A gearing mechanism with 4 degrees of freedom for robotic applications in medicine]

Applications in robot-aided surgery are currently based on modifications of manipulators used in industrial manufacturing processes. In this paper we describe novel rotatory kinematics for a manipulator, specially developed for deployment in robot-aided surgery. The construction of the gearing mechanism used for the positioning and orientation of a linkage point is described. Forward and inverse kinematics were calculated, and a constructive solution proposed. The gearing mechanism is based on two disk systems, each of which consists of two opposing rotatable discs. The construction was designed in such a way that the linkage point can be positioned freely anywhere within the mechanism's range of motion. The kinematics thus permits an x-y-positioning via rotating movements only. The spatial arrangement of two of such disc systems permits movements in four degrees of freedom (DOF). The construction is compact, but can be further miniaturized, is flexible and manufacturing costs are low. On the basis of this mechanical concept a new, small automated manipulator for surgical application will be developed.     

Distances as degrees of freedom

Tertiary contact distance information of varying resolution for large biological molecules abounds in the literature. The results provided herein develop a framework by which information of this type can be used to reduce the allowable configuration space of a macromolecule. The approach combines graph theory and distance geometry. Large molecules are represented as simple, undirected graphs, with atoms, or groups, as vertices, and distances between them as edges. It is shown that determination of the exact structure of a molecule in three dimensions only requires the specification of all the distances in a single tetrahedron, and four distances to every other atom. This is 4N-10 distances which is a subset of the total N(N-1)/2 unique distances in a molecule consisting of N atoms. This requirement for only 4N-10 distances has serious implications for distance geometry implementations in which all N(N-1)/2 distances are specified by bounded random numbers. Such distance matrices represent overspecified systems which when solved lead to non-obvious distribution of any error caused by inherent contradictions in the input data. It is also shown that numerous valid subsets of 4N-10 distances can be constructed. It is thus possible to tailor a subset of distances using all known distances as degrees of freedom, and thereby reduce the configuration space of the molecule. Simple algebraic relationships are derived that relate sets of distances, and complicated rotations are avoided. These relationships are used to construct minimum, complete sets of distances necessary to specify the exact structure of the entire molecule in three dimensions from incomplete distance information, and to identify sets of inconsistent distances. The method is illustrated for the flexible structural types present in large ribosomal RNAs: 1.) A five-membered ring; 2.) a chemically bonded chain with its ends in contact (i.e., a hairpin loop); 3.) the spatial orientation of two separate molecules, and; 4.) an RNA helix that can have variation in individual base pairs, giving rise to global deviation from standardized helical forms.     

Essential degrees of freedom of proteins

Analysis of extended molecular dynamics (MD) simulations of several proteins in aquous solutions reveals that it is possible to separate the configurational space into two subspaces: (1) an essential subspace containing only a few degrees of freedom in which anharmonic motion occurs that comprises most of the positional fluctuations; and (2) the remaining space in which the motion has a narrow Gaussian distribution and which can be considered as physically constrained.     

Antioxidative response of Golden Agave leaves with different degrees of variegation under high light exposure

Variegated mutants are spotted rare in wild, and especially in the high light (HL) conditions. In addition, these plants are cultivated by a growing number of horticulturists due to their high economic value. In this experiment, the antioxidative response of both albino and green tissues from a mutant plant Golden Agave, which possesses leaves with different degrees of variegation, was investigated under normal or HL exposure, respectively. Severe oxidative stress was observed in green tissues of high albinism leaves (30?C40?% albino tissues, muy) over low albinism counterparts (less than 10?% albino tissues, mug). Compared with green tissues, low oxidative damage (relative electrolyte leakage and protein damage) and antioxidant enzyme (SOD, CAT, APX, and GR) activities were observed in the albino than in the adjacent green tissues. Photoinactivation of the CAT and the APX enzyme activities were observed in the albino tissues to a significantly level under HL exposure. In addition, lower redox values (ASC/DHA and GSH/GSSG) and higher levels of reactive oxygen species (ROS) were monitored in the green tissues of the muy over mug mutant even under normal light conditions. This work could help us to understand the HL sensitivity of variegated mutant plants better and allow us to improve variegated mutant plant cultivation skills. At last, the ??oxidative stress hypothesis?? was introduced to illustrate the reduced evolutionary advantage of plant variegation phenomenon in the discussion.     

The sticking region in three chest-press exercises with increasing degrees of freedom

ABSTRACT: Van den Tillaar, R, and S?terbakken, A. The sticking region in three chest-press exercises with increasing degrees of freedom. J Strength Cond Res 26(11): 2962-2969, 2012-The purpose was to investigate the effect of 3 chest-press exercises with different degrees of freedom upon the sticking region and muscle activity in maximal attempts. It was hypothesized that, with increasing degrees of freedom, the sticking region (the weakest region during the lift) would be longer because the muscles need to use a part of their ability to control these increasing degrees of freedom during the exercise. Furthermore, the prime movers would have the same muscle activity, but the biceps muscle activity would increase when the degrees of freedom increases because of the enhanced control of the upward movement. Eleven male subjects (age 22.6 ± 1.7 years, body mass 78.6 ± 8.0 kg, stature 1.80 ± 0.07 m) with at least 1 year of bench press training experience participated in this study. Every subject was tested in 1 repetition maximum (1RM) in the 3 chest-press exercises. During the attempts, kinematics and muscle activity were recorded and analyzed in 4 different regions (downward, presticking, sticking, and poststicking). The participants achieved the highest 1RM strength using the free barbell (106.4 ± 15.5 kg), followed by the Smith machine (103.6 ± 14.8 kg) and dumbbells (89.5 ± 13.7 kg). Furthermore, muscle activity differences (electromyographic) between the 3 different exercises and the muscle activation between the 4 different regions were found. The length of the different lifting regions together with muscle activity was different between the exercises. However, the differences found did not follow the line of increasing degrees of freedom that would result in a longer sticking region. Therefore, it is possible to choose to train a particular chest press exercise with the purpose of training a particular muscle more than the others.     

