Nanophosphor aluminum oxide: Luminescence response of a potential dosimetric material

This work reports on the investigation of the radiation dosimetry properties of Al₂O₃ nanopowders. Samples were produced by solution combustion synthesis using three different organic fuels to check for the effect of synthesis conditions on the properties of interest. Luminescence characteristics were studied by thermoluminescence and optically stimulated luminescence (OSL) techniques. We found that samples produced using urea have characteristics similar to bulk Al₂O₃:C and may be suitable for personal dosimetry, while samples produced using glycine and hexamethylenetetramine (HMT) may be more suitable for applications where fast OSL decay is advantageous. While these results are promising and warrant further investigation, much has to be done to overcome the greatly decreased luminescence intensity of the nanomaterials as compared to bulk Al₂O₃:C.     

A Random Surface Wave Equation for Bosonic QCD(<Emphasis Type="Italic">SU</Emphasis>(∞))

We propose a quantum surface wave functional describing the interaction between a colored SU(N _c ) membrane and a quantized Yang-Mills field. Additionally, we deduce its associated wave equation in the t’Hooft N _c →∞ limit. We show that its reproduces the Yang-Mills Field Theory at a large rigid random surface scale.     

Carotenes and carotenoids in natural biological samples: a Raman spectroscopic analysis

Raman spectroscopic studies of a range of naturally occurring carotenoids in over 50 specimens of plant tissue and a range of standard extracts have been undertaken, and the characteristic bands of CC and C C stretching and C CH bending have been recorded. Comparison of the spectroscopic data with the chemical assignment of the carotenoids from chemical extraction of the plant tissues reveals that there is a problem in the interpretation of the spectroscopic data which can be attributed to significant wavenumber shifts, particularly in the CC stretching band wavenumber, for carotenoids in the organic tissues arising from molecular interactions between the carotenoid and its host matrix. The simple identification of carotenoids in biological tissues on the basis of comparison with the standard spectra of extracted material must be made with caution; the progressive shift in wavenumber of the CC stretching band in the conjugated polyene chain of carotenoids with the number of CC groups, and hence the identification of the carotenoid, cannot be unambiguously interpreted for the range of materials studied here. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and luminescent characteristics of one-dimensional europium doped Gd2O3 phosphors

One-dimensional (1D) Gd₂O₃:Eu³⁺ nano-rods and micro-rods were prepared using a facile sol-gel precipitation method, without a template and with a post-growth heat treatment in air. Based on scanning electron microscopy (SEM) and X-ray diffraction (XRD) data, hexagonal Gd(OH)₃:Eu³⁺ micro-rods, 60∼90 nm in diameter and 700 nm to 1 μm in length, were synthesized and then transformed by calcining (800°C, 2 hr) to cubic Gd₂O₃:Eu³⁺ with the same morphology and dimensions. Nano-rods of Eu³⁺ doped Gd(OH)₃ and calcined Gd₂O₃, 60∼90 nm diameter and 150∼300 nm length, were prepared by adding polyethylene glycol (PEG) as a capping agent during the sol-gel synthesis. Photoluminescence (PL) spectra exhibited the ⁵D₀–⁷F₂ transitions of Eu³⁺ at 612 and 627 nm from excitation at 280 nm. Photoluminescence excitation (PLE) data showed that a small fraction of PL from Eu³⁺ resulted from direct excitation, but most PL resulted from the oxygen to europium charge-transfer band (CTB) between 250 and 280 nm.     

Neutron induced light-ion production from iron and bismuth at 175 MeV

We have measured light-ion (p, d, t, ³He and α) production in the interaction of 175 MeV neutrons with iron and bismuth with low-energy thresholds and for a wide angular range (from 20° to 160°, in steps of 20°). Measurements have been performed with the Medley setup, semi-permanently installed at the The Svedberg Laboratory, Uppsala (Sweden), where a quasi-monoenergetic neutron beam is available and well characterized. Medley is a conventional spectrometer system and consists of eight telescopes, each of them composed of two silicon surface barrier detectors, to perform particle identification, and a CsI(Tl) scintillator to fully measure the kinetic energy of the produced light-ions. We report preliminary double-differential cross sections for production of protons, deuterons and tritons in comparison with model calculations using TALYS-1.0 code. These show better agreement for the production of protons, while the theoretical calculations seem to overestimate the experimental production of deuterons and tritons.     

An upgrade of the SCANDAL setup for measurements of elastic neutron scattering at 175 MeV

The experimental setup SCANDAL, used for measurements of the differential cross section for elastic and inelastic neutron scattering, has recently been upgraded with larger CsI scintillating detectors to enable measurements at energies up to 175 MeV. Measurements on Fe, Bi and Si have been carried out using the quasi mono-energetic neutron beam at the The Svedberg Laboratory, and data is under analysis. The experimental setup can be used for measurements on a wide range of target nuclei, including C and O, which are important for dosimetry applications. SCANDAL can also run in proton mode, for measurements of the (n,p) reaction. This paper describes the new experimental setup, and reports on its properties, such as energy resolution.     

Effect of Bee Pollen on the Mechanical and Thermal Properties of Starch Films

The use of casein, starch and bee pollen as biodegradable materials has been promise. The objective of this work was the development and characterization of films containing casein, pollen and starch. The films were obtained by casting process and the solvent evaporation was performed at 40 °C/24 h. The films characterization was carried out by microscopy, thermal analysis, opacity test, mechanical properties and barrier methods. The starch films presented heterogeneous on microscopy analysis. The thermal behaviors of pollen films were similar. The formulation containing only pollen 3% was unable to form film. The introduction of pollen in starch film formulation improved the mechanical characteristic and thermal stability of films.     

Electrospinning of Polyaniline/Poly(Lactic Acid) Ultrathin Fibers: Process and Statistical Modeling using a Non‐Gaussian Approach

Fibers of poly(lactic acid) (PLA) blended with p‐toluenesulfonic acid‐doped polyaniline, PAni.TSA, were obtained by electrospinning, following a factorial design which was used mainly to study the effect of four process parameters (PLA solution concentration, PAni solution concentration, applied voltage, and flow rate) on fiber diameter. Due to the non‐Gaussian spread of the fiber diameters, probability density functions (PDF's) were used to describe them, and the main effect analysis was performed considering the most representative values of these PDF's. This study suggests that the main factor which governs the fiber dimension is the concentration of the PAni solution and its synergy with the others factors. Furthermore, in spite of the high complexity of the electrospinning process, the statistical model was able to describe the process with 95% confidence, therefore enabling one to precisely predict fiber diameter. Nanofiber formation was simulated using the results of the experimental design and validation tests were performed to minimize the fiber diameter.