Search Results (29,758)

In this study, a modified heat pump system has been designed for heating applications in cold climate regions, enabling the replacement of system components such as the evaporator and heat exchanger within the same system. In this modified heat pump system, which uses R407C and R417A refrigerants instead of the restricted R22 refrigerant, the optimal system conditions that provide the best performance were determined using the Taguchi experimental method, prepared using five different parameters. As a result of the experiments, the optimum operating conditions of the system were determined from the analysis of variance table obtained by considering the COP and exergetic efficiency values. As a result, it was determined that the COP and exergetic efficiency values were higher in the case of using the 8 mm lamella spacing evaporator type and horizontal heat exchanger type. Full article

Basic zinc sulfate with an empirical formula of ZnSO₄∙3 Zn(OH)₂∙3.5 H₂O (or Zn₄SO₄(OH)₆∙3.5 H₂O) was precipitated using stoichiometric amounts of ZnSO₄ and NaOH, followed by drying and storage in air. The XRD pattern suggests that the product contains tri- and tetrahydrate of basic zinc sulfate. Penta-, mono-, and hemihydrates of basic zinc sulfate can be produced by storing the original material in air at various temperatures and humidity levels, and especially by immersion in aqueous solutions. The precipitate was characterized by its specific surface area and zeta potential, and it has an isoelectric point (IEP) at pH 8.9. Ion exchange with an excess of CuSO₄ results in conversion to brochantite Cu₄(OH)₆SO₄ (as detected by XRD) and in an increase in the specific surface area. The conversion was complete at room temperature with a sufficient excess of CuSO₄, but it was not complete at 50 or 60 °C. Apparently, the conversion into brochantite is exothermic. The IEP of brochantites obtained from ZnSO₄∙3 Zn(OH)₂∙3.5 H₂O by ion exchange was at a pH of about 10, which is higher than the previously reported IEP. Full article

Under dynamic loading conditions, the output voltage of proton exchange membrane fuel cells (PEMFCs) exhibits nonlinear degradation characterized by non-Gaussian fluctuations, abrupt changes, and long-range temporal dependence, which are difficult to model using conventional short-correlation or remaining useful life (RUL) prediction approaches. To capture both historical dependency and stochastic jump behavior, this study proposes a SHAP-driven mechanism–data fusion fractional stochastic degradation model based on fractional Brownian motion (fBm) and fractional Poisson process (fPp) for degradation trend forecasting. A terminal voltage mechanism model considering activation, ohmic, and concentration polarization losses is first established, and SHapley Additive exPlanations (SHAP) analysis is employed to quantify the contributions of multi-source operational variables and enhance interpretability. The Hurst exponent is then used to verify long-range dependence and jump characteristics in the voltage sequence. Subsequently, fBm is integrated with a fPp to construct a unified stochastic degradation framework capable of jointly describing continuous decay and discrete abrupt variations, enabling multi-step probabilistic prediction with confidence intervals. Validation on the publicly available FCLAB FC1 and FC2 datasets shows that the proposed model achieves superior overall performance under both steady and dynamic conditions, with MAPE/RMSE/R² of 0.027%/0.00178/0.9895 and 0.056%/0.00259/0.9896, respectively, outperforming fBm, Wiener, WTD-RS-LSTM, and CNN-LSTM methods. The proposed approach provides accurate and interpretable degradation forecasting for PEMFC health management and maintenance decision support. Full article

