bluuebunny/crossref_metadata_2025 huggingface dataset:
Conversation as Planned Behavior
Authors: Hobbs Jerry R. , Evans David Andreoff
Published: July 2005

In this paper, planning models developed in artificial intelligence are applied to the kind of planning that must be carried out by participants in a conversation. A planning mechanism is defined, and a short fragment of a free‐flowing videotaped conversation is described. The bulk of the paper is then devoted to an attempt to understand the conversation in terms of the planning mechanism. This microanalysis suggests ways in which the planning mechanism must be augmented, and reveals several important conversational phenomena that deserve further investigation.
Repair Theory: A Generative Theory of Bugs in Procedural Skills
Authors: Brown John Seely , VanLehn Kurt
Published: July 2005

This paper describes a generative theory of bugs. It claims that all bugs of a procedural skill can be derived by a highly constrained form of problem solving acting on incomplete procedures. These procedures are characterized by formal deletion operations that model incomplete learning and forgetting. The problem solver and the deletion operator have been constrained to make it impossible to derive “star‐bugs”—algorithms that are so absurd that expert diagnosticians agree that the alogorithm will never be observed as a bug. Hence, the theory not only generates the observed bugs, it fails to generate star‐bugs.

The theory has been tested on an extensive data base of bugs for multidigit subtraction that was collected with the aid of the diagnostic systems buggy and debuggy. In addition to predicting bug occurrence, by adoption of additional hypotheses, the theory also makes predictions about the frequency and stability of bugs, as well as the occurrence of certain latencies in processing time during testing. Arguments are given that the theory can be applied to domains other than subtraction and that it can be extended to provide a theory of procedural learning that accounts for bug acquisition. Lastly, particular care has been taken to make the theory principled so that it can not be tailored to fit any possible data.
Default Values, Criteria and Constructivism
Authors: Garnham Alan
Published: July 2005

Wittgenstein, in his later writings, gave an account of the meaning of expressions in terms of criteria for their application. As with many of Wittgenstein's later ideas the notion of a criterion has proved difficult to explicate. A recent account, which ties criteria to the philosophical doctrine of constructivism, provides a link between the concept of a criterion and a series of ideas about language understanding which have emerged in the past few years. It is shown that these ideas can be made to cohere within a general constructivist framework, and that an alternative realist framework is inadequate in this respect.
Unlearning Aristotelian Physics: A Study of Knowledge‐Based Learning*
Authors: DiSessa Andrea A.
Published: July 2005

A study of a group of elementary school students learning to control a computer‐implemented Newtonian object reveals a surprisingly uniform and detailed collection of strategies, at the core of which is a robust “Aristotelian” expectation that things should move in the direction they are last pushed. A protocol of an undergraduate dealing with the same situation shows a large overlap with the set of strategies used by the elementary school children and thus a marked lack of influence of classroom physics training on this student's naive physics. The data from these two studies are pooled and elaborated into a “genetic task analysis” of how one might come to understand Newtonian dynamics as a more or less natural evolution from the naive state.
Challenging “Early Competence”: A Process Oriented Analysis of Children's Classifying
Authors: Thornton Stephanie
Published: July 2005

In some circumstances, children of 5 produce identical classifications to 10 year olds when asked to sort a collection of objects. This has been interpreted as meaning that the process of constructing classifications is very similar at 5 and 10 years. But this conclusion rests on a comparison of the product of children's sortings, rather than on a study of their activity in producing sortings. The present paper argues that the process of classifying is in fact very different for 5 and 10 year olds: whereas the older children treat the whole classification as a single unit composed of interrelated classes, the younger children proceed as though each class were independent of the others. At around 7 years, there is evidence for a transitional phase, in which children directly work on the relations between classes and so organize their initially “juxtaposed” procedures into more coherent systems. The tendency to work on the relations between elements in the process of classifying is not, however, simply an age‐related phenomenon: evidence for a similar effect can be observed in children throughout the age range of 5 to 10 years, during the course of short experimental sessions. Furthermore, the effect is not merely a response to errors or difficulties: the tendency to work on classifying relations can be seen in 5‐year‐old children in a task in which they are already successful. It seems that children spontaneously discover and use information about their procedures and the relations between them. This process is an end in itself. It occurs whether or not its results yield more successful performance. The approach taken in this paper is not confined to one area of behavior. This analysis of children's classifying fits closely with work in a very different domain, i.e. Karmiloff‐Smith's work on children's language and other representational systems. The analysis has implications for computer models of skill acquisition, as well as for psychological theories of development.
A real‐world rational agent: unifying old and new AI
Authors: Verschure Paul F.M.J. , Althaus Philipp
Published: July 2005

