Intense Field Research Articles

Experiment and modeling of metal jet emission in magnetic pulse welding of Cu/Ti tubular joint

Magnetic pulse welding of Cu/Ti tubular joint is performed by creating intense transient magnetic fields that drive the metal components together at high velocity. This leads to interfacial waviness due to Kevin–Helmholtz instability and emission of a metal jet. The process is simulated using a a two-stages modeling methodology in which magnetic pressure at copper tube is calculated from an electromagnetic code and fed to a meshless hydrocode. Key features of the interfacial morphology and jet emission are reproduced. Jet is found to be dominated by titanium and a linear velocity profile observed.

Facile synthesis of intra-nanogap enhanced Raman tags with different shapes.

Hot spot engineering in plasmonic nanostructures plays a significant role in surface enhanced Raman scattering for bioanalysis and cell imaging. However, creating stable, reproducible, and strong SERS signals remains challenging due to the potential interference from surrounding chemicals and locating SERS-active analytes into hot-spot regions. Herein, we developed a straightforward approach to synthesize intra-gap nanoparticles encapsulating 4-nitrobenzenethiol (4-NBT) as a reporter molecule within these gaps to avoid outside interference. We made three kinds of intra-gap nanoparticles using nanorods, bipyramids, and nanospheres as cores, in which the nanorod based intra-gap nanoparticles exhibit the highest SERS activity. The advantage of our method is the ease of preparation of high-yield and stable intra-gap nanoparticles characterized by a short incubation time (10 mins) with 4-NBT and quick synthesis without requiring an additional step to centrifuge for the purification of core nanoparticles. The intense localized field in the synthesized hot spots of these plasmonic gap nanostructures holds great promise as a SERS substrate for a broad range of quantitative optical applications.

Enhanced cryogenic measurement: Rayleigh-Scattering measurements with dual optical fibers for precise decoupling of temperature and strain

Assessing the operational dynamics of high-temperature superconducting coils during cooling and excitation is essential for their reliable performance and longevity. Rayleigh-scattering-based optical frequency-domain reflectometry distributed optical-fiber sensors (DOFSs) offer a promising solution to real-time monitoring in extreme conditions such as in the presence of intense electromagnetic fields and at cryogenic temperatures; these devices boast immunity to electromagnetic interference and high spatial resolution, and they can be embedded in superconducting coils without compromising their integrity. However, they typically face difficulties distinguishing between thermal and mechanical strains in environments above the temperature of liquid nitrogen. To counter this, we embedded a pair of single-mode Rayleigh-scattering DOFSs side by side—one encased in miniscule capillary tubing to exclusively measure temperature, and the other to measure both strain and temperature. Across a wide temperature range from 77 K to room temperature, we systematically calibrated the temperature- and strain-sensitivity coefficients and demonstrated the technique’s accuracy through comparison against conventional sensors by applying nonuniform tensile and thermal stresses. This dual-sensor approach provides a robust and non-disruptive strategy for the precise measurement of distributed temperature and strain in cryogenic environments.

Array strategy enhances low-frequency radiation intensity and low-frequency magnetic field sensing SNR of magnetoelectric antenna

The magnetoelectric (ME) coupling effect is a more effective approach for reducing antenna size. Nevertheless, at low frequencies, a single ME structure generates a weak signal strength and a low signal-to-noise ratio (SNR). This study utilized an array strategy to improve the radiation and induced electromagnetic field performance of ME antennas. In this study, the array ME coupling structure, composed of Metglas and Pb (Zr1−xTix) O3 (PZT) bilayers, was operated through ME coupling resonance modes. The relationship between the sensitivity and SNR of the serially connected ME antenna array and the number of series connections was determined. On the transmission side, the impact of the multi-source power supply modes on the radiation intensity and directivity of the ME antennas was analyzed. The sensitivity, SNR, magnetic detection limit, directivity, and radiation range of the single ME and array ME antennas were tested for the key parameters. Finally, it was demonstrated that at a frequency of 31.75 kHz, the array strategy achieved a low-frequency signal transmission distance of up to 48.1 m, which is 1.7 times that of a single ME antenna. This array strategy significantly enhances the radiation intensity and magnetic field SNR of ME antennas in the low-frequency range, demonstrating its application prospects in the field of low-frequency communication.

