Highly Sensitive THz Refractive Index Sensor Based on Folded Split-Ring Metamaterial Graphene Resonators

Plasmonics - A highly sensitive absorption-based sensor based on folded split-ring metamaterial graphene resonators (FSRMGRs) is designed, and its biomedical application in terahertz (THz) spectrum...     

A High-Performance Refractive Index Sensor Based on Fano Resonance in Si Split-Ring Metasurface

We present a high-performance refractive index sensor based on Fano resonance with a figure of merit (FOM) about 56.5 in all-dielectric metasurface which consists of a periodically arranged silicon rings with two equal splits dividing them into pairs of arcs of different lengths. A Fano resonance with quality factor ~133 and spectral contrast ratio ~100% arises from destructive interference of two antiphase electric dipoles in the two arcs of the split-ring. We can turn on and/or off the Fano resonance with a modulation depth nearly 100% at the operating wavelength of 1067 nm by rotating the polarization of incident light. We believe that our results will open up avenues for the development of applications using Fano resonance with dynamically controllability such as biochemical sensors, optical switching, and modulator.     

Quad-Band Terahertz Absorber Based on Dipolar Resonances of Metamaterial Resonator

Plasmonics - A novel design of a quad-band metamaterial absorber, which consisted of only a metallic resonator on top of a dielectric spacing layer and a metallic board on the bottom, is presented...     

Plasmon-Induced Transparency and Refractive Index Sensing Based on a Trapezoid Cavity Coupled with a Hexagonal Resonator

Plasmonics - Tunable plasmon-induced transparency (PIT) effect is studied in a plasmonic device on the basis of the metal-insulator-metal (MIM) structure which consists of trapezoid and hexagonal...     

A Study of Sensitivity Improved Probe Using Hyperbolic Metamaterial for Optical Fiber SPR (OFSPR)-based Refractive Index Sensor

Plasmonics - In this work, we theoretically study the plasmonic behavior of Ag and Au with a hyperbolic metamaterial (HMM) and propose a numerical simulation of a D-shaped surface plasmon resonance...     

Analysis of a Single Solid Core Flat Fiber Plasmonic Refractive Index Sensor

Plasmonics - In this article, a single solid core flat fiber (SSCFF) refractive index sensor based on surface plasmon resonance (SPR) is proposed and analyzed numerically using the finite element...     

Plasmonic Band Gap: Role of the Slit Width in 1D Metallic Grating on Higher Refractive Index Substrate

This paper reports the excitation of surface plasmon polaritons (SPPs) and associated plasmonic band gap (PBG) while using TM plane wave interacting with 1D metallic grating on higher refractive index GaP substrate. A simple method is introduced to estimate the PBG which is crucial for many plasmonic devices. The PBG is estimated by measuring the transmission spectra obtained through the plasmonic grating structures when slit width is varied while periodicity and the thickness of the gold (Au) film remained fixed. The PBG is observed for the grating devices whose slit width is less than one third of the periodicity which is caused by the presence of a higher plasmonic mode. The PBG is absent for the grating device whose slit width is slightly less than half and greater than one third of the periodicity. Such grating devices support only a fundamental plasmonic mode because the profile/shape of the slit in the grating device is more like a sinusoidal nature. Furthermore, such grating offers intermediate scattering to the incident light and the SPP as well which in turn couple more incident energy to the SPPs. Far-field modelling results also support the results obtained through experiment.

     

Altering the Substrate Specificity of Organophosphorus Hydrolase for Enhanced Hydrolysis of Chlorpyrifos

Chlorpyrifos is one of the most popular pesticides used for agriculture crop protection, and widespread contamination is a potential concern. However, chlorpyrifos is hydrolyzed almost 1,000-fold slower than the preferred substrate, paraoxon, by organophosphorus hydrolase (OPH), an enzyme that can degrade a broad range of organophosphate pesticides. We have recently demonstrated that directed evolution can be used to generate OPH variants with up to 25-fold improvement in hydrolysis of methyl parathion. The obvious question and challenge are whether similar success could be achieved with this poorly hydrolyzed substrate, chlorpyrifos. For this study, five improved variants were selected from two rounds of directed evolution based on the formation of clear haloes on Luria-Bertani plates overlaid with chlorpyrifos. One variant, B3561, exhibited a 725-fold increase in the k_cat/K_m value for chlorpyrifos hydrolysis as well as enhanced hydrolysis rates for several other OP compounds tested. Considering that wild-type OPH hydrolyzes paraoxon at a rate close to the diffusion control limit, the 39-fold improvement in hydrolysis of paraoxon by B3561 suggests that this variant is one of the most efficient enzymes available to attack a wide spectrum of organophosphate nerve agents.     

