利用X射线衍射研究冲击波合成纤锌矿型氮化硼

 用X射线衍射法，对不同结晶度的石墨型氮化硼（gBN）在冲击波作用下转变成的纤锌矿型氮化硼（wBN）产物进行了研究，对wBN中的杂质含量等进行了分析。结果表明：gBN的石墨化指数G.I值对wBN的产率有明显的影响。     

Electroweak tests with τ leptons at LEP

We report on two sensitive tests of lepton universality carried out by the 4 LEP experiments at the Z⁰ pole. From measurements of the τ polarization in e⁺ e^?→τ ⁺ τ ^?, the ratios of the vector and axial vector coupling constants of the electron and the tau lepton to the weak neutral current are obtained to beg _{v e} /g _{a e} =0.066±0.015 andg _{V τ} /g _{A τ} =0.070±0.009 respectively. From measurement of the τ lifetime and the τ leptonic branching ratios, the ratio of the coupling constants describing weak leptonic decays of the τ and the μ is measured to beG _τ /G _μ =0.996±0.008.     

Standard<Emphasis Type="Italic">SU</Emphasis>(5) supergravity grand unification model and predictions

A review is given of the StandardSU(5) supergravity model. This model has passed an important check regarding unification of the electro-weak and the strong couplings using high precision LEP data. It is shown that for a significant domain of the parameter space the model also satisfies constraints on the SUSY spectrum from CDF and LEP, as well as proton stability and cosmological relic density constraints.     

催化光度法测定痕量铁

基于铁对过氧化氢氧化对-氨基二甲基苯胺盐酸盐的催化活性,建立了测定痕量的新方法。灵敏度为1.6×10-11g/mL,测定范围为0～0.50μg Fe/50mL,用于测定几种实物样品中的痕量铁,相对标准偏差0.65～2.6%.     

Growth of suppression in humans based on distortion-product otoacoustic emission measurements

Distortion-product otoacoustic emissions (DPOAEs) were used to describe suppression growth in normal-hearing humans. Data were collected at eight f(2) frequencies ranging from 0.5 to 8 kHz for L(2) levels ranging from 10 to 60 dB sensation level. For each f(2) and L(2) combination, suppression was measured for nine or eleven suppressor frequencies (f(3)) whose levels varied from -20 to 85 dB sound pressure level (SPL). Suppression grew nearly linearly when f(3) ≈ f(2), grew more rapidly for f(3)?< f(2), and grew more slowly for f(3)?> f(2). These results are consistent with physiological and mechanical data from lower animals, as well as previous DPOAE data from humans, although no previous DPOAE study has described suppression growth for as wide a range of frequencies and levels. These trends were evident for all f(2) and L(2) combinations; however, some exceptions were noted. Specifically, suppression growth rate was less steep as a function of f(3) for f(2) frequencies ≤ 1 kHz. Thus, despite the qualitative similarities across frequency, there were quantitative differences related to f(2), suggesting that there may be subtle differences in suppression for frequencies above 1 kHz compared to frequencies below 1 kHz.     

Simulation of island aggregation influenced by substrate temperature, incidence kinetic energy and intensity in pulsed laser deposition

Using kinetic Monte Carlo method, we have simulated a pulsed energetic growth process in pulsed laser deposition. During the growth of film, substrate temperature mainly influences upon film morphology by directly enhancing the adatom mobility through the temperature-dependent thermal vibration. By contrast, the effect of incidence kinetic energy on film growth is complex resulting from the collisions between the incident particles and the adatoms. The results show that improving incident kinetic energy cannot significantly accelerate the migration rate of adatom but change surface microstructure and promote single adatom formation resulting in more island aggregation density. Moreover, since pulse-influx characterizes pulsed laser deposition, the intensity per pulse contributes to the evolvement of nucleation density and the results illustrate that a general scaling law different from ordinary power law still exists in energetic growth of pulsed laser deposition.     

Physics with large extra dimensions

The recent understanding of string theory opens the possibility that the string scale can be as low as a few TeV. The apparent weakness of gravitational interactions can then be accounted by the existence of large internal dimensions, in the sub-millimeter region. Furthermore, our world must be confined to live on a brane transverse to these large dimensions, with which it interacts only gravitationally. In my lecture, I describe briefly this scenario which gives a new theoretical framework for solving the gauge hierarchy problem and the unification of all interactions. I also discuss a minimal embedding of the standard model, gauge coupling unification and proton stability. On leave from: Centre de Physique Théorique, Ecole Polytechnique, 91128 Palaiseau, Cedex, France.     

Simulation and design of a bandpass filter on metasubstrates

This work presents an analysis of the microstrip bandpass filter on metamaterial substrates. The filter is composed of two ring resonators with quarter-wavelength side-coupled sections. The filter input is provided, as well as the output port, using a quarter-wavelength side-coupled microstrip line section. Simulations by finite element method have been carried out to verify the effect of the metamaterial substrate properties on the filter performance, and to compare these results to those obtained considering isotropic substrate.