CHEMical KINetics SimuLATOR (Chemkinlator): A friendly user interface for chemical kinetics simulations / CHEMical KINetics SimuLATOR (Chemkinlator): Una herramienta amigable para realizar simulaciones de cinética química / CHEMical KINetics SimuLATOR (Chemkinlator): Uma ferramenta amigável para realizar simulações de cinética química

Abstract CHEMicalKINetics SimuLATOR (Chemkinlator) is a Graphical User Interface for the simulation of reaction mechanisms. The interface allows the user to see and change the parameters of a reaction network within a single window. Chemkinlator comes with built-in support for three types of kinetic simulations: Time Series, which computes the concentration of all species in an interval of time for the defined model; Bifurcation diagrams, which are the result of running several Time Series simulations over gradually different kinetic rate constants; and Flow/Temperature time series, which takes into account the effect of flow in the Continuous-flow well-Stirred Tank Reactor, and the effect of temperature on the rates constants according to the Arrhenius equation. In our research group, Chemkinlator has been the primary tool used to test the predictions made by algorithms that analyze homochirality phenomena. Chemkinlator is written in C++14 and Qt, and it uses the Fortran subroutine DLSODE to solve the differential equations associated with the reaction networks. Chemkinlator is open source software under the Apache 2.0 license and can be downloaded freely from https://gitlab.com/homochirality/chemkinlator.

Resumen CHEMical KINetics SimuLATOR (Chemkinlator) es una interfaz gráfica para realizar simulaciones de mecanismos de reacción. La interfaz le permite al usuario ver y cambiar los parámetros de una red de reacciones en una única ventana. Chemkinlator puede realizar tres tipos de simulaciones cinéticas: Time Series, calcula la concentración de cada especie en un intervalo de tiempo del modelo estudiado; Bifurcation, es el resultado de ejecutar varias veces las simulaciones del modo Time Series, cambiando gradualmente diferentes constantes de velocidad; y Flow/ Temperature es una serie de tiempo en la que se tiene en cuenta el efecto del flujo considerando un Reactor de Flujo Continuo bien Agitado y el efecto de la temperatura sobre las constantes de velocidad según la ecuación de Arrhenius. En nuestro grupo de investigación, Chemkinlator ha sido la herramienta principal para verificar las predicciones hechas por los algoritmos que analizan el fenómeno de homochiralidad. Chemkinlator está escrito en C++14 y Qt, y usa la subrutina de Fortran DLSODE para resolver las ecuaciones diferenciales relacionadas con los mecanismos de reacción. Chemkinlator es software de código abierto bajo la licencia Apache 2.0 y se puede descargar libremente de https://gitlab.com/homochirality/chemkinlator.

Resumo O CHEMical KINetics SimuLATOR (Chemkinlator) é uma interface gráfica para realizar simulações de mecanismos de reação. A interface permite ao usuário visualizar e alterar os parâmetros de uma rede de reação em uma única janela. O Chemkinlator pode realizar três tipos de simulações cinéticas: Time Series, calcula a concentração de cada espécie em um intervalo de tempo do modelo estudado; Bifurcation, é o resultado de executar várias vezes as simulações do modo Time Series, modificando gradualmente diferentes constantes de velocidade; e Flow/Temperature é uma serie de tempo que se considera o efeito do fluxo considerando um Reator de Fluxo Continuo bem Agitado e o efeito da temperatura sobre as constantes de velocidade pela equação de Arrhenius. No nosso grupo de investigação, o Chemkinlator tem sido a principal ferramenta para verificar as predições realizadas pelos algoritmos que analisam o fenómeno de homoquiralidade. O Chemkinlator está escrito em C++14 e Qt, e usa a sub-rotina de Fortran DLSODE para resolver as equações diferenciais relacionadas com os mecanismos de reação. O Chemkinlator é um software de código aberto baixo a licença Apache 2.0 e pode ser descarregado livremente em https://gitlab.com/homochirality/chemkinlator.

