Fundamental aspects of electrocatalysis

A theory for electrochemical electron transfer is proposed which explicitly accounts for the electronic structure of the electrode; it applies both to simple and to bond-breaking reactions. Interactions with narrow d-bands lead to changes in the local density of states of the reactant as its electronic level fluctuates due to solvent reorganization. More importantly, it can significantly reduce activation barriers, and in extreme cases induce dissociative adsorption. The model gives some justification to recent suggestions that the center of the d-band is a key factor for electrocatalysis, and it offers a route for calculating reaction rates using results from ab initio calculations as input.     

Fundamental and engineering thermal aspects of energy and environment

Journal of Thermal Analysis and Calorimetry -     

Fundamental aspects of rubber-elasticity in real networks

Based on the van der Waals-equation of state a characterization of the elastic properties of molecular networks in the total range of strain is presented by the use of Mooney-Rivlin plots. This discussion elucidates the importance of finite chain extensibility as well as global interactions for a quantitative interpretation of the deformation properties of molecular networks. An interpretation of the so-called Mooney-Rivlin coefficients in terms of the van der Waals-parameters delivers at least a novel, yet very consistent understanding of simple extension of swollen networks.     

Fundamental aspects and applications of glow discharge spectrometric techniques

Glow discharges are kind of plasmas which are used in many fields of application, including analytical spectrometry. This review addresses both the fundamental aspects and analytical applications of glow discharges. In the first part, a systematic overview of the most important plasma processes is presented. To obtain better insight into the complexity of the glow discharge, both mathematical modeling and experimental plasma diagnostics can be carried out. Therefore, the models that were developed for a glow discharge are presented and typical results (e.g. three-dimensional density profiles, fluxes and energy distributions of the various plasma species, the electric field and potential distributions, information about collision processes in the plasma and about sputtering at the cathode, etc.) are summarized. Moreover, the most important plasma diagnostic techniques for glow discharges are discussed. In the second part, an overview is given of the various analytical applications of glow discharges.     

Fundamental aspects and applications of fourier-transform ion-cyclotron resonance spectrometry

The operating principles, features, advantages, applications and potential of Foourier-transform ion-cyclotron resonance (F.t./i.c.r. or F.t.m.s.) mass spectrometry are discussed. It is shown that F.t./i.c.r. technology creates a high-performance mass spectrometer with high speed, high sensitivity, ultrahigh mass resolution, very wide mass range and unparalleled versatility.     

Fundamental aspects of oxidation of electroexplosive nickel nanopowder

Fundamental aspects of the process in which a nickel nanopowder produced by an electric explosion of conductors is oxidized under heating in air at a linearly increasing temperature and in the isothermal mode were studied. It is shown that the dispersion composition of the powder, structure of the metallic core of nickel particles, and characteristics of the oxide shell affect the kinetic parameters of the process. An explanation is suggested for specific features of the macrokinetic reaction mode caused by the joint influence exerted by the relative amounts of fractions of different-size particles in the powder and by the characteristic of the oxide layer. The reaction kinetics is simulated, with the size distribution function of nickel particles taken into account.     

Fundamental aspects of chiral separations by capillary electrophoresis

A review is presented that surveys the basic theory of direct separation of enantiomers by capillary electrophoretic (CE) techniques. These separations are based on the formation of diastereomeric complexes between the enantiomeric analytes and a chiral selector added to the electrolyte solution. The review covers a comprehensive treatment of the equations needed for optimization of selectivity coefficients, resolution and analysis time in the zone electrophoretic mode. In this context, it takes into account combined equilibria of complexation and protonation/deprotonation as well as complexation and paritition into micelles. On the basis of these equations, the benefits of charged selectors and the optimization potential inherent to pH tuning can be documented. In addition, the review deals with some basic aspects of chiral isoelectric focusing and briefly discusses indirect enantioseparation. In a subsequent section a survey is given on particularfeatures of the various types of chiral selectors. Finally, the recent developments in preparative enantioseparation in continuous free-flow system and by use of isoelectric membranes are discussed.     

