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Linear Regression Equations (linear + regression_equation)
Selected AbstractsTemporal stability of an NDVI-LAI relationship in a Napa Valley vineyardAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2 2003LEE F. JOHNSON Abstract Remotely sensed values for normalised difference vegetation index (NDVI) were derived periodically from high-resolution Ikonos satellite images during the 2001 growing season, and compared with ground measurements of vineyard leaf area index (LAI) during that same period. These two derived variables were strongly related in six vineyard blocks on each of four occasions (R2= 0.91 to 0.98). Linear regression equations relating these two derived variables did not differ significantly by time-step, and a single equation accounted for 92 per cent of the variance in the combined dataset. Such temporal stability in that relationship opens the possibility of transforming NDVI maps to LAI units, at least on a localised basis, and minimising (or even eliminating) subsequent ground calibration. This reduction in fieldwork would then decrease information cost for viticulturists who wish to monitor LAI sequentially within season, or who wish to track year-to-year changes in climax LAI with a single image collected annually. To take advantage of this cost reduction, temporal consistency in spectral data values comprising NDVI must be assured. This present paper addresses that issue. [source] Noninvasive Estimation of Pulmonary Vascular Resistance in Pulmonary HypertensionECHOCARDIOGRAPHY, Issue 5 2009Navin Rajagopalan M.D. Background: Determination of pulmonary vascular resistance (PVR) in patients with suspected or known pulmonary hypertension (PH) requires right heart catheterization. Our purpose was to use Doppler echocardiography to estimate PVR in patients with PH. Methods: Patient population consisted of 52 patients (53 ± 12 years; 35 females) who underwent Doppler echocardiography and right heart catheterization within 24 hours of each other. The ratio of peak tricuspid regurgitation velocity (TRV) and right ventricular outflow time-velocity integral (VTIRVOT) was measured via transthoracic echocardiography and correlated to invasively determined PVR. A linear regression equation was generated to determine PVR by echocardiography based upon the TRV/VTIRVOT ratio. PVR by echocardiography was compared to invasive PVR using Bland-Altman analysis. Results: Significant correlation was demonstrated between TRV/VTIRVOT and PVR by catheterization (r = 0.73; P < 0.001). However, Bland-Altman analysis showed that agreement between PVR determined by echocardiography and invasive PVR was poor (bias = 0; standard deviation = 4.3 Wood units). In a subset of patients with invasive PVR < 8 Wood units (26 patients), correlation between TRV/VTIRVOT and invasive PVR was strong (r = 0.94; P < 0.001). In these patients, agreement between PVR by echocardiography and invasive PVR was satisfactory (bias = 0; standard deviation = 0.5 Wood units). There was no correlation between TRV/VTIRVOT and invasive PVR in patients with PVR > 8 Wood units (n = 26; r = 0.17). Conclusion: While TRV/VTIRVOT correlates significantly with PVR, using it to estimate PVR in a PH patient population cannot be recommended. [source] Medication Quantification Scale Version III: Internal Validation of Detriment Weights Using a Chronic Pain PopulationPAIN PRACTICE, Issue 1 2008Michael Gallizzi MS ,,Abstract Introduction: We report an internal validation of the Medication Quantification Scale (MQS III) using a chronic pain population. The MQS was designed as a methodology of quantifying different drug regimens in 1992, updated in 1998 (MQS II), and again updated in 2003 (MQS III) using "detriment" weights determined by surveying physician members of the American Pain Society. The MQS has been used as a unitary clinical and research outcome. Methods: A retrospective chart review was collected from 400 patients in an interdisciplinary outpatient chronic pain clinic. A linear regression equation was developed using the patients' composite MQS III score, and those values were used in a Pearson correlation analysis. Results: The correlation between the subjects' computed regression detriment weights and the corresponding MQS III detriment weights yielded a significant result (r = 0.962, P < 0.01; two-tailed). Discussion: Our chronic pain sample-derived detriment weights did differ in some drug classes from that of the physician consensus, most notably the selective serotonin reuptake inhibitor, Opioid Schedule II, and NSAID class detriment. It is necessary to periodically resurvey large groups of physicians in order to control and modify the detriment weights of our categories in light of new information about detrimental effects (eg, COX-2 inhibitors), or to accommodate medical or political changes in prescribing habits (eg, more liberal opioid prescribing in the later years). This work suggests it may also be important to assess patients' perspective on detriment, as well as statistical and empiric use patterns.,, [source] Estimation of premorbid IQ in individuals with Alzheimer's disease using Japanese ideographic script (Kanji) compound words: Japanese version of National Adult Reading TestPSYCHIATRY AND CLINICAL NEUROSCIENCES, Issue 3 2006KEIKO MATSUOKA