Vector Field Control Methods for Discretely Variable Passive Robotic Devices

Passive transmission-based robotic devices are capable of providing motion guidance while ensuring user safety and engagement. To circumvent some of the drawbacks associated with steering continuously variable transmissions based on rolling contacts, we are exploring a class of discretely variable devices, based on brakes and hydrostatic transmissions. Previously available control methods for discretely variable devices were built on velocity fields and only developed to stabilize a 1D target manifold. For n -DOF devices, methods to stabilize target manifolds of dimension 1 to n—1 are of interest. In this paper we contribute constraint field methods that stabilize n — 1 dimensional target manifolds while leaving the orthogonal subspace free to the control of the operator. We also contribute force-modulated SDOF velocity fields, which add between 1 and n— 2 virtual DOFs to the motion of devices whose physical constraints leave one DOF. Control performance is demonstrated in simulation for 3-DOF devices capable of imposing 1-D or 2-D constraints and in experiment for 2-DOF devices imposing 1-D constraints. Our experimental apparatus features digital hydraulic transmissions that are easily configured for n-dimensional space and capable of imposing constraints of any dimension, thus motivating the contributed methods

Toward Controllable Hydraulic Coupling of Joints in a Wearable Robot

In this paper, we develop theoretical foundations for a new class of rehabilitation robot: body powered devices that route power between a user’s joints. By harvesting power from a healthy joint to assist an impaired joint, novel bimanual and self-assist therapies are enabled. This approach complements existing robotic therapies aimed at promoting recovery of motor function after neurological injury. We employ hydraulic transmissions for routing power, or equivalently for coupling the motions of a user’s joints. Fluid power routed through flexible tubing imposes constraints within a limb or between homologous joints across the body. Variable transmissions allow constraints to be steered on the fly, and simple valve switching realizes free space and locked motion. We examine two methods for realizing variable hydraulic transmissions: using valves to switch among redundant cylinders (digital hydraulics) or using an intervening electromechanical link. For both methods, we present a rigorous mathematical framework for describing and controlling the resulting constraints. Theoretical developments are supported by experiments using a prototype fluid-power exoskeleton

Exclosures: An Experimental Technique for Protection of Northern Bobwhite Nests

Nest predation has been implicated as a factor affecting northern bobwhite (Colinus virginianus) recruitment rates. Public stakeholders are increasingly questioning use of lethal methods to manage predation. We evaluated a nonlethal method consisting of single nest treatments using an exclosure to protect nests from potential predators. The exclosure treatment also included use of Amdrot (hydramethylnon) and Snake-a-wayt repellents to deter red-imported fire ants (Solenopsis invicta) and snakes, respectively. We compared nest success of treated (n 1⁄4 8) to untreated nests (n 1⁄4 18). Treated nests were 88% successful which was a 2-fold increase over unprotected nests. We did not observe any difference in hen behavior between treatment and controls. This technique may be useful to study nest success of wild quail and is not intended to be a management technique to influence overall population growth

Self-Powered Robots to Reduce Motor Slacking During Upper-Extremity Rehabilitation: A Proof of Concept Study

Background: Robotic rehabilitation is a highly promising approach to recover lost functions after stroke or other neurological disorders. Unfortunately, robotic rehabilitation currently suffers from motor slacking , a phenomenon in which the human motor system reduces muscle activation levels and movement excursions, ostensibly to minimize metabolic- and movement-related costs. Consequently, the patient remains passive and is not fully engaged during therapy. To overcome this limitation, we envision a new class of body-powered robots and hypothesize that motor slacking could be reduced if individuals must provide the power to move their impaired limbs via their own body (i.e., through the motion of a healthy limb). Objective: To test whether a body-powered exoskeleton (i.e. robot) could reduce motor slacking during robotic training. Methods: We developed a body-powered robot that mechanically coupled the motions of the user\u27s elbow joints. We tested this passive robot in two groups of subjects (stroke and able-bodied) during four exercise conditions in which we controlled whether the robotic device was powered by the subject or by the experimenter, and whether the subject\u27s driven arm was engaged or at rest. Motor slacking was quantified by computing the muscle activation changes of the elbow flexor and extensor muscles using surface electromyography. Results: Subjects had higher levels of muscle activation in their driven arm during self-powered conditions compared to externally-powered conditions. Most notably, subjects unintentionally activated their driven arm even when explicitly told to relax when the device was self-powered. This behavior was persistent throughout the trial and did not wane after the initiation of the trial. Conclusions: Our findings provide novel evidence indicating that motor slacking can be reduced by self-powered robots; thus demonstrating promise for rehabilitation of impaired subjects using this new class of wearable system. The results also serve as a foundation to develop more sophisticated body-powered robots (e.g., with controllable transmissions) for rehabilitation purposes

Fraudulent financial reporting: 1987-1997 : an analysis of U.S. public companies : research report

https://egrove.olemiss.edu/aicpa_assoc/1330/thumbnail.jp

Quantum transport through a DNA wire in a dissipative environment

Electronic transport through DNA wires in the presence of a strong dissipative environment is investigated. We show that new bath-induced electronic states are formed within the bandgap. These states show up in the linear conductance spectrum as a temperature dependent background and lead to a crossover from tunneling to thermal activated behavior with increasing temperature. Depending on the strength of the electron-bath coupling, the conductance at the Fermi level can show a weak exponential or even an algebraic length dependence. Our results suggest a new environmental-induced transport mechanism. This might be relevant for the understanding of molecular conduction experiments in liquid solution, like those recently performed on poly(GC) oligomers in a water buffer (B. Xu et al., Nano Lett 4, 1105 (2004)).Comment: 5 pages, 3 figure

