Search

Background The combination of fat grafting and negative pressure (VAC) therapy represents a synergistic interaction of all essential components for wound healing. The aim of this experimental study was to determine whether it could promote healing of wounds with exposed bone. Methods Full-thickness wounds with denuded bone in Sprague–Dawley rats were treated with either polyurethane foam dressing, fat grafting alone, polyurethane foam dressing with VAC, or polyurethane foam dressing with VAC combined with a single, or two administrations of fat graft. Wound healing kinetics, tissue growth, cell proliferation (Ki-67) and angiogenesis (platelet endothelial cell adhesion molecule 1 and α-smooth muscle actin) were investigated. Messenger RNA levels related to angiogenesis (vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (b-FGF)), profibrosis (platelet-derived growth factor A and transforming growth factor β), adipocyte expression (fatty acid-binding protein (FABP) 4 and peroxisome proliferator activated receptor γ), and extracellular matrix remodelling (collagen I) were measured in wound tissues. Results Wounds treated by VAC combined with fat grafting were characterized by cell proliferation, neoangiogenesis and maturation of functional blood vessels; they showed accelerated granulation tissue growth over the denuded bone compared with VAC- or foam dressing-treated wounds. Fat grafting alone over denuded bone resulted in complete necrosis. Expression of angiogenesis markers (VEGF and b-FGF) and adipocyte expression factors (FABP-4) was upregulated in wounds treated with VAC combined with fat grafting. Conclusion Fat grafting with VAC therapy may represent a simple but effective clinical solution for a number of complex tissue defects, and warrants testing in clinical models. Surgical relevanceThe combination of fat grafting and vacuum therapy represents a synergistic interaction of regenerative cells, hospitable wound matrix and stimulating micromechanical forces. It could accelerate complex wound healing through cell proliferation, neoangiogenesis and maturation of functional blood vessels. The efficacy of a multimodal wound healing approach is established in this experimental model; it could easily be translated into clinical trials of treatment for difficult wounds.

High-quality epitaxial AlN films were deposited on sapphire substrates at low growth temperature using a helicon sputtering system. SAW filters fabricated on the AlN films exhibited excellent characteristics, with center frequency of 354.2 MHz, which corresponds to a phase velocity of 5667 m/s. An oscillator fabricated using AlN-based SAW devices is presented and applied to deep-UV light detection. A frequency downshift of about 43 KHz was observed when the surface of SAW device was illuminated by a UV source with dominant wavelength of around 200 nm. The results indicate the feasibility of developing remote sensors for deep-UV measurement using AlN-based SAW oscillators.

Synchrotron-based x-ray microbeam fluorescence and diffraction have been used for in situ measurements of Cu concentration and biaxial stress in a 200-μm-long, 10-μm-wide Al(0.25 at. % Cu) conductor line with 1.5-μm-thick SiO2 passivation during electromigration. Measurements over 48 h with T=300 °C and j=1.5×105 A/cm2 show that a stress gradient of 3 MPa/μm develops over the upstream 130 μm of line length where Cu concentration drops below 0.15 at. %, and a 10-μm-long void develops at the cathode end of the line, but little change in stress occurs over the downstream 70 μm of line length where Cu concentration remains above 0.15 at. %. These experimental results have been reproduced by a finite element model in which the downstream Cu transport is accompanied by a counter flow of Al in the upstream direction, and downstream Al motion is blocked where the local Cu concentration is above ∼0.15 at. %. Defect mediated coupling between Al and Cu diffusive flows, e.g., Cu–vacancy binding, is proposed as the ca...

Electromigration and diffusion of Cu have been investigated for polycrystalline Al(0.25 at. % Cu) conductor lines. In situ measurements of the evolution of Cu concentration profiles along 200 μm long, 10 μm wide conductor lines with 1.5 μm thick SiO2 passivation during electromigration have been obtained by synchrotron-based white x-ray microbeam fluorescence. The apparent effective charge ZCu* of Cu in Al(Cu) has been found to be −8.6±1.0. The evolution of Cu concentration profiles can be manipulated by controlling the direction and magnitude of the current flow at different temperatures. The effective grain boundary diffusivity DCueff has been determined by fitting the time dependent experimental Cu concentration profiles. The results show Arrhenius behavior of DCueff=D0 exp(−Q/kT) for T=275–325 °C with D0=10−(2.3±1.6) cm2/s and Q=0.76±0.19 eV.

