Reinforcement Values Research Articles

Vegetation-induced soil stabilization in coastal area: An example from a natural mangrove forest

Mangrove forests provide essential ecosystem services in tropical and semitropical regions by supporting their natural regeneration and other biosystem processes, offering livelihood for local communities, and contributing significantly to the natural resources. Systematic analyses on the protective role of mangrove forests and their effects on reducing coastal erosion have been carried out rarely. Mangroves form a complex ecosystem that increases substrate stabilization and dissipates wave energy favouring the deposition of fine material. This study focuses on assessing the role of white mangrove (Avicennia marina (Forssk.) Vierh.) roots in stabilizing the coastline. In a study site located in Southern Iran, a series of field and laboratory measurements were conducted on root systems that were collected from transects perpendicular to the coastline. Root samples were collected from soil cores at fixed distances from tree stems in three layers at seaward and landward positions. Moreover, Root tensile tests were conducted to estimate their biomechanical characteristics which provided the data of parameters of root reinforcement models. Also, the spatial distribution of root reinforcement and the intrinsic-variability of stabilizing components in relation to horizontal and vertical distances from the tree stem were calculated. Three models of Wu & Waldron (W&W), Fiber Bundle (FBM), and Root Bundle Weibull (RBMw) were applied. results showed that the Root Volume Ratio (RVR) and the Number of Roots (NoR) decreased with distance from the tree stem. Root tensile forces increased with root diameter. Finally, calculated root reinforcements at 0.75 m distance associated with the highest value while the lowest value was observed at 1.50 m from the tree stem. The differences between seaward and landward positions were minor. Soil detachment ratio (SDR) was approximately 10% higher at landwards positions than seaward, due to different geomorphological conditions that affected the soil detachment process. The similartity of root reinforcement values among root systems at seaward and landward positions suggest that stem density may not be an important parameter in managing mangrove forests as a coastal protection measure. Yet, RVR at different distances and NoR increasing significantly with soil depth and being different at seaward and landward positions, could improve their potential role as a nature-based solution for shoreline protection.

Soil reinforcement potential of cultivated cardoon (Cynara cardunculus L.): First data of root tensile strength and density

Plant roots play a key role in erosion control by increasing soil resistance to shear stress. Root tensile strength data have been published for natural systems, less is available on cultivated crops. Cardoon (Cynara cardunculus L.) is raising a growing interest as multipurpose crop for marginal lands. In this work we measured cardoon roots tensile strength, topsoil root area ratio, root length density and estimated soil reinforcement potential. Root samples were collected in late spring and at the beginning of fall and were subjected to tensile strength tests in laboratory. Tensile strength (σmax) ranged between 1.57 and 254.78 MPa, decreasing with by a power-law relationship with high determination coefficients (>0.75), with differences between summer and fall roots. We measured root length density (RLD) and root area ratio (RAR) in surface soil (top 5 cm) at different positions in the row and inter-row. RAR was used to calculate soil reinforcement potential (Cr = 1.2 * ∑σmax (kPa) * RAR (cm2 cm−2)). Average RLD was quite high 8.68 cm cm−3 with a mean value of 9.183 cm cm−3 on the row and 8.179 cm cm−3 on the inter-row, though differences between row and inter-row, were not significant. RAR was on average 0.017 cm2 cm−2. Average soil reinforcement was 194 kPa with values ranging from 67.34 kPa to 265 kPa. This is not to be interpreted as absolute reinforcement values, due to drawbacks of the simple model used, but they are useful for comparisons within the framework of crop choices. Cardoon produces a dense mat of fine roots that can contribute to increase soil cohesion, thus providing important ecosystem services.

