Best-fit Polynomial Research Articles

Evaluating in situ shear strength of bituminous pavements

The friction transfer method described in this paper can be used to estimate the in situ shear strength of bituminous pavement layers. In this method a specially devised apparatus fits on the top of the partial core and is clamped to it. A torque is applied using an ordinary torquemeter, and the maximum shear stress at failure is calculated. Comparative studies of laboratory Marshall stability and friction transfer tests produced correlation coefficients of 0·72 and 0·82 for linear and polynomial best-fit curves respectively, and the respective linear correlation coefficient for the in situ tests was found to be 0·84. The measured values for Marshall and friction transfer tests ranged from 750 to 1100 kg and from 1·2 to 1·8N/mm2 respectively. The average coefficients of variation of eight series of experiments were found to be 11·07% for Marshall stability tests and 11·39% for the friction transfer method. Based on the laboratory and site experiments, and considering such factors as versatility, simplicity, speed, applicability under any site conditions by untrained operators, very low cost, easily interpreted and understood results, and good accuracy, this new method is strongly recommended for the assessment of the in situ shear strength of bituminous materials.

A Biomechanical Comparison of 2 Techniques for Reconstructing Atrophic Edentulous Mandible Fractures

The purpose of this investigation was to evaluate and compare the biomechanical behavior of 2 techniques for the reconstruction of atrophic edentulous mandible fractures. Thirty polyurethane atrophic edentulous mandible replicas (Sawbones, Vashon Island, WA) were used in this investigation (10 controls, 10 replicas of 2 different fixation techniques). The first reconstruction technique was a traditional titanium locking reconstruction plate affixed to the lateral border (buccal surface) of the mandible. The second reconstruction technique used the same type of plate, but placed it on the inferior border of the mandible. Both constructs were subjected to vertical loading at the symphysis and torsional loading at the body regions of the mandible replicas by an Instron 1331 (Instron, Canton, MA) servohydraulic mechanical testing unit. Mechanical deformation data within a 0-900 N range were recorded. Maximum load, displacement at maximum load, and stiffness were determined. Means and standard deviations were derived and compared for statistical significance using a Fisher's Protected Least Significant Differences Test with a confidence level of 95% (P < .05). Second- and third-order polynomial best-fit curves were also created for each group to further evaluate the mechanical behavior. For symphysis loading, statistically significant differences were noted between the control group and both of the plating techniques for displacement at maximum load. However, no differences were noted between the experimental groups for displacement at maximum load, stiffness, or maximum load. For body loading, statistically significant differences were noted between the control group and the inferior border plating group for displacement at maximum load. However, no differences were noted between the experimental groups for displacement at maximum load, stiffness, or maximum load. During this bench top investigation, there were no significant differences noted in mechanical behavior between the 2 specific experimental groups for any of the conditions measured. When placed in the context of functional parameters, both of the plating techniques met or exceeded the requirements for loading.

Estimating chlorophyll a concentrations from remote-sensing reflectance in optically shallow waters

A multi-spectral classification and quantification technique is developed for estimating chlorophyll a concentrations, Chl, in shallow oceanic waters where light reflected by the bottom can contribute significantly to the above-water remote-sensing reflectance spectra, R rs( λ). Classification criteria for determining bottom reflectance contributions for shipboard R rs( λ) data from the west Florida shelf and Bahamian waters (1998–2001; n = 451) were established using the relationship between R rs(412)/ R rs(670) and the spectral curvature about 555 nm, [ R rs(412) ⁎ R rs(670)]/ R rs(555) 2. Chlorophyll concentrations for data classified as “optically deep” and “optically shallow” were derived separately using best-fit cubic polynomial functions developed from the band-ratios R rs(490)/ R rs(555) and R rs(412)/ R rs(670), respectively. Concentrations for transitional data were calculated from weighted averages of the two derived values. The root-mean-square error (RMSE log10) calculated for the entire data set using the new technique was 14% lower than the lowest error derived using the best individual band-ratio. The standard blue-to-green, band-ratio algorithm yields a 26% higher RMSE log10 than that calculated using the new method. This study demonstrates the potential of quantifying chlorophyll a concentrations more accurately from multi-spectral satellite ocean color data in oceanic regions containing optically shallow waters.

