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PubMed2006

[Interrelations between plant communities and environmental factors of wetlands and surrounding lands in mid- and lower reaches of Tarim River].

A total of 16 quadrants of wetlands and surrounding lands in the mid- and lower reaches of Tarim River were surveyed, and the data about the characteristics of plant communities and environmental factors were collected and counted. By using PCA (principal component analysis) ordination and regression procedure, the distribution patterns of plant communities and the relationships between the characteristics of plant community structure and environmental factors were analyzed. The results showed that the distribution of the plant communities was closely related to soil moisture, salt, and nutrient contents. The accumulative contribution rate of soil moisture and salt contents in the first principal component accounted for 35.70%, and that of soil nutrient content in the second principal component reached 25.97%. There were 4 types of habitats for the plant community distribution, i. e., fenny--light salt--medium nutrient, moist--medium salt--medium nutrient, mesophytic--medium salt--low nutrient, and medium xerophytic-heavy salt--low nutrient. Along these habitats, swamp vegetation, meadow vegetation, riparian sparse forest, halophytic desert, and salinized shrub were distributed. In the wetlands and surrounding lands of mid- and lower reaches of Tarim River, the ecological dominance of the plant communities was markedly and unitary-linearly correlated with the compound gradient of soil moisture and salt contents. The relationships between species diversity, ecological dominance, and compound gradient of soil moisture and salt contents were significantly accorded to binary-linear regression model.

Biodiversity↗
PubMedDate not supplied

Regression modelling strategies for improved prognostic prediction.

Regression models such as the Cox proportional hazards model have had increasing use in modelling and estimating the prognosis of patients with a variety of diseases. Many applications involve a large number of variables to be modelled using a relatively small patient sample. Problems of overfitting and of identifying important covariates are exacerbated in analysing prognosis because the accuracy of a model is more a function of the number of events than of the sample size. We used a general index of predictive discrimination to measure the ability of a model developed on training samples of varying sizes to predict survival in an independent test sample of patients suspected of having coronary artery disease. We compared three methods of model fitting: (1) standard 'step-up' variable selection, (2) incomplete principal components regression, and (3) Cox model regression after developing clinical indices from variable clusters. We found regression using principal components to offer superior predictions in the test sample, whereas regression using indices offers easily interpretable models nearly as good as the principal components models. Standard variable selection has a number of deficiencies.

Coronary Disease↗
PubMedDate not supplied

Hemodialysis monitoring in whole blood using transmission and diffuse reflection spectroscopy: A pilot study.

Visible and near infrared transmission and diffuse reflection spectroscopy were used to monitor changes in whole blood resulting from hemodialysis treatment for end-stage renal disease. Blood samples from 8 patients on chronic hemodialysis therapy were measured in the 500- to 1700-nm wavelength range immediately before and after a single treatment. Principal component scores characteristic of each spectrum were derived, and mean pre- and posttreatment scores of the first principal component indicated a significant treatment-dependent change in both optical transmission (P = 0.004) and diffuse reflection (P < 0.001). Significant treatment-induced change persisted (P < 0.05) when the first four principal components were used to account for >97% of the treatment-dependent spectral variation. Some blood spectral changes expressed in terms of difference spectra (posttreatment - pretreatment) were consistent with standard clinical indicators of weight reduction, urea reduction, and potassium change, with probable origins at a molecular level. The results indicate the feasibility of using optical transmission and diffuse reflection spectroscopy to characterize clinically relevant blood changes for the future development of more comprehensive indicators of hemodialysis efficacy and long-term clinical outcomes. Moreover, the optical techniques employed are adaptable for potential online monitoring of blood changes during the hemodialysis treatment.

Adult↗
PubMed2006

Kinematic synergy adaptation to an unstable support surface and equilibrium maintenance during forward trunk movement.

The aim of this investigation was to study the adaptation to an unstable support surface of kinematic synergy responsible for equilibrium control during upper trunk movements. Eight adult subjects were asked to bend their upper trunk forward to an angle of 35 degrees and then to hold the final position for 3 s, first in a standard condition, with two feet on the ground and the second, on a rocking platform swinging in the sagittal plane. The movement characteristics (duration, amplitude, and mean angular velocity of the trunk), the time course of the antero-posterior center of mass (CM) shift during the movement, and the EMG pattern of the main muscles involved in the movement were studied under the two experimental conditions. Kinematic synergy was quantified by performing a principal component analysis on the hip, knee, and ankle angle changes occurring during the movement. The results indicate that (1) the CM shift from the very onset of the movement remains controlled during performance of the forward trunk movement when the equilibrium constraints were increased; (2) the principal component analysis of the hip, knee, and ankle angle changes occurring during the movement showed a transition from one principal component (PC(1)) in the standard condition to two components in the rocking platform condition; (3) the greatest contribution of PC(1) (weight coefficients) was located at the hip level in both the standard and rocking platform conditions, while the greatest contribution of PC(2) in the rocking platform condition was located at the ankle level; and (4) the EMG pattern underlying kinematic synergy is modified. It is concluded that a simple adaptation of kinematic synergy by changing the weight coefficients of each pair of joints participating in the movement is no longer sufficient when the equilibrium constraints increase and, rather, disturbs equilibrium. The CNS has to provide two parallel controls, one to perform the trunk movement and the other to preserve equilibrium.

