A facile approach to the synthesis of hydrophobic iron tetrasulfophthalocyanine (FeTSPc) nano-aggregates on multi-walled carbon nanotubes: A potential electrocatalyst for the detection of dopamine

A facile method has been utilized to synthesize a hydrophobic form of nano-scaled iron (II) tetrasulfophthalocyanine (nanoFeTSPc), integrated with functionalized multi-walled carbon nanotubes (fMWCNT-nanoFeTSPc). The nanocomposite was characterized by UV–visible spectra, EDX, FESEM, and TEM. The electrocatalytic properties of the film on a glassy carbon electrode were investigated using cyclic voltammetry, electrochemical impedance spectroscopy, chronoamperometry and square wave voltammetry. The fMWCNT-nanoFeTSPc modified electrode demonstrated higher catalytic performance in terms of electron transport and current response compared to the other electrodes studied towards dopamine (DA) detection giving a sensitivity of 0.314 μA μM⁻¹ and a limit of detection of 9.86 × 10⁻⁸ mol L⁻¹. A selective detection was realized in elimination of ascorbic acid response on the film of fMWCNT-nanoFeTSPc. The detection limit in the presence of a high concentration of ascorbic acid was 3.5 × 10⁻⁷ mol L⁻¹.     

Facile synthesis of lanthanide vanadates and their luminescent properties

GdVO₄:Eu³⁺, Bi³⁺ with tetragonal phase has been successfully synthesized by employing efficient irradiations. The assembly of composites with fine grains based on acoustic energy and microwave radiation requires low temperature (90 °C) and short reaction time (60 min). All the compounds exhibited red emissions and they can be sensitized through the doped Bi³⁺ ions. The dependence of pH changes and doping concentration on the fluorescence features has been discussed. The photoluminescence measurements show that the optical properties achieved the best results at pH = 9 for GdVO₄:Eu³⁺(5 mol%), Bi³⁺(1 mol%) or pH = 7 for GdVO₄:Eu³⁺.     

WO_3掺杂NiO的气敏性能研究

用水热法制备出NiO纳米粉体,对其进行了WO3系列掺杂。利用XRD对产物晶相结构进行表征,测试了掺杂材料的气敏性能。结果表明:适量WO3的掺杂明显改善了NiO材料的气敏性能,其中,掺杂质量分数为6%的气敏元件性能最好,350℃时对Cl2的灵敏度可达到37.5,200℃时对H2S的灵敏度可达30.4。说明该元件在不同温度下对不同气体具有选择性,且该元件对H2S响应恢复快。     

Preparation and characterization of multifunctional polypyrrole–Au coated NiO nanocomposites and study of their electrocatalysis toward several important bio-thiols

Polypyrrole (PPy) and Au were co-deposited onto the surface of NiO nanoparticles to prepare multifunctional nanocomposites for electroanalysis applications. It is proposed that each component in NiO/PPy–Au nanocomposites plays a great role on their electrocatalytical performance where conductive PPy helps to immobilize the nanocomposites onto the electrode surface due to its outstanding adherence ability, NiO does to mediate the oxidation of thiols through the redox couple of Ni(OH)₂/NiOOH, and Au does to the electron transfer of nanocomposites and the redox transformation between Ni(OH)₂ and NiOOH due to its high conductivity. The obtained NiO/PPy–Au nanocomposites were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, UV–vis spectroscopy and powder X-ray diffraction. The obtained NiO/PPy–Au nanocomposites could be easily immobilized onto the surface of glassy carbon electrodes. They exhibit excellent electrochemical property for the redox couple Ni(OH)₂/NiOOH and high electrocatalytical oxidation toward some typical and important biological thiols such as cysteine, homocysteine and glutathione. Cysteine could be selectively detected at the applied potential of 0.15 V where the interfering of homocysteine and glutathione is somewhat low. The NiO/PPy–Au nanocomposite modified electrode also shows high electrochemical response to the produced thiocholine from the hydrolysis reaction of acetylcholinesterase.     

