Opin vísindi

 

Nýlega bætt við

Verk
Constructing a corporate governance index for SMEs : How it mediates the access to finance-performance relationship
(2026-03) Bilyay-Erdoğan, Seda; Demir, Ender; Cevheroğlu Acar, Merve Gizem; Ozkan, Irem; Department of Business and Economics
SMEs play a vital role in employment, innovation, and competitiveness worldwide, yet their governance structures remain underexplored in academic research. Existing studies on corporate governance predominantly focus on large publicly traded firms, leaving a gap in our understanding of how governance mechanisms operate in SMEs. To fill this gap, the primary purpose of this study is to introduce a novel and comprehensive corporate governance index tailored specifically to SMEs. Using stratified sampling, we conducted a structured survey of 469 SMEs across diverse sectors and firm sizes in Türkiye. This index comprises six subdimensions: board structure, family involvement, female participation, digitalization, corporate accountability, and succession, and its internal validity is confirmed with Cronbach's alpha values above 0.70 for the overall index and most subindices. The second purpose of this study is to investigate the relationship between access to finance and SME performance, emphasizing the mediating role of corporate governance. Using cross-sectional regression analysis, our results show that access to finance significantly improves SME performance. We also find that corporate governance not only enhances performance directly but also mediates this positive association. To the best of our knowledge, this is the first study to demonstrate that access to finance influences SME performance through both direct and indirect channels. Overall, our findings highlight that effective governance structures are essential to maximize the benefits of access to finance. This finding underscores the role of institutional and managerial factors in enhancing firm-level competitiveness by enabling SMEs to leverage access to finance and governance practices to achieve sustainable growth.
Verk
A Rotation-Controlled Anisotropic Hourglass Metasurface for Multiband Reflective Linear-to-Circular and Cross- Polarization Conversion
(2026) Nasir, Muhammad; Koziel, Slawomir; Pietrenko-Dabrowska, Anna; Department of Engineering
This paper presents and experimentally validates a multifunctional anisotropic metasurface (MS) that exhibits linear-to-linear (LTL) reflective cross-polarization (RCP) and circular polarization conversion (CPC) responses across multiple frequency ranges. The proposed MS integrates a single-layer design consisting of 45° oriented truncated circular ring and an hourglass-like structure, providing four LTL-RCP conversion bands (2.41 - 2.48, 3.16 - 3.46, 5.80 - 6.59, and 11.64 - 13.75) GHz with polarization conversion ratio (PCR) exceeding 95%, and seven CPC bands (2.33 - 2.38, 2.55 - 2.99, 3.69 - 5.37, 7.13 - 10.92, 13.95 - 14.25, 14.93 - 15.17, and 15.31 - 15.56) GHz with the axial ratio (AR) less than 3 dB, covering the S-, C-, X-, and Ku-bands. By only adjusting the angle of the hourglass structure at 15° within the same structure, LTL-RCP with PCR greater than 95% is realized in the frequency bands from 13.71 to 14.64 GHz, along with ≤ 3 dB of AR is achieved at four additional CPC bands at (2.20 - 2.36, 2.95 - 8.41, 10.84 - 12.30, and 14.84 - 15.06) GHz. The polarization conversion mechanisms are explained through detailed surface-current distributions analysis and full-wave electromagnetic (EM) simulations. Furthermore, the proposed concept is validated through the measurements of the fabricated prototype consisting of 8× 13 -unit cells. The measurement results are in excellent agreement with the simulation predictions. The proposed MS design demonstrates a simple yet effective solution for achieving tunable multi-band polarization manipulation without structural modification, making it suitable for advanced EM communication applications.
Verk
A reconfigurable array and MIMO antenna for 18 GHz and 28/38 GHz applications
(2026-01-15) Paşalıoğlu, Halil; Wang, Lulu; Bakır, Mehmet; Paul, Liton Chandra; Tetik, Erkan; Karaaslan, Muharrem; Department of Engineering
This study introduces the development and experimental verification of a reconfigurable array and MIMO antenna system designed to operate at 18 GHz, 28 GHz, and 38 GHz—frequency bands that are critically important for next-generation wireless communication technologies, including 5G and beyond. The reconfigurability of both antenna types is achieved through the integration and dynamic control of PINs, allowing for the selective activation and deactivation of specific segments defined by designated geometric parameters. Simulation and experimental results of the proposed antennas, including scattering parameters and radiation patterns, are thoroughly investigated. Simulation results indicate that the array antenna achieves bandwidths of 0.80 GHz at 18 GHz, 2.62 GHz at 28 GHz, and 7.91 GHz at 38 GHz, respectively. This performance encompasses all FCC-designated millimeter-wave 5G bands. The MIMO antenna demonstrates a transmission coefficient below −25 dB for both PIN diode states, significantly exceeding the −10 dB isolation threshold. This result confirms the antenna's suitability for operation across the 18 GHz, 28 GHz, and 38 GHz frequency bands. Subsequently, the fabrication of both antennas was undertaken, and the measured parameters exhibited good agreement with the simulation results. The reconfigurable array antenna exhibits beam steering and pattern diversity capabilities essential for overcoming propagation challenges at millimeter-wave frequencies, while the MIMO antenna system leverages spatial multiplexing and diversity to enhance data rates and link reliability. The presented antenna designs offer versatility for future wireless systems and hold considerable promise for a multitude of advanced applications, including high-capacity data transmission and radar systems operating within the 5G bands.
Verk
Heterologous and homologous prime-boost immunization strategies to enhance immune responses in early life
(University of Iceland, School of Health Sciences, Faculty of Medicine, 2026-09-14) Foroutan Pajoohian, Poorya; Stefanía Bjarnarsson; Ingileif Jónsdóttir; Faculty of Medicine (UI); Læknadeild (HÍ); School of Health Sciences (UI); Heilbrigðisvísindasvið (HÍ)
