Spearman's Partial Rank Correlation Research Articles

Herb layer response to broadleaf tree species with different leaf litter quality and canopy structure in temperate forests

AbstractQuestion: How do broadleaf tree species affect humus characteristics, herb layer composition and species diversity through their leaf litter quality and canopy structure?Location: Mixed broadleaf forests in Brandenburg, NE Germany.Methods: We studied the herb and tree layer composition in 129 undisturbed stands using a 10‐degree cover‐abundance and percentage scale, respectively. The main floristic gradients were extracted by non‐metric multidimensional scaling. Effects of tree species on the herb layer were analysed with partial Spearman rank correlation. We assessed affinities for specific tree species using indicator species analysis.Results: Both beech and oak influenced herb layer composition mainly through their litter quality, which resulted in deep Ol and Of horizons, respectively. The less dense canopy of oak, in contrast to the dense beech canopy, enhanced species diversity in favour of indifferent herb species (species not closely tied to forests). Lime was correlated with a distinct floristic gradient, but a direct effect on the herb layer cannot be proven with the available data. Effects of hornbeam were less pronounced.Conclusions: The relationship between the tree and herb layer must be partly attributed to pH differences. However, tree species effects on humus characteristics and on light flux to the ground were largely responsible as well. The results suggest that tree species can influence herb layer composition and diversity, but the missing correlation with lime and hornbeam raise questions requiring further detailed investigation.

Age-associated leukoaraiosis and cortical cholinergic deafferentation

To investigate the relationship between age-associated MRI leukoaraiosis or white matter hyperintensities (WMH) and cortical acetylcholinesterase (AChE) activity. One possible mechanism of cognitive decline in elderly individuals with leukoaraiosis is disruption of cholinergic fibers by strategically located white matter lesions. Periventricular lesions may have a higher chance of disrupting cholinergic projections compared with more superficial nonperiventricular white matter lesions because of anatomic proximity to the major cholinergic axonal projection bundles that originate from the basal forebrain. Community-dwelling, middle-aged and elderly subjects without dementia (mean age 71.0 +/- 9.2 years; 55-84 years; n = 18) underwent brain MRI and AChE PET imaging. The severity of periventricular and nonperiventricular WMH on fluid-attenuated inversion recovery MRI images was scored using the semiquantitative rating scale of Scheltens et al. [11C]methyl-4-piperidinyl propionate AChE PET imaging was used to assess cortical AChE activity. Age-corrected Spearman partial rank correlation coefficients were calculated. The severity of periventricular (R = -0.52, p = 0.04) but not nonperiventricular (R = -0.20, not significant) WMH was inversely related to global cortical AChE activity. Regional cortical cholinergic effects of periventricular WMH were most significant for the occipital lobe (R = -0.58, p = 0.02). The presence of periventricular but not nonperiventricular white matter hyperintensities (WMH) is significantly associated with lower cortical cholinergic activity. These findings support a regionally specific disruption of cholinergic projection fibers by WMH.

Markers of Inflammation and Hemodynamic Measurements in Obesity: Copenhagen City Heart Study

Low-grade chronic inflammation has been proposed to play a major role in the pathogenesis of hypertension. Low-grade chronic inflammation is also closely associated with obesity, an established causative factor in the development of hypertension. The purpose of this study was to investigate the relationship between two markers of inflammation, C-reactive protein (CRP) and fibrinogen, and blood pressure (BP) and other hemodynamic variables in obese subjects. From a large cardiovascular study based in the general population, we selected subjects with a body mass index (BMI) > or =30 kg/m2, free of major cardiovascular diseases, not taking BP-lowering or lipid-lowering drugs (n = 487; women = 51.1%; median (5th to 95th percentile) age = 62 years (36-80)). The cardiovascular study included measurements of traditional and new risk factors, including ankle brachial BP index, a measure of subclinical atherosclerosis. CRP was determined by a high-sensitive assay. In partial Spearman rank correlation analysis, adjusted for age and sex, we found no significant relationships between either CRP or fibrinogen and systolic BP, diastolic BP, pulse pressure, or ankle brachial index (rho: -0.057 to 0.068; P > 0.13). However, fibrinogen and CRP were found to be significantly related to heart rate (rho: 0.127-0.169; P < 0.01). In this study of generally healthy obese subjects from the general population, we found no significant relationships between markers of inflammation and systolic BP or diastolic BP, showing that obese subjects with higher levels of inflammatory markers do not have higher BP levels than their obese counterparts with lower levels of inflammatory markers.

