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The convergence of sensing, computing, communication and control elements drives the traditional point-to-point control systems towards networked control systems. Sampled-data control systems, which focus on the significant interplay between sampling and control, play a critical role in modern networked control systems, including intelligent transportation systems, smart grids, and advanced manufacturing systems. This paper presents a survey of methods and trends in non-uniform sampled-data control systems, where sampling and control actions are performed in an aperiodic manner. First, some fundamental issues of both continuous- and discrete-time sampled-data control systems are discussed. Next, main methods in both continuous-time and discrete-time domains are elaborated, respectively. Then, event-triggered sampling, under which sampling is executed only when the system needs attention, is examined. Typical triggering mechanisms in the existing literature are reviewed and classified into four types according to different threshold functions. Furthermore, two applications in terms of automated vehicle platoons and islanded microgrids are provided to demonstrate that sampled-data control methods are capable to support relevant practical application scenarios. Finally, several challenging issues are envisioned to direct future research. [ABSTRACT FROM AUTHOR]

This article investigates $H_{\infty }$ synchronization of delayed neural networks under a receding horizon scheme, where two types of interval time-varying delays are considered according to whether the lower bound of the delay derivative is known or not. Note that a receding horizon synchronization law can be regarded as an optimization solution at each timeslot to a minimaxization problem related closely with a certain cost functional. In this article, two cost functionals with some delay-dependent matrices are introduced, respectively, for the two types of time delays. In order to obtain less conservative conditions, a novel inequality on quadratic polynomial functions is established, which includes some existing ones as its special cases. Based on the novel inequality, two sufficient conditions are derived to design the terminal weighting matrices of the cost functionals such that the resulting synchronization error system can be stabilized with a prescribed infinite horizon $H_{\infty }$ performance level. Finally, three numerical examples are used to demonstrate the validity of the proposed results. [ABSTRACT FROM AUTHOR]

Ligand‐protected heterometallic nanoclusters in contrast to homo‐metal counterparts show more broad applications due to the synergistic effect of hetero‐metals but their controllable syntheses remain a challenge. Among heterometallic nanoclusters, monovalent Ag‐Cu compounds are rarely explored due to much difference of Ag(I) and Cu(I) such as atom radius, coordination habits, and redox potential. Encouraged by copper‐catalyzed alkyne‐azide cycloaddition (CuAAC) reaction, comproportionation reaction of Cu(II)X2 and Cu(0) in the presence of (PhC≡CAg)n complex and molybdate generated a core‐shell peanut‐shaped 66‐nuclear Ag(I)‐Cu(I) heterometallic nanocluster, [(Mo4O16)2@Cu12Ag54(PhC≡C)50] (referred to as Ag54Cu12). The structure and composition of Ag‐Cu heterometallic nanocluster are fully characterized. X‐ray single crystal diffraction reveals that Ag54Cu12 has a peanut‐shaped silver(I)/copper(I) heterometallic nanocage protected by fifty phenylacetylene ligands in µ3–modes and encapsulated two mutually twisted tetramolybdates. Heterometallic nanocage contains a 54‐Ag‐atom outer ellipsoid silver cage decorated by 12 copper inside wall. Nanosized Ag54Cu12 is a n‐type narrow‐band‐gap semiconductor with a good photocurrent response. Preliminary experiments demonstrates that Ag54Cu12 itself and activated carbon supported Ag54Cu12/C are effective catalysts for 1,3‐dipole cycloaddition between alkynes and azides at ambient conditions. The work provides not only a new synthetic route toward Ag(I)‐Cu(I) nanoclusters but also an important heterometallic intermediate in CuAAC catalytic reaction. [ABSTRACT FROM AUTHOR]

This study provides an overview and in‐depth analysis of recent advances in stability of linear systems with time‐varying delays. First, recent developments of a delay convex analysis approach, a reciprocally convex approach and the construction of Lyapunov–Krasovskii functionals are reviewed insightfully. Second, in‐depth analysis of the Bessel–Legendre inequality and some affine integral inequalities is made, and recent stability results are also summarised, including stability criteria for three cases of a time‐varying delay, where information on the bounds of the time‐varying delay and its derivative is totally known, partly known and completely unknown, respectively. Third, a number of stability criteria are developed for the above three cases of the time‐varying delay by employing canonical Bessel–Legendre inequalities, together with augmented Lyapunov–Krasovskii functionals. It is shown through numerical examples that these stability criteria outperform some existing results. Finally, several challenging issues are pointed out to direct the near future research. [ABSTRACT FROM AUTHOR]

Global asymptotic stability is an important issue for wide applications of recurrent neural networks with time-varying delays. The Lyapunov–Krasovskii functional method is a powerful tool to check the global asymptotic stability of a delayed recurrent neural network. When the Lyapunov–Krasovskii functional method is employed, three steps are necessary in order to derive a global asymptotic stability criterion: (i) constructing a Lyapunov–Krasovskii functional, (ii) estimating the derivative of the Lyapunov–Krasovskii functional, and (iii) formulating a global asymptotic stability criterion. This paper provides an overview of recent developments in each step with insightful understanding. In the first step, some existing Lyapunov–Krasovskii functionals for stability of delayed recurrent neural networks are anatomized. In the second step, a free-weighting matrix approach, an integral inequality approach and its recent developments, reciprocally convex inequalities and S -procedure are analyzed in detail. In the third step, linear convex and quadratic convex approaches, together with the refinement of allowable delay sets are reviewed. Finally, some challenging issues are presented to guide the future research. [ABSTRACT FROM AUTHOR]

