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Results for “cluster analysis”

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PubMed2001

Subtypes of clinical presentations in malingerers of posttraumatic stress disorder: an MMPI-2 cluster analysis.

This paper investigated subtypes of individuals trained and instructed to malinger Posttraumatic Stress Disorder (PTSD) through a cluster analysis of their Minnesota Multiphasic Personality Inventory-2 (MMPI-2) clinical and validity scales. Participants were 84 men and women college students at a community college in the southeastern United States. Two well fitting MMPI-2 cluster solutions were evaluated with discriminant analyses and multivariate analyses of variance (MANOVAs); a 2-cluster solution was deemed optimal. Significant between-cluster differences emerged in follow-up analyses on most of the content scales of the MMPI-2. Most demographic variables did not account for differences in cluster membership. Clusters differed in their reported clarity of the materials used to educate them about PTSD. Discriminant analyses yielded better correct classification rates than those from previous studies, when the more severely symptomatic cluster was compared with a sample of clinical combat-related PTSD veterans. Implications are considered in conducting future malingered PTSD investigations.

Adolescent↗

PubMed1992

Obstructive sleep apnea subtypes by cluster analysis.

A sample of 84 adult male patients with obstructive sleep apnea (OSA) were classified by a cluster analysis on the basis of apnea index (AI) and body mass index (BMI). Demographic, cephalometric, tongue, soft palate, and upper airway-size data were evaluated for the two subgroups of OSA patients and for 18 control subjects. One OSA group consisted of 43 patients with a high AI and low BMI ratio, the other group was comprised of 41 patients with a low AI and high BMI ratio. The patients with a high AI and low BMI ratio had retruded mandibles with high mandibular plane angles and proclined lower incisors. The patients with a low AI and high BMI ratio had inferior hyoid bones and large soft palates. A multiple regression analysis was performed between AI (the dependent variable) and the other variables (independent variables) for each of the subgroups. In the patients with a high AI and low BMI ratio, a high AI was related to a large skeletal anteroposterior discrepancy, a steep mandibular plane, and an inferoanterior position of the hyoid bone. In the patients with a low AI and high BMI ratio, a high AI was related to a large tongue and a small upper airway. In both groups, BMI was the major contributor to AI. In conclusion, these two groups may represent distinct subgroups of OSA patients and provide some insight into the contribution of obesity to the pathogenesis of OSA. The patients with a high AI and low BMI ratio have a skeletal mismatch, whereas the patients with a low AI and high BMI have atypical soft tissue structures.

Body Mass Index↗

PubMed2004

Microdosimetric analysis of various mammography spectra: lineal energy distributions and ionization cluster analysis.

In view of recent recommendations on the frequency and the starting age of mammography screening in healthy women, it is desirable to quantify the enhanced relative biological effectiveness (RBE) of mammography X rays compared to hard X rays. While there is little doubt that the former are more potent in inducing biological damage than the latter, the magnitude of the effect is still hotly debated in the literature. We used Monte Carlo simulations and track structure analysis in micrometer and nanometer volumes to investigate differences in distributions of lineal energy and ionization clusters for a range of mammography X-ray qualities. Dose-averaged lineal energies, (yD), in breast tissue for various mammography qualities were found to result in quality factors about 40% higher than unity. Among the various mammography qualities studied, the popular molybdenum/molybdenum target/filter combination was found to have the highest (yD) in 1-microm spheres (about 5.0 keV/microm near the entrance surface of breast tissue). In 10-nm radius spheres, the mean ionization cluster order was found to be about 35% higher in mammography X rays compared to 300 keV electrons (roughly representing 60Co or 192Ir photon radiation). In even smaller spheres (2 nm radius), no significant differences were observed for the mean ionization cluster order between mammography X rays and 300 keV electrons. We conclude that the potential of mammography X rays to induce biological damage is probably not much higher than a factor of two compared to hard X rays.

Breast↗

PubMed1994

Grouping of somatosensory neurons in the spinal cord and the gracile nucleus of the rat by cluster analysis.

