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101.
102.
The contributions made to the Working Group activities on neutrinos and astrophysics are summarized in this article. The topics
discussed were inflationary models in Raman-Sundrum scenarios, ultra high energy cosmic rays and neutrino oscillations in
4 flavour and decaying neutrino models. 相似文献
103.
Yang Li Guohui Cao Ruifei Duan Guangcan Che Zhongxian Zhao J. A. Larrea J E. M. Baggio-Saitovitch 《中国科学A辑(英文版)》2000,43(4):400-406
119Sn M?ssbauer research is carried out on (La1-xSrx),Cu1-xSnxO4(x = 0.075 and 0.110) superconductors which are designed under a new concept. The M?ssbauer spectra results show that Sn occupies
Cu position in Sn4+ state, and there is no Sn2+ ion occupying La position. The local lattice deformation near Sn4+ site is small, but displays an increasing tendency with Sn doping. For La2CuO4 matrix, the simultaneous dopings of Sr/Sn induce holes and electrons on CuO2 layer in a new mechanism which influences superconductivity. Under a new mechanism of extra oxygen, the extra oxygen effect
of Sn-doping on superconductivity is discussed 相似文献
104.
To solve the cosmological constant fine tuning problem, we investigate an \begin{document}$(n+1)$\end{document} ![]()
![]()
-dimensional generalized Randall-Sundrum brane world scenario with two \begin{document}$(n-1)$\end{document} ![]()
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-branes instead of two 3-branes. Adopting an anisotropic metric ansatz, we obtain the positive effective cosmological constant \begin{document}$\Omega_{\rm eff}$\end{document} ![]()
![]()
of order \begin{document}$10^{-124}$\end{document} ![]()
![]()
and only require a solution \begin{document}$\simeq50-80$\end{document} ![]()
![]()
. Meanwhile, both the visible and hidden branes are stable because their tensions are positive. Therefore, the fine tuning problem can be solved quite well. Furthermore, the Hubble parameter \begin{document}$H_{1}(z)$\end{document} ![]()
![]()
as a function of redshift \begin{document}$z$\end{document} ![]()
![]()
is in good agreement with the cosmic chronometers dataset. The evolution of the universe naturally shifts from deceleration to acceleration. This suggests that the evolution of the universe is intrinsically an extra-dimensional phenomenon. It can be regarded as a dynamic model of dark energy that is driven by the evolution of the extra dimensions on the brane. 相似文献
105.
Sofia Drakopoulou Emmanouil Orfanakis Ioulia Karagiannaki Fragiskos Gaitis Stavroula Skoulika Andreas Papaioannou George Boukouvalas George Petropoulos Vassilios Katsoudas Renate Kontzedaki Aggelos Philippidis Aikaterini Zoumi Marilena Dasenaki Nikolaos S. Thomaidis Michalis Velegrakis 《Molecules (Basel, Switzerland)》2022,27(4)
Extra virgin olive oil (EVOO) is a key component of the Mediterranean diet, with several health benefits derived from its consumption. Moreover, due to its eminent market position, EVOO has been thoroughly studied over the last several years, aiming at its authentication, but also to reveal the chemical profile inherent to its beneficial properties. In the present work, a comparative study was conducted to assess Greek EVOOs’ quality and authentication utilizing different analytical approaches, both targeted and untargeted. 173 monovarietal EVOOs from three emblematic Greek cultivars (Koroneiki, Kolovi and Adramytiani), obtained during the harvesting years of 2018–2020, were analyzed and quantified as per their fatty acids methyl esters (FAMEs) composition via the official method (EEC) No 2568/91, as well as their bioactive content through liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS) methodology. In addition to FAMEs analysis, EVOO samples were also analyzed via HRMS-untargeted metabolomics and optical spectroscopy techniques (visible absorption, fluorescence and Raman). The data retrieved from all applied techniques were analyzed with Machine Learning methods for the authentication of the EVOOs’ variety. The models’ predictive performance was calculated through test samples, while for further evaluation 30 commercially available EVOO samples were also examined in terms of variety. To the best of our knowledge, this is the first study where different techniques from the fields of standard analysis, spectrometry and optical spectroscopy are applied to the same EVOO samples, providing strong insight into EVOOs chemical profile and a comparative evaluation through the different platforms. 相似文献
106.