Simulation of Drying Process of Single Liuwei Dihuangwan and Analysis of Its Dynamics Based on Weibull Function / 中国实验方剂学杂志

Objective: Taking single Liuwei Dihuangwan(LDW) as the research object,the moisture content change and volumetric shrinkage characteristics in its drying process were investigated,which provided the theoretical basis for improving the drying efficiency of the pills and reducing the quality problems of the pattern pills,crusts and crack pills. Method: The drying characteristics of LDW at drying temperature of 50,75,100,125℃ were studied by constant temperature hot air drying and vacuum drying.Based on sphere model of Fick's second law and Arrhenius equation,the effective diffusion coefficient and activation energy of the drying process were obtained.The volumetric shrinkage characteristics of the pills during the drying process were studied by the projected area method.The Weibull function was used to fit the drying dynamics curve of single LDW. Result: Hot air drying and vacuum drying of LDW both belonged to the decreasing drying processes,and the time required to achieve the same moisture content in vacuum drying was shorter than that in hot air drying.The moisture ratio in the drying process of single LDW obeyed the Weibull function distribution(R2=0.994 5-0.999 7),the scale parameter(α) decreased with the increase of temperature,and drying temperature had significant influence on the shape parameter (β).The effective diffusion coefficients of hot air drying and vacuum drying were 2.626×10-3-7.823×10-2,3.782×10-3-9.042×10-2 m2·s-1, their activation energy were 47.18,42.69 kJ·mol-1,respectively.The volume ratio of hot air drying and vacuum drying of LDW ranged from 0.638 to 0.741 and 0.607 to 0.689,respectively. Conclusion: Weibull function can be adopted to predict the drying and dehydration law of LDW.Under the condition of low temperature drying,slow-down of shrinkage rate of the pills is helpful to prevent the formation of splitting pills,this study provides theoretical and technical basis for dying of LDW.

The Analysis of the Accelerated Degradation Test for Protein-type Biological Standard Substances / 中国药学杂志

OBJECTIVE: To establish a weighted least square method for the accelerated degradation analysis of protein-type biological standard substances.METHODS: A mathematical model was proposed to estimate the parameters of degradation rate constants k at the elevated temperatures based on the Arrhenius or Eyring equation and chemical reaction principles under the suitable assumptions. Hence, it is probably to predict the stability of biological standard at the normal condition by solving the model.RESULTS: According to the experimental data of recombinant human granulocyte colony-stimulating factor and interferon α-2a, the preliminary numerical experiments were also performed and the results confirm the reliability of the method in the paper.CONCLUSION: The same methodology may be applied in the pharmaceutical industry where it is necessary to predict the viable shelf-life of biological products.

INFLUENCE OF TEMPERATURE ON THE AVERAGE VELOCITY OF MUSCLE FATIGUE IN Rhinella marina SARTORIUS / Influencia de la temperatura en la velocidad promedio de la fatiga muscular en el sartorio de rhinella marina

Abstract Objective: To analyze and compare the effect of temperature on the average velocity of the linear phase and the exponential phase stages produced by periodic stimulation with simple twitching or with tetanus in the toad sartorius. Methods: an in vitro experimental study with a sample of 46 toad sartorius muscles randomly selected. At the temperatures studied, peak tension produced with two stimulus patterns (twitching and tetanus) were measured until reaching the corresponding muscle fatigue in each case. The tension velocity drop in the linear phase and the exponential phase for each type of fatigue were calculated, and the regression slopes obtained with the Arrhenius equation were compared. Results: The temperatures used (1 to 12°C) significantly affected the velocity of fatigue in the stages of linear and exponential phases of both types of fatigue (p <0.05). The function of which the fatigue curves were adjusted to the temperatures used was similar to the function used with the curves at room temperature. When comparing the slopes of Arrhenius regression in the exponential phase and the different stages of the linear phase of each fatigue and between both fatigues, no significant differences were found (p>0.05). Conclusions: The temperature significantly affected average development velocity of fatigue in the different phases of the two types of fatigue, but when comparing slopes of most regressions corresponding to Arrhenius there were no significant differences, suggesting that the mechanisms underlying the different stages of fatigue have equal sensitivity to temperature.

