High temperature rapid reactive joining of dissimilar materials: Silicon carbide to an aluminum alloy

An effective method for bonding of silicon carbide (SiC) ceramic to 5083 Aluminum metal-alloys was developed. This method employed the concept of high-temperature rapid heterogeneous combustion reaction to joint dissimilar materials. Scaled-up welding apparatus, which can accommodate specimens of up to 5″ in diameter and 6″ in height and allow a rapid (～10 ms) load application (up to 1000 MPa) on the joining stack during reaction, was designed and built. An exothermic mixture of titanium and carbon powders (molar ratio 1:0.4) was utilized as a joining reactive layer. Uniform crack-free bonding of SiC to 5083 Al-alloy was accomplished both without and with application of loads. SEM and focused ion beam (FIB) images revealed that ～10 μm (without load) and ～500 nm (with load) transitional joining layers along the interfaces were observed, respectively. Compositional and mechanical properties of joined samples were also characterized by EDS analysis and Vickers microhardness investigations.     

The GIF Quantum,a next generation post-column imaging energy filter

We describe a new post-column imaging energy filter for (scanning) transmission electron microscopy from 60 to 300 kV operating voltage. The completely redesigned GIF quantum has a gradient magnetic prism, dodecapole optics, a 10-times faster 40 Mpixel/sec CCD camera, a 1 μs electrostatic shutter, and new user interface, control, and auto-alignment software. An 8 dodecapole lens system, performs full 2nd and 3rd, and partial 4th and 5th order aberration correction. The improved aberration correction has allowed the size of the entrance aperture to be nearly doubled to 9.0 mm compared to current generation post-column designs. The electrostatic shutter provides exposure control down to 1 μs, extending the exposure time range to over 7 orders of magnitude. Spectroscopy operation has been improved with a larger 2 keV field of view at 200 kV, and a maximum acquisition rate of 1000 spectra per second. A high-speed DualEELS mode simultaneously acquires core- and low-loss spectra up to 2 keV apart. A more intuitive user interface includes new capabilities such as automated exposure control and optimized full spectrum acquisition. The auto-alignment software has been significantly enhanced to use the full flexibility of the dodecapole lens system.     

Neuronal degeneration in the gerbil brainstem is associated with spongiform lesions

Spongiform lesions arise in dendrites and glia in the brainstem of domestic Mongolian gerbils. Most pronounced within the cochlear nucleus (CN), this disorder is dynamic and progressive; the lesions increase in number, size, and extent with age. It has not been clear whether these spongioid lesions either cause or are associated with significant neural degeneration. In contrast, feral Mongolian gerbils (wild-trapped in Tuva) and their offspring show few spongiform lesions. The Tuvan gerbils provide an appropriate within-species control. We compared degeneration in the brainstem of domestic and Tuvan gerbils using the amino-cupric-silver (ACS) stain of de Olmos et al. [(1994) Neurotoxicol. Teratol., 16:545-561]. Positive histologic controls were provided by cerebellar stab wounds in domestic gerbils and by unilateral kainic acid injections into the CN of Tuvan gerbils. The ACS stain revealed extensive degeneration of axons, terminals, dendrites, and neurons in the brainstem of domestic gerbils. Neurodegeneration was most pronounced in the CN and was coextensive with spongiform lesions. Neurodegeneration was also seen in the trapezoid body, lateral lemniscus, and inferior colliculus, but was less pronounced than in the CN. The cerebellar stab wounds resulted in silver-stained Purkinje cells restricted to the stab wound local region. Kainic acid produced extensive neuronal and spongiform degeneration of the injected CN that was very similar to that spontaneously occurring in domestic gerbils. In contrast, the non-injected CN of Tuvan gerbils showed no neuronal or spongiform degeneration with the ACS stain. We conclude that, in domestic gerbils, the naturally occurring spongiform lesions of the CN and the accompanying neurodegeneration are both results of a common mechanism, most probably excitotoxic.     

Texturing of YBa2Cu3O6+x by melt processing

Solidification from the melt is an effective method for producing high-critical-temperature superconductors that are highly textured and have relatively high critical current densities. There are various means to generate a textured microstructure, but in all techniques the proper control of solidification parameters is paramount.     

Confirmation of Superconductivity in Sr2YRu1?uCuuO6

Evidence is reported that Sr₂YRu_1–u Cu _u O₆ superconducts with a transition temperature of at least T _c 30 K for u = 0.1, confirming the reports by Wu et al. that this material superconducts despite having no cuprate planes. (Such planes are widely believed to be necessary for high-temperature superconductivity.) Coexisting with the superconductivity, Sr₂YRu_1–u Cu _u O₆ exhibits magnetic order due to antiferromagnetic Ru and Cu.     

