AXSIS - Akademik ve Açık Erişim Bilgi Sistemi (Univ. KTO Karatay)
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Optimal Portfolio Selection Using the Sharpe Ratio and the Tangency Portfolio Approach: A Long-Term Case Study on the Istanbul Stock Exchange (BIST)
No full textTable 1. Company Information
Table 2. Risk ve return stocks (daily)
Table 3. Abnormal return (daily)
Table 4. Variance – covariance matrix
Table 5. Portfolio risk-return with equal weight
Table 6. Parameters of Excel Solver
Table 7. Portfolio risk-return with different weight
Table 8. Stock Weights in Optimized Portfolios
Table 9. Determination of Optimal Portfolio
Table 10. Comparison of Portfolio Returns and Risks
Figure 1. Tangency portfolio and efficient frontierThis paper investigates the practical application of the mean-variance optimization framework and the Sharpe ratio in the Istanbul Stock Exchange (BIST) over a twenty-five-year period from July 2000 to June 2025. An initial portfolio was constructed with ten equally weighted stocks drawn from diverse sectors to achieve effective diversification. Using the Markowitz model, a set of portfolios was generated that minimized variance for specified expected returns, collectively forming the efficient frontier, which illustrates combinations of return and risk that dominate all other alternatives. Among these, the optimal portfolio—identified through the tangency portfolio approach and the Sharpe ratio—yielded returns approximately thirty-five percent higher than those of an equally weighted portfolio of the same ten stocks
Lichen extracts inhibit Candida albicans growth and biofilm formation via cAMP-PKA and Cek1 MAPK signaling pathway
No full textThe increasing prevalence of Candida infections and growing concerns about antifungal resistance have encouraged research into new therapeutic agents from natural sources. This study investigated the antifungal activity of Dermatocarpon miniatum (L.) W. Mann and Parmelia saxatilis (L.) Ach. lichen extracts against Candida species, focusing on their antibiofilm effects and underlying molecular mechanisms. Methanol and aqueous extracts of both lichens were prepared and evaluated against four reference and 19 clinical Candida strains using microdilution methods. This study employed a multi-modal approach to explore the antibiofilm effect of lichen extracts on Candida albicans, including CCK-8 assay for antibiofilm capacity, qRT-PCR for biofilm-related (cAMP-PKA and Cek1 MAPK pathways) gene expressions, field emission scanning electron microscopy for morphological assessment, and Galleria mellonella infection model for in vivo evaluation. Antifungal susceptibility tests revealed only methanol extracts showed antifungal activity, with minimum inhibitory concentrations ranging from 160 to 2500 μg/mL for P. saxatilis methanol extract (ParM) and 320–2500 μg/mL for D. miniatum methanol extract (DerM). ParM (1250 μg/mL) significantly reduced biofilm formation and down-regulated key genes involved in both pathways. Methanol extracts of lichens disrupted hyphal networks and cell integrity. In the Galleria mellonella model, DerM provided protection similar to fluconazole, while ParM provided 60 % survival. These findings indicate that lichen extracts, particularly ParM, inhibit Candida albicans biofilm formation by downregulating genes in the cAMP-PKA and Cek1 MAPK pathways. Despite the promising antibiofilm and in vivo activities of these extracts, their limited antifungal activity against Candida suggests that further research is needed for their therapeutic potential
A Systematic Review of Theses on the Satisfaction of Patients Undergoing Orthopedics and Traumatology Surgery in Turkey
No full textAim: This study aims to systematically review the postgraduate theses on the satisfaction of patients undergoing orthopedics and traumatology surgery in Turkey and to reveal the trends, methodological approaches, and main findings in the existing literature.Methods: In this systematic review, postgraduate theses registered in the National Thesis Center of the Council of Higher Education were scanned between August and September 2024 with the keywords “nurse”, “orthopedics”, and “patient satisfaction”. The year of publication was not taken as a criterion. As a result of the scan, 62 postgraduate theses registered in the database were reached, and 23 theses that met the research criteria were included in the study. The theses included in the study were examined in detail according to data collection methods, study groups, departments and types.Results: It was determined that theses in the field of nursing on orthopedic surgeries and patient satisfaction started to be written in 2014. 