Magnetization of carbonaceous asteroids by nebular fields and the origin of CM chondrites

The solar nebula carried a strong magnetic field that had a stable intensity and direction for periods of a thousand years or more1. The solar nebular field may have produced post-accretional magnetization in at least two groups of meteorites, CM and CV chondrites [1–3], which originated from planetesimals that may have underwent aqueous alteration before gas in the solar nebula dissipated [1,3]. Magnetic minerals produced during aqueous alteration, such as magnetite and pyrrhotite [4], could acquire a chemical remanent magnetization from that nebular field [3]. However, many questions about the size, composition, formation time, and, ultimately, identity of the parent bodies that produced magnetized CM and CV chondrites await answers—including whether a parent body might exhibit a detectable magnetic field today. Here, we use thermal evolution models to show that planetesimals that formed between a few Myr after CAIs and ~1 Myr before the nebular gas dissipated could acquire from the nebular field, and retain until today, a chemical remanent magnetization throughout nearly their entire volume. Hence, in-situ magnetometer measurements of C-type asteroids could help link magnetized asteroids to magnetized meteorites. Specifically, a future mission could search for a magnetic field as part of testing the hypothesis that 2 Pallas is the parent body of the CM chondrites [5]. Overall, large carbonaceous asteroids might record ancient magnetic fields in magnetic remanence that produces strong modern magnetic fields, even without a metallic core that once hosted a dynamo.

Habitat use of common dolphin (Delphinus sp.) in the Mochima National Park, Sucre, Venezuela.

In Venezuela, common dolphin (Delphinus sp.) is considered the cetacean with the highest incidence. Studies in the region indicate a possible isolated coastal population so called Venezuelan stock settled mainly in the northeast of the country. . The objective of this study is to describe the habitat use of common dolphin in the Mochima National Park (MNP), a protected area with a high and growing anthropic pressure. Seventy surveys were carried out, with predefined survey route, from September 2009 to August 2010. Each group sighted was monitored while possible to a maximum of 30min.. During this time we registered location (Latitude-longitude), behaviour, group size and composition every 5min. Additionally, environmental variables were assessed from the sight location in a nautical chart. The study area was divided into a grid (cell: 500 x 500m) and the Coefficient of Area Use (CAU) was calculated for each cell. The proportion of the total observation time where the common dolphin displayed behaviours into the areas being used was estimated. A logistic regression model was applied to identify the variables that better explained usage pattern. In 55h of observation, 111 groups were recorded. The common dolphin used the habitat differentially, showing preferences for shallow areas near to the coast. Areas of greatest intensity of use were Tigrillo inlet and the northeast of the Caracas Islands. The probability of presence of dolphins decreased with depth and distance to the coast. Common dolphin invested more time in feeding and socializing activities. Behaviours were significantly dependent of season, group size, composition, depth and distance to the coast. Finally, these data on habitat use and behaviour allow the identification of priority habitats. Throughout the year, the MNP provided areas for refuge, feeding and resting. , It is therefore imperative to promote management and conservation policies that prevent the negative impacts of the increasing tourism and fishing activities we observed in this Park.

Synthesis, characterization and evaluation of aqueous Zn-based quantum dots for Bioapplications

Semiconducting nanoparticles called quantum dots (Qds) present unique optoelectronic properties based on their extremely small size, composition, and spherical shape, which make them suitable for use as diagnostic and theranostic...

Nanoemulsion and Its Application in Pesticide Formulation

A nanoemulsion is a colloidal dispersion that contains very small particles with size in the range of 20-200 nm, which may be of the oil-in-water (O/W) or water-in-oil (W/O) types depending on whether the oil is dispersed as droplets in water or vice versa. Pesticides play a critical role in controlling agriculture and ensuring food safety. In the future, the utilization of pesticides will become even more important to solve food security problems associated with providing an adequate food supply for the growing world population. Hence, development of new techniques for nanoemulsions formulation in the field of agriculture and forestry are necessary. In this chapter, the synthesis, characterization, and application of nanoemulsion in pesticides formulation are reviewed. In addition, the effect of antifungal or insecticidal and antimicrobial enhancement activity of nanoemulsions with size, composition, and stability are also discussed.

State-of-the-art review of fabrication, application, and mechanical properties of functionally graded porous nanocomposite materials

Functionally graded porous (FGP) nanocomposites are the most promising materials among the manufacturing and materials sector due to their adjustable physical, mechanical, and operational properties for distinctive engineering applications for maximized efficiency. Therefore, investigating the underlying physical and materialistic phenomena of such materials is vital. This research was conducted to analyze the preparation, fabrication, applications, and elastic properties of functionally graded materials (FGMs). The research investigated for both porous and nonporous synthesis, preparation, and manufacturing methods for ceramics, metallic, and polymeric nanocomposites in the first section, which is followed by deep research of the development of elastic properties of the above-mentioned materials. Main nano-reinforcing agents used in FGMs to improve elastic properties were found to be graphene platelets, carbon nanotubes, and carbon nanofibers. In addition, research studied the impact of nano-reinforcing agent on the elastic properties of the FGMs. Shape, size, composition, and distribution of nano-reinforcing agents were analyzed and classified. Furthermore, the research concentrated on modeling of FGP nanocomposites. Extensive mathematical, numerical, and computational modeling were analyzed and classified for different engineering analysis types including buckling, thermal, vibrational, thermoelasticity, static, and dynamic bending. Finally, manufacturing and design methods regarding different materials were summarized. The most common results found in this study are that the addition of reinforcement units to any type of porous and nonporous nanocomposites significantly increases materialistic and material properties. To extend, compressive and tensile stresses, buckling, vibrational, elastic, acoustical, energy absorption, and stress distribution endurance are considerably enhanced when reinforcing is applied to porous and nonporous nanocomposite assemblies. Ultimately, the review concluded that the parameters such as shape, size, composition, and distribution of the reinforcing units are vital in terms of determining the final mechanical and materialistic properties of nanocomposites.

