Sample records for hydrazine
from WorldWideScience.org

Sample records 1 - 9 shown.



1

Decomposição catalítica da hidrazina sobre irídio suportado em compósitos à base de nanofibras de carbono para propulsão espacial: testes em condições reais/ Catalytic decomposition of hydrazine over iridium supported on carbon nanofiber composites for propulsion in space: tests under real-life conditions

Vieira, Ricardo; Netto, Demétrio Bastos; Bernhardt, Pierre; Ledoux, Marc-Jacques; Pham-Huu, Cuong
2005-02-01

Resumo em inglês The aim of this work is to present the catalytic performance of iridium supported on carbon nanofibers with macroscopic shaping in a 2 N hydrazine microthruster placed inside a vacuum chamber in order to reproduce real-life conditions. The performances obtained are compared to those of the commercial catalyst Shell 405. The carbon-nanofiber based catalyst showed better performance than the commercial catalyst from the standpoint of activity due to its texture and its thermal conductivity.

Scientific Electronic Library Online (Portuguese)

2

Eletroanálise de derivados acetaldeído com hidrazina e determinação em amostras de álcool combustível por voltametria de onda quadrada/ Electroanalysis of acetaldehyde derivatized with hydrazine and determination in fuel ethanol by square wave voltammetry

Rodgher, Vanessa S.; Stradiotto, Nelson R.; Zanoni, Maria Valnice B.; Barros, Aquiles A.
2006-07-01

Resumo em inglês A square wave voltammetric method is described for the determination of acetaldehyde using the derivatization reaction with hydrazine sulphate, based on the reduction of hydrazone generated as a product that exhibits a single well-defined peak at -1.19V in acetate buffer at pH 5. Calibration graphs were obtained from 1.0 x 10-6 mol L-1 to 10 x 10-6 mol L-1 of acetaldehyde, using a reaction time of 8 min and a hidrazine concentration of 0.02 mol L-1. The detection limit wa (mais) s 2.38 x 10-7 mol L-1. The method was applied satisfactorily to the determination of total aldehyde in fuel ethanol samples without any pre-treatment.

Scientific Electronic Library Online (Portuguese)

3

Eletrodo modificado com filme de poli aminoácido para determinação de hidrazina em água de caldeira/ Modified electrode with poly aminoacid film for determination of hydrazine in industrial kettle

Brugnera, M. F.; Santos, D. P.; Zanoni, M. V. B.
2006-01-01

Resumo em português Eletrodos de carbono vítreo foram modificados com filmes de poli ácido glutâmico (PAG) pela eletropolimerização do ácido glutâmico em tampão fosfato pH 7,0, utilizando-se varreduras sucessivas de potencial entre ­0,8 a +2,0 V. Os eletrodos modificados foram aplicados na determinação de hidrazina, a qual é pré-concentrada na superfície através da interação entre grupos carboxílicos livres no filme e grupo amino da hidrazina. Embora a hidrazina não sej (mais) a oxidada em intervalo útil de potencial sobre eletrodo convencional, no eletrodo modificado caracteriza-se pelo pico de oxidação em potencial de +0,57 V usado para fins analíticos. Gráfico de calibração linear foi obtido no intervalo de concentração entre 4 x 10-5 a 1 x 10-3 mol L-1, usando voltametria de pulso diferencial. O limite de detecção foi de 1,2 x 10-6 mol L-1. O método foi aplicado para a determinação de hidrazina em amostras coletadas de água de caldeira com recuperação de 94%. Resumo em inglês Glassy carbon electrodes were modified by films of poly glutamic acid (PAG) obtained after electropolymerization of the glutamic acid in pH 7.0 phosphate buffer solution under successive voltammetric scans from -0.8 V to +2.0 V. The modified electrode were applied for determination of hydrazine, which is pre-concentrated on the electrode surface by interaction of free carboxylic groups bearing in the PAG film and amino group of hydrazine. Although, hydrazine is not electr (mais) ochemically oxidized on bare electrode, a well defined peak is observed at + 0.57 V with great analytical potentiality. Linear calibration graphs were obtained for hydrazine at concentrations from 4 x 10-5 to 1 x 10-3 mol L-1, using differential pulse voltammetry. Detection limit was calculated and values around 1.2 x 10-6 mol L-1 were obtained. The proposed method was applied to the determination of hydrazine in samples collected from industrial kettle with recovery of around 94 %.

