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1

Development of a polymeric nanoparticulate delivery system for indocyanine green  

NASA Astrophysics Data System (ADS)

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

Saxena, Vishal

2

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

NASA Astrophysics Data System (ADS)

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

Khurana, Jatin

3

High performance gene delivery polymeric vector: nano-structured cationic star polymers (star vectors).  

PubMed

Nano-structured hyperbranched cationic star polymers, called star vectors, were molecularly designed for a novel gene delivery non-viral vector. The linear and 3, 4 or 6 branched water-soluble cationic polymers, which had same molecular weight of ca. 18,000, were synthesized by iniferter (initiator-transfer agent-terminator)-based photo-living-radical polymerization of 3-(N,N-dimethylamino)propyl acrylamide, initiated from respective multi-dithiocarbamate-derivatized benzenes as an iniferter. All polymers produced polyion complexes 'polyplexes' by mixing with pDNA (pGL3-control plasmid), in which the particle size was ca. 250 nm in diameter [the charge ratio < 2/1 (vevtor/pDNA)] and ca. 150 nm (the charge ratio > 2.5/1), and the zeta-potential was ca. +10 mV (the charge ratio > 1/1). When COS-1 cells were incubated with the polyplexes 12 h after preparation under the charge ratio of 5/1, higher gene expression was obtained as an increase in branching, with a little cytotoxicity. The relative gene expression to the linear polymer was about 2, 5, and 10 times in 3-, 4-, and 6-branched polymers, respectively. The precise change in branching of polymers enabled the control of the gene transfer activity. PMID:16305408

Nakayama, Yasuhide; Masuda, Takeshi; Nagaishi, Makoto; Hayashi, Michiko; Ohira, Moto; Harada-Shiba, Mariko

2005-01-01

4

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

PubMed

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

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

2014-01-01

5

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

6

Hyperbranched polymeric "star vectors" for effective DNA or siRNA delivery.  

PubMed

Although gene therapy offers an attractive strategy for treating inherited disorders, current techniques using viral and nonviral delivery systems have not yielded many successful results in clinical trials. Viral vectors such as retroviruses, lentiviruses, and adenoviruses deliver genes efficiently; however, the possibility of negative outcomes from viral transformation cannot be completely ruled out. In contrast, various types of nonviral vectors are attracting considerable attention because they are easier to handle and induce weak immune responses. Cationic polymers, such as polyethylenimine (PEI) and poly(N,N-dimethylaminopropyl acrylamide) (PDMAPAAm), can generate nanoparticles through the formation of polyion complexes, "polyplexes" with DNA. These nonviral systems offer many advantages over viral systems. The primary obstacle to implementing these cationic polymers in an effective gene therapy remains their comparatively inefficient gene transfection in vivo. We describe four strategies for the development of hyperbranched star vectors (SVs) for enhancing DNA or siRNA delivery. The molecular design was performed by living radical polymerization in which the chain length can be controlled by photoirradiation and solution conditions, including concentrations of the monomer or iniferter (a molecule that serves as a combination of initiator, transfer agent, and terminator). The branch composition is controlled by the types of monomers that are added stepwise. In our first strategy, we prepared a series of only cationic PDMAPAAm-based SVs with no branches or 3, 4, or 6 branching numbers. These SVs could form polyion complexes (polyplexes) by mixing with DNA only in aqueous solution. The relative gene expression activity of the delivered DNA increased according to the degree of branching. In addition, increasing the molecular weight of SVs and narrowing their polydispersity index (PDI) improved their activity. For targeting DNA delivery to the specific cells, we modified the SV with ligands. Interestingly, the SV could adsorb the RGD peptide, making gene transfer possible in endothelial cells which are usually refractory to such treatments. The peptide was added to the polyplex solution without covalent derivatization to the SV. The introduction of additional branching by cross-linking using iniferter-induced coupling reactions further improved gene transfection activity. After block copolymerization of PDMAPAAm-based SVs with a nonionic monomer (DMAAm), the blocked SVs (BSVs) produced polyplexes with DNA that had excellent colloidal stability for 1 month, leading to efficient in vitro and in vivo gene delivery. Moreover, BSVs served as carriers for siRNA delivery. BSVs enhanced siRNA-mediated gene silencing in mouse liver and lung. As an alternative approach, we developed a novel gene transfection method in which the polyplexes were kept in contact with their deposition surface by thermoresponsive blocking of the SV. This strategy was more effective than reverse transfection and the conventional transfection methods in solution. PMID:22353143

Nakayama, Yasuhide

2012-07-17

7

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

PubMed

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

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

2014-02-01

8

C2H2 treatment as a facile method to boost the catalysis of Pd nanoparticulate catalysts.  

PubMed

A facile method to boost the catalysis of Pd nanoparticulate catalysts by simple C2H2 treatment is developed. During the C2H2 treatment, Pd nanoparticles serve as active catalysts to polymerize C2H2 into trans-polyacetylene. The deposition of trans-polyacetylene layer on Pd nanoparticles makes their surface hydrophobic. Such a hydrophobic surface modification helps to accumulate more hydrophobic substrates during catalysis, making the modified Pd nanoparticulate catalysts more active than untreated catalysts in the catalytic reaction involving hydrophobic substrates. Moreover, the coating of polyacetylene on Pd creates encapsulated Pd nanocatalysts, stabilizing Pd nanoparticles against sintering or aggregation. Since the catalytic polymerization of polyacetylene on Pd is not facet dependent, the development is readily applied to enhance the catalysis of commercial Pd nanoparticulate catalysts by simple C2H2 treatment. PMID:24670007

Dai, Yan; Liu, Shengjie; Zheng, Nanfeng

2014-04-16

9

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.

10

Toxicological characteristics of nanoparticulate anatase titanium dioxide in mice  

Microsoft Academic Search

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

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

2010-01-01

11

An investigation on the antibacterial and antibiofilm efficacy of cationic nanoparticulates for root canal disinfection.  

PubMed

This study aimed to investigate the antibacterial and antibiofilm efficacy of cationic nanoparticulates for root canal disinfection. Experiments were performed in two stages. In stage 1, experiments were conducted to examine the physical properties of three types of nanoparticulates. The antibacterial properties of nanoparticulates alone and nanoparticulates mixed with zinc oxide-eugenol-based sealer were studied. In stage 2, the ability of nanoparticulates-treated dentin to prevent bacterial adherence was examined. Zinc oxide nanoparticulates, chitosan nanoparticulates, a mixture of zinc oxide and chitosan nanoparticulates, and zinc oxide nanoparticulates with multilayered coating of chitosan were tested. This study showed that the incorporation of nanoparticulates did not alter the flow characteristics of sealer but improved the direct antibacterial property and the ability to leach out antibacterial components. There was a significant reduction in the adherence of Enterococcus faecalis to nanoparticulates-treated dentin (p < 0.05). These experiments highlighted the potential advantage of nanoparticulates in root canal disinfection. PMID:19026885

Kishen, Anil; Shi, Zhilong; Shrestha, Annie; Neoh, Koon Gee

2008-12-01

12

An Investigation on the Antibacterial and Antibiofilm Efficacy of Cationic Nanoparticulates for Root Canal Disinfection  

Microsoft Academic Search

This study aimed to investigate the antibacterial and antibiofilm efficacy of cationic nanoparticulates for root canal disinfection. Experiments were performed in two stages. In stage 1, experiments were conducted to examine the physical properties of three types of nanoparticulates. The antibacterial properties of nanoparticulates alone and nanoparticulates mixed with zinc oxide–eugenol–based sealer were studied. In stage 2, the ability of

Anil Kishen; Zhilong Shi; Annie Shrestha; Koon Gee Neoh

2008-01-01

13

Treatment of lung cancer via telomerase inhibition: self-assembled nanoplexes versus polymeric nanoparticles as vectors for 2'-O-Methyl-RNA.  

PubMed

Antisense oligonucleotide, 2'-O-Methyl-RNA (OMR), is known as potent telomerase inhibitor for the treatment of lung cancer but limited by poor intracellular uptake. Chitosan-coated polymeric nanoparticles were compared to chitosan solution as non-viral vectors for OMR. The study investigated the role of chitosan properties and concentration in improving the efficiency of the nanocarriers in terms of loading, viability, cellular uptake, and telomerase inhibition in human lung cancer cell lines. Certain concentration of chitosan on nanoparticle surface is necessary to significantly increase the cellular uptake. However, excessive chitosan negatively affected the transfection efficiency. Self-assembled nanoplexes with chitosan polymer are preferentially adsorbed to the cell membrane rather than being internalized. Thus, polymeric nanoparticles proved to be superior to cationic polymers as carrier for antisense oligonucleotides. Charge cannot be considered the principle factor behind improved transfection. Uptake studies carried out on air-interface cell cultures to mimic in vivo conditions supported the results on normal cultures showing enhanced uptake of nanoplexes over naked oligonucleotides. OMR nanoplexes reduced telomerase activity by ?50% in A549 cells concluding the potential of the system as a safe, non-invasive, and efficient treatment for lung carcinoma. These data are prerequisites for the ongoing studies on lung perfusion model and in vivo experiments. PMID:22198416

Nafee, N; Schneider, M; Friebel, K; Dong, M; Schaefer, U F; Mürdter, T E; Lehr, C-M

2012-04-01

14

Polymeric vector-mediated gene transfection of MSCs for dual bioluminescent and MRI tracking in vivo.  

PubMed

MSC's transplantation is a promising cell-based therapy for injuries in regenerative medicine, and in vivo visualization of transplanted MSCs with noninvasive technique is essential for the tracking of cell infusion and homing. A new cationic polymer, poly(ethylene glycol)-block-poly(l-aspartic acid)-grafted polyethylenimine functionalized with superparamagnetic iron oxide nanoparticles (PAI/SPION), was constructed as a magnetic resonance imaging (MRI)-visible non-viral vector for the delivery of plasmids DNA (pDNA) encoding for luciferase and red fluorescence protein (RFP) as reporter genes into MSCs. As a result, the MSCs were labeled with SPION and reporter genes. The PAI/SPION complexes exhibited high transfection efficiency in transferring pDNA into MSCs, which resulted in efficient luciferase and RFP co-expression. Furthermore, the complexes did not significantly affect the viability and multilineage differentiation capacity of MSCs. After the labeled MSCs were transplanted into the rats with acute liver injury via the superior mesenteric vein (SMV) injection, the migration behavior and organ-specific accumulation of the cells could be effectively monitored using the in vivo imaging system (IVIS) and MRI, respectively. The immunohistochemical analysis further confirmed that the transplanted MSCs were predominantly distributed in the liver parenchyma. Our results indicate that the PAI/SPION is a MRI-visible gene delivery agent which can effectively label MSCs to provide the basis for bimodal bioluminescence and MRI tracking in vivo. PMID:24976241

Wu, Chun; Li, Jingguo; Pang, Pengfei; Liu, Jingjing; Zhu, Kangshun; Li, Dan; Cheng, Du; Chen, Junwei; Shuai, Xintao; Shan, Hong

2014-09-01

15

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

16

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

17

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

18

Mechanisms of Tumor Vascular Priming by a Nanoparticulate Doxorubicin Formulation  

PubMed Central

Purpose Tumor vascular normalization by antiangiogenic agents may increase tumor perfusion but reestablish vascular barrier properties in CNS tumors. Vascular priming via nanoparticulate carriers represents a mechanistically distinct alternative. This study investigated mechanisms by which sterically-stabilized liposomal doxorubicin (SSL-DXR) modulates tumor vascular properties. Methods Functional vascular responses to SSL-DXR were investigated in orthotopic rat brain tumors using deposition of fluorescent permeability probes and dynamic contrast-enhanced magnetic resonance imaging. Microvessel density and tumor burden were quantified by immunohistochemistry (CD-31) and quantitative RT-PCR (VE-cadherin). Results Administration of SSL-DXR (5.7 mg/kg iv) initially (3–4 days post-treatment) decreased tumor vascular permeability, ktrans (vascular exchange constant), vascular endothelial cell content, microvessel density, and deposition of nanoparticulates. Tumor vasculature became less chaotic. Permeability and perfusion returned to control values 6–7 days post-treatment, but intratumor SSL-DXR depot continued to effect tumor vascular endothelial compartment 7–10 days post-treatment, mediating enhanced permeability. Conclusions SSL-DXR ultimately increased tumor vascular permeability, but initially normalized tumor vasculature and decreased tumor perfusion, permeability, and nanoparticulate deposition. These temporal changes in vascular integrity resulting from a single SSL-DXR dose have important implications for the design of combination therapies incorporating nanoparticle-based agents for tumor vascular priming.

Chaudhuri, Tista Roy; Arnold, Robert D.; Yang, Jun; Turowski, Steven G.; Qu, Yang; Spernyak, Joseph A.; Mazurchuk, Richard; Mager, Donald E.

2013-01-01

19

Thermal stability and reconstruction of nanoparticulate Au film on model molecular surfaces  

Microsoft Academic Search

Thermally activated morphological reconstruction of nanoparticulate gold films deposited onto model molecular surfaces was investigated at 200?°C as a function of the annealing time. Results show a strong correlation of the spatial reorganization of the metallic particles to the surface chemistry of the underlying substrate. On the nonpolar surface, the thin nanoparticulate Au film dewets by the formation of randomly

K. Mougin; Z. Zheng; N. Piazzon; E. Gnecco; H. Haidara

2009-01-01

20

The use of nanoparticulate delivery systems in metronomic chemotherapy.  

PubMed

Metronomic chemotherapy aiming at inhibiting tumor angiogenesis with conventional chemotherapeutics is a promising strategy for antiangiogenic cancer therapy. However, current metronomic chemotherapy mainly focuses on free small-molecule drugs, without any effort to achieve tumor-specific biodistribution, which may lead to long-term toxicity concerns. Metronomic chemotherapy using nanoparticulate drug delivery system (DDS) offers significant upside to reduce off-target side effects, decrease accumulated dose, and enhance the efficacy of tumor vessel targeting without compromising antitumor efficacy; but there has been a lack of thorough experimental data describing the targeted metronomic chemotherapy. Here, we develop a new nanoparticulate DDS, SP5.2 peptide conjugated, Flt-1 (VEGFR-1) targeted nanoparticles for docetaxel (SP5.2-DTX-NP), as a model for the investigation of targeted metronomic chemotherapy with respect to both antitumor efficacy and toxicity. The results demonstrate that metronomic SP5.2-DTX-NP exerts antitumor activity mainly through the antiangiogenic effect of docetaxel, which is specifically delivered into the tumor vascular endothelial cells through the nanoparticle internalization mediated by the interaction of SP5.2 and over-expressed Flt-1 receptors on tumor vessels. Moreover, the antitumor efficacy of targeted metronomic chemotherapy is better than that of the treatment with the DDS given in the maximum tolerated dose (MTD) regimen, which is shown in significantly prolonged mice survival and minimal drug-associated toxicity (bone marrow suppression, hematological toxicity, and mucosal injury of small intestine). The present research reveals and highlights the significance of targeted metronomic therapy with nanoparticulate DDS in antiangiogenic cancer therapy. PMID:23465835

Yu, De-Hong; Ban, Fu-Qiang; Zhao, Mei; Lu, Qin; Lovell, Jonathan F; Bai, Fan; Wang, Chao; Guan, Ying-Yun; Luan, Xin; Liu, Ya-Rong; Fang, Chao; Chen, Hong-Zhuan

2013-05-01

21

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

22

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

23

Nanoparticulate formulations of mithramycin analogs for enhanced cytotoxicity  

PubMed Central

Mithramycin (MTM), a natural product of soil bacteria from the Streptomyces genus, displays potent anticancer activity but has been limited clinically by severe side effects and toxicities. Engineering of the MTM biosynthetic pathway has produced the 3-side-chain-modified analogs MTM SK (SK) and MTM SDK (SDK), which have exhibited increased anticancer activity and improved therapeutic index. However, these analogs still suffer from low bioavailability, short plasma retention time, and low tumor accumulation. In an effort to aid with these shortcomings, two nanoparticulate formulations, poly(ethylene glycol)-poly(aspartate hydrazide) self-assembled and cross-linked micelles, were investigated with regard to the ability to load and pH dependently release the drugs. Micelles were successfully formed with both nanoparticulate formulations of each drug analog, with an average size of 8.36 ± 3.21 and 12.19 ± 2.77 nm for the SK and SDK micelles and 29.56 ± 4.67 nm and 30.48 ± 7.00 nm for the SK and SDK cross-linked micelles respectively. All of the drug-loaded formulations showed a pH-dependent release of the drugs, which was accelerated as pH decreased from 7.4 to 5.0. The micelles retained biological activity of SK and SDK entrapped in the micelles, suppressing human A549 lung cancer cells effectively.

Scott, Daniel; Rohr, Jurgen; Bae, Younsoo

2011-01-01

24

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

2013-07-23

25

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

26

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

Microsoft Academic Search

BACKGROUND: Drug resistance is a primary hindrance for the efficiency of chemotherapy against osteosarcoma. Although chemotherapy has improved the prognosis of osteosarcoma patients dramatically after introduction of neo-adjuvant therapy in the early 1980's, the outcome has since reached plateau at approximately 70% for 5 year survival. The remaining 30% of the patients eventually develop resistance to multiple types of chemotherapy.

Michiro Susa; Arun K Iyer; Keinosuke Ryu; Francis J Hornicek; Henry Mankin; Mansoor M Amiji; Zhenfeng Duan

2009-01-01

27

Olefin polymerization  

SciTech Connect

This patent describes a process for polymerizing an alpha-olefin, it comprises: contacting the alpha-olefin under polymerization conditions with a catalytic amount of a catalyst system comprising a catalyst produced by contacting an inorganic lanthanide halide with an ether in a suitable diluent, then contacting the resulting lanthanide composition with an alkali metal alkyl stabilized against beta-hydride elimination, and depositing the resulting lanthanide product on a particulate support.

Martin, S.J.; McDaniel, M.P.; Martin, C.; Martin, B.K.; Martin, J.L.

1992-04-14

28

Polymeric nitrogen  

Microsoft Academic Search

Ab initio local-density functional total-energy calculations indicate that a polymeric form should be the stable phase of nitrogen above [approximately] 35 GPa, and that such a polyermic phase is likely to be both energetic and metastable at atmospheric pressure. These results also suggest that such a polymeric form of nitrogen may survive metastably at atompsheric pressure as an energetic, high-melting

C. Mailhiot; L. H. Yang; A. K. McMahan

1992-01-01

29

Nanoparticules d'or: De l'imagerie par resonance magnetique a la radiosensibilisation  

NASA Astrophysics Data System (ADS)

Cette thèse approfondit l'étude de nanoparticules d'or de 5 nm de diamètre recouvertes de diamideéthanethioldiethylènetriaminepentacétate de gadolinium (DTDTPA:Gd), un agent de contraste pour l'imagerie par résonance magnétique (IRM). En guise de ciblage passif, la taille des nanoparticules a été contrôlée afin d'utiliser le réseau de néovaisseaux poreux et perméable des tumeurs. De plus les tumeurs ont un drainage lymphatique déficient qui permet aux nanoparticules de demeurer plus longtemps dans le milieu interstitiel de la tumeur. Les expériences ont été effectuées sur des souris Balb/c femelles portant des tumeurs MC7-L1. La concentration de nanoparticules a pu être mesurée à l'IRM in vivo. La concentration maximale se retrouvait à la fin de l'infusion de 10 min. La concentration s'élevait à 0.3 mM dans la tumeur et de 0.12 mM dans le muscle environnant. Les nanoparticules étaient éliminées avec une demi-vie de 22 min pour les tumeurs et de 20 min pour le muscle environnant. Les nanoparticules ont été fonctionnalisées avec le peptide Tat afin de leur conférer des propriétés de ciblage actif La rétention de ces nanoparticules a ainsi été augmentée de 1600 %, passant d'une demi-vie d'élimination de 22 min à 350 min. La survie des souris a été mesurée à l'aide de courbes Kaplan-Meier et d'un modèle mathématique évalue l'efficacité de traitements. Le modèle nous permet, à l'aide de la vitesse de croissance des tumeurs et de l'efficacité des traitements, de calculer la courbe de survie des spécimens. Un effet antagoniste a été observé au lieu de l'effet synergétique attendu entre une infusion de Au@DTDTPA:Gd et l'irradiation aux rayons X. L'absence d'effet synergétique a été attribuée à l'épaisseur du recouvrement de DTDTPA:Gd qui fait écran aux électrons produits par l'or. De plus, le moyen d'ancrage du recouvrement utilise des thiols qui peuvent s'avérer être des capteurs de radicaux. De plus, contrairement a ce qui était escompté, un effet chimiothérapeutique de ces nanoparticules a été observé in vitro et in vivo. Par contre, le mécanisme précis de cet effet est encore à être expliquer, mais on sait déjà que les nanoparticules d'or affectent les fonctions des macrophages ainsi que l'angiogenèse. MOTS-CLÉS : Radiosensibilisateur, Nanoparticules d'or, Agent de contraste pour l'IRM, Électrons de basses énergies, Kaplan-Meier, Effet chimiothérapeutique.

Hebert, Etienne M.

30

Development and pharmacological evaluation of a PEG based nanoparticulate camptothecin analog for oral administration.  

PubMed

The aim of this study was to formulate polyethylene glycol (PEG) based nanoparticulate camptothecin analog for oral administration and to evaluate its pharmacological activity. Camptothecin analog (CA) belongs to topoisomerase-I inhibitor class of compounds with proven antitumor activity but exhibits poor solubility. To enhance solubility and oral bioavailability, a PEG based nanoparticulate formulation was developed using a high pressure homogenization technique. The saturation solubility and dissolution characteristics of the nanoparticulate formulation were investigated and compared with as-is drug formulation to ascertain the impact of particle size on drug dissolution in physiologically relevant dissolution media. Systemic exposure of nanoparticulate formulation were evaluated in Wistar rats for increase in the rate and extent of drug absorption. The antitumor activity of nanoparticulate formulation was evaluated on human tumor xenografts (NCI-H460 cell lines) grown in athymic nude mice and compared with a positive control, Irinotecan Hydrochloride administered intravenously. The saturation solubility and dissolution rate of the nanoparticulate formulation were significantly higher as compared to as-is drug formulation. Pharmacokinetic (PK) studies in Wistar rats indicated significant increase in the rate and extent of absorption for the nanoparticulate formulation. Pharmacological activity of nanoparticles in athymic nude mice with implanted tumors revealed that the tumor inhibition activity was equivalent to Irinotecan Hydrochloride intravenous formulation with comparable safety profile at lower doses. These studies demonstrated the feasibility of developing a safe and efficacious oral formulation for a sparingly soluble camptothecin analog that may provide a viable, patient compliant and, cost effective option for the treatment of solid tumors. PMID:22313161

Nekkanti, Vijaykumar; Venkateswarlu, Vabalaboina; Ansari, Khalid Akhter; Pillai, Raviraj

2011-11-01

31

Systemic and biophase bioavailability and pharmacokinetics of nanoparticulate drug delivery systems.  

PubMed

The development of the vectorized delivery systems combining advantages of the colloidal carriers, with active targeting to the receptors sites suggests that nanoparticles have a considerable potential for treatment after biophase internalization and pharmacokinetics, as for example gene therapy. Two major mechanisms can be distinguished for addressing the desired sites for drug release: (i) passive and (ii) active targeting. Examples of passive targeting were presented: organ targeting by the Enhanced Permeability and Retention (EPR) effect; targeting the mononuclear phagocitic system; organ targeting by chemoembolization or local (organ) administration;sterical stabilization of nanoparticles (PEGylation). A strategy that could allow active targeting involves the surface functionalization of drug carriers with ligands that are selectively recognized by receptors on the surface of the cells of interest. The source for biophase bioavailability can be the systemic bioavailability following common routes of administration (generally for systemic delivery of medicines), or directly the site specific biophase bioavailability for the formulations capable of cellular or nuclear drug internalization where the drug release only will take place (for nanoparticulate drug delivery systems, DDS). Once the pharmaceutical nanosystem was internalized, begins the release of the active moiety by different mechanisms, as for example the escape from endosome, or biodegradation of the polymer carrier or liberation of the active peptide or gene from a biological construct in the nucleus, etc. The presentation will discusses the pharmacokinetics of drugs after systemic administration but especially the biophase bioavailability and pharmacokinetics after the administration of biotechnology origin of therapeutic proteins like monoclonal antibodies, gene transfer products, plasmid DNAs, nucleotides, antisense oligonucleotides (AODNs) or small interfering RNAs (siRNA). PMID:23116084

Leucuta, Sorin Emilian

2013-04-01

32

Microstructures and Nanostructures for Environmental Carbon Nanotubes and Nanoparticulate Soots  

PubMed Central

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

Murr, L. E.

2008-01-01

33

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

34

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

35

The interplay of catechol ligands with nanoparticulate iron oxides.  

PubMed

The unique properties exhibited by nanoscale materials, coupled with the multitude of chemical surface derivatisation possibilities, enable the rational design of multifunctional nanoscopic devices. Such functional devices offer exciting new opportunities in medical research and much effort is currently invested in the area of "nanomedicine", including: multimodal imaging diagnostic tools, platforms for drug delivery and vectorisation, polyvalent, multicomponent vaccines, and composite devices for "theranostics". Here we will review the surface derivatisation of nanoparticulate oxides of iron and iron@iron-oxide core-shells. They are attractive candidates for MRI-active therapeutic platforms, being potentially less toxic than lanthanide-based materials, and amenable to functionalisation with ligands. However successful grafting of groups onto the surface of iron-based nanoparticles, thus adding functionality whilst preserving their inherent properties, is one of the most difficult challenges for creating truly useful nanodevices from them. Functionalised catechol-derived ligands have enjoyed success as agents for the masking of superparamagnetic iron-oxide particles, often so as to render them biocompatible with medium to long-term colloidal stability in the complex chemical environments of biological milieux. In this perspective, the opportunities and limitations of functionalising the surfaces of iron-oxide nanoparticles, using coatings containing a catechol-derived anchor, are analysed and discussed, including recent advances using dopamine-terminated stabilising ligands. If light-driven ligand to metal charge transfer (LMCT) processes, and pH-dependent ligand desorption, leading to nanoparticle degradation under physiologically relevant conditions can be suppressed, colloidal stability of samples can be maintained and toxicity ascribed to degradation products avoided. Modulation of the redox behaviour of iron catecholate systems through the introduction of an electron-withdrawing substituent to the aromatic ?-system of the catechol is a promising approach towards achieving these goals. PMID:22241454

Yuen, Alexander K L; Hutton, Georgina A; Masters, Anthony F; Maschmeyer, Thomas

2012-03-01

36

Physclips: Vectors  

NSDL National Science Digital Library

This website provides an introduction to vectors. It includes topics such as magnitude and direction, components, unit vectors, vectors in three dimensions, vector addition and subtraction, and scalar and vector products. Animations, still images, graphs, and diagrams are used to illustrate important concepts. This tutorial is part of the PhysClips collection of web-based resources on introductory mechanics, electricity, and magnetism.

Wolfe, Joe

2009-01-20

37

Systematic Performance Evaluation of Nanoparticulate ZnO Thin Film Based Chemoresistive Sensor for Food Safety  

Microsoft Academic Search

Volatile organic compounds (VOCs) such as organic acids released by bacterial pathogens is being used as an indicator for detecting microbial contamination in food by our research group. One of our current research thrust is to develop novel sensor that will be sensitive to a specific compounds (at room or low operating temperature) associated with food safety. Nanoparticulate zinc oxide

Sindhuja Sankaran; Suranjan Panigrahi

38

Optimal Cytocompatibility of a Bioceramic Nanoparticulate Cement in Primary Human Mesenchymal Cells  

Microsoft Academic Search

IntroductionThe aim of this study was to evaluate and compare the cytotoxic effects of BioAggregate (Innovative BioCaramix Inc, Vancouver, BC, Canada), a novel bioceramic nanoparticulate cement, on human mesenchymal cells. White Pro-Root MTA (Dentsply, Tulsa Dental, Tulsa, OK) was used as a reference for comparison.

Gustavo De-Deus; Antonio Canabarro; Gutemberg Alves; Adriana Linhares; Maria Isabel Senne; Jose Mauro Granjeiro

2009-01-01

39

Comparison between aesthetic and thermal performances of copper oxide and titanium dioxide nano-particulate coatings  

Microsoft Academic Search

Nano-particulate coatings with high reflectance against solar irradiation can control undesirable thermal heating by sunlight absorption. It can reduce the energy consumption for air conditioning of houses and cars. For the objects covered by these coatings and subjected to human sight, e.g. roofing surfaces, high dazzle of reflected visible light can offend the human eyes and spoil the fine view

Mehdi Baneshi; Shigenao Maruyama; Atsuki Komiya

2011-01-01

40

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

41

Design issues for improved environmental performance of dye-sensitized and organic nanoparticulate solar cells  

Microsoft Academic Search

Though environmental improvement has been claimed for the application of nanotechnology to solar cells, several characteristics of the fullerene-based organic, and the dye-sensitized nanoparticulate, solar cell are not conducive to such improvement. These include relatively high energy and materials inputs in the production of nanoparticles, a relatively low solar radiation to electricity conversion efficiency, a relatively short service life, the

L. Reijnders

2010-01-01

42

Experimental Study of the Photocatalytic Degradation of Formaldehyde in Indoor Air using a Nano-particulate Titanium Dioxide Photocatalyst  

Microsoft Academic Search

Formaldehyde in the indoor environment may be degraded using nano-particulate titanium dioxide (TiO2) photocatalysis to improve air quality. In the work described, a polytetrafluoroethylene filter is employed as the substrate for a nano-particulate TiO2 coating. This is mounted in an experimental setup developed for the tests, similar to an actual air purification system, which are conducted at room temperature. The

Huili Yu; Kaili Zhang; Carole Rossi

2007-01-01

43

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

44

Analytical Electron Microscopy for Characterization of Fluid or Semi-Solid Multiphase Systems Containing Nanoparticulate Material  

PubMed Central

The analysis of nanomaterials in pharmaceutical or cosmetic preparations is an important aspect both in formulation development and quality control of marketed products. Despite the increased popularity of nanoparticulate compounds especially in dermal preparations such as emulsions, methods and protocols of analysis for the characterization of such systems are scarce. This work combines an original sample preparation procedure along with different methods of analytical electron microscopy for the comprehensive analysis of fluid or semi-solid dermal preparations containing nanoparticulate material. Energy-filtered transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy and high resolution imaging were performed on model emulsions and a marketed product to reveal different structural aspects of both the emulsion bulk phase and incorporated nanosized material. An innovative analytical approach for the determination of the physical stability of the emulsion under investigation is presented. Advantages and limitations of the employed analytical imaging techniques are highlighted.

