O sistema quimiluminescente peróxi-oxalato

The peroxyoxalate system is still one of the most efficient chemiluminescence reactions and the only one supposed to involve the "Chemically Initiated Electron Exchange Luminescence - CIEEL" mechanism, with proved high efficiency. Besides the academic interest in the elucidation of the mechanism of this complex reaction, the peroxyoxalate system has found a variety of applications in analytical chemistry. This review contains (i) a short introduction to basic concepts in chemiluminescence, (ii) a critical summary of mechanistic studies on the peroxyoxalate reaction, (iii) and some examples of analytical applications. Although there are some recent reviews on chemiluminescence, no specific critical revision on mechanistic and analytical features of the peroxyoxalate system has been published.

Valda ungdomsdikter

Josef Julius Wecksell (1838-1907) luetaan aikakautensa lahjakkaimpiin kirjailijoihin, jonka elämäntyö kuitenkin keskeytyi varhain psyykkisen sairauden vuoksi. Wecksell herätti jo koulupoikana Turussa huomiota romanttisilla ja isänmaallisilla runoilla ja näytelmillään. Ennen sairastumistaan hän ehti julkaista vain tämän yhden runokokoelman sekä näytelmän Daniel Hjort (katso Pelasta kirja –kohde 237). Valda ungdomsdikter –kokoelman monet haikeat ja intensiiviset runot ovat tulleet tunnetuiksi laulujen sanoina, kuten Sibeliuksen säveltämä Demanten på marssnön.

Daniel Hjort : sorgespel i fem akter med fyra tablåer

J. J. Wecksellin pääteosta Daniel Hjortia pidetään ainoana huomattavana suomalaisena näytelmänä, joka on syntynyt ennen Aleksis Kiven tuotantoa. Tämä historiallinen aatedraama sijoittuu kuningas Sigismundin ja Kaarle-herttuan taistelujen aikaiseen Turun linnaan. Näytelmä kuvaa sovittamatonta ristiriitaa, johon päähenkilö Daniel Hjort joutuu palvellessaan toisaalta kuningasta ja ajaessaan toisaalta kansan asiaa. Näytelmässä on vaikutteita Wecksellin esikuvilta Shakespearelta, Schilleriltä ja Victor Hugolta, mutta näytelmää on kiitetty myös omaperäisyydestä, sen elävästä, syvällisen psykologisesta henkilökuvauksesta ja draamallisesta voimasta. Näytelmä esitettiin ensimmäisen kerran Helsingin ruotsalaisessa teatterissa marraskuun 26. päivänä vuonna 1862, ja näytelmää on esitetty yhä nykypäiviin saakka.

Mechanism of 3,4-dihydroxybenzaldehyde electropolymerization at carbon paste electrodes: catalytic detection of NADH

Cyclic voltammetry was used to study 3,4-dihydroxybenzaldehyde (3,4-DHB) electropolymerization processes on carbon paste electrodes. The characteristics of the electropolymerized films were highly dependent on pH, anodic switching potential, scan rate, 3,4-DHB concentrations and number of cycles. Film stability was determined in citrate/phosphate buffer solutions at the same pH used during the electropolymerization process. The best conditions to prepare carbon paste modified electrodes were pH 7.8; 0.0 <= Eapl <= 0.25 V; 10 mV s-1; 0.25 mmol L-1 3,4-DHB and 10 scans. These carbon paste modified electrodes were used for NADH catalytic detection at 0.23 V in the range 0.015 <= [NADH] <= 0.21 mmol L-1. Experimental data were used to propose a mechanism for the 3,4--DHB electropolymerization processes, which involves initial phenoxyl radical formation.

Burleska

Soitinnus: viulu, piano.

Om flussers värkan vid järnmalmers proberande genom smältning

Dedicatio: Fredric Ridderstolpe, Josef Bremer [ransk. pr.], Hans Hindric Kijk.

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.

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.

Evaluation of antiradical assays used in determining the antioxidant capacity of pure compounds and plant extracts

The efficiency of the chemiluminescence luminol method and colorimetric DPPH and ABTS methods in evaluating the antiradical capacity of pure compounds and plant extracts with antioxidant potential is compared. In case of pure compounds, the values of parameter 'n' (number of radicals quenched per molecule of antiradical) for ascorbic acid, p-hydroquinone, catechol, quercetin, and rutin are similar when measured by colorimetric assays; however, considerably lower values of n are obtained with the luminol assay. The antiradical activity of extracts from male and female individuals of Baccharis burchelli and Baccharis crispa were determined by the luminol assay and expressed using the new Trolox® percentage (%Trolox®) parameter.

Samlade dikter

Josef Julius Wecksell (1838-1907) luetaan aikakautensa lahjakkaimpiin kirjailijoihin, jonka elämäntyö kuitenkin keskeytyi varhain psyykkisen sairauden vuoksi. Wecksell herätti jo koulupoikana Turussa huomiota romanttisilla ja isänmaallisilla runoilla ja näytelmillään.

Kunnallishallinnon mannereurooppalaiset uudistamissuunnat

Kirjallisuusarvostelu

Teses sobre o estatuto subjetivo do significar e comunicar em Kant e Nietzsche

O presente artigo tem por objetivo, na primeira parte, explorar algumas teses gerais apresentadas por recente pesquisa de Josef Simon acerca do estatuto da linguagem na filosofia de Kant, em especial no que tange ao modo de significar e comunicar presente nas reivindicações de verdade dos juízos. Em segundo lugar, pretende-se pontuar a crítica de Nietzsche a um modo de significar e comunicar ao qual denomina "gregário", contrapondo-o a uma comunicação e significação "individualizada". Como apontamos no final, a visada interlocução entre Kant e Nietzsche acerca do significar e comunicar se dará segundo um aspecto central: o fator subjetivo presente em qualquer reivindicação discursiva da razão.

Var det en dröm?

Soitinnus: lauluääni, piano.

Vill du komma med mig

Soitinnus: lauluääni, piano.