Magnetization transfer using inversion recovery during off-resonance irradiation

Estimation of magnetization transfer (MT) parameters in vivo can be compromised by an inability to drive the magnetization to a steady state using allowable levels of radiofrequency (RF) irradiation, due to safety concerns (tissue heating and specific absorption rate (SAR)). Rather than increasing the RF duration or amplitude, here we propose to circumvent the SAR limitation by sampling the formation of the steady state in separate measurements made with the magnetization initially along the -z and +z axis of the laboratory frame, i.e. with or without an on-resonance inversion pulse prior to the off-resonance irradiation. Results from human brain imaging demonstrate that this choice provides a tremendous benefit in the fitting procedure used to estimate MT parameters. The resulting parametric maps are characterized by notably increased tissue specificity as compared to those obtained with the standard MT acquisition in which magnetization is initially along the +z axis only.     

On linear versions of some addition theorems

Let K ? L be a field extension. Given K-subspaces A, B of L, we study the subspace ?AB? spanned by the product set AB = {ab∣ a ∈ A, b ∈ B}. We obtain some lower bounds on dim _K ?AB? and dim _K ?B ⁿ ? in terms of dim _K A, dim _K B and n. This is achieved by establishing linear versions of constructions and results in additive number theory mainly due to Kemperman and Olson.     

Infinite families of links with trivial Jones polynomial

For each k?2, we exhibit infinite families of prime k-component links with Jones polynomial equal to that of the k-component unlink.     

On inversion of block Toeplitz matrices

In [1] we proved that each inverse of a Toeplitz matrix can be constructed via three of its columns, and thus, a parametrization of the set of inverses of Toeplitz matrices was obtained. A generalization of these results to block Toeplitz matrices is the main aim of this paper.     

Experimental consequences of νe−νμ mixing in neutrino beams

The experimental consequences of neutrino mixing and decay are analyzed. Existing neutrino beam experiments are consistent with a finite but small mixing angle unless |m_νμ²?m_νe²| ? (3.0 eV)². A finite ν_μ lifetime in the range τ/m_νμc² ? 7 × 10³ sec/MeV is shown to be consistent with experimental data.