Response of Water Tetramer to Intense Femtosecond Laser Pulses

Zhiping Wang,Xuefen Xu,Chaoyi Qian,Yanbiao Wang,Xu Wang 한국광학회 2017 Current Optics and Photonics Vol.1 No.4

We theoretically study the dynamics of water tetramer in intense femtosecond laser pulses with differentfrequencies. The simulations are carried out by incorporating the molecular dynamics method non-adiabaticallyinto the time-dependent local-density approximation (TDLDA-MD). Three typical scenarios of watertetramer including the normal vibration with enlarged OH bonds, free OH bonds breaking and the pureCoulomb explosion are presented by investigating the electronic and ionic dynamics. The result indicatesthat the ionization is enhanced and the corresponding fragmentation effect as well as the damping of thedipole moment are found more notably when increasing the laser frequency especially when the frequencyfalls in the resonant region of the absorption spectra. The study of the level depletion reveals that theratio of the emission amount from different levels can be controlled by changing the laser frequencyreferring to the Keldysh parameter.

Bandwidth Allocation Under Multi-Level Service Guarantees of Downlink in the VLC-OFDM System

Shuangxing Liu,Xuefen Chi,Linlin Zhao 한국광학회 2016 Current Optics and Photonics Vol.20 No.6

In this paper, we explore a low-complex bandwidth allocation (BA) scheme with multi-level serviceguarantees in VLC-OFDM systems. Effective capacity theory, which evaluates wireless channel capacityfrom a novel view, is utilized to model the system capacity under delay QoS constraints of the link layer. Since intensity modulation of light is used in the system, problems caused by frequency selectivity canbe neglected. Then, the BA problem can be formulated as an integer programming problem and it is furtherrelaxed and transformed into a concave one. Lagrangian formulation is used to reformulate the concaveproblem. Considering the inefficiency of traditional gradient-based schemes and the demand for distributedimplementation in local area networks, we localize the global parameters and propose a quasi-distributedquadratic allocation algorithm to provide two-level service guarantees, the first level is QoS oriented, andthe second level is QoE oriented. Simulations have shown the efficient performance of the proposedalgorithm. The users with more stringent QoS requirements require more subcarriers to guarantee theirstatistical delay QoS requirements. We also analyze the effect of subcarrier granularity on the aggregateeffective capacity via simulations.

Scheduling with Heterogeneous QoS Provisioning for Indoor Visible-light Communication

Xiaoli Dong,Xuefen Chi,Hongliang Sun,Yuhong Zhu 한국광학회 2018 Current Optics and Photonics Vol.2 No.1

Visible-light communication (VLC) combined with advanced illumination can be expected to become an integral part of next-generation communication networks. One of the major concerns in VLC implementation is developing resource-allocation schemes in a multi-user scenario. However, the scheduling for heterogeneous quality of service (QoS) traffic has not been studied so far, for the indoor VLC downlink system. In this paper, we creatively introduce effective-bandwidth and effective-capacity theory into the multi-user scheduling (MUS) problem, to guarantee the user’s statistical delay QoS. We also take account of the aggregate interference (AI) in the indoor VLC downlink system, and analyze its impact on the user-centric MUS problem for the first time. Simulations show that the AI has a nonnegligible influence on the scheduling result, and that the proposed scheduling scheme could guarantee the user’s QoS requirement under the premise of ensuring sum capacity.

Molecular Cloning, Characterization and Functional Analysis of a 2C-methyl-D-erythritol 2, 4-cyclodiphosphate Synthase Gene from Ginkgo biloba

Gao, Shi,Lin, Juan,Liu, Xuefen,Deng, Zhongxiang,Li, Yingjun,Sun, Xiaofen,Tang, Kexuan Korean Society for Biochemistry and Molecular Biol 2006 Journal of biochemistry and molecular biology Vol.39 No.5

2C-methyl-D-erythritol 2, 4-cyclodiphosphate synthase (MECPS, EC: 4.6.1.12) is the fifth enzyme of the non-mevalonate terpenoid pathway for isopentenyl diphosphate biosynthesis and is involved in the methylerythritol phosphate (MEP) pathway for ginkgolide biosynthesis. The full-length mecps cDNA sequence (designated as Gbmecps) was cloned and characterized for the first time from gymnosperm plant species, Ginkgo biloba, using RACE (rapid amplification of cDNA ends) technique. The full-length cDNA of Gbmecps was 874 bp containing a 720 bp open reading frame (ORF) encoding a peptide of 239 amino acids with a calculated molecular mass of 26.03 kDa and an isoelectric point of 8.83. Comparative and bioinformatic analyses revealed that GbMECPS showed extensive homology with MECPSs from other species and contained conserved residues owned by the MECPS protein family. Phylogenetic analysis indicated that GbMECPS was more ancient than other plant MECPSs. Tissue expression pattern analysis indicated that GbMECPS expressed the highest in roots, followed by in leaves, and the lowest in seeds. The color complementation assay indicated that GbMECPS could accelerate the accumulation of $\beta$-carotene. The cloning, characterization and functional analysis of GbMECPS will be helpful to understand more about the role of MECPS involved in the ginkgolides biosynthesis at the molecular level.

