Cerium(Ⅳ)oxide nanocomposites:Catalytic properties and industrial application

This review article provides a new insight on the application of cerium oxide(CeO₂)-metal oxide nanocomposites as catalyst with enhanced reducibility and improved oxygen(O₂)storage capacity,especially in the varying chemical reaction processes including combustion,oxidation,epoxidation and redox.The CeO₂-metal oxide interaction plays an important role in controlling particle size,O₂ availability and coke resistance properties of the catalyst.Strong metal oxide-CeO₂ interaction also assists in generating small and highly dispersed particles,resists sintering of catalyst particles during the catalysis process,and consequently improves the O₂ availability of the catalyst.Indeed,CeO₂ not only provides an active support to heterogeneous catalyst,but also creates a new active site at the metal-support interface to produce stronger nanoparticle bonding through the surface O₂ vacancy.This consequently produces a heterogeneous catalytic system with promising reaction rate and catalytic stability in many industrial applications such as CO₂ hydrogenation,CO oxidatio n,biodiesel productio n,gas reduction,photocatalytic and methane steam reforming.     

Role of JAK3 in CD40-mediated signaling

Several constitutively activating mutations have been demonstrated in the sixth transmembrane helix of the human LH receptor (hLHR) in boys with gonadotropin-independent precocious puberty. In the current study, we examined two unrelated Brazilian boys with gonadotropin-independent precocious puberty caused by two different heterozygous activating mutations of the hLHR. Direct sequencing of the entire exon 11 of the hLHR revealed a heterozygous substitution of T for G at nucleotide 1370, that converts Leu 457 to Arg in the third transmembrane helix of the hLHR in one affected boy. His biological parents had a normal hLHR gene sequence, establishing the sporadic nature of this novel Leu457Arg mutation. Human embryonic 293 cells expressing hLHR mutant (L457R) or hLHR wild-type bound CG with high affinity. However, cells expressing hLHR(L457R) exhibited significantly higher basal levels of cAMP (7- to 14-fold) than cells expressing the wild-type receptor, indicating constitutive activation of hLHR(L457R). Basal levels of cAMP in hLHR(L457R)-expressing cells were, nonetheless, not as great as the levels of cAMP produced by hLHR wild-type-expressing cells incubated with a saturating concentration of CG. Furthermore, cells expressing hLHR(L457R) were unresponsive to further stimulation by CG. This finding was confirmed in the patient by lack of an increase in serum testosterone after CG stimulation. These results suggest that the conformation of hLHR(L457R) mutant represents a different activated receptor state (R*) than the agonist-occupied wild-type receptor. We also identified the previously described Ala568Val mutation in the third intracellular loop of the LHR in the other affected African-Brazilian boy and his normal prepubertal sister, suggesting the inherited form of precocious puberty in this boy. We conclude that the third transmembrane helix is a potential area for activating mutations of the hLHR that cause male precocious puberty.     

A New Approach for the Wear Failure Risk of Copper Staves in Blast Furnaces

Copper staves are widely used as cooling systems for blast furnaces. Since the inside wall of the furnaces are completely covered with copper staves, the failure of the system plays a significant role for premature blast furnace relining. Especially the bosh area is the critical part of blast furnaces because it faces high heat load. The damage to the bosh area directly affects the service period of BF’s. The lifetime of furnaces can be prolonged considerably by preventing the premature damage of this section. For this purpose, a new approach has been introduced to define the premature risk factor of copper staves based on design and operation parameters. The data of 34 different blast furnaces obtained from the members of World Steel Assoc. are applied to this new approach to calculate the premature risk factors. The results are recorded and analyzed according to service lifetime and actual wear situations of copper staves. Finally, all these analyzes show that the new approach, which is represented in this paper can be a new design check parameter for blast furnaces and a practical solution to define the premature wear risk of copper staves. Therefore, blast furnace designers and users can extend the blast furnace lifetime by using this new approach resulting in high economic benefits.     