This paper deals with the H ∞ dynamic output feedback control problem of a seismic-excited building. The control aims to reduce the vibration of a building caused by an earthquake. Instead of system states, the system output measurements are used to design suitable H ∞ controllers. Depending on whether the system measurements are sampled or not, two kinds of dynamic output feedback control schemes are investigated. By the Lyapunov stability theory, some bounded real lemmas are formulated such that the closed-loop system is asymptotically stable and achieves a prescribed H ∞ disturbance attenuation level. The cone complementary algorithm is employed to design H ∞ controllers based on a solution to a nonlinear minimization problem subject to a set of linear matrix inequalities. Finally, a three-storey building model is given to show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper is concerned with stability of a linear system with a time-varying delay. First, an improved reciprocally convex inequality including some existing ones as its special cases is derived. Compared with an extended reciprocally convex inequality recently reported, the improved reciprocally convex inequality can provide a maximum lower bound with less slack matrix variables for some reciprocally convex combinations. Second, an augmented Lyapunov–Krasovskii functional is tailored for the use of a second-order Bessel–Legendre inequality. Third, a stability criterion is derived by employing the proposed reciprocally convex inequality and the augmented Lyapunov–Krasovskii functional. Finally, two well-studied numerical examples are given to show that the obtained stability criterion can produce a larger upper bound of the time-varying delay than some existing criteria. [ABSTRACT FROM AUTHOR]

This paper is concerned with event-triggered H ∞ control for a class of nonlinear networked control systems. An event-triggered transmission scheme is introduced to select 'necessary' sampled data packets to be transmitted so that precious communication resources can be saved significantly. Under the event-triggered transmission scheme, the closed-loop system is modeled as a system with an interval time-varying delay. Two novel integral inequalities are established to provide a tight estimation on the derivative of the Lyapunov-Krasovskii functional. As a result, a novel sufficient condition on the existence of desired event-triggered H ∞ controllers is derived in terms of solutions to a set of linear matrix inequalities. No parameters need to be tuned when controllers are designed. The proposed method is then applied to the robust stabilization of a class of nonlinear networked control systems, and some linear matrix inequality-based conditions are formulated to design both event-triggered and time-triggered H ∞ controllers. Finally, two numerical examples are given to demonstrate the effectiveness of the proposed method. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Recent research has shown that one can obtain a less conservative stability criterion for a continuous-time linear system with a time-varying delay by introducing a Lyapunov-Krasovskii functional with a polynomial matrix on the time-varying delay. This paper aims at analysing the stability of discrete-time linear systems with time-varying delays by introducing a delay-square-dependent Lyapunov functional. A novel convex method is presented to formulate a less conservative stability criterion, which is demonstrated through numerical simulation. Moreover, it is also shown that, if the polynomial inequality method is employed, the resultant stability criterion is inapplicable due to its extremely high numerical complexity. [ABSTRACT FROM AUTHOR]

Dip coating is widely applied in industries for coating a solid substrate with a fluid because of its simplicity and applicability to substrates with different shapes. An experimental study was reported with dip coater on the film coating of solid plates by withdrawal from a tank filled with silicone oil fluids or polyacrylic acid (PAA) solutions with different rheological properties, the liquid film thickness deposited on the plate substrate was measured using capacitance method, and the evolution of free surface morphology was recorded with photographs. The purpose was to investigate the effects of plate substrate roughness, withdrawal speed, rest time, and fluid viscosity on the liquid film thickness and free surface morphology in detail. Results showed that the increases in coating fluid viscosity, withdrawal speed, and substrate roughness are beneficial to film thickening. The influence of rest time on liquid film thickness could be neglected when it was greater than 3 min. For silicone oil fluids, the free surface exhibited a depression, which gradually deepened, with the increasing in withdrawal speed and viscosities. By contrast, PAA solutions showed a bump on the free surface, exhibiting a curvature that increased with the increasing in withdrawal speed and concentrations. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A correction to this paper has been published: https://doi.org/10.1007/s00280-021-04287-1 [ABSTRACT FROM AUTHOR]

This paper is concerned with stability of linear discrete time-delay systems. Note that a tighter estimation on a finite-sum term appearing in the forward difference of some Lyapunov functional leads to a less conservative delay-dependent stability criterion. By using Abel lemma, a novel finite-sum inequality is established, which can provide a tighter estimation than the ones in the literature for the finite-sum term. Applying this Abel lemma-based finite-sum inequality, a stability criterion for linear discrete time-delay systems is derived. It is shown through numerical examples that the stability criterion can provide a larger admissible maximum upper bound than stability criteria using a Jensen-type inequality approach and a free-weighting matrix approach. [ABSTRACT FROM AUTHOR]

