4 research outputs found
Fabrication and characterization of a new high density Sc/Si multilayer sliced grating
State of the art soft x-ray spectroscopy techniques like Resonant Inelastic X-ray Scattering (RIXS) require diffraction gratings which can provide extremely high spectral resolution of 105-106. This problem may be addressed with a sliced multilayer grating with an ultra-high groove density (up to 50,000 mm-1) proposed in the recent publication [Voronov, D. L., Cambie, R., Feshchenko, R. M., Gullikson, E., Padmore, H. A., Vinogradov, A. V., Yashchuk, V. V., Proc. SPIE 6705, 67050E (2007)]. It has been suggested to fabricate such a grating by deposition of a soft x-ray multilayer on a substrate which is a blazed saw-tooth grating (echellette) with low groove density. Subsequent polishing applied to the coated grating removes part of the coating and forms an oblique-cut multiline structure that is a sliced multilayer grating. The resulting grating has a short-scale periodicity of lines (bilayers), which is defined by the multilayer period and the oblique-cut angle. We fabricated and tested a Sc/Si multilayer sliced grating suitable for EUV applications, which is a first prototype based on the suggested technique. In order to fabricate an echellette substrate, we used anisotropic KOH etching of a Si wafer. The etching regime was optimized to obtain smooth and flat echellette facets. A Sc/Si multilayer was deposited by dc-magnetron sputtering, and after that it was mechanically polished using a number of diamond pastes. The resulting sliced grating prototype with ~;;270 nm line period has demonstrated a dispersive ability in the 41-49 nm photon wavelength range with a diffraction efficiency of ~;;7percent for the optimized 38th order assigned to the echellette grating of 10 mu m period
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Interdiffusion in Sc/Si multilayers
An understanding of interdiffusion in nano-scale multilayers is of great scientific and practical interest because intermixing is responsible for temporal and thermal instability of EUV and soft X-ray multilayer mirrors. In this paper we study the kinetics of silicide growth in Sc/Si layered coatings. It was found that an amorphous ScSi silicide forms at the scandium-silicon interface. The growth of the ScSi silicide layer obeys diffusion kinetics rather than a chemical reaction kinetics. The silicide growth is limited by the diffusion of Si atoms through the silicide layer towards the silicide-scandium interface where the chemical reaction takes place. As a result of a large asymmetry of interdiffusion the growth of the silicide occurs mainly at the silicide-scandium interface. The diffusion growth of the silicide deviates significantly from the classic parabolic law at the early stage of interdiffusion (Fig. 1). Such a nonlinear growth behavior can be explained with a relaxation model. The growth rate is maximal in the beginning of annealing due to a large amount of excess free volume in the as-deposited multilayer. During the annealing a relaxation processes occurs, and diffusion slows down. Eventually the growth rate is stabilized, and a parabolic regime of the silicide growth is observed
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AntigenâSpecific Stimulation and Expansion of CARâT Cells Using Membrane Vesicles as Target Cell Surrogates
Development of CARâT therapy led to immediate success in the treatment of B cell leukemia. Manufacturing of therapyâcompetent functional CARâT cells needs robust protocols for ex vivo/in vitro expansion of modified Tâcells. This step is challenging, especially if nonâviral lowâefficiency delivery protocols are used to generate CARâT cells. Modern protocols for CARâT cell expansion are imperfect since nonâspecific stimulation results in rapid outgrowth of CARânegative T cells, and removal of feeder cells from mixed cultures necessitates additional purification steps. To develop a specific and improved protocol for CARâT cell expansion, cellâderived membrane vesicles are taken advantage of, and the simple structural demands of the CARâantigen interaction. This novel approach is to make antigenic microcytospheres from common cell lines stably expressing surfaceâbound CAR antigens, and then use them for stimulation and expansion of CARâT cells. The data presented in this article clearly demonstrate that this protocol produced antigenâspecific vesicles with the capacity to induce stronger stimulation, proliferation, and functional activity of CARâT cells than is possible with existing protocols. It is predicted that this new methodology will significantly advance the ability to obtain improved populations of functional CARâT cells for therapy.
Antigenic vesicles (AVs) bind specifically to the surface of their cognate CARâT cells. The binding of AVs to CARâT cells results in the activation and proliferation of CARâT cells. AVs induce CARâT cellsâ functional maturation and increase CARâT cellsâ cytotoxic activity. Incubation with AVs results in antigenâspecific expansion of functional CARâT cells