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This paper summarizes some of the experimental procedures used for making homopolymers and copolymers of dimethyldiallylammonium chloride, along with a discussion of some of the experimental variables such as effects of catalyst ratio, monomer concentration, and impurities. Also discussed are some of the procedures used for evaluation of the polymers and copolymers in flocculation and sludge dewatering. 相似文献
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F. M. Leslie 《Liquid crystals》1993,14(1):121-130
This paper presents a constrained theory for smectic C liquid crystals that may be useful for the analysis of some effects in these materials. The theory is based on two simplifying assumptions, namely that the layers although deformed remain of constant thickness, and also that the tilt with respect to the layer normal remains fixed. The equilibrium version of the theory proves to be a non-linear generalization of the earlier Orsay theory, and promises to model a number of static effects satisfactorily. Here our aim is to examine preliminary predictions based on the corresponding dynamic theory, where some progress proves possible for shear flow, and also for a shear wave reflection-refraction experiment useful for the measurement of some viscous coefficients. 相似文献
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We discuss several proposed explanations for the switching and negative differential resistance (NDR) behavior seen in some molecular junctions. Several theoretical models are discussed, and we present results of electronic structure calculations on a series of substituted oligo(phenylene ethynylene) molecules. It is shown that a previously proposed polaron model is successful in predicting NDR behavior, and the model is elaborated with image charge effects and parameters from electronic structure calculations. This model now incorporates substituent effects and includes the effects of conformational change, charging, and image charge stabilization. 相似文献
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Before one starts working with hazardous chemicals a hazards analysis is prudent practice – and also required by law. Not only properties like the flammability or the toxicity of chemicals is to be taken into account but also other effects that can lead to dangerous effects, e. g. the diffusion of chemicals through protective gloves or the formation of explosive peroxides. This paper presents some experiments visualizing such not well‐known effects. 相似文献
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Ion migration in electrophoresis always leads to the formation of ionic boundaries. While some types of the ionic boundaries can be formed intentionally, e.g., to improve separation efficiency or sensitivity of the analysis, other, naturally formed boundaries, may cause unexpected effects during the electrophoretic experiment. Some of the boundaries often go unnoticed in practice; however, many effects of the ionic boundaries formed by the sample matrix and background electrolyte components are frequently observed in capillary electrophoresis (CE). The interpretation of these effects may not be trivial and different explanations of the same phenomena may be found in the literature. This critical article attempts to review some of the important effects of the ionic boundaries observed or utilized during the CE of biologically important samples. 相似文献
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[formula: see text] The 13C and 2H kinetic isotope effects for the bromination of 1-pentene with Br2 in CCl4 were determined and interpreted with the aid of calculationally predicted isotope effects. The isotope effects observed are consistent with rate-limiting bromonium ion formation and do not fit with either rate-limiting production of a pi complex or reaction of a reversibly formed bromonium ion. This rules out some of the mechanistic complexities suggested for other brominations, though the identity of the brominating reagent(s) under these synthetic conditions remains uncertain. 相似文献
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Mohammad F. R. Fouda Mokhles M. Abd‐Elzaher Rafeek A. Abdelsamaia Ammar A. Labib 《应用有机金属化学》2007,21(8):613-625
Organometallic chemistry and biochemistry have been merged in the last two decades into a new field: bioorganometallic chemistry. This new research area was devoted to the synthesis of new organometallic compounds and their biological and medical effects against some types of diseases, such as cancer and malaria. For several years, the use of ferrocene in bioorganometallic chemistry has been growing rapidly, and several promising applications have been developed since ferrocene is a stable, nontoxic compound and has good redox properties. This review will focus on ferrocenyl compounds which have been biologically evaluated against certain diseases. This area has attracted many researchers due to the promising results of some ferrocene compounds in the medicinal applications. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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康承华 《高等学校化学学报》1984,5(3):381
本文用非线性非平衡热力学讨论了动电效应.首先,解释了实验值与旧理论不符的问题.其次,给出了旧理论处理动电效应的近似条件.最后,提出了一个新看法,在一定条件下,对某种液体和某个膜,当△P、△φ达一定值时,动电效应也可能出现耗散结构. 相似文献
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This is partly a tutorial and partly a review paper (with a few original additions) on saturation curves (SC) which describe the dependence of fluorescence intensity on laser intensity in atomic spectroscopy. The interest in SCs stems from applications in analytical chemistry, plasma diagnostics, physical and chemical kinetics, etc., as well as from their fundamental implications. After a brief introduction, some general facts and basic assumptions regarding atom-laser interactions are critically examined (Section 2.1) and the concepts of the “ideal” SC and saturation parameter are defined (Section 2.2). In the following Sections 3–7 various effects are discussed that can distort the SC and shift the (apparent) saturation parameter. The effects of a spatially, a temporally and a spectrally inhomogeneous laser beam, of laser-enhanced chemical reactions and ionization processes, of an optically thick atomic vapour and of various non-steady-state processes are successively reviewed. Atom trapping and polarization effects on the SCs measured recently with an atomic Na beam in vacuo are reported and discussed in some detail. Also, some new observations at high resolution on the spectrum of pulsed and cw multimode dye lasers are reported. In Section 8 some general conclusions are drawn and warnings given, and the possible extension of the concept of SC to multiphoton and multistep excitation processes, as well as to optogalvanic spectroscopy, is suggested. 相似文献
