Synthesis and Magnetic Properties of Spin-Liquid Tb2Ti2O7

Polycrystalline samples of a novel spin-liquid compound Tb2Ti2O7 were prepared by a standard solid-state reaction. X-ray diffraction at room temperature confirms that the synthesized compound of Tb2Ti2O7 is single phase with cubic unit cell constant a0 of 1.015 44 nm. Magnetic susceptibility measurements in the temperature range between 100 and 300 K give an effective moment of 9.44 μB and Curie-Weiss temperature of 12.68 K, respectively, indicating the dominance of antiferromagnetic interactions. However, below 50 K, the magnetic behavior of Tb2Ti2O7 deviates from Curie-Weiss law, whose origin remains suspicion.     

基于雷达极化理论的弹丸飞行姿态电磁散射特征

针对用线极化天线测速雷达测量弹丸飞行姿态问题,利用电磁理论推导并分析了底部刻槽弹丸的姿态特征参数。首先由雷达电轴与刻槽弹丸对称轴之间的关系,建立弹体散射矩阵,得到散射场的粗略表示,说明刻槽测量姿态的原理;其次,利用理想导体上无限长窄槽的表面等效磁流的近似表达式,详细推导了凹槽散射的远场表达式;再次,比较了刻槽后平行极化与垂直极化的远区散射场,用解析法和数值法仿真了不同飞行姿态下刻槽对弹丸散射回波的调制作用并与实测数据进行了比较,数值仿真了姿态特征参数的单调性;最后,对姿态特征参数的增强方法进行了简要的讨论和展望。仿真结果表明,在一定章动角范围内,该姿态特征参数能够表征弹丸的飞行姿态,具有相对稳健性和单调性。     

A Quick Algorithm for Mining Exceptional Rules

Exceptional rules are often ignored because of their small support. However, they have high confidence, so they are useful sometimes. A new algorithm for mining exceptional rules is presented, which creates a large itemset from a relatively small database and scans the whole database only one time to generate all exceptional rules. This algorithm is proved to be quick and effective through its application in a mushroom database.     

Application of the wavelet transforms on axial strain calculation in ultrasound elastography

In ultrasound elastography, the axial strain distribution within biological tissues is calculated as the numerical derivative (differentiation) of the estimated axial displacement field. Unfortunately, the numerical derivative is unstable because it can greatly amplify the noises, especially at high frequencies. This work focuses on the axial strain calculation from the estimated axial displacements using wavelet transforms (WTs), including continuous wavelet transforms (CWTs) and discrete wavelet transforms (DWTs). The feasibility of the WT?based method using the quadratic spline function is verified by computer simulations and some phantom data. Results indicate that the WT?based method can effectively reduce the noise amplification in axial strain calculation.     

Marangoni effect of cracked liquid film of an aqueous electrolyte flowing over a vertical heated plate

An experimental investigation was performed on Marangoni effect of cracked liquid film of aqueous Na_2SO_4 flowing over a vertical heated plate by using a sensitive infrared imaging technique. The results show that the thermal and solutal Marangoni effects, which result from the non-uniform distributions of surface temperature and concentration of the film, respectively, occur in the streamwise and transverse directions of the film, generating different influences on the film heat transfer. Taking account of the Marangoni number (Ma) and the solution concentration (c_0), a correlation of the Nusselt number (Nu) for the cracked liquid film is proposed.     

Probabilistic Analysis and Multicriteria Decision for Machine Assignment Problem with General Service Times

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Structure of mammalian AMPK and its regulation by ADP

The heterotrimeric AMP-activated protein kinase (AMPK) has a key role in regulating cellular energy metabolism; in response to a fall in intracellular ATP levels it activates energy-producing pathways and inhibits energy-consuming processes. AMPK has been implicated in a number of diseases related to energy metabolism including type 2 diabetes, obesity and, most recently, cancer. AMPK is converted from an inactive form to a catalytically competent form by phosphorylation of the activation loop within the kinase domain: AMP binding to the γ-regulatory domain promotes phosphorylation by the upstream kinase, protects the enzyme against dephosphorylation, as well as causing allosteric activation. Here we show that ADP binding to just one of the two exchangeable AXP (AMP/ADP/ATP) binding sites on the regulatory domain protects the enzyme from dephosphorylation, although it does not lead to allosteric activation. Our studies show that active mammalian AMPK displays significantly tighter binding to ADP than to Mg-ATP, explaining how the enzyme is regulated under physiological conditions where the concentration of Mg-ATP is higher than that of ADP and much higher than that of AMP. We have determined the crystal structure of an active AMPK complex. The structure shows how the activation loop of the kinase domain is stabilized by the regulatory domain and how the kinase linker region interacts with the regulatory nucleotide-binding site that mediates protection against dephosphorylation. From our biochemical and structural data we develop a model for how the energy status of a cell regulates AMPK activity.     

Molecular dissection of plant height QTLs using recombinant inbred lines from hybrids between common wheat （Triticum aestivum L.） and spelt wheat （Triticum spelta L.）

In wheat, plant height is an important agronomic trait, and a number of quantitative trait loci (QTLs) controlling plant height have been located. In this study, using the conditional and unconditional QTL mapping methods, combined with data from five different growth stages over two years of field trials, the developmental behavior for plant height in wheat was dissected. Nine unconditional QTLs and 8 conditional QTLs were identified, of which 6 were detected by both methods. None of the 11 QTLs was detected at all of the 5 investigated developmental stages, but 7 QTLs were detected at certain stages in both years. Further analysis identified 9 unconditional QTLs at different stages, which could explain the phenotypic variation from 4.81% to 17.35%. It was noteworthy that one major QTL designated QHt-4B-2, which was located on chromosome 4B, was detected on May 18 and 25 in both years, and its genetic contributions to plant height ranged from 13.42% to 16.13%. Moreover, of the 8 conditional QTLs identified, six were detected in both years, in the order of QHt-3B→QHt-4B-1→QHt-4B-2→QHt-4D→QHt-5A and QHt-2B expressed at the same developmental stage. The results indicate that QTL expression during plant height development is selective and in a temporal order.     

Effect of TiO<Subscript>2</Subscript> on the viscosity and structure of low-fluoride slag used for electroslag remelting of Ti-containing steels

The viscosity of CaF₂-CaO-Al₂O₃-MgO-(TiO₂) slag was measured using a rotating crucible viscometer. Raman spectroscopy analysis was performed to correlate the viscosity to slag structure. The viscosity of the slag was found to decrease with increasing TiO₂ content in the slag from 0 to 9.73wt%. The activation energy decreased from 95.16 kJ/mol to 79.40 kJ/mol with increasing TiO₂ content in the slag. The introduction of TiO₂ into the slag played a destructive role in Al-O-Al structural units and Q4 units by forming simpler structural units of Q2 and Ti₂O₆4- chain. The amount of Al-O-Al significantly decreased with increasing TiO₂ content. The relative fraction of Q4 units in the[AlO₄]5--tetrahedral units shows a decreasing trend, whereas the relative fraction of Q2 units and Ti₂O₆4- chain increases with increasing TiO₂ content accordingly. Consequently, the polymerization degree of the slag decreases with increasing TiO₂ content. The variation in slag structure is consistent with the change in measured viscosity.