Showing papers by "Dublin City University published in 2008"

Improved Cosmological Constraints from New, Old, and Combined Supernova Data Sets

Abstract: We present a new compilation of Type Ia supernovae (SNe Ia), a new data set of low-redshift nearby-Hubble-flow SNe, and new analysis procedures to work with these heterogeneous compilations This "Union" compilation of 414 SNe Ia, which reduces to 307 SNe after selection cuts, includes the recent large samples of SNe Ia from the Supernova Legacy Survey and ESSENCE Survey, the older data sets, as well as the recently extended data set of distant supernovae observed with the Hubble Space Telescope (HST) A single, consistent, and blind analysis procedure is used for all the various SN Ia subsamples, and a new procedure is implemented that consistently weights the heterogeneous data sets and rejects outliers We present the latest results from this Union compilation and discuss the cosmological constraints from this new compilation and its combination with other cosmological measurements (CMB and BAO) The constraint we obtain from supernovae on the dark energy density is ΩΛ = 0713+ 0027−0029(stat)+ 0036−0039(sys) , for a flat, ΛCDM universe Assuming a constant equation of state parameter, w, the combined constraints from SNe, BAO, and CMB give w = − 0969+ 0059−0063(stat)+ 0063−0066(sys) While our results are consistent with a cosmological constant, we obtain only relatively weak constraints on a w that varies with redshift In particular, the current SN data do not yet significantly constrain w at z > 1 With the addition of our new nearby Hubble-flow SNe Ia, these resulting cosmological constraints are currently the tightest available

Optical chemical sensors.

Abstract: Optical chemical sensors have been the focus of much research attention in recent years because of their importance in industrial, environmental and biomedical applications [1]. This class of sensors combines chemical and biological recognition with advances in optoelectronic technologies. The application of solgel materials to these sensors, especially in the form of thin films, has attracted considerable interest due to the ease of fabrication and design flexibility of the process. The nature of the sol-gel process lends itself very well to the deposition of thin films using a variety of techniques such as dip-coating, spin-coating and spraying. In many sensor applications, the sol-gel film is used to provide a micro-porous support matrix in which analyte-sensitive molecules are entrapped and into which smaller analyte species may diffuse and interact [2,3]. Sol-gel films have many advantages as support matrices over polymer supports, including, for example, strong adhesion, good mechanical strength as well as excellent optical transparency. The versatility of the process facilitates tailoring of the physico-chemical film properties to optimize sensor performance. For example, films can be designed which have optimum porosity while minimizing leaching of the indicator molecules. In this chapter, the versatility of the sol-gel process with regard to the design of films for specific optical chemical sensor applications is highlighted.

Active commuting to school: How far is too far?

Abstract: Walking and cycling to school provide a convenient opportunity to incorporate physical activity into an adolescent's daily routine. School proximity to residential homes has been identified as an important determinant of active commuting among children. The purpose of this study is to identify if distance is a barrier to active commuting among adolescents, and if there is a criterion distance above which adolescents choose not to walk or cycle. Data was collected in 2003–05 from a cross-sectional cohort of 15–17 yr old adolescents in 61 post primary schools in Ireland. Participants self-reported distance, mode of transport to school and barriers to active commuting. Trained researchers took physical measurements of height and weight. The relation between mode of transport, gender and population density was examined. Distance was entered into a bivariate logistic regression model to predict mode choice, controlling for gender, population density socio-economic status and school clusters. Of the 4013 adolescents who participated (48.1% female, mean age 16.02 ± 0.661), one third walked or cycled to school. A higher proportion of males than females commuted actively (41.0 vs. 33.8%, χ2 (1) = 22.21, p < 0.001, r = -0.074). Adolescents living in more densely populated areas had greater odds of active commuting than those in the most sparsely populated areas (χ2 (df = 3) = 839.64, p < 0.001). In each density category, active commuters travelled shorter distances to school. After controlling for gender and population density, a 1-mile increase in distance decreased the odds of active commuting by 71% (χ2 (df = 1) = 2591.86, p < 0.001). The majority of walkers lived within 1.5 miles and cyclists within 2.5 miles. Over 90% of adolescents who perceived distance as a barrier to active commuting lived further than 2.5 miles from school. Distance is an important perceived barrier to active commuting and a predictor of mode choice among adolescents. Distances within 2.5 miles are achievable for adolescent walkers and cyclists. Alternative strategies for increasing physical activity are required for individuals living outside of this criterion.

