Nanocompósitos semicondutores ZnO/TiO2: testes fotocatalíticos

Titanium dioxide is an efficient photocatalist, being possible to improve its efficiency with better charge separation which occurs when it is coupled with other semiconductors. Nanometric particles of ZnO were used to impregnate TiO2 P25 in order to optimize its photocatalytic properties. ZnO/TiO2 composites were obtained at different proportions and were characterized by X-ray diffraction (XRD), micro-Raman and diffuse reflectance spectroscopies, measurement of surface area (BET) and scanning electron microscopy (SEM). Raman spectroscopy data revealed a change on the TiO2 surface due the presence of ZnO which was observed by an enlargement of TiO2 peaks and a change on the relation rate between anatase and rutile phases of the composites. The photodegradation of azo-dye Drimaren red revealed better efficiency for ZnO/TiO2 3% nanocomposite and for ZnO pure.

Co2 na desidrogenação oxidativa do etilbenzeno utilizando catalisadores compostos de óxido de ferro e óxido de alumínio

Materials containing aluminum and iron oxide were synthesized through the preparation of hybrid spheres and tested in the dehydrogenation of ethylbenzene in the presence of CO2. The catalytic results suggest that the high initial ethylbenzene conversion is due to the contribution of basic sites. These results also point to a competitive process between CO2 adsorption and the oxidative dehydrogenation of ethylbenzene for the basic sites (lattice oxygen). In spite of the coke deposition is originating from ethylbenzene and CO2, the amount of carbonaceous deposits was smaller with the presence of CO2, if compared with the dehydrogenation in the absence of CO2.

Fotoeletrodegradação do corante AO7 utilizando filmes de nanocompósitos de ZnO-TiO2

The Zn-TiO2nanocomposite films were prepared by electrodeposition, using an acidic zinc sulphate solution with TiO2 nanoparticles in suspension. The as-deposited samples have been heated in air at 450 ºC for 6 h. The XRD and SEM analyses pointed out to the metal matrix conversion from Zn to ZnO and a rich morphology of needles-shaped grains. These materials were used on the photoelectrochemical degradation of AO7, which was efficiently degraded, with 40% of color removal, after 2 h period at 1.0 V, under white light irradiation. The apparent first order rate constant of the photoelectrodegradation reaction was 4.12 x 10-3 min-1.

Síntese e caracterização de nanocompósitos de poliestireno/hidroxissal lamelar

Polystyrene/layered hydroxide salt (LHS) modified with sodium dodecyl sulfate was synthesized by in situ polymerization. The materials synthesized were characterized by gravimetry, X-ray diffraction (XRD), thermogravimetry analyses (TGA), differential scanning calorimetry (DSC) and the flammability test (FT). XRD demonstrated that synthesized nanocomposites in all compositions studied showed poor global dispersion of LHS in polystyrene. TGA showed a slight decrease in thermal stability. DSC curves showed that the glass transition temperature of polystyrene and nanocomposites were similar. The FT showed that the nanocomposite with low load of LHS exhibited good results.

Nanocompósito de polpa de mamão e nanopartículas de quitosana para aplicação em embalagens

Nanocomposite materials have been incorporated into biopolymers, (e.g. hydroxypropyl methylcellulose), to improve their physical and chemical properties and enable them to be applied in food packaging, especially for their biodegradable and renewable properties. With this addition, fruit puree has been incorporated into the films to confer nutritional properties besides color and flavor. Chitosan is of interest in the packaging field since it is a biodegradable, bioabsorbable, antimicrobial agent. Furthermore, chitosan nanoparticles have been widely explored for their interesting properties and potential applications in food packaging. This work was divided into two stages: (1) chitosan nanoparticle synthesis; (2) addition of nanoparticles into HPMC and papaya puree films. Addition of chitosan nanoparticles to HPMC and papaya puree films improved film properties: mechanical, thermal and water vapor barrier. We have developed a novel nanomaterial with great potential for application in packaging to prolong the shelf life of food.

