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1.
This article is the second part of our review of the important role that symmetry plays in atomic and subatomic physics. We
will concentrate on the discrete symmetries — parity, charge conjugation, and time reversal — that have played a significant
part in the development of the ‘standard model’ of particle physics during the latter part of the 20th century. The importance
of experimental tests of these symmetries, in both atomic and particle physics, and their sensitivity to new phenomena is
also discussed. To conclude, we describe how ‘symmetry breaking’ in the standard model leads to the generation of mass via
the Higgs mechanism and how the search for evidence of this symmetry violation is one of the principal goals of the Large
Hadron Collider, which began operating at CERN, Switzerland in 2009. 相似文献
2.
Natural and Treated FeS2 in Li/FeS2 Coin Cell 总被引：1，自引：0，他引：1
TREATED FES, SAMPLES WERE PREPARED BY NATURAL FES, SAMPLES WHICH WERE GROUND FIRST, HEATED IN NITROGEN AND THEN WASHED IN ACID. THE LEVELS OF IMPURITY ELEMENTS, PRIMARILY PRESENT AS METALLIC OXIDES AND SULFIDES, ARE HIGHER IN THE NATURAL FES, THAN THOSE IN THE TREATED SAMPLE. SCANNING ELECTRON MICROSCOPY SHOWS THAT THE GRAIN SIZES OF TREATED FES, PARTICLES ARE SMALLER THAN THOSE OF NATURAL FES, PARTICLES. THE ELECTROCHEMICAL PERFORMANCE OF LI/TREATED FES, CELLS IS ATTRIBUTED TO THE SMALLER GRAIN SIZES AND HIGHER PURITY OF TREATED FES, PARTICLES IN COMPARISON TO THE NATURAL FES, SAMPLE. 相似文献
4.
ZHANG Zhao-di XU Long-jun SHI Jian-hang XU Wei WU Wen-li LIU Cheng-lun 《重庆大学学报(英文版)》2015,14(3):79-86
The effects of the electro-deposition conditions on the crystal structure and the properties of electrolytic manganese dioxide(EMD) were investigated in this paper. The results show that EMD was γ-crystal, with sand-like rough interface. The optimal preparation conditions of EMD were 30 min deposition time, and p H=1.0 in Mn SO4-H2SO4 solution at 50 ?C. Surfactant(P1) was conducive to the uniform and stable surface of γ-Mn O2 film, the impedance and the specific surface area of the electrode modified with γ-Mn O2 increased by 21.4 times and 75.6 times, respectively. The redox reversibility and the resolution ratio of characteristic peaks with the modified electrode were significantly improved in the benzodiazepines electrochemical reaction. The achievement illustrated that the controllable synthesis of γ-Mn O2 film thickness was practical in electrochemical sensors, and the determination reliability of benzodiazepines was improved with γ-Mn O2 modified electrodes used in environment monitoring technology. 相似文献
5.
让我们继续来看看、读读、写写重读音节中包含字母e的单词,正确区别它们发短音(short e)/e/3是长音(long e)/i:/。一起来读一读。 相似文献
6.
Structure and Dielectric Properties of Sb2O5-Doped ZrO2-SnO2-TiO2 Microwave Ceramics 总被引：1，自引：0，他引：1
The microwave frequency band is generally con-sidered in the range of 0.3—3 000 GHz. Its impor-tance is recognizable in the current growth of micro-wave communications systems which make use of thesuperior information density. Many kinds of dielectricmaterials have been developed for microwave applica-tions[1,2]. Among them, solid solution ZrO2-SnO2-TiO2(ZST) has a higher dielectric constant, a highquality factor (Q) value and a lowtemperature coeffi-cient of resonant frequency (TCF). B… 相似文献
7.
SO4^2- / TiO2-La2O3, a novel solid superacid, was prepared and its catalytic activities at different synthetic conditions are discussed with esterification of n-butanoic acid and n-butyl alcohol as probing reaction. The optimum conditions have also been found, mole ratio of n（La^3＋）：n（Ti^4＋） is 1：34, the soaked consistency of H2SO4 is 0.8 tool/L, the soaked time of HESO4 is 24 h, the calcining temperature is 480 ℃, the calcining time is 3 h. Then it was applied in the catalytic synthesis often important ketals and acetals as catalyst and revealed high catalytic activity. Under these conditions on which the molar ratio of aldehyde/ketone to glycol is l： 1.5, the mass ratio of the catalyst used in the reactants is 0.5%, and the reaction time is 1.0 h, the yields of ketals and acetals can reach 41.4%-95.8%. 相似文献
8.
