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Results for “parameter optimization”

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At least 991 records · Page 55Linked to original sources

PubMed2006

Somatotopic organization of the analgesic effects of motor cortex rTMS in neuropathic pain.

BACKGROUND: Motor cortex repetitive transcranial magnetic stimulation (rTMS) was found to relieve chronic neuropathic pain, but the optimal parameters of stimulation remain to be determined, including the site of stimulation. OBJECTIVE: To determine the relationship between cortical stimulation site and pain site regarding the analgesic efficacy of rTMS of motor cortex in chronic neuropathic pain. METHODS: Thirty-six patients with unilateral chronic neuropathic pain located at the face or the hand were enrolled. Motor cortex rTMS was applied at 10 Hz over the area corresponding to the face, hand, or arm of the painful side, whatever pain location. Analgesic effects were daily assessed on visual analogue scale for the week that followed each rTMS session. RESULTS: All types of rTMS session, whatever the target, significantly relieved pain, compared with baseline. However, analgesic effects were significantly better after hand than face area stimulation in patients with facial pain and after face than hand or arm area stimulation in patients with hand pain. CONCLUSION: Repetitive transcranial magnetic stimulation was more effective for pain relief when the stimulation was applied to an area adjacent to the cortical representation of the painful zone rather than to the motor cortical area corresponding to the painful zone itself. This result contradicts the somatotopic efficacy observed for chronic epidural motor cortex stimulation with surgically implanted electrodes.

Adult↗

PubMed2006

Fusion of three-dimensional calcium rendering with rotational angiography to guide the treatment of a giant intracranial aneurysm: technical case report.

OBJECTIVE AND IMPORTANCE: Although three-dimensional (3D) rotational angiography enables the visualization of intracranial vascular anatomy with high spatial resolution, its ability to resolve calcified features is limited. We present a case in which a 3D calcium density rendering was fused with rotational cerebral angiography to guide the treatment strategy of a giant, calcified, partially thrombosed, middle cerebral artery bifurcation aneurysm. CLINICAL PRESENTATION: On screening magnetic resonance imaging, a 57-year-old woman with familial subarachnoid hemorrhage was found to harbor a giant trilobed, partially thrombosed, calcified aneurysm. Three-dimensional (3D) cerebral angiography revealed only partial contrast filling of one lobe with a daughter component. TECHNIQUE: A distinct rotational acquisition volume with parameters optimized for calcium density visualization was acquired just before the conventional contrast acquisition. The resulting 3D calcium volume rendering was fused with the vascular model. Multiplanar interactive visualization of the combined model uncovered heavy calcification at the neck of the aneurysm that precluded direct clipping, and the patient underwent endovascular coil embolization. CONCLUSION: Preoperative assessment of intracranial aneurysms can be facilitated by the current technique, which enables the detection of calcified tissue near the neck, which would otherwise not be possible with 3D rotational cerebral angiography alone.

Angiography, Digital Subtraction↗

PubMed1996

Power at the expense of efficiency in contraction of white muscle fibres from dogfish Scyliorhinus canicula

Work and heat production of white myotomal muscle fibres from dogfish were measured during sinusoidal movement (0.71-5.0 Hz) at 12 C. Stimulus phase (stimulus timing relative to movement) and duty cycle (stimulus duration as a fraction of movement cycle duration) were varied to determine the parameters optimal for power output and for efficiency (work/total energy output). Movements of 0.067 and 0.120L0 were used, where L0 is the muscle fibre length giving maximum force in an isometric tetanus. At each frequency of movement and duty cycle, the stimulus phase giving the highest power was the same as that giving the highest efficiency. In contrast, at each frequency and optimal stimulus phase, the dependence of power on duty cycle was very different from the dependence of efficiency on duty cycle. Power generally increased with increasing duty cycle, whereas efficiency decreased. Thus, high power can be achieved at the expense of efficiency by adjusting stimulus duty cycle. When stimulus phase and duty cycle were optimized, efficiency was always higher for the larger distance of movement. The efficiency of energy conversion can be maintained at a high level as the frequency of movement increases from 1.25 to 5.0 Hz.

Journal Article↗

PubMed1993

Optimal design of a six-bar linkage with one degree of freedom for an anthropomorphic three-jointed finger mechanism.

This research concerns the design of a three-jointed, anthropomorphic, finger mechanism for use as a prosthesis or robotic end-effector. Based on a study of finger configurations for the human hand, a six-bar linkage with one degree of freedom is proposed. A model of the fingertip displacement of the mechanism is derived by a vector analysis approach. The effects of joint friction on the transmission efficiency are analysed. By measuring the joint positions of a human finger, a mathematical model of the pinching and holding configurations are developed. Optimal parameters for the finger mechanism are obtained by non-linear programming based on an objective functional involving motion posture and locus, transmission efficiency and weight subject to geometric and bionic constraints. Simulation results indicate that the mechanism is useful for a variety of prosthetic and robotic applications.

