Asymmetric Peak Research Articles

Structural, dielectric, and electrical study of bismuth ferrite-lithium vanadate

The composite, BiFeO3-LiVO3 was synthesized through a solid-state reaction technique. The X-ray diffraction (XRD) confirmed the formation of the tetragonal structure at room temperature. The dielectric constant and dielectric loss increased with the rise in temperature. The Nyquist plot projected the contribution of bulk effect and a slight indication of grain boundary effect. The presence of a temperature-dependent relaxation process occurred in the material. Electrical modulus confirmed the non-Debye type relaxation and indicated the asymmetric peak broadening for the spread of relaxation time. The activation energies were calculated from the ac conductivity by linear fitting. The fitted Jonscher power law was very close which implied a similar type of charge carrier which exists in the conduction mechanism for the system. Thermistor parameters were evaluated using the grain resistance for different temperatures.

Study of the structure and optoelectronic properties of Cu2Ge(SexS1-x)3 microcrystalline powders

In this study, the Cu2Ge(SexS1-x)3 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) microcrystalline powders were synthesized from elemental precursors in the liquid phase of lithium iodide (LiI) flux material in evacuated quartz ampoules. The crystal structure and lattice parameters of the Cu2Ge(SexS1-x)3 (CGSSe) were determined by X-ray diffraction measurement. Results showed the crystal structure of CGSSe transfers from monoclinic to orthorhombic with increasing the Se content in the powders, which occurs between 0.2 < x < 0.4. Raman spectroscopy showed that all sulfide related peaks in the solid solutions tend to shift toward smaller wavenumbers and the relative intensity of these peaks was decreasing and selenide related peaks shifted toward higher wavenumbers and decreased. Radiative recombination processes in CGSSe microcrystalline powders were studied by using photoluminescence spectroscopy (PL). All spectra of CGSSe were composed of two asymmetric PL peaks. Peak positions of these bands (#1 and #2) as a function of Se/S concentration show nearly linear dependence with a slope about -0.8 eV. Almost the same slope was detected for band gap values (Eg) determined from room temperature external quantum efficiency measurements. Therefore, the peak position shift with x is related to Eg shift for both PL peaks. Both peaks are related to donor-acceptor pair recombination.A best performing solar cell was fabricated by using Cu2Ge(SexS1-x)3x = 0.6 powder crystals as absorber material, exhibiting an open-circuit voltage of 537 mV, current density of 15.8 mA/cm2, fill factor of 37.2% and a conversion efficiency of 3.16%.

Polarity Determination in EBSD Patterns Using the Hough Transformation

Abstract Currently, the automated electron backscatter diffraction (EBSD) technique only allows the differentiation of the Laue groups based on an electron backscatter pattern (EBSP). This article shows that information concerning the lattice plane polarity is not only stored in the EBSP, but also in the Hough transformed EBSP where it can be easily accessed for automated evaluation. Polar Kikuchi bands lead to asymmetric peaks during the Hough transformation that are dependent on the atomic number difference of the involved atoms. The effect can be strong enough to be detected when evaluating the intensities of the regular excess and deficiency lines. Polarity detection from the Hough transformation of an EBSP cannot only enhance the utility of the EBSD technique and expand the information gained from it, but also illustrates a path toward automated polarity determination during EBSD scans.

Electrical characterization of magnetic domain wall via distinctive hysteresis and magnetoresistance

We present a powerful method to detect the magnetic domain wall (DW), based on the intrinsic characteristic of anomalous Hall effect (AHE), by employing magneto-transport measurement on adevice of double Hall cross geometry. We demonstrate that DW propagation manifests its behavior in the distinctive AHE hysteresis and longitudinal magnetoresistance (MR). AsDW propagates along the Hall channel, the AHE hysteresis varies considerably depending on the voltage-pickup position while MR displays abnormal asymmetric peaks. Utilizing this direct correlation, we formulate simple models for AHE switching path and MR peak so that they can be efficiently used to characterize DW behavior. It is revealed that at the nucleation stage, the DW velocity grows exponentially with respect to the field. Additionally, the effects of magnetic pinning sites are taken into account and shed light on. The proposed method could be potentially employed for the detection of DW behavior in nanoscale devices.

