光稳定性拟除虫菊酯的应用研究 Ⅲ.拟除虫菊酯—杀虫脒合剂棉虫防治应用领域的研究——(1)杀灭菊酯—杀虫脒合剂对棉蚜的增效作用研究初报

根据拟除菊酯—杀虫脒合剂对棉铃虫等多种夜蛾科幼虫具有增效作用特性(7,14),我们通过室内触杀毒力试验和两个棉区一、二年田间药效试验,初步发现杀灭菊酯—杀虫脒盐酸盐(1:5—10)合剂对棉蚜也具有明显的增效效果。通过合剂的应用,杀灭菊酯高效控制棉蚜的经济施药剂量可较大幅度降低,这对促进棉花生产、降低进成本具有现实意义。现初步报导于下。     

Carbonate Rocks: Cleaning with Suspensions of Hydrogen-Ion Exchange Resin

The surface of carbonate rocks may be cleaned by etching or polishing or both, with hydrogen-ion exchange resin. This treatment reveals details in texture and fossil morphology so clearly that thin sections may be often dispensed with. Of four cleaning methods, (i) allowing resin to settle around the sample, (ii) stirring with a magnetic stirrer, (iii) agitating with an ultrasonic generator, and (iv) directing a jet stream at the sample, the first method was best for large specimens and the second method was best for well cuttings and chips.     

Comparison of Methods for Amylose Screening Among Amylose‐Extender (ae) Maize Starches from Exotic Backgrounds

Breeding for high‐amylose corn requires a rapid analytical method for determining starch amylose so that generating wet chemistry values does not pose a major limitation in the volume of materials that can be screened. Two methods for determining apparent amylose content (AAC) were examined and compared with an iodine‐binding method involving the solubilization of isolated starch in a sodium hydroxide solution (method 1). These methods included one based on near‐infrared transmittance spectroscopy (NIRT) (method 2) and another iodine‐binding method involving the solubilizing of starch from ground whole corn with a DMSO‐iodine solution (method 3). These methods were chosen because, aside from initial set up costs, they are relatively rapid and inexpensive to perform. The materials evaluated consisted of various exotic corn populations including plant introductions and experimental materials generated from the Germplasm Enhancement of Maize (GEM) project. Crosses were made between these materials and a Corn Belt dent hybrid (OH43 × H99) converted with the amylose‐extender (ae) allele. Grain from F2 ears, presumed to be homozygous for the ae allele based on visual selection of mutant kernels on F1 ears from which they were planted, were then evaluated to identify possible modifiers of ae conditioning high starch AAC. From a total of 1,006 F2 ears, a core set consisting of 155 samples was established and only these were subjected to starch AAC analysis, using all three methods to compare the methods. Method 2 showed poor correlation to method 1 (r = 0.88), however, NIRT did appear to discriminate between samples converted to ae vs. those with a normal or possibly segregating endosperm type. Method 3 showed a slightly better correlation with method 1 (r = 0.92) and appeared to more fully discriminate among samples with AAC values >65% from those at ≈55%. Results from this study suggest that NIRT may be useful when a quick screening method is needed to discriminate mutant from nonmutant genotypes within grain samples of exotic germplasm especially when visual identification is difficult. In addition, method 3 could be used to replace the more time‐consuming method 1 when trying to identify high AAC levels among ae genotypes, even though some inconsistency was observed between the two methods. Finally, this study revealed that exotic germplasm may be an important source of new modifiers to the ae allele because values as high as 70% AAC were identified.     

High Nitrite Levels off Northern Peru: A Signal of Instability in the Marine Denitrification Rate

During February and March 1985, nitrite levels along the northern (approximately 7 degrees to 10 degrees S) Peruvian coast were unusually high. These accumulations occurred in oxygen-deficient waters, suggesting intensified denitrification. In a shallow offshore nitrite maximum, concentrations were as high as 23 micromoles per liter (a record high). Causes for the unusual conditions may include a cold anomaly that followed the 1982-83 El Ni?o. The removal of combined nitrogen (approximately 3 to 10 trillion grams of nitrogen per year) within zones of new or enhanced denitrification observed between 7 degrees to 16 degrees S suggests a significant increase in oceanic denitrification.     

Novel method for the study of the population dynamics of a genetically modified microorganism in the gut of the earthworm Lumbricus terrestris

Summary A laboratory microcosm study was used to investigate the survival and population dynamics of genetically modified microorganisms (GMM) in the gut of Lumbricus terrestris. Three methods of axenic earthworm production were investigated. An antibiotic mixture of streptomycin and cycloheximide was introduced either passively, mixed with sterile soil or cellulose, or actively, by teflon catheter. Worms treated by all methods lost weight but this was least for the catheter method which was also the only method to produce axenic earthworms. Axenic earthworms were used to determine the effect of competition with indigenous gut bacteria on ingested GMM. The GMM used was Pseudomonas fluorescens, strain 10586/FAC510, with chromosomally inserted Lux genes for bioluminescence, and chromosomal resistance to rifampicin. The bacteria were grown up to the mid-exponential phase before inoculation into earthworms. Bacteria in faecal material were enumerated by dilution plate counting using selective agar. The GMM were re-isolated from the casts of both antibiotic-treated and untreated earthworms. Lower concentrations of GMM and higher concentrations of indigenous bacteria in the casts of untreated compared to antibiotic-treated earthworms suggested that competition is a fundamental control on population dynamics of the introduced bacterial inocula ingested by earthworms.The catheter method, developed in this study, is proposed as a technique to contribute to the risk assessment of environmental release of GMM.     

Colossal Magnetoresistance Without Mn3+/Mn4+ Double Exchange in the Stoichiometric Pyrochlore Tl2Mn2O7

Structural analysis from powder neutron and single-crystal x-ray diffraction data for a sample of the Tl2Mn2O7 pyrochlore, which exhibits colossal magnetoresistance (CMR), shows no deviations from ideal stoichiometry. This analysis gives an Mn-O distance of 1.90 angstroms, which is significantly shorter than the Mn-O distances (1.94 to 2.00 angstroms) observed in phases based on LaMnO3 perovskites that exhibit CMR. Both results in Tl2Mn2O7 indicate oxidation states very close to Tl23+Mn24+O7. Thus, Tl2Mn2O7 has neither mixed valence for a double-exchange magnetic interaction nor a Jahn-Teller cation such as Mn3+, both of which were thought to have an important function in CMR materials. An alternate mechanism for CMR in Tl2Mn2O7 based on magnetic ordering driven by superexchange and strong spin-fluctuation scattering above the Curie temperature is proposed here.     

Abnormal spindle protein, Asp, and the integrity of mitotic centrosomal microtubule organizing centers

The product of the abnormal spindle (asp) gene was found to be an asymmetrically localized component of the centrosome during mitosis, required to focus the poles of the mitotic spindle in vivo. Removing Asp protein function from Drosophila melanogaster embryo extracts, either by mutation or immunodepletion, resulted in loss of their ability to restore microtubule-organizing center activity to salt-stripped centrosome preparations. This was corrected by addition of purified Asp protein. Thus, Asp appears to hold together the microtubule-nucleating gamma-tubulin ring complexes that organize the mitotic centrosome.