Biomechanical Phenomena↗

PubMed1982

A new screening method for evaluating antitussives in conscious guinea pigs.

In order to evaluate the effects of antitussive agents, a new method for inducing the cough reflex in guinea pigs was devised. Male guinea pigs weighing 300-450 g were fixed in a supine position under non-anesthesia. A puncture electrode made by a stainless steel wire (0.2 mm diameter, 10 cm length) was inserted into the trachea through a guiding cannula (needle size 23G, Terumo). The optimal parameters of electrical stimulation given on the tracheal mucous membrane were a square-wave pulse with a 40 Hz frequency, duration of application 5 s. Fifty percent of antitussive doses (AtD50) of the drugs used in this study were as follows: codeine, 3.35 mg/kg (i.p.), 7.5 mg/kg (p.o.); morphine, 1.2 mg/kg (i.p.), 2.5 mg/kg (p.o.); picoperidamine, 10.9 mg/kg (i.p.), 22.6 mg/kg (p.o.); benproperine, 14.5 mg/kg (i.p.), 22.6 mg/kg (p.o.); fominoben, 13.9 mg/kg (i.p.), 477 mg/kg (p.o.). These AtD50s are much less as compared with those obtained using other methods. These results suggest that the present method for inducing the cough reflex in guinea pigs is useful for the first screening of antitussives, especially when only a small quantity of the materials is available.

Animals↗

PubMed2000

Spiral CT optimization for measurement of bronchial lumen diameter using an experimental model.

The aim of the study was to determine optimal parameters for demonstrating sublobar bronchi on spiral CT. Measurements were obtained from five parallel polyethylene tubes embedded in foam matrix with similar radiographic characteristics to segmental and subsegmental bronchi and to lung parenchyma, respectively. Collimation widths of 1.5, 2, 3 and 4 mm were used, with a pitch of 1 or 1.5 and a reconstruction interval of 1 mm or 2 mm. Various slice planes were used. Images acquired orthogonally were viewed normally. Images acquired in planes oblique or parallel to the long axes of the tubes were reformatted into a plane orthogonal to the long axes of the tubes to be comparable with the directly acquired orthogonal images. Tube diameters were measured at lung window settings (L, -400; W, 1300) and compared with known true inner and outer tube diameters. Measurements from images acquired orthogonal to the tube long axes were accurate regardless of slice thickness. Images acquired obliquely or parallel only produced accurate measurements at the lowest slice thickness (1.5 mm). Pitch and reconstruction interval had no effect on measurement error in any scan plane. It is concluded that a slice thickness of 1.5 mm or less, with a pitch of 1.5, should be used when acquiring images at angles other than orthogonal to the long axes of experimental tubes equivalent to the segmental and subsegmental bronchi. It is suggested that similar parameters should be used in vivo and that the examination should be targeted to the area of the bronchial tree in question to reduce patient dose and length of breath-hold.

Bronchography↗

PubMed1985

The influence of induced micromovement upon the healing of experimental tibial fractures.

Although it has been well established that fracture healing is influenced by the mechanical environment, the optimal parameters have not yet been established. In two groups of sheep an experimental tibial diaphysial fracture was created, and stabilised using external skeletal fixation. In one group rigid fixation was maintained throughout fracture healing; in the other group controlled axial micromovement, with a loading regime known to be osteogenic in intact bones, was applied for a short period daily. A significant improvement in healing was associated with the application of controlled micromovement. Data from these experiments provide the basis for improving the conditions for fracture healing and may assist in the prevention of delayed union.

Animals↗

PubMed2002

Phase effects at fifth-harmonic generation.

The use of the constant intensity approximation in the theory of fifth-harmonic generation in dissipative media, with an account of reverse harmonic reaction on the exciting wave phase, has been developed. The optimal values of lengths for all three crystals when the conversion efficiency to the fifth harmonic is maximum have been obtained. It has been shown that, when the optimal parameter values of the problem are chosen, the high efficiency of the fifth-harmonic cascade generator can be reached. Under phase-matching conditions in nondissipative media, the maximum efficiency is approximately 40%.

Journal Article↗

PubMed2005

Phase-space formulation for phase-contrast x-ray imaging.