为研究纳米硅晶粒成核生长动力学过程,采用脉冲激光烧蚀(PLA)技术,在室温,50~200 Pa的氩气氛围中,通过引入垂直于烧蚀羽辉轴线的外加气流,在水平放置的衬底上沉积了一系列纳米Si晶薄膜.扫描电子显微镜( SEM)、拉曼(Raman)散射和X射线衍射(XRD)检测结果表明,未引入气流时,衬底上相同位置处晶粒尺寸随气体压强的增大逐渐减小;在距靶1 ~2cm范围内引入气流后,尺寸变化规律与未引入气流时相反.通过分析晶粒尺寸及其在衬底上的位置分布特点,结合流体力学模型和热动力学方程,分析得出在激光能量密度一定的条件下,环境气体压强、烧蚀粒子温度和密度共同影响着纳米晶粒的成核生长. 相似文献
107.
对引力场的能量\|动量和角动量守恒定律研究进展进行了总结。依此探讨了一般五维时空膜宇宙模型中的能量\|动量张量、 角动量张量以及它们的守恒定律。通过计算一个膜宇宙模型中的能动张量, 论证了该模型中“可见膜”上的引力非常弱, 这可认为是从引力的角度反映了规范层次问题。结果与一般的结论, 即引力系统总能量为零是一致的。同时, 分析了这个膜宇宙模型中的角动量张量, 计算了该模型中的总角动量, 讨论了暴涨Randall\|Sundren(RS)模型中的总角动量的一些性质。说明了在这类模型中总角动量的类空分量均为零, 这与普通RS模型是一样的。同时, 分析了RS模型中背景以及膜上的宇宙学常数, 发现在RS模型中五维背景宇宙学常数和两个膜上的真空能都能取它们的自然值。最后通过修改RS模型, 得到了一种可以产生很小的有效宇宙学常数的机制。We summarized both the general covariant energy\|momentum and angular momentum conservation law in the gravitational system and analyzed the general covariant energy\|momentum tensor of the gravitational system in general five\|dimensional cosmological in brane\|universe models. After calculating this energy\|momentum for the cosmological generalization of the Randall\|Sundrum(RS) model which includes the original RS model as the static limit, we are able to show that the weakness of the gravitation on the “visible” brane is a general feature of this model. This is the origin of the gauge hierarchy from a gravitational point of view. Our results are also consistent with the fact that a gravitational system has vanishing total energy. We also discussed the properties of the general covariant angular momentum in five\|dimensional brane-universe model. With calculation of the total angular momentum of this model, we analyzed the properties of the total angular momentum in the inflationary RS model. We pointed that the space-like components of the total angular momentum are zero while the others are non-zero, which agrees with the results from ordinary RS model. We also investigated the bulk cosmological constant and brane vacuum energies in RS model. We show that the five\|dimensional bulk cosmological constant and the vacuum energies of the two branes could take their natural values. Finally we argued how we can generate a small four-dimensional effective cosmological constant on the branes by modifying the original RS model. 相似文献
108.
后处理温度对Ti-ZSM-5载钛量和催化苯乙烯氧化反应的影响 总被引:6,自引:1,他引:5
采用TiCl4气固相同晶取代法合成Ti-ZSM-5分子筛,研究了后处理温度对Ti-ZSM-5分子筛中载钛量的影响,发现分子筛的功钛量随后处理温度的升高而增大,并存在一线性关系,该分子筛催化苯乙烯/H2O2反应的活性在载钛量为1.6%(后处理温度为500℃)时出现最大;用IR,XPS,UV-Vis,XRD等方法对Ti-ZSM-5分子筛进行了表征,发现IR光谱在970cm^-1处吸收峰强度并不与分子筛载钛量成线性关系;XPS,UV-Vis证明用该法所载的钛含有部分非骨架钛。 相似文献
109.
110.