Absence Of Reinforcement Research Articles

Lack of reinforcement is hard to “bear”: Assessing judgment bias in grizzly bears (Ursus arctos horribilis)

ABSTRACT Cognitive biases reveal underlying affective state by indicating optimism and pessimism. This methodology may permit assessment of positive welfare in animals that have few validated positive welfare indicators, such as bears. Our goal was to validate a judgment bias test for assessing optimism in brown bears, using a touchscreen. After training the bears on a conditional discrimination, we compared responses to an ambiguous stimulus in a 2 × 2 nested design involving four experimental conditions representing presence or absence of a behind-the-scenes tour and presence or absence of a keeper training session with food reinforcement. We recorded bears’ behavior during the conditions as a measure of convergent validity. Testing revealed the possibility of pessimism in the absence of reinforcement in one bear. More frustration behaviors were also observed during the no food reinforcement conditions. This is the first experimental demonstration of brown bears using a touchscreen and one of only three reports in which bears have been reported to perform a conditional discrimination. This method of assessing underlying affective state shows promise for the future.

Impact of Eggshell Powder on the Mechanical and Thermal Properties of Lightweight Geopolymer

Adopting proper waste management technology in the place of the construction industry to the extent possible to lower the production of new materials and intern reduces the environmental impact pertaining to the industry. In this work, eggshell powder (ESP; waste from the poultry industry) and fly ash (FA; waste from combustion of coal) were utilized as precursors for producing geopolymer and to substitute conventional cement-based construction materials. Three different weight percentage ratios of precursors, namely, 90FA:10ESP, 80FA:20ESP, and 70FA:30ESP were reinforced with two different weight percentages, namely, 15 and 30 wt% of paddy straw in the presence of suitable combinations of sodium silicate and sodium hydroxide to obtain lightweight geopolymer panels. Results received from different analytical tests, namely, density, water absorption, compressive strength, and flexural strength infer that the incorporation of ESP enhances the performance of the geopolymer products to a considerable extent. The specimen sample made using 70FA:30ESP in the absence of paddy straw reinforcement possesses a compressive strength value of 15.64 MPa, which is higher than that of paddy straw reinforced panels. It was observed that there was a reverse trend noticed in the case of flexural behavior on reinforcement of paddy straw, namely, 15 wt% possesses a higher value than that of the panel (70FA:30ESP) made using in the absence of reinforcement. The lowest thermal conductivity value was observed at 0.0633 W/m·K for the sample 90FA:10ESP reinforced with 30% paddy straw. Data from different studies infer that using ESP and paddy straw reinforcement influences strength properties and thermal conductivity. The present study indicates valid information related to the using biowastes for the production of insulation materials and environmental preservation and energy conservation.

Improvement of the tensile properties of laminated composites reinforced with Heli‐Coil forms of carbon nanotubes

AbstractThe traditional composite laminated structures suffer from the absence of reinforcements in the thickness direction between the laminae and microfibers, which will result in poor interaction between the laminae, individual microfiber filaments, and the resin. In addition, out‐of‐the‐plane properties are generally dominated and controlled by poor matrix properties (e.g., mechanical, electrical, and thermal). Most prior investigations were focused on the use of straight carbon nanotubes (CNTs), graphene, or nanomaterials in particle forms to improve the resin properties. Our previous research has shown that CNTs with helical (Heli‐Coil) geometries (HCNTs) are more effective as a nanoscale reinforcement to improve the properties of polymeric resins. Because of their inertness, the interfacial bonding between CNTs and the resin is generally weak, and they can be easily pulled out of the resin (inefficient load transfer) if the CNTs are in their straight forms. However, the helical geometries of HCNTs can provide unique mechanical‐interlocking mechanisms between the constituents that can substantially improve their effectiveness as a nanoscale reinforcement, leading to improvements in composite performance, properties, and multifunctionality. In this research, HCNTs at low concentrations below 0.1 wt% were processed and then used to fabricate nanocomposite laminates. Tensile test specimens were carefully prepared following the ASTM D3039/D3039M standard and then tested, analyzed, and evaluated. Additionally, the fractured test specimens were inspected and analyzed using optical and 3D scanning laser‐confocal‐microscopy imaging. The test results showed improvements of 12.3%, 11.3%, and 17.5% for the tensile strength, modulus, and strain‐to‐failure, respectively. In conclusion, traditional fiber‐reinforced composites can considerably benefit from the helical forms of HCNTs.Highlights The helical geometry of CNTs (HCNTs) is more effective for composite reinforcement. HCNTs provide unique interlocking mechanisms between the composite constituents. HCNTs can considerably improve the multifunctional characteristics of the composites. HCNTs can considerably improve the tensile properties of composite laminates. Traditional composites can substantially benefit from the helical forms of HCNTs.

