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At least 271 records · Page 15Linked to original sources
PubMed1990

[Parameters for determining the time of death from post-mortem muscle contraction--precision of assessing time of death].

The objectified muscular contraction on excitation with rectangular impulses of 1 sec duration and definite current intensity is in its postmortem course characterised by: 1. Change of the shape of muscular contraction (time-course of muscular contraction) from a two peak to a one peak shape 2. postmortem decrease of the maximum force of muscular contraction on definite current intensity 3. increase of the relaxation time of muscular contraction. On an random sample of fifty bodies decrease of the maximum force and increase of the relaxation time as criteria for extrapolating the time since death were investigated. The extrapolation was performed on the basis of the regression between ln of the maximum force and time using the mean values for slope and intercept and the regression between ln of the relaxation time and the ln of the time since death respectively using the mean values for slope and intercept too. On fifty bodies the calculated 95%--limits of confidence are +/- 2.85 h (decrease of the maximum force) and +/- 2.7 h (increase of relaxation time) up to 13 hpm. The calculated 95% limits of confidence were examined on an independent random sample of 20 bodies and proved to be reliable.

Electric Stimulation↗
PubMed1989

[Dental resin for restoration with unsaturated polyester resin used as base material. Effect of catalyst, accelerator and subaccelerator on working time, setting time and peak temperature].

The fatal demerit of resin materials which causes a marginal sealing defect or marginal fracture is hard to eliminate. A series of studies seeking for dental resin for restoration having no polymerization shrinkage, applying polyester resin used as base resin. This study was conducted to promote the improvement of composite resin, in which the author examined the composition with catalyst, accelerator and subaccelerator having preferable working time, setting time and peak temperature which is not clear, so as to obtain the fundamental data. In accordance with the increase in the amount of catalyst, accelerator and subaccelerator added, peak temperature showed a tendency to increase. Contrarily, working time and setting time showed a tendency to decrease. The composition showing preferable working time, setting time and peak temperature, is as follows: to the base resin, polyester with 38 wt% of shrinkage inhibitor mixed, catalyst by 1.0 wt%, accelerator by 0.50 wt% and subaccelerator by 0.02 wt% were added. The trial product of composite resin a 70 wt% of surface-treated glass beads added showed a working time of 2.3 minutes, setting time of 9 minutes and peak temperature of 57.0 degrees C, approximately the same values as of commercial composite resin.

Dental Restoration, Permanent↗
PubMed1983

Relationships between moment of monitored time-activity curves and regional cerebral mean transit time following common carotid administration of a non diffusible tracer.

By intravenous Radionuclide Angiography it is possible to estimate a whole path regional Arm-Brain mean transit Time as the first moment of monitored activity about injection time. This time is composed by an input mean transit time or transit time in the vein-inflow cerebral path and a circulation time within the monitored cerebral space. By evaluating this last by means of common carotid administration it was concluded that, although calculated by residue detection and not from outflow curves, this time is not far from regional cerebral mean transit time.

Brain↗
PubMedDate not supplied

Factors influencing the time to thrombolysis in acute myocardial infarction. Time to Thrombolysis Substudy of the National Registry of Myocardial Infarction-1.

