Chromatographic determination of phosphine (PH3) and hydrogen sulfide (H2S) in the headspace of anaerobic bacterial enrichments using flame photometric detection

Summary A gas chromatographic method is presented which distinguishes phosphine from hydrogen sulfide and other possible headspace gases of anaerobic microbial cultures. In anaerobic cultures spiked with phosphine, this gas is recovered in the liquid and gaseous phase down to 10 pg per ml of gas or liquid. No biogenically produced phosphine was found. Phosphine in amounts as small as 30 ng per 1 can be stored for several days in glass bottles covered with rubber septa, filled with nitrogen, in the presence or absence of water or of an anaerobic bacterial culture. Due to the selectivity of the detector and the retention characteristics of the porous layer open tubular polymer column alkanes, alkenes and organosulfur compounds routinely found in anaerobic bacterial headspaces do not interfere with the analytical quantification of phosphine.     

Multiple charge-transfer emissions from different metal-ligand pairs in ruthenium diimines

Ruthenium diimines are unique in their emissivity. Optical excitation with light of less than 500 nm leads to a strong emission in the 600-700 nm range. All emissive ruthenium complexes appear to undergo intersystem crossing from the absorptive singlet metal-to-ligand charge-transfer (MLCT) state to an emissive triplet MLCT state localized on the lowest-energy metal-ligand pair. In contrast to this currently accepted model, in which a single emissive state is populated and then equilibrates among other states based on a particular set of conditions, the excitation-wavelength dependence of the [(bpy)2RudppH]3+ emission suggests two emissive pathways. One populates an emissive MLCT state localized on a bpy-Ru pair, and the other populates a lower-energy MLCT state localized on the dpp-Ru pair.     

Plasters in the Cellars of the Visconti Castle in Pavia. Physico-chemical characterization

An archaeometric investigation on plaster samples taken from the cellars of the Visconti Castle in Pavia has brought out the existence of several layers and colour films of various periods. The oldest plaster spread over the masonry is formed with three main layers. Above them, one film of bluish-black colour can be found on the arcs and on the bearing walls. On this black layer, a white film of calcitic composition, containing also apatite fragments, was spread. These ancient materials were subsequently covered in more recent times with plasters having different compositions and textures. In the present paper the properties of the three main plaster layers and those of the black film are reported in detail. The thermal behaviour of these materials was studied by means of differential thermal analysis and thermogravimetric analysis. The study was completed with scanning electron microscopy,microprobe analysis and X-ray diffraction on powders. The results obtained provide interesting clues for advancing reasonable hypotheses both on the methods adopted in ancient building yards, and on the techniques for the production of the pigments employed. This revised version was published online in July 2006 with corrections to the Cover Date.     

HARMONIC ANALYSIS ON THE QUOTIENT k~x非汉字符号k\A~1非汉字符号A~1

0 IntroductionThe group of norm-1 ideles A1 over a global field lt acts by 1111lltip1ication on t11e additivegroup of adeIes A. Let G = A1 be A be tl1eir semidirect product. Let r be its arithnletic sub-group kx oc k. For the case k = Q Dorian Goldfeld gavc ill [2] a Schwartz kernel on r\G whosegeometrical trace equals the prime 11un1ber side of the explicit fOr1llulas of A. Weil. A spectralillterpretatiou in the seuse of the Selberg trace formula is cal1ed for. In order that a geolllet…     

The thermal stabilities of alkali metal alkanoates. Part IV

The thermal stabilities of long-chain lithium and potassiumn-alkanoates from tridecanoate to eicosanoate have been investigated up to 873 K with a MOM derivatograph. The results obtained, together with available data of different kinds, allowed the findings that: (i) in an oxygen atmosphere, stability is limited to crystalline polymorphs; (ii) in nitrogen, the isotropic liquid stability range goes up to 1.3T _F /K when the melt forms on fusion of a lithium soap, but has only a narrow extent when the melt forms on clearing of a potassium soap.One of us (P. Ferloni) gratefully acknowledges a financial contribution jointly supplied by the Hungarian Academy of Sciences and the Italian National Research Council.     

Plasters and mortars in the central building of the university of Pavia

Plasters and mortars taken from the walls of the ancient hospital ‘San Matteo’ of Pavia (Italy), were investigated with thermal and other techniques. From the data collected, two groups of materials were brought out: the first one, containing the plasters, is remarkably richer in calcite than the second group, formed by the mortars. These findings allow one to relate these groups to two historical periods: the middle of the XV century, and the end of the XVIII century. Some hypotheses may also be made on the compositions of the binding/inert fractions adopted in preparing these materials in the building yards of the two periods.     

Marbles in the façade of the "Certosa di Pavia": a physico-chemical study

In the framework of an interdisciplinary research project on the well known monastery "Certosa di Pavia", the thermal and structural properties of marbles employed in the construction of the fa?ade of the basilica were investigated in order to detect the main decomposition phenomena occurring on the monument surface. The results obtained by means of thermogravimetric and differential thermal analyses, as well as by means of X-ray diffraction and IR spectroscopy, allowed one to characterize samples taken from various sculptures of the fa?ade and to bring out the degradation phenomena occurring in some of them, in particular the formation of "black crusts" with a high content in gypsum. The present findings are in fair agreement with those reported by other research groups which also studied with different techniques the construction materials of this monument.     

Short chain copper(II) n-alkanoate liquid crystals

Four short chain members of the copper(II) n-alkanoate series Cu(Cn)₂, from propanoate to hexanoate, have been synthesized, purified and characterized by means of optical microscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), FTIR and Raman spectroscopy. The TGA study shows that decomposition starts on heating above 420-470 K (depending on the sample) in a nitrogen atmosphere. In addition, thermal decomposition was investigated by DSC using special high pressure pans and endo- and exc-thermic processes were found which have not been reported previously. All but one of the compounds melt to a liquid crystal phase, which decomposes before the clearing point. The exception is the propanoate homologue, which decomposes directly from the solid state. Despite this problem of sample decomposition, the identification by optical microscopy of the tetragonal (butanoate) and hexagonal (pentanoate and hexanoate) discotic columnar phases was, for first time, possible by the addition of small amounts of the corresponding acid to the samples. These results are in agreement with the X-ray diffraction study performed using swelled mixtures of these salts with hydrocarbon solvents. Two solid-solid transitions, not previously reported in the literature, were found for the butanoate homologue at 395.9 and 422.9 K with ΔH=8.27 and 1.37 kJ mol^-1, respectively. The solid and liquid crystalline phases were investigated using variable temperature FTIR spectroscopy.