A prototype calix[4]arene-based receptor for carbohydrate recognition containing peptide and phosphate binding groups

A novel class of macrobicyclic receptors for carbohydrate recognition based on upper rim, peptide-bridged calix[4]arenes has been designed and synthesized. Receptor 12, in which a charged phosphate group cooperates with peptide hydrogen-bonding donor and acceptor groups in the binding process, is the most efficient and selective in the complexation of simple carbohydrate derivatives. The selectivity observed is toward beta-glucoside 13a, which is better bound (DeltaG degrees = 19.6 kJ mol(-)(1)) compared to the corresponding alpha anomer 13b (DeltaG degrees = 17.0 kJ mol(-)(1)) and to the beta-galactoside 13c (DeltaG degrees = 17.7 kJ mol(-)(1)) in CDCl(3). A substantial drop in the stability constant is observed by esterification of the phosphate group in the host 12 or by alkylation of the OH groups in the 2 and 3 positions in the beta-glucoside and beta-galactoside derivatives. On the basis of a careful analysis of the (1)H NMR data available, a binding mode of the beta-octylglucoside 13a to receptor 12 is proposed.     

Effect of support on the synergy in HDS of thiophene and HDN of pyridine over Mo sulfide catalysts promoted by Rh

The effect of support (SiO₂-Al₂O₃, Al₂O₃,MgO) of the Rh-Mo(S) sulfide catalysts on the synergy in hydrodesulfurization (HDS) of thiophene and hydrodenitrogenation (HDN) of pyridine was studied. The synergy in HDS was between 7–10 regardless of the kind of support used. The synergy in HDN varied from none over the MgO supported sample to about 3 over SiO₂-Al₂O₃ supported catalyst, in accord with the positive effect of increasing support acidities. This revised version was published online in June 2006 with corrections to the Cover Date.     

Investigations by various analytical techniques to the correct classification of archaeological finds and delineation of technological features: Late Roman lamps from Egnatia: From imports to local production

Late Roman oil lamps from the archaeological site of Egnatia (Fasano, Brindisi, Italy) were characterized from physical–chemical, mineralogical and morphological points of view. Atomic Spectroscopy, Scanning Electron Microscopy and X-Ray Diffraction analyses were carried out on ceramic body and coatings with the aim of identifying the provenance of lamps, in order to arrive at a correct archaeological classification of finds and to outline their technological features.The analytical results show that the finds differ in raw materials and in production technology. The statistical multivariate treatment of compositional data of ceramic bodies groups the objects into two macro clusters and, according to a study of their different petrographic features and by a comparison with coeval pottery whose provenance is already known, suggests one group to have been imported from North Africa and the other to have been locally produced. Moreover, chemical results and in-depth archaeological analyses allow us to split the imported lamps into two subgroups, hypothesizing the first group to originate from central Tunisia and the second from the north of the same country.The analytical characterisation of finds, by different complementary techniques, has allowed us to identify the raw materials and the technological solutions used by the ancient potters from Egnatia to produce lamps. The potters made lamps which had an external appearance very similar to that of African prototypes, but which were nevertheless different as they employed the locally available materials.     

A synthetic divalent cholera toxin glycocalix[4]arene ligand having higher affinity than natural GM1 oligosaccharide

A high-affinity ligand of cholera toxin, the divalent glycocalix[4]arene 1, was obtained by exploiting a combination of structure-based design of glycomimetic monovalent ligands and affinity enhancements by multivalent presentation through a calix[4]arene scaffold. It exhibits a slightly higher affinity for the toxin than its natural ligand, the GM1 oligosaccharide.     

Synchronous fluorescence spectroscopy and gas chromatography to determine the effect of UV irradiation on crude oil

The fate of the crude oil under irradiation was studied. After the UV irradiation, the fraction present in the highest percentage shifted from C8–C9 fraction to C13 one, in GC–MS analysis. An increase of the relative amount of the C13–C25 fraction was observed, while a decrease in the relative amount of the C7–C12 fractions was present. The synchronous fluorescence spectrum showed a maximum at 396 nm. Two hours irradiation of the sample induced an increase of the fluorescence emission in the region 420–550 nm. After 20, 40, 60, and 100 h irradiation we observed a decrease of the fluorescence emission.     

