A new preparation of zinc sulfide nanoparticles by solid-state method at low temperature

A novel solid-state method of the preparation of zinc sulfide nanoparticles is reported. By solid-state reaction of zinc acetate and thioacetamide at low temperature, zinc sulfide nanoparticles of different sizes were prepared. The temperature of preparation varied from room temperature to 300 degrees C. The particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA), and photoluminescence spectrum. X-ray diffraction patterns revealed that the particles exhibited pure zinc-blende crystal structure and that particle size increased with increasing temperature. The TEM micrograph showed that the mean particle size was about 40 nm for the sample heated at 100 degrees C. A blue shift was observed in the photoluminescence emission spectrum. A possible mechanism of the reaction corresponding to our observation is proposed, (C) 2000 Elsevier Science Ltd. All rights reserved.

Investigation into self-assembled monolayers of a polyether dendron thiol: Chemisorption, kinetics, and patterned surface

Different sizes of Frechet-type dendrons with a thiol group at the focal point were synthesized, well characterized, and used as building blocks for the preparation of self-assembled monolayers (SAMs) on metal surfaces. From the studies of the kinetic process of dendron thiol self-assembling on gold, it is shown that the dendron thiol assembling proceeds with different adsorption rates depending on the assembly time. In contrast to normal alkanethiols forming highly molecular structures on metal surfaces, the SAMs of polyether dendron form patterned surfaces with nanometer-sized features and in long-range order. It is found that the patterned stripes are closely related to the size of the dendron, and the patterned stripes can be improved by thermal annealing.

Fabrication of nanometer-sized electrodes and tips for scanning electrochemical microscopy

A novel method for fabrication of nanometer-sized electrodes and tips suitable for scanning electrochemical microscopy (SECM) is reported. A fine etched Pt wire is coated with polyimide, which was produced by polymerization on the Pt surface initiated by heat. This method can prepare electrodes with effective radii varying from a few to hundreds of nanometers. Scanning electron microscopy, cyclic voltammetry, and SECM were used to characterize these electrodes. Well-defined steady-state voltammograms could be obtained in aqueous or in 1,2-dichloroethane solutions. Ibis method produced the nanoelectrodes with exposed Pit on the apex, and they can also be employed as the nanotips for SECM investigations. Different sizes of Pt nanotips made by this method were employed to evaluate the kinetics of the redox reaction of Ru(NH3)6(3+) on the surface of a large Pt electrode by SECM, and the standard rate constant kappa (o) of this system was calculated from the best fit of the SECM approach curve. This result is similar to the values obtained by analysis of the obtained voltammetric data.

Surface photovoltage spectra and photoelectrochemical properties of semiconductor-sensitized nanostructured TiO2 electrodes

Three kinds of TiO2 nanostructured thin films and their CdS-sensitized films, consisting of different sizes of TiO2 nanoparticles prepared with different methods, have been investigated. The surface photovoltage spectra (SPS) measurements indicate that the density of surface states on TiO2 is likely dependent upon the details of prepared methods. TiO2 particles prepared from basic sol have more surface states than that prepared from acidic sol. When the TiO2 thin films prepared using the TiO2 sols were sensitized by CdS particles, the SPS responses relative to the surface states on TiO2 from 350 to 800 nm were decreased. The photoelectrochemical properties of nanostructured TiO2 electrodes suggest that the fewer the surface states and the smaller the particle sizes of TiO2, the larger the photocurrent response. For CdS sensitized TiO2 thin film electrode, it is shown that the semiconductor sensitization is an efficient way to decrease the influence of surface states on the charge separation, and can improve the intensity of photocurrent response. (C) 2001 Elsevier Science B.V. All rights reserved.

Synthesis and properties of cerium oxide nanometer powders by pyrolysis of amorphous citrate

CeO2 nanometer powders of different sizes were prepared at low temperature by pyrolysis of amorphous citrate. XRD patterns show that CeO2 is cubic in structure, space group O-h(5)-F-M3M. TEM indicates that the prepared CeO2 is spherical in shape, and the particle size distribution is in narrow range. It was found that calcination temperature is a more important factor affecting the crystallite size of CeO2 than calcining time, the smaller the particle, the bigger the crystal lattice distortion, the worse the crystal growth. Solubility test of CeO2 in nitric acid reveals that the surface activity of CeO2 decreases with the increasing particle sizes. IR spectra analysis shows that the absorption of Ce-O bond is shifted to higher energy with the decrease of CeO2 particle sizes.

