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2025
The ligand-binding domain (LBD) of the human nuclear receptor pregnane X receptor (PXR) is known to crystallize in two different crystal forms, P212121 or P43212, depending on the construct and the strategy used for protein production, as well as the presence or absence of the coactivator-derived peptide SRC-1. In order to facilitate biophysical and structural studies, a versatile construct was designed that allows access to both forms. This was achieved by introducing a thrombin cleavage site between the PXRLBD and the SRC-1 peptide fused to its C-terminus. Here, we describe the expression, purification and crystallization processes of this novel construct and report two new structures of PXRLBD that were obtained thanks to this strategy.- Book : 81(3)
- Pub. Date : 2025
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2025
A novel polarization conversion radome based on dielectric-embedded metamaterial elements is proposed to decrease the size of antenna profiles. This radome is composed of two kinds of interlaced dielectric-embedded metamaterial elements to realize the polarization conversion and beam deflection. The structures and characteristics of two types of dielectric-embedded metamaterial elements have been studied and analyzed. By selecting an appropriate dielectric material and applying periodic boundary conditions to optimize these two kinds of dielectric-embedded metamaterial elements, the radome made up of these metamaterial elements eventually is mounted atop a square horn antenna. Simulation results indicate that the antenna radome enables the horn antenna to achieve polarization conversion and beam deflection at the operating frequency. The maximum beam deflection angle can be 29° within a gain reduction of 1 dB, while the axial ratio remains below 1.5 dB and the reflection coefficient continuously remains below −22 dB. Moreover, the power-handling capacity of each metamaterial element within the radome is above 60 kW.- Book : 15(2)
- Pub. Date : 2025
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2025
In eMalahleni, high solar irradiation makes it ideal for solar farms. The proposed photovoltaic (PV) systems are designed to meet the entire energy demand of the Tshwane University of Technology’s eMalahleni campus. These systems are expected to produce approximately 876 MWh of electricity per annum. The campus building presentations promoting such designs have roofs tilted at 25 degrees and can support the installation of a 625-kW solar PV system. The current proposal will install a 150 kW PV system with a 100-kW inverter, designed to maximize conversion efficiency and system performance. This setup is expected to be viable, with returns estimated in a period of 14 months due to the low LCOE value of 0.6 Rands/kWh. In total, this project has an estimated lifetime saving of about 30 million Rands. According to detailed simulations, the model used to predict the global solar radiation for the region is highly efficient, that is, it follows actual values very well. This tracking ability is very important for making the best use of how well the system can work. This accuracy is critical for maximizing the efficiency of solar energy production. The performance of the PV system reaches its peak at 125 kW around midday, highlighting the benefits of precise solar radiation modeling in enhancing energy output. Moreover, the shift to solar energy is expected to have substantial environmental benefits. Over a period of ten years, the transition will reduce carbon dioxide (CO2) emissions by 6,515 tons, nitrogen oxides (NOx) by 27 tons, and sulfur oxides (SOx) by 53 tons. This reduction in greenhouse gases and pollutants will contribute significantly to climate change mitigation, improved air quality, and decreased acid rain. The overall impact underscores the significant economic and environmental advantages of adopting solar power in eMalahleni.- Book : 20()
- Pub. Date : 2025
- Page : pp.29-41
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2025
An ultrasound-responsive hydrogel system was developed that provides on-demand release when stimulated by focused ultrasound (fUS). Diels–Alder cycloadducts crosslinked polyethylene glycol (PEG) hydrogels and underwent a retrograde Diels–Alder reaction when exposed to fUS. Four-arm and eight-arm furan-based Diels–Alder hydrogel compositions were used to evaluate the link between the crosslinking density and the fUS-induced release and retention rates. PEG crosslinked with glutaraldehyde was also used as a non-Diels–Alder control hydrogel. By increasing the exposure time and the amplitude of fUS, the Diels–Alder-based hydrogels exhibited a correlative increase in the release of the entrapped BMP-2. Real-time B-mode imaging was used during fUS to visualize the on-demand degradation of the crosslinking matrix for the release of BMP-2. When monitored with a thermocouple, the increase in temperature observed was minimal in the area surrounding the sample during fUS stimulation, indicating fUS to be an external stimulus which could be used safely for spatiotemporally controlled release. PEG hydrogels were characterized using nuclear magnetic resonance, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and compression testing. PEG degradation byproducts were evaluated for cytocompatibility in vitro. Overall, this study demonstrated that Diels–Alder-based PEG hydrogels can encapsulate BMP-2, undergo a retrograde reaction when externally stimulated with fUS, and release active BMP-2 to induce differentiation in human mesenchymal stem cells.- Book : 11(2)
