groups. 4  

Microsoft Academic Search

Anionic polymerization of N,N-diethyl-2-methylene-3-butenamide (DEA), which is a 1,3-butadiene derivative containing a diethylamide function, was carried out in tetrahydrofurane (THF) under various conditions. When DEA was polymerized in THF at -78°C using potassium naphthalenide (K-Naph) or diphenylmethylpotassium (DPMK) as an initiator, a polymer of predictable molecular weight with a narrow molecular weight distribution was obtained. However, the rate of polymerization

Katsuhiko Takenaka; Natsuyo Shibata; Shinsuke Tsuchida; Hiroki Takeshita; Masamitsu Miya; Tomoo Shiomi

2008-01-01

459

Synthesis of zwitterionic block copolymers via RAFT polymerization  

Microsoft Academic Search

A series of poly [2-(dimethylamino)ethyl methacrylate (DMA)–sodium acrylate (SA)] diblock copolymers were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymerization exhibits controlled characters: well-controlled molecular weight, narrow molecular weight distribution, molecular weight increasing with polymerization time. The zwitterionic diblock copolymers show rich solution behaviors. Dynamic light scattering (DLS) indicated the formation of micelles and reverse micelles of copolymers

Xiuqiang Xin; Yanmei Wang; Wei Liu

2005-01-01

460

Interpolating vectors for robust pattern recognition.  

PubMed

This paper proposes a powerful algorithm for pattern recognition, which uses interpolating vectors for classifying patterns. Labeled reference vectors in a multi-dimensional feature space are first produced by a kind of competitive learning. We then assume a situation where virtual vectors, called interpolating vectors, are densely placed along line segments connecting all pairs of reference vectors of the same label. From these interpolating vectors, we choose the one that has the largest similarity to the test vector. Its label shows the result of pattern recognition. In practice, we can get the same result with a simpler process. We applied this method to the neocognitron for handwritten digit recognition and reduced the error rate from 1.52% to 1.02% for a blind test set of 5000 digits. PMID:17714913

Fukushima, Kunihiko

2007-07-24

461

Radical polymerization of methyl methacrylate and styrene in the presence of ferrocene  

Microsoft Academic Search

The influence of ferrocene on the kinetic parameters of methyl methacrylate (MMA) or styrene polymerization is investigated. It is shown, that in the presence of ferrocene the growth of the initial rate of polymerization is accompanied with significant decrease of the polymerization degree of polymer obtained when peroxides are used as the polymerization initiators. The polymerization kinetics parameters are evaluated.

Yu. I. Puzin; R. Kh. Yumagulova; V. A. Kraikin

2001-01-01

462

Hydrolases in Polymer Chemistry: Chemoenzymatic Approaches to Polymeric Materials  

NASA Astrophysics Data System (ADS)

Lipases show high activity in the polymerization of a range of monomers using ring-opening polymerization and polycondensation. The range of polymer structures from this enzymatic polymerization can be further increased by combination with chemical methods. This paper reviews the developments of the last 5-8 years in chemoenzymatic strategies towards polymeric materials. Special emphasis is on the synthesis of polymer architectures like block and graft copolymers and polymer networks. Moreover, the combination of chemical and enzymatic catalysis for the synthesis of unique chiral polymers is highlighted.

Heise, Andreas; Palmans, Anja R. A.

463

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

464

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

465

Effect of filler choice on a binary frontal polymerization system.  

PubMed

Binary frontal polymerization is a process that involves two different systems polymerizing simultaneously but independently of each other. Various factors including filler choice and initiator concentration can affect front temperature and velocity. Like thermal frontal polymerization systems, binary frontal polymerization of a cyanate ester system and multifunctional acrylate is affected by initiator (amine) concentration and filler choice. Systems with higher viscosities and higher initiator concentrations resulted in higher velocities. Front temperature was rarely affected by filler choice. Aniline concentration and initial monomer ratios had a greater effect on front temperature than filler choice does. PMID:21557600

Viner, Veronika; Viner, Gloria

2011-05-10

466

Rechargeable magnesium batteries with polymeric gel electrolytes containing magnesium salts  

Microsoft Academic Search

Novel polymeric gel electrolytes consisting of poly(ethylene oxide)–modified poly(methacrylate) (PEO–PMA) with magnesium imide (Mg[(CF3SO2)2N]2) as the electrolytic salt and mixed alkyl carbonates as the plasticizer have been prepared by photo-induced radical polymerization. The polymeric gel film was flexible and self-standing with proper mechanical strength. The ionic conductivity of the polymeric gel film was about 10?3 S cm?1 at room temperature.

Nobuko Yoshimoto; Shin Yakushiji; Masashi Ishikawa; Masayuki Morita

2003-01-01

467

Immediate GTP hydrolysis upon FtsZ polymerization.  

