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Birefringent crystals (BFCs) have been extensively used in imaging spectrometers, laser devices, and optical components. Seeking new BFCs is important for both fundamental research and industrial applications. Employing first-principles density functional theory, we find that LaOBiS2 (space group: P4/nmm) appearing in the parent phase of the recently discovered BiS2-superconductor exhibits superior birefringence with a maximum value of 2.94, which is 13.4 times larger than the extensively used YVO4 (0.22). Furthermore, LaOBiS2 is an indirect semiconductor with a band gap of 0.9 eV, which is suitable for optical applications. The origin of giant inherent birefringence is also discussed. [ABSTRACT FROM AUTHOR]

The parity-time-reversal (PT )-symmetric quantum mechanics (QM) (PTQM) has developed into a noteworthy area of research. However, to date, most known studies of PTQM focused on the spectral properties of non-Hermitian Hamiltonian operators. In this work, we propose an axiom in PTQM in order to study general time-dependent problems in PTQM, e.g., those with a timedependent PT -symmetric Hamiltonian and with a time-dependent metric. We illuminate our proposal by examining a proper mapping from a timedependent Schrödinger-like equation of motion for PTQM to the familiar timedependent Schrödinger equation in conventional QM. The rich structure of the proper mapping hints that time-dependent PTQM can be a fruitful extension of conventional QM. Under our proposed framework, we further study in detail the Berry-phase generation in a class of PT -symmetric two-level systems. It is found that a closed path in the parameter space of PTQM is often associated with an open path in a properly mapped problem in conventional QM. In one interesting case, we further interpret the Berry phase as the flux of a continuously tunable fictitious magnetic monopole, thus highlighting the difference between PTQM and conventional QM despite the existence of a proper mapping between them. [ABSTRACT FROM AUTHOR]

We apply the second-order Born—Oppenheimer (BO) approximation to investigate the dynamics of the Rabi model, which describes the interaction between a two-level system and a single bosonic mode beyond the rotating wave approximation. By comparing with the numerical results, we find that our approach works well when the frequency of the two-level system is much smaller than that of the bosonic mode. [ABSTRACT FROM AUTHOR]

A possibly fruitful extension of conventional random matrix ensembles is proposed by imposing symmetry constraints on conventional Hermitian matrices or parity-time (PT )-symmetric matrices. To illustrate the main idea, we first study 2 × 2 complex Hermitian matrix ensembles with O(2)-invariant constraints, yielding novel level-spacing statistics such as singular distributions, the half-Gaussian distribution, distributions interpolating between the GOE (Gaussian orthogonal ensemble) distribution and half-Gaussian distributions, as well as the gapped-GOE distribution. Such a symmetry-reduction strategy is then used to explore 2 × 2 PT -symmetric matrix ensembles with real eigenvalues. In particular, PT -symmetric random matrix ensembles with U(2) invariance can be constructed, with the conventional complex Hermitian random matrix ensemble being a special case. In two examples of PT - symmetric random matrix ensembles, the level-spacing distributions are found to be the standard GUE (Gaussian unitary ensemble) statistics or the 'truncated- GUE' statistics [ABSTRACT FROM AUTHOR]

Biocompatible Au nanoparticles with surfaces modified by PEG (polyethylene glycol) were developed in view of possible applications for the enhancement of radiotherapy. Such nanoparticles exhibit preferential deposition at tumor sites due to the enhanced permeation and retention (EPR) effect. Here, we systematically studied their effects on EMT-6 and CT26 cell survival rates during irradiation for a dose up to 10 Gy with a commercial biological irradiator (Eaverage = 73 keV), a Cu-Ka1 x-ray source (8.048 keV), a monochromatized synchrotron source (6.5 keV), a radio-oncology linear accelerator (6 MeV) and a proton source (3 MeV). The percentage of surviving cells after irradiation was found to decrease by [?]2-45% in the presence of PEG-Au nanoparticles ([Au] = 400, 500 or 1000 uM). The cell survival rates decreased as a function of the dose for all sources and nanoparticle concentrations. These results could open the way to more effective cancer irradiation therapies by using nanoparticles with optimized surface treatment. Difficulties in applying MTT assays were also brought to light, showing that this approach is not suitable for radiobiology. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) of nanocrystal present in porous silicon shifts from the near infrared to the ultraviolet depending on the size when the surface is passivated with Si-H bonds. After oxidation, the centre wavelength of PL band is pinned in a region of 700-750 nm and its intensity increases obviously. Calculation shows that trap electronic states appear in the band gap of a smaller nanocrystal when Si = O bonds or Si-O-Si bonds are formed. The changes in PL intensity and wavelength can be explained by both quantum confinement and trap states in an oxidation layer of nanocrystal. In the theoretical model, the most important factor in the enhancement and the pinning effects of PL emission is the relative position between the level of the trap states and the level of the photoexcitation in the silicon nanocrystal. [ABSTRACT FROM AUTHOR]