Path analysis using data derived from genetically randomized inbred mouse strains reveals biological controls affecting bone growth and adult fragility

bone development in children. However, quantifying this relationship in observational studies is often hindered by the measurement error inherent in the commonly used PA measurement method of subjective self-report. In this crosssectional analysis, using an objective and a subjective measure of PA, we examined associations between PA and bone mineral content (BMC) in 449 children (mean age 11.2 years, range 10.5 to 12.4 years). Design: PA was measured using 5-day accelerometry readings (Actigraph 7164) and the Physical Activity Questionnaire for Children (PAQ-C) (from the Saskatchewan Pediatric Bone Mineral Accrual Study). Total body and lumbar spine bone mineral content (BMC) were measured using a Hologic 4500 dual energy X-ray absorptiometry (DXA). Body mass (kg), height (cm), and biological age (pre-or post-peak height velocity) were considered as co-variates in partial correlation analyses and multiple linear regression models. Significance was set at (pb0.05). Results: Accelerometry-determined moderate to vigorous (MVPA) and PAQ-C scores were higher in boys when compared to girls. The Spearman rank correlation coefficient between MVPA and PAQ-Cwas 0.38 for boys and 0.25 for girls (pb0.05). MVPA was significantly associated with total body BMC (r=0.33) and spine BMC (r=0.19) in boys (partial Spearman rank correlation coefficients controlling for weight, height, and maturity). When PAQ-C was substituted for MVPA, the partial correlations were 0.22 for total body BMC and 0.19 for spine BMC. These associations were also statistically significant. When MVPA and PAQ-C were considered together in multiple linear regression models for total body BMC and spine BMC, both entered, although MVPA explained slightly more of the variability in each model. In girls, MVPA was significantly associated with total body BMC (r=0.17, partial Spearman rank correlation coefficients controlling for weight, height, and maturity). MVPA was not associated with spine BMC. PAQ-C was not significantly associated with spine nor total body BMC. Conclusions: Findings indicate that statistically significant and, perhaps important, associations between PA and BMC during late childhood are more likely to be detected with an objective PA measurement method. Self-report PA may be a more sensitive measure of PA for boys than for girls.

Seasonal variation in consumption and plasma concentrations of fatty acids in Japanese female dietitians.

To study seasonal variation in intake and plasma concentrations of fatty acids (FAs) in Japanese female dietitians. We assessed consumption of FAs based on four season 7 consecutive day weighed diet records from 71 Japanese female dietitians in 1996-1997. Using overnight fasting venous blood, plasma concentrations of FAs were analyzed by gas chromatography. Seasonal variation in consumption and plasma concentrations was examined by ANOVA for repeated values, followed by Tukey's multiple t-test. We calculated Spearman's partial rank correlation coefficients (CCs) between intake and plasma concentrations of FAs. Furthermore, we computed inter-seasonal Spearman's partial rank CCs for consumption and plasma concentrations of FAs. Statistically significant seasonal differences were observed in consumption for most FAs, except for myristic acid, monounsaturated FAs, oleic acid, n-6 polyunsaturated FAs (PUFAs), linoleic acid, gamma-linolenic acid, alpha-linolenic acid, PUFAs/saturated FAs, and n-6 PUFAs/n-3 PUFAs, and for most plasma concentrations, except for stearic acid, gamma-linolenic acid, n-3 PUFAs, alpha-linolenic acid, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and n-3 highly unsaturated FAs (HUFAs). However, statistically significant Spearman's partial rank CCs between intake and plasma concentrations were observed for EPA, DHA, n-3 HUFAs, n-6 PUFAs/n-3 PUFAs and n-6 PUFAs/n-3 HUFAs for almost all seasons. Seasonal variation exists in consumption and plasma concentrations of FAs, so that this should be taken into account in epidemiological analyses, including case-control and cohort studies.

Serum Levels of Soluble Transferrin Receptor Correlate with Severity of Disease but Not with Iron Stores in Patients with Malignant Lymphomas

Soluble transferrin receptor levels in serum (s-sTfR) may be useful in differentiating between iron deficiency anemia and anemia of chronic disease. However, there is both theoretical and clinical evidence for elevated s-sTfR levels in patients with various hematological malignancies. In the present study, routine bone marrow aspirations were performed in 82 patients with malignant lymphomas (63 with non-Hodgkin’s lymphoma and 19 with Hodgkin’s disease). Smears were stained for evaluation of iron stores and graded. Patients were also given a disease score based on bone marrow morphology, erythrocyte sedimentation rate and LDH. s-sTfR levels correlated better with disease score [partial Spearman rank correlation coefficient (r_s) controlled for iron stores was 0.51 (95% confidence interval 0.39–0.65); p < 0.001] than with iron stores [partial r_s controlled for disease score was –0.25 (95% confidence interval –0.44 to –0.03); p = 0.027]. This study showed elevated s-sTfR levels in patients with malignant lymphomas without any signs of iron deficiency anemia. The diagnosis of iron deficiency anemia should not be established upon the basis of s-sTfR alone in this group of patients.

