Hertz, definition

The simplest definition of sensitivity is the signal-to-noise ratio. One criterion for judging the sensitivity of an NMR spectrometer or an NMR experiment is to measure the height of a peak under standard conditions and to compare it with the noise level in the same spectrum. Resolution is the extent to which the line shape deviates from an ideal Lorentzian line. Resolution is generally determined by measuring the width of a signal at half-height, in hertz. 

Digital resolution The distance, in hertz, between successive data points determines the extent of peak definition by the data points. 

Cohen A, Hertz HS, Mandel J, Paule RC, Schaffer R, Sniegoski LT, Sun T, Welch MJ, and White E V (1980) Total serum cholesterol by isotope dilution mass spectrometry A candidate definitive method. Chn Chem 26 854-860. 

Welch MJ, Cohen A, Hertz HS, Ruegg FC, Schaefer R, Sniegoski LX and White VE (1984) Determination of serum urea by isotope dilution/mass spectrometry as a candidate definitive method. Anal Chem 56 713-719. 

Franck and Hertz (1913) first demonstrated that an electron has to acquire a minimum energy before it can ionize. Thus, they provided an operational definition of the ionization potential and showed that it is an atomic or molecular property quite free from experimental artifacts. However, this kind of experiment does not tell anything about the nature of the positive ion for this, one needs a mass spectrometric analysis. Although Thompson had demonstrated the existence of H+, H2+, and H3+ in hydrogen discharge, it seems that Dempster (1916) was the first to make a systematic study of the positive ions. 

More radically, it can be argued that chemists recognized before most physicists the conventional character of the basic definitions and premises of scientific explanation systems, an argument usually identified in physics with Heinrich Hertz, Henri Poincare, and Edouard LeRoy at the end of the nineteenth century. And finally, chemists recognized early on that multiple explanations are superior to a simple but wrong explanation. In short, chemistry had a principle of complementarity long before physics did. 

Rotational speeds may be expressed either in terms of rpm or in terms of hertz. The power law exponent, n, has a definite physical significance. The value of n and the corresponding significance are determined either empirically or through theoretical means. Table 1 lists the most common values assigned to n. 

E. Winkler, F. Grashof, H. Hertz,8 etc., have studied the stresses which are set up when two elastic isotropic bodies are in contact over a portion of their surface, when the surfaces of contact are perfectly smooth, and when the press, exerted between the surfaces is normal to the plane of contact. H. Hertz showed that there is a definite point in such a surface representing the hardness defined as the strength of a body relative to the kind of deformation which corresponds to contact with a circular surface of press. and that the hardness of a body may be measured by the normal press, per unit area which must act at the centre of a circular surface of press, in order that in some point of the body the stress may first reach the limit consistent with perfect elasticity. If H be the hardness of a body in contact with another body of a greater hardness than H, then for a circular surface of pressure of diameter d press. p radius of curvature of the line p and the modulus of penetration E,... 

To add to the confusion, some workers take 6, as the negative of the definition (8.35). Some workers use factors of 105 or 107 instead of 106. Some workers use 8, to mean the shift in hertz their 8, is equal to (8.35) multiplied by spectromcter- Pri°r t0 introduction (by Tiers in 1958) of TMS as the reference for proton shifts, a variety of reference compounds (such as benzene, cyclohexane, and water) were used. When examining reported shifts, the definitions used should be noted. 

The most important modem system of units is the SI system, which is based around seven primary units time (second, abbreviated s), length (meter, m), temperature (Kelvin, K), mass (kilogram, kg), amount of substance (mole, mol), current (Amperes, A) and luminous intensity (candela, cd). The candela is mainly important for characterizing radiation sources such as light bulbs. Physical artifacts such as the platinum-iridium bar mentioned above no longer define most of the primary units. Instead, most of the definitions rely on fundamental physical properties, which are more readily reproduced. For example, the second is defined in terms of the frequency of microwave radiation that causes atoms of the isotope cesium-133 to absorb energy. This frequency is defined to be 9,192,631,770 cycles per second (Hertz) —in other words, an instrument which counts 9,192,631,770 cycles of this wave will have measured exactly one second. Commercially available cesium clocks use this principle, and are accurate to a few parts in 1014. 

