Absolute Diameter Research Articles

Stellar radii

Observing a stellar radius basically means observing a center-to-limb intensity variation. The significance and properties of center-to-limb variations, common approximations, the correlation with optical-depth radii in extended-photophere stars, and direct measurements of angular (interferometry, lunar occultation) and absolute diameters (binary eclipses) are discussed. Spectrophotometric and doppler techniques of diameter determination are also briefly outlined.

Effects of intracoronary adenosine triphosphate on coronary flow velocity dynamics in children.

To assess the usefulness of adenosine triphosphate (ATP) as an alternative agent for functional determination of coronary circulation in children and to reveal the dose-response kinetics of intracoronary ATP, systemic hemodynamics and spectral coronary flow velocity dynamics using Doppler guide wire were measured during hyperemic responses to an intracoronary bolus injection of ATP (0.01 microgram/kg, 0.1 microgram/kg and 1.0 microgram/kg) in consecutive 40 Kawasaki disease patients (age: 8.4 +/- 5.1 years, 30 boys and 10 girls) without angiographic coronary lesions. ATP did not produce any significant change in heart rate, systolic blood pressure and mean blood pressure, but mildly decreased diastolic blood pressure. The coronary flow reserve (CFR) calculated as a ratio of hyperemic to basal averaged peak velocity (APV) for ATP was 2.05 +/- 0.31, 2.26 +/- 0.38 and 2.50 +/- 0.51 in LAD, and 2.24 +/- 0.28, 2.44 +/- 0.41 and 2.60 +/- 0.47 in RCA, respectively, for each of the three doses. There was no statistical significance between the mean values of CFR in LAD with ATP (1.0 microgram/kg: 2.39 +/- 0.16) and papaverine (0.15 microgram/kg: 2.43 +/- 0.16) in six patients without angiographic coronary lesions. The maximal coronary hyperemia was reached rapidly after intracoronary bolus injection of ATP in all doses (10, 10-15 and 15-20 seconds in both LAD and RCA, respectively, for each of the three doses). The time required for APV to return to basal levels (< T10%) increased with the dose of ATP (30, 55 and 110 seconds in LAD and 35, 45 and 100 seconds in RCA, respectively, for each of the three doses). Three patients (3/40: 7.5%) developed transient (< 5 seconds) asymptomatic second degree atrioventricular block, but no patient had clinically significant arrhythmias. The change ratio in QTc interval after ATP injection was 1.96 +/- 1.87% (not significant). In addition, an intracoronary injection of ATP did not increase the absolute angiographic coronary luminal diameter. This study indicates that ATP is a safe alternative agent for pharmacological induction of coronary hyperemia for evaluation of coronary stenotic lesions and for the study of coronary circulation and coronary flow reserve in children.

Pulmonary artery growth after bidirectional cavopulmonary shunt: Is there a cause for concern?

Objective: Our objective was to analyze changes in pulmonary artery size after bidirectional cavopulmonary shunt. Methods: All 47 patients who underwent bidirectional cavopulmonary shunt between March 1990 and May 1995 who had preoperative and postoperative angiograms available for review were selected for study. This included 24 patients who had also undergone a modified Fontan operation. Clinical records were reviewed retrospectively and cross-sectional follow-up was obtained by direct physician contact. Angiograms were reveiwed, and the right and left pulmonary artery diameters were each measured at two locations: immediately distal to their origin and at the narrowest point. In addition, the lower lobe pulmonary artery branch was measured just distal to its origin. Cross-sectional areas (left, right, and total) at each point of measurement were indexed to body surface area. Angiographic and hemodynamic data were analyzed. Results: Changes in the various measures of pulmonary artery size after bidirectional cavopulmonary shunt varied considerably. On average the absolute diameters increased for all measures, but the increase in diameter was significant only for the lower lobe arteries. All pulmonary artery indices decreased on average, but these changes did not approach significance. Patients who underwent pulmonary artery augmentation at the time of bidirectional cavopulmonary shunt had significantly smaller pulmonary artery indices before pulmonary artery augmentation, relative to those who did not undergo pulmonary artery repair, and significantly greater changes (possibly to a large extent owing to pulmonary artery repair) in the right and left pulmonary artery index after bidirectionl cavopulmonary shunt. Lower lobe indices did not differ preoperatively or exhibit different degrees of change in size between patients who did and did not undergo pulmonary artery repair. One patient died after Fontan completion (pulmonary artery index: 305 mm 2/m 2), and none of the factors analyzed correlated with Fontan outcomes. Conclusions: A more appropriate measure of pulmonary artery growth is the indexed cross-sectional area of the lower lobe branch of the right and left pulmonary arteries, which is less likely to be altered surgically with systemic-pulmonary shunts, pulmonary artery repair, and the bidirectional cavopulmonary anastomosis itself. Pulmonary artery indices, including the lower lobe index, do not change significantly after bidirectional cavopulmonary shunt during medium-term follow-up and do not influence the Fontan outcome. (J T HORAC C ARDIOVASC S URG 1996;112:1180-92)

