Reinhard Niessner

Morning 7 MHz long-path single-sideband (SSB) contacts between southern Germany and New Zealand are sparse and cluster about one hour after civil dawn in Germany, although weaker signals can be received much earlier. We use archived Weak Signal Propagation Reporter (WSPR) signal-to-noise ratios for 2023–2025, audited for transmitter and receiver activity, together with semi-empirical absorption estimates and PHaRLAP ray tracing, to investigate this narrow interval. WSPR was decoded on 498 of 594 mornings with demonstrated station activity (84%). Published speech requirements and an indicative 500 W link budget narrow the 87 min WSPR detection window to an SSB-equivalent interval of 40–60 min, peaking 60–75 min after dawn, consistent with the timing of 60 documented SSB contacts. Modeled D-region absorption is lowest in this interval, when the Sun is low at both ends of the path, a dual-terminator window. The modeled minimum occurs a median of 15 min after the temporal midpoint between German civil dawn and New Zealand receiver sunset (r = 0.99, 512 mornings); because both times shift together on this nearly antipodal path, the season predicts contact time as well as dawn does. Receivers in Australia show that the window closes at receiver sunset or about 154 min after German dawn, whichever comes first. No systematic difference in closure time was detected between 7 and 10 MHz near New Zealand sunset, which argues against both absorption and a falling maximum usable frequency as the cause; the mechanism remains unresolved.

Grayline (terminator‑adjacent) HF propagation has been exploited operationally for decades, yet its predictability remains limited when defined purely by solar geometry. In this study, we investigate the role of the ionospheric state during grayline transitions using equivalent slab thickness (EST), derived from co‑located total electron content (TEC) and ionosonde peak density (NmF2 via foF2). We combine WSPR spot statistics on the 40 m band from transmissions by DK3TG (Germany) with ionosonde and TEC‑based parameters (foF2, hmF2, TEC, EST) referenced to Juliusruh and relate these diagnostics to long‑distance HF propagation toward North America and New Zealand. The results show that successful long‑distance links are not uniformly distributed across the geometrically defined grayline interval but occur within shorter time windows characterized by rapid F‑region restructuring. WSPR observations indicate that changes in EST mark the onset of propagation, whereas successful SSB communication occurs later, during a phase characterized by decreasing hmF2. For the transatlantic path, the majority of detected links occur after the grayline passage, indicating that optimal propagation conditions develop during the post‑grayline phase rather than within the grayline itself. EST provides a diagnostic of propagation onset, while the subsequent evolution of hmF2 controls the usability of the propagation channel.

Most of the morning Germany-New Zealand long path lies in darkness, but usable 40 m SSB propagation remains intermittent. We evaluate whether usability is associated with a transient combination of European F-region structure, loss conditions, and launch geometry rather than with a single ionospheric threshold. Sixty successful-contact rows represent 58 independent mornings. At morning level, the first documented contact occurs a median 60.0 min after civil-twilight onset (bootstrap 95% confidence interval 53.5-66.0 min) and follows its seasonal displacement. However, a harmonic day-of-year model predicts contact time at least as well in leave-one-out testing as twilight time alone, so the timing relation is descriptive and does not independently identify a twilight-controlled mechanism. Two temporally separated observational series comprising 27 strictly classified mornings show that no individual variable or enumerated one- to three-variable model transfers robustly between series. Late hmF2 descent is the strongest descriptive marker (AUC = 0.701, p = 0.085), whereas cross-series and leave-one-out multivariate performance remains near chance. For the confirmed 12 April 2026 contact, PHaRLAP-2D at 258 degrees azimuth demonstrates viable low-elevation first returns from 12 degrees upward. An independent PHaRLAP-3D homing calculation at a different azimuth identifies a 9.00-degree trajectory that spans 21,850 km in three ground hops and terminates 29.6 km from ZL1KVA. Because both calculations use an unassimilated IRI-2020 background and do not represent the same ray, they establish complementary geometrical plausibility rather than event-specific causality. The observations therefore constrain, but do not confirm, a transient multicomponent access hypothesis for documented 40 m SSB usability.

