Search Results (7,948)

Photosynthesis, the main energy source for life on Earth, confronts escalating challenges of high-light–high-temperature stress (HLHT). Our previous study identified a mutation in ATP synthase, F₁-α-C252Y, that significantly enhances the HLHT tolerance of Synechococcus elongatus PCC 7942 (Sye7942), although the underlying mechanism remains obscure. In this study, we found that this mutation led to elevated levels of the b subunit of F_o, F₁ subunits, and the ATP synthase within cells, without affecting ATP synthetic activity, indicating improved intracellular ATP synthesis activity. Additionally, the mutation altered the transcriptome of Sye7942, impacting the expression of genes involved in crucial processes, such as the electron transport chain, carbon fixation, and regulatory factors, which are crucial for cyanobacteria’s adaptation to stresses. Correspondingly, the mutant exhibited enhanced photosynthesis, accelerated growth, and increased glycogen under HLHT conditions, showing improved adaptation. The higher intracellular ATP synthesis activity, along with enhanced photosynthetic activity, suggests increased ATP production in the mutant under HLHT. Enhancing ATP production and remodeling the cellular transcriptome appear to be key strategies employed by the C252Y mutation for Sye7942 acclimating to HLHT. These findings provide valuable insights for enhancing photosynthetic efficiency and stress resilience in cyanobacteria and other photosynthetic organisms facing HLHT challenges. Full article

This study aimed to describe the endocrine, cellular, and transcriptomic changes associated with mild heat stress responses in Wugu-Hu and Hu rams. Testicular samples from rams exposed to 3 days of scrotal insulation, resulting in an approximate 3 °C increase in scrotal temperature, and corresponding controls were analyzed for endocrine activity, seminiferous tubule morphology, germ cell composition, and transcriptomic profiles. There were no significant changes in testosterone, follicle-stimulating hormone, or luteinizing hormone after 3 days of mild heat exposure in either breed. Wugu-Hu rams showed greater disorganization of seminiferous tubules. Apoptotic events occurred mainly from spermatocytes to spermatids and were accompanied by a greater decline in spermatids in Wugu-Hu rams. Comparative transcriptomic analysis between Wugu-Hu and Hu rams identified 854 differentially expressed genes, mainly enriched in immune response function. We conclude that scrotal heat stress does not disrupt endocrine balance at the level applied in this study, but it induces breed-dependent morphological and testicular cellular responses. The differences in the immune response of Hu and Wugu-Hu rams may contribute to their distinct levels of spermatocytes and spermatids’ response to elevated temperatures. Full article

The distribution and spectral properties of colored dissolved organic matter (CDOM) in the northern Bay of Bengal were investigated in June 2016. Based on in situ data collected from 100 CDOM samples at 25 stations, the distribution characteristics of CDOM in the surface layer differed markedly from those at 30 m, 75 m, and 100 m. The CDOM spectral slope ($S_{350-500}$) exhibited a broad range, varying from 0.0026 to 0.0300 nm${}^{-1}$, and showed a significant negative correlation with the absorption coefficient $a_{\mathrm{CDOM}}\left(443\right)$. Analysis of salinity and temperature profiles revealed no obvious correlation between the distribution of $a_{\mathrm{CDOM}}\left(443\right)$ and these physical parameters. A comparative analysis with satellite-derived wind and current data indicated that elevated $a_{\mathrm{CDOM}}\left(443\right)$ values in the northeastern surface waters were primarily associated with the southwest monsoon. In contrast, $a_{\mathrm{CDOM}}\left(443\right)$ values in the lower mixed layer were mainly influenced by the combined effects of geostrophic and eddy currents. Full article

Africa’s rainfed agricultural systems are highly exposed to climate change, making shifts in temperature and rainfall a major concern for staple-food crop production. Using a MaxENT ecological niche modelling approach with crop occurrence, elevation, soil and climatic predictors, this study assessed current and future suitability for rainfed maize, millet and sorghum under RCP 4.5 and RCP 8.5. The projections show a notable expansion of 11.1–22.0% in areas suitable for maize cultivation, and a decline of 1.6–7.3% in areas suitable for production of millet and sorghum, indicating likelihood for increased food-security risks in regions dependent on drought-tolerant cereals. These differing shifts highlight the need for targeted adaptation measures, including crop diversification and region-specific planning to help sustain crop production under a changing climate. Full article

