ROSAT Detection of an X-ray Shadow in the 1/4-keV Diffuse Background in the Draco Nebula

The detection by the Roentgen satellite (ROSAT) x-ray telescope of a shadow in the 1/4-kiloelectron volt (C band, 0.1 to 0.284 kiloelectron volt) cosmic diffuse background is reported. The location and morphology of the local minimum in x-rays are in clear agreement with a discrete H I cloud. The shadow is very deep with a minimum level at 50 percent of the surrounding emission; therefore, a minimum of 50 percent of the observed off-cloud flux must originate on the far side of the cloud. The analysis of H I velocity components links the cloud with the Draco nebula (distance approximately 600 parsecs); it then follows that there is significant 1/4-kiloelectron volt x-ray emission at a large distance (>400 parsecs) from the galactic plane along this line of sight. The extent of the distant emission region is uncertain, and, if it indicates the existence of a hot galactic corona, it must be patchy in nature.     

Discovery of microwave emission from four nearby solar-type g stars

Radio waves from the sun were detected 50 years ago, but the microwave detection of other single solar-type stars has remained a challenge. Here, the discovery of four solar-type radio stars is reported. These "solar twin" G stars are radio sources up to 3000 times stronger than the quiet sun. The microwaves most likely originate from a large number of relativistic electrons, possibly produced along with coronal heating, a process that is not understood. Two of the stars are younger than the sun and rotate more rapidly; the dynamo process in the stellar interior is therefore presumably more vigorous, resulting in enhanced coronal activity. One of the detections, however, is an old, metal-deficient G dwarf.     

Control of seed-borne pathogens on legumes by microbial and other alternative seed treatments

Greenhouse trials were carried out in order to test the efficacy of different seed treatments as alternatives to chemicals against Colletotrichum lindemuthianum cause of anthracnose on bean and Ascochyta spp. cause of Ascochyta blights on pea, respectively. Resistance inducers, commercially formulated microorganisms, non-formulated selected strains of different microorganisms (fungi, bacteria and yeasts) and plant extracts were applied as dry or liquid seed treatments on naturally infested seeds. Seedling emergence and disease incidence and/or severity were recorded. Almost all seed treatments turned out to be ineffective in controlling the Ascochyta infections, which is in line with the literature stating that these pathogens are difficult to control. The only alternative treatments that gave some control of Ascochyta spp. were thyme oil and a strain of Clonostachys rosea. The resistance inducers tested successfully controlled infections of bean by C. lindemuthianum. Among the formulated microorganisms, Bacillus subtilis-based formulations provided the best protection from anthracnose. Some strains of Pseudomonas putida, a disease-suppressive, saprophytic strain of Fusarium oxysporum and the mustard powder-based product Tillecur also proved to be effective against bean anthracnose. However, among the resistance inducers as well as among the other groups, certain agents caused a significant reduction of plant emergence. Different alternative seed treatments can therefore be used for the control of C. lindemuthianum on bean, while on pea only thyme oil and a strain of Clonostachys rosea showed some effectiveness against Ascochyta spp.     

Spatial analysis of Mycobacterium bovis infection in white-tailed deer (Odocoileus virginianus) in Michigan, USA