Grayline (terminator‑adjacent) HF propagation has been exploited operationally for decades, yet its predictability remains limited when defined purely by solar geometry. In this study, we investigate the role of the ionospheric state during grayline transitions using equivalent slab thickness (EST), derived from co‑located total electron content (TEC) and ionosonde peak density (NmF2 via foF2). We combine WSPR spot statistics on the 40 m band from transmissions by DK3TG (Germany) with ionosonde and TEC‑based parameters (foF2, hmF2, TEC, EST) referenced to Juliusruh and relate these diagnostics to long‑distance HF propagation toward North America and New Zealand. The results show that successful long‑distance links are not uniformly distributed across the geometrically defined grayline interval but occur within shorter time windows characterized by rapid F‑region restructuring. WSPR observations indicate that changes in EST mark the onset of propagation, whereas successful SSB communication occurs later, during a phase characterized by decreasing hmF2. For the transatlantic path, the majority of detected links occur after the grayline passage, indicating that optimal propagation conditions develop during the post‑grayline phase rather than within the grayline itself. EST provides a diagnostic of propagation onset, while the subsequent evolution of hmF2 controls the usability of the propagation channel.

There continues to be a high prevalence of smoking in many European countries. In Germany, for example, there are over 20 million smokers, most of whom exhibit little desire to quit. In other countries, the adoption of smoke-free products (SFPs), including e-cigarettes (ECs), heated tobacco products (HTPs), and oral nicotine pouches (NPs), is helping smokers to transition away from cigarettes. In Germany, debate about SFPs primarily focuses on their potential harms to non-smokers, particularly the underage population. This debate seems one-sided: raising concerns alone does not sufficiently inform the 20 million smokers about the comparative health risks of cigarettes and SFPs, an issue increasingly echoed by practitioners and researchers. Instead, the current discourse is dominated by misconceptions, as evidenced by surveys on smokers’ perceptions of the relative health risks of cigarettes and SFPs. Considering the gravity of the topic, it is essential to revisit the scientific facts. The growing evidence shows that SFPs, including ECs, HTPs, and NPs, expose users to significantly fewer numbers and lower concentrations of toxicants relative to combustible cigarettes. In vitro studies and biomarkers of harm in SFP users suggest that these lower emissions translate to reduced risks of harm. It is the nature of science that the evidence will never be complete, but the totality of data should be considered when discussing the correct handling of SFPs. At present, these data suggest that SFPs can play a useful role in curbing the individual and societal risks associated with smoking.

Sensitive and simultaneous detection of multiple cancer-related biomarkers in serum is essential for diagnosis, therapy, prognosis, and staging of cancer. Herein, we proposed a magnetically assisted sandwich-type surface-enhanced Raman scattering (SERS)-based biosensor for ultrasensitive and multiplex detection of three hepatocellular carcinoma-related microRNA (miRNA) biomarkers. The biosensor consists of an SERS tag (probe DNA-conjugated DNA-engineered fractal gold nanoparticles, F-AuNPs) and a magnetic capture substrate (capture DNA-conjugated Ag-coated magnetic nanoparticles, AgMNPs). The proposed strategy achieved simultaneous and sensitive detection of three miRNAs (miRNA-122, miRNA-223, and miRNA-21), and the limits of detection of the three miRNAs in human serum are 349 aM for miRNA-122, 374 aM for miRNA-223, and 311 aM for miRNA-21. High selectivity and accuracy of the SERS biosensor were proved by practical analysis in human serum. Moreover, the biosensor exhibited good practicability in multiplex detection of three miRNAs in 92 clinical sera from AFP-negative patients, patients before and after hepatectomy, recurred and relapse-free patients after hepatectomy, and hepatocellular carcinoma patients at distinct Barcelona clinic liver cancer stages. The experiment results demonstrate that our SERS-based assay is a promising candidate in clinical application and exhibited potential for the prediction, diagnosis, monitoring, and staging of cancers.