Wide spectral range optical characterization of yttrium aluminum garnet (YAG) single crystal by the universal dispersion model

Pure YAG single crystal was optically characterized in the wide spectral range (from far IR to vacuum UV) by applying the universal dispersion model. Data obtained from a broad range of characterization instruments and methods was simultaneously processed using least-square method and the result were compared with literature findings. The universal dispersion model describes individual elementary electron and phonon excitations in materials as separate contributions. For the first time recorded, an asymmetric Voigt peak approximation was used for modeling the contribution of one-phonon absorption in crystalline material. The optical constants are presented both graphically and in detailed dispersion parameters sets.

Resolving of Overlapping Asymmetrical Chromatographic Peaks by Using Wavelet-Transform and Gram-Charlier Peak Model

The paper describes a method for resolving overlapping asymmetric peaks that make up a chromatogram. The presented method uses the Gram-Charlier model in the form of the first three terms of the Gram-Charlier series as a basis. Using the wavelet transform, the parameters of this model are determined, which is used to describe a single or overlapping chromatographic peak. Hermitian wavelets of the first four orders are used in the computation of the wavelet transform. To speed up the computation of multiple wavelet transforms, the possibility of coding a signal using the Chebyshev-Hermite functions is considered in order to further restore the set of wavelet transforms simultaneously. According to the presented method, the parameters of the peaks are determined by analytical expressions without using the numerical approximation of the chromatogram by the peak model, which avoids the disadvantages of the numerical approach. The resulting method is used to resolve overlapping asymmetric peaks. The advantage of the method over others is shown by calculating the area of each of the resolved peaks.

Formation of Fano resonance in double quantum dot system

Transient electron dynamics and the Fano resonance formation over time in transport through a two quantum dot system in a T-shape geometry (2QD-T) are analyzed for free electrons. Time evolution of the transport characteristics are different for a weak and a strong inter-dot coupling with respect to the dot-electrode coupling. When the dot–dot coupling is weak, we find that transport dynamics is governed by two channel tunneling processes with two different relaxation times and buildup of the Fano resonance is developed much slower, with the longer relaxation time. In the opposite limit, the transmission evolves with a single relaxation time, from the single peak resonance structure into the structure with two asymmetric peaks. One observes large dot-electrode charge oscillations, which can temporarily change direction of transient currents. We find also that the time evolution of entanglement is different in both coupling regimes; in particular rapid Rabi oscillations caused by coherent electron transfer between the 2QD states can be seen for the strong dot–dot coupling.

Concept neurons in the human medial temporal lobe flexibly represent abstract relations between concepts

Concept neurons in the medial temporal lobe respond to semantic features of presented stimuli. Analyzing 61 concept neurons recorded from twelve patients who underwent surgery to treat epilepsy, we show that firing patterns of concept neurons encode relations between concepts during a picture comparison task. Thirty-three of these responded to non-preferred stimuli with a delayed but well-defined onset whenever the task required a comparison to a response-eliciting concept, but not otherwise. Supporting recent theories of working memory, concept neurons increased firing whenever attention was directed towards this concept and could be reactivated after complete activity silence. Population cross-correlations of pairs of concept neurons exhibited order-dependent asymmetric peaks specifically when their response-eliciting concepts were to be compared. Our data are consistent with synaptic mechanisms that support reinstatement of concepts and their relations after activity silence, flexibly induced through task-specific sequential activation. This way arbitrary contents of experience could become interconnected in both working and long-term memory.

Spectroscopic signatures of gate-controlled superconducting phases

We investigate the tunneling conductance of superconductor-insulator-normal metal (SIN) and superconductor-insulator-superconductor (SIS) heterostructures with one superconducting side of the junction that is electrically driven and can exhibit $\pi$-pairing through a modification of the surface inversion asymmetric couplings. In SIN tunneling we find that the variation of the electrically driven interactions generally brings an increase of quasi-particles in the gap due to orbitally polarized depaired states, irrespective of the inter-band phase rearrangement. The peak of SIN conductance at the gap edge varies with a trend that depends both on the strength of the surface interactions as well as on the character of the gate-induced superconducting state. While this shift can be also associated with thermal effects in the SIN configuration, for the SIS geometry at low temperature the electric field does not yield the characteristic matching peak at voltages related with the difference between the gaps of the superconducting electrodes. This observation sets out a distinctive mark for spectroscopically distinguishing the thermal population effects from the quantum gate-driven signatures. In SIS the electrostatic gating yields a variety of features with asymmetric peaks and broadening of the conductance spectral weight. These findings indicate general qualitative trends for both SIN and SIS tunneling spectroscopy which could serve to evaluate the impact of gate-control on superconductors and the occurrence of non-centrosymmetric orbital antiphase pairing.

