Chemical Bond
Mostrando 25-36 de 364 artigos, teses e dissertações.
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25. A METODOLOGIA DE RESOLUÇÃO DE PROBLEMAS: UMA EXPERIÊNCIA PARA O ESTUDO DAS LIGAÇÕES QUÍMICAS
This article presents an experience of the use of the Problem Solving (PR) methodology with undergraduate students of the Licentiate Course in Chemistry of UFRGS, for the study of Ionic Bonding (LI). Salar de Uyuni salts were used to contextualize the problems employed. The Field Log records of the researchers and the presentations of the undergraduates show
Quím. Nova. Publicado em: 2018-04
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26. Evaluation of long-term bond strength and selected properties of self-adhesive resin cements
Abstract This study evaluated the shear bond strength (SBS) of self-adhesive resin cements (SARCs) to dentin and their physical-chemical properties. Five commercial SARCs were evaluated [SmartCem®2 – DENTSPLY (SC2); BisCem® – Bisco (BC); SeT PP® − SDI (SeT); Relyx U100® – 3M ESPE (U100) and YCEM® SA - Yller (YCEM)]. The SARCs were evaluated for
Braz. oral res.. Publicado em: 01/03/2018
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27. N-Acetyl-cysteine Increases Chemical Stability of Hydroquinone in Pharmaceutical Formulations: a Theoretical and Experimental Approach
In this study, the chemistry stability of hydroquinone (HQ) was evaluated according to its effects in redox properties and compared to kojic acid (KA). The HQ oxidation was more inhibited by N-acetylcysteine (NAC) than ascorbic acid (AA). These results were elucidated using theoretical methods at the DFT/B3LYP level of theory. All electronic parameters were
J. Braz. Chem. Soc.. Publicado em: 2018-03
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28. DFT STUDY ON THE MECHANISTIC, ENERGETIC AND STRUCTURAL ASPECTS OF ADSORPTION OF TIRAPAZAMINE ONTO PRISTINE AND FUNCTIONALIZED CARBON NANOTUBES
Using density functional theory, noncovalent interactions and two mechanisms of covalent functionalization of drug tirapazamine with pristine, COOH and COCl functionalized carbon nanotube (NT, NTCOOH and NTCOCl) have been investigated. Quantum molecular descriptors of noncovalent configurations were studied. It was specified that binding of drug tirapazamine
Quím. Nova. Publicado em: 2018-01
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29. Peptidomic analysis of the venom of the solitary bee Xylocopa appendiculata circumvolans
Abstract Background: Among the hymenopteran insect venoms, those from social wasps and bees - such as honeybee, hornets and paper wasps - have been well documented. Their venoms are composed of a number of peptides and proteins and used for defending their nests and themselves from predators. In contrast, the venoms of solitary wasps and bees have not been
J. Venom. Anim. Toxins incl. Trop. Dis. Publicado em: 28/09/2017
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30. BIODEGRADACION FUNGICA DE POLIURETANO RÍGIDO
Polyurethane (PU) is one of the most widely used polymer materials. This generates a serious environmental problem because of its poor biodegradability since most of the native microorganisms cannot use it as a source of nutrients. Several techniques involving mechanical and chemical processes have been used for its recovery and reuse; however, the problem o
Quím. Nova. Publicado em: 2017-09
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31. The distribution of Lignin and Xylan in the Inner and Surface Layers of the Fiber from Eucalyptus Kraft Pulp and its Effects on Oxygen Delignification
The chemical structure and composition of lignin and hemicellulose, as well as the distribution between inner and outer layers of fiber, can adversely affect bleaching operations or fiber-fiber bond on pulp and, consequently the papermaking process. Herein, we have implemented the fractionation and mechanical peeling techniques in order to identify the fines
Mat. Res.. Publicado em: 22/06/2017
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32. Influence of Adherend Surface Roughness on the Adhesive Bond Strength
Abstract Surface treatment of the adherends prior to adhesive bonding plays an important role in the enhancing of strength and durability of bonded joints. In this work, an investigation on effect of adherend surface roughness on adhesive bond strength was performed. Single strap joints with different adherends (mild steel and aluminium) bonded with an epoxy
Lat. Am. j. solids struct.. Publicado em: 2016-12
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33. Effect of silver nanoparticles on the physicochemical and antimicrobial properties of an orthodontic adhesive
ABSTRACT Orthodontic treatment with fixed brackets plays a major role on the formation of white spot lesions. Objective This study aimed to incorporate silver nanoparticle solutions (AgNP) in an orthodontic adhesive and evaluate its physicochemical and antimicrobial properties. Material and Methods Silver nanoparticle solutions were added to a commercial
J. Appl. Oral Sci.. Publicado em: 2016-08
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34. SÍNTESE DE DERIVADOS DE FENANTRIDINONAS POR ARILAÇÃO DIRETA. CARACTERIZAÇÃO DOS ESPECTROS DE ABSORÇÃO E EMISSÃO DE EXEMPLOS REPRESENTATIVOS
The phenanthridinone heterocyclic system has attracted considerable attention in recent years due to the diverse array of physical, chemical and pharmacological properties demonstrated by natural and synthetic derivatives. As a consequence there has been considerable development of synthetic methodology for the synthesis of this and related heterocyclic ring
Quím. Nova. Publicado em: 2016-04
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35. A New Steroidal Saponin from the Tubers of Ophiopogon japonicus and Its Protective Effect Against Cisplatin-Induced Renal Cell Toxicity
A new furostanol saponin, ophiopogonin T, was isolated from the tubers of Ophiopogon japonicus. Its structure was established by extensive spectroscopic techniques including 1D (1H and 13C) and 2D nuclear magnetic resonance (NMR) experiments (correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond correlati
J. Braz. Chem. Soc.. Publicado em: 2016-04
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36. Estimating the Impact of an All-Electron Basis Set and Scalar Relativistic Effects on the Structure, Stability, and Reactivity of Small Copper Clusters
Basis sets of valence double and quadruple zeta qualities and the Douglas-Kroll-Hess (DKH) approximation are used to estimate the impact of an all-electron basis set and scalar relativistic effects on the structure, stability, and electronic properties of small neutral copper clusters (Cun, n ≤ 8). At the Becke three-parameter for exchange and Perdew-Wang
J. Braz. Chem. Soc.. Publicado em: 2016-01