Search Results (2,400)

The persilylated Si₃–Si₇ analogues of the C₃–C₇ aromatic molecules and ions with all hydrogen or all fluorine atoms at silicon have been calculated at high levels of theory, up to MP2/aug-cc-pVTZ for all species and CCSD/6-311++G** for Si₃ and Si₄ species, both in the gas phase and in a polar solvent (water). The aromaticity of the calculated species was estimated using structural, energetic, and NMR criteria. (SiF)₃⁺ cations are more aromatic than (SiH)₃⁺ by the NICS (nuclear-independent chemoical shift) but less aromatic by the ASE (aromatic stabilization energy) criterion. Dications (SiX)₄²⁺ are planar (X = H) or slightly puckered (X = F); the ASE decreases by 4–5 kcal/mol upon going from gas to solution, or from X = H to X = F. Dianions (SiX)₄^2–are nonplanar and antiaromatic. The ASE for the slightly distorted-from-planarity anion Si₅H₅^– is ~53 kcal/mol, vs. 85 kcal/mol for its carbon analogue. The structure of Si₆X₆ molecules strongly depends on the level of calculations. The NICS and ASE values have been calculated for planar Si₆H₆ and (SiH)₇⁺ but not for strongly distorted Si₆F₆ and (SiF)₇⁺ species. Full article

Renal organic anion transporters 1 (OAT1) and 3 (OAT3) mediate the excretion of endogenous metabolites and xenobiotics. Flavonoids interact significantly with these transporters, but the structural determinants—especially regarding in vivo phase II metabolism—remain unclear. This review integrates recent cryogenic electron microscopy (cryo-EM) structural biology and transporter kinetics to delineate the molecular basis of flavonoid–OAT interactions. We highlight phase II metabolites as key in vivo effectors. Structurally, OAT1 strictly favors compact, planar anionic scaffolds, whereas OAT3 accommodates bulkier, conjugated forms. Crucially, flavonoids exert a “double-edged” toxicological effect: high-affinity OAT inhibition risks herb–drug interactions, yet competitively limits the tubular uptake of nephrotoxins. Furthermore, disease states and post-translational regulation reshape these interactions. By bridging structural insights with biomarker-guided pharmacokinetics, we propose a mechanistic framework to improve the precise safety assessment of flavonoid-containing therapeutics. Full article

The design and main parameters of a plasma–chemical reactor containing two compartments are presented. One compartment houses a vacuum-arc evaporator, while the other houses a planar magnetron. The compartments are separated by a diaphragm with a dosing slot for injecting copper vapor into the TiN synthesis compartment. The conditions for the synthesis of superhard TiN-Cu composite coatings are experimentally determined. Based on established process parameters for TiN synthesis in a nitrogen-containing plasma by Ti evaporation using a vacuum-arc discharge, it is proposed to apply TiN-Cu coatings by injecting Cu vapor into the TiN synthesis area and sputtering Cu using a magnetron discharge. XRD analyses of both TiN and TiN-Cu coatings show the presence of WC, Ti₂C, and TiN. EDS analysis confirms 5.57 at. % copper on the surface of the TiN-Cu coating. Real-life operating tests of TiN-Cu coatings on replaceable WC-TiC-Co (79/15/6 wt.%) alloy hexagonal inserts used for cutting 40Kh steel revealed that applying the TiN-Cu coating extends the tool life of WC-TiC-Co inserts by about 2.5 times compared with uncoated tools. Cutting force measurements on TiN-Cu-coated inserts showed no vibration or noise during cutting, driven by a reduced friction coefficient and improved heat dissipation at the contact zone between the cutting edge and the workpiece, thereby lowering the temperature in that area. Full article