1. A set of 11 cutaneous stimuli defined previously to differentiate among different types of cutaneous sensory receptors in the rat hindpaw was also effective in differentially activating second-order sensory neurons in the dorsal horn and the gracile nucleus of rats. 2. All sampled units were responsive to more than 1 of the 11 stimuli. However, none responded to innocuous warming or cooling stimuli. Therefore further analysis was restricted to responses to nine of the selected stimuli. 3. Cluster analysis of the responses to nine selected innocuous and noxious mechanical stimuli and noxious thermal stimuli yielded seven classes that seemed functionally distinct from each other: a class of high-threshold neurons, three classes of convergent (wide dynamic range) neurons, a class of a mixture of poorly responsive neurons and neurons receiving Pacinian inputs, and two classes of low-threshold neurons. 4. High-threshold neurons responded predominantly to noxious mechanical and thermal stimuli and presumably received an input from both mechanically and thermally sensitive nociceptors. These cells were located in the dorsal horn, and some were spinothalamic tract cells. Wide dynamic range neurons were excited by innocuous and noxious stimuli, but better by noxious stimuli. These classes of cells were either in the dorsal horn (some were spinothalamic tract cells) or in the nucleus gracilis.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗

PubMed2003

Toward an empirical taxonomy of suicide ideation: a cluster analysis of the youth risk behavior survey.

In this study we examined adolescent risk behaviors, giving special attention to suicide ideation. Cluster analysis was used to classify adolescents (N = 2,730) on the Youth Risk Behavior Survey. Six clusters of adolescent risk behavior were identified. Although each risk cluster was distinct, some clusters shared overlapping risk behaviors. Suicide ideation was central to two clusters: the Silent Suicide cluster and the Multiple Risk cluster. The findings demonstrate that suicide ideation is both a unique risk behavior for some adolescents and part of a generalized risk syndrome for other adolescents. A multiple subgroup framework is recommended for understanding adolescent risk behaviors.

Adolescent↗

PubMed1995

Hydrophobic cluster analysis predicts an amino-terminal domain of varicella-zoster virus open reading frame 10 required for transcriptional activation.

Varicella-zoster virus open reading frame 10 (ORF10) protein, the homolog of the herpes simplex virus protein VP16, can transactivate immediate-early promoters from both viruses. A protein sequence comparison procedure termed hydrophobic cluster analysis was used to identify a motif centered at Phe-28, near the amino terminus of ORF10, that strongly resembles the sequence of the activating domain surrounding Phe-442 of VP16. With a series of GAL4-ORF10 fusion proteins, we mapped the ORF10 transcriptional-activation domain to the amino-terminal region (aa 5-79). Extensive mutagenesis of Phe-28 in GAL4-ORF10 fusion proteins demonstrated the importance of an aromatic or bulky hydrophobic amino acid at this position, as shown previously for Phe-442 of VP16. Transactivation by the native ORF10 protein was abolished when Phe-28 was replaced by Ala. Similar amino-terminal domains were identified in the VP16 homologs of other alphaherpesviruses. Hydrophobic cluster analysis correctly predicted activation domains of ORF10 and VP16 that share critical characteristics of a distinctive subclass of acidic activation domains.

Amino Acid Sequence↗

PubMed1990

Weak sequence homologies among chitinases detected by clustering analysis.

The amino acid sequences of various endo-N-acetyl-glucosaminidases (chitinases) have been subjected to hydrophobic cluster analysis. A domain of approximately 145 residues was found to be weakly conserved in chitinase A and B from the bacterium Serriata marcescens, in a chitinase from cucumber (Cucumis sativis) and in the endo-N-acetyl-glucosaminidase H of Streptomyces plicatus. A prediction of the putative active site region was made upon analysis of invariant acidic amino acids. On the basis of primary structure homologies, a classification into families of structurally related proteins is proposed for the enzymes hydrolyzing beta-1,4-N-acetyl-glucosamine linkages.

