New Mononuclear Cu(II) Complexes and 1D Chains with 4-Amino-4H-1,2,4-triazole

The crystal structures of two mononuclear Cu(II) NH₂trz complexes [Cu(NH₂trz)₄(H₂O)](AsF₆)₂ (I) and [Cu(NH₂trz)₄(H₂O)](PF₆)₂ (II) as well as two coordination polymers [Cu(μ₂-NH₂trz)₂Cl]Cl·H₂O (III) and [Cu(μ₂-NH₂trz)₂Cl] (SiF₆)_0.5·1.5H₂O (IV) are presented. Cationic 1D chains with bridging bis-monodentate μ₂-coordinated NH₂trz and bridging μ₂-coordinated chloride ligands are present in III and IV. In these coordination polymers, the Cu(II) ions are strongly antiferromagnetically coupled with J = −128.4 cm⁻¹ for III and J = −143 cm⁻¹ for IV (H = −J∑S_iS_i+1), due to the nature of the bridges between spin centers. Inter-chain interactions present in the crystal structures were taken into consideration, as well as g factors, which were determined experimentally, for the quantitative modeling of their magnetic properties.     

Isoconversional kinetic analysis of ring-opening polymerization of ε-caprolactone: Steric influence of titanium(IV) alkoxides as initiators

Four titanium(IV) alkoxides, namely: Ti(IV) n-propoxide (1), Ti(IV) n-butoxide (2), Ti(IV) tert-butoxide (3), and Ti(IV) 2-ethylhexoxide (4), have been used as initiators in the bulk ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). The influence of the alkoxide group on the course of the ROP of ε-CL was investigated by means of ¹H-NMR and differential scanning calorimetry (DSC). The ¹H-NMR spectra confirmed that the ROP reaction of ε-CL proceeded via the widely accepted coordination-insertion mechanism for each of the four initiators. Isoconversional methods have been used to evaluate non-isothermal DSC data via the equations of Friedman, Kissinger-Akahira-Sunose (KAS) and Ozawa-Flynn-Wall (OFW). The kinetic studies showed that the polymerization rate for the four initiators (1-4) was in the order of 1 > 2 ≈ 4 > 3. The lowest activation energies (40–47, 42–44, and 49–52 kJ/mol for the Friedman, KAS and OFW methods respectively) were found in the polymerizations using Ti(IV) n-propoxide (1), while the highest activation energies (84–107, 77–87, and 80–91 kJ/mol for the Friedman, KAS and OFW methods respectively) were obtained using Ti(IV) tert-butoxide (3). Differences in the rates of polymerization and the activation energies amongst the four initiators appeared to be governed mainly by the different degrees of steric hindrance in the initiator structure. These results represent important findings regarding the steric influence of the alkoxide groups on the kinetics of the ROP of ε-CL initiated by titanium(IV) alkoxides.     

Influence of gut microbiota and manipulation by probiotics and prebiotics on host tissue fat: Potential clinical implications

The gut microbiota is considered as one of the most important environmental factors impacting on host metabolism, contributing to variations in body weight, fat distribution, insulin sensitivity and lipid metabolism. Modification of the gut microbiota by dietary interventions such as probiotics and prebiotics may favourably affect host lipid metabolism. We have shown that microbial metabolism in the gut, and its manipulation by administered microbes can influence fatty acid composition of a number of organs in the host. Furthermore, a prebiotic approach was shown to alter polyunsaturated fatty acids in white adipose tissue. Although a deeper knowledge of the interactions between members of the gut microbiota and fatty acids is needed, nutritional modulation of this complex community may represent a realistic target for modification of host fatty acid composition.     

Mathematical modelling of test limits and guardbands

To gain market share on product performance, suppliers will routinely specify product datasheet (DS) performance to tighter than six sigma specifications. To maintain quality levels in this instance, the product must be 100% tested in production to screen out parts that are outside specification. Because of test measurement error and temperature drift, the test limits (TLs) used must be guardbanded tighter than the DS limit to ensure that the shipped product meets the parts per million requirement. These guardbands are protection zones that protect the customer from receiving parts that are outside specification. A review of current guardbanding techniques finds that they are conservative in nature. New guardbanding models are presented, which calculate the limit sets required for production test, quality assurance test and DS limit specifications. These models account for both test measurement error and temperature drift. Model results show that the guardband required varies with Cpk of the TL, test measurement error and temperature correlation coefficient. Copyright © 2009 John Wiley & Sons, Ltd.     

Prediction of long term chloride concentration in concrete

The paper presents a wide range of experimental data of the authors and of other researchers on acid-soluble chloride diffusion in different mixes of concrete, and shows conclusively that the chloride diffusion coefficient D_c is strongly dependent on the period of exposure of concrete to a chloride environment. Consequently, long term prediction of chloride concentrations on the basis of Fick's second law of diffusion, which inherently assumes a constant value of D_c, is not an accurate procedure. A differential equation is derived based on the above law of diffusion, which takes into account the time variation of D_c, and a procedure is outlined for the accurate prediction of long term chloride concentrations in concrete. The chloride concentration profiles derived using this procedure show good correlation with experimental data.     

