Laser flash photolysis of 1,2-diketopyracene and a theoretical study of the phenolic hydrogen abstraction by the triplet state of cyclic alpha-diketones

Laser flash photolysis (LFP) studies, atoms in molecules (AIM) studies, and density functional theory (DFT) calculations have been performed in order to study the mechanism of the hydrogen abstraction by alpha-diketones in the presence of phenols. Laser irradiation of a degassed solution of 1,2-diketopyracene in acetonitrile resulted in the formation of a readily detectable transient with absorption at 610 nm, but with very low absorptivity. This transient decays with a lifetime of around 2 micros. The quenching rate constant for substituted phenols, kq, ranged from 1.10x10(8) L mol-1 s-1 (4-cyanophenol) to 3.87x10(9) L mol-1 s-1 (4-hydroxyphenol). The Hammett plot for the reaction of the triplet of 1,2-diketopyracene with phenols gave a reaction constant rho=-0.9. DFT calculations (UB3LYP/6-311++G**//UB3LYP/6-31G*) of the triplet complex ketone-phenol revealed that hydrogen transfer has predominantly occurred and that the reaction with alpha-diketones are generally 7 kcal/mol less endothermic than the respective reactions of the monoketones. These results together with the geometries obtained from the DFT calculations, natural bond order (NBO) analysis, and AIM results indicate that hydrogen abstraction for alpha-diketones is facilitated by the electrophilicity of the ketone, instead of neighboring group participation by the second carbonyl group.     

Simple DPPH.‐Based Electrochemical Assay for the Evaluation of the Antioxidant Capacity: a Thorough Comparison with Spectrophotometric Assays and Evaluation with Real‐World Samples

An assay based on the electrochemical detection of 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH^.) for the evaluation of the total antioxidant capacity (TAC) was optimized. The assay is interchangeable with the classic spectrophotometric tests for TAC based on the same radical. In addition, it can be used for the analysis of dilute samples with low antioxidant capacities. A good linear correlation (R²=0.97) was obtained between the results obtained with the proposed electrochemical assay and the Trolox Equivalent Antioxidant Capacity test based on ABTS radical. The assay was successfully used to evaluate the antioxidant capacity of two red wines obtained by six different maceration‐fermentation techniques.     

A Ready Synthesis of Some N-Substituted 3-Alkoxycarbonyl-2-Pyrrolinones

Abstract

The synthetic methods for the preparation of pyrrolopyrimidines have been recently reviewed and since that report an increasing number of papers have dealt with the chemistry of these heterocyclic systems for their structural resemblance to purines, natural occurrence and biological significance. Good examples of this are k4 the pyrrolo [2,3-d] pyrimidine nucleosides Q and Q. Among others, 3-alkoxycarbonyl-2-pyrrolinones 2 can be useful intermediates for the preparation of pyrrolo [2,3-d] pyrimidines? However, it appears from the literature that for the preparation of compounds which belong to class g few methods have been described, all preparing the 2-pyrrolinone system by cyclization of a suit able intermediate? The direct functionalization of the carbon 3 of 2-pyrrolinones has not been exploited yet, althogh few examples of related systems have 6 been realized. On the other hand, it has bFen shown that the aldol condensation of 2-pyrrolinone with aromatic aldehydes proceeds at position 3 when a strong electron 7 withdrawing group is attached to the lactamic nitrogen. In this case, the acidity of the hydrogens a to the carbony1 is enhanced, although yields are lmered by competitive condensation at the N-protecting group, if this 8 is an acetyl moiety.     

Hamming graphs in Nomura algebras

Let A be an association scheme on q≥3 vertices. We show that the Bose-Mesner algebra of the generalized Hamming scheme H(n,A), for n?2, is not the Nomura algebra of any type II matrix.This result gives examples of formally self-dual Bose-Mesner algebras that are not the Nomura algebras of type II matrices.     

Linear spaces of matrices of constant rank and instanton bundles

We present a new method to study 4-dimensional linear spaces of skew-symmetric matrices of constant co-rank 2, based on rank 2 vector bundles on P³${\mathbb{P}}^3$ and derived category tools. The method allows one to prove the existence of new examples of size 10×10$10\times 10$ and 14×14$14\times 14$ via instanton bundles of charge 2 and 4 respectively, and it provides an explanation for what used to be the only known example (Westwick 1996 [25]). We also give an algorithm to construct explicitly a matrix of size 14 of this type.     

