A condensation particle counter insensitive to volatile particles

A High Temperature Condensation Particle Counter (HT-CPC) is described that operates at an elevated temperature of up to ca. 300. °C such that volatile particles from typical combustion sources are not counted. The HT-CPC is functionally identical to a conventional CPC, the main challenge being to find suitable non-hazardous working fluids, with good stability, and an appropriate vapour pressure. Some key design features are described, and results of modelling which predict the HT-CPC counting efficiency. Experimental results are presented for several candidate fluids when the HT-CPC was challenged with ambient, NaCl and diesel soot particles, and the results show good agreement with modelled predictions, and confirm that counting of particles of diameters down to at least 10. nm was achievable. Possible applications are presented, including measurement of particles from a diesel car engine and comparison with a near PMP system. © 2014 Elsevier Ltd.

Modelling and comparison of trapped fields in (RE)BCO bulk superconductors for activation using pulsed field magnetization

The ability to generate a permanent, stable magnetic field unsupported by an electromotive force is fundamental to a variety of engineering applications. Bulk high temperature superconducting (HTS) materials can trap magnetic fields of magnitude over ten times higher than the maximum field produced by conventional magnets, which is limited practically to rather less than 2 T. In this paper, two large c-axis oriented, single-grain YBCO and GdBCO bulk superconductors are magnetized by the pulsed field magnetization (PFM) technique at temperatures of 40 and 65 K and the characteristics of the resulting trapped field profile are investigated with a view of magnetizing such samples as trapped field magnets (TFMs) in situ inside a trapped flux-type superconducting electric machine. A comparison is made between the temperatures at which the pulsed magnetic field is applied and the results have strong implications for the optimum operating temperature for TFMs in trapped flux-type superconducting electric machines. The effects of inhomogeneities, which occur during the growth process of single-grain bulk superconductors, on the trapped field and maximum temperature rise in the sample are modelled numerically using a 3D finite-element model based on the H-formulation and implemented in Comsol Multiphysics 4.3a. The results agree qualitatively with the observed experimental results, in that inhomogeneities act to distort the trapped field profile and reduce the magnitude of the trapped field due to localized heating within the sample and preferential movement and pinning of flux lines around the growth section regions (GSRs) and growth sector boundaries (GSBs), respectively. The modelling framework will allow further investigation of various inhomogeneities that arise during the processing of (RE)BCO bulk superconductors, including inhomogeneous Jc distributions and the presence of current-limiting grain boundaries and cracks, and it can be used to assist optimization of processing and PFM techniques for practical bulk superconductor applications. © 2014 IOP Publishing Ltd.

Evaluation of soot particles of biomass fuels with endocrine-modulating activity in yeast-based bioassay

Exposure to indoor air pollution (IAP) from the combustion of biomass fuels is an important cause of morbidity and mortality in developing countries. In the work discussed in this paper we evaluated the endocrine activity of soot particles from biomass fuels by using yeast bioassay. These pollutants could have beta-galactosidase activity with a relative potency (RP) about 10(-7)-10(-9) that of estradiol. Soot particles from wood and straw combustion only partially induced beta-galactosidase activity whereas others produced fully inductive activity in the yeast assay system. These pollutants did not have estrogen antagonist and progesterone agonist activity within the defined concentration range. However, these pollutants require 2-4 orders of magnitude higher IC50 to inhibit the activity of progesterone in a similar dose-response manner to mifepristone. We therefore propose that the endocrine activity of some environmental pollutants may be because of inhibition of the progesterone receptor (hPR). GC-MS results showed that substituted polycyclic aromatic hydrocarbon (PAH) compounds, substituted phenolic compounds and derivatives, aromatic carbonyl compounds, and phytosteroids in these soot particles may be mimicking endogenous hormones.

A trapped field of 17.6 T in melt-processed, bulk Gd-Ba-Cu-O reinforced with shrink-fit steel

The ability of large-grain (RE)Ba2Cu3O7-δ ((RE)BCO; RE = rare earth) bulk superconductors to trap magnetic fields is determined by their critical current. With high trapped fields, however, bulk samples are subject to a relatively large Lorentz force, and their performance is limited primarily by their tensile strength. Consequently, sample reinforcement is the key to performance improvement in these technologically important materials. In this work, we report a trapped field of 17.6 T, the largest reported to date, in a stack of two silver-doped GdBCO superconducting bulk samples, each 25 mm in diameter, fabricated by top-seeded melt growth and reinforced with shrink-fit stainless steel. This sample preparation technique has the advantage of being relatively straightforward and inexpensive to implement, and offers the prospect of easy access to portable, high magnetic fields without any requirement for a sustaining current source. © 2014 IOP Publishing Ltd.