An aggregation growth model of three species A, B and C with the competition between catalyzed birth and catalyzed death is proposed. Irreversible aggregation occurs between any two aggregates of the like species with the constant rate kernels In(n = 1,2,3). Meanwhile, a monomer birth of an A species aggregate of size k occurs under the catalysis of a B species aggregate of size j with the catalyzed birth rate kernel K(k,j) = Kkjv and a monomer death of an A species aggregate of size k occurs under the catalysis of a C species aggregate of size j with the catalyzed death rate kernel L(k,j)=Lkjv, where v is a parameter reflecting the dependence of the catalysis reaction rates of birth and death on the size of catalyst aggregate. The kinetic evolution behaviours of the three species are investigated by the rate equation approach based on the mean-field theory. The form of the aggregate size distribution of A species ak(t) is found to be dependent crucially on the competition between the catalyzed birth and death of A species, as well as the irreversible aggregation processes of the three species: (1) In the v < 0 case, the irreversible aggregation dominates the process, and ak(t) satisfies the conventional scaling form; (2) In the v [?] 0 case, the competition between the catalyzed birth and death dominates the process. When the catalyzed birth controls the process, ak(t) takes the conventional or generalized scaling form. While the catalyzed death controls the process, the scaling description of the aggregate size distribution breaks down completely. [ABSTRACT FROM AUTHOR]

Birefringence attracts increasing attention due to its extensive applications in the imaging spectrometer, laser devices and optical components. Stimulated by the discovery of the giant birefringence (GBF) in LaOBiS2 and AFBiS2, we explore its origin by checking three compounds with and without the BiS2 layer: Bi2OS2 (i.e., BiOBiS2), Bi2O2S and LaOAlS2. It is demonstrated that GBF appears only in the compounds with the BiS2 layer and is furthermore confirmed in MOBiS2 (M=Al, Ga, In and Sc) compounds. The result is useful for discovering/developing new-type birefringent crystal or even multifunctional materials. [ABSTRACT FROM AUTHOR]

We demonstrate that the combination of x-ray irradiation and capping by polyethylene glycol (PEG) produces excellent flexibility in controlling the structure of Au–Pd nanoparticles while preserving their catalytic performance. We specifically adopted two different fabrication methods: co-reduction and seed-assisted reduction. In both cases, precursor composition plays an important role in controlling the phases and size of the bimetallic nanoparticles. The optimal catalytic performance is obtained with the highest Pd concentration and when the nanoparticles consist of a Au core and a Pd shell. [ABSTRACT FROM AUTHOR]

Hinged mirror arrays are widely utilized for display applications and optical communication. They can be fabricated by an self-assembly technique using the strain in lattice-mismatched epitaxial layers. A multilayer structure including a strain-compensated layer, a digital alloy sacrificial layer and a strain bilayer, is grown by molecular-beam epitaxy. Self-assembly hinged mirrors on a GaAs substrate have been successfully fabricated by photolithography and selective etching. The hinge fabrication method with a strain bilayer is simple and flexible. Structures formed by multiple hinged plates will enable the self-assembly of more complex three-dimensional microstructures. [ABSTRACT FROM AUTHOR]

The energy band structure of single-layer graphene under one-dimensional electric and magnetic field modulation is theoretically investigated. The criterion for bandgap opening at the Dirac point is analytically derived with a two-fold degeneracy second-order perturbation method. It is shown that a direct or an indirect bandgap semiconductor could be realized in a single-layer graphene under some specific configurations of the electric and magnetic field arrangement. Due to the bandgap generated in the single-layer graphene, the Klein tunneling observed in pristine graphene is completely suppressed. [ABSTRACT FROM AUTHOR]

