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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
761

Fe3O4 Nanoparticles for Fluorescence Sensing of Specific Substrate and Catecholamines

Liu, Cheng-Hao 04 July 2011 (has links)
The first study reports the development of a reusable, single-step system for the detection of specific substrates using oxidase-functionalized Fe3O4 nanoparticles (NPs) as a bienzyme system and using amplex ultrared (AU) as a fluorogenic substrate. In the presence of H2O2, the reaction pH between Fe3O4 NPs and AU was similar to the reaction of oxidase and the substrate. The catalytic activity of Fe3O4 NPs with AU was nearly unchanged following modification with poly(diallyldimethylammonium chloride) (PDDA). Based on these features, we prepared a composite of PDDA-modified Fe3O4 NPs and oxidase for the quantification of specific substrates through the H2O2-mediated oxidation of AU. By monitoring fluorescence intensity at 587 nm of oxidized AU, the minimum detectable concentrations of glucose, galactose, and choline were found to be 3, 2, and 20 £gM using glucose oxidase-Fe3O4, galactose oxidase-Fe3O4, and choline oxidase-Fe3O4 composites, respectively. The identification of glucose in blood was selected as the model to validate the applicability of this proposed method. The second study follows the first one. Using the catalytic activity of Fe3O4 NPs with AU to detect four kinds of neurotransmitter, such as dopamine, L-DOPA, adrenaline (epinephrine) and noradrenaline (norepinephrine). Because of there is specific interaction between Fe3O4 NPs and catecholamines (CAs), the Fe3O4 NPs will form CAs-Fe3O4 NPs composites in presence of CAs. The CAs on the Fe3O4 NPs surface must shelter the reaction between AU and H2O2, cause the fluorescence to be turned-off. The CAs just like a inhibitor, to inhibit the catalytic activity of Fe3O4 NPs. Therefore, we could use this inhibited system to detect the CAs compound concentration in the real sample.
762

Synthesis Of Novel Blue-emitting Poly(arylene ether)s with Application to Light Emitting Diodes

Chang, Ming-sian 19 July 2012 (has links)
In this thesis, a novel blue Poly (arylene ether) s polymer was prepared for the organic polymer light emitting diodes which was composed of the main material anthracene difluoro monomer derivatives, and object material of triphenylamine with the extension structure similar to the literature seen BD-1 asymmetric derivatives, as the hole transport material of carbazole of the diol derivatives. In general, Anthracene derivatives and BD-1, often seen in the literature as the host, guest blue polymer doping, the main use to Forster energy transfer to transfer energy to the guest, so it has good luminous efficiency. Anthracene, flat Good, easy to crystallization during evaporation, resulting in leakage generated; and the deposition of the multilayer structure will hinder charge injection to the emitting layer. From the angle of the molecular design of this study. (1) Use of the CF bond and Carbazole increase the steric hindrance of the polymer chain and change by fluoride compounds of the highest occupied molecular orbital - lowest unoccupied molecular orbital energy level. (2) The hole transport layer to import into the emitting layer. The two monomers Anthracene derivatives fluoride monomer the Carbazole of diol derivatives via nucleophilic polycondensation synthesis of a novel in proper proportion, Blue polymer. Component parts, the Blue poly aromatic ether polymer doped with a small amount of blue light-emitting guest as a component layer of the component structure: ITO / PEDOT: PSS / emitting layer / LiF / Al light-emitting layer can make use of spin coating of solvent process, and its advantage is the convenience of the process and a large area. The undoped guest before the Blue polymer production the PLED starting voltage can be reduced to 4.5 V, and maximum brightness 7 466 cd/m2, efficiency as high as 4.2 cd / A. C.I.E. coordinates of (0.15,0.08), very close to the official regulations of the NTSC Blue coordinates (0.14,0.08). When doped with 3% of the guest, the starting voltage can be reduced to 4.5 V, maximum brightness of 12104 cd/m2 and efficiency as high as 5.79 cd/A.
763