Experimental analysis of steel fiber reinforced concrete beams in shear

Abstract Some normative recommendations are conservative in relation to the shear strength of reinforced concrete beams, not directly considering the longitudinal reinforcement rate. An experimental program containing 8 beams of (100 x 250) mm2 and a length of 1,200 mm was carried out. The concrete compression strength was 20 MPa with and without 1.00% of steel fiber addition, without stirrups and varying the longitudinal reinforcement ratio. Comparisons between experimental failure loads and main design codes estimates were assessed. The results showed that the increase of the longitudinal reinforcement ratio from 0.87% to 2.14% in beams without steel fiber led to an improvement of 59% in shear strength caused by the dowel effect, while the corresponding improvement was of only 22% in fibered concrete beams. A maximum gain of 109% in shear strength was observed with the addition of 1% of steel fibers comparing beams with the same longitudinal reinforcement ratio (1.2%). A significant amount of shear strength was provided by the inclusion of the steel fibers and allowed controlling the propagation of cracks by the effect of stress transfer bridges, transforming the brittle shear mechanism into a ductile flexural one. From this, it is clear the shear benefit of the steel fiber addition when associated to the longitudinal reinforcement and optimal values for this relationship would improve results.

Влияние исходной величины подкрепления на физиологические показатели условного дыхательного рефлекса

BACKGROUND: Most of the studies of the role of reinforcement in the formation of adaptive behavior were performed on animals. At the same time, such an experimental model as a conditioned respiratory reflex to resistive load, has not been sufficiently studied, although an unconditioned reflex to additional resistance to breathing, on the basis of which a conditioned one is formed, is a stable reaction that has clear quantitative evaluation criteria, and the conditioned reflex itself is relatively strong, easily normalized, reluctantly extinguished and does not require observance of a number of methodological conditions. AIM: To study the influence of the initial value of reinforcement on the physiological parameters of the conditioned respiratory reflex. MATERIALS AND METHODS: The work was carried out on people of both genders, 16 people, aged 18 to 44, practically healthy. The unconditioned stimulus was applied in four gradations of external respiratory resistance: 11; 28; 54; 76 cm water • l/sec. The conditioned reflex was formed by the classic type, the duration of application of the conditioned stimulus was not fixed and its end coincided with the end of the action of the unconditioned stimulus, the period of the isolated action of the conditioned signal was 10 sec. As physiological parameters, we studied the ventilatory and motor parameters of respiration, the temporal parameters of the conditioned reaction. RESULTS: The influence of the unconditioned stimulus on the value of the tidal volume after the combination in all subjects depended on the absolute reinforcement values used in this combination, and was weakly connected with the initial reinforcement value. The influence of the external resistance on breathing used in this combination was significantly higher on such parameters as intraoral pressure of inspiration and expiration; the role of the initial reinforcement value in the dynamics of the given parameters was not confirmed. CONCLUSIONS: Most “sensitive” to the action of the initial value of the resistive load were the temporal parameters of the conditioned respiratory reflex — the latent period and the time of the conditioned reaction; the parameters of the “ventilatory” and “motor” outputs of the external respiration system changed noticeably, the spirometric parameters showed very little dynamics, and the capnographic parameters practically did not change. The dynamics of the parameters of the conditioned respiratory reflex to increased external respiratory resistance permits to single out groups of signs that have the greatest semantic significance for evaluation of the system-forming and discriminating role of the initial gradation of the reinforcement factor.

INFLUENCE OF ROOT SYSTEMS OF DECIDUOUS TREES ON SOIL REINFORCEMENT - A CASE STUDY FROM THE CARPATHIANS, POLAND

Forests play an significant role in the protection of slopes against shallow landslides, and the presence of the tree roots in the soil is considered the most relevant factor increasing its shear strength. Most research on root reinforcement carried out in the European mountains refer to coniferous tree species but there is still not enough information about the root systems of decidous trees and their role in enhancing the slope stability. The aim of this study was to determine root reinforcement of four typical tree species (European hornbeam, common birch, black locust and small-leaved linden) growing in the forests of the Polish Carpathians. The measurements of root systems were performed using the trench wall method and the root reinforcement values were calculated using two fiber-bundle models -RBMw and RBMe, which represented different approaches to tensile force distribution within the root bundle. Studies have shown that the hornbeam roots have the highest, and the black locust roots the lowest values of the tensile strength. Calculations showed that the values of root reinforcement obtained using the RBMw model are 17% higher than the ones calculated using the RBMe model. Root reinforcement values for common birch, black locust and small-leaved linden did not exceed 10 kPa, and in case of hornbeam they were about 20 kPa max. As part of the work, the parameters of the Root Distribution Model were estimated, which after integration with the bundle models allowed to determine the relation between the root reinforcement, the distance from the tree and its diameter.