Scientific Electronic Library Online (Portuguese)

4

Novos materiais à base de nanofibras de carbono como suporte de catalisador na decomposição da hidrazina/ Carbon nanofibers a new catalyst support for hydrazine decomposition

Vieira, Ricardo; Pham-Huu, Cuong; Keller, Nicolas; Ledoux, Marc J.
2003-10-01

Resumo em inglês Today satellites propulsion is based on the use of monopropellant and/or bipropellant chemical systems. The maneuvering of satellite is based on the hydrazine decomposition micropropulsors catalyzed by metallic iridium supported on g-alumina. This reaction is a surface reaction and is strongly exothermic and implies that the operation of the micropropulsor is controlled by the mass and heat diffusions. For this reason and for the fact that the propulsor operation is frequ (mais) ently in pulsed regime, the catalyst should support high pressure and temperature variations within a short time period. The performance and the durability of the commercial catalyst are jeopardized by the low thermal conductivity of the alumina. The low thermal conductivity of the alumina support restricts the heat diffusion and leads to the formation of hot spots on the catalyst surface causing the metal sintering and/or fractures of the support, resulting in loss of the activity and catalyst destruction. This work presents the synthesis and characterization of new carbon composite support for the active element iridium, in substitution of the commercial catalysts alumina based support. These supports are constituted of carbon nanofibers (30 to 40 nm diameter) supported on a macroscopic carbon felt. These materials present high thermal conductivity and mechanical resistance, as well as the easiness to be shaped with different macroscopic shapes. The mechanical stability and the performance of the iridium supported on the carbon composite support, evaluated in a laboratory scale test in hydrazine decomposition reaction, are superior compared to the commercial catalyst.

Scientific Electronic Library Online (Portuguese)

5

Nanocompósitos derivados de dispersões aquosas de poliuretano e argila: influência da argila na morfologia e propriedades mecânicas/ Nanocomposites derived from polyurethane aqueous dispersion and clay: influence of the clay on the morphology and mechanical properties

Ayres, Eliane; Oréfice, Rodrigo L.
2007-12-01

Resumo em português Foi sintetizada uma dispersão aquosa de poliuretano (PUD) na qual o poli(propileno glicol) (PPG) foi utilizado como segmento flexível. O segmento rígido foi baseado nos reagentes isoforona diisocianato (IPDI) e a diamina hidrazina (HZ), produzindo um poli(uretano-uréia). A PUD assim obtida foi modificada com Na+-montmorilonita (Na+-MMT) para gerar nanocompósitos (CPUD’s) com 1, 3 e 5 % de argila. Neste processo, o aumento do espaçamento basal das camadas de silicat (mais) o foi provocado pela água sem necessidade de qualquer tratamento químico da argila. De acordo com as curvas de difração de raios X (XRD), os nanocompósitos obtidos apresentaram partículas de argila intercaladas com o polímero, enquanto a técnica de espalhamento de raios X de baixo ângulo (SAXS) detectou evidências de uma esfoliação parcial da montmorilonita. A esfoliação incompleta das partículas de argila indica re-agregação dos nanocomponentes (inicialmente delaminados na dispersão aquosa) durante a formação do filme. O grau de ligações de hidrogênio, avaliado por espectroscopia no infravermelho (FTIR), foi usado para investigar o efeito da argila no processo de separação de microfases do poliuretano e indicou uma tendência de perturbação da estrutura dos domínios do poliuretano com a presença da argila. A PUD exibiu valores de resistência à tensão na ruptura e alongamento na ruptura na faixa de 30 MPa e 1400% respectivamente. A adição de 1% de argila na PUD promoveu aumentos no módulo e tensão na ruptura de cerca de 230 e 20% respectivamente em relação ao polímero puro, sem perda significativa do alongamento na ruptura. Resumo em inglês Waterborne polyurethane (PUD) was synthesized by using poly(propylene glycol) (PPG) as soft segment. The hard segment was formed by extending isophorone diisocyanate (IPDI) with hydrazine (HZ) producing poly(urethane-urea). PUD was reinforced with Na+-montmorillonite (Na+-MMT) to yield nanocomposites (CPUD’s) with 1, 3 and 5% of clay. Water was used as swelling agent to make the basal space of silicate layers widen without any chemical treatment. According to XRD curves, (mais) the nanocomposites showed intercalation of the polymer with respect to the clay, while small angle X ray scattering (SAXS) results showed that some degree of clay exfoliation was present in the produced film. The incomplete exfoliation of the clay proved that a re-aggregation process of the nanocomponents (originally delaminated in the aqueous dispersion) had occurred during film formation. The degree of hydrogen bonding, evaluated by Fourier-transform infrared spectroscopy (FTIR), was used to investigate the effect of clay on the microphase separation of the polyurethane and indicated that the presence of the clay particles changed the structure of the polymer phase domains. PUD exhibited values of tensile strength and elongation at break about 30 MPa and 1400%, respectively. The incorporation of 1 weight % of MMT improved by 230 and 20% the modulus and strength on the polymer respectively, while keeping the elongation at break almost unchanged.

