1,376 research outputs found
A note on the chemical composition and in vitro digestibility of contrasting stover components of maize grown in climatically marginal conditions and harvested at differing maturities.
peer-reviewedThis study evaluated the nutritive value of three contrasting components of maize
stover (leaf, upper stem, lower stem) at three harvest dates. The leaf component had a
greater in vitro dry matter digestibility (DMD) and a lower NDF concentration, compared
to the stem components. Delaying harvest reduced the in vitro DMD of the stem
components to a greater extent than leaf, reflecting lower increases in the NDF and
lignin concentrations in leaf tissue. The stem components of maize stover had a lower
nutritive value than the leaf component, and had a larger decrease in digestibility with
delayed harvest.Funding for this study was provided under the
National Development Plan through the Research Stimulus fund administered by the Department of Agriculture, Food and the Marine (RSF 07 501
Phenotyping cowpea for seedling root architecture reveals root phenes important for breeding phosphorus efficient varieties
Open Access Article; Published online: 15 Sep 2021Cowpea (Vigna unguiculata L. Walp.) is a key climate-resilient legume for food security, especially in sub-Saharan Africa. Cowpea yields are limited by edaphic stresses including drought and low phosphorus (P) availability. Identifying genotypes with advantageous root phenotypes can facilitate breeding for improved yield in marginal environments. We evaluated 50 elite genotypes from African and U.S. sources for seedling root architecture and root hair length and density. Significant genotypic variation was detected for all phenes, and high heritability was observed for architectural phenotypes including primary root length (77%), basal root number (72%), and taproot branching density (67%). Moderate heritability was detected for root hair length and density among different root classes (34 to 63%), which were positively associated with each other. Principal component analysis identified three clusters, primarily defined by seed dimension and seedling root architecture. Genotypes were identified with longer root hairs (TVu-7778, Vita7, and Sanzi) and longer taproots (IT96D-610, IT98K-111-1, and IT97K-499-35), as potential parents. Root phenotypes, grain, and fodder yield were assessed on a subset of 20 genotypes under contrasting P availability in the field. Some seedling root phenotypes were significantly related to mature plant dry fodder weight (taproot hair density) and to grain yield (lateral root hair density) under low P. Root hairs are positively related to plant productivity under low P. We suggest selection for longer primary roots, as more basal and lateral root roots may be beneficial for cowpea in drought and low P environments. These findings suggest seedling root phenotypes can support cowpea breeding for suboptimal environments
Assessment of water-limited winter wheat yield potential at spatially contrasting sites in Ireland using a simple growth and development model
Publication history: Published online - 19 September 2017Although Irish winter wheat yields are among the highest globally, increases in the profitability of this crop are required to
maintain its economic viability. However, in order to determine if efforts to further increase Irish wheat yields are likely to
be successful, an accurate estimation of the yield potential is required for different regions within Ireland. A winter wheat
yield potential model (WWYPM) was developed, which estimates the maximum water-limited yield achievable, within the
confines of current genetic resources and technologies, using parameters for winter wheat growth and development
observed recently in Ireland and a minor amount of daily meteorological input (maximum and minimum daily temperature,
total daily rainfall and total daily incident radiation). The WWYPM is composed of three processes: (i) an estimation of
potential green area index, (ii) an estimation of light interception and biomass accumulation and (iii) an estimation of
biomass partitioning to grain yield. Model validation indicated that WWYPM estimations of water-limited yield potential
(YPw) were significantly related to maximum yields recorded in variety evaluation trials as well as regional average and
maximum farm yields, reflecting the model’s sensitivity to alterations in the climatic environment with spatial and seasonal
variations. Simulations of YPw for long-term average weather data at 12 sites located at spatially contrasting regions of
Ireland indicated that the typical YPw varied between 15.6 and 17.9 t/ha, with a mean of 16.7 t/ha at 15% moisture content.