Effect of longitudinal steel reinforcement ratio on deflection and ductility in reinforced concrete beams

This search report is an experimental result on load –deflection relationship of various ratios of longitudinal reinforcement for six simply supported reinforced concrete beams. All specimens’ dimensions are (200×300×1750mm) and they were tested under two-point loading. Concrete compressive strength was (37.0-40.7 MPa). The variables studied in this work were tensile steel ratio (0.46-3.0%), bar diameter (12, 16 and 25mm) and number of bars (2 or 3 bars). It is concluded that for low reinforcement values (ρ < 0.013), an increase in ρ is sharply reduced the ductility index μ d . However, this effect decreases with increase in ρ values. All beams exhibit insufficient displacement ductility (less than 3) when reinforced with ρ/ρ b > 0.4. The increase in longitudinal steel ratio using 2 bars is more significant than when using 3 bars in yield and ultimate strengths of specimens as well as the deflection values at yield load, but the deflection values have gradual decrease at the ultimate load as a result of ductility decrease. It was concluded that the increase in longitudinal reinforcement ratio causes an increase in yield and ultimate strength of beams, these increments are compatible with the steel ratio i.e. by increasing the ρ by 50% the strength is increased about this ratio. As well as, the decreasing in ductility compatible with increasing the ρ by 50% the ductility decreased in about 50% on average.

Prediction of Weld Bead Geometry of Mild Steel Using Taguchi Technique and Multiple Regression Analysis

The weld bead geometry is very important in predicting the quality of weld as cooling rate of the weld depends on it. For this purpose, the Taguchi technique was applied to determine optimum process parameters of weld bead geometry in submerged arc welding. The study involves using Taguchi’s L9 orthogonal arrays to conduct nine experiments on a 6 mm plate of IS2062 grade mild steel by using SKU MIL-SubArc AC/DC submerged arc welding machine with constant voltage. Three-levels of the four process parameters- arc voltage, welding current, welding speed and electrode stick out were considered and their effect on weld bead geometry−bead width, depth of penetration and weld reinforcement was observed. The signal to noise ratios was computed to determine the optimum parameters. From the results obtained, optimum process parameters of , and was suggested for weld bead width, weld penetration and weld reinforcement respectively. Regression analysis is done to establish the relationship between the input parameters and geometrical parameters of weld bead. The proposed mathematical model can be used to predict bead width, weld penetration and weld reinforcement values for any given SAW welding conditions.

Bond Behaviour of Epoxy Coated Rebar Induced in Self Compacting Concrete

This paper analyses the bond behaviour of epoxy coated rebar induced self-compacting concrete. Experimental program is designed to check the workability and pullout tested is performed to evaluate the bonding performance of rebars. Two mixes of self-compacting concrete are chosen to form a fine paste of cement that could make bonding between concrete and reinforcement. A reference mix of SCC is made using ordinary reinforcement and pullout test values are compared. Workability and compressive strength values of SCC are also analysed and compared.

Relationship of Knowledge on Healthy Lifestyle to Dietary Practices and Physical Activity as Moderated by Age

