AppliedPhys doi: 10.3390/appliedphys2020004

Authors: Matteo Campostrini Valentino Rigato

X-band copper resonating cavities are key components of future pulsed GHz normal-conductive multi-TeV accelerators. High electric field gradients are required for emerging applications; however, as gradients increase, components’ lifetime decreases, primarily due to radiofrequency (RF) breakdown. Coating technologies are being investigated in several laboratories to improve RF structure, performance and lifetime. To this end, we investigated the feasibility of fabricating nanometer-periodic Cu/Mo metallic multilayers on three-dimensional (3D) aluminum mandrels designed to replicate X-band copper resonating cavities. These nanometer-period multilayers are proposed to mitigate surface degradation due to electric breakdown at high accelerating gradients by stabilizing inner cavity surfaces against dislocation evolution and roughening caused by thermo-mechanical fatigue. High-Power Impulse Magnetron Sputtering (HiPIMS) in a bias-controlled dual closed-field magnetron configuration was employed to deposit alternating Mo and Cu nano-layers onto the 3D geometries. Given the complexity of HiPIMS technology, plasma pulse evolution was studied by combining time-resolved optical emission spectroscopy with electrical measurements of the pulse discharge. The influence of the process parameters, particularly the applied DC bias, on film growth was studied using non-destructive microprobe α-particle elastic backscattering spectrometry (µEBS) and scanning transmission electron microscopy (STEM). STEM and µEBS analyses confirmed that Mo layers with thicknesses of approximately 5–35 nm were successfully deposited repeatedly on thicker Cu layers (30–150 nm), preserving individual layer properties with minimal interdiffusion and alloying. The layers were deposited inside trenches with an aspect ratio of 5:1 representative of X-band irises. This technology, coupled with the replica process, could be applied to highly engineered nanostructured coatings for X-band cavity treatment in compact particle accelerator prototypes, as it may improve electrical breakdown lifetime under high accelerating fields, at least for degradation processes driven by the high mobility of copper dislocations.

AppliedPhys doi: 10.3390/appliedphys2010003

Authors: Ryan Zurick Jonathan Azenon Sophie Stumbo Jonathan Raper Catherine B. Volle

Antimicrobial peptides (AMPs) are found widely as part of nonspecific immune defenses. One class of AMPs forms stable pores in membranes, including the two chemically distinct membranes found in the Gram-negative cell envelope. As the Gram-negative cell envelope is a significant barrier to drug development, some have hypothesized that these AMPs could be used clinically, either alone or in combination with other drugs that cannot cross the Gram-negative cell envelope on their own. Here, we use atomic force microscopy (AFM), fluorescence spectroscopy, and fluorescence microscopy to elucidate the biomechanical changes that occur in Escherichia coli treated with various concentrations of the pore-forming AMP magainin 2 (MAG2). We find that near the minimum inhibitory concentration, MAG2 induces a loss of cell stiffness and a decrease in cell height consistent with pore formation and cellular leakage. Surprisingly, treatment with high concentrations of MAG2 leads to cells becoming stiffer and increasing in height. We confirmed that MAG2 forms pores at high concentrations using a standard propidium iodide (PI) uptake assay, in which PI is added to a cell suspension and is detected only after pores form in the cell membrane. However, when PI was added after 30 min of treatment with high concentrations of MAG2, less PI fluorescence was observed than in the standard PI uptake assay, indicating that movement across the cell membrane was restricted at the end of our experiments. We also observed that the modulus of the cell envelope increased with increasing MAG2 concentration, consistent with greater packing of MAG2 into the cell envelope membranes. Finally, our AFM images in air revealed that cells formed blebs when treated with high concentrations of MAG2. These data suggest that MAG2 initially forms pores at high concentrations, but as membrane packing increases, movement across the cell envelope becomes restricted. Understanding the concentration-dependent restriction of movement across the cell envelope could be important if AMPs are to be used clinically.