Isocyanate-functionalized polystyrene (P(St-co-TMI)) was successfully synthesized by solution free radical polymerization, which was then used to react with (3-aminopropyl) triethoxysilane (APTES) to prepare a precursor of polystyrene/inorganic composites (PS/SiO2). To obtain PS/SiO2 composites with chemical bond, the precursor was mixed with triethoxysilane (TEOS) under the sol-gel reaction condition. The chemical bond between the PS and SiO2 particles made the crosslink network more stable and avoided aggregation compared with the physical connection and barely mechanical mixing. The Fourier transform infrared (FTIR) results indicate that the isocyanate group (-NCO) was completely reacted with APTES. The field-emission scanning electron microscopy results show that the morphology of composites and the distribution of the particles, which exhibit good compatibility between organic and inorganic phases, and the inorganic particles show good spatial uniformity. The differential scanning calorimetry shows that the glass transition temperature (Tg) of the PS/SiO2 composites was shifted to high temperature when the amount of APTES increased. The thermal degradation temperature of the PS/SiO2 composites increases with the increasing of APTES content. Master curves at 200°C are constructed for the storage and loss modulus as well as complex viscosity. [ABSTRACT FROM AUTHOR]

This paper is concerned with network-based H ∞ stabilization for stochastic systems, where network-induced delays, packet dropouts, and packet disorders are taken into account simultaneously. The packet disorders arising from both the sampler-to-controller channel and the controller-to-actuator channel are considered by introducing a logic controller and a logic zero-order hold. The network-induced delays and packet dropouts are modeled as a constant delay plus a non-differentiable time-varying delay in the input. By employing Lyapunov-Krasovskii functional approach, we establish results that parallel well-known bounded real Lemmas. More specifically, these results provide conditions to bound the H ∞ level of the system, which means the worst case energy of the output of the system when subjected to a unitary norm deterministic disturbance signal. On the basis of these results, suitable network-based H ∞ controllers are designed by using cone complementary linearization method. An air vehicle system is finally taken as an example to show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper is concerned with event-based H ∞ filtering for sampled-data systems. First, an event-based data packet processor is introduced to release sampled measurement outputs only if an event condition is violated. As a result, communication resources can be saved significantly while preserving the desired H ∞ performance. Second, the resulting filtering error system is modeled as a system with an interval time-varying delay. By employing the Lyapunov–Krasovskii functional approach, a new bounded real lemma (BRL) is established such that the filtering error system is asymptotically stable with the prescribed H ∞ performance. Third, by performing an invertible linear transformation on the filtering error system, a linear matrix inequality (LMI)-based sufficient condition, which is equivalent to the condition in the BRL, is obtained on the feasibility of the event-based H ∞ filtering problem. Consequently, suitable H ∞ filters and the event parameters in the event condition can be co-designed provided that a set of LMIs are satisfied. Finally, a mechanical system with two masses and two springs is given to show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This study is concerned with the stability of a linear system with an interval time‐varying delay. First, a new augmented Lyapunov–Krasovskii functional (LKF) is constructed, which includes three integral terms in the form of ∫t−ht(h −t)+)s) jẋTRjẋ(s) ds (j)=) 1, 2, 3). Second, three novel integral inequalities are established to estimate the upper bounds of the integrals ∫t−ht(h −t)+)s) jẋTRjẋ(s) ds (j)=) 0, 1, 2) appearing in the derivative of the LKF. Third, a matrix‐based quadratic convex approach is introduced to prove not only the negative definiteness of the derivative of the LKF along with the trajectory of the system, but also the positive definiteness of the LKF. Finally, a novel delay‐derivative‐dependent stability criterion is formulated. The effectiveness of the stability criterion is shown through two numerical examples. [ABSTRACT FROM AUTHOR]

This paper is concerned with the H ∞ performance of discrete-time networked systems subject to network-induced delays and malicious packet dropouts. First, the introduction of a data packet processor enables us to calculate both network-induced delays and the number of consecutive malicious packet dropouts explicitly. Second, a novel Lyapunov functional is constructed, whose forward difference along with the trajectory of the closed-loop system is estimated as a quartic polynomial. A class of necessary and sufficient conditions on such an inequality are established by using the Finsler lemma. By employing the Lyapunov method, a bounded real condition is formulated, which depends on the upper bound of network-induced delays and the maximum number of consecutive malicious packet dropouts. Therefore, their effects on H ∞ performance can be investigated simultaneously. Finally, the effectiveness of the proposed method is shown through an inverted pendulum system. [ABSTRACT FROM AUTHOR]

Abstract: This paper is concerned with global asymptotic stability for a class of generalized neural networks with interval time-varying delays by constructing a new Lyapunov–Krasovskii functional which includes some integral terms in the form of . Some useful integral inequalities are established for the derivatives of those integral terms introduced in the Lyapunov–Krasovskii functional. A matrix-based quadratic convex approach is introduced to prove not only the negative definiteness of the derivative of the Lyapunov–Krasovskii functional, but also the positive definiteness of the Lyapunov–Krasovskii functional. Some novel stability criteria are formulated in two cases, respectively, where the time-varying delay is continuous uniformly bounded and where the time-varying delay is differentiable uniformly bounded with its time-derivative bounded by constant lower and upper bounds. These criteria are applicable to both static neural networks and local field neural networks. The effectiveness of the proposed method is demonstrated by two numerical examples. [Copyright &y& Elsevier]

