Dynamic shim updating on the human brain

Dynamic alteration of shim settings during a multi-slice imaging experiment can improve static magnetic-field homogeneity over extended volumes. In this report, a pre-emphasized dynamic shim updating (DSU) system capable of rapidly updating all non-degenerate zeroth through second-order shims is presented and applied to high-field multi-slice imaging studies on the human brain. DSU is utilized in both non-oblique and oblique slicing geometries while updating in-plane and through-slice shims. Image-based magnetic-field maps are used to quantify homogeneity improvements and comparisons are made on a slice-specific basis between static global shimming and increasing orders of shim inclusion utilized DSU. The influence of oblique slicing geometry on DSU-utilized global homogeneity is also quantified computationally. Finally, the effect of DSU on susceptibility artifact reduction in single-shot axial-sliced EPI is analyzed using experimental acquisitions.     

A neutron diffraction study of the glass transition in (KBr)0.47(KCN)0.53

The molecular crystal (KBr)_0.47 (KCN)_0.53 has been investigated by elastic neutron diffraction at the transition from the paraelastic to the orientational glass state. The freezing temperature is characterized by the onset of a momentum transfer dependent broadening of the diffraction lines indicating the transition from a crystalline to an amorphous state.     

Synthesis of migration-resistant hydroxyethoxy analogues of lysophosphatidic acid

[reaction: see text] The susceptibility of lysophosphatidic acid (LPA) to intramolecular acyl migration impedes the determination of specific receptor activation by the sn-1 and sn-2 LPA regioisomers. An efficient enantioselective synthesis of hydroxyethoxy (HE)-substituted analogues of sn-1-acyl and 2-acyl LPA derivatives that possess palmitoyl and oleoyl chains is described. While the palmitoyl derivatives fail to activate calcium release in cells transfected with LPA(2) or LPA(3) G-protein-coupled receptors, the LPA(3) receptor is activated by both 1-HE and 2-HE oleoyl LPA analogues with a potency 10-fold lower than that of the parent oleoyl LPA.     

Solid phase synthesis of 4-hydroxycinnamic acid and its derivatives for potential use in combinatorial chemistry: a novel route for the synthesis of 4-hydroxycinnamoyl coenzyme A and NMDA receptor antagonists

Synthesis of 4-hydroxycinnamic acid 6 and its N-hydroxysuccinimide ester 8 has been carried out in high yield on solid support. Further development allowed the synthesis of 4-hydroxycinnamoyl CoA 1 in excellent overall yield. The utility of solid phase as a method for the synthesis of 4-hydroxycinnamic acid derivatives was demonstrated by the synthesis of a number of compounds including the NMDA receptor antagonists, N-(phenylalkyl)cinnamides 9 and 10.