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Molecular Ratio (molecular + ratio)
Selected AbstractsRe-creation of the 1744 Heylyn and Frye ceramic patent wares using Cherokee clay: Implications for raw materials, kiln conditions, and the earliest English porcelain productionGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 7 2004W.R.H. Ramsay Porcelain wares have been produced following the directions contained in the Heylyn and Frye patent of 1744, using Cherokee clay and a lime-alkali glass frit. The wares were fired to the bisque (, 950°C), glazed using a clay-glass mixture, and then fired to a "heat-work" level of Orton cone 9,90° deflection at 150°C per hour (1279°C). Modal mineralogy comprises Caplagioclase and two glass phases, one relict frit and the other a melt phase. The bulk chemistry of the body comprises 64.3 wt % SiO2, 21.7 wt % Al2O3, and 5.6 wt % CaO. Molecular ratios are SiO2:Al2O3 5.0 and SiO2:CaO 10.7. It is concluded that the patent, whose significance has been questioned over many years, was a practical working recipe, that close comparison may be made with porcelains of the "A"-marked group, and that the patent represents a remarkable landmark in English ceramic history. © 2004 Wiley Periodicals, Inc. [source] A Study of L-Lactide Ring-Opening Polymerization KineticsMACROMOLECULAR SYMPOSIA, Issue 1 2007Jean-Pierre Puaux Abstract Summary: The paper presents an experimental study of L-lactide polymerization in molten state using as initiator the Stannous Octoate. The experiments were performed in a Haake mixer. The operating temperatures were between 170 and 195°C, the reaction time up to 60 min and monomer to initiator initial molecular ratio between 102 and 5,·,103. The conversion was determined by using 1H NMR and the molecular weights distributions by SEC. A preliminary mathematical modeling study was also performed, based on experimental data and a previously published reaction scheme. [source] Luminescent Excited-State Intramolecular Proton-Transfer (ESIPT) Dyes Based on 4-Alkyne-Functionalized [2,2,-Bipyridine]-3,3,-diol DyesCHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2008Gilles Ulrich Dr. Abstract Functionalized 6,6,-dimethyl-3,3,-dihydroxy-2,2,-bipyridine dyes (BP(OH)2) exhibit relatively intense fluorescence from the relaxed excited state formed by excited-state intramolecular proton transfer (ESIPT). Bromo functionalization of (BP(OH)2) species followed by palladium(0)-catalyzed reactions allows the connection (via alkyne tethers) of functional groups, such as the singlet-emitter diazaboraindacene (bodipy) group or a chelating module (terpyridine; terpy). The X-ray structure of the terpy-based compound confirms the planarity of the 3,3,-dihydroxy-bipyridine unit. The new dyes exhibit relatively intense emission on the nanosecond timescale when in fluid solution, in the solid state at 298,K, and in rigid glasses at 77,K. In some cases, the excitation wavelength luminescence was observed and attributed to 1),inefficiency of the ESIPT process in particular compounds when not enough vibrational energy is introduced in the Franck,Condon state, which is populated by direct light excitation or 2),the presence of an additional excited state that deactivates to the ground state without undergoing the ESIPT process. For some selected species, the effect of the addition of zinc salts on the absorption and luminescence spectra was investigated. In particular, significant fluorescence changes were observed as a consequence of probable consecutive formation of a 1:1 and 1:2 molecular ratio of ligand/zinc adducts owing to coordination of ZnII ions by the bipyridyldiol moieties, except when an additional terpyridine subunit is present. In fact, this latter species preferentially coordinates to the ZnII ion in a 1:1 molecular ratio and further inhibits ZnII interaction. In the hybrid Bodipy/BP(OH)2 species, complete energy transfer from the BP(OH)2 to the bodipy fluorophore occurs, leading to exclusive emission from the lowest-lying bodipy subunit. Des composés colorés à base de 6,6,-dimethyl-3,3,-dihydroxy-2,2,-bipyridine (BP(OH)2) ont été synthétisés et présentent une fluorescence relativement intense issue de la relaxation d,un état excité