Klang, Victoria; Valenta, Claudia; Matsko, Nadejda B.

2013-01-01

45

Nanoparticulates for Antibiofilm Treatment and Effect of Aging on Its Antibacterial Activity  

Microsoft Academic Search

IntroductionIssues pertaining to the effective elimination of bacterial biofilm and disruption of biofilm structure still remains in endodontic disinfection. Nanoparticulates such as chitosan (CS-np) and zinc oxide (ZnO-np) are known to possess significant antibacterial properties. This study aimed to test (1) the efficacy of CS-np and ZnO-np in disinfecting and disrupting biofilm bacteria and (2) the long-term efficacy of these

Annie Shrestha; Shi Zhilong; Neoh Koon Gee; Anil Kishen

2010-01-01

46

Inactivation of Escherichia coli by nanoparticulate zerovalent iron and ferrous ion.  

PubMed

The mechanism of Escherichia coli inactivation by nanoparticulate zerovalent iron (nZVI) and Fe(II) was investigated using reactive oxygen species (ROS) quenchers and probes, an oxidative stress assay, and microscopic observations. Disruption of cell membrane integrity and respiratory activity was observed under deaerated conditions [more disruption by nZVI than Fe(II)], and OH or Fe(IV) appears to play a role. PMID:20870787

Kim, Jee Yeon; Park, Hee-Jin; Lee, Changha; Nelson, Kara L; Sedlak, David L; Yoon, Jeyong

2010-11-01

47

NCL supports the first biocompatible NIST nanoparticulate reference material - Nanotechnology Characterization Laboratory  

Cancer.gov

In late December 2007, the National Institute of Standards and Technology (NIST) released its first reference standards for nanoscale particles targeted for the biomedical research community. The new nanoparticulate reference materials (RMs) consist of colloidal gold nanoparticles with nominal diameters of 10, 30, and 60 nanometers (nm) in suspension. Production of these RMs was supported in part by the National Cancer Institute (NCI) Alliance for Nanotechnology in Cancer and the Nanotechnology Characterization Laboratory (NCL) at NCI-Frederick.

48

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

49

The effect of drying on dispersions of nano-particulate titanium dioxide in ethylene glycol  

Microsoft Academic Search

This paper first demonstrates that the UV attenuation of a well-milled aqueous dispersion of nano-particulate rutile TiO2 is 200 times greater than the attenuation of visible 550 nm light. The corresponding UV attenuation of rutile dispersions in ethylene glycol is however only ?50% of that of the aqueous dispersion. It is shown that the different behaviour of suspensions in water and

Terry A. Egerton; Liwei Wang

2008-01-01

50

Photodegradation of an azo dye by silver-doped nano-particulate titanium dioxide  

Microsoft Academic Search

The synthesis of silver doped nano-particulate titanium dioxide (Ag\\/TiO2) using a microemulsion method and an investigation of its photocatalytic activity for the degradation of Acid Red 27 in distilled water under UV-irradiation is reported. The prepared Ag\\/TiO2 is characterized using transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The size of the Ag nanoparticles is around 5–15?nm, with almost

Mir Ghasem Hosseini; Mohammad Shokri; Morteza Khosravi; Reza Najjar; Masih Darbandi

2011-01-01

51

Study of an ultrasound-based process analytical tool for homogenization of nanoparticulate pharmaceutical vehicles.  

PubMed

There are currently no adequate process analyzers for nanoparticulate viscosity enhancers. This article aims to evaluate ultrasonic resonator technology as a monitoring tool for homogenization of nanoparticulate gels. Aqueous dispersions of colloidal microcrystalline cellulose (MCC) and a mixture of clay particles with xanthan gum were compared with colloidal silicon dioxide in oil. The processing was conducted using a laboratory-scale homogenizing vessel. The study investigated first the homogenization kinetics of the different systems to focus then on process factors in the case of colloidal MCC. Moreover, rheological properties were analyzed offline to assess the structure of the resulting gels. Results showed the suitability of ultrasound velocimetry to monitor the homogenization process. The obtained data were fitted using a novel heuristic model. It was possible to identify characteristic homogenization times for each formulation. The subsequent study of the process factors demonstrated that ultrasonic process analysis was equally sensitive as offline rheological measurements in detecting subtle manufacturing changes. It can be concluded that the ultrasonic method was able to successfully assess homogenization of nanoparticulate viscosity enhancers. This novel technique can become a vital tool for development and production of pharmaceutical suspensions in the future. PMID:21412782

Cavegn, Martin; Douglas, Ryan; Akkermans, Guy; Kuentz, Martin

2011-08-01

52

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

53

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.

White, Jeff; Lippis, Matt; Axelrad, Penny; Yowell, Janet; Zarske, Malinda S.

2004-01-01

54

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

55

Polymeric Applications in Electronics  

NASA Technical Reports Server (NTRS)

Training manual shows how to use polymeric materials in fabrication electronic components. Report discusses polymeric applications in fabrication of electronic components and equipment. Intended as training manual for 6-day quality assurance and technician certification course in use of polymeric materials.

Read, W. S.

1983-01-01

56

Development and in vitro evaluation of a thiomer-based nanoparticulate gene delivery system.  

PubMed

Chitosan-thiobutylamidine was developed and evaluated as a novel tool for gene delivery. The conjugate, displaying 299.1+/-11.5 micromol free thiol groups per gram polymer, formed coacervates with pDNA at a mean size of 125 nm and a zeta potential of +9 mV. Thiol groups, being susceptible for oxidation, were immobilised on the polymeric backbone of chitosan in order to introduce the property of extracellular stability and intracellular pDNA release by forming reversible disulfide bonds. The integrity of the new particles was compared to unmodified chitosan under simulated physiological conditions. Within 10h, pDNA was completely released from chitosan-DNA particles while only 12% were released from the thiomer-based particles. At pH 7, the amount of thiol groups significantly (p<0.05) decreased by more than 25% within 6h. In contrast, in a reducing environment as found intracellularly, chitosan-thiobutylamidine-DNA nanoparticles dissociated continuously, liberating approximately 50% of pDNA within 3h. Transfection studies performed in a Caco2 cell culture evinced the highest efficiency for chitosan-thiobutylamidine-DNA nanoparticles in combination with a glycerol shock solution. The combination of improved stability, enhanced pDNA release under reducing conditions, and higher transfection efficiency identifies chitosan-thiobutylamidine as a promising new vector for gene delivery. PMID:16979757

Schmitz, Thierry; Bravo-Osuna, Irene; Vauthier, Christine; Ponchel, Gilles; Loretz, Brigitta; Bernkop-Schnürch, Andreas

2007-01-01

57

Cloning vector  

DOEpatents

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

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

1994-12-27

58

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

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

59

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

PubMed

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

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

2014-04-01

60

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. 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

2013-11-01

61

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

62

Mediatorless bioelectrocatalysis of dioxygen reduction at indium-doped tin oxide (ITO) and ITO nanoparticulate film electrodes  

Microsoft Academic Search

Bilirubin oxidase was immobilised on ITO electrodes: bare or covered by ITO nanoparticulate film. The latter material was obtained by immersion and withdrawal of the substrate into ITO nanoparticles suspension. Formation of a protein deposit was confirmed by scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The electrode surface is covered by a protein film in the form

Ewa Rozniecka; Martin Jonsson-Niedziolka; Janusz W. Sobczak; Marcin Opallo

2011-01-01

63

The Science Behind Nanosun-Screens: Learning about Nanoparticulate Ingredients Used to Block the Sun's Ultraviolet Rays  

ERIC Educational Resources Information Center

In this article, the authors provide a brief overview of the emerging field of nanoscience and why it is an important area of education. They next explain the science behind the new nanoparticulate sunscreens, describe the different elements of the unit, and reflect on some of the opportunities and challenges of teaching nanoscience at the high…

Wise, Alyssa; Schank, Patricia; Stanford, Tina; Horsma, Geri

2009-01-01

64

Toward living radical polymerization.  

PubMed

Radical polymerization is one of the most widely used processes for the commercial production of high-molecular-weight polymers. The main factors responsible for the preeminent position of radical polymerization are the ability to polymerize a wide array of monomers, tolerance of unprotected functionality in monomer and solvent, and compatibility with a variety of reaction conditions. Radical polymerization is simple to implement and inexpensive in relation to competitive technologies. However, conventional radical polymerization severely limits the degree of control that researchers can assert over molecular-weight distribution, copolymer composition, and macromolecular architecture. This Account focuses on nitroxide-mediated polymerization (NMP) and polymerization with reversible addition-fragmentation chain transfer (RAFT), two of the more successful approaches for controlling radical polymerization. These processes illustrate two distinct mechanisms for conferring living characteristics on radical polymerization: reversible deactivation (in NMP) and reversible or degenerate chain transfer (in RAFT). We devised NMP in the early 1980s and have exploited this method extensively for the synthesis of styrenic and acrylic polymers. The technique has undergone significant evolution since that time. New nitroxides have led to faster polymerization rates at lower temperatures. However, NMP is only applicable to a restricted range of monomers. RAFT was also developed at CSIRO and has proven both more robust and more versatile. It is applicable to the majority of monomers subject to radical polymerization, but the success of the polymerization depends upon the selection of the RAFT agent for the monomers and reaction conditions. We and other groups have proposed guidelines for selection, and the polymerization of most monomers can be well-controlled to provide minimal retardation and a high fraction of living chains by using one of just two RAFT agents. For example, a tertiary cyanoalkyl trithiocarbonate is suited to (meth)acrylate, (meth)acrylamide, and styrenic monomers, while a cyanomethyl xanthate or dithiocarbamate works with vinyl monomers, such as vinyl acetate or N-vinylpyrrolidone. With the appropriate choice of reagents and polymerization conditions, these reactions possess most of the attributes of living polymerization. We have used these methods in the synthesis of well-defined homo-, gradient, diblock, triblock, and star polymers and more complex architectures, including microgels and polymer brushes. Applications of these polymers include novel surfactants, dispersants, coatings and adhesives, biomaterials, membranes, drug-delivery media, electroactive materials, and other nanomaterials. PMID:18700787

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

2008-09-01

65

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

66

Olefin polymerization catalyst and process of polymerization  

SciTech Connect

This patent describes a process of producing a lower [alpha]-olefin polymer. It comprises contacting under polymerization conditions one or more lower [alpha]-olefins with an olefin polymerization catalyst obtained by contacting a catalyst component obtained by contacting a magnesium dialkoxide wherein each alkoxide independently has up to 4 carbon atoms conclusive, titanium tetraalkoxide wherein each alkoxide independently has up to 4 carbon atoms inclusive, and a phenolic compound selected from phenol and activating group-substituted phenol, at elevated temperature, with a tetravalent titanium halide and an electron donor, with an organoaluminum cocatalyst and a selectively control agent.

Job, R.C.

1992-09-08

67

Navigational Vectors  

NSDL National Science Digital Library

This is a high school instructional unit that features nine lessons relating to vectors. Users 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 similar to a private pilot certification program. The unit culminates with a pilot flight test. Participants also 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 with teacher registration.

2008-12-10

68

Halley's polymeric organic molecules  

SciTech Connect

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

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

1989-01-01

69

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

70

Halley's polymeric organic molecules  

NASA Astrophysics Data System (ADS)

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

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

71

Halley's polymeric organic molecules  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

72

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

73

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

74

Ligand-Enhanced Reactive Oxidant Generation by Nanoparticulate Zero-Valent Iron and Oxygen  

PubMed Central

The reaction of zero-valent iron or ferrous iron with oxygen produces reactive oxidants capable of oxidizing organic compounds. However, the oxidant yield in the absence of ligands is too low for practical applications. The addition of oxalate, nitrilotriacetic acid (NTA), or ethylenediaminetetraacetic acid (EDTA) to oxygen-containing solutions of nanoparticulate zero-valent iron (nZVI) significantly increases oxidant yield, with yields approaching their theoretical maxima near neutral pH. These ligands improve oxidant production by limiting iron precipitation and by accelerating the rates of key reactions, including ferrous iron oxidation by oxygen and hydrogen peroxide. Product yields indicate that the oxic nZVI system produces hydroxyl radical (OH·) over the entire pH range in the presence of oxalate and NTA. In the presence of EDTA, probe compound oxidation is attributed to OH· under acidic conditions and a mixture of OH· and ferryl ion (Fe[IV]) at circumneutral pH.

Keenan, Christina R.; Sedlak, David L.

2009-01-01

75

Synthesis of nanoparticulate silica composite membranes by the pressurized sol-gel technique  

SciTech Connect

A crack-free silica composite membrane has been synthesized from a nanoparticulate silica sol (particle diameter < 10 nm) by a pressurized sol-gel coating technique developed in this study. The microporous silica layers with an estimated pore radius of 0.78 nm were deposited inside the pores (average pore size of 0.1 [mu]m) of slip cast [alpha]-alumina support tubes. The microstructure of the coated layers was controlled by adjusting sol properties and pressurizing conditions. The room-temperature intrinsic permeability of N[sub 2] through the silica membrane layer after heat treatment at 200 C is about 4.9 [times] 10[sup [minus]12] mol[center dot]m/m[sup 2][center dot]s[center dot]Pa, and the mechanism of gas transport is Knudsen flow. The thermal stability of the silica composite membrane is excellent up to 500 C.

Hyun, S.H.; Kang, B.S. (Yonsei Univ., Seoul (Korea, Republic of). Dept. of Ceramic Engineering)

1994-12-01

76

Antitumor efficacy of doxorubicin released from crosslinked nanoparticulate chondroitin sulfate/chitosan polyelectrolyte complexes.  

PubMed

It is demonstrated that nanoparticulate PEC with a crosslinked shell sustains DOX release and increases DOX activity against cancer cells. CSMA was synthesized to prepare PEC with chitosan. The double bonds among CSMA were used to form a shell crosslink. The released DOX from DOX-loaded PECs against human cancer KB cells and A549 cells were qualitatively traced by confocal laser scanning microscopy and flow cytometry, and quantitatively measured by capillary electrophoresis. All the results implied the DOX-loaded PEC with a crosslinked shell had the best anti-cancer potency of free DOX and the DOX-loaded PEC prepared from pure chondroitin sulfate and chitosan in both the cell lines. PMID:21360679

Tsai, Hun-Yu; Chiu, Chien-Chih; Lin, Ping-Chih; Chen, Su-Hwei; Huang, Shih-Jer; Wang, Li-Fang

2011-05-12

77

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.

78

Novel low voltage and solution processable organic thin film transistors based on water dispersed polymer semiconductor nanoparticulates.  

PubMed

Two novel organic thin film transistor structures that combine a hygroscopic insulator with the use of water-dispersed polymer nanoparticles as the active layer are presented. In the first device structure, the semiconducting layer was fabricated from a nanoparticulate suspension of poly-(3-hexylthiophene) prepared through a mini-emulsion process using sodium dodecyl sulfate as the surfactant whereas a surfactant-free precipitation method has been used for the second device structure. In both cases, fully solution processable transistors have been fabricated in a top gate configuration with hygroscopic poly(4-vinylphenol) as the dielectric layer. Both device structures operate at low voltages (0 to -4V) but exhibit contrasting output characteristics. A systematic study is presented on the effect of surfactant on the synthesis of semiconducting nanoparticles, the formation of thin nanoparticulate films and, consequently, on device performance. PMID:23623401

Darwis, Darmawati; Elkington, Daniel; Ulum, Syahrul; Bryant, Glenn; Belcher, Warwick; Dastoor, Paul; Zhou, Xiaojing

2013-07-01

79

Kinetics of Silica Polymerization.  

National Technical Information Service (NTIS)

The polymerization of silicic acid in geothermal brine-like aqueous solutions to produce amorphous silica in colloidal form has been studied experimentally and theoretically. A large amount of high quality experimental data has been generated over the tem...

A. Yee L. Tsao O. Weres

1980-01-01

80

Organometallic Polymeric Conductors.  

National Technical Information Service (NTIS)

For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductiv...

W. J. Youngs

1997-01-01

81

Antimicrobial Polymeric Surfaces.  

National Technical Information Service (NTIS)

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 comm...

J. C. Tiller C. J. Liao K. Lewis A. M. Klibanov

2005-01-01

82

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

83

Direct electrochemistry of nanoparticulate Fe2O3 in aqueous solution and adsorbed onto tin-doped indium oxide  

Microsoft Academic Search

Nanoparticulate iron oxides occur naturally, for example, in soil, water, and in the cytoplasm of living cells. The redox properties and detection of these nanoparticles are there- fore of considerable importance. Understanding and mimicking nanoparticle-based redox reactions may lead to new types of water-based electrochemical processes. In this study, the electrochemical detection of 4-5 nm diameter Fe2O3 nanoparticles dissolved in

Katy J. McKenzie; Frank Marken

2001-01-01

84

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

Microsoft Academic Search

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

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

2008-01-01

85

Polymeric nitrogen. Revision 1  

Microsoft Academic Search

Ab initio local-density functional total-energy calculations indicate that a polymeric form should be the stable phase of nitrogen above â¼ 35 GPa, and that such a polyermic phase is likely to be both energetic and metastable at atmospheric pressure. These results also suggest that such a polymeric form of nitrogen may survive metastably at atompsheric pressure as an energetic, high-melting

C. Mailhiot; L. H. Yang; A. K. McMahan

1992-01-01

86

Reduction-responsive polymeric micelles and vesicles for triggered intracellular drug release.  

PubMed

Abstract Significance: The therapeutic effects of current micellar and vesicular drug formulations are restricted by slow and inefficient drug release at the pathological site. The development of smart polymeric nanocarriers that release drugs upon arriving at the target site has received a tremendous amount of attention for cancer therapy. Recent Advances: Taking advantage of a high reducing potential in the tumor tissues and in particular inside the tumor cells, various reduction-sensitive polymeric micelles and vesicles have been designed and explored for triggered anticancer drug release. These reduction-responsive nanosystems have demonstrated several unique features, such as good stability under physiological conditions, fast response to intracellular reducing environment, triggering drug release right in the cytosol and cell nucleus, and significantly improved antitumor activity, compared to traditional reduction-insensitive counterparts. Critical Issues: Although reduction-sensitive micelles and polymersomes have accomplished rapid intracellular drug release and enhanced in vitro antitumor effect, their fate inside the cells including the mechanism, site, and rate of reduction reaction remains unclear. Moreover, the systemic fate and performance of reduction-sensitive polymeric drug formulations have to be investigated. Future Directions: Biophysical studies should be carried out to gain insight into the degradation and drug release behaviors of reduction-responsive nanocarriers inside the tumor cells. Furthermore, novel ligand-decorated reduction-sensitive nanoparticulate drug formulations should be designed and explored for targeted cancer therapy in vivo. Antioxid. Redox Signal. 21, 755-767. PMID:24279980

Sun, Huanli; Meng, Fenghua; Cheng, Ru; Deng, Chao; Zhong, Zhiyuan

2014-08-10

87

Application of Controlled Radical Polymerization for Nucleic Acid Delivery  

PubMed Central

CONSPECTUS Nucleic acid-based therapeutics can potentially address otherwise untreatable genetic disorders and have significant potential for a wide range of diseases. Therapeutic gene delivery can restore protein function by replacing defunct genes to restore cellular health while RNA interference (RNAi) can mask mutated and harmful genes. Cationic polymers have been extensively studied for nucleic acid delivery applications due to their self-assembly with nucleic acids into virus-sized nanoparticles and high transfection efficiency in vitro, but toxicity and particle stability have limited their clinical applications. The advent of controlled radical polymerization has improved the quality, control and reproducibility of synthesized materials. Controlled radical polymerization yields well-defined, narrowly disperse materials of designable architectures and molecular weight, allowing study of the effects of polymer architecture and molecular weight on transfection efficiency and cytotoxicity for improved design of next-generation vectors. Robust methods such as atom transfer radical polymerization (ATRP), reverse addition-fragmentation chain transfer polymerization (RAFT), and ring-opening metastasis polymerization (ROMP) have been used to engineer materials that specifically enhance extracellular stability, cellular specificity, and decrease toxicity. This Account reviews findings from structure-function studies that have elucidated key design motifs necessary for the development of effective nucleic acid vectors. In addition, polymers that are biodegradable, form supramolecular structures, target specific cells, or facilitate endosomal release are also discussed. Finally, promising materials with in vivo applications ranging from pulmonary gene delivery to DNA vaccines are described.

CHU, DAVID S.H.; SCHELLINGER, JOAN G.; SHI, JULIE; CONVERTINE, ANTHONY J.; STAYTON, PATRICK S.; PUN, SUZIE H.

2012-01-01

88

Dual and multi-stimuli responsive polymeric nanoparticles for programmed site-specific drug delivery.  

PubMed

In the past decades, polymeric nanoparticles have emerged as a most promising and viable technology platform for targeted and controlled drug delivery. As vehicles, ideal nanoparticles are obliged to possess high drug loading levels, deliver drug to the specific pathological site and/or target cells without drug leakage on the way, while rapidly unload drug at the site of action. To this end, various "intelligent" polymeric nanoparticles that release drugs in response to an internal or external stimulus such as pH, redox, temperature, magnetic and light have been actively pursued. These stimuli-responsive nanoparticles have demonstrated, though to varying degrees, improved in vitro and/or in vivo drug release profiles. In an effort to further improve drug release performances, novel dual and multi-stimuli responsive polymeric nanoparticles that respond to a combination of two or more signals such as pH/temperature, pH/redox, pH/magnetic field, temperature/reduction, double pH, pH and diols, temperature/magnetic field, temperature/enzyme, temperature/pH/redox, temperature/pH/magnetic, pH/redox/magnetic, temperature/redox/guest molecules, and temperature/pH/guest molecules have recently been developed. Notably, these combined responses take place either simultaneously at the pathological site or in a sequential manner from nanoparticle preparation, nanoparticle transporting pathways, to cellular compartments. These dual and multi-stimuli responsive polymeric nanoparticles have shown unprecedented control over drug delivery and release leading to superior in vitro and/or in vivo anti-cancer efficacy. With programmed site-specific drug delivery feature, dual and multi-stimuli responsive nanoparticulate drug formulations have tremendous potential for targeted cancer therapy. In this review paper, we highlight the recent exciting developments in dual and multi-stimuli responsive polymeric nanoparticles for precision drug delivery applications, with a particular focus on their design, drug release performance, and therapeutic benefits. PMID:23415642

Cheng, Ru; Meng, Fenghua; Deng, Chao; Klok, Harm-Anton; Zhong, Zhiyuan

2013-05-01

89

Expanding the atrane route: Generalized surfactant-free synthesis of mesoporous nanoparticulated xerogels  

NASA Astrophysics Data System (ADS)

A diversity of silica-based and non-silica nanoparticulated mesoporous xerogels have been synthesized from aqueous solution using a surfactant-free strategy, and starting from molecular atrane complexes as precursors. This approach constitutes an extension of the "atrane route" previously described for the surfactant-assisted synthesis of mesoporous materials, and allows us to unify the multiplicity of protocols described for the preparation of conventional xerogels. In fact, we have used exactly the same preparative conditions for obtaining all the compositions reported here. The xerogels synthesized in this way include pure silica (UVM-11), aluminosilicates and titanosilicates (M-UVM-11, M = Al, Ti), hybrid organic-inorganic silica-based derivatives, and also non-silica materials such as pure titania and alumina. Moreover, post-hydrothermal treatments allow modulating the mesopore average size in the ca. 3-30 nm range. The key factor making available such a diversity of materials is the inertness of the atrane complexes, which allows orchestrating the hydrolytic reactivity of different oxide-forming elements. In turn, this avoids subsequent phase segregation and results in chemically homogeneous materials.

Ortiz de Zárate, David; Fernández, Lorenzo; Beltrán, Aurelio; Guillem, Carmen; Latorre, Julio; Beltrán, Daniel; Amorós, Pedro

2008-05-01

90

Effect of nanoparticulate bioactive glass particles on bioactivity and cytocompatibility of poly(3-hydroxybutyrate) composites.  

PubMed

This work investigated the effect of adding nanoparticulate (29 nm) bioactive glass particles on the bioactivity, degradation and in vitro cytocompatibility of poly(3-hydroxybutyrate) (P(3HB)) composites/nano-sized bioactive glass (n-BG). Two different concentrations (10 and 20 wt %) of nanoscale bioactive glass particles of 45S5 Bioglass composition were used to prepare composite films. Several techniques (Raman spectroscopy, scanning electron microscopy, atomic force microscopy, energy dispersive X-ray) were used to monitor their surface and bioreactivity over a 45-day period of immersion in simulated body fluid (SBF). All results suggested the P(3HB)/n-BG composites to be highly bioactive, confirmed by the formation of hydroxyapatite on material surfaces upon immersion in SBF. The weight loss and water uptake were found to increase on increasing bioactive glass content. Cytocompatibility study (cell proliferation, cell attachment, alkaline phosphatase activity and osteocalcin production) using human MG-63 osteoblast-like cells in osteogenic and non-osteogenic medium showed that the composite substrates are suitable for cell attachment, proliferation and differentiation. PMID:19640877

Misra, Superb K; Ansari, Tahera; Mohn, Dirk; Valappil, Sabeel P; Brunner, Tobias J; Stark, Wendelin J; Roy, Ipsita; Knowles, Jonathan C; Sibbons, Paul D; Jones, Eugenia Valsami; Boccaccini, Aldo R; Salih, Vehid

2010-03-01

91

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

PubMed

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

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

2014-01-01

92

Characterization and ecological risk assessment of nanoparticulate CeO2 as a diesel fuel catalyst.  

PubMed

Nanoparticulate cerium dioxide (nano-CeO2 ), when combusted as an additive to diesel fuel, was transformed from 6?nm to 14?nm sizes into particles near 43?nm, with no obvious change in the unit cell dimensions or crystalline form. Cerium sulfate, if formed during combustion, was below detection limits. Ceria nanoparticles were agglomerated within the soot matrix, with a mean aerodynamic diameter near 100?nm. The dissolution of cerium from the dried ceria catalyst in synthetic soft water was extremely small (<0.0006% or <0.2?µg Ce/L), with particles being highly agglomerated (<450?nm). Agglomeration was reduced in the presence of humic acid. In the combusted samples, soot was dominant, and the solubility of cerium in soft water showed an almost 100-fold increase in the <1?nm fraction compared to that before combustion. It appeared that the nano-CeO2 remained agglomerated within the soot matrix and would not be present as dispersed nanoparticles in aquatic or soil environments. Despite the increased dissolution, the solubility was not sufficient for the combusted ceria to represent a risk in aquatic ecosystems. The predicted environmental concentrations were still orders of magnitude below the predicted no effects concentration of near 1?mg/L. In the soil environment, any cerium released from soot materials would interact with natural colloids, decreasing cerium concentrations in soil solutions and further minimizing the potential risk to soil organisms. PMID:23595783

Batley, Graeme E; Halliburton, Brendan; Kirby, Jason K; Doolette, Casey L; Navarro, Divina; McLaughlin, Mike J; Veitch, Colin

2013-08-01

93

Selective electrochemical detection of dopamine in a microfluidic channel on carbon nanoparticulate electrodes.  

PubMed

There is a continuous need for the construction of detection systems in microfluidic devices. In particular, electrochemical detection allows the separation of signals from the analyte and interfering substances in the potential domain. Here, a simple microfluidic device for the sensitive and selective determination of dopamine in the presence of interfering substances was constructed and tested. It employs a carbon nanoparticulate electrode allowing the separation of voltammetric signals of dopamine and common interfering substances (ascorbic acid and acetaminophen) both in quiescent conditions and in flow due to the electrocatalytic effect. These voltammograms were also successfully simulated. The limit of detection of dopamine detected by square wave voltammetry in 1 mM solutions of interfering substances in phosphate buffered saline is about 100 nM. In human serum a clear voltammetric signal could be seen for a 200 nM solution, sufficient to detect dopamine in the cerebral fluid. Flow injection analysis allows a decrease in the limit of detection down to 3.5 nM. PMID:24757708

Rozniecka, Ewa; Jonsson-Niedziolka, Martin; Celebanska, Anna; Niedziolka-Jonsson, Joanna; Opallo, Marcin

2014-06-01

94

New polymerization catalyst  

SciTech Connect

This patent describes a method for preparing polymers of ethylene and copolymers of ethylene and alpha-olefins or diolefins the method comprising effecting polymerization by contacting ethylene or a mixture of ethylene and alpha-olefins or diolefins with an olefin polymerization catalyst comprising the hydrocarbon insoluble reaction product of at least one metallocene of a metal of group IV B, VB, VI B and VIII of the Periodic Table with an alumoxane at a ratio of 1:12 to about 1:100 on a molar basis based on the metal and aluminum.

