Equilibrium distributions of key components of spearmint oil in sub/supercritical carbon dioxide

Effects of temperature (at 35, 45 or 55°C) and pressure (10–110 atm) on the relative distribution coefficients of the twelve key components of spearmint oil (essential oil ofMentha cardiaca; Scotch spearmint) at equilibrium in dense CO₂ were investigated under conditions ranging from subcritical to supercritical regions. Effects of vapor pressure, molecular weight and polarity of the key components on their equilibrium distributions in sub/supercritical CO₂ are discussed. At 35°C, all key components of spearmint oil are equally soluble in dense CO₂ within the 12–102 atm pressure region. At 45 and 55°C, the key components are equally soluble for pressures greater than about 60 atm. However, around either 45°C/27 atm or 55°C/35 atm conditions, the relative distribution coefficients of all monoterpene hydrocarbons and of isomenthone (an oxygenated monoterpene) exhibit maxima, which are due to significantly higher vapor pressures of these components and significantly lower solvating power of the dense-gas solvent at these particular temperatures and pressures. Vapor-pressure effects, coupled with the decrease in solvating power, dominate the effects of polarity and molecular mass of the key components. Deterpenation of spearmint oil with dense CO₂ is possible around either 45°C/27 atm or 55°C/35 atm, where the monoterpene hydrocarbons tend to concentrate in the CO₂-rich phase.     

A microwave method based on amplitude-only reflection measurements for permittivity determination of low-loss materials

A new method based on amplitude-only reflection measurements for complex permittivity determination of low-loss materials backed by a short-circuit termination is presented. There are two main advantages of the proposed method. First, it is insensitive to calibration plane shifts and phase uncertainties in reflection measurements of low-loss materials. Second, it does not require any additional test material with a thickness value different than that of the material under test. The disadvantage of the proposed method is that it is not convenient to apply for complex permittivity determination of dispersive low-loss materials. The method is validated by complex and amplitude-only scattering parameter measurements at X-band of a low-loss sample (polystyrene) fitted into a waveguide section. The method, as other non-resonant methods, can only provide a rough indication of the imaginary part of the permittivity for low-loss samples.     

Effects of Er:YAG laser on bond strength of self‐etching adhesives to caries‐affected dentin

The erbium:yttrium–aluminum–garnet (Er:YAG) laser may be effective the bond strength of adhesive systems on dentine surfaces, the chemical composition and aggressiveness of adhesive systems in clinical practice. The purpose of this study was to evaluate the effects of the Er:YAG laser system with the bonding ability of two different self‐etching adhesives to caries‐affected dentine in primary molars. Ninety mid‐coronal flat dentine surfaces obtained from sound and caries‐affected human primary dentine were treated with an Er:YAG laser or a bur. The prepared surfaces were restored with an adhesive system (Xeno V; Clearfil S³) and a compomer (Dyract Extra). The restored teeth were sectioned with a low‐speed saw and 162 samples were obtained. The bond strength of the adhesive systems was tested using the micro‐tensile test method. The data were statistically analyzed. A restored tooth in each group was processed for scanning electron microscopy evaluation. The values of the highest bond strength were obtained from the Clearfil S³‐Er:YAG laser‐sound dentine group in all groups. (24.57 ± 7.27 MPa) (P > 0.05). The values of the lowest bond strength were obtained from the Xeno V‐Er:YAG laser‐sound dentine group in all groups (11.01 ± 3.89 MPa). It was determined that the Clearfil S³ increased the bond strength on the surface applied with Er:YAG laser according to the Xeno V. Microsc. Res. Tech. 77:282–288, 2014. © 2014 Wiley Periodicals, Inc.     

Effects of grain boundaries on electrical and magnetic properties of melt-processed SmBa2Cu3Ox superconductors

In the present study, we examine the energy dissipation mechanisms and grain boundary effects on the superconducting properties of high-T_c SmBa₂Cu₃O_7?x samples. Sm-123 was synthesized with the top-seeded-melt-growth technique. Grain sizes, as determined by optical microscopy, ranged between 0.5 mm and 1.5 mm. Thus, each specimen, on which the electrical and magnetic measurements were carried out, contained several grains. Some of our findings are as follows: (1) the intragrain T_c is 93.5 K and the intergrain T_c is 87.5 K. Superconducting transition width is narrow and is not affected much by the magnetic field. (2) The intragrain J_c is 110,000 A cm^?2 while the intergrain J_c is 210 A cm^?2 at 10 K. (3) The intergrain J_c shows a secondary peak with the increase in temperature from 10 K to 30 K. The main reasons behind these observations are discussed in detail.     