Application of low loading of collagen in electrospun poly[(l‐lactide)‐co‐(ε‐caprolactone)] nanofibrous scaffolds to promote cellular biocompatibility

Electrospinning of various polymers has been used to produce nanofibrous scaffolds that mimic the extracellular matrix and support cell attachment for the potential repair and engineering of nerve tissue. In the study reported here, an electrospun copolymer of l ‐lactide and ε‐caprolactone (67:33 mol%) resulted in a nanofibrous scaffold with average fibre diameter and pore size of 476 ± 88 and 253 ± 17 nm, respectively. Blending with low loadings of collagen (<2.5% w/w) significantly reduced the average diameter and pore size. The uniformity of fibre diameter distributions was supported with increasing collagen loadings. The nanofibrous scaffolds significantly promoted the attachment and proliferation of olfactory ensheathing cells compared to cells exhibiting asynchronous growth. Furthermore, analysis of cell health through mitochondrial activity, membrane leakage, cell cycle progression and apoptotic indices showed that the nanofibrous membranes promoted cell vigour, reducing necrosis. The study suggests that the use of more cost‐effective, low loadings of collagen supports morphological changes in electrospun poly[(l ‐lactide)‐co‐(ε‐caprolactone)] nanofibrous scaffolds, which also support attachment and proliferation of olfactory ensheathing cells while promoting cell health. The results here support further investigation of the electrospinning of these polymer blends as conduits for nerve repair. © 2013 Society of Chemical Industry     

Novel poly(l‐lactide‐co‐caprolactone)/gelatin porous scaffolds for use in articular cartilage tissue engineering: Comparison of electrospinning and wet spinning processing methods

Some novel polymeric fibrous nonwoven meshes have been processed from solution blends of poly(l ‐lactide‐co‐caprolactone), P(LL‐CL), and gelatin for use as biodegradable porous scaffolds in articular cartilage tissue engineering. P(LL‐CL) copolymers with LL:CL compositions ranging from 50:50 to 80:20 mol% were synthesized via the bulk ring‐opening copolymerization of L‐lactide (LL) and ε‐caprolactone (CL) using tin(II) octoate, Sn(Oct)₂, as the initiator. To make the hydrophobic P(LL‐CL) more hydrophilic for cell culture, it was solution blended with gelatin using trifluoroethanol as a common solvent to give P(LL‐CL):gelatin contents in the final scaffolds ranging from 70:30 to 95:5 wt%. Two different processing methods were used: electrospinning and wet spinning. Although electrospinning gave a more uniform mesh of nanosized fibers, the nonwoven mesh from wet spinning with its much larger pores and greater pliability was found to be more suitable for water absorption, cell infiltration and shape‐forming. Scanning electron micrographs of the scaffolds from the two techniques are compared. From the results obtained, the wet‐spun P(LL‐CL)50:50/gelatin 95:5 scaffold gave the best combination of properties. In particular, the 5% gelatin content resulted in a fivefold increase in the scaffold's equilibrium water uptake from about 10% to over 50% by weight. POLYM. ENG. SCI., 57:875–882, 2017. © 2016 Society of Plastics Engineers     

Comparative analysis of delayed‐onset peroxide crosslinking formulations

Strategies for affecting the onset and yield of peroxide‐initiated polymer crosslinking formulations are demonstrated and discussed in terms of underlying reaction mechanisms. Rheological studies of linear low density polyethylene (LLDPE) crosslinking by dicumyl peroxide show that conventional antioxidants such as 3,5‐di‐tert‐4‐butylhydroxytoluene and 2,2,6,6‐tetramethyl‐1‐piperidinyloxy, as well as reported scorch protectants such as 2,4‐diphenyl‐4‐methyl pentene and 1,1‐diphenylethylene, lower crosslinking rates while suppressing the ultimate state of cure. In contrast, the acrylated nitroxyl, 4‐acryloyloxy‐2,2,6,6‐tetramethylpiperidine‐N‐oxyl (AOTEMPO) is shown to suppress the onset of LLDPE crosslinking entirely, while having little effect on the thermoset's final storage modulus. Moreover, AOTEMPO proved capable of quenching allylic macroradical intermediates in cis‐1,4‐polyisoprene cure formulations, whereas other classes of scorch protecting additives had little effect on crosslinking dynamics and yields. POLYM. ENG. SCI., 54:2645–2653, 2014. © 2013 Society of Plastics Engineers     

Exploiting a novel algorithm and GPUs to break the ten quadrillion pairwise comparisons barrier for time series motifs and joins

Time series motifs are approximately repeated subsequences found within a longer time series. They have been in the literature since 2002, but recently they have begun to receive significant attention in research and industrial communities. This is perhaps due to the growing realization that they implicitly offer solutions to a host of time series problems, including rule discovery, anomaly detection, density estimation, semantic segmentation, summarization, etc. Recent work has improved the scalability so exact motifs can be computed on datasets with up to a million data points in tenable time. However, in some domains, for example seismology or climatology, there is an immediate need to address even larger datasets. In this work, we demonstrate that a combination of a novel algorithm and a high-performance GPU allows us to significantly improve the scalability of motif discovery. We demonstrate the scalability of our ideas by finding the full set of exact motifs on a dataset with one hundred and forty-three million subsequences, which is by far the largest dataset ever mined for time series motifs/joins; it requires ten quadrillion pairwise comparisons. Furthermore, we demonstrate that our algorithm can produce actionable insights into seismology and ethology.