MICROSTRUCTURE ANALYSIS OF 3 SEGMENTED COPOLYMERS CONTAINING POLYDIMETHYLSILOXANE BY SOLID-STATE HIGH-RESOLUTION NMR

The microstructure of two bicomponent and one tricomponent segmented copolymers, based on polydimethylsiloxane, poly(p-hydroxystyrene) or/and polysulfone, were investigated using an extended Goldman-Shen pulse sequence, proton spin-spin relaxation measurements, and C-13 and Si-29 NMR spectra. The results indicate that there exist four phases with different sizes, components and morphological structure in the segmented copolymers studied in this work, i. e., a rigid-chain phase of very slow motion, a rigid-chain-rich phase of slow motion, a flexible-chain-rich phase of fast motion and a flexible-chain phase of faster motion. The sizes of different domains, calculated from the spin diffusion rates, are about 50-100 angstrom for the flexible-chain-rich phase of fast motion and 200-300 angstrom for the flexible-chain phase of faster motion. The relative quantities of polydimethylsiloxane in the flexible-chain phase of fast motion are slightly different in different kinds of segmented copolymers.

Effects of Irradiance and Temperature on the Photosynthesis and Vegetative Propagation of Caulerpa serrulata

The photosynthetic oxygen evolution of Caulerpa serrulata was determined with oxygen electrodes. The effects of light and temperature on the growth and regeneration of fragmented C. serrulata thalli were analyzed. The regenerating rate and establishment of different sizes and portions of C. serrulata were studied. The results showed that the light saturation point of C. serrulata was 200 mu mol photons/m(2) per s and the optimum growth temperature was 25-30 degrees C. Under these conditions, the maximum photosynthetic oxygen evolution rate was 15.1 +/- 0.29 mg O-2/mg Chl a/h, the growth rate and elongation rate reached the highest values, 4.67 +/- 0.09 mg FW/d and 0.78 +/- 0.01 mm/d, respectively. The fragmented C. serrulata thalli was regenerated at 20-35 degrees C and survived at 15 degrees C and 200 mu mol photons/m(2) per s. A different survival rate was detected according to fragment size. All of these results indicated that C. serrulata was a candidate to become an invasive species if introduced into a new place. Therefore, we should pay more attention to C. serrulata for its potential threat to marine ecosystem when it is sold for aquarium use.

Identification of Crassostrea ariakensis and related oysters by multiplex species-specific PCR

Genetic markers are needed for rapid and reliable identification of oysters. In this study, we developed multiplex genus- and species-specific PCR markers for the identification of oysters from China. We used the mitochondrial cytochrome oxidase I (COI) and nuclear 28S ribosomal RNA genes for marker development. DNA sequences from different species were obtained from GenBank or by direct sequencing. Sequences were aligned, and genus- and species-specific nucleotides were identified. Primers were designed for genus/species-specific amplification to generate fragments of different sizes. A multiplex set of genus- and species-specific primers from the 28S gene was able to separate C. ariakensis and C. hongkongensis from other species and assign oysters to four genera. A set of species-specific COI primers provided positive identification of all five Crassostrea species from China, C. ariakensis, C. hongkongensis, C. angulata, C. gigas, and C. sikamea in a single PCR. The multiplex PCR assays do not require fluorescence-labeling or post-PCR enzyme digestion, providing a simple, fast and reliable method for the identification of oysters from China.

The mixing of bubbles in two-dimensional bidisperse foams under extensional shear

Cox, S.J. (2006) The mixing of bubbles in two-dimensional bidisperse foams under extensional shear. Journal of Non-Newtonian Fluid Mechanics . 137:39-45.

Identifying vibrations that destabilize crystals and characterize the glassy state

Greaves, George; Meneau, F.; Majerus, O.; Jones, D.G., (2005) 'Identifying vibrations that destabilize crystals and characterize the glassy state', Science 308(5726) pp.1299-1302 RAE2008

Au nanorods-semiconductor nanowire hybrid nanostructures : nanofabrication techniques and optoelectronic properties