Cisplatin-induced autonomic neuropathy: does it really exist?

The neurotoxic side-effects of cisplatin affect predominantly the large, myelinated fibres of peripheral nerves, leading to a sensory neuropathy. Several reports of cisplatin-associated autonomic neuropathy have been published. Autonomic dysfunction however, is caused by a neuropathy of small unmyelinated nerve fibres. By using the absolute pupil diameter as a parameter of autonomic nervous system function, we studied autonomic neuropathy in the eye of cisplatin-intoxicated rats. In addition, we examined autonomic cardiovascular function by measuring the change in heart rate (HR) and mean arterial blood pressure (MAP) in response to intravenous phenylephrine (PHE) and tyramine (TYR). No significant differences in mean pupil diameter developed in cisplatin-intoxicated rats (n = 12) in the course of 9 weeks (total cumulative dose cisplatin 18 mg/kg) compared with normal controls (n = 9) MANOVA, F1,19 = 0.88, P < 0.36). The PHE- and TYR-induced changes in MAP and HR were virtually the same in cisplatin-intoxicated rats when compared with normal controls. We conclude that cisplatin probably does not cause autonomic dysfunction, at least not in rats, in doses commonly used and which are known to cause a peripheral sensory neuropathy.

Coronary Arterial Flow-Velocity Dynamics in Children With Angiographically Normal Coronary Arteries

There have been few reports about coronary hemodynamics in children during the process of growth. In the present study, to assess the characteristics of coronary flow dynamics in children, we examined the phasic coronary flow-velocity (CFV) patterns at rest and during peak hyperemic responses in children with angiographically normal coronary arteries. Spectral Doppler phasic coronary flow velocity was recorded with a 0.018-in intracoronary Doppler guidewire at rest and during peak responses after intracoronary bolus injection of ATP in 30 patients with Kawasaki's disease (age, 8.2 +/- 5.1 years; 24 boys and 6 girls) without angiographic coronary lesions. Average peak velocity (APV), maximum peak velocity (MPV), and diastolic-to-systolic velocity ratio (DSVR) were evaluated in the left anterior descending coronary artery (LAD), left circumflex artery (LCx), and right coronary artery (RCA). Coronary vasodilator reserve (coronary flow reserve [CFR]) was calculated as the ratio of ATP-induced hyperemic to baseline APV. Flow-velocity parameters in RCA were significantly lower than those in the LAD and LCx in both proximal and distal portions. Although the distal LCx had significantly lower values of APV and MPV than did the proximal LCx, there was no significant difference between the proximal and distal portions of the LAD and RCA for APV and MPV. All three coronary vessels showed a diastolic dominant flow pattern in each segment. This coronary flow pattern was less marked in the RCA than in the LCA. All three coronary vessels showed a significant increase in APV and a significantly decrease in DSVR after ATP administration. CFR was significantly lower in the LCx than in the LAD or RCA (P < .01: 1.93 +/- 0.34 in LCx versus 2.32 +/- 0.42 in LAD and 2.37 +/- 0.44 in RCA). From the view of aging, it was revealed that APV values in three vessels were higher in the younger group than in the older group. CFR values in the LAD and LCx were significantly lower in the younger group than in the older group (P < .001 in LAD: 2.01 +/- 0.28 in the younger versus 2.53 +/- 0.37 in the older; P < .01 in LCx: 1.61 +/- 0.15 in the younger versus 2.06 +/- 0.31 in the older). In addition, intracoronary injection of ATP did not increase the absolute angiographic coronary luminal diameter. With the use of an intracoronary Doppler guidewire, we demonstrated that there are some characteristic findings in CFV dynamics in childhood. These physiological characteristics in CFV dynamics that occur with aging and occur in each vessel must be taken into consideration in the study of the coronary circulation in children.

