Pair Of Fingers Research Articles

The Force Synergy of Human Digits in Static and Dynamic Cylindrical Grasps

This study explores the force synergy of human digits in both static and dynamic cylindrical grasping conditions. The patterns of digit force distribution, error compensation, and the relationships among digit forces are examined to quantify the synergetic patterns and coordination of multi-finger movements. This study recruited 24 healthy participants to perform cylindrical grasps using a glass simulator under normal grasping and one-finger restricted conditions. Parameters such as the grasping force, patterns of digit force distribution, and the force coefficient of variation are determined. Correlation coefficients and principal component analysis (PCA) are used to estimate the synergy strength under the dynamic grasping condition. Specific distribution patterns of digit forces are identified for various conditions. The compensation of adjacent fingers for the force in the normal direction of an absent finger agrees with the principle of error compensation. For digit forces in anti-gravity directions, the distribution patterns vary significantly by participant. The forces exerted by the thumb are closely related to those exerted by other fingers under all conditions. The index-middle and middle-ring finger pairs demonstrate a significant relationship. The PCA results show that the normal forces of digits are highly coordinated. This study reveals that normal force synergy exists under both static and dynamic cylindrical grasping conditions.

Profile of Keith Joung

Profile of Keith Joung

Optimality versus variability: effect of fatigue in multi-finger redundant tasks

We used two methods to address two aspects of multi-finger synergies and their changes after fatigue of the index finger. Analytical inverse optimization (ANIO) was used to identify cost functions and corresponding spaces of optimal solutions over a broad range of task parameters. Analysis within the uncontrolled manifold (UCM) hypothesis was used to quantify co-variation of finger forces across repetitive trials that helped reduce variability of (stabilized) performance variables produced by all the fingers together. Subjects produced steady-state levels of total force and moment of force simultaneously as accurately as possible by pressing with the four fingers of the right hand. Both before and during fatigue, the subjects performed single trials for many force-moment combinations covering a broad range; the data were used for the ANIO analysis. Multiple trials were performed at two force-moment combinations; these data were used for analysis within the UCM hypothesis. Fatigue was induced by 1-min maximal voluntary contraction exercise by the index finger. Principal component (PC) analysis showed that the first two PCs explained over 90% of the total variance both before and during fatigue. Hence, experimental observations formed a plane in the four-dimensional finger force space both before and during fatigue conditions. Based on this finding, quadratic cost functions with linear terms were estimated from the experimental data. The dihedral angle between the plane of optimal solutions and the plane of experimental observations (D (ANGLE)) was very small (a few degrees); it increased during fatigue. There was an increase in fatigue of the coefficient at the quadratic term for the index finger force balanced by a drop in the coefficients for the ring and middle fingers. Within each finger pair (index-middle and ring-little), the contribution of the "central" fingers to moment production increased during fatigue. An index of antagonist moment production dropped with fatigue. Fatigue led to higher co-variation indices during pronation tasks (index finger is an agonist) but opposite effects during supination tasks. The results suggest that adaptive changes in co-variation indices that help stabilize performance may depend on the role of the fatigued element, agonist or antagonist.

MBNL1-RNA recognition: contributions of MBNL1 sequence and RNA conformation.

Muscleblind-like proteins (MBNL) are RNA-binding proteins that bind to the poly(CUG) and poly(CCUG) sequences that are the causative agents of myotonic dystrophy. It has been suggested that as a result of binding to the repeating RNA sequences, MBNL1 is abnormally expressed and translocated, which leads to many of the misregulated events in myotonic dystrophy. In this work, steady-state fluorescence quenching experiments suggest that MBNL1 alters the structure of helical RNA targets upon binding, which may explain the selectivity of MBNL1 for less structured RNA sites. The removal of one pair of zinc fingers greatly impairs the binding affinity of MBNL1, which indicates that the two pairs of zinc fingers might possibly interact with RNA targets cooperatively. Alanine scanning mutagenesis results suggest that the binding energy may be distributed across the protein. Overall, the results presented here suggest that small molecules that stabilize the helical structure of poly(CUG) and poly(CCUG) RNAs will inhibit the formation of complexes with MBNL1.

