Deep Impact observations by OSIRIS onboard the Rosetta spacecraft

The OSIRIS cameras (optical, spectroscopic, and infrared remote imaging system) onboard the European Space Agency's Rosetta spacecraft observed comet 9P/Tempel 1 for 17 days continuously around the time of NASA's Deep Impact mission. The cyanide-to-water production ratio was slightly enhanced in the impact cloud, compared with that of normal comet activity. Dust particles were flowing outward in the coma at >160 meters per second, accelerated by the gas. The slope of the brightness increase showed a dip about 200 seconds after the impact. Dust Afrho values before and long after the impact confirm the slight decrease of cometary activity. The dust-to-water mass ratio was much larger than 1.     

Chimeras of two isoprenoid synthases catalyze all four coupling reactions in isoprenoid biosynthesis

The carbon skeletons of over 55,000 naturally occurring isoprenoid compounds are constructed from four fundamental coupling reactions: chain elongation, cyclopropanation, branching, and cyclobutanation. Enzymes that catalyze chain elongation and cyclopropanation are well studied, whereas those that catalyze branching and cyclobutanation are unknown. We have catalyzed the four reactions with chimeric proteins generated by replacing segments of a chain-elongation enzyme with corresponding sequences from a cyclopropanation enzyme. Stereochemical and mechanistic considerations suggest that the four coupling enzymes could have evolved from a common ancestor through relatively small changes in the catalytic site.     

Management effects on the vegetation and soil seed bank of calcareous grasslands: An 11-year experiment

Calcareous grasslands, most of which are man made and therefore depend on some kind of human interference for their maintenance, are among the most species-rich communities on Earth at a small scale. For many centuries, most of these grasslands have been used as extensive pasture. However, after 1900, and particularly from 1940 onwards, livestock grazing has declined throughout Europe leading to the abandonment of low intensity grasslands over large areas. To conserve the remaining grasslands or to restore recently abandoned grasslands, better insights about the effects of grassland management on above and belowground species diversity are needed. Here, we describe the results of an 11-year experiment to investigate the role of grassland management (grazing, mowing and abandonment) in determining species composition and diversity both in the aboveground vegetation and the seed bank of a calcareous grassland in Belgium. Species diversity declined by about 60% 11 years after abandonment, from 29 species m⁻² to as few as 12 species m⁻². Plots that were grazed remained constant in species richness, whereas mown sites lost about 20% of their original species. Abandoned plots were largely dominated by a few grass species, in particular Festuca rubra. Concomitant with changes in the aboveground vegetation, both the number of species found in the seed bank and seed density (number of seeds m⁻²) had changed significantly 11 years after abandonment. Species diversity and seed density were significantly lower in abandoned plots than in grazed or mown plots. We conclude that abandonment of calcareous grasslands may lead to rapid decline of plant species diversity both in the aboveground vegetation and in the seed bank. As a result, seed banks probably have a limited role to play in the restoration of recently abandoned grasslands.     

Pattern and cause of acidic deposition in the Chongqing region,Sichuan Province,China

The Chongqing region located in Sichuan Province of China, comprises a large city, many small towns and rural areas. The region relies heavily on high-sulfur coal for energy production. Atmospheric pollution by sulfur oxides and other compounds from coal burning has become a major issue. Acid rain is observed throughout the region; volume weighted average pH is about 4.30. Average total S deposition for the region is estimated to be about 8 g S m^?2 yr^?1. In this paper we report concentrations of major ions in rain, fog, dew and clouds, of SO₂ in air and of airborne particles as well as dustfall. The emissions and interactions between important chemical species in air and water droplets are discussed.     

Infiltration of inorganic compounds from the Glatt River,Switzerland, into a groundwater aquifer

The behavior of dissolved (<0.45 μm) inorganic compounds during infiltration of river water into the adjacent aquifer (unconsolidated glacio-fluvial sediments) was investigated at the Glatt River, Switzerland, field site. The water was sampled in the river and from wells at distances of 2.5, 5, 13, and 110 m along an estimated groundwater flow line. Sodium, K, Ca, Mg, Sr, Cr, Cu, Zn, Cd, Pb, Cl^?, NO₃ ^?, SO₄ ^2?, and PO₄ ^3? were measured using AAS, NAA, and ion chromatography. Groundwater concentrations of these species are mainly determined by the concentrations in the river. However, the concentrations of NO₃ ^?, (PO₄ ^3?), Cr, Cu, Zn, Cd, and Pb are also subject to seasonal variations in the near infiltration field (≤ 5 m). These variations are probably triggered by temperature dependent biological processes which influence parameters such as pH, redox potential and complexing agents. The redox potential controls the chemical behavior of Mn, which influences the solubility of heavy metal compounds. The extent of inorganic pollution in the investigated system is still much below drinking water standards, but for Cd, reaches the toxicity limit for aquatic organisms.     

