Novel catalyst systems based on Ni(II), Ti(IV), and Cr(III) complexes for oligo-and polymerization of ethylene

The complex of Brookhart Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6- diisopropylphenyl)-acenaphthenediimine) has been characterized after impregnation on silica (S1) and MAO-modified silicas (4.0, 8.0 and 23.0 wts.% Al/SiO2 called S2, S3 and S4, respectively). The treatment of these heterogeneous systems with MAO produces some active catalysts for the polymerization of the ethylene. A high catalytic activity has been gotten while using the system supported 1/S3 (196 kg of PE/mol[Ni].h.atm; toluene, Al/Ni = 1000, 30ºC, 60 min and atmospheric pressure of ethylene). The effects of polymerization conditions have been tested with the catalyst supported in S2 and the best catalytic activity has been gotten with solvent hexane, MAO as cocatalyst, molar ratio Al/Ni of 1000 and to the temperature of 30°C (285 kg of PE/mol[Ni].h.atm). When the reaction has been driven according to the in situ methodology, the activity practically doubled and polymers showed some similar properties. Polymers products by the supported catalysts showed the absence of melting fusion, results similar to those gotten with the homogeneous systems by DSC analysis. But then, polymers gotten with the transplanted system present according to the GPC’s curves the polydispersity (MwD) varies between 1.7 and 7.0. A polyethylene blend (BPE/LPE) was prepared using the complex Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6-diisopropylphenyl)-acenaphthenediimine) and {TpMs*}TiCl3 (2) (TpMs* = hydridobis(3-mesitylpyrazol-1-yl)(5-mesitylpyrazol-1-yl)) supported in situ on MAO-modified silica (4.0 wts. -% Al/SiO2, S2). Reactions of polymerization of ethylene have been executed in the toluene in two different temperatures (0 and 30°C), varying the molars fraction of nickel (xNi), and using MAO as external cocatalyst. To all temperatures, the activities show a linear variation tendency with xNi and indicate the absence of the effect synergic between the species of nickel and the titanium. The maximum of activity have been found at 0°C. The melting temperature for the blends of polyethylene produced at 0 °C decrease whereas xNi increases indicating a good compatibility between phases of the polyethylene gotten with the two catalysts. The melting temperature for the blends of polyethylene showed be depend on the order according to which catalysts have been supported on the MAO-modified silica. The initial immobilization of 1 on the support (2/1/S2) product of polymers with a melting temperature (Tm) lower to the one of the polymer gotten when the titanium has been supported inicially (1/2/S2). The observation of polyethylenes gotten with the two systems (2/1/S2 and 1/2/S2) by scanning electron microscopy (SEM) showed the spherical polymer formation showing that the spherical morphology of the support to been reproduced. Are described the synthesis, the characterization and the catalytic properties for the oligomerization of the ethylene of four organometallics compounds of CrIII with ligands ([bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine] chromium (III) chloride (3a), [bis[2-(3,5- dimethyl-l-pyrazolyl)ethyl]benzylamine] chromium (III) chloride (3b), [bis[2-(3,5-dimethyl-lpyrazolyl) ethyl]ether] chromiun(III)chloride (3c), [bis[2-(3-phenyl-lpyrazolyl) ethyl]ether]chromiun(III)chloride (3d)). In relation of the oligomerization, at exception made of the compounds 3a, all complex of the chromium showed be active after activation with MAO and the TOF gotten have one effect differentiated to those formed with CrCl3(thf)3. The coordination of a tridentate ligand on the metallic center doesn't provoke any considerable changes on the formation of the C4 and C6, but the amount of C8 are decrease and the C10 and C12+ have increased. The Polymers produced by the catalyst 3a to 3 and 20 bar of ethylene have, according to analyses by DSC, the temperatures of fusion of 133,8 and 136ºC respectively. It indicates that in the two cases the production of high density polyethylene. The molar mass, gotten by GPC, is 46647 g/mols with MwD = 2,4 (3 bar). The system 3c/MAO showed values of TOF, activity and selectivity to different α-olefins according to the pressure of ethylene uses. Himself that shown a big sensibility to the concentration of ethylene solubilized.

