Non-destructive Evaluation of Concrete using Electrical Resistivity and Ultrasonic Wave Propagation

With the intent to investigate the relationship between concrete physical properties and non-destructive evaluation techniques (NDE), several experiments were performed. Specimens were made at varying geometries using a range of different concrete mixes under several different curing conditions. These specimens were subjected to a combination of electrical resistivity and ultrasonic wave propagation measurements. One part of this study investigated determining the orientation of steel fibers using electrical resistivity. This resulted in the fabrication of a four-probe square device with the potential capabilities of determining fiber orientation. The other part of this research applied ultrasonic wave propagation via through-transmission along with electrical resistivity via the uniaxial method. The results from this uncovered an exponential relationship between the pulse wave velocity and formation factor for saturated specimens. With the formation factor’s relationship to strength and microstructural properties, this relationship may lead to predicting strength and pore structure using relationships to a simple ultrasonic property

Responding to the critics: Implementation of TBLT in Japan

This paper outlines a qualitative study of 10 in-service teachers in Japan who use a task-based language teaching (TBLT) approach in their language classrooms. The study investigates the reasons why these teachers began using TBLT, their beliefs about the advantages and disadvantages of implementing TBLT, and whether or not they agree with common criticisms levelled at TBLT for use in foreign language classrooms in Japan and Asia in general. Critics argue that TBLT is not suitable for many language learning situations, explaining that students are used to more ‘traditional’ teacher-centered language classes and that they prefer more ‘passive’ approaches. Such criticisms also hold that TBLT is not able to adequately prepare students for the high-stakes tests that are used for secondary school and university entrance purposes. The results from interviews with these 10 teachers suggest that they reject many of these criticisms, and are in fact successfully using TBLT to develop both language ability and motivation in their students. At the same time, the teachers noted that there may be a need to use a ‘weaker’ form of TBLT with beginner students, or with those used to more passive styles of learning. They also highlighted the importance of heavily scaffolding tasks in such cases. Finally, a number of the teachers discussed the need for the development of more TBLT related materials, both for students and teachers

The arguments of associations

This chapter considers associative solutions to “non‐linear” discrimination problems, such as negative patterning (A+ and B+ vs AB‐) and the biconditional discrimination (AB+ and CD+ vs AC‐ and BD‐). It is commonly assumed that the solution to these discriminations requires “configural” elements that are added to the compound of two stimuli. However, these discriminations can be solved by assuming that some elements of each stimulus are suppressed when two stimuli are presented in compound. Each of these approaches can solve patterning and biconditional discriminations because they allow some elements, as the arguments of associations, to have differential “presence” on reinforced versus nonreinforced trials, and thus differential associability and control over responding. The chapter then presents a more specific version of one of these models, describing how interactions between stimuli, particularly the competition for attention, provide a mechanism whereby some elements are more suppressed than others when stimuli are presented simultaneously as a compound

Nanostructuring silicon and germanium for high capacity anodes in lithium ion batteries

