radio frequency emission

At redshifts beyond [Formula: see text], the 21 cm line from neutral hydrogen is expected to be essentially the only viable probe of the three-dimensional matter distribution. The lunar far-side is an extremely appealing site for future radio arrays that target this signal, as it is protected from terrestrial radio frequency interference, and has no ionosphere to attenuate and absorb radio emission at low frequencies (tens of MHz and below). We forecast the sensitivity of low-frequency lunar radio arrays to the bispectrum of the 21 cm brightness temperature field, which can in turn be used to probe primordial non-Gaussianity generated by particular early universe models...

Integrated quantum photonic circuits require the efficient coupling of photon sources to photonic waveguides. Hybrid plasmonic/photonic platforms are a promising approach, taking advantage of both plasmon modal confinement for efficient coupling to a nearby emitter and photonic circuitry for optical data transfer and processing. In this work, we established directional quantum dot (QD) emission coupling to a planar TiO2 waveguide assisted by a Yagi-Uda antenna. Antenna on waveguide is first designed by scaling radio frequency dimensions to nano-optics, taking into account the hybrid plasmonic/photonic platform...

Transcranial ultrasound plays a limited role in neuroradiology due to its lack of resolution, planar imaging, and user-dependency. By breaching the diffraction limit using injected microbubbles, volumetric ultrasound localization microscopy (ULM) could help alleviate those issues. However, performing 3D ultrasound imaging at a high frame rate with sufficient signal-to-noise ratio to track individual microbubbles through the skull remains a challenge, especially with a portable scanner. In this study, we describe a ULM sequence suitable for volumetric transcranial imaging exploiting cylindrical emissions on multiplexed matrix probes, through simulations, hydrophone measurements, and flow phantoms...

In Greece, 5G New Radio (NR) has started launching in the end of 2020, at the 3400-3800 MHz (FR1) frequency band. Focusing on 117 Base Stations (BSs) which were already equipped with 5G NR antennas, in situ broadband and frequency selective measurements have been conducted at minimum three points of interest, at adjacent rooftops (when accessible). The points have been selected according to the sweeping method and the electric field strength (E) value has been stored on the selected worst-case scenario point...

Lightweight, low-cost metasurfaces and reflectarrays that are easy to stow and deploy are desirable for many terrestrial and space-based communications and sensing applications. This work demonstrates a lightweight, flexible metasurface platform based on flat-knit textiles operating in the cm-wave spectral range. By using a colorwork knitting approach called float-jacquard knitting to directly integrate an array of resonant metallic antennas into a textile, we realize two textile reflectarray devices, a metasurface lens (metalens) and a vortex-beam generator...

The plasma technique has been widely used to modify the surfaces of materials. The purpose of this study was to evaluate the probability of controlling the prednisolone delivery velocity on a polylactic acid (PLA) surface modified by plasma surface treatment. Surface modification of PLA was performed at a low-pressure radio frequency under conditions of 100 W power, 50 mTorr chamber pressure, 100~200 sccm of flow rate, and Ar, O2, and CH4 gases. The plasma surface-modified PLA was characterized using scanning emission microscope, X-ray photoelectron spectroscopy (XPS), and contact angle measurements...

We report an experimental technique to trigger modelocking (ML) emission in frequency-shifted feedback (FSF) lasers. These lasers feature an intracavity modulator driven by a radio frequency tone, which shifts the light spectrum every cavity round trip. The technique consists of the drive of the modulator with a second tone at the cavity free spectral range (FSR) frequency. So, in addition to the frequency shift, a weak amplitude modulation (AM) appears synchronous with the cavity round trip time. The approach is successful as FSF cavities support chirped modes evenly spaced by the FSR, whose AM coupling produces convenient seed pulses for the ML onset...

Magnetars are neutron stars with extremely high magnetic fields (≳1014  gauss) that exhibit various X-ray phenomena such as sporadic subsecond bursts, long-term persistent flux enhancements and variable rotation-period derivative1,2 . In 2020, a fast radio burst (FRB), akin to cosmological millisecond-duration radio bursts, was detected from the Galactic magnetar SGR 1935+2154 (refs. 3-5 ), confirming the long-suspected association between some FRBs and magnetars. However, the mechanism for FRB generation in magnetars remains unclear...

In this work, a new atmospheric pressure plasma generated in a wire-to-multiwire dielectric barrier discharge on pure oxygen is introduced. This special geometry of 13 wires (one central wire and 12 ones on the external tube) is feeding by a radio frequency (RF) power (13.56 MHz, 1 kW) and produces a stable discharge. The capacity of this device to produce oxygen reactive species and the influence of Ar gas mixture (1-3%) on this production are investigated. The main characteristics of this DBD plasma are measured using optical emission spectroscopy techniques...

Fast radio bursts (FRBs) are millisecond transient astrophysical phenomena and bright at radio frequencies. The emission mechanism, however, remains unsolved yet. One scenario is a coherent emission associated with the magnetar flares and resulting relativistic shock waves. Here, we report unprecedentedly large-scale simulations of relativistic magnetized ion-electron shocks, showing that strongly linear-polarized electromagnetic waves are excited. The kinetic energy conversion to the emission is so efficient that the wave amplitude is responsible for the brightness...

