Phenylalkenals in ponerine(Leptogenys sp.) and myrmicine (Pogonomyrmex sp.) ants

Cephalic extracts of two unrelated species of ants,Leptogenys processionalis andPogonomyrmex rugosus, have been found to contain 2-phenylpropenal and 2-phenyl-2-butenal, while two other species related to the first,L. chinensis andL. kitteli, lacked either.L. kitteli also produced a tetrasubstituted pyrazine found previously only in two New Zealand ants in the genusMesoponera. The chemical reactivity of the phenylalkenals suggests their function in repelling attack by predators.     

Unskilled and unaware--but why? A reply to Krueger and Mueller (2002).

J. Kruger and D. Dunning (1999) argued that the unskilled suffer a dual burden: Not only do they perform poorly, but their incompetence robs them of the metacognitive ability to realize it. J. Krueger and R. A. Mueller (2002) replicated these basic findings but interpreted them differently. They concluded that a combination of the better-than-average (BTA) effect and a regression artifact better explains why the unskilled are unaware. The authors of the present article respectfully disagree with this proposal and suggest that any interpretation of J. Krueger and R. A. Mueller's results is hampered because those authors used unreliable tests and inappropriate measures of relevant mediating variables. Additionally, a regression-BTA account cannot explain the experimental data reported in J. Kruger and D. Dunning or a reanalysis following the procedure suggested by J. Krueger and R. A. Mueller. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of individual versus aggregate social comparison and the presence of others on self-evaluations.

In 5 studies, the authors investigated the effects of comparison with an individual versus comparison with the statistical average on self-evaluations of performance and ability. In Studies 1 and 2, participants took a test of lie detection ability and were provided with the average score and the score of an individual coactor. Both types of feedback significantly affected self-evaluations of performance, but only comparison with the coactor significantly affected self-evaluations of ability. Studies 3 and 4 demonstrated that the presence of a coactor moderated the effect of aggregate social comparison on self-evaluations of ability. The results provide preliminary support for the contention that minimizing the impact of comparison with the average is a self-serving strategy that is facilitated by the presence of others. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response to the discussion by I.V. Rokach of the paper entitled: “Analysis of the dynamic responses for a pre-cracked three-point bend specimen”

The following response to the discussion of the above mentioned paper is divided into two parts: (1) a response to the issue of our comparison of the apparent period of specimen oscillation, , and the natural vibration period of a cracked specimen, T, and (2) a verification of the applicability of our model to short time-to-fracture tests, which Rokach has questioned, due to a lack of knowledge of Hopkinson bar techniques.     

Nanowire dye-sensitized solar cells

Excitonic solar cells-including organic, hybrid organic-inorganic and dye-sensitized cells (DSCs)-are promising devices for inexpensive, large-scale solar energy conversion. The DSC is currently the most efficient and stable excitonic photocell. Central to this device is a thick nanoparticle film that provides a large surface area for the adsorption of light-harvesting molecules. However, nanoparticle DSCs rely on trap-limited diffusion for electron transport, a slow mechanism that can limit device efficiency, especially at longer wavelengths. Here we introduce a version of the dye-sensitized cell in which the traditional nanoparticle film is replaced by a dense array of oriented, crystalline ZnO nanowires. The nanowire anode is synthesized by mild aqueous chemistry and features a surface area up to one-fifth as large as a nanoparticle cell. The direct electrical pathways provided by the nanowires ensure the rapid collection of carriers generated throughout the device, and a full Sun efficiency of 1.5% is demonstrated, limited primarily by the surface area of the nanowire array.     

Gold nanoparticle-modified etched capillaries for open-tubular capillary electrochromatography

