Shelf-life of a 2.5% sodium hypochlorite solution as determined by arrhenius equation

Accelerated stability tests are indicated to assess, within a short time, the degree of chemical degradation that may affect an active substance, either alone or in a formula, under normal storage conditions. This method is based on increased stress conditions to accelerate the rate of chemical degradation. Based on the equation of the straight line obtained as a function of the reaction order (at 50 and 70 ºC) and using Arrhenius equation, the speed of the reaction was calculated for the temperature of 20 ºC (normal storage conditions). This model of accelerated stability test makes it possible to predict the chemical stability of any active substance at any given moment, as long as the method to quantify the chemical substance is available. As an example of the applicability of Arrhenius equation in accelerated stability tests, a 2.5% sodium hypochlorite solution was analyzed due to its chemical instability. Iodometric titration was used to quantify free residual chlorine in the solutions. Based on data obtained keeping this solution at 50 and 70 ºC, using Arrhenius equation and considering 2.0% of free residual chlorine as the minimum acceptable threshold, the shelf-life was equal to 166 days at 20 ºC. This model, however, makes it possible to calculate shelf-life at any other given temperature.

Albedo à superfície a partir de imagens Landsat 5 em áreas de cana-de-açúcar e cerrado

Propôs-se, neste trabalho, estimar dados de albedo à superfície terrestre usando-se o sensor Thematic Mapper (TM) do satélite LANDSAT 5 e compará-lo com dados de duas estações agrometeorológicas localizadas em região de Cerrado e a outra em cultivo da cana-de-açúcar. A região de estudo está localizada no município de Santa Rita do Passa Quatro, SP, Brasil. Para a realização do estudo obtiveram-se seis imagens orbitais do satélite Landsat 5 sensores TM, na órbita 220 e ponto 75, nas datas de 22/02, 11/04, 29/05, 01/08, 17/08 e 21/11, todas do ano de 2005, a que correspondem os dias juliano de 53, 101, 149, 213, 229 e 325, respectivamente. As correções geométricas para as imagens foram realizadas e geradas as cartas de albedo. O algoritmo SEBAL estimou satisfatoriamente os valores de albedo de superfícies sobre áreas de cerrado e de cana-de-açúcar, na região de Santa Rita do Passa Quatro, SP, consistentes com observações realizadas do albedo à superfície.

Sildenafil preserves diastolic relaxation after reduction by L-NAME and increases phosphodiesterase-5 in the intercalated discs of cardiac myocytes and arterioles

OBJECTIVES: We investigated the influence of sildenafil on cardiac contractility and diastolic relaxation and examined the distribution of phosphodiesterase-5 in the hearts of hypertensive rats that were treated with by NG-nitro-L-arginine methyl ester (L-NAME). METHODS: Male Wistar rats were treated with L-NAME and/or sildenafil for eight weeks. The Langendorff method was used to examine the effects of sildenafil on cardiac contractility and diastolic relaxation. The presence and location of phosphodiesterase-5 and phosphodiesterase-3 were assessed by immunohistochemistry, and cGMP plasma levels were measured by ELISA. RESULTS: In isolated hearts, sildenafil prevented the reduction of diastolic relaxation (dP/dt) that was induced by L-NAME. In addition, phosphodiesterase-5 immunoreactivity was localized in the intercalated discs between the myocardial cells. The staining intensity was reduced by L-NAME, and sildenafil treatment abolished this reduction. Consistent with these results, the plasma levels of cGMP were decreased in the L-NAME-treated rats but not in rats that were treated with L-NAME + sildenafil. CONCLUSION: The sildenafil-induced attenuation of the deleterious hemodynamic and cardiac morphological effects of L-NAME in cardiac myocytes is mediated (at least in part) by the inhibition of phosphodiesterase-5.

5-HT1A autoreceptor modulation of locomotor activity induced by nitric oxide in the rat dorsal raphe nucleus

