Instrument precision

More informative and precision instruments are devices based on the dynamic methods of indentation. The impedance of a vibrating probe perturbing the medium is related to the... 

A. A. Miehelson (Chicago) optical precision instruments and the spectroscopic and metrological investigations carried out with their aid. 

For smart cards, micro-robots and small precision instruments, thin laminated micro-cells are being developed. Some of these developmental thin-film devices—using an electrolyte of lithium, a copper cathode, and lithium again for the electrode—can charge and discharge up to 3 volts, and can be expected to tolerate up to 1,000 charge-and-discharge cycles. 

As a major branch of nanotribology. Thin Film Lubrication (TFL) has drawn great concerns. The lubricant him of TFL, which exists in ultra precision instruments or machines, usually ranges from a few to tens of nanometres thick under the condition of point or line contacts with heavy load, high temperature, low speed, and low viscosity lubricant. One of the problems of TFL study is to measure the him thickness quickly and accurately. The optical method for measuring the lubricant him thickness has been widely used for many years. Goher and Cameron [3] successfully used the technique of interferometry to measure elastohydrody-namic lubrication him in the range from 100 nm to 1 /rm in 1967. Now the optical interference method and Frustrated Total Reflection (FTR) technique can measure the him thickness of nm order. 

The reaction is an industrial process the micro reactor was taken as a precise instrument giving analytical information which was transferred to the large-scale process in a non-disclosed way. 

Principles and Characteristics High-performance thin-layer chromatography (HPTLC), also known as planar chromatography, is an analytical technique with separation power and reproducibility superior to conventional TLC, which was first used in 1938 [7] and modified in 1958 [8]. HPTLC is based on the use of precoated TLC plates with small particle sizes (3-5 xm) and precise instruments for each step of the chromatographic process. 

Cell cultures. MDCK cells were seeded in the Transwells at a density of 2.2 x 104 cells/cm. Cells were fed by changing medium in both upper (apical) and lower (basal) compartments periodically. Confluent monolayers were obtained at 5-7 days post-inoculation, when the cell density reached 4.5-5.0 x 105 cells/cm2, and a transepithelial electrical resistance (TEER) of about 2,000 ohms cm2 was measured using an epithelial voltohmmeter (EVOM, World Precision Instruments, West Haven, CT). The amount of FBS in the cell culture medium could be decreased as the cells approached their maximum resistance, and could be maintained at that point for 2 days or longer in medium containing 1% FBS. 

The particular colors that are observed at different angles will depend critically on the thickness of the thin film coating. Precision instrumentation is required to carefully control film thickness during production. The magnitude of the optical effect depends on the density of flakes in the ink, while the quality of the optical effect depends on the precise orientation or alignment of these flakes with respect to the paper surface. 

World Precision Instruments, Inc., Sarasota, Florida, USA Huangxian Ju... 

Xueji Zhang, Department of Chemistry, World Precision Instruments Inc., 175 Sarasota Center Boulevard Sarasota, FL 34240-9258, USA... 

You ll notice I ve refrained from calling these precision instruments machines. That s because they are precision instruments, not machines — unless they don t work. 

Information on particle size may be obtained from the sedimentation of particles in dilute suspensions. The use of pipette techniques can be rather tedious and care is required to ensure that measurements are sufficiently precise. Instruments such as X-ray or photo-sedimentometers serve to automate this method in a non-intrusive manner. The attenuation of a narrow collimated beam of radiation passing horizontally through a sample of suspension is related to the mass of solid material in the path of the beam. This attenuation can be monitored at a fixed height in the suspension, or can be monitored as the beam is raised at a known rate. This latter procedure serves to reduce the time required to obtain sufficient data from which the particle size distribution may be calculated. This technique is limited to the analysis of particles whose settling behaviour follows Stokes law, as discussed in Section 3.3.4, and to conditions where any diffusive motion of particles is negligible. 

Units which are used in isotopic work depend on the precision of the measurements. Generally 5 units are used for stable isotopes and correspond to permil relative deviation. It is used occasionally also for non linear effects and then they are permil (%o) deviations without reference to mass differences between the isotopes. Since the beginning of the 70s (e.g., Papanastassiou and Wasserburg 1969) thermal ionization data are often given in e units which are fractional deviation from the normal in 0.01%. With the new generation of more precise instruments, results are sometimes given in ppm (parts per million) relative to a terrestrial standard sample. 

Borosilicate glass capillaries for patch pipettes (World Precision Instruments, Sarasota, EL). 

Some orifice viscometers, such as the Shell dip cup and the European ISO cup, which resembles a Ford cup with a capillary, have long capillaries. These cups need smaller kinetic eneigy corrections and give better precision than the corresponding short-capillary viscometers. However, they are still not precision instruments, and should be used only for control purposes. 

Chemical techniques of analysis deal with a very large number of atoms and yield averages over the sample. Once the concept of isotopes was accepted, a search for different isotopes of every element was pursued. The key to the success of this search was the development of a precision instrument that sampled the atoms one at a time. It had been known since the development of the cathode ray tube that positive ions were also produced, and early experiments with these particles revealed singly and doubly charged species of the atoms and molectrles that were contained in the tube. Sir J.J. Thomson observed in 1912 that when neon was the background gas, particles of mass ntrmber 20 and 22 were observed. Attempts to obtain pure samples of the two different atoms by fractionation techniques were unsuccessful, but in retrospect this was because they were both neon isotopes. 

A more delicate and precise instrument is the Searle s Extensometer, described in Ref 2, p 68 (Compare with Compressibility of Explosives and of Propellants in Vol 3 of Encycl, p C491)... 

Xanthamonas campestris strain engineered to bioluminesce (Shaw et al., 1992). The strain was applied to cabbage plants and surrounding soils in a limited field study conducted in 1990. The fate of the organisms was monitored by both CCD-microscopy and plate counts, Recombinant cells were found for up to six weeks, with the CCD and plate counts giving quantitatively similar results. Bioluminescence in this case was no more sensitive than plate counts, and required a precision instrument,... 

Elinvar, 34% Ni, 57% Fe, 4% Cr, 2% W, has a very low temperature coefficient of elasticity which makes it useful for springs in watches and precision instruments. 

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