Adaptation, Physiological↗
PubMed2004

Microhabitat associations and seedling bank dynamics in a neotropical forest.

We conducted a rigorous test of tropical tree seedling microhabitat differentiation by examining microhabitat associations, survival and growth of established seedlings of ten tropical tree species representing a four-factor gradient in seed size. Eight microhabitat variables describing soil and light conditions were measured directly adjacent to each of 588 seedlings within twelve 10x100 m belt transects at Paracou, French Guiana, and at 264 reference points along the transects. From these measurements, we defined three principal components describing soil richness, soil softness and canopy openness. Six of ten species (in 9 of 30 total cases) were distributed non-randomly with respect to microhabitat along at least one principal component. However, few species demonstrated clear microhabitat specialization. All shifts in distribution relative to reference points were in the same direction (richer, softer soil). Furthermore, of 135 pairwise comparisons among the species, only 7 were significantly different. More than three-fourths of all seedlings (75.3%) survived over the 2-year monitoring period, but survival rates varied widely among species. In no case was the probability of survival influenced by any microhabitat parameter. Relative height growth rates for the seedlings over 2 years varied from -0.031 cm cm(-1) year(-1) (Dicorynia guianensis, Caesalpiniaceae) to 0.088 cm cm(-1) year(-1) (Virola michelii, Myristicaceae). In only 4 of 30 cases was height growth significantly associated with one of the three principal components. Because the conditions in this study were designed to maximize the chance of finding microhabitat differentiation among a group of species differing greatly in life history traits, the lack of microhabitat specialization it uncovered suggests that microhabitat partitioning among tropical tree species at the established seedling stage is unlikely to contribute greatly to coexistence among these species.

Ecosystem↗
PubMed2001

Multivariate methods for characterization and classification of espresso coffees from different botanical varieties and types of roast by foam, taste, and mouthfeel.

Three espresso coffee (EC) samples of different botanical varieties and types of roast were prepared in standard conditions using an experimental EC prototype: Arabica coffee, Robusta Natural blend, and Robusta Torrefacto blend (a special roast by adding sugar). The ECs were characterized with regard to the physical parameters, amount of total solids, total solids on filtrate, lipids, caffeine, trigonelline, and chlorogenic acids by HPLC, and sensory descriptive analysis related to foam appearance, taste, and mouthfeel. Principal component analysis (PCA) was applied to differentiate the EC samples. Arabica and Robusta samples were separated successfully by principal component 1 (55.3% of variance) including physicochemical and sensory parameters related to foam and taste of ECs. Torrefacto and Robusta Natural EC samples were separated by principal component 2 (20.7% of total variance) including mouthfeel and other attributes of color foam. Some interesting correlations among sensory and physicochemical variables were found. A very simple discriminate function was obtained by discriminate analysis allowing the classification of each EC sample into its respective group with a success rate of 100%.

Alkaloids↗
PubMed1997

Effect of acarbose on glucose intolerance in patients with non-insulin-dependent diabetes mellitus.

We evaluated the effect of acarbose, an alpha-glucosidase inhibitor, on glucose intolerance in patients with non-insulin-dependent diabetes mellitus (NIDDM). Acarbose was given orally (300 mg/day) for 24 weeks to 20 NIDDM patients. Data in an oral glucose tolerance test (OGTT) were evaluated before and after 24 weeks of treatment using principal component analysis. Acarbose administration significantly reduced the postprandial plasma glucose level over 24 weeks of treatment. Principal component analysis suggested that the patients were separated into responders and non-responders. There was a significant improvement of fasting and postprandial glucose levels after 12 and 24 weeks in the responders, but not in the non-responders. Plasma glucose level following the OGTT improved significantly after 24 weeks of treatment in the responders (Hotelling T2 value = 47.098, P = 0.022500), but not in the non-responders. The immunoreactive insulin level did not change in either group. Results thus suggest that acarbose improved insulin resistance in some patients with NIDDM (responders as classified by principal component analysis).