Nanocompósitos entre nanotubos de carbono e nanopartículas de platina: preparação, caracterização e aplicação em eletro-oxidação de álcoois

The synthesis and characterization of different platinum nanoparticle/carbon nanotube nanocomposite samples are described along with the application of these nanocomposites as electrocatalysts for alcohol oxidation. Samples were prepared by a biphasic system in which platinum nanoparticles (Pt-NPs) are synthesized in situ in contact with a carbon nanotube (CNT) dispersion. Variables including platinum precursor/CNT ratio, previous chemical treatment of carbon nanotubes, and presence or absence of a capping agent were evaluated and correlated with the characteristic of the synthesized materials. Samples were characterized by Raman spectroscopy, X-ray diffraction, thermogravimetric analysis and transmission electron microscopy. Glassy carbon electrodes were modified by the nanocomposite samples and evaluated as electrocatalysts for alcohol oxidation. Current densities of 56.1 and 79.8/104.7 mA cm-2 were determined for the oxidation of methanol and ethanol, respectively.

INFLUÊNCIA DO TRATAMENTO TÉRMICO NO NANOCOMPÓSITO FOTOCATALISADOR ZnO/TiO2

ZnO/TiO2 nanocomposites were prepared by impregnating zinc acetate dihydrate on the surface of titanium dioxide P25, followed by thermal treatment at 350, 600, 750, and 900 °C, in order to investigate the TiO2 phase and titanate formation and the role of the latter in the photocatalytic activity of the nanocomposite. In the nanocomposites, the anatase-to-rutile transition is favored due to the presence of Zn2+, and the conversion is nearly complete at 750 °C. The presence of zinc metatitanate in the sample heated at 600 °C had no significant effect on the nanocomposite photocatalytic activity.

SÍNTESE E CARACTERIZAÇÃO DE COMPÓSITOS ORGÂNICO-INORGÂNICOS MACROPOROSOS PARA O SENSORIAMENTO DE H2O2

Electrodes modified with poly(5-amino-1-naphthol)/Prussian blue (poly(5-NH2-1-NAP)/PB) hybrid films are able to electrochemically reduce H2O2 in medium containing an excess of Na+ cations. This is an important advantage for biosensing applications over electrodes in which only conventionally (electro) deposited Prussian blue is present. Consequently, the aim of this work was to examine the application of templates of ordered arrays of colloidal poly(styrene) spheres (800, 450 and 100 nm in diameter) to produce inverse opal structures of poly(5-NH2-1-NAP)/PB hybrid platforms, in an effort to study the influence of the increase in surface area/volume ratio and higher exposition of the mediator active sites on material performance during H2O2 determination employing the different sized porous structures. Moreover, since the accentuated hydrophilic character of poly(5-NH2-1-NAP)/PB also allows H2O2 electrochemical reduction in inner active sites, issues concerning the amount of mediator electrodeposited on the electrode were also reflected in the observed results.

HYDROLYTIC DEGRADATION BEHAVIOR OF PLLA NANOCOMPOSITES REINFORCED WITH MODIFIED CELLULOSE NANOCRYSTALS

Bionanocomposites derived from poly(L-Lactide) (PLLA) were reinforced with chemically modified cellulose nanocrystals (m-CNCs). The effects of these modified cellulose nanoparticles on the mechanical and hydrolytic degradation behavior of polylactide were studied. The m-CNCs were prepared by a method in which hydrolysis of cellulose chains is performed simultaneously with the esterification of hydroxyl groups to produce modified nanocrystals with ester groups. FTIR, elemental analysis, TEM, XRD and contact angle measurements were used to confirm and characterize the chemical modifications of the m-CNCs. These bionanocomposites gave considerably better mechanical properties than neat PLLA based on an approximately 100% increase in tensile strength. Due to the hydrophobic properties of the esterified nanocrystals incorporated into a polymer matrix, it was also demonstrated that a small amount of m-CNCs could lead to a remarkable decrease in the hydrolytic degradation rate of the biopolymer. In addition, the m-CNCs considerably delay the degradation of the nanocomposite by providing a physical barrier that prevents the permeation of water, which thus hinders the overall absorption of water into the matrix. The results obtained in this study show the nanocrystals can be used to reinforce polylactides and fine-tune their degradation rates in moist or physiological environments.