Phase-space formulation based on the Wigner distribution has been presented for analyzing phase-contrast image formation. Based on the statistical nature and affine canonical covariance of Wigner distributions in the phase space, we show that the partial coherence effects of incident x-ray wave field on image intensity are simply accounted for by a multiplication factor, which is the reduced complex degree of coherence of the incident x-ray wave field. We show especially that with the undulator sources one cannot obtain the phase-contrast intensity by summing over the contributions from all electron positions, since the van Cittert-Zernike theorem fails in general for undulators. We derive a comprehensive formula that quantifies the effects of partial spatial coherence, polychromatic spectrum, body attenuation, imaging-detector resolution, and radiation dose on phase-contrast visibility in clinical imaging. The results of our computer modeling and simulations show how the formula can provide design guidelines and optimal parameters for clinical x-ray phase-contrast imaging systems.

Algorithms↗

PubMed2001

Wavelength dependence of the Stiles-Crawford effect explained by perception of backscattered light from the choroid.

To explain the wavelength dependence of the directional sensitivity of human foveal cones (Stiles-Crawford I effect) we extended an existing fundus reflectance model for calculation of the total absorption by visual pigment. We took experimental data from literature for both the psychophysical and the optical Stiles-Crawford effect and optimized parameters to fit the experimental data. The wavelength dependence of the Stiles-Crawford effect could be well described with the geometrical optics model. Essential elements are self-screening and the inclusion of backscattered choroidal light for perception.

Choroid↗

PubMed2005

Detection of subwavelength slit-width variation with measurements in the far field by use of an embedded-aperture interferometer configuration.

The dynamic signature of the subwavelength variation of a rectangular aperture has recently been shown to be determinable from far-field irradiance with a precision better than 1 nm [Opt. Lett. 29, 1045 (2004)]. We have proposed, and have theoretically shown, that detection sensitivity can be greatly enhanced with an embedded-aperture Mach-Zehnder interferometer configuration, after parameter optimization. The sensitivity, in terms of derivative intensity of observed subwavelength variations, could be enhanced approximately 2.7 times, compared with the directly detected method. Another method of detection of subwavelength variation from pattern measurement of far-field diffraction has also been proposed. The associated shifting of the dark line of the diffraction pattern had a good linear correlation to subwavelength variation, which was magnified approximately 150 times, and gave good contrast for measurement.

Journal Article↗

PubMed2004

Active correction of thermal lensing through external radiative thermal actuation.

Absorption of laser beam power in optical elements induces thermal gradients that may cause unwanted phase aberrations. In precision measurement applications, such as laser interferometric gravitational-wave detection, corrective measures that require mechanical contact with or attachments to the optics are precluded by noise considerations. We describe a radiative thermal corrector that can counteract thermal lensing and (or) thermoelastic deformation induced by coating and substrate absorption of collimated Gaussian beams. This radiative system can correct anticipated distortions to a high accuracy, at the cost of an increase in the average temperature of the optic. A quantitative analysis and parameter optimization is supported by results from a simplified proof-of-principle experiment, demonstrating the method's feasibility for our intended application.

Journal Article↗

PubMed2006

Optical fiber long-period grating with solgel coating for gas sensor.

The novel long-period fiber grating (LPFG) film sensor is composed of the long-period grating coated with solgel-derived sensitive films. The characteristics of the transmissivity of the LPFG film sensor are studied. By analyzing the relation among the sensitivity Sn, the thin film optical parameters, and the fiber grating parameters, the optimal design parameters of the LPFG film sensor are obtained. Data simulation shows that the resolution of the refractive index of this LPFG film sensor is predicted to be 10(-8). Experimentally, a LPFG film sensor for detection of C(2)H(5)OH was fabricated, and a preliminary gas-sensing test was performed.

Journal Article↗

PubMed2006

SAGE2Splice: unmapped SAGE tags reveal novel splice junctions.

Serial analysis of gene expression (SAGE) not only is a method for profiling the global expression of genes, but also offers the opportunity for the discovery of novel transcripts. SAGE tags are mapped to known transcripts to determine the gene of origin. Tags that map neither to a known transcript nor to the genome were hypothesized to span a splice junction, for which the exon combination or exon(s) are unknown. To test this hypothesis, we have developed an algorithm, SAGE2Splice, to efficiently map SAGE tags to potential splice junctions in a genome. The algorithm consists of three search levels. A scoring scheme was designed based on position weight matrices to assess the quality of candidates. Using optimized parameters for SAGE2Splice analysis and two sets of SAGE data, candidate junctions were discovered for 5%-6% of unmapped tags. Candidates were classified into three categories, reflecting the previous annotations of the putative splice junctions. Analysis of predicted tags extracted from EST sequences demonstrated that candidate junctions having the splice junction located closer to the center of the tags are more reliable. Nine of these 12 candidates were validated by RT-PCR and sequencing, and among these, four revealed previously uncharacterized exons. Thus, SAGE2Splice provides a new functionality for the identification of novel transcripts and exons. SAGE2Splice is available online at http://www.cisreg.ca.