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6

Síntese e caracterização de dispersões aquosas de poliuretanos à base de copolímeros em bloco de poli(glicol etilênico) e poli(glicol propilênico)/ Synthesis and characterization of polyurethane aquous dispersions based on poly(ethylene glycol) and poly(propylene glycol) block copolymers

Coutinho, Fernanda M. B.; Delpech, Marcia C.; Santos, Cristiane C.; Almeida, Rosiléa B. L.
2008-01-01

Resumo em inglês Non-polluting polyurethane aqueous dispersions, with 40% of solids content, were synthesized based on block copolymers of poly(ethylene glycol) and poly(propylene glycol) (PEG-b-PPG), with PEG hydrophilic segments content of 7 and 25%, poly(propylene glycol) (PPG), dimethylolpropionic acid (DMPA), isophorone diisocyanate (IPDI), and hydrazine. Different formulations were synthesized by varying the equivalent-grams ratios between isocyanate and hydroxyl groups (NCO/OH) and (mais) PPG and (PEG-b-PPG). The presence of high amounts of PEG in the formulations provoked the formation of gels. Average particle size and viscosity of the dispersions were determined. Mechanical properties and water absorption resistance of cast films were evaluated.

Scientific Electronic Library Online (Portuguese)

7

O Conhecimento de diferenças raciais pode evitar reações idiossincrásicas na anestesia?/ Could the understanding of racial differences prevent idiosyncratic anesthetic reactions?/ El conocimiento de diferencias raciales puede evitar reacciones idiosincrásicas en la anestesia?

