Diagnosis of aortic graft infection : a case definition by the management of aortic graft infection collaboration (MAGIC)

Objective/Background The management of aortic graft infection (AGI) is highly complex and in the absence of a universally accepted case definition and evidence-based guidelines, clinical approaches and outcomes vary widely. The objective was to define precise criteria for diagnosing AGI. Methods A process of expert review and consensus, involving formal collaboration between vascular surgeons, infection specialists, and radiologists from several English National Health Service hospital Trusts with large vascular services (Management of Aortic Graft Infection Collaboration [MAGIC]), produced the definition. Results Diagnostic criteria from three categories were classified as major or minor. It is proposed that AGI should be suspected if a single major criterion or two or more minor criteria from different categories are present. AGI is diagnosed if there is one major plus any criterion (major or minor) from another category. (i) Clinical/surgical major criteria comprise intraoperative identification of pus around a graft and situations where direct communication between the prosthesis and a nonsterile site exists, including fistulae, exposed grafts in open wounds, and deployment of an endovascular stent-graft into an infected field (e.g., mycotic aneurysm); minor criteria are localized AGI features or fever ≥38°C, where AGI is the most likely cause. (ii) Radiological major criteria comprise increasing perigraft gas volume on serial computed tomography (CT) imaging or perigraft gas or fluid (≥7 weeks and ≥3 months, respectively) postimplantation; minor criteria include other CT features or evidence from alternative imaging techniques. (iii) Laboratory major criteria comprise isolation of microorganisms from percutaneous aspirates of perigraft fluid, explanted grafts, and other intraoperative specimens; minor criteria are positive blood cultures or elevated inflammatory indices with no alternative source. Conclusion This AGI definition potentially offers a practical and consistent diagnostic standard, essential for comparing clinical management strategies, trial design, and developing evidence-based guidelines. It requires validation that is planned in a multicenter, clinical service database supported by the Vascular Society of Great Britain & Ireland

Amorphous hydrogenated carbon-germanium films for hard multilayer IR optical coatings.

Diamondlike amorphous hydogenated carbon (a-C:H) films have found widespread use as hard coatings for IR optical applications. The refractive index of these films (n=2) allows the deposition of quarter-wave antireflection coating on germanium. More complex optical designs, however, require the extension of the range of the optical constants. For this reason we studied amorphous hydrogenated carbon-germanium alloys. The corresponding films with 0 smaller than X smaller than 1 were grown by rf-plasma deposition using mixtures of a hydrocarbon gas and germane or tetramethylgermanium (TMG) as precursors. Film composition, refractive index and IR absorption spectra were measured. This material system offers the possibility to adjust the refractive index between 1:8 and 4:1 and thus allows the deposition of multilayer thin film systems for IR optical applications. As a result of numerical design calculations, a three layer structure with a hard a-C:H top layer is propsed, which acts as a bro adband antireflection coating on germanium substrates for 8-12 mym. We report on the growth and performance of these hard multilayer AR coatings

Correlation between composition and stress for high density plasma CVD silicon nitride films

Intrinsic film stress is an important issue for the fabrication, performance, and application of a device. In the present study, a correlation between stress in high density plasma chemical vapor deposited silicon nitride films and their composition has been established. This has led to the low temperature deposition of low stressed films. The films exhibit a relatively negligible amount of chemically nonbonded hydrogen atoms. The density of the films calculated from the results of Rutherford backscattering spectroscopy and nuclear reaction analysis techniques is high, around 2.4 g/cm3, indicating a dense network. The films exhibit a relatively high coefficient of thermal expansion of around 3.2 ppm/°C, indicating a fairly short-range order in the film. Furthermore, a reversible thermally induced stress, i.e., a negligible stress hysteresis upon thermal cycling between room temperature and 400°C, has been observed in the film. From the stress response to the thermal cycling experiments, contributions from the thermal and athermal components to the net room temperature stress have been deconvoluted

High-density plasma deposited silicon nitride films for coating InGaAlAs high-power lasers