Improved mechanical properties of acrylic bone cement with short titanium fiber reinforcement

Acrylic bone cements are widely used in total joint arthroplasties to grout the prosthesis to bone. The changes in the tensile properties and fracture toughness of polymethylmethacrylate (PMMA) bone cements obtained by the addition of control and heat treated short titanium fibers are studied. Heat treatment of titanium fibers is conducted to precipitate titania particles on the fiber surface to improve the biocompatibility of the metal. Control and heat treated short titanium fibers (250 μ long and 20 μ diameter) were used as reinforcements at 3 volume %. X-ray diffraction indicated the presence of a rutile form of titania due to the heat treatments. The tensile and fracture properties were improved by the addition of fibers. Bone cements reinforced with titanium fibers heated at 550^∘C for 1 h followed by 800^∘C for 30 minutes show the largest increase in fracture toughness along with the smallest changes in elastic modulus and needs to be further investigated.     

Crushed sunflower, flax, or canola seeds in lactating dairy cow diets: Effects on methane production, rumen fermentation, and milk production

The objective of this study was to investigate the potential of reducing enteric methane production from dairy cows by incorporating into the diet various sources of long-chain FA varying in their degree of saturation and ruminal availability. The experiment was conducted as a crossover design with 16 lactating dairy cows maintained in 2 groups and fed 4 dietary treatments in four 28-d periods. Eight ruminally cannulated primiparous cows (96 ± 18 d in milk) were assigned to group 1 and 8 multiparous cows (130 ± 31 d in milk) were assigned to group 2. The dietary treatments were: 1) a commercial source of calcium salts of long-chain fatty acids (CTL), 2) crushed sunflower seeds (SS), 3) crushed flaxseed (FS), and 4) crushed canola seed (CS). The oilseeds added 3.1 to 4.2% fat to the diet (DM basis). All 3 oilseed treatments decreased methane production (g/d) by an average of 13%. When corrected for differences in dry matter intake (DMI), compared with CTL, methane production (g/kg of DM intake) was decreased by feeding FS (−18%) or CS (−16%) and was only numerically decreased (−10%) by feeding SS. However, compared with the CTL, feeding SS or FS lowered digestible DMI by 16 and 9%, respectively, because of lowered digestibility. Thus, only CS lowered methane per unit of digestible DM intake. Feeding SS and CS decreased rumen protozoal counts, but there were no treatment effects on mean ruminal pH or total volatile fatty acid concentration. Milk efficiency (3.5% fat corrected milk/DMI), milk yield, and component yield and concentrations were not affected by oilseed treatments. The study shows that adding sources of long-chain fatty acids to the diet in the form of processed oilseeds can be an effective means of reducing methane emissions. However, for some oilseeds such as SS or FS, the reduction in methane can be at the expense of diet digestibility. The use of crushed CS offers a means of mitigating methane without negatively affecting diet digestibility, and hence, milk production.     

Leucovorin modulation of 5-iododeoxyuridine radiosensitization: a phase I study

Evidence for clinically significant radiosensitization by the halogenated pyrimidine 5-iododeoxyuridine (IdUrd) continues to accumulate. In vitro radiosensitization has been demonstrated in human colon tumor cell lines following exposure to 1-10 micrometer. Coadministration of leucovorin (LV) increases radiosensitization, which correlates directly with increased IdUrd DNA incorporation. Clinical data regarding proliferation rates and thymidine kinase levels in tumors versus normal tissues suggest selective incorporation of IdUrd into gastrointestinal tumors may occur. The objectives of this Phase I study were: (a) to assess the feasibility of LV modulation of IdUrd radiosensitization by determining the maximum tolerated dose (MTD) of IdUrd plus LV; and (b) to perform correlative laboratory studies to investigate the potential of IdUrd plus LV to increase radiosensitization in vivo. Seventeen patients with unresectable or recurrent gastrointestinal adenocarcinomas received a 14-day course of continuous i.v. infusion of IdUrd prior to initiation of radiotherapy. Two additional 14-day infusions of IdUrd with LV were given during the course of radiotherapy (60 Gy in 6 weeks). The initial dose of IdUrd was 250 mg/m2/day and was escalated in subsequent patients to 400 and 600 mg/m2/day. The LV dose remained fixed at 250 mg/m2/day. Leukopenia was the dose-limiting toxicity, and 400 mg/m2/day was the MTD for this trial. At the MTD, the mean +/- SD steady-state plasma concentration of IdUrd during the infusion, measured by high-performance liquid chromatography, was 0.66 +/- 0.23 micrometer. There was no significant influence of LV on IdUrd DNA incorporation in peripheral blood granulocytes as measured by high-performance liquid chromatography. Based on toxicity data and correlative laboratory studies, a meaningful increase in radiosensitization would not be achieved with the IdUrd infusion schedule and dose of LV investigated compared with IdUrd alone.