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The main object of the present work was to develop an electrical discharge abrasive drilling (EDAD) methodology to remove the re-solidified layer through the grinding induced by a metal matrix composite electrode prior to the re-solidification of molten material. A metal matrix composite (Cu/SiCp) electrode, with an electroless pretreatment of Cu coating on SiCp to enhance bonding status between Cu and SiCp, was made with a rotating device and this was employed to study the EDAD technology. The machinability of the mold steel HPM50 and tungsten carbide P20 was investigated by the combined technologies of EDAD. The machined surfaces of these materials were examined by scanning electron microscopy (SEM) and their surface roughness measured by a profilemeter. From the experimental results, it was found that the EDAD machining efficiency was three to seven times than that of normal EDM operation for mold steel. However, the efficiency improvement is hardly detectable for tungsten carbide. In addition, the surface roughness of both materials could be improved in comparison with that achieved after EDM.

This article studies the surface characteristics of quench- and temper-treated AISI 440A martensitic stainless steels, which were rough cut using wire electrical discharge machining (WEDM). The microstructure of the recast layer on the cut surface was investigated using scanning and transmission electron microscopes, and the phase compositions were analyzed with an energy-dispersive X-ray (EDX) spectrometer. Experimental results showed that the thickness of the recast layer varied with the heat-treatment condition of the workpiece, the largest thickness was obtained with a quenched specimen, and the thickness decreased with increasing tempering temperature. Intergranular surface cracks were observed only from the as-quenched specimen, whereas surface cracks were not found in the rough-cut specimens after tempering above 200 °C. It is reckoned that reliefing of the thermal residual stress in the quenched workpiece induced the surface intergranular cracks. Microstructures of the recast layer on the rough-cut surfaces of the 600 °C tempered specimen were examined using cross-sectional transmission electron microscopy (TEM) specimens. An amorphous layer exists at some parts of the outermost cut surface. A high density of wire electrode droplets of spherical shape, approximately 10 to 60 nm in size, was found throughout the porous recast layer. Besides, many high-chromium containing sigma spheres with sizes of approximately 120 to 200 nm were precipitated at the bottom part of the recast layer, and its formation mechanism was proposed. Adjacent to the recast layer was a heat-affected zone (HAZ) with a thickness of about 4 µm, in which temper-induced carbides were fully dissolved. The HAZ comprised basically two distinct regions: the first region adjacent to the recast layer was composed of a lath martensite structure, while the other region was an annealed ferrite structure.

An investigation was made into the combined technologies of electrical discharge machining and grinding (EDMG). A metal matrix (Cu/SiC p ) electrode with a rotating device was made and employed to study the EDMG technology. It was found that 3–7 times the normal electrical discharge machining (EDM) material removal rate (MRR) could be achieved in EDMG under suitable conditions of electrode rotating speed, SiC p particle size and current. This novel achievement is attributed to the fact that, under appropriate conditions, the hump-shaped melted material created by the EDM mechanism is vulnerable to attack by the grinding mechanism during the EDMG operation, greatly increasing the removal rate. Conversely, under inappropriate conditions, in which hump-shaped material solidifies prior to the non-conductive ceramic particle grinding, the above function becomes negligible and results in much lower MRR.

Copper/silicon carbide composites (Cu/SiC p ) were made by the powder metallurgy method. Electroless plating was employed to deposit a copper film on SiC p powder before mixing with Cu powder in order to improve the bonding status between Cu and SiC particles during sintering. Thermal expansion property of as-formed product was measured in the temperature range from 50 to 550 °C. The results showed that copper coating on silicon carbide particles could render uniform distribution of SiC p in the copper matrix. The composites exhibited positive thermal hysteresis behavior when cooled down from the peak temperature to room temperature, which can be explained in terms of the residual stresses and the interfacial bonding between copper and silicon carbide. The magnitude of this strain was a function of the SiC p volume fraction and the number of thermal cycles. The thermal expansion property of composites was measured and compared with those predicted from various theoretical models.

