Influence du pH sur la rétention des révélateurs photographiques hydroquinones par nanofiltration

L’objet de ce travail est d’étudier l’influence du pH sur le taux de rétention lors de la nanofiltration des solutions d’hydroquinone, d’hydroquinone monosulfonate et d’hydroquinone disulfonate seules ou en mélange, qui sont présents dans les bains révélateurs photographiques. Les résultats nous montrent que les taux de rétention et de dissociation de l’hydroquinone sont liés. L’exploitation des courbes de dosage des acides par NaOH conduit à déterminer le pKa pour l’hydroquinone sulfonique acide comme étant égal à 2,82. Les deux acidités de l’hydroquinone disulfonique acide sont caractérisées par pKa1 = 2,28 et pKa2 = 2,44. Quand il n’existe aucune forme ionisée, le taux de rétention reste faible (TR = 10 %). Dès l’apparition d’une ionisation, alors le taux de rétention augmente considérablement (TR = 50 %). A l’apparition de A2-, le taux de rétention subit une nouvelle augmentation (TR = 98 %). Lorsque pH  pKa1 et pH > pKa2, la molécule est ionisée. La rétention est en relation avec la répulsion des charges négatives de la membrane. Les taux de rejet deviennent importants (TR = 90 %). Bien que les taux de rétention de l’hydroquinone, l’hydroquinone sulfonique acide et l’hydroquinone disulfonique acide suivent la même évolution lorsque le composé est seul ou en mélange, on notera un petit décalage entre les courbes du composé en mélange et du composé seul. Nous attribuons ceci aux propriétés chimiques des composés hydroquinones de la solution, à savoir leur mobilité et leur concentration, etc. Une étude relative à l’influence de ces paramètres serait donc envisageable afin de confirmer ces suppositions.Photographic development is the process of transforming the latent images into visible images thanks to a reducer. The principal components of picture development are agents of development, additives, an alkaline substance and an antiscreen. Hydroquinone and its derivatives are the most commonly used agents of development and revealing. Our study aimed to investigate the influence of pH on the retention of hydroquinone, hydroquinone monosulphonate and hydroquinone disulphonate solutions, which are present in the photographic revealing baths after nanofiltration. The results showed that the retention depends on the dissociation state of hydroquinone. In the absence of any ionized form, the retention is weak. As ionization increases, the retention increases considerably. The retention increases further if the A2- form is present. When pH  pKa1 and pH > pKa2, the molecules become ionized, and the retention is affected by repulsion of the negative charges of the membrane. The retention becomes considerable. The retention of hydroquinone, hydroquinone monosulphonate and hydroquinone disulphonate generally follow the same evolution curves when the compound is alone or in a mixture. However a small shift in the curve for compounds in mixtures indicated more retention. We attribute this shift to the chemical properties of the hydroquinone compounds in solution, particularly their mobility and concentration. A further study of influence of these parameters is proposed to confirm these assumptions

Monetary Policy and Bank Excessive Risk -Taking

This paper investigates the linkage between monetary policy and banks excessive risk-taking for a panel of 22 Latin American countries, the OECD and South East Asia over the period 1990-2014. By performing panel cointegration and panel GMM models we found that the adoption of an expansionary monetary policy via an increase in the money supply and the application of low interest rates over an extended period of time may induce an increase in non-performing loans. However, a restrictive monetary policy with high interest rates attracts riskier investors

Petri Nets Models for Analysis and Control of Public Bicycle-Sharing Systems

International audienc

The Use of Ceramic Waste Powder (CWP) in Making Eco-Friendly Concretes

The global production of ceramic waste powder (CWP), which is produced during the final polishing process of ceramic tiles, exceeds 22 billion tons. The disposal of CWP in landfills will cause significant environmental problems (i.e., soil, air, and groundwater pollution). CWP is characterized by its chemical composition that is mainly composed of silica (SiO2) and alumina (Al2O3). Both minerals represent more than 80% of the CWP composition. CWP has potentials to be used as an ingredient to partially or entirely replacing Portland cement to make eco-friendly concretes. This chapter summarizes the effect of using CWP in making eco-friendly concretes, with a particular focus on using CWP as a partial cement replacement in conventional-vibrated concrete (CVC) and self-compacting concrete (SCC), and the production of zero-cement alkali-activated concrete (AAC)

Design grammars as evaluation tools in the first year studio

This paper describes a teaching experience conducted and carried out as part of the coursework of first year students. The workshop is the third of three workshops planned to take place during the course of the first year studio, aimed at introducing new ways of thinking and introducing students to a new pattern of architectural education. The experiment was planned under the theme of “Evaluation” during the final stage. A grammatical approach was chosen to deliver the methodology in the design studio, based on shape grammars

THE ROLE OF SOME OBESITY-RELATED BIOCHEMICAL PARAMETERS IN THE INCIDENCE, DIAGNOSIS, AND PROGNOSIS OF POSTMENOPAUSAL BREAST CANCER

Aim: To figure out the association of insulin resistance, serum resistin, insulin, SHBG, and free estradiol with the etiology, diagnosis, and the prognosis of postmenopausal breast cancer. Subjects and Methods: Serum levels of resistin, insulin, SHBG, free E2, glucose, and albumin were assayed in a case-control study of 40 obese postmenopausal breast cancer females and 40 apparently healthy obese postmenopausal controls. Results: Serum levels of resistin, insulin, and free E2 were significantly elevated in breast cancer patients (9.89±0.49, 23.68±2.95 and 9.34±3.02, respectively) compared with controls (8.24±0.63, 13.55±1.31 and 1.01±0.23, respectively). Insulin resistance (IR) was significantly greater in breast cancer patients (7.33±0.95) than controls (3.46±0.37). However, serum SHBG levels were significantly declined in breast cancer patients (42.93± 2.52) compared with controls (64.2±4.89). Serum free E2 had the greatest significant area under the ROC curve, followed by insulin resistance, insulin, SHBG, and resistin. The odds ratio of serum resistin was 4.33 (95% CI=1.69 – 11.06, P=0.002), insulin was 3.66 (95% CI=1.41 – 9.46, P=0.006), insulin resistance was 3.56 (95% CI=1.39 – 9.08, P=0.007), SHBG was 0.25 (95% CI=0.092-0.67, P=0.005), and free E2 was 5.21(95% CI=1.86 –14.52, P=0.002) in breast cancer patients. CONCLUSIONS: From this study, it could be concluded that although insulin resistance, serum resistin, insulin, SHBG, and free E2 may have a role in the incidence and diagnosis of obese postmenopausal breast cancer females, these biochemical parameters cannot be used for the prognosis of these patients. Serum free E2 was the most superior diagnostic marker followed by insulin resistance, insulin, SHBG, and resistin