Dental tissue regeneration, particularly alveolar bone and gingival repair, remains a major challenge in regenerative medicine. 3D bioprinting offers patient-specific and anatomically precise constructs, representing an advanced alternative to conventional grafting. In this study, nanohydroxyapatite (nHA), chitosan (CS), and collagen (CoL) were combined to fabricate and characterize 3D bioprinted dental grafts. SEM revealed a highly porous, interconnected architecture favorable for cell infiltration and nutrient exchange. EDS confirmed Ca/P ratios of 2.06 for nHA/CoL and 1.83 for nHA/CS/CoL, both of which are above the stoichiometric 1.67, indicating the presence of additional mineral phases and ion substitutions. FTIR and XRD verified characteristic functional groups and crystalline phases, including B-type HA with carbonate substitution. Mechanical testing showed that pure nHA exhibited the lowest compressive strength, whereas CoL incorporation improved stiffness. The nHA/CS/CoL composite achieved the highest compressive strength, elastic modulus, and toughness, demonstrating superior mechanical resilience. DSC analysis indicated endothermic peaks at 106.49 °C and 351.91 °C, with enthalpy values (264.91 J/g and 15.09 J/g) surpassing those of nHA alone. TGA revealed ~28.8% weight loss across three degradation stages, confirming enhanced thermal stability. In vitro cytocompatibility testing using L929 fibroblasts validated the biocompatibility of the composites. Collectively, the synergy between bioceramics and biopolymers markedly improved both mechanical and thermal performance. These findings position the nHA/CS/CoL scaffold as a promising candidate for clinical applications in dental tissue regeneration. Unlike conventional grafting materials, this study introduces a synergistically optimized nHA/CS/CoL bio-ink formulation specifically designed for extrusion-based 3D bioprinting of patient-specific dental constructs. The core innovation lies in the precise integration of nHA within a dual-polymer matrix (CS/CoL), which bridges the gap between mechanical resilience and biological signaling, achieving a compressive strength that mimics native alveolar bone while maintaining high cytocompatibility. Full article

Land-use change contributes significantly to climate change mitigation through biophysical changes (albedo, α) and biogeochemical (greenhouse gases, GHG) emissions (here refers to methane, CH₄, and nitrous oxide, N₂O). While the impact of grassland–cropland conversion on global warming potential (GWP) is well-documented globally, research remains scarce in the saline-alkaline agropastoral transition zone (APTZ) of the western Songnen Plain, Northeast China, an ecotone uniquely characterized by soil-crusting and seasonal inundation. We conducted in situ bi-weekly measurements of N₂O and CH₄ fluxes (June–September) to acquire growing season ${\mathrm{GWP}}_{{\mathrm{N}}_2\mathrm{O}}$ and ${\mathrm{GWP}}_{{\mathrm{C}\mathrm{H}}_4}$, alongside α. The study compared an undisturbed fenced meadow (FMD) with three adjacent land-use types, clipped meadow (CMD), saline-alkaline meadow (SAL), and paddy rice field (PDY), converted from FMD from 2018 to 2022. Annual α-induced GWP (GWPΔα) was positive across all converted sites (CMD, SAL, and PDY), indicating a warming effect due to lower α compared to FMD. The PDY exhibited the highest CH₄ emission (5.04 kg CO₂ m⁻² yr⁻¹), exceeding other land uses by three orders of magnitude (p < 0.05). Conversely, N₂O emissions remained consistently minimal and stable across all sites. When integrating the net ecosystem exchange of CO₂ (NEE), the PDY functioned as a net warming source. In contrast, the warming effects of α and non-CO₂ GHGs were effectively offset by the NEE in other land uses. Machine learning identified soil water content (SWC) as the dominant predictor of α across all land uses in growing season. However, a mechanistic divergence was observed, i.e., α in low saline-alkali ecosystems (FMD, CMD and PDY) was shaped by coupled biotic and soil moisture controls, whereas in the degraded SAL ecosystem, α is almost exclusively abiotic-driven. These findings demonstrate that land-use conversion in the Songnen Plain governs complex land-surface feedbacks through distinct pathways. This study provides a quantitative framework for integrating biophysical and biogeochemical impacts to optimize land management for climate resilience in saline-alkaline agropastoral ecotones. Full article