provenant d,un transfert de proton dans l,état excité (ESIPT). La bromation de dérivés (BP(OH)2) suivie d,un couplage croisé catalysé par du Pd0sous-ligandé permet de connecter (par l,intermédiaire de pont alcyne) des groupes fonctionnels comme un groupe émetteur singulet de type boradiazaindacène (Bodipy) ou un module chélatant universel (une terpyridine). Une structure par diffraction aux rayons X a été obtenu avec le dérivé terpyridine, celle ci confirme la planéité de l,unité 3,3,-dihydroxy-bipyridine. Les nouveaux fluorophores possèdent une émission relativement intense avec une durée de vie de l,ordre de la nanoseconde, en solution et à l,état solide à 298,K ainsi que dans un verre à 77,K. Dans certain cas, la luminescence dépend de la longueur d,onde d,excitation, ce phénomène est attribué à (i) l,inefficacité du processus ESIPT, quand trop peu d,énergie vibrationnelle est introduite dans l,état Franck-Condon peuplé directement par la lumière d,excitation (ii) la présence d,un état excité supplémentaire qui désactive l,état fondamental sans passer par un processus ESIPT. Pour certains composés, l,effet de l,addition de sels de Zinc sur les spectres d,absorption et d,émission a été étudié : en particulier, des changements significatifs de fluorescence ont été observés, probablement due à la formation consécutive de complexes ligand/zinc de st,chiométrie 1:1 et 1:2, provenant de la coordination des cations ZnIIpar l,unité bipyridyl-diol, sauf quand une fonction terpyridine est présente. En fait, dans cette dernière espèce le zinc est préférentiellement coordiné par la terpyridine dans un ratio 1:1, et toute coordination supplémentaire de Zinc semble inhibée. Dans le composé hybride Bodipy/BP(OH)2,un transfert d,énergie quantitatif est observé du BP(OH)2vers le fluorophore Bodipy, entraînant une émission exclusive de la sous-unité Bodipy. Composti basati sulla subunità 6,6,-dimetil-3,3,-dididrossi-2,2,-bipiridina (BP(OH)2), variamente funzionalizzati, presentano fluorescenza relativamente intensa da stati eccitati formati attraverso trasferimento protonico nello stato eccitato (ESIPT). Bromo-funzionalizzazione dei composti di tipo BP(OH)2, seguita da reazioni catalizzate da Pd(0), permettono di connettere (con legame alchinico) gruppi funzionali quali il diazaboroindacene (Bodipy) o un modulo chelante (terpiridina) al frammento BP(OH)2. La struttura ai raggi X del composto contenente la terpiridina conferma la planarità dell,unità 3,3,-diidrossi-bipiridina. Le nuove specie presentano intensa emissione nella scala dei nanosecondi, in soluzione fluida ed allo stato solido a 298,K ed in matrice rigida a 77,K. In alcuni casi, la luminescenza dipende dalla lunghezza d,onda di eccitazione: questo fenomeno è attribuito a (i) inefficienza del processo ESIPT, quando non sufficiente energia vibrazionale è introdotta nello stato Franck-Condon a seguito di eccitazione luminosa o (ii) alla presenza di uno stato eccitato addizionale che si disattiva allo stato fondamentale senza passare dallo stato eccitato prodotto attraverso il meccanismo ESIPT. Per composti selezionati è stato anche studiato l,effetto della presenza di sali di zinco sulle proprietà di assorbimento elettronico e di luminescenza: significativi cambiamenti della fluorescenza sono stati osservati, come conseguenza della consecutiva formazione di addotti 1:1 e 1:2 (rapporto molare BP(OH)2/zinco), dovuta alla coordinazione di cationi di ZnIIda parte del bipiridil-diolo, che si verifica in tutti i casi studiati tranne in presenza di una subunità terpiridinica. In quest,ultimo caso, infatti, si forma soltanto l,addotto 1:1, e ulteriore coordinazione di cationi di ZnIIappare inibita. Nella specie ibrida Bodipy/BP(OH)2si verifica un completo trasferimento di energia elettronica dal BP(OH)2 al Bodipy, che porta ad emissione esclusivamente dalla subunità Bodipy, a piû bassa energia. [source] Yellow-brown earth on Quaternary red clay in Langxi County, Anhui Province in subtropical China: Evidence for paleoclimatic change in late Quaternary period,JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 4 2008Xue-Feng Hu Abstract In order to investigate the paleoclimatic changes in S China during the late Quaternary and their influence on