Magnetic effects at the interface between non-magnetic oxides

The electronic reconstruction at the interface between two insulating oxides can give rise to a highly conductive interface. Here we show how, in analogy to this remarkable interface-induced conductivity, magnetism can be induced at the interface between the otherwise non-magnetic insulating perovskites SrTiO3 and LaAlO3. A large negative magnetoresistance of the interface is found, together with a logarithmic temperature dependence of the sheet resistance. At low temperatures, the sheet resistance reveals magnetic hysteresis. Magnetic ordering is a key issue in solid-state science and its underlying mechanisms are still the subject of intense research. In particular, the interplay between localized magnetic moments and the spin of itinerant conduction electrons in a solid gives rise to intriguing many-body effects such as Ruderman-Kittel-Kasuya-Yosida interactions, the Kondo effect and carrier-induced ferromagnetism in diluted magnetic semiconductors. The conducting oxide interface now provides a versatile system to induce and manipulate magnetic moments in otherwise non-magnetic materials.     

1,25-Dihydroxyvitamin D3 increases the growth-promoting activity of autocrine epidermal growth factor receptor ligands in keratinocytes

Topical treatment of normal skin with 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] or its synthetic analogs results in enhanced keratinocyte proliferation. Autocrine growth factors belonging to the epidermal growth factor (EGF) family play a major role in controlling keratinocyte proliferation. 1,25-(OH)2D3 enhanced the autonomous proliferation of HaCaT human keratinocytes in the absence of exogenous growth factors. Autonomous and 1,25-(OH)2D3-stimulated proliferations were inhibited by a specific inhibitor of EGF receptor (EGFR) tyrosine kinase, an EGFR-neutralizing antibody, heparin, the heparin antagonist hexadimethrine, and the proteoglycan sulfation inhibitor chlorate. These results indicate the involvement of proteoglycan-dependent EGFR ligands. The initial events in EGFR (i.e. ErbB1) mitogenic signal transduction are dimer formation with another ErbB protein and tyrosine cross-phosphorylation. By immunoprecipitation followed by Western blotting we showed that ErbB1/ErbB3 heterodimers are the major mitogenic signaling entity in 1,25-(OH)2D3-stimulated cells. 1,25-(OH)2D3 did not affect the levels of the proteoglycan-dependent EGFR ligands amphiregulin and heparin-binding EGF nor the synthesis of proteoglycans, as assessed by 35S labeling and ion exchange chromatography. 1,25-(OH)2D3 caused a marked increase in the cellular contents of ErbB1, ErbB2, and ErbB3 proteins. The increase in ErbB proteins that mediates signal transduction by EGFR ligands can account for the stimulatory effect of 1,25-(OH)2D3 on autonomous keratinocyte proliferation.     

A highly scalable spray coating technique for electrode infiltration: Barium carbonate infiltrated La0.6Sr0.4Co0.2Fe0.8O3-δ perovskite structured electrocatalyst with demonstrated long term durability

This work demonstrated a highly scalable spray coating process for cathode infiltration with excellent long-term stability for the oxygen reduction reaction. Barium carbonate (BaCO₃) nanoparticles have previously demonstrated excellent catalytic activity for the oxygen reduction reaction and were chosen as a model system to be applied by spray coating onto La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) and LSCF-SDC (Sm_0.2Ce_0.8O_2-δ) cathode materials. In this work, barium acetate solutions were modified by a surfactant to lower the surface tension and decrease the contact angle on LSCF which is a benefit for the infiltration process. In the LSCF electrode, BaCO₃ nano-particles exhibited significant interfacial contact with LSCF particles by the spray coating technique. As a result, the polarization resistance of BaCO₃ infiltrated LSCF was reduced from 2.5 to 1.2 Ωcm² at 700 °C. In addition, commercial full cell SOFCs with BaCO₃ infiltrated LSCF-SDC cathodes also demonstrated higher performance due to the reduced cathode resistance. At 750 °C, the electrode overpotential of the BaCO₃ infiltrated cell was much lower than that of baseline cell during long term testing (500 h). The polarization resistance of the BaCO₃ infiltrated LSCF-SDC electrode only increased by 1.6% after 500 h.     

Electronically coupled complementary interfaces between perovskite band insulators

Perovskite oxides exhibit a plethora of exceptional properties, providing the basis for novel concepts of oxide-electronic devices. The interest in these materials is even extended by the remarkable characteristics of their interfaces. Studies on single epitaxial connections between the wide-bandgap insulators LaAlO3 and SrTiO3 have revealed them to be either high-mobility electron conductors or insulating, depending on the atomic stacking sequences. For device applications, as well as for a basic understanding of the interface conduction mechanism, it is important to investigate the electronic coupling of closely spaced complementary interfaces. Here we report the successful realization of such coupled interfaces in SrTiO3-LaAlO3 thin-film multilayer structures. We found a critical separation distance of six perovskite unit cell layers, corresponding to approximately 23 A, below which a decrease of the interface conductivity and carrier density occurs. Interestingly, the high carrier mobilities characterizing the separate conducting interfaces are found to be maintained in coupled structures down to subnanometre interface spacing.     

