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We study the spin polarization generated by the hydrodynamic gradients. In addition to the widely studied thermal vorticity effects, we identify an undiscovered contribution from the fluid shear. This shear-induced polarization (SIP) can be viewed as the fluid analog of strain-induced polarization observed in elastic and nematic materials. We obtain the explicit expression for SIP using the quantum kinetic equation and linear response theory. Based on a realistic hydrodynamic model, we compute the differential spin polarization along both the beam direction $\hat{z}$ and the out-plane direction $\hat{y}$ in non-central heavy-ion collisions at $\sqrt{s_{NN}}=200$ GeV, including both SIP and thermal vorticity effects. We find that SIP contribution always shows the same azimuthal angle dependence as experimental data and competes with thermal vorticity effects. In the scenario that $\Lambda$ inherits and memorizes the spin polarization of strange quark, SIP wins the competition, and the resulting azimuthal angle dependent spin polarization $P_y$ and $P_z$ agrees qualitatively with the experimental data., Comment: 6 pages, 3 figures

We present a detailed comparison of the optical properties of a quantum well (QW) and a two-dimensional (2D) quantum dot superlattice (QDSL) made of In0.4Ga0.6As on GaAs(311)B substrates under the same growth conditions. The lowest electron to hole transition energy in strained In0.4Ga0.6As/GaAs(311)B QWs is calculated. While good agreement between the calculated transition energy and the measured photoluminescence (PL) peak energy is found in the QW, the PL peak energy of the 2D QDSL significantly shifts to a lower energy with respect to the calculated transition energy for a QW with the same nominal thickness. Based on the linewidth broadening induced by increasing excitation density and temperature, the exciton–exciton and exciton–phonon interaction strengths in the 2D QDSL are found to be much larger than those in the QW. As the exciton–phonon scattering is sufficiently strong, a transition of the exciton motion from coherent to incoherent occurs.

Self-assembled In 0.4 Ga 0.6 As islands on GaAs (3 1 1)B substrates with Al x Ga 1− x As buffer layers of different aluminum compositions have been grown by atomic hydrogen-assisted molecular beam epitaxy. It is found that the critical thickness decreases slightly with the addition of Al in the buffer layer, while the spatial alignment of the In 0.4 Ga 0.6 As islands deteriorates greatly from the well-defined two-dimensional lattice on the GaAs buffer. All these differences are related to the enhanced bond strength of Al in the buffer by slowing the column III atom migration on the growing surface, and the reduced alloying effects between AlGaAs buffer and deposited InGaAs during growth.

By using the atomic force microscopy image, fast Fourier transformation and auto-correlation spectrum analysis, we have systematically investigated the spatial alignment of self-assembled In 0.4 Ga 0.6 As islands on the GaAs(3 1 1)B and the AlGaAs(3 1 1)B surfaces grown by atomic hydrogen assisted molecular beam epitaxy . Surprisingly, it is revealed that InGaAs island arrays are aligned in very different patterns on these two surfaces. They are aligned in a well-defined square two-dimensional (2D) lattice when formed on GaAs surface, but in a nearly perfect hexagonal 2D lattice when formed on AlGaAs surface, despite the fact that both AlGaAs and GaAs have the same lattice mismatch with InGaAs. This striking difference is preliminarily related to the enhanced bond strength of Al in surface, which not only changes the surface energy, but also slows down column III atom migration on the growing surface.

Coherent InAs x P 1− x islands were formed on the InP (1 0 0) and the InP (3 1 1)B surfaces by As/P exchange reaction under As flux and atomic H irradiation at 480°C. Islands on the InP (1 0 0) surface were found only formed at the step edges with an extremely low density. Contrary to the InP (1 0 0) surface, dense islands were formed on the InP (3 1 1)B surface. Especially, the InAs x P 1− x island arrays on the InP (3 1 1)B surface exhibited a significant narrowing of the size dispersion and a surprisingly strong nearest-neighbor correlation. It is suggested that long-range elastic interaction between self-assembled islands via the anisotropically strained substrate play a crucial role in this self-organization process.

Self-assembled In0.4Ga0.6As island arrays have been grown on (3 1 1)B GaAs substrates by using atomic hydrogen-assisted molecular beam epitaxy (H-MBE). The evolution process of surface morphology with deposition has been analyzed by atomic force microscopy (AFM) and the development of lateral ordering has been highlighted by two-dimensional fast Fourier transformation (2DFFT) analysis of the AFM images. It is revealed that the InGaAs islands are arranged in nearly perfect two-dimensional (2D) square-like lattice with two sides parallel to [0 1 −1] and [−2 3 3] azimuths. Such an alignment of islands is coincident with the anisotropy of bulk elastic modulus of the GaAs (3 1 1)B substrate.

