Evidence for changing of cosmic ray composition between 10(17) and 10(18) eV from multicomponent measurements

The average mass composition of cosmic rays with primary energies between 10(17) and 10(18) eV has been studied using a hybrid detector consisting of the High Resolution Fly's Eye (HiRes) prototype and the MIA muon array. Measurements have been made of the change in the depth of shower maximum and the muon density as a function of energy. The results show that the composition is changing from a heavy to lighter mix as the energy increases.     

物理教学中让学生学会提出问题

分析了当前学生缺乏提出问题能力的原因，从教师的教学实际出发，借鉴成功教育的理念，通过培养学生在探究学习中敢问、能问，直到学生会问，逐步提高学生的学习、探究和创新的能力．     

2×n阶网络侧端等效电阻的另一种公式

再次研究了2×n阶梯形网络的侧端等效电阻,通过网络分析构建差分方程模型,给出了2×n阶梯形网络侧端等效电阻的另外一个普适规律,并通过具体的特例进行了比较与验证.     

纳米材料用于吸收电磁波的物理机制

本文从物理学的角度分析吸波材料与电磁波作用的影响因素和纳米材料在吸波应用上的微观机制，随着纳米材料和纳米科技的深入发展，纳米吸波材料将以更优异的性能广泛应用于军事装备和民用电磁波防护上．     

Structural,magnetic and electrical properties of Co1−xZnxFe2O4 synthesized by co-precipitation method

Nanoparticles of Co_1−xZn_xFe₂O₄ with stoichiometric proportion (x) varying from 0.0 to 0.6 were prepared by the chemical co-precipitation method. The samples were sintered at 600 °C for 2 h and were characterized by X-ray diffraction (XRD), low field AC magnetic susceptibility, DC electrical resistivity and dielectric constant measurements. From the analysis of XRD patterns, the nanocrystalline ferrite had been obtained at pH=12.5–13 and reaction time of 45 min. The particle size was calculated from the most intense peak (3 1 1) using the Scherrer formula. The size of precipitated particles lies within the range 12–16 nm, obtained at reaction temperature of 70 °C. The Curie temperature was obtained from AC magnetic susceptibility measurements in the range 77–850 K. It is observed that Curie temperature decreases with the increase of Zn concentration. DC electrical resistivity measurements were carried out by two-probe method from 370 to 580 K. Temperature-dependent DC electrical resistivity decreases with increase in temperature ensuring the semiconductor nature of the samples. DC electrical resistivity results are discussed in terms of polaron hopping model. Activation energy calculated from the DC electrical resistivity versus temperature for all the samples ranges from 0.658 to 0.849 eV. The drift mobility increases by increasing temperature due to decrease in DC electrical resisitivity. The dielectric constants are studied as a function of frequency in the range 100 Hz–1 MHz at room temperature. The dielectric constant decreases with increasing frequency for all the samples and follow the Maxwell–Wagner's interfacial polarization.     

Adaptive synchronization and lag synchronization of uncertain dynamical system with time delay based on parameter identification

In this paper, the adaptive synchronization and lag synchronization are considered for uncertain dynamical system with time delay based on parameter identification and a novel control method is then further given using the Lyapunov functional method. With this new and effective method, parameter identification and lag synchronization can be achieved simultaneously. Simulation results are given to justify the theoretical analysis in this paper.     

Use of elemental size distributions in identifying particle formation modes

The chemical composition of particles generated during pulverized coal combustion is the consequence of their formation processes. This work aims to use the size resolved elemental composition of coal-derived particles to identify their formation modes. A size-classified bituminous coal is burnt in a laboratory drop tube furnace at 1150, 1250, and 1350 °C, respectively. The elemental composition of the size-segregated particles from coal combustion is analyzed and the total mass fraction size distributions of Si and Al are obtained. Three particle formation modes are observed in these distribution profiles. The coarse mode has the highest value of the total mass fraction of Si and Al while the ultrafine mode has the lowest one. The total mass fraction of Si and Al in these two modes is nearly independent of particle size. It is believed that the coarse mode is formed by the mineral coalescence mechanism and the ultrafine mode by the vaporization–condensation mechanism. The difference in the total mass fraction of Si and Al between the central mode and the other two indicates that the central mode is formed by different mechanisms. Based on the observation that the total mass fraction of Si and Al in this mode increases with increasing particle size, heterogeneous condensation of vaporized species on existing fine residual ash particles is proposed to account for the formation of these particles. The study of the elemental composition of the three modes represented in five categories verifies the proposed formation mechanisms for them to some extent.     

Efficient polymer white-light-emitting diodes with a single-emission layer of fluorescent polymer blend

Efficient polymer white-light-emitting diodes (WPLEDs) have been fabricated with a single layer of fluorescent polymer blend. The device structure consists of ITO/PEDOT/PVK/emissive layer/Ba/Al. The emissive layer is a blend of poly(9,9-dioctylfluorene) (PFO), phenyl-substituted PPV derivative (P-PPV) and a copolymer of 9,9-dioctylfluorene and 4,7-di(4-hexylthien-2-yl)-2,1,3-benzothiadiazole (PFO-DHTBT), which, respectively, emits blue, green and red light. The emission of pure and efficient white light was implemented by tuning the blend weight ratio of PFO: P-PPV: PFO-DHTBT to 96:4:0.4. The maximum current efficiency and luminance are, respectively, 7.6 cd/A at 6.7 V and 11930 cd/m² at 11.2 V. The CIE coordinates of white-light emission were stable with the drive voltages.     

Improvement of a low pH antigen-antibody dissociation procedure for ELISA measurement of circulating anti-Aβ antibodies

Background  

Prior work from our group found that acid dissociation (pH 2.5 incubation) of serum from APP transgenic mice vaccinated against Aβ increased the apparent anti-Aβ titers, suggesting antibody masking by antigen in the ELISA assay. Subsequently, we found that pH 2.5 incubation of serum from unvaccinated non-transgenic mice showed antibody binding to Aβ1–42, but no increase when other proteins, including shorter Aβ peptides, coated the ELISA plate. To investigate further the effects of low pH incubation on apparent anti-Aβ1–42 signals, we examined normal sera from nonTg unvaccinated mice, nonTg mice vaccinated with Aβ peptide (to produce authentic anti-Aβ antibodies) or a monoclonal antibody against Aβ (6E10) using competitive-inhibition ELISA and Aβ epitope mapping assays. In addition, we examined use of a less stringent low pH procedure at pH 3.5, to ascertain if it had the same effects as the pH 2.5 procedure.