The wild white-tailed deer (Odocoileus virginianus) population in Michigan, USA, has endemic Mycobacterium bovis. We determined whether there were spatial clusters of retrospective TB cases in white-tailed deer in northeastern Michigan and identified specific factors associated with the spatial clusters. Data from hunter-harvested deer (age, gender, TB status, and geographic section) were collected by the Michigan Department of Natural Resources (MDNR) during TB surveillance from 1995 to 2002. Land cover (vegetation, land-use) and land type (soil types and drainage characteristics, landforms) described potential deer habitats. Specific locations of large-scale supplemental feeding sites were collected from the MDNR aerial surveillance program from 1997 to 2002. Analyses were conducted using principal components derived from environmental data (and other risk factors) on spatial clusters of disease (identified by the spatial scan statistic). Spatial effects were incorporated into the multivariable analyses by using a neighborhood approach. A total of 420 deer with M. bovis infection were identified from 1995 to 2002, out of 39,451 harvested deer from 3216 TRS units, and spatial clusters of cases were identified. A total of seven principal components of environmental data were generated. Clusters were associated with the presence of large expanses of deciduous forests on moraine ridges separated by low areas of forested wetlands, and the presence of many small lakes. Factors that promoted congregation of deer for extended periods of time (natural cover, access to water, and less human contact) appeared to be associated with increased odds of TB positivity. This suggests that there are specific areas where interventions can be implemented to reduce congregation of animals and disrupt the cycle of infection transmission.     

Larvicidal and residual activity of imidazolium salts against Aedes aegypti (Diptera: Culicidae)

BACKGROUND

Aedes aegypti is an important mosquito species that can transmit several arboviruses such as dengue fever, yellow fever, chikungunya and zika. Because these mosquitoes are becoming resistant to most chemical insecticides used around the world, studies with new larvicides should be prioritized. Based on the known biological profile of imidazolium salts (IS), the objective of this study was to evaluate the potential of six IS as larvicides against Ae. aegypti, as tested against Ae. aegypti larvae. Larval mortality was measured after 24 and 48 h, and residual larvicidal activity was also evaluated.

RESULTS

Promising results were obtained with aqueous solutions of two IS: 1‐n‐octadecyl‐3‐methylimidazolium chloride ( C ₁₈ MImCl ) and 1‐n‐hexadecyl‐3‐methylimidazolium methanesulfonate ( C ₁₆ MImMeS ), showing up to 90% larval mortality after 48 h exposure. C ₁₈ MImCl was more effective than C ₁₆ mIMeS , causing mortality until day 15 after exposure. An application of C ₁₈ MImCl left to dry under ambient conditions for at least 2 months and then dissolved in water showed a more pronounced residual effect (36 days with 95% mortality and 80% mortality up to 78 days).

CONCLUSION

This is the first study to show the potential of IS in the control of Ae. aegypti. Further studies are needed to understand the mode of action of these compounds in the biological development of this mosquito species. © 2017 Society of Chemical Industry

     

Dislocation-driven nanowire growth and Eshelby twist

Hierarchical nanostructures of lead sulfide nanowires resembling pine trees were synthesized by chemical vapor deposition. Structural characterization revealed a screwlike dislocation in the nanowire trunks with helically rotating epitaxial branch nanowires. It is suggested that the screw component of an axial dislocation provides the self-perpetuating steps to enable one-dimensional crystal growth, in contrast to mechanisms that require metal catalysts. The rotating trunks and branches are the consequence of the Eshelby twist of screw dislocations with a dislocation Burgers vector along the 110 directions having an estimated magnitude of 6 +/- 2 angstroms for the screw component. The results confirm the Eshelby theory of dislocations, and the proposed nanowire growth mechanism could be general to many materials.     

Organic matter quality of a forest soil subjected to repeated drying and different re‐wetting intensities

