Temporal Detection Threshold of Audio-Tactile Delays With Virtual Button.

Synchronization of audio-tactile stimuli represents a key feature of multisensory interactions. However, information on stimuli synchronization remains scarce, especially with virtual buttons. This work used a click sensation produced with traveling waves and auditory stimulus (a bip-like sound) related to a virtual click for a psychological experiment. Participants accomplish a click gesture and judge if the two stimuli were synchronous or asynchronous. Delay injection was performed on the audio (haptic first) or the click (audio first). In both sessions, one stimulus follows the other with a delay ranging from 0-700 ms. We use weighted and transformed 3-up/1-down staircase procedures to estimate people's sensitivity. We found a threshold of 179 ms and 451 ms for the auditory first and haptic first conditions, respectively. Statistical analysis revealed a significant effect between the two stimuli' order for threshold. Participants' acceptable asynchrony decreased when the delay was on the haptic rather than on the audio. This effect could be due to the natural experience in which the stimuli tend to be first tactile and then sonorous rather than the other way around. Our findings will help designers to create multimodal virtual buttons by managing audio-tactile temporal synchronization.

Mechanisms of Friction Reduction in Longitudinal Ultrasonic Surface Haptic Devices With Non-Collinear Vibrations and Finger Displacement.

Friction reduction using ultrasonic longitudinal surface vibration can modify the user perception of the touched surface and induce the perception of textured materials. In the current paper, the mechanisms of friction reduction using longitudinal vibration are analyzed at different finger exploration velocities and directions over a plate. The development of a non-Coulombic adhesion theory based on experimental results is evaluated as a possible explanation for friction reduction with vibrations that are non-collinear with the finger displacement. Comparison with experimental data shows that the model adequately describes the reduction in friction, although it is less accurate for low finger velocities and depends on motion direction.

Haptigami: A Fingertip Haptic Interface With Vibrotactile and 3-DoF Cutaneous Force Feedback.

Wearable fingertip haptic devices aim todeliver somatosensory feedback for applications such as virtual reality, rehabilitation, and enhancing hardware/physical control interfaces. However, providing various kinds of feedback requires several Degrees of Freedom (DoF) and high mechanical complexity which are mechanically difficult to achieve at the mesoscale. Using compliant low-profile transmissions embedded in an origami structure and PCBmotors as actuators, we designed and fabricated a novel 3-DoF fingertip haptic device, called Haptigami. This under-actuated system, measuring 36 x 25 x 26 mm and weighing 13 g, can render vibrotactile and cutaneous force feedback. We tested our device by creating a novel experimental protocol and robotic platform allowing quantitative characterization of mechanical performance. The current prototype of Haptigami produces 678 mN in compression, and 400 mN and 150 mN in shear for the Y and X directions, respectively. By virtue of its unique origami-inspired design, Haptigami brings a new direction for future designs of lightweight and compact wearable robots.

PCA Model of Fundamental Acoustic Finger Force for Out-of-Plane Ultrasonic Vibration and its Correlation with Friction Reduction.

When a finger touches an ultrasonic vibrating plate, a non-sinusoidal contact force is produced. This force is called acoustic finger force. In a setup where closed-loop control is performed on the vibration amplitude, a component of the acoustic finger force can be measured at the fundamental vibration frequency of the plate. This calculation is obtained from the measurement of the variation of the controller voltage between the no-load case and when a finger is present. This calculation is made for a group of twelve participants. From these results a PCA (Principal Component Analysis) model is created. This model permits estimation of the acoustic finger force response of a participant at any vibration amplitude, based on a one or two point measurement. Finally, a linear relation between the PCA coefficients and the friction reduction is proposed. The objective of this relation would be to ultimately provide the means to create an amplitude reference calibration based on the desired friction reduction level, and thus be able to produce a standardized tactile feedback for each user, despite the biomechanical differences in finger pad properties between subjects.

Plant Defense Stimulator Mediated Defense Activation Is Affected by Nitrate Fertilization and Developmental Stage in Arabidopsis thaliana.