Cu-SiCp composites made by the powder metallurgy method were investigated. To avoid the adverse effect of Cu-SiCp reaction, sintering was controlled at a reaction temperature less than 1032 K. Electroless plating was employed to deposit a copper film on SiCp powder before mixing with Cu powder in order to improve the bonding status between Cu and SiC particles during sintering. It was found that a continuous copper film could be deposited on SiCp by electroless copper plating, and a uniform distribution of SiCp in Cu matrix could be achieved after the sintering and extrusion process. The mechanical properties of Cu-SiCp composites with SiCp contents from 0.6 to 10 wt% were improved evidently, whereas electrical properties remained almost unchanged as compared with that of the pure copper counterpart. In the electrical discharge machining (EDM) test, the as-formed composite electrodes exhibited a character of lower electrode wear ratio, justifying its usage. The optimum conditions for EDM were Cu–2 wt% SiC...

The influence of niobium on the L12 structure phase and thus on the thermal stability of the alloys was investigated for four melt-spun Al-Cr-Zr-Nb alloys; three alloys contain about 4vol% of L12-Al3 (ZrxNb1-x) precipitate with different Zr/Nb ratios and one alloy contains about 8vol% of L12 precipitate. The microstructures of as-spun ribbons were characterized using an optical microscope and scanning transmission electron microscope. DSC and microhardness tests indicated that the alloys aged at 723 and 773K showed excellent thermal stability after annealing at 648 and 673K for up to 1000h. The Al-3.14Cr-4.03Zr-1.95Nb alloy, for example, attains microhardness of 204kgf/mm2 in agehardened condition and retains 93% of that value, i. e. 190kgf/mm2, after annealing at 648K for 1000h. Microstructural changes during annealing were identified and correlated with the microhardness data. The coarsening rate of the L12 structure precipitate is very slow at the test temperatures. The coarsening kinetics of the L12 structure Al3(Zr2/3 Nb1/3) precipitate in the Al-3.14Cr-4.03Zr-1.95Nb alloy were studied at 648, 673 and 723K. Antiphase boundary evolved inside the L12 particles during annealing at 723K.

Hard chromium plating is widely used owing to its good wear and corrosion resistance. This plating technology has been practiced and well developed for many decades [1, 2]. Since reduction of hydrogen ions occurs at electrode surface during chromium plating, the current efficiency for the plating is normally under 25% [1]. However, Hoare [3] shows that rapid flow of the electrolyte over the cathode surface is essential for highspeed chromium plating due to the reduction of the diffusion path in a diffusion-controlled electrode reaction. Plating by using rotating disc electrode (RDE) method is useful to study this effect. Cross-section microstructure of the plated hard chromium was studied with optical microscope and scanning electron microscope (SEM) [4, 5]. The results showed that the grain size of as-plated chromium was so fine that the grain size cannot be estimated, and only the grains after annealing can be observed. Pina [5] showed that a fiber texture existed with 〈111〉 axis perpendicular to the chromium deposit surface by using X-ray diffraction method. The interface microstructure between Cr-Mo steel and chromium deposit has not been studied yet. Especially, little work has been done on the current efficiency and TEM-cross section microstructure of chromium plating using rotating cylinder electrode (RCE), by which a uniform mass transport over all of the electrode surface can be obtained. In this letter the aspects mentioned above are reported using RCE specimens. Cold swaged Cr-Mo steel was the chosen specimen with its chemical composition shown in Table I. The cylinder specimen dimension was 16 mm φ× 5 mm with an exposing plating area of 2.51 cm2. Platinized-Ti mesh with dimension of 25× 35 mm was used as anode. All chromium plating was performed in a conventional bath containing 250 g/l of CrO3 and 2.5 g/l of H2SO4 at 50 ◦C. Cathodic current densities applied were 30, 40, 50 and 60 A/dm2, respectively. Rotating speed of RCE was controlled in the range of 5–1000 rpm. Before electroplating, the RCE specimens were anodically polarized with current density of 40 A/dm2 at 200 rpm for 30 s. The current efficiency was evaluated with three RCE specimens after a constant applied cathodic charge of 1.33 A h under same plating condition. The weight increment of chromium plating was measured and compared with theoretical weight increment according to Faraday’s law. After plating, the RCE specimen was rinsed in acetone, dried with hot air, then prepared for current efficiency evaluation; TEM-cross section specimens were prepared as mentioned elsewhere [6] and their microstructure examined. The current efficiency of applied cathodic current density with respect to logarithmic rotating speed of RCE is shown in Fig. 1. The results show that all current efficiency increases with the increasing of cathodic current density, suggesting that higher electric field tends

