Quadratic Association Research Articles

Esophageal anastomotic failure: An experimental study

Background. Postsurgical complications in patients with esophageal atresia have remained unchanged during the last three decades. This study was aimed at investigating certain risk factors for small-sized esophageal anastomosis and to assess the probable relationship between esophageal length and body weight in rabbit. Methods. Six groups of 10 adult rabbits were subjected to section or 1-cm segmental resection of thoracic esophagus followed by end-to-end anastomosis. Approximation strength of esophageal ends was measured. Three different suture materials were used, and three different surgeons carried out procedures. Observed morbidity was recorded, as well as leakage or stenosis frequency in suture line. Esophageal length and body weight of nonresected rabbits were measured. Results. Fifteen leakages were observed in suture line; there were no differences in relative risk between groups with and without resection, or in ratio of this complication among surgeons; nonetheless, a greater number of leakages ( p<0.05) was observed at higher tension. There were no differences in magnitude of stenosis among surgeons, tension degree, or suture material used. Quadratic association was found between length of thoracic esophagus and body weight in nonresected rabbits. Conclusions. Rabbit esophagus is a suitable model to assess early surgical complications but not for late complications. Among three assessed factors, increased tension in patients with segmental deficit was the most significant factor in development of anastomotic leakage. Existence of nonlineal correlation between esophageal length and body weight in rabbit showed that resection of 1 cm of esophagus represented a different weight-dependent segmental deficit, which increased as weight decreased.

Should infants be screened for anaemia? A prospective study investigating the relation between haemoglobin at 8, 12, and 18 months and development at 18 months

AIMSTo investigate the relation between haemoglobin in children followed longitudinally from 8 to 18 months, and developmental outcome at 18 months.METHODSThe Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC) is...

The effect of accumulation period and harvest date in spring on dry‐matter yield and forage quality in mixed swards containing Lolium spp. and Trifolium subterraneum in Western Australia

The object of this study was to determine the effect of closing date and date of harvest for conservation (accumulation period), on dry‐matter (DM) yield and forage quality of annual pasture in Western Australia. The field study comprised 48 plots, 2 m × 2 m, sown with either annual ryegrass (Lolium rigidum Gaud.) or Italian ryegrass (L. multiflorum Lam.), and mixed with subterranean clover (Trifolium subterraneum L.). Defoliation of swards until the end of winter was at the three leaves tiller–1 stage. In spring, once stem nodal development had commenced, swards were defoliated every 3–4 weeks. Swards were defoliated either twice with three leaves tiller–1 (accumulation period 1 commenced on 15 August); twice with three leaves tiller–1 and then once after 4 weeks (accumulation period 2 commenced on 11 September); twice with three leaves tiller–1 and then twice after 4‐week intervals (accumulation period 3 commenced on 9 October) or; twice with 3 leaves tiller–1 and then twice after 4‐week intervals and then once after 3 weeks (accumulation period 4 commenced on 30 October). From the commencement of the accumulation period, tiller density, DM yield and forage quality were determined weekly for up to 10 weeks.There was a positive quadratic association between DM yield and days after the commencement of the accumulation period. Yields were maximized from accumulation period 1 with 5·3, 6·6 and 9·5 t DM ha–1, and growth rates were 140, 128 and 145 kg DM ha–1 d–1, for Wimmera annual ryegrass and Richmond and Concord cultivars of Italian ryegrass respectively. In contrast, in vitro dry‐matter digestibility (IVDMD) and crude protein (CP) content were negatively associated with days after the commencement of the accumulation period, and initial values were greater than 0·80 and 180 g kg DM–1 for IVDMD and CP content respectively. The rate of decline in IVDMD d–1 for Wimmera annual ryegrass was 0·005, 0·019 and 0·012 d–1 for accumulation periods 1, 2 and 3, respectively, while for Italian ryegrass cultivars Richmond was 0·015, 0·011, 0·02 and 0·012 d–1 and Concord was 0·014, 0·009, 0·013 and 0·01 d–1, for the 4 accumulation periods respectively.It is recommended that annual and Italian ryegrass pastures be harvested between 10% and 20% inflorescence emergence when IVDMD will exceed 0·70 regardless of cultivar and/or defoliation practice prior to the commencement of the accumulation period.