This study is concerned with the event‐triggered control for networked control systems via dynamic output feedback controllers (DOFCs). The output measurement signals of the physical plant are sampled periodically. An output‐based discrete event‐triggering mechanism is introduced to choose those only necessary sampled‐data packets to be transmitted through a communication network for controller design. Under this event‐triggering mechanism, the resultant closed‐loop system is first modelled as a linear system with an interval time‐varying delay. Then a novel stability criterion is established by employing the Lyapunov–Krasovskii functional approach. Based on this stability criterion, a new sufficient condition is derived to co‐design both the desired DOFCs and the event‐triggering parameters. Finally, a satellite control system is taken to show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

SUMMARY This paper studies the stability of linear systems with interval time-varying delays. By constructing a new Lyapunov-Krasovskii functional, two delay-derivative-dependent stability criteria are formulated by incorporating with two different bounding techniques to estimate some integral terms appearing in the derivative of the Lyapunov-Krasovskii functional. The first stability criterion is derived by using a generalized integral inequality, and the second stability criterion is obtained by employing a reciprocally convex approach. When applying these two stability criteria to check the stability of a linear system with an interval time-varying delay, it is shown through some numerical examples that the first stability criterion can provide a larger upper bound of the time-varying delay than the second stability criterion. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: This paper is concerned with the network-based filtering for a stochastic system, where data transmission from the stochastic system to a filter is completed via a communication network. Network-induced delays, packet dropouts and packet disorders are unavoidable due to the use of the network. First, a logic zero-order-hold (ZOH) is designed to discard the disordered packets actively. The network-induced delays and packet dropouts are modeled as an interval time-varying delay. By decomposing the delay interval into subintervals uniformly, the filter to be designed is modeled as a Markov jumping filter with modes governed by a Markov chain. In order to work out the transition rate from one mode to another, a logic jumping-like trigger is embedded into the logic ZOH to simulate the switching of the Markov process. Second, based on the Markov jumping filter model together with a new integral inequality in the stochastic setting, a novel bounded real lemma is presented to ensure that the resultant filtering error system is mean exponentially stable with a prescribed performance. Then, a sufficient condition on the existence of desired Markov jumping filters is provided in terms of a set of linear matrix inequalities. Finally, an air vehicle system is employed to show effectiveness of the proposed design method. [Copyright &y& Elsevier]

This correspondence is concerned with network-based H∞ filtering for discrete-time systems. The output signals of the system under consideration are transmitted to the filter through a constraint communication network, which usually leads to network-induced delays and packet dropouts. By introducing a logic data packet processor to choose the newest data signal from the network to actuate the filter, network-induced delays and packet dropouts are modeled as a Markov chain taking values in a finite set. As a result, the filter to be designed is modeled as a Markov jumping linear filter. By introducing some slack matrix variables in terms of probability identity, a less conservative bounded real lemma (BRL) is derived to ensure that the filtering error system is stochastically stable with a prescribed H∞ level. Based on this BRL, suitable H∞ filters are designed by employing a cone complementary approach. A practical example on the Leslie model about some certain pest's structured population dynamics is given to show the effectiveness of the proposed approach. [ABSTRACT FROM PUBLISHER]

This paper is concerned with global asymptotic stability for a class of generalized neural networks (NNs) with interval time-varying delays, which include two classes of fundamental NNs, i.e., static neural networks (SNNs) and local field neural networks (LFNNs), as their special cases. Some novel delay-independent and delay-dependent stability criteria are derived. These stability criteria are applicable not only to SNNs but also to LFNNs. It is theoretically proven that these stability criteria are more effective than some existing ones either for SNNs or for LFNNs, which is confirmed by some numerical examples. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the effect of a small time-delay on dynamic output feedback control of an offshore steel jacket structure subject to a nonlinear wave-induced force. First, a conventional dynamic output feedback controller is designed to reduce the internal oscillations of the offshore structure. It is found that the designed controller is of a larger gain in the sense of Euclidean norm, which demands a larger control force. Second, a small time-delay is introduced intentionally to design a new dynamic output feedback controller such that (i) the controller is of a small gain in the sense of Euclidean norm and (ii) the internal oscillations of the offshore structure can be dramatically reduced. It is shown through simulation results that purposefully introducing time-delays can be used to improve control performance. [Copyright &y& Elsevier]

The non-classical KP6Mo18O73heteropolyanion has been studied by the density functional theory (DFT) method, and the calculated geometry compares well with the experimental one. In fully oxidized [KP6Mo18O73]7−state, the dxy-orbitals centered at eight “belt” Mo sites in the lower part of the “basket” are the major contributors to the LUMO and LUMO+1, while the LUMO+2 orbital is mostly focused on the two polar parts. In contrast, the HOMOs indicates that the coordination of the KP6Mo18heteropolyanion to metal ions favorably occurs at the oxygen atoms from four external phosphates and two molybdates of the handle of the “basket”. Compared with Wells–Dawson [P2Mo18O62]6−, the HOMO–LUMO gap in fully oxidized [KP6Mo18O73]7−is much smaller, indicating much easier reduction that is consistent with the cyclic voltammogram. Both frontier orbitals and Mulliken analysis indicate that two of three blue electrons in [KP6Mo18O73]10−(KP6Mo18-3e) have spin alpha while third blue electron has spin beta, in agreement with magnetic data. The four-copper complex of the non-classical KP6Mo18-3e heteropolyanion has been synthesized and structurally characterized; its structure supports the theoretical results such as reactivity and basicity of external oxygen sites. [ABSTRACT FROM AUTHOR]

