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1.
São Paulo; s.n; s.n; 2022. 191 p. tab, graf.
Tese em Inglês | LILACS | ID: biblio-1378632

RESUMO

The interaction of the organic ligands with metal nanoparticle has a very important role for applications in catalysis, as well as other processes involving ligands that can activate or poison the surface of metal nanoparticles. Very little has been studied so far on the role of organic ligands used either in the preparation of nanoparticles for applications in catalysis or addition in the reaction to activate the catalyst. In this thesis, we have studied strategies for the synthesis of metal nanoparticles, their use as components for the preparation of supported catalysts and activation and deactivation processes involving the ligands used as stabilizers or purposely added to the reaction medium or support for stimulate new reactivity and selectivity in reactions of industrial interest, such as hydrogenation. Here, the concept of frustrated Lewis pairs (FLPs) has been expanded to surface-FLP analogous formed by combining gold nanoparticles (NPs) and Lewis bases, such as amines or phosphines, creating a new channel for the heterolytic cleavage of H2, and thereby performing selective hydrogenation reactions with gold. A first approach to improve the catalytic activity of gold nanoparticles was to analyze the effect of nitrogen-containing bases. The starting inactive gold nanoparticles became highly active for the selective hydrogenation of alkyne into cis-alkenes. The hydrogenation proceeded smoothly and fully selective using H2 as the hydrogen source and under relatively mild conditions (80 °C, 6 bar H2). Our studies also have revealed that the presence of capping ligands blocks the adsorption of the amine to the gold surface, avoiding the FLPs interface and thereby leading to low catalytic activity. When the capping ligands were removed from the catalyst surface and an amine ligand was added, the FLPs interface is recovered and an enhanced catalytic activity was observed. Furthermore, we have demonstrated the successful use of simple organophosphorus ligands to boost the catalytic activity of Au NPs for a range of important reduction reactions, namely, epoxides, N-oxides, sulfoxides, and alkynes. Furthermore, the choice of phosphorus-containing ligands resulted in a decrease in the amount necessary to reach high conversion and selectivity in comparison with our previous study with N-containing ligands. The ligand-to-metal ratio decreased from 100 (amine/Au) to 1 (phosphite/Au). The synthesis of gold nanoparticles supported on N-doped carbon supports was used as an alternative method for the synthesis of a heterogeneous active gold catalyst for selective hydrogenations. The main advantage with respect to previous studies was to avoid the addition of external ligands, in large excess, for the activation of gold surfaces via FLP, making the whole process environmentally and economically attractive


A interação dos ligantes orgânicos com nanopartículas de metal certamente tem um papel muito importante para aplicações em catálise, bem como outros processos envolvendo ligantes que podem ativar ou envenenar a superfície de nanopartículas metálicas. Até agora, muito pouco foi estudado sobre o papel dos ligantes orgânicos utilizados na preparação de nanopartículas para aplicações em catálise ou adição na reação para ativar o catalisador. Nesta tese, foram estudadas estratégias para a síntese de nanopartículas metálicas, seu uso como componentes para a preparação de catalisadores suportados e processos de ativação e desativação envolvendo ligantes empregados como estabilizantes ou propositalmente adicionados ao meio de reação ou suporte para estimular novas reatividades e seletividade em reações de interesse industrial, como reações de hidrogenação. Aqui, o conceito de pares de Lewis frustrados (FLPs) foi expandido para o seu análogo de superfície formado pela combinação de nanopartículas (NPs) de ouro e bases de Lewis, como aminas ou fosfinas, criando um novo canal para a clivagem heterolítica de H2 e, assim, realizando reações seletivas de hidrogenação com ouro. Uma primeira abordagem para melhorar a atividade catalítica das nanopartículas de ouro foi analisar o efeito de bases contendo nitrogênio. As nanopartículas de ouro inicialmente inativas tornaram-se altamente ativas para a hidrogenação seletiva de alquino em cis-alquenos. A hidrogenação prosseguiu foi factível e totalmente seletiva usando H2 como fonte de hidrogênio e sob condições relativamente amenas (80 °C, 6 bar de H2). Nossos estudos também revelaram que a presença de estabilizantes pode bloquear a adsorção da base na superfície do ouro, impedindo a formação da interface FLPs e, portanto, levando a baixa atividade catalítica. Quando os estabilizantes foram removidos da superfície do catalisador e um ligante foi adicionado, o FLPs é formado sendo a atividade catalítica aprimorada. Além disso, demonstramos o uso bem-sucedido de ligantes organofosforados atuando como ativadores de Au NPs em uma série de importantes reações de redução, como, epóxidos, N-óxidos, sulfóxidos e alquinos. Além disso, a escolha do ligante fosforado resultou em uma diminuição na quantidade necessária para alcançar alta conversão mantendo a seletividade inalterada. A relação ligante/metal diminuiu de 100/1 (amina/Au) para 1/1 (fosfito/Au). A síntese de nanopartículas de ouro suportadas em carbono dopado com nitrogênio foi utilizada como método alternativo para a síntese de um catalisador heterogêneo de ouro ativo para hidrogenações seletivas. A principal vantagem em relação aos estudos anteriores foi evitar a adição de ligantes externos, em grande excesso, para a ativação de superfícies de ouro via FLP, tornando todo o processo ambiental e economicamente atraente