Efficient visual learning by bumble bees in virtual-reality conditions: Size does not matter.

Recent developments allowed establishing virtual-reality (VR) setups to study multiple aspects of visual learning in honey bees under controlled experimental conditions. Here, we adopted a VR environment to investigate the visual learning in the buff-tailed bumble bee Bombus terrestris. Based on responses to appetitive and aversive reinforcements used for conditioning, we show that bumble bees had the proper appetitive motivation to engage in the VR experiments and that they learned efficiently elemental color discriminations. In doing so, they reduced the latency to make a choice, increased the proportion of direct paths toward the virtual stimuli and walked faster toward them. Performance in a short-term retention test showed that bumble bees chose and fixated longer on the correct stimulus in the absence of reinforcement. Body size and weight, although variable across individuals, did not affect cognitive performances and had a mild impact on motor performances. Overall, we show that bumble bees are suitable experimental subjects for experiments on visual learning under VR conditions, which opens important perspectives for invasive studies on the neural and molecular bases of such learning given the robustness of these insects and the accessibility of their brain.

Effects of brief post-sample cues signaling presence or absence of reinforcers in delayed matching-to-sample

When short-term memory is assessed in the delayed matching-to-sample (DMTS) procedure, performance is better when cues signal larger reinforcer magnitudes or higher reinforcer probabilities for correct responding. Previous studies demonstrating signaled-magnitude or signaled-probability effects presented cues for a prolonged period during the sample stimulus and/or retention interval. The present study asked whether a signaled-probability effect would occur with brief post-sample cues that signaled the presence or absence of reinforcement. Five pigeons responded in a DMTS task in which sample stimuli were sometimes followed by a 0.5-s cue signaling that reinforcers would either be available or not available in the current trial, and the retention interval varied from 0.5 s to 20 s. A reliable signaled-probability effect was found when reinforcers were arranged independently and for all correct responses, whereas a smaller, less systematic effect was found when reinforcers were arranged dependently and probabilistically. These findings highlight the importance of reinforcement contingencies and contingency discriminability in remembering, and add to the evidence showing that cues signaling differential reinforcement in DMTS may affect processes during the retention interval and comparison phase, rather than attention to the sample stimulus.

Migration and formation of an iron rich layer during acidic corrosion of concrete with no steel reinforcement

The present study aimed to study the formation, enrichment, and relocation of iron-rich regions in the corroded area of concrete blocks, made without rebar, subjected to severely corrosive highly acidic conditions. In this work, three different concrete mix designs (a proprietary ready-mixed concrete, and laboratory made mortar and concrete) were corroded under induced accelerated conditions in sulfuric acid solutions at pH 1 for a duration of one to six months, in the absence of reinforcement (i.e. rebar) or iron-oxidizing bacteria. A variety of physicochemical and mechanical techniques were applied to monitor and assess the corrosion progress, and physical and chemical changes in the corroded samples. Results indicated a pronounced presence of iron rich layer (iron oxide/hydroxide) at the border of the corrosion front and the transition zone in all mix designs in the form of a ring. While existing papers in the literature describe the iron coming from the rebar, the only source of mobile iron in this experiment was from the iron oxide (Fe2O3) already in the cement. This zone (in a form of a ring) had an average iron content of 2.0 wt% and moved away from the surface to the center of the samples submerged in a sulfuric acid bath with the increase of immersion time, and it was accompanied by hairline cracks. The movement of this zone was in the same direction as sulfate (from acidic media) ingress and the opposite direction of calcium ion leaching, (Ca leaching). The rate of corrosion, the hardness and the compressive strength of concrete are mostly affected by the concrete mix design, the iron-ring enrichment and relocation had no significant impact on them. Detection of the iron-rich zone is an indication of the depth of corrosion at advanced stages in concrete products.

