Influence of Potamogeton crispus growth on nutrients in the sediment and water of Lake Tangxunhu

An incubation experiment was performed on Potamogeton crispus (P. crispus) using sediment collected from Lake Tangxunhu in the center of China, in order to determine the effects of plant growth on Fe, Si, Cu, Zn, Mn, Mg, P, and Ca concentrations in the sediments and overlying waters. After 3 months of incubation, Ca, Mg, and Si concentrations in the water column were significantly lower, and P and Cu concentrations were significantly higher than in unplanted controls. The effect of P. crispus growth on sediment pore waters and water-extractable elements varied. Concentrations of Ca, Mg, Si, Fe, Cu, and Zn were significantly higher, and P was significantly lower, than in pore waters of the control. Water-extracted concentrations of Fe, Mg, and Si in the sediments were lower, and P was higher, than in the control. Presence of P. crispus generally enhanced concentration gradients of elements between pore waters and overlying waters but not for P. The growth of P. crispus was associated with an increase in water pH and formation of root plaques, resulting in complex effects on the sediment nutritional status

Genetic Engineering for Breeding for Drought Resistance and Salt Tolerance in Agropyron Spp. (Wheatgrass)

Genetic engineering for breeding for drought resistance and salt tolerance in wheatgrass, lucerne and tall fescue is one of the main projects in a major national programs as part of the10th’five-year national plan: “Research of gene transfer in plants and its industrialisation”. It is a large project that has financial support for work on forage crops in China and many research institutes and universities take part in it. The Inner Mongolia Agricultural University is in charge of the project on wheatgrass. The research was started in Nov. 2002. The general situation and the primary results are introduced and summarised in this paper

Phase reconstruction of strong-field excited systems by transient-absorption spectroscopy

We study the evolution of a V-type three-level system, whose two resonances are coherently excited and coupled by two ultrashort laser pump and probe pulses, separated by a varying time delay. We relate the quantum dynamics of the excited multi-level system to the absorption spectrum of the transmitted probe pulse. In particular, by analyzing the quantum evolution of the system, we interpret how atomic phases are differently encoded in the time-delay-dependent spectral absorption profiles when the pump pulse either precedes or follows the probe pulse. We experimentally apply this scheme to atomic Rb, whose fine-structure-split 5s\,^2S_{1/2}\rightarrow 5p\,^2P_{1/2} and 5s\,^2S_{1/2}\rightarrow 5p\,^2P_{3/2} transitions are driven by the combined action of a pump pulse of variable intensity and a delayed probe pulse. The provided understanding of the relationship between quantum phases and absorption spectra represents an important step towards full time-dependent phase reconstruction (quantum holography) of bound-state wave-packets in strong-field light-matter interactions with atoms, molecules and solids.Comment: 5 pages, 4 figure

Microscopic correlation between chemical and electronic states in epitaxial graphene on SiC(000-1)

We present energy filtered electron emission spectromicroscopy with spatial and wave-vector resolution on few layer epitaxial graphene on SiC$(000-1) grown by furnace annealing. Low energy electron microscopy shows that more than 80% of the sample is covered by 2-3 graphene layers. C1s spectromicroscopy provides an independent measurement of the graphene thickness distribution map. The work function, measured by photoelectron emission microscopy (PEEM), varies across the surface from 4.34 to 4.50eV according to both the graphene thickness and the graphene-SiC interface chemical state. At least two SiC surface chemical states (i.e., two different SiC surface structures) are present at the graphene/SiC interface. Charge transfer occurs at each graphene/SiC interface. K-space PEEM gives 3D maps of the k_|| pi - pi* band dispersion in micron scale regions show that the Dirac point shifts as a function of graphene thickness. Novel Bragg diffraction of the Dirac cones via the superlattice formed by the commensurately rotated graphene sheets is observed. The experiments underline the importance of lateral and spectroscopic resolution on the scale of future electronic devices in order to precisely characterize the transport properties and band alignments

