Obtaining shorter regular expressions from finite-state automata

We consider the use of state elimination to construct shorter regular expressions from finite-state automata (FAs). Although state elimination is an intuitive method for computing regular expressions from FAs, the resulting regular expressions are often very long and complicated. We examine the minimization of FAs to obtain shorter expressions first. Then, we introduce vertical chopping based on bridge states and horizontal chopping based on the structural properties of given FAs. We prove that we should not eliminate bridge states until we eliminate all non-bridge states to obtain shorter regular expressions. In addition, we suggest heuristics for state elimination that leads to shorter regular expressions based on vertical chopping and horizontal chopping.     

"Temporal encoding in fear conditioning revealed through associative reflex facilitation": Correction to Lindquist and Brown (2004).

Reports an error in "Temporal Encoding in Fear Conditioning Revealed Through Associative Reflex Facilitation" by Derick H. Lindquist and Thomas H. Brown (Behavioral Neuroscience, 2004[Apr], Vol 118[2], 395-402). The article contained several errors. On page 396, second paragraph, the sentence beginning on line 6 should read as follows: "Having a stable baseline is critical for studies of reflex facilitation because the experimental designs invariably entail repetitive CR testing, if only to achieve reasonable statistical power (see Choi et al., 2001b; Lindquist & Brown, 2004)." On page 400, the first heading should read as follows: "Comparison of New and Old Reflex Facilitation Procedures." On page 400, the first sentence under the abovementioned heading should read as follows: "We decided not to use the original measure of reflex facilitation, developed by J. S. Brown et al. (1951), because it suffers from severe interpretational limitations, elaborated in detail elsewhere (Choi et al., 2001b; Leaton & Cranney, 1990; Lindquist & Brown, 2004)." (The following abstract of the original article appeared in record 2004-12681-016.) Temporal encoding in Pavlovian fear conditioning was examined through conditional facilitation of the short-latency (Rl) component of the rat eyeblink reflex. Rats were fear-conditioned to a tone conditional stimulus (CS) with either a 3- or 9-s interstimulus interval (ISI) between CS onset and the onset of the grid-shock unconditional stimulus (US). Rl facilitation was tested over 2 days, in counterbalanced order, at a latency of 3 s and 9 s from CS onset. CS-produced Rl facilitation, the conditional response (CR), was 3-4 times larger when the test latency equaled the conditioning ISI. These results, coupled with the known neurophysiology of Rl facilitation, suggest that this CR could disclose differences in the time course of CS-generated output from the amygdala when driven by cortical versus subcortical CS-CR pathways. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the state complexity of reversals of regular languages

We compare the number of states between minimal deterministic finite automata accepting a regular language and its reversal (mirror image). In the worst case the state complexity of the reversal is 2ⁿ for an n-state language. We present several classes of languages where this maximal blow-up is actually achieved and study the conditions for it. In the case of finite languages the maximal blow-up is not possible but still a surprising variety of different growth types can be exhibited.     

Provision of awareness of learners’ emotions through visualizations in a computer interaction-based environment

One of the challenges of intelligent systems for education is to use low-level data collected in computer environments in the form of events or interactions to infer information with high-level significance using artificial intelligence techniques, and present it through visualizations in a meaningful and effective way. Among this information, emotional data is gaining track in by instructors in their educational activities. Many benefits can be obtained if an intelligent systems can bring teachers with knowledge about their learner’s emotions, learning causes, and learning relationships with emotions. In this paper, we propose and justify a set of visualizations for an intelligent system to provide awareness about the emotions of the learners to the instructor based on the learners’ interactions in their computers. We apply these learner’s affective visualizations in a programming course at University level with more than 300 students, and analyze and interpret the student’s emotional results in connection with the learning process.     

A dynamic fixed windowing problem

Given a point set in the plane and a fixed planar region (window) a window query consists of enumerating the points in a translate of the region. A recently presented result demonstrates that there is astatic data structure, of optimal size, that solves window queries for convex regions in optimal time. We give a data structure, of optimal size, that not only supports window queries in optimal time for, possibly nonconvex, polygonal windows, but also allows updating of the point set in optimal time.     

