Neutron interferometry using a single modulated phase grating.

Neutron grating interferometry provides information on phase and small-angle scatter in addition to attenuation. Previously, phase grating moiré interferometers (PGMI) with two or three phase gratings have been developed. These phase-grating systems use the moiré far-field technique to avoid the need for high-aspect absorption gratings used in Talbot-Lau interferometers (TLI) that reduce the neutron flux reaching the detector. We first demonstrate, through theory and simulations, a novel phase grating interferometer system for cold neutrons that requires a single modulated phase grating (MPG) for phase-contrast imaging, as opposed to the two or three phase gratings in previously employed PGMI systems. The theory shows the dual modulation of MPG with a large period and a smaller carrier pitch P, resulting in large fringes at the detector. The theory was compared to the full Sommerfeld-Rayleigh diffraction integral simulator. Then, we proceeded to compare the MPG system to experiments in the literature that use a two-phase-grating-based PGMI with best-case visibility of around 39%. The simulations of the MPG system show improved visibility in comparison to that of the two-phase-grating-based PGMI. An MPG with a modulation period of 300 µm, the pitch of 2 µm, and grating heights with a phase modulation of (π,0, illuminated by a monochromatic beam produces visibility of 94.2% with a comparable source-to-detector distance (SDD) as the two-phase-grating-based PGMI. Phase sensitivity, another important performance metric of the grating interferometer, was compared to values available in the literature, viz. the conventional TLI with the phase sensitivity of 4.5 × 103 for an SDD of 3.5 m and a beam wavelength of 0.44 nm. For a range of modulation periods, the MPG system provides comparable or greater theoretical maximum phase sensitivity of 4.1 × 103 to 10.0 × 103 for SDDs of up to 3.5 m. This proposed MPG system appears capable of providing high-performance PGMI that obviates the need for the alignment of two phase gratings.

Petrographic and spectroscopic characterization of phosphate-stabilized mine tailings from Leadville, Colorado.

The use of soluble PO4(3-) and lime as a heavy metal chemical stabilization agent was evaluated for mine tailings from Leadville, Colorado. The tailings are from piles associated with the Wolftone and Maid of Erin mines; ore material that was originally mined around 1900, reprocessed in the 1940s, and now requires stabilization. The dominant minerals in the tailings are galena (PbS), cerrusite (PbCO3), pyromorphite (Pb5(PO4)3Cl), plumbojarosite (Pb0.5Fe3(SO4)2(OH)6), and chalcophanites ((Pb,Fe,Zn,Mn)Mn2O5 x 2H2O). The tailings were treated with soluble PO4(3-) and lime to convert soluble heavy metals (principally Pb, Zn, Cu, Cd) into insoluble metal phosphate precipitates. The treatment process caused bulk mineralogical transformations as well as the formation of a reaction rind around the particles dominated by Ca and P. Within the mineral grains, Fe-Pb phosphosulfates, Fe-Pb sulfates (plumbojarosite), and galena convert to Fe-Ca-Pb hydroxides. The Mn-Pb hydroxides and Mn-(+/-Fe)-Pb hydroxides (chalcophanites) undergo chemical alteration throughout the grains during treatment. Bulk and surface spectroscopies showed that the insoluble reaction products in the rind are tertiary metal phosphate (e.g. (Cu,Ca2)(PO4)2) and apatite (e.g. Pb5(PO4)3Cl) family minerals. pH-dependent leaching (pH 4,6,8) showed that the treatment was able to reduce equilibrium concentrations by factors of 3 to 150 for many metals; particularly Pb2+, Zn2+, Cd2+, and Cu2+. Geochemical thermodynamic equilibrium modeling showed that apatite family and tertiary metal phosphate phases act as controlling solids for the equilibrium concentrations of Ca2+, PO4(3-) Pb2+, Zn2+, Cd2+, and Cu2+ in the leachates during pH-dependent leaching. Both end members and ideal solid solutions were seen to be controlling solids.

Structural characterization of MAO and related aluminum complexes. 1. Solid-state (27)Al NMR with comparison to EFG tensors from ab initio molecular orbital calculations.

