Middle East Technical University
  • Çankaya, Ankara, Turkey
Recent publications
Geometrical isomers of dantrolene are considered within the constraints of density functional theory at the level of B3LYP/6-31++G(d,p). Dantrolene is a skeletal muscle relaxant which interferes with the release of calcium ion from the sarcoplasmic reticulum. On the other hand, some evidence exists that dantrolene is Mg2+-dependent at least in certain species. Therefore, the present study not only considers the geometrical isomers of dantrolene but also focused on the interaction of isomers of dantrolene with Ca+2 and Mg+2 ions at the molecular level. All the systems of present interest have exothermic heat of formation values and favorable Gibbs free energy of formation values. They are electronically stable. In the case of composite from the anti isomer, Ca+2 or Mg+2 ion locates itself in the cavity/fjord formed in the composite of dantrolene whereas in the syn composite, Mg+2 prefers a location outside the cavity/fjord of the composite molecule. Various quantum chemical data have been collected and discussed including UV-VIS spectra.
Cyberbullying has become a global threat among adolescents. The aim of the present study, based on a qualitative methodology, is to investigate the perspective of adolescents on cyberbullying in Türkiye. A qualitative research method was employed in the study's design. Individual interviews were conducted with fifteen participants based on inclusion criteria, including being a high school student and spending at least two hours per day on the internet. The research team prepared a semi-structured interview form for data collection. Qualitative Content Analysis (QCA) was used for data analysis. The perception of adolescents on cyberbullying was categorized into five main categories based on the QCA. Emerged categories were the meaning of cyberbullying, reasons for cyberbullying (perpetrators and victims), preventive strategies, dealing with cyberbullying, and suggestions for educational strategies. The study findings draw attention to cultural differences in cyberbullying and the importance of digital interventions in awareness, preventing, and coping with cyberbullying behaviors. Moreover, the findings highlighted the need for educational actions (i.e., prevention and intervention strategies) on awareness , preventing, and coping with cyberbullying. Different methods and techniques can be used to deal with cyberbullying instead of traditional methods like informative seminars.
This study examines the status of teacher-child interaction quality, the nature of teacher beliefs, and their relationship in the context of preschool classrooms in a metropolitan city in Turkey via a mixed-methods research design. Quantitative data were collected from 47 preschool teachers through teacher survey and structured classroom observation methods using the Classroom Assessment Scoring System (CLASS). In the qualitative dimension, semi-structured interviews were conducted with four preschool teachers, purposefully selected based on their CLASS scores. The results revealed that the overall quality of teacher-child interaction was ‘average’ in the classrooms. Preschool teachers were generally positive about their capabilities to teach and tended to espouse developmentally appropriate practice to a great extent, but these beliefs did not consistently align with the teacher-child interaction quality observed in their classrooms. The study highlights the critical need to bridge the gap between teachers’ beliefs and practices to improve the quality of early childhood education.
Playtesting is an essential step in the game design process. Game designers use the feedback from playtests to refine their designs. Game designers may employ procedural personas to automate the playtesting process. In this article, we present two approaches to improve automated playtesting. First, we propose developing persona , which allows a persona to progress to different goals. In contrast, the procedural persona is fixed to a single goal. Second, a human playtester knows which paths she has tested before, and during the consequent tests, she may test different paths. However, reinforcement learning (RL) agents disregard these previous paths. We propose a novel methodology that we refer to as alternative path finder (APF). We train APF with previous paths and employ APF during the training of an RL agent. APF modulates the reward structure of the environment, while preserving the agent’s goal. When evaluated, the agent generates a different trajectory that achieves the same goal. We use the general video game artificial intelligence and VizDoom frameworks to test our proposed methodologies. We use proximal policy optimization RL agent during experiments. First, we compare the playtest data generated by developing and procedural persona. Our experiments show that developing persona provides better insight into the game and how different players would play. Second, we present the alternative paths found using APF and argue why traditional RL agents cannot learn those paths.
