In this study, a novel partially parallel acquisition (PPA) method is presented which can be used to accelerate image acquisition using an RF coil array for spatial encoding. This technique, GeneRalized Autocalibrating Partially Parallel Acquisitions (GRAPPA) is an extension of both the PILS and VD-AUTO-SMASH reconstruction techniques. As in those previous methods, a detailed, highly accurate RF field map is not needed prior to reconstruction in GRAPPA. This information is obtained from several k-space lines which are acquired in addition to the normal image acquisition. As in PILS, the GRAPPA reconstruction algorithm provides unaliased images from each component coil prior to image combination. This results in even higher SNR and better image quality since the steps of image reconstruction and image combination are performed in separate steps. After introducing the GRAPPA technique, primary focus is given to issues related to the practical implementation of GRAPPA, including the reconstruction algorithm as well as analysis of SNR in the resulting images. Finally, in vivo GRAPPA images are shown which demonstrate the utility of the technique.

By studying the adsorption of CO on up to 30 layers of Pt deposited on Ru(0001) the influence of surface strain on the adsorption energy has been disentangled from the residual chemical interaction with the substrate. While the electronic influence of the substrate has largely vanished for three Pt layers, the effect of surface strain due to the 2.5% lattice mismatch of Pt and Ru remains initially intact and is only gradually released for n>/=5 Pt layers. Electronic structure calculations confirm the experimental observations, in particular, the dramatic decrease of the CO adsorption energy on a single Pt layer which is caused by the strong Pt-Ru interlayer coupling.

Key Points• Regulatory T cells are promoters of ischemic stroke by inducing dysfunction of the cerebral microvasculature. We have recently identified T cells as important mediators of ischemic brain damage, but the contribution of the different T-cell subsets is unclear. Forkhead box P3 (FoxP3)-positive regulatory T cells (Tregs) are generally regarded as prototypic antiinflammatory cells that maintain immune tolerance and counteract tissue damage in a variety of immune-mediated disorders. In the present study, we examined the role of Tregs after experimental brain ischemia/reperfusion injury. Selective depletion of Tregs in the DEREG mouse model dramatically reduced infarct size and improved neurologic function 24 hours after stroke and this protective effect was preserved at later stages of infarct development. The specificity of this detrimental Treg effect was confirmed by adoptive transfer experiments in wild-type mice and in IntroductionIschemic stroke induces a profound local inflammatory response involving various types of immune cells that transmigrate across the activated blood-brain barrier to invade the brain in a timed fashion. 1 Although previous research mainly focused on the role of innate immune cells, 2 recent evidence suggests that T cells, which belong to the adaptive immune system, also contribute critically to stroke development, especially in the early phase. 3 T cells have been identified in the postischemic brain as soon as 24 hours after reperfusion, 4 and Abs directed against vascular adhesion receptors expressed on the brain endothelium or leukocyte very late antigen-4 (VLA-4) expressed on lymphocytes inhibited T-cell transmigration and reduced tissue damage in models of stroke. 5 We and others showed recently that recombination activating gene (Rag1)-deficient mice, which lack functional T cells, are largely resistant against ischemic neurodegeneration. 6-8 T cellmediated brain damage became manifest by 24 hours after transient middle cerebral artery occlusion (tMCAO) and did not depend on antigen recognition or costimulation. 8 This clearly argues against TCR-driven mechanisms of tissue damage and suggests instead that T cells act detrimentally in ischemic stroke through antigenindependent pathways, at least during the early phase. Moreover, Rag1 Ϫ/Ϫ mice did not display a gross defect in thrombus formation after artificial vessel wall injury, which could easily explain the stroke protective phenotype in these animals. 8 Although the deleterious effects of T cells in stroke pathophysiology are well accepted, the functional relevance of the different T-cell subsets for stroke progression is less clear, as is their pathologic contribution at the different stages of cerebral ischemia (ie, acute versus chronic). Using adoptive cell transfer in Rag1 Ϫ/Ϫ mice, we could demonstrate that natural killer T cells (NKT cells) Submitted April 26, 2012; accepted October 27, 2012.Prepublished online as Blood First Edition paper, November 15, 2012; DOI 10.1182/blood-2012-04-426734. *C.K. and P.K. ...

Direct evidence for the effect of local strain at a surface on the bonding strength for adsorbates is presented. Scanning tunneling microscopy revealed that adsorbed oxygen atoms on Ru(0001) surfaces are located preferentially on top of nanometer-size protrusions above subsurface argon bubbles, where tensile strain prevails, and are depleted around their rim in regions of compression, relative to the flat surface. Such effects can be considered as the reverse of adsorbate-induced strain, and their direct local demonstration can be used to test theoretical predictions.

Homogeneous hydrogenterminated Si(111) surface formed using aqueous HF solution and waterInfrared spectroscopy is used to study the etching process of stepped Si ( 111 ) 9° surfaces as a function of the pH of the etching HF solutions. This process results in complete H termination of the silicon surface, including terraces, steps, and defects; the surface structure can therefore be well studied using infrared (lR) spectroscopy. Polarized IR absorption spectra of the Si-H stretching vibrations (i.e., in the region 2060-2150 cm -\) vary dramatically as the pH of the etching solutions increases from 2.0 to 7.8. In general, higher pH solutions yield sharper bands and more easily assigned spectra, making it possible to identify the step and terrace species and thus to infer the surface structure and step morphology (i.e., to investigate the etching process). The data are explained by a model involving different etching rates for each individual surface species: The highest rate of removal is for isolated adatom defects located on (Ill) planes and the lowest is for the ideally H-terminated (111) planes themselves. For proper conditions of pH and etching time, atomically straight steps are formed due to faster removal of kinks than etching of the straight step themselves. The influence of steric hindrance is invoked to account for such preferential etching.