BACKGROUND: The Time to Thrombolysis Substudy of the National Registry for Myocardial Infarction provided the opportunity to identify factors that delay thrombolytic treatment of patients with ST-segment elevation acute myocardial infarction. PARTICIPANTS: Forty-two participating registry hospitals volunteered for the Time to Thrombolysis Substudy. METHODS: A case report form was developed to collect time points for emergency department arrival (door), recording of the electrocardiogram (ECG) (data), entry of the order to give a thrombolytic drug (decision), and initiation of the thrombolytic infusion (drug) as defined by the National Heart Attack Alert Program. The impact of mode of transportation to the hospital, sex, policy-driven cardiology consultation and/or contact of the primary care physician on door-to-drug time, and each component interval were determined in 1755 patients who were treated with recombinant tissue-type plasminogen activator (A1-teplase). The t test was used for comparison of means and the nonparametric sign test was used for medians. RESULTS: A minority of patients arrived at the hospital by ambulance, although more women (49.6%) arrived by ambulance than men (40.9%). However, women arrived at hospitals significantly later after onset of symptoms than men. It took half as long for patients arriving by ambulance to be seen by the physician than those who transported themselves to the hospital. It took longer for women to have the initial 12-lead ECG recorded than men. The decision to order a thrombolytic agent was delayed by 22 minutes and median door-to-drug time by 21 minutes in those patients who had a cardiac consultation over those in whom the drug was ordered and infusion was initiated by the emergency physician. Although the initial 12-lead ECG showed ST-segment elevation in 86% of patients who received the thrombolytic drugs, with no difference between men and women and no difference in the rate of cardiology consultation between men and women (77%), door-to-decision time and door-to-drug time were substantially longer for women having consultation than men. There was no significant difference in door-to-decision time between men and women when no consultation was performed, but it still took longer for a drug infusion to be initiated in women. Contacting the primary care physician delayed the decision to give a thrombolytic drug by 18 minutes and the administration of the drug by 20 minutes, but there were no differences between men and women. Preparation of the drug in the pharmacy resulted in significant delay compared with mixing it in the emergency department. CONCLUSIONS: Hospital practices and policies, including contacting the primary care physician prior to the initiation of a lytic drug, cardiology consultation, and preparation of the drug in the pharmacy rather than in the emergency department, significantly delay the goal of early treatment of patients with ST segment elevation acute myocardial infarction. Delays in hospital arrival for women are compounded by delays in the decision to treat them with a thrombolytic drug and initiation of the drug therapy in those women who receive consultation compared with men. Other delays in acquiring the first ECG and initiating the drug infusion in women are not explained.

Aged↗
PubMed2006

Use of multivariate analysis for optimization of separation parameters and prediction of migration time, resolution, and resolution per unit time in micellar electrokinetic chromatography.

The optimization of separation parameters in chromatography for better separation and resolution of analytes continues to be a labor intensive procedure usually performed by a trial and error method. A multivariate analysis in the form of multilinear regression (MLR) is used to optimize separation parameters and predict the migration behavior, resolution, and resolution per unit time of achiral (4-chlorophenol, pentachlorophenol, clonazepam, and diazepam) and chiral (1,1'-binaphthyl 2,2'-dihydrogen phosphate (BNP), and 1,1'-bi-2-naphthol (BOH)) compounds in MEKC. Separations of achiral and chiral analytes were performed using an achiral (poly(sodium N-undecylenic sulfate)) molecular micelle and chiral (poly(sodium N-undecanoyl-L-leucylvalinate) or poly(sodium N-undecanoyl-L-isoleucylvalinate)) molecular micelle, respectively, at various operating temperatures, applied voltages, pH values, and molecular micelle concentrations in the BGE. The separation parameters were subsequently used as input variables for MLR models. The models were validated with independent samples. The root-mean-square percent relative error (RMS%RE) is used as a figure of merit for characterizing the performance of the migration time, resolution, and resolution per unit time models. The RMS%RE obtained for predicted migrated times, resolutions, and resolution per unit time of 4-chlorophenol, pentachlorophenol, clonazepam, diazepam, BNP, and BOH ranged between 8 and 19%. The same experimental procedure was used to optimize the separation parameters of six other chiral analytes of different compound class. The predicted migration times, resolutions, and resolution per unit time of the chiral as well as the achiral analytes compare favorably with the experimental migration times and resolutions, indicating versatility and wide applicability of the technique in MEKC.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2006

Time dependence of 3He diffusion in the human lung: measurement in the long-time regime using stimulated echoes.

