Home About us Contact
|
Home About us Contact | ||
|
|
||
Multiple Linear Regression (multiple + linear_regression)
Terms modified by Multiple Linear Regression Selected AbstractsAre Mechanistic and Statistical QSAR Approaches Really Different?MOLECULAR INFORMATICS, Issue 6-7 2010MLR Studies on 158 Cycloalkyl-Pyranones Abstract Two parallel approaches for quantitative structure-activity relationships (QSAR) are predominant in literature, one guided by mechanistic methods (including read-across) and another by the use of statistical methods. To bridge the gap between these two approaches and to verify their main differences, a comparative study of mechanistically relevant and statistically relevant QSAR models, developed on a case study of 158 cycloalkyl-pyranones, biologically active on inhibition (Ki) of HIV protease, was performed. Firstly, Multiple Linear Regression (MLR) based models were developed starting from a limited amount of molecular descriptors which were widely proven to have mechanistic interpretation. Then robust and predictive MLR models were developed on the same set using two different statistical approaches unbiased of input descriptors. Development of models based on Statistical I method was guided by stepwise addition of descriptors while Genetic Algorithm based selection of descriptors was used for the Statistical II. Internal validation, the standard error of the estimate, and Fisher's significance test were performed for both the statistical models. In addition, external validation was performed for Statistical II model, and Applicability Domain was verified as normally practiced in this approach. The relationships between the activity and the important descriptors selected in all the models were analyzed and compared. It is concluded that, despite the different type and number of input descriptors, and the applied descriptor selection tools or the algorithms used for developing the final model, the mechanistical and statistical approach are comparable to each other in terms of quality and also for mechanistic interpretability of modelling descriptors. Agreement can be observed between these two approaches and the better result could be a consensus prediction from both the models. [source] A Combinatorial Approach to the Variable Selection in Multiple Linear Regression: Analysis of Selwood et al.MOLECULAR INFORMATICS, Issue 6 2003A Case Study, Data Set Abstract A combinatorial protocol (CP) is introduced here to interface it with the multiple linear regression (MLR) for variable selection. The efficiency of CP-MLR is primarily based on the restriction of entry of correlated variables to the model development stage. It has been used for the analysis of Selwood et al data set [16], and the obtained models are compared with those reported from GFA [8] and MUSEUM [9] approaches. For this data set CP-MLR could identify three highly independent models (27, 28 and 31) with Q2 value in the range of 0.632,0.518. Also, these models are divergent and unique. Even though, the present study does not share any models with GFA [8], and MUSEUM [9] results, there are several descriptors common to all these studies, including the present one. Also a simulation is carried out on the same data set to explain the model formation in CP-MLR. The results demonstrate that the proposed method should be able to offer solutions to data sets with 50 to 60 descriptors in reasonable time frame. By carefully selecting the inter-parameter correlation cutoff values in CP-MLR one can identify divergent models and handle data sets larger than the present one without involving excessive computer time. [source] Prediction of biodegradation from the atom-type electrotopological state indicesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2001Jarmo Huuskonen Abstract A group contribution method based on atom-type electrotopological state indices for predicting the biodegradation of a diverse set of 241 organic chemicals is presented. Multiple linear regression and artificial neural networks were used to build the models using a training set of 172 compounds, for which the approximate time for ultimate biodegradation was estimated from the results of a survey of an expert panel. Derived models were validated by using a leave-25%-out method and against two test sets of 12 and 57 chemicals not included in the training set. The squared correlation coefficient (r2) for a linear model with 15 structural parameters was 0.76 for the training set and 0.68 for the test set of 12 molecules. The model predicted correctly the biodegradation of 48 chemicals in the test set of 57 molecules, for which biodegradability was presented as rapid or slow. The use of artificial neural networks gave better prediction for both test sets when the same set of parameters was tested as inputs in neural network simulations. The predictions of rapidly biodegradable chemicals were more accurate than the predictions of slowly bio-degradable chemicals for both the regression and neural network models. [source] Flavor Variability and Flavor Stability of U.S.-Produced Whole Milk PowderJOURNAL OF FOOD SCIENCE, Issue 7 2009M.A. Lloyd ABSTRACT:, Flavor variability and stability of U.S.-produced whole milk powder (WMP) are important parameters for maximizing quality and global competitiveness of this commodity. This study characterized flavor and flavor stability of domestic WMP. Freshly produced (<1 mo) WMP was collected from 4 U.S. production facilities 5 times over a 1 y period. Each sample was analyzed initially and every 2 mo for sensory profile, volatiles, color, water activity, and moisture through 12 mo storage. Selected volatiles were quantified using solid phase microextraction (SPME) with gas chromatography/mass-spectrometry: dimethyl sulfide, 2-methylbutanal, 3-methylbutanal, hexanal, 2-heptanone, heptanal, 1-octen-3-ol, octanal, 3-octen-2-one, and nonanal. Multiple linear regression with backwards elimination was applied to generate equations to predict grassy and painty flavors based on selected volatiles. All WMP were between 2% and 3% moisture and 0.11 and 0.25 water activity initially. WMP varied in initial flavor profiles with varying levels of cooked, milk fat, and sweet aromatic flavors. During storage, grassy