21 of the theses included in the study were master's theses and 2 were doctoral theses. 14 of these theses were descriptive, 3 were randomized controlled, and 5 were experimental and quasi-experimental studies. It was determined that the theses were conducted in sample groups of 4,407 people and with orthopedic patients.Conclusion: It was determined that the theses examined were mostly descriptive and experimental studies were limited in number. It was determined that communication-oriented, educational, and therapeutic approaches by nurses prioritizing patient needs increased patient satisfaction. It is predicted that future experimental studies in this field will make important contributions to the literature.Amaç: Bu çalışma, Türkiye’de ortopedi ve travmatoloji ameliyatı geçiren hastaların memnuniyetine ilişkin yapılan lisansüstü tezleri sistematik bir şekilde inceleyerek mevcut literatürdeki eğilimleri, yöntemsel yaklaşımları ve temel bulguları ortaya koymayı amaçlamaktadır.Gereç ve Yöntem: Bu sistematik derlemede, Yükseköğretim Kurulu Ulusal Tez Merkezi’nde kayıtlı olan lisansüstü tezler Ağustos-Eylül 2024 tarihleri arasında “hemşire”, “ortopedi”, “hasta memnuniyeti” anahtar kelimesiyle taranmıştır. Yayınlanma yılı kriter olarak alınmamıştır. Tarama sonucunda veri tabanına kayıtlı 62 lisansüstü teze ulaşılmış, araştırma kriterlerini karşılayan 23 tez araştırmaya dahil edilmiştir. Araştırmaya dahil edilen tezler, veri toplama yöntemleri, çalışma grupları, anabilim dalları ve türlerine göre detaylı olarak incelenmiştir. Bulgular: Ortopedik ameliyatlar ve hasta memnuniyeti konusuyla ilgili hemşirelik alanında yapılan tezlerin 2014 yılında yapılmaya başlandığı tespit edilmiştir. Araştırmaya dahil edilen tezlerin 21’i yüksek lisans, 2’si doktora tezidir. Bu tezlerin 14’ü tanımlayıcı, 3’ü randomize kontrollü olup 5 tanesi de deneysel ve yarı deneysel çalışmalardan oluşmaktadır. Tezlerin 4.407 kişilik örneklem gruplarında ve ortopedi hastalarıyla gerçekleştirildiği saptanmıştır. Sonuç: İncelenen tezlerin çoğunlukla tanımlayıcı nitelikte olduğu, deneysel çalışmaların ise sınırlı sayıda bulunduğu tespit edilmiştir. Hemşirelerin hasta gereksinimlerine öncelik vererek iletişim odaklı, eğitici ve tedavi edici yaklaşımlarının hasta memnuniyetini artırdığı tespit edilmiştir. Gelecekte bu alanda yapılacak deneysel çalışmaların, literatüre önemli katkılar sağlayacağı öngörülmektedir
Fosil Yakıt Tüketiminin Ekolojik Ayak İzine Etkisi: Seçili AB Üye Ülkelerine Yönelik 1981-2022 Dönemini Kapsayan Bir Uygulama
No full textBu çalışmada 1981-2022 yılları arasındaki veriler kullanılarak seçili AB üye ülkelerinde gerçekleşen fosil yakıt tüketiminin ekolojik ayak izine olan etkisi araştırılmaktadır. Araştırma kapsamında, 2022 ve 2023 yıllarında en yüksek oranda fosil yakıt tüketimini gerçekleştiren ilk 6 ülkeye (Almanya, Fransa, Hollanda, İspanya, İtalya ve Polonya) ait veriler kullanılmıştır. Ampirik analizde bağımlı değişken ekolojik ayak izi iken; kömür tüketimi, petrol tüketimi ve doğal gaz tüketimi ise bağımsız değişken olarak belirlenmiştir. Çalışmanın veri setine uygun modelin tahmin edilmesi amacıyla öncelikle birim bazında yatay kesit bağımlılık testi uygulanmıştır. Bir sonraki adımda, panel birim kök testlerinden CIPS, Fisher PP ile Fisher ADF testleri uygulanmış ve bu analizler sonucunda serilerin durağanlığının birinci mertebede olduğu belirlenmiştir. Üçüncü aşamada, modelin yatay kesit bağımlılık durumu ve homojenlik yapısı incelenmiştir. Analizler sonucunda modelin yatay kesit bağımlılığına sahip ve heterojen bir yapıda olduğu belirlendiğinden, bu duruma uygun olarak Westerlund eş bütünleşme testi uygulanmıştır. Test sonuçları değişkenler arasındaki ilişkinin uzun dönemli olduğunu göstermiştir. Son aşamada ise nihai model, DOLSMG Tahmincisi yöntemi ile tahmin edilmiştir. Ampirik sonuçlar ekolojik ayak izine petrol ve doğal gazın aynı oranda etki ettiğini; kömürün etkisinin ise daha düşük oranda olduğunu göstermiştir.This study uses data from 1981 to 2022 to examine the consequences of using fossil fuels the ecological footprint in a few EU