Acetylglucosamine↗

PubMed2006

A cluster analysis investigation of workaholism as a syndrome.

Workaholism has been conceptualized as a syndrome although there have been few tests that explicitly consider its syndrome status. The authors analyzed a three-dimensional scale of workaholism developed by Spence and Robbins (1992) using cluster analysis. The authors identified three clusters of individuals, one of which corresponded to Spence and Robbins's profile of the workaholic (high work involvement, high drive to work, low work enjoyment). Consistent with previously conjectured relations with workaholism, individuals in the workaholic cluster were more likely to label themselves as workaholics, more likely to have acquaintances label them as workaholics, and more likely to have lower life satisfaction and higher work-life imbalance. The importance of considering workaholism as a syndrome and the implications for effective interventions are discussed.

Adult↗

PubMed2002

Statistical evaluation of morphological data of Japanese head hair and the screening of evidential hair samples by cluster analysis.

Intra-individual and inter-individual variations in Japanese head hair morphology were reevaluated and the screening of evidential hair samples using a statistical method was investigated. A quantification of the morphological data was used as a system in which morphological features obtained by macroscopic and microscopic observations can be objectively processed in the form of numerical information. For confirming the availability of morphological features for hair comparison, the inter-individual comparison of ten male Japanese was investigated by discrimination analysis using 18 variables including five original numerical morphological features (variables) and 13 variables obtained from six morphological features by quantification. The majority of the comparisons showed a high level of discrimination between two individuals. For morphologically narrowing down the number of evidential hair samples collected from a crime scene, a screening method was investigated by cluster analysis using 18 variables. In an experimental model of evidential hair samples derived from 20 individuals, hair samples from 13 individuals were successfully discriminated using the cluster analysis described in the present investigation.

Journal Article↗

PubMed2003

Protein-protein and protein-function relationships in Arabidopsis photosystem I: cluster analysis of PSI polypeptide levels and photosynthetic parameters in PSI mutants.

In flowering plants, photosystem I (PSI) mediates electron transport across the thylakoid membrane and contains at least 14 proteins. The availability of co-suppression and/or mutant lines deficient for individual PSI polypeptides in Arabidopsis thaliana allows one to assign functions to PSI subunits. We have performed cluster analysis on an extensive set of data on PSI polypeptide levels in ten different PSI mutants. This type of analysis serves to group proteins that exhibit similar changes in amount in different genotypes, and also identifies genotypes which show similar PSI compositions. The interdependence of levels of PSI-C, -D and -E, of -H and -L, and of Lhca2 and 3, which was previously proposed based on the study of single genotypes or on cross-linking experiments, was confirmed by our analyses. In addition, the levels of the lumenal subunits F and N are found to be interdependent. The incorporation of photosynthetic parameters into the cluster analysis revealed that the level of photosynthetic state transitions correlates with the abundance of PSI-H in all 8 genotypes tested, supporting the hypothesis that PSI-H serves as a docking site for LHCII during state transitions.

Arabidopsis↗

PubMed1994

Cluster analysis of adult children of alcoholics.

To determine if adult children of alcoholics (ACOA) are heterogeneous with respect to personality characteristics, 97 ACOAs took the California Psychological Inventory (CPI), and the results were analyzed through cluster analysis techniques. The resulting three-cluster solution showed that, in one subgroup (44%), all CPI scales were at or above the mean; another subgroup (40%) achieved scores at or slightly below the mean; and the third subgroup's (16%) scores were considerably below the mean. Therefore, clinical claims regarding ACOAs may only be accurate for a small proportion of ACOAs. Research on resiliency in children may explain why many ACOAs have normal personality profiles.

Adaptation, Psychological↗

PubMed1992

Coverage of widely separate defects of the lower extremity: application of cluster analysis.

A patient with lower extremity reconstruction is presented with a radial forearm free flap designed using the cluster analysis method of cutaneous perforators. The cutaneous vascular anatomy of fasciocutaneous flaps is discussed as well as the application of the mathematical model of analysis of the vascular territories within specific flaps to assist in "custom" flap design. The ultimate goal of this technique is the creation of flaps that provide a more precise and anatomical reconstruction of the proposed defect.

