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PubMed2005

Finite element analysis in functional morphology.

This article reviews the fundamental principles of the finite element method and the three basic steps (model creation, solution, and validation and interpretation) involved in using it to examine structural mechanics. Validation is a critical step in the analysis, without which researchers cannot evaluate the extent to which the model represents or is relevant to the real biological condition. We discuss the method's considerable potential as a tool to test biomechanical hypotheses, and major hurdles involved in doing so reliably, from the perspective of researchers interested in functional morphology and paleontology. We conclude with a case study to illustrate how researchers deal with many of the factors and assumptions involved in finite element analysis.

Anatomy↗

PubMed2001

Development of a patient-orientated instrument to measure service quality in outpatient departments.

AIMS OF THE STUDY: To describe three stages in the development of an instrument to measure service quality from the patients' perspective in hospital outpatient departments. RATIONALE: A reliable and valid service quality instrument is a valuable tool for collecting feedback from patients when improving outpatient services. DESIGN: A multiphase process with several versions of the questionnaire testing its validity and reliability. The first version of the questionnaire was constructed from information collected in a previous interview study of patients' service experiences. Using this version (47 questions) information was collected in 15 outpatient departments (314 patients) and the second version of the questionnaire was developed. At this stage, a survey of employees (n=111) was included in the development process. This second version of the questionnaire (43 questions) was used to collect more data in three outpatient departments of a university hospital and in two outpatient departments of two regional hospitals on three different occasions (1416, 369 and 124 patients) within a period of 2 years. The reliability of the instrument was tested in terms of stability by using three repeated measurements, and using the Cronbach's alpha coefficient as an indicator of internal consistency. Content validity was assessed by means of percentage agreement between staff and patients. Logistic regression analysis was performed to assess construct validity. RESULTS: The final version of the questionnaire contained 12 items. Agreement between patient and staff ratings was found to be acceptable for most questions (content validity). Two measurements on different occasions yielded a similar structure (construct validity). Internal consistency was acceptable (Cronbach's alpha = 0.67-0.93 in the first and 0.71-0.94 in the second survey). The variance of the alpha coefficients was small in the retest (stability). CONCLUSIONS: The instrument developed is general to the extent that it is suitable for assessing service quality improvement needs in individual units and for making cross-departmental comparisons.

Adult↗

PubMed2003

The crystallographic model of rhodopsin and its use in studies of other G protein-coupled receptors.

G protein-coupled receptors (GPCRs) are integral membrane proteins that respond to environmental signals and initiate signal transduction pathways activating cellular processes. Rhodopsin is a GPCR found in rod cells in retina where it functions as a photopigment. Its molecular structure is known from cryo-electron microscopic and X-ray crystallographic studies, and this has reshaped many structure/function questions important in vision science. In addition, this first GPCR structure has provided a structural template for studies of other GPCRs, including many known drug targets. After presenting an overview of the major structural elements of rhodopsin, recent literature covering the use of the rhodopsin structure in analyzing other GPCRs will be summarized. Use of the rhodopsin structural model to understand the structure and function of other GPCRs provides strong evidence validating the structural model.

Amino Acid Motifs↗

PubMed1998

Interrater agreement among psychiatrist in psychiatric emergency assessments.

OBJECTIVE: The authors' purpose in this study was to investigate the interrater agreement among psychiatrists in psychiatric emergency service settings. The interrater reliability of many of the key concepts in psychiatric emergency service settings has not been studied. METHOD: Videotapes of 30 psychiatric emergency service patient assessment interviews conducted by psychiatrists were shown to eight experienced psychiatric emergency service psychiatrists. The eight psychiatrists rated each videotape on dimensions such as severity of depression and psychosis and recommended a disposition for each patient. Interrater reliability was then explored. RESULTS: The level of agreement (intraclass correlation coefficient) among the reviewing psychiatrists was higher for psychosis and substance abuse but lower for psychopathology, impulse control problems, danger to self, and disposition. The reviewers' disposition recommendations did not match well with the assessing psychiatrist's actual disposition, but comparisons with actual practice should be considered only suggestive. CONCLUSIONS: Psychiatric emergency service assessments need improvement. This may be accomplished by exploring the underlying structure of psychiatric emergency service concepts, the creation and validation of structured assessment tools, and the creation of practice guidelines.

Adult↗

PubMedDate not supplied

[Construction and validation of visual analogue scale for risk assessment].

