Sample records for nanoparticulate polymeric vectors

  1. Application of TPGS in polymeric nanoparticulate drug delivery system

    Microsoft Academic Search

    L. Mu; P. H. Seow

    2006-01-01

    d-?-Tocopheryl polyethylene glycol 1000 succinate (TPGS) has great potential in pharmacology and nanotechnology. The present work investigated the molecular behaviour of TPGS at the air–water interface, its effect on a model bio-membrane composed of dipalmitoylphosphatidylcholine (DPPC) lipid monolayer, and the interaction between the TPGS coated nanoparticles with the lipid model membrane. Paclitaxel loaded polymeric nanoparticles with TPGS as surfactant stabiliser

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

    PubMed

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

    2015-03-17

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

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

    NASA Astrophysics Data System (ADS)

    Khurana, Jatin

    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.

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

    PubMed Central

    2009-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

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

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

    PubMed

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

    2014-01-01

    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

  7. Advances in polymeric and inorganic vectors for nonviral nucleic acid delivery

    PubMed Central

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

    2014-01-01

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

  8. A brain-vectored angiopep-2 based polymeric micelles for the treatment of intracranial fungal infection.

    PubMed

    Shao, Kun; Wu, Jiqin; Chen, Zhongqing; Huang, Shixian; Li, Jianfeng; Ye, Liya; Lou, Jinning; Zhu, Liping; Jiang, Chen

    2012-10-01

    One of the most common life-threatening infections in immunosuppressive patients, like AIDs patients, is cryptococcal meningitis or meningoencephalitis. Current therapeutic options are mostly ineffective and mortality rates remain high. Hydrophobic antifungal drug Amphotericin B (AmB), has become a golden standard in severe systemic fungal infection therapy. However, most AmB commercial formulations, including deoxycholate AmB and lipid formulations of AmB, show poor penetration into the CNS and difficulty to reach the therapeutic levels. To improve the CNS permeability of AmB, we have successfully developed an effective brain-targeting polymeric micellar system with angiopep-2 modified, named Angiopep-PEG-PE/AmB polymeric micelles. An immunosuppressive murine model with Cryptococcus neoformans meningoencephalitis (CNME) was established to evaluate the CNS penetration efficiency and antifungal treatment efficacy of the AmB-incorporated brain-vectored polymeric micellar formulation, compared with the AmB commercial formulations. After three consecutive days of i.v. administration, the results showed that the group treated with Angiopep-PEG-PE/AmB achieved the greatest treatment efficacy, which reached the highest AmB level in brain, reduced the brain fungal burden significantly, decreased histopathological severity and prolonged the median survival time. The increased treatment efficacy could be attributed to the brain-targeting delivery system promoted AmB crossing the BBB and penetrating into the brain to reach the therapeutic concentration. The underlying mechanism was also explored in this work. Therefore, the brain-targeting delivery system could have potential and promising implications for treatment of intracerebral fungal infection. PMID:22789719

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

    PubMed

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

    2014-01-01

    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

  10. Dispersion of nanoparticulate suspensions using self-assembled surfactant aggregates

    NASA Astrophysics Data System (ADS)

    Singh, Pankaj Kumar

    The dispersion of particles is critical for several industrial applications such as paints, inks, coatings, and cosmetics. Several emerging applications such as abrasives for precision polishing, and drug delivery systems are increasingly relying on nanoparticulates to achieve the desired performance. In the case of nanoparticles, the dispersion becomes more challenging because of the lack of fundamental understanding of dispersant adsorption and interparticle force prediction. Additionally, many of these processes use severe processing environments such as high normal forces (>100 mN/m), high shear forces (>10,000 s -1), and high ionic strengths (>0.1 M). Under such processing conditions, traditionally used dispersants based on electrostatics, and steric force repulsion mechanism may not be adequate. Hence, the development of optimally performing dispersants requires a fundamental understanding of the dispersion mechanism at the atomic/molecular scale. This study explores the use of self-assembled surfactant aggregates at the solid-liquid interface for dispersing nanoparticles in severe processing environments. Surfactant molecules can provide a feasible alternative to polymeric or inorganic dispersants for stabilizing ultrafine particles. The barrier to aggregation in the presence of surfactant molecules was measured using atomic force microscopy. The barrier heights correlated to suspension stability. To understand the mechanism for nanoparticulate suspension stability in the presence of surfactant films, the interface was characterized using zeta potential, contact angle, adsorption, and FT-IR (adsorbed surfactant film structure measurements). The effect of solution conditions such as pH and ionic strength on the suspension stability, and the self-assembled surfactant films was also investigated. It was determined that a transition from a random to an ordered orientation of the surfactant molecules at the interface was responsible for stability of nanoparticulates. Additionally, the role of the surface in surfactant self-assembly was investigated. Mechanical and thermodynamic properties of the self-assembled layer at the solid-liquid interface were calculated based on experimental results, and compared to the corresponding properties in the bulk solution.

  11. Nanoparticulate drug delivery platforms for advancing bone infection therapies

    PubMed Central

    Uskokovi?, Vuk; Desai, Tejal A

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  13. Vectors

    NSDL National Science Digital Library

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

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

  14. Extracellular stability of nanoparticulate drug carriers.

    PubMed

    Liu, Karen C; Yeo, Yoon

    2014-01-01

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

  15. Intratumoral Drug Delivery with Nanoparticulate Carriers

    PubMed Central

    Holback, Hillary

    2011-01-01

    Stiff extracellular matrix, elevated interstitial fluid pressure, and the affinity for the tumor cells in the peripheral region of a solid tumor mass have long been recognized as significant barriers to diffusion of small-molecular-weight drugs and antibodies. However, their impacts on nanoparticle-based drug delivery have begun to receive due attention only recently. This article reviews biological features of many solid tumors that influence transport of drugs and nanoparticles and properties of nanoparticles relevant to their intratumoral transport, studied in various tumor models. We also discuss several experimental approaches employed to date for enhancement of intratumoral nanoparticle penetration. The impact of nanoparticle distribution on the effectiveness of chemotherapy remains to be investigated and should be considered in the design of new nanoparticulate drug carriers. PMID:21213021

  16. CREDVW-Linked Polymeric Micelles As a Targeting Gene Transfer Vector for Selective Transfection and Proliferation of Endothelial Cells.

    PubMed

    Hao, Xuefang; Li, Qian; Lv, Juan; Yu, Li; Ren, Xiangkui; Zhang, Li; Feng, Yakai; Zhang, Wencheng

    2015-06-10

    Nowadays, gene transfer technology has been widely used to promote endothelialization of artificial vascular grafts. However, the lack of gene vectors with low cytotoxicity and targeting function still remains a pressing challenge. Herein, polyethylenimine (PEI, 1.8 kDa or 10 kDa) was conjugated to an amphiphilic and biodegradable diblock copolymer poly(ethylene glycol)-b-poly(lactide-co-glycolide) (mPEG-b-PLGA) to prepare mPEG-b-PLGA-g-PEI copolymers with the aim to develop gene vectors with low cytotoxicity while high transfection efficiency. The micelles were prepared from mPEG-b-PLGA-g-PEI copolymers by self-assembly method. Furthermore, Cys-Arg-Glu-Asp-Val-Trp (CREDVW) peptide was linked to micelle surface to enable the micelles with special recognition for endothelial cells (ECs). In addition, pEGFP-ZNF580 plasmids were condensed into these CREDVW-linked micelles to enhance the proliferation of ECs. These CREDVW-linked micelle/pEGFP-ZNF580 complexes exhibited low cytotoxicity by MTT assay. The cell transfection results demonstrated that pEGFP-ZNF580 could be transferred into ECs efficiently by these micelles. The results of Western blot analysis showed that the relative ZNF580 protein level in transfected ECs increased to 76.9%. The rapid migration of transfected ECs can be verified by wound healing assay. These results indicated that CREDVW-linked micelles could be a suitable gene transfer vector with low cytotoxicity and high transfection efficiency, which has great potential for rapid endothelialization of artificial blood vessels. PMID:26011845

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

    E-print Network

    Cheng, Jianjun

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

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

    Microsoft Academic Search

    Suh Cem Pang; Wai Hwa Khoh; Suk Fun Chin

    2010-01-01

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

  19. Highly Conductive Nanoparticulate Films Achieved at Low Sintering Temperatures

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  20. Mechanisms of Tumor Vascular Priming by a Nanoparticulate Doxorubicin Formulation

    PubMed Central

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

    2013-01-01

    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. PMID:22798260

  1. A review of research on nanoparticulate flow undergoing coagulation

    NASA Astrophysics Data System (ADS)

    Lin, Jianzhong; Huo, Linlin

    2015-05-01

    Nanoparticulate flows occur in a wide range of natural phenomena and engineering applications and, hence, have attracted much attention. The purpose of the present paper is to provide a review of the research conducted over the last decade. The research covered relates to the Brownian coagulation of monodisperse and polydisperse particles, the Taylor-series expansion method of moment, and nanoparticle distributions due to coagulation in pipe and channel flow, jet flow, and the mixing layer and in the process of flame synthesis and deposition.

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

    PubMed Central

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

    2013-01-01

    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. PMID:23459088

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

    PubMed

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

    2013-01-01

    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. PMID:23459088

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

    E-print Network

    Mu, L.

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

  5. SIMULATION NUMRIQUE DE LA CONDENSATION/VAPORATION ET DE LA COAGULATION DES NANOPARTICULES.

    E-print Network

    Paris-Sud XI, Université de

    SIMULATION NUMÉRIQUE DE LA CONDENSATION/ÉVAPORATION ET DE LA COAGULATION DES NANOPARTICULES. M simulation of condensational growth, evaporation and coagulation of nanoparticles. ABSTRACT Aware. This first study addresses condensational growth, evaporation and coagulation. The model is to be integrated

  6. Polymeric nanoparticles

    PubMed Central

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

    2014-01-01

    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

  7. A TEM analysis of nanoparticulates in a Polar ice core

    SciTech Connect

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

    2004-03-15

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

  8. Multifunctional, stimuli-sensitive nanoparticulate systems for drug delivery

    PubMed Central

    Torchilin, Vladimir P.

    2015-01-01

    The use of nanoparticulate pharmaceutical drug delivery systems (NDDSs) to enhance the in vivo effectiveness of drugs is now well established. The development of multifunctional and stimulus-sensitive NDDSs is an active area of current research. Such NDDSs can have long circulation times, target the site of the disease and enhance the intracellular delivery of a drug. This type of NDDS can also respond to local stimuli that are characteristic of the pathological site by, for example, releasing an entrapped drug or shedding a protective coating, thus facilitating the interaction between drug-loaded nanocarriers and target cells or tissues. In addition, imaging contrast moieties can be attached to these carriers to track their real-time biodistribution and accumulation in target cells or tissues. Here, I highlight recent developments with multifunctional and stimuli-sensitive NDDSs and their therapeutic potential for diseases including cancer, cardiovascular diseases and infectious diseases. PMID:25287120

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

    NASA Astrophysics Data System (ADS)

    Hebert, Etienne M.

    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.

  10. Dynamics of discontinuous coating and drying of nanoparticulate films.

    SciTech Connect

    Schunk, Peter Randall; Dunphy, Darren Robert (University of New Mexico, Albuquerque, NM); Brinker, C. Jeffrey; Tjiptowidjojo, Kristianto (University of New Mexico, Albuquerque, NM)

    2010-09-01

    Heightened interest in micro-scale and nano-scale patterning by imprinting, embossing, and nano-particulate suspension coating stems from a recent surge in development of higher-throughput manufacturing methods for integrated devices. Energy-applications addressing alternative, renewable energy sources offer many examples of the need for improved manufacturing technology for micro and nano-structured films. In this presentation we address one approach to micro- and nano-pattering coating using film deposition and differential wetting of nanoparticles suspensions. Rather than print nanoparticle or colloidal inks in discontinuous patches, which typically employs ink jet printing technology, patterns can be formed with controlled dewetting of a continuously coated film. Here we report the dynamics of a volatile organic solvent laden with nanoparticles dispensed on the surfaces of water droplets, whose contact angles (surface energy) and perimeters are defined by lithographic patterning of initially (super)hydrophobic surfaces.. The lubrication flow equation together with averaged particle transport equation are employed to predict the film thickness and particle average concentration profiles during subsequent drying of the organic and water solvents. The predictions are validated by contact angle measurements, in situ grazing incidence small angle x-ray scattering experiments, and TEM images of the final nanoparticle assemblies.

  11. Microstructures and Nanostructures for Environmental Carbon Nanotubes and Nanoparticulate Soots

    PubMed Central

    Murr, L. E.

    2008-01-01

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

  12. CROISSANCE DE NANOPARTICULES D'ARGENT PAR INSOLATION LASER ULTRAVIOLETTE CONTINUE DANS DES VERRES SODA-LIME

    E-print Network

    Paris-Sud XI, Université de

    CROISSANCE DE NANOPARTICULES D'ARGENT PAR INSOLATION LASER ULTRAVIOLETTE CONTINUE DANS DES VERRES concentration dans des verres soda-lime par insolation laser continue à 244 nm. L'originalité de cette-CLEFS : nanoparticules ; argent ; verres soda-lime ; coalescence. 1. INTRODUCTION La croissance de NP d'argent peut être

  13. A review of the formation and classification of amphiphilic block copolymer nanoparticulate structures: micelles, nanospheres, nanocapsules and polymersomes

    Microsoft Academic Search

    Kevin Letchford; Helen Burt

    2007-01-01

    Amphiphilic block copolymers are able to form a range of different nanoparticulate structures. These include micelles, nanospheres, nanocapsules, and polymersomes. This review attempts to clarify some of the terminology used in the literature by providing an overview of the major features of each type of nanoparticle and the factors that influence the formation of particular nanoparticulate formulations.

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

    PubMed Central

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

    2013-01-01

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

  15. Structure evolution of nanoparticulate Fe2O3.

    PubMed

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

    2015-02-21

    The atomic structure and properties of nanoparticulate Fe2O3 are characterized starting from its smallest Fe2O3 building unit through (Fe2O3)n clusters to nanometer-sized Fe2O3 particles. This is achieved by combining global structure optimizations at the density functional theory level, molecular dynamics simulations by employing tailored, ab initio parameterized interatomic potential functions and experiments. With the exception of nearly tetrahedral, adamantane-like (Fe2O3)2 small (Fe2O3)n clusters assume compact, virtually amorphous structures with little or no symmetry. For n = 2-5 (Fe2O3)n clusters consist mainly of two- and three-membered Fe-O rings. Starting from n = 5 they increasingly assume tetrahedral shape with the adamantane-like (Fe2O3)2 unit as the main building block. However, the small energy differences between different isomers of the same cluster-size make precise structural assignment for larger (Fe2O3)n clusters difficult. The tetrahedral morphology persists for Fe2O3 nanoparticles with up to 3 nm in diameter. Simulated crystallization of larger nanoparticles with diameters of about 5 nm demonstrates pronounced melting point depression and leads to formation of ?-Fe2O3 single crystals with hexagonal morphology. This finding is in excellent agreement with the results obtained for Fe2O3 nanopowders generated by laser vaporization and provides the first direct indication that ?-Fe2O3 may be thermodynamically the most stable phase in this size regime. PMID:25587689

  16. Cellular partitioning of nanoparticulate versus dissolved metals in marine phytoplankton.

    PubMed

    Bielmyer-Fraser, Gretchen K; Jarvis, Tayler A; Lenihan, Hunter S; Miller, Robert J

    2014-11-18

    Discharges of metal oxide nanoparticles into aquatic environments are increasing with their use in society, thereby increasing exposure risk for aquatic organisms. Separating the impacts of nanoparticle from dissolved metal pollution is critical for assessing the environmental risks of the rapidly growing nanomaterial industry, especially in terms of ecosystem effects. Metal oxides negatively affect several species of marine phytoplankton, which are responsible for most marine primary production. Whether such toxicity is generally due to nanoparticles or exposure to dissolved metals liberated from particles is uncertain. The type and severity of toxicity depends in part on whether phytoplankton cells take up and accumulate primarily nanoparticles or dissolved metal ions. We compared the responses of the marine diatom, Thalassiosira weissflogii, exposed to ZnO, AgO, and CuO nanoparticles with the responses of T. weissflogii cells exposed to the dissolved metals ZnCl2, AgNO3, and CuCl2 for 7 d. Cellular metal accumulation, metal distribution, and algal population growth were measured to elucidate differences in exposure to the different forms of metal. Concentration-dependent metal accumulation and reduced population growth were observed in T. weissflogii exposed to nanometal oxides, as well as dissolved metals. Significant effects on population growth were observed at the lowest concentrations tested for all metals, with similar toxicity for both dissolved and nanoparticulate metals. Cellular metal distribution, however, markedly differed between T. weissflogii exposed to nanometal oxides versus those exposed to dissolved metals. Metal concentrations were highest in the algal cell wall when cells were exposed to metal oxide nanoparticles, whereas algae exposed to dissolved metals had higher proportions of metal in the organelle and endoplasmic reticulum fractions. These results have implications for marine plankton communities as well as higher trophic levels, since metal may be transferred from phytoplankton through food webs vis à vis grazing by zooplankton or other pathways. PMID:25337629

  17. Electrochromism of nanoparticulate-doped metal oxides: optical and material properties

    Microsoft Academic Search

    J. P Coleman; J. J Freeman; P Madhukar; J. H Wagenknecht

    1999-01-01

    Nanoparticulate antimony-doped tin oxide (ATO) has been used as the electrochromic material for the production of printed, interdigitated electrochromic displays. We report here some results on elemental and ionic modifications to the ATO in an attempt to improve electrochromic switching. We have also briefly studied the effects of antimony and tin distribution in the mixed oxide by a sequential preparation

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

    NASA Astrophysics Data System (ADS)

    Tang, Xiangyang; Yang, Yi; Tang, Shaojie

    2011-03-01

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

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

    E-print Network

    Orvananos, Bernardo

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

  20. Breakdown and Combustion of JP-10 Fuel Catalyzed by Nanoparticulate CeO2 and Fe2O3

    E-print Network

    Anderson, Scott L.

    Breakdown and Combustion of JP-10 Fuel Catalyzed by Nanoparticulate CeO2 and Fe2O3 Brian Van of nanoparticulate CeO2 and Fe2O3, was studied in a small alumina flow-tube reactor on time scales around 1 ms pyrolyzes at temperatures above 900 K to a variety of hydrocarbon products. In the absence of O2, both CeO2

  1. Anticancer Polymeric Nanomedicines

    Microsoft Academic Search

    Rong Tong; Jianjun Cheng

    2007-01-01

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

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

    PubMed Central

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

    2013-01-01

    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. PMID:24300401

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

    Microsoft Academic Search

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

    2006-01-01

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

  4. 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.

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

    PubMed Central

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

    2015-01-01

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

  6. Dielectrophoretic isolation and detection of cfc-DNA nanoparticulate biomarkers and virus from blood.

    PubMed

    Sonnenberg, Avery; Marciniak, Jennifer Y; McCanna, James; Krishnan, Rajaram; Rassenti, Laura; Kipps, Thomas J; Heller, Michael J

    2013-04-01

    Dielectrophoretic (DEP) microarray devices allow important cellular nanoparticulate biomarkers and virus to be rapidly isolated, concentrated, and detected directly from clinical and biological samples. A variety of submicron nanoparticulate entities including cell free circulating (cfc) DNA, mitochondria, and virus can be isolated into DEP high-field areas on microelectrodes, while blood cells and other micron-size entities become isolated into DEP low-field areas between the microelectrodes. The nanoparticulate entities are held in the DEP high-field areas while cells are washed away along with proteins and other small molecules that are not affected by the DEP electric fields. DEP carried out on 20 ?L of whole blood obtained from chronic lymphocytic leukemia patients showed a considerable amount of SYBR Green stained DNA fluorescent material concentrated in the DEP high-field regions. Whole blood obtained from healthy individuals showed little or no fluorescent DNA materials in the DEP high-field regions. Fluorescent T7 bacteriophage virus could be isolated directly from blood samples, and fluorescently stained mitochondria could be isolated from biological buffer samples. Using newer DEP microarray devices, high-molecular-weight DNA could be isolated from serum and detected at levels as low as 8-16 ng/mL. PMID:23436471

  7. Nanoparticulate adjuvants and delivery systems for allergen immunotherapy.

    PubMed

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

    2012-01-01

    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. PMID:22496608

  8. Nanoparticulate Adjuvants and Delivery Systems for Allergen Immunotherapy

    PubMed Central

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

    2012-01-01

    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. PMID:22496608

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

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

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

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

    PubMed Central

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

    2014-01-01

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

  11. Solid state polymerization

    Microsoft Academic Search

    S. N. Vouyiouka; E. K. Karakatsani; C. D. Papaspyrides

    2005-01-01

    Polyesters and polyamides are commercially important polymers prepared by polycondensation. The conventional solution to melt polymerization techniques stop at a low or medium molecular weight product, due to problems arising from severe increase of the melt viscosity and operating temperatures. Higher molecular weights may be reached by Solid State Polymerization (SSP) at temperatures between the glass transition and the onset

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

    Microsoft Academic Search

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

    2008-01-01

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

  13. Vector Introduction Vector components and example machines

    E-print Network

    California at Berkeley, University of

    vector 1 Vector Introduction Lecture 10 2/21/96 vector 2 Outline Motivation Vector components and example machines Vector instructions & vector program Vector Execution Vector Load/Store Units Vector Length, Stride, Strip Mining Vector Optimizations: Chaining, Gather/Scatter, Conditional Vector Metrics

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

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

    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.

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

    ERIC Educational Resources Information Center

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

    2009-01-01

    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…

  16. Concise polymeric materials encyclopedia

    SciTech Connect

    Salamone, J.C. [ed.

    1999-01-01

    This comprehensive, accessible resource abridges the ``Polymeric Materials Encyclopedia'', presenting more than 1,100 articles and featuring contributions from more than 1,800 scientists from all over the world. The text discusses a vast array of subjects related to the: (1) synthesis, properties, and applications of polymeric materials; (2) development of modern catalysts in preparing new or modified polymers; (3) modification of existing polymers by chemical and physical processes; and (4) biologically oriented polymers.

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

    E-print Network

    , such as the nanoparticulate and semiconducting photoanode of a dye-sensitized solar cell (DSC), with a layer of a second metal. Hupp*,, Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center

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

    PubMed

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

    2014-08-19

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

  19. In vitro and in vivo evaluation of a nanoparticulate bioceramic paste for dental pulp repair.

    PubMed

    Zhu, Lingxin; Yang, Jingwen; Zhang, Jie; Lei, Dongqi; Xiao, Lan; Cheng, Xue; Lin, Ying; Peng, Bin

    2014-12-01

    Bioactive materials play an important role in facilitating dental pulp repair when living dental pulp is exposed after injuries. Mineral trioxide aggregate is the currently recommended material of choice for pulp repair procedures though has several disadvantages, especially the inconvenience of handling. Little information is yet available about the early events and molecular mechanisms involved in bioceramic-mediated dental pulp repair. We aimed to characterize and determine the apatite-forming ability of the novel ready-to-use nanoparticulate bioceramic iRoot BP Plus, and investigate its effects on the in vitro recruitment of human dental pulp stem cells (DPSCs), as well as its capacity to induce dentin bridge formation in an in vivo model of pulp repair. It was found that iRoot BP Plus was nanosized and had excellent apatite-forming ability in vitro. Treatment with iRoot BP Plus extracts promoted the adhesion, migration and attachment of DPSCs, and optimized focal adhesion formation (Vinculin, p-Paxillin and p-Focal adhesion kinase) and stress fibre assembly. Consistent with the in vitro results, we observed the formation of a homogeneous dentin bridge and the expression of odontogenic (dentin sialoprotein, dentin matrix protein 1) and focal adhesion molecules (Vinculin, p-Paxillin) at the injury site of pulp repair model by iRoot BP Plus. Our findings provide valuable insights into the mechanism of bioceramic-mediated dental pulp repair, and the novel revolutionary ready-to-use nanoparticulate bioceramic paste shows promising therapeutic potential in dental pulp repair application. PMID:25182220

  20. Polymerization of vegetable oils

    SciTech Connect

    Korus, R.A.; Mousetis, T.L.; Lloyd, L.

    1982-01-01

    The addition of antioxidants and dispersants is not sufficient to eliminate gum formation in vegetable oils. Even with relatively unsaturated oils like rapeseed the extent of unsaturation overwhelms these additives. Fuel deterioration during storage will be minimized in an anaerobic storage environment and, to a lesser extent, with a lower degree of oil unsaturation. Gum formation and carbon coking can also occur immediately preceding and during combustion. Thermal polymerization may be the dominant gum forming reaction under combustion conditions since thermal polymerization has a higher activation energy than oxidative polymerization and anaerobic conditions can occur within atomized fuel droplets. Carbon coking can be reduced with a lower degree of oil unsaturation and with better atomization of the fuel. 4 figures, 1 table.

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

    PubMed

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

    2013-05-01

    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

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

    E-print Network

    Orvananos, Bernardo; Yu, Hui-Chia; Bazant, Martin Z; Thornton, Katsuyo

    2013-01-01

    In nanoparticulate phase-separating electrodes, phase separation inside the particles can be hindered during their charge/discharge cycles even when a thermodynamic driving force for phase separation exists. In such cases, particles may (de)lithiate discretely in a process referred to as mosaic instability. This instability could be the key to elucidating the complex charge/discharge dynamics in nanoparticulate phase-separating electrodes. In this paper, the dynamics of the mosaic instability is studied using Smoothed Boundary Method simulations at the particle level, where the concentration and electrostatic potential fields are spatially resolved around individual particles. Two sets of configurations consisting of spherical particles with an identical radius are employed to study the instability in detail. The effect of an activity-dependent exchange current density on the mosaic instability, which leads to asymmetric charge/discharge, is also studied. While we show that our model reproduces the results of...

  3. Polymerization in mixed crystals

    Microsoft Academic Search

    V. Enkelmann; Hermann Staudinger Haus

    1980-01-01

    Suitably substituted diacetylenes can be co-crystallized to form substitutional solid solutions. By solid state polymerization of these mixed crystals macroscopic single crystals of statistical copolymers can be obtained. The co-crystallization is described and the influence of crystal composition on structure and reactivity in the solid state is discussed.

  4. Protein specific polymeric immunomicrospheres

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    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.

  5. Flame retardant polymeric materials

    SciTech Connect

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

    1982-01-01

    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.

  6. Innovative application of ultrasonic mixing to produce homogeneously mixed nanoparticulate-epoxy composite of improved physical properties

    Microsoft Academic Search

    M. S. Goyat; S. Ray; P. K. Ghosh

    2011-01-01

    An innovative ultrasonic dual mixing process (ultrasonic mixing along with impeller stirring) has been employed to disperse round Al2O3 (<25nm) particles in epoxy resin. Characterization of the nanoparticulate-epoxy composite has been carried out using TEM, AFM, DTA, TGA and FTIR and compared with the results obtained in epoxy without particles. When epoxy is treated by this dual mixing there is

  7. Vector quantization

    Microsoft Academic Search

    Robert M. Gray

    1984-01-01

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

  8. Plasma polymerization (review)

    SciTech Connect

    Vinogradov, G.K.

    1986-11-01

    The term ''plasma (gaseous discharge) polymerization'' is widely used to denote the process of forming high molecular weight products in electrical discharges. The purpose of the present review is primarily to analyze the state and methodology of research on gaseous discharge polymerization and to clarify the main approaches and trends in the literature. Experimental apparatus, internal plasma parameters, and research on the structure of polymer films and surface processes are discussed. IR spectroscopy and ESCA (electron spectroscopy for chemical analysis) as methods of studying the structure and composition of a polymer film are examined. The proposed models presented here are based primarily on the kinetic behavior of polymer film formation and on general considerations about the relation between the external parameters of discharges and the fluxes of various particle species onto the surface of a growing film which provide for the formation of the film.

  9. POLYMERIZATION OF MONOMERIC TO POLYMERIC VESICLES. CHARACTERIZATION AND APPLICATIONS

    Microsoft Academic Search

    Constantinos N. Paleos

    1990-01-01

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

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

    PubMed

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

    2013-08-01

    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

  11. A novel nanoparticulate system for sustained delivery of acid-labile lansoprazole.

    PubMed

    Alai, Milind Sadashiv; Lin, Wen Jen

    2013-11-01

    In the present study, an effort was made to develop the Eudragit RS100 based nanoparticulate system for sustained delivery of an acid-labile drug, lansoprazole (LPZ). LPZ-loaded Eudragit RS100 nanoparticles (ERSNPs) were prepared by oil-in-water emulsion-solvent evaporation method. The effects of various formulation variables such as polymer concentration, drug amount and solvent composition on physicochemical performance of nanoparticles and in vitro drug release were investigated. All nanoparticles were spherical with particle size 198.9 ± 8.6-376.9 ± 5.6 nm and zeta potential +35.1 ± 1.7 to +40.2 ± 0.8 mV. The yield of nanoparticles was unaffected by change of these three variables. However, the drug loading and encapsulation efficiency were affected by polymer concentration and drug amount. On the other hand, the particle size of nanoparticles was significantly affected by polymer concentration and internal phase composition due to influence of droplet size during emulsification process. All nanoparticles prolonged drug release for 24h which was dominated by a combination of drug diffusion and polymer chain relaxation. The fastest and the slowest release rates were observed in C2-1002-10/0 and C8-4001-10/0, respectively, based on the release rate constant (k). Thus, the developed nanoparticles possessed a potential as a nano-carrier to sustain drug delivery for treatment of acid related disorders. PMID:23867305

  12. Effects of ZnO nanoparticulate addition on the properties of PMNT ceramics

    PubMed Central

    2012-01-01

    This research was conducted in order to study the effect of ZnO nanoparticulate addition on the properties of 0.9 Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 [PMNT] ceramics. The PMNT ceramics were prepared by a solid-state reaction. The ZnO nanoparticles were added into PMNT ceramics to form PMNT/xZnO (x = 0, 0.05, 0.1, 0.5, and 1.0 wt.%). The PMNT/xZnO ceramics were investigated in terms of phase, microstructure, and mechanical and electrical properties. It was found that the density and grain size of PMNT ceramics tended to increase with an increasing amount of ZnO content. Moreover, a transgranular fracture was observed for the samples containing ZnO, while pure PMNT ceramics showed only a intergranular fracture. An addition of only 0.05 wt.% of ZnO was also found to enhance the hardness and dielectric and ferroelectric properties of the PMNT ceramics. PMID:22222049

  13. Effects of ZnO nanoparticulate addition on the properties of PMNT ceramics.

    PubMed

    Promsawat, Methee; Watcharapasorn, Anucha; Jiansirisomboon, Sukanda

    2012-01-01

    This research was conducted in order to study the effect of ZnO nanoparticulate addition on the properties of 0.9 Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 [PMNT] ceramics. The PMNT ceramics were prepared by a solid-state reaction. The ZnO nanoparticles were added into PMNT ceramics to form PMNT/xZnO (x = 0, 0.05, 0.1, 0.5, and 1.0 wt.%). The PMNT/xZnO ceramics were investigated in terms of phase, microstructure, and mechanical and electrical properties. It was found that the density and grain size of PMNT ceramics tended to increase with an increasing amount of ZnO content. Moreover, a transgranular fracture was observed for the samples containing ZnO, while pure PMNT ceramics showed only a intergranular fracture. An addition of only 0.05 wt.% of ZnO was also found to enhance the hardness and dielectric and ferroelectric properties of the PMNT ceramics. PMID:22222049

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

    SciTech Connect

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

    2006-01-01

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

  15. Vector Fields

    NSDL National Science Digital Library

    Dray, Tevian

    2006-01-01

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

  16. Cloning vector

    DOEpatents

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

    1994-12-27

    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.

  17. Polymerization Evaluation by Spectrophotometric Measurements.

    ERIC Educational Resources Information Center

    Dunach, Jaume

    1985-01-01

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

  18. Vector quantization

    NASA Technical Reports Server (NTRS)

    Gray, Robert M.

    1989-01-01

    During the past ten years Vector Quantization (VQ) has developed from a theoretical possibility promised by Shannon's source coding theorems into a powerful and competitive technique for speech and image coding and compression at medium to low bit rates. In this survey, the basic ideas behind the design of vector quantizers are sketched and some comments made on the state-of-the-art and current research efforts.

  19. Polymeric Side Chain Thioxanthone Photoinitiator for Free Radical Polymerization

    Microsoft Academic Search

    Gokhan Temel; Nergis Arsu; Yusuf Yagci

    2006-01-01

    Summary  Side chain thioxanthone-containing polymer (PSt-TX) was synthesized and characterized by modification of polystyrene prepared\\u000a by Atom Transfer Radical Polymerization. PSt-TX exhibits absorption characteristics similar to that of the unsubstitued thioxanthone.\\u000a Its capability to act as initiator for the polymerization of methyl methacrylate was also examined.

  20. Living olefin polymerization processes

    DOEpatents

    Schrock, R.R.; Baumann, R.

    1999-03-30

    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.

  1. Bimorphic polymeric photomechanical actuator

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    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.

  2. Living olefin polymerization processes

    DOEpatents

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

    1999-01-01

    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.

  3. Organometallic Polymeric Conductors

    NASA Technical Reports Server (NTRS)

    1997-01-01

    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.

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

    PubMed

    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

    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

  5. Anticancer efficacy and toxicokinetics of a novel paclitaxel-clofazimine nanoparticulate co-formulation.

    PubMed

    Koot, Dwayne; Cromarty, Duncan

    2015-06-01

    Contemporary chemotherapy is limited by disseminated, resistant cancer. Targeting nanoparticulate drug delivery systems that encapsulate synergistic drug combinations are a rational means to increase the therapeutic index of chemotherapeutics. A lipopolymeric micelle co-encapsulating an in vitro optimized, synergistic fixed-ratio combination of paclitaxel (PTX) and clofazimine (B663) has been developed and called Riminocelles™. The present pre-clinical study investigated the acute toxicity, systemic exposure, repeat dose toxicity and efficacy of Riminocelles in parallel to Taxol® at an equivalent PTX dose of 10 mg/kg. Daily and weekly dosing schedules were evaluated against Pgp-expressing human colon adenocarcinoma (HCT-15) xenografts implanted subcutaneously in athymic mice. Riminocelles produced statistically significant (p

  6. Folate-mediated intracellular drug delivery increases the anticancer efficacy of nanoparticulate formulation of arsenic trioxide

    PubMed Central

    Chen, Haimei; Ahn, Richard; Van den Bossche, Jeroen; Thompson, David H.; O’Halloran, Thomas V.

