SEARCH · PubMed Health

Results for “parameter optimization”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,045 records · Page 58Linked to original sources

PubMedDate not supplied

Histopathological changes in the hair follicle after irradiation of long-pulse alexandrite laser equipped with a cooling device.

Several laser systems are currently used for epilation. However, the optimal parameters and treatment protocols remain largely unknown. In this study, the histopathological changes in the hair follicles after long pulsed alexandrite laser irradiation are discussed and the clinical application of irradiation energy at the time of treatment is described. The laser used in this study is equipped with a computer controlled cooling device. A histopathological study was performed to compare the differences in the degree of degeneration in the epidermis and follicles treated with and without the cooling device. In comparison with normal hair papilla, in the laser irradiated skin, injury of melanin containing cells and hair shafts and external root-sheaths in the periphery were observed, while the epidermis was completely protected by the cooling device. The condition of the hair papilla of the tissue irradiated at a fluence of 25 J/cm2 with a spot diameter of 15 mm and 20 J/cm2, with a spot diameter of 18 mm were investigated thoroughly. Swollen papilla and selective destruction of the site where melanocytes were present were observed. The results of this study strongly indicate the efficacy of a long-pulsed alexandrite laser equipped with a computer controlled cooling device for clinical depilation.

Beryllium↗

PubMed2000

The three point vernier alignment or acuity test (3Pt VA test): an analysis of variance.

A very useful clinical vernier acuity or vernier alignment test has been developed in this and associated laboratories over a span of two decades. We seek to refine further this test, to seek internal inconsistencies and to optimize parameters used in a variety of devices and environments. Vernier testing, and many aspects of this work have been considered by numerous able scientists over a long time period (not reviewed here), but none have encountered conditions faced by this group, particularly in the developing world. The three point vernier alignment (acuity) threshold test (3Pt VeA test) employed here has broad applications; it can be used as a clinical test of vision status, for triage, and as a reference standard for vision testing (in general). As one example, if sufficient luminance is employed, the test is applicable in the presence of truly dense media disorders, even advanced leucomas, mature cataracts, intraocular bleeds, as well as combinations of these disorders, with or without a window to the retina. Only retinal and centrally-based neural disorders, eccentricity from fixation, and about 50% of hypermature cataracts affect outcomes. With minor alterations, this test can be employed to assess the visual field. An analysis of variance (ANOVA) was performed on a defined set of parameters, to enable us to understand better the special properties and requirements associated with this test. Results are not significantly altered between ages 10-94 years (not assessed here). Employing settings well above threshold for test spot detection and well separated individual test spots, changes in test spot luminance, or background luminance (or adaptation level), contrast, veiling glare, test spot size, clear and variously degraded images, seem not to affect meaningfully measured outcomes. If an observer can define well a center of gravity for each test spot viewed, he can align the three points with remarkable precision.

Adult↗

PubMed2000

[Auditory analysis of the sound source approaching and withdrawing: psychoacoustic and neurophysiological correlates].

The findings seemed to be based on direction and velocity of modelling the radial sound source shifting in free acoustic field. The threshold and the optimal parameters of the acoustic model imitating the approaching and withdrawing of the sound source shifting in silence and under conditions of noise, were established. A correlation between peak-to-peak amplitudes of the N1-P2 components of auditory EPs and the imitated direction of the sound shifting, was shown. The role of different left and right hemispheres' areas in perception of the radial sound source was analysed. The detector features of the central auditory neurones were shown as a possible mechanism of estimating the sound source approaching and withdrawal.

Acoustic Stimulation↗

PubMed2000

[Repair of traumatic lesions in peripheral nerves--initial experience with laser anastomosis].

