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Precise Positioning (precise + positioning)

Distribution by Scientific Domains

Engineering	37%
Chemistry	37%

Selected Abstracts

2,- N -(Pyren-1-yl)acetyl-2,-Amino-,-L-LNA: Synthesis and Detection of Single Nucleotide Mismatches in DNA and RNA Targets

CHEMBIOCHEM, Issue 10 2007
T. Santhosh Kumar
Precise positioning of intercalators furnishes a SNP-detection tool. The conformationally locked 2-oxo-5-azabicyclo-[2.2.1]heptane skeleton of 2,-amino-,-L-LNA monomer X directs the N2,-linked pyrene moiety into nucleic acid duplex cores to give highly stabilized duplexes. We have used this precise positioning of pyrene moieties to develop probes that signal the presence of single-nucleotide mismatches in DNA/RNA targets by excimer signal formation. [source]

A New Multilevel Ground Water Monitoring System Using Multichannel Tubing

GROUND WATER MONITORING & REMEDIATION, Issue 4 2002
Murray D. Einarson
A new multilevel ground water monitoring system has been developed that uses custom-extruded flexible 1.6-inch (4.1 cm) outside-diameter (O.D.) multichannel HOPE tubing (referred to as Continuous Multichannel Tubing or CMT) to monitor as many as seven discrete zones within a single borehole in either unconsolidated sediments or bedrock. Prior to inserting the tubing in the borehole, ports are created that allow ground water to enter six outer pie-shaped channels (nominal diameter = 0.5 inch [1.3 cm]) and a central hexagonal center channel (nominal diameter = 0.4 inch [1 cm]) at different depths, facilitating the measurement of depth-discrete piezometric heads and the collection of depth-discrete ground water samples. Sand packs and annular seals between the various monitored zones can be installed using conventional tremie methods. Alternatively, bentonite packers and prepacked sand packs have been developed that are attached to the tubing at the ground surface, facilitating precise positioning of annular seals and sand packs. Inflatable rubber packers for permanent or temporary installations in bedrock aquifers are currently undergoing site trials. Hydraulic heads are measured with conventional water-level meters or electronic pressure transducers to generate vertical profiles of hydraulic head. Ground water samples are collected using peristaltic pumps, small-diameter bailers, inertial lift pumps, or small-diameter canister samplers. For monitoring hydrophobic organic compounds, the CMT tubing is susceptible to both positive and negative biases caused by sorption, desorption, and diffusion. These biases can be minimized by: (1) purging the channels prior to sampling, (2) collecting samples from separate 0.25-inch (0.64 cm) O.D. Teflon sampling tubing inserted to the bottom of each sampling channel, or (3) collecting the samples downhole using sampling devices positioned next to the intake ports. More than 1000 CMT multilevel wells have been installed in North America and Europe to depths up to 260 feet (79 m) below ground surface. These wells have been installed in boreholes created in unconsolidated sediments and bedrock using a wide range of drilling equipment, including sonic, air rotary, diamond-bit coring, hollow-stem auger, and direct push. This paper presents a discussion of three field trials of the system, demonstrating its versatility and illustrating the type of depth-discrete data that can be collected with the system. [source]

Navy Omni-Directional Vehicle (ODV) Development: Where the Rubber Meets the Deck

NAVAL ENGINEERS JOURNAL, Issue 4 2000
H. McGowen
ABSTRACT The Office of Naval Research sponsored the omnidirectional vehicle (ODV) development program of the Coastal Systems Station (CSS). CSS has investigated the application of ODV technology to Navy shipboard materials and ordnance handling. Under the Navy program, ODV technology was developed and a series of vehicles were built and tested. ODT technology was demonstrated to be applicable to the shipboard environment and shown to be able to overcome conditions of confined spaces, reduced traction, ship motion, decks heeled at high angles, and on-deck obstacles. This paper focuses on the Navy's demonstration of the capability of the ODV to operate under demanding environmental conditions, ODV mechanical simplicity, and adaptability of the technology for a wide range of applications. Potential commercial applications were identified in manufacturing and warehousing, and remotely controlled or autonomous platforms employed in nuclear facilities, hazardous waste cleanup, and other operations that require the movement and precise positioning of large, heavy objects. The Navy has implemented two cooperative research and development agreements (CRADA) and others are pending for further development and transfer of ODV technology to the private sector. [source]

Examples for the integration of self-organized nanowires for functional devices by a fracture approach

