http://hdl.handle.net/10027/7334 Sat, 25 May 2013 12:49:51 GMT 2013-05-25T12:49:51Z http://hdl.handle.net/10027/8579 Optimal control of biodiesel production in a batch reactor Part II: Stochastic control. Benavides, Pahola T.; Diwekar, Urmila The determination of time‐varying profiles through dynamic optimization is an exclusive characteristic of optimal control problems; however, these types of problems become more challenging when variability and uncertainty in any parameter is included. In biodiesel production, there are inherent uncertainties arising due to variation in initial composition, operating parameters, and mechanical equipment design that can have a significant impact on the product quantity, quality and process economics. Thus, one of the most influential uncertainties in this process is the feed composition since the percentage and type of triglycerides in biodiesel composition varies considerable. In this work, the optimal control for biodiesel production in a batch reactor developed in part 1 is extended to a problem when uncertainty in the feed composition is considerable. Under control of reactor temperature, we applied a numerical method, based on the steepest Ascent of Hamiltonian to solve the stochastic optimal control problem that involved the application of Ito processes and the stochastic maximum principle. It has been found that the temperature profile obtained using deterministic optimal control is robust in the face of feed composition uncertainties also. NOTICE: this is the author’s version of a work that was accepted for publication in Fuel. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Fuel, [Vol 94, Issue 1, (April 2012)] http://dx.doi.org/10.1016/j.fuel.2011.08.033 Sun, 01 Apr 2012 05:00:00 GMT http://hdl.handle.net/10027/8579 2012-04-01T05:00:00Z http://hdl.handle.net/10027/8574 Blunted Neuronal Calcium Response to Hypoxia in Naked Mole-Rat Hippocampus Peterson, Bethany L.; Larson, John; Buffenstein, Rochelle; Park, Thomas J.; Fall, Christopher P. Naked mole-rats are highly social and strictly subterranean rodents that live in large communal colonies in sealed and chronically oxygen-depleted burrows. Brain slices from naked mole-rats show extreme tolerance to hypoxia compared to slices from other mammals, as indicated by maintenance of synaptic transmission under more hypoxic conditions and three fold longer latency to anoxic depolarization. A key factor in determining whether or not the cellular response to hypoxia is reversible or leads to cell death may be the elevation of intracellular calcium concentration. In the present study, we used fluorescent imaging techniques to measure relative intracellular calcium changes in CA1 pyramidal cells of hippocampal slices during hypoxia. We found that calcium accumulation during hypoxia was significantly and substantially attenuated in slices from naked mole-rats compared to slices from laboratory mice. This was the case for both neonatal (postnatal day 6) and older (postnatal day 20) age groups. Furthermore, while both species demonstrated more calcium accumulation at older ages, the older naked mole-rats showed a smaller calcium accumulation response than even the younger mice. A blunted intracellular calcium response to hypoxia may contribute to the extreme hypoxia tolerance of naked mole-rat neurons. The results are discussed in terms of a general hypothesis that a very prolonged or arrested developmental process may allow adult naked mole-rat brain to retain the hypoxia tolerance normally only seen in neonatal mammals. © 2012 Peterson et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. doi:10.1371/journal.pone.0031568 Wed, 01 Feb 2012 06:00:00 GMT http://hdl.handle.net/10027/8574 2012-02-01T06:00:00Z http://hdl.handle.net/10027/8560 Biomedical systems research - new perspectives opened by quantitative medical imaging. Linninger, Andreas A. Recent advances in quantitative imaging allow unprecedented views into cellular chemistry of whole organisms in vivo. These novel imaging modalities enable the quantitative investigation of spatio-temporal reaction and transport phenomena in the living animal or the human body. This article will highlight the significant role that rigorous systems engineering methods can play for interpreting the wealth of in-vivo measurements. A methodology to integrate medical imaging modalities with rigorous computational fluid dynamics entitled image-based computational fluid dynamics (iCFD) will be introduced. The quantitative analysis of biological systems with rigorous mathematical methods is expected to accelerate the introduction of novel drugs by providing a rational foundation for the systematic development of new medical therapies. Rigorous engineering methods not only advance biomedical research, but also aid the translation of laboratory research results into the bedside practice. NOTICE: this is the author’s version of a work that was accepted for publication in Computers and Chemical Engineering. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Computers and Chemical Engineering, Vol 36, Issue , (10 January 2012). DOI: 10.1016/j.compchemeng.2011.07.010 Sun, 01 Jan 2012 06:00:00 GMT http://hdl.handle.net/10027/8560 2012-01-01T06:00:00Z http://hdl.handle.net/10027/8553 Optimal control of biodiesel production in a batch reactor Part I: Deterministic control Benavides, Pahola; Diwekar, Urmila The continuing depletion of fossil fuel reserves and the increasing environmental concerns has encouraged engineers and scientists to look for an alternative, clean, and renewable fuel that can reduce the negative environmental impact. Biodiesel has been considered as one of the best candidate of one of these renewable fuels. One of the pathways to biodiesel production is the transesterification reaction of triglycerides from vegetable oils and short‐chain alcohols. A batch reactor is employed for the production of biodiesel. The flexibility of the batch process allows operating the reactor with different feed stocks and product specifications. This condition becomes challenging for the reactor modeling and control since uncertainty in the feed composition turns into time‐dependent uncertainty and requires a batch‐process based stochastic optimal control. In the first part of this work, the optimal control in this reactor involves optimization of the concentration of fatty acid methyl esters, well known as biodiesel, under the control of reactor temperature and the strategy applied to solve this problem is based on the maximum principle. The strategy increased the concentration by 8.46%. As far as the minimum time required to obtain the same base concentration, it reduced the reaction time by 69.5%. NOTICE: this is the author’s version of a work that was accepted for publication in Fuel. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Fuel, Vol 94, Issue 1, (April 2012). DOI: 10.1016/j.fuel.2011.08.035 Sun, 01 Apr 2012 05:00:00 GMT http://hdl.handle.net/10027/8553 2012-04-01T05:00:00Z