The attainable region generated by reaction and mixing

The following problem is examined: for a given system of reactions with given kinetics, find all the possible outlet conditions that can be achieved by using any system of steady-flow chemical reactors. The outlet conditions or variables that are considered include concentrations, residence time and temperature. This set of all possible outlet conditions for a given feed was called the Attainable Region by Horn (1964). The boundary of the attainable region is of particular interest as, provided the objective function has open contours over the space of Hie attainable region, the optimum of a system of steady flow reactors will lie in the boundary of the region. More importantly, the optimal reactor structure can be determined from the reactorri that form the boundary of the. attainable region. The prr>-oerties of reaction and mixing are interpreted geometrically and from this a set of necessary conditions for the attainable region is derived. In particular the region must be convex with non-zero reaction vectors on the boundary either pointing into or tangent to the region. A limited, but powerful, sufficiency condition is also derived. The attainable region is constucted for both two and three dimensional examples. It is also shown how the region can be constructed when constraints, such as a specified sequence of reactors, are imposed. The properties of a reactor that lies in the boundary of the attainable region in n-dimensional space are discussed, and in principle the attainable region can be constructed in any number of dimensions. The most important and novel result found is that the method generates the structure of the reactor network that makes up the boundary of the attainable region and hence for many problems the optimal reactor network. This is in contrast to all previous methods where one guessed a network and then optimized it for various parameter values. It was also found that the optimal reactor configuration would in almost also all cases be a series-parallel arrangement of C.S.T.R 's, plug flow reactors and bypasses. Furthermore, the geometry of the boundary of the attainable region gives rise to analytical conditions for optimum reactors structures that are otherwise not readily available. Other interesting results were: - the boundary of the attainable region has very different properties depending on whether the dimension of the space is even or odd, suggesting that the optimization of systems of reactors in even and odd dimensional space could yield rather different results. - the geometric optimization of interstage cooling and coldshot reactors firstly gives insight into the known analytical conditions, but furthermore applies under conditions where the simple analytical optimization breaks down. - the well known properties of plug flow reactors with first order kinetics can be easily explained by the geometric properties of the attainable region

The state of green technologies in South Africa

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Procedure for quantitative evaluation of mineral liberation

Abstract: In mineral processing plant there is a challenge in turnaround time for issuing results timely and consequently the decision making of the process is delayed. The hierarchy of steps involved in procedural analysis could be one of the causes. Mineral liberation is considered as one of the efficiency drivers in informing the decision for the downstream process such as flotation process. Thus, delayed decision could be costly. As a result, the attention of this research was drawn to the development of a procedure to quantify and minimize the time analysis for mineral liberation. The improvement of turnaround time was observed

A review on correction methods to solve limited representativeness in mineralogical analysis of measured liberation data

Abstract: Recent trends in the improvement of the mineral liberation measurements are briefly reviewed. Mineral liberation is the parameter used to suggest action to the flotation process which is intended to render better separation efficiency. The exposed grain surface area of 2D imaging of a polished section with stereological correction is proven to be the appropriate method to measure mineral liberation. Supplementary to 2D imaging, 3D micro CT scanner has also been used to determine the internal structure of the materials to analyze the volumetric grade of mineral of interest. There is a significant development that has been made in correcting measured liberation data acquired from 2 dimensional plane to 3 spatial dimensional. Although progress is being achieved, there are still challenges facing correction methods. Therefore, the advantages and disadvantages of specific issues, such as point spread function and excitation energies, facing the correction methods are discussed

Communications Biophysics

Contains research objectives and reports on six research projects split into three sections.National Institutes of Health (Grant 5 P01 NS13126-07)National Institutes of Health (Training Grant 5 T32 NS07047-05)National Institutes of Health (Training Grant 2 T32 NS07047-06)National Science Foundation (Grant BNS 77-16861)National Institutes of Health (Grant 5 R01 NS1284606)National Institutes of Health (Grant 5 T32 NS07099)National Science Foundation (Grant BNS77-21751)National Institutes of Health (Grant 5 R01 NS14092-04)Gallaudet College SubcontractKarmazin Foundation through the Council for the Arts at M.I.T.National Institutes of Health (Grant 1 R01 NS1691701A1)National Institutes of Health (Grant 5 R01 NS11080-06)National Institutes of Health (Grant GM-21189

Fifteen years of research on oral–facial–digital syndromes: from 1 to 16 causal genes

Oral–facial–digital syndromes (OFDS) gather rare genetic disorders characterised by facial, oral and digital abnormalities associated with a wide range of additional features (polycystic kidney disease, cerebral malformations and several others) to delineate a growing list of OFDS subtypes. The most frequent, OFD type I, is caused by a heterozygous mutation in the OFD1 gene encoding a centrosomal protein. The wide clinical heterogeneity of OFDS suggests the involvement of other ciliary genes. For 15 years, we have aimed to identify the molecular bases of OFDS. This effort has been greatly helped by the recent development of whole-exome sequencing (WES). Here, we present all our published and unpublished results for WES in 24 cases with OFDS. We identified causal variants in five new genes (C2CD3, TMEM107, INTU, KIAA0753 and IFT57) and related the clinical spectrum of four genes in other ciliopathies (C5orf42, TMEM138, TMEM231 and WDPCP) to OFDS. Mutations were also detected in two genes previously implicated in OFDS. Functional studies revealed the involvement of centriole elongation, transition zone and intraflagellar transport defects in OFDS, thus characterising three ciliary protein modules: the complex KIAA0753-FOPNL-OFD1, a regulator of centriole elongation; the Meckel-Gruber syndrome module, a major component of the transition zone; and the CPLANE complex necessary for IFT-A assembly. OFDS now appear to be a distinct subgroup of ciliopathies with wide heterogeneity, which makes the initial classification obsolete. A clinical classification restricted to the three frequent/well-delineated subtypes could be proposed, and for patients who do not fit one of these three main subtypes, a further classification could be based on the genotype

Environmental impacts of electric vehicles in South Africa

Electric vehicles have been seen by some policymakers as a tool to target reductions in greenhouse gas emissions.1,2 Some researchers have shown that the full environmental impact of electric vehicles depends very much on the cleanliness of the electricity grid.3 In countries such as the USA and China, where coal-fired power plants still play a very important role in electricity generation, the environmental impact of electric vehicles is equivalent to, or even higher than that of cars running on internal combustion engines.4,5 In this study, the environmental impacts of electric vehicles in South Africa were investigated. We found that, as the bulk of South Africa’s electricity is generated from relatively low-quality coal and the advanced exhaust clean up technologies are not implemented in the current coal-fired power plants, the use of electric vehicles in South Africa would not help to cut greenhouse gas emissions now (2010) or in the future (in 2030 using the IRP 2010 Revision 2, policy-adjusted IRP scenario), and actually would lead to higher SOx and NOx emissions