Resumen Objetivos: Analizar y comparar el efecto de la temperatura en la velocidad promedio de las etapas de la fase lineal y de la fase exponencial de la fatiga producida por estimulación periódica con sacudida simple o con tétanos en el sartorio de sapo. Métodos: Estudio experimental, in vitro; muestra: 46 músculos de sartorio de sapo seleccionados aleatoriamente. A las temperaturas estudiadas, se midió la tensión pico producida con dos patrones de estímulo (sacudida simple o tétanos) hasta llegar en cada caso a un tipo de fatiga muscular, se calculó la velocidad de caída de la tensión en las etapas de la fase lineal y en la fase exponencial de cada tipo de fatiga y se compararon las pendientes de las regresiones obtenidas con la ecuación de Arrhenius. Resultados: Las temperaturas utilizadas (1 a 12°C) afectaron significativamente (p<0,05) la velocidad de la fatiga en las etapas de las fases lineal y exponencial de ambos tipos de fatiga. La función con que se ajustaron las curvas de fatiga a las temperaturas usadas fue similar a la usada con las curvas a temperatura ambiente. Al comparar entre las pendientes de las regresiones de Arrhenius de la fase exponencial y las diferentes etapas de la fase lineal de cada una de las fatigas y entre ambas fatigas, no hubo diferencias significativas (p>0,05). Conclusiones: La temperatura afectó significativamente la velocidad promedio de desarrollo de la fatiga en las diferentes fases de los dos tipos de fatiga, pero al comparar las pendientes de la mayoría de las regresiones correspondientes de Arrhenius, no se encontraron diferencias significativas, lo cual sugiere que, los mecanismos que subyacen a las diferentes etapas de la fatiga tienen igual sensibilidad a la temperatura.

Thermal and photo-stability of the antioxidant potential of Spirulina platensis powder / Estabilidade térmica e fotoestabilidade do potencial antioxidante de Spirulina platensis em pó

Abstract This work aimed to evaluate the thermal and photo stability of the antioxidant potential (AP) of the Spirulina platensis biomass. Thermal stability was established at 25ºC, 40ºC and 50ºC for 60 days, in the dark, protected from light. Photo stability was evaluated using UV (15 W, λ = 265 nm) and fluorescent (20 W, 0.16 A, power factor FP > 0.5, 50/60 Hz, 60 lm/w, 1200 lm) light for 90 days in capsules, glass and Petri dishes, at room temperature. The AP of the biomass in these conditions was determined at intervals (every 7 and 30 days in the studies of thermal and photo stability, respectively) using the induction of the oxidation of a lipid system by heat and aeration. In this lipid system, the biomass submitted to degradation was used as an antioxidant. The kinetics of the reaction was determined by the Arrhenius method. Thermal degradation was found to follow zero order kinetics, whereas photo degradation followed first order kinetics. The AP decreased 50% after 50 days at 25°C. At 40°C and 50°C, the AP decreased more than 50% after 35 and 21 days of exposition, respectively. The decrease of the AP of Spirulina was more sensible to UV and fluorescence light. After 30 days of exposition, the AP decreased more than 50% in all storage conditions tested. The antioxidant potential of Spirulina platensis is easily degraded when the biomass is exposed to heat and light, indicating the need for care to be taken in its storage.

Resumo Este trabalho objetivou avaliar a estabilidade térmica e a foto-estabilidade do potencial antioxidante (PA) da biomassa da Spirulina platensis. A estabilidade térmica foi avaliada a 25ºC, 40ºC e 50ºC por 60 dias. A foto-estabilidade foi avaliada usando luz UV (15 W, λ = 265 nm) e fluorescente (20 W, 0.16 A, fator de potência FP > 0.5, 50/60 Hz, 60 lm/w, 1200 lm) por 90 dias em cápsulas, vidro e placas de Petri. O PA da biomassa nessas condições foi determinado em intervalos de tempo (a cada 7 e 30 dias nos estudos de estabilidade térmica e foto-estabilidade, respectivamente), usando a indução da oxidação de um sistema lipídico por calor e aeração. Neste sistema lipídico, a biomassa submetida à degradação foi usada como antioxidante. A cinética da reação foi determinada pelo método de Arrhenius. A degradação térmica seguiu uma cinética de zero ordem, enquanto que a fotodegradação seguiu uma cinética de primeira ordem. O PA diminuiu 50% depois de 50 dias a 25°C. A 40°C e 50°C, o PA diminuiu mais de 50% depois de 35 e 21 dias de exposição, respectivamente. A diminuição do PA da Spirulina foi mais sensível à luz UV e fluorescente. Depois de 30 dias de exposição, o PA diminuiu mais de 50% em todas as condições de armazenamento testadas. O potencial antioxidante da Spirulina platensis é facilmente diminuído quando a biomassa é exposta ao calor e a luz, indicando a necessidade de cuidados durante seu armazenamento.