A Reinvestigation by Circular Dichroism and NMR: Ruthenium(II) and Rhodium(III) Metallointercalators Do Not Bind Cooperatively to DNA

Fast, long-range electron transfer mediated by the DNA helix has been questioned by some researchers citing the possible clustering, or cooperative association, of noncovalently bound donors and acceptors on DNA. A systematic investigation of binding to DNA by the metallointercalators Δ-bis(1,10-phenanthroline)(dipyridophenazine)ruthenium(II) (Ru), Δ-bis(9,10-phenanthrenequinone diimine)(2,2‘-bipyridine)rhodium(III) (Rh), and Δ-bis(9, 10-phenanthrenequinone diimine)(5-(amidoglutaryl)-1,10-phenanthroline)rhodium(III) (Rh‘) using circular dichroism and NMR has shown no evidence for their cooperative clustering on a DNA helix. Circular dichroism (CD) studies of Ru and Rh in [poly(dA-dT)]_2, mixed-sequence calf thymus DNA, and [poly(dG-dC)]_2 as a function of loading indicate that the largest perturbations to the CD signal occur upon initial addition of DNA, with no subsequent systematic variation. Difference spectra of the two metallointercalators bound together versus separately are virtually indistinguishable at high and low loadings. Two-dimensional 1H NMR studies of Ru and Rh‘ binding to a DNA decamer duplex in 90:10 H_2O/D_2O have also been conducted. A more direct structural picture of the site occupancies of these complexes on a DNA helix emerges through examination of the dramatic upfield shifts of the imino protons of the DNA bases that occur upon intercalation. These studies reveal that with both complexes present, each intercalates specifically toward either end of the duplex, with a 4 base pair separation between them. In contrast, the complexes individually bound to the duplex showed low site-selectivity, and preferred more central sites. If anything, these data indicate anti-cooperative binding to the helix, which might be expected based upon electrostatic considerations. Time-resolved measurements of the Ru(II) luminescence reveal substantial subnanosecond quenching (approximately 60%) in the presence of Rh(III). Based upon the NMR results, this quenching must proceed over a distance >14 Å via electron transfer through the DNA π-stack. These experiments with noncovalently bound intercalators are fully consistent with earlier studies of electron transfer through DNA utilizing covalently bound donors and acceptors and definitively prove clustering cannot be responsible for the fast photoinduced electron transfer between metallointercalators mediated by the DNA double helix

A Reinvestigation by Circular Dichroism and NMR: Ruthenium(II) and Rhodium(III) Metallointercalators Do Not Bind Cooperatively to DNA

Fast, long-range electron transfer mediated by the DNA helix has been questioned by some researchers citing the possible clustering, or cooperative association, of noncovalently bound donors and acceptors on DNA. A systematic investigation of binding to DNA by the metallointercalators Δ-bis(1,10-phenanthroline)(dipyridophenazine)ruthenium(II) (Ru), Δ-bis(9,10-phenanthrenequinone diimine)(2,2‘-bipyridine)rhodium(III) (Rh), and Δ-bis(9, 10-phenanthrenequinone diimine)(5-(amidoglutaryl)-1,10-phenanthroline)rhodium(III) (Rh‘) using circular dichroism and NMR has shown no evidence for their cooperative clustering on a DNA helix. Circular dichroism (CD) studies of Ru and Rh in [poly(dA-dT)]_2, mixed-sequence calf thymus DNA, and [poly(dG-dC)]_2 as a function of loading indicate that the largest perturbations to the CD signal occur upon initial addition of DNA, with no subsequent systematic variation. Difference spectra of the two metallointercalators bound together versus separately are virtually indistinguishable at high and low loadings. Two-dimensional 1H NMR studies of Ru and Rh‘ binding to a DNA decamer duplex in 90:10 H_2O/D_2O have also been conducted. A more direct structural picture of the site occupancies of these complexes on a DNA helix emerges through examination of the dramatic upfield shifts of the imino protons of the DNA bases that occur upon intercalation. These studies reveal that with both complexes present, each intercalates specifically toward either end of the duplex, with a 4 base pair separation between them. In contrast, the complexes individually bound to the duplex showed low site-selectivity, and preferred more central sites. If anything, these data indicate anti-cooperative binding to the helix, which might be expected based upon electrostatic considerations. Time-resolved measurements of the Ru(II) luminescence reveal substantial subnanosecond quenching (approximately 60%) in the presence of Rh(III). Based upon the NMR results, this quenching must proceed over a distance >14 Å via electron transfer through the DNA π-stack. These experiments with noncovalently bound intercalators are fully consistent with earlier studies of electron transfer through DNA utilizing covalently bound donors and acceptors and definitively prove clustering cannot be responsible for the fast photoinduced electron transfer between metallointercalators mediated by the DNA double helix