The Middle East and North Africa (MENA) region has acquired a prominent place in Turkey’s foreign policy since the coming to power of the AKP in late 2002. In understanding the relationship between AKP’s ideology and pragmatism in AKP’s MENA foreign policy moves, the chapter emphasizes the importance of unit-level variables and focuses on AKP’s domestic political considerations and objectives, specifically identifying ideational and ideological variables (rebranding Turkey’s state identity and ideology) and material variables (achieving the AKP’s domestic political objective of staying in power) as the explanatory variables. While the ideational and ideological variables mainly explain the general continuity of the high level of involvement in the MENA in the last two decades despite the shifts in the international system, the material variables help us to understand the seeming contradiction between ideology and pragmatism in AKP’s foreign policy toward the region. AKP’s “procedural pragmatism” as opposed to “substantive pragmatism” allows for the consideration of different policy alternatives without ultimately changing the overall ideological framework that drives foreign policy toward the MENA region. This chapter shows that the AKP has been trying to justify its pragmatism by drawing not only on the party’s main ideological framework (i.e., claiming that they are solving the problems of the Islamic world) but also on the more recent ideological frame, namely a nationalist one, that the leaders of the AKP have started to use especially since the failed coup attempt in July 2016 (i.e., claiming to help to solve the threat from the Kurdish groups in Syria). In addition, the AKP ultimately argues for the necessity of pragmatism as a way to “save the[ir] authentic rule,” while not challenging the party’s main ideational frame.
This chapter argues that Turkey’s foreign policy choices and initiatives, along with their outcomes, have been largely determined within a geopolitical context where collective memories, history, and perceptions matter, and identities shape existing network of relations. Starting with the assumption that the region is not a homogenous entity, the chapter specifically looks at Turkey’s bilateral relations with three regional states: Azerbaijan, Armenia, and Georgia. Whereas Turkey’s relations with Azerbaijan and Armenia are largely determined by historical friendship and enmity, Turkey-Georgia relations are based on mutual economic and political interests. The chapter concludes by a discussion on three major issues that will dominate whether or not Turkey will be able to continue its pro-active role in shaping regional politics and participating in regional cooperation efforts.
Aggregation, the gathering of individuals into a single group as observed in animals such as birds, bees, and amoeba, is known to provide protection against predators or resistance to adverse environmental conditions for the whole. Cue-based aggregation, where environmental cues determine the location of aggregation, is known to be challenging when the swarm density is low. Here, we propose a novel aggregation method applicable to real robots in low-density swarms. Previously, Landmark-Based Aggregation (LBA) method had used odometric dead-reckoning coupled with visual landmarks and yielded better aggregation in low-density swarms. However, the method’s performance was affected adversely by odometry drift, jeopardizing its application in real-world scenarios. In this article, a novel Reinforcement Learning-based Aggregation method, RLA, is proposed to increase aggregation robustness, thus making aggregation possible for real robots in low-density swarm settings. Systematic experiments conducted in a kinematic-based simulator and on real robots have shown that the RLA method yielded larger aggregates, is more robust to odometry noise than the LBA method, and adapts better to environmental changes while not being sensitive to parameter tuning, making it better deployable under real-world conditions.
Charity sport activities provide a sense of contributing to the lives of others and offer participants an extra source of motivation. SL has been used in a variety of sports and recreational contexts to research dedication to leisure activities. However, no study has investigated SL in charity sports events. In this regard, a model integrating key variables from the studies of serious leisure, charity sport event participation motivation, experience value, and behavioral intentions was proposed and tested on the participants of charity sport events. It is anticipated that the findings of this study will help to understand the multidimensional aspects of charity sports event participation, which may increase the effectiveness of the organization of charity sports events. Besides, this research adds to the literature by providing empirical data analysis regarding charity sports events from an unexplored country (Turkey).
