Selective catalytic reduction of NO with NH3 over Nb2O5-promoted V2O5/TiO2 catalysts

In contrast to previous claims, the addition of niobia to catalysts containing vanadia supported on titania resulted in much enhanced activity for low-temperature SCR of NO with NH₃ only at low vanadia loadings. Niobia promoted catalysts could also be demonstrated to show higher selectivities to N2, especially at high temperatures and low vanadia loading. This enhancement of the activity cannot be explained only on the basis of the observation that niobia stabilized the surface area of the catalyst: calculations of the activation energy suggest that a different mechanism of the reaction may be at work at low vanadia loadings.     

Gamma-irradiation of individual cholesterol oxidation products

Cholesterol and seven of its oxidation products in aqueous suspensions of multilamellar vesicles or sonicated aqueous suspensions were subjected individually to ^7;-radiation (10 KGy) at 0–4
76;C in air, N₂ or N₂O. All compounds underwent some changes under the influence of radiation. β-Epoxide (cholesterol 5β,6β-epoxide) and, to a much lesser extent, α-epoxide (cholesterol 5α,6α-epoxide) were converted in low yield to 6-ketocholestanol (5α-cholestan-3β-ol-6-one). 7β-Hydroxycholesterol (cholest-5-ene-3β,7β-diol) and, to a lesser extent, 7α-hydroxycholesterol (cholest-5-ene-3β,7α-diol) gave low yields of 7-ketocholestanol (5α-cholestan-3β-ol-7-one). The latter compound also was obtained by irradiation of 7-ketocholesterol (cholest-5-ene-3β-ol-7-one). 6-Ketocholestanol and 7-ketocholestanol are potential biomarkers for irradiated meat and poultry.     

7A52铝合金搅拌摩擦焊接头第二相的形貌及相组成

为进一步研究高强铝合金搅拌摩擦焊接头的性能,必须对接头中的第二相进行明确表征.采用光学显微镜、扫描电镜及能谱、透射电镜对7A52铝合金搅拌摩擦焊接头第二相的种类、数量、形状、大小、分布进行了观察.结果表明,基材的第二相组成主要为沿轧制方向分布的粗大Al₆（Mn,Fe）和Mg₂Si,细小的η′相（MgZn₂）和η相（MgZn₂）,其他各区均弥散分布αAl₁₂（Fe,Mn）3Si和Mg₂Si.动态再结晶区主要包含T相（Mg₃₂（Al,Zn）49）、Al₆Mn、S相（Al₂CuMg）.热机影响区晶界处连续分布条带状A_l6Mn,η相发生粗化,分布在晶粒内部,由原来的长条状破碎成椭球状,晶界有无沉淀析出带.热影响区与基材相比,η′相形貌和分布状况并无明显变化,η相明显粗化;与热机影响区相比,Al₆Mn仍然在晶界处呈条带状分布,晶内有S相存在.     

Kinetic analysis of NO-sensitized methane oxidation

The role of NO-sensitized oxidation during the product-gas entrainment of a low-NO_x, multi-jet, natural gas burner is investigated. A detailed kinetic mechanism for the NO-sensitized oxidation of CH₄, consisting of 483 reactions and 69 species, is used for the kinetic analysis. An eigenvalue-eigenvector decomposition is performed on normalized sensitivity coefficients to study the important reactions using principal component analysis (PCA), and the loadings corresponding to the largest eigenvalue are used to identify the reaction pathways of NO-sensitized oxidation. The main reaction pathway is most strongly affected by the temperature profile and equivalence ratio. Also, a reduced kinetic scheme of 110 reactions and 47 species is developed by eliminating reactions with small loadings. The temporal evolution of reactions is investigated using functional PCA, in which the functional loadings reflect the importance of reactions as a function of time. A discretization approach is used to perform the functional PCA.     

Identification of Two Sex Pheromone Components of the Potato Aphid, Macrosiphum euphorbiae (Thomas)

Females of the potato aphid Macrosiphum euphorbiae exhibit typical calling behavior, with virgin female oviparae raising their back legs off the substrate to release sex pheromone from glands on the tibia. Airborne collections from calling oviparae were analyzed by GC and GC-MS to determine if, like the majority of aphids examined to date, they produced (1R,4aS,7S,7aR)-nepetalactol (1) and (4aS,7S,7aR)-nepetalactone (2). Both components were present and produced in ratios that varied with age from 4:1 to 2:1. The relative stereochemical configurations of these components were determined by GC-coinjection of the aphid-derived sample with synthetic standards on both HP-1 and DB-Wax GC columns. The absolute stereochemical configuration of the nepetalactol (determined from approximately 15 microg of material in an air entrainment sample) was determined as (1R,4aS,7S,7aR)-1 by derivatization of the aphid sample with (S)-(+)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl chloride (Mosher's acid chloride) to generate a diastereoisomer that was compared to synthetic samples by NMR spectroscopy and GC. In bioassays in the wind tunnel, M. euphorbiae males responded to potato plants with oviparae but not to unattacked plants or those infested with parthenogenetically reproducing apterae. In no-choice laboratory bioassays, the same level of male response was observed to virgins and to the 3:1-5:1 synthetic blends of nepetalactol (1):nepetalactone (2). However, the time taken to reach the source was significantly less to virgin females than to the synthetic pheromone blends. In all cases, males walked rather than flew to the source. Males showed lower responses to a 1:1 synthetic mixture and did not respond to either of the components when presented alone. Under field conditions, few M. euphorbiae males were captured in traps baited with different ratios of the synthetic pheromone. Possible reasons for the different responses under laboratory and field conditions are discussed.     

