Showing papers by "University of Palermo published in 1974"
TL;DR: In this paper, the authors discuss the ring conversion of type 1→2 characterized by nucleophilic attack from a Z atom on a sp 2 -nitrogen atom with displacement of an atom.
54 citations
TL;DR: In this paper, the rearrangement of N - (1,2,4 - oxadiazol - 3 - yl)β - enamino ketones into 2 - acylamino - imidazolyl derivatives was described.
36 citations
TL;DR: In this paper, the rheological behavior of dilute solutions of flexible macromolecules is studied by means of a freely jointed multiple bead-rod model, which applies to arbitrary flow conditions.
Abstract: The rheological behavior of dilute solutions of flexible macromolecules is studied by means of a freely jointed multiple bead–rod model. The solution of the equations describing the mechanics of the system is obtained by means of a numerical procedure, which applies to arbitrary flow conditions. The case of the transient stress in uniaxial elongational flow is developed in some detail. A comparison with bead–spring models shows both quantitative and qualitative differences which are briefly discussed.
35 citations
34 citations
TL;DR: In this paper, the free ligands, HL, used in this study are:,′-(methylidynenitrilo)diphenol (HSab), -(o-hydroxyphenyl)benzothiazoline (H-Sat), -o_hydroxyanilino)crotonophenone (HBah), 4-(ohydroxymhenylimino)--pentanone (HAah) and -acetonyl--methylbenzithiazoline(HAat).
24 citations
TL;DR: In this article, the Mossbauer parameters isomer shift, δ, and quadrupole splitting, ΔE, of mono-organotin compounds have been collected and tabulated, from which it is deduced that RSn IV behave much more as Sn IV rather than R 2 Sn IV and R 3 Sn IV derivatives.
24 citations
TL;DR: The conductance of tetrabutylammonium tetraphenylboride, picrate, nitrate, and bromide has been measured at 25°C inn-butyronitrile and in mixtures of this solvent with dioxane, benzene, and carbon tetrachloride covering the range of dielectric constants from 10−24.26 as mentioned in this paper.
Abstract: The conductance of tetrabutylammonium tetraphenylboride, picrate, nitrate, and bromide has been measured at 25°C inn-butyronitrile and in mixtures of this solvent with dioxane, benzene, and carbon tetrachloride covering the range of dielectric constants from 10–24.26. For the picrate, nitrate, and bromide, the association constants at a given dielectric constant are independent of the chemical composition of the solvent. The changes of Walden products with solvent composition, however, are different, depending on which other solvent is mixed with the butyronitrile.
22 citations
TL;DR: In this article, a novel complex RClSntrid, where R is Me, Ph, n-Oct, and trid 2− are dianions of tridentate “planar” ligands with ONO and SNO donor atoms, was synthesized and investigated in the solid state by infrared and Mossbauer spectroscopy.
21 citations
TL;DR: Oocytes at the stage of vitellogenesis were isolated from sea urchin gonads and incubated in vitro with labelled lysine and the synthesis of arginine-rich and some other histone fraction was detected by column chromatography and electrophoresis.
21 citations
TL;DR: In this paper, a trans-R 2, cis-Cl 2 configuration is advanced for R 2 SnCl 2 NiSalen, where the square planar structure is maintained around Ni II, and the coordination to tin involves three-coordinate phenolic oxygens.
20 citations
TL;DR: Chromatography of a cyclohexane extract of commercial “dragon's blood” resin yielded a fraction containing pimaric, isopimaric, dehydroabietic and abietic acids, which a fifth component was tentatively identified as sandaracoparlic acid.
TL;DR: In this paper, the crystal structure of the dimethyl derivative is reported, showing that it behaves as a neutral bidentate ligand through its oxygen atoms forming binuclear complexes with organotin(IV) chlorides.
TL;DR: In this article, elongational viscosity data obtained for dilute solutions of Separan NP 20 in glycerol, were presented under transient stress conditions with two different experimental techniques, and the data were taken under different experimental settings.
Abstract: In this work, elongational viscosity data obtained for dilute solutions of Separan NP 20 in glycerol, are presented. The data are taken under transient stress conditions with two different experimental techniques.
TL;DR: In this paper, the conductance of potassium perchlorate in mixtures of ethylene carbonate and acetonitrile covering the range 82.6 ≥ D ≥ 36.0 in dielectric constant has been measured.
Abstract: The conductance of potassium perchlorate in mixtures of ethylene carbonate and acetonitrile covering the range 82.6 ≥ D ≥ 36.0 in dielectric constant has been measured. The Walden products in these aprotic solvents are approximately one-half as large as the products for the same salt in isodielectric mixtures of water and tetramethylene sulfone. This alters the distribution between electrostatic and hydrodynamic terms in the theoretical conductance function in such a way that the calculated association constants for potassium perchlorate are much smaller in the aprotic mixtures.
TL;DR: In this article, the different behavior of dilute and concentrated solutions (or melts) during an elongational flow is discussed and an interpretation of the data is attempted on the basis of well known concepts of macromolecular physics together with assumptions concerning the destruction and reformation of entanglements during the flow of the polymer.
TL;DR: Analysis of the giant RNA labeling kinetics suggested that the heterogeneous RNA, including classes of very slow electrophoretic mobility, found in the cytoplasm of sea urchin embryos, cannot be attributed to artifactual nuclear leakage.
TL;DR: In this article, the optimum plastic design of structures made up, or conceived as assemblies of finite elements, each having an elemental piece-wise linear rigid-plastic behaviour is studied.