Turner, H.W.

1988-12-13

95

Kinetic theory and stochastic simulation for polymeric flow  

NASA Astrophysics Data System (ADS)

Polymeric fluids are non-Newtonian. Thus, they cannot be described by the Navier-Stokes equation, or the energy equation. To date, the understanding of polymeric fluids in industry is still based on empiricisms, or crude models, such as the power law model. To be able to predict polymeric fluid behavior in more precise ways, it is essential to understand further the more complicated problems involving elasticity, heat transfer, and chemical reactions. The traditional approach for polymeric flows, using strictly continuum mechanics, requires a closed form constitutive equation. Thus, restrictions are put on the choice of more realistic models. Here we present a novel approach that combines stochastic simulations with finite element methods (called the ``CONNFFESSIT approach''), and which has no such restrictions. For this approach, the equation of momentum is solved by a traditional finite element scheme, whereas the stress terms are evaluated from the stochastic simulation of the kinetic theory models. Results of stochastic simulations for three types of polymeric liquids-dilute solutions, polymer melts and liquid crystals under various homogeneous flow fields are shown, and compared to experimental observations. Predictions from the simulations are found to largely agree with experimental observations. For the nonhomogeneous flow fields, a one-dimensional transient Couette flow, and a two-dimensional steady-state flow through fibrous media are simulated using the CONNFFESSIT approach. The simulations show the flexibility and robustness of this novel approach. Since nonisothermal effects for the polymeric flow systems are very important, we also extend the current isothermal kinetic theories to be applicable to nonisothermal flows. A FENE (F_initely E_xtensible N_onlinear E_lastic) dumbbell model is considered to derive the nonisothermal transport properties such as the mass flux vector, the heat flux vector, and the stress tensor. The derived heat flux expression shows that the concept of heat flux for polymeric flow should be generalized to be thermal flux, which consists of both isotropic and anisotropic contributions.

Hua, Chi-Chung

96

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

97

Protein specific polymeric immunomicrospheres  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

98

Kinetics of Emulsion Polymerization  

Microsoft Academic Search

As a basis for understanding emulsion polymerization, the kinetics of free radical reactions in isolated loci is discussed subject to the condition that the free radicals are supplied to the loci from an external source. Three cases of interest are considered: that in which the average number of free radicals per locus is small compared with unity, that in which

Wendell V. Smith; Roswell H. Ewart

1948-01-01

99

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

100

Olefin polymerization catalyst compositions and polymerization process  

SciTech Connect

This patent describes a process for the catalytic polymerization of an olefin by contact with a catalyst composition comprising an organoaluminum compound, a selectivity control agent and a solid titanium-containing catalyst component in which the atomic ratio of aluminum to titanium is from 1:1 to 150:1. The solid component is obtained by: (a) halogenating a magnesium compound of the formula MgR'R'' where R' is an alkoxide or aryloxide group and R'' is an alkoxide or aryloxide group or halogen, with a tetravalent titanium halide in the presence of a halohydrocarbon and an electron donor, therein forming a halogenated product; (b) contacting the halogenated product with an acid halide; (c) contacting the resulting acid halide-treated product with a tetravalent titanium halide at a temperature of about 40/sup 0/ to about 140/sup 0/C; and (d) washing the resulting titanium halide-treated product with an inert hydrocarbon liquid.

Job, R.C.

1987-04-14

101

In vitro analysis of nanoparticulate hydroxyapatite/chitosan composites as potential drug delivery platforms for the sustained release of antibiotics in the treatment of osteomyelitis.  

PubMed

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

Uskokovi?, Vuk; Desai, Tejal A

2014-02-01

102

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

PubMed Central

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

USKOKOVIC, VUK; DESAI, TEJAL A.

2014-01-01

103

Iceberg-hosted nanoparticulate Fe in the Southern Ocean: Mineralogy, origin, dissolution kinetics and source of bioavailable Fe  

NASA Astrophysics Data System (ADS)

Sediments from icebergs and glaciers contain nanopartculate Fe(III) oxyhydroxides (including ferrihydrite) which form in aqueous, oxic (micro)environments where Fe(II)-bearing rock minerals oxidise and high degrees of supersaturation are promoted by freezing and thawing. An ascorbic acid extraction dissolves only labile Fe present in fresh (loosely aggregated) ferrihydrite that is directly or indirectly bioavailable. Glacial and iceberg sediments contain ferrihydrite aggregates that provide 0.04 to 0.17% Fe soluble in ascorbic acid, rather larger than the concentrations in a limited suite of atmospheric dusts. The dissolution behaviour of labile Fe from glacial and iceberg sediments by ascorbic acid is controlled by the access of reactant, or removal of solute, through micropores to or from active sites in the interior of ferrihydrite aggregates. A first-order kinetic model is presented to examine the rates at which bioavailable Fe can be supplied by melting icebergs in the Weddell Sea. The model utilizes rate constants from the literature for the processes which solubilise Fe from nanoparticulate ferrihydrite (dissolution, photochemical reduction and grazing) and the processes that remove Fe nanoparticulates (sinking, scavenging and incorporation in faecal material), and render them less reactive (transformation, aging). Model results demonstrate that icebergs can supply bioavailable Fe to the Weddell Sea by the dissolution of nanoparticulate ferrihydrite (despite loss/removal of nanoparticles by sinking, aging, transformation, scavenging and incorporation into faecal pellets) at rates that are comparable to atmospheric dust. Dissolution enhanced by photochemical reduction and grazing provides the most rapid rates of bioavailable Fe production.

Raiswell, Rob

2011-06-01

104

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

Microsoft Academic Search

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

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

2010-01-01

105

Vectors: Tip to Tail  

NSDL National Science Digital Library

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

Linamen, Sharon

2012-07-23

106

An aquaporin 4 antisense oligonucleotide loaded, brain targeted nanoparticulate system design.  

PubMed

Aquaporins (AQPs), members of the water-channel protein family, are highly expressed in brain tissue especially in astrocytic end-feet. They are important players for water hemostasis during development of cytotoxic as well as vasogenic edema. Increased expression of AQPs is important in pathophysiology of neurological diseases such as neuroinflammation and ischemia. Unfortunately, there are a few pharmacological inhibitors of AQP4 with several side effects limiting their translation as a drug for use in clinical conditions. Another therapeutic approach is using antisense oligonucleotides (ASOs) to block AQP4 activity. These are short, synthetic, modified nucleic acids that bind RNA to modulate its function. However, they cannot pass the blood brain barrier (BBB). To overcome this obstacle we designed a nanoparticulate system made up of chitosan nanoparticles surface modified with PEG and conjugated with monoclonal anti transferrin receptor-1 antibody via streptavidin-biotin binding. The nanocarrier system could be targeted to the transferrin receptor-1 at the brain endothelial capillaries through monoclonal antibodies. It is hypothesized that the nanoparticles could pass the BBB via receptor mediated transcytosis and reach brain parenchyma. Particle size, zeta potential, loading capacity and release profiles of nanoparticles were investigated. It was observed that all types of chitosau (CS) nanoparticles had positive zeta potential values and nanoparticle particle size distribution varied between 100 and 800 nm. The association efficiency of ASOs into the nanoparticles was between 80-97% and the release profiles of the nanoparticles exhibited an initial burst effect followed by a controlled release. The results showed that the designed chitosan based nanocarriers could be a promising carrier system to transport nucleic acid based drugs to brain parenchyma. PMID:24855824

Kozlu, S; Caban, S; Yerlikaya, F; Fernandez-Megia, E; Novoa-Carballal, R; Riguera, R; Yemisci, M; Gursoy-Ozdemir, Y; Dalkara, T; Couvreur, P; Capan, Y

2014-05-01

107

Thiomers: preparation and in vitro evaluation of a mucoadhesive nanoparticulate drug delivery system.  

PubMed

It was the aim of this study to develop a mucoadhesive nanoparticulate delivery system. Nanoparticles were generated by in situ gellation of the thiomer chitosan-4-thiobutylamidine (chitosan-TBA) with tripolyphosphate (TPP) followed by stabilization via the formation of inter- and intrachain disulfide bonds by oxidation with H(2)O(2) in various concentrations. Afterwards TPP was removed by exhaustive dialysis at pH 1-2. Incorporation of the model compound fluorescein diacetate (FDA) was achieved by incubation of this fluorescence marker, dissolved in acetonitrile, with aqueous particle suspensions for 1h at room temperature. Mucoadhesion studies were performed on porcine intestinal mucosa. Results showed that the preparation method described above leads to nanoparticles of a mean diameter of 268+/-15 nm and a FDA load of 2%. Due to the removal of the anionic crosslinker TPP, the zeta potential of the nanoparticles was raised from 4+/-1 up to 19+/-2 mV without loosing stability of the nanoparticles. The more H(2)O(2) was added to the particles, the more inter- and intrachain disulfide bonds were formed. The more thiol groups were oxidized within the particles, however, the lower was the improvement in mucoadhesive properties. Nevertheless, even when 91% of all thiol groups on the nanoparticles were oxidized, their mucoadhesive properties were still twice as high as the mucoadhesive properties of unmodified nanoparticles. Thiolated chitosan nanoparticles show a two-fold higher zeta potential (I), improved stability (II) and more than doubled mucoadhesive properties (III) than corresponding unmodified chitosan nanoparticles. Therefore, they seem to be advantageous over ionically crosslinked chitosan nanoparticles. PMID:16595166

Bernkop-Schnürch, Andreas; Weithaler, Andrea; Albrecht, Karin; Greimel, Alexander

2006-07-01

108

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

109

Catalytic polymerization of olefins  

Microsoft Academic Search

Summary 1.Addition of alumina to an impregnation catalyst of NiO on KSK silica gel prepared from nickel formatehas a strong activating effect on the catalyst for the polymerization of ethylene.2.With change in the concentration of the aluminum nitrate solution used for the preparation of an NiO-Al2O3-KSK silica gel catalyst from 0.5% to 10% there is little change in the activity

Ya. T. Éidus; K. V. Puzitskii; B. A. Kazanskii

1960-01-01

110

Frontal Polymerization in Microgravity  

NASA Technical Reports Server (NTRS)

Frontal polymerization systems, with their inherent large thermal and compositional gradients, are greatly affected by buoyancy-driven convection. Sounding rocket experiments allowed the preparation of benchmark materials and demonstrated that methods to suppress the Rayleigh-Taylor instability in ground-based research did not significantly affect the molecular weight of the polymer. Experiments under weightlessness show clearly that bubbles produced during the reaction interact very differently than under 1 g.

Pojman, John A.

1999-01-01

111

[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

112

Supported olefin polymerization catalyst  

SciTech Connect

A solid, hydrocarbon-insoluble, alpha-olefin polymerization catalyst component is described comprising the product formed by: A. complexing a magnesium alkyl composition with an ortho disubstituted hindered carboxylic aromatic acid ester; B. reacting the resulting stable complex with a compatible precipitation agent to form a solid component; and C. reacting the resulting solid with a titanium compound in a suitable diluent containing a suitable electron donor compound.

Johnson, B.V.; Karayannis, N.M.; Hoppin, C.R.; Ornellas, L.

1986-04-08

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

Developments in polymerization lamps.  

PubMed

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

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

2008-02-01

115

Biological tolerance of different materials in bulk and nanoparticulate form in a rat model: sarcoma development by nanoparticles.  

PubMed

In order to study the pathobiological impact of the nanometre-scale of materials, we evaluated the effects of five different materials as nanoparticulate biomaterials in comparison with bulk samples in contact with living tissues. Five groups out of 10 rats were implanted bilaterally for up to 12 months with materials of the same type, namely TiO2, SiO2, Ni, Co and polyvinyl chloride (PVC), subcutaneously with bulk material on one side of the vertebral column and intramuscularly with nanoparticulate material on the contralateral side. At the end of each implantation time, the site was macroscopically examined, followed by histological processing according to standard techniques. Malignant mesenchymal tumours (pleomorphic sarcomas) were obtained in five out of six cases of implanted Co nanoparticle sites, while a preneoplastic lesion was observed in an animal implanted with Co in bulk form. In the Ni group, all animals rapidly developed visible nodules at the implanted sites between 4 and 6 months, which were diagnosed as rhabdomyosarcomas. Since the ratio of surface area to volume did not show significant differences between the Ni/Co group and the TiO2/SiO2/PVC group, we suggested that the induction of neoplasia was not mediated by physical effects, but was mediated by the well-known carcinogenic impact of Ni and Co. The data from the Co group show that the physical properties (particulate versus bulk form) could have a significant influence on the acceleration of the neoplastic process. PMID:17015296

Hansen, Torsten; Clermont, Gaëlle; Alves, Antonio; Eloy, Rosy; Brochhausen, Christoph; Boutrand, Jean Pierre; Gatti, Antonietta M; Kirkpatrick, C James

2006-12-22

116

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

117

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

PubMed

Solution processable Al-doped ZnO (AZO) thin films are attractive candidates for low cost transparent electrodes. We demonstrate here an optimized nanoparticulate ink for the fabrication of AZO thin films using scalable, low-cost direct write processing (ultrasonic spray deposition) in air at atmospheric pressure. The thin films were made via thermal processing of as-deposited films. AZO films deposited using the proposed nanoparticulate ink with further reducing in vacuum and rf plasma of forming gas exhibited optical transparency greater than 95% across the visible spectrum, and electrical resistivity of 0.5 ? cm and it drops down to 7.0 × 10(-2) ? cm after illuminating with UV light, which is comparable to commercially available tin doped indium oxide colloidal coatings. Various structural analyses were performed to investigate the influence of ink chemistry, deposition parameters, and annealing temperatures on the structural, optical, and electrical characteristics of the spray deposited AZO thin films. Optical micrographs confirmed the presence of surface defects and cracks using the AZO NPs ink without any additives. After adding N-(2-Aminoethyl)-3-aminopropylmethyldimethoxy silane to the ink, AZO films exhibited an optical transparency which was virtually identical to that of the plain glass substrate. PMID:24763438

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

2014-05-16

118

Guelph Physics Tutorials: Vectors  

NSDL National Science Digital Library

This page offers a straightforward tutorial on the fundamentals of vector operations. It is an illustrated guide to vector subtraction/addition, vector resolution, and multiplication of two vectors. It could serve as textbook supplementation or as content support for science teachers.

2008-08-15

119

Vector-Borne Diseases  

NSDL National Science Digital Library

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

Artsob, Harvey; Health, Encyclopedia O.

120

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

121

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

PubMed Central

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

2013-01-01

122

Coordination polymerization of heterocyclic and heterounsaturated monomers  

Microsoft Academic Search

Polymerizations and copolymerizations of non-hydrocarbon monomers, such as heterocyclic and heterounsaturated monomers, in the presence of coordination catalysts constitute a distinct group of coordination polymerization processes which differ essentially from the coordination polymerization of unsaturated hydrocarbon monomers in terms of the kinds of catalyst applicable and the polymerization mechanism. While the coordination polymerization and copolymerization of numerous hydrocarbon monomers with

Witold Kuran

1998-01-01

123

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

124

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

125

Bimorphic polymeric photomechanical actuator  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

126

Separation of bacteria with imprinted polymeric films.  

PubMed

Separation of compounds out of complex mixtures is a key issue that has been solved for small molecules by chromatography. However, general methods for the separation of large bio-particles, such as cells, are still challenging. We demonstrate integration of imprinted polymeric films (IPF) into a microfluidic chip, which preferentially capture cells matching an imprint template, and separate strains of cyanobacteria with 80-90% efficiency, despite a minimal difference in morphology and fluorescence, demonstrating its general nature. It is currently thought that the imprinting process, conducted while the polymer cures, transfers chemical information of the cell's external structure to the substrate. Capture specificity and separation can be further enhanced by orienting the imprints parallel to the flow vector and tuning the pH to a lower range. PMID:22324051

Schirhagl, Romana; Hall, Eric W; Fuereder, Ingo; Zare, Richard N

2012-03-21

127

Gratings in polymeric waveguides  

NASA Astrophysics Data System (ADS)

Laser-induced formation of polymer Bragg grating filters for Dense Wavelength Division Multiplexing (DWDM) applications is discussed. Acrylate monomers halogenated with both fluorine and chlorine, which possess absorption losses less than 0.25 dB/cm and wide choice of refractive indices (from 1.3 to 1.5) in the 1.5 ?m telecom wavelength region were used. The monomers are highly intermixable thus permitting to adjust the refractive index of the composition within +/-0.0001. Moreover they are photocurable under UV exposure and exhibit high contrast in polymerization. These properties make halogenated acrylates very promising for fabricating polymeric waveguides and photonic circuits. Single-mode polymer waveguides were fabricated on silicon wafers using resistless contact lithography. Submicron index gratings have been written in polymer waveguides using holographic exposure with He-Cd laser beam (325 nm) through a phase mask. Both uniform and apodized gratings have been fabricated. The gratings are stable and are not erased by uniform UV exposure. The waveguide gratings possess narrowband reflection spectra in the 1.5 ?m wavelength region of 0.4 nm width, nearly rectangular shape of the stopband and reflectivity R > 99%. The fabricated Bragg grating filters can be used for multiplexing/demultiplexing optical signals in high-speed DWDM optical fiber networks.

Mishakov, G.; Sokolov, V.; Kocabas, A.; Aydinli, A.

2007-04-01

128

Organometallic Polymeric Conductors  

NASA Technical Reports Server (NTRS)

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

1997-01-01

129

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

130

Reduced Vector Preisach Model  

NASA Technical Reports Server (NTRS)

A new vector Preisach model, called the Reduced Vector Preisach model (RVPM), was developed for fast computations. This model, derived from the Simplified Vector Preisach model (SVPM), has individual components that like the SVPM are calculated independently using coupled selection rules for the state vector computation. However, the RVPM does not require the rotational correction. Therefore, it provides a practical alternative for computing the magnetic susceptibility using a differential approach. A vector version, using the framework of the DOK model, is implemented. Simulation results for the reduced vector Preisach model are also presented.

Patel, Umesh D.; Torre, Edward Della; Day, John H. (Technical Monitor)

2002-01-01

131

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

132

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

133

Coating of plasma polymerized film  

NASA Technical Reports Server (NTRS)

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

Morita, S.; Ishibashi, S.

1980-01-01

134

Membrane Testing Using Polymeric Dyes  

Microsoft Academic Search

Membranes for use in ultrafiltration are manufactured to obtain a defined pore size which will retain particles, colloids, and soluble polymeric materials with molecular weights above a critical value. The presence of pores or defects which are larger than the desired size will have a deleterious effect. The use of a polymeric dye with a defined molecular weight distribution allows

Anthony R. Cooper; Dena S. Van Derveer

1982-01-01

135

Outdoor high voltage polymeric insulators  

Microsoft Academic Search

Composite polymeric insulators are increasingly being accepted by the traditionally cautious electric utilities worldwide. They currently represent about 70% of installed new high voltage insulators in North America. The tremendous growth in the applications of non-ceramic insulators is due to their advantages over the traditional ceramic and glass insulators. However, because polymeric insulators are relatively new the expected lifetime is

R. Hackam

1998-01-01

136

Radiation formation of polymeric nanogels  

Microsoft Academic Search

An alternative method of synthesis of polymeric nanogels is proposed, based not on polymerization, but on intramolecular crosslinking of polymer chains, initiated by pulse irradiation in dilute aqueous solutions. Kinetic data show that for many water-soluble polymers irradiation under these conditions result in intramolecular crosslinking. Preliminary product studies on poly(vinyl alcohol) indicate that in fact internally crosslinked macromolecules can be

P. Ulanski; I. Janik; J. M. Rosiak

1998-01-01

137

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

138

Understanding Singular Vectors  

ERIC Educational Resources Information Center

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

James, David; Botteron, Cynthia

2013-01-01

139

Coal and tire burning mixtures containing ultrafine and nanoparticulate materials induce oxidative stress and inflammatory activation in macrophages.  

PubMed

Ultra-fine and nano-particulate materials resulting from mixtures of coal and non-coal fuels combustion for power generation release to the air components with toxic potential. We evaluated toxicological and inflammatory effects at cellular level that could be induced by ultrafine/nanoparticles-containing ashes from burning mixtures of coal and tires from an American power plant. Coal fly ashes (CFA) samples from the combustion of high-S coal and tire-derived fuel, the latter about 2-3% of the total fuel feed, in a 100-MW cyclone utility boiler, were suspended in the cell culture medium of RAW 264.7 macrophages. Cell viability, assessed by MTT reduction, SRB incorporation and contrast-phase microscopy analysis demonstrated that CFA did not induce acute toxicity. However, CFA at 1mg/mL induced an increase of approximately 338% in intracellular TNF-?, while release of this proinflammatory cytokine was increased by 1.6-fold. The expression of the inflammatory mediator CD40 receptor was enhanced by 2-fold, the receptor for advanced glycation endproducts (RAGE) had a 5.7-fold increase and the stress response protein HSP70 was increased nearly 12-fold by CFA at 1mg/mL. Although CFA did not induce cell death, parameters of oxidative stress and reactive species production were found to be altered at several degrees, such as nitrite accumulation (22% increase), DCFH oxidation (3.5-fold increase), catalase (5-fold increase) and superoxide dismutase (35% inhibition) activities, lipoperoxidation (4.2 fold-increase) and sulfhydryl oxidation (40% decrease in free SH groups). The present results suggest that CFA containing ultra-fine and nano-particulate materials from coal and tire combustion may induce sub-chronic cell damage, as they alter inflammatory and oxidative stress parameters at the molecular and cellular levels, but do not induce acute cell death. PMID:23856402

Gasparotto, Juciano; Somensi, Nauana; Caregnato, Fernanda F; Rabelo, Thallita K; DaBoit, Kátia; Oliveira, Marcos L S; Moreira, José C F; Gelain, Daniel P

2013-10-01

140

Raven—Vector Editing  

Microsoft Academic Search

\\u000a Raven is used to create fully scalable vector art appropriate for logos or t-shirt designs. Unlike the bitmaps you have used\\u000a in previous chapters, Raven uses vectors. A vector is an object defined by points in space, lines connecting those points together, and color that fills the shape in between\\u000a those lines. Vectors are defined mathematically and are drawn in

Mike Peutz

141

Polymerized carbon nitride nanobells  

NASA Astrophysics Data System (ADS)

Well-aligned carbon nitride nanotubes are fabricated by microwave plasma assisted chemical vapor deposition using iron as the catalyst. These nanotubes are linearly polymerized by carbon nitride nanobells with catalyst particles in the root, as revealed by high-resolution transmission electron microscopy. Carbon nitride nanotube film is analyzed by x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and Raman spectroscopy. Both XPS and AES reveal a nitrogen content of about 2% in the film. Raman spectroscopy exhibits a good crystallization of these carbon nitride nanotubes. Electron energy loss spectroscopy is used to study the local distribution of nitrogen in a single nanotube, which indicates that nitrogen prefers to locate at curved graphite sheets, at the top of the nanobells, and that incorporation of nitrogen results in the decrease of the crystallization. Based on these results, a growth model is proposed to explain this periodically stacked nanobell structure. In this model, we propose that graphite sheets only precipitate along the surface of catalyst particles and that lower growth rate at the top curve surface of the bell-like catalyst particle is the key factor influencing formation of this special microstructure. A heterojunction between a tubular carbon nanotube and a carbon nitride nanobell also has been fabricated by a two-step growth technique. And short carbon nitride nanotubes with a few nanobells or even just one nanobell are obtained by both physical and chemical methods. Furthermore, we studied the field emission properties and have obtained a threshold field of as low as about 1 V/?m. A novel side-emission mechanism has been proposed based on the special polymerized nanobell structures.

Zhang, G. Y.; Ma, X. C.; Zhong, D. Y.; Wang, E. G.

2002-06-01

142

Support vector domain description  

Microsoft Academic Search

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

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

1999-01-01

143

Melting line of polymeric nitrogen  

NASA Astrophysics Data System (ADS)

We made an attempt to predict location of the melting line of polymeric nitrogen using two equations for Helmholtz free energy: proposed earlier for cubic gauche-structure and developed recently for liquid polymerized nitrogen. The P-T relation, orthobaric densities and latent heat of melting were determined using a standard double tangent construction. The estimated melting temperature decreases with increasing pressure, alike the temperature of molecular-nonmolecular transition in solid. We discuss the possibility of a triple point (solid-molecular fluid-polymeric fluid) at ~80 GPa and observed maximum of melting temperature of nitrogen.

Yakub, L. N.

2013-05-01

144

Production of monodisperse, polymeric microspheres  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

145

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

146

Rotations with Rodrigues' vector  

NASA Astrophysics Data System (ADS)

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

Piña, E.

2011-09-01

147

Organometallic Polymeric Conductors  

NASA Technical Reports Server (NTRS)

For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductivity with long-term environmental stability, good processability, and good mechanical properties. Recently, other investigators have reported hybrid films made from an electrically conductive polymer combined with insulating polymers. In all of these instances, the films were prepared by infiltrating an insulating polymer with a precursor for a conductive polymer (either polypyrrole or polythiophene), and oxidatively polymerizing the precursor in situ. The resulting composite films have good electrical conductivity, while overcoming the brittleness inherent in most conductive polymers. Many aerospace applications require a combination of properties. Thus, hybrid films made from polyimides or other engineering resins are of primary interest, but only if conductivities on the same order as those obtained with a polystyrene base could be obtained. Hence, a series of experiments was performed to optimize the conductivity of polyimide-based composite films. The polyimide base chosen for this study was Kapton. 3-MethylThiophene (3MT) was used for the conductive phase. Three processing variables were identified for producing these composite films, namely time, temperature, and oxidant concentration for the in situ oxidation. Statistically designed experiments were used to examine the effects of these variables and synergistic/interactive effects among variables on the electrical conductivity and mechanical strength of the films. Multiple linear regression analysis of the tensile data revealed that temperature and time have the greatest effect on maximum stress. The response surface of maximum stress vs. temperature and time (for oxidant concentration at 1.2 M) is shown. Conductivity of the composite films was measured for over 150 days in air at ambient temperature. The conductivity of the films dropped only half an order of magnitude in that time. Films aged under vacuum at ambient temperature diminished slightly in conductivity in the first day, but did not change thereafter. An experimental design approach will be applied to maximize the efficiency of the laboratory effort. The material properties (initial and long term) will also be monitored and assessed. The experimental results will add to the existing database for electrically conductive polymer materials. Attachments: 1) Synthesis Crystal Structure, and Polymerization of 1,2:5,6:9,10-Tribenzo-3,7,11,13-tetradehydro(14) annulene. 2) Reinvestigation of the Photocyclization of 1,4-Phenylene Bis(phenylmaleic anhydride): Preparation and Structure of (5)Helicene 5,6:9,10-Dianhydride. 3) Preparation and Structure Charecterization of a Platinum Catecholate Complex Containing Two 3-Ethynyltheophone Groups. and 4) Rigid-Rod Polymers Based on Noncoplanar 4,4'-Biphenyldiamines: A Review of Polymer Properties vs Configuration of Diamines.

Youngs, Wiley J.

1997-01-01

148

Thermal conductivity of pressure polymerized C60  

Microsoft Academic Search

60   polymerization in the temperature interval at pressures below by measurements of the time dependence of the thermal conductivity. It has been found at that the polymerization process at is slower than the reverse transformation from “polymeric” to “monomeric” phase at . The thermal conductivity of polymerized C60 was measured in the temperature range and found to increase with increasing

A. Soldatov; O. Andersson

1997-01-01

149

Numerical Analysis of Plasma Initiated Polymerization  

Microsoft Academic Search

Plasma initiated polymerization is a kind of well-known radical polymerization mechanism, but it has the `living' polymerization feature and produces ultra-high molecular weight polymer. In order to explain such phenomena, we calculate the basic data of plasma initiated polymerization of methylmethacrylate (MMA) according to the principle of polymer physics and chemistry. It results in that the radical concentration ranges from

Qingliang You; Jianhua Wang; Yuedong Meng; Xingsheng Shu; Qiongrong Ou; Xu Xu; Keming Shen

2006-01-01

150

Polymeric Media for Tritium Fixation.  

National Technical Information Service (NTIS)

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 ...

J. A. Franz L. L. Burger

1975-01-01

151

Surface Degradation of Polymeric Materials.  

National Technical Information Service (NTIS)

A review of surface degradation of polymeric materials exposed to natural and artificial weathering environments has been carried out. Mechanisms of degradation are discussed, the role of different environmental variables is evaluated, and methods of char...

J. White A. Turnbull

1992-01-01

152

Photoredox catalysis for polymerization reactions.  

