Special Issue "Feature Papers"

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A special issue of Processes (ISSN 2227-9717).

Deadline for manuscript submissions: closed (31 May 2013)

Special Issue Editor

Guest Editor
Prof. Dr. Michael Henson

Director, Center for Process Design and Control, Co-director, Institute for Massachusetts Biofuels Research; Department of Chemical Engineering, University of Massachusetts Amherst, N527 Life Sciences Laboratories, 240 Thatcher Way, Amherst, MA 01003, USA
Website | E-Mail
Fax: +1 413 545 1647
Interests: complex systems modeling; microbial fermentation; particulate processes; systems biology

Special Issue Information

Dear Colleagues,

This special issue contains the first papers of Processes and is intended to highlight a diverse set of topics related to process technology for the chemical, materials, biochemical, pharmaceutical and biomedical industries. To enhance the impact of these industries on society, process innovation that allows large-scale manufacturing is essential for both established and emerging technologies. The scope of this special issue includes, but is not limited to: chemical and biochemical reaction processes: mixing, fluid processing and heat transfer systems; mass transfer, separation and purification processes; integrated process design and scale-up; and process modeling, simulation, optimization and control. We are particularly interested in receiving manuscripts that integrate experimental and theoretical/computational studies as well as contributions from industry. We invite researchers and practitioners from all areas of process technology to submit manuscripts for this important special issue of Processes.

Prof. Dr. Michael A. Henson
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed Open Access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 300 CHF (Swiss Francs). English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.


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Keywords

  • chemical and biochemical reaction processes
  • mass transfer, separation and purification processes
  • mixing, fluid processing and heat transfer systems
  • integrated process design and scale-up
  • process modeling, simulation, optimization and control

Published Papers (17 papers)

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Editorial

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Open AccessEditorial Special Issue “Feature Papers”
Processes 2015, 3(1), 71-74; doi:10.3390/pr3010071
Received: 6 February 2015 / Accepted: 9 February 2015 / Published: 11 February 2015
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Abstract
The Special Issue “Feature Papers” of the journal Processes aims to establish the scope of this new open access journal in chemical, biological, environmental, pharmaceutical, and material-process engineering, as well as the development of general process engineering methods. The Special Issue is available
[...] Read more.
The Special Issue “Feature Papers” of the journal Processes aims to establish the scope of this new open access journal in chemical, biological, environmental, pharmaceutical, and material-process engineering, as well as the development of general process engineering methods. The Special Issue is available online at: http://www.mdpi.com/journal/processes/special_issues/feature-paper.[...] Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available

