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Development of a polymeric nanoparticulate delivery system for indocyanine green  

NASA Astrophysics Data System (ADS)

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

Saxena, Vishal


Polymeric vectors for ocular gene delivery  

PubMed Central

Gene therapy holds promise for the treatment of many inherited and acquired diseases of the eye. Successful ocular to targeted cells with minimal toxicity. A major gene therapy interventions depend on challenge is to overcome both intracellular and extracellular barriers associated with ocular gene delivery. Numerous viral and nonviral vectors were explored to improve transfection efficiency. Among nonviral delivery systems, polymeric vectors have gained significant attention in recent years owing to their nontoxic and non-immunogenic nature. Polyplexes or nanoparticles can be prepared by interaction of cationic polymers with DNA, which facilitate cellular uptake, endolysosomal escape and nuclear entry through active mechanisms. Chemical modification of these polymers allows for the generation of flexible delivery vectors with desirable properties. In this article several synthetic and natural polymeric systems utilized for ocular gene delivery are discussed. PMID:21858246

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



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

NASA Astrophysics Data System (ADS)

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

Khurana, Jatin


Nanoparticulate systems for polynucleotide delivery  

PubMed Central

Nanotechnology has tremendously influenced gene therapy research in recent years. Nanometer-size systems have been extensively investigated for delivering genes at both local and systemic levels. These systems offer several advantages in terms of tissue penetrability, cellular uptake, systemic circulation, and cell targeting as compared to larger systems. They can protect the polynucleotide from a variety of degradative and destabilizing factors and enhance delivery efficiency to the cells. A variety of polymeric and non-polymeric nanoparticles have been investigated in an effort to maximize the delivery efficiency while minimizing the toxic effects. This article provides a review on the most commonly used nanoparticulate systems for gene delivery. We have discussed frequently used polymers, such as, polyethyleneimine, poly (lactide-co-glycolide), chitosan, as well as non-polymeric materials such as cationic lipids and metallic nanoparticles. The advantages and limitations of each system have been elaborated. PMID:18019834

Basarkar, Ashwin; Singh, Jagdish



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


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

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



Advances in polymeric and inorganic vectors for nonviral nucleic acid delivery  

PubMed Central

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

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



Ring-opening polymerization for hyperbranched polycationic gene delivery vectors with excellent serum tolerance.  


In order to improve the transfection efficiency (TE) and biocompatibility, we synthesized a series of hyperbranched cationic polymers by ring-opening polymerization between diepoxide and several polyamines. These materials can condense plasmid DNA efficiently into nanoparticles that have much lower cytotoxicity than those derived from bPEI. In vitro transfection experiments showed that polymers prepared from branched or cyclic polyamine (P1 and P5) exhibited TE several times higher than 25KDa bPEI. More significantly, serum seemed to have no negative effect on P1-P5 mediated transfection. On the contrary, the TE of P1 improved, even when the serum concentration reached 70%. Several assays demonstrated the excellent serum tolerance of such polycationic vectors: bovine serum albumin (BSA) adsorption assay revealed considerably lower protein adsorption of P1-P5 than PEI; P1 showed better DNA protection ability from degradation by DNase I than PEI; flow cytometry results suggested that any concentration of serum may not decrease the cellular uptake of P1/DNA polyplex; and confocal laser scanning microscopy also found that serum has little effect on the transfection. By using specific cellular uptake inhibitors, we found that the polyplexes enter the cells mainly via caveolae and microtubule-mediated pathways. We believe that this ring-opening polymerization may be an effective synthetic approach toward gene delivery materials with high biological activity. PMID:25177769

Zhang, Qin-Fang; Yu, Qing-Ying; Geng, Yanyan; Zhang, Ji; Wu, Wan-Xia; Wang, Gang; Gu, Zhongwei; Yu, Xiao-Qi




NSDL National Science Digital Library

This lesson was created by Larry Friesen and Anne Gillis for Butler Community College. It will help physics and calculus students differentiate between the uses of vectors in mathematics vs. physics. This website provides two PDF documents that give detailed lessons about vectors, including an overview of terminology, sample problems, and an HTML worksheet is also provided. For educators or students, this site offers well laid-out lessons and/or practice with vectors.

Friesen, Larry; Gillis, Anne




NSDL National Science Digital Library

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

Joiner, David; The Shodor Education Foundation, Inc.


Nanoparticulate delivery systems for antiviral drugs.  


Nanomedicine opens new therapeutic avenues for attacking viral diseases and for improving treatment success rates. Nanoparticulate-based systems might change the release kinetics of antivirals, increase their bioavailability, improve their efficacy, restrict adverse drug side effects and reduce treatment costs. Moreover, they could permit the delivery of antiviral drugs to specific target sites and viral reservoirs in the body. These features are particularly relevant in viral diseases where high drug doses are needed, drugs are expensive and the success of a therapy is associated with a patient's adherence to the administration protocol. This review presents the current status in the emerging area of nanoparticulate delivery systems in antiviral therapy, providing their definition and description, and highlighting some peculiar features. The paper closes with a discussion on the future challenges that must be addressed before the potential of nanotechnology can be translated into safe and effective antiviral formulations for clinical use. PMID:21107015

Lembo, David; Cavalli, Roberta



Solution processable interface materials for nanoparticulate organic photovoltaic devices  

NASA Astrophysics Data System (ADS)

Nanoparticulate zinc oxide can be prepared at low temperatures from solution processable zinc acetylacetonate. The use of this material as a cathode interfacial layer in nanoparticulate organic photovoltaic devices results in comparable performances to those based on reactive calcium layers. Importantly, the enhanced degradation stability and full solution processability make zinc oxide a more desirable material for the fabrication of large area printed devices.

Nicolaidis, Nicolas; Vaughan, Ben; Mulligan, Cara J.; Bryant, Glenn; Zillger, Tino; Trnovec, Bystrik; Hübler, Arved C.; Holmes, Natalie; Cooling, Nathan A.; Griffith, Matthew J.; Bilen, Chhinder; Kumar, Pankaj; Feron, Krishna; Zhou, Xiaojing; Elkington, Daniel; Belcher, Warwick J.; Dastoor, Paul C.



Preclinical antitumor activity of a nanoparticulate SN38.  


The present studies were carried out to examine the efficacy of a nanoparticulate formulation of SN38, the potent topoisomerase I inhibitor and active metabolite of irinotecan. Metabolism of irinotecan to SN38 is inefficient and subject to considerable patient-to-patient variability. One approach to more controlled administration of the anticancer agent is direct administration of the active SN38. A nanoparticulate formulation of SN38 was prepared by a method of precipitation with compressed antisolvent. Nanoparticulate SN38 efficiently inhibited the proliferation of colorectal, ovarian, and mesothelial cancer cell lines in vitro. Concentrations resulting in 50 % inhibition of proliferation were approximately 1000 fold lower for nanoparticulate SN38 compared to irinotecan. In vivo effects were examined using colorectal and ovarian mouse model systems. In a mouse model of peritoneally disseminated ovarian cancer intraperitoneal administration of irinotecan was favorable to intravenous delivery however intraperitoneal delivery of nanoparticulate SN38 was significantly more effective than intraperitoneal irinotecan. In addition, in a mouse colorectal cancer model administration of nanoparticulate SN38 once weekly exhibited greater activity compared to daily or weekly administration of irinotecan. Additional studies demonstrated nanoparticulate SN38 administered as a combination therapy with mitomycin C was more effective than the combination of irinotecan and mitomycin C. Results from the present studies using preclinical colorectal and ovarian cancer model systems demonstrate the efficacy of nanoparticulate SN38 and substantiate continued development. PMID:23299391

Al-Kasspooles, Mazin F; Williamson, Stephen K; Henry, David; Howell, Jahna; Niu, Fengui; Decedue, Charles J; Roby, Katherine F



LBPS/CSPBAT Les nanoparticules hybrides rsultent d'un  

E-print Network

objectif, en développant des méthodes de synthèse de nanoparticules à base d'oxyde de fer, de nanoparticules d'oxyde de fer associés à la fonctionnalisation de surface par des molécules spécifiques permet d

Powell, Geoffrey


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


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

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



Berberine hydrochloride: anticancer activity and nanoparticulate delivery system  

PubMed Central

Background Berberine hydrochloride is a conventional component in Chinese medicine, and is characterized by a diversity of pharmacological effects. However, due to its hydrophobic properties, along with poor stability and bioavailability, the application of berberine hydrochloride was hampered for a long time. In recent years, the pharmaceutical preparation of berberine hydrochloride has improved to achieve good prospects for clinical application, especially for novel nanoparticulate delivery systems. Moreover, anticancer activity and novel mechanisms have been explored, the chance of regulating glucose and lipid metabolism in cancer cells showing more potential than ever. Therefore, it is expected that appropriate pharmaceutical procedures could be applied to the enormous potential for anticancer efficacy, to give some new insights into anticancer drug preparation in Chinese medicine. Methods and results We accessed conventional databases, such as PubMed, Scope, and Web of Science, using “berberine hydrochloride”, “anti-cancer mechanism”, and “nanoparticulate delivery system” as search words, then summarized the progress in research, illustrating the need to explore reprogramming of cancer cell metabolism using nanoparticulate drug delivery systems. Conclusion With increasing research on regulation of cancer cell metabolism by berberine hydrochloride and troubleshooting of issues concerning nanoparticulate delivery preparation, berberine hydrochloride is likely to become a natural component of the nanoparticulate delivery systems used for cancer therapy. Meanwhile, the known mechanisms of berberine hydrochloride, such as decreased multidrug resistance and enhanced sensitivity of chemotherapeutic drugs, along with improvement in patient quality of life, could also provide new insights into cancer cell metabolism and nanoparticulate delivery preparation. PMID:21931477

Tan, Wen; Li, Yingbo; Chen, Meiwan; Wang, Yitao



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

E-print Network

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

Cheng, Jianjun


Nanoparticulate bioavailable iron minerals in icebergs and glaciers R. RAISWELL  

E-print Network

Nanoparticulate bioavailable iron minerals in icebergs and glaciers R. RAISWELL 1 , L. G. BENNING 1, Bristol University, Bristol BS8 1SS, UK ABSTRACT Ice-hosted sediments in glaciers and icebergs from by icebergs to the Southern Ocean is comparable to the flux of soluble, bioavailable Fe from aeolian dust

Benning, Liane G.


Multistrain influenza protection induced by a nanoparticulate mucosal immunotherapeutic  

Microsoft Academic Search

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

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



Mechanisms of Tumor Vascular Priming by a Nanoparticulate Doxorubicin Formulation  

PubMed Central

Purpose Tumor vascular normalization by antiangiogenic agents may increase tumor perfusion but reestablish vascular barrier properties in CNS tumors. Vascular priming via nanoparticulate carriers represents a mechanistically distinct alternative. This study investigated mechanisms by which sterically-stabilized liposomal doxorubicin (SSL-DXR) modulates tumor vascular properties. Methods Functional vascular responses to SSL-DXR were investigated in orthotopic rat brain tumors using deposition of fluorescent permeability probes and dynamic contrast-enhanced magnetic resonance imaging. Microvessel density and tumor burden were quantified by immunohistochemistry (CD-31) and quantitative RT-PCR (VE-cadherin). Results Administration of SSL-DXR (5.7 mg/kg iv) initially (3–4 days post-treatment) decreased tumor vascular permeability, ktrans (vascular exchange constant), vascular endothelial cell content, microvessel density, and deposition of nanoparticulates. Tumor vasculature became less chaotic. Permeability and perfusion returned to control values 6–7 days post-treatment, but intratumor SSL-DXR depot continued to effect tumor vascular endothelial compartment 7–10 days post-treatment, mediating enhanced permeability. Conclusions SSL-DXR ultimately increased tumor vascular permeability, but initially normalized tumor vasculature and decreased tumor perfusion, permeability, and nanoparticulate deposition. These temporal changes in vascular integrity resulting from a single SSL-DXR dose have important implications for the design of combination therapies incorporating nanoparticle-based agents for tumor vascular priming. PMID:22798260

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



Intratumoral delivery of IL12 gene by polyvinyl polymeric vector system to murine renal and colon carcinoma results in potent antitumor immunity  

Microsoft Academic Search

We have utilized a nonviral, polymeric interactive non-condensing (PINC) gene delivery system to deliver IL-12 to two different types of murine tumors, an immunogenic renal cell carcinoma, Renca, and a non-immunogenic colon cell carcinoma, CT26. The delivery of IL-12\\/polyvinyl pyrrolidone (PVP) complexes into Renca led to the expression of IL-12 (146 ± 89 pg\\/mg) and IFN-? (160 ± 82 pg\\/mg)

S K Mendiratta; A Quezada; M Matar; J Wang; H L Hebel; S Long; J L Nordstrom; F Pericle



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

E-print Network

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

Mu, L.


Polymeric nitrogen  

SciTech Connect

The equilibrium phase boundary between single-bonded, threefold-coordinated polymeric forms of nitrogen, and the observed, triple-bonded diatomic phases, is predicted to occur at relatively low (50[plus minus]15 GPa) pressure. This conclusion is based on extensive local-density-functional total-energy calculations for polymeric structures (including that of black phosphorus, and another with all [ital gauche] dihedral angles) and diatomic structures (including that of the observed high-pressure [var epsilon]-N[sub 2] phase). We believe the diatomic phase of nitrogen, observed up to 180 GPa and room temperature, to be metastable at these conditions, and that such hysteresis enhances the prospects for the existence of a metastable polymeric form of nitrogen at ambient conditions. In this regard, we show that the black-phosphorus and cubic [ital gauche] polymeric forms of nitrogen would encounter significant barriers along high-symmetry paths to dimerization at atmospheric pressure.

Mailhiot, C.; Yang, L.H.; McMahan, A.K. (Lawrence Livermore National Laboratory, University of California, Livermore, California 94551 (United States))



The synthesis of metal nanoparticulate catalysts within functional microgel particles  

NASA Astrophysics Data System (ADS)

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

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



Multifunctional, stimuli-sensitive nanoparticulate systems for drug delivery.  


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

Torchilin, Vladimir P



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

NASA Astrophysics Data System (ADS)

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

Hebert, Etienne M.


Olefin polymerization  

SciTech Connect

A process is described for producing high density and high flexural modulus olfin polymers comprising polymerizing the olefins in the presence of a catalyst composition. The composition comprises a chromium compound on a xerogel base comprising at least one of iron phosphate and iron polyphosphate and at least one of aluminium phosphate and aluminium polyphosphate.

McDaniel, M.P.



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

NASA Astrophysics Data System (ADS)

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

Hatton, Bryan; Rickard, David



Dynamics of discontinuous coating and drying of nanoparticulate films.  

SciTech Connect

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.

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



Multistrain influenza protection induced by a nanoparticulate mucosal immunotherapeutic.  


All commercial influenza vaccines elicit antibody responses that protect against seasonal infection, but this approach is limited by the need for annual vaccine reformulation that precludes efficient responses against epidemic and pandemic disease. In this study we describe a novel vaccination approach in which a nanoparticulate, liposome-based agent containing short, highly conserved influenza-derived peptides is delivered to the respiratory tract to elicit potent innate and selective T cell-based adaptive immune responses. Prepared without virus-specific peptides, mucosal immunostimulatory therapeutic (MIT) provided robust, but short-lived, protection against multiple, highly lethal strains of influenza in mice of diverse genetic backgrounds. MIT prepared with three highly conserved epitopes that elicited virus-specific memory T-cell responses but not neutralizing antibodies, termed MITpep, provided equivalent, but more durable, protection relative to MIT. Alveolar macrophages were more important than dendritic cells in determining the protective efficacy of MIT, which induced both canonical and non-canonical antiviral immune pathways. Through activation of airway mucosal innate and highly specific T-cell responses, MIT and MITpep represent novel approaches to antiviral protection that offer the possibility of universal protection against epidemic and pandemic influenza. PMID:20736998

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



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

PubMed Central

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

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



Cellular Partitioning of Nanoparticulate versus Dissolved Metals in Marine Phytoplankton.  


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

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



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

E-print Network

Methylation of Mercury by Bacteria Exposed to Dissolved, Nanoparticulate, and Microparticulate bacteria that methylate Hg(II). In sediment porewater, Hg(II) associates with sulfides and natural organic intermediates of heterogeneous mineral precipitation. Here, we exposed two strains of sulfate-reducing bacteria


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

Microsoft Academic Search

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

L. Reijnders



Diode behavior of electrophoretically deposited polyaniline on TiO2 nanoparticulate thin film electrode.  


An inorganic/organic hetrostructure diode was constructed by the electrophoretic deposition of the p-type polyaniline (PANI) on an n-type titanium oxide (TiO2) nanoparticulate thin film. The bonding and internalization of PANI to TiO2 nanoparticulate thin film were confirmed by the morphological, structural and optical studies of electrophoretically deposited PANI/TIO2 nanoparticulate thin film. The increased size of TiO2 nanoparticles indicated the well penetration of PANI molecules into the pores of mesoporous TiO2 nanoparticulate thin film. The XPS studies of PANI/TiO2 heterostructure exhibited the surface bonding and interaction between PANI molecules and TiO2 nanoparticles. The current-voltage (I-V) characterization of PANI/TiO2 heterostructure was carried out in the forward and the reverse bias at the applied voltage ranges from -1 V to +1 V with a scan rate of 2 mV/s. The constructed Pt/PANI/TiO2 heterostructure device established diodic behavior with non-linear nature of I-V curves. PMID:21456236

Ameen, Sadia; Akhtar, M Shaheer; Kim, Young Soon; Yang, O-Bong; Shin, Hyung-Shik



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

PubMed Central

The analysis of nanomaterials in pharmaceutical or cosmetic preparations is an important aspect both in formulation development and quality control of marketed products. Despite the increased popularity of nanoparticulate compounds especially in dermal preparations such as emulsions, methods and protocols of analysis for the characterization of such systems are scarce. This work combines an original sample preparation procedure along with different methods of analytical electron microscopy for the comprehensive analysis of fluid or semi-solid dermal preparations containing nanoparticulate material. Energy-filtered transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy and high resolution imaging were performed on model emulsions and a marketed product to reveal different structural aspects of both the emulsion bulk phase and incorporated nanosized material. An innovative analytical approach for the determination of the physical stability of the emulsion under investigation is presented. Advantages and limitations of the employed analytical imaging techniques are highlighted. PMID:24300401

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



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

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.


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

Microsoft Academic Search

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

Xiangyang Tang; Yi Yang; Shaojie Tang



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


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

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



Vector Voyage!  

NSDL National Science Digital Library

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

Integrated Teaching And Learning Program


Polymerization of perfluorobutadiene  

NASA Technical Reports Server (NTRS)

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

Newman, J.; Toy, M. S.



Ring opening metathesis polymerization  

Microsoft Academic Search

This article intends to provide the reader with a basic knowledge of Ring Opening Metathesis Polymerization. Some historic background, mechanistic aspects, living polymerization, as well as current catalyst development and new applications are discussed.

Marcelo E. Piotti



Nanoparticulate Adjuvants and Delivery Systems for Allergen Immunotherapy  

PubMed Central

In the last decades, significant progress in research and clinics has been made to offer possible innovative therapeutics for the management of allergic diseases. However, current allergen immunotherapy shows limitations concerning the long-term efficacy and safety due to local side effects and risk of anaphylaxis. Thus, effective and safe vaccines with reduced dose of allergen have been developed using adjuvants. Nevertheless, the use of adjuvants still has several disadvantages, which limits its use in human vaccines. In this context, several novel adjuvants for allergen immunotherapy are currently being investigated and developed. Currently, nanoparticles-based allergen-delivery systems have received much interest as potential adjuvants for allergen immunotherapy. It has been demonstrated that the incorporation of allergens into a delivery system plays an important role in the efficacy of allergy vaccines. Several nanoparticles-based delivery systems have been described, including biodegradable and nondegradable polymeric carriers. Therefore, this paper provides an overview of the current adjuvants used for allergen immunotherapy. Furthermore, nanoparticles-based allergen-delivery systems are focused as a novel and promising strategy for allergy vaccines. PMID:22496608

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



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

PubMed Central

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

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



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

NASA Astrophysics Data System (ADS)

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

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




Microsoft Academic Search

This account describes the development of a new type of polymerization catalysis termed ion-pairing polymerization (IPP). IPP utilizes compatible and dually active transition-metal cation–main-group anion ion pairs in which both the cation and the anion can independently catalyze the polymer chain growth in a single polymerization reaction. Furthermore, cations and anions of ion pairs can exhibit different stereoselectivity and growing

Eugene Y.-X. Chen



Vector Fields  

NSDL National Science Digital Library

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

Ay, Tevian



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

NASA Astrophysics Data System (ADS)

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

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



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


The ferritin core is composed of fine nanoparticulate Fe(3+) oxohydroxide, and we have developed a synthetic mimetic, nanoparticulate Fe(3+) polyoxohydroxide (nanoFe(3+)). 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 Fe(2+) sulfate (FeSO4), nanoFe(3+), or no added Fe for a further 4 wk. A control group was Fe sufficient throughout. Direct intestinal absorption of nanoFe(3+) was investigated using isolated duodenal loops. Our data show that FeSO4 and nanoFe(3+) 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 nanoFe(3+) group. Oral iron failed to be utilized by Fpn-KO mice and was retained in enterocytes, irrespective of the iron source. In summary, although nanoFe(3+) 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. PMID:24776745

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



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


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

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



Equivalent Vectors  

ERIC Educational Resources Information Center

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

Levine, Robert



Vector quantization  

NASA Technical Reports Server (NTRS)

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.

Gray, Robert M.



Toward living radical polymerization.  


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

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



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

NASA Astrophysics Data System (ADS)

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

Shin, Dong-Youn



Halley's polymeric organic molecules  

NASA Astrophysics Data System (ADS)

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

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


Thermodynamics of Polymerization. I  

Microsoft Academic Search

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

Hideo Sawada



Multiphase Polymeric Materials  

NSDL National Science Digital Library

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


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


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

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



Effect of Si3N4 nanoparticulates on the mechanical and electrical properties of PZT ceramics  

NASA Astrophysics Data System (ADS)

PZT/xSi3N4 ceramics (when x=0, 0.1, 0.5 and 1 wt.%) were prepared by a solid-state mixed-oxide method and sintered at 1125 °C for 2 h. X-ray diffraction results suggested that the addition of Si3N4 nanoparticulates did not significantly affect the unit cell and tetragonality of PZT. The addition of 0.1 wt.% Si3N4 effectively increased the density and reduced the grain size of PZT ceramics. These changes played an important role in hardness and fracture toughness improvement. The maximum room temperature dielectric constant was achieved in a PZT/0.1 wt.% Si3N4 sample. Within the Si3N4-containing samples, the high-temperature dielectric values and ferroelectric properties seemed to increase with increasing concentrations of Si3N4.

Namsar, Orapim; Watcharapasorn, Anucha; Jiansirisomboon, Sukanda



Self standing nanoparticulate networks by self assembly surfactant H1 mesophase  

NASA Astrophysics Data System (ADS)

We show that nanoparticles (size > 10 nm) that are dispersed in nonionic surfactant/water system, assemble into networks on cooling into the H1 phase, independent of particle surface chemistry. Coating the particles with a crosslinkable polymer, and covalent coupling of the coated particle assemblies in the H1 phase allows us to form free standing particulate networks that are stable after surfactant removal. Thus, dynamic templating of surfactant H1 domains is a facile technique that involves near ambient temperatures, and a benign water wash for template removal. The network mesh size can be varied from the sub-micron to tens of microns by controlling the cooling rate. Particle networks can be flow-oriented prior to crosslinking, and interpenetrating networks can also be formed. We will show examples of macroporous nanoparticulate networks formed using nanoparticles of inorganic oxides, polymer latices, as well as bionanoparticles such as proteins.

Kumaraswamy, Guruswamy; Sharma, Kamendra; Gupta, Sayam Sen



Metallocene Catalysts for Ethylene Polymerization  

Microsoft Academic Search

Metallocene catalysts are the latest addition to the olefin polymerization catalyst family. It has been demonstrated that metallocene catalyst can polymerize olefins at high activities. Some chiral metallocenes are also capable of stereospecific polymerization where isotactic and syndiotactic polymers can be produced. Although it was proven that metallocene catalysts can polymerize ethylene in the late fifties, it took more than

Syriac J. Palackal; Atieh Abu Raqabah


Nanoconfinement Effect on Polymerization  

NASA Astrophysics Data System (ADS)

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

Vaddey, Maitri; Simon, Sindee



Selective Vectorization for Short-Vector Instructions  

E-print Network

Multimedia extensions are nearly ubiquitous in today's general-purpose processors. These extensions consist primarily of a set of short-vector instructions that apply the same opcode to a vector of operands. Vector ...

Amarasinghe, Saman



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

E-print Network

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

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



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


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

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



Protein specific polymeric immunomicrospheres  

NASA Technical Reports Server (NTRS)

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

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



Flame retardant polymeric materials  

SciTech Connect

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

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



Nanoparticulate lipid dispersions for bromocriptine delivery: characterization and in vivo study.  


