Modified DIX model for ion-exchange equilibrium of L-phenylalanine on a strong cation-exchange resin

L-phenylalanine, one of the nine essential amino acids for the human body, is extensively used as an ingredient in food, pharmaceutical and nutrition industries. A suitable equilibrium model is required for purification of L-phenylalanine based on ion-exchange chromatography. In this work, the equilibrium uptake of L-phenylalanine on a strong acid-cation exchanger SH11 was investigated experimentally and theoretically. A modified Donnan ion-exchange （DIX） model, which takes the activiW into account, was established to predict the uptake of L-phenylalanine at various solution pH values. The model parameters including selectivity and mean activity coefficient in the resin phase are presented. The modified DIX model is in good agreement with the experimental data. The optimum operating pH value of 2.0, with the highest t-phenylalanine uptake on the resin, is predicted by the model. This basic information combined with the general mass transfer model will lay the foundation for the prediction of dynamic behavior of fixed bed separation process.

STUDY ON MEAN ACTIVITY C0EFFICIENT OF 5,10,15,20—TETRAKIS PORPHYRIN SODIUM BY FREEZING—POINT DEPRESSION METHOD

The mean activity coefficient of 5, 10,15 , 20-tetrakis (P-methoxyl-O-sulfophenyl)porphyrin sodium in dilute aqueous solution has been determined in the modality range 0. 00547-0. 08871 mol · kg-1at 273. 2 K by the freezing-point depression method . The results of γ± are 0. 9945-0. 7695, it is in close agreement with that by isopiestic method.

Participation in Daily Activities among Working Women Following Breast Cancer

Introduction: This study aimed to identify the variables explaining retained activity level for working women with breast cancer;the variables correlating with their performance in daily activities they prioritize;and factors facilitating or restricting their return to work. Method: Sixty working women with breast cancer aged 25 - 65 years completed a personal data questionnaire, the modified Activity Card Sort, the Canadian Occupational Performance Measure;and two open- ended questions about facilitators and barriers to work. Results: Activity levels dropped by a quarter following BC treatments. Most women (67%) decreased their weekly working hours, although a third identified work as their highest priority. A higher total retained activity level was explained by fewer limitations on the range of motion (upper extremity), age younger than 45 years, and higher educational attainment. Cognitive limitations and limited range of motion negatively correlated with retained activity level at work. Personal and disease factors, job demands, and environmental factors facilitated or restricted return to work. Conclusion: Interventions should focus on physical and cognitive rehabilitation to regain functioning in the context of work and productive daily activities. Special attention should be paid to the greater needs of younger women.

Effect of invasive weed biochar amendment on soil enzymatic activity and respiration of coal mine spoil:a laboratory experiment study

Mining and excavation activities cause massive degradation of land,leading to complete loss of soil resources,vegetation,and biodiversity.Mine spoils support invasive weeds(predominantly Lantana)which can strive in these harsh conditions,causing allelopathy during plantation stage of reclamation.It is hypothesised that biochar produced from invasive weeds will enhance enzymatic activity,CO_(2)flux and overall fertility of coal mine spoil.A 6-month incubation study was conducted on the effect of biochar amendment(2 and 3%,w/w)on mine spoil enzymatic activities(dehydrogenase,invertase,amylase and cellulase),respiration and coal mine spoil fertility.The study showed that biochar significantly improved dehydrogenase(83%)and cellulase activity(78%)at 3%amendment.Geometric mean of enzymatic activities increased from 1.87 in control to 4.51 at 2%and 3.25 at 3%biochar amendment.Mine spoil physio-chemical properties such as soil organic carbon(65%),cation exchange capacity(54%),bulk density(25%)and water holding capacity(19%),were improved significantly com-pared to the unamended mine spoil.Biochar amendment reduced mine spoil CO_(2)flux at 2%(2.85μmol CO_(2)m^(−2)s^(−1))and 3%(2.60μmol CO_(2)m^(−2)s^(−1))compared to control(4.92μmol CO_(2)m^(−2)s^(−1)).The cost of biochar production and application(2%,w/w)in pit plantation during reclamation is estimated to be 844 USD t ha−1(plantation density:1600 trees ha−1).On the basis of present study,biochar preparation from invasive weeds can be used for sustainable reclamation of coal mine spoil.

Application of the quasi-random lattice model to rare-earth halide solutions for the computation of their osmotic and mean activity coefficients

This work dealt with the computation of the mean activity coefficients of rare-earth halide aqueous solutions at 25℃, by means of the Quasi Random Lattice（QRL） model. The osmotic coefficients were then calculated consistently, through the integration of the Gibbs-Duhem equation. Using of QRL was mainly motivated by its dependence on one parameter, given in the form of an electrolyte-dependent concentration, which was also the highest concentration at which the model could be applied. For all the electrolyte solutions here considered, this parameter was experimentally known and ranged from 1.5 to 2.2 mol/kg, at 25 ℃.Accordingly, rare- earth halide concentrations from strong dilution up to 2 mol/kg about could be considered without need for best-fit treatment in order to compute their osmotic and mean activity coefficients. The experimental knowledge about the parameter was an advantageous feature of QRL compared to existing literature models. Following a trend already observed with low charge electrolytes,a satisfactory agreement was obtained with the experimental values for all the investigated rare-earth chlorides and bromides. For the sake of compactness, in this work the considered rare-earth halides were all belonging to the P63/m space group in their crystalline（anhydrous） form.