and painty flavors developed while sweet aromatic flavor intensities decreased (P,< 0.05). Painty and grassy flavors were confirmed by increased levels (P,< 0.05) of lipid oxidation products such as hexanal, heptanal, and octanal. Hexanal, 2-heptanone, 1-octen-3-ol, and nonanal concentrations were best predictors of grassy flavor (R2= 0.38,,P,< 0.0001) while hexanal, 2-methylbutanal, 3-methylbutanal, octanal, and 3-octen-2-one concentrations were best predictors of painty flavor (R2= 0.61,,P,< 0.0001). These results provide baseline information to determine specific factors that can be controlled to optimize U.S. WMP flavor and flavor stability. [source] Psychological comorbidity and complexity of gastrointestinal symptoms in clinically diagnosed irritable bowel syndrome patientsJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 7pt1 2008Antonina Mikocka-Walus Abstract Background and Aim:, The prevalence of psychological disorders is high in patients with irritable bowel syndrome (IBS) but their role in symptom reporting is uncertain. It is thus interesting whether the number of functional gastrointestinal disorders (FGID) determines the load of psychological comorbidity. The Rome III criteria have not been used to evaluate such a relationship as yet. Moreover, not many studies have examined the sensitivity of the Rome III criteria in detecting IBS. Our aims were therefore: (i) to determine whether those IBS participants with more FGID had a tendency to greater psychological comorbidity than those with fewer FGID; and (ii) to assess the performance of the Rome III criteria in detecting IBS versus the diagnosis of the gastroenterologist. Methods:, A cross-sectional survey of 32 consecutive outpatients with clinically diagnosed IBS was performed. The Hospital Anxiety and Depression Scale (HADS), the Short Form 12 Health Survey (SF-12), and the Rome III criteria questionnaire (BDQ-6) were administered. Multiple linear regression was conducted to detect associations among FGID, anxiety, depression and quality of life. Results:, Overall, 50% of participants were anxious and 12% were depressed. Forty-four percent of participants had >two FGID; however, the number of FGID did not correlate with scores for anxiety, depression or quality of life. Amazingly, only 50% (CI: 33,67) of participants clinically diagnosed with IBS met Rome III criteria for IBS. Conclusion:, Contrary to our expectations, a greater load of FGID did not correlate with a greater load of psychological comorbidity. Surprisingly, the Rome III criteria detected only 50% of clinical cases of IBS. [source] The Hispanic Americans Baseline Alcohol Survey (HABLAS): Predictors of Alcohol Attitudes and Expectancies in Hispanic National GroupsALCOHOLISM, Issue 5 2010Britain A. Mills Background:, Multiple theoretical frameworks identify attitudes and expectancies as important predictors of alcohol behavior. Few studies have examined demographic predictors of these evaluative and belief-based cognitive mediators in the general population, and none have examined them in large-scale studies of Hispanics, a group at higher risk for drinking behavior and problems. This study probes the extent to which dimensions of attitudes and expectancies share common demographic predictors in a large sample of Puerto Ricans, Cuban-Americans, Mexican-Americans, and South/Central Americans. Methods:, The 2006 Hispanic Americans Baseline Alcohol Survey (HABLAS) used a multistage cluster sample design to interview 5,224 individuals randomly selected from households in Miami, New York, Philadelphia, Houston, and Los Angeles. This study focused on 2,773 respondents self-identified as current drinkers. Multiple linear regression was used to identify predictors of positive and negative dimensions of attitudes and expectancies, controlling for various background variables. Results:, Religious affiliation selectively predicted alcohol attitudes, with Catholics having more positive and fewer negative attitudes than other religious groups. Hispanic group selectively predicted alcohol expectancies, with Cuban-Americans having less positive and less negative expectancies than other groups. Being U.S.-born or male predicted more positive attitudes and expectancies, but birthplace and gender did not predict negative dimensions of attitudes or expectancies. Higher acculturation and more education were linked to a decreased tendency to agree with any item. Age was positively and negatively associated with negative expectancies and positive attitudes, respectively, and having never been married, higher income, and unemployment were each linked to fewer negative attitudes. Conclusions:, Although there is some overlap, attitudes and expectancies are influenced by different sociodemographic variables. Positive and negative dimensions of those constructs also show distinct patterns of relations. Prevention and treatment programs targeting cognitive mediators of behavior should be mindful of these differential determinants and future modeling endeavors should incorporate them. [source] Quantitative structure,reactivity relationship studies on the catalyzed Michael addition reactionsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 6 2009Bahram Hemmateenejad Abstract Quantitative structure,reactivity relationship (QSRR) can be considered as a variant of quantitative structure,property relationship (QSPR) studies, where the chemical reactivity of reactants or catalysts in a specified chemical reaction is related to chemical structure. In this manner, the Michael addition of some different substrates using different catalysts (SDS, silica gel, and ZrOCl2) was subjected to structure,reactivity relationship, quantitatively. Multiple linear regression (MLR) and partial least square (PLS) were used to perform the QSRR analysis. The resulted models for different catalyzed reactions showed that the catalysts probably act in different mechanisms since the models obtained for the catalysts included different parameters from substrate and enones. Overall, it was found that the reactivity in Michael addition reactions is controlled by coulombic (dipole and charge) interactions as well as the orbital energetic parameters. In the presence of different catalysts, the relative