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A practical guide to radio channel measurement techniques Whilst there are numerous books describing modern wireless communication systems that contain overviews of radio propagation and radio channel modelling, few contain detailed information on the design, implementation and calibration of radio channel measurement equipment, the planning of experiments and the in depth analysis of measured data. This work redresses that balance. Beginning with an explanation of the fundamentals of radio wave propagation, the book progresses through a series of topics, including the measurement of radio channel characteristics, radio channel sounders, measurement strategies, data analysis techniques and radio channel modelling. Application of results for the prediction of achievable digital link performance are discussed with examples pertinent to single carrier, multi-carrier and spread spectrum radio links. It addresses specifics of communications in various different frequency bands for both long range and short range fixed and mobile radio links. Key features: Focuses on radio channel measurements and characterization with analysis of MIMO channels Discusses the physical and technical considerations involved in the proper assessment of radio channel characteristics for efficient radio system planning, design, and implementation Provides in-depth information on the planning of experiments and the detailed analysis of measured data from radio propagation and channel modelling Unique practical approach describing how to design and implement channel sounders

The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs) 1 , sources of high-frequency gravitational waves (GWs) 2 and likely production sites for heavy-element nucleosynthesis by means of rapid neutron capture (the r -process) 3 . Here we present observations of the exceptionally bright GRB 230307A. We show that GRB 230307A belongs to the class of long-duration GRBs associated with compact object mergers 4 – 6 and contains a kilonova similar to AT2017gfo, associated with the GW merger GW170817 (refs.  7 – 12 ). We obtained James Webb Space Telescope (JWST) mid-infrared imaging and spectroscopy 29 and 61 days after the burst. The spectroscopy shows an emission line at 2.15 microns, which we interpret as tellurium (atomic mass A  = 130) and a very red source, emitting most of its light in the mid-infrared owing to the production of lanthanides. These observations demonstrate that nucleosynthesis in GRBs can create r -process elements across a broad atomic mass range and play a central role in heavy-element nucleosynthesis across the Universe. Observations from the JWST of the second brightest GRB ever detected, GRB 230307A, indicate that it belongs to the class of long-duration GRBs resulting from compact object mergers, with the decay of lanthanides powering the longlasting optical and infrared emission.

On 6 September 2017, the Sun emitted two significant solar flares (SFs). The first SF, classified X2.2, peaked at 09:10 UT. The second one, X9.3, which is the most intensive SF in the current solar cycle, peaked at 12:02 UT and was accompanied by solar radio emission. In this work, we study ionospheric response to the two X-class SFs and their impact on the Global Navigation Satellite Systems and high-frequency (HF) propagation. In the ionospheric absolute vertical total electron content (TEC), the X2.2 SF caused an overall increase of 2-4 TECU on the dayside. The X9.3 SF produced a sudden increase of~8-10 TECU at midlatitudes and of~15-16 TECU enhancement at low latitudes. These vertical TEC enhancements lasted longer than the duration of the EUV emission. In TEC variations within 2-20 min range, the two SFs provoked sudden increases of~0.2 TECU and 1.3 TECU. Variations in TEC from geostationary and GPS/GLONASS satellites show similar results with TEC derivative of~1.3-1.7 TECU/min for X9.3 and 0.18-0.24 TECU/min for X2.2 in the subsolar region. Further, analysis of the impact of the two SFs on the Global Navigation Satellite Systems-based navigation showed that the SF did not cause losses-of-lock in the GPS, GLONASS, or Galileo systems, while the positioning error increased by~3 times in GPS precise point positioning solution. The two X-class SFs had an impact on HF radio wave propagation causing blackouts at <30 MHz in the subsolar region and <15 MHz in the postmidday sector.

Background: Fractional microneedle radiofrequency (FMR) devices deliver energy to the deep dermis through insulated microneedles without destroying the epidermis. These FMR devices have been shown to be effective for the treatment of wrinkles, acne scars and large pores. In this study it was postulated that FMR energy could specifically affect the sweat glands, preserving the skin surface even if sweat glands were seated in the deep dermis. Objective: To evaluate the efficacy and safety of FMR for primary axillary hyperhidrosis (PAH) treatment and to conduct a histological analysis before and after treatment. Methods: Twenty patients with PAH had 2 sessions of bipolar FMR treatment at 4-week intervals. Clinical improvement was evaluated using a Hyperhidrosis Disease Severity Scale (HDSS) and photographs were taken using the starch-iodine test at every visit and 2 months after the last treatment. The amount of sweat reduction was indirectly assessed using a Tewameter™. Skin biopsies were obtained from 3 of the enrolled patients before and after treatment. The satisfaction and adverse reactions of the research participants were recorded at every follow-up visit. Results: HDSS scores decreased significantly from a baseline of 3.3 to 1.5 and 1.8 after the first and second months of posttreatment follow-up sessions, respectively (p < 0.001). In response to a subjective assessment at 1 month after the second treatment, 75% of patients (n = 15) had an HDSS score of 1 or 2, and 70% of patients (n = 14) expressed more than 50% improvement in their sweating. The starch-iodine reaction was also remarkably reduced in 95% of patients (n = 19) after FMR treatment. Histological findings showed a decrease in the number and size of both apocrine and eccrine glands 1 month after the final treatment. Side effects were minimal and included mild discomfort, transient swelling and postinflammatory hyperpigmentation. Conclusion: FMR treatment was effective for the treatment of PAH without significant adverse reactions due to direct volumetric heating of the lower dermis.