These results indicate that the majority of sites in Ireland have the potential to grow high-yielding crops of winter wheat
when the effects of very high rainfall and other stresses such as disease incidence and nutrient deficits are not considered.Funding for this study was provided by the Department of Agriculture, Food and the Marine, Ireland
Imaging Sources with Fast and Slow Emission Components
We investigate two-proton correlation functions for reactions in which fast
dynamical and slow evaporative proton emission are both present. In such cases,
the width of the correlation peak provides the most reliable information about
the source size of the fast dynamical component. The maximum of the correlation
function is sensitive to the relative yields from the slow and fast emission
components. Numerically inverting the correlation function allows one to
accurately disentangle fast dynamical from slow evaporative emission and
extract details of the shape of the two-proton source.Comment: 13 pages, 4 figure
Mass Parameterizations and Predictions of Isotopic Observables
We discuss the accuracy of mass models for extrapolating to very asymmetric
nuclei and the impact of such extrapolations on the predictions of isotopic
observables in multifragmentation. We obtain improved mass predictions by
incorporating measured masses and extrapolating to unmeasured masses with a
mass formula that includes surface symmetry and Coulomb terms. We find that
using accurate masses has a significant impact on the predicted isotopic
observables.Comment: 12 pages, 4 figure
Isospin Effects in Nuclear Multifragmentation
We develop an improved Statistical Multifragmentation Model that provides the
capability to calculate calorimetric and isotopic observables with precision.
With this new model we examine the influence of nuclear isospin on the fragment
elemental and isotopic distributions. We show that the proposed improvements on
the model are essential for studying isospin effects in nuclear
multifragmentation. In particular, these calculations show that accurate
comparisons to experimental data require that the nuclear masses, free energies
and secondary decay must be handled with higher precision than many current
models accord.Comment: 46 pages, 16 figure
Donor states in modulation-doped Si/SiGe heterostructures
We present a unified approach for calculating the properties of shallow
donors inside or outside heterostructure quantum wells. The method allows us to
obtain not only the binding energies of all localized states of any symmetry,
but also the energy width of the resonant states which may appear when a
localized state becomes degenerate with the continuous quantum well subbands.
The approach is non-variational, and we are therefore also able to evaluate the
wave functions. This is used to calculate the optical absorption spectrum,
which is strongly non-isotropic due to the selection rules. The results
obtained from calculations for Si/SiGe quantum wells allow us to
present the general behavior of the impurity states, as the donor position is
varied from the center of the well to deep inside the barrier. The influence on
the donor ground state from both the central-cell effect and the strain arising
from the lattice mismatch is carefully considered.Comment: 17 pages, 10 figure
Fragment Isospin as a Probe of Heavy-Ion Collisions
Isotope ratios of fragments produced at mid-rapidity in peripheral and
central collisions of 114Cd ions with 92Mo and 98Mo target nuclei at E/A = 50
MeV are compared. Neutron-rich isotopes are preferentially produced in central
collisions as compared to peripheral collisions. The influence of the size (A),
density, N/Z, E*/A, and Eflow/A of the emitting source on the measured isotope
ratios was explored by comparison with a statistical model (SMM). The
mid-rapidity region associated with peripheral collisions does not appear to be
neutron-enriched relative to central collisions.Comment: 12 pages including figure
Excitation and decay of projectile-like fragments formed in dissipative peripheral collisions at intermediate energies
Projectile-like fragments (PLF:15<=Z<=46) formed in peripheral and
mid-peripheral collisions of 114Cd projectiles with 92Mo nuclei at E/A=50 MeV
have been detected at very forward angles, 2.1 deg.<=theta_lab<=4.2 deg.
Calorimetric analysis of the charged particles observed in coincidence with the
PLF reveals that the excitation of the primary PLF is strongly related to its
velocity damping. Furthermore, for a given V_PLF*, its excitation is not
related to its size, Z_PLF*. For the largest velocity damping, the excitation
energy attained is large, approximately commensurate with a system at the
limiting temperatureComment: 5 pages, 6 figure
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