textColloidally synthesized silicon (Si) and germanium (Ge) were explored as high capacity anode materials in lithium ion batteries. a-Si:H particles were synthesized through the thermal decomposition of trisilane in supercritical n-hexane. Precise control over particle size and hydrogen content was demonstrated. Particles ranged in size from 240-1500 nm with hydrogen contents from 10-60 atomic%. Particles with low hydrogen content had some degree of local ordering and were easily crystallized during Raman spectroscopy. The as-synthesized particles did not perform well as an anode material due to low conductivity. Increasing surface conductivity led to enhanced lithiation potential. Cu nanoparticles were deposited on the surface of the a-Si:H particles through a hydrogen facilitated reduction of Cu salts. The resulting Cu coated particles had a lithiation capacity seven times that of pristine a-Si:H particles. Monophenylsilane (MPS) grown Si nanowire paper was annealed under forming gas to reduce a polyphenylsilane shell into conductive carbon. The resulting paper required no binder or carbon additive and achieved capacities of 804 mA h/g vs 8 mA h/g for unannealed wires. Si and Ge heterostructures were explored to take advantage of the higher inherent conductivity of Ge. Ge nanowires were successfully coated with a-Si by thermal decomposition of trisilane on their surface, forming Ge@a-Si core shell structures. The capacity increased with increasing Si loading. The peak lithiation capacity was 1850 mA h/g after 20 cycles – higher than the theoretical capacity of pure Ge. MPS additives created a thin amorphous shell on the wire surfaces. By incubating the wires after MPS addition the shell was partially reduced, conductivity increased, and a 75% increase in lithiation capacity was observed for the nanowire paper. The syntheses of Bi and Au nanoparticles were also explored. Highly monodisperse Bi nanocrystals were produced with size control from 6-18 nm. The Bi was utilized as seeds for the SLS synthesis of Ge nanorods and copper indium diselenide (CuInSe2) nanowires. Sub 2 nm Au nanocrystals were synthesized. A SQUID magnetometer probed their magnetic behavior. Though bulk Au is diamagnetic, the Au particles were paramagnetic. Magnetic susceptibility increased with decreasing particle diameter.Chemical Engineerin

Changes in the distribution of response rates across the CS-US interval: Evidence that responding switches between two distinct states.

Two experiments used the peak procedure to examine timing of conditioned responses in a magazine approach paradigm with rats. A conditioned stimulus (CS) was reinforced with food on 50% of trials. Food was delivered at a fixed time, either 20 s, 30 s or 40 s into the CS presentation. Response rates were recorded during non-reinforced CS presentations that extended well beyond the scheduled time of food delivery. The mean response rate (averaged over many trials) increased during the CS, peaking at the expected time of reinforcement, and decreased again. Detailed analyses of the frequency distribution of response rates showed that responding was described by two distinct distributions, consistent with the rat being in a low response state on some trials and in a high response state on other trials. Modeling of these frequency distributions showed that the systematic rise and fall in response rate across a trial was primarily explained by a change in the proportion of time that the rat spent in the low versus high response state. However, the change in responding was also explained in part by a continuous shift in the high response state, such that responding in that state increased and then decreased gradually across the trial. These results support accounts that describe response timing as an abrupt change from low to high responding during the CS, but also provide evidence for a continuous change in conditioning strength across the duration of the CS. The implications of these findings for timing and associative theories of conditioning are discussed.Australian Research Counci

Elemental Representations of Stimuli in Associative Learning

This paper reviews evidence and theories concerning the nature of stimulus representations in Pavlovian conditioning. It focuses on the elemental approach developed in Stimulus Sampling Theory (Atkinson & Estes, 1963; Bush & Mosteller, 1951b) and extended by McLaren and Mackintosh (2000; 2002), and contrasts this with models that that invoke notions of configural representations that uniquely code for different patterns of stimulus inputs (e.g., Pearce, 1987, 1994; Rescorla & Wagner, 1972; Wagner & Brandon, 2001). The paper then presents a new elemental model that emphasizes interactions between stimulus elements. This model is shown to explain a range of behavioral findings, including those (e.g., negative patterning and biconditional discriminations) traditionally thought beyond the explanatory capabilities of elemental models. Moreover, the model offers a ready explanation for recent findings reported by Rescorla (2000; 2001; 2002b) concerning the way that stimuli with different conditioning histories acquire associative strength when conditioned in compoun

Possible attenuation of the G2 DNA damage cell cycle checkpoint in HeLa cells by extremely low frequency (ELF) electromagnetic fields

