三峡库区水库型滑坡变形监测剖面选取研究

在三峡水库蓄水和运行条件下,三峡库区水库型滑坡不同部位的地下水位和位移的改变表现出对库水位变化的敏感程度不同的特征.根据位移的变化对库水变化敏感程度的不同与监测信息量获取大小的关系,采用模糊模式识别方法对三峡库区水库型滑坡位移场变化对水库水位变化的敏感程度进行数值分区.借助水库型滑坡位移场变化敏感程度数值分区规律,提出三峡库区水库型滑坡变形监测剖面选取的一般原则.根据该原则,以三峡库区水库型滑坡——泄滩滑坡为工程实例,给出泄滩滑坡变形监测剖面的具体布置.     

Nicotine dependence subtypes among adolescent smokers: Examining the occurrence, development and validity of distinct symptom profiles.

To increase understanding of the etiology and epidemiology of nicotine dependence among adolescent smokers, the present study examined the occurrence and development of distinct nicotine dependence symptom profiles in a sample of adolescent smokers. A total of 25 secondary schools throughout the Netherlands participated in a 1-year longitudinal study. Multiple dimensions of nicotine dependence were assessed, at two time points, among 641 adolescents (aged 14–17 years) who were classified as smokers. Results showed 4 distinct, yet stable, nicotine dependence subtypes that could be characterized by quantitative as well as qualitative differences. The symptom profiles were similar for males and females but differentially associated with previously identified correlates of nicotine dependence, namely parental smoking, peer smoking, and depressive mood. Finally, differential links of the 4 subtypes were found with regard to smoking uptake and cessation. The finding of qualitative different subgroups of adolescent smokers may have important implications for intervention efforts regarding nicotine dependence and smoking cessation. Such efforts may need to be tailored to the specific subgroups’ needs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimization of supercritical CO2 extraction of dried Helichrysum italicum flowers by response surface methodology: GC-MS profiles of the extracts and essential oil

Supercritical (SC) CO₂ extraction of dried Immortelle flowers was performed at different process parameters. The optimal extraction conditions related to the yield were determined by response surface methodology (yield 4.09% at 20 MPa and 52°C). The extracts were analyzed by GC-MS and tremetone derivatives dominated: bitalin A, 12-acetoxytremetone, gnaphaliol, 1-[2-(2-methyl-2,3-dihydroxypropyl)-2,3-dihydro-1-benzofuran-5-yl]ethanone, isobutyl bitalin A, and 1-[2-(acetylprop-1-en-2-yl)-3-hydroxy-2,3-dihydro-1-benzofuran-5-yl]ethanone. Striking differences were found among the essential oil and SC-CO₂ extracts composition. The major oil compounds were γ-curcumene, α-pinene, β-selinene, α-selinene, and limonene. Mono- and sesquiterpene were found among minor constituents of the extracts. Neryl acetate was present in the extracts and essential oil.     

Hydrogen production and metabolic flux analysis of metabolically engineered Escherichia coli strains

Escherichia coli can produce H₂ from glucose via formate hydrogen lyase (FHL). In order to improve the H₂ production rate and yield, metabolically engineered E. coli strains, which included pathway alterations in their H₂ production and central carbon metabolism, were developed and characterized by batch experiments and metabolic flux analysis. Deletion of hycA, a negative regulator for FHL, resulted in twofold increase of FHL activity. Deletion of two uptake hydrogenases (1 (hya) and hydrogenase 2 (hyb)) increased H₂ production yield from 1.20 mol/mol glucose to 1.48 mol/mol glucose. Deletion of lactate dehydrogenase (ldhA) and fumarate reductase (frdAB) further improved the H₂ yield; 1.80 mol/mol glucose under high H₂ pressure or 2.11 mol/mol glucose under reduced H₂ pressure. Several batch experiments at varying concentrations of glucose (2.5–10 g/L) and yeast extract (0.3 or 3.0 g/L) were conducted for the strain containing all these genetic alternations, and their carbon and energy balances were analyzed. The metabolic flux analysis revealed that deletion of ldhA and frdABdirected most of the carbons from glucose to the glycolytic pathway leading to H₂ production by FHL, not to the pentose phosphate pathway.     

