کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5407401 | 1393215 | 2008 | 18 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Paramagnetic relaxation in sandstones: Distinguishing T1 and T2 dependence on surface relaxation, internal gradients and dependence on echo spacing
دانلود مقاله + سفارش ترجمه
دانلود مقاله ISI انگلیسی
رایگان برای ایرانیان
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Paramagnetic relaxation in sandstones: Distinguishing T1 and T2 dependence on surface relaxation, internal gradients and dependence on echo spacing Paramagnetic relaxation in sandstones: Distinguishing T1 and T2 dependence on surface relaxation, internal gradients and dependence on echo spacing](/preview/png/5407401.png)
چکیده انگلیسی
This work provides a generalized theory of proton relaxation in inhomogeneous magnetic fields. Three asymptotic regimes of relaxation are identified depending on the shortest characteristic time scale. Numerical simulations illustrate that the relaxation characteristics in the regimes such as the T1/T2 ratio and echo spacing dependence are determined by the time scales. The theoretical interpretation is validated for fluid relaxation in porous media in which field inhomogeneity is induced due to susceptibility contrast of fluids and paramagnetic sites on pore surfaces. From a set of measurements on model porous media, we conclude that when the sites are small enough, no dependence on echo spacing is observed with conventional low-field NMR spectrometers. Echo spacing dependence is observed when the paramagnetic materials become large enough or form a 'shell' around each grain such that the length scale of the region of induced magnetic gradients is large compared to the diffusion length during the time of the echo spacing. The theory can aid in interpretation of diffusion measurements in porous media as well as imaging experiments in presence of contrast agents used in MRI.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Magnetic Resonance - Volume 190, Issue 1, January 2008, Pages 68-85
Journal: Journal of Magnetic Resonance - Volume 190, Issue 1, January 2008, Pages 68-85
نویسندگان
Vivek Anand, George J. Hirasaki,