Dynamical study of the possible molecular state X(3872) with the s-channel one gluon exchange interaction

The recently observed X(3872) resonance, which is difficult to be assigned a conventional $c\bar{c}$ charmonium state in the quark model, may be interpreted as a molecular state. Such a molecular state is a hidden flavor four quark state because of its charmonium-like quantum numbers. The s-channel one gluon exchange is an interaction which only acts in the hidden flavor multi-quark system. In this paper, we will study the X(3872) and other similiar hidden flavor molecular states in a quark model by taking into account of the s-channel one gluon exchange interaction

Thermal stability of ultrahard polycrystalline diamond composite materials

Thermal stability of the ultrahard polycrystalline diamond (UHPCD) composite material developed by the reinforcement of the polycrystalline diamond (PCD) with chemical vapor deposition (CVD) diamond has been investigated in a flow of argon at 1200 °C. The indentation, Raman spectra and wear test have been performed to compare hardness, C–C structure and wear resistance of untreated and thermal treated UHPCD. It has been shown that the hardness of CVD diamond in UHPCD attains 133±7 GPa after high pressure and high temperature, while after thermal treatment the hardness decreases to 109±3 GPa, and the wear resistance of the thermal treated UHPCD decreases from 0.17 to 0.6 mg/km. The narrowing of full width at half maximum and shift of Raman peak to lower frequencies of CVD diamond in thermal treated UHPCD imply a decrease of crystal structural defects and compressive stresses, which results in a drop of the hardness of CVD diamond in a thermal treated UHPCD. The higher wear rate of thermal treated UHPCD is due to the lower hardness.Досліджено термічну стабільність надтвердого полікристалічного алмазного (UHPCD) композиційного матеріалу, отриманого армуванням полікристалічного алмазу після хімічного осадження (CVD) алмазу в потоці аргону при 1200 °C. Для порівняння твердості, C–C-структури і зносостійкості необробленого та термообробленого UHPCD було досліджено заглиблення індентора, спектри комбінаційного розсіювання та знос. Показано, що твердість CVD-алмазу в UHPCD досягає 133±7 ГПа після дії високого тиску і високої температури, а після термообробки зменшується до 109±3 ГПа, зносостійкість UHPCD після термообробки зменшується від 0,17 до 0,6 мг/км. Звуження напівширини і зсув піку комбінаційного розсіювання в область низьких частот CVD-алмазу в термообробленому UHPCD характеризує зменшення кристалічних структурних дефектів і напружень стиску, що призводить до зниження твердості CVD-алмазу в термообробленому UHPCD. Вища швидкість зносу термообробленого UHPCD пов’язана з більш низькою твердістю.Исследована термическая стабильность сверхтвердого поликристаллического алмазного (UHPCD) композиционного материала, полученного армированием поликристаллического алмаза после химического осаждения (CVD) алмаза в потоке аргона при 1200 °C. Для сравнения твердости, C–C-структуры и износостойкости необработанного и термообработанного UHPCD были исследованы глубина проникновения индентора, спектры комбинационного рассеяния и износ. Показано, что твердость CVD-алмаза в UHPCD достигает 133±7 ГПа после действия высокого давления и высокой температуры, а после термической обработки уменьшается до 109±3 ГПа, износостойкость после термической обработки UHPCD уменьшается от 0,17 до 0,6 мг/км. Сужение полуширины и сдвиг пика комбинационного рассеяния в область низких частот CVD- алмаза в термообработанном UHPCD характеризует уменьшение кристаллических структурных дефектов и напряжений сжатия, что приводит к снижению твердости CVD-алмаза в термообработанном UHPCD. Более высокая скорость износа термически обработанного UHPCD связана с более низкой твердостью

Orbit- and Atom-Resolved Spin Textures of Intrinsic, Extrinsic and Hybridized Dirac Cone States

Combining first-principles calculations and spin- and angle-resolved photoemission spectroscopy measurements, we identify the helical spin textures for three different Dirac cone states in the interfaced systems of a 2D topological insulator (TI) of Bi(111) bilayer and a 3D TI Bi2Se3 or Bi2Te3. The spin texture is found to be the same for the intrinsic Dirac cone of Bi2Se3 or Bi2Te3 surface state, the extrinsic Dirac cone of Bi bilayer state induced by Rashba effect, and the hybridized Dirac cone between the former two states. Further orbit- and atom-resolved analysis shows that s and pz orbits have a clockwise (counterclockwise) spin rotation tangent to the iso-energy contour of upper (lower) Dirac cone, while px and py orbits have an additional radial spin component. The Dirac cone states may reside on different atomic layers, but have the same spin texture. Our results suggest that the unique spin texture of Dirac cone states is a signature property of spin-orbit coupling, independent of topology

Long-term trend of surface ozone at a regional background station in eastern China 1991?2006: enhanced variability