member states. Data from the top 6 nations with the largest fossil fuel use in 2022 and 2023 (Germany, Spain, France, Italy, the Netherlands and Poland) were used in the study. Coal, natural gas, and oil consumption are the independent factors in the empirical study, while the dependent variable is the ecological footprint. To find the best model for the study's dataset, a unit-level cross-sectional dependence test was performed. In the subsequent phase, the data was subjected CIPS, Fisher PP, and ADF. The outcomes of these analyses showed that in the first difference, the series were stationary. Analyzing the model's cross-sectional dependence and homogeneity structure came next. According to the analysis, the model has a horizontal cross-sectional dependence and a heterogeneous structure. The second-generation Westerlund cointegration test was applied in light of this. The test results show a long-term link between the elements. The DOLSMG Estimator method was used in the last step to estimate the final model. Empirical results have shown that oil and natural gas have the same impact on the ecological footprint, while coal has a lower impact
Forecasting with Sarıma Model for an Agricultural Machinery Manufacturer
No full textThe most significant risks encountered in agricultural machinery production today can be considered as shifts in demand times and quantities due to climate change, as well as competitive factors. Therefore, statistical demand forecasting has become an essential issue in the production of agricultural machinery. The aim of this study is to forecast the production quantities of the two most important product produced by a manufacturer in the agricultural machinery sector for the next 12 months using monthly production data from 2011-2021 and to develop recommendations. To reflect seasonality in future forecasts for agricultural machinery production, the SARIMA (Box-Jenkins) model has been employed. The Box-Jenkins method is one of the techniques developed for analyzing time series and is used to analyze univariate time series. In the research, the best statistical results among the SARIMA models for the specified product are indicated. For Product 1, the SARIMA(1,1,2)(0,1,1) model has been identified as the most suitable model, while for Product 2, the SARIMA(0,1,1)(1,1,0) model has been determined to be the best fit. By examining the appropriate SARIMA model determined for the selected two product, the 12-month production forecast and expectations for 2022 have been calculated for the manufacturer.Tarım makineleri üretiminde karşılaşılan en önemli riskler günümüzde iklim değişikliğinden kaynaklı talep zamanlarında ve miktarlarında kayma ve rekabet unsurları olarak değerlendirilebilir. Bu nedenle tarım makineleri üretiminde istatistiksel talep tahmini yapmak elzem bir konu olmuştur. Bu çalışmanın amacı, tarım makineleri sektöründe bir imalatçıdan elde edilen 2011-2021 yılları arasındaki aylık üretim verilerinden yararlanarak gelecek 12 aylık dönemde üreticinin ürettiği en önemli iki ürününe ait üretim miktarlarını tahmin etmek ve gelecek üretim adetlerine dair öneriler geliştirmektir. Tarım makineleri üretimi adedi için gelecek tahmininde bulunurken mevsimselliği yansıtmak adına SARIMA diğer adıyla Box-Jenkins modeli kullanılmıştır. Zaman serilerini analiz etmek için geliştirilen yöntemlerden biri olan SARIMA yöntemi, tek değişkenli zaman serilerini analiz etmek için kullanılan güçlü metotlardandır. Araştırmada, belirlenen iki ürün için SARIMA modelleri arasında en iyi istatistiksel sonuçlar belirtilmiştir. Ürün 1 için SARIMA(1,1,2)(0,1,1) modeli, ürün 2 için ise SARIMA(0,1,1)(1,1,0) modeli en uygun model olarak bulunmuştur Seçilen iki ürün için belirlenen uygun SARIMA modeline bakarak, üretici için 2022 yılı 12 aylık üretim tahmini ve beklentisi hesaplanmıştır
Investigating Λ Baryon Production in p-Pb Collisions in Jets and the Underlying Event Using Angular Correlations