Fundamental aspects of electrospray droplet impact/SIMS

A new ionization method, electrospray droplet impact ionization (EDI), has been developed for matrix-free secondary-ion mass spectrometry (SIMS). The charged droplets formed by electrospraying 1 M acetic acid aqueous solution are sampled through an orifice with a diameter of 400 microm into the first vacuum chamber, transported into a quadrupole ion guide, and accelerated by 10 kV after exiting the ion guide. The droplets impact on a dry solid sample (no matrix used) deposited on a stainless steel substrate. The secondary ions formed by the impact are transported to a second quadrupole ion guide and mass-analyzed by an orthogonal time-of-flight mass spectrometer (TOF-MS). Ten pmol of gramicidin S could be detected with the presence of as much as 10 nmol of NaCl. The ion signal for arginine disappeared with decrease in the substrate temperature below 150 K owing to the formation of ice film over the sample surface. While 10 fmol of gramicidin S could be detected for 30 min, the ionization/desorption efficiency for EDI becomes smaller with an increase in the molecular weight (MW) of a biological sample. The largest protein samples detected to date are cytochrome c and lysozyme. The high sensitivity for EDI is due to the fact that samples only a few monolayers thick are subject to desorption/ionization by EDI, with little fragmentation. A coherent phonon excitation may be the main mechanism for the desorption/ionization of the solid sample.     

Fundamental comparison between non-equilibrium aspects of ICP and MIP discharges

A characterization theory is constructed to relate external control parameters to averaged values of internal plasma properties. It is based on a study on the effect of transport fluxes on elementary balances. This theory is used to compare the inductively coupled plasma (ICP) with the TIA (`torche a injection axiale', a microwave plasma) and to predict properties of He plasmas. The theory is validated by means of laser experiments on the ICP and TIA. Thomson (TS), Rayleigh (RyS) and Raman (RnS) scattering are used to get insight into spatially resolved plasma parameters. TS gives the electron number density and temperature, whereas the combination of RyS and RnS provides the densities of (entrained) air molecules and argon atoms (main gas). In particular, the influence of steep gradients and the air entrainment turn out to be of crucial importance for those situations in which the characterization theory does not properly predict the values of plasma parameters.     

Cathodic electrodeposition of ceramic and organoceramic materials. Fundamental aspects

Electrodeposition of ceramic materials can be performed by electrophoretic (EPD) or electrolytic (ELD) deposition. Electrophoretic deposition is achieved via motion of charged particles towards an electrode under an applied electric field. Electrolytic deposition produces colloidal particles in cathodic reactions for subsequent deposition. Various electrochemical strategies and deposition mechanisms have been developed for electrodeposition of ceramic and organoceramic films, and are discussed in the present article. Electrode-position of ceramic and organoceramic materials includes mass transport, accumulation of particles near the electrode and their coagulation to form a cathodic deposit. Various types of interparticle forces that govern colloidal stability in the absence and presence of processing additives are discussed. Novel theoretical contributions towards an interpretation of particle coagulation near the electrode surface are reviewed. Background information is given on the methods of particle charging, stabilization of colloids in aqueous and non-aqueous media, electrophoretic mobility of ceramic particles and polyelectrolytes, and electrode reactions. This review also covers recent developments in the electrodeposition of ceramic and organoceramic materials.     

Fundamental aspects of initiated oxidation of tridecane and polyethylene in solutions

Specific features of the initiated oxidation of polyethylene and its low-molecular-weight analogue tridecane, associated with the occurrence of the process in the short-chain mode, were studied.     

Fundamental aspects of electrostatic interactions and charge renormalization in electrolyte systems

The consistent inclusion of ion-ion correlations and molecular solvent effects in electrolyte theory can be expressed in a physical formalism, where the particles acquire a renormalized charge density and where they interact electrostatically via a generalized screened Coulomb potential. The latter usually decays for large distances r like a Yukawa function exp(-κr)/r, where 1/κ is the decay length (normally different from the Debye length), but, for smaller r, the screened Coulomb potential is a more complicated function. The resulting electrostatic theory, “Yukawa electrostatics”, differs in many important aspects from ordinary (unscreened) Coulomb electrostatics. In the present paper, we give illustrations and explanations of some important differences between Coulomb and Yukawa electrostatics. The effective “Yukawa charge” of a particle differs from the ordinary Coulombic charge. Furthermore, contributions from multipoles of all orders contribute, in general, to the leading asymptotic term in the potential for large r, which decays like exp(-κr)/r. Thus, the electrostatic potential from, for example, an electroneutral molecule with an internal charge distribution has generally the same range as the potential from an ion. Some implications of these facts are pointed out. The presentation is based on exact statistical mechanical analysis where all particles are treated on the same fundamental level, but the main focus lies on physical consequences and interpretations of the theory. The text was submitted by the author in English.     

