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At least 1,027 records · Page 57Linked to original sources
PubMed1976

Analytical aspects of capillary gas chromatography of lower fatty acids [up to C18].

The principal aspects influencing analytical capillary gas chromatography of fatty acids up to C18 have been evaluated. Selected fundamental problems of interlaboratory exchange of retention data were problems of defined temperature in commercial thermostated air baths, of capillary tubing, and of stationary phases. A modification of commercial thermostats has been proposed in order to secure a defined temperature for glass capillary columns. It has been found that retention data of fatty-acid methyl esters can be measured under standard conditions with the same accuracy as retention data of hydrocarbons on squalane. Metal capillary columns coated with Apiezon L were found to be unsuitable for the analysis of fatty-acid methyl esters when compared with the results of their quantitative analysis in packed Apiezon L and polar capillary columns. Possibilities of a nontraditional statistical evaluation of the results of measurements are suggested. A program in FORTRAN IV language is given for the calculation of Kovats' retention indices for fatty-acid methyl esters.

Butter↗
PubMed1999

The diagnostic accuracy of ultrasound scan in predicting endometrial hyperplasia and cancer in postmenopausal bleeding.

OBJECTIVE: To determine the accuracy of ultrasound scan in the diagnosis of endometrial hyperplasia and cancer in postmenopausal bleeding. DESIGN: A prospective diagnostic accuracy study (1996-97). SETTING: Minimal access surgical training centers in two large teaching hospitals. METHODS: Ultrasound scan and outpatient endometrial sampling were performed on 96 patients with postmenopausal bleeding. Patients unable to have these outpatient procedures had a formal inpatient hysteroscopy and curettage. Test performance characteristics were computed for ultrasound scan comparing its estimate of endometrial thickness with histologic diagnosis that served as a 'gold' standard. OUTCOME MEASURES: Accuracy of the ultrasonic endometrial thickness was estimated using sensitivity, specificity and predictive values for binary data. For multilevel data, the diagnostic accuracy was computed using likelihood ratios (LRs). An LR < decreased the probability that endometrial hyperplasia/cancer was present, whereas an LR > 1 increased the probability that such lesion was present. RESULTS: Using endometrial thickness > or =4 mm, the sensitivity of ultrasound to detect the endometrial malignancy was 92.9%, the specificity was 500%, and the positive and negative predictive values were 24.1% and 97.6% respectively. Analysis using likelihood ratio (LR) revealed that LR was 0.14 for endometrial thickness > or =4.0 mm, 0.94 for endometrial thickness 4.1-9.0 mm, and 3.3 for endometrial thickness >9.0 mm. CONCLUSION: In women with postmenopausal bleeding, malignancy can probably be safely excluded if sonographic endometrial thickness is < or = 4.0 mm. However, the probability of endometrial hyperplasia/cancer is not particularly altered by the knowledge that endometrial thickness on scan is >4.0 mm.

Biopsy↗
PubMed1996

Speech recognition and direct data entry in clinical microbiology.

The aim of this study was to design a system (Vigilante) for the direct entry of urine microscopy, culture and sensitivity test results at bench level using natural continuous speech, removing the need for time-consuming report coding and keyboard entry. Graphical and audio feedback facilitated error recognition and correction, and removed the need for time-consuming report checking and validation stages. The system was evaluated over a three-month period by direct comparison of 2360 urine specimens processed by multiple operators using both Vigilante and traditional methods. The results showed that the Vigilante system reduced the time taken to enter data, improved the accuracy of reporting and reduced the time taken to issue reports. The results suggest that direct data entry using speech offers a practical, reliable and innovative alternative to more conventional means of data entry. The system is now used routinely in this laboratory to report urine microscopy, culture and sensitivity test results, and may be adapted to individual urine methodologies or other data entry tasks.

Humans↗
PubMed2003

Coregistration accuracy and detection of brain shift using intraoperative sononavigation during resection of hemispheric tumors.

