2,712 research outputs found
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
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