Istanbul Technical University
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Chemical Treatment-Induced Indirect-to-Direct Bandgap Transition in MoS₂: Impact on Excitonic Emission
No full text<title>Abstract</title> <p>The unique electrical and optical properties of emerging two-dimensional transition metal dichalcogenides (TMDs) present compelling advantages over conventional semiconductors, including Si, Ge, and GaAs. Nevertheless, realising the full potential of TMDs in electronic and optoelectronic devices, such as transistors, light-emitting diodes (LEDs), and photodetectors, is constrained by high contact resistance. This limitation arises from their low intrinsic carrier concentrations and the current insufficiency of doping strategies for atomically thin materials. Notably, chemical treatment with 1,2-dichloroethane (DCE) has been demonstrated as an effective post-growth method to enhance the n-type electrical conductivity of TMDs. Despite the well-established electrical improvements post-DCE treatment, its effects on optical properties, specifically the retention of optical characteristics and excitonic behaviour, are not yet clearly understood. Here, we systematically investigate the layer- and time-dependent optical effects of DCE on molybdenum disulfide (MoS₂) using photoluminescence (PL) spectroscopy and Density Functional Theory (DFT) simulations. Our PL results reveal a rapid reduction in the indirect bandgap transition, with the direct transition remaining unaffected. DFT confirms that chlorine (Cl) atoms bind to sulphur vacancies, creating in-gap states that facilitate non-radiative recombination, explaining the observed indirect PL suppression. This work demonstrates DCE's utility beyond n-type doping, showcasing its ability to engineer the optical band structure in MoS₂ by selectively suppressing indirect transitions. This capability directly paves the way for enhanced efficiency in 2D optoelectronic devices.</p>https://doi.org/10.21203/rs.3.rs-7212840/v
Characterizations and In Vitro Gut Microbiome Modulatory Effects of Gluco-Oligosaccharides Synthesized by the Acceptor Reactions of Glucansucrase 53
No full textThe production of novel oligosaccharides with potential prebiotic effects is of interest to expand the current market and explore the effectiveness of new functional carbohydrate forms. The utilization of glucansucrases is a cost-effective and environmentally friendly biotechnological strategy for producing novel gluco-oligosaccharides through acceptor reactions. In this study, an active glucansucrase (GS53) was used to produce gluco-oligosaccharides via its acceptor reactions with glucose, maltose, and maltotriose, and these oligosaccharides were tested in terms of structure and their gut microbiome modulatory effects. The formations of oligosaccharides were monitored by TLC analysis, and GS53 was active for the three acceptors but not for the other sugars tested. The structural characterization of the gluco-oligosaccharides by 1H NMR analysis revealed the glycosylation of each acceptor with α-(1 → 3) and α-(1 → 6) linkages, whereas LC-MS analysis demonstrated the formations of DP 8, DP 7, and DP 6 oligosaccharides with acceptors maltose, maltotriose, and glucose, respectively. In vitro fecal fermentation analysis, in which microbial short-chain fatty acids (SCFAs) and microbial compositional changes were assessed using gas chromatography and 16S rRNA sequencing, respectively, demonstrated that the gluco-oligosaccharides formed SCFAs—particularly propionate and butyrate—at levels comparable to those observed with inulin, a well-established prebiotic. Additionally, the gluco-oligosaccharides were found to promote the growth of Bifidobacterium adolescentis and Blautia OTUs, which are known to have important physiological functions beneficial to human health. Overall, these results demonstrate that gluco-oligosaccharides synthesized using GS53 through acceptor reactions exhibit prebiotic potentials and could be utilized in the future as dietary supplements as well as in the development of functional foods targeting colonic health.https://doi.org/10.3390/fermentation11060324https://doaj.org/article/f71ae640535941e9978691556985c429https://avesis.atauni.edu.tr/publication/details/7f49d63e-1716-43db-8001-80a0f0f30e9a/oa
Mechanical performance and ANN-based prediction of Co-Cr dental alloys with gyroid cellular structures produced by LPBF technology
No full textGyroid structures exhibit significant potential in the fields of lightweight structural design, heat transfer, energy absorption, and biological applications. The use of gyroid for implants in dentistry is currently not sufficiently widespread. The research encompasses design, compression testing, cellular investigation using a digital microscope, and the application of artificial neural networks (ANNs) using data gained from the compression test. The ANN study and the test phase in which gyroid geometries are addressed by dental three-point bending tests are novel in this field. In the field of dentistry, this study compares the usability of five distinct gyroid design characteristics, including one model without a gyroid structure. During the testing, we found that the m1 model had an average maximum strength of 600 N, while the m3 model achieved 230 N. The remaining models achieved an approximate strength of 200 N. In the mechanical performance