Experimental and ab initio molecular orbital techniques are developed for study of aluminum species with large quadrupole coupling constants to test structural models for methylaluminoxanes (MAO). The techniques are applied to nitrogen- and oxygen-containing complexes of aluminum and to solid MAO isolated from active commercial MAO preparations. (Aminato)- and (propanolato)aluminum clusters with 3-, 4-, and 6-coordinate aluminum sites are studied with three (27)Al NMR techniques optimized for large (27)Al quadrupole coupling constants: field-swept, frequency-stepped, and high-field MAS NMR. Four-membered (aminato)aluminum complexes with AlN(4) coordination yield slightly smaller C(q) values than similar AlN(2)C(2) sites: 12.2 vs 15.8 MHz. Planar 3-coordinate AlN(2)C sites have the largest C(q) values, 37 MHz. In all cases, molecular orbital calculations of the electric field gradient tensors yields C(q) and eta values that match with experiment, even for a large hexameric (aminato)aluminum cage. A D(3d) symmetry hexaaluminum oxane cluster, postulated as a model for MAO, yields a calculated C(q) of -23.7 MHz, eta = 0.7474, and predicts a spectrum that is too broad to match the field-swept NMR of methylaluminoxane, which shows at least three sites, all with C(q) values greater than 15 MHz but less than 21 MHz. Thus, the proposed hexaaluminum cluster, with its strained four-membered rings, is not a major component of MAO. However, calculations for dimers of the cage complex, either edge-bridged or face-bridged, show a much closer match to experiment. Also, MAO preparations differ, with a gel form of MAO having significantly larger (27)Al C(q) values than a nongel form, a conclusion reached on the basis of (27)Al NMR line widths in field-swept NMR spectra acquired from 13 to 24 T.

Solid-state 2H MAS NMR studies of TNT absorption in soil and clays.

The binding of TNT to a soil and soil components is studied with 2H MAS NMR. This NMR technique clearly shows different interactions for deuterated TNT with soil, quartz, and clays. Basically, this NMR method relies on the well-defined 2H MAS NMR characteristics of a deuterated methyl group attached to an aromatic ring. Stationary rings and rings executing 2- or 3-fold jump motions all yield different NMR spectra. The technique has good sensitivity; these studies were conducted at a TNT loading of 22 mmol/kg. For the soil sample studied, TNT showed binding similar to a TNT/K10-montmorillonite sample.

27Al field-swept and frequency-stepped NMR for sites with large quadrupole coupling constants.

Spectra of nonspinning samples with large quadrupole coupling constants, 16-32 MHz, are acquired by frequency-stepping. A series of spin-echoes are acquired at arbitrary frequency increments, frequency-shifted in the time domain, and co-added as magnitude spectra. This procedure is derived from a method in use for field-swept NMR. The two methods are compared.

Organophosphorus residues in wool grease resulting from specified on-farm lice and flystrike control treatments.

OBJECTIVE: To investigate wool organophosphorus concentrations resulting from a range of farm pesticide application methods. DESIGN: Random sampling of wool for pesticide residues and on-farm interviews to determine associated treatments. PROCEDURE: Tasmanian fleece wool lots were sampled at random and tested for organophosphorus residues. The grower was identified and the pesticide treatments applied to the sheep were ascertained by on-farm interview. RESULTS: The residue concentrations showed a large variation that was not accounted for by differences in treatments by growers. Organophosphorus concentrations were proportional to the number of treatments applied, and inversely related to the time between pesticide application and the subsequent shearing, and were significantly influenced by the method of application. After allowing for the time of application, plunge dipping resulted in pesticide residue concentrations 2 to 2.5 times greater than shower dipping, using spray races or hand jetting, and the use of these methods caused larger residues than the use of jetting races. CONCLUSIONS: We recommend that plunge or shower dipping should not be used more than 7 weeks after shearing, nor at higher concentration than the standard dose rate used for lice control, whereas jetting may be satisfactory for up to 7 months after shearing, provided only one application is administered.

Screening for grain polyphenol variants from high-tannin sorghum somaclones.

