Reversibly Photo-Crosslinkable Polycarbonate-Based Polymersomes for Drug Encapsulation and Delivery

This thesis describes the preparation of polymersomes from poly(ethylene glycol)-block-polycarbonate (PEG-PC) copolymers functionalized with pendant coumarin groups. Coumarin groups undergo photo-reversible dimerization when irradiated with specific ultraviolet wavelengths, so they can be used to prepare polymers with photo-responsive properties. In this case, the pendant coumarin groups enable stabilization of the polymersome membrane through photo-crosslinking of the hydrophobic block. Initially, several novel cinnamoyl and coumarin functionalized cyclic carbonate monomers were synthesized using ester, ether, or amide linkages. While the homopolymerization of these functionalized monomers proved challenging due to their high melting points, both cinnamoyl and coumarin functionalized monomers were successfully copolymerized with trimethylene carbonate (TMC) at 100 ℃ using a catalyst-free melt polymerization process where the TMC doubled as a solvent for the higher melting point monomer. Using this system, polycarbonate copolymers with up to 33% incorporation of the functionalized monomers were prepared. In addition, an investigation of some anomalous polymerization results identified previously unreported triethylamine-based catalysts for the melt polymerization of carbonate monomers. These studies also demonstrated that the catalyst-free polymerization of TMC occurs faster and at lower temperatures than previously reported. Subsequently, the photo-crosslinking of cinnamoyl and coumarin functionalized polycarbonates was compared and coumarin was identified as the more effective crosslinking agent when using 300-400 nm UV. An investigation of the photo-reversibility of the coumarin dimerization revealed no discernible change in the properties of crosslinked networks, but rapid photo-reversion in dilute solutions. The photo-crosslinking and photo-reversion kinetics of the coumarin functionalized polycarbonates were determined to be second-order in both cases. Finally, the self-assembly of PEG-PC diblock copolymers functionalized with coumarin was examined and both reverse solvent evaporation and solvent displacement were found to induce self-assembly, with hydrophilic mass fractions (f-factors) of 12-28% resulting in the formation of solid microparticles and nanoparticles and f-factors of 33-43% resulting in the formation of polymersomes. The stabilization of these polymersome membranes through photo-initiator-free photo-crosslinking was demonstrated with the crosslinking allowing polymersomes to withstand centrifugation at 12,000 x g. In addition, the encapsulation of calcein, as a model small molecule drug, in the stabilized polymersomes was successfully demonstrated using confocal microscopy.

Produzione di alcol furfurilico da furfurale in fase gas con catalizzatori a base di CaO

The hydrogenation of biomass-derived molecules is a key reaction in upgrading these compounds into chemicals and fuels. The use of catalytic transfer hydrogenation, employing alcohols as hydrogen sources, offers an alternative approach to this process, avoiding the use of H2 under high pressure and precious metal catalysts. In this work, the gas-phase conversion of biomass-derived furfural into furfuryl alcohol and 2-methylfuran was studied, using methanol as the H-transfer agent and CaO-based catalysts. The results obtained with this catalyst were compared with those obtained by using MgO, which due to its basic properties and to its high surface area, at present appears to be among the best basic catalysts used for the conversion of biomass-derived molecules. Pure CaO, despite having a very low surface area, compared to MgO catalyst (5 m2/g vs. 172 m2/g), was shown to reduce furfural into its corresponding unsaturated alcohol at 350°C, thus allowing selective H-transfer from methanol to the substrate. These results highlight the potential application of the H-transfer reaction over CaO based catalysts as an efficient process for the selective reduction of biomass-derived molecules.

