SURFACE ALLOYING OF MILD STEEL BY LASER MELTING OF AN ELECTROLESS NICKEL DEPOSIT CONTAINING CHROMIUM CARBIDES

It is possible to realize surface alloys by laser melting an electroless nickel layer containing chromium carbide particles predeposited on a mild steel substrate. By this way the surface alloy is expected to have not only a high nickel content but also an important chromium content in order to improve the corrosion resistance. The presence of chromium in solid solution results from the dissolution or melting of the carbide particles. Typical laser solidification microstructures are obtained. Dendrites consist of an austenitic Fe-Ni-Cr solid solution and interdendritic regions are constituted by an eutectic mixture containing the same austenitic solid solution and complex Fe, Ni, Cr carbides and phosphides. In comparison with a surface alloy obtained by laser melting of an electroless nickel layer without carbide particles, the corrosion resistance was slightly improved in saline aqueous solutions. The limited effect was due to the fact that the final chromium content in the present experimental conditions was not as high as that initially expected.     

The growth and characterization of AlGaAs double heterostructures for the evaluation of reactor and source quality

AlGaAs double heterostructures are grown by low-pressure metalorganic chemical vapor deposition to evaluate the level of oxygen contamination in different trimethylaluminum sources. Effects of arsine purifiers, misoriented substrates, atmospheric exposure of the growth chamber, and possible phosphorus contamination are also studied. Extensive characterization is performed on these films by a variety of methods, including high-resolution x-ray diffraction, photoluminescence (PL), time-resolved photoluminescence, and secondary-ion mass spectrometry. The PL intensities for structures grown with the low-alkoxide grade are reproducibly much greater than those grown with the regular-grade TMA1. The use of AsH₃ purification improves the PL intensity.     

In vitro comparisons between Carica papaya and pancreatic lipases during test meal lipolysis: Potential use of CPL in enzyme replacement therapy

High levels of lipase activity are known to occur in Carica papaya latex, and this activity is being used in some biotechnological applications. The lipolytic activity of C. papaya lipase (CPL) on dietary triacylglycerols (TAG) has not yet been studied. Hence, the aim of this study was to characterise the specific activity of CPL on dietary TAG present in a crude preparation. Also, we have determined its stability during the lipolysis of a test meal at various pH values mimicking those occurring in the gastro-intestinal tract, with or without bile, and have compared these properties with those of porcine pancreatic extract (PPE) and human pancreatic lipase (HPL). CPL showed maximum stability at pH 6.0, both with and without bile. Some residual activity was still observed at pH 2 (20%), whereas the pancreatic lipases tested were immediately completely inactivated at this pH. In the absence of bile, the highest specific activities were measured at pH 6 in the case of CPL, PPE and HPL. Adding bile slightly decreased the CPL activity in the 4–6 pH range, thus shifting the optimum CPL activity to pH 7, where the presence of bile had no effect. Lipolysis levels decreased with the pH, but CPL was still more active than PPE at pH 5 on a relative basis. These results suggest that CPL might be a promising candidate for use as a therapeutic tool on patients with pancreatic exocrine insufficiency.     

Design of New Cardanol Derivative: Synthesis and Application as Potential Biobased Plasticizer for Poly(lactide)

A novel biobased plasticizer made of cardanol is designed for poly(lactide) (PLA). This cardanol‐derived plasticizer, i.e., methoxylated hydroxyethyl cardanol (MeCard), is synthesized through methoxylation of the double bonds on the side chain of cardanol, and characterized by ¹H NMR and mass spectrometry. The plasticization effect of MeCard on the molecular structure, morphology, thermal and mechanical properties of PLA is evaluated and compared to that of a commercial cardanol, i.e., hydroxyethyl cardanol (pCard). The plasticization efficiency of MeCard is demonstrated by a substantial decrease of the glass transition temperature and storage modulus together with a significant increase of the elongation at break as compared to neat PLA. Moreover, MeCard exhibits higher plasticization performance than pCard toward PLA. Such behavior is related to a higher miscibility and compatibility between PLA and MeCard thanks to the methoxylation of the double bonds on the side chain of cardanol as shown by SEM micrographs.

