Biomedical subjects

M Caldeira

Publications and source records attributed to M Caldeira.

3 recordsLinked to original sources

PubMed2006

Comparative study of the whisky aroma profile based on headspace solid phase microextraction using different fibre coatings.

A dynamic headspace solid-phase microextraction (HS-SPME) and gas chromatography coupled to ion trap mass spectrometry (GC-(IT)MS) method was developed and applied for the qualitative determination of the volatile compounds present in commercial whisky samples which alcoholic content was previously adjusted to 13% (v/v). Headspace SPME experimental conditions, such as fibre coating, extraction temperature and extraction time, were optimized in order to improve the extraction process. Five different SPME fibres were used in this study, namely, poly(dimethylsiloxane) (PDMS), poly(acrylate) (PA), Carboxen-poly(dimethylsiloxane) (CAR/PDMS), Carbowax-divinylbenzene (CW/DVB) and Carboxen-poly(dimethylsiloxane)-divinylbenzene (CAR/PDMS/DVB). The best results were obtained using a 75 microm CAR/PDMS fibre during headspace extraction at 40 degrees C with stirring at 750 rpm for 60 min, after saturating the samples with salt. The optimised methodology was then applied to investigate the volatile composition profile of three Scotch whisky samples--Black Label, Ballantines and Highland Clan. Approximately seventy volatile compounds were identified in the these samples, pertaining at several chemical groups, mainly fatty acids ethyl esters, higher alcohols, fatty acids, carbonyl compounds, monoterpenols, C13 norisoprenoids and some volatile phenols. The ethyl esters form an essential group of aroma components in whisky, to which they confer a pleasant aroma, with "fruity" odours. Qualitatively, the isoamyl acetate, with "banana" aroma, was the most interesting. Quantitatively, significant components are ethyl esters of caprilic, capric and lauric acids. The highest concentration of fatty acids, were observed for caprilic and capric acids. From the higher alcohols the fusel oils (3-methylbutan-1-ol and 2.phenyletanol) are the most important ones.

Alcoholic Beverages↗

PubMed1999

4-Chlorophenol degradation by a bacterial consortium: development of a granular activated carbon biofilm reactor.

A bacterial consortium that can degrade chloro- and nitrophenols has been isolated from the rhizosphere of Phragmitis communis. Degradation of 4-chlorophenol (4-CP) by a consortium attached to granular activated carbon (GAC) in a biofilm reactor was evaluated during both open and closed modes of operation. During the operation of the biofilm reactor, 4-CP was not detected in the column effluent, being either adsorbed to the GAC or biodegraded by the consortium. When 4-CP at 100 mg l-1 was fed to the column in open mode operation (20 mg g-1 GAC total supply), up to 27% was immediately available for biodegradation, the rest being adsorbed to the GAC. Biodegradation continued after the system was returned to closed mode operation, indicating that GAC bound 4-CP became available to the consortium. Biofilm batch cultures supplied with 10-216 mg 4-CP g-1 GAC suggested that a residual fraction of GAC-bound 4-CP was biologically unavailable. The consortium was able to metabolise 4-CP after perturbations by the addition of chromium (Cr VI) at 1-5 mg l-1 and nitrate at concentrations up to 400 mg l-1. The development of the biofilm structure was analysed by scanning electron microscopy and confocal laser scanning microscopy (CLSM) techniques. CLSM revealed a heterogeneous structure with a network of channels throughout the biofilm, partially occupied by microbial exopolymer structures.

Anaerobiosis↗

PubMed1990

Problems and pitfalls in the performance and interpretation of color Doppler flow imaging: observations based on the influences of technical and physiological factors on the color Doppler examination of mitral regurgitation.

Color Doppler flow imaging has become an integral part of the echocardiographic examination. By providing real-time, two-dimensional spatial maps of normal and abnormal cardiac blood flows, this technique provides important information that may be used to guide patient management. The acquisition and display of color Doppler flow information may be influenced by technical factors, by the physiological condition of the patient, by abnormalities of cardiac morphology, and, on occasion, by artifact. In this article, the results of a study performed to evaluate the influence of technical factors on the color Doppler assessment of mitral regurgitation are reported. Mitral regurgitation jet area size changed significantly with variation in the control settings for color gain, color process, color map, color image resolution, and sector width. A review of those factors that influence the performance and interpretation of the color Doppler flow examination is provided and their significance discussed.

Echocardiography, Doppler↗