Photoluminescence of ZnO nanowires grown on sapphire (1 1 2¯ 0) substrates

ZnO nanowires were fabricated on c-plane (0 0 0 1), a-plane (1 1 2¯ 0) sapphire, and boron doped p-type (1 0 0) Si substrates in vacuum furnace by simple physical vapor deposition. Room temperature photoluminescence spectra of the nanowires show the near band-edge emission and the deep-level green light emission. The ZnO nanowires formed on sapphire (1 1 2¯ 0) substrates exhibited enhancement on optical properties and better crystalline structures than those of nanowires grown on other substrates. The formation mechanism and the effect of substrate direction on structural and optical properties of the nanowires are discussed.     

Multiferroic characteristics of the strained epitaxial Bi0.9Ho0.1FeO3 thin film

We fabricated high quality epitaxial Bi_0.9Ho_0.1FeO₃ thin films which exhibited the tetragonally stained structure with a c/a ratio of about 1.04. The Bi_0.9Ho_0.1FeO₃ thin film showed a good ferroelectric property with the high remanent polarization (P_r) of about 80 μC/cm². The ferromagnetic hysteresis loop with a clear remanent magnetization was shown. The coercive field and the remanent magnetization of the Bi_0.9Ho_0.1FeO₃ film are 6200 Oe and 1.7 emu/g, respectively. The abrupt conduction due to space charge limited (SCL) was revealed in leakage current density versus electric field.     

A new minor butenolide from <Emphasis Type="Italic">Machilus odoratissima</Emphasis>

A new butenolide, designated odoratinolide (1), was isolated from the bark of the Vietnamese medicinal plant Machilus odoratissima. Its structure was determined by spectroscopic analyses.     

Optimal admission and pricing control problem with deterministic service times and sideline profit

We consider a discrete-time admission control problem in a company operating in service industries with two classes of customers. For the first class of customers, the company then (1) has an option to accept or reject him/her (admission control), or (2) decides on an offering price (pricing control). The second-class (sideline) customers are only served if no first-class customers are in the system, and this yields the sideline profit. In this paper, we discuss both admission control and pricing control problems within an identical framework, and we examine the properties of the optimal policies to maximize the total expected present discounted net profits. We show that when the sideline profit is large, the optimal policies may not be monotone in the number of first-class customers in the system.     

Surface-enhanced vibrational investigation of adsorbed analgesics

Adsorption properties of acetylsalicylic acid (AA), ibuprofen and acetaminophen deposited from volatile solvents with varying protic/aprotic properties on vacuum-evaporated silver films were characterized using surface-enhanced infrared absorption (SEIRA) and surface-enhanced Raman spectroscopy (SERS). SERS preferentially enhances monolayer Raman shifts, while SEIRA can enhance the infrared absorbance of the monolayer and multilayers. To our best knowledge, this is the first reported study of these molecules using a combination of SERS/SEIRA. SERS revealed that AA and ibuprofen adsorbed ionically in monolayers, independent of the deposition solvents used in the process. SEIRA experiments showed that AA multilayers condensed molecularly using a deposition solvent with polar bonds. However, when an alkane deposition solvent with non-polar bonds such as n-heptane was used, AA adsorbed as acetylsalicylate ions in the first few multilayers, while ibuprofen always adsorbed as the free acid in the multilayer. These ionization trends depend upon the affinity of AA and ibuprofen for the underlying silver film. TPD experiments on silver powders further demonstrated that ibuprofen affinity for silver was less than AA. Furthermore, SEIRA indicated that acetaminophen adsorbed as multilayers of metastable polymorphs using protic or polar aprotic deposition solvents. Protic deposition solvents gave higher quality SERS spectra of an acetaminophen monolayer in comparison to polar aprotic deposition solvents. Such studies could find significant applications in biochemical and nanotechnology processes such as drug delivery, catalysis, and tissue engineering and will contribute to the understanding of the impact and fate of analgesics released into the environment.     

Visual performance improvement analytics of predictive model for unbalanced panel data

Journal of Visualization - An unbalanced panel is a dataset in which at least one subject is not observed some times. Moreover, each subject is recorded with irregular periods and intervals....     

Synthesis of poly(p‐phenylenediamine‐ co‐o‐aminophenol)/multi‐walled carbon nanotube composites by emulsion polymerization

Organic–inorganic composites composed of electrically conducting copolymer p‐phenylenediamine‐ co‐o‐aminophenol and carboxylic acid functionalized multi‐walled carbon nanotubes [poly(pPD‐co‐oAP)/c‐MWNTs] were prepared via in situ emulsion pathway using sodium dodecyl sulphate (SDS) as an emulsifier and potassium persulphate as an oxidant. Acid functionalized MWNTs were used as cores in the formation of tubular shells of the composites. TEM and FESEM analysis showed that a tubular layer of coated copolymer film of several nanometer thicknesses is present on the c‐MWNTs surfaces. FT‐IR spectra endorsed the formation of composites. TGA results indicated that the decomposition temperatures of composites were higher than the bare copolymer. UV‐visible absorption spectra of diluted colloidal dispersion of composites were similar to those of the bare copolymer. The composites were also confirmed by XRD and XPS. Room‐temperature conductivity increases with an increasing fraction of c‐MWNTs. Copyright © 2009 John Wiley & Sons, Ltd.     

Removal behavior of Cs from molten salt by using zeolitic materials

Radioactive molten salt generated from a pyrochemical process to separate reusable U and TRU elements is one of problematic wastes to manage for a final disposal. For the minimization of final waste, it is desirable to selectively remove radionuclides from the waste salts. In this paper, structural change of some zeolites in a series of molten salt systems and its removal behavior of CsCl was investigated. Zeolite-4A(LTA) was transformed into LiAlSiO₄ and Li-sodalite with the mol-fraction of LiCl in LiCl–KCl system at 650 °C while it was not changed in NaCl–KCl at 750 °C, regardless of mol-fraction of metal chloride. Other commercial zeolite with specific structure (FAU) had the same trends on the structural stability in molten salt system. From the Cs removal experiments, the decomposed zeolitic materials in molten salt lost their removal ability of Cs. In conclusion, a new selective material or method should be investigated or developed for obtaining the validity on the separation of group I and II radionuclides from a molten waste salt because the zeolite 4A is unstable in the LiCl system and it also showed a low capacity in the LiCl–KCl phase. This paper gives basic information on the removal of radionuclides from molten systems by using zeolitic materials.