Search Results (600)

Preeclampsia (PE) is associated with systemic oxidative stress and vascular dysfunction, yet its effects on red blood cell (RBC) stability and mechanics remain incompletely understood. Here, we investigate the structural and nanomechanical alterations of RBCs in third-trimester pregnancies complicated by non-severe and severe PE, compared with normotensive controls. RBCs are analyzed using differential scanning calorimetry (DSC) to assess protein thermal stability and atomic force microscopy (AFM) to determine membrane elasticity (Young’s modulus) during in vitro aging. Linear mixed-effects models аre applied to evaluate the effects of disease severity, storage time, and their (group × storage time) interaction. DSC reveals that Band 3 and hemoglobin exhibited pronounced destabilization in PE, with severe cases showing earlier and larger reductions in transition temperatures and heat capacities, indicative of disrupted membrane–cytoskeletal interactions. AFM confirms that these molecular changes translate into functional consequences: control and non-severe PE RBCs show physiological softening over time, whereas severe PE RBCs undergo pathological stiffening. Statistical modeling demonstrates strong time, group, and interaction effects for both thermodynamic and mechanical parameters. Together, these findings identify the Band 3–hemoglobin macrocomplex as a primary target of PE-induced RBC alterations and suggest that combined thermodynamic–nanomechanical profiling can serve as a sensitive approach to detect early subclinical RBC damage not detectable by routine hematological tests. Full article

Arterial stiffness has traditionally been interpreted as a marker of vascular ageing and cumulative blood pressure exposure. Increasing evidence, however, indicates that it should be viewed as an active determinant of cardiovascular loading conditions rather than a passive epiphenomenon. By accelerating pulse wave velocity and altering the timing of wave reflection, large artery stiffening increases central systolic pressure, augments late systolic load, and facilitates the transmission of pulsatile energy to the microcirculation. These hemodynamic alterations shape ventricular remodeling, influence ventricular–vascular coupling, and contribute to organ vulnerability even when brachial blood pressure appears adequately controlled. In this review, population-based observations and mechanistic human studies are integrated to position arterial stiffness as a stage-dependent dimension of cardiovascular disease. Community data illustrate its association with different blood pressure phenotypes and early cardiac structural changes, whereas evidence from advanced heart failure settings helps contextualize arterial stiffness within states of marked autonomic activation. Taken together, this perspective suggests that arterial stiffness is not merely a marker of cumulative damage, but a mediator that contributes to disease progression across clinical stages and, in practical terms, a phenotyping dimension along the trajectory from hypertension to heart failure. Full article

In this work, a novel approach for implementing a resonant micro-accelerometer is demonstrated that may extend the operating frequency of such devices to several tens of MHz, which may enable direct wireless signal transfer. The proposed resonant accelerometer consists of a hybrid structure: a piezoelectric micro-resonator and a capacitive mass-spring (CMS) system (that are mechanically separated but electrically interconnected). The sensor utilizes the piezoelectric stiffening mechanism, which translates the acceleration-induced displacement of the capacitive mass-spring (CMS) structure into a shift in the resonance frequency of the interconnected resonator. The operating principle is elaborated upon in detail, supported by simulation and experimental results. Additionally, a novel fabrication technique is presented to realize a suspended fixed bi-layer electrode for the CMS in which a hardened layer of photoresist is utilized as a sacrificial layer. The experimental sensitivity of a fully functional device is reported to be ~6 Hz/g at 25 MHz (~0.23 ppm/g), which closely matches the simulated sensitivity of ~7 Hz/g (~0.278 ppm/g) for the fabricated capacitive gap of ~7 µm. Full article

While macroscopic stress significantly impacts the performance of metallic components, the underlying atom–electron coupling mechanisms governed by distinct crystal symmetries remain insufficiently understood. To address this gap, this work systematically investigates the structural and electronic evolution of representative metallic materials under applied stress. Experimentally, X-ray diffraction (XRD) revealed complex macroscopic residual stress distributions in cold rolled titanium alloy and silicon steel. Motivated by these engineering observations, first-principles density functional theory (DFT) calculations were conducted to uncover the underlying physical mechanisms. Specifically, the responses of face-centered cubic (FCC) aluminum and copper, body-centered cubic (BCC) iron, and hexagonal close-packed (HCP) titanium crystals were investigated under tension and compression using the RPBE functional. Stress-dependent elastic properties, density of states (DOS), band structures, and phonon spectra were calculated. Results show that tension softens all metals (Al becomes mechanically unstable), whereas compression stiffens their lattices. Electronically, tensile loading sharpens DOS peaks near the Fermi level and shifts conduction bands closer to it, whereas compression smooths DOS peaks and shifts bands away. Phonon analysis indicates Cu and Ti remain dynamically stable, while Al and Fe exhibit phonon mode softening under high tension. These stress-induced changes highlight crucial atom–electron coupling mechanisms, providing a theoretical basis for tailoring metallic performance via stress engineering. Full article