Plant defense stimulators, used in crop protection, are an attractive option to reduce the use of conventional crop protection products and optimize biocontrol strategies. These products are able to activate plant defenses and thus limit infection by pathogens. However, the effectiveness of these plant defense stimulators remains erratic and is potentially dependent on many agronomic and environmental parameters still unknown or poorly controlled. The developmental stage of the plant as well as its fertilization, and essentially nitrogen nutrition, play major roles in defense establishment in the presence of pathogens or plant defense stimulators. The major nitrogen source used by plants is nitrate. In this study, we investigated the impact of Arabidopsis thaliana plant developmental stage and nitrate nutrition on its capacity to mount immune reactions in response to two plant defense stimulators triggering two major defense pathways, the salicylic acid and the jasmonic acid pathways. We show that optimal nitrate nutrition is needed for effective defense activation and protection against the pathogenic bacteria Dickeya dadantii and Pseudomonas syringae pv. tomato. Using an npr1 defense signaling mutant, we showed that nitrate dependent protection against D. dadantii requires a functional NPR1 gene. Our results indicate that the efficacy of plant defense stimulators is strongly affected by nitrate nutrition and the developmental stage. The nitrate dependent efficacy of plant defense stimulators is not only due to a metabolic effect but also invloves NPR1 mediated defense signaling. Plant defense stimulators may have opposite effects on plant resistance to a pathogen. Together, our results indicate that agronomic use of plant defense stimulators must be optimized according to nitrate fertilization and developmental stage.

A Review of Surface Haptics: Enabling Tactile Effects on Touch Surfaces.

In this article, we review the current technology underlying surface haptics that converts passive touch surfaces to active ones (machine haptics), our perception of tactile stimuli displayed through active touch surfaces (human haptics), their potential applications (human-machine interaction), and finally, the challenges ahead of us in making them available through commercial systems. This article primarily covers the tactile interactions of human fingers or hands with surface-haptics displays by focusing on the three most popular actuation methods: vibrotactile, electrostatic, and ultrasonic.

Multimodal pipe-climbing robot with origami clutches and soft modular legs.

In nature, climbing trees and pipes of varying diameters or even navigating inside of hollow pipes and tree holes is easy for some climbing animals and insects. However, today's pipe-climbing robots, which are important for automatically conducting periodic inspections and maintenance of pipelines to save time and keep humans away from hazardous environments, are designed mainly for a specific task, limiting their adaptability to different working scenarios and further implementation in real-life. In this paper, we propose a pipe-climbing robot with a soft linear actuator for bioinspired propulsion, two origami clutches to realize multi-degrees-of-freedom (DoF) motion and two pairs of soft modular legs for multimodal climbing. Design, modeling and experimental validation of the origami clutch are introduced in detail. Preliminary experimental results show that we can achieve a stroke of up to 289.6% and a maximum 45° bending angle on the soft linear actuator by regulating the air pressure inside the soft actuator and origami clutches. Additionally, by choosing the leg-type, three climbing modes, including out-pipe versatile mode, out-pipe high-force mode and in-pipe mode can be realized for particular working scenarios. A prototype climbing robot demonstrates that in out-pipe versatile mode, the robot can climb on the exterior of pipes made of various materials including PVC, rubber and metal with diameters ranging from 105 to 117 mm. In the out-pipe high-force mode, the climber can navigate along a specific pipe carrying maximum 675 g external load at the top or 200 g hanging from the bottom, as well as keeping functional without failure under static loads as high as 1968 g. In the in-pipe mode, the robot is able to travel inside pipes. This research might bridge the design gap between in-pipe and out-pipe climbing robots while offering an alternative option for soft robots to execute multi-DoF motion.

Friction Reduction through Ultrasonic Vibration Part 1: Modelling Intermittent Contact.

Ultrasonic vibration is employed to modify the friction of a finger pad in way that induces haptic sensations. A combination of intermittent contact and squeeze film levitation has been previously proposed as the most probable mechanism. In this paper, in order to understand the underlying principles that govern friction modulation by intermittent contact, numerical models based on finite element (FE) analysis and also a spring-Coulombic slider are developed. The physical input parameters for the FE model are optimized by measuring the contact phase shift between a finger pad and a vibrating plate. The spring-slider model assists in the interpretation of the FE model and leads to the identification of a dimensionless group that allows the calculated coefficient of friction to be approximately superimposed onto an exponential function of the dimensionless group. Thus, it is possible to rationalize the computed relative reduction in friction being (i) dependent on the vibrational amplitude, frequency, and the intrinsic coefficient of friction of the device, and the reciprocal of the exploration velocity, and (ii) independent of the applied normal force, and the shear and extensional elastic moduli of the finger skin provided that intermittent contact is sufficiently well developed. Experimental validation of the modelling using real and artificial fingertips will be reported in part 2 of this work, which supports the current modelling.

Enhancing Variable Friction Tactile Display Using an Ultrasonic Travelling Wave.