OBJECTIVE: Sononavigation, which combines real-time anatomic ultrasound data with neuronavigation techniques, is a potentially valuable adjunct during the surgical excision of brain tumors. METHODS: In this study, we report our preliminary observations using this technology on 58 adult patients harboring hemispheric tumors. Data regarding coregistration accuracy was collected from various landmarks that typically do not shift as well as from tumor boundaries and the cortical surface. In a subset of patients, we evaluated the extent and direction of postresection brain displacement and its relationship with patient age, tumor histology, tumor volume, and use of mannitol. RESULTS: For all structures excluding the cortex, average coregistration accuracy measurements between ultrasound and preoperatively acquired magnetic resonance imaging scans were within the range of 2 mm. The most accurate alignments were obtained with the choroid plexus and the falx, and the least reliable structure in terms of coregistration accuracy was the cortical surface. CONCLUSION: Sononavigation provides real-time information during tumor removal in alignment with the preoperative magnetic resonance imaging scans, thus enabling the surgeon to detect intraoperative hemorrhage, cyst drainage, and tumor resection, and it allows for calculation of brain shift during the use of standard navigation techniques.

Adolescent↗
PubMedDate not supplied

Comparison of five glucose meters for self-monitoring of blood glucose by diabetic patients.

This study collected data regarding the accuracy of five currently marketed meters for home use of self-monitoring of blood glucose (SMBG). Data regarding ease of operation of each glucose meter as well as cost and availability of meters and necessary materials were compiled. Fasting blood glucose (BG) samples were drawn from patients in the adult and pediatric diabetes clinics at the University of Kansas College of Health Sciences and Hospital. Specimens were tested by a clinical laboratory as well as by each meter. Unadjusted meter readings of whole BG were plotted against laboratory readings of serum glucose and displayed in scattergrams. Scattergrams showed decreased machine accuracy in upper and lower BG ranges. Whole BG values (meter readings) were adjusted to serum glucose levels by multiplication by 1.12. Adjusted values were compared with laboratory serum values using ANOVA for repeated measures and Dunnett's Multiple Comparisons Test: ANOVA and Dunnett's Multiple Comparisons Test showed only Glucochek II (Medistron, Ltd., West Sussex, England; distributed in U.S. by Larken Industries, Lenexa, Indiana) using Dextrostix reagent strips (Ames Division, Miles Laboratories, Elkhart, Indiana) having a statistically significant difference from laboratory values (P less than 0.01). This meter was recently revised and may show changed accuracy readings. Each meter exhibited inherent advantages and disadvantages regarding price, calibration, strip utilization, and ease of operation, which must be considered before recommendation by the health care provider.

Autoanalysis↗
PubMed2002

Monte Carlo simulation studies of EEG and MEG localization accuracy.

Both electroencephalography (EEG) and magnetoencephalography (MEG) are currently used to localize brain activity. The accuracy of source localization depends on numerous factors, including the specific inverse approach and source model, fundamental differences in EEG and MEG data, and the accuracy of the volume conductor model of the head (i.e., the forward model). Using Monte Carlo simulations, this study removes the effect of forward model errors and theoretically compares the use of EEG alone, MEG alone, and combined EEG/MEG data sets for source localization. Here, we use a linear estimation inverse approach with a distributed source model and a realistic forward head model. We evaluated its accuracy using the crosstalk and point spread metrics. The crosstalk metric for a specified location on the cortex describes the amount of activity incorrectly localized onto that location from other locations. The point spread metric provides the complementary measure: for that same location, the point spread describes the mis-localization of activity from that specified location to other locations in the brain. We also propose and examine the utility of a "noise sensitivity normalized" inverse operator. Given our particular forward and inverse models, our results show that 1) surprisingly, EEG localization is more accurate than MEG localization for the same number of sensors averaged over many source locations and orientations; 2) as expected, combining EEG with MEG produces the best accuracy for the same total number of sensors; 3) the noise sensitivity normalized inverse operator improves the spatial resolution relative to the standard linear estimation operator; and 4) use of an a priori fMRI constraint universally reduces both crosstalk and point spread.

Algorithms↗
PubMed2002

A diffusion model account of response time and accuracy in a brightness discrimination task: fitting real data and failing to fit fake but plausible data.