Research

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Open AccessArticle Interpretation of Cellular Imaging and AQP4 Quantification Data in a Single Cell Simulator
Processes 2014, 2(1), 218-237; doi:10.3390/pr2010218
Received: 22 July 2013 / Revised: 21 January 2014 / Accepted: 22 January 2014 / Published: 4 March 2014
Cited by 2 | PDF Full-text (1644 KB) | HTML Full-text | XML Full-text
Abstract
The goal of the present study is to integrate different datasets in cell biology to derive additional quantitative information about a gene or protein of interest within a single cell using computational simulations. We propose a novel prototype cell simulator as a quantitative
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The goal of the present study is to integrate different datasets in cell biology to derive additional quantitative information about a gene or protein of interest within a single cell using computational simulations. We propose a novel prototype cell simulator as a quantitative tool to integrate datasets including dynamic information about transcript and protein levels and the spatial information on protein trafficking in a complex cellular geometry. In order to represent the stochastic nature of transcription and gene expression, our cell simulator uses event-based stochastic simulations to capture transcription, translation, and dynamic trafficking events. In a reconstructed cellular geometry, a realistic microtubule structure is generated with a novel growth algorithm for simulating vesicular transport and trafficking events. In a case study, we investigate the change in quantitative expression levels of a water channel-aquaporin 4-in a single astrocyte cell, upon pharmacological treatment. Gillespie based discrete time approximation method results in stochastic fluctuation of mRNA and protein levels. In addition, we compute the dynamic trafficking of aquaporin-4 on microtubules in this reconstructed astrocyte. Computational predictions are validated with experimental data. The demonstrated cell simulator facilitates the analysis and prediction of protein expression dynamics. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available
Open AccessArticle Reduced Models in Chemical Kinetics via Nonlinear Data-Mining
Processes 2014, 2(1), 112-140; doi:10.3390/pr2010112
Received: 23 September 2013 / Revised: 10 December 2013 / Accepted: 19 December 2013 / Published: 23 January 2014
Cited by 6 | PDF Full-text (5734 KB) | HTML Full-text | XML Full-text
Abstract
The adoption of detailed mechanisms for chemical kinetics often poses two types of severe challenges: First, the number of degrees of freedom is large; and second, the dynamics is characterized by widely disparate time scales. As a result, reactive flow solvers with detailed
[...] Read more.
The adoption of detailed mechanisms for chemical kinetics often poses two types of severe challenges: First, the number of degrees of freedom is large; and second, the dynamics is characterized by widely disparate time scales. As a result, reactive flow solvers with detailed chemistry often become intractable even for large clusters of CPUs, especially when dealing with direct numerical simulation (DNS) of turbulent combustion problems. This has motivated the development of several techniques for reducing the complexity of such kinetics models, where, eventually, only a few variables are considered in the development of the simplified model. Unfortunately, no generally applicable a priori recipe for selecting suitable parameterizations of the reduced model is available, and the choice of slow variables often relies upon intuition and experience. We present an automated approach to this task, consisting of three main steps. First, the low dimensional manifold of slow motions is (approximately) sampled by brief simulations of the detailed model, starting from a rich enough ensemble of admissible initial conditions. Second, a global parametrization of the manifold is obtained through the Diffusion Map (DMAP) approach, which has recently emerged as a powerful tool in data analysis/machine learning. Finally, a simplified model is constructed and solved on the fly in terms of the above reduced (slow) variables. Clearly, closing this latter model requires nontrivial interpolation calculations, enabling restriction (mapping from the full ambient space to the reduced one) and lifting (mapping from the reduced space to the ambient one). This is a key step in our approach, and a variety of interpolation schemes are reported and compared. The scope of the proposed procedure is presented and discussed by means of an illustrative combustion example. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available
Open AccessArticle Preparation and Characterization of the TiO2 Immobilized Polymeric Photocatalyst for Degradation of Aspirin under UV and Solar Light
Processes 2014, 2(1), 12-23; doi:10.3390/pr2010012
Received: 1 September 2013 / Revised: 2 December 2013 / Accepted: 6 December 2013 / Published: 27 December 2013
Cited by 9 | PDF Full-text (809 KB) | HTML Full-text | XML Full-text
Abstract
