Dilute solution properties of methyl methacrylate—acrylonitrile copolymer (MA2)

This article deals with studies of the dilute solution properties of methyl methacrylate-acrylonitrile (MMA-AN) copolymer of 0.415 mole fraction (mf) of acrylonitrile composition. Mark—Houwink parameters for this copolymer have been evaluated in acetonitrile (MeCN), 2-butanone (MEK), dimethyl formamide (DMF), and γ-butyrolactone (γ-BL). The Mark-Houwink exponent a in all four solvents at all temperatures is larger than the corresponding values of the parent homopolymers. The solvent power is in the order of DMF < γ–BL < MEK < MeCN; [η] decreases with an increase in temperature, which is behavior characteristic of polymers in good solvent. The unperturbed dimensions (K₀) values, obtained by the Stockmayer–Fixman method, are lower than those for the parent homopolymers and depend on solvent as well as temperature. The solute—solvent interaction parameter X₁ values are close to 0.5; X₁ is independent of temperature. The excess interaction parameter X_ABvalues are negative. The results for this copolymer system in regard to low second virial coefficient A₂, large X₁, and high a values suggest that the large extension of these copolymer chains is due to the unusual short-range interactions.     

In water organic synthesis: Introducing itaconic acid as a recyclable acidic promoter for efficient and scalable synthesis of quinoxaline derivatives at room temperature

Substituted quinoxaline derivatives are traditionally synthesized by co-condensation of various starting materials. Herein, we describe a novel environmentally benign in water synthetic route for the synthesis of structurally and electronically diverse ninety quinoxalines with readily available substituted o-phenylenediamine and 1,2-diketones using cheap and biodegradable itaconic acid as a mild acid promotor in 1 hours. The reaction is performed at room temperature, which proceeds through cyclo-condensation reaction followed by obtaining the aforesaid nitrogen-containing heterocyclic adducts without performing the column chromatography up to 96% total yields. The simplicity, high efficiency, and reusable of the catalyst merits this reaction condition as “green synthesis” which enables it to be useful in synthetic transformations upto gram scale level.     

Interconversion of host–guest components in supramolecular assemblies of polycarboxylic acids and reduced Schiff bases

Eight supramolecular assemblies of benzene-1,3,5-tricarboxylic acid (H₃BTC) and benzene-1,2,4,5-tetracarboxylic acid (H₄BTtC) with reduced Schiff base of flexible backbone having phenolic and pyridyl groups, i.e., 1,2-bis(2-hydroxybenzylamino)ethane, 1,3-bis(2-hydroxybenzylamino)propane, 1,4-bis(2-hydroxybenzylamino)butane and 1,4-bis(4-pyridinylmethylamino)butane have been constructed by proton transfer reaction. H₃BTC forms host–guest type assemblies with amines having phenolic functionality, while a layered structure was obtained with pyridyl functionalized amine. H₄BTtC also formed host–guest assemblies with the diamines where reduced Schiff base acts as host and acid moiety acts as the guest. Different conformations of the diamines were observed in these assemblies. Theoretical studies were performed to analyze the effect of varied chain lengths of diamines on hydrogen bond interaction energy of the adducts.     

Ex Situ Conservation of Phyllanthus fraternus Webster and Evaluation of Genetic Fidelity in Regenerates Using DNA-Based Molecular Marker

Germplasm storage of Phyllanthus fraternus by using synseed technology has been optimized. Synseeds were prepared from nodal segments taken from in vitro-grown plantlets. An encapsulation matrix of 3 % sodium alginate and 100 mM calcium chloride with polymerization duration up to 15 min was found most suitable for synseed formation. Maximum plantlet conversion (92.5?±?2.5 %) was obtained on a growth regulator-free ½-strength solid Murashige and Skoog (MS) medium. Multiple shoot proliferation was optimum on a ½ MS medium containing 0.5 mg/l 6-benzylaminopurine (BAP). Shoots were subjected to rooting on MS media containing 1 mg/l α-naphthaleneacetic acid (NAA) and acclimatized successfully. Encapsulated nodal segments can be stored for up to 90 days with a survival frequency of 47.33 %. The clonal fidelity of synseed-derived plantlets was also assessed and compared with that of the mother plant using rapid amplified polymorphic DNA and inter-simple sequence repeat analysis. No changes in molecular profiles were observed among the synseed-derived plantlets and mother plant, which confirms the genetic stability of regenerates. This synseed production protocol could be useful for in vitro multiplication, short-term storage, and exchange of germplasm of this important antiviral and hepatoprotective plant.     

A pursuit and evasion problem with measurement uncertainty

A pursuit-evasion process with uncertain state-dependent measurements, in finite, discrete time and in a finite, discrete state space, is considered. Three types of strategies which might be employed in such a process are compared, and attention is concentrated on the behavior strategy, the least well known of the three types, but often the simplest optimal strategy to employ.A variation of the Brown-Robinson fictitious play algorithm is presented which can be used to compute behavior strategies in the case of perfect recall processes.Two examples are given in which optimal behavior strategies are computed using the algorithm and compared with a type of plausible but nonoptimalseparation strategy.This work was partially supported by NASA Grant No. NGR-15-005-021, NSF Grant No. GK-1970, and AFOSR Grant No. 69-1776.