BACKGROUND: The issue remains unresolved as to whether low frequency magnetic fields can affect cell behaviour, with the possibility that they may be in part responsible for the increased incidence of leukaemia in parts of the population exposed to them. METHODS: Combined treatment of HeLa cells with gamma-irradiation (1, 3 and 5 Grays) and extra low frequency magnetic fields of ~50 Hz was carried out under rigorously controlled conditions. RESULTS: Synchronised cells progressing from S-phase arrived at mitosis on average marginally ahead of irradiation controls not exposed to ELF. In no instance out of a total of twenty separate experiments did this "double-insult" further delay entry of cells into mitosis, as had been anticipated. CONCLUSION: This apparently "non-genotoxic" agent (ELF) appears to be capable of affecting cells that would normally arrest for longer in G2, suggesting a weakening of the stringency of the late cycle (G2) checkpoint

The acquisition of conditioned responding

This report analyzes the acquisition of conditioned responses in rats trained in a magazine approach paradigm. Following the suggestion by Gallistel, Fairhurst and Balsam (2004), Weibull functions were fitted to the trial-by-trial response rates of individual rats. These showed that the emergence of responding was often delayed, after which the response rate would increase relatively gradually across trials. The fit of the Weibull function to the behavioral data of each rat was equaled by that of a cumulative exponential function incorporating a response threshold. Thus the growth in conditioning strength on each trial can be modeled by the derivative of the exponential – a difference term of the form used in many models of associative learning (e.g., Rescorla & Wagner, 1972). Further analyses, comparing the acquisition of responding to a continuously reinforced stimulus (CRf) and a partially reinforced stimulus (PRf), provided further evidence in support of the difference term. In conclusion, the results are consistent with conventional models that describe learning as the growth of associative strength, incremented on each trial by an error-correction process.This work was supported by grant DP0771154 from the Australian Research Council

Response Rate and Reinforcement Rate in Pavlovian Conditioning

Four experiments used delay conditioning of magazine approach in rats to investigate the relationship between the rate of responding, R, to a conditioned stimulus (CS) and the rate, r, at which the CS is reinforced with the unconditioned stimulus (US). Rats were concurrently trained with four variable-duration CSs with different rs, either as a result of differences in the mean CS-US interval or in the proportion of CS presentations that ended with the US. In each case, R was systematically related to r, and the relationship was very accurately characterized by a hyperbolic function, R = Ar/(r+c). Accordingly, the reciprocal of these two variables – response interval, I (=1/R), and CS-US interval, i (=1/r) – were related by a simple affine (straight line) transformation, I = mi+b. This latter relationship shows that each increment in the time that the rats had to wait for food produced a linear increment in the time they waited between magazine entries. We discuss the close agreement between our findings and the Matching Law (Herrnstein, 1970), and consider their implications for both associative theories (e.g., Rescorla & Wagner, 1972) and non-associative theories (Gallistel & Gibbon, 2000) of conditioning.This work was supported by Grants DP0771154 and DP1092695 from the Australian Research Council

NEW BIOINFORMATIC TECHNIQUES FOR THE ANALYSIS OF LARGE DATASETS

A new era of chemical analysis is upon us. In the past, a small number of samples were selected from a population for use as a statistical representation of the entire population. More recently, advancements in data collection rate, computer memory, and processing speed have allowed entire populations to be sampled and analyzed. The result is massive amounts of data that convey relatively little information, even though they may contain a lot of information. These large quantities of data have already begun to cause bottlenecks in areas such as genetics, drug development, and chemical imaging. The problem is straightforward: condense a large quantity of data into only the useful portions without ignoring or discarding anything important. Performing the condensation in the hardware of the instrument, before the data ever reach a computer is even better. The research proposed tests the hypothesis that clusters of data may be rapidly identified by linear fitting of quantile-quantile plots produced from each principal component of principal component analysis. Integrated Sensing and Processing (ISP) is tested as a means of generating clusters of principal component scores from samples in a hyperspectral near-field scanning optical microscope. Distances from the centers of these multidimensional cluster centers to all other points in hyperspace can be calculated. The result is a novel digital staining technique for identifying anomalies in hyperspectral microscopic and nanoscopic imaging of human atherosclerotic tissue. This general method can be applied to other analytical problems as well