This paper presents an analytical framework for the preliminary design of stringer-stiffened composite panels subjected to low-velocity impact. The formulation combines First-Order Shear Deformation Theory with a two-degree-of-freedom spring–mass model, while the super-stringer is represented as a Euler–Bernoulli beam whose bending contribution is transferred to the skin mid-surface through the parallel axis theorem. This provides a computationally efficient tool for rapid parametric assessment of stiffened configurations at the early design stage. To support laminate selection, a Specific Impact Energy Index (SIEI) is introduced to rank configurations according to their elastic energy storage efficiency relative to the product of skin and stringer thicknesses. The tool is validated against both published experimental results and a finite element dynamic explicit model, demonstrating a good approximation of the impact response. It is then applied to identify the optimum laminate configuration for a super-stringer case study within the design space considered. Full article

The modern construction industry has witnessed a marked shift towards the utilization of high-strength steel reinforcement, exhibiting yield strengths exceeding 600 MPa in reinforced concrete structures. Tension stiffening is a critical factor for accurate prediction of deflection and crack width. The current study evaluates the accuracy of state-of-the-art models in predicting curvature in Reinforced Concrete (RC) beams reinforced with high-strength steel (HSS) bars. This study employed three design code methods (Eurocode 2, ACI 318-14, and ACI 318-19) and two other models: the Bischoff model and Kaklauskas and Sokolov’s model. An RC beam with HSS bars was tested, and experimental data on another 63 RC beams reinforced with HSS rebars were collected from various published studies. The test data ranged in various geometrical and material characteristics and were evaluated across a wide range of steel stress intervals. An inverse analysis was carried out to calculate the resultant internal force of tensile concrete (tension stiffening) from the experimental moment–curvature diagram. The inverse analysis demonstrated that the fully cracked RC section reached stiffness at a bending moment of about 3M_cr, where M_cr is the cracking bending moment predicted according to the EC2 design code. Statistical analysis showed that the predicted mean normalized curvature (κ_th/κ_exp) across several reinforcement stress levels ranged from 0.99 to 0.81 for different models. The design codes tend to underestimate curvature. The coefficients of variation ranged between 17.8% and 24.9% for different models. Full article

Background/Objectives: Beeswax, a complex natural secretion primarily derived from Apis mellifera and Apis cerana, has evolved from an ancient remedy into a multifunctional excipient and bioactive material in modern pharmaceutical sciences. This review evaluates its physicochemical properties, pharmaceutical applications, and emerging biomedical potential, while addressing current quality and regulatory challenges. Methods: A narrative review was conducted by analyzing literature on the chemical composition, functional properties, conventional uses, advanced drug delivery applications, pharmacological activities, and quality control of beeswax, emphasizing structural characteristics, formulation roles, and integration into innovative delivery technologies. Results: Beeswax is a lipid-based matrix composed of over 300 constituents, including wax esters, hydrocarbons, and free fatty acids, conferring thermoplasticity, biocompatibility, and structural stability. Traditionally, it functions as a stiffening agent, viscosity modifier, and emulsion stabilizer in topical formulations, forming an occlusive barrier that enhances skin hydration. In advanced systems, it serves as a solid lipid matrix in nanostructured lipid carriers (NLCs), microspheres, and 3D-printed tablets, enabling controlled drug release and improved bioavailability of lipophilic compounds. It also exhibits antimicrobial, anti-inflammatory, and wound-healing activities, while beeswax-derived policosanols show potential cardiovascular and gastroprotective benefits. However, concerns regarding paraffin adulteration and pesticide contamination highlight the need for stringent analytical and regulatory oversight. Conclusions: With rigorous quality control and sustainable sourcing, beeswax remains a versatile, eco-friendly material bridging traditional medicine and advanced pharmaceutical innovation. Full article