A brightness discrimination experiment was performed to examine how subjects decide whether a patch of pixels is "bright" or "dark," and stimulus duration, brightness, and speed versus accuracy instructions were manipulated. The diffusion model (Ratcliff, 1978) was fit to the data, and it accounted for all the dependent variables: mean correct and error response times, the shapes of response time distributions for correct and error responses, and accuracy values. Speed-accuracy manipulations affected only boundary separation (response criteria settings) in the model. Drift rate (the rate of accumulation of evidence) in the diffusion model, which represents stimulus quality, increased as a function of stimulus duration and stimulus brightness but asymptoted as stimulus duration increased from 100 to 150 msec. To address the argument that the diffusion model can fit any pattern of data, simulated patterns of plausible data are presented that the model cannot fit.

Attention↗
PubMed2000

The test of Lasègue: systematic review of the accuracy in diagnosing herniated discs.

STUDY DESIGN: A systematic review of the literature including statistical meta-analysis. OBJECTIVES: To evaluate published methods of the test of Lasègue or straight leg raising test and the cross straight leg raising test by using a recently developed criteria list and to summarize and explore reasons for variation in diagnostic accuracy. SUMMARY OF BACKGROUND DATA: Little evidence exists on the diagnostic accuracy of the widely used straight leg raising test and the cross straight leg raising test in diagnosing herniated discs in patients with low back pain. METHODS: MEDLINE and EMBASE searches up to 1997 showed 17 diagnostic publications evaluating the straight leg raising test with surgery as reference standard. Quality of methods was assessed with a specific checklist. Eleven studies were selected for statistical pooling. Sources of variation and heterogeneity were studied by meta-regression of the diagnostic odds ratio. RESULTS: All studies were surgical case-series at nonprimary care level. Verification-bias was obvious in one study. Pooled sensitivity for straight leg raising test was 0. 91 (95% CI 0.82-0.94), pooled specificity 0.26 (95% CI 0.16-0.38). Pooled diagnostic odds ratio was 3.74 (95% CI 1.2-11.4). Discriminative power was lower in recent studies, in studies with only inclusion of primary hernias, and with blind assessment of both the index-test (straight leg raising test) and the reference (surgery). For the cross straight leg raising test pooled sensitivity was 0.29 (95% CI 0.24-0.34), pooled specificity was 0.88 (95% CI 0.86-0.90), and the pooled diagnostic odds ratio 4.39 (95% CI 0.74-25.9). CONCLUSIONS: The diagnostic accuracy of the straight leg raising test is limited by its low specificity. Discriminative power decreased with a more valid design, a more homogenous case-mix, and year of publication. Although the studies may reflect everyday clinical practice, they do not enable a valid evaluation of the diagnostic accuracy of both tests. Diagnostic research should evaluate the validity of the complete diagnostic process and study the evidence of the added value of the different tests used. [Key words: sensitivity, specificity, diagnosis, meta-analysis, test of Lasègue, straight leg raising test]

Adult↗
PubMed2006

Compton scattering study of water versus ice Ih: intra- and intermolecular structure.

The hydrogen-bond geometries in water and polycrystalline ice Ih are studied using synchrotron radiation-based Compton scattering data of unprecedented statistical accuracy and consistency. By combining the experimental data with model calculations utilizing density functional theory, we show that the technique provides unique and complementary information on hydrogen bonding in water. The comparison of water and ice indicates the necessity of including a local intra-intermolecular geometric correlation for water, relating the intramolecular O-H bond length to the corresponding hydrogen-bond geometry. By using the hydrogen-bond geometries obeying this correlation, we demonstrate a further constraint on the angular distortions of the hydrogen bonds in water.

Journal Article↗
PubMed1996

A system for the analysis of foot and ankle kinematics during gait.

A five-camera Vicon (Oxford Metrics, Oxford, England) motion analysis system was used to acquire foot and ankle motion data. Static resolution and accuracy were computed as 0.86 +/- 0.13 mm and 98.9%, while dynamic resolution and accuracy were 0.1 +/- 0.89 and 99.4% (sagittal plane). Spectral analysis revealed high frequency noise and the need for a filter (6 Hz Butterworth low-pass) as used in similar clinical situations. A four-segment rigid body model of the foot and ankle was developed. The four rigid body foot model segments were 1) tibia and fibula, 2) calcaneus, talus, and navicular, 3) cuneiforms, cuboid, and metatarsals, and 4) hallux. The Euler method for describing relative foot and ankle segment orientation was utilized in order to maintain accuracy and ease of clinical application. Kinematic data from a single test subject are presented.

