Amplification Of Intensity Research Articles

Nonlinear hydrodynamic effects in dense microplasmas interacting with microwaves

Plasmas respond nonlinearly to GHz electromagnetic waves, owing to nonlinear interactions described by the electron momentum equation. These nonlinearities are especially important in high field regions of the plasma as is common in resonant structures that generate plasma discharges with intense localized amplification of the incident field. Most models treat the plasma as a linear Drude material that does not capture the nonlinear polarization terms of a plasma. In this work, we couple the nonlinear electron momentum equation to electromagnetic wave simulation in order to explore the nonlinear behavior. We develop a theoretical foundation via perturbation analysis to guide our expectations from numerical simulation. Through numerical simulation of 2D TE-polarized waves incident on a cylindrical plasma, we show that in the presence of electrical field strengths of ∼MV/m and higher, dense microplasmas have second harmonic power conversion efficiency approaching 10−6 at low pressures. The generated harmonic power is shown to arise mostly from the inertial term in the electron momentum equation. Therefore, a significant portion of the harmonic current density is generated at the surfaces of critical electron density for the fundamental frequency.

Intensity modulation lens on the basis of nano-scale golden rods and liquid crystal layer

In this paper, an active 2D plasmonic lens has been carefully designed to achieve intensity beam modulation. The design has been thoroughly studied by using rigorous finite element method (FEM). Combination of silicon oxide (SiO2), nematic liquid crystal (NLC) layer and array of non-uniform nano-scale golden (Au) rods along with finely optimized geometry paved the way to achieve good modulation intensity in terms of extinction ratio of about 3.5 dB. Further, the tolerance analysis reveals that the performance of the suggested intensity-modulation lens is almost unchangeable with ± 15 nm variation in the nano-scale golden rods dimensions. Additionally, the proposed lens has been examined using different noble metals such as silver (Ag) and Aluminum (Al). In comparison with other reported lenses, the proposed lenses based Ag, Al and Au have relatively smaller dimensions, maximum intensity amplification factors of about 10.4, 16.6 and 12.5; respectively. The proposed lens may render itself as an efficient unit in the ultra-high nano scale integrated optical systems.

Note: A contraction channel design for planar shock wave enhancement.

A two-dimensional contraction channel with a theoretically designed concave-oblique-convex wall profile is proposed to obtain a smooth planar-to-planar shock transition with shock intensity amplification that can easily overcome the limitations of a conventional shock tube. The concave segment of the wall profile, which is carefully determined based on shock dynamics theory, transforms the shock shape from an initial plane into a cylindrical arc. Then the level of shock enhancement is mainly contributed by the cylindrical shock convergence within the following oblique segment, after which the cylindrical shock is again "bent" back into a planar shape through the third section of the shock dynamically designed convex segment. A typical example is presented with a combination of experimental and numerical methods, where the shape of transmitted shock is almost planar and the post-shock flow has no obvious reflected waves. A quantitative investigation shows that the difference between the designed and experimental transmitted shock intensities is merely 1.4%. Thanks to its advantage that the wall profile design is insensitive to initial shock strength variations and high-temperature gas effects, this method exhibits attractive potential as an efficient approach to a certain, controllable, extreme condition of a strong shock wave with relatively uniform flow behind.

Demonstration of Input-to-Output Gain and Temporal Noise Mitigation in a Talbot Amplifier

We experimentally demonstrate intensity amplification of repetitive picosecond optical pulses with an input-to-output gain up to 5.5 dB using a passive Talbot amplifier. Through the dispersion-induced temporal Talbot effect, the amplifier uses electro-optic phase modulation and a low-loss dispersive medium to exploit and coherently redistribute the energy of the original pulse train into fewer, replica, amplified pulses. In addition, we show how our passive amplifier mitigates the pulse train timing-jitter and pulse-to-pulse intensity fluctuations above a specific cutoff frequency.