    2011-01-01

    Arsenic trioxide (As2O3) is a frontline drug for treatment of acute promyelocytic leukemia and is in clinical trials for treatment of other malignancies, including multiple myeloma; however, efforts to expand clinical utility to solid tumors have been limited by toxicity. Nanoparticulate forms of As2O3 encapsulated in 100-nm-scale, folate-targeted liposomes have been developed to lower systematic toxicity and provide a platform for targeting this agent. The resultant arsenic “nanobins” are stable under physiologic conditions but undergo triggered drug release when the pH is lowered to endosomal/lysosomal levels. Cellular uptake and antitumor efficacy of these arsenic liposomes have been evaluated in folate receptor (FR)–positive human nasopharyngeal (KB) and cervix (HeLa) cells, as well as FR-negative human breast (MCF-7) tumor cells through confocal microscopy, inductively coupled plasma mass spectroscopy, and cytotoxicity studies. Uptake of folate-targeted liposomal arsenic by KB cells was three to six times higher than that of free As2O3 or nontargeted liposomal arsenic; the enhanced uptake occurs through folate-mediated endocytosis, leading to a 28-fold increase in cytotoxicity. In contrast, tumor cells with lower FR density on the surface (HeLa and MCF-7) showed much less uptake of the folate-targeted drug and lower efficacy. In cocultures of KB and MCF-7 cells, the folate-targeted arsenic liposomes were exclusively internalized by KB cells, showing high targeting specificity. Our studies further indicate that folate-targeted delivery of As2O3 with coencapsulated nickel(II) ions (as a nontoxic adjuvant) potentiates the As2O3 efficacy in relatively insensitive solid tumor–derived cells and holds the promise of improving drug therapeutic index. PMID:19567824

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

    PubMed

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

    2012-07-01

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

  8. Nanoparticulate delivery of agents for induced elastogenesis in three-dimensional collagenous matrices.

    PubMed

    Venkataraman, Lavanya; Sivaraman, Balakrishnan; Vaidya, Pratik; Ramamurthi, Anand

    2014-04-16

    The degradation of elastic matrix in the infrarenal aortic wall is a critical parameter underlying the formation and progression of abdominal aortic aneurysms. It is mediated by the chronic overexpression of matrix metalloprotease (MMP)-2 and MMP-9, leading to a progressive loss of elasticity and weakening of the aortic wall. Delivery of therapeutic agents to inhibit MMPs, while concurrently coaxing cell-based regenerative repair of the elastic matrix represents a potential strategy for slowing or arresting abdominal aortic aneurysm growth. Previous studies have demonstrated elastogenic induction of healthy and aneurysmal aortic smooth muscle cells and inhibition of MMPs, following exogenous delivery of elastogenic factors such as transforming growth factor (TGF)-?1, as well as MMP-inhibitors such as doxycycline (DOX) in two-dimensional culture. Based on these findings, and others that demonstrated elastogenic benefits of nanoparticulate delivery of these agents in two-dimensional culture, poly(lactide-co-glycolide) nanoparticles were developed for localized, controlled and sustained delivery of DOX and TGF-?1 to human aortic smooth muscle cells within a three-dimensional gels of type I collagen, which closely simulate the arterial tissue microenvironment. DOX and TGF-?1 released from these nanoparticles influenced elastogenic outcomes positively within the collagen constructs over 21 days of culture, which were comparable to that induced by exogenous supplementation of DOX and TGF-?1 within the culture medium. However, this was accomplished at doses ~20-fold lower than the exogenous dosages of the agents, illustrating that their localized, controlled and sustained delivery from nanoparticles embedded within a three-dimensional scaffold is an efficient strategy for directed elastogenesis. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24737693

  9. K-edge ratio method for identification of multiple nanoparticulate contrast agents by spectral CT imaging

    PubMed Central

    Ghadiri, H; Ay, M R; Shiran, M B; Soltanian-Zadeh, H

    2013-01-01

    Objective: Recently introduced energy-sensitive X-ray CT makes it feasible to discriminate different nanoparticulate contrast materials. The purpose of this work is to present a K-edge ratio method for differentiating multiple simultaneous contrast agents using spectral CT. Methods: The ratio of two images relevant to energy bins straddling the K-edge of the materials is calculated using an analytic CT simulator. In the resulting parametric map, the selected contrast agent regions can be identified using a thresholding algorithm. The K-edge ratio algorithm is applied to spectral images of simulated phantoms to identify and differentiate up to four simultaneous and targeted CT contrast agents. Results: We show that different combinations of simultaneous CT contrast agents can be identified by the proposed K-edge ratio method when energy-sensitive CT is used. In the K-edge parametric maps, the pixel values for biological tissues and contrast agents reach a maximum of 0.95, whereas for the selected contrast agents, the pixel values are larger than 1.10. The number of contrast agents that can be discriminated is limited owing to photon starvation. For reliable material discrimination, minimum photon counts corresponding to 140?kVp, 100?mAs and 5-mm slice thickness must be used. Conclusion: The proposed K-edge ratio method is a straightforward and fast method for identification and discrimination of multiple simultaneous CT contrast agents. Advances in knowledge: A new spectral CT-based algorithm is proposed which provides a new concept of molecular CT imaging by non-iteratively identifying multiple contrast agents when they are simultaneously targeting different organs. PMID:23934964

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

    PubMed

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

    2014-10-01

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

  11. Biocompatible Initiators for Lactide Polymerization

    Microsoft Academic Search

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

    2008-01-01

    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

  12. Outdoor high voltage polymeric insulators

    Microsoft Academic Search

    R. Hackam

    1998-01-01

    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

  13. Coating of plasma polymerized film

    NASA Technical Reports Server (NTRS)

    Morita, S.; Ishibashi, S.

    1980-01-01

    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.

  14. Navigational Vectors

    NSDL National Science Digital Library

    2008-12-10

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

  15. Polyelectrolyte-mediated assembly of copper-phthalocyanine tetrasulfonate multilayers and the subsequent production of nanoparticulate copper oxide thin films.

    PubMed

    Chickneyan, Zarui Sara; Briseno, Alejandro L; Shi, Xiangyang; Han, Shubo; Huang, Jiaxing; Zhou, Feimeng

    2004-07-01

    An approach to producing films of nanometer-sized copper oxide particulates, based on polyelectrolyte-mediated assembly of the precursor, copper(II)phthalocyanine tetrasulfonate (CPTS), is described. Multilayered CPTS and polydiallyldimethylammonium chloride (PDADMAC) were alternately assembled on different planar substrates via the layer-by-layer (LbL) procedure. The growth of CPTS multilayers was monitored by UV-visible spectrometry and quartz crystal microbalance (QCM) measurements. Both the UV-visible spectra and the QCM data showed that a fixed amount of CPTS could be attached to the substrate surface for a given adsorption cycle. Cyclic voltammograms at the CPTS/PDADMAC-covered gold electrode exhibited a decrease in peak currents with the layer number, indicating that the permeability of CPTS multilayers on the electrodes had diminished. When these CPTS multilayered films were calcined at elevated temperatures, uniform thin films composed of nanoparticulate copper oxide could be produced. Ellipsometry showed that the thickness of copper oxide nanoparticulate films could be precisely tailored by varying the thickness of CPTS multilayer films. The morphology and roughness of CPTS multilayer and copper oxide thin films were characterized by atomic force microscopy. X-ray diffraction (XRD) measurements indicated that these thin films contained both CuO and Cu2O nanoparticles. The preparation of such copper oxide thin films with the use of metal complex precursors represents a new route for the synthesis of inorganic oxide films with a controlled thickness. PMID:15518398

  16. Pipeline vectorization

    Microsoft Academic Search

    Markus Weinhardt; Wayne Luk

    2001-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  18. APPENDIX D. VECTOR ANALYSIS 1 Vector Analysis

    E-print Network

    Callen, James D.

    APPENDIX D. VECTOR ANALYSIS 1 Appendix D Vector Analysis The following conventions are used in this appendix and throughout the book: f, g, , are scalar functions of x, t; A, B, C, D are vector functions of x, t; A = |A| A · A is the magnitude or length of the vector A; ^eA A/A is a unit vector

  19. Production of monodisperse, polymeric microspheres

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  20. High temperature structural, polymeric foams from high internal emulsion polymerization

    SciTech Connect

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

    1996-02-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  2. Polymerization of anionic wormlike micelles.

    PubMed

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

    2006-01-31

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

  3. Seawater degradation of polymeric composites 

    E-print Network

    Grant, Timothy Sean

    1991-01-01

    SEAWATER DEGRADATION OF POLYMERIC COMPOSITES A Thesis by TIMOTHY SEAN GRANT Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE May 1991 Major... Subject: Mechanical Engineering SEAWATER DEGRADATION OF POLYMERIC COMPOSITES A Thesis by TIMOTHY SEAN GRANT Approved as to style and content by: Walter L. Bradley (Chair of mmittee) lan Letton (Member) arry ogan (Member) r John Whitcomb...

  4. Photoelectrocatalytic hydrogen production using nanoparticulate titania and a novel Pt/carbon electrocatalyst: The concept of the "Photoelectrocatalytic Leaf"

    NASA Astrophysics Data System (ADS)

    Pop, Lucian-Cristian; Dracopoulos, Vassilios; Lianos, Panagiotis

    2015-04-01

    Photoelectrocatalytic hydrogen production was realized my means of a double electrode carrying photocatalyst and electrocatalyst, deposited side by side on an FTO electrode, acting as a "Photoelectrocatalytic Leaf". As photocatalyst we used plain commercial nanoparticulate titania and as electrocatalyst a conductive carbon film made by a commercial carbon paste enriched with a small quantity of Pt nanoparticles (0.0134 mg/cm2). This quantity of Pt is much smaller than used in other applications and it may be further optimized. Hydrogen was produced in an alkaline environment in the presence of ethanol acting as sacrificial agent. A few variants of electrode geometry were studied in order to set the basic terms for efficient hydrogen production. It was found that optimal electrode geometry necessitates a much larger area for photocatalyst coverage than electrocatalyst and that it is preferable to divide photocatalyst and electrocatalyst areas in alternating zones.

  5. Polymeric materials for neovascularization

    NASA Astrophysics Data System (ADS)

    DeVolder, Ross John

    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.

  6. Polymeric materials in Space

    NASA Astrophysics Data System (ADS)

    Skurat, Vladimir

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

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

    PubMed

    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

    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

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

    PubMed

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

    2015-02-01

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

  9. Synthesis of silica-polymer core-shell nanoparticles by reversible addition-fragmentation chain transfer polymerization.

    PubMed

    Moraes, John; Ohno, Kohji; Maschmeyer, Thomas; Perrier, Sébastien

    2013-10-14

    Hybrid nanoparticles hold great promise for a range of applications such as drug-delivery vectors or colloidal crystal self-assemblies. The challenge of preparing highly monodisperse particles for these applications has recently been overcome by using living radical polymerization techniques. In particular, the use of reversible addition-fragmentation chain transfer (RAFT), initiated from silica surfaces, yields well-defined particles from a range of precursor monomers resulting in nanoparticles of tailored sizes that are accessible via the rational selection of polymerization conditions. Furthermore, using RAFT allows post-polymerization modification to afford multifunctional, monodisperse, nanostructures under mild and non-stringent reaction conditions. PMID:23999877

  10. Stereospecific olefin polymerization catalysts

    DOEpatents

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

    1998-01-13

    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.

  11. Stereospecific olefin polymerization catalysts

    DOEpatents

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

    1998-01-01

    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.

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

    PubMed

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

    2015-05-10

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

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

    PubMed

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

    2012-07-24

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

  14. On-demand photoinitiated polymerization

    DOEpatents

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

    2013-12-10

    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.

  15. Segmentation strategies for polymerized volume data sets 

    E-print Network

    Doddapaneni, Venkata Purna

    2006-04-12

    A new technique, called the polymerization algorithm, is described for the hierarchical segmentation of polymerized volume data sets (PVDS) using the Lblock data structure. The Lblock data structure is defined as a 3dimensional isorectangular block...

  16. POLYMER PROGRAM SEMINAR "Targeted polymeric nanoparticles

    E-print Network

    Alpay, S. Pamir

    POLYMER PROGRAM SEMINAR "Targeted polymeric nanoparticles: From discovery to clinical trials" Dr, IMS Room 20 A variety of organic and inorganic materials have been utilized to generate nanoparticles for drug delivery applications, including polymeric nanoparticles, dendrimers, nanoshells, liposomes

  17. Thermally Stable, Piezoelectric and Pyroelectric Polymeric Substrates

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  18. Polymerization of safflower and rapeseed oils

    Microsoft Academic Search

    Roger A. Korus; Traci L. Mousetis

    1984-01-01

    Rates of polymerization of oils from 2 safflower and 2 rapeseed varieties were measured in the air and under vacuum. Thermal\\u000a polymerization rates showed a stronger dependence on the degree of unsaturation than on oxidative polymerization. Molecular\\u000a weight distributions of polymerized oils were determined by size exclusion chromatography, and the relationship between viscosity\\u000a and weight-average molecular weight was determined.

  19. Nonlinear optical and conductive polymeric material

    DOEpatents

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

    1993-10-19

    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].

  20. Nonlinear optical and conductive polymeric material

    DOEpatents

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

    1992-05-19

    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.

  1. The Vector Product Introduction

    E-print Network

    Vickers, James

    The Vector Product 9.4 Introduction In this section we describe how to find the vector product of two vectors. Like the scalar product its definition may seem strange when first met but the definition is chosen because of its many applications. When vectors are multiplied using the vector product the result

  2. Biomass into chemicals: One pot-base free oxidative esterification of 5-hydroxymethyl-2-furfural into 2,5-dimethylfuroate with gold on nanoparticulated ceria

    Microsoft Academic Search

    O. Casanova; S. Iborra; A. Corma

    2009-01-01

    2,5-Dimethylfuroate (DMF) is a valuable biomass derivative that can replace oil dependent PET polymers. 5-Hydroxymethyl-2-furfural (HMF) has been selectively converted into DMF (99mol% yield) under mild conditions (65–130°C, 10bar O2) in the absence of any base, by using gold nanoparticles on nanoparticulated ceria. The catalyst can be reused several times without any loss of activity or selectivity. The absence of

  3. All polymeric transducers for energy harvesting

    Microsoft Academic Search

    G. Di Pasquale; S. Graziani; F. Pagano; E. Umana

    2010-01-01

    The power harvesting properties of a new class of all polymeric ionic electroactive materials, named Ionic Polymer-Polymer composites (IP2Cs) from vibrating sources are introduced and experimentally investigated. Obtained results show that the proposed technology gives better results with respect to other ionic polymeric transducers and allow to foresee the possibility to use in the future all polymeric transducers to power

  4. 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 ...

  5. Outdoor HV composite polymeric insulators

    Microsoft Academic Search

    R. Hackam

    1999-01-01

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

  6. Copper Substrate Catalyzes Tetraazaperopyrene Polymerization

    E-print Network

    Schmidt, Wolf Gero

    Copper Substrate Catalyzes Tetraazaperopyrene Polymerization W.G. Schmidt, E. Rauls, U. Gerstmann-up approach, appears to be a very promising way to fabricate functional systems with nanometer dimensions [1 found that the copper substrate is crucial for the formation of the various aggregates they observed, i

  7. Mechanisms of polymeric film formation.

    PubMed

    Felton, Linda A

    2013-12-01

    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

  8. Electrically controlled polymeric gel actuators

    Microsoft Academic Search

    Douglas B. Adolf; Mohsen Shahinpoor; Daniel J. Segalman; Walter R. Witkowski

    1993-01-01

    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

  9. Electrically controlled polymeric gel actuators

    Microsoft Academic Search

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

    1993-01-01

    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

  10. Vectors: Tip to Tail

    NSDL National Science Digital Library

    Sharon Linamen

    2012-07-23

    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.

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

    PubMed

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

    2015-04-01

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

  12. Polyhomologation. A living C1 polymerization.

    PubMed

    Luo, Jun; Shea, Kenneth J

    2010-11-16

    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

  13. Polymeric anti-HIV therapeutics.

    PubMed

    Danial, Maarten; Klok, Harm-Anton

    2015-01-01

    The scope of this review is to highlight the application of polymer therapeutics in an effort to curb the transmission and infection of the human immunodeficiency virus (HIV). Following a description of the HIV life cycle, the use of approved antiretroviral drugs that inhibit critical steps in the HIV infection process is highlighted. After that, a comprehensive overview of the structure and inhibitory properties of polymeric anti-HIV therapeutic agents is presented. This overview will include inhibitors based on polysaccharides, synthetic polymers, dendritic polymers, polymer conjugates as well as polymeric DC-SIGN antagonists. The review will conclude with a section that discusses the applications of polymers and polymer conjugates as systemic and topical anti-HIV therapeutics. PMID:25185484

  14. Polymeric cationic substituted acrylamide surfactants

    SciTech Connect

    Nieh, E.C.Y.

    1983-11-15

    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.

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

    PubMed

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

    2014-06-25

    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

  16. Radiation-hardened polymeric films

    DOEpatents

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

    1986-01-01

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

  17. Radiation-hardened polymeric films

    DOEpatents

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

    1984-07-16

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

  18. Liftable Vector Kevin Houston

    E-print Network

    Houston, Kevin

    Liftable Vector Fields Kevin Houston Motivation Liftable Vector Fields Minimal Cross-cap The Three Families Applications Shameless Plug Vector Fields Liftable Over Stable Maps Kevin Houston Joint on Singularities in Generic Geometry and Applications, Valencia, Spain 2009 #12;Liftable Vector Fields Kevin

  19. Polymerization of pyrrole into track membranes

    NASA Astrophysics Data System (ADS)

    Zhitariuk, N. I.; Le Moël, A.; Mermilliod, N.; Trautmann, C.

    1995-11-01

    The kinetics of pyrrole (Py) polymerization onto polymeric track membranes and the morphology of obtained composite materials have been investigated. Diaphragmatic method was used. The rate of polymerization depends on the pore size of the membrane and there is an optimum pore size for which the initial polymerization rate is maximum. The appearance of the limiting yield is connected with the filling of the pores by PPy that leads to the formation of microtubules inside the pores. This was revealed by means of SEM study. During polymerization of Py the deposition of PPy occurs both on the pore walls and on the face surfaces of the membrane. The pore size gradually decreases during polymerization. The texture of PPy on the face surfaces and on the pore walls and the formation of microfibers connecting the neighbouring pores are discussed.

  20. Ketoprofen as a photoinitiator for anionic polymerization.

    PubMed

    Wang, Yu-Hsuan; Wan, Peter

    2015-06-01

    A new photoinitiating system for anionic polymerization of acrylates based on the efficient photodecarboxylation of Ketoprofen () and the related derivatives and that generate the corresponding carbanion intermediates is presented. Carbanion intermediates are confirmed by deuterium incorporation in the trapped Michael adducts and by spectroscopic detection using laser flash photolysis (LFP). This novel anionic initiating system features excitation in the near UV and visible regions, potential characteristics of photocontrolled living polymerization, and metal-free photoinitiators generated from photoexcitation, different from typical anionic polymerization where the polymerizations are initiated by heat and strong base containing alkali metals. PMID:25917384

  1. Does topology drive fiber polymerization?

    PubMed

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

    2014-12-16

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

  2. Electrically controlled polymeric gel actuators

    DOEpatents

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

    1993-01-01

    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.

  3. Electrically controlled polymeric gel actuators

    DOEpatents

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

    1993-10-05

    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.

  4. Computational studies of polymeric systems

    NASA Astrophysics Data System (ADS)

    Carrillo, Jan-Michael Y.

    Polymeric systems involving polyelectrolytes in surfaces and interfaces, semiflexible polyelectrolytes and biopolymers in solution, complex polymeric systems that had applications in nanotechnology were modeled using coarse grained molecular dynamics simulation. In the area of polyelectrolytes in surfaces and interfaces, the phenomena of polyelectrolyte adsorption at oppositely charge surface was investigated. Simulations found that short range van der Waals interaction was a major factor in determining morphology and thickness of the adsorbed layer. Hydrophobic polyelectrolytes adsorbed in hydrophobic surfaces tend to be the most effective in forming multi-layers because short range attraction enhances the adsorption process. Adsorbed polyelectrolytes could move freely along the surface which was in contrast to polyelectrolyte brushes. The morphologies of hydrophobic polyelectrolyte brushes were investigated and simulations found that brushes had different morphologies depending on the strength of the short range monomer-monomer attraction, electrostatic interaction and counterion condensation. Planar polyelectrolyte brushes formed: (1) vertically oriented cylindrical aggregates, (2) maze-like aggregate structures, or (3) thin polymeric layer covering a substrate. While, the spherical polyelectrolyte brushes could be in any of the previous morphologies or be in a micelle-like conformation with a dense core and charged corona. In the area of biopolymers and semiflexible polyelectrolytes in solution, simulations demonstrated that the bending rigidity of these polymers was scale-dependent. The bond-bond correlation function describing a chain's orientational memory could be approximated by a sum of two exponential functions manifesting the existence of the two characteristic length scales. The existence of the two length scales challenged the current practice of describing chain stretching experiments using a single length scale. In the field of nanotechnology, simulations of "nanoimprinting lithography" and "nanopropulsion engine" were performed. Nanoimprinting lithography simulations showed that the quality of the process depended on the elastic modulus of the mold, interfacial energy of the injected liquid, and the size of the master. For the nanopropulsion engine, simulations and scaling analysis established that the nozzle velocity was proportional to the chain's polymerization rate with the proportionality coefficient being determined by the nozzle geometry, the nozzle friction coefficient, and the dynamics of the polymer chains inside the nozzle.

  5. The Production and Export of Bioavailable Iron from Ice Sheets - the Importance of Colloidal and Nanoparticulate Phases

    NASA Astrophysics Data System (ADS)

    Hawkings, J.; Wadham, J. L.; Tranter, M.; Raiswell, R.; Benning, L. G.; Statham, P. J.; Tedstone, A.; Nienow, P. W.; Telling, J.; Bagshaw, E.

    2013-12-01

    Glaciers cover approximately 10% of the world's land surface at present, but our knowledge of biogeochemical processes occurring beneath them is still limited, as is our understanding of their impact on downstream ecosystems via the export of nutrients in runoff. Recent work has suggested that glaciers are a primary source of nutrients to near coastal areas(1). For example, macronutrients, such as nitrogen and phosphorus, and micronutrients, such as iron, may support primary production(2,3). Nutrient limitation of primary producers is known to be prevalent in large sectors of the world's oceans and iron is a significant limiting nutrient in Polar waters(4,5). Significantly, large oceanic algal blooms have been observed in polar areas where glacial influence is large(6,7). Our knowledge of iron speciation, concentrations and export dynamics in glacial meltwater is limited due, in part, to problems associated with collecting trace measurements in remote field locations. For example, recent work has indicated large uncertainty in 'dissolved' meltwater iron concentrations (0.2 - 4000 ?M(8,9)). There is currently a dearth of information about labile nanoparticulate iron in glacial meltwaters, as well as export dynamics from large ice sheet catchments. Existing research has focused on small catchment examples(8,10), which behave differently to larger catchments(11). Presented here is the first time series of daily variations in meltwater iron concentrations (dissolved, filterable colloidal/nanoparticulate and bioavailable suspended sediment bound) from two large contrasting glacial catchments in Greenland over the 2012 and 2013 summer melt seasons. We also present the first estimates of iron concentrations in Greenlandic icebergs, which have been identified as hot spots of biological activity in the open ocean(12,13). Budgets for ice sheets based on our data demonstrate the importance of glaciers in global nutrient cycles, and reveal a large and previously under-appreciated component of the global iron cycle. References 1 Hood, E. & Scott, D, Nat Geosci 1, 583-587 (2008) 2 Wadham, J. et al., Earth Env Sci T R So (2013) 3 Gerringa, L. J. A. et al., Deep-Sea Res Pt II 71-76, 16-31 (2012) 4 Martin, J. H. & Fitzwater, S. E., Nature 331, 341-343 (1988) 5 Martin, J. H., Fitzwater, S. E. & Gordon, R. M., Global Biogeochem Cy 4, 5-12 (1990) 6 Perrette, M., Yool, A., Quartly, G. D. & Popova, E. E., Biogeosciences 8, 515-524 (2011) 7 Frajka-Williams, E. & Rhines, P. B., Deep-Sea Res Pt I 57, 541-552 (2010) 8 Statham, P. J., Skidmore, M. & Tranter, M., Global Biogeochem Cy 22 (2008) 9 Mikucki, J. A. et al., Science 324, 397-400 (2009) 10 Bhatia, M. P. et al., Nat Geosci (2013) 11 Wadham, J. L. et al., Global Biogeochem Cy 24 (2010) 12 Smith, K. L. et al., Science 317, 478-482 (2007) 13 Raiswell, R. & Canfield, D. E., Geochemical Perspectives 1, 1-220 (2012)

  6. Nanoparticulate TiO2 protection of midgut damage in the silkworm (Bombyx mori) following phoxim exposure.

    PubMed

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

    2015-04-01

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

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

    PubMed

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

    2008-04-01

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

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

    PubMed

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

    2015-04-10

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

  9. Detecting polymeric nanoparticles with coherent anti-stokes Raman scattering microscopy in tissues exhibiting fixative-induced autofluorescence

    NASA Astrophysics Data System (ADS)

    Garrett, N. L.; Godfrey, L.; Lalatsa, A.; Serrano, D. R.; Uchegbu, I. F.; Schatzlein, A.; Moger, J.

    2015-03-01

    Recent advances in pharmaceutical nanotechnology have enabled the development of nano-particulate medicines with enhanced drug performance. Although the fate of these nano-particles can be macroscopically tracked in the body (e.g. using radio-labeling techniques), there is little information about the sub-cellular scale mechanistic processes underlying the particle-tissue interactions, or how these interactions may correlate with pharmaceutical efficacy. To rationally engineer these nano-particles and thus optimize their performance, these mechanistic interactions must be fully understood. Coherent Anti-Stokes Raman scattering (CARS) microscopy provides a label-free means for visualizing biological samples, but can suffer from a strong non-resonant background in samples that are prepared using aldehyde-based fixatives. We demonstrate how formalin fixative affects the detection of polymeric nanoparticles within kidneys following oral administration using CARS microscopy, compared with samples that were snap-frozen. These findings have implications for clinical applications of CARS for probing nanoparticle distribution in tissue biopsies.

  10. Malaria Vector Species

    NSDL National Science Digital Library

    0000-00-00

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

  11. Sequential Vector Packing

    Microsoft Academic Search

    Mark Cieliebak; Alexander Hall; Riko Jacob; Marc Nunkesser

    2007-01-01

    We introduce a novel variant of the well known d-dimensional bin (or vector) packing problem. Given a sequence of non-negative d-dimensional vectors, the goal is to pack these into as few bins as possible. In the classical problem the bin size vector is given and the sequence can be partitioned arbi- trarily. We study a variation where the vectors have

  12. Vector median filters

    Microsoft Academic Search

    J. Astola; P. Haavisto; Y. Neuvo

    1990-01-01

    Two nonlinear algorithms for processing vector-valued signals are introduced. The algorithms, called vector median operations, are derived from two multidimensional probability density functions using the maximum-likelihood-estimate approach. The underlying probability densities are exponential, and the resulting operations have properties very similar to those of the median filter. In the vector median approach, the samples of the vector-valued input signal are

  13. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, Mohsen (Albuquerque, NM)

    1995-01-01

    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.

  14. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, M.

    1995-02-14

    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.

  15. Escalation of polymerization in a thermal gradient

    PubMed Central

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

    2013-01-01

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

  16. PRION PROLIFERATION WITH UNBOUNDED POLYMERIZATION RATES

    E-print Network

    Walker, Christoph

    PRION PROLIFERATION WITH UNBOUNDED POLYMERIZATION RATES CHRISTOPH WALKER Abstract. A model for prion replication is studied. We prove global existence of weak solutions for unbounded polymerization Prions are widely regarded as the infectious agent causing fatal diseases known as TSE's including BSE

  17. Spacetime vector analysis

    Microsoft Academic Search

    G. Sobczyk

    1981-01-01

    Ordinary Gibbs-Heaviside vector algebra is complexified to apply to spacetime. The resulting algebra is isomorphic to both the Pauli algebra, and to the algebra of complex quaternions. Each inertial system is distinguished by a rest frame of real vectors. The rudiments of a spacetime vector analysis are given.

  18. Balancing sets of vectors

    Microsoft Academic Search

    Noga Alon; E. E. Bergmann; Don Coppersmith; Andrew M. Odlyzko

    1988-01-01

    IntroductionLet K(n , d) denote the minimal k for which there exist 1 vectors v 1 , . . . , v k oflength n such that for any 1 vector w of length n, there is an i, 1 i k, such thatv i.w d, where v.w denotes the usual inner product of two vectors. Sincev.w n (mod 2)

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

    PubMed

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

    2012-06-14

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

  20. Proton transport through polymeric membranes

    NASA Astrophysics Data System (ADS)

    Wang, Xinyu; Woudenberg, Rich; Yavuzcetin, Ozgur; Granados, Sergio; Coughlin, Bryan; Tuominen, Mark

    2006-03-01

    Hydrogen fuel cells have drawn increasing attention from researchers because of the steadily declining supply of fossil fuels. A key component of a fuel cell is a membrane that is an efficient conductor of protons, but not electrons or molecules. Nafion currently is the dominant material chosen for this purpose, with proton conductivity facilitated by an imbibed network of water. Unfortunately, this material loses its conductivity as it becomes dehydrated at elevated temperatures. In this work we make a detailed examination of the physics of proton conductivity in anhydrous polymeric membranes though temperature-dependent DC current-voltage characterization, AC impedance spectroscopy and Hall effect measurements. We assess the relevance of fundamental proton conductivity models involving thermo-mechanical and electro-mechanical transport mechanisms. This work is supported by DOE grant 10759-001-05, NSF grant DMR-0306951 and MRSEC.

  1. Modeling liquid crystal polymeric devices

    NASA Astrophysics Data System (ADS)

    Gimenez Pinto, Vianney Karina

    The main focus of this work is the theoretical and numerical study of materials that combine liquid crystal and polymer. Liquid crystal elastomers are polymeric materials that exhibit both the ordered properties of the liquid crystals and the elastic properties of rubbers. Changing the order of the liquid crystal molecules within the polymer network can induce shape change. These materials are very valuable for applications such as actuators, sensors, artificial muscles, haptic displays, etc. In this work we apply finite element elastodynamics simulations to study the temperature induced shape deformation in nematic elastomers with complex director microstructure. In another topic, we propose a novel numerical method to model the director dynamics and microstructural evolution of three dimensional nematic and cholesteric liquid crystals. Numerical studies presented in this work are in agreement with experimental observations and provide insight into the design of application devices.

  2. Index Sets and Vectorization

    SciTech Connect

    Keasler, J A

    2012-03-27

    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.

  3. Programming magnetic anisotropy in polymeric microactuators.

    PubMed

    Kim, Jiyun; Chung, Su Eun; Choi, Sung-Eun; Lee, Howon; Kim, Junhoi; Kwon, Sunghoon

    2011-10-01

    Polymeric microcomponents are widely used in microelectromechanical systems (MEMS) and lab-on-a-chip devices, but they suffer from the lack of complex motion, effective addressability and precise shape control. To address these needs, we fabricated polymeric nanocomposite microactuators driven by programmable heterogeneous magnetic anisotropy. Spatially modulated photopatterning was applied in a shape-independent manner to microactuator components by successive confinement of self-assembled magnetic nanoparticles in a fixed polymer matrix. By freely programming the rotational axis of each component, we demonstrate that the polymeric microactuators can undergo predesigned, complex two- and three-dimensional motion. PMID:21822261

  4. Polymeric MST - high precision at low cost

    NASA Astrophysics Data System (ADS)

    Elderstig, Håkan; Larsson, Olle

    1997-09-01

    A low-cost production process for fabrication of polymeric microstructures from micromachined silicon is demonstrated in a splice for the splicing of optical fibers and an optical motherboard. Measurements on splices showed less than 0.5 dB insertion losses. The prototype polymeric motherboard concisted of an optical receiver module. The detector that was mounted on the polymeric optical motherboard detected about 70% of the transferred light. Measurements with modulated light indicates an optical bandwidth of 5 GHz at 2 V reverse current on the pin-diode.

  5. Enhanced drug loading in polymerized micellar cargo.

    PubMed

    Ogier, Julien; Arnauld, Thomas; Carrot, Géraldine; Lhumeau, Antoine; Delbos, Jean-Marie; Boursier, Claire; Loreau, Olivier; Lefoulon, Francois; Doris, Eric

    2010-09-01

    A new drug carrier system based on self-assembly and polymerization of polydiacetylenic amphiphiles is described. Although classical amphiphiles can help in solubilizing hydrophobic molecules upon self-arrangement into a variety of nanometric structures, a greater effect on drug loading was observed for our polymerized micelles as compared to the non-polymerized analogues. This permitted higher aqueous solubilization of lipophilic drugs with low micelle concentration. (14)C labeling of a model drug on one side and of the amphiphile on the other side permitted assessment, after intravenous injection, of biodistribution and excretion profiles of the drug cargo. PMID:20617268

  6. Dynamics of polymerization of macromolecules with multiple binding sites

    Microsoft Academic Search

    I. J. Laurenzi; SIL. Diamond

    2002-01-01

    In Nature, there are many examples of biological polymerizations in which the monomers possess multiple binding sites. Under certain circumstances, such branched polymerizations may produce a large macroparticle that constitutes a significant fraction of the monomers. In this paper, we show that the polymerizations of antibodies with antigens and the polymerization of fibrin are of this type. We then present

  7. Introduction Strict vector coloring Vector coloring Quantum coloring Further work Hedetniemi conjecture for strict vector

    E-print Network

    Severini, Simone

    Introduction Strict vector coloring Vector coloring Quantum coloring Further work Hedetniemi conjecture for strict vector chromatic number Robert Sámal (joint with C.Godsil, D.Roberson, S vector coloring Vector coloring Quantum coloring Further work Outline 1 Introduction 2 Strict vector

  8. Vector curvaton without instabilities

    NASA Astrophysics Data System (ADS)

    Dimopoulos, Konstantinos; Kar?iauskas, Mindaugas; Wagstaff, Jacques M.

