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At least 343 records · Page 19Linked to original sources
PubMed1991

An innovation in flow cytometry data collection and analysis producing a correlated multiple sample analysis in a single file.

The problems associated with rapid analysis and interpretation of data from multicolor immunofluorescence panels have been a formidable barrier to their routine use. Using present flow cytometry concepts, a panel of 11 tubes each containing multiple phenotypic markers or controls requires postdata acquisition manipulation of many multiparameter histogram and listmode files. We have developed a method that compresses all of the information from such a panel into a single listmode data file during run time. A single data file is used to record the entire phenotypic analysis for a particular patient or series within an experiment. This is accomplished by the incorporation of a tube identifier parameter (TIP) as well as the fluorescence and light scatter parameters normally collected. The TIP can then be used for gating discrimination of any tube or set of tubes within a panel. When the TIP is correlated with the PRISM parameter the entire patient phenotypic image can be represented within a single two-parameter histogram we have called a phenogram. This phenogram can be generated in real time, providing on-line preprocessing of a complex multicolor experiment. By examining the image created by the phenogram it is possible to rapidly flag abnormalities such as incorrect gating. This procedure was carried out on an EPICS Elite flow cytometer in its standard configuration with the addition of hardware to provide an input for the TIP.

Data Collection↗
PubMed1981

The gramicidin A channel: a review of its permeability characteristics with special reference to the single-file aspect of transport.

Gramicidin A forms univalent cation-selective channels of approximately 4 A diameter in phospholipid bilayer membranes. The transport of ions and water throughout most of the channel length is by a single-file process; that is, cations and water molecules cannot pass each other within the channel. The implications of this single-file mode of transport for ion movement are considered. In particular, we show that there is no significant electrostatic barrier to ion movement between the energy wells at the two ends of the channel. The rate of ion translocation (e.g., Na+ or Cs+) through the channel between these wells is limited by the necessity for an ion to move six water molecules in single file along with it; this also limits the maximum possible value for channel conductance. At all attainable concentrations of NaCl, the gramicidin A channel never contains more than one sodium ion, whereas even at 0.1 M CsCl, some channels contain two cesium ions. There is no necessity to postulate more than two ion-binding sites in the channel or occupancy of the channel by more than two ions at any time.

Cations, Monovalent↗
PubMed1991

Patch-clamp studies on the anomalous mole fraction effect of the K+ channel in cytoplasmic droplets of Nitella: an attempt to distinguish between a multi-ion single-file pore and an enzyme kinetic model with lazy state.

Patch-clamp studies have been employed in order to check whether the assumption of a multi-ion single-file pore is necessary for the explanation of the anomalous mole fraction effect or whether this effect can also be explained by a single-barrier enzyme kinetic model. Experiments in the cell-attached configuration were done on the tonoplast membrane of cytoplasmic droplets of Nitella in solutions containing 150 mol m-3 of K+ plus Tl+ with seven different K+/Tl+ ratios. At first sight, the results seem to support the multi-ion single-file pore, because apparent open channel conductivity displays the anomalous mole fraction effect, whereas open-probability has not been found to be dependent on the K+/Tl+ ratio. Changes in open probability would be expected for a single-barrier enzyme kinetic model with a lazy state. On the other hand, the lazy-state model is more successful in explaining the measured I-V curves. The entire slope of the apparent open channel current-voltage curves rotates with changing K+/Tl+ ratios in the whole voltage range between -100 and +80 mV. Numerical calculations on the basis of multi-ion single-file pores could create the anomalous mole fraction effect only in a limited voltage range with intersecting I-V curves. The apparent absence of an effect on open probability which is postulated by the lazy-state model can be explained if switching into and out of the lazy state is faster than can be resolved by the temporal resolution of 1 msec.

Biological Transport↗
PubMed2004

Medical Image Resource Center--making electronic teaching files from PACS.

A picture archive and communications system (PACS) is a rich source of images and data suitable for creating electronic teaching files (ETF). However, the potential for PACS to support nonclinical applications has not been fully realized: at present there is no mechanism for PACS to identify and store teaching files; neither is there a standardized method for sharing such teaching images. The Medical Image Resource Center (MIRC) is a new central image repository that defines standards for data exchange among different centers. We developed an ETF server that retrieves digital imaging and communication in medicine (DICOM) images from PACS, and enables users to create teaching files that conform to the new MIRC schema. We test-populated our ETF server with illustrative images from the clinical case load of the National Neuroscience Institute, Singapore. Together, PACS and MIRC have the potential to benefit radiology teaching and research.