Silicon nitride (SiN) films deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) technique have been used as optical coatings for the emitting facet of InGaAs/AlGaAs high-power lasers. The films were deposited at 90 deg C from a mixture of Ar, N2 and SiH4 as precursors. The most important properties of the films are low intrinsic stress and a negligible hysteresis in stress upon thermal cycling. Pre-cleaning of the surface to be coated, and the stable low stress in the film used for coating have been found to be highly valuable for the reliability of InGaAs/AlGaAs high-power lasers

Electrical Characterization of InAs/(GaIn)Sb infrared superlattice photodiodes for the 8 to 12 µm range

InAs/(GaIn)Sb superlattice photodiodes with a cutoff wavelength of 8.7 mu m show a dynamic impedance of R(0)A = 1.5 k omega cm2 at 77 K and a responsivity of 2 A/W, corresponding to a detectivity of D* = 1 x 10 (exp 12) cm (root of Hz/W). Diffusion limited performance is observed above 100 K. At lower temperatures the diodes are limited by generation-recombination currents. An analysis of the influence of different diode sidewall passivations on the surface contribution to the diode leakage current is presented. The out-of-plane electron mobility as well as the relative contributions of the electron and hole diffusion currents to the diode current were determined by a measurement of the magnetic field dependence of the reverse saturation current density of the diodes

Depth profile analysis of hydrogenated carbon layers on silicon by x-ray photoelectron spectroscopy, Auger electron spectroscopy, electron energyloss spectroscopy, and secondary ion mass spectrometry

Hydrogenated amorphous carbon layers (a-C:H) on silicon show substantial amounts of silicon carbide in the interface, which has been identified with x-ray photoelectron spectroscopy and Auger electron spectroscopy by comparison to Si, C, and SiC standards. The quality of such layers, in particular, adhesion and hardness, becomes better with increasing width of the depth distribution of this interfacial carbide. (IAF

High-power InAlGaAs laser diodes with high efficiency at 980 nm

Within the last few years, high power laser diodes with remarkable improvements concerning output power. efficiency, and reliability have been investigated in the wavelength range between 780 nm and 1064 nm. The discussion, whether laser diodes fabricated from Al-free material systems can surpass the performance of devices made from the conventional InAlGaAs-material system is still ongoing. In our contribution to this discussion we present 980 nm high- power InAlGaAs-laser diodes and laser diode bars with high conversion efficiencies grown by MBE. Broad area laser diodes with 100 mu m aperture show an output power as high as 9.2 W cw at room temperature corresponding to a COMD level of 17 MW/cm2. Up to this output power the conversion efficiency remains above 46 per cent. The highest efficiency of nearly 60 per cent is reached at 2.5 W of output power. Reliability tests are ongoing and predict a lifetime of at least 20.000 h at a power level of 1.5 W cw. Laser diode bars of 1 cm width comprising 25 of these oscillators have been fabricated. Similar to single emitters these devices achieve a conversion efficiency of 58 per cent at 62 W of cw output power. In terms of conversion efficiency and output power these results are among the best reported for both, Al-containing and Al-free laser diodes and laser diode bars. They can be attributed to the material quality, the facet coating technology, and the design of our devices. Clearly, they show the competitiveness of the material system used here

Optoelectronic properties of Photodiodes for the mid- and far-infrared based on the InAs/GaSB/AlSb materials family

The optoelectronic properties of short-period InAs/(GaIn)Sb superlattices (SLs) grown by molecular beam epitaxy on GaSb substrates are discussed. We report on the optimization of the SL materials properties with special emphasis on the use for infrared detection devices. The materials quality is evaluated by using high resolution x-ray diffraction, atomic force microscopy, and photoluminescence spectroscopy. In- plane magneto-transport investigations were performed applying mobility spectrum analysis. The SL diodes were analyzed performing standard electro-optical measurements. The observation of resonances in the I-V curves in the regime of Zener-tunneling due to Wannier-Stark localization opens a new tool for the electrical investigation of photodiodes with low band gap energy. The status of the processing technology is reported demonstrating the feasibility for the fabrication of 256 X 256 focal plane arrays operating in the 8-to-12 micrometers atmospheric window. In addition, results are given for mid-infrared SL-diodes, grown with lattice matched AlGaAsSb barriers instead in the binary InAs/GaSb SL system