PubMed

Photoredox catalysis is now well-known in organic synthesis for the formation of free radicals under very soft irradiations conditions (e.g. sunlight, household fluorescence or LED bulbs, Xe lamp). This method has been introduced here to the polymer chemistry area to initiate ring opening polymerizations (ROP) or free radical polymerizations (FRP). The present paper will give an up-to date situation of the photocatalyst achievements in FRP and ROP. PMID:22871290

Lalevée, Jacques; Tehfe, Mohamad-Ali; Morlet-Savary, Fabrice; Graff, Bernadette; Dumur, Frédéric; Gigmes, Didier; Blanchard, Nicolas; Fouassier, Jean-Pierre

2012-01-01

153

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

154

Mechanochemical solid-state polymerization. VIII. Novel composite polymeric prodrugs prepared by mechanochemical polymerization in the presence of pharmaceutical aids.  

PubMed

We carried out the mechanochemical polymerization of methacryloyl derivatives of acetoaminophen and 5-fluorouracil in the presence of lactose. The reaction proceeded readily and the polymeric prodrugs were quantitatively produced. This method produces powdered polymeric prodrugs in which fine particles of lactose are homogeneously dispersed, since the reaction proceeds quantitatively through a totally dry process. It is difficult to prepare such a powdered polymeric prodrug by conventional solution polymerization. The rate of drug release of polymeric prodrugs increases with increasing content of lactose, as is shown to be true of the specific surface of polymeric prodrugs. These results suggest that lactose is homogeneously dispersed in powdered polymeric prodrugs. The present method seems applicable to a wide variety of pharmaceutical aids. If one takes the physiochemical property of pharmaceutical aids into consideration, novel polymeric prodrugs with a variety of drug release rates can be synthesized simultaneously with mixing. PMID:9579043

Kondo, S; Hosaka, S; Kuzuya, M

1998-04-01

155

Polymeric materials for neovascularization  

NASA Astrophysics Data System (ADS)

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

DeVolder, Ross John

156

Flexi vector cloning.  

PubMed

A protocol for ligation-dependent cloning using the Flexi Vector method in a 96-well format is described. The complete protocol includes PCR amplification of the desired gene to append Flexi Vector cloning sequences, restriction digestion of the PCR products, ligation of the digested PCR products into a similarly digested acceptor vector, transformation and growth of host cells, analysis of the transformed clones, and storage of a sequence-verified clone. The protocol also includes transfer of the sequence-verified clones into another Flexi Vector plasmid backbone. Smaller numbers of cloning reactions can be undertaken by appropriate scaling of the indicated reaction volumes. PMID:18988018

Blommel, Paul G; Martin, Peter A; Seder, Kory D; Wrobel, Russell L; Fox, Brian G

2009-01-01

157

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.

2008-09-12

158

Shrinkage vector determination of dental composite by ?CT images  

Microsoft Academic Search

Hypotheses about contraction patterns of light-curing dental composites are controversial. The purpose of this study was to develop a method to determine the direction and extent of polymerization shrinkage. Cavities were restored with a modified composite that contained traceable particles, and digitized before and after light-curing with micro-computed tomography (?CT). The resulting displacement vector fields based on the elastic registration

Yu-Chih Chiang; Reinhard Hickel; Chun-Pin Lin; Karl-Heinz Kunzelmann

2010-01-01

159

Stereospecific olefin polymerization catalysts  

SciTech Connect

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

160

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

161

Nanoparticulate Radiolabelled Quinolines Detect Amyloid Plaques in Mouse Models of Alzheimer's Disease  

PubMed Central

Detecting aggregated amyloid peptides (A? plaques) presents targets for developing biomarkers of Alzheimer's disease (AD). Polymeric n-butyl-2-cyanoacrylate (PBCA) nanoparticles (NPs) were encapsulated with radiolabelled amyloid affinity 125I-clioquinol (CQ, 5-chloro-7-iodo-8-hydroxyquinoline) as in vivo probes. 125I-CQ-PBCA NPs crossed the BBB (2.3 ± 0.9?ID/g) (P < .05) in the WT mouse (N = 210), compared to 125I-CQ (1.0 ± 0.4?ID/g). 125I-CQ-PBCA NP brain uptake increased in AD transgenic mice (APP/PS1) versus WT (N = 38; 2.54 × 105 ± 5.31 × 104?DLU/mm2; versus 1.98 × 105 ± 2.22 × 104?DLU/mm2) and in APP/PS1/Tau. Brain increases were in mice intracranially injected with aggregated A?42 peptide (N = 17; 7.19 × 105 ± 1.25 × 105?DLU/mm2), versus WT (6.07 × 105 ± 7.47 × 104?DLU/mm2). Storage phosphor imaging and histopathological staining of the plaques, Fe2+ and Cu2+, validated results. 125I-CQ-PBCA NPs have specificity for A? in vitro and in vivo and are promising as in vivo SPECT (123I), or PET (124I) amyloid imaging agents.

Roney, Celeste A.; Arora, Veera; Kulkarni, Padmakar V.; Antich, Peter P.; Bonte, Frederick J.

2009-01-01

162

Nanoparticulate DNA packaging using terpolymers of poly(lysine-g-(lactide-b-ethylene glycol)).  

PubMed

Terpolymers of poly(lysine-g-(lactide-b-ethylene glycol)) (pK-pLL-pEG) were synthesized by using ring-opening polymerization and functional end-group grafting. Synthesis was characterized with gel permeation chromatography, proton nuclear magnetic resonance spectroscopy, and a trinitrobenzene sulfonic acid binding assay. Polymer association behavior with DNA was investigated using an ethidium bromide exclusion assay, static light scattering, and scanning electron microscopy. Polylactide molecular weight was varied to investigate its impact on DNA association and resulting complex characteristics. Polylysine ( = 8800, DP = 42) modified with either 7400 or 10 870 pLL-pEG reduced the minimum amount of primary amines necessary for complete condensation by 23% and 48%, respectively, compared to unmodified polylysine (pK42). Complexes formed with the highest molecular weight terpolymer demonstrated significantly (p < 0.1) greater resistance to DNase I than lyophilized pK42-DNA particles. This study suggests that modification of pK42 with pLL-pEG diblock copolymers impacts polylysine's associative and binding behavior to DNA and resulting particle characteristics. Modulation of terpolymer composition in complexes can enable control over intracellular plasmid dissociation rates to improve transfection efficiency. PMID:12643741

Park, Susan; Healy, Kevin E

2003-01-01

163

Ligand-directed active tumor-targeting polymeric nanoparticles for cancer chemotherapy.  

PubMed

In recent years, polymeric nanoparticles have appeared as a most viable and versatile delivery system for targeted cancer therapy. Various in vivo studies have demonstrated that virus-sized stealth particles are able to circulate for a prolonged time and preferentially accumulate in the tumor site via the enhanced permeability and retention (EPR) effect (so-called "passive tumor-targeting"). The surface decoration of stealth nanoparticles by a specific tumor-homing ligand, such as antibody, antibody fragment, peptide, aptamer, polysaccharide, saccharide, folic acid, and so on, might further lead to increased retention and accumulation of nanoparticles in the tumor vasculature as well as selective and efficient internalization by target tumor cells (termed as "active tumor-targeting"). Notably, these active targeting nanoparticulate drug formulations have shown improved, though to varying degrees, therapeutic performances in different tumor models as compared to their passive targeting counterparts. In addition to type of ligands, several other factors such as in vivo stability of nanoparticles, particle shape and size, and ligand density also play an important role in targeted cancer chemotherapy. In this review, concept and recent development of polymeric nanoparticles conjugated with specific targeting ligands, ranging from proteins (e.g., antibodies, antibody fragments, growth factors, and transferrin), peptides (e.g., cyclic RGD, octreotide, AP peptide, and tLyp-1 peptide), aptamers (e.g., A10 and AS1411), polysaccharides (e.g., hyaluronic acid), to small biomolecules (e.g., folic acid, galactose, bisphosphonates, and biotin), for active tumor-targeting drug delivery in vitro and in vivo are highlighted and discussed. With promise to maximize therapeutic efficacy while minimizing systemic side effects, ligand-mediated active tumor-targeting treatment modality has become an emerging and indispensable platform for safe and efficient cancer therapy. PMID:24798476

Zhong, Yinan; Meng, Fenghua; Deng, Chao; Zhong, Zhiyuan

2014-06-01

164

Multiclass core vector machine  

Microsoft Academic Search

Even though several techniques have been proposed in the literature for achieving multi- class classication using Support Vector Ma- chine(SVM), the scalability aspect of these approaches to handle large data sets still needs much of exploration. Core Vector Ma- chine(CVM) is a technique for scaling up a two class SVM to handle large data sets. In this paper we propose

S. Asharaf; M. Narasimha Murty; Shirish Krishnaj Shevade

2007-01-01

165

Support Vector Data Description  

Microsoft Academic Search

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

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

2004-01-01

166

Fuzzy learning vector quantization  

Microsoft Academic Search

In this paper, a new supervised competitive learning network model called fuzzy learning vector quantization (FLVQ) which incorporates fuzzy concepts into the learning vector quantization (LVQ) networks is proposed. Unlike the original algorithm, the FLVQ's learning algorithm is derived from optimizing an appropriate fuzzy objective function which takes into accounts of two goals, namely, minimizing the network output error which

Fu-Lai Chung; Tong Lee

1993-01-01

167

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

168

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

169

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

PubMed

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

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

2014-06-01

170

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

PubMed

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

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

2014-12-01

171

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

PubMed Central

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

Uskokovic, Vuk

2013-01-01

172

On-demand photoinitiated polymerization  

DOEpatents

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

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

2013-12-10

173

Deactivator for olefin polymerization catalyst  

SciTech Connect

A method is described comprising deactivating an olefin polymerization catalyst selected from the group consisting of Ziegler-Natta transition element catalysts and catalysts based on transition metal oxides by contacting the catalyst with a copolymer. The copolymer consists of an alpha-olefin having from 2 to about 12 carbon atoms and an unsaturated ester of a carboxylic acid. The deactivating copolymer is present in an amount such that the molar ratio of the unsaturated ester thereof to the sum of the transition element component of the polymerization catalyst and a cocatalyst for the transition element catalyst is in the range of between about 0.1 and about 6.

Rekers, L.J.; Speca, A.N.; Mayhew, H.W.

1987-03-10

174

The polymerization of actin: Thermodynamics near the polymerization line  

NASA Astrophysics Data System (ADS)

Studies of the dependence of actin polymerization on thermodynamic parameters are important for understanding processes in living systems, where actin polymerization and depolymerization are crucial to cell structure and movement. We report measurements of the extent of polymerization, ?, of rabbit muscle actin as a function of temperature [T=(0-35) °C], initial G-actin concentration [[G0]=(1-3) mg/ml], and initiating salt concentration [[KCl]=(5-15) mmol/l with bound Ca2+], in H2O and D2O buffers and in the presence of adenosine triphosphate (ATP). A preliminary account of the data and analysis for H2O buffers has appeared previously [P. S. Niranjan, J. G. Forbes, S. C. Greer, J. Dudowicz, K. F. Freed, and J. F. Douglas, J. Chem. Phys. 114, 10573 (2001)]. We describe the details of the studies for H2O buffers, together with new data and analysis for D2O buffers. The measurements show a maximum in ?(T) for H2O buffers and D2O buffers. For H2O buffers, Tp decreases as either [G0] or [KCl] increases. For D2O buffers, Tp decreases as [KCl] increases, but Tp is not monotonic in [G0]. The measurements are interpreted in terms of a Flory-Huggins-type lattice model that includes the essential steps: monomer activation, dimerization of activated species, and propagation of trimers to higher order polymers. The competition between monomer activation and chain propagation leads to the observed nonmonotonic variation of ?(T). The actin polymerization in D2O buffer differs considerably from that in the H2O buffer and underscores the significant deuterium effect on hydrophobic interactions and hydrogen bonding in the polymerization process.

Niranjan, Priya S.; Yim, Peter B.; Forbes, Jeffrey G.; Greer, Sandra C.; Dudowicz, Jacek; Freed, Karl F.; Douglas, Jack F.

2003-08-01

175

Photochemical transformations of anthraquinone in polymeric alcohols  

NASA Astrophysics Data System (ADS)

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

Tsaplev, Yu. B.

2012-12-01

176

Thermally Stable, Piezoelectric and Pyroelectric Polymeric Substrates  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

177

Polymeric dyes based on thiadiazole derivatives  

Microsoft Academic Search

A series of polymeric dyes were synthesized by free radical addition polymerization of monomeric dyes. The 2-amino-5-mercapto-1,3,4-thiadiazole\\u000a was diazotized and coupled with various N-arylmaleimides to give monomeric dyes. All the polymeric dyes were characterized\\u000a by elemental analysis, infrared spectroscopy, visible absorption spectroscopy, viscometry, and thermogravimetric analysis.\\u000a Color and dyeing properties of the polymeric dyes were discussed by comparing them with

Hari Raghav Maradiya; Vithal Soma Patel

2001-01-01

178

Nonlinear optical and conductive polymeric material  

DOEpatents

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

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

1993-10-19

179

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

180

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

181

Nonlinear optical and conductive polymeric material  

DOEpatents

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

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

1992-05-19

182

The Viscosity of Polymeric Fluids.  

ERIC Educational Resources Information Center

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

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

1983-01-01

183

Polymerization-induced phase separation  

Microsoft Academic Search

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

J. C. Lee

1999-01-01

184

Sleeving nanocelluloses by admicellar polymerization.  

PubMed

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

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

2013-10-15

185

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 ...

186

Mechanisms of polymeric film formation.  

PubMed

Polymeric films are applied to solid dosage forms for decorative, protective, and functional purposes. These films are generally applied by a spray atomization process, where the polymer is sprayed onto the solid substrate. The mechanism by which films are formed is dependent on whether the polymer is in the dissolved or dispersed state. For solutions, film formation occurs as the solvent evaporates, since the polymer chains are intimately mixed. Film formation from polymeric dispersions, however, requires the coalescence of individual polymer spheres and interpenetration of the polymer chains. Films prepared from polymeric dispersions exhibit a minimum film forming temperature and processing conditions must exceed this temperature in order to form the film. In addition, these systems generally require post-coating storage in temperature and humidity controlled environments to ensure complete polymer coalescence. Incomplete coalescence can lead to significant changes in drug release over time. This review article highlights the basic science principles involved in film formation from both polymeric solutions and dispersions and the variables that influence these film formation processes. PMID:23305867

Felton, Linda A

2013-12-01

187

Polymerization Mechanism of ?-Linear Olefin  

NASA Astrophysics Data System (ADS)

The density functional theory on the level of B3LYP/6-31G was empolyed to study the chain growth mechanism in polymerization process of ?-linear olefin in TiCl3/AlEt2Cl catalytic system to synthesize drag reduction agent. Full parameter optimization without symmetry restrictions for reactants, products, the possible transition states, and intermediates was calculated. Vibration frequency was analyzed for all of stagnation points on the potential energy surface at the same theoretical level. The internal reaction coordinate was calculated from the transition states to reactants and products respectively. The results showed as follows: (i) Coordination compounds were formed on the optimum configuration of TiCl3/AlEt2Cl. (ii) The transition states were formed. The energy difference between transition states and the coordination compounds was 40.687 kJ/mol. (iii) Double bond opened and Ti-C(4) bond fractured, and the polymerization was completed. The calculation results also showed that the chain growth mechanism did not essentially change with the increase of carbon atom number of ?-linear olefin. From the relationship between polymerization activation energy and carbon atom number of the ?-linear olefin, it can be seen that the ?-linear olefin monomers with 6-10 carbon atoms had low activation energy and wide range. It was optimum to synthesize drag reduction agent by polymerization.

Xing, Wen-guo; Zhang, Chang-qiao; Yu, Ping; Liu, Cheng-bu; Wei, Yun-he

2010-02-01

188

Chondroitin sulphate decorated nanoparticulate carriers of 5-fluorouracil: development and in vitro characterization.  

PubMed

The present study investigates prospective of tailored nanoparticles as vectors to provide improved therapeutic efficacy of encapsulated anti-cancer drug 5-FU. Condritin Sulphate (CS) conjugated PLGA nanoparticles were prepared using PEG-bis-amine and adipic dihydrazide as spacers and loaded with an anti-cancer drug 5-FU (CS-PEG-PLGA-FU and CS-ADH-PLGA-FU). The formulations were then compared with non CS-anchored monomethoxy(polyethylene glycol) (MPEG-PLGA-FU) nanoparticles. Nanoparticlulate systems were further characterized by FTIR, NMR, TEM studies and particle size/polydispersity index (PDI) analysis. DSC and XRD were also performed to assess the nature of 5-FU inside the nanoparticles. The nanoparticles prepared using amphiphilic block copolymer CS-PEG-PLGA were able to sustain the release of 5-FU up to 48 h whereas those of CS-ADH-PLGA and MPEG-PLGA released the drug up to 24 h. The CS-PEG-PLGA-FU nanoparticles were found to be least haemolytic when compared to free drug, CS-ADH-PLGA-FU and MPEG-PLGA-FU nanoparticles. Cytotoxicity studies were performed on MCF-7/MDA-MD 231 breast cancer cells. PLGA nanoparticles exhibited more potent cytotoxic effect on MCF-7/MDA-MD 231 cells than free doxorubicin. Further, enhanced cytotoxicity and lower hemolytic potential of CS-PEG-PLGA-FU nanoparticles suggest a potential application in cancer chemotherapy. PMID:21323107

Yadav, Awesh K; Agarwal, Abhinav; Jain, Sanyog; Mishra, Anil K; Bid, Hemant; Rai, Gopal; Agrawal, Hirnanshu; Agrawal, Govind P

2010-08-01

189

Plasma-polymerized coatings on various substrates  

SciTech Connect

Plasma polymerized coatings can possibly be used to provide protection for moisture-sensitive substrates such as lithium hydride and depleted uranium. Paraxylene, benzene, perfluoro-2-butene, tetrahydrofuran, and other monomers have been used to deposit plasma polymerized coatings on these substrates. Coatings on glass slides, other metals, and glass microballoons have yielded additional information on the plasma polymerization process in general.

Weatherspoon, K.A.; Wilkerson, M.H.

1987-07-01

190

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

191

Diffractive vector meson production  

NASA Astrophysics Data System (ADS)

This is a brief introduction to diffractive vector meson production, both exclusive ?p?V and large momentum transfer ?p?VX processes. I overview the theoretical basis for the perturbative description and some recent developments.

Enberg, R.

2005-06-01

192

Baculovirus as vaccine vectors.  

PubMed

Application of viral vectors derived from human viruses to mediate immune response in animals and humans has been greatly hampered by the problems associated with pre-existing immunity and associated toxicities. Among few non-human viral vectors, baculovirus has now evolved as a novel tool for vaccine vector development. With broad tissue tropism and expanded bio-safety profile suitably supplemented with intrinsic immunostimulatory properties, baculovirus has now attained a niche position in the arena of vaccine development. Recombinant envelope-modified baculovirus equipped with novel shuttle promoters for in vivo transduction has shown promising results in several animal models. Baculovirus mediated induction of systemic and mucosal immune responses through intranasal or oral administration has now open an entirely new way for the development of new generation vaccines. Gaining additional insight into the baculovirus biology and its interaction with non-native hosts will certainly promote this human-friendly virus as a potential vector for clinical applications. PMID:20394572

Madhan, Selvaraj; Prabakaran, Mookkan; Kwang, Jimmy

2010-06-01

193

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

PubMed

We present a study of the growth of the p-type inorganic semiconductor CuI on n-type TiO2 anatase single crystal (101) surfaces and on nanoparticulate anatase surfaces using synchrotron radiation photoemission spectroscopy. Core level photoemission data obtained using synchrotron radiation reveal that both the substrate (TiO2) and the overlayer (CuI) core levels shift to a lower binding energy to different degrees following the growth of CuI on TiO2. Valence band photoemission data show that the valence band maximum of the clean substrate differs from that of the dosed surface which may be interpreted qualitatively as due to the introduction of a new density of states within the band gap of TiO2 as a result of the growth of CuI. The valence band offset for the heterojunction n-TiO2p-CuI has been measured using photoemission for both nanoparticulate and single crystal TiO2 surfaces, and the band energy alignment for these heterojunction interfaces is presented. With the information obtained here, it is suggested that the interface between p-CuI and single crystal anatase-phase n-TiO2 is a type-II heterojunction interface, with significant band bending. The measured total band bending matches the work function change at the interface, i.e., there is no interface dipole. In the case of the nanoparticulate interface, an interface dipole is found, but band bending within the anatase nanoparticles remains quite significant. We show that the corresponding depletion layer may be accommodated within the dimension of the nanoparticles. The results are discussed in the context of the functional properties of dye-sensitized solid state solar cells. PMID:17887866

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

2007-09-21

194

Poynting-vector filter  

DOEpatents

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

Carrigan, Charles R. (Tracy, CA)

2011-08-02

195

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

196

Immobilized metal affinity chromatography of histidine-tagged lentiviral vectors using monolithic adsorbents  

Microsoft Academic Search

Histidine-tagged lentiviral vectors were separated from crude cell culture supernatant using labscale monolithic adsorbents by immobilized metal affinity chromatography. The capture capacity, concentration factor, purification factor, and elution efficiency of a supermacroporous cryogel monolith were evaluated against the BIA Separations convective interaction media (CIM) disc, which is a commercial macroporous monolith. The morphology of the polymeric cryogel material was characterised

M. C. Cheeks; N. Kamal; A. Sorrell; D. Darling; F. Farzaneh; N. K. H. Slater

2009-01-01

197

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

198

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

199

Micro-CT Based Experimental Liver Imaging Using a Nanoparticulate Contrast Agent: A Longitudinal Study in Mice  

PubMed Central

Background Micro-CT imaging of liver disease in mice relies on high soft tissue contrast to detect small lesions like liver metastases. Purpose of this study was to characterize the localization and time course of contrast enhancement of a nanoparticular alkaline earth metal-based contrast agent (VISCOVER ExiTron nano) developed for small animal liver CT imaging. Methodology ExiTron nano 6000 and ExiTron nano 12000, formulated for liver/spleen imaging and angiography, respectively, were intravenously injected in C57BL/6J-mice. The distribution and time course of contrast enhancement were analysed by repeated micro-CT up to 6 months. Finally, mice developing liver metastases after intrasplenic injection of colon carcinoma cells underwent longitudinal micro-CT imaging after a single injection of ExiTron nano. Principal Findings After a single injection of ExiTron nano the contrast of liver and spleen peaked after 4–8 hours, lasted up to several months and was tolerated well by all mice. In addition, strong contrast enhancement of abdominal and mediastinal lymph nodes and the adrenal glands was observed. Within the first two hours after injection, particularly ExiTron nano 12000 provided pronounced contrast for imaging of vascular structures. ExiTron nano facilitated detection of liver metastases and provided sufficient contrast for longitudinal observation of tumor development over weeks. Conclusions The nanoparticulate contrast agents ExiTron nano 6000 and 12000 provide strong contrast of the liver, spleen, lymph nodes and adrenal glands up to weeks, hereby allowing longitudinal monitoring of pathological processes of these organs in small animals, with ExiTron nano 12000 being particularly optimized for angiography due to its very high initial vessel contrast.

Boll, Hanne; Nittka, Stefanie; Doyon, Fabian; Neumaier, Michael; Marx, Alexander; Kramer, Martin; Groden, Christoph; Brockmann, Marc A.

2011-01-01

200

Polyhomologation. A living C1 polymerization.  

PubMed

The physical properties of synthetic macromolecules are strongly coupled to their molecular weight (MW), topology, and polydispersity index (PDI). Factors that contribute to their utility include the control of functionality at the macromolecule termini and copolymer composition. Conventional polymerization reactions that produce carbon backbone polymers (ionic, free radical, and coordination) provide little opportunity for controlling these variables. Living polymerizations, sometimes referred to as controlled polymerizations, have provided the means for achieving these goals. Not surprisingly, these reactions have had a profound impact on polymer and materials science. Three basic reaction types are used for the synthesis of most carbon backbone polymers. The first examples of "living" polymerizations were developed for ionic polymerizations (cationic and anionic). These reactions, which can be technically challenging to perform, can yield excellent control of molecular weight with very low polydispersity. The second reaction type, free radical polymerization, is one of the most widely used polymerizations for the commercial production of high molecular weight carbon backbone polymers. Nitroxide mediated polymerization (NMP), reversible addition-fragmentation chain transfer polymerization (RAFT), and atom transfer radical polymerization (ATRP) have emerged as three of the more successful approaches for controlling these reactions. The third type, transition metal mediated coordination polymerization, is the most important method for large-scale commercial polyolefin production. Simple nonfunctional hydrocarbon polymers such as polyethylene (PE), polypropylene, poly-?-olefins, and their copolymers are synthesized by high pressure-high temperature free radical polymerization, Ziegler-Natta or metallocene catalysts. Although these catalysts of exceptional efficiency that produce polymers on a huge scale are in common use, control that approaches a "living polymerization" is rare. Although the controlled synthesis of linear "polyethylene" described in this Account is not competitive with existing commercial processes for bulk polymer production, they can provide quantities of specialized materials for the study of structure-property relationships. This information can guide the production of polymers for new commercial applications. We initiated a search for novel polymerization reactions that would produce simple hydrocarbon polymers with the potential for molecular weight and topological control. Our research focused on polymerization reactions that employ nonolefin monomers, more specifically the polymerization of ylides and diazoalkanes. In this reaction, the carbon backbone is built one carbon at a time (C1 polymerization). These studies draw upon earlier investigations of the Lewis acid catalyzed polymerization of diazoalkanes and build upon our discovery of the trialkylborane initiated living polymerization of dimethylsulfoxonium methylide 1. PMID:20825177

Luo, Jun; Shea, Kenneth J

2010-11-16

201

Metal containing polymeric functional microspheres  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

202

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

203

Polymeric Nanofibers in Tissue Engineering  

PubMed Central

Polymeric nanofibers can be produced using methods such as electrospinning, phase separation, and self-assembly, and the fiber composition, diameter, alignment, degradation, and mechanical properties can be tailored to the intended application. Nanofibers possess unique advantages for tissue engineering. The small diameter closely matches that of extracellular matrix fibers, and the relatively large surface area is beneficial for cell attachment and bioactive factor loading. This review will update the reader on the aspects of nanofiber fabrication and characterization important to tissue engineering, including control of porous structure, cell infiltration, and fiber degradation. Bioactive factor loading will be discussed with specific relevance to tissue engineering. Finally, applications of polymeric nanofibers in the fields of bone, cartilage, ligament and tendon, cardiovascular, and neural tissue engineering will be reviewed.

Dahlin, Rebecca L.; Kasper, F. Kurtis

2011-01-01

204

Polymeric cationic substituted acrylamide surfactants  

SciTech Connect

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

Nieh, E.C.Y.

1983-11-15

205

New electrochromic polymeric pyridinium salts  

Microsoft Academic Search

A series of new anode-cathode conjugated electrochromic polymeric pyridinium salts containing mainchain triphenylamine units\\u000a and demonstrating multicolor electrochromism has been synthesized. All of the polymers exhibit intense UV absorption with\\u000a maxima of absorption and fluorescence at 340–343 and 336–338 nm in DMF solutions and 460–461 and 410–438 nm in films. The\\u000a electrochromic properties of the films are investigated by electrochemical

M. L. Keshtov; T. E. Grigor’ev; A. R. Khokhlov

2009-01-01

206

Starch Based Solid Polymeric Electrolytes  

Microsoft Academic Search

New solid polymeric electrolytes were obtained from amylopectin rich starch plasticized with glycerol and containing lithium perchlorate salt. The transparent film samples were characterized by X-ray diffraction and thermal analysis (DSC). The ionic conductivity measurements were obtained by impedance complex spectroscopy as a function of temperature three different salt contents. The conductivity of 5.05·10 ?5 S\\/cm at room temperature were

D. C. Dragunski; A. Pawlicka

2002-01-01

207

Polymerization inhibitors for polyunsaturated oils  

Microsoft Academic Search

Several edible anionic surfactants were found to function as polymerization inhibitors for safflower oil. The most effective\\u000a additive was the sodium salt of phosphated mono- and diglycerides. Additional inhibitors included sodium diacetyltartaric\\u000a acid esters of mono- and diglycerides, sodium stearoyl-2-lactylate, sodium stearyl fumarate, sodium succinoylated mono- and\\u000a diglycerides, dioctyl sodium sulfosuccinate, and sodium sulfoacetate esters of mono- and diglycerides. It

R. J. Sims; J. A. Fioriti; M. J. Kanuk

1973-01-01

208

Polymeric nanoparticles for molecular imaging.  

PubMed

Conventional imaging technologies (X-ray computed tomography, magnetic resonance, and optical) depend on contrast agents to visualize a target site or organ of interest. The imaging agents currently used in clinics for diagnosis suffer from disadvantages including poor target specificity and in vivo instability. Consequently, delivery of low concentrations of contrast agents to region of interest affects image quality. Therefore, it is important to selectively deliver high payload of contrast agent to obtain clinically useful images. Nanoparticles offer multifunctional capabilities to transport high concentrations of imaging probes selectively to diseased site inside the body. Polymeric nanoparticles, incorporated with contrast agents, have shown significant benefits in molecular imaging applications. These materials possess the ability to encapsulate different contrast agents within a single matrix enabling multimodal imaging possibilities. The materials can be surface conjugated to target-specific biomolecules for controlling the navigation under in vivo conditions. The versatility of this class of nanomaterials makes them an attractive platform for developing highly sensitive molecular imaging agents. The research community's progress in the area of synthesis of polymeric nanomaterials and their in vivo imaging applications has been noteworthy, but it is still in the pioneer stage of development. The challenges ahead should focus on the design and fabrication of these materials including burst release of contrasts agents, solubility, and stability issues of polymeric nanomaterials. For further resources related to this article, please visit the WIREs website. Conflict of interest: The authors declare no competing financial interest. PMID:24616442

Srikar, R; Upendran, Anandhi; Kannan, Raghuraman

2014-05-01

209

Two Photon Polymerization of Ormosils  

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

210

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

211

Polymeric nanocomposites: compounding and performance.  