Computer Communication Networks↗
PubMed2004

A cost-effective web-based teaching file system.

Teaching files are common in radiology. Although there is an increasing role of digital technology in radiology departments, today's teaching files have not yet seen the application of this new technology. This may have been due in part to poor or incomplete implementation in many commercial software packages. We have demonstrated that by utilizing free software from the Internet, a web-based teaching file system, which is easy to use, low cost, and secure, can be created.

Cost-Benefit Analysis↗
PubMed1983

Rate theory models for ion transport through rigid pores. II. Time-dependent analysis of the single-file model with special reference to oscillatory behavior.

This article deals with the time-dependent evolution of the single-file movement of ions through channels of both biological and artificial membranes. The single-file transport process may exhibit not only the usual relaxation behaviour but also oscillatory behaviour as a steady state is approached after an initial perturbation. A necessary condition for the occurrence of oscillations is that the system acts sufficiently far from equilibrium. The occurrence of oscillations is due to the interactions within the transport system which are taken into account by the single-file model; these are the electrostatic repulsion between the ions being transported, and the competition of the ions for the free binding sites within the pore. Information about the strength of the interactions can be obtained by measuring the damping of the transport observables (e.g. the electric current): The stronger the inter-ionic repulsion, the more apparent the oscillatory behaviour will become. Furthermore, the damping is influenced by the microscopic structure of the transport system (i.e. the energy profile of the pores). With an increasing degree of microscopicity, i.e. with a decreasing number of binding sites and an increasingly irregular pore profile, the oscillations become more damped. However, a considerable oscillatory behaviour can only be predicted for pores with both a sufficiently regular structure and a sufficiently large number of binding sites. For this class of pores, however, the measurement of the damping represents an appropriate method of gaining information which could exceed that obtainable from the usual methods of measuring stationary quantities (e.g. stationary conductance). Moreover, our goal is to explain theoretically how the oscillatory behaviour can be interpreted in terms of the order inherent in the ionic movement, which is determined by both the external and internal forces and the microscopic properties of the system.

Binding Sites↗
PubMed1983

An in vitro study of the comparative effectiveness of obturating curved root canals with gutta-percha cones, silver cones, and stainless steel files.

The quality of apical seal obtained with gutta-percha cones, silver cones, and stainless steel files was assessed in 120 freshly extracted teeth with moderately or severely curved root canals. Teeth were coated with wax, except in the apical foramen area, and immersed in 2 percent methylene blue solution for 48 hours. Apical leakage was quantitated by a linear measurement of the distance that the dye penetrated along the root canal and by a volumetric measurement of the quantity of dye within the root. There was a highly significant (p less than 0.001) correlation between the two measurements. Root canals filled with silver cones showed significantly less apical leakage than those filled with gutta-percha or stainless steel files, regardless of degree of curvature. For both silver cones and stainless steel files, leakage was less in severely curved roots than in moderately curved roots.

Dental Bonding↗
PubMed1991

Radiographic interpretation of endodontic file length.

The purpose of this study was to evaluate the accuracy of examiners when asked to make file length adjustments with only a radiograph. The examiners viewed several radiographs under proper viewing conditions but without the aid of measuring devices. Two files of varying lengths (sizes 10 and 15) were placed in maxillary and mandibular premolars and molars from cadavers. The nine examiners were 67.91% in agreement of actual file length adjustment needed when adjustments of up to 0.5 mm were needed, 17.76% when adjustments of from 0.5 up to 1.0 mm were needed, and 14.33% when adjustments of greater than 1.0 mm were needed.

Dental Pulp Cavity↗
PubMed1996

A large-scale processing of kinetic data files with derivation of the inhibitory constant Ki: an application to proline isomerases.

