Phytochemical Characterization of Phagnalon graecum Boiss. by HPLC and GC-MS with its Enzyme Inhibitory and Antioxidant Activity Profiling by Spectrophotometric Methods

In the current study, the n-hexane, chloroform, ethyl acetate, methanol, and water extracts of Phagnalon graecum Boiss. (Asteraceae), a spice plant, were investigated for their enzyme inhibitory activity against acetylcholinesterase, butyrylcholinesterase, lipoxygenase, tyrosinase, and antioxidant activities. Antioxidant activity of the extracts was determined by 2,2-diphenyl-1-picrylhydrazyl radical scavenging, ferric ion-chelation activity, and ferric-reducing antioxidant power tests. Total phenol (gallic acid equivalent) and flavonoid (quercetin equivalent) contents were calculated. Essential oil of the plant was analyzed by GC-MS, while the selected phenolic acids were analyzed by HPLC. The extracts had insignificant inhibition against the tested enzymes, whereas they displayed a remarkable antioxidant activity. Therefore, to the best of our knowledge, this study presents the first data on biological activity and phytochemical content of P. graecum and this species could be utilized as potential antioxidant applicable for food preservation.     

Integration of GIS with USLE in Assessment of Soil Erosion

A Geographic Information System (GIS) has been integrated with the USLE (Universal Soil Loss Equation) model in identification of rainfall-based erosion and the transport of nonpoint source pollution loads to the Gediz River, which discharges into the Aegean Sea along the western coast of Turkey. The purpose of the study is to identify the gross erosion, sediment loads, and organic N loads within a small region of the Gediz River basin. Similar studies are available in literature, ranging from those that use a simple model such as USLE to others of a more sophisticated nature. The study presented here reflects the difficulties in applying the methodology when the required data on soil properties, land use and vegetation are deficient in both quantity and quality, as the case is with most developing countries.     

Geothermal applications in Turkey

Geothermal energy is mostly utilised in direct applications in Turkey. The equivalent of 61,000 residences are currently heated by geothermal fluids. A total of 665 MW_t is utilised for space heating of residential, public and private property, and 565,000 m² of greenhouses. Geothermal fluids are also used in 195 spas (327 MW_t), bringing the total direct use capacity to 992 MW_t. ORME Geothermal Inc. has completed the engineering design of a geothermal district heating system that serves the equivalent of nearly 300,000 residences. A total of 170 geothermal fields have been explored so far in Turkey. At Kizildere a single-flash power plant with 20.4 MW_e installed capacity is integrated with a factory producing liquid CO₂ and dry-ice. A binary cycle power plant with an installed capacity of 25 MW_e will be constructed shortly at Aydin/Germencik. The proven geothermal heat capacity, according to data from existing geothermal wells and natural discharges, is 3132 MW_t (I. Akkus, MTA General Directorate, oral communication, January 2003).     

Determination of optical properties of amorphous Ta2O5 films deposited by spin- and dip-coating methods

The optical properties of amorphous Ta₂O₅ films prepared by the sol-gel dip- and spin-coating deposition technique and dried at 60°C have been investigated. Refractive index, extinction coefficient and optical energy gap have been calculated from optical transmission measurements using the Swanepoel method. The films of similar thickness deposited by the two methods were compared. It is shown that the optical properties are dependent on the deposition methods. The energy band gap of the Ta₂O₅ films is 3.75 ± 0.12 eV and is independent of the coating methods.     

Sintering behaviour of nano-crystalline γ-Al2O3 powder without additives at 2-7 GPa

Al₂O₃ ceramics were fabricated without additives under high pressure (2-7 GPa) at different temperatures (600-1200 °C) using nanocrystalline alumina powder with metastable γ-Al₂O₃ phase as the starting material.It was shown that high pressure increases the nucleation rate while reducing the growth rate of the transformed α phase so that its grain size decreases and nano-scale grains in the sintered structure can be achieved.On the other hand the sintered samples at 7 GPa and high temperature (1000 °C) have shown micron-scale large grain sizes compared to those sintered at lower pressures, for the same temperature and sintering time. This could be attributed to the higher input energy in the system at high pressure and high temperature conditions, thereby reaching the final stage in sintering more quickly.In this work, the best combination of grain size (∼200 nm) and density (98.0% TD) was obtained under the sintering condition of 1000 °C at 7 GPa with a holding time of 1 min.Thus for high pressure/high temperature conditions, the sintering time should be reduced to prevent grain growth.     

