Efficiency, economics, and environmental implications of phosphorus resource use and the fertilizer industry in China

Phosphorus (P) is an essential nutrient for crop production and is often in short supply. The necessary P fertilizers are derived from deposits in the lithosphere, which are limited in size and nonrenewable. China is one of the world's largest consumers and producers of P fertilizers. Thus, P resource use efficiency in China has an important impact on the worldwide efficiency of P resource use. This study examined the P fertilizer industry in China in terms of P resource use efficiency, economics, and environmental risk, and explored options for improvement through scenario analysis. P resource use efficiency decreased from a mean of 71% before 1995 to 39% in 2003, i.e., from every 10 kg P in rock material, only 3.9 kg P was used to produce fertilizer, 5.6 kg of the residues were discarded at the mining site, and 0.5 kg was manufacturing waste. The decreased efficiency was caused by increased P rock mining activities, especially from small, inefficient miners. Enhanced mining was supported by local governments and by the growing P fertilizer industry, where high-analysis P fertilizers have fourfold higher gross margins than traditional low-analysis fertilizers. Although the growing fertilizer industry is contributing significantly to the development of some regions, the economic efficiency is still lower than in other countries, e.g., in the USA. The P resource is depleting quickly, and the environmental consequences of inefficient use are serious. The amount of accumulated phosphor gypsum was estimated to be 110 Tg, the amount of deteriorated land reached 475 km(2), and the consumption of ground water was 1.8 billion m(3) per year. The low efficiency and serious environmental risk could be attributed to the numerous small inefficient miners, which were supported by intervention of governmental subsidies and taxes after 1995. This study proved that there is a great deal of room for improvement in the resource use efficiency up to 77% by integrated measures, which need broad cooperation of miners, fertilizer plants, and agriculture

Processing, microstructure and mechanical properties of bimodal size SiCp reinforced AZ31B magnesium matrix composites

AbstractThe bimodal size SiC particulates (SiCp) reinforced magnesium matrix composites with different ratios of micron SiCp and nano SiCp (M-SiCp:N-SiCp = 14.5:0.5, 14:1, and 13.5:1.5) were prepared by semisolid stirring assisted ultrasonic vibration method. The AZ31B alloy and all as-cast SiCp/AZ31B composites were extruded at 350 °C with the ratio of 12:1. Microstructural characterization of the extruded M14 + N1 (M-SiCp:N-SiCp = 14:1) composite revealed the uniform distribution of bimodal size SiCp and significant grain refinement. Optical Microscopy(OM) observation showed that, compared with the M14.5 + N0.5 (M-SiCp:N-SiCp = 14.5:0.5) composite, there are more recrystallized grains in M14 + N1 (M-SiCp:N-SiCp = 14:1) and M13.5 + N1.5 (M-SiCp:N-SiCp = 13.5:1.5) composites, but in comparison to the M13.5 + N1.5 composite, the average grain size of the M14 + N1 composite is slightly decreased. The evaluation of mechanical properties indicated that the yield strength and ultimate tensile strength of the M14 + N1 composite were obviously increased compared with other composites

Development Of A Cathode Designing Method To Avoid Electrodes’ Interference During Blisk Electrochemical Machining

Electrochemical machining plays a prominent role in blisk (bladed integrated disk) construction process. Since blisk channel is narrow and twisted, interference between electrodes may happen during electrochemical machining. Therefore, this paper develops a cathode designing method to avoid interference. Firstly, according to theory of electrochemical machining, machined channel is predicted by calculation. Second, with this channel, interference analysis is carried out and a cathode is designed. Finally, the cathode is employed in experiment and no interference appears

Ancilla models for quantum operations: For what unitaries does the ancilla state have to be physical?

Any evolution described by a completely positive trace-preserving linear map can be imagined as arising from the interaction of the evolving system with an initially uncorrelated ancilla. The interaction is given by a joint unitary operator, acting on the system and the ancilla. Here we study the properties such a unitary operator must have in order to force the choice of a physical- that is, positive-state for the ancilla if the end result is to be a physical-that is, completely positive-evolution of the system.Comment: Quantum Information Processing, (2012

Tree method for quantum vortex dynamics

We present a numerical method to compute the evolution of vortex filaments in superfluid helium. The method is based on a tree algorithm which considerably speeds up the calculation of Biot-Savart integrals. We show that the computational cost scales as Nlog{(N) rather than N squared, where $N$ is the number of discretization points. We test the method and its properties for a variety of vortex configurations, ranging from simple vortex rings to a counterflow vortex tangle, and compare results against the Local Induction Approximation and the exact Biot-Savart law.Comment: 12 pages, 10 figure

Friedmann Equation and Stability of Inflationary Higher Derivative Gravity

Stability analysis on the De Sitter universe in pure gravity theory is known to be useful in many aspects. We first show how to complete the proof of an earlier argument based on a redundant field equation. It is shown further that the stability condition applies to $k \ne 0$ Friedmann-Robertson-Walker spaces based on the non-redundant Friedmann equation derived from a simple effective Lagrangian. We show how to derive this expression for the Friedmann equation of pure gravity theory. This expression is also generalized to include scalar field interactions.Comment: Revtex, 6 pages, Add two more references, some typos correcte

Single-cell analysis of the 3D topologies of genomic loci using genome architecture mapping

Although each cell within an organism contains a nearly identical genome sequence, the three-dimensional (3D) packing of the genome varies among individual cells, influencing cell-type-specific gene expression. Genome Architecture Mapping (GAM) is the first genome-wide experimental method for capturing 3D proximities between any number of genomic loci without ligation. GAM overcomes several limitations of 3C-based methods by sequencing DNA from a large collection of thin sections sliced from individual nuclei. The GAM technique measures locus co-segregation, extracts radial positions, infers chromatin compaction, requires small numbers of cells, does not depend on ligation, and provides rich single-cell information. However, previous analyses of GAM data focused exclusively on population averages, neglecting the variation in 3D topology among individual cells. We present the first single-cell analysis of GAM data, demonstrating that the slices from individual cells reveal intercellular heterogeneity in chromosome conformation. By simultaneously clustering both slices and genomic loci, we identify topological variation among single cells, including differential compaction of cell cycle genes. We also develop a geometric model of the nucleus, allowing prediction of the 3D positions of each slice. Using GAM data from mouse embryonic stem cells, we make new discoveries about the structure of the major mammalian histone gene locus, which is incorporated into the Histone Locus Body (HLB), including structural fluctuations and putative causal molecular mechanisms. Our methods are packaged as SluiceBox, a toolkit for mining GAM data. Our approach represents a new method of investigating variation in 3D genome topology among individual cells across space and time

Teachers’ motivation to participate in continuous professional development: relationship with factors at the personal and school level

Teachers’ motivation to participate in professional learning is a significant factor in explaining the effectiveness of continuous professional development programmes. The present study investigated how factors at teachers’ personal and school levels are related to their motivation to participate in professional learning activities. A questionnaire was completed by 472 Chinese teachers. Multivariate analysis revealed that several factors at the teacher level (teachers’ prior experience with learning activities, teaching experience, self-efficacy and conceptions of learning) and the school level (work and emotional pressure, colleague support and principal leadership) were related to their motivation to participate in professional learning. These findings are discussed in the context of the professional development of Chinese teachers. Implications are generated for teacher education and continuous professional development. Teaching and Teacher Learning (ICLON