The Very Low Frequency (VLF) radio wave propagation characteristics play a very important role in understanding the behaviour of the D-region. The earth-ionosphere wave guide theory has been used to evaluate the reflection height of VLF radio waves using the electron density profiles obtained from the International Reference Ionosphere (IRI) 2012 and 2016 models. For calculating the conductivity parameter, two different collision frequency models have been used. The diurnal shift in reflection height of 16-kHz VLF waves is evaluated for the midpoint of Visakhapatnam-Rugby path using the two IRI models and the results are compared with those values derived from VLF phase measurements made at Visakhapatnam. The theoretically evaluated values using the FT-2001 option for the D-region electron density profile in the IRI-2012 and IRI–2016 models are in good agreement with those obtained from phase measurements, especially in summer. The day to night shift in reflection height obtained using exponential collision critical frequency model are in good agreement with those derived from VLF phase measurements. The diurnal shift in reflection height of VLF radio waves during winter months derived from IRI models are much lower than those obtained from measurements.

By using 3-year global positioning system (GPS) measurements from December 2013 to November 2016, we provide in this study a detailed survey on the climatology of the GPS signal loss of Swarm onboard receivers. Our results show that the GPS signal losses prefer to occur at both low latitudes between ±5 and ±20∘ magnetic latitude (MLAT) and high latitudes above 60∘ MLAT in both hemispheres. These events at all latitudes are observed mainly during equinoxes and December solstice months, while totally absent during June solstice months. At low latitudes the GPS signal losses are caused by the equatorial plasma irregularities shortly after sunset, and at high latitude they are also highly related to the large density gradients associated with ionospheric irregularities. Additionally, the high-latitude events are more often observed in the Southern Hemisphere, occurring mainly at the cusp region and along nightside auroral latitudes. The signal losses mainly happen for those GPS rays with elevation angles less than 20∘, and more commonly occur when the line of sight between GPS and Swarm satellites is aligned with the shell structure of plasma irregularities. Our results also confirm that the capability of the Swarm receiver has been improved after the bandwidth of the phase-locked loop (PLL) widened, but the updates cannot radically avoid the interruption in tracking GPS satellites caused by the ionospheric plasma irregularities. Additionally, after the PLL bandwidth increased larger than 0.5 Hz, some unexpected signal losses are observed even at middle latitudes, which are not related to the ionospheric plasma irregularities. Our results suggest that rather than 1.0 Hz, a PLL bandwidth of 0.5 Hz is a more suitable value for the Swarm receiver. Keywords. Ionosphere (equatorial ionosphere; ionospheric irregularities) – radio science (radio wave propagation)

Radical pair kinetics is determined by the coherent and incoherent spin dynamics of spin pair and spin-selective chemical reactions. In a previous paper, reaction control and nuclear spin state selection by designed radiofrequency (RF) magnetic resonance was proposed. Here, we present two novel types of reaction control calculated by the local optimization method. One is anisotropic reaction control and the other is coherent path control. In both cases, the weighting parameters for the target states play an important role in the optimizing of the RF field. In the anisotropic control of radical pairs, the weighting parameters play an important role in the selection of the sub-ensemble. In coherent control, one can set the parameters for the intermediate states, and it is possible to specify the path to reach a final state by adjusting the weighting parameters. The global optimization of the weighting parameters for coherent control has been studied. These manifest calculations show the possibility of controlling the chemical reactions of radical pair intermediates in different ways.

Saturn Kilometric Radiation (SKR), being the dominant radio emission at Saturn, has been extensively investigated. The low‐frequency extension of SKR is of particular interest due to its strong association with Saturn's magnetospheric dynamics. However, the highly anisotropic beaming of SKR poses challenges for observations. In most cases, the propagation of SKR is assumed to follow straight‐line paths. We explore the propagation characteristics of SKR across different frequencies in this study. An extended equatorial shadow region for low‐frequency SKR is identified, resulting from the merging of the Enceladus plasma torus and the previously known equatorial shadow zone. Ray‐tracing simulations reveal that low‐frequency (≲ $\\lesssim $100 kHz) SKR is unable to enter the shadow region and is instead reflected toward high latitudes. In contrast, high‐frequency SKR (≳ $\\gtrsim $100 kHz) generally propagates without hindrance. Observations suggest that some low‐frequency SKR can enter the shadow region through reflection by the magnetosheath or leakage from the plasma torus. Plain Language Summary Saturn Kilometric Radiation (SKR) is a natural electromagnetic wave generated in Saturn's high‐latitude region along its magnetic field lines. Variations in SKR frequency could offer insights into Saturn's magnetic conditions, especially its interaction with the solar wind. However, the observed frequency characteristics of SKR depend on viewing geometry due to its directional nature. While past studies assumed SKR travels in straight lines, this may not hold true for low‐frequency SKR. These emissions can change direction when they encounter dense plasma, similar to light reflecting off a mirror or bending when entering water. At Saturn's equatorial region, the plasma torus created by Enceladus, one of Saturn's moons, contains dense plasma and significantly affects radio wave propagation. Our study investigates the distribution of SKR at different frequencies and identifies a shadow region where low‐frequency SKR emissions are rarely seen. Using numerical simulations of ray propagation paths, we discover that low‐frequency SKR emissions cannot reach these shadow regions because they are reflected by the dense plasma torus. However, occasionally, we observe low‐frequency SKR in the shadow region, suggesting the possibility of reflection by Saturn's magnetosheath or leakage through the plasma torus. Key Points The propagation characteristics of Saturn Kilometric Radiation (SKR) are established statistically and by ray‐tracing A shadow region of the low‐frequency SKR near the equatorial region at large radial distances is discovered and discussed Low‐frequency SKR may enter the shadow region due to torus leakage or reflection at the magnetosheath