Academic Services Division - Papers

Tuning core-shell SiO2@CdTe@SiO2 fluorescent nanoparticles for cell labeling

Yian Zhu — Fri, 03 May 2013 00:00:18 PDT

Highly fluorescent SiO2@CdTe@SiO2 (SQS) nanoparticles as a new nanoprobe in biomedical imaging have been successfully synthesized by a novel approach. The size of SQS can be tuned from 39 to 76 nm by controlling reaction parameters, including the amount and the type of silica precursor, the ratio of silica precursor to ammonia solution, and the ratio of H2O to surfactant. The photo- and chemical stability, cytotoxicity and cell uptake of these nanoparticles were investigated. The results demonstrate that these properties are strong size-dependent, and reveal that the minimal shell thickness for effective protection of the embedded CdTe quantum dots is 6 nm. Our findings highlight the importance of controlling particle size and shell thickness during the preparation of fluorescent silica-QDs core-shell nanoparticles, and their potential in cell labeling and imaging. This journal is The Royal Society of Chemistry.

A solid-state pH sensor for nonaqueous media including ionic liquids

Brianna C. Thompson — Thu, 02 May 2013 23:55:09 PDT

We describe a solid state electrode structure based on a biologically derived proton-active redox center, riboflavin (RFN). The redox reaction of RFN is a pH-dependent process that requires no water. The electrode was fabricated using our previously described 'stuffing' method to entrap RFN into vapor phase polymerized poly(3,4-ethylenedioxythiophene). The electrode is shown to be capable of measuring the proton activity in the form of an effective pH over a range of different water contents including nonaqueous systems and ionic liquids (ILs). This demonstrates that the entrapment of the redox center facilitates direct electron communication with the polymer. This work provides a miniaturizable system to determine pH (effective) in nonaqueous systems as well as in ionic liquids. The ability to measure pH (effective) is an important step toward the ability to customize ILs with suitable pH (effective) for catalytic reactions and biotechnology applications such as protein preservation. 2013 American Chemical Society.

Single-pulse terahertz coherent control of spin resonance in the canted antiferromagnet YFeO3, mediated by dielectric anisotropy

Zuanming Jin — Thu, 02 May 2013 23:50:10 PDT

We report on the coherent control of terahertz (THz) spin waves in a canted antiferromagnet yttrium orthoferrite, YFeO3, associated with a quasiferromagnetic (quasi-FM) spin resonance at a frequency of 0.3 THz, using a single-incident THz pulse. The spin resonance is excited impulsively by the magnetic field component of the THz pulse. The intrinsic dielectric anisotropy of YFeO3 in the THz range allows for coherent control of both the amplitude and the phase of the excited spin wave. The coherent control is based on simultaneous generation of two interfering phase-shifted spin waves whose amplitudes and relative phase, dictated by the dielectric anisotropy of the YFeO3 crystal, can be controlled by varying the polarization of the incident THz pulse with respect to the crystal axes. The spatially anisotropic decay of the THz-excited FM spin resonance in YFeO3, leading to an increasingly linear polarization of the THz oscillation at the spin resonance frequency, suggests a key role of magnon-phonon coupling in spin-wave energy dissipation. 2013 American Physical Society.

Single step, pH induced gold nanoparticle chain formation in lecithin/water system

Damyanti Sharma — Thu, 02 May 2013 23:50:10 PDT

Gold nanoparticle (AuNP) chains have been formed by a single step method in a lecithin/water system where lecithin itself plays the role of a reductant and a template for AuNP chain formation. Two preparative strategies were explored: (1) evaporating lecithin solution with aqueous gold chloride (HAuCl4) at different pHs and (2) dispersing lecithin vesicles in aqueous HAuCl4 solutions of various pHs in the range of 2.5-11.3. In method 1, at initial pH 2.5, 20-50nm AuNPs are found attached to lecithin vesicles. When pH is raised to 5.5 there are no vesicles present and 20nm monodisperse particles are found aggregating. Chain formation of fine nanoparticles (3-5nm) is observed from neutral to basic pH, between 6.5-10.3 The chains formed are hundreds of nanometers to micrometer long and are usually 2-3 nanoparticles wide. On further increasing pH to 11.3, particles form disk-like or raft-like structures. When method (ii) was used a little chain formation was observed. Most of the nanoparticles formed were found either sitting together as raft like structures or scattered on lecithin structures. 2013 Elsevier B.V.

