Piezoelectric gate for a two-dimensional electron system transport in LiNbO3-GaAs/AlGaAs sandwich structures

Standing-wave piezoelectric fields in the LiNbO(3) driving plate are used to form depleted and accumulated electron densities in GaAs/AlGaAs quantum wells (QWs). The photoluminescence spectrum of the two-dimensional electron system varies both spatially and temporally, exhibiting an electron-hole plasma recombination and exciton and trion emissions at large and small electron densities, respectively. Controlling the piezoelectric field component perpendicular to the QW layers offers a versatile tool to achieve the spatially indirect exciton luminescence in double QW structures.     

Microbial respiration as an indication of metal toxicity in contaminated organic materials and soil

The effect of heavy metals on microbial respiration in organic materials used as soil amendments was evaluated to assess the stability of the materials. Solutions of Pb (II), Cu (II) and Zn (II) at rates of 5, 10 and 50mg metal g(-1) were added to green waste compost, peat, coir and wood bark. Metal toxicity led to a significant decrease in carbon dioxide evolved by the contaminated materials, up to 80% less at the highest rate of addition compared to the untreated material. There was a significant negative correlation between the organic carbon content of an amendment and the inhibition of CO(2) evolution by all three heavy metals. There was also a significant negative correlation between an amendment's cation exchange capacity and the inhibition of CO(2) evolution caused by Cu and Zn. The ability of the organic materials to enhance respiration in a soil from the vicinity of a Pb/Zn mine was also evaluated, by applying them to the soil at rates of 1, 10 and 20%. CO(2) evolution from the contaminated soil was enhanced significantly by the addition of all of the amendments, with coir causing up to 90% enhancement at high levels of addition.     

生命至上 隐患必除——九龙坡区消防“火患”排查专项整治成效显著

3月28日部消防局召开关于加强春季防火工作暨火灾隐患排查整治电视电话会议后，九龙坡区消防支队迅速行动，积极部署，在火灾隐患普查整治工作的基础上，坚持“以人为本，生命至上，隐患必除”的理念，采取“紧紧依靠政府，建立部门执法联动、深挖派出所监督潜力和突出重点隐患整治”等手段，不断推动火灾隐患整改，取得了较好进展。     

整治消防产品市场不能“隔靴搔痒”

4月6日，沈阳汽配城一把大火又烧痛了我们敏感的神经。这场大火整整肆虐了一天一夜，1000多名消防官兵奋不顾身地参与扑救，经济损失估计上亿元。造成这起大火的原因很多，如市场内布局混乱、消防通道堵塞、消防喷淋系统老化等。也许有人认为，这场大火与消防产品干系不大。试想，如果消防喷淋系统能够正常工作，[第一段]     

Determination by high performance chromatography, steroid saponins in a biologically active food supplements containing the extract of Tribulus terrestris

Steroidal saponins are bioactive substances of Tribulus terrestris and can be used to assess the quality of raw materials and processed products from them. For this purpose has been developed the method of qualitative and quantitative determination of steroidal saponins by high performance liquid chromatography with spectrophotometric and mass-selective detection and optimal conditions of sample preparation (70% methanol extraction with sonication and heating); also has been studied steroidal saponins composition of Tribulus terrestris (protodioscin, tribulosaponin B, metilprotodiostsin, terrestrozin H, prototribestin, gracillin and others were found).     

Error analysis of nonconstant admittivity for MR-based electric property imaging

Magnetic resonance electrical property tomography (MREPT) is a new imaging modality to visualize a distribution of admittivity γ = σ+iωε inside the human body where σ and ε denote electrical conductivity and permittivity, respectively. Using B1 maps acquired by an magnetic resonance imaging scanner, it produces cross-sectional images of σ and ε at the Larmor frequency. Since current MREPT methods rely on an assumption of a locally homogeneous admittivity, there occurs a reconstruction error where this assumption fails. Rigorously analyzing the reconstruction error in MREPT, we showed that the error is fundamental and may cause technical difficulties in interpreting MREPT images of a general inhomogeneous object. We performed numerical simulations and phantom experiments to quantitatively support the error analysis. We compared the MREPT image reconstruction problem with that of magnetic resonance electrical impedance tomography (MREIT) to highlight distinct features of both methods to probe the same object in terms of its high- and low-frequency conductivity distributions, respectively. MREPT images showed large errors along boundaries where admittivity values changed whereas MREIT images showed no such boundary effects. Noting that MREIT makes use of the term neglected in MREPT, a novel MREPT admittivity image reconstruction method is proposed to deal with the boundary effects, which requires further investigation on the complex directional derivative in the real Euclidian space [Formula: see text].     

Alginate fibers as photocatalyst immobilizing agents applied in hybrid photocatalytic/ultrafiltration water treatment processes

Ca alginate polymer fibers were developed to effectively disperse and stabilize an efficient photocatalyst such as AEROXIDE^® TiO₂ P25 in their matrix. The biopolymer/TiO₂ fibers were prepared and tested either in the hydrogel non-porous form or in the highly porous aerogel form prepared by sc-CO₂ drying. Batch photocatalytic experiments showed that the porous, Ca alginate/TiO₂ fibers, exhibited high efficiency for the removal of methyl orange (MO) from polluted water. In addition, their high porosity and surface area led to high MO degradation rate which was faster than that observed not only for their non-porous analogs but also of the bulk P25 TiO₂ powder. Specifically, 90% removal for 20 μM MO was achieved within 220 min for the porous sc-CO₂ dried fibers while for their non-porous analogs at 325 min. The corresponding value (at 60 μM MO) for the porous sc-CO₂ dried fibers was 140 min over 240 min for the AEROXIDE^® TiO₂ P25 as documented in the literature. Furthermore the composite alginate/photocatalyst porous fibers were combined with TiO₂ membranes in a continuous flow, hybrid photocatalytic/ultrafiltration water treatment process that led to a three fold enhancement of the MO removal efficiency at 400 ml of 20 μM MO total treated volume and to dilution rather than condensation in the membrane retentate as commonly observed in filtration processes. Furthermore the permeability of the photocatalytic membrane was enhanced in the presence of the fibers by almost 20%. This performance is achieved with 26 cm² and 31 cm² of membrane and stabilized photocatalyst surfaces respectively and in this context there is plenty of room for the up-scaling of both membranes and fibers and the achievement of much higher water yields since the methods applied for the development of the involved materials (CVD and dry-wet phase inversion in a spinning set-up) are easily up-scalable and are not expected to add significant cost to the proposed water treatment process.     

The method of the simultaneous determination of the citrinin and ochratoxin A content in cereals and cereal products

The simplifyed method of simultaneous determination of the citrinin (CT) and ochratoxin A (OTA) in cereals is described. The extraction of mycotoxins was carried out by small volumes of solvents (water/aceton/hexane) without additional sample clean up and concentration. The extracts were analysed by HPLC using mixture of methanol/ethylacetate/phosphoric acid, pH 2.2 as a mobile phase and fluorescence detection (lamda ex 330 nm, lamda em 495 nm). The reliability and reproducibility of results were improved by usage of internal standard--methyl-derivative of ochratoxin A. Average recovery of CT and OTA was 70%, relative standard deviation 12% and 7%, respectively, limit of detection 0.003 mg/kg.