Novas metodologias para a determinação do conteúdo de ácido árcobico em alimentos frescos

A vitamina C é uma das vitaminas mais importantes para a nutrição humana e destacase pela sua eficiente acção antioxidante e participação em inúmeras reacções metabólicas como cofactor enzimático. A vitamina C inclui vários compostos que têm actividade biológica semelhante ao ácido L-ascórbico (L-AA), incluindo o produto da sua oxidação, ácido desidroascórbico (DHAA), e as formas sintéticas. Os seres humanos não são capazes de sintetizar a vitamina C, sendo necessário obter este nutriente através da alimentação. As frutas e vegetais são alimentos ricos em vitamina C, ao contrário das carnes e cereais. Existem diversos métodos analíticos disponíveis para quantificação dos teores de vitamina C nos alimentos, sendo os métodos cromatográficos os mais utilizados devido à sua capacidade de separação e elevada sensibilidade e precisão. Neste trabalho, foi desenvolvido e validado um método de cromatografia líquida de ultra-eficiência (UHPLC) para determinar o conteúdo de vitamina C total (L-AA + DHAA) em várias frutas e vegetais com proveniências diferentes. A produção de produtos hortofrutícolas na ilha da Madeira não é auto-suficiente, sendo necessário importar alguns alimentos. Realizou-se um pequeno estudo comparativo do teor total de vitamina C e a sua degradação nos produtos locais e importados. O DHAA foi medido indirectamente através da reacção com o redutor DL-1,4-ditiotreitol (DTT), antes da injecção cromatográfica. Os resultados obtidos foram comparados com a titulação iodométrica. As amostras foram extraídas durante 5 dias consecutivos sendo os extractos resultantes armazenados a -80ºC imediatamente após a extracção até ao dia de análise. A estabilidade do L-AA nos extractos conservados a diferentes temperaturas e os efeitos do cozimento dos alimentos sobre esta molécula foram avaliados. A actividade antioxidante dos produtos hortofrutícolas foi também medida pelo método ABTS (2,2-azino-bis(3-etilbenzotiazolina- 6-sulfonato). O estudo da validação do método apresentou resultados bastante satisfatórios, demonstrando uma boa repetibilidade e sensibilidade elevada. Além disso, o método proposto revelou ser uma abordagem melhorada, simples e rápida para a determinação do conteúdo de vitamina C total em diversos produtos alimentares.

Detecção e caracterização de biomarcadores voláteis em indivíduos com patologias oncológicas

Com a realização deste trabalho, pretendeu-se traçar o perfil padrão da composição volátil típico de fluidos biológicos (urina) de indivíduos sem patologia oncológica (grupo de controlo) comparando-os com os de pacientes (grupo com patologia oncológica). As amostras de urina de ambos os grupos foram analisadas por microextracção em fase sólida em modo de headspace acoplada à espectrometria de massa (HS-SPME-GC/qMS). Com o intuito de aumentar a eficiência de extracção da SPME, foram optimizados alguns parâmetros com influência no processo extractivo, nomeadamente o tipo de fibra, o tempo e a temperatura de extracção. Assim sendo, foram testadas e comparadas seis fibras comercialmente disponíveis, polidimetilsiloxano (PDMS, 100 m), poliacrilato (PA, 85 m), carboxeno-polidimetilsiloxano (CAR/PDMS, 75 m), carbowax-divinilbenzeno (CW/DVB, 65 m), divinilbenzeno-carboxen-polidimetilsiloxano (DVB/CAR/PDMS, 50/30 m) e polidimetilsiloxano-divinilbenzeno (PDMS/DVB, 65 m). A influência do tempo (30, 45, 60 e 75 min) e temperatura (30, 50 e 60 ºC) de extracção foram optimizados de modo a obter uma melhor eficiência de extracção dos compostos voláteis presentes nas amostras de urina. Os melhores resultados foram obtidos usando a fibra carboxeno-polidimetilsiloxano (CAR/PDMS, 75 m), com uma velocidade de agitação de 800 rpm durante 75 min a uma temperatura de 50 ºC. Para os dois grupos em estudo, foram identificados 80 compostos voláteis pertencentes a diversas famílias químicas, nomeadamente, aldeídos, cetonas, derivados benzénicos, compostos terpénicos, ácidos orgânicos, compostos furânicos, compostos sulfurados, fenóis voláteis, ésteres, álcoois superiores e derivados do naftaleno. Os compostos maioritários pertencentes aos grupos analisados foram a 4-heptanona, a 2-pentanona, a acetona, a 2-butanona, o 1(2- furanil)etanona, o 3-metil-3-fenil-2-propenal, o 3,4-dimetilbenzaldeído, o decanal, o dissulfureto de dimetilo, o metanotiol, o 2-metoxitiofeno, o 4-metil-fenol, o p-tert-butil-fenol, o 2,4-bis(1,1- dimetiletil)fenol, o fenol, o m-cimeno, o p-cimeno, o tolueno, o 1-etil-3,5-diisopropilbenzeno, o 2,6-dimetil-7-octen-2-ol, a D-carvona, o vitispirano I e o vitispirano II. O teste One-Way ANOVA foi aplicado aos resultados com o intuito de verificar se existiam diferenças significativas entre os grupos avaliados (Controlo e Oncológico), sendo o dissulfureto de dimetilo, o 2-metoxitiofeno, e o p-cimeno estatisticamente significativos. A aplicação da análise multivariável às amostras de urina das diferentes patologias permitiu diferenciá-las no qual se obteve 81,02% da variância total.A aplicação da análise multivariável às amostras de urina das diferentes patologias permitiu diferenciá-las no qual se obteve 81,02% da variância total. A patologia de Hodgkin é influenciada pelas variáveis heptanal e o 2-metil-3-fenil-2-propenal. O Controlo é afectado essencialmente pelas variáveis p-cimeno, 1,4,5-trimetilnaftaleno e o dissulfureto de dimetilo. O Cólon é influenciado pelo 4-metilfenol, anisole e 1,2-dihidro-1,1,6-trimetil-naftaleno. O 1-octanol e a 3-heptanona influenciam, essencialmente as patologias da Mama e Leucemia.

