Estudo do mecanismo de corros��o por pites em ��gua do mar de a��os inoxid��veis supermartens��ticos microligados com Nb e Ti

Os a��os inoxid��veis supermartens��ticos (SMSS) s��o usados em ambientes agressivos devido �� sua boa soldabilidade, boas propriedades mec��nicas em temperaturas elevadas e superior resist��ncia �� corros��o sob tens��o. Aplica����es na explora����o de petr��leo demandam superior combina����o de propriedades e os a��os inoxid��veis duplex e superduplex t��m sido aplicados nessa ��rea, a despeito de seus custos elevados. Os SMSS consistem numa alternativa t��cnica e econ��mica ao uso daqueles a��os. Nesse trabalho, adi����es de Nb e Ti foram realizadas com o intuito de minimizar o efeito de sensitiza����o, promover o refino de gr��os e foram estudados os aspectos microestruturais e a resist��ncia �� corros��o por pites em ��gua do mar. A forma����o e a evolu����o dos pites foram acompanhadas por ensaios de corros��o, microscopia ��ptica e eletr��nica, focalizando suas morfologias. O a��o com Ti apresentou o melhor desempenho quanto �� corros��o, com o maior potencial de corros��o e menor potencial de pite entre os a��os em estudo. O a��o com Nb, apesar de apresentar potencial de corros��o superior ao do a��o sem adi����o, teve um potencial de pite inferior ao do mesmo.

��cido clavul��nico e cefamicina c: uma perspectiva da bioss��ntese, processos de isolamento e mecanismo de a����o

The present article reviews different aspects of the chemistry of two widely used β-lactam antibiotics Clavulanic Acid and Cephamycin C. The article discusses important details of the biosynthesis of these compounds, their action mechanism and, principally, the methods employed in their isolation and purification, in accordance with the available literature. Despite the large quantity of available articles and patents concerning β-lactam antibiotics, those which describe the isolation and purification of Clavulanic Acid and Cephamycin C are rare. Overall, the intention of this article is to discuss the up-to-date scientific research related to the compounds under review.

A fuzzy reed-frost model for epidemic spreading

In this paper, we present a fuzzy approach to the Reed-Frost model for epidemic spreading taking into account uncertainties in the diagnostic of the infection. The heterogeneities in the infected group is based on the clinical signals of the individuals (symptoms, laboratorial exams, medical findings, etc.), which are incorporated into the dynamic of the epidemic. The infectivity level is time-varying and the classification of the individuals is performed through fuzzy relations. Simulations considering a real problem with data of the viral epidemic in a children daycare are performed and the results are compared with a stochastic Reed-Frost generalization

A Geometric Approach for Turbo Decoding of Reed-Solomon Codes in QAM Modulation Schemes

This work studies the turbo decoding of Reed-Solomon codes in QAM modulation schemes for additive white Gaussian noise channels (AWGN) by using a geometric approach. Considering the relations between the Galois field elements of the Reed-Solomon code and the symbols combined with their geometric dispositions in the QAM constellation, a turbo decoding algorithm, based on the work of Chase and Pyndiah, is developed. Simulation results show that the performance achieved is similar to the one obtained with the pragmatic approach with binary decomposition and analysis.

A fuzzy Reed-Frost model for epidemic spreading

In this paper, we present a fuzzy approach to the Reed-Frost model for epidemic spreading taking into account uncertainties in the diagnostic of the infection. The heterogeneities in the infected group is based on the clinical signals of the individuals (symptoms, laboratorial exams, medical findings, etc.), which are incorporated into the dynamic of the epidemic. The infectivity level is time-varying and the classification of the individuals is performed through fuzzy relations. Simulations considering a real problem with data of the viral epidemic in a children daycare are performed and the results are compared with a stochastic Reed-Frost generalization.

