Following the cat: A preface for the next three papers

The three papers to follow, by Chris Rasmussen and three of his students, build from a task design the authors of this note developed in the 1990s. To introduce these papers, which extend our prior work in new directions, we sketch some background here.     

Connecting mem-models with classical theories

A family of mem-models, including the mem-dashpots, mem-springs, and most recently, mem-inerters, is emerging as a new and powerful way of capturing complex nonlinear behaviors of materials and systems under various types of dynamic loads involving different frequency, amplitude, and loading histories (e.g., hysteresis). Under the framework of nonlinear state-space representation and hybrid dynamical systems, mem-springs may be formulated to effectively represent an inherent degradation of material state. It is shown in this study, for the first time, how the absement (time integral of strain/displacement), a signature state variable for a mem-spring, can be connected with the damage variable, a key quantity in continuum damage mechanics. The generalized momentum (time integral of stress), on the other hand, is shown to be efficient in modeling strain ratcheting via the concept of mem-dashpot. It is also shown in this study, for the first time, how two formulations of the memcapacitive system models (for mem-springs) are special cases of the Preisach model.

     

Shape Matters: A Gold Nanoparticle Enabled Shape Memory Polymer Triggered by Laser Irradiation

With incorporation of gold nanoparticles, i.e., nanorods (AuNR) and nanospheres (AuNS), into a polyurethane‐based shape‐memory polymer (SMP) EG‐72D matrix, SMP nanocomposite films capable of being remotely triggered by low‐power laser are fabricated and characterized using UV‐vis‐NIR spectroscopy, X‐ray scattering, and dynamic mechanical analysis (DMA). It is demonstrated that, with incorporation of very low concentration of gold nanorods (≈0.1 wt%), the mechanically programmed EG‐72D/AuNR nanocomposite presents rapid response to low power laser irradiation (785 nm, ≈10 mW). Comparative studies on the laser irradiation response of EG‐72D/AuNS and EG‐72D/AuNR nanocomposite films suggest that AuNRs have significantly higher photothermal conversion efficiency than AuNS and on‐resonance laser irradiation, matching the wavelength of the incident laser with the longitudinal plasmon resonance of AuNR, is necessary to induce the fast response of gold nanoparticle enabled SMP nanocomposites.     

Synthesis of some heterocyclic skeletons via organoiron complexes. Crystal and molecular structure of (5a,6,7,8,9,9a-η6-1,4-benzoxathiino[3,2-b]pyridine)(η5-cyclopentadienyl)iron hexafluorophosphate

Synthesis of the heterocyclic skeletons of some biologically active compounds from (η⁶-o-dichlorobenzene)(η⁵-cyclopentadienyrl)iron hexafluorophosphate in a two step procedure is described. Cyclopentadienyliron hexafluorophosphate complexes of 1,4-benzodioxino[2,3-b]pyridine, 1,4-benzoxathiino[3,2-b]pyridine, 10H-pyrido[3,2-b]benzoxazine, benzo[b]naphtho[2,3-e][1,4]dioxin, 4-methylbenzo[b]benzopyran-2-one[7,6-e][1,4]dioxin and benzo[b]anthracen-9,10-diono[1,2-e][1,4]dioxin were isolated and characterized. Upon pyrolytic sublimation of these complexes the free heterocycles were obtained and characterized. (η⁶-1,4-Benzoxathiino[3,2-b]pyridine)(η⁵-cyclopentadienyl)iron hexafluorophosphate crystalizes in the orthothombic system, space group Pbca; the dihedral angle between the planes of outer rings was found to be 176.8 (1).     

Air-stable titanium alkoxide based metal-organic framework as an initiator for ring-opening polymerization of cyclic esters

An air-stable titanium-organic framework, prepared from Ti(OiPr)4 and 1,4-butanediol, has been characterized via single-crystal X-ray diffraction, revealing a unique supramolecular structure. Its functionality as a highly active initiator for the ring-opening polymerization of cyclic esters is demonstrated. A discrete titanium trimer containing the related ligand (2R,3R)-2,3-butanediol has also been prepared, and it shows analogous activity as a polymerization initiator.     