PubMed

To understand the polymerization dynamics of FtsZ, a bacterial cell division protein similar to tubulin, insight is required into the nature of the nucleotide bound to the polymerized protein. In a previous study, we showed that the FtsZ polymers contain mostly GDP. A recent study challenged this result, suggesting that the polymerized FtsZ is in a GTP-bound state. Here, we show that, when radiolabelled [gamma-32P]-GTP is used to polymerize FtsZ, GTP is hydrolysed instantaneously. The FtsZ polymer contains both GDP and the radiolabelled inorganic phosphate. PMID:11952901

Scheffers, Dirk-Jan; Driessen, Arnold J M

2002-03-01

468

Sorption of organics from aqueous solution onto polymeric resins  

SciTech Connect

The uptake of phenol, toluene, chlorobenzene, and benzoic acid by several polymeric resins and activated carbon was investigated experimentally. Presentation of the sorption data in terms of the number of sorbed monolayers and fractional pore volume filled indicated that, for the polymeric resins, solute uptake cannot be viewed as only a surface adsorption phenomenon. It is suggested that the aqueous phase uptake of phenol, toluene, chlorobenzene, and benzoic acid by the polymeric resins is attributable, in part, to solute absorption. The present study also suggests that solute uptake is affected by the swelling of some of the polymeric resins in water.

Gusler, G.M.; Browne, T.E.; Cohen, Y. (Univ. of California, Los Angeles, CA (United States). Dept. of Chemical Engineering)

1993-11-01

469

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

470

Polysaccharide-Modified Synthetic Polymeric Biomaterials  

PubMed Central

This review presents an overview of polysaccharide-conjugated synthetic polymers and their use in tissue-engineered scaffolds and drug-delivery applications. This topic will be divided into four categories: (1) polymeric materials modified with non-mammalian polysaccharides such as alginate, chitin, and dextran; (2) polymers modified with mammalian polysaccharides such as hyaluronan, chondroitin sulfate, and heparin; (3) multi-polysaccharide-derivatized polymer conjugate systems; and (4) polymers containing polysaccharide-mimetic molecules. Each section will discuss relevant conjugation techniques, analysis, and the impact of these materials as micelles, particles, or hydrogels used in in-vitro and in-vivo biomaterial applications.

Baldwin, Aaron D.; Kiick, Kristi L.

2010-01-01

471

New Polymeric Membrane Electrode for Azithromycin Determination  

Microsoft Academic Search

A new polymeric membrane electrode has been developed for the determination of azithromycin. The electrode was constructed by incorporating the azithromycin?tetraiodomercurate ion pair complex into a polyvinylchloride matrix plasticized by nitrobenzene. This sensor exhibited good linear response (?29.8 mV\\/decade) over the concentration range 1.0×10–7.0×10 M, using a mixed solution as supporting electrolyte containing phosphate buffer (pH=6.5; I=0.1 M) and acetonitrile (3?1, v\\/v). The

M. Rachidi; J. Elharti; K. Digua; Y. Cherrah; A. Bouklouze

2007-01-01

472

Polymerization of 1-Naphthylamine by DC discharge  

NASA Astrophysics Data System (ADS)

Thin polymer films from 1-naphthylamine have been obtained for the first time by polymerization at the cathode and anode in DC discharge. The morphology of the films synthesized at the cathode was examined by SEM and AFM. The elemental composition, chemical structure, and thermal stability of the polymer have been studied by pyrolysis chromatography, IR and UV spectroscopy, and thermogravimetry, respectively. The surface contact properties of the films and their thickness have been determined with a microinterferometer. Polymer was also investigated by ESR method.

Gilman, A.; Yablokov, M.; Augustyniak-Jablokov, M.; Tadyszak, K.; Kuznetsov, A.

2012-12-01

473

Stimuli-responsive supramolecular polymeric materials.  

PubMed

Supramolecular materials, dynamic materials by nature, are defined as materials whose components are bridged via reversible connections and undergo spontaneous and continuous assembly/disassembly processes under specific conditions. On account of the dynamic and reversible nature of noncovalent interactions, supramolecular polymers have the ability to adapt to their environment and possess a wide range of intriguing properties, such as degradability, shape-memory, and self-healing, making them unique candidates for supramolecular materials. In this critical review, we address recent developments in supramolecular polymeric materials, which can respond to appropriate external stimuli at the fundamental level due to the existence of noncovalent interactions of the building blocks. PMID:22618080

Yan, Xuzhou; Wang, Feng; Zheng, Bo; Huang, Feihe

2012-05-22

474

Catalyst composition for polymerizing alpha-olefins  

SciTech Connect

A process is described for preparing a supported catalyst composition for use in alpha-olefin polymerization reactions. The process consists essentially of the following steps in the recited order: (i) contacting a solid, porous carrier having reactive OH groups with a liquid; (ii) removing the liquid from step (i) to obtain a magnesium-containing carrier in the form of a dry, free-flowing powder; and (iii) contacting the powder of step (ii) with a solution comprising a liquid medium, an aluminum-containing brominating and/or chlorinating agent.

Nowlin, T.E.

