Imprinting the nanostructures on the high refractive index semiconductor glass

The centimeter range one- and two-dimensional nanostructures of 70 nm pitch have been imprinted by hot pressing with a quartz, silicon or nickel mold, at 240 °C, onto the surface of Ge₂₀As₂₀Se₁₄Te₄₆ semiconductor glass. Excellent glass stability of this glass allows multiple re-pressing of the nano-structures. With increasing the Te/Se ratio in the glass formula, the refractive index reaches a value of 3.5 with an option of free electron absorption at elevated temperatures pointing out the use of such nanostructures in submicron and micron scale electronic devices/chips, moth eye structures and photonic crystals.     

Effects of Montmorillonite on the Nonisothermal Crystallization Behavior of the Poly(trimethylene terephthalate)/Polypropylene/Montmorillonite Nanocomposites

Organic montmorillonite (MMT) reinforced poly(trimethylene terephthalate) (PTT)/ polypropylene (PP) nanocomposites were prepared by melt blending. The effects of MMT on the nonisothermal crystallization of the matrix polymers were investigated using differential scanning colorimetry (DSC) and analyzed by the Avrami equation. The DSC results indicated that the effects of MMT on the crystallization processes of the two polymers exhibited great disparity. The PTT's crystallization was accelerated significantly by MMT no matter whether PTT was the continuous phase or not, but the thermal nucleation mode and three-dimensional growth mechanism remained unchanged. However, in the presence of MMT, the PP's crystallization was slightly retarded with PP as the dispersed phase, and was influenced little with PTT as the dispersed phase. When the MMT content was increased from 2_wt% to 7_wt%, the crystallization of the PTT phase was slightly accelerated, whereas the crystallization of the PP phase was severely retarded, especially at lower temperatures. Moreover, the nucleation mechanism for the PP's crystallization changed from a thermal mode to an athermal one. In the polypropylene-graft-maleic anhydride (PP-g-MAH) compatibilized PTT/PP blends, with the addition of 2_wt% MMT during melt blending, the T _c (PTT) shifted 7.8°C to lower temperature and had a broadened exotherm, whereas the T _c (PP) shifted 17.1°C to higher temperature, with a narrowed exotherm. TEM analysis confirmed that part of the PP-g-MAH was combined with MMT during blending.     

High-resolution recordings of the magnetic activity of the His-Bundle in man

Summary The activity of the His-Purkinje system (HPS) in man has been measured magnetically with a SQUID magnetometer in the Berlin magnetically shielded room (BMSR) by using in addition band pass filtering (band width 0.5 Hz to 300 Hz) and averaging. The BMSR reduces the background noise level to less than in the region of white noise. Within thePR interval a ramp pattern was observed, changing its slope when crossing the median line of the heart. In addition, definite signals were recorded approximately 40 ms before the onset of ventricular activation.

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Riassunto L'attività del sistema di His-Purkinje è stata misurata magneticamente usando un magnetometro SQUID nella camera schermata magneticamente di Berlino (BMSR) e usando in aggiunta filtraggio (banda passante da 0.5 Hz a 300 Hz) e tecniche di mediazione. La camera riduce il livello di rumore di fondo a meno di 4 nella regione a spettro bianco. All'interno dell'intervalloPR è stata osservata una struttura a rampa, la cui pendenza cambia segno attraversando la linea mediana del cuore. In aggiunta, sono stati registrati segnali ben definiti approssimativemente 40 ms prima dell'inizio dell'attivazione ventricolare.

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Резюме йзмеряется активность НР системы у человека с помощью SQUID магнетометра в Берлинской магнитно экранированной комнате, используя фильтртрацию полосы пропускания (ширина полосы от 0.5 Гц до 300 Гц) и усреднение. Берлинская магнитно экранированная комната уменьшает уровень фонового шума до величины в области белого шума. ВнутриPR интервла наблюдается диаграмма с уклоном, причем величина ыклона меняется при пересечении медианной линии сердца. Кроме того, ориблизительно за 40 мс до наступления активности желудочка регистрируются определенные сигналы.

     

On the influence of the volume conductor in magnetocardiography: an experimental approach

Summary To study the effect of the volume conductor geometry on the MCG, experiments using isolated rabbit hearts were done. An increase of the magnetic signal when increasing the volume conductor’s size was observed. The results are discussed by using a fixed-origin current dipole and a voltage source model for the heart. Work supported by Brazilian Agencies CNPq, CAPES and FINEP.     

Somatosensory evoked magnetic fields: Mappings and the influence of the stimulus repetition rate

Summary Somatosensory evoked magnetic fields were compared with corresponding electric scalp potentials in order to study their neural sources. Mappings of the magnetic responses showed activity at the primary and secondary somatosensory cortices. Additional sources besides these areas seem to be involved in the generation of the somatosensory vertex scalp potentials. Paper presented at the ?IV International Workshop on Biomagnetism?, held in Rome, September 14–16, 1982.     