Using a transient thermoreflectance (TTR) technique, several Au films with different thicknesses on glass and SiC substrates are measured for thermal characterization of metallic nano-films, including the electron-phonon coupling factor G, interfacial thermal resistance R, and thermal conductivity Ks of the substrate. The rear heating-front detecting (RF) method is used to ensure the femtosecond temporal resolution. An intense laser beam is focused on the rear surface to heat the film, and another weak laser beam is focused on the very spot of the front surface to detect the change in the electron temperature. By varying the optical path delay between the two beams, a complete electron temperature profile can be scanned. Different from the normally used single-layer model, the double-layer model involving interfacial thermal resistance is studied here. The electron temperature cooling profile can be affected by the electron energy transfer into the substrate or the electron-phonon interactions in the metallic films. For multiple-target optimization, the genetic algorithm (GA) is used to obtain both G and R. The experimental result gives a deep understanding of the mechanism of ultra-fast heat transfer in metals. [ABSTRACT FROM AUTHOR]

According to the theory of optical films, we simulate the reflectivity of antireflection coatings (ARCs) for solar cells of Ga0.5In0.5P/GaAs/Ge based on an optical transfer matrix. In order to provide sufficient consideration of the refractive index dispersion effect of multilayer ARCs, we use multi-dimensional matrix data for reliable simulation. After the reflection curves are obtained, the effective average reflectance Re is introduced to optimize the film system by minimizing Re. Optimization of single layer (Al2O3), double layer (MgF2/ZnS) and triple layer (MgF2/Al2O3/ZnS) ARCs is realized by using this method for space and terrestrial applications. Effects of these ARCs are compared after optimization. These theoretical parameters can be used to guide experiments. [ABSTRACT FROM AUTHOR]

The quasistatic nanoindentation process of a spherical indenter in a single crystal copper is investigated with the molecular statistical thermodynamics (MST) method based on the embedded atom method (EAM) potential. The indentation modulus obtained in the MST simulation is 129.9 GPa, which agrees well with the theoretical prediction (129 GPa). In the elastic regime, the obtained maximum displacement of the indenter is two times the contact depth and the contact area is qualitatively proportional to the contact depth, which agrees well with Hertzian elastic theory of contact. The MST simulation can reproduce the nucleation of dislocation as well. Moreover, the efficiency of the MST method is about 8 times higher than that of traditional MD simulations. [ABSTRACT FROM AUTHOR]

The phase transformation activation energy of the Cu61.13Zn33.94Al 4.93 alloys, which were treated at 4 GPa and 700 degC for 15 minutes, was calculated by means of differential scanning calorimetry curves obtained at various heating and cooling rates. Then, the effects of high-pressure heat treatments on the solid-state phase transformation and the microstructures of Cu61.13Zn33.94Al4.93 alloys were investigated. The results show that high-pressure heat treatments can refine the grains and can change the preferred orientation from (111) to (200) of a phase. Compared with the as-cast alloy, the sample with high-pressure heat treatment has finer grains, lower b' - b and b - b' transformation temperature and activation energy. Furthermore, we found that high cooling rate favours the formation of fine needle-like a phase in the range of 5-20 degC/min. [ABSTRACT FROM AUTHOR]

The emission spectrum of a two-level atom interacting dispersively with a single mode radiation field in the dissipative cavity is investigated. A general expression for the emission spectrum is derived. The numerical results for the initial field in coherent state are calculated. It is found that the spectrum structure is influenced significantly by the cavity damping constant k, and the spectrum structure is dependent on the interaction time T when the cavity dissipation is present. Only one peak located at oa appears in the atomic spectra for larger T. [ABSTRACT FROM AUTHOR]

The polyethylene glycol (PEG) modified gold nanoparticle complex was synthesized by a one-solution synchrotron x-ray irradiation method. The impact on the structure and morphology of the gold nanoparticles of process parameters such as the PEG molecular weight, the PEG/gold molar ratio and the x-ray dosage were investigated. The size of PEG modified gold particles was found to decrease with increasing PEG addition and x-ray dosage. With the capability to monitor the absorption spectra in situ during the fast synthesis process, this opens the way to accurate control of the size and distribution. PEG chains with an intermediate length (MW6000) were found optimal for size control and colloidal stability in biologically relevant media. Our x-ray synthesized PEG-gold nanoparticles could find interesting applications in nanoparticle-enhanced x-ray tumour imaging and therapy. [ABSTRACT FROM AUTHOR]

