Polarized (letter ‘8’) memory effects in hetero-systems and non hetero-systems

In order to clarify whether or not the existence of the heterojunction is a necessary condition for the observation of polarized memory effect, experimental observation has been performed on heterosystems which have evaporated thin film on single crystal. The experiments on the reversal of switching polarity have also been carried out. The results suggest that heteojunctions are not essentially related to the polarized memory effect.     

Polarized memory effect in Se thin film diodes

Polarized memory effect in thin film of SnO₂SeCu structure, in which Cu electrode is deposited, is observed. Current-voltage characteristics and impedance characteristics of this element are described.     

On Young's (1805) equation and Finn's (2006) ‘counterexample’

In 1805, Thomas Young considered the balance of forces acting on the contact line formed at the intersection of a liquid-fluid interface with a solid surface and introduced a macroscopic concept of “contact angle”. From Young's reasoning it follows that in equilibrium the contact angle is a material property of the liquid/fluid/solid system independent of a particular configuration. Two centuries later, Robert Finn considered a model problem which seems to suggest that there is a fundamental flaw in Young's force diagram and the reasoning behind it. In the present note, we show that the apparent paradox in Finn's model problem disappears once Young's original concepts are applied in a correct way.     

高压下1,1’-二羟基-5,5’-联四唑二羟胺盐的振动光谱及同位素效应

用密度泛函理论方法研究1,1’-二羟基-5,5’-联四唑二羟胺盐(HATO)晶体在高压(<40 GPa)下性质。在GGA-PW91计算水平并结合超软势基组对HATO晶体结构进优化,其优化结构能再现实验结果。分子间O…H间距随压力的增加而显著减小;但O—H和N—H键长呈现非单调变化。基于不同压力下的优化晶体结构,利用非周期性计算并经校正因子0.967 9校正,求得相应压力下的红外和拉曼谱。预测最强拉曼峰对应于C—C伸缩和NH₂对称变形,位于1 580 cm-1,与实验结果一致。虽然阴离子不含氢原子,但阳离子的氘代仍对阴离子的振动光谱产生影响。高压导致分子间氢键增强,导致参与氢键的O—H和O—D振动的拉曼波数减小。氘代后,ND₂的拉曼位移的最明显变化是ν₂伸缩振动波数在高压下急剧增加,导致ND₂ ν₂/ν₃在高压下发生偶合。计算出的ν₁至ν₃振动的同位素效应比ν(NH₂)/ν(ND₂)均为1.36～1.38,与由折合质量所求得的值相一致。氘代和压力的变化可引起不同振动模式的偶合。     

Negative boron isotope effect of a ‘2Δ’ gap peak in Raman spectra from non-magnetic borocarbide superconductors

The nickel borocarbides RNi₂B₂C, R=Y or Lu, have a superconducting T_c of 15-16 K and exhibit properties consistent with an anisotropic s-wave gap. We briefly review their properties. Electronic Raman scattering results are presented on YNi₂B₂C containing ¹¹B or ¹⁰B. In A_1g and B_1g Raman symmetries, there is no shift in the position of the ‘2Δ’ peak with B-isotope. There is a distinct negative shift, however, in B_2g symmetry. This is interpreted as a negative isotope shift for the gap Δ on that portion of the Fermi surface where the magnitude of the B_2g Raman vertex is large.     

有机激光染料-1,4-双[5’-(2’-苯基恶唑基)]苯及其2’-(3”-取代苯基)衍生物的光性能研究(Ⅱ)

本文报导了1,4-双[5’-(2’-苯基恶唑基)]苯及其2’-(3”-取代苯基)衍生物共八个化合物,其中除母体化合物外,其余化合物至今尚未见报导。测定了它们的红外光谱、质谱、紫外光谱、荧光光谱、荧光量子产率和激光转换效率。     

Silicon nanowires for ‘turn-on’ fluorescence detection of Zn(II)

The surface of the silicon nanowire was covalently modified with silane derivative of acenaphthene to form a ‘turn-on’ fluorescence sensor for Zn(II). The fluorescent intensities of the sensor were linearly increased with the increment of the Zn(II) concentration in the range of 0.0-20 μM, and a good selectivity and sensitivity to Zn(II) were obtained. Differently from conventional Zn(II) ion fluorescence sensor, the present sensor could be repeatedly used and exhibit a facilitation in practical application.     

