The changes on microstructure and electrical properties of Bi:2223/Ag composite as a function of the granulation and the content of the added silver powder

The Bi-Sr-Ca-Cu-O system has been one of the most studied superconducting ceramic materials for industry applications. The most of the studies with this aim are on silver/ceramic composites, due to the benefits and great compatibility of this metal with the oxide. In this paper we describe a systematic and comparative study on Ag/BSCCO composite, made by the citrate route, in which the ceramic pellets are sintered in the presence of silver powder using several proportions and having several granulations. It was observed that the introduction of fine (0.5 and 2 μm) silver powder in the proportions of 5 wt. % always implies in a better critical current density compared to the no silver pellet. According to the results, the silver powder in excess of 5 wt.% may not promote best electrical properties, depending on the size of the silver particles.

Using Fluid Bed Granulation to Improve the Dissolution of Poorly Water-Soluble Drugs

In this study, fluid bed granulation was applied to improve the dissolution of nimodipine and spironolactone, two very poorly water-soluble drugs. Granules were obtained with different amounts of sodium dodecyl sulfate and croscarmellose sodium and then compressed into tablets. The dissolution behavior of the tablets was studied by comparing their dissolution profiles and dissolution efficiency with those obtained from physical mixtures of the drug and excipients subjected to similar conditions. Statistical analysis of the results demonstrated that the fluid bed granulation process improves the dissolution efficiency of both nimodipine and spironolactone tablets. The addition of either the surfactant or the disintegrant employed in the study proved to have a lower impact on this improvement in dissolution than the fluid bed granulation process.

Using fluid bed granulation to improve the dissolution of poorly water-soluble drugs

In this study, fluid bed granulation was applied to improve the dissolution of nimodipine and spironolactone, two very poorly water-soluble drugs. Granules were obtained with different amounts of sodium dodecyl sulfate and croscarmellose sodium and then compressed into tablets. The dissolution behavior of the tablets was studied by comparing their dissolution profiles and dissolution efficiency with those obtained from physical mixtures of the drug and excipients subjected to similar conditions. Statistical analysis of the results demonstrated that the fluid bed granulation process improves the dissolution efficiency of both nimodipine and spironolactone tablets. The addition of either the surfactant or the disintegrant employed in the study proved to have a lower impact on this improvement in dissolution than the fluid bed granulation process.

On the mechanism of skin wound "contraction": a granulation tissue "knockout" with a normal phenotype.

This report explores the mechanism of spontaneous closure of full-thickness skin wounds. The domestic pig, often used as a human analogue for skin wound repair studies, closes these wounds with kinetics similar to those in the guinea pig (mobile skin), even though the porcine dermis on the back is thick and nearly immobile. In the domestic pig, as in the guinea pig, daily full-thickness excisions of the central granulation tissue up to but not including the wound edges in both back and flank wounds do not alter the rate or completeness of wound closure or the final pattern of the scar. A purse-string mechanism of closure was precluded by showing that surgical interruption of wound edge continuity does not alter closure kinetics or wound shape. We conclude that "tightness" of skin is not a key factor nor is the central granulation tissue required for normal wound closure. These data imply that in vitro models such as contraction of isolated granulation tissue or of the cell-populated collagen lattice may not be relevant for understanding the cell biology of in vivo wound closure. Implications for the mechanism for wound closure are discussed.

Des inflammations spéciales du tissu muqueux, et en particulier de la diphthérite ou inflammation pelliculaire ... /

Mode of access: Internet.

Recherches sur le tissu muqueux, ou L'organe cellulaire, et sur quelques maladies de la poitrine /

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Considérations sur le développement du tissu osseux et sur les lésions élémentaires des cartilages et des os /

Mode of access: Internet.

Traité expérimentale et clinique de la régénération des os et de la production artificielle du tissu osseux /

Mode of access: Internet.

Recherches sur le tissu muqueux, ou, L'Organe cellulaire, et sur quelques maladies de la poitrine /

Mode of access: Internet.

