Molecularly engineered graphene surfaces for sensing applications: A review

Graphene is scientifically and commercially important because of its unique molecular structure which is monoatomic in thickness, rigorously two-dimensional and highly conjugated. Consequently, graphene exhibits exceptional electrical, optical, thermal and mechanical properties. Herein, we critically discuss the surface modification of graphene, the specific advantages that graphene-based materials can provide over other materials in sensor research and their related chemical and electrochemical properties. Furthermore, we describe the latest developments in the use of these materials for sensing technology, including chemical sensors and biosensors and their applications in security, environmental safety and diseases detection and diagnosis.     

Polarization-dependent Goos-Hänchen shift at a graded dielectric interface

We examine the polarization differential Goos-Hänchen beam shift upon total internal reflection, for a graded-index dielectric interface. We find a generic scaling law where the magnitude of this shift depends solely on the product of wavelength and gradient steepness. The analytic results are extended using transmission matrix calculations in cases where the assumptions made to allow analytical treatment might become questionable. Two important cases in this category are: (i) incident angle close to the critical angle and (ii) gradients with an overall thickness of the order of a wavelength. We demonstrate this effect experimentally using a polymer-blend sample with a gradual refractive-index transition induced by diffusion.     

Non-Specific GH30_7 Endo-β-1,4-xylanase from Talaromyces leycettanus

This study describes the catalytic properties of a GH30_7 xylanase produced by the fungus Talaromyces leycettanus. The enzyme is an ando-β-1,4-xylanase, showing similar specific activity towards glucuronoxylan, arabinoxylan, and rhodymenan (linear β-1,3-β-1,4-xylan). The heteroxylans are hydrolyzed to a mixture of linear as well as branched β-1,4-xylooligosaccharides that are shorter than the products generated by GH10 and GH11 xylanases. In the rhodymenan hydrolyzate, the linear β-1,4-xylooligosaccharides are accompanied with a series of mixed linkage homologues. Initial hydrolysis of glucuronoxylan resembles the action of other GH30_7 and GH30_8 glucuronoxylanases, resulting in a series of aldouronic acids of a general formula MeGlcA²Xyl_n. Due to the significant non-specific endoxylanase activity of the enzyme, these acidic products are further attacked in the unbranched regions, finally yielding MeGlcA²Xyl_2-3. The accommodation of a substituted xylosyl residue in the −2 subsite also applies in arabinoxylan depolymerization. Moreover, the xylose residue may be arabinosylated at both positions 2 and 3, without negatively affecting the main chain cleavage. The catalytic properties of the enzyme, particularly the great tolerance of the side-chain substituents, make the enzyme attractive for biotechnological applications. The enzyme is also another example of extraordinarily great catalytic diversity among eukaryotic GH30_7 xylanases.     

Screening an In-House Isoquinoline Alkaloids Library for New Blockers of Voltage-Gated Na+ Channels Using Voltage Sensor Fluorescent Probes: Hits and Biases

Voltage-gated Na⁺ (Na_V) channels are significant therapeutic targets for the treatment of cardiac and neurological disorders, thus promoting the search for novel Na_V channel ligands. With the objective of discovering new blockers of Na_V channel ligands, we screened an In-House vegetal alkaloid library using fluorescence cell-based assays. We screened 62 isoquinoline alkaloids (IA) for their ability to decrease the FRET signal of voltage sensor probes (VSP), which were induced by the activation of Na_V channels with batrachotoxin (BTX) in GH3b6 cells. This led to the selection of five IA: liriodenine, oxostephanine, thalmiculine, protopine, and bebeerine, inhibiting the BTX-induced VSP signal with micromolar IC₅₀. These five alkaloids were then assayed using the Na⁺ fluorescent probe ANG-2 and the patch-clamp technique. Only oxostephanine and liriodenine were able to inhibit the BTX-induced ANG-2 signal in HEK293-hNa_V1.3 cells. Indeed, liriodenine and oxostephanine decreased the effects of BTX on Na⁺ currents elicited by the hNa_V1.3 channel, suggesting that conformation change induced by BTX binding could induce a bias in fluorescent assays. However, among the five IA selected in the VSP assay, only bebeerine exhibited strong inhibitory effects against Na⁺ currents elicited by the hNav1.2 and hNav1.6 channels, with IC₅₀ values below 10 µM. So far, bebeerine is the first BBIQ to have been reported to block Na_V channels, with promising therapeutical applications.     