Development of surface plasmon resonance sensor utilizing GaSe and WS2 for ultra-sensitive early detection of dengue virus

This manuscript introduces highly sensitive surface plasmon resonance (SPR) sensor for early detection of the dengue virus. Through extensive optimization using MATLAB, the sensor architecture is meticulously constructed with a BK7 prism, Copper (Cu) layer, Gallium selenide (GaSe), Tungsten disulphide (WS2), and a sensing medium (SM) containing blood components (infected platelets and normal platelets) to ensure optimal performance. Use of WS2 emerges as a highly effective biomolecular recognition element (BRE) layer, leading to exceptional sensor capabilities. The proposed sensor achieves a peak sensitivity (S) of 303.28 (˚/RIU) and a resonance angle shift (∆θres.) of 10˚ specifically during the detection of infected platelets. Computational modeling using COMSOL Multiphysics validates the ability of the sensor to generate an intense electric field with a magnitude of 1.68×105 (V/m) and a penetration depth (PD) extending to 153.24 nm in the SM. This unique combination of PD and enhanced performance parameters positions the proposed SPR biosensor as a promising tool for the early-stage detection of the dengue virus.

Dosimetric Study and Robustness Analysis of Base Note Intensive Locked Field Radiotherapy for Left Breast Cancer.

The locked vision plan can make the left breast cancer heart and lung organs dose. The aim of the present study was to compare the dosimetric differences between field-locked and field-split plans in intensity-modulated radiotherapy for left-sided breast cancer, to explore the effect of field-locking on the low-dose region, and to evaluate its robustness to the radiotherapy target, in order to provide a reference for the selection of clinical radiotherapy protocols. A total of 30 patients were selected after radical left breast cancer surgery, and 7-field locked-field and split-field plans were developed to compare the dose difference (∆D) between the target area and each organ at risk, and to introduce offsets of 3, 5 and 7 mm in six directions and recalculate the perturbed dose distributions, and to compare the ∆D between the original and the perturbed plans according to the robustness of the plans. The results revealed that the D98%, D95% and Dmean values of the planning target volume (PTV) of the two plans differed little and were not statistically different. The locked field plan provided better protection for the left lung, right lung, heart, right breast and left anterior descending coronary artery. For PTV∆D98%, PTV∆D95%, PTV∆Dmean, the ∆D was higher for the Locked Fields plan, and for LungL∆5, LungL∆20 and Heart∆mean, the ∆D was higher for the original plan. It was concluded that the field-locking plan could reduce the low-dose area of the affected lung and provide improved protection to the remaining critical organs, and the field-locking plan was more robust in protecting critical organs. Meanwhile, the field-locking plan showed higher sensitivity to positional deviation for target PTV.

Role of crystal orientation in attosecond photoinjection dynamics of germanium.

Understanding photoinjection in semiconductors-a fundamental physical process-represents the first step toward devising new opto-electronic devices, capable of operating on unprecedented time scales. Fostered by the development of few-femtosecond, intense infrared pulses, and attosecond spectroscopy techniques, ultrafast charge injection in solids has been the subject of intense theoretical and experimental investigation. Recent results have shown that while under certain conditions photoinjection can be ascribed to a single, well-defined phenomenon, in a realistic multi-band semiconductor like Ge, several competing mechanisms determine the sub-cycle interaction of an intense light field with the atomic and electronic structure of matter. In this latter case, it is yet unclear how the complex balance between the different physical mechanisms is altered by the chosen interaction geometry, dictated by the relative orientation between the crystal lattice and the laser electric field direction. In this work, we investigate ultrafast photoinjection in a Ge monocrystalline sample with attosecond temporal resolution under two distinct orientations. Our combined theoretical and experimental effort suggests that the physical mechanisms determining carrier excitation in Ge are largely robust against crystal rotation. Nevertheless, the different alignment between the laser field and the crystal unit cell causes non-negligible changes in the momentum distribution of the excited carriers and their injection yield. Further experiments are needed to clarify whether the crystal orientation can be used to tune the photoinjection of carriers in a semiconductor at these extreme time scales.

