Work flow control in the flexible flow line

This research involves the development and evaluation of a part flow control model for a type of flexible manufacturing system (FMS) called a dedicated flexible flow line (FFL). In the FFL, all part types flow along the same path between successive machine groups. The specific objective of the part flow control model for the FFL is to minimize makespan for a given set of parts produced in a FFL near-term schedule, given fixed available buffer constraints. The control model developed in this research involved the repeated, real-time execution of a mathematical programming algorithm. The algorithm attempts to release the right mix of parts at the tight time to keep the FFL operating smoothly. The focus of the approach is directed toward managing WIP buffers for each machine group queue. The algorithm specifically incorporates stochastic disturbance factors such as machine failures. Through a limited number of simulation experiments, performance of the control model is shown to be superior to other parts releasing and control methods reported in the literature.     

Simulation of sequential batch reactor (SBR) operation for simultaneous removal of nitrogen and phosphorus

Modeling of the operation of sequential batch reactor (SBR) was performed to find out optimum design parameters for simultaneous removal of nitrogen and phosphorus in a small-scale wastewater treatment plant. The models were set up with material balances on SBR operation and Monod kinetics. The model parameters were obtained to best fit the experimental results in a small scale SBR. The models were useful in optimizing hydraulic retention time (HRT) and successfully simulated operations of SBR in a larger scale. Especially the model predicted well the reactions occurring in the filling period as well as the effect of dilution, and evaluated the performance of SBR process under diverse operating conditions.     

Mitochondrial membrane potential regulates PINK1 import and proteolytic destabilization by PARL

PINK1 is a mitochondrial kinase mutated in some familial cases of Parkinson's disease. It has been found to work in the same pathway as the E3 ligase Parkin in the maintenance of flight muscles and dopaminergic neurons in Drosophila melanogaster and to recruit cytosolic Parkin to mitochondria to mediate mitophagy in mammalian cells. Although PINK1 has a predicted mitochondrial import sequence, its cellular and submitochondrial localization remains unclear in part because it is rapidly degraded. In this study, we report that the mitochondrial inner membrane rhomboid protease presenilin-associated rhomboid-like protein (PARL) mediates cleavage of PINK1 dependent on mitochondrial membrane potential. In the absence of PARL, the constitutive degradation of PINK1 is inhibited, stabilizing a 60-kD form inside mitochondria. When mitochondrial membrane potential is dissipated, PINK1 accumulates as a 63-kD full-length form on the outer mitochondrial membrane, where it can recruit Parkin to impaired mitochondria. Thus, differential localization to the inner and outer mitochondrial membranes appears to regulate PINK1 stability and function.     

Feasibility of hydrogen production from ripened fruits by a combined two-stage (dark/dark) fermentation system

Anaerobic fermentation for hydrogen (H₂) production was studied in a two-stage fermentation system fed with different ripened fruit feedstocks (apple, pear, and grape). Among the feedstocks, ripened apple was the most efficient substrate for cumulative H₂ production (4463.7 mL-H₂ L⁻¹-culture) with a maximum H₂ yield (2.2 mol H₂ mol⁻¹ glucose) in the first stage at a hydraulic retention time (HRT) of 18 h. The additional cumulative biohydrogen (3337.4 mL-H₂ L⁻¹-culture) was produced in the second stage with the reused residual substrate from the first stage. The major byproducts in this study were butyrate, acetate, and ethanol, and butyrate was dominant among them in all test runs. During the two-stage system, the energy efficiency (H₂ conversion) obtained from mixed ripened fruits (RF) increased from 4.6% (in the first stage) to 15.5% (in the second stage), which indicated the energy efficiency can be improved by combined hydrogen production process. The RF could be used as substrates for biohydrogen fermentation in a two-stage (dark/dark) fermentation system.     

The Arabidopsis RING E3 ubiquitin ligase AtAIRP2 plays combinatory roles with AtAIRP1 in abscisic acid-mediated drought stress responses

The ubiquitin (Ub)-26S proteasome pathway is implicated in various cellular processes in higher plants. AtAIRP1, a C3H2C3-type RING (for Really Interesting New Gene) E3 Ub ligase, is a positive regulator in the Arabidopsis (Arabidopsis thaliana) abscisic acid (ABA)-dependent drought response. Here, the AtAIRP2 (for Arabidopsis ABA-insensitive RING protein 2) gene was identified and characterized. AtAIRP2 encodes a cytosolic C3HC4-type RING E3 Ub ligase whose expression was markedly induced by ABA and dehydration stress. Thus, AtAIRP2 belongs to a different RING subclass than AtAIRP1 with a limited sequence identity. AtAIRP2-overexpressing transgenic (35S:AtAIRP2-sGFP) and atairp2 loss-of-function mutant plants exhibited hypersensitive and hyposensitive phenotypes, respectively, to ABA in terms of seed germination, root growth, and stomatal movement. 35S:AtAIRP2-sGFP plants were highly tolerant to severe drought stress, and atairp2 alleles were more susceptible to water stress than were wild-type plants. Higher levels of drought-induced hydrogen peroxide production were detected in 35S:AtAIRP2-sGFP as compared with atairp2 plants. ABA-inducible drought-related genes were up-regulated in 35S:AtAIRP2-sGFP and down-regulated in atairp2 progeny. The positive effects of AtAIRP2 on ABA-induced stress genes were dependent on SNF1-related protein kinases, key components of the ABA signaling pathway. Therefore, AtAIRP2 is involved in positive regulation of ABA-dependent drought stress responses. To address the functional relationship between AtAIRP1 and AtAIRP2, FLAG-AtAIRP1 and AtAIRP2-sGFP genes were ectopically expressed in atairp2-2 and atairp1 plants, respectively. Constitutive expression of FLAG-AtAIRP1 and AtAIRP2-sGFP in atairp2-2 and atairp1 plants, respectively, reciprocally rescued the loss-of-function ABA-insensitive phenotypes during germination. Additionally, atairp1/35S:AtAIRP2-sGFP and atairp2-2/35S:FLAG-AtAIRP1 complementation lines were more tolerant to dehydration stress relative to atairp1 and atairp2-2 single knockout plants. Overall, these results suggest that AtAIRP2 plays combinatory roles with AtAIRP1 in Arabidopsis ABA-mediated drought stress responses.     

Peroxiredoxin 2 deficiency reduces white adipogenesis due to the excessive ROS generation

Reactive oxygen species (ROS) act as signaling molecules to regulate various cell functions. Numerous studies have demonstrated ROS to be essential for the differentiation of adipocytes. Peroxiredoxins (Prxs) are a ubiquitous family of antioxidant enzymes in mammalian cells. Prx2 is present in the cytoplasm and cell membranes and demonstrates ROS scavenging activity. We focused on Prx2 involvement in regulating adipogenesis and lipid accumulation and demonstrated that Prx2 expression was upregulated during adipocyte differentiation. In addition, the silencing of Prx2 (shPrx2) inhibited adipogenesis by modulating adipogenic gene expression, and cell death was enhanced via increased ROS production in shPrx2‐3T3‐L1 cells. These results demonstrate that shPrx2 triggers adipocyte cell death and weakens adipocyte function via ROS production. Taken together, our data suggest the participation of Prx2 in adipocyte function and differentiation. Our results also imply that the downregulation of Prx2 activity could help prevent obesity. Overall, findings support the development of ROS‐based therapeutic solutions for the treatment of obesity and obesity‐related metabolic disorders.