En-route to the fission-fusion reaction mechanism: a status update on laser-driven heavy ion acceleration

The fission-fusion reaction mechanism was proposed in order to generate extremely neutron-rich nuclei close to the waiting point N = 126 of the rapid neutron capture nucleosynthesis process (r-process). The production of such isotopes and the measurement of their nuclear properties would fundamentally help to increase the understanding of the nucleosynthesis of the heaviest elements in the universe. Major prerequisite for the realization of this new reaction scheme is the development of laser-based acceleration of ultra-dense heavy ion bunches in the mass range of A = 200 and above. In this paper, we review the status of laser-driven heavy ion acceleration in the light of the fission-fusion reaction mechanism. We present results from our latest experiment on heavy ion acceleration, including a new milestone with laser-accelerated heavy ion energies exceeding 5 MeV/u

Effects of Ru Substitution on Dimensionality and Electron Correlations in Ba(Fe_{1-x}Ru_x)_2As_2

We report a systematic angle-resolved photoemission spectroscopy study on Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$ for a wide range of Ru concentrations (0.15 $\leq$ \emph{x} $\leq$ 0.74). We observed a crossover from two-dimension to three-dimension for some of the hole-like Fermi surfaces with Ru substitution and a large reduction in the mass renormalization close to optimal doping. These results suggest that isovalent Ru substitution has remarkable effects on the low-energy electron excitations, which are important for the evolution of superconductivity and antiferromagnetism in this system.Comment: 4 pages, 4 figure

Synthesis of Nitrogen-doped Carbon Nanotubes with Layered Double Hydroxides Containing Iron, Cobalt or Nickel as Catalyst Precursors

Nitrogen-doped carbon nanotubes (CNx) were synthesized by the catalytic chemical vapour deposition of ethylenediamine with layered double hydroxides (LDHs) containing iron, cobalt or nickel as catalyst precursors at 650 °C. The catalytically active metal particles were obtained by calcination of LDHs followed by reduction. X-ray diffraction was used to characterize the structures of the precursors and their calcined products. Transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy were used to characterize the grown CNx. The results show that the CNx grown with Mg2Fe-LDH as catalyst precursor have a bamboo-like morphology and large diameter, while hollow tubes are obtained with CoMgAl- andNiMgAl-LDH as catalyst precursors. The CNx grown with CoMgAl-LDH have the highest N-doped content and the CNx grown with NiMgAl-LDH have the highest degree of graphitization among these three products.Keywords: N-doped Carbon Nanotubes, Layered Double Hydroxides, Chemical Vapour Depositio

Density of States for a Specified Correlation Function and the Energy Landscape

The degeneracy of two-phase disordered microstructures consistent with a specified correlation function is analyzed by mapping it to a ground-state degeneracy. We determine for the first time the associated density of states via a Monte Carlo algorithm. Our results are described in terms of the roughness of the energy landscape, defined on a hypercubic configuration space. The use of a Hamming distance in this space enables us to define a roughness metric, which is calculated from the correlation function alone and related quantitatively to the structural degeneracy. This relation is validated for a wide variety of disordered systems.Comment: Accepted for publication in Physical Review Letter

Modeling Heterogeneous Materials via Two-Point Correlation Functions: I. Basic Principles

Heterogeneous materials abound in nature and man-made situations. Examples include porous media, biological materials, and composite materials. Diverse and interesting properties exhibited by these materials result from their complex microstructures, which also make it difficult to model the materials. In this first part of a series of two papers, we collect the known necessary conditions on the standard two-point correlation function S2(r) and formulate a new conjecture. In particular, we argue that given a complete two-point correlation function space, S2(r) of any statistically homogeneous material can be expressed through a map on a selected set of bases of the function space. We provide new examples of realizable two-point correlation functions and suggest a set of analytical basis functions. Moreover, we devise an efficient and isotropy- preserving construction algorithm, namely, the Lattice-Point algorithm to generate realizations of materials from their two- point correlation functions based on the Yeong-Torquato technique. Subsequent analysis can be performed on the generated images to obtain desired macroscopic properties. These developments are integrated here into a general scheme that enables one to model and categorize heterogeneous materials via two-point correlation functions.Comment: 37 pages, 26 figure

Effect of Grazing on Soil Fertility and Trace Elements of Temperate Desert Steppe in Northwestern China

Grazing is the dominant land use of temperate desert steppe in northwestern China. It is well established that the grazing process has impacts on plant production and biodiversity (Li 1997), but less is known about the effects of grazing chemical characteristics of grassland soils. Livestock feeding activities, especially the provision of supplementary sources, may influence pasture nutrient cycle, and in turn change the chemical composition of the grassland soil (Rong et al. 2001). Soil fertility may be affected by the type use and grazing intensities because these may cause alterations in soil physical and chemical properties as well as the soil biotia (Marzaioli et al. 2010; Caravacaa et al. 2002). The combination of these factors can reduce pasture productivity (Islam and Weil 2000; Sánchez-Marañón et al. 2002). Soil was the nutrient carrier to forage and livestock. Since changes in soil property will be reflected in both forage and livestock production directly or indirectly, it was important to study the effect of soil on grassland and grazing (Zhang et al. 2002), especially trace elements such as iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn). In Alxa (Inner Mongolia), for example, Wu et al. (2008) reported a difference in the accumulation of these elements due to grassland type with a sequence of Fe\u3eMn\u3eZn\u3eCu in alpine meadow soil compared to a sequence of Fe \u3e Mn\u3eCu\u3eZn in mountainous steppe and desert steppe soils. The objective of this study is to investigate the effect of grazing on the concentrations of Fe, Mn, Cu and Zn in temperate desert steppe in Gansu Province

Appearance of Flat Bands and Edge States in Boron-Carbon-Nitride Nanoribbons

Presence of flat bands and edge states at the Fermi level in graphene nanoribbons with zigzag edges is one of the most interesting and attracting properties of nanocarbon materials but it is believed that they are quite fragile states and disappear when B and N atoms are doped at around the edges. In this paper, we theoretically investigate electronic and magnetic properties of boron-carbon-nitride (BCN) nanoribbons with zigzag edges where the outermost C atoms on the edges are alternately replaced with B and N atoms using the first principles calculations. We show that BCN nanoribbons have the flat bands and edge states at the Fermi level in both H_2 rich and poor environments. The flat bands are similar to those at graphene nanoribbons with zigzag edges, but the distributions of charge and spin densities are different between them. A tight binding model and the Hubbard model analysis show that the difference in the distribution of charge and spin densities is caused by the different site energies of B and N atoms compared with C atoms.Comment: 5 pages; 3 figure

Failure analysis of EB03 crankshaft

Study on the fracture specimen of EB03 crankshaft which produced by a crankshaft company. It is found that there is a phenomenon of high temperature oxidation on the surface of EB03 fractured crankshaft’s journal by the macroscopic analysis of the fracture of the crankshaft. And there are a lot of sintered metal particles on the surface of the neck journal. These phenomena indicate that the axle diameter of the connecting rod is gradually locked in the process of operation, during this process, a lot of heat is generated with the holding of the tile and causes the phenomenon of burning and melting. It is found that the graphite has different degrees of deformation by observing the graphite morphology on the surface of the neck journal