The primary productivity of phytoplankton (PP_eu) is critical to the carbon cycle in aquatic ecosystems. However, in complex lakes covered by ice, the estimation of PP_eu using remote sensing techniques is constrained. To address this limitation, this study developed an estimation model for ice-covered PP_eu by incorporating optical parameters such as the ice surface refractive index and the extinction coefficient of the ice layer into the vertical generalized production model (VGPM). This approach overcomes the challenges associated with remote sensing-based estimation of PP_eu during ice-covered periods. The results indicate that the annual carbon sequestration of the WLSHL is 1.72 × 10⁴ t C, with an average annual PP_eu of 316.96 mg C·m⁻²·d⁻¹. In addition to the indicators that are directly involved in the estimation of PP_eu, the environmental factors that affect PP_eu include water temperature (WT), ice thickness (IT), snow, water depth (D), total dissolved solids (TDSs), salinity (S), ammonia nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃⁻-N), and oxidation–reduction potential (ORP). The PP_eu in the ice period is found to be only 17% lower than that in the ice-free period. However, the PP_eu during the ice period is considerably higher than that during the ice + snow period. The findings indicate that the impact of freezing on PP_eu during the winter is relatively limited, whereas the influence of snowfall is more pronounced. In order to mitigate the elevated PP_eu and the occurrence of algal blooms during the summer, the intensity of underwater radiation can be regulated on a periodic basis. To optimize the function of the carbon sink in winter lakes, the PP_eu can be enhanced through initiatives such as water replenishment prior to freezing and snow removal following freezing. Full article

To address the environmental sensitivity and low bioavailability of riboflavin, this study constructed a soybean protein isolate fibril (SPF)/κ-carrageenan (κC) composite gel delivery system. This study systematically investigated the effects of two independent variables (protein type: SPI/SPF; κC concentration: 2, 4, 6, 8 mg/mL) on the gel structural stability, riboflavin encapsulation performance, and in vitro digestive delivery characteristics of the system. Thioflavin T (ThT) fluorescence and ultraviolet (UV) absorption spectroscopy confirmed the successful preparation of SPF and verified specific intermolecular interactions between SPF and κC. Intermolecular forces, protein leaching rates, and differential scanning calorimetry (DSC) results indicated that compared with SPI-κC composite gels, κC regulates SPF molecular conformation via hydrogen bonding and hydrophobic interactions to exert a synergistic effect. This conformational regulation significantly reduced the protein leaching rates in SPF-κC composite gels, elevated the thermal denaturation temperatures (up to 79.82 °C), and enhanced the gel structural stability. As the κC concentration increased, the environmental stability of SPF-κC riboflavin-loaded composite gels were markedly enhanced, which effectively delayed the gel degradation during simulated gastrointestinal digestion. This was manifested as a reduced protein loss rate (reduced to 22.23%). At a κC concentration of 8 mg/mL, the in vitro release mechanism of riboflavin shifted from Fickian to non-Fickian diffusion. Full article

Global warming is reshaping the global dry–wet pattern, yet its future trajectory remains uncertain, with important implications for sustainable water resources. China, influenced by both the monsoon system and the mid-latitude westerlies, requires an integrated assessment linking net water balance (precipitation minus evaporation, PME) to moisture transport. Here we use precipitation, evaporation, and air temperature records for 1981–2023, together with Lagrangian moisture tracking and precipitation recycling diagnostics, to quantify changes in PME across China and to identify the underlying mechanisms. We further assess future evolution under different warming levels (1.5 °C, 2 °C, and 3–4 °C) for 2024–2099 using a CMIP6 multi-model ensemble. China experienced a pronounced warming during the historical period, while precipitation declined overall and evaporation remained nearly stable. As a result, reduced moisture supply strengthened drought sensitivity. Spatially, warming-driven drying is concentrated in the eastern and southern monsoon regions. In contrast, the inland arid and semi-arid Northwest and parts of high-elevation transition zones show a relative shift toward warmer and wetter conditions. Moisture transport diagnostics indicate that China’s moisture supply is jointly sustained by the mid- to high-latitude westerlies and low-latitude oceanic monsoon pathways. These pathways form a continuous transition from the Northwest to the Southeast. Land–atmosphere recycling is stronger in the Southeast, whereas the Northwest depends more on imported moisture, with plateau topography further reshaping the main transport corridors. In the future, PME continues to decline under 1.5 °C warming. Under 2 °C warming, PME enters a transitional state with patchy regional patterns. Under 3–4 °C warming, PME shifts to an overall increase, but uncertainty becomes larger. These results identify a critical turning window at around 2–3 °C warming for China’s PME response, providing a physical basis for sustainable water-resource management and adaptation planning. Full article

