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We investigate the existence and stability of localized gap states at a non-linear interface of non-linear fractional systems in a one-dimensional photonic lattice. By using the direct numerical simulations and linear stability analysis, we obtain the stability of the asymmetric localized gap states in the first and second finite gaps. Our theoretical results show that the power of the localized gap states decrease gradually as the increase of propagation constant and the non-linear landscape (non-linear coefficient ratio between the left and right interface), providing insights into soliton physics in non-linear periodic systems with fractional-order diffraction.

Regulation of membrane receptor mobility tunes cellular response to external signals, such as in binding of B cell receptors (BCR) to antigen, which initiates signaling. However, whether BCR signaling is regulated by BCR mobility, and what factors mediate this regulation, are not well understood. Here we use single molecule imaging to examine BCR movement during signaling activation and a novel machine learning method to classify BCR trajectories into distinct diffusive states. Inhibition of actin dynamics downstream of the actin nucleating factors, Arp2/3 and formin, decreases BCR mobility. Constitutive loss or acute inhibition of the Arp2/3 regulator, N-WASP, which is associated with enhanced signaling, increases the proportion of BCR trajectories with lower diffusivity. Furthermore, loss of N-WASP reduces the diffusivity of CD19, a stimulatory co-receptor, but not that of FcγRIIB, an inhibitory co-receptor. Our results implicate a dynamic actin network in fine-tuning receptor mobility and receptor-ligand interactions for modulating B cell signaling., B cell receptors (BCR) capture antigen and initiate downstream antibody responses, but whether and how BCR signaling is regulated by BCR mobility is still unclear. Here the authors show, using single molecule imaging and machine learning analyses, that BCR and CD19 mobility is modulated by the actin nucleation regulators Arp2/3 and N-WASP to control BCR signaling.

Respiration signals reflect many underlying health conditions, including cardiopulmonary functions, autonomic disorders and respiratory distress, therefore continuous measurement of respiration is needed in various cases. Unfortunately, there is still a lack of effective portable electronic devices that meet the demands for medical and daily respiration monitoring. This work showcases a soft, wireless, and non-invasive device for quantitative and real-time evaluation of human respiration. This device simultaneously captures respiration and temperature signatures using customized capacitive and resistive sensors, encapsulated by a breathable layer, and does not limit the user's daily life. Further a machine learning-based respiration classification algorithm with a set of carefully studied features as inputs is proposed and it is deployed into mobile clients. The body status of users, such as being quiet, active and coughing, can be accurately recognized by the algorithm and displayed on clients. Moreover, multiple devices can be linked to a server network to monitor a group of users and provide each user with the statistical duration of physiological activities, coughing alerts, and body health advice. With these devices, individual and group respiratory health status can be quantitatively collected, analyzed, and stored for daily physiological signal detections as well as medical assistance. Published version This research is supported by the Ministry of Education, Singapore, under its MOE ARF Tier 2 (Award no.MOE2019-T2-2-179). his researchis also supported by the Agency for Science, Technology and Research(A*STAR) under its IAF-ICP Programme ICP1900093 and the Schaeffler Hub for Advanced Research at NTU.

β-Ga2O3-based deep-ultraviolet photodetector (PD) has versatile civil and military applications especially due to its inherent solar-blindness. In this work, pristine and N-doped β-Ga2O3 thin films are prepared on c-plane sapphire substrates by radio frequency magnetron sputtering. The influences of N impurity on the micromorphology, structural and optical properties of β-Ga2O3 film are investigated in detail by scanning electron microscopy, X-ray diffraction, and Raman spectra. The introduction of N impurities not only degrades the crystal quality of β-Ga2O3 films, but also affects the surface roughness. The β-Ga2O3 films doped with N undergoes a transition from a direct optical band gap to an indirect optical band gap. Then, the resulting metal-semiconductor-metal (MSM) PD is constructed. Comparing with the pure β-Ga2O3-based photodetector, the introduction of N impurities can effectively depress dark current and improve response speed of the β-Ga2O3 device. The N-doped β-Ga2O3-based photodetector achieves a dark current of 1.08 × 10–11 A and a fast response speed (rise time of 40 ms and decay time of 8 ms), which can be attributed to the decrease of oxygen vacancy related defects. This study demonstrates that the acceptor doping provides a new opportunity for producing ultraviolet photodetectors with fast response for further practical applications.