An electroanalytical application of 2-aminothiazole-modified silica gel after adsorption and separation of Hg(II) from heavy metals in aqueous solution

2-Aminothiazole covalently attached to a silica gel surface was prepared in order to obtain an adsorbent for Hg(II) ions having the following characteristics: good sorption capacity, chemical stability under conditions of use, and, especially, high selectivity. The accumulation voltammetry of mercury(II) was investigated at a carbon paste electrode chemically modified with silica gel functionalized with 2-aminothiazole (SIAMT-CPE). The repetitive cyclic voltammogram of mercury(II) solution in the potential range -0.2 to + 0.6 V versus Ag/AgCl (0.02 mol L-1 KNO3; V = 20 mV s(-1)) show two peaks one at about 0.1 V and other at 0.205 V. The anodic wave peak at 0.205 V is well defined and does not change during the cycles and it was therefore further investigated for analytical purposes using differential pulse anodic stripping voltammetry in differents supporting electrolytes. The mercury response was evaluated with respect to pH, electrode composition, preconcentration time, mercury concentration, cleaning solution, possible interferences and other variables. The precision for six determinations (n = 6) of 0.02 and 0.20 mg L-1 Hg(II) was 4.1 and 3.5% (relative standard deviation), respectively. The detection limit was estimated as 0.10 mu g L-1 mercury(II) by means of 3:1 current-to-noise ratio in connection with the optimization of the various parameters involved and using the highest-possible analyser sensitivity. (c) 2006 Elsevier Ltd. All rights reserved.

Otimização de modelos de predição da perda de propagação aplicáveis em 3,5GHZ utilizando algoritmos genéticos

The telecommunications industry has experienced recent changes, due to increasing quest for access to digital services for data, video and multimedia, especially using the mobile phone networks. Recently in Brazil, mobile operators are upgrading their networks to third generations systems (3G) providing to users broadband services such as video conferencing, Internet, digital TV and more. These new networks that provides mobility and high data rates has allowed the development of new market concepts. Currently the market is focused on the expansion of WiMAX technology, which is gaining increasingly the market for mobile voice and data. In Brazil, the commercial interest for this technology appears to the first award of licenses in the 3.5 GHz band. In February 2003 ANATEL held the 003/2002/SPV-ANATEL bidding, where it offered blocks of frequencies in the range of 3.5 GHz. The enterprises who purchased blocks of frequency were: Embratel, Brazil Telecom (Vant), Grupo Sinos, Neovia and WKVE, each one with operations spread in some regions of Brazil. For this and other wireless communications systems are implemented effectively, many efforts have been invested in attempts to developing simulation methods for coverage prediction that is close to reality as much as possible so that they may become believers and indispensable tools to design wireless communications systems. In this work wasm developed a genetic algorithm (GA's) that is able to optimize the models for predicting propagation loss at applicable frequency range of 3.5 GHz, thus enabling an estimate of the signal closer to reality to avoid significant errors in planning and implementation a system of wireless communication