PTEN and PIK3CA mutations are the most prevalent PI3K pathway alterations in prostate, breast, colorectal, and endometrial cancers. p110β becomes the prominent PI3K isoform upon PTEN loss. In this study, we aimed to understand the molecular mechanisms of PI3K dependence in the absence of PTEN. Using online bioinformatical tools, we examined two publicly available microarray datasets with aberrant PI3K activation. We found that the rate‐limiting enzyme of cholesterol biogenesis, SQLE, was significantly upregulated in p110β‐hyperactivated or PTEN‐deficient mouse prostate tumors. Concomitantly, the expression of cholesterol biosynthesis pathway enzymes was directly correlated with PI3K activation status in microarray datasets and diminished upon PTEN re‐expression in PTEN‐null prostate cancer cells. Particularly, PTEN re‐expression decreased SQLE protein levels in PTEN‐deficient prostate cancer cells. We performed targeted metabolomics and detected reduced levels of cholesteryl esters as well as free cholesterol upon PTEN re‐expression. Notably, PTEN‐null prostate and breast cancer cell lines were more sensitive to pharmacological intervention with the cholesterol pathway than PTEN‐replete cancer cells. Since steroid hormones use sterols as structural precursors, we studied whether cholesterol biosynthesis may be a metabolic vulnerability that enhances antihormone therapy in PTEN‐null castration‐resistant prostate cancer cells. Coinhibition of cholesterol biosynthesis and the androgen receptor enhanced their sensitivity. Moreover, PTEN suppression in endocrine therapy‐resistant luminal‐A breast cancer cells leads to an increase in SQLE expression and a corresponding sensitization to the inhibition of cholesterol synthesis. According to our data, targeting cholesterol biosynthesis in combination with the hormone receptor signaling axis can potentially treat hormone‐resistant prostate and breast cancers.
Cappadocia in Turkey is an important region with emphasis on ethnic and historic structures and geological features. Because of volcanic eruptions, ash flow materials deposited at different levels. These different colored ignimbrite levels have a wide range of geomechanical properties. In the region, the Kızılkaya ignimbrite covers a very large area and is frequently used as building dimension stone in for the restoration of old historical buildings such as churches, caravansaries and mosques as well as new buildings. It contains tuffaceous matrix with some minerals and rock fragments. The rock has variable character. In this study, the relationship between petrographic and physico-mechanical properties of the Kızılkaya ignimbrite was investigated. Rate of change between uniaxial compressive strength and the other index properties of the rock was statistically examined utilizing multiple regression analysis (MRA) and Artificial Neural Network (ANN) methods. The study has shown that uniaxial compressive strength (UCS) of the ignimbrite can be successfully estimated by the use of dry unit weight, effective porosity, sonic velocity, and grain matrix ratio (GMR) parameters. A new UCS prediction equation is proposed in this paper for the ignimbrite with variable character. Since properties of the ignimbrite at different distances from the eruption area changes significantly, the approach presented in this study can be considered for the ignimbrites especially covering a large area with different welding degrees and grains.
The potato chloroplast was transformed with codon optimized synthetic hybrid cry gene (SN19) to mitigate crop losses by Colorado potato beetle (CPB). The bombarded explants (leaves and internode) were cultured on MS medium supplemented with BAP (2.0 mg/l), NAA (0.2 mg/l), TDZ (2.0 mg/l) and GA3 (0.1 mg/l); spectinomycin 50 mg/l was used as a selection agent in the medium. Leaf explants of cultivar Kuroda induced highest percentage (92%) of callus where cultivar Santae produced the highest percentage (85.7%) of transplastomic shoots. Sante and Challenger showed 9.6% shoot regeneration efficiency followed by cultivar Simply Red (8.8%). PCR amplification yielded 16 postive transplastomic plantlets out of 21 spectinomycin resistant ones. Target gene integration was confirmed by PCR and Southern blot, whereas RT-qPCR was used to assess the expression level of transgene. The localization of visual marker gene gfp was tracked by laser scanning confocal microscopy which confirmed its expression in chloroplasts of leaf cells. The transplastomic plants ensured high mortality to both larvae and adult CPB. Foliage consumption and weight gain of CPB fed on transplastomic leaves were lower compared to the control plants. Sucessful implementation of current research findings can lead to a viable solution to CPB mediated potato losses globally.