AppliedPhys doi: 10.3390/appliedphys2010002

Authors: Lucian Milica

This paper presents a dynamic analysis of ultrasonic motors (USMs) used in camera lens systems, which achieve high-precision motion via piezoelectric stators rather than electromagnetic components. The study focuses on the coupling of radial and tangential vibrations that create elliptical particle trajectories, driving the rotor through friction. The methodology is divided into two stages: Stage I: A discrete mass-spring model simplifies the coupled motion to a single degree of freedom. This analytical approach approximates natural frequencies and identifies modal degeneracy and the upper limits of representable modes via the Nyquist–Shannon criterion. Stage II: Based on continuous ring elasticity theory, the research establishes the actual coupled modal shapes. This stage demonstrates the manner in which kinematically linked displacements result in an elliptical trajectory on the stator surface. The analytical findings are validated using Finite Element Analysis (FEA) in CATIA. The simulations confirm the degeneracy of natural modes, proving that biphasic excitation is strictly necessary to maintain the progressive waves required for USM operation.

AppliedPhys doi: 10.3390/appliedphys2010001

Authors: Arti Devi Hirofumi Kadono Uma Maheswari Rajagopalan

Rapid evaluation of water toxicity requires biological methods capable of detecting sub-lethal physiological changes without depending on chemical identification. Conventional microscopy-based bioassays are limited by low throughput and difficulties in observing small, transparent and fast-moving microorganisms. This study applies a laser-biospeckle, non-imaging microbioassay to assess the motility responses of Paramecium caudatum and Euglena gracilis exposed to two organic pollutants, trichloroacetic acid (TCAA) and acephate. Dynamic speckle patterns were recorded using a 638 nm laser diode (Thorlabs Inc., Tokyo, Japan) and a CCD camera (Gazo Co., Ltd., Tokyo, Japan) at 60 fps for 120 s. Correlation time, derived from temporal cross-correlation analysis, served as a quantitative indicator of motility. Exposure to TCAA (0.1–50 mg/L) produced strong concentration-dependent inhibition, with correlation time increasing up to 16-fold at 500× PL in P. caudatum (p < 0.01), whereas E. gracilis showed a delayed response, with significant inhibition only above 250× PL. In contrast, acephate exposure (0.036–3.6 mg/L) induced motility enhancement in both species, reflected by decreases in correlation time of up to 57% in P. caudatum and 40% in E. gracilis at 100× PL. Acute trends diminished after 24–48 h, indicating time-dependent physiological adaptation. These results demonstrate that biospeckled-derived correlation time sensitively captures both inhibitory and stimulatory behavioral responses, enabling real-time, high-throughput water toxicity screening without microscopic imaging. The method shows strong potential for integration into automated water-quality monitoring systems.

AppliedPhys doi: 10.3390/appliedphys1020006

Authors: Syed Hussain Bushra Hussain Michael Cottam

In this paper, we explore the magnetization dynamics in a long ferromagnetic nanostripe with finite width in the presence of antisymmetric Dzyaloshinskii–Moriya exchange interactions (DMIs). It is known that DMIs, which are currently of great interest because they give rise to chiral and nonreciprocal properties and influence surface topologies, can be enhanced by interfacing the nanostripe with a heavy metal. Our theoretical approach employs a microscopic (or Hamiltonian-based) analysis that includes symmetric bilinear exchange, antisymmetric DMI, long-range dipole–dipole interactions, and Zeeman energy due to an external magnetic field applied out of the plane of the nanostripe. In this geometry, we calculate the frequencies and amplitudes of the discrete spin-wave modes that have a standing-wave character across the finite width of the stripe and a propagating character (with wavenumber k) along the stripe length. The individual spin-wave modes display nonreciprocal propagation in their dispersion relations due to DMI. We also find that there may be localized edge spin waves with amplitudes that undergo spatial decay near the stripe edges.

AppliedPhys doi: 10.3390/appliedphys1010005

Authors: Ioana Craciun

AppliedPhys (ISSN 3042-6553) is a new Open Access journal launched under the leadership of Prof [...]

