On state fusers over long-haul networks
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long-haul sensor networks↗
Engineering topics
Liu, Q
Publications and source records attributed to Liu, Q.
Thermal Equation of State of CaIrO3 Post-perovskite
The pressure-volume-temperature (P-V-T) relation of CaIrO{sub 3} post-perovskite (ppv) was measured at pressures and temperatures up to 8.6 GPa and 1,273 K, respectively, with energy-dispersive synchrotron X-ray diffraction using a DIA-type, cubic-anvil apparatus (SAM85). Unit-cell dimensions were derived from the Le Bail full profile refinement technique, and the results were fitted using the third-order Birth-Murnaghan equation of state. The derived bulk modulus K{sub T0} at ambient pressure and temperature is 168.3 {+-} 7.1 GPa with a pressure derivative K{sub T0} = 5.4 {+-} 0.7. All of the high temperature data, combined with previous experimental data, are fitted using the high-temperature Birch-Murnaghan equation of state, the thermal pressure approach, and the Mie-Grueneisen-Debye formalism. The refined thermoelastic parameters for CaIrO{sub 3} ppv are: temperature derivative of bulk modulus ({partial_derivative}K{sub T}/{partial_derivative}T){sub P} = -0.038 {+-} 0.011 GPa K{sup -1}, {alpha}K{sub T} = 0.0039 {+-} 0.0001 GPa K{sup -1}, ({partial_derivative}K{sub T}/{partial_derivative}T){sub V} = -0.012 {+-} 0.002 GPa K{sup -1}, and ({partial_derivative}{sup 2}P/{partial_derivative}T{sup 2}){sub V} = 1.9 {+-} 0.3 x 10{sup -6} GPa{sup 2} K{sup -2}. Using the Mie-Grueneisen-Debye formalism, we obtain Grueneisen parameter {gamma}{sub 0} = 0.92 {+-} 0.01 and its volume dependence q = 3.4 {+-} 0.6. The systematic variation of bulk moduli for several oxide post-perovskites can be described approximately by the relationship K{sub T0} = 5406.0/V(molar) + 5.9 GPa.
58 GEOSCIENCES↗
Pressure-Induced Isostructural Phase Transition and Correlation of FeAs Coordination with the Superconducting Properties of 111-Type Na1-xFeAs
The effect of pressure on the crystalline structure and superconducting transition temperature (T{sub c}) of the 111-type Na{sub 1-x}FeAs system using in situ high-pressure synchrotron X-ray powder diffraction and diamond anvil cell techniques is studied. A pressure-induced tetragonal to tetragonal isostructural phase transition was found. The systematic evolution of the FeAs{sub 4} tetrahedron as a function of pressure based on Rietveld refinements on the powder X-ray diffraction patterns was obtained. The nonmonotonic T{sub c}(P) behavior of Na{sub 1-x}FeAs is found to correlate with the anomalies of the distance between the anion (As) and the iron layer as well as the bond angle of As-Fe-As for the two tetragonal phases. This behavior provides the key structural information in understanding the origin of the pressure dependence of T{sub c} for 111-type iron pnictide superconductors. A pressure-induced structural phase transition is also observed at 20 GPa.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Multi-crystal Anomalous Diffraction for Low-resolution Macromolecular Phasing
Multiwavelength anomalous diffraction (MAD) and single-wavelength anomalous diffraction (SAD) are the two most commonly used methods for de novo determination of macromolecular structures. Both methods rely on the accurate extraction of anomalous signals; however, because of factors such as poor intrinsic order, radiation damage, inadequate anomalous scatterers, poor diffraction quality and other noise-causing factors, the anomalous signal from a single crystal is not always good enough for structure solution. In this study, procedures for extracting more accurate anomalous signals by merging data from multiple crystals are devised and tested. SAD phasing tests were made with a relatively large (1456 ordered residues) poorly diffracting (d{sub min} = 3.5 {angstrom}) selenomethionyl protein (20 Se). It is quantified that the anomalous signal, success in substructure determination and accuracy of phases and electron-density maps all improve with an increase in the number of crystals used in merging. Structure solutions are possible when no single crystal can support structural analysis. It is proposed that such multi-crystal strategies may be broadly useful when only weak anomalous signals are available.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Structural Basis for the cAMP-dependent Gating in the Human HCN4 Channel
Hyperpolarization-activated cAMP-regulated (HCN) channels play important physiological roles in both cardiovascular and central nervous systems. Among the four HCN isoforms, HCN2 and HCN4 show high expression levels in the human heart, with HCN4 being the major cardiac isoform. The previously published crystal structure of the mouse HCN2 (mHCN2) C-terminal fragment, including the C-linker and the cyclic-nucleotide binding domain (CNBD), has provided many insights into cAMP-dependent gating in HCN channels. However, structures of other mammalian HCN channel isoforms have been lacking. Here we used a combination of approaches including structural biology, biochemistry, and electrophysiology to study cAMP-dependent gating in HCN4 channel. First we solved the crystal structure of the C-terminal fragment of human HCN4 (hHCN4) channel at 2.4 {angstrom}. Overall we observed a high similarity between mHCN2 and hHCN4 crystal structures. Functional comparison between two isoforms revealed that compared with mHCN2, the hHCN4 protein exhibited marked different contributions to channel function, such as a {approx}3-fold reduction in the response to cAMP. Guided by structural differences in the loop region between {beta}4 and {beta}5 strands, we identified residues that could partially account for the differences in response to cAMP between mHCN2 and hHCN4 proteins. Moreover, upon cAMP binding, the hHCN4 C-terminal protein exerts a much prolonged effect in channel deactivation that could have significant physiological contributions.
59 BASIC BIOLOGICAL SCIENCES↗
Unusual oxidation states give reversible room temperature magnetocaloric effect on perovskite-related oxides SrFe{sub 0.5}Co{sub 0.5}O{sub 3}
The magnetic properties and the magnetocaloric effect are presented for the perovskite-related oxide SrFe{sub 0.5}Co{sub 0.5}O{sub 3} prepared using electrochemical oxidation. SrFe{sub 0.5}Co{sub 0.5}O{sub 3} exhibits a second order paramagnetic-ferromagnetic transition close to room temperature (T{sub C}=330 K). The maximal magnetic entropy change {Delta}S{sub M}{sup Max} , the maximal adiabatic temperature change {Delta}T{sub ad} and the refrigerant capacity are found to be equal to respectively 4.0 J/kgK, 1.8 K and 258 J/kg while raising the B-field change from 0 to 5 T. - Graphical Abstract: Moderate but reversible magnetocaloric properties are associated with the 2nd order paramagnetic to ferromagnetic phase transition exhibited at 330 K. A metal-like behavior is seen for the first time on the ferromagnetic regime. Highlights: Black-Right-Pointing-Pointer Both Fe{sup 4+} and Co{sup 4+} are stabilized on perovskite-related phase SrFe{sub 0.5}Co{sub 0.5}O{sub 3} using electrochemical oxidation. Black-Right-Pointing-Pointer Its crystallographic structure is cubic. Black-Right-Pointing-Pointer SrFe{sub 0.5}Co{sub 0.5}O{sub 3} is metal-like/ferromagnetic below 330 K Black-Right-Pointing-Pointer SrFe{sub 0.5}Co{sub 0.5}O{sub 3} exhibits magnetocaloric properties associated with the sharp paramagnetic to ferromagnetic phase transition.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