Assuntos
Catálise , Catalisador , Bases de Lewis/antagonistas & inibidores , Ouro/agonistas , Ligantes , Carbono/agonistas , Estratégias de Saúde , Alcenos/classificação , Nanopartículas Metálicas , Categorias de Trabalhadores
2.
Braz. j. med. biol. res ; 50(12): e6351, 2017. graf
Artigo em Inglês | LILACS | ID: biblio-888959

RESUMO

Lippia sidoides Cham is a typical herb species of Northeast Brazil with widespread use in folk medicine. The major constituents of the essential oil of L. sidoides (EOLs) are thymol, p-cymene, myrcene, and caryophyllene. Several studies have shown that the EOLs and its constituents have pharmacological effects, including antibacterial, anti-inflammatory, antioxidant and neuroprotective activity. Therefore, this work aimed to investigate the effects of the EOLs and their main constituents on rat sciatic nerve excitability. The sciatic nerves of adult Wistar rats were dissected and mounted in a moist chamber. Nerves were stimulated by square wave pulses, with an amplitude of 40 V, duration of 100 μs to 0.2 Hz. Both EOLs and thymol inhibited compound action potential (CAP) in a concentration-dependent manner. Half maximal inhibitory concentration for CAP peak-to-peak amplitude blockade were 67.85 and 40 µg/mL for EOLs and thymol, respectively. CAP peak-to-peak amplitude was significantly reduced by concentrations ≥60 µg/mL for EOLs and ≥30 µg/mL for thymol. EOLs and thymol in the concentration of 60 µg/mL significantly increased chronaxie and rheobase. The conduction velocities of 1st and 2nd CAP components were also concentration-dependently reduced by EOLs and thymol in the range of 30-100 µg/mL. Differently from EOLs and thymol, p-cymene, myrcene and caryophyllene did not reduce CAP in the higher concentrations of 10 mM. These data demonstrated that EOLs and thymol inhibited neuronal excitability and were promising agents for the development of new drugs for therapeutic use.


Assuntos
Animais , Masculino , Feminino , Alcenos/farmacologia , Lippia/química , Monoterpenos/farmacologia , Óleos Voláteis/farmacologia , Nervo Isquiático/efeitos dos fármacos , Sesquiterpenos/farmacologia , Timol/farmacologia , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Bloqueio Nervoso/métodos , Condução Nervosa/efeitos dos fármacos , Óleos Voláteis/química , Ratos Wistar , Reprodutibilidade dos Testes , Nervo Isquiático/fisiologia , Fatores de Tempo
3.
J. appl. oral sci ; 23(2): 145-152, Mar-Apr/2015. graf
Artigo em Inglês | LILACS, BBO - Odontologia | ID: lil-746536

RESUMO

Periodontal ligament mesenchymal stem cells (PDLMSCs) are an important alternative source of adult stem cells and may be applied for periodontal tissue regeneration, neuroregenerative medicine, and heart valve tissue engineering. However, little is known about the impact of bacterial toxins on the biological properties of PDLSMSCs, including self-renewal, differentiation, and synthesis of extracellular matrix. Objective : This study investigated whether proliferation, expression of pro-inflammatory cytokines, and osteogenic differentiation of CD105-enriched PDL progenitor cell populations (PDL-CD105+ cells) would be affected by exposure to bacterial lipopolysaccharide from Escherichia coli (EcLPS). Material and Methods : Toll-like receptor 4 (TLR4) expression was assessed in PDL-CD105+ cells by the immunostaining technique and confirmed using Western blotting assay. Afterwards, these cells were exposed to EcLPS, and the following assays were carried out: (i) cell viability using MTS; (ii) expression of the interleukin-1 beta (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor alpha (TNF-α) genes; (iii) osteoblast differentiation assessed by mineralization in vitro, and by mRNA levels of run-related transcription factor-2 (RUNX2), alkaline phosphatase (ALP) and osteocalcin (OCN) determined by quantitative PCR. Results : PDL-CD105+ cells were identified as positive for TLR4. EcLPS did not affect cell viability, but induced a significant increase of transcripts for IL-6 and IL-8. Under osteogenic condition, PDL-CD105+ cells exposed to EcLPS presented an increase of mineralized matrix deposition and higher RUNX2 and ALP mRNA levels when compared to the control group. Conclusions : These results provide evidence that CD105-enriched PDL progenitor cells are able to adapt to continuous Escherichia coli endotoxin challenge, leading to an upregulation of osteogenic activities. .