Synthesis and characterization of BaIn0.3−xYxCe0.7O3−δ (x = 0, 0.1, 0.2, 0.3) proton conductors

The morphological and electrical properties of yttrium (Y) and indium (In) doped barium cerate perovskites of the form BaIn_0.3−xY_xCe_0.7O_3−δ (with x = 0–0.3) prepared by a modified Pechini method were investigated as potential high temperature proton conductors with improved chemical stability and conductivity. The sinterability increased with the increase of In-doping, and the perovskite phase was found in the BaIn_0.3−xY_xCe_0.7O_3−δ solid solutions over the range 0 ≤ x ≤ 0.3. The conductivities decreased from x = 0.3 to 0 while the tolerance to wet CO₂ improved for BaIn_0.3−xY_xCe_0.7O_3−δ samples with an increase of In-doping. BaIn_0.1Y_0.2Ce_0.7O_3−δ was found to have relatively high conductivity as well as acceptable wet CO₂ stability.     

基于光纤微弯的缠绕式管道形变传感器

利用多模光纤的微弯特性 ,提出并实现了一种新颖的光纤缠绕式管道形变传感器 ;也给出了它的基本实验原理 .研究表明多模光纤的微弯损耗对导管的变形响应灵敏 ,其灵敏度可达 3.5 d B/ με.并且实验与理论符合的很好     

Studies on the diffusion of zinc and iodine into CdTe

Studies on the diffusion of iodine and zinc into CdTe are reported. Each iodine profile was divided up into four distinct regions and described mathematically by a function consisting of the sum of four complementary error functions. When plotted on an Arrhenius graph, the diffusivities gave four straight line relationships with similar slopes and the Arrhenius parameters for the fastest component of D₀₁ = (7 ±3). 10^-11 cm² s^-1 and E₁ = (0.21 ±0.05) eV. When extrapolated down to 20°C this gave a diffusivity of 10^-14 cm² s^-1 indicating that when iodine is diffused from the vapor it is not suitable as a long term stable dopant in devices where sharp impurity profiles are required. In the case of the zinc diffusions, each profile can be divided into two parts and was fitted satisfactorily by the sum of two complementary error functions giving two values of the diffusivities: D_slow due to zinc diffusion into the slice from the vapor and D_fast due to interdiffusion between a surface layer of Zn_x Cd_1-x Te formed on the slice and the remaining CdTe.     

Crash costs and safety investment

Injury crashes cost society more than $34 billion annually. Expending up to $2.3 million to prevent one fatal crash appears to be rational public policy, although the crash costs society only $500,000. Prevention of severe, nonfatal head and spinal cord injuries warrants even larger expenditures. The estimated rational investment to prevent an average nonfatal injury crash is $22,000, while society's cost is $8,000. Rational investment levels for increased safety are estimated by summing the amount individuals typically pay for small increases in their safety and the cost the rest of society bears when someone is killed or injured, including transfer payments.     

An efficient strategy for detection of known and new mutations of the CYP2D6 gene using single strand conformation polymorphism analysis

To detect mutations in the cytochrome P450 CYP2D6 gene (CYP2D6), we developed a strategy based on single-strand conformation polymorphism (SSCP) analysis of the gene amplified by polymerase chain reaction (PCR). The efficiency of the method was evaluated by analysing DNA samples from extensive metabolizers (EM) and poor metabolizers (PM) of debrisoquine. Haplotypes, alleles and mutations of CYP2D6 had previously been characterized in each individual using PCR assays, Xba I restriction fragment length polymorphism (RFLP) and sequencing. PCR-SSCP results were in complete agreement with those obtained using established methods. All previously characterized mutations were associated with particular shifts in the electrophoretic mobility of DNA fragments allowing their identification. We further tested the efficiency of PCR-SSCP for detecting new CYP2D6 mutations. DNA from a PM subject presumed to carry an unknown non-functional mutant allele of CYP2D6 was amplified and bands with aberrant migration patterns were observed on SSCP gels. Sequence analysis of the corresponding DNA fragments revealed the causative mutations. In this way, a novel non-functional allele of the gene, carrying three previously reported mutations and a new mutation in the third exon which results in a premature termination codon, was characterized. Finally, CYP2D6 SSCP analysis was performed on DNA amplified with fluorescent primers and an automated DNA sequencer was used for SSCP analysis of products. We conclude that the PCR-SSCP approach is a powerful method of identifying simultaneously known and new mutations of the CYP2D6 gene.