Background: Guanine-rich DNA regions can fold into G-quadruplex (G4) structures, which are prevalent in telomeres and oncogene promoters, making them attractive targets for anticancer therapeutics. Small molecules capable of selectively stabilizing G4 DNA can disrupt telomerase activity and oncogene expression, offering a promising strategy for cancer intervention. Methods: A rationally designed series of DPPZ–anhydride-conjugated ligands (1 and 2) and their corresponding quaternized derivatives (1-q and 2-q) were synthesized to investigate the combined effects of π-extension, bromine substitution, and cationic modification on DNA recognition. The synthetic strategy relied on the incorporation of a highly planar DPPZ–anhydride scaffold to enhance π-surface area, followed by selective quaternization to introduce permanent positive charge and reinforce electrostatic interactions with the DNA backbone. All compounds were fully characterized by NMR and spectroscopic methods. The DNA-binding properties of the ligands were systematically evaluated toward duplex (ds-DNA) and G-quadruplex (G4-DNA) structures using UV–Vis absorption titration, fluorescence intercalator displacement (FID) assays, and competitive dialysis experiments. Quaternization markedly enhanced intrinsic binding constants and significantly reduced DC₅₀ values, particularly for G4-DNA. While bromine substitution increased overall binding affinity, it did not substantially improve topology selectivity. Among the series, compound 1-q exhibited the most favorable balance between affinity and G4 selectivity. Results: The interaction of the compounds with BSA was quantified using Stern–Volmer quenching constants, which demonstrated a clear trend of enhanced quenching efficiency upon modification. The binding strength followed a descending order of 1-q > 2-q > 1 > 2, highlighting the superior performance of the first series over the second. These findings indicate that the structural features of 1-q facilitate a more robust interaction within the hydrophobic pockets of the protein. Conclusions: Overall, the results demonstrate that strategic π-conjugation combined with electrostatic reinforcement provides an effective approach for the development of topology-selective DNA-binding ligands. Full article

This paper presents the design and experimental validation of a compact low-pass filter based on a quasi-eight-shaped defected ground structure (DGS). The study begins with a single DGS resonator that perturbs the ground-plane current distribution, introducing additional effective inductance and capacitance. An equivalent circuit model is developed to provide physical insight into the resonant mechanism and to establish the relationship between the DGS geometry and the electromagnetic response. By incorporating microstrip stubs on the top layer, the resonant structure is transformed into a low-pass filtering configuration with improved passband characteristics. Subsequently, a higher-order topology composed of two identical quasi-eight DGS units and three microstrip stubs is implemented to significantly enhance the rejection performance and extend the stopband bandwidth. The fabricated prototype exhibits a measured cutoff frequency of approximately 2.1 GHz, with an insertion loss lower than 1 dB in the passband. A wide stopband extending from 2.8 GHz to 8 GHz is achieved, with attenuation exceeding 26 dB. The close agreement between the equivalent circuit model, full-wave electromagnetic simulations, and measured results confirms the effectiveness and physical consistency of the proposed design. Owing to its compact planar implementation and strong harmonic suppression capability, the proposed filter is suitable for microwave front-end and antenna applications. Full article

In this investigation, the nonlinear dust-acoustic waves in the lunar terminator region are studied in a three-component complex plasma comprising Boltzmann-distributed electrons and ions and inertial, cold, negatively charged dust grains. The fluid model is reduced, via the reductive perturbation technique, to a planar Korteweg–de Vries (KdV) equation that governs the evolution of small-amplitude dust-acoustic structures in this environment. Hirota’s direct method is then employed to derive exact multiple-soliton solutions, which allow us to examine the parameter dependence of dust-acoustic solitons and to characterize their overtaking collisions. The analysis shows that the soliton polarity and amplitude are controlled by the equilibrium electron–ion density ratio and the electron-to-ion temperature ratio, and that multi-soliton interactions remain elastic, with only finite phase shifts after collision. In the second part of the study, the planar integer KdV model is generalized to a time-fractional KdV (FKdV) equation to incorporate nonlocal temporal memory effects in the dust-acoustic dynamics. This FKdV equation is analyzed using two analytical approximation schemes: the Tantawy technique, recently proposed as a direct and rapidly convergent approach to fractional evolution equations, and the new iterative method, a widely used high-accuracy scheme in the fractional literature. For both methods, higher-order approximations are constructed, and their absolute and global maximum residual errors are quantified. The results demonstrate that the Tantawy technique provides compact approximations with superior accuracy and stability compared with the new iterative method for the present FKdV-soliton problem. The combined integer- and fractional-analytic framework provides a physically transparent framework for understanding how nonlinearity, dispersion, and fractional memory jointly shape dust-acoustic solitary structures in the electrostatically complex lunar terminator plasma, which is of paramount interest for future lunar missions like Luna-25 and Luna-27. Full article