Structural and thermodynamic consequences of the replacement of zinc with environmental metals on estrogen receptor α–DNA interactions

Estrogen receptor α (ERα) acts as a transcription factor by virtue of the ability of its DNA‐binding (DB) domain, comprised of a tandem pair of zinc fingers, to recognize the estrogen response element within the promoters of target genes. Herein, using an array of biophysical methods, we probe the structural consequences of the replacement of zinc within the DB domain of ERα with various environmental metals and their effects on the thermodynamics of binding to DNA. Our data reveal that whereas the DB domain reconstituted with divalent ions of zinc, cadmium, mercury, and cobalt binds to DNA with affinities in the nanomolar range, divalent ions of barium, copper, iron, lead, manganese, nickel, and tin are unable to regenerate DB domain with DNA‐binding potential, although they can compete with zinc for coordinating the cysteine ligands within the zinc fingers. We also show that the metal‐free DB domain is a homodimer in solution and that the binding of various metals only results in subtle secondary and tertiary structural changes, implying that metal coordination may only be essential for binding to DNA. Collectively, our findings provide mechanistic insights into how environmental metals may modulate the physiological function of a key nuclear receptor involved in mediating a plethora of cellular functions central to human health and disease. Copyright © 2011 John Wiley & Sons, Ltd.

Frequency Response Optimization of Saw Filter using Canonical Genetic Algorithm

An optimization program is employed to design the inter-digital transducer (IDT) structure of the surface acoustic wave (SAW) transducer to aim at improvement in the transducer characteristics and to improve the frequency response of SAW filter. In this paper, Genetic algorithm is used to optimize the response of a SAW filter. Then, the comparison of the response of SAW filter is done by using GA and without GA. The goal of optimization is to find best value for each variable in order to achieve minima or maxima of an objective function within the given constraints. In present study, three design variables of SAW filter i.e. number of finger pairs in input IDT (Np1), number of finger pairs in `output IDT (Np2), center to center distance between two electrodes in a finger pair (d), are optimized. After getting the optimized parameters of SAW filter, the frequency response of bandpass SAW filter is obtained, which is better as compared to the frequency response of SAW filter getting from other methods in terms of bandwidth and ripples amplitude.

Photoelectrochemistry on a planar, interdigitated electrochemical cell

The construction of a planar electrochemical cell with two interdigitated electrodes, with a finger spacing of 25–100 μm and 200–50 pairs of fingers and gaps, respectively, is described. The working electrode consists of n-type semiconducting titanium dioxide (anatase). Under UV light, photocurrents are produced. No reduction in the photocurrent due to iR drop was observed, even in electrolytes of low ionic strength. This makes the device an interesting candidate for photoelectrocatalytic purification of drinking water. An example is shown in the degradation of the azo-dye AO7 (acid orange 7). k(photoelectrocatalysis) on a device with 50 finger pairs was 3.29 × 10 −6/s and the corresponding kinetic parameter, p = kFV/ i photo (rate constant normalized to unit volume and photocurrent), was 404 M −1.

Joint coupling design of underactuated hands for unstructured environments

This paper examines joint coupling in underactuated robotic grippers for unstructured environments where object properties and location may not be well known. A simplified grasper consisting of a pair of two-link planar fingers with compliant revolute joints was simulated as it grasped a target object. The joint coupling configuration of the gripper was varied in order to maximize successful grasp range and minimize contact forces for a wide range of target object sizes and positions. The number of actuators was also varied in order to test performance for varying degrees of underactuation. A normal distribution of object position was used to model sensing uncertainty and weight the results accordingly. There are three main results: distal/proximal joint torque ratios of around 1.0 produced the best results, both for cases in which sensory information available for the task was poor and when sensing was good; an actuator for each gripper finger performs no better than a single actuator for both fingers; and that for good sensing, the gripper should be positioned off-center from the object, resulting in an increased lever arm and lower unbalanced contact forces on the object.

