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Imagine a glacier. Are you thinking "glittering snow" or "plastic pollution?" A new study underscores the pervasive nature of plastic pollution, even in such remote and apparently pristine areas.

Ethiopia's Afar and Oromia regions have been hit by several earthquakes and tremors since the beginning of 2025. The strongest, with a magnitude of 5.7, struck on 4 January. The US Geological Survey and the German Research Centre for Geosciences reported that its epicenter was 142km east of the capital, Addis Ababa, which is in the Oromia region. It came just a day after a quake with a magnitude of 5.5 hit the same area. Two more quakes were reported over the weekend of 11 January.

Eastern North America and Central Europe could see their most extreme heat waves become twice as intense as previously projected due to variations in soil moisture, according to a new study.

Near-inertial internal waves (NIWs) are crucial energy sources for deep-sea mixing, but the origins of deep NIWs have remained largely unknown. A research team led by Prof. Wang Fan from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) has made advancements in understanding the generation mechanisms of deep near-inertial kinetic energy (NIKE). Their findings were published in Geophysical Research Letters.

The processes that form continental crust from the denser basaltic rocks of the upper mantle may make the lower lithosphere denser than the underlying mantle. One theory holds that the lower lithosphere splits away and sinks into the mantle in a process called foundering. Conclusive evidence of foundering, however, has been hard to come by.

Abstract

The process of forming edge metallization on input windows (germanium, silicon, and other discs) used for introducing the received light flux into a photodetector housed in a protective hermetic casing is being investigated. This work presents the results of an experimental study on the dependence of the edge metallization profile of Ge discs, formed by magnetron sputtering, on the design parameters of the loading device. Various designs of loading devices are presented. The experimental results demonstrate the influence of thickness on the edge metallization profiles of the components of the loading device that mask the discs during sputtering.

Abstract

Methods to solve the problem of traceability and reproducibility for the measurement of parameters of second-generation photodetectors are proposed. An improved block diagram of the measurement methods and division into groups of the methods for measurement of second-generation photodetector devices and monitoring of auxiliary equipment is presented.

Abstract

Effect of illumination distribution in the circle of confusion on the measurement of the photoelectric coupling coefficient of the second-generation photodetector devices is studied. A theoretical study is carried out using mathematical modeling for illumination patterns of different structure and several ratios of photodetector pitch to the effective size of the photosensitive area. A formula is derived for calculation of the photoelectric coupling coefficient for a known distribution of photodetector sensitivity. The main conditions that affect the reliability of the results on the simulated measurement process are presented.

Abstract

Distributions of dark currents, lifetimes of minority carrier, and microdefects revealed by selective etching are compared. The main reason for increased dark currents and decreased photosensitivity in silicon photodiodes fabricated on n-type silicon using the Czochralski method are the generation–recombination processes on fine oxide precipitates.

Abstract

The results of the development of a recursive algorithm for temporal noise reduction with an adaptive threshold for thermal imaging systems are presented. This algorithm is designed to reduce the level of temporal noise based on the results of analyzing a sequence of images obtained using a thermal imaging channel. A mathematical model of the algorithm is provided, as well as the required amount of computing resources needed for its hardware implementation in field programmable gate arrays (FPGAs). Several characteristics of the thermal imaging system with the developed algorithm were measured and conclusions were made about the positive influence of the algorithm on its noise equivalent temperature difference (NETD).

Abstract

The resonant scattering spectra by the main magnetic mode of a subwavelength linear structure consisting of two dielectric flat thin rings located along the wave vector and excited by the displacement currents of the incident plane electromagnetic wave of the microwave range are investigated experimentally and using computer modeling. As distinct from a single ring, splitting of the resonant frequency is observed in the scattering spectra of the magnetic field in the far wave zone, near wave zone, and near the centers of the rings. The measured spectra coincide with the spectra resulting from computer calculations at all measurement points.

Abstract

For the task of Earth remote sensing (ERS) in the short-wave infrared (IR) range of the spectrum, the most promising are matrix and multi-row photodetector modules of the short-wave infrared (IR) range of the spectrum based on heteroepitaxial structures of materials of the ternary solution of cadmium-mercury-tellurium (HgCdTe) and the ternary solution of indium-gallium-arsenide (InGaAs), sensitive in the spectral range from 1 to 2.5 μm. Possible architectures of photosensitive elements that provide reduced dark currents and noise are analyzed. Ways of improvement are considered and dark currents and parameters of n-on-p-type heterostructures based on HgCdTe in a wide temperature range, as well as the parameters of p+-B–n-N+-type barrier structures based on InGaAs are investigated.

Abstract

An overview of various sensor designs for recording the parameters of microparticles in the accelerator path is provided, which are used to simulate the impact of micrometeoroids and space debris particles on structural elements of a spacecraft. A model of a cylindrical induction sensor (a Faraday cup) and a possible modification of its design for measuring the microparticle distribution in the accelerator path are considered in more detail.

Abstract

The parameters of photodetectors based on photosensitive barrier structures and photodiodes with absorbing layers of InAs1–xSbx and In1–xGaxSb ternary solutions of the mid-wave infrared spectrum range are studied. Temperature dependences of lifetime and dark current in InAs1–xSbx and In1–xGaxSb layers have been calculated. The signal-to-noise ratio in the operating temperature range was determined. Parameter modeling has shown that for photodetectors based on InAs0.8Sb0.2 with a cutoff wavelength λ0.5 ∼ 4.8 µm the detectability at T = 100 K will be D* ≈ 1012 cm W–1 Hz1/2; for photodiodes based on In0.7Ga0.3Sb with cutoff wavelength λ0.5 ∼ 5.2 µm the detectability at T = 100 K will be D* ≈ 1011 cm W–1 Hz1/2, which is suitable for high temperature applications.