The interactions between high-intensity laser and matter produce particle flux and electromagnetic radiation over a wide energy range. The generation of extremely intense transient fields in the radio frequency-microwave regime has been observed in femtosecond-to-nanosecond laser pulses with 1011 -1020 -W/cm2 intensity on both conductive and dielectric targets. These fields typically cause saturation and damage to electronic equipment inside and near an experimental chamber; nevertheless, they can also be effectively used as diagnostic tools...

Nigerian bituminous tar sands are among the world's largest deposits of bitumen and heavy oil. They are estimated to contain 38-40 billion barrels of heavy oil and bitumen, spanning approximately 120 km in length and 4-6 km in breadth. With global commitments to net zero emissions and various energy transition plans, improvements in the recovery methods for heavy oil and bitumen are being sought. To address this, renewable energy electrothermal enhanced oil recovery is considered an eco-friendly alternative...

INTRODUCTION: Osteoid osteoma is a common benign osteoblastic lesion of the bone. Although it commonly affects the cortex of long bones, it rarely involves the cancellous portion of the small bones such as phalanges. The occurrence of osteoid osteoma in phalanges poses a diagnostic dilemma. CASE REPORT: In our case report, we presented a 26-year-old patient with long-standing pain over the great toe. The radiographs and magnetic resonance imaging (MRI) were unable to diagnose the lesion, and a single-photon emission computerized tomography scan picked up the nidus...

INTRODUCTION AND OBJECTIVE: Mobile phones and Wi-Fi are the most commonly used forms of telecommunications. Initiated with the first generation, the mobile telephony is currently in its fifth generation without being screened extensively for any biological effects that it may have on humans or on animals. Some studies indicate that high frequency electromagnetic radiation emitted by mobile phone and Wi-Fi connection can have a negative effect upon human health, and can cause cancer, including brain tumour...

BACKGROUND: Simultaneous positron emission tomography (PET)/magnetic resonance imaging (MRI) scanners and inserts are valuable tools for accurate diagnosis, treatment planning, and monitoring due to their complementary information. However, the integration of a PET system into an MRI scanner presents technical challenges for a distortion-free operation. PURPOSE: We aim to develop a PET insert dedicated to breast imaging in combination with the 3T PET/MRI scanner Biograph mMR (Siemens Healthineers) as well as a brain PET insert for the 7T MRI scanner MAGNETOM Terra (Siemens Healthineers)...

The effect of pulse-modulated sub-RF range (100 kHz-1 MHz) excitation on atmospheric pressure argon plasma jet characteristics is studied. For this, a suitable power supply is developed, offering a sub-µs rise time with control of different parameters, such as voltage amplitude, pulse modulation frequency in the range of 1-30 kHz, and an oscillation frequency of ∼520 kHz, which can affect the plasma behavior. Plasma characteristics, such as reactive species generation, ionic composition, plasma plume length, and gas temperature, are evaluated qualitatively and quantitatively by employing diagnostics such as optical emission spectroscopy, molecular beam mass spectrometry, and optical imaging...

This study proposed a simple method to evaluate the spectral reflectance of the inner wall of a vacuum chamber. A method for calculating spectral emission coefficients by taking the spectral reflectance of the chamber inner wall into account was proposed. Furthermore, plasma diagnosis based on optical emission spectroscopic (OES) measurement was performed so as to obtain radial dependence of electron temperature Te and density Ne of a radio frequency inductively coupled Argon (Ar) plasma by applying a collisional-radiative model to radially resolved emission spectra of the Ar plasma assuming axial symmetry...

A ppbv-level mid-infrared photoacoustic spectroscopy sensor was developed for mouth alcohol tests. A compact CO2 laser with a sealed waveguide and integrated radio frequency (RF) power supply was used. The emission wavelength is ∼9.3 µm with a power of 10 W. A detection limit of ∼18 ppbv (1σ) for ethanol gas with an integration of 1 s was achieved. The sensor performed a linear dynamic range with an R square value of ∼0.999. A breath measurement experiment after consuming lychees was conducted...

The pursuit of efficient, profitable, and ecofriendly materials has defined solar cell research from its inception to today. Some materials, such as copper nitride (Cu3 N), show great promise for promoting sustainable solar technologies. This study employed reactive radio-frequency magnetron sputtering using a pure nitrogen environment to fabricate quality Cu3 N thin films to evaluate how both temperature and gas working pressure affect their solar absorption capabilities. Several characterization techniques, including X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), Raman spectroscopy, scanning electron microscopy (SEM), nanoindentation, and photothermal deflection spectroscopy (PDS), were used to determine the main properties of the thin films...

This study introduces a novel method for preconcentrating As, Cu, and Pb from seawater samples using manganese oxide octahedral molecular sieve (OMS-2), as a sorbent, and the analysis by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The OMS-2 nanomaterial was synthesized and characterized using X-ray diffraction and scanning electron microscopy, revealing a crystallite size of 20.9 nm and a typical needle-like morphology of cryptomelane structure. To optimize the ICP-OES operating conditions and the preconcentration process, a central composite design was used...