The objective of this thesis is the exploration and characterization of novel Au nanorod-semiconductor nanowire hybrid nanostructures. I provide a comprehensive bottom-up approach in which, starting from the synthesis and theoretical investigation of the optical properties of Au nanorods, I design, nanofabricate and characterize Au nanorods-semiconductor nanowire hybrid nanodevices with novel optoelectronic capabilities compared to the non-hybrid counterpart. In this regards, I first discuss the seed-mediated protocols to synthesize Au nanorods with different sizes and the influence of nanorod geometries and non-homogeneous surrounding medium on the optical properties investigated by theoretical simulation. Novel methodologies for assembling Au nanorods on (i) a Si/SiO2 substrate with highly-ordered architecture and (ii) on semiconductor nanowires with spatial precision are developed and optimized. By exploiting these approaches, I demonstrate that Raman active modes of an individual ZnO nanowire can be detected in non-resonant conditions by exploring the longitudinal plasmonic resonance mediation of chemical-synthesized Au nanorods deposited on the nanowire surface otherwise not observable on bare ZnO nanowire. Finally, nanofabrication and detailed electrical characterization of ZnO nanowire field-effect transistor (FET) and optoelectronic properties of Au nanorods - ZnO nanowire FET tunable near-infrared photodetector are investigated. In particular we demonstrated orders of magnitude enhancement in the photocurrent intensity in the explored range of wavelengths and 40 times faster time response compared to the bare ZnO FET detector. The improved performance, attributed to the plasmonicmediated hot-electron generation and injection mechanism underlying the photoresponse is investigated both experimentally and theoretically. The miniaturized, tunable and integrated capabilities offered by metal nanorodssemicondictor nanowire device architectures presented in this thesis work could have an important impact in many application fields such as opto-electronic sensors, photodetectors and photovoltaic devices and open new avenues for designing of novel nanoscale optoelectronic devices.

Fiber-optic interferometric two-dimensional scattering-measurement system.

We present a fiber-optic interferometric system for measuring depth-resolved scattering in two angular dimensions using Fourier-domain low-coherence interferometry. The system is a unique hybrid of the Michelson and Sagnac interferometer topologies. The collection arm of the interferometer is scanned in two dimensions to detect angular scattering from the sample, which can then be analyzed to determine the structure of the scatterers. A key feature of the system is the full control of polarization of both the illumination and the collection fields, allowing for polarization-sensitive detection, which is essential for two-dimensional angular measurements. System performance is demonstrated using a double-layer microsphere phantom. Experimental data from samples with different sizes and acquired with different polarizations show excellent agreement with Mie theory, producing structural measurements with subwavelength accuracy.

Task-driven adaptive statistical compressive sensing of gaussian mixture models

A framework for adaptive and non-adaptive statistical compressive sensing is developed, where a statistical model replaces the standard sparsity model of classical compressive sensing. We propose within this framework optimal task-specific sensing protocols specifically and jointly designed for classification and reconstruction. A two-step adaptive sensing paradigm is developed, where online sensing is applied to detect the signal class in the first step, followed by a reconstruction step adapted to the detected class and the observed samples. The approach is based on information theory, here tailored for Gaussian mixture models (GMMs), where an information-theoretic objective relationship between the sensed signals and a representation of the specific task of interest is maximized. Experimental results using synthetic signals, Landsat satellite attributes, and natural images of different sizes and with different noise levels show the improvements achieved using the proposed framework when compared to more standard sensing protocols. The underlying formulation can be applied beyond GMMs, at the price of higher mathematical and computational complexity. © 1991-2012 IEEE.

Testing the role of expansion in the prospective control of locomotion

The constant bearing angle (CBA) strategy is a prospective strategy that permits the interception of moving objects. The purpose of the present study is to test this strategy. Participants were asked to walk through a virtual environment and to change, if necessary, their walking speed so as to intercept approaching targets. The targets followed either a rectilinear or a curvilinear trajectory and target size was manipulated both within trials (target size was gradually changed during the trial in order to bias expansion) and between trials (targets of different sizes were used). The curvature manipulation had a large effect on the kinematics of walking, which is in agreement with the CBA strategy. The target size manipulations also affected the kinematics of walking. Although these effects of target size are not predicted by the CBA strategy, quantitative comparisons of observed kinematics and the kinematics predicted by the CBA strategy showed good fits. Furthermore, predictions based on the CBA strategy were deemed superior to predictions based on a required velocity (V-REQ) model. The role of target size and expansion in the prospective control of walking is discussed.

Assessing the Transaction Costs of Firms in the EU ETS: Lessons form Ireland

Until now, there has been little empirical evidence that EU Emissions Trading Scheme (ETS) transaction costs are incurred at firm level. The transaction costs (internal costs, capital costs, consultancy and trading costs) incurred by Irish firms under the EU ETS during its pilot phase (2005-2007) were measured and analysed. Evidence for the sources of transaction costs, their magnitude and the distribution of costs shows that these were mainly administrative in nature. Considerable variation in costs was found due to economies of scale, as the costs per tonne of CO2 were lower for participants with larger allocations. For the largest firms - accounting for over half the emissions - average transaction costs were €0.05 per tonne. However, for small firms, average transaction costs were €2.02 - over 18% of the current allowance price. This supports the concerns that transaction costs are excessive for smaller participants. The immediate policy implication is that additional attention will be needed to address different sizes of firms, number of installations per firm, and the size of the initial allocations.