ALBERT

Description: Author(s): B. B. Tian, L. F. Chen, Y. Liu, X. F. Bai, J. L. Wang, Sh. Sun, G. L. Yuan, J. L. Sun, B. Dkhil, X. J. Meng, and J. H. Chu Polarization switching kinetics is one of the key issues for future development of nanoelectronic devices based on ferroelectrics. Up to now, such kinetics still remains poorly studied despite its crucial impact on the device performances. Here, the switching mechanism in 11-nm-thick ferroelectric f… [Phys. Rev. B 92, 060102(R)] Published Wed Aug 26, 2015

Description: Author(s): Y. Y. Chin, H.-J. Lin, Z. Hu, Masanori Nagao, Yongping Du, Xiangang Wan, B.-J. Su, L. Y. Jang, T. S. Chan, H.-Y. Chen, Y. L. Soo, and C. T. Chen The x-ray absorption spectra at the Bi- L 1 and S- K edges of LaO 1 − x F x BiS 2 show a decrease of spectral weight close to the absorption thresholds upon F substitution for O, indicating a reduction of the unoccupied Bi 6 p and S 3 p states, as expected for electron doping. This doping-induced spectral weigh… [Phys. Rev. B 94, 035150] Published Mon Jul 25, 2016

Description: Author(s): H. Jiang, N. Wang, Lie-Wen Chen, Y. M. Zhao, and A. Arima In this paper we investigate the model dependence of I 4 term in theoretical symmetry energy for a few popular mass models. Our results show that, interestingly and unexpectedly, the coefficients of the I 4 term in finite nuclei extracted from different mass models correlate strongly with the correspo... [Phys. Rev. C 91, 054302] Published Tue May 05, 2015

Description: Author(s): F. H. Chao, C. H. Chen, Y. C. Huang, and P. J. Chou A radio-frequency photoinjector is widely used for generating picosecond-femtosecond electron bunches. During particle acceleration, the electron bunch shape varies under the influence of both the acceleration fields and space charge fields. To restore a distorted electron bunch, we propose an injec... [Phys. Rev. ST Accel. Beams 18, 051301] Published Thu May 07, 2015

Description: 〈span〉〈div〉ABSTRACT〈/div〉Viscoacoustic migration can significantly compensate for the amplitude loss and phase distortion in migration images computed from highly attenuated data. However, solving the viscoacoustic wave equation requires a significant amount of storage space and computation time, especially for least-squares migration methods. To mitigate this problem, we used acoustic reverse time migration (RTM) instead of viscoacoustic migration to migrate the viscoacoustic data and then we correct the amplitude and phase distortion by hybrid deblurring filters in the image domain. Numerical tests on synthetic and field data demonstrate that acoustic RTM combined with hybrid deblurring filters can compensate for the attenuation effects and produce images with high resolution and balanced amplitudes. This procedure requires less than one-third of the storage space and is O(N−1) times faster compared with the viscoacoustic migration, but at the cost of mildly reduced accuracy. Here, N represents the number of iterations used for least-squares migration method. This method can be extended to 3D migration at even a greater cost saving.〈/span〉

Description: Distributed acoustic sensing (DAS) is a novel technology that uses an optical fiber cable as a sensor for acoustic signals and can take almost any downhole fiber-optic installation or deployment and turn the fiber-optic cable into a large downhole seismic array. This array can provide enhanced vertical seismic profile (VSP) imaging and monitor fluids and pressure changes in the hydrocarbon-production reservoir. Walkaway VSP data acquired over a formerly producing well in northeastern China provided a rich set of high-quality DAS walkaway VSP data. A standard VSP data preprocessing workflow was applied, followed by prestack Kirchhoff time migration. In the DAS preprocessing step, we were faced with additional challenges: strong coherent noise due to cable slapping and ringing along the borehole casing. Compared with an earlier offset VSP data set using 327 levels acquired with conventional 3C downhole geophones in the same well, the final preprocessed DAS walkaway VSP has a larger vertical aperture, resulting in a wider lateral image. The single-well DAS walkaway VSP images provide a good result with higher vertical and lateral resolution than the surface seismic in the objective area. The vertical-well environment, which lacks the ability to effectively "clamp" the sensor to the borehole-casing wall by touching, creates a unique set of challenges. Although earth signal was recorded with almost all the shots, there was also a considerable amount of noise. Much of the noise was due to the physical placement of the wireline in the well and was expressed by slapping and ringing. Reported here are lessons learned in handling the wireline cable and subsequent special DAS data processing steps developed to remediate some of the practical wireline deployment issues. Optical wireline cable as a conveyance of fiber-optic cables for VSP in vertical wells will open the use of the DAS system to wider applications.

