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Yoshiyuki Mizuhata Shiori Fujimori 《Phosphorus, sulfur, and silicon and the related elements》2020,195(11):936-939
AbstractThe reaction of 2-t-Bu-germabenzenylpotassium with Me2(t-Bu)SiCl (TBDMSCl) resulted in the coupling among two TBDMS-substituted germabenzenes and the germabenzenylpotassium. The structure of the product was determined by X-ray crystallographic analysis. Its formation mechanism was proposed with the help of theoretical calculations. 相似文献
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我们提出利用频率为ω,3ω和强度较弱的2ω组成的三色圆偏振激光组合脉冲驱动氦原子能够得到椭偏率较大的阿秒脉冲链的一种方法.通过强场近似方法,计算了氦原子在两色和三色圆偏振激光组合脉冲驱动下发射高次谐波谱及其合成阿秒脉冲链,比较了氦原子(初态为s态)在这两种情况下发射高次谐波谱的特点及其合成阿秒脉冲链椭偏率的大小,结果发现,在反旋的两色ω,3ω激光脉冲基础上加入了频率为2ω的第三色激光脉冲联合作用到氦原子上,所得到的阿秒脉冲链的椭偏率相对于双圆场情况下有所增加,通过调整ω,3ω激光的强度比,并且选择适当的第三色激光的强度,对初态为s态的原子,仍能够得到具有较大椭偏率的阿秒脉冲链. 相似文献
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Nikolay Yanshin Aleksandra Kushnareva Valeriia Lemesheva Claudia Birkemeyer Elena Tarakhovskaya 《Molecules (Basel, Switzerland)》2021,26(9)
Though numerous valuable compounds from red algae already experience high demand in medicine, nutrition, and different branches of industry, these organisms are still recognized as an underexploited resource. This study provides a comprehensive characterization of the chemical composition of 15 Arctic red algal species from the perspective of their practical relevance in medicine and the food industry. We show that several virtually unstudied species may be regarded as promising sources of different valuable metabolites and minerals. Thus, several filamentous ceramialean algae (Ceramium virgatum, Polysiphonia stricta, Savoiea arctica) had total protein content of 20–32% of dry weight, which is comparable to or higher than that of already commercially exploited species (Palmaria palmata, Porphyra sp.). Moreover, ceramialean algae contained high amounts of pigments, macronutrients, and ascorbic acid. Euthora cristata (Gigartinales) accumulated free essential amino acids, taurine, pantothenic acid, and floridoside. Thalli of P. palmata and C. virgatum contained the highest amounts of the nonproteinogenic amino acid β-alanine (9.1 and 3.2 μM g−1 DW, respectively). Several red algae tend to accumulate heavy metals; although this may limit their application in the food industry, it makes them promising candidates for phytoremediation or the use as bioindicators. 相似文献
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Luyao Tong Pengcheng Li Fupeng Li Yongjia Wang Qingfeng Li Fanxin Liu 《中国物理C(英文版)》2020,44(7):074103-074103-8
By incorporating an iso spin-dependent form of the momentum-dependent potential in the ultra-relativistic quantum molecular dynamics(UrQMD) model,we systematically investigate effects of the neutron-proton effective mass splitting m*_(n-p)=m*_n-m*_p/m and the density-dependent nuclear symmetry energy E_(sym)(ρ) on the elliptic flow v_2 in~(197)Au+~(197) Au collisions at beam energies from 0.09 to 1.5 GeV/nucleon.It is found that at higher beam energies(≥0.25 GeV/nucleon) with the approximately 75 MeV difference in slopes of the two different E_(sym)(ρ),and the variation of m*_(n-p) ranging from-0.03 to 0.03 at saturation density with isospin asymmetry δ=(ρ_n-ρ_p)/ρ-0.2,the E_(sym)(ρ) has a stronger influence on the difference in v_2 between neutrons and protons,i.e.,v_2~n-v_2~p,than m*_(n-p) has.Meanwhile,at lower beam energies(≤0.25 GeV/nucleon),v_2~n-v_2~p is sensitive to both the E_(sym)(ρ) and the m*_(n-p).Moreover,the influence of m*_(n-p) on v_2~n-v_2~p is more evident with the parameters of this study when using the soft,rather than stiff,symmetry energy. 相似文献
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Julian G. Sereni 《哲学杂志》2020,100(10):1211-1225
ABSTRACTWith the aim to improve the performance of classical paramagnetic salts for adiabatic refrigeration processes at the sub-Kelvin range, relevant thermodynamic parameters of some new Yb-based intermetallic compounds are analysed and compared. Two main applications are considered: (i) those requiring temperature fixed-points to be reached applying magnetic fields of moderate intensity for satellite applications, and (ii) those which can be used for controlled thermal drifts in laboratory applications. Different thermomagnetic trajectories of the entropy are identified depending on respective specific heat behaviours and the constraints imposed by the Nernst postulate at the sub-Kelvin range. Some simple relationships are proposed to compare the diverse magnetocaloric characteristics of different systems. This procedure allows to include the classical Cerium-Magnesium-Nitride (CMN) salt in that comparison. 相似文献
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ABSTRACT The present work describes a phenomenological approach to explain the instantaneous behaviour of tungsten heavy alloys (WHAs) in heat-treated and swaged conditions. The strengths and elongation values of heat-treated materials are lower and higher than those of the swaged samples respectively. The heat-treated materials exhibit two slopes in true stress–true plastic strain curves and follow the Ludwigson constitutive equation. On the other hand, swaged materials display a single slope and adhere to typical Swift constitutive equation. The latter reflect the presence of pre-strain in the materials due to swaging deformation. The fracture surfaces in heat-treated materials consist of W-W decohesion along with matrix rupture and W-cleavage, while swaged samples consist of mainly W-cleavage. Both the materials display three typical stages (I, II and III) of work hardening. The second derivatives of true stress–true plastic strain curves of these alloys exhibit a perfect parabola although the nature of true stress–true strain as well as true stress–true plastic strain curves is quite different in heat-treated and swaged materials. This has been observed for the first time in WHAs consisting of matrix and W-grains. The shape of the parabola is simple and easy to fit. The fitting parameters of parabolas have been successfully employed to explain the flow behaviour of a large number of tungsten heavy alloys having two-phase microstructure in different processing conditions. 相似文献
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Fluctuations of dilepton production from two photon interactions γγ→l~+l~- are studied in semicentral and peripheral nuclear collisions.Based on the Weizsacker-Williams approach,electromagnetic(EM) fields generated by moving nuclear charges are approximated as quasi-real photons.As fluctuating EM fields in each collision event are hard to be measured directly in experiments due to its short lifetime,we study the dilepton photoproduction with fluctuating EM fields,which are crucial for the EM fields induced chiral and charged particle evolutions,and calculate the relative standard deviation of the dilepton mass spectrum with the event-by-event fluctuating nuclear charge distributions.This fluctuation effect becomes smaller in more peripheral collisions where the shift of proton positions is implicit for EM fields outside the nucleus.The uncertainty of effective impact parameter △b on the standard deviation is also studied,and its effect is around one-third of the effect of nuclear charge fluctuations when △b is taken as~1 fm. 相似文献