A process of biosorption of Cu2 , Zn2 and Cd2 on Bacillus subtilis was investigated. The experiments show that the process of biosorption is quite fast. The maximum adsorption was reached after 5 min and hardly changed with time. The experimental data was analyzed using four sorption kinetic models: the pseudo-first-order, the Ritchie second-order, the modified second-order and the Elovich equations, which helped to determine the best-fit equation for the sorption of metal ions onto biomass. The results show that both the Ritchie second-order and modified second-order equations can fit the experimental data. The Langmuir model is able to accurately describe adsorption of Cu2 and Zn2 on B. subtilis. The experimental data points of adsorption Cd2 and Zn2 on B. subtilis are described by Freundlich isotherms model. 相似文献
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跟着青春的节拍,因为有了这一群性格各异的同学,我们班是如此的团结和美好!咱班的帅哥一排排,咱班的美女数不来,别看他们古灵精怪,但是同学请别生气,他们个个成绩还真不赖。 相似文献
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lintroductionMOrpnologicalandnlediantiltersasaclassofnonlineardiscretetilters11avegotWideapplicationsinsignalandimageprocessing.Incontrastwithlinearfilters,medianfiltersandtheirgenerationsareattractivebecausetheyareeasytoimplenlentandcansuppressimpulsenoi… 相似文献
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A kind of modified epoxy resins was obtained by condensation of epoxy resin with silicic acid tetraethyl ester(TEOS) and nano-SiO2. The reactions were performed with hydrochloric acid as a catalyst at 63℃. The structure, thermal stability and morphological characteristics of the modified epoxy resins were studied through infrared spectra (FF-IR) analysis, thermogravimetric (TG) analysis and scanning electron microscopy respectively. It has been found from the IR and TG study that modified epoxy resins have greater thermal stability than epoxy resins, and its thermal stability has been improved by the formation of inter-crosslinked network structure. The modified epoxy resins exhibit heterogeneous morphology and heterogeneity increases with more TEOS feeding, which in turn confirms the formation of inter-crosslinked network structure in modified epoxy resins. 相似文献
15.
esponse curves of SMA to NE and Ca~(2 ) on 1,2h after shock shifted to the right,the maximal contractions(Emax) of NE and Ca~(2 相似文献
16.
This study sought to better understand the adoption of multiple achievement goals at an intra-individual level, and its links
to emotional well-being, learning, and academic achievement. Participants were 480 Secondary Two students (aged between 13
and 14 years) from two coeducational government schools. Hierarchical cluster analysis revealed the presence of five clusters
of students with significantly different achievement goal profiles. MANOVAs and ANOVA, followed by post-hoc tests showed that
these clusters also differed significantly in terms of their experience of achievement emotions, use of learning strategies,
and mathematics performance. The cluster with high endorsement of mastery approach goal and low endorsement of mastery avoidance
goal was noted to have the most adaptive profile. The presence of a cluster of lowly motivated students was highlighted. Findings
emphasised the importance of investigating achievement emotions, and how the different achievement goals combine to influence
achievement-related variables. 相似文献
17.
Herbert W. Marsh 《Structural equation modeling》2013,20(3):246-254
Marsh and Balla (1986) and Marsh, Balla, and McDonald (1988) proposed an index of fit called χ2I2, but McDonald and Marsh (1990) subsequently demonstrated that the index is biased and recommended that it not be used. Bollen (1989) independently proposed Δ2 which is the same as χ2I2 (hereafter referred to as χ2I2‐Δ2), indicating that it adjusts for sample size and degrees of freedom (df). Gerbing and Anderson (1992), apparently based on the assumption that the χ2I2‐Δ2 index is unbiased and appropriately corrects for df (penalizes a lack of parsimony), recommended its use, and the index is routinely presented by major computer programs (e.g., EQS and LISREL 8). However, a more critical evaluation of the χ2I2‐Δ2 index reveals that: (a) it is systematically biased (i.e., its value varies systematically with N) although the size of the bias may be small; (b) the adjustment for df is inappropriate in that it penalizes model parsimony instead of model complexity; and (c) the inappropriate penalty for model parsimony is larger for small N. Because of these undesirable properties, the χ2I2‐Δ2 index is not recommended for routine use. 相似文献
18.
A new lighting and enlargement on phase spectrogram （PS） and frequency spectrogram （FS） is presented in this paper. These representations result from the coupling of power spectrogram and short time Fourier transform （STFT）. The main contribution is the construction of the 3D phase spectrogram （3DPS） and the 3D frequency spectrogram （3DFS）. These new tools allow such specific test signals as small slope linear chirp, phase jump case of musical signal analysis is reported. The main objective is to and small frequency jump to be analyzed. An application detect small frequency and phase variations in order to characterize each type of sound attack without losing the amplitude information given by power spectrogram 相似文献
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Wan-ling HE Ying FENG Xiao-li LI Yan-yan WEI Xiao-e YANG 《Journal of Zhejiang University. Science. B》2008,9(9)
The objective of the present study was to compare the toxicity and availability of Fe(Ⅱ) and Fe(Ⅲ) to Caco-2 cells.Cellular damage was studied by measuring cell proliferation and lactate dehydrogenase (LDH) release. The activities of two major antioxidative enzymes [superoxide dismutase (SOD) and glutathione peroxidase (GPx)] and differentiation marker (alkaline phosphatase) were determined after the cells were exposed to different levels of iron salts. The cellular iron concentration was investigated to evaluate iron bioavailability. The results show that iron uptake of the cells treated with Fe(Ⅱ) is significantly higher than that of the cells treated with Fe(Ⅲ) (P＜0.05). Fe(Ⅱ) at a concentration>1.5 mmol/L was found to be more effective in reducing cellular viability than Fe(Ⅲ). LDH release investigation suggests that Fe(Ⅱ) can reduce stability of the cell membrane. The activities of SOD and GPx of the cells treated with Fe(Ⅱ) were higher than those of the cells treated with Fe(Ⅲ), although both of them increased with raising iron supply levels. The results indicate that both Fe(Ⅱ) and Fe(Ⅲ) could reduce the cellular antioxidase gene expression at high levels. 相似文献