Interaction between poly(vinyl pyrrolidone) PVP and fullerene C60 at the interface in PVP-C60 nanofluids–A spectroscopic study

Fourier transform infrared and Raman bands shows a discernible enhancement in band intensity of C–H stretching, C=O stretching, C–N stretching, C–H2 bending, and C–H2 in-plane bending in PVP molecules in the presence of C60 molecules. Amplification in intensity is ascribed to microscopic interactions results when a donation of nonbonding electron (n) occurs from a “>N–C=O” entity of PVP into a lowest unoccupied molecular orbital of the C60 molecule in PVP-C60 charge transfer (CT) complex. The C=O stretching band intensity (integrated) Vs C60 content plot exhibits a peak near a critical 13.9 μM C60 value owing to percolation effect. Light emission spectra show that even a small addition of 4.63 μM C60 able to suppress the band intensity by ~23% as a result of an energy loss. The integrated band intensity also decreases through a peak near 13.9 μM when plotted against the C60-content. In correlation to the vibration spectra, the maximum effect observed both in light emission and excitation spectra suggests a percolation effect in the CT complex. Exhibition of percolation threshold in C60-PVP donor-acceptor complex will be helpful in optimizing the photovoltaic properties vital for solar cell applications.

Next-generation sequencing analysis reveals novel insights of B chromosome evolution of the grasshopper Abracris flavolineata

B chromosomes are additional elements in a normal karyotype that has been considered frequently as parasitic and dispensable. These elements do not recombine with A chromosomes, could be accumulated and present non-mendelian patterns of inheritance. In most of the cases they comprise an enrichment of heterochromatic repetitive DNA, such as Satellite DNAs (satDNA). To contribute to understanding about origin, composition and evolutionary patterns of B chromosome in the grasshopper Abracris flavolineata, in this work we characterized through Illumina sequencing and graph-based clustering the most abundant tandem repeats of A. flavolineata, karyotype 2n = 22,X0+B?.The analyses revealed the occurrence of ten families of satDNAs comprising about 6.279% of the male genome harboring one B chromosome. For the X chromosome and autosomes, distinct patterns of hybridization was observed between the satDNAs showing variability among them, like scattered blocks on euchromatic areas or specific ones on heterochromatic regions of the chromosomes. Five of the satDNAs recovered were distributed on centromeric and both terminal regions of the B chromosome, reinforcing the hypothesis of B chromosome origin through isochromosome formation. Two satDNA families were located only in centromere, while three families were not present in B chromosome. CL220 satDNA was the unique family shared between the B chromosome and only one A element, the chromosome 1, supporting strongly the hypothesis of its origin from this autosomal pair, also noticed previously by U2 snDNA mapping. In addition, this analysis provides new information regarding the composition and evolution of B chromosome of A. flavolineata. Furthermore, the non-spreading and specific location of satDNAs and other repetitive sequences restrict to telomeres and centromere reinforces the possible idea that this B chromosome could harbor unknown euchromatic sequences along chromosomal arms and do not present intense amplification of heterochromatic ones, as have been commonly described for other species.

Stochastic resonance characteristic analysis of new potential function under Levy noise and bearing fault detection

Based on the output saturation of classcial bistable stochastic resonance (CBSR), a new type of piecewise nonlinear bistable stochastic resonance (PNBSR) system is constructed. The mean signal-to-noise ratio gain is regarded as an index to measure the stochastic resonance phenomenon. The laws for the resonant output of piecewise nonlinear bistable system governed by l, c, a, b and D of Levy noise are explored under different characteristic index α and symmetry parameter β of Levy noise. The results show that the output of PNBSR system has increased 4 dB by comparing with the output signal-to-noise ratio of CBSR system. And the stochastic resonance phenomenon can be induced by adjusting the piecewise nonlinear system's parameters under any α or β of Levy noise. The interval of the parameters of system which induces good stochastic resonance is roughly the same. And the output signal waveform of resonance is very similar to the input signal waveform, which has some reference value for the signal recovery. Moreover, we can find the good stochastic resonance interval of the system parameters do not change with D of Levy noise under the different noise intensity D of Levy noise. On the basis of this, adjusting the intensity amplification factor D of Levy noise, which induces good stochastic resonance, and the interval does not change with α or β. At last, the piecewise nonlinear bistable system is applied to detect bearing fault signals, which achieves better performance compared with the classical bistable system.