Facile synthesis of hierarchical SnO2 semiconductor microspheres for gas sensor application

Hierarchical SnO₂ microspheres were synthesized by a hydrothermal method at 140 °C using stannic chloride hydrate and sodium hydroxide as starting materials. The individual hierarchical SnO₂ microsphere ranged from 700 to 900 nm in diameter. After these microspheres were heated at 600 °C for 2 h, the spheres were cross-linked into clusters by short SnO₂ nanorods as revealed by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Most importantly, SnO₂ hierarchical microsphere sensor exhibits excellent selectivity and fast response to ethanol. Response and recovery times were 0.6 s and 11 s when the sensor was exposed to 50 ppm ethanol at an operating temperature of 300 °C. Thus, hierarchical structures play a significant role in the field of gas sensing.     

NiO电极中YSZ添加量对NOx传感器气敏性能的影响

以钇稳氧化锆(简称YSZ,Yttria-Stabilized Zirco nia)为固体电解质,添加不同摩尔比例YSZ的NiO+YSZ混合体为敏感电极材料,通过丝网印刷技术制备了相应的混合电势型NOx传感器.采用XRD和SEM手段对NiO混合物进行了物理性能分析,利用电势和阻抗测量设备对传感器样品的输出电势(EMF)和交流阻抗等电学参数随NO浓度的变化进行了研究.结果显示:NiO+YSZ的混合体中,物相独立,没有新相产生;在相同NO检测环境下,敏感电极中YSZ所占摩尔比例为20mol%时传感器的响应电势最大且在0.O1 Hz～100 kHz范围内的阻抗谱最小,SEM也显示此时具有很好的TPB.     

Electrochemical behavior of graphene doped carbon paste electrode and its application for sensitive determination of ascorbic acid

In present paper, the graphene doped carbon paste electrode (CPE) was firstly prepared with the addition of graphene into the carbon paste mixture. Compared with conventional CPE, an improved electrochemical response of graphene doped CPE toward the redox couple of Fe(CN)₆^3−/4− was demonstrated owing to the excellent electrical conductivity of graphene. The graphene doped CPE was further used for the successful determination of ascorbic acid (AA), and it showed an excellent electrocatalytic oxidation activity toward AA with a lower overvoltage, pronounced current response, and good sensitivity. Under the optimized experimental conditions, the proposed electrochemical AA sensor exhibited a rapid response to AA within 5 s and a linear calibration plot ranged from 1.0 × 10⁻⁷ to 1.06 × 10⁻⁴ M was obtained with a detection limit of 7.0 × 10⁻⁸ M.     

NiO敏感电极NH3传感器制备及其响应性能

以NiO为敏感电极材料,钇稳定氧化锆(YSZ)陶瓷片为电解质材料,采用丝网印刷技术制备了片式混合电势型NH3传感器,对传感器在不同NH3浓度和不同工作温度下响应性能进行了研究.结果显示:在工作温度为550℃时,传感器对NH3的响应值最大,达到-57 mV.制备的传感器在550℃时,对(50～600)×10-6 NH3具有良好的响应性能,响应信号与NH3浓度的对数呈现出良好的线性关系.在550℃高温时,传感器表现较好的重复性,但其交叉敏感性有待提高.为阐述传感器的敏感机理,进行了交流阻抗测试研究.     

Improving the performance of the BioHEL learning classifier system

The identification of significant attributes is of major importance to the performance of a variety of Learning Classifier Systems including the newly-emerged Bioinformatics-oriented Hierarchical Evolutionary Learning (BioHEL) algorithm. However, the BioHEL fails to deliver on a set of synthetic datasets which are the checkerboard data mixed with Gaussian noises due to the fact the significant attributes were not successfully recognised. To address this issue, a univariate Estimation of Distribution Algorithm (EDA) technique is introduced to BioHEL which primarily builds a probabilistic model upon the outcome of the generalization and specialization operations. The probabilistic model which estimates the significance of each attribute provides guidance for the exploration of the problem space. Experiment evaluations showed that the proposed BioHEL systems achieved comparable performance to the conventional one on a number of real-world small-scale datasets. Research efforts were also made on finding the optimal parameter for the traditional and proposed BioHEL systems.     