The effect of surface treatments on the bonding strength of ceramic inlays to dentin

Aim: To compare and evaluate the effects of different surface treatments on surface roughness and the microtensile bonding strengths of four different ceramics to dentin. Methods: 160 human molar teeth were used. The teeth were divided into four groups (n = 40). FC (Finesse), LC (IPS Empress Esthetics), LDC (IPS Empress e-Max) and MZC (Zirkonzahn Prettau) ceramic restorations were prepared. The specimens were divided into eight groups: (1) control, (2) air abrasion (AA), (3) HF acid etching (HF), (4) experimental hot etching (EHE), (5) Nd:YAG laser irradiation, (6) Nd:YAG laser + air abrasion, (7) Nd:YAG laser + HF acid, and (8) Nd:YAG laser + experimental hot etching. The surface roughness of the ceramics was determined with atomic force microscopy. After the cementation process, the specimens were thermal cycled and subjected to a microtensile bond strength (MBS) test. Two-way ANOVA and a Tukey’s test were used to analyse the surface roughness and MBS values of variance (p = 0.05). Results: HF acid etching showed the highest surface roughness in FC (p < 0.05). HF increased MBS in LC specimens where AA and HF increased MBS in LCD specimens. For the MZC specimens, AA and Nd:YAG + AA was effective in increasing the MBS (p < 0.05). Conclusion: Different surface treatments must be applied to different ceramics to improve the mechanical retention and MBS.     

Antibacterial effect of dental cements evaluated using agar diffusion test

Purpose: Secondary caries can occur around the restoration, fixed prosthesis, and orthodontic band margins because of cariogenic bacteria. Long-lasting antibacterial effectiveness of dental cements used contemporarily can reduce this phenomenon. The purpose of this study was to examine the antibacterial activities of nine dental cements (BisCem^®, Super-Bond C&B, Rely X^TM, Panavia^TM F 2.0, Variolink^® II, Unitek^TM Multi Cure, Multilink^® Automix, Clearfil^TM Esthetic Cement, Transbond^TM LR) using agar diffusion test. Materials and methods: The test materials were inserted into the wells of Muller Hinton agar plates inoculated with Streptococcus mutans and Streptococcus salivarious. The diameters of the inhibition zones produced around the materials were measured after 24 h of incubation. Two-Way ANOVA, the Kruskal-Wallis, and the Mann–Whitney U tests at a significance level of p < 0.05 were analyzed for the results. Results: Unitek Multi Cure cement exhibited a significant difference from the control group against both S. mutans and S. salivarious (p < 0.05). While the zone of inhibition of Unitek Multi Cure cement was shorter (8.50 ± 1.77) than the control group (12.63 ± 1.30), Unitek Multi Cure had antibacterial effect against S. mutans and S. salivarious (p < 0.05). S. mutans displayed a significantly lower resistance to Unitek Multi Cure, BisCem, and Superbond C&B than S. salivarious (p < 0.05). Conclusion: Conventional glass ionomer cement, Unitek Multi Cure, exhibited greatest in vitro antibacterial activity against both S. mutans and S. salivarious. Formation of dental caries had been suppressed by the fluoride-releasing GICs.     

Crystallite size and lattice strain of lithiated spinel material for rechargeable battery by X‐ray diffraction peak‐broadening analysis

High‐energy ball milling is performed on Li_1.1Mn_1.95Fe_0.05O₄ spinel material, synthesized by sol‐gel method for lithium rechargeable battery, at different durations to obtain nanopowders of finite size distributions. The powders are investigated by means of scanning electron microscopy, particle size distribution, and X‐ray diffraction (XRD) measurements. The structural analysis of the powders is performed to investigate the effect of milling on the particle size, crystallite size, and lattice strain. The scanning electron micrographs and size distribution measurements show that the particle size decreases with the increase in milling duration. The XRD results show that the widths of the diffraction peaks increase with the decrease of particle size (increase of milling duration). This broadening is analyzed according to Scherrer, Williamson‐Hall, and Halder‐Wagner methods. Peak broadening is attributed to contributions of crystallite size and lattice strain. While reducing the particle and crystallite sizes is desirable to achieve higher specific capacity and energy density of the battery active material, lattice strain leads to material degradation and a reduced capacity retention. Thus, when performing mechanical milling, lattice strain should be taken seriously into consideration to optimize the milling parameters and to enhance the materials electrochemical performance.     

Investigation of the elastic properties of poly (methyl methacrylate) reinforced with graphene nanoplatelets

The technique for synthesis of poly (methyl methacrylate) (PMMA) by atom transfer radical polymerization has been strengthened by using graphene nanoplatelets (GNPs) to enhance the elastic properties of the polymer. In order to improve practical, economical and mechanical performance, the requirements for effective implementation of production control as a smart bulk polymer nanocomposite were determined for cost-effective bulk production. Three-dimensional inspection (using an ultrasound interrogation method for the whole volume under test) confirmed the synthesis of the nanocomposite to be free of agglomeration and bubbles. As a result of this elimination of defects, an enhancement in compressive strength of 42.7% was achieved and the Rockwell hardness was increased by 19.9% through the addition of GNPs at 2 wt% by mass. The deformation and mechanical failure properties have been characterized in the mechanical enhancement of the polymer nanocomposite. Elastic parameters determined using ultrasound testing identified that changes in the structural features following the addition of these GNPs were uniquely connected to the enhancements in these elastic parameters (such as Young's modulus, Poisson's ratio, shear modulus, and microhardness) of the PMMA/GNPs nanocomposite.