Large Amplification Research Articles

Transformation of amplification and attenuation through PT-symmetry structure under modulation of resonators

In order to achieve the transformation of amplification and attenuation with one device, we design a parity-time—symmetry structure through resonator modulation. We use the transfer matrix method to study the optical properties of the designed structure. The structure performs amplification along one incidence direction, and attenuation by absorption along the other incidence direction. The contrast of amplification and attenuation, and the corresponding bandwidth can be modulated through the structure parameters. An optimized structure is obtained with the transformation of large amplification and perfect absorption.

Quantitative View on the Processes Governing the Upscale Error Growth up to the Planetary Scale Using a Stochastic Convection Scheme

Abstract Two diagnostics based on potential vorticity and the envelope of Rossby waves are used to investigate upscale error growth from a dynamical perspective. The diagnostics are applied to several cases of global, real-case ensemble simulations, in which the only difference between the ensemble members lies in the random seed of the stochastic convection scheme. Based on a tendency equation for the enstrophy error, the relative importance of individual processes to enstrophy-error growth near the tropopause is quantified. After the enstrophy error is saturated on the synoptic scale, the envelope diagnostic is used to investigate error growth up to the planetary scale. The diagnostics reveal distinct stages of the error growth: in the first 12 h, error growth is dominated by differences in the convection scheme. Differences in the upper-tropospheric divergent wind then project these diabatic errors into the tropopause region (day 0.5–2). The subsequent error growth (day 2–14.5) is governed by differences in the nonlinear near-tropopause dynamics. A fourth stage of the error growth is found up to 18 days when the envelope diagnostic indicates error growth from the synoptic up to the planetary scale. Previous ideas of the multiscale nature of upscale error growth are confirmed in general. However, a novel interpretation of the governing processes is provided. The insight obtained into the dynamics of upscale error growth may help to design representations of uncertainty in operational forecast models and to identify atmospheric conditions that are intrinsically prone to large error amplification.

Site effects in Mexico City basin: Past and present

Due to the unique subsoil conditions prevailing in the Mexico City basin, seismic risk has been strongly correlated to site effects. Thus, during the Mw 8.1 09/19/1985 subduction fault earthquake, and its strong aftershock Mw 7.5 09/21/1985, extensive damage was observed in the area, along with the loss of thousands of lives, despite these events had an epicentral distance of around 430 km from Mexico City. The observed damage was mostly due to site affects originated by the high plastiCity clay deposits found in the basin, which lead to large amplifications, and duration elongation of the ground motions coming from the epicenter. In addition, a frequency content modification occurs, which in turn, leads to a double resonance effect between the incoming ground motions, soil deposits, and the damaged buildings. Exactly 32 years after this devastating event, the Mw 7.1 09/19/2017 normal fault earthquake, reminded us of the importance of accounting for site effects, and most importantly the need to carry out a proper characterization of basin geometry, soil profile configuration, hydraulic conditions, and maintenance-structure periodic assessments of the building stock in Mexico City. This is required to reduce uncertainties of seismic vulnerability studies for extreme-event seismic hazard scenarios. In this paper, the role of site response and seismic soil-structure interaction as key factors responsible of the observed damage in the City is revisited, through series of 3D finite difference models of typical structure-foundation-soil typologies found at the areas where most of the damage was observed, highlighting its clear impact in the final damage distribution observed around the City.

Experimental probe of weak-value amplification and geometric phase through the complex zeros of the response function

The extraordinary concept of weak value amplification has attracted considerable attention for addressing foundational questions in quantum mechanics and for metrological applications in high precision measurement of small physical parameters. Here, we experimentally demonstrate a fundamental relationship between the weak value of an observable and complex zero of the response function of a system by employing weak value amplification of spin Hall shift of a Gaussian light beam. Using this relationship, we show that arbitrarily large weak value amplification far beyond the conventional weak measurement limit can be experimentally obtained from the position of the minima of the pointer intensity profile corresponding to the real part of the complex zero of the response function. The imaginary part of the complex zero, on the other hand, is related to the spatial gradient of geometric phase of light, which in this particular scenario evolves due to the weak interaction and the pre and post selections of the polarization states. These universal relationships between the weak values and the complex zeros of the response function may provide new insights on weak measurements in a wide class of physical systems. Extremely large weak value amplification and extraction of system parameters outside the region of validity of conventional weak measurements may open up a new paradigm of weak measurement enhancing its metrological applications.