We explored a very interesting gold nanoparticle system--pegylated gold in colloidal solution--and analyzed its uptake by mice colorectal adenocarcinoma CT26 tumor cells and the impact on the cell's response to x-ray irradiation. We found that exposure to polyethylene glycol (PEG) modified ('pegylated') 4.7 ± 2.6 nm gold nanoparticles synthesized by a novel synchrotron-based method enhances the response of CT26 cells to x-ray irradiation. Transmission electron microscopy (TEM) and confocal microscopy revealed that substantial amounts of such nanoparticles are taken up and absorbed by the cells and this conclusion is supported by quantitative induced coupled plasma (ICP) results. Standard tests indicated that the internalized particles are highly biocompatible but strongly enhance the cell damage induced by x-ray irradiation. Synchrotron radiation Fourier transform infrared (SR-FTIR) spectromicroscopy analyzed the chemical aspects of this phenomenon: the appearance of C = O stretching bond spectral features could be used as a marker for cell damage and confirmed the enhancement of the radiation-induced toxicity for cells. [ABSTRACT FROM AUTHOR]

The influences of optical fields on the group delay of chiral tunneling in graphene are investigated in real time using the finite-difference time-domain method. The group delay of tunneling electrons irradiated by an optical field is significantly different from that observed in traditional quantum tunneling. We found that when the barrier width increases, the group delay becomes constant for the reflected wave packet, but increases linearly for the transmitted wave packet. This peculiar tunneling effect can be attributed to current leakage in a time-dependent barrier generated via the optical Stark effect. [ABSTRACT FROM AUTHOR]

Eigenvalue problems for linear differential equations, such as time-independent Schrödinger equations, can be generalized to eigenvalue problems for nonlinear differential equations. In the nonlinear context a separatrix plays the role of an eigenfunction and the initial conditions that give rise to the separatrix play the role of eigenvalues. Previously studied examples of nonlinear differential equations that possess discrete eigenvalue spectra are the first-order equation and the first, second, and fourth Painlevé transcendents. It is shown here that the differential equations for the first and second Painlevé transcendents can be generalized to large classes of nonlinear differential equations, all of which have discrete eigenvalue spectra. The large-eigenvalue behavior is studied in detail, both analytically and numerically, and remarkable new features, such as hyperfine splitting of eigenvalues, are described quantitatively. [ABSTRACT FROM AUTHOR]

Diamond anvil cells combined with Raman spectroscopy and angle-dispersive x-ray diffraction (ADXRD) were used to investigate the compression behavior of cinchomeronic acid (C7H5NO4, CA), a hydrogen-bonded polymorphs. The compression of form-I at approximately 6.5 GPa caused an irreversible phase transition that produced the new polymorph form-III. Lattice and internal modes in the Raman spectra were analyzed to determine the modifications in the local environment of CA form-I molecules. The form-III was indexed and refined to a low-symmetry triclinic structure with space group P1. The mechanism for the phase transition involved the reconstructions in the hydrogen-bonded networks in CA form-I. [ABSTRACT FROM AUTHOR]

LaOsSi3 single crystals are synthesized for the first time by an arc melting method. The crystal features a tetragonal BaNiSn3-type structure (space group I4mm) which lacks inversion symmetry along the crystallographic c axis and is isostructural with the intensively studied Rashba-type noncentrosymmetric superconductors LaRhSi3 and LaIrSi3. Unlike LaRhSi3 and LaIrSi3 displaying superconductivity, LaOsSi3 shows only metallic behavior over the measured temperature range of 2 K–300 K. The Sommerfeld coefficient γ derived from specific heat is 5.76 mJ·mol−1K−2, indicating that LaOsSi3 has a weak electronic correlation effect. The absence of superconductivity in LaOsSi3 may lie in the Os 5d bands in the electronic structure. If it is true, it would be useful to provide complementary knowledge in understanding the relation between conduction and the d bands of M in LaMSi3 compounds (M = transition metals). [ABSTRACT FROM AUTHOR]

An epitaxial ZnO thin film was entirely fabricated by pulsed laser deposition. Both the orientation and the size of the crystallites were studied. The X-ray diffraction (XRD) patterns of the film show strong c-axis oriented crystal structure with preferred (002) orientation. The Phi-scan XRD pattern confirms that the epitaxial ZnO exhibits a single-domain wurtzite structure with hexagonal symmetry. In situ high-temperature XRD studies of ZnO thin film show that the crystallite size increases with increasing temperature, and (002) peaks shift systematically toward lower 2th values due to the change of lattice parameters. The lattice parameters show linear increase in their values with increasing temperature. [ABSTRACT FROM AUTHOR]