1986-10-21

475

Novel hybrid polymeric materials for barrier coatings  

NASA Astrophysics Data System (ADS)

Polymer-clay nanocomposites, described as the inclusion of nanometer-sized layered silicates into polymeric materials, have been widely researched due to significant enhancements in material properties with the incorporation of small levels of filler (1--5 wt.%) compared to conventional micro- and macro-composites (20--30 wt.%). One of the most promising applications for polymer-clay nanocomposites is in the field of barrier coatings. The development of UV-curable polymer-clay nanocomposite barrier coatings was explored by employing a novel in situ preparation technique. Unsaturated polyesters were synthesized in the presence of organomodified clays by in situ intercalative polymerization to create highly dispersed clays in a precursor resin. The resulting clay-containing polyesters were crosslinked via UV-irradiation using donor-acceptor chemistry to create polymer-clay nanocomposites which exhibited significantly enhanced barrier properties compared to alternative clay dispersion techniques. The impact of the quaternary alkylammonium organic modifiers, used to increase compatibility between the inorganic clay and organic polymer, was studied to explore influence of the organic modifier structure on the nanocomposite material properties. By incorporating just the organic modifiers, no layered silicates, into the polyester resins, reductions in film mechanical and thermal properties were observed, a strong indicator of film plasticization. An alternative in situ preparation method was explored to further increase the dispersion of organomodified clay within the precursor polyester resins. In stark contrast to traditional in situ polymerization methods, a novel "reverse" in situ preparation method was developed, where unmodified montmorillonite clay was added during polyesterification to a reaction mixture containing the alkylammonium organic modifier. The resulting nanocomposite films exhibited reduced water vapor permeability and increased mechanical properties. The novel preparation of hybrid films coupling the advantageous properties of organic-inorganic hybrids formed through sol-gel chemistry with polymer-clay nanocomposite technology was also explored. Alkoxysilane-functional copolymer-clay nanocomposites were first synthesized, followed by crosslinking via simultaneous hydrolysis and condensation reactions to create the novel hybrid barrier films. By dispersing organomodified clay throughout the hybrid network, dramatic improvements in several film properties were observed, particularly regarding the viscoelastic properties. Additional studies with the same organic-inorganic preparation technique were performed to incorporate amine-functionality into the hybrid film for potential applications as protective membranes in carbon dioxide capture and separation technologies. Finally, controlled free-radical polymerization techniques were combined with the preparation of the organic-inorganic hybrids.

Pavlacky, Erin Christine

476

Multiphoton polymerization using optical trap assisted nanopatterning  

NASA Astrophysics Data System (ADS)

In this letter, we show the combination of multiphoton polymerization and optical trap assisted nanopatterning (OTAN) for the additive manufacturing of structures with nanometer resolution. User-defined patterns of polymer nanostructures are deposited on a glass substrate by a 3.5 ?m polystyrene sphere focusing IR femtosecond laser pulses, showing minimum feature sizes of ?/10. Feature size depends on the applied laser fluence and the bead surface spacing. A finite element model describes the intensity enhancement in the microbead focus. The results presented suggest that OTAN in combination with multiphoton processing is a viable technique for additive nanomanufacturing with sub-diffraction-limited resolution.

Leitz, Karl-Heinz; Tsai, Yu-Cheng; Flad, Florian; Schäffer, Eike; Quentin, Ulf; Alexeev, Ilya; Fardel, Romain; Arnold, Craig B.; Schmidt, Michael

2013-06-01

477

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

478

Diffusive transport in modern polymeric materials  

SciTech Connect

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Polymers, composites, and synthetic modern materials are replacing traditional materials in many older scientific, engineering, commercial, and military applications. This project sought to focus on the new polymeric materials, deriving and analyzing models that predict their seemingly mysterious transport properties. It sought to identify the dominant physical mechanisms and the pertinent dimensionless parameters, produce viable theoretical models, and devise asymptotic and numerical methods for use in specific problems.

Doering, C.; Bier, M.; Christodoulou, K. [and others

1996-10-01

479

Physical properties of a single polymeric nanofiber  

NASA Astrophysics Data System (ADS)

The nanostructural and elastic properties of a single polymeric nanofiber extracted from a nanofibrous scaffold are investigated using atomic force microscopy (AFM). AFM imaging of the nanofibers reveals a ``shish-kebab'' structure. A portion of the nanofiber is suspended over a microscale groove etched on a silicon wafer. A nanoscale three-point bend test is performed to obtain the elastic modulus. This elastic modulus is found to be 1.0+/-0.2 GPa for fibers less than 350 nm but decrease with increase in fiber diameter in excess of 350 nm. This is due to the significance of shear deformation as the length to diameter ratio decreases.

Tan, E. P. S.; Lim, C. T.

2004-03-01

480

Radiation-induced graft polymerization of amphiphilic monomers with different polymerization characteristics onto hydrophobic polysilane  

NASA Astrophysics Data System (ADS)

The structures of poly(methyl-n-propylsilane) (PMPrS) amphiphilically modified through ?-ray-induced graft polymerization were investigated with 1H NMR measurement. By the use of methyl methacrylate (MMA) or diethyl fumarate (DEF) as monomers for the graft polymerization, grafting yield rose with increasing total absorption dose and monomer concentrations, but decreas