نتایج جستجو برای: ultrasonic oscillations

تعداد نتایج: 76188  

2010
Bradley Voytek Ryan T. Canolty Avgusta Shestyuk Nathan E. Crone Josef Parvizi Robert T. Knight

The phase of ongoing theta (4-8 Hz) and alpha (8-12 Hz) electrophysiological oscillations is coupled to high gamma (80-150 Hz) amplitude, which suggests that low-frequency oscillations modulate local cortical activity. While this phase-amplitude coupling (PAC) has been demonstrated in a variety of tasks and cortical regions, it has not been shown whether task demands differentially affect the r...

Journal: :گوارش 0
fariborz mansour-ghanaei ahmad alizadeh zahra pourrasouli hamid vahidi mohammadreza naghipour farahnaz joukar

background: ultrasonography is an imaging method which, due to its relative economy, is becoming more widely available in regions of the world where fasciola hepatica infection occurs most frequently. in this report, we describe the sonographic findings of hepatic lesions in patients with fascioliasis to help confirmation of the sonographic characteristics of this disease and thus aid in its di...

2014
Hong Wei Peng Yu Jie Cheng Zhi Guo Hu Chu Chen Zhang

This document presents the principle of ultrasonic distance measurement is described, the main error sources of ultrasonic distance measurement are analyzed also. A method of improving precision of ultrasonic distance measurement in air, in which the transmission speed of ultrasonic wave if corrected by measured air temperature and the forward edge of receive wave can be determined accurately b...

2014
Dong Xinyuan

Aiming at the problem that echo signal is hard to recognize caused by ultrasonic energy’s overquick dispersion and attenuation, a kind of ultrasonic horn is designed. According to the acoustic theory analysis, the ultrasonic horn can increase its radiation energy by improving impedance matching. The ultrasonic horn can make the directivity of sound source sharper and energy more centralized bec...

Journal: :Trends in neurosciences 2017
Michael X Cohen

Electroencephalography (EEG) has been instrumental in making discoveries about cognition, brain function, and dysfunction. However, where do EEG signals come from and what do they mean? The purpose of this paper is to argue that we know shockingly little about the answer to this question, to highlight what we do know, how important the answers are, and how modern neuroscience technologies that ...

Journal: :Journal of the Royal Society, Interface 2015
Riku Fagerlund Marcelo Behar Karen T Fortmann Y Eason Lin Jesse D Vargas Alexander Hoffmann

The magnitude, duration and oscillation of cellular signalling pathway responses are often limited by negative feedback loops, defined as an 'activator-induced inhibitor' regulatory motif. Within the NFκB signalling pathway, a key negative feedback regulator is IκBα. We show here that, contrary to current understanding, NFκB-inducible expression is not sufficient for providing effective negativ...

Journal: :The Journal of neuroscience : the official journal of the Society for Neuroscience 2015
Jérémie Lefebvre Axel Hutt Jean-François Knebel Kevin Whittingstall Micah M Murray

Rhythmic activity plays a central role in neural computations and brain functions ranging from homeostasis to attention, as well as in neurological and neuropsychiatric disorders. Despite this pervasiveness, little is known about the mechanisms whereby the frequency and power of oscillatory activity are modulated, and how they reflect the inputs received by neurons. Numerous studies have report...

2011
R. VanRullen N. A. Busch J. Drewes Julien Dubois

Even in well-controlled laboratory environments, apparently identical repetitions of an experimental trial can give rise to highly variable perceptual outcomes and behavioral responses. This variability is generally discarded as a reflection of intrinsic noise in neuronal systems. However, part of this variability may be accounted for by trial-by-trial fluctuations of the phase of ongoing oscil...

Journal: :Human brain mapping 2013
Simon Hanslmayr Heidelore Backes Sarah Straub Tzvetan Popov Berthold Langguth Göran Hajak Karl-Heinz T Bäuml Michael Landgrebe

Patients suffering from schizophrenia have been characterized by an apparent lack of theta (around 6 Hz) and gamma (>40 Hz) brain oscillatory activity during task execution. The neurocognitive reasons for these abnormal synchronization patterns, however, remain elusive. Recording the electroencephalogramm (EEG) during a selective visual attention task, the current study investigates whether abn...

Journal: :iranian journal of oil & gas science and technology 2014
behnam keshavarzi mohammad javad shojaei mohammad hossein ghazanfari cyrus ghotbi

it has been proved that ultrasonic energy can considerably increase the amount of oil recovery in animmiscible displacement process. although many studies have been performed on investigating theroles of ultrasonic waves, based on the best of our knowledge, little attention has been paid to evaluatewave attenuation parameter, which is an important parameter in the determination of the energydel...

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