Determination of L‐ and D‐Enantiomers of Leucine Using Amperometric Biosensors Based on Diamond Paste

Abstract

Four amperometric biosensors, based on diamond paste, are proposed for the determination of the enantiopurity of leucine. The design of the biosensors used physical immobilization in diamond paste of L‐amino acid oxidase for the assay of L‐leucine and D‐amino acid oxidase for the assay of D‐leucine. The response characteristics of the different diamond paste based biosensors were obtained and compared. The linear concentration ranges for the biosensors were in pmol/L to nmol/L magnitude order. The biosensors showed high reliability for the determination of enantiopurity of leucine as a raw material.     

Identification and quantification of β-caryophyllene in copaiba oil using Raman spectroscopy

Copaiba oleoresin presents several compounds with known biologic activity and physiologic effects, including analgesic and insecticide properties. Among them are the terpenoids (mainly diterpenes and sesquiterpenes) with β-caryophyllene, the main representative of the terpenoids and considered to be a chemical marker. This study employed Raman spectroscopy and principal component analysis (PCA) techniques to identify and quantify the β-caryophyllene marker in copaiba oil samples purchased from popular markets in Brazil. A dispersive Raman spectrometer (830?nm, 250?mW, 2?cm^?1 spectral resolution) was used. Results showed the identification of the main Raman peaks from the β-caryophyllene in copaiba oil samples (main peaks at 507, 771, 1442, 1638, and 1673?cm^?1). The loading vector 2 (PC2) extracted the spectral information from β-caryophyllene in the samples and the eigenvalue 2 (score 2) allowed the estimation of the concentration of this marker in commercial samples, with the concentrations from 15 to 34%. Raman spectroscopy combined with PCA may be considered to be a potential analytical tool for the quality control of Copaifera oil samples by quantifying β-caryophyllene using its unique spectral information.     

A Novel Consideration of Species Distribution of Copper(II)/Histidine System at Physiological pH

Abstract

The copper(II)–L‐histidine system plays a pivotal role in copper transport across cell membranes. The coordination mode of copper(II)–L‐histidine species at physiological pH has been elusive in aqueous solution for the last four decades, despite exhaustive characterization studies. Recently, the isolation and the X‐ray crystal structure of the physiological [Cu(His)₂] complex have been reported. The X‐ray structure is different from all the structures suspected for this complex in solution.

We carried out a polarographic analysis to identify copper(II)–L‐histidine species at physiological pH. In our experimental conditions, three copper(II)–L‐histidine species coexist around the physiological pH. These novel considerations can explain the controversy encountered in the investigation of the coordination mode in aqueous solution.     

Improved single neuron controller for multivariable stochastic systems with non-Gaussianities and unmodeled dynamics

In this paper, a new adaptive control approach is presented for multivariate nonlinear non-Gaussian systems with unknown models. A more general and systematic statistical measure, called (h,?)$(h,?)$-entropy, is adopted here to characterize the uncertainty of the considered systems. By using the “sliding window” technique, the non-parameter estimate of the (h,?)$(h,?)$-entropy is formulated. Then, the improved neuron based controllers are developed for multivariate nonlinear non-Gaussian systems by minimizing the entropies of the tracking errors in closed loops. The condition to guarantee the strictly decreasing entropy of tracking error is presented. Moreover, the convergence in the mean-square sense has been analyzed for all the weights in the neural controllers. Finally, the comparative simulation results are presented to show that the performance of the proposed algorithm is superior to that of PID control strategy.     

End-grafted Sugar Chains as Aqueous Lubricant Additives: Synthesis and Macrotribological Tests of Poly(<Emphasis Type="SmallCaps">l</Emphasis>-lysine)-<Emphasis Type="Italic">graft</Emphasis>-Dextran (PLL-<Emphasis Type="Italic">g</Emphasis>-dex) Copolymers

Comb-like graft copolymers with carbohydrate side chains have been developed as aqueous lubricant additives for oxide-based tribosystems, in an attempt to mimic biological lubrication systems, whose surfaces are known to be covered with sugar-rich layers. As adopted in the previous studies of the graft copolymer poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), which showed both excellent lubricating and antifouling properties, a similar approach was chosen to graft dextran chains onto the same backbone, thus generating PLL-g-dex. PLL-g-dex copolymers readily adsorb from aqueous solution onto negatively charged oxide surfaces. Tribological characterization at the macroscopic scale, either under pure sliding conditions or a mixed sliding/rolling contact regime, shows that PLL-g-dex is very effective for the lubrication of oxide-based tribosystems. The relative lubricating capabilities of PLL-g-dex copolymers compared with PLL-g-PEG copolymers were observed to be highly dependent on the molecular structure of the copolymers (in particular, side-chain density along the backbone) and the measurement conditions (in particular, time between tribocontacts); the PLL-g-dex copolymers with a low degree of grafted side chains (≤20% grafting of available protonated primary amine groups along the backbone) showed better lubricating performance than their PLL-g-PEG counterparts at high tribocontact frequency (≥ca. 0.32 Hz).     