Soil salinization poses a severe threat to global wheat production, yet the physiological mechanisms underlying photosynthetic responses to neutral, alkaline, and combined salt stress remain poorly understood. This study systematically evaluated the photosynthetic physiology and salt tolerance of six spring wheat genotypes under three types of salt stress at varying concentrations. By integrating phenotypic data, gas exchange parameters, chlorophyll fluorescence indices, and biomass measurements, and applying structural equation modeling and multivariate analysis, key traits regulating biomass were identified. The results revealed significant interactions among salt stress type, genotype, and concentration on photosynthetic parameters. Structural equation modeling analysis revealed that under neutral salt stress, both gas exchange parameters and chlorophyll content had significant direct effects on seedling biomass, with standardized path coefficients of 0.421 and 0.400, respectively. Under alkaline and combined salt stresses, only chlorophyll content showed a significant direct effect on biomass, with standardized path coefficients of 0.873 and 0.790, respectively. Multiple regression analysis further identified key photosynthetic factors influencing growth under different stress types. Under neutral salt stress, phi (Ro) and E significantly affected biomass, whereas under alkaline and combined salt stresses, biomass was primarily co-regulated by phi (Ro) and phi (Eo). Based on a comprehensive evaluation of salt tolerance index, damage index, and biomass response, genotypes W06 and W02 exhibited the strongest overall salt tolerance. This study systematically elucidates the differential response mechanisms of photosynthesis in spring wheat under distinct salt stress types, providing an important theoretical basis and elite germplasm resources for breeding salt-tolerant wheat varieties. Full article

Acidic polysaccharides, valued for their outstanding bioactivity and physicochemical properties, represent a promising strategy for metabolic disease intervention. In this study, three acidic polysaccharide fractions (BRP-1, BRP-2, and BRP-3) were isolated from Brassica rapa L. using membrane filtration and ion-exchange chromatography. BRP-3, notable for its high galacturonic acid content (76.64%), was further purified to yield the homogeneous fraction BRP-3-1 (Mw = 22.3 kDa). Combining GC-MS, FTIR, and NMR analyses, we report for the first time the detailed structure of BRP-3-1—a heteropolysaccharide composed of rhamnose (1.687%), galacturonic acid (75.584%), galactose (14.452%), and arabinose (8.277%)—with a backbone composed with T-α-L-Araf-(1 → 5)-α-L- Araf -(1 → 4)-α-D-GalpA-(1 → 4)-α-D-2-O- GalpA Me-(1 → 4)-α-D-GalpA-(1 → 4)-α-D-GalpA-(1 → 3)-Galp-(1 → 4)-α-D-GalpA, and T-Rhap, T-Galp as well as T-GalpA for branched chain and terminals. In HepG2 insulin-resistant cells, BRP-3-1 demonstrated potent dual regulation of glucose and lipid metabolism—enhancing glucose consumption, lowering total cholesterol, and significantly reducing triglyceride levels in the high-dose group (800 μg/mL), outperforming BRP-2. This work systematically defines the structure of a highly bioactive acidic polysaccharide from B. rapa L. and confirms its metabolic regulatory effects, offering a strong scientific foundation for its application in functional foods and as an adjuvant therapeutic for metabolic disorders. Full article

Spring and autumn phenology jointly regulate terrestrial carbon, water, and energy exchanges, yet the mechanisms linking seasonal transitions remain debated under increasing hydroclimatic stress. Here, we integrate satellite-derived phenology with reanalysis-based indicators of land–atmosphere coupling to examine how spring onset interacts with growing season controlling factors and how these interactions shape autumn senescence at the global scale. Globally, start-of-season (SOS) and end-of-season (EOS) timings are positively coupled, with later SOS generally followed by later EOS, and this relationship becomes stronger when only later-SOS years are considered. However, SOS does not induce coherent global shifts in growing season climate limitation. Piecewise structural equation modeling reveals that SOS influences EOS primarily through a direct phenological pathway, with a mean path coefficient of ~0.4 day·day⁻¹ explaining approximately 26% of global EOS variability. In contrast, energy and water-mediated pathways contribute smaller but spatially heterogeneous effects, together accounting for ~5% of explained variance on average. SOS–EOS coupling is strongest in water-limited regimes, particularly in grasslands and shrublands. Managed croplands exhibit distinct and more heterogeneous responses, reflecting partial decoupling of phenology from natural hydroclimatic constraints. Collectively, our results indicate that spring phenology exerts a robust but spatially variable influence on autumn timing, dominated by direct effects rather than indirect mediation through growing season climate limitations, with regional modulation imposed by background hydroclimatic conditions. Full article