Adult↗

PubMedDate not supplied

Cluster analysis of apoptosis-associated bcl2 family proteins in diffuse large B-cell lymphomas. Relations with the apoptotic index, the proliferation profile and the B-cell differentiation immunophenotypes.

BACKGROUND: There is evidence that apoptotic mechanisms mediated by bcl2 family proteins are involved in the pathogenesis of diffuse large B-cell lymphomas (DLBCL). In order to gain further insight into the apoptosis profile of DLBCL, 79 cases were investigated to determine whether distinct clusters of the combined expression levels of bcl2 family proteins can be identified in these lymphomas. MATERIALS AND METHODS: The combined immunohistochemical expression levels of the proteins bax, bak, bad, bid, bcl2 and bcl-xl were evaluated by cluster and discriminant analysis. The produced clusters were analyzed in relation to the apoptotic index, the proliferation profile and the B-cell differentiation immunophenotypes. RESULTS: Cluster analysis produced: a) a low expression (69/79 cases) and a high expression pro-apoptotic cluster (10/79 cases) for the combined expression levels of the pro-apoptotic proteins bax, bak, bad and bid and b) a low expression (37/76 cases) and a high expression antiapoptotic cluster (39/76 cases) for the combined expression levels of anti-apoptotic proteins bcl2 and bcl-xl. The decreasing order of discriminant power for the percentages of tumor cells expressing pro-apoptotic and anti-apoptotic proteins was % bax + cells> % bak+ cells> % bid+ cells> % bad+ cells and % bcl2+ cells> % bcl-xl+ cells, respectively. The high expression pro-apoptotic cluster was significantly associated with higher mean values of Ki67 (p=0.047) and cyclin A (p=0.033) expression. The high expression pro-apoptotic cluster was significantly associated with the germinal center B-cell bc16/CD10/MUM1/CD138 differentiation immunophenotype (p=0.043). CONCLUSION: This study identified distinct clusters of DLBCL with respect to the combined expression levels of the apoptosis-associated bcl2 family proteins. These findings, taken together with our previous observations that distinct clusters with respect to the apoptotic index and the proliferation profile are identified in DLBCL, indicate that subgroups with distinct cellular kinetic properties can be defined in these lymphomas. The cluster analysis approach might be useful for the identification of subgroups of DLBCL with different clinical behavior since increased proliferation and apoptosis were reported to be associated with aggressive tumor behavior in these lymphomas.

Apoptosis↗

PubMed1990

Market segmentation for multiple option healthcare delivery systems--an application of cluster analysis.

Healthcare providers of multiple option plans may be confronted with special market segmentation problems. This study demonstrates how cluster analysis may be used for discovering distinct patterns of preference for multiple option plans. The availability of metric, as opposed to categorical or ordinal, data provides the ability to use sophisticated analysis techniques which may be superior to frequency distributions and cross-tabulations in revealing preference patterns.

Cluster Analysis↗

PubMed1994

[Application of cluster analysis to chemical identification of the drugs from fruits of Zingiberaceae].

The present paper deals with an application of cluster analysis to the chemical identification of the drugs from fruits of Zingiberaceae. Thirty numerical characters were obtained from thin layer chromatograms of volatile oils and flavonoids. The coefficient of Seuclid was used to show quantitative index of similarities among the samples. By methods of systematic cluster, 4 dendrograms from each method were created respectively. The results show that the fruit drugs from Amomum are similar to each other, but different from those from Alpinia; the results from median method are in accordance with the classification of fruit drugs from Zingiberaceae by their traditional effects. This paper may be helpful in seeking new resources as well as in identifying the fruit drugs from Zingiberaceae.

Chromatography, Thin Layer↗

PubMed1998

Cluster analysis of the genetic heterogeneity and disease distributions in purebred dog populations.

