A Hybrid Time-Scaling Transformation for Time-Delay Optimal Control Problems

In this paper, we consider a class of nonlinear time-delay optimal control problems with canonical equality and inequality constraints. We propose a new computational approach, which combines the control parameterization technique with a hybrid time-scaling strategy, for solving this class of optimal control problems. The proposed approach involves approximating the control variables by piecewise constant functions, whose heights and switching times are decision variables to be optimized. Then, the resulting problem with varying switching times is transformed, via a new hybrid time-scaling strategy, into an equivalent problem with fixed switching times, which is much preferred for numerical computation. Our new time-scaling strategy is hybrid in the sense that it is related to two coupled time-delay systems—one defined on the original time scale, in which the switching times are variable, the other defined on the new time scale, in which the switching times are fixed. This is different from the conventional time-scaling transformation widely used in the literature, which is not applicable to systems with time-delays. To demonstrate the effectiveness of the proposed approach, we solve four numerical examples. The results show that the costs obtained by our new approach are lower, when compared with those obtained by existing optimal control methods

A Cost-Effective ELP-Intein Coupling System for Recombinant Protein Purification from Plant Production Platform

BACKGROUND: Plant bioreactor offers an efficient and economical system for large-scale production of recombinant proteins. However, high cost and difficulty in scaling-up of downstream purification of the target protein, particularly the common involvement of affinity chromatography and protease in the purification process, has hampered its industrial scale application, therefore a cost-effective and easily scale-up purification method is highly desirable for further development of plant bioreactor. METHODOLOGY/PRINCIPAL FINDINGS: To tackle this problem, we investigated the ELP-intein coupling system for purification of recombinant proteins expressed in transgenic plants using a plant lectin (PAL) with anti-tumor bioactivity as example target protein and rice seeds as production platform. Results showed that ELP-intein-PAL (EiP) fusion protein formed novel irregular ER-derived protein bodies in endosperm cells by retention of endogenous prolamins. The fusion protein was partially self-cleaved in vivo, but only self-cleaved PAL protein was detected in total seed protein sample and deposited in protein storage vacuoles (PSV). The in vivo uncleaved EiP protein was accumulated up to 2-4.2% of the total seed protein. The target PAL protein could be purified by the ELP-intein system efficiently without using complicated instruments and expensive chemicals, and the yield of pure PAL protein by the current method was up to 1.1 mg/g total seed protein. CONCLUSION/SIGNIFICANCE: This study successfully demonstrated the purification of an example recombinant protein from rice seeds by the ELP-intein system. The whole purification procedure can be easily scaled up for industrial production, providing the first evidence on applying the ELP-intein coupling system to achieve cost-effective purification of recombinant proteins expressed in plant bioreactors and its possible application in industry

A randomized trial to compare two dosing intervals of misoprostol following mifepristone administration in second trimester medical abortion

BACKGROUND: The conventional timing of misoprostol administration after mifepristone for second trimester medical abortion is 36-48 h, but simultaneous administration, which may make the regimen more convenient, has not been studied. The objective of this randomized comparison study is to compare two intervals of administration of misoprostol after pretreatment with mifepristone for second trimester medical abortion. METHODS: Eligible women with gestational age between 12 and 20 weeks were randomized to receive mifepristone 200 mg orally followed by 600 μg misoprostol vaginally either immediately or 36-38 h later, followed by 400 μg vaginal misoprostol every 3 h for a maximum of four doses. The primary outcome measure was the success rate at 24 h after the start of misoprostol treatment and the secondary outcome measures were the induction-to-abortion interval and the frequency of side effects. RESULTS: There was a significant difference in the success rate at 24 h (36-38 h: 100%; immediate: 91.5%). The median induction-to-abortion interval was significantly shorter in the 36-38 h regimen (4.9 h) compared with the immediate regimen (10 h). Side effects in terms of febrile episodes and chills/rigors were significantly higher in the immediate administration group. CONCLUSIONS: Simultaneous use of mifepristone and misoprostol for second trimester medical abortion is not as effective as the regimen using a 36-38 h dosing interval. © The Author 2008. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.link_to_subscribed_fulltex

cDNA sequence and expression analysis of an antimicrobial peptide, theromacin, in the triangle-shell pearl mussel Hyriopsis cumingii

Bivalve molluscs rely on the interaction between cellular and humoral factors for protection against potential pathogens. Antimicrobial peptides (AMPS) have been proven to be one of the most important humoral components that afford resistance to pathogen infection. The AMP gene to be identified was that encoding theromacin in the triangle-shell pearl mussel Hyriopsis cumingii (Hc theromacin); this gene was identified from a suppression subtractive hybridization library, and subsequently cloned by 3 ' and 5 ' rapid amplification of cDNA ends polymerase chain reaction (RACE-PCR). The full-length theromacin cDNA contains 547 bp, with a 294-bp open reading frame that encodes a 97-amino acid peptide, and the deduced peptide sequence contains a 61-amino acid putative mature peptide. The sequence also contains 10 cysteine residues. Reverse transcriptase (RT)-PCR analysis showed that Hc theromacin transcripts were constitutively expressed in the liver, foot, gill, adductor muscle, heart, mantle, intestine, and hemocytes, with the highest level in hemocytes. Theromacin mRNA levels were found to increase after challenge with Gram-positive and Gram-negative bacteria. After injection of the Gram-positive bacteria Staphylococcus aureus and Bifidobacterium bifidum, Hc theromacin expression showed the highest fold-change at 48 and 36 h after infection, respectively, and its levels decreased gradually thereafter. Crown Copyright (C) 2010 Published by Elsevier Inc. All rights reserved

Detailed modeling of the kraft pulping chemistry : carbohydrate reactions

The article introduces a detailed model for carbohydrate chemistry in kraft pulping. This article is continuation to the modeling work carried out for hot water extraction and chemical pulp bleaching. The model includes galactoglucomannan, xylan, and cellulose acid‐base equilibria, in addition to peeling, stopping, and alkaline hydrolysis reactions of the same carbohydrates, as well as hexenuronic acid formation and degradation reactions. The Arrhenius parameters were applied from the literature or regressed against experimental data in the present study. The model is very successful in predicting the experimental data of carbohydrate reactions during kraft pulping. Many features of the pulping‐related model can be applied to specific fractionation chemistry considerations. The detailed knowledge on carbohydrates composition at any stage of pulping gives possibility for further development of biorefinery cases based on kraft pulping, such as biofuel and chemicals production.peerReviewe