Surgery for rheumatic mitral regurgitation in patients below twenty years of age. An analysis of failures

BACKGROUND AND AIM OF THE STUDY: Mitral valve repair is less stable in rheumatic than in degenerative disease. This failure rate is inversely related to the age of the patient. Based on our clinical experience, we selected the group of patients with the worst results for this study: (i) rheumatic, (ii) age 20 or under, (iii) pure mitral regurgitation (MR), and, (iv) no aortic disease. MATERIALS AND METHODS: Between 1988 and 1995, 83 consecutive patients complied with these characteristics. No patient was excluded. Replacement (MVR) was performed in 26 and repair (MRp) in 57 (69%). RESULTS: There was one hospital death (1%) with an actuarial survival at 48 months of 74.8% +/- 19% for MVR and of 97.9% +/- 2.1% at 78 months for MRp. There were no thromboembolic events. Reoperation was required in one MVR (4%) and in 21 MRp (37%), within same admission in six, within three months in eight, under one year in three, and beyond in four cases. Severe MR appeared in five further cases. No statistical difference was found between the preoperative clinical data, operative findings and surgical maneuvers of those patients with successful and unsuccessful repair. The rate of failure was similar after Kay (14/29) and Duran (12/28) annuloplasty. All patients showed a rapid decrease in left ventricular dimensions. Early failures showed elongation of previously shortened chordae at reoperation, together with more reduction in systolic dimension than the other groups. Late failures were more related to progression of the rheumatic process. No clear relationship between rheumatic activity and failure rate was found. CONCLUSION: Rheumatic mitral regurgitation in the young remains a serious problem. The treatment of this frequent pathology in the developing countries needs a new approach based on the knowledge that it starts at the annulus. Earlier surgery at this level might prevent its further progression, avoiding the problems of secondary chordal elongation.     

FILTER INLET VELOCITY REDISTRIBUTION WITH FILTER LOADING

Previous flow visualizations and laser Doppler anemometer velocity measurements have shown that clean engine air filters are presented with very non-uniform velocity distributions when tested in the SAE universal panel Filter test housing. Experiments were conducted to measure the changes that occur in the velocity distribution in the plane 12.7 mm upstream of the filter as it is loaded with dust. Laser Doppler anemometer measurements of velocity profiles were performed for a production engine air Filter in the SAE universal panel filter test housing. Test conditions corresponded to a clean Filter, and dust-loaded Filters at additional pressure drops corresponding to 50 percent, 100 percent, and 150 percent of the design terminating pressure value. The results show that dust loading does make the velocity profiles less non-uniform, but that the changes are not dramatic. The inlet velocity profiles for the design capacity Filter remain very non-uniform.     

Compositional and quantitative microtextural characterization of historic paintings by micro-X-ray diffraction and Raman microscopy

This work shows the benefits of characterizing historic paintings via compositional and microtextural data from micro-X-ray diffraction (μ-XRD) combined with molecular information acquired with Raman microscopy (RM) along depth profiles in paint stratigraphies. The novel approach was applied to identify inorganic and organic components from paintings placed at the 14th century Islamic University-Madrasah Yusufiyya-in Granada (Spain), the only Islamic University still standing from the time of Al-Andalus (Islamic Spain). The use of μ-XRD to obtain quantitative microtextural information of crystalline phases provided by two-dimensional diffraction patterns to recognize pigments nature and manufacture, and decay processes in complex paint cross sections, has not been reported yet. A simple Nasrid (14th century) palette made of gypsum, vermilion, and azurite mixed with glue was identified in polychromed stuccos. Here also a Christian intervention was found via the use of smalt, barite, hematite, Brunswick green and gold; oil was the binding media employed. On mural paintings and wood ceilings, more complex palettes dated to the 19th century were found, made of gypsum, anhydrite, barite, dolomite, calcite, lead white, hematite, minium, synthetic ultramarine blue, and black carbon. The identified binders were glue, egg yolk, and oil.     

Stability analysis of five-phase induction motor drives with variable third harmonic injection

Five-phase induction motor drives have recently drawn attention among multiphase drives because the third harmonic injection (THI) allows obtaining both a higher output torque/volume relationship and broader stability margins. Previous studies have been focused on constant percentages of THI, requiring high and permanent injection if stability becomes main concern. This procedure is not optimal in the whole range of operation, degrading the drive performance. This paper proposes the use of a variable third harmonic injection (VTHI) control scheme that achieves similar robustness of constant third harmonic injection (CTHI) schemes but allows lower percentages of THI at light loads. A bifurcation analysis is presented for both constant and variable THI schemes, fully analyzing the steady state for different parameters conditions. Both the bifurcation analysis and the simulation of the proposed drive confirm the advantage of the proposed VTHI drive over existing CTHI schemes.     

