Fingerprinting the sources of water-mobilized sediment threatening agricultural and water resource sustainability: Progress, challenges and prospects in China

Sediment source fingerprinting apportions the sources of sediment produced by water erosion by linking sampled sediment mixtures and landscape source materials using diagnostic and conservative fingerprints. Using this approach, the nature and location of active sediment sources across the catchment can be elucidated, generating information which is a key prerequisite for the design and implementation of catchment management strategies. The science of sediment source fingerprinting continues to attract much research globally, but to date, there have been relatively few fingerprinting studies in China. Here, there remain major challenges for the fingerprinting approach arising from the uniqueness of Chinese landscapes, including for instance, the complex land use configuration with highly fragmented or mosaic patches and the highly dynamic land use conversion rates, generating a need to test the physical basis for the discriminatory power and environmental behavior of bothtraditional and novel tracers. Future research is needed to investigate the applicability of tracer properties in different physiographic settings and to evaluate the potential strategic utility of the approach for supporting the improved management of soil and water sustainability. Here, the strategic availability of independent observation data for different components of catchment sediment budgets and well-maintained research infrastructure for plots, micro-catchments and drainage basins provides immediate opportunity for testing the approach and refining procedures. Such detailed testing across scales would be invaluable for promoting sedimen

Azimuthal asymmetries in lepton-pair production at a fixed-target experiment using the LHC beams (AFTER)

A multi-purpose fixed-target experiment using the proton and lead-ion beams of the LHC was recently proposed by Brodsky, Fleuret, Hadjidakis and Lansberg, and here we concentrate our study on some issues related to the spin physics part of this project (referred to as AFTER). We study the nucleon spin structure through $pp$ and $pd$ processes with a fixed-target experiment using the LHC proton beams, for the kinematical region with 7 TeV proton beams at the energy in center-of-mass frame of two nucleons $\sqrt{s}=115$ GeV. We calculate and estimate the $\cos2\phi$ azimuthal asymmetries of unpolarized $pp$ and $pd$ dilepton production processes in the Drell--Yan continuum region and at the $Z$-pole. We also calculate the $\sin(2\phi-\phi_S)$, $\sin(2\phi+\phi_S)$ and $\sin2\phi$ azimuthal asymmetries of $pp$ and $pd$ dilepton production processes with the target proton and deuteron longitudinally or transversally polarized in the Drell--Yan continuum region and around $Z$ resonances region. We conclude that it is feasible to measure these azimuthal asymmetries, consequently the three-dimensional or transverse momentum dependent parton distribution functions (3dPDFs or TMDs), at this new AFTER facility.Comment: 15 pages, 40 figures. Version accepted for publication in EPJ

Divergent behaviour of soil nutrients imprinted by different land management practices in the Three Gorges Reservoir Area, China

Soil nutrients are essentially regulated by land management practices via modulating biotic element input and metabolism. The Three Gorges Reservoir Area in China was dominated by a farming landscape, but land management has become diversified over recent decades. How these restorative management practices may have affected soil nutrients is not completely understood. In this study, a space-time substitution approach was applied to evaluate soil nutrients and their stoichiometric changes in response to post-farming land management practices. Soil samples(0–10 cm, 10–20 cm, and 20–40 cm) were collected from present-day croplands, cypress plantations, eucalyptus plantations, abandoned croplands, and citrus plantations. Soil organic matter, soil organic carbon, total nitrogen, alkaline hydrolyzed nitrogen, total phosphorus, and available phosphorus were determined. The results showed that soil organic matter and total nitrogen in abandoned croplands, cypress plantations, eucalyptus plantations and citrus plantations were increased by 186% and 190%, 184% and 107%, 45% and 33%, and 45% and 54%, respectively, in comparison with present-day croplands. Soil nutrients except for total phosphorus decreased more with soil depth by exclusion of tillage mixing. The analysis of the comprehensive soil nutrient index showed that abandoned croplands (0.90) and cypress plantations(0.72) exhibited better nutrient recovery capacity. Soil C:P and N:P ratios increase in abandoned croplands, cypress plantations, and eucalyptus plantations. Phosphorus may become a limiting factor for plant growth with prolonged recovery in abandoned croplands, cypress plantations, and eucalyptus plantations, while soil organic matter and total nitrogen deficiencies are exacerbated in citrus plantations and present-day croplands. Therefore, cropland abandonment and reforestation (particularly cypress trees plantation) are recommended practices for restoring soil nutrients in the Three Gorges Reservoir Area

Experimental realization of the one qubit Deutsch-Jozsa algorithm in a quantum dot