    2010-01-01

    A vector curvaton model with a Maxwell kinetic term and varying kinetic function and mass during inflation is studied. It is shown that, if light until the end of inflation, the vector field can generate statistical anisotropy in the curvature perturbation spectrum and bispectrum, with the latter being predominantly anisotropic. If by the end of inflation the vector field becomes heavy, then particle production is isotropic and the vector curvaton can alone generate the curvature perturbation. The model does not suffer from instabilities such as ghosts and is the only concrete model, to date, which can produce the curvature perturbation without direct involvement of fundamental scalar fields.

  9. 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.

  10. Hydrocarbon polymeric binder for advanced solid propellant

    NASA Technical Reports Server (NTRS)

    Potts, J. E. (editor)

    1972-01-01

    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.

  11. 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...

  12. Dielectric films improve life of polymeric insulators

    NASA Technical Reports Server (NTRS)

    Hudis, M.; Wydeven, T.

    1975-01-01

    Degradation of polymeric insulators may be significantly reduced when polymer surfaces are coated with film having gradation of dielectric constants, larger where it is in contact with polymer and smaller at its exposed surface.

  13. Physicochemically functional ultrathin films by interfacial polymerization

    DOEpatents

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

    1990-08-14

    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.

  14. Physicochemically functional ultrathin films by interfacial polymerization

    DOEpatents

    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

    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.

  15. Reverse-osmosis membranes by plasma polymerization

    NASA Technical Reports Server (NTRS)

    Hollahan, J. R.; Wydeven, T.

    1972-01-01

    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.

  16. Giant vesicles compressed by actin polymerization

    E-print Network

    Carrel, Hyman A. (Hyman Andrew), 1979-

    2004-01-01

    Actin polymerization plays a critical role in generating propulsive force to drive many types of cell motility. The discovery of actin based motility of the bacterial pathogen Listeria monocytogenes has lead to clearer ...

  17. Aging of polymeric composites : a literature review

    E-print Network

    Treviño-Garrido, Margie N

    2013-01-01

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

  18. Post polymerization cure shape memory polymers

    DOEpatents

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

    2014-11-11

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

  19. Polycaps: Reversibly formed polymeric?capsules

    PubMed Central

    Castellano, Ronald K.; Rudkevich, Dmitry M.; Rebek, Julius

    1997-01-01

    Described are assemblies consisting of polymeric capsules, “polycaps,” formed from two calix[4]arene tetraureas covalently connected at their lower rims. In these structures self-assembly leads to reversibly formed capsule sites along a chain, reminiscent of beads on a string. Their dynamic behavior is characterized by 1H NMR spectroscopy through encapsulation of guest species, reversible polymerization, and the formation of sharply defined hybrid capsules. PMID:11038556

  20. Polymeric micelles: authoritative aspects for drug delivery

    Microsoft Academic Search

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

    2012-01-01

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

  1. Identification and Control of Polymerization Reactors

    Microsoft Academic Search

    Eric J. Hukkanen; Jeremy G. VanAntwerp; Richard D. Braatz

    This chapter considers the identification and control of free-radical polymerization reactors. A discussion of the modeling\\u000a and simulation of such reactors is followed by an optimal control study that demonstrates the potential of optimal control\\u000a of the molecular-weight distribution based on mechanistic models. Achieving this potential in a batch reactor requires an\\u000a accurate estimation of the free-radical polymerization kinetic parameters.

  2. Biaxially oriented film on flexible polymeric substrate

    DOEpatents

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

    2009-10-13

    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.

  3. Vector-valued Malvar wavelets

    NASA Astrophysics Data System (ADS)

    Xia, Xiang-Gen; Suter, Bruce W.; Huang, Ying

    1996-06-01

    Scalar-valued Malvar wavelets have been used to eliminate the blocking effects in scalar transform coding. In this paper, we introduce vector-valued Malvar wavelets for vector-valued signals. While constructing window vectors, we present a connection between vector-valued Malvar wavelets and vector Lemarie-Meyer band-limited wavelets. Similar to scalar-valued Malvar wavelets, vector-valued Malvar wavelets have applications in eliminating the blocking effects in vector transform coding.

  4. Nonperturbative Renormalization Group Approach to Polymerized Membranes

    NASA Astrophysics Data System (ADS)

    Essafi, Karim; Kownacki, Jean-Philippe; Mouhanna, Dominique

    2014-03-01

    Membranes or membrane-like materials play an important role in many fields ranging from biology to physics. These systems form a very rich domain in statistical physics. The interplay between geometry and thermal fluctuations lead to exciting phases such flat, tubular and disordered flat phases. Roughly speaking, membranes can be divided into two group: fluid membranes in which the molecules are free to diffuse and thus no shear modulus. On the other hand, in polymerized membranes the connectivity is fixed which leads to elastic forces. This difference between fluid and polymerized membranes leads to a difference in their critical behaviour. For instance, fluid membranes are always crumpled, whereas polymerized membranes exhibit a phase transition between a crumpled phase and a flat phase. In this talk, I will focus only on polymerized phantom, i.e. non-self-avoiding, membranes. The critical behaviour of both isotropic and anisotropic polymerized membranes are studied using a nonperturbative renormalization group approach (NPRG). This allows for the investigation of the phase transitions and the low temperature flat phase in any internal dimension D and embedding d. Interestingly, graphene behaves just as a polymerized membrane in its flat phase.

  5. Denoising 2-D Vector Fields by Vector Wavelet Thresholding

    E-print Network

    Westenberg, Michel A.

    Denoising 2-D Vector Fields by Vector Wavelet Thresholding Michel A. Westenberg and Thomas Ertl for denoising 2-D vector fields that are corrupted by additive noise. The method is based on the vector wavelet introduce modifications to scalar wavelet coefficient thresholding for dealing with vector

  6. Highly elastic conductive polymeric MEMS

    NASA Astrophysics Data System (ADS)

    Ruhhammer, J.; Zens, M.; Goldschmidtboeing, F.; Seifert, A.; Woias, P.

    2015-02-01

    Polymeric structures with integrated, functional microelectrical mechanical systems (MEMS) elements are increasingly important in various applications such as biomedical systems or wearable smart devices. These applications require highly flexible and elastic polymers with good conductivity, which can be embedded into a matrix that undergoes large deformations. Conductive polydimethylsiloxane (PDMS) is a suitable candidate but is still challenging to fabricate. Conductivity is achieved by filling a nonconductive PDMS matrix with conductive particles. In this work, we present an approach that uses new mixing techniques to fabricate conductive PDMS with different fillers such as carbon black, silver particles, and multiwalled carbon nanotubes. Additionally, the electrical properties of all three composites are examined under continuous mechanical stress. Furthermore, we present a novel, low-cost, simple three-step molding process that transfers a micro patterned silicon master into a polystyrene (PS) polytetrafluoroethylene (PTFE) replica with improved release features. This PS/PTFE mold is used for subsequent structuring of conductive PDMS with high accuracy. The non sticking characteristics enable the fabrication of delicate structures using a very soft PDMS, which is usually hard to release from conventional molds. Moreover, the process can also be applied to polyurethanes and various other material combinations.

  7. Lapped Orthogonal Vector Quantization

    Microsoft Academic Search

    Henrique S. Malvar; Gary J. Sullivan; Gregory W. Wornell

    1996-01-01

    The blocking artifacts that arise in the use of traditional vector quantization (VQ) schemes can, in general, be virtually eliminated via an efficient lapped VQ strategy. With lapped VQ, blocks are obtained from the source in an overlapped manner, and reconstructed via superposition of overlapped codevectors. The new scheme, which we term lapped orthogonal vector quantization (LOVQ), requires no increase

  8. Exploring acceleration through vectors

    NSDL National Science Digital Library

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

  9. Insect vector transmission assays.

    PubMed

    Bosco, Domenico; Tedeschi, Rosemarie

    2013-01-01

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

  10. New Support Vector Algorithms

    Microsoft Academic Search

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

    2000-01-01

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

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

    SciTech Connect

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

    2009-12-14

    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.

  12. Vector Piezoresponse Force Microscopy

    SciTech Connect

    Kalinin, Sergei V [ORNL; Rodriguez, Brian J [ORNL; Jesse, Stephen [ORNL; Shin, Junsoo [ORNL; Baddorf, Arthur P [ORNL; Gupta, P. [Lehigh University, Bethlehem, PA; Jain, H. [Lehigh University, Bethlehem, PA; Williams, D. B. [Lehigh University, Bethlehem, PA; Gruverman, A. [North Carolina State University

    2006-01-01

    A novel approach for nanoscale imaging and characterization of the orientation dependence of electromechanical properties - vector piezoresponse force microscopy (Vector PFM) - is described. The relationship between local electromechanical response, polarization, piezoelectric constants, and crystallographic orientation is analyzed in detail. The image formation mechanism in vector PFM is discussed. Conditions for complete three-dimensional (3D) reconstruction of the electromechanical response vector and evaluation of the piezoelectric constants from PFM data are set forth. The developed approach can be applied to crystallographic orientation imaging in piezoelectric materials with a spatial resolution below 10 nm. Several approaches for data representation in 2D-PFM and 3D-PFM are presented. The potential of vector PFM for molecular orientation imaging in macroscopically disordered piezoelectric polymers and biological systems is discussed.

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

    PubMed

    Battal, Dilek; Çelik, Ayla; Güler, Gizem; Akta?, Ayça; Yildirimcan, Saadet; Ocakoglu, Kasim; Çömeleko?lu, Ülkü

    2015-04-01

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

  14. Polymeric micelles as drug delivery systems: a reactive polymeric micelle carrying aldehyde groups

    Microsoft Academic Search

    Carmen Scholz; Michihiro Iijima; Yukio Nagasaki; Kazunori Kataoka

    1998-01-01

    WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW Nanospheric particles as drug delivery systems are gaining increasing interest in the biomedical field. Nanospheres have been proven as efficient drug delivery systems for intravenous administration because of their comparatively long bloodstream circulation. A novel approach in the field of polymeric drug delivery systems was introduced by the formation of polymeric micelles and subsequently by functionalized

  15. Thermal conductivity of a polymerizing liquid

    NASA Astrophysics Data System (ADS)

    Venkateshan, K.; Johari, G. P.

    2006-08-01

    Thermal conductivity ? of seven polymerizing liquids has been measured in real time at different temperatures, and calorimetry and dielectric spectroscopy of one liquid are performed to help interpret the results. As a covalently bonded linear chain or a network structure in the liquid grows, ? of the Debye equation initially increases with the polymerization time tpolym as the molecular weight, density, and sound velocity increase, as on cooling a liquid. The measured ? reaches a maximum and then decreases, thus showing a peak at a certain tpolym and finally becomes constant, which is not the true behavior of steady state ?. The dielectric relaxation time of the covalently bonded structure at the tpolym for the ? peak is less than 5s and the extent of polymerization is below the vitrification plateau value. The peak height increases when the pulse time for ? measurement is increased. An increase in the liquid's temperature shifts the ? peak to a shorter tpolym. Liquid compositions polymerizing rapidly show a similar shift, and those polymerizing slowly or whose viscosity does not reach a high enough value show a small ? peak or none. The ? peak may be an artifact of the time dependence of heat capacity during the pulse time used for the ? measurement, as proposed for glasses and supercooled liquids, similar to the changes in other properties observed as an artifact of kinetic freezing/unfreezing. For a polymerizing liquid, the peak may additionally arise when the rate of increase in the elastic modulus becomes equal to the rate of decrease in equilibrium Cp. In either case, its appearance does not distinguish the Brownian motions' slowing on polymerization from that on cooling or compressing a liquid.

  16. Investigation of Solution Polymerizations in Microgravity and 1 G

    NASA Technical Reports Server (NTRS)

    Kennedy, Alvin P.

    1998-01-01

    The in-situ dielectric spectra for the solution polymerization of polydiacetylene has been successfully measured. The results show a distinct difference between the response for the bulk solution and surface polymerization. It also shows a low frequency peak in the dissipation factor which is present in both the bulk and surface polymerizations. These features may prove to be significant indicators for important polymerization processes. Future studies will investigate the mechanisms responsible for these dielectric responses. This technique will eventually be used to monitor microgravity polymerizations and provide in-situ data on how microgravity affects solution polymerization.

  17. Cell motility driven by actin polymerization.

    PubMed Central

    Mogilner, A; Oster, G

    1996-01-01

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

  18. Universal metastability of sickle hemoglobin polymerization

    NASA Astrophysics Data System (ADS)

    Weng, Weijun

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

  19. Self-Healing of biocompatible polymeric nanocomposities

    NASA Astrophysics Data System (ADS)

    Espino, Omar; Chipara, Dorina

    2014-03-01

    Polymers are vulnerable to damage in form of cracks deep within the structure, where detection is difficult and repair is near to impossible. These cracks lead to mechanical degradation of the polymer. A method has been created to solve this problem named polymeric self healing. Self healing capabilities implies the dispersion within the polymeric matrix of microcapsules filled with a monomer and of catalyst. Poly urea-formaldehyde microcapsules used in this method are filled with dicyclopentadiene that is liberated after being ruptured by the crack propagation in the material. Polymerization is assisted by a catalyst FGGC that ignites the self healing process. Nanocomposites, such as titanium oxide, will be used as an integration of these polymers that will be tested by rupturing mechanically slowly. In order to prove the self healing process, Raman spectroscopy, FTIR, and SEM are used.

  20. Engineering Polymeric Aptamers for Selective Cytotoxicity

    PubMed Central

    Yang, Liu; Meng, Ling; Zhang, Xiaobing; Chen, Yan; Zhu, Guizhi; Liu, Haipeng; Xiong, Xiangling; Sefah, Kwame; Tan, Weihong

    2011-01-01

    Chemotherapy strategies thus far reported can result in both side effects and drug resistance. To address both of these issues at the cellular level, we report a molecular engineering strategy which employs polymeric aptamers to induce selective cytotoxicity inside target cells. The polymeric aptamers, composed of both multiple cell-based aptamers and a high ratio of dye-labeled short DNA, exploit the target recognition capability of the aptamer, enhanced cell internalization via multivalent effects, and cellular disruption by the polymeric conjugate. Importantly, the polymer backbone built into the conjugate is cytotoxic only inside cells. As a result, selective cytotoxicity is achieved equally in both normal cancer cells and drug-resistant cells. Control assays have confirmed the nontoxicity of the aptamer itself, but they have also shown that the physical properties of the polymer backbone contribute to target cell cytotoxicity. Therefore, our approach may shed new light on drug design and drug delivery. PMID:21702469

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

    PubMed Central

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

    2013-01-01

    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. PMID:23445497

  2. Poynting-vector filter

    DOEpatents

    Carrigan, Charles R. (Tracy, CA)

    2011-08-02

    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.

  3. Bloch vector projection noise

    NASA Technical Reports Server (NTRS)

    Wang, Li-Jun; Bacon, A. M.; Zhao, H.-Z.; Thomas, J. E.

    1994-01-01

    In the optical measurement of the Bloch vector components describing a system of N two-level atoms, the quantum fluctuations in these components are coupled into the measuring optical field. This paper develops the quantum theory of optical measurement of Bloch vector projection noise. The preparation and probing of coherence in an effective two-level system consisting of the two ground states in an atomic three-level lambda-scheme are analyzed.

  4. Polymeric matrix materials for infrared metamaterials

    DOEpatents

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

    2014-04-22

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

  5. Method of Making Thermally Stable, Piezoelectric and Proelectric Polymeric Substrates

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

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

    PubMed

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

    2015-04-10

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

  7. Hierarchal scalar and vector tetrahedra

    Microsoft Academic Search

    J. P. Webb; B. Forgahani

    1993-01-01

    A novel set of scalar and vector tetrahedral finite elements are presented. The elements are hierarchical, allowing mixing of polynomial orders. Scalar orders up to three and vector orders up to two are defined. The vector elements impose tangential continuity on the field but not normal continuity, making them suitable for representing the vector electric or magnetic field. The scalar

  8. Polymerized liposomes as potential oral vaccine carriers: Stability and bioavailability

    Microsoft Academic Search

    Hongming Chen; Vladimir Torchilin; Robert Langer

    1996-01-01

    The potential of polymerized liposomes as oral vaccine carriers is evaluated. The stability of polymerized liposomes is demonstrated in mouse gastrointestinal tracts using dual-labeled liposomes. Similar transit kinetics displayed by the two labels of different hydrophobicity indicate the intactness of the polymerized liposomes inside the gastrointestinal tract. Uptake of liposomes from mouse gastrointestinal tract by Peyer's patches is quantified by

  9. Self-healing polymeric materials: A review of recent developments

    Microsoft Academic Search

    Dong Yang Wu; Sam Meure; David Solomon

    2008-01-01

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

  10. 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...

  11. The morphology of emulsion polymerized latex particles

    SciTech Connect

    Wignall, G.D.; Ramakrishnan, V.R.; Linne, M.A.; Klein, A.; Sperling, L.H.; Wai, M.P.; Gelman, R.A.; Fatica, M.G.; Hoerl, R.H.; Fisher, L.W.

    1987-11-01

    Under monomer starved feed conditions, emulsion polymerization of perdeuterated methyl methacrylate and styrene in the presence of preformed polymethylmethacrylate latexes resulted in particles with a core-shell morphology, as determined by small-angle neutron scattering (SANS) analysis for a hollow sphere. The locus of polymerization of the added deuterated monomer is therefore at the particle surface. In similar measurements a statistical copolymer of styrene and methyl methacrylate was used as seed particles for further polymerization of trideuteromethyl methacrylate. The resulting polymer latex was again shown to have a core-shell morphological structre as determined by SANS. SANS experiments were also undertaken on polystyrene latexes polymerized by equilibrium swelling methods, with deuterated polymer forming the first or second step. The experiments covered a molecular weight range of 6 x 10/sup 4/ < M < 6 x 10/sup 6/ g/mol. For M > 10/sup 6/ the molecular weights are consistent with the experimental errors, indicating that the deuterium labeled molecules are randomly distributed in the latex. These results led to the finding that the polymer chains were constrained in the latex particles by factors of 2 to 4 from the relaxed coil dimensions. For M < 10/sup 6/ g/mol SANS gave zero angle scattering intensities much higher than expected on the basis of a random distribution of labeled molecules. Several models were examined, including the possible development of core-shell structures at lower molecular weights. 25 refs., 6 figs., 3 tabs.

  12. Polymeric biomaterials for tissue and organ regeneration

    Microsoft Academic Search

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

    2001-01-01

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

  13. Biodegradable polymeric nanoparticles as drug delivery devices

    Microsoft Academic Search

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

    2001-01-01

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

  14. Polymeric Electrolytic Hygrometer For Harsh Environments

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  15. Electrochemically formed fullerene-based polymeric films

    Microsoft Academic Search

    Krzysztof Winkler; Alan L. Balch; W?odzimierz Kutner

    2006-01-01

    The recent results of investigations involving the electrochemical formation of polymers containing fullerenes and studies of their properties and applications are critically reviewed. From a structural point of view, these polymers can be divided into four main categories including (1) polymers with fullerenes physically incorporated into the foreign polymeric network without forming covalent bonds, (2) fullerene homopolymers formed via [2+2

  16. Cell motility driven by actin polymerization

    Microsoft Academic Search

    Alexander Mogilner; George Oster

    1996-01-01

    Certain kinds of cellular movements are apparently driven by actinpolymerization. Examples include the lamellipodia of spreading andmigrating embryonic cells, and the bacterium Listeriamonocytogenes, that propels itself through its host's cytoplasm byconstructing behind it a polymerized tail of cross-linked actinfilaments. Peskin et al. (1993) formulated a model to explain how apolymerizing filament could rectify the brownian motion of anobject so as

  17. Polymeric Sensors to Monitor Cockroach Locomotion

    Microsoft Academic Search

    Hyungoo Lee; Rodrigo Cooper; Bartosz Mika; David Clayton; Rajesh Garg; Jorge M. Gonzalez; S. Bradleigh Vinson; Sunil Khatri; Hong Liang

    2007-01-01

    We have developed a method using a polyvinylidene fluoride (PVDF) polymeric sensor to monitor the leg movements of cockroaches. The PVDF sensor was coated with gold as electrodes. It was attached to the leg of a roach. The voltage signals generated through bending directly correlate to the movement of the legs. It was found that the output voltage was a

  18. Polymeric Micellar Delivery Systems in Oncology

    Microsoft Academic Search

    Yasuhiro Matsumura

    2008-01-01

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

  19. Study of Sections of Polymerized Liquid Crystals

    Microsoft Academic Search

    Y. Bouligand; P. E. Cladis; L. Liebert; L. Strzelecki

    1974-01-01

    With the polarizing microscope, we have examined thin sections and polished slices of the polymerized nematic and cholesteric mesophases. We have found that the textures we have observed are compatible with what one would expect to find in their liquid counterparts without, however, the complication of surface effects.

  20. Adhesion of polymeric films to pharmaceutical solids

    Microsoft Academic Search

    Linda A. Felton; James W. McGinity

    1999-01-01

    The two major forces influencing polymer adhesion include the strength of the interfacial bonds between the polymeric film and the surface of the solid and the internal stresses within the film coating. While good adhesion between the polymer and the substrate is desirable for pharmaceutical products, the small size of the dosage form and the non-uniform surface roughness have created

  1. Plasma polymerization and surface treatment of polymers

    Microsoft Academic Search

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

    1992-01-01

    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

  2. Switchable Adhesion from Bicomponent Polymeric Brushes

    Microsoft Academic Search

    Haris Retsos; Ganna Gorodyska; Costantino Creton

    2005-01-01

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

  3. Design strategies for fluorescent biodegradable polymeric biomaterials

    E-print Network

    Yang, Jian

    Chemistry B FEATURE ARTICLE #12;1 Introduction Biomaterials are critical components of biomedical devicesDesign strategies for fluorescent biodegradable polymeric biomaterials Yi Zhangab and Jian Yang versatile fluorescent biomaterials due to their promising applications in biological/biomedical labeling

  4. Patterning Polymerized Lipid Vesicles with Soft Lithography

    E-print Network

    Wu, Shin-Tson

    microscopy shows that these patterned vesicle structures are stable on glass substrates. The simple, stable to be transferred from a PDMS stamp onto a glass substrate to form two-dimensional stripes with a controlled the polymerized vesicle into three-dimensional stripes and one-dimension lines on glass substrates. Atomic force

  5. Influence of air humidity on polymeric microresonators

    Microsoft Academic Search

    The influence of air humidity on polymeric microresonators is investigated by means of three different resonator types. SU-8 microbeams, SU-8 microstrings and a silicon micromirror with SU-8 hinges are exposed to relative humidities between 3% and 60%. The shifts of the resonant frequencies as a function of the relative humidity (RH) are explained based on mechanical models which are extended

  6. Impregnated metal-polymeric functional beads

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    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.

  7. Impregnated metal-polymeric functional beads

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    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.

  8. Alternatives in Polymerization Contraction Stress Management

    Microsoft Academic Search

    R. R. Braga; J. L. Ferracane

    2004-01-01

    Polymerization contraction stress of dental composites is often associated with marginal and interfacial failures of bonded restorations. The magnitude of stress depends on composite composition (filler content and matrix composition) and its ability to flow before gelation, which is related to the cavity configuration and curing characteristics of the composite. This article reviews variations among studies regarding contraction-stress-testing methods and

  9. 3D polymeric microfluidic device fabrication via contact liquid photolithographic polymerization (CLiPP)

    Microsoft Academic Search

    K. Tommy Haraldsson; J. Brian Hutchison; Robert P. Sebra; Brian T. Good; Kristi S. Anseth; Christopher N. Bowman

    2006-01-01

    In this contribution, a new method for the fabrication of complex polymeric microfluidic devices is presented. The technology, contact liquid photolithographic polymerization (CLiPP), overcomes many of the drawbacks associated with other rapid prototyping schemes, such as limited materials choices and time-consuming microassembly protocols. CLiPP shares many traits with other photolithographic methods, but three distinct features: (i) liquid photoresists in contact

  10. Free heme and sickle hemoglobin polymerization

    NASA Astrophysics Data System (ADS)

    Uzunova, Veselina V.

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

  11. Vectorized garbage collection

    SciTech Connect

    Appel, A.W.; Bendiksen, A.

    1988-01-01

    Garbage collection can be done in vector mode on supercomputers like the Cray-2 and the Cyber 205. Both copying collection and mark-and-sweep can be expressed as breadth-first searches in which the queue can be processed in parallel. The authors have designed a copying garbage collector whose inner loop works entirely in vector mode. The only significant limitation of the algorithm is that if the size of the records is not constant, the implementation becomes much more complicated. The authors give performance measurements of the algorithm as implemented for Lisp CONS cells on the Cyber 205. Vector-mode garbage collection performs up to 9 times faster than scalar-mode collection.

  12. Antibiotic polymeric nanoparticles for biofilm-associated infection therapy.

    PubMed

    Cheow, Wean Sin; Hadinoto, Kunn

    2014-01-01

    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

  13. Topochemical polymerization of C70 controlled by monomer crystal packing.

    PubMed

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

    2001-07-27

    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

  14. Redshifts and Killing Vectors

    E-print Network

    Alex Harvey; Engelbert L. Schucking; Eugene J. Surowitz

    2005-08-31

    Courses in introductory special and general relativity have increasingly become part of the curriculum for upper-level undergraduate physics majors and master's degree candidates. One of the topics rarely discussed is symmetry, particularly in the theory of general relativity. The principal tool for its study is the Killing vector. We provide an elementary introduction to the concept of a Killing vector field, its properties, and as an example of its utility apply these ideas to the rigorous determination of gravitational and cosmological redshifts.

  15. Revisiting the Seven Vectors.

    ERIC Educational Resources Information Center

    Reisser, Linda

    1995-01-01

    The second edition of "Education and Identity" (Chickering & Reisser, 1993), updating Chickering's 1969 theory, describes institutional influences and broad changes in students as they move through higher education. The seven revised vectors are summarized in this article, and current issues related to the updated theory are discussed. (JBJ)

  16. Killing vectors and anisotropy

    E-print Network

    J. P. Krisch; E. N. Glass

    2009-08-03

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

  17. Killing vectors and anisotropy

    SciTech Connect

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

    2009-08-15

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

  18. Singular Vectors' Subtle Secrets

    ERIC Educational Resources Information Center

    James, David; Lachance, Michael; Remski, Joan

    2011-01-01

    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.

  19. Support vector machines

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  20. Vectors Point Toward Pisa

    ERIC Educational Resources Information Center

    Dean, Richard A.

    1971-01-01

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

  1. Vector Autoregressions and Reality

    Microsoft Academic Search

    David E. Runkle

    1987-01-01

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

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

    PubMed

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

    2013-01-01

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

  3. 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

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Kim, Jinsoo; Kim, Jonghyun; Lee, Myeongkyu

    2010-08-01

    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.

  5. Therapeutic Strategies Based on Polymeric Microparticles

    PubMed Central

    Vilos, C.; Velasquez, L. A.

    2012-01-01

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

  6. Latent and delayed action polymerization systems.

    PubMed

    Naumann, Stefan; Buchmeiser, Michael R

    2014-04-01

    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

  7. Antibacterial polymeric nanostructures for biomedical applications.

    PubMed

    Chen, Jing; Wang, Fangyingkai; Liu, Qiuming; Du, Jianzhong

    2014-12-01

    The high incidence of bacterial infection and the growing resistance of bacteria to conventional antibiotics have resulted in the strong need for the development of new generation of antibiotics. Nano-sized particles have been considered as novel antibacterial agents with high surface area and high reactivity. The overall antibacterial properties of antimicrobial nanostructures can be significantly enhanced compared with conventional antibacterial agents not in a regular nanostructure, showing a better effect in inhibiting the growth and reproduction of microbials such as bacteria and fungi, etc. In this review, recent advances in the research and applications of antimicrobial polymeric nanostructures have been highlighted, including silver-decorated polymer micelles and vesicles, antimicrobial polymer micelles and vesicles, and antimicrobial peptide-based vesicles, etc. Furthermore, we proposed the current challenges and future research directions in the field of antibacterial polymeric nanostructures for the real-world biomedical applications. PMID:25110921

  8. Living anionic polymerization using a microfluidic reactor.

    PubMed

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

    2009-01-21

    Living anionic polymerizations were conducted within aluminum-polyimide microfluidic devices. Polymerizations of styrene in cyclohexane were carried out at various conditions, including elevated temperature (60 degrees C) and high monomer concentration (42%, by volume). The reactions were safely maintained at a controlled temperature at all points in the reactor. Conducting these reactions in a batch reactor results in uncontrolled heat generation with potentially dangerous rises in pressure. Moreover, the microfluidic nature of these devices allows for flexible 2D designing of the flow channel. Four flow designs were examined (straight, periodically pinched, obtuse zigzag, and acute zigzag channels). The ability to use the channel pattern to increase the level of mixing throughout the reactor was evaluated. When moderately high molecular mass polymers with increased viscosity were made, the patterned channels produced polymers with narrower PDI, indicating that passive mixing arising from the channel design is improving the reaction conditions. PMID:19107294

  9. Polymeric membrane studied using slow positron beam

    NASA Astrophysics Data System (ADS)

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

    2008-10-01

    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 30 keV in a polyamide membrane prepared by the interfacial polymerization between triethylenetetraamine (TETA) and trimesoyl chloride (TMC) on modified porous polyacrylonitrile (PAN) asymmetric membrane. The multilayer structures and free-volume depth profile for this asymmetric membrane system are obtained. Positron annihilation spectroscopy coupled with a slow beam could provide new information about size selectivity of transporting molecules and guidance for molecular designs in polymeric membranes.

  10. Growth kinetics of plasma-polymerized films.

    PubMed

    Hwang, Sukyoung; Seo, Hosung; Jeong, Dong-Cheol; Wen, Long; Han, Jeon Geon; Song, Changsik; Kim, Yunseok

    2015-01-01

    The growth kinetics of polymer thin films prepared by plasma-based deposition method were explored using atomic force microscopy. The growth behavior of the first layer of the polythiophene somewhat differs from that of the other layers because the first layer is directly deposited on the substrate, whereas the other layers are deposited on the polymer itself. After the deposition of the first layer, each layer is formed with a cycle of 15?s. The present work represents the growth kinetics of the plasma-polymerized films and could be helpful for further studies on growth kinetics in other material systems as well as for applications of plasma-polymerized thin films. PMID:26084630

  11. Living anionic polymerization using a microfluidic reactor

    SciTech Connect

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

    2009-02-01

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

  12. Growth kinetics of plasma-polymerized films

    PubMed Central

    Hwang, Sukyoung; Seo, Hosung; Jeong, Dong-Cheol; Wen, Long; Han, Jeon Geon; Song, Changsik; Kim, Yunseok

    2015-01-01

    The growth kinetics of polymer thin films prepared by plasma-based deposition method were explored using atomic force microscopy. The growth behavior of the first layer of the polythiophene somewhat differs from that of the other layers because the first layer is directly deposited on the substrate, whereas the other layers are deposited on the polymer itself. After the deposition of the first layer, each layer is formed with a cycle of 15?s. The present work represents the growth kinetics of the plasma-polymerized films and could be helpful for further studies on growth kinetics in other material systems as well as for applications of plasma-polymerized thin films. PMID:26084630

  13. Supported polymeric liquid membranes for wastewater treatment

    SciTech Connect

    Ho, S.V. [Monsanto Co., St. Louis, MO (United States)

    1997-12-31

    The removal or elimination of organic residues from aqueous waste streams represents a major need in the chemical industry. A class of membrane has been developed called supported polymeric liquid membranes capable of removing and concentrating low molecular weight organic compounds from dilute aqueous solutions, especially those that also contain high concentrations of inorganic salts. These membranes are prepared by filling the pores of microfiltration or ultrafiltration membranes with polymeric (oligomeric) liquids having affinity for the organic compounds of interest. With this approach, membrane`s separation characteristics are decoupled from its mechanical stability and depend primarily on the chemical properties of the liquid polymer used. As a result, membranes of diverse separation capabilities can be conveniently prepared using liquid polymers possessing the appropriate functional groups. Physical properties typical of polymeric liquids such as high viscosity, extremely low volatility and insolubility in water contribute to the observed stability of the membranes under broad operating conditions. This membrane process has been successfully applied to several aqueous waste streams. This paper describes the early development activities for treating a waste stream containing a dilute mixture of C2-C6 carboxylic acids. Feasibility testings were initially carried out with flat sheet membranes in a small stirred cell. Scaleup was then conducted using hollow fiber membranes, first with small modules prepared in the laboratory, then with a much larger commercial module. Attractive features of this membrane process include the ability to recover the contaminants in concentrated form for either recycle or more economical disposal, low pressure (ambient) operation, simple scale-up using commercial hollow fiber modules, and ease of in-situ regeneration of the polymeric liquid.

  14. A fully polymeric micropump with piezoelectric actuator

    Microsoft Academic Search

    Nam-Trung Nguyen; Thai-Quang Truong

    2004-01-01

    This paper presents a new concept of designing and fabricating polymeric micropumps. The micro pump is made of SU-8 photoresist and polymethylmethacrylate (PMMA). The key elements of the micropump are the micro check valves, which are fabricated in a 100-?m-thick SU-8 film. The SU-8 part is designed as a disc with 10-mm diameter. The check valves are 1-mm discs suspended

  15. X-ray microscopy of polymeric materials

    SciTech Connect

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

    1995-09-01

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

  16. A stability analysis of polymerization fronts

    NASA Astrophysics Data System (ADS)

    Comissiong, Donna M. G.

    Frontal Polymerization (FP) is a process of converting monomer into polymer via a localized zone that propagates through the monomer. It bears a strong resemblance to self-propagating high-temperature synthesis (SHS), which uses combustion waves to synthesize desired inorganic materials. The reaction front propagates through the coupling of thermal diffusion and the Arrhenius reaction kinetics of the exothermic polymerization process. This thesis utilizes a moving free-boundary model to describe free-radical FP. The focus of attention here is the self-sustaining wave which travels through the reaction vessel as polymer molecules are being formed. Numerical and analytical techniques are used to determine one-dimensional traveling waves, and stability analysis (linear and weakly nonlinear) of the reaction front is performed. It is then possible to suggest ways to curb instabilities in the propagating reaction front. After our initial analysis, we account for autoacceleration and determine its effect on frontal stability. In an effort to facilitate the propagation of weakly exothermic fronts, we consider a one-dimensional polymerization wave in a sandwich-type two-layer setting. First one layer is reactive while the other is considered to be inert. Heat exchange between layers is possible, and the effect this has on frontal stability is investigated. Next, we allow both layers to be reactive, thus further enhancing inter-layer heat exchange. We comment on the effect that the second reactive layer has on the basic state of the system. Finally, two future research directions are presented in detail. One of our goals is to determine how the propagating front is affected by bulk polymerization at the far end of the reaction vessel. This is an important aspect to be studied in greater depth and incorporated into existing FP models, since bulk reactions can influence the speed and long-term stability of the reaction front. We end with a theoretical discussion for the manufacture of polymer-dispersed liquid crystal films via FP.

