PubMed · 10139587
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J Morrissey. 1995-01-23. Systems test performance measures.. https://pubmed.ncbi.nlm.nih.gov/10139587/
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Predictive microbiology is an emerging research domain in which biological and mathematical knowledge is combined to develop models for the prediction of microbial proliferation in foods. To provide accurate predictions, models must incorporate essential factors controlling microbial growth. Current models often take into account environmental conditions such as temperature, pH and water activity. One factor which has not been included in many models is the influence of a background microflora, which brings along microbial interactions. The present research explores the potential of autonomous continuous-time/two-species models to describe mixed population growth in foods. A set of four basic requirements, which a model should satisfy to be of use for this particular application, is specified. Further, a number of models originating from research fields outside predictive microbiology, but all dealing with interacting species, are evaluated with respect to the formulated model requirements by means of both graphical and analytical techniques. The analysis reveals that of the investigated models, the classical Lotka-Volterra model for two species in competition and several extensions of this model fulfill three of the four requirements. However, none of the models is in agreement with all requirements. Moreover, from the analytical approach, it is clear that the development of a model satisfying all requirements, within a framework of two autonomous differential equations, is not straightforward. Therefore, a novel prototype model structure, extending the Lotka-Volterra model with two differential equations describing two additional state variables, is proposed to describe mixed microbial populations in foods.
Separations below 1 s of a mixture of organic compounds ranging from C5 to C8 have been performed to investigate the performance of a time-of-flight mass spectrometer in fast gas chromatography. The gaseous samples were focussed on a cold trap, and then injected after thermal desorption to obtain the required narrow input band-widths. Also, to obtain a very fast separation, a short narrow bore column was used, operated at above-optimum inlet pressures. With this system, it was possible to identify ten compounds within 500 ms, showing peak-widths (2.354sigma) as narrow as 12 ms. The spectral acquisition rate used for these analyses was 500 Hz. The quality of the recorded spectra and the comparison with library spectra was very high. Deconvolution algorithms offer the possibility of identifying overlapping peaks. It is shown that the spectral scan speed of the time-of-flight mass spectrometer is high enough for very fast separations.
BACKGROUND: To assess the validity of the Spanish version of the King's Health Questionnaire (KHQ) for measuring the quality of life of women with different types of urinary incontinence. PATIENTS AND METHODS: 77 women with urinary stress incontinence (USI), 51 with urge incontinence (UUI) and 34 with mixed urinary incontinence (MUI) were consecutively recruited. Subjects were diagnosed using urodynamic tests. Patients completed the KHQ and SF-36 questionnaires on inclusion in the study, after 15 days, and again after one month. RESULTS: There were no significant differences in socio-demographic and QOL characteristics between different UI groups. UUI and MUI patients had greater urinary frequency and urge than USI patients, and USI and MUI patients had a greater number of leakage episodes than UUI patients. Correlations between dimensions on the KHQ and the SF-36 were moderate to strong. Women with greater urinary frequency, greater urgency, more incontinence episodes during the week and who used pads and nappies perceived a worse quality of life. Changes in these variables correlated with changes in HRQOL. The internal consistency of dimensions was good (0.65-0.92) as was test-retest reliability (0.68-0.88). Dimensions most sensitive to change after one month of treatment were impact of UI, seriousness of UI, and the symptoms scale (effect size greater than 0.6). CONCLUSION: The KHQ is a valid instrument for measuring the quality of life of patients with different types of UI. Improvements in urinary frequency, urinary urgency, number of leakage episodes, and changes in the type of protective material produces an increase in HRQOL.