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At least 955 records · Page 53Linked to original sources
PubMed2004

Time domain system identification of unknown initial conditions.

System identification is a method for using measured data to create or improve a mathematical model of the object being tested. From the measured data however, noise is noticed at the beginning of the response. One solution to avoid this noise problem is to skip the noisy data and then use the initial conditions as active parameters, to be found by using the system identification process. This paper describes the development of the equations for setting up the initial conditions as active parameters. The simulated data and response data from actual shear buildings were used to prove the accuracy of both the algorithm and the computer program, which include the initial conditions as active parameters. The numerical and experimental model analysis showed that the value of mass, stiffness and frequency were very reasonable and that the computed acceleration and measured acceleration matched very well.

Algorithms↗
PubMedDate not supplied

Identification of drugs by principal components analysis of Rf data obtained by TLC in different eluent systems.

The retention factor of 54 drugs in eight eluent mixtures is reported. Principal component analysis (PCA) of these data provided a significant two-components model. These two parameters characteristic for each drug allowed an objective identification of unknown samples, provided they were included in the considered set. The analysis showed that the eluent mixtures cluster into three groups. The PCA model, using only three eluents (one for each group), was also able to restrict the range of inquiry to a few "candidates" and, in some cases, to allow unambiguous identification of the drug. These results, based on a simple and quick analytical determination (thin layer chromatography) and a reliable statistical procedure (PCA), appear to be of significant practical importance in the field of analytical toxicology.

Chromatography, Thin Layer↗
PubMed2005

Identification of copper sources in urban surface waters using the principal component analysis based on aquatic parameters.

The goal of this work was to identify the sources of copper loads in surface urban waters using principal component analysis under the aquatic parameters data evaluation approach. Water samples from the Irai and Iguacu rivers were collected monthly during a 12-month period at two points located upstream and downstream of a metropolitan region. pH, total alkalinity, dissolved chloride, total suspended solids, dissolved organic matter, total recoverable copper, temperature, and precipitation data provided some reliable information concerning the characteristics and water quality of both rivers. Principal component analysis indicated seasonal and spatial effects on copper concentration and loads in both environments. During the rainy season, non-point sources such as urban run-off are believed to be the major source of copper in both cases. In contrast, during the lower precipitation period, the discharge of raw sewage seems to be the primary source of copper to the Iguacu River, which also exhibited higher total metal concentrations.

Cities↗
PubMed1989

Limitations of flow cytometric DNA analysis for the diagnosis of bladder cancer.

Flow cytometric analysis was done on exfoliated urothelial cells from 11 control patients and 31 patients with transitional cell carcinoma: 9 grade I, 11 grade II, and 11 grade III. The determination of aneuploidy by DNA analysis did not provide identification of low-grade tumor cells. Other flow cytometric parameters of cellular change such as cell size, nuclear size, nuclear/cytoplasmic ratio, or cell refractivity may provide better identification of low-grade lesions.

Carcinoma, Transitional Cell↗
PubMed2003

Toxicological screening with formula-based metabolite identification by liquid chromatography/time-of-flight mass spectrometry.

An analytical procedure was evaluated for the comprehensive toxicological screening of drugs, metabolites, and pesticides in 1-mL urine samples by TurboIon spray liquid chromatography/time-of-flight mass spectrometry (LC/TOFMS) in the positive ionization mode and continuous mass measurement. The substance database consisted of exact monoisotopic masses for 637 compounds, of which an LC retention time was available for 392. A macroprogram was refined for extracting the data into a legible report, utilizing metabolic patterns and preset identification criteria. These criteria included +/-30 ppm mass tolerance, a +/-0.2-min window for absolute retention time, if available, and a minimum area count of 500. The limit of detection, determined for 90 compounds, was <0.1 mg/L for 73% of the compounds studied and >1.0 mg/L for 6% of the compounds. For method comparisons, 50 successive autopsy urine samples were analyzed by this method, and the results confirmed by gas chromatography/mass spectrometry (GC/MS). Findings for parent drugs were consistent with both methods; in addition, LC/TOFMS regularly revealed apparently correct findings for metabolites not shown by GC/MS. Mean and median mass accuracy by LC/TOFMS was 7.6 and 5.4 ppm, respectively. The procedure proved well-suited for tentative identification without reference substances. The few false positives emphasized the fact that all three parameters, exact mass, retention time, and metabolite pattern, are required for unequivocal identification.

Journal Article↗
PubMed1997

The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure in primary rat astroglia: identification of biochemical and cellular targets.

