Piezoelectric micromotors for microrobots

The authors have begun research into piezoelectric ultrasonic motors using ferroelectric thin films. The authors have fabricated the stator components of these millimeter diameter motors on silicon wafers. Ultrasonic motors consist of two pieces: a stator and a rotor. The stator includes a piezoelectric film in which bending is induced in the form of a traveling wave. A small glass lens placed upon the stator becomes the spinning rotor. Piezoelectric micromotors overcome the problems currently associated with electrostatic micromotors such as low torque, friction, and the need for high voltage excitation. More importantly, they may offer a much simpler mechanism for coupling power out. Using thin films of lead zirconate titanate on silicon nitride membranes, various types of actuator structures can be fabricated. By combined new robot control systems with piezoelectric motors and micromechanics, the authors propose creating micromechanical systems that are small, cheap and completely autonomous     

Covalent structure of botulinum neurotoxin type E: location of sulfhydryl groups, and disulfide bridges and identification of C-termini of light and heavy chains

Botulinum neurotoxin (NT) serotype E is synthesized by Clostridium botulinum as an approximately 150-kDa single-chain polypeptide of 1252 amino acid residues of which 8 are Cys residues [Puolet et al. (1992); Biochem. Biophys. Res. Commun. 183, 107-113]. The posttranslational processing of the gene product removes only the initiating methionine. A very narrow segment of this 1251-residue-long mature protein--at one-third the distance from the N-terminus (between residues Lys 418 and Arg 421)--is highly sensitive to proteases, such as trypsin. The single-chain NT easily undergoes an exogenous posttranslational modification by trypsin; residues 419-421 (Gly-Ile-Arg) are excised. The proteolytically processed NT is a dichain protein in which Pro 1-Lys 418 constitute the approximately 50-kDa light chain, Lys 422-Lys 1251 constitute the approximately 100-kDa heavy chain; Cys 411-Cys 425 and Cys 1196-Cys 1237 form the interchain and intrachain disulfide bonds, respectively; the other four Cys residues at positions 25, 346, 941, and 1035 remain as free sulfhydryl groups. The approximately 150-kDa dichain NT, and separated light and heavy chains, were fragmented with CNBr and endoproteases (pepsin and clostripain); some of these fragments were carboxymethylated with iodoacetamide (with or without 14C label) before and after fragmentation. The fragments were separated and analyzed for amino acid compositions and sequences by Edman degradation to determine the complete covalent structure of the dichain type E NT. A total of 208 amino acid residues, i.e., 16.5% of the entire protein's sequence deduced from nucleotide sequence, was identified. Direct chemical identification of these amino acids was in complete agreement with that deduced from nucleotide sequence.     

Immunohistochemical identification of the receptor for urokinase plasminogen activator associated with fibrin deposition in normal and ectopic human placenta

The receptor for urokinase plasminogen activator (uPAR) is a key molecule in cell surface-directed plasminogen activation. uPAR binds urokinase plasminogen activator (uPA) and thereby focuses plasminogen activation on the cell surface. Plasmin dissolves fibrin deposits and facilitates cell migration during tissue repair processes by degrading the extracellular matrix. During human implantation and placental development, plasmin is considered important for both trophoblast migration/invasion and for fibrin surveillance. This study examined the expression of uPAR in normal and ectopic human placentae by immunohistochemistry. In first and third trimester normal placentae as well as in tubal ectopic placental tissues, a high uPAR expression was seen in the trophoblast associated with deposits of fibrin-type fibrinoid. Extravillous trophoblast of the basal plate, of the cell islands, and of the cell columns was also positive for uPAR in the first trimester whereas at term the expression of the protein was decreased. Moreover, uPAR immunostaining was observed in decidual cells throughout normal gestation and in endometrial tissues of patients with ectopic pregnancies. These findings suggest that uPAR participates in placental development and in trophoblast invasion particularly in the first trimester of pregnancy and that uPAR is involved in repair mechanisms of the trophoblast and fibrin surveillance.     

Cost-efficient high-radix division

Digital signal processing implementations require fast and efficient arithmetic units. This paper proposes a fast, cost-efficient enhancement to high-radix, recursive dividers. Recursive dividers are commonly implemented using a subtractor and/or a multiplier, and hardware to determine an estimate of the quotient. Traditionally, these dividers have required an off-chip ROM or a large programmable logic array (PLA) to store a truncated quotient estimate. An interesting alternative is to simplify the hardware realization with a less accurate estimate of the quotient. This paper introduces an algorithm of this type called the expanded redundancy method which is based on Renato Stefanelli's algorithm and a further enhancement by David Mandelbaum.This study compares implementations of byte-quotient estimators (radix-256) using a ROM look-up table, a direct combinational switching network, and the proposed expanded redundancy method. The estimators will be compared by area (in terms of gate count), by gate levels of delay, and by accuracy (in terms of number of iterations to converge). Three recursive algorithms are used for this comparison: 1) nonrestoring method, 2) constant convergence method, and 3) quadratic convergence method. This study will show that the proposed implementation of a byte-quotient estimator is comparable in gate delay and accuracy and can easily be integrated on-chip with other division hardware.     

Single-bone fixation of both-bone forearm fractures

Seventeen children with diaphyseal both-bone forearm fractures, for which closed reduction had failed, were treated with fixation of either the radius or ulna. Sixteen were followed up to their clinical end point. Results in all children were excellent; all had a full return of motion except two who lacked 5 degrees of pronation. This retrospective series is the first reported to date looking exclusively at diaphyseal both-bone forearm fractures in children treated with fixation of a single bone. The rationale of treatment is to stabilize one bone while the other is rotated into reduction. Repeated anesthetics are avoided, and malreduction is prevented without adult-style both-bone plating. We prefer intramedullary fixation as hardware is easier and safer to place and remove.