Fabrication and Pseudo-Analog Characteristics of Ta2O5 -Based ReRAM Cell

Memristori on yksi elektroniikan peruskomponenteista vastuksen, kondensaattorin ja kelan lisäksi. Se on passiivinen komponentti, jonka teorian kehitti Leon Chua vuonna 1971. Kesti kuitenkin yli kolmekymmentä vuotta ennen kuin teoria pystyttiin yhdistämään kokeellisiin tuloksiin. Vuonna 2008 Hewlett Packard julkaisi artikkelin, jossa he väittivät valmistaneensa ensimmäisen toimivan memristorin. Memristori eli muistivastus on resistiivinen komponentti, jonka vastusarvoa pystytään muuttamaan. Nimens mukaisesti memristori kykenee myös säilyttämään vastusarvonsa ilman jatkuvaa virtaa ja jännitettä. Tyypillisesti memristorilla on vähintään kaksi vastusarvoa, joista kumpikin pystytään valitsemaan syöttämällä komponentille jännitettä tai virtaa. Tämän vuoksi memristoreita kutsutaankin usein resistiivisiksi kytkimiksi. Resistiivisiä kytkimiä tutkitaan nykyään paljon erityisesti niiden mahdollistaman muistiteknologian takia. Resistiivisistä kytkimistä rakennettua muistia kutsutaan ReRAM-muistiksi (lyhenne sanoista resistive random access memory). ReRAM-muisti on Flash-muistin tapaan haihtumaton muisti, jota voidaan sähköisesti ohjelmoida tai tyhjentää. Flash-muistia käytetään tällä hetkellä esimerkiksi muistitikuissa. ReRAM-muisti mahdollistaa kuitenkin nopeamman ja vähävirtaiseman toiminnan Flashiin verrattuna, joten se on tulevaisuudessa varteenotettava kilpailija markkinoilla. ReRAM-muisti mahdollistaa myös useammin bitin tallentamisen yhteen muistisoluun binäärisen (”0” tai ”1”) toiminnan sijaan. Tyypillisesti ReRAM-muistisolulla on kaksi rajoittavaa vastusarvoa, mutta näiden kahden tilan välille pystytään mahdollisesti ohjelmoimaan useampia tiloja. Muistisoluja voidaan kutsua analogisiksi, jos tilojen määrää ei ole rajoitettu. Analogisilla muistisoluilla olisi mahdollista rakentaa tehokkaasti esimerkiksi neuroverkkoja. Neuroverkoilla pyritään mallintamaan aivojen toimintaa ja suorittamaan tehtäviä, jotka ovat tyypillisesti vaikeita perinteisille tietokoneohjelmille. Neuroverkkoja käytetään esimerkiksi puheentunnistuksessa tai tekoälytoteutuksissa. Tässä diplomityössä tarkastellaan Ta2O5 -perustuvan ReRAM-muistisolun analogista toimintaa pitäen mielessä soveltuvuus neuroverkkoihin. ReRAM-muistisolun valmistus ja mittaustulokset käydään läpi. Muistisolun toiminta on harvoin täysin analogista, koska kahden rajoittavan vastusarvon välillä on usein rajattu määrä tiloja. Tämän vuoksi toimintaa kutsutaan pseudoanalogiseksi. Mittaustulokset osoittavat, että yksittäinen ReRAM-muistisolu kykenee binääriseen toimintaan hyvin. Joiltain osin yksittäinen solu kykenee tallentamaan useampia tiloja, mutta vastusarvoissa on peräkkäisten ohjelmointisyklien välillä suurta vaihtelevuutta, joka hankaloittaa tulkintaa. Valmistettu ReRAM-muistisolu ei sellaisenaan kykene toimimaan pseudoanalogisena muistina, vaan se vaati rinnalleen virtaa rajoittavan komponentin. Myös valmistusprosessin kehittäminen vähentäisi yksittäisen solun toiminnassa esiintyvää varianssia, jolloin sen toiminta muistuttaisi enemmän pseudoanalogista muistia.

