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Öğe Green bonds and financial markets: Interdependence across different market situations(Academic Press, 2025) Gök, Remzi; Şenol, Zekai; Durgun, Burhan; Bouri, ElieThis study examines the multifaceted return interdependence between green bonds and various assets and markets (conventional bonds, Islamic and conventional stocks, Bitcoin, Ethereum, crude oil, and gold), covering various market conditions. Daily data are from January 11, 2016 to February 12, 2024, and the methods employed include quantile-on-quantile return connectedness (QQC), cross-quantilogram (CQ), and Granger causality in quantiles (GC), which allow us to make inferences about the safe-haven ability of green bonds. The QQC results establish that the connectedness at directly related quantiles is more pronounced than those of inversely related quantiles for all cases. The degree of return connectedness is highest with conventional bonds, followed by gold and stocks. Green bonds act as the net transmitter of spillover shocks to Bitcoin and gold markets, whereas it serves as the receiver of shocks from the remaining markets. The CQ results indicate that positive returns in green bonds significantly follow negative returns in conventional bonds 5 days later, suggesting that green bonds have a one-week lagged safe-haven ability. The GC from green bonds is bidirectional and mostly intensified in extreme quantiles with oil, cryptocurrencies, and conventional stocks, but unidirectional and visible with Islamic stocks during market downturns.Öğe Upper bounds of the third hankel determinant for bi-univalent functions in crescent-shaped domains(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Shakir, Qasim Ali; Tayyah, Adel Salim; Breaz, Daniel; Cotîrlă, Luminita-Ioana; Rapeanu, Eleonora; Sakar, Fethiye MügeThis paper investigates the third Hankel determinant, denoted (Formula presented.), for functions within the subclass (Formula presented.) of bi-univalent functions associated with crescent-shaped regions (Formula presented.). The primary aim of this study is to establish upper bounds for (Formula presented.). By analyzing functions within this specific geometric context, we derive precise constraints on the determinant, thereby enhancing our understanding of its behavior. Our results and examples provide valuable insights into the properties of bi-univalent functions in crescent-shaped domains and contribute to the broader theory of analytic functions. © 2024 by the authors.Öğe Risk spillovers and diversification benefits between crude oil and agricultural commodity futures markets(Elsevier Ltd., 2025) Mensi, Walid; Rehman, Mobeen Ur; Gök, Remzi; Gemi̇ci̇, Eray; Vo, Xuan VinhThis study examines the dependence structure and risk spillovers between crude oil and eight major agricultural futures (wheat, corn, soybean coffee, cotton, lumber, cocoa, and live cattle) markets. It also analyzes the potential conditional diversification benefits using a variety of copula functions and Conditional Value at Risk (CoVaR) measure. The results show significant crisis-sensitive and temporal dependence between oil and agricultural markets. Moreover, crude oil shows a symmetric tail dependence with both wheat, corn, soybeans, and cotton futures, whereas oil exhibits an average dependence with coffee. A strong dependence is observed between oil and cocoa (lumber) during bearish (bullish) market conditions. Oil and Live cattle have a symmetric dependence during bearish and bullish market conditions. On the other hand, we find asymmetric and bidirectional risk spillovers from oil to agricultural markets. Furthermore, the wheat futures contract appears to be the most dominating and vulnerable asset to oil price shocks, followed by lumber and corn futures, respectively, while the live cattle contracts are the least. Finally, an equally weighted portfolio offers the highest diversification benefits at a 5 % expected shortfall.Öğe Air pollution and firm performance: the role of innovation and happiness(Emerald Publishing, 2024) Kalash, IsmailPurpose: The detrimental effects of air pollution on the continuity of corporations attract more and more attention in the economic and financial studies. Prior literature investigates the impact of air pollution on corporate financial performance. This study aims to extend this research area by exploring the role of corporate innovation and happiness as factors that mitigate the adverse effects of air pollution and moderate the relationship between air pollution and financial performance. Design/methodology/approach: This study uses two-step system generalized method of moments models to analyze the data of 200 firms listed on Istanbul Stock Exchange over the period 2009–2022. Findings: The results show that firms located in regions with higher air pollution are more likely to invest in innovation. In addition, firms that are more exposed to air pollution and have investments in research and development (R&D) have less ability to improve their financial performance compared to firms that have no investments in R&D. In a similar vein, although R&D has positive effect on financial performance, this effect diminishes in the presence of higher air pollution. The results also show that happiness has no significant moderating effect on the relationship between air pollution and financial performance. Practical