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SKIN-PHOTOSENSITIZING FUROCOUMARINS: PHOTOCHEMICAL INTERACTION BETWEEN DNA AND —O14 CH3 BERGAPTEN (5-METHOXY-PSORALEN) 总被引:4,自引:0,他引:4
L. Musajo G. Rodighiero A. Breccia F. Dall''Acqua G. Malesani 《Photochemistry and photobiology》1966,5(9):739-745
Abstract— For some years the mechanism of the photosensitizing effects displayed by some furocoumarins on various biological substrates (human and guinea-pig skin, bacteria cultures, mammalian cells adapted to in vitro growth, viruses) have been studied. Recently it has been pointed out that a photoreaction occurs between the photosensitizing furocoumarins and DNA after irradiation at 3655 Å. By use of a labeled furocoumarin, i.e.—O14 CH3 bergapten or 5-methoxy-psoralen, this has been confirmed and more extensively studied. During the irradiation a stable combination of the furocoumarin with native DNA takes place with a quantum yield of 5·2 × 10-3 . It is probable that the reactive sites of DNA are the pyrimidine bases. Yeast-RNA and the same DNA after heat-denaturation or in the presence of high NaCl concentration photoreact at a much reduced rate. This photoreaction may explain some various biological photosensitizing effects produced by furocoumarins. 相似文献
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Thermodynamic parameters for adsorption equilibrium of heavy metals and dyes from wastewater with low-cost adsorbents 总被引:1,自引:0,他引:1
This note revisits the literature evaluating the thermodynamic parameters of adsorption equilibrium uptakes of heavy metals and dyes from water and wastewater streams using low-cost adsorbents derived from agricultural waste, industrial wastes, inorganic particulates, or some natural products. We highlighted the possible flaws in some adsorption studies when their thermodynamic parameters were assessed, since compensation effects during enthalpy and entropy evaluation were possibly overlooked. 相似文献
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This article surveys some medical aspects of inorganic photochemistry, in particular those involving the use of coordination compounds. Examples of beneficial (therapeutic, diagnostic) and deleterious effects of the interaction between light and metallopharmaceuticals have been selected for presentation. The use of light as a tool in studying and modelling the different biochemical processes is also discussed. 相似文献
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Many fluorine containing compounds utilized in plasma processing, namely plasma polymerization and treatment of materials, have marked greenhouse characteristics as they are able to absorb IR-radiation and have long lifetimes in the atmosphere. The unreacted portion of the feeds and some by-products released in the atmosphere during plasma processing contribute to the global warming of the Earth. This is a problem whose general aspects are discussed in this paper, together with the evaluation of the effects on global warming of the effluents of plasmas fed with some fluorine containing compounds. 相似文献
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The reciprocity relation in solid state NMR has been extended to include the effects of spin-lattice relaxation in the rotating frame. This method was successfully applied to the experiments of Hartmann–Hahn cross polarization, making the originally non-quantified NMR spectra quantitative. In addition, it provides detailed dynamics of cross polarization that is often obscured by spin-lattice relaxation in the rotating frame and by some other effects. 相似文献
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《中国化学快报》2023,34(6):107927
Proteolysis targeting chimeras (PROTACs) are bifunctional degrader molecules via hijacking the ubiquitin-proteasome system (UPS) to specifically eliminate targeted proteins. PROTACs have gained momentum as a new modality of attractive technologies in the drug discovery landscape, since it allows to degrade disease-related proteins effectively. Although some PROTACs drugs reached the clinical research, they are still facing some bottlenecks and challenges that should not be neglected, such as poor oral bioavailability and potential toxic side effects. To overcome these limitations, herein, we provide an overview of recent strategies for improving the durability of PROTACs by enhancing cell permeability and reducing toxic side effects. Meanwhile, the impact of these strategies on improving oral bioavailability as well as their advantages and drawbacks will also be discussed. This review will give a useful reference toolbox for PROTACs design and further promote its clinical application. 相似文献
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Christopher Robertson Jesús González-Vázquez Ines Corral Sergio Díaz-Tendero Cristina Díaz 《Journal of computational chemistry》2019,40(6):794-810
The presence of nonadiabatic effects during the interaction of small molecules with metals has been observed experimentally for the last decades. Specially remarkable are the effects found for NO/Au, where experiments have suggested the presence of very strong vibronic coupling during the molecular scattering. However, the accurate inclusion of the nonadiabatic effects in periodic boundary conditions (PBC) theoretical methods remain an unapproachable challenge. Here, aiming to give some theoretical insight to the strong vibronic coupling, we have adopted a pragmatic point of view, taking use of an auxiliary simplified system, NO/Au3. We show the importance of nonadiabatic coupling, during the scattering of NO from a Au3 cluster, using a diabatic representation of 12 electronic states of the system, including a few charge-transfer states. Our diabatic representation is obtained by rotating the orbital and configuration interaction (CI) vectors of a restricted active space (RAS) wavefunction. We present a strategy for extracting the best effective manifold of states relevant to the system, below some prescribed energy, directly from the RAS CI vectors. This scheme is able to disentangle a large dense manifold of adiabatic states with strong coupling and crossings. This approach is also shown to work for multireference configuration interaction (MRCI). By performing quantum propagations, we observed an increase in vibrational redistribution with increasing initial vibrational or translational energies. We suggest that these nonadiabatic effects should also be present at smaller energies in larger clusters. © 2018 Wiley Periodicals, Inc. 相似文献