Preservation of Azotobacter chroococcum vegetative cells in dry polymers / Preservación de células vegetativas de Azotobacter chroococcum en polímeros secos / Preservação de células vegetativas de Azotobacter chroococcum em polímeros secos

We studied the preservation of Azotobacter chroococcum C26 using three dry polymers: carrageenin, sodium alginate, and HPMC, using a method of accelerated degradation. Bacterial viability, as response variable, was measured at three temperatures in four different times, which was followed by calculation of bacterial degradation rates. Results showed that temperature, time of storage, and protective agent influenced both viability and degradation rates (P<0.05). We observed, using the Arrhenius thermodynamic model, that the use of polymers increased the activation energy of bacterial degradation compared to control. We obtained thermodynamic models for each polymer, based on the Arrhenius equation, which predicted the required time for thermal degradation of the cells at different temperatures. Analysis of the models showed that carrageenin was the best polymer to preserve A. chroococcum C26 since ~ 900 days are required at 4 °C to reduce its viability in two log units. We conclude, therefore, that long-term preservation of A. chroococcum C26 using dry polymers is suitable under adequate preservation and storage conditions.

Se estudió la preservación de Azotobacter chroococcum C26 usando tres polímeros secos: carragenina, alginato de sodio y HPMC, usando un método de degradación acelerada. Viabilidad bacteriana, como variable de respuesta, fue medida a tres temperaturas en cuatro tiempos diferentes, lo cual fue seguido por el cálculo de tasas de degradación bacteriana. Los resultados mostraron que la temperatura, el tiempo de almacenamiento, y el agente protectivo influenciaron tanto la viabilidad como las tasas de degradación (P<0.05). Se observó, usando el modelo termodinàmico de Arrhenius, que el uso de polímeros incremento la energía de activación de degradación bacteriana comparado con el control. Adicionalmente, se obtuvieron modelos para cada polímero, basados en la ecuación de Arrhenius, para predecir el tiempo requerido para la degradación térmica de las células a diferentes temperaturas. El análisis de los modelos mostró que la carragenina fue el mejor polímero para preservar A. chroococcum C26 dado que un tiempo de aproximadamente 900 días a 4 °C son necesarios para reducir en dos unidades logarítmicas la viabilidad. Se concluye, por lo tanto, que la preservación a largo término usando polímeros es eficaz para la preservación de A. chroococcum C26 bajo condiciones adecuadas de preservación y mantenimiento.

Estudamos a preservado do Azotobacter chroococcum C26 utilizando tres polímeros secos: carragenina, alginato de sòdio, e HPMC, utilizando um método de degradado acelerada. Viabilidade bacteriana, como variável de resposta, foi medida a tres temperaturas em quatro momentos diferentes, que foi seguido pelo cálculo das taxas de degradado bacteriana. Os resultados mostraram que a temperatura, tempo de armazenamento, e agente protetor influenciado as taxas de viabilidade e de degradado (P <0,05). Observou-se, utilizando o modelo de Arrhenius termodinàmico, que a utilizac.ao do polímeros de aumento da energia de activado do degradado bacteriana em comparado com o controlo. Adicionalmente, obtivemos modelos termodinámicos para cada polímero, com base na equação de Arrhenius, para prever o tempo necessàrio para a degradação térmica das células a diferentes temperaturas. Análise dos modelos mostrou que a carragenina é o melhor polímero para preservar A. chroococcum C26, porque ~ 900 dias são necessários a 4 °C para reduzir a viabilidade de duas unidades logarítmicas. Nós concluímos, portanto, a preservação a longo prazo de A. chroococcum C26 utilizando polímeros secos é adequado sob condic.öes de preservalo e armazenamento adequadas.

