M.A. Jimenez

The evolution of robotics research

This article surveys traditional research topics in industrial robotics and mobile robotics and then expands on new trends in robotics research that focus more on the interaction between human and robot. The new trends in robotics research have been denominated service robotics because of their general goal of getting robots closer to human social needs, and this article surveys research on service robotics such as medical robotics, rehabilitation robotics, underwater robotics, field robotics, construction robotics and humanoid robotics. The aim of this article is to provide an overview of the evolution of research topics in robotics from classical motion control for industrial robots to modern intelligent control techniques and social learning paradigms, among other aspects.

Streamlined Syntheses of (−)-Dictyostatin, 16-Desmethyl-25,26-dihydrodictyostatin, and 6-epi-16-Desmethyl-25,26-dihydrodictyostatin

The dictyostatins are a promising class of potential anti-cancer drugs because they are powerful microtubule-stabilizing agents, but the complexity of their chemical structures is a severe impediment to their further development. On the basis of both synthetic and medicinal chemistry analyses, 16-desmethyl-25,26-dihydrodictyostatin and its C6 epimer were chosen as potentially potent yet accessible dictyostatin analogues, and three new syntheses were developed. A relatively classical synthesis involving vinyllithium addition and macrocyclization gave way to a newer and more practical approach based on esterification and ring-closing metathesis reaction. Finally, aspects of these two approaches were combined to provide a third new synthesis based on esterification and Nozaki-Hiyama-Kishi reaction. This was used to prepare the target dihydro analogues and the natural product. All of the syntheses are streamlined because of their high convergency. The work provided several new analogues of dictyostatin, including a truncated macrolactone and a C10 E-alkene, which were 400- and 50-fold less active than (-)-dictyostatin, respectively. In contrast, the targeted 16-desmethyl-25,26-dihydrodictyostatin analogues retained almost complete activity in preliminary biological assays.

Ship building with ROWER

A four-legged mobile platform increases productivity and improves quality and working conditions for industrial naval applications. It is an automatic welding system for ship construction processes. It increases productivity by increasing total arc time, improving weld quality, and creating better working conditions for operators. The overall system consists of a commercial welding system handled by a commercial manipulator. These subsystems are carried on a mobile platform that provides mobility in the working area. A stereo vision system finds the starting and ending points of the welding seam. All four subsystems are remote-controlled by a computer supervised by an operator located off the work site. The supervisor computer also contains a database of the geometric description of each working cell.

Application of CLAWAR Machines

In the last two decades in particular, climbing and walking robots have been the subject of important research activity worldwide. However, the practical use of these robots is still limited and only a few are in actual use in live situations. In the general framework of the CLAWAR Thematic Network, several working groups have been established to formulate requirements, to define specifications and to investigate those aspects of climbing and walking robot technology that are more relevant with respect to selected application domains. The aim of this paper is to present an overview of the investigations carried out by the CLAWAR network, and to show various realizations that could offer a good picture of how to rise above the barriers to exploit this innovative class of robotic systems.

A study of the NH NMR signals of Gly-Gly-X-Ala tetrapeptides in H2O at low temperature.

Abstract The effect of temperature, pH and addition of denaturing agents on the amide and side chain NH δ values of a series of random coil linear tetrapeptides (Gly-Gly-X-Ala with X=Glu, Asp, His, Trp, Arg, Gly, Pro, Asn, Gln) has been measured in dilute aqueous solutions at two temperatures (24 and 0°C). Amide shift temperature coefficients were within the −5.8 to −9.1 ppb/K range. Amide δ changes following urea addition were ⩽ 0.03 ppm, with the exception of the Ala terminal residue of all peptides, and the His residue as well. Signs of a non-random structure near the COO − terminus were found for the Gly-Gly-His-Ala tetrapeptide.

NMR Spectroscopy Reveals that RNase A is Chiefly Denatured in 40% Acetic Acid: Implications for Oligomer Formation by 3D Domain Swapping

Protein self-recognition is essential in many biochemical processes and its study is of fundamental interest to understand the molecular mechanism of amyloid formation. Ribonuclease A (RNase A) is a monomeric protein that may form several oligomers by 3D domain swapping of its N-terminal alpha-helix, C-terminal beta-strand, or both. RNase A oligomerization is induced by 40% acetic acid, which has been assumed to mildly unfold the protein by detaching the terminal segments and consequently facilitating intersubunit swapping, once the acetic acid is removed by lyophilization and the protein is redissolved in a benign buffer. Using UV difference, near UV circular dichroism, folding kinetics, and multidimensional heteronuclear NMR spectroscopy, the conformation of RNase A in 40% acetic acid and in 8 M urea has been characterized. These studies demonstrate that RNase A is chiefly unfolded in 40% acetic acid; it partially retains the native helices, whereas the beta-sheet is fully denatured and all X-Pro peptide bonds are predominantly in the trans conformation. Refolding occurs via an intermediate, I(N), with non-native X-Pro peptide bonds. I(N) is known to be populated during RNase A refolding following denaturation in concentrated solutions of urea or guanidinium chloride, and we find that urea- or GdmCl-denatured RNase A can oligomerize during refolding. By revealing the importance of a chiefly denaturated state and a refolding intermediate with non-native X-Pro peptide bonds, these findings revise the model for RNase A oligomerization via 3D domain swapping and have general implications for amyloid formation.

