Naturwissenschaftliche Reise nach Mossambique : auf befehl Seiner Majestät des königs Friedrich Wilhelm IV, in den jahren 1842 bis 1848 ausgeführt /

Errata: p. [576].

Systematische Beschreibung der bekannten europäischen zweiflügeligen Insecten / von Johann Wilhelm Meigen.

Vol. 7-10: Siebenter [-zehnter] Theil oder [erster]- vierter Supplementband; v. 8-10 have added t.p.: Beschreibungen europaischer Dipteren, von H. Loew.

Vollständiges Verzeichniss der Leih- und Lesebibliothek für alle Stände : bei der Buch-Papier- und Kunsthandlung von Conrad Wilhelm Crone in Osnabrück

In Fraktur

Wilhelm Gesenius' hebräisches und aramäisches Handwörterbuch über das Alte Testament

in Verbindung mit Prof. Dr. H. Zimmern bearbeitet von Dr. Frants Buhl, Professor an der Universität Koppenhagen

Hs. Rothschild 2° 15 - Fünf Reisepässe, ausgestellt für die Freiherren Carl Mayer und Wilhelm von Rothschild und Freifrau Lionel von Rothschild

Vorbesitzer: Freiherrlich Carl von Rothschild'sche Bibliothek Frankfurt am Main; Akzessionsnummer: x20230

Wilhelm von Humboldt: Briefe an Friedrich August Wolf. Textkritisch herausgegeben und kommentiert von Philip Mattson. Berlin/New York: Walter de Gruyter 1990 [...] [Sammelrezension]

Sammelrezension von: 1. Wilhelm von Humboldt: Briefe an Friedrich August Wolf. Textkritisch herausgegeben und kommentiert von Philip Mattson. Berlin/New York: Walter de Gruyter 1990 635 S. 2. Italien im Bannkreis Napoleons. Die römischen Gesandtschaftsberichte Wilhelm von Humboldts an den Landgraf I Großherzog von Hessen-Darmstadt 1803-1809. Bearbeitet von Eva-Maria Feldschow und Ulrich Hussong. Herausgegeben von Eckhart G. Franz. Darmstadt: Hessische Historische Kommission 1989, 459 S.

Transferência de elétron inversa na quimiexcitação da reação peróxi-oxalato usando ativadores facilmente redutíveis

Chemiluminescence properties of the peroxyoxalate reaction in the presence of activators bearing electron withdrawing substituents were studied, to evaluate the possible occurrence of an inverse electron transfer, from the peroxide intermediate to the activator, in its chemiexcitation step. Relative catalytic rate constants and singlet quantum yields were obtained for the peroxyoxalate reaction, using 9-chloro, 9,10-dichloro, 9-cyano and 9,10-dicyanoanthracenes as activators. The linear free-energy correlation of the relative rate constants with the activators' reduction potentials and the dependence of the quantum yields on the released energy confirm, for the first time, the occurrence of this inverse electron transfer.

Eletrodo de hidrogênio: o que há nos livros didáticos além de E¸ = 0?

The results of an exercise on electrochemistry for General Chemistry students are presented. The difficulty encountered by students in predicting the shift in the potential of the hydrogen electrode under non-standard conditions prompted a search in textbooks on how the subject is developed. Besides several instances of inconsistencies in defining the standard state, such as including the temperature in the definition, a number of incorrect depictions of the hydrogen electrode were discovered. Of the 28 General Chemistry books, 16 Physical Chemistry books and 24 Internet pages, 30, 20 and 46%, respectively, showed devices that would not work in practice.

Luz: um raro produto de reação

The production of visible light by chemical reactions constitutes interesting and fascinating phenomena and several reaction mechanisms are discussed to rationalize excited state formation. Most efficient chemiluminescence reactions are thought to involve one or more electron transfer steps and chemiexcitation is believed to occur by radical annihilation. A brief introduction to the general principles of light production and the main known chemiexcitation mechanisms will be given here. Subsequently, recent results on the mechanistic elucidation of efficient chemiluminescence systems, as the peroxyoxalate reaction, the induced decomposition of phenoxy-substituted 1,2-dioxetanes and the catalyzed decomposition of new a-peroxylactones will be discussed.

A SEARCH FOR FIELD HORIZONTAL-BRANCH STARS NEAR THE SOUTH GALACTIC POLE

Searches for field horizontal-branch (FHB) stars in the halo of the Galaxy in the past have been carried out by several techniques, such as objective-prism surveys and visual or infrared photometric surveys. By choosing adequate color criteria, it is possible to improve the efficiency of identifying bona fide FHB stars among the other objects that exhibit similar characteristics, such as main-sequence A-stars, blue stragglers, subdwarfs, etc. In this work, we report the results of a spectroscopic survey carried out near the south Galactic pole intended to validate FHB stars originally selected from the HK objective-prism survey of Beers and colleagues, based on near-infrared color indices. A comparison between the stellar spectra obtained in this survey with theoretical stellar atmosphere models allows us to determine T(eff), log g, and [Fe/H] for 13 stars in the sample. Stellar temperatures were calculated from measured (B-V)(o), when this measurement was available (16 stars). The color index criteria adopted in this work are shown to correctly classify 30% of the sample as FHB, 25% as non-FHB (main-sequence stars and subdwarfes), whereas 40% could not be distinguished between FHB and main-sequence stars. We compare the efficacy of different color criteria in the literature intended to select FHB stars, and discuss the use of the Mg II 4481 line to estimate the metallicity.

Chemiluminescence-based uphill energy conversion

The conversion of red excitation light into blue emission light (uphill energy conversion) using unstable 1,2-dioxetanes is described. The method is based on 1,2-dioxetane formation by red-light sensitized photooxygenation of adequate alkenes and subsequent blue-light emission due to thermal 1,2-dioxetane cleavage. The energy gain resulting from the chemical energy obtained in the transformation of an alkene into two carbonyl compounds transforms a red-light excitation laser beam into a blue-light chemiluminescence emission, producing thereby a formal anti-Stokes shift of 200-250 nm, opening up a whole spectrum of possible applications.