The traditional use of TiO2 powder as a photocatalyst for degradation of organic compounds has several post-degradation treatment problems, such as filtration, precipitation, etc. A novel method was developed to immobilize TiO2 to minimize/eliminate such problems. Polymeric membrane was used
[...] Read more.
The traditional use of TiO2 powder as a photocatalyst for degradation of organic compounds has several post-degradation treatment problems, such as filtration, precipitation, etc. A novel method was developed to immobilize TiO2 to minimize/eliminate such problems. Polymeric membrane was used as a base material, over which the TiO2 photocatalyst was immobilized as a thin layer. Preparation and characterization of five different types of polymeric/TiO2 film photocatalysts were elucidated. The catalysts’ films were cross-linked by physical, chemical, and combination of these two processes. The polymers used in the formulation of the catalysts membranes are nontoxic in nature (approved by the World Health Organization (WHO) and Food and Drug Administration (FDA). The morphology of the films were studied by SEM. Photocatalytic degradation of acetylsalicylic acid was carried out to study the efficacy and efficiency of the polymeric membrane based TiO2 as photocatalysts under both UV and solar light irradiation. The degradation was observed to be dependent on the catalyst loading as well as the film thickness. The effects of the types of cross-link bonds on the photocatalytic degradation were also investigated. Full article
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Open AccessArticle Averaging Level Control to Reduce Off-Spec Material in a Continuous Pharmaceutical Pilot Plant
Processes 2013, 1(3), 330-348; doi:10.3390/pr1030330
Received: 13 September 2013 / Revised: 26 October 2013 / Accepted: 25 November 2013 / Published: 29 November 2013
Cited by 8 | PDF Full-text (2691 KB) | HTML Full-text | XML Full-text
Abstract
The judicious use of buffering capacity is important in the development of future continuous pharmaceutical manufacturing processes. The potential benefits are investigated of using optimal-averaging level control for tanks that have buffering capacity for a section of a continuous pharmaceutical pilot plant involving
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The judicious use of buffering capacity is important in the development of future continuous pharmaceutical manufacturing processes. The potential benefits are investigated of using optimal-averaging level control for tanks that have buffering capacity for a section of a continuous pharmaceutical pilot plant involving two crystallizers, a combined filtration and washing stage and a buffer tank. A closed-loop dynamic model is utilized to represent the experimental operation, with the relevant model parameters and initial conditions estimated from experimental data that contained a significant disturbance and a change in setpoint of a concentration control loop. The performance of conventional proportional-integral (PI) level controllers is compared with optimal-averaging level controllers. The aim is to reduce the production of off-spec material in a tubular reactor by minimizing the variations in the outlet flow rate of its upstream buffer tank. The results show a distinct difference in behavior, with the optimal-averaging level controllers strongly outperforming the PI controllers. In general, the results stress the importance of dynamic process modeling for the design of future continuous pharmaceutical processes. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available
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Open AccessArticle Improved Large-Scale Process Cooling Operation through Energy Optimization
Processes 2013, 1(3), 312-329; doi:10.3390/pr1030312
Received: 11 September 2013 / Revised: 26 October 2013 / Accepted: 18 November 2013 / Published: 22 November 2013
Cited by 8 | PDF Full-text (362 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a study based on real plant data collected from chiller plants at the University of Texas at Austin. It highlights the advantages of operating the cooling processes based on an optimal strategy. A multi-component model is developed for the entire
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This paper presents a study based on real plant data collected from chiller plants at the University of Texas at Austin. It highlights the advantages of operating the cooling processes based on an optimal strategy. A multi-component model is developed for the entire cooling process network. The model is used to formulate and solve a multi-period optimal chiller loading problem, posed as a mixed-integer nonlinear programming (MINLP) problem. The results showed that an average energy savings of 8.57% could be achieved using optimal chiller loading as compared to the historical energy consumption data from the plant. The scope of the optimization problem was expanded by including a chilled water thermal storage in the cooling system. The effect of optimal thermal energy storage operation on the net electric power consumption by the cooling system was studied. The results include a hypothetical scenario where the campus purchases electricity at wholesale market prices and an optimal hour-by-hour operating strategy is computed to use the thermal energy storage tank. Full article