Lifestyle – related diseases remained to be on the top ten killer according to the World HealthOrganization. Literature indicates that diseases are highly related to lifestyle practices. Onthe other hand, optimal health is a perceived goal of the greater population, however, puttingit into practice is a challenge. The study determined the following: 1) the level of knowledgeon healthy lifestyle, dietary practices and physical activity; 2) the relationship of knowledgeon healthy lifestyle to dietary practices and physical activities, and 3) the relationship ofknowledge to dietary practice and relationship of knowledge to physical activities accordingto age group. A Descriptive-correlational design was employed. The data were gatheredamong 66 randomly selected university students staying in the dormitories; who are at least18 years of age, in which 24 are males and 42 are females, and 40 have earned at most abachelor’s degree and 26 have at least earned units in a master’s program. Utilizing adaptedinstruments, respondents were scored on a 12-item instrument in knowledge where in eachcorrect answer correspond to one point, 27-item instrument on healthy lifestyle in terms ofdiet where in each appropriate response correspond to one point, and 4-item instrument onhealthy lifestyle in terms of physical activities. In turn, the highest possible score ofknowledge, diet, and physical activities are 12, 27, and 4, respectively. Descriptive resultsrevealed that respondents have high knowledge on healthy lifestyle, have fair dietarypractices and moderate practice of physical activities. Furthermore, knowledge on healthylifestyle is not significantly correlated to dietary practices physical activities. However, asignificant relationship was found when respondents were grouped according to age; onlythose 24 years old and above were found to have significant results. Hence, arecommendation to increase the accessibility and reinforcement values of exercise andphysical activity that will have immediate and long term health benefits for college students.

Comparing Reinforcement Values of Facial Expressions: An Eye-Tracking Study

Reinforcement values of facial expressions for visual fixation remain underdeveloped in extant literature, though numerous studies have investigated the function of facial expressions as antecedents of gaze behavior. This study used a concurrent gaze-contingent reinforcement procedure to compare reinforcement values of positive and negative facial expressions for gaze fixation. In total, 7 of the 20 typical adults fixated more frequently on the side that was followed by positive facial expressions. The results suggest that a novel application of eye tracking technology could allow for the evaluation and comparison of reinforcement values of social visual stimuli.

Dispersed droplets as tunable fillers in water-in-oil emulsions stabilized with fat crystals

The role of water droplets as rheology modifiers in fat crystal-stabilized emulsions is not widely studied, but relevant to many fields and industries such as foods and cosmetics. The degree to which water droplets interact with the surrounding fat crystal network can impart a significant effect on rheology. The objective of this study was to investigate how the rheology of water-in-oil (W/O) emulsions stabilized by a surrounding fat crystal network is impacted by the ability of emulsifiers that promote interfacial fat crystallization and whether droplet size is a contributing factor. Three emulsifiers imparting different interfacial characteristics were chosen: glycerol monooleate (GMO) and glycerol monostearate (GMS) both promoted interfacial crystallization in the presence of hydrogenated soy oil (HSO) whereas polyglycerol polyricinoleate (PGPR) did not. Different homogenization methods were used to create emulsions with two distinct average droplet sizes with narrow size distributions for each emulsifier. Amplitude sweeps showed that GMS emulsions, independently of droplet size, displayed the highest elastic modulus (Gʹ) values followed by GMO, and then PGPR. Reinforcement (R = Gʹemulsion/GʹHSO network) values increased with each emulsifier over time, but its extent was dependent on emulsifier-mediated droplet-droplet interactions. In both GMO and GMS-stabilized emulsions, smaller droplets enhanced reinforcement whereas the opposite was observed in PGPR-stabilized emulsions. This study has shown that, through the use of different emulsifiers, the droplet interface should be considered a functional component that can used to tailor the consistency of fat crystal-stabilized W/O emulsions.

Evaluation of the effects of three European forest types on slope stability by field and probabilistic analyses and their implications for forest management

