136 research outputs found
Relationship between chemical composition of native forage and nutrient digestibility by Tibetan sheep on the Qinghai–Tibetan Plateau
Publication history: Accepted - 06 March 2018; Published - 02 april 2018.To better utilize native pasture at the
high altitude region, three-consecutive-year feeding
experiments and a total of seven metabolism trials
were conducted to evaluate the impact of three forage
stages of maturity on the chemical composition,
nutrient digestibility, and energy metabolism of native
forage in Tibetan sheep on the Qinghai–Tibetan
Plateau (QTP). Forages were harvested from June to
July, August to October, and November to December
of 2011 to 2013, corresponding to the vegetative,
bloom, and senescent stages of the annual forages.
Twenty male Tibetan sheep were selected for each
study and fed native forage ad libitum. The digestibility
of DM, OM, CP, NDF, ADF, DE, DE/GE, and
ME/GE were greatest (P < 0.01) from the vegetative
stage, intermediate (P < 0.01) from the bloom stage,
and least (P < 0.01) from the senescent stage. Nutrient
digestibility and energy parameters correlated positively
(linear, 0.422 to 0.778; quadratic, 0.568 to
0.815; P < 0.01) with the CP content of forage but
correlated negatively with the content of NDF (linear,
0.343 to 0.689; quadratic, 0.444 to 0.777; P ≤ 0.02),
ADF (linear, 0.563 to 0.766; quadratic, 0.582 to 0.770;
P < 0.01), and ether extract (EE, linear, 0.283 to 0.574;
quadratic, 0.366 to 0.718; P ≤ 0.04) of forage. For each
predicted variable, the prediction of DMI expressed
as grams per kilogram of BW (g/kg BW·d) yielded
a greater R2 value (0.677 to 0.761 vs. 0.616 to 0.711)
compared with the equations of DMI expressed
as g/kg metabolic BW by step-wise regression. The
results suggest that parameters of forage CP, NDF,
and ADF content were most closely related to nutrient
digestibility. Contrary to previous studies, in this
study, ADF content had a greater linear relationship
(0.766 vs. 0.563 to 0.732) with OM digestibility than
the other parameters of nutrient digestibility. The
quadratic relationship between forage CP content and
CP digestibility indicates that when forage CP content
exceeds the peak point (9.7% DM in the present
study), increasing forage CP content could decrease
CP digestibility when Tibetan sheep were offered
native forage alone on the QTP. Additionally, using
the forage CP, EE, NDF, and ADF content to predict
DMI (g/kg BW·d) yielded the best fit equation
for Tibetan sheep living in the northeast portion of
the QTPThis work was supported by the National Key Project
of Scientific and Technical Supporting (2014CB138706),
National Natural Science Foundation of China (31672472),
Program for Changjiang Scholars and Innovative Research
Team in University (IRT13019), and the 111 project (B12002)
A review of the wave gradiometry method for seismic imagingKey points
As dense seismic arrays at different scales are deployed, the techniques to make full use of array data with low computing cost become increasingly needed. The wave gradiometry method (WGM) is a new branch in seismic tomography, which utilizes the spatial gradients of the wavefield to determine the phase velocity, wave propagation direction, geometrical spreading, and radiation pattern. Seismic wave propagation parameters obtained using the WGM can be further applied to invert 3D velocity models, Q values, and anisotropy at lithospheric (crust and/or mantle) and smaller scales (e.g., industrial oilfield or fault zone). Herein, we review the theoretical foundation, technical development, and major applications of the WGM, and compared the WGM with other commonly used major array imaging methods. Future development of the WGM is also discussed
Thermoplastic deformation of ferromagnetic CoFe-based bulk metallic glasses
The superplastic deformation behavior of the ferromagnetic Co31Fe31Nb8B30 bulk metallic glass (BMG) in the supercooled liquid region was investigated. At a given temperature, the BMG exhibits a Newtonian behavior at low strain rates but a non-Newtonian behavior at high strain rates. The high thermal stability of this glassy alloy system offers an enough processing window to thermoplastic forming (TPF), and the strong processing ability was examined by simple micro-replication experiments. It is demonstrated that the TPF formability on length scales ranging down to nanometers can be achieved in the selected experimental condition. Based on the analysis of deformation behavior, the nearly full density sample (i.e. nearly 100%), was produced from water-atomized glassy powders and consolidated by the hot-pressing technique. The sample exhibits good soft-magnetic and mechanical properties, i.e., low coercive force of 0.43 Oe, high initial permeability of 4100 and high Vickers hardness 1398. These results suggest that the hot-pressing process opens up possibilities for the commercial exploitation of BMGs in engineering applications
Pronounced enhancement of glass-forming ability of Fe-Si-B-P bulk metallic glass in oxygen atmosphere
It is widely accepted that oxygen will severely deteriorate the glass-forming ability (GFA) of an alloy. In this work, we report that the GFA of a Fe76Si9B10P5 glassy alloy can be significantly improved (the critical diameter for fully glass formation is increased from 1 to 3 mm) under oxygen casting atmosphere. Furthermore, the pressure of oxygen atmosphere gives an obvious enhancement in the critical diameter of Fe76Si9B10P5 glassy alloy. A dependence of GFA on casting atmosphere species (argon, nitrogen, air, and oxygen) is also observed for this glassy alloy, and its critical diameter is 1, 1.5, 2.5, and 3 mm, respectively. In addition, the Fe-based glassy alloy exhibits excellent soft magnetic properties regardless of the applied casting atmosphere. The mechanism for such an unusual oxygen effect on the GFA of Fe76Si9B10P5 glassy alloy is attributed to the reduced nucleation rate caused by the enhancement of surface tension of the alloy melt
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