Atomic signatures

C and 180 atomic signatures observed by radio astronomers (Glassgold et al. 1985 van Dishoeck Black 1988 Langer Penzias 1990 Sheffer et al. 2002 Dartois etal. 2003 Pietu etal. 2007) and anomalous meteoritic [Pg.117]

Similar to —> MNA descriptors, signature descriptors are holographic vectors of count numbers of all the atomic signatures present in the data set molecules, the signature of an atom being a canonical representation of the atom environment up to a predefined depth, that is, a circular substructure descriptor [Visco, Pophale et al, 2002 Faulon, Visco et al, 2003]. 

Diverse Inverse QSAR/Atomic signature Visco DP Jr et al. 2002 [225]... 

Here, is the normalised property operator for property p, is the lower limit for the normalised property operator, and is the upper limit for the normalised property operator. As signature-based molecular design technique is employed in this developed methodology, normalised property operators are used to express molecules as linear combinations of atomic signatures. 

Another example of noncysteinyl coordination of a [4Fe-4S] center was provided by the resolution of the X-ray structure of D. gigas hy-drogenase, which revealed that one iron atom of the distal [4Fe-4S] center was ligated by the atom of a histidine residue (164). Unfortunately, the EPR signature of this center could not be determined because of intercenter spin—spin interactions with other iron—sulfur centers (95). 

A permanent EDM of a stable atomic or molecular state can arise only when both P and T invariance are broken (see Fig.l). It is often said that polar molecules possess permanent EDMs and exhibit a linear Stark effect. However, the Stark effect exhibited by the polar molecule is not really linear for sufficiently small E at zero temperature, and moreover, it violates neither P nor T symmetry [10]. We emphasize that a permanent EDM that exhibits a linear Stark effect even for an infinitesimally weak is a genuine signature of P and T violation or CP violation... 

It has been known for some time that the spectroscopic signature of Ob-vacs can be healed by exposure to 02 [42-46], In addition, Epling etal. [47] show that temperature-programmed desorption (TPD) spectra of water and ammonia are perturbed when the surface is predosed with 02. This implies that oxygen is left on the surface in some form when Ob-vacs are healed by 02, As such, Epling et al. proposed that one Ob-vac is healed per 02 molecule with the other O atom being adsorbed at a Ti5c site (Oad), a dissociation mechanism supported by theoretical calculations [48, 49]. 

As we have already pointed out in the section dealing with heteronuclear coupling that it is not always necessary to confirm the presence of a particular hetero atom by acquiring the NMR spectrum of that nucleus. More often than not, the hetero atom will have a clear signature in the proton or carbon spectrum. Fluorine and phosphorus are both examples of nuclei that couple to protons over two, three, four and even more bonds. 

In general, the -dependent variations of natural atomic charges in dative bonds are significantly larger than those in covalent bonds. Indeed, the Q (R) variations in dative bonds resemble those in ionic bonds (cf. Fig. 2.9), to which they are evidently related by similarities in donor-acceptor character. The strong AQ /AR dependence tends to be associated with enhanced infrared vibrational intensity and other spectroscopic signatures characteristic of ionic bonding. 

EXO 0748-676, Cottam et al. (2002) have found absorption spectral line features, which they identify as signatures of Fe XXVI (25-time ionized hydrogenlike Fe) and Fe XXV from the n = 2 —> 3 atomic transition, and of O VIII (n = 1 —> 2 transition). All of these lines are redshifted, with a unique value of the redshift z = 0.35. Interpreting the measured redshift as due to the strong gravitational field at the surface of the compact star (thus neglecting general relativistic effects due to stellar rotation on the spectral lines (Oezel Psaltis 2003)), one obtains a relation for the stellar mass-to-radius ratio ... 

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