Catalytic dehydration of glycerol to acrolein: catalysts and processes

The valorization of glycerol has been widely studied notably due to the oversupply of the latter from biodiesel production. Among the different upgrading reactions, dehydration to acrolein is of high interest due to the importance of acrolein as an intermediate for polymer industry (via acrylic acid) and for feed additive (synthon for DL-methionine). It is known that acrolein can be obtained by glycerol catalytic dehydration over acid catalysts. Zeolites and heteropolyacid catalysts are initially highly active, but deactivate rapidly with time on stream by coking, whilst mixed metal oxides are more stable catalytic systems but less selective and in addition they require an activation period. In this talk, the strategy we followed is described. It consisted in a parallel approach in which we developed supported heteropolyacid-based catalysts with increased stability and acrolein selectivity by using a ZrO2-grafted SBA-15 playing the role of the support for silico-tungstic acid active phase, as well as a new concept based on a two zones fluidized bed reactor (TZFBR) to tackle the unavoidable deactivation issue of the HPA catalysts. This type of reactor comprises – in one single capacity – reaction and regeneration zones. In the second part of the lecture the REALCAT platform was introduced. REALCAT (French acronym standing for ‘Advanced High-Throughput Technologies Platform for Biorefineries Catalysts Design’) is an highly integrated platform devoted to the acceleration of innovation in all the fields of industrial catalysis with an emphasis on emergent biorefinery catalytic processes. In this extremely competitive field, REALCAT consists in a versatile High-Throughput Technologies (HTT) platform devoted to innovation in heterogeneous, homogeneous or biocatalysts AND their combinations under the ultra-efficient very novel concept of hybrid catalysis.

High performance of Cu/CeO2-Nb2O5 catalysts for preferential CO oxidation and total combustion of toluene

Copper-based catalysts supported on niobium-doped ceria have been prepared and tested in the preferential oxidation of CO in excess of H2 (PROX) and in total oxidation of toluene. Supports and catalysts have been characterized by several techniques: N2 adsorption, ICP-OES, XRF, XRD, Raman Spectroscopy, SEM, TEM, H2-TPR and XPS, and their catalytic performance has been measured in PROX, with an ideal gas mixture (CO, O2 and H2) with or without CO2 and H2O, and in total oxidation of toluene. The effects of the copper loading and the amount of niobium in the supports have been evaluated. Remarkably, the addition of niobia to the catalysts may improve the catalytic performance in total oxidation of toluene. It allows us to prepare cheaper catalysts (niobia it is far cheaper than ceria) with improved catalytic performance.

Enhanced oxidation activity from modified ceria: MnOx-ceria, CrOx-ceria and Mg doped VOx-ceria

Ceria is an important component of catalysts for oxidation reactions that proceed through the Mars-van Krevelen mechanism, promoting activity. A paradigm example of this is the VOx–CeO2 system for oxidative dehydrogenation reactions, where vanadium oxide species are supported on ceria and a special synergy between them is behind the enhanced activity: reduction of the catalyst is promoted by ceria undergoing reduction. This leads to favourable oxygen vacancy formation and hydrogen adsorption energies—useful descriptors for the oxidation activity of VOx–CeO2 catalysts. In this paper, we examine if this promoting effect on ceria-based catalysts holds for other metal oxide modifiers and we investigate MnOn– and CrOn–CeO2(111) (n = 0 − 4) as examples. We show, combining density functional theory calculations and statistical thermodynamics that similarly to the vanadia modifier, the stable species in each case is MnO2– and CrO2–CeO2. Both show favourable energetics for oxygen vacancy formation and hydrogen adsorption, indicating that VO2–CeO2 is not the only system of this type that can have an enhanced activity for oxidation reactions. However, the mechanism involved in each case is different: CrO2–CeO2 shows similar properties to VO2–CeO2 with ceria reduction upon oxygen removal stabilising the 5+ oxidation state of Cr. In contrast, with MnO2–CeO2, Mn is preferentially reduced. Finally, a model system of VO2–Mg:CeO2 is explored that shows a synergy between VO2 modification and Mg doping. These results shed light on the factors involved in active oxidation catalysts based on supported metal oxides on ceria that should be taken into consideration in a rational design of such catalysts.

