Small-angle neutron and dynamic light scattering study of gelatin coacervates

The state of intermolecular aggregates and that of folded gelatin molecules could be characterized by dynamic laser light and small-angle neutron scattering experiments, which implied spontaneous segregation of particle sizes preceding coacervation, which is a liquid-liquid phase transition phenomenon. Dynamic light scattering (DLS) data analysis revealed two particle sizes until precipitation was reached. The smaller particles having a diameter of ～50 nm (stable nanoparticles prepared by coacervation method) were detected in the supernatant, whereas the inter-molecular aggregates having a diameter of ～400 nm gave rise to coacervation. Small-angle neutron scattering (SANS) experiments revealed that typical mesh size of the networks exist in polymer dense phase (coacervates) [1]. Analysis of the SANS structure factor showed the presence of two length scales associated with this system that were identified as the correlation length or mesh size, ξ = 10.6 Å of the network and the other is the size of inhomogeneities = 21.4 Å. Observations were discussed based on the results obtained from SANS experiments performed in 5% (w/v) gelatin solution at 60°C (ξ = 50 Å, ζ = 113 Å) and 5% (w/v) gel at 28°C (ξ = 47 Å, ζ = 115 Å) in aqueous phase [2] indicating smaller length scales in coacervate as compared to sol and gel.     

A Method for Improving the Solution of an Inventory Problem under Certainty

This paper gives a procedure for improving the optimum solution of inventory problems under certainty having varying demand. The procedure is typically applicable to those inventory problems where the arrival of fresh supplies is not restricted to concide with the beginning of the basic time unit. An example has been solved to illustrate the method.     

Study of anharmonic elastic properties of mixed diatomic crystals AgCl−AgBr and NaCl−NaBr

Summary An interionic-force model has been employed to analyse the anharmonic elastic properties of mixed-diatomic-crystal systems with varying compositions. The interaction system consists of long-range Coulomb and three-body interactions within the framework of Hafemeister-Zarht (HZ) short-range repulsion, effective up to second-neighbour ions. This interionic potential has been used for predicting the third-order elastic constants, the first pressure derivative of second-order elastic constants and the Anderson-Grüneisen (AG) parameter in NaCl−NaBr and AgCl−AgBr mixed crystals. The values of the hardness parameter between nearest neighbours as well as between second nearest neighbours have been evaluated by using the overlap integral method. The results obtained in the present study are generally in good agreement with the available experimental data as compared to those obtained by earlier investigations. The experimental values of the Anderson-Grüneisen parameter have been calculated by using Chang’s relation.

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Riassunto Un modello di forza interionica è stato usato per analizzare le proprietà anarmoniche elastiche di sistemi di cristalli diatomici misti con composizioni variabili. Il sistema d’interazione consiste in interazioni di Coulomb a largo raggio e a tre corpi nell’àmbito della repulsione a corto raggio di Hagemeister-Zorht (HZ), efficaci fino a ioni secondi vicini. Questo potenziale interionico è stato usato per prevedere costanti elastiche di terz’ordine, la prima derivata di pressione delle costanti elastiche di second’ordine e il parametro di Anderson-Grüneisen (AG) in cristalli misti NaCl−NaBr e AgCl−AgBr. I valori del parametro di durezza tra vicini prossimi e tra secondi vicini prossimi sono stati calcolati usando il metodo dell’integrale di sovrapprosizione. I risultati ottenuti in questo studio sono generalmente in buon accordo con i dati sperimentali disponibili se confrontati con quelli ottenuti da precedenti ricerche. I valori sperimentali del parametro di Anderson-Grüneisen sono stati calcolati usando la relazione di Chang.

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Резюме Используется модель междуионной силы для анализа ангармонических упругих свойств смешанных двухатомных кристаллических систем с изменяющимся составом. Взаимодействие системы состоит из длиннодействующего кулоновского взаимодействия и взаимодействий трех тел в рамках короткодействующего отталкивания Хафемайстера-Зарта, с учетом взаимодействий с ионами, следующими за соседями. Предложенный междуионный потенциал используется для предсказания упругих постоянных третьего порядка, первой производной упругих постоянных второго порядка по давлению и параметра Андерсона-Грюнайзена в смешанных кристаллах NaCl−NaBr и AgCl−AgBr. Оцениваются параметры жесткости между соседними ионами, а также между ионами, следующими за соседними. Полученные результаты хорошо согласуются с имеущимися экспериментальными данными. Используя соотношение Чанга, вычисляются экспериментальные значения параметра Андерсона-Грюнайзена.

     

Production capacity planning and control in multi-stage manufacturing

This paper develops a mathematical model for determining the optimum lot-sizes for a set of products and the capacity required to produce them in a multi-stage production system. The purpose of the modelling is to support capacity planning at the production function level and the basic criterion considered for the optimisation is the minimisation of the total system cost (TSC) per unit time. The TSC consists of (i) set-up cost, (ii) cost due to the quenching of batches, and (iii) hiring cost of the machines. An example is presented to explain the model.     

Variational analysis of directional couplers with graded index profile

A variational analysis of graded optical directional couplers is presented. Fabrication of such directional couplers by an electron-beam writing method has recently been reported. We have shown that our analysis gives better results than the WKB method which has been used previously to analyse such couplers. Further, our analysis involves much less algebraic and numerical work than the WKB method.