The dorsal raphe nucleus (DRN) is the origin of ascending serotonergic projections and is considered to be an important component of the brain circuit that mediates anxiety- and depression-related behaviors. A large fraction of DRN serotonin-positive neurons contain nitric oxide (NO). Disruption of NO-mediated neurotransmission in the DRN by NO synthase inhibitors produces anxiolytic- and antidepressant-like effects in rats and also induces nonspecific interference with locomotor activity. We investigated the involvement of the 5-HT1A autoreceptor in the locomotor effects induced by NO in the DRN of male Wistar rats (280-310 g, N = 9-10 per group). The NO donor 3-morpholinosylnomine hydrochloride (SIN-1, 150, and 300 nmol) and the NO scavenger S-3-carboxy-4-hydroxyphenylglycine (carboxy-PTIO, 0.1-3.0 nmol) were injected into the DRN of rats immediately before they were exposed to the open field for 10 min. To evaluate the involvement of the 5-HT1A receptor and the N-methyl-D-aspartate (NMDA) glutamate receptor in the locomotor effects of NO, animals were pretreated with the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 8 nmol), the 5-HT1A receptor antagonist N-(2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl)-N-2-pyridinyl-cyclohexanecarboxamide maleate (WAY-100635, 0.37 nmol), and the NMDA receptor antagonist DL-2-amino-7-phosphonoheptanoic acid (AP7, 1 nmol), followed by microinjection of SIN-1 into the DRN. SIN-1 increased the distance traveled (mean ± SEM) in the open-field test (4431 ± 306.1 cm; F7,63 = 2.44, P = 0.028) and this effect was blocked by previous 8-OH-DPAT (2885 ± 490.4 cm) or AP7 (3335 ± 283.5 cm) administration (P < 0.05, Duncan test). These results indicate that 5-HT1A receptor activation and/or facilitation of glutamate neurotransmission can modulate the locomotor effects induced by NO in the DRN.

Modified silicas covalently bounded to 5,10,15,20-tetrakis(2-hydroxy-5-nitrophenyl)porphyrinato iron(III): synthesis, spectroscopic and EPR characterization. Catalytic studies

In this work we have studied cyclooctene epoxidation with PhIO, using a new iron porphyrin, 5,10,15,20-tetrakis(2-hydroxy-5-nitrophenyl)porphyrinato iron(III), supported on silica matrices via eletrostatic interaction and / or covalent bonds as catalyst. These catalysts were obtained and immobilized on the solid supports propyltrimethylammonium silica (SiN+); propyltrimethylammonium and propylimidazole silica [SiN+(IPG)] and chloropropylsilica (CPS) via elestrostatic interactions and covalent binding. Characterization of the supported catalysts by UV-Vis spectroscopy and EPR (Electron paramagnetic resonance) indicated the presence of a mixture of FeII and FeIII species in all of the three obtained catalysts. In the case of (Z)-cyclooctene epoxidation by PhIO the yields observed for cis-epoxycyclooctane were satisfactory for the reactions catalyzed by the three materials (ranging from 68% to 85%). Such results indicate that immobilization of metalloporphyrins onto solid supports via groups localized on the ortho positions of their mesophenyl rings can lead to efficient catalysts for epoxidation reactions. The catalyst 1-CPS is less active than 1-SiN and 1-SiN(IPG), this argues in favour of the immobilization of this metalloporphyrin onto solids via electrostatic interactions, which is easier to achieve and results in more active oxidation catalysts. Interestingly, the activity of the supported catalysts remained the same even after three successive recyclings; therefore, they are stable under the oxidizing conditions.

Synthesis of novel O-acylated-D-ribono-1,5-lactones and structural assignment supported by conventional NOESY-NMR and x-ray analysis

A practical method for the structural assignment of 3,4-O-benzylidene-D-ribono-1,5-lactones and analogues using conventional NMR techniques and NOESY measurements in solution is described. 2-O-Acyl-3,4-O-benzylidene-D-ribono-1,5-lactones were prepared in good yields by acylation of Zinner’s lactone with acyl chlorides under mildly basic conditions. Structural determination of 2-O-(4-nitrobenzoyl)-3,4-O-benzylidene-D-ribono-1,5-lactone was achieved by single crystal x-ray diffraction, which supports the results based on spectroscopic data.

Determination of 5-aminosalicylic acid in pharmaceutical formulations by square wave voltammetry at pencil graphite electrodes

An analytical method for the determination of the anti-inflammatory drug 5-aminosalicylic acid (5-ASA) in pharmaceutical formulations using square wave voltammetry at pencil graphite electrodes was developed. After the optimization of the experimental conditions, calibration curves were obtained in the linear concentration range from 9.78 × 10-7 to 7.25 × 10-5 mol L-1 resulting in a limit of detection of 2.12 ± 0.05 x 10-8 mol L-1. Statistical tests showed that the concentrations of 5-ASA in commercial tablets and enemas obtained with the proposed voltammetric method agreed with HPLC values at a 95% confidence level.