Several hundred somaclones established from plants regenerated from embryogenic callus cultures of six high tannin sorghum lines were screened for variants with altered levels of polyphenols in the grain. Grain from over 6000 plants including the R 1 (primary), R2, and R3 generations were analyzed for total phenols, flavan-4-ols, and proanthocyanidins (condensed tannins). Although many variants which had lost the ability to synthesize chlorophyll were found, none of the somaclones tested had lost or greatly reduced the ability to synthesize any of the polyphenols assayed. However, we did observe statistically significant differences in polyphenol concentration between tissue culture-derived R1 plants and the parental controls. In the R2 generation the proportion of somaclones which differed significantly from the parents varied from 47% to 68% depending upon genotype. The average somaclonal variation rate and somaclonal variant frequency estimated in the tested population for the three polyphenol characteristics ranged from 37.3% to 40.7% and 5.3% to 7.8%, respectively. Variants with decreased levels of polyphenols were usually epigenetic and reverted back to normal levels in subsequent generations, but those with increased levels usually persisted after two meiotic cycles, indicating they are heritable. Variants with polyphenol levels increased up to 80% or decreased by 30% were selected for in the R3 generation.

Development and maturation of surghum seeds on detached panicles grown in vitro.

A procedure for culturing detached panicles of sorghum, Sorghum bicolor (L.) Moench, was developed to achieve flowering, fertilization, and subsequent seed development and maturation in vitro. Sixteen sorghum genotypes (five high and eleven low in tannin) were tested for their ability to develop normally in culture. Panicles collected one to two days before the initiation of anthesis were cultured in flasks containing liquid medium. Contamination and medium darkening were the major obstacles encountered. Up to 55% of the panicles cultured reached physiological maturity in vitro. The frequency of seed set ranged from 30 to 97% depending upon genotype and medium. Seed and glume color were normal. Seed produced in vitro resembled those grown in vivo and germinated well, but were smaller than normal (100 kernel weight reached 50 to 70% of the control). Grain polyphenols were synthesized in the cultured panicles. Seed of high tannin genotypes produced in vitro were lower in total phenols and tannins and higher in flavan-4-ols and the 3-deoxyanthocyanidin pigments than control seed. This technique can be used for harvesting late-maturing stocks and for various sorghum studies.

Transgenic sorghum plants via microprojectile bombardment.

Transgenic sorghum plants have been obtained after microprojectile bombardment of immature zygotic embryos of a drought-resistant sorghum cultivar, P898012. DNA delivery parameters were optimized based on transient expression of R and C1 maize anthocyanin regulatory elements in scutellar cells. The protocol for obtaining transgenic plants consists of the delivery of the bar gene to immature zygotic embryos and the imposition of bialaphos selection pressure at various stages during culture, from induction of somatic embryogenesis to rooting of regenerated plantlets. One in about every 350 embryos produced embryogenic tissues that survived bialaphos treatment; six transformed callus lines were obtained from three of the eight sorghum cultivars used in this research. Transgenic (T0) plants were obtained from cultivar P898012 (two independent transformation events). The presence of the bar and uidA genes in the T0 plants was confirmed by Southern blot analysis of genomic DNA. Phosphinothricin acetyltransferase activity was detected in extracts of the T0 plants. These plants were resistant to local application of the herbicide Ignite/Basta, and the resistance was inherited in T1 plants as a single dominant locus.

The medium frequency (7.5 MHz) ultrasound image characteristics of cattle skin.

The medium frequency (7.5 MHz) ultrasound images of cattle skin, as a model for other domestic animals, are described and compared with the published information for human skin. Although some difficulties are apparent in identifying the skin surface and therefore measuring tissue thicknesses, the papillary and reticular layers of cattle skin, about 2 and 4 mm thick, respectively, can be differentiated using a water standoff with a vegetable oil coupling medium. The difference in echo intensities and patterns between these dermal components supports the concept that ultrasound tissue characterisation using higher frequencies may prove to be a useful non-invasive procedure in livestock production and veterinary science. However, a detailed protocol is required. Care is needed in the choice of ultrasound coupling medium for good resolution of cattle skin. Higher frequency ultrasound equipment would be necessary for imaging the skin of small animals. Potential applications of this new technology are discussed.