Nitronyl nitroxides (NNs) are widely employed in chemistry, physics, and materials science due to their inherently high stability and magnetic properties. However, the synthesis of C(2)-organoelement derivatives remains a challenging task. This paper reports on the efficient synthesis and characterization of an unusual organosilver complex consisting of the [Ag–(IPr)₂]⁺ cation and the [Ag–(NN)₂]⁻ anion. The salt [Ag–(IPr)₂][Ag–(NN)₂] was prepared in high yields (88–96%) by two synthetic routes: by reacting the carbene ligand precursor IPr·HCl with Ag₂O and nitronyl nitroxide NN–H, or by addition of NN–H/^tBuONa to a THF solution of IPrAgCl (generated in situ from IPr·HCl and Ag₂O) under microwave irradiation. Electrochemical analysis of [Ag–(IPr)₂][Ag–(NN)₂] revealed a reversible one-electron oxidation peak at E_1/2 = −0.258 V and an irreversible reduction peak at E_p = −2.169 V, which is likely related to the electrochemical transformation of the nitronyl nitroxide moieties. Crystallization from an acetone/benzene solution yielded crystals of [Ag–(IPr)₂][Ag–(NN)₂]·2H₂O solvate, in which the diradical anion [Ag–(NN)₂]⁻ is bound to two water molecules by hydrogen bonds. These hydrogen bonds stabilize a planar conformation of the [Ag–(NN)₂]⁻ anion, in which both NN fragments lie in the same plane and, according to DFT calculations, are linked by fairly strong antiferromagnetic interaction. DFT calculations also predict the dissociation of the complex with water in toluene solution and a conformational change leading to the appearance of about 90° between NN fragments and a significant decrease in exchange interaction. Full article

Background/Objectives: Positive end-expiratory pressure (PEEP) is a standardized component of the invasive mechanical ventilation (IMV) settings to improve oxygenation; however, its physiological effects in patients with no documented prior lung disease remain poorly defined. This study evaluated the impact of moderate PEEP variations on macrohemodynamic parameters, gas exchange, and driving pressure (ΔP). Methods: This single-arm, non-randomized, crossover study included adult intensive care unit (ICU) patients with no documented prior lung disease during the early phase of IMV. Sequential PEEP levels of 6, 8, and 10 cmH₂O were applied for 30 min each within the first 24 h of ICU admission, while all other ventilatory parameters were kept constant. Arterial blood gases [partial pressure of oxygen (PaO₂), partial pressure of carbon dioxide (PaCO₂), and arterial oxygen saturation (SaO₂)], oxygenation index [PaO₂/fraction of inspired oxygen (FiO₂)], systolic, diastolic, and mean arterial pressures, ΔP, and static compliance (Cstat) were measured. Friedman and Mann–Whitney U tests were used, with adjustment for multiple comparisons. Results: A total of 150 patients were enrolled (64.7% male). The observed mortality rate was 53.3%; however, mortality was not defined as a primary or secondary outcome, and was used only as a grouping variable for comparative analyses. Intraindividual comparison across PEEP levels of 6, 8, and 10 cmH₂O showed small but significant reductions in systolic and mean arterial pressure at higher PEEP (p-value < 0.05), with Bonferroni-adjusted significance for PEEP 6 vs. 10. No significant differences were observed in oxygenation (SaO₂, PaO₂, and PaO₂/FiO₂), PaCO₂, ΔP, or Cstat. These results suggest that moderate PEEP changes produced limited macrohemodynamic effects without relevant impact on gas exchange or respiratory mechanics. Overall, no clinically relevant or statistically significant differences were observed in gas exchange, macrohemodynamic parameters, ΔP, or Cstat across PEEP levels when mortality was used as the grouping variable. Among survivors, higher PEEP was associated with modest reductions in systolic and mean arterial pressures and higher PaCO₂ values; however, these findings did not translate into consistent physiological benefits. Conclusions: In mechanically ventilated patients with no documented prior lung disease, PEEP may exert divergent effects on macrohemodynamics, gas exchange, and ΔP, supporting a cautious and individualized approach to PEEP selection in this population. Full article

