Functional magnetic resonance imaging and spectroscopic

Play media Visualization of the T1 and T2 relaxation times. The process of population relaxation refers to nuclear spins that return to thermodynamic equilibrium in the magnet. This process is also called T1" spin-lattice " or "longitudinal magnetic" relaxation, where T1 refers to the mean time for an individual nucleus to return to its thermal equilibrium state of the spins. After the nuclear spin population has relaxed, it can be probed again, since it is in the initial, equilibrium mixed state.

Functional magnetic resonance imaging and spectroscopic

This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Introduction As a member of the III-V compound semiconductors family, the growth of ultrathin films of indium antimonide has attracted a great deal of attention for its use in midwavelength infrared detectors viz.

The InSb material can be used as a lattice-matched substrate for epitaxial growth of CdTe [ 34 ] and other relevant heterostructures and superlattices [ 35 ]. The InSb-based ternary as well as quaternary alloys are equally valuable for realizing midwavelength infrared detectors [ 36 — 39 ].

In optoelectronic devices, one must grow ultrathin layers of InSb on semi-insulating infrared transparent substrates to prevent current leakage. Hence, many alternative materials viz.

Despite a Functional magnetic resonance imaging and spectroscopic Efforts have been made to grow InSb thin films on four-inch GaAs substrates [ 313247 ].

Functional magnetic resonance imaging and spectroscopic

However, the incompatibility of the lattice constants between the two materials strongly limits the quality of InSb epilayers grown on GaAs [ 23 ]. These defects propagating throughout the entire material create antiphase domains and cause autodoping effects.

The layers with intrinsic defects may also affect the carrier mobility and leakage current in both the electronic and photonic devices. Accurate estimation of InSb epifilm thickness is of paramount importance using them for device engineering. Traditionally, the thin semiconducting films are characterized by using Hall measurements, XRD, ultraviolet-visible spectrophotometry, cross-sectional scanning electron microscopy [ 2021234950 ], and so on.

Being destructive, most of these methods are not convenient for assessing material quality required in electronic industry for device productions. Therefore, a variety of nondestructive and penetrative tools have been exploited, providing nanoscale resolution for evaluating film thickness with greater degree of accuracy.

Some of these techniques used in characterizing large area wafers include the atomic force microscopy, energy-dispersive X-ray spectroscopy, secondary-ion-mass spectrometry, and SE. RSS is another valuable and nondestructive tool to offer useful information on the crystalline quality and other parameters necessary for optimizing the InSb epifilm growth [ 31 ].

This work provides a helpful guide to thin film characterization procedures required to monitor the growth processes, understanding the chemical and physical properties of materials and guiding the designs of high-performance InSb thin film devices. Material Growth The growth of ultrathin uniform InSb thin epilayers was carried out on 4-inch semi-insulating SI GaAs substrates using a low-pressure MOCVD method in vertical configuration by exploiting a high-speed rotating disk mm diameter reactor [ 3147 ].

Table 1 summarizes the growth relevant parameters of the samples used from the MOCVD growth [ 31 ] and their thicknesses determined in this study. Spectroscopic Ellipsometry SE is a valuable nondestructive technique commonly used for determining thickness, optical constants of materials; the method has also been employed for a complete depth profiling in semiconducting epitaxially grown ultrathin or thin films.

While the conventional SE approach suffers from the drawback of slow data acquisition process and covers a limited spectral range, the phase-modulated method that we have employed here offers the fast and precise data acquisition over a large wavelength range.

Later on, after more years, we performed further Raman measurements using nm laser excitation on these samples, with similar results obtained. To avoid duplication, these data were not presented here. X-Ray Diffraction Spectroscopy As a common technique for material characterization, the XRD is widely used to evaluate the quality of crystal structure.

Furthermore, the peak position and the full width at half maximum FWHM of X-ray diffraction spectra give the information of crystal orientation and crystal quality.

The diffractometer we used in experiments is Rigaku MiniFlexJapan. The intensity of X-ray was monitored by a liquid N2—filled ionization chamber, and fluorescence emitted from the sample was measured by an argon-filled Stern-Held-Lytle detector.

A Si double-crystal monochromater with a 0. A filter was inserted between the sample and the detector window to reduce the noise from scattering and to improve the spectrum quality. The incident photon direction was 45 degree to surface of the sample, and the flux I0 of incident photon was monitored simultaneously by an ion chamber located just before the sample chamber.

All measurements were made at RT, and all X-ray absorption spectra were normalized to I0. Results and Discussion 3. The quality of the fit can be judged by the mean square error MSE defined as follows: In this study, the SE data were fitted using Tauc—Lorentz multiple oscillator modes [ 48 ]: Equation 2 is useful for evaluating the dielectric function or n, k.

The real part of the dielectric function is obtained by exploiting the Kramers—Kronig integrations, that is, In 3the term P is the main part of the Cauchy integral, where is added as a fitting parameter.

Functional magnetic resonance imaging and spectroscopic

The spectral oscillations of the five samples are similar, indicating that they have similar optical properties. The thicknesses of InSb films were extracted through analyzing the SE data.

The simulation results showed the surface oxidation layer with the thickness of 0. This is physically meaningless, that is, the thickness of the surface oxidation layer should be zero.Arxivsorter ranks papers from attheheels.com based on your own interests..

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It is not a filter and therefore does not lose any information. Functional magnetic resonance imaging (fMRI) is the use of MRI to measure the haemodynamic response related to neural activity in the brain or spinal cord of humans or other animals. It is one of the most recently developed forms of neuroimaging.

Functional magnetic resonance spectroscopy of the brain (fMRS) uses magnetic resonance imaging (MRI) to study brain metabolism during brain activation. The data generated by fMRS usually shows spectra of resonances, instead of a . Inventor's name Country City/State Last publication Number of Patent applications; Eveline Maria Van Der Aa: US: Gainesville: / - Supramolecular Polymers Associative to .

Non-invasive metabolic imaging of brain tumours in the era of precision medicine - Cancerworld

A SPECIAL ISSUE Advances in Quantum Simulators and Quantum Design Guest Editors:Hisazumi Akai, Wilson Agerico Diño, Koichi Kusakabe, Tsuyoshi Miyazaki, Yoshitada Morikawa, Susumu Okada, and Tomoya Ono J. Comput. Functional magnetic resonance imaging (fMRI) and functional magnetic resonance spectroscopy (fMRS) have been used to study adults and children with developmental reading disabilities.

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