The corrosion fatigue (CF) behaviour, under constant deflection bending conditions with a pulsating tension stress form, of 2024-T3 aluminium alloy, unanodized and anodized to form a thick porous film, in 3.5% NaCl solution has been investigated. It was found that E corr varies very little until specimen fracture under low frequency CF conditions, whereas E corr drops rapidly when approaching the later fracturing stage of the CF process under high-frequency conditions for unanodized specimens. However, a slow drop in E corr was detected from the commencement of the CF process, and lasted up to a much more rapid drop at a later fracturing stage for the anodized specimen. This behaviour presumably can be explained by the cracking of the anodic film and the theory of imperfect recovery of the surface film. It is suggested that the E corr monitoring technique may be useful for determining the remnant CF life for existing structural parts of this alloy or other aluminium alloys regardless of whether or not they are anodized. Furthermore, the T3 temper provides a microstructure which may retard main-crack formation and penetration in the CF process of the anodized alloy, thus mitigating partly the negative effect of the readily crackable anodic film.

High-Tc superconducting Bi-Pb-Sr-Ca-Cu oxide with Tc (zero) of 108 K was obtained by ultrastructure processing via the EDTA route, using nitrates as the starting materials. Excellent sinterability of precursor induced by the EDTA processing permits a relatively short time to achieve the desirable Bi-based superconducting compound compared with that obtained by the traditional solid-state reaction method. Fourier transform-infrared spectroscopy, thermal analysis, X-ray diffraction analysis and energy-dispersive X-ray fluorescence analysis were employed in this study to elucidate the reaction mechanisms and/or identify the phase transformations.

The temperature rise in the substrate as well as in the bulk solution and the development of a local brown-coloured 'burnt' region on the anodic film are the characteristics of high rate anodizing of aluminum in oxalic acid. In this study, measurement of the barrier layer thickness in both the predicted burning region and the normal region indicates that they increase simultaneously as the voltage builds up to form the secondary voltage peak on the voltage/time transient; a depletion of oxalate anions allied with the temperature rise at the pore base is thought to govern this behaviour. Characteristic strong dotted anodic glows occurred simultaneously with a slight drop of voltage, about 1V, from the secondary peak value were observed just prior to the initiation of the local burning sector; also, the local substrate temperature always rises when burning is approaching. These studies suggest that a thermal modified electronic breakdown process is responsible for the burning phenomenon.

Electrical discharge machining (EDM) has been shown to be a versatile method for machining difficult-to-work materials including heated-treated steels, tungsten carbides and various conductive ceramics. However, low machining efficiency is one of the main EDM disadvantages. The topic of how to reduce machining time and maintains reasonable accuracy has always been of research interest. The main object of the present work was to develop an electrical discharge machining and grinding (EDMG) methodology to remove the re-solidified layer through the grinding induced by a metal matrix composite electrode prior to the re-solidified layer solidification. A metal matrix composite (Cu/SiCp ) electrode, with an electroless pretreatment of Cu coating on SiCp to enhance bonding status between Cu and SiCp , with a rotating device was made and employed to study the EDMG technology. Machinabilities of mold material, HPM50 mold steel and P20 WC/Co, were investigated by the combined technologies of EDMG. The machined surfaces of these materials were examined by scanning electron microscopy (SEM) and their surface roughness measured by a profile meter. From the experimental results, it was found that higher material removal rate and lower surface roughness can be achieved when suitable electrode rotating speed, SiCp size and working current are chosen. In addition, the surface roughness of both materials could be improved as compared with that following the EDM process.Copyright © 2004 by ASME