Surface-initiated ring opening polymerization of N-carboxy anhydride of benzyl-l-glutamate monomers on soft flexible substrates

The potential of pulsed plasma deposited polyallylamine (PAA) adlayer has been successfully demonstrated for fabrication of polypeptide brushes functionalized soft flexible polymeric surfaces. Polymeric substrates functionalized with the plasma deposition PAA adlayer resulted in polymeric surfaces functionalized with amino groups, which are the suitable initiating moieties for ring-opening polymerization (ROP) of N-carboxy anhydride of benzyl-l-glutamate (NCA-BLG) monomer. Poly(γ-benzyl-l-glutamate) (PBLG) brushes were grown on PAA functionalized polypropylene (PP), and polytetrafluoroethylene (PTFE) polymeric substrates. These substrates were intentionally chosen for their inert chemical nature towards most wet chemical surface modification reactions. Surface grafted thin films of poly(γ-benzyl-l-glutamate) PBLG on both the PP and PTFE polymeric substrates yielded high density PBLG brushes. PBLG chain orientation, secondary structure and grafting density were characterized by infra-red spectroscopy. The synthesis of PBLG brushes on a flexible polymeric substrate is unprecedented and technologically important, since PBLG possess good electro-optical activity. Analysis of brush layers by Attenuated Total Reflectance Infra-Red (ATR-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) as well as atomic force microscopy (AFM) fully corroborated the success of the plasma activated soft surface grafting approach.     

A comparative study on protective properties of electrosynthesized poly(pyrrole)/poly(N-methylpyrrole), poly(pyrrole)/poly(N-phenylpyrrole), poly(pyrrole)/poly(N-methoxyphenylpyrrole) composite coatings

In this study, three sets of different bilayered composite coatings of pyrrole and N-substituted pyrroles were synthesized by a layer-by-layer approach on copper surface and corrosion performances of the synthesized materials were compared. Electrodepositions of poly(N-methylpyrrole), poly(N-phenylpyrrole), and poly(N-methoxyphenylpyrrole) were performed in nonaqueous medium on a poly(pryrrole)-coated copper surface using cyclic voltammetry. The morphologies of the resulting bilayered composite coatings of poly(pyrrole)/poly(N-methylpyrrole), poly(pyrrole)/poly(N-phenylpyrrole), and poly(pyrrole)/poly(N-methoxyphenylpyrrole) were investigated by scanning electron microscopy. Stabilities of a doping-dedoping process of the composites were determined from the cyclic voltammetric study of the bilayer-coated electrodes in a monomer-free solution. Corrosion performances of the bilayer composite-coated and uncoated copper electrodes were investigated in 0.1 M H₂SO₄ solution using open circuit potential–time (E _ocp–t) curves, anodic polarization, and electrochemical impedance spectroscopy. All the investigated bilayered coatings gave significant enhancement in the corrosion resistance of copper, compared to the single poly(pyrrole) coating. Stability and corrosion tests revealed that the composite material poly(pyrrole)/poly(N-methoxyphenylpyrrole) exhibited higher electrochemical stability and corrosion resistant behavior than the other bilayered composite coatings.     

Electropolymerization, characterization and corrosion performance of poly(N-ethylaniline) on copper

Poly(N-ethylaniline) (PNEA) coatings were grown by cyclic voltammetry technique on copper from 0.1 M N-ethylaniline (NEA) in 0.3 M oxalic acid solution. The optimum conditions (e.g. upper potential limit, scan rate and cycle number) effect on corrosion performance of synthesized PNEA films were determined in order to obtain best protection results against corrosion. The electrodeposited coatings were characterized by cyclic voltammetry (CV), Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy and scanning electron microscopy (SEM). Redox parameters were found after electrochemical tests and results of stability tests of these films impart an electroactive behavior that is composed of both diffusion control and thin film behavior. In addition, corrosion performance of PNEA coatings were investigated in 0.1 M H₂SO₄ by Tafel extrapolation and electrochemical impedance spectroscopy (EIS) techniques.