Ageing mediated silicon suboxide interlayer growth in porous silicon: p-Si heterostructured metal-semiconductor-metal device for enhanced UV-visible photodetection

Present work reports development of silicon oxide within metal-semiconductor-metal Schottky contact photodiode from Al: porous silicon (PS):p-Si heterojunction mediated by ageing to investigate its effect on its light sensing property. Oxide layer formation is achieved by auto-ageing. Formation of silicon suboxide (SiOx, x≤2) layers on PS:p-Si surface in aged heterostructure is confirmed from elemental energy dispersive X-ray analyses. X-ray diffraction patterns of as-prepared and aged heterostructure show broadening of strong (400) reflection peak compared to that of bare p-Si one due to nanocrystallite formation. PS crystallite size is found to be ∼45 nm. Raman spectra of as-prepared and aged heterostructure for an excitation wavelength of 633 nm show intense, broad and asymmetric peak at 519 cm−1 along with c-Si related peak at 522 cm−1. Photoluminescence spectra of as-prepared heterostructure shows red shift of ∼15 nm of the strong characteristic emission peak from 590 to 605 nm for increasing excitation wavelengths in the range of 275–400 nm. Aged heterostructure for fixed excitation wavelength of 275 nm shows strong characteristic emission peak at 590 nm along with weak emission peaks at 470 and 500 nm related to defect levels present in SiOx layers developed on PS surface. Ideality factor and Schottky barrier height for the aged device show enhancement of 12.4 and 0.15 eV respectively over the as-prepared one. The enhancement in maximum photo to dark current ratio of the aged device is 4.8, whereas maximum values of responsivity and external quantum efficiency improves up to 0.47 AW−1 and 145 % respectively for illumination wavelength of 400 nm for bias of -3 V. In contrast, however, the response and recovery times remain unchanged at 0.16 and 0.24 s respectively. These results suggest application potential of the device in the optoelectronic field particularly as an efficient ultraviolet-visible photo-detector.

Microscopic self-consistent description of induced fission: Dynamical pairing degree of freedom

The role of dynamical pairing in induced fission dynamics is investigated using the time-dependent generator coordinate method in the Gaussian overlap approximation, based on the microscopic framework of nuclear energy density functionals. A calculation of fragment charge yields for induced fission of $^{228}$Th is performed in a three-dimensional space of collective coordinates that, in addition to the axial quadrupole and octupole intrinsic deformations of the nuclear density, also includes an isoscalar pairing degree of freedom. It is shown that the inclusion of dynamical pairing has a pronounced effect on the collective inertia, the collective flux through the scission hyper-surface, and the resulting fission yields, reducing the asymmetric peaks and enhancing the contribution of symmetric fission, in better agreement with the empirical trend.

Enumerating symmetric peaks in non-decreasing Dyck paths

Local maxima and minima of a Dyck path are called peaks and valleys, respectively. A Dyck path is non-decreasing if the heights (y-coordinates) of its valleys increase from left to right. A peak is symmetric if it is surrounded by two valleys (or endpoints of the path) at the same height. In this paper we give multivariate generating functions, recurrence relations, and closed formulas to count the number of symmetric and asymmetric peaks in non-decreasing Dyck paths. Finally, we use Riordan arrays to study weakly symmetric peaks, namely those for which the valley preceding the peak is at least as high as the valley following it.