Lorus Therapeutics (formerly GeneSense Technologies) is developing GTI-2501, directed against the R1 component of ribonucleotide reductase, for the potential treatment of cancer [348928]. In November 2000, the company filed an IND with the FDA in preparation to begin a phase I trial in the US in the first quarter of 2001 [389975], [396537], [397960]. In March 2001, the FDA approved the IND application [402350], and in June 2001, a phase I, dose-escalating trial in patients with lymphomas or solid tumors which have not responded to standard therapy commenced in the US [412225]. The company expected the phase I trial of GTI-2501 to be completed within 12 to 15 months [420582]. In November 1999, the company reported that in preclinical trials, GTI-2501 was an effective anticancer agent when tested in standard mouse models bearing a variety of different human cancer lines including tumor cells derived from lung, breast, colon, kidney, ovary pancreas and skin cancers [348928]. Lorus received a patent from the US PTO in January 2000, covering the design and use of unique anitisense anticancer drugs, including GTI-2501 and GTI-2040 [353538]. In June 2000, the USPTO allowed a patent to specifically protect GTI-2501 [370810].

The cyclic voltammetry stripping (CVs) behavior of the tin-doped indium oxide (ITO) on SiO2 in 0.3M HCl is reported. The CVs result showed an obvious reduction-current peak that occurred during the first cathodic potential scanning. Smaller reduction current and more negative potential of the reduction-current peak were also observed for the ITO that was annealed at 500 °C. The result was attributed to the replenished oxygen-deficient site and the oxygen anion density is decreased in the ITO. The present study has proved that CVs is a useful method to differentiate the carrier concentration in ITO film controlled by different pretreatments. Many spherical In-Sn particles were formed on the ITO when the reduction current took place. During precipitation of these spherical particles, the grain boundaries of the ITO were dissolved and the ITO surface nearby the grain boundaries offered a preferred nucleation site for the formation of these spherical In-Sn particles. Based on the microstructure observed and the result derived from the short potential range scanning, the formation mechanism of the spherical particle is proposed.

Kupffer cells play an important role in the pathogenesis of liver diseases. During endotoxemia and alcohol-induced liver disease, tissue injury is preceded by an excessive release of cytokines by these macrophages. Tumor necrosis factor-alpha (TNF-alpha) is one of the key cytokines associated with liver injury. Pre-exposure of animals to TNF-alpha antibodies has been shown to prevent macrophage-mediated liver injury in experimental animals. In this article, we describe a method to encapsulate in pH-sensitive liposomes and to deliver an antisense phosphorothioate oligonucleotide (TJU-2755) against TNF-alpha. We describe the efficacy of this formulation in inhibiting endotoxin-mediated production of TNF-alpha. The liposomes prepared were stable for over 4 weeks at pH 7.4, but readily released their contents when exposed to an acidic environment below pH 6, similar to the pH that exists in early endosomes. Male Sprague-Dawley rats were administered (i.v.) liposome-encapsulated TJU-2755 (1-2 mg/kg body wt.). Empty liposomes served as controls. Forty-eight hours postinjection, the animals were administered a single dose of lipopolysaccharide (50 microg/kg body wt.) and were sacrificed 90 min later. The TNF-alpha produced by excised liver incubated ex vivo and the levels of plasma TNF-alpha were determined. After a single administration of liposome-encapsulated antisense TJU-2755, a 30% reduction in TNF-alpha produced by liver slices was observed. Two daily doses of the antisense oligonucleotide inhibited TNF-alpha production by 50%. This was associated with a 65 to 70% reduction in plasma levels of TNF-alpha, compared with controls. These results indicate that oligonucleotide TJU-2755 encapsulated in pH-sensitive liposomes can be used to effectively reduce endotoxin-mediated production of TNF-alpha in macrophages in vivo and thus may be of value in attenuating or preventing macrophage-mediated liver injury.