No full textPurpose This study was conducted to investigate the relationship between nursing and midwifery undergraduate students' health beliefs and breast cancer knowledge levels and breast self-examination (BSE) behavior. Materials and method This study was based on a cross-sectional research design and conducted in a Web environment. Four hundred and forty-eight female students were included who study in the 3rd or 4th years of the nursing and midwifery departments. Research data were collected between December 2020 and January 2021 by utilizing the Introductory Information Form, the Champion's Health Belief Model Scale, and the Comprehensive Breast Cancer Knowledge Test. Results It was revealed that 52.7% of the students performed BSE on a regular basis. Based on the practice of BSE, it was found that there was a statistically significant difference between the mean scores of benefits, obstacle perception, confidence/self-efficacy, and motivation subscales of CHBMS (p < 0.05). In terms of the risk of not performing BSE among students, having an extended family increased the risk by 3.29 times, not applying a clinical breast examination by 6.53 times, and a 1-unit increase in weighted GPA by 2.18 times; a 1-unit increase in the obstacle perception score related to BSE practice increased risk by 1.11 times. Conclusion and recommendations Nurses' and midwives' health beliefs, attitudes, and behaviors should be improved with regard to the importance of breast cancer and BSE throughout their education, so that they can be role models for preventive healthcare practices in society
Systematic Study of Flow Vector Fluctuations in √SNN=5.02 TeV Pb-Pb Collisions
No full textDrought is a prolonged period of significantly reduced precipitation, resulting in water scarcity and environmental stress. In this study, A & gbreve;r & imath; province, situated in the eastern region of T & uuml;rkiye, where most of the land cannot be irrigated and the livelihood is based on agriculture, was selected as the study area. Meteorological droughts in A & gbreve;r & imath; province were forecasted using hybrid machine-learning models, leveraging monthly precipitation and temperature series from 1965 to 2022. The study employed the standardized precipitation index (SPI), relying solely on precipitation data, and the standardized precipitation evapotranspiration index (SPEI), which also considers both temperature and precipitation data. Various timescales, including 1M (1 month), 3M, 6M, 9M, and 12M, were taken into consideration. The best model for each hybrid model was determined using data at time points t, t-1, t-2, t-3, and t-4 for the relevant time series. The study combined ensemble least squares boosting algorithms (LSBoosting), adaptive network-fuzzy inference system (ANFIS), support vector machines (SVM), Gaussian process regression (GPR), and M5 model tree (M5Tree) approaches with the variational mode decomposition (VMD) technique to create hybrid models. The results indicate that certain models perform better at different timescales, with M5Tree and GPR generally providing higher accuracy. For instance, the M5Tree model achieved the lowest MAE (0.0714 and 0.0555) and RMSE (0.0909 and 0.0732) values for the 9MSPI and 12MSPI timescales, respectively, making it the best-performing model at these scales. Similarly, the GPR model stood out for the 1MSPI and 6MSPI scales with the lowest MAE values (0.1336 and 0.0736, respectively). Based on the performance criteria, the best hybrid model for the 1MSPI was the GPR approach. For the SPEI, except for 3MSPEI, the M5Tree approach showed the best performance at other timescales. However, since the prediction outcomes gave similar results according to classical performance criteria, a one-sided Wilcoxon sign rank test was applied to the outcomes of ANFIS, GPR, and M5Tree models for 3MSPEI, 6MSPI, 9MSPI, and 12MSPI. It has been determined that these three models are not superior to each other. Additionally, the one-sided Wilcoxon signed-rank test found no statistically significant difference between ANFIS, GPR, SVM, and M5Tree models for the 3MSPI. This research concluded that the performance of hybrid machine-learning methods applied to different timescales of SPI and SPEI varies
Higher-Order Symmetry Plane Correlations in Pb-Pb Collisions at √sNN=5.02 TeV