Here we report a mini-three-dimensional dye-sensitized solar cell (3D DSSC) based on TiO2 nanotube arrays (TNAs). TNAs were directly grown on spiral-shaped titanium wire via a facile potentiostatic anodization. Furthermore, the TNAs film was characterized by scanning electron microscopy, x-ray diffraction and transmission electron microscopy, indicating that the annealed TNAs were composed of single-crystalline anatase particles. Unlike conventional flat DSSC, this mini-3D DSSC could easily hold liquid electrolyte due to the capillary force which facilitated sealing the cell. This mini-3D DSSC showed an energy conversion efficiency of 4.1% under the AM 1.5 condition, which was much higher compared with that (3.2%) of the backside illuminated TNAs based DSSC of the same projected area. [ABSTRACT FROM AUTHOR]

We present the experimental observations and theoretical calculations of two electromagnetically induced transparency (EIT) windows and an enhanced EIT signal in a four-level tripod system of D1 line of 87Rb atoms. The two EIT dips produced by a strong coupling beam and a weak trigger beam were observed in the absorption spectrum of probe field, when the frequency detuning of the trigger beam was different from that of the coupling beam. When the frequency detuning of the trigger beam was near or equal to that of the coupling beam, the total depth of the EIT dip created by the coupling beam clearly became larger. The experimental measurements were in agreement with theoretical calculations. [ABSTRACT FROM AUTHOR]

In this paper multiple delay feedback control (MDFC) with different and independent delay times is shown to be an efficient method for stabilizing fixed points in finite-dimensional dynamical systems. Whether MDFC can be applied to infinite-dimensional systems has been an open question. In this paper we find that for infinite-dimensional systems modelled by delay differential equations, MDFC works well for stabilizing (unstable) steady states in long-, moderate-and short-time delay regions, in particular for the hyperchaotic case. [ABSTRACT FROM AUTHOR]

We have performed the first-principles calculation to investigate the origins of ferroelectricities and different polarization behaviours of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. The density of state (DOS) and electronic charge profiles show that there are strong hybridizations between atoms Ti and O and between atoms Pb and O which play very important roles in producing the ferroelectricities of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. Owing to the decline of internal electric field in SrTiO3 (ST) layer, the tetragonality and polarizations of superlattices decrease with increasing the fraction of SrTiO3 in the superlattices. We find that the polarization of PbTiO3/SrTiO3 is largerthan that of BaTiO3/SrTiO3 at the same ratio of components, because the polarization mismatch between PbTiO3 and SrTiO3 is larger than that between BaTiO3 and SrTiO3. The polarization and tetragonality are enhanced with respect to those of bulk tetragonal BaTiO3 in the superlattices BaTiO3/SrTiO3, while the polarization and tetragonality are reduced with respect to those of bulk tetragonal PbTiO3 in superlattices PbTiO3/SrTiO3. [ABSTRACT FROM AUTHOR]

The Keda Torus eXperiment (KTX) is still operated in the commissioning phase, and preparation for the operation capability of the KTX phase II upgrade is underway. The diagnostics in the KTX have been greatly developed: (1) the terahertz interferometer has been upgraded to seven chords for electron density profile inversion; (2) a Thomson scattering system with a 5 Joule laser has been installed and commissioning is in progress; (3) a 3D movable probe system has been developed for the electromagnetic turbulence measurement; (4) double-foil soft x-ray imaging diagnostics have been set up and a bench test has been completed; (5) an edge capacitive probe has been installed for the radial electrical field measurement; (6) a multi-channel spectrograph system has been built for detecting impurities of carbon and oxygen. In addition, the design of a new compact torus injection system has been completed for feeding and momentum driving. Pilot research, such as the 3D reversed field pinch physics and electromagnetic turbulence, etc, have been conducted in the discharge status of the KTX. The 3D spectra characters of electromagnetic turbulence are firstly measured using a classical two-point technique by Langmuir probe arrays set on the 3D movable probe system and edge magnetic sensors. The forward scattering is collected by the interferometer system, which shows the potential for turbulence research. The electromagnetic turbulence is tentatively investigated in the KTX. The formation of a quasi-single-helicity state in the KTX regime is also preliminarily explored in simulation. [ABSTRACT FROM AUTHOR]