CARACTERIZAÇÃO E AVALIAÇÃO IN VITRO DE NANOCOMPÓSITOS DE POLI (L-ÁCIDO LÁTICO) E NANOTUBOS DE CARBONO DE PAREDES MÚLTIPLAS PURIFICADOS

Carbon nanotubes (CNT) have been studied for biomedical applications due to their unique properties. However, pristine CNT have structural features and impurities that can cause toxicity to biological systems. In this work, we describe a method to purify multiwalled carbon nanotubes (MWCNT) by chemical modification and subsequent attachment of hydroxyl and carboxyl groups to improve dispersion and to decrease toxic effects. Nanocomposites from poly (L-lactic acid) (PLLA) and nanotubes were produced by the solvent casting method and characterized and evaluated for cytocompatibility with Vero cells. The nanocomposite interactions with Vero cells demonstrated that the cells were able to adhere and sustain proliferation and showed favorable cytocompatibility. In vitro studies also revealed an increase in fibroblast cell viability in the nanocomposites, compared with neat PLLA.

Resultados científicos do cruzeiro do "Baependi" e do "Vega" à Ilha da Trindade: contribuição para o conhecimento da plataforma insular da Ilha da Trindade

The oceanographic work realized during 10 days in the surroundings of the eruptive island of Trindade, 20º30'36" lat. S - 29º19'26" long. W, had as principal aim the determination of the insular plateau, whose knowledge was very insufficient. Thus were established some oceanographic stations and sounding lines were realized by means of an echobathymeter whose responses were initially verified with mechanical soundings obtaneid by means of a Thomson sounder. The insular plateau is very narrow and exhibits a sudden fall between the 100 and 120 m. depth line at 740 m. - 2950 m. from the coast. Its greatest depth is of 108,30 m. and its mean inclination is of 8,12%. The plateau of the island of Trindade is separated from that of the neighbouring group of Martim Yaz by great depths. The bottoms are rocky near the coast, the blocks having been produced by the rupture of the magmatic mass of the island. Further away from the coast, the size of the rocks gradually diminishes up to the fine sand thickness. In the litoral zone there are abundant tufts of living Lithothamnion with a rich associated flora and fauna, which partly covers the rocks themselves. Further off at sea, the spheres of the dead alga with its commensals are cimented together by sedimentation. The spheres are further broken up and become an integrating part of the sand. The results of the physical and chemical analyses of the sand bottoms are shown in tables 2 and 3. The coast is either of abrupt rocky walls falling down to sea level, or of shores, made of pebbles or of sand. Anyhow, there are frequently Lithothamnion terraces slightly inclinated towards the bottom (chemical analysis table 1).

Att förstå det stora i det lilla : byskolan som pedagogik, kultur och struktur

I det lilla sammanhanget synliggörs de stora frågorna om både pedagogik, kultur och struktur och om samverkan mellan dem. Studiet av de minsta enheterna i den finländska utbildningen ger kunskap om det viktiga i pedagogiska relationer och i skolgemenskaper, men synliggör också samhällsskeendets inbyggda konflikter om mål och värderingar. Det övergripande syftet med studien är att fördjupa kunskapen om de små skolornas pedagogiska, kulturella och strukturella innebörd och betingelser. Genom djupintervjuer med 12 finlandssvenska lärare i byskolor med färre än 30 elever, analys av skolindragningsdebatt och utbildningspolitiska styrdokument, samt genom teoretiskt förankrade reflektioner skapas en förståelse av såväl lärares arbete och pedagogiska tänkande som skolans funktion i samhället. Avhandlingen byggs upp enligt ett hermeneutiskt och narrativt tänkande. I studien framkommer att byskollärares pedagogiska tänkande syftar till det enskilda barnets optimala och balanserade helhetsutveckling i en gemenskap, där det är centralt att finna den pedagogiska balansen och möjligheten inom kontinuum mellan bl.a. elevbemyndigande och beledsagande. De pedagogiska intentionerna bär syftet att ge rötter och vingar, samhörighet och frihet. I lärarnas beskrivningar uttrycks en sammanvävning mellan deras pedagogiska intentioner och de kontextuella möjligheterna att realisera dessa. Byskollärarna är bärare av en pedagogisk professionalitet som utvecklas i relation till arbetets betingelser. Det praktiska yrkeskunnandet innefattar en balansgång mellan å ena sidan systematik och organisering och å andra sidan flexibilitet och frihet. Att samma lärare handhar eleverna en lång tid är en pedagogisk möjlighet och utmaning. I lärarnas berättelser aktualiseras vad balansgången i en god pedagogisk relation innebär. Både lärare och elever fostras in i en särskild skolkultur och undervisningskultur, i en växelverkan. Yrkeskulturen präglas av olika former av samverkan, både med skolans hela personal som ett teamarbete och med lokalsamhället. Lärarna uttrycker god arbetstrivsel, men friheten och ansvaret i arbetet kan vara både stimulerande och betungande. I en metaanalys skapas teoretiska modeller för vad arbete i närhetens och litenhetens spänningsfält kan innebära och hur det kan påverka lärares professionella utveckling och ork. Den lilla byskolan relaterad till en större samhällskontext öppnar för frågor om vad kvalitet innebär och vilka värderingar som är riktgivande inom utbildningsplanering. Kampen för kontinuiteten i byskolans berättelse tolkas som en kamp för det lokala rummet, för gemenskap, existens, framtid, likvärdighet och trygghet. Kampen för byskolan är ett försvar av både lokal livskvalitet och pedagogisk kvalitet för den enskilde eleven. I det övergripande kulturella sammanhanget synliggörs motsättningar. Det verkar finnas en inbyggd konflikt i utbildningsplaneringens föresatser att samtidigt uppnå jämlikhet, kostnadseffektivitet och kvalitet. En teoretisk modell synliggör hur pedagogik, kultur och struktur samverkar inom utbildning/byskola och påverkar lärares och elevers handlingsutrymme.

