Primary pars plana vitrectomy is still flawed by a relatively high primary redetachment rate following the initial procedure. The advantages of the technique are a high final reattachment rate and relatively good functional results in a subset of patients with more complicated types of RRD. The risk factors for postoperative failures following PPPV for RRD match to a large extent those following scleral buckling surgery (SBS). Future improvements of the technique will have to focus on modifiable risk factors, such as details of the surgical procedures, surgical training and case selection, to distinguish it from SBS.

A metal-insulator transition study of VO 2 thin films grown on sapphire substrates

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Titanium aluminum nitride films (Ti 1Ϫx Al x N) have been deposited by reactive magnetron cosputtering. Elemental compositions of these films have been determined by core level photoelectron spectroscopy. Scanning electron microscopy reveals a columnar film growth. This is also reflected by the topography of film surfaces as studied by atomic force microscopy. By x-ray diffraction a crystalline atomic structure is revealed. Single phase samples can be obtained, consisting of the substitutional solid solution ͑Ti, Al͒N. Crystallites show preferential orientation. The optical properties of these films have been investigated by spectrophotometry in the UV-VIS-NIR wavelength range. Depending on the elemental composition, the optical constants vary from metallic to dielectric behavior. For film compositions with xϽ0.5 typical features are a tunable transmission maximum and reflection minimum in the visible spectral range, a high infrared reflection, and a low infrared absorption. Due to these optical properties, Ti 1Ϫx Al x N films are promising candidates for applications such as coatings for solar control windows and optical selective solar absorbers.

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