Two-Dimensional Motor Based on Surface Acoustic Wave

With the development of high precision processing, the miniaturization demand of motors with super-precision positioning and simple fabrication become an urgent problem. This paper illustrates a surface acoustic wave (SAW) motor for two-dimensional positioning. The SAW motor include a SAW stator and a slide. In order to realize the two-dimensional moving, four Interdigital Transducer (IDTs) are fabricated on the four directions of a 0.5-mm thick, 128°YX- LiNbO3substrate. Comparing the aluminum material, the copper material selected to be used as IDT in our experiment has many advantages. Each of the four copper IDTs has 10 straight finger pairs in a simple repeating pattern, the IDT aperture is 10mm and the pitch is 400μm. The SAW stator is fabricated by the lift-off process. The dimension of the device is 29mm (width) X29mm (length). The slide consists of three ruby balls with the diameter of 1mm and an plastic disc with the thickness of 0.5mm and the diameter is 8mm. With the four radio frequency driving sources, two-dimensional motion is possible. The maximum speed of the slide that was placed on the SAW propagating surface was 5mm/s when the applied driving power was 28W and the applied driving frequency was 9.6MHz. The experiments indicate the two-dimensional motor based on SAW would be applicable to miniature motor and improve the resolution.

The effect of geometry and post-annealing on surface acoustic wave characteristics of AlN thin films prepared by magnetron sputtering

This paper describes experimental relationship between surface acoustic wave (SAW) properties of two-port SAW resonators based on polycrystalline aluminum nitride (AlN) thin films grown on Si substrates by using a pulsed reactive magnetron sputtering system and their geometry's parameters. Moreover, the influence of post-deposition heat treatment on SAW properties of AlN thin films was investigated at different annealing temperature (600 °C and 900 °C). The measurement results show the number of the inter-digital transducers (IDT) finger pairs ( N), the number of reflectors grating pairs ( R) and the IDT center-to-center distance ( L) related to insertion loss of SAW resonators. The best result of insertion loss was 15.6 dB for SAW resonators with R = 160 pair, N = 5 pair and L = 750 μm. At the same geometry parameters, the SAW velocity and insertion loss were improved slightly after annealing at 600 °C and were worse for the films annealed at 900 °C by changes in the surface morphology and stress on the film.

Polarization and angle independent terahertz metamaterials with high Q-factors

We propose polarization and angle insensitive metamaterials at terahertz frequencies consisting of two concentric ring resonators with interdigitated fingers placed between the rings. We experimentally demonstrate that the bandstop resonance remains unaffected by changes in both the incident angle and the polarization. Furthermore, high quality-factors of more than 16 are observed as Fano-like modes with small dipole moments are excited. We show that the sharpness of the resonance can be controlled by the number of interdigitated finger pairs. The structures exhibit pronounced normal phase dispersion near the resonance, which renders them attractive candidates for electromagnetic induced transparency and slow light applications.

Modeling and Control of a Pair of Robot Fingers with Soft Tips and Orderless Saddle-joint Actuations

Modeling and Control of a Pair of Robot Fingers with Soft Tips and Orderless Saddle-joint Actuations

Transient and steady-state responses to mechanical stimulation of different fingers reveal interactions based on lateral inhibition