- Pub. Date : 2025
- Page : pp.120-120
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2025
New higher-count-rate, integrating, large-area X-ray detectors with framing rates as high as 17400 images per second are beginning to be available. These will soon be used for specialized macromolecular crystallography experiments but will require optimal lossy compression algorithms to enable systems to keep up with data throughput. Some information may be lost. Can we minimize this loss with acceptable impact on structural information? To explore this question, we have considered several approaches: summing short sequences of images, binning to create the effect of larger pixels, use of JPEG-2000 lossy wavelet-based compression, and use of Hcompress, which is a Haar-wavelet-based lossy compression borrowed from astronomy. We also explore the effect of the combination of summing, binning, and Hcompress or JPEG-2000. In each of these last two methods one can specify approximately how much one wants the result to be compressed from the starting file size. These provide particularly effective lossy compressions that retain essential information for structure solution from Bragg reflections.- Book : 32(2)
- Pub. Date : 2025
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2025
ABSTRACTIn situ leaching (ISL) is an important method for green and efficient development of sandstone‐type uranium ore. It achieves ISL of uranium through the deployment of injection and extraction vertical well patterns. The optimization of parameter matching between injection and extraction wells is key to improving the efficiency of uranium development. However, as the depth of mining and the scale of development increase, the small area controlled by vertical wells leads to a large number of vertical wells and high drilling costs, which severely affect the benefits of mine development. In this paper, taking the development case of the LK mine area in Xinjiang as an example, an extraction method of “horizontal well injection–vertical well extraction” was innovatively proposed for the first time. By using the well‐storage coupling model and particle tracking technology, this study systematically investigated the impact of well types and injection–extraction parameters on the leaching range and the distribution of leaching dead zones. Furthermore, a hybrid multiobjective optimization algorithm was used to complete the parameter optimization of well‐storage coupling for ISL of uranium. The research content of this paper explores the impact of injection–extraction parameters and well spacing on the leaching effect of “horizontal well injection–vertical well extraction,” providing a method and approach for the optimization study of ISL uranium parameters. In addition, the research results of this paper have certain guiding significance for enhancing the leaching and extraction effect of the existing uranium mining plan in the LK mining area.- Book : ()
- Pub. Date : 2025
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2025
Red sandstone is widely distributed in southern China. Due to the significant difference in mechanical properties before and after hydration and its poor water stability, red sandstone often triggers landslide accidents. In this paper, red sandstone from an open pit slope in Jiangxi Province was taken as the research object. Two variables, namely the initial saturation degree (25%, 50%, 75%, and 100%) and the number of wetting–drying cycles (0, 10, 20, 30, and 40), were set. With the help of nuclear magnetic resonance, the Brazilian disc test, and fractal theory, the relationships among its meso-structure, macroscopic fracture mechanics characteristics, and deterioration mechanism were analyzed. The research results are as follows: (1) Wetting–drying cycles have a significant impact on the pore structure and fracture mechanics characteristics of red sandstone. Moreover, the higher the initial saturation degree, the more obvious the deterioration effect of the wetting–drying cycles on the rock mass. (2) After further subdividing the pores according to their size for research, it was found that sandstone is mainly composed of mesopores, and the deterioration laws of different types of