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Roberts SF, Koditschek DE. Virtual Energy Management for Physical Energy Savings in a Legged Robot Hopping on Granular Media. Front Robot AI 2022; 8:740927. [PMID: 34993236 PMCID: PMC8724561 DOI: 10.3389/frobt.2021.740927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 11/29/2021] [Indexed: 11/17/2022] Open
Abstract
We discuss an active damping controller to reduce the energetic cost of a single step or jump of dynamic locomotion without changing the morphology of the robot. The active damping controller adds virtual damping to a virtual leg spring created by direct-drive motors through the robot’s leg linkage. The virtual damping added is proportional to the intrusion velocity of the robot’s foot, slowing the foot’s intrusion, and thus the rate at which energy is transferred to and dissipated by the ground. In this work, we use a combination of simulations and physical experiments in a controlled granular media bed with a single-leg robot to show that the active damping controller reduces the cost of transport compared with a naive compression-extension controller under various conditions.
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Affiliation(s)
- Sonia F Roberts
- Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA, United States
| | - Daniel E Koditschek
- Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA, United States
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Roberts SF, Koditschek DE, Miracchi LJ. Examples of Gibsonian Affordances in Legged Robotics Research Using an Empirical, Generative Framework. Front Neurorobot 2020; 14:12. [PMID: 32153382 PMCID: PMC7044146 DOI: 10.3389/fnbot.2020.00012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Accepted: 01/31/2020] [Indexed: 01/17/2023] Open
Abstract
Evidence from empirical literature suggests that explainable complex behaviors can be built from structured compositions of explainable component behaviors with known properties. Such component behaviors can be built to directly perceive and exploit affordances. Using six examples of recent research in legged robot locomotion, we suggest that robots can be programmed to effectively exploit affordances without developing explicit internal models of them. We use a generative framework to discuss the examples, because it helps us to separate-and thus clarify the relationship between-description of affordance exploitation from description of the internal representations used by the robot in that exploitation. Under this framework, details of the architecture and environment are related to the emergent behavior of the system via a generative explanation. For example, the specific method of information processing a robot uses might be related to the affordance the robot is designed to exploit via a formal analysis of its control policy. By considering the mutuality of the agent-environment system during robot behavior design, roboticists can thus develop robust architectures which implicitly exploit affordances. The manner of this exploitation is made explicit by a well constructed generative explanation.
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Affiliation(s)
- Sonia F Roberts
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA, United States
| | - Daniel E Koditschek
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA, United States
| | - Lisa J Miracchi
- Department of Philosophy, University of Pennsylvania, Philadelphia, PA, United States
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Triphan T, Nern A, Roberts SF, Korff W, Naiman DQ, Strauss R. A screen for constituents of motor control and decision making in Drosophila reveals visual distance-estimation neurons. Sci Rep 2016; 6:27000. [PMID: 27255169 PMCID: PMC4891706 DOI: 10.1038/srep27000] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 05/09/2016] [Indexed: 11/29/2022] Open
Abstract
Climbing over chasms larger than step size is vital to fruit flies, since foraging and mating are achieved while walking. Flies avoid futile climbing attempts by processing parallax-motion vision to estimate gap width. To identify neuronal substrates of climbing control, we screened a large collection of fly lines with temporarily inactivated neuronal populations in a novel high-throughput assay described here. The observed climbing phenotypes were classified; lines in each group are reported. Selected lines were further analysed by high-resolution video cinematography. One striking class of flies attempts to climb chasms of unsurmountable width; expression analysis guided us to C2 optic-lobe interneurons. Inactivation of C2 or the closely related C3 neurons with highly specific intersectional driver lines consistently reproduced hyperactive climbing whereas strong or weak artificial depolarization of C2/C3 neurons strongly or mildly decreased climbing frequency. Contrast-manipulation experiments support our conclusion that C2/C3 neurons are part of the distance-evaluation system.
