Effects of ion motion on linear Landau damping

The effects of ion motion on Landau damping has been studied by the use of one-dimensional Vlasov-Poisson simulation. It is shown that the ion motion may significantly change the development of the linear Landau damping. When the ion mass is multiple of proton mass, its motion will halt the linear Landau damping at some time due to the excitation of ion acoustic waves. The latter will dominate the system evolution at the later stage and hold a considerable fraction of the total energy in the system. With very small ion mass, such as in electron-positron plasma, the ion motion can suppress the linear Landau damping very quickly. When the initial field amplitude is relatively high such as with the density perturbation amplitude δn/n0 > 0.1, the effect of ion motion on Landau damping is found to be weak or even ignorable

Entanglement and quantum phase transition in the one-dimensional anisotropic XY model

In this paper the entanglement and quantum phase transition of the anisotropic s=1/2 XY model are studied by using the quantum renormalization group method. By solving the renormalization equations, we get the trivial fixed point and the untrivial fixed point which correspond to the phase of the system and the critical point, respectively. Then the concurrence between two blocks are calculated and it is found that when the number of the iterations of the renormalziation trends infinity, the concurrence develops two staturated values which are associated with two different phases, i.e., Ising-like and spin-fluid phases. We also investigate the first derivative of the concurrence, and find that there exists non-analytic behaviors at the quantum critical point, which directly associate with the divergence of the correlation length. Further insight, the scaling behaviors of the system are analyzed, it is shown that how the maximum value of the first derivative of the concurrence reaches the infinity and how the critical point is touched as the size of the system becomes large.Comment: 10 pages, 5 figure

Recent advances in polyoxometalate-based lanthanide–oxo clusters

Polyoxometalate (POM)-based lanthanide-oxo clusters (LnOCs) are a class of polynuclear lanthanide–oxygen complexes formed by polyoxometalate stabilization through oxygen bridges in which POMs can be viewed as multidentate inorganic ligands. POM-based LnOCs have received interest owing to their interesting structures and potential applications. In this paper, we summarize the classification, synthesis strategies, and properties of POM-based LnOCs. POM-based LnOCs are classified into three main categories according to their metal core element type and quantity: pure 4f clusters, 5d–4f clusters, and 3d–4f clusters. Their synthetic strategies are divided into four categories based on the source of the POM involved in the structural assembly: the lacunary POMs ligand-directed method, the in-situ transformation of lacunary POMs ligand-directed method, the in-situ generation of lacunary POMs ligand-directed method, and mixed synthesis strategies. In addition, the single-molecule magnets of POM-based LnOCs and their proton conduction properties are summarized

Magnetooptical Properties of Chiral [Co2Ln] Clusters.

Two pairs of enantiomeric 3d-4f metal clusters, [Co2Ln[( R )/( S )-L]4]·Cl5·(H2O)2·CH3OH·CH3CH2OH [ Co 2 Ln ; Ln = Gd ( 1S and 1R ), Dy ( 2S and 2R )], were synthesized by the reaction of chiral Schiff-base ligand ( R )/( S )-3-[(2-hydroxybenzylidene) amino]propane-1,2-diol [( R )/( S )-HL] with CoCl2·6H2O and LnCl3·6H2O. The circular dichroism spectra of ( S )/( R )-Co 2 Ln display a mirror-symmetry effect with seven peaks at 210-800 nm, which can be ascribed to π-π* transitions, exciton coupling, charge-transfer transitions between ligands and Co3+, and characteristic d-d transitions of Co3+ ions. Interestingly, the chiral Co 2 Ln metal clusters display strong magnetic circular dichroism signals at room temperature. This work suggests that the chiromagnetic metal cluster is expected to show a strong magnetooptical response

Structures, magnetic and catalytic properties of three sandwich-type silicotungstates containing tetranuclear copper(II) clusters

Three sandwich-type silicotungstates. formulated as [Cu-4(H2O)(2)(SiW9O34)(2)] 12NH(4) 22H(2)O (1), [Cu-4(H2O)(2)(SiW9O34)(2)] 12NH(4) 11H(2)P (2) and {[Cu(NH3)(4)](2)[Cu(H2O)(4)][Cu-4(H2O)(2)(SiW9O34)(2)]} 2[Cu(NH3)(4)(H2O)] 2NH(4) 6H(2)O (3), were synthesized by microwave irradiation and hydrothermal reaction Crystal structural analysis reveals that 1-3 possess the same dimeric polyoxoanions [Cu(2)StW(9)O(34) (H2O)(2)(12-) featuring tetranuclear copper(II) clusters Magnetic studies indicate that the Cu., clusters exhibit ferromagnetic coupling interactions Investigation on their catalytic activity for the oxidation of ethylbenzene suggests that catalytic activity of 1-3 is closely related to the acidity of complexes and the existence of unsaturated coordination sites in the complexNNSFC [20825103, 20721001, 90922031]; MSTC [200703815304]; Natural Science Foundation of Fujian Province of China [2008J0010