An integral system of algorithms (file preprocessor + the adapted KORE program + the Powell non-linear least-squares minimizer) named KINMIN is described. This system was applied to simultaneously process a large number of kinetic data files for cis/trans isomerization of Xaa-Pro bonds in synthetic peptides catalysed by peptidylproline cis/trans isomerases which can be inhibited by nanomolar concentrations of the immunosuppressive compounds cyclosplorin-A, FK506 or rapamycin. The system allows preprocessing of kinetics data files and derives from them the first-order rate constants which are used to optimize the inhibitory constant Ki of each inhibitor. The KINMIN program may be also applied to derive Ki for other sets of enzymes and their inhibitors.

Algorithms↗
PubMed1989

Electrochemical engineering approach to the irrigation of tooth canals under the influence of a vibrating file.

Doubt exists concerning the irrigation of secondary tooth canals when the vibration of a file introduced into the main root canal is superimposed on flow-through irrigation of the main canal. Depending on the type of commercial equipment used, the vibrations of the file are sonic or ultrasonic. We use the methodology of an electrochemical engineering approach in a study of the intensity of the irrigation of the secondary canals under the influence of sonic and ultrasonic vibrations of a file located at various heights in the main canal. The tooth canals are simulated by small electrochemical cells containing electrodes located at the end of cavities simulating the secondary canals. An electrochemical method is used to measure the mass transfer coefficients at these electrodes, a classical method in electrochemical engineering laboratories. The values of the mass transfer coefficients are representative of the importance of the irrigation of the electrodes. Thus they give a quantitative idea of the vibrations on the irrigation of secondary tooth canals. The work demonstrates the usefulness of the electrochemical engineering approach in contributing to the solution of a biomedical problem.

Electrochemistry↗
PubMed1994

IS & C system and file protection mechanism.

This paper reports a new extension of IS & C (Image Save And Carry) project. Because IS & C is an off-line system and requires full compatibility so as to enable medical data interchange with ease among hospitals and clinics, specifications that are indispensable for compatibility have been standardized by the IS & C committee. The IS & C system is supposed to be used in medicine, so the file protection mechanism for the security of the recorded files has been also developed. The characteristics of IS & C volume and file structure and the second national project being carried out in National Cancer Center Hospital are briefly explained as well.

Computer Communication Networks↗
PubMedDate not supplied

User discipline in a personal computer-based filing of ultrasound records.

The discipline of entering ultrasound examination data in a personal computer file was studied over two periods. During the first period (19 weeks), the use of the computer was limited to one laboratory. During the second period (14 weeks), the computer was shared by three laboratories operating in nearby premises. During the study, 2857 (89%) of a total of 3209 ultrasound examinations performed were duly recorded in the data file. The frequency of failure to enter data was markedly higher during the second period (7-45%) than during the first period (5%) of the study. Overall, there was a highly significant (p less than 0.001) tendency to enter pathological findings at the expense of normal and non-diagnostic findings. The ease of access to the computer and the number of examinations recorded appear to determine user conscientiousness in filing data. Selection and omission of data impair the usefulness of the data log in research.

Humans↗
PubMed2006

In vitro radiographic determination of distances from working length files to root ends comparing Kodak RVG 6000, Schick CDR, and Kodak insight film.

Previous studies suggest that digital and film-based radiography are similar for endodontic measurements. This study compared the accuracy and acceptability of measured distances from the tips of size #10 and #15 files to molar root apices in cadaver jaw sections using the newly developed Kodak RVG 6000, and the Schick CDR digital systems to digitized Kodak film. Standardized images were taken of files placed 0.5 to 1.5 mm short of true radiographic lengths. Images were imported into Adobe PhotoShop 7.0, thereby blinding observers who measured distances from files to root apices and assessed images for clarity (acceptability). Repeated measures ANOVA and Tukey-Kramer post hoc tests demonstrated that Kodak RVG 6000 images with enhanced contrast produced significantly less measurement error than unenhanced contrast Schick CDR images (p < 0.05) and significantly higher acceptability ratings than all other systems (all p < 0.002). Among these conditions, the newly developed Kodak RVG 6000 system provided the best overall images.

Analysis of Variance↗
PubMed2004

Effect of modified Hedstrom files on instrumentation area produced by ProFile instruments in oval canals.