The correlation memory matrix for parameter estimation

Dynamic systems described by nonlinear differential or difference equations are abound in the literature. Until recently, estimation of system parameters has been mainly carried out using iterative (search) techniques such as conjugate gradient, steepest descent and evolutionary algorithms. These methods vary in terms of their noise immunity and robustness but they all tend to require a considerable number of iterations in order for the solution to converge, especially in the presence of noise. This is a disadvantage for systems requiring real-time control. In continuation of a series of papers utilizing linear associative memories (LAM) for parameter estimation, this paper proposes a non-iterative single-pass technique for estimating these parameters using the well-known correlation memory matrix (CMM), previously used in pattern recognition. The CMM method is used to estimate the parameters of the Lotka–Volterra predator–prey model and the Van der Pol oscillator. It is shown that this class of linear associators is superior to other types of LAM in that it provides equally good parameter estimates while requiring neither matrix inversion nor extensive training. As nonlinear (quadratic) associations are incorporated into the CMM, the method becomes more robust than the linear version.

Haemostatic and Lipid Determinants of Prothrombin Fragment F1.2 and D-dimer in Plasma

The determinants of plasma levels of prothrombin fragment F1.2 (F1.2) and D-dimer in different populations are unclear and this may complicate their interpretation as predictors of thrombotic risk, particularly in the case of D-dimer. We therefore measured F1.2 and D-dimer levels together with a number of other haemostatic and lipid variables in a cross-sectional community-based study of 150 healthy adults (73 male, 77 female), age range 23-80 years, identified from the list of a general practice by stratified random sampling within sex and decade of age. Plasma F1.2 was significantly higher in females than males and was independently and positively associated with age, factor VII activity (FVIIc) and C1 inhibitor, and inversely associated with high density lipoprotein (HDL) cholesterol. Plasma D-dimer showed a quadratic association with age (p <0.0001). In those < or =55 years D-dimer was inversely associated with dilute clot lysis time (DCLT) and activated protein C (APC) ratio. In those >55 years it was significantly higher in females than males and associated positively with age, fibrinogen and, in males, activated factor XII (FXIIa). In a multiple-linear model which combined both age groups, F1.2 and D-dimer were independently associated with each other (r = 0.22, p = 0.03). Thus, thrombin generation and fibrin turnover/fibrinolysis are associated in healthy subjects. HDL cholesterol (inversely) and FVIIc are associated with basal thrombin generation (i.e. F1.2). Determinants of D-dimer differ according to age and interpretation of the biological significance of D-dimer levels in epidemiological studies may therefore not be straightforward.

Mortality from non-Hodgkin lymphoma and UV exposure in the European Community

There has been a large, unexplained rise in the incidence of non-Hodgkin's lymphoma (NHL) in many countries. It has been hypothesised that increased exposure to solar ultraviolet (UV) radiation may have been a factor in this increase. The hypothesis that exposure to ultraviolet radiation is a factor in NHL can be tested by examining whether geographical variations in UV and in the incidence of the disease are positively correlated. Previous studies have given mixed results but some of these have failed to take into account confounding by socio-economic factors and the multilevel structure of data derived from several different countries. It was therefore decided to carry out a study using data on NHL mortality for the period 1971–80 for level II administrative units in 9 countries in the European Community. Estimated levels of solar UV and per capita GDP were also derived. Poisson regression models of the relationship between NHL mortality, UV and per capita GDP, taking into account the multilevel structure of the data, were fitted using the MLn package. Simple models that did not adjust for the effects of variations in per capita GDP or account adequately for the structure of the data produced apparent negative or quadratic associations between NHL and UV. However, further models show that there is a highly significant positive association between NHL and per capita GDP. Once this is included in the fixed and random parts of the multilevel model the association between NHL and UV becomes positive although non-significant ( p=0.081) at the conventional 0.05 level. These results underline the need to control for socio-economic factors and to take into account the multilevel structure of the data. Studies using international data that do not do this run the risk of producing misleading results.

Predictors of pain self-report in nursing home residents.

The purpose of this study was to examine the influence of cognitive function and other biopsychosocial factors on test-retest agreement, four-week variability, and intensity of self-reported pain using the verbal 0 to 10 scale and a pain thermometer in 115 nursing home residents over four weeks. Pain was assessed twice on three days during week 1, and once each during weeks 2, 3 and 4. A forward stepwise regression procedure was used to examine the influence of biopsychosocial parameters (age, race, gender, educational status, marital status, comorbidity, cognitive function, depression, social support, physical function and self-rated health) on pain intensity, test-retest agreement and variability. There was a quadratic association between cognitive function and test-retest agreement with the 0-10 scale; residents with Folstein scores of 22-26 were more likely to show disagreement (50% of 34) than residents with scores < 22 or > 26 (7% of 71). Higher Folstein scores were also associated with greater pain intensity for both pain scales (p < 0.001). Baseline pain intensity was significantly related to pain variability (0-10 scale only). The clinician should be cognizant of these relationships when interpreting verbalizations of pain in long-term care facilities.

