The reflectance method for testing the effectiveness of fungicides against surface mould growth on materials: I. Wood

Summary An instrumental method for the measurement of the toxic value of preservatives against mould fungi on wood and wood products was tested as an alternative to the widely used visual method with its inherent disadvantage of subjectivity. The new criterion of effectiveness to be used was light reflectance as measured by either the Zeiss photometer (Leukometer) or the Zeiss spectrophotometer (Spekol 10) fitted with the Rd/0 reflectance adapter. Sodium pentachlorophenate and the WR-3 (quaternary ammonium compound), applied to pine and birch wood samples were tested for effectiveness against five species of fungi capable of causing surface moulding. Although the reflectance method was more laborious, the results obtained seem to be better than those obtained by the visual method. The proposed method appears to be of practical value in eliminating difficulties involved in the subjective assessment of both the intensity of surface growth and the effectiveness of the wood preservatives themselves.Paper sponsored by the State Enterprise of Conservation of Fine Arts Objects, Warszawa ul. Zielna 3The authors thank Dr. J. D. Thornton, CSIRO Division of Forestry and Forest Products, Highett, Australia, for kindly correcting the English text of this paper     

Effects of Culture Area,Stocking Density,and Shrimp and Fish Polyculture on the Cost Efficiency of Hard Clam,Meretrix meretrix,Culture: A Case Study of Hard Clam Farms in Yunlin,Taiwan

Using the hard clam farms in Yunlin, Taiwan as examples, this study analyzes the effects of culture area, stocking density, and shrimp and fish polyculture on the cost efficiency (CE) of hard clam farming. A data envelopment analysis (DEA) is used to estimate the farms' technical efficiency (TE), allocative efficiency (AE), and CE values. The findings show that the mean TE, AE, and CE values of hard clam farms are 0.74, 0.57, and 0.43, respectively. The TE value is higher than the AE value, which indicates that cost inefficiency is mainly attributable to poor AE. Tobit regression results suggest that there are positive relationships between CE and both culture area and operator experience. Hard clam stocking density and age of the operators have negative effects on CE. Hard clam culture areas larger than 2 ha and a stocking density of 1.1–1.2 million hard clams per hectare have higher CEs than smaller culture areas and smaller or larger stocking densities. The use of sand shrimp, white shrimp, kuruma shrimp, and grass shrimp for polyculture and the use of milkfish and silver sea bream for polyculture are both associated with high CEs.     

Construction of mouse ESC line stably expressing Pdx1 by Tet-On system

AIM To construct the mouse embryonic stem cell （ESC） line with stable pancreatic and duodenal homeobox 1 （Pdx1） expression by Tet-On system, which may lay a foundation for further research on the differentiation of Pdx1⁺ definitive endoderm cells into pancreatic cells. METHODS The Pdx1-overexpressing lentiviral vector with green fluorescent protein marker and puromycin resistance was constructed by Tet-On system and was used to infect the mouse ESC. The cells were divided into 3 groups： blank control group （ESC group）, empty lentivirus control group （PDX1^- ESC group） and Pdx1 lentivirus transfection group （PDX1⁺ ESC group）. Flow cytometry was used to detect the transfected cells after screening by doxycycline （DOX）. The function of Tet-On system and the expression of Pdx1 gene were detected. The transfected cells in PDX1^- ESC group and PDX1⁺ ESC group were sorted by flow cytometry, and constructed ESC line with stable expression of Pdx1 and negative control ESC line were verified. RESULTS （1） The positive rates of transfected cells in PDX1^- ESC group and PDX1⁺ ESC group were 90.72% and 94.01% after screening by DOX, respectively. The positive rates of transfected cells in PDX1^- ESC group and PDX1⁺ ESC group was 97.84% and 98.13% after sorting by flow cytometry, respectively. （2） With DOX, green fluorescence was observed in PDX1^- ESC group and PDX1⁺ ESC group. The mRNA and protein expression of Pdx1 was significantly increased in PDX1⁺ ESC group （P<0.05）. Without DOX, no green fluorescence was observed in the cells of the 3 groups, and no significant difference in the mRNA and protein expression of Pdx1 was observed （P>0.05）. （3） After 3 months of cryopreservation, the cell lines still survived in resuscitation culture and were regulated by DOX. CONCLUSION Using Tet-On system, the mouse ESC line with inducible Pdx1 expression were successfully established and could be used as an effective cell model to research the differentiation of Pdx1⁺ definitive endoderm cells into pancreatic cells.     

