1,058 research outputs found
Effects of Sand Addition to Heavy Saline-Alkali Soil on the Infiltration and Salt Leaching in Hetao Irrigation District, China
Proceeding PaperSoil salinity is a matter of great economic and environmental implications. In Hetao
Irrigation District, soil salinity limits crop productivity affecting about 69% of its total cultivated
land due to natural soil salinisation and salt accumulation caused by irrigation. The goal of this
study is to contribute to the alleviation of this problem through the technique of adding wind-sand to
the top layer of heavy saline-alkali soil, and to evaluate and analyse their effects on the infiltration
and salt leaching. The experiment was carried out on a laboratory scale. Clayey soil with 21 g/kg
of salts collected at the Ulat Front Banner site was used. Wind-sand was added to the top 30 cm
layer of this soil. The infiltration tests were carried out in plastic columns with 9 cm diameter and
45 cm high, loaded with a soil and wind-sand mixture (from 2% to 30% ratio), supplied by a constant
hydraulic head. Soil water samples were collected for 15 days for quantification of the soil salt
leaching. A significant increase of the infiltration rate was observed in the first infiltration hour, rising
from 1 to 9 mm/h, in response to the addition of 8% and 30% of sandy particles, respectively. The
effects of wind-sand in salt leaching were relevant in the top 20 cm layer. After 7 days of infiltration
there was a decrease in the salt content in soils with 4%, 8%, and 30% of sand particles added, of 35%,
55%, and 95%, respectively, in relation to the control. In conclusion, the practice of adding sandy
particles to the topsoil is a soil melioration method that allows a positive impact on soil infiltration
and salt leaching. An addition of 8% of sand seems to be a good choice, as it favours an increase in
salt leaching of about 55% after 7 days. These results are encouraging and appeal to field studies
to assess the impact on a field-scale system, and the effects of this soil melioration on irrigation,
drainage, and agronomic aspectsinfo:eu-repo/semantics/publishedVersio
An assessment of the resolution limitation due to radiation-damage in x-ray diffraction microscopy
X-ray diffraction microscopy (XDM) is a new form of x-ray imaging that is
being practiced at several third-generation synchrotron-radiation x-ray
facilities. Although only five years have elapsed since the technique was first
introduced, it has made rapid progress in demonstrating high-resolution
threedimensional imaging and promises few-nm resolution with much larger
samples than can be imaged in the transmission electron microscope. Both life-
and materials-science applications of XDM are intended, and it is expected that
the principal limitation to resolution will be radiation damage for life
science and the coherent power of available x-ray sources for material science.
In this paper we address the question of the role of radiation damage. We use a
statistical analysis based on the so-called "dose fractionation theorem" of
Hegerl and Hoppe to calculate the dose needed to make an image of a lifescience
sample by XDM with a given resolution. We conclude that the needed dose scales
with the inverse fourth power of the resolution and present experimental
evidence to support this finding. To determine the maximum tolerable dose we
have assembled a number of data taken from the literature plus some
measurements of our own which cover ranges of resolution that are not well
covered by reports in the literature. The tentative conclusion of this study is
that XDM should be able to image frozen-hydrated protein samples at a
resolution of about 10 nm with "Rose-criterion" image quality.Comment: 9 pages, 4 figure
Dimensional Reduction via Noncommutative Spacetime: Bootstrap and Holography
Unlike noncommutative space, when space and time are noncommutative, it seems
necessary to modify the usual scheme of quantum mechanics. We propose in this
paper a simple generalization of the time evolution equation in quantum
mechanics to incorporate the feature of a noncommutative spacetime. This
equation is much more constraining than the usual Schr\"odinger equation in
that the spatial dimension noncommuting with time is effectively reduced to a
point in low energy. We thus call the new evolution equation the spacetime
bootstrap equation, the dimensional reduction called for by this evolution
seems close to what is required by the holographic principle. We will discuss
several examples to demonstrate this point.Comment: 15 pages, harvmac. v2: typos corrected and some changes mad
On the positive mass theorem for manifolds with corners
We study the positive mass theorem for certain non-smooth metrics following
P. Miao's work. Our approach is to smooth the metric using the Ricci flow. As
well as improving some previous results on the behaviour of the ADM mass under
the Ricci flow, we extend the analysis of the zero mass case to higher
dimensions.Comment: 21 pages, incorporated referee's comment
X-ray image reconstruction from a diffraction pattern alone
A solution to the inversion problem of scattering would offer aberration-free
diffraction-limited 3D images without the resolution and depth-of-field
limitations of lens-based tomographic systems. Powerful algorithms are
increasingly being used to act as lenses to form such images. Current image
reconstruction methods, however, require the knowledge of the shape of the
object and the low spatial frequencies unavoidably lost in experiments.
Diffractive imaging has thus previously been used to increase the resolution of
images obtained by other means. We demonstrate experimentally here a new
inversion method, which reconstructs the image of the object without the need
for any such prior knowledge.Comment: 5 pages, 3 figures, improved figures and captions, changed titl
Issues Concerning Loop Corrections to the Primordial Power Spectra
We expound ten principles in an attempt to clarify the debate over infrared
loop corrections to the primordial scalar and tensor power spectra from
inflation. Among other things we note that existing proposals for nonlinear
extensions of the scalar fluctuation field introduce new ultraviolet
divergences which no one understands how to renormalize. Loop corrections and
higher correlators of these putative observables would also be enhanced by
inverse powers of the slow roll parameter . We propose an extension
which should be better behaved.Comment: 36 pages, uses LaTeX2e, version 3 revised for publication with a much
expanded section 4, proving that our proposed extension of the zeta-zeta
correlator absorbs the one loop infrared divergences from graviton
Exact Solution of Quantum Field Theory on Noncommutative Phase Spaces
We present the exact solution of a scalar field theory defined with
noncommuting position and momentum variables. The model describes charged
particles in a uniform magnetic field and with an interaction defined by the
Groenewold-Moyal star-product. Explicit results are presented for all Green's
functions in arbitrary even spacetime dimensionality. Various scaling limits of
the field theory are analysed non-perturbatively and the renormalizability of
each limit examined. A supersymmetric extension of the field theory is also
constructed in which the supersymmetry transformations are parametrized by
differential operators in an infinite-dimensional noncommutative algebra.Comment: 70 pages AMSTe
The design and evaluation of travelling gun irrigation systems: enrolador software
Technical Paperinfo:eu-repo/semantics/publishedVersio
Exploratory Biomarker Analysis In The Ph 3 Echelonâ1 Study: Worse Outcome With Abvd In Patients With Elevated Baseline Levels Of Scd30 And Tarc
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149507/1/hon99_2630.pd
- âŠ