Explanations of cognitive processes provided by traditional artificial intelligence were based on the notion of the knowledge level. This perspective has been challenged by new AI that proposes an approach based on embodied systems that interact with the real‐world. We demonstrate that these two views can be unified. Our argument is based on the assumption that knowledge level explanations can be defined in the context of Bayesian theory while the goals of new AI are captured by using a well established robot based model of learning and problem solving, called Distributed Adaptive Control (DAC). In our analysis we consider random foraging and we prove that minor modifications of the DAC architecture renders a model that is equivalent to a Bayesian analysis of this task. Subsequently, we compare this enhanced, “rational,” model to its “non‐rational” predecessor and a further control condition using both simulated and real robots, in a variety of environments. Our results show that the changes made to the DAC architecture, in order to unify the perspectives of old and new AI, also lead to a significant improvement in random foraging.
Visualization, pattern recognition, and forward search: effects of playing speed and sight of the position on grandmaster chess errors
Authors: Chabris Christopher F. , Hearst Eliot S.
Published: July 2005

A new approach examined two aspects of chess skill, long a popular topic in cognitive science. A powerful computer‐chess program calculated the number and magnitude of blunders made by the same 23 grandmasters in hundreds of serious games of slow (“classical”) chess, regular “rapid” chess, and rapid “blindfold” chess, in which opponents transmit moves without ever seeing the actual position. Rapid chess led to substantially more and larger blunders than classical chess. Perhaps more surprisingly, the frequency and magnitude of blunders did not differ in rapid versus blindfold play, despite the additional memory and visualization load imposed by the latter. We discuss the involvement of various cognitive processes in human problem‐solving and expertise, especially with respect to chess. Prior opposing views about the basis of general chess skill have emphasized the dominance of either (a) swift pattern recognition or (b) analyzing ahead, but both seem important and the controversy appears currently unresolvable and perhaps fruitless.
Intra‐sentential context effects on the interpretation of logical metonymy⋆
Authors: Lapata Mirella , Keller Frank , Scheepers Christoph
Published: July 2005

Verbs such as enjoy in the student enjoyed the book exhibit logical metonymy: enjoy is interpreted as enjoy reading. Theoreticalwork [Computational Linguistics 17 (4) (1991) 409; The Generative Lexicon, MIT Press, Cambridge, MA, 1995] predicts that this interpretation can be influenced by intra‐sentential context, e.g., by the subject of enjoy. In this article, we test this prediction using a completion experiment and find that the interpretation of a metonymic verb is influenced by the semantic role of its subject. We present a Bayesian model that accounts for the interpretation of logical metonymy and achieves a good fit on our experimental data. We show that the parameters of the model can be estimated from completion data or from corpus data.
The effects of self‐explaining when learning with text or diagrams
Authors: Ainsworth Shaaron , Th Loizou Andrea
Published: July 2005

Self‐explaining is an effective metacognitive strategy that can help learners develop deeper understanding of the material they study. This experiment explored if the format of material (i.e., text or diagrams) influences the self‐explanation effect. Twenty subjects were presented with information about the human circulatory system and prompted to self‐explain; 10 received this information in text and 10 in diagrams. Results showed that students given diagrams performed significantly better on post‐tests than students given text. Diagrams students also generated significantly more self‐explanations that text students. Furthermore, the benefits of self‐explaining were much greater in the diagrams condition. To discover why diagrams can promote the self‐explanation effect, results are interpreted with reference to the multiple differences in the semantic, cognitive and affective properties of the texts and diagrams studied.
Multidisciplinary creativity: the case of Herbert A. Simon
Authors: Dasgupta Subrata
Published: July 2005

In the twentieth century, no person epitomized more dramatically the “Renaissance mind” than Herbert A. Simon (1916–2001). In aworking life spanning over 60 years, Simon made seminal contributions to administrative theory, axiomatic foundations of physics, economics, sociology, econometrics, cognitive psychology, logic of scientific discovery, and artificial intelligence. Simon's life of the mind, thus, affords nothing less than a “laboratory” in which to observe and examine at close quarters the phenomenon of multidisciplinary creativity. In this paper, we attempt to shed some light on the nature of Simon's creativity and the nature of his particular Renaissance mind. In particular, we have attempted here to articulate the cognitive style underlying Simon's multidisciplinary creativity.
How toddlers represent enclosed spaces
Authors: Huttenlocher Janellen , Vasilyeva Marina
Published: July 2005

Recent findings indicate that toddlers can use geometric cues to locate an object hidden in a corner of a rectangular room after being disoriented [Cognition 61 (1996) 195]. It has been suggested that locating the object involves reestablishing one's initial heading. The present experiments examine search behavior after disorientation. We find that toddlers go directly to a particular corner, indicating that they do not have to reestablish their original heading. It also has been suggested that toddlers ability to use geometric cues is limited to surrounding spaces. We find that toddlers can locate an object from outside as well as from inside a space, although the task is harder from outside. Based on these results, we argue that while toddlers do not represent their position relative to a particular portion of a space, they nevertheless may represent their position relative to the entire space (i.e., outside vs. inside).
The ghost of Christmas future: didn't Scrooge learn to be good? Commentary on Magnuson, McMurray, Tanenhaus, and Aslin (2003)
Authors: McQueen James M.
Published: July 2005