T-wave alternans: desempenho cl��nico, limita����es, metodologias de an��lise

Reconhecer com precis��o indiv��duos com maior risco imediato de morte s��bita card��aca (MSC) ainda �� uma quest��o em aberto. A natureza fortuita dos eventos cardiovasculares agudos n��o parece se adequar ao conhecido modelo de indu����o de taquicardia/fibrila����o ventricular por um gatilho em sincronia a um substrato arritmog��nico est��tico. Quanto ao mecanismo da MSC, uma instabilidade el��trica din��mica explicaria melhor a raridade da associa����o simult��nea de um gatilho certo a um substrato card��aco apropriado. Diversos estudos tentaram medir essa instabilidade el��trica card��aca (ou um equivalente v��lido) em uma sequ��ncia de batimentos card��acos no ECG. Dentre os mecanismos poss��veis podemos citar o prolongamento do QT, dispers��o do QT, potenciais tardios, altern��ncia de onda T ou T-wave alternans (TWA), e turbul��ncia da frequ��ncia card��aca. Este artigo se at��m em particular ao papel da TWA no panorama atual da estratifica����o de risco card��aco. Os achados sobre TWA ainda s��o heterog��neos, variando de um desempenho progn��stico muito bom at�� um quase nulo, dependendo da popula����o cl��nica observada e protocolo cl��nico usado. Para preencher as atuais lacunas no conhecimento sobre TWA, profissionais m��dicos e pesquisadores devem explorar melhor as caracter��sticas t��cnicas das diversas tecnologias dispon��veis para a avalia����o de TWA e atentar ao fato de que os valores de TWA respondem a diversos outros fatores, al��m de medicamentos. Informa����es sobre mecanismos celulares e subcelulares da TWA est��o fora do escopo deste artigo, mas s��o referenciados alguns dos principais trabalhos sobre este t��pico, com o intuito de auxiliar no entendimento dos conceitos e fatos cobertos neste artigo.

Isolation of Pseudomonas aeruginosa strains from dental office environments and units in Barretos, state of S��o Paulo, Brazil, and analysis of their susceptibility to antimicrobial drugs

A wide variety of opportunistic pathogens has been detected in the tubing supplying water to odontological equipment, in special in the biofilm lining of these tubes. Among these pathogens, Pseudomonas aeruginosa, one of the leading causes of nosocomial infections, is frequently found in water lines supplying dental units. In the present work, 160 samples of water, and 200 fomite samples from forty dental units were collected in the city of Barretos, State of S��o Paulo, Brazil and evaluated between January and July, 2005. Seventy-six P. aeruginosa strains, isolated from the dental environment (5 strains) and water system (71 strains), were tested for susceptibility to six antimicrobial drugs most frequently used against P. aeruginosa infections. Susceptibility to ciprofloxacin, followed by meropenem was the predominant profile. The need for effective means of reducing the microbial burden within dental unit water lines is emphasized, and the risk of exposure and cross-infection in dental practice, in special when caused by opportunistic pathogens like P. aeruginosa, are highlighted.

Evaluation of DNA extraction protocols for Brucella abortus pcr detection in aborted fetuses or calves born from cows experimentally infected with strain 2308

The objective of the present study was to improve the detection of B. abortus by PCR in organs of aborted fetuses from infected cows, an important mechanism to find infected herds on the eradication phase of the program. So, different DNA extraction protocols were compared, focusing the PCR detection of B. abortus in clinical samples collected from aborted fetuses or calves born from cows challenged with the 2308 B. abortus strain. Therefore, two gold standard groups were built based on classical bacteriology, formed from: 32 lungs (17 positives), 26 spleens (11 positives), 23 livers (8 positives) and 22 bronchial lymph nodes (7 positives). All samples were submitted to three DNA extraction protocols, followed by the same amplification process with the primers B4 and B5. From the accumulated results for organ, the proportion of positives for the lungs was higher than the livers (p=0.04) or bronchial lymph nodes (p=0.004) and equal to the spleens (p=0.18). From the accumulated results for DNA extraction protocol, the proportion of positives for the Boom protocol was bigger than the PK (p<0.0001) and GT (p=0.0004). There was no difference between the PK and GT protocols (p=0.5). Some positive samples from the classical bacteriology were negative to the PCR and viceversa. Therefore, the best strategy for B. abortus detection in the organs of aborted fetuses or calves born from infected cows is the use, in parallel, of isolation by classical bacteriology and the PCR, with the DNA extraction performed by the Boom protocol.

O enigma da "rea����o espermatof��rica": breve s��ntese do conhecimento sobre a estrutura e o funcionamento dos espermat��foros dos cefal��podes (Mollusca: Cephalopoda)