Mössbauer spectra of iron oxides in the bulk and nanocrystalline states

Magnetic nanoparticles are very important in modern industry. These particles are used in many different spheres of life. Nanoparticles have unusual physical and chemical properties connected both with quantum dimensional effects and with the increased role of the surface atoms. Most clearly the difference between the properties of bulk materials and nanoparticles can be seen in the magnetic properties of these materials. The most typical magnetic properties of nanomaterials are superparamagnetism with the size of the cluster from 1 to 10 nm; single-domain magnetic state of nanoclusters and nanostructures up to 20 nm; magnetization processes connected with magnetic cluster ordering and with its forms and sizes; quantum magnetic tunneling effects when magnetization changes by jumps and giant magnetoresistance effects. For research of the magnetic properties of iron-containing nanostructures, it is convenient to apply Mӧssbauer spectroscopy. In this work a number of nano-sized samples of iron oxides were examined by Mössbauer spectroscopy. The Mössbauer spectra of nanoparticles with various sizes were obtained. Mössbauer spectra of iron oxide nanoparticles were compared with the spectra of bulk samples. It was shown how the spectra of iron oxide nanoparticles change depending on the particle sizes.

JOHTAMISOPIT KUNTAORGANISAATIOSSA – diskursiivinen tutkimus sosiaali- ja terveystoimesta 1980-luvulta 2000-luvulle