This paper describes the factor structure and validity of a visual analogue scale designed to rate risk proneness: EVAR (EVAluation of Risk). Risk behaviors and sensation seeking are related, therefore we correlated EVAR (24 100 mm items) with Zuckerman Sensation Seeking Scale (SSS) (40 conventional items) in a population of 199 volunteers. Subjects had an age range of 18-68 years (mean age of 31), and 49 were females. Factor analysis using a principal component solution and an orthogonal rotation of the factor matrix were computed. Five factors were selected, accounting for 46 per cent of the total variation: F1 "self control", F2 "danger seeking", F3 "energy", F4 "impulsiveness", F5 "invincibility". F1, F2 and F3 from EVAR were correlated with SSS factors "general", "danger seeking", "experience seeking" and "boredom susceptibility". F4 was correlated with "general", "boredom susceptibility" and "disinhibition" whereas F5 was not correlated with any of SSS factors. This visual analogue scale is likely to reveal change in subjects, regarding risk proneness, when submitted to various stressors (sleep deprivation, fatigue...).

Adolescent↗

PubMedDate not supplied

The Depression Interview and Structured Hamilton (DISH): rationale, development, characteristics, and clinical validity.

OBJECTIVE: The Depression Interview and Structured Hamilton (DISH) is a semistructured interview developed for the Enhancing Recovery in Coronary Heart Disease (ENRICHD) study, a multicenter clinical trial of treatment for depression and low perceived social support after acute myocardial infarction. The DISH is designed to diagnose depression in medically ill patients and to assess its severity on an embedded version of Williams' Structured Interview Guide for the Hamilton Depression scale (SIGH-D). This article describes the development and characteristics of the DISH and presents a validity study and data on its use in ENRICHD. METHODS: In the validity study, the DISH and the Structured Clinical Interview for DSM-IV (SCID) were administered in randomized order to 57 patients. Trained interviewers administered the DISH, and clinicians administered the SCID. In ENRICHD, trained research nurses administered the DISH and recorded a diagnosis. Clinicians reviewed 42% of the interviews and recorded their own diagnosis. The Beck Depression Inventory (BDI) was administered in both studies. RESULTS: In the validity study, the SCID diagnosis agreed with the DISH on 88% of the interviews (weighted kappa = 0.86). In ENRICHD, the clinicians agreed with 93% of the research nurses' diagnoses. The BDI and the Hamilton depression scores derived from the DISH in the two studies correlated 0.76 (p < .0001) in the validity study and 0.64 (p < .0001) in ENRICHD. CONCLUSIONS: These findings support the validity of the DISH as a semistructured interview to assess depression in medically ill patients. The DISH is efficient in yielding both a DSM-IV depression diagnosis and a 17-item Hamilton depression score.

Analysis of Variance↗

PubMed2003

Optimized set of two-dimensional experiments for fast sequential assignment, secondary structure determination, and backbone fold validation of 13C/15N-labelled proteins.

NMR experiments are presented which allow backbone resonance assignment, secondary structure identification, and in favorable cases also molecular fold topology determination from a series of two-dimensional 1H-15N HSQC-like spectra. The 1H-15N correlation peaks are frequency shifted by an amount +/- omegaX along the 15N dimension, where omegaX is the Calpha, Cbeta, or Halpha frequency of the same or the preceding residue. Because of the low dimensionality (2D) of the experiments, high-resolution spectra are obtained in a short overall experimental time. The whole series of seven experiments can be performed in typically less than one day. This approach significantly reduces experimental time when compared to the standard 3D-based methods. The here presented methodology is thus especially appealing in the context of high-throughput NMR studies of protein structure, dynamics or molecular interfaces.

Bacterial Proteins↗

PubMed1978

Effects of proximal intra-atrial Wenckebach on distal atrioventricular nodal, and His-Purkinje, block with special reference to the theory of alternating Wenckebach periods.

