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101.
The resistance of some NiCr alloys to Na2SO4-induced hot corrosion at 900°C has been found to be strongly affected by surface treatments such as grit-blasting and mechanical indentation. These cold-work procedures, when followed by recrystallization anneal, produced a large number of new grain boundaries in the deformed region. When deformed-and-annealed specimens of NiCr, Ni15 Cr and IN 738 were placed directly in contact with molten Na2SO4, the grain boundaries facilitated sulphur penetration and enhanced metal wastage. The deleterious effects of mechanical treatments could, in the case of Ni15 Cr, be offset by suitable thermal treatments such as pre-oxidation prior to Na2SO4 exposure. 相似文献
102.
Christian P. Deck Gregg S. B. McKee Kenneth S. Vecchio 《Journal of Electronic Materials》2006,35(2):211-223
The unique properties of carbon nanotubes (CNTs) have suggested applications in a variety of fields. Multiwalled nanotubes
were synthesized using chemical vapor deposition (CVD) procedures and subsequently characterized. Reaction parameters such
as catalyst type and carrier gas flow rate were optimized to produce well-aligned multiwalled nanotubes with lengths between
a few microns to several millimeters. Characterization was performed with scanning electron microscopy (SEM), transmission
electron microscopy (TEM), x-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDS), thermo-gravimetric analysis,
and Raman spectroscopy, focusing on composition and purity. Results show the synthesis of high-purity nanotubes of several
millimeters in length from iron, nickel, cobalt, and titanium carbide catalysts with thermal stability to above 550°C. 相似文献
103.
GJ Ruiz-Argüelles D Arizpe-Bravo S Sánchez-Sosa S Rojas-Ortega V Moreno-Ford A Ruiz-Argüelles 《Canadian Metallurgical Quarterly》1999,60(1):82-83
Inherited thrombophilia has been suggested as a cause of Legg-Calvé-Perthes disease in up to 75% of patients. This prevalence seems high compared to the prevalence of inherited thrombophilia in other thrombotic disorders (average, 30%). Therefore, we investigated 44 patients with Legg-Calvé-Perthes disease for antithrombin-III, protein-C, and protein-S deficiency and activated protein C (APC) resistance. Three (6.8%) of our patients were positive for APC resistance, and one patient (2.2%) showed deficiency of protein-C activity. Our results suggest that inherited thrombophilia is not associated with avascular necrosis of the femoral head (Legg-Calvé-Perthes disease). 相似文献
104.
Krishnan-Sarin Suchitra; Duhig Amy M.; McKee Sherry A.; McMahon Thomas J.; Liss Thomas; McFetridge Amanda; Cavallo Dana A. 《Canadian Metallurgical Quarterly》2006,14(3):306
This pilot study evaluated the use of contingency management (CM) procedures in combination with cognitive-behavioral therapy (CBT) for smoking cessation in adolescents. Twenty-eight treatment-seeking adolescent smokers participated in a 1-month, school-based smoking cessation program and were randomly assigned to receive either CM with weekly CBT or CBT alone. In the CM+CBT group, biochemical verification of abstinence was obtained twice daily during the first 2 weeks, followed by daily appointments during the 3rd week and once every other day during the 4th week. Participants were monetarily reinforced for abstinence on an escalating magnitude schedule with a reset contingency. At the end of 1 week and 1 month of treatment, abstinence verified using quantitative urine cotinine levels was higher in participants in the CM+CBT group (1 week: 76.7%; 1 month: 53.0%) when compared with the CBT-alone group (1 week: 7.2%; 4 weeks: 0%). These preliminary results provide a strong initial signal supporting the utility of CM techniques for smoking cessation in adolescents and demonstrate the feasibility of implementing such a program in a school setting. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
105.