Magnuson, McMurray, Tanenhaus, and Aslin [Cogn. Sci. 27 (2003) 285] suggest that they have evidence of lexical feedback in speech perception, and that this evidence thus challenges the purely feedforward Merge model [Behav. Brain Sci. 23 (2000) 299]. This evidence is open to an alternative explanation, however, one which preserves the assumption in Merge that there is no lexical–prelexical feedback during on‐line speech processing. This explanation invokes the distinction between perceptual processing that occurs in the short term, as an utterance is heard, and processing that occurs over the longer term, for perceptual learning.
Renal regulation of plasma glucose in the freshwater rainbow trout
Authors: Bucking Carol , Wood Chris M.
Published: July 2005

This study examined the effects of prolonged hyperglycemia on renal handling of glucose and explored the in vivo pharmacological effects of phlorizin on glucose transport in the rainbow trout. The transport of glucose was examined by experimentally elevating the rate of renal glucose reabsorption via infusion of the fish with exogenous glucose at a rate of 70 μmol kg–1 h–1 and by inactivating the glucose transporters via the simultaneous administration of phlorizin (1 μmol kg–1h–1). Glucose was reabsorbed against a concentration gradient, until plasma glucose levels reached ∼22 μmol l–1 and the transport maximum of glucose in the kidney(∼145 μmol kg–1 h–1) was exceeded. At this point, glucose was lost to the urine, resulting in glucosuria. Glucosuria affected water reabsorption, approximately doubling the water clearance ratio,and resulted in osmotic diuresis. This in turn reduced Na+reabsorption, increasing the amount lost to the urine from 0.5% to 2% of the filtered load. Glucose reabsorption was found to be correlated with Na+ reabsorption, though the latter was almost 10-fold higher than glucose transport rates. Phlorizin treatment reduced glucose reabsorption,although it did not block it entirely until 48–72 h of infusion. The glucosuria resulting from the blockade of the glucose transporters resulted in a similar osmotic diuresis and a greater Na+ loss to the urine (9%of filtered load). The results are discussed with respect to the net renal`wasting' of glucose and the detrimental osmoregulatory and ionoregulatory effects associated with glucosuria caused by carbohydrate-rich diets.
The effects of acclimation to reversed seasonal temperatures on the swimming performance of adult brown troutSalmo trutta
Authors: Day N. , Butler P. J.
Published: July 2005

Adult brown trout (Salmo trutta) were acclimatised to and maintained at seasonal temperatures (5°C in winter; 15°C in summer)and acclimated to reversed seasonal temperatures (15°C in winter; 5°C in summer) while exposed to the natural (i.e. seasonally variable)photoperiod. The mean critical swimming speeds (Ucrit) of animals acclimatised to the seasonal temperatures were similar, but more than 30% greater than those for fish acclimated to the reversed seasonal temperatures. The lower values of Ucrit that accompanied acclimation to reversed seasonal temperatures appeared largely to result from the inability of white muscle to function maximally, since the concentrations of lactate and ammonia in white muscle of fish swum to Ucrit at reversed seasonal temperatures were significantly lower than those in fish swum at seasonal temperatures. These observations,together with biochemical and morphometric attributes of muscle tissue,suggest that swimming ability is influenced, at least in part, by seasonal factors other than temperature. These data have important implications for the design of experiments using fish that experience predictable, usually seasonal, changes in their natural environment (temperature, dissolved oxygen,changes in water levels, etc.).
Alkaline tide and nitrogen conservation after feeding in an elasmobranch(Squalus acanthias)
Authors: Wood Chris M. , Kajimura Makiko , Mommsen Thomas P. , Walsh Patrick J.
Published: July 2005

We investigated the consequences of feeding for acid–base balance,nitrogen excretion, blood metabolites and osmoregulation in the Pacific spiny dogfish. Sharks that had been starved for 7 days were surgically fitted with indwelling stomach tubes for gastric feeding and blood catheters for repetitive blood sampling and were confined in chambers, allowing measurement of ammonia-N and urea-N fluxes. The experimental meal infused via the stomach tube consisted of flatfish muscle (2% of body mass) suspended in saline (4% of body mass total volume). Control animals received only saline(4% of body mass). Feeding resulted in a marked rise in both arterial and venous pH and HCO3– concentrations at 3–9 h after the meal, with attenuation by 17 h. Venous ṖO2 also fell. As there were negligible changes in ṖCO2,the response was interpreted as an alkaline tide without respiratory compensation, associated with elevated gastric acid secretion. Urea-N excretion, which comprised >90% of the total, was unaffected, while ammonia-N excretion was very slightly elevated, amounting to <3% of the total-N in the meal over 45 h. Plasma ammonia-N rose slightly. Plasma urea-N,TMAO-N and glucose concentrations remained unchanged, while free amino acid and β-hydroxybutyrate levels exhibited modest declines. Plasma osmolality was persistently elevated after the meal relative to controls, partially explained by a significant rise in plasma Cl–. This marked post-prandial conservation of nitrogen is interpreted as reflecting the needs for urea synthesis for osmoregulation and protein growth in animals that are severely N-limited due to their sporadic and opportunistic feeding lifestyle in nature.
V-ATPase inhibition prevents recovery from anoxia inArtemia franciscanaembryos: quiescence signaling through dissipation of proton gradients
Authors: Covi Joseph A. , Treleaven W. Dale , Hand Steven C.
Published: July 2005