In early life the immune system is characterized by generation of weaker and less durable vaccine-induced antibody responses than in adulthood. This poses a major challenge for the development of vaccines targeting pathogens that require that both strong systemic and mucosal immune responses are elicited to achieve protective immunity. The overall aim of this thesis project was to determine how heterologous prime-boost immunization routes in comparison with the conventional parenteral homologous immunization shape early life humoral immunity to a pneumococcal conjugate vaccine, Pn1-CRM197, and to develop and characterize immunization strategies capable of improving both systemic and mucosal responses in early life. A neonatal mouse model was used in the study. Mice were immunized with Pn1-CRM197 formulated with the adjuvants CAF01 or mmCT for subcutaneous or intranasal administration, respectively. Across this PhD study, vaccine-specific IgG and IgA antibody responses, antibody-secreting cells, germinal center activity, T follicular helper and T follicular regulatory cells, memory B cell generation, plasmablast/plasma cell differentiation and their expression of the survival and activation receptors BAFF-R, TACI and BCMA were examined in spleen, cervical and inguinal lymph nodes and bone marrow. Immunization schedules that included a mucosal administration enhanced vaccinespecific IgA responses in serum and mucosal compartments compared with homologous subcutaneous immunization. However, heterologous subcutaneous priming followed by intranasal booster, while improving mucosal output and generating combined systemic–mucosal responses, did not induce systemic IgG responses comparable to homologous subcutaneous/subcutaneous immunization. Our results showed that the routes of immunizations determined the anatomical site of germinal center induction and shaped the germinal center output. Homologous subcutaneous/subcutaneous immunization preferentially induced germinal center responses in spleen and inguinal lymph nodes, promoted plasmablast/plasma cell differentiation in spleen, increased expression of the survival receptor BCMA on plasma cells in inguinal lymph nodes and yielded high systemic IgG responses. In contrast, heterologous subcutaneous/intranasal immunization redirected the induction of plasmablast/plasma cells responses, BCMA expression toward cervical lymph nodes and favoured the generation of IgM⁺ germinal center-derived memory B cells in all lymphoid organs assessed, and with enhanced BAFF-R and TACI expression, receptor crucial for survival and re-activation, together with stronger IgA responses. The major finding of my study was that reversal of the heterologous immunization schedule, consisting of intranasal priming and subcutaneous booster, successfully overcame the main limitation of the heterologous immunization schedule. It preserved the mucosal advantage of intranasal immunization while inducing systemic IgG responses comparable to homologous subcutaneous/subcutaneous immunization, alongside enhanced serum and salivary IgA responses, increased bone marrow homing of BCMA⁺ plasmablasts/plasma cells, expanded memory B cell output but maintained the favoured generation of IgM⁺ germinal center-derived memory B cells in all lymphoid organs. Together, these studies demonstrate that in early life, the route and order of primeboost immunization affect not only the magnitude, but also the localization and quality of humoral immunity. Among the immunization strategies tested, intranasal priming followed by subcutaneous booster emerged as the most suitable approach, combining robust systemic immunity and mucosal responses, enhanced bone marrow homing of BCMA⁺ plasmablasts/plasma cells and expanded memory B cell output. These findings provide a framework for the rational design of early life vaccination strategies against respiratory pathogens.
Verk
Anxiety and Distress Tolerance as Mediators between Complex Posttraumatic Stress Disorder Symptoms and Gambling Severity in Veterans
(2026-03) Dighton, Glen; Whiteford, Seb; Quigley, Martyn; Dymond, Simon; Department of Psychology
Experiences of gambling-related harm are significant concerns among military veterans, particularly those with posttraumatic stress disorder (PTSD) and complex PTSD (CPTSD). CPTSD, as outlined in the ICD-11, includes disturbances in self-organisation (DSO), encompassing affective dysregulation, negative self-concept, and interpersonal difficulties. While anxiety and distress tolerance (DT) have been implicated in PTSD-related maladaptive behaviours, their roles in the relationship between CPTSD and gambling risk severity remain unclear. This study examines whether anxiety and DT mediate the association between CPTSD symptom clusters (PTSD and DSO) and gambling severity in UK Armed Forces veterans. A cross-sectional study was conducted with UK ex-service personnel (n = 346) who completed the International Trauma Questionnaire for CPTSD, the Generalised Anxiety Disorder scale, the Distress Tolerance Scale, and the Problem Gambling Severity Index. Mediation analyses were conducted using bootstrapped regression models. Anxiety was found to be a significant indirect pathway between CPTSD symptoms and gambling risk severity, with a stronger indirect effect observed for DSO symptoms than PTSD-specific symptoms. In contrast, DT did not show a significant indirect pathway, indicating that deficits in DT may not be central to gambling behaviours in veterans with CPTSD. These findings highlight the critical role of anxiety in gambling-related harm among veterans with symptoms of CPTSD, suggesting that interventions targeting anxiety regulation may be beneficial than those targeting distress tolerance in reducing gambling risk severity. Future research should explore additional potential pathways, such as impulsivity and trauma-related dissociation to further clarify associations between CPTSD and gambling severity.

Flokkar í Opnum vísindum

Veldu flokk til að skoða.

Niðurstöður 1 - 9 af 9

Öll gögn í Opnum vísindum eru vernduð af ákvæðum höfundalaga og með öllum réttindum áskildum, nema annað sé tekið fram.