A stimulated-echo-based technique was developed to measure the long-time-scale apparent diffusion coefficient (ADC) of hyperpolarized 3He during a single breath-hold acquisition. Computer simulations were used to evaluate the performance of the technique and guide the selection of appropriate parameter values for obtaining accurate ADC values. The technique was used in 10 healthy subjects and two subjects with chronic obstructive pulmonary disease (COPD) to measure the global ADC for diffusion times between a few tenths of a second and several seconds, and to acquire spatial maps of the ADC for a diffusion time of 1.5 s. The reproducibility of the technique and its sensitivity to the direction of diffusion sensitization were also investigated. In healthy subjects, global ADC values decreased by severalfold over the range of diffusion times measured (mean values = 0.039 and 0.023 cm2/s at diffusion times of 0.61 and 1.54 s, respectively). ADC maps were generally uniform, with mean values similar to the corresponding global values. For the two COPD subjects, global ADC values were substantially greater than those of every healthy subject at all diffusion times measured. In addition, regional elevations of ADC values were far more conspicuous on long-time-scale ADC maps than on short-time-scale ADC maps.

Adult↗
PubMed1999

Real-time fMRI paradigm control, physiology, and behavior combined with near real-time statistical analysis.

This study presents an integrated approach to on-line fMRI data processing that combines real-time paradigm control and real-time MR image statistical analysis with nearly real-time integration of fMRI behavioral and physiological data. The real-time paradigms involve accurate timing control of multiple independent processing streams for stimulus presentation, physiological monitoring, behavioral response recording, and scanner synchronization. The real-time image analysis provides high resolution MR image reconstruction, head motion detection, translational motion correction, and t test statistical activation maps for either block design or single-trial based paradigms. The near real-time analysis allows physiological and behavioral data collected during a paradigm to be combined with the MR time series and provides extended data filtering and statistical processing within a few minutes after the end of the scan. This integrated approach improves fMRI reliability for both clinical and research studies.

Adult↗
PubMed1987

Generalizations in linear pharmacokinetics using properties of certain classes of residence time distributions. II. Log-concave concentration-time curves following oral administration.

The present approach enables a noncompartmental assessment of log-concave plasma concentration-time profiles following oral drug administration. Observed log-concavity corresponds to a nonparametric class of residence time distributions with the following properties: (1) The fractional rate of elimination kB(t) (failure rate of the distribution) increases monotonically until reaching the terminal exponential coefficient kB,Z. (2) The relative dispersion of body residence times CVB2 (ratio of variance to the squared mean, VBRT/MBRT2) acts as a shape parameter of the curve. The role of the input process in determining the shape of the concentration profile is discussed. In this connection evidence is provided for the importance of log-concave percent undissolved versus time plots, introducing the general concept of a time-varying fractional rate of dissolution. The governing factor for the appearance of log-concavity is the ratio of mean absorption time to mean disposition residence time (MAT/MDRT); this factor exceeds a particular threshold value which depends on the distributional properties of the drug. Generalizing previous approaches which are valid for first-order input processes, the "flip-flop" phenomenon and the problem of "vanishing of exponential terms" are explained using fewer assumptions. Upper bounds for the elimination time (more than 90% eliminated) and the cutoff error in AUC determination are presented. The concept of log-concavity reveals general features of the pharmacokinetic behavior of oral dosage forms exhibiting a dominating influence of the absorption/dissolution process.

Administration, Oral↗
PubMed2002

Real-time three-dimensional echocardiography for improved evaluation of diastolic function using volume-time curves.

BACKGROUND: Accurate assessment of left ventricular function is of the greatest importance in clinical cardiology for decision making. Diastolic dysfunction is getting more concern as a cause of heart failure while, currently used non-invasive modalities for diagnosing diastolic abnormalities have significant limitations. Dynamic left ventricular volume change was applied for the evaluation of diastolic function by various techniques that have been demonstrated to be of diagnostic value. However, it has not been accepted into clinical practice because existing techniques are either invasive, inaccurate, expensive or time consuming. REAL-TIME THREE-DIMENSIONAL ECHOCARDIOGRAPHY: Real-time three-dimensional (3-D) echocardiography is a new ultrasound technique that provides transthoracic volumetric images of the heart in real time. Thereby, the acquired images are ideally suited for the assessment of dynamic left ventricular volume change. Generation and analysis of left ventricular volume-time curves by real-time 3-D echocardiography has been demonstrated to be feasible in normal subjects and patients and accuracy of volume-time curves was good compared to magnetic resonance imaging. We compare the new real-time 3-D echo approach with the advantages and limitations of existing noninvasive and invasive techniques.