Age affects pigeons\u2019 (Columba livia) memory capacity but not representation of serial order during a locomotor sequential-learning task

Aging affects individuals of every species, with sometimes detrimental effects on memory and cognition. The simultaneous-chaining task, a sequential-learning task, requires subjects to select items in a predetermined sequence, putting demands on memory and cognitive processing capacity. It is thus a useful tool to investigate age-related differences in these domains. Pigeons of three age groups (young, adult and aged) completed a locomotor adaptation of the task, learning a list of four items. Training began by presenting only the first item; additional items were added, one at a time, once previous items were reliably selected in their correct order. Although memory capacity declined noticeably with age, not all aged pigeons showed impairments compared to younger pigeons, suggesting that inter-individual variability emerged with age. During a subsequent free-recall memory test in the absence of reinforcement, when all trained items were presented alongside novel distractor items, most pigeons did not reproduce the trained sequence. During a further forced-choice test, when pigeons were given a choice between only two of the trained items, all three age groups showed evidence of an understanding of the ordinal relationship between items by choosing the earlier item, indicating that complex cognitive processing, unlike memory capacity, remained unaffected by age.

Incorporation of Smart Concrete in Large-Scale RC Beams for Evaluating Self-Sensing and structural Properties

Only using a small number of samples in the absence of reinforcement, the concrete self-monitoring behaviour is tested, which is inaccurate for real-world structures. The behaviour of concrete is primarily tested, which can be inaccurate for structures in real time. This study examined the self-sensing ability of large-scale reinforced concrete beams that are 1500 mm long and 125 mm wide embedded with smart concrete at top and bottom surfaces for a length of 350 mm. As shear failure is catastrophic, the present study focused on evaluating RC beams' self-sensing property failing under shear, and shear reinforcement was not given for the same reason. A total of six RC beams, 3 of are 250 mm deep and 3 are 350 mm deep with variable reinforcement ratios, were tested in a four-point bending test to study the self-sensing properties such as strain and crack/damage sensing. Mechanical/structural properties of all the beams have been documented, along with self-sensing properties. The results obtained showed that partially placed smart concrete in the RC beam's pure bending region successfully sensed all strain and damage/cracks without any impact due to beam depth and reinforcement ratio. During testing, it was observed that 250-mm-deep beams failed due to flexure/concrete crushing, and 350-mm-deep beams failed due to shear. In particular, smart concrete's self-sensing property showed promising results for the beams that failed due to flexure by representing all the cracks developed in the pure bending region. Fraction change in resistance (FCR) has also been obtained for all the beams during self-sensing testing, and this FCR has been successfully co-related with concrete strain in compression and steel strain in tension. An empirical equation was also derived separately for beams that failed in shear and flexure, which provides a co-relation between FCR and concrete or steel strain.

Prefrontal NMDA-receptor antagonism disrupts encoding or consolidation but not retrieval of incidental context learning

The Context Preexposure Facilitation Effect (CPFE) is a variant of contextual fear conditioning in which learning about the context, acquiring a context-shock association, and retrieval of this association occur separately across three phases (context preexposure, immediate-shock training, and retention). We have shown that prefrontal inactivation or muscarinic-receptor antagonism prior to any phase disrupts retention test freezing during the CPFE in adolescent rats (Heroux et al., 2017; Robinson-Drummer et al., 2017). Furthermore, the medial prefrontal cortex (mPFC) is the only region in which robust learning-related expression of the immediate early genes c-Fos, Arc, Egr-1 and Npas4 is observed during immediate-shock training in the CPFE (Asok et al., 2013; Heroux et al., 2018; Schreiber et al., 2014). However, the role of prefrontal NMDA-receptor plasticity in supporting preexposure- and training-day processes of the CPFE is not known. Therefore, the current study examined the effects of intra-mPFC infusion of the NMDA-receptor antagonist MK-801 or saline vehicle prior to context preexposure (Experiment 1) or immediate-shock training (Experiment 2) in adolescent Long-Evans male and female rats. This infusion given prior to context preexposure but not training abolished retention test freezing, with no difference between MK-801-infused rats and non-associative controls preexposed to an alternative context (pooled across drug). These results demonstrate a role of prefrontal NMDA-receptor plasticity in the acquisition and/or consolidation of incidental context learning (i.e., encoded in the absence of reinforcement). In contrast, this plasticity is not required for context retrieval, or acquisition, expression, or consolidation of a context-shock association during immediate-shock training in the CPFE. These experiments add to a growing body of work implicating the mPFC in Pavlovian contextual fear conditioning processes in rodents.