Gap Partitioning Among Maples (Acer) in Central New England: Survival and Growth

We measured survival and growth of three shade—tolerant species of maple (Acer pensylvanicum, A. rubrum, and A. saccharum) in response to understory and experimentally created small canopy gaps of two sizes (8 x 12m, 75 m2; 16 x 24 m, 300 m2) in central New England. Seedlings of the three species (2160 total, 720 per species) were transplanted into five plot locations (center plus northwest, northeast, southwest, and southeast gap edges) within all gap and understory sites. Measurements of microclimates, architecture, photosynthetic performance, survival, and growth were made over 1 yr before, and 2 yr following, gap release. Red maple (A. rubrum) survived better overall across the study due to greater persistence in the north and center plots of large gaps. The small gaps and understories showed no differences among the species. Survival rates exceeded 80% in most sites and plots, with low values (30—65%) only in the exposed plots of large gaps. There were no relationships between post—gap survival and previous age, height, or basal diameter. By the end of 2 yr of gap release, both gap sizes induced greater distinctions among the species in all growth variables than the understory. Striped maple (A. pensylvanicum) exhibited greater leader extension, absolute stem height, net height change, absolute basal diameter, and net basal diameter change than red maple and sugar maple (in that order) in nearly all sites and plots. The exception was large—gap center and north plots, where red maple equalled or exceeded striped maple in net basal diameter change, but not net height increase. Sugar maple (A. saccharum) was the least responsive of the species to the gap—understory gradient. As with survival, there were no predictable relationships between pregap age or size and post—gap growth. Photosynthetic performance paralleled growth by these species across the gradient, particularly for shoot assimilation. When growth variables were plotted against irradiance and temperature measured at seedling plot positions, there were consistent and clear distinctions among species across the gap—understory gradient, providing limited evidence for gap partitioning in our system. Striped maple appears to be a superior generalist, red maple is a weaker generalist, and sugar maple shows the poorest performance in a manner that is nearly insensitive to the gap—understory gradient, in our experimental system.

Angiographic stenosis progression and coronary events in patients with 'stabilized' unstable angina.

Recent studies suggest that angiographically complex coronary stenoses are associated with an adverse short-term outcome. It is not known, however, if this applies to unstable angina patients who stabilize on medical therapy. We prospectively studied 85 consecutive patients with unstable angina who stabilized on medical therapy but were found to require angioplasty for treatment of obstructive coronary disease. Angiography was carried out at admission, and patients were restudied 8 +/- 4 months (mean +/- SD) after the first angiogram. Ischemia-related stenoses were identified and classified as "complex" (irregular borders, overhanging edges, or thrombus) or "smooth" (absence of complex features). Stenosis progression (> or = 20% diameter reduction or new total occlusion) was assessed by automated edge detection. At initial angiography, there were 198 stenoses (> or = 50%, 102), of which 85 (54 complex and 31 smooth) were ischemia related. At restudy, 21 ischemia-related stenoses and 8 non-ischemia-related stenoses progressed (25% versus 7%, P = .001). Seventeen of the 21 ischemia-related stenoses that progressed developed into total occlusion compared with 3 of the 8 non-ischemia-related stenoses (P = .02). Changes in average stenosis severity and in absolute stenosis diameter were significantly larger in ischemia-related stenoses than in non-ischemia-related stenoses (P = .03). Eighteen (34%) complex stenoses progressed, compared with 3 (10%) smooth lesions (P = .02). During follow-up, 1 patient died (myocardial infarction) and 25 patients had nonfatal coronary events that were associated with progression of ischemia-related stenoses in 14 (56%). In unstable angina patients who stabilize medically, subsequent short-term stenosis progression and coronary events are common. The unstable coronary lesion (particularly complex stenoses) is often not stabilized and will continue to progress over the ensuing months.