Pulse generators for enhanced magnetomotive ultrasound: Toward a cost-effective imaging for tissue characterization.

Magnetomotive ultrasound (MMUS) stands out as a promising and effective ultrasound-based method for detecting magnetic nanoparticles (MNPs) within tissues. This innovative technique relies on the precise estimation of micrometric displacements induced by the interaction of an external magnetic field with MNPs. Pulsed MMUS has emerged as a strategic alternative to address limitations associated with harmonic excitation, such as heat generation in amplifiers and coils, frequency-dependent tissue mechanical responses, and prolonged magnetic field rise times. Despite the growing interest in MMUS, the devices conventionally employed to excite the coil are not specifically tailored to generate intense magnetic fields while minimizing interference with the transient behavior of induced displacements. To bridge this gap, our work introduces the design and fabrication of two pulse generators: one based on a capacitor-discharge circuit and the other on a resonant-inverter circuit. We evaluated the performance of these pulse generators by considering parameters such as the magnetic field generated, rise and fall times, and their ability to supply sustained current for varied pulse widths across different pulse repetition frequencies. Furthermore, we carried out a practical MMUS implementation using tissue-mimicking phantoms, demonstrating the capability of both devices to achieve magnetic fields of up to 1T and average displacements of 25 µm within the phantom. In addition, we estimated the shear wave velocity, effective shear modulus, and their temperature-dependent variations. Our findings highlight the versatility and efficacy of the proposed pulse generators and emphasize their potential as low-cost platforms for theranostic applications, enabling the assessment of targeted entities within biological tissues.

Violent Starbursts and Quiescence Induced by Far-ultraviolet Radiation Feedback in Metal-poor Galaxies at High Redshift

JWST observations of galaxies at z ≳ 8 suggest that they are more luminous and clumpier than predicted by most models, prompting several proposals on the physics of star formation and feedback in the first galaxies. In this paper, we focus on the role of ultraviolet (UV) radiation in regulating star formation by performing a set of cosmological radiation hydrodynamics simulations of one galaxy at subparsec resolution with different radiative feedback models. We find that the suppression of cooling by far-UV (FUV) radiation (i.e., H2 dissociating radiation) from Population II stars is the main physical process triggering the formation of compact and massive star clusters and is responsible for the bursty star formation observed in metal-poor galaxies at z ≳ 10. Indeed, artificially suppressing FUV radiation leads to a less intense continuous mode of star formation distributed into numerous but low-mass open star clusters. Due to the intense FUV field, low-metallicity clouds remain warm (∼104 K) until they reach a relatively high density (≳103 cm−3), before becoming self-shielded and transitioning to a colder (∼100 K), partially molecular phase. As a result, star formation is delayed until the clouds accumulate enough mass to become gravitationally unstable. At this point, the clouds undergo rapid star formation, converting gas into stars with high efficiency. We therefore observe exceptionally bright galaxies (10 times brighter than for continuous star formation) and subsequent quenched “dead” galaxies that did not form stars for tens of Myr.