Structure and evolution of the genomes ofsorghum bicolor andZea mays.

Cloned maize genes and random maize genomic fragments were used to construct a genetic map of sorghum and to compare the structure of the maize and sorghum genomes. Most (266/280) of the maize DNA fragments hybridized to sorghum DNA and 145 of them detected polymorphisms. The segregation of 111 markers was analyzed in 55 F2 progeny. A genetic map was generated with 96 loci arranged in 15 linkage groups spanning 709 map units. Comparative genetic mapping of sorghum and maize is complicated by the fact that many loci are duplicated, often making the identification of orthologous sequences ambiguous. Relative map positions of probes which detect only a single locus in both species indicated that multiple rearrangements have occurred since their divergence, but that many chromosomal segments have conserved synteny. Some sorghum linkage groups were found to be composed of sequences that detect loci on two different maize chromosomes. The two maize chromosomes to which these loci mapped were generally those which commonly share duplicated sequences. Evolutionary models and implications are discussed.

Multiple pulse NMR imaging of polymers and chemistry.

Multiple pulse line narrowing techniques can be used to improve resolution and sensitivity in solid state NMR imaging. For example, pulse sequences which remove homonuclear dipolar broadening have been used to image proton-containing materials. Further enhancements in resolution and sensitivity are obtained by removing inhomogeneous interactions such as chemical shift, susceptibility, and heteronuclear dipolar broadening. Pulse sequences have been designed which provide efficient line narrowing over large spectral widths by taking into account the experimenter's control over the amplitude and time dependence of the gradient-induced resonance offset. These methods have been applied to centimeter sized samples to obtain images of polymers, composite materials, and gas-solid chemical reactions. T1 and T2 contrast allows differentiation between materials.

Antinutritional effects of condensed and hydrolyzable tannins.

Despite major structural differences, hydrolyzable and condensed tannins often produce similar antinutritional effects. The most common effects are diminished weight gains and lowered efficiency of nutrient utilization. The major biochemical basis for these effects appears not to be inhibition of dietary protein digestion but rather a systemic inhibition of the metabolism of digested and absorbed nutrients, particularly protein. In the case of condensed tannins, this inhibition is probably not due to polymeric tannin molecules, which are not absorbed from the digestive tract, but to associated lower MW polyphenols, which are readily absorbed.

Somaclonal variation in high tannin sorghums.

Genetic variants were found among over 6,000 primary plants (R1) regenerated from embryogenic tissue cultures of eight high tannin sorghums [Sorghum bicolor (L.) Moench]. Field assessment of somaclonal variation has progressed to the R2 population, with over 48,000 R2 seedlings (27,000 plants) in 1,126 rows from 1,055 R1 plants. A total of 43 variant phenotypes was recovered, including several types of chlorophyll deficiencies, dwarfism, short culm, sterility, narrow leaf, and several previously unreported variants, such as ragged leaf, multibranched heads, and Hydra, a developmental variant which produces large numbers of panicles. Variation production greatly depends on parent genotype and appears to increase with increasing time in cultures. The toal average somaclonal variation rate (based per 100 R1 plants) and somaclonal variant frequency (based per 100 R2 plants) estimated in the tested population were 11.3 and 1.6, respectively. Chimerism was found in regenerants. The estimated size of the mutated sector carried by mutant regenerants ranged from the whole plant to less than 3% of a single head. The average proportion of mutated R1 heads carrying large (80%-100%), medium (40%-80%), and small (<40%) mutated sectors was 38.7%, 26.0% and 35.3%, respectively. Some sector mutations do not appear until the R3 generation. In order to avoid losing variants, the population for selecting somaclonal variation should be as large as possible. Some of these variants found may be useful for further study or for use in breeding programs.

Choosing appropriate methods and standards for assaying tannin.