Safe-by-design planner–tracker synthesis with a hierarchy of system models

We present a safe-by-design trajectory planning and tracking framework for nonlinear dynamical systems using a hierarchy of system models. The planning layer uses a low-fidelity model to plan a feasible trajectory satisfying the planning constraints, and the tracking layer utilizes the high-fidelity model to design a controller that restricts the error states between the low- and high-fidelity models to a bounded set. The simplicity of the low-fidelity model enables the planning to be performed online (e.g. using Model Predictive Control) and the tracking controller and error bound are derived offline (e.g. using sum-of-squares programming). This error bound is then used by the planner to ensure safety for the combined planner–tracker system To provide freedom in the choice of the low-fidelity model, we allow the tracking error to depend on both the states and inputs of the planner. The goal of this article is to provide a tutorial review of this hierarchical framework and to illustrate it with examples, including a design for vehicle obstacle avoidance.     

Modeling, analyzing, and synthesizing expressive piano performance with graphical models

Trained musicians intuitively produce expressive variations that add to their audience’s enjoyment. However, there is little quantitative information about the kinds of strategies used in different musical contexts. Since the literal synthesis of notes from a score is bland and unappealing, there is an opportunity for learning systems that can automatically produce compelling expressive variations. The ESP (Expressive Synthetic Performance) system generates expressive renditions using hierarchical hidden Markov models trained on the stylistic variations employed by human performers. Furthermore, the generative models learned by the ESP system provide insight into a number of musicological issues related to expressive performance. Editor: Gerhard Widmer     

Effects of cognitive and social factors on system utilization and performance outcomes

This study examines the effects of cognitive and social factors on system utilization and performance outcomes. The literature has paid considerable attention to social influence as a determinant of individual behavior. We combine the concept of task-technology fit with concepts from adaptive structuration theory to elucidate social influence. In our model, we propose that support from a proper social construction in addition to task-technology fit leads in performance improvement in individuals. Empirical data from 317 individuals across 43 teams in ten companies are used to assess the theoretical model. Our theoretical model is supported by the data.     

数据集的粒化树及其建模应用

通过对数据集的不同划分,得到了基于数据集的粒化树。结合关联元素的信息,建立了基于不同数据集粒化树之间的关联关系,确定了两种粒化树中的两条关联链,促成了它们经关联元素的相互联系。由于每一关联链中的粒从粗到细逐步变化,使得关联元素与粒度的逐步细化密切相关,这是粒计算数据处理模式的体现。相关的结论为人才供求问题的算法描述提供了数学模型,并通过实例予以展示。     

Deformed nanostructure of photo‐induced biaxial cholesteric films and their application in VA‐mode LCDs

Abstract— Novel biaxial retardation films made from photo‐induced deformed cholesteric liquid‐crystal (LC) nanostructures using reactive mesogen mixtures (RMMs) for a viewing‐angle compensation of vertically aligned liquid‐crystal displays (VA‐LCDs) was developed. The deformed cholesteric LC nanostructure has been observed by X‐ray‐diffraction (XRD) measurement. The birefringence of the film was described well by our optical model based on a form birefringence theory. The VA‐LCDs with photo‐induced biaxial cholesteric films have excellent viewing‐angle properties.     

Flow injection analysis of ascorbic acid based on its thermoelectrochemistry at disposable screen-printed carbon electrodes

The thermoelectrochemistry of ascorbic acid (AA) at a disposable screen-printed carbon electrode (SPE) was studied in this paper. The response of AA is greatly suppressed at higher temperatures when the electrolyte solution containing AA is directly heated. On the other hand, as a light beam is applied to heat an SPE, it is interesting that the heated electrode is capable of increasing the detection sensitivity without decomposing the substrates. It is further applied for flow injection analysis (FIA) of AA by using a specifically designed electrochemical cell coupled with the disposable SPE. Possible reason for the enhancement in oxidation peak intensity at elevated temperature by the proposed heated electrodes operating in a non-isothermal mode is examined through in situ impedance technique as well as diffusion coefficient measurement by cyclic voltammetry. The slope of calibration plot obtained at elevated temperature (46 °C) is 0.034 μA/μM, which is 1.5 times improved than that at room temperature. Applicability in real sample shows in good agreement with the quoted value as well as the results observed by other methods.     