Unusual 1,6-diphenyl-1,3,5-hexatriene (DPH) spectrophotometric behavior in water/ethanol and water/DMSO mixtures

The absorption spectra of DPH at fixed concentration do not change with water content in organic solvents. It exhibits monomer bands, such as those obtained in ethanol. The absorption did not change for solutions up to 54 and 46% of water in ethanol and DMSO, respectively, for [DPH] = 5.0 × 10-6 mol L-1 at 30 °C. However, at the same experimental conditions, a gradual sharp decay of the DPH fluorescence is observed. It is proposed that water molecules below these water concentration limits act as quenchers of the excited states of DPH. Stern-Volmer quenching constants by intensities measurements are 7.4 × 10-2 (water/ethanol) and 2.6 × 10-2 L mol-1 (water/DMSO). DPH lifetime measurements in the absence and presence of water resulted in 7.1 × 10-2 L mol-1 in water/ethanol, which pointed out that the process is a dynamic quenching by water molecules. For experiments using DPH as probe, this process can affect data, leading to misunderstanding interpretation.

Time resolved emission spectroscopy of poly(2,5-dicyano-p-phenylene-vinylene) films

Films of poly (2,5-dicyano-p-phenylene vinylene), DCNPPV, were obtained by electrochemical synthesis over gold thin layer (20 nm) transparent electrode deposited on a glass plate. The DCNPPV films of 4 µm thickness were produced by electropolymerization process of ^5;,^5;,^5;',^5;'-tetrabromo-2-5-dicyano-p-xilene at different applied potentials (-0.15, -0.25, -0.40, -0.60, -0.80, and -1.0 V) using 0.1 mol L-1 of tetraethylammonium bromide in acetonitrile as the supporting electrolyte. The emission decays have three exponential components: a fast component in the picosecond range (200-400 ps), and two other of about one and five nanoseconds at 293 K. The fluorescence quenching process seems to occur by exciton trapping in a low-energy site and quenching by residual bromine monomer attached at the end of the polymer chain. However, the electrochemical synthesis generates entrapped bromide or ion pairs during the growth step of the film which also contributes to the deactivation. The change of the electrolyte from bromide to perchlorate reduces significantly this additional quenching effect by allowing ion exchange of formed bromide with the nonquenching perchloride anion.

Antioxidant and antimicrobial properties of 2-(4,5-dihydro-1H-pyrazol-1-yl)-pyrimidine and 1-carboxamidino-1H-pyrazole derivatives

Five previously synthesized 4-trifluoromethyl-2-(5-aryl-3-styryl-1H-pyrazol-1yl)-pyrimidines and six 5-aryl-3-styryl-1-carboxamidino-1H-pyrazole derivatives were screened for their antioxidant proprieties. The antioxidant activities were evaluated by using the DPPH and the HRP/luminol/H2O2 chemiluminescence assay systems and for their antimicrobial activity (MIC). The results were good for those series in some concentration in comparison with the standards.

A theoretical study of the tautomerism and vibrational spectra of 4,5-diamine-2,6-dimercaptopyrimidine

The 4,5-diamine-2,6-dimercaptopyrimidine (DADMcP) compound is an interesting multifunctional species exhibiting a rather complex tautomerism, encompassing nine tautomeric forms. Investigation of tautomerism in this compound has been carried out by means of FTIR spectroscopy, in association with ab-initio HF/SCF and DFT calculations. According to this study three tautomers are energetically favored; the thione form being the most stable one. The theoretical vibrational spectra of such tautomeric forms have been successfully simulated by means of DFT calculations, allowing the elucidation and assignment of the complex composition of the vibrational bands observed for the mixture of isomers.

Solid-phase microextraction for determination of 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone in water

Solid-phase microextraction, using on-line bis(trimethylsilyl)trifluoroacetamide derivatisation, gas chromatography, and mass spectrometry, was evaluated in the quantification of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) in water samples. Fibres encompassing a wide range of polarities were used with headspace and direct immersion sampling. For the immersion procedure, various parameters affecting MX extraction, including pH, salinity, temperature, and extraction time were evaluated. The optimised method (polyacrylate fibre; 20% Na2SO4; pH 2.0; 60 min; 20 °C) was applied for reservoir chlorinated water samples-either natural or spiked with MX (50 ng L-1 and 100 ng L-1). The recovery of MX ranged from 44 to 72%. Quantification of MX in water samples was done using external standard and the selected ion monitoring mode. Correlation coefficient (0.98%), relative standard deviation (5%), limit of detection (30 ng L-1) and limit of quantification (50 ng L-1) were obtained from calibration curve.