Liposomes, spherical bilayer lipid-containing vesicles, are promising nanocarriers used for constructing drug delivery systems (DDS). Various strategies can be employed to loosen or break the liposome and release drugs as the tumor cells-targeting DDS made of liposomes reach the targeted sites. One of the most commonly used strategies is to heat the liposomal DDS by letting the gold nanoparticles or other light-absorbing substances that partition in various portions (inner water core, lipid bilayer or outside) of the liposome absorb light irradiation. Then, which portion can lead to the largest liposome structure change due to the same temperature variation? The answer is essential to aid the design of liposomal DDS; thus, wet lab experiments were carried out. However, even though irradiation-absorbing substances in different portions were irradiated for the same time and with the same irradiation intensity, it was impossible to ensure the three portions have the same temperature increase in the experiments. Furthermore, it is impossible to learn the related micromechanism and molecular-level details of the effects of temperature changes on the liposome structure with experimental methods. The molecular dynamics (MD) method is extensively employed by researchers to obtain in-depth molecular-level insights. Most researchers tend to simulate only a planar lipid bilayer structure, but Amărandi et al. demonstrated that such simplification strategy may give wrong simulation results contrary to the experimental results. Though Jämbeck et al. and Zhu et al. established whole spherical liposome systems with a diameter of about a dozen nanometers and simulated the systems with MD simulations, they did not simulate temperature-relevant properties of the liposome. Therefore, currently there is a lack of research on simulating the structure change in a whole spherical liposome due to temperature variations. So, we established the whole spherical structure of the liposome, simulated how it changes with temperatures and obtained molecular-level research results. It is observed that the temperature increase in the lipid bilayer causes the largest increase in lipid strand sway amplitude, the largest changes in lipid positions, the largest decrease in the distribution density of lipids and water around a lipid and the largest decrease in the interactions between lipids and lipids and between lipids and water, leading to the largest change in the liposome structure. We also studied how the degree of lipid tail unsaturation affects liposome structure changes with temperatures. Due to the C3 kinks in the unsaturated lipid tails, the distribution density of unsaturated lipids is not as high as saturate ones, leading to smaller attraction interactions and consequently larger liposome structure change with temperature. The obtained results are useful for the liposomal DDS design for the purpose of improving DDS performances and delivery outcomes. Full article

Deepwater sandwich pipes (SPs) offer high collapse resistance and thermal insulation, making them promising for hydrocarbon transport under high-pressure and low-temperature conditions. However, mechanical damage such as local dents increases cross-sectional ovality and can substantially degrade their external pressure capacity. This study develops a numerical model using ABAQUS to assess the collapse pressure of dented deepwater SPs under hydrostatic loading. The model is validated against existing reference data. A total of 2316 FE models are constructed to investigate the effects of material properties, geometric configurations, and dent characteristics on collapse performance. Results show that the collapse pressure decreases significantly with increasing dent depth, and spherical dents have a more pronounced effect than planar dents. Enhanced collapse resistance is observed as both the thickness ratio and the core thickness of the sandwich structure increase. The use of higher-strength materials in the core layer and the internal and external layers also improves compressive capacity. Drawing on these results, a simplified formula for estimating the collapse pressure of dented sandwich pipes is proposed. Full article

In this paper, we have synthesized silicon nanoparticles (SiNPs) via a simple, scalable hydrothermal method using [3-(2-aminoethylamino)propyl] trimethoxysilane (AEAPTMS) as the Si precursor and L-ascorbic acid (L-AA) as the reductant. In order to improve carrier transport in the synthesized NPs to enhance their applicability in optoelectronic devices, a surface modification process had been carried out to replace the original long-chain dehydroascorbic acid (DHA) ligand with a shorter-chain 3-mercaptopropionic acid (MPA) ligand. A hybrid test structure was then fabricated composed of the surface-modified SiNP layer with a conductive polymer, PEDOT:PSS, which served as the hole transport layer. This SiNP-PEDOT:PSS planar heterostructure served as a platform to probe the photoresponse and carrier dynamics of the modified nanoparticles. Compared to the as-synthesized SiNPs, the surface-modified SiNPs achieved a 20% increase in carrier lifetime and an on/off ratio of 7.28 at ±1 V applied bias under UV illumination. These findings highlight the potential of SiNPs for integration into solution-processed optoelectronic devices. Full article

