Sulfuric acid leaching kinetics of South African chromite

The sulfuric acid leaching kinetics of South African chromite was investigated. The negative influence of a solid product layer constituted of a silicon-rich phase and chromium-rich sulfate was eliminated by crushing the chromite and by selecting proper leaching con- ditions. The dimensionless change in specific surface area and the conversion rate of the chromite were observed to exhibit a proportional re- lationship. A modified shrinking particle model was developed to account for the change in reactive surface area, and the model was fitted to experimental data. The resulting model was observed to describe experimental findings very well. Kinetics analysis revealed that the leach- ing process is controlled by a chemical reaction under the employed experimental conditions and the activation energy of the reaction is 48 kJ.mol-1.

Improved Survival and Neurological Outcomes after Cardiopulmonary Resuscitation in Toll-like Receptor 4-mutant Mice

Background：Toll-like receptor 4 （TLR4） is a crucial receptor in the innate immune system and noninfectious immune responses.It has been reported that TLR4 participates in the pathological course of ischemia/reperfusion （I/R） injury.However,the role of TLR4 in the process of I/R injury after cardiac arrest （CA） and cardiopulmonary resuscitation （CPR） is still unknown.In this study,we investigated the effects of TLR4 mutation on survival and neurological outcome in a mouse model of CA/CPR.Methods：A model of potassium-induced CA was performed on TLR4-mutant mice （C3H/HeJ） and wild-type mice （C3H/HeN）.After 3 min of untreated CA,resuscitation was attempted with chest compression,ventilation,and intravenous epinephrine.Behavioral tests were performed on mice on day 3 after CPR.The morphological changes in hippocampal neurons were assessed by light and electron microscopy.Expressions of TLR4 and intercellular adhesion molecule-1 （ICAM-l） were detected by Western blot.Levels of tumor necrosis factor-α （TNF-α） and myeloperoxidase （MPO） were measured with enzyme-linked immunosorbent assay （ELISA）.Results：On day 3 after resuscitation the overall mortality was 33.33％ in C3H/HeJ group compared with 53.33％ in C3H/HeN group （P ＜ 0.05）.And there was much higher central tendency in C3H/HeJ group than C3H/HeN group during open field test （P ＜ 0.05）.Meanwhile,the percentage of nonviable neurons was 2 1.16％ in C3 H/HeJ group compared with 53.11％ in C3H/HeN group （P ＜ 0.05）.And there were significantly lower levels ofhippocampal TNF-α and MPO in C3H/HeJ mice （TNF-α：6.85±1.19 ng/mL,MPO：0.33±0.11 U/g） than C3 H/HeN mice （TNF-α：11.36±2.12 ng/mL,MPO：0.54±0.17 U/g） （all P ＜ 0.01）.CPR also significantly increased the expressions of TLR4 and ICAM-1 in C3H/HeN group.However,the expression ofICAM-l was much lower in C3H/HeJ group than in C3H/HeN group after CPR （P ＜ 0.01）.Conclusion：TLR4 signaling is involved in brain damage and in inflammation triggered by CA/CPR.

Formation and evolution behavior of inclusions in Al-killed resulfurized free-cutting steel with magnesium treatment

To reveal the formation and evolution behavior of inclusions during magnesium treatment and resulfurization in Al-killed free-cutting steel, both laboratory experiments and thermodynamic calculations were carried out. The extracted samples were polished and analyzed by scanning electron microscopy and energy-dispersive spectroscopy. The results indicated that MgO formed immediately and then transferred to MgO·Al2O3 with the homogenization of [Mg] in steel in the case of low magnesium addition (w[Mg] < 0.0020%). However, MgO would keep stable in the case of high magnesium addition (w[Mg] ≥ 0.0020%). In the process of resulfurization, the addition of sulfur forced the transformation of MgO to MgO·Al2O3 accompanied with the formation of MgS if the mass fraction of [S] in steel was in the range 0.15%-0.70%. MgS precipi-tated as a solid solution containing a quantity of MnS, and the composition of the sulfide solution was calculated to be (Mg0.85Mn0.15)S when the mass fraction of [Mn] was 1.2%. The formation mechanisms of inclusions after magnesium and sulfur additions were discussed comprehensively, and proper models for the evolution of inclusions were set up.

Rare earth element-doped porous In_(2)O_(3) nanosheets for enhanced gas-sensing performance

Rare earth(La,Pr,Sm,Ce and Yb)-doped porous In_(2)O_(3) nanosheets are prepared by a solvothermal method.The effect of rare earth elements on the structure,morphologies and gas-sensing performance of In_(2)O_(3) nanosheets is systematically investigated.The mixed phase composed of c-In_(2)O_(3) and rh-In_(2)O_(3) can be transformed into rh-In_(2)O_(3) by doping with rare earth elements.After doping with rare earth elements,the morphology can be changed from compact nanosheets to porous sheets.Compared with pure In_(2)O_(3) and La,Pr,Sm,Ce-doped porous In_(2)O_(3) nanosheets,Yb-doped In_(2)O_(3) nanosheets present the best gas-sensing performance.Among 3%-10%Yb-doped samples,6%Yb-doped In_(2)O_(3) porous nanosheets exhibit the optimal gas-sensing performance to 5×10^(-6)-750×10^(-6) acetone,giving a high response of 15.3 toward 50×10^(-6) acetone and fast response/recovery time at the operating temperature of 220℃.Moreover,6% Yb-doped porous In_(2)O_(3) nanosheet sensor also exhibits excellent selectivity and stability,indicating its potential in the nextgeneration gas sensor.

Male Paraurethral Duct Infection and Subsequent Paraurethral Duct Dilation

To the Editor： Only a small amount of studies were reported about paraurethral duct infection in males. To investigate the pathogens causing paraurethral duct infection and the secondary paraurethral duct dilation in males, and to understand the clinical characteristics and treatment options in paraurethral duct dilation, we retrospectively analyzed the data of male patients with paraurethral duct infection and subsequent paraurethral duct dilation who were treated at the Department of Dermatology of Changshu First People＇s Hospital from January 2000 to October 2013.

Pollen Morphology of Tundra Shrubs and Submarginal Plants from Barrow, Alaska

Investigation of plant morphological features, pollen, and habitat have been made for two shrub species from Barrow, Alaska, namely Dryas integrifoila M. Vahl and Salix rotundifolia Trautv., both of which are endemic to the Arctic floristic area. The former species has small lanceolate or plate leaves, whereas the latter has rounded leaves with distinct veins, rich in vitamin C. Both have dwarf and sprawling habits. Pollen studies showed that the pollen grains of the two species are spheroidal to sub-spheroidal or prolate. The type of aperture was tricolporate; pollen size 26.3-31.3 μm; ornamentation finely reticulate under a light microscope （LM） and strlate-reticulate under a scanning electron microscope （SEM） for D. integrafoila and finely reticulate under the LM and SEM for S. rotundifolia. Comparisons were made between the pollen from the same species from Arctic collections with those from China and Japan. Investigation of pollen morphology of tundra plants can provide significant data for comparative studies of fossil pollen and for the reconstruction of paleovegetation and paleoclimate in the Barrow area.