Catalytic behaviour of La4PdO7 based catalysts when exposed to car exhaust conditions

The catalytic properties of ex situ prepared La₄PdO₇ were studied under automotive exhaust conditions. Monophasic La₄PdO₇ was deposited onto7137242p24741/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-Al₂O₃ coated cordierite monoliths and light-off curves were recorded under oxidising and reducing conditions. Initially the catalytic activity for oxidation of CO and C₃H₆ and reduction of NO was low but after the catalyst had been exposed to a reducing atmosphere of simulated car exhaust composition at 600°C a three-way catalytic behaviour was obtained with aT ₅₀ value of about 340°C. Using oxidising conditions and a similar activation procedure, a catalyst with CO and C₃H₆ oxidation activity (T ₅₀=405° C) but minor activity for reduction of NO was obtained. This behaviour is interpreted in terms of La₄PdO₇ being decomposed and nanosized PdO particles being formed; these in turn are reduced to Pd and Pd is the catalytically active component in the catalyst. These conclusions are supported by X-ray diffraction, infrared spectroscopy, scanning and transmission electron microscopy studies combined with element analysis of freshly prepared and thermally activated catalysts.     

Identification of sex pheromones of two sibling species in dingy cutworm complex,Feltia jaculifera (GN.) (Lepidoptera: Noctuidae)

The sex pheromone components of the two sibling species of the dingy cutworm that occur on the prairies of western Canada were identified in abdomen-tip extracts from calling female moths. Three monounsaturated acetates, (Z)-7-dodecenyl acetate, (Z)-9-tetradecenyl acetate, and (Z)-11-hexadecenyl acetate, are common to both species in ratios of 100758.gif" alt="ratio" align="BASELINE" BORDER="0">13758.gif" alt="ratio" align="BASELINE" BORDER="0">3 for species A and 0.3758.gif" alt="ratio" align="BASELINE" BORDER="0">0.5758.gif" alt="ratio" align="BASELINE" BORDER="0">100 for species B. The most effective synthetic blends for the attraction of male moths in the field consisted of these three components in ratios of 10758.gif" alt="ratio" align="BASELINE" BORDER="0">1758.gif" alt="ratio" align="BASELINE" BORDER="0">0 at 8.8g/lure for species A and 1758.gif" alt="ratio" align="BASELINE" BORDER="0">1758.gif" alt="ratio" align="BASELINE" BORDER="0">2000 at 500g/lure for species B. The addition of Z5-12758.gif" alt="ratio" align="BASELINE" BORDER="0">Ac to either blend reduced the catches and the addition of Z7-12758.gif" alt="ratio" align="BASELINE" BORDER="0">OH orZ11-16758.gif" alt="ratio" align="BASELINE" BORDER="0">OH to the three-component blend reduced the catches of species B males. The species are morphologically indistinguishable, but the identity of the males attracted to the synthetic blends could be confirmed by their antennal responses to a test blend of the three components using a GC-EAD system. Both synthetic attractant blends are competitive with females and will be useful for studying the distribution, biology, and relative abundances of the two species.Contribution no. 3879005 of the Lethbridge Research Station.     

LabVIEW与S7-200PLC基于PPI协议通讯的设计与实现

针对工控领域中实时监控S7-200PLC状态和显示、处理其采集数据的需求,使用LabVIEW作为开发平台,通过调用VISA接口函数,在分析PPI协议读写指令的基础上,实现了LabVIEW与PLC串口通讯。     

基于CY7C68013的面阵CCD图像传输系统设计

针对面阵CCD图像的特点,提出了一种基于CY7C68013的图像实时传输系统.系统从面阵CCD模块中直接荻取数字图像信号,利用CPLD控制图像数据的时序,以CY7C68013作为数据传输的核心,实现了基于USB2.0的高速图像信号传输.该系统结构简单,性能稳定,实用性强.     

基于网络的河流水质远程监测系统设计及应用

针对河流水质传统检测方式的不足之处,本文把计算机技术、PLC网络技术与就地的水质检测仪器结合起来,组建了一个基于网络的河流水质远程监测系统。此系统的网络有两层,第一层网络是由S7-200与SC1000组成的Modbus网络,第二层网络是由检测站的控制器与监控室的PC机组成。通过网络,系统实现了远程水质检测和数据采集,通过组态王V6.52,实现了数据的集中分析处理。