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Results for “parameter optimization”

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At least 1,063 records · Page 59Linked to original sources

PubMed2002

[Study on tetrazolium salt colorimetric assay for growth and survival of bacteria].

To establish a tetrazolium salt(MTT) colorimetric assay for bacteria growth and survival, living or boiling killed bacteria S. aureus and E. coli were incubated with MTT in microdilution plate for 36-37 degrees C at different time. DMSO was added as formazan dissolvent and the mixtures were measured for optical density(A) or absorbence at 510 nm wave length. Living bacteria were incubated with different amount of MTT for different time. The formazan were dissolved with different amount of DMSO and the A value were measured at different wave length. The results showed that yellow MTT could be reduced into blue formazan by living bacteria S. aureus and E. coli and the A value was directly proportional to concentration of the bacteria. A values of bacteria decreased with increasing of boiling time. To some extents, absorbence of living bacteria was direct proportion to MTT concentration and incubation time in the range of 0-2 hours. DMSO was good dissolvent for bacteria formazan and the highest absorbence could be reached in wave length range of 510-530 nm. It was suggested that MTT colorimetric assay could be used for measurement of bacteria growth and survival, and its optimal parameters were as follows: MTT concentration is 0.3 mg/ml. MTT incubation time was 2 hours. DMSO amount as dissoventis was 2-fold volume of bacteria suspension. Measurement wave length was 510-530 nm.

Colony Count, Microbial↗

PubMed1998

Electroretinographic oscillatory potentials in different aged rats: an analysis in the domains of time and frequency.

OBJECTIVES: Electroretinographic Oscillatory Potentials (Ops) are considered to be the optimal parameter to study the retinal circulation disturbances the present we compared parameters of OPs between different aged rats under dark adaptation. METHODS: The scotopic ERG were performed in anaesthetized rats aged 3, 12, 24 months. According a window of collective power spectrum field of the OPs was isolated by using the FFT and IFFT of the spectrum analysis program. The parameters in the time and frequency domains were calculated. RESULTS: Results showed that the amplitudes of wavelets and the summed amplitudes of OPs declined with the increase of age. A reduction of the total power and dominated power of OPs was also found after the FFT. But implicit time of each OP and dominant frequency did not change obviously. CONCLUSIONS: The present study indicated that change of OPs of rat might be related to senile degeneration of the retina and circulative deficiency in retina in elder rats.

Aging↗

PubMed2003

Percutaneous catheter cryothermal ablation of atrioventricular nodal reentrant tachycardia: efficacy and safety of a new ablation technique.

BACKGROUND: Radiofrequency catheter ablation is nowadays a widely used technique for the treatment of arrhythmias; however, due to the possible complications such as atrioventricular block when radiofrequency is delivered in the septal area, this type of energy is not optimal. In contrast, cryoenergy has several positive features; first of all, it allows for the creation of reversible lesions and hence to test the effects of the ablation while the lesion is still forming thus reducing the number of ineffective and useless lesions. In addition, it also allows for the evaluation of the acute effects on the structures adjacent to the ablation site. The aim of the present study was to analyze the effectiveness and safety of catheter cryoablation in the treatment of atrioventricular nodal reentrant tachycardia (AVNRT). METHODS: Thirty-two patients presenting with AVNRT underwent catheter cryoablation using a 7F catheter. When the optimal parameters were recorded, "ice mapping" at -30 degrees C was performed for 80 s to validate the ablation site by means of a reversible lesion. If the expected result was achieved, the cryoablation was carried out lowering the temperature to -75 degrees C for 4 min thus creating a permanent lesion. RESULTS: Slow pathway ablation guided by a slow pathway potential was successfully performed in 31 out of the 32 patients with a mean of 2.6 +/- 1.0 cryoapplications. No complications occurred in any patients. Transient AH prolongation was observed in 2 patients in a midseptal site during the ice mapping phase of AVNRT ablation. CONCLUSIONS: Cryoablation is a safe and effective technique for AVNRT ablation. It may be useful particularly when the ablation must be performed close to the atrioventricular node or His bundle, due to the possibility of validating the site of ablation by means of ice mapping that creates only a reversible lesion.

Adolescent↗

PubMed2003

[Basic investigation of data acquisition system for next generation PET scanner].

