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This article investigates the validity of the different types (conditional, unconditional, deterministic, stochastic) of ß-convergence in per capita GDP for EU-28 and EU-19 between 1990 and 2019.

The study uses nonstationary heterogeneous panel-data methodology.

The panel data reveal that both conditional and unconditional ß-convergence are valid in EU-28 countries However, only conditional convergence exists in EU-19 countries; group-specific findings show that the income levels of 10-EU countries converge toward the EU-19 average and 11-EU countries converge to the EU-28. The convergence speed to EU average varies between 15 and 18%. The robustness of the augmented mean group (AMG) findings are checked with common correlated effects mean group (CCEMG) and are consistent. Moreover, panel unit root tests are applied to examine the stochastic and deterministic convergence of the average EU per capita income in the two groups of EU economies. The findings show no evidence of deterministic or stochastic convergence in EU countries. Besides, conditional convergence has not been experienced in countries such as Bulgaria, Croatia, Czech Republic, Hungary, Latvia, Malta, Romania, Slovakia and Slovenia, which are new members of the EU. As a remarkable aspect of the study, the evidence suggests that the Brexit is economically rational for the UK.

The growth and convergence processes of economies differ from each other. Convergence studies in the literature are generally based on the cross-section OLS methodology. In this context, the study is one of the rare studies to examine convergence using heterogeneous panel techniques and allows the convergence of countries to the EU average to be analyzed individually.

This study aims to investigate the relationship between dietary polyamine levels, metabolic risk parameters and anthropometric measurements in postmenopausal women.

This cross-sectional study was conducted with 562 45–64-year-old postmenopausal women who presented to a Family Health Center. To collect the data, the Descriptive Information Form and Food Frequency Questionnaire were used. In the data analysis, numbers, percentages, mean, standard deviation and multiple linear regression analysis were used.

The multiple linear regression analysis demonstrated that dietary putrescine intake was negatively associated with systolic blood pressure (ß = −0.179, p < 0.001), dietary spermidine intake was positively associated with waist circumference (WC) (ß = 0.142, p = 0.013), systolic blood pressure (ß = 0.188, p = 0.001), diastolic blood pressure (ß = 0.218, p < 0.001), body mass index (BMI) (ß = 0.169, p = 0.003) and waist-to-height ratio (WHtR) (ß = 0.156, p = 0.006), and dietary spermine intake was negatively associated with WC (ß = −0.158, p = 0.003), systolic blood pressure (ß = −0.195, p < 0.001), BMI (ß = −0.107, p = 0.042) and WHtR (ß = −0.138, p = 0.009).

Owing to the study’s cross-sectional nature, the lack of succession in the cause–effect relationship, the use of self-report Food Frequency Questionnaire to determine dietary polyamine intake and the inability to analyze seasonal differences are among the limitations of the study.

In this study, an association was determined between dietary polyamines, metabolic risk parameters and anthropometric measurements. The findings suggest that dietary polyamines in human health should be further investigated owing to the increasing metabolic risk parameters.

This study aims to explore the relationship between authoritarian leadership and commitment and the mediating roles of silence and trust in school principals.

This study employed a cross-sectional design to illustrate the relationships among authoritarian leadership, trust in the principal, silence and affective commitment using path analysis evidence provided by 409 K–12 teachers.

The findings revealed that authoritarian leadership indirectly affected teacher commitment through trust in the principal and acquiescent silence. Furthermore, trust in the principal played a partial mediating role between authoritarian leadership and defensive silence. Authoritarian leadership behaviours decreased teachers' affective commitment by decreasing trust in the principal and increasing organisational silence.

Although leadership and culture have been studied intensively in recent years, authoritarian leadership, which is more commonly seen in Eastern societies, has been less studied in school contexts in the Middle East and Asia. Thus, this study contributes to the literature by examining the factors that might influence affective commitment in schools in an urban setting: authoritarian leadership, silence and trust in school principals.

This study sought to provide an understanding of what a culturally contextualized model of instructional leadership looks like in Turkey, and how this differs from models disseminated in the USA.

This study employed qualitative meta-synthesis to systematically review the full set of 22 qualitative studies of instructional leadership in Turkey. A systematic synthesis strategy was applied to code the findings from each study to develop broad themes that describe key domains of principal instructional leadership practice.

The results showed that instructional leadership of school principals in Turkey is composed of four main dimensions and ten subdimensions. The main dimensions include: (1) emphasis on national goals and competition, (2) maintaining the learning environment, (3) motivating and enabling teachers, and (4) monitoring program alignment and test results.

While broad dimensions of instructional leadership described in the international literature are relevant in Turkey, some practices used to enact those dimensions appear poorly aligned with the institutional–cultural context of Turkish schools. Thus, findings from this study support the assertion that the specific practices used to measure, assess and practice instructional leadership must be adapted to the context of a specific society.

This paper contributes to international efforts to develop a globally validated knowledge base in educational leadership and management.

The purpose of this study is to inspect the corrosion inhibition of API N80 steel pipelines in uninhibited solution and inhibited with a synthesized surfactant compound [N-(3-(dimethyl octyl ammonio) propyl) palmitamide bromide] (DMDPP), which is prepared through a simple and applicable method.

Weight loss was inspected at five different temperatures of 25°C, 30°C, 40°C, 50°C and 60°C Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation were used at room temperature. Density functional theory was used to study the relation between the molecular structure and inhibition theoretically.

Adsorption of the prepared DMDPP fits the Langmuir isotherm model. The inhibition efficiency of the prepared DMDPP amphipathic inhibitor is directly proportional to temperature increase. Polarization results reveal that the investigated DMDPP amphipathic compound behaves as a mixed-type inhibitor. EIS spectra produced one individual capacitive loop.

The originality is the preparation of cationic surfactants through a simple method, which can be used as corrosion inhibitors in oil production. The synthesized inhibitors were prepared from low-price materials. The work studied the behavior of the synthesized surfactants in inhibiting the corrosion of the steel in an acidic medium. Electrochemical and theoretical studies were presented, besides gravimetric and surface examination.