Screen-printed potentiometric Ag/AgCl chloride sensors: Lifetime performance and their use in soil salt measurements

Silver – silver chloride electrodes (Ag/AgCl) for the detection of chloride ions were fabricated using thick-film technology. Five different formulations were prepared and chloride responses were investigated over time. Almost identical and near Nernstian responses were observed over the first 162 days with an average chloride sensitivity for all formulations of -51.12 mV ± 0.45 mV per decade change in chloride concentration compared with a value of -50.59 mV ± 0.01 mV over 388 days for the best two formulations. After 6-months continuous immersion in tap water, pastes formulated with a glass binder began to exhibit a loss in sensitivity whilst those formulated from a commercial thick-film dielectric paste remained functional for the best part of a year. This difference in lifetime performance is attributed to the inclusion of proprietary additives in the commercial paste aiding adhesion and minimising AgCl leaching. The mechanical and chemical robustness of these electrodes has been demonstrated through their ability to detect changing levels of chloride when immersed in soil columns. This particular capacity will make them an invaluable tool in the fields of hydrology, agricultural science, soil science and environmental science

Island nucleation in the presence of step edge barriers: Theory and applications

We develop a theory of nucleation on top of two-dimensional islands bordered by steps with an additional energy barrier $\Delta E_S$ for descending atoms. The theory is based on the concept of the residence time of an adatom on the island,and yields an expression for the nucleation rate which becomes exact in the limit of strong step edge barriers. This expression differs qualitatively and quantitatively from that obtained using the conventional rate equation approach to nucleation [J. Tersoff et al., Phys. Rev. Lett.72, 266 (1994)]. We argue that rate equation theory fails because nucleation is dominated by the rare instances when two atoms are present on the island simultaneously. The theory is applied to two distinct problems: The onset of second layer nucleation in submonolayer growth, and the distribution of the sizes of top terraces of multilayer mounds under conditions of strong step edge barriers. Application to homoepitaxial growth on Pt(111) yields the estimate $\Delta E_S \geq 0.33$ eV for the additional energy barrier at CO-decorated steps.Comment: 13 pages, 3 figure

Probabilistic approaches for modeling text structure and their application to text-to-text generation

Since the early days of generation research, it has been acknowledged that modeling the global structure of a document is crucial for producing coherent, readable output. However, traditional knowledge-intensive approaches have been of limited utility in addressing this problem since they cannot be effectively scaled to operate in domain-independent, large-scale applications. Due to this difficulty, existing text-to-text generation systems rarely rely on such structural information when producing an output text. Consequently, texts generated by these methods do not match the quality of those written by humans – they are often fraught with severe coherence violations and disfluencies. In this chapter, I will present probabilistic models of document structure that can be effectively learned from raw document collections. This feature distinguishes these new models from traditional knowledge intensive approaches used in symbolic concept-to-text generation. Our results demonstrate that these probabilistic models can be directly applied to content organization, and suggest that these models can prove useful in an even broader range of text-to-text applications than we have considered here.National Science Foundation (U.S.) (CAREER grant IIS- 0448168)Microsoft Research. New Faculty Fellowshi

The Kuiper Belt and Other Debris Disks

We discuss the current knowledge of the Solar system, focusing on bodies in the outer regions, on the information they provide concerning Solar system formation, and on the possible relationships that may exist between our system and the debris disks of other stars. Beyond the domains of the Terrestrial and giant planets, the comets in the Kuiper belt and the Oort cloud preserve some of our most pristine materials. The Kuiper belt, in particular, is a collisional dust source and a scientific bridge to the dusty "debris disks" observed around many nearby main-sequence stars. Study of the Solar system provides a level of detail that we cannot discern in the distant disks while observations of the disks may help to set the Solar system in proper context.Comment: 50 pages, 25 Figures. To appear in conference proceedings book "Astrophysics in the Next Decade

D* Production in Deep Inelastic Scattering at HERA

This paper presents measurements of D^{*\pm} production in deep inelastic scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The data have been taken with the ZEUS detector at HERA. The decay channel $D^{*+}\to (D^0 \to K^- \pi^+) \pi^+$ (+ c.c.) has been used in the study. The $e^+p$ cross section for inclusive D^{*\pm} production with $5<Q^2<100 GeV^2$ and $y<0.7$ is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region {$1.3<p_T(D^{*\pm})<9.0$ GeV and $| \eta(D^{*\pm}) |<1.5$}. Differential cross sections as functions of p_T(D^{*\pm}), $\eta(D^{*\pm}), W$ and $Q^2$ are compared with next-to-leading order QCD calculations based on the photon-gluon fusion production mechanism. After an extrapolation of the cross section to the full kinematic region in p_T(D^{*\pm}) and $\eta$(D^{*\pm}), the charm contribution $F_2^{c\bar{c}}(x,Q^2)$ to the proton structure function is determined for Bjorken $x$ between 2 $\cdot$ 10$^{-4}$ and 5 $\cdot$ 10$^{-3}$.Comment: 17 pages including 4 figure

