Higher Intercept Research Articles

Plant Geometry and Self-Thinning

SUMMARY (1) Monocultures of Agrostemma githago, Cichorium endivium and Festuca pratensis were grown at high densities to investigate the effects of plant geometry on self-thinning. Whilst populations of all three species followed the -3/2 power law when weight was plotted against density on logarithmic scales the intercepts were different and fell in the order Festuca > Agrostemma > Cichorium. These differences are related to plant geometry. (2) Published reports show that coniferous trees generally have higher intercepts than deciduous trees and that grasses have higher intercepts than dicotyledons. (3) The mean volume of canopy available to each plant was also found to be related to density by the -3/2 power law. However, the intercepts for a number of species on a volume-density plot on logarithmic scales all fell within one order of magnitude in comparison with two orders of magnitude on a weight-density plot. (4) The biomass which could be packed into a given volume of space generally increased with canopy height, but the range was nevertheless relatively narrow (1 .5-5.2 kg m-3) for the three species. Only part of the variation in intercept between species on a weight-density plot could be related to differences in biomass packing. (5) Variation in the biomass per unit volume through time means that the gradient of the thinning line on a weight-density plot may be different to that on a volume plot. It is suggested that the -3/2 power law might be better stated in terms of canopy volume rather than weight.

The array size function in simple visual search tasks: a comparison between "go-no go" and "yes-no" tasks under conditions of high and low target-noise similarity.

In research on visual search within a single eye-fixation a number of different tasks are used and referred to interchangeably. Research with other types of tasks suggests that there are possibly important differences between these tasks. In the present study, two types of search tasks were compared under conditions as equal as possible: the ‘go-no go’ task and the ‘yes-no’ task. Conditions of low and high target-noise similarity were used. The results obtained showed: a) a steeper slope of the array size function in ‘yes-no’ tasks than in ‘go-no go’ tasks on the first day of practice but not on the second: b) a higher intercept value of the same function for ‘yes-no’ tasks than for ‘go-no go’ tasks; and c) a greater proportion of errors with ‘yes-no’ tasks than with comparable ‘go-no go’ tasks. A tentative model, describing the main features of the results obtained, is briefly sketched.

The response of mouse mammary tumor to microwave heating at 2.45 GHz

We have conducted experiments quantitating the effects of microwave heating on the regrowth time of mammary tumors implanted on the flank of C3H mice. To minimize the size and shape dependence of the microwave heating, we immersed the tumors in tissue equivalent bolus and treated them with parallel opposed transverse electromagnetic applicators. The animals were not anesthetized during microwave irradiation. Two types of bolus were used: a semisolid gel and a temperature‐controlled solution of isotonic saline and alcohol. During tumor irradiation in the gel, temperatures were monitored adjacent to, but not inside of, the tumors. During irradiation in the liquid bolus, tumor temperatures were monitored for one out of each six animals per data point. Data from tumors treated in the semisolid bolus yielded lower regrowth slopes and higher intercepts than those heated by water baths. Both findings can be interpreted as indicating thermal nonuniformity of the microwave‐heated tumors. Plots of thermal sensitivity versus temperature are parallel to, but displaced from, those determined with water bath heating, suggesting that at least some small part of the tumor treated with microwaves was about 1°C lower than the target temperature. Tumors which were heated in the liquid bolus yielded regrowth curves consistent with homogeneous heating. A plot of thermal sensitivity versus temperature suggests that all parts of the tumors were at or slightly above target temperature. Regrowth time of the probed tumors was significantly greater than that of tumors in which no probe was present during microwave irradiation.

The relationship between left ventricular functional response to isometric exercise and asynergic contraction and diastolic stiffness.