Phase stability and elastic properties of chromium borides with various stoichiometries

Bing Wang — Thu, 02 May 2013 23:40:10 PDT

Phase stability is important to the application of materials. By first-principles calculations, we establish the phase stability of chromium borides with various stoichiometries. Moreover, the phases of CrB3 and CrB4 have been predicted by using a newly developed particle swarm optimization (PSO) algorithm. Formation enthalpy-pressure diagrams reveal that the MoB-type structure is more energetically favorable than the TiI-type structure for CrB. For CrB2, the WB2-type structure is preferred at zero pressure. The predicted new phase of CrB3 belongs to the hexagonal P-6m2 space group and it transforms into an orthorhombic phase as the pressure exceeds 93 GPa. The predicted CrB4 (space group: Pnnm) phase is more energetically favorable than the previously proposed Immm structure. The mechanical and thermodynamic stabilities of predicted CrB 3 and CrB4 are verified by the calculated elastic constants and formation enthalpies. The full phonon dispersion calculations confirm the dynamic stability of WB2-type CrB2 and predicted CrB3. The large shear moduli, large Young's moduli, low Poisson ratios, and low bulk and shear modulus ratios of CrB4-PS C and CrB4-PSD indicate that they are potential hard materials. Analyses of Debye temperature, electronic localization function, and electronic structure provide further understanding of the chemical and physical properties of these borides. Mix and match: Two new structures of CrB3 (P-6m2 and Pmmn) are predicted by using a newly developed particle swarm optimization (PSO) algorithm and the experimental structures of CrB4 (Immm and Pnnm) are also reproduced successfully (see picture). The strong covalent Cr-B bonding in CrB4 induced hardness and the Pnnm phase is thermodynamically stable up to 100 GPa. Copyright 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of dopant pK(a) and the solubility of corresponding acid on the electropolymerisation of pyrrole

Eimear M. Ryan — Thu, 02 May 2013 23:40:10 PDT

In this paper, attempts to dope polypyrrole (PPy) with two small sized anionic drugs, diclofenac sodium salt (NaDF) and valproic acid sodium salt (NaVPA), are described. For PPy doped with DF-, unusual patterns in growth and morphology were observed. During the deposition of the polymer, the rate of electropolymerisation decreased with increasing time and higher applied potentials. The polymer had features of an insulating film, while SEM confirmed the presence of crystal-like shards on the surface of the polymer. Analyses of these crystals indicate them to be drug that may have precipitated out of solution. These findings suggest that insoluble drug crystals are formed during electropolymerisation. The formation of PPy doped with a small soluble anti-epilepsy anionic drug, VPA(-), was also studied; however it was not possible to incorporate this drug during electrochemical polymerisation. Again, this was explained in terms of the equilibrium between the anion and the acid forms of VPA. At pH values below 5.6, the equilibrium of the VPA- is shifted towards the insoluble HVPA. As the monomer is oxidised, there is a decrease in the local pH in the vicinity of the electrode and this causes the HVPA to precipitate from solution. This, in turn, prevents any PPy from being deposited at the electrode. (C) 2012 Elsevier Ltd. All rights reserved.

Come here Aeneas, I want you

Victoria Willis — Thu, 02 May 2013 23:30:17 PDT

'The epoch of logocentrism is a moment of the global effacement of the signifier', writes Derrida in Of Grammatology.3 Logocentrism fantasizes writing as a transcription of, or as a transparent vehicle for, speech; similarly, it fantasizes speech as a transparent vehicle for the communication of signifieds between a speaker and a listener who are present to each other. In other words, logocentrism's 'effacement of the signifier' means that writing is thought as a medium for the communication of signifieds across space and through time, merely extending the range of speech, which in turn is thought as a transparent medium of presence-to-presence communication across space and through time.4 This fantasy is enabled by the invention of phonetic writing. It is this technological moment which enables logocentrism's effacement of the signifier, that is, of technologies of inscription: it aims at suppressing consideration of historically and technologically specific organizations of the relationship between speech, writing, and presence in space and time, as well as of the labour of writing, speaking, reading and listening.

Supporting the language and learning development of EAL students in Australian Higher Education

Paul J. Moore — Thu, 02 May 2013 23:25:09 PDT

The role of learning advising in improving the educational outcomes of students for whom English is an additional language (EAL) in Australian universities has received significant attention in recent years. A combination of research findings, governmental pressure and media scrutiny has provided renewed impetus for universities to address issues of language proficiency and academic literacy amongst the growing population of onshore international students for whom English is an additional language (EAL). In this paper, I discuss the role of academic language and learning advising in the Australian university context, including how this practice is influenced by a range of political, pedagogical and practical factors. In doing so, I draw on Carson and Mynard's (2012) analysis of the aims, practices, skills, locations and discourses of advising in language learning to explore how the two fields might inform each other.