Pr3+-doped calcium niobium gallium garnet (Pr:CNGG) single crystals with different Pr3+concentrations are successfully grown by the micro-pulling-down (μ-PD) method. The crystal structure, room-temperature absorption spectra, and fluorescence spectra of Pr:CNGG crystals are measured and discussed. The fluorescence results indicate their large dependence on the doping concentration. The fluorescence lifetime of the energy level is also determined. The results indicate that Pr:CNGG crystal could be a potential solid-state laser gain medium. [ABSTRACT FROM AUTHOR]

The dynamic recrystallization (DRX) behavior of Inconel 718 superalloy containing second phase particles (δ phase) was investigated through isothermal compression deformation tests under the deformation temperatures of 960 °C–1000 °C and strain rates of 0.01, 0.1, 1 s−1. A developed cellular automaton (CA) model was established to describe the DRX process, considering the ellipsoid particle effects of particle stimulated nucleation and pinning grain boundary mobility. The comparisons of average grain size evolution and DRX kinetics were carried out between the studied superalloy with and without a δ phase. The results show that the δ phase could reduce the critical strain triggering DRX, average grain size at steady state and peak stress while increase the value of the Avrami exponent. And the effects of δ phase on average grain size is more and more obvious with the increase of strain rate. A great agreement between the simulated and experimental results was obtained, which indicates that the developed CA model considering the δ phase effects could well describe the DRX process of the studied superalloy. [ABSTRACT FROM AUTHOR]

The bounce solutions of self-interacting scalar fields coupled to gravity are studied using a semi-classical approach. We found that bounce solutions have a maximum required barrier curvature, in addition to the known minimum required barrier curvature. In particular, as the maximum barrier curvature is approached, the scale factor of the well-known Coleman–De Luccia (CDL) bounce solutions become divergent. Unlike the CDL or its more general oscillating bounce counterparts, this cannot be considered as a subset of the Hawking–Turok solution. [ABSTRACT FROM AUTHOR]

The Keda Torus eXperiment (KTX) is a new reversed field pinch (RFP) device at the University of Science and Technology of China. The construction and assembly of KTX, including the vacuum chamber, conducting shell, magnetic field windings, power supply system, active control coils, vacuum pump and data acquisition system, have been completed on August 1, 2015. Immediately following that, the first plasma was obtained on August 15, 2015. Intensive conditioning of the machine is underway to ramp up the plasma current toward its full operation. An active feedback mode control system has been built and has been implemented to control the error field around the vertical gaps of the conducting shell. The pulsed power supply systems of ohmic heating field and toroidal field (TF), using thyristor and energy storage capacitors, have been tested and commissioned. The TF power supply has flexibility in being able to operate with a reversed TF configuration and stable TF configuration. The fundamental diagnostic tools are developed for early KTX operation. Currently, the plasma current is up to 205 kA and the maximum discharge length is 21 ms, approaching to the conducting shell penetration time. Furthermore, typical RFP discharges are being produced with RFP state lasting 2 ms. These initial operation results for KTX are described in detail. [ABSTRACT FROM AUTHOR]

A high-performance supercapacitor electrode is designed and fabricated with the 3D interconnected continuous nanoporous Co/CoO core–shell hybrid nanostructure grown on nickel foam. The Co/CoO core–shell hybrid nanostructures are obtained via a hydrothermal method, followed by high-temperature annealing in hydrogen atmosphere, and finally placed in air at 50 °C for 1 h. The Co/CoO core–shell nanostructure assembled by a conductive metal–core and a CoO shell, brings low resistance, high specific capacitance of 5.632 F cm−2 and good capability stability (81.5% capacitance retention after 6000 cycles). An asymmetric supercapacitor device built by the Co/CoO (positive electrode) and activated carbon (negative electrode) can deliver a working voltage of 1.7 V and display a high energy density of 0.002 67 Wh cm−2 at a power density of 0.001 62 W cm−2, which is far superior to that of a supercapacitor at a similar power density. [ABSTRACT FROM AUTHOR]

