Dynamic changes in multiple quantum dots-cavity coupled system

It has been demonstrated that InGaN/GaN blue light-emitting diodes (LEDs) with multiple quantum dot (MQD) were successfully fabricated by metal-organic chemical vapor deposition. We have formed nanoscale InGaN self-assembled QDs in the well layers of the active region with a typical 3-nm height and 10-nm lateral dimension. With a 20-mA DC injection current, the forward voltage was 3.1 and 3.5 V for MQD LED and conventional nitride-based multi-quantum well (MQW) LED with the same structure, respectively. It was also found that EL peak position of the MQD LED is more sensitive to the amount of injection current, as compared to the conventional MQW LEDs. (C) 2003 Elsevier B.V. All rights reserved.

Based on the recursive Green-function method together with Landauer–Büttiker formalism, the spin-dependent transport properties of electrons in a zigzag silicene nanoribbon embedding multiple rectangular quantum dots (QDs) are investigated. According to an analysis of the energy band under the periodically distributed electric field and exchange ferromagnetic field, the parallel exchange field induced by the ferromagnetic insulators eliminates the spin degeneracy, which leads to spin-polarized transport in the proposed structure. By tuning a periodic electric field, we found the relationship between the number of QDs and the splitting peak for conductance in the anti-parallel exchange field. We discover the population of electrons near QDs by calculating the local density of states. The effect of the geometry of periodic QDs on the shift of resonance peak is evaluated. The spin polarization is further explored for various configurations of electric field and exchange field in order to manipulate the spin filtering more effectively. The results provide an avenue to design a controllable spin bandpass filter with the modulation of electric field and exchange field.

Respiratory infectious diseases spread rapidly and have a wide range of impacts, posing a serious threat to public health security. The development of a sensitive, accurate, and rapid detection method for respiratory viruses is crucial for disease prevention and control. However, existing methods are inadequate in satisfying the demand for accurate and convenient detection simultaneously. Therefore, an ultrasensitive point-of-care testing (POCT) platform based on a multiple aptamer recognition-based quantum dot lateral flow immunoassay (MARQ-LFIA) was developed in this work. This platform consisted of multiple high-affinity aptamers for recognizing different sites on a respiratory infectious virus protein, enhancing the efficiency of virus identification in complex environments. By combining a multiple aptamer recognition strategy with quantum dot fluorescent technique to construct LFIA test strips and pairing them with a high-gain portable fluorescence reader, excellent detection sensitivity and specificity were achieved in the case of coronavirus disease 2019 (COVID-19). The limits of detection were 1.427 pg mL-1 and 1643 U mL-1 towards the nucleocapsid protein and inactivated viruses, respectively, indicating that MARQ-LFIA improved detection sensitivity compared to reported methods. More critically, by testing thirty COVID-19 positive and twenty negative patient samples, the positive detection rate increased from 55.17% to 86.67% compared with commercially similar products. The universality of MARQ-LFIA was also investigated for diagnosing influenza B. We believe that MARQ-LFIA can be a promising POCT tool with potential applications in the areas of public health for the growing demand for precision diagnosis and treatment.

We demonstrate multiple wavelength InGaAs quantum dot lasers using ion implantation induced intermixing. Proton implantation, followed by annealing is used to create differential interdiffusion in the active region of the devices. The characteristics (lasing-spectra, threshold currents and slope efficiencies) of the multi-wavelength devices are compared to those of as-grown devices and the differences are explained in terms of altered energy level spacing in the annealed quantum dots.

A superluminescent diode (SLD) using J-shaped ridge waveguide and chirped multiple InAs quantum dots (QDs) with three different energy bandgap wavelengths, which are controlled by QD size, is demonstrated. The fabricated QD SLDs exhibit high continuous wave output power of 32 mW and wide spectral bandwidth up to 98 nm, covering the range 1084–1182 nm.

The optical absorbance spectra of the intersubband transition in 3 MeV proton irradiated In0.3Ga0.7As∕GaAs multiple quantum dot samples, cut from the same wafer, were investigated as a function of irradiation dose. The intensity of the intersubband transition is observed to decrease as the irradiation dose is increased. The behavior of the intersubband transition in irradiated In0.3Ga0.7As∕GaAs multiple quantum dot samples is compared to those of intersubband transitions in irradiated GaAs∕AlGaAs and InGaAs∕InAlAs multiple quantum well samples. The intersubband transition absorbance spectrum was completely depleted in a multiple quantum dot sample irradiated with 5×1014cm−2. Post-irradiation thermal annealing was performed on the latter sample where thermal annealing recovery of the depleted intersubband transition was not observed. Instead, a broadband with a peak at 5μm is observed after annealing the sample at 500 °C for 15 min. The absence of the broadband in an unirradiated sample that was subject to the same annealing conditions suggests that this band may be related to irradiation-induced defects.