Description: Toll receptors play an important role in the innate immunity of invertebrates. All reported Tolls have only one Toll/interleukin-1 receptor (TIR) domain at the C-terminal. In this study, numerous Tolls with tandem TIRs at the C-terminal were found in molluscs. Such Tolls presented an extra TIR (TIR-1) compared with Toll-I. Thus, Toll-I might be the ancestor of tandem TIRs containing Toll. To test this hypothesis, 83 Toll-I and Toll-2 (most have two TIRs, but others seem to be the evolutionary intermediates) genes from 29 shellfish species were identified. These Tolls were divided into nine groups based on phylogenetic analyses. A strong correlation between phylogeny and motif composition was found. All Toll proteins contained the TIR-2 domain, whereas the TIR-1 domain only existed in some Toll-2 protein, suggesting that TIR-1 domain insertion may play an important role in Toll protein evolution. Further analyses of functional divergence and adaptive evolution showed that some of the critical sites responsible for functional divergence may have been under positive selection. An additional intragenic recombination played an important role in the evolution of the Toll-I and Toll-2 genes. To investigate the functional difference of Toll-I and Toll-2, over expression of Hcu_Toll-I or Hcu_Toll-2-2 in Drosophila S2 cells was performed. Results showed that Hcu_Toll-2-2 had stronger antimicrobial peptide (AMP) activity than Hcu_Toll-I. Therefore, enhanced AMP-induced activity resulted from tandem TIRs in Toll-2s of molluscs during evolution history.

Description: Author(s): F. Sun, N. N. Li, B. J. Chen, Y. T. Jia, L. J. Zhang, W. M. Li, G. Q. Zhao, L. Y. Xing, G. Fabbris, Y. G. Wang, Z. Deng, Y. J. Uemura, H. K. Mao, D. Haskel, W. G. Yang, and C. Q. Jin We used x-ray magnetic circular dichroism (XMCD) to probe the ferromagnetic properties of As p -symmetric ( 4 p ) states in the recently synthesized diluted magnetic semiconductor ( B a 1 − x K x ) ( Z n 1 − y M n y ) 2 A s 2 system under ambient- and high-pressure conditions. The As K -edge XMCD signal scales with the sample… [Phys. Rev. B 93, 224403] Published Fri Jun 03, 2016

Description: Author(s): B. Tu, J. Xiao, K. Yao, Y. Shen, Y. Yang, D. Lu, W. X. Li, M. L. Qiu, X. Wang, C. Y. Chen, Y. Fu, B. Wei, C. Zheng, L. Y. Huang, B. H. Zhang, Y. J. Tang, R. Hutton, and Y. Zou Photon absorption spectroscopy is a powerful tool for uncovering the structure of atoms, molecules, and solids. Symmetric Lorentzian and asymmetric Fano line shapes are fundamental spectroscopic signatures related to the structural and dynamical properties. Recently, Ott et al. [ Science 340 , 716 (20... [Phys. Rev. A 91, 060502(R)] Published Mon Jun 22, 2015

Description: The cutoff value of nuclear magnetic resonance (NMR) transversal relaxation time $${T}_{2}$$ is vital for pore structure characterization, permeability prediction, and irreducible water saturation calculation. Conventional default values often lead to inaccurate results for rocks with complex pore structure. Based on NMR experiments and multifractal theory, we have developed an effective statistical method to predict $${T}_{2}$$ cutoff values without other petrophysical information. The method is based on multifractal theory to analyze the NMR $${T}_{2}$$ spectrum with the assumption that the $${T}_{2}$$ spectrum is an indicator of pore size distribution. Multifractal parameters, such as multifractal dimension, singularity strength, and mass exponent, are calculated to investigate the multifractal behavior of $${T}_{2}$$ spectrum via NMR experiments and a dyadic scaling-down algorithm. To obtain the optimal $${T}_{2}$$ cutoff value, the rotation speed and time of centrifugation are enlarged increasingly to optimal centrifugal state. A predicating model for $${T}_{2}$$ cutoff value based on multiple linear regressions of multifractal parameters was proposed after studying the influential factors. On the basis of the multifractal analysis of NMR $${T}_{2}$$ spectrum, a reasonable predication model for $${T}_{2}$$ cutoff value was rendered. Upon testing, the predicted results were highly consistent with the experimental results.