Synthesis of (R)-3-Methylpyrrolidine Alkaloids Using (S)-Malic Acid as a Chiral Pool

Previous work in our laboratory was around the development of chiral 2-pyrrolidinone synthon A. Malimides 1 and 2, which can be easily prepared from (S)-malic acid, have been shown to be versatile chiral synthetic intermediates. All the reactivities showed in synthon A have been exploited.1     

Reformed Solitary Kinetic Alfven Waves due to Dissipations and Auroral Electron Acceleration

The physical nature of the auroral electron acceleration has been an outstanding problem in space physics for decades. Some recent observations from the auroral orbit satellites, FREJA and FAST, showed that large amplitude solitary kinetic Alfvén waves (SKAWs) are a common electromagnetic active phenomenon in the auroral magnetosphere. In a low-β (i.e., β/2<<m_e/m_i<<1) plasma, the drift velocity of electrons relative to ions within SKAWs is much larger than thermal velocities of both electrons and ions. This leads to instabilities and causes dissipations of SKAWs. In the present work, based on the analogy of classical particle motion in a potential well, it is shown that a shock-like structure can be formed from SKAWs if dissipation effects are included. The reformed SKAWs with a shock-like structure have a local density jump and a net field-aligned electric potential drop of order of m_ev_A²/e over a characteristic width of several λ_e. As a consequence, the reformed SKAWs can efficiently accelerate electrons field-aligned to the order of the local Alfvén velocity. In particular, we argue that this electron acceleration mechanism by reformed SKAWs can play an important role in the auroral electron acceleration problem. The result shows that not only the location of acceleration regions predicted by this model is well consistent with the observed auroral electron acceleration region of 1—2 R_E above the auroral ionosphere, but also the accelerated electrons from this region can obtain an energy of several keV and carry a field-aligned current of several μA/m² which are comparable to the observations of auroral electrons.     

A NEW APPROACH TO SIMULATING FISHERIES DATA FOR POLICY MAKING

The main objective of natural resource management is to create social and economic value while maintaining sustainability. In this paper, we introduce an enhanced method for simulating high‐dimensional time series and apply it to Icelandic fishing resource management data. The methodology can be used in many contexts, but is particularly appropriate for simulating the many complex interactions involved in natural resource management. The simulations can be used to explore the sensitivity of resource management policies to future changes using an affinity parameter. Affinity, qualitatively similar to correlation, is a ordinal measure between –1 and +1 that models one's belief how much the future might behave like, or different from, the past. The main appeal of the method is its reliance on data and relative independence from assumptions about that data. In the paper, we apply it on data on Icelandic cod with encouraging results.     

石墨烯基磁量子环的低态能谱对磁场的依赖关系

我们采用狄拉克-韦尔 (Dirac-Weyl) 模型, 计算出二维石墨烯基磁量子环和磁量子点分别在垂直非均匀磁场下的低态能谱, 并讨论包括两组旋量分量的低态能谱跟磁场的依赖关系。从直接对角计算法所获得的数值结果表明, 在非均匀磁场下, 磁量子点和磁量子环的能谱中的最低朗道能级(N-=0)皆为高度简并, 且数值恒等为零。在其邻近较高的朗道能级, 磁量子环出现了由磁场诱导的轨道角动量间的跃迁, 而磁量子点则没有。最后本文指出, 除了最低朗道能级(N-=0)外, 两组旋量分量的能谱完全一样, 只是其朗道能级所标记的两组量子数不同而已。     

Noises in Detecting Relic Gravitational Wave

We analyse the three basic kinds of noises in detecting the relic gravitational wave （GW）, which are the noises caused by the thermal radiation in the detecting cavity and by the scattering of the Gaussian beam in the detecting cavity, and noise in the microwave radiometers. The analysis shows that a reasonable signal-to-noise ratio may be achieved for a detecting device with a suitable geometric structure only when the temperature of the environment is no more than T = 0.6 K, and the power of the radiation of the Gaussian beam is no less than P=10^5 W.     

Stability of hypersurface sections of quadric threefolds

Let S be a complete intersection of a smooth quadric 3-fold Q and a hypersurface of degree d in P4.We analyze GIT stability of S with respect to the natural G=SO(5,C)-action.We prove that if d 4 and S has at worst semi-log canonical singularities then S is G-stable.Also,we prove that if d 3 and S has at worst semi-log canonical singularities then S is G-semistable.     

可溶性聚酰亚胺液晶取向膜的制备与性能

液晶取向膜是液晶显示器中的关键材料,为了制得性能优良的液晶取向膜,我们通过铃木偶联反应制备了3种含有不同末端基团的3,5-二氨基联苯,将制得的3种二胺单体分别与环丁烷四甲酸二酐聚合得到3种新型的聚酰亚胺。 利用核磁氢谱对单体和聚合物的结构进行了表征,测试了聚合物的溶解性、热稳定性以及用作液晶取向膜的性能。 结果表明,所得的聚酰亚胺具有良好的溶解性和热稳定性,经过机械摩擦后,末端带有甲氧基的聚酰亚胺能使液晶分子平行于摩擦方向取向,末端带有苯氧羰基和联苯氧羰基的聚酰亚胺能使液晶分子垂直于摩擦方向取向。 此类可溶性的聚酰亚胺液晶取向膜将简化制备工艺并在柔性显示器件中具有较大的应用价值。     

New Diarylheptanoid from the Barks of Alnus japonica Steudel

A new diarylheptanoid glycoside, 1,7-bis-（3,4-dihydroxyphenyl）-5-hydroxyheptane- 3-O-β-D-xylopyranoside （1）, together with nine known diarylheptanoids （2-10） were isolated from the fresh bark of Alnus japonica which is a species of the genus Alnus species, growing throughout Korea.     

Effect of the Pulse Duty Cycle on Characteristics of Plasma Electrolytic Oxidation Coatings Formed on AZ31 Magnesium Alloy

Ceramic coatings are synthesized on AZ31 magnesium alloy in alkaline silicate solution by the method of plasma electrolytic oxidation. The effect of two different duty cycles （10% and 50%） on the structure and corrosive properties of the coatings is investigated. It is found that the coatings are mainly composed of MgO, Mg2SiO4 and MgF2 through XRD analysis. SEM images indicate that coatings formed at 50% duty cycle have a relatively coarse surface with larger pore size and fewer pores, and have a slower growth rate than those formed at 10% duty cycle with the same treatment time. However, the results of potentiodynamic polarization tests demonstrate that coatings formed at 50% duty cycle exhibit better corrosion resistance as a result of more compact microstructure.     

POPULATION‐LEVEL ANALYSIS AND VALIDATION OF AN INDIVIDUAL‐BASED CUTTHROAT TROUT MODEL

ABSTRACT. An individual‐based model of stream trout is analyzed by testing its ability to reproduce patterns of population‐level behavior observed in real trout: (1) “self‐thinning,” a negative power relation between weight and abundance; (2) a “critical period” of density‐dependent mortality in young‐of‐the‐year; (3) high and age‐specific inter‐annual variability in abundance; (4) density dependence in growth; and (5) fewer large trout when pool habitat is eliminated. The trout model successfully reproduced these patterns and was useful for evaluating their theoretical basis. The model analyses produced new explanations for some field observations and indicated that some patterns are less general than field studies indicate. The model did not reproduce field‐observed patterns of population variability by age class, discrepancies potentially explained by site differences, predation mortality being more stochastic than the model assumes, or uncertainty in the field study's age estimates.