Abstract

A new deselection method has been developed for detecting defects in infrared photomodules (IR PMs) with time delay and accumulation mode (TDM). The developed method is used to detect and deselect defective photosensitive elements (PSEs), which most reduce the signal-to-noise ratio (SNR) in IR PM channels. This method increases the SNR of IR PM channels, which improves the ability of IR PMs to detect low-power infrared optical signals. This result is ensured by the fact that the detection of defective PSEs is achieved by processing the signals and noise of all PSEs using the detection criterion of PSEs that most reduce the SNR of the IR PM channels. This method is a general rule for detecting defective PSEs, since the criterion analyzes the influence of all PSEs on the SNR of IR PM channels, including the noisiest elements.

Abstract

The electric field on the surface of a metal electrode immersed in plasma with an electron temperature of Te ∼ 10 eV and plasma density ne from 1010 to 1013 cm−3 has been calculated under negative electric potential Ψ0 of the electrode and large values of parameter |eΨ0|/Te  \( \gg \)  1. The obtained asymptotic formula for the field strength at |eΨ0|/Te  \( \gg \)   1 differs significantly from the classical formulas for calculating the electric field and the Debye length of field screening near the electrode surface in plasma, which are valid under condition |eΨ0|/Te  \( \ll \)  1. It has been shown that, at |eΨ0|/Te  \( \gg \)  1, near the electrode in a plasma, a modified Debye layer can exceed the classical Debye length by two orders of magnitude. To calculate the electric field on the electrode surface in plasma, a generalized formula has been proposed in the explicit form, which is valid in a wide range of parameter 0 < |eΨ0|/Te < 104 at negative electrode potentials of up to 10 kV.

Abstract

The electrostatic reflection method is formulated and proven for a point charge located near a plane-layered medium consisting of two films on a dielectric half-space. The method is generalized to the case of an arbitrary system of charges and is used to solve mathematically similar problems of electrostatics and the stationary thermal conductivity of plane-layered media. The problem of finding the electrostatic potential distributions around a conducting sphere located near a plane-layered structure consisting of two dielectric films on a dielectric half-space is solved. Solutions to similar problems of finding the temperature distribution of uniformly heated bodies located near a heat-conducting plane-layered structure of two heat-conducting films on a heat-conducting half-space are discussed.

Abstract

Global ionospheric total electron content (TEC) map prediction is important for improving the accuracy of global navigation satellite systems. There are two main issues with the current TEC prediction: (1) The deep learning models used for TEC prediction are mainly designed using a stacked structure. When stacking multiple layers, the input data will undergo continuous multi-layer convolution operations, leading to the loss of fine-grained features and the degradation of model performance; (2) The model optimization methods for TEC prediction are relatively outdated, mainly using manual optimization or grid search methods. To address these two issues, an automatic framework for global TEC map prediction and optimization is proposed, named as CGAOA-STRA-BiConvLSTM. It includes a global TEC map prediction model, STRA-BiConvLSTM, which can simultaneously extract both coarse-grained and fine-grained spatiotemporal features. It also contains an optimization algorithm, CGAOA, to optimize the model. We first experimentally verified the effectiveness of CGAOA. Then, the effectiveness of STRA-BiConvLSTM was verified through ablation experiments. Finally, we conducted comparative experiments from multiple perspectives between our framework and 5 mainstream methods: C1PG, C2PG, ConvLSTM, ConvGRU, and ED-ConvLSTM. The results show that in all cases, the proposed CGAOA-STRA-BiConvLSTM outperforms the comparative models.

Nature Geoscience, Published online: 20 January 2025; doi:10.1038/s41561-024-01634-8

The Martian dichotomy boundary receded hundreds of kilometres in the Mawrth Vallis region and left behind mounds that record changing aqueous conditions during the Noachian (4.1–3.7 Ga), according to a geomorphological and spectroscopic study.

SummaryForward modeling is crucial for seismic data processing, which is the core of reverse time migration and full-waveform inversion. Numerical simulation based on conventional elastic wave equations in stationary solids neglects the fluidity of fluids (e.g., seawater), making it difficult to simulate the propagation of seismic waves in moving fluids accurately. To solve the problem, we start with classical equations of fluid mechanics and derive a new set of elastic wave equations that can be used to simultaneously model wave propagation both in moving fluids and stationary solids. For high-precision numerical simulations, a staggered-grid finite-difference scheme is used to solve the proposed equations. Numerical tests on a homogeneous uniformly moving model demonstrate that the dynamic and kinematic characteristics (e.g., wavelength, amplitude) of elastic waves in moving fluids are quite different from those in stationary medium. Forward modeling for a two-layer model that has a flowing water layer and a stationary rock layer is used to study the reflection and transmission patterns of elastic waves in the solid-fluid interface. With the help of the superposition principle of vectors and Snell's law, the transmission angles can be easily calculated. A further test for a more complex stratified model indicates that the energy and travel time differences of reflected waves are expected to be evidence for the identification of moving fluids. Numerical experiments on the Marmousi II model demonstrate that the relative wavefield error is positively correlated with the maximum moving velocity and the wavelet dominant frequency.