Influence of γ-radiation on photoconductivity spectra of InSe monocrystals

The influences of γ-radiation with photon energy hν ～ 1.23 MeV on photoconductivity of layered InSe crystals have been studied. The photosensitivity is increased because of small doses of γ-radiation. It has been observed that γ-radiation makes the impurity peaks in the photoconductivity spectra disappear. This process is attributed to the phenomenon of irradiation annealing characterized by formation of the complexes including fine impurity centers and specific γ-radiation defects.     

Basics of diamond- partial dynamic calculus on time scales

In this paper we introduce partial diamond-α dynamic derivatives for two-variable functions and the double integral calculus via the diamond-α dynamic integral on time scales. Also we establish a two-dimensional weighted Hardy–Knopp type integral inequality on time scales.     

Preparation of Ga<Subscript>2</Subscript>Se<Subscript>3</Subscript> thin films by sol–gel technique

In this study we describe the preparation of Ga₂Se₃ semiconductor compound thin films by sol–gel method for different crystal formation temperatures. The films were characterized by X-ray diffraction analyses (XRD), UV–visible spectrometer, and scanning electron microscope (SEM). The XRD spectrum showed that the formation of Ga₂Se₃ crystals were between 743 and 823 K. The thin film crystals that were formed at 773 K corresponded to the β phase and the preferred crystal structure was monoclinic. The value of band gap from optical absorption spectra for the Ga₂Se₃ thin films was estimated to be about E _g ~ 2.56 eV. The thickness of the one-coat Ga₂Se₃ thin films, which was measured by a Spectroscopic Ellipsometer, was about ~200 nm. The average grain sizes of scattered particles were within the limits between 200 and 500 nm.     

Indoor radon levels of spas and dwellings located around Bayındır geothermal region

Western part of Turkey is rich area in terms of geothermal sources. The one of these geothermal areas is Bay?nd?r-Dereköy/Ergenli located in Küçük Menderes Graben. In this study, indoor radon concentrations were determined in some places (spas and some dwellings) located on Bay?nd?r-Dereköy/Ergenli. Measurements were realized using LR-115 type 2 solid state nuclear track detectors in the course of 10 months. The indoor radon concentrations were found between 39.3 and 235.4 Bq m^?3 for spas, 39.3 and 405 Bq m^?3 for houses. Indoor radon concentrations were compared with reference levels determined by international agencies. Radon concentrations in this area were quite low than reference levels revised by international health agencies.     

Room temperature ferromagnetism in Mn-doped ZnS nanocrystalline thin films grown by sol–gel dip coating process

Nanocrystalline Zn_1?xMn_xS (x = 0.00, 0.01, 0.02, 0.03, 0.05, and 0.1) thin films having different Mn content were grown by the sol–gel dip coating process. The effect of Mn content on the structural, optical and magnetic properties of Zn_1?xMn_xS nanocrystalline thin films were investigated. X-ray diffraction results showed the presence of single hexagonal phase corresponding to ZnS with a preferred orientation along the ZnS (002) hexagonal plane direction without any detectable secondary phase, suggesting the incorporation of Mn ions into the ZnS lattice. Scanning electron microscope revealed the surface of the nanocrystalline films to be homogeneous and dense and the grains of the film surface were randomly scattered. In ultraviolet–visible measurements, the band gap energy corresponding to the absorption edge estimated were found to be 3.59–3.23 eV depending on the Mn doping ratio. Magnetic measurements showed that a paramagnetic behavior at 5 K and ferromagnetic behavior at 300 K.     

Interparticle interaction effects on magnetic behaviors of hematite (α-Fe2O3) nanoparticles