Influence of copper solute on the creep rate sensitivities of aluminium

The presence of copper atoms as continuous networks at the grain boundaries of an aluminium-copper alloy has been considered not preventing the moving of dislocations during creep (or at least partially). The dislocations can bs absorbed by these boundaries and penetrate through them. That leads to changés of shape and structure of grains and also to the sliding of grains against each other. This was deduced from the accelerating increase in the sensitivity of the steady state creep rate to the applied stress of an aluminium 2·8 wt% copper alloy examined at wide range of temperatures (50–350 °C) and applied stresses (7–170 MPa). This rapid increase in the sensitivity parameter of the steady state creep rate occurs in Al-Cu alloys at quite higher ranges of applied stresses and may be attributed mainly to the contribution of the grain boundary movements to the creep strain.     

Study of the Crystallization Kinetics. Poly(ethylene oxide) and a blend of poly(ethylene oxide) and poly(bisphenol A-co-epichlorohydrin)

A kinetic study of the crystallization of poly(ethylene oxide) (PEO) and of a blend of PEO+poly(bisphenol A-co-epichlorohydrin) (PBE) was performed by using DSC in a non-isothermal program at constant cooling rates. The curves obtained were analyzed by the Kissinger, Ozawa and Friedman methods, with determination of the kinetic parameters in each case. As a consequence of the presence of PBE, the kinetic parameters were altered, leading to the conclusion that PBE has some influence on the crystallization of PEO, modifying its mechanism. This revised version was published online in July 2006 with corrections to the Cover Date.     

The method of interpolating integral equations for quantum Fluids.—III

Summary A method for interpolating between the (F)HNC and (F)PY approaches in order to take into account elementary contributions has been presented in two preceding papers concerned with the properties of zero-temperature quantum fluids, described by short-range correlated wave functions. In the present paper, both for Bose and for Fermi systems, the technique is extended to the case in which the two-body radial distribution function contains a long-range tail, going asr ⁻⁴. The results obtained for the energy per particle and momentum distribution of liquid⁴He, polarized hydrogen and³He are presented in correspondence to variational wave functions containing only two-particle correlations.

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Riassunto In due precedenti lavori è stata sviluppata una tecnica di interpolazione tra le approssimazioni (F)HNC e (F)PY per tenere conto dei cosiddetti contributi elementari nel calcolo delle proprietà dei fluidi quantistici a temperatura zero e descritti da funzioni d’onda con fattori di correlazione a corto raggio. Nel presente lavoro il metodo è esteso, per sistemi sia bosonici che fermionici, al caso in cui la funzione radiale di distribuzione contenga una coda con andamentor ⁻⁴. Sono presentati i risultati ottenuti per l’energia per particella e la distribuzione di quantità di moto dell’⁴He liquido, dell’idrogeno polarizzato e dell’³He liquido, in corrispondenza a funzioni d’onda variazionali contenenti solo correlazioni di coppia.

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Резюме В двух предыдущих работах был предложен метод интерполяции между (F)HNC и (F)PY подходами. В этих работах рассматривались свойства квантовых жидкостей при нулевой температуре, которые описываются волновыми функциями с короткодействующими корреляциями. В данной работе, для Бозеи Ферми-систем, предложенная тенхика обобщается на случай, когда двух-частичная радиальная функция распределения содержит длиннодействующий хвост, который спадает какr ⁻⁴. Приводятся результаты для энергии на одну частицу и импульсное распределение для жидкого⁴He, поляризованного водорода и³H, причем соответствующие вариационные волновые функции содержат только двух-частичные корреляции.

     

Theoretical calculation of electron impact widths and shifts of XeII lines

Summary The shifts and widths of prominent XeII transitions are calculated in the semi-empirical approach; a very good agreement with experimental values is obtained. The oscillator strengths were calculated using complete intermediate coefficients after energy matrix diagonalization. The author of this paper has agreed to not receive the proofs for correction.     

Depth selective conversion electron spectrometer for magnetic characterisation of thin films

A high transmission spherical electrostatic electron spectrometer for Mössbauer conversion electron spectroscopy was built. Depth selective Mössbauer studies can be carried out from T=4 K to 350 K in a 10^?8 Torr vacuum changing the electron energies and/or the electron escape angles.