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Further advancement in the technology of hearing aids requires solution of several questions. They are associated with determination of optimal parameters and plotting the corresponding electro-acoustical routes (channels) within apparatus, providing necessary level of comfort during their use, metrologic provision for apparatus design and production, and with development of an assessment method for integral quality index of hearing aids.
Temporal characteristics of muscle contraction evoked by bipolar macrostimulation of cat motor cortex were studied in chronic experiments. Cortically induced flexion of the contralateral hindlimb was recorded isometrically and in some cases isotonically. Latency of muscle contraction exceeded 100 ms when low frequency (100-150/s) stimulation was applied. An increase in the stimulation frequency and intensity led to the shortening of the latency: under "optimal" parameters of the stimulation the minimal values were 30-35 ms. Time constant of the contraction increment was 50-80 ms whereas that of the contraction decrement after stimulation cessation reached 150-300 ms. The results obtained are considered from the view point of automatic regulation theory.
The authors' experience in the use of interference currents (IC) in postapoplectic (PA) and cervical osteochondrosis (CO) patients led them to the following conclusions: a course of IC treatment (dynamic field) brings the response in 62-70% of PA patients, but a complete response is not reached because of the disease severity; in CO patients the response is achieved in 86% of patients; a single IC procedure entails a significant reduction in heart rate; IC course in CO patients increases blood filling of brachial vessels and decreases vascular tone on the affected side; IC course in PA patients significantly increases blood filling and reduces vascular tone in the vessels on both affected and unaffected sides; single and course IC improves hemodynamics in the external carotid arteries and normalizes venous outflow in the region of vertebral and external carotid arteries in 1/3 of PA patients; in CA patients cerebral circulation improves in 90%. In the above diseases optimal parameters are thought to be: frequency change per second 40-60 Hz within 7 minutes and 100-120-100-40-60-40 Hz during 7 minutes.
Staphylococcal Coagglutination was used as method for a rapid identification of mycoplasmas that could be performed by non specialized laboratories. Suspensions of Staphylococcus aureus (Cowan I) sensitized with rabbit antibodies against NCTC mycoplasma strains have identified these microorganisms and the strains isolated from humans, cell cultures rats and mice in concentrated suspensions from cultures of 4.0 ml. Fourty eight strains of M.pulmonis, 6 of M. arthritidis, 8 of M.arginini, 3 of M.orale, 15 of A.laidlawii, 8 of M.hominis and 3 of M.pneumoniae were identified by staphylococcal coagglutination and confirmed by Growth Inhibition Test. Optimal parameters of coagglutination were established and the stability of the conjugates were preserved for 90 days when added with acetyl cysteine. The reaction was visualized without optical resources. The sera were previously absorbed with heterologous NCTC strains and with the pellet of the sterile broth.
A frequency domain filtering method provides accurate frequency response. In order to provide optimal radionuclide image quality, Butterworth or Wiener filters were applied in the frequency domain. A method is developed to determine automatically their optimal parameters from the power spectra of the object images. Phantom studies showed that proper parameters were derived by this method. Thirty-one cases of multigated cardiac blood-pool images and phantom images modeled on the cardiac images were filtered by 3 x 3 points temporal smoothing, frequency domain Butterworth and Wiener filters. From these images, ejection fractions were calculated and evaluated the correlation between the actual ejection fractions in the phantom study or the values derived from the contrast left ventriculography. The better correlation coefficients were derived with the frequency domain Butterworth filter than with the temporal smoothing. And more desirable correlation coefficients were derived with the frequency domain Wiener filter than with the frequency domain Butterworth filter, especially in the low count studies. Butterworth or Wiener filtering in the frequency domain reduces noise and improves the capacity for quantitative analysis in the radionuclide images.
Some biological properties of polyreactive antibodies (PRABs) from the serum of mice, rabbit and cattle are investigated. Optimal parameters of the activation process are determined. It is shown that solution of KSCN (potassium rhodanide) more effectively impedes interaction of PRABs with the antigen on the immunological plate than interaction between specific antibodies. Dynamics of binding of PRABs and affine-purified antibodies to an immobilized antigen is analyzed. The competitive ELISA shows the absence of specificity of PRABs and their less avidity in comparison with the usual antibodies. It is supposed that PRABs play an essential role in the immune system of animals and man.
Optimal critical values and times of intermediate testing points are determined to minimize expected sample size in a variety of situations. Two-stage and three-stage models are considered for a variety of values of power. We investigate the robustness of the optimality parameters.
Single-chip digital signal processors (DSPs) allow the flexible implementation of a large variety of speech analysis, synthesis, and processing algorithms for the hearing impaired. A series of experiments was carried out to optimize parameters of the adaptive beamformer noise reduction algorithm and to evaluate its performance in realistic environments with normal-hearing and hearing-impaired subjects. An experimental DSP system has been used to implement a multiband loudness correction (MLC) algorithm for a digital hearing aid. Speech tests in quiet and noise with 13 users of conventional hearing aids demonstrated significant improvements in discrimination scores with the MLC algorithm. Various speech coding strategies for cochlear implants were implemented in real time on a DSP laboratory speech processor. Improved speech discrimination performance was achieved with high-rate stimulation. Hybrid strategies incorporating speech feature detectors and complex decision algorithms are currently being investigated.