Tannins are chemically diverse polyphenolics that have multiple biological activities. Attempts to establish the ecological significance of tannins have been hindered by the complexities of tannin analysis. A multitude of analytical procedures for tannins has been described, but it is difficult for the nonspecialist to select appropriate methods. We have classified the most common procedures for determining tannin as either chemical assays, appropriate for determining the amount and the chemical nature of the tannin in a sample, or as protein-binding assays, suitable for determining the potential biological activity of the tannin in a sample. We have recommended procedures that are particularly reliable and straightforward for general use. We have also considered the problems encountered in selecting appropriate standards for tannin analysis and have recommended standards that are readily available.

Antinutritional effects and ecological significance of dietary condensed tannins may not be due to binding and inhibiting digestive enzymes.

The digestive enzymes alkaline phosphatase and 5'-nucleotide phosphodiesterase, solubilized from bovine intestinal mucosa and purified to homogeneity, were found to be strongly inhibited in vitro by condensed tannins (proanthocyanidins) purified from sorghum seeds and from quebracho. Tannin inhibition was prevented and reversed by the detergent Triton X-100 (protein-binding agent), by soluble polyvinylpyrrolidone (tannin-binding agent), or by phosphatidylcholine (membrane component). When tested as a crude particulate membrane fraction more characteristic of their in vivo condition, both enzymes were inhibited much less than either purified enzyme at the same tannin concentration. Because the enzymes appear to be relatively insensitive to inhibition by tannin in conditions which mimic in vivo conditions, and because the proportion of the dietary tannin which is available to interact with these enzymes in the digestive tract is likely to be rather small, we suggest that the antinutritional effects and ecological significance of dietary tannins are not due to tannin inhibition of these or other digestive enzymes by direct binding to them.

Induction of proline-rich proteins in hamster salivary glands by isoproterenol treatment and an unusual growth inhibition by tannins.

Treatment of hamsters with the beta-agonist isoproterenol caused a dramatic increase in a series of unusual proteins in the parotid and submandibular glands. These proteins are acid soluble and they contain high amounts (mol%) of glutamate plus glutamine (30-35), proline (23-30), and glycine (12-25). Three proteins (HP45, HP43a, and HP43b) were isolated from trichloroacetic acid extracts of parotid glands of isoproterenol-treated hamsters. The basic protein (HP45) was not retained by DEAE-cellulose and did not contain phosphate or carbohydrate. Two acidic proteins (HP43a and HP43b) had the same apparent molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, but these were separated by DEAE-cellulose chromatography. HP43a and HP43b contained 4.3 and 5.7 phosphate residues/mol of protein, respectively. Levels of mRNAs encoding this series of proteins showed striking increases following isoproterenol treatment as determined by cell-free translations and Northern analysis. Feeding tannins to rats and mice mimicks the effects of isoproterenol treatment on the parotid gland (Mehansho, H., Hagerman, A., Clements, S., Butler, L., Rogler, J., and Carlson, D.M. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 3948-3952; Mehansho, H., Clements, S., Sheares, B. T., Smith, S., and Carlson, D. M. (1985) J. Biol. Chem. 260, 4418-4423]. However, hamsters on a high tannin diet (2%) did not respond like rats and mice and instead displayed an unusual growth inhibition. Weanling hamsters maintained on a 2% tannin diet initially lost weight for 3 days and then failed to gain weight for up to 6 months when kept on this diet. Essentially a normal growth rate was observed when the tannin-fed hamsters were switched to a normal diet.

Improving the in vitro protein digestibility of sorghum with reducing agents.

We have shown in previous reports that cooked sorghum protein is less digestible than other cooked cereal proteins. The pepsin-indigestible proteins in sorghum were found to be mainly prolamin proteins. Cooking sorghum in the presence of 2-mercaptoethanol increased protein digestibility (in vitro with pepsin or trypsin/chymotrypsin) to a level comparable with other cereals. At a concentration of 100 mM, other reducing agents (dithiothreitol, sodium bisulfite, and L-cysteine) were equally effective in improving sorghum digestibility. When maize was cooked in the presence of 2-mercaptoethanol, protein digestibility increased 5% compared to 25% for sorghum. Cooking barley, rice, and wheat with 2-mercaptoethanol had no significant effect on protein digestibility. The addition of reducing agents appears to prevent the formation of protein polymers linked by disulfide bonds.