The physico-chemical properties and in vivo efficacies of two nanoparticulate systems delivering the antiparkinsonian drug bromocriptine (BC) were compared in the present study. Monoolein Aqueous Dispersions (MADs) and Nanostructured Lipid Carriers (NLCs) were produced and characterized. Cryogenic transmission electron microscopy (cryo-TEM) and X-ray diffraction revealed the morphology of MAD and NLC. Dimensional distribution was determined by Photon Correlation Spectroscopy (PCS) and Sedimentation Field Flow Fractionation (SdFFF). In particular, BC was shown to be encapsulated with high entrapment efficiency both in MAD and in NLC, according to SdFFF combined with HPLC. Two behavioral tests specific for akinesia (bar test) or akinesia/bradykinesia (drag test) were used to compare the effects of the different BC formulations on motor disabilities in 6-hydroxydopamine hemilesioned rats in vivo, a model of Parkinson's disease. Both free BC and BC-NLC reduced the immobility time in the bar test and enhanced the number of steps in the drag test, although the effects of encapsulated BC were longer lasting (5h). Conversely, BC-MAD was ineffective in the bar test and improved stepping activity in the drag test to a much lower degree than those achieved with the other preparations. We conclude that MAD and NLC can encapsulate BC, although only NLC provide long-lasting therapeutic effects possibly extending BC half-life in vivo. PMID:22061262

Esposito, Elisabetta; Mariani, Paolo; Ravani, Laura; Contado, Catia; Volta, Mattia; Bido, Simone; Drechsler, Markus; Mazzoni, Serena; Menegatti, Enea; Morari, Michele; Cortesi, Rita



Deep penetration of nanoparticulate drug delivery systems into tumors: challenges and solutions.  


In recent decades, nanoparticulate drug delivery systems have attracted extensive attention in cancer therapy for such appealing properties as small particle size, huge surface area, narrow size distribution and prolonged circulation time. Although several nanomedicines have successfully reached the clinical, evidences have proved that therapeutic efficacy isn't improved significantly, except for better toleration and less side effects. Given that the physiological abnormalities in tumors, multiple biobarriers need to be overcome before nanomedicines are delivered to the target site. Passive targeting nanoparticles ensure nanomedicines' extensive extravasation from tumor vessels via enhanced permeation and retention effect, but the diffusion distance is limited to 2-3 cell layer thicknesses. Active targeting nanoparticles tend to bind the peripheral cells of the tumor mass, hindering nanoparticles further penetration into the tumor core region. Therefore, how to improve the deep penetration of nanomedicines into tumors is a formidable task for achieving the desired anticancer therapeutic efficacy. This review demonstrates the penetration obstacles existing in tumor region for nanoparticles, summarizes the important properties of nanomedicines affecting tumor deep penetration and highlights the solutions to improve tumor deep penetration of nanoparticles. PMID:23651305

Li, L; Sun, J; He, Z



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


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

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



Lightweight polymeric exhaust components  

US Patent & Trademark Office Database

Disclosed is a muffler assembly including: a) polymeric housing having an interior surface and at least one opening for at least one inlet and one outlet exhaust pipe; b) at least one metal inlet exhaust pipe and at least one metal outlet exhaust pipe positioned within the openings to provide housing-exhaust pipe interfaces; c) a thermal insulating material coating the interior surface of the polymeric housing and extending through the housing-exhaust pipe interfaces; wherein the thermal insulating material seals the muffler assembly at the housing-exhaust pipe interfaces; and wherein the muffler assembly has a leak rate of 105 Liters/minute or less at 4.5 psig pressure. An optional muffler assembly has body mounting adapters attached to the inlet and outlet exhaust pipes and positioned within the openings to provide housing-body mounting adapter interfaces. Also disclosed are processes for manufacturing the muffler assemblies.



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

NASA Astrophysics Data System (ADS)

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

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



Surface polymerization agents  

SciTech Connect

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

Taylor, C.; Wilkerson, C.



Polymeric battery separators  

Microsoft Academic Search

Configurations of cross-linked or vulcanized amphophilic or quaternized block copolymer of haloalkyl epoxides and hydroxyl terminated alkadiene polymers are useful as battery separators in both primary and secondary batteries, particularly nickel-zinc batteries. The quaternized block copolymers are prepared by polymerizing a haloalkyl epoxide in the presence of a hydroxyl terminated 1,3-alkadiene to form a block copolymer that is then reacted

R. J. Minchak; W. N. Schenk



Vector Addition Calculator  

NSDL National Science Digital Library

The Vector Addition Calculator lets students add vectors graphically in 2 dimensions by dragging the tips of the vectors. The results of a component method of addition for the same problem are also displayed.

Joiner, David; The Shodor Education Foundation, Inc.


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


The physicochemical and biological properties of calcium silicate-based cement (CS) associated to microparticulated (micro) or nanoparticulated (nano) zirconium oxide (ZrO2 ) were compared with CS and bismuth oxide (BO) with CS. The pH, release of calcium ions, radiopacity, setting time, and compression strength of the materials were evaluated. The tissue reaction promoted by these materials in the subcutaneous was also investigated by morphological, immunohistochemical, and quantitative analyses. For this purpose, polyethylene tubes filled with materials were implanted into rat subcutaneous. After 7, 15, 30, and 60 days, the tubes surrounded by capsules were fixed and embedded in paraffin. In the H&E-stained sections, the number of inflammatory cells (ICs) in the capsule was obtained. Moreover, detection of interleukin-6 (IL-6) by immunohistochemistry and number of IL-6 immunolabeled cells were carried out. von Kossa method was also performed. The differences among the groups were subjected to Tukey test (p???0.05). The solutions containing the materials presented an alkaline pH and released calcium ions. The addition of radiopacifiers increased setting time and radiopacity of CS. A higher compressive strength in the CS?+?ZrO2 (micro and nano) was found compared with CS?+?BO. The number of IC and IL-6 positive cells in the materials with ZrO2 was significantly reduced in comparison with CS?+?BO. von Kossa-positive structures were observed adjacent to implanted materials. The ZrO2 associated to the CS provides satisfactory physicochemical properties and better biological response than BO. Thus, ZrO2 may be a good alternative for use as radiopacifying agent in substitution to BO. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 4336-4345, 2014. PMID:24497271

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



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

PubMed Central

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

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



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


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

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



Ethylene polymerization catalyst  

SciTech Connect

A process is described for the polymerization or co-polymerization of ethylene comprising passing ethylene with or without an alpha-olefin comonomer into contact with a vanadium catalyst under polymerization conditions, the catalyst comprising: (i) the reaction product of a vanadium trihalide wherein the halogen is chlorine, bromine, or iodine, or mixtures thereof, and an electron donor, which is a liquid organic Lewis base in which the vanadium trihalide is soluble; (ii) a modifier, BX/sub 3/ or a compound having the formula AIR/sub (3-a)/X/sub a/ wherein each R is an alkyl radical having 1 to 14 carbon atoms and is alike or different; X is chlorine, bromine, or iodine, or mixtures thereof; and a is 0, 1, or 2; (iii) a silican support into which components (i) and (ii) are impregnated; (iv) a salt admixed with the silica support, the cation of the salt being selected from Groups I and II of the Periodic Chart of the Atoms and the anion of the salt being a carbonate or a sulfate; (v) a halocarbon promoter; and (vi) a hydrocarbyl aluminum cocatalyst, wherein the molar ratio of (a) electron donor to vanadium trihalide is about 1:1 to about 20:1; (b) modifier to electron donor is about 0.1:1 to about 10:1; (c) cocatalyst to component (i) is about 5:1 to 500:1; and (d) promoter to cocatalyst is about 0.1:1 to about 10:1.

Zoeckler, M.T.; Karol, F.J.



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


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

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



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

PubMed Central

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

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



Bimorphic polymeric photomechanical actuator  

NASA Technical Reports Server (NTRS)

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

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



Motion filter vector quantization  

Microsoft Academic Search

Motion-compensated prediction of video is formulated as a novel vector quantization scheme called motion filter vector quantiza- tion (MFVQ). In MFVQ, the motion vector and the pixel-intensity interpolation filter are combined into a motion filter and the en- tire filter is vector quantized. A codebook design algorithm is proposed for designing unit gain and entropy constrained MFVQ codebooks. The algorithm

Dariusz Blasiak; Wai-yip Chan



Rotations with Rodrigues' Vector  

ERIC Educational Resources Information Center

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

Pina, E.



Nanoparticulate assemblies of amphiphiles and diagnostically active materials for multimodality imaging.  


Modern medicine has greatly benefited from recent dramatic improvements in imaging techniques. The observation of physiological events through interactions manipulated at the molecular level offers unique insight into the function (and dysfunction) of the living organism. The tremendous advances in the development of nanoparticulate molecular imaging agents over the past decade have made it possible to noninvasively image the specificity, pharmacokinetic profiles, biodistribution, and therapeutic efficacy of many novel compounds. Several types of nanoparticles have demonstrated utility for biomedical purposes, including inorganic nanocrystals, such as iron oxide, gold, and quantum dots. Moreover, natural nanoparticles, such as viruses, lipoproteins, or apoferritin, as well as hybrid nanostructures composed of inorganic and natural nanoparticles, have been applied broadly. However, among the most investigated nanoparticle platforms for biomedical purposes are lipidic aggregates, such as liposomal nanoparticles, micelles, and microemulsions. Their relative ease of preparation and functionalization, as well as the ready synthetic ability to combine multiple amphiphilic moieties, are the most important reasons for their popularity. Lipid-based nanoparticle platforms allow the inclusion of a variety of imaging agents, ranging from fluorescent molecules to chelated metals and nanocrystals. In recent years, we have created a variety of multifunctional lipid-based nanoparticles for molecular imaging; many are capable of being used with more than one imaging technique (that is, with multimodal imaging ability). These nanoparticles differ in size, morphology, and specificity for biological markers. In this Account, we discuss the development and characterization of five different particles: liposomes, micelles, nanocrystal micelles, lipid-coated silica, and nanocrystal high-density lipoprotein (HDL). We also demonstrate their application for multimodal molecular imaging, with the main focus on magnetic resonance imaging (MRI), optical techniques, and transmission electron microscopy (TEM). The functionalization of the nanoparticles and the modulation of their pharmacokinetics are discussed. Their application for molecular imaging of key processes in cancer and cardiovascular disease are shown. Finally, we discuss a recent development in which the endogenous nanoparticle HDL was modified to carry different diagnostically active nanocrystal cores to enable multimodal imaging of macrophages in experimental atherosclerosis. The multimodal characteristics of the different contrast agent platforms have proven to be extremely valuable for validation purposes and for understanding mechanisms of particle-target interaction at different levels, ranging from the entire organism down to cellular organelles. PMID:19435319

Mulder, Willem J M; Strijkers, Gustav J; van Tilborg, Geralda A F; Cormode, David P; Fayad, Zahi A; Nicolay, Klaas



Cationic Polymerization of Cyclic Sulfides  

Microsoft Academic Search

The mechanism of the cationic polymerization of several thietanes and of propylene sulfide under the influence of triethyloxonium tetrafluoroborate in methylene chloride is described. The thietane polymerizations stop at limited conversions because of a termination reaction occurring between the reactive chain ends (cyclic sulfonium salts) and the sulfur atoms of the polymer chain. The maximum conversions obtained under identical conditions

E. J. Goethals; W. Drijvers; D. Van Ooteghem; A. M. Buyle



Outdoor high voltage polymeric insulators  

Microsoft Academic Search

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

R. Hackam



Reduced Vector Preisach Model  

NASA Technical Reports Server (NTRS)

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

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



Approche moléculaire par le procédé sol-gel de nanoparticules de TiO2 dopées et/ou fonctionnalisées : applications en imagerie médicale et en catalyse d'oxydation.  

E-print Network

??Un procédé sol-gel développé au laboratoire a été appliqué à des précurseurs hétéroleptiqueset/ou hétérométalliques pour l’élaboration de nouveaux matériaux hybrides et/ou dopés.Des nanoparticules de TiO2… (more)

Mendez, Violaine



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

NASA Astrophysics Data System (ADS)

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

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



Adding Two Vectors  

NSDL National Science Digital Library

This website from David M. Harrison of the University of Toronto's physics department provides an animation of the addition of two vectors. Instructors may use this animation in explaining the concept of adding vectors and demonstrating the steps involved.

Harrison, David M.



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


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

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



Support vector domain description  

Microsoft Academic Search

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

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



Rhotrix Vector Spaces  

ERIC Educational Resources Information Center

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

Aminu, Abdulhadi



Free radical polymerization-practical aspects  

SciTech Connect

This tutorial lecture will discuss practical difficulties encountered in conducting free radical initiated polymerization and how these difficulties are accomodated by bulk, solution, dispersion, suspension and emulsion polymerization techniques. Practical applications of polymeric products obtained by these polymerization techniques will also be discussed.

Harwood, H.J. [Univ. of Akron, OH (United States)



Polymerization of anionic wormlike micelles.  


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

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



Polymeric optical MEMS  

NASA Astrophysics Data System (ADS)

As micro-opto-electro-mechanical systems and devices evolve from prototypes to products, the need for cost-effective mass production techniques becomes crucial. This challenging cost goal can be reached using mass replication techniques like injection molding and hot embossing.In order to meet the special demands of miniaturization these replication techniques have been modified incorporating variothermal process control, an evacuation of the mold chamber and a modification of the molding parameters including elevated temperatures. Based on these techniques numerous micro- optical systems have been developed including a twelve fold multi-fiber connectors with an average insertion loss of 0.35 dB, an optical bench using polymeric alignment structures on a silicon substrate, a 4 by 4 star coupler with passive fiber alignment, a 1 by 2 singlemode fiber switch, and a singlemode 4 by 4 optical matrix switch. In these systems geometrical tolerances of one micrometers and below have been obtained allowing passive alignment of multimode and singlemode fibers during the assembly process and high precision positioning of fibers during operation.

Hossfeld, Jens; Paatzsch, Thomas; Schulze, Jens; Neumeier, Michel; Weber, Lutz; Bauer, Hans-Dieter; Ehrfeld, Wolfgang



Direct polymerization of proteins.  


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

Albayrak, Cem; Swartz, James R



Seawater degradation of polymeric composites  

E-print Network

to moist environments. As this distribution of strengths shifts, a transition in failure mechanism occurs. Hypothetically, the composite would initially fail in the resin. After limited exposure to moisture one might see a localized interfacial failure... the absorption in polymer resins and subsequently in polymeric composites. Experimentation performed has made an effort to support the use of the Fickian model of absorption in polymeric composites [2, 6, 7]. Secondly, researchers studied the effect...

Grant, Timothy Sean



Photoredox catalysis for polymerization reactions.  


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

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



Polycaps: Reversibly formed polymeric capsules  

PubMed Central

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

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



ContentsContents2828vector 1. Background to Vector Calculus  

E-print Network

ContentsContents2828vector calculus 1 1. Background to Vector Calculus 2. Differential Vector;Background to Vector Calculus 28.1 Introduction Vector Calculus is the study of the various derivatives (VERSION 1: April 14, 2004): Workbook Level 1 28.1: Background to Vector Calculus #12;Solution In the first

Vickers, James


Anomalous electrical and optical properties of polymeric carbons  

NASA Astrophysics Data System (ADS)

Semiconducting polymeric carbons were prepared by pyrolyzing phenol formaldehyde resin in a nitrogen atmosphere between 500 to 800 °C for 0.5 to 48 h. Their logarithmic resistivity values were found to vary linearly with the temperature in the range of 20 to 200 °C. Properties such as switching, radiative recombination, and Mott's minimum metallic conductivity were observed in these materials. These three characteristics, which are common with the inorganic amorphous semiconductors, suggest that these polymeric carbons can be included in the class of materials which satisfy the Ioffe-Regel condition, kL?1 (where k is the electron wave vector and L is the mean-free path). The switching and the radiative recombination phenomena observed in these materials provide experimental proof for the double injection model proposed by N. F. Mott [Adv. Phys. 16, 4 (1967)] for describing conduction processes in amorphous chalcogenide semiconductors.

Chellappa, V.; Jang, B. Z.



Polymeric materials in Space  

NASA Astrophysics Data System (ADS)

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

Skurat, Vladimir


Coupling of two multistep catalytic cycles for the one-pot synthesis of propargylamines from alcohols and primary amines on a nanoparticulated gold catalyst.  


A one-pot reaction was performed with a nanoparticulated gold catalyst. A secondary amine is formed through N-monoalkylation of a primary amine with an alcohol by a borrowing hydrogen methodology in a three-step reaction. The secondary amine formed enters into a second A(3)-coupling cycle to give propargylamines. The multistep reaction requires a gold species formed and stabilized on a ceria surface. PMID:22996294

Corma, Avelino; Navas, Javier; Sabater, María J



Preparation of polymer-clay nanocomposites via dispersion polymerization using tailor-made polymeric surface modifiers.  

E-print Network

??ENGLISH ABSTRACT: Fully exfoliated polystyrene-clay nanocomposites were prepared via free radical polymerization in dispersion polymerization, in a mixture of ethanol and water. Sodium montomorillonite clay… (more)

Nagi, Greesh



Stereospecific olefin polymerization catalysts  


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

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



Symbolic computer vector analysis  

NASA Technical Reports Server (NTRS)

A MACSYMA program is described which performs symbolic vector algebra and vector calculus. The program can combine and simplify symbolic expressions including dot products and cross products, together with the gradient, divergence, curl, and Laplacian operators. The distribution of these operators over sums or products is under user control, as are various other expansions, including expansion into components in any specific orthogonal coordinate system. There is also a capability for deriving the scalar or vector potential of a vector field. Examples include derivation of the partial differential equations describing fluid flow and magnetohydrodynamics, for 12 different classic orthogonal curvilinear coordinate systems.

Stoutemyer, D. R.



MAC3: Vectors  

NSDL National Science Digital Library

This resource is a set of instructional materials developed to help beginning physics students build a solid understanding of vector algebra. It contains two lecture presentations in PDF format and a companion assessment. It gives an overview of terminology, vector notation, and a variety of methods for solving problems relating to vectors. One of the authors' goals is to help students differentiate between the uses of vectors in mathematics vs. physics. This resource is part of a collection developed by the NSF-funded Mathematics Across the Community College Curriculum (MAC 3).

Friesen, Larry; Gillis, Anne



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.



Vector Calculus Spring 1997  

E-print Network

Vector Calculus Math 241 Spring 1997 Instructor Information: Professor: Bob Sharpley Office: 313D­ tor calculus including vector fields, line integrals, and Green's theorem in the plane. Exams in Math 142 or an equivalent course. Text: Calculus with Analytic Geometry, by D. Varberg and E.J. Purcell

Sharpley, Robert


Retroviruses as vectors.  


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

Vile, R G; Russell, S J



Hunting the Vector Hybrid  

E-print Network

The current state of analysis of e+e- annihilation below 2.0 GeV and of the vector component of tau decay is reviewed. The evidence for and against the presence of hybrid vectors is discussed. It is concluded that the data strongly favour their inclusion, and the consequences of this are outlined.

A Donnachie; Yu S Kalashnikova



Support Vector Data Description  

Microsoft Academic Search

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

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



Qualitative Vector Algebra  

Microsoft Academic Search

A significantaspect of reasoning about physicalsituationsinvolvesanalysisof the interactionof physical parameters that have both magnitude and direction. There have been some attempts to model motion and rotationin two dimensions, but none ofthese approaches have been extended togeneral vectoranalysis. Humans, however, are exceptionally good in reasoning about directionand motion . In thispaper, we definea framework calledQualitative Vector Algebra (QVA) forqualitativereasoning about vector

Uckun Serdar


Vector theories in cosmology  

SciTech Connect

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

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



Vector generator scan converter  


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

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



Vector generator scan converter  


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

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



Experiment: Micro Dispersive Suspension Polymerization of MMA.  

E-print Network

Experiment: Micro Dispersive Suspension Polymerization of MMA. Procedures: 1. Prepare PVA solution the weight of plate+solid 12. After finishing the polymerization, turn off the agitator, nitrogen gas

Choi, Kyu Yong


Segmentation strategies for polymerized volume data sets  

E-print Network

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...

Doddapaneni, Venkata Purna



Lecture outline Support vector machines  

E-print Network

Lecture outline · Support vector machines #12;Support Vector Machines · Find a linear hyperplane (decision boundary) that will separate the data #12;Support Vector Machines · One Possible Solution #12;Support Vector Machines · Another possible solution #12;Support Vector Machines · Other possible solutions

Terzi, Evimaria


Lecture outline Support vector machines  

E-print Network

Lecture outline · Support vector machines #12;Support Vector Machines · Find a linear hyperplane (decision boundary) that will separate the data #12;Support Vector Machines · One Possible Solution B1 #12;Support Vector Machines · Another possible solution B2 #12;Support Vector Machines · Other possible

Terzi, Evimaria


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


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

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



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


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

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



Effect of Ni precursor solution concentration on the magnetic properties and exchange bias of Ni-NiO nanoparticulate systems  

NASA Astrophysics Data System (ADS)

We report on a comparative study of the exchange bias effect and magnetic properties of Ni-NiO nanoparticulate systems synthesized by the chemical reduction of NiCl2 solution of two different molar concentrations—1 M (high) and 0.05 M (low)—followed by annealing of the dried precipitate in the temperature range 400-600 °C in air. Interestingly, the samples derived from the low molarity solution have higher Ni content and larger crystallite size than those prepared from their high molarity counterparts. These molarity dependent features subsequently modulate the magnitude of the exchange bias field in the samples, which is found to be absent or small in the 0.05 M series, but of moderate value in the 1 M samples. The different physical attributes of the particles derived from different concentrations of Ni-precursor solution are explained by invoking different nucleation kinetics and supersaturation degrees surrounding the viable growing nucleus. Furthermore, an observed increase of exchange bias with increasing annealing temperature, in contrast to the reported agglomeration of particles on annealing and subsequent reduction in bias magnitude, has been explained in correlation to the Ni-NiO interface density.

Roy, Aparna; De Toro, J. A.; Amaral, V. S.; Marques, D. P.; Ferreira, J. M. F.



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

PubMed Central

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

Uskokovic, Vuk



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

E-print Network

emitted diode LED . Due to the highly light dispersive nature of dental resins, the polymerization processPhotothermal determination of thermal diffusivity and polymerization depth profiles of polymerized diffusivity depth dependence on degree and depth of polymerization has been developed. The thermal diffusivity

Mandelis, Andreas


Outdoor HV composite polymeric insulators  

Microsoft Academic Search

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

R. Hackam



Sleeving nanocelluloses by admicellar polymerization.  


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

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



Mechanisms of polymeric film formation.  


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

Felton, Linda A



Fire Retardance of Polymeric Materials  

Microsoft Academic Search

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

Irving N. Einhorn



A disulfide polymerized protein crystal.  


The vDED coiled coil domain from human BAP29 was crystallized in dimeric and tetrameric forms. For the dimer, a disulfide bond was unexpectedly found to bridge a crystal contact, resulting in complete cross-linking along the c-axis. This indicates that it is in principle possible to design spontaneously polymerizing protein crystals. PMID:25327138

Quistgaard, Esben M



Membrane curvature controls dynamin polymerization  

PubMed Central

The generation of membrane curvature in intracellular traffic involves many proteins that can curve lipid bilayers. Among these, dynamin-like proteins were shown to deform membranes into tubules, and thus far are the only proteins known to mechanically drive membrane fission. Because dynamin forms a helical coat circling a membrane tubule, its polymerization is thought to be responsible for this membrane deformation. Here we show that the force generated by dynamin polymerization, 18 pN, is sufficient to deform membranes yet can still be counteracted by high membrane tension. Importantly, we observe that at low dynamin concentration, polymer nucleation strongly depends on membrane curvature. This suggests that dynamin may be precisely recruited to membrane buds’ necks because of their high curvature. To understand this curvature dependence, we developed a theory based on the competition between dynamin polymerization and membrane mechanical deformation. This curvature control of dynamin polymerization is predicted for a specific range of concentrations (?0.1–10 ?M), which corresponds to our measurements. More generally, we expect that any protein that binds or self-assembles onto membranes in a curvature-coupled way should behave in a qualitatively similar manner, but with its own specific range of concentration. PMID:20160074

Roux, Aurélien; Koster, Gerbrand; Lenz, Martin; Sorre, Benoît; Manneville, Jean-Baptiste; Nassoy, Pierre; Bassereau, Patricia



Electrically controlled polymeric gel actuators  

Microsoft Academic Search

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

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



Electrically controlled polymeric gel actuators  

Microsoft Academic Search

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

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



The Viscosity of Polymeric Fluids.  

ERIC Educational Resources Information Center

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

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



Robust controller design for batch polymerization reactors  

Microsoft Academic Search

This paper discusses several robust controller design methods for the batch polymerization reactors. The dynamic characteristics of batch polymerization reactors considerably change according to the progress of reaction because the reactors have strong nonlinearity. The reactor models have parameter uncertainty. On the other hand, both reactor temperature control and polymer quality control are important specifications for batch polymerization. In this

T. Yumotot; T. Ohtani; H. Ohmori; A. Sano



Plasma-polymerized coatings on various substrates  

SciTech Connect

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

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



Amphiphilic polysaccharide-hydrophobicized graft polymeric micelles for drug delivery nanosystems.  


Self-assembled amphiphilic graft copolymers in aqueous solution to form polymeric micelles, have received growing scientific attention over the years. Among the polymeric micelles, hydrophobicized polysaccharides have currently become one of the hottest researches in the field of drug delivery nanosystems. It is attributable to such appealing properties as small particle size and narrow size distribution, distinctive core-shell structure, high solubilization capacity and structural stability, tumor passive localization by enhanced permeability and retention (EPR) effect, active targeting ability via tailored targeting promoiety, long-circulation property and facile preparation. The polymeric micelles self-assembled by hydrophobicized polysaccharides can be employed as targeted drug delivery nanosystem by including thermo- or pH-sensitive components or by attaching specific targeted moieties to the outer hydrophilic surface. Beside encapsulation of water-insoluble drugs, hydrophobicized polysaccharide polymeric micelles can complex with charged proteins or peptide drugs through electrostatic force or hydrogen bond, and serve as an effective non-viral vector for gene delivery. In the latter case, polymeric micelles can not only markedly protect these macromolecules from degradation by protease or ribozymes, but also increase the gene transfection efficiency. This review will highlight the state of the art self-assembled mechanism, characterization, preparation methods and surface modification of hydrophobicized polysaccharide polymeric micelles and their recent rapid applications as drug delivery nanosystems. PMID:21568897

Liu, Y; Sun, J; Zhang, P; He, Z



Polycistronic viral vectors.  