Fundamental aspects of the behavior of various lignosulfonates in solutions

Fundamental aspects of associative-dissociative and acid-base transformations of technical-grade high-and low-molecular mass lignosulfonates were identified by carrying out a set of physicochemical studies.     

Fundamental and practical aspects of ultrahigh pressure liquid chromatography for fast separations

The ongoing development of HPLC has been focused on increasing the speed and efficiency of separations over the past decade. The advances in separation speed have been primarily related to the development of column technology and instrumentation. Relatively short columns packed with sub-2 microm particles provide high-speed separations while maintaining or increasing resolution. Ultrahigh pressure pump systems have been developed to overcome the high-pressure drop generated by such sub-2 microm packings. In this review, fundamental and practical aspects of ultrahigh pressure or ultrahigh performance liquid chromatography (U-HPLC) are discussed. Applications of fast U-HPLC separations are also presented.     

Reply to “Fundamental symmetry aspects of optical activity”

Confusion exists between the notion of a single molecule interacting with its environment, and the theoretical notion of an isolated molecule having no interaction with its environment. The space-inversion properties of the isolated-molecule model preclude optical activity: the model is therefore inadequate, leading to the idea that the environment provides the mechanism for generating optical activity.     

Neurophysins: molecular and cellular aspects.

Neurophysins are linear cystine-rich proteins containing 93–95 amino acid residues which like the neurohypophysial hormones oxytocin and vasopressin are formed in the hypothalamus and travel from there to the hypophysial posterior lobe. A species usually contains two (or three) neurophysins which differ only slightly in chain length and/or sequence. Many observatios suggest that both oxytocin and one of the neurophysins as well as vasopressin and the other neurophysin have a common precursor whose long chain is split into neurophysin and hormone. It can be shown on rats having considerable diabetes insipidus that a single gene controls the biosynthesis of the vasopressin and one of the neurophysins.     

In silico modeling and molecular docking insights of kaempferitrin for colon cancer-related molecular targets

Colorectal cancer is one of the most common cancers worldwide, and it is also one of the major causes of mortality from cancer. Chemotherapy drugs are generally limited due to various complications, as well as the development of resistance and recurrence. The in silico docking investigation involved exploration of protein or nucleotide, 3D structural modeling, molecular docking, and binding energy calculation. Protein-protein interactions are significant to many biological processes, and their disruption is a leading cause of disease. The use of small molecules to modulate them is gaining popularity, but protein interfaces usually lack specific cavities for processing small molecules. MMP-2, PARP, iNOS, Chk1, proteins were used in the molecular docking analysis of kaempferitrin and 5-flurouracil. The compound kaempferitrin had the highest binding energy scores with most of the target proteins, according to molecular docking results. The findings suggest it could be used to develop new drugs for cancer therapy.     

Fundamental aspects of sorption of copper ions by aminohydroxyl-containing fibrous complexite

Fundamental aspects of sorption of copper ions by a complexite based on an aminohydroxyl-containing grafted copolymer of polycaproamide and poly(glycidyl methacrylate) were studied. The main kinetic and capacity parameters of the sorption process were determined. The possibility of reaching a high degree of recovery of copper ions from low-concentration solutions was demonstrated.     

Fundamental aspects of ion extraction in inductively coupled plasma mass spectrometry

The present understanding of the ion extraction process in inductively coupled plasma mass spectrometry (ICP-MS) is reviewed critically. Topics include ion production in the ICP, origins of polyatomic ions, causes of and remedies for the secondary discharge, properties of the supersonic jet and of the beam leaving the skimmer, space charge effects, and matrix interferences. Areas of recent interest are also described from the perspective of the ion extraction process. These recent topics include “cool” plasmas, the three-aperture interface, ion extraction from helium plasmas, and ion sampling considerations unique to magnetic sector, time-of-flight, and ion trap mass spectrometers.