It is well known that forests play a crucial role in preventing soil erosion and landslides; however, forests are also subjected to dynamic evolution driven by natural processes and anthropogenic factors. This dynamic evolution affects spruce and chestnut forests in some European regions (e.g., Italian Alps, central and northern Europe), where these species have been forced by management practice to establish over long periods where other species, such as European beech, would be expected to occur as a result of natural processes.Using a large dataset of field and laboratory measurements of root density and root mechanical properties, the performances of Norway spruce, Sweet chestnut and European beech are analyzed from a slope stability perspective by using a model based on the limit equilibrium principle within a probabilistic framework.The results showed differences and similarities between the root systems of the analyzed species, both in terms of root distribution and mechanical properties. However, the probabilistic distribution that better fits the root reinforcement values obtained by the experimental work is, in all cases, a lognormal function.The developed method can be used to estimate the factor of safety for several combinations of geotechnical and hydrological parameters and different root reinforcement probability distributions using Monte Carlo techniques. The obtained values have been evaluated in terms of probability to have a factor of safety of less than 1 for increasing values of slope steepness.Although each single hillslope should be studied individually to account for local stand conditions that strongly affect root system performance, European beech is generally more efficient than Sweet chestnut and Norway spruce in terms of enhancing slope stability.Based on our results, in all cases where the stability of slopes represents a concern and spruce and chestnut communities are perishing, the natural colonization by European beech should be evaluated positively and possibly promoted by forest managers. Moreover, the developed method provides a general framework that could be applied to other species and conditions to define the consequences of different forest management scenarios in terms of slope stability.

The effect of gap openings on soil reinforcement in two conifer stands in northern Italy

Gap-oriented forestry is a subject that is gaining interest worldwide as a compromise between economic and operational requirements on the one hand and environmental and safety concerns on the other. In principle, the approach mimics the effects of fine-scale natural disturbance while avoiding the threats of soil degradation and instability associated with large clearcuts, but at the same time, it does not limit the productivity associated with single-tree selection.Despite this interest, studies of the real effects of gap-oriented forestry are still limited, particularly those dealing with its impact on slope stability. This paper provides quantitative results about the slope stability of two mixed-conifer stands subjected to gap management in the Italian Central Alps that were monitored for five years after felling.The results showed that root decay, both in strength and density, further reduces additional root cohesion by approximately 60% in the first two years after felling and by another 20% in the third year; it completely vanishes by the fifth year. The observed reduction in root reinforcement values has dramatic consequences for slope stability. In fact:–In undisturbed conditions, the contribution of forest root systems guarantees a very low probability of instability (approximately 10% for a factor of safety of less than 1 as well as for steep slopes and high levels of saturation).–After only two years, the probability of instability dramatically increases for gentle slopes and low levels of saturation. We estimated a 50% probability of a factor of safety less than 1 when steepness was greater than 36–38° and soil saturation was 25% and when steepness was greater than 24–26° and soil saturation was 75%.–The probability of instability is highest five years after felling when the contribution of the root system has vanished. The probability of failure exceeded 50% when steepness was greater than 25–28° and saturation was 25%, and the slopes were practically unstable when saturation was 75%.–At the point when the contribution of the root system to slope stability was null, the regeneration process was still too undeveloped to contribute to soil reinforcement in any way.These results suggest that although the gap-oriented approach is, in principle, more conservative than large clearcuts, the pace of natural regeneration could be slower than the process of root decay, so instability could occur, especially where local slopes exceed 25° and soils are frequently saturated.

Effects of choice opportunities between activities with high- and low-reinforcement values on self-control behavior in children with typical development: a pilot study

ABSTRACTSelf-control is evident in the choice of a delayed consequence with greater magnitude over an immediate one of lesser import. Impulsivity opts for the reverse, i.e., immediate gratification. Two studies were conducted of the enhancement of self-control behavior in a 5-year-old boy with typical development. The objective of the first study was to train the participant to choose between consequences based on their comparative magnitudes and delays. The initial study involved three training phases: simple discrimination, reinforcement magnitude, and delayed reinforcement. In the first study, the participant chose the delayed consequence of greater magnitude 90% of the time. Following the first study, the participant took part in a second. Its objective was to examine the effect on self-control responses of providing choices between high- and low-preference activities. The second study comprised four phases: abrupt increase in reinforcement delay (AIRD), choice opportunity with high-preference activities (CO-HPA), no choice opportunity with high-preference activities (NCO-HPA), and no choice opportunity with low-preference activities (NCO-LPA). In the AIRD phase, the response rate to the delayed consequence of greater magnitude averaged 20%. In the CO-HPA and NCO-HPA phases, the response to the delayed consequence of greater magnitude was 100%. During the NCO-LPA phase, the response rate to the delayed consequence of greater magnitude averaged 50%. The results suggest that reinforcement values play a greater role in self-control behavior than choice opportunity.