Inhibition of peroxidase activity and scavenging of reactive oxygen species by astilbin isolated from Dimorphandra mollis (Fabaceae, Caesalpinioideae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência de fatores de risco na prevalência de hábitos bucais deletérios em crianças de 0 a 5 anos na cidade do Natal-RN

Literature has demonstrated to the narrow relation between deleterious habits and the occurrence of malocclusion in minors of 5 years. The existence of these habits, however, already considered as risk factors, having also, its determinative ones, which present cultural dimensions and economic social, many of them related to the parents of the child, having in account that such habits if develop in phases in which the child establish a narrow relation of dependence. This study it had an objective to investigate the prevalence of deleterious buccal habits in children and its relation with the economic social and characteristics of the parents. It was developed an epidemiologist study of transversal character with interview, through daily pay-tested form, with 218 parents in the day of the National Campaign of Vaccination. In the cast of the variable that had composed the study, they had been used, as changeable dependents, the use of the baby's bottle, bottle and the digital suction, being considered as outcomes of the research. Amongst the independent variable, the economic social factors (type of occupation, number of children, civil state, sort, schooling and age) and staffs of the parents (self perception in oral health) had entered as the variable to be analyzed in the problems of the infantile odontology. The collected data had been submitted to the analysis descriptive and inferential statistics, being used the test qui-square and the analysis of the possibility reasons. As main results, it was found that breast feeding before the six months if presents as one of the main factors of risk for the use of baby's bottle (p< 0.001, OR= 2.8, I.C= 1.589 4.906), bottle (p< 0.001, OR= 3.7, I.C.= 2.076 6.624) and digital suction (p< 0.014, OR= 3.5, I.C.= 1.225 10.181). From the data found, one concludes that breast-feeding is considered a primordial factor for not the installation of deleterious oral habits and that the economic social and cultural factors can reflect in central way in the performance of this act

Study of copper complexes adsorbed on a silica gel surface chemically modified with 2-amino-1,3,4-thiadiazole

The isotherms of adsorption of CuX2 (X=Cl-, Br-, ClO4-) by silica gel chemically modified with 2-amino-1,3,4-thiadiazole were studied in acetone and ethanol solutions: at 298 K. The following equilibria constants (in 1 mol(-1)) were determined: (a) CuCl2: 3.5 x 10(3) (ac), 2.0 x 10(3) (eth); (b) CuBr2: 2.8 x 10(3) (ac), 2.0 x 10(3) (eth); (c) Cu(ClO4)(2): 1.8 x 10(3) (ac), 1.0 x 10(3) (eth); ac = acetone, eth = ethanol. The electron spin resonance spectra of the surface complexes indicated a tetragonal distorted structure in the case of lower degrees of metal loading on the chemically modified surface. The d-d electronic transition spectra showed that for the ClO4-, complex, the peak of absorption did not change for any degree of metal loading, and for Cl- and Br- complexes, the peak maxima shifted to a higher energy region with a lower metal loading. (C) 1998 Elsevier B.V. B.V. All rights reserved.

Uso do 5-fluorouracil no intra-operatório da cirurgia do pterígio

Objetivo: Avaliar a efetividade e as complicações com a aplicação do 5- fluorouracil (5-FLU) no intra-operatório da cirurgia do pterígio. Método: Foram avaliados 28 olhos de 26 indivíduos quanto ao tipo e tamanho do pterígio, cirurgias prévias e a resposta ao tratamento cirúrgico (no 7º , 21º , 60º e 90º dia de pós-operatório). Logo após a exerese do pterígio, aplicou-se 5-FLU (25 mg/ml) no leito cirúrgico, durante cinco minutos; a seguir, realizou-se a técnica de deslizamento de retalho conjuntival. Resultados: A maioria dos pacientes tinha mais de 50 anos de idade e apresentava pterígio primário (70,0%), grau II (60,7%), do tipo involutivo (60,7%). No pós-operatório observaram-se: isquemia (10,7%), deiscência da conjuntiva (7,1%), ceratite (3,5%), conjuntivite (3,5%) e recidiva da lesão em 1 olho (3,5%).Conclusão: O 5-FLU se mostrou droga segura e efetiva na prevenção das recidivas, podendo ser usado como coadjuvante no tratamento do pterígio para prevenir recidivas.