The non-classical KP6Mo18O73heteropolyanion has been studied by the density functional theory (DFT) method, and the calculated geometry compares well with the experimental one. In fully oxidized [KP6Mo18O73]7−state, the dxy-orbitals centered at eight “belt” Mo sites in the lower part of the “basket” are the major contributors to the LUMO and LUMO+1, while the LUMO+2 orbital is mostly focused on the two polar parts. In contrast, the HOMOs indicates that the coordination of the KP6Mo18heteropolyanion to metal ions favorably occurs at the oxygen atoms from four external phosphates and two molybdates of the handle of the “basket”. Compared with Wells–Dawson [P2Mo18O62]6−, the HOMO–LUMO gap in fully oxidized [KP6Mo18O73]7−is much smaller, indicating much easier reduction that is consistent with the cyclic voltammogram. Both frontier orbitals and Mulliken analysis indicate that two of three blue electrons in [KP6Mo18O73]10−(KP6Mo18-3e) have spin alpha while third blue electron has spin beta, in agreement with magnetic data. The four-copper complex of the non-classical KP6Mo18-3e heteropolyanion has been synthesized and structurally characterized; its structure supports the theoretical results such as reactivity and basicity of external oxygen sites. [ABSTRACT FROM AUTHOR]

Abstract: The mechanism of the Ni-mediated coupling reaction of CO2 with epoxyethane has been extensively investigated by the density functional theory (DFT) calculations. All the possible pathways are examined, and their corresponding energetics are demonstrated. On the basis of the comparison of three mechanisms, it is determined that the preferred mechanism for the catalytic production of cyclic carbonate can be divided into three main steps involving epoxide oxidative addition, carbon dioxide insertion, and reductive elimination of cyclic carbonate (route IC), none of which contains significantly large barriers. The overall reaction is exothermic and the rate-determining step is associated with the reductive elimination of cyclic carbonate from the six-membered metallacyclic intermediate 15. All reaction pathways with solvent effects taken into consideration have been studied by means of a PCM-UAHF model. The calculations indicate that the introduction of solvent effects does not change the general trends for the reaction potential energy surfaces. Our results provide a theoretical support for the reaction mechanism proposed from previous experimental observations. At the same time, the present theoretical study gives a clear profile for the cycloaddition of carbon dioxide with epoxyethane promoted by (Ph3P)2Ni. [Copyright &y& Elsevier]

Abstract: This paper deals with the problem of delay-dependent robust filtering for uncertain linear systems with time-varying delay. Two cases of time-varying delays are fully considered; one is the time-varying delay being continuous uniformly bounded while the other is the time-varying delay being differentiable uniformly bounded with delay-derivative bounded by a constant. A stable linear filter is designed to ensure that the filtering error system is asymptotically stable with a prescribed level of noise attenuation. Based on a new integral inequality, delay-dependent sufficient conditions for the existence of such a filter are established in terms of linear matrix inequalities (LMIs). Through deriving these conditions, neither model transformation nor bounding technique for cross terms is employed. Moreover, the relationship between the sufficient conditions for the two cases of time-varying delay is disclosed. Finally, two examples are also given to illustrate the effectiveness of the proposed methodology. [Copyright &y& Elsevier]

Abstract: The integral-inequality method is a new way of tackling the delay-dependent stabilization problem for a linear system with time-varying state and input delays: . In this paper, a new integral inequality for quadratic terms is first established. Then, it is used to obtain a new state- and input-delay-dependent criterion that ensures the stability of the closed-loop system with a memoryless state feedback controller. Finally, some numerical examples are presented to demonstrate that control systems designed based on the criterion are effective, even though neither nor is stabilizable. [Copyright &y& Elsevier]

Abstract: Hydro(solvo)thermal in situ ligand synthesis has rapidly developed over the past several years due to its effectiveness, simplicity and environmental friendliness. More than 10 types of in situ ligand reactions have been enumerated, which include carbonnd formation, hydroxylation, tetrazole formation, triazole formation, substitution, alkylation, ether bond formation, hydrolysis, oxidation–hydrolysis, acylation, amination and decarboxylation. Hydrothermal in situ ligand synthesis has become a powerful approach in the crystal engineering of coordination complexes and in organic synthesis, and is becoming an alternative approach in the isolation of organic isomers. In the crystal engineering of coordination complexes, in situ ligand synthesis is suitable to prepare novel coordination complexes from metal ions and organic precursors and most of these complexes are not accessible from a direct reaction of metal ions and ligands. In organic synthesis, hydrothermal in situ ligand syntheses have become very useful pathways to organic ligands, which are difficult to obtain by routine synthetic methods. In isolating organic isomers, in situ ligand synthesis is becoming an alternative route because in some special cases, only one of the several isomers of a ligand is found in crystalline complexes involving in situ ligand reactions. [Copyright &y& Elsevier]