Arthropod assemblages in a savanna invaded by Opuntia stricta (Cactaceae) in the Kruger National Park, South Africa

Invasive alien species are considered the second greatest threat to global biodiversity after habitat loss. South Africa is not immune from such threats and it is estimated that 10 million ha (8.28%) of land has been invaded to some extent by invasive alien species. Although South Africa has been invaded by several taxa, it is the effect of invasive trees and shrubs that has been environmentally and economically most damaging. The concerns raised due to the effects of biological invasion are not only restricted to off-reserve areas, but also protected areas where invasive alien organisms often pose a greater threat than habitat loss. Kruger National Park (KNP), South Africa’s flagship conservation area has been invaded by numerous plant taxa. The most damaging of these is Opuntia stricta (Cactaceae) and current sources estimate that the weed has invaded approximately 35 000 ha of conserved land, despite the initiation of a biological control programme against it. However, little is known about the effect of O. stricta on biodiversity in the KNP despite the large number of resources allocated to its eradication, including a successful biological control programme against it. In this study, I investigated the effect of O. stricta infestation on beetle (Order Coleoptera) and spider (Order Araneae) assemblages across four treatments of varying O. stricta infestation levels (heavy infestation, medium infestation, surrounded sites and pristine sites). Species characteristic of each treatment (indicator species) were identified using the indicator method. In addition, spiders were collected to gauge the effectiveness of three collecting methods (pitfall traps, leaf litter sifting and active searching) in a savanna characterized by O. stricta invasion. One hundred and thirty one spider species (1050 individuals) and 72 beetle species (2162 individuals) were collected in the treatments. I found no significant differences in species richness, species density and species assemblages for both beetles and spiders across the treatments. In addition, no beetle or spider species were found to be characteristic indicator species for a given treatment, which further indicates that arthropod assemblages are similar when compared across treatments. These results indicate that O. stricta does not appear to have a significant effect on beetle and spider assemblages at its current infestation level, possibly because of the similarity in vegetation structure across the treatments. Regarding spiders, different collecting methods captured different species and only 17% of the species were shared, indicating that the methods complement each other. Therefore, in order to sample the spider community, all three methods should be employed. Of the 131 spider species collected, 54 species (41%) are new records for the KNP. In light of the results, it is suggested that KNP’s successful biological control programme has played an important role in reducing the extent of the O. stricta infestation and should be continued to further mitigate the impacts of O. stricta.Dissertation (MSc)--University of Pretoria, 2009.Zoology and Entomologyunrestricte

Choosing how to choose : Institutional pressures affecting the adoption of personnel selection procedures

The gap between science and practice in personnel selection is an ongoing concern of human resource management. This paper takes Oliver´s framework of organizations´ strategic responses to institutional pressures as a basis for outlining the diverse economic and social demands that facilitate or inhibit the application of scientifically recommended selection procedures. Faced with a complex network of multiple requirements, practitioners make more diverse choices in response to any of these pressures than has previously been acknowledged in the scientific literature. Implications for the science-practitioner gap are discussed

Customer emotions in service failure and recovery encounters

Emotions play a significant role in the workplace, and considerable attention has been given to the study of employee emotions. Customers also play a central function in organizations, but much less is known about customer emotions. This chapter reviews the growing literature on customer emotions in employee–customer interfaces with a focus on service failure and recovery encounters, where emotions are heightened. It highlights emerging themes and key findings, addresses the measurement, modeling, and management of customer emotions, and identifies future research streams. Attention is given to emotional contagion, relationships between affective and cognitive processes, customer anger, customer rage, and individual differences

Providing the Context for Intentional Learning

This article is written in response to Sharon Derry's article “Remediating Academic Difficulties Through Strategy Training: The Acquisition of Useful Knowledge.” The features of effective strategy instruction, to which Derry refers, are illustrated by examining the nature of the decisions the teacher confronts; specifically, determining the purposes of instruction, the context in which instruction occurs, and the roles of the teacher and students in instruction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69150/2/10.1177_074193259001100608.pd