Either augmentation or impairment of left ventricular function has previously been reported in different patients, in response to isometric exercise. To identify the mechanisms associated with these disparate responses, the effects of submaximal sustained handgrip upon left ventricular systolic and diastolic properties were studied in 29 patients during diagnostic catheterization. In 16 patients (group I), ejection fraction, mean Vcf, and the mean systolic ejection rate remained constant, while the ratio of peak systolic pressure to end systolic volume increased significantly from 2.81 +/- 0.6 to 3.17 +/- 0.6 ml/mm Hg. In 13 patients (group II) ejection fraction declined from 0.6 +/- 0.03 to 0.51 +/- 0.03, Vcf from 0.96 +/- 0.09 to 0.85 +/- 0.09 circ/sec, mean normalized systolic ejection rate from 1.79 +/- 0.1 to 1.50 +/- 0.09 sec-1, and the peak systolic pressure to end systolic volume ratio from 2.23 +/- 0.3 to 1.99 +/- 0.3 (p less than 0.05 for each). Systemic arterial mean pressure increased similarly by 19% and 21% in groups I and II, respectively (p less than 0.05 for each). Systemic vascular resistance increased significantly by 23% in group I and by 5% in group II (p less than 0.05). Left ventricular end diastolic volume declined from 85.4 +/- 7 to 77.3 +/- 11 ml/m2 in group I, while end diastolic and end systolic volumes increased by 13% and 35%, respectively in group II (p less than 0.05 for each). In both groups, baseline exponential pressure-volume relations were similar, though higher intercepts on the pressure-volume relations upon the Y-axis suggested greater "diastolic tone," and steeper volume-normalized pressure-volume elasticity relations indicated "stiffer" left ventricular chambers in group II patients. While the incidence of coronary artery disease was similar, both the severity and extent of left ventricular asynergy were greater in group II patients. We conclude that dilatation and deterioration of left ventricular ejection function in response to isometric exercise are causally related to, and comprise a useful predictor of, severe underlying left ventricular asynergy and impaired chamber distensibility.

543 EFFECT OF RACE AND OTHER VARIABLES ON TRANSCUTANEOUS BILIRUBINOMETRY

A non-invasive device for measuring cutaneous bilirubin has been evaluated on newborn infants to assess the effect of race, serum albumin level, site of measurement, breast feeding, and phototherapy. More than 560 comparisons between the Minolta transcutaneous bilirubinmeter (Pediatrics 65:195) and conventional serum bilirubin determinations (A.O. Bilirubinometer) confirmed Yamanouchi and Lucey's report (Ped. Res. 14:604) of a correlation coefficient near 0.9, P <.001. Phototherapy produced a pronounced decrement in the correlation, apparently by reducing cutaneous bilirubin levels and increasing melanin pigmentation. Both of these effects of phototherapy were circumvented by placing an opaque patch on a skin site between measurements. Formula-fed black (n = 32), Oriental (n = 24), and white (n = 47) babies all had similar slopes (1.0), but the background signal was progressively higher for the darker races and phototherapy augmented this rise in the intercept. Native Americans (n = 24) had a lower slope (0.55) but a higher intercept than the other races. Surprisingly, the correlation coefficient for each of the other three racial groups was higher for bottle-fed (n = 103) than for breast-fed (n = 137) infants. As predicted, the ratio of skin to serum bilirubin level was inversely related to the serum albumin concentration for formula-fed infants (P <0.05) which raises the question of whether skin or serum measurements provide a better index of critical CNS levels.

Crude Protein, IVOMD, and Yield of Stockpiled Limpograsses1

AbstractMost tropical grasses show a marked decline in digestibility with age, thus a system of field stockpiling is not suitable. The purpose of this research was to investigate the use of three limpograss (Hemarthria altissima [Poir] Stapf. et C. E. Hubb) cultivars as autumn‐winter conserved forage. In 1976, plots of each cultivar were clipped and allowed to regrow from 1 July, 29 July, and 26 August. Six yield and quality harvests were taken at 6 week intervals beginning on 23 Sept. 1976. In 1977 all plots were clipped and allowed to regrow from 1 August with five harvest for yield and quality taken at 4‐week intervals beginning on 26 Sept. 1977. The yield results from 1976 suggest that stockpiling should begin by 1 August to allow for adequate dry matter accumulation by first freeze. ‘Redalta’ had higher yields than either ‘Greenalta’ or ‘Bigalta’ in both years, but dry matter accumulation patterns were similar for all grasses. In vitro organic matter digestion (IVOMD) of Bigalta was higher than Redalta or Greenalta at all sampling dates in both years. Regression analysis indicated a higher intercept and lower rate of decline in IVOMD of Bigalta than either Redalta or Greenalta.Log transformation of crude protein (CP) increased (P &gt; 0.05) the fit over the linear model for all grasses. The decay in CP occurred rapidly in all grasses and by the time the grasses would be consumed as a stockpiled forage it had dropped below the level necessary to maintain zero N balance in the grazing animal. No meaningful differences in CP among grasses were observed. Our results suggest that Bigalta Limpograss has potential fot autumn‐winter stockpiling, but Redalta and Greenalta are probably not acceptable.