An In Vitro Comparison of an Adjustable Bone Fixation System

The purpose of this study was to biomechanically compare an adjustable plating system and several variations with an inverted-L pattern of 3 bicortical screws to fix a bilateral sagittal split osteotomy. Sixty polyurethane mandible replicas (Synbone, Laudquart, Switzerland) were used in this study. Ten uncut mandibular replicas served as control models. Fifty experimental synthetic mandibles had bilateral sagittal split osteotomies created with a 7-mm advancement. Fixation modalities included 3 bicortical screws in an inverted-L pattern, a 4-hole sagittal split plate with adjustable slider (slide 0), an adjustable plate with an additional bicortical screw (slide 1), an adjustable plate with 2 additional bicortical screws (slide 2), and an adjustable plate with 3 additional bicortical screws (slide 3). The alloplastic mandibles were secured in a custom fabricated jig and subjected to vertical loads at the incisal edge and torsional loading at the molar region by an Instron 1331 (Instron, Canton, MA) servohydraulic mechanical testing unit. Mechanical deformation data within a 0- to 900-N range were recorded. Yield load, yield displacement, and stiffness were determined. Means and standard deviations were derived and compared for statistical significance using a Fisher's Protected Least Significant Differences Test with a confidence level of 95% (P < .05). Second-order best-fit polynomials were created for the experimental data curves. For incisal edge loading, the control was significantly greater for yield load than the experimental models. No significant difference was noted between slide 0, slide 1, and slide 2, but significant differences were seen with slide 3 and the inverted-L. There were no significant differences between slide 1, slide 2, slide 3, and inverted-L. For molar load, the control was significantly different than the experimental models. However, there was no significant difference between the experimental models. Mandibular advancements of 7 mm in a synthetic mandible fixed with a 4-hole sagittal split plate with adjustable slider alone is resistant to torsional forces and comparable to that seen with 3 bicortical screws placed in an inverted-L fashion. However, when loading at the incisal edge, additional bicortical screws are necessary to achieve the similar resistance to vertical load as that seen with 3 bicortical screws.

A Biomechanical Evaluation of Bilateral Sagittal Ramus Osteotomy Fixation Techniques

The purpose of this investigation was to evaluate and compare the biomechanical behavior of various rigid internal fixation plates designed to aid in the condylar positioning of bilateral sagittal ramus osteotomies, to positional screws in an inverted-L pattern, and a control. Fifty polyurethane synthetic mandible replicas (Synbone, Laudquart, Switzerland) were used in this investigation. Five controls and 5 each of 4 different fixation modalities (3 bicortical positional screws in an inverted-L pattern, monocortical 4-hole straight plates, monocortical 6-hole curved plates, and monocortical adjustable 4-hole slide plates) were subjected to vertical loading at the incisal edge and torsional loading at the molar region by an Instron 1331 (Instron, Canton, MA) servohydraulic mechanical testing unit. Mechanical deformation data within a 0 to 900 N range were recorded. Yield load, yield displacement, and stiffness were determined. Means and standard deviations were derived and compared for statistical significance using a Fisher's Protected Least Significant Differences Test with a confidence level of 95% (P < .05). Second-order polynomial best-fit curves were also created for each group to further evaluate mechanical behavior. For incisal edge loading, statistically significant differences were noted between the control group and all other groups for yield load and stiffness, and between the control group and straight, curved, and slide plates for yield displacement. Differences were also noted between the inverted-L and straight, strut, and slide plates for yield load; and inverted-L and straight, curved, and slide, as well as straight and slide for yield displacement. For molar loading, statistically significant differences were noted between the control group and all other groups for yield load and stiffness. Differences were noted between the slide and straight, curved, and control; as well as between the inverted-L and straight and strut plates for yield displacement. Lastly, differences were noted between the straight and curved plates, and the slide and straight, curved, and inverted-L for stiffness. In this in vitro study, differences were noted between the control and all experimental groups in their abilities to resist loads under all of the conditions tested. Differences were also noted among specific experimental groups. Yet when placed in the context of functional parameters, only the bicortical positional screws in an inverted-L pattern met the requirements for both molar loading and incisal edge loading.