pores after the wetting–drying cycles are different. The porosities of total pores and macropores increase, while the proportions of mesopores and micropores decrease. The fractal dimensions of macropores and total pores of each group of rock samples are all within the range of 2–3, and the fractal dimension value increases with the increase in the number of wetting–drying cycles, showing significant and regular fractal characteristics. Micropores and some mesopores do not possess fractal characteristics. The fractal dimension of rock samples basically satisfies the rule that the larger the pore diameter, the larger the fractal dimension and the more complex the pore structure. (3) Both the type I and type II fracture toughness of rock samples decrease with the increase in the number of cycles, and the decrease is the most significant when the initial saturation degree is 100%. After 40 cycles, the decreases in type I and type II fracture toughness reach 23.578% and 30.642%, respectively. The fracture toughness is closely related to the pore structure. The porosity and fractal dimension of rock samples and their internal macropores are linearly negatively correlated with the type II fracture toughness. The development of the macropore structure is the key factor affecting its fracture mechanics performance. (4) After the wetting–drying cycles, the internal pores of red sandstone continue to develop. The number of pores increases, the pore diameter enlarges, and the proportion of macropores rises, resulting in internal damage to the rock mass. When bearing loads, the expansion and connection of internal cracks intensify, ultimately leading to the failure of the rock mass. The research results can provide important reference for the stability analysis of sandstone slope engineering.- Book : 15(2)
- Pub. Date : 2025
- Page : pp.158-158
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2025
This paper presents a study of brane formation in six-dimensional space. There is no a priori assumption of the existence of brane(s). However, an analysis of the generalized Einstein equations shows that there is a set of metrics describing two static branes even in the absence of matter fields. At the same time, no one-brane configurations were found. The trapping of massive particles on branes is a consequence of the metric structure, which prevents these particles from moving between branes. It is shown that communication between charged particles on different branes is provided by photons. Such positron–electron annihilation could be studied experimentally at the LHC collider. The Higgs field is distributed between the branes in such a way that it can serve as a Higgs portal connecting two worlds located on different branes. The values of the 4D physical parameters depend on the extra metric structure near the branes. We also found a non-trivial effect of the decompactification of extra space during the Hubble parameter variation.- Book : 17(2)
- Pub. Date : 2025
- Page : pp.252-252
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2025
Abstract
Near the ends of their lives, supernova remnants (SNRs) enter a “radiative phase,” when efficient cooling of the postshock gas slows expansion. Understanding SNR evolution at this stage is crucial for estimating feedback in galaxies, as SNRs are expected to release energy and momentum into the interstellar medium near the ends of their lives. A standard prediction of SNR evolutionary models is that the onset of the radiative stage precipitates the formation of a dense shell behind the forward shock. In Paper I, we showed that such shell formation yields detectable nonthermal radiation from radio to γ-rays, most notably emission brightening by nearly 2 orders of magnitude. However, there remains no observational evidence for such brightening, suggesting that this standard prediction needs to be investigated. In this paper, we perform magnetohydrodynamic simulations of SNR evolution through the radiative stage, including cosmic rays (CRs) and magnetic fields to assess their dynamical roles. We find that both sources of nonthermal pressure impede shell formation, reducing shell densities by a factor of a few to more than an order of magnitude. We also use a self-consistent model of particle acceleration to estimate the nonthermal emission from these modified SNRs and demonstrate that, for reasonable CR acceleration efficiencies and magnetic field strengths, the nonthermal signatures of shell formation can all but disappear. We therefore conclude that the absence of observational signatures of shell formation represents strong evidence that nonthermal pressures from CRs and magnetic fields play a critical dynamical role in late-stage SNR evolution.- Book : 980(2)
- Pub. Date : 2025
- Page : pp.167-167
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2025
- Book : ()
- Pub. Date : 2025
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