Vale, Nilton Bezerra do; Delfino, José; Vale, Lúcio Flávio Bezerra do
2003-04-01

Resumo em português JUSTIFICATIVA E OBJETIVOS: No campo da variabilidade inter-étnica da resposta de drogas anestésicas e adjuvantes existem várias questões sem resposta. Estamos na iminência de sermos capazes de identificar diferenças raciais herdadas que podem prever a resposta de cada paciente aos anestésicos pelo atual desenvolvimento farmacogenético. CONTEÚDO: O conhecimento de fatores inter-étnicos que alteram a resposta à droga permitirá ao anestesiologista evitar reaçõe (mais) s idiossincrásicas: (1) Branco caucasiano - aumento do efeito diurético da dopamina; apnéia prolongada após succinilcolina ou mivacúrio; arritmias cardíacas após uso de halotano e catecolaminas na síndrome de Riley-Day; ataques agudos de porfiria após tiopental. (2) Negro americano: diferentes abordagens terapêuticas, hipertensão arterial essencial advêm da pior resposta aos anti-hipertensivos de IECA, inibidores do AT1, bloqueadores beta e à clonidina, contrastando com a melhor resposta anti-hipertensiva dos diuréticos, antagonistas de canais de cálcio e clarvedilol; ação vasodilatadora atenuada do isoproterenol (beta2) e uma maior resposta vasodilatadora à nitroglicerina sublingual; menor ação fibrinolítica do t-PA; recuperação mais lenta da anestesia venosa pela associação de remifentanil e propofol; menor glicuronidação do paracetamol e menos analgesia da codeína nos fracos metabolizadores (CYP2D6); a melanina retarda o início da analgesia epidérmica do creme anestésico EMLA; menor midríase pela adrenalina; maior broncoespasmo à metacolina em crianças asmáticas; deficit da G-6-PD nas hemácias eleva o risco de hemólise a drogas oxidativas (10% da população negra). (3) Asiáticos: alterações cinéticas tóxicas da meperidina e codeína; maior duração da ansiólise do diazepam; espasmo coronariano pela injeção de metilergonovina no pós-parto; inter-relação do receptor GABA, das desidrogenases e do comportamento de beber nipônico, contribui para sua maior sensibilidade etanólica. Isoenzimas do citocromo P450 apresentam polimorfismo genético no metabolismo de neuropsicotrópicos e a lenta acetilação da N-acetiltransferase na população equatorial (95%) aumenta a toxicidade de isoniazida e hidralazina. CONCLUSÕES: A presente revisão pretende dar algumas respostas específicas na área da idiossincrasia anestésica relacionada ao efeito da etnicidade sobre a farmacocinética, a farmacodinâmica das drogas e a segurança do paciente cirúrgico, objetivando otimizar uma neuropsicofarmacologia mais individualizada. Resumo em espanhol JUSTIFICATIVA Y OBJETIVOS: En el campo de la variabilidad inter-étnica de la respuesta de drogas anestésicas y coadyuvantes existen varias cuestiones sin respuesta. Estamos en la inminencia de ser o no capaces de identificar diferencias raciales heredadas que pueden prever la respuesta de cada paciente a los anestésicos por el actual desenvolvimiento farmacogenético. CONTENIDO: El conocimiento de factores inter-étnicos que alteran la respuesta a la droga permitirá a (mais) l anestesiologista evitar reacciones idiosincrásicas: (1) Blanco caucasiano - aumento del efecto diurético de la dopamina; apnea prolongada después de succinilcolina o mivacúrio; arritmias cardíacas después del uso de halotano y catecolaminas en la síndrome de Riley-Day; ataques agudos de porfiria después de tiopental. (2) Negro americano: diferentes abordajes terapéuticas, hipertensión arterial esencial adviene de la peor respuesta a los anti-hipertensivos de IECA, inhibidores del AT1, bloqueadores beta y a la clonidina, contrastando con la mejor respuesta anti-hipertensiva de los diuréticos, antagonistas de canales de calcio y clarvedilol; acción vasodilatadora atenuada del isoproterenol (beta2) y una mayor respuesta vasodilatadora a la nitroglicerina sublingual; menor acción fibrinolítica del t-PA; recuperación mas lenta de la anestesia venosa por la asociación de remifentanil y propofol; menor glucuronidación del paracetamol y menos analgesia de la codeína en los flacos matabolizadores (CYP2D6); la melanina retarda el inicio de la analgesia epidérmica de la crema anestésica EMLA; menor midriasis por la adrenalina; mayor broncoespasmo a la metacolina en niños asmáticos; deficit de la G-6-PD en las hemácias eleva el riesgo de hemólisis a drogas oxidativas (10% de la población negra). (3) Asiáticos: alteraciones cinéticas tóxicas de la meperidina y codeína; mayor duración de la ansiólisis del diazepam; espasmo coronariano por la inyección de metilergonovina en el pós-parto; inter-relación del receptor GABA, de las desidrogenasis y del comportamiento de beber nipónico, contribuye para su mayor sensibilidad etanólica. Isoenzimas del citocromo P450 presentan polimorfismo genético en el metabolismo de neuropsicotrópicos y a lenta acetilación de la N-acetiltransferasis en la población ecuatorial (95%) aumenta a toxicidad de isoniazida e hidralazina. CONCLUSIONES: La presente revisión pretende dar algunas respuestas específicas en la área de la idiosincrasia anestésica relacionada al efecto de la etnicidad sobre la farmacocinética, la farmacodinámica de las drogas y a la seguridad del paciente quirúrgico, objetivando optimizar una neuropsicofarmacologia más individualizada. Resumo em inglês BACKGROUND AND OBJECTIVES: There are several unanswered questions about the interethnic variability in anesthetic and adjuvant drugs responses. Current pharmacogenetic developments are taking us to the verge of being able to identify inherited racial differences which could predict individual patient’s anesthetic response. CONTENTS: The understanding of interethnic factors affecting drug response will allow anesthesiologists to prevent idiosyncratic reactions: (1) Caucas (mais) ian: increased dopamine diuretic effect; prolonged apnea following succinylcholine or mivacurium; cardiac arrhythmias after halothane and catecholamines in Riley-Day syndrome; acute porphyria episodes after thiopental. (2) Afro-American: different therapeutic approaches, essential arterial hypertension caused by the poorert response to ACEI anti-hypertensives, AT1 blockers, beta-blockers and clonidine, contrasted with the best anti-hypertensive response of diuretics, calcium channel blockers, claverdilol; attenuated isoproterenol-mediated vasodilatation (beta2) and a better vasodilating response to sublingual nitroglycerine; lower t-PA-induced thrombolytic effect; slower recovery from intravenous anesthesia with propofol and remifentanil; less glycuronide conjugation of paracetamol and less pain relief by codeine in weak metabolizers (CYP2D6); melanin slows onset of epidermal analgesia with EMLA anesthetic cream; less epinephrine-induced mydriasis; major metacholine-induced bronchocospasm in asthmatic children; G-6-PD deficit in erythrocytes increases the risk for hemolysis to oxidative drugs in 10% of the Afro-American population. (3) Asians: toxic kinetic changes of meperidine and codeine; longer diazepam-induced anxiolysis; postpartum intravenous ergonovine-induced coronary artery spasm; inter-relationships of GABA receptor, dehydrogenases and Japanese drinking behavior contribute to their higher sensitivity to alcohol. Cytochrome P450 isoenzymes show genetic polymorphisms in neuropsychotropic drugs metabolism and the slow acetylation of N-acetyltransferase in equatorial populations (95%) increases isoniazid and hydrazine toxicity. CONCLUSIONS: This review aimed at answering specific questions in the area of anesthetic idiosyncrasy related to the effect of ethnicity on drugs’ pharmacokinetics and pharmacodynamics, in addition to surgical patients safety by optimizing a more individualized neuropsychopharmacotherapy.