Numerical Analysis of Single Negative Broadband Metamaterial Absorber Based on Tri Thin Layer Material in Visible Spectrum for Solar Cell Energy Harvesting

Plasmonics - A broadband nanostructure metamaterial absorber (MA) based on tri-layer metallic-optical-thin film molded shape is proposed for visible spectrum solar energy scavenging. This MA is...     

Plasmonic Coupling Effects on the Refractive Index Sensitivities of Plane Au-Nanosphere-Cluster Sensors

Plasmonic coupling effects (between neighboring components) are able to red shift the peak wavelengths of dipolar-localized surface plasmon resonances (LSPRs) and increase the corresponding refractive index sensitivity of nanoparticle sensors. The coupling effects on plane Au-nanosphere-cluster (including nanosphere dimer, trimer, pentamer, and heptamer) sensors are numerically investigated by finite element method (FEM). We found that the coupling does not violate the quadratic response characteristics of LSPR peak wavelengths, hence the linear responses of the sensitivities to the bulk refractive index of Au cluster sensors. Yet, for nanosphere dimer sensors, they contribute to the exponential decrease of sensitivities with their gap distances, which follow the universal plasmon ruler behavior. The amplitude of their fractional sensitivity shift is revealed to be bulk refractive index independent, which is different from that of their fractional LSPR peak wavelength shift. These are analytically explained well in terms of an effective nanoparticle model. The present work also gives an upper sensitivity limit for Au nanosphere dimer systems and provides a method to estimate the interparticle separation between the two component nanospheres of the dimer.

     

The C-terminal Tails of the Bacterial Chaperonin GroEL Stimulate Protein Folding by Directly Altering the Conformation of a Substrate Protein

Many essential cellular proteins fold only with the assistance of chaperonin machines like the GroEL-GroES system of Escherichia coli. However, the mechanistic details of assisted protein folding by GroEL-GroES remain the subject of ongoing debate. We previously demonstrated that GroEL-GroES enhances the productive folding of a kinetically trapped substrate protein through unfolding, where both binding energy and the energy of ATP hydrolysis are used to disrupt the inhibitory misfolded states. Here, we show that the intrinsically disordered yet highly conserved C-terminal sequence of the GroEL subunits directly contributes to substrate protein unfolding. Interactions between the C terminus and the non-native substrate protein alter the binding position of the substrate protein on the GroEL apical surface. The C-terminal tails also impact the conformational state of the substrate protein during capture and encapsulation on the GroEL ring. Importantly, removal of the C termini results in slower overall folding, reducing the fraction of the substrate protein that commits quickly to a productive folding pathway and slowing several kinetically distinct folding transitions that occur inside the GroEL-GroES cavity. The conserved C-terminal tails of GroEL are thus important for protein folding from the beginning to the end of the chaperonin reaction cycle.     

Optimizing the Refractive Index Sensitivity of Plasmonically Coupled Gold Nanoparticles

Plasmonics - The possibility to enhance the local refractive index sensitivity using plasmonic coupling between spherical gold nanoparticles (Au-NPs) has been investigated. A strong and distinct...     

生物组织的折射率对漫反射光分布的影响

采用杂合算法,讨论了折射率对不同吸收系数的生物组织漫反射光分布的影响。计算结果表明,在近源处生物组织的折射率越小,漫反射光模拟计算的相对误差越小;而在远离源处,其相对误差随折射率的增大而减小。同时也说明杂合模型不太适合模拟吸收生物组织的漫反射光分布。     

Dependence of Apertureless Scanning Near-Field Spectroscopy on Nanoscale Refractive Index Changes

We numerically investigate the spectral dependence of the electric field enhancement on a gold tip above PbTiO₃ on platinum systems by means of a finite element approach. The localized surface plasmon resonance (LSPR) is verified to change with the incident angle, the tip radius, and the tip-sample distance as well as with the refractive index of the sample underneath the tip. The refractive index sensitivity reveals detectable variations of the LSPR peak’s wavelength and maximum field enhancement, respectively, large enough to discriminate, e.g., between ferroelectric and paraelectric PbTiO₃ in tip-enhanced Raman spectroscopy (TERS) configuration.     

Effects of Refractive Index Variations on the Optical Transmittance Spectral Properties of the Nano-Hole Arrays

The 3D finite difference time domain technique was carried out to study the optical transmission properties of nano-hole arrays in the gold thin film supported by materials with different index of refraction in the visible and infrared regions. A series of perforated nano-hole structures on the gold film at different hole radius, hole depth of 100 nm, and structural periodicity of 400 nm were studied. It was found that transmission properties (i.e., intensity, FWHM, and resonance position) were strongly affected by hole radius and surrounding medium index of refraction. The maximum optical transmittance was observed as 31.9 % in a nano-hole array of hole radius of 125 nm and refractive index of 1.3. The maximum sensitivity of 300 nm/RIU was obtained at index of refraction of 1.7, whereas the minimum one was calculated as 110 nm/RIU in a nano-hole array of hole radius of 50 nm. It was also found that on increasing the hole radius from 50 to 125 nm, the spectral sensitivity was decreased, whereas the index sensitivity was increased on increasing the refractive index.     

