Sensor-Fusion-Based Simultaneous Positioning and Vibration Suppression Method for a Three-Degrees-of-Freedom Isolator.

For vibration isolation systems, vibration suppression and platform positioning are both important. Since absolute velocity feedback causes difficulty in achieving positioning while suppressing vibration, an H∞ control strategy based on sensor fusion feedback is proposed in this paper. The signals of inertial and displacement sensors are fused through a pair of complementary filters. Thus, active control based on the fusion signal could concurrently achieve vibration and position control since it is a displacement signal. In addition, the obtained fusion signals have a lower noise level. In this way, simultaneous positioning and vibration suppression can be established using the sensor fusion strategy. On this basis, in order to obtain an optimal H∞ controller, system damping can be maximized by using the performance weight function to attenuate noise; the system bandwidth is determined by the uncertainty weight function, which can avoid the effect of high-frequency modes of the system. The effectiveness of the proposed strategy is verified by comparing it with the conventional absolute velocity feedback strategy on a 3-DOF isolator.

Exogenous methyl jasmonate promotes salt stress-induced growth inhibition and prioritizes defense response of Nitraria tangutorum Bobr.

Jasmonates (JAs) play a key role in the regulation of growth and the defense response to environmental stresses. JAs inhibit plant growth and promote defense response. However, their roles in desert halophyte in the response to salt stress remain poorly understood. The effects of the combination of methyl jasmonate (MeJA) and NaCl treatment (the "MeN" condition) on the growth regulation and defense response of Nitraria tangutorum seedlings were investigated. Compared with NaCl treatment alone, exogenous MeJA aggravated the growth inhibition of seedlings by antagonizing to growth-related hormones and suppressing the transcript levels of these hormones-responsive genes, including gibberellin (GA)-responsive NtPIF3, NtGAST1, NtGSAT4, and cytokinin (CYT)-responsive NtARR1, NtARR11, NtARR12. Meanwhile, exogenous MeJA enhanced defense response and alleviated the stress damage by increasing antioxidase activity and antioxidant content, accumulating more osmolytes, maintaining lower Na+ /K+ ratios in shoots and higher Na+ efflux rates in roots of plants. In addition, exogenous MeJA increased the contents of endogenous JA and ABA, and the transcript levels of genes involved in their biosynthesis and responsiveness, thereby further regulating the transcript levels of defense response genes. These findings suggest that exogenous MeJA increases salt stress-induced growth inhibition and prioritizes the defensive responses (e.g. antioxidant defense, osmotic adjustment, and ion homeostasis) of N. tangutorum. These effects may be related to the amplification of jasmonic acid (JA) and abscisic acid (ABA) signals.

A coumarin-based two-photon probe for hydrogen peroxide.

A new fluorescence probe was developed for hydrogen peroxide (H2O2) detection based on donor-excited photo induced electron transfer (D-PET) mechanism, together with the benzil as a quenching and recognizing moiety. The benzil could convert to benzoic anhydride via a Baeyer-Villiger type reaction in the presence of H2O2, followed by hydrolysis of benzoicanhydride to give benzoic acid, and the fluorophore released. The probe was synthesized by a 6-step procedure starting from 4-(diethylamino)salicylaldehyde. A density functional theory (DFT) calculation was performed to demonstrate that the benzil was a fluorescence quencher. The probe was evaluated in both one-photon and two-photon mode, and it exhibited high selectivity toward H2O2 over other reactive oxygen species and high sensitivity with a detection limit of 0.09 µM. Furthermore, the probe was successfully applied to cell imaging of intracellular H2O2 levels with one-photon microscopy and two-photon microscopy. The superior properties of the probe made it of great potential use in more chemical and biological researches.

A highly fluorescent chemosensor for Zn(2+) and the recognition research on distinguishing Zn(2+) from Cd(2+).