Speed-varying ol systems

A new type of L system is introduced in which each rule has a “delay”, a word over some alphabet, associated with it. This results in a new characterization of the etol languages, which only partially carries over to the eol languages.     

Effects of linear alkylbenzene sulfonate on the sorption of Brij 30 and Brij 35 onto aquifer sand

Surfactant sorption is of considerable importance to environmental applications, including surfactant flushing to mobilize hydrophobic contaminants; effects of surfactants on the transport of dissolved contaminants, microorganisms, and colloids through porous media; and bioremediation of hydrophobic organic compounds, as well as understanding the fate and transport of surfactants as environmental contaminants themselves. Although most sorption studies consider pure surfactants, commercial detergent formulations typically consist of mixtures of nonionic and anionic surfactants. In this study, the effects of varying concentrations of the anionic surfactant linear alkylbenzene sulfonate (LAS) on micelle formation and sorption behavior of the two commonly used nonionic surfactants Brij 30 and Brij 35 onto aquifer sand were examined. A strong linear relationship was observed between the critical micelle concentration (CMC) of the Brij surfactants and the concentration of LAS in the mixture, with the CMC decreasing with increasing concentration of LAS. The relative change in CMC as a function of the LAS concentration was identical forthe two Brij surfactants, indicating that LAS interacted with their common alkyl chains. Sorption isotherms were developed for Brij 30 and Brij 35 present as single surfactants in an aqueous solution as well as when present with LAS. Although LAS had minor effects on the maximum sorption plateaus of the Brij surfactants, Brij sorption at was significantly enhanced as a function of the LAS concentration for Brij aqueous concentrations below the CMC. Application of a multi-interaction isotherm model indicated that the formation of surface aggregates (e.g., hemimicelles) decreased with increasing LAS concentration. Overall, these results provide insight into the complex sorption behavior of surfactant mixtures.     

Dependence of thermal sensitivity of LPFG on waveguide and material parameters

This article demonstrates the effect of waveguide and material parameters on thermal sensitivity trends adopted by different cladding modes based on long-period fiber grating. Three-layer fiber geometry-based mathematical model has been implemented to estimate cladding modes. It is observed that for a cladding mode, the sign and magnitude of thermal sensitivity slope depend upon the designed grating period closer to period at dispersion turn around point. The \(\hbox {LP}_{10}\) and \(\hbox {LP}_{11}\) cladding modes have shown blueshift and maximum thermal sensitivity above all other modes at designed grating periods of 225 and \(195\,\upmu \hbox {m}\), respectively. The material parameter of fiber (thermo-optic coefficient) has also resulted in increment in sensitivity with the increase in difference amid its values for core and cladding region.     

Effects of nonionic surfactants on the cell surface hydrophobicity and apparent hamaker constant of a Sphingomonas sp

Nonionic surfactants of the form CxEy were studied for their ability to alter the cell surface hydrophobicity and apparent Hamaker constants of a Sphingomonas sp. Through contact angle measurements on hydrated and dried bacterial lawns, it was found that the cell surface hydrophobicity changed systematically with both the alkyl (x) and polyoxyethylene (y) chain lengths. While differences in contact angles were observed between hydrated and dried lawns, they could not be attributed to the mere presence or absence of water, suggesting that reorientation of cell surface components may occur during drying. All surfactants examined reduced the hydrophilicity of the bacterial cell surface, with one surfactant (C18E10) making the cells hydrophobic. Effective bacterial Hamaker constants for bacteria interacting across a vacuum (Abb) and water (Abwb) and bacteria interacting in water with quartz sand (Abws) were calculated from the contact angles. It was found that the surfactants have the potential to reduce the Hamaker constants, but that the overall effects differed between dried and hydrated lawns, indicating that lawn preparation method can have a significant impact in interpretation of cell surface properties. The results also indicate that the Abws value of 10-20 J, which is often assumed in bacterial attachment and transport studies, may be an order of magnitude higher than the actual value. Finally, the results suggest that alteration of bacterial adhesion due to the presence of surfactants cannot be attributed to a single cell surface property but is rather due to multiple interactions.