Critical leg ischaemia with tissue loss : a challenge for the vascular surgeon

There is a widespread reporting habit of combining the outcomes for patients with rest pain (Fontaine III) and tissue loss (Fontaine IV) under the single category of critical leg ischaemia (CLI). This study focused on patients with ischaemic tissue loss treated with infrainguinal bypass surgery (IBS). All patients included in the study were treated at Helsinki University Central Hospital in 2000-2007. First, ulcer healing time after IBS and factors influencing healing time were prospectively assessed in 2 studies including 148 and 110 patients, respectively. Second,the results of redo IBS were retrospectively evaluated in 593 patients undergoing primary IBS for CLI with tissue loss . Third,long-term outcome were retrospectively analysed in 636 patients who underwent IBS for CLI with tissue loss . Fourth, the outcome of IBS was retrospectively compared with endovascular treatment (PTA) of the infrapopliteal arteries in 1023 CLI patients. Fifth, the influence multidrug resistant Pseudomans aeruginosa (MDR Pa) bacteria contamination in CLI patients treated with IBS was retropectively assessed. Sixty-four patients with positive MDR Pa -culture were matched with 64 MDR Pa - negative controls. Complete ulcer healing rate, including the ischemic ulcers and incisional wounds, was 40% at 6 months after IBS and 75% at one year. Diabetes was a risk factor for prolonged complete ulcer healing time. Ischaemic tissue lesions located in mid-and hindfoot healed poorly. At one year after IBS 50% of the patients were alive with salvaged leg and completely healed ulcers. The absence of gap between tertiary graft patency and leg salvage rates indicates the importance of a patent infrainguinal graft to save a leg with ischaemic tissue loss. Long-term survival for patients with ischaemic tissue loss was poor, 38% at 5 years. Only 30% of the patients were alive without amputation at 5 years. Several of the patient comorbidities increased independently the mortality risk; coronary artery disease, renal insufficiency, chronic obstructive lung disease and high age. When both PTA and bypass is feasible, infrapopliteal PTA as a first-line strategy is expected to achieve similar long-term results to bypass surgery in CLI when redo surgery is actively utilized. MDR Pa in a patient with CLI should be considered as a serious event with increased risk of early major amputation or death. Conclusion: Despite a successful infrainguinal bypass healing of the ischaemic ulcers and incisional wounds ulcer healing is a slow process especially in diabetics. Bypass surgery and PTA improve the outcome of the ischaemic leg but the mortality rate of the patients is high due to their severe comorbidities.

Hypersonic stagnation‐point boundary layers with massive blowing in the presence of a magnetic field

The effect of massive blowing rates on the steady laminar hypersonic boundary‐layer flow of an electrically conducting fluid in the stagnation region of an axisymmetric body with an applied magnetic field has been studied. The governing equations have been solved numerically by combining the implicit finite‐difference scheme with the quasi‐linearization technique. It is observed that the effect of massive blowing rates is to remove the viscous layer away from the boundary, whereas the effect of the magnetic field is just the opposite. It is also found that the velocity overshoot increases with blowing rates and also with magnetic field. The effect of the variation of the density‐viscosity product across the boundary layer is strong only when the blowing rate is small, but for the massive blowing rate the effect is negligible.

Segmenting point-sampled surfaces

Extracting features from point-based representations of geometric surface models is becoming increasingly important for purposes such as model classification, matching, and exploration. In an earlier paper, we proposed a multiphase segmentation process to identify elongated features in point-sampled surface models without the explicit construction of a mesh or other surface representation. The preliminary results demonstrated the strength and potential of the segmentation process, but the resulting segmentations were still of low quality, and the segmentation process could be slow. In this paper, we describe several algorithmic improvements to overcome the shortcomings of the segmentation process. To demonstrate the improved quality of the segmentation and the superior time efficiency of the new segmentation process, we present segmentation results obtained for various point-sampled surface models. We also discuss an application of our segmentation process to extract ridge-separated features in point-sampled surfaces of CAD models.