A Modified Power Law for Creep Analysis

The creep strengths for an annealed Ni-33Fe-25Cr alloy, UNS N08120 (HAYNES® HR-120® alloy) are presented from 593°C to 1204°C at every 56°C for lives up to 30,000 hours. The creep data are used as a basis for converting the power law method (log stress versus log time at a defined temperature) to the usefulness of the Larson-Miller method for design creep analysis. A new empirical relationship was developed between stress, temperature and creep rupture life. Power Law equations were generated at each temperature using linear regression of the transformed data to obtain the best-fit constants. The constants were then plotted and a best-fit polynomial of the constants as a function of temperature was determined. The polynomial then replaced the constants in the original power law equation to obtain a single expression of stress as a function of time and temperature. Using this new Modified Power Law (MPL) equation, interpolation or extrapolation to obtain stress becomes possible for any temperature and time.

A New Precession Formula

We adapt J. G. Williams' expression of the precession and nutation using the 3-1-3-1 rotation to an arbitrary inertial frame of reference. The modified formulation avoids a singularity caused by finite pole offsets near the epoch. By adopting the planetary precession formula numerically determined from DE405 and by using a recent theory of the forced nutation of the nonrigid Earth by Shirai & Fukishima, we analyze the celestial pole offsets observed by VLBI for 1979-2000 and determine the best-fit polynomials of the lunisolar precession angles. We then translate the results into classical precession quantities and evaluate the difference due to the difference in the ecliptic definition. The combination of these formulae and the periodic part of the Shirai-Fukishima nutation theory serves as a good approximation of the precession-nutation matrix in the International Celestial Reference Frame. As a by-product, we determine the mean celestial pole offset at J2000.0 as 0 = -(17.12 ± 0.01) mas and 0 = -(5.06 ± 0.02) mas. Also, we estimate the speed of general precession in longitude at J2000.0 as p = 50287955 ± 00003 per Julian century, the mean obliquity at J2000.0 in the inertial sense as (0)I = 8438140621 ± 000001 and in the rotational sense as (0)R = 8438140955 ± 000001, and the dynamical flattening of Earth as Hd = (3.2737804 ± 0.0000003) × 10-3. Furthermore, we establish a fast way to compute the precession-nutation matrix and provide a best-fit polynomial of an angle to specify the mean Celestial Ephemeris Origin.

Does plate adaptation affect stability? A biomechanical comparison of locking and nonlocking plates

Purpose: The purpose of this investigation was to determine whether the degree of plate adaptation and effects of locking influenced the mechanical behavior of the plate/screw/substrate system for 2.0-mm monocortical superior border plates and 2.4-mm reconstruction plates secured at the inferior border intended to stabilize simulated mandibular angle fractures. Materials and Methods: A total of 130 polyurethane synthetic mandible replicas (Synbone, Landquart, Switzerland) were used in this investigation. Five controls each, for incisal edge and molar loading, as well as 5 samples each for 2.4-mm locking and nonlocking reconstruction plates and 2.0-mm locking and nonlocking monocortical superior border plates, intimately adapted (0.0-mm offset), 1.0-mm offset and 2.0-mm offset were subjected to loading at the incisal edge and molar region with an Instron 1331 (Instron Corp, Canton, MA) servohydraulic mechanical testing unit. Load/displacement data were recorded, and yield load, yield displacement, and stiffness were determined. Mean and standard deviation values were calculated. Statistically significant differences were determined for the effects of locking and degree of plate adaptation using a 1-way analysis of variance (P <.05). For differences within categories and among groups, a Sheffé multiple-comparison test was performed. First-order polynomial best-fit curves were created for each group to further evaluate and compare the mechanical behavior. Results: There were no statistically significant differences (P <.05) for yield load, yield displacement, and stiffness within the 2.4 and the 2.0 locking categories for both molar and incisal edge loading. For the 2.4 nonlocking category, there were statistically significant differences for yield load, yield displacement, and stiffness between the 0.0-mm offset group and both the 1.0-mm and 2.0-mm offset groups for both molar and incisal edge loading but not between the 1.0-mm and 2.0-mm groups. For the 2.0 nonlocking category, there were statistically significant differences for yield load, yield displacement, and stiffness between both the 0.0-mm and 1.0-mm offset groups and the 2.0-mm offset group for both molar and incisal edge loading but not between the 0.0-mm and 1.0-mm groups. Conclusions: The degree of adaptation (amount of offset) affected the mechanical behavior of the nonlocking systems evaluated. It did not affect the locking systems. Failure occurred as an “all-or-nothing” pattern. © 2002 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 60:1319-1326, 2002

