Search results for "SUBSTITUTION"
showing 10 items of 536 documents
Radical Cyclization and 1,5-Hydrogen Transfer in Selected Aromatic Diazonium Salts
2014
2-(Methyl(3-methyl-1-phenyl-1H-pyrazol-5-yl)carbamoyl)thiophene-3-diazonium hydrogen sulfate 20, 2-(methyl(3-methyl-isoxazol-5yl)carbamoyl)-benzenediazonium hydrogen sulfate 21 and 2-(methyl(phenyl)carbamoyl)-benzenediazonium hydrogen sulphate 22 were synthesized and reacted with a CuSO4/NaCl/ascorbic acid combination to give complex mixtures. The structures of the reaction products were elucidated, depending upon the pathways followed. Compound 20 almost exclusively afforded an Ar-5 cyclization product and trace amounts of the product derived from a competing Ar-6 Pschorr closure. In the case of compound 21, the Ar-6 cyclization was not observed, while the Ar-5 cyclization and 1,5-hydrogen…
The Reactivity of 4’-Substituted Spiro[Isoindole-1,3’-pyrazoles] Derivatives: Substitution/Elimination Reactions and Access to Biaryl Derivatives
2017
This paper describes aspects of the chemistry of 4’-substituted spiro [indole-1,3’-pyrazoles]. These compounds underwent substitution and/or elimination reactions to afford some new spiro- as well as biaryl derivatives of potential pharmaceutical relevance. Mechanistic considerations are discussed as well.
Long term outcomes of pharmacological treatments for opioid dependence: does methadone still lead the pack?
2014
The aim of this review was to update and summarize the scientific knowledge on the long term outcomes of the different pharmacological treatment options for opioid dependence currently available and to provide a critical discussion on the different treatment options based on these results. We performed a literature search using the PubMed databases and the reference lists of the identified articles. Data from research show that the three pharmacological options reviewed are effective treatments for opioid dependence with positive long term outcomes. However, each one has its specific target population and setting. While methadone and buprenorphine are first line options, heroin-assisted tre…
Phase Transitions in Li, K and Ag Modified Na1/2Bi1/2TiO3-SrTiO3-PbTiO3Solid Solutions
2012
Influence of moderate substitution of Na by monovalent metals Li, K and Ag on structure, phase transitions and dielectric properties of 0.4Na1/2Bi1/2TiO3-0.4SrTiO3-0.2PbTiO3 is studied. Substitution by Li increases, while substitution by K and Ag decreases tetragonality of unit cell. Li increases, Ag decreases while K weakly influences phase transition temperature. The characteristic for the parent phase relaxor state with Tt approaching Tm in case of substitution by K and Li transfers into diffused phase transition without Tm dependence on frequency and extended region of thermal hysteresis.
Vibrational Analysis of Paraelectric–Ferroelectric Transition of LiNbO3: An Ab-Initio Quantum Mechanical Treatment
2021
FSG acknowledges the CINECA award under the ISCRA initiative (HP10BJO47B) for the availability of high-performance computing resources and support.
On Formalizing Logical Modalities
2021
This paper is in the scope of the philosophy of modal logic; more precisely, it concerns the semantics of modal logic, when the modal elements are interpreted as logical modalities. Most authors have thought that the logic for logical modality—that is, the one to be used to formalize the notion of logical truth (and other related notions)—is to be found among logical systems in which modalities are allowed to be iterated. This has raised the problem of the adequacy, to that formalization purpose, of some modal schemes, such as S4 and S5 . It has been argued that the acceptance of S5 leads to non-normal modal systems, in which the uniform substitution rule fails. The thesis supported in this…
Refutation systems for a system of nonsense-logic
2013
In the paper rejection systems for a system of nonsense-logic are investigated. The first rejection system consists of four rejected axioms and only one rejection rule the rule of rejection by detachment. The second one consists of one rejected axiom and two rejection rules: the rule of rejection by detachment and the rule of rejection by substitution. The aim of the paper is to present also a proof of Ł-decidability for the considered systems.
Single amino acids in the lumenal loop domain influence the stability of the major light-harvesting chlorophyll a/b complex.
2004
The major light-harvesting complex of photosystem II (LHCIIb) is one of the most abundant integral membrane proteins. It greatly enhances the efficiency of photosynthesis in green plants by binding a large number of accessory pigments that absorb light energy and conduct it toward the photosynthetic reaction centers. Most of these pigments are associated with the three transmembrane and one amphiphilic alpha helices of the protein. Less is known about the significance of the loop domains connecting the alpha helices for pigment binding. Therefore, we randomly exchanged single amino acids in the lumenal loop domain of the bacterially expressed apoprotein Lhcb1 and then reconstituted the muta…
Implementation of analytic gradients for CCSD and EOM-CCSD using Cholesky decomposition of the electron-repulsion integrals and their derivatives: Th…
2019
We present a general formulation of analytic nuclear gradients for the coupled-cluster with single and double substitution (CCSD) and equation-of-motion (EOM) CCSD energies computed using Cholesky decomposition (CD) representations of the electron repulsion integrals. By rewriting the correlated energy and response equations such that the storage of the largest four-index intermediates is eliminated, CD leads to a significant reduction in disk storage requirements, reduced I/O penalties, and an improved parallel performance. CD thus extends the scope of the systems that can be treated by (EOM-)CCSD methods, although analytic gradients in the framework of CD are needed to extend the applicab…
Isotope Effects and Collective Excitations
1983
Isotopic substitution in the aqueous solvent is discussed as an effective method for probing the role of solvent dynamics in the stability of biomolecular conformation.