Sharp sides to the African superplume

Beneath southern Africa is a large structure about 1200 kilometers across and extending obliquely 1500 kilometers upward from the core-mantle boundary with a shear velocity reduction of about 3%. Using a fortuitous set of SKS phases that travel along its eastern side, we show that the boundary of the anomaly appears to be sharp, with a width less than 50 kilometers, and is tilted outward from its center. Dynamic models that fit the seismic constraints have a dense chemical layer within an upwardly flowing thermal structure. The tilt suggests that the layer is dynamically unstable on geological time scales.     

Water-assisted highly efficient synthesis of impurity-free single-walled carbon nanotubes

We demonstrate the efficient chemical vapor deposition synthesis of single-walled carbon nanotubes where the activity and lifetime of the catalysts are enhanced by water. Water-stimulated enhanced catalytic activity results in massive growth of superdense and vertically aligned nanotube forests with heights up to 2.5 millimeters that can be easily separated from the catalysts, providing nanotube material with carbon purity above 99.98%. Moreover, patterned, highly organized intrinsic nanotube structures were successfully fabricated. The water-assisted synthesis method addresses many critical problems that currently plague carbon nanotube synthesis.     

A 5-micron-bright spot on Titan: evidence for surface diversity

Observations from the Cassini Visual and Infrared Mapping Spectrometer show an anomalously bright spot on Titan located at 80 degrees W and 20 degrees S. This area is bright in reflected light at all observed wavelengths, but is most noticeable at 5 microns. The spot is associated with a surface albedo feature identified in images taken by the Cassini Imaging Science Subsystem. We discuss various hypotheses about the source of the spot, reaching the conclusion that the spot is probably due to variation in surface composition, perhaps associated with recent geophysical phenomena.     

The 2.6 angstrom crystal structure of a human A2A adenosine receptor bound to an antagonist

The adenosine class of heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) mediates the important role of extracellular adenosine in many physiological processes and is antagonized by caffeine. We have determined the crystal structure of the human A2A adenosine receptor, in complex with a high-affinity subtype-selective antagonist, ZM241385, to 2.6 angstrom resolution. Four disulfide bridges in the extracellular domain, combined with a subtle repacking of the transmembrane helices relative to the adrenergic and rhodopsin receptor structures, define a pocket distinct from that of other structurally determined GPCRs. The arrangement allows for the binding of the antagonist in an extended conformation, perpendicular to the membrane plane. The binding site highlights an integral role for the extracellular loops, together with the helical core, in ligand recognition by this class of GPCRs and suggests a role for ZM241385 in restricting the movement of a tryptophan residue important in the activation mechanism of the class A receptors.     

MICROWAVE DRYING OF HERBAGE

Microwave heating has recently been suggested as a method of drying herbage. A slightly modified commercial microwave cooking-oven has been tested for this purpose and was found to dry 400 g of fresh herbage in 15-20 min. The water-soluble-carbohydrate contents of herbage samples dried ( a ) by microwaves and ( b ) by freezing were similar.     

Fifty years after deep-ploughing: Effects on yield,roots, nutrient stocks and soil structure

Deep-ploughing far beyond the common depth of 30 cm was used more than 50 years ago in Northern Germany with the aim to break root-restricting layers and thereby improve access to subsoil water and nutrient resources. We hypothesized that effects of this earlier intervention on soil properties and yields prevailed after 50 years. Hence, we sampled two sandy soils and one silty soil (Cambisols and a Luvisol) of which half of the field had been deep-ploughed 50 years ago (soils then re-classified as Treposols). The adjacent other half was not deep-ploughed and thus served as the control. At all the three sites, both deep-ploughed and control parts were then conventionally managed over the last 50 years. We assessed yields during the dry year 2019 and additionally in 2020, and rooting intensity at the year of sampling (2019), as well as changes in soil structure, carbon and nutrient stocks in that year. We found that deep-ploughing improved yields in the dry spell of 2019 at the sandy sites, which was supported by a more general pattern of higher NDVI indices in deep-ploughed parts for the period from 2016 to 2021 across varying weather conditions. Subsoil stocks of soil organic carbon and total plant-available phosphorus were enhanced by 21%–199% in the different sites. Root biomass in the subsoil was reduced due to deep-ploughing at the silty site and was increased or unaffected at the sandy sites. Overall, the effects of deep-ploughing were site-specific, with reduced bulk density in the buried topsoil stripes in the subsoil of the sandy sites, but with elevated subsoil density in the silty site. Hence, even 50 years after deep-ploughing, changes in soil properties are still detectable, although effect size differed among sites.     

海南岛桉林土壤肥力的研究

海南岛主要植枝区的土壤肥力状况差异极大,其中大部分桉林分布在贫瘠的褐色砖红壤、燥红土和滨海砂土上,这些土壤有效肥力和潜在肥力都不高。在热带地区营造桉林后,林地土壤肥力下降,土壤明显酸化。初步拟定了桉树速生丰产的土壤肥力指标,供桉树配方平衡施肥参考。     

Genetic studies of antifreeze proteins and their correlation with winter survival in wheat

Antifreeze proteins (AFPs) accumulate in the leaves of winter cereals during cold acclimation, where they may inhibit ice recrystallization during freezing and thawing cycles and provide nonspecific disease resistance. In this study, 21 wheat chromosome substitution lines and the parental lines Chinese Spring and Cheyenne wheat were used to determine the heritability of AFPs and the relationship between the accumulation of AFPs and winter survival. In cold-acclimated lines, antifreeze activity in leaf apoplastic extracts ranged from 1 (low) to 5 (high) with an average value of 3.2, and the accumulation of apoplastic proteins ranged from 30 μg (g FW)^-1 to 115 μg (g FW)^-1 with a mean value of 70 μ (g FW)^-1. Examination of the individual lines revealed that Cheyenne chromosomes 5B and 5D carry major regulatory genes that increase both antifreeze activity and the accumulation of antifreeze proteins in plants grown at low temperature. Substitution lines carrying Cheyenne chromosomes 2A, 3A, 6B, and 7A exhibited lower freezing tolerance and also showed a marked decrease in the accumulation of specific AFPs during cold acclimation. Antifreeze activity and apoplastic protein content were not correlated with freezing tolerance (defined as % survival at -11 °C), but they were both significantly and positively correlated with winter field survival rates. Antifreeze activity (positively correlated) and total leaf fresh weight (negatively correlated) together accounted for about 55% of the variation in winter survival, indicating that high antifreeze activity and slow vegetative growth at low temperature are both important quantitative traits for winter survival. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of Roasting and Malting on Physicochemical Properties of Select Cereals and Legumes

Pearl millet, teff, cowpea, and peanut used in the formulation of experimental weaning foods were evaluated for changes in physicochemical properties resulting from roasting and malting. The particle size index (PSI) value for cowpea was significantly higher, indicating a finer flour than that obtained from pearl millet. Pearl millet and teff flours did not have significantly different PSI values, water absorption index values, or gruel viscosities. Viscosities for control and roasted cowpea gruels (15%, w/v) were significantly higher than those obtained from peanut gruels. Malting had the greatest impact on physicochemical properties for all grains, whereas roasting produced no significant differences from control flours. Malting yielded apparent increases in grain protein content, and malted seeds yielded finer flours with reduced water absorption and pasting qualities.