Locally and Densely Sulfonated Poly(arylene ether)s as Proton Exchange Membrane

Tang, Kai-Chun 20 July 2012 (has links)
The proton exchange membrane fuel cells should have three major advantages: 1. micro-phase separation, 2. mechanical properties and 3. thermal stability. According to the recent literature and the material of core benzene ring poly (arylene ether)s studied by our group, this paper synthesize a series of the locally and densely sulfonated polymer. We use core benzene ring as the diol monomer and the containing CF3 groups as the fluorine monomer to synthesis poly (arylene ether)s via nucleophilic displacement reactions, and then use the different concentrations synthesized sulfonated polymer by sulfonic acid reaction. According to NMR¡¦s result we confirmed that the structure of synthetic materials is correct. By using GPC we get that the KP1, KP2, and KP3¡¦s molecular weight about 20000 (g/mol) ; The thermal stability up to 530OC for 5% loss in TGA under nithtrogen, to prove thisseries of polymer excellent thermal stability. After sulfonation, SKP1, SKP2 and SKP3¡¦s decomposition temperature decreased about 200OC ~ 250OC ranging with increasing degree of sulfonation. By DSC analysis, K1, K2 and K3 monomer's Tg followed up with the increase of the benzene ring number, however, the polymer does not have any apparent peak. About the Proton conductive, SKP2C IEC 2.23mequiv / g, water uptake 94%, the highest proton conductivity can be as high as 68.2 mS / cm, has been similar to Nafion 117 of 70 mS / cm.
764

Synthesis and Application of Poly(arylene ether)s for Proton Exchange Membrane

Chu, Meng-Han 21 July 2012 (has links)
Proton Exchange Membrane Fuel Cell has the potential to become an important energy conversion technigne. Lots of efforts oriented toward the electrochemical conversion of energy using proton exchange membrane (PEM) fuel cells have been enormously accelerated with the hope to promote as an alternative power source for transport and portable purposes. However, they still suffer from such disadvantages as limited operation temperature, high cost, insufficient durability and high methanol permeability.Good membranes should meet several strict requirements as follows; reasonable proton conductivity, high stability and durny the performance of a fuel cell environment,outstanding mechanical toughness, high heat endurance, and impermeability to fuel gas or liquid. Presently,a lot of references have mentioned some sulfonatied polymer sulfonated of poly(ether ether ketone) (SPEEK), sulfonatedpolysulfone (SPSF), sulfonated polysulfide sulfone(SPSS), and polybenzimidazole(PBI) and so on.To achieve high proton conductivity usually match with a high degree of sulfonation that means owning a large Ion Exchange Capacity, IEC.But which in turn leads to a decrease in the electrochemical¡Bdimensional stability¡Bwater uptake¡Boxidative stability. Therefore they suffer from such disadvantages as limited operation range of temperature.Three aromatic poly(arylene ether)s P4b¡BP4c¡BP4d were synthesized from the polymer consists nine of polyaromatic groups with bisfluoride monomer at studying long time in our laboratory with S1¡BS2¡BS3 diol monomer.The molecular weight of the polymer (Mw:1.49¡Ñ105~5.3¡Ñ105 g/mol ,PDI: 1.82~2)This polymer has high strength,thermal stability and all of polymers own very high Td ,which are over than 500oC.We sulfonatied the polymer in order to apply as the proton exchange membrane of a fuel cell.The results showed after sulfonation of P4b¡BP4c¡BP4d.All IEC reaches 3.9~1(meq/g).According to above result, we propose the aromatic poly(arylene ether)s is good matenal can be used on all application as a proton exchange membrane.
765

Evaluation of PM10 and Total Suspended Particulate Sampler Performance Through Wind Tunnel Testing

Thelen, Mary Katherine 2010 August 1900 (has links)
Particulate matter (PM) concentrations in ambient air can be monitored by gravimetric sampling near a source using Federal Reference Method (FRM) samplers. PM is regulated by size, with PM10, which is comprised of particles with aerodynamic equivalent diameters less than or equal to 10 μm, being the main focus of this research. FRM PM10 samplers exhibit sampling errors when sampling dusts with mass median diameters (MMDs) that are larger than the 10 μm sampler cutpoint. For industries to be regulated equitably, these sampler errors must be quantified and understood. This research evaluates the performance of FRM PM10 and low volume total suspended particulate (TSP) samplers under the controlled conditions of a wind tunnel. The performance evaluation was conducted by observing the sampler cutpoints, slopes, and measured concentrations. These measured values were compared to values obtained using a collocated isokinetic reference sampler. The results of this research indicate that PM10 samplers do not operate as intended under all conditions. The cutpoint of the PM10 inlets was significantly higher than the maximum FRM limit of 10.5 μm when sampling dust with MMDs larger than the cutpoint of the sampler. The slope values for the PM10 inlets were significantly higher than the maximum FRM limit of 1.6. MMDs and geometric standard deviations of PM collected by TSP samplers were significantly different than those of PM collected using the collocated isokinetic sampler. The concentrations measured by the TSP samplers were significantly higher than the collocated isokinetic sampler. The results of this research provide a better understanding of the performance of TSP and PM10 samplers operating under different conditions and shows that these samplers are not operating as intended. Because of this, industries may be suffering the consequences of inequitable regulation.
766

