Shadow Analysis of Soil Surface Roughness Compared to the Chain Set Method and Direct Measurement of Micro-relief.

Erosion potential and the effects of tillage can be evaluated from quantitative descriptions of soil surface roughness. The present study therefore aimed to fill the need for a reliable, low-cost and convenient method to measure that parameter. Based on the interpretation of micro-topographic shadows, this new procedure is primarily designed for use in the field after tillage. The principle underlying shadow analysis is the direct relationship between soil surface roughness and the shadows cast by soil structures under fixed sunlight conditions. The results obtained with this method were compared to the statistical indexes used to interpret field readings recorded by a pin meter. The tests were conducted on 4-m2 sandy loam and sandy clay loam plots divided into 1-m2 subplots tilled with three different tools: chisel, tiller and roller. The highly significant correlation between the statistical indexes and shadow analysis results obtained in the laboratory as well as in the field for all the soil?tool combinations proved that both variability (CV) and dispersion (SD) are accommodated by the new method. This procedure simplifies the interpretation of soil surface roughness and shortens the time involved in field operations by a factor ranging from 12 to 20.

Direct measurement of nitric oxide generation from nitric oxide synthase

Although nitric oxide synthase (NOS) is widely considered as the major source of NO in biological cells and tissues, direct evidence demonstrating NO formation from the purified enzyme has been lacking. It was recently reported that NOS does not synthesize NO, but rather generates nitroxyl anion (NO−) that is subsequently converted to NO by superoxide dismutase (SOD). To determine if NOS synthesizes NO, electron paramagnetic resonance (EPR) spectroscopy was applied to directly measure NO formation from purified neuronal NOS. In the presence of the NO trap Fe2+-N-methyl-d-glucamine dithiocarbamate, NO gives rise to characteristic EPR signals with g = 2.04 and aN = 12.7 G, whereas NO− is undetectable. In the presence of l-arginine (l-Arg) and cofactors, NOS generated prominent NO signals. This NO generation did not require SOD, and it was blocked by the specific NOS inhibitor N-nitro-l-arginine methyl ester. Isotope-labeling experiments with l-[15N]Arg further demonstrated that NOS-catalyzed NO arose from the guanidino nitrogen of l-Arg. Measurement of the time course of NO formation demonstrated that it paralleled that of l-citrulline. The conditions used in the prior study were shown to result in potent superoxide generation, and this may explain the failure to measure NO formation in the absence of SOD. These experiments provide unequivocal evidence that NOS does directly synthesize NO from l-Arg.

Direct Measurement of Calcium Transport across Chloroplast Inner-Envelope Vesicles1

The initial rate of Ca2+ movement across the inner-envelope membrane of pea (Pisum sativum L.) chloroplasts was directly measured by stopped-flow spectrofluorometry using membrane vesicles loaded with the Ca2+-sensitive fluorophore fura-2. Calibration of fura-2 fluorescence was achieved by combining a ratiometric method with Ca2+-selective minielectrodes to determine pCa values. The initial rate of Ca2+ influx in predominantly right-side-out inner-envelope membrane vesicles was greater than that in largely inside-out vesicles. Ca2+ movement was stimulated by an inwardly directed electrochemical proton gradient across the membrane vesicles, an effect that was diminished by the addition of valinomycin in the presence of K+. In addition, Ca2+ was shown to move across the membrane vesicles in the presence of a K+ diffusion potential gradient. The potential-stimulated rate of Ca2+ transport was slightly inhibited by diltiazem and greatly inhibited by ruthenium red. Other pharmacological agents such as LaCl3, verapamil, and nifedipine had little or no effect. These results indicate that Ca2+ transport across the chloroplast inner envelope can occur by a potential-stimulated uniport mechanism.

Direct measurement of oligonucleotide binding stoichiometry of gene V protein by mass spectrometry.

The binding stoichiometry of gene V protein from bacteriophage f1 to several oligonucleotides was studied using electrospray ionization-mass spectrometry (ESI-MS). Using mild mass spectrometer interface conditions that preserve noncovalent associations in solution, gene V protein was observed as dimer ions from a 10 mM NH4OAc solution. Addition of oligonucleotides resulted in formation of protein-oligonucleotide complexes with stoichiometry of approximately four nucleotides (nt) per protein monomer. A 16-mer oligonucleotide gave predominantly a 4:1 (protein monomer: oligonucleotide) complex while oligonucleotides shorter than 15 nt showed stoichiometries of 2:1. Stoichiometries and relative binding constants for a mixture of oligonucleotides were readily measured using mass spectrometry. The binding stoichiometry of the protein with the 16-mer oligonucleotide was measured independently using size-exclusion chromatography and the results were consistent with the mass spectrometric data. These results demonstrate, for the first time, the observation and stoichiometric measurement of protein-oligonucleotide complexes using ESI-MS. The sensitivity and high resolution of ESI-MS should make it a useful too] in the study of protein-DNA interactions.

