An amperometric ethanol sensor based on foam nickel electrode

An amperometric sensor using foam nickel electrode as the working electrode for the measurement of ethanol in alkaline solution has been developed. Cyclic voltammetry and chronoamperometry are employed to analyze electrochemical behavior of the electrode. The results show that the oxidation of ethanol is more efficient on the foam nickel electrode than that on the nickel foil electrode. The sensor exhibits a good linear relationship between response current and ethanol concentration in the range of 4 to 1400 ppm with a detection limit of 0.8 ppm. The sensitivity and the response time of the sensor are 4.63 μA/ppm and 10 s respectively. Additionally, the sensor has 60 days shelf-life time at least.     

Bondi-Sachs metrics and photon rockets

We study the Bondi-Sachs rockets with nonzero cosmological constant. We observe that the acceleration of the systems arises naturally in the asymptotic symmetries of (anti-) de Sitter spacetimes. Assuming the validity of the concepts of energy and mass previously introduced in asymptotically flat spacetimes, we find that the emission of pure radiation energy balances the loss of the Bondi mass in certain special families of the Bondi-Sachs rockets, so in these there is no gravitational radiation.     

Loading of cold ~(87)Rb atom with diffuse light in an integrating sphere

<正>Cold ~(87)Rb atom's loading in an integrating sphere with diffuse light is analyzed theoretically and experimentally. The experimental results show that diffuse light cooling has the greatest efficiency to cool the most atoms when the red detuning between the frequencies of cooling light and atom transition is about 3.3r(Γis the natural linewidth,6.065 MHz).Theoretical analysis using rate equation and numerical calculations on the cold atom number and loading time agree with the experimental results.This integrating sphere cooling would be a novel method for cooling atoms and lead to a new and robust cold atom source for atomic clock.     

Role of Hydrocarbon Radicals CHx (x=1, 2, 3) in Graphene Growth: A Theoretical Perspective

Many outstanding properties of graphene are blocked by the existence of structural defects. Herein, we propose an important healing mechanism for the growth of graphene, which is produced via plasma‐enhanced chemical vapor decomposition (PECVD), that is, the healing of graphene with single vacancies by decomposed CH₄ (hydrocarbon radical CH_x, x=1, 2, 3). The healing processes undergo three evolutionary steps: 1) the chemisorption of the hydrocarbon radicals, 2) the incorporation of the C atom of the hydrocarbon radicals into the defective graphene, accompanied by the adsorption of the leaving H atom on the graphene surface, 3) the removal of the adsorbed H atom and H₂ molecule to generate the perfect graphene. The overall healing processes are barrierless, with a huge released heat of 530.79, 290.67, and 159.04 kcal mol^?1, respectively, indicative of the easy healing of graphene with single vacancies by hydrocarbon radicals. Therefore, the good performance of the PECVD method for the generation of graphene might be ascribed to the dual role of the CH_x (x=1, 2, 3) species, acting both as carbon source and as defect healer.     

Src kinase up-regulates the ERK cascade through inactivation of protein phosphatase 2A following cerebral ischemia

Background  

The regulation of protein phosphorylation requires a balance in the activity of protein kinases and protein phosphatases. Our previous data indicates that Src can increase ERK activity through Raf kinase in response to ischemic stimuli. This study examined the molecular mechanisms by which Src activates ERK cascade through protein phosphatases following cerebral ischemia.     

Characterization of coal oil using three-dimensional excitation and emission matrix fluorescence spectroscopy

Three-dimensional （3D） excitation-emission matrix （EEM） fluorescence spectroscopy is applied to characterize the coal oil. The results show that the 3D fluorescence spectra of coal oil in aqueous solution mainly have one broad peak. This peak is identified at the excitation/emission wavelengths of 270/290 nm. The relation between the fluorescence intensity and the concentration of coal oil is also studied. When the concentration lies between 2 - 2000 ppm, the relation between the fluorescence intensity and the concentration of coal oil is well linear. The nature of solvents significantly affects the EEM fluorescence of coal oil.     

A diamine ligand with long “arms” and its corresponding dinuclear rhenium(I) complex: Synthesis,characterization, photophysical property,and sensing activity towards molecular oxygen

In this paper, we synthesize a novel diamine ligand of 4,7-dinonadecyl-1,10-phenanthroline (DN-Phen) with two long alkyl chain arms serving as a shield and its corresponding dinuclear Re(I) complex of Re₂(CO)₆(bpy)(DN-Phen)₂ (bpy=4,4′-bipyridine), aiming at an optical sensor immune to the surrounding interferences. Its geometric and electronic structures are investigated, which suggest that the introduced long alkyl chains act as a shield for the excited state of emissive center. The promising photophysical parameters of Re₂(CO)₆(bpy)(DN-Phen)₂, including the immunity of emission towards the surrounding interferences and long excited state lifetime, make itself a potential probe for oxygen detection. By doping Re₂(CO)₆(bpy)(DN-Phen)₂ into two silica matrixes of MCM-41 and SBA-15, oxygen sensing performances of the resulted composite materials are investigated. Finally, a high sensitivity of 20.1 is realized, with short response/recovery time of 8 s/42 s. Here, sensitivity is defined as the ratio of emission maximum under pure nitrogen to emission minimum under pure oxygen, response and recovery times are the times for a sample to lose (response time) or recover (recovery time) 95% of its emission maximum upon periodically changed atmosphere.     

Electromagnetically induced phase grating controlled by spontaneous emission

Electromagnetically induced phase grating controlled by spontaneous emission is studied. The results show that the diffraction efficiency of phase grating is strikingly enhanced due to the existence of spontaneously generated coherence (SGC), and the diffraction efficiency of 35% can be obtained in optimal SGC parameter case. Furthermore, at large SGC parameter, the high efficiency of phase grating can be maintained by the application of weak coupled and relatively strong probe fields, and choosing the proper length of atomic sample. At the same time, in such an atomic system, the SGC effect depends on incoherent pump.     

Microwave Magnetic Properties and Natural Resonance of e-Co Nanoparticles

Owing to the novel crystal structure, ε-Co nanoparticles with an average diameter of 12 nm are synthesized and the microwave magnetic properties of the epoxy resin composite with 50voi% ε-Co particles are measured in the frequency range 0.1-7 GHz. The experimental resonance frequency （4.7 GHz） matches well with the values obtained by the theoretical calculation with the Kittel equation and fitting the experimental permeability dispersion curve via the Landan-Lifshitz equation. Hence the resonance peak is attributed to natural resonance mode. This work is believed to be beneficial for further understanding microwave applications of the novel ε-Co nanoparticles.     

关于罗尔定理的进一步讨论

对罗尔定理进行深入系统的探讨和研究.给出在更弱条件下的各种区间类型(包括有限区间和无限区间)的罗尔定理的推广形式.