Avaliação de modelos matemáticos na descrição das curvas de secagem por convecção de Pectis brevipedunculata (Gardner) Sch. Bip. / Assessment of mathematical models for the description of Pectis brevipedunculata (Gardner) Sch. Bip. convective drying curves

O presente trabalho foi realizado com o objetivo de selecionar, dentre cinco modelos matemáticos, aquele que melhor descreve as curvas experimentais de secagem da parte aérea de P. brevipedunculata. Os testes foram realizados em protótipo de secador de leito fixo, em camada delgada, a 30, 40 e 50°C, com fluxo mássico de ar seco de 0,27 e 0,54 kg s-1 m-2. O grau de ajuste dos modelos foi avaliado por meio do coeficiente de determinação, da raiz do erro quadrático médio, do erro percentual absoluto médio, do chi-quadrado reduzido, pela análise de dispersão de resíduos, e considerando o princípio da parcimônia. O modelo exponencial simples de três parâmetros foi o que melhor representou as curvas experimentais de secagem podendo ser utilizado com segurança na simulação do processo em camada espessa. Embora o modelo de Lewis não tenha sido capaz de descrever as curvas de secagem com grau de acurácia satisfatório, observou-se que a relação funcional entre a constante de secagem k e a temperatura, pode ser representada pela equação de Arrhenius.

The aim of this study was to select, among five mathematical models, the one that best describes the experimental drying curves of the shoot of P. brevipedunculata. Tests were conducted in a thin-layer prototype laboratory drier, at 30, 40 and 50°C, employing a dry air mass flow rate of 0.274 and 0.542 kg s-1 m-2. The goodness of fit of the models was assessed based on correlation coefficient, root mean square error, mean absolute percentage error, reduced chi-squared, residual plot analysis, and taking into account the principle of parsimony. The model that best described the experimental drying curves was the simple-exponential, three-parameter model, which can be safely used to simulate the deep-bed process. Although the Lewis model was found not to produce accurate predictions of the drying curves, an Arrhenius-type equation represents the relationship between the drying constant k and the temperature.

Determinação do prazo de validade do medicamento carbocisteína xarope através do método de Arrhenius / Determination of carbocysteine syrup shelf life by Arrhenius method

A carbocisteína é um agente mucolítico utilizado como adjuvante no tratamento de infecções do trato respiratório. A qualidade, segurança e eficácia do medicamento durante o seu prazo de validade são responsabilidades da indústria farmacêutica. A validade pode ser determinada através de estudos de estabilidade acelerados, nos quais fatores extrínsecos provocam a degradação do produto. De acordo com Arrhenius, existe uma relação entre temperatura e cinética química. Desta forma, amostras do produto foram expostas a condições drásticas: 40, 50, 60 e 70 ºC. O método de doseamento do xarope de carbocisteína foi validado podendo ser aplicado nas avaliações de rotina do controle de qualidade e no estudo de estabilidade deste produto. O prazo de validade proposto para o xarope de carbocisteína, calculado através da equação de Arrhenius, para a temperatura de 25 ºC foi de 240,9 dias. No entanto, foi observada diferença entre o prazo proposto e a validade usualmente praticada para este produto. Este estudo, ainda, demonstrou a presença de picos endógenos, que precisam ser melhor estudados a fim de se confirmar a presença de produtos de degradação.

Carbocysteine is a mucolytic agent in adjunctive therapy of respiratory tract infections. The pharmaceutical industry is responsible for quality, safety and efficiency of the product during its shelf life. Shelf life can be determinated through an accelerated stability study where the degradation of the drug is managed with the extrinsic factors. According to Arrhenius, there is a relationship between temperature and chemical kinetic, so, the samples were exposed to drastic conditions at 40, 50, 60 and 70 ºC. The syrup assay method has been validated and it may be applied to analysis of carbocysteine syrup in routine quality control and stability studies. Through Arrhenius equation the proposed shelf life of carbocysteine syrup was 240.9 days when the dosage form is stored in appropriated conditions, 25 ºC. However difference was found between the proposed shelf life and the usual shelf life of this drug. In addition, this study has showed the presence of endogenous peaks that must be better evaluated to confirm or not the presence of degradation products.