Finite element modeling of hybrid FRP-concrete-steel tubular columns under axial compression

Tao Yu — Thu, 02 May 2013 23:25:09 PDT

Hybrid FRP-concrete-steel double-skin tubular columns: An overview of existing research

Tao Yu — Thu, 02 May 2013 23:20:09 PDT

Hybrid FRP concrete steel double-skin tubular columns (DSTCs) are a new form of hybrid columns recently proposed by the second author. The column consists of an outer tube made of fiber-reinforced polymer (FRP) and an inner tube made of steel, with the space between filled with concrete. In this new form of hybrid columns, the three constituent materials are optimally combined to achieve several advantages not available with existing columns. This paper provides a summary of existing research on this new form of structural members, clarifying its structural behavior under axial compression, bending, and combined axial compression and bending. Test results of hybrid DSTCs are presented that demonstrate that they are very ductile under different loading conditions. A finite element (FE) model for its axial compressive behavior is also presented, which was employed in a parametric study leading to a simple stress-strain model for the confined concrete in hybrid DSTCs described in the paper. In addition, a conventional section analysis based on the plane section assumption and the fiber element approach is presented for predicting the behavior of hybrid DSTCs subjected to bending and eccentric compression. A variable confinement model that accounts for the effect of load eccentricity is adopted in this section analysis for the confined concrete, and is recommended for design use.

Are there differences between disabled and normal readers in their processing of visual information

Dale Willows — Thu, 02 May 2013 23:20:09 PDT

Disabled-normal reader comparisons have represented a major research approach to investigating the possible involvement of visual processing deficits in reading disabilities. Studies using this approach have normally tested the performance of disabled and normal readers on one or more tasks thought to be tapping some aspect of visual processing to determine whether the disabled readers have significantly more difficulty. Conclusions about whether or not there is evidence of visual processing differences between disabled and normal readers are mixed: Some researchers and theoreticians have contended that the evidence shows disabled readers do not differ from normal readers in their processing of visual information (e.g., Calfee, 1983; Stanovich, 1985; Vellutino, 1979, 1987), whereas others have concluded the contrary (e.g., Di Lollo, Hansen, & MacIntyre, 1983; Lovegrove, Martin, & Slaghuis, 1986; Willows, Kershner, & Corcos, 1986). The conclusion drawn may depend on the stage of processing under investigation.

Visual temporal processing deficits in specific reading disability

William Lovegrove — Thu, 02 May 2013 23:15:10 PDT

Specific reading disability is a broad term encompassing reading disabilities that may arise from a number of sources. A specific-reading-disabled child (SRD) is defined here as one of normal or better intelligence with no known behavioral or organic disorders who, despite normal schooling and average progress in other subjects, has a reading disability of at least 1.5 years. Because reading is a dynamic visual processing task requiring the analysis and integration of visual pattern information across fixation-saccade sequences, studies in the area of reading disability have explored the possibility that visual processing abnormalities contribute to reading difficulties. A number of studies have provided evidence for basic visual processing differences between normal and disabled readers, especially at early stages of visual processing ( Lovegrove & Brown, 1978; Stanley, 1975). These results indicate that some disabled readers process information more slowly and have a more limited processing capacity than normal readers. Studies that used tasks relying less on dynamic visual processing and temporal resolution, and more on pattern-formation processes and long-term visual memory, however, have failed to show visual processing differences between normal and disabled readers ( Benton, 1975; Vellutino, 1979), although the validity of some of these studies has been called into question ( Fletcher & Satz, 1979). Thus the long-standing debate as to whether visual factors play a significant role in reading disabilities has been complicated by the differences in methodological factors and the failure to distinguish between the measurement of temporal versus pattern-formation processes. In the following section an approach to vision that considers different mechanisms for the processing of temporal and pattern information is outlined.

Processing text on monitors

Richard Kruk — Thu, 02 May 2013 23:15:10 PDT

The display of text on computer screens is commonplace for a variety of purposes--electronic journals, library cataloging, computer networks, computeraided instruction and design, desktop publishing, and electronic-mail are some examples--and the range of day-to-day applications is expanding. As the use of computer monitors for information processing and disseminating activities increases, the importance of maintaining or improving reading performance with text presented on monitors becomes critical. Recent research activity, investigating text displayed on monitors, has focused on questions of legibility and readability. These issues have enjoyed a renewed interest since the introduction of computer monitors to display reading materials; investigators have become aware of the possibility that findings from previous research on printed text may not transfer to computer monitor presentation of text ( Daniel & Reinking, 1987). This is evident in data that have shown performance differences between paper and monitor reading. Although the findings are mixed ( Reinking & Bridwell- Bowles , 1991), comparison studies of monitor and paper text presentation have shown that reading from a monitor is slower than reading from paper (e.g., Gould & Grischkowsky, 1984; Heppner, Anderson, Farstrup, & Weiderman, 1985; Kruk & Muter, 1984). A number of variables have been proposed to account for the difference, both in terms of the physical characteristics of monitors and in terms of how text is displayed.