Sabancı University

The chemical stability of liquid-phase epitaxy (LPE) materials plays a decisive role in the quality of high-temperature Bi2Sr2Can-1CunO2n+4+δ (BSCCO) superconducting films. In this study, the corrosion and dissolution behavior of two commonly used crucibles (made of Pt, and Pt-Rh alloy) and two substrates (MgO and NdGaO3) in BSCCO/KCl solution were systematically investigated during the growth of Bi2Sr2CaCu2O8+δ (Bi-2212) films. Corrosion effects observed by optical and SEM imaging on the Pt–Rh crucible and NdGaO₃ substrate led to a detailed investigation of impurity incorporation into the films. The presence and origin of these impurities were identified by SEM-EDS, while their influence on the crystal structure and superconducting properties was evaluated using XRD and SQUID magnetometry, respectively. Imaging and elemental analysis show that films incorporating impurity atoms from the substrate exhibit degraded texture, correlated with the solubility of the surface material. This degradation is further accompanied by a marked suppression of superconductivity, arising from the combined effects of extrinsic impurities and the compromised microstructure. Overall, the findings underscore the critical importance of LPE material’s inertness in controlling impurity incorporation and preserving both the textural integrity and superconducting behavior of LPE-grown Bi-2212 films. This work provides essential insights into impurity–flux interactions and highlights pathways to improve the reproducibility and quality of epitaxial Bi-2212 film growth.

Vascular Endothelial Growth Factor (VEGF) is a critical factor in pathological neovascularization, making it the primary target for ocular anti-angiogenic therapies. Anti-VEGF treatments suffer from requiring frequent intraocular injections for effective treatment due to limited half-life. This study aimed to utilize a composite nanoparticle-hydrogel drug delivery system consisting of poly(glycerol sebacate) (PGS) nanoparticles and cross-linked hyaluronic acid hydrogel to achieve an extended release of anti-VEGF agent, HRH peptide, with the objective of reducing the frequency of intravitreal injections required for treatment of neovascular diseases. Our findings reveal a promising 42.54% ± 5.99% drug release from HA-PGS NP@HRH within the first 3 months, indicating potential for sustained drug release applications. Cell viability studies demonstrate biocompatibility with human retinal pigment epithelium (ARPE-19) cells and reveal anti-angiogenic effects by binding to VEGF receptors on human umbilical vein endothelial (HUVEC) cells, inhibiting VEGF activity, cell growth (with 55.19% cell viability), and tube formation of HUVECs. In vivo experiments with an oxygen-induced retinopathy (OIR) model demonstrated a suppression of neovascularization in mice treated with PGS NPs@HRH. Our research strives to contribute to the development of these new-generation materials, promising improved treatment efficacy and ultimately enhancing the quality of life for patients affected by these challenging conditions.

The growing need for electroactive components in modern electronics, autonomous vehicles, and miniaturized medical equipment requires new sustainable materials with improved piezoelectric performance. The lead-free perovskite system (Ba,Ca)(Zr,Ti)O3 has already been demonstrated to be an excellent alternative to Pb(Zr,Ti)O3 for soft-type piezoelectric applications, but its adaptability to hard-type piezoelectric requirements remains unclear. Here, we demonstrate hardening of (Ba,Ca)(Zr,Ti)O3 via targeted defect formation using Fe acceptor doping. We reveal the underlying defect equations and provide experimental evidence for the formation of ({Fe\prime}_{Zr,Ti}-vO••)• defect complexes using electron paramagnetic resonance. We describe the influence of Fe-doping on the crystal structure, phase transition behavior, and electromechanical properties, and found outstanding electrostrictive coefficients, up to 0.063 m²/C⁴, in highly doped relaxor-like (Ba,Ca)(Zr,Ti)O₃. Aging experiments on poled compositions with <1% Fe revealed that piezoelectric hardening through defect complexes occurs in BCZT only after prolonged aging. This resulted in an increase of the figure of merit for resonance applications by over 280% and considerably improved high-power behavior, exceeding the stability of commercial Pb(Zr,Ti)O3 materials. Our results demonstrate the large potential of (Ba,Ca)(Zr,Ti)O3 for resonant piezoelectric applications and simultaneously give insights into the defect chemistry of acceptor-doped (Ba,Ca)(Zr,Ti)O3.