Before performing the FT, there are two things we can do to enhance the quality of the spectrum. First, the size of the data set can be artificially increased by adding zeroes to the end of the list of FID data. This process of zero filling has no effect on the peak positions, intensities, or linewidths of the spectrum, but it does increase the digital resolution (fewer hertz per data point) in the spectrum (Fig. 3.31). This can be useful to give better definition... 

EUerbe P, Myers GL, Cooper GR, Hertz HS, Sniegoski LT, Welch MJ, White Et. A comparison of results for cholesterol in human serum obtained by the Reference Method and by the Definitive Method of the National Reference System for cholesterol. Clin Chem 1990 36 370-5. 

The local representation of multipole photons is compatible with the Mandel operational definition of photon localization [20]. In addition to the localization at photodetection, it permits us to describe a complete Hertz-type experiment with two identical atoms used as the emitter and detector (Section VI.A). Although the photon path is undefined from the quantum-mechanical point of view, the measurement process in such a system obeys the causality principle (Section IV.B). The two-atom Hertz experiment can be realized for the trapped... 

X-ray absorption is not really a new technique since the first absorption spectra were obtained by Fricke, Hertz or Lindh at the beginning of the century, but the EXAFS technique appeared as a definite tool for experimentalists in the 1970s when, at the same time, synchrotron radiation and a new physical model became available. 

Bohr s fundamental concepts of discrete stationary states and a quantum frequency condition receive their most direct confirmation from a class of investigations initiated by Franck and Hertz, and subsequently extended and refined by these and other investigators. The fundamental idea of these experiments is that definite amounts of energy can be communicated to atoms by bombarding them with electrons of known velocity. As the velocity of the bombarding electrons is increased, the abrupt occurrence of the stationary states is indicated on the one hand by the sudden appearance of electrons which have lost some of their incident energy, and on the other by the sudden production of radiation of those frequencies which are associated with transitions from the stationary state in question to other stationary states of lower energy. 

Being the actual numerical model mainly a rationalization of the experimental facts, let s involve other estimable quantities. The IP, closely related also with the actual absolute electronegativity (4.253) definition, is a quite accessible spectral atomic index, either theoretical from the limit frequency from which the continuum spectmm is achieved, or experimentally by a Franck-Hertz experiment. Nevertheless, as far as all the valence... 

It is seen that the problem of Hertz is of more than historical interest. In the case of mercury, the acceptance of the equilibrium assumption has been fully justified by the definitive work of Volmer and Estermann (1922) who showed that the coefficient a was equal to unity or that the actual rate of evaporation was equal within experimental error to the mtiximum rate given by (2.3.8). 

In condensation problems dealing with very small droplets (with radius far below the mean free path) Gyarmathy s equations converge with the much simpler Hertz-Knudsen model involving the condensation coefficient a. This model is widely used although the condensation coefficient is not known. Mostly it is taken to be unity, however values as low as 0.01 are perpetuated [2]. Some of the uncertainty may be due to considerable confusion in the literature regarding its definition. Here we deal with it because our results render valuable information on its magnitude. 

For the Hertz-Knudsen model and the definition of the condensation coefficient we follow Hill [4]. The bombardment of small droplets by vapor molecules is described by the impingement rate... 

All of the equalization effects operate on the frequency of the sound. Frequency is a strict definition of the pitch or key in terms of the number of waves of sound per second, measured from peak to peak in a pure tone. Cycles per second are measured in Hertz (Hz). 

We introduced the microcanonical analysis in Section 2.7 and found that the density of states g E) already contains all relevant information about the phases of the system. Alternatively, one can also use the phase space volume AG(E) of the energetic shell that represents the macrostate in the microcanonical ensemble in the energetic interval (E,E+ AE) with AE being sufficiently small to satisfy AG E)=g E)AE. In the limit AE —> 0, the total phase space volume up to the energy E can thus be expressed as G E) = dE g(E ). Since g E) is positive for all E, G(E) is a monotonically increasing function and this quantity is suitably related to the microcanonical entropy S(E) of the system. In the definition of Hertz,... 

---