We perform quantum interference experiments on a single self-assembled semiconductor quantum dot. The presence or absence of a single exciton in the dot provides a qubit that we control with femtosecond time resolution. We combine a set of quantum operations to realize the single-qubit Deutsch-Jozsa algorithm. The results show the feasibility of single qubit quantum logic in a semiconductor quantum dot using ultrafast optical control.Comment: REVTex4, 4 pages, 3 figures. Now includes more details about the dephasing in the quantum dots. The introduction has been reworded for clarity. Minor readability fixe

Next-to-leading order QCD evolution of transversity fragmentation functions

We derive the next-to-leading order splitting kernels for the scale evolution of fragmentation functions for transversely polarized quarks into transversely polarized hadrons.Comment: 9 pages, LaTe

Azimuthal Spin Asymmetries of Pion Electroproduction

Azimuthal spin asymmetries, both for charged and neutral pion production in semi-inclusive deep inelastic scattering of unpolarized charged lepton beams on longitudinally and transversely polarized nucleon targets, are analyzed and calculated. Various assumptions and approximations in the quark distributions and fragmentation functions often used in these calculations are studied in detail. It is found that different approaches to the distribution and fragmentation functions may lead to quite different predictions on the azimuthal asymmetries measured in the HERMES experiments, thus their effects should be taken into account before using the available data as a measurement of quark transversity distributions. It is also found that the unfavored quark to pion fragmentation functions must be taken into account for $\pi^-$ production from a proton target, although they can be neglected for $\pi^+$ and $\pi^0$ production. Pion production from a proton target is suitable to study the $u$ quark transversity distribution, whereas a combination of pion production from both proton and neutron targets can measure the flavor structure of quark transversity distributions.Comment: 31 latex pages, 13 figure, to appear in PR

Simultaneous Embeddability of Two Partitions

We study the simultaneous embeddability of a pair of partitions of the same underlying set into disjoint blocks. Each element of the set is mapped to a point in the plane and each block of either of the two partitions is mapped to a region that contains exactly those points that belong to the elements in the block and that is bounded by a simple closed curve. We establish three main classes of simultaneous embeddability (weak, strong, and full embeddability) that differ by increasingly strict well-formedness conditions on how different block regions are allowed to intersect. We show that these simultaneous embeddability classes are closely related to different planarity concepts of hypergraphs. For each embeddability class we give a full characterization. We show that (i) every pair of partitions has a weak simultaneous embedding, (ii) it is NP-complete to decide the existence of a strong simultaneous embedding, and (iii) the existence of a full simultaneous embedding can be tested in linear time.Comment: 17 pages, 7 figures, extended version of a paper to appear at GD 201

Theory of the optical absorption of light carrying orbital angular momentum by semiconductors

We develop a free-carrier theory of the optical absorption of light carrying orbital angular momentum (twisted light) by bulk semiconductors. We obtain the optical transition matrix elements for Bessel-mode twisted light and use them to calculate the wave function of photo-excited electrons to first-order in the vector potential of the laser. The associated net electric currents of first and second-order on the field are obtained. It is shown that the magnetic field produced at the center of the beam for the $\ell=1$ mode is of the order of a millitesla, and could therefore be detected experimentally using, for example, the technique of time-resolved Faraday rotation.Comment: Submitted to Phys. Rev. Lett. (23 Jan 2008

Chandra Observation of the Edge-on Spiral NGC 5775: Probing the Hot Galactic Disk/Halo Connection

We study the edge-on galaxy NGC 5775, utilizing a 58.2 ks {\sl Chandra} ACIS-S observation together with complementary {\sl HST} ACS, {\sl Spitzer} IRAC and other multi-wavelength data sets. This edge-on galaxy, with its disk-wide active star formation, is particularly well-suited for studying the disk/halo interaction on sub-galactic scales. We detect 27 discrete X-ray sources within the $D_{25}$ region of the galaxy, including an ultra-luminous source with a 0.3-7 keV luminosity of $\sim7\times10^{40}\rm ergs s^{-1}$. The source-removed diffuse X-ray emission shows several prominent extraplanar features, including a $\sim10\rm kpc$ diameter ``shell-like'' feature and a ``blob'' reaching a projected distance of $\sim25\rm kpc$ from the galactic disk. The bulk of the X-ray emission in the halo has a scale height of $\sim$1.5 kpc and can be characterized by a two-temperature optically thin thermal plasma with temperatures of $\sim$ 0.2 and 0.6 keV and a total 0.3-2 keV luminosity of $\sim3.5\times10^{39}\rm ergs s^{-1}$. The high-resolution, multi-wavelength data reveal the presence of several extraplanar features around the disk, which appear to be associated with the in-disk star formation. We suggest that hot gas produced with different levels of mass loading can have different temperatures, which may explain the characteristic temperatures of hot gas in the halo. We have obtained a sub-galactic scale X-ray-intensity-star formation relation, which is consistent with the integrated version in other star forming galaxies.Comment: 25 pages, 10 figures, 4 tables, accepted for publication in MNRA