Ovarian superstimulatory response and embryo production in mares treated with equine pituitary extract twice daily

Equine pituitary extract (EPE), has been reported to induce multiple ovulation in mares, however ovulation rates are poor in comparison to those obtained in other species. Attempts to improve the effectiveness of EPE for induction of superovulation in cyclic mares has focused on daily frequency of EPE treatment. Two experiments were performed to compare the ovarian response of cyclic mares given EPE once or twice-daily. Mares were assigned to one of two treatment groups 6 to 8 days after ovulation: prostaglandin was given once and EPE (25 mg) was given once daily (Group 1) or twice daily (Group 2). In Experiment 1, more (P < 0.05) follicles 35 mm were detected in mares treated with EPE twice daily (6.1 +/- 3.1) than in mares treated once a daily (2.0 +/- 0.6). In a second experiment, the embryo recovery rates of mares given the two EPE protocols used in Experiment 1 were compared. The number of ovulations per mare was higher (P < 0.05) for mares treated twice-daily (7.1 +/- 5.1, range 3 to 18) than for mares treated once daily (2.4 +/- 1.8, range 1 to 6). The number of embryos produced per mare was higher (P < 0.05) in mares in Group 2 (3.5) than in Group 1 (1.6).Although it is not clear whether the increased ovulation rate is due specifically to dose or frequency, twice-daily administration of a high dose of EPE significantly improved follicular development, ovulation and embryo recovery over the standard treatment of once-daily injection. (C) 2001 by Elsevier B.V.

Fatigue performance of joints executed in pure titanium structures with several diameters

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fatigue strength: effect of welding type and joint design executed in Ti-6Al-4V structures

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Three-dimensional structure of ribonuclease T-1 complexed with an isosteric phosphonate substrate analogue of GpU: Alternate substrate binding modes and catalysis

The X-ray crystal structure of a complex between ribonuclease T-1 and guanylyl(3'-6')-6'-deoxyhomouridine (GpcU) has been determined at 2.0 Angstrom resolution. This Ligand is an isosteric analogue of the minimal RNA substrate, guanylyl(3'-5')uridine (GpU), where a methylene is substituted for the uridine 5'-oxygen atom. Two protein molecules are part of the asymmetric unit and both have a GpcU bound at the active site in the same manner. The protein-protein interface reveals an extended aromatic stack involving both guanines and three enzyme phenolic groups. A third GpcU has its guanine moiety stacked on His92 at the active site on enzyme molecule A and interacts with GpcU on molecule B in a neighboring unit via hydrogen bonding between uridine ribose 2'- and 3'-OH groups. None of the uridine moieties of the three GpcU molecules in the asymmetric unit interacts directly with the protein. GpcU-active-site interactions involve extensive hydrogen bonding of the guanine moiety at the primary recognition site and of the guanosine 2'-hydroxyl group with His40 and Glu58. on the other hand, the phosphonate group is weakly bound only by a single hydrogen bond with Tyr38, unlike ligand phosphate groups of other substrate analogues and 3'-GMP, which hydrogen-bonded with three additional active-site residues. Hydrogen bonding of the guanylyl 2'-OH group and the phosphonate moiety is essentially the same as that recently observed for a novel structure of a RNase T-1-3'-GMP complex obtained immediately after in situ hydrolysis of exo-(S-p)-guanosine 2',3'-cyclophosphorothioate [Zegers et al. (1998) Nature Struct. Biol. 5, 280-283]. It is likely that GpcU at the active site represents a nonproductive binding mode for GpU [:Steyaert, J., and Engleborghs (1995) fur. J. Biochem. 233, 140-144]. The results suggest that the active site of ribonuclease T-1 is adapted for optimal tight binding of both the guanylyl 2'-OH and phosphate groups (of GpU) only in the transition state for catalytic transesterification, which is stabilized by adjacent binding of the leaving nucleoside (U) group.

Efficiency of extrinsic and intrinsic charge-carrier photogeneration processes obtained from the steady-state photocurrent action spectra of poly(p-phenylene vinylene) derivatives

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Detection of DNA Nucleotides on Pretreated Boron Doped Diamond Electrodes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)