In Variable Friction Tactile Displays, an ultrasonic standing wave can be used to reduce the friction coefficient between a user's finger sliding and a vibrating surface. However, by principle, the effect is limited by a saturation due to the contact mechanics, and very low friction levels require very high vibration amplitudes. Besides, to be effective, the user's finger has to move. We present a device which uses a travelling wave rather than a standing wave. We present a control that allows to realize such a travelling wave in a robust way, and thus can be implemented on various plane surfaces. We show experimentally that the force produced by the travelling wave has two superimposed contributions. The first one is equal to the friction reduction produced by a standing of the same vibration amplitude. The second produces a driving force in the opposite direction of the travelling wave. As a result, the modulation range of the tangential force on the finger can be extended to zero and even negative values. Moreover, the effect is dependant on the relative direction of exploration with regards to the travelling wave, which is perceivable and confirmed by a psycho-physical study.

Physical and Perceptual Independence of Ultrasonic Vibration and Electrovibration for Friction Modulation.

Two different principles are available to modulate the user perceived roughness of a surface: electrovibration and ultrasonic vibration of a plate. The former enhances the perceived friction coefficient and the latter reduces it. This paper will highlight the independence of the two effects on the physical and perceptual point of view to confirm the increased range of sensation and stimulation that can be supplied by the two coupled techniques to the users. Firstly, a tribometric analysis of the induced lateral force on the finger by the two coupled effects will be presented, then a study on the dynamic of the two effects will be reported. In the end, a psychophysical experiment on the perception of the two coupled techniques will be shown.

Brown rust disease control in winter wheat: II. Exploring the optimization of fungicide sprays through a decision support system.

A decision support system (DSS) involving an approach for predicting wheat leaf rust (WLR) infection and progress based on night weather variables (i.e., air temperature, relative humidity, and rainfall) and a mechanistic model for leaf emergence and development simulation (i.e., PROCULTURE) was tested in order to schedule fungicide time spray for controlling leaf rust progress in wheat fields. Experiments including a single fungicide treatment based upon the DSS along with double and triple treatment were carried out over the 2007-2009 cropping seasons in four representative Luxembourgish wheat field locations. The study showed that the WLR occurrences and severities differed according to the site, cultivar, and year. We also found out that the single fungicide treatment based on the DSS allowed a good protection of the three upper leaves of susceptible cultivars in fields with predominant WLR occurrences. The harvested grain yield was not significantly different from that of the double and triple fungicide-treated plots (P < 0.05). Such results could serve as basis or be coupled to cost-effective and environmentally friendly crop management systems in operational context.

Vector control method applied to a traveling wave in a finite beam.

This paper presents the closed-loop control of exciters to produce a traveling wave in a finite beam. This control is based on a dynamical modeling of the system established in a rotating reference frame. This method allows dynamic and independent control of the phase and amplitude of two vibration modes. The condition to obtain the traveling wave is written in this rotating frame, and requires having two vibration modes with the same amplitude, and imposing a phase shift of 90° between them. The advantage of the method is that it allows easy implementation of a closed loop control that can handle parameter drift of the system, after a temperature rise, for example. The modeling is compared with measurement on an experimental test bench which also implements real-time control. We managed to experimentally obtain a settling time of 250 ms for the traveling wave, and a standing wave ratio (SWR) of 1.3.

Contribution of slip cue to curvature perception through active and dynamic touch.

Haptic perception of curvature depends largely on the kind of touch. An active and dynamic touch is considered to be the most natural way of exploring. In this study, we have designed and evaluated a kinematic platform for curvature perception through active and dynamic touch. This platform can independently orient, elevate, and translate a flat plate; by exploring forward and backward along the flat plate with a finger, users can achieve curvature feeling of extruded objects. The mechanism of platform and the way of touch have maximally respected the cues for curvature perception, especially the slip cue. Psychophysical evaluation demonstrated that the discrimination threshold of curvature for virtual shapes is close to that for real shapes, and the virtual shape is felt equally curved as the real one. The curvature perception of mono-convex surfaces was then expanded to perception of more complex surfaces: large textures, which have a sinusoidal profile. The evaluation has accessed the correspondence between the virtual and real large textures.

Fusarium head blight and associated mycotoxin occurrence on winter wheat in Luxembourg in 2007/2008.