Manipulating the polarization state of light is important in numerous applications in photonics and electromagnetism. Among many possible approaches, plasmonic polarizers have attracted widespread attention, due to their flexibility in structural design and convenience in on-chip integration. The authors demonstrate a VO${}_{2}$-based composite plasmonic nanostructure that can dynamically modulate the polarization of reflected light, via the thermally induced insulator-metal transition of the oxide. The composite structure can also be applied to realize switchable infrared imaging.

As is well known, plasmonics bridges the gap between nanoscale electronics and dielectric photonics, and is expected to be applied to light generation, photonic integration and chips, optical sensing and nanofabrication technology. So far, most of plasmonic microstructures and nanostructures cannot dynamically tune the properties once their structures are fabricated. Therefore, developing active plasmonic materials and devices is especially desired and necessary. Recently, dynamically tunable plasmonic materials and devices have been intensively investigated with the aim of practical applications. Here in this paper, we review recent research advances in active plasmonic materials and devices. Firstly we summarize three approaches to dynamically tuning plasmonic materials and devices. The first approach is to dynamically change the effective permittivity of metallic microstructures and nanostructures. The second approach is to dynamically adjust the ambient environments of the materials and devices. The third approach is to real-time tune the coupling effects in the nanostructures. Then we take ordinary plasmonic materials, plasmonic metamaterials, and plasmonic metasurfaces for example to show how to make them dynamically tunable. With external fields (such as electrical field, light field, thermal field, and mechanical force field, etc.), various approaches have been demonstrated in dynamically tuning the physical properties of plasmonic systems in real time. We anticipate that this review will promote the further development of new-generation subwavelength materials and optoelectrionic devices with new principles and better performances.

We have observed strong scattering of a probe light by dilute Bose-Einstein condensate (BEC) Rb-87 gas in a tight magnetic trap. The scattering light forms fringes at the image plane. It is found that we can infer the real size of the condensation and the number of the atoms by modelling the imaging system. We present a quantitative calculation of light scattering by the condensed atoms. The calculation shows that the experimental results agree well with the prediction of the generalized diffraction theory, and thus we can directly observe the phase transition of BEC in a tight trap.

We report an experiment of trapping of neutral Rb-87 atoms on a, self-made atomchip. The H-shaped atomchip is made by magnetron sputtering technology, which is different from the atomchip technology of other teams. We collect 3 x 10(6) Rb-87 atoms in the mirror magneto-optical trap (MOT) using the external MOT coils, and 1 X 10(5) Rb-87 atoms are transferred to U-MOT using U-shaped wire in chip and a pair of bias coils.

We experimentally study the ac Stark splitting in D2 line of cold 87Rb atoms. The frequency span between the Autler–Townes doublets is obviously larger than that derived from theoretical calculation. Two physical effects, which increase the effective Rabi frequency, contribute to the splitting broadening. First, atoms tend to distribute in strong field places of a inhomogeneous red-detuned light field. Second, atoms reabsorb scattered light when they are huge in number and high in density.

From the 12C(π+, K+)12ΛC reaction, the γ-rays of 261.6±0.24 keV (7/2+→5/2+) and 1481.7±0.7 keV (1/2+→5/2+) of 11ΛB, and 2667.3±2.8 keV (12−→21−) of 12ΛC hypernuclei have been identified using a large germanium detector array Hyperball2 at K6 beam line of KEK. The observed energies of the transitions 1481.7 keV and 261.6 keV are significantly different from the values predicted by the shell model using the Δ and SN parameters determined from the 7ΛLi data.

The γ-rays and protons from Ed = 20 keV deuterons incident on a D–Ti target are measured. The branching ratio of the 2H (d,γ)4He reaction to the 2H (d,p)3H reaction is obtained to be Γγ/Γp = (1.06±0.42)×10−7, and the astrophysical S factor of the 2He(d,γ)4He reaction is deduced to be (5.7±2.4)×10−6.