phd Abstract The National Adult Reading Test (NART) is widely used as a measure of premorbid IQ of the English-speaking patients with dementia. The purpose of the present study was to develop a Japanese version of the NART (JART), using 50 Japanese irregular words, all of which are Kanji (ideographic script) compound words. Reading performance based on JART and IQ as measured by the Wechsler Adult Intelligence Scale,Revised (WAIS-R) was examined in a sample of 100 normal elderly (NE) persons and in 70 age-, sex-, and education-matched patients with Alzheimer's disease (AD). The NE group was randomly divided into the NE calculation group (n = 50) and the NE validation group (n = 50). Using the NE calculation group, a linear regression equation was obtained in which the observed full-scale IQ (FSIQ) was regressed on the reading errors of the JART. When the regressed equation computed from the NE calculation group was applied to the NE validation group, the predicted FSIQ adequately fit the observed FSIQ (R2 = 0.78). Further, independent t -tests showed that the JART-predicted IQs were not significantly different between the NE and AD groups, whereas the AD group performed worse in the observed IQs. The reading ability of Kanji compound words is well-preserved in Japanese patients with AD. The JART is a valid scale for evaluating premorbid IQ in patients with AD. [source] CLONING DATA: GENERATING DATASETS WITH EXACTLY THE SAME MULTIPLE LINEAR REGRESSION FITAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 4 2009S. J. Haslett Summary This paper presents a simple computational procedure for generating ,matching' or ,cloning' datasets so that they have exactly the same fitted multiple linear regression equation. The method is simple to implement and provides an alternative to generating datasets under an assumed model. The advantage is that, unlike the case for the straight model-based alternative, parameter estimates from the original data and the generated data do not include any model error. This distinction suggests that ,same fit' procedures may provide a general and useful alternative to model-based procedures, and have a wide range of applications. For example, as well as being useful for teaching, cloned datasets can provide a model-free way of confidentializing data. [source] Temperature-dependent development and distribution in the soil profile of pupae of greyback canegrub Dermolepida albohirtum (Waterhouse) (Coleoptera: Scarabaeidae) in Queensland sugarcaneAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 1 2007David P Logan Abstract, The temperature-dependent development rate of pupae of greyback canegrub, Dermolepida albohirtum (Waterhouse) (Coleoptera: Scarabaeidae), a major pest of sugarcane in central and northern Queensland, was determined under six constant temperature regimes: 18, 20, 23, 25, 27 and 30°C, and for four geographically separated populations. Development rate increased significantly with increasing temperature. Parameters of the linear regression equation did not differ among populations and common coefficients were calculated. Developmental zero, at and below which no development occurs, for pupae was 12.0°C and the thermal constant was 476 day-degrees (D°). Minimum and maximum periods for pupal development were 26 days at 30°C and 75 days at 18°C, respectively. The phenology of pupae was determined in soil-filled cubicles in a shade house and in the field at Ayr (19°35,S, 147°25,E), north Queensland, using D. albohirtum field-collected as late-stage third-instar larvae and kept in containers. Pupation of D. albohirtum began in late August or early September and eclosion was complete by mid- to late October. The phenology data were used to validate the development model. Eclosion was predicted by summing hourly fractions of day-degrees until 476 D° was reached and was close to actual eclosion. As temperature, and hence pupal development rate, varies with soil depth, the distribution of the third instars in pupal cells in the soil profile was determined in recently harvested fields of sugarcane in the Burdekin sugarcane district centred on Ayr. Numbers of late third instars in pupal cells peaked at 300,400 mm, with pupae found from 30 to 700 mm. Pupal development was simulated using hourly soil temperatures measured at depths of 200 and 400 mm at Ayr and at Sarina (21°22,S, 149°13,E). The pupal stage was predicted to take up to 2,10 days longer at 200 mm deep than at 400 mm depending on pupation site and date. When pupation was simulated in late August, as is likely in the field, pupal development at 400 mm deep took 48,56 days at Ayr and 58,62 days at Sarina. [source] Calibration model of microbial biomass carbon and nitrogen concentrations in soils using ultraviolet absorbance and soil organic matterEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2008X. Xu Summary There is a need for a rapid, simple and reliable method of determining soil microbial biomass (SMB) for all soils because traditional methods are laborious. Earlier studies have reported that SMB-C and -N concentrations in grassland and arable soils can be estimated by measurement of UV absorbance in soil extracts. However, these previous studies focused on soils with small soil organic matter (SOM) contents, and there was no consideration of SOM content as a covariate