pedogenesis and soil classification, a yellow-brown earth (YBE),red clay (RC) profile in Langxi County, Anhui Province was studied. The grain-size distribution and the major- and trace-element compositions of the profile indicate that the YBE of the profile shares the same origin with the YBE in Jiujiang and Xuancheng and the Xiashu loess in Zhenjiang, and the underlying RC also has aeolian characteristics and shares the same origin with the Xiashu loess. Grain-size characteristics, molecular ratios of SiO2/Al2O3, SiO2/(Al2O3+Fe2O3), and BA ([CaO+MgO+K2O+Na2O]/Al2O3) and other weathering indices (CaO/TiO2, MgO/TiO2, K2O/TiO2, Na2O/TiO2, and Rb/Sr) of the profile indicate that the RC is more strongly weathered than the YBE. Magnetic susceptibility (,lf) of the uniform red clay (URC) of the profile is significantly enhanced. However, that of the underlying reticulate red clay (RRC) is significantly decreased because of the paleogroundwater movement and cannot indicate its strong weathering properties. The YBE-RC profile in Langxi County recorded a great climatic change during late Quaternary: At that time, the pedogenic development of the RC was terminated and widespread dust deposition occurred. The parent material of the RC may be aeolian deposits which were accumulated before the last interglacial and were strongly weathered and rubified under the subsequent interglacial climate. It is observed that red soils, derived from the RC, and yellow-brown soils, derived from the YBE, coexist in the study area, which is contradictive to the theory of the zonal distribution of soils. Therefore, it is necessary to take into account the history of Quaternary climatic changes when studying pedogenesis. [source] A geochemical study of bituminous mixtures from Failaka and Umm an-Namel (Kuwait), from the Early Dilmun to the Early Islamic periodARABIAN ARCHAEOLOGY AND EPIGRAPHY, Issue 2 2007Jacques Connan This paper is the last in a series presenting geochemical analyses of fragments of bituminous mixtures excavated from archaeological sites in Kuwait. The first was devoted to bituminous boat remains from the Ubaid-related Neolithic site of H3, As-Sabiyah, while the second dealt with bituminous amalgams from the Partho-Sasanian site of cAkkaz, a former island now joined to the south side of Kuwait Bay. This, the third, refers to bitumen-bearing samples from two other islands, Failaka and Umm an-Namel, and covers a time span including the Early Dilmun period, the Kassite period and the Hellenistic to Early Islamic periods. The composition of the bituminous amalgams was studied in detail. The proportions of soluble and insoluble organic matter as well as vegetal organic matter were evaluated. Mineralogical composition by X-Ray diffraction and thin-section analysis was used to estimate the mineral input in the bituminous mixtures. It can be confirmed that the recipes used in the preparation of these bituminous amalgams comply with those traditionally used in antiquity, as seen at many sites in Mesopotamia and the Gulf. Analysis of the soluble organic matter, and especially its ,,saturates'' fraction, provided sterane and terpane distributions and the measurement of diagnostic molecular ratios. These data, complemented by the isotopic composition of asphaltenes, allowed the identification of the sources of the bitumen, by calibration with numerous references from Iran and northern Iraq (oil seeps, bitumen from archaeological sites). It was established that the bitumen from Failaka and Umm an-Namel was mainly imported from central Iraq (Hit-Abu Jir) and northern Iraq (around Mosul). One sample of oil-stained sand, dating to the Early Dilmun period, originated from Burgan and thus documents small-scale imports from inland Kuwait. These results, and those of previous analyses, agree with the geopolitical context of the Early Dilmun, Kassite and Hellenistic periods, and the maritime trade routes that linked Mesopotamia to the settlements of the Gulf and beyond. The paper concludes with an overview of recent bitumen provenance analyses, and discerns chronological patterns in the distribution of Iraqi and Iranian bitumen in the Gulf and Indian Ocean, from the Neolithic to the Islamic periods. [source] | ||||||||||