Acarbose↗
PubMed1990

The effects of generation and gender on the joint distributions of lipid and apolipoprotein phenotypes in the population at large.

The generation and gender effects on the joint distributions of total plasma cholesterol (Total-C), ln triglycerides (lnTrig), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), apolipoproteins AI (Apo AI), AII (Apo AII), and E (lnApo E) were studied in 184 male grandparents (MGP), 242 female grandparents (FGP), 237 male parents (MP), 235 female parents (FP), 202 male children (MC), and 200 female children (FC). Homogeneity of variance tests revealed that lipid variances were gender and/or generation specific while apolipoprotein variances were homogeneous across strata. In the absence of heterogeneity of variance, significant heterogeneity in LDL:lnTrig and lnTrig:Apo AII covariation was found between genders in the parental generation. In the presence of heterogeneity of variance, significant heterogeneity of correlation between genders and/or across generations was found for the HDL-C:LDL-C, Total-C:LDL-C, Total-C:lnTrig, lnTrig:LDL-C, Total-C:lnApo E and HDL-C:lnApo E bivariate distributions. Analyses of principal components revealed that the generation and gender specific cohorts have similar eigenvalues but distinct eigenvectors for the first two principal components underlying the seven dimensional lipid and apolipoprotein distribution. We conclude that the amount of variability explained by the first two principal components is the same across cohorts but how the interindividual variability is distributed among the lipid and apolipoprotein traits is generation and gender specific. This study documents the role that variance and covariance might play in determining risk of disease for special subgroups of the population at large. It also demonstrates how variances and covariances between risk factors traits characterize life processes of aging and sexual dimorphism. This study argues that future biometrical genetic and epidemiological studies of coronary artery disease must take into account age and gender effects on interindividual variability and covariability of risk factors.

Adult↗
PubMed2005

A study of genetic association with electrophysiological measures related to alcoholism: GAW14 data.

Recently, alcohol-related traits have been shown to have a genetic component. Here, we study the association of specific genetic measures in one of the three sets of electrophysiological measures in families with alcoholism distributed as part of the Genetic Analysis Workshop 14 data, the NTTH (non-target case of Visual Oddball experiment for 4 electrode placements) phenotypes: ntth1, ntth2, ntth3, and ntth4. We focused on the analysis of the 786 Affymetrix markers on chromosome 4. Our desire was to find at least a partial answer to the question of whether ntth1, ntth2, ntth3, and ntth4 are separately or jointly genetically controlled, so we studied the principal components that explain most of the covariation of the four quantitative traits. The first principal component, which explains 70% of the covariation, showed association but not genetic linkage to two markers: tsc0272102 and tsc0560854. On the other hand, ntth1 appeared to be the trait driving the variation in the second principal component, which showed association and genetic linkage at markers in four regions: tsc0045058, tsc1213381, tsc0055068, and tsc0051777 at map distances 53.26, 85.42, 89.31, and 172.86, respectively. These results show that the partial answer to our starting question for this brief analysis is that the NTTH phenotypes are not jointly genetically controlled. The component ntth1 displays marked genetic linkage.

Alcoholism↗
PubMed2004

Dimensions of oral-health-related quality of life.

Oral-health-related quality of life (OHRQoL) is expected to have multiple dimensions. It was the aim of this study to investigate the dimensional structure of OHRQoL measured by the Oral Health Impact Profile (German version) (OHIP-G) and to derive a summary score for the instrument. Subjects (N = 2050; age, 16-79 yrs) came from a national survey. We used rotated principal-components analysis to derive a summary score and to explore the dimensional structure of OHIP-G. The first principal component explained 50% of the variance in the data. The sum of OHIP-G item responses was highly associated with the first principal component (r = 0.99). This simple but informative OHIP-G summary score may indicate that simple sums are also potentially useful scores for other OHRQoL instruments. Four dimensions (psychosocial impact, orofacial pain, oral functions, appearance) were found. These OHIP-G dimensions may serve as a parsimonious set of OHRQoL dimensions in general.

Adolescent↗
PubMed1996

[Phenotypic plasticity of wing size and shape in Drosophila melanogaster and D. simulans].

Variation of 13 morphometric wing characters in relation to temperature of development was studied in two sibling species Drosophila melanogaster and D. simulans. Three principal components that accounted for 73% of variation of these characters were identified. The first component was interpreted as general wing size, while the second and third components described wing shape. Temperatures of maximal wing size and temperatures corresponding to the highest values of the third principal component (proximal-distal ratio) were different in the species studied. In each of the species, reaction norm curves of the three-principal components were different, indicating qualitative differences between reaction norms of characters belonging to the same organ. Variances of both general wing size and shape were different at different temperatures. Variance of general wing size was lower at intermediate temperatures and higher at high and low temperatures. Correlations between wing measurements were significantly different at different temperatures.

