Automated parallel anionic polymerizations: Enhancing the possibilities of a widely used technique in polymer synthesis

Anionic polymerization techniques have been implemented successfully in a commercial automated synthesizer. The main problems for a successful adaptation of the experimental technique in the automated synthesizer are addressed, as well as some simple potential applications, such as the anionic polymerization of styrene, isoprene, and methyl methacrylate. The obtained results were reproducible and in concordance with literature knowledge. The apparent rate constant of the anionic polymerization of styrene in cyclohexane initiated by sec‐butyllithium could be determined at two different concentrations of the monomer and initiator in a temperature range of 10–60 °C. All the synthesis and characterization experiments of the polymers were performed within a short time period. Moreover, the syntheses of poly(styrene‐b‐isoprene) and poly(styrene‐b‐methyl methacrylate) block copolymers were also successfully carried out within the automated synthesizer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4151–4160, 2005     

Analytical science for the development of microelectronic devices

Summary The new technical revolution, the development and introduction of microelectronics poses a great challenge for Analytical Chemistry: the material and process related analytical problems largely refer to extremely small concentrations and spatial dimensions. A successful treatment of such problems is only possible through the use of the most modern, mainly physical techniques, for which reason it seems appropriate to speak of Analytical Science.This paper tries to demonstrate the potential of Analytical Science for the development of sophisticated microelectronic devices, taking as an example the most highly integrated circuit, the Direct Random Access Memory (DRAM). Referring to the various steps of production of such a device in MOS. technology the most important analytical problems and their treatment with analytical methods are discussed: purity and chemical surface structure of silicon wafers, behaviour of dopant elements during the basic operations of MOS technology (oxidation, implantation, annealing), chemical and physical features of metallization layers, and functional and chemical investigation of devices. Special emphasis is placed on the behaviour of the dopant elements which are decisive for the electrical properties of a device. It is shown that mainly physical analytical techniques like SIMS, NAA, RBS, TEM provide valuable new and quantitative information about the chemical and physical processes occurring in the semiconductor material during production of a device. This information enables substantial progress in process modelling, which is an important basis for further development of devices towards higher integration and complexity.

---

Analytische Wissenschaft für die Entwicklung mikroelektronischer Bauelemente

Zusammenfassung Die neue technologische Revolution, nämlich Entwicklung und Einführung der Mikroelektronik, stellt für die Analytische Chemie eine der größten Herausforderungen dar: Die material- und prozeßbezogenen Fragestellungen beziehen sich nämlich in hohem Maße auf extrem kleine Konzentrationen und räumliche Dimensionen. Eine erfolgreiche Behandlung derartiger Fragestellungen ist nur durch Einsätz modernster, überwiegend auf der Physik basierender Hochleistungsanalytik (Analytische Wissenschaft) möglich.In der vorliegenden Arbeit wird versucht, die Rolle dieser Analytischen Wissenschaft für die Entwicklung mikroelektronischer Bauelemente am Beispiel des höchstintegrierten Direct Random Access Memory (DRAM) darzustellen. Ausgehend von den verschiedenen Stufen der Herstellung eines solchen Bauelementes in MOS-Technologie werden die wichtigsten analytischen Fragestellungen und deren Behandlung mit analytischen Methoden diskutiert: Reinheit und chemische Oberflächenstruktur der Siliciumwafer, Verteilung und Reaktionen der Dotierungselemente während der Grundoperationen des MOS-Prozesses (Oxidation, Implantation, Ausheilung), chemische und physikalische Eigenschaften der Metallisierungsstrukturen und funktionelle sowie chemische Untersuchungen der Bauelemente. Besonders eingegangen wird auf die Dotierungselemente, welche die elektrischen Eigenschaften eines Bauelementes bestimmen. Es wird gezeigt, daß in erster Linie physikalische Methoden wie SIMS, NAA, RBS, TEM wichtige neue und quantitative Informationen über die bei der Herstellung eines Bauelementes im Halbleiter ablaufenden chemischen und physikalischen Prozesse liefern. Diese Informationen ermöglichen wesentliche Verbesserungen in der Modellierung dieser Prozesse. Dies ist wiederum eine wesentliche Grundlage für die Weiterentwicklung mikroelektronischer Bauelemente in Richtung höherer Integration und Komple-xität.