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Open AccessArticle Flexible Design and Operation of Multi-Stage Flash (MSF) Desalination Process Subject to Variable Fouling and Variable Freshwater Demand
Processes 2013, 1(3), 279-295; doi:10.3390/pr1030279
Received: 25 June 2013 / Revised: 1 August 2013 / Accepted: 13 August 2013 / Published: 11 October 2013
Cited by 1 | PDF Full-text (460 KB) | HTML Full-text | XML Full-text
Abstract
This work describes how the design and operation parameters of the Multi-Stage Flash (MSF) desalination process are optimised when the process is subject to variation in seawater temperature, fouling and freshwater demand throughout the day. A simple polynomial based dynamic seawater temperature and
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This work describes how the design and operation parameters of the Multi-Stage Flash (MSF) desalination process are optimised when the process is subject to variation in seawater temperature, fouling and freshwater demand throughout the day. A simple polynomial based dynamic seawater temperature and variable freshwater demand correlations are developed based on actual data which are incorporated in the MSF mathematical model using gPROMS models builder 3.0.3. In addition, a fouling model based on stage temperature is considered. The fouling and the effect of noncondensable gases are incorporated into the calculation of overall heat transfer co-efficient for condensers. Finally, an optimisation problem is developed where the total daily operating cost of the MSF process is minimised by optimising the design (no of stages) and the operating (seawater rejected flowrate and brine recycle flowrate) parameters. Full article
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Open AccessArticle Complex Nonlinear Behavior in Metabolic Processes: Global Bifurcation Analysis of Escherichia coli Growth on Multiple Substrates
Processes 2013, 1(3), 263-278; doi:10.3390/pr1030263
Received: 2 July 2013 / Revised: 23 September 2013 / Accepted: 25 September 2013 / Published: 30 September 2013
Cited by 6 | PDF Full-text (2532 KB) | HTML Full-text | XML Full-text
Abstract
The nonlinear behavior of metabolic systems can arise from at least two different sources. One comes from the nonlinear kinetics of chemical reactions in metabolism and the other from nonlinearity associated with regulatory processes. Consequently, organisms at a constant growth rate (as experienced
[...] Read more.
The nonlinear behavior of metabolic systems can arise from at least two different sources. One comes from the nonlinear kinetics of chemical reactions in metabolism and the other from nonlinearity associated with regulatory processes. Consequently, organisms at a constant growth rate (as experienced in a chemostat) could display multiple metabolic states or display complex oscillatory behavior both with potentially serious implications to process operation. This paper explores the nonlinear behavior of a metabolic model of Escherichia coli growth on mixed substrates with sufficient detail to include regulatory features through the cybernetic postulate that metabolic regulation is the consequence of a dynamic objective function ensuring the organism’s survival. The chief source of nonlinearity arises from the optimal formulation with the metabolic state determined by a convex combination of reactions contributing to the objective function. The model for anaerobic growth of E. coli was previously examined for multiple steady states in a chemostat fed by a mixture of glucose and pyruvate substrates under very specific conditions and experimentally verified. In this article, we explore the foregoing model for nonlinear behavior over the full range of parameters, γ (the fractional concentration of glucose in the feed mixture) and D (the dilution rate). The observed multiplicity is in the cybernetic variables combining elementary modes. The results show steady-state multiplicity up to seven. No Hopf bifurcation was encountered, however. Bifurcation analysis of cybernetic models is complicated by the non-differentiability of the cybernetic variables for enzyme activities. A methodology is adopted here to overcome this problem, which is applicable to more complicated metabolic networks. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available
Open AccessArticle A Real-Time Optimization Framework for the Iterative Controller Tuning Problem
Processes 2013, 1(2), 203-237; doi:10.3390/pr1020203
Received: 7 June 2013 / Revised: 1 August 2013 / Accepted: 27 August 2013 / Published: 12 September 2013
Cited by 4 | PDF Full-text (932 KB) | HTML Full-text | XML Full-text
Abstract
We investigate the general iterative controller tuning (ICT) problem, where the task is to find a set of controller parameters that optimize some user-defined performance metric when the same control task is to be carried out repeatedly. Following a repeatability assumption on the
