General energy decay of solutions for a weakly dissipative Kirchhoff equation with nonlinear boundary damping

In this article, we study the weak dissipative Kirchhoff equation \({u_{tt}} - M\left( {\left\| {\nabla u} \right\|_2^2} \right)\Delta u + b\left( x \right){u_t} + f\left( u \right) = 0\), under nonlinear damping on the boundary \(\frac{{\partial u}}{{\partial v}} + \alpha \left( t \right)g\left( {{u_t}} \right) = 0\). We prove a general energy decay property for solutions in terms of coefficient of the frictional boundary damping. Our result extends and improves some results in the literature such as the work by Zhang and Miao (2010) in which only exponential energy decay is considered and the work by Zhang and Huang (2014) where the energy decay has been not considered.     

Microwave-assisted,regioselective one-pot synthesis of quinolines and bis-quinolines catalyzed by Bi(III) immobilized on triazine dendrimer stabilized magnetic nanoparticles

Fe₃O₄-TDSN-Bi(III) was utilized as an efficient and reusable catalyst for the regioselective one-pot synthesis of quinoline derivatives from arylamines, arylaldehydes and methyl propiolate under microwave irradiation and solvent-free conditions. Also, bis-quinolines were obtained in high yields from dialdehydes or diamines. Atom-economy, high to excellent yields, easy work-up, as well as simple catalyst recovery and reusability are the key features of this procedure.     

Direct profiling of the phospholipid composition of adult <Emphasis Type="Italic">Caenorhabditis elegans</Emphasis> using whole-body imaging mass spectrometry

A protocol for the direct analysis of the phospholipid composition in the whole body of adult soil nematode, Caenorhabditis elegans (C. elegans), was developed, which combined freeze-cracking of the exoskeletal cuticle and matrix-assisted laser desorption/ionization-imaging mass spectrometry (MALDI-IMS). Biomolecules in the m/z range from 700 to 900 were more effectively detected in the freeze-cracked than from simple frozen adult nematode bodies. Different distribution of biomolecules was observed in a nematode body when the matrix was applied with a sublimation deposition method. The whole-body IMS technique was applied on genetically deficient mutant C. elegans to combine whole-body lipidomics and genetics, by comparing the fatty acid compositions, especially of the phosphatidylcholine (PC) species, between the wild-type and fat-1 mutants, which lack the gene encoding an n-3 fatty acid desaturase. A significant reduction of PC(20:5/20:5) and PC(20:4/20:5) and a marked increase of PC(20:4/20:4), PC(20:3/20:4), and PC(20:3/20:3) were detected in the fat-1 mutants in positive ion mode. In addition, phospholipid compositions other than PCs were analyzed in negative ion mode. A loss of a possible phosphatidylinositol (PI) with 18:0/20:5 and a compensative accumulation of putative PI(18:0/20:4) were detected in the fat-1 mutants. In conclusion, the whole-body MALDI-IMS technique is useful for the profiling of multiple biomolecules in C. elegans in both intra- and inter-individual levels.     

Synthesis of Polybenzoquinolines as Precursors for Nitrogen‐Doped Graphene Nanoribbons

Graphene nanoribbons (GNRs) represent promising materials for the next generation of nanoscale electronics. However, despite substantial progress towards the bottom‐up synthesis of chemically and structurally well‐defined all‐carbon GNRs, strategies for the preparation of their nitrogen‐doped analogs remain at a nascent stage. This scarce literature precedent is surprising given the established use of substitutional doping for tuning the properties of electronic materials. Herein, we report the synthesis of a previously unknown class of polybenzoquinoline‐based materials, which have potential as GNR precursors. Our scalable and facile approach employs few synthetic steps, inexpensive commercial starting materials, and straightforward reaction conditions. Moreover, due to the importance of quinoline derivatives for a variety of applications, the reported findings may hold implications across a diverse range of chemical and physical disciplines.     

Tracing Binding Modes in Hit‐to‐Lead Optimization: Chameleon‐Like Poses of Aspartic Protease Inhibitors

Successful lead optimization in structure‐based drug discovery depends on the correct deduction and interpretation of the underlying structure–activity relationships (SAR) to facilitate efficient decision‐making on the next candidates to be synthesized. Consequently, the question arises, how frequently a binding mode (re)‐validation is required, to ensure not to be misled by invalid assumptions on the binding geometry. We present an example in which minor chemical modifications within one inhibitor series lead to surprisingly different binding modes. X‐ray structure determination of eight inhibitors derived from one core scaffold resulted in four different binding modes in the aspartic protease endothiapepsin, a well‐established surrogate for e.g. renin and β‐secretase. In addition, we suggest an empirical metrics that might serve as an indicator during lead optimization to qualify compounds as candidates for structural revalidation.     