Hyteroatoms Si, P, S as possible factors for the formation of the structure of pyrolyzed carbon materials

The aim of the study was to investigate the effect of heteroatoms on the deformation of graphene, as well as on the formation of the Stone-Wallace defect. To date, research on processes involving nanocarbon materials is relevant. In particular, in the formation of fullerenes, nanoonions and a number of other carbon nanoforms, the five-membered carbon cycles (pentactagonis) of the hepatogenesis (pentactagon) play the most important role in the curvature of initially flat graphene sheets and the formation of fullerene-like structures in the form of closed, skeletal, macromolecular formations. It should be noted, however, that the Pentagon is not the only factor in distorting the flat structure of graphene sheets in layered carbon materials. Some other defects of the carbon lattice (in particular, seven-membered carbon cycles and heteroatoms of a number of nonmetals with covalent radii exceeding the radius of the carbon atom) may play a similar role to one degree or another. These heteroatoms (primarily Si, P, S) are usually part of the precursors of mineral or vegetable origin and can be embedded in the carbon lattice in the process of coal production. Stone-Wallace there is their mutual compensation and preservation of a flat structure. The calculations were performed using quantum chemical modeling of doped nanographs in clusters of different size, composition and morphology, using the theory of density functional (DFT) with exchange-correlation functional B3LYP, based on the extended valence-split basis 6-31G (d) with full optimism clusters using the Firefly software package. It has been found that heteroatoms of non-metals with covalent radii exceeding the radius of the C atom, which are usually present in the precursors of mineral or vegetable origin used to produce pyrolyzed carbon materials, can play a significant role in energy. a number of nanoforms of carbon, activated carbon and other pyrolyzed nanostructured carbon materials.

The Content and Sources of Potentially Toxic Elements in the Road Dust of Surgut (Russia)

The chemical and particle size composition of road dust in Surgut, which is a rapidly developing city in Western Siberia, was studied for the first time. Contents of major and trace elements were determined using ICP-MS and ICP-AES, respectively. It was found that the road dust had an alkaline pH (from 7.54 to 9.38) and that the particle size composition was dominated by the 100–250-μm fraction. The contamination assessment based on calculations of the enrichment factor (EF) showed that the road dust was significantly enriched in Sb and Cu and moderately enriched in Zn, Pb, Mo, Ni and W. The sources of these elements are probably associated with the abrasion of car tires and brake pads. Based on calculations of global pollution index (PIr) and total enrichment factor (Ze), the road dust of Surgut was characterized by a generally low level of potential ecological risk, except for stretches of road subject to regular traffic jams, where a moderate ecological risk level was identified. In comparison to the other Russian cities (Moscow, Chelyabinsk, Tyumen, etc.) where studies of road dust composition have been carried out, Surgut had similar contents of Cr and Cu and relatively lower contents of Sb, Cd, As and Pb.

STUDY OF THE INFLUENCE OF DISPERSITY AND CHEMICAL COMPOSITION OF NICKEL RENEUAL ALLOYS ON THE SPECIFICITY OF REDUCTION OF ADAMANTANE-CONTAINING UNSATURED NITRILE

The regularities of the reduction of adamantane-containing unsaturated nitrile-nickel-aluminum alloy are investigated. It has been shown that under the conditions of synthesis it is possible to carry out the simultaneous reduction of both the double bond and the nitrile group. It was found that the reduction of nitriles containing 1 hydroxyl group in the position leads to a significant decrease in the rate of the process. The effect of the grain size composition of the alloy and damping additives on the reduction of unsaturated nitriles has been studied.

Formation of Complex Inclusions in Gear Steels for Modification of Manganese Sulphide

Suitable MnS inclusions in gear steel can significantly improve the steel machinability and reduce the manufacturing costs. Two gear steel samples with different sulphur contents were prepared via aluminium deoxidation followed by calcium treatment. The shape, size, composition and percentage distribution of the inclusions present in the steel samples were analyzed using an electron probe micro-analysis (EPMA) technique. The average diameter of MnS precipitated on an oxide inclusion is less than 5 µm. It was found that the steel with high sulphur content contains a greater number of elongated MnS precipitates than low sulphur steel. Moreover, there are more oxide inclusions such as calcium-aluminates and spinels with a small amount of solid solution of (Ca,Mn)S in low content sulphur steel after calcium treatment, which indicates the modification of solid alumina inclusions into liquid aluminates. The typical inclusions generated in high sulphur steel are sulphide encapsulating oxide inclusions and some core oxides were observed as spinel. The formation mechanisms of complex inclusions with different sulphur and calcium contents are discussed. The results are in good agreement with thermodynamic calculations.

Effects of habitat destruction on coevolving metacommunities

Habitat destruction is a growing threat to biodiversity and ecosystem services. The ecological consequences of habitat loss and fragmentation involve reductions in species abundance and even the extinction of species and interactions. However, we do not yet understand how habitat loss can alter the coevolutionary trajectories of the remaining species or how coevolution, in turn, affects their response to habitat loss. To investigate this, we develop a spatially explicit model which couples metacommunity and coevolutionary dynamics. We show that, by changing the size, composition and structure of local networks, habitat destruction increases the diversity of coevolutionary outcomes across the landscape. Furthermore, we show that while coevolution dampens the negative effects of habitat destruction in mutualistic networks, its effects on the persistence of antagonistic communities are less predictable.