Magnetic silica colloids for catalysis

Monodisperse magnetizable colloidal silica particles in a stable dispersion have been functionalized with a homogeneous catalyst: a PCP–pincer Pd-complex. In a proof-of-principle experiment we demonstrate the catalytic activity of the colloids in a C–C bond formation reaction. Advantages of the magnetic silica carriers are the large surface-to-volume ratio and the easy recovery by magnetic separation. After magnetic separation, the catalyst-loaded particles are readily redispersed for further use.     

X-ray fluorescence intensity distribution in circular specimens

Summary The relative X-ray fluorescence (XRF) intensities for annular source and various annular specimen are measured with a Ge-Li detection system and calculated by the Monte Carlo numerical techniques (MCNT).Kα X-ray intensities of annular specimens with different radii prepared from a pure-molybdenum foil are measured and it is seen that the measured values are in good agreement with the values calculated by MCNT. The variation of the fluorescence intensity due to the collimator radius is also studied. The differences between the MCNT and experimental results are discussed in terms of the possible sources of errors.     

BNL/AGS10.7A GeV金核诱发作用中核碎裂与粒子产生

研究了在美国BNL/AGS上能量10.7AGeV的¹⁹⁷Au离子诱发核作用,报告了EMU–01国际合作实验关于射弹核碎裂和产生粒子密度等最新实验结果.     

Recent results from large electron positron collider

We summarize here the recent results from the four experiments at the large electron positron collider (LEP). These experiments provide precise measurements of theW and Z boson properties and their couplings to leptons and quarks. These measurements, together with measurements of the top quark andW boson masses in the Tevatron collider provide a stringent test of the standard electroweak theory. Searches for Higgs boson and supersymmetric particles have yielded null results so far giving rise to lower bounds in the parameter space.     

Annealing effects on the magnetization of Co–Ni–B amorphous nanoparticles

Chemically prepared (Co_xNi_1−x)_1−yB_y (x=0.5, 0.75, 1; y≈0.4) amorphous fine particles were characterized by X-ray diffraction, DTA and TGA, and in situ magnetic measurement as a function of annealing temperature in an inert atmosphere. Magnetic measurement performed in as-prepared and 150°C annealed samples shows an increase of the saturation magnetization and magnetic moment after thermal treatment. Room temperature magnetization increases by factors of 3.5, 1.8, and 1.5, for x=0.5, 0.75, and 1, respectively. These measurements may indicate a local re-ordering of the amorphous phase at temperatures much lower than the full crystallization temperature.     

Nd掺杂的Bi4Ti3O12变温X射线衍射分析

利用变温X射线衍射技术，在预烧过程中分析了Nd掺杂Bi4Ti3O12后生成Bi3.15Nd0.85Ti3O12（BNT）相的形成过程以及微结构的变化．实验观察到以30℃／min的升温速率，BNT相在700℃时开始形成，其衍射峰强度随温度的继续升高而增强，衍射峰半高宽随烧结时间延长而减小．X射线衍射分析结果表明，在900℃恒温条件下，烧结约2h，可形成单一的BNT相．     

Photon interaction studies using 241Am γ-rays

We have carried out some photon interaction measurements using 59.54 keV γ-rays from a ²⁴¹Am source. These include γ attenuation studies as well as photoelectric absorption studies in various samples. The attenuation studies have been made using leaf and wood samples, samples like sand, sugar etc., which contain particles of varying sizes as well as pellets and aqueous solutions of rare earth compounds. In the case of the leaf and wood samples, we have used the γ-ray attenuation technique for the determination of the water content in fresh and dried samples. The variation of the attenuation coefficient with particle size has been investigated for sand and sugar samples. The attenuation studies as well as the photoelectric studies in the case of rare earth elements have been carried out on samples containing such elements whose K-absorption edge energies lie below and close to the γ-energy used. Suitable compounds of the rare earth elements have been chosen as mixture absorbers in these investigations. A narrow beam good geometry set-up was used for the attenuation measurements. A well-shielded scattering geometry was used for the photoelectric measurements. The mixture rule was invoked to extract the values of the mass attenuation coefficients for the elements from those of the corresponding compounds. The results are consistent with theoretical values derived from the XCOM package.     

A complementary thermodynamic limit for classical Coulomb matter

The canonical equilibrium measure of classical two-component Coulomb matter with regularized interactions is analyzed in a finite volume. It is shown that, in the mean-field regime, the one-particle density is inhomogeneous on a new characteristic length scale _inh. For a system ofN positive andN negative particles, _inh and the characteristic length scale of correlations _corr (=Debye screening length) are related via _inh=(2N)^1/2 _corr. The major conceptual conclusion that is drawn from this is that one needs two nontrivial complementary thermodynamic limits to define the equilibrium thermodynamics of two-component Coulomb systems. One of them is the standard thermodynamic limit (infinite volume), where one takesN, _corr fixed. Its complementary limit is characterized byN, _inh fixed, and is a finite-volume inhomogeneous mean-field limit. The most prominent new feature in the mean-field thermodynamic limit, which is absent in the standard thermodynamic limit, is an anomalous first-order phase transition where the Coulomb system explodes or implodes, respectively. The phase transition is connected with the existence of a metastable plasma phase far below the ionization temperature.     

ZnO超微粒子光催化氧化降解n-C7H16的研究

利用ZnO光催化氧化技术对气相n-C7H16进行了降解研究，考察了氧气、水燕气体积分数等因素对n-C7H16光催化氧化的影响，利用气相色谱－质谱联用仪和气相色谱仪对气相光催化反应过程中的气体组成进行了定性分析，并对主要中间产物丙醛进行了定量分析，结果发现，ZnO超微粒子光催化氧化n-C7H16的降解率较高，n-C7H16绝大部分被完全氧化成CO2，探讨了n-C7H16光催化氧化反尖的动力学行为及机理。     

SARS CoV内对照RNA病毒样颗粒的构建和表达

在SARS-CoV的核酸检测方法中,由于普遍缺乏安全、稳定、特异的内对照,而不能对样品处理、反转录、扩增以及定量检测实施全程监控。构建的病毒样核蛋白颗粒内对照,能够对SARS-CoV临床检测实施监控。本文通过克隆1.7Kb大肠杆菌噬菌体MS2的装配蛋白和壳蛋白基因以及SARS冠状病毒经过突变产生的270bp内对照片断,并将这些基因连接到载体pTrc99a上表达,进行纯化、定量分析、RT-PCR检测和稳定性试验。获得SARS内对照病毒样核蛋白颗粒,在人血清和SM缓冲液中37℃稳定性可达到30天,能抵抗核糖核酸酶降解。将内对照颗粒加入临床样本中一同检测,能够对检测的全过程(样品处理、反转录和PCR)有效进行监控,与SARS-CoV没有交叉反应。研究表明制备的该病毒样核蛋白颗粒稳定、安全、可靠,可作为SARS冠状病毒RT-PCR检测、定量分析的有效内对照参考品。