硅引起6063铝合金型材腐蚀的分析

分析了游离硅引起6063铝合金型材腐蚀的原因及由此带来的特征现象，提出了预防措施。     

Relation between phase composition of compound zone and growth kinetics of diffusion zone during nitriding of steel

The present work is devoted to an investigation of the influence of the micro-structural evolution of the compound zone (iron (carbo)nitrides zone) upon the development of hardness profiles in the diffusion zone. A different phase structure of iron (carbo)nitrides zone on steel as compared to iron, further changing with the process, may result in upsetting of the quasi-equilibrium of nitrogen concentration in the iron (carbo)nitrides zone/diffusion zone interface. This, as a result, may have an impact on the kinetics of this layer's growth. The research carried out was aimed at solving this problem. It was to evaluate the influence of (carbo)nitrides zone, with an intentionally created diametrically different phase composition, on hardness profiles in the diffusion zone. The nitrided layers were characterised by a light optical microscopy, X-ray diffraction and measurements of hardness. It was observed that the evolution of the phase structure and phase composition of the compound zone contributes significantly, regardless of nitrogen potential and temperature, to the formation of the diffusion zone and in particular to its effective thickness. It makes this complex picture of nitrided case development on steel even more intricate.     

Complex aerohydrodynamic research and the effectiveness of arresting dispersed particles for barbotage‐rotation

The design of barbotage‐rotation installation with different profiles of blades of the rotator has been created on the basis of modeling method. As a result of the complex of aerohydrodynamic research in the system “gas–liquid” carried out on the barbotage‐rotation unit, certain recommendations on the improvement of the construction and operating conditions have been developed with a view to a rise in the effectiveness of dust removal. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

GEOCHEMICAL AND GEOPHYSICAL ANOMALIES AT THE ZDANICE OIL- AND GASFIELD, SE CZECH REPUBLIC

Oil at the Zdanice field in the SE Czech Republic is reservoired at a depth of 900 m in weathered Precambrian granitoids and Lower Miocene sandstones and conglomerates. Tertiary claystones, siltstones and sandstones form the top seal. Surface gamma-ray spectrometry carried out along two profiles across the field (6,880 m and 8,335 m in length, respectively) found perceptible decreases of K, U, and Th concentrations relative to background values. This can be explained in terms of enhanced leaching of these radionuclides by groundwater acids derived from hydrocarbons. Observed increases in radon and thoron in soil gas above the oil-producing zone at Zdanice may be caused by enhanced gas emanation from U- and Th-bearing minerals decomposed by groundwater acids. Laboratory analyses of 444 samples collected from 18 shallow boreholes (20 m deep) pointed to a trend of decreasing K, U and Th concentrations above the oil-producing zone at Zdanice. Decreases in rock porosity and organic carbon content were also noted together with an increase in mineralogical density, magnetic susceptibility and sulphur content. Petrophysical analyses of 330 samples from deep boreholes showed lower values of K and U in samples from oil-producing wells. These observations of minor petrophysical alterations in rocks overlying the Zdanice oilfield may be characteristic and may be applicable to hydrocarbon exploration operations elsewhere.     

A numerical integration Green's function model for ultrasonic field profiles in mildly anisotropic media

A numerical integration technique utilizing a point source Green's function is introduced to analyze the wave behavior in transversely isotropic-type anisotropic media allowing us to make fast and accurate computations of the acoustic field. The centrifugally cast stainless steel (CCSS) used in nuclear power plants is chosen as a sample medium because of its columnar grain character leading to material anisotropy. A representative number of field profiles are computed and plotted to illustrate the quasi-longitudinal, quasi-transverse, and horizontally-polarized shear wave propagation in a transversely-isotropic medium. Phenomena such as beam skewing, beam splitting, beam focusing, unsymmetrical beams, and other anisotropic effects, some of which are already known from earlier experimental observations, emerge as a computational result of the introduced technique.