1,720,959 research outputs found
Achieving continuous manufacturing in lyophilization: technologies and approaches
No full textThis paper provides an organic overview of the most interesting continuous freeze-drying concepts that have been proposed over the years. Attention has mainly been focused on the field of pharmaceuticals, but some
background has also been given on the food industry. This work aims at providing a solid starting point for future research on continuous manufacturing for the freeze-drying of pharmaceuticals
A multi-scale computational framework for modelling the freeze-drying of microparticles in packed-beds
No full textThis work investigates the behavior during freeze-drying of packing structures formed by spray-frozen microparticles. A multi-scale approach is used to study spray freeze-drying, and in particular, mass transfer during primary drying and its duration. The procedure starts with the generation of realistic packings of microparticles using DEM, and CFD simulations are used to determine some relevant characteristics at pore scale, i.e., porosity, tortuosity, the average size of the particle-to-particle voids, and permeability. Finally, these parameters are used to describe mass transfer within the packed-bed. This procedure is used to describe some actual case studies and evaluate drying time and mass transfer resistance within the packing. We also investigated the role of packing structure on freeze-drying by generating packings from monodisperse and Gaussian-polydisperse microparticles, demonstrating that polydispersity increased the mass transfer resistance, and, finally, drying time
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Image segmentation and 3D reconstruction for improved prediction of the sublimation rate during freeze drying
Get PDFIn a freeze drying process, the freezing step determines the pore size distribution within the product, which, in turn, affects the sublimation rate. Traditionally, pore analysis is carried out on SEM images by means of a manual, time-consuming approach. Here, an image segmentation technique was used to automatize this process and improve its reliability. A 3D structure of the cake was then reconstructed from the distribution of the super-pixels. We show that the approach herein proposed can remarkably improve prediction of the sublimation rate with respect to traditional methods
Characterization of the mass transfer of lyophilized products based on X-ray micro-computed tomography images
No full textThis paper proposes a systematic work process for the rapid determination of resistance to vapor flow given by the products being freeze-dried. This approach couples mathematical modeling and 3D nondestructive X-ray imaging to reconstruct the internal structure of lyophilized samples.
Knowledge of the internal structure is fundamental to better understand the relationship between freezing and within-product heterogeneity as well as between freezing and the drying behavior of the product being lyophilized. The method was validated upon mannitol-based formulations using various freezing protocols. This stepwise approach was demonstrated to be helpful to lyophilization professionals for the control of within-product heterogeneity and for the optimization of the cycle
Computational methods based on X-ray microtomography for quantitative analysis of lyophilized products
Get PDFIn this work, X-ray microcomputed tomography is used to analyse and reconstruct the inner structure of lyophilized products. Various computational methods were used to determine the structural parameters that impact on mass transport of vapor during drying, i.e., pore size, tortuosity, and permeability. These methods include slice-by-slice 2D image analysis of the entire sample, 3D image analysis of small portions of the product and CFD simulations
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Supporting data and methods for the multi-scale modelling of freeze-drying of microparticles in packed-beds
Get PDFA multi-scale approach can be used to simulate the drying behavior of microparticles in packed-bed. Data outcomes from discrete element method (DEM) and computational fluid dynamics (CFD) simulations can be used to estimate some relevant product characteristics, such as the porosity, tortuosity, voids in the bed and permeability which are required by the multi scale model. Data from DEM simulations are presented, with a particular focus on the influence of the model parameters, packing characteristics and inhomogeneities (wall effect and particles segregation); computational costs and scala bility are also considered. Data on the properties of packings as modeled at the macroscale are presented with regard to the thermal conductivity of gases in the Knudsen regime and effective properties of packed-beds modeled as a pseudo-homogeneous medium. A mathematical model of the freeze-drying of single microparticles and its outcomes are first presented. Data outcomes from the mathematical model at the macroscale concerning the drying behavior of microparticles in a tray and in a vial are then presented and can be used for process design. Some further data, with detailed interpretation and discussion of the presented data, can be found in the related research data article, “A multi-scale computational framework for modelling the freeze-drying of microparticles in packed-beds” (Capozzi et al., 2019). Keywords: Freeze-drying, Packed-bed, Lyophilization, DEM, CFD, Spray-freeze dryin
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