Reinforcement of epoxy resin composites with fluorinated carbon nanotubes

Abstract Epoxy resin (diglycidyl ether bisphenol-A type) polymer composites with added unmodified and fluorinated carbon nanotubes (CNTs) were studied by FTIR, TGA, DSC and electron microscopy. Composites tensile and flexural strength were measured. CNTs fluorination markedly (by a factor of 2.26) increased its specific surface. Fluorination did not influence CNTs thermal stability below 260 °C and did not worsen thermal stability of filled composites. Insertion of 0.1 wt% of CNTs fluorinated at 150 °C into polymer matrix resulted in the composite tensile strength increase to 89.6 ± 4.1 MPa (35% increase as compared with unfilled composites). Flexural strength of composite filled with 0.2 wt% fluorinated at 150 °C CNTs was increased to 199.7 ± 4.8 MPa (+58% as compared with unfilled composite). Obtained reinforcement values exceeded all the available literature reinforcement data reported for epoxy composites based on epoxy resins similar to used in the current project. Unmodified CNTs were less effective in composite tensile and flexural strength improvement as compared with fluorinated CNTs. Insertion of fluorinated CNTs into a polymer matrix increased glassy temperature and did not influence the composites thermal stability. Surface of composites cuts was studied by electron microscopy technique. The reinforced composites can be applied in several industries: aviation, automotive, wind turbine propeller blades, for producing yachts and boats etc.

Assessing the effect of Alnus roots on hillslope stability in order to use in soil bioengineering

The role of plant roots in stabilizing slopes is obvious, but the amount of the effect is varied in different species. The purpose of this study was to evaluate the effect of alder (Alnus subcordata) roots on hillslope stability. The profile trenching method was used to obtain root characteristics and a standard Instron testing machine was used for determining the tensile strength of roots. Direct shear test with undisturbed samples was used for determining the soil strength parameters. Using the results of biotechnical characteristics and the Wu model, the reinforcement effect was calculated. Using the reinforcement values and soil strength parameters and Slip4Ex program, factor of safety with and without vegetation was calculated. The obtained results indicated that the root density and number of roots decreased with increasing depth and the average root area ratio was 0.071% ± 0.01. Tensile strength decreased with increasing diameter of roots following the power function with an average of 16.29 ± 3.10 MPa. The minimum and maximum of reinforcement were 0.55 KPa and 110.76 KPa, respectively. The results of this paper augment the knowledge about biotechnical characteristics of root systems of Alder species and indicate that this species increases the factor of safety about 16.79%.

Altered emotional and motivational processing in the transgenic rat model for Huntington’s disease

Huntington disease (HD) is caused by an expansion of CAG repeat in the Huntingtin gene. Patients demonstrate a triad of motor, cognitive and psychiatric symptoms. A transgenic rat model (tgHD rats) carrying 51 CAG repeats demonstrate progressive striatal degeneration and polyglutamine aggregates in limbic structures. In this model, emotional function has only been investigated through anxiety studies. Our aim was to extend knowledge on emotional and motivational function in symptomatic tgHD rats. We subjected tgHD and wild-type rats to behavioral protocols testing motor, emotional, and motivational abilities. From 11 to 15 months of age, animals were tested in emotional perception of sucrose using taste reactivity, acquisition, extinction, and re-acquisition of discriminative Pavlovian fear conditioning as well as reactivity to changes in reinforcement values in a runway Pavlovian approach task. Motor tests detected the symptomatic status of tgHD animals from 11 months of age. In comparison to wild types, transgenic animals exhibited emotional blunting of hedonic perception for intermediate sucrose concentration. Moreover, we found emotional alterations with better learning and re-acquisition of discriminative fear conditioning due to a higher level of conditioned fear to aversive stimuli, and hyper-reactivity to a negative hedonic shift in reinforcement value interpreted in term of greater frustration. Neuropathological assessment in the same animals showed a selective shrinkage of the central nucleus of the amygdala. Our results showing emotional blunting and hypersensitivity to negative emotional situations in symptomatic tgHD animals extend the face validity of this model regarding neuropsychiatric symptoms as seen in manifest HD patients, and suggest that some of these symptoms may be related to amygdala dysfunction.