Algorithms↗

PubMed2025

AutoPVPrimer: A comprehensive AI-Enhanced pipeline for efficient plant virus primer design and assessment.

Plant viruses pose a significant threat to global agriculture and require efficient tools for their timely detection. We present AutoPVPrimer, an innovative pipeline that integrates artificial intelligence (AI) and machine learning to accelerate the development of plant virus primers. The pipeline uses Biopython to automatically retrieve different genomic sequences from the NCBI database to increase the robustness of the subsequent primer design. The design_primers_with_tuning module uses a random forest classifier that optimizes parameters and provides flexibility for different experimental conditions. Quality control measures, including the evaluation of poly-X content and melting temperature, increase primer reliability. Unique to AutoPVPrimer is the visualize_primer_dimer module, which supports the visual evaluation of primer dimers-a feature missing in other tools. Primer specificity is validated via primer BLAST, which contributes to the overall efficiency of the pipeline. AutoPVPrimer has been successfully applied to the tomato mosaic virus, proving its adaptability and efficiency. The modular design allows customization by the user and extends the applicability to different plant viruses and experimental scenarios. The pipeline represents a significant advance in primer design and provides researchers with an effective tool to accelerate molecular biology experiments. Future developments aim to extend compatibility and incorporate user feedback to consolidate AutoPVPrimer as an innovative contribution to the bioinformatics toolbox and a promising resource for the advancement of plant virology research.

DNA Primers↗

PubMed1994

Using H2(15)O and C15O in noninvasive pulmonary measurements.

Regional pulmonary blood flow (PBF), regional pulmonary extravascular water (PEW), and regional pulmonary blood volume (PBV) were measured quantitatively with positron emission tomography (PET) using H2(15)O and C15O in normal human subjects and patients before and after thoracotomy. The method was based on the Kety's model and a modification of the Mintun's method of measuring regional PBF with H2(15)O. The method consisted of intravenous injection of H2(15)O and dynamic PET scanning of the lung field and the right heart blood pool. Another scan following C15O inhalation was performed to visualize the blood pool, and the influence of the blood pool radioactivity to the H2(15)O image was subtracted. A mathematic model was applied to the data analysis, and the least-square fitting procedure was used with a computer for obtaining the optimal parameters. The mean values of the measured PBF, PEW, and PBV in two normal human subjects were 67.2 +/- 23 ml/min/100 ml, 17 +/- 5 ml/100 ml, and 19 +/- 6 ml/100 ml, respectively. The PBF, PEW, and PBV increased in the direction of gravity in the transverse cross-section image of the lung. Using this method, we studied the condition of patients who underwent lung surgery with thoracotomy. The PEW increased and the PBF decreased in the patients after surgery. This condition lasted for a few days, and the patients then recovered. The well-known phenomenon of pulmonary edema occurring after thoracotomy, which is usually recognized by symptoms and radiologically, was thus confirmed quantitatively by our method.

Aged↗

PubMed2004

Genetic algorithms for classification of olfactory stimulants.

We have developed and tested a genetic algorithm (GA) for pattern recognition, which identifies molecular descriptors that optimize the separation of the activity classes of olfactory stimulants in a plot of the two or three largest principal components of the data. Because principal components maximize variance, the bulk of the information encoded by these descriptors is about differences between olfactory classes in the dataset. In addition, the GA focuses on those classes and or samples that are difficult to classify as it trains using a form of boosting to modify the fitness landscape. Boosting minimizes the problem of convergence to a local optimum, because the fitness function of the GA is changing as the population is evolving toward a solution. Over time, compounds that consistently classify correctly are not as heavily weighted in the analysis as compounds that are difficult to classify. The pattern recognition GA learns its optimal parameters in a manner similar to a neural network. The algorithm integrates aspects of both strong and weak learning to yield a "smart" one-pass procedure for feature selection and classification.

Algorithms↗

PubMedDate not supplied

Decolorization of Ranocid Fast Blue dye by bacterial consortium SV5.

Synthetic dyes are not uniformly susceptible to degradation in conventional wastewater treatment processes. A number of biotechnological processes have been suggested as of potential interest in combating these pollutants in an ecofriendly manner. We determined the optimal parameters necessary for the bacterial consortium SV5 to decolorize Ranocid Fast Blue dye. The best results were obtained with a 0.1% (w/v) concentration of both starch and yeast extract supplemented in Bushnell Hass Medium under static conditions at a temperature of 37 degrees C in less than 24 h with an initial dye concentration of 100 ppm.

Amidines↗