984,730 research outputs found
Incipient ferralization and weathering indices along a soil chronosequence in Taiwan
The low hilly topography of Green Island, a volcanic island off southeastern Taiwan, includes an altitudinal sequence of sub-horizontal benches. We examined eight profiles along this sequence, ranging from pale brown loamy coral sand on the lowest bench that fringes the coast at an elevation of about 10 m to deep, intensely red and acid clay on the highest bench at about 240 m. Chemical analyses, differential Fe extractions, thin sections, X-ray diffraction of the clay minerals and indices of pedochemical weathering and strain indicated that soil development progressed by weathering of primary and secondary phyllosilicates through argilluviation in the intermediate stages to the generation of increasing quantities of free Fe. The Fe accumulates as free sesquioxides, which crystallize with age. Taxonomically the soil types progress from sandy coral Arenosol, through Eutric Cambisol, Hypereutric Lixisol and Acrisol to incipient Ferralsol (Udipsamment → Eutrudept → Udalf → Udultisol → Udox in Soil Taxonomy). The profiles are interpreted as a chronosequence, although this is complicated by minor and upwardly diminishing contributions of reef coral to the mainly igneous parent materials. There are also variations in the andesitic-basaltic bedrock, and minor aeolian inputs in the higher and older soil types. Regional eustatic sea-level correlations, 14C dating of carbonates on the two lowest benches and estimates of local tectonic uplift indicate that the incipient Ferralsols on the upper bench might date from about 150 ka. The transition through argilluvial Acrisols to incipient sesquioxide-dominated Ferralsols appears, therefore, to develop within 100–200 ka on Green Island, which is faster than usual
Supplementation of Sapindus Rarak and Garlic Extract in Feed Containing Adequate Cr, Se, and Zn on Rumen Fermentation
The objective of the study was to evaluate the effect of Sapindus rarak extract (SRE) with or without garlic extract (GE) on in vitro ruminal fementation. This research was conducted experimentally with a randomized block design, with 7 treatments and 5 blocks. The treatments were: R0: dairy cow feed; R1: R0 + 1.5 ppm Cr + 0.3 ppm Se + 40 ppm Zn; R2: R1 + 1.8 g/kg methanol extract of lerak fruit meal (SRE); R3: R2 + 0.25 ppm of garlic extract (GE); R4: R2 + 0.50 ppm of GE; R5: R2 + 0.75 ppm of GE; R6: R2 +1.0 ppm of GE. The results showed that the supplementation of SRE alone or without GE did not affect the pH, however, it decreased crude fiber digestibility. The supplementations of SRE and GE, decreased crude fibre digestibility as much as 13.01% up to 16.6%. The supplementation of 1.8 g/kg SRE + 0.25 ppm GE in the dairy cattle diet was able to decrease ace-tate, protozoal population and increase propionate. The supplementation of 1.8 g/kg SRE and 0.25 ppm garlic represents the best combination for dairy cattle feed in improving ruminal fermentation based on feed digestibility, fermentation products, and rumen bacterial population
Cavitation Scaling Experiments With Headforms: Bubble Acoustics
Recently Ceccio and Brennen [1][2][3] have
examined the interaction between individual traveling
cavitation bubbles and the structure of the boundary layer
and flow field in which the bubble is growing and
collapsing. They were able to show that individual
bubbles are often fissioned by the fluid shear and that this
process can significantly effect the acoustic signal
produced by the collapse. Furthermore they were able to
demonstrate a relationship between the number of
cavitation events and the nuclei number distribution
measured by holographic methods in the upstream flow.
Kumar and Brennen [4][5] have further examined the
statistical properties of the acoustical signals from
individual cavitation bubbles on two different headforms
in order to learn more about the bubble/flow interactions.
All of these experiments were, however, conducted in the
same facility with the same size of headform (5.08cm in
diameter) and over a fairly narrow range of flow
velocities (around 9m/s). Clearly this raises the issue of
how the phenomena identified change with speed, scale
and facility. The present paper will describe further
results from experiments conducted in order to try to
answer some of these important questions regarding the
scaling of the cavitation phenomena. These experiments
(see also Kuhn de Chizelle et al. [6][7]) were conducted
in the Large Cavitation Channel of the David Taylor
Research Center in Memphis Tennessee, on similar
Schiebe headforms which are 5.08, 25.4 and 50.8cm in
diameter for speeds ranging up to 15m/s and for a range
of cavitation numbers
Phase String Effect in the t-J Model: General Theory
We reexamine the problem of a hole moving in an antiferromagnetic spin
background and find that the injected hole will always pick up a sequence of
nontrivial phases from the spin degrees of freedom. Previously unnoticed, such
a string-like phase originates from the hidden Marshall signs which are
scrambled by the hopping of the hole. We can rigorously show that this phase
string is non-repairable at low energy and give a general proof that the
spectral weight Z must vanish at the ground-state energy due to the phase
string effect. Thus, the quasiparticle description fails here and the quantum
interference effect of the phase string dramatically affects the long-distance
behavior of the injected hole. We introduce a so-called phase-string
formulation of the t-J model for a general number of holes in which the phase
string effect can be explicitly tracked. As an example, by applying this new
mathematical formulation in one dimension, we reproduce the well-known
Luttinger-liquid behaviors of the asymptotic single-electron Green's function
and the spin-spin correlation function. We can also use the present phase
string theory to justify previously developed spin-charge separation theory in
two dimensions, which offers a systematic explanation for the transport and
magnetic anomalies in the high-T_c cuprates.Comment: Revtex, 36 pages, no figure, to appear in Phys. Rev. B
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