importance of these parameters is changed and hence the catalytic activity is changed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Predicting Root Density in Streambanks,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2008Candice Piercy Abstract:, Roots of riparian vegetation increase streambank erosion resistance and structural stability; therefore, knowledge of root density and distribution in streambanks is useful for stream management and restoration. The objective of this study was to compare streambank root distributions for herbaceous and woody vegetation and to develop empirical models to predict root density. Root length density, root volume ratio, soil physical and chemical properties, and above-ground vegetation densities were measured at 25 sites on six streams in southwestern Virginia. The Mann-Whitney test was used to determine differences in root density along stream segments dominated by either woody or herbaceous vegetation. Multiple linear regression was used to develop relationships between root density and site characteristics. Study results showed that roots were evenly distributed across the bank face with the majority of roots having diameters less than 2 mm. Soil bulk density and above-ground vegetation were key factors influencing root density. While significant relationships were developed to predict root density, the predictive capabilities of the equations was low. Because of the highly variable nature of soil and vegetation properties, it is recommended at this time that soil erodibility and root density be measured in the field for design and modeling purposes, rather than estimated based on empirical relationships. [source] Colour characteristics of honeys as influenced by pollen grain content: a multivariate studyJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2004Anass Terrab Abstract A chromatic analysis by tristimulus colorimetry and a pollen analysis (pollen grains contained in each honey sample, considering their volume and geometrical shape) were carried out on 33 Eucalyptus unifloral honeys; the colour of the pollen grains was also considered. Multiple linear regression (MLR) and partial least squares regression (PLSR) were used to establish equations relating the chromatic variables to the pollen data, ie number and morphology of the pollen grains, thus allowing the prediction of the ultimate colour from the botanical characteristics. The results obtained show that lightness (L*) is significantly (p < 0.05) related to the pollen type Olea europaea; on the other hand, the variable that better relates to the chroma is the Zea mays pollen type. Copyright © 2004 Society of Chemical Industry [source] The German version of the chronic urticaria quality-of-life questionnaire: factor analysis, validation, and initial clinical findingsALLERGY, Issue 6 2009ynek Background:, Chronic urticaria (CU) is a common skin disorder that causes a substantial burden on patients' quality-of-life (QoL). The aim of this work was to generate and validate a German version of the Chronic Urticaria Quality of Life Questionnaire (CU-Q2oL) and to provide reference assessments of QoL. Methods:, The Italian CU-Q2oL was translated into German and administered to 157 CU patients. They also completed two well-established general dermatology QoL questionnaires, the Dermatology Life Quality Index (DLQI) and Skindex-29. Factor analysis was used to identify scales of the German CU-Q2oL. Correlation to the DLQI and Skindex-29 was used for validation. Multiple linear regression was used to determine which patient characteristics were associated with which dimensions of QoL. Results:, The factor analysis identified six scales of the German CU-Q2oL: functioning, sleep, itching/embarrassment, mental status, swelling/eating, and limits looks, which accounted for 70% of the data variance. Five of these six scales showed good internal consistency, and another five demonstrated convergent validity. On a percentile scale, they had these median CU-Q2oL scores: 29 functioning, 44 sleep, 50 itching/embarrassment, 50 mental status, 31 swelling/eating, 31 limits looks. Disease severity significantly predicted scores on all scales. Age predicted functioning, sleep, itching/embarrassment, and swelling/eating. Sex predicted itching/embarrassment and limits looks. Conclusion:, This study yielded a robust validation of the German version of the CU-Q2oL. It confirmed previous studies that CU has a clinically meaningful burden on QoL, especially for sleep and mental health, and that women are more severely affected by pruritus. The German CU-Q2oL should be widely adopted in clinical research on the treatment of CU. [source] Maternal use of nicotine replacement therapy during pregnancy and offspring birthweight: a study within the Danish National Birth CohortPAEDIATRIC & PERINATAL EPIDEMIOLOGY, Issue 3 2010Tina H. Lassen Summary Lassen TH, Madsen M, Skovgaard LT, Strandberg-Larsen K, Olsen J, Andersen A-MN. Maternal use of nicotine replacement therapy during pregnancy and offspring birthweight: a study within the Danish National Birth Cohort. Paediatric and Perinatal Epidemiology 2010; 24: 272,281. Smoking is a well-established risk factor for fetal growth restriction and other adverse pregnancy outcomes, and nicotine may be one of the chemical compounds that drive these associations. Nicotine replacement therapy (NRT) is a smoking cessation aid, which can facilitate smoking cessation. It is, however, unknown whether NRT used during pregnancy impairs fetal growth. The aim of this study was to estimate the association between the use of NRT during pregnancy and offspring birthweight. The study population consisted of 72 761 women enrolled in the Danish National Birth Cohort between 1996 and 2002. Information on NRT and potential confounders was obtained from two computer-assisted telephone interviews conducted in the second and third trimesters, respectively. Multiple linear regression in a multilevel model was used to estimate the association between NRT use and birthweight adjusted for gestational age and potential confounders. The adjusted analyses showed no significant association between the duration of NRT use and birthweight (b = 0.25 g per week of NRT use [95% CI ,2.31, 2.81]) and