implications: The findings of this study related to the role of corporate innovation in determining the effect of air pollution on financial performance indicate that the costs of investment in R&D weaken the firm’s ability to mitigate the adverse impact of air pollution on financial performance, which provides important signals to policymakers to concentrate more on supporting investment in corporate innovation by providing the necessary facilities for firms to improve their innovative performance and decrease the costs of investment in innovation. Originality/value: To the author’s knowledge, this research is the first to explore the influence of happiness on the air pollution–financial performance relationship. In addition, this study differs from most prior ones by examining how responding to air pollution through investment in innovation can moderate the association between air pollution and financial performance.Öğe Gender differences in the academic career: evidence from the accounting and finance departments(Emerald Publishing, 2024) Kalash, IsmailPurpose: The aim of this research is to examine gender differences in the context of research productivity, research collaboration and academic promotion. Design/methodology/approach: This research analyzes data related to 863 academics in the accounting and finance departments in Turkish universities by using OLS, Binary Logistic, Ordered Probit and Multinomial Probit Regressions. Findings: The findings show that female academics have in overall a representation ratio of 32%, and that there are no significant differences regarding the opportunities for female academics to be employed in public compared to private, and in high-rank compared to low-rank universities. The results also indicate that female academics have lower research impact compared to male academics, and that this difference is more pronounced for professors, and in universities with low ratio of female representation, and also in public universities. In addition, female academics engage more in research collaboration and are less likely to hold the academic title of full professor than male academics. Practical implications: The findings of this study provide significant signals about the need for improving gender policies that mitigate the conditions adversely affecting research productivity and impact by considering the supporting circumstances for female academics and improving the representation ratio, which also can play vital role in reducing discrimination and bias and contribute to better research and scientific environment. Originality/value: To the author’s knowledge, this article is the first to examine gender effect regarding research productivity, research collaboration and academic promotion in Turkish universities.Öğe Examination of corporate reputation ccores, market value and financial performance with the perspective of corporate brand sustainability(2023) Yıldırım, Yusuf Ozan; Uslu, AyparIn theory and practice, sustainability research offer important doctrines for carrying corporate brands into the future. As for maintaining the sustainability of corporate brands, researchers imply the necessity of various changing parameters, including corporate reputation. In addition, researchers highlight for long-term corporate reputation firms should also focus their market performance and financial performance. With this perspective, the aim of this paper is to examine the relationship amongst long term sustained corporate reputation, market value and financial performance. In parallel to prior research, reputation is conceptualized by pulse scores from reputation institutes’ reports. For the perspective of sustainability, data is put through some filters such as “most repeated corporate brands over 15 years”. After sampling, market values and financial performance indicators taken from online credible sources. As a result, 6 corporate brands and 15 years long data a panel has constructed. Finally, the relationship amongst corporate reputation, market value and financial performance is assessed with panel data. According to panel data correlation results, corporate reputation is only significantly correlated with ROE and ROI. Relationship between market value and financial performance indicators is significantly correlated.Öğe Do agency costs and business risk affect the corporate sustainability-financial performance relationship?(Emerald Group Publishing Ltd, 2024) Kalash, IsmailPurposeThe aim of this research is to examine the effect of corporate sustainability performance on financial performance and the role of agency costs and business risk in determining this effect.Design/methodology/approachThis study uses the data of 83 non-financial Turkish firms listed on Istanbul Stock Exchange during the period 2014-2021. Two-step system GMM models are applied to examine the study's hypotheses.FindingsThe results indicate a positive effect of corporate sustainability performance on financial performance, and that this effect is significant only for firms that are more likely to suffer agency costs of equity, firms with R&D expenditures and firms with lower business risk.Practical implicationsThe results of this study confirm the importance of regulations introduced by regulators to support the sustainability initiatives for firms that have less ability to access funds required for their investments. In addition, the findings provide important insight into the role of the persistence of corporate sustainability performance in enhancing financial performance through mitigating managers' opportunistic behavior.Originality/valueTo the author's knowledge, this research is one of few that examine the effect of agency costs and business risk on the corporate sustainability-financial performance relationship in emerging markets.