The metabolic downregulation critical for long-term survival of Artemia franciscana embryos under anoxia is mediated, in part, by a progressive intracellular acidification. However, very little is known about the mechanisms responsible for the pH transitions associated with exposure to, and recovery from, oxygen deprivation. In the present study, we demonstrate with 31P-NMR that incubation of intact embryos with the V-ATPase inhibitor bafilomycin A1 severely limits intracellular alkalinization during recovery from anoxia without affecting the restoration of cellular nucleotide triphosphate levels. Based on these data, it appears that oxidative phosphorylation and ATP resynthesis can only account for the first 0.3 pH unit alkalinization observed during aerobic recovery from the 1 pH unit acidification produced during 1 h of anoxia. The additional 0.7 pH unit increase requires proton pumping by the V-ATPase. Aerobic incubation with bafilomycin also suggests that V-ATPase inhibition alone is not enough to induce an acute dissipation of proton gradients under anoxia. In intact embryos, the dissipation of proton gradients and uncoupling of oxidative phosphorylation with carbonyl cyanide 3-chlorophenylhydrazone (CCCP) leads to an intracellular acidification similar to that seen after 1 h of anoxia. Subsequent exposure to anoxia, in the continued presence of CCCP, yields little additional acidification, suggesting that proton gradients are normally dissipated under anoxia. When combined with protons generated from net ATP hydrolysis, these data show that the dissipation of proton chemical gradients is sufficient to account for the reversible acidification associated with quiescence in these embryos.
The effects of cortisol administration on social status and brain monoaminergic activity in rainbow troutOncorhynchus mykiss
Authors: DiBattista Joseph D. , Anisman Hymie , Whitehead Megan , Gilmour Kathleen M.
Published: July 2005

The hypothesis that circulating cortisol levels influence the outcome of social interactions in rainbow trout was tested. Juvenile rainbow trout Oncorhynchus mykiss were given a single intraperitoneal (i.p.)implant containing either cortisol (110 mg kg–1 fish), or cortisol plus the glucocorticoid receptor antagonist RU486 (mifepristone; 1100 mg kg–1 fish), and sampled after 5 days of social interactions with either a similar sized (<1.5% difference in fork length)or smaller conspecific (>5% difference). Within size-matched pairs of fish,cortisol treatment significantly increased the probability that the treated fish within each pair became subordinate, an effect that was abolished by simultaneous administration of RU486. Cortisol treatment also reduced the usual success of the larger fish within a pair to preferentially become dominant from 86% to 40% of pairs. To investigate one potential mechanism underlying the apparent effect of cortisol in predisposing trout to low social status, fish were treated with cortisol or cortisol+RU486 for 5 days, after which brain monoamines [5-hydroxytryptamine (5-HT); dopamine (DA)] and their major metabolites [5-hydroxyindolacetic acid (5-HIAA);3,4-dihydroxy-phenylacetic acid (DOPAC)] were measured. Significant increases of serotonergic activity ([5-HIAA]/[5-HT] ratio) were detected in the telencephalon with cortisol treatment, an effect that was eliminated by simultaneous administration of RU486. Also, cortisol treatment significantly decreased dopaminergic activity in the telencephalon. Somewhat surprisingly,the effects of cortisol treatment on monoaminergic activity in the hypothalamus were opposite to those in the telencephalon. Moreover, in no case did administration of RU486 abolish these effects. These results suggest that the effects of cortisol on social status in rainbow trout may be mediated via the modulation of central signaling systems and subsequent changes in behaviour and/or competitive ability, although the exact site of action in the brain remains uncertain.
Sprint running: a new energetic approach
Authors: di Prampero P. E. , Fusi S. , Sepulcri L. , Morin J. B. , Belli A. , Antonutto G.
Published: July 2005

The speed of the initial 30 m of an all-out run from a stationary start on a flat track was determined for 12 medium level male sprinters by means of a radar device. The peak speed of 9.46±0.19 m s–1 (mean± s.d.) was attained after about 5 s, the highest forward acceleration (af), attained immediately after the start,amounting to 6.42±0.61 m s–2. During acceleration, the runner's body (assumed to coincide with the segment joining the centre of mass and the point of contact foot terrain) must lean forward, as compared to constant speed running, by an angle α=arctang/af(g=acceleration of gravity). The complement (90–α) is the angle, with respect to the horizontal, by which the terrain should be tilted upwards to bring the runner's body to a position identical to that of constant speed running. Therefore, accelerated running is similar to running at constant speed up an `equivalent slope' ES=tan(90–α). Maximum ES was 0.643±0.059. Knowledge of ES allowed us to estimate the energy cost of sprint running (Csr, J kg–1m–1) from literature data on the energy cost measured during uphill running at constant speed. Peak Csr was 43.8±10.4 J kg–1 m–1; its average over the acceleration phase (30 m) was 10.7±0.59 J kg–1 m–1, as compared with 3.8 for running at constant speed on flat terrain. The corresponding metabolic powers (in W kg–1) amounted to 91.9±20.5 (peak) and 61.0±4.7(mean).
The effect of spinning forces on spider silk properties
Authors: Pérez-Rigueiro J. , Elices M. , Plaza G. , Real J. I. , Guinea G. V.
Published: July 2005