Adsorption Behavior of Environmental Hormone Bisphenol A onto Mesoporous Silicon Dioxide

Xianghong Fan,Bing Tu,Hongmei Ma,Xuefen Wang 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.8

Mesoporous silicon dioxide (meso-SiO)2) was prepared using cetyltrimethylammonium bromide as the structure-directing reagent and tetraethyl orthosicate as the silicon source. The influence of pH value on the adsorption behavior of bisphenol A (BPA) was investigated. The adsorption capacity of BPA onto meso-SiO_2increases slightly with pH value from 2 to 6, and then gradually decreases as further improving pH value. The effect of temperature was also studied, and the adsorption capacity of BPA gradually declines with increasing temperature. The adsorption kinetics and thermodynamics of BPA were examined. It is found that the adsorption of BPA onto meso-SiO_2 is in good agreement with Langmuir adsorption model. The rate constant of adsorption is 5.17 × 10^−3 g mg−1 min−1, and the maximum adsorption capacity is as high as 353.4 mg g^−1 at 20 ^oC.

Adsorption Behavior of Environmental Hormone Bisphenol A onto Mesoporous Silicon Dioxide

Fan, Xianghong,Tu, Bing,Ma, Hongmei,Wang, Xuefen Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.8

Mesoporous silicon dioxide (meso-$SiO_2$) was prepared using cetyltrimethylammonium bromide as the structure-directing reagent and tetraethyl orthosicate as the silicon source. The influence of pH value on the adsorption behavior of bisphenol A (BPA) was investigated. The adsorption capacity of BPA onto meso-$SiO_2$ increases slightly with pH value from 2 to 6, and then gradually decreases as further improving pH value. The effect of temperature was also studied, and the adsorption capacity of BPA gradually declines with increasing temperature. The adsorption kinetics and thermodynamics of BPA were examined. It is found that the adsorption of BPA onto meso-$SiO_2$ is in good agreement with Langmuir adsorption model. The rate constant of adsorption is $5.17{\times}10^{-3}g\;mg^{-1}\;min^{-1}$, and the maximum adsorption capacity is as high as 353.4 $mg\;g^{-1}$ at 20 $^{\circ}C$.

In Vitro Evaluation of Swine-Derived Lactobacillus reuteri: Probiotic Properties and Effects on Intestinal Porcine Epithelial Cells Challenged with Enterotoxigenic Escherichia coli K88

( Zhilin Wang ),( Li Wang ),( Zhuang Chen ),( Xianyong Ma ),( Xuefen Yang ),( Jian Zhang ),( Zongyong Jiang ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.6

Probiotics are considered as the best effective alternatives to antibiotics. The aim of this study was to characterize the probiotic potential of lactobacilli for use in swine farming by using in vitro evaluation methods. A total of 106 lactic acid bacterial isolates, originating from porcine feces, were first screened for the capacity to survive stresses considered important for putative probiotic strains. Sixteen isolates showed notable acid and bile resistance, antibacterial activity, and adherence to intestinal porcine epithelial cells (IPEC-1). One isolate, LR1, identified as Lactobacillus reuteri, was selected for extensive study of its probiotic and functional properties in IPEC-1 cell models. L. reuteri LR1 exhibited good adhesion to IPEC-1 cells and could inhibit the adhesion of enterotoxigenic Escherichia coli (ETEC) to IPEC-1 cells. L. reuteri LR1 could also modulate transcript and protein expression of cytokines involved in inflammation in IPEC-1 cells; the Lactobacillus strain inhibited the ETEC-induced expression of proinflammatory transcripts (IL-6 and TNF-α) and protein (IL-6), and increased the level of anti-inflammatory cytokine (IL-10). Measurement of the permeation of FD-4 showed that L. reuteri LR1 could maintain barrier integrity in monolayer IPEC-1 cells exposed to ETEC. Immunolocalization experiments showed L. reuteri LR1 could also prevent ETEC-induced tight junction ZO-1 disruption. Together, these results indicate that L. reuteri LR1 exhibits desirable probiotic properties and could be a potential probiotic for use in swine production.

Uniform Side Illumination Generated from LEDs Arranged by an Annealing Algorithm

Xu Wang,Panling Lei,Chaoyi Qian,Zhiping Wang,Xuefen Xu,Zhouping Su 한국광학회 2022 Current Optics and Photonics Vol.6 No.3

Given a cubic space, it is easy to uniformly illuminate the floor with light sources placed on top. However, little has been reported about uniform illumination on walls with the same configuration of light sources. Here we present a luminaire consisting of nine light-emitting diodes (LEDs) with perfect Lambertian distribution, placed on the top as a 3 × 3 rectangular LED array. The distances between LEDs and tilt angles of each individual LED are adjustable and optimized by an annealing algorithm. After optimization, the array produces a rectangular illumination pattern on one wall with a uniformity of about 89%. Analysis shows that the tilt angles of individual LEDs are key parameters for uniform side illumination. In a scenario that is more practical, the tilt angles of all the LEDs are set to be the same, only decreasing the uniformity to 83%.