Lower-limb rehabilitation exoskeletons must balance biomechanical compatibility, structural safety, and low mass to enable practical, repeatable gait assistance. This paper proposes a planar pantograph-derived exoskeleton leg driven by a Chebyshev Lambda linkage and develops an integrated workflow from mechanism synthesis to manufacturable optimization and experimental verification. A mannequin-coupled multibody model was built in MSC ADAMS to evaluate joint kinematics, end-point (foot) trajectories, and joint reaction forces under multiple scenarios (fixed-frame, ramp, stair ascent, and inclined-plane walking). The extracted joint loads were transferred to a parametric finite element model in ANSYS Workbench 2019, where response surface surrogates and a multi-objective genetic algorithm (MOGA) were used to minimize mass under stiffness and strength constraints. For the optimized load-bearing link, the selected minimum-mass design reached a component mass of 0.542 kg while respecting the imposed structural limits, i.e., a maximum total deformation below 0.2 mm and a maximum equivalent (von Mises) stress below 50 MPa (e.g., ~0.188 mm deformation and ~39 MPa stress in the optimal candidate). A rapid prototype was manufactured by 3D printing and experimentally evaluated using CONTEMPLAS high-speed video tracking, providing measured X_M(t) and Y_M(t) trajectories and joint-angle histories for quantitative comparison with simulations via RMSE metrics. Full article

We present a checkerboard metasurface integrating interleaved Helmholtz resonator arrays with distinct geometrical parameters, enabling decoupled dual-band coherent perfect absorption (CPA) in both in-phase and anti-phase excitation conditions. Full-wave simulations confirm that the proposed structure achieves absorption rates exceeding 99% at 2.904, 3.024, 3.788 and 3.856 THz, corresponding to two pairs of resonant modes enabled by the asymmetric transmission characteristics. Notably, by actively manipulating the relative phase difference between the two excitation modes, the absorption frequencies associated with each CPA channel can be independently and continuously tuned. Benefiting from the planar checkerboard configuration, which combines compact geometry, suppressed mutual coupling, and balanced energy distribution, the metasurface achieves stable and independent dual-band absorption characteristics. The proposed design provides a promising pathway for the development of terahertz coherent absorbers with enhanced frequency stability and spectral flexibility of dual-mode operations, offering strong potential for practical photonic and electromagnetic applications. Full article

The self-assembly of a novel synthesized chiral dipeptide, Boc-p-nitro-L-phenylalanyl-tyrosine, into supramolecular structures is investigated by optical absorption and photoluminescence spectroscopy as well as single crystal X-ray diffraction. The compound is a diphenylalanine derivative belonging to a family of aromatic dipeptides that spontaneously self-organize into nanostructures through molecular recognition. The dipeptide exhibits several step-like peaks in its absorption band, indicative of self-assembly into quantum-confined nanostructures. In contrast, the parent Boc-p-nitro-L-phenylalanine amino acid lacks these features, indicating that the tyrosine residue favors quantum-confined self-assembly. Crystal structure determination reveals distinct packing styles: Boc-p-nitro-L-phenylalanine forms two-dimensional hydrogen-bonded layers, while the related p-nitro-free Boc-L-phenylalanyl-tyrosine dipeptide organizes into a 3D helical columnar architecture, driven by the additional hydrogen-bonding capacity of the peptide bond and tyrosine hydroxyl group, which favors the formation of a channel-type tetragonal architecture network over the planar sheets of the monomer. Furthermore, the introduction of a tyrosine residue into the Boc-p-nitro-L-phenylalanine molecule alters its supramolecular assembly, as the dipeptide Boc-p-nitro-L-phenylalanyl-tyrosine crystallizes as a monohydrate. The water molecule present in the structure acts as a bridge, participating in a hydrogen-bonding network between the tyrosine hydroxyl groups of neighboring columns through intermolecular interactions. Full article

