Automatic on-line monitoring of atmospheric volatile organic compounds: gas chromatography-mass spectrometry and gas chromatography-flame ionization detection as complementary systems

Traditionally air quality networks have been carrying out the continuous, on-line measurement of volatile organic compounds (VOC) in ambient air with GC-FID. In this paper some identification and coelution problems observed while using this technique in long-term measurement campaigns are described. In order to solve these problems a GC-MS was set up and operated simultaneously with a GC-FID for C₂-C₁₁ VOCs measurement.There are few on-line, unattended, long term measurements of atmospheric VOCs performed with GC-MS. In this work such a system has been optimized for that purpose, achieving good repeatability, linearity, and detection limits of the order of the GC-FID ones, even smaller in some cases. VOC quantification has been made by using response factors, which is not frequent in on-line GC-MS. That way, the identification and coelution problems detected in the GC-FID, which may led to reporting erroneous data, could be corrected.The combination of GC-FID and GC-MS as complementary techniques for the measurement of speciated VOCs in ambient air at sub-ppbv levels is proposed. Some results of the measurements are presented, including concentration values for some compounds not found until now on public ambient air VOC databases, which were identified and quantified combining both techniques. Results may also help to correct previously published VOC data with wrongly identified compounds by reprocessing raw chromatographic data.     

Cisapride in neurologically impaired children with chronic constipation

The efficacy of cisapride as a treatment for chronic constipation in children with severe brain damage was studied in 20 children. Each subject was randomly assigned to double-blind treatment with either cisapride (N = 10) or placebo (N = 10) for 12 weeks. Stool habits, total gastrointestinal transit time, colonic segmental transit times, and anorectal motility were evaluated in all children before and at the end of the treatment period. Although cisapride significantly (P < 0.05) increased stool frequency from baseline to week 12 and no significant change was documented in the placebo group, the mean change in stool frequency per week from baseline to 12 week was not significantly different between the two treatment groups. The use of laxatives or suppositories was significantly (P < 0.05) decreased by cisapride, but remained unchanged in the placebo group. Furthermore, cisapride significantly (P < 0.05) reduced rectal compliance but had no effect on total gastrointestinal transit time and colonic segmental transit times. In summary, in neurologically impaired children with chronic constipation, cisapride increased bowel frequency but did not alter the delay in total and segmental gastrointestinal transit times.     

On fault-tolerant observers

The problem of designing asymptotic observers for multioutput systems with one unreliable output measurement is addressed. It is shown that observers designed on the basis of observability indexes are not fault tolerant, and an observer for linear systems which tolerates failures in one a priori known output is given. The results are extended to nonlinear systems with no inputs: it is pointed out that the proposed design procedure may enlarge the class of nonlinear systems for which a nonlinear observer can be obtained     

Effect of forage to concentrate ratio on growth performance, and on carcass and meat quality of Podolian young bulls

The effect of forage to concentrate ratio: 60-40 [high concentrate group (HC) and 70-30 [low concentrate group (LC)] on growth, slaughtering performance and meat quality were evaluated in twenty organically farmed Podolian young bulls. Meat quality characteristics were measured on three different muscles [Longissimus dorsi (LD), Semimembranosus (SM) Semitendinosus (ST)], vacuum-packaged and chilled stored at 2-4°C for 15 days. The animals in the HC group had higher weight gain than those in the LC group (P<0.05). Slaughter data were not influenced by ration composition. The higher forage to concentrate ratio produced an improvement in fatty acid composition of the three muscles, with a higher polyunsaturated to saturated ratio (P<0.001). Vitamin E and malondialdehyde (MDA) contents were not affected by the feeding treatment. Panel scores for tenderness and flavour (P<0.01) and Warner-Bratzler Shear force (P<0.001) were significantly affected by muscle, the LD muscle being the most tender and the richest in flavour but they not affected by dietary treatment.     