We report an experimental study of electromagnetically induced transparency (EIT)-based light storage in a cloud of cold atoms loaded into a magneto-optical-trap (MOT). After the MOT is turned off, the retrieval efficiencies of right- and left-circularly polarized signal light fields each as a function of storage time are measured for different time delays between MOT off and the storage event, respectively. The results show that in the delay ranging from 0.015 ms to 3.5 ms, the retrieval efficiency for a zero-storage time (0.2 μs) and the storage lifetime can exceed 15% and 1.4 ms, respectively. The measured results will provide important help for optimizing the storage of the polarized entanglement photons in cold atomic ensembles. [ABSTRACT FROM AUTHOR]

We report an experimental and theoretical investigation to extend lifetimes of light storages by applying guiding magnetic fields in a room-temperature atomic vapor. The storages are based on dynamic electromagnetically induced transparency. Retrieval efficiencies versus storage time are experimentally measured for different strengths of the guiding magnetic fields. The measured results show that the 1/e storage times are ∼6 μs and ∼59 μs for the guiding field B0z = 0 and B0z = 93 mG, respectively. Physical processes causing decoherence in an atomic ensemble have been discussed and analyzed. A theory model which is used to evaluate the decoherence caused by fluctuations of transverse magnetic fields is developed. Based on this evaluation, the fact that storage lifetimes can be increased by applying guiding magnetic fields is well explained. [ABSTRACT FROM AUTHOR]

InGaN based light-emitting diodes (LEDs) with different electron blocking layers have been numerically investigated using the APSYS simulation software. It is found that the structure with a p-AlInN electron blocking layer showes improved light output power, lower current leakage, and smaller efficiency droop. Based on numerical simulation and analysis, these improvements of the electrical and optical characteristics are mainly attributed to the efficient electron blocking in the InGaN/GaN multiple quantum wells (MQWs). [ABSTRACT FROM AUTHOR]

High-mobility vanadyl phthalocyanine (VOPc)/5,5'''-bis(4-fluorophenyl)-2,2':5',2'':5'',2'''-quaterthiophene (F2-P4T) thin-film transistors are demonstrated by employing a copper hexadecafluorophthalocyanine (F16CuPc)/copper phthalocyanine (CuPc) heterojunction unit, which are fabricated at different substrate temperatures, as a buffer layer. The highest mobility of 4.08cm2/Vs is achieved using a F16CuPc/CuPc organic heterojunction buffer layer fabricated at high substrate temperature. Compared with the random small grain-like morphology of the room-temperature buffer layer, the high-temperature organic heterojunction presents a large-sized fiber-like film morphology, resulting in an enhanced conductivity. Thus the contact resistance of the transistor is significantly reduced and an obvious improvement in device mobility is obtained. [ABSTRACT FROM AUTHOR]

To understand the surface morphology evolution of fused silica induced by 10.6-um CO2 laser irradiation at different parameters, this paper reports that optical microscopy, profilometry, and hydrophilicity tests are utilized to characterize the surface structure and roughness of the laser irradiated area. The results show that three typical surface morphologies and two typical hydrophilicity test images are observed at different laser powers and pulse durations. The correlations between surface temperature and surface morphology as well as hydrophilicity behaviours are presented. The different hydrophilicity behaviours are related to surface structures of the laser-induced crater and thermal diffusion area. The thermal diffusion length monotonously increases with increasing laser power and pulse duration. The crater width is almost determined by the laser beam size. The crater depth is more sensitive to the laser power and pulse duration than the crater width. [ABSTRACT FROM AUTHOR]

A novel bilayer photoresist insulator is applied in flexible vanadyl-phthalocyanine (VOPc) organic thin-film transistors (OTFTs). The micron-size patterns of this photoresisit insulator can be directly defined only by photolithography without the etching process. Furthermore, these OTFTs exhibit high field-effect mobility (about 0.8 cm2/Vs) and current on/off ratio (about 106). In particular, they show rather low hysteresis (< 1 V). The results demonstrate that this bilayer photoresist insulator can be applied in large-area electronics and in the facilitation of patterning insulators. [ABSTRACT FROM AUTHOR]

We studied the polarization spectroscopy of a linearly-polarized optical (probe) field in a multi-Zeeman-sublevel atomic system of the 87Rb D1 line. The polarization spectroscopy signals of the probe light result from the changes in its polarization, which are caused by a left-circularly polarized pumping beam. A theoretical analysis involving multiple Zeeman sublevels is presented and the results are in qualitative agreement with the experimental observations. Based on this phenomenon, we demonstrated a light switch at low light level ([?]68 photons per l2/2p) with a switching efficiency of [?]3%. [ABSTRACT FROM AUTHOR]