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We investigate the general iterative controller tuning (ICT) problem, where the task is to find a set of controller parameters that optimize some user-defined performance metric when the same control task is to be carried out repeatedly. Following a repeatability assumption on the system, we show that the ICT problem may be formulated as a real-time optimization (RTO) problem, thus allowing for the ICT problem to be solved in the RTO framework, which is both very flexible and comes with strong theoretical guarantees. In particular, we propose the use of a recently released RTO solver and outline a simple procedure for how this solver may be configured to solve ICT problems. The effectiveness of the proposed method is illustrated by successfully applying it to four case studies—two experimental and two simulated—that cover the tuning of model-predictive, general fixed-order and PID controllers, as well as a system of controllers working in parallel. Full article
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Open AccessArticle Systematic Sustainable Process Design and Analysis of Biodiesel Processes
Processes 2013, 1(2), 167-202; doi:10.3390/pr1020167
Received: 5 June 2013 / Revised: 27 July 2013 / Accepted: 13 August 2013 / Published: 3 September 2013
Cited by 7 | PDF Full-text (1193 KB) | HTML Full-text | XML Full-text
Abstract
Biodiesel is a promising fuel alternative compared to traditional diesel obtained from conventional sources such as fossil fuel. Many flowsheet alternatives exist for the production of biodiesel and therefore it is necessary to evaluate these alternatives using defined criteria and also from process
[...] Read more.
Biodiesel is a promising fuel alternative compared to traditional diesel obtained from conventional sources such as fossil fuel. Many flowsheet alternatives exist for the production of biodiesel and therefore it is necessary to evaluate these alternatives using defined criteria and also from process intensification opportunities. This work focuses on three main aspects that have been incorporated into a systematic computer-aided framework for sustainable process design. First, the creation of a generic superstructure, which consists of all possible process alternatives based on available technology. Second, the evaluation of this superstructure for systematic screening to obtain an appropriate base case design. This is done by first reducing the search space using a sustainability analysis, which provides key indicators for process bottlenecks of different flowsheet configurations and then by further reducing the search space by using economic evaluation and life cycle assessment. Third, the determination of sustainable design with/without process intensification using a phenomena-based synthesis/design method. A detailed step by step application of the framework is highlighted through a biodiesel production case study. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available
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Open AccessArticle Photochemical Patterning of Ionically Cross-Linked Hydrogels
Processes 2013, 1(2), 153-166; doi:10.3390/pr1020153
Received: 5 June 2013 / Revised: 24 July 2013 / Accepted: 15 August 2013 / Published: 22 August 2013
Cited by 8 | PDF Full-text (421 KB) | HTML Full-text | XML Full-text
Abstract
Iron(III) cross-linked alginate hydrogel incorporating sodium lactate undergoes photoinduced degradation, thus serving as a biocompatible positive photoresist suitable for photochemical patterning. Alternatively, surface etching of iron(III) cross-linked hydrogel contacting lactic acid solution can be used for controlling the thickness of the photochemical pattering.
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Iron(III) cross-linked alginate hydrogel incorporating sodium lactate undergoes photoinduced degradation, thus serving as a biocompatible positive photoresist suitable for photochemical patterning. Alternatively, surface etching of iron(III) cross-linked hydrogel contacting lactic acid solution can be used for controlling the thickness of the photochemical pattering. Due to biocompatibility, both of these approaches appear potentially useful for advanced manipulation with cell cultures including growing cells on the surface or entrapping them within the hydrogel. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available
Open AccessArticle Dynamic Modeling for the Design and Cyclic Operation of an Atomic Layer Deposition (ALD) Reactor
Processes 2013, 1(2), 128-152; doi:10.3390/pr1020128
Received: 8 June 2013 / Revised: 2 August 2013 / Accepted: 7 August 2013 / Published: 19 August 2013
Cited by 11 | PDF Full-text (516 KB) | HTML Full-text | XML Full-text
Abstract
A laboratory-scale atomic layer deposition (ALD) reactor system model is derived for alumina deposition using trimethylaluminum and water as precursors. Model components describing the precursor thermophysical properties, reactor-scale gas-phase dynamics and surface reaction kinetics derived from absolute reaction rate theory are integrated to