PubMed

Polymeric nanocomposites (PNC) are binary mixtures of strongly interacting, inorganic platelets dispersed in a polymeric matrix. For full exfoliation, the thermodynamic miscibility is required. There are three basic methods of organically-modified clay dispersion that might result in PNC: (1) in polymer solution (followed by solvent removal), (2) in a monomer (followed by polymerization), and (3) in molten polymer (compounding). Most commercial PNC are produced by the second method, but it is the third one that has the greatest promise for the plastics industry. Similarly as during the manufacture of polymer blends, the layered silicates must be compatibilized by intercalation with organic salts and/or addition of functionalized macromolecules. Compounding affects the kinetics of dispersion process, but rarely the miscibility. Melt compounding is carried out either in a single-screw (SSE) or a twin-screw extruder (TSE). Furthermore, an extensional flow mixer (EFM) might be attached to an extruder. Two versions of EFM were evaluated: (1) designed for polymer homogenization and blending, and (2) designed for dispersing nano-particles. In this review, the dispersion of organoclay in polystyrene (PS), polyamide-6 (PA-6) or in polypropylene (PP) is discussed. The PNC based on PS or PA-6 contained two components (polymer and organoclay), whereas those based on PP in addition had a compatibilizer mixture of two maleated polypropylenes. Better dispersion was found compounding PNC's in a SSE + EFM than in TSE with or without EFM. The mechanical performance (tensile, flexural and impact) was examined. PMID:18572559

Utracki, L A

2008-04-01

212

Application of x-ray nano-particulate markers for the visualization of intermediate layers and interfaces using scanning electron microscopy  

NASA Astrophysics Data System (ADS)

In this study the methodology of biological sample preparation for dental research using SEM/EDX has been elaborated. (1)The original cutting equipment supplied with 3D user-controlled sample fixation and an adjustable cooling system has been designed and evaluated. (2) A new approach to the root dentine drying procedure has been developed to preserve structure peculiarities of root dentine. (3) A novel adhesive system with embedded X-Ray nanoparticulate markers has been designed. (4)The technique allowing for visualization of bonding resins, interfaces and intermediate layers between tooth hard tissues and restorative materials of endodontically treated teeth using the X-ray nano-particulate markers has been developed and approved. These methods and approaches were used to compare the objective depth of penetration of adhesive systems of different generations in root dentine. It has been shown that the depth of penetration in dentine is less for adhesive systems of generation VI in comparison with bonding resins of generation V, which is in agreement with theoretical evidence. The depth of penetration depends on the correlation between the direction of dentinal tubules, bonding resin delivery and gravity.

Bessudnova, Nadezda O.; Bilenko, David I.; Zakharevich, Andrey M.

2011-10-01

213

Fabrication of nanoparticulate porous LaOF films through film growth and thermal decomposition of ion-modified lanthanum diacetate hydroxide.  

PubMed

This paper first reports fabrication of macro/nanotextured rare-earth oxyfluoride films. Usage of ion-modified lanthanum diacetate hydroxide (LDAH) as self-templates was successful in producing nanoparticulate lanthanum oxyfluoride (LaOF) films. LDAH template films were deposited on glass substrates through a chemical bath deposition in solutions composed of lanthanum acetate sesquihydrate, methanol, trifluoroacetic acid, and aqueous ammonia. The LDAH films had a unique, nestlike morphology owing to a two-dimensional hexagonal crystal growth. Modification of LDAH with trifluoroacetate ions led to formation of LaOF after pyrolyzing the template films at temperatures of 400-600 degrees C in air. The resultant LaOF films had a nanoparticulate porous microstructure, maintaining the morphology of the original LDAH template films. It was also successful to incorporate Eu3+ ions into LaOF through deposition of the LDAH film in a solution containing europium acetate tetrahydrate. The characteristic photoluminescence from Eu(3+) was observed with an ultraviolet-light excitation at 273 nm, indicating that Eu3+ was homogeneously distributed in LaOF host crystals. Thus the ion-modification of LDAH was also demonstrated to be a useful method for preparing nanostructured rare-earth oxyfluoride materials havingvarious cationic compositions. PMID:15875413

Hosono, Eiji; Fujihara, Shinobu; Kimura, Toshio

2004-04-27

214

Biosafety of lentiviral vectors.  

PubMed

The characteristics of lentiviral vectors (stable integration in non-dividing and dividing cells, long-term expression of the transgene, absence of immune response) make them ideal gene transfer vehicula for future gene therapy. However, the most potent lentiviral vectors are derived from highly pathogenic human viruses, such as HIV. We describe how the field has engineered lentivectors with increasing biosafety both for the lab worker and for the patient. The risk associated with state-of-the-art lentivectors is therefore minimal, although a psychological barrier to use these vectors in the clinic may still have to be overcome. Due to their increased performance, care should be taken to avoid accidental transduction of the lab worker with potential hazardous genes. The precautions which have to be taken are described in detail. PMID:14683448

Debyser, Zeger

2003-12-01

215

Singularly perturbed vector fields  

NASA Astrophysics Data System (ADS)

A geometrically invariant concept of singularly perturbed systems of ordinary differential equations (singularly perturbed vector fields) is proposed in this paper. Singularly perturbed vector fields can be represented locally as singularly perturbed systems (for corresponding coordinate system choice. The paper focuses on possible ways of fast and slow directions/manifolds evaluations. A special algorithm for the evaluation is proposed. The algorithm is called as a global quasi-linearization procedure. A practical application of the proposed algorithm for numerical simulations is the main issue of the paper.

Bykov, V.; Goldfarb, I.; Gol'dshtein, V.

2006-12-01

216

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

217

Vector Addition with Integer Components  

NSDL National Science Digital Library

The Vector Addition with Integer 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 this simulation the x and y components of each vector are all integers. 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 Addition with Integer Components 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_components_integer.jar file will run the program if Java is installed.

Duffy, Andrew

2010-05-02

218

Massively parallel vector processing computer  

SciTech Connect

This patent describes a vector processing node for a computer of the type having a network of simultaneously operating vector processing nodes interconnected by bidirectional external busses for conveying parallel data words between the vector processing nodes. The vector processing node comprising: a bi-directional first bus for conveying parallel data words; a bi-directional second bus for conveying parallel data words; vector memory means connected for read and write access through the second bus for storing vectors comprising sequences of parallel data words conveyed on the second bus; vector processing means connected to the second bus for transmitting parallel data words to and receiving parallel data words from the vector memory means for generating output vectors comprising functions of input vectors stored in the vector memory means and for storing the output vectors in the vector memory means; and control means including a computer processor connected to the first bus, external port means controlled by the computer processor and connected between the first bus and the external busses, and local port means controlled by the computer processor connected between the first and second busses, for transmitting parallel data words to and receiving parallel data words from the first bus, the second bus, the external busses, and the vector memory.

Call, D.B.; Mudrow, A.; Johnson, R.C.; Bennion, R.F.

1990-01-02

219

Numerical Analysis of Plasma Initiated Polymerization  

NASA Astrophysics Data System (ADS)

Plasma initiated polymerization is a kind of well-known radical polymerization mechanism, but it has the `living' polymerization feature and produces ultra-high molecular weight polymer. In order to explain such phenomena, we calculate the basic data of plasma initiated polymerization of methylmethacrylate (MMA) according to the principle of polymer physics and chemistry. It results in that the radical concentration ranges from 10-12mol/L to 10-16mol/L corresponding to the radical life in 104s to 108s, which means the radicals have a long lifetime. Moreover because of the long lifetime radicals it causes a unique feature rather than the common radical polymerization, and also shows no ``living polymerization''. It is noticed in experiments that there are two key factors playing important roles. One is the effective radical amount produced during the plasma discharging while the another is the diffusion factor.

You, Qingliang; Wang, Jianhua; Meng, Yuedong; Shu, Xingsheng; Ou, Qiongrong; Xu, Xu; Shen, Keming

2006-07-01

220

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

221

Vector potential methods  

NASA Technical Reports Server (NTRS)

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

Hafez, M.

1989-01-01

222

Techniques for Vector Quantization.  

National Technical Information Service (NTIS)

The second year of AFOSR support at the University of California, Santa Barbara has allowed us to make significant strides in exploring the potential of vector quantization for source coding. Some of this work is described in the attached list of referenc...

A. Gersho

1984-01-01

223

Polyaniline nanotubes doped with polymeric acids  

Microsoft Academic Search

Self-assembled polyaniline (PANI) nanotubes were prepared in the presence of three different polymeric acids as dopants, namely poly(4-styrenesulfonic acid) (PSSA), poly(acrylic acid) (PAA) and poly(methyl vinyl ether-alt-maleic acid) (PMVEA) by oxidative polymerization using ammonium persulfate as the oxidant. The molecular structure of polymeric acids had a significant effect on the morphology and size of the polyaniline nanotubes as determined by

Lijuan Zhang; Hui Peng; Jing Sui; Paul A. Kilmartin; Jadranka Travas-Sejdic

2008-01-01

224

Polymeric membrane materials for artificial organs  

Microsoft Academic Search

Many polymeric materials have already been used in the field of artificial organs. However, the materials used in artificial\\u000a organs are not necessarily created with the best material selectivity and materials design; therefore, the development of\\u000a synthesized polymeric membrane materials for artificial organs based on well-defined designs is required. The approaches to\\u000a the development of biocompatible polymeric materials fall into

Hiroyoshi Kawakami

2008-01-01

225

(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

226

Polymerization of ?-Hydroxyacetylenes by Transition Metal Catalysts  

Microsoft Academic Search

?-Hydroxyacetylenes (2-propyn-1-ol, DL-3-butyn-2-ol, 1-octyn-3-ol, 2-phenyl-3-butyn-2-ol) with a hydroxy functional group were polymerized by various Mo- and W-based catalysts. In general, the catalytic activities of Mo-based catalysts were greater than those of W-based catalysts for these polymerizations. In the polymerization of 2-propyn-l-ol, MoCl5 alone and the MoCl5-EtAlCl2 catalyst system gave a quantitative yield of polymer. In the polymerization of 2-propyn-l-ol and

Yeong-Soon Gal; Bal Jung; Ji-Heung Kim; Won-Chul Lee; Sam-Kwon Choi

1994-01-01

227

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

228

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

229

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

230

Ionene modified small polymeric beads  

NASA Technical Reports Server (NTRS)

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

Rembaum, Alan (Inventor)

1977-01-01

231

A vector asymmetrical NNV equation  

NASA Astrophysics Data System (ADS)

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

Yu, Guo-Fu; Tam, Hon-Wah

2008-08-01

232

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

PubMed

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

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

2012-04-01

233

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

234

Vectors from A to B  

NSDL National Science Digital Library

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

235

Solar Polymerization of Atmospheric Aerosol  

NASA Astrophysics Data System (ADS)

Alpha-oxoacids are ubiquitous constituents of the aqueous fraction of ambient aerosol as products common to the oxidation of most atmospheric organic species. The environmental fate of alpha-oxoacids is in turn determined by the photoreactions of their carbonyl groups under solar (lambda longer than 300 nm) irradiation. We report that, in addition to CO2 extrusion, the photodecomposition of alpha-oxoacids in water leads to hitherto unidentified, colored oligomers. These oligomers are separated by high performance liquid chromatography, and identified as thermolabile polyfunctional oxo-, hydroxy- and carboxylic acid derivatives of aliphatic polyethers by electrospray ionization-negative ion mass spectrometry (ESI-MS) and 13C-NMR. Polymerization is initiated by photoinduced electron transfer between carbonyl groups of adjacent alpha-oxoacid molecules, and most likely propagated by alkoxyl radicals. The degree of polymerization increases with irradiation time until oligomers heavier than about 1 kDa separate as yellow solids. It is found that these oligomers pyrolyze into simpler species under conventional gas chromatographic conditions. Present results require a fundamental revision of current mechanisms of aerosol growth and stabilization, and a critical reappraisal of the analytical techniques used to characterize aerosol.

Colussi, A. J.; Guzman, M. I.; Hoffmann, M. R.

2005-12-01

236

Preloadable vector sensitive latch  

NASA Technical Reports Server (NTRS)

A preloadable vector-sensitive latch which automatically releases when the force vector from a latch memebr reaches a specified release angle is presented. In addition, it contains means to remove clearance between the latched members and to preload the latch to prevent separation at angles less than the specified release angle. The latch comprises a triangular main link, a free link connected between a first corner of the main link and a yoke member, a housing, and an actuator connected between the yoke member and the housing. A return spring bias means connects the main link to a portion of the housing. A second corner of the main link is slidably and pivotally connected to the housing via a slot in a web portion of the housing. The latch housing has a rigid docking ring alignable with a mating locking ring which is engageable by a locking roller journalled on the third corner of the triangular main link.

Acres, William R. (inventor)

1987-01-01

237

Eliminating malaria vectors  

PubMed Central

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

2013-01-01

238

Vertical vector face lift.  

PubMed

Facial rejuvenation using local anesthesia has evolved in the past decade as a safer option for patients seeking fewer complications and minimal downtime. Mini- and short-scar face lifts using more conservative incision lengths and extent of undermining can be effective in the younger patient with lower face laxity and minimal loose, elastotic neck skin. By incorporating both an anterior and posterior approach and using an incision length between the mini and more traditional face lift, the Vertical Vector Face Lift can achieve longer-lasting and natural results with lesser cost and risk. Submentoplasty and liposuction of the neck and jawline, fundamental components of the vertical vector face lift, act synergistically with superficial musculoaponeurotic system plication to reestablish a more youthful, sculpted cervicomental angle, even in patients with prominent jowls. Dramatic results can be achieved in the right patient by combining with other procedures such as injectable fillers, chin implants, laser resurfacing, or upper and lower blepharoplasties. PMID:21276163

Somoano, Brian; Chan, Joanna; Morganroth, Greg

2011-01-01

239

Statistical analysis of cointegration vectors  

Microsoft Academic Search

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

Soren Johansen

1988-01-01

240

Vector-valued rational forms  

NASA Astrophysics Data System (ADS)

We define rational Hermite interpolants to vector-valued functions and show that, in the context of Clifford algebras, the numerator and denominator polynomials belong to a complex extension of the Lipschitz group. We also discuss the problem of constructing an algebraic representation for the generalized inverse of a vector, which is at the heart of the usual development of vector rational approximation.

Roberts, D. E.

1993-11-01

241

Insecticide Resistance and Vector Control  

Microsoft Academic Search

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

William G. Brogdon; Janet C. McAllister

1998-01-01

242

Division and New Vector Multiplication  

Microsoft Academic Search

The division between two vectors that belong to the same vector space is obtained by elementary algebra vectorial procedures. It is defined as a matrix. This representation is obtained, first for the vector space of two and three dimensions and then to a space of dimension N with inner product defined. The relationship of the obtained result with the quaternions

J E Hernández; E Roca O; R Betancourt R

243

Containment of Arthropod Disease Vectors  

Microsoft Academic Search

Effective containment of arthropod vectors of infectious diseases is necessary to prevent transmission of pathogens by released, infected vectors and to prevent vectors that escape from establishing populations that subsequently con- tribute to increased disease. Although rare, past releases illustrate what can go wrong and justify the need for guide- lines that minimize risks. An overview of recommendations for insectary

Thomas W. Scott

244

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

2013-01-01

245

Vector Magnetograph Design  

NASA Technical Reports Server (NTRS)

This report covers work performed during the period of November 1994 through March 1996 on the design of a Space-borne Solar Vector Magnetograph. This work has been performed as part of a design team under the supervision of Dr. Mona Hagyard and Dr. Alan Gary of the Space Science Laboratory. Many tasks were performed and this report documents the results from some of those tasks, each contained in the corresponding appendix. Appendices are organized in chronological order.

Chipman, Russell A.

1996-01-01

246

21 CFR 870.3650 - Pacemaker polymeric mesh bag.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870.3650...Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted device used to...

2009-04-01

247

21 CFR 870.3650 - Pacemaker polymeric mesh bag.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870.3650...Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted device used to...

2010-04-01

248

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

249

Flexible Polymerization Apparatus for Homo-, CO- and Terpolymerization of Olefins.  

National Technical Information Service (NTIS)

The purpose of the report is to introduce the polymerization apparatus to the reader and at the same time to serve as a polymerization procedure instruction. The polymerization apparatus was developed in Helsinki University of Technology during 1988-1990....

J. Koivumaeki

1991-01-01

250

MEMS based polymeric drug delivery system  

Microsoft Academic Search

In this paper, MEMS based polymeric drug delivery system for the treatment of cardiovascular disorder such as hypertension is presented. The major components of proposed system are drug delivery device, blood pressure sensor, flow sensor, electronic module, and power supply. Drug delivery device consists of piezoelectric actuator and reservoir integrated with side open polymeric microneedles. The in-depth theoretical and numerical

M. W. Ashraf; S. Tayyaba; N. Afzulpurkar

2010-01-01

251

Polymeric Additives For Graphite/Epoxy Composites  

NASA Technical Reports Server (NTRS)

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

Kourtides, D. A.; Nir, Z.

1990-01-01

252

Nanofibers of polyaniline synthesized by interfacial polymerization  

Microsoft Academic Search

The average diameter of polyaniline nanofibers obtained by interfacial polymerization using a solution of aniline in toluene as the top organic phase and acidic ammonium peroxydisulfate as the bottom aqueous phase can be controlled by using surface active dopants and\\/or surfactants in the aqueous phase. The average diameter of polyaniline nanofibers doped with camphorsulfonic acid (CSA) synthesized by interfacial polymerization

Xinyu Zhang; Roch Chan-Yu-King; Anil Jose; Sanjeev K Manohar

2004-01-01

253

Polymeric precursors to refractory metal borides  

Microsoft Academic Search

Polymeric precursors to zirconium and hafnium diboride are described. Initial studies concentrated on carbothermal\\/borothermal reduction of metal alkoxides; however, improved results were obtained from oxide free-precursors prepared from the metal borohydride and borazine. The metal borides are obtained in good chemical and ceramic yield upon pyrolysis, and the polymeric precursors obtained through the reaction of borazine with the metal borohydride

S. T. Schwab; C. A. Stewart; K. W. Dudeck; S. M. Kozmina; J. D. Katz; B. Bartram; E. J. Wuchina; W. J. Kroenke; G. Courtin

2004-01-01

254

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

255

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

256

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

257

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

258

Amorphous Polymeric Nitrogen from Dynamic Shock Simulation  

NASA Astrophysics Data System (ADS)

In recent years there has been significant interest in polymeric phases of nitrogen at low pressure for potential application as an energetic material. This interest was bolstered by experimental evidence of metastable amorphous polymeric nitrogen at low pressure.ootnotetextGoncharov, A. F. et al., Phys. Rev. Lett. 85, 1262 (2000)^,ootnotetextEremets, M. I. et al., Nature 411, 170 (2001) While considerable theoretical work has been done on many crystal phases of nitrogen, simulating amorphous polymeric nitrogen has been more challenging. Starting from first principles dynamic shock simulation of cubic-gauche nitrogenootnotetextMattson, William D. and Balu, Radhakrishnan, Phys. Rev. B 83, 174105 (2011) we demonstrate a form of polymeric nitrogen at low pressure that may be directly related to amorphous polymeric nitrogen.

Beaudet, Todd; Mattson, William; Rice, Betsy

2012-02-01

259

Vector representation of tourmaline compositions  

NASA Technical Reports Server (NTRS)

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

Burt, Donald M.

1989-01-01

260

Polymeric piezoelectric acoustic semicircular transducers  

NASA Astrophysics Data System (ADS)

In commercial applications it is important to be able to either cancel noise, such as in the cabin of a combine, or to generate audible noise, such as in the case of an alarm. Piezoelectrics have demonstrated promise for active noise control and sound generation applications. In this investigation, the dynamic and acoustic capabilities of polymer piezoelectric semi-circular transducers were studied for such applications. The dynamic response of semi-circular piezoelectric transducers was determined numerically using the general purpose finite element code ABAQUS, then verified analytically and experimentally. The acoustic response was modeled using the commercial code COMET/Acoustics with the dynamic velocity response calculated by ABAQUS as initial boundary conditions. Experimental studies were performed on fixed-fixed polymeric piezoelectric curved transducers. The sensitivity of the sound generation capabilities of the transducer was investigated with respect to variations in radius, thickness and width parameters to demonstrate the potential of these devices for noise cancellation and audible sound applications.

Bailo, Kelly C.; Brei, Diann E.; Grosh, Karl

1998-07-01

261

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

262

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

263

Cell penetrating peptides: efficient vectors for delivery of nanoparticles, nanocarriers, therapeutic and diagnostic molecules.  

PubMed

Efficient delivery of therapeutic and diagnostic molecules to the cells and tissues is a difficult challenge. The cellular membrane is very effective in its role as a selectively permeable barrier. While it is essential for cell survival and function, also presents a major barrier for intracellular delivery of cargo such as therapeutic and diagnostic agents. In recent years, cell-penetrating peptides (CPPs), that are relatively short cationic and/or amphipathic peptides, received great attention as efficient cellular delivery vectors due to their intrinsic ability to enter cells and mediate uptake of a wide range of macromolecular cargo such as plasmid DNA (pDNA), small interfering RNA (siRNAs), drugs, and nanoparticulate pharmaceutical carriers. This review discusses the various uptake mechanisms of these peptides. Furthermore, we discuss recent advances in the use of CPP for the efficient delivery of nanoparticles, nanocarriers, DNA, siRNA, and anticancer drugs to the cells. In addition, we have been highlighting new results for improving endosomal escape of CPP-cargo molecules. Finally, pH-responsive and activable CPPs for tumor-targeting therapy have been described. PMID:24795041

Farkhani, Samad Mussa; Valizadeh, Alireza; Karami, Hadi; Mohammadi, Samane; Sohrabi, Nasrin; Badrzadeh, Fariba

2014-07-01

264

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

2013-01-01

265

Method for forming polymerized microfluidic devices  

DOEpatents

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

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

2011-11-01

266

Statistical properties of contact vectors.  

PubMed

We study the statistical properties of contact vectors, a construct to characterize a protein's structure. The contact vector of an N-residue protein is a list of N integers n(i), representing the number of residues in contact with residue i. We study analytically (at mean-field level) and numerically the amount of structural information contained in a contact vector. Analytical calculations reveal that a large variance in the contact numbers reduces the degeneracy of the mapping between contact vectors and structures. Exact enumeration for lengths up to N=16 on the three-dimensional cubic lattice indicates that the growth rate of number of contact vectors as a function of N is only 3% less than that for contact maps. In particular, for compact structures we present numerical evidence that, practically, each contact vector corresponds to only a handful of structures. We discuss how this information can be used for better structure prediction. PMID:12005870

Kabakçioglu, A; Kanter, I; Vendruscolo, M; Domany, E

2002-04-01

267

Polymerization in emulsion microdroplet reactors  

NASA Astrophysics Data System (ADS)

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

Carroll, Nick J.

268

Polymeric Coatings for Electrodynamic Tethers  

NASA Technical Reports Server (NTRS)

Two polymeric coatings have been developed for the Propulsive Small Expendable Deployer System (ProSEDS) mission. ProSEDS is designed to provide an on-orbit demonstration of the electrodynamic propulsion capabilities of tethers in space. The ProSEDS experiment will be a secondary payload on a Delta II unmanned expendable booster scheduled for launch in August 2000. A 5-km conductive tether is attached to the Delta 11 second stage and collects current from the low Earth orbit (LEO) plasma to facilitate de-orbit of the spent stage. The conductive tether is attached to a 10-km non-conductive tether, the other end of which is attached to an endmass containing several scientific instruments. A bare metal tether would have the best conductivity but thermal concerns preclude this design. A conductive polymer developed by Triton Systems has been optimized for conductivity and thermo-optical properties. The current design for the ProSEDS conductive tether is seven strands of 28 AWG aluminum wire individually coated with 8.7 micrometers (0.35 mil) of an atomic oxygen-resistant conductive polymer composed of a mixture of 87% Clear Oxygen-Resistant polymer (COR) and 13% polyanaline (PANi), wrapped around a braided Kevlar (TM) 49 core. Extensive testing has been performed at the Marshall Space Flight Center (MSFC) to qualify this material for flight on ProSEDS. Atomic oxygen exposure was performed, with solar absorptance and infrared emittance measured before and after exposure. Conductivity was measured before and after atomic oxygen exposure. High voltage tests, up to 1500 V, of the current collecting ability of the COR/PANi have been completed. Approximately 160 meters of the conductive tether closest to the Delta 11 second stage is insulated to prevent any electron reconnection to the tether from the plasma contactor. The insulation is composed of polyimide overcoated with TOR-BP, another polymeric coating developed by Triton for this mission. TOR-BP acts as both insulator and a protective coating against atomic oxygen erosion. The insulation has been tested to withstand 5000 V.

Vaughn, Jason A.; Kamenetzky, Rachel R.; Finckenor, Miria M.; Schuler, Peter

2000-01-01

269

Safety considerations in vector development.  

PubMed

The inadvertent production of replication competent retrovirus (RCR) constitutes the principal safety concern for the use of lentiviral vectors in human clinical protocols. Because of limitations in animal models to evaluate lentiviral vectors for their potential to recombine and induce disease, the vector design itself should ensure against the emergence of RCR in vivo. Issues related to RCR generation and one approach to dealing with this problem are discussed in this chapter. To assess the risk of generating RCR, a highly sensitive biological assay was developed to specifically detect vector recombination in transduced cells. Analysis of lentiviral vector stocks has shown that recombination occurs during reverse transcription in primary target cells. Rejoining of viral protein-coding sequences of the packaging construct and cis-acting sequences of the vector was demonstrated to generate env-minus recombinants (LTR-gag-pol-LTR). Mobilization of recombinant lentiviral genomes was also demonstrated but was dependent on pseudotyping of the vector core with an exogenous envelope protein. 5' sequence analysis has demonstrated that recombinants consist of U3, R, U5, and the psi packaging signal joined with an open gag coding region. Analysis of the 3' end has mapped the point of vector recombination to the poly(A) tract of the packaging construct's mRNA. The state-of-the-art third generation packaging construct and SIN vector also have been shown to generate env-minus proviral recombinants capable of mobilizing retroviral DNA when pseudotyped with an exogenous envelope protein. A new class of HIV-based vector (trans-vector) was recently developed that splits the gag-pol component of the packaging construct into two parts: one that expresses Gag/Gag-Pro and another that expresses Pol (RT and IN) fused with Vpr. Unlike other lentiviral vectors, the trans-vector has not been shown to form recombinants capable of DNA mobilization. These results indicate the trans-vector design prevents the generation of env-minus recombinant lentivirus containing a functional gag-pol structure (LTR-gag-pol-LTR), which is absolutely required for retroviral DNA mobilization and the emergence of RCR. Quality assurance based on monitoring for RCR may have limitations as a predictor of safety in vivo, especially in the long term. The demonstration of lentivirus infection via alternative entry mechanisms supports this notion. Therefore, the approach of monitoring trans-vector stocks for env-minus recombinant virus in vitro as a surrogate marker for the possible emergence of RCR in vivo should represent a significant advancement in vector safety quality assurance. PMID:12465466

Kappes, J C; Wu, X

2001-11-01

270

Maths Help: Working with Vectors  

NSDL National Science Digital Library

Analysis of a wide range of physical properties such as force, velocity, and acceleration, requires a firm understanding of the mathematics of vectors. This comprehensive Web site covers many aspects of vector algebra and trigonometry. The often-used dot product and cross product are defined, as well as vector representations of lines and planes. Illustrations are used to demonstrate vector analysis and its real-world applications. A few extra sections delve into related topics, including transformation between Cartesian and spherical coordinates. The material is mostly suitable for high school or college students who have taken pre-calculus.

271

Electroless deposition of polyaniline film via autocatalytic polymerization of aniline  

Microsoft Academic Search

Different from electropolymerization and chemical polymerization, autocatalytic polymerization is a new method for synthesizing polyaniline films. In autocatalytic polymerization, aniline molecules were oxidized to polyaniline film by soluble oxygen on a platinum or palladium substrate. The reaction is initiated by catalysis of the substrate and then proceeds continuously with autocatalysis of the polyaniline film being deposited. The autocatalytic polymerization of

Chuanping Liao; Mingyuan Gu

2002-01-01

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 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

273

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

274

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

275

Polymeric Gels as an Environment for Electrochemistry.  

National Technical Information Service (NTIS)

The program Objectives are to study (1) the transport of ions and molecules in polymeric gels; (2) volume phase transitions of gels and their influence on the transport properties of ions and molecules; (3) electrochemical generation of volume phase trans...

M. Ciszkowska

1998-01-01

276

Hydrocarbon polymeric binder for advanced solid propellant  

NASA Technical Reports Server (NTRS)

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

Potts, J. E. (editor)

1972-01-01

277

Frontal Polymerization in Microgravity Summary of Research.  

National Technical Information Service (NTIS)

The project began with frontal polymerization (FP). We studied many aspects of FP on the ground and performed two successful weeks of flying on the KC-135. The project evolved into the current flight investigation, Transient Interfacial Phenomena in Misci...

