Complexes of organometallic compounds : XXXVII. Mössbauer and other studies on adducts of organotin(IV) chlorides with N,N′-ethylenebis(salicylideneiminato)-nickel(II)

Novel 1/1 adducts have been obtained from the complex N,N′-ethylenebis(salicylideneiminato)nickel(II) (NiSalen) with di- and mono-organotin(IV) chlorides, and their solid state configuration investigated by Mössbauer , IR and electronic spectroscopy and magnetic measurements. In coordinated NiSalen the square planar structure is maintained around Ni^II, and the coordination to tin involves three-coordinate phenolic oxygens. The environment of Sn^IV is judged to be octahedral in both types of compounds. A trans-R₂, cis-Cl₂ configuration is advanced for R₂SnCl₂NiSalen.     

Testing the hypothesis of absence of unobserved confounding in semiparametric bivariate probit models

Lagrange multiplier and Wald tests for the hypothesis of absence of unobserved confounding are extended to the context of semiparametric recursive and sample selection bivariate probit models. The finite sample size properties of the tests are examined through a Monte Carlo study using several scenarios: correct model specification, distributional and functional misspecification, with and without an exclusion restriction. The simulation results provide some guidelines which may be important for empirical analysis. The tests are illustrated using two datasets in which the issue of unobserved confounding arises.     

Synthesis and characterization of isoprene polymers with polar groups via reversible addition-fragmentation chain-transfer polymerization

Homo and copolymerization of isoprene (IP) with small amounts (1% wt) of glycidyl methacrylate) were conducted using the reversible addition-fragmentation chain-transfer process (RAFT) at 125 °C in a solution polymerization process using toluene as solvent. Suitable reaction conditions to avoid Diels–Alder dimerization of IP and crosslinking were determined; and 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl] pentanoic acid was found to be the best transfer agent among those tested. Theoretical calculations were used to understand why some RAFT agents work better than others in these polymerizations. Molecular weights M_n higher than 100,000 Da were reached by successive chain extension experiments, confirming the livingness of the intermediate polymers. All the successful polymerizations yielded average molar masses (M_n) of about 75% compared to the theoretical M_n (M_n,theo) depending on the agent used for control. The dispersity (Ð) ranged from 1.20 to 1.70 being a function of the control agent. The polymers were characterized by FTIR spectroscopy, ¹H NMR, and gel permeation chromatography. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2463–2474     

Hybrid Calixarene/Inorganic Salt/Diiodoperfluorocarbon Supramolecular Assemblies

1,3-Bis(α-picolyloxy)-p-tert-butylcalix[4]crown-5 in the cone conformation (2), 1,8-diiodoperfluorooctane or 1,6-diiodoperfluorohexane, and potassium iodide ternary mixtures undergo in solution self-sorting and afford crystalline “supramolecular salts”. These hybrid materials consist of supercation [K⁺ ? 2] and superanion [I–(CF₂) _n –I…I^? …I–(CF₂) _n –I…I^? …] (n = 6,8) components. In the supercations the potassium ion is embedded in the ionophoric pocket created by the heteroatoms present at the lower rim. In the superanions the iodide ions form infinite fluorous polyanionic chains as a result of a self-assembly process which relies on halogen bonding. Both cation encapsulation and anion-perfluorocarbon halogen bonding were detected in solution by ¹H and ¹⁹F NMR, and in the gas phase by ESI MS.     

A note on domain decomposition approaches for solving 3D variational data assimilation models

Data assimilation (DA) is a methodology for combining mathematical models simulating complex systems (the background knowledge) and measurements (the reality or observational data) in order to improve the estimate of the system state (the forecast). The DA is an inverse and ill posed problem usually used to handle a huge amount of data, so, it is a big and computationally expensive problem. In the present work we prove that the functional decomposition of the 3D variational data assimilation (3D Var DA) operator, previously introduced by the authors, is equivalent to apply multiplicative parallel Schwarz (MPS) method, to the Euler–Lagrange equations arising from the minimization of the data assimilation functional. It results that convergence issues as well as mesh refininement techniques and coarse grid correction—issues of the functional decomposition not previously addressed—could be employed to improve performance and scalability of the 3D Var DA functional decomposition in real cases.

     

Acute stress alters transcript expression pattern and reduces processing of proBDNF to mature BDNF in <Emphasis Type="Italic">Dicentrarchus labrax</Emphasis>

Background  

Stress involves alterations of brain functioning that may precipitate to mood disorders. The neurotrophin Brain Derived Neurotrophic Factor (BDNF) has recently been involved in stress-induced adaptation. BDNF is a key regulator of neuronal plasticity and adaptive processes. Regulation of BDNF is complex and may reflect not only stress-specific mechanisms but also hormonal and emotional responses. For this reason we used, as an animal model of stress, a fish whose brain organization is very similar to that of higher vertebrates, but is generally considered free of emotional reactions.     

Toward Understanding the Molecular Recognition of Fungal Chitin and Activation of the Plant Defense Mechanism in Horticultural Crops

Large volumes of fruit and vegetable production are lost during postharvest handling due to attacks by necrotrophic fungi. One of the promising alternatives proposed for the control of postharvest diseases is the induction of natural defense responses, which can be activated by recognizing molecules present in pathogens, such as chitin. Chitin is one of the most important components of the fungal cell wall and is recognized through plant membrane receptors. These receptors belong to the receptor-like kinase (RLK) family, which possesses a transmembrane domain and/or receptor-like protein (RLP) that requires binding to another RLK receptor to recognize chitin. In addition, these receptors have extracellular LysM motifs that participate in the perception of chitin oligosaccharides. These receptors have been widely studied in Arabidopsis thaliana (A. thaliana) and Oryza sativa (O. sativa); however, it is not clear how the molecular recognition and plant defense mechanisms of chitin oligosaccharides occur in other plant species or fruits. This review includes recent findings on the molecular recognition of chitin oligosaccharides and how they activate defense mechanisms in plants. In addition, we highlight some of the current advances in chitin perception in horticultural crops.     

Settling the question of optimum concentration and methodology used for adding an antioxidant to PS/PP polyblend

The method of addition of antioxidants to immiscible polymer blends can influence the end use performance of a polyblend artifact. This work is aimed at determining the most suitable procedure for adding antioxidants to a polystyrene (PS)‐polypropylene (PP) blend (80/20), and its optimum concentration using three different methodologies. The effects of UV exposure on mechanical properties of the polyblends were examined. Results show that both the method of addition and concentration of the antioxidant do not alter mechanical properties, nevertheless, a concentration of 0.1% w/w is recommended.     

Evaluation of a fibre optic device in solution equilibria studies. Application to 3-hydroxybenzoic acid ionization

The use of a fibre optic device for spectrophotometric measurements in solution equilibria studies is presented. In particular the precision obtainable with such equipment is evaluated as a function of different experimental conditions, such as path length, averaging time and stirring of the solution. Analysis of 3-hydroxybenzoic acid ionization is presented to assess the results obtained in the study of an equilibrium system.