Darwin effect

Another method, devised by Cohen et al. to determine oxygen-rate gas collision parameters is to define an effective spin-orbit operator that includes r dependence, Zeff/r3, where the value of Zeff is adjusted to match experimental data (76). Langhoff has compared this technique with all-electron calculations using the full microscopic spin-orbit Hamiltonian for the rare-gas-oxide potential curves and found very good agreement (77). This operator has also been employed in REP calculations on Si (73), UF6 (78), U02+ and Th02 (79), and UF5 (80). The REPs employed in these calculations are based on Cowen-Griffin atomic orbitals, which include the relativistic mass-velocity and Darwin effects but do not include spin-orbit effects. Wadt (73), has made comparisons with calculations on Si by Stevens and Krauss (81), who employed the ab initio REP-based spin-orbit operator of Ermler et al. (35). 

Scalar relativistic (mass-velocity and Darwin) effects for the valence electrons were incorporated by using the quasi-relativistic method (55), where the first-order scalar relativistic Pauli Hamiltonian was diagonalized in the space of the nonrelativistic basis sets. The Pauli Hamiltonian used was of the form... 

The tenn and the total Darwin effect nearly cancel each other out for unclear reasons. This cancellation is being persistently confirmed in other systems as well. Strangely enough, this pertains not only to the ionization energy, but also to the polarizability. 

The most common description of relativistic quantum mechanics for Fermion systems, such as molecules, is the Dirac equation. The Dirac equation is a one-electron equation. In formulating this equation, the terms that arise are intrinsic electron spin, mass defect, spin couplings, and the Darwin term. The Darwin term can be viewed as the effect of an electron making a high-frequency oscillation around its mean position. 

As expected, Ap vanishes if the strength of the spin-orbit coupling is reduced to 0 by reducing (co/c) or respectively. Both sets "f model calculations give nearly the same results indicating that the so-called scalar relativistic effects due to the mass-velocity and Darwin-term, are of minor importance for the absolute value of Ap. 

Figure 1. Diagram of the venom duct of Conus. The venom is produced in the venom duct, apparently expelled from the duct into the proboscis by contraction of the venom bulb. Simultaneously, a harpoon-like tooth is transferred from the radula sac to the proboscis. When injection takes place, the venom is pushed through the hollow tooth and flows into the prey through a hole at the tip of the tooth. Typically, fish-hunting cones will strike at a fish only once and grasp the tooth after injection has occurred, effectively harpooning their prey while injecting the paralytic venom. In contrast, snail-hunting cones will usually sting their prey several times before total paralysis occurs. (Reprinted with permission from the Second Revised Edition of Ref. 8. Copyright 1988 Darwin Press, Inc.)...

Particular thanks go to those who read over the chapter in draft form Verena Brink, Jean Colley, Darwin H. Stapleton, and Christian Simon. For DDT s effects on public health, I am indebted to Richard Fenske, MD. 

Darwin was a pluralist. He was very careful to state that natural selection is not the only motor of evolutionary change. He invented the concept of sexual selection, the only addition to natural selection which evolutionary psychology theorists are prepared to include in their pantheon. We need not be Lamarckian to accept that other processes are at work. The existence of neutral mutations, founder effects, genetic drift, exaptations and adoptations (Dover, 2000) all enrich the picture. 

The detection of small extrasolar planets (of around the size of the Earth) will be done by registering the infrared light which they emit. Interference filters will blot out the light emitted by the star in question. Because of the huge distance from the Earth, effects due to its atmosphere and its IR radiation will not interfere. Darwin is intended not only to discover planets but to analyse their atmospheres for possible signs of life. 

Besant also highlighted, for instance, Professor Darwin s claim to the British Association at Cape Town that Although even the dissociative stage of the alchemistic problem still lay beyond the power of the chemist, yet, modern researches seemed to furnish a sufficiently clear idea of the structure of atoms to enable them to see what would have to be done to effect a transformation of the elements ([Besant] 1905, 2). 

Up to this point, we have considered the nonrelativistic Schrodinger equation. However, to calculate AEs to an accuracy of a few kJ/mol, it is necessary to account for relativistic effects, even for molecules containing only hydrogen and first-row atoms. Fortunately, the major relativistic contributions to the AEs of such molecules - the mass-velocity (MV), one-electron Darwin (ID), and first-order spin-orbit (SO) terms - are easily obtained [58]. 