Öğe The efficiency of the new reference rate in Türkiye(Borsa İstanbul Anonim Şirketi, 2024) Gök, Remzi; Pirgaip, Burak; Bouri, ElieThe transition from the reference rate based on interbank offered rates, such as the Turkish lira interbank offer rate (TRLIBOR), to the risk-free rate (RfR), the Turkish lira overnight reference rate (TLREF), in Türkiye is a critical juncture, but it is not clear how it affects the market's ability to incorporate information precisely and promptly. Drawing on the adaptive market hypothesis (AMH), we examine the impact of transitioning from TRLIBOR to TLREF on the efficiency of Turkish financial markets. Our results reveal pronounced and time-varying persistence patterns in both reference rates and highlight heterogeneity in their efficiency, which seems influenced by fluctuations in national political conditions and monetary policies. TLREF consistently demonstrates higher market efficiency than TRLIBOR. The findings offer insights into the dynamics of market efficiency in Türkiye and highlight the broader implications of switching to RfR-based reference rate regimes.Öğe Do geopolitical risk, economic policy uncertainty, and oil implied volatility drive assets across quantiles and time-horizons?(Elsevier B.V., 2024) Bouri, Elie; Gök, Remzi; Gemi̇ci̇, Eray; Kara, ErkanThis paper examines the impact of three global risk factors (geopolitical risk (GPR), economic policy uncertainty (EPU), and crude oil volatility (OVX)) on the returns and variance of commodity, Islamic stock, and green bond markets across quantile distributions and various time horizons. To this end, Granger causality tests in quantiles and distributions along with wavelet-based correlation and causality approaches are applied to daily data from February 1, 2013 to June 30, 2023. The results of the Granger causality in quantiles tests show strong evidence that all three global risk factors Granger-cause returns across all quantiles, except the lowest and middle quantiles. The Granger causality is significant for both returns and variances, where GPR is the least predictor and OVX is the most predictor. Evidence of causation in risk spillovers is in the right tail and center of the distribution rather than the left tail, indicating no evidence of down-to-down risk spillover. The upside risk of OVX causes both the upside and downside risk of asset returns. The positive volatility of EPU and GPR drives the positive and negative volatility of the green bond and Islamic stock markets, respectively. Green bond markets are completely immune to risk spillover from geopolitical risks. The effects of risk factors are negligible at the lower and somewhat middle quantiles but strengthen with varying magnitude and significance for the remaining quantiles. The results of the wavelet analysis indicate that asset returns co-move with the global risk factors in the short term but decouple in the longer term. Risk factors exert short-lived causal impacts in the short term, but the duration of significant causal periods rises with time and the effect intensifies during crisis periods.Öğe Classes of harmonic functions related to mittag-leffler function(Multidisciplinary Digital Publishing Institute (MDPI), 2023) Al-Dohiman, Abeer A.; Frasin, Basem Aref; Taşar, Naci; Sakar, Fethiye MügeThe purpose of this paper is to find new inclusion relations of the harmonic class (Formula presented.) with the subclasses (Formula presented.) (Formula presented.) and (Formula presented.) of harmonic functions by applying the convolution operator (Formula presented.) associated with the Mittag-Leffler function. Further for (Formula presented.), several special cases of the main results are also obtained.Öğe Can Twitter-based economic uncertainty predict safe-haven assets under all market conditions and investment horizons?(Elsevier Inc., 2022) Gök, Remzi; Bouri, Elie; Gemici, ErayThis paper examines the Granger causality from Twitter-based economic uncertainty (TEU) to three safe-haven assets – Bitcoin, gold, and US10 year Treasury notes. Using daily data (June 1, 2011–August 30, 2021) and causality-in-quantiles and wavelets methods, the results indicate variability in the causality between the mean and variance, as well as the market conditions. TEU Granger-causes the returns and volatility of Treasuries, the volatility but not returns of Bitcoin, and neither the volatility nor the returns of gold for the raw series, and the causality is mostly significant at low and middle quantiles for Bitcoin and Treasuries. We include other risk factors and confirm the variability in the causality. Considering the possibility of a hidden causality over various frequency domains due to investors' heterogeneous expectations and perceptions of risk, the wavelet transforms-based causality tests reveal an increase in the predictability of risk indicators under specific investment horizons and market conditions. During the pandemic, TEU strongly predicts future volatility of Treasury and Bitcoin returns, reflecting the importance of social-media posts for safe-haven pricing. These findings highlight the benefits of applying the causality-in-quantiles test to decomposed series to determine the contribution of each scale to the causality over various market conditions.