Groundwater fluctuations in bedrock affect the mechanical behavior of rock masses hosting geo-energy recovery systems utilizing borehole heat exchangers. To investigate the combined influencing mechanism of changes in groundwater saturation and fracture dip angle on mechanical properties of typical fractured rock masses, triaxial compressive tests were conducted using specimens containing fissures at different angles (15° and 75°) under three conditions: conventional dry, water-immersed, and immersed-dried. The results reveal a combined influencing mechanism of groundwater saturation and fracture dip angle on mechanical properties of typical fractured rock mass. Since specimens with gentle fissure angles tend to fail through fracturing of the intact rock, while those with steeper fissure angles are more prone to failure via slippage along fissure planes, the stress–strain response exhibits greater variability among samples with gentle fissures, attributable to the material heterogeneity of the rock matrix; an increase in water saturation reduces the strength of steeper fissures more pronouncedly due to the relatively homogeneous properties of these fissures, and gravitational water present along fissure planes reduces effective stress and weakens interfacial bonding. Therefore, rock masses with steeper fissures are more susceptible to water-induced weakening and pose a higher risk of shear slippage by fissure reactivation. The findings have a practical value in offering theoretical support for assessing stability risks in geo-energy structures in shallow bedrocks. Full article

Background: Severe lung compromise from COVID-19, ARDS, and recently AH3N2 can progress to life-threatening hypoxia. Past experience led to standardized protocols that assumed similarity to SARS-CoV. Methods: COVID-19 pathophysiology and histopathological lung biopsy photomicrographs are analyzed. Results: Pneumolysis is defined as progressive alveolar–capillary destruction resulting from SARS-CoV-2 attack on pneumocytes. In the final stages preceding pneumolysis, molecular mechanisms in the lungs include apoptosis in alveolar epithelial type I and II cells, compromising alveolar regeneration, and necrosis, resulting in leakage of intracellular contents and amplifying inflammation. Pyroptosis, driven by inflammasome activity, further disrupts alveolar integrity in ARDS. Histopathological findings include Masson bodies, alveolar-coating cells with nuclear atypia, reactive pneumocytes and reparative fibrosis, intra-alveolar hemorrhage, moderate inflammatory infiltrates and abscesses, microthrombi, hyaline membrane remnants, and emphysema. The three theoretical pathophysiological stages of progressive hypoxemia (silent hypoxemia, gasping, and death zone) are shown. Conclusions: Silent hypoxemia rapidly progresses to critical hypoxemia. This progression results from progressive pneumolysis, inflammation, immune overexpression, autoimmunity, and HAPE-type edema, leading to acute pulmonary insufficiency. Long-lasting COVID-19 can result in fibrosis and, as a compensatory mechanism, polierythrocythemia. The proposed treatment (based on tolerance to hypoxia and the hemoglobin factor) includes prompt oxygen administration, control of inflammatory and immune responses, antibiotics, rehydration, erythropoietin and platelet aggregation inhibitors. Full article

Premium coffee depends on high-quality beans, influenced by a combination of genetic, environmental, and postharvest factors. This review summarizes the mechanisms underlying coffee bean quality, with an emphasis on the genetic differences between Coffea arabica and Coffea canephora, as well as the integrated roles of environmental conditions, agronomic practices, including nutrient and shade management, and postharvest processing technologies. The allotetraploid genome of C. arabica is influenced by homoeologous exchanges and subgenome-biased expression (such as decreased DXMT activity that reduces caffeine), which contribute to its complex flavor profile. Key lipid metabolism genes, particularly FADS2, play a critical role in regulating lipid metabolism. The effects of altitude (1600–2000 m) and shade influence various metabolic pathways. Cooler temperatures promote sugar accumulation, while excessive shading hinders carbon assimilation and the development of flavor precursors. Postharvest processing significantly influences flavor, where microbial or enzymatic treatments enhance sensory attributes. In addition, methods like natural, washed, or honey processing modulate various nonvolatile compounds, impacting lipid emulsification and aroma retention. Multi-omics analyses suggest that MYB proteins play a key role in regulating pathways involved in caffeine, chlorogenic acids, and terpenes. Effective hermetic packaging prevents oxidation, thereby preserving freshness. Overall, superior coffee quality stems from synergistic interactions across genetic, ecological, agronomic, and processing factors, highlighting the need for the development of an integrated strategy to support the sustainable production of premium coffee. Full article