Cardiac Volume↗
PubMed1989

Effects of average movement velocity on reaction time and spatiotemporal accuracy in single-aiming and rapid-timing movement tasks.

The effects of instructed movement speed were investigated in two experiments. First, rapid-timing and single-aiming movement tasks were compared. Unlike rapid timing, single aiming implies spatial accuracy. The aim of the first experiment was twofold: (a) to examine whether the requirement of accurate placement termination in single aiming affects the negative relationship between instructed average velocity and reaction time found in rapid timing, and (b) to test the speed-accuracy relationships predicted by the symmetric impulse variability model of these movement tasks. For this purpose, four average velocities (5, 24, 75, and 140 cm/s) were investigated in both types of movement tasks in a two-choice reaction task. The effects of average velocity on reaction time were similar in both single-aiming and rapid-timing tasks, and the predicted linear relationship between instructed average velocity and spatial accuracy was not found. The results suggest that the movement control mode, that is, open loop or closed loop, interferes with effects of instructed average velocity. The movement control mode explanation was confirmed in the second experiment with respect to the effect of paired velocities on reaction time. It is argued that the type of movement control mode must be considered in the interpretation of effects of instructed average velocity on reaction time and spatiotemporal measures.

Journal Article↗
PubMed2000

Time-frequency analysis of heart rate variability using short-time fourier analysis.

This study was done to introduce new parameters derived by time frequency analysis of heart rate variability data. Four simulation experiments were carried out to compare the short-time Fourier transform (STFT) analysis method to the traditional overall spectral analysis method. Sinusoidal signals were generated with identical total power in the high-frequency band, but varying time-frequency and time-amplitude information. The STFT method was also applied to heart rate variability data from the stages of normal human sleep. Data analysis included computation of the power in the high-frequency band by overall spectral analysis. The instability coefficients (ICs) of the frequency and power in the high-frequency band were derived by STFT analysis. The ICs derived by the STFT method were able to describe time-frequency and time-amplitude variations in sinusoidal signals which contained identical total power in a specified frequency range. The ICs of the frequency and power were able to differentiate variations in vagal activity between the stages of human sleep and waking. The ICs represent new parameters derived by the STFT method, and allow the detection and quantification of short-lasting time-frequency and time-amplitude variations that remain obscured by overall spectral analysis.

Adult↗
PubMed1997

Time-to-event analysis of longitudinal follow-up of a survey: choice of the time-scale.

Following individuals sampled in a large-scale health survey for the development of diseases and/or death offers the opportunity to assess the prognostic significance of various risk factors. The proportional hazards regression model, which allows for the control of covariates, is frequently used for the analysis of such data. The authors discuss the appropriate time-scale for such regression models, and they recommend that age rather than time since the baseline survey (time-on-study) be used. Additionally, with age as the time-scale, control for calendar-period and/or birth cohort effects can be achieved by stratifying the model on birth cohort. Because, as discussed by the authors, many published analyses have used regression models with time-on-study as the time-scale, it is important to assess the magnitude of the error incurred from this type of incorrect modeling. The authors provide simple conditions for when incorrect use of time-on-study as the time-scale will nevertheless yield approximately unbiased proportional hazards regression coefficients. Examples are given using data from the first National Health and Nutrition Examination Survey (NHANES I) Epidemiologic Followup Study. Additional issues concerning the analysis of longitudinal follow-up of survey data are briefly discussed.

Adult↗
PubMed2000

Comparative studies of two-times-daily versus three-times-daily indinavir in combination with zidovudine and lamivudine.

