18 research outputs found
Higher Fatty Acid Composition of Immature Forages as Affected by N Fertilization
High levels of both N and total higher fatty acids
(HFA) in forage have been associated with increasing the
grass tetany hazard to grazing cattle. The objective of this
study was to determine the relationship between forage
N, total HFA, and HFA species distribution in several
forages.
Forage N, HFA, HFA species concentration, and total
chlorophyll were determined in immature vegetative
growth of Agropyron desertorum (Fisch.) Schult., Cynodon
dactylon L., Lolium perenne L., Trifolium repens L.,
and Triticum aestivum L. established with soil fertility
levels up to 500 ppm N in the growth chamber. Forage
HFA concentrations were positively and linearly related
to forage N levels, but regression coefficients were not the
same for all species. The HFA concentrations were as
high as 16 mmol COOH/100g DM at 6% total N in first
cutting Lolium perenne L. The relative HFA species distribution
was the same within a given forage, even though
total N concentrations ranged from 2 to 6%. The mean
HFA specie concentrations (determined by gas-liquid-chromatography
relative to mean total HFA concentrations
determined by titration) when expressed as percent
for the grasses were: C14:0 — 2%, C16:0 — 13%, C16:1
— 1%, C18:0 plus C18:1 — 1%, C18:2 — 11%, and C18:3
— 67%. The total HFA concentrations were positively
correlated with chlorophyll a + b concentrations which
was expected, since the HFA of green plants is largely
associated with chloroplast membrane
Scaling Properties of Random Walks on Small-World Networks
Using both numerical simulations and scaling arguments, we study the behavior
of a random walker on a one-dimensional small-world network. For the properties
we study, we find that the random walk obeys a characteristic scaling form.
These properties include the average number of distinct sites visited by the
random walker, the mean-square displacement of the walker, and the distribution
of first-return times. The scaling form has three characteristic time regimes.
At short times, the walker does not see the small-world shortcuts and
effectively probes an ordinary Euclidean network in -dimensions. At
intermediate times, the properties of the walker shows scaling behavior
characteristic of an infinite small-world network. Finally, at long times, the
finite size of the network becomes important, and many of the properties of the
walker saturate. We propose general analytical forms for the scaling properties
in all three regimes, and show that these analytical forms are consistent with
our numerical simulations.Comment: 7 pages, 8 figures, two-column format. Submitted to PR
Higher Fatty Acid Composition of Immature Forages as Affected by N Fertilization
High levels of both N and total higher fatty acids
(HFA) in forage have been associated with increasing the
grass tetany hazard to grazing cattle. The objective of this
study was to determine the relationship between forage
N, total HFA, and HFA species distribution in several
forages.
Forage N, HFA, HFA species concentration, and total
chlorophyll were determined in immature vegetative
growth of Agropyron desertorum (Fisch.) Schult., Cynodon
dactylon L., Lolium perenne L., Trifolium repens L.,
and Triticum aestivum L. established with soil fertility
levels up to 500 ppm N in the growth chamber. Forage
HFA concentrations were positively and linearly related
to forage N levels, but regression coefficients were not the
same for all species. The HFA concentrations were as
high as 16 mmol COOH/100g DM at 6% total N in first
cutting Lolium perenne L. The relative HFA species distribution
was the same within a given forage, even though
total N concentrations ranged from 2 to 6%. The mean
HFA specie concentrations (determined by gas-liquid-chromatography
relative to mean total HFA concentrations
determined by titration) when expressed as percent
for the grasses were: C14:0 — 2%, C16:0 — 13%, C16:1
— 1%, C18:0 plus C18:1 — 1%, C18:2 — 11%, and C18:3
— 67%. The total HFA concentrations were positively
correlated with chlorophyll a + b concentrations which
was expected, since the HFA of green plants is largely
associated with chloroplast membrane