Intra-atrial Wenckebach patterns of stimulus-to-response intervals coexisting with distal, A-V nodal, and His-Purkinje, blocks occurred in eight patients during high right atrial stimulation at rapid rates. In two patients with 2:1 St-H block and in two patients with 4:1 St-V block, an increase in the degree of block occurred when the proximal intra-atrial Wenckebach cycle was completed with the stimulus which otherwise would have been propagated to the distal levels. However, the degree of block did not increase when the intra-atrial Wenckebach terminated in distally blocked stimuli. In one patient progression of 4:1 into 5:1 St-V block was due to the association of intra-atrial Wenckebach with alternating 2:1 block at the A-V nodal, and His-Purkinje, levels. Contrasting with most reports dealing with the mechanisms of alternating Wenckebach in a single structure, this study permitted the determination of the boundaries between proximal and more distal levels. It also showed that alternating Wenckebach cycles (of St-H intervals) ending with two consecutively blocked stimuli could result from the association of proximal intra-atrial Wenckebach with distal, A-V nodal Wenckebach, or abortive AW, cycles. The electrophysiology of documented two, or three, level block in different structures has validated previously made assumptions regarding multilevel block in a single structure.

Atrioventricular Node↗

PubMed2003

Weak alignment offers new NMR opportunities to study protein structure and dynamics.

Protein solution nuclear magnetic resonance (NMR) can be conducted in a slightly anisotropic environment, where the orientational distribution of the proteins is no longer random. In such an environment, the large one-bond internuclear dipolar interactions no longer average to zero and report on the average orientation of the corresponding vectors relative to the magnetic field. The desired very weak ordering, on the order of 10(-3), can be induced conveniently by the use of aqueous nematic liquid crystalline suspensions or by anisotropically compressed hydrogels. The resulting residual dipolar interactions are scaled down by three orders of magnitude relative to their static values, but nevertheless can be measured at high accuracy. They are very precise reporters on the average orientation of bonds relative to the molecular alignment frame, and they can be used in a variety of ways to enrich our understanding of protein structure and function. Applications to date have focused primarily on validation of structures, determined by NMR, X-ray crystallography, or homology modeling, and on refinement of structures determined by conventional NMR approaches. Although de novo structure determination on the basis of dipolar couplings suffers from a severe multiple minimum problem, related to the degeneracy of dipolar coupling relative to inversion of the internuclear vector, a number of approaches can address this problem and potentially can accelerate the NMR structure determination process considerably. In favorable cases, where large numbers of dipolar couplings can be measured, inconsistency between measured values can report on internal motions.

Anisotropy↗

PubMed2005

The factor validity of the Western Ontario Rotator Cuff Index.

BACKGROUND: The Western Ontario Rotator Cuff Index (WORC) is a self-report questionnaire developed specifically to evaluate disability in persons with pathology of the rotator cuff of the shoulder. The authors created items in 5 categories based on a model of quality of life, but never validated this structure. The purpose of this study was to examine the validity of the original 5-domain model of the WORC by performing factor analysis. METHODS: Three hundred twenty nine subjects (age, mean: 52, SD: 12) were tested prior to undergoing surgery for rotator cuff pathologies. They completed the WORC, a self-report questionnaire, which has 21 items on the effect of the rotator cuff problem on symptoms, activities and emotions. Statistical calculations included correlations between items, Cronbach's alpha of the total scale and subscales, and principal component factor analysis with oblique rotation. RESULTS: Correlations ranged from .09 to .70 between all the items, from .29 to .70 between items within a subscale, and from .53 to .72 between subscale scores. Cronbach's alpha was .93 for the total scale, and .72 to .82 for the subscales. The factor analysis produced 3 factors that explained 57% of the variance. The first factor included symptoms and emotional items, the second included strength items and the third included daily activities. CONCLUSION: The results of this study did not support the 5-domain model of the WORC.

Adult↗

PubMedDate not supplied

[Effects of intra-arterial Wenckebach's periods on the nodal and intranodal A-V 2:1 and 4:1 (their significance in the electrogenesis of the so-called alternating Wenckebach's periods)].

Intra-atrial Wenckebach patterns coexisting with distal, A-V nodal, and His-Purkinje blocks occurred in eight patients during high atrial stimulation at rapid rates. In two patients with 2:1 St-H block and in two patients with 4:1 St-V block, an increase in the degree of block occurred when the proximal intraatrial Wenckebach cycle was completed with the stimulus which otherwise would have been propagated to the distal levels. However, the degree of block did not increase when the intraatrial Wenckebach terminated in distally blocked stimuli. In one patient progression of 4:1 into 5:1 St-V block was due to the association of intraatrial Wenckebach with alternating 2:1 block at the A-V nodal, and His-Purkinje levels. Contrasting with most reports dealing with the mechanisms of alternating Wenckebach in a single structure, this study permitted the determination of the boundaries between proximal and more distal levels. The electrophysiology of documented two or three level block in different structures has validated previously made assumptions regarding multilevel block in a single structure.