Kavallieratos K Danby A Van Berkel GJ Kelly MA Sachleben RA Moyer BA Bowman-James K 《Analytical chemistry》2000,72(21):5258-5264
A systematic study of a dual-host system exhibiting pairwise anion/cation separations has been performed for CsNO3 extraction. Tripodal triamides 1-4 and 9 derived from condensation of hexanoic (for 1), octanoic (for 2), decanoic (for 3), lauric (for 4), and p-tert-butylbenzoic (for 9) acid with tris(2-aminoethyl)amine (tren) were used together with tetrabenzo-24-crown-8, a well-known Cs+ cation receptor. By using 5 mM crown ether in the organic phase and 10 mM CsNO3 with 0.1 mM HNO3 in the aqueous phase, tripods 1, 2, and 9 enhance CsNO3 extraction by factors of 2.4, 1.7, and 4.4, respectively (for 50 mM amide concentration), while the corresponding monoamide controls 5-8 derived from n-propylamine (5, 6) or N,N'-dimethylethylenediamine (7, 8) and hexanoic (5, 7) or octanoic (6, 8) acid derivatives gave no significant enhancement under the same conditions. This behavior may be ascribed to nitrate complexation by the triamides, which lowers the overall thermodynamic barrier for the salt transfer to the organic phase. The nitrate binding was confirmed by 1H NMR titration of receptor solutions, using tetrabutylammonium nitrate. Association constants for the formation of the anion-nitrate complexes were found to vary between 33 and 52 M-1 for the more soluble triamides. The synergistic effects for CsNO3 extraction are in reasonable agreement with the values predicted theoretically from the measured association constants. Electrospray ionization mass spectrometry confirmed the predominant formation of 1:1 tripod-nitrate complexes. Monoamide controls gave no evidence of anion complexation. 相似文献
106.
107.
Breda virus (BRV), a member of the genus torovirus, is an established etiological agent of diarrhea of cattle, which is found as two separate serotypes, BRV-1 and BRV-2. In this study, a 7.5 kb fragment of the BRV-1 genome that bracketed the genes for the structural proteins of BRV was amplified by long RT-PCR and the amplicon purified and sequenced directly. Sequence analysis revealed the presence of four open reading frames (ORF) corresponding to the peplomer (S), envelope (M), and nucleocapsid (N) genes, and an ORF for a novel 1.2 kb gene located between the M and N genes. This new gene was identical in nucleotide sequence to the hemagglutinin-esterase (HE) gene of BRV-2. With the exception of this new ORF, BRV-1 manifests 80% nucleotide sequence identity with the torovirus prototype, Berne virus (BEV) in the 7.5 kb region from the 3' end of the genome that contains the genes for the structural proteins. A 504 base segment containing the ORF for the BRV-1 N gene was amplified by RT-PCR, and cloned into an Escherichia coli expression system. The resulting protein was purified by SDS-PAGE and used to immunize guinea pigs. Hyperimmune serum was reactive with bovine torovirus (BTV) and human torovirus (HTV) antigens. By immunoelectron microscopy, it was shown to aggregate broken but not intact torovirus particles from BTV-positive fecal specimens. By immunoblot, the hyperimmune serum reacted specifically with the 20 kD N proteins of both BTV and HTV, as well as with the expressed N protein. BRV-1 and BRV-2 immune sera from gnotobiotic calves, but not human convalescent sera from HTV-infected patients, reacted with the expressed N protein by immunoblot. These findings were applied to the design of a dot blot assay that could specifically detect BTV and HTV from fecal specimens. 相似文献
108.
