Search results for "MRI"

Towards peptide-based tunable multistate memristive materials

2021

Development of new memristive hardware is a technological requirement towards widespread neuromorphic computing. Molecular spintronics seems to be a fertile field for the design and preparation of this hardware. Within molecular spintronics, recent results on metallopeptides demonstrating the interaction between paramagnetic ions and the chirality induced spin selectivity effect hold particular promise for developing fast (ns–μs) operation times. [R. Torres-Cavanillas et al., J. Am. Chem. Soc., 2020, DOI: 10.1021/jacs.0c07531]. Among the challenges in the field, a major highlight is the difficulty in modelling the spin dynamics in these complex systems, but at the same time the use of inexp…

Funktionelle Bildgebung der Lunge mit gasförmigem Kontrastmittel: ³Helium-Magnetresonanztomographie

2005

Current imaging methods of the lung concentrate on morphology as well as on the depiction of the pulmonary parenchyma. The need of an advanced and more subtle imaging technology compared to conventional radiography is met by computed topography as the method of choice. Nevertheless, computed tomography yields very limited functional information. This is to be derived from arterial blood gas analysis, spirometry and body plethysmography. These methods, however, lack the scope for regional allocation of any pathology. Magnetic resonance imaging of the lung has been advanced by the use of hyperpolarised (3)Helium as an inhaled gaseous contrast agent. The inhalation of the gas provides function…

Can histographic analysis of apparent diffusion coefficient help discriminate between benign and malignant nodes in head and neck squamous cell carci…

2011

Objective: To investigate histographic analysis of apparent diffusion coefficient (ADC) measurements as discriminators of benign from malignant lymph nodes in patients with head and neck (H&N) squamous cell carcinoma (SCC) Materials and Methods: Seventeen patients with H&N SCC staged for nodal disease using anatomical MRI, contrast enhanced CT and ultrasound ± fine needle aspiration gave informed consent for additional MR diffusion weighted imaging (DWI). Axial DWI was performed by short tau inversion recovery (STIR) echo planar imaging and trace weighted images obtained b 0, 50, 100, 300, 600 and 1000. Image analysis was conducted using Jim 5.0. Nodal disease and contralateral benign nodal…

STAFNE BONE CYST IN THE ANTERIOR MANDIBLE: AN UNUSUAL LOCATION

2017

To describe clinical features of the anterior Stafne bone cyst. To supply radiologist a guide for diagnosis and classification of Stafne bone cyst.

Importance of the Window Function Choice for the Predictive Modelling of Memristors

2021

Window functions are widely employed in memristor models to restrict the changes of the internal state variables to specified intervals. Here, we show that the actual choice of window function is of significant importance for the predictive modelling of memristors. Using a recently formulated theory of memristor attractors, we demonstrate that whether stable fixed points exist depends on the type of window function used in the model. Our main findings are formulated in terms of two memristor attractor theorems, which apply to broad classes of memristor models. As an example of our findings, we predict the existence of stable fixed points in Biolek window function memristors and their absenc…

Dynamical attractors of memristors and their networks

2018

It is shown that the time-averaged dynamics of memristors and their networks periodically driven by alternating-polarity pulses may converge to fixed-point attractors. Starting with a general memristive system model, we derive basic equations describing the fixed-point attractors and investigate attractors in the dynamics of ideal, threshold-type and second-order memristors, and memristive networks. A memristor potential function is introduced, and it is shown that in some cases the attractor identification problem can be mapped to the problem of potential function minimization. Importantly, the fixed-point attractors may only exist if the function describing the internal state dynamics dep…

Handbook of Memristor Networks

2019

Noise-induced resistive switching in a memristor based on ZrO2(Y)/Ta2O5 stack

2019

Resistive switching (RS) is studied in a memristor based on a ZrO2(Y)/Ta2O5 stack under a white Gaussian noise voltage signal. We have found that the memristor switches between the low resistance state and the high resistance state in a random telegraphic signal (RTS) mode. The effective potential profile of the memristor shows from two to three local minima and depends on the input noise parameters and the memristor operation. These observations indicate the multiplicative character of the noise on the dynamical behavior of the memristor, that is the noise perceived by the memristor depends on the state of the system and its electrical properties are influenced by the noise signal. The det…

Nonstationary distributions and relaxation times in a stochastic model of memristor

2020

We propose a stochastic model for a memristive system by generalizing known approaches and experimental results. We validate our theoretical model by experiments carried out on a memristive device based on multilayer structure. In the framework of the proposed model we obtain the exact analytic expressions for stationary and nonstationary solutions. We analyze the equilibrium and non-equilibrium steady-state distributions of the internal state variable of the memristive system and study the influence of fluctuations on the resistive switching, including the relaxation time to the steady-state. The relaxation time shows a nonmonotonic dependence, with a minimum, on the intensity of the fluct…

Anomalous diffusion and nonlinear relaxation phenomena in stochastic models of interdisciplinary physics

2020

The study of nonlinear dynamical systems in the presence of both Gaussian and non-Gaussian noise sources is the topic of this research work. In particular, after shortly present new theoretical results for statistical characteristics in the framework of Markovian theory, we analyse four different physical systems in the presence of Levy noise source. (a) The residence time problem of a particle subject to a non-Gaussian noise source in arbitrary potential profile was analyzed and the exact analytical results for the statistical characteristics of the residence time for anomalous diffusion in the form of Levy flights in fully unstable potential profile was obtained. Noise enhanced stability …