Ankle Joint↗
PubMed2006

Accurate and fast off and online fuzzy ARTMAP-based image classification with application to genetic abnormality diagnosis.

We propose and investigate the fuzzy ARTMAP neural network in off and online classification of fluorescence in situ hybridization image signals enabling clinical diagnosis of numerical genetic abnormalities. We evaluate the classification task (detecting a several abnormalities separately or simultaneously), classifier paradigm (monolithic or hierarchical), ordering strategy for the training patterns (averaging or voting), training mode (for one epoch, with validation or until completion) and model sensitivity to parameters. We find the fuzzy ARTMAP accurate in accomplishing both tasks requiring only very few training epochs. Also, selecting a training ordering by voting is more precise than if averaging over orderings. If trained for only one epoch, the fuzzy ARTMAP provides fast, yet stable and accurate learning as well as insensitivity to model complexity. Early stop of training using a validation set reduces the fuzzy ARTMAP complexity as for other machine learning models but cannot improve accuracy beyond that achieved when training is completed. Compared to other machine learning models, the fuzzy ARTMAP does not loose but gain accuracy when overtrained, although increasing its number of categories. Learned incrementally, the fuzzy ARTMAP reaches its ultimate accuracy very fast obtaining most of its data representation capability and accuracy by using only a few examples. Finally, the fuzzy ARTMAP accuracy for this domain is comparable with those of the multilayer perceptron and support vector machine and superior to those of the naive Bayesian and linear classifiers.

Artificial Intelligence↗
PubMed1994

Integration of competing ancillary assertions in genome assembly.

Assembly of genomic sequences and maps relies on a primary set of experimental data (e.g., the sequences of individual DNA fragments, or hybridization fingerprints of individual clone inserts), but almost always also relies on several streams of related but distinct kinds of data for completeness and accuracy of the final construction. These secondary data sets, which we term ancillary information, usually contain errors (as do the primary data sets, therefore creating the possibility of conflict between data sets), often arise from different experimental protocols and correspond to different scales of measurement, and occasionally include non-quantitative statements about the data. We present an approach for integration of ancillary assertions in the optimization of genome assembly, based on simultaneous balancing among the primary and secondary data sets, and include specific examples in the context of assembling DNA sequencing fragments to reconstruct a parent sequence.

Animals↗
PubMed1993

Protein secondary structure prediction using two-level case-based reasoning.

We have developed a two-level case-based reasoning architecture for predicting protein secondary structure. The central idea is to break the problem into two levels: first, reasoning at the object (protein) level, and using the global information from this level to focus on a more restricted problem space; second, decomposing objects into pieces (segments), and reasoning at the internal structures level; finally, synthesizing the pieces back to the objects. The architecture has been implemented and tested on a commonly used data set with 69.3% predictive accuracy. It was then tested on a new data set with 67.3% accuracy. Additional experiments were conducted to determine the effects of using different similarity matrices.

Amino Acid Sequence↗
PubMed2001

Radiologic determination of intravascular volume status using portable, digital chest radiography: a prospective investigation in 100 patients.

