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Modulation Frequency (modulation + frequency)

Distribution by Scientific Domains

Medical Sciences	28%

Selected Abstracts

Kindling Limits the Interictal Neuronal Temporal Response Properties in Cat Primary Auditory Cortex

EPILEPSIA, Issue 2 2005
Pamela A. Valentine
Summary:,Purpose: The present study examined the effect of electrical kindling on the interictal temporal response properties of single units recorded from primary auditory cortex (AI) of the adult cat. Methods: Cats were permanently implanted with electrodes in AI, kindled twice daily for 40 sessions, and the contralateral AI was subsequently mapped. Kindling stimulation consisted of 1-s trains of biphasic square-wave pulses applied at a frequency of 60 Hz, 100 ,A above the afterdischarge (AD) threshold. The EEG activity was recorded during each kindling session, and the behavioral manifestation was scored. Subsequent to kindling, multiple single-unit responses were recorded under ketamine anesthesia in response to 1-s-long periodic click trains, with click rates between 2 and 64 Hz. Neuronal responses were characterized according to their ability to respond in time-locked fashion to the clicks. Results: Kindling stimulation resulted in progression of the AD characteristics and seizure behavior, with six of 10 kindled cats reaching a fully generalized state. In the fully kindled cats, the best modulation frequencies and limiting following rates for the single-unit responses were significantly lower compared with those of naive and sham controls. Conclusions: Repeated epileptiform activity interferes with temporal processing in cat auditory cortex in the interictal state. This may have implications for people with epileptic foci in auditory-related areas. [source]

Effect of low frequency modulated microwave exposure on human EEG: Individual sensitivity

BIOELECTROMAGNETICS, Issue 7 2008
Hiie Hinrikus
Abstract The aim of this study was to evaluate the effect of modulated microwave exposure on human EEG of individual subjects. The experiments were carried out on four different groups of healthy volunteers. The 450 MHz microwave radiation modulated at 7 Hz (first group, 19 subjects), 14 and 21 Hz (second group, 13 subjects), 40 and 70 Hz (third group, 15 subjects), 217 and 1000 Hz (fourth group, 19 subjects) frequencies was applied. The field power density at the scalp was 0.16 mW/cm2. The calculated spatial peak SAR averaged over 1 g was 0.303 W/kg. Ten cycles of the exposure (1 min off and 1 min on) at fixed modulation frequencies were applied. All subjects completed the experimental protocols with exposure and sham. The exposed and sham-exposed subjects were randomly assigned. A computer also randomly assigned the succession of modulation frequencies. Our results showed that microwave exposure increased the EEG energy. Relative changes in the EEG beta1 power in P3-P4 channels were selected for evaluation of individual sensitivity. The rate of subjects significantly affected is similar in all groups except for the 1000 Hz group: in first group 3 subjects (16%) at 7 Hz modulation; in second group 4 subjects (31%) at 14 Hz modulation and 3 subjects (23%) at 21 Hz modulation; in third group 3 subjects (20%) at 40 Hz and 2 subjects (13%) at 70 Hz modulation; in fourth group 3 subjects (16%) at 217 Hz and 0 subjects at 1000 Hz modulation frequency. Bioelectromagnetics 29:527,538, 2008. © 2008 Wiley-Liss, Inc. [source]

Potential Modulated Attenuated Total Reflectance Spectroscopy of Prussian Blue Films on ITO

ISRAEL JOURNAL OF CHEMISTRY, Issue 3 2006
Zeynep Ozkan Araci
Potential modulated attenuated total reflectance (PM-ATR) spectroscopy has been employed to study charge transfer processes in Prussian blue (PB) films deposited on indium tin oxide (ITO) electrodes. PM-ATR is a planar waveguide-based spectroelectrochemical technique in which the optical response of an electroactive film is measured as a function of applied potential and modulation frequency. The multiple internal reflection geometry of PM-ATR provides a significant sensitivity advantage over the single external reflectance geometry that has been employed in most prior electroreflectance studies. The apparent electron transfer rate of PB on ITO obtained using PM-ATR was compared to that obtained with conventional cyclic voltammetry; the respective rates, 0.33 ± 0.15 s,1 (n = 3) and 0.71 ± 0.37 s,1 (n = 10), are in good agreement. [source]

Magneto-motive detection of tissue-based macrophages by differential phase optical coherence tomography

LASERS IN SURGERY AND MEDICINE, Issue 3 2007
Junghwan Oh PhD
Abstract Background and Objectives A novel method to detect tissue-based macrophages using a combination of superparamagnetic iron oxide (SPIO) nanoparticles and differential phase optical coherence tomography (DP-OCT) with an external oscillating magnetic field is reported. Study Design/Material and Methods Magnetic force acting on iron-laden tissue-based macrophages was varied by applying a sinusoidal current to a solenoid containing a conical iron core that substantially focused and increased magnetic flux density. Results Nanoparticle motion was detected with DP-OCT, which can detect tissue movement with nanometer resolution. Frequency response of iron-laden tissue movement was twice the modulation frequency since the magnetic force is proportional to the product of magnetic flux density and gradient. Conclusions Results of our experiments indicate that DP-OCT can be used to identify tissue-based macrophage when excited by an external focused oscillating magnetic field. Lasers Surg. Med. 39:266,272, 2007. © 2007 Wiley-Liss, Inc. [source]

Fast-response organic,inorganic hybrid light-emitting diode

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 6 2008
Takeshi Fukuda
Abstract We demonstrated important changes produced on the modulation frequency of hybrid organic,inorganic light-emitting diodes to examine the applicability as a light source for visible optical communications. The fabricated device structure was 4,4,-bis[N -(1-napthyl)- N -phenyl-amino]biphenyl/4,4,-(bis(9-ethyl-3-carbazovinylene)-1,1,-biphenyl:4,4,-bis[9-dicarbazolyl]-2,2,-biphenyl/ZnS/LiF/MgAg. This device showed an improvement in the modulation frequency using ZnS instead of an organic material, tris(8-hydroxyquinoline)aluminum. A maximum cutoff frequency of 20.6 MHz was achieved. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]