Generation of discontinuous gaits for quadruped walking vehicles

Discontinuous gaits for walking machines have not yet been properly studied. Research has focused on the investigation, comprehension, and mathematical formulation of natural gaits. These gaits feature the fact that the body is in constant motion. The results have been significant, but they seem more adequate for animals than machines. On the other hand, discontinuous gaits, executed by animals under extreme conditions, exhibit excellent attributes for implementation in walking machines. This article presents a comparative study of continuous and discontinuous gaits with regard to their maximum achievable velocity and stability. Other aspects such as implementation in real machines, power requirements, and control under terrain difficulties are mentioned briefly. An elemental discontinuous gait is stated, and some variations on deriving crab and turning gaits are performed. Different methods for enlarging the achievable crab angle and improving stability are discussed for discontinuous crab gaits. A similar study is also done for turning gaits. (c) 1995 John Wiley & Sons, Inc.

Terrain-adaptive gait for walking machines

One of the primary advantages of walking machines is their inherent capacity for moving over different terrains. However, it is important to provide algorithms that modify the gait ac cording to the terrain. Existing articles about terrain-adaptive locomotion are based on intelligent foothold selection, and use periodic and/or aperiodic gaits. This article proposes a strategy to adapt walking robot locomotion to an irregular terrain in real time that is based on the variations of parameters of a periodic gait affecting leg coordination. Its main feature is that it does not require knowledge of footholds. In addition, this adaptive gait control can be incorporated into a system with external stereoceptive sensors to select footholds. As a working example, a particular class of periodic gaits, called wave-crab gaits, are used in a quadruped robot. However, the proposed adaptive-gait method can be used for any other periodic gait and for robots with a greater number of legs. Adaptive-gait control has been implemented in a quadruped robot named RIMHO, demonstrating its ability to move over different ter rains. Static stability results from computer simulations and experimentally obtained velocity results are also presented.

ACYLATED FLAVONOL SOPHOROTRIOSIDES FROM PEA SHOOTS

Seven flavonols were isolated and identified from Pisum sativum (cv Solara) shoots. The 3-glucoside, and 3-sophorotrioside [beta-D-glucopyranosyl(1-->2)-beta-D- glucopyranosyl(1-->2)-beta-D-glucopyranoside] of quercetin, the 3-sophorotrioside of kaempferol, and the acylated derivatives of quercetin 3-sophorotrioside with p-coumaric, caffeic, ferulic and sinapic acids on the hydroxyl at the 6-position of the terminal sugar. The caffeic and sinapic acid esters are two new naturally occurring compounds. This is the first report in which the structures of the p-coumaryl- and ferulyl-sophorotriosides of quercetin, which were previously reported from pea leaves, have been completely established by means of 1H NMR studies including COSY, NOESY and TOCSY experiments.

A bacterial antirepressor with SH3 domain topology mimics operator DNA in sequestering the repressor DNA recognition helix

Direct targeting of critical DNA-binding elements of a repressor by its cognate antirepressor is an effective means to sequester the repressor and remove a transcription initiation block. Structural descriptions for this, though often proposed for bacterial and phage repressor–antirepressor systems, are unavailable. Here, we describe the structural and functional basis of how the Myxococcus xanthus CarS antirepressor recognizes and neutralizes its cognate repressors to turn on a photo-inducible promoter. CarA and CarH repress the carB operon in the dark. CarS, produced in the light, physically interacts with the MerR-type winged-helix DNA-binding domain of these repressors leading to activation of carB. The NMR structure of CarS1, a functional CarS variant, reveals a five-stranded, antiparallel β-sheet fold resembling SH3 domains, protein–protein interaction modules prevalent in eukaryotes but rare in prokaryotes. NMR studies and analysis of site-directed mutants in vivo and in vitro unveil a solvent-exposed hydrophobic pocket lined by acidic residues in CarS, where the CarA DNA recognition helix docks with high affinity in an atypical ligand-recognition mode for SH3 domains. Our findings uncover an unprecedented use of the SH3 domain-like fold for protein–protein recognition whereby an antirepressor mimics operator DNA in sequestering the repressor DNA recognition helix to activate transcription.