CloudRoots-Amazon22: Integrating Clouds with Photosynthesis by Crossing Scales

Abstract How are rain forest photosynthesis and turbulent fluxes influenced by clouds? To what extent are clouds affected by local processes driven by rain forest energy, water, and carbon fluxes? These interrelated questions were the main drivers of the intensive field experiment CloudRoots-Amazon22 which took place at the Amazon Tall Tower Observatory (ATTO)/Campina supersites in the Amazon rain forest during the dry season, in August 2022. CloudRoots-Amazon22 collected observational data to derive cause–effect relationships between processes occurring at the leaf level up to canopy scales in relation to the diurnal evolution of the clear-to-cloudy transition. First, we studied the impact of cloud and canopy radiation perturbations on the subdiurnal variability of stomatal conductance. Stoma opening is larger in the morning, modulated by the cloud optical thickness. Second, we combined 1-Hz frequency measurements of the stable isotopologues of carbon dioxide and water vapor with measurements of turbulence to determine carbon dioxide and water vapor sources and sinks within the canopy. Using scintillometer observations, we inferred 1-min sensible heat flux that responded within minutes to the cloud passages. Third, collocated profiles of state variables and greenhouse gases enabled us to determine the role of clouds in vertical transport. We then inferred, using canopy and upper-atmospheric observations and a parameterization, the cloud cover and cloud mass flux to establish causality between canopy and cloud processes. This shows the need for a comprehensive observational set to improve weather and climate model representations. Our findings contribute to advance our knowledge of the coupling between cloudy boundary layers and primary carbon productivity of the Amazon rain forest.

Quantitative estimates of the metachromasia reaction of volutin granules of yeast using neural networks

The metachromatic coloration of volutinous granules of the yeast Saccharomyces cerevisiae is one of the indicators of the influence of sharp geomagnetic field (GMF) perturbations. The metachromasia reaction is based on the aggregation of dye molecules in interaction with inorganic polyphosphates, which are components of volutinous granules. To determine the characteristics of the geomagnetic field that cause the appearance of different colors of the metachromasia reaction, it is necessary to simultaneously monitor this reaction and changes in the GMF. High-quality monitoring is possible with rapid automated counting of cells with all possible color changes during the metachromasia reaction. The aim of the work was to develop a neural network architecture for recognizing and quantifying color changes and heterogeneity in real time during monitoring of the metachromasia reaction of volutinous granules of the yeast S. cerevisiae, which is necessary for further determining their correlations with changes in the geomagnetic field of different intensities. A program based on a nonrecursive labeling algorithm was created to count the number of cells in the study groups. In the course of the work, the software of two neural network architectures was compared to determine the best results in recognizing and quantifying yeast cells with different colors during the volutinous granule metachromasia reaction. It was determined that the Unet architecture type coped with the tasks of cell classification and segmentation much more efficiently than the Inception v3 architecture. The average relative error for automatic recognition of all cell groups was 3.85%, and the maximum relative error was 4.56%. The performance of the neural network was 89.9% when detecting cell segmentation and 86.4% when detecting color differences in the metachromasia reaction.

Electrical insulation and dielectric properties of aramid fiber reinforced epoxy composites under mechanical stress

In this work, an in-situ testing platform that could simultaneously apply high voltage (HV) and mechanical stress has been established. The dielectric properties evolution of aramid fiber reinforced composite (AFRC) under different tensile stresses is investigated systematically. The results show that there is a significant influence on the electrical insulation performance of AFRC, when the applied tensile stress reaches 45 % of the ultimate tensile stress (UTS). Elevated tensile stress will induce interface strain concentration inside composites under this condition, which is prone to cause local damage and defects, consequently enhancing charge accumulation under HV. As the tensile stress continues to increase, it is observed that the absorbed charge around defects increases by 49.4 % under 60 % UTS, accompanied by a discernible decline in the partial discharge inception voltage (PDIV) by 46.9 %. With the increase of absorbed charge, the localized intense electric field is formed, thereby fostering partial discharge and breakdown failure. Therefore, it is important to pay more attention to the evolution of dielectric properties of AFRC under mechanical stress in the design and assessment of aramid-based insulation rods. © 2014 xxxxxxxx. Hosting by Elsevier B.V. All rights reserved.