Direct measurement of salt-bridge solvation energies using a peptide model system: implications for protein stability.

The solvation energies of salt bridges formed between the terminal carboxyl of the host pentapeptide AcWL- X-LL and the side chains of Arg or Lys in the guest (X) position have been measured. The energies were derived from octanol-to-buffer transfer free energies determined between pH 1 and pH 9. 13C NMR measurements show that the salt bridges form in the octanol phase, but not in the buffer phase, when the side chains and the terminal carboxyl group are charged. The free energy of salt-bridge formation in octanol is approximately -4 kcal/mol (1 cal = 4.184 J), which is equal to or slightly larger than the sum of the solvation energies of noninteracting pairs of charged side chains. This is about one-half the free energy that would result from replacing a charge pair in octanol with a pair of hydrophobic residues of moderate size. Therefore, salt bridging in octanol can change the favorable aqueous solvation energy of a pair of oppositely charged residues to neutral or slightly unfavorable but cannot provide the same free energy decrease as hydrophobic residues. This is consistent with recent computational and experimental studies of protein stability.

Direct measurement of hydrogen bonding in DNA nucleotide bases by atomic force microscopy.

We have used self-assembled purines and pyrimidines on planar gold surfaces and on gold-coated atomic force microscope (AFM) tips to directly probe intermolecular hydrogen bonds. Electron spectroscopy for chemical analysis (ESCA) and thermal programmed desorption (TPD) measurements of the molecular layers suggested monolayer coverage and a desorption energy of about 25 kcal/mol. Experiments were performed under water, with all four DNA bases immobilized on AFM tips and flat surfaces. Directional hydrogen-bonding interaction between the tip molecules and the surface molecules could be measured only when opposite base-pair coatings were used. The directional interactions were inhibited by excess nucleotide base in solution. Nondirectional van der Waals forces were present in all other cases. Forces as low as two interacting base pairs have been measured. With coated AFM tips, surface chemistry-sensitive recognition atomic force microscopy can be performed.

Laser frequency locking by direct measurement of detuning

We present a new method of laser frequency locking in which the feedback signal is directly proportional to the detuning from an atomic transition, even at detunings many times the natural linewidth of the transition. Our method is a form of sub-Doppler polarization spectroscopy, based on measuring two Stokes parameters (I-2 and I-3) of light transmitted through a vapor cell. It extends the linear capture range of the lock loop by as much as an order of magnitude and provides frequency discrimination equivalent to or better than those of other commonly used locking techniques. (C) 2004 Optical Society of America

Piggery pond sludge as a nitrogen source for crops - 2. Assay of wet and stockpiled piggery pond sludge by successive cereal crops or direct measurement of soil available N

The appropriate use of wastes is a significant issue for the pig industry due to increasing pressure from regulatory authorities to protect the environment from pollution. Nitrogen contained in piggery pond sludge ( PPS) is a potential source of supplementary nutrient for crop production. Nitrogen contribution following the application of PPS to soil was obtained from 2 field experiments on the Darling Downs in southern Queensland on contrasting soil types, a cracking clay ( Vertosol) and a hardsetting sandy loam (Sodosol), and related to potentially mineralisable N from laboratory incubations conducted under controlled conditions and NO3- accumulation in the field. Piggery pond sludge was applied as-collected ( wet PPS) and following stockpiling to dry ( stockpiled PPS). Soil NO3- levels increased with increased application rates of wet and stockpiled PPS. Supplementary N supply from PPS estimated by fertiliser equivalence was generally unsatisfactory due to poor precision with this method, and also due to a high level of NO3- in the clay soil before the first assay crop. Also low recoveries of N by subsequent sorghum ( Sorghum bicolor) and wheat ( Triticum aestivum) assay crops at the 2 sites due to low in-crop rainfall in 1999 resulted in low apparent N availability. Over all, 29% ( range 12 - 47%) of total N from the wet PPS and 19% ( range 0 - 50%) from the stockpiled PPS were estimated to be plant-available N during the assay period. The high concentration of NO3- for the wet PPS application on sandy soil after the first assay crop ( 1998 barley, Hordeum vulgare) suggests that leaching of NO3- could be of concern when high rates of wet PPS are applied before infrequent periods of high precipitation, due primarily to the mineral N contained in wet PPS. Low yields, grain protein concentrations, and crop N uptake of the sorghum crop following the barley crop grown on the clay soil demonstrated a low residual value of N applied in PPS. NO3- in the sandy soil before sowing accounted for 79% of the variation in plant N uptake and was a better index than anaerobically mineralisable N ( 19% of variation explained). In clay soil, better prediction of crop N uptake was obtained when both anaerobically mineralisable N (39% of variation explained) and soil pro. le NO3- were used in combination (R-2 = 0.49).

