Coupling of dry matter and nitrogen accumulation in ryegrass

The logistic model has proven very useful in relating dry matter production of warm season perennial forage grasses to applied nitrogen. A recent extension of the model coupled dry matter and plant N accumulation through a common response coefficient c. The objective of this analysis was to apply the extended logistic model to cool season Gulf annual ryegrass (Lolium multiflorum Lam.) and to establish a common response coefficient c between accumulation of dry matter and plant N. Analysis of variance established the validity of this hypothesis. The model accurately described response of dry matter, plant N removal, and plant N concentration to applied N, with an overall correlation coefficient of 0.9954. Furthermore, the model closely described the relationship between yield and plant N removal, as well as between plant N concentration and plant N removal. The logistic equation is well-behaved and simple to use on a pocket calculator. It can be used to estimate yields and plant N removal in evaluation of agricultural production and environmental quality.     

Conversion of Nuclear Waste to Molten Glass: Cold‐Cap Reactions in Crucible Tests

The feed‐to‐glass conversion, which comprises complex chemical reactions and phase transitions, occurs in the cold cap during nuclear waste vitrification. To investigate the conversion process, we analyzed heat‐treated samples of a simulated high‐level waste feed using X‐ray diffraction, electron probe microanalysis, leaching tests, and residual anion analysis. Feed dehydration, gas evolution, and borate phase formation occurred at temperatures below 700°C before the emerging glass‐forming melt was completely connected. Above 700°C, intermediate aluminosilicate phases and quartz particles gradually dissolved in the continuous borosilicate melt, which expanded with transient foam. Knowledge of the chemistry and physics of feed‐to‐glass conversion will help us control the conversion path by changing the melter feed makeup to maximize the glass production rate.     

Object recognition versus object discrimination: Comparison between human infants and infant monkeys.

Human infants (aged 12–32 mo old) and adults learned a delayed nonmatching-to-sample (DNMS) task and single- and multiple-pair discrimination tasks using nonverbal procedures previously used with monkeys. Infants learned discriminations rapidly and at a young age (12 mo), but they required prolonged training and maturation before learning the DNMS task. Adults learned all tasks rapidly. After learning the DNMS task to criterion, memory performance declined systematically in an inverse relation to age. The dissociation in ability of infants on the DNMS vs discrimination tasks closely resembles the dissociation previously reported with infant monkeys (J. Bachevalier & M. Mishkin, 1984). Results from both infant humans and monkeys support a neurocognitive maturational model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Controlling Stereoselection in Aza-Cope-Mannich Reactions

The synthesis of 2-substituted cis-octahydroindolones from the reaction of cis-2-amino-1-alkenylcyclopentanols with aldehydes was studied to examine whether stereoselection in the aza-Cope–Mannich reaction could be controlled by the nature of the nitrogen substituent. 2-Alkylamino-1-(1-phenylethenyl)cyclopentanols 7 and 8 , which contain nitrogen substituents of widely differing size (Me and CHPh₂), were condensed with four aldehydes to give oxazolidines 9a–d and 10a-c. Rearrangement of these intermediates at 23–60 °C, in the presence of 0.9 equiv of (±)-10-camphorsulfonic acid in acetonitrile, gave cis-octahydroindolones 11a-d and 12a–c in yields of 77–95%. Using a combination of single-crystal X-ray crystallography, ¹H nOe measurements, and comparisons with known materials it was established that the N-methyl oxazolidines 9a–d provided exclusively cis-octahydroindolones having the 2-substituent trans to the angular substituents, while N-benzhydryl analogs 10a–c provided exclusively the all-cis products 12a–c. These results are interpreted to mean: (1) When the nitrogen substituent is small (Me), the stereochemistry-determining [3,3]-sigmatropic rearrangement occurs preferentially through a transition-state topography having the R² substituent oriented quasiequatorially ( 14 → 15 → 16 ); (2) When this substituent is large (CHPh₂), destabilizing steric interactions between the vicinal R¹ and R² substituents causes the rearrangement to occur preferentially through the alternate iminium ion stereoisomer ( 17 → 18 → 19 ).     

Ontogeny of place learning in children as measured in the Radial Arm Maze, Morris Search Task, and Open Field Task.

Children and adults were tested on 3 place learning tasks. Children under the age of 7 yrs were inferior to older Ss in solving the tasks by using spatial relational solutions, but Ss of all ages were equally proficient in solving the task by using simple stimulus-reward associations (cued solutions). Accurate performance on the cued versions suggests that neither the general response demands nor the large size of testing environments rendered the tasks differentially inappropriate for young children. Instead, the nature of the cognitive demands were responsible for different levels of performance across the age groups. Because, in animal studies, spatial relational solutions but not cued solutions of these tests require mature and undamaged medial temporal lobe structures, the results suggest that these systems are not fully developed in humans before approximately 7 yrs of age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Effect of Homogenization Heat Treatment on the Texture Evolution in U-10Mo Alloy

Metallurgical and Materials Transactions A - Uranium alloyed with 10 wt pct Mo (U-10Mo) undergoes discontinuous precipitation (DP) when subjected to sub-eutectoid heat treatment. It is hypothesized...     

Cognitive gender differences in very young children parallel biologically based cognitive gender differences in monkeys.

Infant humans were trained on 2 cognitive tests that have previously revealed, in infant monkeys, a double dissociation that was reversible by perinatal manipulations of androgens and ablations of specific brain sites. Children showed the same sex-linked behavior found with infant monkeys: young boys were superior on the object reversal task and young girls were superior on the concurrent discrimination task. As happened previously with infant monkeys, the gender difference was not apparent in older human subjects. Thus, early in ontogeny, cognitive gender differences have now been discovered in both humans and monkeys, probably a result of gender differences in androgens that influence the maturation rate of specific brain systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amide modes of the alpha-helix: Raman spectroscopy of filamentous virus fd containing peptide 13C and 2H labels in coat protein subunits

The filamentous virus fd consists of a single-stranded DNA genome sheathed by 2700 copies of a 50-residue alpha-helical subunit (protein pVIII) and serves as a model assembly of alpha-helices. To advance vibrational assignments for the alpha-helix, we have investigated Raman spectra of fd virions containing 13C and 2H (deuterium) labels at various main-chain sites of the pVIII subunits. 13C was introduced at specific peptide carbonyls, while deuterium was introduced at selected alpha-carbon (Calpha) and amide nitrogen positions. Interpretation of the Raman spectra reveals a previously unrecognized alpha-helix band in the spectral interval 730-745 cm-1, tentatively assigned to a carbonyl in-plane bending mode (amide IV). Experimental evidence has also been obtained for a distinctive alpha-helix marker near 1345 cm-1, assigned to a coupled Calpha-H bending and Calpha-C stretching mode. The fd virions containing 13C-labeled carbonyls exhibit unexpectedly complex amide I profiles, consisting of multiple band components. Amide I splitting resulting from 13C substitution of carbonyls is attributed to decoupling of transition-dipole interactions normally occurring in the extended pVIII helix. The present study identifies novel conformation-dependent Raman bands in a native alpha-helix assembly, confirms amide I and amide III assignments proposed previously for filamentous viruses, and facilitates new Raman assignments for the packaged ssDNA. The alpha-helix markers identified here should also be useful in conformation analyses of other proteins by Raman spectroscopy.