to improve the estimation. In this study, using tropical and temperate forest soils with a wide range of total C (5,204 mg C g,1 soil) and N (1,12 mg N g,1 soil) contents and pH values (4.1,5.9), it was found that increase in UV absorbance of soil extracts at 280 nm (UV280) after fumigation could account for 92,96% of the variance in estimates of the SMB-C and -N concentrations measured by chloroform fumigation and extraction (P < 0.001). The data were combined with those of earlier workers to calibrate UV-based regression models for all the soils, by taking into account their varying SOM content. The validation analysis of the calibration models indicated that the SMB-C and -N concentrations in the 0,5 cm forest soils simulated by using the increase in UV280 and SOM could account for 86,93% of the variance in concentrations determined by chloroform fumigation and extraction (P < 0.001). The slope values of linear regression equations between measured and simulated values were 0.94 ± 0.03 and 0.94 ± 0.04, respectively, for the SMB-C and -N. However, simulation using the regression equations obtained by using only the data for forest profile soils gave less good agreement with measured values. Hence, the calibration models obtained by using the increase in UV280 and SOM can give a rapid, simple and reliable method of determining SMB for all soils. [source] Fractionated extraction of polycyclic aromatic hydrocarbons (PAHs) from polluted soils: estimation of the PAH fraction degradable through bioremediationEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2004S. Thiele-Bruhn Summary Chemical extractions were tested to estimate the fraction of 15 polycyclic aromatic hydrocarbons (PAHs) in polluted soils degradable through bioremediation. Of 30 soil samples, differing in PAH concentrations, from 10 long-term polluted sites, four were used in screening tests conducted with 14 different extractants. PAH extractability increased in the order salt solutions < surfactant solutions < organic solvents and organic solvent,water mixtures. Closest correlations (r = 0.73,0.91) and ratios of c. 1:1 of the extracted to the degradable PAH concentrations were found with aqueous solutions of two surfactants (Genapol UDD 88, Synperonic LF/RA 30). The PAH extractability by surfactant solutions increased with surfactant concentration (0,50 mg ml,1) and with decreasing degree of PAH condensation (6,2 rings). Kinetic behaviour of PAH solubilization by surfactants resembled the kinetics of PAH degradation (r = 0.84,0.99). With repeated extractions, a finite fraction of PAHs was extracted, which is thought to be the mobile and mobilizable PAH fraction, the latter being controlled by back-diffusion from intra- and inter-particle sites. Experiments with all 30 soil samples and a priori testing with an additional 10 soil samples confirmed that single extractions with surfactant solutions (5 mg ml,1; soil:solution ratio 1:20) were suitable for estimating the degradable fraction of PAHs in soil. With separate linear regression equations for PAHs grouped according to their degree of condensation, the extracted concentrations described the degradable concentrations with correlation coefficients (r) ranging from 0.62 to 0.80 (P < 0.001). PAH extractions with the surfactant solutions can be used to assess the prospects of bioremediation of PAH-polluted sites. [source] Leaf litter nitrogen concentration as related to climatic factors in Eurasian forestsGLOBAL ECOLOGY, Issue 5 2006Chunjiang Liu ABSTRACT Aim, The aim of this study is to determine the patterns of nitrogen (N) concentrations in leaf litter of forest trees as functions of climatic factors, annual average temperature (Temp, °C) and annual precipitation (Precip, dm) and of forest type (coniferous vs. broadleaf, deciduous vs. evergreen, Pinus, etc.). Location, The review was conducted using data from studies across the Eurasian continent. Methods, Leaf litter N concentration was compiled from 204 sets of published data (81 sets from coniferous and 123 from broadleaf forests in Eurasia). We explored the relationships between leaf litter N concentration and Temp and Precip by means of regression analysis. Leaf litter data from N2 -fixing species were excluded from the analysis. Results, Over the Eurasian continent, leaf litter N concentration increased with increasing Temp and Precip within functional groups such as conifers, broadleaf, deciduous, evergreen and the genus Pinus. There were highly significant linear relationships between ln(N) and Temp and Precip (P < 0.001) for all available data combined, as well as for coniferous trees, broadleaf trees, deciduous trees, evergreen trees and Pinus separately. With both Temp and Precip as independent variables in multiple regression equations, the adjusted coefficient of determination () was evidently higher than in simple regressions with either Temp or Precip as independent variable. Standardized regression coefficients showed that Temp had a larger impact than Precip on litter N concentration for all groups except evergreens. The impact of temperature was particularly strong for Pinus. Conclusions, The relationship between leaf litter N concentration and temperature and precipitation can be well described with simple or multiple linear regression equations for forests over Eurasia. In the context