evaluation of the samples, a 40% weight reduction was achieved. An ANN model has been developed to predict the force experienced by gyroid structures under certain deformations depending on the infill ratio. This model was trained with data obtained from a three-point bending test. Using grid search and Monte Carlo cross-validation, the optimal multilayer perceptron structure was determined to have 12 neurons in the hidden layer, a mini-batch size of 8, and a learning rate of 0.0001. The Adam optimization algorithm was used to train the ANN model, which was constructed using the TensorFlow library. Evaluation metrics were used to test the model’s performance, and the results showed strong generalization capability and high accuracy with coefficient of determination ( R 2 ) of 0.997, mean squared error (MSE) of 3.337E-05 kN 2 , root mean square error of (RMSE) 0.005777 kN, and mean absolute error (MAE) of 0.003633 kN on the test dataset.https://doi.org/10.1177/09544062241307458https://avesis.yildiz.edu.tr/publication/details/48ac3d63-0db3-4b50-9614-5e25024f0348/oa
Improving the evaluation of static bifurcations in locally damaged parabolic arches
No full textAbstract Even local small cracks may induce instability and failure or operativity loss before the crisis for the intact material is actually attained. Thus, damage models and the possibility of their identification have become trendy subjects in structural mechanics. We previously studied buckling and post-buckling of parabolic arches with a local transverse small crack by two perturbations of the finite field equations and boundary conditions. One perturbation describes non-trivial fundamental paths adjacent to the undamaged initial shape, the second describes the germ of a bifurcated path in the vicinity of a critical point. We think the arch consisiting of two undamaged parts, connected by lumped elasticities quantified by notions of linear fracture mechanics, at the cracked cross-section. In this paper we highlight that in a previous investigation of ours on the same subject some physically meaningful terms were wrong in the perturbed equations. This implies that the values of the incremental external load considered in the applications of that investigation need to be amended. Thus, here we present perturbed equations that are complete and, by the same procedure, we find more reliable numerical results for the critical loads and a more refined description of the germ of the post-buckling path, besides providing clear physical interpretation for seemingly paradoxical results.https://doi.org/10.1007/s11012-024-01932-whttps://zbmath.org/806926
Temperature‐Enhanced Supramolecular Polymer Adhesion Provided by Concurrent Utilization of Calix[4]Pyrrole and Crown Ether Molecular Recognition
No full textAbstractLow molecular weight (LMW) supramolecular polymer adhesives built up from functional small molecules suffer from temperature sensitivity, which limits their utility in applications requiring high temperature ranges. It is reported here a linear supramolecular polymer that incorporates concurrent anion‐ and cation‐recognition in an orthogonal manner by means of calix[4]pyrrole (CP) and crown ether (CE) macrocycle monomers functionalized with secondary alkylammonium and carboxylate functional groups, respectively. The resulting alternating supramolecular polymer, named CPCE, is fully characterized and possesses dynamic non‐covalent bonding both in solution and solid state. Its high degree of polymerization provides good processability and temperature‐enhanced adhesive property when used on glass and steel substrates with up to 5.09 MPa adhesion strength at 75 °C. Furthermore, this low‐molecular‐weight (LMW) supramolecular polymer adhesive allows for stable reusability over 10 cycles, as well as good long‐term durability. The favorable adhesion performance of the CPCE leads to suggests that it can be useful in high‐tech special settings requiring elevated temperatures.https://doi.org/10.1002/adfm.20250385
Search for Nuclear Modifications of B+ Meson Production in p -Pb Collisions at sNN=8.16 TeV
No full textNuclear medium effects on <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msup><a:mrow><a:mi>B</a:mi></a:mrow><a:mrow><a:mo>+</a:mo></a:mrow></a:msup></a:mrow></a:math> meson production are studied using the binary-collision scaled cross section ratio between events of different charged-particle multiplicities from proton-lead collisions. Data, collected by the CMS experiment in 2016 at a nucleon-nucleon center-of-mass energy of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:msqrt><c:mrow><c:msub><c:mrow><c:mi>s</c:mi></c:mrow><c:mrow><c:mi>NN</c:mi></c:mrow></c:msub></c:mrow></c:msqrt><c:mo>=</c:mo><c:mn>8.16</c:mn><c:mtext> </c:mtext><c:mtext> </c:mtext><c:mi>TeV</c:mi></c:mrow></c:math>, corresponding to an integrated luminosity of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mn>175</e:mn><e:mtext> </e:mtext><e:mtext> </e:mtext><e:msup><e:mi>nb</e:mi><e:mrow><e:mo>−</e:mo><e:mn>1</e:mn></e:mrow></e:msup></e:math>, were used. The scaling factors in the ratio are determined using a novel approach based on the <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mrow><g:mi>Z</g:mi><g:mo stretchy="false">→</g:mo><g:msup><g:mrow><g:mi>μ</g:mi></g:mrow><g:mrow><g:mo>−</g:mo></g:mrow></g:msup><g:msup><g:mrow><g:mi>μ</g:mi></g:mrow><g:mrow><g:mo>+</g:mo></g:mrow></g:msup></g:mrow></g:math> cross sections measured in the same events. The scaled ratio for <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:mrow><j:msup><j:mrow><j:mi>B</j:mi></j:mrow><j:mrow><j:mo>+</j:mo></j:mrow></j:msup></j:mrow></j:math> is consistent with unity for all event multiplicities, putting stringent constraints on nuclear modification for heavy flavor.https://doi.org/10.1103/physrevlett.134.11190