Experimental Evaluation of Structural Intensity in Two-Dimensional Plate-Type Locally Resonant Elastic Metamaterials

Elastic metamaterials utilize locally resonant mechanical elements to onset band gap characteristics that are typically exploited in vibration suppression and isolation applications. The present work employs a comprehensive structural intensity analysis (SIA) to depict the structural power distribution and variations associated with band gap frequency ranges, as well as outside them along both dimensions of a two-dimensional (2D) metamaterial. Following a brief theoretical dispersion analysis, the actual mechanics of a finite metamaterial plate undergoing flexural loading and consisting of a square array of 100 cells is examined experimentally using a fabricated prototype. Scanning laser Doppler vibrometer (SLDV) tests are carried out to experimentally measure the deformations of the metamaterial in response to base excitations within a broad frequency range. In addition to confirming the attenuation and blocked propagation of elastic waves throughout the elastic medium via graphical visualizations of power flow maps, the SIA reveals interesting observations, which give additional insights into energy flow and transmission in elastic metamaterials as a result of the local resonance effects. A drastic reduction in power flow magnitudes to the bulk regions of the plate within a band gap is noticeably met with a large amplification of structural intensity around and in the neighborhood of the excitation source as a compensatory effect. Finally, the theoretical and experimentally measured streamlines of power flow are presented as an alternative tool to predict the structural power patterns and track vortices as well as confined regions of energy concentrations.

Prospects for femtosecond ultrahigh intensity laser system towards Exawatt level

The new generation system for ultrahigh-power laser running over Exawatt (EW, 10 18 W) level is emerging recently, which is under a mechanism called Raman backscattering (RBS) in plasma. The main advantage of using plasma is that it can tolerate much higher laser intensities, 10 17 W cm −2 , more than five order of solid-state devices limited, 10 12 W cm −2 . Although Petawatt (PW, 10 15 W) laser pulses have been realized by some groups based on the chirped pulse amplification scheme (CPA), many cutting-edge scientific researches and technical applications, such as inertial confinement fusion (ICF), plasma physics, astrophysics, plasma-based particle accelerators, and X-ray lasers, need even higher laser power than EW level. For these purposes, huge laser projects like the extreme light infrastructure (ELI) have been proposed to offer new paradigm in EW class laser power. However, such an ultrahigh intensity laser system could only be achieved by CPA using very large (beyond 1 m 2 ) and expensive compressor gratings. In addition, to extrapolate CPA to the EW power range, hundreds of such gratings would be required. Even if there is enough budget, the problem of energy restriction on the last grating is still under question. Therefore, it is crucial to find a new medium or new technology for generating femtosecond ultra-intense laser pulses. This paper introduces a solution for generating laser intensities many orders of magnitude higher than currently results. This technology of optical amplification that a process known as Raman backscattering amplification and compression could enable the generation of femtosecond pulses of 20000 times the original seed intensity in a column of plasma just a few millimeters in length and less than a millimeter in width, without stretcher and compressor. Such sufficient high intensity and lower frequency of the pulse amplification indeed have got into super-radiant amplification regime (SRA) or stimulated Raman backscattering (SRBS). It has revealed that an unprecedented large pulse intensity amplification could be realized. The seed pulse will be compressed to 25 fs and its unfocused intensity increased from 1×10 15 to 4×10 17 W cm −2 . Furthermore, it could be increased further to around 1×10 23 W cm −2 by focusing the resulting beam to 1 μm. Therefore, it might be possible to increase this power up to EW in a larger plasma and using more powerful optical pumping.

Nanoantenna-Microcavity Hybrids with Highly Cooperative Plasmonic-Photonic Coupling.

