Time, standard

Cesium metal is used for time standards based on the natural vibration of the Cs atom, which oscillates 9,192,631,770 times per second, and in high precision oscillators to synchronize fiber optic telecommunication. 

Sponsor/Developing Organization LLNL. Developer. Laurence E. Fried LLNL, P.O. Box 808 Livermore, CA 94551, E-mail cheetah llnl.gov. Hardware-. IBM-PC or clone, Windows 3.1, Windows 95, Mac OS 7.x or later, SUN and SGI workstations, 4.3 MB of hard disk. Software ANSI C. Run execution time for typical problem (CPU or real time). Standard run About 30 seconds on a Power Macintosh 6100/80. Cost None from LLNL. Source code is available, with the stipulations that all modifications be preapproved and forwarded to the sponsor for tracking... 

Decay Time. Many organic and Inorganic materials In various solvents have been suggested as decay-time standards. Selected standards listed In Table V cover the decay-time range from nanoseconds to... 

All of the initial CGC organobromine degradation products assignments were based on the use of relative retention time standards. The relative retention times for the partially brominated degradation products were established either by the synthesis of the expected degradation products or by the use of selective debromination reactions. 

For the decabromodiphenyl oxide (DBDPO) pyrolysis reactions, two different procedures were used to synthesize the series of brominated diphenyl oxides and dibenozofurans employed as the relative retention time standards AlBr3/Br2 in ethylene dibromide and Fe° (metal)/Br2 in tetrachloroethylene. The rate of the initial bromination steps in the former reaction was so rapid that only the higher degree of bromination adducts could be isolated. The rate of the Fe°/Br2 reaction was found to be much slower, especially during the initial stages, and these reactions yielded a broader range of relative retention time reference peaks. 

An analogous series of dibenzodioxin relative retention time standards were prepared from dibenzodioxin (DBD) using Fe°/Br2 and the same procedure used to brominate the ether and the furan. The DBD itself was prepared by refluxing ortho-chlorophenol with NaOH. 

Obtained from CGC and CGC/MS Analysis of the Relative Retention Time Standards... 

Time of flight (TOF), 75 660-661 Time-of-flight (ToF) mass analyzers, 24 109 Time of flight diffraction (TOFD), 79 486 Time-of-flight instrumentation, in particle counting, 78 150—151 Time-of-flight-SIMS technique, 24 109 Time-resolved fluorimetry, 74 148-149 Time-resolved spectra, analysis of, 74 613 Time standards, 75 749—750 Time-temperature parameters (TTP), 73 471, 478, 479 creep properties and, 73 480 Time-temperature superposition, 27 746-747... 

The separation efficiency in chromatography and the sample throughput in CFA and FIA are better the narrower the test substances zones. The experimental conditions must therefore be selected so that the zone broadening in the detection system is as low as possible. The zone width is conveniently expressed in terms of the time standard deviation, o, or the volume standard deviation, oy, which are related by the expression,... 

The long time standard, now discontinued, Mattach-Herzog instrument was the CEO (Dupont) 21-110, while JEOL, Varian MAT and AEI still build instruments of this geometry. 

The effect of the detector time constant on the apparent efficiency depends only on the time width of the bands. It has been shown by Sch-mauch 41) and by Me William and Bolton 42) that the profile recorded with a detector having a time constant r is wider than the actual profile by a factor (1 -f r/ert), where is the time standard deviation of the profile, provided this factor is less than about 1.2. Moreover, the peak heigh becomes smaller although the peak area remains unchanged. 1 he (list mu ment (retention time) of a peak increases by r and the retention time of the... 

POLLUTANT PRIMARY STANDARDS. .. -n. SECONDARY AVERAGING TIMES STANDARDS... 

Figure 3. Sample matrix effect on reproducibility of internal standard retention times , standards in sample A, standards alone. (Reproduced with permission from reference 26. Copyright 1985 Lewis Publishers.)...

Table I. Retention Time Standard Deviations of Internal Alkane Standards of Composite XAD Resin Water Samples With and Without Cleanup...

In 1972 a 100-fold increase in the accuracy of the known speed of light was achieved by measuring the frequency of a helium-neon laser line in terms of the Cs time standard (Appendix Table A.2) and measuring its wavelength in terms of the Kr length standard. [K. M. Evenson et al., Phys. Rev. Letters, 29, 1346 (1972).] The improved value is... 

Substance Relative Mean Retention Time Standard Deviation Number of Tests... 

Work processes take many forms, from the simplest of structure techniques to the most complex multifunctional processes. They are important, and the more complex the innovation task is, the more important they are. Work processes capture the best practices over time, standardize those practices for everyone on the team, and provide a common language for everyone to use. Additionally, they are key to defining success on multiple levels. 

Equilibration time Standard methods typically specify a minimum of 24 hours for cells and 72-hours for chambers. In practice, equilibration times can be as low as 15-20 minutes for cells. 

Traceability of measurement results of the effective acquisition time was achieved by implementing the calibration of clocks with the DCF 77 radio signal controlled by the German time standard. By verifying the measurement results the traceability of the calibration is extended to the range of counting conditions where the deviations between the expected and measured count rates are covered by the introduction of a 1% uncertainty. 

There are a variety of techniques available to aid in the identification of sample components matching retention times, standard addition, internal standard, isotopic labeling, enzyme peak shift, and UV and mass spectral libraries. 

It seems likely that the genetic structure of a population will be altered by different selective pressures encountered as a population colonizes a new habitat. Therefore, the processes responsible for genetic structure need to be reviewed within the context of colonization. By any evolutionary time standard colonization is short term and mutation rates... 

A natural direction to improve the resolution of R measurements beyond the present level is to attempt the experiments at longer wavelengths, In a domain where the frequency of the radiation can be linked directly to the atomic time standard. A possible way is to measure R on microwave transitions involving what is called circular Rydberg atoms [4,73. 

One way of varying the the Grashof number in experimental studies involving air is to keep the model size fixed and to vary the air pressure. Consider a situation in which the model height is 5 cm. the model surface is at a temperature of 60°C, and the air at a temperature of 20°C. Plot the variation of Grashof number with air pressure for air pressures between 0.1 and 10 times standard atmospheric pressure. 

Semi-solid foods, such as soft butter and some cheeses, cannot be formed into samples capable of supporting their own weight. For such foods, compression testing takes the form of cone or die penetrometry, in which a cone, die, needle or sphere is made to penetrate the sample (held in a suitable container) either under constant load or at constant speed, and the penetration depth measured as a function of time. Standard methods for penetrometry of fats are published by the AOCS (AOCS Official Method Cc 16-60, Firestone, 1998) and the British Standards Institution (BS 684 Section 1.11 1976, BSI, 1976c). 

The third element originates from quantum physics relating an electromagnetic frequency v to an energy difference between energy eigenstates, quantum base states (N. Bohr relation) see discussion section and Section 4.2. These elements allow for the introduction of length and time standards. 

Being one of the long-time standards in basic psychopharmacology, there are few major variants to the procedure apart from the kind of barbiturate employed. Several barbiturates undergo clear hepatic metabolism, for example pentobarbital and phenobarbital, thereby confounding interpretations because of pharmacokinetic and metabolic factors. Indeed, one modification of the method has been specifically employed to estimate enzyme induction in the liver as indicated by more rapid barbiturate metabolism. Animals given a pre-exposure to a test substance are then exposed to a standard dose of phenobarbital (80 mg/kg i.p.) 24 hours later and assessed for sleep duration. The presence or absence of a decrease in sleep duration is taken as an index of the hepatic enzyme induction produced by the test substance (Kushikata et al. 2003). 

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