Abstract: Three new metal pyridinecarboxylates, namely [Co2(pydc)2(H2O)5] (1), [Mn(pydc)(H2O)2] (2) and [Cd2(OH)2(2,4-pydc)] (3), were hydrothermally synthesized. X-ray single crystal structural analysis revealed: 1 and 2 have polymeric one-dimensional chain-like structure constructed by dinuclear cobalt units and Mn–O chains, respectively; 3 has a three-dimensional layer pillared structure constructed from inorganic Cd–O layer and pydc pillars. 1 shows antiferromagnetic interaction but 2 shows alternative antiferromagnetic and ferromagnetic interactions. [Copyright &y& Elsevier]

Purpose: In our previous study, quercetin was found to induce apoptosis of murine melanoma B16-BL6 cells. The cellular and molecular mechanism of quercetin-induced apoptosis was investigated in the present study.Methods: Nuclear morphology was determined by fluorescence microscopy. DNA fragmentation was analyzed by electrophoresis and quantified by the diphenylamine method. The transmembrane potential of mitochondria was measured by flow cytometry. Bcl-2, Bcl-X(L), PKC-alpha, PKC-beta, and PKC-delta were detected by Western blotting. Caspase activity was determined spectrophotometrically.Results: Quercetin induced the condensation of nuclei of B16-BL6 cells in a dose-dependent pattern as visualized by Hoechst 33258 and propidium iodide dying. Phorbol 12-myristate 13-acetate (PMA), a PKC activator, significantly enhanced apoptosis induced by quercetin, while doxorubicin, a PKC inhibitor, markedly decreased it. Both PMA and doxorubicin showed a consistent effect on the fragmentation of nuclear DNA caused by various dosages of quercetin. Quercetin dose-dependently led to loss of the mitochondrial membrane potential, which was also significantly reinforced or antagonized by PMA and doxorubicin, respectively. Moreover, PMA showed reinforcement, while doxorubicin showed significant antagonization, of the quercetin-mediated decrease in the expression of Bcl-2. Quercetin promoted caspase-3 activity in a dose-dependent manner, which was also regulated by PMA and doxorubicin with a pattern similar to that seen in their effect on apoptosis, mitochondrial membrane potential and Bcl-2 expression, but none of these were directly affected by PMA and doxorubicin. Free fatty acid and chlorpromazine, a PKC activator and inhibitor, respectively, did not interfere with these effects of quercetin. B16-BL6 cells expressed PKC-alpha, PKC-beta, and PKC-delta. Quercetin dose-dependently inhibited the expression of PKC-alpha but not that of PKC-beta and PKC-delta. Doxorubicin almost completely blocked the effect of quercetin on the expression of PKC-alpha. Quercetin was also involved in the translocation of PKC-delta from the cytosol to the nucleus. PMA enhanced the effect of quercetin on the translocation of PKC-delta.Conclusions: These results indicate that quercetin induced apoptosis of murine melanoma B16-BL6 cells by injuring their mitochondria, increasing the activity of caspase-3, inhibiting the expression of Bcl-2 and PKC-alpha, and inducing the translocation of PKC-delta. Doxorubicin inhibited these effects of quercetin by blocking the decreased expression of PKC-alpha induced by quercetin while PMA increased these effects by enhancing the translocation of PKC-delta induced by quercetin. [ABSTRACT FROM AUTHOR]

Three cluster-based coordination polymers, namely [Zn3(bpy)3(hip)2] · 5H2O (1), [Co3(bpy)3(hip)2] · 5H2O (2) and [Cd3(bpy)3(hip)2] (3) (bpy=2,2′-bipyridine, hip=4-hydroxyl-isophthalate) were synthesized and structurally characterized. X-ray single-crystal structural analyses revealed that both 1 and 2 crystallize in the chiral space group P21, while 3 crystallizes in the centric space group Pccn. Compounds 1 and 2 are isomorphous and both have (4,4) topological layered structures constructed from trinuclear metal clusters. Compound 3 also shows layered structure of (4,4) topology constructed from trinulear Cd(II) cores. The layers are stacked in a staggered ⋯ABAB⋯ fashion in 1 and 2 but in an overlapped ⋯AAA⋯ fashion in 3. There are two types of coordination modes of hip ligand in 1 and 2 but only one in 3. The structural difference between 1 (or 2) and 3 may be attributed to the difference of metal ion nature such as the ionic radius and coordination preference, resulting in the different orientation fashions of the auxiliary bpy ligands, stacking fashions of the layers, as well as chirality of the crystals. The chiral structures of 1 and 2 were also confirmed by measurements of powder second-harmonic-generation (SHG) measurements, which show that 1 and 2 have SHG intensity of 0.50 and 0.02 relative to that of urea, respectively. [Copyright &y& Elsevier]