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2010
Dawit Gedamu
Abstract Simple and versatile methods to form nanowires on microchips are of interest for fundamental research and hold the potentials for an industrial fabrication. In this review article, one of these methods based on thin film fracture will be described introducing the experimental parameters and the potential for research. The advantages of the utilization of thin film cracks as a template for the nanowire formation are numerous: nanowire generation ready with contacts, a wide ranging freedom in the choice of materials, influence on the internal structure of the nanowire or the precise positioning on a microchip. A detailed discussion about the fabrication steps and some preliminary experiments revealing the possibilities of the fracture approach will be given for obtained metallic, semiconducting and anodized nanowires. In contrast to their macroscopic counterparts, the conductivity through the nanowires is entirely different. The influence of the surrounding gas atmospheres and the application of electrical fields demonstrate the applicability of these nanowires fabricated by using such a fracture approach. Perspective scanning electron microscopy micrograph of Au nanowires fabricated by thin film fracture approach between Au contact lines. The wires form a zigzag pattern on the thermally oxidized layer substrate on a silicon chip. [source]

The case for MR-compatible robotics: a review of the state of the art

THE INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY, Issue 2 2008
Haytham Elhawary
Abstract Background The numerous imaging capabilities of magnetic resonance imaging (MRI) coupled with its lack of ionizing radiation has made it a desirable modality for real-time guidance of interventional procedures. The combination of these abilities with the advantages granted by robotic systems to perform accurate and precise positioning of tools has driven the recent development of MR-compatible interventional and assistive devices. Methods The challenges in this field are presented, including the selection of suitable materials, actuators and sensors in the intense magnetic fields of the MR environment. Results Only a small number of developed systems have made it to the clinical level (only two have become commercial ventures), showing that the field has not yet reached maturity. Conclusions A brief overview of the current state of the art is given, along with a description of the main opportunities, possibilities and challenges that the future will bring to this exciting and promising field. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Tracking control of a piezo-actuated stage based on a frictional model,

ASIAN JOURNAL OF CONTROL, Issue 3 2009
Yi-Cheng Huang
Abstract The tracking control accuracy of a piezoelectric actuator (PEA) is limited due to the actuator's inherent hysteretic nonlinearity. Direct drive of PEA on a positioning stage with friction force will cause control problems. An approximated dynamic model of PEA with consideration of friction force is novel synthesized for control. This model is based on a second-order transfer function with two parameterization terms. The first time delay term consists of the hysteresis of piezo effect combined with frictional force lag with varying velocity. The second term is comprised of both presliding and sliding regimes. The H-infinite tracking controller is designed to compensate for the structural uncertainty associated with time delay and the unstructured frictional force in the PEA stage. Iterative Learning Control is implemented to reduce the unmodeled repetitive error by a factor of 20. Numerical simulations and experimental tests consolidate the root mean square (RMS), positioning error close to the hardware reproducibility and accuracy level. Experimental results show the controlled stage can be potentially used for precise positioning. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]

Ribosomal crystallography: Peptide bond formation and its inhibition

BIOPOLYMERS, Issue 1 2003
Anat Bashan
Abstract Ribosomes, the universal cellular organelles catalyzing the translation of genetic code into proteins, are protein/RNA assemblies, of a molecular weight 2.5 mega Daltons or higher. They are built of two subunits that associate for performing protein biosynthesis. The large subunit creates the peptide bond and provides the path for emerging proteins. The small has key roles in initiating the process and controlling its fidelity. Crystallographic studies on complexes of the small and the large eubacterial ribosomal subunits with substrate analogs, antibiotics, and inhibitors confirmed that the ribosomal RNA governs most of its activities, and indicated that the main catalytic contribution of the ribosome is the precise positioning and alignment of its substrates, the tRNA molecules. A symmetry-related region of a significant size, containing about two hundred nucleotides, was revealed in all known structures of the large ribosomal subunit, despite the asymmetric nature of the ribosome. The symmetry rotation axis, identified in the middle of the peptide-bond formation site, coincides with the bond connecting the tRNA double-helical features with its single-stranded 3, end, which is the moiety carrying the amino acids. This thus implies sovereign movements of tRNA features and suggests that tRNA translocation involves a rotatory motion within the ribosomal active site. This motion is guided and anchored by ribosomal nucleotides belonging to the active site walls, and results in geometry suitable for peptide-bond formation with no significant rearrangements. The sole geometrical requirement for this proposed mechanism is that the initial P-site tRNA adopts the flipped orientation. The rotatory motion is the major component of unified machinery for peptide-bond formation, translocation, and nascent protein progression, since its spiral nature ensures the entrance of the nascent peptide into the ribosomal exit tunnel. This tunnel, assumed to be a passive path for the growing chains, was found to be involved dynamically in gating and discrimination. © 2003 Wiley Periodicals, Inc. Biopolymers, 2003 [source]