  17. Gold wire bonding onto flexible polymeric substrates

    Microsoft Academic Search

    Elizabeth Hall; Alan M. Lyons; John D. Weld

    1995-01-01

    Copper clad polymeric materials were examined as potential substrates for wire bonded chip-on-flex circuits. New thermoplastic flex and a PTFE\\/woven glass substrate were evaluated along with polyimides using high temperature copper laminate adhesives and adhesiveless constructions. Initial wire bond pull tests indicated all the materials were suitable for high temperature gold wire bonding. Similarly, conventional glob top encapsulants were found

  18. Gold wire bonding onto flexible polymeric substrates

    Microsoft Academic Search

    E. Hall; A. M. Lyons; J. D. Weld

    1996-01-01

    As part of a program to develop very thin, low cost packages using available technology, copper clad polymeric materials were examined as potential substrates for high temperature wire bonded chip-on-flex circuits. New thermoplastic flex and a PTFE\\/woven glass substrate were evaluated along with polyimides using high temperature copper laminate adhesives and adhesiveless constructions. Initial wire bond pull tests indicated all

  19. Effect of mixing on polymerization of styrene 

    E-print Network

    Treybig, Michael Norris

    1977-01-01

    was performed by co- feeding styrene monomer, batch prepared living polystyrllithium seed and benzene. Reaction conditions such as temperature, initial monomer and polymer concentrations, residence time and mixing speed were varied to achieve different... polymerization runs, residence time distribution (RTD) studies using 30 weight percent polystyrene in benzene were conducted to determine the impeller configuration and mixing speeds required to maintain an exponential residence time distribution during...

  20. Nanostructural magnetism of polymeric fullerene crystals

    Microsoft Academic Search

    E. F. Sheka; V. A. Zaets; I. Ya. Ginzburg

    2006-01-01

    The nature of magnetism in all-carbon crystals composed of polymeric layers of covalently bound fullerene (C60) molecules is considered. The results of quantum-chemical calculations performed using the unrestricted Hartree-Fock approximation\\u000a and the semiempirical AM1 method are presented. It is shown that the exchange integrals J of both a free C60 molecule and a monomer unit of the polymer are too

  1. The presence of ?’ chain impairs fibrin polymerization

    PubMed Central

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

    2009-01-01

    Introduction A fraction of fibrinogen molecules contain an alternatively spliced variant chain called ?’. Plasma levels of this variant have been associated with both myocardial infarction and venous thrombosis. Because clot structure has been associated with cardiovascular risk, we examined the effect of ?’ chain on clot structure. Materials and Methods We expressed three fibrinogen variants in Chinese hamster ovary (CHO) cells: ?/? homodimer, ?/?’ heterodimer, and ?’/?’ homodimer. We observed thrombin-catalyzed fibrinopeptide release by HPLC, fibrin polymerization by turbidity, and clot structure by scanning electron microscopy. We characterized post-translational modifications by mass spectrometry. Results Fibrinopeptide A was released at the same rate for all three fibrinogens, while fibrinopeptide B was released faster from the ?’/?’ homodimer. The rise in turbidity was slower and final absorbance was lower during polymerization of ?’-containing fibrinogens than for ?/? fibrinogen. Micrographs showed that ?’/?’ fibrin clots are composed of very thin fibers, while the diameter of ?/?’ fibers is similar to ?/? fibers. Further, the fiber networks formed from ?’-containing samples were non-uniform. Mass spectrometry showed heterogeneous addition of N-glycans and tyrosine sulfation in the ?’ chain. Conclusions The presence of ?’ chains slows lateral aggregation and alters fibrin structure. We suggest these changes are likely due to charge-charge repulsion, such that polymerization of the ?’/?’ homodimer is more impaired than the heterodimer since these repulsions are partially offset by incorporation of ? chains in the ?/?’ heterodimer. PMID:19138790

  2. Highly promiscuous nature of prion polymerization.

    PubMed

    Makarava, Natallia; Lee, Cheng-I; Ostapchenko, Valeriy G; Baskakov, Ilia V

    2007-12-14

    The primary structure of the prion protein (PrP) is believed to be the key factor in regulating the species barrier of prion transmission. Because the strength of the species barrier was found to be affected by the prion strain, the extent to which the barrier can indeed be attributed to differences in the PrP primary structures of either donor and acceptor species remains unclear. In this study, we exploited the intrinsic property of PrP to polymerize spontaneously into disease-related amyloid conformations in the absence of a strain-specified template and analyzed polymerization of mouse and hamster full-length recombinant PrPs. Unexpectedly, we found no evidence of species specificity in cross-seeding polymerization assays. Even when both recombinant PrP variants were present in mixtures, preformed mouse or hamster fibrils displayed no selectivity in elongation reactions and consumed equally well both homologous and heterologous substrates. Analysis of individual fibrils revealed that fibrils can elongate in a bidirectional or unidirectional manner. Our work revealed that, in the absence of a cellular environment, post-translational modifications, or strain-specified conformational constraints, PrP fibrils are intrinsically promiscuous and capable of utilizing heterologous PrP variants as a substrate in a highly efficient manner. This study suggests that amyloid structures are capable of accommodating local perturbations arising because of a mismatch in amino acid sequences and highlights the promiscuous nature of the self-propagating activity of amyloid fibrils. PMID:17940285

  3. Performance of selected polymeric materials on LDEF

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  4. Insect Vectors of Human Pathogens

    NSDL National Science Digital Library

    0000-00-00

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

  5. Nonviral Vectors for Gene Delivery

    E-print Network

    Baoum, Abdulgader Ahmed

    2011-04-26

    The development of nonviral vectors for safe and efficient gene delivery has been gaining considerable attention recently. An ideal nonviral vector must protect the gene against degradation by nuclease in the extracellular matrix, internalize...

  6. Some experiences with Krylov vectors and Lanczos vectors

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  7. Kernel uncorrelated optimal discriminant vectors

    NASA Astrophysics Data System (ADS)

    Yang, Yuwang; Yang, Jingyu; Jin, Zhong

    2003-09-01

    We construct kernel uncorrelated optimal discriminant vectors(KUODV) for non-linear feature extraction and discrimination. Employing the uncorrelated optimal discriminant vectors(UODV) and kernel method, we propose non-linear generalization of uncorrelated optimal discriminant vectors, and then enhance the performance of original UODV. Human face recognition experiments show the utility of our new method.

  8. Statistical analysis of cointegration vectors

    Microsoft Academic Search

    Soren Johansen

    1988-01-01

    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

  9. Nonlinear Vector Analyzers [review of \\

    Microsoft Academic Search

    Alfy Riddle

    2012-01-01

    This book offers the reader a tour of how nonlinear vector analyzers work and how they can be used in circuit design. It contains nine chapters and no appendices. The two key chapters describe nonlinear vector instrumentation and describe behavioral modeling. In many places, the book goes into lengthy descriptions of nonlinear vector analyzer calibration, device heating, semiconductor traps, and

  10. Student Preconceptions about Vector Kinematics.

    ERIC Educational Resources Information Center

    Aguirre, Jose M.

    1988-01-01

    Examines preconceptions regarding several implicit vector characteristics that 15- to 17-year-old students possess just before taking their first physics course. Shows seven vector characteristics and three tasks for interviewing students. Presents the most common student preconceptions regarding each of the implicit vector characteristics. (YP)

  11. Vector spaces Linear independence & bases

    E-print Network

    Geuvers, Herman

    Vector spaces Linear independence & bases Linear maps Linear maps and matrices Radboud University Nijmegen Matrix Calculations: Vector Spaces and Linear Maps H. Geuvers Institute for Computing: fall 2014 Matrix Calculations 1 / 40 #12;Vector spaces Linear independence & bases Linear maps Linear

  12. On Multi-Vector Spaces

    E-print Network

    Linfan Mao

    2005-10-22

    A Smarandache multi-space is a union of $n$ spaces $A_1,A_2,..., A_n$ with some additional conditions holding. Combining Smarandache multi-spaces with linear vector spaces in classical linear algebra, the conception of multi-vector spaces is introduced. Some characteristics of a multi-vector space are obtained in this paper.

  13. Support vector networks Sance svn

    E-print Network

    Bouzy, Bruno

    Support vector networks Séance « svn » de l'UE « apprentissage automatique » Bruno Bouzy bruno.bouzy@parisdescartes.fr www.mi.parisdescartes.fr/~bouzy #12;Support-vector networks Reference · These slides present the following paper: ­ C.Cortes, V.Vapnik, « support vector networks », Machine Learning (1995

  14. Vector Theory of Gravity

    E-print Network

    V. N. Borodikhin

    2011-04-14

    We proposed a gravitation theory based on an analogy with electrodynamics on the basis of a vector field. For the first time, to calculate the basic gravitational effects in the framework of a vector theory of gravity, we use a Lagrangian written with gravitational radiation neglected and generalized to the case of ultra-relativistic speeds. This allows us to accurately calculate the values of all three major gravity experiments: the values of the perihelion shift of Mercury, the light deflection angle in the gravity field of the Sun and the value of radar echo delay. The calculated values coincide with the observed ones. It is shown that, in this theory, there exists a model of an expanding Universe.

  15. Photothermal determination of thermal diffusivity and polymerization depth profiles of polymerized dental resins

    NASA Astrophysics Data System (ADS)

    Martínez-Torres, P.; Mandelis, A.; Alvarado-Gil, J. J.

    2009-12-01

    The degree and depth of curing due to photopolymerization in a commercial dental resin have been studied using photothermal radiometry. The sample consisted of a thick layer of resin on which a thin metallic gold layer was deposited, thus guaranteeing full opacity. Purely thermal-wave inverse problem techniques without the interference of optical profiles were used. Thermal depth profiles were obtained by heating the gold coating with a modulated laser beam and by performing a frequency scan. Prior to each frequency scan, photopolymerization was induced using a high power blue light emitted diode (LED). Due to the highly light dispersive nature of dental resins, the polymerization process depends strongly on optical absorption of the blue light, thereby inducing a depth dependent thermal diffusivity profile in the sample. A robust depth profilometric method for reconstructing the thermal diffusivity depth dependence on degree and depth of polymerization has been developed. The thermal diffusivity depth profile was linked to the polymerization kinetics.

  16. Maximally symmetric vector propagator

    SciTech Connect

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

    2007-05-15

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

  17. Vector Magnetograph Design

    NASA Technical Reports Server (NTRS)

    Chipman, Russell A.

    1996-01-01

    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.

  18. Vector BPS Skyrme model

    NASA Astrophysics Data System (ADS)

    Adam, C.; Naya, C.; Sanchez-Guillen, J.; Wereszczynski, A.

    2012-10-01

    We analyze the vector meson formulation of the Bogomol’nyi-Prasad-Sommerfield (BPS) Skyrme model in (3+1) dimensions, where the term of sixth power in first derivatives characteristic for the original, integrable BPS Skyrme model (the topological or baryon current squared) is replaced by a coupling between the vector meson ?? and the baryon current. We find that the model remains integrable in the sense of generalized integrability and almost solvable (reducible to a set of two first-order ordinary differential equations) for any value of the baryon charge. Further, we analyze the appearance of topological solitons for two one-parameter families of one-vacuum potentials: the old Skyrme potentials and the so-called BPS potentials. Depending on the value of the parameters, we find several qualitatively different possibilities. In the massless case, we have a parameter region with no Skyrmions, a unique compact Skyrmion with a discontinuous first derivative at the boundary (equivalently, with a source term located at the boundary, which screens the topological charge), and Coulomb-like localized solitons. For the massive vector meson, besides the no-Skyrmion region and a unique C-compact soliton, we find exponentially as well as power-like localized Skyrmions. Further, we find (for a specific potential) BPS solutions, i.e., Skyrmions saturating a Bogomolny bound (both for the massless and massive vector mesons), which are unstable for higher values of the baryon charge. The properties of the model are finally compared with its baby version in (2+1) dimensions and with the original BPS Skyrme model, contributing to a better understanding of the latter.

  19. Recurrent Support Vector Machines

    Microsoft Academic Search

    Matteo Gagliolo; Daan Wierstra; Faustino Gomez; IDSIA Galleria

    Abstract Existing Support Vector Machines (SVMs) need pre-wired finite time windo ws to predict and classify time series. They do not have an internal state necessary to deal with sequences involving arbitrary long-term dependencies. Here we introduce the first recurrent, truly s equential SVM-like devices with internal adaptive states, trained by a novel method called EVOlution of systems with KErnel-based

  20. Vector representation of tourmaline compositions

    NASA Technical Reports Server (NTRS)

    Burt, Donald M.

    1989-01-01

    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.

  1. New ruthenium porphyrin polymeric membranes: Preparation and characterization

    Microsoft Academic Search

    M. Giovanna Buonomenna; Emma Gallo; Fabio Ragaini; Alessandro Caselli; Sergio Cenini; Enrico Drioli

    2008-01-01

    In this work, the ruthenium porphyrin complex Ru(4-(CF3)TPP)CO (1) (TPP=dianion of tetraphenylporphyrin) was entrapped into polymeric membranes during the phase inversion process to obtain new heterogeneous catalysts for aziridination reactions. In order to study the effect of the polymeric environment on the activity of the metallic complex, symmetric dense polymeric catalytic membranes were prepared using three different polymers: polyethersulphone (PES),

  2. Shape of the Polymerization Rate in the Prion Equation

    E-print Network

    Gabriel, Pierre

    2010-01-01

    We consider a polymerization (fragmentation) model with size-dependent parameters involved in prion proliferation. Using power laws for the different rates of this model, we recover the shape of the polymerization rate using experimental data. The technique used is inspired from an article of Zampieri et al. where the fragmentation dependency on prion strains is investigated. Our improvement is to use power laws for the rates whereas Zampieri et al. used a constant polymerization coefficient and linear fragmentation.

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

    Microsoft Academic Search

    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

    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

  4. Polymerization of Vesicles Composed of N-(4-Vinylbenzoyl)phosphatidylethanolamine

    E-print Network

    Smith, Bradley D.

    Polymerization of Vesicles Composed of N-(4-Vinylbenzoyl)phosphatidylethanolamine Glenn E. Lawson groups with phosphatidylethanolamines. This produces N-acyl-phosphatidylethanolamines (N-acyl-PEs) which

  5. Online observation of emulsion polymerization by fluorescence technique

    NASA Astrophysics Data System (ADS)

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

    1999-05-01

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

  6. Microemulsion polymerization of styrene initiated with gamma ray

    NASA Astrophysics Data System (ADS)

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

    1997-04-01

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

  7. Adjusting the polymerization time of isobutyl-2 cyanoacrylate.

    PubMed

    Spiegel, S M; Viñuela, F; Goldwasser, J M; Fox, A J; Pelz, D M

    1986-01-01

    Isobutyl-2 cyanoacrylate (IBCA) polymerizes by an anionic mechanism. The initiation of polymerization depends on an alkaline medium and can be inhibited with the addition of small amounts of acid. Using small amounts of glacial acetic acid (3.7%-7.1% by volume), the polymerization time was prolonged from 2.3 sec to 7.8 sec. In vivo experiments in dogs demonstrated no additional inflammatory reactions to the mixture of IBCA, iophendylate, and tantalum powder when acetic acid was added. Glacial acetic acid offers a safe and effective way, without increase in viscosity, to manipulate the polymerization time of IBCA. PMID:3082125

  8. Free Radical Polymerization of Styrene: A Radiotracer Experiment

    ERIC Educational Resources Information Center

    Mazza, R. J.

    1975-01-01

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

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

    PubMed

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

    2014-01-01

    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

  10. 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

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

    2013-11-01

    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

  11. Glycosylated polyacrylate nanoparticles by emulsion polymerization

    PubMed Central

    Abeylath, Sampath C.; Turos, Edward

    2007-01-01

    A selection of glycosylated polyacrylate nanoparticles has been prepared by radical-initiated emulsion polymerization in aqueous media. Using ethyl acrylate as a co-monomer, carbohydrate acrylates were incorporated into the poly(ethyl acrylate) framework to give stable emulsions of glyconanoparticles with an average particle size of around 40 nm. Using this technique a variety of glyconanoparticles were prepared from 3-O-acryloyl-1,2:5,6-di-O-isopropylidene-?-D-glucofuranose, 1-O-acryloyl-2,3:5,6-di-O-isopropylidene-?-D-mannofuranose, 6-O-acryloyl-1,2:3,4-di-O-isopropylidene-?-D-galactopyranose, 2-N-acryloyl-1,3,4,6-tetra-O-acetyl-?-D-glucosamine, 5-O-acryloyl-2,3-isopropylidene-1-methoxy-?-D-ribofuranose and 4-N-acetyl-5’-O-acryloyl-2’,3’-O-isopropylidene cytidine. Scanning electron microscopy, dynamic light scattering and proton NMR analysis of the emulsions indicated essentially 100% incorporation of the carbohydrate acrylate monomer into the polymer with the exception of O-benzyl- and O-benzoyl-protected carbohydrate acrylates, which gave incomplete incorporation. Formation of larger glyconanoparticles of ~80nm with (unprotected) 3-O-acryloyl-D-glucose and 5-O-acryloyl-1-methoxy-?-D-ribofuranose revealed the influence of free hydroxyl groups in the monomer on the particle size during polymerization, a feature which is also apparently dependent on the amount of carbohydrate in the matrix. This methodology allows for a new, simple route to the synthesis of polymeric glyconanoparticles with potential applications in targeted drug delivery and materials development. PMID:18677404

  12. Targeting intracellular compartments by magnetic polymeric nanoparticles.

    PubMed

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

    2013-09-27

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

  13. Light-Driven Polymeric Bimorph Actuators

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  14. Vector Spaces and Linear Transformations Beifang Chen

    E-print Network

    Chen, Beifang

    Vector Spaces and Linear Transformations Beifang Chen Fall 2006 1 Vector spaces A vector space is a nonempty set V , whose objects are called vectors, equipped with two operations, called addition and scalar multiplication: For any two vectors u, v in V and a scalar c, there are unique vectors u + v and cu in V

  15. CNS drug delivery by using polymeric nanoparticles

    Microsoft Academic Search

    L. Costantino; L. Bondioli; G. Tosi; B. Ruozi; F. Forni; M. A. Vandelli

    Summary Polymeric nanoparticles (Np) are nanosized carriers (10-200 nm) made of a polymer in which a drug can be included. In the present research we showed that Np made of the biocompatible polyester poly(D,L- lactide-coglycolide), carrying on their surface the peptide R-HN-Gly-L-Phe-D-Thr-Gly-L-Phe-L-Leu-L- Ser(O-?-D-glucose)-CONH2 (1) are able to cross the blood brain barrier (BBB) and are able to deliver a great

  16. Polymerization of Formic Acid under High Pressure

    NASA Astrophysics Data System (ADS)

    Goncharov, Alexander F.; Manaa, M. Riad; Zaug, Joseph M.; Gee, Richard H.; Fried, Laurence E.; Montgomery, Wren B.

    2005-02-01

    We report Raman, infrared, and x-ray diffraction (XRD) measurements, along with ab initio calculations on formic acid (FA) under pressure up to 50 GPa. We find an infinite chain Pna21 structure to be a high-pressure phase at room temperature. Our data indicate the symmetrization and a partially covalent character of the intrachain hydrogen bonds above approximately 20 GPa. Raman spectra and XRD patterns indicate a loss of long-range order at pressures above 40 GPa, with a large hysteresis upon decompression. We attribute this behavior to a three-dimensional polymerization of FA.

  17. Frontal Polymerization in Microgravity Summary of Research

    NASA Technical Reports Server (NTRS)

    Pojman, John A.

    2002-01-01

    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 Miscible Polymer Systems (TIPMPS), as we recognized that an essential question could best be studied using a non-frontal approach. We present detailed results from our ground-based work on FP, KC-135 results and the background, justification and numerical work for the TIPMPS project.

  18. Shock-induced activation of acrylamide polymerization

    SciTech Connect

    Dodson, B.W.; Arnold, C. Jr.

    1983-08-04

    We have subjected polycrystalline acrylamide to planar impact loading to peak pressures of 4.8 and 6.7 GPa using an air-driven projectile. In contrast to previous experiments involving explosive loading, postshock chemical analysis shows no formation of polyacrylamide associated with the shock loading. However, the impact shocked acrylamide spontaneously polymerizes when dissolved in tetrahydrofuran. This result implies that the stress history produced by the impact experiment results in the formation of a large density of stable active centers, which become mobile in solution. ESR measurements of the shocked acrylamide samples confirms the presence of substantial densities of free radicals. 2 figures.

  19. Polysaccharide-Modified Synthetic Polymeric Biomaterials

    PubMed Central

    Baldwin, Aaron D.; Kiick, Kristi L.

    2010-01-01

    This review presents an overview of polysaccharide-conjugated synthetic polymers and their use in tissue-engineered scaffolds and drug-delivery applications. This topic will be divided into four categories: (1) polymeric materials modified with non-mammalian polysaccharides such as alginate, chitin, and dextran; (2) polymers modified with mammalian polysaccharides such as hyaluronan, chondroitin sulfate, and heparin; (3) multi-polysaccharide-derivatized polymer conjugate systems; and (4) polymers containing polysaccharide-mimetic molecules. Each section will discuss relevant conjugation techniques, analysis, and the impact of these materials as micelles, particles, or hydrogels used in in-vitro and in-vivo biomaterial applications. PMID:20091875

  20. Polymeric metallic electrodes for rechargeable battery applications

    NASA Technical Reports Server (NTRS)

    Somoano, R.

    1982-01-01

    A review is presented on the status of plastic metal electrodes, emphasizing the use of polyacetylene as a prototype polymeric material. The electrochemical characteristics of polyacetylene are examined; and the potential use of this material, as well as other types of plastic metal electrodes, in batteries is evaluated. Several problem areas which must be solved before polyacetylene can be widely used in battery applications are discussed, including the problem of electrolyte stability, the problem that the depth of discharge and the energy density is limited by the metal-semiconductor transition, and also the poor electrochemical performance of impure material.

  1. Novel hybrid polymeric materials for barrier coatings

    NASA Astrophysics Data System (ADS)

    Pavlacky, Erin Christine

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

  2. A thermophone on porous polymeric substrate

    NASA Astrophysics Data System (ADS)

    Chitnis, G.; Kim, A.; Song, S. H.; Jessop, A. M.; Bolton, J. S.; Ziaie, B.

    2012-07-01

    In this Letter, we present a simple, low-temperature method for fabricating a wide-band (>80 kHz) thermo-acoustic sound generator on a porous polymeric substrate. We were able to achieve up to 80 dB of sound pressure level with an input power of 0.511 W. No significant surface temperature increase was observed in the device even at an input power level of 2.5 W. Wide-band ultrasonic performance, simplicity of structure, and scalability of the fabrication process make this device suitable for many ranging and imaging applications.

  3. Vectoring: Steering a Plane

    NSDL National Science Digital Library

    2011-08-20

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

  4. 40 CFR 721.10568 - Diethanolamine salt of polymeric acid (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

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

  5. Characterization of Polymerized Liposomes Using a Combination of dc and Cyclical Electrical Field-Flow Fractionation

    E-print Network

    Utah, University of

    Characterization of Polymerized Liposomes Using a Combination of dc and Cyclical Electrical Field Information ABSTRACT: Characterization of polymerized liposomes (PolyPIPosomes) was carried out using polymerized liposomes are used to demonstrate the applicability of the system to biomedical samples

  6. Effect of vector--axial-vector mixing to dilepton spectrum

    E-print Network

    Masayasu Harada; Chihiro Sasaki

    2010-03-01

    In this write-up we summarize main results of our recent analyses on the mixing between transverse rho and a1 mesons in hot and/or dense matter. We show that the axial-vector meson contributes significantly to the vector spectral function in hot matter through the mixing. In dense baryonic matter, we include a mixing through a set of omega rho a1 -type interactions. We show that a clear enhancement of the vector spectral function appears below \\sqrt{s}=m_\\rho for small three-momenta of the rho meson, and thus the vector spectrum exhibits broadening.

  7. Eliminating malaria vectors

    PubMed Central

    2013-01-01

    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

  8. Organic polymeric matrix resins for composites

    SciTech Connect

    Arnold-McKenna, C.A. [White House Office of Science & Technology, Washington, DC (United States)

    1993-12-31

    This talk will highlight the basic chemistry of important representative polymeric matrices for composites and discuss some composite applications, particularly for advanced composites. The advanced composites market is primarily within the aerospace industry, with recreational, industrial, and automotive applications accounting for the remainder. As the large military component of the aerospace market declines, however, penetration into more cost-sensitive markets such as automotive and building and construction is important. Polymers that are used for composite applications may be either thermosetting or thermoplastic, and each offers advantages and disadvantages. Widespread use of thermoplastics, however, requires processability improvements. A major research thrust for thermosetting resins is to improve toughness; an important approach involves the incorporation of functionalized and non-functionalized thermoplastic additives, such as poly(arylene ether)s. A wide variety of technologies for polymeric composites are being explored in federal laboratories and the private sector. Some applications of these technologies include advanced aircraft, missiles, and spacecraft ; wind turbines; light-weight, tough aircraft and automobile structures; waste storage filter containers; and dental restorations and implants.

  9. Protein encapsulation in polymeric microneedles by photolithography

    PubMed Central

    Kochhar, Jaspreet Singh; Zou, Shui; Chan, Sui Yung; Kang, Lifeng

    2012-01-01

    Background Recent interest in biocompatible polymeric microneedles for the delivery of biomolecules has propelled considerable interest in fabrication of microneedles. It is important that the fabrication process is feasible for drug encapsulation and compatible with the stability of the drug in question. Moreover, drug encapsulation may offer the advantage of higher drug loading compared with other technologies, such as drug coating. Methods and results In this study, we encapsulated a model protein drug, namely, bovine serum albumin, in polymeric microneedles by photolithography. Drug distribution within the microneedle array was found to be uniform. The encapsulated protein retained its primary, secondary, and tertiary structural characteristics. In vitro release of the encapsulated protein showed that almost all of the drug was released into phosphate buffered saline within 6 hours. The in vitro permeation profile of encapsulated bovine serum albumin through rat skin was also tested and shown to resemble the in vitro release profile, with an initial release burst followed by a slow release phase. The cytotoxicity of the microneedles without bovine serum albumin was tested in three different cell lines. High cell viabilities were observed, demonstrating the innocuous nature of the microneedles. Conclusion The microneedle array can potentially serve as a useful drug carrier for proteins, peptides, and vaccines. PMID:22787403

  10. Strong liquid-crystalline polymeric compositions

    DOEpatents

    Dowell, F.

    1993-12-07

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

  11. Photoradiation processes in combined polymeric materials

    NASA Astrophysics Data System (ADS)

    Zhdanov, G. S.; Klinshpont, E. R.; Iskakov, L. I.

    2001-12-01

    The methods of ESR, optical and mass-spectroscopy have been used to study the formation and decay of active intermediates, radiation and photoradiation gas evolution in a series of combined polymeric materials. The investigated samples were films of polyimide (PI), one- or two-side coated PI-fluoroplast, poly(ethylene terephthalate) (PET), PET coated with polyacryl on both sides, etc. Different coatings and polymeric substrates have been established to produce a mutual effect on the radiation- and photo-induced transformations of the combined polymers at the stage of radical formation and gas evolution. Thus, ?-irradiation of PI-fluoroplast films at 300 K intensifies the radiation-chemical processes in the fluorinated coatings, namely, the radiation-chemical yield of macroradicals in the coatings is several times higher than that in fluoro-containing polymers. In the PET film coated with polyacryl the yield of macroradicals related to polyacrylic acid is significantly lower than the value generally cited in the publications. A mutual effect of the coatings and substrates on the radiation and photoradiation-induced gas evolution is even more noticeable. Thus, a gas mixture of the PI-fluoroplast film contains lower amounts of carbon oxide and fluorinated products and no hydrogen at all. The interphase processes, distortion of the boundary layer structure, electronic equilibrium, mutual effect of the evolved gases, etc. can account for the reasons of such non-additivity.

  12. Functionalized nanoparticle interactions with polymeric membranes

    PubMed Central

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

    2011-01-01

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

  13. Progress towards the synthesis of polymeric nitrogen

    SciTech Connect

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

    1994-06-01

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

  14. Vector continued fractions using a generalized inverse

    NASA Astrophysics Data System (ADS)

    Haydock, Roger; Nex, C. M. M.; Wexler, Geoffrey

    2004-01-01

    A real vector space combined with an inverse (involution) for vectors is sufficient to define a vector continued fraction whose parameters consist of vector shifts and changes of scale. The choice of sign for different components of the vector inverse permits construction of vector analogues of the Jacobi continued fraction. These vector Jacobi fractions are related to vector and scalar-valued polynomial functions of the vectors, which satisfy recurrence relations similar to those of orthogonal polynomials. The vector Jacobi fraction has strong convergence properties which are demonstrated analytically, and illustrated numerically.

  15. Polypyrrole\\/MWNT nanocomposites synthesized through interfacial polymerization

    Microsoft Academic Search

    Vasilios Georgakilas; Panagiotis Dallas; Dimitrios Niarchos; N. Boukos; Christos Trapalis

    2009-01-01

    Polypyrrole\\/carbon nanotubes (CNTs) composites were synthesized by dispersion of organically modified multiwall carbon nanotubes during an interfacial polymerization of pyrrole. During the polymerization, the carbon nanotubes are entrapped by the polymer chains and the nanocomposite is formed in the interphase between two immiscible solvents. The method favours a better dispersion of the nanotubes in the polypyrrole offering enhanced electrical properties.

  16. Polymeric Micelles - The Future of Oral Drug Delivery

    Microsoft Academic Search

    Isaac Godfroy

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

  17. Developments of rare earth metal catalysts for olefin polymerization

    Microsoft Academic Search

    Yuushou Nakayama; Hajime Yasuda

    2004-01-01

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

  18. Polymerization Simulator for Introductory Polymer and Material Science Courses

    ERIC Educational Resources Information Center

    Chirdon, William M.

    2010-01-01

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

  19. Polymeric Nanocomposites—Polyhedral Oligomeric Silsesquioxanes (POSS) as Hybrid Nanofiller

    Microsoft Academic Search

    Mangala Joshi; Bhupendra Singh Butola

    2004-01-01

    Polyhedral oligomeric silsesquioxane (POSS), a hybrid nanostructured macromer has been used in the last decade for preparation of polymeric nanocomposites. Its versatile chemistry, which lends it for almost infinite chemical modification, sets it apart from other nanostructured fillers like nanoclays, carbon nanotubes, and carbon nanofibers. Depending on its functionality, 3?D network, bead or pendant type?POSS based polymeric nanocomposites can be

  20. Smart polymeric gels: Redefining the limits of biomedical devices

    Microsoft Academic Search

    Somali Chaterji; Il Keun Kwon

    2007-01-01

    This review describes recent progresses in the development and applications of smart polymeric gels, especially in the context of biomedical devices. The review has been organized into three separate sections: defining the basis of smart properties in polymeric gels; describing representative stimuli to which these gels respond; and illustrating a sample application area, namely, microfluidics. One of the major limitations

  1. Dramatically enhanced effective electrostriction in ferroelectric polymeric composites

    E-print Network

    Li, Jiangyu

    , and electromechanical coupling factor, where high-dielectric-constant ceramics are arranged in series with ferroelectricDramatically enhanced effective electrostriction in ferroelectric polymeric composites JiangYu Lia-0526 Received 2 May 2002; accepted for publication 17 July 2002 This letter reports a ferroelectric polymeric

  2. Conduction mechanism in plasma polymerized lemongrass oil films

    Microsoft Academic Search

    D. Sakthi Kumar; M. G. Krishna Pillai

    1999-01-01

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

  3. Surface properties of artificially contaminated polymeric cable terminations

    Microsoft Academic Search

    R. Sundararajan; S. Madhavan; M. Lynch; S. Sundhar

    1997-01-01

    Low voltage surface resistance measurement and Scanning Probe Microscopy (SPM) have been used to investigate the surface recovery properties of artificially contaminated polymeric cable terminations. Due to the basic functionality difference between cable terminations and insulators, it will be of practical interest to investigate the surface recovery properties of polymeric cable terminations under contaminated conditions. Results show that the surface

  4. Polymeric Particles for the Removal of Endocrine Disruptors

    Microsoft Academic Search

    Shudong Sun; Jingyun Hunag; Changsheng Zhao

    2011-01-01

    Endocrine disruptors (EDs) have threatened our daily life severely through drinking water, cosmetics, foodstuff, and drugs. Various treatment processes for removal of EDs are studied in recent years, including membrane filtration, advanced oxidation process, biological treatment and adsorption. In this present paper, the progress of researches on various polymeric particles used as adsorbents of EDs including porous polymeric particles, hybrid

  5. A recoverable versatile photo-polymerization initiator catalyst

    E-print Network

    Chen, Dianyu; Roy, Soumyajit

    2012-01-01

    A photo-polymerization initiator based on an imidazolium and an oxometalate, viz., (BMIm)2(DMIm) PW12O40 (where, BMIm = 1-butyl-3-methylimizodium, DMIm = 3,3'-Dimethyl-1,1'-Diimidazolium) is reported. It polymerizes several industrially important monomers and is recoverable hence can be reused. The Mn and PDI are controlled and a reaction pathway is proposed.