Purpose. On the basis of the inhibitory effect of quercetin on the invasion of melanoma B16-BL6 cells previously reported by us, the mechanisms of quercetin-mediated inhibition of invasion were further investigated in the present study. Methods. The ability of B16-BL6 cells to invade and migrate was evaluated in terms of the numbers of cells penetrating a reconstituted basement membrane in the Transwell coculture system. The relative levels and activities of matrix metalloproteinase-9 (MMP-9) and MMP-2 were determined by gelatin zymography and quantified using LabWorks 4.0 software. Results. The quercetin-mediated inhibition of invasion was partially blocked by phorbol-12,13-dibutyrate (PDB), a PKC (protein kinase C) activator, and by doxorubicin, a PKC inhibitor. Only the proforms of MMP-9 (92 kDa) and MMP-2 (72 kDa) were detected by gelatin zymography. Quercetin dose-dependently decreased the gelatinolytic activity of pro-MMP-9. Doxorubicin also markedly reversed the quercetin-induced decrease. Quercetin showed a dose-dependent antagonism of increases in gelatinolytic activity of pro-MMP-9 induced by PDB and free fatty acid (another PKC activator). Conclusions. Together with the report that quercetin directly reduces PKC activity, the results reported here suggest that quercetin may inhibit the invasion of B16-BL6 cells by decreasing pro-MMP-9 via the PKC pathway. [ABSTRACT FROM AUTHOR]

Two two-dimensional inorganic–organic hybrid materials formulated as [{Cu(phen)}2(VVO2)2VIVO2(H2O)(PO4)2] 1 and [V4O7(2,2′-bpy)2(HPO4)2] 2 have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. Both crystallize in the triclinic space group P1¯ (no. 2), with cell parameters a=8.118(3), b=9.272(3), c=10.348(5) A˚, α=96.71(1), β=100.97(1), γ=104.66(1)°, V=728.5(5) A˚3, Z=1 for 1 and a=8.402(4), b=9.270(5), c=9.676(7) A˚, α=97.10(1), β=110.29(1), γ=98.92(1)°, V=685.4(7) A˚3, Z=1 for 2. The structure of 1 is analogous to that of [{Cu(phen)}2(VVO2)3(OH)(PO4)2] (1′) and consists of [{Cu(phen)}2VIVO6(H2O)]∞ chains that are bridged by {(VO2)(PO4)}2 4-membered rings via oxygen atoms into a two-dimensional network. Compounds 1 and 1′ are isostructural but the oxidization states of vanadium atoms in them are not fully same. Thus, 1 and 1′ are relatively rare examples of all V(V) and V(V)/V(IV) mixed valence analogues in the solid state. Compound 2 is also relatively uncommon and features 2,2′-bipy ligands directly coordinated to vanadium atoms. The structure of 2 is constructed by 4-, 6- and 8-membered rings and is topologically relevant to [V3O7(phen)]. The temperature-dependent magnetic susceptibility of 1 shows alternating ferro- and antiferromagnetic interactions. [Copyright &y& Elsevier]

The reaction of Ag2O and carboxylate ligands in ammonium solution results in three coordination polymers, [Ag(fbc)]n 1, [Ag2(cpd)]n 2 and [Ag2(idc)]n 3, where fbcH is 4-fluorobenzoic acid, cpdH2 is cyclopentane-1,1-dicarboxylic acid and idcH2 is iminodiacetic acid. The X-ray crystal structural analysis indicates that compounds 1 and 2 are two-dimensional frameworks and 3 is a three-dimensional framework. All the three complexes show clear Ag–Ag bonds and high cytotoxicity properties to normal cells and carcinoma cells. [Copyright &y& Elsevier]

Two compounds (NH4)2[M(dod)(H2O)4]2V10O28·6H2O (M = Zn, Mn) have been prepared in aqueous medium. X-ray single-structure analyses reveal that they are isostructural and crystallize in the triclinic space group P1. The structures of the two compounds consist of decavanadate anionic clusters and dimeric [M(dod)(H2O)4]24+ units, in which the two oxygen atoms from dod ligands ligating M2+ are in a cis fashion. There are a variety of hydrogen bonds including O–H⋯O and N–H⋯O among lattice water molecules, ammonium cations, oxygen atoms of decavanadate and oxygen atoms of dod, which extend the structures into three-dimensional supramolecular arrays. [Copyright &y& Elsevier]

Hybrid metal halides (HMHs) have emerged as a promising platform for optically functional crystalline materials, but it is extremely challenging to thoroughly elucidate the electron transition coupled to additional ligand emission. Herein, to discover sequences of lead‐free HMHs with distinct optically active metal cations are aimed, that is, Sb3+ (5s2) with the lone‐pair electron configuration and In3+ (4d10) with the fully‐filled electron configuration. (Me2NH2)4MCl6·Cl (Me = −CH3, M = Sb, In) exhibits the superior temperature/component‐dependent luminescence behaviors resulting from the competition transition between triplet‐states (Tn‐S0) self‐trapped excitons (STEs) of inorganic units and singlet‐state (S1‐S0) of organic cations, which is manipulated by the optical activity levels of [SbCl6]3− and [InCl6]3−. The bonding differences between Sb3+/In3+ and Cl− in terms of electronic excitation and hybridization are emphasized, and the different electron‐transition mechanisms are established according to the PL spectra at the extreme temperature of 5 to 305 K and theoretical calculations. By fine‐tuning the B‐site Sb3+/In3+ alloying, the photoluminescence quantum yield (PLQY = 81.5%) and stability are optimized at 20% alloying of Sb3+. This research sheds light on the rules governing PL behaviors of HMHs, as well as exploring the optical‐functional application of aviation temperature sensors and access‐control systems. [ABSTRACT FROM AUTHOR]