Reproducibility of gastric emptying in overweight and obese males

Background & aim To understand whether any change in gastric emptying (GE) is physiologically relevant, it is important to identify its variability. Information regarding the variability of GE in overweight and obese individuals is lacking. The aim of this study was to determine the reproducibility of GE in overweight and obese males. Methods Fifteen overweight and obese males [body mass index 30.3 (4.9) kg/m2] completed two identical GE tests 7 days apart. GE of a standard pancake breakfast was assessed by 13C-octanoic acid breath test. Data are presented as mean (±SD). Results There were no significant differences in GE between test days (half time (t1/2): 179 (15) and 176 (19 min), p = 0.56; lag time (tlag): 108 (14) and 104 (8) min, p = 0.26). Mean intra-individual coefficient of variation for t1/2 was 7.9% and tlag 7.5%. Based on these findings, to detect a treatment effect in a paired design with a power of 80% and α = 0.05, minimum mean effect sizes for t1/2 would need to be ≥14.4 min and tlag ≥ 8.1 min. Conclusions These data show that GE is reproducible in overweight and obese males and provide minimum mean effect sizes required to detect a hypothetical treatment effect in this population.

Child sexual abuse in China : a meta-analysis of 27 studies

Objective: To examine whether Chinese studies of child sexual abuse (CSA) in the general population show lower prevalence rates than other international studies, and whether certain features of these studies may help to account for variation in estimates. Methods: A meta-analysis and meta-regression were conducted on 27 studies found in the English and Chinese language peer reviewed journals that involved general populations of students or residents, estimated CSA prior to age 18, and specified rates for males or females individually. Results: Estimates for Chinese females were lower than the international composites. For total CSA for females, the Chinese pooled estimate was 15.3% (95% CI = 12.6–18.0) based on the meta-analysis of 24 studies, lower than the international estimate (Stoltenborgh, van IJzendoorn, Euser, & Bakermans-Kranenburg, 2011) but not significantly. For contact CSA for females, the pooled estimate was 9.5% (95% CI = 7.5–11.5), based on 16 studies, significantly lower than the international prevalence. For penetrative CSA for females, the pooled estimate was 1% (95% CI = 0.7–1.3), based on 15 studies, significantly lower than the international estimate of 15.1%. Chinese men reported significantly less penetrative CSA but significantly more total CSA than international estimates; while contact CSA reported by Chinese and international males appeared to be roughly equivalent. Chinese CSA prevalence estimates were lower in studies from urban areas and non-mainland areas (Hong Kong and Taiwan), and in surveys with larger and probability samples, multiple sites, face-to-face interview method and when using less widely used instruments. Conclusions: The findings to date justify further research into possible cultural and sociological reasons for lower risk of contact and penetrative sexual abuse of girls and less penetrative abuse of boys in China. Future research should examine sociological explanations, including patterns of supervision, sexual socialization and attitudes related to male sexual prowess. Practice implications: The findings suggest that future general population studies in China should use well validated instruments, avoid face-to-face interview formats and be careful to maintain methodological standards when sampling large populations over multiple sites.

Catalytic hydrogen combustion for treatment of combustible gases from fuel cell processors

Catalytic combustion of H-2 was carried out over combustion synthesized noble metal (Pd or Pt) ion-substituted CeO2 based catalysts using a feed stream that simulated exhaust gases from a fuel cell processor The catalysts showed a high activity for H-2-combustion and complete conversion was achieved below 200 C over all the catalysts when O-2 was used in a stoichiometric amount With higher amounts of O-2 the reaction rates Increased and complete conversions were possible below 100 C The reaction was also carried out over Pd-impregnated CeO2 The conversions of H-2 with stoichiometric amount of O-2 were found to be higher over Pd-substituted compound The mechanism of the reaction over noble metal-substituted compounds was proposed on the basis of X-ray photoelectron spectroscopy studies The redox couples between Ce and metal ions were established and a dual site redox mechanism was pi posed for the reaction (C) 2010 Elsevier B V All rights reserved