A Finite Element-based Heuristic Estimation of Local Preform Permeability for Resin Transfer Molding

Uniformity of fabrics significantly affects the resin flow behavior in the resin transfer molding (RTM) process. Due to fabric defects or improper fiber preform preparation/loading, non-uniformity in fabric structure frequently occurs in RTM processing and creates local permeability variations. Such variations often lead to unbalanced resin flow patterns and thus result in defects of finished composite parts. In RTM process modeling, an accurate estimation of the whole field permeability profile of the fiber preform is critical for predicting resin flow pattern correctly. In this article, a finite element-based heuristic computing method is introduced for estimating the in situ whole-field isotropic permeability profile of the preform using a steady flow of gas. Compared with conventional approaches, this method is effective in measuring local permeability variations and applicable to molds with complex 2-D geometries, as well as diverse injection strategies. Several case studies were presented with experimental designs and numerical computations to illustrate the effectiveness and efficiency of the method.     

A novel approach to synthesis of the cinnoline ring system via organoiron(cyclopentadienyl) complexes

An efficient synthesis of 3-mono or 3,4-disubstituted cinnolines from (o-dichlorobenzene)(cyclopentadienyl)iron hexafluorophosphate in three or four steps has been achieved. o-Chlorophenyl-alkyl or alkylaryl ketone complexes obtained from the o-dichlorobenzene complex upon treatment with enolate anions, react with hydrazine forming 3-mono or 3,4-disubstituted 1,4-dihydrocinnoline complexes. Treatment of the later with sodium amide leads to an aromatization-demetallation reaction resulting in formation of cinnolines, i.e. 3-methyl-, 3-phenyl- and 3,4-dimethylcinnoline. The influence of substituents bonded to the carbon atom adjacent to the complexed benzene ring in o-chlorophenyl -alkyl or -alkylaryl ketone prior to cyclization on the cyclization reaction is discussed.     

Silver phosphanes partnered with carborane monoanions: synthesis, structures and use as highly active Lewis acid catalysts in a hetero-Diels-Alder reaction

Four Lewis acidic silver phosphane complexes partnered with [1-closo-CB(11)H(12)](-) and [1-closo-CB(11)H(6)Br(6)](-) have been synthesised and studied by solution NMR and solid-state X-ray diffraction techniques. In the complex [Ag(PPh(3))(CB(11)H(12))] (1), the silver is coordinated with the carborane by two stronger 3c-2e B-H-Ag bonds, one weaker B-H-Ag interaction and a very weak Ag.C(arene) contact in the solid state. In solution, the carborane remains closely connected with the [Ag(PPh(3))](+) fragment, as evidenced by (11)B chemical shifts. Complex 2 [Ag(PPh(3))(2)(CB(11)H(12))](2) adopts a dimeric motif in the solid state, each carborane bridging two Ag centres. In solution at low temperature, two distinct complexes are observed that are suggested to be monomeric [Ag(PPh(3))(2)][CB(11)H(12)] and dimeric [Ag(PPh(3))(2)(CB(11)H(12))](2). With the more weakly coordinating anion [CB(11)H(6)Br(6)](-) and one phosphane, complex 3 [Ag(PPh(3))(CB(11)H(6)Br(6))] is isolated. Complex 4, [Ag(PPh(3))(2)(CB(11)H(6)Br(6))], has been characterised spectroscopically. All of the complexes have been assessed as Lewis acids in the hetero-Diels-Alder reaction of N-benzylideneaniline with Danishefsky's diene. Exceptionally low catalyst loadings for this Lewis acid catalysed reaction are required (0.1 mol %) coupled with turnover frequencies of 4000 h(-1) (quantitative conversion to product after 15 minutes using 3 at room temperature). Moreover, the reaction does not occur in rigorously dry solvent as addition of a substoichiometric amount of water (50 mol %) is necessary for turnover of the catalyst. It is suggested that a Lewis assisted Br?nsted acid is formed between the water and the silver. The effect of changing the counterion to [BF(4)](-), [OTf](-) and [ClO(4)](-) has also been studied. Significant decreases in reaction rate and final product yield are observed on changing the anion from [CB(11)H(6)Br(6)](-), thus demonstrating the utility of weakly coordinating carborane anions in organic synthesis.     

Determination of metal ion content of beverages and estimation of target hazard quotients: a comparative study

Background  

Considerable research has been directed towards the roles of metal ions in nutrition with metal ion toxicity attracting particular attention. The aim of this study is to measure the levels of metal ions found in selected beverages (red wine, stout and apple juice) and to determine their potential detrimental effects via calculation of the Target Hazard Quotients (THQ) for 250 mL daily consumption.