A dynamic model of an environmental system withn interacting components andp degrees of freedom

The nonlinear differential equations of growth proposed by Volterra (1931) are used as the basis for a dynamic model of ann-element system withp specified, terminal conditions andp missing initial conditions. The resulting two-point boundary-value problem can be solved, ifp is not large, by the shooting method used previously by Huddleston (1967). A numerical example withn=4 andp=2 is solved on a digital computer, and some results are presented.     

Assessment of the accuracy of a human arm model with seven degrees of freedom

We are proposing a human arm model that consists of three rigid segments with seven degrees of freedom. The shoulder joint was modeled as a ball-and-socket joint and the elbow and wrist joints were modelled as skew-oblique joints. Optimal parameters for this model were calculated on the base of in vivo recordings with a spatial tracking system. The criterion of optimality was defined as the minimum of the mean-square deviation between the experimentally obtained sensor positions and orientations and their positions and orientations calculated by solving the direct kinematics problem. The minimal value of the direct kinematics error was found to be 0.5-0.6cm for sensor positions and 5-7 degrees for sensor orientations. We are proposing that these values serve as the assessment for the accuracy of the arm model.     

Small-sample degrees of freedom for multi-component significance tests with multiple imputation for missing data

When performing multi-component significance tests with multiply-imputeddatasets, analysts can use a Wald-like test statistic and areference F-distribution. The currently employed degrees offreedom in the denominator of this F-distribution are derivedassuming an infinite sample size. For modest complete-data samplesizes, this degrees of freedom can be unrealistic; for example,it may exceed the complete-data degrees of freedom. This paperpresents an alternative denominator degrees of freedom thatis always less than or equal to the complete-data denominatordegrees of freedom, and equals the currently employed denominatordegrees of freedom for infinite sample sizes. Its advantagesover the currently employed degrees of freedom are illustratedwith a simulation.     

A holistic model for an internal representation to control the movement of a manipulator with redundant degrees of freedom

The paper proposes a model for the control of a multisegmented manipulator with redundant degrees of freedom. On the basis of an earlier model, the so-called MMC net, a simplified version is proposed here which has several advantages. First, it can easily be scaled up for the 3D case. Second, for the linear version a complete convergence proof is possible. Third, an easy way of implementing a damping parameter is shown. Fourth, the properties of the earlier model are unchanged, namely versatile control of the redundant system, immediate change from direct kinematics to inverse kinematics or any mixed control task, as well as robustness in the case of singularities. Received: 4 October 1997 / Accepted in revised form: 26 August 1998     

Kinematics of helical motion of microorganisms capable of motion with four degrees of freedom.

The kinematics of helical motion are described for an organism with four degrees of freedom, relative to the organism's frame of reference. It can rotate about any of three orthogonal axes, but can translate only in the direction of one axis. In particular, equations are developed for calculating the pitch, radius, and angular frequency of the helical path from the translational and rotational velocities of the microorganism, correcting, and expanding the analysis of Gray J. (1955. J. Exp. Biol. 32:775-801).     

Significance of kinetic degrees of freedom in operation of the actomyosin motor

The actomyosin motor as a principal functional component of cell motility is highly coordinated in regulating the participating molecular components. At the same time, it has to be flexible and plastic enough to accommodate itself to a wide variety of operational conditions. We prepared two different types of actomyosin systems. One is a natural intact actomyosin system with no artificial constraint on the kinetic degrees of freedom of the actin filaments, and the other is a regulated one with actin filaments supplemented by intra- and intermolecular crosslinking to suppress the kinetic degrees of freedom to a certain extent. Crosslinked actomyosin systems were found to remain almost insensitive to calcium regulation even when intact troponin-tropomyosin regulatory component was incorporated. Both the ATPase and the motile activities of the actin filaments sliding on myosin molecules were markedly lowered by the crosslinking. In contrast, once the crosslinking was cleaved, both properties returned to the normal as with intact actomyosin systems.     

The relation of workspace and installation space of epicyclic kinematics with six degrees of freedom]

INTRODUCTION: The kinematics of a robotic device significantly determines its installation space when it comes to technical realisation. With regard to the deployment of robotic manipulators in surgery, manipulators with a preferably small installation space are needed. MATERIALS AND METHODS: This study describes six versions of novel epicyclic kinematics with six degrees of freedom (DOF). At first, the kinematics functionality was analysed using Gruebler's formula. Subsequently, the quantitative determination of the relation of workspace and installation space was performed using Matlab algorithms. To qualitatively describe the shape of the workspace, the Matlab visualisation features were utilised. For comparison, the well-known Hexapod was used. RESULTS: The assessed kinematics had 6-DOF-functionality. It became apparent that one version of the epicyclic kinematics having two 3-DOF disk systems mounted in a parallel way featured a particularly good relation of workspace and installation space. Compared to the Hexapod, this is approximately four times better. The shape of the workspaces of all epicyclic kinematics assessed was convex and compact. CONCLUSION: It could be shown that a novel epicyclic kinematics has a notably advantageous relation of workspace and installation space. Apparently, it seems to be well suited for the deployment in robotic machines for surgical procedures.