Traditionally, vectors for gene transfer/therapy experiments were mono- or bicistronic. In the latter case, vectors express the gene of interest coupled with a marker gene. An increasing demand for more complex polycistronic vectors has arisen in recent years to obtain complex gene transfer/therapy effects. In particular, this demand is stimulated by the hope of a more powerful effect from combined gene therapy than from single gene therapy in a process whose parallels lie in the multi-drug combined therapies for cancer or AIDS. In the 1980's we had only splicing signals and internal promoters to construct such vectors: now a new set of biotechnological tools enables us to design new and more reliable bicistronic and polycistronic vectors. This article focuses on the description and comparison of the strategies for co-expression of two genes in bicistronic vectors, from the oldest to the more recently described: internal promoters, splicing, reinitiation, IRES, self-processing peptides (e.g. foot-and-mouth disease virus 2A), proteolytic cleavable sites (e.g. fusagen) and fusion of genes. I propose a classification of these strategies based upon either the use of multiple transcripts (with transcriptional mechanisms), or single transcripts (using translational/post-translational mechanisms). I also examine the different attempts to utilize these strategies in the construction of polycistronic vectors and the main problems encountered. Several potential uses of these polycistronic vectors, both in basic research and in therapy-focused applications, are discussed. The importance of the study of viral gene expression strategies and the need to transfer this knowledge to vector design is highlighted. PMID:12189721

de Felipe, P



MAC^3: Vectors Worksheet  

NSDL National Science Digital Library

This page contains a worksheet on the topic of vectors for beginning physics students. It was developed as a companion to the lecture presentations by the same authors (see Related Items on this page for a link.) A primary goal of the full instructional unit is to help physics and calculus students differentiate the uses of vectors for physics vs. mathematics, a difficulty known as the "vector calculus gap". This resource is part of a collection developed by the NSF-funded Mathematics Across the Community College Curriculum (MAC 3).

Friesen, Larry; Gillis, Anne



Understanding Vector Fields.  

ERIC Educational Resources Information Center

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

Curjel, C. R.



Poynting-vector filter  


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

Carrigan, Charles R. (Tracy, CA)



Vector sampling expansion  

Microsoft Academic Search

The vector sampling expansion (VSE) is an extension of Papoulis' (1977) generalized sampling expansion (GSE) to the vector case. In VSE, N bandlimited signals, all with the same bandwidth B, are passed through a multi-input-multi-output (MIMO) linear time invariant system that generates M (M⩾N) output signals. The goal is to reconstruct the input signals from the samples of the output

D. Seidner; M. Feder



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

Microsoft Academic Search

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

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



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

PubMed Central

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

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



Polymeric nanofibers in tissue engineering.  


Polymeric nanofibers can be produced using methods such as electrospinning, phase separation, and self-assembly, and the fiber composition, diameter, alignment, degradation, and mechanical properties can be tailored to the intended application. Nanofibers possess unique advantages for tissue engineering. The small diameter closely matches that of extracellular matrix fibers, and the relatively large surface area is beneficial for cell attachment and bioactive factor loading. This review will update the reader on the aspects of nanofiber fabrication and characterization important to tissue engineering, including control of porous structure, cell infiltration, and fiber degradation. Bioactive factor loading will be discussed with specific relevance to tissue engineering. Finally, applications of polymeric nanofibers in the fields of bone, cartilage, ligament and tendon, cardiovascular, and neural tissue engineering will be reviewed. PMID:21699434

Dahlin, Rebecca L; Kasper, F Kurtis; Mikos, Antonios G



Radiation-hardened polymeric films  


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

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



Radiation-hardened polymeric films  


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

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



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


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

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



Polymeric nanoparticles for molecular imaging.  


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

Srikar, R; Upendran, Anandhi; Kannan, Raghuraman



Two Photon Polymerization of Ormosils  

NASA Astrophysics Data System (ADS)

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

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



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

Microsoft Academic Search

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

Markus Hütter; Clarisse Luap; Hans Christian Öttinger



EVA: an explicit vector language  

Microsoft Academic Search

Fortran is the main language used on supercomputer today. Indeed, all supercomputers compilers have extensions, providing language features for explicit vector handling, to Fortran 77. These extensions are different on each machine and their functions are limited. Even with the next standard Fortran 8x, vector syntax is incomplete. EVA is an explicit vector language with powerful vector handling tools. Taking

Jean-Luc Dekeyser; Philippe Marquet; Philippe Preux; Philippe Marquet



Bit vector encoding via decomposition  

Microsoft Academic Search

The decomposition encoding of an n-bit vector V is an approach to the problem of how best to encode a bit vector under the constraints that this vector be encoded into blocks of t bits, and that access time for each bit of the original vector be constant, i.e. \\

Ralph D. Jeffords



Bunyavirus-Vector Interactions  

PubMed Central

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

Horne, Kate McElroy; Vanlandingham, Dana L.



Effect of mixing on polymerization of styrene  

E-print Network

Molecular Weight Distributions Calculated Degrees of Polymerization . Calculated Molecular Weight Distributions Streaking Observed in Reaction Medium During Continuous Polymerizations DISCUSSION Evaluation of 50 ml Glass Reactor Errors... Science. of segregation, if any, occurring in a bench scale laboratory reactor; and to evaluate the usefulness of reactor flow models based on micro- and macro-mixing in a constant-flow, stirred-tank reactor. Styrene was polymerized in a bench scale...

Treybig, Michael Norris



Mechanism of Nitrogen-Containing Cyclic Polymerization  

Microsoft Academic Search

The comprehensive polymerization mechanism of the nitrogen-containing cycles 1-azobicyclo (3,1,0)-hexane (ABH), conidine, quinuclidine, and triethylenediamine under the action of quaternary ammonium salts, ammonium salts, and BF3 complex with conidine is studied. Polymerization is of the living polymers type, and the active centers of monomer polymerization are ions and ion pairs: the activity of the latter is comparable to and exceeds

E. F. Rasvodovskii; A. V. Nekrasov; L. M. Pushchaeva; I. S. Morozova; M. A. Markevich; A. T. Ponomarenko; N. S. Enikolopyan



Polymerization Kinetics of Pre-heated Composite  

Microsoft Academic Search

Temperature affects the polymerization behavior of dimethacrylate-based materials. This study describes the influence of pre-polymerization temperature and exposure duration on polymerization kinetics of a commercial dental photo-activated composite at the top and at 2-mm depth. We used the temperature-controlled stage of a diamond-attenuated-total-reflectance unit to pre-set composite temperature between 3° and 60°C. Composite was light-exposed by a conventional quartz-tungsten-halogen curing

M. Daronch; F. A. Rueggeberg; M. F. De Goes; R. Giudici



Vector cross product in n-dimensional vector space  

E-print Network

The definition of vector cross product (VCP) introduced by Eckmann only exists in thethree- and the seven- dimensional vector space. In this paper, according to the orthogonal completeness, magnitude of basis vector cross product and all kinds of combinations of basis vector $\\hat{e}_i$, the generalized definition of VCP in the odd n-dimensional vector space is given by introducing a cross term $X_{AB}$. In addition, the definition is validated by reducing the generalization definition to the fundamental three- and seven-dimensional vector space.

Xiu-Lao Tian; Chao Yang; Yang Hu; Chao Tian



Properties of polymeric compositions based on epoxy and functional petroleum polymeric resins  

Microsoft Academic Search

We studied cross-linking, water resistance, and impedance characteristics of polymeric compositions based on epoxydiane and\\u000a maleinized petroleum polymeric resins. It is shown that epoxy and petroleum polymeric components interact at temperatures\\u000a of 150C and higher to form cross-linked copolymers. The gel-fraction content of the composition increases with the acid number\\u000a of the petroleum polymeric component. Small amounts of tertiary amine

V. I. Pokhmurs'kyi; T. V. Humenets'kyi; L. M. Bilyi; Yu. V. Dums'kyi



Ionene modified small polymeric beads  

NASA Technical Reports Server (NTRS)

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

Rembaum, Alan (Inventor)



Electrically controlled polymeric gel actuators  


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

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



Electrically controlled polymeric gel actuators  


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

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



Development of multinuclear polymeric nanoparticles as robust protein nanocarriers.  


One limitation of current biodegradable polymeric nanoparticles is their inability to effectively encapsulate and sustainably release proteins while maintaining protein bioactivity. Here we report the engineering of PLGA-polycation nanoparticles with a core-shell structure that act as a robust vector for the encapsulation and delivery of proteins and peptides. The optimized nanoparticles can load high amounts of proteins (>20?% of nanoparticles by weight) in aqueous solution without organic solvents through electrostatic interactions by simple mixing, thereby forming nanospheres in seconds with diameters <200?nm. The relationship between nanosphere size, surface charge, PLGA-polycation composition, and protein loading is also investigated. The stable nanosphere complexes contain multiple PLGA-polycation nanoparticles, surrounded by large amounts of protein. This study highlights a novel strategy for the delivery of proteins and other relevant molecules. PMID:24990548

Wu, Jun; Kamaly, Nazila; Shi, Jinjun; Zhao, Lili; Xiao, Zeyu; Hollett, Geoffrey; John, Rohit; Ray, Shaunak; Xu, Xiaoyang; Zhang, Xueqing; Kantoff, Philip W; Farokhzad, Omid C



Fractal vector measures and vector calculus on planar fractal domains  

Microsoft Academic Search

We define an abstract framework for self-similar vector-valued Borel measures on a compact space X based upon a formulation of Iterated Function Systems (IFS) on such measures. This IFS method permits the construction of tangent and normal vector measures to planar fractal curves. Line integrals of smooth vector fields over planar fractal curves may then be defined. These line integrals

F. Mendivil; E. R. Vrscay



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

...2014-07-01 false Polymeric MDI based polyurethanes (generic). 721.10299 Section...721.10299 Polymeric MDI based polyurethanes (generic). (a) Chemical substance...identified generically as polymeric MDI based polyurethanes (PMNs P-00-2,...



Escalation of polymerization in a thermal gradient  

PubMed Central

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

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



Insight into Organometallic-Mediated Radical Polymerization  

Microsoft Academic Search

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

Marie Hurtgen; Christophe Detrembleur; Christine Jerome; Antoine Debuigne




E-print Network

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

Walker, Christoph


Spring-loaded polymeric gel actuators  


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

Shahinpoor, Mohsen (Albuquerque, NM)



Polymeric Additives For Graphite/Epoxy Composites  

NASA Technical Reports Server (NTRS)

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

Kourtides, D. A.; Nir, Z.



Polymeric Membranes for Natural Gas Conditioning  

Microsoft Academic Search

All raw natural gas needs conditioning. Polymeric membrane based gas separation processes, being cost and energy effective, environmentally friendly, as well as simple and versatile, have proven their potential as better alternatives to traditional processes for natural gas over the last three decades. In this article, the polymeric membrane based separation mechanisms for natural gas are analyzed. Two major membrane-based

H. Feng; H. Zhang; L. Xu



Viral vectors for veterinary vaccines.  


Whatever strategy is adopted for the development of viral vectors for delivery of veterinary vaccines there are several key points to consider: (1) Will the vectored vaccine give a delivery advantage compared to what's already available? (2) Will the vectored vaccine give a manufacturing advantage compared to what's already available? (3) Will the vectored vaccine provide improved safety compared to what's already available? (5) Will the vectored vaccine increase the duration of immunity compared to what's already available? (6) Will the vectored vaccine be more convenient to store compared to what's already available? (7) Is the vectored vaccine compatible with other vaccines? If there is no other alternative available then the answer to these questions is easy. However, if there are alternative vaccines available then the answers to these questions become very important because the answers will determine whether a vectored vaccine is merely a good laboratory idea or a successful vaccine. PMID:9890015

Sheppard, M



Vectors from A to B  

NSDL National Science Digital Library

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


Fluidic thrust vector control  

NASA Astrophysics Data System (ADS)

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

Haloulakos, V. E.


Preloadable vector sensitive latch  

NASA Technical Reports Server (NTRS)

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

Acres, William R. (inventor)



Kinematics of vector fields  

E-print Network

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

S. Manoff



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


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

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



Vector Magnetograph Design  

NASA Technical Reports Server (NTRS)

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

Chipman, Russell A.



Fractional Vector Calculus  

Microsoft Academic Search

\\u000a The calculus of derivatives and integrals of non-integer order go back to Leibniz, Liouville, Grünwald, Letnikov and Riemann.\\u000a The fractional calculus has a long history from 1695, when the derivative of order ? = 0.5 was described by Leibniz (Oldham and Spanier, 1974; Samko et al., 1993; Ross, 1975). The history of fractional vector\\u000a calculus (FVC) is not so long.

Vasily E. Tarasov


Vector Difference Calculus  

Microsoft Academic Search

Space is filled with triangulating graph \\\\calG to serve as a quadrature grid. A discrete analog of the theory of differential forms is constructed using the associated simplical complex. The role of a basis for Lambda^p at a point is played by the set of (p+1) -simplices containing a given vertex. Vector difference operations analogous to div, grad and curl,

W. A. Schwalm; M. K. Schwalm; M. Giona



Applications of Vector Calculus  

Microsoft Academic Search

\\u000a This chapter provides a brief introduction to some of the many applications of vector calculus to physics. Each of these is\\u000a a vast topic in itself and is the subject of numerous books and a great deal of current research, so it is not possible to\\u000a go into any detail in this book. However, a number of important governing equations

Paul C. Matthews


Elusive vector glueball  

SciTech Connect

If the vector glueball {Omicron} exists in the mass range that theory suggests, its resonant production cross section can be detected in e{sup +}e{sup -} annihilation only if the decay width is very narrow ({le} a few MeV). Otherwise {Omicron} will be observed only indirectly through its mixing with {psi}{prime}. We propose a few tests of the {Omicron}-{psi}{prime} mixing for future charm factories.

Suzuki, Mahiko



A vector product in R  

Microsoft Academic Search

In nearly all undergraduate textbooks on applied analysis, the vector product is introduced only in R, giving many students the impression, that this is a special feature of this particular vector space. The author suggests avoiding this conclusion by introducing the complex numbers as an example of a vector product in R. The purpose of this paper is twofold: first,

A. R. Walter



Scientific processor vector file organization  

SciTech Connect

This patent describes in a scientific vector processor having multiple independent instruction execution pipelines, a vector file memory system. It comprises: a first vector file means for addressable storing a plurality of vector files made up of vector elements in a predetermined storage configuration and a second equal vector file means for addressably storing a second plurality of vector files made up of vector elements in the predetermined storage configuration. Each of the first and second vector file means including an identical plurality of N memory blocks, wherein each of the memory blocks comprises a random access memory means having storage locations for storing vector elements, addressing means for providing address signals for addressing the storage locations, and a separate writing means for writing vector elements in addressed ones of the storage locations. Each of the random access memory means including a plurality of successive addressable storage locations wherein each such successive location stores contiguous information successively separated by N locations, where N equals the number of the N memory blocks; N address registers; and a time slot management mechanism coupled to each of the vector file means to allocate and maintain memory access.

Lahti, A.E.



Vector representation of tourmaline compositions  

NASA Technical Reports Server (NTRS)

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

Burt, Donald M.



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

SciTech Connect

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

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



Polymer Reaction Engineering Laboratory -University of Maryland at College Park Olefin Polymerization  

E-print Network

. Polymerization of olefins through heterogeneous catalysis. IV. Modeling of heat and mass transfer resistance. Polymerization of olefins through heterogeneous catalysis. I. Low pressure propylene polymerization in slurry Polymerization (Polyolefins, Cyclo-olefin copolymers, syndiotactic polystyrene) 1. Propylene polymerization

Rubloff, Gary W.


Mechanistic studies of plasma polymerization of allylamine.  


Plasma polymerization of allylamine is performed both in continuous wave and pulsed mode. Chemical derivatization is applied to determine primary and secondary amine concentration. Primary amines are efficiently formed, but secondary amines are more abundant. A polymerization mechanism is proposed to account for the difference in amine content obtained from comparison between continuous wave and pulsed mode plasma polymerization. The AFM measurements performed on ultrathin (1-10 nm) plasma polymers confirm the continuity of films and that the film growth on silicon occurs via a layer-by-layer mechanism because no islandlike structures were detected. PMID:16854007

Choukourov, Andrei; Biederman, Hynek; Slavinska, Danka; Hanley, Luke; Grinevich, Andrey; Boldyryeva, Hanna; Mackova, Anna



Vectoring: Steering a Plane  

NSDL National Science Digital Library

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




Polymerization in emulsion microdroplet reactors  

NASA Astrophysics Data System (ADS)

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

Carroll, Nick J.


Free-standing, single-bilayer-thick polymeric nanosheets via spatially confined polymerization.  


Polymeric nanosheets organized by molecular building blocks bearing specifically oriented reactive groups provide abundant and versatile strategies for tailoring structure and chemical functionality periodically over extended length scales that complement graphene. Here we report the bulk synthesis of free-standing polymeric nanosheets via spatially confined polymerization from an elaborate 2D supramolecular system composed of two liquid-crystalline lamellar bilayer membranes of a self-assembled nonionic surfactant--dodecylglyceryl itaconate (DGI)--sandwiched by a water layer. By employing a covalent polymerization on the lamellar bilayer membranes, single-bilayer-thick (4.2 nm), and large area (greater than 100 ?m(2)) polymeric nanosheets of bilayer membranes are achieved. The polymeric nanosheets could serve as a well-defined 2D platform for post-functionalization for producing advanced hybrid materials by introducing the reactions on the hydroxyl groups at the head of DGI on the outer surfaces. PMID:24700401

Qin, Haili; Wang, Dong; Xiong, Xiong; Jin, Jian



Stable crosslinkedp-conjugated boron containingpolymers prepared by hydroboration polymerization orallylboration polymerization  

Microsoft Academic Search

Summary Stable crosslinked p-conjugated organoboron polymers and poly(cyclodiborazane)s were prepared by hydroboration polymerization or allylboration polymerization. The obtained gels, especially prepared by allylboration polymerization using 2,5-dicyanothiophene, 1,3,5-tricyanobenzene and triallylborane, showed good thermal stability and bathochromic shifts were observed in UV-vis absorption spectrum and the fluorescence emission spectrum, probably due to the interaction between polymer chains and more planer structure of

Mamoru Miyata; Yoshiki Chujo



Coupling of actin hydrolysis and polymerization: Reduced description with two  

E-print Network

OFFPRINT Coupling of actin hydrolysis and polymerization: Reduced description with two nucleotide of actin hydrolysis and polymerization: Reduced description with two nucleotide states X. Li1,2 , R PACS 87.15.rp ­ Polymerization Abstract ­ The polymerization of actin filaments is coupled

Kierfeld, Jan


Vector wave propagation method.  


In this paper, we extend the scalar wave propagation method (WPM) to vector fields. The WPM [Appl. Opt.32, 4984 (1993)] was introduced in order to overcome the major limitations of the beam propagation method (BPM). With the WPM, the range of application can be extended from the simulation of waveguides to simulation of other optical elements like lenses, prisms and gratings. In that reference it was demonstrated that the wave propagation scheme provides valid results for propagation angles up to 85 degrees and that it is not limited to small index variations in the axis of propagation. Here, we extend the WPM to three-dimensional vectorial fields (VWPMs) by considering the polarization dependent Fresnel coefficients for transmission in each propagation step. The continuity of the electric field is maintained in all three dimensions by an enhanced propagation vector and the transfer matrix. We verify the validity of the method by transmission through a prism and by comparison with the focal distribution from vectorial Debye theory. Furthermore, a two-dimensional grating is simulated and compared with the results from three-dimensional RCWA. Especially for 3D problems, the runtime of the VWPM exhibits special advantage over the RCWA. PMID:20360813

Fertig, M; Brenner, K-H



Physicochemically functional ultrathin films by interfacial polymerization  


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

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



Dielectric films improve life of polymeric insulators  

NASA Technical Reports Server (NTRS)

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.

Hudis, M.; Wydeven, T.



Giant vesicles compressed by actin polymerization  

E-print Network

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 ...

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



Aging of polymeric composites : a literature review  

E-print Network

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

Treviño-Garrido, Margie N



Biaxially oriented film on flexible polymeric substrate  


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

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



Polymeric micelles: authoritative aspects for drug delivery  

Microsoft Academic Search

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

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



Bridging the Vector Calculus Gap  

NSDL National Science Digital Library

This paper was written collaboratively by a physicist and a mathematician to raise awareness about the "vector calculus gap" and offer realistic solutions to bridge the gap. The authors define the vector calculus gap as a disparity between the way mathematicians and physical scientists think about vectors, which they argue results in performance difficulties for students of physics and engineering. In this paper, they advocate emphasizing geometric reasoning over algebraic computation when introducing vectors. In addition, their proposed instructional method uses differentials to bridge the vector calculus gap. Included are sample group activities and tips for incorporating these ideas in the classroom. SEE RELATED ITEMS BELOW for a link to the authors' full web site on Bridging the Vector Calculus Gap.

Dray, Tevian; Manogue, Corinne A.



Polymeric micelles for acyclovir drug delivery.  


Polymeric prodrug micelles for delivery of acyclovir (ACV) were synthesized. First, ACV was used directly to initiate ring-opening polymerization of ?-caprolactone to form ACV-polycaprolactone (ACV-PCL). Through conjugation of hydrophobic ACV-PCL with hydrophilic methoxy poly(ethylene glycol) (MPEG) or chitosan, polymeric micelles for drug delivery were formed. (1)H NMR, FTIR, and gel permeation chromatography were employed to show successful conjugation of MPEG or chitosan to hydrophobic ACV-PCL. Through dynamic light scattering, zeta potential analysis, transmission electron microscopy, and critical micelle concentration (CMC), the synthesized ACV-tagged polymeric micelles were characterized. It was found that the average size of the polymeric micelles was under 200nm and the CMCs of ACV-PCL-MPEG and ACV-PCL-chitosan were 2.0mgL(-1) and 6.6mgL(-1), respectively. The drug release kinetics of ACV was investigated and cytotoxicity assay demonstrates that ACV-tagged polymeric micelles were non-toxic. PMID:25193154

Sawdon, Alicia J; Peng, Ching-An




Microsoft Academic Search

Purpose: PMMA-based heat-polymerized acrylic resins used in the fabrication of denture bases may be cured in different ways. As the polymerization cycle length affects fabrication costs and time, a fast cycle is more advantageous. However, polymerization cycles may influence mechanical properties. Objective: The purpose of this study was to evaluate the influence of the polymerization cycle on the flexural strength



3-D Vector Field Simulation  

NSDL National Science Digital Library

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

Falstad, Paul



Adenoviral vectors for gene therapy  

Microsoft Academic Search

Vectors based on human adenovirus serotypes 2 (Ad2) and 5 (Ad5) of species C possess a number of features that have favored\\u000a their widespread employment for gene delivery both in?vitro and in?vivo. However, the use of recombinant Ad2- and Ad5-based\\u000a vectors for gene therapy also suffers from a number of disadvantages. These vectors possess the tropism of the parental viruses,

Joanne T. Douglas



VLSI Processor For Vector Quantization  

NASA Technical Reports Server (NTRS)

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.

Tawel, Raoul



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.


Chameleon vector bosons  

SciTech Connect

We show that for a force mediated by a vector particle coupled to a conserved U(1) charge, the apparent range and strength can depend on the size and density of the source, and the proximity to other sources. This chameleon effect is due to screening from a light charged scalar. Such screening can weaken astrophysical constraints on new gauge bosons. As an example we consider the constraints on chameleonic gauged B-L. We show that although Casimir measurements greatly constrain any B-L force much stronger than gravity with range longer than 0.1 {mu}m, there remains an experimental window for a long-range chameleonic B-L force. Such a force could be much stronger than gravity, and long or infinite range in vacuum, but have an effective range near the surface of the earth which is less than a micron.

Nelson, Ann E. [Department of Physics, Box 1560, University of Washington, Seattle, Washington 98195-1560 (United States); Instituto de Fisica Teorica UAM/CSIC, Facultad de Ciencias, C-XVI Universidad Autonoma de Madrid Cantoblanco, Madrid 28049 (Spain); Walsh, Jonathan [Department of Physics, Box 1560, University of Washington, Seattle, Washington 98195-1560 (United States)



Computer simulations of polymeric systems  

NASA Astrophysics Data System (ADS)

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

Zhang, Dongsheng


Vector Calculus on Weighted Networks  

Microsoft Academic Search

Abstract We present here a vector calculus on weighted networks following the guidelines of Dierential,Geometry. The key to develop an ecient,calculus on weighted net- works which mimetizes the calculus in the smooth case is an adequate construction of the tangent space at each vertex. This allows to consider discrete vector fields, inner products and general metrics. Then, we obtain discrete

Enrique Bendito; Angeles Carmona; Andres M. Encinas



E-print Network

DIPLOMA THESIS VECTOR ANTENNA FOR ULTRAHIGH ENERGY COSMIC NEUTRINO DETECTION IN THE ANTARCTIC ICE or Environment 35 5.1.1 Electromagnetic Wave in Ice 35 5.2 UHEC Antenna Amplification 35 5.3 Vector Measurements) detection in the Antarctic ice. Neutrinos are elementary parti- cles that travel close to the speed of light


Vector reconstruction from firing rates  

Microsoft Academic Search

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

Emilio Salinas; L. F. Abbott



Evolutionary studies of malaria vectors  

Microsoft Academic Search

The rationales given for studies of the population genetics of vectors are usually: (1) to predict the spread of genes, such as genes conferring insecticide resistance or possibly refractoriness to parasites and (2) to reveal novel insights into the epidemiology and transmission of vector-borne disease. The successful genetic transformation of mosquitoes has highlighted the need for a critical assessment of

Martin J. Donnelly; Frédéric Simard; Tovi Lehmann



A neural support vector machine.  


