Yıldız Technical University Research Information System
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Preparation of pullulanase/Cu3(PO4)2 hybrid nanoflower and its catalytic performance as an immobilized enzyme
No full textA commercially important pullulanase enzyme that hydrolyzes α-1,6 glycosidic linkages in pullulan was immobilized as pullulanase/Cu3(PO4)2 hybrid nanoflower. Free and immobilized enzymes both showed the highest activity at 25 °C. The optimum pH of the free enzyme was 4.5, and the immobilized enzyme was 5.5. Immobilization provided the enzyme with good thermal and pH stability. Even after 18 weeks, immobilized enzyme stored at 4 or −20 °C still have 40 % and 60 % activity, respectively. The reusability of the immobilized enzyme was very good with nearly 75 % activity after 8 cycles. Immobilization provided good protection against Cu2+, which is one of the main inhibitors of the pullulanase
Sustainable maritime passenger transport: energy analysis and transition strategies in Istanbul Strait
No full textMaritime transportation plays a significant role in global trade by connecting countries and facilitating the movement of goods and people. Sustainable transportation systems are essential for environmental, social, economic challenges, and climate change, congestion, air pollution. Istanbul faces some significant problems in passenger transport and quests new dynamics. A tailored reference energy system has been built for Kadıköy-Eminönü maritime route with Low Emissions Analysis Platform. Moreover, an alternative scenario has been designed to demonstrate the consequences of electrification in the Istanbul Strait. As a result of the tightening in energy transition conditions with IMO GHG strategy, LPG usage is analysed on LEAP platform. Main propulsion is indicated as the largest energy consumer, accounting for approximately 80% of total demand, indicating a critical area for optimization, while achieving the emission reduction targets will require coordinated efforts from policymakers, industry stakeholders, and researchers to develop effective decarbonization strategies in the Istanbul Strait
Juglone Encapsulation in PLGA Nanoparticles Improves Solubility and Enhances Apoptosis in HeLa Cells
No full textThe anticancer potential of juglone, a naphthoquinone derived from walnut trees, has been extensively studied; however, its hydrophobicity and toxicity obstruct its therapeutic applications. This study aimed to overcome these challenges by encapsulating juglone into poly (lactic-co-glycolic acid) (PLGA) nanoparticles and evaluating their antiproliferative and apoptotic effects on HeLa cells. Juglone nanoparticles (JNP) were obtained by single emulsion solvent evaporation method. Its key physicochemical properties, such as particle size, zeta potential, drug loading, release yield, and encapsulation efficiency values were calculated as 207.45 ± 1.67 nm, −24.12 ± 2.21 mV, 47.80, 66.90 and 90.12%, respectively. JNP’s antiproliferative effects were compared to those of free juglone on HeLa cells. The calculated IC50 values for free juglone and JNPs were 17.07 µM and 20.64 µM, respectively. Both formulations exhibited comparable dose-dependent antiproliferative effects across the tested concentrations. However, the nanoparticle-based delivery system demonstrated enhanced apoptotic activity, as evidenced by increased caspase-3 activation and greater suppression of BCL-2 levels relative to free juglone. These findings were further corroborated by TUNEL and immunocytochemical analyses, which confirmed the superior apoptotic induction by the nanosystem. Collectively, the results highlight the potential advantages of PLGA-based nanoparticle systems for the delivery of juglone, thereby improving its water solubility—a key limiting factor for its use—while minimizing its toxicity. These findings offer a promising approach for its application as an effective anticancer agent via nanoparticle-based delivery
Interactions of black carrot concentrate powder as a natural coloring agent with gelatine and sucrose in model gummy samples