Preparation de couches supraconductrices avec T c (O)=97 K pour le systeme Bi(Pb)-Sr-Ca-Cu-O

Selecting effective antisense target sites on a given mRNA molecule constitutes a major problem in antisense therapeutics. By trial-and-error, only 1 in 18 (6%) of antisense oligonucleotides designed to target the primary RNA transcript of tumor necrosis factor-alpha (TNF-alpha) strongly inhibited TNF-alpha synthesis. Subsequent studies showed that the area in RNA targeted by antisense oligonucleotides could be moved effectively 10-15 bases in either direction from the original area. We observed that only molecules that incorporated a tetranucleotide motif TCCC (complementary to GGGA on RNA) yielded potent antisense oligonucleotides against TNF-alpha. A comprehensive literature survey showed that this motif is unwittingly present in 48% of the most potent antisense oligonucleotides reported in the literature. This finding was prospectively used to predict the sequences of additional antisense oligonucleotides for the rat TNF-alpha primary RNA transcript. Over 50% of antisense constructs (13 of 22) containing the TCCC motif were found to effectively inhibit TNF-alpha synthesis. Marked reductions in mRNA were also observed. This motif was found to be most effective when targeting introns in the primary RNA transcript, suggesting a nuclear localization for the antisense action. Predicting target sites based on the presence of this motif in primary RNA transcripts should be of value in the development on new antisense pharmacotherapy.

Variations in stress and grain size of Ti- and TiN- capped Al thin films passivated by fluorinated silicon dioxide (SiOF) during repetitive thermal cycling are investigated. The amount of stress relaxation, elastic and plastic behavior of these thin film structures are compared. Ti and TiN cap layers strengthen the single Al film significantly while the presence of SiOF induces plastic deformation of metal layers. Less grain growth is associated with a dielectric passivated Al film. The penetration of fluorine into Al upon annealing can be reduced by a TiN barrier layer.

High-Tc superconducting Bi-Pb-Sr-Ca-Cu oxide with zero resistance temperature at above lOOK has been synthesized via the use of ethylenediamine-tetra-acetate(EDTA) colloid and corresponding metal nitrates. Remarkable sinterability of the precursor requires shorter time to achieve superconducting phases than conventional solid-state reactions. Superconducting properties were measured electrically and magnetically. The thermal decomposition, X-ray diffraction and microstructural characteristics of the precursor and the sintered samples were also discussed.

The purpose of this work is to study the electrocrystallization behavior of the copper deposit on pure titanium substrate. The electroplating was conducted at 0.7 A/cm 2 , 65°C in cupric sulfate-sulfuric acid bath with various chloride additions (45-350 ppm). Initial growth morphology and microstructure of the deposit were examined with a field-emission scanning electron microscope (FESEM) and a high-resolution transmission electron microscope integrated with an energy-dispersive X-ray spectrometer. Results of cathodic polarization and galvanostatic plating experiments show that the increasing concentration of chloride ions in the plating bath would significantly increase the cathodic potential. This cathodic potential increase was found to be induced by the presence of CuCl precipitates on the cathodic surface as well as on the copper cluster formed during the electrocrystallization process. At the initial plating stage, both copper and hexagonal-shaped CuCl precipitates were produced simultaneously. Eventually, the pyramid-shaped CuCl precipitates were observed, which consisted of many parallel hexagonal planes stemming from a screw dislocation. The polarization effect of CuCl precipitate on the Ti substrate was further confirmed and clarified. Through measurement of the electrode response and investigation of the deposit using FESEM, it was observed that under identical electroplating conditions, much less CuCl forms on a copper substrate in the initial stages than on a titanium substrate, leading to lower polarization.

Anodisation dure dans l'acide sulfurique. Les resultats experimentaux des courbes transitoires courant/temps, de microdurete, de rugosite, de resistance a l'abrasion, d'etude metallographique et d'analyse de composition, montrent que dans les conditions utilisees le courant pulse alternatif donne de mauvais resultats et le courant pulse continu de meilleurs resultats

Polyclonal antibodies prepared against horse liver mitochondrial aldehyde dehydrogenase (ALDH) crossreact with both cytoplasmic and mitochondrial ALDH. Antibodies prepared against the cytosolic enzymes were more specific in that they only precipitated enzymes derived from cytosol. These polyclonal antibodies were used to determine the subcellular localization of aldehyde dehydrogenase isozymes isolated from other species and other tissues. A sequential precipitation technique was developed which allowed for the determination if samples contain both antigens. The polyclonal antibodies contained antibodies which recognize peptide fragments of mitochondrial ALDH. These antibodies can be used to probe for structural homology between similar regions in different forms of ADLH.