Large roomtemperature magnetocaloric effect with negligible magnetic hysteresis losses in Mn1−xVxCoGe alloys

The magnetic and magnetocaloric properties have been investigated in a series of Mn_1−xV_xCoGe (x=0.01, 0.02, 0.03, and 0.05) alloys. The substitution of V for Mn reduces the structural transformation temperature of MnCoGe alloy effectively and results in a second-order magnetic transition in Mn_0.95V_0.05CoGe alloys. Large room temperature magnetocaloric effect and almost zero magnetic hysteresis losses are simultaneously achieved in the alloys with x=0.01, 0.02, and 0.03. The reasons for the negligible magnetic hysteresis losses and the potential application for the roomtemperature magnetic refrigeration are discussed.     

Synthesis and biological evaluation of thiophene derivatives as acetylcholinesterase inhibitors

A series of new thiophene derivatives has been synthesized using the Gewald protocol. The acetylcholinesterase inhibition activity was assayed according to Ellman's method using donepezil as reference. Some of the compounds were found to be more potent inhibitors than the reference. 2-(2-(4-(4-Methoxyphenyl)piperazin-1-yl)acetamido)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (IIId) showed 60% inhibition, compared to only 40% inhibition by donepezil.     

Target-oriented multifunctional organocatalysis for enantioselective synthesis of bicyclo[3.3.1]nona-2,6-dien-9-ones. A formal asymmetric synthesis of huperzine A

A target-oriented highly enantioselective multifunctional organocatalytic approach has been developed to construct the bicycle-[3.3.1]nona-2,6-dien-9-one core of (?)-huperzine A for the first time, with up to 95% ee in the gram-scale procedure. The newly established methodology is also eligible to synthesize a variety of bicyclo[3.3.1]nona-2,6-dien-9-ones in high enantiopurities, and thus is useful for the future development of novel huperzine A analogs with medicinal interests.     

An efficient synthesis of 2H-indazoles via reductive cyclization of 2-nitrobenzylamines induced by low-valent titanium reagent

An efficient and improved synthesis of 2H-indazoles via reductive cyclization of 2-nitrobenzylamines induced by low-valent titanium reagent (TiCl₄/Zn) is described. In this reaction triethylamine (TEA) was used to control the pH value. This method has the advantages of easily accessible starting materials, convenient manipulation, higher yield, shorter reaction time, and wider substrate scope.     

Time-dependent partitioning theory of the control of radiationless transitions in 24-mode pyrazine

We consider the control of internal conversion between the S(2)((1)B(2u)) excited electronic state of pyrazine and the S(1)((1)B(3u)) state. The study is performed both during and after the femtosecond excitation of the ground electronic state S(0)((1)A(g)) to form the S(2) state. The dynamics is examined using the newly developed "effective modes" technique which enables the full computation of quantum dynamics in multi-dimensional spaces. Using this technique, we also investigate the coherent control of population transfer from S(0) to the S(2) and S(1) electronic states. We find that the use of shaped laser pulses enables a significant delay of the internal conversion. For example, after 60 fs, the S(2) population amounts to ～60% of the initial S(0) population, and remains at ～20% after 100 fs, in contrast to the S(0) electronic state which is completely depopulated within 75 fs.     

Amyloid peptide Aβ40 inhibits aggregation of Aβ42: evidence from molecular dynamics simulations

Effects of amyloid beta (Aβ) peptide Aβ(40) on secondary structures of Aβ(42) are studied by all-atom simulations using the GROMOS96 43a1 force field with explicit water. It is shown that in the presence of Aβ(40) the beta-content of monomer Aβ(42) is reduced. Since the fibril-prone conformation N? of full-length Aβ peptides has the shape of beta strand-loop-beta strand this result suggests that Aβ(40) decreases the probability of observing N? of Aβ(42) in monomer state. Based on this and the hypothesis that the higher is the population of N? the higher fibril formation rates, one can expect that, in agreement with the recent experiment, Aβ(40) inhibit fibril formation of Aβ(42). It is shown that the presence of Aβ(40) makes the salt bridge D23-K28 and fragment 18-33 of Aβ(42) more flexible providing additional support for this experimental fact. Our estimation of the binding free energy by the molecular mechanics-Poisson-Boltzmann surface area method reveals the inhibition mechanism that Aβ(40) binds to Aβ(42) modifying its morphology.     

New method for determining size of critical nucleus of fibril formation of polypeptide chains

A new method for determining the size of critical nucleus of fibril formation of polypeptide chains is proposed. Based on the hypothesis that the fibril grows by addition of a nascent peptide to the preformed template, the nucleus size N(c) is defined as the number of forming template peptides above which the time to add a new monomer becomes independent of the template size. Using lattice models one can show that our method and the standard method which is based on calculation of the free energy, provide the same result for N(c).     

On a two-fluid model of two-phase compressible flows and its numerical approximation

We consider a two-fluid model of two-phase compressible flows. First, we derive several forms of the model and of the equations of state. The governing equations in all the forms contain source terms representing the exchanges of momentum and energy between the two phases. These source terms cause unstability for standard numerical schemes. Using the above forms of equations of state, we construct a stable numerical approximation for this two-fluid model. That only the source terms cause the oscillations suggests us to minimize the effects of source terms by reducing their amount. By an algebraic operator, we transform the system to a new one which contains only one source term. Then, we discretize the source term by making use of stationary solutions. We also present many numerical tests to show that while standard numerical schemes give oscillations, our scheme is stable and numerically convergent.     

广义Ekeland变分原理的应用

研究了广义Ekeland变分原理在拟度量空间中的一些重要应用.利用广义Ekeland变分原理证明了函数f满足关于α的Takahashi ε-条件当且仅当f满足关于相同α的Hamel ε-条件.此外,利用关于α的Takahashi ε-条件得到了一些重要结论.     

弱耗散抽象发展方程全局吸引子的存在性

采用定义泛函,忽略粘性阻尼项时,在特定空间中研究了弱耗散抽象发展方程,得到了该方程全局吸引子的存在性结论,丰富了该类方程全局吸引子存在性的证法.