The reaction of pyrroles with trimethylhalosilanes-dialkyl sulfoxides

Pyrroles are powerful nucleophiles in the reaction with dialkyl sulfoxides and trimethylchlorosilane (TMCS) or trimethylbromosilane (TMBS), affording sulfonium salts or halo derivatives, generally in good yields.     

Weitere Vereinfachung der Mikrobestimmung von Jod in organischen Verbindungen

Zusammenfassung Die Mikromethode zur Jodbestimmung in organischen Substanzen durch Verbrennen nachSchöniger und nachfolgende Titration mit 0,005-n Quecksilberperchlorat wird dahingehend vereinfacht, daß die Jodabsorption nach der Verbrennung anstatt mit Natronlauge direkt mit Quecksilberperchlorat erfolgt.

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Summary The micro method for determining iodine in organic materials through combustion afterSchöniger and subsequent titration with 0.005N mercuric perchlorate is modified to the extent that after the combustion the iodine is absorbed directly in mercuric perchlorate rather than in sodium hydroxide.

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Résumé On a simplifié la microméthode pour le dosage de l'iode dans les substances organiques avec combustion suivantSchöniger et titrage consécutif par le perchlorate de mercure 0,005N. L'absorption de l'iode après la combustion s'effectue directement par le perchlorate de mercure à la place de la lessive de soude.

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Riassunto La microdeterminazione dello iodio nelle sostanze organiche per combustione secondoSchöniger e successiva titolazione con perclorato di mercurio 0,005-n, è stata semplificata riprendendo direttamente il prodotto di combustione in una soluzione di perclorato di mercurio invece di una soluzione di idrato sodico.

     

Hydrogen-Related Paramagnetic Centers in Ge-Doped Sol-Gel Silica Induced by γ-Ray Irradiation

We have studied the generation mechanisms of H(II) paramagnetic centers in Ge-doped silica by investigating up to 10⁴ mol ppm sol-gel Ge-doped silica materials. We have considered materials with the same concentrations of Ge but that are produced by two different densification routes that give rise to different concentrations of Ge-related oxygen deficient centers (GeODC(II)). These centers are characterized by an optical absorption band at ∼5.2 eV (B_2β band) and two related emissions at ∼3.2 eV and ∼4.3 eV. The GeODC(II) content was estimated by absorption and emission measurements. The H(II) centers were induced by room temperature γ-ray irradiation and their concentration was determined by electron paramagnetic resonance measurements. The comparison between the two kinds of materials, obtained by different preparations, shows that the GeODC(II) concentration increases with the Ge content and is enhanced by vacuum densification. The comparison of irradiated samples shows that beyond the already known process of conversion of preexisting GeODC(II) into H(II) centers, another generation process of H(II) centers is effective that involves irradiation induced GeODC(II).     

Oxidation of α-Acetoxy Acetals with Trichloroisocyanuric Acid

α-Acetoxy acid methyl esters are prepared in excellent yields by treating aliphatic α-acetoxy dimethyl acetals with trichloroisocyanuric acid in DMF.     

Effects of Regioisomerism on the Antiproliferative Activity of Hydroxystearic Acids on Human Cancer Cell Lines

A series of regioisomers of the hydroxystearic acid (HSA) was prepared, and the effect of the position of the hydroxyl group along the chain on a panel of human cancer cell lines was investigated. Among the various regioisomers, those carrying the hydroxyl at positions 5, 7, and 9 had growth inhibitor activity against various human tumor cell lines, including CaCo-2, HT29, HeLa, MCF7, PC3, and NLF cells. 10-HSA and 11-HSA showed a very weak effect. 8-HSA did not show inhibitory activity in all cell lines. The biological role of 7-HSA and 9-HSA is widely recognized, while little is known about the effects of 5-HSA. Therefore, the biological effects of 5-HSA in HeLa, HT29, MCF7, and NLF cell lines were investigated using the Livecyte’s ptychography technology, which allows correlating changes in proliferation, motility, and morphology as a function of treatment at the same time. 5-HSA not only reduces cell proliferation but also induces changes in cell displacement, directionality, and speed. It is important to characterize the biological effects of 5-HSA, this molecule being an important component of fatty acyl esters of hydroxy fatty acids (FAHFA), a class of endogenous mammalian lipids with noticeable anti-diabetic and anti-inflammatory effects.     

A thermal X-RAY and resistivity study of the heusler alloy Cu2NiSn

The compound Cu₂NiSn was analyzed by DTA, X-ray and electrical resistivity measurements. No single-phase structure was found at room temperature. The alloy decomposes upon heating, starting at 160°, forming copper and two hcp structures. At 500° the Heusler structure is restored. Electrical resistivity results are discussed in terms of Markowitz's theory for disordered metals.

