Electro-absorption Modulator with Dual Carrier Accumulation Layers Based on Epsilon-Near-Zero ITO

An electro-absorption modulator based on indium tin oxide is proposed by constructing a waveguide consisting of metal-dielectric-ITO-dielectric-Si stack. Applying a negative voltage bias on the ITO layer, carrier accumulation occurs at both dielectric-ITO interfaces, which dramatically changes the guided mode properties due to the epsilon-near-zero effect. By tuning the real part of the permittivity around zero, the guided plasmonic mode concentrates in either ITO or dielectric layers, resulting in a high propagation loss. These dual carrier accumulation layers significantly improve the extinction ratio of the modulator. A further improvement is obtained by using high refractive index dielectric thin layers, which provides a strong optical confinement in the carrier accumulation layers. The dual carrier accumulation layer device shows a 200 % increase of the modulation efficiency compared to a single accumulation layer design. A modulation depth of 9.9 dB/μm can be achieved by numerical simulation.     

降水量及N添加对荒漠草原植物和土壤微生物C∶N∶P生态化学计量特征的影响

基于2017年在宁夏荒漠草原设立的降水量(减少50%、减少30%、自然降水、增加30%以及增加50%)和N添加(0和5 g·m~(-2)·a~(-1))野外试验,研究了植物和土壤微生物C∶N∶P生态化学计量特征,分析二者与土壤C∶N∶P生态化学计量特征及其他土壤因子的关系,以探讨降水格局改变和大气N沉降增加下荒漠草原植物和土壤微生物C∶N∶P平衡特征及其主要影响因素。结果表明:(1)减少降水量对荒漠草原植物和土壤微生物C∶N∶P生态化学计量特征的影响较小,反映了二者对短期干旱的适应性;增加降水量降低了植物和土壤微生物生物量N和P含量,不同程度地提高了C∶N和C∶P,但其影响程度与N添加有关。(2)增减降水量条件下, N添加对植物生态化学计量特征影响较小,但对土壤微生物C∶N∶P生态化学计量特征影响较大,尤其在增加降水量条件下表现得更明显,意味着降水激发了N添加效应。(3)植物全N含量、N∶P以及土壤微生物生物量N含量的内稳性较低,可较好地反映土壤N供给水平以及N、P受限类型。(4)与植物C∶N∶P生态化学计量特征关系较强的土壤因子为速效P含量、磷酸酶活性、电导率、C∶P和有机C含量,与土壤微生物C∶N∶P生态化学计量特征关系较强的土壤因子有电导率、含水量、蔗糖酶活性和磷酸酶活性,表明植物和土壤微生物C∶N∶P平衡特征主要受其他土壤因子的调控,而非土壤元素平衡关系。     

QTL mapping of panicle blast resistance in japonica landrace heikezijing and its application in rice breeding

The rice blast caused by Magnaporthe oryzae is one of the most devastating diseases worldwide, and the panicle blast could result in more loss of yield in rice production. However, the quantitative trait loci (QTLs) and genes related to panicle-blast resistance have not been well studied due to the time-consuming screening methodology involved and variation in symptoms. The QTLs for panicle blast resistance have been mapped in a population of 162 RILs (recombination inbreeding lines), derived from a cross between a highly blast-resistant rice landrace, Heikezijing, and a susceptible variety, Suyunuo. Two QTLs for panicle-blast resistance, qPbh-11–1 and qPbh-7-1, were identified, which were distributed on chromosomes 11 and 7. The QTL qPbh-11–1 was stably detected in three independent experiments, at Nanjing in 2013 and 2014 and at Hainan in 2014, located between the region of RM27187 and RM27381 on the distal end of chromosome 11 far from the reported resistant loci Pb1 and qPbm11 for panicle blast. The QTL qPbh-7-1 was detected only at Nanjing in 2013 and located between the region of M18 and RM3555 on chromosome 7. With marker-assisted selection (MAS) three introgression lines with the major panicle blast-resistance QTL qPbh-11–1 were developed from a recurrent parent Nanjing 44 (NJ44) and the panicle resistance of introgression lines was improved 46.36–55.47 % more than NJ44. Based on the results provided, Heikezijing appears to be a valuable source for panicle blast resistance.     