Resolvent-analysis-based design of airfoil separation control

We use resolvent analysis to design active control techniques for separated flows over a NACA 0012 airfoil. Spanwise-periodic flows over the airfoil at a chord-based Reynolds number of$23\,000$and a free-stream Mach number of$0.3$are considered at two post-stall angles of attack of$6^{\circ }$and$9^{\circ }$. Near the leading edge, localized unsteady thermal actuation is introduced in an open-loop manner with two tunable parameters of actuation frequency and spanwise wavelength. To provide physics-based guidance for the effective choice of these control input parameters, we conduct global resolvent analysis on the baseline turbulent mean flows to identify the actuation frequency and wavenumber that provide large perturbation energy amplification. The present analysis also considers the use of a temporal filter to limit the time horizon for assessing the energy amplification to extend resolvent analysis to unstable base flows. We incorporate the amplification and response mode from resolvent analysis to provide a metric that quantifies momentum mixing associated with the modal structure. This metric is compared to the results from a large number of three-dimensional large-eddy simulations of open-loop controlled flows. With the agreement between the resolvent-based metric and the enhancement of aerodynamic performance found through large-eddy simulations, we demonstrate that resolvent analysis can predict the effective range of actuation frequency as well as the global response to the actuation input. We believe that the present resolvent-based approach provides a promising path towards mean flow modification by capitalizing on the dominant modal mixing.

Ultrasensitive mushroom-like electrochemical immunosensor for probing the activity of histone acetyltransferase

A novel mushroom-like electrochemical immunoassay for the ultrasensitive detection of histone acetyltransferase activity (HAT p300) has been established on account of the new composite graphene oxide (GO) nanolayer. The immunoassay involves immobilization of substrate peptide onto Au electrode, acetylation in lysine of substrate peptide, and the interaction between acetyl group of lysine and acetyl-antibody (AbAc) of the GO nanolayer. The GO nanolayer comprises large amounts of methylene blue molecules (MB), giving rise to large signal amplification. Only in the presence of HAT p300, an obvious electrochemical signal appears and the peak linear current is proportion to the HAT p300 concentrations ranging from 0.01 to 150 nM with a detection limit of 0.0036 nM. The great enhancement on sensitivity of the proposed mushroom-like immunosensor derives from both the constructed Faraday cage and the extended outer Helmholtz plane (OHP). Further, the immunosensor with excellent sensitivity and selectivity can be applied for the HAT p300 activity detection in Hela cell lysates, serum and urine, hinting an improved and splendid analytical performance. Briefly, this stable, simple and ultrasensitive electrochemical immunoassay has considerable promise for further applications in the HATs-interrelated epigenetic studies and drug development.

An Optimum Shift-and-Weighted brightness mapping for low-illumination image restoration

ABSTRACTImages captured under low-illumination environments often impose difficulties in revealing objects of interest. An effective approach, Optimum Shift-and-Weighted Brightness Mapping, is here proposed that can optimally enhance the image for higher brightness, information content, and colour vividness. Specifically, the input-output brightness mapping is determined by a shifted spline curve and a larger amplification is allowed for low-brightness pixels. A weighting function is further applied such that high brightness pixels are preserved. The final enhanced image is obtained by inserting the extracted high frequency components from the original input to the brightness boosted image. The algorithm is adaptive to image contents where parameters are optimized using the efficient golden section search instead of relying on user specified coefficients. Experimental results, from a large set of test images, showed that better quality images could be obtained on a variety of low-illumination scenarios as compared to several recent approaches.

Non-canonical inflation and primordial black holes production

We study a mechanism for the amplification of the inflationary scalar perturbation when the inflaton field action is non-canonical, i.e. the inflaton kinetic term has a non-standard form. For such a case the speed of sound of the perturbations generated during inflation is less than one and in general changes with time. Furthermore in such models, even when the scalar field potential is negligible, diverse inflationary attractors may exist. The possible effects of a speed of sound approaching zero during some stage of inflation may lead to a large amplification for the amplitude of the scalar spectrum which, on horizon re-entry during the radiation dominated phase, can collapse and form primordial black holes (PBH) of a mass MBH∼10−15M⊙ which may constitute a large fraction of the total Dark Matter (DM) today.