728-1 Determination of Stenosis Length by Magnetic Resonance Coronary Angiography

Magnetic resonance coronary angiography (MRA) can identify significant stenoses ( &gt; 50%) as regions with reduced signal intensity due to disturbed intraluminal flow. To determine whether MRA stenosis length reflects true lesion length by x-ray angiography (XA). 12 patients (10 male and 2 female: age 65 ± 8 years) underwent both MRA and XA with an average of 2.1 ± 1.7 days between procedures. MRA was performed with the patient prone on an elliptical spine coil using a fat suppressed. TurboFlash, breath hold, segmented k-space sequence during late diastole. MRA defects were quantified off-line by manual tracing of digital images. XA stenoses were analyzed from 35 mm cine films using an electronic caliper which reported defect length, stenosis diameter and area. Matched MRA-XA stenoses included 5 in the left anterior descending (LAD), 8 right coronary artery (RCA) and 2 left circumflex (LCX). MRA and XA results were highly correlated (r = 0.96). MRA reported a slightly longer stenoses length 9.65 ± 2.0 mm versus 8.32 ± 2.1 mm for XA (p &lt; 0.05 paired t-test). The ratio (MRA stenosis length/XA stenosis length) was not dependent on stenosis severity, absolute stenosis lumen diameter or area (MANOVA). Thus, in addition to detecting the presence of coronary lesions. MRA allows quantification of stenosis length.

968-30 Does Insertion/Deletion Polymorphism of the Angiotensin Converting Enzyme Influence the Occurrence of Restenosis After Percutaneous Transluminal Coronary Angioplasty?

The insertion/deletion (I/D) polymorphism of the angiotensin converting enzyme (ACE) is related to the pathogenesis of coronary artery disease. The deletion allele is strongly associated with the level of circulating ACE and is a potent risk factor for myocardial infarction (MI). Recently, the deletion allele was also associated with the occurrence of visually diagnosed restenosis after percutaneous transluminal coronary angioplasty (PTCA) in a selected population of patients with acute MI. We investigated the influence of the ACE I/D polymorphism on the occurrence of restenosis after PTCA, using quantitative coronary angiography. ACE I/D genotypes were analysed in 118 consecutive patients with one vessel disease. All of them underwent PTCA and had a systematic angiographic follow-up (Fup). Coronary angiograms were analysed before and after PTCA, and at Fup (7.5 ± 3 months). Before PTCA, no clinical or angiographic differences were detected between the three groups of genotypes. At Fup, the absolute minimal lumen diameter and percent stenosis were similar in the 3 groups of genotypes. DD (n = 39) ID (n = 62) II (n = 17) Acute gain (mm) 1.25 ± 0.51 1.29 ± 0.47 1.15 ± 0.48 Late loss (mm) –0.43 ± 0.78 –0.41 ± 0.55 –0.40 ± 0.67 Stenosis &gt; 50% (Fup) 43.6% 32.3% 47.1% The loss index (late loss/acute gain) was identical in the 3 groups. In conclusion, in this quantitative study, the deletion polymorphism of the ACE gene did not influence the occurence of restenosis after PTCA.

Genetic parameters of greenhouse growth and performance of 2‐yearpinus contortssubsp.latifolia

Stand differentiation, heritabilities and genetic correlations in 16 growth, bud and branch traits in Pinus contorta subsp. latifolia were studied for two growth periods in the greenhouse. Data for analyses were based on 116. open‐pollinated families from 33 stands in one breeding region in central Alberta, Canada. Family effect was significant at the 1% level of probability for all traits. The narrow‐sense heritabilities (h2) from 0.43 + 0.09 to 0.71 + 0.12 for traits of absolute height and diameter were the highest reported for growth traits in this conifer. In contrast, h2 varied between 0.15±0.06 and 0.33 ± 0.08 for bud, branch and growth increment traits. Except for relative branch length, all traits showed convariation with the other traits. Levels of heritability and genetic correlation suggest that selection procedures that exploit additive genetic variance and covariance might be practised, provided there would be high juvenile‐mature correlation for this sample of P. contorta subsp. latifolia.

