Optical transitions between Landau levels: AA-stacked bilayer graphene

The low-frequency optical excitations of AA-stacked bilayer graphene are investigated by the tight-binding model. Two groups of asymmetric LLs lead to two kinds of absorption peaks resulting from only intragroup excitations. Each absorption peak obeys a single selection rule similar to that of monolayer graphene. The excitation channel of each peak is changed as the field strength approaches a critical strength. This alteration of the excitation channel is strongly related to the setting of the Fermi level. The peculiar optical properties can be attributed to the characteristics of the LL wave functions of the two LL groups. A detailed comparison of optical properties between AA-stacked and AB-stacked bilayer graphenes is also offered. The compared results demonstrate that the optical properties are strongly dominated by the stacking symmetry. Furthermore, the presented results may be used to discriminate AABG from MG, which can be hardly done by STM

Ricci Flat Black Holes and Hawking-Page Phase Transition in Gauss-Bonnet Gravity and Dilaton Gravity

It is well-known that there exists a Hawking-Page phase transition between a spherical AdS black hole and a thermal AdS space. The phase transition does not happen between a Ricci flat AdS black hole whose horizon is a Ricci flat space and a thermal AdS space in the Poincare coordinates. However, the Hawking-Page phase transition occurs between a Ricci flat AdS black hole and an AdS soliton if at least one of horizon coordinates for the Ricci flat black hole is compact. We show a similar phase transition betwen the Ricci flat black holes and deformed AdS solitons in the Gauss-Bonnet gravity and the dilaton gravity with a Liouville-type potential including the gauged supergravity coming from the spherical reduction of Dp-branes in type II supergravity. In contrast to Einstein gravity, we find that the high temperature phase can be dominated either by black holes or deformed AdS solitons depending on parameters.Comment: Latex, 17 pages without figure

Tetra­aqua­tetra­kis{μ3-3,3′-[(E,E)-ethane-1,2-diylbis(nitrilo­methyl­idyne)]benzene-1,2-diolato}octa­zinc(II) N,N-dimethyl­formamide hexa­solvate

The asymmetric unit of the title compound [Zn8(C16H12N2O4)4(H2O)4]·6C3H7NO, consists of eight ZnII cations, four tetra­valent anionic ligands, L 4− (L 4− = 3,3′-(1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1-yl­idene))bis­(methan-1-yl-1-yl­idene)dibenzene-1,2-bis­(olate), four coordinated water mol­ecules and six N,N-dimethyl­formamide solvate mol­ecules. The coordination complex comprises an octa­nuclear ZnII unit with its ZnII centers coordinated in two discrete distorted square-pyramidal geometries. Four ZnII atoms each coordinate to two nitro­gen atoms and two phenolate oxygen atoms from an individual L 4− ligand and one coordinated water mol­ecule. The other four ZnII atoms each bind to five phenolate oxygen atoms from three different L 4− ligands. In the crystal structure, the ZnII complex unit, coordinated water mol­ecules and dimethyl­formamide solvate mol­ecules are linked via O—H⋯O and C—H⋯O hydrogen bonds. Mol­ecules are connected by additional inter­molecular O—H⋯O and C—H⋯O hydrogen bonds, forming an extensive three dimensional framework

Comparison of the protein acetylome of endothelial cells upon shear flow and resveratrol treatment

Background: Posttranslational acetylation/deacetylation known as the acetylome is important in regulating protein activity. Shear flow (SF) and resveratrol (RSV) are two stimuli that represent physical and chemical signal separately. The acetylome co-regulated by these two stimuli remain unclear. Methods: Human umbilical cord vein endothelial cells (HUVECs) were subjected to either SF of 12 dynes/cm2 or 10 μM RSV. The purified acetylated peptides were labeled by isobaric tags for relative and absolute quantitation (iTRAQ) analysis. The signaling cascades of the identified acetylome were predicted by ingenuity pathway analysis (IPA). Co-immunoprecipitation was applied to confirm the acetylation status of proteins. Results: Five groups of proteins showed an increased acetylation upon SF and RSV treatment. After algorithm, 628 proteins with increased acetylation and 22 proteins with decreased acetylation were identified in the SF acetylome. For the acetylome regulated by RSV, 145 proteins with increased acetylation and 23 proteins with decreased acetylation were identified. Compared these two acetylomes, 129 proteins with increased acetylation and 2 proteins with decreased acetylation were co-regulated by both SF and RSV treatments. IPA analysis showed that this co-regulated acetylome was involved in heat shock response, and the signals of eNOS, STAT3, JAK/STAT and ERK/MAPK. Co-immunoprecipitation analysis further confirmed the acetylated status of mitochondrial HSP60 and mitochondrial citrate synthase. Conclusions: This study indicated that physical signal is more complicated than chemical signal in the case of acetylome. The co-regulated proteins are worthy for further study in discussing synergetic effect between physical and chemical signal in cardioprotection

Halogen Bonds in Two Silver(I) Mixed-ligand Supramolecular Frameworks: Synthesis, Structure and Photoluminescence

Two silver(I) tetrachlorophthalates incorporating aminopyrimidyl ligands, namely [Ag 4 (apym) 4 (tcpta) 2 ] n (1) and [Ag 2 (dmapym)(tcpta)] n (2), (apym = 2-aminopyrimidine, dmapym = 2-amino-4,6-dimethylpyrimidine, H 2 tcpta = tetrachlorophthalic acid), were synthesized and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Both 1 and 2 form sheets which are assembled into 3D supramolecular frameworks via halogen bonds, hydrogen bonds and π ···π interactions. Even adding two more methyl groups to the pyrimidyl ring does not change the dimensions of 1 and 2, but it influences the arrangement of the N-and O-donors in the solid state which in turn results in different types of halogen bonds. The photoluminescence properties of 1 and 2 were investigated in the solid state at room temperature