OBJECTIVE: To answer the following questions: Can the digital chest roentgenogram (CXR) be used to differentiate patients' volume status? Do clinical data alter radiologists' accuracy in interpreting the digital CXR? DESIGN: Prospective cohort study. SETTING: Nine adult intensive care units of a tertiary care medical center. PATIENTS: One hundred thirty-five consecutive patients with pulmonary artery catheters, of whom 35 were excluded because of unacceptable pulmonary artery occlusion pressure (PAOP) tracings. METHODS: Each patient had a portable, anteroposterior, supine digital CXR. Clinicians evaluated volume status and then measured hemodynamic data within 1 hr of the CXR. Digital CXRs were independently interpreted on two separate occasions (with and without clinical information) by three experienced chest radiologists, and these interpretations were compared with hemodynamic data. RESULTS: Of the 100 patients, 39 had PAOP >18 mm Hg, whereas 61 had PAOP <18 mm Hg. Radiologists' accuracy in differentiating volume status increased with incorporation of clinical data (56% without vs. 65% with clinical data, p =.009). Using objective receiver operating characteristic-derived cutoffs of 70 mm for vascular pedicle width and 0.55 for cardiothoracic ratio, radiologists' accuracy in differentiating PAOP >18 mm Hg from PAOP <18 mm Hg was 70%. The intrareader and the inter-reader correlation coefficients were very high. The likelihood ratio of the CXR in determining volume status using the objective vascular pedicle width and cardiothoracic ratio measures was 3.1 (95% confidence interval, 1.9-6.0), significantly higher than subjective CXR interpretations with and without clinical data (p <.001). CONCLUSIONS: Differentiating intravascular volume status with portable, supine, digital CXRs may be improved by using objective cutoffs of vascular pedicle width >70 mm and cardiothoracic ratio >0.55 or by incorporating clinical data.

Adult↗
PubMed1985

An obstetric microcomputer information system.

A systems analysis has been done to determine how computer technology can provide an information system to improve the care of the mother and her baby. A minimum data base was established complying with the recommendations of the Körner Committee and designed to meet the needs of the health personnel looking after the mother and baby. An ICL DRS 20/50 network of four microcomputers has been installed in the obstetric unit of a district teaching hospital with a link to the regional mainframe. There have been no significant software or hardware faults since the system became fully operational in January 1984. All women are registered on the system at their first visit allowing the pregnancy to be followed prospectively. Subsequently midwives enter data on line at delivery and at discharge. The on line validation and range checks improves the accuracy of the data allowing a reliable perinatal audit to be obtained routinely. The system has been accepted by the staff since much of the routine pregnancy documentation is produced automatically. This includes booking letters and summaries for general practitioners, admission slips, birth notification forms, registers and forms for the community midwives and health visitors. Immediate production of reports for community health staff allows better communication and improved patient care. No additional staff are needed in the obstetric unit and one job which was mainly of a clerical nature has been saved and the salary transferred to provide one more midwife for the postnatal wards.(ABSTRACT TRUNCATED AT 250 WORDS)

Computers↗
PubMed2003

Measurements of contact potential difference (work functions) of metals and semiconductors surface by the static ionized capacitor method.

Electron work functions of several metals (Au, W, Ag, Cu, Mo, Ti, Al) and Si at atmospheric conditions have been measured by the method of the static capacitor with an ionized gap between the electrodes. Results for all samples, excluding Au, Al and Si, conform to reference data with an accuracy of +/- 1.0%. For samples Au, Al and Si, the electron work function values conform to reference data after short-time heat treatment at atmospheric conditions at 200 degrees C (for Al) and 600 degrees C (for Au, Si).

Aluminum↗
PubMed1978

A computerized single entry system for recording and reporting data on high-risk newborn infants.

A computer-assisted system for data collection in an intensive care nursery is described. Maternal history, infant history, diagnoses, and treatment are sequentially identified on a single form and then entered in batches into a computer at the time of patient discharge. Computer production of a discharge summary and letters to referring and follow-up physicians from a single data-entry form account for an approximately 80% savings in physician record-keeping time per patient. Accuracy of the data is approximately two and one-half times greater than with existing methods of data gathering. Survey of disease occurrence and case fatality rates are rapidly available.

California↗
PubMed2006

An accurate analytic potential function for ground-state N2 from a direct-potential-fit analysis of spectroscopic data.

Two types of combined-isotopologue analysis have been performed on an extensive spectroscopic data set for ground-state N2 involving levels up to v=19, which is bound by half the well depth. Both a conventional Dunham-type analysis and a direct-potential-fit (DPF) analysis represent the data within (on average) the estimated experimental uncertainties. However, the Dunham-type parameters do not yield realistic predictions outside the range of the data used in the analysis, while the potential function obtained from the DPF treatment yields quantum mechanical accuracy over the data region and realistic predictions of the energies and properties of unobserved higher vibrational levels. Our DPF analysis also introduces a compact new analytic potential function form which incorporates the two leading inverse-power terms in the long-range potential.

Journal Article↗