Trend analysis methodology for water quality time series

AbstractA general trend analysis methodology is developed for detecting and modelling trends in water quality time series measured in rivers and streams. The procedure is specifically designed for use with typically ill‐behaved river quality series characterized by problematic features such as non‐normal positively skewed populations, irregularly spaced instantaneous observations, seasonal periodicities, and dependence among water quality variables and riverflows. In order to analyze these “messy” environmental data in a systematic and rigorous fashion, the overall trend analysis approach is divided into the two main categories of graphical studies and trend tests. Within these two main steps, specific graphical, parametric and nonparametric statistical techniques are utilized. Graphical methods used in the procedure include time series plots, robust regression smooths, as well as box and whisker graphs. Nonparametric techniques include the Mann‐Kendall and Kruskal‐Wallis tests. Additionally, a test based on Spearman's partial rank correlation is introduced as a means for eliminating seasonal effects when testing for the presence of a trend. The efficacy of the trend analysis methodology is explained and demonstrated by applying it to water quality time series observed in the Saugeen and Grand Rivers of Southwestern Ontario, Canada.

An X-ray survey of a complete sample of 3CR radio galaxies

view Abstract Citations (201) References (100) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An X-ray survey of a complete sample of 3CR radio galaxies. Fabbiano, G. ; Miller, L. ; Trinchieri, G. ; Longair, M. ; Elvis, M. Abstract The X-ray survey of the galaxies, 40 in all, was made with the Einstein Observatory. By comparing the distributions of X-ray luminosities, it is found that 3CR galaxies with double radio morphology (FR 2) and optical emission-line spectra tend to be the more powerful X-ray emitters, with broad-line galaxies at the top of the distribution. It is also found that the X-ray luminosity is strongly correlated with the 5 GHz radio nuclear luminosity. Through an analysis of the complete optical and radio sample with the Spearman partial rank correlation technique, it is determined that nuclear radio luminosity at 5 GHz is correlated with both total radio luminosity at 178 MHz and with galaxy optical luminosity. Other weaker correlations are found of the X-ray luminosity with the total radio luminosity at 178 MHz and the optical luminosity of the galaxy. The results are seen as underlining the importance of nuclear phenomena in radio galaxies and indicating a nuclear origin of their X-ray emission. In addition, it is found that the 3CR emission-line galaxies are similar to both Seyfert galaxies and quasars with double radio morphology in their X-ray properties, strongly reinforcing a unified picture of active nuclei. Publication: The Astrophysical Journal Pub Date: February 1984 DOI: 10.1086/161676 Bibcode: 1984ApJ...277..115F Keywords: Galactic Nuclei; Luminosity; Radio Galaxies; X Ray Sources; Elliptical Galaxies; Galactic Radiation; Galactic Structure; Heao 2; Optical Emission Spectroscopy; Quasars; Seyfert Galaxies; Astrophysics full text sources ADS | data products SIMBAD (48) NED (42) Related Materials (1) Erratum: 1984ApJ...283..469F

Statistical investigations of the physical properties of radio sources

Six complete samples of radio sources have been analysed by the Spearman rank and the Spearman partial-rank correlation coefficients. The relations between the radio luminosities and linear sizes as well as between linear sizes and redshift indicate that the observed angular diameter-redshift diagram may be explained by the changes of linear sizes with radio luminosity of radio sources.

An investigation of the properties of double radio sources using the Spearman partial rank correlation coefficient

The methods available for analysing correlations between two variables in the presence of a third are reviewed, and it is concluded that the Spearman partial rank correlation coefficient makes the most efficient use of the available data. This is therefore used to study the correlations of the properties of double radio sources with size and redshift z, and with z and luminosity P. Results for a sample of 3CR sources show that larger sources are more diffuse, but their spectral indices are not steeper. If all sources have similar expansion speeds, these results provide information about how sources evolve, since then larger sources are older ones. Spectral index is fundamentally related to z, and only part of this correlation arises because spectra are curved. The values of ‘compactness’ (the fraction of the emission, excluding any nuclear component, from double radio sources which originates from their hot spots) measured by Jenkins & McEllin are fundamentally related to P, but this result requires confirmation because some of their values may be in error. Results for a sample of 3CR and 4C quasars rule out (at the 2σ level) cosmological evolution of physical size which is stronger than |${(1+z)}^{-1.3}$|⁠. The possibility of determining the density parameter Ω of the Universe from the relation between z, P and physical size is considered, and the extension of the Spearman partial rank correlation coefficient to correlations involving more than three parameters is discussed.

A computer program for testing average partial association in three-way contingency tables (PARCAT)

PARCAT is a computer program which implements alternative tests for average partial association in three-way contingency tables within the framework of the product multiple hypergeometric probability model. Primary attention is directed at the relationship between two of the variables, controlling for the effects of a covariable. This approach is essentially a multivariate extension of the Cochran/Mantel-Haenszel test to sets of ( s × r) tables. A set of scores such as uniform, ridits, or probits can be assigned to categories which are ordinally scaled. In particular, if ridit scores with midranks assigned for ties are utilized, this procedure is equivalent to a partial Kruskal-Wallis test when one variable is ordinally scaled, and is equivalent to a partial Spearman rank correlation test when both variables are ordinally scaled.