The interparticle magnetic interactions of hematite (α-Fe₂O₃) nanoparticles were investigated by temperature and magnetic field dependent magnetization curves. The synthesis were done in two steps; milling metallic iron (Fe) powders in pure water (H₂O), known as mechanical milling technique, and annealing at 600 °C. The crystal and molecular structure of prepared samples were determined by X-ray powder diffraction (XRD) spectra and Fourier transform infrared (FTIR) spectra results. The average particle sizes and the size distributions were figured out using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The magnetic behaviors of α-Fe₂O₃ nanoparticles were analyzed with a vibrating sample magnetometer (VSM). As a result of the analysis, it was observed that the prepared α-Fe₂O₃ nanoparticles did not perform a sharp Morin transition (the characteristic transition of α-Fe₂O₃) due to lack of unique particle size distribution. However, the transition can be observed in the wide temperature range as “a continuously transition”. Additionally, the effect of interparticle interaction on magnetic behavior was determined from the magnetization versus applied field (σ(M)) curves for 26±2 nm particles, dispersed in sodium oxalate matrix under ratios of 200:1, 300:1, 500:1 and 1000:1. The interparticle interaction fields, recorded at 5 K to avoid the thermal interactions, were found as ∼1082 Oe for 26±2 nm particles.     

The annealing effect on structural,optical and photoelectrical properties of CuInS2/In2S3 films

Successive Ionic Layer Adsorption and Reaction (SILAR) technique was used to deposit the CuInS₂/In₂S₃ multilayer thin film structure at room temperature. The as-deposited film was annealed at 100, 200, 300, 400 and 500 °C for 30 min in nitrogen atmosphere and the annealing effect on structural, optical and photoelectrical properties of the film was investigated. X-ray diffraction (XRD) and optical absorption spectroscopy were used for structural and optical studies. Current–Voltage (I–V) measurements were performed in dark environment and under 15, 30 and 50 mW/cm² light intensity to investigate the photosensitivity of the structure. Also, the electrical resistivity of the film was determined in the temperature range of 300–470 K. It was found that annealing temperature drastically affects the structural, optical and photoelectrical properties of the CuInS₂/In₂S₃ films.     

Monolithic valves for microfluidic chips based on thermoresponsive polymer gels

The direct preparation of thermoresponsive monolithic copolymers by photopatterning of a liquid phase consisting of an aqueous solution of N-isopropylacrylamide, N-ethylacrylamide, N,N'-methylenebisacrylamide, and 4,4'-azobis(4-cyanovaleric acid) has been studied and the products used as valves within the channels of microfluidic devices. The volume change associated with the polymer phase transition at its lower critical solution temperature (LCST) leads to the rapid swelling and the deswelling of the 2.5% cross-linked monolithic gel thus enabling the polymer to close or open the channel and to function as a nonmechanically actuated valve. The LCST at which the valve switches was easily adjusted within a range of 35 degrees C-74 degrees C by varying the proportions of the monovinyl monomers in the polymerization mixture. The closed valve holds pressures of up to 18 MPa without noticeable dislocation, structural damage, or leakage. In contrast, following deswelling by raising the temperature above LCST the valve offers no appreciable flow resistance since its large, micrometer-size pores are open. Laser-triggered photobleaching of a fluorescent dye contained in the liquid phase enabled monitoring of flow through the device and determination of the times required to open and close the valve. The valves are characterized by very fast actuation times in a range of 1-4 s depending on the type of device. No changes in performance were observed even after repeated open-close cycling of the valves.     

Dual-frequency division de-multiplexer based on cascaded photonic crystal waveguides

A dual-frequency division de-multiplexing mechanism is demonstrated using cascaded photonic crystal waveguides with unequal waveguide widths. The de-multiplexing mechanism is based on the frequency shift of the waveguide bands for the unequal widths of the photonic crystal waveguides. The modulation in the waveguide bands is used for providing frequency selectivity to the system. The slow light regime of the waveguide bands is utilized for extracting the desired frequency bands from a wider photonic crystal waveguide that has a relatively larger group velocity than the main waveguide for the de-multiplexed frequencies. In other words, the wider spatial distribution of the electric fields in the transverse direction of the waveguide for slow light modes is utilized in order to achieve the dropping of the modes to the output channels. The spectral and spatial de-multiplexing features are numerically verified. It can be stated that the presented mechanism can be used to de-multiplex more than two frequency intervals by cascading new photonic crystal waveguides with properly selected widths.     

Thermal behaviour and photoluminescence properties of Er- and Nd-doped yttrium aluminate glasses

Journal of Thermal Analysis and Calorimetry - Yttrium aluminate glasses (76.8&nbsp;mol% of Al2O3, 23.2&nbsp;mol% of Y2O3) doped with Er3+ and Nd3+ ions at different concentration levels...