A new forced silking procedure has been developed that allows measurement of the low forces involved in the silking process and, subsequently, retrieval and tensile testing of the samples spun at the measured silking forces. A strong correlation between silking force and tensile behaviour of spider silk has been established. Fibres spun at high silking force – compared with the conventional yield stress – are stiff and show stress–strain curves previously found in forcibly silked fibres. By contrast, fibres spun at low and very low silking forces are more compliant, and their tensile behaviour corresponds to that of fibres naturally spun by the spider or to fibres subjected to maximum supercontraction, respectively. It has also been found that samples retrieved from processes with significant variations in the silking force are largely variable in terms of force–displacement curves, although reproducibility improves if force is re-scaled into stress. Fibres retrieved from processes with constant silking force show similar tensile properties both in terms of force–displacement and stress–strain curves.
Ectothermy and endothermy: evolutionary perspectives of thermoprotection by HSPs
Authors: Shabtay Ariel , Arad Zeev
Published: July 2005

Living organisms respond to heat exposure by selectively expressing heat shock proteins (HSPs). Accumulation of HSPs confers thermotolerance in cell cultures and in ectotherms and is an important component of the heat shock response. This response, however, has not been directly examined in relation to different `thermal states', namely ectothermy vs endothermy. By using avian development as a model system for transition from ectothermy to endothermy, we show that, in contrast to the ectothermic state, in the endothermic state the organism is more resistant to heat but relies less on HSPs as a first-line thermoprotective mechanism. Moreover, intraspecific,real-time, in vivo measurements in genetically diverse fowl strains relate improvement of thermoresistance in endotherms to improved body temperature (Tb) regulation, with a concomitant delay in the expression of HSPs. The time course of this delay and the Tb at which it occurs imply that the ontogenetic and evolutionary pathways leading to improved thermoresistance may have followed two, apparently non-related, parallel routes – cellular and peripheral(non-cellular). In search of other cellular components that differentially participate in the heat shock response, we revealed a significant expression of fatty acid synthase (FAS) in heat-exposed endotherms but not in ectotherms.
Dorsal and anal fin function in bluegill sunfishLepomis macrochirus: three-dimensional kinematics during propulsion and maneuvering
Authors: Standen E. M. , Lauder G. V.
Published: July 2005

Dorsal and anal fins are median fins located above and below the centre of mass of fishes, each having a moment arm relative to the longitudinal axis. Understanding the kinematics of dorsal and anal fins may elucidate how these fins are used in concert to maintain and change fish body position and yet little is known about the functions of these fins. Using three synchronized high-speed cameras (500 frames s–1) we studied the three-dimensional kinematics of dorsal and anal fins during steady swimming(0.5–2.5 TL s–1, where TL=total length) and during slow speed maneuvers (0.5 TLs–1). By digitizing points along every other fin ray in the soft-rayed portion of the fins we were able to determine not only the movement of the fin surface but also the curvature of individual fin rays and the resulting fin surface shape. We found that dorsal and anal fins begin oscillating, in phase, at steady swimming speeds above 1.0 TLs–1 and that maximum lateral displacement of the trailing edge of the fins as well as fin area increase with increasing steady swimming speed. Differences in area, lateral displacement and moment arm between the dorsal and anal fin suggest that dorsal and anal fins produce balancing torques during steady swimming. During maneuvers, fin area is maximized and mean lateral excursion of both fins is greater than during steady swimming,with large variation among maneuvers. Fin surface shape changes dramatically during maneuvers. At any given point in time the spanwise (base to tip)curvature along fin rays can differ between adjacent rays, suggesting that fish have a high level of control over fin surface shape. Also, during maneuvers the whole surface of both dorsal and anal fins can be bent without individual fin rays exhibiting significant curvature.
Spatial and temporal patterns of water flow generated by suction-feeding bluegill sunfishLepomis macrochirusresolved by Particle Image Velocimetry
Authors: Day Steven W. , Higham Timothy E. , Cheer Angela Y. , Wainwright Peter C.
Published: July 2005