Fusarium head blight (FHB) is among the major causes of reduced quality in winter wheat and its products. In addition, the causal fungi produce a variety of toxins. A relatively high FHB infection rate in winter wheat was observed in 2007 and 2008 in Luxembourg. A fusariotoxin survey was carried out in 17 different geographical locations. Three groups of Fusarium mycotoxins (trichothecenes A and B and zearalenone) were analysed by a multi-detection HPLC-MS/MS method. Fusarium strains were also investigated by morphological and molecular methods. In addition, questionnaires relating to cultural practices were sent to the farmers managing the 17 fields investigated. FHB prevalence ranged from 0.3 to 65.8% (mean: 8.5%) in 2007 and from 0 to 24.5% (mean: 8.3%) in 2008. Results of morphological and molecular identification showed that the most common species isolated from diseased wheat spikes was F. graminearum (33.1%), followed by F. avenaceum (20.3%) and F. poae (17.8%). The chemical analysis revealed that 75% of the investigated fields were contaminated by deoxynivalenol (DON, range 0-8111 microg/kg). The preceding crop was highly and significantly correlated to the number of grains infected and had a significant impact on disease prevalence (p = 0.025 and 0.017, respectively, Fisher's F-test). A trend was found for maize as the preceding crop (p = 0.084, Tukey's test) to predict the amount of DON in the fields. This is the first report on the occurrence of DON and ZON in naturally infected wheat grains sampled from Luxembourg.

Toxin induction and protein extraction from Fusarium spp. cultures for proteomic studies.

Fusaria are filamentous fungi able to produce different toxins. Fusarium mycotoxins such as deoxynivalenol, nivalenol, T2, zearelenone, fusaric acid, moniliformin, etc... have adverse effects on both human and animal health and some are considered as pathogenicity factors. Proteomic studies showed to be effective for deciphering toxin production mechanisms (Taylor et al., 2008) as well as for identifying potential pathogenic factors (Paper et al., 2007, Houterman et al., 2007) in Fusaria. It becomes therefore fundamental to establish reliable methods for comparing between proteomic studies in order to rely on true differences found in protein expression among experiments, strains and laboratories. The procedure that will be described should contribute to an increased level of standardization of proteomic procedures by two ways. The filmed protocol is used to increase the level of details that can be described precisely. Moreover, the availability of standardized procedures to process biological replicates should guarantee a higher robustness of data, taking into account also the human factor within the technical reproducibility of the extraction procedure. The protocol described requires 16 days for its completion: fourteen days for cultures and two days for protein extraction (figure 1). Briefly, Fusarium strains are grown on solid media for 4 days; they are then manually fragmented and transferred into a modified toxin inducing media (Jiao et al., 2008) for 10 days. Mycelium is collected by filtration through a Miracloth layer. Grinding is performed in a cold chamber. Different operators performed extraction replicates (n=3) in order to take into account the bias due to technical variations (figure 2). Extraction was based on a SDS/DTT buffer as described in Taylor et al. (2008) with slight modifications. Total protein extraction required a precipitation process of the proteins using Aceton/TCA/DTT buffer overnight and Acetone /DTT washing (figure 3a,3b). Proteins were finally resolubilized in the protein-labelling buffer and quantified. Results of the extraction were visualized on a 1D gel (Figure 4, SDS-PAGE), before proceeding to 2D gels (IEF/SDS-PAGE). The same procedure can be applied for proteomic analyses on other growing media and other filamentous fungi (Miles et al., 2007).

Microsatellite loci to recognize species for the cheese starter and contaminating strains associated with cheese manufacturing.

We report the development of 17 microsatellite markers in the cheese fungi Penicillium camemberti and P. roqueforti, using an enrichment protocol. Polymorphism and cross-amplification were explored using 23 isolates of P. camemberti, 26 isolates of P. roqueforti, and 2 isolates of each of the P. chrysogenum and P. nalgiovense species, used to produce meat fermented products. The markers appeared useful for differentiating species, both using their amplification sizes and the sequences of their flanking regions. The microsatellite locus PC4 was particularly suitable for distinguishing contaminant species closely related to P. camemberti and for clarifying the phylogenetic relationship of this species with its supposed ancestral form, P. commune. We analyzed 22 isolates from different culture collections assigned to the morphospecies P. commune, most of them occurring as food spoilers, mainly from the cheese environment. None of them exhibited identical sequences with the ex-type isolate of the species P. commune. They were instead distributed into two other distinct lineages, corresponding to the old species P. fuscoglaucum and P. biforme, previously synonymized respectively with P. commune and P. camemberti. The ex-type isolate of P. commune was strictly identical to P. camemberti at all the loci examined. P. caseifulvum, a non toxinogenic species described as a new candidate for cheese fermentation, also exhibited sequences identical to P. camemberti. The microsatellite locus PC4 may therefore be considered as a useful candidate for the barcode of these economically important species.