Platinum and gold have the similar crystal structure but different electronic affinities, as well as different effective electron densities near the implanted ions. Both the differences favour larger decay rate of 7Be in Pd than that in Au. We measured the variation of the decay rate of 7Be implanted in Pd and Au host materials. We have found that the decay rate of 7Be in Pd is larger than that in Au by 0.8%.

We report the realization of Bose-Einstein condensation (BEC) in dilute rubidium gas. The BEC was achieved in a quadrupole and Ioffe configuration trap. The number of condensed atoms is around 4×104 in total 5×105, and the transition temperature is 250 nK. We have studied the light scattering of the atom cloud and the condensate in a tightly confined magnetic trap. We show that it is possible to use the diffraction patterns in the near-resonant imaging of the trapped cold atomic samples to give the information of the BEC phase transition.

The root-mean-square (rms) radii of the last nucleons in the 2s1/2 states of 21Ne, 21Na, 17O and 17F are found to be 4.4±0.5, 5.2±0.6, 4.3±0.5 and 5.0±0.6 fm, respectively, from transfer reaction data. The results show that the 2s1/2 states of 21Na and 17F are proton halo states, while the analogous states in their mirror nuclei 21Ne and 17O can be considered as neutron skin states. Comparisons among the rms radii of these states lead us to expect that a neutron halo nucleus has a proton halo mirror partner, and the Coulomb barrier is a determinant factor limiting the extension of the rms radius of the loosely bound proton.

We propose constructing a quantum interference configuration for cold atoms in a magneto-optical trap by applying a radio frequency field, which coherently couples adjacent Zeeman sublevels, in combination with a repumping laser field. One effect of this interference is that a dip exists in the absorption of the repumping light when the radio frequency is scanned. Our prediction has been indirectly detected through the fluorescence of cold atoms in a preliminary experiment.

Quantum Fourier transform (QFT) is a quantum analogue of the classical discrete Fourier transform. It is a fundamental quantum gate in quantum algorithms which has an exponential advantage over the classical computation and has been excessively studied. Normally, an n-qubit quantum Fourier transform could be resolved into the tensor product of n single-qubit operations, and each operation could be implemented by a Hadamard gate and a controlled phase gate. Then the complexity of an n-qubit QFT is of order O(n2). To reduce the complexity of quantum operations, optimal control (OC) method has recently been used successfully to find the minimum time for implementing a quantum operation. Up to now, two types of quantum optimal control methods have been presented, i.e. analytical and numerical methods. The analytical approach is to change the problem of efficient synthesis of unitary transformations into the geometrical one of finding the shortest paths. Numerical optimal control procedures are based on the gradient methods (GRAPE, Gradient Ascent Pulse Engineering) and Krotov methods. Notable application mainly focus on nuclear magnetic resonance fields, including imaging, liquid-state NMR, solid-state NMR, and NMR quantum computation. One obvious advantage of optimal control NMR quantum computation is that the OC unitary evolution transformation pulse sequences are normally shorter than the conventional corresponding ones. Here we use the optimal control method to find the minimum duration for implementing QFT quantum gate. A linear spin chain with nearest-neighbor Ising interaction is used to find the optimization. And the optimized pulse sequence is experimentally demonstrated on an NMR quantum information processor. By using optimal control method with numerical calculation, a three-qubit QFT in an indirect-linear-coupling chain system is optimized. The duration of the OC QFT is obviously shorter than that of conventional approaches. The OC pulse sequence has been experimentally implemented on a liquid-state NMR spectrometer. To verify the optimally controlled pulse sequence for the three-qubit QFT, different initial states are assumed. The accuracy of the OC pulse sequence could be demonstrated by the consistency of theoretical simulation spectra with the experimental results. The good consistency between the simulation and the experimental spectra demonstrates that the OC QFT is of high fidelity.