We are under development of a 3D PET scanner with depth of interaction (DOI) capable of high sensitivity and high resolution. In this paper, we estimated the data transfer rate of data acquisition system of this PET scanner by the simulation studies. A maximum data transfer rate of coincidence pair's event information is 10 Mcps and one coincidence event is a 64-bit data format. A data acquisition system, which fulfills the specification of this scanner, is considered for parallel collection with banks including several coincidence units. Simulator of parallel collection system composed of two stand-alone simulators and the server PC. Each stand-alone simulator is composed of data generation PC, data processing circuit, SCSI and data acquisition PC. As the result of simulation studies, the maximum data transfer rate of the stand-alone simulator was 12.0 MB/s, and the maximum data transfer rates at the server PC with one and two nodes were 11.0 and 21.8 MB/s, respectively. Data transfer rate was improved by parameter optimization of a message size and multi-processing of data acquisition software using RAM-DISK.

Computer Simulation↗

PubMed2003

[Development of a system of plasmid transfer in the strains Streptomyces avermitilis ATCC 31272 and Saccharopolyspora erythraea ATCC 11635 by the method of intergeneric conjugation].

A new method of plasmid DNA transfer from the donor strain Escherichia coli S17-1 to the erythomycin-producing strain Saccharopolyspora erythraea and avermectin-producing strain Streptomyces avermitilis via intergeneric conjugation was proposed. The optimal parameters of the method were chosen for increasing the efficiency of crosses and ensuring easily reproducible results. The behavior of the multicopy plasmid pPM803 and the integration vector pTO1 along with a number of new plasmids specially created by us, was examined in these strains. A new plasmid vector (pSI60) capable of integrating into the chromosome of actinomycetes at the integration site of the temperate actinophage phi C31 was constructed. This vector possesses unique sites convenient for cloning and may be stably maintained in exconjugants of S. avermitilis and in the model strain Streptomyces lividans. The gene encoding resistance to spectinomycin and streptomycin was cloned into the vector pSI60 in this strain. For cloning in strain Sac. erythraea, vectors pSI261-280, which integrate into the chromosome via homology with the cloned DNA and can be stably maintained in exconjugants, were constructed.

Attachment Sites, Microbiological↗

PubMedDate not supplied

Therapeutic effects of pulsed magnetic fields on joint diseases.

The present paper describes the effects of pulsed magnetic fields (MF) on diseases of different joints, in chronic as well as acute conditions where the presence of a phlogistic process is the rule. Optimal parameters for MF applications were sought at the beginning of the study and then applied for 11 years; a technical modification in the MF generator was introduced 5 years ago to satisfy the requirement of a hypothesis advanced to understand the mechanism of MF treatment. 3,014 patients were treated by means of MF at extremely low frequencies and intensities. Patient follow-up was pursued as constantly as possible. Pain removal, recovery of joint mobility and maintenance of the improved conditions represented the parameters for judging the results as good or poor. The chi-square test was applied in order to evaluate the probability that the results are not casual. A general average value of 78.8% of good results and 21.2% of poor results was obtained. Higher (82%) percentages of good results were observed when single joint diseases were considered with respect to multiple joint diseases (polyarthrosis); in the latter, the percentage of good results was definitely lower (66%). The high percentage of good results obtained and the absolute absence of both negative results and undesired side-effects, together with the therapeutic advantage due to a technical modification in the MF generator, led to the conclusion that magnetic field treatment is an excellent physical therapy in cases of joint diseases. A hypothesis is advanced that external magnetic fields influence transmembrane ionic activity.

Adolescent↗

PubMedDate not supplied

[The effect of physicochemical factors on the activity of DNA-dependent DNA polymerases in Acholeplasma laidlawii PG-8].

The biological and physico-chemical properties of DNA-dependent DNA-polymerases of Acholeplasma laidlawii PG-8 have been studied. The optimal parameters of maximal enzymatic activity are determined. It is stated that N-ethylmaleimide in concentration of 1 mM activated DNA-polymerase I by 52%, whereas DNA-polymerase II with reagent concentration of 0.5 mM demonstrated the peak of activity exceeding the control only by 10%. Spermidine in concentration of 1.5 mM for the first form of DNA-polymerase and 0.15 mM-for the second one increased the ability of both forms of polymerases to synthesize DNA by 10%. Aphidicolin added to the reaction medium up to concentration of 10 mg/ml decreased activity of forms I and II of enzymes by 83 and 68%, respectively. The presence of 0.6 mM of EDTA in the medium also negatively affected the activity of polymerases inhibiting it by 83% in form I and by 77%-in form II.