Cefal��podes cole��ides (lulas, s��pias e polvos) produzem espermat��foros muito complexos que s��o transferidos �� f��mea durante a c��pula por meio do hectoc��tilo, um ap��ndice modificado nos machos. Durante a transfer��ncia �� f��mea, ocorre a chamada "rea����o espermatof��rica", complexo processo de evagina����o do aparato ejaculat��rio do espermat��foro, que conduz �� exterioriza����o da massa esperm��tica e corpo cimentante. A presente revis��o sintetiza o conhecimento acerca da morfologia e funcionamento desta estrutura exclusiva dos cole��ides, identificando lacunas e definindo estrat��gias que possibilitem avan��os na ��rea. Poucos trabalhos abordam com detalhes a morfologia e anatomia funcional dos espermat��foros dos cefal��podes, grande parte do conhecimento acerca da estrutura do espermat��foro tendo sido gerada por trabalhos cl��ssicos do s��culo XIX e in��cio do s��culo XX. Investiga����es acerca do funcionamento dos espermat��foros s��o consideravelmente mais raras, estando o conhecimento b��sico sobre a rea����o espermatof��rica restrito a apenas 19 esp��cies de cole��ides. A revis��o da literatura especializada permite sugerir que existem dois tipos b��sicos de fixa����o de espermat��foros em Decapodiformes (lulas e sepi��ides): fixa����o superficial e implante profundo (ou intra-d��rmico). Na fixa����o superficial, comum em diversas esp��cies (e.g., Loliginidae, Sepiidae, Ommastrephidae), a base dos espermat��ngios �� aderida ao tecido-alvo aparentemente por meio do corpo cimentante, a partir de subst��ncias adesivas e, em alguns casos, estruturas de fixa����o. No implante profundo, comum em alguns grupos de lulas oce��nicas e de ��guas profundas (e.g., Architeuthidae, Cranchiidae, Octopoteuthidae, Sepiolidae), os espermat��foros implantam-se inteiramente no corpo da f��mea, de forma aut��noma. Permanece desconhecido o mecanismo respons��vel pelo implante profundo. Em Octopodiformes (polvos), o espermat��foro �� inserido no gonoduto feminino, alcan��ando a gl��ndula oviducal, onde est��o localizadas as espermatecas, ou a cavidade do ov��rio. Como o funcionamento extracorp��reo dos espermat��foros depende exclusivamente da intrincada estrutura e organiza����o de seus componentes (e.g., membranas e t��nicas), somente investiga����es detalhadas dessas estruturas prover��o as bases para a compreens��o do funcionamento e da exata fun����o do complexo espermat��foro dos cole��ides. Recomenda-se o desenvolvimento de um protocolo simples e eficiente para colora����o e prepara����o total de espermat��foros, de forma que seja poss��vel expandir as descri����es morfol��gicas do espermat��foro em estudos taxon��micos e anat��micos, permitindo, portanto, amplia����o do conhecimento acerca desta enigm��tica estrutura.

Protector mechanisms of the association between gastroesophageal reflux disease and asthma: experimental study in rats

BACKGROUND: It is well known the association between gastroesophageal reflux disease and asthma. The hyperreactivity of the airways is a characteristic of an asthmatic. Many studies associate the increase of the airways reactivity with gastroesophageal reflux disease. AIM: In this study we have evaluated the effect of the intraluminal exposition to gastric juice of trachea on the reactivity to methacholine from rats submitted to a pulmonary allergic inflammation. METHODS: Group of rats were sensitized and challenged with ovalbumin. After 24 hours the animals were sacrificed, and their tracheae were removed to be cultured with gastric juice. The gastric juice was obtained from a donor rat. Subsequently the segments were placed into plastic plates with RPMI-1640 for incubation, under suitable atmosphere and time. After the period of incubation the segments were put into chambers for the analysis of the contractile response to methacholine. RESULTS: We observed reduction in the contractile response of trachea cultured with gastric juice from allergic rats. This result was confirmed by the pharmacological treatments with compound 48/80 and dissodium cromoglicate (mast cells blockade), L-NAME (nitric oxide inhibitor, NO), capsaicin (neuropeptides depletion) and indomethacin (ciclooxigenase inhibitor). CONCLUSIONS: Our results highlight to the existence of a complex interaction between pulmonary allergy and gastric juice in the airways. The involvement of the non-adrenergic non-cholinergic system, NO, prostanoids and mast cells are directly related to this interaction. We suggest that the reduced contractile response observed in vitro may represent a protector mechanism of the airways. Despite its presence in the human body it can not be observed due to the predominant effects of excitatory the non-adrenergic non-cholinergic system.

Reaction time assessment in children with ADHD

Attention deficit, impulsivity and hyperactivity are the cardinal features of attention deficit hyperactivity disorder (ADHD) but executive function (EF) disorders, as problems with inhibitory control, working memory and reaction time, besides others EFs, may underlie many of the disturbs associated with the disorder. OBJECTIVE: To examine the reaction time in a computerized test in children with ADHD and normal controls. METHOD: Twenty-three boys (aged 9 to 12) with ADHD diagnosis according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, 2000 (DSM-IV) criteria clinical, without comorbidities, Intelligence Quotient (IQ) >89, never treated with stimulant and fifteen normal controls, age matched were investigated during performance on a voluntary attention psychophysical test. RESULTS: Children with ADHD showed reaction time higher than normal controls. CONCLUSION: A slower reaction time occurred in our patients with ADHD. This findings may be related to problems with the attentional system, that could not maintain an adequate capacity of perceptual input processes and/or in motor output processes, to respond consistently during continuous or repetitive activity.