Basic study on nanofabrication of biodegradable plastics applying biochemical machining

Plastics are regarded as proper materials for microfluidic chips, and, in particular, biodegradable plastics will be more appropriate from the viewpoint of environmental friendliness. In addition, when they are utilized as chip substrate, biochemical machining can be applied. Biochemical machining is a process, which utilizes enzymatic biodegradation. This paper describes studies on application of biochemical machining to nanofabrication of poly(l-lactic acid) (PLLA), which is one of the most widely used biodegradable plastics industrially. The degradation performance of enzyme (proteinase K) was experimentally evaluated to extrapolate a suitable condition for nanofabrication. Additionally, in order to make arbitrary channels with nano-order depth on PLLA, mask fabrication was proposed. It is a fabrication method to control degraded regions and obtain desired shapes with a mask, which has penetrating grooves. Using this method, we achieved fabrication of straight grooves with nano-scale depth. In conclusion, it is clear that biochemical machining can realize an effective process of arbitrarily shaped nanogrooves on PLLA.     

Self-healing behavior of a polyelectrolyte-based lubricant additive for aqueous lubrication of oxide materials

We report on the self-healing behavior of a polyelectrolyte-based aqueous lubricant additive, poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), during aqueous lubrication of an oxide-based tribosystem. Combined pin-on-disk tribometry and fluorescence microscopy experiments have shown that stable lubricating performance was enabled by means of rapid healing of the worn tribopair surface by polymers dissolved in the adjoining bulk lubricant. This rapid ‘self-healing’ of PLL-g-PEG is attributed to electrostatic interactions between the polycationic poly(l-lysine) (PLL) backbone of the polymer and negatively charged oxide surface. In contrast, a similar healing effect was not readily achievable in the case of methoxy-poly(ethylene glycol)-trimethylsilylether (Sil-PEG), a lubricant additive that is covalently bonded to the surface prior to tribological stress.     

单价银离子在 CaO-P2O5 系统玻璃中的发光特性

在弱还原气氛下制备了单价银离子(Ag⁺)掺杂的CaO-P₂O₅系统玻璃,测试了其在室温下的吸收光谱、激发光谱和发射光谱。Ag⁺-CaO-P₂O₅玻璃的吸收光谱表明两个吸收峰。高能峰位于220nm波长,由4d¹⁰→4d⁹5P¹跃迁引起,低能峰中心位于240nm波长,归因于4d¹⁰→4d⁹5s¹跃迁,该吸收与其发射特性有关。紫外波段的宽带吸收产生了可见波段强烈的荧光发射,发光峰位于440nm波长,半宽度为130nm.研究了掺质浓度与发光特性的关系,随着掺质浓度的增加(0.05～0.25mol%),发光峰向较长波段移动。在Ag₂O含量为0.5mol%时,出现了浓度猝灭现象。为了比较起见,同时还研制了Cu⁺-CaO-P₂O₅及Cu⁺-Ag⁺-CaO-P₂O₅玻璃。     

Image simulation of high resolution energy filtered TEM images

Inelastic image simulation software is presented, implementing the double channeling approximation which takes into account the combination of multiple elastic and single inelastic scattering in a crystal. The approach is described with a density matrix formalism. Two applications in high resolution energy filtered (EFTEM) transmission electron microscopy (TEM) images are presented: thickness-defocus maps for _SrTiO3${\mathrm{SrTiO}}_3$ and exit plane intensities for an (_LaAlO3)3(_SrTiO3)3$({\mathrm{LaAlO}}_3{)}_3({\mathrm{SrTiO}}_3{)}_3$ multilayer system. Both systems show a severe breakdown in direct interpretability which becomes worse for higher acceleration voltages, thicker samples and lower excitation edge energies. Since this effect already occurs in the exit plane intensity, it is a fundamental limit and image simulations in EFTEM are indispensable just as they are indispensable for elastic high resolution TEM images.     