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A laboratory-scale atomic layer deposition (ALD) reactor system model is derived for alumina deposition using trimethylaluminum and water as precursors. Model components describing the precursor thermophysical properties, reactor-scale gas-phase dynamics and surface reaction kinetics derived from absolute reaction rate theory are integrated to simulate the complete reactor system. Limit-cycle solutions defining continuous cyclic ALD reactor operation are computed with a fixed point algorithm based on collocation discretization in time, resulting in an unambiguous definition of film growth-per-cycle (gpc). A key finding of this study is that unintended chemical vapor deposition conditions can mask regions of operation that would otherwise correspond to ideal saturating ALD operation. The use of the simulator for assisting in process design decisions is presented. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available
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Open AccessArticle Scale-Up Design Analysis and Modelling of Cobalt Oxide Silica Membrane Module for Hydrogen Processing
Processes 2013, 1(2), 49-66; doi:10.3390/pr1020049
Received: 24 May 2013 / Revised: 28 June 2013 / Accepted: 26 July 2013 / Published: 5 August 2013
Cited by 3 | PDF Full-text (796 KB) | HTML Full-text | XML Full-text
Abstract
This work shows the application of a validated mathematical model for gas permeation at high temperatures focusing on demonstrated scale-up design for H2 processing. The model considered the driving force variation with spatial coordinates and the mass transfer across the molecular sieve
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This work shows the application of a validated mathematical model for gas permeation at high temperatures focusing on demonstrated scale-up design for H2 processing. The model considered the driving force variation with spatial coordinates and the mass transfer across the molecular sieve cobalt oxide silica membrane to predict the separation performance. The model was used to study the process of H2 separation at 500 °C in single and multi-tube membrane modules. Parameters of interest included the H2 purity in the permeate stream, H2 recovery and H2 yield as a function of the membrane length, number of tubes in a membrane module, space velocity and H2 feed molar fraction. For a single tubular membrane, increasing the length of a membrane tube led to higher H2 yield and H2 recovery, owing to the increase of the membrane area. However, the H2 purity decreased as H2 fraction was depleted, thus reducing the driving force for H2 permeation. By keeping the membrane length constant in a multi-tube arrangement, the H2 yield and H2 recovery increase was attributed to the higher membrane area, but the H2 purity was again compromised. Increasing the space velocity avoided the reduction of H2 purity and still delivered higher H2 yield and H2 recovery than in a single membrane arrangement. Essentially, if the membrane surface is too large, the driving force becomes lower at the expense of H2 purity. In this case, the membrane module is over designed. Hence, maintaining a driving force is of utmost importance to deliver the functionality of process separation. Full article
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Open AccessArticle Density and Viscosity Measurement of Diesel Fuels at Combined High Pressure and Elevated Temperature
Processes 2013, 1(2), 30-48; doi:10.3390/pr1020030
Received: 20 May 2013 / Revised: 24 June 2013 / Accepted: 2 July 2013 / Published: 19 July 2013
Cited by 8 | PDF Full-text (398 KB) | HTML Full-text | XML Full-text
Abstract
We report the measurement of the viscosity and density of various diesel fuels, obtained from British refineries, at elevated pressures up to 500 MPa and temperatures in the range 298 K to 373 K. The measurement and prediction procedures of fluid properties under
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We report the measurement of the viscosity and density of various diesel fuels, obtained from British refineries, at elevated pressures up to 500 MPa and temperatures in the range 298 K to 373 K. The measurement and prediction procedures of fluid properties under high pressure conditions is of increasing interest in many processes and systems including enhanced oil recovery, automotive engine fuel injection, braking, and hydraulic systems. Accurate data and understanding of the fluid characteristic in terms of pressure, volume and temperature is required particularly where the fluid is composed of a complex mixture or blend of aliphatic or aromatic hydrocarbons. In this study, high pressure viscosity data was obtained using a thermostatically-controlled falling sinker-type high pressure viscometer to provide reproducible and reliable viscosity data based on terminal velocity sinker fall times. This was supported with density measurements using a micro-pVT device. Both high-pressure devices were additionally capable of illustrating the freezing points of the hydrocarbon mixtures. This work has, thus, provided data that can extend the application of mixtures of commercially available fuels and to test the validity of available predictive density and viscosity models. This included a Tait-style equation for fluid compressibility prediction. For complex diesel fuel compositions, which have many unidentified components, the approach illustrates the need to apply appropriate correlations, which require accurate knowledge or prediction of thermodynamic properties. Full article
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Review

