Solid interfaces as analytical problem solvers in flow injection analysis

An overview of the advantages gained by using solid interfaces in flow injection analysis is presented. The enhancing effect on such basic analytical features as selectivity and sensitivity, diminished sample and reagent consumption, ease of automation of the preliminary steps of the analytical process and of implementation of multideterminations arising from the use of solid interfaces are discussed and illustrated by selected examples.     

Assessment of linear finite‐difference Poisson–Boltzmann solvers

CPU time and memory usage are two vital issues that any numerical solvers for the Poisson–Boltzmann equation have to face in biomolecular applications. In this study, we systematically analyzed the CPU time and memory usage of five commonly used finite‐difference solvers with a large and diversified set of biomolecular structures. Our comparative analysis shows that modified incomplete Cholesky conjugate gradient and geometric multigrid are the most efficient in the diversified test set. For the two efficient solvers, our test shows that their CPU times increase approximately linearly with the numbers of grids. Their CPU times also increase almost linearly with the negative logarithm of the convergence criterion at very similar rate. Our comparison further shows that geometric multigrid performs better in the large set of tested biomolecules. However, modified incomplete Cholesky conjugate gradient is superior to geometric multigrid in molecular dynamics simulations of tested molecules. We also investigated other significant components in numerical solutions of the Poisson–Boltzmann equation. It turns out that the time‐limiting step is the free boundary condition setup for the linear systems for the selected proteins if the electrostatic focusing is not used. Thus, development of future numerical solvers for the Poisson–Boltzmann equation should balance all aspects of the numerical procedures in realistic biomolecular applications. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Finite element modelling of mode I delamination specimens by means of implicit and explicit solvers

The simulation of delamination using the Finite Element Method (FEM) is a useful tool to analyse fracture mechanics. In this paper, simulations are performed by means of two different fracture mechanics models: Two Step Extension (TSEM) and Cohesive Zone (CZM) methods, using implicit and explicit solvers, respectively.TSEM is an efficient method to determine the energy release rate components G_Ic, G_IIc and G_IIIc using the experimental critical load (P_c) as input, while CZM is the most widely used method to predict crack propagation (P_c) using the critical energy release rate as input.The two methods were compared in terms of convergence performance and accuracy to represent the material behaviour and in order to investigate their validity to predict mode I interlaminar fracture failure in unidirectional AS4/8552 carbon fibre composite laminates.The influence of increasing the loading speed and using mass scaling was studied in order to decrease computing time in CZ models.Finally, numerical simulations were compared with experimental results performed by means of Double Cantilever Beam specimens (DCB).Results showed a good agreement between both FEM models and experimental results.     

A survey of the parallel performance and accuracy of Poisson solvers for electronic structure calculations

We present an analysis of different methods to calculate the classical electrostatic Hartree potential created by charge distributions. Our goal is to provide the reader with an estimation on the performance—in terms of both numerical complexity and accuracy—of popular Poisson solvers, and to give an intuitive idea on the way these solvers operate. Highly parallelizable routines have been implemented in a first‐principle simulation code (Octopus ) to be used in our tests, so that reliable conclusions about the capability of methods to tackle large systems in cluster computing can be obtained from our work. © 2013 Wiley Periodicals, Inc.     

亚健康问题与防治的研究

通过对亚健康、人体健康与疾病间的关系研究，以探讨亚健康产生的实质原因，首先从理论上阐述了其产生的机现及有关亚健康的表征与测断见解，同时提出从人体内微量元素的变化，揭示亚健康的信息以及防治亚健康的措施办法。     

食品质量安全——问题与对策

分析了我国食品质量安全中存在的问题 ,建议在食品污染源化学物质和药残的监测与监控 ,食源性病原微生物污染的分子监控 ,以及能与国际接轨的相应技术标准规范与方法学方面进一步采取有效措施并加强相应的基础研究。     

SMPBS: Web server for computing biomolecular electrostatics using finite element solvers of size modified Poisson‐Boltzmann equation

SMPBS (Size Modified Poisson‐Boltzmann Solvers) is a web server for computing biomolecular electrostatics using finite element solvers of the size modified Poisson‐Boltzmann equation (SMPBE). SMPBE not only reflects ionic size effects but also includes the classic Poisson‐Boltzmann equation (PBE) as a special case. Thus, its web server is expected to have a broader range of applications than a PBE web server. SMPBS is designed with a dynamic, mobile‐friendly user interface, and features easily accessible help text, asynchronous data submission, and an interactive, hardware‐accelerated molecular visualization viewer based on the 3Dmol.js library. In particular, the viewer allows computed electrostatics to be directly mapped onto an irregular triangular mesh of a molecular surface. Due to this functionality and the fast SMPBE finite element solvers, the web server is very efficient in the calculation and visualization of electrostatics. In addition, SMPBE is reconstructed using a new objective electrostatic free energy, clearly showing that the electrostatics and ionic concentrations predicted by SMPBE are optimal in the sense of minimizing the objective electrostatic free energy. SMPBS is available at the URL: smpbs.math.uwm.edu © 2017 Wiley Periodicals, Inc.     