Quantitative Coronary Arteriography and Its Assessment of Atherosclerosis

Assessment of coronary artery disease by quantitative coronary arteriography (QCA), while highly accurate, is more expensive than visual estimates of disease and involves the measurement of numerous variables requiring specialized equipment and personnel, thereby reducing its clinical applicability. In part 1 of this paper, the independent variables that influence flow of 1040 coronary artery segments were analyzed. Using the information previously reported in part 1 of this paper, we set out to determine the importance of each of the independent variables (percent diameter and area stenosis, length, absolute diameter, entry and exit angles) in the prediction of stenosis flow reserve (SFR). Analysis of variance (ANOVA) was used to determine the importance of each of these variables, as well as their interactions, on the determination of SFR. Only percent diameter stenosis (%DS) demonstrated statistical significance (P < 0.001) in determining stenosis flow reserve. When the results of SFR were plotted against %DS, a quadratic relationship was demonstrated with an R2 value of 0.903 (r = 0.95). To verify the quadratic equation, the %DS of 100 different arterial stenoses was measured and used to calculate an SFR by the quadratic formula. The QCA and quadratic (calculated) determined SFRs compared favorably, with a correlation of 0.97. The ability to calculate SFR directly from measured %DS allows the incorporation of calculated SFR into the clinical setting, where cardiologists can interpret lesion severity both anatomically and hemodynamically. This incorporation can be done without additional cost to the physician, hospital, patient, or third-party payers.

Quantitative coronary arteriography and its assessment of atherosclerosis. Part I. Examining the independent variables.

Previous work has demonstrated that quantitative coronary arteriography (QCA) can accurately measure phantom images to within +/- 0.1 mm and has been accepted as a reliable and reproducible method of measuring human coronary artery disease (CAD). Assessment of CAD by QCA involves the measurement of numerous variables, which are currently required to calculate stenosis flow reserve (SFR). In this study 1040 stenotic lesions were analyzed by two well-accepted methods with demonstrated accuracy and reproducibility. These methods measure percent diameter stenosis (%DS), absolute diameter, percent area stenosis, length, as well as entry and exit angles to and from a stenotic coronary artery lesion respectively. Based upon these results, the mean +/- standard deviations and range seen in CAD were determined for each of these independent variables. This study demonstrated that atherosclerotic coronary artery lesions do not appear to exceed an entry angle of -39 degrees, and exit angle of +35 degrees, or an absolute length of 4.84 cm when accurately measured by QCA. It was also noted that, once percent diameter stenosis exceeded 89% (regardless of the visual estimate) or percent area stenosis exceeds 99%, coronary arteries become completely occluded as measured by QCA. While previously suspected that once certain critical limits are exceeded in the deposit of cholesterol and calcium within the coronary artery, the artery will close, this study demonstrated by QCA what the limitations in human coronary arteries appear to be. These limits may be in part due to turbulent factors resulting in platelet activation or local mediators from endothelium of the coronary artery.

Measurement, characterization and volume determination of approximately spherical objects

The roundness and sphericity of manufactured single crystal silicon spheres of nearly perfect geometry have been measured using a high-accuracy rotating probe instrument. Automated data collection, spindle error separation and fitting algorithms have been applied to generate 3D sphericity data. A two-dimensional roundness error profile of any great circle is determined with a standard uncertainty of 2.3 nm, and three dimensional sphericity error surface is determined with a standard uncertainty of 2.8 nm. When scaled with absolute diameter data, the sphericity error surface is transformed to a 3D data set of absolute radial dimensions. Two methods of computing the volume of an approximate sphere are presented. They are direct numerical integration and spherical harmonics. The algorithmic precision of the volume calculation is twelve significant digits for the direct numerical integration method and ten significant digits for the spherical harmonics method. These accuracies are several orders of magnitude better than the target uncertainty of 0.1 ppm or seven significant digits. Assuming a standard uncertainty in absolute diameter measurement of 2.8 nm, the volume is shown to be calculable with a standard uncertainty of 0.1 ppm.