Adaptation, Physiological↗
PubMed2006

Changes in headspace volatile concentrations of coffee brews caused by the roasting process and the brewing procedure.

Headspace-solid-phase microextraction technique (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O) were used to characterize the aroma compounds of coffee brews from commercial conventional and torrefacto roasted coffee prepared by filter coffeemaker and espresso machine. A total of 47 volatile compounds were identified and quantified. Principal component analysis (PCA) was applied to differentiate coffee brew samples by volatile compounds. Conventional and torrefacto roasted coffee brews were separated successfully by principal component 1 (68.5% of variance), and filter and espresso ones were separated by principal component 2 (19.5% of variance). By GC olfactometry, a total of 34 aroma compounds have been perceived at least in half of the coffee extracts and among them 28 were identified, among which octanal was identified for the first time as a contributor to coffee brew aroma.

Coffee↗
PubMed2006

Raman mapping of low-content API pharmaceutical formulations. I. Mapping of Alprazolam in Alprazolam/Xanax tablets.

PURPOSE: Raman chemical imaging of API was carried out to provide information on whether there is any structural difference between the commercial Xanax and Alprazolam tablets (the API content less than 1% w/w in both cases) in the batches with low and good recovery. MATERIALS AND METHODS: Raman mapping spectra were collected from the flattened surfaces of six tablets. The mapping spectra were analyzed by principal component analysis because the Raman signal of the API (Alprazolam) was not reliably detected from the raw spectra. The complexity of the obtained grey-scale score images was such that no information about the domain sizes of the API could be obtained and thus binarization was applied to simplify these images. RESULTS: It was found that reliable detection of the Raman signal of the API was only achieved after principal component analysis was employed with the mapping being facilitated by a surprising similarity between a high principal component loading and the spectrum of the API. The binarization was successful only if the outlying pixels in the score images are eliminated. SUMMARY: The final chemical images represent quantitative characterization of the domains of the API in the tablets in contrast to chemical images of tablets that have been reported so far in the literature which have usually been descriptive only. The abundance of Alprazolam in all six tablets of Xanax and Alprazolam, respectively, was very similar. The domain sizes were found to be below 75 mum in diameter for all the tablets analyzed.

Alprazolam↗
PubMed2007

Application of fluorescence spectroscopy for monitoring changes in nonfat dry milk during storage.

The objective of this study was to determine if fluorescence spectroscopy could be used to characterize the biochemical characteristics of nonfat dry milk (NDM) caused by manufacturing and storage conditions. Nine low-heat NDM samples were collected from 3 manufacturers and stored at 4 temperatures (4, 22, 35, and 50 degrees C) for 8 wk. The spectra of Maillard products, tryptophan, and riboflavin were recorded and analyzed with principal components analysis. Colorimetric indices L*, a*, and b* were also determined. The before-storage NDM samples collected from each manufacturer had different fluorescent characteristics. Inconsistency was observed for the NDM samples collected from 1 manufacturer, whereas the samples from the other 2 manufacturers displayed consistent fluorescence characteristics. Biochemical reactions, such as Maillard reaction, modification of the tryptophan environment, and degradation of riboflavin occurred during the manufacturing process. For each of the data collections, discrimination of the NDM samples stored at 50 degrees C from the samples stored at 4, 22, and 35 degrees C was observed in the similarity maps. The factor loadings of the first 2 principal components for the fluorescence spectra of the samples before storage were similar to the principal components analysis results of the samples during storage. It appears that similar factors are responsible for the variation in the samples before storage and their changes during storage. Additionally, storage of the samples at 50 degrees C accelerated these reactions. The results demonstrate that front-face fluorescence spectroscopy, coupled with multivariate statistical methods, can be utilized as an analytical technique to monitor variation in NDM samples from different manufacturers and changes during storage.

Animals↗
PubMed1991

[Addition to the article by Iu. E. Dubrova et al. "Influence of heterozygosity on the variation of anthropometric traits in newborns." Determination of intersample differences by covariation and correlation statistics].

