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排序方式: 共有134条查询结果,搜索用时 31 毫秒
91.
92.
Rajan Singh Mohit Manhas Ankush Kumar Bedyal Fahim Durani Hendrick C. Swart Vinay Kumar 《Luminescence》2024,39(2):e4665
The present study investigates the impact of the ligand environment on the luminescence and thermometric behavior of Sm3+ doped A3(PO4)2 (A = Sr, Ca) phosphors prepared by combustion synthesis. The structural and luminescent properties of Sm3+ ions in the phosphate lattices were investigated using powder X-ray diffraction (PXRD) and photoluminescence (PL) techniques. PXRD results of the synthesized phosphors exhibit the expected phases that are in agreement with their respective standards. Fourier-transform infrared (FTIR) spectroscopy confirms the presence of PO4 vibrational bands. Upon excitation with near ultraviolet light, the PL studies indicated that Sr3(PO4)2:Sm3+ phosphors exhibit a yellow light emission, whereas Ca3(PO4)2:Sm3+ phosphors exhibit an emission of orange light. The PL emission results are in accordance with the CIE coordinates, with the Sr3(PO4)2:Sm3+ phosphors showing coordinates of (0.56, 0.44), and the Ca3(PO4)2:Sm3+ phosphors displaying coordinates of (0.60, 0.40). Thermal analysis shows improved stability of Ca3(PO4)2:Sm3+ based on lower weight reduction in thermogravimetric analysis. The effect of temperature on the luminescence properties of the phosphor has been examined upon a 405 nm excitation. By using the fluorescence intensity ratio (FIR) method, the temperature responses of the emission ratios from the Sm3+: the 4F3/2 → 6H5/2 transition to the 4G5/2 → 6H7/2 and 4F3/2 → 6H5/2 transition to the 4G5/2 → 6H9/2 emissions are characterized. The Ca3(PO4)2:Sm3+ phosphors are more sensitive as compared with the Sr3(PO4)2:Sm3+ phosphors. The earlier research findings strongly indicate that these phosphors hold great promise as ideal candidates for applications in non-invasive optical thermometry and solid-state lighting devices. 相似文献
93.
94.
Evaluation of the double-quantum filter for the measurement of intracellular sodium concentration 总被引:1,自引:0,他引:1
R B Hutchison D Malhotra R E Hendrick L Chan J I Shapiro 《The Journal of biological chemistry》1990,265(26):15506-15510
Evaluation of the double-quantum filter for sodium was performed on several sample series of bovine serum albumin in water. Both single-quantum (1Q) and double-quantum (2Q) measurements were obtained. The quality of the 2Q filter was found to be quite sensitive to pulse width setting. Ordinary 1Q measurements of sodium in albumin-containing solutions show 100% visibility. At high ionic strengths, the 2Q albumin results confirm earlier conclusions demonstrating the tendency for the albumin molecule to unfold under a variety of influences. At physiological sodium concentrations, the magnitude of the 2Q/1Q ratio is controlled not only by the concentration of albumin, but also by the solution pH. Non-zero, double-quantum signals were observed in physiological samples consisting of essentially intracellular material (packed red blood cells) as well as in extracellular material (plasma and urine). Measurements in human urine showed no 2Q signal. However, high-concentration NaCl solutions did produce real, measurable 2Q signals. Therefore, the 2Q filter does not measure intracellular sodium exclusively. Although packed red blood cells gave the highest 2Q/1Q ratio (8.5 x 10(-3), plasma gave a very considerable 2Q/1Q ratio (2.3 x 10(-3). Because of its relatively high extracellular concentration, extracellular sodium may give a greater absolute 2Q signal than intracellular sodium in unmodified tissue samples. Based on these data, we conclude that a 2Q filter will not provide a useful measurement of intracellular sodium in in vivo tissue samples. 相似文献
95.
96.
Keller TL Zocco D Sundrud MS Hendrick M Edenius M Yum J Kim YJ Lee HK Cortese JF Wirth DF Dignam JD Rao A Yeo CY Mazitschek R Whitman M 《Nature chemical biology》2012,8(3):311-317
Febrifugine, the bioactive constituent of one of the 50 fundamental herbs of traditional Chinese medicine, has been characterized for its therapeutic activity, though its molecular target has remained unknown. Febrifugine derivatives have been used to treat malaria, cancer, fibrosis and inflammatory disease. We recently demonstrated that halofuginone (HF), a widely studied derivative of febrifugine, inhibits the development of T(H)17-driven autoimmunity in a mouse model of multiple sclerosis by activating the amino acid response (AAR) pathway. Here we show that HF binds glutamyl-prolyl-tRNA synthetase (EPRS), inhibiting prolyl-tRNA synthetase activity; this inhibition is reversed by the addition of exogenous proline or EPRS. We further show that inhibition of EPRS underlies the broad bioactivities of this family of natural product derivatives. This work both explains the molecular mechanism of a promising family of therapeutics and highlights the AAR pathway as an important drug target for promoting inflammatory resolution. 相似文献
97.