neither was the type of NRT product (patch, gum, inhaler) associated with reduced birthweight. However, simultaneous use of more than one NRT product was associated with reduced birthweight (b = ,10.73 g per week of NRT use [95% CI ,26.51, 5.05]), although the association was not statistically significant. The results of this study suggest that maternal use of NRT in pregnancy does not seriously affect birthweight, but there could be a negative effect on birthweight associated with simultaneous use of more than one type of NRT product. [source] Antenatal steroid treatment prevents severe hyperkalemia in very low-birthweight infants*PEDIATRICS INTERNATIONAL, Issue 6 2003Naoki Uga AbstractBackground:,Hyperkalemia is seen quite often in very low-birthweight (VLBW) infants and concentrations sometimes become high enough to cause cardiac arrhythmia. The purpose of the present study was to identify factors that increase serum concentrations of potassium in VLBW infants. Methods:,Retrospective comparative analysis was performed on 140 VLBW infants who had been admitted to the Toho University Perinatal Center between January 1993 and December 1999 and needed mechanical ventilation for respiratory distress. Serum concentrations of potassium at 24 and 48 h of age were compared in two groups of infants, those whose mothers did and did not receive antenatal steroid treatment. Risk factors for severe hyperkalemia were analyzed by multiple linear regression models and Pearson's partial correlation analysis. Results:,Antenatal steroid treatment reduced serum potassium concentrations significantly at 24 and 48 h, as well as the incidence of cardiac arrhythmia and necessity for glucose insulin treatment for severe hyperkalemia. Multiple linear regression showed the serum potassium concentration at 24 h of age was associated with antenatal steroid hormone treatment, 24 h fluid intake volume, serum sodium concentrations at 24 h, gestational weeks and sampling site. Serum concentration of potassium at 48 h of age was associated with blood urea nitrogen, gestational week, serum sodium concentration at 48 h of age and fluid intake between 24 and 48 h of age. Urine output volume and serum creatinine concentrations were not correlated with potassium concentrations at either age. Conclusion:,Antenatal steroid hormone treatment can reduce early hyperkalemia in VLBW infants and also the incidence of cardiac arrhythmia and the use of glucose insulin treatment. [source] Estimation of height in elderly Japanese using region-specific knee height equationsAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 3 2002Barbara Lohse Knous Two knee height equations to predict standing height of Japanese elderly were cross-validated with Joetsu City elders. One equation was derived with Hawaiian residents of Japanese ancestry and the other with elders from the Kumamoto Prefecture in Japan. Subjects included 40 men and 39 women free-dwelling, healthy elders with mean ages of 68.0 ± 2.2 years and 68.0 ± 2.7 years, respectively. Heights of the subjects were representative of Japanese elderly. Experienced nurses, trained to measure knee height, also measured standing height with an automatic stadiometer. A pilot study refined measurement skills. Differences between actual and predicted heights for both equations were significant. Multiple linear regression was used to derive knee height equations specific for elderly males and females living in Joetsu City: women, 63.06 + (2.38 × knee height in cm) ,(0.34 × age in years); men, 71.16 + (2.61 × knee height in cm) - (0.56 × age in years). Geographic-specific knee height equations for Japanese elderly and cross-validation with other locations are suggested to facilitate the accurate use of knee height in nutritional assessment of Japanese elders. Am. J. Hum. Biol. 14:300,307, 2002. © 2002 Wiley-Liss, Inc. [source] Welfare Index and Reproductive Performance in the SowREPRODUCTION IN DOMESTIC ANIMALS, Issue 6 2006C Munsterhjelm Contents To study the relationship between on-farm welfare and reproductive performance in the sow, the TGI 35L Animal Needs Index was modified for use in Finnish pig production. The modified index had a maximal total score of 100. It was comprised of six categories: ,locomotion' (maximal score 21 for dry sows and 11 for lactating sows), ,social interaction' (12/8), ,floor quality' (16/9), ,stable climate' (16/21), ,feeding' (16/23) and ,health and stockmanship' (19/29). Index scorings were performed separately in farrowing, breeding and gestation units on 28 representative Finnish sow farms. One-year production parameters were collected. Multiple linear regression was used for statistical analysis. Total ANI-points varied between 36.5,68.0 for lactating and 39.5,86.0 for dry sows. Litter size increased with increasing scores for ,feeding' in the dry sow unit. Controlling for breed, high scores for ,health and stockmanship' and ,floor quality' shortened the reproductive cycle, probably because of good leg health. The number of weaned piglets per sow per year (PSY) increased with increasing scores for dry sow ,health and stockmanship', ,floor quality' and an interaction of ,feeding' in the farrowing and mating units. PSY increased with decreasing scores for farrowing pen ,climate'. High-quality floors and stockmanship appear to correlate positively with reproductive performance in the sow. Effects of a welfare-promoting feeding strategy on reproduction are contradictory. [source] Infant developmental milestones and subsequent cognitive functionANNALS OF NEUROLOGY, Issue 2 2007Graham K. Murray MD Objective Developmental delay is associated with a subsequent diagnosis of learning disability. However, the relationship between the age of reaching infant developmental milestones and later intellectual function within the general population remains unresolved. We hypothesized that earlier attainment of developmental milestones would be associated with better subsequent intellectual performance throughout the range of abilities, rather than confined to extremes. Methods Developmental data were obtained at age 2 years in the National Survey of Health and Development, a representative sample of 5,362 children born in the United Kingdom in 1946. Data on intellectual