Nanoantennas offer the ultimate spatial control over light by concentrating optical energy well below the diffraction limit, whereas their quality factor (Q) is constrained by large radiative and dissipative losses. Dielectric microcavities, on the other hand, are capable of generating a high Q-factor through an extended photon storage time but have a diffraction-limited optical mode volume. Here we bridge the two worlds, by studying an exemplary hybrid system integrating plasmonic gold nanorods acting as nanoantennas with an on-resonance dielectric photonic crystal (PC) slab acting as a low-loss microcavity and, more importantly, by synergistically combining their advantages to produce a much stronger local field enhancement than that of the separate entities. To achieve this synergy between the two polar opposite types of nanophotonic resonant elements, we show that it is crucial to coordinate both the dissipative loss of the nanoantenna and the Q-factor of the low-loss cavity. In comparison to the antenna-cavity coupling approach using a Fabry-Perot resonator, which has proved successful for resonant amplification of the antenna's local field intensity, we theoretically and experimentally show that coupling to a modest-Q PC guided resonance can produce a greater amplification by at least an order of magnitude. The synergistic nanoantenna-microcavity hybrid strategy opens new opportunities for further enhancing nanoscale light-matter interactions to benefit numerous areas such as nonlinear optics, nanolasers, plasmonic hot carrier technology, and surface-enhanced Raman and infrared absorption spectroscopies.

The phenomenon of tristable stochastic resonance driven by $$\alpha $$ α -noise

In this paper, the tristable stochastic resonance (SR) phenomenon induced by $$\alpha $$ -stable noise is analysed. The mechanism for realizing resonance is explored based on research concerning the potential function and resonant output of a system. The rules for resonance system parameters q, p, skewness parameter r and intensity amplification factor Q of $$\alpha $$ -stable noise to act on the resonant output are explored under different values of stability index $$\alpha $$ and asymmetric skewness $$\beta $$ of $$\alpha $$ -stable noise. The results will contribute to a reasonable selection of parameter-induced tristable SR system parameters under $$\alpha $$ -stable noise, and lay the foundation for a practical engineering application of weak signal detection based on the SR.

Dual Amplification Fluorescence Assay for Alpha Fetal Protein Utilizing Immunohybridization Chain Reaction and Metal-Enhanced Fluorescence of Carbon Nanodots.

As an emerging fascinating fluorescent nanomaterial, carbon nanodots (CDs) have attracted much attention owing of their unique properties such as small size, antiphotobleaching, and biocompatibility. However, its use in biomedical analysis is limited because of its low quantum yield. Herein, we constructed a dual amplification fluorescence sensor by incorporating immunohybridization chain reaction (immuno-HCR) and metal-enhanced fluorescence (MEF) of CDs for the detection of alpha fetal protein (AFP). The immunoplasmonic slide and detection antibodies-conjugated oligonucleotide initiator are served to capture and probe AFP molecules, respectively. Then, CD-tagged hairpin nucleic acids were introduced to trigger the HCR, in which the hairpin nucleic acid and oligonucleotide initiator are complementary. The interaction between CDs and the gold nanoisland film greatly improves the radiative decay rate, increases the quantum yield, and enhances the fluorescence emission of the CDs. Furthermore, the HCR provides secondary amplification of fluorescence intensity. Therefore, the MEF-capable immunohybridization reactions provide obvious advantages and result in exceptional sensitivity. In addition, the sandwich immunoassay method offers high specificity. The results show a wide linearity between the fluorescence intensity and AFP concentration over 5 orders of magnitude (0.0005-5 ng/mL), and the detection limit reaches as low as 94.3 fg/mL. This method offers advantages of high sensitivity and reliability, wide detection range, and versatile plasmonic chips, thus presenting an alternative for the technologies in biomedical analysis and clinical applications.

Quantitative detection of exosomal microRNA extracted from human blood based on surface-enhanced Raman scattering

