Electron transfer in biological media

La flavohémoprotéine (FHP) de Ralstonia eutropha, sous sa forme active, a pu être confinée à la surface d'une électrode de carbone vitreux dans un film de méthyle-cellulose. Sa réponse électrochimique, en voltammétrie cyclique, est stable et reproductible, ce qui permet une estimation du potentiel redox de l'hème, raisonnablement proche de celle obtenue par potentiométrie. Un essai d'estimation de la constante de vitesse de transfert d'électron homogène entre le méthyle-viologène et la FHP a été effectué par chronocoulométrie à double saut de potentiel. La réduction du dioxygène est activée d'environ 400 mV sur une électrode de carbone vitreux recouverte par un film de méthylcellulose contenant de la FHP.Des oxométalates de type Dawson substitués par du vanadium ont été synthétisés. La présence du vanadium permet d'élargir le domaine de stabilité de ces composés vers des valeurs de pH plus élevées; en faisant varier la composition atomique des composés, il a été possible de sélectionner et de synthétiser des polyoxométallates pour lesquels les processus redox du vanadium s'observent entre + 569 mV et + 122 mV par rapport à ECS à pH 7. Cette vaste gamme de potentiels permet un choix important pour réaliser des processus électrocatalytiques. Plus généralement, les résultats de ce travail montrent que le(s) centre(s) vanadium porté(s) par ces polyoxométallates peuvent se comporter comme des catalyseurs d'oxydation ou de réduction vis à vis de substrats convenablement choisis. Ces possibilités sont illustrées par l'oxydation des nitrites ou leur réduction, l'oxydation électrocatalytique de NADPH et l'oxydation de L-cystéine.A flavohaemoprotein (FHP) from Ralstonia eutropha, obtained in a pure and active form has been entrapped in a film of methyl cellulose on the electrode surface and gives a stable and reproducible electrochemical response at pH 7.00 when subject to cyclic voltammetry using a GC electrode. A single couple is observed which is assigned to the haem moiety of the protein. The data collected were further confirmed by potentiometry. The homogeneous electron transfer rate between methyl viologen (MV) and this FHP was estimated by double potential step chronocoulometry. The protein activates the reduction of dioxygen by about 400 mV, the reduction current being proportional to the concentration of dioxygen up to 10% in volume in the gas mixture.A selected series of mono- and multi-V-substituted polyoxometalates (POMs) of Dawson type structure were synthesized and characterizedwith the aim of exploring their electrochemistry and their electrocatalytic abilities. Mono-substituted derivatives display very small or no pH-dependence of the V-wave. Finally, combination of the diversity in the number of V atoms in the presence of As or P as the central heteroatom modulates substantially the apparent formal potentials that span the range from + 569 mV to + 122 mV vs SCE at pH 7. This leaves considerable flexibility in the choice of POMs for electrocatalytic purposes. Such possibilities were illustrated by the homogeneous oxidation and the electrocatalytic reduction of nitrite, the electrocatalytic oxidation of NAD(P)H et L-Cysteine using an appropriate selection of these V-substituted POMs.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

بررسی اهمیت ارتباط نهادهای سلامت و درمانی با مراکز آموزشی در تمدن اسلامی (موردکاوی بیمارستان نظامیه نیشابور در قرن 5 و 6 قمری)