The cDNA sequence of cytochrome b5 associated with cytokinin-induced haustoria formation in Cuscuta reflexa

A cDNA clone isolated by differentially screening a cytokinin-induced haustorial cDNA library of Cuscuta reflexa was sequenced and identified as the gene coding for cytochrome b(5), based on the similarity of the deduced amino-acid sequence with that of the cauliflower (60% identity) and tobacco (78% identity) proteins. The 5'-UTR is unusually long (720 bp) and contains 14 potential start codons (ATG) and 10 short ORFs.

Association Rule Sharing Model for Privacy Preservation and Collaborative Data Mining Efficiency

The disclosure of information and its misuse in Privacy Preserving Data Mining (PPDM) systems is a concern to the parties involved. In PPDM systems data is available amongst multiple parties collaborating to achieve cumulative mining accuracy. The vertically partitioned data available with the parties involved cannot provide accurate mining results when compared to the collaborative mining results. To overcome the privacy issue in data disclosure this paper describes a Key Distribution-Less Privacy Preserving Data Mining (KDLPPDM) system in which the publication of local association rules generated by the parties is published. The association rules are securely combined to form the combined rule set using the Commutative RSA algorithm. The combined rule sets established are used to classify or mine the data. The results discussed in this paper compare the accuracy of the rules generated using the C4. 5 based KDLPPDM system and the CS. 0 based KDLPPDM system using receiver operating characteristics curves (ROC).

High Catalytic Activity of Amorphous Ir-Pi for Oxygen Evolution Reaction

Large-scale production of hydrogen gas by water electrolysis is hindered by the sluggish kinetics of oxygen evolution reaction (OER) at the anode. The development of a highly active and stable catalyst for OER is a challenging task. Electrochemically prepared amorphous metal-based catalysts have gained wide attention after the recent discovery of a cnbalt-phosphate (Co-Pi) catalyst: Herein, an amorphous iridium-phosphate (Ir-Pi) is investigated as an oxygen evolution catalyst. The catalyst is prepared by the anodic polarization of carbon paper electrodes in neutral phosphate buffer solutions containing IrCl3. The Ir-Pi film deposited on the substrate has significant amounts of phosphate and It centers in an oxidation state higher than +4. Phosphate plays a significant role in the deposition of the catalyst and also in its activity toward OER. The onset potential of OER on the Ir-Pi is about 150 mV lower in comparison with the Co-Pi under identical experimental conditions. Thus, Ir-Pi is a promising catalyst for electrochemical oxidation of water.

Hydrogen energy future with formic acid: a renewable chemical hydrogen storage system

Formic acid, the simplest carboxylic acid, is found in nature or can be easily synthesized in the laboratory (major by-product of some second generation biorefinery processes); it is also an important chemical due to its myriad applications in pharmaceuticals and industry. In recent years, formic acid has been used as an important fuel either without reformation (in direct formic acid fuel cells, DFAFCs) or with reformation (as a potential chemical hydrogen storage material). Owing to the better efficiency of DFAFCs compared to several other PEMFCs and reversible hydrogen storage systems, formic acid could serve as one of the better fuels for portable devices, vehicles and other energy-related applications in the future. This perspective is focused on recent developments in the use of formic acid as a reversible source for hydrogen storage. Recent developments in this direction will likely give access to a variety of low-cost and highly efficient rechargeable hydrogen fuel cells within the next few years by the use of suitable homogeneous metal complex/heterogeneous metal nanoparticle-based catalysts under ambient reaction conditions. The production of formic acid from atmospheric CO2 (a greenhouse gas) will decrease the CO2 content and may be helpful in reducing global warming.