Altered kinetic properties of liver mitochondrial membrane-bound enzyme activities following paracetamol hepatotoxicity in the rat.

The effects of treatment with subtoxic (375 mg/kg) and toxic (750 mg/kg) doses of paracetamol on NADH oxidase, succinoxidase and Mg2+-ATPase activities in rat liver submitochondrial particles were examined. In the NADH oxidase system, treatment with subtoxic doses of paracetamol resulted in a 37% increase in activation energy in the high temperature range (E1) while the phase transition temperature (Tt) for this system decreased by 9°C. Subtoxic doses caused a 43% decrease in E1. For the succinoxidase system, Tt decreased by 2·4 to 3·4°C after paracetamol administration. E2 increased by 42% only in the subtoxic-treatment group while E1 remained unaltered in both paracetamol-treated groups. For the Mg2+-ATPase system, subtoxic doses of paracetamol treatment did not change the values of E1, E2 and Tt whereas toxic dose treatment resulted in a 29% decrease in E2 with a concomitant increase in Tt by 2·4°C without any change in the value of E1 · The results thus suggest that treatment with toxic and subtoxic doses of paracetamol results in possible differential alterations in the membrane lipid milieu.

Altered kinetic properties of rat heart mitochondrial enzymes following experimental-thyrotoxicosis.

Effects of T3- and T4-induced thyrotoxicosis on temperature-dependent Arrhenius kinetics of succinate oxidase and Mg2+- and Mg2+ + 2,4-dinitrophenoldependent ATPase activities in rat heart mitochondria were examined, For succinate oxidase system, treatment with T3 and T4 caused increase in the energy of activation in high temperature range in a dose-dependent manner. For low temperature range, increase in energy of activation was apparent only with higher doses of the hormones; with low doses a small but reproducible decrease was evinced. The phase transition temperature decreased significantly under these conditions. For the Mg2+- and Mg2++2,4-dintrophenol- dependent-ATPase activities, the activation energy values in high temperature range decreased in general. Activation energy values in low temperature range recorded a generalized increase in the Mg2+-ATPase enzyme system while the value did not change significantly for the Mg2+ + 2,4-dinitrophenol-ATPase; phase transition temperature registered a small but reproducible decrease under these conditions. The results are suggestive of increased membrane fluidization possibly through increased proportion of unsaturated fatty acids. The differential effects seen for succinate oxidase and ATPase systems are consistent with different lipid protein domains of these enzyme systems.

Interaction of lanthanum chloride with human erythrocyte membrane in relation to acetylcholinesterase activity.

Lanthanum chloride (1 mM) inhibits the activity of acetylcholinesterase in vitro in the human erythrocyte membrane. Lineweaver-Burk analysis indicates that lanthanum chloride induced inhibition of acetylcholinesterase activity is competitive in nature. The Arrhenius plot shows that the transition temperature of erythrocyte membrane-bound acetylcholinesterase is significantly reduced in the presence of lanthanum chloride. These results suggest that lanthanum chloride increases the fluidity of the erythrocyte membrane and this may be a cause of inhibition of membrane-bound acetylcholinesterase activity.

Mitochondrial functions during experimentally induced cardiac hypertrophy.

When the hearts of albino rats are subjected to pressure-induced stress through constriction of ascending aorta, changes in the mitochondrial functions are observed as early as 24 h after the imposition of the stress. These include the abolition of oxidative phosphorylation, decrease in the energy dependent [45Ca]-uptake and decrease in the rate of energized swelling. A large influx of calcium ions and an increase in the fluidity of mitochondrial membranes also occur in this period. At later stages of hypertrophy (17, 28, 40%), these mitochondrial functions gradually return to normal levels.