Über die Aggregatdichte und deren mögliche Auswirkung auf den Bodenlösungstransport

On the bulk density of aggregates and its possible impact on the movement of soil solutions The bulk densities of the aggregate fractions 15-18 mm, 10-15 mm, 5-10 mm, and 3-5 mm from a Typic Hapludalf, an Aquic Hapludalf, and a Typic Chromudert, all used as cropland and grassland, and that of aggregates of the 3-5 mm fraction from a Typic Dystrochrept used for a farm manure and crop residue trial, lay between 1.8 and 2.0 g/cm³. Sampling was done down to depths of 85 cm, 70 cm, 55 cm, and 80 cm. respectively. The bulk density values increase in most cases with decreasing aggregate size and indicate the aggregate pore volumes to generally range from 25 to 35% b.v. This means that either soil aggregates often contain only fine pores or that fine and medium pores also act as inter-aggregate pores. As a consequence, movement and exchange of soil water and soil solution between inter- and intra-aggregate pores is severely restricted.     

Soil‐ and plant‐based nitrogen‐fertilizer recommendations in arable farming

Under‐ as well as overfertilization with nitrogen (N) will result in economic loss for the farmer due to reduced yields and quality of the products. Also from an ecological perspective, it is important that the grower makes the correct decision on how much and when to apply N for a certain crop to minimize impacts on the environment. To aggravate the situation, N is a substance that is present in many compartments in different forms (nitrate, ammonium, organic N, etc.) in the soil‐plant environment and takes part in various processes (e.g., mineralization, immobilization, leaching, denitrification, etc.). Today, many N‐recommendation systems are mainly based on yield expectation. However, yields are not stable from year to year for a given field. Also the processes that determine the N supply from other sources than fertilizer are not predictable at the start of the growing season. Different methodological approaches are reviewed that have been introduced to improve N‐fertilizer recommendations for arable crops. Many soil‐based methods have been developed to measure soil mineral N (SMN) that is available for plants at a given sampling date. Soil sampling at the start of the growing period and analyzing for the amount of NO ‐N (and NH ‐N) is a widespread approach in Europe and North America. Based on data from field calibrations, the SMN pool is filled up with fertilizer N to a recommended amount. Depending on pre‐crop, use of organic manure, or soil characteristics, the recommendation might be modified (±10–50 kg N ha^–1). Another set of soil methods has been established to estimate the amount of N that is mineralized from soil organic matter, plant residues, and/or organic manure. From the huge range of methods proposed so far, simple mild extraction procedures have gained most interest, but introduction into practical recommendation schemes has been rather limited. Plant‐analytical procedures cover the whole range from quantitative laboratory analysis to semiquantitative “quick” tests carried out in the field. The main idea is that the plant itself is the best indicator for the N supply from any source within the growth period. In‐field methods like the nitrate plant sap/petiole test and chlorophyll measurements with hand‐held devices or via remote sensing are regarded as most promising, because with these methods an adequate adjustment of the N‐fertilizer application strategy within the season is feasible. Prerequisite is a fertilization strategy that is based on several N applications and not on a one‐go approach.     

Gingerol content of diploid and tetraploid clones of ginger (Zingiber officinale Roscoe)

Ginger (Zingiber officinale Roscoe), a monocotyledonous, sterile cultigen, is widely used as a spice, flavoring agent, and herbal medicine. The pungency of fresh ginger is due to a series of homologous phenolic ketones of which [6]-gingerol is the major one. The gingerols are thermally unstable and can be converted to their corresponding shogaols, which are present in dried ginger. Fresh rhizomes of 17 clones of Australian ginger, including commercial cultivars and experimental tetraploid clones, were assayed by HPLC for gingerols and shogaols. [6]-Gingerol was identified as the major pungent phenolic compound in all samples, while [8]- and [10]-gingerol occurred in lower concentrations. One cultivar known as "Jamaican" contained the highest concentrations of all three gingerols and was the most pungent of the clones analyzed. Gingerols were stable in ethanolic solution over a 5-month period when stored at 4 degrees C. Shogaols were not identified in the extracts prepared from fresh rhizomes at ambient temperature, confirming that these compounds are not native constituents of fresh ginger. In contrast to previous findings, this study did not find significant differences in gingerol concentrations between the tetraploid clones and their parent diploid cultivar.     

Mass spectrometric detection and formation of D-amino acids in processed plant saps, syrups, and fruit juice concentrates

Liquid and syrupy dietary saps and juices of plant origin, characterized by the presence of large quantities of saccharides (glucose, fructose, or sucrose) and containing amino acids, were analyzed for the presence of D-amino acids using enantioselective gas chromatography-mass spectrometry. D-amino acids were detected in processed saps and juices of trees (maple, palm, birch), fruits (grape, apple, pear, pomegranate, date), and various other plants (agave, beetroot, sugar cane, carob). D-Ala was detected in all plant products and amounted to approximately 34% D-Ala (relative to L-Ala + D-Ala) in Canadian maple syrups, to approximately 13% in palm saps, and to 48 and 13% D-Ala, respectively, in concentrated grape juices (Spanish Arrope and Turkish Pekmez). Varying amounts and kinds of other D-amino acids were also detected. To test the hypothesis that racemization, that is, partial conversion of L-amino acids into their corresponding D-enantiomers, occurs at reversible stages of the Maillard reaction, the Amadori compound fructose-L-phenylalanine was synthesized. On heating at 200 degrees C for 5 (20) min, release of 10.8% (24.2%) D-Phe was detected. From the data it is concluded that the Amadori compounds formed in the course of the Maillard reaction are pecursors of D-amino acids in foodstuffs.