Until few years ago, MR assessment of pancreatic carcinoma was thought to be feasible only with high-strength equipment, but today also low- and midfield units allow pancreatic lesion detection, thanks to parameter optimization. The authors retrospectively analyzed the MR findings of 57 patients examined with a midfield MR unit; all the patients had clinically suspected pancreatic carcinoma, which was confirmed in 54 cases. The lesions were more easily detected using T1-weighted sequences, thanks to their high intrinsic contrast, while T2-weighted sequences often confirmed the glandular changes already depicted by T1-weighted sequences. MRI correctly depicted vascular and lymph node involvement and detected liver metastases with no i.v. contrast agent injection. The only limitations of this technique are the unfeasibility of MR exams of diagnostic value in uncooperative patients (5% of cases) and the very similar MR features of parenchymal scars, due to previous acute pancreatitis, to those of pancreatic carcinoma. In conclusion, CT remains the gold standard in the study of pancreatic cancers, but midfield strength MRI, if correctly performed, can be proposed as a complementary tool to CT, especially in questionable cases and in the patients with known reactions to iodinated contrast agents.
PURPOSE: To optimize parameters of rotational angiography for examination of the internal carotid circulation; to compare rotational angiography with standard digital subtraction angiography (DSA) in the evaluation of aneurysms of the intracranial internal carotid circulation; and to determine tolerance and safety limits of prolonged internal carotid injection angiography. METHODS: Rotational angiograms were obtained during injection of the internal carotid circulation as part of the clinical angiographic evaluation of aneurysms in 41 patients. Injection rates, X-ray delays, and fields of view were studied retrospectively. Findings at rotational angiography and standard DSA were compared. Nonionic contrast material was injected over 6 seconds, and patients were studied before and after prolonged injection angiography by physical and laboratory examination, including measurement of blood pressure, pulse, and intracranial pressure. RESULTS: Vascular conspicuity was equivalent at carotid injection rates of 4 and 5 mL/s delivered over 6 seconds. At 3 mL/s, more image manipulation was required to see small vascular structures. One-second X-ray delay combined with 6-second injection duration provided the best arterial depiction of intracranial vessels from start to end of rotational angiography. Maximal rotational resolution was with a 17-cm field of view. Identification of aneurysms and small vessels was equivalent at all injection rates. Aneurysm detection was equivalent with rotational angiography and DSA. In 9 of 31 aneurysms, the neck was defined more clearly with rotational angiography than with DSA, compared with 2 of 31 that were seen better with DSA. Aneurysms of the intracranial internal carotid circulation were seen with rotational angiography and not DSA in 12 of 41 cases. No change was noted in clinical or laboratory findings. CONCLUSION: Rotational angiography provided better definition of the aneurysmal neck and greater clarity of aneurysms than did DSA; it also improved the level of confidence in predicting the presence or absence of aneurysms, especially in the anterior communicating artery; however, in our small series it did not significantly increase the detection of aneurysms. Prolonged injection angiography was well tolerated in all patients.
Direct current polarography and cyclic voltammetry was used to study quinolone antibiotics: ciprofloxacin, enoxacin, norfloxacin, ofloxacin and pefloxacin on a mercury and carbon electrode. The dependence of limiting currents and half-wave potentials on the pH of the solution, mercury head, temperature, ionic strength of the solution, methyl cellulose concentration, scan rate and quinolone concentration was studied. The optimal parameters and background solutions have been chosen. It was concluded that on mercury electrode quinolones are reduced in two one-electron waves and the process of the reduction is accompanied by an acid-base equilibrium. An anodic peak observed on graphite electrode is probably caused by the oxidation of piperazine ring in the molecule.
Differential pulse polarography was used to study quinolone antibiotics: ciprofloxacin, enoxacin, norfloxacin, ofloxacin and pefloxacin on a mercury electrode. The optimal parameters and background solutions have been chosen. New polarographic method of quinolone determination in pure form and pharmaceutical formulations was found. Statistical analysis of the results obtained showed that proposed method is of good accuracy and precision.
The possibility of using polymerase chain reaction (PCR) for the laboratory diagnosis of brucellosis was tested with a representative regional collection of 44 Brucella strains. The strains differed by the test and source of isolation, virulence, and phenotypical characteristics. Optimal parameters of PCR have been defined and the possibility of detecting the agents in pathological material from cattle demonstrated.
The results of experimental tests performed upon 16 human stapes taken from cadavers were presented. The aim of the experiment was to define optimal parameters of laser stapedotomy. The less harmful range of argon laser energy for making the hole 0.6 mm diameter in the stape footplate was determined. There were two zones of tissue damage around the footplate's hole seen in scanning microscope. The internal area was made of carbonized tissue. The osseous tissue of the external zone had cavernous-cystic structure and lamellar stratification.