基于桨叶模态修型的直升机减振优化

基于Hamilton原理推导了模态修型减振优化的有限元动力学模型,通过修改桨叶的剖面刚度和线密度来改变结构的动力学模态。以最小振动载荷为目标函数,以桨叶剖面刚度及质量为设计变量,以桨叶的频率、自转惯量、质量及模态修型参数等为约束条件,进行了减振优化。算例表明:在约束条件都满足的情况下,优化后,3/转的桨根剪力减小了55.4%,4/转的桨根剪力减小了66.5%,5/转的桨根剪力减小了53.4%,优化效果明显。     

Effects of tilt on high-resolution ADF-STEM imaging

A study of the effects of small-angle specimen tilt on high-resolution annular dark field images was carried out for scanning transmission electron microscopes with uncorrected and aberration-corrected probes using multislice simulations. The results indicate that even in the cases of specimen tilts of the order of 1 degree a factor of 2 reduction in the contrast of the high-resolution image should be expected. The effect holds for different orientations of the crystal. Calculations also indicate that as the tilted specimen gets thicker the contrast reduction increases. Images simulated with a low-angle annular dark field detector show that tilt effects are more pronounced in this case and suggest that these low-angle detectors can be used to correct specimen tilt during scanning transmission electron microscopes operation.     

Partially decentralized control for ALSTOM gasifier

The gasifier plays a key role in the operation of the whole IGCC power plant. It is a typical multivariable control system with strict constraints on the inputs and outputs which makes it very difficult to control. This paper presents a partially decentralized controller design method based on the stabilizer idea. The method only requires identifying some closed-loop transfer functions and solving an H_∞ optimization problem. The final partially decentralized controller is easy to implement and test in practice. Two partially decentralized controllers are designed for the ALSTOM gasifier benchmark problem, and simulation results show that they both meet the design specifications.     

LncRNA <i>ZFAS1</i> regulates cardiomyocyte differentiation of human embryonic stem cells

Background: Cardiomyocytes derived from human embryonic stem cells (hESCs) are regulated by complex and stringent gene networks during differentiation. Long non-coding RNAs (lncRNAs) exert critical epigenetic regulatory functions in multiple differentiation processes. However, the involvement of lncRNAs in the differentiation of hESCs into cardiomyocytes has not yet been fully elucidated. Here, we identified the key roles of ZFAS1 (lncRNA zinc finger antisense 1) in the differentiation of cardiomyocytes from hESCs. Methods: A model of cardiomyocyte differentiation from stem cells was established using the monolayer differentiation method, and the number of beating hESCs-derived cardiomyocytes was calculated. Gene expression was analyzed by quantitative real-time PCR (qRT-PCR). Immunofluorescence assays were performed to assess the expression of cardiac troponin T (cTnT) and α-actinin protein in cardiomyocytes. Results: qRT-PCR showed that ZFAS1 expression in the mesoderm was significantly higher than that in embryonic stem cells, cardiac progenitor cells, and cardiomyocytes. Knockdown of ZFAS1 inhibited cardiomyocyte differentiation from hESCs, which was characterized by reduced expression of the cardiac-specific markers cTnT, α-actinin, myosin heavy chain 6 (MYH6), and myosin heavy chain 7 (MYH7). In contrast, ZFAS1 overexpression remarkably increased the percentage of spontaneously beating cardiomyocytes. In terms of the mechanism, we found that ZFAS1 is an antisense lncRNA at the 5′ end of the protein-coding gene ZNFX1. Knockdown of ZFAS1 could increase the mRNA expression level of ZNFX1. Furthermore, qRT-PCR demonstrated that the silencing of ZNFX1 led to an increase in cardiac-specific markers that predicted the promotion of cardiomyocyte differentiation. Conclusion: Altogether, these data suggest that lncRNA-ZFAS1 is required for cardiac differentiation by functionally inhibiting the expression of ZNFX1, which may provide a reference for the treatment of heart disease to a certain extent.     

Exploring the attenuation mechanisms of <i>Dalbergia odorifera</i> leaves extract on cerebral ischemia-reperfusion based on weighted gene co-expression network analysis