A comparison of the growth curves of the foliose lichen Parmelia conspersa determined by a cross-sectional study and by direct measurement

Changes in the radial growth rate (RGR mm/yr) through life were studied in thalli of the foliose lichen Parmelia conspersa by two methods: (1) a cross-sectional study (Study A) in which the RGR was measured in 60 thalli from 0.2 to 13 cm in diameter, and (2) by radial growth measurements over 4.5 years of fragments, consisting of a single major lobe, which were removed from large thalli and glued to pieces of slate (Study B). Both studies suggested there was a phase of increasing RGR in small thalli followed by a more constant phase, the latter beginning at approximately a thallus radius of 6-8 mm. However, in Study B significantly increased RGR was observed during the second 6-month growth period. This phase of growth was more likely to be due to an increase in lobe width than to an effect of climate. In addition, a lobe in a large thallus with both adjacent lobes removed significantly increased in width over 1 year compared with control lobes. These results suggest that (1) mean lobe width in a thallus may be determined by the intensity of marginal competition between adjacent lobes, and (2) changes in lobe width during the life of a lichen thallus may be a factor determining the establishment of the linear phase of growth in foliose lichens. © 1992.

Direct measurement of coherency limits for strain relaxation in heteroepitaxial core/shell nanowires

The growth of heteroepitaxially strained semiconductors at the nanoscale enables tailoring of material properties for enhanced device performance. For core/shell nanowires (NWs), theoretical predictions of the coherency limits and the implications they carry remain uncertain without proper identification of the mechanisms by which strains relax. We present here for the Ge/Si core/shell NW system the first experimental measurement of critical shell thickness for strain relaxation in a semiconductor NW heterostructure and the identification of the relaxation mechanisms. Axial and tangential strain relief is initiated by the formation of periodic a/2 〈110〉 perfect dislocations via nucleation and glide on {111} slip-planes. Glide of dislocation segments is directly confirmed by real-time in situ transmission electron microscope observations and by dislocation dynamics simulations. Further shell growth leads to roughening and grain formation which provides additional strain relief. As a consequence of core/shell strain sharing in NWs, a 16 nm radius Ge NW with a 3 nm Si shell is shown to accommodate 3% coherent strain at equilibrium, a factor of 3 increase over the 1 nm equilibrium critical thickness for planar Si/Ge heteroepitaxial growth. © 2012 American Chemical Society.

Measurement of the charge asymmetry in semileptonic B-s(0) decays

We have performed the first direct measurement of the time-integrated flavor untagged charge asymmetry in semileptonic B-s(0) decays A(SL)(s,unt) by comparing the decay rate of B-s(0) -> mu(+) D-s(-) nu X, where D-s(-) -> phi pi(-) and phi -> K+K-, with the charge-conjugate (B) over bar (0)(s) decay rate. This sample was selected from 1: 3 fb(-1) of data collected by the D0 experiment in run II of the Fermilab Tevatron collider. We obtain A(SL)(s,unt) = [1.23 +/- 0.97(stat) +/- 0.17(syst)] x 10(-2). Assuming that Delta m(s)/(Gamma) over bar (s) >> 1, this result can be translated into a measurement of the CP-violating phase in B-s(0) mixing: Delta Gamma(s)/Delta m(s) tan phi(s) = [2.45 +/- 1.93(stat) +/- 0.35(syst)] x 10(-2).

Measurement of the WZ -> lvll cross section and limits on anomalous triple gauge couplings in p(p)over-bar collisions at root s=1.96 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)