Scientific Electronic Library Online (Portuguese)

8

Filmes de metal-hexacianoferrato: uma ferramenta em química analítica/ Metal-hexacyanoferrate films: a tool in analytical Chemistry

Mattos, Ivanildo Luiz de; Gorton, Lo
2001-04-01

Resumo em inglês Chemically modified electrodes based on hexacyanometalate films are presented as a tool in analytical chemistry. Use of amperometric sensors and/or biosensors based on the metal-hexacyanoferrate films is a tendency. This article reviews some applications of these films for analytical determination of both inorganic (e.g. As3+, S2O3(2-)) and organic (e.g. cysteine, hydrazine, ascorbic acid, gluthatione, glucose, etc.) compounds.

Scientific Electronic Library Online (Portuguese)

9

Estudos sôbre a anemia produzida em cães por benzoato de estradiol

Cruz, W. O.; Mello, R. Pimenta de; Silva, E. M. da
1944-08-01

Resumo em português A anemia que se processa em caes quando se administra grandes doses de benzoato de estradiol, nao parece ser produzida por processes conhecidos de destrui?ao intra-organica. Esta substantia paraliza os fenomenos de rege¬nerate hematica, parece interferir por processo desconhecido na fisiologia sanguinea, produz graves lesoes na rede circulatoria que irriga a mucosa do intestino, principalmente jejuno, ocasipnando nesse orgao «extravasamento variavel de sangue, fator seguramente coadjuvante na formação da anemia. Resumo em inglês The characteristic findings in the pathological picture presented by 60 dogs when administered large doses of estradiol benzoate subcutaneously in an oil vehicle are: thrombocytopenia, aplastic anemia, which follows a brief latent period, intestinal tract haemorrhages, haemorrhagic lesions occurring principally in the mucosa of the jejunum, followed by prostration and death generally within 1 to 3 weeks. Irregular findings are leucocytosis, purpuric skin lesions, visceral (mais) haemorrhages and pyoid bone marrow. The total circulating hemoglobin was determined in 9 dogs before and after the anemia was established, thus verifying the total hemoglobin loss. The blood loss through intestinal haemorrhages during the observation period was determined by benzidine test. The quantity of hemoglobin recovered from the feces in the form of hematin varied between 30 and 70% of the total hemoglobin which disappeared from the circulation. In order to ascertain the degree of intra-organic blood destruction the bilirubin eliminated in the urine of dogs with gall-bladder renal type of fis¬tula was determined daily and these values compared with those obtained for normal animals. The blood destruction as measured by this method was practically nil. An attempt was made to determine whether the presence of large quan¬tities of blood in the intestine might exert a paralyzing effect on the regene¬ration of hemoglobin in dogs rendered anemic through haemorrhage. Ne¬gative results were obtained. Estradiol benzoate administered to dogs during the period of hematic regeneration which occurs in the recovery stage of ane-mia produced by acetyl-phenyl hydrazine demonstrated that the estradiol in¬terferes but little when the regenerative processes have already begun. Repeated transfusions given during the stage of acute anemia practi¬cally do not affect the period of survival. The authors conclude that the main action of estradiol benzoate on the blood physiology of dogs is still obscure. The anemia is not produced by the intra-organic destruction of hemoglobin by known processes and doubtless the blood loss through the intestinal haemarrhages constitutes an important ac¬cessory factor in the mechanism of bringing out this anemia.

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