This paper introduces a compact sub-6 GHz multiple-input multiple-output (MIMO) antenna array developed for 5G smartphone applications. The design employs eight planar inverted-F antenna (PIFA) elements arranged to realize dual-band and dual-polarized operation. The antenna achieves impedance bandwidths of 3.3–3.7 GHz (11.4%) and 5.3–5.8 GHz (10%), covering key sub-6 GHz fifth-generation (5G) bands. To enhance diversity performance, the elements are distributed along the edges of the smartphone mainboard, enabling excitation of orthogonal polarization modes while maintaining an overall board size of 75 mm × 150 mm on an FR4 substrate. Even without the use of dedicated decoupling structures, the closely spaced antenna elements exhibit satisfactory isolation levels, varying between −12 dB and −22 dB across the operating bands. The antenna array achieves wide impedance bandwidths of approximately 400 MHz at 3.5 GHz and more than 500 MHz at 5.5 GHz, supporting high data-rate communication. In addition, the proposed system demonstrates very low correlation and active reflection, with envelope correlation coefficient (ECC) values below 0.002 and total active reflection coefficient (TARC) levels better than −20 dB. User interaction effects are also investigated, and the results confirm acceptable SAR levels and stable radiation behavior in the presence of the human body. Owing to its planar, dual-band/dual-polarization capability and compliance with safety requirements, the proposed antenna represents a promising practical solution for contemporary 5G handheld devices and future multi-band mobile platforms. Full article

Ginkgetin (GK) is a naturally occurring biflavonoid predominantly isolated from Ginkgo biloba and has attracted increasing attention because of its broad pharmacological activities. Structurally, GK belongs to the 3′-8″-linked biflavone subclass, which distinguishes it from other biflavonoids like amentoflavone (the parent compound of this subclass) and its monomeric counterparts such as apigenin. This unique C-C linked dimeric architecture confers distinct molecular planarity and lipophilicity, contributing to its enhanced membrane permeability and multitarget engagement capabilities. GK has been shown to exert pleiotropic biological effects in preclinical studies, including anti-inflammatory, antioxidant, antifibrotic, anticancer, neuroprotective, cardioprotective, metabolic regulatory and antibacterial activities. Mechanistically, preclinical evidence indicates that GK functions as a multitarget modulator of key signaling pathways involved in oxidative stress, inflammation, cell death and tissue remodeling, such as nuclear factor erythroid 2–related factor 2/heme oxygenase-1 (Nrf2/HO-1), nuclear factor kappa-B(NF-κB), Janus kinase/signal transducer and activator of transcription(JAK/STAT), mitogen-activated protein kinases(MAPKs), AMP-activated protein kinase/mechanistic target of rapamycin(AMPK/mTOR), phosphoinositide 3-kinase/protein kinase B(PI3K/Akt) and cyclic GMP-AMP synthase–stimulator of interferon genes(cGAS–STING). Notably, GK has been observed to display context-dependent regulation of cell fate decisions, including apoptosis, autophagy and ferroptosis, thereby enabling the selective elimination of pathological cells while preserving normal tissue function. Preclinical studies further demonstrate that GK exhibits therapeutic potential across diverse disease systems, including cancer, metabolic disorders, cardiovascular diseases, neurological disorders and musculoskeletal diseases. In addition, emerging evidence highlights its antibacterial and antivirulence properties through the inhibition of biofilm formation and quorum sensing. It is crucial to note, however, that this promising profile is predominantly derived from preclinical studies, and clinical evidence in humans remains to be established. Despite these promising findings, the clinical translation of GK remains limited by challenges related to pharmacokinetics, bioavailability and druggability. This review systematically summarizes the chemical characteristics, pharmacological activities and molecular mechanisms of GK, with an emphasis on its multitarget actions and therapeutic potential across disease systems, and discusses current limitations and future perspectives to facilitate the rational development of GK-based interventions. Full article

Chemical investigation of the marine sponge-derived Streptomyces xiamenensis 1310KO-148 afforded six polycyclic tetramate macrolactams (PTMs), including three known compounds (1–3) and three previously undescribed chlorohydrin-containing analogues, chlokamycins B–D (4–6). Their planar structures were elucidated by extensive analysis of 1D and 2D NMR spectra and HR-ESIMS data, while the relative configurations were assigned using NOESY correlations. The absolute configurations were further confirmed by electronic circular dichroism (ECD) calculations. Compounds 3–6 exhibited significant cytotoxic activity against 14 human cancer cell lines (GI₅₀ = 2.68–24.92 μM) and antibacterial activity against Staphylococcus aureus (MIC = 16.00–32.00 μg/mL) and Micrococcus luteus (MIC = 4.00–32.00 μg/mL) among six tested bacterial strains. Full article