Influence of the Shape on Magnetic Properties of Ising Nanostructures

We study magnetic behaviors of phase diagrams and hysteresis loops in a cubic, hexagonal, and cylindrical type transverse Ising nanowire within the effective-field theory with correlations. From these studies, we investigate the influence of the shape on magnetic properties of Ising nanostructures. We find that the behavior of phase diagrams is more similar for the cubic and hexagonal nanowires than the cylindrical one and the system undergoes a second-order phase transition at the lowest temperature for the hexagonal nanowire and at the highest temperature for the cylindrical one. Hysteresis loop areas are the largest for a hexagonal nanowire and smallest for a cylindrical one. Hysteresis loop areas disappear at the highest temperature for a cylindrical nanowire and at the lowest temperature for a cubic one.     

Diversity analysis of single and multiple beamforming

In this letter, we study two techniques, known as single and multiple beamforming, to exploit the perfect channel state information (CSI) available both at the transmitter and the receiver of a multiantenna wireless system. Assuming N and M are the number of antennas at the transmitter and the receiver, respectively, we show that single beamforming (transmission of a single symbol from all transmit antennas at the same time, employing the best subchannel) can achieve the maximum spatial diversity order in the channel (NM). We extend our analytical results to multiple beamforming (transmission of S symbols simultaneously, S>1) and calculate that the diversity order achievable for this system is (N-S+1)(M-S+1).     

Turkey's output in social science publications: 1970-1999

Publications originating from Turkey in SSCI were analyzed for changes in the thirty-year span between 1970 and 1999. There has been a high rate of increase in the number of publications and most of these publications were in the form of articles and review papers. The rate of increase was lower than the increase in science publications but the rankings among other countries in sciences and social sciences were comparable. The analysis of impact factors and citations received by published work showed a decline across years. Many of the high-impact publications were joint work with foreign authors. The low level of impact was attributed in part by the difficulty of international scholars in belonging to research networks. This revised version was published online in June 2006 with corrections to the Cover Date.     

Metal recognition of septapeptides via polypod molecular architecture

The understanding of the nature of recognition of inorganic materials by proteins is one of the core elements of and has profound implications in biological materials science and engineering. Using combinatorial display methods, a considerable number of short polypeptides have recently been selected with affinity to engineering materials. During these selections, more than several polypeptides are identified with binding specificity to a chosen inorganic material. Understanding the nature of surface recognition of materials by polypeptides is essential for rational design and biomimetic engineering of these inorganic-binding polypeptides for use as linkers, catalyzers, and growth modifiers in nanotechnology and nanobiotechnology. Although there may not be direct homology among the amino acids constituting the polypeptides, their function may come from conserved molecular architecture. Here we study crystallographic surface recognition of platinum metal-binding septapeptides by conformational analysis. We find that the septapeptides conform into certain molecular architectures containing multiple protrusions (polypods) that spatially match with the crystallographic metal surfaces. While the physical recognition may originate from how well the molecular polypods spatially match a given crystallographic surface, the degree of binding may be due to the reactive groups that form the polypods, e.g., charged or polar groups (e.g., hydroxyl and amine). These results are highly consistent with the experimental binding characteristics of the Pt binders with various degrees of affinities.     

Valorization of bio-calcium carbonate based Chamelea gallina shell waste fillers in shape memory polymer composites

In recent years, the focus has been on the use of calcium carbonate-based seashell wastes in the production of new thermoplastic and thermoset polymer materials, paving the way for their use as biofillers in polymeric composites. In this study, it is aimed to obtain a new polymeric composite material by doping Chamelea gallina shells, on polylactic acid (PLA)/polyethylene glycol (PEG) blend. Structural characterization of the obtained PLA/PEG blend/C. gallina composite films was performed with attenuated total reflection infrared spectroscopy (ATR-IR). When the thermal properties of composite materials were examined by thermogravimetric analysis (TGA), it was determined that the thermal stability of polymeric composites increased with the addition of C. gallina. SEM images showed that the polymer blend films, which appeared to have a porous structure, filled the pores with increasing C. gallina ratio. It was observed that the biodegradability of PLA/PEG blend composite films decreased with increasing C. gallina shells addition. However, C. gallina had a positive effect on the swelling and water absorption capacities of polymeric composites. The increase in tensile strength and elongation at break values of PLA/PEG blend/C. gallina composite films with increasing C. gallina means that the mechanical properties of the polymer are improved.     

Synthesis of urethane acrylate based electromagnetic interference shielding materials

In this work, a new method, consists of synthesis of urethane acrylate (UA) followed by in situ polymerization of pyrrole using cerium (IV) as an oxidant and UV‐curing of the composites, for preparing polypyrrole–UA (PPy–UA) composite films was described. It appeared that dielectric constants of the composites increased with increasing the PPy content and decreased with increasing the frequency from 10^?2 to 10⁷, indicating an interfacial Maxwell–Wagner contribution to the permittivity. An incorporation of a small amount of PPy (15% Py) to UA matrix increased their dielectric constants more than 4 × 10⁴ (41,259) at 10^?2 Hz. So, the incorporation of PPy was very effective for enhancing the dielectric properties of UA matrix. Furthermore, the significant enhancement in dielectric properties (loss tangent and dielectric constant) contributes to the improvement in electromagnetic interference shielding efficiency. Composite films were characterized using Fourier transform infrared attenuated total reflectance (FTIR‐ATR) spectrophotometer and ¹H‐NMR. It was seen that PPy is blended with the UA matrix at the molecular level through H‐bonding interactions. A linear relationship was also observed between the characteristic groups' absorbances of PPy (from FTIR‐ATR) and dielectric constant values (from dielectric spectrometer). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013     

Triangular Ising Ferromagnet with Mixed Spins (<Emphasis Type="Italic">A</Emphasis> = 1/2, <Emphasis Type="Italic">B</Emphasis> = 1/2, <Emphasis Type="Italic">C</Emphasis> = 1): Dynamic Magnetic Properties and Hysteresis Curves

The dynamic properties of the triangular Ising ferromagnet consisting of the mixed spins A = 1/2, B = 1/2, and C = 1 is studied by using the mean-field theory (MFT) as well as Glauber-type stochastic dynamics (GSD). The coupling equations to investigate dynamic behaviors of the system are calculated, and phase transitions, phase diagrams, and hysteresis curves are obtained. From these studies, first- and second-order transition lines, the dynamic phase diagrams (DPDs) in the (T,h ₀) and (T,d) planes, and single hysteresis curves are presented. In the DPDs, dynamic tricritical point due to the first- and second-order phase transitions are observed. It is found that the dynamic hysteresis properties of the triangular system strongly depend on the temperature and crystal field.