Synthesis and Characterization of Benzobisthiazole Derived Polymers

Chen, Chien-Fan 29 March 2004 (has links)
In this study, two series of polymers based on benzobisthiazole were synthesized. The poly(benzobisthiazoles) (PBTs) have been synthesized by the solution polycondensation of 2,5-diamino-1,4-benzenedithiol in poly(phosphoric acid)s (PPA). The diacids used were systematically varied to find the best for the solubilization of the aromatic heterocyclic rigid-rod polymers. The role of PPA is identified and the effects of phosphorous pentoxide and water on PBT during polycondensation are discussed. Polymer properties such as the inherent viscosity, decomposition temperature are correlated to systematically varied diacids. Finally, the effect of diacid architecture on the synthesis and microstructure of PBT is studied. The results are further discussed in terms of resonance, symmetry, and solubilization of the diacids. Next, we extend the rigidity and resonance of benzobisthiazole for the application as second-order nonlinear optics. Novel nonlinear optical (NLO) polyimides containing benzobisthiazole chromophores have been synthesized. The soluble polyimides containing different ratios of carboxylic acids (COOH) were first prepared and the precursors of NLO chromophores reacted with those carboxylic acids, followed by the benzobisthiazole derived chromophores synthesized at 300 oC under vaccum. The formation of benzobisthiazole was evidenced by FTIR and UV-vis spectra in combination with the analysis of model polyimides. The excellent thermal properties of those NLO polyimides were examined by TGA and TMA. PI-1 shows thermal decomposition temperature as high as 554 oC at 10 wt % loss and a Tg of 324 oC. The amorphous morphology of those polyimides was verified by XRD traces and some ordered alignments were found, due to the rigidity of the benzobisthiazole derivatize chromophores. The electrooptic coefficient of PI-1 (r33 = 5.3 pm/V) was obtained.
767

Investigation on Electrical Analysis and Physics Mechanism of Low Temperature Polycrystalline-silicon Thin Film Transistor

Huang, Sung-yu 20 July 2006 (has links)
There were three poly-Si TFT made by ELA, SLS, and HREC. The HREC TFT had better reliability than ELA TFT and SLS TFT under AC and hot carrier stress. And the effect of bending in SLS TFT was more obvious then ELA TFT, it provide us a better choose to develop a flexible TFT LCD. In poly-Si TFT, the photon current would decrease if there was a grain boundary in the channel. In all parameters include both manufacture and measurement the HREC TFT had better behaviors than ELA TFT and SLS TFT. But there also some shortcomings we must overcome include we muse growth a heat-retaining layer extra and must etch it and the poly-Si/heat-retaining etch rate and so on.
768

Modified Acrylic Hydrogels As Controlled Release Systems

Pinardag, Fatma Esra 01 May 2006 (has links) (PDF)
In this study, pH-sensitive poly(acrylamide-co-acrylic acid) hydrogels were synthesized as controlled release systems in the presence of N,N-methylene bisacrylamide as crosslinker and ammonium persulfate as initiator. A set of hydrogels were used in the form they were prepared. One set of hydrogels were prepared as porous networks by incorporating sodium chloride into the reaction medium and then leaching of it after the completion of polymerization reaction. Two sets of hydrogels were modified by argon-plasma at different discharge powers. Hydrogels were characterized by 13C-NMR, XPS, SEM, ATR-FTIR, ESR as well as equilibrium degree of swelling (EDS) and contact angle measurements. Prepared hydrogels were loaded with a model antibiotic, ciprofloxacin-HCl (CPFX), and in-vitro release of CPFX from hydrogel matrices were examined in buffer solutions of varying pH values. There are two factors determining the release rates of CPFX / one is the pH-dependent solubility of CPFX and the other is EDS of the hydrogel samples. For porous samples drug loading and release rates were higher when compared to the control samples and CPFX solubility dominated over release kinetics. Plasma treatment resulted in prolonged release rates in acidic medium.
769