Enhancement of protective immunity in blue gourami,Trichogaster trichopterus (Pallas), against Aeromonas hydrophila and Vibrioanguillarum by A. hydrophila major adhesin

Blue gourami, Trichogaster trichopterus (Pallas), were intraperitoneally immunized with major adhesin, a 43 kDa OMP protein isolated from fish Aeromonas hydrophila, in the presence of Freund's complete adjuvant (FCA). Three weeks later, a booster injection of adhesin without FCA was administered. Control group fish were similarly treated with phosphate‐buffered saline (PBS) and FCA. Results showed that anti‐adhesin serum obtained from fish after booster immunization exhibited very strong ability in agglutinating bacterial cells. Although this antiserum had no bactericidal effect, it could significantly inhibit serologically different strains of A. hydrophila from invading EPC (Epithelioma papillosum of carp) cells in vitro. In addition, the proliferative response of head kidney leucocytes of these immune fish was significantly increased as compared to that of the control. The results also showed that the major adhesin could provide significant protective immunity to fish against the challenge by homologous and heterologous strains of A. hydrophila and one virulent strain of Vibrio anguillarum.     

Composition and structure of the martian upper atmosphere: analysis of results from viking

Densities for carbon dioxide measured by the upper atmospheric mass spectrometers on Viking 1 and Viking 2 are analyzed to yield height profiles for the temperature of the martian atmosphere between 120 and 200 kilometers. Densities for nitrogen and argon are used to derive vertical profiles for the eddy diffusion coefficient over the same height range. The upper atmosphere of Mars is surprisingly cold with average temperatures for both Viking 1 and Viking 2 of less than 200 degrees K, and there is significant vertical structure. Model calculations are presented and shown to be in good agreement with measured concentrations of carbon monoxide, oxygen, and nitric oxide.     

Greenhouse Effects due to Man-Mad Perturbations of Trace Gases

Nitrous oxide, methane, ammonia, and a number of other trace constituents in the earth's atmosphere have infrared absorption bands in the spectral region 7 to 14 microm and contribute to the atmospheric greenhouse effect. The concentrations of these trace gases may undergo substantial changes because of man's activities. Extensive use of chemical fertilizers and combustion of fossil fuels may perturb the nitrogen cycle, leading to increases in atmospheric N(2)O, and the same perturbing processes may increase the amounts of atmospheric CH(4) and NH(3). We use a one-dimensional radiative-convective model for the atmospheric thermal structure to compute the change in the surface temperature of the earth for large assumed increases in the trace gas concentrations; doubling the N(2)O, CH(4), and NH(3) concentrations is found to cause additive increases in the surface temperature of 0.7 degrees , 0.3 degrees , and 0.1 degrees K, respectively. These systematic effects on the earth's radiation budget would have substantial climatic significance. It is therefore important that the abundances of these trace gases be accurately monitored to determine the actual trends of their concentrations.     

基于鲁棒自适应控制策略的混合型步进电机低速伺服控制性能

针对混合型步进电机低速运行状态下脉动转矩较大的特点,应用鲁棒自适应控制策略来设计其低速伺服控制器,以实现高精度的跟踪控制性能.首先,根据混合型步进电机转矩形成的机理,揭示了其固有的脉动转矩对低速运动控制产生不利影响的动力学特征,并将它归结为两种结构不确定性,便于控制器的设计;其次,采取标准的自适应控制及其鲁棒化设计思想,借助于μ-修整策略来实现相应的控制律,确保脉动转矩的最大化补偿及伺服系统低速跟踪控制满足高性能的要求;最后对所建立的低速跟踪控制系统的性能进行了试验评估,并与作者前期的工作进行了比较,试验结果验证了其有效性与可行性.     

Isotopic fractionation of stratospheric nitrous oxide

We propose an isotopic fractionation mechanism, based on photolytic destruction, to explain the 15N/14N and 18O/16O fractionation of stratospheric nitrous oxide (N2O) and reconcile laboratory experiments with atmospheric observations. The theory predicts that (i) the isotopomers 15N14N16O and 14N15N16O have very different isotopic fractionations in the stratosphere, and (ii) laboratory photolysis experiments conducted at 205 nanometers should better simulate the observed isotopic fractionation of stratospheric N2O. Modeling results indicate that there is no compelling reason to invoke a significant chemical source of N2O in the middle atmosphere and that individual N2O isotopomers might be useful tracers of stratospheric air parcel motion.