Generation of In-Plane Light Beam with Orbital Angular Momentum with an Asymmetrical Plasmonic Waveguide

Based on silicon plasmonic waveguide with asymmetrical metal and dielectric coatings, we show that in-plane light beam with orbital angular momentum (OAM) in its axis field component could be generated by forming a π/2 phase difference between two fundamental modes of the asymmetrical waveguide. At the same time, the transverse field components contain a spin angular momentum due to the polarization rotation in the asymmetrical waveguide. The whole structure is ultracompact with a footprint less than < 3 × 0.5 × 0.5 μm. The proposed method to generate OAM beam in a waveguide would be interesting for on-chip integrated optical tweezers, information processing, etc.     

草甘膦胁迫对中华大蟾蜍（Bufo gargarizans）神经冲动产生和传导的影响

应用电生理方法研究了除草剂草甘膦对中华大蟾蜍（Bufo gargarizans Cantor）坐骨神经干冲动产生和传导的影响。用不同浓度的草甘膦溶液对中华大蟾蜍进行胁迫处理,草甘膦有效成分经由皮肤进入蟾蜍体内而作用于神经系统,利用生物信号采集处理系统测定草甘膦胁迫下中华大蟾蜍离体坐骨神经干的应激反应时间、动作电位幅度和冲动传导速度,结果表明：随着草甘膦溶液浓度的升高,中华大蟾蜍坐骨神经干接受刺激后产生冲动所需的时间逐渐延长,动作电位峰值降低,神经冲动传导速度亦逐渐减慢。草甘膦施用后,中华大蟾蜍7d内的平均应激反应时间与草甘膦浓度呈正相关,而动作电位幅度及传导速度均与草甘膦浓度呈负相关。草甘膦溶液浓度达到推荐农田使用浓度1.64~2.87ml/L时,各处理组蟾蜍的应激反应时间、动作电位幅度和冲动传导速度均与对照组差异极显著（P〈0.01）。同时,随着试验处理时间的延长,中华大蟾蜍神经干对刺激的反应变得更为迟钝,神经冲动的传导速度也进一步减慢。回归分析可知,中华大蟾蜍坐骨神经干的应激反应时间与草甘膦施用后天数呈正相关,而神经传导速度与药后天数呈负相关。由此可以说明,草甘膦胁迫条件下,中华大蟾蜍神经细胞对刺激反应的灵敏性降低,动作电位的产生及传导受到一定程度的抑制和阻碍。     

Function of Mouse Embryonic Stem Cell-Derived Supporting Cells in Neural Progenitor Cell Maturation and Long Term Cxpansion

Background

In the differentiation of mouse embryonic stem (ES) cells into neurons using the 5-stage method, cells in stage 4 are in general used as neural progenitors (NPs) because of their ability to give rise to neurons. The choice of stage 4 raises several questions about neural progenitors such as the type of cell types that are specifically considered to be neural progenitors, the exact time when these progenitors become capable of neurogenesis and whether neurogenesis is an independent and autonomous process or the result of an interaction between NP cells and the surrounding cells.

Methodology/Principal Findings

In this study, we found that the confluent monolayer cells and neural sphere like cell clusters both appeared in the culture of the first 14 days and the subsequent 6 weeks. However, only the sphere cells are neural progenitors that give rise to neurons and astrocytes. The NP cells require 14 days to mature into neural lineages fully capable of differentiation. We also found that although the confluent monolayer cells do not undergo neurogenesis, they play a crucial role in the growth, differentiation, and apoptosis of the sphere cells, during the first 14 days and long term culture, by secreted factors and direct cell to cell contact.

Conclusions/Significance

The sphere cells in stage 4 are more committed to developing into neural progenitors than monolayer cells. Interaction between the monolayer cells and sphere cells is important in the development of stage 4 cell characteristics.     

Age and growth of the tropical oviparous shark,Chiloscyllium punctatum in Indonesian waters

The brown-banded bamboo shark, Chiloscyllium punctatum, is the most common shark caught in coastal commercial fisheries throughout Southeast Asia, yet there is a lack of the life-history information necessary for reliable stock assessments. The authors estimated growth rates and age at maturity using analysis of growth bands in vertebral centra. They trialled four different techniques to enhance the visibility and improve identification of the putative annual growth bands necessary for age estimation. The authors found that the burn method on whole vertebral centra provided the most readable and consistent results for age analysis. The logistic model was chosen as the best-fit growth model for age estimation of 330 individual C. punctatum from Indonesia. Several age verification methods, including marginal increment ratio and length-frequency analysis, were performed with the support of age validation through the use of calcein-labelled vertebrae from two sharks maintained in captivity. This study found that C. punctatum from Indonesian waters is a fast-growing species that can grow up to 18 cm year⁻¹, reach an estimated maximum total length of 1 m, mature at c. 6.5 years and live for up to 14 years.