Design and analysis of an integrated antiresonant reflecting optical waveguide refractive-index sensor

An integrated optical waveguide refractometer, believed to be novel, is presented. The sensor is based on an antiresonant reflecting optical waveguide and uses the strong attenuation dependence on the refractive index of antiresonant cladding layers as the sensing principle. The theory and the operation of the sensor are discussed in terms of one- and two-dimensional geometry. The theoretical predictions and numerical analysis show that a versatile sensor can be realized. The design trade-offs are discussed, and the sensitivity and measurement range are presented.     

Hourly indoor radon measurements in a research house

This paper reports and discusses the behaviour of radon concentration with time in an uninhabited dwelling. The relationship between variations in radon concentrations and indoor-outdoor temperatures and wind intensity has also been discussed. Radon concentration was measured hourly in a house located at a height of 800 m in the Lombard Prealps, at the top of the Valassina valley. The wind velocity and indoor-outdoor temperatures were measured by means of a meteorological station located on the terrace of the house. The data were analysed using the LBL model for indoor-outdoor air exchange and the models for the indoor accumulation of radon due to exhalation from building materials and pressure-driven infiltrations located underground. The role of wind and indoor-outdoor temperatures were analysed. The agreement of measurements with modelling clearly demonstrates the importance of the different sources of indoor radon. As the investigation was conducted in an uninhabited house, the measurements were not affected by the behaviour of people, e.g. opening and closing of windows. Measurements of the outdoor atmospheric concentrations of (222)Rn provide an index of the atmospheric stability, the formation of thermal inversions and convective turbulence.     

Reduction of immunoreactivity of bovine beta-lactoglobulin upon combined physical and proteolytic treatment

Bovine beta-lactoglobulin was hydrolyzed with trypsin or chymotrypsin before, during and after treatment at 600 MPa and pH 6.8 for 10 min at 30, 37 and 44 degrees C. The extent of beta-lactoglobulin hydrolysis under pressure was noticeably higher than at atmospheric pressure, particularly when chymotrypsin was used. Addition of proteases at ambient pressure to previously pressure-treated beta-lactoglobulin gave only a modest increase in proteolysis with respect to the untreated protein. Products of enzyme hydrolysis under pressure were separated by reverse-phase HPLC, and were found to be different from those obtained at atmospheric pressure when chymotrypsin was used. The residual immunochemical reactivity of the products of combined pressure-enzyme treatment was assessed on the unresolved hydrolysates by ELISA tests using polyclonal and monoclonal antibodies, and on individual hydrolytic fractions by Western Blotting using sera of paediatric patients allergic to whey proteins in cow milk. The immunoreactivity of the whole hydrolysates was related to their content of residual intact beta-lactoglobulin, and no immunochemical reactivity was found for all the products of chymotrypsin hydrolysis under pressure. The results indicate that chymotrypsin effectively hydrolysed hydrophobic regions of beta-lactoglobulin that were transiently exposed during the pressure treatments and that were not accessible in the native protein or in the protein that had been previously pressure treated.     

A cyclic CCK8 analogue selective for the cholecystokinin type A receptor: design, synthesis, NMR structure and binding measurements

A cyclic CCK8 analogue, cyclo(29,34)[Dpr(29),Lys(34)]-CCK8 (Dpr=L-2,3-diaminopropionic acid), has been designed on the basis of the NMR structure of the bimolecular complex between the N-terminal fragment of the CCK(A) receptor and its natural ligand CCK8. The conformational features of cyclo(29,34)[Dpr(29),Lys(34)]-CCK8 have been determined by NMR spectroscopy in aqueous solution and in water containing DPC-d(38) micelles (DPC=dodecylphosphocholine). The structure of the cyclic peptide in aqueous solution is found to be in a relaxed conformation, with the backbone and Dpr29 side chain atoms making a planar ring and the N-terminal tripeptide extending approximately along the plane of this ring. In DPC/water, the cyclic peptide adopts a "boat-shaped" conformation, which is more compact than that found in aqueous solution. The cyclic constraint between the Dpr29 side chain and the CCK8 carboxyl terminus (Lys34) introduces a restriction in the backbone conformational freedom. However, the interaction of cyclo(29,34)[Dpr(29),Lys(34)]-CCK8 with the micelles still plays an important role in the stabilisation of the bioactive conformation. A careful comparison of the NMR structure of the cyclic peptide in a DPC micelle aqueous solution with the structure of the rationally designed model underlines that the turn-like conformation in the Trp30-Met31 region is preserved, such that the Trp30 and Met31 side chains can adopt the proper spatial orientation to interact with the CCK(A) receptor. The binding properties of cyclo(29,34)[Dpr(29),Lys(34)]-CCK8 to the N-terminal receptor fragment have been investigated by fluorescence spectroscopy in a micellar environment. Estimates of the apparent dissociation constant, K(d), were in the range of 70-150 nM, with a mean value of 120+/-27 nM. Preliminary nuclear medicine studies on cell lines transfected with the CCK(A) receptor indicate that the sulfated-Tyr derivative of cyclo(29,34)[Dpr(29),Lys(34)]-CCK8 displaces the natural ligand with an IC(50) value of 15 microM.     

Experimental validation of the discrete-time MCS adaptive strategy

This paper is concerned with the implementation and experimental validation of a discrete-time model reference adaptive control strategy, known as Minimal Control Synthesis (MCS) algorithm. After discussing the proof of stability of the algorithm when applied to discretized models of continuous-time plants, the problem of controlling a highly nonlinear electro-mechanical device is taken as a representative case of study. It is shown that the discrete-time MCS is an effective strategy to solve the problem while guaranteeing robustness to unmodeled nonlinear dynamics over a wide range of test manoeuvres.     

