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Ratio Curves (ratio + curve)
Selected AbstractsMechanical behavior of bovine periodontal ligament under tension-compression cyclic displacementsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2006Tatsuya Shibata In the present study, the mechanical response of bovine periodontal ligament (PDL) subjected to displacement-controlled tension,compression harmonic oscillations and subsequent rupture was examined. Specimens including dentine, cementum, PDL, and alveolar bone were extracted from different depths and locations of bovine first molars. They were immersed in a saline solution at room temperature and clamped on their bone and dentine extremities. The samples were tested at ±35% of the PDL's width, with a frequency of 1 Hz. The mechanical parameters evaluated were hysteresis, phase lag, and the modulus of the stress,stretch ratio curves in tension and compression. The tensile strength and the corresponding stretch ratio were also recorded. Stress,stretch ratio curves indicated a non-linear, time-dependent response with hysteresis and preconditioning effects. The hysteresis and phase lag in compression were much higher than in tension, suggesting that the dissipated energy was higher in compression than in tension. The root depth and location did not play essential roles for the tension or compression data, with the exception of limited statistical differences for tensile strength and corresponding stretch ratio. Thus, biological variability in the specimens, as a result of different bone contours, PDL width, and fiber orientation, did not affect the energy-absorbing capacity of the PDL. The evolution of the stress rate with stress demonstrated a constant increase of stiffness with stress. The stiffness values were twofold higher in tension than in compression. The data also showed that the stiffness of the PDL was comparable with data reported for other soft tissues. [source] Hydrometeorological behaviour of pine and larch forests in eastern SiberiaHYDROLOGICAL PROCESSES, Issue 1 2004Shuko Hamada Abstract Seasonal changes in the water and energy exchanges over a pine forest in eastern Siberia were investigated and compared with published data from a nearby larch forest. Continuous observations (April to August 2000) were made of the eddy-correlation sensible heat flux and latent heat flux above the canopy. The energy balance was almost closed, although the sum of the turbulent fluxes sometimes exceeded the available energy flux (Rn , G) when the latent heat flux was large; this was related to the wind direction. We examined the seasonal variation in energy balance components at this site. The seasonal variation and magnitude of the sensible heat flux (H) was similar to that of the latent heat flux (,E), with maximum values occurring in mid-June. Consequently, the Bowen ratio was around 1·0 on many days during the study period. On some clear days just after rainfall, ,E was very large and the sum of H and ,E exceeded Rn , G. The evapotranspiration rate above the dry canopy from May to August was 2·2 mm day,1. The contributions of understory evapotranspiration (Eu) and overstory transpiration (Eo) to the evapotranspiration of the entire ecosystem (Et) were both from 25 to 50% throughout the period analysed. These results suggest that Eu plays a very important role in the water cycle at this site. From snowmelt through the tree growth season (23 April to 19 August 2000), the total incoming water, comprised of the sum of precipitation and the water equivalent of the snow at the beginning of the melt season, was 228 mm. Total evapotranspiration from the forest, including interception loss and evaporation from the soil when the canopy was wet, was 208,254 mm. The difference between the incoming and outgoing amounts in the water balance was from +20 to ,26 mm. The water and energy exchanges of the pine and larch forest differed in that ,E and H increased slowly in the pine forest, whereas ,E increased rapidly in the larch forest and H decreased sharply after the melting season. Consequently, the shape of the Bowen ratio curves at the two sites differed over the period analysed, as a result of the differences in the species in each forest and in soil thawing. Copyright © 2003 John Wiley & Sons, Ltd. [source] Flexible modelling of neuron firing rates across different experimental conditions: an application to neural activity in the prefrontal cortex during a discrimination taskJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 4 2006Carmen Cadarso-Suárez Summary., In many electrophysiological experiments the main objectives include estimation of the firing rate of a single neuron, as well as a comparison of its temporal evolution across different experimental conditions. To accomplish these two goals, we propose a flexible approach based on the logistic generalized additive model including condition-by-time interactions. If an interaction of this type is detected in the model, we then establish that the use of the temporal odds ratio curves is very useful in discriminating between the conditions under which the firing probability is higher. Bootstrap techniques are used for testing for interactions and constructing pointwise confidence bands for the true odds ratio curves. Finally, we apply the new methodology to assessing relationships between neural response and decision-making in movement-selective neurons in the prefrontal cortex of behaving monkeys. [source] Investigation into the traction coefficient in elastohydrodynamic lubricationLUBRICATION SCIENCE, Issue 2 2004Y. S. Wang Abstract The elastohydrodynamic traction coefficients of two Chinese aviation lubricating oils were investigated for various loads, rolling velocities, and lubricant inlet temperatures using a self-made test rig. Traction coefficient versus slide-to-roll ratio curves were generated. The concept of critical load varying with the lubricant temperature is proposed. This paper presents a new empirical formula for the dynamic performance design of high-speed rolling bearings, that relates traction coefficient with normal load, rolling velocity, and lubricant inlet temperature. The coefficients of the formula may be computed by regression analysis of the experimental data. Two example calculations are presented. The predicted results from the formula agree well with experimental observations. [source] Fluctuation in self-perceived stress and increased risk of flare in patients with lupus nephritis carrying the serotonin receptor 1A ,1019 G alleleARTHRITIS & RHEUMATISM, Issue 10 2006Daniel J. Birmingham Objective Stress is believed to be a risk factor for systemic lupus erythematosus (SLE) flare. Two serotonin-related gene polymorphisms, the serotonin receptor 1A (5-HT1A) polymorphism at ,1019C>G and the serotonin transporter LS polymorphism, have been reported to affect stress-related behaviors. The purpose of this study was to assess the relationship between self-perceived stress (SPS), variability in SPS, and the 2 serotonin-related gene polymorphisms as risk factors for SLE flare. Methods Seventy-seven SLE patients (50 with lupus nephritis) were evaluated every 2 months (mean ± SD total followup 18.5 ± 8.5 months), and patients recorded their daily SPS levels (0,10 scale). Values for mean SPS and coefficient of variation (CV) for SPS were calculated from the 60-day block of daily measurements between study visits. Serotonin-related gene polymorphism genotypes were determined by polymerase chain reaction,based methods. Results Of the 77 patients, 53 experienced 80 flares of SLE (32 renal flares) based on prespecified criteria. Multivariate analysis revealed that whereas neither the serotonin-related gene polymorphisms nor the mean SPS was predictive of an SLE flare, an increased CV for SPS was predictive (P = 0.0031). Interaction between the CV for SPS and the 5-HT1A ,1019C>G polymorphism was also found to be a predictor of SLE flare (P = 0.0039). Subset analysis revealed that only in lupus nephritis patients were increasing CVs for SPS (P = 0.0002) and the interaction between CVs for SPS and 5-HT1A (P < 0.0001) predictive of a flare. Odds ratio curves demonstrated that the predictive effect of increasing CVs for SPS required the presence of the 5-HT1A ,1019 G allele, but appeared to be independent of the G allele number. Conclusion Fluctuation in the level of SPS is a risk factor for the onset of flare in SLE patients with major renal manifestations when it occurs on the background of a stress-related susceptibility gene (the 5-HT1A ,1019 G allele). [source] | |||||||||||||