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Affiliation(s)
- Tilman Triphan
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Aljoscha Nern
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Sonia F Roberts
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Wyatt Korff
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Daniel Q Naiman
- Johns Hopkins University, Department of Applied Mathematics and Statistics, 3400 North Charles Street, Baltimore, MD 21218, USA
| | - Roland Strauss
- Johannes Gutenberg-Universität Mainz, Institut für Zoologie III, Col.-Kleinmann-Weg 2, 55099 Mainz, Germany
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Roberts SF, Hirokawa J, Rosenblum HG, Sakhtah H, Gutierrez AA, Porter ME, Long JH. Testing Biological Hypotheses with Embodied Robots: Adaptations, Accidents, and By-Products in the Evolution of Vertebrates. Front Robot AI 2014. [DOI: 10.3389/frobt.2014.00012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Stinstra JG, Roberts SF, Pormann JB, MacLeod RS, Henriquez CS. A Model of 3D Propagation in Discrete Cardiac Tissue. Comput Cardiol 2006; 33:41-44. [PMID: 17404606 PMCID: PMC1847422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
A model was developed of a bundle of cardiac fibers embedded in an extracellular space. In contrast to the classical bidomain approach, the model is constructed such that the intracellular and extracellular spaces are spatially distinct. The model was used to test the hypothesis that the distribution of the extracellular fluid in the tissue can affect the conduction velocity. The preliminary results suggest that under nominally normal conditions, the propagation speed depends on the fraction of extracellular space and less on the actual distribution of extracellular space within the bundle.
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Affiliation(s)
- JG Stinstra
- University of Utah, UT, USA
- Address for correspondence: Jeroen Stinstra, University of Utah, CardioVascular Research and Training Institute, Room 207, Bldg 5000, 95 South 2000 East., Salt Lake City, UT-84112, USA,
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Abstract
The purpose of the present study was to characterize the psychological status (attitudes toward selective abortion, perceived risk, comprehension, patient satisfaction, coping, and state anxiety) of pregnant women at increased risk for fetal genetic anomalies who were referred for prenatal genetic counseling and amniocentesis; to determine which of these factors would predict amniocentesis use; and to identify patient outcomes associated with counseling and testing. Participants were 129 women aged 18 years and older who had one or more fetal genetic risk factors. All were recruited from an urban women's health clinic. The results revealed elevated perceptions of risk and moderate state anxiety despite adequate comprehension of, and patient satisfaction with, the process and content of genetic counseling. Approximately 78% agreed to testing; those who consented were more likely to hold favorable attitudes toward abortion than those who refused. Post-counseling, women experienced decrease in their perceived risk of having a baby born with a birth defect although perceived risk estimates remained higher than actual risks. Anxiety was clinically elevated and highest at the pre-counseling stage, though it dissipated to normal levels over time. Previous experience with prenatal diagnostic testing, increased perceived risk of a birth anomaly, and favorable attitudes toward abortion were independently associated with increased pre-counseling anxiety. Women who were more anxious pre-counseling remained more anxious post-counseling. Coping (high versus low monitoring) was unrelated to anxiety. These findings suggest that women who participate in prenatal counseling and testing may be subject to experience distress and unrealistic perceptions of their risk and may benefit from interventions designed to lessen these states.
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Affiliation(s)
- K P Tercyak
- Department of Clinical and Health Psychology, University of Florida, Gainesville, FL, USA.
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Pancu DM, Lee DC, Salen PN, Roberts SF, Rudolph GS, Ryan J, Heller MB, Arcona S. Do age and gender affect β-blocker utilization in emergency department management of acute myocardial infarction? Ann Emerg Med 1999. [DOI: 10.1016/s0196-0644(99)80263-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Lohnas GL, Roberts SF, Pilon A, Tramontano A. Epitope-specific antibody and suppression of autoantibody responses against a hybrid self protein. J Immunol 1998; 161:6518-25. [PMID: 9862676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
This study addresses the relationship of epitope-specific Ab responses and alternative autoantibody responses in a model system in which an antigenized self protein serves as the carrier for a defined heterologous B cell epitope. Ubiquitin, a nonimmunogenic self protein, was engineered to present heterologous B and T cell epitopes in the recombinant molecule. Fusion to the C terminus introduced a universal T cell epitope from a Mycobacterium tuberculosis Ag. The B cell epitope was created by inserting a 12-residue loop sequence of HIV-1 gp120 at a surface-exposed position of ubiquitin. These modifications preserved the ubiquitin fold, allowing a new conformational epitope to be presented among native self epitopes. Mice immunized with the hybrid protein bearing only the mycobacterial T cell epitope elicited a strong autoantibody response to native ubiquitin. In contrast, antisera elicited against hybrid ubiquitin presenting the HIV B cell epitope reacted specifically with the foreign epitope but not with native ubiquitin. Absence of autoantibody in the response was attributed to poor competition of autoreactive B cells for limiting T cell help. Both types of responses were associated with Th responses to defined epitopes of the ubiquitin hybrid protein. These results may have implications for a tolerance mechanism dependent on B-T cell cooperation.