Analytical and graphical design of lead–lag compensators

In this article an approach based on inversion formulae is used for the design of lead–lag compensators which satisfy frequency domain specifications on phase margin, gain margin and phase (or gain) crossover frequency. An analytical and graphical procedure for the compensator design on the Nyquist and Nichols planes is presented with some numerical examples.     

Influence of mediator immobilization on the electrochemically assisted microbial dechlorination of trichloroethene (TCE) and cis‐dichloroethene (cis‐DCE)

BACKGROUND: A bioelectrochemical process for trichloroethene (TCE) dechlorination was developed. In this new process, a solid‐state electrode polarized to ?450 mV versus the standard hydrogen electrode (SHE), in combination with a redox mediator (i.e., methyl viologen, MV) is employed as an electron donor for the microbial reductive dechlorination of TCE. In this study we compared the performance of the process with the redox mediator immobilized at the surface of electrodes or dissolved in the bulk liquid, using both a culture highly enriched in Desulfitobacterium spp., capable of dechlorinating TCE to cis‐dichloroethene (cis‐DCE), and a culture highly enriched in Dehalococcoides spp. capable of dechlorinating cis‐DCE to ethene. RESULTS: Short‐term potentiostatic (?450 mV versus SHE) experiments showed that TCE or cis‐DCE was dechlorinated both in the presence of soluble (500 µmol L^?1) and immobilized MV. However, TCE or cis‐DCE dechlorination rates with MV‐modified electrodes were remarkably lower than with soluble MV. Both cultures produced significant amounts of H₂ in the presence of electrically reduced, soluble MV, whereas no H₂ was produced when the mediator was immobilized at the electrode surface, regardless of the potential applied to the electrode, in the range ?425 to ?500 mV versus SHE. CONCLUSIONS: The process, operated with modified electrodes, supports the microbial dechlorination of TCE to ethene. Immobilization not only allows retention of the mediator within the system, but also increases process efficiency by preventing bioelectrochemical H₂ formation. On the other hand, strategies to increase dechlorination rates with modified electrodes need to be developed. Copyright © 2009 Society of Chemical Industry     

Implementation of response surface methodology to optimise extraction of onion (Allium cepa) solid waste phenolics

An experimental setup based on a 2³-full factorial, central composite design was implemented with the aim to optimising recovery of polyphenols from onion solid wastes (OSW). In order to allow for the establishment of a sustainable process, reusable and non-toxic solutions composed of water/ethanol/citric acid were employed as extracting media. The factors considered were (i) the pH of the medium, (ii) the extraction time and (iii) the ethanol concentration. The model obtained produced a satisfactory fitting of the experimental data with regard to total polyphenol extraction (R² = 0.97, p = 0.0025) and the reducing power of the extracts (R² = 0.97, p = 0.0033), but not with the antiradical activity (R² = 0.89, p = 0.0592). The 2nd order polynomial equations obtained after elaboration of the experimental data indicated that all parameters considered were significant in respect with the efficiency of total polyphenol recovery. The highest total polyphenol yield was theoretically predicted to be 9342 ± 1435 mg gallic acid equivalents per 100 g dry weight, under optimal conditions (60% EtOH, pH 2 and 4.2 h). Liquid chromatography-electrospray ionisation mass spectrometry of the optimally obtained extract revealed that the principal phytochemicals recovered were quercetin 3,4′-diglucoside, quercetin 4′-glucoside and quercetin. Simple linear regression analysis between the total polyphenol and the antiradical activity of the OSW extracts showed that there was no correlation in a statistically significant manner, as opposed to reducing power.Industrial relevanceThe recovery of value-added substances from agri-food industrial wastes is an issue with importance pertaining to both the reduction of the waste load released to the environment, and the development of novel, natural food additives with functional properties. Up to date, the examinations pertaining to the clarification of factors that can affect extractability were based on rather unilateral assessment, while it is generally accepted that the retrieval depends on several parameters, which render the phenomenon a particular complexity. In this view, the implementation of factorial design with respect to investigating in parallel several factors pertaining to efficient polyphenol recovery becomes imminent. Thus the establishment of models on such a sound experimental basis is expected to provide a reliable background for more costand resource-effective processes, with a potential direct industrial applicability.     

Identification of new epidemiological molecular markers by comparative proteomics of serogroup A meningococcal isolates from three pandemic waves

We previously described the first reference map for the proteome of one strain of serogroup A Neisseria meningitidis (MenA), a major cause of epidemic meningitis in humans. As a preliminary finding, in that work we noted that 2‐DE protein maps of closely related MenA isolates from different epidemics spreads could be easily compared to detect minor differences and that 2‐DE phenotypes attributable to the well‐known epidemiological marker tbpB agreed with the genoclouds model of MenA epidemiological variation during pandemic waves. We explored here the possibility that an extended comparative study of 2‐DE maps of isolates representative of the nine genoclouds described by Achtman and collaborators could be used to discriminate between strains otherwise undistinguishable. We showed the example of 14 proteins with different 2‐DE spot patterns in different genoclouds that could be considered as putative tracers for alike‐strains discrimination. We introduce the novel concept that comparative proteomics can be useful in identifying new epidemiological markers for N. meningitidis.