On strong summability of multiple Fourier series and smoothness properties of functions

_n —n- — ƒ()L _v (T _n ), 1f, - -. -.     

Waiting Time in a Two Station Series Queueing System: The Effect of Dependent Interarrival Times

An analysis taking into account the dependencies in the departure process from the first station of the M/E _k /1→./M/1 system is conducted. Arrivals to the second station are approximated as a general independent distribution, and the waiting times in this station are compared to those found through computer simulation.     

Eine Tüpfelreaktion für den Nitritnachweis

Zusammenfassung Durch Tüpfeln auf Chromatographiepapier, das mit Brucin, Benzidin und Phosphorsäure imprägniert wurde, läßt sich Nitrit empfindlieh und spezifisch nachweisen. 20 ng Nitrit können neben Nitrat und anderen Anionen festgestellt werden.

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Summary Nitrite can be detected sensitively and specifically by spotting on Chromatograph paper impregnated with brucine, benzidine and phosphoric acid. It is possible to detect 20g nitrite in the presence of nitrate and other anions.

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Résumé On peut rechercher les nitrites d'une manière sensible et spécifique sur les taches du papier chromatographique et qui a été imprégné de brucine, de benzidine et d'acide phosphorique. On peut déceler 20g de nitrite en présence de nitrates et d'autres ions A-.

     

Plasma desorption mass spectrometry of transition metal complexes of thio- and selenosemicarbazones of 2-acetylpyridines

Summary Californium-252 plasma desorption mass spectra were recorded for complexes of the anions of various thio-and seleno-semicarbazones of 3-acetylpyridines(1–4) with the transition metal ions iron(III) and cobalt(II). Positive ion spectra gave clear evidence of the cation present and fragmentation with loss of ligands or parts of ligands was straightforward. Negative ion spectra likewise provided evidence of the intact anion except with tetracoordinate metal halide systems [MX₄]^– which lost one or more halide atoms. Evidence of fragmentation of the ligand and recombination of the fragments with the metal ion was also observed in the negative ion mode. Spectra were used to revise the structure of a complex previously reported as [FeLCl₂]⁽¹⁾ to [FeL₂]⁺[FeCl₄]^–.     

Eine Tüpfelreaktion zur Unterscheidung oxydierender Anionen

Zusammenfassung Die Herstellung eines Reagenspapiers wird beschrieben, mit dessen Hilfe die Identifizierung oxydierender Anionen [Nitrit, Hypochlorit, Chromat, Bromat, Hexacyanoferrat(III), Peroxydisulfat, Jodat, Chlorat und Nitrat ] durch einen einfachen Tüpfeltest möglich ist.

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Summary The preparation of a reagent is described with whose aid it is possible to identify oxidant anions through a simple spot test. The anions are: nitrite, hypochlorite, chromate, bromate, hexacyanoferrate (III), peroxodisulfate, iodate, chlorate, nitrate.

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Résumé On décrit la préparation d'un papier-réactif permettant l'identification des anions oxydants (nitrite, hypochlorite, chromate, bromate, ferricyanure, peroxydisulfurique, iodate, chlorate et nitrate) par une réaction à la touche simple.

     

FLUORESCENCE QUANTUM YIELDS AND LIFETIMES FOR BACTERIOCHLOROPHYLL c

Abstract— Absorption and emission spectra of bacteriochlorophyll c dissolved in a variety of solvents were measured and fluorescence quantum yields determined from the integrated emission spectra. Values for the emission maxima calculated from the positions and bandwidths of the red absorption band using the Stepanov relationship agreed closely with the experimental values. Fluorescence quantum yields varied between 0.10 in methanol and 0.36 in tetrahydrofuran and in dibutylamine. Fluorescence lifetimes were also determined for bacteriochlorophyll c in four of the solvents, and ranged from 2.7 ns in methanol to 7.6 ns in dimethylsulfoxide.     