Background and Aim: Studying the history of hospitals in Iran and Islam is one of the important studies in the field of health institutions development in Islamic civilization. With the spread of Islam in all fields, especially in the field of medicine, governments have generally recognized the importance of medical knowledge in some periods of Islamic and Iranian history and established well-established medical centers in most lands. The purpose of the present study is to better understand the evolution of health care institutions in Iran, especially Neyshabour Hospital and its role in the development of medical science. Materials and Methods: This paper examines the texts and documents and explains the process of creation, growth and evolution of this hospital and its role in promoting health and medical education in Islamic civilization by relying on books such as Encyclopedia. The Islamic world deals. Ethical Considerations: The ethical and literary aspects of the subject have been taken into account in the analysis and inference of the material, especially in reference books. Findings: The findings of the study indicate that the mentioned hospital, as a scientific and sovereign necessity, was also one of the most important educational centers in northeast of Iran where some of the most prominent physicians have undergone a course of medical and scientific activity. In addition to the task of treating and caring for patients, these centers also covered other tasks such as training medical students and playing the role of research and research centers (dedicated libraries). The dimensions and impact of these systems on the evolution of health care institutions can be summarized in the prominent medical practitioners and their ideas that were presented to the medical community by the military schools, as these schools are the most important developmental point in medical research in the Islamic world. It has been the basis of study cycles in the field, strengthened by the training of hands-on physicians, who first tried to treat the disease and then tried methods of prevention and outbreak. Conclusion: The educational or so-called "laboratory and academic research departments" have always been an integral part of hospitals, as these subgroups, in addition to accepting and treating patients, have practiced medicine through methods and methods sometimes scientifically and sometimes formally. It was empirical, and this led many Taliban scientists and practitioners around the world to seek science related to this style and method.   Please cite this article as: Shafaie M, Abbas-Aliizade F, Ranjbari A, Hosseini AR. Investigating the Importance of Health and Medical Institutions' Relationship with Educational Centers in Islamic Civilization (Case Study of Neyzabour Nezamieh Hospital in 5th and 6th Centuries AH). Med Hist J 2019; 10(37): 75-88.زمینه و هدف: بررسی تاریخ بیمارستان‌ها در ایران و اسلام، بخشی از مطالعات مهم حوزه تکامل نهادهای سلامت و درمان در تمدن اسلامی است. با گسترش اسلام در تمامی زمینه‌ها به ویژه حوزه طب، حکومت‌ها معمولاً در برخی از دوره‌های تاریخ اسلام و ایران، به اهمیت دانش پزشکی پی برده و به ایجاد مراکز درمانی مجهز در بیشتر سرزمین‌ها اقدام کرده‌اند. هدف از پژوهش حاضر، شناخت بیشتر تکامل نهادهای سلامت و درمان در ایران به ویژه بیمارستان نظامیه نیشابور و نقش آن در گسترش علم طب است. مواد و روش‌ها: این مقاله با رویکرد تحلیلی ـ تاریخی و کتابخانه‌ای ـ اسنادی به بررسی متون و اسناد و تبیین روند ایجاد، رشد و تکامل این بیمارستان و نقش آن در ارتقای بهداشت و درمان و آموزش پزشکی در تمدن اسلامی با تکیه بر کتاب‌هایی مانند دانشنامه جهان اسلام می‌پردازد. ملاحظات اخلاقی: در نقل و تحلیل و استنباط مطالب به ویژه در مراجعه به کتب مرجع، جنبه‌های اخلاقی و ادبی موضوع رعایت گردیده است. یافته‌ها: یافته‌های پژوهش نشان می‌دهد بیمارستان مذکور که به عنوان یک ضرورت علمی و حاکمیتی به شمار می‌رفته، یکی از مهم‌ترین مراکز آموزشی و درمانی در شمال شرق ایران نیز بوده است که تعدادی از برجسته‌ترین پزشکان‌، دوره‌ای از فعالیت علمی و طبی خود را در آنجا گذرانده‌اند، به طوری که این مراکز علاوه بر وظیفه درمان و مراقبت از بیماران، وظایف دیگری نظیر تربیت دانشجویان طب و ایفای نقش مراکز تحقیقاتی و پژوهشی (کتابخانه تخصصی) را نیز پوشش می‌دادند. ابعاد و نحوه تأثیر این نظامیه‌ها در تکامل نهادهای سلامت و درمان را می‎توان در افراد برجسته حوزه طب و آرای ایشان خلاصه کرد که توسط مدارس نظامیه به جامعه پزشکی تقدیم گردیدند، چراکه این مدارس، مهم‌ترین نقطه تحول تحقیقات در حوزه طبی جهان اسلام بوده و بنیان چرخه‌های مطالعاتی این حوزه با تربیت پزشکان چیره‌دست تحکیم یافته است که ابتدا سعی در درمان بیماری داشته و سپس به روش‎های پیشگیری و شیوع بیماری‎ها اهتمام می‌ورزیدند. نتیجه‌گیری: همواره بخش‌های آموزشی یا به اصطلاح امروزی «بخش‌های آزمایشگاهی و تحقیقاتی دانشگاهی» جزء لاینفک بیمارستان‌ها بوده است، چراکه این زیرمجموعه‌ها علاوه بر پذیرش و مداوای بیماران، طبابت را با روش‌ها و متدهایی انجام می‌دادند که گاهی علمی و گاهی نیز به صورت تجربی بود و این امر سبب می‌شد بسیاری از طالبان علم و طبابت از گوشه و کنار جهان در جستجوی علوم مرتبط با این سبک و متد باشند

