Photobiomodulation Therapy on the Guided Bone Regeneration Process in Defects Filled by Biphasic Calcium Phosphate Associated with Fibrin Biopolymer

The aim is to evaluate the effects of photobiomodulation therapy (PBMT) on the guided bone regeneration process (GBR) in defects in the calvaria of rats filled with biphasic calcium phosphate associated with fibrin biopolymer. Thirty male Wistar rats were randomly separated: BMG (n = 10), defects filled with biomaterial and covered by membrane; BFMG (n = 10), biomaterial and fibrin biopolymer covered by membrane; and BFMLG (n = 10), biomaterial and fibrin biopolymer covered by membrane and biostimulated with PBMT. The animals were euthanized at 14 and 42 days postoperatively. Microtomographically, in 42 days, there was more evident bone growth in the BFMLG, limited to the margins of the defect with permanence of the particles. Histomorphologically, an inflammatory infiltrate was observed, which regressed with the formation of mineralized bone tissue. In the quantification of bone tissue, all groups had a progressive increase in new bone tissue with a significant difference in which the BFMLG showed greater bone formation in both periods (10.12 ± 0.67 and 13.85 ± 0.54), followed by BFMG (7.35 ± 0.66 and 9.41 ± 0.84) and BMG (4.51 ± 0.44 and 7.11 ± 0.44). Picrosirius-red staining showed greater birefringence of collagen fibers in yellow-green color in the BFMLG, showing more advanced bone maturation. PBMT showed positive effects capable of improving and accelerating the guided bone regeneration process when associated with biphasic calcium phosphate and fibrin biopolymer.     

Imidazolium molecular motifs located on dicationic frameworks. Electrospray mass spectrometric observation of carbenes: imidazolylidenes

Electrospray ionization mass spectral analysis of simple dicationic imidazolium prototypes (M.2X) is reported and direct observation was obtained for proton-mediated ion-molecule reactions in the gas phase. The comparative ESI-MS study with heterophanes 1a.2Cl and 3.2Br, the open chain system 5.2Br, and their regiospecific deuterated counterparts 2a.2Cl, 4.2Br and 6.2Br showed that the nature of the frameworks containing two imidazolium subunits modulates their electrospray ionization, changing the stability of the common characteristic peaks: the carbene specie [M - H](+) or [M - D](+) as well as [M](2+) and [M. X](+).Copyright 2000 John Wiley & Sons, Ltd.     

The star exponential and SU(2) path integrals

An expression is found for the Feynman path integral on SU(2) in terms of the star-exponential.     

Thermal phase transition for some spin-boson models

In this work we study two different spin-boson models. Such models are generalizations of the Dicke model, it means they describe systems of N$N$ identical two-level atoms coupled to a single-mode quantized bosonic field, assuming the rotating wave approximation. In the first model, we consider the wavelength of the bosonic field to be of the order of the linear dimension of the material composed of the atoms, therefore we consider the spatial sinusoidal form of the bosonic field. The second model is the Thompson model, where we consider the presence of phonons in the material composed of the atoms. We study finite temperature properties of the models using the path integral approach and functional methods. In the thermodynamic limit, N→∞$N\to \infty$, the systems exhibit phase transitions from normal to superradiant phase at some critical values of temperature and coupling constant. We find the asymptotic behavior of the partition functions and the collective spectrums of the systems in the normal and the superradiant phases. We observe that the collective spectrums have zero energy values in the superradiant phases, corresponding to the Goldstone mode associated to the continuous symmetry breaking of the models. Our analysis and results are valid in the limit of zero temperature β→∞$\beta \to \infty$, where the models exhibit quantum phase transitions.     

Synthèse de derivès du nitro-5 imidazole potentiellement actifs en chimiothèrapie

The synthesis of six derivatives of 2-methyl-5-nitroimidazole 1-substituted by a CH₂CH₂Het group (Het being a pyridinium or a 1-substituted imidazolium) has been carried out. A careful ¹H and ¹³C nmr study of these compounds and other nitroimidazoles has been made. None of the synthesized compounds show any significant cytostatic kactivity.     

Aromatic systems with 10 π electrons derived from 3a-azapentalene. XXVIII. Electronic and molecular structure of the pyrazolo[1,5-d]tetrazole system

The molecular structure of 1,6-dimethyl-7-ethoxycarbonylpyrazolo[1,5-d]tetrazole, a 3a-azapentalene derivative having only nitrogens as ring heteroatoms, has been determined by X-ray dif-raction. The compound crystallizes in the space group P2₁/a with four molecules in a unit cell of dimensions a = 10.184, b = 28.827, c = 4,090 Å, β = 123.37°. The structure, which was solved by direct methods and refined to a final value of R = 0.039, shows a clear difference in bond localization in the two fused rings, in agreement with CNDO/2 calculations. The position of the N-methyl group corroborates an empirical rule based on pmr.     

Quantitative evaluation of the chloride template effect in the formation of dicationic [1(4)]imidazoliophanes

The formation of macrocycles containing two imidazolium rings such as 1.2X and 2.2X is anion-directed through hydrogen bonding. The template effect exerted by the chloride anion in the ring-closure reaction of the monocationic model intermediate 9+ to yield the [1(4)]imidazoliophane 2(2+) has been evaluated. This effect was quantified following the kinetics of the macrocyclization by using a UV-vis technique. The rate of the ring closure of monocation 9+ is increased up to 10 times, in the presence of Bu4NCl 0.04 M. This finding confirms that the template effect is operative in the macrocyclization leading to dicationic [1(4)]imidazoliophanes.     

Systèmes aromatiques à 10 électrons π derivés de l'aza-3a pentalène. XVII. Tautomérie azido/tétrazole dans la série du pyrazole

The IR and NMR study of twelve 3- (or 5-) azidopyrazoles shows that the azide is the only tautomer present under neutral conditions. The most stable isomer (tautomer) is 3-azido in N-acetyl and N-H derivatives. 3-Azidopyrazoles are the only polyazoles in which coupling with the N-H in NMR (solvent: DMSO) is observed. In a basic medium, the corresponding anions of the 3-azidopyrazoles N-H are formed: these anions slowly evolve, following first-order kinetics, to the bicyclic anions of pyrazolo-[1,5-d] tetrazoles, derived from 3a-azapentalene. This evolution has been checked by means of IR and NMR spectroscopy.     

Structures of alkyl benzoate binary mixtures. A Kirkwood-Buff fluctuation theory study using UNIFAC

The structure of the alkyl benzoate + n-alkane, and + alkan-1-ol binary mixtures were analyzed according to the Kirkwood-Buff fluctuation theory on the basis of both the mixture properties measured over a wide temperature range and the activity coefficients calculated with the modified UNIFAC (Dortmund) model as well. Application of this model reveals that both the microheterogeneous structure and the clustering effects are strongly dependent on the chain length of the n-alkane and alkan-1-ol cosolvents. Knowledge of the local composition around each type of molecule is drawn from the Kirkwood-Buff integrals and the excess (or deficit) molecules aggregated around a central one. The rather high values of the integrals evaluated for some of these systems provide first-hand evidence for phase splitting. The conclusions drawn support previous analyses and confirm the adequacy of the methodology put forward for studying liquid mixtures at microscopic level; easily measurable experimental properties can advantageously be used with the fluctuation theory.