Solar-blind ultraviolet photodetector based on Ti-doped Ga2O3/Si p–n heterojunction

A solar-blind ultraviolet photodetector based on Ti-doped Ga₂O₃/Si p–n heterojunction is demonstrated for the first time. It is found that the heterojunction quality forming between Ga₂O₃ and Si becomes better after Ti incorporation in Ga₂O₃. The current–voltage and temporal response measurements show that the detector based on Ti-doped Ga₂O₃/Si p–n heterojunction has a responsivity of 0.382 A/W and a fast rise time of 73 ms as well, which are much better than those undoped Ga₂O₃/Si p–n heterojunction analogues.

     

A comparative study on structural,morphological and photocatalytic properties of anodically grown ZnO nanowires under varying parameters

Journal of Materials Science: Materials in Electronics - In this study, zinc oxide (ZnO) nanowires (NWs) were successfully produced on Zn plates through electrochemical anodization in potassium...     

Carotid-jugular arteriovenous fistula and cerebrovascular infarct: a case report of an iatrogenic complication following internal jugular vein catheterization

Central venous catheterization is frequently performed for perioperative management and long-term intravenous access. Although complications associated with central venous catheter insertion have been widely reported, there are few reports of carotid-jugular arteriovenous fistula formation. Endovascular procedures are associated with a risk of immediate and delayed thromboembolic and ischemic complications. We describe a case of a carotid-jugular arteriovenous fistula and a cerebrovascular infarct following the insertion of a double-lumen catheter for hemodialysis access. We provide recommendations for the prevention and the early detection of this iatrogenic complication.     

An investigation into the mechanical and tribological properties of plasma electrolytic oxidation and hard-anodized coatings on 6082 aluminum alloy

A ceramic coating on AA6082 aluminum alloy prepared by plasma electrolytic oxidation (PEO) has been studied and compared against a sulphuric acid hard-anodized coating on the same alloy. Surface morphology and microstructures of the coatings have been examined by scanning electron microscopy. X-ray diffraction is used to determine the phase composition of the coatings. The adhesion strength of the coatings has been evaluated using a scratch test method. The coating's mechanical properties such elastic modulus and hardness data have been generated using a dynamic ultra-microhardness tester. Sliding wear tests with different loading rates are performed on the coatings in order to assess their wear resistance. Test results show that the PEO treated samples exhibit significantly better mechanical properties compared to hard anodized samples. The elastic modulus and hardness of the PEO coating are 2-3 times greater than of the hard anodized coating and subsequently, an improved wear resistance of the PEO coating has been achieved. The mechanical properties of the coatings and their relations to their tribological performance are discussed.     

Effects of Mn and Gd Co-substituted into ZnO on Structural and Magnetic Properties

We have worked on the structural and magnetic properties of Zn_0.99?xMn_0.01Gd _x O _δ (for x = 0.02, 0.03, and 0.04) compounds prepared by using a sol–gel method. The x-ray diffraction, scanning electron microscopy, and energy dispersive x-ray spectroscopy were used to understand the structural properties of the samples. We observed that co-substitution of Mn (1 %) and Gd (2–4 %) into the ZnO does not change the hexagonal structure. Scanning electron microscope (SEM) images show us that the grain size decreases with the increasing amount of the Gd into the ZnO matrix. The magnetic properties of the samples have been investigated by using magnetic hysteresis and DC susceptibility measurements. The ZMG1 sample shows a weak ferromagnetic behavior at room temperature, whereas the ZMG2 and ZMG3 samples exhibit a paramagnetic nature. Furthermore, it is also found that the magnetizations of the samples decrease with increasing Gd content in the ZnMnO system due to the enhancing interaction between Gd ³⁺ ions. We summarize that the co-substitution of Mn and Gd into the ZnO generates a room-temperature ferromagnetism, but it still needs more work to obtain strong and high coercivity magnetic loops for applications.