In Bacillus transformation, sexual isolation is known to be an exponential function of the sequence divergence between donor and recipient. Here, we have investigated the mechanism under which sequence divergence results in sexual isolation. We tested the effect of mismatch repair by comparing a wild-type strain and an isogenic mismatch-repair mutant for the relationship between sexual isolation and sequence divergence. Mismatch repair was shown to contribute to sexual isolation but was responsible for only a small fraction of the sexual isolation observed. Another possible mechanism of sexual isolation is that more divergent recipient and donor DNA strands have greater difficulty forming a heteroduplex because a region of perfect identity between donor and recipient is required for initiation of the heteroduplex. A mathematical model showed that this heteroduplex-resistance mechanism yields an exponential relationship between sexual isolation and sequence divergence. Moreover, this model yields an estimate of the size of the region of perfect identity that is comparable to independent estimates for Escherichia coli. For these reasons, and because all other mechanisms of sexual isolation may be ruled out, we conclude that resistance to heteroduplex formation is predominantly responsible for the exponential relationship between sexual isolation and sequence divergence in Bacillus transformation. 相似文献
109.
RD Barr T Simpson CE Webber GJ Gill J Hay M Eves AC Whitton 《Canadian Metallurgical Quarterly》1998,34(6):873-877
Mature and post-translational precursor gastrin forms are growth factors for colorectal tumours. The immunogen Gastrimmune is composed of the amino terminus of gastrin-17 linked to diphtheria toxoid and raises antibodies in situ which neutralise amidated and glycine-extended gastrin-17. The aim of the study was to determine the effect of treatment with 5-fluorouracil(5-FU)/leucovorin on the antibody titres induced by Gastrimmune and the effect of combination therapy on the growth of the rat colon tumour DHDK12. Gastrimmune was administered to rats s.c. at 3 weekly intervals. The rat colon tumour line DHDK12 was injected into the abdominal wall of BDIX rats. Combinations of 5-FU/leucovorin were injected i.v. on days 1, 3 and 5, with the cycle repeated every 4 weeks. Antibody titres were measured by an ELISA technique. Antibody titres were followed for 40 weeks after Gastrimmune (500 microg.ml(-1)) immunization, with titres peaking between 10 and 20 weeks after a single immunisation and falling by week 30. At termination, no effect was observed on either the histological appearance of the gastro-intestinal tract or the proliferation of the colonic mucosa. Pre- and post-treatment with 5-FU/leucovorin (30 mg.kg(-1)) had no effect on the kinetics and level of antibody response to Gastrimmune. Gastrimmune (200 microg.ml(-1)) and 5-FU/leucovorin combinations (12.5 and 20 mg.kg(-1)) increased the therapeutic effects on the in vivo growth of DHDK12 tumors when compared to the agents given singly. Gastrimmune immunisation may be a therapeutic option for the treatment of colorectal cancer in combination with 5-FU/leucovorin. 相似文献
110.
We have used a ribonuclease protection assay to investigate RNase H cleavage of HIV-1 mRNA mediated by phosphorothioate antisense oligonucleotides complementary to the gag region of the HIV-1 genome in vitro. Cell lysate experiments in H9 and U937 cells chronically infected with HIV-1 IIIB showed RNase H cleavage of unspliced gag message but no cleavage of spliced message which did not contain the target gag region. RNase H cleavage products were detected at oligonucleotide concentrations as low as 0.01 microM and the RNase H activity was seen to be concentration dependent. Similar experiments with 1-, 3- and 5-mismatch oligonucleotides demonstrated sequence specificity at low concentrations, with cleavage of gag mRNA correlating with the predicted activities of the parent and mismatch oligonucleotides based on their hybridization melting temperatures. Experiments in living cells suggested that RNase H-specific antisense activity was largely determined by the amount of oligonucleotide taken up by the different cell lines studied. RNase H cleavage products were detected in antisense oligonucleotide treated MT-4 cells acutely infected with HIV-1 IIIB, but not in infected H9 cells treated with oligonucleotide under the same conditions. The data presented demonstrate potent and specific RNase H cleavage of HIV-1 mRNA mediated by an antisense oligonucleotide targeted to HIV-1 gag mRNA, and are in agreement with previous reports that the major obstacle to demonstrating antisense activity in living cells remains the lack of penetration of these agents into the desired cellular compartment. 相似文献