Background: Chronic heart failure (CHF) in older adults requires sustained self-management and close follow-up, yet day-to-day care is often carried out by families with support from primary healthcare nurses. In Saudi Arabia, where family caregiving is culturally normative, collaboration between nurses and patients’ families may be pivotal to effective CHF management, but remains insufficiently understood in primary healthcare contexts. Methods: A qualitative study informed by an interpretive phenomenological approach was conducted. Participants (n = 24; 12 nurses and 12 family caregivers) were recruited using purposive sampling from primary healthcare centers in Riyadh, Saudi Arabia. In-depth, semi-structured interviews were conducted in Arabic or English, audio-recorded, transcribed verbatim, and analyzed using reflexive thematic analysis following Braun and Clarke’s six-phase framework. Strategies to enhance trustworthiness included member checking, peer debriefing, maintenance of an audit trail, and reflexive journaling. Results: Twenty-four participants (12 nurses and 12 family caregivers) were interviewed. Four interrelated themes were generated from both nurses’ and family caregivers’ accounts. (1) “We Are Caring Together”: Collaboration was experienced as shared responsibility for daily CHF management, grounded in trust; (2) Navigating Roles and Boundaries: Participants described unclear expectations, role overlap, and tension between professional authority and family knowledge; (3) Communication as the Engine of Collaboration: Effective partnerships depended on clear information exchange, caregiver-tailored education, and continuity of contact, while communication gaps created uncertainty and delayed support-seeking; and (4) Cultural and System Constraints Shaping Collaboration: Strong family obligation motivated caregiving but also intensified moral pressure and limited help-seeking, while time pressure and fragmented services constrained meaningful engagement and continuity across settings. Conclusions: Nurse–family collaboration in CHF management is relational, shaped by trust, role negotiation, and communication, and constrained by cultural norms and system pressures. This study contributes to the literature by demonstrating how moral obligation, hierarchical professional norms, and system fragmentation distinctively shape collaboration in the Saudi primary care context, extending existing conceptualizations derived primarily from Western individualist settings. Strengthening collaboration requires explicit role clarification, health literacy–informed caregiver education, continuity of contact, and organizational supports. Findings are limited by purposive sampling, single-city context, and exclusion of patient perspectives. Full article

Authentic, situated learning experiences which mirror the collaborative nature of healthcare practice are essential in preparing students for their future professions. Feedback literacy may be thought of as the understanding, capacity, and disposition needed to make sense of information and use it to enhance work or learning strategies. This study explored how feedback literacy can be developed through situated, interprofessional peer-to-peer feedback within a community-based paediatric health screening programme. Using an exploratory Action Research qualitative design, the planning activities stage explored current practice, gathering student insights via interviews, reflections, and a workshop to co-design an Interprofessional Feedback Conversation Guide (IPFCG). The IPFCG was piloted, integrating structured feedback tools and protected time for peer exchange, within the community screening activity. Feedback regarding use of the IPFCG contributed to the gathering data stage, which was followed by the evaluation and reflection stage. Evaluation revealed four key themes: value, engagement, optimising relationships, and structuring conversations. Students valued receiving feedback from peers outside their discipline, actively engaged with the process, emphasised the importance of building rapport, and utilised structured dialogue. These findings highlight how authentic, field-based learning can foster feedback literacy, enhancing the development of professional identity. The interprofessional nature of the program reflects the complexity of modern healthcare and demonstrates how curriculum-integrated models of authentic learning can enhance student engagement and workplace readiness. This study contributes to the evolving conversation about embedding authenticity in higher education and offers a practical model for building collaborative communication within situated learning experiences at scale. Full article