Transcutaneous Oxygen Measurement in Adult Intensive Care

Transcutaneous oxygen measurement (PtcO2-measurement) gives by a non-invasive technique continuous information about central PO2. The method has as yet been tested mainly on newborns, and systematic studies of the applicability of the method on adults are still few. The current systematic study reports on consecutive PtcO2 measurements in 15 patients, all with indwelling arterial catheters: 13 of the patients were artificially ventilated; 5 patients had normal body structure and normal skin circulation; 5 patients were obese and had normal skin circulation; and 5 patients were hypothermic with a normal heart frequency or slight bradycardia. The Radiometer equipment TCM1 was used. The electrode surface tempertaure was 45.0 degrees C (within +/- 0.2 degrees C). The oxygen concentration in the inspired air was altered several times for all patients, and arterial samples were drawn at a stable PtcO2 level. On average, seven samples were drawn from each patient. The correlation between PtcO2 and PaO2 was highly significant in 4/5 patients, in both the "obese patient" group and the "normal patient" group. In the "hypothermic patient" group, the correlation between PtcO2 and PaO2 was highly statistically significant in 2/5 patients. The regression line between PtcO2 and PaO2 was calculated for each patient, and a mean regression line was obtained for each group. It was found that the regression line in the "obese patient" group was displaced to the right and parallel to the regression line in the "normal patient" group, while the regression line in the "hypothermic patient" group was less sloping and showed a higher intercept. The PtcO2 monitoring technique reliably reflects changes in the central oxygenation of adult intensive care patients. In some patients with decreased skin circulation, the relationship between PtcO2 and PaO2 seemed to be constant for the same patient, yielding statistically sifnificant correlations. However, the study cannot determine whether this would be true in all clinical situations; the relationship betwee PtcO2 and PaO2 should therefore be checked frequently when measruements are performed in patients with decreased skin circulation. The author's experience with the PtcO2 monitoring method in patients near death has been consistent with the obvious fact that the reliability of the method decreases with decreased skin circulation.

The effect of insulin on bile-salt-independent canalicular secretion.

Mongrel dogs were prepared by cholecystectomy, ligation of the lesser pancreatic duct, and insertion of gastric and duodenal cannulas. The common bile duct was cannulated through the duodenal fistula. After stabilization of bile flow by intravenous infusion of sodium taurocholate, the dogs received an intravenous injection of insulin or 0.9% NaCl (control). This procedure was repeated with varying concentrations of sodium taurocholate to obtain taurocholate dose-response tests with and without insulin. Insulin caused marked increases in bile flow and the biliary clearance of erythritol, with no increase in bile-salt output The regression of bile-salt output on erythritol clearance was calculated for experiments with and without insulin. The resulting lines were compared by covariate analysis, which revealed a significantly higher intercept during insulin choleresis. This observation demonstrated that insulin stimulated the bile-salt-independent fraction of canalicular bile formation.

Pelage Color Polymorphism in Peromyscus polionotus

In addition to the normal dark brown old-field mice, a pale brown phenotype occurs on the Savannah River Plant in South Carolina. A linear model can be used to describe the reflectance spectrum of the dorsal pelage of the two color variants. The reflectance spectrum of pale brown adults had a higher intercept and slope than the darker adults. The paler mice occurred in high frequency only on the lighter, Lakeland Sand soils. Pleiotrophic effects of the autosomal pale brown gene were noted in reproductive performance in the laboratory, trappable life span, and number of captures per unit time, but not in the growth rate of the two variants. Under field conditions, presence or absence of supplementary food also modifies the expression of the phenotype. The complex interaction of genetic and environmental factors and inadequate knowledge about the environment of the two phenotypes makes their distribution difficult to interpret. It is apparent, however, that the simple hypothesis of predators selecting mice that contrast with their background is not sufficient to explain all of the data.