J. A. Pojman

2002-01-01

278

Reverse-osmosis membranes by plasma polymerization  

NASA Technical Reports Server (NTRS)

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

Hollahan, J. R.; Wydeven, T.

1972-01-01

279

PERMEABILITY OF POLYMERIC MEMBRANE LINING MATERIALS  

EPA Science Inventory

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

280

Polymeric heart valves: new materials, emerging hopes.  

PubMed

Heart valve (HV) replacements are among the most widely used cardiovascular devices and are in rising demand. Currently, clinically available devices are restricted to slightly modified mechanical and bioprosthetic valves. Polymeric HVs could represent an attractive alternative to the existing prostheses, merging the superior durability of mechanical valves and the enhanced haemodynamic function of bioprosthetic valves. After early unsatisfactory clinical results, polymeric HVs did not reach commercialization, mainly owing to their limited durability. Recent advances in polymers, nanomaterials and surface modification techniques together with the emergence of novel biomaterials have resulted in improved biocompatibility and biostability. Advances in HV design and fabrication methods could also lead to polymeric HVs that are suitable for long-lasting implantation. Considering all these progresses, it is likely that the new generation of polymeric HVs will find successful long-term clinical applications in future. PMID:19406497

Ghanbari, Hossein; Viatge, Helene; Kidane, Asmeret G; Burriesci, Gaetano; Tavakoli, Mehdi; Seifalian, Alexander M

2009-06-01

281

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

282

Oligonucleotide and Long Polymeric DNA Encoding.  

National Technical Information Service (NTIS)

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 ...

R. P. Mariella A. T. Christian J. A. Young S. N. Gardner D. S. Clague J. M. Williams E. L. Miller

2003-01-01

283

Solar imaging vector magnetograph  

NASA Astrophysics Data System (ADS)

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

Canfield, Richard C.

1993-12-01

284

Are Bred Vectors The Same As Lyapunov Vectors?  

Microsoft Academic Search

Regional loss of predictability is an indication of the instability of the underlying flow, where small errors in the initial conditions (or imperfections in the model) grow to large amplitudes in finite times. The stability properties of evolving flows have been studied using Lyapunov vectors (e.g., Alligood et al, 1996, Ott, 1993, Kalnay, 2002), singular vectors (e.g., Lorenz, 1965, Farrell,

Eugenia Kalnay; Matteo Corazza; M. Cai

2002-01-01

285

Radiation effects on polymeric materials  

NASA Technical Reports Server (NTRS)

It is important to study changes in properties of polymeres after irradiation with charged particles, with ultraviolet radiation, and with combinations of both. An apparatus for this purpose has been built at the NASA Langley Research Center. It consists of a chamber 9 inches in diameter and 9 inches high with a port for an electron gun, another port for a mass spectrometer, and a quartz window through which an ultraviolet lamp can be focused. The chamber, including the electron gun and the mass spectrometer, can be evacuated to a pressure of 10 to the 8th power torr. A sample placed in the chamber can be irradiated with electrons and ultraviolet radiation separately, sequentially, or simultaneously, while volatile products can be monitored during all irradiations with the mass spectrometer. The apparatus described above has been used to study three different polymer films: lexan; a polycarbonate; P1700, a polysulfone; and mylar, a polyethylene terephthalate. All three polymers had been studied extensively with both electrons and ultraviolet radiation separately, but not simultaneously. Also, volatile products had not been monitored during irradiation for the materials. A high electron dose rate of 530 Mrads/hr was used so that a sufficient concentration of volatile products would be formed to yield a reasonable mass spectrum.

Kiefer, Richard L.

1988-01-01

286

Polymeric conjugates for drug delivery  

PubMed Central

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

Larson, Nate; Ghandehari, Hamidreza

2012-01-01

287

Polymeric waveguide Fabry Perot resonators  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

288

Graft polymerization of vinyl acetate onto silica  

Microsoft Academic Search

The free-radical graft polymerization of vi- nyl acetate onto nonporous silica particles was studied ex- perimentally. The grafting procedure consisted of surface activation with vinyltrimethoxysilane, followed by free-rad- ical graft polymerization of vinyl acetate in ethyl acetate with 2,2-azobis(2,4-dimethylpentanenitrile) initiator. Initial monomer concentration was varied from 10 to 40% by vol- ume and the reaction was spanned from 50 to

Van Nguyen; Wayne Yoshida; Yoram Cohen

2003-01-01

289

Coupling Membrane Dynamics to Actin Polymerization  

Microsoft Academic Search

\\u000a WASP\\/WAVE family proteins are important regulators of the Arp2\\/3 complex, which causes exponential growth of actin filaments.\\u000a WASP\\/WAVE proteins mediate actin polymerization for both cellular protrusions, such as filopodia and lamellipodia, and invaginations,\\u000a such as coated pits for endocytosis. However, it had been unclear how the direction of actin polymerization for these topologically\\u000a different structures is precisely regulated. Recently, the

Shiro Suetsugu; Tadaomi Takenawa

290

Ultrasound initiated miniemulsion polymerization of methacrylate monomers  

Microsoft Academic Search

The ultrasound initiated emulsion polymerization of methyl methacrylate (MMA), n-butyl methacrylate (BMA) and 2-ethylhexyl methacrylate (2EHMA) in the presence of sodium dodecylsulfate as a stabiliser produced latex particles in the size range of 70nm to 110nm with molecular weights of the order of 2–6×106gmol?1. The experimental data obtained show significant differences in the rates of polymerization of the methacrylate monomers

Boon M. Teo; Stuart W. Prescott; Muthupandian Ashokkumar; Franz Grieser

2008-01-01

291

Fabrication of polyaniline nanoparticles using microemulsion polymerization  

Microsoft Academic Search

Polyaniline (PANI) nanospheres, 4 nm in diameter, were fabricated by the microemulsion polymerization of octyltrimethyl ammonium\\u000a bromide (OTAB). The size of the PANI nanoparticles could be controlled as functions of the surfactant concentration, surfactant\\u000a spacer length and polymerization temperature. The diameter of the PANI nanospheres decreased with increasing surfactant concentration\\u000a and decreasing temperature. The PANI nanoparticles revealed enhanced conductivity compared

Jyongsik Jang; Jungseok Ha; Sunhee Kim

2007-01-01

292

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

293

Polymerizations in Liquid and Supercritical Carbon Dioxide  

Microsoft Academic Search

In the past few years, remarkable progress has been made in defining the scope and limitations of carbon dioxide (CO2) as an inert polymerization medium. It has appear that CO2 represents a viable solvent choice for a variety of propagation mechanisms including both chain growth and step growth polymerizations.\\u000a When the environmental advantages of CO2 are combined with its ability

Dorian A. Canelas; Joseph M. DeSimone

294

Polymeric Gel Electrolytes for Electrochemical Capacitors  

Microsoft Academic Search

Three kinds of the polymer matrix, poly(ethylene oxide)-grafted polymethacrylate (PEO-PMA), poly(vinyldene fluoride) (PVdF) and poly(vinyldene-co-hexafluoropripylene) (PVdF-HFP), were used for gel preparation. A proper amount of organic salts or acids were dissolved in the polymer matrix together with organic plasticizers, dimethylformamide (DMF) and\\/or poly-(efhylene glycol)-dimethylether (PEGDE), without water. Thin films of the polymeric gel were obtained by either direct polymerization of

Masayuki Morita; Jin-Li Qiao; Naoki Ohsumi; Nobuko Yoshimoto; Minato Egashira

2006-01-01

295

Vector-Valued Active Contours  

Microsoft Academic Search

A framework for object segmentation in vector-valued images is presented in this paper. The first scheme proposed is based on geometric active contours moving towards the objects to be detected in the vector-valued image. Objects boundaries are obtained as geodesics or minimal weighted distance curves in a Riemannian space. The metric in this space is given by a definition of

Guillermo Sapiro

1996-01-01

296

Vector reconstruction from firing rates  

Microsoft Academic Search

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

Emilio Salinas; L. F. Abbott

1994-01-01

297

Science of NFL Football: Vectors  

NSDL National Science Digital Library

NBC's Lester Holt looks at the role vectors play every time an NFL quarterback throws a pass. With the help of former NFL quarterback Joey Harrington, NSF-funded scientist John Ziegert of Clemson University and NSF-funded mathematician Rhonda Hughes of Bryn Mawr College explain how to use vectors to calculate the speed and direction needed for a completed pass.

Learn, Nbc

2010-10-07

298

Speaker adaptation through vector quantization  

Microsoft Academic Search

Vector quantization (VQ) is a technique that reduces the computation amount and memory size drastically. In this paper, speaker adaptation algorithms through VQ are proposed in order to improve speaker-independent recognition. The speaker adaptation algorithms use VQ codebooks of a reference speaker and an input speaker. Speaker adaptation is performed by substituting vectors in the codebook of a reference speaker

K. Shikano; Kai-Fu Lee; R. Reddy

1986-01-01

299

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

300

Paleomagnetic vectors and tilted dikes  

Microsoft Academic Search

Where tectonic deformation reorients rocks without penetrative strain, their paleomagnetic vectors may be restored to their original attitudes by untilting. For strata, paleomagnetic inclination is readily restored but the tilt axis must be precisely known if paleodeclination is required. For dikes, without the knowledge of the rotation(s), neither declination nor inclination of the paleomagnetic vector can be uniquely defined. Furthermore,

G. J. Borradaile

2001-01-01

301

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

2010-06-01

302

Computer simulations of polymeric systems  

NASA Astrophysics Data System (ADS)

This document contains two projects that use computer simulations as a powerful research tool to study polymeric systems. The first project is to study the crystallization of polymer melts in the presence of nanoparticles. Experimental results show that the presence of nanoparticles enhances the crystallization of polymer melts whether the interaction between particles and polymers is attractive or repulsive. The results imply that the effect of particles on the crystallization of polymer melts is entropic. Molecular dynamics simulations with a coarse-grained model were performed to investigate the mechanism of the enhancement. My simulation results show that the presence of particles locally induces the ordering of polymers in the melt state and modifies the free energy landscape of the system. As a result, it promotes the crystallization of polymer melts. My findings are consistent with experimental observations which indicate the entropic effect of the included particles. In the second project, I study the effective interactions in poloxamer-lipid mixture at the air/water interface and try to understand the sealing mechanism of poloxamers to the damaged cell membrane. After a careful analysis of the systems under study, we proposed a simple model to describe them. Extensive Monte Carlo simulations were performed. My simulation results agree well with experimental observations, namely, the adsorption of poloxamers onto the air/water interface induces large amount of lateral pressure jump and crystal-like clusters of lipids formed and corralled by poloxamers. The compression of the interface will squeeze out poloxamers, and the structure of lipid clusters remains and the cluster size increases. My results also show that the driving force for the cluster formation of lipids and the corralling effect of poloxamers to lipids are the size mismatch between lipids and poloxamers and the soft long-range repulsion between poloxamers. These two conditions are necessary for the observations. Because our model is generic, our finding can provide a guideline for how to form high-ordered clusters of nanoparticles in two dimensions.

Zhang, Dongsheng

303

Drug-Initiated Ring-Opening Polymerization of O-Carboxyanhydrides for the Preparation of Anticancer Drug-Poly(O-Carboxyanhydride) Nanoconjugates  

PubMed Central

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

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

2013-01-01

304

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

Microsoft Academic Search

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

Meiran Xie; Huijing Han; Liang Ding; Jiaxin Shi

2009-01-01

305

Vector-vector production in photon-photon interactions  

SciTech Connect

Measurements of exclusive untagged /rho//sup 0//rho//sup 0/, /rho//phi/, K/sup *//bar K//sup */, and /rho/..omega.. production and tagged /rho//sup 0//rho//sup 0/ production in photon-photon interactions by the TPC/Two-Gamma experiment are reviewed. Comparisons to the results of other experiments and to models of vector-vector production are made. Fits to the data following a four quark model prescription for vector meson pair production are also presented. 10 refs., 9 figs.

Ronan, M.T.

1988-12-09

306

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

307

The exploitation of differential endocytic pathways in normal and tumor cells in the selective targeting of nanoparticulate chemotherapeutic agents  

PubMed Central

Polymeric micelles with cross-linked ionic cores of poly(methacrylic acid) and nonionic shell of poly(ethylene oxide) (cl-micelles) are shown here to readily internalize in epithelial cancer cells but not in normal epithelial cells that form tight junctions (TJ). The internalization of such cl-micelles in the cancer cells proceeded mainly through caveolae-mediated endocytosis. In confluent normal epithelial cells this endocytosis route was absent at the apical side and the cl-micelles sequestered in TJ regions of the cell membrane without entering the cells for at least 24 hours. Disruption of the TJ by calcium deprivation resulted in redistribution of cl-micelles inside the cells. In cancer cells following initial cellular entry the cl-micelles bypassed the early endosomes and reached the lysosomes within 30 minutes. This allowed designing cl-micelles with cytotoxic drug, doxorubicin, linked via pH-sensitive hydrazone bonds, which were cleaved in the acidic environment of lysosomes resulting in accumulation of the drug in the nucleus after 5 hours. Such pH-sensitive cl-micelles displayed selective toxicity to cancer cells but were nontoxic to normal epithelial cells. In conclusion, we describe major difference in interactions of cl-micelles with cancer and normal cells that can lead to development of novel drug delivery system with reduced side effects and higher efficacy in cancer chemotherapy.

Sahay, Gaurav; Kim, Jong Oh; Kabanov, Alexander V; Bronich, Tatiana K

2011-01-01

308

Design, synthesis and in vitro evaluation of a novel "stealth" polymeric gene vector.  

PubMed

We report on the synthesis of a novel gene carrier that has low interaction with serum components, as well as low cytotoxicity. Cationic copolymers composing branched poly(ethylenimine) (PEI) grafted with hydrophilic poly(ethylene glycol) (PEG) and poly(l-lactic acid) (PLLA) or small-molecule oleoyl were synthesized and evaluated as novel gene carriers in this study. The copolymers were complexed with plasmid DNA and the resulting polyplexes were approximately 140nm in diameter and had a positive surface potential (zeta=+13.8mV) at the N/P ratio of 10/1. The experiments showed that copolymers with the oleoyl moiety were superior to the other two copolymers (with PLLA), in terms of in vitro gene transfection efficiency. Safety studies using MTT assay indicated much lower cytotoxicity of the oleoyl polyplexes than the pDNA/PEI complexes. The intracellular behavior of the polyplexes was monitored by confocal laser scanning microscopy, and it was found that the polyplexes were internalized into HeLa cells very effectively. At the same time, the plasmid DNA carried by the oleoyl-containing copolymers was found to localize in the nucleus of the recipient cells. One experiment comparing serum-free and serum-containing media indicated that the oleoyl polyplexes may be able to evade the reticulo-endothelial system (RES) better than the PEI-pDNA complex. PMID:17928176

Guosen, He; Min, Feng; Xin, Luo; Venkatraman, Subbu

2008-02-28

309

Polymeric filament thinning and breakup in microchannels  

NASA Astrophysics Data System (ADS)

The effects of elasticity on filament thinning and breakup are investigated in microchannel cross flow. When a viscous solution is stretched by an external immiscible fluid, a low 100ppm polymer concentration strongly affects the breakup process, compared to the Newtonian case. Qualitatively, polymeric filaments show much slower evolution, and their morphology features multiple connected drops. Measurements of filament thickness show two main temporal regimes: flow- and capillary-driven. At early times both polymeric and Newtonian fluids are flow-driven, and filament thinning is exponential. At later times, Newtonian filament thinning crosses over to a capillary-driven regime, in which the decay is algebraic. By contrast, the polymeric fluid first crosses over to a second type of flow-driven behavior, in which viscoelastic stresses inside the filament become important and the decay is again exponential. Finally, the polymeric filament becomes capillary-driven at late times with algebraic decay. We show that the exponential flow thinning behavior allows a measurement of the extensional viscosities of both Newtonian and polymeric fluids.

Arratia, P. E.; Gollub, J. P.; Durian, D. J.

2008-03-01

310

Structural basis of reverse nucleotide polymerization  

PubMed Central

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

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

2013-01-01

311

Structural basis of reverse nucleotide polymerization.  

PubMed

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

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

2013-12-24

312

Polymeric filament thinning and breakup in microchannels.  

PubMed

The effects of elasticity on filament thinning and breakup are investigated in microchannel cross flow. When a viscous solution is stretched by an external immiscible fluid, a low 100 ppm polymer concentration strongly affects the breakup process, compared to the Newtonian case. Qualitatively, polymeric filaments show much slower evolution, and their morphology features multiple connected drops. Measurements of filament thickness show two main temporal regimes: flow- and capillary-driven. At early times both polymeric and Newtonian fluids are flow-driven, and filament thinning is exponential. At later times, Newtonian filament thinning crosses over to a capillary-driven regime, in which the decay is algebraic. By contrast, the polymeric fluid first crosses over to a second type of flow-driven behavior, in which viscoelastic stresses inside the filament become important and the decay is again exponential. Finally, the polymeric filament becomes capillary-driven at late times with algebraic decay. We show that the exponential flow thinning behavior allows a measurement of the extensional viscosities of both Newtonian and polymeric fluids. PMID:18517513

Arratia, P E; Gollub, J P; Durian, D J

2008-03-01

313

How do polymeric micelles cross epithelial barriers?  

PubMed

Non-parenteral delivery of drugs using nanotechnology-based delivery systems is a promising non-invasive way to achieve effective local or systemic drug delivery. The efficacy of drugs administered non-parenterally is limited by their ability to cross biological barriers, and epithelial tissues particularly present challenges. Polymeric micelles can achieve transepithelial drug delivery because of their ability to be internalized into cells and/or cross epithelial barriers, thereby delivering drugs either locally or systematically following non-parenteral administration. This review discusses the particular characteristics of various epithelial barriers and assesses their potential as non-parenteral routes of delivery. The material characteristics of polymeric micelles (e.g., size, surface charge, and surface decoration) and of unimers dissociated from polymeric micelles determine their interactions (non-specific and/or specific) with mucus and epithelial cells as well as their intracellular fate. This paper outlines the mechanisms governing the major modes of internalization of polymeric micelles into epithelial cells, with an emphasis on specific recent examples of the transport of drug-loaded polymeric micelles across epithelial barriers. PMID:23619286

Pepi?, Ivan; Lovri?, Jasmina; Filipovi?-Gr?i?, Jelena

2013-09-27

314

Generalized interpolating refinable function vectors  

NASA Astrophysics Data System (ADS)

Interpolating scalar refinable functions with compact support are of interest in several applications such as sampling theory, signal processing, computer graphics, and numerical algorithms. In this paper, we shall generalize the notion of interpolating scalar refinable functions to compactly supported interpolating d-refinable function vectors with any multiplicity r and dilation factor d. More precisely, we are interested in a d-refinable function vector such that [phi] is an r×1 column vector of compactly supported continuous functions with the following interpolation property where [delta]0=1 and [delta]k=0 for k[not equal to]0. Now for any function , the function f can be interpolated and approximated by Since [phi] is interpolating, for all , that is, agrees with f on . Moreover, for r[greater-or-equal, slanted]2 or d>2, such interpolating refinable function vectors can have the additional orthogonality property: <[phi]l([dot operator]-k),[phi]l'([dot operator]-k')>=r-1[delta]l-l'[delta]k-k' for all and 1[less-than-or-equals, slant]l,l'[less-than-or-equals, slant]r, while it is well-known that there does not exist a compactly supported scalar 2-refinable function with both the interpolation and orthogonality properties simultaneously. In this paper, we shall characterize both interpolating d-refinable function vectors and orthogonal interpolating d-refinable function vectors in terms of their masks. We shall study their approximation properties and present a family of interpolatory masks, for compactly supported interpolating d-refinable function vectors, of type (d,r) with increasing orders of sum rules. To illustrate the results in this paper, we also present several examples of compactly supported (orthogonal) interpolating refinable function vectors and biorthogonal multiwavelets derived from such interpolating refinable function vectors.

Han, Bin; Kwon, Soon-Geol; Zhuang, Xiaosheng

2009-05-01

315

Fire-Retardant Polymeric Additives  

NASA Technical Reports Server (NTRS)

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

Williams, Martha K.; Smith, Trent M.

2011-01-01

316

Mixing in polymeric microfluidic devices.  

SciTech Connect

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

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

2006-04-01

317

Adding Vectors with Microsoft Word  

NASA Astrophysics Data System (ADS)

One can use Microsoft® Word,1 a text word processing program, for quantitative analysis of vector addition. The advantages include the ubiquitous availability of MS Word for students and teachers alike in a variety of settings and its flexibility of usage. This paper describes a simple method of practicing vector addition skills using the drawing package that comes with MS Word. The method provides the student with a convenient hands-on approach to visualizing vector arithmetic that is both geometric (pictorial)and quantitative.

Rauber, Joel

2005-11-01

318

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

319

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

320

Initial conditions for vector inflation  

SciTech Connect

Recently, a model of inflation using non-minimally coupled massive vector fields has been proposed. For a particular choice of non-minimal coupling parameter and for a flat Friedmann-Robertson-Walker model, the model is reduced to the model of chaotic inflation with massive scalar field. We study the effect of non-zero curvature of the universe on the onset of vector inflation. We find that in a curved universe the dynamics of vector inflation can be different from the dynamics of chaotic inflation, and the fraction of the initial conditions leading to inflationary solutions is reduced as compared with the chaotic inflation case.

Chiba, Takeshi, E-mail: chiba@phys.chs.nihon-u.ac.jp [Department of Physics, College of Humanities and Sciences, Nihon University, Tokyo 156-8550 (Japan)] [Department of Physics, College of Humanities and Sciences, Nihon University, Tokyo 156-8550 (Japan)

2008-08-15

321

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

322

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

PubMed Central

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

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

2014-01-01

323

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

324

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

PubMed Central

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

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

2007-01-01

325

Are Bred Vectors The Same As Lyapunov Vectors?  

NASA Astrophysics Data System (ADS)

Regional loss of predictability is an indication of the instability of the underlying flow, where small errors in the initial conditions (or imperfections in the model) grow to large amplitudes in finite times. The stability properties of evolving flows have been studied using Lyapunov vectors (e.g., Alligood et al, 1996, Ott, 1993, Kalnay, 2002), singular vectors (e.g., Lorenz, 1965, Farrell, 1988, Molteni and Palmer, 1993), and, more recently, with bred vectors (e.g., Szunyogh et al, 1997, Cai et al, 2001). Bred vectors (BVs) are, by construction, closely related to Lyapunov vectors (LVs). In fact, after an infinitely long breeding time, and with the use of infinitesimal ampli- tudes, bred vectors are identical to leading Lyapunov vectors. In practical applications, however, bred vectors are different from Lyapunov vectors in two important ways: a) bred vectors are never globally orthogonalized and are intrinsically local in space and time, and b) they are finite-amplitude, finite-time vectors. These two differences are very significant in a dynamical system whose size is very large. For example, the at- mosphere is large enough to have "room" for several synoptic scale instabilities (e.g., storms) to develop independently in different regions (say, North America and Aus- tralia), and it is complex enough to have several different possible types of instabilities (such as barotropic, baroclinic, convective, and even Brownian motion). Bred vectors share some of their properties with leading LVs (Corazza et al, 2001a, 2001b, Toth and Kalnay, 1993, 1997, Cai et al, 2001). For example, 1) Bred vectors are independent of the norm used to define the size of the perturba- tion. Corazza et al. (2001) showed that bred vectors obtained using a potential enstro- phy norm were indistinguishable from bred vectors obtained using a streamfunction squared norm, in contrast with singular vectors. 2) Bred vectors are independent of the length of the rescaling period as long as the perturbations remain approximately linear (for example, for atmospheric models the interval for rescaling could be varied between a single time step and 1 day without affecting qualitatively the characteristics of the bred vectors. However, the finite-amplitude, finite-time, and lack of orthogonalization of the BVs introduces important differences with LVs: 1) In regions that undergo strong instabilities, the bred vectors tend to be locally domi- 1 nated by simple, low-dimensional structures. Patil et al (2001) showed that the BV-dim (appendix) gives a good estimate of the number of dominant directions (shapes) of the local k bred vectors. For example, if half of them are aligned in one direction, and half in a different direction, the BV-dim is about two. If the majority of the bred vectors are aligned predominantly in one direction and only a few are aligned in a second direction, then the BV-dim is between 1 and 2. Patil et al., (2001) showed that the regions with low dimensionality cover about 20% of the atmosphere. They also found that these low-dimensionality regions have a very well defined vertical structure, and a typical lifetime of 3-7 days. The low dimensionality identifies regions where the in- stability of the basic flow has manifested itself in a low number of preferred directions of perturbation growth. 2) Using a Quasi-Geostrophic simulation system of data assimilation developed by Morss (1999), Corazza et al (2001a, b) found that bred vectors have structures that closely resemble the background (short forecasts used as first guess) errors, which in turn dominate the local analysis errors. This is especially true in regions of low dimensionality, which is not surprising if these are unstable regions where errors grow in preferred shapes. 3) The number of bred vectors needed to represent the unstable subspace in the QG system is small (about 6-10). This was shown by computing the local BV-dim as a function of the number of independent bred vectors. Convergence in the local dimen- sion starts to occur at about 6 BVs, and is essentially

Kalnay, E.; Corazza, M.; Cai, M.

326

Ultrasound initiated miniemulsion polymerization of methacrylate monomers.  

PubMed

The ultrasound initiated emulsion polymerization of methyl methacrylate (MMA), n-butyl methacrylate (BMA) and 2-ethylhexyl methacrylate (2EHMA) in the presence of sodium dodecylsulfate as a stabiliser produced latex particles in the size range of 70 nm to 110 nm with molecular weights of the order of 2-6 x 10(6) g mol(-1). The experimental data obtained show significant differences in the rates of polymerization of the methacrylate monomers in the order 2EHMA>BMA>MMA. The rate trend is discussed with respect to the physicochemical properties of the monomers. It is suggested from the results obtained that the mechanism involved in sonochemical formation of the latex particles is very similar to that of a conventional miniemulsion polymerization process. PMID:17382571

Teo, Boon M; Prescott, Stuart W; Ashokkumar, Muthupandian; Grieser, Franz

2008-01-01

327

Molecular Probe Fluorescence Monitoring of Polymerization  

NASA Technical Reports Server (NTRS)

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

Bunton, Patrick

2002-01-01

328

Involvement of actin polymerization in podosome dynamics  

PubMed Central

Podosomes, which are formed by different monocyte derivatives, are small adhesion structures whose coordinated dynamics and cytoskeletal reorganization drive their motile and invasive features. Using live-cell microscopy, we explored the temporal molecular steps of the de novo assembly and disassembly of podosomes in cultured osteoclasts. We demonstrate here that the earliest visible step in podosome assembly is the local accumulation of the plaque protein paxillin, along with cortactin, which stabilizes actin networks, followed by robust polymerization of actin filaments and their association with ?-actinin. Only then is a local increase in integrin ?3 levels apparent in the podosome ring domain. Thus, local actin polymerization in cortactin- and paxillin-rich locations nucleates podosome assembly before the local accumulation of ?3 integrin. We further show that actin polymerization is also important for the recruitment and maintenance of plaque proteins in the mature podosome ring domain. Our model implies that core bundle dynamics play a central role in regulating podosome stability.

Luxenburg, Chen; Winograd-Katz, Sabina; Addadi, Lia; Geiger, Benjamin

2012-01-01

329

Design of a novel polymeric heart valve.  

PubMed

Polymeric heart valves could offer an optimum alternative to current prostheses, by joining the advantages of mechanical and bioprosthetic valves. Though a number of materials suitable for this application have recently become available, significant improvements in the valve design are still needed. In this paper, a novel polymeric heart valve design is proposed and its optimization procedure, based on the use of finite elements, is described. The design strategy was aimed at reducing the energy absorbed during the operating cycle, resulting in high hydrodynamic performances and reduced stress levels. The efficacy of the design strategy was assessed by comparing the valve dynamics and stress levels predicted numerically during the cycle with those of an existing and well qualified polymeric valve design. The improved hydrodynamic performance of the proposed design was confirmed experimentally, by in vitro testing in a pulse duplicator. PMID:19995147

Burriesci, G; Marincola, F Cavallo; Zervides, C

2010-01-01

330

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

331

Polynomial interpretation of multipole vectors  

SciTech Connect

Copi, Huterer, Starkman, and Schwarz introduced multipole vectors in a tensor context and used them to demonstrate that the first-year Wilkinson microwave anisotropy probe (WMAP) quadrupole and octopole planes align at roughly the 99.9% confidence level. In the present article, the language of polynomials provides a new and independent derivation of the multipole vector concept. Bezout's theorem supports an elementary proof that the multipole vectors exist and are unique (up to rescaling). The constructive nature of the proof leads to a fast, practical algorithm for computing multipole vectors. We illustrate the algorithm by finding exact solutions for some simple toy examples and numerical solutions for the first-year WMAP quadrupole and octopole. We then apply our algorithm to Monte Carlo skies to independently reconfirm the estimate that the WMAP quadrupole and octopole planes align at the 99.9% level.

Katz, Gabriel; Weeks, Jeff [Bennington College, Bennington, Vermont 05201 (United States); 15 Farmer Street, Canton, New York 13617 (United States)

2004-09-15

332

Vector Fields and Line Integrals  

NSDL National Science Digital Library

Created by Oliver Knill and Dale Winter for the Connected Curriculum Project, this module introduces vector fields, the concept of "work," and the line integral. This is one of a much larger set of learning modules hosted by Duke University.