Plant toxin β-ODAP activates integrin β1 and focal adhesion : a critical pathway to cause neurolathyrism

Neurolathyrism is a unique neurodegeneration disease caused by beta-N-oxalyl-L-alpha, beta-diaminopropionic (beta-ODAP) present in grass pea seed (Lathyrus stativus L.) and its pathogenetic mechanism is unclear. This issue has become a critical restriction to take full advantage of drought-tolerant grass pea as an elite germplasm resource under climate change. We found that, in a human glioma cell line, beta-ODAP treatment decreased mitochondrial membrane potential, leading to outside release and overfall of Ca2+ from mitochondria to cellular matrix. Increased Ca2+ in cellular matrix activated the pathway of ECM, and brought about the overexpression of beta 1 integrin on cytomembrane surface and the phosphorylation of focal adhesion kinase (FAK). The formation of high concentration of FA units on the cell microfilaments further induced overexpression of paxillin, and then inhibited cytoskeleton polymerization. This phenomenon turned to cause serious cell microfilaments distortion and ultimately cytoskeleton collapse. We also conducted qRT-PCR verification on RNA-sequence data using 8 randomly chosen genes of pathway enrichment, and confirmed that the data was statistically reliable. For the first time, we proposed a relatively complete signal pathway to neurolathyrism. This work would help open a new window to cure neurolathyrism, and fully utilize grass pea germplasm resource under climate change

Atomically-precise lanthanide-iron-oxo clusters featuring the ε-Keggin ion.

Atomically precise molecular metal-oxo clusters provide ideal models to understand metal oxide surfaces, self-assembly, and form-function relationships. Devising strategies for synthesis and isolation of these molecular forms remains a challenge. Here, we report the synthesis of four Ln-Fe oxo clusters that feature the ε -{Fe 13 } Keggin cluster in its core. The {Fe 13 } metal-oxo cluster motif is the building block of two important iron oxyhydroxyide phases in nature and technology, ferrihydrite (as the δ -isomer) and magnetite (the ε -isomer). The reported ε -{Fe 13 } Keggin isomer as an isolated molecule provides opportunity to study the formation of ferrihydrite and magnetite from this building unit. The next metal layer surrounding the ε -{Fe 13 } core within these clusters exhibit a similar arrangement as the magnetite lattice, and Fe and Ln can occupy the same positions. This provides opportunity to construct a family of compounds and optimize magnetic exchange in these molecules via composition tuning. Small angle X-ray scattering (SAXS) and high-resolution electrospray ionization mass spectrometry (HRESI-MS) show these clusters are stable upon dissolution in both water and organic solvents, as a first step to perform further chemistry towards building magnetic arrays or invetigating ferrihydrite and magnetite assembly from pre-nucleation clusters

Catalytic promiscuity of O-methyltransferases from Corydalis yanhusuo leading to the structural diversity of benzylisoquinoline alkaloids

O-methyltransferases play essential roles in producing structural diversity and improving the biological properties of benzylisoquinoline alkaloids (BIAs) in plants. In this study, Corydalis yanhusuo, a plant used in traditional Chinese medicine due to the analgesic effects of its BIA-active compounds, was employed to analyze the catalytic characteristics of O-methyltransferases in the formation of BIA diversity. Seven genes encoding O-methyltransferases were cloned, and functionally characterized using seven potential BIA substrates. Specifically, an O-methyltransferase (CyOMT2) with highly efficient catalytic activity of both 4′- and 6-O-methylations of 1-BIAs was found. CyOMT6 was found to perform two sequential methylations at both 9- and 2-positions of the essential intermediate of tetrahydroprotoberberines, (S)-scoulerine. Two O-methyltransferases (CyOMT5 and CyOMT7) with wide substrate promiscuity were found, with the 2-position of tetrahydroprotoberberines as the preferential catalytic site for CyOMT5 (named scoulerine 2-O-methyltransferase) and the 6-position of 1-BIAs as the preferential site for CyOMT7. In addition, results of integrated phylogenetic molecular docking analysis and site-directed mutation suggested that residues at sites 172, 306, 313, and 314 in CyOMT5 are important for enzyme promiscuity related to O-methylations at the 6- and 7-positions of isoquinoline. Cys at site 253 in CyOMT2 was proved to promote the methylation activity of the 6-position and to expand substrate scopes. This work provides insight into O-methyltransferases in producing BIA diversity in C. yanhusuo and genetic elements for producing BIAs by metabolic engineering and synthetic biology