We measured the in-plane photocurrent of a self-assembled In0.4Ga0.6As/GaAs(311)B quantum dot (QD) superlattice. A significant negative differential conductance (NDC) was found signifying an metal–insulator transition. The metal phase before NDC is argued arising from the miniband transport, which is likely controlled by acoustic-phonons scattering. The insulator-phase conduction after NDC turns out to be hopping, suggesting a field-induced miniband destruction.

We have carried out magnetoluminescence measurements to evaluate the effect of ordering structure of quantum dots (QDs) on lateral coupling. The size and the density are almost same but the special fast Fourier transform indicates that the ordering of QDs on (3 1 1)B is much better than that on (1 0 0). The photoluminescence from QDs formed on GaAs(3 1 1)B showed a larger shift with applied magnetic field compared to that of QDs on (1 0 0). This indicates a possibility that the QDs on (3 1 1)B are coupled over a larger area than those on (1 0 0).

Self-assembled In 0.4 Ga 0.6 As quantum dots (QDs) on GaAs (3 1 1)B surface has been grown by atomic hydrogen-assisted molecular beam epitaxy (H-MBE). The lateral ordering and size homogenization of islands is studied by using atomic force microscopy (AFM), fast Fourier transformation (FFT) and auto correlation (AC) spectra. It is revealed that strikingly well-defined square two-dimensional (2D) lattice of InGaAs dots are formed on the GaAs (3 1 1)B surface. This remarkable self-organization behavior is explained by the special ordering mechanism in our material system, originating from the high elastic anisotropy of the GaAs as well as the chosen (3 1 1)B growth orientation.

We investigated the growth of QDs on AlGaAs/GaAs(3 1 1)B by atomic hydrogen assisted molecular beam epitaxy. In the growth of QDs directly on AlGaAs, the QDs size fluctuation increased with increasing Al composition of the AlGaAs underlying layer. However, the uniformity of QDs size and the ordering were improved by introduction of a thin GaAs spacer layer. It was concluded that there is a strong interaction between the InGaAs-strained and underlying layers. The strong photoluminescence intensity of QDs confined in AlGaAs with GaAs spacer layers was maintained up to room temperature. Hence, the carrier collection efficiency into the QDs was improved and the escape of carriers from the QDs was suppressed by introducing higher potential AlGaAs barrier layers.

Formation of extended states or minibands in two-dimensional (2D) In0.4Ga0.6As/GaAs(311)B quantum dot superlattices (QDSLs) is directly demonstrated in time-resolved photoluminescence measurements. At a low excitation density of 1 W/cm2, photoluminescence transients with ∼15 ps rise time and ∼25 ps decay time are observed. Both rise and decay times are found to increase with increasing excitation density. The excitons in 2D QDSLs exhibit different relaxation and recombination behaviors as compared to those in quantum wells and quantum dots. A physical model treating 2D QDSLs as disordered systems containing localized and extended states can successfully interpret all of the experimental observations.

Remarkably different characteristics were found on isolated and close-packed self-assembled In 0.4 Ga 0.6 As/GaAs (311)B quantum dots (QDs). Sub-peaks superimposed on the regular Gaussian photoluminescence (PL) peak were observed in a close-packed QD array, in contrast to the single Gaussian PL peak in an isolated one. A tunneling-current peak in an isolated QD array changes into several equidistant features in a close-packed one. The possible mechanisms of the fine structures are discussed.

A blue photoluminescence band centered at 440 nm was observed from SiGeSiO 2 co-sputtered films at room temperature. This band gains intensity after the film was annealed at a temperature around 900°C in N 2 atmosphere. From analysis of photoluminescence excitation, Raman and X-ray photoelectron spectra, it turns out that the luminescence is probably from some interfacial state between Si 1− x Ge x nanoparticles and the SiO 2 matrix.

Our work was begun in 1949. through many yera's effort, several chemicals (such as 6 MP, 5 FU and others) were found to be effective for the treatment of choriocarcinoma (C.C.) and invasive mole (I.M.). From 1959 through 1985, 1500 patients were consecutively treated. The mortality rate of CC was reduced from > 90% to < 20%. No more death occurred in IM. All Survivors followed up for 10-38 years showed no evidence of residual disease. 80% of the young patients treated with chemotherapy alone conceived after recovery. The pregnancy outcome showed no deviation from that of the general population. All children are growing up normally many married and gave birth to normal third generations. The results indicated that chemotherapy with 5 FU achieves not only a complete remission, but also a cure, even with wide-spread metastases. The results of choriocarcinoma and invasive mole treated with mainly 5 FU were reported. The clinical experience in the management of metastases at different sites were also summarized.