This paper presents a theoretical approach based on the FSDT to study the acoustic vibration performance of rib-stiffened PVC foam sandwich structures with reinforcing and weakening phases when submerged in water. The complex core layer with reinforcing and weakening phases is homogenized to an equivalent orthotropic layer. Building upon this framework, the governing equations of motion for rib-stiffened PVC foam sandwich structures under the boundary conditions of a simply supported type are derived, incorporating the coupling interaction between the reinforcing ribs and the sandwich plates. Considering the influence of the underwater environment, with the Helmholtz equation governing the continuity of the acoustic pressure field and the Euler equation regulating the fluid–structure interaction interface continuity, the Navier method is subsequently employed to solve for the natural frequencies and acoustic vibration responses. For the purpose of verifying the proposed approach, the predicted results are contrasted with both the literature-derived data and numerical simulation results. Finally, parametric research is further conducted to explore the effect of the parameters of the rib and core layers on the underwater acoustic vibration characteristics. The conclusions drawn from this study can provide meaningful guidance for engineering design and optimization of such rib-stiffened sandwich structures, incorporating both reinforcing and weakening phases in underwater engineering applications. Full article

This study investigates the interaction between the skin and stiffeners under tension and the structural failure mechanisms of aluminum alloy stiffened panels after battle damage, employing an integrated approach of experimental testing and numerical simulation. The variation in the residual strength of the stiffened panels with the characteristics of ruptures was explored, and an assessment method for residual strength was proposed based on the net-section failure criterion. The results indicate that the residual strength of the stiffened panels is closely related to the location and size of the rupture. For panels with ruptures of equal area, the residual strength is lowest for those with web damage, followed by those with flange damage, and highest for those with skin damage only. By employing an area-based conversion method, the three-dimensional stiffened panel was simplified to a two-dimensional plate. A stress averaging coefficient was introduced for large eccentric ruptures, while a conversion factor was applied for small eccentric ruptures to modify the residual strength assessment. The results demonstrate high accuracy. This study provides an efficient and precise method for evaluating the residual strength of damaged stiffened panels, offering a theoretical basis for aircraft battle damage repair. Full article

In order to study the stability of orthotropic steel box girders and the characteristics of the synergistic stress mechanism of key components, the test method of axial compression using the scale model of steel box girder segments was carried out, and the collaborative working performance of the plate ribs of the U-shaped stiffener plate and the influence mechanism of the diaphragm on the structural stability were systematically studied. The results show that the strain difference between the deckplate and the U rib increases significantly with the increase in load, and the distribution law of the end chamber is larger than the middle, and the bottom plate is larger than the top plate and the web plate. The diaphragm mainly bears the tensile force under axial load, which provides out-of-plane restraint for the stiffener, and its restraint effect is the strongest at the web plate and the weakest at the bottom plate. This paper clarifies the synergistic stress mechanism of U-rib stiffeners under high axial pressure conditions, quantifies the contribution of diaphragms to local stability, and provides a theoretical basis for the structural design of similar bridges. Full article

Metallic Shear Plate Dampers (MSPDs) are essential components in passive vibration control systems and require rapid post-earthquake inspection to assess damage and determine replacement needs. Traditional visual inspection methods suffer from low efficiency and limited ability to detect concealed damage. This study proposes a novel MSPD damage detection method based on active sensing and the k-nearest neighbor (KNN) algorithm, featuring high accuracy, efficiency, and low cost. Quasi-static tests were conducted to simulate various damage states. Sweep-frequency excitation was applied using a charge amplifier, and piezoelectric sensors were employed to generate and receive stress wave signals corresponding to different damage conditions. The acquired signals were processed using wavelet packet transform (WPT) and energy spectrum analysis to extract discriminative time–frequency features, which were used to train and validate the KNN model. Results show that the model achieved a validation accuracy of 98.9% using all valid data and 98.1% using a single excitation-sensing channel. When tested on an MSPD with a similar overall structure but lacking stiffeners, the model achieved an accuracy of 92.6% in distinguishing between healthy and damaged states. This indicates that the proposed method has good robustness and practical potential for MSPDs with similar damage evolution and failure modes despite certain structural variations. Full article