On subgroups of residually nilpotent metabelian groups

ABSTRACT

We study conditions on an ideal A of a self-injective R such that the factor ring R/ A is again self-injective, extending certain of our results for PF rings (Faith, 2006 Faith , C. ( 2006 ). Factor rings of pseudo-Frobenius rings . J. Algebra and Its Applications 6 :(to appear). [CSA] [Web of Science ®] , [Google Scholar]). We also consider the same question for p -injective, and for CS -rings. For the CS -rings we consider conditions under which A splits off as a ring direct factor, equivalently, when A is generated by a central idempotent. Definitive results are obtained for an ideal A which is semiprime as a ring, that is, has no nilpotent ideals except zero, and which is a right annihilator ideal. Then A is said to be an r -semiprime right annulet ideal, and is generated by a central idempotent in the following cases: (1) whenever A is generated by an idempotent as a right (or left) ideal (Theorems 3.4, 3.6); (2) in any Baer ring R (Theorem 3.5); (3) in any right and left CS -ring R (Theorem 4.2), and (4) in any right nonsingular right CS -ring R (Theorem 5.5).

These results also generalize results of the author in Faith (1985 Faith , C. ( 1985 ). The maximal regular ideal of self-injective and continuous rings splits off . Arch. Math. 44 : 511 – 521 . [CROSSREF] [CSA] [Crossref], [Web of Science ®] , [Google Scholar]), where it is proven that the maximal regular ideal M( R) splits off in any right and left continuous ring.

The results are applied in Section 6 to extend theorems of Faith (1996 Faith , C. ( 1996 ). New characterizations of von Neumann regular rings and a conjecture of Shamsuddin . Publ. Mat. 40 : 383 – 385 . [CSA] [Crossref], [Web of Science ®] , [Google Scholar]) characterizing VNR rings, and, as the title of Faith (1996 Faith , C. ( 1996 ). New characterizations of von Neumann regular rings and a conjecture of Shamsuddin . Publ. Mat. 40 : 383 – 385 . [CSA] [Crossref], [Web of Science ®] , [Google Scholar]) suggests, extend the conjecture of Shamsuddin.     

Multi-degree cyclic scheduling of a no-wait robotic cell with multiple robots

This paper addresses cyclic scheduling of a no-wait robotic cell with multiple robots. In contrast to many previous studies, we consider r-degree cyclic (r > 1) schedules, in which r identical parts with constant processing times enter and leave the cell in each cycle. We propose an algorithm to find the minimal number of robots for all feasible r-degree cycle times for a given r (r > 1). Consequently, the optimal r-degree cycle time for any given number of robots for this given r can be obtained with the algorithm. To develop the algorithm, we first show that if the entering times of r parts, relative to the start of a cycle, and the cycle time are fixed, minimizing the number of robots for the corresponding r-degree schedule can be transformed into an assignment problem. We then demonstrate that the cost matrix for the assignment problem changes only at some special values of the cycle time and the part entering times, and identify all special values for them. We solve our problem by enumerating all possible cost matrices for the assignment problem, which is subsequently accomplished by enumerating intervals for the cycle time and linear functions of the part entering times due to the identification of the special values. The algorithm developed is shown to be polynomial in the number of machines for a fixed r, but exponential if r is arbitrary.     

Initiation and inhibition of protein biosynthesis studies at high resolution

Analysis of the high resolution structure of the small subunit from Thermus thermophilus shed light on its inherent conformational variability and indicated an interconnected network of features allowing concerted movements during translocation. It also showed that conformational rearrangements may be involved in subunit association and that a latch-like movement guarantees processivity and ensures maximized fidelity. Conformational mobility is associated with the binding and the anti association function of initiation factor 3, and antibiotics interfering with prevent the initiation of the biosynthetic process. Proteins stabilize the structure mainly by their long basic extensions that penetrate into the ribosomal RNA. When pointing into the solution, these extensions may have functional roles in binding of non-ribosomal factors participating in the process of protein biosynthesis. In addition, although the decoding center is formed of RNA, proteins seem to serve ancillary functions such as stabilizing ist required conformation and assisting the directionality of the translocation.     

Teoremi di esistenza del minimo per problemi di Bolza e di Lagrange in spazi di Banach

Summary Nonconvex control problems of Bolza and Lagrange with state constraints are considered, in which the state is V-valued, with derivative V-valued, where VHVV is a Banach space and H is a Hilbert space. For these problems some existence theorems for the minimum are proved.

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Lavoro eseguito nell'ambito del Laboratorio per la Matematica Applicata del C.N.R. presso l'Università di Genova.     

Teoremi di esistenza del minimo per problemi di Bolza con stato a valori in spazi di Banach

Summary We examine nonconvex problems of Bolza, in which the state is V-valued, with derivative V-valued, where VHV, V is a Banach space, V is its dual space and H is a Hilbert space. For these problems we prove some existence theorems for the minimum, when we consider state constraints and other constraints that are represented by a nonlinear differential equation that relates the state and the control.

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Lavoro eseguito nell'ambito del Laboratorio per la Matematica Applicata del C.N.R. presso l'Università di Genova.