Sonochemical synthesis of 2,3-dihydro-4(1<Emphasis Type="Italic">H</Emphasis>)-quinazolinones and 1-amidoalkyl-2-naphthols using magnetic nanoparticle-supported ionic liquid as a heterogeneous catalyst

Ultrasound-promoted synthesis of 2,3-dihydro-4(1H)-quinazolinones and 1-amidoalkyl-2-naphthols were carried out using magnetic nanoparticle-immobilized ionic liquid (IL@MNP) as a magnetically separable catalyst. Ultrasound accelerates the reaction at ambient temperature making the protocol clean, simple and greener compared to conventional procedures. The catalyst showed high activity and stability during the reaction. The heterogeneous nature of the catalyst enabled easy recovery through an external magnet and it was reused up to six times without the loss of its activity. The synergistic effect of IL@MNP and ultrasound facilitate the reaction with excellent isolated yield in a shorter reaction time.     

Bayesian Monte Carlo estimation for profile hidden Markov models

Hidden Markov models are used as tools for pattern recognition in a number of areas, ranging from speech processing to biological sequence analysis. Profile hidden Markov models represent a class of so-called “left–right” models that have an architecture that is specifically relevant to classification of proteins into structural families based on their amino acid sequences. Standard learning methods for such models employ a variety of heuristics applied to the expectation-maximization implementation of the maximum likelihood estimation procedure in order to find the global maximum of the likelihood function. Here, we compare maximum likelihood estimation to fully Bayesian estimation of parameters for profile hidden Markov models with a small number of parameters. We find that, relative to maximum likelihood methods, Bayesian methods assign higher scores to data sequences that are distantly related to the pattern consensus, show better performance in classifying these sequences correctly, and continue to perform robustly with regard to misspecification of the number of model parameters. Though our study is limited in scope, we expect our results to remain relevant for models with a large number of parameters and other types of left–right hidden Markov models.     

Laser Raman spectroscopic investigations of biodegradable vehicle of active agents eluting LVM 316 stainless steel cardiovascular stents for in vivo degradation characteristics

Laser Raman spectroscopy is an effective tool for the study of biodegradable polymers, which play a vital role in the new developments in coronary implants such as stents. There is much excitement around the potential capabilities of synthetic biodegradable polymers and the effect they will have on the design and function of implanted devices. In the present investigation, heparin‐conjugated biodegradable copolymers were evaluated for their durability as drug‐eluting stent coatings. Laser Raman spectroscopic studies were carried out and spectra recorded and analyzed of explanted stents coated with different amounts of polymer alone, showing the existence of different levels at different quantities of polymer. The polymer was detected on every stent analyzed. On the stents coated with a thick layer of polymer, a firm layer of polymer still existed on the stent. In contrast, this layer was degraded and spread around on the stents coated with only a thin layer of the polymer. This indicates that the polymers used in the stents in the present investigation exhibit acceptable biodegradability. Such polymers can be used as efficient drug carriers, as these materials show good degradation after the stipulated period. Copyright © 2009 John Wiley & Sons, Ltd.     

Neat reaction technology for the synthesis of 4-oxo-thiazolidines derived from 2-SH-benzothiazole and antimicrobial screening of some synthesized 4-thiazolidinones

The synthesis of 4-thiazolidinones 4a-j in a good yields from the heterocyclization reaction of 2-(benzothiazol-2-ylthio)-N’-benzylideneacetohydrazide 3a-j with SHCH₂COOH in DMF in the presence of a catalytic amount of anhydrous ZnCl₂ under microwave irradiation is described and compared with conventional synthesis methods. All structures of the newly synthesized compounds were elucidated by elemental analysis and spectral data. Some of the new compounds were tested against bacteria (Gram? ve and Gramt+ ve) and fungi.     

A convenient,rapid microwave assisted synthesis of some novel 3-[(4-chloro-3-methylphenoxy)methyl]-6-aryl-5,6-dihydro-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles using acidic alumina

A facile synthesis of 3-[(4-chloro-3-methylphenoxy)methyl]-6-aryl-5,6-dihydro-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles 3a–n has been achieved by microwave promoted condensation of 3-mercapto-4-amino-5-[(4-chloro-3-methylphenoxy)methyl]-4H-1,2,4-triazole 1 with various aromatic aldehydes 2a–n in presence of catalytic amount of p-TsOH (para-toluenesulphonic acid). The structures of 3a–n are supported by IR and ¹H and ¹³C NMR spectral data.     

Preparation of Inorganic Oxides via a Non-Hydrolytic Sol-Gel Route

Inorganic oxides have been synthesized successfully under mild reaction conditions using a solvent-free non-hydrolytic sol-gel process based on the condensation reaction of metal chlorides with oxygen donors such as alkoxides, aldehydes and ethers. Iron(III) chloride was found to be an effective catalyst for the reactions. The order of reactivity of the halides was generally titanium > aluminium > silicon, but in some cases reaction was halted by premature gelation of intermediate species. Silica, alumina and titania were all prepared and characterized by various methods. Calcination studies on the silicas showed these materials to be amorphous up to at least 700°C, but devitrification occurred at 1000°C. Crystallization was studied by X-ray powder diffraction.     

From local adsorption stresses to chiral surfaces: (R,R)-tartaric acid on Ni(110).

The chiral molecule (R,R)-tartaric acid adsorbed on nickel surfaces creates highly enantioselective heterogeneous catalysts, but the nature of chiral modification remains unknown. Here, we report on the behavior of this chiral molecule with a defined Ni(110) surface. A combination of reflection absorption infrared spectroscopy, scanning tunneling microscopy, and periodic density functional theory calculations reveals a new mode of chiral induction. At room temperatures and low coverages, (R,R)-tartaric acid is adsorbed in its bitartrate form with two-point bonding to the surface via both carboxylate groups. The molecule is preferentially located above the 4-fold hollow site with each carboxylate functionality adsorbed at the short bridge site via O atoms placed above adjacent Ni atoms. However, repulsive interactions between the chiral OH groups of the molecule and the metal atoms lead to severely strained adsorption on the bulk-truncation Ni(110) surface. As a result, the most stable adsorption structure is one in which this adsorption-induced stress is alleviated by significant relaxation of surface metal atoms so that a long distance of 7.47 A between pairs of Ni atoms can be accommodated at the surface. Interestingly, this leads the bonding Ni atoms to describe a chiral footprint at the surface for which all local mirror symmetry planes are destroyed. Calculations show only one chiral footprint to be favored by the (R,R)-tartaric acid, with the mirror adsorption site being unstable by 6 kJ mol(-1). This energy difference is sufficient to enable the same local chiral reconstruction and motif to be sustained over 90% of the system, leading to an overall highly chiral metal surface.     

Fast magnetic resonance in vascular diseases of the abdomen

Fast magnetic resonance (MR) imaging provides a consistent and predictable appearance of vascular abnormalities as shown by four patients with thrombi, dissection and aneurysm. Fast MR images are obtained during breath-holding, resulting in an absence of respiratory motion artifacts. The time of MR study is much less with fast MR than with spin echo sequences.