Effect of channel restrictions on the axial heat transport in subcooled superfluid helium

The present study investigates the influence of partial restrictions on the axial heat transport and critical heat flux limits in subcooled superfluid helium (helium II) channels. Different size orifices are used to simulate partial plugging of superconducting magnets cooling channels by frozen oxygen, nitrogen, hydrogen, neon or moisture during the cool down process. Thin stainless steel sharp edged orifices of sizes 0.5, 1, 2 and 5 mm id are mounted between stainless steel flanges attached to 9 mm diameter (helium II) channel. The helium II channel is heated at one end with a copper block heater while the other end heat sinks to an atmospheric superfluid helium heat exchange. Temperature drop across the restriction is measured by two calibrated carbon resistors. Measurements are carried out at both temperatures ranging from 1.8 to 2.2 K.As the orifice/channel area ratio decreases, data show a considerable decrease in the axial heat transported by internal convection process resulting in lower critical heat flux at the phase transition from helium II to helium I by the destruction of superfluidity and inititation of boiling. A linear correlation between critical channel heat flux and orificeI channel area ratio gives a good fit to the experimental data. For heat fluxes higher than the critical heat flux, transient temperature measurements for a step heat input are correlated with the time required to reach the phase transition.     

Stereoselective disposition of hydroxychloroquine and its metabolite in rats

Racemic hydroxychloroquine-sulfate (HCQ-sulfate) was administered to rats orally. Groups of 9 male and 9 female rats received doses of 0, 8, 16, or 24 mg/kg/day for 6 weeks, followed by a reduction of the higher doses to 8 mg/kg/day for the duration of the study. Whole blood samples were collected at 0, 3, 6, 8, and 10 weeks, and eleven tissues were harvested after the tenth week. The concentrations and enantiomer ratios of the parent drug and three metabolites, desethylhydroxychloroquine (DHCQ), desethylchloroquine (DCQ), and bisdesethylchloroquine (BDCQ), were determined. The highest concentration of HCQ was found in the intestinal smooth muscle, and the lowest in the brain and adipose tissue. The highest concentrations of the metabolites were found in the liver, adrenals, and lung tissue. The metabolism of HCQ in the rats was found to be stereoselective with R/S > 1 for the drug and < 1 for the metabolites. Gender-specific differences in the proportions of the drug and its metabolites and their enantiomers in blood and tissue were found. Varying dosages appeared to have only a temporary influence on blood concentrations and not to effect the enantiomer ratios in blood. Only a limited number of tissues exhibited significant differences between dose groups. There were no observed differences in enantiomer ratios among the blood collection times.     

Sudanese mucosal leishmaniasis: epidemiology, clinical features, diagnosis, immune responses and treatment

The epidemiology, clinical features, pathology, immune responses, diagnosis and treatment of 14 patients with mucosal leishmaniasis in the Sudan are described. The condition occurred mainly in adult males, particularly in certain closely related tribes from the western Sudan. It affected the mucosa of the upper respiratory tract and/or the oral mucosa and sometimes followed treated kala azar. The parasites were sometimes confined to the mucosa, sometimes spread to the lymph nodes, and rarely infected the bone marrow and spleen. One of the 2 patients with both visceral and mucosal leishmaniasis differed from classical kala azar cases; his infection was longer lasting, he was leishmanin positive, and his peripheral mononuclear cells proliferated in response to leishmanial antigens. Mucosal leishmaniasis following treated kala azar is a similar phenomenon to post-kala azar dermal leishmaniasis and post-kala azar uveitis. Post-kala azar mucosal leishmaniasis can therefore be added to the other post-kala azar leishmanial infections. Using the polymerase chain reaction, Southern blot analysis with specific probes, and isoenzyme characterization, the causative parasite was identified as Leishmania donovani in 4 patients and as L. major in one. Unlike American mucocutaneous leishmaniasis, mucosal leishmaniasis in the Sudan was not preceded or accompanied by cutaneous lesions and the response to pentavalent antimony or ketoconazole was good.     

A real Schur form method for modeling singularly perturbed systems

A method is presented for modeling a two-time-scale system in the singularly perturbed form. The method uses an ordered real Schur decomposition, which can be efficiently computed using standard subroutines from EISPACK. Three results are given. First, it is shown that any two-time-scale system can be modeled in the singularly perturbed form by a transformation into an ordered real Schur form, followed by balancing. Second, under some conditions on the ordered real Schur decomposition, a procedure is given to achieve the modeling task with all fast variables chosen from the original state variables. Third, necessary and sufficient conditions are given to achieve modeling by permutation of the original state variables