Anti-deadzone adaptive fuzzy dynamic surface control for planar space robot with elastic base and flexible links.

In order to combat the impact of the dead zone and reduce vibration of the space robot's elastic base and flexible links, the trajectory tracking and vibration suppression of a multi-flexible-link free-floating space robot system are addressed. First, the elastic connection between the base and the link is considered as a linear spring. Then the assumed mode approach is used to derive the dynamic model of the flexible system. Secondly, a slow subsystem characterizing the rigid motion and a fast subsystem relating to vibration of the elastic base and multiple flexible links are generated utilizing two-time scale hypotheses of singular perturbation. For the slow subsystem with a dead zone in joint input torque, a dynamic surface control method with adaptive fuzzy approximator is designed. Dynamic surface control scheme is adopted to avoid calculation expansion and to simplify calculation. The fuzzy logic function is applied to approximate uncertain terms of the dynamic equation including the dead zone errors. For the fast subsystem, an optimal linear quadratic regulator controller is used to suppress the vibration of the multiple flexible links and elastic base, ensuring the stability and tracking accuracy of the system. Lastly, the simulation results verify the effectiveness of the proposed control strategy.

Circadian genes period1b and period2 differentially regulate inflammatory responses in zebrafish.

The circadian clock has been shown to regulate various immune processes in different animals. Our previous report demonstrated that the innate immune responses in zebrafish show significant rhythmicity that could be regulated by melatonin. Here, we used diurnal zebrafish to determine the role of circadian genes in the inflammatory responses. Our results indicate that circadian genes exhibit rhythmic oscillations in zebrafish leukocytes, and mutations of the clock genes period1b (per1b) and period2 (per2) considerably affect these oscillations. Using a wounded zebrafish inflammation model, we found that under constant dark conditions (DD), the expression of pro-inflammatory cytokines is significantly downregulated in per1b gene mutant zebrafish and significantly upregulated in the per2 gene mutant zebrafish. Furthermore, using real-time imaging technology, we found that the per1b gene markedly disturbs the rhythmic recruitment of neutrophils toward the injury, whereas the per2 gene does not show a significant effect. Taken together, our results reveal differential functions of the circadian genes per1b and per2 in the inflammatory responses, serving as evidence that circadian rhythms play a vital role in immune processes.

Zebrafish Lacking Circadian Gene per2 Exhibit Visual Function Deficiency.

The retina has an intrinsic circadian clock, but the importance of this clock for vision is unknown. Zebrafish offer many advantages for studying vertebrate vision and circadian rhythm. Here, we explored the role of zebrafish per2, a light-regulated gene, in visual behavior and the underlying mechanisms. We observed that per2 mutant zebrafish larvae showed decreased contrast sensitivity and visual acuity using optokinetic response (OKR) assays. Using a visual motor response (VMR) assay, we observed normal OFF responses but abnormal ON responses in mutant zebrafish larvae. Immunofluorescence showed that mutants had a normal morphology of cone photoreceptor cells and retinal organization. However, electron microscopy showed that per2 mutants displayed abnormal and decreased photoreceptor ribbon synapses with arciform density, which resulted in retinal ON pathway defect. We also examined the expression of three cone opsins by quantitative real-time PCR (qRT-PCR), and the expression of long-wave-sensitive opsin (opn1lw) and short-wave-sensitive opsin (opn1sw) was reduced in mutant zebrafish larvae. qRT-PCR analyses also showed a down-regulation of the clock genes cry1ba and bmal1b in the adult eye of per2 mutant zebrafish. This study identified a mechanism by which a clock gene affects visual function and defined important roles of per2 in retinal information processing.

Effects of circadian clock protein Per1b on zebrafish visual functions.

