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At least 505 records · Page 28Linked to original sources

PubMed2006

In vitro investigation of ceruminolytic activity of various otic cleansers for veterinary use.

Knowledge of the ceruminolytic activity of commercially available ear cleansing products assists the practitioner to choose the best available product for specific clinical situations. The aim of this study was to quantify and compare the ceruminolytic activity of commercially available canine ear cleansers. For this purpose, the ceruminolytic activity of 13 ear cleansers was evaluated using a standardized synthetic cerumen (SSC) that mimics the composition and texture of canine cerumen. The test products were incubated with mild agitation for 20 min with 500 mg of SSC previously compacted at the bottom of a test tube. Ceruminolytic activity was then assessed by quantifying the SSC removed by decantation. This procedure was repeated five consecutive times on each tube simulating repeated applications in the canine ear canal. Good repeatability among replicates was found in this assay, allowing direct comparisons between products. The final percentage of SSC elimination ranged from none (similar to water), between 8 and 39% for three products and up to 90% for one product (P<0.001). It is concluded that, in the experimental conditions used in this study, only 1/13 products had significant ceruminolytic activity.

Animals↗

PubMed2003

Automatic detection of small lung nodules on CT utilizing a local density maximum algorithm.

Increasingly, computed tomography (CT) offers higher resolution and faster acquisition times. This has resulted in the opportunity to detect small lung nodules, which may represent lung cancers at earlier and potentially more curable stages. However, in the current clinical practice, hundreds of such thin-sectional CT images are generated for each patient and are evaluated by a radiologist in the traditional sense of looking at each image in the axial mode. This results in the potential to miss small nodules and thus potentially miss a cancer. In this paper, we present a computerized method for automated identification of small lung nodules on multislice CT (MSCT) images. The method consists of three steps: (i) separation of the lungs from the other anatomic structures, (ii) detection of nodule candidates in the extracted lungs, and (iii) reduction of false-positives among the detected nodule candidates. A three-dimensional lung mask can be extracted by analyzing density histogram of volumetric chest images followed by a morphological operation. Higher density structures including nodules scattered throughout the lungs can be identified by using a local density maximum algorithm. Information about nodules such as size and compact shape are then incorporated into the algorithm to reduce the detected nodule candidates which are not likely to be nodules. The method was applied to the detection of computer simulated small lung nodules (2 to 7 mm in diameter) and achieved a sensitivity of 84.2% with, on average, five false-positive results per scan. The preliminary results demonstrate the potential of this technique for assisting the detection of small nodules from chest MSCT images.

Algorithms↗

PubMed2003

Four-channel coarse-wavelength division multiplexing demultiplexer with a modified Mach-Zehnder interferometer configuration on a silicon-on-insulator waveguide.

A coarse wavelength division multiplexer is designed on a silicon-on-insulator waveguide using the Mach-Zehnder interferometers with novel multimode interface-periodically segmented waveguide couplers and segmented waveguide arms. It is viable for metro and access applications, since it can be inexpensive and provide easy fabrication, compact size, and good output performance. As a design example, the channel spacing of the demultiplexer is chosen to be 24.5 nm for applications to the 10-Gigabit Ethernet. The simulation results show that the wide-passband demultiplexer can have insertion loss less than 2.3 dB and crosstalk better than 18 dB.

Journal Article↗

PubMed2003

The complete folding pathway of a protein from nanoseconds to microseconds.

Combining experimental and simulation data to describe all of the structures and the pathways involved in folding a protein is problematical. Transition states can be mapped experimentally by phi values, but the denatured state is very difficult to analyse under conditions that favour folding. Also computer simulation at atomic resolution is currently limited to about a microsecond or less. Ultrafast-folding proteins fold and unfold on timescales accessible by both approaches, so here we study the folding pathway of the three-helix bundle protein Engrailed homeodomain. Experimentally, the protein collapses in a microsecond to give an intermediate with much native alpha-helical secondary structure, which is the major component of the denatured state under conditions that favour folding. A mutant protein shows this state to be compact and contain dynamic, native-like helices with unstructured side chains. In the transition state between this and the native state, the structure of the helices is nearly fully formed and their docking is in progress, approximating to a classical diffusion-collision model. Molecular dynamics simulations give rate constants and structural details highly consistent with experiment, thereby completing the description of folding at atomic resolution.

Animals↗

PubMedDate not supplied

A new cardiology patient simulator.

We report a new cardiology patient simulator developed through the application of new digital computer technology, capable of playing back selected physical findings (jugular-venous waves, arterial pulses of carotid, brachial, radial and femoral arteries, and cardiac impulses), as well as cardiac sounds, murmurs and respiratory sounds that have been prerecorded from actual patients. The examining physician uses an ordinary type of stethoscope. Four built-in speakers are located in the human-sized mannequin at the classic auscultatory sites (aortic, pulmonic, tricuspid and mitral). This compact and portable educational apparatus should facilitate medical training in the bedside cardiac examination, of physicians, medical students, nurses and paramedics throughout the world.