Purebred dog populations have been subject to strong selection which has resulted in extreme differences between breeds and decreased heterogeneity within breeds. As a result, breed-specific inherited diseases have accumulated in many populations. The aim of this study was to analyse genetic heterogeneity in relation to the distribution of elbow dysplasia in labrador retrievers, portosystemic shunts in Irish wolfhounds, and hepatic copper toxicosis, in Bedlington terriers. Decreased heterogeneity was demonstrated in the multiple genetic interrelations in the three populations. In pedigrees containing seven generations of ancestors, the average number of common ancestors in all pair-wise combinations of dogs was five to six (range 0 to 18). These complex interrelationships were resolved by a cluster analysis on matrices of relatedness. This analysis gave clusters of highly related animals, the average relatedness of these clusters, and the average relatedness of the entire population, as expressions of its genetic variability. The mean relatedness was 0.032 for Irish wolfhounds and Bedlington terriers, and 0.002 for labrador retrievers. The labrador retriever cohort was resolved into 31 clusters, and all cases of elbow dysplasia were concentrated in five highly related clusters with an overall incidence of 17 per cent. The Bedlington terrier cohort consisted of 12 clusters which all contained cases of copper toxicosis, with an overall incidence of 46 per cent. The Irish wolfhounds were divided into 14 clusters with a disease incidence of 4 per cent. Dogs with portosystemic shunts were found in four averagely related clusters. A genetic distribution became obvious only when relatedness due to common ancestors of the cases was used as a criterion, and the cases were then concentrated in five highly related clusters.

Animals↗

PubMed2000

[Styles of interpersonal conflict in patients with panic disorder, alcoholism, rheumatoid arthritis and healthy controls: a cluster analysis study].

OBJECTIVE: Conflict and conflict resolution in intimate relationships are not only among the most important factors influencing relationship satisfaction but are also seen in association with clinical symptoms. Styles of conflict will be assessed in patients suffering from panic disorder with and without agoraphobia, in alcoholics and in patients suffering from rheumatoid arthritis. METHODS: 176 patients and healthy controls filled out the Styles of Conflict Inventory and questionnaires concerning severity of clinical symptoms. RESULTS: A cluster analysis revealed 5 types of conflict management. Healthy controls showed predominantely assertive and constructive styles, patients with panic disorder showed high levels of cognitive and/or behavioral aggression. Alcoholics showed high levels of repressed aggression, and patients with rheumatoid arthritis often did not exhibit any aggression during conflict. CONCLUSIONS: 5 Clusters of conflict pattern have been identified by cluster analysis. Each patient group showed considerable different patterns of conflict management.

Adult↗

PubMed2000

A multistep unsupervised fuzzy clustering analysis of fMRI time series.

A paradigm independent multistage strategy based on the Unsupervised Fuzzy Clustering Analysis (UFCA) and its potential for fMRI data analysis are presented. The influence of the fuzziness index is studied using Receiver Operating Characteristics (ROC) methodology and an interval of choice, around the widely used value 2, is shown to yield the best performance. The ill-balanced data problem is also overcome using a pre-processing step to reduce the number of voxels presented to the method. Statistical and anatomical criteria are proposed to exclude some voxels and enhance the UFCA sensitivity. An original postprocessing step aiming at statistically characterizing the obtained clusters is also developed. Two similarity criteria are used: the correlation coefficient on temporal profiles and a novel fuzzy overlap coefficient on membership degree maps. This final step provides a useful analysis tool to study intra-individual reproducibility of the classes across series (stimulation vs. stimulation, noise vs. noise or stimulation vs. noise). Finally, a comparison between this technique and some existing or locally developed postprocessing algorithms is presented using ROC methods. Its sensitivity and robustness is compared to the classical FCA or other techniques as a function of several parameters such as Contrast-to-Noise Ratio (CNR) and noise amplitude. Even without knowledge about the paradigm, the hemodynamic response function and the number of clusters, the performances of the proposed strategy are comparable to those of the classical approaches where extensive prior knowledge has to be added.

Algorithms↗