Self-organized criticality model for brain plasticity

Networks of living neurons exhibit an avalanche mode of activity, experimentally found in organotypic cultures. Here we present a model that is based on self-organized criticality and takes into account brain plasticity, which is able to reproduce the spectrum of electroencephalograms (EEG). The model consists of an electrical network with threshold firing and activity-dependent synapse strengths. The system exhibits an avalanche activity in a power-law distribution. The analysis of the power spectra of the electrical signal reproduces very robustly the power-law behavior with the exponent 0.8, experimentally measured in EEG spectra. The same value of the exponent is found on small-world lattices and for leaky neurons, indicating that universality holds for a wide class of brain models.     

Palladium-catalyzed synthesis of 2-(aminomethyl)indoles from ethyl 3-(o-trifluoroacetamidophenyl)-1-propargyl carbonate

[reaction: see text] The palladium-catalyzed reaction of ethyl 3-(o-trifluoroacetamidophenyl)-1-propargyl carbonate with piperazines in the presence of Pd(PPh(3))(4) in THF at 80 degrees C affords 2-(piperazin-1-ylmethyl)indoles in excellent yields. Good to excellent yields are also obtained with other secondary amines.     

Near- to far-field characterization of a parametric loudspeaker and its application in non-destructive detection of detachments in panel paintings

The particular properties of the parametric loudspeaker make this class of sources an attractive investigation tool especially for non-destructive testing (NDT). Recently actual applications mainly in the field of material’s acoustical characterization are emerging. The authors present the analysis of the pressure field generated by a commercial parametric loudspeaker both in the near- and far-field, aiming at the understanding of the modality of its employment as excitation source in a measuring system. Successively the parametric source was integrated in a system purposely developed for acoustic diagnostics on objects of heritage interest. It was used in an in situ investigation on the renaissance panel painting Annunciazione by the Italian artist Benozzo Gozzoli (XV century) revealing pictorial film detachments. Preliminary results are here presented, disclosing the potential of the parametric loudspeaker for the enhancement of the spatial resolution in the acoustic measurement, of the non invasiveness of the investigation tool, and also of the operator comfort.     

Preparation of 2,5-disubstituted oxazoles from N-propargylamides

[reaction: see text] 2,5-Disubstituted oxazoles have been prepared through the reaction of N-propargylamides with aryl iodides in the presence of Pd(2)(dba)(3), tri(2-furyl)phosphine, and NaO(t)()Bu. The reaction appears to proceed through a palladium-catalyzed coupling step followed by the in situ cyclization of the resultant coupling product.     

CH3ReO3/H2O2 in room temperature ionic liquids: an homogeneous recyclable catalytic system for the Baeyer-Villiger reaction

The Baeyer-Villiger oxidation of cyclic ketones can be effected by methyltrioxorhenium/hydrogen peroxide in the ionic liquid [bmim]BF₄. After simple extraction of the lactone with diethyl ether, the catalyst can be repeatedly recycled and efficiently reused for the lactonisation process in the same reaction medium.     

2-Alkylindoles via palladium-catalyzed reductive cyclization of ethyl 3-(o-trifluoroacetamidophenyl)-1-propargyl carbonates

The reaction of ethyl 3-(o-trifluoroacetamidophenyl)-1-propargyl carbonates with formate anions in the presence of Pd(PPh₃)₄ affords 2-alkylindoles in good to excellent yields.     

Palladium-catalyzed reaction of o-alkynyltrifluoroacetanilides with 1-bromoalkynes. An approach to 2-substituted 3-alkynylindoles and 2-substituted 3-acylindoles

The palladium-catalyzed reaction of o-alkynyltrifluoroacetanilides with 1-bromoalkynes affords free N-H 2-substituted 3-alkynylindoles in satisfactory to high yield. 2-Substituted 3-alkynylindoles revealed useful intermediates for the regioselective synthesis of 2-substituted 3-acylindoles. The latter can be prepared from o-alkynyltrifluoroacetanilides and 1-bromoalkynes via a one-pot cyclization-hydration protocol, omitting the isolation of 2-substituted 3-alkynylindoles.     

The mechanism of the phosphine-free palladium-catalyzed hydroarylation of alkynes

The mechanism of the Pd-catalyzed hydroarylation and hydrovinylation reaction of alkynes has been studied by a combination of experimental and theoretical methods (B3LYP), with an emphasis on the phosphine-free version. The regioselectivity of the hydroarylation and hydrovinylation shows unexpected differences, which could be attributed mainly to the higher steric demand of the cyclohexenyl group as compared to the phenyl group. Hydroarylation of alpha,beta-acetylenic carbonyl substrates yields a very unusual anti-Michael selectivity, which is shown to result from reaction of the nonconjugated double bond, leaving the conjugation intact. In all cases were the regioselectivities reproduced by the calculations.     

2-Aryl and 2-heteroaryl indoles from 1-alkynes and o-iodotrifluoroacetanilide through a domino copper-catalyzed coupling-cyclization process

[reaction: see text] A general method for the synthesis of 2-aryl and 2-heteroaryl indoles from aryl iodides and 1-alkynes through a domino copper-catalyzed process is reported. The best results have been obtained with [Cu(phen)(PPh(3))(2)]NO(3) in the presence of K(3)PO(4) in toluene or dioxane at 110 degrees C. 2-Aryl and 2-heteroaryl indoles can also be isolated in good yields by using catalysts derived from CuI and PPh(3) in dioxane at 110 degrees C.