Acholeplasma laidlawii↗

PubMed1992

[Evaluation of cerebral blood circulation using fast magnetic resonance imaging (turbo-FLASH)].

In its initial stage of development, poor time resolution was supposed to be inevitable for magnetic resonance imaging (MRI). The development of the gradient echo technique, however, has made an opening for a breakthrough to a fast MRI technique. However, conventional gradient echo technique is not fast enough to disclose the cerebral blood circulation. A new technique (turbo-FLASH), which combines gradient echo and preparation pulse, has opened the door to a true dynamic (high time resolution) MRI. The authors performed a basic study of this new fast imaging technique (Turbo-FLASH) for the evaluation of cerebral blood circulation. Using this dynamic MRI, the conventional Gd-DTPA administration (0.1mmol/kg, intravenous manual administration) has produced sufficient contrast to reveal a difference of the extent of enhancement between normal gray matter and white matter. In patients of cerebral infarction, the infarcted brain does not show any significant increase of signal intensity after the administration of contrast medium, whereas the normal brain shows a sharp increase of signal intensity after the administration of contrast medium. Indeed, many puzzling questions remain to be solved for clinical application of this new dynamic MRI. For example, the optimal quantity of contrast medium and optimal parameters for this sequence (T1 weighted or T2 weighted?) are still unknown. But, in any case, this dynamic MRI is expected to be a clinically powerful tool for the evaluation of cerebral blood flow.

Brain↗

PubMed2003

[The lithotriptor "Compact" used in urinary bladder diseases].

The stroke-wave complex "Compact" is the first home-produced lithotriptor with electromagnetic system of stroke-wave generation and ultrasonic diagnosis. During its development it was possible to achieve the optimal parameters of focused waves, good technical characteristics and economic indices. The clinical use of lithotriptor has shown its efficiency in nephrolith and ureterolith remote destruction in the absence of complications connected with negative influence of stroke waves on kidneys and surrounding organs and tissues.

Adolescent↗

PubMed2004

[Stereotactic mapping for radiosurgical treatment of vestibular schwannomas].

RATIONALE: As an exclusively image-guided surgery method, radiosurgery requires special attention in the choice of imaging modalities and acquisition parameters must be set with extreme care. METHODS: Quality control for resolution and accuracy of computed tomography (CT) scanners must be performed. Magnetic resonance imaging (MRI) distortions should be limited through magnetic field homogeneity adjustment (shimming) and acquisition parameters optimization. These inaccuracies should then be quantified through systematic combination of MRI and CT in the radiosurgery planning system. MRI pulse sequences selection criteria are defined by their ability to delineate tumor contrast enhancement and to image cranial nerves and vessels relative arrangement in the cistern and canal. Topography of the petrous structures, such as cochlea, vestibulum and facial nerve canal should be visible. Exact definition of real extension of the lesion at the end of the canal may require specific technical solutions. These technical requirements must be balanced depending on the lesion Volume staging (Koos), the treatment history (microsurgery), the clinical condition (hearing quality), the pathological context (NF2) or the age of the patient. RESULTS: T1-weighted Volumetric MRI pulse sequences (3D-T1) show a contrast enhanced signal that is useful for both the pons interface delineation in Koos III cases, and the canal ending in Ohata A and B. On the other hand, 3D-T1 introduce inaccuracies from magnetic susceptibility distortions and partial Volume effects. High resolution CISS T2-weighted Volumetric pulse sequences (3D-T2) give superior stereotaxic definition attributable to their better resolution (half a millimeter) minimizing partial Volume effects and to their lower magnetic susceptibility minimizing distortions. 3D-T2 allows direct nerve visualization. Moreover, this pulse sequence with contrast injection, show improved distinction between the pons and the nerves due to signal differences within the schwannomas. Fat saturation pulse sequences are of interest in post-microsurgery conditions. CONCLUSIONS: Radiology phase quality is critical and its complexity requires a high commitment to obtain satisfactory clinical results. Solelt the 3D-T1 MRI modality seems to us not to comply to minimum security criteria.

Diffusion Magnetic Resonance Imaging↗

PubMedDate not supplied

[The use of extracorporeal detoxication methods in treating infectious disease patients].