The suction-feeding fish generates a flow field external to its head in order to draw prey into the mouth. To date there are very few empirical measurements that characterize the fluid mechanics of suction feeding,particularly the temporal and spatial patterns of water velocity in front of the fish. To characterize the flow in front of suction-feeding bluegill sunfish Lepomis macrochirus, measurements with high spatial (<1 mm) and temporal (500 Hz) resolution were taken using Particle Image Velocimetry (PIV). In an analysis separate from the PIV, high-speed video sequences were used for a novel method of visually tracking every seed particle for the duration of each feeding in order to determine directly the total parcel of water that the fish ingests. PIV measurements and particle tracking show that water is drawn from all around the mouth. Fluid velocity decreases rapidly with distance from the mouth and is only significant (>5%of speed at the mouth) within roughly 1 mouth diameter of the fish. Suction feeders gain little in terms of extending this flow field by even substantial increases in the fluid speed at the mouth opening. Instead, the chief advantage of increased flow speed at the mouth may be the increased magnitude of generated forces within the space very close to the mouth. After scaling of the velocity field based on size of the mouth opening and the measured fluid speed at a fixed position, the measured velocity profiles for all feedings are very similar to one another, so that a functional relationship for the magnitude of fluid speed as a function of distance from the predator mouth is presented and shown to be accurate over the range of kinematic variables tested. This relationship describes the velocity field both along the centerline of the fish and along transects lying at an angle to the centerline within both the mid-sagittal and frontal planes. Comparison of the time-resolved fluid velocity measurements to gape kinematics demonstrate that peak fluid speed occurs simultaneously with 95% of peak gape, showing that the bluegill maximizes nearly simultaneously both the generated forces and size of the region over which these forces act. The magnitude of peak fluid speed during each strike decreases as a function of increasing time to peak gape(r2=0.87), demonstrating a strong relationship between the rate of buccal cavity expansion and maximum generated flow speed.
The effect of piston bowl temperature on diesel exhaust emissions
Authors: Ladommatos N , Xiao Z , Zhao H
Published: July 2005

In modern, high-speed, direct injection diesel engines for passenger vehicles, there is extensive impingement of the fuel sprays on to the piston bowl walls. Recent trends towards smaller engine sizes, equipped with high-pressure common-rail fuel injection systems, have tended to increase the spray/piston wall interaction. This paper describes tests carried out in a high-speed direct injection automotive diesel engine, during which the temperature of the piston was increased in a controlled manner between 189 and 227 °C while being continuously monitored. The aim of the work was to quantify the effects of piston temperature on pollutant exhaust emissions. The results show a significant reduction in unburned hydrocarbon emission, a significant increase in smoke emission, and no significant change in the emission of oxides of nitrogen. The increase in smoke emission cannot be ascribed to changes in the engine volumetric efficiency or air-fuel ratio. The paper demonstrates that fuel spray deposition on the piston surface was in the form of a thin film that did not experience bulk boiling. A number of suggestions are put forward to help explain the observed changes in exhaust emissions with increasing piston temperature.
Effect of road conditions on the fatigue life of an automatic transmission output shaft
Authors: Ilie S , Ninic D , Stark H L , Tordon M , Katupitiya J
Published: July 2005

The analysis reported compares the effects of different road conditions on the fatigue life of a transmission output shaft. Four routes having differing driving conditions were investigated and, of those routes, the route with most stop-start events resulted in the greatest reduction to fatigue life. In-vehicle loading data have been compared with shaft fatigue testing, indicating that the shaft should not fail by fatigue in service, despite a generous prediction of daily use. To introduce a theoretical failure, a load-scaling factor has been used, thus providing a factor enabling comparison of the routes.
Analysis of the effect of variations in fuel line pressure in high-speed direct injection diesel engines, with high-pressure common rail fuel injection systems on heat release, cylinder pressure, performance, and NOx emissions
Authors: Wallace F J , Hawley J G
Published: July 2005

This paper is a further development of work previously reported on a wholly analytical approach to heat release modelling and is applicable to high-speed direct injection (HSDI) diesel engines operating with high-pressure common rail fuel injection systems under conditions of predominantly mixing-controlled combustion.

The key variable in this treatment is the fuel preparation or combustion rate factor WH which, in conjunction with the primary injection variables, i.e. rail pressure, injection velocity and duration, defines the shape and amplitude of the heat release curve.

It was shown in a previous paper that by expressing the fuel preparation rate factor WH as a function of time rather than crank angle, i.e. WHt instead of WHθ, the former can be presented as a nearly linear function of the square of injection velocity, i.e. WHt is directly proportional to the kinetic energy of the injected fuel spray, the latter evidently being the primary influence on the rate of the fuel-air mixing process.

The analytical treatment developed in the authors' previous paper then allows heat release rates in the engine, dQ/dθ, to be calculated over a wide range of engine speeds and loads, with the aid of the existing engine simulation code ODES (Otto diesel engine simulation) to predict the associated engine performance and emissions, without resorting to further engine testing.
Properties, performance, and emissions of methanol-gasoline blends in a spark ignition engine
Authors: Qi D H , Liu Sh Q , Zhang Ch H , Bian Y Zh
Published: July 2005