The microsecond Photoluminescence decay of as-prepared porous silicon varies from sample to sample, but atmospheric oxidation at 200°C for 200 h gives rise to exactly identical exponential distribution of decay time with luminescence energy for any porous silicon sample. Discussion is made to demonstrate that we observe the characteristic photoluminescence decay and the related parameters for oxidized porous silicon.

Exposed to strong laser in air, the photoluminescence (PL) peak position of porous silicon (PS) shifts first to blue side followed by a pinning at a constant wave-length, while PL intensity degrades rapidly first, then increases slowly. Fourier transform infrared absorption spectra show a continuous enhancement of vibrations related to oxygen and a continuous attenuation of vibrations related to hydrogen with exposure time. A new physical model on light emission of PS, which says that incident light excites electron-hole pairs in nanoscale silicon units (NSUs) and the electron-hole pairs diffuse outwards and recombine through the luminescence centers (LCs) outside NSUs, can explain the experimental results successfully. We think the main LCs are hydrides, such as polysilanes or Si-H bonds, in as-prepared PS samples but transfer tinder laser illumination to be point defects or impurities in SiO2 layers which cover the NSUs.

On self-assembled ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}(311)B$ quantum dots (QD's), photocurrent in the plane of QD arrays was measured under irradiation with wavelengths longer than 850 nm (1.46 eV). A sample with rather inhomogeneous QD sizes shows hopping conduction, indicating the localization of carriers in individual QD's. A two-dimensional QD superlattice, consisting of highly ordered and homogeneously sized QD's, exhibits negative differential conductance (NDC), i.e., photocurrent decrease with increasing applied voltage, in a limited electric-field range. The pre-NDC conduction is argued to arise from the miniband, which is evidenced by the photoluminescence, while the post-NDC conduction is found to be hopping as in a localized QD system, suggesting a miniband destruction under an in-plane electric field as low as $\ensuremath{\sim}{10}^{3}{\mathrm{V}\mathrm{}\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}.$ The miniband transport is likely controlled by two-dimensional acoustic-phonon scattering.

We have evaluated the photoluminescence (PL) properties of quantum dots (QDs) embedded in a p-n junction on GaAs(311)B and were compared with the identical structure grown on GaAs(001). The QDs on these two surfaces were fabricated with a similar size and density by optimizing the growth conditions. The PL emission from the QDs grown on GaAs(001) rapidly disappeared when the excitation power was decreased below 0.4W/cm2, while that from on GaAs(311)B was clearly observable even at a lower excitation power of 0.1W/cm2. From the measurements of PL intensity dependence on temperature and applied electric field, it was found that there are clear differences between the QDs grown on (001) and the QDs grown on (311)B in the recombination rates through non-radiative processes and/or the escape rates of carriers out of QDs to the GaAs host through a tunneling process.

It was found that porous silicon (PS) layers formed on 0.01 Ωcm (111) and 0.02 Ωcm (100) Si substrates show high photoluminescence (PL) peak energies on both lower and higher porosity sides and a minimum of PL peak energy at the moderate porosity, while those formed on 0.8 and 10Ωcm (111) p-type Si substrates show an increase of PL peak energy with porosity on the lower side and a saturation of PL peak energy with porosity on the higher side. These experimental facts are not consistent with the quantum confinement model for light emission of PS, which predicts a monotonous increase of PL peak energy with PS porosity.

With InGaAs quantum dots (QDs) embedded in the vicinity, GaAs/AlGaAs two-dimensional electron gas (2DEG) was studied by transport measurements and by calculations with QDs charges as Coulomb scattering centers. The mobility of 2DEG decreases with increasing QDs density up to 5×1010 cm-2, which can be fitted by considering the finite spatial extension of QD-charge distribution. However, two distinct effects are observed as the QDs density increases from 5×1010 cm-2 to 2×1011 cm-2. One is that the 2DEG mobility is saturated at a low level, and the other is that it gradually approaches the high value of 2DEG without QDs. The former can be reproduced by taking into account the interdot overlapping of electron probability distributions, while the latter is argued to be the result of interdot coupling through wavefunction overlapping. These explanations are supported further by the temperature dependence of the conductance.

This paper describes the application of the Galerkin finite element method and the treatment of unknown heat flow boundary condition by an hybrid method to compute the crustal temperature distribution in the North China bay area. It has been shown that: (1) temperature along the Moho discontinuity is not a constant as generally assumed, but varies from a lower value of about 700°C at its downwarping portion to a higher value around 810°C at its upwarping portion; and (2) large shallow earthquakes occurred along a belt of steep thermal gradient just above a low velocity (i.e. low resistivity) zone where the temperature is about 600°C. This may be due to the high temperature below such a zone weakening the materials of the lower crust, which are unable to concentrate stress, thus causing large earthquakes.