Root tensile strength of three shrub species: Rosa canina, Cotoneaster dammeri and Juniperus horizontalis

Abstract The presence of vegetation increases soil burden stability along slopes and therefore reduces soil erosion. The contribution of the vegetation is due to mechanical (reinforcing soil shear resistance) and hydrologic controls on stream banks and superficial landslides. This study focused on the biotechnical characteristics of the root system of three shrub species: Rosa canina (L.), Cotoneaster dammeri (C.K. Schneid) and Juniperus horizontalis (Moench). The aim of this paper is to increase our understanding on root biomechanical properties of shrubs species and their contribution to soil reinforcement. The considered shrubs grew up in wood containers, exposed to natural conditions in a village near Asti (Northern Italy) for 2 years. Laboratory tests were conducted to measure the ultimate root tensile strength and to estimate the root density distribution with depth (root area ratio), in order to quantify the soil mechanical reinforcement. Root tensile strength measurements were carried out on single root specimens and root area ratio was estimated analyzing the whole root system. The improvement of soil mechanical properties obtained by the presence of shrubs was estimated using two different models. The first model, based on a simple force equilibrium model, considers that the tensile strength of all roots crossing the shear plane is fully mobilized. This classical approach is implemented by the Fiber Bundle Model concept, to account for non-simultaneous root breaking. C. dammeri roots presented the highest tensile strength and soil reinforcement values, while R. canina and J. horizontalis were characterized by lower values. Similarly at each considered depth C. dammeri showed the highest soil reinforcement effect.

Efectos de diferentes probabilidades de reforzamiento sobre la precisión de palomas en tareas de igualación a la muestra: alargando la duración del intervalo entre reforzadores

Using a matching to sample task pigeons were exposed to different durations of interreinforcer interval (19, 38, 76 and 152 s) according to different probability of reinforcement values (1.0, 0.5, 0.25, 0.12). The speed of acquisition was quicker and the discrimination index was higher for the pigeons exposed to a longer interreinforcer interval. It is identified to the interreinforcer interval like a more general variable that controls the accuracy levels and the acquisition speed of conditional discriminations.

Quantifying lateral root reinforcement in steep slopes – from a bundle of roots to tree stands

AbstractA review of present modelling approaches for root reinforcement in vegetated steep hillslopes reveals critical gaps in consideration of plant–soil interactions at various scales of interest for shallow landslide prediction. A new framework is proposed for systematic quantification of root reinforcement at scales ranging from single root to tree root system, to a stand of trees. In addition to standard basal reinforcement considered in most approaches, the critical role of roots in stabilizing slopes through lateral reinforcement is highlighted. Primary geometrical and mechanical properties of root systems and their function in stabilizing the soil mass are reviewed. Stress–strain relationships are considered for a bundle of roots using the formalism of the fiber bundle model (FBM) that offers a natural means for upscaling mechanical behavior of root systems. An extension of the FBM is proposed, considering key root and soil parameters such as root diameter distribution, tortuosity, soil type, soil moisture and friction between soil and root surface. The spatial distribution of root mechanical reinforcement around a single tree is computed from root diameter and density distributions based on easy to measure properties. The distribution of root reinforcement for a stand of trees was obtained from spatial and mechanical superposition of individual tree values with regard to their positions on a hillslope. Potential applications of the proposed approach are illustrated in a numerical experiment of spatial strength distribution in a hypothetical slope with 1000 trees randomly distributed. The analyses result in spatial distribution of weak and strong zones within the soil where landslide triggering is expected in large and continuous zones with low reinforcement values. Mapping such zones would enhance the quality of landslide susceptibility maps and optimization of silvicultural measures in protection forests. Copyright © 2010 John Wiley &amp; Sons, Ltd.