The natural history of thoracic aortic aneurysms

Because improved understanding of the natural history of thoracic aneurysms would enhance our ability to determine in which cases the risk of surgical treatment is justified, the rate of enlargement of thoracic aneurysms and thoracoabdominal aneurysms was studied in 67 patients by means of serial computer-generated three-dimensional reconstructions of computed tomographic scans. Patients were followed for a mean of 1.5 +/- 0.15 years (0.2 to 5.35 years) with an average interval between examinations of 0.9 +/- 0.1 year (0.2 to 5.0 years). Thirty-nine patients continue to be followed; 7 were lost to follow-up; 14 died during follow-up (4 after aneurysm rupture), and 10 underwent an operation. Indications for operation included the presence of pain, an absolute aortic diameter larger than 8 cm, an increase in aortic diameter of more than 1 cm per year, or marked irregularity of aneurysm contour. Aortic diameter and volume data were generated from the aortic silhouette obtained by tracing each computed tomographic slice with a translucent digitizing tablet. Estimated change in aortic diameter after 1 year was 0.43 cm; estimated change in aortic volume was 88.1 ml. The impact of possible risk factors on the enlargement of aneurysms was examined by analysis of variance (p < 0.05). A significantly higher rate of aneurysm expansion was found in patients with a larger aortic diameter (> 5 cm) at diagnosis (change in diameter = 0.17 cm versus 0.79 cm; change in volume = 40 ml versus 141.8 ml), and in smokers (change in diameter = 0.35 cm versus 0.70 cm; change in volume = 78.3 ml versus 120.8 ml). Changes in diameter and volume for aneurysms of different initial diameters and volumes was predicted by exponential regression by the equations: change in diameter = 0.0167 (initial aortic diameter)2.1; change in volume = 0.0356 (initial aortic volume)1.322. No correlation was noted between the rate of enlargement and age, sex, or the presence of dissection. A history of hypertension correlated with a greater aortic diameter at diagnosis but did not significantly affect the rate of enlargement.(ABSTRACT TRUNCATED AT 250 WORDS)

Color Doppler Ultrasound of Changes in Small Vessel Diameter and Cerebral Blood Flow during Acute Anemia in the Newborn Lamb

The relationship between changes in small vessel diameter as determined by arteriography and those estimated by color Doppler ultrasound were tested. These techniques were used to examine the effects of acute isovolemic anemia on cerebral blood flow and small vessel diameter in the newborn lamb. Validation of Doppler measurements was obtained in two lambs. Color Doppler diameter estimates of the anterior tibial artery (1-2 mm) were compared with simultaneous arteriographic measurements during vasodilatation and vasoconstriction effected by intra-arterial infusions of papaverine and norepinephrine, respectively. Acute anemia was produced in five newborn lambs by serial isovolemic exchange transfusions with adult sheep plasma. Doppler estimates of intracranial vessel diameter and mean blood flow velocity were correlated with simultaneous cerebral blood flow (CBF) determinations corrected for cerebral oxygen consumption (CBF/CMRO2). In the anterior tibial artery, color Doppler measurements of vessel diameter correlated well with arteriographic measurements (r2 = .77, P = .001), but overestimated the absolute vessel diameter by 10% to 27%. Hemodilution resulted in significant increases in CBF/CMRO2 (r2 = .61, P = .001), and estimated diameter of small cerebral arteries (r2 = .93, P = .001). Percent change in mean blood flow velocity correlated well with changes in CBF/CMRO2, but underestimated true changes in blood flow by approximately 40% (r2 = .93, P = .0001). Conversely, changes in Doppler volume flow overestimated true change in flow by approximately 50% (r2 = .84, P = .0001). Under certain physiological conditions, small cerebral arteries may make an important contribution to the overall regulation of CBF. Doppler estimates of relative flow and vessel diameter correlate well with true changes in CBF and small vessel diameter.