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

Jändel, Magnus



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

PubMed Central

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

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



Inclusion polymerization of isoprene in deoxycholic acid  

NASA Astrophysics Data System (ADS)

The radiation-induced polymerization of isoprene was made on its inclusion (or clathrate) complex with deoxycholic acid (DOCA) at 150 and 300 kGy. The microstructure of the resulting polyisoprene (PIP) was studied by FTIR spectroscopy and found fully comparable to that of PIP prepared by emulsion polymerization by a free radical initiator. Thus, the 1,4-trans content was found to be 48% and that of 1,4-cis units was 28% of the polymer structure; the remaining are being 1,2 and 3,4 units. The PIP irregular microstructure was justified in terms of monomer dynamics inside the DOCA channels. PIP from inclusion polymerization is fully amorphous as studied by differential thermal analysis (DTA) in comparison to an authentic sample of trans-1,4-polyisoprene, which instead has a crystalline melting point of 71.5 °C. The inclusion complex of PIP with DOCA (PIP@DOCA) shows a DTA melting point of 194.4 °C, 12.4 °C higher than the melting point of pure DOCA. PIP isolated from inclusion polymerization from DOCA and its complex PIP@DOCA was studied also by thermogravimetry (TGA) and differential thermogravimetry (DTG). Isoprene does not form inclusion complexes with urea and thiourea. When irradiated with these two compounds it produces an oily PIP oligomer whose microstructure was found by FTIR spectroscopy analogous to that of PIP prepared by emulsion polymerization by a free radical initiator.

Cataldo, Franco; Ragni, Pietro; Rosati, Aldo; Ursini, Ornella



Symbolic Vector Analysis in Plasma Physics  

Microsoft Academic Search

Many problems in plasma physics involve substantial amounts of analytical vector calculation. The complexity usually originates from both the vector operations themselves and the choice of underlying coordinate system. A computer algebra package for symbolic vector analysis in general coordinate systems, General Vector Analysis (GVA), is developed using Mathematica. The modern viewpoint for 3D vector calculus, differential forms on 3-manifolds,

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



The isotropic vector fleld decomposition methodology  

Microsoft Academic Search

In this paper I introduce the isotropic vector fleld decomposition methodology. This new methodology decomposes a vector fleld into six components at every node (thus it is a colocated scheme) within an associated isotropic vector matrix grid and provides an algorithm whereby the vector calculus curl is obtained. Preliminary resolution studies on this new spatial operator (i.e., the vector calculus

J. F. Nystrom


Fire-Retardant Polymeric Additives  

NASA Technical Reports Server (NTRS)

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

Williams, Martha K.; Smith, Trent M.



Engineering Polymeric Aptamers for Selective Cytotoxicity  

PubMed Central

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

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



Chikungunya Virus–Vector Interactions  

PubMed Central

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes chikungunya fever, a severe, debilitating disease that often produces chronic arthralgia. Since 2004, CHIKV has emerged in Africa, Indian Ocean islands, Asia, Europe, and the Americas, causing millions of human infections. Central to understanding CHIKV emergence is knowledge of the natural ecology of transmission and vector infection dynamics. This review presents current understanding of CHIKV infection dynamics in mosquito vectors and its relationship to human disease emergence. The following topics are reviewed: CHIKV infection and vector life history traits including transmission cycles, genetic origins, distribution, emergence and spread, dispersal, vector competence, vector immunity and microbial interactions, and co-infection by CHIKV and other arboviruses. The genetics of vector susceptibility and host range changes, population heterogeneity and selection for the fittest viral genomes, dual host cycling and its impact on CHIKV adaptation, viral bottlenecks and intrahost diversity, and adaptive constraints on CHIKV evolution are also discussed. The potential for CHIKV re-emergence and expansion into new areas and prospects for prevention via vector control are also briefly reviewed. PMID:25421891

Coffey, Lark L.; Failloux, Anna-Bella; Weaver, Scott C.



Possible mediators of the ``living'' radical polymerization  

NASA Astrophysics Data System (ADS)

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

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



Recombinant vectors as influenza vaccines.  


The antiquated system used to manufacture the currently licensed inactivated influenza virus vaccines would not be adequate during an influenza virus pandemic. There is currently a search for vaccines that can be developed faster and provide superior, long-lasting immunity to influenza virus as well as other highly pathogenic viruses and bacteria. Recombinant vectors provide a safe and effective method to elicit a strong immune response to a foreign protein or epitope. This review explores the advantages and limitations of several different vectors that are currently being tested, and highlights some of the newer viruses being used as recombinant vectors. PMID:19768410

Kopecky-Bromberg, Sarah A; Palese, Peter



Are Bred Vectors The Same As Lyapunov Vectors?  

NASA Astrophysics Data System (ADS)

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

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


Mono-dispersed Functional Polymeric Nanocapsules with Multi-lacuna via Soapless Microemulsion Polymerization  

E-print Network

Abstract The mono-dispersed crosslinked polymeric multi-lacuna nanocapsules (CP(St–OA) nanocapsules) about 40 nm with carboxylic groups on their inner and outer surfaces were fabricated in the present work. The small conglomerations of the oleic acid modified spindlelike a-Fe2O3 nanoparticles (OA–Fe2O3) were encapsulated in the facile microemulsion polymerization with styrene (St) as monomer and divinyl benzene (DVB) as crosslinker. Then the templates, small conglomerations of OA– Fe2O3, were etched with HCl in tetrahydrofuran (THF). The surface carboxylic groups of the crosslinked polymeric multi-lacuna nanocapsules were validated by the Zeta potential analysis.

Guangfeng Liu; Æ Peng Liu


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

PubMed Central

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

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



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


Poor interfacial contact is often encountered in nanoparticulate film-based devices. The dye-sensitized solar cell (DSSC) is a representative case in which a nanoporous TiO(2) electrode needs to be prepared on the transparent conducting oxide (TCO)-coated glass substrate. In this study, we demonstrate that the inter-electrode contact resistance accounts for a considerable portion of the total resistance of a DSSC and its efficiency can be greatly enhanced by welding the interface with a laser. TiO(2) films formed on the TCO-coated glass substrate were irradiated with a pulsed ultraviolet laser beam at 355 nm; this transmits through the TCO and glass but is strongly absorbed by TiO(2). Electron microscopy analysis and impedance measurements showed that a thin continuous TiO(2) layer is formed at the interface as a result of the local melting of TiO(2) nanoparticles and this layer completely bridges the gap between the two electrodes, improving the current flow with a reduced contact resistance. We were able to improve the efficiency by 35-65% with this process. DSSCs fabricated using a homemade TiO(2) paste revealed an efficiency improvement from eta = 3.3% to 5.4%, and an increase from 8.2% to 11.2% was achieved with the TiO(2) electrodes made from a commercial paste. PMID:20671364

Kim, Jinsoo; Kim, Jonghyun; Lee, Myeongkyu



Physicochemical characterization and aerosol dispersion performance of organic solution advanced spray-dried microparticulate/nanoparticulate antibiotic dry powders of tobramycin and azithromycin for pulmonary inhalation aerosol delivery.  


The purpose of this study was to systematically design pure antibiotic drug dry powder inhalers (DPIs) for targeted antibiotic pulmonary delivery in the treatment of pulmonary infections and comprehensively correlate the physicochemical properties in the solid-state and spray-drying conditions effects on aerosol dispersion performance as dry powder inhalers (DPIs). The two rationally chosen model antibiotic drugs, tobramycin (TOB) and azithromycin (AZI), represent two different antibiotic drug classes of aminoglycosides and macrolides, respectively. The particle size distributions were narrow, unimodal, and in the microparticulate/nanoparticulate size range. The SD particles possessed relatively spherical particle morphology, smooth surface morphology, low residual water content, and the absence of long-range molecular order. The emitted dose (ED%), fine particle fraction (FPF%) and respirable fraction (RF%) were all excellent. The MMAD values were in the inhalable range (<10 ?m) with smaller MMAD values for SD AZI powders in contrast to SD TOB powders. Positive linear correlations were observed between the aerosol dispersion performance parameter of FPF with increasing spray-drying pump rates and also with the difference between thermal parameters expressed as Tg-To (i.e. the difference between the glass transition temperature and outlet temperature) for SD AZI powders. The aerosol dispersion performance for SD TOB appeared to be influenced by its high water vapor sorption behavior (hygroscopicity) and pump rates or To. Aerosol dispersion performance of SD powders were distinct for both antibiotic drug aerosol systems and also between different pump rates for each system. PMID:24215736

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



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


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

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



Microwave-assisted fabrication of nanoparticulate TiO(2) microspheres for synergistic photocatalytic removal of Cr(VI) and methyl orange.  


High yield production of micro/nanostructured nanoparticulate TiO2 microspheres (NTMs) via a facile microwave-assisted hydrothermal approach was investigated. The rapid and uniform microwave heating could reduce the reaction time to 30 min, an order of magnitude shorter than that of conventional hydrothermal methods. The characterization data confirmed that the resultant NTMs were highly uniform in size, having an average diameter of ?0.5 ?m. The obtained NTMs were found to be constructed by well-crystallized anatase phase nanoparticles ranging from 5 to 10 nm that can be readily controlled by the microwave radiation temperature. Nitrogen sorption isotherm analysis revealed that the obtained NTMs possessed abundant mesoporous structures with a high specific surface area of 124 m(2) g(-1). An in situ self-aggregation formation process under controllable pH in presence of urea was proposed. The results obtained from the application of NTMs for simultaneous photocatalytic decontamination of Cr(VI) and methyl orange (MO) demonstrated a strong synergistic effect that dramatically enhanced both Cr(VI) reduction and MO oxidation removal efficiencies. This work not only enriched the synthesis methods of the micro/nanostructured TiO2, but also provided a new means to improve the photocatalytic efficiency via structural-induced synergistic effect, applicable to the other catalysis systems. PMID:24433013

Yang, Yong; Wang, Guozhong; Deng, Quan; Ng, Dickon H L; Zhao, Huijun



Simulations of polymeric and colloidal dispersions in micro-channels  

E-print Network

Simulations of polymeric and colloidal dispersions in micro-channels Amir Pirayandeh Arash microscopically dispersed in any other substance (solvent), such as monomer. · Polymer: Any large molecule in simulations with 0.00 polymeric concentration along with Polymer

Petta, Jason


Stall force of polymerizing microtubules and filament bundles  

E-print Network

. Copyright c EPLA, 2011 Introduction. ­ Polymerization of cytoskeletal fila- ments is essential for various or lamellipodia [1,2]. Single polymerizing fila- ments can generate forces in the piconewton range, as has been

Kierfeld, Jan


21 CFR 178.3740 - Plasticizers in polymeric substances.  

... false Plasticizers in polymeric substances. 178.3740 Section 178.3740...3740 Plasticizers in polymeric substances. Subject to the provisions of this regulation, the substances listed in paragraph (b) of...



Vector Fields and Line Integrals  

NSDL National Science Digital Library

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

Knill, Oliver; Winter, Dale



Polynomial Interpretation of Multipole Vectors  

E-print Network

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.

Gabriel Katz; Jeffrey Weeks



Brief history of vector Doppler  

NASA Astrophysics Data System (ADS)

Since the development of the directional Doppler by McLeod in 1967, methods of acquiring, analyzing, and displaying blood velocity information have been under constant exploration. These efforts are motivated by a variety of interest and objectives including, to: a) simplify clinical examination, examiner training, and study interpretation, b) provide more hemodynamic information, and c) reduce examination variability and improve accuracy. The vector Doppler technique has been proposed as one potential avenue to achieve these objects. Vector Doppler systems are those that determine the true 2D or 3D blood flow velocity by combining multiple independent velocity component measurements. Most instruments can be divided into two broad categories: 1) cross-beam and 2) time-domain. This paper provides a brief synopsis of the progression of vector Doppler techniques, from its onset in 1970 to present, as well as possible avenues for future work. This is not intended to be a comprehensive review of all vector Doppler systems.

Dunmire, Barbrina; Beach, Kirk W.



Gauge theories of vector particles  

Microsoft Academic Search

The possibility of generalizing the Yang-Mills trick is examined. Thus we seek theories of vector bosons invariant under continuous groups of coordinate-dependent linear transformations. All such theories may be expressed as superpositions of certain \\

Sheldon L. Glashow; Murray Gell-Mann



Rate determination from vector observations  

NASA Technical Reports Server (NTRS)

Vector observations are a common class of attitude data provided by a wide variety of attitude sensors. Attitude determination from vector observations is a well-understood process and numerous algorithms such as the TRIAD algorithm exist. These algorithms require measurement of the line of site (LOS) vector to reference objects and knowledge of the LOS directions in some predetermined reference frame. Once attitude is determined, it is a simple matter to synthesize vehicle rate using some form of lead-lag filter, and then, use it for vehicle stabilization. Many situations arise, however, in which rate knowledge is required but knowledge of the nominal LOS directions are not available. This paper presents two methods for determining spacecraft angular rates from vector observations without a priori knowledge of the vector directions. The first approach uses an extended Kalman filter with a spacecraft dynamic model and a kinematic model representing the motion of the observed LOS vectors. The second approach uses a 'differential' TRIAD algorithm to compute the incremental direction cosine matrix, from which vehicle rate is then derived.

Weiss, Jerold L.



Adaptive neural network vector predictor  

NASA Astrophysics Data System (ADS)

In this paper, an adaptive neural network vector predictor is designed in order to improve the performance of the predictive component of the predictive vector quantizer (PVQ). The proposed vector predictor consists of a set of dedicated predictors (experts) where each predictor is optimized for a particular class of input vectors. In our simulations, we used five multi-layer perceptrons (MLP) to design our expert predictors. Each MLP predictor is separately trained by using a set of training vectors that belong to a particular class. The class identity of each training vector is determined by its directional variances. In our current implementation, one predictor is optimized for stationary blocks and four other predictors are designed for horizontal, vertical, 45 degree and 135 degree diagonally oriented edge blocks. The back-propagation algorithm is used for training each network. The directional variances of the neighboring blocks are used to select the appropriate expert predictor for the current input block. Therefore, no overhead information is transmitted in order to inform the receiver about the predictor selection. Our simulation shows that the proposed scheme gives an improvement of more than 1 dB over the predictor consisting of a single MLP predictor. The perceptual quality of the predicted images are also significantly improved.

Wang, Lin-Cheng; Rizvi, Syed A.; Nasrabadi, Nasser M.; Mirelli, Vincent



Cell motility driven by actin polymerization  

Microsoft Academic Search

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

Alexander Mogilner; George Oster



Microscale abrasive wear of polymeric materials  

Microsoft Academic Search

Polymeric materials are now commonly employed as components in mechanical devices, and as such are subject to wear. Abrasive wear of polymer components may occur either by sliding against a rough counterface or by abrasion by hard particles. Whilst previous work has considered the three body abrasion of polymers using large abrasives common in the ASTM G65 test, this work

P. H Shipway; N. K Ngao



Thermostatistics of the polymeric ideal gas  

NASA Astrophysics Data System (ADS)

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

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



A polymeric microgripper with integrated thermal actuators  

NASA Astrophysics Data System (ADS)

This paper describes the design, simulation, fabrication and characterization of a polymeric microgripper with integrated thermal actuators. The microgripper was fabricated by a polymeric surface micromachining process, which utilizes SU-8 as the functional material and silicon as the sacrificial material. A thin double layer of titanium and platinum was evaporated on the gripper structure and served as the electrically conducting and heat dissipating material. The polymeric microgripper offers the advantage of large displacement and gentle handling forces, which may be ideal for handling bioparticles such as cells. Furthermore, an operating temperature below 100 °C allows the handling of living cells and tissues. The unique characteristic that SU-8 does not soften at elevated temperature allows the use of thermal actuation for the microgripper. To the best knowledge of the authors, the presented device is the first polymeric microgripper with integrated actuators. Each thermal actuator consists of two thin arms and one thick arm. Heat is generated by electrical current passing through the thin titanium/platinum on top of the 100 µm thick SU-8 structure. Based on an electrical/thermal/structural coupled simulation, the gripper can operate in both normally closed mode and normally open mode. The different electrical configurations of the gripper arms allow this flexibility. Results of the simulation and the measurement are also presented in this paper.

Nguyen, Nam-Trung; Ho, Soon-Seng; Lee-Ngo Low, Cassandra



Limiting Conversion Phenomenon in Hybrid Miniemulsion Polymerization  

Microsoft Academic Search

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

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



Epoxide functionalized polymerized crystalline colloidal arrays  

Microsoft Academic Search

We report the development of a novel method for functionalizing polymerized crystalline colloidal arrays (PCCA). This new method enables us to easily incorporate molecular recognition agents into the PCCA to produce chemical sensing materials that report on analyte concentration via diffraction of visible light. We copolymerize glycidyl methacrylate with acrylamide and N,N?-methylenebisacrylamide around crystalline colloidal arrays. The incorporated epoxide groups

Marta Kamenjicki; Sanford A. Asher



Viscoelastic models for polymeric composite materials  

Microsoft Academic Search

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

S. G. Bardenhagen; E. N. Harstad; J. C. Jr. Foster; P. J. Maudlin



Supramolecular and polymeric structures for gas sensors  

Microsoft Academic Search

Molecular, supramolecular and polymeric compounds are particularly suitable for tailoring chemically sensitive coatings of thin-film gas sensors to monitor volatile organic compounds (VOC's). The molecular recognition occurs either by specific key\\/lock interactions in the first monolayer, or by incorporation in the bulk. The separation of surface reactions from bulk dissolution effects is deduced from the thickness dependence of sensor effects

Wolfgang Göpel



Biodegradable polymeric nanoparticles as drug delivery devices  

Microsoft Academic Search

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

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



Microwave welding of polymeric-microfluidic devices  

Microsoft Academic Search

This paper describes a novel technique for bonding polymeric-microfluidic devices using microwave energy and a conductive polymer (polyaniline). The bonding is achieved by patterning the polyaniline features at the polymer joint interface by filling of milled microchannels. The absorbed electromagnetic energy is then converted into heat, facilitating the localized microwave bonding of two polymethylmethacrylate (PMMA) substrates. A coaxial open-ended probe

A. A. Yussuf; I. Sbarski; J. P. Hayes; M. Solomon; N. Tran



Radiation sterilization of polymeric implant materials  

SciTech Connect

High-energy irradiation sterilization of medical devices and implants composed of polymeric biomaterials that are in contact with tissue and/or blood, may adversely affect their long-term mechanical and/or biological performance (tissue and/or blood compatibility). Since many polymeric implants may contain trace quantities of catalysts and/or other additives, the effect of high-energy radiation on these additives, and possible synergistic effects with the polymer chains under the influence of high-energy radiation, must be considered. It is essential to indicate whether polymeric implants are used in short-term (acute) or long-term (chronic) applications. Relatively small changes in their physicochemical, mechanical, and biological properties may be tolerable in the short term, whereas similar changes may lead to catastrophic failures in long-term applications. Therefore, polymeric implants which are to be sterilized by high-energy irradiation should be carefully evaluated for long-term property changes which may be induced by the radiation.

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



Polymeric biomaterials for tissue and organ regeneration  

Microsoft Academic Search

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

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



Actin polymerization in a thermal gradient Andrew Pomerance1  

E-print Network

objects, a mechanism that is used by e.g. Lysteria bacteria who propel themselves by polymerizing actin (globular actin or G-actin) polymerize completely in the presence of K+ or Mg2+ to a double stranded chain temperature increases may cause a decrease in the polymerized fraction. Based on these data, Niranjan et al.7

Urbach, Jeff



E-print Network

SEGMENTATION STRATEGIES FOR POLYMERIZED VOLUME DATA SETS A Thesis by PURNA DODDAPANENI Submitted FOR POLYMERIZED VOLUME DATA SETS A Thesis by PURNA DODDAPANENI Submitted to Texas A&M University in partial Strategies for Polymerized Volume Data Sets (December 2004) Purna Chandra Rao Doddapaneni, B.Tech., Indian



E-print Network

and validation of the resulting PVDS is shown in both cases. #12;iv Finally the procedures of polymerized volumeSTRATEGY FOR CONSTRUCTION OF POLYMERIZED VOLUME DATA SETS A Thesis by PRATHYUSHA ARAGONDA Submitted OF POLYMERIZED VOLUME DATA SETS A Thesis by PRATHYUSHA ARAGONDA Submitted to Texas A&M University in partial


Polymeric derivatives of plant growth regulators: synthesis and properties  

Microsoft Academic Search

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

Aristidis M. Tsatsakis; Michail I. Shtilman



Microphase separation in binary polymeric micelles A. Halperin  

E-print Network

131 Microphase separation in binary polymeric micelles A. Halperin The Fritz Haber Research Center of a multicomponent system. Specifically, we consider microphase separation in binary polymeric micelles i. e. , micelles composed of two chemically distinct polymeric surfactants. We shall consider micelles formed

Boyer, Edmond


Multifunctional Polymeric Micelles as Cancer-Targeted, MRI-Ultrasensitive  

E-print Network

Multifunctional Polymeric Micelles as Cancer-Targeted, MRI-Ultrasensitive Drug Delivery Systems describe the development of multifunctional polymeric micelles with cancer-targeting capability via rv 3 and rv 3-specific cytotoxic response of these multifunctional polymeric micelles. Over the past several

Gao, Jinming


Magnetite-Loaded Polymeric Micelles as Ultrasensitive Magnetic-Resonance  

E-print Network

Magnetite-Loaded Polymeric Micelles as Ultrasensitive Magnetic-Resonance Probes** By Hua Ai* Polymeric micelles offer a powerful multifunctional plat- form for drug delivery and diagnostic imaging- tions, polymeric micelles have also received increasing atten- tion in diagnostic imaging applications

Gao, Jinming


Free heme and sickle hemoglobin polymerization  

NASA Astrophysics Data System (ADS)

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

Uzunova, Veselina V.


Image coding using vector quantization: a review  

Microsoft Academic Search

A review of vector quantization techniques used for encoding digital images is presented. First, the concept of vector quantization is introduced, then its application to digital images is explained. Spatial, predictive, transform, hybrid, binary, and subband vector quantizers are reviewed. The emphasis is on the usefulness of the vector quantization when it is combined with conventional image coding techniques, or




Replicative retroviral vectors for cancer gene therapy  

Microsoft Academic Search

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

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



Bitmap Vectorization and Realization of Shoes Style  

Microsoft Academic Search

Bitmap vectorization is the key technique for shoes remodeling design and color matching during shoes design. In this paper through experiments, Vectorizing methods and techniques for black & white bitmap and color bitmap of shoes style are studied, the main influencing factors for effect of vectorization are analyzed, fast and efficient vectorizing methods for shoes image are summarized. All these

Wan Pengbo; Jia Haichun; Peng Wenli


Mechanisms of Drug Diffusion from Polymeric Devices.  

NASA Astrophysics Data System (ADS)

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

Sharma, Kuldeepak



Symbolic Vector Analysis in Plasma Physics  

Microsoft Academic Search

Many problems in plasma physics involve substantial amounts of analytical vector calculation. The complexity usually originates from both the vector operations;\\u000athemselves and the choice of underlying coordinate system. A computer algebra package for symbolic vector analysis in general coordinate systems,;\\u000aGeneralVectorAnalysis (GVA), is developed using Mathematica. The modern viewpoint for 3D vector calculus, differential forms on 3-manifolds, is adopted

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



Symbolic vector analysis in plasma physics  

Microsoft Academic Search

Many problems in plasma physics involve substantial amounts of analytical vector calculation. The complexity usually originates from both the vector operations themselves and the underlying coordinate systems. A computer algebra package for symbolic vector analysis in general coordinate systems, GeneralVectorAnalysis (GVA), is developed using Mathematica. The modern viewpoint for 3D vector calculus, differential forms on 3-manifolds, is adopted to unify

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



Vector finite elements for electromagnetic field computation  

Microsoft Academic Search

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

Zoltan J. Cendes



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

NASA Astrophysics Data System (ADS)

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

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



Vector 33: A reduce program for vector algebra and calculus in orthogonal curvilinear coordinates  

Microsoft Academic Search

This paper describes a package with enables REDUCE 3.3 to perform algebra and calculus operations upon vectors. Basic algebraic operations between vectors and between scalars and vectors are provided, including scalar (dot) product and vector (cross) product. The vector differential operators curl, divergence, gradient and Laplacian are also defined, and are valid in any orthogonal curvilinear coordinate system. The package

David Harper



Toward lattice fractional vector calculus  

NASA Astrophysics Data System (ADS)

An analog of fractional vector calculus for physical lattice models is suggested. We use an approach based on the models of three-dimensional lattices with long-range inter-particle interactions. The lattice analogs of fractional partial derivatives are represented by kernels of lattice long-range interactions, where the Fourier series transformations of these kernels have a power-law form with respect to wave vector components. In the continuum limit, these lattice partial derivatives give derivatives of non-integer order with respect to coordinates. In the three-dimensional description of the non-local continuum, the fractional differential operators have the form of fractional partial derivatives of the Riesz type. As examples of the applications of the suggested lattice fractional vector calculus, we give lattice models with long-range interactions for the fractional Maxwell equations of non-local continuous media and for the fractional generalization of the Mindlin and Aifantis continuum models of gradient elasticity.

Tarasov, Vasily E.



Boosting with Averaged Weight Vectors  

NASA Technical Reports Server (NTRS)

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.

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



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

NASA Astrophysics Data System (ADS)

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

White, Emma Marie Hamilton


Living anionic polymerization using a microfluidic reactor  

SciTech Connect

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

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



Therapeutic Strategies Based on Polymeric Microparticles  

PubMed Central

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

Vilos, C.; Velasquez, L. A.



Surface-initiated enzymatic polymerization of DNA.  