Morphologie und Wachstumskinetik von Crazes in amorphen Polymeren

Zusammenfassung Im vorfibrillaren Stadium besitzt die Crazematerie eine in Verformungsrichtung deformierte Netzwerkstruktur, die sich bei Polystyrol und Styrol-Acrylnitril-Copolymerisat elektronenoptisch an Oberflächenabdrücken sauerstoffionengeätzter Proben nachweisen läßt. Während die durchschnittlichen Globulitverformungen zumeist deutlich unterhalb von 50% liegen, werden partiell Spitzenwerte von bis zu 300% erreicht. Am Beispiel des Polystyrols verdeutlichen quantitative Strukturvergleiche mit warmgerecktem Material, daß die molekulare Beweglichkeit während des Crazewachstums und der Schulter-Hals-Verstreckung derjenigen entspricht, die für thermisch aktiviertes Material oberhalb der Glastemperatur charakteristisch ist.Mit 7 Abbildungen und 2 Tabellen     

Unambiguous Proof for Alcoxycarbonyl-group Migration in Wagner-Meerwein Rearrangements

In HSO₃F/SO₂ClF the β-hydroxy esters Ph-CHOH-CMe₂-COOR ( 1 , R?Me, Et) are doubly protonated, then transformed into the fluorosulfates 7 and (partly) into the fluorides 8. At ?15°, both 7 and 8 undergo a rearrangement, forming derivatives of Me₂C?C(Ph)COOR ( 2 ). By labelling 1 with ¹³C, singly (¹³C(3)) and doubly (¹³C(1,3)), it could be shown that exclusively the ROOC groups undergo a 1,2-shift. Compound 2 is also formed in HSO₃F/SO₂ClF from the isomeric Me₂COH-CHPh-COOR ( 3 ) by elimination, and less easily from the α-hydroxy ester Ph-CMe₂-CHOH-COOR (5) via a phenyl 1,2-shift. Another isomer, Ph-C(OH)Me-CHMe-COOR (4) gives products different from 2 . Using more acidic systems containing SbF₅, the free carbenium ions 13 (Ph-CH⁺-CMe₂-COOR) can be stabilized; they do not form 2 , possibly because of complexation of the ester group with SbF₅. The energy profile and the mechanism of the rearrangement 1 → 2 are discussed.     

An Efficient Strategy to Orthogonally Protected (R)- and (S)-alpha-Methyl(alkyl)serine-Containing Peptides via a Novel Azlactone/Oxazoline Interconversion Reaction

A novel strategy for the synthesis of (R)- and (S)-alpha-methyl(alkyl)serine-containing peptides is presented. Using (S)-phenylalanine cyclohexylamide 6 as chiral auxiliary, the optically pure azlactones (R)- and (S)-2 were synthesized via a novel azlactone/oxazoline interconversion reaction (Figures 3 and 6). These azlactones constitute fully protected and activated synthetic equivalents of (R)- and (S)-alpha-methylserine and can be directly incorporated into peptides without further protective group manipulations. Like other alpha,alpha-dialkylated glycines, optically pure alpha-alkylserines can be used to stabilize beta-turn and alpha-helical conformations in short peptides.     

Analysis of impact-excited HeI states by applying magnetic and electric depolarization techniques

The magnetic depolarization of the impact radiation at λ(4¹ D?2¹ P)=492 nm and λ(3¹ D?2¹ P) = 668 nm as well as the splitting of the magnetic depolarisation signals in electric fields were investigated for 10–25 keV H ₂ ⁺ (D ₂ ⁺ )-He collisions (only 492 nm line) and for 5-22.5 keV He-He collisions (both lines). The results are compared with analogous measurements for He⁺- He and Ne⁺ - He collisions and the dynamics of the excitation process are qualitatively discussed. In particular, we emphasize the importance of inertia for the evolution of the electron cloud during the final phase of the collision process.