Acoustical tomography based on the second-order Born transformperturbation approximation

Reconstruction algorithms and their numerical examples of acoustical tomography based on the second-order Born transform perturbation approximation are presented. The reconstruction algorithms in the second-order Born approximation are similar in form to those in the first-order Born approximation. Replacing the angular spectrum of the scattered wave in the first-order case by the result of applying a first-order operator to the angular spectrum of the scattered wave or applying a second-order operator to the angular spectrum of the incident wave leads to the second-order reconstruction algorithms. Also, comparisons of reconstruction algorithms of the first- and second-order Born approximations are given, and they show that the second-order Born approximation algorithms have a distinct advantage over the first-order approximations in many cases     

川东地区长兴组缝洞型储层的识别

本文针对四川东部地区上二叠统长兴组(P_2~2)缝洞型储层的低孔、低渗及非均质性等特点,分析了影响这类储层识别的主要因素,提出了利用现有的地球物理测井手段定性识别储层的指标和定量综合识别储层的方法,这可望提高测试成功率。     

Synthesis and release of ATP by soluble mitochondrial F1 in complex with its inhibitor protein during dimethylsulfoxide-water transitions

Soluble mitochondrial F1 and F1 in complex with the natural ATPase inhibitor protein (F1-IP) catalyze the spontaneous synthesis of [gamma-32P]ATP from medium [32P]phosphate and enzyme-bound ADP when incubated in media with dimethylsulfoxide (Me2SO); under these conditions, the synthesized [gamma-32P]ATP is not released into the media, it remains tightly bound to the enzymes [Gómez-Puyou, A., Tuena de Gómez-Puyou, M. & de Meis, L. (1986) Eur. J. Biochem. 159, 133-140]. Some of the characteristics of the synthesized [gamma-32P]ATP were studied in F1 and F1-IP (ATPase activities of 70 and 1-3 micromol x min(-1) x mg(-1), respectively). In Me2SO media, gamma-phosphate of synthesized ATP in F1 or F1-IP exchanges with medium phosphate. From the rates of the exchange reaction, the half-times for hydrolysis of the synthesized ATP in F1 and F1-IP were calculated: 45 min and 58 min for F1 and F1-IP, respectively. The course that synthesized [gamma-32P]ATP follows after dilution of the Me2SO synthetic mixture with aqueous buffer was determined. After dilution, the half-life of synthesized ATP in F1 was less than 1 min. In F1-IP, ATP was also hydrolyzed, but at significantly lower rates. In F1-IP, dilution also produced release of the synthesized [gamma-32P]ATP. This was assayed by the accessibility of [gamma-32P]ATP to hexokinase. About 25% of [gamma-32P]ATP synthesized in F1-IP, but not in F1, was released into the media after dilution with aqueous buffer that contained 20 mM phosphate. Release of tightly bound ATP required the binding energy of phosphate and solvation of F1-IP, however, the particular kinetics of F1-IP were also central for medium ATP synthesis in the absence of electrochemical H+ gradients.     

A three-dimensional non-epitaxial atomistic growth model for thin-film deposition: effect of surface mobility

The effect of the atomic mobility on a film surface has been studied by using a three-dimensional atomistic thin-film deposition model which simulates three-dimensional thin-film images, surface profiles and cross-sectional area pictures. In addition, quantitative results of surface RMS roughness, average film thickness, atomic coordination number and its distribution, and solid fraction of the deposited thin films, were obtained from the simulations. When the film surface mobility increased from 0.3 to 3.0, RMS roughness decreased from 6.5 to 1.1, solid fraction increased from 0.27 to 0.56 and average film thickness decreased from 40 to 28, due to the reduction of the voids within the film. The full-width half magnitude of the atomic coordination distribution became narrower indicating the increased degree of crystallization. With increase in surface mobility crossing the boundary to 1.5, the film evolved from a porous or loose columnar structure with voids, to a densely packed fibrous grain structure which can be categorized by the zone structure models.     

Pressure release of containments during severe accidents in Switzerland

As required by the Swiss Federal Nuclear Safety Inspectorate (HSK) all Switzerland's five nuclear power plants have to install a containment filtered venting system. The integrity of the containment (the last barrier for radioactive releases to the environment) can be threatened by overpressure due to inadequate heat removal. Design requirements have been provided for a specific class of severe accident scenarios. In general the capacity of the system is considered sufficient if it is able to vent the steam production corresponding to a decay heat level of 1% of the thermal reactor power. The mitigation capacity for the reduction of released radioactive material is specified by a retention factor of 1000 for aerosols to prevent or limit a long term ground contamination and a factor of 100 for elementary iodine for prevention or limiting of thyroid doses and to avoid short term evacuation. Besides existing requirements for design, maintenance and operation, additional claims such as passivity and operability at any pressure conditions inside the containment have to be met. Passivity implies that the system can be initiated after a severe accident without any operator action. The system also has to allow early manual venting. Various filtered venting systems are presently available. The nuclear power plants of Beznau, Gosgen, Leibstadt and Muhleberg have already selected such systems and already implemented them or are going to install them step by step. Beznau selected the Sulzer-EWI system which is using a water pool with nozzles-baffle plates and mixing elements to achieve the required filtration of the aerosols. In both Beznau units, the systems are installed and in standby mode. Gosgen, a pressurized water reactor as well as Beznau, is going to implement a filter system developed by Siemens-KWU, known as sliding pressure venting process, combining a venturi scrubber in a water pool and a mesh filter. The boiling water reactor of Leibstadt also selected the same system as Beznau while Müheberg choose the ABB system but not in the common design. The venturi pipes are thereby integrated in the water pool of the outer torus. The system in all five nuclear power plants is fully operable and in standby mode since December 1993.     

Measurement of the dielectric constant of highly absorbing polar liquids at microwave frequencies

Nomograms are given for claculating the dielectric constant and dielectric loss of polar liquids by measuring the standing wave ratio for an infinitely thick layer of fluid and the layer thickness at which wave reflection is minimum. Translated from Izmeritel'naya Tekhnika, No. 2, pp. 46–47, February, 1996.     

COIL中BHP浓度对发生O_2(~1△)的影响

本文实验研究了BHP的浓度对产生O2（1△）的影响。实验结果表明：当BHP浓度大于3.5M时，Cl2利用率以及O2（1△）的产率将不依赖于BHP浓度的变化而变化，同时，实验结果表明，使用低浓度的BHP对COIL的操作是可行的。     

Cellular UDP-glucose deficiency caused by a single point mutation in the UDP-glucose pyrophosphorylase gene

We previously isolated a mutant cell that is the only mammalian cell reported to have a persistently low level of UDP-glucose. In this work we obtained a spontaneous revertant whose UDP-glucose level lies between those found in the wild type and the mutant cell. The activity of UDP-glucose pyrophosphorylase (UDPG:PP), the enzyme that catalyzes the formation of UDP-glucose, was in the mutant 4% and in the revertant 56% of the activity found in the wild type cell. Sequence analysis of UDPG: PP cDNAs from the mutant cell showed one missense mutation, which changes amino acid residue 115 from glycine to aspartic acid. The substituted glycine is located within the largest stretch of strictly conserved residues among eukaryotic UDPG:PPs. The analysis of the cDNAs from the revertant cell indicated the presence of an equimolar mixture of the wild type and the mutated mRNAs, suggesting that the mutation has reverted in only one of the alleles. In summary, we demonstrate that the G115D substitution in the Chinese hamster UDPG:PP dramatically impairs its enzymatic activity, thereby causing cellular UDP-glucose deficiency.     

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