Tendência temporal e desigualdades na mortalidade por diarreias em menores de 5 anos

OBJETIVO: Analisar a tendência da mortalidade por diarreia entre menores de 5 anos, no município de Osasco (SP), entre 1980 e 2000. MÉTODOS: Trata-se de estudo observacional com dois delineamentos. Um descritivo, que toma o indivíduo como unidade do estudo, e outro ecológico, analisando agregado populacional que incluiu análise de séries temporais. A fonte de dados foi o sistema de informação de mortalidade do Estado de São Paulo e censos de 1980, 1991 e 2000. Descreveu-se a variação sazonal e para a análise de tendência aplicaram-se modelos log lineares de regressão polinomiais, utilizando-se variáveis sociodemográficas da criança e da mãe. Foram analisadas a evolução de indicadores sociodemográficos do município de 1980 a 2000, as taxas médias de mortalidade por diarreia nos menores de 5 anos e seus diferenciais por distrito nos anos 90. RESULTADOS: Dos 1.360 óbitos, 94,3 e 75,3% atingiram, respectivamente, menores de 1 ano e de 6 meses. O declínio da mortalidade foi de 98,3%, com deslocamento da sazonalidade do verão para o outono. A mediana da idade elevou-se de 2 meses nos primeiros períodos para 3 meses no último. O resíduo de óbitos manteve-se entre filhos de mães de 20 a 29 anos e escolaridade < 8 anos. O risco relativo entre o distrito mais atingido e a taxa média do município diminuiu de 3,4 para 1,3 do primeiro para o segundo quinquênio dos anos 90. CONCLUSÃO: Nossos resultados apontam uma elevação da idade mais vulnerável e a provável mudança do agente mais frequentemente associado ao óbito por diarreia.

Health Related Quality of Life Assessment questionnaire for children aged 5 to 11 years with HIV/AIDS: cross-cultural adaptation for the Portuguese language

The objective of this study is to describe preliminary results from the cross-cultural adaptation of the Quality of Life Assessment Questionnaire, used to measure health related quality of life (HRQL) in Brazilian children aged between 5 and 11 with HIV/AIDS. The cross-cultural model evaluated the Concept, Item, Semantic and Measurement Equivalences (internal consistency and intra-observer reliability). Evaluation of the conceptual, item, semantic equivalences showed that the Portuguese version is pertinent for the Brazilian context. Four of seven domains showed internal consistency above 0.70 (^5;: 0.76-0.90) and five of seven revealed intra-observer reliability (ricc: 0.41-0.70). This first Portuguese version of the HRQL questionnaire can be understood as a valuable tool for assessing children's HRQL, but further studies with large samples and more robust analyses are recommended before use in the Brazilian context.

Irrompimento do primeiro molar permanente em crianças de 5 e 6 anos de idade: implicações da análise longitudinal para prevenção da cárie oclusal

O tempo de irrompimento dentário é essencial para o planejamento de medidas de prevenção da cárie oclusal. Com a ampliação do ensino fundamental de oito para nove anos de duração, um número maior de crianças entre cinco e seis anos de idade é incluído na primeira série do ensino fundamental. OBJETIVO: O objetivo foi estimar as tendências do irrompimento dos primeiros molares permanentes em meninos e meninas de 5 e 6 anos de idade. MÉTODOS: Em estudo longitudinal, espaços dentários de 497 crianças de 60 meses e mais de idade foram examinados quatro vezes por um dentista calibrado (kappa > 0,97) durante 18 meses. O primeiro molar permanente foi considerado irrompido quando qualquer parte de sua superfície podia ser tocada por uma sonda de ponta esférica. A idade dos participantes foi medida em meses. Intervalos para 95% de confiança dos valores de prevalência e incidência foram apurados conforme o sexo para três coortes etárias: 60,0 a 65,9; 66,0 a 71,9; 72,0 a 77,9 meses. A razão entre as taxas de incidência foi estimada por meio de análise de regressão de Poisson. RESULTADOS: A maioria das crianças entre 66,0 e 71,9 meses e entre 72,0 e 77,9 meses tem pelo menos um molar permanente irrompido. No grupo de 66,0 a 71,9 meses, de cada três crianças pelo menos uma apresentou os quatro primeiros molares permanentes irrompidos. CONCLUSÃO. As tendências de irrompimento observadas justificam a necessidade da adoção de medidas de vigilância e de proteção específica em relação à lesão de cárie oclusal.