A biomechanical evaluation of mandibular condyle fracture plating techniques

Objectives: The purpose of this investigation was to evaluate the biomechanical behavior of various rigid internal fixation techniques for mandibular condylar process fractures. Materials and Methods: Synthetic mandible replicas (Synbone, Landquart, Switzerland) were used to evaluate a control, and four monocortical mandibular condyle plating techniques. Each group was subjected to linear loading in lateral to medial, medial to lateral and posterior to anterior directions by an Instron 1331 (Instron, Canton, MA) servohydraulic mechanical testing unit. Yield load, yield displacement, and stiffness were measured. In addition, each group was subjected to torsional loading using an Instron 8521 (Instron). Yield torque, yield rotation, and stiffness were measured. Five samples were tested for each group and method of loading (n = 100). Means and standard deviations were derived and compared for statistical significance using a 1-way analysis variance (P <.05). Third-order polynomial best-fit curves were also created for each group to further evaluate and compare the mechanical behavior. Results: Statistically significant differences were noted between fixation groups for the different mechanical measures evaluated under the different conditions of linear loading. Statistically significant differences were noted between groups for yield rotation during torsional loading. Although different in magnitude, similar patterns of mechanical behavior were observed in the third-order polynomial best-fit curves for lateral to medial loading, medial to lateral loading and torsional loading. For posterior to anterior loading, different patterns of mechanical behavior were noted between the experimental groups, but similar behavior was noted between the control and mini dynamic compression plate Conclusions: While differences were noted between each of the fixation systems in their abilities to resist loads under the conditions tested, the mini dynamic compression plate provided the most favorable mechanical behavior. Based on the presumed clinical parameters, we can suggest that none of the systems evaluated were ideal for the treatment of mandibular condyle fractures, but that the mini dynamic compression plate is the closest to an effective means for reconstruction. © 2002 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 60:73-80, 2002

Scaling analysis of trends using DFA

We study two aspects of the detrended fluctuation analysis (DFA) method, namely the scaling behavior of the leading terms of the best-fit polynomials and the detection of trends. We show analytically and numerically that the standard deviation of the leading terms of the best-fit polynomials used in DFA displays scaling behavior. Furthermore, we demonstrate that the distribution of these terms can be used to reveal the presence of trends in the data. We also argue that this distribution can be used as a sensitive tool for identifying weak trends.

A biomechanical evaluation of mandibular angle fracture plating techniques

Purpose: The purpose of this investigation was evaluate the biomechanical behavior of a vast array of fixation philosophies and techniques that address mandibular angle fractures.Materials and Methods: A total of 150 polyurethane synthetic mandible replicas (Synbone, Laudquart, Switzerland,) were used in this investigation. Five controls and 5 each of 14 different fixation philosophies and techniques were subjected to vertical loading at the incisal edge and then repeated for contralateral loading in the molar region by an Instron 1331 (Instron, Canton, MA) servohydraulic mechanical testing unit. The fixation philosophies and techniques evaluated were the lag screw technique, monocortical superior border plating techniques with varying sizes of plates and screws, monocortical 2-plate techniques with varying forms of fixation, monocortical tension band systems with associated bicortical stabilization plates of various types, and various forms of reconstruction plates. Load/displacement data within a 0 to 200 N range were recorded. Yield load, yield displacement, and stiffness were determined. Mean and standard deviations were calculated, and statistically significant differences within and among categories were determined using an analysis of variance (P <.05). Second-order polynomial best-fit curves were also created for each group to further evaluate and compare the mechanical behavior.Results: For incisal edge loading, statistically significant differences (P <.05) were found for stiffness between some of the monocortical superior border fixation techniques, as well as for yield displacement between several forms of monocortical 2-plate fixation techniques. No other differences were found within categories or among the groups that best represented their categories. For contralateral molar loading, statistically significant differences existed within and among categories.Conclusions: Under the conditions of this experiment, all systems met or exceeded currently identified postoperative functional requirements for incisal edge loading, but failed to meet them for contralateral molar loading. © 2001 American Association of Oral and Maxillofacial Surgeons