Bundle-Branch Block↗

PubMed2002

MR image-based measurement of rates of change in volumes of brain structures. Part I: method and validation.

A detailed analysis procedure is described for evaluating rates of volumetric change in brain structures based on structural magnetic resonance (MR) images. In this procedure, a series of image processing tools have been employed to address the problems encountered in measuring rates of change based on structural MR images. These tools include an algorithm for intensity non-uniformity correction, a robust algorithm for three-dimensional image registration with sub-voxel precision and an algorithm for brain tissue segmentation. However, a unique feature in the procedure is the use of a fractional volume model that has been developed to provide a quantitative measure for the partial volume effect. With this model, the fractional constituent tissue volumes are evaluated for voxels at the tissue boundary that manifest partial volume effect, thus allowing tissue boundaries be defined at a sub-voxel level and in an automated fashion. Validation studies are presented on key algorithms including segmentation and registration. An overall assessment of the method is provided through the evaluation of the rates of brain atrophy in a group of normal elderly subjects for which the rate of brain atrophy due to normal aging is predictably small. An application of the method is given in Part II where the rates of brain atrophy in various brain regions are studied in relation to normal aging and Alzheimer's disease.

Aged↗

PubMed1995

Validation and coding of the NIC taxonomy structure. Iowa Intervention Project. Nursing Interventions Classification.

Processes for validation and coding of the taxonomy for the Nursing Interventions Classification (NIC) are described. A sample of nurses expert in theory development rated the NIC taxonomy using five criteria. Following identification of a stable structure, the taxonomy was coded with each intervention receiving a unique number. A coded and valid taxonomic structure facilitates use of the classification in computerization and makes possible the collection of comparable data. A coded classification can also be used in reimbursement systems.

Cluster Analysis↗

PubMed1999

Measuring nursing work in long-term care. The reliability and validity of the Leatt Measure of Nursing Technology.

A projected 400% increase in the number of people age 85 and older by the year 2010, with one fourth of them needing nursing home care, forces attention on long-term care. This study establishes the validity and reliability of the Leatt Measure of Nursing Technology (LMNT) as a measure of the nature of nursing work in long-term care settings. The LMNT subscales measure the amount of uncertainty, instability, and variability of work which includes, but is not limited to, the technical equipment used. The LMNT was administered to licensed nursing staff in nine long-term care facilities in the Seattle area to evaluate its use in this environment. The nursing homes represented both for-profit and not-for-profit, and large (more than 250 beds) and small (70 beds) facilities. A total of 113 usable questionnaires were returned (45% response rate). Cronbach's alpha for subscales were .71 for Uncertainty, .66 for Instability, and .56 for Variability, with .77 for the total scale. Construct validity was evaluated by factor analysis, which confirmed the original factor structure. Content validity was evaluated using focus group discussions with key informants at each facility. A comparative analysis was used to determine major and minor themes in each of the instrument subscale topic areas. Qualitative analysis, combined with reliability and item level analyses, resulted in suggested minor changes in the instrument to make it more usable in long-term care settings. While some revisions are suggested, a concerted effort must be made to preserve the ability to compare findings with those obtained using the LMNT in acute care settings by retaining the general structures and factors of the measure.

Aged↗

PubMed1993

Cross validation of the Hypnotic Induction Profile factor structure: simultaneous confirmatory factor analysis of two published samples.

This study cross-validated factor structure and psychometric characteristics of the Hypnotic Induction Profile (HIP). Earlier studies identified two constructs of the HIP, but their methodology did not allow empirical confirmation of the number of factors. I have used a new methodology, confirmatory factor analysis, and submitted the data from the previous studies to a simultaneous, multisample, factor analysis. The results showed that the HIP indeed consists of two factors. Although the HIP two-factor model is statistically adequate, 7 of the 10 scales have very low item reliability. Issues of measurement error and clinical implications of the study are also discussed in relation to the current findings.

Factor Analysis, Statistical↗

PubMed2003

Homology modeling of the central catalytic domain of insertion sequence ISLC3 isolated from Lactobacillus casei ATCC 393.