Infection and propagation of lymphocystis virus isolated from the cultured flounder Paralichthys olivaceus in grass carp cell lines

The causative agent of lymphocystis disease that frequently occurs in cultured flounder Paralichthys olivaceus in China is lymphocystis virus (LV). In this study, 13 fish cell lines were tested for their susceptibility to LV. Of these, 2 cell lines derived from the freshwater grass carp Ctenopharyngodon idellus proved susceptible to the LV, and 1 cell line, GCO (grass carp ovary), was therefore used to replicate and propagate the virus. An obvious cytopathic effect (CPE) was first observed in cell monolayers at 1 d post-inoculation, and at 3 d this had extended to about 75% of the cell monolayer. However, no further CPE extension was observed after 4 d. Cytopathic characteristics induced by the LV were detected by Giemsa staining and fluorescence microscopic observation with Hoechst 33258 staining. The propagated virus particles were also observed by electron microscopy. Ultrastructure analysis revealed several distinct cellular changes, such as chromatin compaction and margination, vesicle formation, cell-surface convolution, nuclear fragmentation and the occurrence of characteristic 'blebs' and cell fusion. This study provides a detailed report of LV infection and propagation in a freshwater fish cell line, and presents direct electron microscopy evidence for propagation of the virus in infected cells. A possible process by which the CPEs are controlled is suggested.

Transparent and Light-Emitting Epoxy Super-Nanocomposites Containing ZnO-QDs/SiO2 Nanocomposite Particles as Encapsulating Materials for Solid-State Lighting

In this article, the ZnO quantum dots-SiO2 (Z-S) nanocomposite particles were first synthesized. Transparent Z-S/epoxy super-nanocomposites were then prepared by introducing calcined Z-S nanocomposite particles with a proper ratio of ZnO to SiO2 into a transparent epoxy matrix in terms of the filler-matrix refractive index matching principle. It was shown that the epoxy super-nanocomposites displayed intense luminescence with broad emission spectra. Moreover, the epoxy super-nanocomposites showed the interesting afterglow phenomenon with a long phosphorescence lifetime that was not observed for ZnO-QDs/epoxy nanocomposites. Finally, the transparent and light-emitting Z-S/epoxy super-nanocomposites were successfully employed as encapsulating materials for synthesis of highly bright LED lamps.

Development of current-based microscopic defect analysis method using optical filling techniques for the defect study on heavily irradiated high-resistivity Si sensors/detectors

Current-based microscopic defect analysis method such as current deep level transient spectroscopy (I-DLTS) and thermally stimulated current have been developed over the years at Brookhaven National Laboratory (BNL) for the defect characterizations on heavily irradiated (Phi(n) >= 10(13) n/cm(2)) high-resistivity (>= 2 k Omega cm) Si sensors/detectors. The conventional DLTS method using a capacitance transient is not valid on heavily irradiated high-resistivity Si sensors/detectors. A new optical filling method, using lasers with various wavelengths, has been applied, which is more efficient and suitable than the traditional voltage-pulse filling. Optimum defect-filling schemes and conditions have been suggested for heavily irradiated high-resistivity Si sensors/detectors. (c) 2006 Published by Elsevier Ltd.

Nonadiabatic geometric quantum computation with trapped ions

We propose a nonadiabatic scheme for geometric quantum computation with trapped ions. By making use of the Aharonov-Anandan phase, the proposed scheme not only preserves the globally geometric nature in quantum computation, but also provides the advantage of nonadiabaticity that overcomes the problem of slow evolution in the existing adiabatic schemes. Moreover, the present scheme requires only two atomic levels in each ion, making it an appealing candidate for quantum computation.

Assembly of side-functional monomers with inorganic nanometer particles

Monomers of methacrylate with various pi -conjugated pendants were designed and prepared in our laboratory, The monomer with suitable end-group was successfully assembled with nano-scale inorganic particles to form an orderly-aligned structure that showed special optical properties, both absorption and emission band were much red-shifted compared with the monomer, A new type of organic/inorganic hybrid materials was obtained by in situ polymerization of the assembly, The hybrid materials could also show special optical properties as the assembly, This might open a new route to tune the emission color.

Comparison of cooling rates for hot carriers in GaAs AlAs quantum wells based on macroscopic and microscopic phonon models

