共查询到20条相似文献,搜索用时 15 毫秒
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We reported the magnetic properties and magnetocaloric effects (MCE) of (La0.8Ho0.2)2/3Ca1/3MnO3 and (La0.5Ho0.5)2/3Ca1/3MnO3 nanoparticles by sol-gel technique. With this method, we were able to obtain the samples with particle diameters ranging from 50 to 200 nm. In the (La1-xHox)2/3Ca1/3MnO3 compound, an external magnetic field induced a magnetic transition from an paramagnetic phase to a ferromagnetic phase above Ts=105-135 K, leading to magnetocaloric effects. The maximum value of ΔSM was 1.19 J/(kg·K) at 100 K and 2.03 J/(kg·K) at 152 K for a magnetic field change of 5 T. Because both samples had large relative cooling power (RCP) and wide δTFWHM, the study on systems with the (La1-xHox)2/3Ca1/3MnO3-related magnetic transitions may open an important field in searching good magnetic materials. 相似文献
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X Fei 《Canadian Metallurgical Quarterly》1994,49(2):1470-1472
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Sets of benzimidazole and benzotriazole derivatives bearing on position 1 or 2 a tetrahydrofuranyl or tetrahydropyranyl moieties were prepared through the addition of the suitable benzazoles on 2,3-dihydrofuran and 3,4-dihydro-2H-pyran. The reactions were carried on either without solvent or in carbon tetrachloride solution. In the last case some peculiar chlorinated side products were isolated and characterized. Twenty compounds were screened for in vitro antitumoral and anti-HIV-1 activities and found poorly active or completely inactive. On the other hand several compounds exhibited good tracheal relaxant activity in vitro; compound 8, 11, 16, 24 and 26 resulted more active than theophylline in this test, while compound 11 was comparable to amrinone till the concentration of 3 micrograms/ml. Finally, compound 5 resulted endowed with a strong diuretic and saluretic activity at the dose of 3 mg/Kg, thus representing a new lead for discovering new diuretic agents. 相似文献
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J Liu 《Canadian Metallurgical Quarterly》1987,35(11):3447-3450
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LIu Dederer IS Sokolova AA Bakhmedova TD Miniker SIa Mel'nik LB Gorbacheva 《Canadian Metallurgical Quarterly》1995,60(9):1521-1529
O6-Methyl-2'-deoxyguanosine (O6-MedG), a novel inhibitor of O6-alkylguanine-DNA alkyltransferase (O6-AGT), has been synthesized. The ability of O6-MedG to deplete the O6-AGT activity in leukemia L1210 and melanoma B16 cells in vivo has been studied. After intraperitoneal administration of O6-MedG to mice bearing leukemia L1210 or melanoma B16, the activity of O6-AGT in tumour cells decreased by 50%. Pretreatment of leukemia L1210 bearing mice with O6-MedG (200 mg/kg) 24 hours prior to ACNU (15 mg/kg) administration resulted in six out of seven 60-day survivors. Treatment of mice with ACNU (15 mg/kg) alone increased the life span by 200%. Treatment of melanoma B16 bearing mice with O6-MedG and 3 hours thereafter with ACNU resulted in a 50% inhibition of tumour growth, whereas the inhibiting effect of ACNU alone was 16%. There was no difference in leukemia growth when L1210/BCNU bearing mice were treated with O6-MedG followed by ACNU treatment. In vivo ACNU (15 mg/kg) produced a deep and prolonged inhibition of DNA, RNA and protein synthesis in leukemia L1210 cells. The DNA synthesis in leukemia L1210/BCNU cells was shown to recover more rapidly than in L1210 cells. The activities of DNA-polymerases alpha and beta and, especially, of O6-AGT were elevated in ACNU-resistant leukemia cells as compared with ACNU-sensitive cells. The activation of some repairing enzymes, such as O6-AGT, DNA-polymerases alpha and beta as well as increased levels of GSH may play a role in the development of drug resistance to ACNU. 相似文献