Multi‐level modelling of geographically aggregated health data: a case study on malignant melanoma mortality and UV exposure in the European Community

A multi-level modelling approach is used to examine the variance in mortality rates from malignant melanoma at different geographical scales within nine European nations with reference to exposure to ultraviolet light (UVB). For males and females, the greatest variations in the relationship between UVB exposure and mortality are seen between nations, rather than regions and sub-regions within nations. This suggests that factors and characteristics acting at a national scale, such as genetic and behavioural differences, are of importance. Multi-level modelling is used to show how a previous suggestion of a quadratic association between UVB exposure and malignant melanoma across Europe is unlikely to be true. The general usefulness of multi-level modelling in the analysis of disease data which is structured in a hierarchy is discussed, with particular reference to geographical analyses of small area data. © 1998 John Wiley & Sons, Ltd.

Multi-level modelling of geographically aggregated health data: a case study on malignant melanoma mortality and UV exposure in the European Community.

A multi-level modelling approach is used to examine the variance in mortality rates from malignant melanoma at different geographical scales within nine European nations with reference to exposure to ultraviolet light (UVB). For males and females, the greatest variations in the relationship between UVB exposure and mortality are seen between nations, rather than regions and sub-regions within nations. This suggests that factors and characteristics acting at a national scale, such as genetic and behavioural differences, are of importance. Multi-level modelling is used to show how a previous suggestion of a quadratic association between UVB exposure and malignant melanoma across Europe is unlikely to be true. The general usefulness of multi-level modelling in the analysis of disease data which is structured in a hierarchy is discussed, with particular reference to geographical analyses of small area data.

QUANTITATIVE GENETICS OF OVARIOLE NUMBER IN DROSOPHILA MELANOGASTER. I. SEGREGATING VARIATION AND FITNESS.

The number of ovarioles of the Drosophila melanogaster ovary is a trait thought to be associated with female fecundity, and therefore is expected to be under strong natural selection. This hypothesis may be tested by examining patterns of genetic and environmental variation for ovariole number in natural populations, and by determining the association between ovariole number and fitness in isogenic lines derived from a natural population. We measured ovariole number, and competitive fitness and its components, for 48 homozygous chromosome 3 substitution lines in a standard inbred background; and body size in a sample of 15 chromosome 3 substitution lines. We found significant segregating genetic variation for ovariole number, with a broad-sense heritability (H2 ) of 0.403 and correspondingly high coefficients of genetic variation (CVC = 20.8) and residual variation (CVR = 25.3). Estimates of quantitative genetic parameters for body size (H2 = 0.191, CVG = 2.15, and CVR = 3.87) are similar to those previously reported for this trait. Although the isogenic chromosome 3 substitution lines varied significantly for components of fitness, there was no significant linear or quadratic association of ovariole number and body size with fitness. There was, however, highly significant sex × genotype interaction for fitness among these lines. This special case of genotype × environment interaction for fitness may contribute to the maintenance of genetic variation for fitness in natural populations.

From check‐off to direct debit? Trade union subscriptions in UK universities

Examines trade union subscriptions in relation to the 1993 Trade Union Reform and Employment Rights Act focusing on the Association of University Teachers, where the relationship is examined between subscription payments and hypothesized factors relating to staff, union and institutional characteristics. Finds significant indicators include staff grade, age, gender, the number of part‐time staff, a substitution effect in relation to check‐off together with a quadratic association for union density. Given this series of findings the continued dominance of check‐off as the favoured method of subscription payment, within the confines of this study, appears to be problematic.

The association between ionized calcium in blood and selected parameters in dairy cows with left displaced abomasum.