function and educational attainment at ages 8, 26, and 53 years were also obtained. Multiple linear regression and logistic regression were used to analyze the effect of age of reaching developmental milestones on subsequent cognition and educational attainment. Results The age of reaching developmental milestones was associated with intellectual performance at ages 8, 26, and 53 years; for every month earlier a child learned to stand, there was, on average, a gain of one half of one intelligence quotient point at age 8. Speech development had a small but statistically significant effect on subsequent educational attainment (later developers were less likely to progress beyond basic education); this effect was not apparent for motor development. Effect sizes were reduced when the slowest developers were excluded, but many effects remained significant. Interpretation The association between later development and poorer subsequent intellectual function is small, but it does have theoretical implications; we suggest it is secondary to suboptimal cortical-subcortical connectivity. Ann Neurol 2007 [source] Prediction of herbage yield in grassland: How well do Ellenberg N-values perform?APPLIED VEGETATION SCIENCE, Issue 1 2007Markus Wagner Wisskirchen & Haeupler (1998) Abstract Question: How useful are Ellenberg N-values for predicting the herbage yield of Central European grasslands in comparison to approaches based on ordination scores of plant species composition or on soil parameters? Location: Central Germany (11°00,-11°37'E, 50°21-50°34'N, 500,840 m a.s.l.). Methods: Based on data from a field survey in 2001, the following models were constructed for predicting herbage yield in montane Central European grasslands: (1) Linear regression of mean Ellenberg N-, R- and F-values; (2) Linear regression of ordination scores derived from Non-metric Multidimensional Scaling (NMDS) of vegetation data; and (3) Multiple linear regression (MLR) of soil variables. Models were evaluated by cross-validation and validation with additional data collected in 2002. Results: Best predictions were obtained with models based on species composition. Ellenberg N-values and NMDS scores performed equally well and better than models based on Ellenberg R- or F-values. Predictions based on soil variables were least accurate. When tested with data from 2002, models based on Ellenberg N-values or on NMDS scores accurately predicted productivity rank order of sites, but not the actual herbage yield of particular sites. Conclusions: Mean Ellenberg N-values, which are easy to calculate, are as accurate as ordination scores in predicting herbage yield from plant species composition. In contrast, models based on soil variables may be useful for generating hypotheses about the factors limiting herbage yield, but not for prediction. We support the view that Ellenberg N-values should be called productivity values rather than nitrogen values. [source] On the Origins of Enzyme Inhibitor Selectivity and Promiscuity: A Case Study of Protein Kinase Binding to StaurosporineCHEMICAL BIOLOGY & DRUG DESIGN, Issue 1 2009Duangrudee Tanramluk Relationships between ligand binding and the shapes of the binding sites in families of homologous enzymes are investigated by comparing matrices of distances between key binding site atoms. Multiple linear regression is used to help identify key distances that influence ligand binding affinity. In order to illustrate the utility of this generic approach, we study protein kinase binding sites for ATP and the promiscuous competitive inhibitor, staurosporine. We show that the size of the gatekeeper residue and the closure between the first glycine of the GXGXXG motif and the aspartate of the DFG loop act together to promote tight binding. Our web-based tool, ,mapping analogous hetero-atoms onto residue interactions' (MAHORI), indicates that the greater the number of hydrogen bonds made by the kinase around the methylamine group of staurosporine, the tighter the binding. The conservation of surrounding atoms identified using our novel grid-based method clearly demonstrates that the most structurally conserved part of the binding site for staurosporine is the main chain of the hinge region. The critical role of interactions that are not dependent on side-chain identities is consistent with the promiscuous nature of this inhibitor. [source] Validation of the Depression and Somatic Symptoms Scale by comparison with the Short Form 36 scale among psychiatric outpatients with major depressive disorderDEPRESSION AND ANXIETY, Issue 6 2009Ching-I Hung M.D. Abstract Background: The Depression and Somatic Symptoms Scale (DSSS) is a self-administered scale developed for monitoring both depression and somatic symptoms. The aims of this study were to establish the criterion-related validity of the DSSS by testing the correlation between the DSSS and the Short Form 36 (SF-36) scale and to compare the ability of the DSSS and two other scales in predicting the outcome of the SF-36. Methods: The study enrolled 135 outpatients with a major depressive episode, 95 of whom received treatment for 1 month. Four scales were administered and evaluated: the DSSS, the SF-36, the Hospital Anxiety and Depression Scale, and the Hamilton Depression Rating Scale. Pearson correlation was used to test correlations among scales. Multiple linear regressions were used to find the scales most effective in predicting the SF-36. Results: The three scales were significantly correlated with most of the SF-36 subscales. The depression and somatic subscales of the DSSS significantly correlated with the mental and physical subscales of the SF-36, respectively. The DSSS and the Hospital Anxiety and Depression Scale were better able to predict physical and mental subscales of the SF-36, respectively. The Hamilton Depression Rating Scale had a good ability to predict functional impairment. Conclusions: Psychometric scales with appropriate somatic symptoms might be more compatible with both physical and mental dimensions of the SF-36. DSSS proved to be a valid scale for monitoring both depression and somatic symptoms in patients with depression. Future studies should test whether the DSSS is better at predicting the treatment and prognosis of