Mechanical probing

The nanoscale world is exciting because it is governed by rules differing from those in the macroscopic, or even microscopic, realm. It is a world where quantum mechanics dominates the scene, and events on the single-molecule scale are critical. What we know about the behavior of material on our scale is no longer true on the nanometer scale, and our formularies must be re-written. In order to study this quantum world, a quantum-mechanical probe is essential. Electron tunneling provides that quantum-mechanical tool. 

In a sense, the mechanical probing of DNA molecules is a form of nanofabrication, albeit organised vertically and often reversibly. In a more invasive... 

Atomic force microscopy AFM Similar to STM. An extremely delicate mechanical probe is used to scan the topography of a surface by measuring forces exerted by surface atoms. Light interference is used to measure the deflection of the mechanical surface probe. This is designed to provide STM-type images of insulating surfaces or to detect mechanical properties at the molecular level. Atomic structure... 

Molecular probes, such as optical or magnetic tweezers,64-71 micropipets,72 and microfibers,73-74 have been developed to manipulate single molecules and to measure their response to mechanical actions such as stretching, torsion, and compression. A force resolution down to 0.1 pN enabled quantitative measurement of the molecular forces and provided novel information on the basic principles of folding, motion, and interactions of individual molecules. Complementary to the local mechanical probes, actions of external fields were monitored on individual polymer molecules.75 77... 

Mixed Mechanism Probes. Several probe systems appear to function by both hydrolysis and hybridization mechanisms. These include hairpin probes, self-probing amplicon primers, and displacement probes. A hairpin probe functions similarly to a hairpin primer in that it is designed to increase in fluorescence when the distance between the quencher and the reporter increases upon target hybridization (see Figure 37-24, row five). Similarly, primers that... 

A tip-based piso-scanning instrument able to image surfaces to molecular accuracy by mechanically probing their surface contours. It can be used for analyzing the material surface all the way down to the atoms and molecules level. A combination of mechanical and electronic probe is used in AFM to magnify surfaces up to 100,000,000 times to produce 3-D images of them. 

J. Zhou, B. Berry, J.F. Douglas, A. Karim, C. Snyder, and C. Soles, Nanoscale thermal-mechanical probe determination of softening transitions in thin polymer films, Nanotechnol, 19, 495703 95703 (2008). 

An important caveat to remember is that currently accepted core mechanisms for the catalytic cycles discussed will be used. A common rule of thumb is that one cannot prove that a proposed mechanism is correct. All the catalytic reactions discussed here have been extensively studied and the mechanisms shown fit the known data, but remain as proposed mechanisms. Probing the detailed mechanism of a catalytic cycle can be exceedingly difficult. Many of the fundamental reactions shown to construct the catalytic cycles are assumed to be occurring based on more than 50 years of organometallic research and many stoichiometric examples. 

Chen YJ, Ku WC et al (2008) Nitric oxide physiological responses and delivery mechanisms probed by water-soluble Roussin s red ester and Fe(NO)2) DNIC. J Am Chem Soc 130 10929-10938... 

The traceability and uncertainty of the coordinates as measured (see section Definitions ) must be taken into account, as well of uncertainties in the used probe size, filtering, sampling, reference line or surface, etc. For 3-D measurements it is a problem that the default measurement system is a mechanical probing system. As 3-D mechanical roughness measurements are very time-consuming, most measurements are taken using optical techniques that may have artifacts that are not easily recognized. 

Yet the observation and measurement of cell adhesion are difficult because the cells have small diameters, between 1-10 pm, and the adhesion force is generally low, typically 0.1-100 nN. Usually, cell adhesion must be studied in a microscope. Attachment of cells may then be observed in relation to the chemical environment, and the cells may be pulled apart and sensed by various techniques including direct mechanical probing, shearing with a flow, or cytometry (cell counting) to determine the adhesion quantitatively. 

These methods use mechanical probes or hygrometers that respond to the variations in the relative humidity of air that are caused by variations in dielectric resistance or capacity. These probes directly measure the relative humidity of air, and the most commonly used is lithium chloride. In general, these methods require frequent calibration and should only be used within a narrow range. 

Because of the above dependence on frequency, sound waves represent a mechanical probe for particular wave motions, namely, motion that can occur in the period of the sound wave. Viewed as one technique for making mechanical measurements on polymers, sound wave measurements using ultrasonic or Brillouin scattering probe motions of the polymer on short length scales while methods such as audio or low frequency DMA measurements probe large-scale motions. 

Viscometers n. Instruments for measuring viscosity including mechanical probe and torque types as the Brookfield viscometer, capillary tube types as the Cannon-Fenske or Ostwald-Fenske, and flow through orifice types as the Ford cup. 

Electrocontact probes. The electrocontact, or mechanical, probes are of a more complex design and are mainly used for the determination of low detonation velocities. Closure or breakage of the electrical circuit by means of these probes is accomplished mechanically due to a detonation wave pressure action. 

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