of global warming, these regression equations are useful for a better understanding and modelling of the effects of geographical and climatic factors on leaf litter N at a regional and continental scale. [source] Age Estimation by Pulp/Tooth Ratio in Canines by Peri-Apical X-RaysJOURNAL OF FORENSIC SCIENCES, Issue 1 2007Roberto Cameriere Ph.D. ABSTRACT: Estimation of age in individuals has received considerable attention in forensic science, in which it is a widely used method for individual identification, together with paleo-demographic analyses to establish mortality patterns in past populations. The present investigation, which is a continuation of a previously published pilot study, was conducted to examine the possible application of the pulp/tooth area ratio by peri-apical images as an indicator of age at death. A total of 200 peri-apical X-rays of upper and lower canines were assembled from 57 male and 43 female skeletons of Caucasian origin, aged between 20 and 79 years. They belong to the Frassetto osteological collection of Sassari (Sardinia) and are housed in the Museum of Anthropology, Department of Experimental and Evolutionistic Biology, University of Bologna. For each skeleton, dental maturity was evaluated by measuring the pulp/tooth area ratio on upper (x1) and lower (x2) canines. Very good agreement was found between intraobserver measurements. Statistical analysis was performed in order to obtain multiple regression formulae for dental age calculation, with chronological age as dependent variable, and gender, and upper and lower canines as independent variables. Stepwise regression analysis showed that gender did not contribute significantly to the fit (p=0.881) whereas variables x1 and x2 and the first-order interaction between them did. These two variables explained 92.5% of variations in estimated chronological age and the residual standard error was 4.06 years. Lastly, two simple linear regression equations were obtained for age estimation using canines from the maxilla and mandible separately. Both models explained 86% of variations in estimated chronological age and allowed an age-at-death estimate with a residual standard error of about 5.4 years. [source] Large differences in serum leptin levels between nonwesternized and westernized populations: the Kitava studyJOURNAL OF INTERNAL MEDICINE, Issue 6 2001S. Lindeberg Abstract.,Lindeberg S, Söderberg S, Ahrén B, Olsson T (Lund University; and Umeå University, Malmö, Sweden). Large differences in serum leptin levels between nonwesternized and westernized populations: the Kitava study. J Intern Med 2001; 249: 553,558. Objectives.,To compare serum leptin between nonwesternized and westernized populations. Setting., (i) The tropical island of Kitava, Trobriand Islands, Papua New Guinea and (ii) the Northern Sweden MONICA study population. Design.,Cross-sectional survey. Methods.,Fasting levels of serum leptin were analysed in 163 randomly selected Kitavans aged 20,86 years and in 224 Swedes aged 25,74. Main outcome measures.,Mean and determinants of serum leptin. Results.,Geometric mean of serum leptin in Kitavan males and females were 1.5 and 4.0 vs. 4.9 and 13.8 ng mL,1 in Swedish male and females (P < 0.0001 for both sexes). In Kitavans, observed geometric mean were close to predicted levels (1.8 ng mL,1 for males and 4.5 ng mL,1 for females) based on multiple linear regression equations including body mass index (BMI), triceps skinfolds (TSF) and age from the Swedish population-based sample. In Kitavans serum leptin was positively related to TSF amongst both sexes and, amongst females, to BMI. In Kitavans leptin was not related to fasting serum insulin. TSF explained 55% of the variation of leptin amongst females. There was a slight age-related increase of leptin amongst males. In Kitava leptin was not related to fasting serum insulin which was substantially lower than in Sweden. Conclusion.,The low concentrations of serum leptin amongst Kitavans probably relates to the absence of overweight and hyperinsulinaemia. At a population level serum leptin can apparently be predicted from simple measures of adiposity. [source] A research on determination of explosive gases utilizing cataluminescence sensor arrayLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 4-5 2005Xiaoan Cao Abstract In this paper, we propose a model of a sensor array system, which consists of three cataluminescence sensors based on nanosized SrCO3, , -Al2O3 and BaCO3 as catalysts, for quantitative analysis of the explosive gases of propane, n -butane and iso-butane in a mixture. Six linear regression equations of the cataluminescence intensity vs. the gas concentrations in the range 2000,10 000 ppm were established from the sensor array system at two working temperatures, as the explosive gases show different sensitivity to the three sensors. The least squares method was employed for solving the simultaneous equations and quantifying the concentrations of the three components. The detection limits (3,) of propane, n -butane and iso-butane on SrCO3, , -Al2O3 and BaCO3 sensors are 50, 40 and 20 ppm, 80, 60 and 40 ppm, and 20, 10 and 5 ppm, respectively. The concentrations of two artificial samples containing the tertiary mixture were analysed with satisfactory results. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||||||||