Generalized thermo-elastic interaction in a fiber-reinforcedmaterial with spherical holes

In this paper, a mathematical model is used to the evaluation of thermoelastic interactions in fiber-reinforced material with a spherical cavity. With the goal of establishing the generalized thermoelastic model with thermal relaxation time are exploited. inner surface of the spherical cavity is tractions free and loaded by the uniform step in temperature. The finite element scheme is used to get the problem numerical solutions. The numerical results have been discussed graphically to show the impacts of the presence and the absence of reinforcement.

Barefoot Running: Between Fashion and Real Way to Prevent Joint Osteo Lesions?

Background and objectivesRunning has gone from a vital necessity for the man to a playful sport. Different rheumatic and orthopedic pathologies have appeared, in front of which the shoe industry has reacted by creating reinforced shoes that are supposed to overcome the induced lesions. Several years later, the trend toward reinforcement has gone toward minimalism, which is the absence of reinforcement, that is, a more natural race.MethodWe observed variations of kinetics and kinematics in young, unprofessional, healthy runners during a shoe race and a shoeless race, which is the form of maximum minimalism. We then correlated minimalism variations with the variables of the race and the joint angles.ResultsWe observed significant difference (P < 0.01) in the cycle rate, the cycle length, the step rate, and the angle of attack between running with and without shoes. A small variation of the minimalism index is associated with an increase in knee angle (r2> 0.5). Conversely, a large variation in the minimalism index is related to a decrease in the knee angle (r2> 0.5). The minimalism index has no impact on the angulation of the ankle and hip (r2< 0.3).ConclusionSlow transition will bring gains in terms of decreasing the length of the stride, which limits the load on the shin. Greater flexibility can be achieved by decreasing the flexion angle of the knee, which decreases the demand for quadriceps muscles and the risk of knee injury with a greater risk of injury at the tibial level.

Human Choice Predicted by Obtained Reinforcers, Not by Reinforcement Predictors.

Macphail (1985) proposed that “intelligence” should not vary across vertebrate species when contextual variables are accounted for. Focusing on research involving choice behavior, the propensity for choosing an option that produces stimuli that predict the presence or absence of reinforcement but that also results in less food over time can be examined. This choice preference has been found multiple times in pigeons (Stagner and Zentall, 2010; Zentall and Stagner, 2011; Laude et al., 2014) and has been likened to gambling behavior demonstrated by humans (Zentall, 2014, 2016). The present experiments used a similarly structured task to examine adult human preferences for reinforcement predictors and compared findings to choice behavior demonstrated by children (Lalli et al., 2000), monkeys (Smith et al., 2017; Smith and Beran, 2020), dogs (Jackson et al., 2020), rats (Chow et al., 2017; Cunningham and Shahan, 2019; Jackson et al., 2020), and pigeons (Roper and Zentall, 1999; Stagner and Zentall, 2010). In Experiment 1, adult human participants showed no preference for reinforcement predictors. Results from Experiment 2 suggest that not only were reinforcement predictors not preferred, but that perhaps reinforcement predictors had no effect at all on choice behavior. Results from Experiments 1 and 2 were further assessed using a generalized matching equation, the findings from which support that adult human choice behavior in the present research was largely determined by reinforcement history. Overall, the present results obtained from human adult participants are different than those found from pigeons in particular, suggesting that further examination of Macphail (1985) hypothesis is warranted.

Discriminative control of saccade latencies.