Relationships between heterozygosity of 13 polymorphic loci and variation of the set of anthropometric traits were studied in 302 singleton newborns (174 boys, 128 girls). Statistically significant correlation between heterozygosity and all traits were not found. Variances of four traits--body weight, body length, circumference of head and breast measured by first principal component decrease with increase of heterozygosity in boys and girls. At the same time, variance of body proportions (second principal component) increase significantly in boys only. The highest values of correlation between four traits were found in the group of low heterozygous boys. The groups of newborns with different level of heterozygosity are characterized by different combinations of first principal component and the number of minor deviations from development (stigma). It is concluded from the whole set of data that newborn boys with the average level of heterozygosity have the highest level of viability.

Anthropometry↗
PubMed2006

Four symptom dimensions in outpatients with schizophrenia.

OBJECTIVE: The aim of this study was to assess the dimensional structure of the Positive and Negative Symptoms Scale (PANSS) to identify the psychopathological profiles of outpatients with schizophrenia. METHOD: Two hundred and thirty-one persons with schizophrenia (DSM-IV criteria) were randomly selected from a register that included all patients under treatment in 5 mental health care centers in Spain. Patients were evaluated with a sociodemographic and clinical questionnaire, the PANSS, the Disability Assessment Scale short version, and the Global Assessment Functioning Scale. A principal component analysis with oblimin rotation was used to examine the factor structure of the PANSS. Different statistical analyses were done to compare the resulting factors with clinical, disability, and social functioning variables. RESULTS: Mean age of patients included was 39.6 years and approximately 65% were male. Four principal components, each of them with eigenvalues greater than 1.5, accounted for 56.22% of the variance. After oblimin rotation, these factors were identified as the Negative (32.48%), Excitement (11.29%), Affective (7.45%), and Positive (5.01%) components. Significant positive correlation between age and the negative dimension was found. Also, we observed significant negative correlations between global assessment functioning and negative and positive dimensions. Total disability was significantly positively related to all dimensions. CONCLUSION: Positive and negative dimensions are common in all principal component analysis results, but we also found affective and excitement dimensions. The present finding suggests that further investigation of symptom dimensions may help to improve symptom-specific treatments; future research should focus on the design of new treatment programs considering these results.

Adolescent↗
PubMed2004

Sperm subpopulations in Iberian red deer epididymal sperm and their changes through the cryopreservation process.

We have applied a statistical protocol based on principal component analysis, clustering methods, and discriminant analysis for the identification of sperm subpopulations in computer-assisted sperm analysis (CASA) data. Samples were obtained from the cauda epididymis of 11 Iberian red deer and cryopreserved following a standard protocol. Motility by CASA was analyzed just after sperm recovery, just before freezing, and after thawing, and eight motility descriptors for each individual spermatozoon were recorded. Sperm viability and acrosomal status were also assessed. Subpopulation analysis was performed in four sequential steps: principal component analysis using the eight motility descriptors; nonhierarchical clustering analysis (k-means) using the first two principal components; hierarchical clustering analysis (UPGMA); and selection of the final number of clusters. Three clusters were obtained for each motility analysis: slow and nonlinear; rapid and linear; and rapid, high ALH, nonlinear. We detected variations in the clusters between treatments (initial, prefreezing and postthawed). Indeed, motility increased and linearity decreased in the prefreezing analysis. A discriminant analysis isolated three descriptors that were used again in the same statistical analysis, giving four clusters that resembled the pattern found in the first classification. We also performed a clustering analysis of the males according to prefreezing/postthawed variation of total motility, viability, and acrosomal status. The proportion of the linear subpopulations in the prefreezing treatment, in both clustering analyses, correlated positively with postthawed viability recovery. Our results show that clustering analysis of CASA data gives useful and practical information that is not obtained by conventional sperm analysis.

Acrosome↗
PubMed2002

Genetic evidence for the phylogenetic relationship between Na-Dene and Yeniseian speakers.

Ruhlen's hypothesis, based on linguistic evidence, for a common phylogenetic origin of Na-Dene and Yeniseian speakers is tested using genetic data. Gene frequency data for the Kets, the only surviving Yeniseian speakers, were collected during a field study in 1993. Data for several Na-Dene groups, as well as other New World and Siberian populations, were compiled from the literature. These data were analyzed using R-matrix, principal components analysis, and Mantel tests. In a comparison of 10 New World and Siberian populations using eight alleles, 55.8% of the variation was accounted for by the first principal component, and 22.1% of the variation was subsumed by the second principal component. Contrary to Ruhlen's interpretation of the linguistic data, analysis of the genetic data shows that the Na-Dene cluster with other Native American populations, while the Kets genetically resemble the surrounding Siberian groups. This conclusion is further supported by correlations that are higher when the Kets are considered unrelated to Na-Dene speakers, and an insignificant partial correlation between genes and language when geography is held constant, indicating that spatial patterning accounts for most of the variation present in these populations.

Alleles↗