Reply to the comment on: ‘Magnetoresistance in La1−xCaxMnO3(0≤x<0.4)’

The author of the comment objects to the characterization and the interpretation of magnetoresistance (MR) effects observed by us in La_1−xCa_xMnO₃ (0≤x<0.4) samples. In this reply, arguments are used to show that the samples' characterization and explanation of the MR by considering the role of the short-charge ordering (CO) regions and magnetic domains are reasonable and acceptable.     

Anti-resonance and the “0.7 anomaly” in conductance through a quantum point contact

We investigate the transmission of electrons through a quantum point contact by using a quasi-one-dimensional model with an extra local bound state staying below the band bottom. While the complete transmission in lower channels gives rise to plateaus of conductance at multiples of 2e²/h, the electrons in the lowest channel are scattered by the local bound state when it is singly occupied. This scattering produces a wide anti-resonant zero-transmittance for singlet formed by tunneling and local electrons, and has no effect on triplets, leading to an exact 0.75(2e²/h) shoulder prior to the first 2e²/h plateau. While at low temperature, the formation of Kondo cloud screens magnetic moment of the local bound state and reduces the scattering to the singlet channel, complementing the shoulder from 0.75 to 1.     

High temperature (T>300 K) light emitting diodes for 8–12 μm spectral range

Contrary to conventional light emitting diodes for visible and very near infrared utilizing interband (ω>E_g) luminescence, the longer infrared emitting diodes (LIREDs) we describe here utilize intraband (ω<E_g) electron transitions and emit beyond the fundamental absorption range of the material used. Made of indirect band gap semiconductors (like Ge, Si) and, therefore, free from the Auger recombination impact, LIREDs efficiently operate at higher temperatures (T>300 K) in the longer wavelength atmospheric window (8–12 μm). Electrically modulated power emitted is comparable to that for black body sources whereas shorter rise–fall times are due to recombination processes (200 μs) and not dependent on pixel thermal mass and thermal conduction. LIREDs can be made of different semiconductor structures provided the controllable modulation of free carrier concentration in the device base is achieved. The main parameters of Ge based LIREDs under injection mode are reported.     

Microhydrodynamical modeling of transverse susceptibility of magnetic inks (Theory of ‘DIMAG’)

The time and field dependence of the transverse susceptibility, χ_t, of a suspension of single domain ferromagnetic Brownian particles in a viscous fluid is calculated. Magnetic interactions are taken into account through the mean field model. The model is used to interpret (so far qualitatively) the so-called DIMAG experiment, in which a DC field is applied to the ink sample for a short period of time and a small perpendicular AC field probes χ_t before, during and after the DC field impact. The relative increase in χ_t, after the DC field is switched on was used earlier to characterize the dispersion quality of inks. We show that in the systems with negative interactions (acicular particles) this increase has a maximum when plotted as a function of the DC field. The maximum shifts to higher fields as the interaction increases, which corresponds to what happens in the DIMAG testing of less dispersed inks.     

Determination of the spin polarization of half-metallic CrO(2) by point contact Andreev reflection.

Andreev reflection at a Pb/CrO(2) point contact has been used to determine the spin polarization of single-crystal CrO(2) films made by chemical vapor deposition. The spin polarization is found to be 0.96 +/- 0.01, which confirms that CrO(2) is a half-metallic ferromagnet, as theoretically predicted.     

Triplet-to-singlet exciton formation in poly(p-phenylene-vinylene) light-emitting diodes

The triplet to singlet exciton formation ratio in a MEH-PPV light-emitting diode is measured by comparing the triplet-induced absorptions with optical and electric excitations at the same singlet exciton density. The ratio is a strong universal decreasing function of the averaged electric field. Using 4 ns for singlet to triplet intersystem crossing time, the ratio is significantly larger than the spin-independent value 3 at intermediate field but is reduced to about 2 for higher field.