The article summarizes the results of 1090 operations of extracorporal detoxication (ED) performed on severe infectious patients. ED was realized by methods of hemosorption, plasmasorption, plasmapheresis for viral hepatitis, typhoid diseases and mixed infections. For each category of patients indications and counterindications for ED application were worked out. Positive results were marked at 54-92% of cases, depending on nosological forms, period of illness and ED type. The authors propose a scheme of indications, optimal parameters and criteria for ED efficiency estimation. ED methods adopted for Afghan conditions can be successfully used in other regions with dry and hot climate.

Afghanistan↗

PubMedDate not supplied

Automatic flow procedure for the determination of ethanol in wine exploiting multicommutation and enzymatic reaction with detection by chemiluminescence.

An automatic procedure for the determination of ethanol in wines using a flow system based on multicommutation and enzymatic reaction is described. Alcohol oxidase was immobilized on aminopropyl glass beads and packed in an acrylic column. The peroxide due to enzymatic reaction with ethanol reacted with luminol and generated the chemiluminescence radiation that was monitored by using a laboratory-made detector based on photodiodes. The system manifold comprised a set of 3-way solenoid valves controlled by a microcomputer furnished with electronic interfaces, which ran on software written in Quick BASIC 4.5 to provide facilities to perform on-line sample dilution, reagent addition, and data acquisition. After system parameters optimization, ethanol samples were processed without prior pretreatment. The following suitable features were achieved: linear response ranging from 2.5 to 25% (v/v) ethanol, relative standard deviation of 1.8% (n = 10), detection limit of 0.3% (v/v) ethanol, sampling rate of 23 determinations per hour, and low reagent consumption of 0.23 mg luminol and 7 mg hexacyanoferrate (III) per determination. When the results were compared with those obtained using the AOAC Official Method, no significant difference at the 90% confidence level was observed.

Acetaldehyde↗

PubMed2004

SWGDAM developmental validation of a 19-locus Y-STR system for forensic casework.

A Scientific Working Group on DNA Analysis Methods (SWGDAM) developmental validation study was carried out on two Y-STR multiplex systems (MPI and MPII) that collectively permit the co-amplification of 19 Y-STR markers, including DYS393, DYS392, DYS391, DYS389I, DYS389II, Y-GATA-A7.2 (DYS461), DYS438, DYS385a and DYS385b (MPI); DYS425, DYS388, DYS390, DYS439, DYS434, DYS437, Y-GATA-C.4, Y-GATA-A7.1 (DYS460), Y-GATA-H.4, and DYS 19 (MPII). Performance checks subsequent to PCR parameter optimization indicated that MPI and MPII were suitably reproducible, precise and accurate for forensic use. The sensitivity of the systems was such that a full 19-locus Y-STR profile was obtainable with 150-200 pg of male DNA, and some loci were detectable even with as little as 20-30 pg of input DNA. Primate specificity was demonstrated by the lack of cross-reactivity with a variety of commonly encountered bacterial and animal species, with the single exception of a monomorphic canine product that was outside of the size range of human alleles from any of the 19 loci. Not surprisingly, cross-reactivity was observed with a number of male and female nonhuman primates. Environmentally compromised samples produced full or partial Y-STR profiles. For example, a semen stain exposed to the outdoor elements for six months still gave a 13-locus Y-STR profile. Although a limited number of female DNA artifacts were observed in mixed stains in which the male DNA comprised 1/300 of the total, the full 19-locus male profile was easily discernible. Even at a 1500-to-2000-fold dilution of male DNA with female DNA partial Y-STR profiles were obtained. Furthermore, the potential utility of MPI and MPII for forensic casework is exemplified by their ability to dissect out the male haplotype in a variety of case-type samples, including, inter alia, post-coital vaginal swabs, admixed male and female bloodstains, the nonsperm fraction from a differentially extracted semen stain, and determination of the number of male donors in mixed semen stains.

Animals↗

PubMed2004

Artificial neural networks in nuclear medicine.

An analysis of the accessible literature on the diagnostic applicability of artificial neural networks in coronary artery disease and pulmonary embolism appears to be comparative to the diagnosis of experienced doctors dealing with nuclear medicine. Differences in the employed models of artificial neural networks indicate a constant search for the most optimal parameters, which could guarantee the ultimate accuracy in neural network activity. The diagnostic potential within systems containing artificial neural networks proves this calculation tool to be an independent or/and an additional device for supporting a doctor's diagnosis of artery disease and pulmonary embolism.

Algorithms↗

PubMed1992

[Noninvasive evaluation of hemodynamics in changes in the atrioventricular interval in patients with dual-chamber pacemakers].