AppliedPhys doi: 10.3390/appliedphys1010004

Authors: Ivan Piza-Davila Javier Salinas-Luna Guillermo Sanchez-Diaz Roger Chiu Miguel Mora-Gonzalez

We present some numerical results on piston and tilt detection by using the Young experiment with Genetic Algorithms (GAs). We have simulated the cophasing of a flat surface by following the experimental setup and the mathematical model for Optical Path Difference (OPD) in the Young experiment to characterize piston and tip–tilt misalignment images in the order of a few nanometers, considering diffraction effects and random noise of 5%. Thus, the best fitness obtained by the genetic algorithm is considered as a determining factor to decide a complete error measurement because the proposed algorithm is capable of extracting the values of piston and tilt separately, regardless of which error is present or both. As a result, we have developed a study on piston detection from (0.001, 10) mm with a tilt present in the same pattern from (0, λ/2) by using GAs embedded in a computational application.

AppliedPhys doi: 10.3390/appliedphys1010003

Authors: Daniele Iannarelli Francesco Napoli Antonella De Ninno Antonella Ingenito Simone Mannori

This research paper provides a conceptualization of a new type of plasma thruster based on screw-pinch physics and on the magnetic mirror concept. The article proposes a method to size a screw-pinch with a non-uniform axial magnetic field as a plasma thruster and to estimate its propulsive performance. The results obtained show that the plasma thruster is suitable for space missions inside the Earth’s sphere of influence and for space transportation of small satellites.

AppliedPhys doi: 10.3390/appliedphys1010002

Authors: Yingjia Li Jorge Casanova Xi Chen Evgeny Ya. Sherman

We studied the quantum control of the classical motion of a two-dimensional exciton by optimizing the time-dependent electric field of a stripe-like gate acting on the exciton and inducing its time-dependent quantum dipole moment. We propose a search method that significantly reduces computational requirements while efficiently identifying optimal control parameters. By leveraging this method, we can precisely manipulate the exciton’s final position and velocity over a specified evolution time. These results can be applied for the control of exciton fluxes and populations, and for spatially resolved light emission in two-dimensional semiconducting structures.

AppliedPhys doi: 10.3390/appliedphys1010001

Authors: Lavista Tyagi Hirofumi Kadono Uma Maheswari Rajagopalan

The increasing use of nanoparticles (NPs) in various industries has intensified research into plant–NP interactions. NP properties significantly impact their cellular uptake and plant effects, highlighting the need for advanced monitoring techniques to understand their influence on plant growth and seed germination. This study uses biospeckle optical coherence tomography (bOCT) to investigate the size-dependent effects of zinc oxide (ZnO) NPs and microparticles (MPs) on lentil seed internal activity, visualizing dynamic changes under ZnO particle stress. ZnO was selected for its agricultural relevance as a micronutrient. Lentil seeds were submerged in ZnO particle dispersions (<50 nm, <100 nm, 5 μm, 45 μm) at concentrations of 0 (control), 25, 50, 100, and 200 mg/L. OCT structural images were obtained at 12.5 frames per second using a swept-source OCT (central wavelength 1.3 μm, bandwidth 125 nm, sweep frequency 20 kHz). OCT scans were performed before immersion (0 h) and 5, 10, and 20 h after lentil seed exposure to particle dispersion. The biospeckle image, representing dynamic speckle patterns characteristic of biological tissues, was calculated as the ratio of standard deviation to mean of 100 OCT structural images over 8 s. Biospeckle contrast was compared 0, 5, 10, and 20 h post-exposure. ZnO NPs <50 nm and 100 nm negatively impacted lentil seed biospeckle contrast at all concentrations. In contrast, 45 µm ZnO MPs significantly increased it even at 100 mg/L, while 5 μm MPs decreased biospeckle contrast at higher concentrations. bOCT results were compared with conventional morphological (germination percentage, growth, biomass) and biochemical (superoxide dismutase, catalase, and hydrogen peroxide) measurements. Conventional methods require one week, whereas bOCT detects significant changes in only five hours. The results from bOCT were consistent with conventional measurements. Unlike standard OCT, which monitors only structural images, bOCT is capable of monitoring internal structural changes, allowing rapid, non-invasive assessment of nanomaterial effects on plants.