We describe a technique to synthesize DNA homopolymers on a surface using surface-initiated enzymatic polymerization (SIEP) with terminal deoxynucleotidyl transferase (TdTase), an enzyme that repetitively adds mononucleotides to the 3'-end of oligonucleotides. The thickness of the synthesized DNA layer was found to depend on the deoxymononucleotide monomer, in the order of dATP > dTTP > dGTP approximately dCTP. In addition, the composition and the surface density of oligonucleotide initiators were also important in controlling the extent of DNA polymerization. The extension of single-stranded DNA chains by SIEP was further verified by their binding to antibodies specific to oligonucleotides. TdTase-mediated SIEP can also be used to grow spatially defined three-dimensional DNA structures by soft lithography and is a new tool for bioinspired fabrication at the micro- and nanoscale. PMID:17929953

Chow, Dominic C; Chilkoti, Ashutosh



Durability of Polymeric Glazing and Absorber Materials  

SciTech Connect

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

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



Energetics and electronic structures of polymerized cyclobutadiene  

NASA Astrophysics Data System (ADS)

We investigated electronic and geometric properties of polymerized cyclobutadiene (C4) as a metallic form of a two-dimensional carbon allotrope using first-principles calculations. Our calculations show that the polymerized structure is stable with a total energy that is slightly higher than that of C60 fullerene and close to that of small fullerene polymers. This two-dimensional covalent network with tetragonal symmetry is a metal with linear dispersion bands at the Fermi level due to the inflection point in the cosine bands. We also studied the stable stacking arrangement and electronic structures of layered system comprising the C4 polymer. The calculations show that the AA stacking is a favorable stacking arrangement among four representative stacking structures. Although small but substantial interlayer interaction, electronic structures of the layered system of C4 polymer are almost the same as that of the monolayer of C4 polymer.

Maruyama, Mina; Nakada, Kyoko; Okada, Susumu



Antibacterial polymeric nanostructures for biomedical applications.  


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

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



Charge-transfer magnetoelectrics of polymeric multiferroics.  


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

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



Anisotropic inflation from vector impurity  

SciTech Connect

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

Kanno, Sugumi [Institute for the Physics and Mathematics of the Universe, University of Tokyo, Chiba 277-8568 (Japan)] [Institute for the Physics and Mathematics of the Universe, University of Tokyo, Chiba 277-8568 (Japan); Kimura, Masashi [Department of Mathematics and Physics, Graduate School of Science, Osaka City University, Osaka 558-8585 (Japan)] [Department of Mathematics and Physics, Graduate School of Science, Osaka City University, Osaka 558-8585 (Japan); Soda, Jiro [Department of Physics, Kyoto University, Kyoto 606-8501 (Japan)] [Department of Physics, Kyoto University, Kyoto 606-8501 (Japan); Yokoyama, Shuichiro, E-mail:, E-mail:, E-mail:, E-mail: [Department of Physics and Astrophysics, Nagoya University, Aichi 464-8602 (Japan)] [Department of Physics and Astrophysics, Nagoya University, Aichi 464-8602 (Japan)



Helper-Dependent Adenoviral Vectors  

PubMed Central

Helper-dependent adenoviral vectors are devoid of all viral coding sequences, possess a large cloning capacity, and can efficiently transduce a wide variety of cell types from various species independent of the cell cycle to mediate long-term transgene expression without chronic toxicity. These non-integrating vectors hold tremendous potential for a variety of gene transfer and gene therapy applications. Here, we review the production technologies, applications, obstacles to clinical translation and their potential resolutions, and the future challenges and unanswered questions regarding this promising gene transfer technology. PMID:24533227

Rosewell, Amanda; Vetrini, Francesco; Ng, Philip



On Spinors and Null Vectors  

E-print Network

We investigate the relations between spinors and null vectors in Clifford algebra with particular emphasis on the conditions that a spinor must satisfy to be simple (also: pure). In particular we prove: i) a new property for null vectors: each of them bisects spinor space into two parts of equal size; ii) that simple spinors form one-dimensional subspaces of spinor space; iii) a necessary and sufficient condition for a spinor to be simple that generalizes a theorem of Cartan and Chevalley that appears now as a corollary of this result. We also show how to write down easily the most general spinor with a given associated totally null plane.

Budinich, Marco



On Spinors and Null Vectors  

E-print Network

We investigate the relations between spinors and null vectors in Clifford algebra with particular emphasis on the conditions that a spinor must satisfy to be simple (also: pure). In particular we prove: i) a new property for null vectors: each of them bisects spinor space into two parts of equal size; ii) that simple spinors form one-dimensional subspaces of spinor space; iii) a necessary and sufficient condition for a spinor to be simple that generalizes a theorem of Cartan and Chevalley that appears now as a corollary of this result. We also show how to write down easily the most general spinor with a given associated totally null plane.

Marco Budinich



Requirements for airborne vector gravimetry  

NASA Technical Reports Server (NTRS)

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.

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



Vector field based shape deformations  

Microsoft Academic Search

Abstract We present an approach to dene,shape deformations by constructing and,interactively modifying,C, continuous,time-dependent divergence-free vector elds. The deformation is obtained by a path line integration of the mesh vertices. This way, the deformation is volume-preserving, free of (local and global) self-intersections, feature preserving, smoothness preserving, and local. Different modeling metaphors,support the approach,which is able to modify,the vector eld,on-the-y according to

Wolfram Von Funck; Holger Theisel; Hans-peter Seidel



Biologically produced acid precipitable polymeric lignin  


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

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



Durability of Polymeric Glazing and Absorber Materials  

Microsoft Academic Search

The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes.

G. J. Jorgensen; K. M. Terwilliger; C. E. Bingham; M. Milbourne



Dye loading of unimolecular, amphiphilic polymeric nanocontainers  

Microsoft Academic Search

Unimolecular, amphiphilic polymeric nanocontainers based on poly(2-vinylpyridine)-b-polystyrene-polymacromonomers are dispersed in organic solvents and loaded with different hydrophilic dyes in solution. The poly-2-vinylpyridine core of the nanocontainers is responsible for the dye uptake, whereas the polystyrene corona grants the solubility and stabilization of the particles. The nanocontainers are 20–30nm in diameter and possess an excellent ability to sequester dye molecules up

Michael Groß; Michael Maskos



Performance of selected polymeric materials on LDEF  

NASA Technical Reports Server (NTRS)

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

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



Template Polymerization using a controlled reaction scheme  

NASA Astrophysics Data System (ADS)

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

Datta, Preeta; Genzer, Jan



In Situ Forming Polymeric Drug Delivery Systems  

PubMed Central

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

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



Homogeneous catalysts for stereoregular olefin polymerization  


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

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



Homogeneous catalysts for stereoregular olefin polymerization  


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

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



Homogeneous catalysts for stereoregular olefin polymerization  


The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C[sub 5]R[prime][sub 4[minus]x]R*[sub x])-A-(C[sub 5]R[double prime][sub 4[minus]y]R[prime][double prime][sub y])-M-Q[sub p], where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R[prime], R[double prime], R[prime][double prime], and R* represent substituted and unsubstituted alkyl groups having 1--30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3 [<=] p [<=] 0. Related complexes may be prepared by alkylation of the corresponding dichlorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form cation-like'' species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other [alpha]-olefin polymerization can be effected with very high efficiency and isospecificity. 1 fig.

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



Vector Acoustics, Vector Sensors, and 3D Underwater Imaging  

NASA Astrophysics Data System (ADS)

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

Lindwall, D.



Kinetics of polymerization of a liquid with nanosize structural heterogeneities.  


We report the effects of chemically reacting, nanometer-size structural heterogeneity on a polymerization process. Heterogeneity is introduced by adding 2 nm size molecules of polyhedral oligomeric silsesquioxane with multiepoxide groups (POSS) while maintaining stoichiometry of a polymerizing triamine-diepoxide mixture. Calorimetric studies show that POSS addition first increases the polymerization rate and then decreases it progressively more. In the presence of nanometer-scale structural heterogeneity, diffusion-controlled kinetics begins sooner in time. The enthalpy of polymerization decreases with the amount of POSS heterogeneity according to the mixture rule; the glass-liquid transition endotherm of the partially polymerized state becomes broader, and the enthalpy of post polymerization decreases. The POSS-alone mixture polymerizes relatively slower, and the glass-liquid transition exotherm of the polymerized state is indistinguishably broad. Both are attributed to the distribution of diffusion rates or dispersive kinetics, and the development of dynamic heterogeneity more rapidly for the POSS-only mixture than for others. Increase in the polymerization rate on initial addition of nanometer-size POSS and then decrease on further addition is explained in terms of decoupling of diffusion from viscous flow, that is, when the diffusion rate decreases less rapidly with the polymerization time than the viscosity increases. PMID:21962116

Khouri, Joseph; Johari, G P



Internet Supplement for Vector Calculus  

E-print Network

Page i Internet Supplement for Vector Calculus Fifth Edition Version: October, 2003 Jerrold E Answers for the Internet Supplement 107 Practice Final Examination 123 Practice Final Examination Solutions 129 #12;Page iii Preface The Structure of this Supplement. This Internet Supplement is in- tended

Wilkerson, Clarence


Internet Supplement for Vector Calculus  

E-print Network

Page i Internet Supplement for Vector Calculus Fifth Edition Version: October, 2003 Jerrold E Answers for the Internet Supplement 107 Practice Final Examination 123 Practice Final Examination Solutions 129 #12; Page iii Preface The Structure of this Supplement. This Internet Supplement is in­ tended

Hulshof, Joost



Microsoft Academic Search

We describe a short module on the geometry of parametric surfaces in space suitable for use in an introductory vector analysis class. Emphasis is placed on the geometric meaning on Gauss and mean curvature. Computational difficulties are avoided by judicious use of computers. *Support for this project was provided in part by NSF grant DUE-9351272.

Timothy A. Murdoch



Primer vector theory and applications  

NASA Technical Reports Server (NTRS)

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

Jezewski, D. J.



Hydrogen as an energy vector  

NASA Technical Reports Server (NTRS)

The feasibility of utilizing hydrogen as an energy vector is considered, with special attention given to means of hydrogen production. The state-of-the-art in thermochemical processes is reviewed, and criteria for the technical and economic feasibility of large-scale thermochemical water splitting processes are presented. The production of hydrogen from coal and from photolysis of water is discussed.

Powers, W. D.



RF Vector Network User's Guide  

E-print Network

Agilent FieldFox RF Vector Network Analyzer N9923A User's Guide Manufacturing Part Number: N9923­90001 Print Date: July 2, 2013 Supersedes: March 25, 2013 ©Agilent Technologies, Inc. #12;2 N9923A Field by applicable law, Agilent disclaims all warranties, either express or implied with regard to this manual

Ravikumar, B.


September 2012 Malaria: vector mosquitoes  

E-print Network

N° 413 September 2012 Malaria: vector mosquitoes are constantly adapting Scientific news Actualidad cientifica Actualité scientifique On the recommendations of the WHO, 290 million impregnated mosquito nets ability of the mosquitoes that carry it to adapt to pyrethrinoids, the officially recommended insecticides


Interframe vector wavelet coding technique  

NASA Astrophysics Data System (ADS)

Wavelet coding is often used to divide an image into multi- resolution wavelet coefficients which are quantized and coded. By 'vectorizing' scalar wavelet coding and combining this with vector quantization (VQ), vector wavelet coding (VWC) can be implemented. Using a finite number of states, finite-state vector quantization (FSVQ) takes advantage of the similarity between frames by incorporating memory into the video coding system. Lattice VQ eliminates the potential mismatch that could occur using pre-trained VQ codebooks. It also eliminates the need for codebook storage in the VQ process, thereby creating a more robust coding system. Therefore, by using the VWC coding method in conjunction with the FSVQ system and lattice VQ, the formulation of a high quality very low bit rate coding systems is proposed. A coding system using a simple FSVQ system where the current state is determined by the previous channel symbol only is developed. To achieve a higher degree of compression, a tree-like FSVQ system is implemented. The groupings are done in this tree-like structure from the lower subbands to the higher subbands in order to exploit the nature of subband analysis in terms of the parent-child relationship. Class A and Class B video sequences from the MPEG-IV testing evaluations are used in the evaluation of this coding method.

Wus, John P.; Li, Weiping



Learning Vector Quantization and Monotonicity  

Microsoft Academic Search

Learning vector quantization neural networks are competitive tools for classification problems. Most classification problems in business possess in- herent monotonicity properties. Credit worthiness is a prominent example. The present paper gives a simple, however eective, technique, which guarantees that the predictions of the network obey the required monotonicity properties in a strict fashion. The new method is based on a

Peter Lory


Retrovirus Vectors: Toward the Plentivirus?  

Microsoft Academic Search

Recombinant retroviral vectors based upon simple gammaretroviruses, complex lentiviruses, or potentially nonpathogenic spumaviruses represent relatively well characterized tools that are widely used for stable gene transfer. Different members of the Retroviridae family have developed distinct and potentially useful features related to their life cycle. These natural differences can be exploited for specialized applications in gene therapy and could conceivably be

Christopher Baum; Axel Schambach; Jens Bohne; Melanie Galla



Scalar calibration of vector magnetometers  

Microsoft Academic Search

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

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



Training Invariant Support Vector Machines  

Microsoft Academic Search

Practical experience has shown that in order to obtain the best possible performance, prior knowledge about invariances of a classification problem at hand ought to be incorporated into the training procedure. We describe and review all known methods for doing so in support vector machines, provide experimental results, and discuss their respective merits. One of the significant new results reported

Dennis Decoste; Bernhard Schölkopf



Portfolio Analysis for Vector Calculus  

ERIC Educational Resources Information Center

Classic stock portfolio analysis provides an applied context for Lagrange multipliers that undergraduate students appreciate. Although modern methods of portfolio analysis are beyond the scope of vector calculus, classic methods reinforce the utility of this material. This paper discusses how to introduce classic stock portfolio analysis in a…

Kaplan, Samuel R.



Form Factors and Vector Mesons  

Microsoft Academic Search

The 2pi and 3pi resonances are re-examined from the point of view that they are vector mesons coupled to conserved currents. The theory of unstable mesons is discussed and formulas are then derived for the emission and propagation of these mesons. The connection with electromagnetic form factors is then given, particularly for the simple case of infinite bare mass. The

Murray Gell-Mann; Fredrik Zachariasen



Fabricating antigen recognition and anti-bioadhesion polymeric surface via a photografting polymerization strategy.  


A polymeric platform for immunodiagnostic bioassay was constructed based on biostable polymeric support and two functional monomers, low-fouling methacryloyloxyethyl phosphorylcholine (MPC) and acrylic acid (AAc), by a photografting polymerization approach. Covalent binding of antibody to pAAc chains was achieved by activating carboxyl with NHS/EDC partner. The resultant surface showed obvious suppression of nonspecific protein adsorption and platelet adhesion relative to the control sample, exhibiting good anti-bioadhesion performances. Based on the polymer-supported matrix, a highly sensitive antibody-antigen specific recognition was confirmed in both native plasma and diluted human plasma due to the enhanced antibody loading capacity and lowered bioadhesion as compared to the reference. PMID:24433887

Song, Lingjie; Zhao, Jie; Jin, Jing; Ma, Jiao; Liu, Jingchuan; Luan, Shifang; Yin, Jinghua



Vectors and vector-borne diseases of horses.  


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

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



Polymeric composite systems modified with allotropic forms of carbon (review)  

Microsoft Academic Search

Most widely occurring classes of carbon nanoparticles used to create polymeric composite systems are considered. The possibility\\u000a is demonstrated of using “polymer-carbon nanoparticles” composites for raising the level of mechanical properties of polymeric\\u000a materials, creating friction units with improved tribological characteristics, developing new electrochemical, microelectronic,\\u000a and optical devices, and modifying barrier properties of polymeric membranes. Methods for treatment of nanoparticles

A. M. Valenkov; I. V. Gofman; K. S. Nosov; V. M. Shapovalov; V. E. Yudin



Plasma-Polymerized Films as Orientating Layers for Liquid Crystals  

NASA Astrophysics Data System (ADS)

Polymeric films were deposited onto a glass plate by RF glow-discharge polymerization. Monomer gases tried were ethylene, allylamine and tetrafluoroethylene. The effects of such surface properties as the contact angle, surface energy, and those measured by FT-IR or XPS on liquid crystal alignment were studied. It is shown that liquid crystal alignment can be controlled systematically by plasma copolymerization of different monomers or plasma treatment after polymerization which can vary surface properties continuously.

Watanabe, Ryoichi; Nakano, Toshiki; Satoh, Taketoshi; Hatoh, Hitoshi; Ohki, Yoshimichi



Nonlinear Optical Polymeric Materials: From Chromophore Design to Commercial Applications  

Microsoft Academic Search

Polymeric electro-optic materials have recently been developed that, when fabricated into devices such as Mach-Zehnder interferometers,\\u000a permit drive ( V?) voltages of less than 1 V to be realized at the telecommunications wavelength of 1.3 and 1.55 microns. Operation of polymeric\\u000a electro-optic modulators to frequencies (bandwidths) of greater than 100 GHz has been demonstrated. The total insertion loss\\u000a of polymeric

Larry Dalton


Microwave-assisted radical polymerization of dialkyl fumarates  

NASA Astrophysics Data System (ADS)

Free radical polymerization of dialkyl fumarates (R:isopropyl, cyclohexyl, 2-ethylhexyl, 2-phenylethyl) under microwave irradiation was investigated. The polymerizations were carried out at different powers of irradiation and initiator concentrations (benzoyl peroxide, BP) and the effect of the monomer structure on the conversion, average molecular weights and the polydispersity index ( Mw/ Mn) was analyzed. A significant enhancement of the rates of polymerization was found, as compared with those obtained under thermal conditions.

Cortizo, M. Susana; Laurella, Sergio; Alessandrini, José Luis



Shape of the Polymerization Rate in the Prion Equation  

E-print Network

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.

Gabriel, Pierre



Lentiviral Vectors for Immune Cells Targeting  

PubMed Central

Lentiviral vectors are efficient gene delivery vehicles suitable for delivering long-term transgene expression in various cell types. Engineering lentiviral vectors to have the capacity to transduce specific cell types is of great interest to advance the translation of lentiviral vectors towards the clinic. Here we provide an overview of innovative approaches to target lentiviral vectors to cells of the immune system. In this overview we distinguish between two types of lentiviral vector targeting strategies: 1) targeting of the vectors to specific cells by lentiviral vector surface modifications, and 2) targeting at the level of transgene transcription by insertion of tissue-specific promoters to drive transgene expression. It is clear that each strategy is of enormous value but ultimately combining these approaches may help reduce the effects of off-target expression and improve the efficiency and saftey of lentiviral vectors for gene therapy. PMID:20085508

Froelich, Steven; Tai, April; Wang, Pin



Linear Prediction Of Stationary Sequences Of Vectors  

NASA Technical Reports Server (NTRS)

Report discusses direct approach to linear prediction of stationary sequence of vectors. Derives set of equations constituting minimal-order linear predictor. Using this approach, it proposes two specific computationally efficient schemes to predict vectors in sequence.

Baram, Yoram



Symbolic Vector Analysis in Plasma Physics.  

National Technical Information Service (NTIS)

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

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



Symbolic Vector Analysis in Plasma Physics  

SciTech Connect

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

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



Compilation techniques for short-vector instructions  

E-print Network

Multimedia extensions are nearly ubiquitous in today's general-purpose processors. These extensions consist primarily of a set of short-vector instructions that apply the same opcode to a vector of operands. This design ...

Larsen, Samuel (Samuel Barton), 1975-



Symbolic Vector Analysis in Plasma Physics  

SciTech Connect

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

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



Acoustic vector-sensor array performance  

E-print Network

Classical hydrophones measure pressure only, but acoustic vector-sensors also measure particle velocity. Velocity measurements can increase array gain and resolve ambiguities, but make vector-sensor arrays more difficult ...

Kitchens, Jonathan Paul



Acoustic vector-sensor array performance .  

E-print Network

??Classical hydrophones measure pressure only, but acoustic vector-sensors also measure particle velocity. Velocity measurements can increase array gain and resolve ambiguities, but make vector-sensor arrays… (more)

Kitchens, Jonathan Paul



Vector-thread architecture and implementation  

E-print Network

This thesis proposes vector-thread architectures as a performance-efficient solution for all-purpose computing. The VT architectural paradigm unifies the vector and multithreaded compute models. VT provides the programmer ...

Krashinsky, Ronny (Ronny Meir), 1978-



Alphavirus Vectors Having Attentuated Virion Structural Proteins.  

National Technical Information Service (NTIS)

The present invention provides immunogenic compositions and methods that may be used to administer safer (i.e., attenuated) alphavirus vectors (such as alphavirus vectors comprising a VEE virion shell) that retain improved immunogenicity as compared with ...

A. West, J. Smith, N. L. Davis, R. E. Johnston



Idea Bank: Vectors on the Basketball Court  

NSDL National Science Digital Library

An Idea Bank published in the April/May 2009 issue of The Science Teacher describes an experiential physics lesson on vectors and vector addition (Brown 2009). Like its football predecessor, the basketball-based investigation presented in this I

Bergman, Daniel



Effect of filler choice on a binary frontal polymerization system.  


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

Viner, Veronika; Viner, Gloria



Control over Colloidal Particle Morphology by Dispersion Polymerization.  

E-print Network

??The main subject of this thesis is the structure and morphology control of colloidal polymer particles, in particular, poly(methyl methacrylate) (PMMA) particles, by dispersion polymerization… (more)

Peng, B.



Preparation of polymeric diacetylene thin films for nonlinear optical applications  

NASA Technical Reports Server (NTRS)

A method for producing polymeric diacetylene thin films having desirable nonlinear optical characteristics has been achieved by producing amorphous diacetylene polymeric films by simultaneous polymerization of diacetylene monomers in solution and deposition of polymerized diacetylenes on to the surface of a transparent substrate through which ultraviolet light has been transmitted. These amorphous polydiacetylene films produced by photo-deposition from solution possess very high optical quality and exhibit large third order nonlinear optical susceptibilities, such properties being suitable for nonlinear optical devices such as waveguides and integrated optics.

Frazier, Donald O. (inventor.); Mcmanus, Samuel P. (inventor.); Paley, Mark S. (inventor.); Donovan, David N. (inventor.)



Microfluidic approaches to the synthesis of complex polymeric particles  

E-print Network

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

Dendukuri, Dhananjay, 1978-



Two-photon polymerization microstructuring in regenerative medicine.  


Two-photon polymerization has developed as a powerful tool for making micro- and nanoscale structures for regenerative medicine applications. This review discusses micro- and nanoscale aspects of tissue engineering, which are followed by a brief description of the two-photon polymerization process and how it has been used thus far in tissue engineering and other regenerative medicine applications. Lastly, potential future applications of two-photon polymerization in regenerative medicine are presented. This review provides a comprehensive summary of the uses of two-photon polymerization thus far in regenerative medicine and a look into how this technique will be used in the future. PMID:23277016

Gittard, Shaun Davis; Koroleva, Anastasia; Nguyen, Alexander Khoa; Fadeeva, Elena; Gaidukeviciute, Arune; Schlie-Wolter, Sabrina; Narayan, Roger Jagdish; Chichkov, Boris



Microemulsion polymerization of styrene initiated with gamma ray  

NASA Astrophysics Data System (ADS)

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

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


Microemulsion polymerization of styrene initiated with gamma ray  

NASA Astrophysics Data System (ADS)

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

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



Online observation of emulsion polymerization by fluorescence technique  

NASA Astrophysics Data System (ADS)

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

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



Assessing Long-term Reliability of Polymeric Housing Materials  

NASA Astrophysics Data System (ADS)

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

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


Light-Driven Polymeric Bimorph Actuators  

NASA Technical Reports Server (NTRS)

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

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



Polymer Reaction Engineering Laboratory -University of Maryland at College Park Free Radical Polymerization  

E-print Network

Polymerization Micro-Dispersive Suspension Polymerization 1. Polymerization of methyl methacrylate with a pomegranate-like internal structure via micro-dispersive polymerization in a geometrically confined reaction). 4. Experimental and theoretical study of the reaction locus during the dispersion polymerization

Rubloff, Gary W.


A polymeric flame retardant additive for rubbers  

SciTech Connect

Synthesis of a polyphosphonate by the interfacial polymerization of bisphenol-A (BPA) and dichloro-phenyl phosphine oxide (DCPO) using cetyltrimethyl ammonium chloride (TMAC) as phase transfer catalyst (PTC) was reported. The polyphosphonate was characterized by elemental analysis, IR, TGA, DSC and 1H-NMR spectroscopy. The flame retardancy of the polymer was done by OI study. The polymer was used as a fire retardant additive to rubbers such as natural rubber (NR), styrene-butadiene rubber(SBR), nitrile rubber (NBR) and chloroprene rubber (CR). The efficiency of the fire retardant property of this additive was determined by LOI measurements of the various rubber samples.

Ghosh, S.N.; Maiti, S. [Indian Institute of Technology, Kharagpur (India)



Targeted polymeric magnetic nanoparticles for brain imaging  

NASA Astrophysics Data System (ADS)

The purpose of this study was to develop targeted polymeric magnetic nanoparticle system for brain imaging. Near infrared dye indocyanine green (ICG) or p-gycoprotein substrate rhodamine 123 (Rh123) were encapsulated along with oleic acid coated magnetic nanoparticles (OAMNP) in a matrix of poly(lactide-co-glycolide) (PLGA) and methoxy poly(ethyleneglycol)-poly(lactide) (Met-PEG-PLA). The nanoparticles were evaluated for morphology, particle size, dye content and magnetite content. The in vivo biodistribution study was carried out using three groups of six male Sprague Dawley rats each. Group I received a saline solution containing the dye, group II received dye-loaded polymeric magnetic nanoparticles without the aid of a magnetic field, and group III received dye-loaded polymeric magnetic nanoparticles with a magnet (8000 G) placed on the head of the rat. After a preset exposure period, the animals were sacrificed and dye concentration was measured in the brain, liver, kidney, lungs and spleen homogenates. Brain sections were fixed, cryotomed and visualized using fluorescence microscopy. The particles were observed to be spherical and had a mean size of 220 nm. The encapsulation efficiency for OAMNP was 57%, while that for ICG was 56% and for Rh123 was 45%. In the biodistribution study, while the majority of the dose for all animals was found in the liver, kidneys and spleen, group III showed a significantly higher brain concentration than the other two groups (p < 0.001). This result was corroborated by the fluorescence microscopy studies, which showed enhanced dye penetration into the brain tissue for group III. Further studies need to be done to elucidate the exact mechanism responsible for the increased brain uptake of dye to help us understand if the magnetic nanoparticles actually penetrate the blood brain barrier or merely deliver a massive load of dye just outside it, thereby triggering passive diffusion into the brain parenchyma. These results reinforce the potential use of polymeric magnetically-targeted nanoparticles in active brain targeting and imaging.