Recent studies have demonstrated that saccadic reaction times (SRTs) are influenced by the temporal regularities of dynamic environments (Vullings & Madelain, 2018). Here, we ask whether discriminative control (i.e., the possibility to use external stimuli signaling the future state of the environment) of latencies in a search task might be established using reinforcement contingencies. Eight participants made saccades within 80-750 ms toward a target displayed among distractors. We constructed two latency classes, "short" and "long," using the first and last quartiles of the individual baseline distributions. We then used a latency-contingent display paradigm in which finding the visual target among other items was made contingent upon specific SRTs. For a first group, the postsaccadic target was displayed only following short latencies with leftward saccades, and following long latencies with rightward saccades. The opposite was true for a second group. When short- and long-latency saccades were reinforced (i.e., the target was displayed) depending on the saccade direction, median latencies differed by 74 ms on average (all outside the 98% null hypothesis confidence intervals). Posttraining, in the absence of reinforcement, we still observed strong differences in latency distributions, averaging 64 ms for leftward versus rightward saccades. Our results demonstrate the discriminative control of SRTs, further supporting the effects of reinforcement learning for saccade. This study reveals that saccade triggering is finely controlled by learned temporal and spatial properties of the environment using predictive mechanisms.

Impact of inhomogeneous fiber-reinforced layer with frictional interface on Rayleigh-type wave propagation

The effect of frictional boundary on the propagation of Rayleigh-type wave in an initially stressed inhomogeneous fiber-reinforced layer overlying an initially stressed homogeneous semi-infinite medium has been analyzed by an approximate analytical method. A realistic model has been considered for sliding boundary friction at the interface. The frequency equation has been obtained in closed form. The substantial effects of various affecting parameters, viz. reinforcement, inhomogeneity, bonding parameter, spectral decay parameter, and horizontal initial stress on phase and damped velocity have been discussed graphically in detail. The remarkable observation has been obtained through the comparative study in the presence and the absence of reinforcement in the layer.

An imprinting object rapidly acquires high attractiveness when associated with food delivery

Abstract Young precocial birds develop a preference for an imprinting object by mere visual exposure to it in the absence of conventional physiological reinforcement. The lack of the necessity of conventional reinforcement for imprinting, however, does not mean that such reinforcement is unimportant. The evidence presented here shows that an imprinting object rapidly acquires high attractiveness to young chicks when it is associated with food provisioning. Domestic chicks, Gallus gallus domesticus, were first exposed to two different imprinting objects in the absence of any reinforcement. Subsequently, two groups of chicks received a single feeding session wherein they were provided with prey from one of the imprinting objects. A third group served as a control in which the chicks were exposed to one of the imprinting objects and prey delivery in an unpaired way. Finally, all chicks received two choice tests to assess their preferences for the two imprinting objects. The chicks that received food from an imprinting object strongly preferred that object to the alternative familiar-only object, and preferred the familiar-only object to a novel object. The control group did not show any preference between the two imprinting objects, but preferred the unpaired imprinting object to a novel object. These results suggest that primary-need reinforcers such as food contribute to increasing the attractiveness of an imprinting object by promoting rapid associative learning.

When is the rat retrosplenial cortex required for stimulus integration?

The rodent retrosplenial cortex is known to be vital for spatial cognition, but evidence has also pointed to a role in processing nonspatial information. It has been suggested that the retrosplenial cortex may serve as a site of integration of incoming sensory information. To examine this proposal, the current set of experiments assessed the impact of excitotoxic lesions in the retrosplenial cortex on two behavioral tasks that tax animals’ ability to process multiple and overlapping environmental stimuli. In Experiment 1, rats with retrosplenial lesions acquired a negative patterning discrimination, a form of configural learning that can be solved only by learning the conjunction of cues. Subsequent transfer tests confirmed that both the lesion and control animals had solved the task by using configural representations. Furthermore, in Experiment 2, a 2nd cohort of retrosplenial lesion animals successfully acquired conditioned inhibition. Nevertheless, the same animals failed a subsequent summation test that assesses the ability to transfer what has been learned about one stimulus to another stimulus in the absence of reinforcement. Taken together, these results suggest that in the nonspatial domain, the retrosplenial cortex is not required for forming associations between multiple or overlapping environmental stimuli and, consequently, retrosplenial engagement in such processes is more selective than was previously envisaged.

