Detection of the intrinsic size of Sagittarius A* through closure amplitude imaging

We have detected the intrinsic size of Sagittarius A*, the Galactic center radio source associated with a supermassive black hole, showing that the short-wavelength radio emission arises from very near the event horizon of the black hole. Radio observations with the Very Long Baseline Array show that the source has a size of 24 +/- 2 Schwarzschild radii at 7-millimeter wavelength. In one of eight 7-millimeter epochs, we also detected an increase in the intrinsic size of 60(-17)(+25)%. These observations place a lower limit to the mass density of Sagittarius A* of 1.4 x 10(4) solar masses per cubic astronomical unit.     

The ultrastructure of low temperature stimulated rubber-producing cortical parenchyma in guayule

The low temperatures of the Chihuahuan Desert stimulate rubber biosynthesis in guayule plants, primarily by promoting rubber-producing cortical parenchyma cells and inducing the activity of enzymes in the pathway of rubber biosynthesis. Further progress in increasing rubber production in guayule requires a better understanding of the ultrastructure of the organelles in the rubber producing cortical parenchyma. The objective of this study was to investigate the ultrastructure of the organelles in the rubber producing cortical parenchyma. The electron photomicrographs show that the rubber-producing cortical parenchyma, in contrast to mature cortical parenchyma in stems not exposed to the low temperatures, contain a high population of rubber particles, an abundant number of mitochondria, chloroplasts, a well-structured nucleus, rough endoplasmic reticulum and Golgi apparati. The double membrane nucleus is important in the low temperature induction of rubber-forming enzymes: rubber transferase and 3-hydroxy-3-methylglutaryl coenzyme A reductase. Photographic enlargements of the population of mitochondria show well-developed inner membrane folding that functions in ATP production to support the energy requirements of rubber biosynthesis. Electron photomicrographs show dividing chloroplasts that increase the number of plastids in the rubber-producing parenchyma. The well-structured grana and stroma lamellae may produce energy for the stroma production of carbon precursors of rubber. Photographic enlargements show a cortical parenchyma with an active Golgi apparatus, producing an abundant number of vesicles. Features of this electron photomicrograph is the fusion of a Golgi vesicle with a rubber particle, suggesting the transport of Golgi-processed glycolipids and glycoproteins to the rubber particles, and the rubber particles extending into the central cytosol still attached to the RER indicating an earlier origin of the rubber particle from the RER. The electron photomicrographs of the ultrastructure of rubber-producing cortical parenchyma in guayule stems support the conclusion that these cells contain an abundant number of organelles relating to the low temperature stimulated rubber synthesis.     

Potentially mineralizable nitrogen from organic materials applied to a sandy soil: fitting the one-pool exponential model

Abstract. Over the last three decades there has been a great increase in the production of waste from urban, industrial and agricultural activity that could be recycled as a source of plant nutrients, and used to enhance soil quality. The use of these materials could partially offset the need for mineral fertilizers, giving both economic and environmental benefits. An incubation experiment was carried out using different organic waste materials applied to a Cambic Arenosol. Air-dried soil was mixed with increasing amounts of composted solid municipal waste, secondary pulp-mill sludge, hornmeal, poultry manure, solid phase from pig slurry, and composted pig manure, resulting in applications equivalent to 0, 40, 80, 120, 160 and 200 kg ha⁻¹ of Kjeldahl nitrogen. The samples were incubated for 244 days under a controlled environment of 24 °C and 60% water holding capacity of the soil. The increasing amounts of waste applied always led to a greater amount of potentially available nitrogen present in the soil/waste mixture. Based on the proportion of their active N fraction, wastes were ranked: poultry manure>hornmeal>solid phase from pig slurry>composted pig manure>secondary pulp-mill sludge>composted municipal solid waste. The results were well described by a one-pool exponential mineralization model, and mineral N formation was proportional to the quantity of waste applied. Of the wastes tested, those from animal sources showed greater nitrogen mineralisation. Nitrification was rapid, and concentrations of ammonium nitrogen remained relatively small.     

ESTIMATING SHORT- AND MEDIUM-TERM AVAILABILITY TO CEREALS OF NITROGEN FROM ORGANIC RESIDUES

Overused soil resources and the build-up of organic residues from industrial processes have resulted in increased risk of environmental contamination. Recycling of organic residues from industry by incorporation into agricultural soil, can provide valuable organic amendment as well as supply nutrients to crops. The effect of applying organic amendments to an agricultural sandy soil on the nitrogen nutrition of wheat (Triticum aestivum L.) and residual effects on the growth of a following maize crop (Zea mays, L.), were assessed under semi-controlled environmental conditions and were compared to nitrogen mineralization prediction obtained from an aerobic incubation. Six different organic residues (composted municipal solid waste, secondary pulp-mill sludge, hornmeal, poultry manure, the solid phase from pig slurry and composted pig manure) were added to a Cambic arenosol, incubated or used in pot experiments, to evaluate and try to predict the availability to crop plants of nitrogen released from these materials. Poultry manure was the most effective amendment in making nitrogen available and enhancing nitrogen uptake by wheat plants resulting in greater dry matter yield. The dried solid phase from pig slurry and hornmeal were also beneficial to wheat growth. There was a greater recovery of nitrogen (N), from organic materials studied, by a maize crop. Poultry manure was the residue that provided a greater residual effect on N supply to maize.     

Movement of Faecal Bacteria through the Vadose Zone

The impact of biosolid and soil type on the movement of faecal coliforms through the vadose zone was investigated following the application of animal manure to soil. Two types of biosolid, solid and liquid manure, were applied to two soil types at a wide range of initial water contents. Bacteria present in the soil solution were collected using calibrated ceramic-porous-cup samplers. Estimated bacterial migration velocities in the soil profile were consistent with the hypothesis that bacteria move mostly through soil macropores, as the rate of transport was faster than the average pore-water velocity. Macropore transport was more likely to occur in wet soils, but it was not necessarily restricted to soils with high initial soil water content. A larger soil clay content, lower total soil porosity, and lower saturated hydraulic conductivity resulted in a greater likelihood that suspended bacteria would be funnelled through pores of larger diameter and faster pore water velocity, increasing the potential vertical transport length of bacteria through the vadose zone. Total porosity was not a significant factor in enhancing deep transport of faecal bacteria. The potential of faecal bacteria to be transported to depth in soil was correlated with the water content of the manure. We conclude that application of animal manure to soil can readily lead to groundwater contamination with faecal bacteria especially under moist soil conditions, and that macropores are important in the transport.     

Distributions of microbial activities in deep subseafloor sediments

Diverse microbial communities and numerous energy-yielding activities occur in deeply buried sediments of the eastern Pacific Ocean. Distributions of metabolic activities often deviate from the standard model. Rates of activities, cell concentrations, and populations of cultured bacteria vary consistently from one subseafloor environment to another. Net rates of major activities principally rely on electron acceptors and electron donors from the photosynthetic surface world. At open-ocean sites, nitrate and oxygen are supplied to the deepest sedimentary communities through the underlying basaltic aquifer. In turn, these sedimentary communities may supply dissolved electron donors and nutrients to the underlying crustal biosphere.