Öğe Do bubbles in the bitcoin market impact stock markets? Evidence from 10 major stock markets(SAGE Publications Inc., 2023) Gemici, Eray; Polat, Müslüm; Gök, Remzi; Khan, Muhammad Asif; Khan, Mohammed Arshad; Kılıç, YunusIn this paper, we examine the effect of explosive behaviors in the Bitcoin market on the top 10 largest stock markets of developed and emerging countries. The daily dataset, including the Dow Jones Industrial Index (DJIA), Nasdaq (NSQ), Shanghai Composite Index (SSE), Nikkei 225 (N225), Hang Seng Index (HSI), Shenzhen Composite Index (SZSE), Euronext Amsterdam Index (AEX), London Stock Exchange (LSE), Toronto Stock Exchange (TSX), and Bombay Stock Exchange (BSE), spans July 21, 2010, to December 9, 2022. We first investigate the existence of explosive price behaviors using the bubble detection test of Phillips and Shi and the results provide evidence of multiple bubble episodes, coinciding with the monetary policy actions of the FED and ECB. Then, we address the question of whether the explosive behaviors detected affect the variance of equity returns by employing a GARCH model. The impact is negative, albeit its magnitude and significance vary among stock indices.Öğe Psychological symptom profile of butchers working in slaughterhouse and retail meat packing business: a comparative study(Kafkas Üniversitesi Veteriner Fakültesi, 2012) Emhan, Abdurrahim; Yıldız, Ahmet Şener; Bez, Yasin; Kırgır, SaidIn this study we aimed to test the hypothesis that butchers have more psychological problems than any other occupation. For this purpose, we applied SCL-90-R (Symptom Check List-90 Revised) to 43 butchers working in a slaughterhouse and 39 butchers working in meat processing or packing in supermarkets, and as a control group 82 office workers. In the research, a statistical significance between butchers and the control group in that the Global Severity Index (GSI) scores (P<0.001) was found. In terms of the GSI scores, there was no significant relationship between the slaughter house workers and the supermarket workers at P<0.05. However, there were significant relationships among the somatization, anxiety, anger-hostility, and psychotism (P<0.01). As a result, when comparing the two groups, butchers, especially those who work in slaughterhouses, have higher levels of psychological disorders than the office workers.Öğe İş örgütlerinde çevre muhasebesi algısına yönelik bir araştırma: Diyarbakır ili örneği(Mustafa Süleyman ÖZCAN, 2016) Bilen, Abdulkadir; Seyitoğulları, OsmanÇevre canlılar adına hayatın sürdürülmesinde önemli bir unsurdur. Söz konusu önemine rağmen çevre, yoğun sanayileşme, hızlı nüfus artışı ve düzensiz kentleşme gibi faktörlere bağlı olarak büyük ölçüde tahribata uğramıştır. Sosyal sorumluluk ilkesi gereğince, işletmelerin muhasebe sürecinde çevresel etkenleri gözetebileceği bir model olarak çevre muhasebesi ortaya konulmuştur. Çevre muhasebesi ile birlikte işletmelerin hem çevresel maliyetleri önemseyerek çevresel sorunlarını minimize edebilmesi hem de yoğun rekabetin hüküm sürdüğü iş dünyasında tutunabilmesi mümkün olmaktadır. Bu çalışma, Diyarbakır sanayi sektöründe faaliyet gösteren işletmelerinin çevresel konulara ve çevre muhasebesine ilişkin algılarını ankete dayalı bir uygulama ekseninde sunmayı amaçlamaktadır. Araştırma kapsamında elde edilen veriler, araştırmanın amacı doğrultusunda çeşitli istatistik metot ve test teknikleri (frekans dağılımı, tanımlayıcı faktör analizi, t testi, Anova, korelasyon) kullanılarak SPSS 18.0 istatistik paket programı yardımıyla değerlendirilmiştirÖğe Causality between stock market and macroeconomic variables in Turkey: New evidence from wavelet coherence analysis(Erciyes Üniversitesi, 2020) Gök, RemziWe examine the dependence and causal linkages among selected macroeconomic variables, namely BIST100, bond yields, CDS, currency basket, and gold prices, in Turkey. Using daily data covering the period 2011-01-14 to 2019-04-30, we find the following empirical results. First, all variables are found to be integrated into the first order, namely stationary in first log-difference. Second, our paper detects evidence of significant interdependence in thirteen out of twenty pairs of variables. Third, the findings of the VECM test reveal unidirectional and bidirectional causalities in the short- and long-run. Fourth, the results of wavelet coherence analysis highlight a negative relationship for the pairs of BIST100-currency basket and BIST100-gold prices while positive linkages are observed for the pairs of bond rates-currency basket, bond rates-gold prices, and CDSgold prices. In addition, the BIST100 index unidirectionally leads currency basket between 16- and 128-day holding periods between 2013-2017 years. Lastly, there exist unidirectional causal linkages among changes in prices for all the pairs of variables, except for BIST100-CDS with noncausality and gold-currency basket with two-way causality. Our findings yield significant implications for portfolio and risk management and financial stability.