     

Ultrasonic and structural characterization of anisotropic austenitic stainless steel welds: Towards a higher reliability in ultrasonic non-destructive testing

The non-destructive testing of austenitic stainless steel welds of the primary coolant piping system is a significant problem for the nuclear industry. Ultrasonic techniques would be very helpful to detect, locate and size potential defects. Unfortunately, austenitic welds are coarse-grained, heterogeneous and anisotropic. This leads to aberration and scattering of the ultrasonic waves. In this paper, we present several experimental results of ultrasonic testing of two austenitic welds exhibiting high anisotropy. In order to explain the observed display of wave propagation phenomena such as beam deviation, we use finite element modeling. The modeling is associated with a complete characterization of the inspected welds. Two essential characteristics of the welds are determined: the average elastic constants of the weld and the grain orientations. The capability of the model is illustrated in different testing configurations. This work associating structural characterization and modeling shows that a better understanding of the phenomena of ultrasonic propagation should allow the interpretation and reliability of the industrial inspections of heterogeneous anisotropic welds to be improved.     

Initial in-orbit results from a low-cost atmospheric ozone monitor operating on board the FASat-Bravo microsatellite

In 1994, a collaborative programme was set up between the University of Surrey and the Chilean Air Force to design and build a low-cost 50 kg microsatellite with instrumentation capable of monitoring the distribution and concentration of stratospheric ozone, particularly over Chilean territory. This resulted in the joint design and development of the ozone-layer monitoring experiment (OLME), which was flown on board the resultant FASat-Bravo microsatellite, launched in July 1998 into an 820 km altitude Sun-synchronous orbit. The nadir-pointing OLME measures the solar ultraviolet light backscattered from the atmosphere in four spectral bands. From these raw radiometric data, total column ozone concentrations can be deduced. Since the launch, a series of high-spatial-resolution measurements have been made over Chilean scientific stations, while continuous low-spatial-resolution measurements have been used to provide global coverage. To date, the University of Surrey has concentrated on these global measurements, and has used a simplified ozone retrieval algorithm to check the results qualitatively against ozone maps produced by NASA's Earth Probe Total Ozone Mapping Spectrometer (TOMS) payload. These initial results look promising, with apparently good correlation between the two datasets. A novel, more-complex retrieval algorithm has been applied to the high-resolution data, and early results have shown agreement with the TOMS.     

Optimisation of CO2 laser beam edge‐to‐edge welding of Al‐Mg alloy sheets

Steels applied for construction of oil and gas pipelines are analysed; examples of X70 and X80 steel pipelines are given. The mechanical properties and weldability of X70 and X80 steel as well as principles of quality inspection of pipelines performed at a building site are described. On the grounds of the literature survey and the author's own experience, both shortcomings and advantages of application of advanced high-yield-strength steels, for instance X80 steel, for construction of high-pressure pipelines are presented.     

Structural diversity of nucleophilic adducts from flavanols and oak wood aldehydes

The reactions between (+)-catechin and a representative oak wood aldehyde (furfuraldehyde, 5-(hydroxymethyl)furfuraldehyde, 5-methylfurfuraldehyde, vanillin, or syringaldehyde) in a wine-like model solution were studied and the formed condensation products were characterized by LC/MS and LC/MS/MS.     

Variability in captan residues in apples from a Canadian orchard

Apple trees in an orchard in Quebec, Canada were treated, following label directions, with the fungicide captan (1,2,3,6-tetrahydro-N-(trichloromethylthio)phthalimide) during the 2003 agricultural season. A total of 142 apples from three rows of trees were selected for determination of captan by GC/MS. Individual apples were found to contain captan levels ranging from 16.9 to 6350 ng g^-1. Only two individual apple samples exceeded the Canadian maximum residue limit (5000 ng g^-1) for captan in apples. Six composite samples, comprising half portions of eight individual apples, were analysed from each of the three experimental rows. Composite samples ranged in concentration from 166 to 2620 ng g^-1. The greatest uncertainty associated with the measured concentrations was due to variability among apples rather than the measurement of residue levels.