Julkisen sektorin johtamista on uudistettu viime vuosikymmeninä uuden julkisjohtamisen suuntauksen kautta. Tässä keskeistä ovat olleet markkinamekanismin sekä yksityissektorin johtamisoppien soveltaminen julkiselle sektorille. Tämän tutkimuksen tarkoituksena on tuottaa tietoa johtamisoppien soveltamisesta kuntaorganisaation sosiaalija terveystoimessa. Mielenkiinnon kohteena ovat kysymykset, miten johtamisopit ovat tulleet kuntaorganisaatioon ja miten ne ovat levinneet, rakentuneet sekä rakentaneet kontekstiaan tarkasteluajanjaksolla 1985 - 2007. Tutkimuksen lähestymistapa on diskurssianalyyttinen ja nojaa epistemologialtaan tulkinnallisesta tieteen filosofiasta nousseeseen sosiaaliseen konstruktivismiin. Oppien leviämistä tarkastellaan tässä tutkimuksessa translaationa, kääntämisprosessina, jossa opin johtoportaaseen tullut ensimmäinen versio tulkitaan ja käännetään organisaation kielelle ja käytännöiksi. Oppien rakentumista kontekstissaan käsitteellistetään sedimentoitumisen käsitteen kautta, mikä auttaa ymmärtämään uusien ja vanhojen oppien elementtien kerrostumista lähes muuttumattomista syvärakenteista nopeasti muuttuviin pintarakenteisiin. Tutkimuksen kohdeorganisaationa on suomalainen, keskikokoinen kuntaorganisaatio. Aineistona on käytetty kirjallisia dokumentteja ja haastatteluja. Johtamisoppeja kuntaorganisaatioon välittäviä tahoja ovat olleet konsulttiyritykset, yliopistot, kuntien johtoportaan verkostot, uudet johtajat sekä koulutuspäivät. Organisaation valmius uuden johtamisopin omaksumiseen on yhteydessä organisaatioon, johtoon, tarjolla oleviin oppeihin sekä toimintaympäristöön liittyviin tekijöihin Levitäkseen organisaatiossa oppi tarvitsee johdon tasolta kannattajan, joka markkinoi sitä muulle virkamies- ja luottamushenkilöjohdolle. Kun oppi saavuttaa johdon enemmistön tuen, käynnistyy sen kääntämisprosessi johdon puheesta henkilöstön puheen ja käytäntöjen tasolle. Uudet johtamisopit kyseenalaistavat vanhoja ”totuuksia” ja samalla ne määrittävät, mikä on tärkeää ja mikä jää huomiotta. Uudet opit eivät syrjäytä kokonaan vanhoja, vaan opit sedimentoituvat: vanhojen oppien diskursiivisia elementtejä jää pois ja uusien oppien elementtejä tulee mukaan johtamispuheeseen. Johtamisopit rakentavat kontekstiaan sekä puheen, käytäntöjen että organisaatiorakenteiden tasolla, mutta joihinkin syvärakenteisiin ne eivät ole pystyneet vaikuttamaan tai vaikuttavat äärimmäisen hitaasti. Asiakaslähtöisyys muun muassa on ollut useimpien johtamisoppien diskursiivinen elementti, mutta se on jäänyt toistuvasti kuntaorganisaation sosiaali- ja terveystoimessa organisaatiolähtöisen palvelujen järjestämistavan ja talouden kautta tapahtuvan tuloksellisuuden arvioinnin varjoon. Diskurssit muutoksesta ja sen välttämättömyydestä, tehokkuudesta sekä julkisen rinnastaminen yksityiseen näyttäytyivät tässä tutkimuksessa metatason diskursseina, jotka oikeuttavat yksityiseltä sektorilta lähtöisin olevien johtamisdiskurssien soveltamisen muutoksen ja tehokkuuden aikaansaamiseksi julkiselle sektorille. Kuntien sosiaali- ja terveystoimen tuloksellisuuden ja tehokkuuden arviointi on kapeutunut liikkeenjohdon peruslähtökohdista nousevaksi talouden kautta tapahtuvaksi arvioinniksi. Tässä julkisen toiminnan omiin arvolähtökohtiin ja teoriataustaan pohjautuvien toiminnan tulosten ja saavutettujen hyvinvointivaikutusten arviointi sekä näistä kertovien mittarien kehittäminen yhdessä talouden mittarien kanssa on marginaaliin jäänyttä, mutta nousevaa puhetta.

Utilisation of magnetic field in membrane filtration

As it is known, the major problem of membrane filtration is fouling of membrane during the filtration process. There are a lot of methods to prevent or reduce fouling. One very little studied method is applying of magnetic field in membrane filtration. Magnetic field has such advantages as bulk, contact free, nondestructive impact on the sample, thus it can be combined with different types of processes. In addition, the use of magnetic fields has given positive results in various areas of science and life. So, the present thesis is devoted to the research of influence of magnetic field on performances of nanofiltration. In the literature part of the thesis a short description of membrane process and mechanism of reorientation of nanoparticals in magnetic field is presented. The utilization of magnetic field in different spheres of life, in general, and membrane area, in particular, is represented. In the experimental part the influence of magnetic field created by two permanent magnets on filtration of two solutions (citric acid and sodium dodecyl sulfate) was investigated. Factors, which affect on the impact of magnetic field was estimated. The effect of magnetic field was evaluated by measuring a change of pure water permeability after the filtration of model solution. This work demonstrated that direction of magnetic field and the type of molecules of filtered solution has significant effect to the efficiency of nanofiltration. Utilization of magnetic field might increase retention of membrane and flux through membrane and reduce fouling.