Kirthivasan, Bharat; Singh, Dhirender; Raut, Sangram; Bommana, Murali Mohan; Squillante, Emilio, III; Sadoqi, Mostafa



Polar order disruption in achiral polymeric composites  

NASA Astrophysics Data System (ADS)

In polar composites, the molecular structure of the monomer component strongly affects the mesophase properties in the polymer matrix. High ordered smectic phases detected in the monomer molecule produces its segregation. The observed destructive phenomenon to achieve antiferroelectric phases is related to the new structure of the low molar mass molecule, which directly affect their mesomorphic properties and the affinity in the polymeric matrix. There is enough evidence about the importance of mesophase affinity between monomer and polymer in the composites that allows the development of antiferroelectric phases.

Soto-Bustamante, E. A.; Vergara-Toloza, R. O.; González-Henríquez, C. M.



Polymeric complexes in comets and in space  

NASA Astrophysics Data System (ADS)

The detection of long-chain organic polymers similar to polymethylene in the positive ions within the coma of Comet Halley is considered within the context of a class of grain model (Wickramasinghe, 1974). A distribution of fluffy polymeric aggregates similar to that found in the dust from Comet Halley, together with an admixture of free polymers and graphite, is consistent with the observed wavelength dependence of interstellar extinction. The results suggest that the properties of interstellar dust would be similar to the more easily observable properties of cometary dust.

Hoyle, F.; Wickramasinghe, N. C.



Rotational dynamics of optically trapped polymeric nanofibers  

E-print Network

The optical trapping of polymeric nanofibers and the characterization of the rotational dynamics are reported. A strategy to apply a torque to a polymer nanofiber, by tilting the trapped fibers using a symmetrical linear polarized Gaussian beam is demonstrated. Rotation frequencies up to 10 Hz are measured, depending on the trapping power, the fiber length and the tilt angle. A comparison of the experimental rotation frequencies in the different trapping configurations with calculations based on optical trapping and rotation of linear nanostructures through a T-Matrix formalism, accurately reproduce the measured data, providing a comprehensive description of the trapping and rotation dynamics.

Neves, Antonio Alvaro Ranha; Pagliara, Stefano; Saija, Rosalba; Borghese, Ferdinando; Denti, Paolo; Iati, Maria Antonia; Cingolani, Roberto; Marago, Onofrio M; Pisignano, Dario



Microscale polymeric helical structures produced by electrospinning  

NASA Astrophysics Data System (ADS)

Microscale helical coils consisting of a composite of one conducting and one nonconducting polymer were produced using electrospinning. The nonconducting polymer was poly(ethylene oxide) and the conducting polymer was poly(aniline sulfonic acid). The coil structures were studied over a range of processing conditions and fiber composition. The data suggest that the helical structures are formed due to viscoelastic contraction upon partial neutralization of the charged fibers. Polymeric microcoils may find applications in microelectromechanical systems, advanced optical components, and drug delivery systems.

Kessick, Royal; Tepper, Gary



Studies of molecular properties of polymeric materials  

NASA Technical Reports Server (NTRS)

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

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



Frontal Polymerization in Microgravity Summary of Research  

NASA Technical Reports Server (NTRS)

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.

Pojman, John A.



Diffusive transport in modern polymeric materials  

SciTech Connect

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

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



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

NASA Astrophysics Data System (ADS)

The structures of poly(methyl-n-propylsilane) (PMPrS) amphiphilically modified through ?-ray-induced graft polymerization were investigated with 1H NMR measurement. By the use of methyl methacrylate (MMA) or diethyl fumarate (DEF) as monomers for the graft polymerization, grafting yield rose with increasing total absorption dose and monomer concentrations, but decreased with increasing dose rate. This result means that grafting yield of modified PMPrS can be controlled by changing irradiation conditions. However, the number of PMMA or PDEF graft chains per PMPrS chain was estimated to be less than 1.0 by analysis of 1H NMR spectra, and this value was lower than that we had expected. To improve graft density, maleic anhydride (MAH), which is known as a non-homopolymerizable monomer in radical polymerization, was used as a monomer for grafting. As a result, high density grafting (one MAH unit for 4.2 silicon atoms) was attained. It demonstrates that the structure of ?-ray-modified polysilane strongly depends on the polymerization characteristics of grafted monomers.

Tanaka, Hidenori; Iwasaki, Isao; Kunai, Yuichiro; Sato, Nobuhiro; Matsuyama, Tomochika



Synthesis of Petroleum Polymeric Resin by Cationic Polymerization of the C 9 Fraction  

Microsoft Academic Search

Cationic oligomerization of the C9 fraction of liquid pyrolysis products of petroleum raw materials, catalyzed by aluminum trichloride diphenyl ether complex, was studied, and a procedure was developed for preparation of a petroleum polymeric resin and petroleum polymerizate to be used as film-forming agents in paint-and-varnish materials.

F. N. Kaputskii; V. P. Mardykin; L. V. Gaponik; V. P. Lesnyak; S. V. Kostyuk; T. L. Mil'chanina



Viral vectors for vaccine applications  

PubMed Central

Traditional approach of inactivated or live-attenuated vaccine immunization has resulted in impressive success in the reduction and control of infectious disease outbreaks. However, many pathogens remain less amenable to deal with the traditional vaccine strategies, and more appropriate vaccine strategy is in need. Recent discoveries that led to increased understanding of viral molecular biology and genetics has rendered the used of viruses as vaccine platforms and as potential anti-cancer agents. Due to their ability to effectively induce both humoral and cell-mediated immune responses, viral vectors are deemed as an attractive alternative to the traditional platforms to deliver vaccine antigens as well as to specifically target and kill tumor cells. With potential targets ranging from cancers to a vast number of infectious diseases, the benefits resulting from successful application of viral vectors to prevent and treat human diseases can be immense. PMID:23858400

Choi, Youngjoo



Medium Modification of Vector Mesons  

SciTech Connect

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

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



Gene targeting with retroviral vectors  

SciTech Connect

The authors have designed and constructed integration-defective retroviral vectors to explore their potential for gene targeting in mammalian cells. Two nonoverlapping deletion mutants of the bacterial neomycin resistance (neo) gene were used to detect homologous recombination events between viral and chromosomal sequences. Stable neo gene correction events were selected at a frequency of approximately 1 G418/sup r/ cell per 3 x 10/sup 6/ infected cells. Analysis of the functional neo gene in independent targeted cell clones indicated that unintegrated retroviral linear DNA recombined with the target by gene conversion for variable distances into regions of nonhomology. In addition, transient neo gene correction events which were associated with the complete loss of the chromosomal target sequences were observed. These results demonstrated that retroviral vectors can recombine with homologous chromosomal sequences in rodent and human cells.

Ellis, J.; Bernstein, A. (Toronto Univ., ON (Canada))



ELVIS - ELectromagnetic Vector Information Sensor  

E-print Network

The ELVIS instrument was recently proposed by the authors for the Indian Chandrayaan-1 mission to the Moon and is presently under consideration by the Indian Space Research Organisation (ISRO). The scientific objective of ELVIS is to explore the electromagnetic environment of the moon. ELVIS samples the full three-dimensional (3D) electric field vector, E(x,t), up to 18 MHz, with selective Nyqvist frequency bandwidths down to 5 kHz, and one component of the magnetic field vector, B(x,t), from a few Hz up to 100 kHz.As a transient detector, ELVIS is capable of detecting pulses with a minimum pulse width of 5 ns. The instrument comprises three orthogonal electric dipole antennas, one magnetic search coil antenna and a four-channel digital sampling system, utilising flexible digital down conversion and filtering together with state-of-the-art onboard digital signal processing.

Bergman, J E S; Thidé, B; Ananthakrishnan, S; Wahlund, J E; Karlsson, R L; Puccio, W; Carozzi, T D; Kale, P



ELVIS - ELectromagnetic Vector Information Sensor  

E-print Network

The ELVIS instrument was recently proposed by the authors for the Indian Chandrayaan-1 mission to the Moon and is presently under consideration by the Indian Space Research Organisation (ISRO). The scientific objective of ELVIS is to explore the electromagnetic environment of the moon. ELVIS samples the full three-dimensional (3D) electric field vector, E(x,t), up to 18 MHz, with selective Nyqvist frequency bandwidths down to 5 kHz, and one component of the magnetic field vector, B(x,t), from a few Hz up to 100 kHz.As a transient detector, ELVIS is capable of detecting pulses with a minimum pulse width of 5 ns. The instrument comprises three orthogonal electric dipole antennas, one magnetic search coil antenna and a four-channel digital sampling system, utilising flexible digital down conversion and filtering together with state-of-the-art onboard digital signal processing.

J. E. S. Bergman; L. Åhlén; O. Stål; B. Thidé; S. Ananthakrishnan; J. -E. Wahlund; R. L. Karlsson; W. Puccio; T. D. Carozzi; P. Kale



2-D Vector Field Simulation  

NSDL National Science Digital Library

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

Falstad, Paul



Quantum electrodynamics for vector mesons  

E-print Network

Quantum electrodynamics for $\\rho$ mesons is considered. It is shown that, at tree level, the value of the gyromagnetic ratio of the $\\rho^+$ is fixed to 2 in a self-consistent effective quantum field theory. Further, the mixing parameter of the photon and the neutral vector meson is equal to the ratio of electromagnetic and strong couplings, leading to the mass difference $M_{\\rho^0}-M_{\\rho^\\pm}\\sim 1 {\\rm MeV}$ at tree order.

D. Djukanovic; M. R. Schindler; J. Gegelia; S. Scherer



Thrust-Vector-Control System  

NASA Technical Reports Server (NTRS)

Control gains computed via matrix Riccati equation. Software-based system controlling aim of gimbaled rocket motor on spacecraft adaptive and optimal in sense it adjusts control gains in response to feedback, according to optimizing algorithm based on cost function. Underlying control concept also applicable, with modifications, to thrust-vector control on vertical-takeoff-and-landing airplanes, control of orientations of scientific instruments, and robotic control systems.

Murray, Jonathan



Biological rhythms and vector insects  

PubMed Central

The adjustment of all species, animals and plants, to the Earth’s cyclic environments is ensured by their temporal organisation. The relationships between parasites, vectors and hosts rely greatly upon the synchronisation of their biological rhythms, especially circadian rhythms. In this short note, parasitic infections by Protozoa and by microfilariae have been chosen as examples of the dependence of successful transmission mechanisms on temporal components. PMID:24473803

Marques, Mirian David



Characterizing Vectors of Marine Invasion  

Microsoft Academic Search

The arrival of an invasive species in a new region is the culmination of a set of relatively discrete steps, including the\\u000a invader ' s initial association with a transport vector, its tolerance of environmental conditions encountered during transit,\\u000a and its survival upon entering its new ecosystem (Ruiz and Carlton 2003). In the chapters that follow, a number of issues

Dan Minchin; Stephan Gollasch; Andrew N. Cohen; Chad L. Hewitt; Sergej Olenin


Vector wind profile gust model  

NASA Technical Reports Server (NTRS)

A methodology was developed for the derivation and analysis of small scale perturbations in Jimsphere wind profiles. Gusts in various wavelength bands have been derived from these perturbations; the probability distribution of gust components and associated gust length has been shown to be accurately represented by a gamma distribution. Theoretical and observed distributions of component gust vary significantly with season, altitude, and wavelength range. The results of this study provide the basis for a vector wind model for Cape Kennedy, Florida.

Adelfang, S. I.; Evans, B. A.




SciTech Connect

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

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



Vinyl Polymerization. 274. Polymerization of Acrylonitrile Initiated by the System Tetramethyl Tetrazene and Co(II) Chloride  

Microsoft Academic Search

The binary system of tetramethyl tetrazene (TMT) and Co(II) chloride was used as initiator of acrylonitrile (AN) in dimethylformamide. The initial rate of polymerization (Rp) was found to be expressed by Rp = k[TMT][Co(II) chloride] [AN] The polymerization was confirmed to proceed via a radical mechanism. The over-all activation energy for the polymerization was estimated as 15.1 kcal\\/mole. On the

Kazuo Sugiyama; Tadao Nakaya; Minoru Imoto



THE VECTOR CALCULUS GAP: Mathematics = Physics  

E-print Network

THE VECTOR CALCULUS GAP: Mathematics = Physics Tevian Dray Department of Mathematics, Oregon State discuss some of the differences between the way mathematicians and physicists view vector calculus and the way physicists use it. We also give some suggestions for narrowing the gap. Keywords: vector calculus


Vector Knowledge of Beginning Physics Students.  

ERIC Educational Resources Information Center

Presents the Vector Knowledge Test that was designed to see if beginning physics students possess the minimal basic knowledge of vectors that will allow them to proceed with a study of Newtonian mechanics. Concludes that only one-third of the students in a calculus-based introductory course at California Polytechnic had sufficient vector

Knight, Randall D.



Vector Calculus: a quick review Selected Reading  

E-print Network

Appendix A Vector Calculus: a quick review Selected Reading H.M. Schey,. Div, Grad, Curl and all that: An informal Text on Vector Calculus, W.W. Norton and Co., (1973). (Good physical introduction on tensors but lots of worked problems) Marsden, J.E. and Tromba, A.J. . Vector Calculus. W.H. Freeman (or

Spiegelman, Marc W.


VEST: Abstract Vector Calculus Simplication in Mathematics.  

National Technical Information Service (NTIS)

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

H. Qin, J. Burby, J. Squire



Could dark energy be vector-like?  

Microsoft Academic Search

In this paper I explore whether a vector field can be the origin of the present stage of cosmic acceleration. In order to avoid violations of isotropy, the vector has be part of a 'cosmic triad', that is, a set of three identical vectors pointing in mutually orthogonal spatial directions. A triad is indeed able to drive a stage of

C. Armendáriz-Picón



Vector coding for partial response channels  

Microsoft Academic Search

A linear technique for combining equalization and coset codes on partial response channels with additive white Gaussian noise is developed. The technique, vector coding, uses a set of transmit filters or `vectors' to partition the channel into an independent set of parallel intersymbol interference (ISI)-free channels for any given finite (or infinite) block length. The optimal transmit vectors for such

Sanjay Kasturia; James T. Aslanis; John M. Cioffi



Visualizing vector field topology in fluid flows  

NASA Technical Reports Server (NTRS)

Methods of automating the analysis and display of vector field topology in general and flow topology in particular are discussed. Two-dimensional vector field topology is reviewed as the basis for the examination of topology in three-dimensional separated flows. The use of tangent surfaces and clipping in visualizing vector field topology in fluid flows is addressed.

Helman, James L.; Hesselink, Lambertus



Copyright protection for GIS vector data production  

Microsoft Academic Search

Limited by the characters of GIS vector data, such as variety and complexity of expression, universality, mass, disorder and pretty good privacy, etc., the traditional copyright protection methods for image and audio productions cannot be applied into GIS vector data productions directly. In this paper, a solution to copyright protection of GIS vector data productions is proposed. Firstly, information characteristics,

A. Li; W. Zhou; B. Lin; Y. Chen



Vector Sensor Arrays in Underwater Acoustic Applications  

E-print Network

Vector Sensor Arrays in Underwater Acoustic Applications Paulo Santos1, Paulo Felisberto1. A vector sensor measures both the acoustic pressure and the three components of particle velocity of the use of vector sensors in underwater acoustic applications such as direction of arrival (DOA

Jesus, Sérgio M.


Quantum mechanics without state vectors  

NASA Astrophysics Data System (ADS)

Because the state vectors of isolated systems can be changed in entangled states by processes in other isolated systems, keeping only the density matrix fixed, it is proposed to give up the description of physical states in terms of ensembles of state vectors with various probabilities, relying only on density matrices. The density matrix is defined here by the formula giving the mean values of physical quantities, which implies the same properties as the usual definition in terms of state vectors and their probabilities. This change in the description of physical states opens up a large variety of new ways that the density matrix may transform under various symmetries, different from the unitary transformations of ordinary quantum mechanics. Such new transformation properties have been explored before, but so far only for the symmetry of time translations into the future, treated as a semigroup. Here, new transformation properties are studied for general symmetry transformations forming groups, not just semigroups. Arguments that such symmetries should act on the density matrix as in ordinary quantum mechanics are presented, but all of these arguments are found to be inconclusive.

Weinberg, Steven



Protein encapsulation in polymeric microneedles by photolithography  

PubMed Central

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

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



Metastable Polymerization of Sickle Hemoglobin in Droplets  

PubMed Central

Sickle cell disease arises from a genetic mutation of one amino acid in each of the two hemoglobin ? chains, leading to the polymerization of hemoglobin in the red cell upon deoxygenation, and is characterized by vascular crises and tissue damage due to the obstruction of small vessels by sickled cells. It has been an untested assumption that, in red cells that sickle, the growing polymer mass would consume monomers until the thermodynamically well-described monomer solubility was reached. By photolyzing droplets of sickle hemoglobin suspended in oil we find that polymerization does not exhaust the available store of monomers, but stops prematurely, leaving the solutions in a supersaturated, metastable state typically 20% above solubility at 37°C, though the particular values depend on the details of the experiment. We propose that polymer growth stops because the growing ends reach the droplet edge, whereas new polymer formation is thwarted by long nucleation times, since the hemoglobin concentration is lowered by depletion of monomers into the polymers that have formed. This finding suggests a new aspect to the pathophysiology of sickle cell disease, namely, that cells deoxygenated in the microcirculation are not merely undeformable, but will actively wedge themselves tightly against the walls of the microvasculature by a ratchet-like mechanism driven by the supersaturated solution. PMID:17493634

Aprelev, Alexey; Weng, Weijun; Zakharov, Mikhail; Rotter, Maria; Yosmanovich, Donna; Kwong, Suzanna; Briehl, Robin W.; Ferrone, Frank A.



Space environmental effects on polymeric materials  

NASA Technical Reports Server (NTRS)

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

Kiefer, Richard L.; Orwoll, Robert A.



Engineering topochemical polymerizations using block copolymer templates.  


With the aim to achieve rapid and efficient topochemical polymerizations in the solid state, via solution-based processing of thin films, we report the integration of a diphenyldiacetylene monomer and a poly(styrene-b-acrylic acid) block copolymer template for the generation of supramolecular architectural photopolymerizable materials. This strategy takes advantage of non-covalent interactions to template a topochemical photopolymerization that yields a polydiphenyldiacetylene (PDPDA) derivative. In thin films, it was found that hierarchical self-assembly of the diacetylene monomers by microphase segregation of the block copolymer template enhances the topochemical photopolymerization, which is complete within a 20 s exposure to UV light. Moreover, UV-active cross-linkable groups were incorporated within the block copolymer template to create micropatterns of PDPDA by photolithography, in the same step as the polymerization reaction. The materials design and processing may find potential uses in the microfabrication of sensors and other important areas that benefit from solution-based processing of flexible conjugated materials. PMID:25208609

Zhu, Liangliang; Tran, Helen; Beyer, Frederick L; Walck, Scott D; Li, Xin; Agren, Hans; Killops, Kato L; Campos, Luis M



Predicting Polymeric Crystal Structures by Evolutionary Algorithms  

E-print Network

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

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



Polymerization of nitrogen in lithium azide  

NASA Astrophysics Data System (ADS)

Additional electrons can drastically change the bonding trend of light elements. For example, N atoms in alkali metal azides form the linear N3- anions instead of N2 molecules with the introduction of additional electrons. The effect of the additional electrons on the polymerization of N under pressure is important and thus far unclear. Using first principles density functional methods and the particle swarm optimization structure search algorithm, we systematically study the evolution of LiN3 structures under pressures up to 600 GPa. A stable structure featuring polymerized N under pressures higher than 375 GPa is identified for the first time. It consists of zig-zag N polymer chains that are formed by N5- five-member rings sharing N-N pairs. Throughout the stable pressure range, the structure is insulating and consists of N atoms in sp3 hybridizations. Comparing with the atomic and electronic structures of previous phases, our study completes the structural evolution of LiN3 under pressure and reveals the structural changes which are accompanied and driven by the change of atomic orbital hybridization, first from sp to sp2 and then from sp2 to sp3.

Wang, Xiaoli; Li, Jianfu; Botana, Jorge; Zhang, Meiguang; Zhu, Hongyang; Chen, Li; Liu, Hongmei; Cui, Tian; Miao, Maosheng



Predicting polymeric crystal structures by evolutionary algorithms.  


The recently developed evolutionary algorithm USPEX proved to be a tool that enables accurate and reliable prediction of structures. Here we extend this method to predict the crystal structure of polymers by constrained evolutionary search, where each monomeric unit is treated as a building block with fixed connectivity. This greatly reduces the search space and allows the initial structure generation with different sequences and packings of these blocks. The new constrained evolutionary algorithm is successfully tested and validated on a diverse range of experimentally known polymers, namely, polyethylene, polyacetylene, poly(glycolic acid), poly(vinyl chloride), poly(oxymethylene), poly(phenylene oxide), and poly (p-phenylene sulfide). By fixing the orientation of polymeric chains, this method can be further extended to predict the structures of complex linear polymers, such as all polymorphs of poly(vinylidene fluoride), nylon-6 and cellulose. The excellent agreement between predicted crystal structures and experimentally known structures assures a major role of this approach in the efficient design of the future polymeric materials. PMID:25338876

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



The Physics Classroom: Vectors - Fundamentals and Operations  

NSDL National Science Digital Library

This interactive tutorial provides comprehensive help and practice in understanding vector quantities. It is organized into six sections: vector direction, vector addition, resultants, components, vector resolution, and component addition. It closes with relative velocity and riverboat problems, plus a discussion of the interdependence of perpendicular components of motion. Each section explains a topic and provides exercises for learner self-assessment. Images, animations, and graphs are placed throughout to illustrate the concepts. Editor's Note: Fluency in vector operations requires practice, and this tutorial provides it. Additional guidance is offered by clicking "Student Extras" at the top of the tutorial page.

Henderson, Tom


Chern classes of tropical vector bundles  

NASA Astrophysics Data System (ADS)

We introduce tropical vector bundles, morphisms and rational sections of these bundles and define the pull-back of a tropical vector bundle and of a rational section along a morphism. Most of the definitions presented here for tropical vector bundles will be contained in Torchiani, C., Line Bundles on Tropical Varieties, Diploma thesis, Technische Universität Kaiserslautern, Kaiserslautern, 2010, for the case of line bundles. Afterwards we use the bounded rational sections of a tropical vector bundle to define the Chern classes of this bundle and prove some basic properties of Chern classes. Finally we give a complete classification of all vector bundles on an elliptic curve up to isomorphisms.

Allermann, Lars



Studentsâ Consistency of Graphical Vector Addition Method on 2-D Vector Addition Tasks  

NSDL National Science Digital Library

In a series of ten two-dimensional graphical vector addition questions with varying visual representations, most students stuck to a single solution method, be it correct or incorrect. Changes to the visual representation include placing vectors on a grid, making the vectors arrangements symmetric, varying the separation between vectors, and reversing the direction of either vector. We discuss the questions asked of students and their responses, emphasizing the results of one student who did change solution methods during an interview.

Hawkins, Jeffrey M.; Thompson, John R.; Wittmann, Michael C.



Dynamic Spectrum Management for Upstream Mixtures of Vectored & Non-Vectored DSL  

Microsoft Academic Search

As field trials and initial deployments of Vectored DSL systems materialize in the next few years, Vectored DSL systems will often co-exist with non-vectored DSL systems sharing the same cable. For such mixed-binder scenarios with vectored and non-vectored lines, this paper presents an optimal Dynamic Spectrum Management (DSM) technique referred to as Mixed-binder Optimum Spectrum Balancing (MixOSB) to find the

Aakanksha Chowdhery; John M. Cioffi




E-print Network

DYNAMIC MODELLING OF LIVING ANIONIC SOLUTION POLYMERIZATION OF STYRENE model for the living anionic solution polymerization of styrene/butadiene/divinylbenzene in a continuous kinetic reactor model for the living anionic solution polymerization of styrene

Schittkowski, Klaus


Microbial Extracellular Polymeric Substances Reduce Ag+ Nanoparticles and Antagonize Bactericidal Activity  

E-print Network

Microbial Extracellular Polymeric Substances Reduce Ag+ to Silver Nanoparticles and Antagonize demonstrate that extracellular polymeric substances (EPS) produced by bacteria constitute a permeability that extracellular polymeric substances (EPS) secreted by bacteria could play a significant protective role.5

Alvarez, Pedro J.


Spectroscopic Study of Extracellular Polymeric Substances from Bacillus subtilis: Aqueous Chemistry and Adsorption  

E-print Network

Spectroscopic Study of Extracellular Polymeric Substances from Bacillus subtilis: Aqueous Chemistry March 3, 2004 Reactions at ionizable functional groups in extracellular polymeric substances (EPS) from lipopolysaccharides, teichoic acids and extra- cellular polymeric substances.6-9 Mineral surfaces exhibit positive

Chorover, Jon


Interpolating vectors for robust pattern recognition.  


