Hole dispersions in the G- and C-type orbital ordering backgrounds: Doped manganese oxides

In the framework of the linear spin-wave theory and orbital-charge separation, we calculate quasiparticle (QP) dispersions for two different antiferromagnetic orbital structures in the fully saturated spin phase of manganese oxides. Although with the same orbital wave excitations, the QP bands of C- and G-type orbital structures exhibit completely different shapes. The pseudogap observed in the density of states and spectral functions around ω=0 is related with the large antiferromagnetic orbital fluctuation. The minimal band energy for G-type is lower than that for C-type orbital order, while these band curves almost coincide in some momentum points. Larger energy splitting occurs between the two branches of k z=0 and k z=π when increasing the superexchange coupling J, suggesting that the orbital scattering plays an essential role in the QP dispersions. ©2000 The American Physical Society.published_or_final_versio

Accurate prediction of heat of formation by combining Hartree-Fock/density functional theory calculation with linear regression correction approach

A linear regression correction (LRC) approach was developed to account for the electron correlation energy missing in Hartree-Fock (HF) calculation. This method was applied to evaluate the standard heats of formation of 180 small-sized to medium-sized organic molecules at 298.15 K. The descriptors in the LRC scheme are the number of lone-pair electrons, bonding electrons and inner layer electrons in molecules, and the number of unpaired electrons in ground state atoms. It is observed that the large systematic deviations for the calculated heat of formation are reduced drastically, in particular, for the HF results.published_or_final_versio

Competition between ferromagnetic metallic and paramagnetic insulating phases in manganites

La 0.67Ca 0.33Mn 1-xCu xO 3 (x=0 and 0.15) epitaxial thin films were grown on the (100) LaAlO 3 substrates, and the temperature dependence of their resistivity was measured in magnetic fields up to 12 T by a four-probe technique. We found that the competition between the ferromagnetic metallic (FM) and paramagnetic insulating (PI) phases plays an important role in the observed colossal magnetoresistance (CMR) effect. Based on a scenario that the doped manganites approximately consist of phase-separated FM and PI regions, a simple phenomenological model was proposed to describe the CMR effect. Using this model, we calculated the resistivity as functions of temperature and magnetic field. The model not only qualitatively accounts for some main features related to the CMR effect, but also quantitatively agrees with the experimental observations. © 2002 American Institute of Physics.published_or_final_versio

Catalytic Cracking and Heat Sink Capacity of Aviation Kerosene Under Supercritical Conditions

Catalytic cracking of China no. 3 aviation kerosene using a zeolite catalyst was investigated under supercritical conditions. A three-stage heating/cracking system was specially designed to be capable of heating 0.8 kg kerosene to a temperature of 1050 K and pressure of 7.0 MPa with maximum mass flow rate of 80 g/s. Sonic nozzles of different diameters were used to calibrate and monitor the mass flow rate of the cracked fuel mixture. With proper experiment arrangements, the mass flow rate per unit throat area of the cracked fuel mixture was found to well correlate with the extent of fuel conversion. The gaseous products obtained from fuel cracking under different conditions were also analyzed using gas chromatography. Composition analysis showed that the average molecular weight of the resulting gaseous products and the fuel mass conversion percentage were a strong function of the fuel temperature and were only slightly affected by the fuel pressure. The fuel conversion was also shown to depend on the fuel residence time in the reactor, as expected. Furthermore, the heat sink levels due to sensible heating and endothermic cracking were determined and compared at varying test conditions. It was found that at a fuel temperature of similar to 1050 K, the total heat sink reached similar to 3.4 MJ/kg, in which chemical heat sink accounted for similar to 1.5 MJ/kg

Management of Drinking Water Source in Rural Communities under Climate Change

In rural communities where central public water supply systems can hardly reach, the acquisition and management of safe drinking water sources are challenging due to population growth, environmental pollution, and climate change. Numerous endeavours have been made over the past several decades to help rural communities manage drinking water sources and obtain safe drinking water under climate change, which are summarized in this review. Firstly, the crises of rural drinking water safety under climate change are overviewed based on the extensive investigation of recent studies on rural water security. Second, the sustainable management of rural drinking water sources are systematically reviewed, mainly focusing on issues of water quality assessments, drinking water quantity and quality improvement, system maintenance and community management, and decision making in rural regions across the world. Finally, knowledge gaps of recent endeavors are highlighted, emerging threats and complications to water security under climate change are identified and perspectives for future works are discussed.This research was supported by the Natural Science and Engineering Research Council of Canada, and the National Foreign Expert Project (G2021111016L and (G2021111017L)