Assuntos
Alcenos/metabolismo , /química , Staphylococcaceae/enzimologia , Catálise , Estabilidade Enzimática , Microbiologia Industrial , Concentração Osmolar
4.
Rev. salud pública ; 10(1): 113-125, ene.-feb. 2008. tab
Artigo em Espanhol | LILACS | ID: lil-479057

RESUMO

Objetivo: Determinar el perfil de salud de los trabajadores de una Planta procesadora de Olefinas del Estado Zulia. Métodos: Se realizó un estudio observacional descriptivo, evaluando a 142 trabajadores de las áreas administrativa- técnica, operaciones y mantenimiento. A cada trabajador se le realizó una historia médico ocupacional, examen físico, exámenes de laboratorio, audiometría y evaluación visual. El grado de obesidad se determinó mediante la clasificación de la OMS, el riesgo cardiovascular se estableció aplicando las tablas de riesgo de las Sociedades Europeas. Resultados: El promedio de edad de los trabajadores fue de 36,2 ± 6,9 años. Los individuos del área de operaciones mostraron promedio de peso, y tensión arterial sistólica más elevada que el resto de las áreas. Se determinó una alta frecuencia de factores de riesgo cardiovascular predominando el consumo de alcohol (89,4 por ciento), obesidad (62,7 por ciento), hipertrigliceridemia (46,5 por ciento), y presión arterial sistólica elevada (45,1 por ciento); siendo los operadores los más afectados. Se encontró una frecuencia moderada de trabajadores con enzimas hepáticas alteradas AST (38 por ciento) y GGT (29,6 por ciento). Las patologías más frecuentes fueron ametropia (64,1 por ciento), dislipidemia (57,8 por ciento), obesidad I (50 por ciento), e hipertensión (45,1 por ciento). Los mayores de 40 años mostraron cifras de tensión arterial sistólica más elevadas. Se encontró una correlación positiva y significativa entre IMC y tensión sistólica. Conclusión: Existe una alta prevalencia de factores de riesgo cardiovascular. Se recomienda diseñar y aplicar acciones de promoción de la salud, encaminadas a modificar los estilos de vida para disminuir el riesgo de enfermedad cardiovascular.


Objective: Determining the profile of health for people working in an olefin plant. Methods: This was an observational, descriptive study carried out on 142 workers from technical-administrative, operator and maintenance areas. Each worker's employment and medical history was examined; they had a physical examination and laboratory, audiometric and visual tests. The degree of obesity was determined by WHO classification; cardiovascular risk was classified by using the European Societies' risk table. Results: The workers had a mean age of 36,2±6,9. The operators presented mean weight and systolic pressure which was higher than that of the rest of the workers. A high risk factor frequency was determined for cardiovascular pathologies: alcohol consumption (89,4 percent), obesity (62,7 percent), hypertriglycerides in the blood (46,5 percent) and high systolic pressure (45,1 percent); operators were the most affected workers. A moderate frequency of workers having altered hepatic enzymes, AST (38 percent) and GGT (29,6 percent) were observed The most frequently encountered pathologies were ametropia (64,1 percent), dyslipidaemia (57,8 percent), obesity (50 percent) and hypertension (45,1 percent). Workers aged more than 40 presented higher systolic pressure. A significant correlation between IMC and systolic pressure was found. Conclusion A high prevalence of cardiovascular risk factors was found. Health-care should be designed and promoted and action should be taken towards modifying lifestyles, aimed at reducing the risk of cardiovascular disease.


Assuntos
Adulto , Humanos , Masculino , Pessoa de Meia-Idade , Alcenos , Exposição Ocupacional , Saúde Ocupacional , Venezuela
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