CO分子在Co(0001)表面吸附的第一性原理研究

应用第一性原理对CO分子在Co(0001)表面( squar3× squar3)R30°−CO吸附结构进行不同形式的密度泛函计算研究. 结果表明：吸附能修正前,仅RPBE泛函预测CO顶位吸附;而修正后PW91、PBE和PKZB泛函结果也表明CO分子Top顶位吸附最稳定,与实验结果一致.对于吸附几何结构、吸附前后体系功函、C-O伸缩振动频率和CO分子态密度分布,所有泛函给出一致的结果,且与已有实验结果符合.     

光折变晶体钛酸秘的折射率和光学均匀性的测量

本文报导光折变晶体钛酸铋的折射率和光学均匀性的测量结果。     

无限方势阱本征态的稳定性

我们用存活率(SP)的概念研究了无限方势阱本征态的稳定性,做了理论上的推导,并进行了数值计算,发现基态在外界的扰动下非常稳定,而激发态则非常不稳定,能级越高,越不稳定.     

Atrial activity during thePR segment of the MCG

Summary Sloping signals were observed in thePR segment of normal magnetocardiograms recorded from five dogs. Larger ramps were observed after first-degree AV nodal blockade was induced pharmacologically, and complete atrial repolarization was observed following isolated atrial contractions in two animals with second-degree block. These ramps, ranging up to 6.7 pT in size and arising from the atria, may complicate magnetic detection of His-Purkinje activity. This work was supported by the National Institute of Health under Grant No. HL 23184.     

Optimization of the second-order gradiometer base length that has been designed for the measurement of weak inhomogeneous magnetic fields

Summary In this paper we deal with an optimization problem of the second-order superconducting gradiometric sensor systems that have been designed for measurement of the weak inhomogeneous magnetic fields in a magnetically disturbed environment. The conditions of maximum signalto-noise ratio of the output of superconducting quantum magnetometers (SQM) are considered. The influence of measured signal source parameters, of an outside disturbing source and of the own noise of the magnetometer on the gradiometer base length selection is analysed. Paper presented at the “IV International Workshop on Biomagnetism”, held in Rome, September 14–16, 1982     

The influence of inhomogeneities on the cardiac-magnetic-field distribution

Summary Numerical computations were performed on the magnetic field generated by the heart during ventricular depolarization. The purpose of this study was to investigate the contribution of inhomogeneities in the volume conductor to the total field and to establish the influence of gradiometers as used in experimental recordings. Paper presented at the ≪IV International Workshop on Biomagnetism≫, held in Rome, September 14–16, 1982.     

Analysis of the generalized Camassa and Holm equation with the improved element-free Galerkin method

In this paper, we analyze the generalized Camassa and Holm （CH） equation by the improved element-free Galerkin （IEFG） method. By employing the improved moving least-square （IMLS） approximation, we derive the formulas for the generalized CH equation with the IEFG method. A variational method is used to obtain the discrete equations, and the essential boundary conditions are enforced by the penalty method. Because there are fewer coefficients in the IMLS approximation than in the MLS approximation, and in the IEFG method, fewer nodes are selected in the entire domain than in the conventional EFG method, the IEFG method should result in a higher computing speed. The effectiveness of the IEFG method for the generalized CH equation is investigated by numerical examples in this paper.     

Slow magnetic fields of the brain preceding movement and speech

Summary Magnetic fields of the brain were recorded preceding selfinitiated finger, foot, toe movements, stimulus-triggered finger and toe movements, and speech. Slow magnetic-field shifts were found with morphology similar to coincident electrical potentials, but with very different distributions. Inferences from the data about localization of cerebral generators were discussed. These studies were supported by grants from the B.C. Research Council and N.S.E.R.C. of Canada.     

Active Q-switching of the Alexandrite laser

An alexandrite-laser rod was actively Q-switched in the transversal fundamental mode at λ = 758 nm with an double crystal KD^*P Pockels cell. Pulse width, pulse energy and optical pulse delay (the build-up time of the photon field in the resonator) were measured as functions of pumping energy, rod temperature and reflectivity of the output coupling mirror. As the laser gain of alexandrite strongly depends on temperature, the pulse width and pulse energy were also investigated as functions of the temperature of the active material. A comparison of experimental data with theory was made.     