Seismic Interaction between a Lined Tunnel and a Hill under Plane SV Waves by IBEM

This paper investigates the dynamic interaction between a lined tunnel and a hill under plane SV waves using the indirect boundary element method (IBEM), with the displacement and stress characteristics of the system presented in frequency domain. The IBEM has several unique advantages such as reducing calculation dimension, automatically satisfying the infinite radiation condition, etc. The numerical results indicated that the dynamic response of the tunnel–hill system is strongly dependent on incident wave characteristics, geometrical and material properties of the lined tunnel, as well as the topography of the hill. For a dimension ratio between the hill and tunnel of less than 10.0, the lined tunnel has large amplification or deamplification effect on the dynamic response of the hill. Correspondingly, the hill also greatly amplifies the displacement and stress concentration of the tunnel especially in the lower-frequency range, due to the complicated interference effect among the reflected waves and diffracted waves induced by the tunnel and hill. Also demonstrated is that the displacement and stress amplitude spectrums highly depend on the incident frequency and the space location, and there exist multiple peaks and troughs in the spectrum curve with the peaks usually appearing in the low-frequency range. Thus, for the seismic safety assessment of a hill slope or hill tunnel in practice, the dynamic interaction within the tunnel–hill system should be taken into consideration.

Weak measurement of the Goos–Hänchen shift of partially coherent light beams

Optical beam shifts are very small and challenging phenomena to measure. Weak measurement techniques have been developed to amplify and more easily measure the shifts of spatially coherent beams. We here investigate theoretically a weak measurement technique for measuring the Goos–Hanchen shift of partially spatially coherent beams. We show that the amplification factor of the technique depends on the global coherence degree of the field and on the size of the Goos–Hanchen shift experienced by the beam. Large amplification factors can be obtained for low shifts, even for very incoherent beams. But, for higher beam shifts, such as those occurring near critical incidence, the amplification factors are modest to low for beams of low coherence.

Effect of vacuum polarization on the magnetic fields around a Schwarzschild black hole

It is a well known result that the effect of vacuum polarization in gravitational fields will lead to a non-minimal coupling between gravity and electromagnetism. We investigate this phenomenon further by considering the description of static magnetic field around a Schwarzschild black hole. It is found that close to the Schwarzschild horizon the magnetic fields can be strongly modified with respect to both cases of magnetic fields on flat spacetime and magnetic fields minimally coupled on curved spacetime. Under the proper sign of the non-minimal coupling parameter, $q$, the effective fields can undergo large amplifications. Furthermore, we discuss the physical meaning of the singularities that arise in the considered problem. We conclude by discussing the potential observational effects of vacuum polarization on the magnetic fields. In the case of astrophysical black holes, depending on the value of the coupling parameter, significant modifications of the magnetic near the black hole horizons are possible -- which could be used to detect the vacuum polarization effect or at least to put constraints on the values of the coupling parameter. Moreover, we show how the considered effect directly constraints the viability of primordial black holes of sizes smaller than that of the Compton wavelength for the electron, and also impacts the distribution of magnetic fields in the early Universe.

Surface-enhanced Raman scattering of subwavelength metallic structures

Surface-enhanced Raman scattering (SERS) makes the Raman signals, as fingerprints of different vibration modes of chemical bonds, significant in practical applications. Two main mechanisms, chemical and physical, are attributed to the SERS of molecules adsorbed on metals. The physical mechanism plays a major role in SERS, which is the focus of our paper. Recent SERS systems are mostly based on dimer structures, i.e. nanoparticle pairs, of noble metals. Large amplification of electrical field occurs in the gap of a dimer structure compared with a single nanoparticle. The above gap positions are called as " hot spots” of SERS. In addition, the reproducibility and reliability of SERS substrates are also important for practical applications. Here we use periodical subwavelength metallic structures to meet such needs, and develop other kinds of electrical field enhancement mechanisms. We present the electrical field enhancement of the band-edge mode of surface plasmon polariton, gap plasmon polariton mode, as well as their coupling mode. We choose one-dimensional subwavelength metallic structures to clarify the physical mechanism. Our purpose is to develop subwavelength metallic structures with even and intensive " hot spots”, serving as ultrasensitive solid-state SERS substrates with excellent reproducibility and reliability.