depression than conventional scales for depression. Depression and Anxiety, 2009. © 2009 Wiley-Liss, Inc. [source] Microanatomical diversity of the humerus and lifestyle in lissamphibiansACTA ZOOLOGICA, Issue 2 2009Aurore Canoville Abstract A study of body size and the compactness profile parameters of the humerus of 37 species of lissamphibians demonstrates a relationship between lifestyle (aquatic, amphibious or terrestrial) and bone microstructure. Multiple linear regressions and variance partitioning with Phylogenetic eigenVector Regressions reveal an ecological and a phylogenetic signal in some body size and compactness profile parameters. Linear discriminant analyses segregate the various lifestyles (aquatic vs. amphibious or terrestrial) with a success rate of up to 89.2%. The models built from data on the humerus discriminate aquatic taxa relatively well from the other taxa. However, like previous models built from data on the radius of amniotes or on the femur of lissamphibians, the new models do not discriminate amphibious taxa from terrestrial taxa on the basis of body size or compactness profile data. To make our inference method accessible, spreadsheets (see supplementary material on the website), which allow anyone to infer a lissamphibian lifestyle solely from body size and bone compactness parameters, were produced. No such easy implementation of habitat inference models is found in earlier papers on this topic. [source] Highways block gene flow and cause a rapid decline in genetic diversity of desert bighorn sheepECOLOGY LETTERS, Issue 10 2005Clinton W. Epps Abstract The rapid expansion of road networks has reduced connectivity among populations of flora and fauna. The resulting isolation is assumed to increase population extinction rates, in part because of the loss of genetic diversity. However, there are few cases where loss of genetic diversity has been linked directly to roads or other barriers. We analysed the effects of such barriers on connectivity and genetic diversity of 27 populations of Ovis canadensis nelsoni (desert bighorn sheep). We used partial Mantel tests, multiple linear regression and coalescent simulations to infer changes in gene flow and diversity of nuclear and mitochondrial DNA markers. Our findings link a rapid reduction in genetic diversity (up to 15%) to as few as 40 years of anthropogenic isolation. Interstate highways, canals and developed areas, where present, have apparently eliminated gene flow. These results suggest that anthropogenic barriers constitute a severe threat to the persistence of naturally fragmented populations. [source] Microemulsion electrokinetic chromatography of drugs varying in charge and hydrophobicity: I. Impact of parameters on separation performance evaluated by multiple linear regression modelsELECTROPHORESIS, Issue 1 2004Valérie Harang Abstract The separation of anionic, cationic and neutral drugs in microemulsion electrokinetic chromatography (MEEKC) was studied with a statistical experimental design. The concentration of sodium dodecyl sulfate (SDS, surfactant), 1-butanol (co-surfactant) and borate buffer and the factors Brij 35 (surfactant), 2-propanol (organic solvent) and cassette temperature were varied simultaneously, while the parameters pH (9.2), the concentration of octane (oil, 0.8% w/w), the voltage (10 kV) and the dimension of the fused-silica capillary, were kept constant. Eight different model substances were chosen with different hydrophobicities. Two of the analytes were positively charged, two were negatively charged, and the remaining four were neutral or close to neutral at the pH explored. The importance of each parameter on the separation window, the plate height and the retention factor for each of the analytes was studied by means of multiple linear regression (MLR) models. A new response was evaluated for anions, the quotient between the effective mobility in the microemulsion and the effective mobility in the corresponding buffer. Factors affecting selectivity changes were also explored, and it was found that SDS and 2-propanol had the largest effect on selectivity. [source] A new biodegradation prediction model specific to petroleum hydrocarbonsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2005Philip Howard Abstract A new predictive model for determining quantitative primary biodegradation half-lives of individual petroleum hydrocarbons has been developed. This model uses a fragment-based approach similar to that of several other biodegradation models, such as those within the Biodegradation Probability Program (BIOWIN) estimation program. In the present study, a half-life in days is estimated using multiple linear regression against counts of 31 distinct molecular fragments. The model was developed using a data set consisting of 175 compounds with environmentally relevant experimental data that was divided into training and validation sets. The original fragments from the Ministry of International Trade and Industry BIOWIN model were used initially as structural descriptors and additional fragments were then added to better describe the ring systems found in petroleum hydrocarbons and to adjust for nonlinearity within the experimental data. The training and validation sets had r2 values of 0.91 and 0.81, respectively. [source] Laboratory to field validation in an integrative assessment of an acid mine drainage,impacted watershedENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2000David J. Soucek Abstract An integrative assessment was conducted in the Puckett's Creek watershed of southwestern Virginia, USA, to investigate the environmental impacts of acid mine drainage (AMD) inputs. Twenty-one sampling stations were categorized into groups based on five degrees of AMD input: (1) none, (2) intermittent acidic/circum-neutral AMD, (3) continuous acidic AMD, (4) continuous circum-neutral AMD, and (5) receiving system stations with at least two levels of dilution. Bioassessment techniques included water/sediment chemistry, benthic macroinvertebrate sampling, laboratory acute water column toxicity testing, laboratory chronic sediment toxicity testing, and in situ toxicity testing with Asian clams (Corbicula fluminea [Müller]). Group 3 stations had significantly altered water