Why hasn't technology disrupted academics' teaching practices? Understanding resistance to change through the lens of activity theory

Abstract: The advent of the Internet heralded predictions that e-learning would transform and disrupt teaching practices in higher education. E-learning also promised to expand opportunities for lifelong and flexible learning, and offered a panacea for practical issues such as decreased funding and increasing student numbers. The anticipated disruption to teaching and learning has not come to fruition however. Although technology is now common place in most higher education institutions - most institutions have invested in a virtual learning environment (VLE) and employ staff dedicated to supporting e-learning - there is little evidence of significant impact on teaching practices and current implementations are accused of being focused on improving administration and replicating behaviourist, content-driven models. This paper discusses a preliminary analysis, rooted in Activity Theory, of the transformation of teaching practices, which did or did not take place in our university following the institution-wide deployment of a VLE. In particular, factors limiting a full uptake of the VLE more advanced functionalities by the wider university community are explored.

Ultra-low shrinkage hybrid photosensitive material for two-photon polymerization microfabrication.

Abstract: Investigations into the structuring by two-photon polymerization of a nonshrinking, photosensitive, zirconium sol−gel material are presented This hybrid material can be photostructured even when it contains up to 30 mol % of zirconium propoxide (ZPO); by varying the material’s inorganic content, it is possible to modify and tune its refractive index The introduction of ZPO significantly increases the photosensitivity of the resulting photopolymer The fabricated three-dimensional photonic crystal structures demonstrate high resolution and a clear band-stop in the near-IR region In contrast to common practice, no additional effort is required to precompensate for shrinkage or to improve the structural stability of the fabricated photonic crystals; this, combined with the possibility of tuning this material’s optical, mechanical, and chemical properties, makes it suitable for a variety of applications by two-photon polymerization manufacturing

Green Consumption Life-politics, risk and contradictions

Abstract: In recent times, much has been written about consumers' co-responsibility for addressing environmental problems, with consumers expected to steer or regulate their consumption in an instrumental wa...

GaAs interfacial self-cleaning by atomic layer deposition

Abstract: The reduction and removal of surface oxides from GaAs substrates by atomic layer deposition (ALD) of Al2O3 and HfO2 are studied using in situ monochromatic x-ray photoelectron spectroscopy. Using the combination of in situ deposition and analysis techniques, the interfacial “self-cleaning” is shown to be oxidation state dependent as well as metal organic precursor dependent. Thermodynamics, charge balance, and oxygen coordination drive the removal of certain species of surface oxides while allowing others to remain. These factors suggest proper selection of surface treatments and ALD precursors can result in selective interfacial bonding arrangements.

NanoECC: testing the limits of elliptic curve cryptography in sensor networks

Abstract: By using Elliptic Curve Cryptography (ECC), it has been recently shown that Public-Key Cryptography (PKC) is indeed feasible on resource-constrained nodes This feasibility, however, does not necessarily mean attractiveness, as the obtained results are still not satisfactory enough In this paper, we present results on implementing ECC, as well as the related emerging field of Pairing-Based Cryptography (PBC), on two of the most popular sensor nodes By doing that, we show that PKC is not only viable, but in fact attractive for WSNs As far as we know pairing computations presented in this paper are the most efficient results on the MICA2 (8-bit/73828-MHz ATmega128L) and Tmote Sky (16-bit/8192-MHz MSP-430) nodes

Wireless sensor networks and chemo-/biosensing.

Abstract: 3.4.5. Example 5: Volcanic Activity 658 3.4.6. Example 6: Soil Moisture 659 3.5. Discussion and Conclusions 659 4. Body Sensor Networks 661 4.1. Wearable Sensors 661 4.2. Functionalized Fabrics 662 4.2.1. Metal Fibers 662 4.2.2. Conductive Inks 662 4.2.3. Inherently Conducting Polymers 662 4.2.4. Optical Fibers 662 4.2.5. Coating with Nanoparticles 662 4.2.6. Integrated Components 663 4.2.7. Wearable Actuators 663 4.2.8. Interconnects and Infrastructure 664 4.3. Applications of Wearable Sensors 665 4.4. Wearable Chemosensing 667 4.5. Applications in Personalized (p)Health 668 4.6. Conclusions 670 5. Materials SciencesThe Future 670 5.1. Microfluidics and Lab-on-a-Chip Devices 670 5.2. Controlling Liquid Movement in Surfaces and on Channels 671

Towards an Analytical Framework of Science Communication Models

Abstract: This chapter reviews the discussion in science communication circles of models for public communication of science and technology (PCST). It questions the claim that there has been a large-scale shift from a ‘deficit model’ of communication to a ‘dialogue model’, and it demonstrates the survival of the deficit model along with the ambiguities of that model. Similar discussions in related fields of communication, including the critique of dialogue, are briefly sketched. Outlining the complex circumstances governing approaches to PCST, the author argues that communications models often perceived to be opposed can, in fact, coexist when the choices are made explicit. To aid this process, the author proposes an analytical framework of communication models based on deficit, dialogue and participation, including variations on each.