Above the band gap structures in Ge nanoparticles: optical-absorption spectra

Summary We report absorption measurements on Ge nanoparticles in the range 0.6–6 eV. By reducing the dot average radius to about 13 ?, one observes a relevant blue-shift of theE ₁+Δ ₁ andE ₂ peaks and a change of the oscillator strength of the two main structures. Simulations using effective-medium theories have been carried out and the embedding matrix contribution to the measured properties has been evaluated. The different behaviour of the absorption peaksE ₁,E ₁+Δ ₁ andE ₂ under quantum confinement has been related to their specific nature within the whole Brillouin zone. The authors of this paper have agreed to not receive the proofs for correction.     

The transmission performance of the single sideband optical millimeter-wave with BPSK signal in the duplex radio-over-fiber link

This paper has investigated the transmission performance of the single sideband (SSB) optical millimeter (mm)-wave with signal carried by the sideband in BPSK format in duplex radio-over-fiber (RoF) system theoretically and numerically. The SSB optical mm-wave signal is generated by a LiNbO₃ Mach–Zehnder modulator and there exists an optimal modulation index to generate the SSB optical mm-wave with a maximal RF photocurrent. The SSB optical mm-wave is much suitable for the duplex ROF link with the uplink lightwave recovered from the downlink because the optical carrier carries no signal. In such a duplex RoF link, although there are the spurs on the optical carrier, they have little influence on the downlink and the uplink signal even if the modulation index is large.     

Determination of the angular and energy dependence of hard constituent scattering from π0 pair events at the CERN intersecting storage rings

We present data on proton-proton collisions, obtained at the CERN Intersecting Storage Rings, in which two roughly back-to-back π⁰'s of high transverse momentum (p_T) were produced. The angular distribution of the dipion axis relative to the collision axis is found to be independent of both the effective mass m of the dipion system and the centre-of-mass energy √s of the proton-proton collision. The cross-sections $\text{d}\text{σ}\text{d}\text{m}$ at the values of √s satisfy a scaling law of the form $\text{d}\text{σ}\text{d}\text{m}\text{=}\text{G(x)}\text{m}{}^{\mathrm{n}}\text{,}\text{where}\text{x = m(π}{}^0\text{, π}{}^0\text{)//trs}\text{and}\text{n = 6.5 ± 0.5}$. We show from our data that the leading π⁰ carries most of the momentum of the scattered parton. Given this fact, the axis of the dipion system follows closely the direction of the scattered constituents, and we exploit this to determine the angular dependence of the hard-scattering subprocess. We also compare our data with the lowest order QCD predictions using structure functions as determined in deep-inelastic scattering and fragmentation functions from electron-positron annihilation.     

四角晶相HfO2(001)表面原子和电子结构研究

采用基于第一性原理的密度泛函理论研究了四角晶相二氧化铪(t-HfO2)体相及其(001)表面的原子几何与电子结构.理论计算结果表明,t-HfO2(001)表面不会产生重构现象.与体相电子结构相比, t-HfO2(001)表面态密度明显高于体相态密度.其次,表面原子的态密度更靠近费米能级(EF),价带往低能量处移动,并有表面态产生.计算结果表明了t-HfO2表面禁带宽度明显低于体相的禁带宽度. t-HfO2(001)的表面态产生以及表面禁带宽度减小是由于Hf原子与O原子的配位数减少,表面原子周围的环境发生变化而引起的.     

ASE Noise-Reduced Optical Receiver Based on MZI Diversity Scheme

A novel method is proposed that reduces the bit error rate (BER) in an optically amplified system by using a Mach–Zender interferometer coherence manipulation at the receiver. Exact analysis is presented, which shows that the signal-to-noise ratio can be improved by 3 dB. Resulting BER improvements are presented.     

铜箔碳掺杂对化学气相沉积生长的六方氮化硼中含碳色心的高效制备及其调控

缺陷和掺杂对材料的力学、 电子和光学性能均具有重要影响. 六方氮化硼(Hexagonal Boron Nitride, hBN)由于具有a6 eV 的宽带隙, 其中的点缺陷可以在带隙内产生发射波长覆盖近紫外-近红外波段的室温稳定发光的深能级色心, 是量子光源等光学的理想载体. 近年来的实验和理论研究表明, 碳缺陷是h-BN 可见光波段单光子发射的主要可能来源之一; 然而, 当前对h-BN 中碳缺陷的有效制备和精确调控仍存在挑战. 本文报道了一种有效方法, 通过在化学气相沉积(Chemicalvapordeposition, CVD) 过程中预先控制用于催化生长h-BN 的铜箔衬底中的碳含量, 制备得到了不同密度的零声子发射(Zero-phononlines, ZPL)波长位于626±3 nm 的色心; 此外, 我们还观察到气氛退火对色心发光显著的调控作用. 该色心优良的单色性和可调控性有助于推动基于h-BN 的量子光源和光子学器件的潜在应用, 对理解h-BN 中碳缺陷的形成亦具有重要意义.