  6. Surfing pathogens and the lessons learned for actin polymerization

    Microsoft Academic Search

    Freddy Frischknecht

    2001-01-01

    A number of unrelated bacterial species as well as vaccinia virus (ab)use the process of actin polymerization to facilitate and enhance their infection cycle. Studies into the mechanism by which these pathogens hijack and control the actin cytoskeleton have provided many interesting insights into the regulation of actin polymerization in migrating cells. This review focuses on what we have learnt

  7. Molecular weight distribution in non-linear emulsion polymerization

    Microsoft Academic Search

    Hidetaka Tobita; Mamoru Nomura

    1999-01-01

    A modelistic study is conducted for an emulsion polymerization that involves chain transfer to the polymer, by focusing our attention to the effect of very small reaction volume on the formed molecular weight distribution. In emulsion polymerization, a polymer radical that causes the polymer transfer reaction must choose the partner only within the same particle, which makes the expected size

  8. Emulsion Polymerized Polystyrene\\/Montmorillonite Nanocomposite and its Viscoelastic Characteristics

    Microsoft Academic Search

    Bong Jun Park; Tae Heon Kim; Hyoung Jin Choi; Jae Heung Lee

    2007-01-01

    A novel polystyrene (PS)\\/clay nanocomposite was synthesized using a simple emulsion polymerization method in the presence of sodium ion exchanged montmorillonite (Na?MMT). Prior to the radical polymerization procedure with potassium persulfate (KPS) as an initiator, the hydrophobic styrene monomer was intercalated into hydrophilic clay layers using sodium dodecyl sulfate (SDS) as a surfactant. The FTIR spectra of the products showed

  9. Oxygen-Mediated Enzymatic Polymerization of Thiol–Ene Hydrogels

    PubMed Central

    Zavada, S.R.; McHardy, N. R.; Scott, T. F.

    2014-01-01

    Materials that solidify in response to an initiation stimulus are currently utilized in several biomedical and surgical applications; however, their clinical adoption would be more widespread with improved physical properties and biocompatibility. One chemistry that is particularly promising is based on the thiol–ene addition reaction, a radical-mediated step-growth polymerization that is resistant to oxygen inhibition and thus is an excellent candidate for materials that polymerize upon exposure to aerobic conditions. Here, thiol–ene-based hydrogels are polymerized by exposing aqueous solutions of multi-functional thiol and allyl ether PEG monomers, in combination with enzymatic radical initiating systems, to air. An initiating system based on glucose oxidase, glucose, and Fe2+ is initially investigated where, in the presence of glucose, the glucose oxidase reduces oxygen to hydrogen peroxide which is then further reduced by Fe2+ to yield hydroxyl radicals capable of initiating thiol–ene polymerization. While this system is shown to effectively initiate polymerization after exposure to oxygen, the polymerization rate does not monotonically increase with raised Fe2+ concentration owing to inhibitory reactions that retard polymerization at higher Fe2+ concentrations. Conversely, replacing the Fe2+ with horseradish peroxidase affords an initiating system is that is not subject to the iron-mediated inhibitory reactions and enables increased polymerization rates to be attained. PMID:24995128

  10. Incorporation of polymeric nanoparticles into solid dosage forms

    Microsoft Academic Search

    Christoph Schmidt; Roland Bodmeier

    1999-01-01

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

  11. Cationic Polymerization of Vegetable Oils in Supercritical Carbon Dioxide

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Polymers derived from vegetable oils have been prepared in supercritical carbon dioxide (scCO2) medium by cationic polymerization. Boron trifluoride diethyl etherate BF3.O(C2H2)2 are used as initiator. Influences of polymerization temperature, initiator amount, and carbon dioxide pressure on the m...

  12. Polymerization of Plant Oils in Carbon Dioxide Medium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lewis acid catalyst, boron trifluoride diethyl etherate (BF3•OEt2), catalyzed polymerization of epoxidized soybean oil (ESO) in liquid carbon dioxide was conducted in an effort to develop useful biodegradable polymers. The ring-opening polymerization was employed at mild conditions, such as at room...

  13. VLSI Processor For Vector Quantization

    NASA Technical Reports Server (NTRS)

    Tawel, Raoul

    1995-01-01

    Pixel intensities in each kernel compared simultaneously with all code vectors. Prototype high-performance, low-power, very-large-scale integrated (VLSI) circuit designed to perform compression of image data by vector-quantization method. Contains relatively simple analog computational cells operating on direct or buffered outputs of photodetectors grouped into blocks in imaging array, yielding vector-quantization code word for each such block in sequence. Scheme exploits parallel-processing nature of vector-quantization architecture, with consequent increase in speed.

  14. An adaptive vector quantization scheme

    NASA Technical Reports Server (NTRS)

    Cheung, K.-M.

    1990-01-01

    Vector quantization is known to be an effective compression scheme to achieve a low bit rate so as to minimize communication channel bandwidth and also to reduce digital memory storage while maintaining the necessary fidelity of the data. However, the large number of computations required in vector quantizers has been a handicap in using vector quantization for low-rate source coding. An adaptive vector quantization algorithm is introduced that is inherently suitable for simple hardware implementation because it has a simple architecture. It allows fast encoding and decoding because it requires only addition and subtraction operations.

  15. 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.

  16. Polymeric vehicles for topical delivery and related analytical methods.

    PubMed

    Cho, Heui Kyoung; Cho, Jin Hun; Jeong, Seong Hoon; Cho, Dong Chul; Yeum, Jeong Hyun; Cheong, In Woo

    2014-04-01

    Recently a variety of polymeric vehicles, such as micelles, nanoparticles, and polymersomes, have been explored and some of them are clinically used to deliver therapeutic drugs through skin. In topical delivery, the polymeric vehicles as drug carrier should guarantee non-toxicity, long-term stability, and permeation efficacy for drugs, etc. For the development of the successful topical delivery system, it is of importance to develop the polymeric vehicles of well-defined intrinsic properties, such as molecular weights, HLB, chemical composition, topology, specific ligand conjugation and to investigate the effects of the properties on drug permeation behavior. In addition, the role of polymeric vehicles must be elucidated in in vitro and in vivo analyses. This article describes some important features of polymeric vehicles and corresponding analytical methods in topical delivery even though the application span of polymers has been truly broad in the pharmaceutical fields. PMID:24643380

  17. Preparation and evaluation of carboplatin biodegradable polymeric nanoparticles.

    PubMed

    Nanjwade, Basavaraj K; Singh, Jeet; Parikh, Kemy A; Manvi, F V

    2010-01-29

    The present study was designed to evaluate targeting efficiency of carboplatin anticancer drug. Drug was encapsulated in natural biodegradable polymer sodium alginate. The nanoparticles were prepared by the ion gelification technique and evaluated for encapsulation efficiency, loading capacity, in vitro release pattern and targeting efficiency. Drug encapsulation efficiency was about 52.24-68.70% for different formulations. In vitro release profile showed duration of drug release was also increased (more than 12 h) by nanoparticulate formulation as compared to pure drug (up to 3 h). The formulations were parenterally administered to laca mice and the drug was detected in body organs like liver, lungs and spleen. In case of free drug, less amount of drug was found in liver, lungs and spleen as compared to drug encapsulated nanoparticles. Thus sodium alginate nanoparticles can be used for targeting carboplatin and it can be a promising tool in the delivery of anticancer drugs. PMID:19854254

  18. Nano Polymeric Carrier Fabrication Technologies for Advanced Antitumor Therapy

    PubMed Central

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

    2013-01-01

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

  19. The Vector Product 6.1 Parallel vectors

    E-print Network

    Bullett, Shaun

    to Algebra. Thus, parallelism is a equivalence relation on the set of nonzero vectors Note. A wording like "u (see below) are symmetric? Be careful of the zero vector for the latter relation.] Also, when one as the general case when u and v are parallel.) The relation of collinearity is reflexive and symmetric (in all

  20. Covariant Lyapunov vectors

    NASA Astrophysics Data System (ADS)

    Ginelli, Francesco; Chaté, Hugues; Livi, Roberto; Politi, Antonio

    2013-06-01

    Recent years have witnessed a growing interest in covariant Lyapunov vectors (CLVs) which span local intrinsic directions in the phase space of chaotic systems. Here, we review the basic results of ergodic theory, with a specific reference to the implications of Oseledets’ theorem for the properties of the CLVs. We then present a detailed description of a ‘dynamical’ algorithm to compute the CLVs and show that it generically converges exponentially in time. We also discuss its numerical performance and compare it with other algorithms presented in the literature. We finally illustrate how CLVs can be used to quantify deviations from hyperbolicity with reference to a dissipative system (a chain of Hénon maps) and a Hamiltonian model (a Fermi-Pasta-Ulam chain). This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Lyapunov analysis: from dynamical systems theory to applications’.

  1. The MSFC vector magnetograph

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J.; Cumings, N. P.; West, E. A.

    1981-01-01

    The NASA/Marshall Space Flight Center's solar vector magnetograph system allows measurements of all components of the Sun's photospheric magnetic field over a 5 x 5 or 2.5 x 2.5 arc min square field of view with an optimum time resolution of approximately 100 sec and an optimum signal-to-noise of approximately 1000. The basic system components are described, including the optics, detector, digital system, and associated electronics. Automatic sequencing and control functions are outlined as well as manual selections of system parameters which afford unique system flexibility. Results of system calibration and performance are presented, including linearity, dynamic range, uniformity, spatial and spectral resolutions, signal-to-noise, electro-optical retardation and polarization calibration.

  2. Vector-Tensor and Vector-Vector Decay Amplitude Analysis of B0->phi K*0

    E-print Network

    The BABAR Collaboration; B. Aubert

    2007-02-12

    We perform an amplitude analysis of the decays B0->phi K^*_2(1430)0, phi K^*(892)0, and phi(K pi)^0_S-wave with a sample of about 384 million BBbar pairs recorded with the BABAR detector. The fractions of longitudinal polarization f_L of the vector-tensor and vector-vector decay modes are measured to be 0.853 +0.061-0.069 +-0.036 and 0.506 +-0.040 +-0.015, respectively. Overall, twelve parameters are measured for the vector-vector decay and seven parameters for the vector-tensor decay, including the branching fractions and parameters sensitive to CP-violation.

  3. Preparation, development and in vitro release evaluation of amphotericin B-loaded amphiphilic block copolymer vectors.

    PubMed

    Pippa, Natassa; Mariaki, Maria; Pispas, Stergios; Demetzos, Costas

    2014-10-01

    The aim of this work is to design and develop a suitable polymeric formulation incorporating amphotericin B (Ampho B) in order to overcome its water insolubility problem. To this end, we have chosen the poly(isoprene-b-ethylene oxide) amphiphilic block copolymer (IEO) family. We investigate the self assembly behavior and the stability kinetics of IEO copolymer based nanostructures formed in HPLC grade water and in phosphate buffer saline (PBS). The IEO block copolymer samples investigated have different molecular weights and compositions. A gamut of light scattering techniques (static, dynamic and electrophoretic) were used in order to extract information on the size, ?-potential and morphological characteristics of the structures formed, as a function of the molar ratio of incorporated lipophilic drug Ampho B. The amphiphilic character and the colloidal stability of the particular polymeric drug vectors indicate that these nanostructures can be utilized as effective containers for the particular hydrophobic drug. The incorporation of Ampho B led to alteration of the physicochemical and morphological characteristics of the pure polymeric carriers. It is observed that the in vitro release of Ampho B from the prepared vectors IEO-b:Ampho B was quite slow, while the IEO-a carriers did not release Ampho B. PMID:24998505

  4. Magnetron Enhanced Plasma-Polymerization for Biocompatible Sensor Coatings and Membranes on Polymeric Based Materials

    Microsoft Academic Search

    F. Olcaytug; L. Ledernez; G. Dame; P. Zahn; H. Yasuda; G. Urban

    One of the key questions in the application of miniaturized sensors and actuators for acute and\\/or chronic use in living-body\\u000a environment is the biocompatibility. In case of gas sensors additionally a very fine balance between the biocompatibility\\u000a of the device and the gas (e.g. O2, NO, CO) permeability of its coating must be maintained. In many sensor configurations\\u000a polymeric substrate

  5. Modification of Cellulose by Using Atom Transfer Radical Polymerization and Ring-Opening Polymerization

    Microsoft Academic Search

    Fuxiang Chang; Kazuhiro Yamabuki; Kenjiro Onimura; Tsutomu Oishi

    2008-01-01

    The cellulose chloroacetate (Cell-ClAc) with a degree of substitution (DS) value of about 2.1 was synthesized through acylation reaction of microcrystalline cellulose in a homogeneous solution of dimethylacetamide\\/lithium chloride (DMAc\\/LiCl), and pyridine as the acid acceptor. Atom transfer radical polymerizations (ATRP) of 3-ethyl-3-methacryloyloxymethyloxetane (EMO) and methyl methacrylate (MMA) were carried out by using Cell-ClAc as the initiator. Furthermore, the second

  6. Fluorescent polymeric nanocomposite films generated by surface-mediated photoinitiation of polymerization

    Microsoft Academic Search

    Heather J. Avens; Erin L. Chang; Allison M. May; Brad J. Berron; Gregory J. Seedorf; Vivek Balasubramaniam; Christopher N. Bowman

    2011-01-01

    Incorporation of nanoparticles (NPs) into polymer films represents a valuable strategy for achieving a variety of desirable\\u000a physical, optical, mechanical, and electrical attributes. Here, we describe and characterize the creation of highly fluorescent\\u000a polymer films by entrapment of fluorescent NPs into polymer matrices through surface-mediated eosin photoinitiation reactions.\\u000a Performing surface-mediated polymerizations with NPs combines the benefits of a covalently anchored

  7. Improving interface through surface modification by plasma polymerization, in carbon\\/graphite fiber reinforced polymeric composites

    Microsoft Academic Search

    Dagli

    1986-01-01

    Carbon\\/graphite fiber surfaces were modified by plasma polymerization. An inductively coupled electrodeless glow-discharge system was utilized to treat the surfaces with acrylonitrile or styrene at the established operating conditions. Critical surface erosion for wetting measured by the sessile drop method, of plasma treated pyrolytic graphite blocks, used as a model surface for carbon\\/graphite fibers, were lower than of untreated block.

  8. Science of NFL Football: Vectors

    NSDL National Science Digital Library

    NBC Learn

    2010-10-07

    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.

  9. Vectors for cancer gene therapy

    Microsoft Academic Search

    J. Zhang; S. J. Russell

    1996-01-01

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

  10. Classified Vector Quantization of Images

    Microsoft Academic Search

    BHASKAR RAMAMURTHI; A. Gersho

    1986-01-01

    Vector quantization (VQ) provides many attractive features for image coding with high compression ratios. However, initial studies of image coding with VQ have revealed several difficulties, most notably edge degradation and high computational complexity. We address these two problems and propose a new coding method, classified vector quantization (CVQ), which is based on a composite source model. Blocks with distinct

  11. Approaches to flame resistant polymeric materials

    NASA Technical Reports Server (NTRS)

    Liepins, R.

    1975-01-01

    Four research and development areas are considered for further exploration in the quest of more flame-resistant polymeric materials. It is suggested that improvements in phenolphthalein polycarbonate processability may be gained through linear free energy relationship correlations. Looped functionality in the backbone of a polymer leads to both improved thermal resistance and increased solubility. The guidelines used in the pyrolytic carbon production constitute a good starting point for the development of improved flame-resistant materials. Numerous organic reactions requiring high temperatures and the techniques of protected functionality and latent functionality constitute the third area for exploration. Finally, some well-known organic reactions are suggested for the formation of polymers that were not made before.

  12. Suicidal nucleotide sequences for DNA polymerization.

    PubMed Central

    Samadashwily, G M; Dayn, A; Mirkin, S M

    1993-01-01

    Studying the activity of T7 DNA polymerase (Sequenase) on open circular DNAs, we observed virtually complete termination within potential triplex-forming sequences. Mutations destroying the triplex potential of the sequences prevented termination, while compensatory mutations restoring triplex potential restored it. We hypothesize that strand displacement during DNA polymerization of double-helical templates brings three DNA strands (duplex DNA downstream of the polymerase plus a displaced overhang) into close proximity, provoking triplex formation, which in turn prevents further DNA synthesis. Supporting this idea, we found that Sequenase is unable to propagate through short triple-helical stretches within single-stranded DNA templates. Thus, DNA polymerase, by inducing triplex formation at specific sequences in front of the replication fork, causes self-termination. Possible biological implications of such 'conformational suicide' are discussed. Our data also provide a novel way to target DNA polymerases at specific sequences using triplex-forming oligonucleotides. Images PMID:8262040

  13. Recent Progresses in Polymeric Smart Materials

    NASA Astrophysics Data System (ADS)

    Liu, Yan-Ju; Lan, Xin; Lu, Hai-Bao; Leng, Jin-Song

    Smart materials can be defined as materials that sense and react to environmental conditions or stimuli. In recent years, a wide range of novel smart materials have been developed in biomaterials, sensors, actuators, etc. Their applications cover aerospace, automobile, telecommunications, etc. This paper presents some recent progresses in polymeric smart materials. Special emphasis is laid upon electroactive polymer (EAP), shape memory polymer (SMP) and their composites. For the electroactive polymer, an analysis of stability of dielectric elastomer using strain energy function is derived, and one type of electroactive polymer actuator is presented. For the shape memory polymer, a new method is developed to use infrared laser to actuate the SMP through the optical fiber embedded within the SMP. Electrically conductive nanocarbon powders are utilized as the fillers to improve the electrical conductivity of polymer. A series of fundamental investigations of electroactive SMP are performed and the shape recovery is demonstrated.

  14. Space environmental effects on polymeric materials

    NASA Technical Reports Server (NTRS)

    Kiefer, Richard L.; Orwoll, Robert A.

    1987-01-01

    Polymeric materials that may be exposed on spacecraft to the hostile environment beyond Earth's atmosphere were subjected to atomic oxygen, electron bombardment, and ultraviolet radiation in terrestrial experiments. Evidence is presented for the utility of an inexpensive asher for determining the relative susceptibility of organic polymers to atomic oxygen. Kapton, Ultem, P1700 polysulfone, and m-CBB/BIS-A (a specially formulated polymer prepared at NASA Langley) all eroded at high rates, just as was observed in shuttle experiments. Films of Ultem, P1700 polysulfone, and m-CBB/BIS-A were irradiated with 85 keV electrons. The UV/VIS absorbance of Ultem was found to decay with time after irradiation, indicating free radical decay. The tensile properties of Ultem began to change only after it had been exposed to 100 Mrads. The effects of dose rate, temperature, and simultaneous vs. sequential electron and UV irradiation were also studied.

  15. Micro Injection Moulding of Polymeric Components

    NASA Astrophysics Data System (ADS)

    Trotta, G.; Surace, R.; Modica, F.; Spina, R.; Fassi, I.

    2011-01-01

    Micro components and micro devices are strongly used in several fields: IT components, biomedical and medical products, automotive industry, telecommunication area and aerospace. A micro component is characterized by small dimensions of the product itself or small dimensions of the functional features. The development of new micro parts is highly dependent on manufacturing systems that can reliably and economically produce micro components in large quantities. In this context, micro-electrical discharge machining (EDM) for mould production and micro-injection moulding of polymer materials are the key technologies for micro manufacturing. This paper will focus on the production and quality evaluation of polymeric micro components manufactured by micro injection moulding. In particular the authors want to investigate the process parameters on the overall quality of the product. The factors affecting micro flow behavior, components weights and dimension definition are experimentally studied basing on DoE approach and then discussed.

  16. Polymeric slot waveguide interferometer for sensor applications.

    PubMed

    Hiltunen, Marianne; Hiltunen, Jussi; Stenberg, Petri; Aikio, Sanna; Kurki, Lauri; Vahimaa, Pasi; Karioja, Pentti

    2014-03-24

    A refractive index sensor based on slot waveguide Young interferometer was developed in this work. The interferometer was fabricated on a polymer platform and operates at a visible wavelength of 633 nm. The phase shift of the interference pattern was measured with various concentrations of glucose-water solutions, utilizing both TE and TM polarization states. The sensor was experimentally observed to detect a refractive index difference of 6.4 × 10(-6) RIU. Furthermore, the slot Young interferometer was found to compensate for temperature variations. The results of this work demonstrate that high performance sensing capability can be obtained with a polymeric slot Young interferometer, which can be fabricated by a simple molding process. PMID:24664071

  17. pH-responsive smart polymeric materials

    NASA Astrophysics Data System (ADS)

    Srivastava, Jyoti; Shukla, S.; Lal, Babu; Kandpal, L. D.; Mathur, G. N.

    1999-11-01

    Polymer systems which undergo changes in volume with change in temperature, solvent or any other external stimuli find application in medicine, biotechnology and Industry. The changes which are observed are reversible and do not show any hesterisis over number of times, the experiments are repeated. The pH of systems are important in biochemical reactions and in industrial chemical reactions. Polymeric intelligent systems that can show a change in light transmission over a wide pH range can be devised to develop light induced switches to monitor the program of reaction, addition of ingredients and also control other related factors such as temperature. Such close control chemical reactions are often desired where addition/substitution of ingredients in responsible for one type of spatial order.

  18. Nanostructural magnetism of polymeric fullerene crystals

    SciTech Connect

    Sheka, E. F., E-mail: sheka@icp.ac.ru; Zaets, V. A. [Peoples Friendship University (Russian Federation); Ginzburg, I. Ya. [Russian Academy of Sciences, Institute for Problems of Chemical Physics (Russian Federation)

    2006-11-15

    The nature of magnetism in all-carbon crystals composed of polymeric layers of covalently bound fullerene (C{sub 60}) molecules is considered. The results of quantum-chemical calculations performed using the unrestricted Hartree-Fock approximation and the semiempirical AM1 method are presented. It is shown that the exchange integrals J of both a free C{sub 60} molecule and a monomer unit of the polymer are too large ensure the required magnetic susceptibility of the fullerene crystal. However, the J value exhibits an approximately n-fold decrease for an oligomer molecule consisting of n C{sub 60} units. Therefore, in the case of large n, the exchange integral can be reduced to a low level sufficient to provide for a significant magnetic susceptibility. A nanosize (scaly) model of the observed magnetism is proposed that is consistent with recent experimental data, which are indicative of a nanostructural character of magnetic fullerene samples.

  19. Elastic, Conductive, Polymeric Hydrogels and Sponges

    PubMed Central

    Lu, Yun; He, Weina; Cao, Tai; Guo, Haitao; Zhang, Yongyi; Li, Qingwen; Shao, Ziqiang; Cui, Yulin; Zhang, Xuetong

    2014-01-01

    As a result of inherent rigidity of the conjugated macromolecular chains resulted from the delocalized ?-electron system along the polymer backbone, it has been a huge challenge to make conducting polymer hydrogels elastic by far. Herein elastic and conductive polypyrrole hydrogels with only conducting polymer as the continuous phase have been simply synthesized in the indispensable conditions of 1) mixed solvent, 2) deficient oxidant, and 3) monthly secondary growth. The elastic mechanism and oxidative polymerization mechanism on the resulting PPy hydrogels have been discussed. The resulting hydrogels show some novel properties, e.g., shape memory elasticity, fast functionalization with various guest objects, and fast removal of organic infectants from aqueous solutions, all of which cannot be observed from traditional non-elastic conducting polymer counterparts. What's more, light-weight, elastic, and conductive organic sponges with excellent stress-sensing behavior have been successfully achieved via using the resulting polypyrrole hydrogels as precursors. PMID:25052015

  20. A neural support vector machine.

    PubMed

    Jändel, Magnus

    2010-06-01

    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

  1. Vacuum stability requirements of polymeric material for spacecraft application

    NASA Technical Reports Server (NTRS)

    Craig, J. W.

    1984-01-01

    The purpose of this document is to establish outgassing requirements and test guidelines for polymeric materials used in the space thermal/vacuum environment around sensitive optical or thermal control surfaces. The scope of this document covers the control of polymeric materials used near or adjacent to optical or thermal control surfaces that are exposed to the thermal/vacuum environment of space. This document establishes the requirements and defines the test method to evaluate polymeric materials used in the vicinity of these surfaces in space applications.

  2. Intrinsic embedded sensors for polymeric mechatronics: flexure and force sensing.

    PubMed

    Jentoft, Leif P; Dollar, Aaron M; Wagner, Christopher R; Howe, Robert D

    2014-01-01

    While polymeric fabrication processes, including recent advances in additive manufacturing, have revolutionized manufacturing, little work has been done on effective sensing elements compatible with and embedded within polymeric structures. In this paper, we describe the development and evaluation of two important sensing modalities for embedding in polymeric mechatronic and robotic mechanisms: multi-axis flexure joint angle sensing utilizing IR phototransistors, and a small (12 mm), three-axis force sensing via embedded silicon strain gages with similar performance characteristics as an equally sized metal element based sensor. PMID:24573310

  3. Preparation of acrylate IPN copolymer latexes by radiation emulsion polymerization

    NASA Astrophysics Data System (ADS)

    Wu, Minghong; Zhou, Ruimin; Ma, Zue-Teh; Bao, Borong; Lei, Jianqiu

    1997-03-01

    Radiation-induced and chemical initiation are compared in the initiation of acrylate emulsion copolymer latexes. The particle diameter, distribution and microstructure are influenced by emulsifier concentration, radiation dose and temperature. The results show that the emulsion particle diameter of radiation polymerization is smaller and better distributed in comparison to using chemical polymerization. In addition, interlude polymer net (IPN) core-shell copolymer latexes are observed by transmission electron microscope (TEM). The bounding face of core-shell acrylate copolymmer texes of radiation polymerization is clearer. The morphology of acrylate IPN copolymer latexes is further investigated.

  4. Unidirectional polymerization leading to homochirality in the RNA world

    NASA Astrophysics Data System (ADS)

    Nilsson, M.; Brandenburg, A.; Andersen, A. C.; Höfner, S.

    2005-10-01

    The differences between unidirectional and bidirectional polymerization are considered. The unidirectional case is discussed in the framework of the RNA world. Similar to earlier models of this type, where polymerization was assumed to proceed in a bidirectional fashion (presumed to be relevant to peptide nucleic acids), left- and right-handed monomers are produced via an autocatalysis from an achiral substrate. The details of the bifurcation from a racemic solution to a homochiral state of either handedness is shown to be remarkably independent of whether the polymerization is unidirectional or bidirectional. Slightly larger differences are seen when dissociation is allowed and the dissociation fragments are recycled into the achiral substrate.

  5. Ecology and vector control

    PubMed Central

    Davis, D. H. S.

    1963-01-01

    One of the primary functions of ecological work is to conduct surveys of those species of vertebrates and/or invertebrates that are involved directly or indirectly in vector-borne diseases of man. The aim in southern Africa has been to contribute to a stable nomenclature at the species level, to determine the range of each species and to make an attempt to single out key environmental limiting factors. Once the taxonomic status and range of the species have been established with some degree of certainty, species may be studied in relation to the distribution and prevalence of any particular disease in order to provide the basis for control. The bio-geographical approach that has been adopted arose when the geographical distribution of human plague derived from wild-rodent sources came to be compared with the distribution of the small mammals and their respective fleas. This threw much light on the factors concerned in the limitation and persistence of plague. These comparative studies were facilitated by plotting the distribution data on grid maps. ImagesFIG. 1FIG. 1(continued) PMID:20604161

  6. Semismooth support vector machines.

    SciTech Connect

    Ferris, M. C.; Munson, T. S.; Mathematics and Computer Science; Univ. of Wisconsin

    2004-09-01

    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.

  7. Method of preparing water purification membranes. [polymerization of allyl amine as thin films in plasma discharge

    NASA Technical Reports Server (NTRS)

    Hollahan, J. R.; Wydeven, T. J., Jr. (inventors)

    1974-01-01

    Allyl amine and chemically related compounds are polymerized as thin films in the presence of a plasma discharge. The monomer compound can be polymerized by itself or in the presence of an additive gas to promote polymerization and act as a carrier. The polymerized films thus produced show outstanding advantages when used as reverse osmosis membranes.

  8. Unit I-1 Vector spaces and subspaces 1 Vector spaces and subspaces

    E-print Network

    Birkett, Stephen

    Unit I-1 Vector spaces and subspaces 1 Unit I-1 Vector spaces and subspaces Unit I-1 Vector spaces and subspaces 2 Vector spaces · need two mathematical objects.... · set V of things called vectors u,v,w... V · set F of numbers called scalars k,l,m... F ­ a real vector space uses real scalars R ­ a complex

  9. Vectors of rickettsiae in Africa.

    PubMed

    Bitam, Idir

    2012-12-01

    Vector-borne diseases are caused by parasites, bacteria, or viruses transmitted by the bites of hematophagous arthropods. In Africa, there has been a recent emergence of new diseases and the re-emergence of existing diseases, usually with changes in disease epidemiology (e.g., geographical distribution, prevalence, and pathogenicity). In Africa, rickettsioses are recognized as important emerging vector-borne infections in humans. Rickettsial diseases are transmitted by different types of arthropods, ticks, fleas, lice, and mites. This review will examine the roles of these different arthropod vectors and their geographical distributions. PMID:23168053

  10. Initial Conditions for Vector Inflation

    E-print Network

    Takeshi Chiba

    2008-08-05

    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 FRW 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 chaotic inflation, and the fraction of the initial conditions leading to inflationary solutions is reduced compared with the chaotic inflation case.

  11. Inflation with Massive Vector Fields

    E-print Network

    Junyu Liu; Yi Wang; Siyi Zhou

    2015-02-26

    We investigate the coupling between the inflaton and massive vector fields. All renormalizable couplings with shift symmetry of the inflaton are considered. The massive vector can be decomposed into a scalar mode and a divergence-free vector mode. We show that the former naturally interacts with the inflaton and the latter decouples at tree level. The model in general predicts $f_{NL}^\\mathrm{equil} = \\mathcal{O}(1)$, while in some regions of the parameter space large non-Gaussianity can arise.

  12. Actin Polymerization Overshoots and Hydrolysis as Assayed by Pyrene Fluorescence

    E-print Network

    Carlsson, Anders

    undergo a two-step hydrolysis (12). First, the ATP con- taining subunits (F-ATP) hydrolyze to a state- ing an independent measurement of the amount of polymerized actin that had completely hydrolyzed (F

  13. 21 CFR 872.6070 - Ultraviolet activator for polymerization.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6070 ...ultraviolet radiation intended to polymerize (set) resinous dental pit and fissure sealants or restorative...

  14. 21 CFR 872.6070 - Ultraviolet activator for polymerization.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6070 ...ultraviolet radiation intended to polymerize (set) resinous dental pit and fissure sealants or restorative...

  15. 21 CFR 872.6070 - Ultraviolet activator for polymerization.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6070 ...ultraviolet radiation intended to polymerize (set) resinous dental pit and fissure sealants or restorative...

  16. 21 CFR 872.6070 - Ultraviolet activator for polymerization.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6070 ...ultraviolet radiation intended to polymerize (set) resinous dental pit and fissure sealants or restorative...

  17. 21 CFR 872.6070 - Ultraviolet activator for polymerization.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6070 ...ultraviolet radiation intended to polymerize (set) resinous dental pit and fissure sealants or restorative...

  18. Tension modulates actin filament polymerization mediated by formin and profilin

    PubMed Central

    Courtemanche, Naomi; Lee, Ja Yil; Pollard, Thomas D.; Greene, Eric C.

    2013-01-01

    Formins promote processive elongation of actin filaments for cytokinetic contractile rings and other cellular structures. In vivo, these structures are exposed to tension, but the effect of tension on these processes was unknown. Here we used single-molecule imaging to investigate the effects of tension on actin polymerization mediated by yeast formin Bni1p. Small forces on the filaments dramatically slowed formin-mediated polymerization in the absence of profilin, but resulted in faster polymerization in the presence of profilin. We propose that force shifts the conformational equilibrium of the end of a filament associated with formin homology 2 domains toward the closed state that precludes polymerization, but that profilin–actin associated with formin homology 1 domains reverses this effect. Thus, physical forces strongly influence actin assembly by formin Bni1p. PMID:23716666

  19. Emulsion Polymerization of Butyl Acrylate: Spin Trapping and EPR Study

    NASA Technical Reports Server (NTRS)

    Kim, S.; Westmoreland, D.

    1994-01-01

    The propagating radical in the emulsion polymerization reaction of butyl acrylate was detected by Electron Paramagnetic Resonance spectroscopy using two spin trapping agents, 2-methyl-2nitrosopropane and alpha -N-tert-butylnitrone.

  20. Direct-Write Piezoelectric Polymeric Nanogenerator with High Energy Conversion

    E-print Network

    Lin, Liwei

    Nanogenerator, near-field electrospinning, direct-write nanofibers, piezoelectric, energy harvestingDirect-Write Piezoelectric Polymeric Nanogenerator with High Energy Conversion Efficiency Chieh for many applications, including energy harvesters. In this work, near-field electrospinning is used

  1. PREDICTIVE MODELS: PERMEATION OF POLYMERIC MEMBRANES BY ORGANIC SOLVENTS

    EPA Science Inventory

    Protective clothing (for example, gloves, aprons, masks, and protective ensembles) is often constructed in the form of barrier polymeric membranes. Permeation testing, which is used frequently to screen candidate polymers for use as protective barrier is expensive and time consum...

  2. Novel Printing------Using Polymeric Gel as Ink

    NASA Astrophysics Data System (ADS)

    Toyama, Noboru; Fukumoto, Hiroshi; Tanioka, Hiroshi; Arahara, Kohzoh; Koizumi, Norihiko; Yuasa, Toshiya; Kobayashi, Motokazu; Kan, Fumitaka

    1989-07-01

    Novel printing ink has been developed based on polymeric gel having the nature of gel to sol transition caused by application of electric voltage. The polymeric gel ink consisted of polyvinyl alcohol) (PVA) partially crosslinked with borax, carbon black as a pigment, and water. Printing facilities was also designed. Polymeric gel ink with electric conductivity 4.0 x 10-3 ?-1cm-1 was used. It could offer resolution of more than 200 dots per inch (dpi). Image density was fully controlled from 0.05 to 1.5 as optical density by application of electric voltage of 3 - 12 V. An advantage of this printing system was that polymeric gel ink not only acted as ink but also as the support.

  3. Free-radical solution-polymerization of trifluoronitrosomethane with tetrafluoroethylene

    NASA Technical Reports Server (NTRS)

    Gdickman, S. A.

    1972-01-01

    Heavy-walled glass reactor, equipped with aerosol-compatible couplings and needle valve and charged with solvent and initiator, is utilized for polymerization. Polymer conversions and reactor/vessel operation are discussed.

  4. Activity of polymerized trichloroacetic acid for highway vegetation control 

    E-print Network

    Wiedenfeld, R. P

    1974-01-01

    to 200 pW/cm of ultra. ? 2 violet light. Extensive degradation of the ester of picloram (96~/o) occured in open petri dishes after 72-hr exposure to ultraviolet light (Bovey, Ketchersid and Merkle, 1970) ~ Isensee, Plimmer and Turner ('IQ6$) showed... by ultraviolet radiation. Recovery also was greater from an asphaltic emulsion than from a cutback asphalt or an asphaltic cement. Polymerization increased the effectiveness of TCA in controlling vegetation. However, increased sucept- ibility of polymerized...