Assessment of fetal cerebellar volume using three-dimensional ultrasound

The purposes of this study were to assess the fetal cerebellar volume during normal gestation using three-dimensional (3-D) ultrasound (US) and to establish a normal chart of fetal cerebellar volume using Altman’s model of statistics. In total, 231 healthy fetuses were studied for assessment of cerebellar volume using a 3-D US volume scanner. The fetuses to be studied were selected to give a cross-sectional series ( i.e., each fetus was examined only once). Polynomial regression analysis was calculated to find the best-fit model using gestational age as the independent variable and cerebellar volume as the dependent variable. Altman’s model was used to calculate the age-related reference centiles for the variance of cerebellar volume. In addition, common fetal growth indices, such as biparietal diameter, occipitofrontal diameter, head circumference, abdominal circumference, femur length and estimated fetal weight, were also measured for the correlation between cerebellar volume and these indices. Our results indicated that the fetal cerebellar volume was highly correlated with gestational age in normal pregnancies with the best-fit polynomial regression equation of a second-order (r = 0.91, p < 0.0001). In addition, fetal cerebellar volume in normal gestation is also highly correlated with common fetal growth indices, such as biparietal diameter, occipitofrontal diameter, head circumference, abdominal circumference, femur length and estimated fetal weight (all p < 0.0001). Following the Altman’s model, a normal growth chart of fetal cerebellar volume was established for clinical reference. In conclusion, with 3-D US, the assessment of fetal cerebellar volume becomes feasible. We believe that fetal cerebellar volume assessed by 3-D US may be useful in detecting cerebellar hypoplasia and relevant syndromes prenatally.

An in vitro evaluation of distractors used for osteogenesis

Objective. The objective of this investigation was to evaluate and compare the mechanical behaviors of distractors used for osteogenesis under various conditions by means of common engineering standards. Study design. Five groups of 5 synthetic mandibles were used in this study (N = 25). The first portion of the investigation compared mandibles without intervention (group A [controls]; n = 5), mandibles that had uniform osteotomies stabilized with an external distractor (group B; n = 5), and mandibles that had simulated sagittal osteotomies rigidly fixated with 3 positional screws (group C; n = 5). The second portion of the investigation compared uniform osteotomies (group B; n = 5) and uniform corticotomies (group D; n = 5) that were stabilized with the same external distractor. The last portion of the investigation compared osteotomies stabilized with an external distractor (group B; n = 5) and osteotomies stabilized with an internal distractor (group E; n = 5). Each construct was subjected to vertical loads on a mechanical testing unit. Common engineering standards, including yield load, yield displacement, maximum load, displacement at maximum load, and stiffness, were measured, recorded, and compared by means of a 1-way analysis of variance and a Scheffé multiple comparison test or independent-samples t test. The means between groups were considered significant for P < .05. A polynomial best-fit curve was calculated for the load/displacement data for each group. Results. During the first portion of the investigation, no significant differences were noted between the control, rigidly fixated sagittal osteotomy, and external distractor with osteotomy groups for displacement at maximum load ( P = .19). Significant differences were noted between groups for yield displacement ( P = .009), yield load ( P < .001), maximum load ( P < .001), and stiffness ( P < .007). Failures occurred in the control and rigidly fixated groups with fractures of the synthetic mandibles. Failures occurred in the external distractor group with permanent deformation or torsion of the pins. During the second portion of the experiment, no statistically significant differences were noted between the corticotomy and osteotomy groups in stiffness ( P = .363), maximum load ( P = .207), or yield displacement ( P = .940). Statistically significant differences were noted between groups for yield load ( P = .036) and displacement at maximum load ( P = .010). Failures occurred in both groups with permanent deformation or torsion of the pins. During the last portion of the investigation, statistically significant differences were noted between the external distractor and internal distractor groups in yield load ( P < .001), yield displacement ( P < .001), maximum load ( P = .001), and displacement at maximum load ( P = .01); no significant differences were noted in stiffness ( P = .71). Failures occurred in the external distractor group with permanent deformation or torsion of the pins. Failures occurred in the internal distractor group with fracture of the model or displacement beyond 30.0 mm. Conclusions. Different patterns of mechanical behavior were found between the control and rigidly fixated sagittal osteotomy groups and the external distractor group, between the corticotomy and osteotomy groups, and between the internal and external distractor groups.