The use of nanoparticles in anti-microbial materials and their characterization

Abstract: Anti-microbial materials have multiple applications in medicine, industry and commercial products. Recent research has proposed the use of nanoparticles in a range of materials, as some metal nanoparticles are known to possess antibacterial properties. The development of such materials presents both the chemist and the biologist with the challenge to effectively choose analytical methods that provide relevant information regarding these materials. Herein, we describe techniques for the characterization of the nanoparticle-doped materials and methods for the determination of their efficacy against biofilm formation.

Micro-photochemistry: photochemistry in microstructured reactors. The new photochemistry of the future?

Abstract: The use of a confined space in which to carry out reactions has proven popular in recent years, as demonstrated by the large volume of work published on ‘molecular microreactors’ such as zeolites, micelles and nanoparticles. This article looks at reactions in microstructured reactors, also known as microchannelled reactors or microreactors. In general, these consist of a ‘chip’ with narrow channels etched into it. Microstructured reactors have been the subject of several review articles to date, focusing on preparation, types of reactions that may be carried out and on the potential for ‘green’ applications. However, the use of microstructured reactor technology in photochemistry has, until now, not been subject to review. This perspective aims to outline the work done to date in this area and in particular to demonstrate the advantages and future prospectives of this technology in photochemical processes. Photochemistry in microstructured reactors is an emerging area of interest and to date has demonstrated significant potential as a viable alternative to traditional photochemical synthesis.

Using Taguchi method to optimize welding pool of dissimilar laser-welded components

Abstract: In the present work, CO 2 continuous laser welding process was successfully applied and optimized for joining a dissimilar AISI 316 stainless-steel and AISI 1009 low carbon steel plates. Laser power, welding speed and defocusing distance combinations were carefully selected with the objective of producing welded joint with complete penetration, minimum fusion zone size and acceptable welding profile. Fusion zone area and shape of dissimilar austenitic stainless-steel with ferritic low carbon steel were evaluated as a function of the selected laser welding parameters. Taguchi approach was used as statistical design of experiment (DOE) technique for optimizing the selected welding parameters in terms of minimizing the fusion zone. Mathematical models were developed to describe the influence of the selected parameters on the fusion zone area and shape, to predict its value within the limits of the variables being studied. The result indicates that the developed models can predict the responses satisfactorily.

Absorbance Based Light Emitting Diode Optical Sensors and Sensing Devices.

Abstract: The ever increasing demand for in situ monitoring of health, environment and security has created a need for reliable, miniaturised sensing devices. To achieve this, appropriate analytical devices are required that possess operating characteristics of reliability, low power consumption, low cost, autonomous operation capability and compatibility with wireless communications systems. The use of light emitting diodes (LEDs) as light sources is one strategy, which has been successfully applied in chemical sensing. This paper summarises the development and advancement of LED based chemical sensors and sensing devices in terms of their configuration and application, with the focus on transmittance and reflectance absorptiometric measurements.

MHz Unidirectional Rotation of Molecular Rotary Motors

Abstract: A combination of cryogenic UV−vis and CD spectroscopy and transient absorption spectroscopy at ambient temperature is used to study a new class of unidirectional rotary molecular motors. Stabilization of unstable intermediates is achieved below 95 K in propane solution for the structure with the fastest rotation rate, and below this temperature measurements on the rate limiting step in the rotation cycle can be performed to obtain activation parameters. The results are compared to measurements at ambient temperature using transient absorption spectroscopy, which show that behavior of these motors is similar over the full temperature range investigated, thereby allowing a maximum rotation rate of 3 MHz at room temperature under suitable irradiation conditions.