One of the major problems for the successful application of a methanol-gasoline blend as a motor fuel was the realization of a stable homogeneous liquid phase. This paper studied the effect of ethanol as the co-solvent in the methanol-gasoline blend in order to overcome this problem. In this way, not only was the phase separation problem solved but the methanol ratio in the blend was also increased. The critical phase separation temperature (CPST) of the methanol-gasoline blend increased with increasing water content in the blend, and the addition of ethanol caused the CPST to decrease. M10 (gasoline containing 8.5 vol % methanol and 1.5 vol % ethanol) and M25 (gasoline containing 19 vol % methanol and 6 vol % ethanol) were exploited to test the performance, the fuel consumption, and the exhaust emissions. The results show that the specific fuel consumption of M10 was almost the same as that of gasoline, but that of M25 was higher for all engine speeds at full load. The specific energy consumption of gasoline was higher than that of blends for all engine speeds at full load and that of M25 was lower under low load at a fixed engine speed. The engine torque and power output were observed to be lower than those of gasoline, and it was found that the higher the volume fraction of methanol in blend, the larger the reduction. The hydrocarbon emission concentration of M25 was higher and the nitrogen oxides emission concentration was lower than those of gasoline and M10 for all engine loads. Under low and moderate loads, the carbon monoxide concentration of gasoline was higher than that of methanol-gasoline blends, but under high loads that of M25 was higher.
A systemic analysis of railway accidents
Authors: Santos-Reyes J , Beard A N , Smith R A
Published: July 2005

Over the last 15 years many railway accidents have happened in Britain and worldwide. Following these train accidents, there has been a large amount of public debate about safety management on the British railways. These accidents have raised issues regarding the effectiveness of the safety management of the railway system. This paper presents a summary of the results of a preliminary systemic analysis of several British rail accidents, i.e. those at Clapham Junction (1988), Paddington (1999), Hatfield (2000), Selby (2001), and Potters Bar (2002). It also includes the train accident at Eschede, Germany (1998). It is hoped that this systemic analysis will help to identify ‘learning points’, which are relevant for preventing accidents in the railway industry. The model is described in the context of the British railway industry. However, the model itself is general and not specific to any particular country.
Ultrasonic waves for effective assessment of wheel-rail contact anomalies
Authors: Pau M
Published: July 2005

Ultrasonic waves are routinely used in the railway industry to supply information about integrity of wheels, rails, and axles for both quality control assessment (during the production process) and ‘in situ’ when the rolling stock has to be periodically checked for maintenance purposes.

Nevertheless, recently the authors proposed a different application of this technique which, although employing the same kind of equipment as a standard NDE control, is able to investigate the main features of the wheel-rail contact interface such as nominal contact area, real contact area, and contact pressure distribution.

On the grounds of the promising results obtained in the previous tests, this study proposes a further practical approach to common problems of wheel-rail contact that possibly affect the regular development of railway operations.

To this end, a number of wheel-rail systems were altered by artificially producing several kind of defects on their surfaces and thus obtained couplings were then analysed by the ultrasonic method in order to assess the capability of the technique to faithfully reproduce the modification introduced in the contact patch.

The results of the experimental tests allow us to state that the ultrasonic analysis of wheel-rail contact interfaces can be effectively employed to detect any sort of irregularities potentially present due to normal operations, and foresees a future application of the method as a tool to monitor critical points of a railway line in order to ensure significant improvements in safety conditions.
Noradrenergic Modulation of Emotion-Induced Forgetting and Remembering
Authors: Hurlemann René , Hawellek Barbara , Matusch Andreas , Kolsch Heike , Wollersen Heike , Madea Burkhard , Vogeley Kai , Maier Wolfgang , Dolan Raymond J.
Published: July 2005

We used a free-recall paradigm to establish a behavioral index of the retrograde and anterograde interference of emotion with episodic memory encoding. In two experiments involving 78 subjects, we show that negatively valenced items elicit retrograde amnesia, whereas positively valenced items elicit retrograde hypermnesia. These data indicate item valence is critical in determining retrograde amnesia and retrograde hypermnesia. In contrast, we show that item arousal induces an anterograde amnesic effect, consistent with the idea that a valence-evoked arousal mechanism compromises anterograde episodic encoding. Randomized double-blind administration of the β-adrenoceptor antagonist propranolol compared with the selective norepinephrine (NE) reuptake-inhibitor reboxetine, and placebo, demonstrated that the magnitude of this emotional amnesia and hypermnesia can be upregulated and downregulated as a function of emotional arousal and central NE signaling. We conclude that a differential processing of emotional arousal and valence influences how the brain remembers and forgets.
Globus Pallidus Neurons Dynamically Regulate the Activity Pattern of Subthalamic Nucleus Neurons through the Frequency-Dependent Activation of Postsynaptic GABAAand GABABReceptors
Authors: Hallworth Nicholas E. , Bevan Mark D.
Published: July 2005