The use of gold nanoparticles in conjunction with etched capillary-based open-tubular capillary electrochromatography (OTCEC) to improve the efficiency of separation and the selectivity between selected solutes is described. The fused-silica capillaries (50-microm i.d.) were etched with ammonium hydrogen difluoride, followed by prederivatization of the new surface with (3-mercaptopropyl)trimethoxysilane (MPTMS) for the immobilization of dodecanethiol gold nanoparticles, for OTCEC. The electrochromatography of a "reversed-phase" test mixture and of selected polycylic aromatic hydrocarbons was investigated, and efficient separations and high theoretical plate numbers per meter were obtained. The electroosmotic flow characteristics of the etched gold nanoparticle capillary, unetched gold nanoparticle capillary, bare capillary, and etched bare capillary were studied by varying the percentage of organic modifier in buffer, buffer pH, and separation voltage. Optical microscopy and scanning electron microscopy were used to examine the process of etching and modification and the surface features of the etched gold nanoparticle capillary. The results confirm that dodecanethiol gold nanoparticles bonded on the etched inner wall of the fused-silica capillary can provide sufficient solute-bonded phase interactions to obtain OTCEC separations with reproducible retention, as well as characteristic reversed-phase behavior, even with the inner diameter of the capillary of 50 microm.     

NONMEMory: a run management tool for NONMEM

NONMEM is an extremely powerful tool for nonlinear mixed-effect modelling and simulation of pharmacokinetic and pharmacodynamic data. However, it is a console-based application whose output does not lend itself to rapid interpretation or efficient management. NONMEMory has been created to be a comprehensive project manager for NONMEM, providing detailed summary, comparison and overview of the runs comprising a given project, including the display of output data, simple post-run processing, fast diagnostic plots and run output management, complementary to other available modelling aids. Analysis time ought not to be spent on trivial tasks, and NONMEMory's role is to eliminate these as far as possible by increasing the efficiency of the modelling process. NONMEMory is freely available from http://www.uct.ac.za/depts/pha/nonmemory.php.     

Learning curves for stochastic gradient descent in linear feedforward networks

Gradient-following learning methods can encounter problems of implementation in many applications, and stochastic variants are sometimes used to overcome these difficulties. We analyze three online training methods used with a linear perceptron: direct gradient descent, node perturbation, and weight perturbation. Learning speed is defined as the rate of exponential decay in the learning curves. When the scalar parameter that controls the size of weight updates is chosen to maximize learning speed, node perturbation is slower than direct gradient descent by a factor equal to the number of output units; weight perturbation is slower still by an additional factor equal to the number of input units. Parallel perturbation allows faster learning than sequential perturbation, by a factor that does not depend on network size. We also characterize how uncertainty in quantities used in the stochastic updates affects the learning curves. This study suggests that in practice, weight perturbation may be slow for large networks, and node perturbation can have performance comparable to that of direct gradient descent when there are few output units. However, these statements depend on the specifics of the learning problem, such as the input distribution and the target function, and are not universally applicable.     

Comparison of stream merging algorithms for media-on-demand

Stream merging is a technique for efficiently delivering popular media-on-demand using multicast and client buffers. Recently, several algorithms for stream merging have been proposed, and in this paper we perform a comprehensive comparison of these algorithms. We present the differences in philosophy and mechanics among the various algorithms and illustrate the tradeoffs between their system complexity and performance. We measure performance in total, maximum, and time-varying server bandwidth usage under different assumptions for the client request patterns. We also consider the effects on clients when the server has limited bandwidth. The result of this study is a deeper understanding of the system complexity and performance tradeoffs for the various algorithms.Amotz Bar-Noy: This work was done in part while the author was a member of the AT&T Labs-Research, Shannon Lab, Florham Park, NJ.Justin Goshi: Corresponding author. This work was done in part at AT&T Labs-Research, Shannon Lab, Florham Park, NJ.Richard E. Ladner: This work was done in part at AT&T Labs-Research, Shannon Lab, Florham Park, NJ and partially supported by NSF grants No. CCR-9732828 and CCR-0098012.A preliminary version of this paper appeared in Multimedia Computing and Networking 2002.     

Efficient plagiarism detection for large code repositories

Unauthorized re‐use of code by students is a widespread problem in academic institutions, and raises liability issues for industry. Manual plagiarism detection is time‐consuming, and current effective plagiarism detection approaches cannot be easily scaled to very large code repositories. While there are practical text‐based plagiarism detection systems capable of working with large collections, this is not the case for code‐based plagiarism detection. In this paper, we propose techniques for detecting plagiarism in program code using text similarity measures and local alignment. Through detailed empirical evaluation on small and large collections of programs, we show that our approach is highly scalable while maintaining similar levels of effectiveness to that of the popular JPlag and MOSS systems. Copyright © 2006 John Wiley & Sons, Ltd.