No full textThe correlations between event-by-event fluctuations of symmetry planes are measured in Pb-Pb collisions at a center-of-mass energy per nucleon pair root sNN = 5.02 TeV recorded by the ALICE detector at the Large Hadron Collider. This analysis is conducted using the Gaussian estimator technique, which is insensitive to biases from correlations between different flow amplitudes. The study presents, for the first time, the centrality dependence of correlations involving up to five different symmetry planes. The correlation strength varies depending on the harmonic order of the symmetry plane and the collision centrality. Comparisons with measurements from lower energies indicate no significant differences within uncertainties. Additionally, the results are compared with hydrodynamic model calculations. Although the model predictions provide a qualitative explanation of the experimental results, they overestimate the data for some observables. This is particularly true for correlators that are sensitive to the nonlinear response of the medium to initial-state anisotropies in the collision system. As these new correlators provide unique information-independent of flow amplitudes-their usage in future model developments can further constrain the properties of the strongly interacting matter created in ultrarelativistic heavy-ion collisions
First Polarisation Measurement of Coherently Photoproduced J/ψ in Ultra-Peripheral Pb–Pb Collisions at sNN=5.02 TeV
No full textThe first measurement of the polarisation of coherently photoproduced J/ψ mesons in ultra-peripheral Pb–Pb collisions, using data at sNN=5.02 TeV, is presented. The J/ψ meson is measured via its dimuon decay channel in the forward rapidity interval −4.0θ, λφ, λθφ are extracted. The analysis is carried out in the helicity frame. The results are found to be consistent with a transversely polarised J/ψ. These values are compared with previous measurements by the H1 and ZEUS experiments. The polarisation parameters of coherent J/ψ photoproduction in Pb–Pb collisions are found to be consistent with the s-channel helicity conservation hypothesis. © 2025 CERN for the benefit of the ALICE Collaboratio
Effect of Manufacturing Orientation on Solid Particle Erosion at High Temperatures in Inconel 718 Alloys Produced by SLM Method
No full textThis study investigates durability of turbine blades made from Inconel 718 alloy against solid particle erosion under high-temperature conditions. Solid particle erosion wear tests were conducted in accordance with the ASTM G76 standard to carry out the research activity. Experiments were conducted on Inconel 718 specimens produced via selective laser melting (SLM) at orientations of 0°, 45°, and 90°, and compared with cast specimens. Erosion tests were performed using 375-micron aluminium oxide (Al2O3) particles with impact angles of 30° and 45°, at temperatures of 22 °C, 250 °C, and 500 °C. In the experimental process, the effects of temperature increase and specimen build orientation, an important parameter in metal additive manufacturing, on solid particle erosion wear were investigated. After the tests, the wear of the specimens was measured using a precision balance. In addition, the worn specimen surfaces were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX). The results showed that, at room temperature, conventionally manufactured (cast) specimens experienced approximately 0.050 g of weight loss, whereas additively manufactured SLM specimens exhibited lower losses: ~ 0.038 g for horizontally oriented (0°), ~ 0.035 g for inclined (45°), and ~ 0.039 g for vertically oriented (90°) samples. Accordingly, SLM-produced specimens were found to undergo approximately 22–30% less wear compared to cast specimens. With increasing temperature, wear decreased in all specimens. Detailed surface examinations further revealed that 250 °C constitutes a critical temperature for IN718 material. At this temperature, a distinctive erosion damage mechanism, namely particle embedment into the surface, was observed. Moreover, under high-temperature tests, SLM specimens with different orientations exhibited ~ 0.005 to 0.01 g lower wear than their counterparts. Additive manufacturing technologies represent a contemporary innovation, and while studies exist in the literature focusing on processing parameters, there is still a lack of research addressing the erosion wear behavior of additively manufactured components for aerospace applications. In particular, the combined effects of build orientation and elevated temperature on erosion remain underexplored. Therefore, this study helps to clarify this gap in the literature and provides new findings, including the identification of 250 °C as a critical temperature and the demonstration of orientation-dependent erosion behavior in layer-by-layer manufacturing. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025