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

Fukushima, Kunihiko



Polymerization dynamics of double-stranded biopolymers: Chemical kinetic approach  

E-print Network

Polymerization dynamics of double-stranded biopolymers: Chemical kinetic approach Evgeny B 19 November 2004; accepted 20 December 2004; published online 10 March 2005 The polymerization, the exact analytical expressions for the growth velocity and dispersion for two-stranded polymers


Chemical Modification of Cellulose Nanofibrils by Graft Polymerization  

E-print Network

Chemical Modification of Cellulose Nanofibrils by Graft Polymerization Arie Mulyadi and Yulin Deng by UV-spectroscopy at 260 nm from PS absorbance of supernatant for case of graft polymerization hydrogen bond interaction Steric repulsion of grafted polymer Dispersion Quality in Nanocomposites

Das, Suman


Actin Polymerization Overshoots and Hydrolysis as Assayed by Pyrene Fluorescence  

E-print Network

Actin Polymerization Overshoots and Hydrolysis as Assayed by Pyrene Fluorescence F. J. Brooks and A observed in the flu- orescence intensity of pyrene-labeled actin during rapid polymerization. We show coefficients: 0.37 for F-ATP actin; 0.55 for F-ADP+Pi actin; and 0.75 for F-ADP actin. Finally, we present

Carlsson, Anders


Polymeric Particles for the Removal of Endocrine Disruptors  

Microsoft Academic Search

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

Shudong Sun; Jingyun Hunag; Changsheng Zhao



Developments of rare earth metal catalysts for olefin polymerization  

Microsoft Academic Search

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

Yuushou Nakayama; Hajime Yasuda



Snell's law of refraction observed in thermal frontal polymerization  

Microsoft Academic Search

We demonstrate that Snell's law of refraction can be applied to thermal fronts propagating through a boundary between regions that support distinct frontal velocities. We use the free-radical frontal polymerization of a triacrylate with clay filler that allows for two domains containing two different concentrations of a peroxide initiator to be molded together. Because the polymerization reaction rates depend on

John A. Pojman; Veronika Viner; Burcu Binici; Shanna Lavergne; Melanie Winsper; Dmitry Golovaty; Laura Gross



Diamagnetic Orientation of Polymerized Molecules under High Magnetic Field  

Microsoft Academic Search

Diamagnetic alignment of polymerized organic molecules is discussed both from the theoretical and experimental points of view. When a number of molecules aggregate with their diamagnetic principal axes along the same direction, the resultant diamagnetic anisotropy energy becomes comparable to the thermal energy and the aggregated molecule can align under a conventional magnetic field, even at room temperatures. Polymerization of

Akio Yamagishi; Tetsuya Takeuchi; Terumasa Higashi; Muneyuki Date



The Synthesis and Assembly of Polymeric Microparticles Using Microfluidics  

E-print Network

such as paper, metals and wood.[1] Gradually, polymeric particles have also found use in high value biological and analytical applications including as column supports for chromatography, beads for flow cytometry polymeric particles in the range of several micrometers and above for chromatography and liquid

Doyle, Patrick S.


Modeling of Particle Fragmentation in Heterogeneous Olefin Polymerization Reactions  

Microsoft Academic Search

A model?based methodology is proposed to describe fragmentation of polymer particles during the very early stages of heterogeneous olefin polymerization reactions. The method is based on the analysis of the particle capacity to release the amount of energy that is accumulated in its interior during the polymerization, due to the fast polymer production. The balance between the rates of energy

Douglas M. Merquior; Enrique L. Lima; José Carlos Pinto




Microsoft Academic Search

The proper operation of the industrial polymerization reactor is a challenging problem and a significant business opportunity for Process System Engineering application, which is in a broad sense, commonly called Polymerization Reactor Engineering. The technical challenges are specific to the particular case, but they are mainly due to some general characteristics such as their complex nonlinear, multivariable and interactive dynamic

Oscar A. Z. Sotomayor; Darci Odloak; Reinaldo Giudici; Edwin Dextre Jara


Probing polymerization forces by using actin-propelled lipid vesicles  

Microsoft Academic Search

Actin polymerization provides a powerful propulsion force for numerous types of cell motility. Although tremendous progress has been made in identifying the biochemical components necessary for actin-based motility, the precise biophysical mechanisms of force generation remain unclear. To probe the polymerization forces quantitatively, we introduce an experimental system in which lipid vesicles coated with the Listeria monocytogenes virulence factor ActA

Arpita Upadhyaya; Jeffrey R. Chabot; Albina Andreeva; Azadeh Samadani; Alexander van Oudenaarden



Product property and production rate control of styrene polymerization  

Microsoft Academic Search

A multivariable multi-rate nonlinear model predictive control (NMPC) strategy is applied to styrene polymerization. The NMPC algorithm incorporates a multi-rate Extended Kalman Filter (EKF) to handle state variable and parameter estimation. A fundamental model is developed for the styrene polymerization CSTR, and control of polymer properties such as number average molecular weight (NAMW) and polydispersity is considered. These properties characterize

Vinay Prasad; Matthias Schley; Louis P. Russo; B. Wayne Bequette



Suspension Graft Polymerization of Methyl Methacrylate onto Selected Backbones  

Microsoft Academic Search

Methyl methacrylate was grafted onto poly(vinyl oxazoline ester) and poly(stearyl methacrylate) by a chain transfer suspension polymerization method to produce specialty polymeric products. These graft polymers should find application in powder coating, toner resin, and for encapsulating electronic components.

M. B. Amin; A. M. Usmani



Polymerization and surface modification by low pressure plasma technique  

NASA Astrophysics Data System (ADS)

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

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



Polypropylene carbon nanotube composites by in situ polymerization  

Microsoft Academic Search

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

Andreas Funck; Walter Kaminsky



Thrust Vector Control System Study for a Large Liquid Booster.  

National Technical Information Service (NTIS)

This effort consisted of evaluating six thrust vector control systems for application on a Large Liquid Booster. The thrust vector control systems evaluated were liquid injection thrust vector control, hot gas secondary injection thrust vector control and...

D. Stump, V. Olivier



Reconstituting dynamic microtubule polymerization regulation by TOG domain proteins.  


Microtubules (MTs) polymerize from soluble ??-tubulin and undergo rapid dynamic transitions to depolymerization at their ends. Microtubule-associated regulator proteins modulate polymerization dynamics in vivo by altering microtubule plus end conformations or influencing ??-tubulin incorporation rates. Biochemical reconstitution of dynamic MT polymerization can be visualized with total internal reflection fluorescence (TIRF) microscopy using purified MT regulators. This approach has provided extensive details on the regulation of microtubule dynamics. Here, I describe a general approach to reconstitute MT dynamic polymerization with TOG domain microtubule regulators from the XMAP215/Dis1 and CLASP families using TIRF microscopy. TIRF imaging strategies require nucleation of microtubule polymerization from surface-attached, stabilized MTs. The approaches described here can be used to study the mechanism of a wide variety of microtubule regulatory proteins. PMID:24630105

Al-Bassam, Jawdat



Rapid Stiffening of a Microfluidic Endoskeleton via Frontal Polymerization.  


Materials capable of rapidly modifying their physical properties in response to stimuli are desirable for on-demand deployment and adaptive engineering structures. Frontal polymerization is a self-propagating reaction that can quickly transform liquid reactants into solid products. In this contribution, we demonstrate that frontal polymerization enables facile, rapid stiffening of a vascular network embedded in a flexible matrix. Systematic variation of the vascular architecture shows that polymerization fronts in a polydimethylsiloxane (PDMS) matrix are self-propagating in channels as small as 838 ?m and even when curves, branch points and converging geometries are present. After polymerization the composite structure was dramatically stiffened (up to 18 times the original Young's modulus) based on tensile testing results. This work demonstrates the use of frontal polymerization as an efficient methodology for transforming flexible materials into functional supports or surfaces through endoskeletal stiffening. PMID:25321345

Robertson, Ian D; Hernandez, Hector Lopez; White, Scott R; Moore, Jeffrey S



Self-Organized and Cu-Coordinated Surface Linear Polymerization  

NASA Astrophysics Data System (ADS)

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

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



Dynamic bioactive stimuli-responsive polymeric surfaces  

NASA Astrophysics Data System (ADS)

This dissertation focuses on the design, synthesis, and development of antimicrobial and anticoagulant surfaces of polyethylene (PE), polypropylene (PP), and poly(tetrafluoroethylene) (PTFE) polymers. Aliphatic polymeric surfaces of PE and PP polymers functionalized using click chemistry reactions by the attachment of --COOH groups via microwave plasma reactions followed by functionalization with alkyne moieties. Azide containing ampicillin (AMP) was synthesized and subsequently clicked into the alkyne prepared PE and PP surfaces. Compared to non-functionalized PP and PE surfaces, the AMP clicked surfaces exhibited substantially enhanced antimicrobial activity against Staphylococcus aureus bacteria. To expand the biocompatibility of polymeric surface anticoagulant attributes, PE and PTFE surfaces were functionalized with pH-responsive poly(2-vinyl pyridine) (P2VP) and poly(acrylic acid) (PAA) polyelectrolyte tethers terminated with NH2 and COOH groups. The goal of these studies was to develop switchable stimuli-responsive polymeric surfaces that interact with biological environments and display simultaneous antimicrobial and anticoagulant properties. Antimicrobial AMP was covalently attached to --COOH terminal ends of protected PAA, while anticoagulant heparin (HEP) was attached to terminal --NH2 groups of P2VP. When pH < 2.3, the P2VP segments are protonated and extend, but for pH > 5.5, they collapse while the PAA segments extend. Such surfaces, when exposed to Staphylococcus aureus, inhibit bacterial growth due to the presence of AMP, as well as are effective anticoagulants due to the presence of covalently attached HEP. Comparison of these "dynamic" pH responsive surfaces with "static" surfaces terminated with AMP entities show significant enhancement of longevity and surface activity against microbial film formation. The last portion of this dissertation focuses on the covalent attachment of living T1 and ?11 bacteriophages (phages) on PE and PTFE surface. This was accomplished by carbodiimide coupling between --COOH groups on PE and PTFE surfaces and --NH2 moieties present on T1 and ?11 phages. These studies show that covalently attached T1 and ?11 phages retain their antimicrobial activity manifested by the effective destruction of both Gram negative Escherichia coli (?11) phages and Gram positive Staphylococcus aureus bacteria (T1).

Pearson, Heather Marie


Kinetic and thermal analysis of polymeric materials  

NASA Astrophysics Data System (ADS)

Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques have been used to study the thermal degradation of polymeric materials. These polymers were subjected to a variety of heating programs as well as numerous types of atmospheric conditions. The results from these analyses were then used to determine activation energies as a function of an extent of reaction variable, alpha. This technique, known as the model-free isoconversional method, allows for changes in energies to occur as decomposition pathways change. This produces a more realistic means of observing complex kinetic schemes and is a better representation of kinetic analysis. Chapters 1 and 2 provide introductory backgrounds into both polymer chemistry and the isoconversional analysis technique, respectively. A brief description of the research goals and motivations is also discussed. Thermal analysis of pure polystyrene (PS), polyethylene (PE), and polypropylene (PP) samples are presented in Chapter 3. The obtained activation energy dependencies are interpreted in terms of degradation mechanisms. These mechanisms vary greatly according to the gaseous environment in which they were analyzed. The thermal degradation of poly(methyl methacrylate) (PMMA) in both pure nitrogen and in various oxygen-containing atmospheres is discussed in Chapter 4. It was observed that oxygen exhibits a stabilizing effect on PMMA decomposition. Activation energies for these processes, and their mechanistic interpretations, will also be presented. Chapter 5 builds off the understanding gained in Chapter 4 by investigating the char-forming effects of silica gel and potassium carbonate additives on PMMA. These additives are known for their fire-resistant properties when combined in a 3:1 silica gel to potassium carbonate ratio. The effects of these additives, and their respective ratio amounts, on PMMA char formation are reported. Chapters 6 and 7 conclude the dissertation by looking at the thermal decomposition of two polymeric-based energetic materials. Both substances utilize HMX as their key energetic component. How the various polymeric binders and plasticizers affect the HMX decomposition is a main focus point. Finally, both activation energies and kinetic prediction methods will be used to investigate the energetic material decomposition.

Peterson, Jeffery David



Kinematics in Vector Boson Fusion  

E-print Network

The vector boson fusion process leads to two forward/backward jets (tag jets) and the produced state, a Higgs boson in this case, moving slowly in the p-p C.M. frame at the LHC. For the case of Higgs decaying to W+W (W*) with Higgs mass below 180 GeV, the W bosons have low momentum in the Higgs C.M. For the case of W leptonic decays, this fact allows for an approximate reconstruction of the two final state neutrinos. In turn, those solutions then provide additional kinematic cuts against background.

D. Green



Properties of Vector Preisach Models  

NASA Technical Reports Server (NTRS)

This paper discusses rotational anisotropy and rotational accommodation of magnetic particle tape. These effects have a performance impact during the reading and writing of the recording process. We introduce the reduced vector model as the basis for the computations. Rotational magnetization models must accurately compute the anisotropic characteristics of ellipsoidally magnetizable media. An ellipticity factor is derived for these media that computes the two-dimensional magnetization trajectory for all applied fields. An orientation correction must be applied to the computed rotational magnetization. For isotropic materials, an orientation correction has been developed and presented. For anisotropic materials, an orientation correction is introduced.

Kahler, Gary R.; Patel, Umesh D.; Torre, Edward Della



Nonviral Vectors for Gene Delivery  

NASA Astrophysics Data System (ADS)

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 the plasma membrane, escape from the endosomal compartment, unpackage the gene at some point and have no detrimental effects. In comparison to viruses, nonviral vectors are relatively easy to synthesize, less immunogenic, low in cost, and have no limitation in the size of a gene that can be delivered. Significant progress has been made in the basic science and applications of various nonviral gene delivery vectors; however, the majority of nonviral approaches are still inefficient and often toxic. To this end, two nonviral gene delivery systems using either biodegradable poly(D,L-lactide- co-glycolide) (PLG) nanoparticles or cell penetrating peptide (CPP) complexes have been designed and studied using A549 human lung epithelial cells. PLG nanoparticles were optimized for gene delivery by varying particle surface chemistry using different coating materials that adsorb to the particle surface during formation. A variety of cationic coating materials were studied and compared to more conventional surfactants used for PLG nanoparticle fabrication. Nanoparticles (˜200 nm) efficiently encapsulated plasmids encoding for luciferase (80-90%) and slowly released the same for two weeks. After a delay, moderate levels of gene expression appeared at day 5 for certain positively charged PLG particles and gene expression was maintained for at least two weeks. In contrast, gene expression mediated by polyethyleneimine (PEI) ended at day 5. PLG particles were also significantly less cytotoxic than PEI suggesting the use of these vehicles for localized, sustained gene delivery to the pulmonary epithelium. On the other hand, a more simple method to synthesize 50-200 nm complexes capable of high transfection efficiency or high gene knockdown was also explored. Positively charged CPPs were complexed with pDNA or siRNA, which resulted in 'loose' (˜1 micron) particles. These were then condensed into small nanoparticles by using calcium, which formed "soft" crosslinks by interacting with both phosphates on nucleic acids and amines on CPPs. An optimal amount of CaCl2 produced stable, ˜100 nm complexes that exhibited higher transfection efficiency and gene silencing than PEI polyplexes. CPPs also displayed negligible cytotoxicity up to 5 mg/mL. Biophysical studies of the pDNA structure within complexes suggested that pDNA within CPP complexes (condensed with calcium) had similar structure, but enhanced thermal stability compared to PEI complexes. Thus, CPP complexes emerged as simple, attractive candidates for future studies on nonviral gene delivery in vivo.

Baoum, Abdulgader Ahmed


The Magsat precision vector magnetometer  

NASA Technical Reports Server (NTRS)

This paper examines the Magsat precision vector magnetometer which is designed to measure projections of the ambient field in three orthogonal directions. The system contains a highly stable and linear triaxial fluxgate magnetometer with a dynamic range of + or - 2000 nT (1 nT = 10 to the -9 weber per sq m). The magnetometer electronics, analog-to-digital converter, and digitally controlled current sources are implemented with redundant designs to avoid a loss of data in case of failures. Measurements are carried out with an accuracy of + or - 1 part in 64,000 in magnitude and 5 arcsec in orientation (1 arcsec = 0.00028 deg).

Acuna, M. H.



Fz2 and Cdc42 Mediate Melanization and Actin Polymerization but Are Dispensable for Plasmodium Killing in the Mosquito Midgut  

PubMed Central

The midgut epithelium of the mosquito malaria vector Anopheles is a hostile environment for Plasmodium, with most parasites succumbing to host defenses. This study addresses morphological and ultrastructural features associated with Plasmodium berghei ookinete invasion in Anopheles gambiae midguts to define the sites and possible mechanisms of parasite killing. We show by transmission electron microscopy and immunofluorescence that the majority of ookinetes are killed in the extracellular space. Dead or dying ookinetes are surrounded by a polymerized actin zone formed within the basal cytoplasm of adjacent host epithelial cells. In refractory strain mosquitoes, we found that formation of this zone is strongly linked to prophenoloxidase activation leading to melanization. Furthermore, we identify two factors controlling both phenomena: the transmembrane receptor frizzled-2 and the guanosine triphosphate–binding protein cell division cycle 42. However, the disruption of actin polymerization and melanization by double-stranded RNA inhibition did not affect ookinete survival. Our results separate the mechanisms of parasite killing from subsequent reactions manifested by actin polymerization and prophenoloxidase activation in the A. gambiae–P. berghei model. These latter processes are reminiscent of wound healing in other organisms, and we propose that they represent a form of wound-healing response directed towards a moribund ookinete, which is perceived as damaged tissue. PMID:17196037

Zachary, Daniel; Hoffmann, Jules A; Levashina, Elena A



Polymeric Microring Resonator Enabling Variable Extinction Ratio  

NASA Astrophysics Data System (ADS)

A polymeric ring resonator filter enabling electrically variable extinction ratio has been implemented, incorporating a ring waveguide coupled to a bus waveguide and an electrode which is separated from it with a gap. When an electrical power is applied to the electrode, the refractive index of the polymers underneath it is lowered through the thermo-optic effect so that the guided-mode confinement in the ring is strengthened to reduce its bending loss. Consequently, for a constant bus-to-ring coupling the attenuation depth at resonant wavelengths could be adjusted electrically. As for the achieved performance, the extinction ratio was changed by ˜9 dB for the electrical power of ˜12 mW while the corresponding bending loss was improved by ˜86 dB/cm.

Song, Ju-Han; Kim, Do-Hwan; Lee, Sang-Shin



Nanostructural magnetism of polymeric fullerene crystals  

SciTech Connect

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.

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



Hydrogen cyanide polymerization: a preferred cosmochemical pathway.  


Current research in cosmochemistry shows that crude organic solids of high molecular weight are readily formed in planetary, interplanetary and interstellar environments. Underlying much of this ubiquitous chemistry is a low energy route leading directly to the synthesis of hydrogen cyanide and its polymers. Evidence from laboratory and extraterrestrial investigations suggests that these polymers plus water yield heteropolypeptides, a truly universal process that accounts not only for the past synthesis of protein ancestors on Earth but also for reactions proceeding elsewhere today within our solar system, on planetary bodies and satellites around other stars and in the dusty molecular clouds of spiral galaxies. The existence of this preferred pathway - hydrogen cyanide polymerization - surely increases greatly the probability that carbon-based life is widespread in the universe. PMID:11539467

Matthews, C N



Improving immobilized biocatalysts by gel phase polymerization  

SciTech Connect

A new method is presented for the treatment of gel-type supports, used for immobilizing microbial cells and enzymes, to obtain high mechanical strength. It is particularly useful for ethanol fermentation over gel beads containing immobilized viable cells, where the beads can be ruptured by gas production and the growth of cells within the gels. This method consists of treating agar or carrageenan gel with polyacrylamide to form a rigid support which retains the high catalytic activity characteristic of the untreated biocatalysts. The size and shape of the biocatalyst is unaffected by this treatment. The method involves the diffusion of acrylamide, N,N'-methylenebisacrylamide and BETA-dimethylaminopropionitrile (or N,N,N',N'-tetramethylethylenediamine) into the preformed biocatalyst beads followed by the addition of an initiator to cause polymerization within the beads. Treated gels have been used for the continuous fermentation of glucose to ethanol in a packed column for over two months.

Kuu, W.Y.; Polack, J.A.



Approaches to flame resistant polymeric materials  

NASA Technical Reports Server (NTRS)

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.

Liepins, R.



Elastic, conductive, polymeric hydrogels and sponges.  


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

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



Shear-induced polymerization of benzene  

SciTech Connect

Both slow and fast chemical reactions can be induced by strains; with or without the assistance of temperature. Shear strains are especially effective. Defects, particularly dislocations, are also important as strain amplifiers. In covalent solids metallization has been associated with the bending (shearing) of chemical bonds. In ionic solids isotropic compression is also important. Metals may be influenced by distortions of the spd-hybrid bonds. A prototype is the polymerization of benzene. Normally, benzene rings are flat. It is proposed that compression buckles the rings into the chair'' configuration. This will close the HOMO-LUMO energy gap, thereby delocalizing the bonding electrons which then rearrange to link two or more molecules. The criteria for this, and the implications, are discussed. [copyright] 1994 American Institute of Physics

Gilman, J.J. (Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States)); Armstrong, R.W. (University of Maryland, College Park, Maryland 20742 (United States))



Heterogeneous Initiators for Sustainable Polymerization Processes  

NASA Astrophysics Data System (ADS)

One of the main challenges facing the twenty-first century is the need to produce chemicals from renewable resources. The dwindling supplies of fossil fuels coupled with instability in supply mean that technologies that were once deemed too expensive are now becoming more economically viable options. The majority of man-made polymers are derived from crude oil based monomers. However, in recent years a tremendous effort has been channeled into the preparation of polymers from sustainable chemicals. Two classic examples are polylactide (derived from corn starch) and polycarbonates (prepared directly from CO2). This chapter serves as an introduction into these two polymers and reviews the literature associated with heterogeneous catalyst for the polymerizations, concentrating on approaches describing the heterogenization of homogeneous catalysts.

Jones, Matthew D.


Dengue Vectors and their Spatial Distribution  

PubMed Central

The distribution of dengue vectors, Ae. aegypti and Ae. albopictus, is affected by climatic factors. In addition, since their life cycles are well adapted to the human environment, environmental changes resulting from human activity such as urbanization exert a great impact on vector distribution. The different responses of Ae. aegypti and Ae albopictus to various environments result in a difference in spatial distribution along north-south and urban-rural gradients, and between the indoors and outdoors. In the north-south gradient, climate associated with survival is an important factor in spatial distribution. In the urban-rural gradient, different distribution reflects a difference in adult niches and is modified by geographic and human factors. The direct response of the two species to the environment around houses is related to different spatial distribution indoors and outdoors. Dengue viruses circulate mainly between human and vector mosquitoes, and the vector presence is a limiting factor of transmission. Therefore, spatial distribution of dengue vectors is a significant concern in the epidemiology of the disease. Current technologies such as GIS, satellite imagery and statistical models allow researchers to predict the spatial distribution of vectors in the changing environment. Although it is difficult to confirm the actual effect of environmental and climate changes on vector abundance and vector-borne diseases, environmental changes caused by humans and human behavioral changes due to climate change can be expected to exert an impact on dengue vectors. Longitudinal monitoring of dengue vectors and viruses is therefore necessary. PMID:22500133

Higa, Yukiko



Genetics of Mosquito Vector Competence  

PubMed Central

Mosquito-borne diseases are responsible for significant human morbidity and mortality throughout the world. Efforts to control mosquito-borne diseases have been impeded, in part, by the development of drug-resistant parasites, insecticide-resistant mosquitoes, and environmental concerns over the application of insecticides. Therefore, there is a need to develop novel disease control strategies that can complement or replace existing control methods. One such strategy is to generate pathogen-resistant mosquitoes from those that are susceptible. To this end, efforts have focused on isolating and characterizing genes that influence mosquito vector competence. It has been known for over 70 years that there is a genetic basis for the susceptibility of mosquitoes to parasites, but until the advent of powerful molecular biological tools and protocols, it was difficult to assess the interactions of pathogens with their host tissues within the mosquito at a molecular level. Moreover, it has been only recently that the molecular mechanisms responsible for pathogen destruction, such as melanotic encapsulation and immune peptide production, have been investigated. The molecular characterization of genes that influence vector competence is becoming routine, and with the development of the Sindbis virus transducing system, potential antipathogen genes now can be introduced into the mosquito and their effect on parasite development can be assessed in vivo. With the recent successes in the field of mosquito germ line transformation, it seems likely that the generation of a pathogen-resistant mosquito population from a susceptible population soon will become a reality. PMID:10704476

Beerntsen, Brenda T.; James, Anthony A.; Christensen, Bruce M.



Multiferroic nanoparticulate thin film composites by Co implantation of ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal targets  

NASA Astrophysics Data System (ADS)

Two-phase magnetostrictive-piezoelectric thin film composites are key materials to the development of a range of potentially disruptive magnetoelectric technologies, such as electrical-writing magnetic-reading random access memories. However, multiferroic thin film composites prepared so far show neither magnetoelectric switching nor magnetoelectric responses comparable to those of related bulk ceramic materials and cermets. Here we show that ion implantation of magnetic species into ferroelectric single crystal targets can be an effective alternative means of obtaining nanoparticulate thin film composites of this type. Concept is proved by the implantation of Co into a Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal with ultrahigh piezoelectricity. Formation of an ensemble of ferromagnetic nanoparticles embedded in an amorphized layer within the ferroelectric crystal is clearly shown.