The electronic structures, Born effective charges (BECs), and full phonon dispersions of cubic, tetragonal, orthorhombic, and rhombohedral K0.5Na0.5NbO3 are investigated by the first principles method based on density functional theory. The hybridized states of Nb 4d and O 2p states are observed in the valence band, showing the formation of a strong Nb—O covalent bond which should be responsible for the displacement of Nb and O atoms. The abnormally large BECs of Nb and O indicate the possibility of phase instability induced by the off-center displacement of Nb and O atoms. The phonon dispersions reveal that the ferroelectric instability of K0.5Na0.5NbO3 is dominated by Nb and O displacements with significant Na characteristics. In addition to the ferroelectric instability, there is also rotational instability coming from the oxygen octahedra rotation around one axis. Moreover, the Γ phonon properties of orthorhombic KNbO3, NaNbO3, and K0.5Na0.5NbO3 are also studied in detail.

Heavily terbium‐doped boron‐silicate glasses (Tb3+10.4 at. %) with a Verdet constant (632.8 nm, room temperature) as large as −0.338 min/Oe cm, 38% larger than that of the famous FR‐5 glasses, have been made. The wavelength and temperature dependencies of the Verdet constants of samples have been investigated in the ranges of 400 to 800 nm and 100 to 300 K. The results show paramagnetic Faraday rotations. The measured susceptibilities between 77 and 300 K support this point but with an effective Bohr magneton number 7% smaller than the theoretical value for free Tb3+ ions. Susceptibilities are further measured at temperatures from 1.5 to 100 K and magnetic fields from 0.2 to 5.0 T. The results show saturation of magnetization and give a Neel temperature of about −9 K. The effective Bohr magneton number in the state of saturated magnetization is 55% smaller than the free ion value. These results may indicate the single ion anisotropy reduction of the magnetization of the disordered Tb3+ ions at low tempera...

We propose a scheme to implement single-qubit operations for singlet-triplet qubits located in an isolated double-well potential with fixed inter-site tunneling when superexchange interactions predominate. Arbitrary single-qubit gates can be realized by a sequence composed of two elementary operations which can be switched between different parameter regimes by adjusting slightly the relative energy bias of trapped atoms in each sub-well site. The experimental feasibility of the strategy and the fidelity of basic rotation operations are also analyzed.

We demonstrate continuous imaging of a single 87Rb atom confined in a steep magneto-optical trap with an electron-multiplying charge-coupled device (EMCCD) camera and realize a one-dimensional micro-optical trap array with a Dammann grating. We adopt several methods to reduce the noise in the fluorescence signal we obtain with the EMCCD. Step jumping characteristics of the fluorescence demonstrate capturing and losing of individual atoms.

The decay rate variation of 7Be implanted into platinum and aluminum host materials has been measured via detecting the 478 keV ?-rays from the first excited state of 7Li populated in the electron capture decay of 7Be. The result (?Pt ? ?A1)/?0 = (?0.17 ? 0.13)% is obtained. It is smaller than the theoretical estimate from the TB-LMTO calculation (0.38%). This is quite different from our previous study which showed a larger decay rate variation ((0.8 ? 0.2)%) than the TB-LMTO calculation (0.30%) of 7Be in palladium and gold. It is suggested that the effective quasi-free electron density near the implanted ions in different metal host materials may play an important role in 7Be EC decay rate variation in addition to the electronic affinity and crystal structure of different host materials.

We employ a sample of cold 87Rb atoms in a magneto-optical trap to study the impulse responses and spatial characters of backward conjugate waves in a four-wave mixing process. We measure the slow and superluminal group velocities of backward conjugate waves, and find the sensitive variation of the spatial mode of backward waves with the probe-pump detuning and the dependence of the reflectance on the magnetic field, while the trapping magnetic field exists.

We numerically simulate the dynamical behavior of BEC in one-dimensional incommensurable optical lattice by split-step Fourier method in a time-dependent one-dimensional Gross—Pitaevskii equation. It is indicated that the atom-atom interaction will weaken the localization and broaden the wave function, and it will destroy the adiabaticity of the ramped loading process in both single lattice and incommensurate lattice due to the broadening effect. A band structure model can interpret the difference of the adiabatic condition with non-interacting BEC in these optical lattices.

We have measured the change of fluorescence from cold 87Rb atoms after magnetic field of the magneto-optic trap is turn off. A rise in fluorescence within several tens of milliseconds was observed. Analyzing this phenomenon in connection with the experimental conditions, we found that incoherent pumping field due to radiation trapping in the high density cold-atom cloud was the reason of fluorescence weakening under tight confinement by the magneto-optic trap. We have also performed a simple numerical simulation, which indicated that the calculations agree with experimental results only when the effect of frequency redistribution of scattered light is taken into account.

