The mealybug chromosome system I: unusual methylated bases and dinucleotides in DNA of a Planococcus species

The methylation status of the nuclear DNA from a mealybug, a Planococcus species, has been studied. Analysis of this DNA by High Performance Liquid Chromatography and Thin Layer Chromatography revealed the presence of significant amounts of 5--methylcytosine. Since analysis of DNA methylation using the Msp I/Hpa II system showed only minor differences in susceptibility of the DNA to the two enzymes, it seemed possible that 5-methylcytosine (5mC) occurred adjacent to other nucleotides in addition to its usual position, next to guanosine. This was verified by dinucleotide analysis of DNA labelledin vitro by nick translation. These data show that the total amount of 5-methylcytosine in this DNA is slightly over 2.3 mol %, of which 0.61% occurs as the dinucleotide 5mCpG, 0.68% as 5mCpA, 0.59% as 5mCpT and 0.45% as 5mCpC. 5mCpG represents approximately 3.3% of all CpG dinucleotides. The experimental procedure would not have permitted the detection of 5mCp5mC, if it occurs in this system. Unusually high amounts of 6-methyladenine (approximately 4 mol %) and 7-methylguanine (approximately 2 mol %) were also detected, 6-methyladenine and 7-methylguanine occurred adjacent to all four nucleotides. The total G+C content was 33.7% as calculated from dinucleotide data and 32.9% as determined from melting profiles

Valency of rare earths in RIn3 and RSn3: Ab initio analysis of electric-field gradients

In RIn3 and RSn3 the rare earth (R) is trivalent, except for Eu and Yb, which are divalent. This was experimentally determined in 1977 by perturbed angular correlation measurements of the electric-field gradient on a 111Cd impurity. At that time, the data were interpreted using a point charge model, which is now known to be unphysical and unreliable. This makes the valency determination potentially questionable. We revisit these data, and analyze them using ab initio calculations of the electric-field gradient. From these calculations, the physical mechanism that is responsible for the influence of the valency on the electric-field gradient is derived. A generally applicable scheme to interpret electric-field gradients is used, which in a transparent way correlates the size of the field gradient with chemical properties of the system.Comment: 10 page

Improving agricultural knowledge management: The AgTrials experience

Background: Opportunities to use data and information to address challenges in international agricultural research and development are expanding rapidly. The use of agricultural trial and evaluation data has enormous potential to improve crops and management practices. However, for a number of reasons, this potential has yet to be realized. This paper reports on the experience of the AgTrials initiative, an effort to build an online database of agricultural trials applying principles of interoperability and open access. Methods: Our analysis evaluates what worked and what did not work in the development of the AgTrials information resource. We analyzed data on our users and their interaction with the platform. We also surveyed our users to gauge their perceptions of the utility of the online database. Results: The study revealed barriers to participation and impediments to interaction, opportunities for improving agricultural knowledge management and a large potential for the use of trial and evaluation data. Conclusions: Technical and logistical mechanisms for developing interoperable online databases are well advanced. More effort will be needed to advance organizational and institutional work for these types of databases to realize their potential

The Present and Future Role of Insect-Resistant Genetically Modified Maize in IPM

Commercial, genetically-modified (GM) maize was first planted in the United States (USA, 1996) and Canada (1997) but now is grown in 13 countries on a total of over 35 million hectares (\u3e24% of area worldwide). The first GM maize plants produced a Cry protein derived from the soil bacteriumBacillus thuringiensis (Bt), which made them resistant to European corn borer and other lepidopteran maize pests. New GM maize hybrids not only have resistance to lepidopteran pests but some have resistance to coleopteran pests and tolerance to specific herbicides. Growers are attracted to the Btmaize hybrids for their convenience and because of yield protection, reduced need for chemical insecticides, and improved grain quality. Yet, most growers worldwide still rely on traditional integrated pest management (IPM) methods to control maize pests. They must weigh the appeal of buying insect protection “in the bag” against questions regarding economics, environmental safety, and insect resistance management (IRM). Traditional management of maize insects and the opportunities and challenges presented by GM maize are considered as they relate to current and future insect-resistant products. Four countries, two that currently have commercialize Bt maize (USA and Spain) and two that do not (China and Kenya), are highlighted. As with other insect management tactics (e.g., insecticide use or tillage), GM maize should not be considered inherently compatible or incompatible with IPM. Rather, the effect of GM insect-resistance on maize IPM likely depends on how the technology is developed and used

Novel behaviour of iron moments in new magnetic systems RuFeSi and RuFeB

New magnetic systems RuxFeySi and RuxFey are reported having extremely unusual properties like small ordered moments ≈0.5 μB, large ordering temperatures Tm ≈ 400-800 K and surprising lack of hyperfine field (HF) at Fe for temperatures > T* (≈0.2 Tm) in spite of bulk magnetization in the system. The HF appears at Fe below T* implying evolution of local moments far below Tm

Reliable Detection of Individuals Seropositive for the Human Immunodeficiency Virus (HIV) by Competitive Immunoassays Using \u3ci\u3eEscherichia coli\u3c/i\u3e - Expressed HIV Structural Proteins

We molecularly cloned the gag and env genes of the human immunodeficiency virus (HIV) and expressed fragments of these genes in Escherichia coli. Using the recombinant core and envelope proteins, we developed two competitive immunoassays (CIAs). Samples that recognized either the envelope or core proteins were considered positive for antibodies to HIV. This test system was comparable with western blot in detecting antibodies in patients with AIDS or AIDS-related complex that were repeatably reactive in the HIV screening test. All 360 individuals who were positive by western blot were positive by the CIA. A total of 844 samples repeatably reactive by an ELISA screening test were negative both by western blot and by the CIA; 48 samples positive by ELISA, but negative or indeterminate by western blot, were positive by the CIA. Alternate research procedures verified the positivity of these individuals. These data indicate that the CIA described here may be useful as an adjunct or alternative to the western blot

A new and unique Eu-based mixed valence system: EuPd<SUB>2</SUB>Si<SUB>2</SUB>

Reports the results of studies on a new and a very interesting intermediate valence (IV) material EuPd2Si2, which exhibits some unique features not observed so far in any Eu-based IV system. The magnetic susceptibility exhibits a very clear maximum and the isomer shift shows an unusually large temperature dependence in the interval 120-200K

Thermally induced transition from itinerant to local behaviour of Fe moment in new alloys RuFeSi and RuFeB

A new class of magnetic systems, RuxFeySi and RuxFeyB, have been identified in which the magnetic momwnt at Fe, as sensed by 57Fe Mossbauer effect, is seen to evolve at a characteristic temperature far below the magnetic ordering temperatures