This paper reports the results from in vitro experiments utilizing vital fluorescent probes and biochemical assays to examine the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and related compounds in primary rat astroglia in an effort to identify the cellular site(s) involved in toxicity. Application of 100 nM 2,3,7,8-TCDD, a strong Ah receptor agonist, resulted in altered astroglial intracellular Ca2+, a significant decrease in glutathione, a disrupted mitochondrial membrane potential, a significant decrease in glutamine synthetase immunoreactivity and eventual loss of pH maintenance. In contrast, application of 10 microM 1,2,3,4-TCDD, a weak Ah receptor agonist, had no effect on any parameters measured. These findings, coupled with the identification of the 9-10S cytosolic Ah receptor in cultured rat astroglia, are consistent with typical structure-activity relationships observed for other Ah receptor mediated responses. However, the time course of the Ca2+, as well as other responses observed in this study, suggest that the above effects may not necessarily involved the formation of the nuclear Ah receptor complex.

Animals↗
PubMed2002

Peptide mass fingerprinting peak intensity prediction: extracting knowledge from spectra.

Matrix-assisted laser desorption/ionization-time of flight mass spectrometry has become a valuable tool in proteomics. With the increasing acquisition rate of mass spectrometers, one of the major issues is the development of accurate, efficient and automatic peptide mass fingerprinting (PMF) identification tools. Current tools are mostly based on counting the number of experimental peptide masses matching with theoretical masses. Almost all of them use additional criteria such as isoelectric point, molecular weight, PTMs, taxonomy or enzymatic cleavage rules to enhance prediction performance. However, these identification tools seldom use peak intensities as parameter as there is currently no model predicting the intensities based on the physicochemical properties of peptides. In this work, we used standard datamining methods such as classification and regression methods to find correlations between peak intensities and the properties of the peptides composing a PMF spectrum. These methods were applied on a dataset comprising a series of PMF experiments involving 157 proteins. We found that the C4.5 method gave the more informative results for the classification task (prediction of the presence or absence of a peptide in a spectra) and M5' for the regression methods (prediction of the normalized intensity of a peptide peak). The C4.5 result correctly classified 88% of the theoretical peaks; whereas the M5' peak intensities had a correlation coefficient of 0.6743 with the experimental peak intensities. These methods enabled us to obtain decision and model trees that can be directly used for prediction and identification of PMF results. The work performed permitted to lay the foundations of a method to analyze factors influencing the peak intensity of PMF spectra. A simple extension of this analysis could lead to improve the accuracy of the results by using a larger dataset. Additional peptide characteristics or even PMF experimental parameters can also be taken into account in the datamining process to analyze their influence on the peak intensity. Furthermore, this datamining approach can certainly be extended to the tandem mass spectrometry domain or other mass spectrometry derived methods.

Acrylamide↗
PubMed1987

An identification technique for the spike artefact of saccadic eye movements.

Many subjects have a negative spike in the beginning of a saccade in electro-oculographic signals. The amplitude of the spike depends on the location of the electrodes. The spike distorts the saccades and causes errors in the parameters. The saccade spike can assist in the identification of small saccades. A syntactic technique based on formal languages and parsing is presented which looks for spikes from the electro-oculographic signal. For calculation of the algorithm, saccades from the photoelectric signal have been concurrently recorded and compared with the electro-oculographic signal.

Algorithms↗
PubMed1997

Increased number of cancer cells in bronchial washing fluid detected by combining conventional cytology and high-resolution flow cytometry.

The present study was performed to improve early lung cancer diagnosis in bronchial washing fluid, thereby increasing the diagnostic sensitivity of bronchoscopy by means of high-resolution flow cytometry (FC). We combined dual-parameter DNA/protein FC and conventional cytology in bronchial washing fluid samples from 112 patients with neoplastic and non-neoplastic lung diseases and found 43% of histologically confirmed tumor cases to be cytologically positive; 63% of the tumor samples were aneuploid, 52% of the aneuploid cases were cytologically positive and 48% were negative. In the negative cases, FC was an independent diagnostic factor. In 32% of the cases, FC also failed to detect abnormalities. However, the combination of both techniques increased the sensitivity in detecting neoplastic cells to 73%. Furthermore, simultaneous DNA/protein analysis allowed the recognition of aneuploid cell lines not detectable by single DNA measurement. Identification of aneuploid subpopulations by dual-parameter analysis in cytologically negative one-parameter FC "diploid" samples assumes an important diagnostic value. Dual-parameter DNA/protein FC is a valuable technique that increases the diagnostic yield of bronchoscopy with no risk for the patient and a low additional cost.

Aneuploidy↗
PubMedDate not supplied

Study on 480 hospitalized febrile children: evaluation of the septic risk and results of the antibiotic and corticosteroid combined therapy.