This study introduces an enhanced formulation of the Particle Inverse Method (PIM) tailored for shape sensing and crack propagation monitoring of laminated composite plates. Building upon the foundational concept of PIM as a novel particle-based structural health monitoring method for isotropic plates, the approach presented herein enables full-field deformation reconstruction and real-time crack propagation monitoring of laminated composite plates from discrete strain measurements, without requiring knowledge of loading conditions or material properties. The method utilizes a mesh-free particle discretization and a nonlocal differential operator inspired by peridynamics to approximate spatial gradients of the displacement field. Through a variational least-squares principle, the algorithm minimizes discrepancies between numerically reconstructed strains and experimental strain data obtained via distributed sensors. A damage parameter is defined based on bond-level interactions to capture the initiation and progression of cracks in composite plates. The proposed framework supports continuous assessment even as damage evolves. The performance of the method is demonstrated through numerical and experimental case studies on composite laminates with various ply configurations and crack orientations. Results confirm the method’s capability to accurately reconstruct full-field displacements while predicting crack opening and propagation behavior, validating its potential for real-time health monitoring of composite structures.

This study assesses the diaper choices, diapering practices, and irritant diaper dermatitis (IDD) prevention strategies in Turkey and compares them to the practices worldwide. A Computer-Assisted Web Interview was conducted with 306 mothers, nursing their infants between 0 and 3 years. The average daily diaper usage was 6.3, with a higher utilization during daytime. Concerningly, 44.4% of infants exhibited skin issues. In total, 63.7% of parents observed the occurrence of IDD during the first month, with 39.9% indicating its continued presence afterwards. The IDD predominantly affected the buttocks and genitalia. Many parents sought medical advice for IDD. Regarding interventions, 56.9% of parents believed that anti-rash products were effective. The primary reason for brand preference was the presence of an elastic waistband. Parents were willing to adopt a novel anti-rash diaper. The research underscored the widespread occurrence of IDD, emphasizing the susceptibility of young infants. Diapering practices and preventive measures varied across various countries.

The CRISPR/Cas9 system has revolutionized molecular biology and gene editing, yet key aspects of its regulation, especially within eukaryotic environments, remain enigmatic. In this Viewpoint article, I will speculate on and explore the provocative hypothesis that Cas9 may possess previously unrecognized effector-like functions when expressed in host cells, potentially shaped by host-mediated post-translational modifications (PTMs). Of particular interest is SUMOylation at lysine 848, a key residue for DNA binding within the catalytic site, raising the possibility that this modification is not incidental, but functionally significant and precisely regulated. SUMOylation, a eukaryotic PTM, is increasingly recognized as a mechanism that also targets bacterial and viral effector proteins and virulence factors during infection, exerting context-dependent effects that may either enhance or hinder pathogen replication. Could Cas9, beyond its canonical role in bacterial CRISPR immunity, act as a host-modulating effector during infection, akin to known bacterial nucleomodulins such as transcription activator-like (TAL) effectors? If so, this would imply that certain pathogenic bacteria may have evolved Cas9 variants capable of exploiting host PTM machinery and targeting the host genome-an adaptation with potential implications for microbial virulence, host-pathogen interactions, and co-evolutionary dynamics. This perspective underscores the importance of systematically mapping Cas9 PTMs and examining their evolutionary conservation, functional significance, and pharmacological tunability, not only for basic biological insight and to deepen our understanding of microbial strategies, but also to refine the precision and safety of Cas9-based therapeutic platforms.

2D Ti3C2Tx(MXene) is attracting significant attention in tissue engineering. The incorporation of these promising materials into conventional scaffolds remains challenging, particularly with physicochemical properties compatible with biological systems. Melt electrowriting (MEW) has emerged as a powerful additive manufacturing technique for biofabrication of customized three-dimensional (3D) scaffolds composed of bioactive materials. This study introduces MEW of 2D MXene and polycaprolactone (PCL) nanocomposite scaffolds for tissue engineering applications. First, Ti3C2Txwas functionalized using (3-aminopropyl) triethoxysilane (referred to asf-MXene) to obtain a blended nanocomposite in PCL matrix (referred to as MX/PCL). Fourier transform infrared spectroscopy revealed the nanocomposite composition. X-ray diffraction analysis showed the reduced crystallinity in PCL after incorporation off-MXene. Differential scanning calorimetry helped to establish the optimal MEW parameters. Thermogravimetric analysis conducted on nanocomposites containing 0.1, 0.5, and 1% (w/w)f-MXene showed the thermal stability of MXene during the MEW process. The extrudability and printability of the nanocomposites with varying concentrations was demonstrated using MEW in 0-90-degree mesh scaffolds with fine filament dimensions. Scanning electron microscopy and Energy-dispersive x-ray spectroscopy mapping showed the shape fidelity, printing accuracy, and structural integrity of 3D MEW scaffolds with uniform distribution off-MXene, respectively. Further characterization showed the concentration-dependent enhancement in hydrophilicity and compressive modulus and yield strength of scaffolds upon integration off-MXene. Atomic force microscopy analysis demonstrated that the topography of the 3D MEW MX/PCL scaffolds changed compared to the pristine PCL and the roughness of the surfaces increased as the concentration of thef-MXene increased. Accelerated degradation tests demonstrated that increasing filler concentration in the reinforced scaffolds progressively delayed degradation compared to the control. Thein vitrocharacterization showed the adherence of MC3T3-E1 preosteoblast cells on MX/PCL scaffolds and their enhanced osteogenic differentiation. The findings indicate that 3D printed MX/PCL nanocomposite scaffolds have significant potential as mechanically robust scaffolds with controlled degradation rate and cytocompatibility for tissue regeneration, with properties tunable for specific applications.