Objective Simultaneous tactile finger stimulation evokes transient ERP responses that are smaller than the linear summation of ERP responses to individual stimulation. Occlusion and lateral inhibition are two possible mechanisms responsible for this effect. The present study disentangles these two effects using steady-state somatosensory evoked potentials (SSSEP). Simultaneous stimulation on adjacent and distant finger pairs with the same and different stimulation frequencies are compared. Methods The index finger (IF), middle finger (MF) and little finger (LF) were mechanically stimulated with a frequency of 18, 22 or 26 Hz, respectively. Stimulation was applied for each finger separately, and for the IF (18 Hz) in combination with either the MF or LF for 22 and 26 Hz, respectively. A measure for interaction (IR) was calculated for the P60 component and the SSSEP amplitude. Results Significant interactions were found in both the P60 response and in the SSSEP response. Stimulation of adjacent finger combinations caused more interaction than distant finger combinations. No difference was found between stimulation of two fingers with the same or a different frequency. Conclusions Our results indicate that lateral inhibition is mainly responsible for the interaction effect. Significance These observations provide further insight in the mechanisms behind interaction between somatosensory inputs.

Dynamics of Grasping a Rigid Object with Arbitrary Smooth Surfaces under Rolling Contacts

Modeling and control of dynamics of three-dimensional object grasping by using a pair or triplet of multi-joints robot fingers are investigated under rolling contact constraints and arbitrary shape...

Modeling and Control of 2D Grasping under Rolling Contact Constraints between Arbitrary Shapes: A Riemannian-Geometry Approach

Modeling, control, and stabilization of dynamics of two-dimensional object grasping by using a pair of multijoint robot fingers are investigated under rolling contact constraints and arbitrariness of the geometry of the object and fingertips. First, modeling of rolling motion between 2D rigid bodies with arbitrary shape is treated under the assumption that the two contour curves coincide at the contact point and share the same tangent. The rolling constraints induce the Euler equation of motion that is parameterized by a pair of arclength parameters and constrained onto the kernel space as an orthogonal complement to the image space spanned from all the constraint gradients. Furthermore, it is shown that all the Pfaffian forms of the rolling constraints are integrable in the sense of Frobenius and therefore the rolling contacts are regarded as a holonomic constraint. The Euler-Lagrange equation of motion of the overall fingers/object system is rederived together with a couple of first-order differential equations that express evolution of contact points in terms of quantities of the second fundamental form. A control signal called “blind grasping” is defined and shown to be effective in maintenance or stabilization of grasping without using the details of object shape and parameters or external sensing. An extension of the Dirichlet-Lagrange stability theorem to a system of DOF-redundancy under constraints is discussed by introducing a Morse-Bott function and deriving its Hessian, in a special case that the object to be grasped is a parallelepiped.

A Riemannian-Geometric Approach for Intelligent Control and Fingertip Design of Multi-fingered Hands

Based upon the analysis of modeling and control of two-dimensional (2-D) grasping and manipulation of arbitrary rigid objects under rolling contact constraints, geometrical conditions for the design of desired fingertip shapes of robot fingers are discussed from the Riemannian-geometric standpoint. A required condition is given as an inequality expressed in terms of quantities of the second fundamental form of fingertip contour curves, although the quantities do not enter into the Euler–Lagrange equation of motion of the overall fingers/object system. Satisfaction of the inequality is necessary for stabilization of grasping by using fingers–thumb opposable control signals without use of external sensings or knowledge of an object to be grasped. At the same time, asymptotic convergence of a solution to the closed-loop dynamics of 2-D precision prehension by a pair of multi-joint robot fingers is proved under rolling contact constraints and the existence of redundancy in the system's degrees of freedom. This is regarded as an extension of the Dirichlet–Lagrange stability theorem to a dynamical system with redundancy and geometric constraints.

物理世界と情報世界をつなぐソフトインターフェース

This article proposes a concept of soft interface for the connection between physical world where robots act and information world where robot intelligence is realized. First, this author summarizes modeling and control of object grasping and manipulation performed by a pair of soft fingertips. This author points out that a soft fingertip works as a soft interface for stable grasping and manipulation. This author also introduces two-stage control law for stable manipulation by a pair of 2-DOF fingers based on qualitative mapping between control variables and state variables. The proposed control law includes soft interface to cope with uncertainties in real world. This mapping-based approach is then applied to the control of a flexible arm based on polar coordinates.