Avalia����o manom��trica anal de crian��as com encoprese

INTRODU����O: A constipa����o cr��nica �� doen��a comum na inf��ncia, ocorrendo em 5 a 10% dos pacientes pedi��tricos, considerada a segunda maior causa de procura nos consult��rios de pediatria, sendo a encoprese decorrente de constipa����o grave associada �� impacta����o fecal no reto. Dentre os exames diagn��sticos, a manometria anal �� utilizada para a avalia����o de pacientes com dist��rbios funcionais, como a constipa����o intestinal e a incontin��ncia fecal, em alguns servi��os para a avalia����o de pacientes com encoprese, pois pode trazer informa����es sobre o mecanismo evacuat��rio e poss��veis les��es esfincterianas anais. OBJETIVO: Verificar altera����es manom��tricas em pacientes com encoprese. M��TODOS: Foi realizado estudo de 40 manometrias anais de crian��as constipadas com encoprese (G1) e 12 crian��as constipados sem encoprese (G2). Foram obtidos os seguintes dados: press��es de repouso, contra����o e evacua����o do canal anal e ampola retal, ponto de maior press��o, reflexo inibit��rio anal e sensibilidade retal. As manometrias foram realizadas com o aparelho Alacer de perfus��o com 8 canais. RESULTADOS: N��o foram encontradas diferen��as nas press��es de repouso, contra����o e evacua����o do canal anal entre os grupos. Chamou-nos a aten����o a aus��ncia de necessidade de maior volume retal para desencadear o reflexo inibit��rio anal. N��o houve diferen��a da incid��ncia de anismus entre os dois grupos, demonstrando que n��o se trata de fator importante na manuten����o da encoprese, mas sim da constipa����o. CONCLUS��O: N��o houve necessidade de maior volume para desencadear o reflexo inibit��rio anal. O anismus n��o foi diferente entre os dois grupos, n��o sendo importante na manuten����o da encoprese.

Enzyme kinetics, structural analysis and molecular modeling studies on a series of Schistosoma mansoni PNP inhibitors

The enzyme purine nucleoside phosphorylase from Schistosoma mansoni (SmPNP) is an attractive molecular target for the development of novel drugs against schistosomiasis, a neglected tropical disease that affects about 200 million people worldwide. In the present work, enzyme kinetic studies were carried out in order to determine the potency and mechanism of inhibition of a series of SmPNP inhibitors. In addition to the biochemical investigations, crystallographic and molecular modeling studies revealed important molecular features for binding affinity towards the target enzyme, leading to the development of structure-activity relationships (SAR).

Thermal decomposition of mercerized linter cellulose and its acetates obtained from a homogeneous reaction

Cellulose acetates with different degrees of substitution (DS, from 0.6 to 1.9) were prepared from previously mercerized linter cellulose, in a homogeneous medium, using N,N-dimethylacetamide/lithium chloride as a solvent system. The influence of different degrees of substitution on the properties of cellulose acetates was investigated using thermogravimetric analyses (TGA). Quantitative methods were applied to the thermogravimetric curves in order to determine the apparent activation energy (Ea) related to the thermal decomposition of untreated and mercerized celluloses and cellulose acetates. Ea values were calculated using Broido's method and considering dynamic conditions. Ea values of 158 and 187 kJ mol-1 were obtained for untreated and mercerized cellulose, respectively. A previous study showed that C6OH is the most reactive site for acetylation, probably due to the steric hindrance of C2 and C3. The C6OH takes part in the first step of cellulose decomposition, leading to the formation of levoglucosan and, when it is changed to C6OCOCH3, the results indicate that the mechanism of thermal decomposition changes to one with a lower Ea. A linear correlation between Ea and the DS of the acetates prepared in the present work was identified.

Photo-fenton degradation of poly(Ethyleneglycol)

Polyethyleneglycol (PEG) was photooxidized in a photo-Fenton system and results compared with the dark reaction. The products were analysed using GPC and HPLC. In the absence of light, PEG samples needed 490 min to reduce their <img src="/img/revistas/jbchs/v22n3/a18Mlinha.jpg" align=absmiddle>w by 50%, whereas under UV irradiation, only 10 min were necessary. The exponential decay of <img src="/img/revistas/jbchs/v22n3/a18Mlinha.jpg" align=absmiddle>w with a concomitant increase in polydispersity and number of average chain scission, characterized a random chain scission mechanism. The degradation products of PEG in both systems showed the presence of lower molecular weight products, including smaller ethyleneglycols and formic acid. The mechanism involves consecutive processes, were the larger ethyleneglycols give rise, successively, to smaller ones. This suggests that the mechanism involves successive scissions of the polymer chain. Irradiated samples decomposed faster than those kept in the dark This study proves that the foto-Fenton method associated with UV-light is a good reactant for PEG photodegradation.