OBJECTIVES: To compare the efficacy and safety of two-times-daily versus three-times-daily indinavir in combination with zidovudine and lamivudine. DESIGN: Two multicenter, open-label, randomized 24-week studies. METHODS: Adults HIV-1 infection, HIV-1 RNA greater than 10000 copies/ml, and no prior lamivudine or protease inhibitor therapy were eligible. In a pilot study (Study A), patients received indinavir at 800 mg every 8 h, 1000 mg every 12 h, or 1200 mg every 12 h. In a subsequent study (Study B), patients received indinavir at 800 mg every 8 h or 1200 mg every 12 h. All subjects received zidovudine (300 mg) and lamivudine (150 mg) every 12 h. An intent-to-treat analysis was used. RESULTS: In Study A, which enrolled 88 patients, neither HIV-1 RNA nor CD4 cell responses differed significantly between treatment groups at 24 weeks when corrected for multiple comparisons. Study B enrolled 433 patients, but was prematurely discontinued when interim analysis suggested greater efficacy of three-times-daily indinavir. Of the first 87 patients reaching week 24, HIV-1 RNA was less than 400 copies/ml in 91% receiving three-times-daily versus 64% receiving two-times-daily indinavir (P < 0.01). CONCLUSION: Three-times-daily indinavir appears more efficacious than two-times-daily dosing when administered with zidovudine and lamivudine. Two-times-daily indinavir dosing should only be considered in situations characterized by favorable pharmacokinetic drug-drug interactions.

Adult↗
PubMed2004

Testing time symmetry in time series using data compression dictionaries.

Time symmetry, often called statistical time reversibility, in a dynamical process means that any segment of time-series output has the same probability of occurrence in the process as its time reversal. A technique, based on symbolic dynamics, is proposed to distinguish such symmetrical processes from asymmetrical ones, given a time-series observation of the otherwise unknown process. Because linear stochastic Gaussian processes, and static nonlinear transformations of them, are statistically reversible, but nonlinear dynamics such as dissipative chaos are usually statistically irreversible, a test will separate large classes of hypotheses for the data. A general-purpose and robust statistical test procedure requires adapting to arbitrary dynamics which may have significant time correlation of undetermined form. Given a symbolization of the observed time series, the technology behind adaptive dictionary data compression algorithms offers a suitable estimate of reversibility, as well as a statistical likelihood test. The data compression methods create approximately independent segments permitting a simple and direct null test without resampling or surrogate data. We demonstrate the results on various time-series-reversible and irreversible systems.

Journal Article↗
PubMed1976

Noninvasive differentiation of cardiomyopathy from coronary disease; pulse transmission time and systolic time intervals.

Systolic time intervals and central pulse transmission time were compared in cardiomyopathy (CM) patients and age-and sex-matched patients with coronary artery disease (CAD). Significant differences were found in pulse transmission time (shorter in the CAD patients (p less than .001) and in the pre-ejection period (p less than .001), ejection time index (p less than .05), and in the ratio of the pre-ejection period to the left ventricular ejection time (p less than .001); all were markedly abnormal in the CM group. Pulse transmission time differences may have been the result of more generalized arteriosclerotic disease in the CAD patients. It appears that both systolic time intervals and pulse transmission time clearly distinguish CM from CAD.

Cardiomyopathies↗
PubMed2004

Formulation design of double-layer in the outer shell of dry-coated tablet to modulate lag time and time-controlled dissolution function: studies on micronized ethylcellulose for dosage form design (VII).

