نتایج جستجو برای: impedance
تعداد نتایج: 35930 فیلتر نتایج به سال:
OBJECTIVE To investigate whether perioperative changes in bioelectrical impedance reflect the severity of illness in pediatric patients after heart surgery. DESIGN Prospective, controlled study. SETTING University-affiliated children's hospital. PATIENTS A total of 107 patients admitted to a pediatric intensive care unit after congenital heart surgery. INTERVENTIONS None. MEASUREMENTS...
The measurement of the physical extent of opening of the upper esophageal sphincter (UES) during bolus swallowing has to date relied on videofluoroscopy. Theoretically luminal impedance measured during bolus flow should be influenced by luminal diameter. In this study, we measured the UES nadir impedance (lowest value of impedance) during bolus swallowing and assessed it as a potential correlat...
This study explored a novel method for measuring cerebrovascular impedance to quantify the relationship between pulsatile changes in cerebral blood flow (CBF) and arterial pressure. Arterial pressure in the internal or common carotid artery (applanation tonometry), CBF velocity in the middle cerebral artery (transcranial Doppler), and end-tidal CO(2) (capnography) were measured in six young (28...
OBJECTIVES Breaking the skin when applying scalp electroencephalographic (EEG) electrodes creates the risk of infection from blood-born pathogens such as HIV, Hepatitis-C, and Creutzfeldt-Jacob Disease. Modern engineering principles suggest that excellent EEG signals can be collected with high scalp impedance ( approximately 40 kOmega) without scalp abrasion. The present study was designed to e...
Impedance control facilitates the performance of tasks that involve contact with the environment. Two generic strategies for implementing impedance control have been described in the literature: the dynamic based approach [4] and the position based approach [7]. The second method has been introduced to eliminate the inherent sensitivity of the first method to the accuracy of the dynamic model. ...
Rapid differentiation of fermentative gram-negative bacilli (fermenters) from nonfermentative gram-negative bacilli (nonfermenters) in positive blood cultures may help physicians to narrow the choice of appropriate antibiotics for empiric treatment. An impedance method for direct differentiation of fermenters from nonfermenters was investigated. The bacterial suspensions (or positive culture br...
Stroke is a severe cerebrovascular disease and is the second greatest cause of death worldwide. Because diagnostic tools (CT and MRI) to detect acute stroke cannot be used until the patient reaches the hospital setting, a portable diagnostic tool is urgently needed. Because biological tissues have different impedance spectra under normal physiological conditions and different pathological state...
Impedances and joint angles were simultaneously measured during ankle and knee movements. The correlation coefficients of the joint angle and the impedance change from human leg movement were obtained using an electro-goniometer and a four-channel impedance measurement system. Because the impedance changes resulting from ankle and knee movements depended heavily on the electrode placement, we d...
We report on the characterization of two variable friction electroadhesive displays using careful electrical and electrochemical impedance measurements. We qualitatively and quantitatively examine the properties of the skin, body, surface coating, and various electrode interface impedances in isolation using different contact interface conditions and measurement types. A lumped series impedance...
The low-temperature asymptotic expressions for the Casimir interaction between two real metals described by Leontovich surface impedance are obtained in the framework of thermal quantum field theory. It is shown that the Casimir entropy computed using the impedance of infrared optics vanishes in the limit of zero temperature. By contrast, the Casimir entropy computed using the impedance of the ...
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