Experience with conventional repair of peripheral nerves clearly indicates that there is still room for improvement, mainly in so far as functional results are concerned. It appears that the present microtechnique has reached its limitation given by physical and technological means, materials and methodology. The use of CO2 laser was tried on rat sciatic nerve. An equal number of nerves were severed surgically and sutured, using microsuture technique in one group and the same number of nerves were repaired using the CO2 laser technique. For the setting of the parameters, optimal for our purpose of reuniting the tissues, we have utilised morphological and electrophysiological qualitative and quantitative characteristics. The results were assessed by comparing both functionally and morphologically, the functional comparison being made electrophysiologically and the morphological comparison microscopically and morphometrically. The comparison shows a larger degree of scarring and constriction of the nerves anastomosed by classical microsuture than that of the laser technique. Action potentials going through the anastomosis have been noticed in both groups without significant difference in quality of CMAP, with the exception the latency.

Anastomosis, Surgical↗

PubMed2000

[Reestablishing of nasal respiration with Holmium laser in distortion of nasal septum in cartilaginous part].

To study mechanisms of cartilage modelling, estimation of optimal parameters and regimens of laser radiation, the authors made in vitro and human experiments on nasal septum cartilages and in vivo experiments on cartilages of the floor of the auricle in rabbits and pig. Ho-laser radiation is thought the most appropriate tool for cartilage shaping. A method of non-invasive correction of the nasal septum cartilage in its distortion has been designed. 2/3 of the patients recovered or improved nasal respiration. Laser operation has no age restrictions, is non-invasive, can be made outpatiently, is not followed by pharmacological treatment.

Adolescent↗

PubMedDate not supplied

Inhibitors of neovascularization.

The use of neovascular inhibitors in the treatment of CNV will no doubt have a profound impact in the future. However, complex issues surround the use of these agents. Careful clinical trials will be necessary to determine the optimal parameters for their use. Furthermore, it must be determined whether these inhibitors will be most efficacious as primary agents or as agents used to augment the efficacy of photoreactive laser treatment or feeder vessel treatment.

Angiogenesis Inhibitors↗

PubMedDate not supplied

Radiofrequency tissue ablation: physical principles and techniques for increasing coagulation necrosis.

Radiofrequency tumor ablation has been demonstrated as a reliable method for creating thermally-induced coagulation necrosis using either a percutaneous approach with image-guidance or direct surgical placement of thin electrodes into tissues to be treated. Early clinical trials with this technology have studied the treatment of hepatic, cerebral, and bony malignancies. The extent of coagulation necrosis induced with conventional monopolar radiofrequency electrodes is dependent on overall energy deposition, the duration of radiofrequency application, and radiofrequency electrode tip length and gauge. This article will discuss these technical considerations with the goal of defining optimal parameters for radiofrequency ablation. Strategies to further increase induced coagulation necrosis including: multiprobe and bipolar arrays, and internally-cooled radiofrequency electrodes, with or without pulsed-radiofrequency or cluster technique will be presented. The development and laboratory results for many of these radiofrequency techniques and potential biophysical limitations to radiofrequency induced coagulation, such as perfusion mediated tissue cooling (vascular flow) will likewise be discussed.

Animals↗

PubMed2001

[Use of low-frequency ultrasound with special gas agents in acute generalized peritonitis].

Optimal parameters of peritoneal cavity treatment by low-frequency ultrasound with alternative use of carbon dioxide and oxygen were selected in experimental animals. Sanitation of peritoneal cavity in fecal peritonitis led to a significant desintoxication effect. The results of treatment of acute generalized peritonitis by this method in 28 patients were good. On day 2 or 3 after surgery all the patients underwent extracorporeal detoxication with hemosorbent AUSRITC-1 with good result. In severe toxemia and water-electrolyte disturbances plasmapheresis was applied. 4 patients of 28 died, lethality was 14.2%.

Acute Disease↗

PubMedDate not supplied

Liquid chromatography/electrospray ionization/isotopic dilution mass spectrometry analysis of n-(phosphonomethyl) glycine and mass spectrometry analysis of aminomethyl phosphonic acid in environmental water and vegetation matrixes.