Engineering and Characterization of Cytochrome P450 Enzymes for Nitrogen-Atom Transfer Reactions

The creation of novel enzyme activity is a great challenge to protein engineers, but nature has done so repeatedly throughout the process of natural selection. I begin by outlining the multitude of distinct reactions catalyzed by a single enzyme class, cytochrome P450 monooxygenases. I discuss the ability of cytochrome P450 to generate reactive intermediates capable of diverse reactivity, suggesting this enzyme can also be used to generate novel reactive intermediates in the form of metal-carbenoid and nitrenoid species. I then show that cytochrome P450 from Bacillus megaterium (P450_BM3) and its isolated cofactor can catalyze metal-nitrenoid transfer in the form of intramolecular C–H bond amination. Mutations to the protein sequence can enhance the reactivity and selectivity of this transformation significantly beyond that of the free cofactor. Next, I demonstrate an intermolecular nitrene transfer reaction catalyzed by P450_BM3 in the form of sulfide imidation. Understanding that sulfur heteroatoms are strong nucleophiles, I show that increasing the sulfide nucleophilicity through substituents on the aryl sulfide ring can dramatically increase reaction productivity. To explore engineering nitrenoid transfer in P450BM3, active site mutagenesis is employed to tune the regioselectivity intramolecular C–H amination catalysts. The solution of the crystal structure of a highly selective variant demonstrates that hydrophobic residues in the active site strongly modulate reactivity and regioselectivity. Finally, I use a similar strategy to develop P450-based catalysts for intermolecular olefin aziridination, demonstrating that active site mutagenesis can greatly enhance this nitrene transfer reaction. The resulting variant can catalyze intermolecular aziridination with more than 1000 total turnovers and enantioselectivity of up to 99% ee.

Conversão do metanol em olefinas catalisada por zeólitas com diferentes características ácidas e estruturais

A reação de transformação de metanol em olefinas leves foi investigada sobre as peneiras moleculares HZSM-5, HFER, SAPO-34 e HMCM-22. A caracterização físico-química das amostras foi realizada através das técnicas de FRX, DRX, fisissorção de nitrogênio, MEV, espectrometria no IV com adsorção de piridina e TPD de NH3. O desempenho catalítico das mesmas foi comparado em condições de isoconversão inicial de 755%. Verificou-se que as características ácidas e estruturais exerceram forte influência sobre o desempenho catalítico quanto à atividade, estabilidade e seletividade aos produtos da reação. A amostra mais estável foi a HZSM-5 que apresentou maior densidade de sítios fortes e uma estrutura porosa que permite uma circulação tridimensional das moléculas. Já a menos estável, SAPO-34, apresentou a menor concentração de sítios ácidos fortes dentre os materiais estudados e uma estrutura com cavidades com aberturas estreitas (4Å) que oferecem restrições ao acesso dos reagentes aos sítios ácidos do catalisador. Quanto à seletividade a olefinas, a primeira foi mais seletiva a propeno e a segunda, a eteno. A ferrierita não se mostrou seletiva às olefinas leves tendo apresentado, no entanto, comportamento promissor quanto a formação de DME a partir do metanol. Já a HMCM-22 foi seletiva às olefinas leves e aos hidrocarbonetos com 4, 5 e 6 ou mais átomos de carbono. A influência da temperatura no desempenho catalítico foi investigada variando-se a temperatura de reação (300, 400 e 500C). Verificou-se que para a HZSM-5 e HMCM-22, perda da atividade catalítica foi intensificada a partir de 400C. Quanto à seletividade a olefinas leves, apenas a SAPO-34 não se mostrou sensível a variações na temperatura, efeito este que foi nitidamente observado nos outros três catalisadores: um aumento na temperatura promoveu um aumento na seletividade a olefinas leves no caso da HZSM-5 e da HMCM-22 e queda nesse valor para a HFER