Reciprocally connected GABAergic neurons of the globus pallidus (GP) and glutamatergic neurons of the subthalamic nucleus (STN) are a putative generator of pathological rhythmic burst firing in Parkinson's disease (PD). Burst firing of STN neurons may be driven by rebound depolarization after barrages of GABAAreceptor (GABAAR)-mediated IPSPs arising from pallidal fibers. To determine the conditions under which pallidosubthalamic transmission activates these and other postsynaptic GABARs, a parasagittal mouse brain slice preparation was developed in which pallidosubthalamic connections were preserved. Intact connectivity was first confirmed through the injection of a neuronal tracer into the GP. Voltage-clamp and gramicidin-based perforated-patch current-clamp recordings were then used to study the relative influences of GABAAR- and GABABR-mediated pallidosubthalamic transmission on STN neurons. Spontaneous phasic, but not tonic, activation of postsynaptic GABAARs reduced the frequency and disrupted the rhythmicity of autonomous firing in STN neurons. However, postsynaptic GABABRs were only sufficiently activated to impact STN firing when pallidosubthalamic transmission was elevated or pallidal fibers were synchronously activated by electrical stimulation. In a subset of neurons, rebound burst depolarizations followed high-frequency, synchronous stimulation of pallidosubthalamic fibers. Although GABABR-mediated hyperpolarization was itself sufficient to generate rebound bursts, coincident activation of postsynaptic GABAARs produced longer and more intense burst firing. These findings elucidate a novel route through which burst activity can be generated in the STN, and suggest that GABARs on STN neurons could act in a synergistic manner to generate abnormal burst activity in PD.
cAMP Responsive Element-Binding Protein Phosphorylation Is Necessary for Perirhinal Long-Term Potentiation and Recognition Memory
Authors: Warburton E. Clea , Glover Colin P. J. , Massey Peter V. , Wan Humin , Johnson Ben , Bienemann Alison , Deuschle Ule , Kew James N. C. , Aggleton John P. , Bashir Zafar I. , Uney James , Brown Malcolm W.
Published: July 2005

We established the importance of phosphorylation of cAMP responsive element-binding protein (CREB) to both the familiarity discrimination component of long-term recognition memory and plasticity within the perirhinal cortex of the temporal lobe. Adenoviral transduction of perirhinal cortex (and adjacent visual association cortex) with a dominant-negative inhibitor of CREB impaired the preferential exploration of novel over familiar objects at a long (24 h) but not a short (15 min) delay, disrupted the normal reduced activation of perirhinal neurons to familiar compared with novel pictures, and impaired long-term potentiation of synaptic transmission in perirhinal slices. The consistency of these effects across the behavioral, systems, and cellular levels of analysis provides strong evidence for involvement of CREB phosphorylation in synaptic plastic processes within perirhinal cortex necessary for long-term recognition memory.
Functionally Segregated Neural Substrates for Arbitrary Audiovisual Paired-Association Learning
Authors: Tanabe Hiroki C. , Honda Manabu , Sadato Norihiro
Published: July 2005

To clarify the neural substrates and their dynamics during crossmodal association learning, we conducted functional magnetic resonance imaging (MRI) during audiovisual paired-association learning of delayed matching-to-sample tasks. Thirty subjects were involved in the study; 15 performed an audiovisual paired-association learning task, and the remainder completed a control visuo-visual task. Each trial consisted of the successive presentation of a pair of stimuli. Subjects were asked to identify predefined audiovisual or visuo-visual pairs by trial and error. Feedback for each trial was given regardless of whether the response was correct or incorrect. During the delay period, several areas showed an increase in the MRI signal as learning proceeded: crossmodal activity increased in unimodal areas corresponding to visual or auditory areas, and polymodal responses increased in the occipitotemporal junction and parahippocampal gyrus. This pattern was not observed in the visuo-visual intramodal paired-association learning task, suggesting that crossmodal associations might be formed by binding unimodal sensory areas via polymodal regions. In both the audiovisual and visuo-visual tasks, the MRI signal in the superior temporal sulcus (STS) in response to the second stimulus and feedback peaked during the early phase of learning and then decreased, indicating that the STS might be key to the creation of paired associations, regardless of stimulus type. In contrast to the activity changes in the regions discussed above, there was constant activity in the frontoparietal circuit during the delay period in both tasks, implying that the neural substrates for the formation and storage of paired associates are distinct from working memory circuits.
Periodic High-Conductance States in Spinal Neurons during Scratch-Like Network Activity in Adult Turtles
Authors: Alaburda A. , Russo R. , MacAulay N. , Hounsgaard J.
Published: July 2005

Intense synaptic activity may alter the response properties of neurons in highly interconnected networks. Here we investigate whether the excitability and the intrinsic response properties of neurons in the spinal cord are affected by the increased synaptic conductance during functional network activity. Scratch episodes were induced by mechanical stimulation in the isolated carapace-spinal cord preparation from the adult turtle. Intracellular recordings revealed a dramatic increase in synaptic activity in interneurons and motoneurons during scratch activity. Superimposed slow depolarizing waves were phase-related to the rhythmic bouts of spike activity in the hip flexor nerve. The increase in synaptic conductance in interneurons and motoneurons varied with the scratch rhythm. During individual episodes, the conductance shifted smoothly with the scratch rhythm from near-resting levels to levels two to four times higher. In slice experiments, we found that even moderate increases in the conductance of motoneurons suppressed the slow afterhyperpolarization and the plateau potentials. We conclude that the excitability and the intrinsic response properties of spinal neurons are periodically quenched by high synaptic conductance during functional network activity.