  5. 2-Mercaptothioxanthone as a Novel Photoinitiator for Free Radical Polymerization

    Microsoft Academic Search

    Lerzan Cokbaglan; Nergis Arsu; Yusuf Yagci; Steffen Jockusch; Nicholas J. Turro

    2003-01-01

    Mercaptothioxanthone (TX-SH), a hydrogen abstraction type photoinitiator for free radical polymerization, is synthesized and characterized. Its capability to act as an initiator for the polymerization of methyl methacrylate (MMA), styrene (St), and multifunctional monomers is examined. The relative efficiencies of TX-SH, the parent thioxanthone (TX), and their combination with an amine synergist such as N-methyldiethanolamine (MDEA) are compared in the

  6. Photoinitiated polymerization of methyl methacrylate by phenacyl type salts

    Microsoft Academic Search

    Fatmanur Kasapoglu; Meral Aydin; Nergis Arsu; Yusuf Yagci

    2003-01-01

    Phenacyl onium salts, namely N-phenacyl-N,N-dimethylanilinium-N,N-diethyldithiocarbamate (Ia), phenacyl-triphenylphosphonium-N,N-diethyldithiocarbamate (II), 1-phenacyl pyridinium-N,N-diethyldithiocarbamate (III), are shown to be efficient photoinitiators for polymerization of methyl methacrylate (MMA). Plausible mechanism of the photoinitiation involves both free radical and zwitterionic processes. Phenacyl radicals formed from the homolytic cleavage of carbon heteroatom bond initiates the free radical polymerization while Lewis bases formed from homolytic cleavage followed by

  7. Preparation and Characterization of Polypyrrole Silver Nanocomposites via Interfacial Polymerization

    Microsoft Academic Search

    Mahesh D. Bedre; S. Basavaraja; Raghunandan Deshpande; D. S. Balaji; A. Venkataraman

    2010-01-01

    Conducting polypyrrole silver (Ppy-AgNC) nanocomposite was synthesized by an interfacial polymerization method. Ag ions from the AgNO3 solution were taken in the formation of Ppy-AgNC. The incorporated silver was confirmed by X-ray diffraction (XRD). During the polymerization in a nitrate ion-containing solution, the impregnation leads to the formation of metallic silver. The size distribution of Ag into the polymer is

  8. Photoresponsive cross-linked polymeric particles for phototriggered burst release.

    PubMed

    Wang, Zhen; Yu, Lili; Lv, Cong; Wang, Peng; Chen, Yedong; Tang, Xinjing

    2013-01-01

    We synthesized a series of cross-linked photoresponsive polymeric particles with photolabile monomers and cross-linkers through miniemulsion polymerization. These particles are quite stable in dark, while light irradiation caused the breakage of particles and the efficient release of encapsulated contents up to 95% based on Nile red fluorescence. Photoswitches of particle systems were confirmed by fluorescence spectroscopy, SEM and colorimetry. Particle uptake and triggered release in RAW264.7 cells were confirmed by fluorescein diacetate loaded particles. PMID:23294131

  9. Thermally crosslinked polymeric compositions and methods of making the same

    SciTech Connect

    Koros, William John; Kratochvil, Adam Michal

    2014-03-04

    The various embodiments of the present disclosure relate generally to thermally crosslinked polymeric compositions and methods of making thermally crosslinked polymeric compositions. An embodiment of the present invention comprises a composition comprising: a first polymer comprising a first repeat unit, the first repeat unit comprising a carboxyl group, wherein the first polymer crosslinks to a second polymer formed from a second repeat unit, and wherein the first polymer crosslinks to the second polymer without formation of an ester group.

  10. Organic and Polymeric TFTs for Flexible Displays and Circuits

    Microsoft Academic Search

    Michael G. Kane

    Organic and polymeric thin-film transistors are a natural complement to flexible substrates. This is because organic thin-film\\u000a transistors (OTFTs) can be made using a very low temperature process, not much above room temperature, allowing electronic\\u000a circuits and systems to be made on plastic films.1 The organic and polymeric materials that can be used as semiconductors,\\u000a dielectrics, and conductors are themselves

  11. Surface modification of polymeric microspheres by gold nanoparticles

    Microsoft Academic Search

    A. Yu. Men’shikova; T. B. Boitsova; T. G. Evseeva; N. N. Shevchenko; B. M. Shabsel’s; E. I. Isaeva; V. V. Gorbunova

    2009-01-01

    The role of the polymer nature and surface functionality in the modification of polymeric microspheres by gold nanoparticles\\u000a was investigated. Monodisperse cross-linked polymer microspheres with diameters up to 5 ?m were prepared by core\\/shell heterophase\\u000a polymerization with the use of seeding polystyrene cores and styrene, divinylbenzene, or ethylene glycol dimethacrylate as\\u000a monomers. The deposition of gold nanoparticles on the surface

  12. Chemical in situ polymerization of polypyrrole on bacterial cellulose nanofibers

    Microsoft Academic Search

    D. Müller; C. R. Rambo; D. O. S. Recouvreux; L. M. Porto; G. M. O. Barra

    2011-01-01

    Conducting porous nanofibrous composite membranes of bacterial cellulose (BC) and polypyrrole (PPy) were prepared through in situ oxidative chemical polymerization of pyrrole (Py) on the surface of synthetized BC nanofibers by using FeCl3 as oxidant agent. The influence of polymerization conditions on electrical conductivity, morphological and thermal stability of the BC\\/PPy composites was investigated. The amount of PPy deposited on

  13. Nitroxide-Mediated Radical Polymerization: Limitations and Versatility

    Microsoft Academic Search

    Robert B. Grubbs

    2011-01-01

    Since its introduction in the early 1990s, nitroxide-mediated radical polymerization (NMP) has been widely adopted for the preparation of a panoply of new polymer architectures. While NMP provides a number of advantages for the preparation of specific types of polymers, several inherent limitations with NMP have led to the more widespread use of other reversible-deactivation radical polymerization (RDRP) methods, chiefly

  14. 2-Methylol-thioxanthone as a free radical polymerization initiator

    Microsoft Academic Search

    Gokhan Temel; Nergis Arsu

    2007-01-01

    2-Methylol-thioxanthone (TX-M) was synthesized and characterized as a new photoinitiator. Photopolymerization experiments were performed with methyl methacrylate and also trimethylolpropanetriacrylate (TMPTA) as a multifunctional monomer in the presence of TX-M with N-methyl diethanol amine. Polymerization did not occur in an air atmosphere with TX-M without adding MDEA. The inhibiting effect of oxygen on the rate of polymerization was observed to

  15. Study of formulation and stability of emulsions with polymeric emulsifiers

    Microsoft Academic Search

    Marie-France Bobin; Valérie Michel; Marie-Claude Martini

    1999-01-01

    Polymeric emulsifiers have appeared recently and have got emulsifying and thickness properties. These emulsifiers provide exceptional stability to oil-in-water-emulsions. This study shows formulations of new emulsifiers. The polymeric emulsifiers used were acrylate C10–C30 alkyl–acrylate cross polymer (Tr1–Tr2). They provide exceptional stability to oil-in-water emulsions at very low usage levels (0.1,0.3%), they can be used with any oil phase, easily prepared

  16. Stabilization of supported liquid membranes by plasma polymerization surface coating

    Microsoft Academic Search

    X. J. Yang; A. G. Fane; J. Bi; H. J. Griesser

    2000-01-01

    Plasma polymerization coating is shown to be an effective method for improving the stability of supported liquid membranes (SLM) containing LIX 984N for copper transport. Hexamethyldisiloxane and heptylamine were employed as monomers and hydrophobic microporous microfiltration membranes with pore sizes of 0.05–0.2?m were used as substrates. Electronmicroscopy revealed that the plasma polymerization film mainly occurred on the surface of the

  17. Polymeric compositions incorporating polyethylene glycol as a phase change material

    Microsoft Academic Search

    Ival O. Salyer; Charles W. Griffen

    1989-01-01

    A polymeric composition comprising a polymeric material and polyethylene glycol or end-capped polyethylene glycol as a phase change material, said polyethylene glycol and said end-capped polyethylene glycol having a molecular weight greater than about 400 and a heat of fusion greater than about 30 cal\\/g; the composition is useful in making molded and\\/or coated materials such as flooring, tiles, wall

  18. Identification of particle-particle interactions in suspension polymerization reactors

    Microsoft Academic Search

    Eric J. Hukkanen; Richard D. Braatz

    2005-01-01

    Suspension polymerization is commonly used to produce micron-sized (10-1000 ?m) polymer beads, in which the final particle size distribution is an important end-use property. This paper presents an integrated approach for the modeling, simulation, and parameter estimation of particle-particle dynamics during suspension polymerization. This approach integrates in situ particle size measurement with a high resolution finite volume algorithm to estimate

  19. Prosthetic sockets of polymerized metal: materials, design, technology.

    PubMed

    Yaramenko, D A; Sytenko, A N; Bazhina, E N; Krasnov, A I; Borisov, A I

    1987-12-01

    The process of fabricating polymerized metal sockets for above-knee and below-knee prostheses is described. The technique is based on pulse stamping of metal blanks over a matrix imitating the negative mould of the stump and subsequent polymeric coating by vibro-vortex spraying. The monitoring of more than 500 patients fitted with metal-polymer sockets since 1978 is reported. PMID:3438158

  20. Photoinitiated polymerization of vinyl ether-based systems

    Microsoft Academic Search

    C Decker; C Bianchi; D Decker; F Morel

    2001-01-01

    The photoinitiated polymerization of vinyl ether (VE)-based coatings has been studied by real-time infrared (RTIR) spectroscopy. In the presence of diaryliodonium or triarylsulfonium photoinitiators, the cationic polymerization occurs rapidly upon UV-exposure and continues to proceed upon storage in the dark. Increasing the formulation viscosity by introduction of telechelic VE oligomers was found to have a strong slowing down effect on

  1. Polymerization of ?-pinene using Lewis acidic ionic liquid as catalyst

    Microsoft Academic Search

    Shiwei Liu; Congxia Xie; Shitao Yu; Fusheng Liu

    2009-01-01

    Polymerization of ?-pinene was investigated in the presence of various Lewis acidic ILs. The results showed that ILs 1-n-butyl-3-methylimidazolium chloroaluminate-[C4mim]Cl-AlCl3, especially molar fraction of AlCl3x=0.67, indicated excellent catalytic performance for the polymerization of ?-pinene. It is also found that the product was easily separated from reaction mixture and the IL catalyst was of good reusability. Hence, a clean and environmentally

  2. Vector boson plus multijet production

    E-print Network

    Marek Schonherr

    2013-02-15

    In this contribution the developments in the description of vector boson plus jets signatures at hadron colliders in recent years are summarised. Particular focus is put on its relevance as background to top physics.

  3. Polynomial Interpretation of Multipole Vectors

    E-print Network

    Gabriel Katz; Jeffrey Weeks

    2004-06-01

    Copi, Huterer, Starkman and Schwarz introduced multipole vectors in a tensor context and used them to demonstrate that the first-year 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 re-confirm the estimate that the WMAP quadrupole and octopole planes align at the 99.9% level.

  4. Exclusive vector meson electroproduction @ CLAS

    SciTech Connect

    Ahmed Fradi

    2011-05-01

    We present the results of exclusive electroproduction of vector mesons on the proton at CLAS. We discuss the interpretation of these cross sections in terms of t-channel Reggeon exchanges and in terms of Generalized Parton Distributions (GPDs) formalism.

  5. Exclusive vector meson electroproduction @ CLAS

    E-print Network

    Ahmed Fradi

    2010-09-20

    We present the results of exclusive electroproduction of vector mesons on the proton at CLAS. We discuss the interpretation of these cross sections in terms of t-channel Reggeon exchanges and in terms of Generalized Parton Distributions (GPDs) formalism.

  6. Engineering fibrin polymers through engagement of alternative polymerization mechanisms

    PubMed Central

    Stabenfeldt, Sarah E.; Gourley, Merek; Krishnan, Laxminarayanan; Hoying, James B.; Barker, Thomas H.

    2012-01-01

    Fibrin is an attractive material for regenerative medicine applications. It not only forms a polymer but also contains cryptic matrikines that are released upon its activation/degradation and enhance the regenerative process. Despite this advantageous biology associated with fibrin, commercially available systems (e.g. TISSEEL) display limited regenerative capacity. This limitation is in part due to formulations that are optimized for tissue sealant applications and result in dense fibrous networks that limit cell infiltration. Recent evidence suggests that polymerization knob ‘B’ engagement of polymerization hole ‘b’ activates an alternative polymerization mechanism in fibrin, which may result in altered single fiber mechanical properties. We hypothesized that augmenting fibrin polymerization through the addition of PEGylated knob peptides with specificity to hole ‘b’ (AHRPYAAC-PEG) would result in distinct fibrin polymer architectures with grossly different physical properties. Polymerization dynamics, polymer architecture, diffusivity, viscoelasticity, and degradation dynamics were analyzed. Results indicate that specific engagement of hole ‘b’ with PEGylated knob ‘B’ conjugates during polymerization significantly enhances the porosity of and subsequent diffusivity through fibrin polymers. Paradoxically, these polymers also display increased viscoelastic properties and decreased susceptibility to degradation. As a result, fibrin polymer strength was significantly augmented without any adverse effects on angiogenesis within the modified polymers. PMID:22018389

  7. Optical investigations of various polymeric materials used in dental technology

    NASA Astrophysics Data System (ADS)

    Negrutiu, Meda Lavinia; Sinescu, Cosmin; Topala, Florin Ionel; Ionita, Ciprian; Goguta, Luciana; Marcauteanu, Corina; Rominu, Mihai; Podoleanu, Adrian Gh.

    2011-10-01

    Dental prosthetic restorations have to satisfy high stress as well as aesthetic requirements. In order to avoid deficiencies of dental prostheses, several alternative systems and procedures were imagined, directly related to the material used and also to the manufacturing technology. Increasing the biomechanical comportment of polymeric materials implies fiber reinforcing. The different fibers reinforcing products made very difficult the evaluation of their performances and biomechanical properties analysis. There are several known methods which are used to assess the quality of dental prostheses, but most are invasive. These lead to the destruction of the samples and often no conclusion could be drawn in the investigated areas of interest. Using a time domain en-face OCT system, we have recently demonstrated real time thorough evaluation of quality of various dental treatments. The aim of this study was to assess the quality of various polymeric materials used in dental technology and to validate the en face OCT imagistic evaluation of polymeric dental prostheses by using scanning electron microscopy (SEM) and microcomputer tomography (?CT). SEM investigations evidenced the nonlinear aspect of the interface between the polymeric material and the fiber reinforcement and materials defects in some samples. The results obtained by microCT revealed also some defects inside the polymeric materials and at the interfaces with the fiber reinforcement. The advantages of the OCT method consist in non-invasiveness and high resolution. In addition, en face OCT investigations permit visualization of the more complex stratified structure at the interface between the polymeric material and the fiber reinforcement.

  8. Bouncing scalar field cosmology in the polymeric minisuperspace picture

    E-print Network

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

    2014-08-20

    We study a cosmological setup consisting of a FRW metric as the background geometry with a massless scalar field in the framework of classical polymerization of a given dynamical system. To do this, we first introduce the polymeric representation of the quantum operators. We then extend the corresponding process to reach a transformation which maps any classical variable to its polymeric counterpart. It is shown that such a formalism has also an analogue in terms of the symplectic structure, i.e., instead of applying polymerization to the classical Hamiltonian to arrive its polymeric form, one can use a new set of variables in terms of which Hamiltonian retains its form but now the corresponding symplectic structure gets a new deformed functional form. We show that these two methods are equivalent and by applying of them to the scalar field FRW cosmology see that the resulting scale factor exhibits a bouncing behavior from a contraction phase to an expanding era. Since the replacing of the big bang singularity by a bouncing behavior is one of the most important predictions of the quantum cosmological theories, we may claim that our polymerized classical model brings with itself some signals from quantum theory.

  9. Two Photon Polymerization of Microneedles for Transdermal Drug Delivery

    PubMed Central

    Gittard, Shaun D.; Ovsianikov, Aleksandr; Chichkov, Boris N.; Doraiswamy, Anand; Narayan, Roger J.

    2010-01-01

    Importance of the field Microneedles are small-scale devices that are finding use for transdermal delivery of protein-based pharmacologic agents and nucleic acid-based pharmacologic agents; however, microneedles prepared using conventional microelectronics-based technologies have several shortcomings, which have limited translation of these devices into widespread clinical use. Areas covered in this review Two photon polymerization is a laser-based rapid prototyping technique that has been recently used for direct fabrication of hollow microneedles with a wide variety of geometries. In addition, an indirect rapid prototyping method that involves two photon polymerization and polydimethyl siloxane micromolding has been used for fabrication of solid microneedles with exceptional mechanical properties. What the reader will gain In this review, the use of two photon polymerization for fabricating in-plane and out-of-plane hollow microneedle arrays is described. The use of two photon polymerization-micromolding for fabrication of solid microneedles is also reviewed. In addition, fabrication of microneedles with antimicrobial properties is discussed; antimicrobial microneedles may reduce the risk of infection associated with formation of channels through the stratum corneum. Take home message It is anticipated that the use of two photon polymerization as well as two photon polymerization-micromolding for fabrication of microneedles and other microstructured drug delivery devices will increase over the coming years. PMID:20205601

  10. Simplified Support Vector Decision Rules

    Microsoft Academic Search

    Christopher J. C. Burges

    1996-01-01

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

  11. Vector fields in multidimensional cosmology

    E-print Network

    Boris E. Meierovich

    2011-10-06

    Vector fields in the expanding Universe are considered within the multidimensional theory of General Relativity. Vector fields in general relativity form a three-parametric variety. Our consideration includes the fields with a nonzero covariant divergence. Depending on the relations between the particular parameters and the symmetry of a problem, the vector fields can be longitudinal and/or transverse, ultrarelativistic (i.e. massless) or nonrelativistic (massive), and so on. The longitudinal and transverse vector fields are considered separately in detail in the background of the de Sitter cosmological metric. In most cases the field equations reduce to Bessel equations, and their temporal evolution is analyzed analytically. The energy-momentum tensor of the most simple zero-mass longitudinal vector fields enters the Einstein equations as an additive to the cosmological constant. In this case the de Sitter metric is the exact solution of the Einstein equations. Hence, the most simple zero-mass longitudinal vector field pretends to be an adequate tool for macroscopic description of dark energy as a source of the expansion of the Universe at a constant rate. The zero-mass vector field does not vanish in the process of expansion. On the contrary, massive fields vanish with time. Though their amplitude is falling down, the massive fields make the expansion accelerated. The macroscopic analysis of vector fields in cosmology gives up the hope that the major puzzle -- attraction between individual objects and expansion of the Universe as a whole -- can be solved within the Einstein's theory of general relativity.

  12. Entropy-constrained vector quantization

    Microsoft Academic Search

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

    1989-01-01

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

  13. Graft polymerization of glycidylmethacrylate onto coralline hydroxyapatite.

    PubMed

    Murugan, R; Panduranga Rao, K

    2003-01-01

    Graft polymerization of glycidylmethacrylate (GMA) onto coralline hydroxyapatite (CHA) was carried out using potassium persulfate (K2S2O8) and sodium metabisulfite (Na2S2O5) as initiators in aqueous medium. To optimize the reaction conditions for getting maximum grafting yield, the concentrations of backbone, monomer, initiator, temperature and time were varied. The percent grafting was found to increase initially and then gradually decrease with respect to reaction parameters. The results obtained imply that the optimum temperature and time was 60 degrees C and 180 min, respectively, to obtain higher grafting yield. The grafting results have been discussed and a mechanism involved in the grafting of GMA onto CHA is described. The grafted materials were analyzed with Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) measurements. The results of FT-IR confirmed the presence of epoxy group on the grafted CHA. The XRD pattern showed that there was no secondary phase in the apatite lattice due to chemical modification. PMID:12807147

  14. Cell Motility Resulting form Spontaneous Polymerization Waves

    NASA Astrophysics Data System (ADS)

    Kruse, Karsten

    2014-03-01

    The crawling of living cells on solid substrates is often driven by the actin cytoskeleton, a network of structurally polar filamentous proteins that is intrinsically driven by the hydrolysis of ATP. How cells organize their actin network during crawling is still poorly understood. A possible general mechanism underlying actin organization has been offered by the observation of spontaneous actin polymerization waves in various different cell types. We use a theoretical approach to investigate the possible role of spontaneous actin waves on cell crawling. To this end, we develop a meanfield framework for studying spatiotemporal aspects of actin assembly dynamics, which helped to identify possible origins of self-organized actin waves. The impact of these waves on cell crawling is then investigated by using a phase-field approach to confine the actin network to a cellular domain. We find that spontaneous actin waves can lead to directional or amoeboidal crawling. In the latter case, the cell performs a random walk. Within our deterministic framework, this behavior is due to complex spiral waves inside the cell. Finally, we compare the seemingly random motion of our model cells to the dynamics of cells of the human immune system. These cells patrol the body in search for infected cells and we discuss possible implications of our theory for the search process' efficiency. Work was funded by the DFG through KR3430/1, GK1276, and SFB 1027.

  15. Design Strategies for Fluorescent Biodegradable Polymeric Biomaterials

    PubMed Central

    Zhang, Yi; Yang, Jian

    2013-01-01

    The marriage of biodegradable polymer and fluorescent imaging has resulted in an important area of polymeric biomaterials: biodegradable fluorescent polymers. Researchers have put significant efforts on developing versatile fluorescent biomaterials due to their promising in biological/biomedical labeling, tracking, monitoring, imaging, and diagnostic applications, especially in drug delivery, tissue engineering, and cancer imaging applications. Biodegradable fluorescent polymers can function not only as implant biomaterials but also as imaging probes. Currently, there are two major classes of biodegradable polymers used as fluorescent materials. The first class is the combination of non-fluorescent biodegradable polymers and fluorescent agents such as organic dyes and quantum dots. Another class of polymers shows intrinsic photoluminescence as polymers by themselves carrying integral fluorescent chemical structures in or pendent to their polymer backbone, such as Green Fluorescent protein (GFP), and the recently developed biodegradable photoluminescent polymer (BPLP). Thus there is no need to conjugate or encapsulate additional fluorescent materials for the latter. In the present review, we will review the fluorescent biodegradable polymers with emphases on material fluorescence mechanism, design criteria for fluorescence, and their cutting-edge applications in biomedical engineering. We expect that this review will provide insightful discussion on the fluorescent biomaterial design and lead to innovations for the development of the next generation of fluorescent biomaterials and fluorescence-based biomedical technology. PMID:23710326

  16. Characterization of Polymeric Nanomaterials Using Analytical Ultracentrifugation.

    PubMed

    Diaz, Leosveys; Peyrot, Caroline; Wilkinson, Kevin J

    2015-06-16

    The characterization of nanomaterials represents a complex analytical challenge due to their dynamic nature (small size, high reactivity, and instability) and the low concentrations in the environment, often below typical analytical detection limits. Analytical ultracentrifugation (AUC) is especially useful for the characterization of small nanoparticles (1-10 nm), which are often the most problematic for the commonly used techniques such as electron microscopy or dynamic light scattering. In this study, small polymeric nanomaterials (allospheres) that are used commercially to facilitate the distribution of pesticides in agricultural fields were characterized under a number of environmentally relevant conditions. Under most of the studied conditions, the allospheres were shown to have a constant hydrodynamic diameter (dH) of about 7.0 nm. Only small increases in diameter were observed, either at low pH or very high ionic strength or hardness, demonstrating their high physicochemical stability (and thus high mobility in soils). Furthermore, natural organic matter had little effect on the hydrodynamic diameters of the allospheres. The concentration of the nanoparticles was an important parameter influencing their agglomeration-results obtained using dynamic light scattering at high particle concentrations showed large agglomerate sizes and significant particle losses through sedimentation, clearly indicating the importance of characterizing the nanomaterials under environmentally relevant conditions. PMID:25988704

  17. Viscoelastic models for polymeric composite materials

    SciTech Connect

    Bardenhagen, S.G.; Harstad, E.N. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Foster, J.C. Jr. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)]|[Wright Laboratory, Armament Directorate, Eglin AFB, Florida 32542 (United States); Maudlin, P.J. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    1996-05-01

    An improved model of the mechanical properties of the explosive contained in conventional munitions is needed to accurately simulate performance and accident scenarios in weapons storage facilities. A specific class of explosives can be idealized as a mixture of two components: energetic crystals randomly suspended in a polymeric matrix (binder). Strength characteristics of each component material are important in the macroscopic behavior of the composite (explosive). Of interest here is the determination of an appropriate constitutive law for a polyurethane binder material. A Taylor Cylinder impact test, and uniaxial stress tension and compression tests at various strain rates, have been performed on the polyurethane. Evident from time resolved Taylor Cylinder profiles, the material undergoes very large strains ({gt}100{percent}) and yet recovers its initial configuration. A viscoelastic constitutive law is proposed for the polyurethane and was implemented in the finite element, explicit, continuum mechanics code EPIC. The Taylor Cylinder impact experiment was simulated and the results compared with experiment. Modeling improvements are discussed. {copyright} {ital 1996 American Institute of Physics.}

  18. Mechanism of plasma polymerization of methyl methacrylate

    SciTech Connect

    Denes, F.; Sarmadi, A.M.; Hop, C.E.C.A.; Young, R.A. [Univ. of Wisconsin, Madison, WI (United States)

    1993-12-31

    Molecular fragments from radio-frequency plasma polymerization of methylmethacrylate (MMA) were cold-trapped and characterized by gas chromatography-mass spectroscopy (GC/MS). The gas phase and the liquid phase products from the cold trap were analyzed separately. The gas phase contained a predominance of the saturated aliphatic compounds butane, pentane, and isopentane and unsaturated l-butene, in addition to saturated MMA monomer (methyl isobutyrate); the liquid phase contained mainly isopropenyl alcohol, saturated MMA and a methylated form of the saturated MMA. Calculations of the predominant plasma-generated molecular clusters using the CG/MS data for both the gas and liquid phases indicated that saturated and unsaturated propyl radicals (molecular weight 41-43) were by far the predominant radical species in the plasma reactions and would lead to a hydrocarbon-type polymer with considerable unsaturation and crosslinking. The occurrence of other radical species containing methyl ester and hydroxyl groups accounts for the presence of these functional groups in the final polymer. Infrared and ultraviolet spectra confirmed the participation of the predominant aliphatic radicals in the formation of PPMMA. Clearly PPMA is a distinctly different polymer when compared to conventional PMMA.

  19. Smart materials based on polymeric systems

    SciTech Connect

    Crowson, A. [Army Research Office, Research Triangle Park, NC (United States)

    1995-12-01

    The science and technology of the 21st century will rely heavily on the development of new materials. Such materials are expected to be innovative with regards to structure, functionality, and design. One concept in achieving this goal is what has been termed {open_quotes}smart materials{close_quotes}. A smart material is defined as a material which has been atomically or molecularly engineered in such a way that the microstructure itself is imbued with embedded sensors, actuators, and control mechanisms, giving it the capability of sensing and responding to external stimuli in a predetermined and controlled fashion. Programs in this area have involved technological advances in a number of scientific disciplines inclusive of materials science, chemistry, biotechnology, molecular electronics, nanotechnology, etc. These have encompassed research themes into the design of polymeric materials which are capable of altering their mechanical and electrical properties when exposed to specific molecular species, the synthesis of amphiphlic molecules with easily modified ferroelectric, photochromic and nonlinear properties, the design of stress sensitive molecules capable of monitoring damage and redistributing stresses in composites, and the merging of biological and chemical technologies to create assemblies with signal transduction properties. This presentation will highlight some of these activities.

  20. Waveguides in Thin Film Polymeric Materials

    NASA Technical Reports Server (NTRS)

    Sakisov, Sergey; Abdeldayem, Hossin; Venkateswarlu, Putcha; Teague, Zedric

    1996-01-01

    Results on the fabrication of integrated optical components in polymeric materials using photo printing methods will be presented. Optical waveguides were fabricated by spin coating preoxidized silicon wafers with organic dye/polymer solution followed by soft baking. The waveguide modes were studied using prism coupling technique. Propagation losses were measured by collecting light scattered from the trace of a propagation mode by either scanning photodetector or CCD camera. We observed the formation of graded index waveguides in photosensitive polyimides after exposure of UV light from a mercury arc lamp. By using a theoretical model, an index profile was reconstructed which is in agreement with the profile reconstructed by the Wentzel-Kramers-Brillouin calculation technique using a modal spectrum of the waveguides. Proposed mechanism for the formation of the graded index includes photocrosslinking followed by UV curing accompanied with optical absorption increase. We also developed the prototype of a novel single-arm double-mode interferometric sensor based on our waveguides. It demonstrates high sensitivity to the chance of ambient temperature. The device can find possible applications in aeropropulsion control systems.

  1. Oligonucleotide and Long Polymeric DNA Encoding

    SciTech Connect

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

    2003-11-24

    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 long molecule, errors in DNA sequence occur during hybridization and/or the subsequent enzymatic process. The work done on this project has resulted in a novel synthesis scheme that we call the parallel pyramid synthesis protocol, the development of a suit of computational tools to minimize and quantify errors in the synthesized DNA sequence, and experimental proof of this technique. The modeling consists of three interrelated modules: the bioinformatics code which determines the specifics of parallel pyramid synthesis for a given chain of long DNA, the thermodynamics code which tracks the products of DNA hybridization and polymerase extension during the later steps in the process, and the kinetics model which examines the temporal and spatial processes during one thermocycle. Most importantly, we conducted the first successful syntheses of a gene using small starting oligomers (tetramers). The synthesized sequence, 813 base pairs long, contained a 725 base pair gene, modified green fluorescent protein (mGFP), which has been shown to be a functional gene by cloning into cells and observing its green fluorescent product.

  2. Controlled release polymeric ocular delivery of acyclovir.

    PubMed

    Deshpande, Praful Balavant; Dandagi, Panchaxari; Udupa, Nayanabhirama; Gopal, Shavi V; Jain, Samata S; Vasanth, Surenalli G

    2010-01-01

    The aim of the present study was to formulate and evaluate controlled release polymeric ocular delivery of acyclovir. Reservoir-type ocular inserts were fabricated by sandwiching hydroxypropyl methylcellulose (HPMC) matrix film containing acyclovir between two rate controlling membranes of cellulose acetate phthalate (CAP). The solubility and dissolution rate of poorly soluble acyclovir was enhanced by preparing binary systems with beta-cyclodextrin and then incorporated into HPMC matrix. Nine formulations (AB-1 to AB-9) with varying ratio of HPMC (drug matrix) and CAP (rate controlling membrane) were developed and sterilized by gamma radiation. The formulations were subjected to various physico-chemical evaluations. The in vitro release profile of all the formulations showed a steady, controlled drug release up to 20 h with non-Fickian diffusion behavior. A high correlation coefficient found between in vitro/in vivo release rate studies. Formation of acyclovir complex was confirmed by differential scanning calorimetry. In addition, dissolution rate studies revealed improved solubility of acyclovir when complexed with beta-cyclodextrin. Stability studies showed that the ocular inserts could be stored safely at study storage conditions. In conclusion, the present study demonstrated controlled release formulation of acyclovir inserts for ocular delivery using biodegradable polymers. PMID:19772377

  3. Pressure-induced polymerization in substituted acetylenes

    SciTech Connect

    Chellappa, Raja S.; Dattelbaum, Dana M.; Sheffield, Stephen; Robbins, David (LANL)

    2012-04-10

    A fundamental understanding of shock-induced chemical reactions in organics is still lacking and there are limited studies devoted to determining reaction mechanisms, evolution of bonding, and effect of functional group substitutions. The fast timescale of reactions occurring during shock compression create significant experimental challenges (diagnostics) to fully quantify the mechanisms involved. Static compression combined with temperature provides a complementary route to investigate the equilibrium phase space and metastable intermediates under extreme P-T conditions. In this study, we present our results from our ongoing high pressure in situ synchrotron x-ray diffraction experiments on substituted acetylenes: tert-butyl acetylene [TBA: (CH{sub 3}){sub 3}-C=CH] and ethynyl trimethylsilane [ETMS: (CH{sub 3}){sub 3}-SiC=CH]. We observed that the onset pressure of chemical reactions (at room temperature) in these compounds is higher under static compression (TBA: 12 GPa and ETMS: 17.6 GPa) when compared to shock input pressures (TBA: 6.1 GPa and ETMS: 6.6 GPa). At elevated temperatures, reactivity was observed to occur at pressures comparable to shock conditions. The products were polymeric in nature, recovered to ambient conditions with little degradation.

  4. Pressure-induced Polymerization in Substituted Acetylenes

    NASA Astrophysics Data System (ADS)

    Chellappa, Raja; Dattelbaum, Dana; Sheffield, Stephen

    2012-02-01

    A fundamental understanding of shock-induced chemical reactions in organics is still lacking and there are limited studies devoted to determining reaction mechanisms, evolution of bonding, and effect of functional group substitutions. The fast timescale of reactions occurring during shock compression create significant experimental challenges (diagnostics) to fully quantify the mechanisms involved. Static compression provides a complementary route to investigate the equilibrium phase space and metastable intermediates during high pressure chemistry, although at a much slower timescale. In this study, we present our results from our ongoing high pressure in situ synchrotron x-ray diffraction and vibrational spectroscopy experiments on substituted acetylenes: tert-butyl acetylene [TBA: (CH3)3-C?CH] and ethynyl trimethylsilane [ETMS: (CH3)3-SiC?CH]. We observed that the onset pressure of chemical reactions (at room temperature) in these compounds is significantly higher in static compression (TBA: 11 GPa and ETMS: 26 GPa) when compared to shock input pressures (TBA: 6.1 GPa and ETMS: 6.6 GPa). The products were polymeric in nature, recovered to ambient conditions with little degradation and fully characterized using spectroscopy, calorimetry, and other techniques to identify reaction mechanisms.

  5. Pressure-induced polymerization in substituted acetylenes

    NASA Astrophysics Data System (ADS)

    Chellappa, Raja; Dattelbaum, Dana M.; Sheffield, S. A.; Robbins, David L.

