Physical properties and phase separation structure of Antheraea pernyi/Bombyx mori silk fibroin blend films

The physical structure and compatibility of solution-cast Antheraea pernyi/Bombyx mori silk fibroin blend films were stuided by differential scanning calorimetry (DSC), thermomechanical (TMA) and thermogravimetric (TGA) analysis, dynamic viscoelastic measurement, infrared spectroscopy, and x-ray diffractometry. The DSC curves of the blend films showed independent endotherms at 280 and 358°C, corresponding to the thermal decomposition of B. mori and A. pernyi silk fibroins with random coil conformation. The intensity was roughly proportionate to the amount of each component in the blend. The thermal behavior corresponding to the conformational transitions induced by heating on A. pernyi and B. mori silk fibroins overlapped in the temperature range 190–230°C. Thermal expansion and contraction properties, as well as weight retention behavior of the blend films were intermediate between the pure components, as shown by the TMA and TGA curves. The onset temperature of the storage modulus curve decreased markedly, approaching that of B. mori silk fibroin film when the amount of this component in the blend increased. The loss modulus curve of the blend films showed two peaks at ca. 190 and 210°C, the former corresponding to B. mori, and the latter to A. pernyi silk fibroin. Infrared spectra of the blends exhibited absorption bands characteristic of the pure components overlapping in the spectral region 2000–400 cm^?1. The x-ray diffraction peaks at 23 and 21.5°, attributed to the crystalline spacings of A. pernyi and B. mori fibroins, respectively, overlapped in the diffraction curves of the blends, while the peak at 11.4°, of A. pernyi, increased as the content of this fibroin in the blend increased. The degree of crystallinity, calculated from the x-ray diffraction curves, diminished as the amount of B. mori silk fibroin decreased. A low degree of compatibility exists between the two fibroins when they are cast from aqueous solution in the experimental conditions adopted in this work. © 1994 John Wiley & Sons, Inc.     

Air monitoring of volatile aromatic compounds by means of long-term exposure diffusive samplers

Results obtained by using "Analyst", a long-term diffusive sampler, in some monitoring campaigns, performed for the determination of benzene and the volatile aromatic pollutants, in five cities of the Italian Umbria Region and at the city of Forlì, are presented and discussed. First results of an inter comparison between the "Analyst" and "radial-type" diffusive samplers, carried out by the Regional Agency for the Ambient Protection (ARPA) of Forlì, point out substantial advantages with the long-time sampling devices.     

Testing equality in lisp-like environments

A function is presented to test equality between lists. In any case the function requires at most one single traversal of the lists and behaves as follows:

1. if there are no cycles, it works as standardEQU AL functions;
2. if there are cycles, it does not give information about equality, but it can detect cycles, i.e. it signals which lists are cyclic.

A simplified version of the function is also considered which is always at least as efficient as standardEQU AL; it grants protection against cycles without signaling them. A coroutine organized version of the function is shown.     

An iterative extended Hückel calculation for some amino acids containing sulphur and selenium

Semiempirical iterative extended Hückel calculations are performed for the dipolar ions of cystine, cysteine, methionine and their selenium analogues. An attempt has been made to interprete the wave function of cysteine in terms of localized molecular orbitals.

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Zusammenfassung Semiempirische iterative Rechnungen wurden nach der erweiterten Hückeltheorie für die dipolaren Ionen Cystin, Cystein, Methionin und ihre Selen-Homologen durchgeführt. Für den Fall des Cysteins wurde die Wellenfunktion auf lokalisierte Orbitale transformiert.

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Résumé On a analisé les ions dipolaires de la cystine, cystéine, methionine et leurs analogues séléniates avec la méthode semiempirique de Hückel étendue itérative. On a cherché à intérpreter la fonction d'onde pour la cystéine dans le schème des orbitales moleculaires localisées.

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Work performed with the financial support of the Consiglio Nazionale delle Ricerche.     

Reaction of electrochemically produced radical cations with organic monomers

The reactivity of free radical cations, produced by anodic oxidation of 9, 10-diphenylanthracene (and perylene), with polymerizable organic monomers has been investigated by amperometry.It results that the radical cations, which are relatively stable in acetonitrile and nitrobenzene, decay with the monomer substrate by either an addition reaction or an electron transfer process. The cationic species of the monomer thus produced by catalyze the cationic polymerization of the substrate.The cationic polymerization initiated in this way has been investigated in the case of styrene: this reaction shows some similarity with the process initiated by perchloric acid, but carbonium ion carriers seem to give the main contribution to the propagation stage.     