A population balance model for high shear granulation

In a previous paper, Hoornaert et al. (Powder Technol. 96 (1998); 116-128) presented data from granulation experiments performed in a 50 L Lodige high shear mixer. In this study that same data was simulated with a population balance model. Based on an analysis of the experimental data, the granulation process was divided into three separate stages: nucleation, induction, and coalescence growth. These three stages were then simulated separately, with promising results. it is possible to derive a kernel that fit both the induction and the coalescence growth stage. Modeling the nucleation stage proved to be more challenging due to the complex mechanism of nucleus formation. From this work some recommendations are made for the improvement of this type of model.

Process systems modelling and applications in granulation: A review

Granulation is one of the fundamental operations in particulate processing and has a very ancient history and widespread use. Much fundamental particle science has occurred in the last two decades to help understand the underlying phenomena. Yet, until recently the development of granulation systems was mostly based on popular practice. The use of process systems approaches to the integrated understanding of these operations is providing improved insight into the complex nature of the processes. Improved mathematical representations, new solution techniques and the application of the models to industrial processes are yielding better designs, improved optimisation and tighter control of these systems. The parallel development of advanced instrumentation and the use of inferential approaches provide real-time access to system parameters necessary for improvements in operation. The use of advanced models to help develop real-time plant diagnostic systems provides further evidence of the utility of process system approaches to granulation processes. This paper highlights some of those aspects of granulation. (c) 2005 Elsevier Ltd. All rights reserved.

Modelling nucleation in wet granulation

Nucleation is the first stage in any granulation process where binder liquid first comes into contact with the powder. This paper investigates the nucleation process where binder liquid is added to a fine powder with a spray nozzle. The dimensionless spray flux approach of Hapgood et al. (Powder Technol. 141 (2004) 20) is extended to account for nonuniform spray patterns and allow for overlap of nuclei granules rather than spray drops. A dimensionless nuclei distribution function which describes the effects of the design and operating parameters of the nucleation process (binder spray characteristics, the nucleation area ratio between droplets and nuclei and the powder bed velocity) on the fractional surface area coverage of nuclei on a moving powder bed is developed. From this starting point, a Monte Carlo nucleation model that simulates full nuclei size distributions as a function of the design and operating parameters that were implemented in the dimensionless nuclei distribution function is developed. The nucleation model was then used to investigate the effects of the design and operating parameters on the formed nuclei size distributions and to correlate these effects to changes of the dimensionless nuclei distribution function. Model simulations also showed that it is possible to predict nuclei size distributions beyond the drop controlled nucleation regime in Hapgood's nucleation regime map. Qualitative comparison of model simulations and experimental nucleation data showed similar shapes of the nuclei size distributions. In its current form, the nucleation model can replace the nucleation term in one-dimensional population balance models describing wet granulation processes. Implementation of more sophisticated nucleation kinetics can make the model applicable to multi-dimensional population balance models.

Optimal control and operation of drum granulation processes

Process optimisation and optimal control of batch and continuous drum granulation processes are studied in this paper. The main focus of the current research has been: (i) construction of optimisation and control relevant, population balance models through the incorporation of moisture content, drum rotation rate and bed depth into the coalescence kernels; (ii) investigation of optimal operational conditions using constrained optimisation techniques; (iii) development of optimal control algorithms based on discretized population balance equations; and (iv) comprehensive simulation studies on optimal control of both batch and continuous granulation processes. The objective of steady state optimisation is to minimise the recycle rate with minimum cost for continuous processes. It has been identified that the drum rotation-rate, bed depth (material charge), and moisture content of solids are practical decision (design) parameters for system optimisation. The objective for the optimal control of batch granulation processes is to maximize the mass of product-sized particles with minimum time and binder consumption. The objective for the optimal control of the continuous process is to drive the process from one steady state to another in a minimum time with minimum binder consumption, which is also known as the state-driving problem. It has been known for some time that the binder spray-rate is the most effective control (manipulative) variable. Although other possible manipulative variables, such as feed flow-rate and additional powder flow-rate have been investigated in the complete research project, only the single input problem with the binder spray rate as the manipulative variable is addressed in the paper to demonstrate the methodology. It can be shown from simulation results that the proposed models are suitable for control and optimisation studies, and the optimisation algorithms connected with either steady state or dynamic models are successful for the determination of optimal operational conditions and dynamic trajectories with good convergence properties. (c) 2005 Elsevier Ltd. All rights reserved.