Abstract: We study optimum plastic design of structures made up, or conceived as assemblies of finite elements, each having an elemental piece-wise linear rigid-plastic behaviour Since cost function linearly dependent on design variables are considered, optimization problems in linear programming are encountered Allowance is made for design dependent mass forces, and for some technological constraints The design growing process is studied in the case of various sets of alternative applied loads, and the optimality conditions are written in a proper geometrical form which leads to a generalization of the concept of Foulkes mechanism
TL;DR: The configuration in the solid state and in solution phase of complexes of SuIV wit,li tridentate ligands, Sn(trid)2 and HNEt3Cl3 Sntrid, have been investigated by infrared and MOSSBAUER spectroscopy, as well as by osmometry, conductivity, and electronic and PMR spectroscopic.
Abstract: The configuration in the solid state and in solution phase of complexes of SuIV wit,li tridentate “planar” ligands, Sn(trid)2 and HNEt3Cl3 Sntrid, have been investigated by infrared and MOSSBAUER spectroscopy, as well as by osmometry, conductivity, and electronic and PMR spectroscopy. The presence of monomeric Sn(trid)2 and ionic [HNEt] [Cl3Sn trid−] species has been inferred. Octahedral type configurations are advanced for both classes of compounds.
Komplexe des Zinn (IV) mit dreizahigen Liganden. Mossbauer- und IR-Spektren sowie Untersuchungen von Losungen
Die Struktur von SnIV-Komplexen mit dreizahnigen “planaren” Liganden, Sn(trid)2 und HNEt3Cl2Sntrid, wurde in fester Phase und in Losung untersucht mit Hilfe von IR- und MOSSBAUER-Spektroskopie (fur den festen Zustand) sowie osmometrisch, mit Leitfahigkeitsmessungen, UV-VIS- und NMR-Spektroskopie. Danach wird das Vorliegen von monomerem Sn(trid)2 und ionischem [HKEt3]+[Cl3Sntrid]− angenommen. Bei beiden Arten von Verbindungen liegt vermutlich oktaedrische Konfiguration vor.
TL;DR: It is shown by sucrose gradient analysis, by Sepharose chromatography, and by electrophoresis under denaturing conditions, that the slow electrophoretic mobility of part of the heterogeneous cytoplasmic RNA of sea urchin embryos is actually due to its very high molecular weight.
TL;DR: It is demonstrated that some heterogeneous RNA including gigantic classes is extractable from polysomes of sea urchin embryos and it is suggested that a substantial part of this RNA contains poly-A sequences.
TL;DR: In this article, it was shown that the general theory of simple fluids with fading memory is based on certain assumptions of smoothness for the constitutive functional which are violated by constitutive equations of the type discussed.
Abstract: Many constitutive equations for viscoelastic materials which have appeared in the literature are modifications of the linear viscoelasticity model. Their general form is:
[5]
$$\tau = \int\limits_0^\infty {(f_1 C + f_2 C^{ - 1)} ds.} $$
The memory functionsf
1 andf
2, are assumed to depend explicitly on either some instantaneous or some timeaveraged value of the invariants of the rate of strain. It is shown in this paper that the general theory of simple fluids with fading memory is based on certain assumptions of smoothness for the constitutive functional which are violated by constitutive equations of the type discussed. This implies that, should any real material obey eq. [5], with an explicit dependency of thef
i's on the rate of strain, such a material would not obey the general theorems of the simple fluid theory which are based on different smoothness hypotheses. A critical analysis of available experimental evidence shows that it supports the validity of the smoothness hypotheses underlying the theory of simple fluids with fading memory, while contradicting those implied by an explicit dependency of the memory functions on the rate of strain.
TL;DR: In this paper, tetraphenylarsonium and tetramethylammonium salts of the complex anions Ph 3 Pb(N 3 ) − 2, Ph 3 pb(n 3 )(NCS) −, Ph 2 PbN 3 (2 − 4 )) and Ph 2 pb n 3 (NCS 1 )(S 2 )− 2 have been prepared and characterized.
TL;DR: In this paper, the 1/1 adducts of organolead(IV) and organothallium(III) chlorides with the complexes N,N′-ethylenebis(salicylideneiminato)nickel(II) and bis(β-mercaptoethylamine)Nickel (II) have been synthesized.
TL;DR: The Mossbauer parameters of Ph 2 SnDB, PhClSnDB and Sn(DB) 2 were determined, where DB 2− is the dianion of the multidentate ligand diacetylbis(benzoylhydrazone) as mentioned in this paper.
TL;DR: The author has studied the influence of different temperatures on oviposition and longevity ofOpius concolor siculusMon.
Abstract: The author has studied the influence of different temperatures (22°, 24°, 26°, 28°C) on oviposition and longevity ofOpius concolor siculusMon., studying separately 13 couples at 22°, 15 at 24°, 100 at 26° and 11 at 28°C.
TL;DR: In this paper, conductance measurements of potassium perchlorate and iodide have been carried out on the following mixtures: methanol-ethylene carbonate, acetone-methylene carbonates, acetonitrile-ethylenes carbonate with water; and in benzene-sulfolane.
Abstract: Conductance measurements of potassium perchlorate and iodide have been carried out on the following mixtures: methanol-ethylene carbonate, acetone-ethylene carbonate, acetonitrile-ethylene carbonate, sulfolane-ethylene carbonate, isodielectric with water; and in benzene-sulfolane, benzene-acetonitrile, ethanol-sulfolane, isodielectric with methanol. The extent of ionic association at a given concentration in two solvents of the same dielectric constant is greater in the aprotic solvent.