This paper studies a two-stage oxygen-alkaline treatment and subsequent bleaching of softwood sulfate pulp obtained from healthy and deadwood of spruce and larch. Delignification was carried out at elevated temperature and pressure in an alkaline medium with the addition of hydrogen peroxide, after which the pulp was subjected to classic ECF cycles with chlorine dioxide, hydrogen peroxide and, if necessary, elemental chlorine. The selected and washed mass was ground to a specified degree of grinding and formed into laboratory sheets of standard density on a sheet-forming apparatus. The results showed that oxygen-alkaline pretreatment significantly reduces the residual lignin content, and subsequent bleaching cycles make it possible to obtain high-brightness pulp with minimal losses of cellulose and viscosity. The structural, morphological and mechanical characteristics of the obtained samples were studied. After a full bleaching cycle, the fibers become slightly shorter and thinner, their surface is leveled, the proportion of small fractions decreases, and the homogeneity of the structure improves. The resulting cellulose samples demonstrate mechanical characteristics that meet industrial requirements for high-quality printing and thin-layer paper grades. Full article

The primary objective of this research is to quantitatively isolate the complex driving factors of slope deformation and explicitly reveal the long-term creep mechanism induced by early excavation unloading, thereby providing a theoretical basis for long-term stability evaluation. To achieve this, this study adopts a combined approach of multivariate statistical regression and numerical simulation inversion based on long-sequence monitoring data. First, a multivariate statistical regression model incorporating time-dependent, rainfall, temperature, valley width, and excavation components was constructed to quantitatively separate the contribution weights of each factor. Second, by introducing a rock–soil creep constitutive model, a refined finite element model was established to perform back-analysis of creep parameters and numerical simulation. The results indicate that two large-scale slope-cutting excavations were the direct triggers for the deformation, resulting in shear dislocation of the deep ancient sliding zone and superficial slippage. The dominant factors exhibit distinct phasic and spatial differences: before impoundment, the time-dependent component was absolutely dominant (>80%); after impoundment, low-elevation areas were significantly affected by valley width shrinkage (>60%), while high-elevation areas remained dominated by time-dependent deformation (>74%). Numerical simulation confirmed that the nature of the deformation is “excavation unloading-induced creep along the ancient sliding zone,” and the simulation results considering creep effects accurately reproduced the actual deformation characteristics observed in situ. It is concluded that the rheological effects induced by early excavation unloading are central to the control of long-term stability. Full article

Low-temperature Cu sintering is used as a die-bonding strategy for the third-generation power device, and the Cu-sintered joints require long-term stability at elevated temperature. In this work, we investigate the thermal stability and microstructural evolution of the Cu interconnect joints with an ultra-thin sintered layer at the temperature of 250 °C in air. The as-prepared joint shows a dense well-bonded interface with low porosity before the thermal aging test. The average shear strength of the joints increases from 85.5 MPa to 91.3 MPa after aging up to 300 h. With further increase in aging time, the shear strength begins to decrease. However, the strength remains at a high level of 69.8 MPa even after 500 h of aging, satisfying the requirements for high-temperature stability. At short aging times, the porosity within the interface reduces slightly, and the fracture exhibits distinct ductile characteristics. When the aging time exceeds 300 h, the oxide content at the interface increases from the outer region toward the inner part, and aging cracks eventually appear at the edge of the sintered layer. Therefore, it is demonstrated that the dense and thin sintered layer limits oxygen diffusion, guaranteeing the high-temperature stability of the sintered joint. Full article

Carbon fiber-reinforced polyimide composites are critical for aerospace applications in high-temperature environments of 300–500 °C. However, conventional PMR-15- and PEPA-terminated polyimides are limited by their insufficient glass transition temperatures (T_g) and low crosslinking densities. This study proposes a reactive backbone construction strategy by employing 4,4′-(ethyne-1,2-diyl)diphthalic anhydride (EBPA) as a difunctional monomer copolymerized with asymmetric 2,3,3′,4′-biphenyl tetracarboxylic dianhydride (α-BPDA) and 4,4′-oxydianiline to synthesize polyimide resins containing both backbone ethynyl and terminal phenylethynyl groups. The effects of EBPA content on the curing behavior, thermomechanical properties, and elevated temperature mechanical performance were systematically investigated. The incorporation of EBPA significantly elevated T_g from 378 °C to 486 °C. Compared to the EBPA-0 control, the optimized EBPA-2 composite exhibited 7.3% and 3.6% improvements in room temperature flexural strength and modulus, respectively. Notably, at 400 °C, EBPA-2 demonstrated retention rates of 69.9%, 93.7%, and 61.6% for flexural strength, flexural modulus, and interlaminar shear strength, exceeding EBPA-0 by 16.9, 8.9, and 18.6 percentage points. SEM analysis confirmed the effective suppression of interfacial debonding at elevated temperatures. These findings elucidate the structure–property relationships between molecular structure, T_g, and short-term high-temperature mechanical retention, providing a promising resin matrix for advanced aerospace carbon fiber composites. Full article