Background: The attenuation function of Dalbergia odorifera leaves on cerebral ischemia-reperfusion (I/R) is little known. The candidate targets for the Chinese herb were extracted from brain tissues through the high-affinity chromatography. The molecular mechanism of D. odorifera leaves on cerebral I/R was investigated. Methods: Serial affinity chromatography based on D. odorifera leaves extract (DLE) affinity matrices were applied to find specific binding proteins in the brain tissues implemented on C57BL/6 mice by intraluminal middle cerebral artery occlusion for 1 h and reperfusion for 24 h. Specific binding proteins were subjected to mass-spectrometry to search for the differentially expressed proteins between control and DLE-affinity matrices. The hub genes were screened based on weighted gene co-expression network analysis (WGCNA). Then, predictive biology and potential experimental verification were performed for the candidate genes. The protective role of DLE in blood-brain barrier damage in cerebral I/R mice was evaluated by the leakage of Evans blue, western blotting, immunohistochemistry, and immunofluorescent staining. Results: 952 differentially expressed proteins were classified into seven modules based on WGCNA under soft threshold 6. Based on WGCNA, AKT1, PIK3CA, NOS3, SMAD3, SMAD1, IL6, MAPK1, TGFBR2, TGFBR1, MAPK3, IGF1R, LRG1, mTOR, ROCK1, TGFB1, IL1B, SMAD2, and SMAD5 18 candidate hub proteins were involved in turquoise module. TGF-β, MAPK, focal adhesion, and adherens junction signaling pathway were associated with candidate hub proteins. Gene ontology analysis demonstrated that candidate hub proteins were related to the TGF-β receptor signaling pathway, common-partner SMAD protein phosphorylation, etc. DLE could significantly reduce the leakage of Evans blue in mice with cerebral I/R, while attenuating the expression of occludin, claudin-5, and zonula occludens-1. Western blotting demonstrated that regulation of TGF-β/SMAD signaling pathway played an essential role in the protective effect of DLE. Conclusion: Thus, a number of candidate hub proteins were identified based on DLE affinity chromatography through WGCNA. DLE could attenuate the dysfunction of blood-brain barrier in the TGF-β/SMAD signaling pathway induced by cerebral I/R.     

紫外-真空紫外波段的Al+MgF2膜

Al+MgF₂膜是真空紫外波段常用的一种反射膜。根据薄膜光学的电磁场理论计算了正入射条件下Al+MgF₂膜在真空紫外波段的反射率随氟化镁膜厚度的变化规律。研究了Al+MgF₂膜的制备工艺,利用Seya-Namioka紫外-真空紫外反射率计测得Al+MgF₂膜的反射率在150nm～340nm的波段上高于80%。Al+MgF₂膜制备一年后,其真空紫外波段的反射率未有明显变化。     

Elastic–plastic spherical contact under combined normal and tangential loading in full stick

The behavior of an elastic–plastic contact between a deformable sphere and a rigid flat under combined normal and tangential loading with full stick contact condition is investigated theoretically. Sliding inception is treated as a plastic yield failure mechanism, which allows static friction modeling under highly adhesive conditions. Several contact parameters such as: junction tangential stiffness, static friction force and static friction coefficient are extensively investigated. The phenomenon of junction growth and the evolution of the plastic zone in the contact region are briefly described. It is found that at low normal dimensionless loads the static friction coefficient decreases sharply with increasing normal load, in breach with the classical laws of friction. As the normal load further increases the static friction coefficient approaches a constant value that is about 0.3 for many material properties combinations.     

Determination of Linear Attenuation Coefficients of Materials by Using Timing Method

Abstract

In this work, gamma-ray linear attenuation coefficients of aluminum (Al) and lead (Pb) materials were determined by using timing method. The used setup is different from the conventional ones. The goal of the presented setup is the fact that it is used the timing technique. The detection system is composed of a 3″ × 3″ NaI(Tl) inorganic scintillation detector and related equipment together with ¹³⁷Cs and ⁶⁰Co radioactive sources. Obtained results are in good agreement with each other.     

The Influence of Anchoring-Group Structure on the Lubricating Properties of Brush-Forming Graft Copolymers in an Aqueous Medium

We have compared the lubricating properties of two different PEG-grafted, polycationic, brush-forming copolymers to gain a deeper understanding of the role of the polyionic backbone in the lubricating behavior of such materials, when used as additives in aqueous lubricant systems. Previously, poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) has been shown to adsorb onto oxide surfaces from aqueous solution and substantially lower frictional forces. Poly(allylamine)-graft-poly(ethylene glycol) (PAAm-g-PEG), which also has a polycationic backbone, has been synthesized in several different architectures, and its performance investigated via adsorption tests, rolling- and sliding-contact tribometry, and the surface forces apparatus. These tests show a clear reduction of friction forces with PAAm-g-PEG compared to water alone. However, when compared with PLL-g-PEG, while PAAm-g-PEG copolymers did not adsorb to the same extent or exhibit as high a lubricity in sliding geometry, they showed a similar lubricating effect under rolling conditions. The difference in the chemical structure of the backbones, especially the flexibility of the anchoring groups, appears to significantly influence both the extent and kinetics of polymer adsorption, which in turn influences lubrication behavior.