Investigations on the effect of swift heavy silicon ion irradiation on hydroxyapatite

The effect of swift heavy silicon ion irradiation on hydroxyapatite prepared by hydrothermal technique was analyzed. The physical and biological properties were studied using G1XRD, Micro-Raman, photoluminescence, AFM, SEM, EDX, in vitro bioactivity, antimicrobial activity and drug release. When compared with pristine the crystallinity increases with an increase in fluence. Slight reduction in crystallinity was noted for irradiated samples at higher fluence (1×1013 and 1×1014 ions/cm2) than lower fluence (1×1012 ions/cm2). After irradiation the υ4 O-P-O asymmetric bending mode peak at 583 cm−1 disappeared. The PL intensity increases with an increase in fluence and it had become narrow and showed red shift. This suggests the material could find application as phosphors. The enhancement in band gap was attained for irradiated samples than Hpris (5.38–5.5 eV). AFM studies revealed the enhancement of roughness, particle size and pores on irradiation. SEM exposed the creation of pores along with an increase in porosity (2 µm to 30 µm). Formation of platy crystals was noted for 1×1013 ions/cm2 sample. In vitro bioactivity results with the formation of spherical (2 µm) apatite deposition along with the presence of interconnected pores (2–10 µm) which could enhance osteointegration and osteoconduction. In addition, Ca/P ratio was found to increase after soaking in SBF. Initial burst release followed by sustained release was obtained upto 45 h. Therefore it could assist in the treatment of bone and joint infection. Hence, SHI had improved the material to be used in biomedical field as an implant due to its enhanced properties such as crystallinity, pore size, surface roughness, PL intensity, antimicrobial activity, drug release and bioactivity.

Coulombic effects on resolution of ion mobility spectrometry and its application in online qualitative analysis

Ion mobility spectrometry is an important gas analysis method used in the rapid detection field. However, due to a lacking of explicit mathematical model of ion peak, it is difficult to extract characteristic analyte peaks from a spectrum containing overlapping peaks to achieve online qualitative analysis. Here, we present an asymmetric peak model for processing ion mobility peaks. For the asymmetric peak model, the key is to accurately estimate the standard deviation of the peak model and the fitting function of the tailing edge. We focused on the Coulombic effects on resolution of ion mobility spectrometry based on a new hypothesis of ion cloud shape and derived a formula for calculating the standard deviation taking the initial pulse width, diffusion and Coulomb repulsion factors into account. The proposed asymmetric peak model combines the advantages of optimal physical and chemical interpretation and explicit mathematical meaning. A fast decomposition method based on the peak model was developed to decompose overlapping peaks. Two overlapping simulated data sets and one real data set (a mixture of acetone and methyl salicylate) were used to test the method. The results indicated that our proposed method successfully decomposed the overlapping spectrum into individual peaks and performed markedly better than other three available methods in terms of the execution time. The proposed method meets the requirements for online qualitative analysis.

Ionic liquid-assisted ultrasonic exfoliation of phosphorene nanocomposite with single walled carbon nanohorn as nanozyme sensor for derivative voltammetric smart analysis of 5-hydroxytryptamine

Ultrasonic-assisted liquid-phase exfoliation is one of high-efficiency strategies for preparing two-dimensional (2D) materials. Herein, we report a facile and green synthesis of the phosphorene (BP) obtained from bulk black phosphorus crystal in the ionic liquid (IL) 1-ethyl-3-methylimidazoliumtetrafluoroborate ([EMIm]BF4) through ultrasonic-assisted liquid-phase exfoliation under the continuous nitrogen atmosphere. To gain more insight, the morphology and composition of the as-prepared BP were characterized. The prepared BP showed satisfactory stability in ambient condition containing oxygen and water. In the following, single walled carbon nanohorn (SWCNH) was selected to enhance electrocatalytic capacity and endow oxidase-like (nanozyme) characteristics, which was further applied for electrochemical sensing of 5-hydroxytryptamine (5-HT). Derivative techniques were employed for treating voltammograms to obtain sharper and narrower voltammetric peak, transform asymmetric peak into much more symmetrical peak, reduce background interference, eliminate personal error and directly read the accurate value. Machine learning (ML) model based on artificial neural network (ANN) algorithm as an artificial intelligence approach is adopted to establish smart sensing system via the relationship between concentrations and currents in comparison with traditional linear regression model. The BP-IL-SWCNH nanozyme sensor displayed excellent electrocatalytic ability for second-order derivative voltammetric smart analysis of 5-HT range from 0.3 to 115 µM under optimal conditions.