Torres, María; Ricote, Jesús; Amorín, Harvey; Jaafar, Miriam; Holgado, Susana; Piqueras, Juan; Asenjo, Agustina; García-Hernández, Mar; Algueró, Miguel



411. Trapping of Adenovirus Vectors in Blood  

Microsoft Academic Search

In an attempt to circumvent the limitations of Adenovirus (Ad) vectors derived from group C serotype Ad5 we recently developed vectors based on group B serotype Ad11. These vectors are benefited by the low prevalence of Ad11-neutralizing antibodies in humans, and the CD46-dependent tropism of Ad11. CD46 is expressed at high levels in cell types including hematopoietic stem cells, dendritic

Daniel Stone; Shaoheng Ni; Zong-Yi Li; Dmitry M. Shayakhmetov; Andre Lieber



Z Physics Constraints on Vector Leptoquarks  

E-print Network

We analyze the constraints on vector leptoquarks coming from radiative corrections to $Z$ physics. We perform a global fitting to the LEP data including the oblique and non-universal contributions of the most general effective Lagrangian for vector leptoquarks, which exhibits the $SU(2)_L \\times U(1)_Y$ gauge invariance. We show that the $Z$ physics leads to stronger bounds on second and third generation vectors leptoquarks than the ones obtained from low energy and the current collider experiments.

O. J. P. Eboli; M. C. Gonzalez-Garcia; J. K. Mizukoshi



[What makes an insect a vector?].  


Blood-feeding insects transmit numerous viruses, bacteria, protozoans and helminths to vertebrates. The developmental cycles of the microorganisms in their vectors and the mechanisms of transmission are generally extremely complex and the result of a long-lasting coevolution of vector and vectored pathogen based on mutual adaptation. The conditions necessary for an insect to become a vector are multiple but require an innate vector competence as a genetic basis. Next to the vector competence plenty of entomological, ecological and pathogen-related factors are decisive, given the availability of infection sources. The various modes of pathogen transmission by vectors are connected to the developmental routes of the microorganisms in their vectors. In particular, pathogens transmitted by saliva encounter a lot of cellular and acellular barriers during their migration from the insect's midgut through the hemocele into the salivary fluid, including components of the insect's immune system. With regard to intracellular development, receptor-mediated invasion mechanisms are of relevance. As an environmental factor, the temperature has a paramount impact on the vectorial roles of hematophagous insects. Not only has it a considerable influence on the duration of a pathogen's development in its vector (extrinsic incubation period) but it can render putatively vector-incompetent insects to vectors ("leaky gut" phenomenon). Equally crucial are behavioural aspects of both the insect and the pathogen such as blood host preferences, seasonal appearance and circadian biting activity on the vector's side and diurnal/nocturnal periodicity on the pathogen's side which facilitate a contact in the first place. PMID:19999381

Kampen, Helge



[Research progress on malaria vector control].  


Vector control plays a crucial role in the stages of malaria control and elimination. Currently, it mainly relies on the chemical control methods for adult mosquitoes in malaria endemic areas, however, it is undergoing the serious threat by insecticide resistance. In recent years, the transgenic technologies of malaria vectors have made a great progress in the laboratory. This paper reviews the challenges of the traditional methods and the rapid developed genetic modified technology in the application of vector control. PMID:24024458

Zhu, Guo-Ding; Cao, Jun; Zhou, Hua-Yun; Gao, Qi



Well-posedness for vector equilibrium problems  

Microsoft Academic Search

We introduce and study two notions of well-posedness for vector equilibrium problems in topological vector spaces; they arise\\u000a from the well-posedness concepts previously introduced by the same authors in the scalar case, and provide an extension of\\u000a similar definitions for vector optimization problems. The first notion is linked to the behaviour of suitable maximizing sequences,\\u000a while the second one is

M. Bianchi; G. Kassay; R. Pini



Plasma polymerized allylamine coated quartz particles for humic acid removal.  


Allylamine plasma polymerization has been used to modify the surface of quartz particles for humic acid removal via an inductively coupled rotating barrel plasma reactor. Plasma polymerized allylamine (ppAA) films were deposited at a power of 25 W, allylamine flow rate of 4.4 sccm and polymerization times of 5-60 min. The influence of polymerization time on surface chemistry was investigated via X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectrometry (ToF-SIMS) and electrokinetic analysis. Acid orange 7 adsorption/desorption quantified the number of surface amine groups. Humic acid removal via ppAA quartz particles was examined by varying pH, removal time, humic acid concentration, and particle mass. Increasing the polymerization time increased the concentration of amine groups on the ppAA quartz surface, thus also increasing the isoelectric point. ToF-SIMS demonstrated uniform distribution of amine groups across the particle surface. Greatest humic acid removal was observed at pH 5 due to electrostatic attraction. At higher pH values, for longer polymerization times, humic acid removal was also observed due to hydrogen bonding. Increasing the initial humic acid concentration increased the mass of humic acid removed, with longer polymerization times exhibiting the greatest increases. Plasma polymerization using a rotating plasma reactor has shown to be a successful method for modifying quartz particles for the removal of humic acid. Further development of the plasma polymerization process and investigation of additional contaminants will aid in the development of a low cost water treatment system. PMID:22633110

Jarvis, Karyn L; Majewski, Peter



Homological Algebra for Diffeological Vector Spaces.  

E-print Network

Diffeological spaces are natural generalizations of smooth manifolds, introduced by J.M.~Souriau and his mathematical group in the 1980's. Diffeological vector spaces (especially fine diffeological vector spaces) were first used by P. Iglesias-Zemmour to model some infinite dimensional spaces in~\\cite{I1,I2}. K.~Costello and O.~Gwilliam developed homological algebra for differentiable diffeological vector spaces in Appendix A of their book~\\cite{CG}. In this paper, we present homological algebra of general diffeological vector spaces via the projective objects with respect to all linear subductions, together with some applications in analysis.

Enxin Wu


The Theory of Witt Vectors Joseph Rabinoff  

E-print Network

The Theory of Witt Vectors Joseph Rabinoff Contents 1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2. Definition of the Witt Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Proof of the Existence of the Witt Rings

Rabinoff, Joseph


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


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

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



Ionically Fixed Polymeric Nanoparticles as a Novel Drug Carrier  

Microsoft Academic Search

Purpose  In this study, we have prepared a novel polymeric drug delivery system comprised of ionically fixed polymeric nanoparticles\\u000a (IFPN) and investigated their potential as a drug carrier for the passive targeting of water-insoluble anticancer drugs.\\u000a \\u000a \\u000a \\u000a Materials and Methods  For this purpose, the physicochemical characteristics of the IFPN were investigated by comparing them with conventional polymeric\\u000a micelles. IFPN containing paclitaxel were prepared

Sa-Won Lee; Dong-Hoon Chang; Myung-Seop Shim; Bong-Oh Kim; Sun-Ok Kim; Min-Hyo Seo



Preparation of acrylate IPN copolymer latexes by radiation emulsion polymerization  

NASA Astrophysics Data System (ADS)

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

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



Unidirectional polymerization leading to homochirality in the RNA world  

NASA Astrophysics Data System (ADS)

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.

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



Intrinsic Embedded Sensors for Polymeric Mechatronics: Flexure and Force Sensing  

PubMed Central

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

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



Synthesis of shape memory polyurethane using bulk polymerization  

NASA Astrophysics Data System (ADS)

In this paper, a series of shape memory polyurethanes (SMPUs) containing polycaprolactone diol (PCL4000), 1,4-butanediol (BDO), and 4,4'-diphenylmethane diisocyanate (MDI) were synthesized using bulk polymerization. Their thermal properties, thermomechanical properties were analyzed by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA), and the shape memory effect was also investigated. Moreover, one kind of shape memory polyurethane fiber was spinned by melting method from these prepared SMPUs and its shape memory properties were also investigated. The results showed that synthesis of shape memory polyurethane using bulk polymerization can effectively enhance the properties of polyurethanes, save cost and improve efficiency compared with solution polymerization.

Yang, Ziming; Jiang, Qiongling; He, Guanru; Zhou, Wuyi; Yang, Zhuohong



An Elusive Vector Dark Matter  

E-print Network

Even though the sensitivity of direct dark matter search experiments reach the level about $10^{-45}~{\\rm cm}^2$, there is no confident signal of dark matter been observed. We point out that, if dark matter is a vector boson, the null result in direct dark matter search experiments may due to the destructive effects in dark-matter-nucleon elastic scattering. We illustrate the scenario using a modified Higgs portal model that includes exotic quarks. The significant cancellation can occur for certain mass gap between heavy quark and dark matter. As a result, the spin-independent dark-matter-nucleon elastic scattering is so suppressed that the future direct search experiments can hardly observe the signal of dark matter.

Chen, Chuan-Ren; Tsai, Ho-Chin



Vector wind profile gust model  

NASA Technical Reports Server (NTRS)

Work towards establishing a vector wind profile gust model for the Space Transportation System flight operations and trade studies is reported. To date, all the statistical and computational techniques required were established and partially implemented. An analysis of wind profile gust at Cape Kennedy within the theoretical framework is presented. The variability of theoretical and observed gust magnitude with filter type, altitude, and season is described. Various examples are presented which illustrate agreement between theoretical and observed gust percentiles. The preliminary analysis of the gust data indicates a strong variability with altitude, season, and wavelength regime. An extension of the analyses to include conditional distributions of gust magnitude given gust length, distributions of gust modulus, and phase differences between gust components has begun.

Adelfang, S. I.



Diversity Cascades and Malaria Vectors  

PubMed Central

The interactions between predator diversity and primary consumer abundance can include direct effects and indirect, cascading effects. Understanding these effects on immature Anopheles mosquitoes is important in sub-Saharan Africa, where most cases of malaria occur. Aquatic predators and immature mosquitoes were collected from shallow pools of varying age previously excavated by brickmakers in the western highlands of Kenya. Path analysis showed an indirect negative effect of habitat age on An. gambiae (Giles, 1902) mediated by effects on predator diversity. Disturbance resets habitats to an earlier successional stage, diminishing predator diversity and increasing An. gambiae populations. The increase in vector abundance as a result of reduced predator diversity highlights the public health value in conserving native insect diversity. PMID:19496413




An Elusive Vector Dark Matter  

E-print Network

Even though the sensitivity of direct dark matter search experiments reach the level about $10^{-45}~{\\rm cm}^2$, there is no confident signal of dark matter been observed. We point out that, if dark matter is a vector boson, the null result in direct dark matter search experiments may due to the destructive effects in dark-matter-nucleon elastic scattering. We illustrate the scenario using a modified Higgs portal model that includes exotic quarks. The significant cancellation can occur for certain mass gap between heavy quark and dark matter. As a result, the spin-independent dark-matter-nucleon elastic scattering is so suppressed that the future direct search experiments can hardly observe the signal of dark matter.

Chuan-Ren Chen; Yu-Kuang Chu; Ho-Chin Tsai



The Haleakala Imaging Vector Magnetograph  

NASA Astrophysics Data System (ADS)

The Imaging Vector Magnetograph, now in daily use at Mees Solar Observatory, Haleakala, Hawaii, extends our capabilities in the measurement of solar vector magnetic fields by providing high spatial and temporal resolution, together with extended area coverage. The instrument is based on a fast-readout CCD camera as its primary detector, a tunable air-spaced Fabry-Perot filter for spectral selection, and variable nematic liquid-crystal retarders for polarization selection. A 28 cm aperture reflecting telescope provides an image the size of a large active region; it is coupled to the magnetograph in a configuration compact enough to mount on the Observatory's 3.6 m equatorial spar. The assembly can be pointed independently of the spar to select a region of interest, so the telescope is always used on-axis. A tip-tilt image stabilizer corrects for image displacement due to spar shake or large-scale atmospheric turbulence. A workstation-based computer control system, incorporating separate processors for user interface, process management and device control, permits accurate process timing along with a flexible user interface. The latter is implemented in an X-windows framework, so that in fact we have found it quite reasonable to operate the instrument from an X terminal at a remote location. The raw data images are stored on 8mm tape for off-line processing, or can be reduced in a few minutes using the instrument's built-in array processor to provide near-real-time magnetograms. Instrument operational parameters can be adjusted in several ways to favor spatial resolution, spatial field, temporal resolution or magnetic sensitivity, but typically we have a 4.5 x 4.5 arcminute field, 1 arcsecond spatial sampling, and an observation interval of five minutes. Initial solar observations showing current capabilities will be presented.

Mickey, D. L.; Canfield, R. C.; Labonte, B. J.; Metcalf, T. R.



Motion vector coding using decoder-side estimation of motion vector  

Microsoft Academic Search

The H.264\\/AVC standard employs the predictive motion vector coding technique using the median predictor of spatially neighboring three motion vectors. Although the median is effective in reducing redundancy, it is not always optimal in minimizing bits. To solve the matter, a new motion vector coding scheme, known as, MV competition in which decoder is signaled on the selected optimal PMV,

Kwanghyun Won; Jungyoup Yang; Byeungwoo Jeon



Introduction to vectors and tensors, Vol 2: vector and tensor analysis  

E-print Network

This is the second volume of a two-volume work on vectors and tensors. Volume 1 is concerned with the algebra of vectors and tensors, while this volume is concerned with the geometrical aspects of vectors and tensors. This volume begins with a...

Bowen, Ray M.; Wang, C.-C.



Non-linear viscoelastic deformation of polymeric solutions  

E-print Network

The dynamics of entangled polymeric solutions were studied using drag of borosilicate discs and conventional shear rheometry devices in order to understand the effect of deformation on the relaxation process and the possible influence of slower...

Sanchez Reyes, Javier



Structural studies of the human polymeric immunoglobulin receptor  

E-print Network

The human polymeric immunoglobulin receptor, pIgR, is a glycosylated type I transmembrane protein expressed on the basolateral surface of secretory epithelial cells. pIgR plays a key role in mucosal immunity and, together ...

Hamburger, Agnes Eva, 1976-



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

NASA Astrophysics Data System (ADS)

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.

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




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...


Free-radical solution-polymerization of trifluoronitrosomethane with tetrafluoroethylene  

NASA Technical Reports Server (NTRS)

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.

Gdickman, S. A.



The structural basis of RNA-catalyzed RNA polymerization  

E-print Network

The Class I ligase is an artificial ribozyme that catalyzes a reaction chemically identical to a single turnover of RNA-dependent RNA polymerization. Such an activity would have been requisite for the emergence of a ...

Shechner, David M



Laccase-catalyzed oxidative polymerization of phenolic compounds.  


Enzymatic polymerization of phenolic compounds (catechol, resorcinol, and hydroquinone) was carried out using laccase. The mechanism of polymerization and the structures of the polymers were evaluated in terms of UV-Vis and Fourier transform infrared spectroscopy. The molecular weights of the produced polyphenols were determined with GPC. The results showed that the phenolic monomers firstly turned into quinone intermediates by laccase catalysis. Through further oxidation, the intermediates formed covalent bonds. Finally, catechol units were linked together with ether bonds, and both resorcinol and hydroquinone units were linked together with C-C bonds. The number-average molecular weights of the polyphenols ranged from 1,000 to 1,400 Da (corresponding to the degree of polymerization that varied from 10 to 12) with a lower polydispersity value of about 1.10, showing selective polymerization of phenolic compounds catalyzed by laccase. PMID:23996120

Sun, Xuejiao; Bai, Rubing; Zhang, Ya; Wang, Qiang; Fan, Xuerong; Yuan, Jiugang; Cui, Li; Wang, Ping



Strategy for construction of polymerized volume data sets  

E-print Network

data set, using an existing segmentation method. The strategy of constructing polymerized volume data sets is initially tested on synthetic data sets which resemble neuronal volume data obtained by three-dimensional microscopy. The strategy...

Aragonda, Prathyusha



'Green' reversible addition-fragmentation chain-transfer (RAFT) polymerization  

NASA Astrophysics Data System (ADS)

Reversible addition-fragmentation chain-transfer (RAFT) polymerization has revolutionized the field of polymer synthesis as a versatile tool for the production of complex polymeric architectures. As for all chemical processes, research and development in RAFT have to focus on the design and application of chemical products and processes that have a minimum environmental impact, and follow the principles of 'green' chemistry. In this Review, we summarize some of the green features of the RAFT process, and review the recent advances in the production of degradable polymers obtained from RAFT polymerization. Its use to modify biodegradable and renewable inorganic and organic materials to yield more functional products with enhanced applications is also covered. RAFT is a promising candidate for answering both the increasing need of modern society to employ highly functional polymeric materials and the global requirements for developing sustainable chemicals and processes.

Semsarilar, Mona; Perrier, Sébastien



Tension modulates actin filament polymerization mediated by formin and profilin  

PubMed Central

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

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



Novel polymeric nanocomposites and porous materials prepared using organogels  

NASA Astrophysics Data System (ADS)

We propose a new method for preparing polymeric nanocomposites and porous materials using self-assembled templates formed by 1,3:2,4-dibenzylidene sorbitol (DBS) organogels. DBS is capable of self-assembling into a 3D nanofibrillar network at relatively low concentrations in some organic solvents to produce organogels. In this study, we induced the formation of such physical cross-linked networks in styrene. Subsequently, we polymerized the styrene in the presence of chemical cross-linkers, divinyl benzene (DVB), with different amounts of DBS using thermal-initiated polymerization. The resulting materials were transparent, homogeneous polystyrene (PS) nanocomposites with both physical and chemical cross-links. The porous polymeric materials were obtained by solvent extraction of the DBS nanofibrils from the PS. Brunauer-Emmett-Teller (BET) measurements show that the amounts of DBS and DVB influenced the specific surface area after the removal of the DBS fibrils.

Lai, Wei-Chi; Tseng, Shen-Chen



Novel polymeric nanocomposites and porous materials prepared using organogels.  


We propose a new method for preparing polymeric nanocomposites and porous materials using self-assembled templates formed by 1,3:2,4-dibenzylidene sorbitol (DBS) organogels. DBS is capable of self-assembling into a 3D nanofibrillar network at relatively low concentrations in some organic solvents to produce organogels. In this study, we induced the formation of such physical cross-linked networks in styrene. Subsequently, we polymerized the styrene in the presence of chemical cross-linkers, divinyl benzene (DVB), with different amounts of DBS using thermal-initiated polymerization. The resulting materials were transparent, homogeneous polystyrene (PS) nanocomposites with both physical and chemical cross-links. The porous polymeric materials were obtained by solvent extraction of the DBS nanofibrils from the PS. Brunauer-Emmett-Teller (BET) measurements show that the amounts of DBS and DVB influenced the specific surface area after the removal of the DBS fibrils. PMID:19875871

Lai, Wei-Chi; Tseng, Shen-Chen



Modified Paving Bitumens Based on Tar and Petroleum Polymeric Resins  

Microsoft Academic Search

Modification of tar with petroleum polymeric resins yields paving-grade bitumens with enhanced cohesion. With respect to the heat resistance and other parameters, these bitumens meet the requirements of GOST (State Standard) for BND 90\\/130 paving bitumens.

V. V. Fedorov; A. M. Syroezhko; O. Yu. Begak; V. A. Proskuryakov; G. I. Borovikov



Sulfonated Petroleum Polymeric Resins as Plasticizers for Cement Mortars  

Microsoft Academic Search

Sulfonation of petroleum polymeric resins based on the C9 fraction with various suilfonatic agents was studied, and procedure was developed for preparing sulfonated resins. The possibility of using sulfo resins as effective plasticizers for concrete was examined.

V. P. Lesnyak; L. V. Gaponik; V. P. Mardykin; F. N. Kaputskii



Pressure-induced polymerization in substituted acetylenes  

SciTech Connect

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.

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



[Polymeric forms of the influenza virus nucleoprotein].  


Two high-molecular-weight types of in vivo formed nucleoproteins (NP) capable of reacting with anti-NP monoclonal antibodies were detected in continuous MDCK cells and primary CEFs, along with the monomeric virus NP. High-molecular NP were stable at 37 degrees C, despite the presence of dodecyl sulfate and B-mercaptoethanol, but were converted to monomeric NP at 37 degrees C in the presence of 6 M urea, 1 M NaCl, and at acid pH. Hence, high-molecular-weight NP may be the polymeric forms of NP, which are probably stabilized by noncovalent bonds. The kinetics of NP-polymers formation suggests that NP-monomers are their precursors and NP-polymers are formed rapidly after monomeric NP molecules synthesis. Both forms of NP-polymers are detected in the sedimented and soluble fractions of not only cell lysate, but in the extracellular maintenance medium as well. NP-polymers are resistant to RNAse and are more resistant to protease than NP-monomers. PMID:7477040

Semenova, N P; Prokudina, E P; Chumakov, V M; Zuev, E A; Zolotareva, I L



Switchable Adhesion from Bicomponent Polymeric Brushes  

NASA Astrophysics Data System (ADS)

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.

Retsos, Haris; Gorodyska, Ganna; Creton, Costantino



Polymeric micelle as multifunctional pharmaceutical carriers.  


A number of formulations have been developed and reported in literature as a carrier for drug, gene, and diagnostic agents. Amphiphilic block copolymers have achieved increasing attention due to their high stability both in vitro and in vivo and their good biocompatibility. In comparison to other long-circulating nanocarriers, micelles possess a number of advantages such as tissue penetrability, reduced toxicity, and controlled drug release. The characteristic features of micelle as carriers, such as particle size, shape, drug loading, cellular internalization, stability, and release kinetics of drugs can be improved by altering the physicochemical properties of the constituent block copolymers and method of preparation. Polymeric micelles formed from amphiphilic blocks have been successfully used for delivery of drugs that lack water solubility. Chelation or incorporation of a diagnostic agent in ligand conjugated micelle may help in tracing in vivo biodistribution. We review a number of research articles demonstrating that micelle formulations can be used efficiently in clinical situations by taking care of the toxicity of surfactants, and the interaction between polymer and drug, to prepare a formulation carrying a more therapeutic agent with a minimum amount of polymer. PMID:24730264

Kore, Girish; Kolate, Atul; Nej, Ajanta; Misra, Ambikanandan



Improving immobilized biocatalysts by gel phase polymerization  

SciTech Connect

A new method is presented for the treatment of gel-type supports, used for immobilizing microbial cells and enzymes, to obtain high mechanical strength. It is particularly useful for ethanol fermentation over gel beads containing immobilized viable cells, where the beads can be ruptured by gas production and the growth of cells within the gels. This method consists of treating agar or carrageenan gel with polyacrylamide to form a rigid support which retains the high catalytic activity characteristic of the untreated biocatalysts. The size and shape of the biocatalyst is unaffected by this treatment. The method involves the diffusion of acrylamide, N,N'-methylenebisacrylamide and ..beta..-dimethylaminopropionitrile (or N,N,N',N'-tetramethylethylenediamine) into the preformed biocatalyst beads followed by the addition of an initiator to cause polymerization within the beads. Treated gels have been used for the continuous fermentation of glucose to ethanol in a packed column for over two months. During this operation, the gel beads maintained their rigidity, and the maximum productivity was as high as 50 gh/sup -1/ L/sup -1/ gel. There was no appreciable decay of cell activity.

Kuu, W.Y.; Polack, J.A.



Nanospheres with polymerization ability coated by polyrotaxane.  


BETA-cyclodextrin (beta-CD)-based nanosphere 1 initiated the oligomerization of delta-valerolactone (delta-VL) on the surface of 1 to give oligo(delta-VL)-tethered beta-CD nanosphere 2 in bulk. Atomic force microscopy indicated that the molecular size of 2 is twice that of 1. The addition of alpha-CD to 2 leads to the formation of poly-pseudo-rotaxane on the surface of 2 to give a nanosphere with poly-pseudo-rotaxane (alpha-CD[symbol: see text]2). 2D-NOESY NMR experiments showed correlation peaks between the inner protons of alpha-CD and the oligo(delta-VL) chains in an aqueous solution, indicating that the oligo(delta-VL) chains are included in the alpha-CD cavity. Alpha-CD[symbol: see text]2 has a core of beta-CDs with poly-pseudo-rotaxanes on the surface. It should be noted that 2 did not show polymerization ability for delta-VL, but after the formation of poly-pseudo-rotaxanes, oligo(delta-VL) of alpha-CD[symbol: see text]2 repropagated upon the addition of delta-VL. Alpha-CD[symbol: see text]2 is significantly larger than nanospheres 1 and 2. Additionally, postpolymerization increases the size of alpha-CD[symbol: see text]2. These behaviors are reminiscent of the function of a spherical virus, which forms an ordered spherical structure and releases RNA chains from the capsid surface. PMID:19183040

Osaki, Motofumi; Takashima, Yoshinori; Yamaguchi, Hiroyasu; Harada, Akira



Polymeric components for all-optical networks  

NASA Astrophysics Data System (ADS)

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.

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



Waveguides in Thin Film Polymeric Materials  

NASA Technical Reports Server (NTRS)

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.

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



How do entangled polymeric liquids flow?  

NASA Astrophysics Data System (ADS)

This work focused on investigating fundamental questions in polymer dynamics such as how entangled polymeric liquids respond to fast external deformation. By developing an effective particle tracking velocimetric (PTV) method, along with conventional rheometric measurements, new insights can be gained into the phenomenology of entangled polymers in presence of startup shear, step strain and large amplitude oscillatory shear (LAOS). During startup shear of well entangled systems, the shear field becomes inhomogeneous after the stress overshoot for a range of applied shear rates beyond the Newtonian region [1]. The emergence of shear banding after stress overshoot helped us to identify the stress overshoot as indicating yielding, whose characteristics obey some scaling laws. In step shear, contrary to the conventional perception that entangled polymers would undergo quiescent relaxation, the PTV observations reveal macroscopic motions after shear cessation [2]. The recoil-like macroscopic motions appears to reflect an elastic breakdown of the entanglement network due to sufficient build-up of retractive forces. LAOS experiments also demonstrate that entangled polymers cannot sustain a high magnitude of fast deformation without undergoing cohesive failure [3]. [1] Macromolecules 2008, 41, 2663 [2] Macromolecules 2007, 40, 8031 [3] J. Rheol. 2008, 52, 341.

Sundar Ravindranath, Sham; Wang, Shi-Qing



Design Strategies for Fluorescent Biodegradable Polymeric Biomaterials  

PubMed Central

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

Zhang, Yi; Yang, Jian



Confocal Raman Imaging of Polymeric Materials  

NASA Astrophysics Data System (ADS)

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.