China
Africa
Explore chapters and articles related to this topic
Magnetic Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
What is spin-spin relaxation? It is the magnetic relaxation, observed after application of a weak magnetic field, in which the excess potential energy associated with electron spins in a magnetic field is redistributed among the spins, resulting in heating of the spin system. It is a complex phenomenon corresponding to a decoherence or dephasing of the transverse nuclear spin magnetization. What is spin-spin relaxation time? Spin-spin relaxation time, also known as transverse relaxation time (T2), is a time constant in NMR and MRI. It is named in contrast to T1, the spin-lattice relaxation time. T2 characterizes the rate at which the Mxy component of the magnetization vector in the transverse magnetic plane undergoes decay. It is the time taken by the transverse signal to fall to 37% (1/e) of its initial value after flipping into the transverse magnetic plane. Hence, the following formula describes the process: Mxyt=Mxy0exp−tT2
Multispectral Image Segmentation in Magnetic Resonance Imaging
Published in Edward R. Dougherty, Digital Image Processing Methods, 2020
Joseph R. Hornak, Lynn M. Fletcher
The definition of T2 is therefore the time to reduce the transverse magnetization by a factor of e. Spin-spin relaxation is caused by fluctuating magnetic fields that perturb the energy levels of the spin states and dephase the transverse magnetization. T2 is inversely proportional to the number of molecular motions less than and equal to the Larmor frequency. Scientists break down T2 further into a pure T2 due to molecular interactions and one due to inhomogeneities in the B0 field.
Nanoprobes for Early Diagnosis of Cancer
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
MRI is one of the most widely used and powerful imaging modalities for cancer detection. In in vivo MRI, the signal intensity is inherently related to the tissue characteristics, such as the proton density and relaxation time (T1, spin–lattice relaxation and T2, spin–spin relaxation), and it does not always generate sufficient contrast in a clinical setting. To increase contrast, various contrast agents (UCAs), which can vary the relaxation time and produce hyperintense or hypointense signals in shorter times, are administered prior to the scanning.
A review on magnetic polymeric nanocomposite materials: Emerging applications in biomedical field
Published in Inorganic and Nano-Metal Chemistry, 2023
However, MNPs suffer a serious disadvantage of aggregation or agglomeration. Therefore, modification of these nanoparticles is necessary using inorganic[251,252] or organic materials.[253,254] Among other potentially clinical applications of magnetic nanocomposite, MRI contrast agents remain the most intensively investigated issues in cancer research. MRI has evolved as a powerful noninvasive modality to produce high-quality images of the inside of the human body. Various magnetic nanocomposites have been developed as targeted MRI contrast agents because of significant susceptibility effects resulting in strong T2 (spin-spin relaxation process), T2- contrast, as well as T1 effects (spin- lattice relaxation process). Iron oxide cores are commonly used in this procedure and can be divided into SPIOs, with diameters greater than 50 nm, or ultra-small SPIOs with diameters smaller than 50 nm.
Effects of drying methods on quality attributes of peach (Prunus persica) leather
Published in Drying Technology, 2019
S. M. Roknul Azam, Min Zhang, Chung Lim Law, Arun S. Mujumdar
Nuclear magnetic resonance (NMR) is an analysis method through the transverse relaxation time (T2) of hydrogen protons in a constant magnetic field, the migration information of the water molecules can be reflected by their absorbance by the material. PQ001 nuclear magnetic resonance analyzer (MicroMR20-030 V-1 Niumag Electric Corporation, Shanghai, China) was used to investigate the moisture distribution of the fresh puree and dried PL at 20 MHz. About 3.0 g of peach puree or dried PL sample was inserted into a 10-mm NMR glass tube, later the NMR probe was inserted into the analyzer. Carr–Purcell–Meiboom–Gill sequences were used to measure spin–spin relaxation time with four scans, 3000 echoes, 13.8 s between scans, and 200 μs between pulses of 90° and 180°. T2 measurement was triplicated for each sample. The data were analyzed by applying multi-exponential fitting of T2 relaxation data with the MultiExp Inv Analysis 4.09.
The effect of periodic intermittency on the cyclic behavior of marine sedimentary clay
Published in Marine Georesources & Geotechnology, 2019
Qingqing Zheng, Tangdai Xia, Zhi Ding, Shaoheng He
Magnetic resonance is a unique physical phenomenon based on proton spin. The process by which a magnetized vector returns to a balanced state is called relaxation. There are two types of relaxation: longitudinal relaxation and transverse relaxation. The process by which a horizontally magnetized vector that is vertical to an external magnetic field B0 transforms from an unbalanced state to a balanced state is called the transverse relaxation process (or spin-spin relaxation). The transverse relaxation time T2 represents the speed of the recovery process. The time variation of the nuclear magnetic signal is called a free induction decay (FID) curve. The first point on the FID curve is proportional to the water content of the specimen. The FID curve is converted to a T2 spectrum via a Fourier transform. The T2 distribution measured by nuclear magnetic resonance is the key to calculations relevant to the pores: where is the surface relaxation rate of the material, which is related to the type of soil, and refers to the specific surface area of the pores. The specific surface area and the pore diameter D are reciprocals. In this case, we set T2=CD (Li, Zhu, and Guo 2008). C is the aperture conversion coefficient, which is related to and the pore shape defined in the calculation. For isotropic soil, C is approximately constant.