Optimized Finite Difference Methods for Seismic Acoustic Wave Modeling

The finite difference (FD) methods are widely used for approximating the partial derivatives in the acoustic/elastic wave equation. Grid dispersion is one of the key numerical problems and will directly influence the accuracy of the result because of the discretization of the partial derivatives in the wave equation. Therefore, it is of great importance to suppress the grid dispersion by optimizing the FD coefficient. Various optimized methods are introduced in this chapter to determine the FD coefficient. Usually, the identical staggered grid finite difference operator is used for all of the first-order spatial derivatives in the first-order wave equation. In this chapter, we introduce a new staggered grid FD scheme which can improve the efficiency while still preserving high accuracy for the first-order acoustic/elastic wave equation modeling. It uses different staggered grid FD operators for different spatial derivatives in the first-order wave equation. The staggered grid FD coefficients of the new FD scheme can be obtained with a linear method. At last, numerical experiments were done to demonstrate the effectiveness of the introduced method

The Productivity Consequences of Pollution-Induced Migration in China

Migration and pollution are two defining features of China\u27s impressive growth performance over the last 30 years. In this paper we study the migration response to pollution in Chinese cities, and its consequences for productivity and welfare. We document a robust pattern in which skilled workers emigrate more in response to pollution than the unskilled. Their greater sensitivity to air quality holds up in cross-sectional variation across cities, panel variation with individual fixed-effects, and when instrumenting for pollution using distant power-plants upwind of cities, or thermal inversions that trap pollution. Pollution therefore changes the spatial distribution of skilled and unskilled workers, which results in higher returns to skill in cities that the educated migrate away from. We quantify the loss in aggregate productivity due to this re-sorting by estimating a model of demand and supply of skilled and unskilled workers across Chinese cities. Counterfactual simulations from the estimated model show that reducing pollution would increase productivity through spatial re-sorting by approximately as much as the direct health benefits of clean air. Physical and institutional restrictions on mobility exacerbate welfare losses. People\u27s dislike of pollution explains a substantial portion of the wage gap between cities

Restrictions on Migration Create Gender Inequality: The Story of China\u27s Left-Behind Children

About 11% of the Chinese population are rural-urban migrants, and the vast majority of them (124 million people) possess a rural hukou which severely restrict their children’s access to urban public schools. As a result, 61 million children are left behind in rural areas. We use a regression-discontinuity design based on school enrollment age cutoffs to document that migrants are significantly more likely to leave middle-school-aged daughters behind in poor rural areas without either parent present when schooling becomes expensive, compared to middle-school-aged sons. The effect is larger when the daughter has a male sibling. Migrant parents send significantly less remittances back to daughters than sons. Migrants from rural areas adjacent to cities with more restrictive hukou policies are more likely to separate from children as new job opportunities arise in nearby cities due to trade-induced shocks to labor demand. This produces a shift-share IV strategy, when paired with a longitudinal dataset shows that those children complete 3 fewer years of schooling, are 41% more likely to fail high school entrance exams, have worse mental and physical health, and remain poor as adults. Although China’s hukou mobility restrictions are not gender-specific in intent, they have larger adverse effects on girls

Polysorbate cationic synthetic vesicle for gene delivery

Synthetic nonionic surfactant vesicles (niosomes) are a colloidal system with closed bilayer structures, displaying distinct advantages in stability and cost compared with liposomes. In this article, polysorbate cationic niosomes (PCNs) were developed as gene carriers. The PCNs comprised nonionic surfactants (i.e., polysorbates) and a cationic cholesterol, and were synthesized using a film hydration method. The niosomes thus prepared possessed a regular morphology, and a particle size of 100 ∼ 200 nm, and a zeta potential of +30 ∼ 45 mV. The PCNs showed great physical stability over the course of 4 weeks at room temperature. The binding capacity of PCNs toward oligodeoxynucleotides (ODN) was assessed by a gel retardation approach, which demonstrated that the ionic complexes were formed when ± charge ratio reached to 4 or greater. Gene transfer study showed that the PCNs exhibited a high efficiency in mediating cellular uptake and transferred DNA expression. Based on these findings, PCNs may offer the potential to function as an effective gene delivery system. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A:, 2011.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79430/1/32999_ftp.pd

Identification and characterization of the expression profile of microRNAs in Anopheles anthropophagus