Spectrally efficient single carrier 400G optical signal transmission

In this paper, the recent progress on spectrally efficient single carrier (SC) 400G optical signal transmission was summarized. By using quadrature phase shift keying (QPSK), 16 quadrature amplitude modulation (16QAM) and 64QAM, we can realize transmission distance over 10000, 6000 and 3000 km, respectively, with large area fiber and all-Raman amplification. To improve the system performance and generate high-order QAM, advanced digital signal processing algorithms such as probabilistic shaping and look-up table pre-distortion are employed to improve the transmission performance.

Adjoint-based parametric sensitivity analysis for swirling M-flames

A linear numerical study is conducted to quantify the effect of swirl on the response behaviour of premixed lean flames to general harmonic excitation in the inlet, upstream of combustion. This study considers axisymmetric M-flames and is based on the linearised compressible Navier–Stokes equations augmented by a simple one-step irreversible chemical reaction. Optimal frequency response gains for both axisymmetric and non-axisymmetric perturbations are computed via a direct–adjoint methodology and singular value decompositions. The high-dimensional parameter space, containing perturbation and base-flow parameters, is explored by taking advantage of generic sensitivity information gained from the adjoint solutions. This information is then tailored to specific parametric sensitivities by first-order perturbation expansions of the singular triplets about the respective parameters. Valuable flow information, at a negligible computational cost, is gained by simple weighted scalar products between direct and adjoint solutions. We find that for non-swirling flows, a mode with azimuthal wavenumber $m=2$ is the most efficiently driven structure. The structural mechanism underlying the optimal gains is shown to be the Orr mechanism for $m=0$ and a blend of Orr and other mechanisms, such as lift-up, for other azimuthal wavenumbers. Further to this, velocity and pressure perturbations are shown to make up the optimal input and output showing that the thermoacoustic mechanism is crucial in large energy amplifications. For $m=0$ these velocity perturbations are mainly longitudinal, but for higher wavenumbers azimuthal velocity fluctuations become prominent, especially in the non-swirling case. Sensitivity analyses are carried out with respect to the Mach number, Reynolds number and swirl number, and the accuracy of parametric gradients of the frequency response curve is assessed. The sensitivity analysis reveals that increases in Reynolds and Mach numbers yield higher gains, through a decrease in temperature diffusion. A rise in mean-flow swirl is shown to diminish the gain, with increased damping for higher azimuthal wavenumbers. This leads to a reordering of the most effectively amplified mode, with the axisymmetric ($m=0$) mode becoming the dominant structure at moderate swirl numbers.

Ultrastructural Changes in the Mucosa of Neobladder in Mini-pigs Three Months After Ileocystoplasty (Experimental Study)

The problem of bladder cancer in Ukraine remains relevant position, as approximately 5000 new cases are recorded each year. Tissues of the gastrointestinal tract have been actively used in reconstructive surgery of the urinary system for the past thirty years, especially in the formation of the neocyst.The objective: the aim of the study was investigation of the ultrastructural changes in the mucous membrane of the artificial bladder in mini-pigs under experimental conditions, three months after the ileacystoplasty.Materials and methods. The material of this study was the results obtained in the study of 18 female mini-pigs aged 4–15 months and weighing 8–15 kg. Experimental animal models of the neobladder were performed by cystectomy followed by ileocystoplasty.Results. Thus, the epithelial layer of the mucosa after cystectomy is completely destroyed in places, especially on the lateral surfaces of the villi. The aggressive and toxic environment of the urine of the artificial bladder, in which the ileum mucosa appeared to be in the postoperative period three months after the formation of the conduit, causes damage to the plasmolemmas and the organelle of the cells of the lamina propria. The compensatory-reduction processes are included at this early stage. It is evidenced by accumulations of large mitochondria and amplification in the cells of protein-synthesizing processes.Conclusion. Extreme conditions of life lead to the suppression of immunity and protective properties in the tissues of the neobladder mucosa, as well as the development of allergic reactions and inflammation of neocyst tissues.

Surface plasmon polariton at the interface of dielectric and graphene medium using Kerr effect

We theoretically investigate the control of surface plasmon polariton (SPP) generated at the interface of dielectric and graphene medium under Kerr nonlinearity. The controlled Kerr nonlinear signal of probe light beam in a dielectric medium is used to generate SPPs at the interface of dielectric and graphene medium. The positive, negative absorption, and dispersion properties of SPPs are modified and controlled by the control and Kerr fields. A large amplification (negative absorption) is noted for SPPs under the Kerr nonlinearity. The normal/anomalous slope of dispersion and propagation length of SPPs is modified and controlled with Kerr nonlinearity. This leads to significant variation in slow and fast SPP propagation. The controlled slow and fast SPP propagation may predict significant applications in nano-photonics, optical tweezers, photovoltaic devices, plasmonster, and sensing technology.