Modulation of nonlinear optical rectification, second, and third harmonic generation coefficients in n-type quadruple δ-doped GaAs quantum wells under external fields

The paper theoretically explores the variations in nonlinear optical rectification (NOR), second (SHG), and third harmonic generation (THG) coefficients of an n-type quadruple δ-doped GaAs quantum well in the presence of electric, magnetic, and THz laser fields. The energies of subbands and associated wave functions are derived through the solution of the Schrödinger equation, utilizing effective mass and parabolic band approximations. The findings indicate that the applied external electric and magnetic fields significantly influence both the magnitudes and the positions of the peaks in NOR, SHG, and THG concerning the incident photon energies. In addition to the influences of electric and magnetic fields, subjecting the system to an intense laser field results in noticeable changes in the THG, SHG, and NOR coefficients. These numerical findings regarding the optical properties of quadruple δ-doped quantum wells in the presence of external fields could offer valuable guidance for experimental studies.

Photon and neutron dose evaluation at the Beam Test Facility of the INFN - National Laboratory of Frascati

Dose evaluation and direct measurements are fundamental for radiation protection in non-conventional accelerator facilities, both before and after the primary and secondary shielding. In this paper, we will report about the experimental setup, data acquisition and analysis, together with FLUKA modeling, of the dose measurements test carried out in the Beam Test Facility (BTF) of the INFN - Frascati’s National Laboratories (LNF), where an intense mixed field is produced and measured with thermoluminescent dosimeters. BTF is an extraction and transport line of DAΦNE LINAC (Buonomo et al. 2021; Mazzitelli et al. 2003). It is optimized for electrons and positrons production in a wide range of intensity, energy (30 MeV–800 MeV), beam spot dimensions and divergence, using both primary and secondary beam of the DAΦNE LINAC. Through the years, the BTF has gained an important role in particle detectors test and development with electron/positron beam. A small fraction of the BTF’s shifts have been dedicated to radiation damage test using LINAC electron primary beam up to 5×1010 e-/s. As radiation protection group of the LNF, we evaluated the dose when electrons impinging on a Pb target from: (i) photon Bremsstrahlung production; (ii) photoneutron production. Three dedicated tests with 503 MeV electrons impinging on a ∼16 cm thick Pb target have been carried out in February, June 2022 and in January 2023, using TLD700 and TLD600, measuring doses at several charge intervals. The aim of this study focuses on evaluating dosimetric quantities produced by the mixed field, air kerma for the photon component, and ambient dose equivalent for the neutron one, using thermoluminescence dosimeters calibrated with low-energy standards: Cs-137 and Am-Be. The approach adopted involves the use of Monte Carlo simulations of the experiment, both to benchmark against experimental measurements and to validate the results obtained for energies higher than those of calibration. The results of this comparison show excellent agreement between measured and simulated quantities in the forward direction, allowing us to conclude and confirm the validity of the calibrations themselves.

Control of light-induced torque in quantum well waveguides through electron spin coherence

We explore the mechanical effects of light interacting with a quantum well waveguide, specifically focusing on the emergence of quantized torque. We investigate the response of the waveguide to the influence of two intense coupling fields in conjunction with two weaker fields. We find that the electron spin coherence plays a crucial role in amplifying the torque applied to the waveguide emitters. This heightened torque, in turn, triggers a distinctive circular current flow pattern within the waveguide. Furthermore, we explore different scenarios for modulating the torque by adjusting system parameters, thereby establishing a means to control current flow. The emergence of a light-induced quantized torque not only illuminates the interplay between quantum emitters and electromagnetic fields but also opens up exciting possibilities for innovative approaches to govern induced-torque behavior within quantum well waveguides.

An overview of light ray deflection calculation by magnetars in nonlinear electrodynamics

Due to the lack of experimental confirmation of the effects of nonlinear electrodynamics (NED) of vacuum on the electromagnetic wave, it remains the most pressing issue. One of the most optimal media for studying these effects, occurring in astrophysics, are magnetars. Various methods of studying the bending of a wave passing through the magnetospheres of magnetars play a key role in a deeper understanding of vacuum NED. This article reviews modern methods for determining the angle of bending of the electromagnetic wave under the effect of NED of vacuum and gravity, with special attention paid to NED of vacuum in intense electromagnetic fields, which is a characteristic feature of magnetars. The article discusses various methods and techniques used to measure these angles, as well as their potential astrophysical applications.