BACKGROUND: Anopheles anthropophagus, one of the most important mosquito-borne disease vectors in Asia, mainly takes blood meals from humans and transmits both malaria and filariae. MicroRNAs (miRNAs) are small non-coding RNAs, and play a critical role in many cellular processes, including development, differentiation, apoptosis and innate immunity. METHODS: We investigated the global miRNA expression profile of male and female adults of A. anthropophagus using illumina Hiseq2000 sequencing combined with Northern blot. RESULTS: By using the miRNAs of the closely-related species Anopheles gambiae and Aedes aegypti as reference, we obtained 102 miRNAs candidates out of 12.43 million raw sequencing reads for male and 16.51 million reads for female, with 81 of them found as known miRNAs in An. gambiae and/or Ae. aegypti, and the remaining 21 miRNAs were considered as novel. By analyzing the revised read count of miRNAs in male and female, 29 known miRNAs show sexual difference expression: >2-fold in the read count of the same miRNAs in male and female. Especially for miR-989, which is highly expressed in the female mosquitoes, but shows almost no detected expression in male mosquitoes, indicating that miR-989 may be involved in the physiological activity of female mosquito adults. The expression of four miRNAs in different growth stages of mosquito were further identified by Northern blot. Several miRNAs show the stage-specific expression, of which miR-2943 only expressed in the egg stage, suggesting that miR-2943 may be associated with the development of mosquito eggs. CONCLUSIONS: The present study represents the first global characterization of An. anthropophagus miRNAs in sexual differences and stage-specific functions. A better understanding of the functions of these miRNAs will offer new insights in mosquito biology and has implications for the effective control of mosquito-borne infectious diseases

Complex responses of spring vegetation growth to climate in a moisture-limited alpine meadow.

Since 2000, the phenology has advanced in some years and at some locations on the Qinghai-Tibetan Plateau, whereas it has been delayed in others. To understand the variations in spring vegetation growth in response to climate, we conducted both regional and experimental studies on the central Qinghai-Tibetan Plateau. We used the normalized difference vegetation index to identify correlations between climate and phenological greening, and found that greening correlated negatively with winter-spring time precipitation, but not with temperature. We used open top chambers to induce warming in an alpine meadow ecosystem from 2012 to 2014. Our results showed that in the early growing season, plant growth (represented by the net ecosystem CO2 exchange, NEE) was lower in the warmed plots than in the control plots. Late-season plant growth increased with warming relative to that under control conditions. These data suggest that the response of plant growth to warming is complex and non-intuitive in this system. Our results are consistent with the hypothesis that moisture limitation increases in early spring as temperature increases. The effects of moisture limitation on plant growth with increasing temperatures will have important ramifications for grazers in this system

A novel universal real-time PCR system using the attached universal duplex probes for quantitative analysis of nucleic acids

BACKGROUND: Real-time PCR techniques are being widely used for nucleic acids analysis, but one limitation of current frequently employed real-time PCR is the high cost of the labeled probe for each target molecule. RESULTS: We describe a real-time PCR technique employing attached universal duplex probes (AUDP), which has the advantage of generating fluorescence by probe hydrolysis and strand displacement over current real-time PCR methods. AUDP involves one set of universal duplex probes in which the 5' end of the fluorescent probe (FP) and a complementary quenching probe (QP) lie in close proximity so that fluorescence can be quenched. The PCR primer pair with attached universal template (UT) and the FP are identical to the UT sequence. We have shown that the AUDP technique can be used for detecting multiple target DNA sequences in both simplex and duplex real-time PCR assays for gene expression analysis, genotype identification, and genetically modified organism (GMO) quantification with comparable sensitivity, reproducibility, and repeatability with other real-time PCR methods. CONCLUSION: The results from GMO quantification, gene expression analysis, genotype identification, and GMO quantification using AUDP real-time PCR assays indicate that the AUDP real-time PCR technique has been successfully applied in nucleic acids analysis, and the developed AUDP real-time PCR technique will offer an alternative way for nucleic acid analysis with high efficiency, reliability, and flexibility at low cost.Litao Yang, Wanqi Liang, Lingxi Jiang, Wenquan Li, Wei Cao, Zoe A Wilson, and Dabing Zhan

Seismic modeling by optimizing regularized staggered-grid finite-difference operators using a time-space-domain dispersion-relationship-preserving method

The staggered-grid finite-difference (FD) method is widely used in numerical simulation of the wave equation. With stability conditions, grid dispersion often exists because of the discretization of the time and the spatial derivatives in the wave equation. Therefore, suppressing grid dispersion is a key problem for the staggered-grid FD schemes. To reduce the grid dispersion, the traditional method uses high-order staggered-grid schemes in the space domain. However, the wave is propagated in the time and space domain simultaneously. Therefore, some researchers proposed to derive staggered-grid FD schemes based on the time-space domain dispersion relationship. However, such methods were restricted to low frequencies and special angles of propagation. We have developed a regularizing technique to tackle the ill-conditioned property of the symmetric linear system and to stably provide approximate solutions of the FD coefficients for acoustic-wave equations. Dispersion analysis and seismic numerical simulations determined that the proposed method satisfies the dispersion relationship over a much wider range of frequencies and angles of propagation and can ensure FD coefficients being solved via a well-posed linear system and hence improve the forward modeling precision