Creep is one of the main failure mechanisms of materials at elevated temperatures, and the creep rate curve is a key descriptor of creep deformation and damage evolution. However, existing creep models are mainly phenomenological or stage-wise, and the physical origin of the bathtub-shaped creep rate curve over the full creep process has not been systematically clarified. In this study, creep damage is treated as an aging failure process of a material system, and a physically interpretable hierarchical model is established based on statistical physics for disordered complex systems. By linking the evolution and interaction of microscopic material units with macroscopic creep behavior, the proposed model provides a unified description of the primary, secondary, and tertiary creep stages and offers a theoretical explanation for the bathtub-shaped creep rate curve. Validation using representative metallic and composite material cases shows that the model can reasonably reproduce the overall three-stage creep rate evolution, with residual sums of squares of 1.3088 and 0.5369, respectively. These results demonstrate the ability of the model to capture full-process creep behavior in different material systems. The main advantage of the proposed approach is its physical interpretability within a unified framework, while its current limitation is that the validation remains limited in scale and broader benchmark comparisons with conventional methods are still needed. This work provides a statistical perspective for creep behavior modeling and for understanding the microscopic mechanisms and interactions underlying creep degradation in structural materials. Full article

Vacuum drying is a promising alternative to conventional dehydration for heat-sensitive vegetables, although process temperature can significantly affect both drying behavior and product quality. In this study, vacuum drying of cauliflower florets (Brassica oleracea) was evaluated at 40, 50, 60, 70, and 80 °C under 10 kPa, using freeze-drying as a reference. Desorption isotherms were determined at 50 and 70 °C and fitted to common models, where the GAB model provided excellent fits (R² = 0.9999 and 0.9997, respectively). The drying kinetics were successfully described by four thin-layer models, with the Midilli–Kucuk and Weibull models performing best overall. Color was significantly affected, with total color differences (ΔE) ranging from 15.9 to 20.6 and higher browning indices at elevated temperatures. Bioactive compounds (total phenols, flavonoids, and glucosinolates) and antioxidant potential (by DPPH and ORAC assays) were quantified to assess changes in functional quality across treatments. Bioactive compounds showed the highest values at the highest temperatures (60–80 °C). The DPPH assay remained stable between 50 and 80 °C, but ORAC assay decreased with increasing temperature, suggesting that vacuum drying at 60–70 °C offers the best balance between overall bioactive retention and functionality for producing cauliflower powder. Full article

Identifying the heterogeneous characteristics of habitat quality (HQ) trajectories is a key prerequisite for refined ecological spatial management. We used kernel Normalized Difference Vegetation Index (kNDVI) to correct the highly sensitive parameters, validated the correction results based on their consistency with the prior study findings, developed a framework for the evolution of HQ using Sen+MK and Pettitt’s tests, and utilized XGBoost and partial correlation analysis to identify the primary drivers of dynamic changes in HQ from both spatiotemporal perspectives. Our findings include the following: (1) between 2000 and 2023, the average annual rate of change in the HQ index was 0.0037 per year, indicating a continuous improvement in HQ. Compared with the period from 2011 to 2023 (0.0026 per year), the rate of improvement in HQ was faster during 2000–2011 (0.0047 per year). (2) Mutational improvement and progressive improvement were the main evolutionary trajectories, accounting for over 50.33% of the total. (3) Precipitation, land-use intensity (LUI), temperature, and elevation show a strong correlation with HQ distribution. The magnitude of HQ variation is related to HQ status, LUI, precipitation, and elevation. This study establishes a scientific foundation for developing differentiated regulatory strategies for YRB. Full article

Modern dentistry increasingly relies on light-curing units (LCUs) and lasers in essential clinical procedures such as composite resin polymerization, caries treatment, and periodontal therapy. This review aims to outline the evolution of light-emitting technologies and to assess their potential biological risks, with particular emphasis on effects on the visual system, oral tissues, and microbiome. The development of curing devices is presented chronologically, from the first-generation ultraviolet (UV-A) lamps introduced in the 1970s to current light-emitting diode (LED-LCU) systems and dental lasers (e.g., Er:YAG, Nd:YAG). The progressive increase in light intensity—now exceeding 3000 mW/cm²—has shortened curing times but simultaneously raised safety concerns. Major hazards include the so-called blue-light hazard, where exposure to high-energy visible (HEV) blue light may accelerate macular degeneration, and temperature elevations in the pulp chamber, which may damage the dentin–pulp complex. Laser radiation also exerts significant microbiological effects: Er:YAG and diode lasers demonstrate bactericidal activity against biofilms and oral pathogens (e.g., P. gingivalis), although therapeutic outcomes depend on wavelength, dose, and exposure time. Suboptimal parameters may lead to microbiome disturbances, whereas low-level laser therapy (LLLT; 600–1200 nm) supports tissue regeneration and helps restore microbial balance. The individualization of irradiation parameters, combined with thorough theoretical knowledge, operator expertise, and technical understanding of LCUs and lasers, is essential for maximizing clinical benefits while minimizing health risks and preserving oral microbiome homeostasis. Full article