Öğe Coefficient bounds for a new subclass of analytic bi-close-to-convex functions by making use of Faber polynomial expansion(TUBITAK, 2017) Sakar, Fethiye Müge; Güney, Hatun ÖzlemRecently, in the literature, we can see quite a few papers about general coefficient bounds for subclasses of bi-univalent functions. However, we can find just a few papers about general coefficient estimates for subclasses of bi-close-to-convex functions. In the present study, we give and look into a new subclass of analytic and bi-close-to-convex functions in the open unit disk. Making use of the Faber series, we have an upper bound for the general coefficient of functions in this class. We also demonstrate the invisible behavior of the beginning coefficients of a special subclass of bi-close-to-convex functions.Öğe A study on the existence of numerical and analytical solutions for fractional integrodifferential equations in hilfer type with simulation(American Institute of Mathematical Sciences, 2023) George, Reny; Aydoǧan, Seher Melike; Sakar, Fethiye Müge; Ghaderi, Mehran; Rezapour, ShahramPrevious studies have shown that fractional derivative operators have become an integral part of modeling natural and physical phenomena. During the progress and evolution of these operators, it has become clear to researchers that each of these operators has special capacities for investigating phenomena in engineering sciences, physics, biological mathematics, etc. Fixed point theory and its famous contractions have always served as useful tools in these studies. In this regard, in this work, we considered the Hilfer-type fractional operator to study the proposed integrodifferential equation. We have used the capabilities of measure theory and fixed point techniques to provide the required space to guarantee the existence of the solution. The Schauder and Arzela-Ascoli theorems play a fundamental role in the existence of solutions. Finally, we provided two examples with some graphical and numerical simulation to make our results more objective.Öğe The multiple mediation roles of trust and satisfaction in the effect of perceived corporate social responsibility on loyalty(Vilnius Gediminas Technical University, 2021) Uslu, Abdullah; Şengün, Halil İbrahimPurpose – This study aims at investigating the effect of corporate social responsibility perceptions of local people living in Diyarbakır on bank loyalty in terms of banking services and the mediator roles of trust and satisfaction in this effect. Research methodology – Cronbach’s Alpha coefficients, reliability, convergent and discriminant validity and multicollinearity were examined before testing the hypotheses of the research. The validity of the measurement model for the variables that are included in the model was examined by the confirmatory factor analysis. Partial least squares path modelling was used to analyze the research model and hypotheses, and multiple mediation analysis was used to test the mediation effects. The collected data were analyzed by the software SPSS 22.0 and SmartPLS 3.3.0. Findings – The research results exposed that the corporate social responsibility perceptions of bank customers have significant and positive effects on bank loyalty. Furthermore, satisfaction has had partial mediation effects on the relationship between CSR perception and loyalty. Research limitations – The population covers individuals with regular wage or salary who live in Diyarbakır. The survey was conducted between October 1 and December 1, 2019, with convenience sampling technique and 400 questionnaires were collected. Practical implications – When conducting CSR activities, businesses should emphasize that trust and satisfaction have an essential effect as well as loyalty. Originality/Value – This study investigated the simultaneous multiple mediator effects of trust and satisfaction in the relationship between CSR and loyalty.Öğe New classes of harmonic functions defined by fractional operator(Isik University, 2018) Sakar, Fethiye Müge; Bağcı, Yasemin; Güney, Hatun ÖzlemIn the present study, we introduce an investigation of new subclasses of harmonic functions which are defined by fractional operator. Firstly, using by fractional operator, we define new subclasses of harmonic functions. Later, we obtain main theorems of our study which contain sufficient and necessary coefficient bounds for functions related to the classes newly defined. Also, several particular characterization properties of these classes are given. Some of these properties involve extreme points, convex combination, distortion bounds. Finally, several corollaries of the main theorems are presented.Öğe Some general coefficient estimates for a new class of analytic and bi-univalent functions defined by a linear combination(University of Nis, 2018) Srivastava, Hari M.; Sakar, Fethiye Müge; Güney, Hatun ÖzlemIn the present paper, we introduce and investigate a new class of analytic and bi-univalent functions f (z) in the open unit disk U. For this purpose, we make use of a linear combination of the following three functions: f (z)z, f′ (z) and z f′′ (z) for a function belonging to the normalized univalent function class S. By applying the technique involving the Faber polynomials, we determine estimates for the general Taylor-Maclaurin coefficient of functions belonging to the analytic and bi-univalent function class which we have introduced here. We also demonstrate the not-too-obvious behaviour of the first two Taylor-Maclaurin coefficients of such functions.