Assessment of vertebral canal diameter and bony malformations of the cervical part of the spine in horses with cervical stenotic myelopathy

Summary Magnification of cervical radiographs prevents accurate interpretation of vertebral canal absolute minimum sagittal diameter (msd) values and application of the established msd values for diagnosis of cervical stenotic myelopathy (csm). Variability in msd determination in human beings, owing to radiographic magnification, is minimized by assessing a ratio of the vertebral canal diameter to the sagittal width of the vertebral body. This relative measurement technique improves the accuracy of diagnosis of cervical spinal stenosis in human beings. The msd of the vertebral canal was determined in 50 horses with csm and 50 control horses, using a radiopaque marker method for correction of magnification. In addition, a ratio of the absolute msd to the sagittal width of the vertebral body and a ratio of the absolute msd to the length of the vertebral body were determined in 100 csm-affected and 100 control horses. Response operating characteristic curve analysis of each method determined that the sagittal ratio method of canal diameter assessment provided the most accurate interpretation of cervical radiographs for diagnosis of csm, with sensitivity and specificity of ≥ 89% at each vertebral site. The accuracy of the ratio method, without consideration of bony malformation, supports the importance, and perhaps prerequisite, of generalized vertebral canal stenosis in the pathogenesis of csm. Subjective evaluation of bony malformations from cervical radiographs of 100 csm-affected horses and 100 control horses indicated that csm-affected horses have more severe bony malformation than do control horses. However, moderate to marked degenerative joint disease of the articular processes was frequently observed in control horses. Subjective evaluation of bony malformation does not distinguish between csm-affected and unaffected horses.

Finite element modelling of rock‐socketed piles

AbstractRock socketed piles have a number of features which differentiate them from other types of piles. The generally stubby geometry leads to more even distribution of capacity between shaft and base. However, the low ratio of pile modulus to rock modulus leads to high compressibility and this, coupled with a tendency for the load transfer response along the shaft to exhibit strain‐softening, gives rise to an overall response where the shaft capacity may be fully mobilized, and potentially degraded, before significant mobilization of base load.The paper presents results of finite element analyses of the response of rock‐socketed piles, with particular attention to the shaft response with and without intimate base contact. The shaft interface uses a model, developed from principles of tribology, that includes dilation (and strain‐hardening) prior to peak shaft friction, followed by strain‐softening at larger displacements. The results of the study are shown to be consistent with field measurements, and to capture effects of the absolute pile diameter on the peak shaft friction. It is also shown that intimate base contact mitigates significantly the degree of strain‐softening of the shaft response.

Failure of epoprostenol (prostacyclin, PGI2) to inhibit platelet aggregation and to prevent restenosis after coronary angioplasty: results of a randomised placebo controlled trial.