    2012-03-01

    A fundamental understanding of shock-induced chemical reactions in organics is still lacking and there are limited studies devoted to determining reaction mechanisms, evolution of bonding, and effect of functional group substitutions. The fast timescale of reactions occurring during shock compression create significant experimental challenges (diagnostics) to fully quantify the mechanisms involved. Static compression combined with temperature provides a complementary route to investigate the equilibrium phase space and metastable intermediates under extreme P-T conditions. In this study, we present our results from our ongoing high pressure in situ synchrotron x-ray diffraction experiments on substituted acetylenes: tert-butyl acetylene [TBA: (CH3)3-C=CH] and ethynyl trimethylsilane [ETMS: (CH3)3-SiC=CH]. We observed that the onset pressure of chemical reactions (at room temperature) in these compounds is higher under static compression (TBA: 12 GPa and ETMS: 17.6 GPa) when compared to shock input pressures (TBA: 6.1 GPa and ETMS: 6.6 GPa). At elevated temperatures, reactivity was observed to occur at pressures comparable to shock conditions. The products were polymeric in nature, recovered to ambient conditions with little degradation.

  6. Pressure-induced Polymerization in Substituted Acetylenes

    NASA Astrophysics Data System (ADS)

    Chellappa, Raja; Dattelbaum, Dana; Sheffield, Stephen; Robbins, David

    2011-06-01

    A fundamental understanding of shock-induced chemical reactions in organics is still lacking and there are limited studies devoted to determining reaction mechanisms, evolution of bonding, and effect of functional group substitutions. The fast timescale of reactions occurring during shock compression create significant experimental challenges (diagnostics) to fully quantify the mechanisms involved. Static compression provides a complementary route to investigate the equilibrium phase space and metastable intermediates during high pressure chemistry, although at a much slower timescale. In this study, we present our results from our ongoing high pressure in situ synchrotron x-ray diffraction and vibrational spectroscopy experiments on substituted acetylenes: tert-butyl acetylene [TBA: (CH3)3 -C ?CH] and ethynyl trimethylsilane [ETMS: (CH3)3 -Si ?CH]. We observed that the onset pressure of chemical reactions (at room temperature) in these compounds is significantly higher in static compression (TBA: 11 GPa and ETMS: 26 GPa) when compared to shock input pressures (TBA: 6.1 GPa and ETMS: 6.6 GPa). The products were polymeric in nature, recovered to ambient conditions with little degradation and fully characterized using spectroscopy, calorimetry, and other techniques to identify reaction mechanisms. LDRD-DR (PI: Dana Dattelbaum)

  7. Dead Sea Minerals loaded polymeric nanoparticles.

    PubMed

    Dessy, Alberto; Kubowicz, Stephan; Alderighi, Michele; Bartoli, Cristina; Piras, Anna Maria; Schmid, Ruth; Chiellini, Federica

    2011-10-15

    Therapeutic properties of Dead Sea Water (DSW) in the treatment of skin diseases such as atopic dermatitis, psoriasis and photo aging UV damaged skin have been well established. DSW is in fact rich in minerals such as calcium, magnesium, sodium, potassium, zinc and strontium which are known to exploit anti-inflammatory effects and to promote skin barrier recovery. In order to develop a Dead Sea Minerals (DSM) based drug delivery system for topical therapy of skin diseases, polymeric nanoparticles based on Poly (maleic anhydride-alt-butyl vinyl ether) 5% grafted with monomethoxy poly(ethyleneglycol) 2000 MW (PEG) and 95% grafted with 2-methoxyethanol (VAM41-PEG) loaded with DSM were prepared by means of a combined miniemulsion/solvent evaporation process. The resulting nanoparticles were characterized in terms of dimension, morphology, biocompatibility, salt content and release. Cytocompatible spherical nanoparticles possessing an average diameter of about 300 nm, a time controlled drug release profile and a high formulation yield were obtained. PMID:21676600

  8. Polymeric Bladder for Storing Liquid Oxygen

    NASA Technical Reports Server (NTRS)

    Walker, David H.; Harvey, Andrew C.; Leary, William

    2009-01-01

    A proposed system for storing oxygen in liquid form and dispensing it in gaseous form is based on (1) initial subcooling of the liquid oxygen; (2) containing the liquid oxygen in a flexible vessel; (3) applying a gas spring to the flexible vessel to keep the oxygen compressed above the saturation pressure and, thus, in the liquid state; and (4) using heat leakage into the system for vaporizing the oxygen to be dispensed. In a typical prior system based on these principles, the flexible vessel is a metal bellows housed in a rigid tank, and the gas spring consists of pressurized helium in the tank volume surrounding the bellows. Unfortunately, the welds in the bellows corrugations are subject to fatigue, and, because bellows have large ullage, a correspondingly large fraction of the oxygen content cannot be expelled. In the proposed system, the flexible vessel would be a bladder made of a liquid- crystal polymer (LCP). (LCPs are strong and compatible with liquid oxygen.) In comparison with a metal bellows, a polymeric bladder would have less ullage and would weigh less. In experiments involving fatigue cycling at liquid-nitrogen temperatures, two LCPs were found to be suitable for this application.

  9. Simulation of polymeric integrated Young interferometer sensor

    NASA Astrophysics Data System (ADS)

    Kusko, Mihai

    2012-06-01

    The use of photonic integrated circuits made of polymer materials represents a solution for obtaining low-cost immunosensors for fast clinical diagnosis. In this paper are presented the simulation studies of a photonic integrated sensor on silicon substrate based on the configuration of Young interferometer. The core and cladding materials of the photonic sensor are polymeric materials. This sensor works for the detection of the surrounding medium refractive index variation and also for the detection of a thin adsorbed layer on the sensor surface. Simulations are performed using the Beam Propagation Method and 2D mode solvers for obtaining the relation between the variation of the surrounding refractive index or the presence of an adsorbed layer and the displacement of the interference fringe position. From this dependence one can calculate the sensor sensitivity and also one can estimate the detection limit. In order to obtain reliable results it is necessary to have waveguides which presents single mode operation regime both on the horizontal and vertical direction. Rib waveguides which are more prone for satisfying single mode condition were considered. The suppression of the higher order modes on the vertical direction by leakage in the silicon substrate is made by adjusting the thickness of the silicon dioxide buffer layer.

  10. Polymeric components for all-optical networks

    NASA Astrophysics Data System (ADS)

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

    2000-04-01

    All-optical networks that exhibit high speed, high capacity, scalability, configurability, and transparency are becoming a reality through the exploitation of the unique properties of fiber and integrated optics. An advanced polymeric waveguide technology was developed for affordable passive and active integrated optical elements that address the needs of these networks. We engineered high-performance organic polymers that can be readily made into photonic circuits of controlled numerical apertures and geometries. These materials are formed from highly-crosslinked acrylate monomers with specific linkages that determine properties such as flexibility, robustness, optical loss, thermal stability, and humidity resistance. These monomers are intermiscible, providing for precise continuous adjustment of the refractive index over a wide range. In polymer form, they exhibit state-of-the-art optical loss values, suppressed polarization effects, and exceptional environmental stability. A wide range of rigid and flexible substrates can be used. The devices we describe include demultiplexers, tunable wavelength filters, digital optical switches, and variable optical attenuators.

  11. Hyperbranched Polycarbosilanes and Polycarbosiloxanes via Hydrosilylation Polymerization

    NASA Astrophysics Data System (ADS)

    Schüle, Hanna; Frey, Holger

    As pointed out in Chapter 1, silicon chemistry offers a variety of quantitative, high yielding reactions, i.e. hydrosilylation, Grignard reactions and controlled condensation of silanols that are suitable for the synthesis of organic-inorganic hybrid materials. Thus, silicon-based chemistry played a prominent role in the evolution of dendrimer chemistry [1-4], and it did not take long until the first examples of silicon-containing hyperbranched polymers were reported. Hyperbranched polymers are generally prepared by one-pot polymerization of ABx (x ? 2) (see also Section 1.2) monomers and are characterized by polydispersity as well as a randomly branched structure due to the multifunctional polycondensation or polyaddition process. The statistical treatment of such polyfunctional polycondensations was achieved in the early 1950s by Flory, who calculated both molecular weights and polydispersity in such systems, as is discussed in Section 13.3 of this chapter [5, 6]. The properties of hyperbranched polymers are significantly different from their linear analogs and are characterized by good solubility, low viscosity and a large number of end-groups that can be used for further functionalization. Despite imperfections in branching and structure of hyperbranched polymers compared to monodisperse dendrimers, these properties render them easily accessible competitors for dendrimers, particularly in applications where structural perfection is not a mandatory prerequisite.

  12. Confocal Raman Imaging of Polymeric Materials

    NASA Astrophysics Data System (ADS)

    Schmidt, Ute; Müller, Jörg; Koenen, Joachim

    Polymers play an essential role in modern materials science. Due to the wide variety of mechanical and chemical properties of polymers, they are used in almost every field of application and are still a dynamic area in the development of new materials with demanding requirements. Raman spectroscopy is one of the standard characterization techniques used to uniquely determine the chemical composition of a polymer. Modern materials, however, are generally heterogeneous, in which various chemical components or polymorphs of the same chemical species can be present in a very small sample volume. For the analysis of such heterogeneous materials, the combination of Raman spectroscopy with confocal microscopy delivers information about the spatial distribution of the various chemical species with a resolution down to 200 nm. The aim of this contribution is to demonstrate the power of confocal Raman imaging for the characterization of heterogeneous polymeric materials. The first section will deal with polymorphs of polypropylene in polymer films, followed by the nondestructive analysis of polymer blends. A later section will deal with multi-layer polymer coatings and paints and finally various additives to polymer matrices will be discussed.

  13. Switchable Adhesion from Bicomponent Polymeric Brushes

    NASA Astrophysics Data System (ADS)

    Retsos, Haris; Gorodyska, Ganna; Creton, Costantino

    2005-03-01

    We investigated the adhesive and wetting properties of bicomponent polymeric brushes made from end functionalized hydrophilic and hydrophobic polymer chains. The molecular organization of the mixed brush could be varied reversibly by exposure to selective solvents for the two polymers. Adhesive properties were tested by debonding a flat ended probe from soft pressure-sensitive-adhesives (hydrophobic & hydrophilic) and wetting properties were tested by contact angle measurements of water & diiodomethane droplets. The bicomponent brushes were chemically grafted on silicon wafers from end-functionalized chains. Wetting experiments were done directly on the wafers while for adhesion experiments, the wafers were glued on the flat end of the probe prior to the tests. In all cases the organization of the bicomponent brush could be modified reproducibly and reversibly by exposure to selective solvents. Following this strategy we succeeded to create remarkably stable adaptive polymer surfaces that can modify their adhesion and wetting reversibly and also tune them by varying the ratio of the bicomponent brush layer.

  14. Spontaneous polymerization and chain microstructure evolution in high-temperature solution polymerization of n-butyl acrylate

    Microsoft Academic Search

    Felix S. Rantow; Masoud Soroush; Michael C. Grady; Georgios A. Kalfas

    2006-01-01

    This study concerns understanding of the underlying mechanistic pathways in high temperature solution polymerization of n-butyl acrylate (nBA) in the absence of added thermal initiators. The particular system of interest is the batch polymerization of nBA in xylene at temperatures between 140 and 180°C with initial monomer content between 20 and 40wt%. A mechanistic process model is developed to capture

  15. Large Scale Laser Two-Photon Polymerization Structuring for Fabrication of Artificial Polymeric Scaffolds for Regenerative Medicine

    Microsoft Academic Search

    M. Malinauskas; V. Purlys; A. Zukauskas; M. Rutkauskas; P. Danilevicius; D. Paipulas; G. Bickauskaite; L. Bukelskis; D. Baltriukiene; R. Sirmenis; A. Gaidukeviciute; V. Bukelskiene; R. Gadonas; V. Sirvydis; A. Piskarskas

    2010-01-01

    We present a femtosecond Laser Two-Photon Polymerization (LTPP) system of large scale three-dimensional structuring for applications in tissue engineering. The direct laser writing system enables fabrication of artificial polymeric scaffolds over a large area (up to cm in lateral size) with sub-micrometer resolution which could find practical applications in biomedicine and surgery. Yb:KGW femtosecond laser oscillator (Pharos, Light Conversion. Co.

  16. Aggregate breakdown of nanoparticulate titania

    NASA Astrophysics Data System (ADS)

    Venugopal, Navin

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

  17. Self-Propagating Frontal Polymerization in Water at Ambient Pressure

    NASA Technical Reports Server (NTRS)

    Olten, Nesrin; Kraigsley, Alison; Ronney, Paul D.

    2003-01-01

    Advances in polymer chemistry have led to the development of monomers and initiation agents that enable propagating free-radical polymerization fronts to exist. These fronts are driven by the exothermicity of the polymerization reaction and the transport of heat from the polymerized product to the reactant monomer/solvent/initiator solution. The thermal energy transported to the reactant solution causes the initiator to decompose, yielding free radicals, which start the free radical polymerization process as discussed in recent reviews. The use of polymerization processes based on propagating fronts has numerous applications. Perhaps the most important of these is that it enables rapid curing of polymers without external heating since the polymerization process itself provides the high temperatures necessary to initiate and sustain polymerization. This process also enables more uniform curing of arbitrarily thick samples since it does not rely on heat transfer from an external source, which will necessarily cause the temperature history of the sample to vary with distance from the surface according to a diffusion-like process. Frontal polymerization also enables filling and sealing of structures having cavities of arbitrary shape without having to externally heat the structure. Water at atmospheric pressure is most convenient solvent to employ and the most important for practical applications (because of the cost and environmental issues associated with DMSO and other solvents). Nevertheless, to our knowledge, steady, self-propagating polymerization fronts have not been reported in water at atmospheric pressure. Currently, polymerization fronts require a high boiling point solvent (either water at high pressures or an alternative solvent such as dimethyl sulfoxide (DMSO) (boiling point 189 C at atmospheric pressure.) Early work on frontal polymerization, employed pressures up to 5000 atm in order to avoid boiling of the monomer/solvent/initiator solution. High boiling point solutions are needed because in order to produce a propagating front, a high front temperature is needed to produce sufficiently rapid decomposition of the free radical initiator and subsequent free radical polymerization and heat release at a rate faster than heat losses remove thermal energy from the system. (While the conduction heat loss rate increases linearly with temperature, the free radical initiator decomposition is a high activation energy process whose rate increases much more rapidly than linearly with temperature, thus as the temperature decreases, the ratio of heat loss to heat generation increases, eventually leading to extinction of the front if the temperature is too low.) In order to obtain atmospheric pressure frontal polymerization in water, it is necessary to identify a monomer/initiator combination that is water soluble and will not extinguish even when the peak temperature (T*) is less than 100 C. In this work acrylic acid (AA) was chosen as the monomer because is it one of the most reactive monomers and can polymerize readily at low temperatures even without initiators. Ammonium persulfate (AP) was chosen as the initiator because it decomposes readily at low temperatures, produces relatively few bubbles and is commercially available. The propagation rates and extinction conditions of the fronts are studied for a range of AA and AP concentrations. Small amounts of fumed silica powder (Cab-o-sil, Cabot Corporation) were added to the solutions to inhibit buoyancy induced convection in the solutions; future studies will investigate the effects of buoyant convection within the solutions.

  18. Schurian vector space categories of polynomial growth

    E-print Network

    Bielefeld, University of

    space categories over an algebraically closed field. A list of all infinitely sincere schurian vector; ') of dimension vector ~ d is called sincere if d 0 6= 0 and d Y 6= 0 for all Y 2 ind K: The vector space category K is called sincere if there exists a sincere indecomposable factor space of K. The vector space

  19. Schurian vector space categories of polynomial growth

    E-print Network

    Bekkert, Viktor

    space categories. A list of all infinitely sincere schurian vector space categories of polynomial growth, ) of dimension vector d is called sincere if d0 = 0 and dY = 0 for all Y ind K. A vector space category K is called sincere if there exists a sincere indecomposable factor space of K. The vector space category K

  20. Color edge detection using vector order statistics

    Microsoft Academic Search

    Panos E. Trahanias; Anastasios N. Venetsanopoulos

    1993-01-01

    Abstruct- Color edge detection based on vector order statistics is proposed in this work In this approach, a color image is treated as a vector field and the edge information carried directly by the vectors is exploited. A class of color edge detectors is defined as the minimum over the magnitudes of linear combinations of the sorted vector samples. From

  1. Vector Algebra 13.1. Basic Concepts

    E-print Network

    McKay, Benjamin

    CHAPTER 13 Vector Algebra Ü13.1. Basic Concepts A vector V in the plane or in space is an arrow: it is determined by its length, denoted V and its direction. Two arrows represent the same vector if they have the same length and are parallel (see figure 13.1). We use vectors to represent entities which

  2. Polymerization in narrow fractions of coal tar wash-oil

    SciTech Connect

    Volkov, E.L.; Akulov, P.V.; Zhilyaev, Yu. A.; Samarkina, A.A.

    1981-01-01

    Certain changes take place in coal tar wash-oil as it is circulated through the benzol hydrocarbons recovery and distillation cycle. It undergoes condensation, loses much of its light distillates content and attains a higher cp. One major problem with coal tar wash-oil is its tendency to form polymers as it circulates through the processing cycle and comes into contact with coke-oven gas. The polymerization rate is affected by a number of factors relating to the composition of the wash-oil, the concentrations in the coke-oven gas of components capable of promoting condensation and the operating conditions in the processing cycle. It has been shown that H/sub 2/S and O/sub 2/ in the coke-oven gas greatly accelerate polymerization processes in the wash-oil. Cyanide compounds and oxides of nitrogen also impair the quality of coal tar wash-oil.The deterioration of wash-oil in circulation leads to a serious rise in its cp and the rapid build-up of deposits on the scrubber packings, with serious effects on the performances of the benzol recovery and distillation sections. We have attempted to evaluate the polymerization tendencies of individual narrow wash-oil fractions. The tests were planned to simulate the conditions under which wash-oil can condense and polymerize. The results show that polymerization proceeds most rapidly in the fractions boiling at 280 to 285 and 285 to 295/sup 0/C. They rapidly increase in density and viscosity and lower the quality of the entire oil. The most stable fractions in respect of polymerization are those boiling up to 270/sup 0/C and up to 280/sup 0/C. These tests have shown that wash-oil boiling up to 280/sup 0/C is the least liable to polymerization; its processing quality is superior and the specific consumption can thus be reduced.

  3. Elliptic-symmetry vector optical fields.

    PubMed

    Pan, Yue; Li, Yongnan; Li, Si-Min; Ren, Zhi-Cheng; Kong, Ling-Jun; Tu, Chenghou; Wang, Hui-Tian

    2014-08-11

    We present in principle and demonstrate experimentally a new kind of vector fields: elliptic-symmetry vector optical fields. This is a significant development in vector fields, as this breaks the cylindrical symmetry and enriches the family of vector fields. Due to the presence of an additional degrees of freedom, which is the interval between the foci in the elliptic coordinate system, the elliptic-symmetry vector fields are more flexible than the cylindrical vector fields for controlling the spatial structure of polarization and for engineering the focusing fields. The elliptic-symmetry vector fields can find many specific applications from optical trapping to optical machining and so on. PMID:25321015

  4. Flexible pressure sensor on polymeric materials

    NASA Astrophysics Data System (ADS)

    Teng, M. F.; Hariz, A.; Hsu, H. Y.; Omari, T.

    2007-12-01

    In this work we investigate the use of polymer materials as a basis for fabrication of a novel type of pressure sensors for use in medical diagnostics. Experience with solid-state micro-electromechanical systems (MEMS) sensors has proved them to provide a number of desirable characteristics in sensory applications, including miniaturization and low production cost. However, owing to their rigidity, and bio-incompatibility, the solid-state sensors are not ideally suited for applications in biomedical implants and in-vivo diagnostics. They often require extra encapsulation protection, and thus diminishing their sensitivity and selectivity. Polymeric materials such as polyimide have been for a number of years utilized to manufacture flexible printed circuit board (FPCB) and membrane switches used in computer keyboards. Related work on polymer electronics has shown feasible the fabrication of micro sensors using polymer materials. In this paper we show that combining the polymer thick-film (PTF) technology with the MEMS micromachining process yields a workable platform for the realization of a flexible sensor for pressure measurements. We will show simulation results that establish the validity of the model and which will confirm the promise that these devices hold for future biomedical instrumentations. Recent sensor research by another group demonstrated a multi-model tactile sensor which consists of hardness, temperature, and thermal conductivity sensing features, all combined and built on a polymer substrate [1] and [2]. Advantages of using polymer materials include flexibility, biocompatibility, robust characteristics, reduced fabrication complexity and reduced production costs, as well as the use of environmentally friendly manufacturing.

  5. Polymerization processes in simulated free space conditions

    NASA Astrophysics Data System (ADS)

    Kondyurin, A.; Lauke, B.

    2003-09-01

    The creation of large-size space constructions by the way of deployment structures needs a rigidization of shell material after unfolding. The best way for rigidization is chemical reaction. But there is a negative influence of space factors on a liquid polymer matrix and on the polymerisation process. We suggest that the free space factors can initiate the polymerisation reaction, for example a curing reaction of epoxy resin composition. This paper contains the results of experiments on polymerization processes under action of separate free space factors: vacuum and plasma action. For the simulation of space plasma a discharge of microwave plasma and radio-frequency plasma were used. Structures of polymer materials cured under plasma and in usual curing conditions were compared. The results on degradation processes in liquid epoxy resin under plasma action were taken into account at the curing kinetic study. The formation of new active groups in liquid composition under plasma action and the ability of new groups to take part in curing reaction was analysed. The process of layers mixing in liquid epoxy resin during plasma action was observed. The mixing of oxidised layers with initial bulk layers of resin leads to an acceleration of the curing reaction. Due to layers mixing the plasma treatment becomes a method for bulk modification of polymers. The way of utilisation of negative free space factors for the curing process of composite materials in free space is proposed. In comparison with plasma discharge the space plasma can be used for polymerisation process of a composite material on Earth orbit.

  6. Endocytic internalization of nanoparticles into polymeric vesicles.

    NASA Astrophysics Data System (ADS)

    Kroeger, Anja; Jaskiewicz, Karmena; Larsen, Antje; Fytas, George

    2011-03-01

    The monitoring of transport through cell membranes is essential for proper functioning of all living organisms. Poorly understood mechanisms of endocytosis have become the focus of intense investigations. Here we present a photon correlation spectroscopy study of the uptake of polystyrene nanoparticles (hydrodynamic radius, Rh = 16nm) by poly(dimethylsiloxane)-b-poly(2-methyloxazoline) polymersomes (Rh = 150nm) in aqueous solution. The relaxation function C(q,t) for a particle/polymersome mixture with a molar ratio 100:1 at different scattering wave vectors (q) reveal the presence of free and bound particles. Both the experimental form factor P(q) and the effective diffusion coefficient D(q) of the polymersome in the q-range of 0.005- 0.033 nm -1 are consistently described by modeling these q-patterns by a filled polymersome with about 30 particles under the examined conditions. The emerged picture is supported by cryo-TEM imaging.

  7. 12.2 Vectors in 2D and 3D 1. Vector and Magnitude

    E-print Network

    Anderson, Douglas R.

    12.2 Vectors in 2D and 3D 1. Vector and Magnitude: 2. Examples: 3. Equivalent Vectors: 4. Vector a vector with magnitude 6 in the direction of 2, 2, -1 . 19. The thrust of an airplane's engine produces, in other words in the direction of -i? 21. Two forces F1 and F2 with magnitudes 10 lbs and 12 lbs

  8. Arrow/Vector Plots 6.1 Quiver/Arrow/Vector Plots/Porcupine Plot

    E-print Network

    Boyd, John P.

    Chapter 6 Arrow/Vector Plots 6.1 Quiver/Arrow/Vector Plots/Porcupine Plot To plot vectors, it is useful to draw arrows such that the direction in which the arrow points is the direction of the vector. Unfortunately, there is no standard name for this type of plot: "arrow", "quiver" and "vector" are all in common

  9. Boosting with Averaged Weight Vectors

    NASA Technical Reports Server (NTRS)

    Oza, Nikunj C.; Clancy, Daniel (Technical Monitor)

    2002-01-01

    AdaBoost is a well-known ensemble learning algorithm that constructs its constituent or base models in sequence. A key step in AdaBoost is constructing a distribution over the training examples to create each base model. This distribution, represented as a vector, is constructed to be orthogonal to the vector of mistakes made by the previous base model in the sequence. The idea is to make the next base model's errors uncorrelated with those of the previous model. Some researchers have pointed out the intuition that it is probably better to construct a distribution that is orthogonal to the mistake vectors of all the previous base models, but that this is not always possible. We present an algorithm that attempts to come as close as possible to this goal in an efficient manner. We present experimental results demonstrating significant improvement over AdaBoost and the Totally Corrective boosting algorithm, which also attempts to satisfy this goal.

  10. Characterization of polymeric microneedle arrays for transdermal drug delivery.

    PubMed

    Demir, Yusuf K; Akan, Zafer; Kerimoglu, Oya

    2013-01-01

    Microfabrication of dissolvable, swellable, and biodegradable polymeric microneedle arrays (MNs) were extensively investigated based in a nano sensitive fabrication style known as micromilling that is then combined with conventional micromolding technique. The aim of this study was to describe the polymer selection, and optimize formulation compounding parameters for various polymeric MNs. Inverse replication of micromilled master MNs reproduced with polydimethylsiloxane (PDMS), where solid out of plane polymeric MNs were subsequently assembled, and physicochemically characterized. Dissolvable, swellable, and biodegradable MNs were constructed to depth of less than 1 mm with an aspect ratio of 3.6, and 1/2 mm of both inter needle tip and base spacing. Micromolding step also enabled to replicate the MNs very precisely and accurate. Polymeric microneedles (MN) precision was ranging from ± 0.18 to ± 1.82% for microneedle height, ± 0.45 to ± 1.42% for base diameter, and ± 0.22 to ± 0.95% for interbase spacing. Although dissolvable sodium alginate MN showed less physical robustness than biodegradable polylactic-co-glycolic acid MN, their thermogravimetric analysis is of promise for constructing these polymeric types of matrix devices. PMID:24194879

  11. Pressure Effects on the Abiotic Polymerization of Glycine

    NASA Astrophysics Data System (ADS)

    Ohara, Shohei; Kakegawa, Takeshi; Nakazawa, Hiromoto

    2007-06-01

    Polymerization experiments were performed using dry glycine under various pressures of 5 100 MPa at 150°C for 1 32 days. The series of experiments was carried out under the assumption that the pore space of deep sediments was adequate for dehydration polymerization of pre-biotic molecules. The products show various colors ranging from dark brown to light yellow, depending on the pressure. Visible and infrared spectroscopy reveal that the coloring is the result of formation of melanoidins at lower pressures. High-performance liquid chromatography and mass spectrometry analyses of the products show that: (1) glycine in all the experimental runs oligomerizes from 2-mer to 10-mer; (2) the yields are dependent on pressure up to 25 MPa and decrease slightly thereafter; and (3) polymerization progressed for the first 8 days, while the amounts of oligomers remained constant for longer-duration runs of up to 32 days. These results suggest that pressure inhibits the decomposition of amino acids and encourages polymerization in the absence of a catalyst. Our results further imply that abiotic polymerization could have occurred during diagenesis in deep sediments rather than in oceans.

  12. High-temperature-pressure polymerized resin-infiltrated ceramic networks.

    PubMed

    Nguyen, J F; Ruse, D; Phan, A C; Sadoun, M J

    2014-01-01

    The aim of this study was to produce composite blocks (CB) for CAD/CAM applications by high-temperature-pressure (HT/HP) polymerization of resin-infiltrated glass-ceramic networks. The effect of network sintering and the absence/presence of initiator was investigated. Mechanical properties were determined and compared with those of Paradigm MZ100 (3M ESPE) blocks and HT/HP polymerized experimental "classic" CB, in which the filler had been incorporated by conventional mixing. The networks were made from glass-ceramic powder (VITA Zahnfabrik) formed by slip casting and were either sintered or not. They were silanized, infiltrated by urethane dimethacrylate, with or without initiator, and polymerized under HT/HP (300 MPa, 180°C) to obtain resin-infiltrated glass-ceramic network (RIGCN) CB. HT/HP polymerized CB were also made from an experimental "classic" composite. Flexural strength (?f), fracture toughness (KIC), and Vickers hardness were determined and analyzed by one- or two-way analysis of variance (ANOVA), Scheffé multiple-means comparisons (? = 0.05), and Weibull statistics (for ?f). Fractured surfaces were characterized with scanning electron microscopy. The mechanical properties of RIGCN CB were significantly higher. Sintering induced significant increases in ?f and hardness, while the initiator significantly decreased hardness. The results suggested that RIGCN and HT/HP polymerization could be used to obtain CB with superior mechanical properties, suitable for CAD/CAM applications. PMID:24186559

  13. Factors affecting toxicity and efficacy of polymeric nanomedicines

    SciTech Connect

    Igarashi, Eiki [NanoCarrier Co., Ltd., Chiba 277-0882 (Japan)], E-mail: igarashi@nanocarrier.co.jp

    2008-05-15

    Nanomedicine is the application of nanotechnology to medicine. The purpose of this article is to review common characteristics of polymeric nanomedicines with respect to passive targeting. We consider several biodegradable polymeric nanomedicines that are between 1 and 100 nm in size, and discuss the impact of this technology on efficacy, pharmacokinetics, toxicity and targeting. The degree of toxicity of polymeric nanomedicines is strongly influenced by the biological conditions of the local environment, which influence the rate of degradation or release of polymeric nanomedicines. The dissemination of polymeric nanomedicines in vivo depends on the capillary network, which can provide differential access to normal and tumor cells. The accumulation of nanomedicines in the microlymphatics depends upon retention time in the blood and extracellular compartments, as well as the type of capillary endothelium surrounding specific tissues. Finally, the toxicity or efficacy of intact nanomedicines is also dependent upon tissue type, i.e., non-endocrine or endocrine tissue, spleen, or lymphatics, as well as tumor type.

  14. High-temperature-pressure Polymerized Resin-infiltrated Ceramic Networks

    PubMed Central

    Nguyen, J.F.; Ruse, D.; Phan, A.C.; Sadoun, M.J.

    2014-01-01

    The aim of this study was to produce composite blocks (CB) for CAD/CAM applications by high-temperature-pressure (HT/HP) polymerization of resin-infiltrated glass-ceramic networks. The effect of network sintering and the absence/presence of initiator was investigated. Mechanical properties were determined and compared with those of Paradigm MZ100 (3M ESPE) blocks and HT/HP polymerized experimental “classic” CB, in which the filler had been incorporated by conventional mixing. The networks were made ??from glass-ceramic powder (VITA Zahnfabrik) formed by slip casting and were either sintered or not. They were silanized, infiltrated by urethane dimethacrylate, with or without initiator, and polymerized under HT/HP (300 MPa, 180°C) to obtain resin-infiltrated glass-ceramic network (RIGCN) CB. HT/HP polymerized CB were also made from an experimental “classic” composite. Flexural strength (?f), fracture toughness (KIC), and Vickers hardness were determined and analyzed by one- or two-way analysis of variance (ANOVA), Scheffé multiple-means comparisons (? = 0.05), and Weibull statistics (for ?f). Fractured surfaces were characterized with scanning electron microscopy. The mechanical properties of RIGCN CB were significantly higher. Sintering induced significant increases in ?f and hardness, while the initiator significantly decreased hardness. The results suggested that RIGCN and HT/HP polymerization could be used to obtain CB with superior mechanical properties, suitable for CAD/CAM applications. PMID:24186559

  15. Polymeric materials synthesis and processing in supercritical carbon dioxide

    SciTech Connect

    DeSimone, J.M. [Univ. of North Carolina, Chapel Hill, NC (United States)

    1995-12-31

    Fluoropolymers are used in technologically demanding applications because of their high-performance properties. An impediment to the synthesis of commercially available fluoropolymers is their general insolubility in most solvents except chlorofluorocarbons (CFC`s). The environmental concerns about CFC`s can be avoided by preparing fluoropolymers in supercritical fluids (SCF`s). The homogeneous solution homo- and copolymerization of highly fluorinated acrylic, styrenic and olefinic monomers in SC CO{sub 2} using free radical methods will be discussed. Homogeneous solution polymerization studies allowed us to consider heterogeneous polymerizations in a CO{sub 2} continuous phase. Conventional heterogeneous polymerization of unsaturated monomers is performed in either aqueous or organic dispersing media with addition of surfactants. An environmentally responsible alternative to aqueous and organic dispersing media for heterogeneous polymerizations utilizes SC CO{sub 2} in conjunction with molecularly engineered amphiphilic molecules designed to be interfacially active in CO{sub 2}. Conventional lipophilic monomers can be polymerized heterogeneously using conventional initiators in liquid, and SC CO{sub 2} in the presence of added stabilizer, to form stable emulsions of monodisperse, micron-size spherical particles. Quantitative yields can be achieved. This process opens the way to new structured latexes, composite materials, and interpenetrating polymer networks not accessible by conventional methods.

  16. Requirements for airborne vector gravimetry

    NASA Technical Reports Server (NTRS)

    Schwarz, K. P.; Colombo, O.; Hein, G.; Knickmeyer, E. T.

    1992-01-01

    The objective of airborne vector gravimetry is the determination of the full gravity disturbance vector along the aircraft trajectory. The paper briefly outlines the concept of this method using a combination of inertial and GPS-satellite data. The accuracy requirements for users in geodesy and solid earth geophysics, oceanography and exploration geophysics are then specified. Using these requirements, accuracy specifications for the GPS subsystem and the INS subsystem are developed. The integration of the subsystems and the problems connected with it are briefly discussed and operational methods are indicated that might reduce some of the stringent accuracy requirements.

  17. Vector models for dark energy

    E-print Network

    Jose Beltran Jimenez; Antonio L. Maroto

    2008-07-16

    We explore the possibility that the present stage of accelerated expansion of the universe is due to the presence of a cosmic vector field. We show that vector theories allow for the generation of an accelerated phase without the introduction of potential terms or unnatural scales in the Lagrangian. We propose a particular model with the same number of parameters as LCDM and excellent fits to SNIa data. The model is scaling during radiation era, with natural initial conditions, thus avoiding the cosmic coincidence problem. Upcoming observations will be able to clearly discriminate it from standard LCDM cosmology

  18. Vector 1 Vector 2 Zone Axis (h k l) d (h k l) d [U V W] Angle

    E-print Network

    Cambridge, University of

    ------------------------------------------------------------------------------ Vector 1 Vector 2 of d-spacings obtained from two reciprocal lattice vectors, and the acute angle between these vectors. If the camera constant is unknown, then the ratio of the vectors may be used instead

  19. 75 FR 70254 - Typographical Error in Summary Notice of Filing in Docket for Polymerized Fatty Acid Esters With...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-17

    ...Filing in Docket for Polymerized Fatty Acid Esters With Aminoalcohol Alkoxylates...Petition (PP) 0E7699 for polymerized fatty acid esters with aminoalcohol alkoxylates...Petition (PP) 0E7699 for polymerized fatty acid esters with aminoalcohol...