Quantitative precipitation estimates obtained by weather radars are prone to errors. Gauge-based observations are known to be complementary data for mitigating radar-based estimation. This study investigates, implements, and validates four gauge adjustment and four time-independent bias correction methods over all the operating radars of Turkey during the years 2014–2019. The objective is to investigate the performance of methods over large regions using long time series, where such implementations are rarely done. The results provide detailed information regarding the performance of these methods in different spatiotemporal scenarios. Gauge adjustment methods can mitigate the mean error and/or the dispersion of the error in the original radar data. On average, gauge adjustment methods reduce the mean error from −0.81 to −0.05 mm/h, the root mean squared error from 2.63 to 1.50 mm/h, and the correlation coefficient from 0.53 to 0.83. Time-independent methods can improve the mean error from −0.81 to −0.08 mm/h.
The spin-3/2 to spin-1/2 doubly heavy baryon transition magnetic dipole GM and electric quadrupole GE form factors are calculated in the framework of the light cone sum rules method. Moreover, the decay widths of corresponding radiative transitions are estimated. Obtained results of magnetic dipole moments GM and decay widths are compared with the results present in the literature.
Aquatic invertebrates play a pivotal role in (eco)toxicological assessments because they offer ethical, cost-effective and repeatable testing options. Additionally, their significance in the food chain and their ability to represent diverse aquatic ecosystems make them valuable subjects for (eco)toxicological studies. To ensure consistency and comparability across studies, international (eco)toxicology guidelines have been used to establish standardised methods and protocols for data collection, analysis and interpretation. However, the current standardised protocols primarily focus on a limited number of aquatic invertebrate species, mainly from Arthropoda, Mollusca and Annelida. These protocols are suitable for basic toxicity screening, effectively assessing the immediate and severe effects of toxic substances on organisms. For more comprehensive and ecologically relevant assessments, particularly those addressing long-term effects and ecosystem-wide impacts, we recommended the use of a broader diversity of species, since the present choice of taxa exacerbates the limited scope of basic ecotoxicological studies. This review provides a comprehensive overview of (eco)toxicological studies, focusing on major aquatic invertebrate taxa and how they are used to assess the impact of chemicals in diverse aquatic environments. The present work supports the use of a broad-taxa approach in basic environmental assessments, as it better represents the natural populations inhabiting various ecosystems. Advances in omics and other biochemical and computational techniques make the broad-taxa approach more feasible, enabling mechanistic studies on non-model organisms. By combining these approaches with in vitro techniques together with the broad-taxa approach, researchers can gain insights into less-explored impacts of pollution, such as changes in population diversity, the development of tolerance and transgenerational inheritance of pollution responses, the impact on organism phenotypic plasticity, biological invasion outcomes, social behaviour changes, metabolome changes, regeneration phenomena, disease susceptibility and tissue pathologies. This review also emphasises the need for harmonised data-reporting standards and minimum annotation checklists to ensure that research results are findable, accessible, interoperable and reusable (FAIR), maximising the use and reusability of data. The ultimate goal is to encourage integrated and holistic problem-focused collaboration between diverse scientific disciplines, international standardisation organisations and decision-making bodies, with a focus on transdisciplinary knowledge co-production for the One-Health approach.
The main purpose of this study was to observe the degree of the improvement on the film adhesive joining performance of Poly(phenylene sulfide)/Carbon Fiber (PPS/CF) thermoplastic composite laminates when their surfaces were treated by atmospheric plasma technique. For this purpose, plasma treated surfaces were compared with untreated and the traditional grit-blasted surfaces. Treated surfaces were characterized by various techniques including contact angle, surface energy, surface roughness, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. Then, joining performance of the PPS/CF composite samples bonded by an epoxy-based film adhesive was determined by using three different mechanical tests; single-lap shear strength, mode-I interlaminar fracture toughness energy, and drop-weight impact toughness. Grit-blasting surface treatment increased surface roughness of the specimens enormously (7 times more), leading to mechanical interlocking as the dominant bonding mechanism. Contrarily, plasma surface treatment resulted in formation of chemically reactive sites, thus dominant bonding mechanisms in the film adhesive joining were certain polar interactions and chemical bonding. Mechanical tests pointed out that compared to grit-blasting, plasma surface treatment resulted in considerably higher joint performance regarding interlaminar shear strength (35% more), interlaminar fracture toughness (67% more) and impact toughness (28% more), with the cohesive failure mode. Accordingly, it could be stated that traditional grit-blasting could be replaced with plasma surface treatment applied before film adhesive joining of PPS/CF composite parts in aircraft industry.