The objective of this study was to examine the association between blood calcium (Ca) and left displaced abomasum (LDA), and between Ca and selected anamnestic, blood and urine parameters in cows diagnosed with LDA. One hundred and forty-four cows diagnosed with LDA and 20 controls were used. The association between Ca and LDA was evaluated using linear regression. Possible associations between anamnestic, blood and urine parameters and blood calcium were assessed using a forward stepwise procedure in linear regression. Ca was not significantly associated with LDA. In control cows, Ca was explained by urea alone (R2 = 0.6); this was a negative association. In cows diagnosed with LDA, the final model of Ca included base excess (partial R2 = 0.31), urea (partial R2 = 0.11), phosphorus (partial R2 = 0.03) and potassium (partial R2 = 0.03). A negative linear association was found between base excess and Ca. A quadratic association was found between urea and Ca. We conclude that Ca is significantly associated with urea in dairy cows. Ca is not significantly associated with displaced abomasum in cows diagnosed with LDA. Blood base excess and urea explain Ca in cows diagnosed with LDA.

Anger expression and lipid concentrations

We used 2 different strategies to examine the relation between anger expression and lipid concentrations in 116 middle-aged men. Using the common analytic method used in the literature, the group crossing approach, we examined whether Anger-In. Anger-Out, and their interaction were related to lipids. Regression analyses revealed that Anger-In and Anger-Out were marginally related to total cholesterol. These associations disappeared after controlling for hostility, anger, and anxiety. Using a new intraindividual difference approach, we determined individuals' relative dominance of Anger-In and Anger-Out and examined linear and quadratic associations with lipids. Regression analyses revealed the quadratic was related to both total cholesterol and low-density lipoprotein-cholesterol (LDL-c), indicating that individuals who almost always express their anger or almost never express their anger had both elevated total cholesterol and LDL-c. The curvilinear association with total cholesterol persisted even after controlling for hostility, anger, and anxiety.

Effects of Aerosolized Amiloride on Mucociliary Transport Velocity and Transepithelial Potential Difference in Isolated Frog Palate

An in vitro dose-response study was performed to determine the effects of aerosolized amiloride on transepithelial potential difference and mucociliary velocity. A preparation of isolated frog palate (Rana sculenta) was used for two groups: one submitted to amiloride nebulization (n = 7) and a control group submitted to vehicle (NaCl 0.45%) nebulization (n = 7). Transepithelial potential difference was measured by means of agar-filled microelectrodes connected to the high input of a grounded electrometer. Mucociliary velocity was determined by monitoring the movement of aluminum disks as tracer particles. Amiloride nebulization caused a significant dose-dependent increase in mucociliary velocity when compared to the control group (p < 0.05). The amiloride also turned the luminal surface more positive, promoting a decrease (in absolute value) in transepithelial potential difference when compared to the control group (p < 0.05). A positive and continuous (quadratic) association between mucociliary velocity and transepithelial potential difference was verified in the group treated with amiloride (p = 0.019). The results presented are in agreement with a decrease in mucus rigidity due to increased hydration of the mucous gel, induced by the blockade of sodium channels by the drug. In the range of concentrations used in this study (10−7 to 10−3 M amiloride in NaCl 0.45% solution) there was no evidence of uncoupling between the mucous gel and the tips of the cilia. The model should prove to be valuable for studying agents which can act as modulators of transepithelial ionic conductance.

Associations between sea temperature, catch per unit of fishing effort, and yield in the Bermuda spiny lobster fishery, 1975-1989

Results of graphical analyses of annual records of catch, effort and sea temperature indicate empirical quadratic associations between industry catch per unit of fishing effort (CPUE) in Bermudan spiny lobster (Panulirus argus and P. guttatus) fisheries and the annual average sea temperature at Hamilton Harbour, Bermuda. CPUE and yield of P. argus and of P. guttatus were each associated by quadratic expressions with the annual average sea temperature of the Bermuda Platform. Annual growth and survival of late juvenile P. argus and P. guttatus into the fishable stock at Bermuda is controlled in a quadratic fashion chiefly by sea temperature with a six-month lag. The optimum annual average sea temperature for the survival and growth of late benthic juvenile P. argus into the fishery stock was 23.6 � 0.2�C (mean � s.e.), and the comparable optimum for P. guttatus juvenile recruitment was 24.1 � 0.1�C. The maximum equilibrium catch of P. guttatus lobsters on Bermuda Platform was estimated at approximately 33 000 lobsters from quadratic regression of yield on fishing effort.

Effects of data structure on variance of prediction error and accuracy of genetic evaluation.