Hybrid ns2 metal halides have attracted extensive attention due to the unique photophysical behavior. However, the reasonable improvement of photoluminescence efficiency by accurate structural modulation remains a great challenge. Herein, two kind of antimony halides with formulae as (S)/(R)‐[C6H16N2]3[SbCl5]2·2Cl ((S)/(R)‐1·2Cl) and (S)/(R)‐[C6H16N2]2[SbCl5]2 ((S)/(R)‐2) ([C6H16N2]2+ = 1,2‐Diaminocyclohexane) are developed, in which 0D [Sb4Cl20]8− clusters and 1D infinite [SbCl5]n2n− polyanion chains are adopted, respectively. The stoichiometric tunability enables metastable (S)/(R)‐1·2Cl being transformed to dynamic stable (S)/(R)‐2. All compounds contain a large number of Sb─Cl secondary bonds because of the strong chemical activity of 5s2 electrons. The obtained compounds exhibit broadband orange‐light emission, while photoluminescence quantum yield of (S)/(R)‐2 is significantly enhanced to ≈76% due mainly to the generation of more localized electrons onto 1D chains. Experimental and computational results reveal that efficient broadband emission derives from the synergistic emission of singlet and triplet states, where the presence of shallow trap energy levels leads to anti‐thermal quenching behavior. Furthermore, the highly efficient photoluminescence property allows (S)‐2 to become excellent down‐conversion phosphor for white‐light emitting diode. This work proves that exploring structure‐property relationship in hybrid systems is helpful in promoting the rapid development of high‐performance broadband emission metal halides. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The photocatalytic oxidative coupling of thiols is one of the most popular methods to synthesize the disulfides. Triphenylamine and its derivatives (TPAs) are promising for the above reaction, but suffer from the easy polymerization and difficult separation. To overcome these obstacles while controlling the photogenerated electrons transfer directly to target substrates, herein, we constructed one TPA‐based metal‐organic framework (MOF), (Me2NH2)[Sr(TCBPA)]·DMA·3H2O (1), by direct self‐assembly of tris(4′‐carboxybiphenyl)amine (H3TCBPA) and photoredox inert strontium ion (Sr2+). DFT calculations revealed that the valence band maximum (VBM) and the conduction band minimum (CBM) are mainly located on TCBPA3–, successfully inhibiting the undesirable electron migration to metal nodes. Experimental results indicated that 1 displays superior performance than homogeneous H3TCBPA, which may result from the abundant π···π and C—H···π interactions between the well‐arranged TCBPA3– and the build‐in electric field between the anionic framework and the Me2NH2+. This work highlights that immobilizing TPAs into MOFs is one promising approach to designing heterogeneous photocatalysts for the synthesis of disulfides by oxidative coupling of thiols. [ABSTRACT FROM AUTHOR]

This paper is concerned with sufficient conditions for a class of matrix-valued polynomial inequalities on closed intervals and their application to H ∞ filtering for linear systems with time-varying delays. First, a class of higher degree matrix-valued polynomial inequalities are transformed into the first degree matrix-valued polynomial inequalities by introducing some slack matrices. As a result, a convex property is applied to derive sufficient conditions for a class of higher degree matrix-valued polynomial inequalities on closed intervals. Second, by choosing a Lyapunov–Krasovskii functional with a quadratic matrix-valued polynomial on a time-varying delay, and estimating its time-derivative as a third-degree matrix-valued polynomial on the time-varying delay, the proposed sufficient conditions are utilized to formulate a novel bounded real lemma on the existence of H ∞ filters for time-delay systems. Third, some algorithms to filter design are provided and discussed in detail. It is pointed out that, if the filter gain is derived through a generalized inverse matrix method, it may be a fake solution, which is demonstrated through a liquid monopropellant rocket motor with a pressure feeding system. [ABSTRACT FROM AUTHOR]

The thermal design of natural convection heat sinks is critical to the heat management of electronic devices. In this paper, topology optimization (TO) with a new parameter advancing scheme is employed to study the effect of the heating power, heat source size, allowed volume and material thermal conductivity on the optimized design of natural convection heat sinks. Except for the heating power, the other three factors also play an important role on the optimization results. For the small heating power, TO predicts the tree-like heat sink with many secondary-branches to improve heat conduction, but the specific structure is highly dependent on the heat source size, allowed volume and material thermal conductivity. For the large heating power, TO prefers to produce the taper-like heat sink where the tiny branches fade away to adapt to the strong flow, and the influences of the other three factors are reduced. However, two primary branches that connect the heat source and top corners of the design domain always exist, indicating that they are the most effective ways to improve heat transfer. This work has highlighted the impact of different parameters in TO of natural convection heat sinks and provides a more in-depth understanding of the design guidelines. [ABSTRACT FROM AUTHOR]