Photocatalytic degradation of thiabendazole by using porous organic polymers (POP) under visible light

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Novel kinetic modeling of thiabendazole removal by adsorption and photocatalysis on porous organic polymers : effect of pH and visible light intensity

Visible light mediated heterogeneous photocatalysis of the fungicide thiabendazole (TBZ; initial concentration of 50 mu mol/L) has been investigated using amorphous porous organic polymers (POPs). Reversible adsorption in the dark and photocatalytic degradation under light irradiation are experimentally monitored. Then, both TBZ concentrations in liquid phase and on the catalyst surface are for the first time kinetically quantified via coupled continuity equations during a sequence of dark/light periods. The final model takes into account the effect of light intensity (28-120 W/m(2)) and pH (3-9) on the adsorption and photocatalytic degradation processes. It is found that light intensity maintains a linear relation with both the degradation rate in the solution and on the catalyst surface, while it does not significantly affect the adsorption/desorption rates. The effect of pH was investigated in relation to the speciation of TBZ and its impact on adsorption/desorption and degradation coefficients. Accordingly, the different TBZ species have distinct adsorption and desorption coefficients with their charge conditions. Furthermore, changes in pH can exert a significant effect on the overall removal by either adsorption (highest at pH 6.8) or actual degradation (highest at pH 4.4).The proposed model was satisfactory to describe the experimental data with a root-mean-square deviation (RMSD) of 1.88 mu mol/L (i.e., deviations below 4%). In addition, photocatalytic experiments under natural sunlight with a variable visible light intensity of 10 to 125 W/m(2) were successfully accounted for with the aid of the proposed model. Furthermore, the reusability of the photocatalysts was validated along with superior performance in terms of calculated quantum yield (2.8 x 10(-6) molecules/photon) and the space time yield (1.5 x 10(-6) molecules/(photon mg(cat))), which is an order of magnitude higher than earlier reported values

Characterization of metal hydrides using pneumato-chemical impedance spectroscopy

International audiencePneumato-chemical impedance spectroscopy (PIS) is a tool derived from electrochemical impedance spectroscopy (EIS). PIS can be used to analyze the kinetics of various solid-gas reactions, such as the hydriding kinetics of metals in the presence of hysteresis. Pneumato-chemical impedance diagrams are obtained from simple gas transfer experiments, using non-harmonic pressure perturbations. In single-phase domains, the global sorption mechanism consists of mainly two steps, a surface chemisorption step and a bulk hydrogen transport step, controlled by diffusion. In two-phase domains, an additional phase transformation step must be considered. Model impedances are obtained by interconnecting microscopic impedances associated with each reaction step. By fitting model impedances to the experimental ones, microscopic rate parameters such as the surface dissociation resistance, the bulk hydrogen diffusion coefficient and the phase transformation resistance can be obtained. Different results obtained on palladium, palladium–silver and LaNi5 samples (foils and powder) are presented to illustrate the potentialities of this spectroscopy