Current legislations typically characterize systems of aerosols, such as from vehicle exhaust, primarily by number concentration and size distributions. While potential health threats have a dependence on the particle size, the chemical composition of particles, including the volatile and semi-volatile components adsorbed onto nonvolatile particle cores present at roadside and urban settings, is important in understanding the impact of exhaust particles on health. To date, the only tools suitable for an online in-depth chemical aerosol characterization are aerosol mass spectrometers, which are typically composed of complex and cost intensive instrumentation. We present a new analytical system, which combines a novel inexpensive infrared-radiation-based evaporation system (HELIOS) with a commercially available highly efficient atmospheric ionization source (SICRIT) connected to a rather low-price ion-trap mass spectrometer. Our inexpensive, robust and mobile aerosol characterization HELIOS/SICRIT/Mass Spectrometry system enables highly sensitive chemical analysis of particle-associated volatile substances. We validate the HELIOS/SICRIT/Mass Spectrometry system in laboratory experiments with coated particles generated under controlled conditions, and show that the system is capable of identification of combustion-generated polycyclic aromatic hydrocarbons and relative quantification of individual chemical species adsorbed on particle surfaces. We then employ our system to analyze real-world vehicle engine exhaust aerosol and show through time-resolved measurements with high time resolution (<10 s) that the chemical composition of the particles changes during different parts of an engine test cycle. Copyright © 2021 American Association for Aerosol Research

Nanoplastic pollution is of emerging environmental concern, but current analytical approaches are facing limitations in this size range. However, the coupling of nanoparticle separation with chemical characterization bears potential to close this gap. Here, we realize the hyphenation of particle separation / characterization (field-flow fractionation (FFF), UV and multi angle light scattering (MALS)) with subsequent chemical identification by on-line Raman microspectroscopy (RM). The problem of low Raman scattering was overcome by trapping particles with 2D optical tweezers. This setup enabled RM to identify particles of different materials (polymers and inorganic) in the size range from 200 nm to 5 µm, with concentrations in the order of 1 mg/L (10⁹ particles L^-1). The hyphenation was realized for asymmetric flow FFF (AF4) and centrif-ugal FFF (CF3), which separate particles based on different properties. This technique shows potential for application in nanoplastic analysis, as well as many other fields of nanomaterials.

With the introduction of gas-based contactless electrochemical biosensors lies the prospects of separating the sensing interface from the bioassembly platform, enhancing stability and exploring signal transduction mechanism, all intimately linking to development of immunoassay. Herein, we reported H2-based electrochemical biosensor whose signals derived from the chemical signal transduction between H2 and Pd [email protected] (ZIF: Zeolitic Imidazolate Frameworks) bilayered sensing interface for immunoassay. Dendritic Pt nanoparticles (DPNs) conjugated on the detection antibody were introduced on the interface of magnetic microsphere according to immune sandwich assembly between the antigen and antibody. H2 as a bridge originates from DPNs catalyzing NH3BH3 and links biological signals to the electric signal by reacting with Pd nanowires. Nevertheless, the response of Pd nanowires extremely effected by O2 in air due to the competitive adsorption on the surface of Pd nanostructures as well as the reaction between chemisorbed O (Pd-O) and adsorbed dihydrogen, leading to the decrease of H absorption into the PdHx and poor sensing responses under low target concentration. Porous ZIF-67 (window aperture 0.331 nm) as molecular sieve self-assembling on the surface of the Pd nanowires film could easily permeate H2 (kinetic diameter of 0.289 nm), while interferential O2 (kinetic diameter of 0.346 nm) difficultly passed through the ZIF-67 layer to contact Pd nanowires, and achieved the response of lower concentrations target as well as faster response rate. Under optimal conditions, H2-based electrochemical biosensor exhibits great response towards target alpha-fetoprotein (AFP) within a dynamic working range of 0.1-50 ng mL-1 at a detection limit of 0.04 ng mL-1. Our strategy provides reusable sensing interface, high specificity, and acceptable accuracy for the immunoassay. In addition, it also expands a promising platform for the application as a molecular sieve in electrochemical biosensors.