Cardiology↗

PubMed2000

A simulation study for the design of a control system for the blood concentration process in autotransfusion.

Autotransfusion is the process in which a patient serves as his or her own blood donor; its most important application is the intraoperative blood salvage, in which the blood collected during a surgical operation is filtered, concentrated, washed, and then reinfused. In an automatic autotransfusion device, such as the DIDECO Compact Advanced, red blood cells (RBCs) are separated from the other unwanted components and concentrated by using a rotating bowl and the effect of centrifugal force. An important characteristic of concentrated RBCs is their hematocrit (Hct), i.e., percent RBC volume divided by total blood volume. The aim of this study is to assess the feasibility of a controller, based on the artificial neural network approach, which is able to provide a closed loop control of the hematocrit of the blood in the bowl at the end of the concentration phase. A simulation approach was adopted both for training the network and for assessing its performances. The results obtained are quite satisfactory, since the target Hct was typically reached within a 3% error, and always within 6% in highly challenging situations.

Biomedical Engineering↗

PubMed1991

[Obturation of curved canals: in vitro study of lateral compaction].

The instrumentation and filling of teeth with curved canals are always difficult, therefore, the current study indicates solutions to problems encountered while preparing curved canals. The gutta condensation techniques and their ability to seal curved canals are also discussed. This study uses endodontic simulators to show the incidence of protocols and instrumentation on the ability of the lateral condensation technique to fill curved canals. This study, also, evaluate the lateral condensation technique combined with the thermomechanical in filling curved canals.

Dental Cavity Preparation↗

PubMed2004

Accelerated dynamic Fourier velocity encoding by exploiting velocity-spatio-temporal correlations.

OBJECTIVE: To describe how the information content in a Fourier velocity encoding (FVE) scan can be transformed into a very sparse representation and to develop a method that exploits the compactness of the data to significantly accelerate the acquisition. MATERIALS AND METHODS: For validation, fully sampled FVE datasets were acquired in phantom and in vivo experiments. Fivefold and eightfold acceleration was simulated by using only one fifth or one eighth of the data for reconstruction in the proposed method based on the k-t BLAST framework. Reconstructed images were compared quantitatively to those from the fully sampled data. RESULTS: Velocity spectra in the accelerated datasets were comparable to the spectra from fully sampled datasets. The detected peak velocities remained accurate even at eightfold acceleration, and the overall shape of the spectra was well preserved. Slight temporal smoothing was seen in the accelerated datasets. CONCLUSION: A novel technique for accelerating time-resolved FVE scan is presented. It is possible to accelerate FVE to acquisition speeds comparable to a standard time-resolved phase-contrast scan.

Algorithms↗

PubMed2005

Characterisation of a duplex TiO2/CaP coating on Ti6Al4V for hard tissue replacement.

An initial TiO(2) coating was applied on Ti6Al4V by electrochemical anodisation in two dissimilar electrolytes. The secondary calcium phosphate (CaP) coating was subsequently applied by immersing the substrates in a simulated body fluid (SBF) with three times concentration (SBFx3), mimicking biomineralisation of biological bone. Electrochemical impedance spectroscopy and potentiodynamic polarisation assessments in SBF revealed that the anodic TiO(2) layer is compact, exhibiting up to four-folds improvement in in vitro corrosion resistance over unanodised Ti6Al4V. X-ray photoelectron spectroscopy analysis indicates that the anodic Ti oxide is thicker than air-formed ones with a mixture of TiO(2-x) compound between the TiO(2)/Ti interfaces. The morphology of the dense CaP film formed, when observed using scanning electron microscopy, is made up of linked globules 0.1-0.5microm in diameter without observable delamination. Fourier transform infrared spectrometry with an attenuated total internal reflection analysis revealed that this film is an amorphous/poorly crystallised calcium-deficient-carbonated CaP system. The calculated Ca:P ratios of all samples (1.14-1.28) are lower than stoichiometric hydroxyapatite (1.67). These results show that a duplex coating consisting of (1) a compact TiO(2) with enhanced in vitro corrosion resistance and (2) bone-like apatite coating can be applied on Ti6Al4V by anodisation and subsequent immersion in SBF.

Alloys↗

PubMed1988

Evaluation of a typology of reading disability.