Improvements of polymerase chain reaction and capillary electrophoresis single-strand conformation polymorphism methods in microbial ecology: toward a high-throughput method for microbial diversity studies in soil.

The molecular signature of bacteria from soil ecosystems is an important tool for studying microbial ecology and biogeography. However, a high-throughput technology is needed for such studies. In this article, we tested the suitability of available methods ranging from soil DNA extraction to capillary electrophoresis single-strand conformation polymorphism (CE-SSCP) for high-throughput studies. Our results showed that the extraction method does not dramatically influence CE-SSCP profiles, and that DNA extraction of a 0.25 g soil sample is sufficient to observe overall bacterial diversity in soil matrices. The V3 region of the 16S rRNA gene was amplified by PCR, and the extension time was found to be critical. We have also found that proofreading DNA polymerases generate a better signal in CE-SSCP profiles. Experiments performed with different soil matrices revealed the repeatability, efficiency, and consistency of CE-SSCP. Studies on PCR and CE-SSCP using single-species genomic DNA as a matrix showed that several ribotypes may migrate at the same position, and also that single species can produce double peaks. Thus, the extrapolation between number of peaks and number of species remains difficult. Additionally, peak detection is limited by the analysis software. We conclude that the presented method, including CE-SSCP and the analyzing step, is a simple and effective technique to obtain the molecular signature of a given soil sample.

Phylogenetic analysis of the Aspergillus niger aggregate in relation to feruloyl esterase activity.

Species of the Aspergillus niger aggregate are known to produce feruloyl esterases, enzymes involved in the degradation of cell wall polymers. However, species delineation is difficult in these fungi. We combined AFLP analysis with ITS rDNA and beta-tubulin sequencing to characterize the isolates of this aggregate in terms of feruloyl esterase production. A preliminary re-examination of isolates based on comparison of ITS rDNA and beta-tubulin sequences with those of typical taxa deposited in international collections led us to re-identify the isolates as members of the species A. niger, A. foetidus and A. tubingensis. Molecular clustering based on beta-tubulin data and AFLP analysis showed that the strains of A. niger formed a homogenous phylogenetic group distinguished by either zero or type A feruloyl esterase activity, while strains A. foetidus and A. tubingensis exhibited type B feruloyl esterase activity when grown on sugar beet pulp.

Squeeze film effect for the design of an ultrasonic tactile plate.

Most tactile displays currently built rely on pin-based arrays. However, this kind of tactile device is not always appropriate when we need to give the illusion of finely textured surfaces. In this paper, we describe the squeeze film effect between a plate and a finger, and we use this effect to design an ultrasonic tactile plate. The plate is actuated by piezoelectric ceramics. Ultrasonic vibrations are thus produced and are capable of generating the squeeze film effect. This enables us to simulate variable friction on the surface of the plate. In order to identify the squeeze film phenomenon, this study considers the case where a finger, with a planar bottom surface and with epidermal ridges, is placed on a rapidly vibrating plate. The overpressure is calculated and the result enables us to assess the relative coefficient of friction as a function of the vibration amplitude of the plate. Based on this principle, and using both analytic and FE method studies, and given ergonomic and stimulation (squeeze film) requirements, we show that it is possible to design a tactile plate which is capable of giving programmable tactile sensations. We conclude by comparing the results obtained from our simulations with experimental results.

A torque estimator for a traveling wave ultrasonic motor--application to an active claw.

Depending on its electrical-to-mechanical energy conversion process, the torque on a traveling wave ultrasonic motor (TWUM)'s shaft is not directly proportional to a measurable electrical variable, such as current or voltage. But it is derived from a complicated process at the stator/rotor interface. The load torque is thus quite unknown, and this can be a disadvantage in applications in which a torque limitation is required or a torque measurement is needed. The aim of this article is to come up with a straightforward torque estimator on a TWUM. For that purpose, the motor is modeled; this modeling leads to different estimator strategies. More specifically, we chose a strategy for which a speed sensor is useless, relying only on the stator's resonant behavior. The parameters of the motor needed for the estimator are measured afterward, and some nonlinearities are identified and taken into account. Several experimental trials then are carried out to check the performance of the estimator. A claw actuated by a TWUM is presented because this is a typical application in which the knowledge of the torque helps guarantee the safety of the device.