A new fluorescent sensor, 2-(2-oxo-2-(quinolin-8-ylamino)ethoxy)-N-(pyridine-2-ylmethyl) benzamide (L), composed of a quinoline group as the fluorogenic unit and a pyridin-2-ylmethanamine as the binding unit for metal ions has been synthesized. The sensor shows excellent selectivity and sensitivity with a fluorescence enhancement to Zn(2+) over other cations in acetonitrile aqueous solution. The X-ray crystal structure analysis reveals that sensor L coordinates to Zn(2+)via a 1 : 1 binding mode but to Cd(2+)via a 2 : 1 binding mode, which lead to a different spatial arrangement of the fluorogenic unit in these complexes. In addition, density functional theory calculations on L, and the Zn(2+)/L and Cd(2+)/L complexes also imply that the different structures of L significantly affect the molecular orbital energy levels and electron transition, which would result in the spectral changes to distinguish Zn(2+) from Cd(2+). The absorption study results may also suggest the Cd(2+) in the complex can be displaced by Zn(2+). Furthermore, the fluorescence imaging of Zn(2+) in living cells was obtained.

A highly selective fluorescent sensor for distinguishing cadmium from zinc ions based on a quinoline platform.

A fluorescent sensor, N-(quinolin-8-yl)-2-(quinolin-8-yloxy)acetamide (HL), based on 8-aminoquinoline and 8-hydroxyquinoline platforms has been synthesized. This sensor displays high selectivity and sensitive fluorescence enhancement to Cd(2+) in ethanol. Moreover, sensor HL can distinguish Cd(2+) from Zn(2+) via two different sensing mechanisms (photoinduced electron transfer for Cd(2+); internal charge transfer for Zn(2+)). The composition of the complex Cd(2+)/HL or Zn(2+)/L(-) has been found to be 1:1, based on the fluorescence/absorption titration and further confirmed by X-ray crystallography.

Diverse lanthanide coordination polymers tuned by the flexibility of ligands and the lanthanide contraction effect: syntheses, structures and luminescence.

Two new flexible exo-bidentate ligands were designed and synthesized, incorporating different backbone chain lengths bearing two salicylamide arms, namely 2,2'-(2,2'-oxybis(ethane-2,1-diyl)bis(oxy))bis(N-benzylbenzamide) (L(I)) and 2,2'-(2,2'-(ethane-1,2-diylbis(oxy))bis(ethane-2,1-diyl))bis(oxy)bis(N-benzylbenzamide) (L(II)). These two structurally related ligands are used as building blocks for constructing diverse lanthanide polymers with luminescent properties. Among two series of lanthanide nitrate complexes which have been characterized by elemental analysis, TGA analysis, X-ray powder diffraction, and IR spectroscopy, ten new coordination polymers have been determined using X-ray diffraction analysis. All the coordination polymers exhibit the same metal-to-ligand molar ratio of 2 : 3. L(I), as a bridging ligand, reacts with lanthanide nitrates forming two different types of 2D coordination complexes: herringbone framework {[Ln(2)(NO(3))(6)(L(I))(3)·mC(4)H(8)O(2)](∞) (Ln = La (1), and Pr (2), m = 1, 2)} as type I,; and honeycomb framework {[Ln(2)(NO(3))(6)(L(I))(3)·nCH(3)OH](∞) (Ln = Nd (3), Eu (4), Tb (5), and Er (6), n = 0 or 3)} as type II, which change according to the decrease in radius of the lanthanide. For L(II), two distinct structure types of 1D ladder-like coordination complexes were formed with decreasing lanthanide radii: [Ln(2)(NO(3))(6)(L(II))(3)·2C(4)H(8)O(2)](∞) (Ln = La (7), Pr (8), Nd (9)) as type III, [Ln(2)(NO(3))(6)(L(I))(3)·mC(4)H(8)O(2)·nCH(3)OH](∞) (Ln = Eu (10), Tb (11), and Er (12), m, n = 2 or 0) as type IV. The progressive structural variation from the 2D supramolecular framework to 1D ladder-like frameworks is attributed to the varying chain length of the backbone group in the flexible ligands. The photophysical properties of trivalent Sm, Eu, Tb, and Dy complexes at room temperature were also investigated in detail.