The dry-coated tablet with optimal lag time was designed to simulate the dosing time of drug administration according to the physiological needs. Different compositions of ethylcellulose (EC) powder with a coarse particle (167.5 microm) and several fine particles (< 6 microm), respectively, were mixed to formulate the whole layer of the outer shell of dry-coated tablets. The formulations containing different weight ratios of coarse/fine particles of EC powders or 167.5 microm EC powder/excipient in the upper layer of the outer shell to influence the release behavior of sodium diclofenac from dry-coated tablet were also explored. The results indicate that sodium diclofenac released from all the dry-coated tablets exhibited an initial lag period, followed by a stage of rapid drug release. When the mixture of the coarse/fine particles of EC powders was incorporated into the whole layer, the lag time was almost the same. The outer shell broke into 2 halves to make a rapid drug release after the lag time, which belonged to the time-controlled disruption of release mechanism. When the lower layer in the outer shell was composed of 167.5 microm EC powder and the upper layer was formulated by mixing different weight ratios of 167.5 microm and 6 microm of EC powders, the drug release also exhibited a time-controlled disruption behavior. Its lag time might be freely modulated, depending on the amount of 6 microm EC powder added. Once different excipients were respectively incorporated into the upper layer of the outer shell, different release mechanisms were observed as follows: time-controlled explosion for Explotab, disruption for Avicel and spray-dried lactose, erosion for dibasic calcium phosphate anhydrate, and sigmoidal profile for hydroxypropyl methylcellulose.

Cellulose↗
PubMed1986

Influence of feeding time and diet on time of parturition in multiparous ewes.

Three hundred three pregnant ewes were randomly allotted to treatments in a 2 (diet) X 2 (feeding time) factorial arrangement 10 d before the first lambs were due in two lambing seasons to study the effect of time of feeding and diet on time of lambing. Behavioral activities were observed to determine if there was a relationship to time of parturition. All ewes were fed .5 kg ground whole corn per day plus either: alfalfa hay fed at 2200 each day, alfalfa hay fed at 1000 each day, alfalfa haylage fed at 2200 each day or alfalfa haylage fed at 1000 each day. Lambing data from 1983 and 1984 were combined across years because no treatment X year interactions (P greater than .05) were detected. Average time of day for lambing did not differ (P greater than .05) among treatments. In general, no differences due to treatments were observed in lambing time or behavioral activities studied. When data were pooled across treatments, two peak lambing times were observed. These peak times for lambing were from 0300 to 0700 (22.1%) and from 1500 to 1900 (22.5%). During these two 4-h periods (8 h total) 44.6% of the ewes gave birth.

Animal Husbandry↗
PubMed2004

[Focal liver lesions: characterization with quantitative analysis of T2 relaxation time in TSE sequence with double echo time].

PURPOSE: To evaluate the accuracy of calculation of T2 relaxation time with simplified algorithm in characterization of liver focal lesions with Turbo Spin Echo (TSE) T2-weighted sequences with double echo time (TE). MATERIALS AND METHODS: We carried out a retrospective analysis of 113 hyperintense hepatic focal lesions in T2-weighted sequences (52 metastases, 51 hemangiomas and 10 cysts). We have employed a single TSE T2-weighted sequence with effective TE of 83 and 165 msec and turbo factor 9. Signal intensity (IS) of each lesion was measured on different TE. Using these values, we calculated T2 relaxation time by the following simplified algorithm: T2(ms)=(TE2-TE1)/ (lnIS1-lnIS2). T2 relaxation time has been correlated with the final diagnosis, obtained by percutaneous biopsy, surgical resection or three months follow-up. RESULTS: The mean T2 relaxation time for metastases was 108,7 msec (+/-30), for hemangiomas 166,5 msec (+/- 29) and for cysts 312,4 msec (+/-19). The difference between the mean T2 relaxation time for metastases and hemangiomas was statistically significant (p<0.0001). Most metastases were best characterized between the threshold value of 130 and 140 msec. The values of specificity and sensitivity of the diagnosis of malignant hepatic lesion was respective 0,86 and 0,88. All false positive diagnoses were hemangiomas of less than one centimeter. CONCLUSIONS: Introducing double echo time TSE sequences in the protocol of liver study concurs to obtain high diagnostic accuracy in the characterization of the hepatic lesions. The quantitative analysis of T2 represents a useful additional instrument to the morphologic analysis in discrimination between hepatic lesions and can be carried out by TSE sequences with elevated reliability reducing the imaging time compared with conventional sequences. The evaluation of hepatic lesions of less than one centimeter should always include analysis of dynamic gadolinium-contrast images.

Adult↗