Simple Metals at High Pressure

In this lecture we review high-pressure phase transition sequences exhibited by simple elements, looking at the examples of the main group I, II, IV, V, and VI elements. General trends are established by analyzing the changes in coordination number on compression. Experimentally found phase transitions and crystal structures are discussed with a brief description of the present theoretical picture.Comment: 22 pages, 4 figures, lecture notes for the lecture given at the Erice course on High-Pressure Crystallography in June 2009, Sicily, Ital

Assessment on the research trend of low-carbon energy technology investment: A bibliometric analysis

Based on databases of Science Citation Index Expanded (1981-present) and Social Sciences Citation Index (2002-present), this paper applies the bibliometric method to analyze the scientific publications of low-carbon energy technology investment. By characterizing the basic information of the publications, we found: the historical development process is clearly divided into two stages; the field of low-carbon energy technology investment has entered a stage of rapid development; the strength of developed countries is far greater than that of developing countries; the comprehensive strength of the United States ranks the first in the field, followed by UK and Denmark and only China and Turkey are developing countries among the top 15 countries; the auctorial collaboration degree in this field shows a clear upward trend, but institutional and national collaboration degrees are steady and relatively low. In addition, distributions of geography, journals and subjects, productive authors and institutions, frequently cited articles, etc. are obtained: articles in this area are mainly distributed in the USA, several countries in Europe and China; the most productive journal, author and institution are Energy Policy, Lund H from Denmark and National Technical University of Athens in Greece; Energy Fuel is the most popular subject among all the outcomes; the most frequently cited article is written by Demirbas published in Energy Policy in 2007. According to the frequency analysis of keywords, it reveals that: “renewable energy” is a kind of keyword used most frequently; “carbon capture and storage technology” is an emerging keyword which is increasingly concerned about; scholars pay widespread attention to electricity issues, especially the feed-in tariff; the policy mainly includes energy policy and climate policy; the real option theory is the most widely used theory; the existing uncertainty is summarized as the cost uncertainty and policy uncertainty. In the end, several suggestions for the future research are given

A New Method of Probing the Phonon Mechanism in Superconductors including MgB2_{2}

Weak localization has a strong influence on both the normal and superconducting properties of metals. In particular, since weak localization leads to the decoupling of electrons and phonons, the temperature dependence of resistance (i.e., $\lambda_{tr}$) is decreasing with increasing disorder, as manifested by Mooij's empirical rule. In addition, Testardi's universal correlation of $T_{c}$ (i.e., $\lambda$) and the resistance ratio (i.e., $\lambda_{tr}$) follows. This understanding provides a new means to probe the phonon mechanism in superconductors including MgB$_{2}$. The merits of this method are its applicability to any superconductors and its reliability because the McMillan's electron-phonon coupling constant $\lambda$ and $\lambda_{tr}$ change in a broad range, from finite values to zero, due to weak localization. Karkin et al's preliminary data of irradiated MgB$_{2}$ show the Testardi correlation, indicating that the dominant pairing mechanism in MgB$_{2}$ is the phonon-mediated interaction.Comment: 9 pages, latex, 3 figure

Spatial imaging of the spin Hall effect and current-induced polarization in two-dimensional electron gases

Spin-orbit coupling in semiconductors relates the spin of an electron to its momentum and provides a pathway for electrically initializing and manipulating electron spins for applications in spintronics and spin-based quantum information processing. This coupling can be regulated with quantum confinement in semiconductor heterostructures through band structure engineering. Here we investigate the spin Hall effect and current-induced spin polarization in a two-dimensional electron gas confined in (110) AlGaAs quantum wells using Kerr rotation microscopy. In contrast to previous measurements, the spin Hall profile exhibits complex structure, and the current-induced spin polarization is out-of-plane. The experiments map the strong dependence of the current-induced spin polarization to the crystal axis along which the electric field is applied, reflecting the anisotropy of the spin-orbit interaction. These results reveal opportunities for tuning a spin source using quantum confinement and device engineering in non-magnetic materials.Comment: Accepted for publication (2005