The febrile child, previously healthy, represents a frequent diagnosis and management problem for pediatricians who work in private offices and those in hospital emergency departments. We are specifically interested in the identification, for the febrile child with septic risk, of severity parameters permitting to assess the likelihood of a serious bacterial infection. In the retrospective study we present, carried out on children admitted for febrile illness, two factors were mainly evaluated: 1. identification of the septic risk on the basis of some laboratory and clinical parameters; 2. effectiveness of an early antibiotic plus corticosteroid treatment in a sub-group of children with septic risk. The parameters we considered have been the degree of temperature upon admission, the clinical appearance and the C-reactive protein (C-RP) values. A significant correlation resulted for levels of temperature over 39 degrees C, toxic-appearing child and very positive C-RP values. We have defined this condition as a "threatening" fever requiring an immediate hospitalization in order to administer appropriate blood tests and cultures, and also, according to our rationale, to start an early antibiotic plus corticosteroid therapy (within 6-12 hours from the disease onset).

Adjuvants, Immunologic↗
PubMed1993

Common factors in the identification of an assortment of brief everyday sounds.

Acoustic, ecological, perceptual and cognitive factors that are common in the identification of 41 brief, varied sounds were evaluated. In Experiment 1, identification time and accuracy, causal uncertainty values, and spectral and temporal properties of the sounds were obtained. Experiment 2 was a survey to obtain ecological frequency counts. Experiment 3 solicited perceptual-cognitive ratings. Factor analyses of spectral parameters and perceptual-cognitive ratings were performed. Identification time and causal uncertainty are highly interrelated, and both are related to ecological frequency and the presence of harmonics and similar spectral bursts. Experiments 4 and 5 used a priming paradigm to verify correlational relationships between identification time and causal uncertainty and to assess the effect of sound typicality. Results support a hybrid approach for theories of everyday sound identification.

Adult↗
PubMed1991

An approach to select the appropriate statistical method for testing bioequivalence.

Since most bioavailability studies are usually done with only a limited number of volunteers (usually 10-30), the statistical properties of the calculated bioavailability parameters are not well defined. The established statistical methods to test bioequivalence are usually based on either the assumption of normality or a symmetrical distribution. However, the decision of which method to apply, depends primarily on the distributional assumption of the data. In this study, an approach is followed where the small data base of a limited number of volunteers is expanded by adding pseudo-volunteers by "bootstrap" simulations. From such a larger data base it is easier to determine the statistical distributional properties of bioavailability parameters, which in its turn leads to the identification of an appropriate statistical method. With more certainty on which statistical method to apply, the original data can be used more effectively in testing for bioequivalence. In this paper, comparisons are made between the distributions of bioavailability parameters of an actual 60-volunteer study and those of two simulated data sets. Each such data set contained a random sample of 10 volunteers each (from the 60 volunteers), together with 50 pseudo-volunteers. These 50 volunteers were simulated from the random sample of 10 real volunteers. Good correspondences were obtained when comparing these two data sets with the original data, which indicated the validity to use this approach in bioavailability studies where a small number of volunteers had been used. This method proved useful to define the distributional properties for a relative small number of parameter-values available.

Biological Availability↗
PubMed2005

cis-regulatory logic of short-range transcriptional repression in Drosophila melanogaster.

Bioinformatics analysis of transcriptional control is guided by knowledge of the characteristics of cis-regulatory regions or enhancers. Features such as clustering of binding sites and co-occurrence of binding sites have aided enhancer identification, but quantitative predictions of enhancer function are not yet generally feasible. To facilitate the analysis of regulatory sequences in Drosophila melanogaster, we identified quantitative parameters that affect the activity of short-range transcriptional repressors, proteins that play key roles in development. In addition to the previously noted distance dependence, repression is strongly influenced by the stoichiometry, affinity, spacing, and arrangement of activator binding sites. Repression is insensitive to the type of activation domain, suggesting that short-range repression may primarily affect activators at the level of DNA binding. The activity of several short-range, but not long-range, repressors is circumscribed by the same quantitative parameters. This cis-regulatory "grammar" may aid the identification of enhancers regulated by short-range repressors and facilitate bioinformatic prediction of the functional output of transcriptional regulatory sequences.

Animals↗
PubMed1992

Noninvasive identification of severe coronary artery disease using exercise tomographic thallium-201 imaging.

