Identification of the tension force in cables with insulators

Meccanica - The present paper explores two approaches which, based on the measurement of the two first natural frequencies, allow the identification of the tension force in cables with insulators....     

Synthesis and Characterization of m‐Terphenyl (1,3‐Diphenylbenzene) Compounds Containing Trifluoromethyl Groups

The bis(silyl)triazene compound 2,6‐(Me₃Si)₂‐4‐Me‐1‐(N?N? NC₄H₈)C₆H₂ ( 4 ) was synthesized by double lithiation/silylation of 2,6‐Br₂‐4‐Me‐1‐(N?N? NC₄H₈)C₆H₂ ( 1 ). Furthermore, 2,6‐bis[3,5‐(CF₃)₂‐C₆H₃]‐4‐Me‐C₆H₂‐1‐(N?N? NC₄H₈)C₆H₂ derivative 6 can be easily synthesized by a C,C‐bond formation reaction of 1 with the corresponding aryl‐Grignard reagent, i.e., 3,5‐bis[(trifluoromethyl)phenyl]magnesium bromide. Reactions of compound 4 with KI and 6 with I₂ afforded in good yields novel phenyl derivatives, 2,6‐(Me₃Si)₂‐4‐MeC₆H₂? I and 2,6‐bis[3,5‐(CF₃)₂? C₆H₃]‐4‐MeC₆H₂? I ( 5 and 7 , resp.). On the other hand, the analogous m‐terphenyl 1,3‐diphenylbenzene compound 2,6‐bis[3,5‐(CF₃)₂? C₆H₃]C₆H₃? I ( 8 ) could be obtained in moderate yield from the reaction of (2,6‐dichlorophenyl)lithium and 2 equiv. of aryl‐Grignard reagent, followed by the reaction with I₂. Different attempts to introduce the ^tBu (Me₃C) or neophyl (PhC(Me)₂CH₂) substituents in the central ring were unsuccessful. All the compounds were fully characterized by elemental analysis, melting point, IR and NMR spectroscopy. The structure of compound 6 was corroborated by single‐crystal X‐ray diffraction measurements.     

BODIPY Dye,the Most Versatile Fluorophore Ever?

BODIPY laser dyes constitute a fascinating topic of research in modern photochemistry due to the large variety of options its chromophore offers, which is ready available for a multitude of synthetic routes. Indeed, in the literature one can find a huge battery of compounds based on the indacene core. The possibility of modulating the spectroscopic properties or inducing new photophysical processes by the substitution pattern of the BODIPY dyes has boosted the number of scientific and technological applications for these fluorophores. Along the following lines, I will overview the main results achieved in our laboratory with BODIPYs oriented to optoelectronic as well to biophotonic applications, stressing the more relevant photophysical issues to be considered in the design of a tailor‐made BODIPY for a certain application and pointing out some of the remaining challenges.

     

Phytochemical Constituents and Ameliorative Effect of the Essential Oil from Annona muricata L. Leaves in a Murine Model of Breast Cancer

Annona muricata leaves are traditionally used as an anticancer plant in the world. The aim of this study was to evaluate the ameliorative effect of the essential oil from Annona muricata leaves (EOAm) in an experimental model of breast cancer and to determine the volatile constituents with gas chromatography-mass spectrometry (GC-MS). Thirty female rats were assigned to five groups: the control group; the DMBA (7,12-dimethylbenz[α]anthracene) group; and three groups received daily EOAm doses of 50, 100, and 200 mg/kg/day, plus DMBA, respectively. After 13 weeks of treatment, tumors were analyzed pathologically and biochemical markers in serum were noted. As a result, in GC-MS analysis, 40 compounds were identified and 4 of them were abundant: Z-caryophyllene (40.22%), followed by α-selinene (9.94%), β-pinene (8.92%), and β-elemene (7.48%). Furthermore, EOAm in a dose-dependent form produced a reduction in tumor frequency and the accumulated tumor volume was reduced by 50% and 71% with doses of 100 and 200 mg/kg, respectively. Serum levels of reduced glutathione (GSH) increased and malondialdehyde (MDA) decreased significantly compared to the DMBA group. Serum levels of vascular endothelial growth factor (VEGF) decreased significantly from 70.75 ± 7.15 pg/mL in the DMBA group to 46.50 ± 9.00 and 34.13 ± 11.50 pg/mL in groups treated with doses of 100 and 200 mg/kg, respectively. This study concludes that the EOAm leaves showed an ameliorative effect in a murine model of breast cancer.     

Tetrameric aggregate of 1,c‐3‐diphenyltetran‐r‐1‐ol via an R44(8) homodromic ring

The compound 1,c‐3‐diphenyltetran‐r‐1‐ol (systematic name: 1,c‐3‐diphenyl‐1,2,3,4‐tetrahydro‐r‐1‐naphthol), C₂₂H₂₀O, which possesses the tetrahydronaphthalene core that is found in a large number of natural products, crystallizes with Z′ = 4 and with the four molecules forming a hydrogen‐bonded cyclic aggregate. The aliphatic six‐membered rings are present with two different conformations in the molecules of the asymmetric unit. A comparison with similar fragments reveals their conformational flexibility. In addition, the structure demonstrates the relative stereochemistries of the chiral centers, which are important since the title compound is used in the stereoselective synthesis of compounds with therapeutic activity.     

Claisen rearrangements-xiv : Synthesis of the coumarin, benahorin and revision of the structure of marmelide

The natural coumarin, benahorin 1 has been synthesised in five steps from xanthotoxol 4. Marmelide has been shown to be the 3,3-dimethylallyl ether of xanthotoxol (imperatorin 9) and not as believed the 1,1-dimethylallyl ether 7.     

Unified model of loop quantum gravity and matter

We reconsider the unified model of gravitation and Yang–Mills interactions proposed by Chakraborty and Peldán, in the light of recent formal developments in loop quantum gravity. In particular, we show that one can promote the Hamiltonian constraint of the unified model to a well defined anomaly-free quantum operator using the techniques introduced by Thiemann, at least for the Euclidean theory. The Lorentzian version of the model can be consistently constructed, but at the moment appears to yield a correct weak field theory only under restrictive assumptions, and its quantization appears problematic.     

Magnetic and Mössbauer data of Fe in K2ZnF4, analyzed in the spin Hamiltonian formalism

Magnetic measurements on single crystals and Mössbauer spectra of powders under magnetic field, recorded on Fe²⁺ doped K₂ZnF₄, have been analyzed in the spin Hamiltonian formalism. The data slightly depart from the expectations of a spin 2 in D_4h symmetry. The occurrence of vibronic effects is discussed.     

Identification of polymeric procyanidins from pine bark by mass spectrometry

Pine bark is an important source of polyphenolic compounds, mainly procyanidins, with reported protective effects against disease. In previous works, barks of two varieties of pine (P. pinaster and P. radiata) were extracted with ethanol, and partially purified to obtain the aqueous fractions (FA), that contained mainly polymeric procyanidins. The mean degree of polymerization was 7.9 for radiata (rFA) and 10.6 for pinaster (pFA). FAs were chromatographed on Sephadex LH‐20 by using a gradient of methanol, water and acetone, to render a series of sub‐fractions. In this work, the procyanidin compositions of these sub‐fractions were analyzed using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). The mass spectra of sub‐fractions from FA of P. pinaster showed signals of procyanidin polymers up to tridecamers, whereas for those from P. radiata the maximum degree of polymerization was 15. For this latter case, the MALDI‐TOF mass spectra detected the presence of prodelphinidins in a small amount. Copyright © 2009 John Wiley & Sons, Ltd.