No full textWith growing consumer concerns about the sustainability and safety of synthetic food colorings, the food industry is increasingly turning to natural colorants derived from plants. Anthocyanins from black carrots are preferred as natural food colorants in the food industry. However, the product composition in which the colorants are used affects the pigments' color properties and stability behaviors. This study aims to determine the interaction between black carrot juice concentrate powder (BCCP) with gelatine and sucrose for model gummy samples and to develop models for the optimal composition of the product. Hardness (9.90–21.77 N), resilience (0.61–0.82), cohesiveness (0.95–0.98), springiness (0.27.5–0.63 mm), gumminess (9.63–21.30 N), and chewiness (3.15–13.36 Nxmm) properties of model gummy samples were determined by texture profile analysis. TPC values for gummy candy samples ranged from 6.87 to 44.3 mg GAE/kg, while inhibition values for AAC were 0.00%–13.4%. BCCP x gelatin and BCCP × sucrose interactions were determined to be significant for texture parameters such as hardness, gumminess, chewiness, and L∗, a∗, b∗, and chroma values (P < 0.05). The optimal composition for samples was determined as 32.03 g/100 g sucrose, 21 g/100 g gelatin solution, and 0.27 g/100 g BCCP, respectively, by considering changes in hardness, springiness, hardness variation and ΔE∗ values at the end of accelerated shelf-life (ASL) conditions. Incorporating polyphenol-containing BCCP affects gummies' colour stability and texture
Firm performance through green orientation, environmental culture and green absorptive capacity
No full textPurpose: The purpose of this article is to examine the effects of green internal orientation and external orientation on firm performance and to evaluate the mediating role of green absorptive capacity in this effect. It also investigates the moderating role of environmental culture in the relationship between green absorptive capacity and firm performance. Design/methodology/approach: This study was conducted based on field research with surveys conducted on 343 technology-oriented companies operating in Istanbul. SmartPLS 4 statistical software was used to analyze the data. Findings: Research results show that green internal and external orientation has a positive and significant effect on firm performance. Additionally, green absorptive capacity has a mediating role in this effect. It has been determined that environmental culture plays a moderating role in the relationship between green absorptive capacity and firm performance. Research limitations/implications: This study has some limitations; for example, the fact that the data was obtained only from technology-focused companies in Istanbul may limit generalizability. However, this research makes important contributions to our understanding of the effects of green internal and external orientation on firm performance and the mediating effect of green absorptive capacity. Practical implications: This study shows that strengthening businesses’ green internal and external orientations and improving their green absorptive capacity can increase firm performance. It is also an important warning to businesses that environmental culture can play an important role in these relationships. Social implications: Strengthening green internal and external orientation and improving green absorptive capacity can provide social benefits through their contributions to environmental sustainability. This study can help businesses take steps to reduce their environmental impact and achieve a sustainable future. Originality/value: This study is one of the few studies examining the effects of green internal and external orientation on firm performance and the mediating role of green absorptive capacity. Additionally, it makes a unique contribution by focusing on the moderating role of environmental culture in these relationships. This study can be a valuable guide for businesses in developing environmental sustainability strategies
Non-equilibrium molecular dynamics simulation of anisotropic heat transfer and thermal conductivity of single crystalline magnesium antimonide
No full textMagnesium antimonide (Mg3Sb2) based materials are potential candidates as thermoelectric materials in thermoelectric devices with enhanced performance. Thermal conductivity and its temperature dependence are key factors in their practical applications. The present work aims to evaluate the temperature dependence of lattice thermal conductivity (κL) of single crystalline Mg3Sb2 along the in-plane and out-of-plane directions between 300K and 700K. Non-equilibrium molecular dynamics (NEMD) simulation combined with two regions thermostatting method is followed to mimic the real experiment. It is found that the κL exhibits strong anisotropy at low and mid temperatures and becomes nearly isotropic at high temperatures. The κL is significantly low along both in-plane and out-of-plane directions, and reduces from ∼2.1 to ∼1.1 W m−1K−1and ∼1.3 to ∼1.1 W m−1K−1, respectively, but with different temperature dependences. Deviating from the typical T−1 law, calculated κL demonstrates an anomalously weaker temperature dependence in the in-plane direction described as T−0.67, and even weaker in the out-of-plane direction as T−0.14. Anisotropic low thermal conductivity is crucial for searching thermoelectric materials with enhanced figure of merit, and hence this work may provide guideline and encourage future studies on Mg3Sb2 based materials