OBJECTIVE: To study the effect of a modified Hedstrom file called IqFile on the instrumentation shape of oval canals prepared with ProFile instruments. STUDY DESIGN: Fifty extracted premolars were divided into 3 groups of 16 teeth each. Group 1 was subjected to ProFile 0.04 rotary instrumentation to a size 6. Group 2 followed the same technique, but also received buccolingual hand instrumentation with IqFiles to ISO size 70. Group 3 was instrumented similarly to group 2 but unmodified Hedstrom files were used. Teeth were sectioned at 1 and 3 mm from working length and photographed at 26x magnification. AutoCAD was used for measuring the percentage of instrumented area of the canal. RESULTS: ANOVA revealed that Group 2 was significantly better than Groups 1 (P=.00) and 3 (P=.00) at the 1 mm level. At the 3 mm level Group 2 was significantly better than Group 1 (P=.03), but no differences were found between Groups 2 and 3 (P=.15). CONCLUSION: The combination of ProFile and IqFile was found more effective in instrumenting oval canals at both the 1 and the 3 mm levels. However, at the 3 mm level no difference was detected between the use of IqFiles and the use of unmodified Hedstrom files.

Bicuspid↗
PubMed2005

Effectiveness of a hand file and three nickel-titanium rotary instruments for removing gutta-percha in curved root canals during retreatment.

OBJECTIVE: This study intended to compare the effectiveness of hand files and FlexMaster, ProTaper, and RaCe rotary instruments for removing gutta-percha in curved root canals during retreatment. STUDY DESIGN: Sixty curved mandibular premolars were randomly divided into 4 groups of 15 specimens each. The canals were enlarged and obturated using lateral condensation technique. After repreparation with the test instruments the specimens were cleared. The area of remaining obturation material was measured from 2 directions. Statistical analysis was performed using the Kruskal-Wallis test and a closed test procedure. RESULTS: RaCe instruments revealed significantly less residual obturation material than FlexMaster files (P < .05). No significant difference was found among the hand file, ProTaper, and FlexMaster groups (P > .05). There were 5 fractured instruments in the ProTaper group and 3 in the FlexMaster group. CONCLUSION: The RaCe system is an efficient and safe device for gutta-percha removal in curved root canals.

Bicuspid↗
PubMed1994

Transport properties of single-file pores with two conformational states.

Complex facilitative membrane transporters of specific ligands may operate via inner channels subject to conformational transitions. To describe some properties of these systems, we introduce here a kinetic model of coupled transport of two species, L and w, through a two-conformational pore. The basic assumptions of the model are: a) single-file of, at most, n molecules inside the channel; b) each pore state is open to one of the compartments only; c) there is at most only one vacancy per pore; d) inside the channel, a molecule of L occupies the same positions as a molecule of w; and e) there is at most only one molecule of L per pore. We develop a general representation of the kinetic diagram of the model that is formally similar to the one used to describe one-vacancy transport through a one-conformational single-file pore. In many cases of biological importance, L could be a hydrophilic (ionic or nonionic) ligand and w could be water. The model also finds application to describe solute (w) transport under saturation conditions. In this latter case, L would be another solute, or a tracer of w. We derive steady-state expressions for the fluxes of L and w, and for the permeability coefficients. The main results obtained from the analysis of the model are the following. 1) Under the condition of equilibrium of w, the expression derived for the flux of L is formally indistinguishable from the one obtainable from a standard four-state model of ligand transport mediated by a two-conformational transporter. 2) When L is a tracer of w, we can derive an expression for the ratio between the main isotope and tracer permeability coefficients (Pw/Pd). We find that the near-equilibrium permeability ratio satisfies (n - 1) < or = (Pw/Pd)eq < or = n, a result previously derived for the one-conformational, single-file pore for the case that n > or = 2. 3) The kinetic model studied here represents a generalization of the carrier concept. In fact, for the case that n = 1 (corresponding to the classical single-occupancy carrier), the near-equilibrium permeability ratio satisfies 0 < or = (Pw/Pd)eq < or = 1, which is characteristic of a carrier performing exchange-diffusion.

Binding Sites↗
PubMed1995

Comparison of three files to prepare curved root canals.

Flex-R, Ultra-Flex (Ni-Ti construction), and K-type files were compared using a circumferential filing technique on 96 extracted human maxillary molars. Buccal canals with minimal initial curvature of 24 degrees were used. The maximal initial curvature was 52 degrees. Canal curvature was measured before and after filling, and changes were analyzed statistically. The angle of curvature was better maintained with the Flex-R and Ultra-Flex files.

Analysis of Variance↗