---

Symbols used d _A diameter of analyzed volume - d _z depth of analyzed volume - (rel) DL (relative) detection limit - E _o excitation energy - iB (primary) beam intensity Dedicated to Prof. Dr. K. Komarek on the occasion of his 60th birthday     

Weak convergence in Hilbert space and weak uncertainty relations in quantum theory

A suitable weak topology is considered on the Hilbert phase space of a quantum-mechanical system. It is then shown that if two bounded observables of the system have no common eigenvector, the sum of their variances in any state is always greater than some positive constant. Consequences of this result on some observables of simple physical systems are examined. First of all, the case of the position and momentum of the elementary particle in one dimension is studied and a comparation with Heisenberg's indeterminacy principle is carried out. Then, the case of angular variables is also examined, with special emphasis on spin 1/2. An experiment with neutrons is finally suggested and analysed with the help of the theory developed.     

The revised structure of mortonin

The structure 1 previously proposed tor mortonin, is revised to 2 based on spectroscopic and chemical evidence, and on biogenetic considerations.     

Shot noise in magnetic tunnel junctions: evidence for sequential tunneling

We report the experimental observation of sub-Poissonian shot noise in single magnetic tunnel junctions, indicating the importance of tunneling via impurity levels inside the tunnel barrier. For junctions with weak zero-bias anomaly in conductance, the Fano factor (normalized shot noise) depends on the magnetic configuration being enhanced for antiparallel alignment of the ferromagnetic electrodes. We propose a model of sequential tunneling through nonmagnetic and paramagnetic impurity levels inside the tunnel barrier to qualitatively explain the observations.     

Optimisation of a key cross-coupling reaction towards the synthesis of a promising antileishmanial compound

During the course of a research program aimed at identifying novel antileishmanial compounds, a multi-gram synthesis of N-(trans-4-((4-methoxy-3-((R)-3-methylmorpholino)-1H-pyrazolo[3,4-d]pyrimidin-6-yl)amino)cyclohexyl)-2-methylpropane-1-sulfonamide ((R)-1) was required. This letter describes optimisation of the reaction conditions and protecting group strategy for a key Buchwald-Hartwig coupling, delivering the required quantities of (R)-1, as well as further compounds in the series.     

Voltammetric Electronic Tongue Based on Carbon Paste Electrodes Modified with Biochar for Phenolic Compounds Stripping Detection

Biochar is a charcoal produced from the biomass pyrolysis process that presents a highly porous and functionalized surface. In the present work an array of carbon paste electrodes (CPE) made of different forms of carbon (graphite, carbon nanotubes and activated biochar) was evaluated in the development of an electronic tongue for discrimination and stripping voltammetric determination of catechol (CAT), 4‐ethylcatechol (4‐EC) and 4‐ethylguaiacol (4‐EG) phenolic compounds. Morphological characterization of carbon materials and electrodes surfaces was performed by scanning electron microscopy (SEM) and semi‐quantitative elemental composition by energy dispersive spectroscopy (EDS). Electrochemical Impedance Spectroscopy (EIS) measurements were used for electrochemical characterization of electrodes. Cyclic voltammetry measurements were performed for the phenolic compounds evaluated using different concentrations. Principal component analysis (PCA) was performed to evaluate the qualitative analysis. Quantitative data modeling was done using artificial neural networks (ANN). The proposed sensor array presented analytical potentiality allowing the distinction and determination of CAT, 4‐EC and 4‐EG by using chemometric processing. The method showed sensibility, reproducibility and a good linearity (R²>0.9940) for three compounds evaluated. Spontaneous preconcentration of three compounds was possible using all three sensors, which can allow the application of these as passive samplers for remote determinations of phenolic compounds in wine and food samples.