The tertiary structure of the central catalytic domain of insertion sequence ISLC3 isolated from Lactobacillus casei ATCC 393 was predicted using the homology modeling approach. The novel insertion sequence was isolated by us from the template bacteriophage phiA3 of L.casei ATCC 393. The number of amino acid residues of the ISLC3 central catalytic domain was 116 and was treated as the query sequence. There were five Web-available threading methods used to find some primary structure templates for the query sequence. These primary templates were further screened using the SWISS-MODEL Protein Modeling Server and the default parameter settings therein to give six final structure templates. All of these final structure templates were the integrase (IN) protein of retroviruses. Multiple sequence alignment using these IN sequences against the query one revealed the signature DDE motif. Based on the structures of these final templates, the structure of the query sequence was constructed using the InsightII/Discover/Homology programs. A metal ion, Mg(2+), was inserted into the center of the putative catalytic pocket formed by the DDE residues of the predicted structure in the final rounds of refinement by molecular dynamics (MD) simulations. The structure with a metal ion included was designated with Mg and that without a metal ion was designated free Mg. The average exposed surface area of some hydrophobic residues of both the predicted free Mg and with Mg structures were computed and compared with those computed for the six structure templates. Whereas the predicted with Mg structure was slightly more exposed than the predicted free Mg structure, the former appeared to be more stable than the latter, as revealed by the lower conformation energy recorded for the former during the structure refinement by MD simulations. To verify further the predicted structures, the coordinates of both predicted structures were fed into the ERRAT Protein Verification Server. It was found that the quality of the predicted with Mg structure was much better than that of the free Mg structure. The validation results also indicated that regions of the predicted with Mg structure that can be rejected at the 95% confidence level were approximately 20% whereas those which can be rejected at the same level for the six structure templates were approximately 10%. The predicted with Mg structure was also docked into a short oligonucleotide representing the substrate of the ISLC3 transposase using the DOCK_4.0.2 program. It was found that both Glu140 and Asp68 residues of the DDE motif of the predicted with Mg structure were able to form hydrogen bonds with the DNA substrate, which was similar to what was observed in a docking study using the retrovirus IN 1asu and its DNA substrate.

Amino Acid Sequence↗

PubMed1999

Postural tachycardia syndrome: clinical features and follow-up study.

OBJECTIVE: To define the clinical features and outcome of postural tachycardia syndrome (POTS). MATERIALS AND METHODS: In this cross-sectional study of the autonomic symptom profile, inclusion criteria were orthostatic heart rate increment of 30 beats/min or greater, orthostatic symptoms, completion of a standardized autonomic test battery, and follow-up of 18 months or longer. We used 2 instruments. The first part was a structured and validated autonomic symptom profile (108 patients). The second part was a structured questionnaire focused on autonomic status on prospective follow-up (40 patients) (mean +/- SD follow-up, 67+/-52 months). RESULTS: Most patients had frequent, persistent, and at least moderately severe symptoms for less than 5 years. The following orthostatic symptoms occurred in more than 75% of subjects: light-headedness or dizziness, lower extremity or diffuse weakness, disequilibrium, tachycardia, and shakiness. Nonorthostatic symptoms included dry eyes or mouth, gastrointestinal complaints of bloating, early satiety, nausea, pain, and alternating diarrhea and constipation. Half of the patients reported an antecedent illness presumed to be of viral origin. On follow-up, 80 % of patients were improved, 60% were functionally normal, and 90% were able to return to work. Patients who had an antecedent event appeared to do better than those with spontaneous POTS. Salt supplementation and beta-blockers were the most efficacious therapies. CONCLUSION: In the majority of patients, POTS is self-resolving, especially in those with a triggering event.

Adult↗

PubMed1988

An examination of the factor structure and convergent and discriminant validity of the SCL-90R in an outpatient clinic population.

This study investigated the factor structure of the SCL-90R using an outpatient psychology clinic population. Six relatively homogeneous and stable factors were identified: Depression, Somatization, Anger-Hostility, Paranoid-Psychoticism, Phobic Anxiety, and Obsessive-Compulsive. However, a principal component analysis revealed that the first factor accounted for a large percentage of the variance, suggesting that this instrument measures a general dimension of psychopathology. In addition, significant correlations between the SCL-90R symptom dimensions and both the BDI and several MMPI scales were found. The results of the study lead to questions regarding the utility of the SCL-90R.

Adolescent↗