Multi-response optimization of CO2 laser-welding process of austenitic stainless steel

Abstract: Recently, laser welding of austenitic stainless steel has received great attention in industry. This is due to its widespread application in petroleum refinement stations, power plants, the pharmaceutical industry and also in households. Therefore, mechanical properties should be controlled to obtain good welded joints. The welding process should be optimized by the proper mathematical models. In this research, the tensile strength and impact strength along with the joint-operating cost of laser-welded butt joints made of AISI304 was investigated. Design-expert software was used to establish the design matrix and to analyze the experimental data. The relationships between the laser-welding parameters (laser power, welding speed and focal point position) and the three responses (tensile strength, impact strength and joint-operating cost) were established. Also, the optimization capabilities in design-expert software were used to optimize the welding process. The developed mathematical models were tested for adequacy using analysis of variance and other adequacy measures. In this investigation, the optimal welding conditions were identified in order to increase the productivity and minimize the total operating cost. Overlay graphs were plotted by superimposing the contours for the various response surfaces. The process parameters effect was determined and the optimal welding combinations were tabulated.

Responding mindfully to distressing psychosis: A grounded theory analysis

Abstract: This study investigates the psychological process involved when people with current distressing psychosis learned to respond mindfully to unpleasant psychotic sensations (voices, thoughts, and images). Sixteen participants were interviewed on completion of a mindfulness group program. Grounded theory methodology was used to generate a theory of the core psychological process using a systematically applied set of methods linking analysis with data collection. The theory inducted describes the experience of relating differently to psychosis through a three-stage process: centering in awareness of psychosis; allowing voices, thoughts, and images to come and go without reacting or struggle; and reclaiming power through acceptance of psychosis and the self. The conceptual and clinical applications of the theory and its limits are discussed.

Stabilization and Destabilization of Nonlinear Differential Equations by Noise

Abstract: This paper considers the stabilization and destabilization by a Brownian noise perturbation that preserves the equilibrium of the ordinary differential equation x'(t) = f(x(t)). In an extension of earlier work, we lift the restriction that f obeys a global linear bound, and show that when f is locally Lipschitz, a function g can always be found so that the noise perturbation g(X(t)) dB(t) either stabilizes an unstable equilibrium, or destabilizes a stable equilibrium. When the equilibrium of the deterministic equation is nonhyperbolic, we show that a nonhyperbolic perturbation suffices to change the stability properties of the solution.

A Software Engineering Lifecycle Standard for Very Small Enterprises

Abstract: Industry recognizes that very small enterprises (VSE), that develop parts involving software components are very important to the economy. These parts are often integrated into products of larger enterprises. Failure to deliver a quality product on time and within budget threatens the competitiveness of both organizations. One way to mitigate these risks is to haveall suppliers of a product chain put recognized engineering practices in place. Many international standards and models such as ISO/IEC12207 or CMMI have been developed to capture proven engineering practices. However, these standards were not designed for very small development organizations, those with less than 25 employees, and are consequently difficult to apply in such settings. An ISO/IEC JTC1/SC7 Working Group has been established to address these difficulties by producing a software engineering standard tailored to VSE.

Learning Morphology with Morfette

Abstract: Morfette is a modular, data-driven, probabilistic system which learns to perform joint morphological tagging and lemmatization from morphologically annotated corpora. The system is composed of two learning modules which are trained to predict morphological tags and lemmas using the Maximum Entropy classifier. The third module dynamically combines the predictions of the Maximum-Entropy models and outputs a probability distribution over tag-lemma pair sequences. The lemmatization module exploits the idea of recasting lemmatization as a classification task by using class labels which encode mappings from word forms to lemmas. Experimental evaluation results and error analysis on three morphologically rich languages show that the system achieves high accuracy with no language-specific feature engineering or additional resources.

Integrated microfluidic tmRNA purification and real-time NASBA device for molecular diagnostics

Abstract: We demonstrate the first integrated microfluidic tmRNA purification and nucleic acid sequence-based amplification (NASBA) device incorporating real-time detection. The real-time amplification and detection step produces pathogen-specific response in < 3 min from the chip-purified RNA from 100 lysed bacteria. On-chip RNA purification uses a new silica bead immobilization method. On-chip amplification uses custom-designed high-selectivity primers and real-time detection uses molecular beacon fluorescent probe technology; both are integrated on-chip with NASBA. Present in all bacteria, tmRNA (10Sa RNA) includes organism-specific identification sequences, exhibits unusually high stability relative to mRNA, and has high copy number per organism; the latter two factors improve the limit of detection, accelerate time-to-positive response, and suit this approach ideally to the detection of small numbers of bacteria. Device efficacy was demonstrated by integrated on-chip purification, amplification, and real-time detection of 100 E. coli bacteria in 100 microL of crude lysate in under 30 min for the entire process.