The heat current through multiple semiconductor quantum dots embedded in an insulator matrix connected with electrodes is investigated in the framework of Green's function technique. The electrical conductance, thermal conductance, thermal power and figure of merit of a system are calculated and analyzed. Although the interdot as well as intradot Coulomb interactions significantly suppress the figure of merit, the effect of electron Coulomb interactions on ZT can be neglected when the electron Coulomb interactions are ten times larger than the thermal temperature. The temperature-dependent Lorenz number shows a violation of the Wiedemann–Franz law.

A novel approach of blind constant modulus algorithm (CMA) for single carrier frequency domain equalization is proposed to solve the application of CMA implemented in frequency domain, based on the constant modulus property from frequency domain to time domain. It is illustrated that this method has lower complexity than time-domain subspace algorithm has in broad wireless systems. And compared with the frequency-domain algorithm in [5], the complexity of the new idea is greatly reduced as well. In this research, the transformation of constant modulus algorithm from time domain to frequency domain is obtained under the assumption that the source signal amplitude remains 1. Therefore, the validity of equation (8) results in the conclusion that the performance of symbol error of the method would not be influenced by the transformation from time domain to frequency domain. Simulation results demonstrate it.

Extracting Business Cycles using Semi-Parametric Time-Varying Spectra with Applications to US Macroeconomic Time Series

Calcium-dependent changes in the internal dynamics and average structures of the opposing globular domains of calmodulin (CaM), as well as their relative spatial arrangement, contribute to the productive association between CaM and a range of different target proteins, affecting their functional activation. To identify dynamic structural changes involving individual alpha-helical elements and their modulation by calcium activation, we have used site-directed mutagenesis to engineer a tetracysteine binding motif within helix A near the amino terminus of calmodulin (CaM), permitting the selective and rigid attachment of the fluorescent probe 4',5'-bis(1,3,2-dithioarsolan-2-yl)fluorescein (FlAsH) with full retention of function. The rigid tetracoordinate linkage of FlAsH to CaM, in conjunction with frequency domain fluorescence anisotropy measurements, allows assessment of dynamic changes associated with calcium activation without interference from independent probe motion. Taking advantage of the large fluorescence enhancement associated with binding of FlAsH to CaM, we determined rates of binding of FlAsH to apo-CaM and calcium-activated CaM to be 2800 +/- 80 and 310 +/- 10 M(-)(1) s(-)(1), respectively. There is no difference in the solvent accessibility of the bound FlAsH irrespective of calcium binding to CaM. Thus, given that FlAsH selectively labels disordered structures, the large difference in rates of FlAsH binding indicates that calcium binding stabilizes helix A. Frequency domain anisotropy measurements of bound FlAsH indicate that prior to calcium activation, helix A undergoes large amplitude nanosecond motions. Following calcium activation, helix A becomes immobile, and structurally coupled to the overall rotation of CaM. We discuss these results in the context of a model that suggests stabilization of helix A relative to other domain elements in the CaM structure is critical to defining high-affinity binding clefts, and in promoting specific and ordered binding of the opposing lobes of CaM to target proteins.

A CMOS compatible interference-based Mach-Zehnder modulator with each arm comprising a metal-insulator-silicon-insulator-metal structure and a simpler, single-arm variant is considered for electro-optic and electroabsorption modulation, respectively, using finite-element electromagnetic simulations. In the calculation of electron density profiles in bias-induced accumulation layers, the size-quantization effects at oxide-silicon interfaces are considered. These are then used to find the complex refractive index profiles across the structure, in its biased and unbiased states, and eventually the modulator insertion loss and extinction ratio, as they depend on various structural parameters. Furthermore, an alternative modulator, comprising a metalized stub filled with SiGe/Ge multiple quantum wells or quantum dots in a silicon matrix, coupled to a dielectric waveguide structure is also investigated using 3-D finite-element simulations. The principle behind its modulation is the change of electromagnetic field profile after the stub, relative to the incoming mode, which happens when the absorption of the stub material varies. This affects the field coupling into a single-mode output waveguide, resulting in a controllable transmission.