Perhaps the simplest and most cost-effective way of treating relativistic contributions in an all-electron framework is the first-order perturbation theory of the one-electron Darwin and mass-velocity operators [46, 47]. For variational wavefunctions, these contributions can be evaluated very efficiently as expectation values of one-electron operators. 

Early band structure calculations for the actinide metals were made both with and without relativistic effects. As explained above, at least the mass velocity and Darwin shifts should be included to produce a relativistic band structure. For this reason we shall discuss only the relativistic calculations. There were some difficulties with the f-band structure in these studies caused by the f-asymptote problem , which have since been elegantly solved by linear methods . Nevertheless the non-self-consistent RAPW calculations for Th through Bk indicated some interesting trends that have also been found in more recent self-consistent calculations ... 

For an elementary proton r )p = 0, g = 2, and only the first term in the square brackets survives. This term leads to the well known local Darwin term in the electron-nuclear effective potential (see, e.g., [1]) and generates the contribution proportional to the factor Sio in (3.4). As was pointed out in [2], in addition to this correction, there exists an additional contribution of the same order produced by the term proportional to the anomalous magnetic moment in (6.6). 

In M0ller-Plesset theory, first-order perturbation theory does not improve on the HF energy because the zeroth-order Hamiltonian is not itself the HF Hamiltonian. However, first-order perturbation theory can be useful for estimating energetic effects associated with operators that extend the HF Hamiltonian. Typical examples of such terms include the mass-velocity and one-electron Darwin corrections that arise in relativistic quantum mechanics. It is fairly difficult to self-consistently optimize wavefunctions for systems where these tenns are explicitly included in the Hamiltonian, but an estimate of their energetic contributions may be had from simple first-order perturbation theory, since that energy is computed simply by taking the expectation values of the operators over the much more easily obtained HF wave functions. 

The first-order perturbation theory estimate of relativistic effects (inclusion of the mass-velocity and one-electron Darwin terms as suggested by Cowan and Griffin) is cheap and easy to compute as a property value at the end of a calculation. It is therefore very valuable as a check on the importance of relativistic effects, and should certainly be included in accurate calculations on, for example, transition-metal compounds. For even heavier elements relativistic effective core potentials should be used. 

Jenkins, A.J., B.A. Holicky, T.M. Grant, W.D. Darwin, et al., Blood concentrations and pharmacological effects after oral heroin administration, paper presented at Society of Forensic Toxicolo-gists/The International Association of Forensic Toxicologists, Joint Conference (October 1994), abstr. 127, 1994. 

SS) Costlow, Jr., J. D. Effect of carbonate anhydrase inhibitors on shell development and growth of Balanus improvisus DARWIN. Biol. Bull. 116, 177-184 (1959). 

Considered together, the effects of a diverse array of drugs all signify that your brain is a racecar and that dopamine is the gas pedal. Your brain feels euphoria when the gas pedal is pushed quickly (by ever increasing lipid-solubility), and your thoughts are allowed to fly as fast as possible around your mental track. The forces of evolution have shaped your brain to truly enjoy working fast the faster the better because fast brains are more likely to exist within creatures who survive and who will therefore pass on this trait to the next generation. Thus, classic Darwinism underlies why we enjoy what we enjoy so much, be... 

Maki, J.S., Yule, A.B., Rittschof, D., and Mitchell, R., The effect of bacterial films on the temporary adhesion and permanent fixation of cypris larvai, Balanus amphitrite Darwin, Biofouling, 8,121, 1994. 

Dineen, J.F., Jr. and Hines, A.H., Interactive effects of salinity and adult extract upon settlement of the estuarine barnacle Balanus improvisus (Darwin, 1854), J. Exp. Mar. Biol. Ecol., 56, 239, 1992. 

O Connor, N.J. and Richardson, D.L., Effects of bacterial films on attachment of barnacle (Balanus improvisus Darwin) larvae laboratory and field studies, J. Exp. Mar. Biol. Ecol., 206, 69, 1996. 

The quasirelativistic (QR) PP of Hay and Wadt [61] use two-component wave functions, but the Hamiltonian includes the Darwin and mass-velocity terms and omits the spin-orbit effects. The latter are then included via the perturbation operator after the wave functions have been obtained. The advantage of die method is the possibility to calculate quite economically rather large systems. The method is implemented in the commercial system Gaussian 98 It has extensively been applied to calculations of transition-element and actinide systems [62],... 

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