Field Study on Mobility and Persistence of Linuron and Monolinuron in Agricultural Soil

Abstract

A field site equipped with suction cup lysimeters was installed at Treviglio (BG) to assess the migration capacity of the herbicides linuron and monolinuron from topsoil to groundwater and to verify the appearance of their relevant transformation products in soil and water samples. A constant hydraulic head was applied in order to develop water saturation conditions in the upper layers. KCl was used as a tracer to evaluate water infiltration velocity through the vertical soil profile. The constant hydraulic head accelerated infiltration rates, while herbicide concentrations reached maximum contamination because soil adsorption capacity was underdeveloped. The results indicated two main processes of pesticide transport: firstly transport due mainly to water infiltration through macropores; secondly the transport driven by matrix flow. Linuron was found to be the most mobile herbicide, while chloroanilines were found to be the major transformation products of the herbicides considered.     

Synthesis of Glycosyl Azides by the Addition of Phenylselenenyl Azide to Glycals

Abstract

The addition of phenylselenenyl azide to glycals is carried out under conditions that give 2-deoxy-2-phenylselenoglycosyl azides. This regiochemistry is opposite to that obtained under free-radical conditions, which are known to produce 2-azido-2-deoxyselenoglycosides. The addition reaction is carried out with phenylselenenyl chloride and sodium azide in dimethylformamide, and is stereoselective for trans addition. Tri-O-benzyl-d-glucal and di-O-benzyl-l-rhamnal each gave two addition products, in which the phenylselenyl and azido groups were either trans diaxial or trans diequatorial. Tri-O-benzyl-d-galactal gave only the trans diaxial addition product.     

Electronic properties of nonhomovalent alloys: A study of the b.c.c. Li−Mg solid solution

Summary The influence of the alloying on the electronic properties of the b.c.c. Li−Mg solid solution has been investigated within the KKR-CPA framework. Such an influence has been studied by computing the band structure, Fermi surface, soft X-ray spectra, residual resistivity and Auger spectra for chosen values of the composition. The theoretical results we obtained are in fair agreement with the surface existing experimental data and support the view that also in ?simple metals? alloys care has to be taken in studying such systems in terms of low-order perturbation approaches.

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Riassunto Sono state studiate varie proprietà elettroniche delle leghe di Li−Mg nell’intervallo di concentrazione in cui questi sistemi cristallizzano nel reticolo b.c.c. In particolare sono state calcolate la struttura a bande, le superfici di Fermi, la resistività residua, gli spettri X ed Auger e si sono confrontati i risultati con i dati sperimentali esistenti. Il buon accordo fra risultati teorici e dati sperimentali indica che, anche per leghe di metalli semplici, gli approcci perturbativi a basso ordine possono essere insufficienti a descrivere il comportamento di tali sistemi.

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Резюме В рамках KKR-CPA исследуется влияние процесса сплавления на электронные свойства объемноцетририованного кубического твердого раствора Li−Mg. Проводятся вычисления зонной структуры, поверхности Ферми, спектров мягкого рентгеновского излучения, остаточного сопротивления и Ож-ye-спектров для выбранных величин состава. Полученные теоретические величины хорошо согласуются с существуюими экспериментальными данными.

     

Robust and efficient generator of almost maximal multipartite entanglement

Quantum chaotic maps can efficiently generate pseudorandom states carrying almost maximal multipartite entanglement, as characterized by the probability distribution of bipartite entanglement between all possible bipartitions of the system. We show that such multipartite entanglement is robust, in the sense that, when realistic noise is considered, distillable entanglement of bipartitions remains almost maximal up to a noise strength that drops only polynomially with the number of qubits.     

Electronic properties of b.c.c. transition metal solid solutions. a study of the Nr−Nb system

Summary Calculations of electron densities of states and of soft—X-ray absorption spectra in Zr−Nb alloys have been performed in the frame of the coherent potential approximation in its multiple-scattering version (KKR-CAP). It is shown that a lot of care is needed in applying the simple rigid-band model to these systems, in order to explain experimental data. Results are also diseussed in connection with existing experimental data and good agreement is found.

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Riassunto Sono stati eseguiti calcoli di densità di stati elettronici e di spettri di assorbimento di raggi X molli nella lega Zr−Nb a varie concentrazioni, nell'àmbito dell'approssimazione di potenziale coerente nella sua versione di scattering multiplo (KKR-CPA). Si mostra che è necessaria molta attenzione per poter interpretare dati sperimentali come semplice modello a bande rigide. I risultati sono inoltre, discussi in connessione con, i dati sperimentali esistenti con i quali si riscontra un buon accordo.

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Резюме в рамках приближения когерентного потенциала и его модификации для многократного рассеяния проводится вычисление плотностей электронных состояний и спектров поглощения мягких рентгеновских лучей в Zn−Nb сплавах. Показывается, что необходимо проявлять особое внимание при интерпретации экспериментальных данных с помощью простой модели недеформируемых зон. Полученные результаты обсуждаются в связи с имеющимися экспериментальными данными и овнаружено хорошее согласие.

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Work also sponsored by Assessorato Industria della Regione Siciliana.