To study the effect of epoprostenol (prostacyclin, PGI2) given before, during, and for 36 h after coronary angioplasty on restenosis at six months and to evaluate the transcardiac gradient of platelet aggregation before and after percutaneous transluminal coronary angioplasty (PTCA) in treated and placebo groups. Double blind placebo controlled randomised study. 135 patients with successful coronary angioplasty. Intravenous infusion of PGI2 (4 ng/kg/ml) or buffer was started before balloon angioplasty and continued for 36 hours. Platelet aggregation was measured in blood from the aorta and coronary sinus before and after PTCA in each group. Routine follow up was at six months with repeat angiography and there was quantitative assessment of all angiograms (those undertaken within the follow up period and at routine follow up). PRESENTATION OF RESULTS: Restenosis rates in treated and placebo groups determined according to the National Heart, Lung and Blood Institute definition IV. Comparison at follow up between the effect of treatment on mean absolute luminal diameter and mean absolute follow up diameter in the placebo group. Comparison of acute gain and late loss between groups. Of 125 patients available for assessment 23 were re-admitted because of angina within the follow up period. Quantitative angiography showed restenosis in 15 (10 in the PGI2 group and five in the placebo group). Of 105 patients evaluated at six month angiography there was restenosis in nine more in the PGI2 group and 18 more in the placebo group. Total restenosis rates (for patients) were 29.2% for PGI2 and 38.3% for placebo (NS). The mean absolute gain in luminal diameter was 1.84 (0.76) mm in the PGI2 group and 1.58 (0.56) mm in the placebo group (p = 0.04); the late loss in the PGI2 group was also greater (0.65 (0.94) mm vs 0.62 (0.89) mm (NS) and there was no significant difference in final luminal diameter at follow up between the two groups (1.83 (0.88) mm v 1.59 (0.60) mm). The transcardiac gradient of quantitative platelet aggregation increased after PTCA in both groups, indicating that PGI2 in this dose did not affect angioplasty-induced platelet activation. Mean (SD) platelet activation indices in the PGI2 group were pre PTCA aorta 8.4 (4.1) v coronary sinus 8.8 (4.0) (p = 0.001) and post PTCA aorta 8.9(3.0) v coronary sinus 12.9 (5.7) (p = 0.001). In the placebo group the values were pre PTCA aorta 7.6 (3.3) v coronary sinus 7.4 (3.6) (p = 0.001) and post PTCA aorta 7.6(2.8) v coronary sinus 11.2(4.3) (p = 0.001). The dose of PGI2 given was designed to limit side effects and as a short-term infusion did not significantly decrease the six month restenosis rate after PTCA. The sample size, which was determined by the original protocol and chosen because of the potency of the agent being tested, would have detected only a 50% reduction in restenosis rate. There was, however, no effect in the treated patients on the increased platelet aggregation seen in placebo group as a result of angioplasty. Angioplasty is a powerful stimulus to blood factor activation. Powerful agents that prevent local platelet adhesion and aggregation are likely to be required to reduce restenosis.

Intra- and interobserver variability of a fast on-line quantitative coronary angiographic system

To evaluate intra- and interobserver variability of an on-line quantitative coronary angiographic system, 2 independent observers measured 166 primary lesions excluding total occlusions before and after coronary angioplasty. Each observer repeated his measurement 3 times at 14 days interval. The average percent diameter stenosis results obtained by observer 1 and 2 were almost identical, before (62.2% +/- 12.0% and 62.6% +/- 11.4%, NS) and after (27.1% +/- 12.0% and 26.9% +/- 11.3%, NS) angioplasty. Variability was expressed as 95% limits of agreement (mean difference +/- 2 x SD). The intra-observer variability of observer 1 ranged from -6.6% to 6.6% before angioplasty and from -9.6% to 9.6% after angioplasty. The corresponding limits of observer 2 were -8.0% to 7.5% and -8.3% to 8.5%, respectively. The interobserver variability ranged from -10.4% to 9.6% before versus -12.5% to 13.1% after angioplasty. This variability was not influenced by vessel size. The widening of the limits observed after angioplasty was largely due to an increased variability in the measurements of the absolute minimal luminal diameter but not of the reference segment. We conclude that the intra- and interobserver variability of measurements obtained with an on-line quantitative angiographic system used for guiding coronary interventions is acceptable and without systematic bias in any direction for a wide range of primary coronary stenoses. However, the variability increases when images are acquired immediately after angioplasty.

Respiratory and laryngeal measures of children during vocal intensity variation

Simultaneous aerodynamic, acoustic, and kinematic measurements from the laryngeal and respiratory systems were made in order to study mechanisms for changing vocal intensity. Aerodynamic and acoustic measures include an approximation of open quotient, maximum flow declination rate, alternating glottal airflow, estimated tracheal pressure, sound pressure level, and fundamental frequency. Respiratory measures included lung volume, rib cage, and abdominal displacements. Adults were used as a comparison group to twenty 4-year-olds and twenty 8-year-olds. Laryngeal and respiratory results indicate that speech production differences between the children and adults are based both on size and function. For example, children's absolute anteroposterior diameters of the rib cage are smaller than adults, but their rib cage movement is larger and encompasses a different range during speech breathing. Since children are functionally different than adults, age specific speech production models need to be developed.