A typology of reading disability was derived from a cluster analysis of psychological and educational tests administered to 63 moderately to severely reading-disabled children and adolescents. The quality of the cluster solution was evaluated through the use of statistics designed to measure the degree to which the clusters were compact and well separated. The values of the evaluation statistics for the reading clusters were compared to the distribution of these statistics in a sample of 100 cluster solutions from comparable simulated data sets. The results of this comparison suggest that the derived reading-disability clusters represent true subtypes rather than a random partitioning of a homogeneous group of subjects. The commonalities among subjects in the same clusters appear to be such as to permit hypotheses about treatment based on cluster membership. The clusters included a language disorder with associated deficits in auditory memory and sound blending, an auditory processing disorder, a mixed auditory and visual processing disorder, and an auditory memory and visual processing disorder. This study did not find the "normal" and visual-perceptual subtypes reported in some other recent investigations.

Adolescent↗

PubMed1992

[Choice of respirators for anesthesia].

Criteria of quality of gases and vapours supply, ventilator, patient's circle circuit and monitoring devices are recalled to help the anesthetist to choose his anesthesia machine. Advantages of compact or modular apparatus are discussed. Four, now wellknown, anesthesia machines (modulus II+, Siemens 900 D+SAC985, Roche Kontron 4300 and Engstrom Elsa) were analysed in clinical controlled ventilation and in simulated spontaneous ventilation to study the imposed work of breathing. Results are discussed with regard to safety rules and to ergonomics, bearing in mind their respective prices. Comparison is made with an original "bisontin" prototype.

Anesthesia, Inhalation↗

PubMed1989

[Mechanical analysis of the denture bases using the photoelastic-coating method. 2. Upper complete denture bases under uniform bending moment load].

Deformation of the anterior teeth and palatal regions on upper complete dentures was investigated using the photoelastic coating method and strain gages. In this experiment, an uniform-moment bending load method was employed to simulate the occlusal situation, and the distribution of strain in epoxy resin, stainless swaged and Co-Cr alloy cast dentures were measured and analyzed. The 030-series reflection polariscope is compact and lightweight with its main components consisting of two polarizer/quarter-wave-plate assemblies attached to a common frame. The highest level of strain was seen in the anterior region of the palate and the low strain was observed in other regions. Differences in strain magnitude of the three dentures were not observed with test at the same point. But, when denture base materials with high flexural rigidity and bending strength were used on the palatal region of the denture base, strain was decreased in the anterior and other regions of the palate. Therefore, dentures using those materials could be effectively reinforced.

Dental Stress Analysis↗

PubMed2004

Structure of star-burst dendrimers: a comparison between small angle x-ray scattering and computer simulation results.

We investigated the generation dependent shape and internal structure of star-burst dendrimers under good solvent conditions using small angle x-ray scattering and molecular modeling. Measurements have been performed on poly(amidoamine) dendrimers with generations ranging from g=0 up to g=8 at low concentrations in methanol. We described the static form factor P(q) by a model taking into account the compact, globular shape as well as the loose, polymeric character of dendrimers. Monomer distributions within dendrimers are of special interest for potential applications and have been characterized by the pair correlation function gamma(r), as well as by the monomer and end-group density profile, rho(r) and rho(e)(r), respectively. Monomer density profiles and gamma(r) can be derived from P(q) by modeling and via a model independent approach using the inverse Fourier transformation algorithm first introduced by Glatter. Experimental results are compared with computer simulations performed for single dendrimers of various generations using the cooperative motion algorithm. The simulation gives direct access to gamma(r) and rho(r), allows an independent determination of P(q), and yields in addition to the scattering experiment information about the distribution of the end groups. Excellent qualitative agreement between experiment and simulation has been found.

Journal Article↗

PubMed2006

D-trehalose/D-maltose-binding protein from the hyperthermophilic archaeon Thermococcus litoralis: the binding of trehalose and maltose results in different protein conformational states.

In this work, we used fluorescence spectroscopy, molecular dynamics simulation, and Fourier transform infrared spectroscopy for investigating the effect of trehalose binding and maltose binding on the structural properties and the physical parameters of the recombinant D-trehalose/D-maltose binding protein (TMBP) from the hyperthermophilic archaeon Thermococcus litoralis. The binding of the two sugars to TMBP was studied in the temperature range 20 degrees-100 degrees C. The results show that TMBP possesses remarkable temperature stability and its secondary structure does not melt up to 90 degrees C. Although both the secondary structure itself and the sequence of melting events were not significantly affected by the sugar binding, the protein assumes different conformations with different physical properties depending whether maltose or trehalose is bound to the protein. At low and moderate temperatures, TMBP possesses a structure that is highly compact both in the absence and in the presence of two sugars. At about 90 degrees C, the structure of the unliganded TMBP partially relaxes whereas both the TMBP/maltose and the TMBP/trehalose complexes remain in the compact state. In addition, Fourier transform infrared results show that the population of alpha-helices exposed to the solvent was smaller in the absence than in the presence of the two sugars. The spectroscopic results are supported by molecular dynamics simulations. Our data on dynamics and stability of TMBP can contribute to a better understanding of transport-related functions of TMBP and constitute ground for targeted modifications of this protein for potential biotechnological applications.