The ability of exercise thallium-201 tomographic imaging to predict the presence of left main or 3-vessel coronary artery disease (CAD) was examined in 688 patients who underwent both exercise thallium-201 testing and coronary angiography. Significant differences existed for multiple variables between patients with (n = 196) and without (n = 492) severe left main or 3-vessel CAD. Logistic regression analysis identified 4 variables as independently predictive of left main or 3-vessel CAD. These variables were the magnitude of ST-segment depression with exercise, the number of visually abnormal short-axis thallium-201 segments, the presence or absence of diabetes mellitus, and the change in systolic blood pressure with exercise. Using these variables, patients were classified by nomograms into low-, intermediate- and high-probability groups. Patients at high probability (n = 205) had a 52% prevalence of 3-vessel or left main CAD, whereas those at low probability (n = 170) had only a 12% prevalence. Only 53 patients (29%) with 3-vessel or left main CAD had perfusion abnormalities in all 3 coronary territories. Clinical and exercise parameters provide important independent information in the identification of left main or 3-vessel CAD by exercise thallium-201 tomographic imaging, because thallium scintigraphy alone is suggestive of extensive CAD in few patients.

Aged↗
PubMed1987

Metabolic changes during the defunctionalized stage after ileal pouch-anal anastomosis.

Metabolic changes between the preoperative period and the defunctionalized stage after ileal pouch-anal anastomosis were investigated in 21 patients. Aspects studied included weight change, renal function, liver function, lipid metabolism, and two hematologic parameters. Of 21 patients, 19 lost weight. Cholesterol levels decreased from 183 +/- 30 IU/1 to 122 +/- 48 IU/1 (P less than .0001). Triglyceride levels rose from 95 +/- 29 IU/1 to 190 +/- 86 IU/1 (P less than .01). Significant elevations were seen in values of four liver function tests: SGOT, SGPT, lactic dehydrogenase, and alkaline phosphatase (P less than .05). Blood urea nitrogen levels increased from 11.1 +/- 4.7 mg/100 ml to 21.8 +/- 24.8 mg/100 ml (P less than .05). Serum creatinine levels rose from 0.97 +/- .18 mg/100 ml to 1.5 +/- 1.2 mg/100 ml (P less than .05). Uric acid levels increased from 5.6 +/- 1.8 mg/100 ml to 7.5 +/- 2.3 mg/100 ml (P less than .001). Hemoglobin values did not change significantly. Platelet counts rose from 304,000 +/- 79,000 to 447,800 +/- 189,000 (P less than .05). Identification of these systematic alterations in metabolic parameters during the defunctionalized stage can aid the physician in management of these patients.

Adenomatous Polyposis Coli↗
PubMedDate not supplied

[Role of tests of the total pressure of gases (O2 and CO2) in blood plasma in studying gaseous homeostasis in man].

Sixty essentially healthy subjects were examined manometrically with blood withdrawn from the coronary sinus, pulmonary artery, aorta, veins of the right kidney and the right liver lobe. Together with the traditional parameters of the gas contents and gradients of plasma, it is proposed to use tests measuring additive O2 and CO2 parameters. It has been demonstrated that the above organs can be discriminated using tests that are additive with respect to the gas pressure. It is emphasized that the tests proposed here, when used in addition to the traditional ones, allow identification of the gas and non-gas parameters of homeostasis as a single system of tests to assess the human body function.

Aorta↗
PubMed2004

Analysis of curated and predicted plastid subproteomes of Arabidopsis. Subcellular compartmentalization leads to distinctive proteome properties.

Carefully curated proteomes of the inner envelope membrane, the thylakoid membrane, and the thylakoid lumen of chloroplasts from Arabidopsis were assembled based on published, well-documented localizations. These curated proteomes were evaluated for distribution of physical-chemical parameters, with the goal of extracting parameters for improved subcellular prediction and subsequent identification of additional (low abundant) components of each membrane system. The assembly of rigorously curated subcellular proteomes is in itself also important as a parts list for plant and systems biology. Transmembrane and subcellular prediction strategies were evaluated using the curated data sets. The three curated proteomes differ strongly in average isoelectric point and protein size, as well as transmembrane distribution. Removal of the cleavable, N-terminal transit peptide sequences greatly affected isoelectric point and size distribution. Unexpectedly, the Cys content was much lower for the thylakoid proteomes than for the inner envelope. This likely relates to the role of the thylakoid membrane in light-driven electron transport and helps to avoid unwanted oxidation-reduction reactions. A rule of thumb for discriminating between the predicted integral inner envelope membrane and integral thylakoid membrane proteins is suggested. Using a combination of predictors and experimentally derived parameters, four plastid subproteomes were predicted from the fully annotated Arabidopsis genome. These predicted subproteomes were analyzed for their properties and compared to the curated proteomes. The sensitivity and accuracy of the prediction strategies are discussed. Data can be extracted from the new plastid proteome database (http://ppdb.tc.cornell.edu).

Arabidopsis↗