Filter Optimization for Grid Interactive Voltage Source Inverters

Higher order LCL filters are essential in meeting the interconnection standard requirement for grid-connected voltage source converters. LCL filters offer better harmonic attenuation and better efficiency at a smaller size when compared to the traditional L filters. The focus of this paper is to analyze the LCL filter design procedure from the point of view of power loss and efficiency. The IEEE 1547-2008 specifications for high-frequency current ripple are used as a major constraint early in the design to ensure that all subsequent optimizations are still compliant with the standards. Power loss in each individual filter component is calculated on a per-phase basis. The total inductance per unit of the LCL filter is varied, and LCL parameter values which give the highest efficiency while simultaneously meeting the stringent standard requirements are identified. The power loss and harmonic output spectrum of the grid-connected LCL filter is experimentally verified, and measurements confirm the predicted trends.

Performance prediction and loss analysis of low specific speed submersible pumps

A performance prediction procedure is presented for low specific speed submersible pumps with a review of loss models given in the literature. Most of the loss theories discussed in this paper are one dimensional and improvements are made with good empiricism for the prediction to cover the entire range of operation of the low specific speed pumps. Loss correlations, particularly in the low flow range, are discussed. Prediction of the shape of efficiency-capacity and total head-capacity curves agrees well with the experimental results in almost the full range of operating conditions. The approach adopted in the present analysis, of estimating the losses in the individual components of a pump, provides means for improving the performance and identifying the problem areas in existing designs of the pumps. The investigation also provides a basis for selection of parameters for the optimal design of the pumps in which the maximum efficiency is an important design parameter. The scope for improvement in the prediction procedure with the nature of flow phenomena in the low flow region has been discussed in detail.

Turbulent flow computations on a hybrid cartesian point distribution using meshless solver LSFD-U

This paper may be considered as a sequel to one of our earlier works pertaining to the development of an upwind algorithm for meshless solvers. While the earlier work dealt with the development of an inviscid solution procedure, the present work focuses on its extension to viscous flows. A robust viscous discretization strategy is chosen based on positivity of a discrete Laplacian. This work projects meshless solver as a viable cartesian grid methodology. The point distribution required for the meshless solver is obtained from a hybrid cartesian gridding strategy. Particularly considering the importance of an hybrid cartesian mesh for RANS computations, the difficulties encountered in a conventional least squares based discretization strategy are highlighted. In this context, importance of discretization strategies which exploit the local structure in the grid is presented, along with a suitable point sorting strategy. Of particular interest is the proposed discretization strategies (both inviscid and viscous) within the structured grid block; a rotated update for the inviscid part and a Green-Gauss procedure based positive update for the viscous part. Both these procedures conveniently avoid the ill-conditioning associated with a conventional least squares procedure in the critical region of structured grid block. The robustness and accuracy of such a strategy is demonstrated on a number of standard test cases including a case of a multi-element airfoil. The computational efficiency of the proposed meshless solver is also demonstrated. (C) 2010 Elsevier Ltd. All rights reserved.

Electron energy loss spectroscopic study of Cr(CO)6, Mo(CO)6 and W(CO)6 in the vapour phase

Electron energy loss spectra (EELS) of Cr, Mo and W hexacarbonyls in the vapour phase are reported. Most of the bands observed are similar to those in optical spectra, but the two high energy transitions in the 9·8–11·2 eV region are reported here for the first time. Based on the orbital energies from the ultraviolet photoelectron spectra and the electronic transition energies from EELS and earlier optical studies, the molecular energy level schemes of these molecules are constructed.

Continuous ordering below the tricritical point: A critical test for the kinetic pathway in Fe-12at.% Si alloy

A critical test has been presented to establish the nature of the kinetic pathways for the decomposition of Fe-12 at.% Si alloy below the metastable tricritical point. The results, based on the measurements of saturation magnetization, establish that a congruent ordering from B2 --> D0(3) precedes the development of a B2 + D0(3) two-phase field, consistent with the predictions in 1976 of Allen and Cahn.

Behaviour of the curve of critical exponents near and away from a double critical point

To investigate the nature of the curve of critical exponents (as a function of the distance from a double critical point), we have combined our measurements of the osmotic compressibility with all published data for quasibinary liquid mixtures. This curve has a parabolic shape. An explanation of this result is advanced in terms of the geometry of the coexistence dome, which is contained in a triangular prism.