Carrier Proteins↗

PubMed1999

Monte Carlo simulations of beta-hairpin folding at constant temperature.

Monte Carlo simulations were applied to beta-hairpin folding of a valine-based peptide. Two valine residues in the middle of the peptide were substituted with glycine, to serve as turn residues. Unlike lattice model simulations, structure prediction methods, and unfolding simulations, our simulations used an atom-based model, constant temperature (274 K), and non-beta-hairpin initial conformations. Based on the concept of solvent reference, the effective energy function simplified the solvent calculation and overcame the multiple minima problem. Driven by the hydrophobic interaction, the peptide first folded into a compact U-shaped conformation with a central turn, in analogy to the initial collapse with simultaneous nucleation in protein folding. The peptide units in the U-shaped conformation then reoriented, gradually forming hydrogen bonds in the beta-hairpin pattern from the beta-turn to the ends of the strands. With the same energy function, an alanine-based peptide folded into helix-dominated structures. The basic structure types (alpha-helix or beta-hairpin) that formed during the simulations depended upon the amino acid sequence. Compared with helix, beta-hairpin folding is driven mainly by the hydrophobic interaction. Hydrogen bonding is necessary to maintain the ordered secondary structure.

Alanine↗

PubMed1990

Comparison and testing of least-squares time domain inverse solutions in electrocardiography.

The use of several mathematical methods for estimating epicardial ECG potentials from arrays of body surface potentials has been reported in the literature; most of these methods are based on least-squares reconstruction principles and operate in the time-space domain. In this paper we introduce a general Bayesian maximum a posteriori (MAP) framework for time domain inverse solutions in the presence of noise. The two most popular previously applied least-squares methods, constrained (regularized) least-squares and low-rank approximation through the singular value decomposition, are placed in this framework, each of them requiring the a priori knowledge of a 'regularization parameter', which defines the degree of smoothing to be applied to the inversion. Results of simulations using these two methods are presented; they compare the ability of each method to reconstruct epicardial potentials. We used the geometric configuration of the torso and internal organs of an individual subject as reconstructed from CT scans. The accuracy of each method at each epicardial location was tested as a function of measurement noise, the size and shape of the subarray of torso sensors, and the regularization parameter. We paid particular attention to an assessment of the potential of these methods for clinical use by testing the effect of using compact, small-size subarrays of torso potentials while maintaining a high degree of resolution on the epicardium.

Algorithms↗

PubMed2001

Image reconstruction from electron and X-ray diffraction patterns using iterative algorithms: experiment and simulation.

The hybrid input-output iterative algorithm, which solves the phase problem for scattering from non-periodic objects, is reviewed for application to X-ray and electron diffraction data. Desirable convex constraints, including the sign of the scattering potential for electrons, and compact support, are discussed. The cases of complex and real exit-face wavefunctions, strong and weak phase objects, various supports, and the use of coherent focussed radiation are reviewed. Reconstruction of general complex objects requires accurate knowledge of the support, which should consist of two holes or a triangle in an opaque mask. The support boundaries should be as sharp as possible. Strong phase objects without absorption can be recovered if the support consists of one hole, is accurately known and has sufficiently sharp boundaries. Real and weak phase objects with absorption can be recovered without accurate knowledge of the support area if the support boundaries are sufficiently sharp and the support consists of one or more holes. A sign constraint on the scattering potential is used to recover weak phase objects. The experimental realization of theoretically desirable support conditions is discussed. A two-stage method of finding the support for complex objects is proposed. Experimental results from applying the Gerchberg-Saxton-Fienup HiO-algorithm to coherent electron diffraction patterns are presented, using specially made e-beam lithographed support structures. Images with a resolution of about 5 nm are thus recovered from the intensities alone in coherent electron diffraction patterns from non-periodic objects. Limitations of the present experiments are identified and suggestions made for development of both X-ray and electron work.

Journal Article↗

PubMed2006

Topology of pseudoknotted homopolymers.

We consider the folding of a self-avoiding homopolymer on a lattice, with saturating hydrogen bond interactions. Our goal is to numerically evaluate the statistical distribution of the topological genus of pseudoknotted configurations. The genus has been recently proposed for classifying pseudoknots (and their topological complexity) in the context of RNA folding. We compare our results on the distribution of the genus of pseudoknots, with the theoretical predictions of an existing combinatorial model for an infinitely flexible and stretchable homopolymer. We thus obtain that steric and geometric constraints considerably limit the topological complexity of pseudoknotted configurations, as it occurs for instance in real RNA molecules. We also analyze the scaling properties at large homopolymer length, and the genus distributions above and below the critical temperature between the swollen phase and the compact-globule phase, both in two and three dimensions.

Binding Sites↗