Fabrication of high temperature moiré grating and its application

The fabrication technique of high temperature moiré grating has been presented, which combines thermal nanoimprint process method and high temperature transferring technique. And the quality of grating was evaluated by analyzing its configuration through the Atomic Force Microscope (AFM) images. From the analysis, it was found that the optimal depth of grating will cause different stress condition in the process of vacuum deposition, and thicker deposited metal film on the grating may enhance the oxidation resistant ability. However, with the increase of the thickness of the metal film, cracks may occur in the film, In order to avoid this mechanical failure, the optimization of the depth of grating was performed. The optimized depth was obtained by analyzing the stress intensity using Finite Element Method (FEM). In order to verify the reliability of high temperature grating, the tensile experiment of high temperature alloy (GH3030) at 650 °C was carried out, and the experimental results demonstrated that fabricated high temperature grating was feasible.     

Fractional Generalized Random Fields on Bounded Domains

Using the theory of generalized random fields on fractional Sobolev spaces on bounded domains, and the concept of dual generalized random field, this paper introduces a class of random fields with fractional-order pure point spectra. The covariance factorization of an α-generalized random field having a dual is established, leading to a white-noise linear-filter representation, which reduces to the usual Markov representation in the ordinary case when α∈N and the covariance operator of the dual random field is local. Fractional-order differential models commonly arising from anomalous diffusion in disordered media can be studied within this framework.     

加镁合金GH2036M的晶内和晶界沉淀相分析

观察了加镁合金ＧＨ２０３６Ｍ不同热处理状态下沉淀相ＭＣ和Ｍ２３Ｃ６的形貌和分布特征，并测定了它们的数量、化学组成及主要强化相ＶＣ与γ的错配度，探讨了适量镁对提高合金晶界强度及改善持久性能的作用机理。     

The protective effect of growth hormone on Cu/Zn superoxide dismutase-mutant motor neurons

Background

Amyotrophic lateral sclerosis (ALS) is characterized by selective degeneration of motor neurons. The gene encoding Cu/Zn superoxide dismutase (SOD1) is responsible for 20% of familial ALS cases. Growth hormone (GH) concentrations are low in the cerebrospinal fluid of patients with ALS; however, its association with motoneuronal death is not known. We tested the neuroprotective effects of GH on human SOD-1-expressing cultured motor neurons and SOD1G93A transgenic mice.

Results

In cultured motor neurons, cytotoxicity was induced by {"type":"entrez-nucleotide","attrs":{"text":"A23187","term_id":"833253","term_text":"A23187"}}A23187, GNSO, or homocysteine, and the effects of GH were determined by MTT, bax, PARP cleavage pattern, Hoechst nuclear staining, MAPK, and PI3K assay. In SOD-1 transgenic mice, rotarod motor performance was evaluated. Survival analysis of motoneuronal loss was done using cresyl violet, GFAP, and Bcl-2 staining. GH prevents motorneuronal death caused by GSNO and homocysteine, but not that by {"type":"entrez-nucleotide","attrs":{"text":"A23187","term_id":"833253","term_text":"A23187"}}A23187. It activates MAPK and PI3K. GH-treated mice showed prolonged survival with improved motor performance and weight loss. GH decreased cresyl violet positive motoneuronal loss with strong Bcl-2 and less GFAP immunoreactivity.

Conclusions

Our results demonstrate that GH has a protective effect on mutant SOD-1-expressing motor neurons.     

Large lateral shift in a multi-layer waveguide with indefinite media

We explore the basic properties of lateral shift in a multi-layer waveguide including isotropic metamaterial and indefinite media. Effective index method is used to calculate the refractive index of indefinite media and stationary-phase approach is applied to analysis the lateral shift of reflected light. The influences of thicknesses of isotropic metamaterial and indefinite media, off-diagonal parameters of indefinite media, the loss of metamaterial and the permeability of lateral shift on the lateral shift are discussed based on simulation results, which give us a guidance in designing multi-functional devices by use of the lateral shift in the proposed structure.     

盐酸-硝酸体系溶解―ICP-OES法测定镍-铬基高温合金GH4133B中铝铌钛铬铁

GH4133B是Ni-Cr基沉淀硬化型变形高温合金,近年来我国还没有适宜的国家标准,基于此对样品主要元素含量准确测定方法进行了研究和探讨。采用盐酸-硝酸体系对GH4133B镍基高温合金进行溶解,确定了盐酸和硝酸比列为8:3,混合酸用量为11mL;采用ICP-OES法快速准确的对GH4133B镍基高温合金中铝、铌、钛、铬、铁元素含量进行测定;确定了各元素分析谱线为Al396.152nm、Nb309.417nm、Ti334.941nm、Cr267.716nm、Fe238.204nm;建立了校准工作曲线,各元素线性相关系数均在0.999以上;优化仪器参数消除基体干扰,测定了方法检出限,各元素检出限均小于0.003%,各元素测定结果的RSD/%在0.26%～0.47%之间(n=7),加标回收率在103.0％~104.5％之间。有效解决了GH4133B镍基高温合金快有效速溶解及准确测定问题。