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Affiliation(s)
- G L Lohnas
- Proteinix Company, Gaithersburg, MD 20877, USA
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Roberts SF. Prenatal diagnosis: chances, choices. J Fla Med Assoc 1997; 84:374-8. [PMID: 9379162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Genetic counseling for prenatal diagnostic testing should provide accurate, unbiased, and value-sensitive information to women and their families, enabling them to make decisions most consistent with their personal values and circumstances.
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Affiliation(s)
- S F Roberts
- Department of Obstetrics and Gynecology, University of Florida, Gainesville, USA
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Roberts SF, Irvine JW, Lindberg I. Characterization of proenkephalin-cleaving proteinases in bovine adrenal chromaffin granules using [35S]proenkephalin copolymerized into sodium dodecyl sulfate-polyacrylamide gel electrophoresis. J Neurochem 1992; 58:593-9. [PMID: 1729404 DOI: 10.1111/j.1471-4159.1992.tb09760.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Proteinases capable of cleaving proenkephalin into smaller peptides have been identified in bovine adrenal chromaffin granules using [35S]methionine-labeled recombinant rat proenkephalin as a selective substrate in sodium dodecyl sulfate-polyacrylamide gel electrophoresis proteinase radiozymography. This technique was used for the screening of subcellular fractions, general characterization of pH optima, and the mechanistic characterization of proteinases with both reversible and irreversible inhibitors. Two enzymes with approximate molecular masses of 76 and 30 kDa were shown to be localized to the highest-density fractions of chromaffin granules by sucrose density gradient fractionation. Both were enriched in a 1 M NaCl wash of purified chromaffin granule membranes, were active at high pH, and were characterized as serine proteinases based on inhibition by soybean trypsin inhibitor. The 30-kDa enzyme was also inhibited by diisopropyl fluorophosphate, D-Phe-Pro-Arg-CH2Cl, and D-Val-Phe-Lys-CH2Cl and appeared to be the previously described adrenal trypsin-like enzyme. A third enzyme, of 66 kDa, was also associated with the 1 M NaCl wash of purified chromaffin granule membranes but was not localized exclusively to chromaffin granules in sucrose gradients. This proteinase was found to be Ca2+ activated and inhibited by EDTA but not diisopropyl fluorophosphate, soybean trypsin inhibitor, p-chloromercuriphenylsulfonic acid, 1,10-phenanthroline, or pepstatin.
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Affiliation(s)
- S F Roberts
- Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, New Orleans 70112
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Irvine JW, Roberts SF, Lindberg I. Electrophoretic analysis of proteinases in sodium dodecyl sulfate-polyacrylamide gels containing copolymerized radiolabeled protein substrates: application to proenkephalin processing enzymes. Anal Biochem 1990; 190:141-6. [PMID: 2285141 DOI: 10.1016/0003-2697(90)90147-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A novel method is described for the zymographic analysis of proteinases in sodium dodecyl sulfate-polyacrylamide gels containing copolymerized radiolabeled protein substrates such as [35S]methionine-labeled proenkephalin or 125I-labeled proinsulin. After electrophoresis the enzyme is reactivated and cleaves the radiolabeled in situ substrate into smaller peptides. These small peptides are able to diffuse out of the gel, leaving clear areas against a dark background when visualized by autoradiography. The technique can be used to detect as little as 200 fg of trypsin using only 50 ng (1.25 microCi) of [35S]proenkephalin. Soluble- and membrane-bound adrenal trypsin-like enzyme were isolated from bovine adrenal chromaffin granules. Both proteinases cleaved [35S]methionine-labeled proenkephalin but not 125I-labeled proinsulin. Moreover, both had a Mr of approximately 30,000. The potential of this technique for general use is discussed. An additional method using the synthetic fluorogenic substrate t-butoxycarbonyl Glu-Lys-Lys aminomethylcoumarin is also described.