Predation and the distribution and abundance of tropical sea urchin populations

Nine species of herbivorous sea urchin commonly inhabit shallow-water coral reefs of the Indian Ocean. The abundance, distribution and diversity of these species were studied in seven reef lagoons over a 7-year period to determine the factors that control population variation in time and space and the role that predation plays in their ecology at a scale ≥0.1 hectare. Field studies of predation included experimentally tethering sea urchins (Predation Index), visual transects of fish to estimate the predator biomass and line transects of reef substrate rugosity (bottom contour complexity) which allowed for five possible measures of the hypothesized limiting resource — refuge from predators. The amount of refuge was used to predict the abundance of individual species of sea urchin, species richness and diversity. It was predicted from pervious manipulative species interaction studies that the top competitor in the guild ( Echinometra mathaei (de Blainville)) would be directly and closely controlled by predation because competitive dominance may often reflect an evolutionary and energetic trade-off with predator susceptibility and, therefore, E. mathaei abundance would decrease either linearly or logarithmically with measures of predation. Competitively-subordinate species were predicted to have unimodal (“hump-shaped”) abundance relationships with refuge because these species should make an evolutionary trade-off between increased predator resistance and decreased competitive ability. Spatial and temporal variation in wet-weight estimates was high for all species except the numerical and competitive dominant, E. mathaei, and for all species combined. Spatial variation in species abundance was highest under conditions of high predation and low species dominance and decreased as the total wet weight of urchins increased and the competitive dominant occupied resources. The most common subordinate species frequently exhibited the predicted unimodal relationships with the best measure of refuge from predation but variation was high and the best-fit second-order polynomials predicted less than 55% of the variation in sea urchin biomass. There was evidence for partitioning of the spatial refuge resource among species particularly for E. mathaei (de Blainville), Tripneustes gratilla Linn. and Diadema setosum Leske at the low to intermediate levels of predation. There was, however, a large overlap in the peak abundance of Diadema savignyi (Michelin), Echinothrix diadema Linn., Toxopneustes pileolus Lam. and Stomopneustes variolaris Lam. at the highest levels of predation. Nonetheless, the partitioning of refuge among many species occurs more at the smaller scale of reef crevices (<10 m 2) than at the larger scale of ∼0.1 hectare sites or whole sections of reef. Diversity and number of species, however, were strongly associated with measures of refuge and exhibited unimodal curves.

Accurate area and delay estimation from RTL descriptions

In this paper, we present a method for efficiently obtaining area and delay estimates from RTL descriptions of a logic design. The estimates are obtained through fast compiler-type optimizations on the RTL descriptions followed by application of best-fit polynomial area and delay models on the resulting technology-independent representation. The estimation techniques were incorporated into a tool called QUEST. QUEST was used by designers of a large commercial CPU to obtain quick feedback on the area and delay impart of behavioral modifications, resulting In significant savings in design schedule.

Analysis of cumulus solar irradiance reflectance (CSIR) events

Clouds are extremely important with regard to the transfer of solar radiation at Earth's surface. This study investigates Cumulus Solar Irradiance Reflection (CSIR) using ground-based pyranometers. CSIR events are short-term increases in solar radiation observed at the surface as a result of reflection off the sides of convective clouds. When Sun-cloud observer geometry is favorable, these occurrences produce characteristic spikes in the pyranometer traces and solar irradiance values may exceed expected clear-sky values. Ultraviolet CSIR events were investigated during the summer of 1995 using UVA and UVB pyranometers. Observed data were compared to clear-sky curves which were generated using a third degree polynomial best-fit line technique. Periods during which the observed data exceeded this clear-sky curve were identified as CSIR events. The magnitude of a CSIR event was determined by two different quantitative calculations. The MAC (magnitude above clear-sky) is an absolute measure of the difference between the observed and clear-sky irradiances. Maximum MAC values of 3.4 Win −2 and 0.0169 Wm −2 were observed at the UV-A and UV-B wavelengths, respectively. The second calculation determined the percentage above clear-sky (PAC) which indicated the relative magnitude of a CSIR event. Maximum UV-A and UV-B PAC magnitudes of 10.1% and 7.8%, respectively, were observed during the study. Also of interest was the duration of the CSIR events which is a function of Sun-cloud-sensor geometry and the speed of cloud propagation over the measuring site. In both the UV-A and UV-B wavelengths, significant CSIR durations of up to 30 minutes were observed. C 1997 Elsevier Science B.V.

