The shielding tensor, which describes the anisotropic chemical shift, plays an important role in nuclear magnetic resonance (NMR) because it can extract valuable information about the molecular dynamics and the local electronic structures in solids. The tensor, which is second rank, can be expressed by three independent principal components in its principal axis system (PAS). These components can be easily converted into chemical zhift anisotropies, as three principal components, i.e. a,,, dZ2 and d,, , with conventionally d, > 6,, > 6,, .The average of the three components is the isotropic chemical shift do :(1)The other two necessary parameters are the chemical shift anisotropy, which we denote here as Ad, and the asymmetric parameter 9. They can be written as follows:6 0 = @ l l + 6 2 2 + 8 3 3 ) 6 2 2 -6 3 3The isotropic chemical shift of a dilute nucleus, such as 13C, in a solid is usually obtained from its highresolution NMR spectrum, which can be routinely yielded by the magic angle spinning (MAS) and heteronuclear dipolar decoupling techniques combined with cross-polarization (CP). ' p 3

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A method is presented for multislice measurements of quantitative cerebral perfusion based on magnetic labeling of arterial spins. The method combines a pulsed arterial inversion, known as the FAIR (Flow-sensitive Alternating Inversion Recovery) experiment, with a fast spiral scan image acquisition. The short duration (22 ms) of the spiral data collection allows simultaneous measurement of up to 10 slices per labeling period, thus dramatically increasing efficiency compared to current single slice acquisition protocols. Investigation of labeling efficiency, suppression of unwanted signals from stationary as well as intraarterial spins, and the FAIR signal change as a function of inversion delay are presented. The assessment of quantitative cerebral blood flow (CBF) with the new technique is demonstrated and shown to require measurement of arterial transit time as well as suppression of intraarterial spin signals. CBF values measured on normal volunteers are consistent with results obtained from H2O15 positron emission tomography (PET) studies and other radioactive tracer approaches. In addition, the new method allows detection of activation-related perfusion changes in a finger-tapping experiment, with locations of activation corresponding well to those observed with blood oxygen level dependent (BOLD) fMRI.

Scaffolds mimicking hierarchical features of native extracellular matrices may facilitate cell growth and anatomical tissue regeneration. In our previous study, esophageal basement membrane (BM) was shown to be composed of interwoven fibers with mean diameter of 66 ± 24 nm (range 28-165 nm) and with abundant pores of unequal sizes. The main extracellular matrix (ECM) contents found in porcine esophageal BM were collagen IV, laminin, entactin, and proteoglycans. In this work, biodegradable polycaprolactone (PCL) and silk fibroin (SF) were spun with electrospinning technology, both individually and in combination, to fabricate fibrous scaffolds with diameters between 64 and 200 nm. The surface morphologies of PCL, PCL/SF, and SF scaffolds were observed under scanning electron microscopy. Their mechanical properties were tested and the cytocompatibility was evaluated in vitro via culture of primary epithelial cells (ECs). The SF or PCL/SF scaffold favorably promoted epithelial cell attachment and proliferation comparing with PCL scaffold. However, mitochondrial activity of epithelial cells was greatly promoted when major BM proteins were coated onto the electrospun scaffold to provide an ECM-like structure. Results from in vivo tests revealed that the electrospun scaffolds coated with BM protein possess good biocompatibility and capability to promote epithelium regeneration.

Meshes play important roles to repair human tissue defect. In this work, human amniotic membrane (HAM) was decellularized and explored the efficacy as an implantable biological mesh. Surfactant, hypertonic saline, lipase and DNAase were used individually or collectively to remove all cell components and remain the extracellular matrix. Results of H&E and DAPI staining demonstrated that the method of surfactant and lipase combining with DNAase is the most effective treatment for HAM decellularization. Primary smooth muscle cells were seeded to evaluate the decellularized HAM's (dHAM) in vitro cytocompatibility. The in vivo test was performed via implantation at rabbits' uterus with clinic polypropylene mesh (PP) as the control. The results indicated that dHAM possessed good biocompatibility and will be a potential candidate for biological mesh.