X-ray microbeam techniques (spot size=3×20 μm2) have been applied to characterize the composition and structure of rare earth activated Gd(La, Sr)AlO3 phosphor thin films grown by combinatorial synthesis. Using x-ray fluorescence, x-ray diffraction and near-edge x-ray absorption spectroscopy, we have measured the chemical composition, crystallographic structure, and valence state of the rare earth activator atom Eu. These measurements represent the direct application of x-ray techniques to solid-state materials prepared by combinatorial synthesis and demonstrate the power of x-ray microbeam analysis to nondestructively characterize as-grown combinatorial libraries.

We have used x-ray microbeam fluorescence and diffraction for in-situ measurements of electromigration-induced Cu diffusion and stress evolution in passivated, polycrystalline 10[.proportional]m-wide, 200[.proportional]m-long Al(0.25 at.% Cu) conductor lines. Cu migration is in the direction of the electron flow and is determined by the direction and magnitude of the current and by the temperature during electromigration. The effective charge and diffusivity of Cu in Al(Cu) have been obtained from analysis of the Cu concentration profiles. The evolution of electromigration-induced strains normal to the sample surface has been monitored by x-ray microbeam diffraction. A linear strain profile developed after about 9 hrs of electromigration with 1.5[.dotmath]105 A/cm2 at 300°C, corresponding to 3MPa/[.proportional]m equi-biaxial stress. From the Cu profile measured at the same time, the critical Cu concentration for significantly slowing down Al grain boundary diffusion is estimated to be ∼0.15 at. %. These data also confirm that downstream Cu transport is accompanied by a counter flow of Al in the upstream direction.

The interplay between stress and electromigration has been recognized since I. A. Blech et al. used x-ray topography in 1976 to demonstrate that stress gradients developed during electromigration. Availability of high brightness synchrotron x-ray sources, high stability energy dispersive detectors, high resolution area detectors, and pinholes, capillaries and other optical elements for forming x-ray microbeams, has made possible more quantitative, real time measurements of strains and composition changes which develop in polycrystalline metal conductor lines during electromigration. This paper describes advances made in this area, implications of results which have been obtained, and prospects for further progress.

We have used x-ray microbeam fluorescence and diffraction for in-situ measurements of Cu concentration and strain during 36 hours of electromigration with current density 5×105 A/cm2 at temperature 310°C for a passivated 10μm-wide, 200μm-long Al(0.5 at.% Cu) conductor line. These measurements indicate that Cu is quickly depleted at the cathode end of the line and is piled up at the anode end, where the Cu concentration first increases, then decreases, and finally remains constant. A void begins growing at the cathode end of the line about two hours after the start of current flow, with a nearly constant void growth rate of 1 μm/hr for the remainder of the test. The evolution of stresses within the line during electromigration involves changes by 100's of MPa and is more complex than seen previously for electromigration under similar conditions for pure Al conductor lines.

In an earlier paper3 which appeared in this Transactions, the author showed in the appendixes two methods of estimating the shape and scale parameters of a Weibull distribution from a set of life testing data. They are: (I) the method of least squares for the transformed data, and (II) the method of maximum likelihood for ungrouped data. It was pointed out that since the method of least squares was the simpler of the two, it could be used as a first approximation for getting the maximam likelihood estimate which involves solving, by trial and error, two simultaneous transcendental equations. As a measure of simplifying the computation of the analysis, the author suggested fixing the shape parameters at m = 1.7, when studying the reliability of electron tubes. This value of m = 1.7 was an average value based upon the life experience data, then available to the author, of some 2,000 electron tubes. With the wide popularity and availability of electronic computer, the above simplifications are no longer necessary, though still desirable for reasons explained in the text. This paper describes two additional methods for which the computers are almost indispensable. They are: (III) the method of maximum likelihood for grouped data, and (IV) the method of minimized chi-squares. For the sake of discussion, the two previous methods (I and II) are briefly reviewed.

It is widely recognized that electron tube failures may be classified into two types: sudden and delayed. A mixture of two Weibull distributions, each representing one type of tube failure, is proposed, and a simple graphical method for estimating the parameters of the mixed Weibull distribution described.

(1975). MIL-STD-414 Sampling Procedures and Tables for Inspection by Variables for Percent Defective. Journal of Quality Technology: Vol. 7, Standards and Specifications, pp. 51-60.