Transformations of actinides fission product yields due to post-scission emission of nuclear particles: 232Th

The “many ensembles” method was proposed to investigate the influence of nuclear particles’ post-scission emission on mass and charge distributions of fission products. The post-scission approximation was used: each of these ensembles consists of the fission fragments after emission of chains of different lengths, both the beta (β±) particles and neutrons. The theory allows one to find the most probable two-fragment clusters of fission products and study their evolution after the post-scission emission of nuclear particles. The isotope 232Th was chosen as an example, the fission fragments of which have been intensively studied experimentally. It is shown that the post-scission emission of nuclear particles eventually leads to the convergence of the asymmetric peaks, which looks like enhanced symmetric fission mode over the asymmetric mode for fission product yields. A comparison of the theoretical results and experimental data for the 232Th fission fragments indicates their satisfactory matching.

MOA-2006-BLG-074: Recognizing Xallarap Contaminants in Planetary Microlensing

Abstract MOA-2006-BLG-074 was selected as one of the most promising planetary candidates in a retrospective analysis of the MOA collaboration: its asymmetric high-magnification peak can be perfectly explained by a source passing across a central caustic deformed by a small planet. However, after a detailed analysis of the residuals, we have realized that a single lens and a source orbiting with a faint companion provides a more satisfactory explanation for all the observed deviations from a Paczynski curve and the only physically acceptable interpretation. Indeed the orbital motion of the source is constrained enough to allow a very good characterization of the binary source from the microlensing light curve. The case of MOA-2006-BLG-074 suggests that the so-called xallarap effect must be taken seriously in any attempts to obtain accurate planetary demographics from microlensing surveys.

Microstructure and defect gradients in DC and AC flash sintered ZnO

In this study, the microstructure and defect characteristics of flash sintering under direct current (DC) and alternating current (AC) were investigated and compared for the ZnO system. DC flash sintering resulted in grain size and porosity gradients within the sample, whereas AC flash sintering produced a sample with homogeneous and fine grain size. Raman spectroscopy revealed asymmetric peaks correlated to the lattice disorder. Using the Breit-Wigner-Fano model, the asymmetric peak fitting revealed redistribution of defects within the DC flash sintered ZnO, while the AC flash sintered ZnO had a comparable defect concentration to conventionally sintered ZnO.

Refractive index sensing based on multiple Fano resonances in a plasmonic defective ring-cavity system

A type of coupled plasmonic resonant system using a metal–insulator -metal (MIM) waveguide is proposed and investigated for generating multiple Fano resonances in this paper. The multi-mode interference coupled-mode theory (MICMT) is mainly employed to analyze the system theoretically, and these results agree well with the results numerically obtained with the finite-difference time-domain (FDTD) method. In this proposed system, multiple asymmetrical Fano-resonant peaks are achieved in the spectra by employing two waveguides separated by a metallic baffle and coupled with a defective ring cavity at one side of the MIM waveguide. According to standing wave theory, we can easily manipulate these Fano peaks by adjusting the main parameters of the defective ring cavity, such as the radius and the notch range. As a result, the structures with three and nine ultra-sharp Fano resonances are obtained and discussed, and the sensitivities and figures of merit (FOMs) are also represented. Furthermore, the phase shifts and the group delays that are induced by the mode interactions are investigated. The designed structures show great potential for the high integrated optical circuits of chip-scale optical sensors, slow light devices or splitters.

A creep model of pile-frozen soil interface considering damage effect and ice effect

An important source of time-dependent pile deformation is creep behavior at pile-frozen soil interface in permafrost regions. A creep model for pile-frozen soil/ice interfaces was proposed based on a series of multistage creep tests. The test results show that the creep behavior of the pile-frozen soil/ice interfaces is easily observed at a steady rate larger than 0 even at a small load level, which increases as the increase of load level. The elastic shear modulus increases at a slowing down rate with the increase of load level. The interfaces are mainly strengthened during the creep process until the occurrence of the accelerating creep, which is more obvious for frozen soil. A large amount of ice in frozen soil can enhance the creep rate and reduce the carrying capacity of pile foundation. The viscosity [Formula: see text] reflecting steady creep rate, the instantaneous shear modulus [Formula: see text], and the critical stress [Formula: see text] required for describing damage behaviors distribute in the form of Bigaussian asymmetric peak function with ice content. The Burger model considering ice effect and damage effect is feasible to describe the entire creep behavior of the interfaces. Sensitivity analysis reveals that ice content in frozen soil has a marked influence on pile deformation, a cooling method can probably adjust the creep deformation of pile in frozen soil with high ice content.