We present information on the prey taken by the Bat Hawk Macheiramphus alcinus in two different areas of lowland western central Madagascar. These are the first dietary data from Madagascar for this widespread Old World species. The recovered remains were almost exclusively of bats and birds, with a few examples of reptiles and insects. In total, 178 pellets were analysed. On the basis of minimum number of individuals and biomass, bats accounted for 58.3% and 30.3%, respectively, and birds 36.1% and 69.7%, respectively. Amongst the nine species of bats recovered from the pellets, four were represented by multiple individuals, particularly taxa belonging to the families Molossidae and Vespertilionidae that fly in open areas, and for the 11 species of identified birds, all were represented by a single individual. These patterns are interpreted as a specialisation of feeding on bats during a narrow window of time at dusk, as they leave day roost sites, and then using birds in a more general manner to fill in nutritional needs. 相似文献
98.
Prasad CV Zheng M Vig S Bergstrom C Smith DW Gao Q Yeola S Polson CT Corsa JA Guss VL Loo A Wang J Sleczka BG Dangler C Robertson BJ Hendrick JP Roberts SB Barten DM 《Bioorganic & medicinal chemistry letters》2007,17(14):4006-4011
We report on the design of benzodiazepinones as peptidomimetics at the carboxy terminus of hydroxyamides. Structure-activity relationships of diazepinones were investigated and orally active gamma-secretase inhibitors were synthesized. Active metabolites contributing to Abeta reduction were identified by analysis of plasma samples from Tg2576 mice. In particular, (S)-2-((S)-2-(3,5-difluorophenyl)-2-hydroxyacetamido)-N-((S,Z)-3-methyl-4-oxo-4,5-dihydro-3H-benzo[d][1,2]diazepin-5-yl)propanamide (BMS-433796) was identified with an acceptable pharmacodynamic and pharmacokinetic profile. Chronic dosing of BMS-433796 in Tg2576 mice suggested a narrow therapeutic window and Notch-mediated toxicity at higher doses. 相似文献
99.
Human alpha-globin gene expression following chromosomal dependent gene transfer into mouse erythroleukemia cells. 总被引:29,自引:0,他引:29
We have used the genetic marker, adenine phosphoribosyl transferase (APRT), an enzyme known to be on human chromosome 16, to establish a method for the transfer of human α-globin genes into mouse erythroleukemia cells. Mouse erythroleukemia cells devoid of detectable levels of APRT were fused with fractions of human marrow enriched in human erythroid cells. The hybrid cells arising from this fusion were isolated in medium supplemented with aminopterin and thymidine, and used adenine as the sole purine source. This population of hybrid cells was dominated by cells (80%) in which human chromosome 16 was present. Human chromosomes 4, 5 and 6 were also found in these cells. The hybrid cells were then placed in medium supplemented with diaminopurine (DAP), which is lethal for cells containing APRT. Greater than 95% of the DAP-selected hybrid cells lacked human chromosome 16. Cytoplasmic RNA was extracted from the two hybrid cell populations and assayed by molecular hybridization for sequences coding for human α-globin. Carboxymethyl cellulose chromatography was used to study the level of synthesis of human a-globin in the hybrids. The original hybrid cell, which contained a high frequency of human chromosome 16, also contained high levels of human a-globin mRNA and human α-globin chains. Hybrid cells counter-selected in DAP and thus lacking human chromosome 16 were devoid of detectable levels of human APRT, human α-globin mRNA and human α-globin chains. This work shows that transfer of human chromosome 16 into the MEL cell is possible using a chromosomedependent, APRT-mediated method of gene transfer. Using this system in which expression of the human α-globin gene occurs, we were also able to confirm our earlier assignment of the human α-globin gene to human chromosome 16. This system may be of further use in identifying genetic elements governing expression of the human α-globin gene which can be carried with human chromosome 16 as it is donated to the mouse erythroleukemia cell by donor cells of different epigenotypes. 相似文献
100.
Using complementary DNA prepared from adult chicken globin messenger RNA, we show the existence of 2-3 non-cross-hybridising globin sequences in the chicken genome, each of which is present in only one copy per haploid genome. This was done by solution hybridization to total DNA under conditions of cDNA excess. The data agreses with results of RNA-driven hybridisation of globin complementary DNA, and with protein data. 相似文献