Extended drought periods followed by heavy rainfall may increase in many regions of the Earth, but the consequences for the quality of soil organic matter and soil microbial communities are poorly understood. Here, we investigated the effect of repeated drying and re‐wetting on microbial communities and the quality of particulate and dissolved organic matter in a Haplic Podzol from a Norway spruce stand. After air‐drying, undisturbed soil columns were re‐wetted at different intensities (8, 20 and 50 mm per day) and time intervals, so that all treatments received the same amount of water per cycle (100 mm). After the third cycle, SOM pools of the treatments were compared with those of non‐dried control columns. Lignin phenols were not systematically affected in the O horizons by the treatments whereas fewer lignin phenols were found in the A horizon of the 20‐ and 50‐mm treatments. Microbial biomass and the ratio of fungi to bacteria were generally not altered, suggesting that most soil microorganisms were well adapted to drying and re‐wetting in this soil. However, gram‐positive bacteria and actinomycetes were reduced whereas gram‐negative bacteria and protozoa were stimulated by the treatments. The increase in the (cy 17: 0 + cy 19: 0)/(16:1ω7c + 18:1ω7c) ratio indicates physiological or nutritional stress for the bacterial communities in the O, A and B horizons with increasing re‐wetting intensity. Drying and re‐wetting reduced the amount of hydrolysable plant and microbial sugars in all soil horizons. However, CO₂ and dissolved organic carbon fluxes could not explain these losses. We postulate that drying and re‐wetting triggered chemical alterations of hydrolysable sugar molecules in organic and mineral soil horizons.     

Organic matter dynamics in a temperate forest as influenced by soil frost

In the future, climate models predict an increase in global surface temperature and during winter a changing of precipitation from less snowfall to more raining. Without protective snow cover, freezing can be more intensive and can enter noticeably deeper into the soil with effects on C cycling and soil organic matter (SOM) dynamics. We removed the natural snow cover in a Norway spruce forest in the Fichtelgebirge Mts. during winter from late December 2005 until middle of February 2006 on three replicate plots. Hence, we induced soil frost to 15 cm depth (at a depth of 5 cm below surface up to –5°C) from January to April 2006, while the snow‐covered control plots never reached temperatures < 0°C. Quantity and quality of SOM was followed by total organic C and biomarker analysis. While soil frost did not influence total organic‐C and lignin concentrations, the decomposition of vanillyl monomers (Ac/Ad)_V and the microbial‐sugar concentrations decreased at the end of the frost period, these results confirm reduced SOM mineralization under frost. Soil microbial biomass was not affected by the frost event or recovered more quickly than the accumulation of microbial residues such as microbial sugars directly after the experiment. However, in the subsequent autumn, soil microbial biomass was significantly higher at the snow‐removal (SR) treatments compared to the control despite lower CO₂ respiration. In addition, the water‐stress indicator (PLFA [cy17:0 + cy19:0] / [16:1ω7c + 18:1ω7c]) increased. These results suggest that soil microbial respiration and therefore the activity was not closely related to soil microbial biomass but more strongly controlled by substrate availability and quality. The PLFA pattern indicates that fungi are more susceptible to soil frost than bacteria.     

Repeated freeze–thaw cycles changed organic matter quality in a temperate forest soil

Under temperate climate, the frequency of extreme weather events such as intensive freezing or frequent thawing periods during winter might increase in the future. It was shown that frost and subsequent thawing may affect the fluxes of C and N in soils. In a laboratory study, we investigated the effect of frost intensity and repeated freeze–thaw cycles on the quality and quantity of soil organic matter (SOM) in a Haplic Podzol from a Norway spruce forest. Undisturbed soil columns comprising O layer and top mineral soil were treated as followed: control (+5°C), frost at –3°C, –8°C, and –13°C. After a 2‐week freezing period, frozen soils were thawed at +5°C and irrigated with 80 mm water at a rate of 4 mm d^–1. Lignin contents were not significantly affected by repeated freeze–thaw cycles. Phospholipid fatty acid (PLFA) contents decreased in the mineral soil, and PLFA patterns indicate that fungi are more susceptible to soil frost than bacteria. Amounts of both plant and microbial sugars generally decreased with increasing frost intensity. These changes cannot be explained by increased mineralization of sugars or by leaching with DOM nor by a decreased microbial activity and, thus, sugar production with increasing frost intensity. Also physical stabilization of sugars due to frost‐induced changes in soil structure can be ruled out as sugar extraction was carried out on ground bulk soil. Therefore, the only possible explanation for the disappearance of plant and microbial sugars upon soil freezing are chemical alterations of sugar molecules leading to SOM stabilization.