4 resultados para Quantitative measure of algae viability
em Brock University, Canada
Resumo:
An efficient way of synthesizing the deuterium labelled analogues of three methoxypyrazine compounds: 2-d3-methoxy-3-isopropylpyrazine, 2-d3-methoxy-3- isobutylpyrazine, and 2-d3-methoxy-3-secbutylpyrazine, has been developed. To confirm that the deuterium labels had been incorporated into the expected positions in the molecules synthesized, the relevant characterization by NMR, HRMS and GC/MS analysis was conducted. Another part of this work involved quantitative determination of methoxypyrazines in water and wines. Solid-phase extraction (SPE) proved to be a suitable means for the sample separation and concentration prior to GC/MS analysis.Such factors as the presence of ethanol, salt, and acid have been investigated which can influence the recovery by SPE for the pyrazines from the water matrix. Significantly, in this work comparatively simple fractional distillation was attempted to replace the conventional steam distillation for pre-concentrating a sample with a relatively large volume prior to SPE. Finally, a real wine sample spiked with the relevant isotope-labelled methoxypyrazines was quantitatively analyzed, revealing that the wine with 10 beetles per litre contained 138 ppt of 2-methoxy-3-isopropylpyrazine. Interestingly, we have also found that 2-methoxy-3-secbutylpyrazine exhibits an extremely low detection limit in GC/MS analysis compared with the detection limit of the other two methoxypyrazines: 2- methoxy-3-isopropylpyrazine and 2-methoxy-3-isobutylpyrazine.
Resumo:
Objectlve:--This study examined the intraclass reliability· of different measures of the
excitability of the Hoffmann reflex, derived from stimulus-response curves. The slope of the
regression line of the H-reflex stimulus-response curve advocated by Funase et al. (1994) was
also compared to the peak of the first derivative of the H-reflex stimulus-response curve
(dHIdVmax), a new measure introduced in this investigation. A secondary purpose was to explore
the possibility of mood as a covariate when measuring excitability of the H-reflex arc.
Methods: The H-reflex amplitude at a stimulus intensity corresponding to 5% of the
maximum M-wave (Mmax) is an established measure that was used as an additional basis of
comparison. The H-reflex was elicited in the soleus for 24 subjects (12 males and 12 females)
on five separate days. Vibration was applied to the Achilles tendon prior to stimulation to test
the sensitivity of the measures on test day four. The means of five evoked potentials at each
gradually increasing intensity, from below H-reflex threshold to above Mmax, were used to create
both the H-reflex and M-wave stimulus response curves for each subject across test days. The
mood of the subjects was assessed using the Subjective Exercise Experience Scale (SEES) prior
to the stimulation protocol each day.
Results: There was a modest decrease in all H-reflex measures from the first to third test day,
but it was non-significant (P's>0.05). All measures of the H-reflex exhibited a profound
reduction following vibration on test day four, and then returned to baseline levels on test day
five (P's<0.05). The intraclass correlation coefficient (ICC) for H-reflex amplitude at 5% of
Mmax was 0.85. The ICC for the slope of the regression line was 0.79 while it was 0.89 for
dH/dVmax. Maximum M-wave amplitude had an ICC of 0.96 attesting to careful methodological
controls. The SEES subscales of fatigue and psychological well-being remained unchanged
IV
across the five days. The psychological distress subscale (P
Resumo:
As a result of increased acid precipitation, the pH of a large
number of Canadian Shield lakes has been falling. Prior to this study
there was no documentation available to explain the history of lake
acidification for the Algoma area lakes. In order to obtain this
information the diatom inferred pH technique was developed in this
study.
During two field seasons, July 1981 and July 1982, short sediment
cores (circa 25-30 cm) were collected from 28 study lakes located north
of Lake Superior, District Algoma, Ontario. The surface sediment
diatoms (0-1 cm) from each of these lakes were carefully identified,
enumerated, and classified in terms of their pH indicator status.
The surface sediment diatom analysis indicated that lake pH is one of
the most important factors affecting the species composition and
relative abundance of diatom populations. Thus diatom assemblages can
be sensitive indicators of lake acidification. When Nygaard's index
alpha was plotted against observed lake pH, a statistically
significant relationship resulted (r=-0.89; p=
Resumo:
This quantitative descriptive co-relational study used telephone survey interviews and stratified random sampling to collect data related to Social Capital (SC) and its components (trust and safety, reciprocity, civic engagement and collective action) and selected determinants of health variables in Niagara Region, Canada. Among the four components of social capital, trust and safety levels were highest among all participants (m=5.42, SD=1.0), with community engagement yielding the lowest mean score for the sample (m=1.93, SD=.8). Reciprocity had the strongest association with all other components of SC (r=0.51). Those most likely to report low levels of SC and health were unattached and low-income females. Males were more likely to report higher trust and safety levels and higher levels of self-rated health. In this study, a linear relationship between self-reported health status and SC was not found. Marital and employment status were associated with differences in mean scores of SC and self-reported health.