The Cyclobutadiene Problem

Cyclobutadiene has recently become the center of reawakened interest. By use of the matrix isolation technique, cyclobutadienes can now be prepared as monomers frozen in matrices. Thus both the unsubstituted parent compound and its alkyl-substituted derivatives are amenable to study. The present progress report surveys the entire field; however, particular emphasis is placed on the author's own results from investigations concerning this classical problem of organic chemistry.     

The Norcaradiene Problem

Compounds having the norcaradiene structure are stable if one of the double bonds of the norcaradiene also belongs to a benzene ring or if C atoms 1 and 6 are fixed in position by a bridge. A similar effect that favors the norcaradiene form is produced by the incorporation of nitrogen atoms in positions 3 and 4. Cycloheptatriene and most of the simply substituted tropilidenes exist exclusively in the monocyclic triene form. It has been possible in some cases to detect a valence-tautomeric equilibrium between the norcaradiene and the cycloheptatriene ring system. Non-classical stabilization of compounds having norcaradiene or cycloheptatriene structure in the sence of a pseudoaromatic “homobenzene” is only very slight, if it occurs at all.     

Humphry Davy and the Problem of Analogy

Analogy, the comparison of one set of relations to another, was essential to Humphry Davy’s understanding of chemistry. Throughout his career, Davy used analogical reasoning to direct and to interpret his experimental analyses of the chemical reactions between substances. In his writing, he deployed analogies to organise and to explain his theories about the relations between physical processes and between the properties of different chemical elements and compounds. But Davy also regularly expressed two concerns about analogical comparison: first, that it was founded not on the rational interpretation of facts but on imaginative speculation; and second, that it was a kind of rhetoric, the persuasiveness of which depended not on material evidence but on misleading figures of speech. This article discusses the influences that informed Davy’s ambivalent assessment of the value of analogy, and it examines the distinct yet overlapping ways in which this assessment was expressed in his notebooks, his lectures and treatises on chemistry, his philosophical writings, and his poetry.     

Zum Problem der Carbohydride

Zusammenfassung Ein Zirkoniumcarbohydrid-Pulver, das aus ZrC_0,6 hergestellt wird und etwa 20 At% H enthält, wird mittels Neutronenbeugung untersucht. Die dabei beobachtete Überstruktur — der Gitterparameter der kfl. Zelle des Carbohydrids ist gleich dem doppelten von ZrC_0,6 bzw. der erneut dehydrierten Probe —läßt sich durch teilweise geordneten Einbau der H-Atome auf Tetraederpositionen deuten.

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Powder of Zr-carbohydride containing about 20 atomic % H, prepared out of ZrC_0,6, has been examined by neutron diffraction a superstructure being observed according:a _{zrC 0,6}H_0,4=2a _{zrC 0,6}. The structural type can be explained by partial ordered filling of the tetrahedral sites.

     

Zum Problem des Phenolphthaleins

Zusammenfassung Kernrescnanzspektroskopische Untersuchungen bestätigen das Vorliegen dreier verschiedener Formen des Phenolphthaleins im alkalischen Medium.

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The phenolphthalein problem

A nuclear magnetic resonance investigation confirms the existence of three different phenolphthalein anions in aqueous alkali.

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Mit 1 Abbildung     

Force Constant Transportability Problem

For XY₃ complexes with light and heavy terminal atoms, the force constant transportability problem is solved by the extrapolation method using semiempirical relations. A potential function is constructed using the transport relations, and the fundamental frequencies are calculated for the hydroxonium ion.     

Zum Problem der Photo-Gelatine

Ohne ZusammenfassungZur Untersuchung kamen zehn Gelatinemuster, die mir liebenswürdigerweise von den Firmen zur Verfügung gestellt worden waren.An dieser Stelle spreche ich den Gelatinefabriken in Winterthur (Schweiz), Nelson (London) und D. G. F. in Schweinfurt (Deutschland) meinen allerbesten Dank aus.     

Blutgerinnnng als kolloidchemisches Problem

Ohne Zusammenfassung     

Zum Problem der Vervielfachung

Zusammenfassung Eine Methode zur jodometrischen Bestimmung von Kupfer, Nickel und Kobalt wurde beschrieben, bei der die Metalle zunächst elektrolytisch abgeschieden werden. Das Metall wird dann mit Silbernitratlösung umgesetzt, wobei eine äquivalente Menge Silber abgeschieden wird. Diese wird gelöst, als Silberjodid gefällt und nach Vervielfachung mit Thiosulfat titriert.

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Summary A method is described for the iodometric determination of copper, nickel and cobalt in which the metals are previously deposited electrolytically. The metal is then allowed to react with silver nitrate solution, with the result that an equivalent quantity of silver is deposited. The latter is dissolved, precipitated as silver iodide, and then after multiplication titrated with sodium thiosulfate.

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Herrn Prof. Dr.Hans Lieb zum 80. Geburtstag freundlichst gewidmet.     

Die Blutgerinnung als kolloidchemisches Problem

Ohne Zusammenfassung     

Zum Problem der komplexometrischen Sulfatbestimmung

Ohne Zusammenfassung