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Open AccessReview CHO Quasispecies—Implications for Manufacturing Processes
Processes 2013, 1(3), 296-311; doi:10.3390/pr1030296
Received: 30 July 2013 / Revised: 10 September 2013 / Accepted: 22 September 2013 / Published: 11 October 2013
Cited by 24 | PDF Full-text (418 KB) | HTML Full-text | XML Full-text
Abstract
Chinese hamster ovary (CHO) cells are a source of multi-ton quantities of protein pharmaceuticals. They are, however, immortalized cells, characterized by a high degree of genetic and phenotypic diversity. As is known for any biological system, this diversity is enhanced by selective forces
[...] Read more.
Chinese hamster ovary (CHO) cells are a source of multi-ton quantities of protein pharmaceuticals. They are, however, immortalized cells, characterized by a high degree of genetic and phenotypic diversity. As is known for any biological system, this diversity is enhanced by selective forces when laboratories (no sharing of gene pools) grow cells under (diverse) conditions that are practical and useful. CHO cells have been used in culture for more than 50 years, and various lines of cells are available and have been used in manufacturing. This article tries to represent, in a cursory way, the history of CHO cells, particularly the origin and subsequent fate of key cell lines. It is proposed that the name CHO represents many different cell types, based on their inherent genetic diversity and their dynamic rate of genetic change. The continuing remodeling of genomic structure in clonal or non-clonal cell populations, particularly due to the non-standardized culture conditions in hundreds of different labs renders CHO cells a typical case for “quasispecies”. This term was coined for families of related (genomic) sequences exposed to high mutation rate environments where a large fraction of offspring is expected to carry one or more mutations. The implications of the quasispecies concept for CHO cells used in protein manufacturing processes are significant. CHO genomics/transcriptomics may provide only limited insights when done on one or two “old” and poorly characterized CHO strains. In contrast, screening of clonal cell lines, derived from a well-defined starting material, possibly within a given academic or industrial environment, may reveal a more narrow diversity of phenotypes with respect to physiological/metabolic activities and, thus, allow more precise and reliable predictions of the potential of a clone for high-yielding manufacturing processes. Full article
(This article belongs to the Special Issue Feature Papers) Print Edition available
Open AccessReview Thermo-Responsive Hydrogels for Stimuli-Responsive Membranes
Processes 2013, 1(3), 238-262; doi:10.3390/pr1030238
Received: 26 August 2013 / Revised: 17 September 2013 / Accepted: 18 September 2013 / Published: 30 September 2013
Cited by 9 | PDF Full-text (413 KB) | HTML Full-text | XML Full-text
Abstract
Composite membranes with stimuli-responsive properties can be made by coating a thermo-responsive hydrogel onto a micro- or macroporous support. These hydrogels undergo a temperature induced volume-phase transition, which contributes towards the composite membrane’s stimuli-responsive properties. This paper reviews research done on complimentary forms
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Composite membranes with stimuli-responsive properties can be made by coating a thermo-responsive hydrogel onto a micro- or macroporous support. These hydrogels undergo a temperature induced volume-phase transition, which contributes towards the composite membrane’s stimuli-responsive properties. This paper reviews research done on complimentary forms of temperature responsive “thermophilic” hydrogels, those exhibiting positive volume-phase transitions in aqueous solvent. The influences of intermolecular forces on the mechanism of phase-transition are discussed along with case examples of typical thermophilic hydrogels. Full article
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Open AccessReview Modeling of Particulate Processes for the Continuous Manufacture of Solid-Based Pharmaceutical Dosage Forms
Processes 2013, 1(2), 67-127; doi:10.3390/pr1020067
Received: 31 May 2013 / Revised: 11 July 2013 / Accepted: 26 July 2013 / Published: 19 August 2013
Cited by 8 | PDF Full-text (2395 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this work is to present a review of computational tools and models for pharmaceutical processes, specifically those for the continuous manufacture of solid dosage forms. Relevant mathematical methods and simulation techniques are discussed, as is the development of process models
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The objective of this work is to present a review of computational tools and models for pharmaceutical processes, specifically those for the continuous manufacture of solid dosage forms. Relevant mathematical methods and simulation techniques are discussed, as is the development of process models for solids-handling unit operations. Continuous processing is of particular interest in the current study because it has the potential to improve the efficiency and robustness of pharmaceutical manufacturing processes. Full article
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