单细胞生物进化研究的进步

20世纪60年代,生物大致分为5界的谱系图,　经历了几次翻新,开始提出了线粒体和叶绿体的内共生学说。 由于分子生物学的发展,首先将各种生物的蛋白质的分子进行比较,构建成蛋白质的分子系统树。再转向核糖核酸,将核糖体的小亚单位,作为区别生命类型之间亲缘关系的指标。发现有些嗜极端条件的细菌,它们不同于原核生物也不同于真核生物,是第三种类型的生命形式。因此,在 80年代为生命建立了细菌、古细菌和真核生物三界的系统树。对许许多多单个基因的系统树的分析,又使人们认识到,古细菌与细菌和真核微生物之间以及各个物种之间,显然皆发生过大量的基因交换。对单细胞进化来说,基因除垂直传递外,横向的或叫侧向的基因转移也十分繁多。在一张完全的系统图中,要同时表现几千个不同的基因家族的超联结的种系型式才符合实际。因而,最新版本的系统树是分枝交缠、无主干的。 Abstract:In 1960s,kimgdoms of organisms were charted generally in a five branching form.Later,the endosymbiont hypothesis for the mitochondria and the chloroplast was proposed.The life-form is divided into two forms,the prokaryotes (bacteria) and the eukaryotes.The study of the molecular biology made the progress faster.In 1980s,Woese,CR.asserted that two-domain view of life was no longer true,a three-domain construct,the Bacteria,the Archaea,and the Eukaryotes had to take its place.At first,phylogeny trees based on differences in the amino acid sequences,then among ribosomal RNAs and also nuclear gene from hundreds of microbial species were depicted and many mini phylogenetic trees grouped the species according to their differences in the sequences.It was found that they shared genes between their contemporaries and across the species barriers.At the root of the phylogeny tree,there was not a single common cell,it was replaced by a common ancestral community of primitive cells.Genes transfered rather freely as the transposons swapping between those cells.There was no last universal common ancestor of single cell that could be found in the revised Tree of Life,It was not easy to represent the genealogical patterns of thousands of different families of genes,in one systematic map,therefor there was no trunk at all.     

SCGE法检测敌敌畏对大鳞副泥鳅DNA损伤的研究

目的 采用SCGE技术检测敌敌畏对大鳞副泥鳅DNA的损伤效应.方法 设置敌敌畏0.64 μg/L、1.28μg./L、1.92μg/L、2.56μg/L、3.20μg/L 5个浓度组和一个空白对照组(15尾大鳞副泥鳅/组),通过单细胞凝胶电泳技术(scGE)研究各浓度敌敌畏处理组在分别处理l d、2 d、3 d后对大鳞...     

The Influence of Element Deformation on Terahertz Mode Interaction in Split-Ring Resonator-Based Meta-Atoms

The interaction between terahertz (THz) resonance modes and element deformation in rectangular split-ring resonator (RSRR)-based meta-atoms (MAs) is investigated experimentally. Two types of RSRR-based MAs are presented: lateral-varied SRR (LV-SRR) and arm-twisted SRR (AT-SRR). When the distances from the gaps to the opposite sides of above meta-atoms increase from 10 to 40 μm, the inductive-capacitive (LC) resonance modes and dipole oscillation modes exhibit redshift behavior. The quality factor (Q factor) of LC resonance decreases while that of dipole oscillation modes increases. The THz mode interaction is subject to the distance between the gap and opposite side. An extension of lateral side contributes much more to the enhancement of Q factor of dipole oscillation mode than the twisted arms. The relationship between the near-field coupling effect and THz modes is revealed by the analysis of surface currents as well as the electric energy density distribution, as is in agreement with the experimental results.     

Ambiguous Refractive Index Sensitivity of Fano Resonance on an Array of Gold Nanoparticles

We investigate the optical response to refractive index changes of a Fano resonance occurring in a random array of gold nanoparticles supported on a glass substrate. The Fano resonance results from the interference between localized surface plasmon on a gold nanoparticle and the light reflected at the boundary of the glass substrate. We demonstrate that the sensitivity of the resonance to the refractive index of the surrounding medium is highly dependent on the excitation geometry and can assume either positive or negative values. We furthermore present a theoretical analysis explaining this behavior based on the rigorous coupled wave analysis (RCWA) as well as the island film theory.