Knill, Oliver; Winter, Dale

2010-05-20

333

Parallel Vector Tile Optimizing Library.  

National Technical Information Service (NTIS)

PVTOL is a C++ library that allows cross-platform software portability without sacrificing high performance. Researchers at MIT Lincoln Laboratory developed the Parallel Vector Tile Optimizing Library (PVTOL) to address a primary challenge faced by develo...

E. M. Rutledge

2011-01-01

334

Perturbative induction of vector potentials  

Microsoft Academic Search

Degenerate perturbation theory, without geometrical tools, directly yields vector potentials in the Born-Oppenheimer approximation. The derivation uses only the algebra of the dynamical operators, and the slow variables need not commute.

Y. Aharonov; E. Ben-Reuven; S. Popescu; D. Rohrlich

1990-01-01

335

Implementation of Poynting Vector Measurements.  

National Technical Information Service (NTIS)

This report covers the design, construction, and field testing of an experimental device capable of measuring the magnitude of the Poynting vector associated with an electromagnetic field. With mechanical manipulation, it can determine the direction of th...

W. W. Cowles N. Farhat R. M. Showers

1966-01-01

336

Vectors And The Quarterback Pass  

NSDL National Science Digital Library

The following resource is a NFL sponsored, National Science Foundation funded program intended to teach students about scientific concepts by using the popular sport of Football. Each lesson is accompanied by an informative and fast paced video. In this activity, students will watch as NBC's Lester Holt looks at the role vectors play every time an NFL quarterback throws a pass. Then they will be shown how to use vectors to calculate the speed and direction needed for a completed pass.

2010-01-01

337

Vector triplets at the LHC  

NASA Astrophysics Data System (ADS)

Several popular extensions of the Standard Model predict extra vector fields that transform as triplets under the gauge group SU(2)L. These multiplets contain Z' and W' bosons, with masses and couplings related by gauge invariance. We review some model-independent results about these new vector bosons, with emphasis on di-lepton and lepton-plus-missing-energy signals at the LHC.

Lizana, Javier M.; Pérez-Victoria, Manuel

2013-11-01

338

Molecular dynamics on vector computers  

NASA Astrophysics Data System (ADS)

An algorithm called the method of lights (MOL) has been developed for the computerized simulation of molecular dynamics. The MOL, implemented on the CYBER 205 computer, is based on sorting and reformulating the manner in which neighbor lists are compiled, and it uses data structures compatible with specialized vector statements that perform parallel computations. The MOL is found to reduce running time over standard methods in scalar form, and vectorization is shown to produce an order-of-magnitude reduction in execution time.

Sullivan, F.; Mountain, R. D.; Oconnell, J.

1985-10-01

339

Possible mediators of the ``living'' radical polymerization  

NASA Astrophysics Data System (ADS)

The stable radicals derived from different compounds were detected in process of styrene autopolymerization. The nitroxide radicals are produced from nitrosocompound, hindered hydroxylamine, nitrophenols and nitroanisoles. The phenoxyl radicals are formed from quinine methides, and naphtoxyl radicals are generated from 2-nitro-1-naphtol. The radicals are identified, the kinetics of their formation and follow-up evolution are studied. These radicals can participate in process of living radical polymerization as the mediators and can effect significantly on kinetics of polymerization and structure of the resulting polymer.

Motyakin, M. V.; Wasserman, A. M.; Stott, P. E.; Zaikov, G. E.

2006-03-01

340

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

341

Catalyst composition for polymerizing alpha-olefins  

SciTech Connect

This patent describes improvement in a process for preparing an alpha-olefin polymerization catalyst composition for polymerizing ethylene and at least one C{sub 3}-C{sub 10} alpha-olefin to produce a linear low density copolymer having a density of about 0.940 gm/cc or less, comprising, a precursor composition which comprises a halogen-containing transition metal compound and a magnesium compound, which precursor composition is supported on a solid, porous carrier, and a metal alkyl activator. The improvement comprises using trimethylaluminum as the metal alkyl activator.

Allen, L.M.; Hagerty, R.O.; Mohring, R.O.

1991-09-03

342

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

343

Method of Making Thermally Stable, Piezoelectric and Proelectric Polymeric Substrates  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

344

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

345

Polymerization of vegetable oils and their uses in printing inks  

Microsoft Academic Search

Ink vehicles were prepared by the polymerization of vegetable oils. By controlling the polymerization conditions, the desired\\u000a viscosity, color and molecular weight could be achieved for a variety of vegetable oils with a broad range of iodine values\\u000a and fatty acid compositions. The effect of temperature and catalyst on polymerization rates were evaluated, and polymerization\\u000a rate constants were calculated. Of

S. Z. Erhan; M. O. Bagby

1994-01-01

346

Study on Nanofibers of Polyaniline via Interfacial Polymerization  

Microsoft Academic Search

Uniform polyaniline nanofibers were prepared by interfacial polymerization. The nanofibers had a diameter of 80 nm and a length of about 1?m. The effect of centrifugal force on the morphology of the nanofibers is discussed. In situ UV?Vis spectra indicated that the interfacial polymerization process was similar to the solution polymerization process. An “expanded?partly doped” stage of interfacial polymerization was observed

Wei Li; Qinghua Zhang; Dajun Chen; Lan Li

2006-01-01

347

Radiation-Induced Polymerization of a Series of Vinyl Ethers  

Microsoft Academic Search

The radiation-induced polymerization of methyl, ethyl, isobutyl, isopropyl, and tert-butyl vinyl ethers was studied under super-dry conditions. Methyl vinyl ether did not polymerize at measurable rates; ethyl vinyl ether polymerized readily but with a dose rate dependence of the rate of only 0.3. The other ethers polymerized with a square-root dependence of the rate on the dose rate. Good agreement

A. M. Goineau; J. Kohler; V. Stannett

1977-01-01

348

Synthesis of patterned polymer brushes from flexible polymeric films  

Microsoft Academic Search

Surface-initiated polymerizations were carried out from polymeric surfaces of commercially important polyester films, poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN). These plastic films were modified prior to polymerization by plasma oxidation, exposing surface hydroxyl groups, in order to immobilise patterned self assembled monolayers (SAMs) of trichlorosilane initiator, through the soft lithographic method of microcontact printing (?CP). Subsequently, polymerizations were initiated

Tamer Farhan; Wilhelm T. S Huck

2004-01-01

349

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

350

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

351

Wetting of cork by polymeric adhesives  

Microsoft Academic Search

The cohesion of cork agglomerates is determined by the strength of the adhesive joint established between the polymeric adhesive and the cork particles. The ability of adhesives to form good joints depends, among other factors, on the wetting of cork by the adhesives. The main objective of this research was to study the behaviour of adhesive drops deposited on cork

M. H. Adao; G. M. Cabrita; C. M. Gomes; B. S. Almeida; A. C. Fernandez; J. C. Bordado

1993-01-01

352

Durability of Polymeric Coatings: UV-Irradiation  

Microsoft Academic Search

Durability of polymeric coatings is investigated by using positron annihilation spectrscopy and gloss measurements in a variety of commercial coatings and model polyurethane under UV irradiation of both accelerated and natural weathering conditions. Significant variations of sub-nanometer defect parameters determined from PAS results are observed as a function of depth, of exposure time, and of weathering conditions. The loss of

Ying Li; Renwu Zhang; Chia-Ming Huang; Junjie Zhang; Peter Mallon; R. Suzuki; Y. Y. Huang; T. C. Sandreczki; Q. Peng; J. R. Richardson; T. Ohdaira; Y. C. Jean

2001-01-01

353

Experimental Hot Mix Project Using Polymerized Asphalt.  

National Technical Information Service (NTIS)

The report compiles all the data involved in the production and construction of a hot mix overlay in Lee County, Project CSR 114-7-51, on US 290 through the city of Giddings. The hot mix ACP was produced with a polymerized asphalt. The report merely docum...

K. H. Hargett

1987-01-01

354

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

355

Polymeric membrane studied using slow positron beam  

Microsoft Academic Search

A radioisotope slow positron beam has been built at the Chung Yuan Christian University in Taiwan for the research and development in membrane science and technology. Doppler broadening energy spectra and positron annihilation lifetime have been measured as a function of positron energy up to 30keV in a polyamide membrane prepared by the interfacial polymerization between triethylenetetraamine (TETA) and trimesoyl

Wei-Song Hung; Chia-Hao Lo; Mei-Ling Cheng; Hongmin Chen; Guang Liu; Lakshmi Chakka; D. Nanda; Kuo-Lun Tung; Shu-Hsien Huang; Kueir-Rarn Lee; Juin-Yih Lai; Yi-Ming Sun; Chang-Cheng Yu; Renwu Zhang; Y. C. Jean

2008-01-01

356

Polymeric slot waveguide at visible wavelength.  

PubMed

Polymeric slot waveguide structure, which pushes the mode field toward the surrounding media, was designed and characterized. The slot waveguide was fabricated by using nanoimprint lithography, and the operation of the slot was demonstrated at 633 nm wavelength with an integrated Young interferometer. The experimental result shows that the nanolithography method provides possibilities to fabricate disposable slot waveguide sensors. PMID:23114325

Hiltunen, Marianne; Hiltunen, Jussi; Stenberg, Petri; Petäjä, Jarno; Heinonen, Esa; Vahimaa, Pasi; Karioja, Pentti

2012-11-01

357

Organic electroluminescent devices with polymeric materials  

NASA Astrophysics Data System (ADS)

Electroluminescent devices with double organic layers were fabricated using polymeric materials as the hole transport layer and tris(8-quinolinolato)aluminum(III) complex (Alq) as the emitting layer, respectively. The polymeric materials used are poly(methylphenylsilane), plasma-polymerized carbon disulfide, and polycarbonate (TPD). A cell structure of glass substrate/indium-tin-oxide (ITO)/polymer layer/Alq/Mg:Ag (10:1) or Mg/Ag was employed. Among the polymeric systems, the doped PC system affords efficient electroluminescence from the Alq layer. In this cell, bright green emission with luminance of 7,700 cd/m2 was observed at a drive voltage of 16 V. Single-layer-type EL devices were also fabricated using poly(methyl methacrylate) (PMMA) molecularly doped with both TPD and Alq. A cell structure of glass substrate/ITO/doped PMMA/Mg:Ag (10:1) was employed. Green emission with luminance of 920 cd/m2 was achieved for a cell with a TPD/Alq ratio of 0.67 at a drive voltage of 17 V, and the EL color was tuned to blue-green and yellow-orange by further doping the PMMA layer with suitable organic dyes.

Kido, Junji; Kohda, Masafumi; Okuyama, Katsuro; Nagai, Katsutoshi; Okamoto, Yoshiyuki

1993-08-01

358

Novel polymeric dyes for bottom antireflective coatings  

Microsoft Academic Search

In lithographic processing, implementation of a bottom antireflective coating can reduce or eliminate reflective notching and swing effects, thereby improving linewidth (CD) control. We have recently synthesized a series of novel polymeric dyes and evaluated them as bottom antireflective coatings for i-line lithographic applications. This work has led to the development of the BARLiTM II commercial bottom coat material. The

Shuji Ding; Ping-Hung Lu; Ralph R. Dammel; J. Shan; S. Mehtsun; T. T. Hannigan; D. E. Eberly; Dinesh N. Khanna; Hatsuyuki Tanaka

1997-01-01

359

Plasma polymerization and surface treatment of polymers  

Microsoft Academic Search

In this articlc surfacc trcatmcnt of polymcrs by both surfacc modification and plasma polymerization has bccn discussed. A low pressure 70 kHz dischargc with corona conciguration of clcctrodes (H.V. hollow bladc - groundcd cylinder) has becn cmployed in order to simulatc thc industrial surface treatment of polymcrs. In thc case of non polymcrizing plasmas such as N2 thc modifications crcated

F. Arefi; V. Andre; P. MOTJTAZER-RAHMATI; J. Amouroux

1992-01-01

360

Rolling Friction of Polymeric Materials. II. Thermoplastics  

Microsoft Academic Search

The results of rolling friction studies of several thermoplastics provide additional evidence for the correlation of such friction with dynamic mechanical losses in polymeric materials. Among the polymers discussed are polymethyl methacrylate, polytetrafluoroethylene, polyethylene, nylon, polyvinyl chloride, polyvinyl acetate, and polystyrene. The effects of spin and other deviations from pure rolling are demonstrated for polymethyl methacrylate, polytetrafluoroethylene, and nylon by

D. G. Flom

1961-01-01

361

Modeling the free radical polymerization of acrylates  

NASA Astrophysics Data System (ADS)

Acrylates have gained importance because of their ease of conversion to high-molecular-weight polymers and their broad industrial use. Methyl methacrylate (MMA) is a well-known monomer for free radical polymerization, but its ?-methyl substituent restricts the chemical modification of the monomer and therefore the properties of the resulting polymer. The presence of a heteroatom in the methyl group is known to increase the polymerizability of MMA. Methyl ?-hydroxymethylacrylate (MHMA), methyl ?-methoxymethylacrylate (MC1MA), methyl ?-acetoxymethylacrylate (MAcMA) show even better conversions to high-molecular-weight polymers than MMA. In contrast, the polymerization rate is known to decrease as the methyl group is replaced by ethyl in ethyl ?-hydroxymethylacrylate (EHMA) and t-butyl in t-butyl ?-hydroxymethylacrylate (TBHMA). In this study, quantum mechanical tools (B3LYP/6-31G*) have been used in order to understand the mechanistic behavior of the free radical polymerization reactions of acrylates. The polymerization rates of MMA, MHMA, MC1MA, MAcMA, EHMA, TBHMA, MC1AN (?-methoxymethyl acrylonitrile), and MC1AA (?-methoxymethyl acrylic acid) have been evaluated and rationalized. Simple monomers such as allyl alcohol (AA) and allyl chloride (AC) have also been modeled for comparative purposes.

Günaydin, Hakan; Salman, Seyhan; Tüzün, Nurcan ?enyurt; Avci, Duygu; Aviyente, Viktorya

362

Impregnated metal-polymeric functional beads  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

363

Impregnated metal-polymeric functional beads  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

364

Mixed metal alkyl catalyst for olefin polymerization  

SciTech Connect

This patent describes a catalyst composition for use in polymerizing alpha olefins which comprises: (a) a solid supported titanium tetrahalide complex; complex is prepared by contacting a mechanically pulverized solid support with titanium tetrahalide in the absence of mechanical pulverization; and (b) a cocatalyst comprising a mixture of a dialkyl aluminum halide and a dialkyl magnesium compound.

Bacskai, R.

1987-06-23

365

Preparation of hydrogels via ultrasonic polymerization  

Microsoft Academic Search

Several acrylic hydrogels were prepared via ultrasonic polymerization of water soluble monomers and macromonomers. Ultrasound was used to create initiating radicals in viscous aqueous monomer solutions using the additives glycerol, sorbitol or glucose in an open system at 37°C. The water soluble additives were essential for the hydrogel production, glycerol being the most effective. Hydrogels were prepared from the monomers

Peter Cass; Warren Knower; Eliana Pereeia; Natalie P. Holmes; Tim Hughes

2010-01-01

366

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

367

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

EPA Science Inventory

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

368

Synthesis of barium titanate nanopowder using polymeric precursor method  

Microsoft Academic Search

Barium titanate powder was prepared by a polymerized complex method based on the Pechini type reaction route, where barium and titanium ions were polymerized in mixed solution of citric acid, ethylene glycol, to form a transparent resin, which was used as a precursor. Barium titanate powder was formed by heat treating the polymeric precursor in air at 500–900°C. The thermal

V. Vinothini; Paramanand Singh; M. Balasubramanian

2006-01-01

369

Polymerization of amino acid methyl esters via their copper complexes  

Microsoft Academic Search

Polymerization of glycine methyl ester catalyzed by cupric ions in organic solvents yields oligoglycines with a degree of polymerization up to nine. With a trifunctional amino acid, the yeild and degree of polymerization were much lower. Extension of this reaction to an aqueous medium was not successful even when copper ions were complexed with substances like montmorillonite or fatty acids.

A. Brack; D. Louembe; G. Spach

1975-01-01

370

Acylation of linalool in the presence of polymeric pyrrolidinopyridines  

Microsoft Academic Search

The effects of a number of factors on the efficiency of polymers containing immobilized pyrrolidinopyridine groups as polymeric activating reagents for the acylation of weakly reactive sterically hindered alcohols was studied. The conditions of the acylation of linalool with acetic anhydride in the presence of polymeric pyrrolidinopyridines were selected in such a way that the activity of polymeric systems under

E. D. Alieva; N. I. Truhmanova; N. A. Platé

1996-01-01

371

The effect of reactor geometry on frontal polymerization spin modes  

Microsoft Academic Search

Using reactors of different sizes and geometries the dynamics of the frontal polymerization of 1,6-hexanediol diacrylate (HDDA) and pentaerythritol tetraacrylate (PETAC), with ammonium persulfate as the initiator were studied. For this system, the frontal polymerization exhibits complex behavior that depends on the ratio of the monomers. For a particular range of monomers concentration, the polymerization front becomes nonplanar, and spin

John A. Pojman; Jonathan Masere; Enrico Petretto; Mauro Rustici; Do-Sung Huh; Min Suk Kim; Vladimir Volpert

2002-01-01

372

Generalized vector spaces model in information retrieval  

Microsoft Academic Search

In information retrieval, it is common to model index terms and documents as vectors in a suitably defined vector space. The main difficulty with this approach is that the explicit representation of term vectors is not known a priori. For this reason, the vector space model adopted by Salton for the SMART system treats the terms as a set of

S. K. Michael Wong; Wojciech Ziarko; Patrick C. N. Wong

1985-01-01

373

Resultant of Forces (Addition of Vectors)  

NSDL National Science Digital Library

This java applet gives a visual representation of the addition of vectors. The user can choose to sum from two to five arbitrary vectors. The applet adds the vectors visually, moving each to the sum of the previous vectors. This is part of a large collection of physics applets available in a wide range of languages.

Fendt, Walter

2008-05-21

374

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

375

Finding resultant vectors using a rubber band  

NASA Astrophysics Data System (ADS)

Most students have difficulty finding a resultant vector of graphical vector addition and subtraction. We offer here an alternative and simple way of finding a result of vector addition; using a rubber band, the magnitude and direction of a resultant vector can be shown immediately.

Wutchana, U.; Emarat, N.

2014-03-01

376

Surface-initiated atom transfer radical polymerization: A new method for preparation of polymeric membrane adsorbers  

Microsoft Academic Search

This contribution demonstrates a method for preparing high-capacity membrane adsorbers by growing surface-tethered, charged polymer nanolayers from the surfaces of regenerated cellulose (RC) membranes (average pore diameter 1?m). Surface-initiated atom transfer radical polymerization was used to grow the cation-exchanger poly(acrylic acid) (PAA). By varying the polymerization time, the thickness of the nanolayer was controlled. Characterization was done by ATR-FTIR spectroscopy

Nripen Singh; Jun Wang; Mathias Ulbricht; S. Ranil Wickramasinghe; Scott M. Husson

2008-01-01

377

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

378

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  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

379

Recombinant viral vectors: cancer vaccines.  

PubMed

To date cancer vaccines have yet to show efficacy in a phase III trial. However, the clinical benefit seen with monoclonal antibody mediated therapies (e.g., Herceptin) has provided proof of principle that immune responses directed against tumour-associated antigens could have therapeutic potential. The failure of past cancer vaccine trials is likely due to several factors including the inappropriate choice of tumour antigen, use of an unoptimised antigen delivery system or vaccination schedule or selection of the wrong patient group. Any one of these variables could potentially result in the induction of an immune response of insufficient magnitude to deliver clinical benefit. Live recombinant viral vaccines have been used in the development of cancer immunotherapy approaches for the past 10 years. Though such vectors are self-adjuvanted and offer the ability to express multiple tumour-associated antigens (TAAs) along with an array of immune co-factors, arguably, they have yet to demonstrate convincing efficacy in pivotal clinical trials. However, in recent years, more coordinated studies have revealed mechanisms to optimise current vectors and have lead to the development of new advantageous vector systems. In this review, we highlight that live recombinant viral vectors provide a versatile and effective antigen delivery system and describe the optimal properties of an effective viral vector. Additionally, we discuss the advantages and disadvantages of the panel of recombinant viral systems currently available to cancer vaccinologists and how they can work in synergy in heterologous prime boost protocols and with other treatment modalities. PMID:17030074

Harrop, Richard; John, Justin; Carroll, Miles W

2006-10-01

380

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

381

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

382

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

PubMed

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

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

2014-06-01

383

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

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

2013-11-01

384

Extrapolation methods for vector sequences  

NASA Technical Reports Server (NTRS)

This paper derives, describes, and compares five extrapolation methods for accelerating convergence of vector sequences or transforming divergent vector sequences to convergent ones. These methods are the scalar epsilon algorithm (SEA), vector epsilon algorithm (VEA), topological epsilon algorithm (TEA), minimal polynomial extrapolation (MPE), and reduced rank extrapolation (RRE). MPE and RRE are first derived and proven to give the exact solution for the right 'essential degree' k. Then, Brezinski's (1975) generalization of the Shanks-Schmidt transform is presented; the generalized form leads from systems of equations to TEA. The necessary connections are then made with SEA and VEA. The algorithms are extended to the nonlinear case by cycling, the error analysis for MPE and VEA is sketched, and the theoretical support for quadratic convergence is discussed. Strategies for practical implementation of the methods are considered.

Smith, David A.; Ford, William F.; Sidi, Avram

1987-01-01

385

Antibiotic polymeric nanoparticles for biofilm-associated infection therapy.  

PubMed

Polymeric nanoparticles are highly attractive as drug delivery vehicles due to their high structural integrity, stability during storage, ease of preparation and functionalization, and controlled release capability. Similarly, lipid-polymer hybrid nanoparticles, which retain the benefits of polymeric nanoparticles plus the enhanced biocompatibility and prolonged circulation time owed to the lipids, have recently emerged as a superior alternative to polymeric nanoparticles. Drug nanoparticle complex prepared by electrostatic interaction of oppositely charged drug and polyelectrolytes represents another type of polymeric nanoparticle. This chapter details the preparation, characterization, and antibiofilm efficacy testing of antibiotic-loaded polymeric and hybrid nanoparticles and antibiotic nanoparticle complex. PMID:24664837

Cheow, Wean Sin; Hadinoto, Kunn

2014-01-01

386

Autoacceleration and kinetics of electrochemical polymerization of aniline  

SciTech Connect

A convenient method is presented for determining the rate of polyaniline formation in the electrochemical polymerization of aniline in aqueous HCl solution utilizing cyclic potential sweep techniques. In this method, the mass of polyaniline deposited on a platinum electrode is correlated with the polymer anodic peak current that is recorded during the polymerization. The rates of polymer deposition were therefore monitored by the increases in the anodic peak current at various concentrations of aniline. A kinetic expression obtained for the polymerization accounts well for the autoacceleration process in the electrochemical polymerization of aniline and supports the mechanism of polymerization in which monomeric aniline is incorporated in the growing polymer.

Wei, Yen; Sun, Yan; Tang, Xun (Drexel Univ., Philadelphia, PA (USA))

1989-06-15

387

Topochemical polymerization of C70 controlled by monomer crystal packing.  

PubMed

Polymeric forms of C60 are now well known, but numerous attempts to obtain C70 in a polymeric state have yielded only dimers. Polymeric C70 has now been synthesized by treatment of hexagonally packed C70 single crystals under moderate hydrostatic pressure (2 gigapascals) at elevated temperature (300 degrees C), which confirms predictions from our modeling of polymeric structures of C70. Single-crystal x-ray diffraction shows that the molecules are bridged into polymeric zigzag chains that extend along the c axis of the parent structure. Solid-state nuclear magnetic resonance and Raman data provide evidence for covalent chemical bonding between the C70 cages. PMID:11474107

Soldatov, A V; Roth, G; Dzyabchenko, A; Johnels, D; Lebedkin, S; Meingast, C; Sundqvist, B; Haluska, M; Kuzmany, H

2001-07-27

388

Anisotropic inflation from vector impurity  

SciTech Connect

We study an inflationary scenario with a vector impurity. We show that the universe undergoes anisotropic inflationary expansion due to a preferred direction determined by the vector. Using the slow roll approximation, we find a formula for determining the anisotropy of the inflationary universe. We discuss possible observable predictions of this scenario. In particular, it is stressed that primordial gravitational waves can be induced from curvature perturbations. Hence, even in low scale inflation, a sizable amount of primordial gravitational waves may be produced during inflation.

Kanno, Sugumi [Institute for the Physics and Mathematics of the Universe, University of Tokyo, Chiba 277-8568 (Japan)] [Institute for the Physics and Mathematics of the Universe, University of Tokyo, Chiba 277-8568 (Japan); Kimura, Masashi [Department of Mathematics and Physics, Graduate School of Science, Osaka City University, Osaka 558-8585 (Japan)] [Department of Mathematics and Physics, Graduate School of Science, Osaka City University, Osaka 558-8585 (Japan); Soda, Jiro [Department of Physics, Kyoto University, Kyoto 606-8501 (Japan)] [Department of Physics, Kyoto University, Kyoto 606-8501 (Japan); Yokoyama, Shuichiro, E-mail: sugumi@hep.physics.mcgill.ca, E-mail: mkimura@sci.osaka-cu.ac.jp, E-mail: jiro@tap.scphys.kyoto-u.ac.jp, E-mail: shu@a.phys.nagoya-u.ac.jp [Department of Physics and Astrophysics, Nagoya University, Aichi 464-8602 (Japan)] [Department of Physics and Astrophysics, Nagoya University, Aichi 464-8602 (Japan)

2008-08-15

389

Helper-Dependent Adenoviral Vectors  

PubMed Central

Helper-dependent adenoviral vectors are devoid of all viral coding sequences, possess a large cloning capacity, and can efficiently transduce a wide variety of cell types from various species independent of the cell cycle to mediate long-term transgene expression without chronic toxicity. These non-integrating vectors hold tremendous potential for a variety of gene transfer and gene therapy applications. Here, we review the production technologies, applications, obstacles to clinical translation and their potential resolutions, and the future challenges and unanswered questions regarding this promising gene transfer technology.

Rosewell, Amanda; Vetrini, Francesco; Ng, Philip

2012-01-01

390

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

391

Two-photon polymerization with optimized spatial light modulator  

NASA Astrophysics Data System (ADS)

The application of diffractive optical elements can enhance the efficiency of the two-photon polymerization (TPP) process by multiplying the polymerizing beams. Spatial light modulators (SLMs) can dynamically change the light intensity pattern used for polymerization, making single shot polymerization possible. Most reflective, liquid crystal-based instruments, however, suffer from various surface aberrations. In order to enable SLMs to generate suitable polymerizing beams for TPP, these aberrations need to be corrected. Several methods were introduced earlier to compensate SLM aberrations in different applications. For the nonlinear process of TPP, we developed and specifically characterized a correction procedure. We used a simple interferometric method to determine the surface distortion of the SLM, calculated a correcting hologram and confirmed the correction with the polymerization of test structures. The corrected SLM was capable of parallel polymerization of 3D structures with a quality achievable with non-SLM beams.

Kelemen, L.; Ormos, P.; Vizsnyiczai, G.

2011-05-01

392

Silver nanoparticles and polymeric medical devices: a new approach to prevention of infection?  

Microsoft Academic Search

Objectives: Implantable devices are major risk factors for hospital-acquired infection. Biomaterials coated with silver oxide or silver alloy have all been used in attempts to reduce infection, in most cases with controversial or disappointing clinical results. We have developed a completely new approach using supercritical carbon dioxide to impregnate silicone with nanoparticulate silver metal. This study aimed to evaluate the

Franck Furno; Kelly S. Morley; Ben Wong; Barry L. Sharp; Polly L. Arnold; Steven M. Howdle; Roger Bayston; Paul D. Brown; Peter D. Winship; Helen J. Reid

393

Vector Acoustics, Vector Sensors, and 3D Underwater Imaging  

NASA Astrophysics Data System (ADS)

Vector acoustic data has two more dimensions of information than pressure data and may allow for 3D underwater imaging with much less data than with hydrophone data. The vector acoustic sensors measures the particle motions due to passing sound waves and, in conjunction with a collocated hydrophone, the direction of travel of the sound waves. When using a controlled source with known source and sensor locations, the reflection points of the sound field can be determined with a simple trigonometric calculation. I demonstrate this concept with an experiment that used an accelerometer based vector acoustic sensor in a water tank with a short-pulse source and passive scattering targets. The sensor consists of a three-axis accelerometer and a matched hydrophone. The sound source was a standard transducer driven by a short 7 kHz pulse. The sensor was suspended in a fixed location and the hydrophone was moved about the tank by a robotic arm to insonify the tank from many locations. Several floats were placed in the tank as acoustic targets at diagonal ranges of approximately one meter. The accelerometer data show the direct source wave as well as the target scattered waves and reflections from the nearby water surface, tank bottom and sides. Without resorting to the usual methods of seismic imaging, which in this case is only two dimensional and relied entirely on the use of a synthetic source aperture, the two targets, the tank walls, the tank bottom, and the water surface were imaged. A directional ambiguity inherent to vector sensors is removed by using collocated hydrophone data. Although this experiment was in a very simple environment, it suggests that 3-D seismic surveys may be achieved with vector sensors using the same logistics as a 2-D survey that uses conventional hydrophones. This work was supported by the Office of Naval Research, program element 61153N.