Since the nature of the exosomal lipid bilayer can allow miRNAs to be protected from degradation by cellular RNAses in body fluids, exosomal microRNA (miRNA) has become an ideal source of non-invasive biomarkers for the early diagnosis and prognosis. In this paper, a new surface-enhanced Raman scattering (SERS) analysis strategy combining stable SERS reporter element and duplex-specific nuclease (DSN)-assisted signal amplification for quantitative detection of exosomal miRNA extracted from human blood is proposed. Firstly, we prepared SERS signal reporter of Au@R6G@AgAu nanoparticles (R6G attachment on the gold nanoparticles, then encapsulated in AgAu alloy shell nanoparticles named as ARANPs) with an inter small nanogap to generate stable SERS signal. Then, ARANPs and separating substrate of silicon microbead (SiMB) were then covalently attached to the 3′- and 5′- end of capture probe (CP) targeting exosomal miRNA. Upon target miRNA binding, DNA in heteroduplexes could be specifically cleaved by DSN and resulted in the release of ARANPs from the surface of SiMB. Meanwhile, target miRNA remained intact and subsequently involved in the next round of target-recycling amplification. The combination of stable SERS intensity and signal amplification significantly improved the sensitivity of the sensing systems, resulting in detection limits of 5 fM. More importantly, this method also could be used for the detection of exosomal miRNAs extracted from the blood collected from patients of recurrence in non-small-cell lung cancer (NSCLC), with a detection of 5.0μL of sample volume, which has potential for point-of-care testing (POCT) in clinical analysis.

Future summer mega-heatwave and record-breaking temperatures in a warmer France climate

This study focuses on future very hot summers associated with severe heatwaves and record-breaking temperatures in France. Daily temperature observations and a pair of historical and scenario (greenhouse gas radiative concentration pathway 8.5) simulations with the high-resolution (∼12.5 km) ALADIN regional climate model provide a robust framework to examine the spatial distribution of these extreme events and their 21st century evolution.Five regions are identified with an extreme event spatial clustering algorithm applied to observed temperatures. They are used to diagnose the 21st century heatwave spatial patterns. In the 2070s, we find a simulated mega-heatwave as severe as the 2003 observed heatwave relative to its contemporaneous climate. A 20-member initial condition ensemble is used to assess the sensitivity of this future heatwave to the internal variability in the regional climate model and to pre-existing land surface conditions. Even in a much warmer and drier climate in France, late spring dry land conditions may lead to a significant amplification of summer extreme temperatures and heatwave intensity through limitations in evapotranspiration. By 2100, the increase in summer temperature maxima exhibits a range from 6 °C to almost 13 °C in the five regions in France, relative to historical maxima. These projections are comparable with the estimates given by a large number of global climate models.

Visualization of photoacoustic images in a limited-View measuring system using eigenvalues of a photoacoustic transmission matrix

Photoacoustic imaging is a unique imaging method that involves extracting information from points at different depths, an advantage of ultrasound imaging, while maintaining functional information, a key feature of conventional photo imaging. This makes it easy to add functional images to ultrasound images by adding a laser pulse source to the conventional ultrasound imaging device and detecting a photo-ultrasound signal via a conventional ultrasound probe. One challenge when using normal one-dimensional (1D) probes and generating photoacoustic images is the limited-view problem, in which artefacts are observed due to the positions of the ultrasound transducers. In this study, we used a photoacoustic transmission matrix (PA-TM) for simulation and performed a verification test using a 1D probe and a phantom. The results confirmed that the eigenvalues of the PA-TM visualized the light absorber itself in the limited-view measurement system, which eliminates reconstruction artefacts and further scattering artefacts, and that visualization is possible by signal intensity amplification through further phase modulation.

Facial affect processing in social anxiety disorder with early onset: evidence of an intensity amplification bias

ABSTRACTThe present event-related potential (ERP) study investigated for the first time whether children with early-onset social anxiety disorder (SAD) process affective facial expressions of varying intensities differently than non-anxious controls. Participants were 15 SAD patients and 15 non-anxious controls (mean age of 9 years). They were presented with schematic faces displaying anger and happiness at four intensity levels (25%, 50%, 75%, and 100%), as well as with neutral faces. ERPs in early and later time windows (P100, N170, late positivity [LP]), as well as affective ratings (valence and arousal) for the faces, were recorded. SAD patients rated the faces as generally more arousing, regardless of the type of emotion and intensity. Moreover, they displayed enhanced right-parietal LP (350–650 ms). Both arousal ratings and LP reflect stimulus intensity. Therefore, this study provides first evidence of an intensity amplification bias in pediatric SAD during facial affect processing.

