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

Spinor field realizations of the non-critical W2,4W_{2,4} string based on the linear W1,2,4W_{1,2,4} algebra

In this paper, we investigate the spinor field realizations of the $W_{2,4}$ algebra, making use of the fact that the $W_{2,4}$ algebra can be linearized through the addition of a spin-1 current. And then the nilpotent BRST charges of the spinor non-critical $W_{2,4}$ string were built with these realizations.Comment: 10 pages, no figures, revtex4 style, accepted by Commun.Theor.Phy

Microheated substrates for patterning cells and controlling development

Here, we seek to control cellular development by devising a means through which cells can be subjected to a microheated environment in standard culture conditions. Numerous techniques have been devised for controlling cellular function and development via manipulation of surface environmental cues at the micro- and nanoscale. It is well understood that temperature plays a significant role in the rate of cellular activities, migratory behavior (thermotaxis), and in some cases, protein expression. Yet, the effects and possible utilization of micrometer-scale temperature fields in cell cultures have not been explored. Toward this end, two types of thermally isolated microheated substrates were designed and fabricated, one with standard backside etching beneath a dielectric film and another with a combination of surface and bulk micromachining and backside etching. The substrates were characterized with infrared microscopy, finite element modeling, scanning electron microscopy, stylus profilometry, and electrothermal calibrations. Neuron culture studies were conducted on these substrates to 1) examine the feasibility of using a microheated environment to achieve patterned cell growth and 2) selectively accelerate neural development on regions less than 100$mu m$wide. Results show that attached neurons, grown on microheated regions set at 37$~^circ C$, extended processes substantially faster than those incubated at 25$~^circ C$on the same substrate. Further, unattached neurons were positioned precisely along the length of the heater filament (operating at 45$~^circ C$) using free convection currents. These preliminary findings indicate that microheated substrates may be used to direct cellular development spatially in a practical manner.$hfillhbox[1414]

Evaluating the Corrosion Level of Bare Steel Bars with Pitting Corrosionby DOFS

Steel corrosion is one of the main causes of the deterioration of reinforced concrete structures. Localized pitting corrosion of rebar is particularly harmful, as it can severely damage mechanical properties of steel rebar including both the load and deformation capacities. Moreover, unlike uniform corrosion which can give a warning by causing extensive longitudinal cracking, pitting corrosion is often more hidden with the absence of obvious corrosion cracks. Traditional non-destructive methods based on electrochemistry may encounter large errors when estimating the pitting corrosion level in concrete; as a result, more effective methods/tools are in necessity for a timely and accurate detection of localized pitting corrosion. This study investigates the ability of distributed optical fiber sensors (DOFS) to measure pitting corrosion of steel bars, which is based on the principle that pitting corrosion causes strain localization of steel bar under tension and DOFS enable to capture the strain distribution with high spatial resolution. DOFS were attached on bare steel bars, which have mechanical notches to simulate corrosion pits, to measure the strain distribution along the notched bars under direct tension. Through experiments, the present study explores the possibility of attaching DOFS on the surface of a steel bar to monitor its pitting corrosion, and the positive results are of interest to the development of non-destructive detection method of steel pitting corrosion in concrete structures. Further quantitative analysis is required to find the correlations between the strain distribution along the notched bars and notch geometries, so that the pitting corrosion level could be assessed from the monitored DOFS strains of rebar

Mapping QTLs for mineral accumulation and shoot dry biomass under different Zn nutritional conditions in Chinese cabbage ( Brassica rapa L. ssp. pekinensis )

Abstract Chinese cabbage (Brassica rapa L. ssp. pekinensis) is one of the most important vegetables in China. Genetic dissection of leaf mineral accumulation and tolerance to Zn stress is important for the improvement of the nutritional quality of Chinese cabbage by breeding. A mapping population with 183 doubled haploid (DH) lines was used to study the genetics of mineral accumulation and the growth response to Zn. The genetic map was constructed based on 203 AFLPs, 58 SSRs, 22 SRAPs and four ESTPs. The concentration of 11 minerals was determined in leaves for 142 DH lines grown in an open field. In addition shoot dry biomass (SDB) under normal, deficient and excessive Zn nutritional conditions were investigated in hydroponics experiments. Ten QTLs, each explaining 11.1¿17.1% of the Na, Mg, P, Al, Fe, Mn, Zn and Sr concentration variance, were identified by multiple-QTL model (MQM) mapping. One common QTL was found affecting SDB under normal, deficient and excessive Zn nutritional conditions. An additional QTL was detected for SDB under Zn excess stress only. These results offer insights into the genetic basis of leaf mineral accumulation and plant growth under Zn stress conditions in Chinese cabbag

Numerical study on the response of shoreline change to the tidal channel after a beach nourishment project on an embayed beach

Beach erosion is a severe problem worldwide and beach nourishment is widely regarded today as an environmentally acceptable method to protect and enlarge beaches. In many beach nourishment projects on headland-bay beaches, artificial headlands were constructed on the natural headlands to form an embayed beach in static equilibrium to protect the beach more effectively. However, the construction of artificial headland would weaken the water exchange in the bay and make the water quality easy to deteriorate. In a beach nourishment project in Qinhuangdao, China to dispose this discrepancy an engineering measure was conducted: to reserve a tidal channel between the artificial headland and the natural headland to allow the tidal current to pass. In this paper, a shoreline change model was set up based on GENESIS model to evaluate the influence of the reserve of the tidal channel on the shoreline change after the project. The model was verified by reproducing the post-project shoreline. Four different project schemes with different scales of tidal channel were simulated and discussion was given based on the analysis of simulated results. The numerical evaluation of various scheme options indicates that it is feasible to involve the tidal channel in beach nourishment projects with artificial headland and the scale of the tidal channel should be designed based on the hydrodynamic processes and the state of the beach

Threshold image target segmentation technology based on intelligent algorithms

This paper briefly introduces the optimal threshold calculation model and particle swarm optimization (PSO) algorithm for image segmentation and improves the PSO algorithm. Then the standard PSO algorithm and improved PSO algorithm were used in MATLAB software to make simulation analysis on image segmentation. The results show that the improved PSO algorithm converges faster and has higher fitness value; after the calculation of the two algorithms, it is found that the improved PSO algorithm is better in the subjective perspective, and the image obtained by the improved PSO segmentation has higher regional consistency and takes shorter time in the perspective of quantitative objective data. In conclusion, the improved PSO algorithm is effective in image segmentation

Spinor Field Realizations of Non-critical W2,sW_{2,s} Strings

In this paper, we construct the nilpotent Becchi-Rouet-Stora-Tyutin($BRST$) charges of spinor non-critical $W_{2,s}$ strings. The cases of $s=3,4$ are discussed in detail, and spinor realization for $s=4$ is given explicitly. The $BRST$ charges are graded.Comment: 9 pages, no figure

Superradiance of low density Frenkel excitons in a crystal slab of three-level atoms: Quantum interference effect

We systematically study the fluorescence of low density Frenkel excitons in a crystal slab containing $N_T$ V-type three-level atoms. Based on symmetric quasi-spin realization of SU(3) in large $N$ limit, the two-mode exciton operators are invoked to depict various collective excitations of the collection of these V-type atoms starting from their ground state. By making use of the rotating wave approximation, the light intensity of radiation for the single lattice layer is investigated in detail. As a quantum coherence effect, the quantum beat phenomenon is discussed in detail for different initial excitonic states. We also test the above results analytically without the consideration of the rotating wave approximation and the self-interaction of radiance field is also included.Comment: 18pages, 17 figures. Resubmit to Phys. Rev.