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Affiliation(s)
- J W Irvine
- Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, New Orleans 70112
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Shen FS, Roberts SF, Lindberg I. A putative processing enzyme for proenkephalin in bovine adrenal chromaffin granule membranes. Purification and properties. J Biol Chem 1989; 264:15600-5. [PMID: 2768280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
A putative processing enzyme for proenkephalin, with activity directed toward basic residues, was purified over 2000-fold from washed bovine adrenal medullary chromaffin granule membranes. The molecular mass of this membrane-bound adrenal trypsin-like enzyme (mATLE) is 31 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the enzyme is extremely basic, binding to carboxymethyl-Sephadex at pH 8.5. The pH optimum of mATLE using t-butoxycarbonyl-Glu-Lys-Lys-aminomethylcoumarin as a substrate is 8.5-8.7, and its Km value for this substrate is 2.2 mM. mATLE activity was inhibited by soybean trypsin inhibitor, lima bean trypsin inhibitor, and aprotinin but not by metal chelators or thiol-directed reagents. Sequencing of cleavage products released from Peptide B revealed that the enzyme preferentially cleaves between and following the paired basic residues at positions 23 and 24 of Peptide B (thus generating [Met-enkephalin]-Arg-Phe and Arg-[Met-enkephalin]-Arg-Phe). Dynorphin A was cleaved following a single lysine at position 11 but not at the paired arginine site. Our results suggest that mATLE is a trypsin-like serine protease with the specificity appropriate to that of a proenkephalin processing enzyme.
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Affiliation(s)
- F S Shen
- Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, New Orleans, Louisiana 70112
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May SW, Herman HH, Roberts SF, Ciccarello MC. Ascorbate depletion as a consequence of product recycling during dopamine beta-monooxygenase catalyzed selenoxidation. Biochemistry 1987; 26:1626-33. [PMID: 3036204 DOI: 10.1021/bi00380a021] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The competence of dopamine beta-monooxygenase (DBM) to process selenide substrates was investigated, in anticipation that the expected selenoxide products would exhibit unique reactivity and redox properties. The prototypical selenide phenyl 2-aminoethyl selenide (PAESe) was synthesized and shown to be a substrate for DBM with the characteristic e/O2 ratio of 2:1 for monooxygenation. The kinetic parameters for oxygenation of PAESe were found to be similar to those for the DBM-catalyzed sulfoxidation of the cognate sulfide phenyl 2-aminoethyl sulfide [May, S. W., & Phillips, R. S. (1980) J. Am. Chem. Soc. 102, 5981-5983], and selenoxidation was stimulated by fumarate in a manner similar to other well-characterized DBM monooxygenation reactions. Identification of phenyl 2-aminoethyl selenoxide (PAESeO) as the enzymatic product was accomplished by the demonstration of coincident elution of authentic PAESeO with the enzymatic product in three significantly different HPLC systems. PAESeO was found to oxidize ascorbic acid with the concomitant and stoichiometric reduction of PAESeO back to the selenide, PAESe. As a consequence of this nonenzymatic reaction, ascorbate-supported DBM turnover was prematurely terminated under standard assay conditions due to depletion of reduced ascorbate. The kinetics of the redox reaction between PAESeO and ascorbate were investigated with a spectrophotometric assay of ascorbate at 300 nm, and a second-order rate constant of 3.4 M-1 s-1 was determined at pH 5.0, 25 degrees C. Spectrophotometric assay of cytochrome c (cyt c) reduction at 550 nm during the oxidation of ascorbate by PAESeO demonstrated that no cyt c trappable semidehydroascorbate was produced in this nonenzymatic reaction.(ABSTRACT TRUNCATED AT 250 WORDS)
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