Stochastic resonance of a tri-stable system with α stable noise

A tri-stable system excited by weak periodic signal is taken as a model and the stochastic resonance phenomenon is investigated by additive α stable noise in this paper. The laws for the resonance system parameters q, p, skewness parameter r and intensity amplification factor Q of α stable noise to act on the resonant output are explored under different stability indicies α and asymmetric skewness β of α stable noise. The results indicate that a weak signal can be realized by tuning the system parameters q, p and r under the joint action of additive α stable noise, and the interval of q and p which can induce stochastic resonance does not change with α or β. Moreover, a certain rule is found in which adjusting the intensity amplification factor Q of α stable noise can also realize a synergistic effect when studying the noise-induced stochastic resonance, and the interval of Q does not change with α or β; the best value of the characteristic index is α=1 under any system parameter, and the best value of the symmetry parameter is β=1 under any system parameter. So, the system performance is best when α=1 and β=1. The results will contribute to a reasonable selection of parameter-induced stochastic resonance system parameters and noise intensity of noise-induced stochastic resonance under α stable noise.

Centrifuge tests to assess seismic site response of partially saturated sand layers

Seismic response of unsaturated soil layers may differ from that of saturated or dry soil deposits. A set of centrifuge experiments was conducted to study the influence of partial saturation on seismic response of sand layers under scaled Northridge earthquake motion. Steady state infiltration was implemented to control and provide uniform degree of saturation profiles in depth. The amplification of peak ground acceleration at the soil surface was inversely proportional to the degree of saturation, especially in low period range. The cumulative intensity amplification of the motion was also higher in unsaturated soils with higher suctions. The lateral deformation and surface settlement of partially saturated sand with higher stiffness were generally lower than that in dry soil. Although neglecting the effect of partial saturation in sand layers might be conservative with respect to seismic deformations, it may result in underestimating the surface design spectra.

Stability of thermovibrational convection of pseudoplastic fluid in plane vertical layer

Based on equations for thermal vibrational convection, the structure of the plane-parallel convective flow in a vertical layer of Williamson’s fluid is investigated. The layer is subjected to high frequency linear polarized vibrations directed along the layer. It is shown that with the growth of vibrations, the nonlinear-viscous properties of a pseudoplastic fluid stop producing the effect on the structure and intensity of its main flow, which becomes very similar to that of the Newtonian fluid. For the case of longitudinal high-frequency linear polarized vibrations, a linear stability problem is formulated and solved. This problem deals with the stability of the averaged plain parallel flow of the pseudoplastic Williamson’s fluid with respect to small periodic perturbations directed along the layer. Numerical calculations show that, as in the case of the Newtonian fluid, at small values of the Prandtl number the monotonic hydrodynamic perturbations are the most dangerous. With increasing Prandtl number, the oscillatory thermal perturbations become more dangerous. Strengthening of the pseudoplastic fluid properties leads to destabilization of the main flow relative to the both types of instabilities. The presence of vibrations, as in the case of the Newtonian fluid, causes the appearance of an additional vibration mode of instability and the relatively small values of the Graschof number corresponding to it. The influence of this vibration mode on the stability of the main flow is determined by the vibration frequency and the magnitude of a temperature gradient. Amplification of the vibration intensity leads to flow destabilization in all examined instability modes. For the given set of rheological parameters of Williamson’s fluid, there are critical values of the modified and vibration Graschof number, at which the averaged flow becomes absolutely unstable with respect to all types of the instabilities. The absolute destabilization of the main flow occurs at higher values of the vibration Graschof number compared to that for the Newtonian fluid.

Plasmonic response and SERS modulation in electrochemical applied potentials.

We study the optical response of individual nm-wide plasmonic nanocavities using a nanoparticle-on-mirror design utilised as an electrode in an electrochemical cell. In this geometry Au nanoparticles are separated from a bulk Au film by an ultrathin molecular spacer, giving intense and stable Raman amplification of 100 molecules. Modulation of the plasmonic spectra and the SERS response is observed with an applied voltage under a variety of electrolytes. Different scenarios are discussed to untangle the various mechanisms that can be involved in the electronic interaction between NPs and electrode surfaces.