Palladium nanoclusters-coated polyfuran as a novel sensor for catecholamine neurotransmitters and paracetamol

A promising electrochemical biosensor was developed by electrodeposition of palladium nanoclusters on polyfuran film modified platinum electrode. This biosensor electrode was used to determine some catecholamines, namely dopamine, epinephrine and norepinephrine, ascorbic acid and paracetamol. The method of formation of the polymer film and deposition of Pd particles plays a key role in the electroactivity of the resulting hybrid material. This sensor effectively resolved the overlapping anodic peaks of ascorbic acid (AA), dopamine (DA) and paracetamol (ACOP) into three well-defined voltammetric peaks in differential pulse voltammetry analysis. The detection limit of DA in the absence and presence of AA and ACOP are eventually the same which indicates that the oxidation processes of DA, AA and ACOP are independent and that the simultaneous measurements of the three analytes are possible without interference. The electrodeposition of Pd on polyfuran improved exceptionally the detection limit about four decades. Moreover, diffusion coefficient measurements confirmed the fast electron transfer kinetics of the electrochemical oxidation of the analyte molecules at the sensor/solution interface. It is very interesting to note that the electrocatalytic effect of PF/Pd composite has been increased to be sometimes 21 times that of the pristine PF which has been considered for a long time to be of low conductivity and attracted low attention as a result of the difficulty of its formation and poor conductivity.     

Facile synthesis and characterization of rhodamine-based colorimetric and “off-on” fluorescent chemosensor for Fe

A fluorescent chemosensor for Fe³⁺, rhodamine-aminobenzothiazole conjugate has been synthesized and characterized by ¹H NMR, ¹³C NMR and X-ray crystallography. The sensor demonstrates strong Fe³⁺- selective orange fluorescence and a pink color switch. Furthermore, the recognizing behavior has been investigated both experimentally and computationally.     

Evaluating the impact of locality on the performance of large-scale SCI multiprocessors

Hierarchical ring-based multiprocessor systems are attractive and enjoy several advantages over other type of systems. They ensure unique paths between nodes, simple node interfaces and simple cross-ring connections. Furthermore, employing point-to-point links allows the system to run at high clock rate which increases bandwidth and decreases latency. This paper investigates the performance of hierarchical ring-based shared-memory multiprocessors. Rings in the hierarchy are composed of point-to-point, unidirectional links and apply the Scalable Coherent Interface (SCI) protocol. We pay special emphasis on the impact of locality on processor and interconnection design issues such as number of outstanding requests, and ring topology. We find that in order to exploit the power of hierarchical multiprocessors an accurate and appropriate model of locality must be used. Hierarchical multiprocessors that are well balanced (uniform) tend to provide lower latency and higher system throughput. For non-uniform systems, high degree of locality is required for the hierarchies to perform well. However, restricting the number of outstanding transactions per processor is important in decreasing packets latency and avoiding network contention.     

Too much face and not enough books: The relationship between multiple indices of Facebook use and academic performance

Because of the social media platform’s widespread adoption by college students, there is a great deal of interest in how Facebook use is related to academic performance. A small number of prior studies have examined the relationship between Facebook use and college grade point average (GPA); however, these studies have been limited by their measures, sampling designs and failure to include prior academic ability as a control variable. For instance, previous studies used non-continuous measures of time spent on Facebook and self-reported GPA. This paper fills a gap in the literature by using a large sample (N = 1839) of college students to examine the relationship among multiple measures of frequency of Facebook use, participation in Facebook activities, and time spent preparing for class and actual overall GPA. Hierarchical (blocked) linear regression analyses revealed that time spent on Facebook was strongly and significantly negatively related to overall GPA, while only weakly related to time spent preparing for class. Furthermore, using Facebook for collecting and sharing information was positively predictive of the outcome variables while using Facebook for socializing was negatively predictive.