Probing secondary carbohydrate-protein interactions with highly dense cyclodextrin-centered heteroglycoclusters: the heterocluster effect

Comparison of the lectin-binding properties for highly dense beta-cyclodextrin-centered homo- and heteroglycoclusters with defined architecture provides evidence for the existence of strong synergic effects (heterocluster effect) on carbohydrate-protein recognition events.     

A general entry to linear, dendritic and branched thiourea-linked glycooligomers as new motifs for phosphate ester recognition in water

A blockwise iterative synthetic strategy for the preparation of linear, dendritic and branched full-carbohydrate architectures has been developed by using sugar azido(carbamate) isothiocyanates as key templates; the presence of intersaccharide thiourea bridges provides anchoring points for hydrogen bond-directed molecular recognition of phosphate esters in water.     

Mass transfer enhancement in supercritical fluids extraction by means of power ultrasound

The use of high-intensity ultrasound represents an efficient manner of producing small scale agitation, enhancing mass transfer on supercritical fluids (SF) extraction processes. In this way, a supercritical CO(2) extraction of oil from particulate almonds using power ultrasound was studied. To examine the effect of the acoustic waves all experiments were performed with and without ultrasound. A power ultrasonic transducer for a working frequency of about 20 kHz was constructed and installed inside a high-pressure 5 l SF extractor. The experimental tests were carried out with CO(2) at 280 bar and 55 degrees C. Grounded almonds with an oil content of about 55%, in an amount of 1500 g were deposited inside the SF reactor where the solvent was introduced at a flow rate of 20 kg/h. The results show that the kinetics and the extraction yield of the oil were enhanced by 30% and 20% respectively, when a power of about 50 W was applied to the transducer. The average time of each extraction process was of about 8 h and 30 min. In addition, the transducer was also used as a sensitive probe capable to detect the phase behavior of supercritical fluids when it was driven with low power signals.     

Synthesis of natural ecteinascidins (ET-729, ET-745, ET-759B, ET-736, ET-637, ET-594) from cyanosafracin B

The semisynthetic process initially described for the synthesis of 1 (ET-743) has been extended to the preparation of other natural ecteinascidins. For the synthesis of 2 (ET-729) a demethylation of a N-Me intermediate was carried out by a selective oxidation with MCPBA. Other natural ecteinascidins (ET-745, ET-759B, ET-736, ET-637, ET-594) were accessible from key intermediate 25. The described methodologies allow for the preparation of a wide variety of ecteinascidins by procedures that can be easily scaled up.     

On a covariant version of Caianiello’s model

Caianiello’s derivation of Quantum Geometry through an isometric embedding of the spacetime (M, g̃) in the pseudo-Riemannian structure (T*M, g* _AB ) is reconsidered. In the new derivation, using a non-linear connection and the bundle formalism, we obtain a Lorentzian-type structure in the 4-dimensional manifold M that is covariant under arbitrary local coordinate transformations in M. We obtain that if models with maximal acceleration are non-trivial, gravity should be supplied with other interactions in a unification framework.     

Determination of halonitromethanes in treated water

As halonitromethanes (HNMs) have begun to play an increasingly important role as disinfection by-products, the development of a highly sensitive method for their analysis has become a priority. The mass spectrometric behavior of the 9 HNMs revealed that trihalonitromethanes are more unstable than di- or monohalonitromethanes under common chromatographic conditions. The absence of a comprehensive method for HNMs has given rise to the development of the first method for the whole array of these species, involving the selection of a solventless technique. Single drop microextraction in the headspace mode (HS-SDME) was selected as it is inexpensive and easy to operate. Comparative measurements through EPA liquid-liquid extraction (LLE) method for halogenated volatile compounds, show this approach to be superior to the manual LLE procedure (the average limits of detection (LODs) for the 9 HNMs were 0.5 and 1 μg/L for the HS-SDME and EPA methods, respectively), adequate precision (8.2 and 7.0% for HS-SDME and EPA methods, respectively) and does not consume excessive solvent since the total extract (～2 μL) was injected completely into the GC-MS instrument. The method was used to measure HNMs in treated water and the results were compared to the EPA method in parallel.     

Microcanonical equations obtained from the Tsallis entropy

Microcanonical equations for some of the most usual thermodynamic properties of a system, suitable for molecular dynamics simulations, are derived from the Tsallis entropy functional using both the usual definition of temperature as a derivative of entropy and a modified physical one introduced by Abe. The practical consequences of each choice are then discussed.     

Semiautomatic method for the screening and determination of 23 organochlorine pesticides in horticultural samples by gas chromatography with electron-capture detection.

A rapid, simple, efficient device for the extraction-preconcentration of 23 organochlorine pesticides currently applied to vegetables is proposed. Pesticide residues are extracted from chopped samples by using a mixture of distilled water and light petroleum (1:1, v/v). After phase separation, an aliquot of the organic layer is continuously evaporated to dryness under a N2 stream as it is dropped into a glass tube containing distilled water. The aqueous phase, containing the analytes, is then passed through a miniaturized RP-C18 column for preconcentration, clean-up and subsequent elution with 150 microliters of ethyl acetate. A volume of 1 microliter of the extract containing pesticides is injected into the gas chromatograph, fitted with an electron-capture detector, for their selective determination. Limits of detection vary between 0.04 and 10 ng/ml, with linear ranges from 0.2 to 500 ng/ml; the average relative standard deviation at the low nanogram-per-millilitre level is 5.3%. The potential of the proposed method was realized by applying it to the screening/determination of organochlorine pesticides in horticultural commodities.     

Quadratic Phase Coupling Detection in Harmonic Vibrations via an Order-Recursive AR Bispectrum Estimation

The paper proposes a bispectral scheme for quadratic phase-coupling (QPC) detection in harmonic signals in white and colored noise, possibly generated by non-linear vibrations. This scheme is carried out via an autoregressive bispectrum (AR) using several criteria to fix an optimum order for the AR model used. First, we propose a recursive-in-order algorithm for AR model-parameter calculation in the bispectrum estimation problem. This algorithm is based on the recursion-in-order minimization of appropriate squared errors with respect to the reflection coefficients, introduced by the Levinson recursion for Toeplitz and non-Hermitian matrices. The recursive nature in this method allows us to obtain the bispectrum of several orders up to the desired one, with significant computational savings. In computer simulations this method demonstrates its potential both in the estimation of signal bispectra and in QPC bispectral detection problems in noisy environments.     

Thermodynamics of water sorption in acrylic homonetworks and IPNs

The equilibrium thermodynamic properties of poly(hydroxyethyl acrylate) and poly(ethyl acrylate)-i-poly(hydroxyethyl acrylate) hydrogels are investigated starting from the water sorption isotherms of the systems. Partial enthalpy and entropy of the sorbed water in the gel differ markedly from the values of pure water at the lowest water contents, and tend to those of liquid water as saturation is approached. The residual mixing free energy is calculated, as a means of assessing the intensity of the water-polymer interaction. Its small positive magnitude shows that water-polymer hydrogen bonds are labile compared to water-water and polymer-polymer hydrogen bonds, and thus the stability of the gel state is still mainly due to the combinatorial entropic contribution to the mixing free energy. An equation correctly describing the sorption isotherms, when combined with the thermodynamic equations, can deliver the true water-polymer interaction parameter and its dependence on the polymer volume fraction in the gel.