UNLABELLED: The feasibility of imaging pentose cycle (PC) glucose utilization in human gliomas with PET was explored in two rat glioma models by means of glucose radiolabeled in either the carbon-1 (C-1) or carbon-6 (C-6) position. METHODS: In vitro, monolayers of T-36B-10 glioma, tissue slices of intracerebral glioma grafts or slices of normal brain were fed [1-14C]glucose or [6-14C]glucose, and the generated [14C]CO2 was trapped to quantitate the ratio of [14C]CO2 from 14C-1 versus 14C-6. In vivo, rats bearing grafts of either T-36B-10 or T-C6 rat gliomas at six subcutaneous sites received simultaneous intravenous injections of either [1-11C]glucose and [6-14C]glucose, or [1-14C]glucose and [6-11C]glucose. Tumors were excised between 5 and 55 min postinjection to quantify tracer uptake while arterial plasma was collected to derive time-activity input curves. RESULTS: In vitro, the C-1/C-6 ratio for CO2 production from T-36B-10 monolayers was 8.8 +/- 0.4 (s.d.), in glioma slices it was 6.1 +/- 2.1 and in normal brain slices it was 1.1 +/- 0.7. PC metabolism in T-36B-10 was 1.8% +/- 0.5 of total glucose utilization. In vivo, tumor radioactivity levels normalized by plasma isotopic glucose levels showed that retained C-1 relative to C-6 radiolabeled glucose was significantly lower in both gliomas, 4.9% lower in T-36B-10 (p < 0.01) and 4.7% lower in T-C6 (p < 0.01). In an additional group of rats bearing T-36B-10 gliomas and exposed to 10 Gy of 137Cs irradiation 4 hr before isotope injection, the C-1 level was 5.6% lower than that for C-6 (p < 0.05). These results were analyzed with a model of glucose metabolism that simultaneously optimized parameters for C-1 and C-6 glucose kinetics by simulating the C-1 and C-6 tumor time-activity curves. The rate constant for loss of radiolabeled carbon from the tumors, k4, was higher for C-1 than for C-6 in all groups of rats (19% higher for T-36B-10 unirradiated, 32% for T-36B-10 irradiated and 32% for T-C6 unirradiated). CONCLUSION: Mathematical modeling, Monte Carlo simulations and construction of receiver-operator-characteristic curves show that if human gliomas have a similar fractional use of the PC, it should be measurable with PET using sequential studies with [1-11C]glucose and [6-11C]glucose.
Mechanical heart assistance, performed by the PUlsatile CAtheter (PUCA) pump, chronologically takes place by sucking blood from the left ventricle and ejecting it into the ascending aorta. Within the pump activity the problem of hemolysis and clotting is encountered. In this study the influence of valve geometry on blood cell damage and stagnant zones has been investigated. A variable valve length coupled to a catheter ejection gap and a variable valve angle have been studied. In case of the studied valve, optimal parameter values have been determined. Compared to small catheter ejection gaps with a corresponding valve length, blood damage is found to be less for large ejection gaps with corresponding valve dimensions. In systole a valve positioned in a 0 degree angle proves to be best, whereas in diastole a +20 degree angle is preferable. Because the system is operating in both systole and diastole, a 0 degree angle valve is applied.
A rapid and simple method for the in vitro evaluation of the virulence of F. tularensis is proposed. The optimal parameters--the concentrations of bacteria and the substrate (phenolphthalein phosphate), the time incubation in the serum--have been developed and special conditions for strains of different subspecies have been selected. The proposed method makes it possible to greatly reduce the time of obtaining results and to exclude labor-consuming experiments on laboratory animals when working with large collections of F. tularensis laboratory and natural wild strains. Moreover, the method widens the possibilities of experimenters in the evaluation of the effect of some mutation on the virulence of the strain under study.
Progress in the treatment of bronchogenic carcinoma, the leading cause of cancer death in men and women in the United States, has been slow throughout the past few years, and no major breakthroughs have occurred in the past 12 months. Significant developments in monoclonal antibody techniques and tissue cellular markers offer hope for improved diagnosis and are useful in staging and following disease response to treatment. Advances in patient selection and staging have been primarily responsible for improved surgical outcomes, but some new surgical alternatives like video-assisted thoracoscopy and other tissue-sparing procedures may offer reasonable outcomes with a lower morbidity. New drugs and new drug combinations are being evaluated with hematopoietic growth factors in the management of small cell lung cancer. Neoadjuvant chemotherapy and radiotherapy are finding a definite role in the management of non-small cell lung cancer. The optimal parameters for radiotherapy in the management of small cell lung cancer are being defined. The use of immunotoxins, adjuvant immunotherapy, and monoclonal antibodies offers major theoretical promise, but are as yet in the early stages of development. Ancillary techniques for palliation of local airway obstruction, including both laser and endobronchial stents, are proving beneficial in selected patients.