Atom number density

The analysis of steady-state and transient reactor behavior requires the calculation of reaction rates of neutrons with various materials. If the number density of neutrons at a point is n and their characteristic speed is v, a flux effective area of a nucleus as a cross section O, and a target atom number density N, a macroscopic cross section E = Na can be defined, and the reaction rate per unit volume is R = 0S. This relation may be appHed to the processes of neutron scattering, absorption, and fission in balance equations lea ding to predictions of or to the determination of flux distribution. The consumption of nuclear fuels is governed by time-dependent differential equations analogous to those of Bateman for radioactive decay chains. The rate of change in number of atoms N owing to absorption is as follows ... 

Several of the reactor physics parameters are both measurable and calculable from more fundamental properties such as the energy-dependent neutron cross sections and atom number densities. An extensive database. Evaluated Nuclear Data Files (ENDF), has been maintained over several decades. There is an interplay between theory and experiment to guide design of a reactor, as in other engineering systems. 

The atomic PDF is related to the probability to find a spherical shell around a generic atom (scattering center) in the material - it is defined as G(r) = Anp[p r)-p(, where p r) and po are, respectively, the local and average atomic number densities and r the radial distance. G(r) is the Fourier transform of the total structure factor Sid). ... 

Here I stands for the intensity of the spectral hnes N is the atom number density in cm Z is the partition function E and y are the energies and degeneracy s of the upper levels, respectively and A and A are the Einstein coefficient and wavelength, respectively, for the observed transitions. When changing the concentration Nt relative to that Nm the line intensities ft and 7m will likewise change, and according to (6.1) one should obtain a cahbration curve with constant slope (Davies et al. 1995 Ciucci et al. 1999 Hou and Jones 2000). 

Simulate the process using a perfectly stirred reactor model. For the nominal processing conditions, plot the O-atom number density as a function of pressure for... 

Diamond has the highest atom-number density of any known material at terrestrial pressures. Because of its high atom-number density and strong covalent bonding, diamond has the highest hardness and elastic modulus of any material and is the least compressible substance known. 

The atomic number density of DLHC (more than 0.19 gram-atom per cubic centimeter) falls between that of admantane and diamond. It is... 

Spacecraft in low Earth orbit (LEO) must function in a harsh oxidizing environment. At LEO altitudes, ranging from 200 to 700 km, the residual atmosphere is predominantly neutral, with the dominant component being atomic oxygen. A typical 0-atom number density at space shuttle altitudes ( 300 km) is on the order of 10 cm . At orbital altitudes of 300-400 km, the LEO environment subjects materials on the ram side of a spacecraft to collisions with ambient oxygen atoms that have an average impact velocity of 7.4 km corresponding to a mean collision en-... 

The fact that glow discharges have much lower atom number densities than atmospheric pressure plasmas is responsible for the fact that the measurement of fundamental parameters such as electron number densities, electron temperatures, etc. by techniques such as Thomson scattering is much more difficult than in the case of atmospheric pressure plasma discharges, and that this is only now becoming a field of active research. Moreover, the lower collision frequency, which causes large departures from local thermal equilibrium, is responsible for the fact that many more processes are significantly involved in the excitation mechanisms than in the case of atmospheric pressure plasmas. 

The fluorescence radiation itself is also only proportional to the atom number densities and the pathlength through the atom reservoir in a first approximation because of self-absorption. 

Except for polonium, boiling points and melting points of the group 16 elements increase with increasing atomic number. Density increases with increasing atomic number for all group 16 elements. 

Next, in Section 8.3.2, we describe long-time full atomic MD simulations (longer than 150 ns) for a small peptide, met-enkephalin (M-Enk), in addition to a larger chymotrypsin inhibitor 2 (CI2), both in ectoine aqueous solutions with the same concentration and in pure water at room temperature. To determine the spatial distribution of each solvent component, the atom number densities of water molecules and ectoine molecules around both solutes were analyzed. We found that one dominant structure of M-Enk does not preferentially exclude the ectoine molecules from its surface as CI2 does. To understand the reason for this difference in ectoine exclusion, in addition to the effect of direct interaction between M-Enk and ectoine, the influence of hydration (i.e., property alteration of the hydration layer near the solute surface) on the development of ectoine preferential exclusion around each solute was examined at the molecular level. 

Surficial Kirkwood-Buff Theory 8.2.3.1 Solvent-Atom Number Density... 

In this section, assuming mixed solvent systems, the subscript i of a quantity stands for a certain solvent component, while a stands a protein as the solute molecule. Then, the time-resolved solvent atom number density (TRSAND) p j(r, t) of a certain solvent component i is defined as a function of the distance r from the solute molecule a (see Figure 8.1) by... 

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