Objective: Quantitative measurement of the dynamic changes in autonomic nervous system (ANS) during and after exercise has great significance in clinical, sports training and other fields. A consecutive ultra-short-term (30 s, UST) heart rate variability (HRV) method was proposed to track the exercise-induced autonomic control of heart rate (HR). Approach: Twenty-three healthy young men participated in the study. The first four stages of the Modified Bruce Protocol (S0–S3) were performed. Six HRV indices, i.e. HF (power of high frequency ranged from 0.15 to 0.4 Hz), LF (power of low frequency ranged from 0.04 to 0.15 Hz), LF/HF, SD1 and SD2 of Poincaré plot, and SD2/SD1, over 30 s were calculated every 5 s over 3 min RR time series during, as well as after, exercise. Main results: The results showed that during exercise, SD1, SD2, HF and LF dropped down quickly and tended to stabilize. Particularly, SD1 and HF showed a slight upward trend in the lower three stages while the declining time of SD2 in S3 lasted longer than the other stages. SD2/SD1 increased rapidly first and then decreased slowly. The values of SD2/SD1 in S3 remained higher than those in the other stages. After exercise, SD1, SD2, HF and LF kept increasing first and then declined slowly or fluctuated with decaying amplitudes. SD2/SD1 increased initially, then decreased and fluctuated slightly. Significance: Compared with the indices in frequency domain, the Poincaré indices were more sensitive and accurate in UST measurement of ANS during exercise. The results demonstrated that the UST method could characterize the dynamic changing tendency of ANS during and after exercise and quantify the differences of changes in ANS induced by exercise with different intensities. In particular, the vagal branch functioned dominantly in controlling HR in S0 but the effect of the sympathetic branch on HR enhanced with the increase of exercise intensity. In addition, the transient changes of ANS related with the sudden onset of exercise could also be reflected, despite perhaps being limited by the computation window width to some extent. Thus, the consecutive UST Poincaré indices could provide a feasible and simple method to measure quantitatively the exercise-induced dynamic changes in ANS.

Raman spectra of Er:LiNbO3 crystal and Ti-diffusedEr:LiNbO3 strip waveguide, in which the Li/Nb ratio was altered using a vapor-phase equilibration (VPE) technique, were measured at room temperature in the wave-number range 50–3500 cm-1. Both 488 and 514.5 nm radiations were used to excite Raman scattering, A1(TO) and E(TO) modes were recorded at backward scattering geometry. The results indicated that the lattice vibrational spectra of the as-grown Er:LiNbO3 are almost the same as those of pure LiNbO3 except for the little shift of the peak position and the change of relative intensity of some peaks. In comparison with the spectra of as-grown Er:LiNbO3 crystal the vapor-phase equilibrated Er:LiNbO3 and Er:Ti:LiNbO3 crystals in the lattice vibrational region exhibit the following features: firstly, Raman peaks become narrow, indicating that the VPE process has brought Er:LiNbO3 and Er:Ti:LiNbO3 crystals closer to a stoichiometric composition; secondly, relative intensity of some peaks varies with the VPE time; and finally, slight blue shifting in peak position was observed. Some of these features were correlated with the NbO6 octahedra and with the site distribution of the doped Er ions. In addition, green fluorescence peaks and/or bands associated with the electron transitions 2H11/2?4I15/2 and 4S3/2?4I15/2 of the doped Er3+ were also observed. For 488 nm excitation they appear in the wavenumber range of 1200–3000 cm-1 and are well separated from lattice vibrational region; for 514.5 nm excitation, however, these fluorescence peaks shift towards the low wavenumber region and overlap partially with the lattice vibrational spectra.

The synthesis, and structural and retrostructural analysis of a library of second-generation conical dendrons that self-assemble into spherical supramolecular dendrimers is reported. This library consists of amphiphilic dendrons with n-alkyl groups containing from 4 to 16 carbon atoms. The dendrons containing 6 to 16 carbon atoms in their n-alkyl groups self-assemble into spherical supramolecular dendrimers that self-organize in a Pm3n cubic lattice. The structural and retrostructural analysis of the Pm3n lattices generated from the supramolecular dendrimers demonstrated that the volume of the aromatic core of the spherical dendrimers is not dependent on the number of carbon atoms from their alkyl groups. This result facilitated the calculation of the average values of the absolute electron density of the aliphatic and aromatic domains of the spherical supramolecular dendrimers. The relative intensity of the higher order diffraction peaks of the Pm3n lattice increases as the volume of the aliphatic part of the sphere mediated by the number of carbon atoms in the n-alkyl groups decreases. This study demonstrates the maximum increase of the relative intensity of the higher order diffraction peaks of the Pm3n lattice generated from non-hollow supramolecular dendrimers.

Thermoluminescence data, obtained from majolica pottery after irradiation in the laboratory with gamma rays, were studied using the principal components technique to determine if the places of manufacture of this ceramic are differentiated one from another. A total of ten provenances in Holland, Spain and Italy was established by principal components. Six variables were used for the statistical analysis: the three glow-peaks positions, the relative intensity of the second peak to the first peak, the relative intensity of the third peak to the first peak, and the area under the glow curve.The precision for these parameters was about ± 5%, but the precision of the variables for a suite of standards was much higher. In addition, two groups of sherds collected in Latin America, and previously assigned to the provenances of Cataluna and Sevilla (Spain) by artistic criteria, were investigated in this study. All six samples of Cataluna agreed well with their previous assignment of provenance, but several of the samples assigned previously to Sevilla were not related unambiguously to this provenance, although they were with certainty excluded from other provenances.