A rubidium double magneto-optical trap(MOT) system for Bose-Einstein condensation experiments has been set up. A slow atomic beam has been obtained with a low-velocity intense source (LVIS) and used to transfer atoms into an ultra-high-vacuum (UHV) MOT. By maintaining a pressure difference of 3 orders between LVIS-MOT and UHV-MOT, a lowest pressure of 1×10-9Pa can be achieved in UHV-MOT. The flux of the slow atomic beam is 1×109/s. About 4×108 87Rb atoms can be loaded into UHV-MOT. In this paper, maximum number of atoms captured in MOTs under two typical conditions have also been discussed.

A virtual network is defined as a logical network, in which users exhibit their access behaviors. Virtual networks rely on physical computer networks like the Internet, but have different topologies, and cause significant influence on the physical networks. In this paper, a novel two-tier model is proposed to study influences of virtual networks to Internet collective behavior. It is shown that the queue lengths of the node data packets present phase transition characteristics. Moreover, the phase transition critical point moves to the left and network performance is deteriorated. In a free flow, the nodes are independent of each other or short-range correlative. In the critical state, the nodes are long-range correlative, and there exists a higher power exponent H which means stronger long-range correlation. When the system state is on the right of critical point, virtual network behaviors make the network to present consistent long-range correlative characteristic.

Turbo Codes can approach the Shannon limit very closely with the help of its special iterative decoding algorithm. This paper establishes a nonlinear dynamic system to analyze the relationship between Turbo decoding output and the number of iterations. Here, the number of iterations is taken as the time axis, decoding output as the state variable, SNR and information bits N as system parameters. It is shown that with SNR increasing, the decoding algorithm undergoes three stages, namely the indecisive fix-point, singular region and unequivocal fix-point. Bifurcations occur during the transformation from the indecisive fix-point to the singular region. It is first proposed that fold, period doubling and Neimark-Sacker bifurcation all have the possibility to occur, depending on the value of N. In the singular region, phase trajectories may appear as period-two, period-three, quasiperiod and chaos. This paper first observed and confirmed the existence of period-three and chaos. Singular region deteriorates the performance of Turbo codes under low SNR. This paper proposes a time-delay feedback control method to stablize the fix-point. Simulation results show that this method achieves 0.1—0.3 dB improvement for Turbo codes under low SNR condition.

By evaporative cooling in QUIC trap, Bose-Einstein condensate (BEC) was achieved with 2×105 87Rb atoms in |F=2, mF=2〉 state. We have demonstrated the criterion of BEC transition by the variation of the axial size of the atoms in tight confinement, and observed phase transition from thermal atomic gases to Bose-Einstein condensate, and measured the shift of aspect ratio of BEC during free expansion, which compared with theoretical prediction.

The frequency dependence of A.C. conductance of organic solid thin films have been discussed. It is pointed out that the dependence of conductance on the square of frequency is an artifact due to the electrode contact resistance and the capacity of the film. In this paper a method of an added external resistance is proposed to evaluate the electrode contact resistance and thereby the experimentally measured frequency dependences of conductance and capacity of the film could be corrected for the effect of electrode contact resistance. In order to characterize the A.C. conductance of organic solid thin films three parameters are suggested. That is, the D.C. specific conductance σd.c. at extremely low frequencies, the exponent n in the expression σ(f)∝fn for the region of higher frequencies and the value of fx at which the straight line on the lgσ-lgf plot intersects the horizontal line σ=σd.c. For a solution cast film of poly-vinylcarbazole (PVK)-2,4,7-trinitrofluorenone (TNF) (1:0.75) charge transfer complex and an evaporated film of copper phthalocyanine (PcCu) the following results were obtained:PVK-TNF(1:0.75):σd.c.=1.9·10-16(Ω·cm)-1,n=0.96,fx=6.1·10-3Hz at 14℃, PcCu: σd.c.=1.6·10-9(Ω·cm)-1,n=1.2,fx=1·105Hz at 17℃.