A liquid chromatography/electrospray/mass spectrometry (LC/ES/MS) method was developed for the analysis of glyphosate (n-phosphonomethyl glycine) and its metabolite, aminomethyl phosphonic acid (AMPA) using isotope-labelled glyphosate as a method surrogate. Optimized parameters were achieved to derivatize glyphosate and AMPA using 9-fluorenylmethyl chloroformate (FMOC-Cl) in borate buffer prior to a reversed-phase LC analysis. Method spike recovery data obtained using laboratory and real world sample matrixes indicated an excellent correlation between the recovery of the native and isotope-labelled glyphosate. Hence, the first performance-based, isotope dilution MS method with superior precision, accuracy, and data quality was developed for the analysis of glyphosate. There was, however, no observable correlation between the isotope-labelled glyphosate and AMPA. Thus, the use of this procedure for the accurate analysis of AMPA was not supported. Method detection limits established using standard U.S. Environmental Protection Agency protocol were 0.06 and 0.30 microg/L, respectively, for glyphosate and AMPA in water matrixes and 0.11 and 0.53 microg/g, respectively, in vegetation matrixes. Problems, solutions, and the method performance data related to the analysis of chlorine-treated drinking water samples are discussed. Applying this method to other environmental matrixes, e.g., soil, with minimum modifications is possible, assuring accurate, multimedia studies of glyphosate concentration in the environment and the delivery of useful multimedia information for regulatory applications.

Chromatography, Liquid↗

PubMed2001

[Usefulness of visual evoked potentials in visual acuity examination].

Determination of visual acuity by means of VEP is carried out usually by the calculation of the amplitude function response from the value of pattern single element. That purpose is achieved by carrying out several tests of transient VEP performed each time with stimulation, using the pattern of different size of individual elements or changing sweep the following sizes of the pattern single element. Concentration of a patient is necessary during any examination and therefore in clinical practise the second of the listed methods is preferred because of its short duration. Correlation factor of visual acuity, determined by means of VEP and Snellen tests, differs depending on the examined group from about 0.4 to 0.9 and it is the lowest in case of ophthalmological disorders connected with optic nerve. Fixing of VEP optimal parameters when evaluating the visual acuity remains an open matter.

Evoked Potentials, Visual↗

PubMed1975

[Methods and specificity of internal medicine specialties in multiphasic screening].

Issuing from the classical definitions for the diagnostic sensitivity and specifity of examination methods in multiphasic screenings is deduced that out of the whole methodical spectre of internal specialities only limited parts are to be applied in multiphasic screenings. At the instance of a multiple multiphasic screenings (model study Sternberg '70) ways to the establishment of reduced optimal parameter combinations are demonstrated. With multivariate statistical methods (facotor analysis, discriminative methods) we succeeded in finding parameter combinations for special groups of diagnosis (liver diseases, hypertension and obesity), by means which these groups in multiphasic screenings are clearly to be differentiated from the healthy symptom-free residual population.

Cardiovascular Diseases↗

PubMed2002

[Evaluation of PROPELLER MR imaging: preliminary experiences].

Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER) MR imaging (MRI) has a unique ability to correct motion artifacts and is expected to be useful in diffusion-weighted MRI. This article describes preliminary experiences with PROPELLER MRI. PROPELLER uses a radial scan variation of the fast spin-echo sequence and it shows much less spatial deterioration than the echo-planar imaging sequence. To determine the optimal parameters of this technique, we calculated the signal intensities of phantoms and brains in various settings. PROPELLER MR examinations were also performed in 66 patients for clinical use. PROPELLER MRI appears to be a promising and useful technique.

Artifacts↗

PubMed2002

[Bioremediation of PAHs contaminated soil using bio-slurry reactor process].

Studies on bioremediation of PAHs contaminated soil were carried out using bio-slurry reactor process. Phenanthrene (PHE) and pyrene (PY) were chosen as the test pollutants. The results showed that the physical and chemical properties of the pollutants were key factor affecting the bio-remedying possibility of PAHs in soil. PAHs with less benzene rings and lower molecule weight were easier to be biodegraded. So, phenanthrene had higher bio-remedying possibility than pyrene. Temperature and airflow were important control factors in bio-slurry reactor process. In this research, the optimized parameters were operating temperature as 20-30 degrees C, ratio between water and soil as 2:1, airflow as 8 L.h-1.L-1, and the inoculating amount as 50 g.kg-1.

Air↗

PubMed1968

Life in the spacecraft and planetary station.