Detection of Escherichia coli O157:H7 Using Interdigitated Array Microelectrode-Based Immunosensor

In this study, a label-free interdigitated array (IDA) microelectrode-based immunosensor was designed and tested for rapid and sensitive detection of E. coli O157:H7. The surface of gold IDA microelectrodes (25 pairs of fingers with 700 m length and 10 m width and space) was modified with protein A and further immobilized with polyclonal antibodies against E. coli O157:H7. A 20 L sample containing E. coli O157:H7 in 0.01 M phosphate buffered saline (PBS) at pH 7.4 was dropped on the surface of the modified microelectrodes and incubated for 2 h at room temperature. After the target bacteria were captured by the antibodies immobilized on the microelectrode, a wash with PBS was applied to rinse off all unbound parts of the sample. Finally, the impedance, both magnitude and phase angle, was measured over a broad frequency range from 1 Hz to 1 MHz. The results showed that the impedance in a frequency range of 1 Hz to 1 kHz increased with the increasing number of E. coli O157:H7 in a range from 80 to 2 105 cells per 20 L. A linear relationship between the magnitude of measured impedance and the log number of cells was determined at the frequency of 1 kHz. This biosensing method was able to detect as few as 80 cells of E. coli O157:H7 within 2 h. The specificity of the immunosensor was validated using five non-target bacteria, and none of them generated detectable signals. The application of the immunosensor for food safety was demonstrated with food samples including chicken carcasses, ground beef, and fresh cut broccoli inoculated with E. coli O157:H7. At the same time, the capture of E. coli O157:H7 cells on the microelectrode surface was confirmed using atomic force microscopy.

Hunchback and Ikaros-like zinc finger genes control reproductive system development in Caenorhabditis elegans

Here we provide evidence for a C2H2 zinc finger gene family with similarity to Ikaros and hunchback. The founding member of this family is Caenorhabditis elegans ehn-3, which has important and poorly understood functions in somatic gonad development. We examined the expression and function of four additional hunchback/Ikaros-like (HIL) genes in C. elegans reproductive system development. Two genes, ehn-3 and R08E3.4, are expressed in somatic gonadal precursors (SGPs) and have overlapping functions in their development. In ehn-3; R08E3.4 double mutants, we find defects in the generation of distal tip cells, anchor cells, and spermatheca; three of the five tissues derived from the SGPs. We provide in vivo evidence that C. elegans HIL proteins have functionally distinct zinc finger domains, with specificity residing in the N-terminal set of four zinc fingers and a likely protein–protein interaction domain provided by the C-terminal pair of zinc fingers. In addition, we find that a chimeric human Ikaros protein containing the N-terminal zinc fingers of EHN-3 functions in C. elegans. Together, these results lend support to the idea that the C. elegans HIL genes and Ikaros have similar functional domains. We propose that hunchback, Ikaros, and the HIL genes arose from a common ancestor that was present prior to the divergence of protostomes and deuterostomes.

The structural parameter optimization of interdigital transducer in single electron transport devices

We investigate the influence of the interdigital transducer (IDT) structure on the amplitude of the surface acoustic wave (SAW) in a SAW device. The SAW amplitude at the entrance of the quantum point contact (QPC) is obtained by using coupling-of-modes theory and p-matrix method. The calculated results indicate that a device with an IDT with a relatively small aperture, large pairs of IDT fingers, and short distance between the active IDT and the QPC, the SAW amplitude is typically enhanced under the same radio frequency (rf) power. Based on these results, we design the corresponding SAW devices, and good agreement is achieved between the experimental data and the numerical results. In experiment, for the devices with optimal IDTs, the rf powers required to observe the quantized acoustoelectric current are reduced; correspondingly, the rf heating effect is reduced. Most importantly, the improvement of the accuracy of the quantized plateau is achieved.