Several features of data structure were studied to determine their effects on variance of prediction error and accuracy of evaluation. Assigning 50 sires with progeny to a portion of 10, 25, or 50 contemporary groups according to a sire model with and without additive genetic relationships, or assigning 50 individuals with their own record to one of 2, 5, or 10 contemporary groups according to an animal model, established the designs. Additive genetic relationships were based on stimulated pedigree files. Low, medium, and high heritabilities (.10, .25, and .40, respectively) were considered. The inverse of coefficient matrices gave variances of prediction error. Populations derived from the sire model (n = 8,100) consisted solely of progeny-tested individuals. For them, number of progeny had a quadratic (P < .001) association with variance of prediction error (R2 = 56 to 82%), which selection index theory underestimated when there were < 100 progeny. Number of direct connections (sires of contemporaries of progeny) together with progeny numbers explained variance of prediction error (R2 = 76 to 90%) better than either variable alone. With no direct connections, variance of prediction error was maximum unless a relative with at least one direct connection itself existed. Populations derived from the animal model (n = 900) consisted of animals with designs representing a progeny test, performance test, or a combination of both (34, 41, and 25% of the total, respectively). For performance-tested animals (without progeny), number of genetic connections was not highly correlated with variance of prediction error (r = -.10, across h2), but relatives prevented zero accuracies when contemporary groups consisted of one animal. Even when animals had no relatives, more than five members per contemporary group gave little additional increase in accuracy. For other than a progeny test, designs were complex, being described by many variables that were confounded.

Granulocyte and Granulocyte-Macrophage Colony-Stimulating Factors in Cord and Maternal Serum at Delivery

Impaired neutrophil responses contribute to the neonate's increased susceptibility to infection. Because granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) enhance granulocyte and macrophage number and function, their use in the management of neonatal sepsis may be beneficial. Little is known about the endogenous levels of G-CSF and GM-CSF. In adults, raised values for G-CSF, but not GM-CSF, have been demonstrated in patients with infection, and conflicting data has emerged regarding CSF levels in neonates. We have used an ELISA to measure maternal and cord serum G-CSF and GM-CSF at the time of delivery, with gestational age between 25 and 42 wk. In mothers, an inverse linear relationship between gestational age and GM-CSF levels (p = 0.049) was found, but no association with G-CSF levels was observed. In neonates, a quadratic association was found between GM-CSF levels and gestational age (p = 0.019), whereas G-CSF levels showed an inverse linear association (p = 0.015). In addition, an association was found between maternal and cord GM-CSF (p = 0.007) but not G-CSF levels in paired samples. The effect of gestational age on the cytokine levels could not be explained by the white cell count, the absolute neutrophil count, pregnancy-induced hypertension, or the presence of infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Toward a contingency approach to marital interaction: An empirical integration of three approaches

Dindia and Fitzpatrick (1985) identified three main approaches to the study of marital communication: the satisfaction approach, the pragmatic approach, and the typological approach. This study reports an empirical integration of the key variables of each approach: Fitzpatrick's couple types, relational control, and marital satisfaction. It is hypothesized that (a) control behaviors and patterns have nonlinear associations with marital satisfaction and (b) different behaviors and patterns are satisfying to different types of couples. Marital couples discussed eight potential problem areas and their coded behaviors were submitted to interaction analysis using Morley's (1984) procedure. The results suggest that: (a) → behaviors had a positive association with marital satisfaction, and ↓↑ and →↓ interacts had significant convex quadratic associations with satisfaction, (b) ↓ control behaviors and ↑↓, ↓→, and ↑→ patterns interacted with couple type in predicting marital satisfaction. These results suggest a c...

Obesity and mortality in the lipid research clinics program follow-up study

Using data from the Lipid Research Clinics Program for 1972–1983, the study presented here examined weight history and two indices of obesity: the body mass index (BMI) and the triceps skinfold (TSF) thickness. Cox regression analyses with and without adjustment for cardiovascular disease risk factors revealed a significant ( p < 0.05) quadratic association between BMI and all-causes mortality among men, but not women, after an average 8.4 years of follow-up; mortality was relatively high at both extremes of the BMI distribution. The association was stronger among smokers compared with nonsmokers, and it was apparent among male normotensives, but not hypertensives. All TSF-mortality associations and BMI associations with cancer and coronary heart disease mortality were weak and nonsignificant. Among men, per cent weight change in adulthood showed a significant inverse association with all-causes and cancer mortality. Because BMI and weight history were significantly associated with mortality after adjustment for other risk factors, they appear to be independent predictors of mortality among men.