Further exploration of outer space and the solar system, performance of interplanetary flights and establishment of planetary stations necessitate extensive physiological studies and development of reliable life-support systems. When developing the systems, particular attention should be paid to the concept and testing of new processes which can provide a highly efficient regeneration of vitally important materials and decrease the weight of expendables. Of great significance is the establishment of optimal parameters of the environment for long-term manned spaceflights and selection of facilities securing them. The development of new life-support systems should be based on a thorough study of the particular environment, proper selection and physiological and hygienical evaluation of their components. Long duration space missions can be planned from studies on the effects of space flight factors upon the human body to reveal its variability limits under peculiar conditions of the spacecraft or planetary station.

Ecological Systems, Closed↗

PubMed2002

[Determination of eight trichothecene mycotoxins using GCMSMS methods. I. elaboration of MS/MS conditions].

Trichothecene mycotoxins are commonly distributed in cereals in the world. Rapid and accurate methods for the determination of these toxins are required to prevent the intoxication of human and to contribute to the supply of safe foods and feed. MSMS mode was applied for identification of eight trichothecene mycotoxins with Finnigan/Mat GCQ GC/MS system. We describe here optimal parameters of CID and to obtain best pairs of ions (precursor ions and daughter ions) for all analysed toxins.

Edible Grain↗

PubMedDate not supplied

[Biosynthesis of inulinases by Bacillus bacteria].

Biosynthesis of extracellular inulinase by bacteria Bacillus polymyxa 29, B. polymyxa 722, and B. subtilis 68 was studied. The optimal parameters for the producer growth were as follows: pH 7.0, 33-35 degrees C, the growth duration within 72 h. The presence of mineral reduced or of organic nitrogen was necessary for the enzyme biosynthesis. The inulinase biosynthesis was sharply activated in the presence of carbohydrates. B. polymyxa 722 and B. polymyxa 29 displayed the maximal activity on a starch-containing culture medium, the maximal activity of B. subtilis 68 was found in the presence of sucrose. Inulin did not induce the inulinase biosynthesis by the strains studied. The time course of bacteria growth and of the enzyme biosynthesis was studied.

Bacillus↗

PubMed2001

[Resolution of overlapping chromatographic peaks by radial basis function neural network].

A new algorithm-resolution of overlapping chromatographic peaks by radial basis function neural network(RBFNN) is presented. A two-phase genetic algorithm(GA) which has robustness and random globe optimization is used to train RBFNN so that it has the ability on the resolution of overlapping chromatographic peaks. The two-phase genetic algorithm involves two procedures: training structure and optimizing parameter. The first procedure uses GA to train the architectures of RBFNN, the second procedure uses gradient descent to train the center(tR) and the width(sigma) of RBFNN. The alternate use of these two procedures makes the network having the ability to learn structure, therefore makes itself adaptable to resolution of the chromatographic peaks with unknown number of components. The method proposed here needs no artificial interference, not only has it robustness and globalism, but also the ability of accurate resolution to completely overlapped chromatographic peaks. The simulation experiments show that this method is more accurate than other methods.

Algorithms↗

PubMed2002

[Development of capillary electrophoretic method for determination of the inorganic anions in the ash of black powder].

A capillary electrophoretic method for determining the inorganic anions in the ash of black powder has been developed. The components and pH of the buffer solution, the concentration of osmotic flow modifier and the separation voltage were investigated. The optimized parameters were 5.0 mmol/L sodium chromate buffer solution (pH 8.20) containing 0.5 mmol/L cetyltrimethylammonium bromide (CTAB) as osmotic flow modifier, a separation voltage of -20 kV and a detection wavelength of 254 nm. Under the specified conditions five anions were completely separated in four minutes, and the repeatabilities (RSD) of migration time and peak area were in the range of 0.17%-1.4% and 3.9%-5.0%, respectively. The detection limits were in the range of 5.0 mumol/L to 10.0 mumol/L. To show the usefulness, the method was applied to analyze the ash of a black powder and the results showed that the relative standard deviations of the determination for Cl- and NO2- were 6.0% and 3.9%, respectively.

English Abstract↗