Molecular docking studies and in vitro cholinesterase enzyme inhibitory activities of chemical constituents of Garcinia hombroniana

Garcinia species are reported to possess antimicrobial, anti-inflammatory, anticancer, anti-HIV and anti-Alzheimer's activities. This study aimed to investigate the in vitro cholinesterase enzyme inhibitory activities of garcihombronane C (1), garcihombronane F (2), garcihombronane I (3), garcihombronane N (4), friedelin (5), clerosterol (6), spinasterol glucoside (7) and 3β-hydroxy lup-12,20(29)-diene (8) isolated from Garcinia hombroniana, and to perform molecular docking simulation to get insight into the binding interactions of the ligands and enzymes. The cholinesterase inhibitory activities were evaluated using acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. In this study, compound 4 displayed the highest concentration-dependent inhibition of both AChE and BChE. Docking studies exhibited that compound 4 binds through hydrogen bonds to amino acid residues of AChE and BChE. The calculated docking and binding energies also supported the in vitro inhibitory profiles of IC₅₀. In conclusion, garcihombronanes C, F, I and N (1–4) exhibited dual and moderate inhibitory activities against AChE and BChE.     

Cesium carbonate supported on hydroxyapatite coated Ni0.5Zn0.5Fe2O4 magnetic nanoparticles as an effi cient and green catalyst for the synthesis of pyrano[2,3-c]pyrazoles

Cesium carbonate supported on hydroxyapatite coated Ni0.5Zn0.5Fe2O4 magnetic nanoparticles (Ni0.5Zn0.5Fe2O4@Hap-Cs2CO3) was found to be magnetically separable, highly efficient, green and recyclable heterogeneous catalyst. The synthesized nanocatalyst has been characterized with several methods (FT-IR, SEM, TEM, XRD and XRF) and these analyzes confirmed which the cesium carbonate is well supported to catalyst surface. After full characterization, its catalytic activity was investigated in the synthesis of pyranopyrazole derivatives and the reactions were carried out at room temperature in 50:50 water/ethanol with excellent yields (88-95%). More importantly, the Ni0.5Zn0.5Fe2O4@Hap-Cs2CO3 was easily separated from the reaction mixture by external magnetic field and efficiently reused at least six runs without any loss of its catalytic activity. Thus, the developed nanomagnetic base catalyst is potentially useful for the green and economic production of organic compounds.     

Equivalent dynamic thermoviscoelastic modeling of ionic polymers

Ionic polymers have attracted considerable attention due to their interesting sensing and actuating behavior which make them a proper choice for use in a wide range of applications including biomimetic robots and biomedical devices. The complicated electro‐chemo‐mechanical dynamics of ionic polymer actuators is a drawback for their applications in functional devices. Therefore, establishing a mathematical model which could effectively predict the actuators' dynamic behavior is of great interest. In this paper, a mathematical model, named equivalent dynamic thermoviscoelastic (EDT) model, based on thermal analogy and beam theory is proposed for dynamic analysis of bending‐type ionic polymer actuators. Then, the developed model is extended for analyzing the performance of the actuator in finite element software. The finite element analysis of the actuator enables consideration of material and geometric nonlinearities and facilitates modeling of functional devices based on the ionic polymer actuators. The proposed modeling approach is validated using experimental data. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of water‐soluble conductive copolymer based on polyaniline

Synthesis and characterization of polyaniline‐grafted poly(styrene‐alt‐maleic anhydride) (PANI‐g‐PSMA) was carried out to obtain conductive comb copolymers with highly improved processability. First, polyaniline (PANI) was prepared in nano‐scale by chemical synthesis under ultrasonic irradiation. Then the poly(styrene‐alt‐maleic anhydride) (PSMA) was synthesized by free radical polymerization. Moreover, the PANI was grafted on the PSMA backbone to prepare a comb‐like conductive copolymer for improving its processability as a new method. The products were characterized by Fourier transform infrared, ultraviolet–visible spectroscopy and X‐ray diffraction patterns. Morphology of the samples was also investigated by scanning electron microscopy images. Finally, the solubility and conductivity of the products were studied, and it resulted in high solubility of the products in water and other common organic solvents in comparison to the pure PANI. Copyright © 2015 John Wiley & Sons, Ltd.     

Surface modification of MWCNTs with glucose and their utilization for the production of environmentally friendly nanocomposites using biodegradable poly(amide‐imide) based on N‐trimellitylimido‐S‐valine matrix

In the present investigation, the preparation, characterization, and surface morphology of poly(amide‐imide) (PAI)/multi‐walled carbon nanotubes (MWCNTs) bionanocomposites (BNCs) were the main goals of the study. At first, an optically active PAI based on S‐valine as a biodegradable segment was synthesized. Then, carboxyl‐modified MWCNTs were functionalized with glucose (f‐MWCNT) as a biological active molecule in a green method to achieve a fine dispersion of f‐MWCNT bundles in the PAI matrix. The existence of S‐valine in the PAI matrix and functionalized MWCNT with glucose resulted in a series of potentially biodegradable nanocomposites. The obtained BNCs were characterized by various techniques. Field emission scanning and transmission electron microscopy micrographs of the composites showed a fine dispersion of f‐MWCNTs in the polymer matrix because of hydrogen bonding and π–π stacking interaction between f‐MWCNTs and polymer functional groups and aromatic moieties. Adding f‐MWCNTs into polymer matrix significantly improved the thermal stability of BNCs because of the increased interfacial interaction between the PAI matrix and f‐MWCNTs and also good dispersion of f‐MWCNT in the polymer matrix. Copyright © 2015 John Wiley & Sons, Ltd.