Effect of different tillage methods on maize growth on a tropical inceptisol with impeded drainage

Two trials to compare the effect of coventional, minimum and zero tillage on maize growth on a lowland tropical clay soil with impeded drainage were carried out during the rainy season of 1980 in Trinidad. During the first trial where low levels of nitrogen (50 kg/ha) and grass mulch (2 t/ha) were used, the mean fresh weight yield of ears from conventional tillage was 5.64 t/ha. Zero and minimum tillage treatments yielded about 40% less. Conventional tillage also produced significantly taller plants and more stem and leave dry matter (P = 0.05) than the other two tillage methods. The growth and yield of maize resulting from minimum and zero tillage were not significantly different.During the second trial where rainfall was heavy and higher levels of nitrogen (85 kg/ha) and grass mulch (6 t/ha) were used, seedling emergence was reduced but yields were at least 100% higher than those from the first trial and the fresh weight yield of ears from zero tillage was only 19% less than conventional tillage. Yields from zero tillage plots which had been tilled conventionally for the previous trial were only 1% higher than yields from continuous zero tillage. This improved performance of the zero tillage treatment indicates its potential for maize production on this fine textured soil and suggests the need for further studies with accompanying economic analysis.     

Activity measurements of Ni2+ in soils

Nickel activities were measured in 11 alkaline and slightly acidic soils using the chelate method. The measured activities ranged from 10^?6.82 to 10^?8.78 M and were inversely related to the pH of the soils. The measured Ni²⁺ activities in the 11 soils could be predicted using the following expression: (Ni²⁺) = 10^6.95 (H⁺)². The solubility of Ni was plotted on a log (Ni²⁺) vs. pH solubility diagram for various Ni solid phase compounds. It is most likely that NiFe₂O₄ (trevorite) is the solid phase controlling Ni solubility in these soils. Identification of the presence of this mineral needs further investigation.     

Images of the DNA double helix in water

The scanning tunneling microscope can image uncoated DNA submerged in water. The grooves of the double helix were clearly resolved in images of the 146-base pair fragment extracted from calf thymus nucleosome. In contrast to images obtained with dry DNA, the helix pitch varied only a small amount (36 +/- 5 angstroms). The path of the helix shows considerable variation. It is quite straight when the molecules are densely packed, but it curves and bends in isolated molecules.     

Spectroscopic Observation of the Formyl Cation in a Condensed Phase

The formyl cation, HCO+, has long been believed to be an important intermediate in the chemistry of carbon monoxide (CO) in acidic environments, but its spectroscopic observation in solution has been elusive. This species was generated by the reaction of CO with the liquid superacid hydrofluoric acid-antimony pentafluoride (HF-SbF5) under pressure and was observed by nuclear magnetic resonance and infrared spectroscopy. Equilibria between CO in the gas phase, CO dissolved in HF-SbF5, the SbF5 adduct of formyl fluoride, and HCO+ associated with several equilibrating anions of the type [SbxF5x+1]- are proposed to describe the system.     

A persistent oxygen anomaly reveals the fate of spilled methane in the deep Gulf of Mexico

Methane was the most abundant hydrocarbon released during the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. Beyond relevancy to this anthropogenic event, this methane release simulates a rapid and relatively short-term natural release from hydrates into deep water. Based on methane and oxygen distributions measured at 207 stations throughout the affected region, we find that within ~120 days from the onset of release ~3.0 × 10(10) to 3.9 × 10(10) moles of oxygen were respired, primarily by methanotrophs, and left behind a residual microbial community containing methanotrophic bacteria. We suggest that a vigorous deepwater bacterial bloom respired nearly all the released methane within this time, and that by analogy, large-scale releases of methane from hydrate in the deep ocean are likely to be met by a similarly rapid methanotrophic response.     

A bond-fluctuation mechanism for stochastic switching in wired molecules

Stochastic on-off conductivity switching observed in phenylene-ethynylene oligomers has been explained in terms of changes in ring conformations, or electron localization, or both. We report the observation of stochastic on-off switching in the simplest of wired molecules: octanedithiol, decanedithiol, and dodecanedithiol bonded on an Au(111) surface. Stochastic switching was observed even when a top gold contact was pressed on by a conducting atomic force microscope tip at constant force. The rate of switching increased substantially at 60 degrees C, a temperature at which these films are commonly annealed. Because such switching in alkanethiols is unlikely to be caused by internal molecular electronic changes and cannot be fully accounted for by breaking of the top contact, we argue that the cause is the well-known mobility of molecules tethered to gold via a thiol linkage.     

Predatory Dinosaurs from the Sahara and Late Cretaceous Faunal Differentiation

Late Cretaceous (Cenomanian) fossils discovered in the Kem Kem region of Morocco include large predatory dinosaurs that inhabited Africa as it drifted into geographic isolation. One, represented by a skull approximately 1.6 meters in length, is an advanced allosauroid referable to the African genus Carcharodontosaurus. Another, represented by a partial skeleton with slender proportions, is a new basal coelurosaur closely resembling the Egyptian genus Bahariasaurus. Comparisons with Cretaceous theropods from other continents reveal a previously unrecognized global radiation of carcharodontosaurid predators. Substantial geographic differentiation of dinosaurian faunas in response to continental drift appears to have arisen abruptly at the beginning of the Late Cretaceous.     

Hydroxylysyl pyridinoline cross-link concentration affects the textural properties of fresh and smoked Atlantic salmon (Salmo salar L.) flesh

A simple HPLC method is presented to quantify the low concentration of hydroxylysyl pyridinoline (PYD) cross-links in Atlantic salmon (Salmo salar L.) muscle. The method involved the extraction of tissue with NaOH prior to hydrolysis, which greatly reduced the amount of protein to be hydrolyzed and made downstream operations easier and more reproducible. The concentration of PYD was 426 pmol g(-)(1) dry mass muscle in post-rigor muscle stored at 0 degrees C and sampled 3 d after death. Hydroxproline (HYP) concentration was determined following NaOH extraction as a measure of collagen content. In post-rigor samples, the alkaline-insoluble HYP fraction comprised 18.3% of the total HYP. Scanning electron microscopy revealed shrinkage of muscle fibers and a retraction of the connective tissue matrix in smoked salmon. PYD concentration was relatively resistant to processing to the smoked product, decreasing by around 11.7%, as compared to a 22.2% decrease in HYP. There was a positive correlation between PYD concentration and the firmness of post-rigor muscle samples as measured by an instrumental texture analyzer, explaining 25% of the total variation. A weaker but still significant correlation was found between PYD concentration and firmness in the smoked product. There was no relationship between fillet firmness and total collagen concentration, although the correlation with HYP in the alkaline-insoluble fraction was significant at the 6% level (P = 0.057). Our results indicate that only 1-3% of collagen molecules are linked by nonreducible mature cross-links in harvest size farmed Atlantic salmon and that PYD concentration is an important raw material characteristic for flesh quality.