Motion perception relies on at least two distinct systems: a velocity-based motion system driven by early direction-selective cells and a position-based motion system that tracks objects over space and time. However, how these systems interact when operating in parallel remains unclear. We explored their respective contributions to the perceptual organization of motion using a bistable stimulus of eight moving dots, perceived either as rotating in local pairs (local motion percept) or as forming two illusory squares translating around fixation (global motion percept). To disrupt the velocity-based motion system, we varied interstimulus intervals (ISIs) stroboscopically from 0 to 116.6ms - selectively impairing early direction-selective cells with short temporal integration windows ( ms). Additionally, we manipulated contrast polarity to bias perceptual grouping (local-group, global-group, or no-group). We found that the pattern of perceptual bistability shifted markedly at ISIs of 33ms. For ISIs 33ms, contrast- and proximity-based grouping strongly influenced perception. For ISIs ms, the global motion percept dominated even in the presence of strong static grouping cues (i.e., contrast and proximity), suggesting that the velocity-based motion system introduces a perceptual bias that can override or counteract static grouping cues. These findings reveal distinct, and at times opposing, contributions of velocity- and position-based motion systems to the perceptual organization of motion.

Working memory (WM) has a limited capacity, allowing storage of only three or four objects simultaneously. However, individuals often encounter more information than this limit allows. A potential strategy to handle this overload is transferring existing information to long-term memory (LTM) to free up WM capacity. In a study, we tested participants' strategies under the expectation of additional memory load. In Phase 1, participants (n=30) studied images of real-world objects, each paired with a distinct color. This would allow the recruitment of LTM for these objects. In Phase 2, their memory accuracy for these colors was assessed to ensure learning has taken place. The main experiment (Phase 3) utilized a blocked design with two anticipated load conditions (extra load expected and low load expected) and two memory conditions (studied and novel). In the extra load expected condition, 80% of the trials included two additional novel memory items, while 20% had no additional items. In the low load expected condition, these probabilities were reversed. This design allowed participants to anticipate the likelihood of additional memory load. After a retention interval, participants selected the color of one of the presented objects on a color wheel. To assess participants’ strategies under load expectations, we measured contralateral delay activity (CDA) via EEG. The CDA was larger for novel vs studied items, demonstrating reliance on LTMs when available. However, this effect was unaffected by expectations of additional memory load. These findings suggest that participants prioritize relying on LTM whenever possible, and their memory strategies operate independently of expectations about future memory load.

Recent efforts to digitize textual, visual, and physical forms of cultural heritage require advanced tools for preservation and analysis. The availability of extensive online data creates a need for intelligent systems to help users and archivists understand latent relationships in these collections. A major challenge in cultural heritage studies is the labor-intensive process of analyzing these materials. Inconsistent linguistic terms and ambiguous concepts in digital documents make it difficult to uncover relationships without expert supervision. Moreover, while advanced models based on large-scale pretraining demonstrate strong performance in extracting semantic relationships, they depend on extensive pretraining on large external datasets, limiting their applicability for smaller or specialized collections. We propose a system that combines natural language processing for entity extraction with graph representation learning to model relationships among documents, categories, and n-grams, resulting in a fully-connected network representation. Unlike methods requiring large-scale pretraining, our approach operates effectively using only the information available in the dataset itself, making it particularly suited for smaller cultural heritage document collections. The system extracts significant terms from document metadata, produces embeddings for each document, and uses these embeddings to build a recommendation system for entity discovery. We tested the system on a collection of early 20th-century documents from Crete, evaluating its performance against alternative methods in collaboration with experts from the archival research organization SALT. This approach not only facilitates deeper insights into smaller, specialized collections but also reduces dependency on vast external training resources, enhancing its practical utility in cultural heritage studies.