Sustainable Digital Transformation in Geotechnical-Related Engineering Disciplines: An Integrated Framework for Türkiye
No full textThis study proposes the Sustainability-Aligned Digital Integration Model for Geotechnical-Related Engineering Disciplines in Türkiye (SDIM–Geo–TR) as a roadmap for sustainable digital transformation. Built on a four-stage methodology—global technology mapping, national contextualization, criteria definition, and phased integration—the model synthesizes emerging technologies such as GIS, BIM, UAV, IoT and Digital Twin into a maturity framework. It illustrates how digital adoption in Türkiye has evolved from early GIS use to more integrated multi-technology ecosystems but remains hampered by interoperability gaps, skill shortages and cost constraints. SDIM–Geo–TR organizes this evolution into four maturity stages and assesses progress using sustainability impact, technical feasibility, data compatibility, cost effectiveness and adoption level. The findings highlight that achieving fully integrated digital geotechnical practice requires coordinated policy interventions, standardization efforts and capacity building. By aligning international best practices with Türkiye-specific drivers, the model offers a practical roadmap for guiding sustainable and digitally enabled geotechnical engineering.https://doi.org/10.3390/su1720915
PalmCity: An Emerging Benchmark Dataset for Semantic Segmentation of Panoramic Street View Images in Under-Represented Developing Countries
No full texthttps://doi.org/10.1007/978-3-031-97663-6_1
Turkish music instruments in a western-style orchestra setting: Orchestration analysis of Oğuzhan Balcı’s “Ninni”
No full textThis study examines the orchestration techniques employed in Oğuzhan Balcı’s composition Ninni for the ITU TMDK Traditional Instruments Orchestra. The research focuses on how traditional Turkish instruments are adapted within a polyphonic orchestral work. Through an orchestration analysis, the study explores instrument combinations, textural layering, and scoring techniques. The methodology includes content analysis of the piece, evaluating orchestration methods applied to different instrument families such as wind, bowed string, and plucked string sections. The study also discusses the role of each instrument in contributing to the overall orchestral sound, emphasizing their textural interactions. The findings highlight the challenges and solutions in achieving harmonic balance and intonational accuracy with traditional Turkish instruments. Moreover, it explores how Balcı strategically uses orchestration to highlight the expressive qualities of each instrument while maintaining coherence within the ensemble. The results suggest that composers working with traditional Turkish instruments in an orchestral setting must adopt specific scoring techniques to accommodate the unique characteristics of these instruments. By providing insights into the orchestral use of these instruments, this study serves as a resource for composers and arrangers working with similar ensembles. The research contributes to the broader field of orchestration studies by offering a detailed examination of techniques that facilitate the integration of traditional Turkish instruments into a polyphonic orchestral setting.https://doi.org/10.31811/ojomus.168010
Multi-Objective Robust Optimization of Blood Supply Planning using Mobile Blood Collection Centers after Earthquakes: A Case of Istanbul
No full text<title>Abstract</title> <p>The critical elements of any healthcare system involve ensuring a secure, steady, and well-balanced provision of life-saving materials and products to aid injured individuals. Blood products present challenges due to their perishability, limited availability, and constraints on inventory management. Managing the blood supply chain effectively is imperative to consistently meet demand, especially during disasters. This study aims to develop a robust blood supply plan utilizing mobile blood centers to address uncertain demand following earthquakes. The goal is to minimize the total anticipated supply shortfall and delivery time. To achieve this, we developed a multi-objective robust optimization (MORO) model to tackle the high levels of uncertainty inherent in disaster scenarios. A practical application of the proposed methodology is examined through a case study involving a significant earthquake in Istanbul, focusing on the Avcilar district. The price of robustness is calculated to compare the performance of the proposed deterministic and robust models in achieving their objectives. A sensitivity analysis is also conducted on uncertain parameters to validate the model's reliability. The findings offer valuable managerial insights, such that reinforcement of the main blood center buildings and alternative modes of transportation may help cope with more-than-expected blood demand in major earthquake scenarios.</p>https://doi.org/10.21203/rs.3.rs-7784950/v