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Zusammenfassung Die Verbindung Cu₂NiSn wurde durch DTA, Röntgen- und elektrische Widerstandsmessungen analysiert. Keine Einphasenstruktur wurde bei Zimmertemperatur gefunden. Die Legierung zersetzt sich beim Erhitzen ab 160°, wobei Kupfer und zwei hcp-Strukturen gebildet werden. Bei 500° wird die Heusler-Struktur wieder hergestellt. Die Ergebnisse der elektrischen Widerstandsmessungen werden aufgrund der Markowitzschen Theorie für ungeordnete Metalle diskutiert.

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Résumé Le composé Cu₂NiSn a été examiné par ATD, rayons X et mesures de résistance électrique. A température ambiante on n'a pas trouvé de structure correspondant à une phase unique. L'alliage se décompose par chauffage à partir de 160° en formant du cuivre et deux structures hcp. A 500° la structure Heusler est rétablie. On discute les résultats des mesures de résistance électrique à partir de la théorie de Markowitz pour des métaux désordonnés.

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Cu₂NiSn , . . , 160° . 500° . a .

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Work supported in part by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) and Financiadora de Estudos e Projetos (FINEP).     

Role of interfacial structure in nanostructured elemental metals: a new thermo-mechanical process for the preparation of nanostructured binary alloys

In this article we present the first results obtained for nanostructured γ-Ni₂₀Zn₈₀ alloy prepared by a thermo-mechanical (TM) process developed in our laboratory. The process uses the energy stored in the defect structure, generated via mechanical milling of the nickel, to accelerate the reaction in the solid state, allowing a more rapid alloy formation. The process presents several advantages, when compared with techniques currently used for the production of this class of materials. The X-ray diffraction pattern for the alloy produced by the TM process is compared with that measured for the same alloy, produced by the mechanical alloying technique. The results show that the TM process holds the potential to become a valuable alternative method for the production of nanostructured materials.     

A computational method for the hydrodynamics of fractured-porous media

A numerical method based on the boundary-fitted finite difference method (BFDM) is presented in this paper. The boundaries are external (the boundary of the physical domain) and internal (which corresponds to the fracture network). The difference between this approach and the usual one lies in the inclusion of discrete fractures in the volume that represents the porous medium. The numerical model has been used in the prediction of the flow pattern in several internationally recognized verification cases and applied to the solution of hypothetical problems of interest to us in the field of nuclear waste repository modelling. The results obtained show that the numerical approach considered gives accurate and reliable predictions of the hydrodynamics of fractured-porous media, thus justifying its use for the above-mentioned studies.     

Photoinduced π-π* band gap renormalization in graphite

As is well-known, the character of the π orbitals is of paramount importance for the chemical properties of the carbon allotropes and their derived compounds. While at equilibrium the nature of these orbitals is well understood, their photoinduced nonequilibrium behavior is under investigation. Here, we demonstrate that when a UV-laser pulse excites a carrier density larger than 10% of the π* density of state in graphite, a renormalization of the π-π* band gap takes place. This result has been achieved by detecting the transient reflectivity and the associated decay time of an infrared probe following the excitation of a UV pump pulse tuned across the π-π* absorption resonance. The pump photon energy at which both the transient reflectivity and the decay time are maximum is downshifted by 500 meV with respect to the relative absorption maximum at equilibrium. This finding is interpreted as a transient π-π* band gap shrinking of similar magnitude, near the M point of the Brillouin zone.     

Structural, thermal and optical studies of mechanical alloyed Ga40Se60 mixture

A mixture of elemental Ga and Se with the nominal composition Ga₄₀Se₆₀ was submitted to the Mechanical alloying technique and their structural, thermal and optical properties were followed by X-ray diffraction, differential thermal analysis, photoacoustic spectroscopy, UV-VIS‐NIR absorbance spectroscopy and Raman spectroscopy techniques. After 10 h of milling the X-ray pattern showed monoclinic Ga₂Se₃ phase nucleation, which is in the nanometric form, and also a minority amorphous phase. The DSC results showed exothermic reactions between 430 and 720 K attributed to amorphous-crystalline phase transition and structural relaxation of Ga₂Se₃ phase. Based on this a small amount of the as-milled sample was annealed at 723 K. Its XRD pattern showed evidences of grain growth, reduction of the interfacial component, as well as, disappearance of the amorphous phase. The annealing process induced thermal diffusivity increasing, while the optical band gap energy and Raman profile remained practically unchanged.