Contribution central

There are a number of side-effects of opiates that are due to their actions on opiate receptors outside the central nervous system. Opiates constrict the pupils by acting on the oculomotor nucleus and cause constipation by activating a maintained contraction of the smooth muscle of the gut which reduces motility. This diminished propulsion coupled with opiates reducing secretion in the gut underlie the anti-diarrhoeal effect. Opiates contract sphincters throughout the gastrointestinal tract. Although these effects are predominantly peripheral in origin there are central contributions as well. Morphine can also release histamine from mast cells and this can produce irritation and broncho-spasm in extreme cases. Opiates have minimal cardiovascular effects at therapeutic doses. 

The electron density centered at M is the only central contributor at the nuclear position M, as in this case the nucleus coincides with the field point P, which is excluded from the integrals. For transition metal atoms, the central contributions are the largest contributors to the properties at the nuclear position, which can be compared directly with results from other experimental methods. The electric field gradient at the nucleus, for instance, can be measured very accurately for certain nuclei with nuclear quadrupole resonance and/or Mdssbauer spectroscopic methods, while the electrostatic potential at the nucleus is related to the inner-shell ionization energies of atoms, which are accessible by photoelectron and X-ray spectroscopic methods. 

The operators for the potential, the electric field, and the electric field gradient have the same symmetry, respectively, as those for the atomic charge, the dipole moment, and the quadrupole moment discussed in chapter 7. In analogy with the moments, only the spherical components on the density give a central contribution to the electrostatic potential, while the dipolar components are the sole central contributors to the electric field, and only quadrupolar components contribute to the electric field gradient in its traceless definition. 

For transition metal atoms, the dominant contribution to the electric field gradient at a nucleus originates in the valence shell centered on that nucleus. The expressions for this central contribution are given in Eq. (8.43) for Slater-type, exponential, density functions, defined as in Eq. (3.34) ... 

As in chapter 8, we will refer to contributions from the electron density centered on the nucleus as central contributions, and to the remainder as peripheral contributions. In the spectroscopic literature, the latter are commonly referred to as lattice contributions, a term we will avoid as it conflicts with the common definition of the lattice as a mathematical concept. 

The calculations show that the central contribution to the EFG, due to the valence electrons, is shielded rather than antishielded, but the effect is less pronounced. The shielding factor R is the density-weighted average of y(r), <7( ) "3>core,vaience/core,valence, where the average is to be taken separately over the core and valence shells, depending on the shell in which polarization is induced. 

Though the peripheral contribution is considerably enhanced by the antishielding, it is nevertheless small relative to the central contribution, except for very short metal-ligand distances (Coppens 1990). 

An obvious question arises do these peripheral sympathetic activations reflect direct effects of the drugs on the peripheral autonomic nervous system, or are they secondary to the central effects Although we cannot rule out a contribution from the direct route, a central contribution seems very likely for the following reasons. 

Chi, S.I., Levine, J.D., andBasbaum, A.I. Peripheral and central contributions to the persistant expression of spinal cord fos-like immunoreactivity produced by sciatic nerve transection in the rat. Brain Res. 617, 225-237 ( 993). 

The studies on lead molecules and their optimisation are consistent with each other and together provide strong support for the lead-like concept as a central contributing component in achieving ultimate optimization success. The average changes in mol. wt and cLogP are consistent and in these studies are... 

Renormalization factors grijUt) calculated for A 208 nuclei with HO wave functions ha> = 6.88 MeV) and both the H7B and HBB residual interactions. Results are for the ten possible RO transitions in the model space of Fig. 2. For HO wave functions the qs are given by 1 — gj = qj- — 1. A breakdown into the tensor and central contributions is given. The columns labeled central also contain a small spin-orbit contribution. Note the similarity of the central contributions for the H7B and HBB interactions and that the H7B tensor component is larger than that of the HBB interaction... 

By exploiting the state selectivity that ionization of small molecules by ultraviolet radiation provided, ionic collision dynamics made a central contribution to the emerging field of chemical dynamics. A key question in chemical dynamics is how energy that is placed in specific modes of reactant motion affects the outcome of a chemical reaction. The first example of a chemical reactant prepared in a quantized excited vibrational state and... 

In summary, the Ravello NATO ASI was a very special workshop which we remember as an intense but collegial scientific discussion, a forum for interaction among individuals from broadly different cultures and languages, and the reinforcement or initiation of cameraderie which continues. We hope that this volume reflects all of these aspects, provides current status reports in diversified fields, and, most significantly, acts as a benchmark for the discipline of organic synthesis as it surveys and reaches towards its central contributions in the 21st Century. 

In Table 2.2 the ground configurations of the atoms are listed. Obviously, the field in atoms is only approximately central. Besides a central part, the electrostatic repulsion between electrons causes a non-central contribution, which can be treated as a perturbation. The spin-orbit interaction must also be taken into account. If the non-central electrostatic part strongly dominates over the spin-orbit interaction, the latter is neglected as a first approximation. A coupling between the individual angular momenta is then obtained... 

The first non-central term is of order (d/r) ihere is no term in djr. We thus see that the non-central contribution, even if not negligible, is small. (It is smaller than e.g. for an asymmetric molecules, where terms in dfr would no longer vanidi ... 

At small densities the non-central contribution is negligibly small in all these cases. 

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