Surface plasmon amplification in refractory transition metal nitrides based nanoparticle dimers

Abstract Aggregates of plasmonic nanoparticles (NPs) are known to show greater electric field amplification, multiple resonant peaks, and precisely controlled spectral tuning compared to their isolated counterpart. The ability of localized surface plasmon mediated electric field amplification is an important criterion for a plasmonic system to act as an efficient Surface Enhanced Raman Scattering (SERS) substrate. Conventional coinage metals like gold (Au), silver (Ag) and copper (Cu) are most widely used SERS substrates, mainly due to their well established synthesis process and large Raman signal amplification. However, there is a pressing need to expand the list of plasmonic materials feasible for SERS substrates to match the exponential growth in SERS research. Identification of new plasmonic substrates will reduce the dependence on conventional plasmonic materials and SERS applications will extend into unexplored spectral regions. Moreover, one can circumvent the limitations arising due to the intrinsic nature of conventional plasmonic materials. Refractory Transition Metal Nitrides (RTMN) such as zirconium nitride (ZrN) and titanium nitride (TiN) has emerged as viable alternatives to coinage metals due mainly to, high electron conductivity, suitability for high temperature applications, optical response in Vis–NIR region, flexible spectral fine-tuning, and bio/CMOS compatibility. To the best of our knowledge, this article presents first-ever theoretical assessment of ZrN and TiN nanoparticle dimers for their suitability in enhancing electric field. Moreover, the role of nanoparticle size, embedding medium and inter-particle separation is quantified through fitting relations whose usefulness is demonstrated by designing nitrides based SERS substrates for selected wavelengths. The present work will provide handy tools to the designers and manufacturers.

Interfacial self-assembly of nanostructured silver octahedra for surface-enhanced Raman spectroscopy

A novel robust and effective approach is suggested to form thin film substrates for surface-enhanced Raman spectroscopy (SERS) using interfacial self-assembly in demixing water/toluene Pickering emulsions collecting silver octahedral mesocages onto a finally flat interfacial region. The freely floating self-assembled silver films obtained after toluene evaporation can be transferred onto various substrates including those with an ordered superficial relief causing a further alignment of silver octahedra. A special porous aggregative structure of the octahedra mesocages provokes a great number of hot spots allowing a large amplification of Raman scattering signal of model dye analytes and molecular thiol products of crude oil desulfurization. The suggested method seems to be an easy scaling route for SERS active material production.

Common source power amplifier design for 5G application in 28-nm UTBB FD-SOI technology

The telecommunication market examines a highly growing demand for RF mobile devices where low latency and high performance are ongoing improvement. The power amplifier (PA) is a major element of the radio frequency front-end; especially if power consumption and bandwidth are considered. This paper presents the design of 5G mm-wave PA using both Common Source Class-AB and Class-J topologies utilizing 28-nm UTBB FD-SOI technology and its body bias technique. Upon taking into consideration the parasitic extraction of the transistor, RF pads, and interconnection to ground, a comparison is made and the theoretical effectiveness of Class-J topology for single stage large signal amplification is simulated. Moreover, two distinct transistors - widths of 250 µm and 350 µm - are simulated where each has its own topology in order to study the impact of increasing the width on the performance of the PA. The stability of the designed Power Amplifiers is taken into consideration and the unconditional stability conditions are approved. While 5G spectral band is not yet specified and determined, recent studies proved that the 28 GHz band is particularly effective for 5G mobile standardization.

Graded resonator arrays for spatial frequency separation and amplification of water waves

A structure capable of substantially amplifying water waves over a broad range of frequencies at selected locations is proposed. The structure consists of a small number of C-shaped cylinders in a line array, with the cylinder properties graded along the array. Using linear potential-flow theory, it is shown that the energy carried by a plane incident wave is amplified within specified cylinders for wavelengths comparable to the array length and for a range of incident directions. Transfer-matrix analysis is used to attribute the large amplifications to excitation of local Rayleigh–Bloch waves and gradual slowing down of their group velocity along the array.