  20. Polymerization of tellurophene derivatives by microwave-assisted palladium-catalyzed ipso-arylative polymerization.

    PubMed

    Park, Young S; Wu, Qin; Nam, Chang-Yong; Grubbs, Robert B

    2014-09-26

    We report the synthesis of a tellurophene-containing low-bandgap polymer, PDPPTe2T, by microwave-assisted palladium-catalyzed ipso-arylative polymerization of 2,5-bis[(?-hydroxy-?,?-diphenyl)methyl]tellurophene with a diketopyrrolopyrrole (DPP) monomer. Compared with the corresponding thiophene analog, PDPPTe2T absorbs light of longer wavelengths and has a smaller bandgap. Bulk heterojunction solar cells prepared from PDPPTe2T and PC71 BM show PCE values of up to 4.4%. External quantum efficiency measurements show that PDPPTe2T produces photocurrent at wavelengths up to 1?µm. DFT calculations suggest that the atomic substitution from sulfur to tellurium increases electronic coupling to decrease the length of the carbon-carbon bonds between the tellurophene and thiophene rings, which results in the red-shift in absorption upon substitution of tellurium for sulfur. PMID:25145499

  1. Holographic recording in polymeric materials with applications

    NASA Astrophysics Data System (ADS)

    Steckman, Gregory J.

    2001-12-01

    This thesis presents the results of research in volume holographic recording in several polymeric recording materials and their use in selected applications. The first chapter discusses the key properties of holographic recording materials. The second chapter develops a technique for calculating exposure schedules for photorefractive polymers which do not exhibit mono- exponential recording dynamics. It is determined that these materials require performance improvements before they can be successfully applied to many interesting applications of volume holography, such as holographic data storage and optical correlators which are described in later chapters. The third chapter investigates recording in diffusion amplification based polymer materials. This class of materials overcomes many limitations of other polymer types, such as limited thicknesses and volume shrinkage. A new material based on the diffusion amplification principle is developed with the goal of increasing dynamic range. The new material, a naphtoquinone and PMMA based co-polymer, is demonstrated in holographic recording experiments. In the fourth chapter, holographic data storage experiments are performed and a storage density of 7 bits/?m2 is achieved. A holographic data storage system which utilizes shift multiplexing is modeled and simulated to determine optimal system parameters and material characteristics. It is discovered that the dynamic range of the material used, phenanthrenequinone doped poly(methyl methacrylate), is insufficient to provide very high data storage densities. In the fifth chapter attention is focused on the development and characterization of an optical holographic correlator system using the DuPont BRF-150 photopolymer. The system is used for image recognition and tracking. The performance of the system is characterized with multiple 2-d and 3-d objects with respect to camera resolution, magnification, rotation, and other transformations. The system is demonstrated to be capable of simultaneously recognizing and tracking multiple targets, even in the presence of extraneous objects and partial obscuring of the targets. The final chapter describes the development of a high- speed holographic movie camera. Utilizing a Q-switched Nd:YAG pulse laser and Aprilis ULSH500-7A recording material, multi-frame holographic exposures with a 80 MHz frame rate are recorded.

  2. Polymeric salt bridges for conducting electric current in microfluidic devices

    DOEpatents

    Shepodd, Timothy J. (Livermore, CA); Tichenor, Mark S. (San Diego, CA); Artau, Alexander (Humacao, PR)

    2009-11-17

    A "cast-in-place" monolithic microporous polymer salt bridge for conducting electrical current in microfluidic devices, and methods for manufacture thereof is disclosed. Polymeric salt bridges are formed in place in capillaries or microchannels. Formulations are prepared with monomer, suitable cross-linkers, solvent, and a thermal or radiation responsive initiator. The formulation is placed in a desired location and then suitable radiation such as UV light is used to polymerize the salt bridge within a desired structural location. Embodiments are provided wherein the polymeric salt bridges have sufficient porosity to allow ionic migration without bulk flow of solvents therethrough. The salt bridges form barriers that seal against fluid pressures in excess of 5000 pounds per square inch. The salt bridges can be formulated for carriage of suitable amperage at a desired voltage, and thus microfluidic devices using such salt bridges can be specifically constructed to meet selected analytical requirements.

  3. Fluorescent-magnetic Janus particles prepared via seed emulsion polymerization.

    PubMed

    Kaewsaneha, Chariya; Bitar, Ahmad; Tangboriboonrat, Pramuan; Polpanich, Duangporn; Elaissari, Abdelhamid

    2014-06-15

    Anisotropic polymeric colloidal or Janus particles possessing simultaneous magnetic and fluorescent properties were successfully prepared via the swelling-diffusion or the in situ emulsion polymerization method. In the swelling-diffusion process, magnetic emulsions (an organic ferrofluid dispersed in aqueous medium) were synthesized and used for seeds of submicron magnetic Janus particles. After swelling the anisotropic particles obtained by 1-pyrene-carboxaldehyde fluorescent dye dissolved in tetrahydrofuran, well-defined fluorescent-magnetic Janus particles were produced. In the in situ emulsion polymerization, styrene monomer mixed with fluorescent dye monomers, i.e., 1-pyrenylmethyl methacrylate (PyMMA) or fluorescein dimethacrylate (FDMA), and an oil-soluble initiator (2,2'-azobis(2-isobutyronitrile)) were emulsified in the presence of magnetic seed emulsions. The confocal microscopic images showed the fluorescent-magnetic Janus particles with high fluorescent intensity when a fluorescent crosslinker monomer FDMA was employed. PMID:24767504

  4. Processes for microemulsion polymerization employing novel microemulsion systems

    DOEpatents

    Beckman, Eric J. (Kennewick, WA); Smith, Richard D. (Richland, WA); Fulton, John L. (Richland, WA)

    1990-06-12

    This invention is directed to a microemulsion system comprising a first phase including a low-polarity fluid material which is a gas at standard temperature and pressure, and which has a cloud-point density. It also includes a second phase including a polar fluid, typically water, a monomer, preferably a monomer soluble in the polar fluid, and a microemulsion promoter for facilitating the formation of micelles including the monomer in the system. In the subject process, micelles including the monomer are formed in the first phase. A polymerization initiator is introduced into the micelles in the microemulsion system. The monomer is then polymerized in the micelles, preferably in the core of the micelle, to produce a polymeric material having a relatively high molecular weight.

  5. Electron-beam analysis of polymerized KC{sub 60}

    SciTech Connect

    Chopra, N.G.; Hone, J.; Zettl, A. [Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States)] [Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States)

    1996-04-01

    We have conducted high-resolution transmission electron microscopy (HRTEM) and electron-energy-loss spectroscopy (EELS) studies on polymerized KC{sub 60}. The chainlike structure proposed for the polymerized material is confirmed. Lattice constants extracted from the HRTEM images are consistent with those determined earlier by x-ray diffraction. The fine structure in the EELS spectrum of KC{sub 60} shows the {ital sp}{sup 2} nature of the carbon bonds along with features which distinguish the bonding in this alkali fulleride from that of other fullerenes. Both the HRTEM and EELS studies show that polymerized KC{sub 60} is exceedingly resilient against damage induced by a 200-keV electron beam, in sharp contrast to the behavior of pristine C{sub 60}. {copyright} {ital 1996 The American Physical Society.}

  6. Studies of polymerization and crosslinking of aqueous acrylamide

    NASA Astrophysics Data System (ADS)

    Rosiak, J.; Burczak, K.; P?kala, W.; Pi?lewski, N.; Idziak, S.; Charlesby, A.

    The two radiation-induced reactions of polymerization and crosslinking have been followed by various techniques including T2 pulsed NMR, solubility (conversion rate) and intrinsic viscosity [ ?]. The monomer is acrylamide (20%) in water (D 2O). Polymerization is largely completed at the very low dose of 0.03 kGy, and the molecular weight then further increases as shown by T2 and [ ?] measurements. The indirect effect due to water is clearly seen. The dose for incipient network formation is greater ( Dg = 0.18 kGy) and the soluble fraction then decreases according to the Charlesby-Pinner formula. The T2 relaxation time shows at first a rise due to the reduction in non-polymerized monomer, and then falls as the Mc between successive crosslinks diminishes with increasing dose. This behaviour is also shown in irradiated aqueous polyethylene oxide samples.

  7. Various aspects of ultrasound assisted emulsion polymerization process.

    PubMed

    Korkut, Ibrahim; Bayramoglu, Mahmut

    2014-07-01

    In this paper, the effects of ultrasonic (US) power, pulse ratio, probe area and recipe composition were investigated on two process responses namely, monomer (methyl methacrylate, MMA) conversion and electrical energy consumption per mass of product polymer (PMMA). Pulsed mode US is more suitable than continuous mode US for emulsion polymerization. The probe (tip) area has little effect on the yield of polymerization when comparing 19 and 13 mm probes, 13 mm probe performing slightly better for high conversion levels. Meanwhile, large probe area is beneficial for high conversion efficiency of electric energy to US energy as well as for high radical generation yield per energy consumed. The conversion increased slightly and electrical energy consumption decreased substantially by using a recipe with high SDS and monomer concentrations. Conclusions presented in this paper may be useful for scale-up of US assisted emulsion polymerization. PMID:24444489

  8. Polymeric Materials for Tissue Engineering of Arterial Substitutes

    PubMed Central

    Ravi, Swathi; Qu, Zheng; Chaikof, Elliot L.

    2009-01-01

    Cardiovascular disease is the leading cause of mortality in the United States. The limited availability of healthy autologous vessels for bypass grafting procedures has led to the fabrication of prosthetic vascular conduits. Synthetic polymeric materials, while providing the appropriate mechanical strength, lack the compliance and biocompatibility that bioresorbable and naturally occurring protein polymers offer. Vascular tissue engineering approaches have emerged in order to meet the challenges of designing a vascular graft with long-term patency. In vitro culture techniques that have been explored with vascular cell seeding of polymeric scaffolds and the use of bioactive polymers for in situ arterial regeneration have yielded promising results. This review describes the development of polymeric materials in various tissue engineering strategies for the improvement in the mechanical and biological performance of an arterial substitute. PMID:19426609

  9. Tunable Diacetylene Polymerized Shell Microbubbles as Ultrasound Contrast Agents

    PubMed Central

    Park, Yoonjee; Luce, Adam C.; Whitaker, Ragnhild D.; Amin, Bhumica; Cabodi, Mario; Nap, Rikkert J.; Szleifer, Igal; Cleveland, Robin O.; Nagy, Jon O.; Wong, Joyce Y.

    2012-01-01

    Monodisperse gas microbubbles, encapsulated with a shell of photopolymerizable diacetylene lipids and phospholipids, were produced by microfluidic flow focusing, for use as ultrasound contrast agents. The stability of the polymerized shell microbubbles against both aggregation and gas dissolution under physiological conditions was studied. Polyethylene glycol (PEG) 5000, which was attached to the diacetylene lipids, was predicted by molecular theory to provide more steric hindrance against aggregation than PEG 2000 and this was confirmed experimentally. The polymerized shell microbubbles were found to have higher shell-resistance than nonpolymerizable shell microbubbles and commercially available microbubbles (Vevo MicroMarker). The acoustic stability under 7.5 MHz ultrasound insonation was significantly greater than for the two comparison microbubbles. The acoustic stability was tunable by varying the amount of diacetylene lipid. Thus, our polymerized shell microbubbles are a promising platform for ultrasound contrast agents. PMID:22260537

  10. Polymeric Nanoparticles for Drug Delivery to the Central Nervous System

    PubMed Central

    Patel, Toral; Zhou, Jiangbing; Piepmeier, Joseph M.; Saltzman, W. Mark

    2012-01-01

    The central nervous system (CNS) poses a unique challenge for drug delivery. The blood-brain barrier significantly hinders the passage of systemically-delivered therapeutics and the brain extracellular matrix limits the distribution and longevity of locally-delivered agents. Polymeric nanoparticles represent a promising solution to these problems. Over the past 40 years, substantial research efforts have demonstrated that polymeric nanoparticles can be engineered for effective systemic and local delivery of therapeutics to the CNS. Moreover, many of the polymers used in nanoparticle fabrication are both biodegradable and biocompatible, thereby increasing the clinical utility of this strategy. Here, we review the major advances in the development of polymeric nanoparticles for drug delivery to the CNS. PMID:22210134

  11. Energetics of protein nucleation on rough polymeric surfaces.

    PubMed

    Curcio, Efrem; Curcio, Valerio; Di Profio, Gianluca; Fontananova, Enrica; Drioli, Enrico

    2010-11-01

    Metropolis Monte Carlo (MC) algorithm of the two-dimensional Ising model is used to study the heterogeneous nucleation of protein crystals on rough polymeric surfaces. The theoretical findings are compared to those obtained from classical nucleation theory (CNT), and to experimental data from protein model hen egg white lysozyme (HEWL) crystallized on poly(vinylidene fluoride) or PVDF, poly(dimethylsiloxane) or PDMS and Hyflon homemade membranes. The reduction of the activation energy for the nucleation process on polymeric membranes, predicted to occur at increasing surface roughness, results in a nucleation kinetics that is many orders of magnitude faster than in homogeneous phase. In general, MC stochastic dynamics offers the unique opportunity to investigate the effects of collective molecular aggregation at site level on the nucleation rate and, consequently, allows to identify optimal morphological and structural properties of polymeric membranes for a fine control of the crystallization kinetics. PMID:20939543

  12. [Omics of vector mosquitoes: a big data platform for vector biology and vector-borne diseases].

    PubMed

    Wu, Yang; Xie, Li-Hua; Liu, Pei-Wen; Li, Xiao-Cong; Yan, Gui-Yun; Chen, Xiao-Guang

    2015-05-20

    Recently the studies on mosquito genomics, transcriptomics and small RNAomics developed rapidly with the novel biotechnologies of the next generation sequencing techniques. The genome sequences of several important vector mosquitoes including Anopheles gambiae, Culex quinquefasciatus, and Aedes aegypti have been published. The genome sizes vary among the different species of mosquitoes and are consistent with the number of the repeat regions. The released genome sequences facilitate gene cloning and identification as for OBP, OR and dsx genes. Transcriptomics provides a useful tool for functional analyses of the mosquito genes, and using this technique, the molecular basis of mosquito blooding, gland proteins and diapauses have been explored. Studies on small RNAomics suggest important roles of miRNAs and piRNAs in ovary development, blood digestion, and immunity against virus infection. The studies on mosquito omics have generated a big data platform for investigation of vector biology and vector-transmitted disease prevention. PMID:26018253

  13. Stimulus-dependent actin polymerization in bovine neutrophils.

    PubMed

    Bochsler, P N; Neilsen, N R; Dean, D F; Slauson, D O

    1992-08-01

    Polymorphonuclear leukocytes (PMNs) are responsible for much of the first wave of leukocyte-mediated host defense against microbial pathogens. In order to migrate through the endothelium of vessel walls, undergo chemotaxis, and phagocytize microbes, PMNs must modulate their cytoskeletal elements and undergo change of cellular shape. We have used fluorescence flow cytometric analysis and cellular microscopic observations to demonstrate actin polymerization in bovine PMNs and to examine the kinetics of PMN actin polymerization utilizing different PMN stimuli. In addition, we compared temporal relationships between cellular shape and actin polymerization. Actin polymerization occurred rapidly, and the kinetics of actin polymerization were similar for each of the three PMN agonists used, ZAS (10%), PAF (10(-6) M), and rhC5a (10(-7) M). Actin polymerization was near-maximal by 10 sec poststimulation (95.4% of maximal F-actin content attained by 10 sec poststimulation with ZAS stimulation), and reached peak values by 30 sec. The maximal increase in F-actin content of agonist-stimulated cells as compared to resting cells was 2.8-fold with ZAS; 2.3-fold with PAF; and 2.3-fold with rhC5a. PMN shape change (pseudopodia, membrane ruffles) was not as rapid, with only 22.4% of cells attaining visible membrane deformation by 10 sec and requiring 120 sec to reach peak shape-change values. After attaining peak values, the two events also differed. Whereas the percent of shape-changed PMNs remained plateaued up to 5 min poststimulation, the F-actin content gradually decreased after 30 sec, approaching F-actin values of unstimulated PMNs. PMID:1526666

  14. Vector Fields Resembling Dark Energy

    NASA Astrophysics Data System (ADS)

    Bretón, Nora

    We review how vector fields have been introduced to produce inflationary scenarios in early universes and recently they have been invoked to mimick dark energy. These last approaches have been mostly qualitatives, requiring then to be tested with cosmological probes, in order to seriously be considered as one of the possible causes of the present accelerated expansion of the universe.

  15. Constructing support vector machine ensemble

    Microsoft Academic Search

    Hyun-chul Kim; Shaoning Pang; Hong-mo Je; Daijin Kim; Sung Yang Bang

    2003-01-01

    Even the support vector machine (SVM) has been proposed to provide a good generalization performance, the classi6cation result of the practically implemented SVM is often far from the theoretically expected level because their implementations are based on the approximated algorithms due to the high complexity of time and space. To improve the limited classi6cation performance of the real SVM, we

  16. Adaptive Vector-Quantization Scheme

    NASA Technical Reports Server (NTRS)

    Cheung, Kar-Ming

    1992-01-01

    Adaptive vector-quantization scheme provides for rapid encoding of signals for transmission in compressed form and for rapid decoding at receiver. Based on simple heuristic "move-to-front" protocol effecting lossless compression of high-rate textual data. Audio, video, or other signals compressed efficiently.

  17. Improved Locally Adaptive Vector Quantization

    NASA Technical Reports Server (NTRS)

    Cheung, Kar-Ming; Sayano, Masahiro

    1994-01-01

    Several refinements introduced to improve performance of data-compression scheme described in "Adaptive Vector-Quantization Scheme" (NPO-18186). Principal advantages of LAVQ are that complexity and coding time less than those of some other data-compression schemes. Also, does not require priori knowledge of either codebook or statistics of source data.

  18. Complementary adenoviral vectors for oncolysis

    Microsoft Academic Search

    Ramon Alemany; Shoupeng Lai; Yan Chun Lou; Hsing-Yi Jan; Xiangming Fang; Wei-Wei Zhang

    1999-01-01

    Replication-competent adenoviruses (Ads) were used for oncolytic virotherapy soon after they were discovered. Recently mutated and genetically engineered Ads have been shown to selectively lyse tumor cells. We have split the human Ad type 5 genome into two defective viruses that complement each other only in certain tumor cells. The genome of one of these vectors, GT5610, contains only the

  19. Prior Selection for Vector Autoregressions

    Microsoft Academic Search

    Domenico Giannone; Michele Lenza; Giorgio E. Primiceri

    2012-01-01

    Vector autoregressions (VARs) are flexible time series models that can capture complex dynamic interrelationships among macroeconomic variables. However, their dense parameterization leads to unstable inference and inaccurate out-of-sample forecasts, particularly for models with many variables. A potential solution to this problem is to use informative priors, in order to shrink the richly parameterized unrestricted model towards a parsimonious naïve benchmark,

  20. Vector meson electromagnetic form factors

    E-print Network

    B. G. Lasscock; J. Hedditch; D. B. Leinweber; A. G. Williams

    2006-11-23

    The charge, magnetic and quadrupole form factors of vector mesons and the charge form factor of pseudo-scalar mesons are calculated in quenched lattice QCD. The charge radii and magnetic moments are derived. The quark sector contributions to the form factors are calculated separately and we highlight the environmental sensitivity of the light-quark contribution to charge radii.

  1. Active Support Vector Machine Classification

    Microsoft Academic Search

    Olvi L. Mangasarian; David R. Musicant

    2000-01-01

    An active set strategy is applied to the dual of a simple reformula- tion of the standard quadratic program of a linear support vector machine. This application generates a fast new dual algorithm that consists of solving a finite number of linear equations, with a typically large dimensionality equal to the number of points to be classified. However, by making

  2. DIPLOMA THESIS VECTOR ANTENNA FOR

    E-print Network

    DIPLOMA THESIS VECTOR ANTENNA FOR ULTRAHIGH ENERGY COSMIC NEUTRINO DETECTION IN THE ANTARCTIC ICE Contents iii List of Figures v 1 Introduction 1 2 Introduction to Antennas 5 2.1 Wire antennas 5 2.2 Dipole antennas 6 2.3 Half-wavelenght Dipole 8 2.4 Radiation Pattern of a Dipole Antenna 8 2.5 Antenna

  3. Proximal support vector machine classifiers

    Microsoft Academic Search

    Glenn Fung; Olvi L. Mangasarian

    2001-01-01

    Instead of a standard support vector machine (SVM) that classifies points by assigning them to one of two disjoint half-spaces, points are classified by assigning them to the closest of two parallel planes (in input or feature space) that are pushed apart as far as possible. This formulation, which can also be interpreted as regularized least squares and considered in

  4. Antimicrobial Polymeric Materials with Quaternary Ammonium and Phosphonium Salts

    PubMed Central

    Xue, Yan; Xiao, Huining; Zhang, Yi

    2015-01-01

    Polymeric materials containing quaternary ammonium and/or phosphonium salts have been extensively studied and applied to a variety of antimicrobial-relevant areas. With various architectures, polymeric quaternary ammonium/phosphonium salts were prepared using different approaches, exhibiting different antimicrobial activities and potential applications. This review focuses on the state of the art of antimicrobial polymers with quaternary ammonium/phosphonium salts. In particular, it discusses the structure and synthesis method, mechanisms of antimicrobial action, and the comparison of antimicrobial performance between these two kinds of polymers. PMID:25667977

  5. Imaging nanowire plasmon modes with two-photon polymerization

    NASA Astrophysics Data System (ADS)

    Gruber, Christian; Hirzer, Andreas; Schmidt, Volker; Trügler, Andreas; Hohenester, Ulrich; Ditlbacher, Harald; Hohenau, Andreas; Krenn, Joachim R.

    2015-02-01

    Metal nanowires sustain propagating surface plasmons that are strongly confined to the wire surface. Plasmon reflection at the wire end faces and interference lead to standing plasmon modes. We demonstrate that these modes can be imaged via two-photon (plasmon) polymerization of a thin film resist covering the wires and subsequent electron microscopy. Thereby, the plasmon wavelength and the phase shift of the nanowire mode picked up upon reflection can be directly retrieved. In general terms, polymerization imaging is a promising tool for the imaging of propagating plasmon modes from the nano- to micro-scale.

  6. Convective instabilities in traveling fronts of addition polymerization

    NASA Technical Reports Server (NTRS)

    Pojman, John A.; Jones, Chris E.; Khan, Akhtar M.

    1993-01-01

    An autocatalytic reaction in an unstirred vessel can support a constant velocity wavefront resulting from the coupling of diffusion to the chemical reaction. A flare front is a common example in which heat is the autocatalytic species that diffuses into unreacted regions stimulating a reaction that produces more heat. Traveling fronts were studied in synthetic polymerization reactions under high pressure by workers in the former USSR. More recently, propagating fronts of methacrylic acid polymerization were studied under ambient conditions, both with video techniques and by NMR.

  7. Allergic stomatitis caused by self-polymerizing resin.

    PubMed

    Giunta, J; Zablotsky, N

    1976-05-01

    This is a fully documented case, including biopsy and patch testing, of a patient who was hypersensitive to self-polymerizing polymethyl methacrylate. On two occasions, a 24-year-old woman with a history of multiple allergies developed allergic reactions to temporary acrylic dental restorations. The lesions disappeared upon removal of the restorations. Microscopic findings were consistent with an allergic reaction. Patch testing confirmed that the allergen was the monomer and indicated methods of processing the self-polymerizing resin to allow it to become essentially nonreactive in a sensitized patient. PMID:1063962

  8. Femtosecond laser microstructuring for polymeric lab-on-chips.

    PubMed

    Eaton, Shane M; De Marco, Carmela; Martinez-Vazquez, Rebeca; Ramponi, Roberta; Turri, Stefano; Cerullo, Giulio; Osellame, Roberto

    2012-08-01

    This paper provides an overview of femtosecond laser microfabrication in polymeric materials, with emphasis on lab-on-chip applications. Due to the nonlinear interaction of femtosecond laser pulses with polymers, laser-induced modifications are localized to the focal volume, enabling high resolution patterning in 3D. Femtosecond laser microfabrication offers unmatched versatility in fabricating surface microchannels and diffractive optics by means of laser ablation, buried optical waveguides and micro-optics through refractive index modification and complex 3D microstructures in photoresists by two-photon polymerization. Femtosecond laser microfabrication technology opens the door to fabricating integrated lab-on-chip devices with a single tool. PMID:22589025

  9. Stall force of polymerizing microtubules and filament bundles

    E-print Network

    Jaroslaw Krawczyk; Jan Kierfeld

    2011-02-10

    We investigate stall force and polymerization kinetics of rigid protofilaments in a microtubule or interacting filaments in bundles under an external load force in the framework of a discrete growth model. We introduce the concecpt of polymerization cycles to describe the stochastic growth kinetics, which allows us to derive an exact expression for the stall force. We find that the stall force is independent of ensemble geometry and load distribution. Furthermore, the stall force is proportional to the number of filaments and increases linearly with the strength of lateral filament interactions. These results are corroborated by simulations, which also show a strong influence of ensemble geometry on growth kinetics below the stall force.

  10. Polymeric compositions incorporating polyethylene glycol as a phase change material

    SciTech Connect

    Salyer, Ival O. (Dayton, OH); Griffen, Charles W. (Mason, OH)

    1989-01-01

    A polymeric composition comprising a polymeric material and polyethylene glycol or end-capped polyethylene glycol as a phase change material, said polyethylene glycol and said end-capped polyethylene glycol having a molecular weight greater than about 400 and a heat of fusion greater than about 30 cal/g; the composition is useful in making molded and/or coated materials such as flooring, tiles, wall panels and the like; paints containing polyethylene glycols or end-capped polyethylene glycols are also disclosed.

  11. Functional polymeric microparticles engineered from controllable microfluidic emulsions.

    PubMed

    Wang, Wei; Zhang, Mao-Jie; Chu, Liang-Yin

    2014-02-18

    Functional polymeric microparticles with typical sizes of 1-1000 ?m have received considerable attention for many applications. Especially in biomedical fields, polymeric microparticles with advanced functions such as targeted delivery, controlled encapsulation, or "capture and release" show great importance as delivery systems for active molecules and drugs, as imaging agents for analytics and diagnostics, as microreactors for confined bioreactions, and more. Generally, the functions of these microparticles rely on both their structures and the properties of their component materials. Thus, creating unique structures from functional materials provides an important strategy for developing advanced functional polymeric microparticles. Several methods, such as dispersion polymerization, precipitation polymerization, copolymer self-assembly, and phase-separated polymer precipitation can be used to make functional microparticles, but each has limitations, for example, their limited control over the particle size and structure. Using emulsions as templates, however, allows precise control over the size, shape, composition, and structure of the resulting microparticles by tuning those of the emulsions via specific emulsification techniques. Microfluidic methods offer excellent control of emulsion droplets, thereby providing a powerful platform for continuous, reproducible, scalable production of polymeric microparticles with unprecedented control over their monodispersity, structures, and compositions. This approach provides broad opportunities for producing polymeric microparticles with novel structure-property combinations and elaborately designed functions. In this Account, we highlight recent efforts in microfluidic fabrication of advanced polymeric microparticles with well-designed functions for potential biomedical applications, and we describe the development of microfluidic techniques for producing monodisperse and versatile emulsion templates. We begin by describing microparticles made from single emulsions and then describe those from complex multiple emulsions, showing how the resulting microparticles combine novel structures and material properties to achieve their advanced functions. Monodisperse emulsions enable production of highly uniform microparticles of desired sizes to achieve programmed release rates and passive targeting for drug delivery and diagnostic imaging. Phase-separated multiple emulsions allow combination of a variety of functional materials to generate compartmental microparticles including hollow, core-shell, multicore-shell, and hole-shell structures for controlled encapsulation and release, selective capture, and confined bioreaction. We envision that the versatility of microfluidics for microparticle synthesis could open new frontiers and provide promising and exciting opportunities for fabricating new functional microparticles with broad implications for myriad fields. PMID:24199893

  12. Hydrogen activated polymerization of solid CO and CO2

    NASA Astrophysics Data System (ADS)

    Tse, John

    2013-06-01

    Recent experiments have revealed unexpectedly ease of promoting chemical reactions between closed shell atoms or molecules under moderate pressure (<20 GPa). In this study, the possibilities of pressure-induced polymerization reactions in solid CO and CO2 at the presence of molecular hydrogen were investigated with static and dynamic calculations based on the density functional theory. Static geometry optimization calculations on a CO-H2 (10:1) system show polymerization of CO initiates at pressure as low as 5 GPa. The resulting polymer is stable upon heating under pressure and recoverable under ambient conditions. No reaction was found to occur on a 1:1 CO2/H2 system up to 40 GPa by static geometry optimization calculations. However, reactions proceed readily when the system is heated. Once again, the polymeric structure is recoverable when the pressure is removed. We will report the calculated vibrational and optical spectra for comparison with experiments. Mechanisms for the H2 assisted polymerization reactions will be discussed. Recent experiments have revealed unexpectedly ease of promoting chemical reactions between closed shell atoms or molecules under moderate pressure (<20 GPa). In this study, the possibilities of pressure-induced polymerization reactions in solid CO and CO2 at the presence of molecular hydrogen were investigated with static and dynamic calculations based on the density functional theory. Static geometry optimization calculations on a CO-H2 (10:1) system show polymerization of CO initiates at pressure as low as 5 GPa. The resulting polymer is stable upon heating under pressure and recoverable under ambient conditions. No reaction was found to occur on a 1:1 CO2/H2 system up to 40 GPa by static geometry optimization calculations. However, reactions proceed readily when the system is heated. Once again, the polymeric structure is recoverable when the pressure is removed. We will report the calculated vibrational and optical spectra for comparison with experiments. Mechanisms for the H2 assisted polymerization reactions will be discussed. In collaboration with Yong Xue, University of Saskatchewan.

  13. Polymeric micelles: nanocarriers for cancer-targeted drug delivery.

    PubMed

    Zhang, Yifei; Huang, Yixian; Li, Song

    2014-08-01

    Polymeric micelles represent an effective delivery system for poorly water-soluble anticancer drugs. With small size (10-100 nm) and hydrophilic shell of PEG, polymeric micelles exhibit prolonged circulation time in the blood and enhanced tumor accumulation. In this review, the importance of rational design was highlighted by summarizing the recent progress on the development of micellar formulations. Emphasis is placed on the new strategies to enhance the drug/carrier interaction for improved drug-loading capacity. In addition, the micelle-forming drug-polymer conjugates are also discussed which have both drug-loading function and antitumor activity. PMID:24700296

  14. Preparing polymeric matrix composites using an aqueous slurry technique

    NASA Technical Reports Server (NTRS)

    Johnston, Norman J. (inventor); Towell, Timothy W. (inventor)

    1993-01-01

    An aqueous process was developed to prepare a consolidated composite laminate from an aqueous slurry. An aqueous poly(amic acid) surfactant solution was prepared by dissolving a poly(amic acid) powder in an aqueous ammonia solution. A polymeric powder was added to this solution to form a slurry. The slurry was deposited on carbon fiber to form a prepreg which was dried and stacked to form a composite laminate. The composite laminate was consolidated using pressure and was heated to form the polymeric matrix. The resulting composite laminate exhibited high fracture toughness and excellent consolidation.

  15. Progress in malaria vector control*

    PubMed Central

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

    1981-01-01

    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. PMID:6976842

  16. Chemoenzymatic synthesis of polymeric materials using lipases as catalysts: a review.

    PubMed

    Yang, Yan; Zhang, Jianxu; Wu, Di; Xing, Zhen; Zhou, Yulin; Shi, Wei; Li, Quanshun

    2014-01-01

    In the past two decades, enzymatic polymerization has rapidly developed and become an important polymer synthesis technique. However, the range of polymers resulting from enzymatic polymerization could be further expanded through combination with chemical methods. This review systematically introduces recent developments in the combination of lipase-catalyzed polymerization with atom transfer radical polymerization (ATRP), kinetic resolution, reversible addition-fragmentation chain transfer (RAFT), click reaction and carbene chemistry to construct polymeric materials like block, brush, comb and graft copolymers, hyperbranched and chiral polymers. Moreover, it presents a thorough and descriptive evaluation of future trends and perspectives concerning chemoenzymatic polymerization. It is expected that combining enzymatic polymerization with multiple chemical methods will be an efficient tool for producing more highly advanced polymeric materials. PMID:24768887

  17. Enhanced Mechanical Stability of Microtubules Polymerized with a Slowly Hydrolyzable Nucleotide Analogue

    E-print Network

    Smith, Marc L.

    Enhanced Mechanical Stability of Microtubules Polymerized with a Slowly Hydrolyzable Nucleotide of microtubules polymerized using guanylyl-R- -methylene diphosphonate (GMPCPP), a slowly hydrolyzable analogue- ing hydrolyzed GTP are intrinsically unstable, hindering direct in vitro studies of their mechanical

  18. Ultrasonic monitoring of earlystage biofilm growth on polymeric surfaces Elmira Kujundzic a

    E-print Network

    Pace, Norman

    Ultrasonic monitoring of earlystage biofilm growth on polymeric surfaces Elmira Kujundzic a , A Biofilm growth on polymeric surfaces was monitored using ultrasonic frequency-domain reflectometry (UFDR biofilms. When compared to clean (virgin) conditions, biofilms growing on coupons induced consistent

  19. 49 CFR 173.221 - Polymeric beads, expandable and Plastic molding compound.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...false Polymeric beads, expandable and Plastic molding compound. 173.221 Section...221 Polymeric beads, expandable and Plastic molding compound. (a) Non-bulk...expandable, evolving flammable vapor and Plastic molding compound in dough, sheet...

  20. 49 CFR 173.221 - Polymeric beads, expandable and Plastic molding compound.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...false Polymeric beads, expandable and Plastic molding compound. 173.221 Section...221 Polymeric beads, expandable and Plastic molding compound. (a) Non-bulk...expandable, evolving flammable vapor and Plastic molding compound in dough, sheet...