International audienceInformation about the long-term trends of surface and tropospheric ozone is important for assessing the impact of ozone on human health, vegetation, and climate. Long-term measurements from East Asia, especially China's eastern provinces, are urgently needed to evaluate potential changes of tropospheric ozone over this economically rapid developing region. In this paper, surface ozone data from the Linan Regional Background Station in eastern China are analyzed and results about the long-term trends of surface ozone at the station are presented. Surface ozone data were collected at Linan during 6 periods between August 1991 and July 2006. The seasonality and the long-term changes of surface ozone at the site are discussed, with focus on changes in the diurnal variations, the extreme values, and the ozone distribution. Some long-term trends of surface ozone, e.g., decrease in the average concentration, increase in the daily amplitude of the relative diurnal variations, increase in the monthly highest 5% of the ozone concentration, decrease in the monthly lowest 5% of the ozone concentration, increase in the frequencies at the high and low ends of the ozone distribution have been uncovered by the analysis. All the trends indicate that the variability of surface ozone has been enhanced. Possible causes for the observed trends are discussed. The most likely cause is believed to be the increase of NOx concentration

Anisotropic softening of magnetic excitations in lightly electron doped Sr2_2IrO4_4

The magnetic excitations in electron doped (Sr$_{1-x}$La$_x$)$_2$IrO$_4$ with $x = 0.03$ were measured using resonant inelastic X-ray scattering at the Ir $L_3$-edge. Although much broadened, well defined dispersive magnetic excitations were observed. Comparing with the magnetic dispersion from the parent compound, the evolution of the magnetic excitations upon doping is highly anisotropic. Along the anti-nodal direction, the dispersion is almost intact. On the other hand, the magnetic excitations along the nodal direction show significant softening. These results establish the presence of strong magnetic correlations in electron doped Sr$_{1-x}$La$_x$)$_2$IrO$_4$ with close analogies to the hole doped cuprates, further motivating the search for high temperature superconductivity in this system

LNK (SH2B3): paradoxical effects in ovarian cancer.

LNK (SH2B3) is an adaptor protein studied extensively in normal and malignant hematopoietic cells. In these cells, it downregulates activated tyrosine kinases at the cell surface resulting in an antiproliferative effect. To date, no studies have examined activities of LNK in solid tumors. In this study, we found by in silico analysis and staining tissue arrays that the levels of LNK expression were elevated in high-grade ovarian cancer. To test the functional importance of this observation, LNK was either overexpressed or silenced in several ovarian cancer cell lines. Remarkably, overexpression of LNK rendered the cells resistant to death induced by either serum starvation or nutrient deprivation, and generated larger tumors using a murine xenograft model. In contrast, silencing of LNK decreased ovarian cancer cell growth in vitro and in vivo. Western blot studies indicated that overexpression of LNK upregulated and extended the transduction of the mitogenic signal, whereas silencing of LNK produced the opposite effects. Furthermore, forced expression of LNK reduced cell size, inhibited cell migration and markedly enhanced cell adhesion. Liquid chromatography-mass spectroscopy identified 14-3-3 as one of the LNK-binding partners. Our results suggest that in contrast to the findings in hematologic malignancies, the adaptor protein LNK acts as a positive signal transduction modulator in ovarian cancers

Cryo-EM of full-length α-synuclein reveals fibril polymorphs with a common structural kernel.

α-Synuclein (aSyn) fibrillar polymorphs have distinct in vitro and in vivo seeding activities, contributing differently to synucleinopathies. Despite numerous prior attempts, how polymorphic aSyn fibrils differ in atomic structure remains elusive. Here, we present fibril polymorphs from the full-length recombinant human aSyn and their seeding capacity and cytotoxicity in vitro. By cryo-electron microscopy helical reconstruction, we determine the structures of the two predominant species, a rod and a twister, both at 3.7 Å resolution. Our atomic models reveal that both polymorphs share a kernel structure of a bent β-arch, but differ in their inter-protofilament interfaces. Thus, different packing of the same kernel structure gives rise to distinct fibril polymorphs. Analyses of disease-related familial mutations suggest their potential contribution to the pathogenesis of synucleinopathies by altering population distribution of the fibril polymorphs. Drug design targeting amyloid fibrils in neurodegenerative diseases should consider the formation and distribution of concurrent fibril polymorphs

Characteristics of trace gaseous pollutants at a regional background station in Northern China

International audienceWe present measurement results of trace gaseous pollutants obtained at the Shangdianzi (SDZ) Global Atmosphere Watch (GAW) regional station in Northern China, from September 2003 to December 2006. The gases include ozone (O3), nitrogen oxide(s) (NOx=NO+NO2), sulfur dioxide (SO2), and carbon monoxide (CO). During the study period, the mean annual O3 concentrations were 30.1±21.0, 32.8±19.1 and 30.9±19.8 ppbv in 2004, 2005 and 2006. The corresponding NOx values were 14.5±14.0, 11.0±11.3 and 12.7±11.8 ppbv, respectively. The mean annual SO2 concentrations were 5.9±10.0, 6.1±9.9 and 7.6±10.2 ppbv in 2004, 2005 and 2006, while the mean CO levels were 586±415 and 742±558 ppbv in 2005 and 2006. The data obtained at SDZ station are compared with the results measured at other background sites in China as well as abroad. The concentrations of O3, NOx, SO2, and CO at the SDZ background station are found to have clear seasonal and diurnal variations. The impacts of local and remote pollution sources on the regional air quality are assessed using trace gases concentration roses and 3-day back trajectories of air masses arriving at the SDZ station