By using three analytical phonon models in quantum wells-the slab model, the guided-mode model, and the improved version of the Huang-Zhu model [Phys. Rev. B 38, 13 377 (1998)], -and the phonon modes in bulk, the energy-loss rates of hot carriers due to the Frohlich potential scattering in GaAs/AlAs multiple quantum wells (MQW's) are calculated and compared to those obtained based on a microscopic dipole superlattice model. In the study, a special emphasis is put on the effects of the phonon models on the hot-carrier relaxation process when taking the hot-phonon effect into account. Our numerical results show that, the calculated energy-loss rates based on the slab model and on the improved Huang-Zhu model are almost the same when ignoring the hot-phonon effect; however, with the hot phonon effect considered, the calculated cooling rate as well as the hot phonon occupation number do depend upon the phonon models to be adopted. Out of the four analytical phonon models investigated, the improved Huang-Zhu model gives the results most close to the microscopic calculation, while the guided-mode model presents the poorest results. For hot electrons with a sheet density around 10(12)/cm(2), the slab model has been found to overestimate the hot-phonon effect by more than 40% compared to the Huang-Zhu model, and about 75% compared to the microscopic calculation in which the phonon dispersion is fully included. Our calculation also indicates that Nash's improved version [J. Lumin. 44, 315 (1989)] is necessary for evaluating the energy-loss rates in quantum wells of wider well width, because Huang-Zhu's original analytical formulas an only approximately orthogonal for optical phonons associated with small in-plane wave numbers. [S0163-1829(99)08919-5].

High-frequency ferromagnetic resonance on ultrafine cobalt particles

We report on high-frequency (300-700 GHz) ferromagnetic resonance (HF-FMR) measurements on cobalt superparamagnetic particles with strong uniaxial effective anisotropy. We derive the dynamical susceptibility of the system on the basis of an independent-grain model by using a rectangular approach. Numerical simulations give typical line shapes depending on the anisotropy, the gyromagnetic ratio, and the damping constant. HF-FMR experiments have been performed on two systems of ultrafine cobalt particles of different sizes with a mean number of atoms per particles of 150 +/- 20 and 310 +/- 20. In both systems, the magnetic anisotropy is found to be enhanced compared to the bulk value, and increases as the particle size decreases, in accordance with previous determinations from magnetization measurements. Although no size effect has been observed on the gyromagnetic ratio, the transverse relaxation time is two orders of magnitude smaller than the bulk value indicating strong damping effects, possibly originating from surface spin disorders.

Analysis of atomic force microscopic results of InAs islands formed by molecular beam epitaxy

Atomic force microscopy (AFM) measurements of nanometer-sized islands formed by 2 monolayers of InAs by molecular beam epitaxy have been carried out and the scan line of individual islands was extracted from raw AFM data for investigation. It is found that the base widths of nanometer-sized islands obtained by AFM are not reliable due to the finite size and shape of the contacting probe. A simple model is proposed to analyze the deviation of the measured value From the real value of the base width of InAs islands. (C) 1998 Elsevier Science B.V. All rights reserved.

High-field ferromagnetic resonance in fine particles

We investigate high-field ferromagnetic resonance of superparamagnetic particles with uniaxial anisotropy, In this case, since the field is large enough to saturate the magnetization, the thermal orientational fluctuations of the magnetic moment of the particle are negligible. Thus, we derive the dynamic susceptibility of the system on the basis of an independent particle model. High-field ferromagnetic resonance has been performed on fine cobalt particles, The analysis of the spectra obtained at different frequencies allows us to estimate the effective magnetic anisotropy, the gyromagnetic ratio, and the transverse relaxation time. (C) 1998 Elsevier Science B.V. All rights reserved.

Formation, structure and fluorescence of CdS clusters in a mesoporous zeolite

CdS clusters are formed in the pores of a mesoporous zeolite in which the size of the clusters may be adjusted. The size of the clusters increases as the CdS loading is increased. X-ray diffraction investigation shows that the lattice constants of the clusters contract upon increasing size. This contraction is attributed to an increase of the static pressure exercised by the zeolite framework as the clusters grow bigger. Both the excitonic and trapped emission bands are detected and become more intensive upon decreasing size. Three absorption bands appear in the photoluminescence excitation (PLE) spectra and they shift to the blue as cluster size decreases. Based on the effective-mass approximation, the three bands are assigned to the 1S-1S, 1S-1P and 1S-1D transitions, respectively. The size-dependence of the PLE spectra can also be explained. (C) 1997 Elsevier Science Ltd.

Development of current-based microscopic defect analysis method using optical filling techniques for the defect study on heavily irradiated high-resistivity Si sensors/detectors

Current-based microscopic defect analysis method such as current deep level transient spectroscopy (I-DLTS) and thermally stimulated current have been developed over the years at Brookhaven National Laboratory (BNL) for the defect characterizations on heavily irradiated (Phi(n) >= 10(13) n/cm(2)) high-resistivity (>= 2 k Omega cm) Si sensors/detectors. The conventional DLTS method using a capacitance transient is not valid on heavily irradiated high-resistivity Si sensors/detectors. A new optical filling method, using lasers with various wavelengths, has been applied, which is more efficient and suitable than the traditional voltage-pulse filling. Optimum defect-filling schemes and conditions have been suggested for heavily irradiated high-resistivity Si sensors/detectors. (c) 2006 Published by Elsevier Ltd.