The authors evaluated in 19 patients with Dual Chamber pacemakers, using pulsed Doppler echocardiography, changes of the cardiac output after stimulation type DDD with an A-V interval of 100, 150, 175 and 200 ms. They evaluated also haemodynamic changes when changing the stimulation programme type DDD to ventricular stimulation type VVI. The group of patients was characterized by a left ventricular ejection fraction of 50.3 +/- 9.1%, a dimension of the left atrium of 37.1 +/- 5.6 mm and a end diastolic left ventricular dimension of 52.8 +/- 3.9 mm. The highest values of the cardiac output were recorded in 11 patients with an A-V interval of 175 ms, in 7 patients at 150 ms and in one patient at 200 ms. The difference of the cardiac output between the haemodynamically optimal and pessimal A-V interval assessed for individual patients during stimulation type DDD was 15.5 +/- 9.5%. The difference of the cardiac output during a change of stimulation type DDD with a haemodynamically optimal A-V interval to ventricular stimulation type VVI was 22.8 +/- 8.3%. Doppler echocardiography is a satisfactory non-invasive method for the evaluation of haemodynamic changes when assessing optimal parameters in patients with multiprogrammable dual chamber pacemakers.

Adult↗

PubMed2003

[Studies of enzymatic synthesis of biodiesel].

Biodiesel, an alternative diesel fuel, fatty acid alkyl ester, is made from renewable biological sources such as vegetable oils and animal fats. Two processes for biodiesel synthesis, enzymatic lipase catalytic esterification from fatty acid and transesterification from oils and fats, was investigated. The effects of various lipases, enzyme amount and purity, solvent, water absorbent, inhibition of short chains alcohol, specificity of substrate, molar ratio of substrate on esterification were studied in detail. The esterification degree with the optimal parameter and process can reach up to 92%. The purity of biodiesel obtained by separation and purification is up to 98%, and the half-life of the immobilized lipase for the esterification process can be up to 360hr, Moreover, the preliminary studies of the transesterification including the amount of methanol and mode of adding methanol into reaction system were made. The transesterification degree with adding methanol stepwise can reach 83%.

Biofuels↗

PubMed2005

Monitoring of trace elements in breast milk sampling and measurement procedures.

The aims of this study were to test analytical procedures for the determination of Cd, Cu, Mn, Pb, Se and Zn in breast milk and to establish optimum sampling conditions for monitoring purposes. Two population groups were analysed: (1) Seven women from Prague whose breast milk was sampled on days 1,2, 3, 4, 10, 20 and 30 after delivery; (2) 200 women from four (two industrial and two rural) regions whose breast milk was sampled at defined intervals. All samples were mineralised in a microwave oven in the mixture of HNO3 + H2O2 and analysed by atomic absorption spectrometry. Conditions for the measurement of the elements under study (i.e. those for the electrothermal atomisation for Cd, Mn and Pb, flame technique for Cu and Zn, and hydride generation technique for Se) were optimized. Using optimized parameters the analysis was performed and the following conclusion has been made: the concentrations of zinc and manganese decreased very sharply over the first days, that of copper slightly increased within the first two days and then slightly decreased, that of selenium did not change significantly. Partial "stabilisation" was achieved after the second decade. No correlation among the elements was found. A significant difference between whole and skim milk was only found for selenium (26% rel. higher in whole milk). The majority concentrations of cadmium and lead were below the detection limit of the method (0.3 microg x l(-1) and 8.2 microg x l(-1), respectively, as calculated for the original sample). To provide biological monitoring, the maintenance of sampling conditions and especially the time of sampling is crucial.

Czech Republic↗

PubMed2005

[Repeated surgical treatment of varicosity: the causes and specific features].

The paper is concerned with repeated surgical treatment for varicosity. The studies were carried out of the efficacy of surgical treatment at the specialized angio-surgical and general surgery hospitals. It has been discovered that after treatment at the specialized hospitals the patients applied for repeated surgical assistance 6 times less frequently. It is shown that the incompetent perforating veins provoke the recurrence of the symptoms of varicosity. An original technique for their obliteration is offered using highly intensive laser radiation (HILR) under permanent ultrasound guidance. The optimal parameters of HILR for venous obliteration were worked out in animal experiments. The experimental data were confirmed by microscopy and electron scanning microscopy. The clinical observations have demonstrated the high efficacy and safety of the treatment method offered.

Adult↗