chemistry (low pH, high conductivity, and high water column metals) relative to the other groups and significantly higher sediment iron concentrations. Both group 3 and group 4 stations had significantly decreased ephemeroptera-plecoptera-trichoptera richness and percent ephemeroptera abundance relative to unimpacted stations. Group 3 stations also had decreased total taxon richness. Water column toxicity testing was sensitive to AMD impacts, with samples from group 3 stations being significantly more toxic than those from groups 2 and 4, which in turn were more toxic than those from groups 1 and 5. Similar results were observed for in situ toxicity testing. No differences in sediment toxicity test survival and impairment results were observed among the station groups. Stepwise multiple linear regression and simple bivariate correlation analyses were used to select parameters for use in an ecotoxicologic rating system, which was successful in differentiating between two levels of environmental impact relative to stations receiving no AMD input. [source] EORTC QLQ-C30 and FACT-BMT for the measurement of quality of life in bone marrow transplant recipients: a comparisonEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 2 2000Martin Kopp Abstract: The purpose of the study was to compare two differentquality-of-life self-rating instruments, namely the EORTC QLQ-C30, developed by the quality-of-life study group of the European Organisation for Research and Treatment of Cancer, and the FACT-BMT (version 3), the Functional Assessment of Cancer Therapy , Bone Marrow Transplantation scale, which is the FACT-G(eneral measure) in combination with a module developed specifically for evaluating quality of life of bone marrow transplant (BMT) patients. Fifty-six BMT recipients completed both the EORTC QLQ-C30 and the FACT-BMT (German language version) during the same session. Questionnaire data were analyzed on a subscale basis using correlation analysis and multiple linear regression. Correlations between corresponding subscales of EORTC QLQ-C30 and the FACT-BMT ranged from r=0.30 for the emotional domain (poor agreement) to r=0.77 for global QOL (good agreement). This suggests that the instruments, despite considerable overlap, possibly focus on different aspects of QOL, in particular in addressing emotional and social issues of BMT patients. It appears that the FACT-BMT gives a more comprehensive overview regarding the multidimensional construct of quality of life. The EORTC QLQ-C30 gives more insight into the physical aspects of quality of life and helps to identify symptoms which effectively decrease quality of life from the patient's perspective. The QLQ-C30 might be improved by the incorporation of a BMT-specific module currently under development. We therefore conclude that neither of the two instruments can be replaced by the other in the assessment of QOL of BMT patients and that a direct comparison of results obtained with the two instruments is likely to be misleading. [source] A Statistical Estimator of the Spatial Distribution of the Water-Table AltitudeGROUND WATER, Issue 1 2003Nicasio Sepúlveda An algorithm was designed to statistically estimate the areal distribution of water-table altitude. The altitude of the water table was bounded below by the minimum water-table surface and above by the land surface. Using lake elevations and stream stages, and interpolating between lakes and streams, the minimum water-table surface was generated. A multiple linear regression among the minimum water-table altitude, the difference between land-surface and minimum water-table altitudes, and the water-level measurements from surficial aquifer system wells resulted in a consistently high correlation for all groups of physiographic regions in Florida. A simple linear regression between land-surface and water-level measurements resulted in a root-mean-square residual of 4.23 m, with residuals ranging from , 8.78 to 41.54 m. A simple linear regression between the minimum water table and the water-level measurements resulted in a root-mean-square residual of 1.45 m, with residuals ranging from ,7.39 to 4.10 m. The application of the multiple linear regression presented herein resulted in a root-mean-square residual of 1.05 m, with residuals ranging from , 5.24 to 5.63 m. Results from complete and partial F tests rejected the hypothesis of eliminating any of the regressors in the multiple linear regression presented in this study. [source] Insulin resistance and liver injury in hepatitis C is not associated with virus-specific changes in adipocytokines,HEPATOLOGY, Issue 1 2007Ian Homer Y. Cua The role of tumor necrosis factor ,, interleukin 6, leptin, and adiponectin in the pathogenesis of hepatitis C virus (HCV)-associated insulin resistance (IR) remains controversial. We tested the hypothesis that these adipocytokines contribute to chronic HCV-associated IR and liver injury by first comparing their serum levels and homeostasis model assessment of insulin resistance (HOMA-IR) in 154 untreated, non-diabetic, HCV-infected male subjects with fibrosis stage 0-2, to that in 75 healthy volunteers matched for age, body mass index (BMI), and waist-hip ratio (WHR). We next examined whether the adipocytokine levels were associated with the extent of hepatic steatosis, portal/periportal inflammation and fibrosis in our total cohort of 240 HCV-infected male subjects. Significantly higher levels of HOMA-IR (2.12 versus 1.63, P = 0.01), TNF, (1.28 versus 0.60 pg/ml, P < 0.001) and IL6 (2.42 versus 1.15 pg/ml, P = 0.001) were noted in the HCV cohort compared with healthy controls respectively, but there were no significant differences in leptin and adiponectin concentrations. By multiple linear regression, independent predictors of HOMA-IR included the body mass index, and the serum levels of leptin (positive correlation) and adiponectin (negative correlation), but not that of TNF, and IL6. Only TNF, levels were correlated with the extent of histological injury (portal/periportal inflammation, P = 0.02). Conclusion: Whereas leptin and adiponectin contribute to IR, none of the adipocytokines accounted for the elevated IR in HCV-infected subjects. The adipocytokines were not associated with histological features