The circadian clock is an endogenous and entrainable time-keeping mechanism with a period of approximately 24 h, operated by transcription/translation feedback loops composed of circadian clock genes and their proteins. The visual system displays robust circadian changes. Relatively little, however, is known about the mechanisms underlying visual circadian rhythmicity. Zebrafish period1b (per1b), as a canonical circadian clock gene, is involved in circadian regulation. Here, we observed that zebrafish per1b mutants exhibit visual defects including reduced behavioral contrast sensitivity and significant retinal dopaminergic deficiency. Further, partially damaged dopaminergic interplexiform cells in wild-type larvae also led to reduced behavioral contrast sensitivity, while exogenous dopamine administration effectively restored the contrast sensitivity of per1b mutants. Taken together, these results suggest that retinal dopaminergic deficiency derived from loss of per1b results in visual defects in zebrafish. ABBREVIATIONS: per1b, period1b; per, period; per1, period1; per2, period2; per3, period3; ERG, electroretinogram; DA-IPCs, dopaminergic interplexiform cells; IRBP, interphotoreceptor retinoid binding protein; MS-222, methane-sulfonate; USTC, University of Science and Technology of China; OKR, optokinetic response; dpf, day postfertilization; 6-OHDA, 6-hydroxydopamine; TH, tyrosine hydroxylase; DA, dopaminergic; INL, inner nuclear; IPL, innerplexiform layers; hpf, hours postfertilization; cpd, cycle per degree; ADHD, attention deficit and hyperactivity disorder.

Improving the computational efficiency of recursive cluster elimination for gene selection.

The gene expression data are usually provided with a large number of genes and a relatively small number of samples, which brings a lot of new challenges. Selecting those informative genes becomes the main issue in microarray data analysis. Recursive cluster elimination based on support vector machine (SVM-RCE) has shown the better classification accuracy on some microarray data sets than recursive feature elimination based on support vector machine (SVM-RFE). However, SVM-RCE is extremely time-consuming. In this paper, we propose an improved method of SVM-RCE called ISVM-RCE. ISVM-RCE first trains a SVM model with all clusters, then applies the infinite norm of weight coefficient vector in each cluster to score the cluster, finally eliminates the gene clusters with the lowest score. In addition, ISVM-RCE eliminates genes within the clusters instead of removing a cluster of genes when the number of clusters is small. We have tested ISVM-RCE on six gene expression data sets and compared their performances with SVM-RCE and linear-discriminant-analysis-based RFE (LDA-RFE). The experiment results on these data sets show that ISVM-RCE greatly reduces the time cost of SVM-RCE, meanwhile obtains comparable classification performance as SVM-RCE, while LDA-RFE is not stable.

Display of Candida antarctica lipase B on Pichia pastoris and its application to flavor ester synthesis.

Two alternative cell-surface display systems were developed in Pichia pastoris using the alpha-agglutinin and Flo1p (FS) anchor systems, respectively. Both the anchor cell wall proteins were obtained originally from Saccharomyces cerevisiae. Candida antarctica lipase B (CALB) was displayed functionally on the cell surface of P. pastoris using the anchor proteins alpha-agglutinin and FS. The activity of CALB displayed on P. pastoris was tenfold higher than that of S. cerevisiae. The hydrolytic and synthetic activities of CALB fused with alpha-agglutinin and FS anchored on P. pastoris were investigated. The hydrolytic activities of both lipases displayed on yeast cells surface were more than 200 U/g dry cell after 120 h of culture (200 and 270 U/g dry cell, respectively). However, the synthetic activity of CALB fused with alpha-agglutinin on P. pastoris was threefold higher than that of the FS fusion protein when applied to the synthesis of ethyl caproate. Similarly, the CALB displayed on P. pastoris using alpha-agglutinin had a higher catalytic efficiency with respect to the synthesis of other short-chain flavor esters than that displayed using the FS anchor. Interestingly, for some short-chain esters, the synthetic activity of displaying CALB fused with alpha-agglutinin on P. pastoris was even higher than that of the commercial CALB Novozyme 435.