Graft Copolymerization Of P-acryloyloxybenzoic Acid Onto Polypropylene

Isik, Buket 01 December 2006 (has links) (PDF)
Acryloyloxybenzoic acid (ABA) was prepared by the condensation reaction of acryloyl chloride with p-hydroxybenzoic acid in alkaline medium. The polymerization and grafting of ABA onto Polypropylene were anticipated to occur simultaneously in melt mixing at high temperature. The monomer showed liquid crystalline property. For a better dispersion of ABA in PP before graft copolymerization, a masterbatch of 50-50 (by weight) low density polyethylene + ABA was prepared, which was then used for 5, 10, 15 % ABA + PP mixtures in the Brabender Plasti Corder. Furthermore, these compositions were reprocessed at the same temperature in the molten state. Compression molding was used to prepare films for characterization experiments at 200 &ordm / C under 15000 psi for approximately 3-5 minutes. The graft copolymers were characterized by several techniques / DSC, FTIR, MFI, SEM and mechanical testing. In DSC thermograms the crystallization of PP was seen at approximately 160&ordm / C. An endothermic peak was also assigned to grafted PABA at 280&ordm / C . The incorporation of ABA onto the PP backbone as a graft copolymer (PABA-g-PP) at low percentages results in a possible rearrangement, where tensile strength values increased, while strain decreased. The grafting goes through thermal radicalic mechanism. MFI values were found to increase from 8.7 to 16.35 g/10 min at 10 wt % ABA, then decreased to 10.57 g/10 min at 15 wt % ABA. It is most likely that the presence of PABA produced easy orientational flow up to 10 % of ABA, but at 15 % ABA addition caused a slight decrease in MFI. The tensile test specimens were analyzed by Scanning Electron Microscope. None of the three samples exhibited phase separation. This observation confirms that the graft copolymerization occurrs in a homogenous manner onto PP. The brittle nature of material is observed at all three compositions.
770

Self Reinforcement Of Poly(ethylene Terephthalate) And Polyethylene Blends

Kurtulus, Ceren 01 April 2007 (has links) (PDF)
In this study, 20/80 (weight %) Poly(ethylene terephthalate) (PET) /High Density Polyethylene (HDPE) Microfibrillar Reinforced Composites (MFC) were prepared by using high density polyethylene (HDPE) as the matrix material, poly(ethylene terephthalate) (PET) as the reinforcing component. Ethylene n-butyl acrylate-glycidyl methacrylate (E-nBA-GMA) and ethylene methyl acrylate (E-MA) as the compatibilizers in 1, 5, and 10 wt. %. The objective of this study is to produce MFCs based on PET and HDPE via extrusion-drawing-injection method and to characterize as extruded, as drawn and injection molded materials in terms of morphologies, and mechanical and thermal properties. In addition, the effect of compatibilizer type and content on properties of PET-HDPE composites was studied. For comparison purposes, conventional PET-HDPE composites with and without compatibilizer were prepared. Also, the effect of screw speed and drawing speed on the morphologies and mechanical and thermal properties were investigated. The effect of low and high injection temperature molding on morphologies were also observed. SEM analyses showed that, extruded blends became oriented after drawing. The fibrillar structure was preserved after injection molding. High injection molding temperature destroyed the structure of PET microfibers. In addition, it was also observed that the adhesion between HDPE and PET improved with the addition of the compatibilizers. Tensile strength and tensile modulus values of PET/HDPE MFCs increased with increasing drawing speed. Increasing the screw speed resulted in a slight decrease in tensile strength values. Addition of the compatibilizers to the system decreased tensile strength and tensile modulus values. Results of impact tests designated that the impact strength of the materials with and without MFC structure increased with the increasing amounts of E-nBAGMA. DSC analyses pointed out that, melting temperatures of HDPE and PET phase did not change significantly with increasing drawing speed or with the addition of the compatibilizer. As the drawing speed increased from 2.7 m/min to 6.2 m/min, degree of crystallinity of the drawn samples of the PET phase increased.

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