Does a negative discriminative stimulus function as a punishing consequence?

The study and use of punishment in behavioral treatments has been constrained by ethical concerns. However, there remains a need to reduce harmful behavior unable to be reduced by differential-reinforcement procedures. We investigated whether response-contingent presentation of a negative discriminative stimulus previously correlated with an absence of reinforcers would punish behavior maintained by positive reinforcers. Across four conditions, pigeons were trained to discriminate between a positive discriminative stimulus (S+) signaling the presence of food, and a negative discriminative stimulus (S-) signaling the absence of food. Once learned, every five responses on average to the S+ produced S- for a duration of 1.5 s. S+ response rate decreased for a majority of pigeons when responses produced S-, compared to when they did not, or when a neutral control stimulus was presented. In Condition 5, choice between two concurrently presented S+ alternatives shifted away from the alternative producing S-, despite a 1:1 reinforcer ratio. Therefore, presenting contingent S- stimuli punishes operant behavior maintained on simple schedules and in choice situations. Development of negative discriminative stimuli as punishers of operant behavior could provide an effective approach to behavioral treatments for problem behavior and subverting suboptimal choices involved in addictions.

Finite Element Analysis of Thermoelastic Fiber-Reinforced Anisotropic Hollow Cylinder with Dual-Phase-Lag Model

In the present paper, we have constructed the equations for generalized thermoelasticity of a fiber-reinforced anisotropic hollow cylinder. The formulation is applied in the context of dualphase-lag model. An application of hollow cylinder is investigated for the outer surface is traction free and thermally isolated, while the inner surface is traction free and subjected to thermal shock. The problem is solved numerically using a finite element method. The results of displacement, temperature and radial and hoop stress are obtained and then presented graphically. Finally, the comparisons are made between the results predicted by the coupled theory, Lord and Shulman theory and dual-phase-lag model in presence and absence of reinforcement.

On point source influencing Love-type wave propagation in a functionally graded piezoelectric composite structure: A Green’s function approach

Green’s function plays an important role in solving the problems concerning point action or impulse responsible for wave motions in materials. Prime objective of the this article is to investigate the propagation behaviour of Love-type wave influenced by a point source in a composite structure comprising a functionally graded piezoelectric material layer lying over a functionally graded fibre-reinforced material half-space. Green’s function technique is adopted in order to obtain the dispersion equation, which is further reduced to the classical Love wave equation as a particular case of the problem. The effect of increasing thickness of functionally graded piezoelectric material layer on the circular frequency and wave number is unravelled and depicted graphically. Moreover, influence of heterogeneity, piezoelectricity and dielectric constant associated with functionally graded piezoelectric material layer and effect of heterogeneity parameter and corresponding magnification factor concerned with functional gradedness of functionally graded fibre-reinforced material half-space have been reported through numerical computation and graphical delineation. For sake of computation, numerical data of PZT-5H ceramics for the functionally graded piezoelectric material layer and carbon-fibre epoxy-resin for functionally graded fibre-reinforced material half-space have been considered. Comparative study is performed to elucidate the effect of presence and absence of reinforcement in functionally graded half-space on the phase velocity of Love-type wave propagating in composite structure.

Effect of gravity field and moving internal heat source on a 2-D problem of thermoelastic fiber-reinforced medium: Comparison of different theories

ABSTRACTA new fiber-reinforced model has been constructed by taking into account the deformation of a generalized thermoelastic medium with internal heat source. A general model of the equations of the formulation in the context of the Lord–Shulman theory that includes one relaxation time and Green–Lindsay theory with two relaxation times, as well as the classical dynamical coupled theory, is applied to study the influence of gravity and reinforcement on the total deformation of a thermoelastic medium. The normal mode analysis is used to obtain the exact expressions for the physical quantities. The variations of the considered variables with the horizontal distance are illustrated graphically. Comparisons are made with the results in the three theories in the presence and absence of reinforcement, gravity, and moving internal heat source.