The Fixed-Time Observer-Based Adaptive Tracking Control for Aerial Flexible-Joint Robot with Input Saturation and Output Constraint

The aerial flexible-joint robot (AFJR) manipulation system has been widely used in recent years. To handle uncertainty, the input saturation and the output constraint existing in the system, a fixed-time observer-based adaptive control scheme (FTOAC) is proposed. First, to estimate the input saturation and disturbances from the internal force between the robot and the flight platform, a fixed-time observer is designed. Second, a tangent-barrier Lyapunov function is introduced to implement the output constraint. Third, adaptive neural networks are introduced for the online identification of nonlinear unknown dynamics in the system. In addition, a fixed-time compensator is designed in this paper to eliminate the adverse effects caused by filtering errors. The stability analysis shows that all the signals of the closed-loop system are bounded, and the system satisfies the condition of fixed-time convergence. Finally, the simulation results prove the superiority of the proposed control strategy by comparing it with the previous schemes

Insights into Characteristic Volatiles in Wuyi Rock Teas with Different Cultivars by Chemometrics and Gas Chromatography Olfactometry/Mass Spectrometry

Wuyi rock tea (WRT) is one of the most famous subcategories of oolong tea, exhibiting distinct aroma characteristics with the application of different cultivars. However, a comprehensive comparison of the characteristic volatiles among WRTs with different cultivars has rarely been carried out. In this study, non-targeted analyses of volatile fragrant compounds (VFCs) and targeted aroma-active compounds in WRTs from four different cultivars were performed using chemometrics and gas chromatography olfactometry/mass spectrometry (GC-O/MS). A total of 166, 169, 166, and 169 VFCs were identified for Dahongpao (DHP), Rougui (RG), Shuixian (SX), and Jinfo (JF), respectively; and 40 components were considered as the key differential VFCs among WRTs by multivariate statistical analysis. Furthermore, 56 aroma-active compounds were recognized with predominant performances in “floral & fruity”, “green & fresh”, “roasted and caramel”, “sweet”, and “herbal” attributes. The comprehensive analysis of the chemometrics and GC-O/MS results indicated that methyl salicylate, p-cymene, 2,5-dimethylpyrazine, and 1-furfurylpyrrole in DHP; phenylethyl alcohol, phenethyl acetate, indole, and (E)-β-famesene in RG; linalool, phenethyl butyrate, hexyl hexanoate, and dihydroactinidiolide in JF; and naphthalene in SX were the characteristic volatiles for each type of WRT. The obtained results provide a fundamental basis for distinguishing tea cultivars, recombination, and simulation of the WRT aroma

Cardiac telocytes and fibroblasts in primary culture: different morphologies and immunophenotypes.

Telocytes (TCs) are a peculiar type of interstitial cells with very long prolongations termed telopodes. TCs have previously been identified in different anatomic structures of the heart, and have also been isolated and cultured from heart tissues in vitro. TCs and fibroblasts, both located in the interstitial spaces of the heart, have different morphologies and functionality. However, other than microscopic observation, a reliable means to make differential diagnosis of cardiac TCs from fibroblasts remains unclear. In the present study, we isolated and cultured cardiac TCs and fibroblasts from heart tissues, and observed their different morphological features and immunophenotypes in primary culture. Morphologically, TCs had extremely long and thin telopodes with moniliform aspect, stretched away from cell bodies, while cell processes of fibroblasts were short, thick and cone shaped. Furthermore, cardiac TCs were positive for CD34/c-kit, CD34/vimentin, and CD34/PDGFR-β, while fibroblasts were only vimentin and PDGFR-β positive. In addition, TCs were also different from pericytes as TCs were CD34 positive and α-SMA weak positive while pericytes were CD34 negative but α-SMA positive. Besides that, we also showed cardiac TCs were homogenously positive for mesenchymal marker CD29 but negative for hematopoietic marker CD45, indicating that TCs could be a source of cardiac mesenchymal cells. The differences in morphological features and immunophenotypes between TCs and fibroblasts will provide more compelling evidence to differentiate cardiac TCs from fibroblasts

Light microscope shows telocytes (TCs) with typical morphological features.

<p><b>(A)</b> A TC with small cell body and extremely thin and long telopode (Tp). <b>(B)</b> and <b>(C)</b> A TC with significant moniliform aspect: alternation of podoms-podomeres (enlarged in inset). <b>(D-F)</b> show more TCs with typical morphological features. Original magnification 200×; Scale bar = 50 μm.</p

Cell surface markers of cardiac telocytes (TCs) and bone marrow-derived mesenchymal stem cells (BMSC).

<p>Cells collected are shown in A and D. Flow cytometry analysis show that cardiac TCs are homogenously positive for mesenchymal marker CD 29 (B) as BMSC (E), but negative for hematopoietic marker CD45 (C) as BMSC (F). Unlabeled cell (black) controls are included for comparison. FSC: forward scatter; SSC,side scatter.</p

Light microscope shows cardiac telocytes (TCs, A-F) and fibroblasts (FB, G-L) in primary culture from heart tissues at 48 h, 72 h, and 96 h after the day of primary culture.

<p>Arrows show typical TCs with long and thin telopodes in primary culture. Original magnification 200×; Scale bar = 50 μm.</p

Double immunofluorescent staining for CD34/α-SMA and CD34/PDGFR-β of cardiac telocytes (TCs) and pericytes in primary culture.

<p>Fluorescent inverted microscope shows that TCs are positive for <b>(A)</b> CD34 (green) and relatively weak positive for <b>(B)</b> α-SMA (red), while pericytes are negative for <b>(G)</b> CD34 (green) but strong positive for <b>(H)</b> PDGFR-β (red). Co-localization of α-SMA and CD34 (yellow) is extremely weak in TCs <b>(C)</b>, while absent in pericytes <b>(I)</b>. TCs are positive for <b>(D)</b> CD34 (green) and <b>(E)</b> PDGFR-β (red), while pericytes are negative for <b>(J)</b> CD34 (green), but positive for <b>(K)</b> PDGFR-β (red). Co-localization of PDGFR-β and CD34 (yellow) was significant in TCs <b>(F)</b>, while absent in pericytes <b>(L)</b>. Nuclei were counterstained with DAPI (blue). Original magnification 200×; Scale bar = 50 μm. BF, bright field.</p