Amorphous calcium carbonate (ACC) is a nontoxic and degradable nanomaterial. ACC can be synthesized using the coprecipitation technique, which enables the incorporation of ions into its amorphous structure. Although ACC has been investigated for various applications, such as wastewater treatment, in vivo imaging, and drug delivery, its antibacterial properties have not been explored. Considering the extraordinary capability of bacteria to adapt antimicrobial strategies, as well as the extensive burden of bacteria-induced problems on healthcare systems and the world economy, the need for effective antibacterial agents is becoming a pressing issue. Herein, we introduced selenite-incorporated magnesium-stabilized amorphous calcium carbonate (ACMC) nanoparticles as a sustainable antibacterial material. For the first time, we demonstrated that selenite ions could be incorporated into ACMC nanoparticles while preserving the amorphous structure. Antibacterial activity analysis showed that selenite-incorporated ACMC (Se-ACMC) nanoparticles at 1 g/L concentration could significantly reduce the growth of Gram-positive (Staphylococcus aureus and Staphylococcus epidermidis) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria strains within 24 h of interaction. As an important observation, even the lowest selenite incorporation (4.38 ± 0.19 mg selenium per g of nanoparticles) led to a more than 3-log reduction in the number of S. epidermidis colonies. Additionally, the antibacterial activity was enhanced with an increase in the amount of incorporated selenite. These results indicated that ion-incorporated ACMC nanoparticles can pave the way for applications as antibacterial agents.
The donor-acceptor type indole chromophore motif presents an interesting molecular architecture to the scientific world, unfortunately, as in every special and beautiful formation needed; their synthesis represents a synthesis challenge. In the current search, new donor-acceptor typed indole derivatives, 1-methyl-phenyl-3-aldehyde indole (HAN-1), 2-((1-methyl-2-phenyl-1H-indol-3-yl)methylene)malononitrile (HAN-2), 1-ethyl-2-phenyl-3-aldehyde indole (HAN-3), 2-((1-ethyl-2-phenyl-1H-indol-3-yl)methylene)malononitrile (HAN-4) were successfully synthesized and the results supported with FTIR and NMR spectra analysis. All the molecules undergo excited state intramolecular electron transfer with unique charge transfer reaction. Their electrochemical and optical properties were investigated in relation to the acceptor effect of functional groups on the indole units in the conjugated structure. Density functional theory (DFT) calculations exhibited that higher electron withdrawing ability strength resulted in decreased HOMO-LUMU gaps of the molecules. Futhermore, donor acceptor typed indole derivatives undergo irreversibly one electron oxidation in the medium of 0.1 M TBAPF6/ACN solution with a similar onset oxidation potentials. Both experimental and theoretical studies showed that the electron withdrawing ability of the molecules affect more LUMO energy level of the molecules. Moreover, they suggest that donor acceptor indole molecules herein are potential candidates for fabrication of dye synthesized solar cells.
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20,478 members
Huseyin Hacihabiboglu
  • Graduate School of Informatics
Osman Yavuz Ataman
  • Department of Chemistry
Yavuz Topkaya
  • Department of Metallurgical and Materials Engineering
  • Department of Mechanical Engineering
Üniversiteler Mah., Eskişehir Yolu No:1, 06800, Çankaya, Ankara, Turkey
Head of institution
Mustafa Verşan Kök