Separate and joint effects of arginine and glucose on ovine fetal insulin secretion

To determine separate and joint effects of increases (delta) in fetal plasma concentrations of arginine (Af) and glucose (Gf) on fetal insulin (If) secretion (delta If), 15 late-gestation fetal sheep were given 5-min arginine bolus infusions (40, 86, 144, 201, and 402 mumol/kg estimated fetal wt) at 90 min of 120 min steady-state glucose clamps (basal Gf, basal + 0.6 mM Gf, and basal + 1.1 mM Gr), producing absolute and percent increases above basal Af of 25.8 +/- 1.3 microM (+33%), 50.9 +/- 6.3 microM (+66%), 83.8 +/- 7.1 microM (+108%), 122.1 +/- 9.4 microM (+156%), and 302.2 +/- 28.2 microM (+386%), respectively. Acute hyperglycemia alone produced an increase above basal If of 9 +/- I microU/ml (+80%) and 19 +/- 2 microU/ml (+170%) after basal + 0.6 mM Gf and basal + 1.1 mM Gf, respectively. Increasing values of delta Af showed separate but lesser effects on delta If, which were significant only at very high values of Af (> 100% above mean normal Af) unless marked hyperglycemia (1.5- to 2-fold normal) was also present, demonstrating joint effects of delta Af and delta Gf on delta If according to a best-fit inverse polynomial response surface. We conclude that physiological increases in Af at normal glucose concentrations are not a potent-stimulus to insulin secretion in fetal sheep.

The saturated vapor pressure of desflurane at various temperatures.

The saturated vapor pressure of desflurane at various temperatures.

Stochastic analysis of sonic logs from the upper crystalline crust: methodology

To relate local fluctuations observed in sonic logs to small-scale velocity fabric along boreholes, both filtering effects and noise introduced by the logging procedure must be taken into account. Sonic log velocities are represented as a time series consisting of a large-scale deterministic and a small-scale stochastic component. The deterministic trend, approximated by a low-order polynomial best-fit, contains information on the average velocity structure, whereas the small-scale stochastic variations consist of noise plus in situ velocity variations convolved with the logging system response. The velocity fluctuations of the sonic data considered here are zero-mean and have quasi-Gaussian probability density functions. Therefore, they are well characterised by their second statistical moment, i.e. their autocovariance function. Tests on synthetic data indicate that the autocovariance function corresponding to this data model may be used to extract information on the second-order statistics of the in situ velocity variations along the borehole and to constrain the level of white noise in sonic logs. Ignoring the presence of filtering effects and noise in sonic logs may result in seriously flawed estimates of the second-order statistics of the actual velocity structure. Assuming a von Kármán autocovariance function for the in situ velocity variations, this model provides a good match to the autocovariance functions of sonic log data from the Siljan Ring (Sweden) and Sudbury areas (Canada). Although differing significantly in their noise content, these two data sets yield similar results for the small-scale velocity structure, which is modelled as a bandlimited self-affine time series. For the Siljan Ring borehole we found a close relation between small-scale variations of the borehole diameter as determined from caliper logs and the level of uncorrelated noise present in the sonic log data.

Three-Dimensional rendering and phase analysis of the CaO-Al2O3-SiO2 system

A program for rendering ternary phase equilibria in 3-point perspective was developed using Microsoft Visual Basic. Algorithms for rendering and phase analysis are described. With the software, liquidus, subliquidus, and solidus surfaces can be generated, and the three-dimensional object can be rotated to any angle for viewing. The operator can select a composition on the top-view 2-dimensional projection, and surfaces pertinent to an isoplethal study will be displayed. A phase analysis plot is simultaneously displayed wherein relative proportions and compositions of phases are enumerated for any chosen temperature. Phase analysis calculations were based on methods of analytical geometry using best-fit polynomials for liquidus surfaces and their contact boundaries. Phase analysis involved separation into one of five possible modes of phase evolution during cooling.