Lindwall, D.

2007-12-01

394

Testing Studentsâ Understanding of Vector Concepts  

NSDL National Science Digital Library

After four years of research we designed a 20-item multiple choice vector concept test (Test of Understanding of Vectors, TUV). In this article we analyze: 1) the reliability and discriminatory power of the test, and 2) studentsâ understanding of the vector concepts evaluated in the test. The final version of the test was administered in English to 423 students who were finishing an Electricity and Magnetism course at a large private Mexican university. In the first part of the article, we show results indicating that the TUV is a reliable assessment tool. In the second part, we examine studentsâ overall performance on the test and analyze the results of the five most difficult items for students: geometric interpretation of dot product, calculation of dot product of two vectors written in unit-vector notation, graphic representation of a unit vector, calculation of the direction of a vector written in unit-vector notation, and graphical subtraction of vector in 2D.

Barniol, Pablo; Zavala, Genaro

2013-12-21

395

Polymeric quantization and black hole thermodynamics  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

396

Hemoglobin loaded polymeric nanoparticles: preparation and characterizations.  

PubMed

In the present work polymeric nanoparticles based on Poly (maleic anhydride-alt-butyl vinyl ether) 5% grafted with m-PEG (2000) and 95% grafted with 2-methoxyethanol (VAM41-PEG) were loaded with human hemoglobin (Hb) and characterized from a physicochemical point of view. The assessment of structural and functional features of the loaded Hb was performed and the effect of the introduction of different reducing agents as aimed at minimizing Hb oxidation during the nanoparticles formulation process, was also investigated. Nanoparticles possessing an average diameter of 138±10 nm and physicochemical features suitable for this kind of application were successfully obtained. Although the oxidation of the protein was not avoided during its loading into nanoparticles, the presence of acidic moieties in the polymeric structure is proposed to be directly involved in the protein inactivation mechanism. PMID:21443949

Dessy, Alberto; Piras, Anna M; Schirò, Giorgio; Levantino, Matteo; Cupane, Antonio; Chiellini, Federica

2011-05-18

397

Latent and delayed action polymerization systems.  

PubMed

Various approaches to latent polymerization processes are described. In order to highlight recent advances in this field, the discussion is subdivided into chapters dedicated to diverse classes of polymers, namely polyurethanes, polyamides, polyesters, polyacrylates, epoxy resins, and metathesis-derived polymers. The described latent initiating systems encompass metal-containing as well as purely organic compounds that are activated by external triggers such as light, heat, or mechanical force. Special emphasis is put on the different chemical venues that can be taken to achieve true latency, which include masked N-heterocyclic carbenes, latent metathesis catalysts, and photolatent radical initiators, among others. Scientific challenges and the advantageous application of latent polymerization processes are discussed. PMID:24519912

Naumann, Stefan; Buchmeiser, Michael R

2014-04-01

398

Tubulin polymerization promoting protein 1 (TPPP1)  

PubMed Central

The eukaryotic cell cycle relies heavily on the mechanical forces vested by the dynamic rearrangement of the microtubule (MT) network. Tubulin Polymerization promoting Protein 1 (TPPP1) alters MT dynamics by driving MT polymerization as well as stabilization, via increasing MT acetylation. It increases MT rigidity, which results in reduced cell proliferation through downregulation of G1/S-phase and mitosis to G1-phase cell cycle transitioning. In this communication, we provide further evidence that TPPP1 may be an important regulator of genomic homeostasis. Our preliminary data show that long-term TPPP1 overexpression reduces cell viability via induction of apoptotic cell death pathways. Moreover, induction of DNA-damage results in increased TPPP1 expression, which is inhibited in the absence of expression of the tumor suppressor p53.

Schofield, Alice; Bernard, Ora

2013-01-01

399

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

2012-09-21

400

Cooperative polymerization of one-patch colloids  

NASA Astrophysics Data System (ADS)

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

Vissers, Teun; Smallenburg, Frank; Munaò, Gianmarco; Preisler, Zden?k; Sciortino, Francesco

2014-04-01

401

Chemical characterization of selected LDEF polymeric materials  

NASA Technical Reports Server (NTRS)

The chemical characterization of selected polymeric materials which received exposure on the LDEF is reported. The specimens examined include silvered fluorinated ethylene propylene (FEP) teflon thermal blanket material, polysulfone matrix resin/graphite fiber reinforced composites, and several high performance polymer films. These specimens came from numerous LDEF locations and, thus, received different environmental exposures. The results of infrared, thermal, x ray photoelectron, and various solution property analyses have shown no significant change at the molecular level in the polymer that survived exposure. However, scanning electron and scanning tunneling microscopies show resin loss and a texturing of the surface of some specimens which resulted in a change in optical properties. The potential effect of a silicon containing molecular contamination on these materials is addressed. The possibility of continued post-exposure degradation of some polymeric films is also proposed.

Young, Philip R.; Slemp, Wayne S.

1992-01-01

402

Cooperative polymerization of one-patch colloids.  

PubMed

We numerically investigate cooperative polymerization in an off-lattice model based on a pairwise additive potential using particles with a single attractive patch that covers 30% of the colloid surface. Upon cooling, these particles self-assemble into small clusters which, below a density-dependent temperature, spontaneously reorganize into long straight tubes. We evaluate the partition functions of clusters of all sizes to provide an accurate description of the chemical reaction constants governing this process. Our calculations show that, for intermediate sizes, the partition functions retain contributions from two different structures, differing in both energy and entropy. We illustrate the microscopic mechanism behind the complex polymerization process in this system and provide a detailed evaluation of its thermodynamics. PMID:24735313

Vissers, Teun; Smallenburg, Frank; Munaò, Gianmarco; Preisler, Zden?k; Sciortino, Francesco

2014-04-14

403

Polymeric Gel Electrolytes for Electrochemical Capacitors  

NASA Astrophysics Data System (ADS)

Three kinds of the polymer matrix, poly(ethylene oxide)-grafted polymethacrylate (PEO-PMA), poly(vinyldene fluoride) (PVdF) and poly(vinyldene-co-hexafluoropripylene) (PVdF-HFP), were used for gel preparation. A proper amount of organic salts or acids were dissolved in the polymer matrix together with organic plasticizers, dimethylformamide (DMF) and/or poly-(efhylene glycol)-dimethylether (PEGDE), without water. Thin films of the polymeric gel were obtained by either direct polymerization of the mixed monomer solution or a thermal casting method. The composition of the polymer-electrolyte complex system is optimized to obtain good capacitor performances of the electrochemical capacitor (ECC) system.

Morita, Masayuki; Qiao, Jin-Li; Ohsumi, Naoki; Yoshimoto, Nobuko; Egashira, Minato

2006-06-01

404

Charge-transfer magnetoelectrics of polymeric multiferroics.  

PubMed

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

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

2014-04-22

405

Multiclass Proximal Support Vector Machines  

Microsoft Academic Search

Abstract. We propose an extension of proximal support vector machines (PSVM) to the multiclass case. Unlike the one-versus-rest approach that constructs the decision rule based on multiple binary classication tasks, the multiclass PSVM (MPSVM) considers all classes simultaneously and provides a unifying framework when there are either equal or unequal misclassication costs. The MPSVM is built in a regularization framework

Yongqiang Tang; Hao Helen Zhang

2006-01-01

406

Vectorized Adaptive Quadrature in Matlab  

Microsoft Academic Search

Adaptive quadrature codes process a collection of subintervals one at a time. We show how to process them all simultaneously and so exploit vectorization and the use of fast built-in functions and array operations that are so important to e-cient computation in Matlab. Using algebraic transformations we have made it just as easy for users to solve problems on inflnite

L. F. Shampine

2006-01-01

407

Science of NHL Hockey: Vectors  

NSDL National Science Digital Library

NHL players are celebrated for their ability to pass the puck quickly and accurately as play moves from one end of the ice to the other. These pinpoint passes, requiring both magnitude and direction, are perfect examples of velocity vectors. "Science of NHL Hockey" is a 10-part video series produced in partnership with the National Science Foundation and the National Hockey League.

Learn, Nbc

2010-10-07

408

Algorithms for Fast Vector Quantizaton  

Microsoft Academic Search

Nearest neighbor searching is an important geometric subproblem in vector quanti- zation. Existing studies have shown that the difficulty of solving this problem efficiently grows rapidly with dimension. Indeed, existing approaches on unstructured codebooks in dimension 16 are little better than brute-force search. We show that if one is willing to relax the requirement of finding the true nearest neighbor

Sunil Arya; David M. Mount

1993-01-01

409

Primer vector theory and applications  

NASA Technical Reports Server (NTRS)

A method developed to compute two-body, optimal, N-impulse trajectories was presented. The necessary conditions established define the gradient structure of the primer vector and its derivative for any set of boundary conditions and any number of impulses. Inequality constraints, a conjugate gradient iterator technique, and the use of a penalty function were also discussed.

Jezewski, D. J.

1975-01-01

410

Bounded Support Vector Machines, Semidefinite  

Microsoft Academic Search

Credit risk assessment is a basic and critical factor in credit risk management. In addition to conventional statistical method, neural network, decision tree and Support Vector Machine are the popular methods in this field in recent years. However, they all have weakness in two aspects: poor classification accuracy for unbalanced data and poor interpretability in real applications. A novel method,

Jianping Li; Zhenyu Chen; Weixuan Xu

2006-01-01

411

Scalar calibration of vector magnetometers  

Microsoft Academic Search

The calibration parameters of a vector magnetometer are estimated only by the use of a scalar reference magnetometer. The method presented in this paper differs from those previously reported in its linearized parametrization. This allows the determination of three offsets or signals in the absence of a magnetic field, three scale factors for normalization of the axes and three non-orthogonality

J. M. G. Merayo; P. Brauer; F. Primdahl; J. R. Petersen; O. V. Nielsen

2000-01-01

412

Paleomagnetic vectors and tilted dikes  

NASA Astrophysics Data System (ADS)

Where tectonic deformation reorients rocks without penetrative strain, their paleomagnetic vectors may be restored to their original attitudes by untilting. For strata, paleomagnetic inclination is readily restored but the tilt axis must be precisely known if paleodeclination is required. For dikes, without the knowledge of the rotation(s), neither declination nor inclination of the paleomagnetic vector can be uniquely defined. Furthermore, back-rotating dike orientations to an upright attitude assumes primary verticality whereas primary dike dips are bimodal across the spreading axes (e.g. Troodos ophiolite, Cyprus). In the Cyprus ophiolite, the dikes of the Limassol Forest Transform Zone are tilted due to uplift of the mantle-sequence rocks and deflected against the Arakapas Fault. Their paleomagnetic vectors may be restored rotating about the two axes defined by the strike and the vertical, or about a net axis that is possibly the actual tectonic rotation axis. This net axis is determined from the tectonic regional dispersion of the dike orientations. In this test case, the results of the restorations differ slightly but underline the difficulty in selecting the best restoration procedure and the greater difficulty of restoring the paleomagnetic data from dikes vis à vis strata. For dikes, it is recommended that the paleomagnetic vectors are restored using average dike orientations to minimize the inaccuracies due to the large primary variation in dike orientation.

Borradaile, G. J.

2001-04-01

413

The Magsat precision vector magnetometer  

Microsoft Academic Search

This paper examines the Magsat precision vector magnetometer which is designed to measure projections of the ambient field in three orthogonal directions. The system contains a highly stable and linear triaxial fluxgate magnetometer with a dynamic range of + or - 2000 nT (1 nT = 10 to the -9 weber per sq m). The magnetometer electronics, analog-to-digital converter, and

M. H. Acuna

1980-01-01

414

Vinyl acetate polymerization by ionizing radiation  

Microsoft Academic Search

For this work an irradiation system to be used in the polymerization of the vinyl acetate in methylethylketone and in ethyl alcohol solution using the gamma radiation as initiator was projected and built. The molecular weights of the polymers obtained by irradiation with gamma rays in methylethylketone and in ethyl alcohol solution were 33,000 and 44,000g\\/mol, respectively. >From the characterization

A. C. Mesquita; M. N. Mori; J. M. Vieira; L. G. Andrade e. Silva

2002-01-01

415

Vinyl acetate polymerization by ionizing radiation  

Microsoft Academic Search

For this work an irradiation system to be used in the polymerization of the vinyl acetate in methylethylketone and in ethyl alcohol solution using the gamma radiation as initiator was projected and built. The molecular weights of the polymers obtained by irradiation with gamma rays in methylethylketone and in ethyl alcohol solution were 33,000 and 44,000g\\/mol, respectively. From the characterization

A. C Mesquita; M. N Mori; J. M Vieira; L. G. Andrade e Silva

2002-01-01

416

Viscosity behavior of polymeric flocculant solutions  

Microsoft Academic Search

Viscosity measurements of polymeric flocculant solutions of poly-dimethyldiallylammonium chloride (DMDAAC) and poly-acrylamide\\/acrylic acid (AM\\/AA) families at various concentrations and solution chemistry have been carried out using the Cannon–Fenske routine viscometer. In this study, the viscosity behavior of these polymer solutions is described in terms of reduced viscosity. From the reduced viscosity-polymer concentration (?red-C) plot, the linearity of the viscosity behavior

C. Rattanakawin; R. Hogg

2007-01-01

417

Biologically produced acid precipitable polymeric lignin  

DOEpatents

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

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

1984-01-01

418

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

419

Synthesis of polyaniline films by plasma polymerization  

Microsoft Academic Search

This work presents a study on the formation of polyaniline films by plasma polymerization using RF glow discharges with resistive coupling between stainless-steel electrodes. The polymer was obtained at a frequency of 13.5 MHz and pressure in the range (2–8)×10?2 Torr. Polyaniline and I2-doped polyaniline films were synthesized as thin films that can be adhered to glass and metal surfaces.

G. J Cruz; J Morales; M. M Castillo-Ortega; R Olayo

1997-01-01

420

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

421

Vibrating polymeric microsieves: Antifouling strategies for microfiltration  

Microsoft Academic Search

Constant flux performance in time is achieved with polyethersulfone (PES) polymeric microsieves when filtering protein solutions, skimmed milk and white beer in combination with backpulsing. Such microsieves are fabricated by phase separation micromolding (PS?M) and possess pores around 2?m. The filtration of bovine serum albumin (BSA) solutions at neutral pH results in constant flux when backpulsing. The constant flux performance

Míriam Gironès i Nogué; Imam J. Akbarsyah; Lydia A. M. Bolhuis-Versteeg; Rob G. H. Lammertink; Matthias Wessling

2006-01-01

422

Polymeric synthesis of biomimetic artificial compound eyes  

Microsoft Academic Search

Biologically inspired compound eyes have been developed by a 3D microfabrication method, which mimicking the unique optical scheme of the natural compound eyes found in many insects. The combination of polymer microlenses, reconfigurable microtemplating, soft lithography and self-written waveguides by self-aligned 3D optical polymerization step enables the realization of complicated optical structures with thousands of omni-directional self-aligned microlens and waveguide

Ki-Hun Jeong; Jaeyoun Kim; Luke P. Lee

2005-01-01

423

Photochemical initiated polymerization of single microdroplets  

Microsoft Academic Search

The production of polymeric microspheres via aerocolloidal processing is explored. A droplet consisting of a mixture of 1,6-hexanediol diacrylate and trimethylolpropane ethoxy triacrylate monomers was levitated electrodynamically in the path of an argon ion laser beam (?=488 nm). The laser beam served as the source of illumination for elastic and inelastic light-scattering measurements. The reaction was followed by Raman spectroscopy,

J. F. Widmann; E. J. Davis

1996-01-01

424

Electrophoresis of polymeric dyes in macroporous polymer  

Microsoft Academic Search

Summary  \\u000a Macroporous poly(styrene-co-divinylbenzene), with poly(vinyl alcohol) (PVA)-coated pores, was investigated as a novel medium\\u000a for thin-layer electrophoresis. The system was tested using polymeric dyes having polyelectrolyte character, which were prepared\\u000a by reaction of a vinylsulphone reactive dye (CI Reactive Blue 19) with PVA. Higher molar mass samples exhibited higher mobility\\u000a on electrophoresis in the macroporous medium.

Adrian D. Price; Peter M. Budd

2002-01-01

425

[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

426

Effect of Electron Donor on PE Polymerization  

Microsoft Academic Search

Ziegler-Natta catalyst was prepared from colloidal MgCl2 (from reaction between magnesium ethyl carbonate and aluminium sesquichloride, Al2Et3Cl3) followed by contact with TiCl4. Al\\/Mg and Ti\\/Mg molar ratios were studied as parameters affecting the catalyst synthesis. Catalytic performance and effect of electron donor on ethylene polymerization were investigated. Results showed that addition of electron donor (ethyl benzoate) increased activity balance when

Roman HELMUTH STRAUSS

427

Multicomponent transport across nonporous polymeric membranes  

Microsoft Academic Search

The theoretical description of multicomponent transport across nonporous polymeric membranes was investigated using two alternative frameworks: the phenomenological approach of irreversible thermodynamics and the mechanistic Stefan—Maxwell formulation. The transport models developed account for potential equilibrium and\\/or kinetic coupling of fluxes and the contribution of diffusion induced non-selective flow within the polymer. The models were validated against transient dialysis and pervaporation

S. A. A Ghoreyshi; F. A. Farhadpour; M. Soltanieh

2002-01-01

428

Polymerization of conducting polymers inside carbon nanotubes  

NASA Astrophysics Data System (ADS)

Supercritical carbon dioxide is an universal tool to impregnate carbon nanotubes with a wide range of organic molecules. In this Letter, we present our results of carbon nanotubes filled with the photo-conducting polymer poly( N-vinyl carbazole) and the conducting polymer polypyrrole which were prepared by polymerizing the monomers inside the nanotubes. The endohedral nanotubes were characterized by HRTEM and 1H NMR which confirmed that the encapsulated material was indeed the conducting polymer.

Steinmetz, Johannes; Kwon, Soyoung; Lee, Hyun-Jung; Abou-Hamad, Edy; Almairac, Robert; Goze-Bac, Christophe; Kim, Hwayong; Park, Yung-Woo

2006-11-01

429

Progress in malaria vector control*  

PubMed Central

Malaria control, except in tropical Africa, will probably continue to be based to a large extent on the use of insecticides for many years. However, the development of resistance to insecticides in the vectors has caused serious difficulties and it is necessary to change the strategy of insecticide use to maximize their efficacy. A thorough knowledge of the ecology and behaviour of each vector species is required before the control strategy can be adapted to different epidemiological situations. The behavioural differences between sibling species have been recognized for several years, but study of this problem has recently been simplified by improved means of identification that involve chromosomal banding patterns and electrophoretic analysis. Behavioural differences have also been associated with certain chromosomal rearrangements. New records of insecticide resistance among anophelines continue to appear and the impact of this on antimalaria operations has been seriously felt in Central America (multi-resistance in Anopheles albimanus), Turkey (A. sacharovi), India and several Asian countries (A. culicifacies and A. stephensi), and some other countries. Work continues on the screening and testing of newer insecticides that can be used as alternatives, but DDT, malathion, temephos, fenitrothion, and propoxur continue to be used as the main insecticides in many malaria control projects. The search for simpler and innovative approaches to insecticide application also continues. Biological control of vectors is receiving increased attention, as it could become an important component of integrated vector control strategies, and most progress has been made with the spore-forming bacterium, serotype H-14 of Bacillus thuringiensis. Larvivorous fish such as Gambusia spp. and Poecilia spp. continue to be used in some programmes. Application of environmental management measures, such as source reduction, source elimination, flushing of drainage and irrigation channels, and intermittent irrigation have been re-examined and currently a great deal of interest is being shown in these approaches. There has been limited interest in the genetic control of mosquitos and the phenomenon of refractoriness in some strains of the disease vectors, with the idea of replacing the vector species with the refractory strain. More research is needed before this approach can become a practical tool. It is apparent that in future a more integrated approach will have to be used for vector control within the context of antimalaria programmes. Training of staff, research, and cooperation at all levels will be an essential requirement for this approach.

Pant, C. P.; Rishikesh, N.; Bang, Y. H.; Smith, A.

1981-01-01

430

In Situ Forming Polymeric Drug Delivery Systems  

PubMed Central

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.

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

2009-01-01

431

Performance of selected polymeric materials on LDEF  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

432

Binding of human angiogenin inhibits actin polymerization  

PubMed Central

Angiogenin is a potent inducer of angiogenesis, a process of blood vessel formation. It interacts with endothelial and other cells and elicits a wide range of cellular responses including migration, proliferation, and tube formation. One important target of angiogenin is endothelial cell-surface actin and their interaction might be one of essential steps in angiogenin-induced neovascularization. Based on earlier indications that angiogenin promotes actin polymerization, we studied the binding interactions between angiogenin and actin in a wide range of conditions. We showed that at subphysiological KCl concentrations, angiogenin does not promote, but instead inhibits polymerization by sequestering G-actin. At low KCl concentrations angiogenin induces formation of unstructured aggregates, which, as shown by NMR, may be caused by angiogenin's propensity to form oligomers. Binding of angiogenin to preformed F-actin does not cause depolymerization of actin filaments though it causes their stiffening. Binding of tropomyosin and angiogenin to F-actin is not competitive at concentrations sufficient for saturation of actin filaments. These observations suggest that angiogenin may cause changes in the cell cytoskeleton by inhibiting polymerization of G-actin and changing the physical properties of F-actin.

Pyatibratov, Mikhail G.; Tolkatchev, Dmitri; Plamondon, Josee; Xu, Ping; Ni, Feng; Kostyukova, Alla S.

2010-01-01

433

Polymerization initated at sidewalls of carbon nanotubes  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

434

Homogeneous catalysts for stereoregular olefin polymerization  

SciTech Connect

The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C[sub 5]R[prime][sub 4[minus]x]R*[sub x])-A-(C[sub 5]R[double prime][sub 4[minus]y]R[prime][double prime][sub y])-M-Q[sub p], where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R[prime], R[double prime], R[prime][double prime], 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 [<=] p [<=] 0. Related complexes may be prepared by alkylation of the corresponding dichlorides. 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. 1 fig.

Marks, T.J.; Eisen, M.S.; Giardello, M.A.

1994-07-19

435

Homogeneous catalysts for stereoregular olefin polymerization  

SciTech Connect

The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C{sub 5}R{prime}{sub 4{minus}x}R*{sub x})A(C{sub 5}R{double_prime}{sub 4{minus}y}R{double_prime}{prime}{sub y})MQ{sub p}, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R{prime}, R{double_prime}, R{double_prime}{prime}, 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{>=}p{>=}0. Related complexes may be prepared by alkylation of the corresponding dichlorides. 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. 1 fig.

Marks, T.J.; Eisen, M.S.; Giardello, M.A.

1995-10-03

436

Homogeneous catalysts for stereoregular olefin polymerization  

SciTech Connect

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

437

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

438

Synthesis and in vitro evaluation of novel star-shaped block copolymers (blocked star vectors) for efficient gene delivery.  

PubMed

Novel 4-branched diblock copolymers consisting of cationic chains as an inner domain and nonionic chains as an outer domain were prepared by iniferter-based living radial polymerization and evaluated as a polymeric transfectant. The cationic polymerization of 3-(N,N-dimethylamino)propyl acrylamide (DMAPAAm) using 1,2,4,5-tetrakis( N,N-diethyldithiocarbamylmethyl)benzene as a 4-functional iniferter followed by the nonionic block polymerization of N,N-dimethylacrylamide (DMAAm) afforded 4-branched diblock copolymers with controlled compositions. By changing the solution or irradiation conditions, 4-branched PDMAPAAms with molecular weights of 10,000, 20,000, and 50,000 were synthesized. In addition, by graft polymerization, PDMAPAAm-PDMAAm blocked copolymers with copolymer composition (unit ratio of DMAAm/DMAPAAm) ranging from 0.18 to 1.0 for each cationic polymer were synthesized. All polymers were shown to interact with and condense plasmid DNA to yield polymer/DNA complexes (polyplexes). A transfection study on COS-1 cells showed that the polyplexes from block copolymers with cationic chain length of approximately 50,000 and a nonionic chain length of 30,000, which were approximately 200 nm in diameter and very stable in aqueous media, had the most efficient luciferase activity with minimal cellular cytotoxicity under a charge ratio of 20 (vector/pDNA). The PDMAPAAm-PDMAAm-blocked, star-shaped polymers are an attractive novel class of nonviral gene delivery systems. PMID:17922548

Nakayama, Yasuhide; Kakei, Chiaki; Ishikawa, Ayaka; Zhou, Yue-Min; Nemoto, Yasushi; Uchida, Kingo

2007-01-01

439

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

2013-03-01

440

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

441

An Example of Vector Algebra in Navigation.  

ERIC Educational Resources Information Center

A technique is illustrated for solving relative motion problems using a maneuvering board and vector algebra. The technique can be used to visually illustrate properties of vector algebra in a non-theoretical context. (MP)

Kjeseth, Steve

1979-01-01

442

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

443

Securing Distance-Vector Routing Protocols  

Microsoft Academic Search

We analyze the security requirements of distance-vector routing protocols, identify their vulnerabilities, and pro- pose countermeasures to these vulnerabilities. The inno- vation we propose involves the use of mechanisms from the path-finding class of distance-vector protocols as a solution to the security problems of distance-vector protocols. The result is a proposal that effectively and efficiently secures distance-vector protocols in constant

Bradley R. Smith; Shree Murthy; J. J. Garcia-luna-aceves

1997-01-01

444

Deciding Bit-Vector Arithmetic with Abstraction  

Microsoft Academic Search

We present a new decision procedure for finite-precision bit- vector arithmetic with arbitrary bit-vector operations. Our procedure alternates between generating under- and over-approximations of the original bit-vector formula. An under-approximation is obtained by a translation to propositional logic in which some bit-vector variables are encoded with fewer Boolean variables than their width. If the under- approximation is unsatisfiable, we use

Randal E. Bryant; Daniel Kroening; Joël Ouaknine; Sanjit A. Seshia; Ofer Strichman; Bryan A. Brady

2007-01-01

445

Polymeric micelles as drug carriers: their lights and shadows.  

PubMed

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

Yokoyama, Masayuki

2014-08-01

446

Medium Modification of Vector Mesons  

SciTech Connect

The theory of the strong interaction, Quantum Chromodynamics (QCD), has been remarkably successful in describing high-energy and short-distance-scale experiments involving quarks and gluons. However, applying QCD to low energy and large-distance scale experiments has been a major challenge. Various QCD-inspired models predict a partial restoration of chiral symmetry in nuclear matter with modifications of the properties of hadrons from their free-space values. Measurable changes such as a shift in mass and/or a change of width are predicted at normal nuclear density. Photoproduction of vector mesons off nuclei have been performed at different laboratories. The properties of the ?, ? and ? mesons are investigated either directly by measuring their mass spectra or indirectly through transparency ratios. The latest results regarding medium modifications of the vector mesons in the nuclear medium will be discussed.

Chaden Djalali, Michael Paolone, Dennis Weygand, Michael H. Wood, Rakhsha Nasseripour

2011-03-01

447

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

448

Viral vectors for vaccine applications.  

PubMed

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. PMID:23858400

Choi, Youngjoo; Chang, Jun

2013-07-01

449

Vectorizing and Querying Large XML Repositories  

Microsoft Academic Search

Vertical partitioning is a well-known technique for optimizing query performance in relational databases. An extreme form of this technique, which we call vectorization, is to store each col- umn separately. We use a generalization of vectorization as the basis for a native XML store. The idea is to decompose an XML document into a set of vectors that contain the

Peter Buneman; Byron Choi; Wenfei Fan; Robert Hutchison; Robert Mann; Stratis D. Viglas

2005-01-01

450

Fast Support Vector Machines for Continuous Data  

Microsoft Academic Search

Support vector machines can be trained to be very accurate classifiers and have been used in many applications. However, the training and to a lesser extent predic- tion time of support vector machines on very large data sets can be very long. This paper presents a fast compression method to scale up support vector machines to large data sets. A

Kurt A. Kramer; Lawrence O. Hall; Dmitry B. Goldgof; Andrew Remsen; Tong Luo

2009-01-01

451

MISR Level 3 Cloud Motion Vector  

MISR Level 3 Cloud Motion Vector Level 3 Wednesday, November 7, 2012 ... A new version, F02_0002, of the MISR L3 CMV (Cloud Motion Vector) data product is now available. This new release provides finer ... coverage. These enhancements are the result of reorganizing motion vector information present in the recent Level 2 Cloud product as ...

2013-07-10

452

Transmission parameters of vector-borne infections.  

PubMed

Vector-borne infections are those for which the agent (virus, bacteria, or parasite) is transmitted from an infected host (animal or human) to another by a hematophagous arthropod (mosquito, tick, lice, and flea). Two parameters quantify the dynamics of a vector-borne infection: (1) the basic reproductive number (R(0)) that is the mean number of secondary infections transmitted from an infectious host by the bite of the vector and (2) the generation interval that explores the speed of occurrence of secondary cases transmitted by the vector from an infectious case. In a population in which some individuals are immune, the parameter of interest is the net reproduction number (R) function of R(0) and the proportion of those immune. For vector-borne infectious agents, R(0) is determined by the number of vectors in contact with a given individual (m), the number of a given vector bites/day on individuals (a), the daily survival rate of the vector (p), the duration of the pathogenic agent's development cycle in the vector (n), the proportion of infected vectors that are really infectio