People with HIV experience a disproportionate burden of myocardial fibrosis and diastolic dysfunction that is not fully explained by traditional cardiovascular risk factors or systemic inflammation. Emerging evidence suggests that HIV-associated cardiomyopathy originates from persistent disturbances in cardiomyocyte homeostasis driven by chronic immune-metabolic stress. Metabolic dysregulation, antiretroviral-related toxicity, and residual inflammatory signaling converge at the cardiomyocyte organelle level, leading to mitochondrial dysfunction, endoplasmic reticulum stress, and impaired autophagy. These interrelated processes precede overt structural heart disease and promote progressive myocardial stiffening, despite effective viral suppression. Framing myocardial remodeling as a consequence of unresolved organelle stress highlights opportunities for earlier intervention, including aggressive management of metabolic risk factors, the use of established cardioprotective therapies with antifibrotic effects, and emerging strategies targeting mitochondrial and proteostatic pathways. This organelle-centered perspective supports prevention-focused approaches that combine accessible imaging modalities and circulating biomarkers to mitigate the long-term cardiovascular risk in people with HIV, particularly in resource-limited settings. Full article

Enhancing the vibroacoustic performance of underwater vehicles remains a critical challenge in marine engineering. Increasing geometric stiffness is a conventional strategy to suppress vibration, yet its effectiveness in reducing underwater sound radiation can be practically limited. This paper presents a numerical investigation of the vibroacoustic response of composite grillage sandwich structures, with a focus on separating the contributions of geometric stiffening and core damping. A coupled acoustic structural model is developed based on the equivalent single layer theory and implemented in a finite element framework, then validated against analytical benchmark solutions. The parametric study reveals a stiffness saturation phenomenon in the acoustic domain. Although increasing rib height significantly reduces the mean square velocity, the radiated sound power reaches a saturation plateau and can even show a slight rebound at higher frequencies. This behavior is attributed to an increase in structural phase velocity that shifts modal components toward a more efficient radiation regime, thereby increasing radiation efficiency. To address this limitation, the damping modulation role of the core material is examined. The results show that introducing a high damping core into the grillage skeleton suppresses broadband noise and resonance peaks, without a comparable rise in radiation efficiency that may accompany geometric stiffening. The study indicates that a hierarchical synergistic design strategy that uses geometric stiffness for load bearing and low frequency control, while leveraging core damping to mitigate the acoustic saturation limit, provides useful physical insight into more efficient noise control approaches than purely stiffness based approaches. Full article

This study investigated the linear and nonlinear viscoelastic properties of cherry Jell-O^® samples through oscillatory shear methods including small-amplitude (SAOS), medium-amplitude (MAOS), and large-amplitude (LAOS) experiments. Cherry Jell-O^® showed solid-like gel behavior (tanδ < 1) up to γ₀:160%. The sample transitioned into nonlinear behavior above γ_cri: 16% and was classified as type III (weak strain overshoot). Chebyshev coefficients revealed that the samples exhibited strain-stiffening (e₃/e₁ > 0) and shear-thickening (v₃/v₁ > 0) intracycle behavior in the nonlinear region. Both elastic and viscous Lissajous–Bowditch curves showed distortions from elliptical trajectories in the nonlinear region. FTIR spectra showed LAOS deformation-induced structural changes, particularly in the Amide I and Amide II regions. Tanδ decreased below 1 upon the removal of the LAOS deformation. These findings showed that although LAOS deformation induced molecular changes in the cherry Jell-O^® samples, their elasticity was largely preserved by a strong, resilient network. Full article

This study analyzes the effect of two bioactive additives—caffeic acid and natamycin (Natamax^®)—on the properties of poly(butylene succinate) (PBS) in the context of applications in biodegradable active packaging. Materials containing 1, 3, and 5 wt.% of the additives were prepared by melt blending and characterized in terms of density, rheological behavior (MFR), mechanical properties, thermal stability (TGA), and thermal behavior and crystallization (DSC). Caffeic acid strongly reduced the melt viscosity (reflected by a significant increase in MFR) and, at higher concentrations, led to material stiffening and increased strength at the expense of a pronounced reduction in deformability. Natamycin exhibited a milder rheological effect; at 1 wt.% it simultaneously improved strength and elastic modulus, whereas at higher loadings it deteriorated mechanical performance due to structural effects. Both additives were thermally compatible with PBS; caffeic acid introduced an additional degradation step, while Natamax^® did not significantly alter the degradation mechanism. The results indicate that both the type and concentration of the additive govern the structure–property–function relationships and enable the design of PBS-based packaging materials with controlled performance and functional characteristics. Full article