Thermal cracking of aviation kerosene for scramjet applications

Thermal cracking of China No.3 aviation kerosene was studied experimentally and analytically under supercritical conditions relevant to regenerative cooling system for Mach-6 scramjet applications. A two-stage heated tube system with cracked products collection/analysis was used and it can achieve a fuel temperature range of 700-1100 K, a pressure range of 3.5-4.5 MPa and a residence time of approximately 0.5-1.3 s. Compositions of the cracked gaseous products and mass flow rate of the kerosene flow at varied temperatures and pressures were obtained experimentally. A one-step lumped model was developed with the cracked mixtures grouped into three categories: unreacted kerosene, gaseous products and residuals including liquid products and carbon deposits. Based on the model, fuel conversion on the mass basis, the reaction rate and the residence time were estimated as functions of temperature. Meanwhile, a sonic nozzle was used for the control of the mass flow rate of the cracked kerosene, and correlation of the mass flow rate gives a good agreement with the measurements

Electric-field-induced alignment of electrically neutral disk-like particles: modelling and calculation

This work reveals a torque from electric field to electrically neutral flakes that are suspended in a higher electrical conductive matrix. The torque tends to rotate the particles toward an orientation with its long axis parallel to the electric current flow. The alignment enables the anisotropic properties of tiny particles to integrate together and generate desirable macroscale anisotropic properties. The torque was obtained from thermodynamic calculation of electric current free energy at various microstructure configurations. It is significant even when the electrical potential gradient becomes as low as 100 v/m. The changes of electrical, electroplastic and thermal properties during particles alignment were discussed

Flow characteristic of highly underexpanded jets from various nozzle geometries

Flow characteristics of highly underexpanded jets at the same nozzle pressure ratio of 5.60 but issuing from four different nozzles, i.e., the circular, elliptic, square, and rectangular nozzles, are studied using large eddy simulations. The results show that the square jet penetrates fastest, although the turbulence transition is similar for different jets. The penetration rates of different jets show the similar linear dependency on the square root of time, but the penetration constant Gamma for the noncircular jets deviates more than 5% from the theoretical value of 3.0. The circular and square jets both correspond to a three-dimensional helical instability mode, while the elliptic and rectangular jets haveatwo-dimensional flapping instability in their minor axis planes. All the jets undergo a Mach reflection forming the Mach disk, but the Mach disk in the elliptic and rectangular jets is not easily visible. The intercepting shocks in the square jet originate at the four corners of the nozzle exit at first, while the formation of the intercepting shocks is only observed in the major axis planes for the elliptic and rectangular jets. In addition, great differences are observed on the mixing characteristics between different jets. In particular, the elliptic jet penetrates slowest, has the shortest length of jet potential core, and takes the largest mixing area. (C) 2017 Elsevier Ltd. All rights reserved.</p

Prognostic utility of HOXB13 : IL17BR and molecular grade index in early-stage breast cancer patients from the Stockholm trial

Background: A dichotomous index combining two gene expression assays, HOXB13:IL17BR (H:I) and molecular grade index (MGI), was developed to assess risk of recurrence in breast cancer patients. The study objective was to demonstrate the prognostic utility of the combined index in early-stage breast cancer. Methods: In a blinded retrospective analysis of 588 ER-positive tamoxifen-treated and untreated breast cancer patients from the randomized prospective Stockholm trial, H:I and MGI were measured using real-time RT-PCR. Association with patient outcome was evaluated by Kaplan-Meier analysis and Cox proportional hazard regression. A continuous risk index was developed using Cox modeling. Results: The dichotomous H:I+MGI was significantly associated with distant recurrence and breast cancer death. The &gt;50% of tamoxifen-treated patients categorized as low-risk had &lt;3% 10-year distant recurrence risk. A continuous risk model (Breast Cancer Index (BCI)) was developed with the tamoxifen-treated group and the prognostic performance tested in the untreated group was 53% of patients categorized as low-risk with an 8.3% 10-year distant recurrence risk. Conclusion: Retrospective analysis of this randomized, prospective trial cohort validated the prognostic utility of H:I+MGI and was used to develop and test a continuous risk model that enables prediction of distant recurrence risk at the patient level.Original Publication:Piiha-Lotta Jerevall, Xiai-Jun Ma, Hongying Li, Ranelle Salunga, Nicole C. Kesty, Mark G. Erlander, Dennis Sgroi, Birgitta Holmlund, Lambert Skoog, Tommy Fornander, Bo Nordenskjöld and Olle Stål, Prognostic utility of HOXB13:IL17BR and Molecular Grade Index in early-stage breast cancer patients from the Stockholm trial, 2011, British Journal of Cancer, (104), 11, 1762-1769.http://dx.doi.org/10.1038/bjc.2011.145Copyright: Nature Publishing Grouphttp://npg.nature.com