Influences of crop diversification on yield, resource use efficiency, and environmental footprint in farmland landscapes in intensive farming

Enhancing crop diversification in intensive fields has the potential to increase crop yield and reduce environmental footprint. However, these relationships at the landscape scale remained unclear in intensive farming. Addressing this gap, this paper aims to elucidate how crop yield, resources use efficiency (RUE), and environmental footprint (EF) vary with crop diversification levels in the North China Plain. Management practices, including crop pattern, field size, and agronomic inputs, were collected for 421 landscapes of 1 × 1 km subplots using Sentinel-2 and Landsat-8 images and survey. The results showed that, at the landscape scale, energy and fertilizer contributed over 53 %, and 37 % of the carbon footprint, respectively. N fertilizer constituted >98 % of the nitrogen footprint. P fertilizer accounted for over 80 %, while electricity comprised >13 % of the phosphorus footprint. Compared with simplified landscapes, diversified landscapes exhibited several significant features: 1) 56 % reduction of the area ratio of winter wheat-summer maize double crop pattern (WM), 2) a significant decrease in field size, 3) the decreased use of total NPK fertilizers at 32 %, 30 %, and 30 %, respectively, 4) the increased inputs of irrigation water, diesel, electricity, pesticide and labour at 21 %, 19 %, 21 %, 77 %, and 92 %, respectively. Although yield could be reduced at 33 % when transforming simplified landscapes into moderately diversified ones, they increased with the further promotion of crop diversification. Thus, the diversified landscapes could achieve a balance in yield, RUE, and EF to enhance sustainability, whereas simplified landscapes can similarly achieve a balance to benefit productivity. We emphasize the viable potential of diversified landscapes to enhance sustainable agricultural development by optimizing crop composition. This analysis offers pioneering evidence of landscape-scale agronomic and environmental performances of crop diversification.

Soil Microbial Stress Responses under External Chemical and Physical Environmental Stresses

AbstractSoil microorganisms play a crucial role in maintaining soil ecosystem health. Their metabolic processes are directly impacted by various environmental stresses caused by the increasing release of chemical pollutants and changes in the physical environment due to rapid societal development. This paper aimed to investigate the mechanisms underlying the changes in soil microbial stress responses under various external environmental stresses. The impact of pollutants on soil ecological structure was analyzed by summarizing the stress response patterns of soil microorganisms to inorganic pollutants, organic pollutants, and extreme physical environmental factors. Additionally, the migration and transformation behaviors of various complex pollutants, facilitated by the involvement of soil microorganisms, were investigated. Moreover, a novel approach was proposed for pollutant control, suggesting that manipulating the external physical field of a certain intensity could guide microbial communities and their functions towards controllable evolution within the soil environment. Therefore, this paper was essential for exploring the diversity of soil microbial stress responses, strategically regulating contaminant transport, mitigating risks associated with soil complexity, and ultimately reshaping soil ecological functions.

All-optical steering on the proton emission in laser-induced nanoplasmas

Nanoplasmas induced by intense laser fields have attracted enormous attention due to their accompanied spectacular physical phenomena which are vigorously expected by the community of science and industry. For instance, the energetic electrons and ions produced in laser-driven nanoplasmas are significant for the development of compact beam sources. Nevertheless, effective confinement on the propagating charged particles, which was realized through magnetic field modulation and target structure design in big facilities, are largely absent in the microscopic regime. Here we introduce a reliable scheme to provide control on the emission direction of protons generated from surface ionization in gold nanoparticles driven by intense femtosecond laser fields. The ionization level of the nanosystem provides us a knob to manipulate the characteristics of the collective proton emission. The most probable emission direction can be precisely steered by tuning the excitation strength of the laser pulses. This work opens new avenue for controlling the ion emission in nanoplasmas and can vigorously promote the fields such as development of on-chip beam sources at micro-/nano-scales.

Multiphoton fusion of light nuclei in intense laser fields

Multiphoton fusion of light nuclei in intense laser fields