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81.
Pavel L. Katsel Tamara M. Dmitrieva Rashid B. Valeyev Yuri P. Kozlov 《Journal of chemical ecology》1992,18(11):2003-2010
Three components of the male yellowfin Baikal sculpin pheromonal signal have been isolated from urine by diethyl ether extraction, thinayer chromatography (TLC), and high-performance liquid chromatography (HPLC). Using mass spectrometry, we have identified two of them as testosterone (T) and 11-hydroxytestosterone (11HT). These steroids are synthesized in testes during full spermatogenesis, and they are excreted in male urine with milt. The third component is not a steroid. It is more likely to be a polyene alcohol (farnesol). 2Z,6E-Farnesol possesses behavioral activity. 相似文献
82.
A microsecond-resolution pulse heating technique was used for the measurement of the heat of fusion of titanium and a titanium alloy (90Ti-6Al-4V). The method is based on rapid (50- to 100-s) resistive self-heating of the specimen by a high-current pulse from a capacitor discharge system and measuring, as functions of time, current through the specimen, voltage across the specimen, and radiance of the specimen. Melting of the specimen is manifested by a plateau in the measured radiance. The time integral of the net power absorbed by the specimen during melting yields the heat of fusion. The values obtained for heat of fusion were 272 J · g–1 (13.0 kJ · mol–1) for titanium and 286 J · g–1 for the alloy 90Ti-6Al-4V, with an estimated maximum uncertainty of ±6% in each value.Paper presented at the Second Workshop on Subsecond Thermophysics, September 20–21, 1990, Torino, Italy. 相似文献
83.
N. Guskos V. Lyvkodimos C. A. Londos A. Kondos S. M. Paraskevas A. Koufoudakis C. Mitros H. Gamari-Seale D. Niarchos I. Kruk 《Journal of Superconductivity》1992,5(5):457-461
EPR, XRD, and magnetic studies are presented for Pr0.5Re0.5Ba2Cu3O7– compounds (Re= La, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, Tm, Yb, and Lu) in the orthorhombic and tetragonal (large oxygen deficiency) phase. For the samples with Re=Dy, Ho, Y, Er, Tm, Yb, and Lu in the orthorhombic phase, the transition to the superconducting state has been observed in the temperatures rangeT
c
between 18 and 40 K. For the samples with Nd and Yb in the tetragonal phase, EPR spectra coming from trivalent rare earth ions have been recorded. In the nonoxygenated sample Pr0.5La0.5Ba2Cu3O7–
the EPR spectrum arising from the non-Kramers trivalent praseodymium ion has been observed. A broad EPR line appearing in all our samples was attributed to superexchange interaction between copper ions over oxygen (O
2
–
) bridges. Interestingly, for the Pr0.5Re0.5Ba0.5Cu3O7– (Re = Er and Lu) compounds in the tetragonal phase at liquid-nitrogen temperature, a nonresonant microwave absorption in low magnetic fields has been detected. 相似文献
84.
85.
Ahmad Hassan Chaudhry Shafa Nayab Syed Bilal Hussain Muqarrab Ali Zhiyong Pan 《International journal of molecular sciences》2021,22(4)
The productivity of agricultural produce is fairly dependent on the availability of nutrients and efficient use. Magnesium (Mg2+) is an essential macronutrient of living cells and is the second most prevalent free divalent cation in plants. Mg2+ plays a role in several physiological processes that support plant growth and development. However, it has been largely forgotten in fertilization management strategies to increase crop production, which leads to severe reductions in plant growth and yield. In this review, we discuss how the Mg2+ shortage induces several responses in plants at different levels: morphological, physiological, biochemical and molecular. Additionally, the Mg2+ uptake and transport mechanisms in different cellular organelles and the role of Mg2+ transporters in regulating Mg2+ homeostasis are also discussed. Overall, in this review, we critically summarize the available information about the responses of Mg deficiency on plant growth and development, which would facilitate plant scientists to create Mg2+-deficiency-resilient crops through agronomic and genetic biofortification. 相似文献
86.
Improved Controlled Release and Brain Penetration of the Small Molecule S14 Using PLGA Nanoparticles
Vanesa Nozal Elisa Rojas-Prats Ins Maestro Carmen Gil Daniel I. Perez Ana Martinez 《International journal of molecular sciences》2021,22(6)
Phosphodiesterase 7 (PDE7) is an enzyme responsible for the degradation of cyclic adenosine monophosphate (cAMP), an important cellular messenger. PDE7’s role in neurotransmission, expression profile in the brain and the druggability of other phosphodiesterases have motivated the search for potent inhibitors to treat neurodegenerative and inflammatory diseases. Different heterocyclic compounds have been described over the years; among them, phenyl-2-thioxo-(1H)-quinazolin-4-one, called S14, has shown very promising results in different in vitro and in vivo studies. Recently, polymeric nanoparticles have been used as new formulations to target specific organs and produce controlled release of certain drugs. In this work, we describe poly(lactic-co-glycolic acid) (PLGA)-based polymeric nanoparticles loaded with S14. Their preparation, optimization, characterization and in vivo drug release profile are here presented as an effort to improve pharmacokinetic properties of this interesting PDE7 inhibitor. 相似文献
87.
Surface nanocrystallization of 7A04 aluminium alloy induced by circulation rolling plastic deformation 总被引:3,自引:0,他引:3
The surface nanocrystalline microstructures of 7A04 aluminium alloy was obtained by means of circulation rolling plastic deformation(CRPD), the grain refinement behavior and the hardness variation were examined. X-ray diffraction(XRD) and transmission electron microscopy(TEM) were applied to characterize the microstructure of the surface layer. The experimental evidences show that, after the CRPD treatment, the mean grain size in the surface layer is about 50 nm. The microhardness of the nanostructured surface layers is enhanced significantly after CRPD compared with that of the matrix, which can be attributed primarily to the grain refinement. The microhardness at the top surface can reach about HV0.05335, while the value of the matrix is HV0.05160 or so. The surface hardening effect is obtained obviously. Besides, the thermal stability of nanocrystalline layer was investigated. The results of the XRD analysis and the microhardness measurement show that the nanocrystalline layer has better thermal-stability than the matrix. And the DSC measurement shows that the synthesis of nanostructured surface layer has influence on the phase transformation of 7A04 aluminum alloy. 相似文献
88.
张京萍 《特种铸造及有色合金》2002,(Z1)
分析了国际、国内镁业现状及国际市场对我国镁出口的反倾销的原因 ,提出了我国镁业应付反倾销的对策及发展方向 相似文献
89.
研究了在250℃、不同挤压比下挤压变形对Mg95 Zn4.3 Y0.7合金组织及性能的影响。结果表明,Mg95 Zn4.3 Y0.7经过挤压变形后,合金中晶界处的共晶相破碎,弥散分布至晶粒内部,并且晶粒显著细化。同时,随着挤压比的增大,晶粒细化程度增加,合金的力学性能单调增加。当挤压比为16时,合金晶粒尺寸为5-8μm,抗拉强度为288.9MPa,显微硬度HV值为117.8。 相似文献
90.
采用盐类熔剂对大体积Al-4.5wt%Cu合金进行净化处理,研究了熔剂净化对Al-4.5wt%Cu合金过冷及组织的影响。通过大量的实验研究证明:粘性熔剂更能有效地去除合金中的异质核心,使合金获得较大的过冷度;随着过冷度的增大,合金的宏观组织由细小的等轴晶逐渐过渡到粗大的柱状晶,其临界转变过冷度为40℃;二次枝晶间距随过冷度的增大而增大,其转变过冷度为50℃。 相似文献