of chronic HCV infection except for TNF, which correlated with portal/periportal inflammation. HCV-associated IR is most likely an adipocytokine-independent effect of the virus to modulate insulin sensitivity. (HEPATOLOGY 2007;46:66,73.) [source] The effect of solvents on the rate of catalytic hydrogenation of 6-ethyl-1,2,3,4-tetrahydroanthracene-9,10-dioneINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2008ch Fajt The rate of hydrogenation of 6-ethyl-1,2,3,4-tetrahydroanthracene-9,10-dione was investigated at 313 K and 0.1 MPa in 20 solvents. A multiple linear regression was used to describe the solvent effect. The regression of the reaction rates was carried out using two five-parameter linear regression models: the Abraham,Kamlet,Taft (AKT) and the Koppel,Palm (KP) model. After the elimination of the insignificant terms from the regression models, it was found that the basic character of the solvent and its Hildebrand cohesion energy density were the most important attributes influencing the hydrogenation rate. The analysis of both models led to the same conclusion. The resultant simplified AKT model gave closer fitting in comparison to the KP model. The results could facilitate the solvent selection for the industrial process of hydrogen peroxide production by the anthraquinone method with respect to the kinetics of anthraquinone hydrogenation. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 240,252, 2008 [source] A modified support vector machine based prediction model on streamflow at the Shihmen Reservoir, TaiwanINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 8 2010Pei-Hao Li Abstract The uncertainty of the availability of water resources during the boreal winter has led to significant economic losses in recent years in Taiwan. A modified support vector machine (SVM) based prediction framework is thus proposed to improve the predictability of the inflow to Shihmen reservoir in December and January, using climate data from the prior period. Highly correlated climate precursors are first identified and adopted to predict water availability in North Taiwan. A genetic algorithm based parameter determination procedure is implemented to the SVM parameters to learn the non-linear pattern underlying climate systems more flexibly. Bagging is then applied to construct various SVM models to reduce the variance in the prediction by the median of forecasts from the constructed models. The enhanced prediction ability of the proposed modified SVM-based model with respect to a bagged multiple linear regression (MLR), simple SVM, and simple MLR model is also demonstrated. The results show that the proposed modified SVM-based model outperforms the prediction ability of the other models in all of the adopted evaluation scores. Copyright © 2009 Royal Meteorological Society [source] Downscaling daily maximum and minimum temperatures in the midwestern USA: a hybrid empirical approachINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2007J. T. Schoof Abstract A new hybrid empirical downscaling technique is presented and applied to assess 21st century projections of maximum and minimum daily surface air temperatures (Tmax, Tmin) over the Midwestern USA. Our approach uses multiple linear regression to downscale the seasonal variations of the mean and standard deviation of daily Tmax and Tmin and the lag-0 and lag-1 correlations between daily Tmax and Tmin based on GCM simulation of the large-scale climate. These downscaled parameters are then used as inputs to a stochastic weather generator to produce time series of the daily Tmax and Tmin at 26 surface stations, in three time periods (1990,2001, 2020,2029, and 2050,2059) based on output from two coupled GCMs (HadCM3 and CGCM2). The new technique is demonstrated to exhibit better agreement with surface observations than a transfer-function approach, particularly with respect to temperature variability. Relative to 1990,2001 values, downscaled temperature projections for 2020,2029 indicate increases that range (across stations) from 0.0 K to 1.7 K (Tmax) and 0.0 K to 1.5 K (Tmin), while increases for 2050,2059 relative to 1990,2001 range from 1.4 K to 2.4 K (Tmax) and 0.8 to 2.2K (Tmin). Although the differences between GCMs demonstrate the continuing uncertainty of GCM-based regional climate downscaling, the inclusion of weather-generator parameters represents an advancement in downscaling methodology. Copyright © 2006 Royal Meteorological Society [source] Impartial graphical comparison of multivariate calibration methods and the harmony/parsimony tradeoffJOURNAL OF CHEMOMETRICS, Issue 11-12 2006Forrest Stout Abstract For multivariate calibration with the relationship y,=,Xb, it is often necessary to determine the degrees of freedom for parsimony consideration and for the error measure root mean square error of calibration (RMSEC). This paper shows that degrees of freedom can be estimated by an effective rank (ER) measure to estimate the model fitting degrees of freedom and the more parsimonious model has the smallest ER. This paper also shows that when such a measure is used on the X-axis, simultaneous graphing of model errors and other regression diagnostics is possible for ridge regression (RR), partial least squares (PLS) and principal component regression (PCR) and thus, a fair comparison between all potential models can be accomplished. The ER approach is general and applicable to other multivariate calibration methods. It is often noted that by selecting variables, more parsimonious models are obtained; typically by multiple linear regression (MLR). By using the ER, the more parsimonious model is graphically shown to not always be the MLR model. Additionally, a harmony measure is proposed that expresses the bias/variance tradeoff for a particular model. By plotting this new measure against the ER, the proper harmony/parsimony tradeoff can be graphically assessed for RR, PCR and PLS. Essentially, pluralistic criteria for fairly valuating and characterizing models are better than a dualistic or a single criterion approach which is the usual tactic. Results are presented using spectral, industrial and quantitative structure activity relationship (QSAR) data. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||||||||