Preferential killing of cancer cells using silicon carbide quantum dots

Silicon carbide quantum dots are highly luminescent biocompatible nanoparticles whose properties might be of particular interest for biomedical applications. In this study we investigated Silicon Carbide Quantum Dots (3C-SiC QDs) cellular localisation and influence on viability and proliferation on oral squamous carcinoma (AT-84 and HSC) and immortalized cell lines (S-G). They clearly localize into the nuclei, but the presence of 3C-SiC QDs in culture medium provoke morphological changes in cultured cells. We demonstrate that 3C-SiC QDs display dose- and time-dependent selective cytotoxicity on cancer versus immortalized cells in vitro. Since one of the limitations of classical antineoplastic drugs is their lack of selectivity, these results open a new way in the search for antiproliferative drugs.     

Synthesis and Functionalization of Unsymmetrical Arylsulfonyl Bisindoles and Bisbenzazoles

A three‐component coupling of two different benzazole compounds with p‐toluenesulfinic acid allows the efficient preparation of unsymmetrical arylsulfonyl bisbenzazole derivatives. Substitution of the arylsulfonyl group from these adducts using sodium borohydride leads to the corresponding bisbenzazoles. Functional implementation of the bisbenzazole system can be achieved using Grignard and Reformatsky reagents.     

Quality of milk and of Canestrato Pugliese cheese from ewes exposed to different ventilation regimens

Effects of ventilation regimen on the quality of ewes' milk and on proteolysis in Canestrato Pugliese cheese during ripening were studied. Cheeses were manufactured from the bulk milk of Comisana ewes subjected to three different ventilation regimens, which were designated low (LOV, 23 m3/h per ewe), moderate (MOV, 47 m3/h per ewe) and programmed ventilation regimen (PROV, 73 m3/h per ewe; fan set to maintain 70% relative humidity). Bulk milk was analysed for chemical and microbial composition, renneting parameters and plasmin-plasminogen activities. At 1, 15, 30 and 45 d of ripening, the cheeses were analysed for gross chemical composition, nitrogen fractions, and plasmin and plasminogen activities. The pH 4.6-insoluble nitrogen fractions were analysed by urea-PAGE. Free amino acid content was determined at the end of ripening. Lower concentrations of bulk milk somatic cell count (BMSCC) and of mesophilic bacteria were found in the MOV group than in the LOV and the PROV groups. A lower plasminogen (PG) to plasmin (PL) ratio (PG/PL) was observed in the MOV and PROV than in the LOV cheeses. Irrespective of treatment, PL activity in cheeses was higher at 15d of ripening, while a sudden decrease of PL and PG activities was observed at 30 d, which was associated with a marked increase in non-protein nitrogen. The peptide profile characterized in the urea-PAGE showed a greater intensity of alpha- and beta-CN hydrolysis in the MOV than in the PROV and LOV cheeses. The results provide evidence that a proper ventilation regimen is critical for optimizing the hygienic quality of milk and the proteolysis of Canestrato Pugliese cheese during ripening.     

Phase-locked laser system for use in atomic coherence experiments

We describe a phase-coherent laser system designed for use in experiments involving coherently prepared atomic media. We implement a simple technique based on a sample-and-hold circuit together with a reset of the integrating electronics that makes it possible to scan continuously the relative frequency between the lasers of over tens of gigahertz while keeping them phase locked. The system consists of three external-cavity diode lasers operating around 795 nm. A low-power laser serves as a frequency reference for two high-power lasers which are phased locked with an optical phase-locked loop. We measured the residual phase noise of the system to be less than 0.04 rad(2). In order to show the application of the system towards atomic coherence experiments, we used it to implement electromagnetically induced transparency in a rubidium vapor cell and obtained a reduction in the absorption coefficient of 92%.     

Voltammetric stability of anodic films on the Ti6Al4V alloy in chloride medium

The biocompatibility and mechanical integrity of Ti and Ti6Al4V alloy can be affected by corrosion processes. This paper presents studies on the stability of anodic oxide films on Ti6Al4V and Ti in chloride medium. The oxides were grown potentiodynamically up to 8.0 V in the phosphate buffer saline (PBS) solution (pH 6.8) at 25 and 37 °C. The morphology of the obtained anodic oxides and the type of corrosion that occurred were analyzed by SEM–EDS. The Ti6Al4V alloy presented less corrosion resistance than pure Ti. Elemental analyses showed that the decrease of the alloy corrosion resistance is due mainly to the corrosion of Al.