The vibrational predissociation rates of triatomic van der Waals complexes were investigated by a new, computationally simple method. The method is based on three approximations: (a) metastable vibrationally excited states of the complex are described by the vibrational self-consistent field (VSCF) approximation, (b) the coupling among the rotational states of the dissociating diatomic fragment is treated by the infinite order sudden (IOS) approximation, and (c) the vibrational transition that leads to dissociation is treated by the distorted wave Born approximation (DWBA). The predissociation rates, the product rotational state distributions, and the lifetimes of vibrationally excited states of He-ICl and He-I-2 are all computed and are in reasonable agreement with other theoretical and/or experimental results. The suggested VSCF-DWBA-IOS scheme is found to be a very simple but efficient theoretical tool to investigate the dissociation dynamics of van der Waals complexes.
The visualization and endurance of fingerprints on cartridge cases after the firing process have been examined. Cartridges of M16, AK-47 (Kalashnikov) and Parabellum have been tested. Despite difficulties in visualizing these fingerprints, it was found that in some cartridge cases under laboratory conditions--for instance, on M16 brass cartridges--substantial parts of the fingerprints remain intact after shooting. The careful use of illumination after metal vapor deposition enabled visualization. Different possible mechanisms responsible for the partial destruction of the fingerprints are discussed.[on SciFinder (R)]
Reports an error in "What can we learn from the morphology of Hebrew? A masked-priming investigation of morphological representation" by Ram Frost, Kenneth I. Forster and Avital Deutsch (Journal of Experimental Psychology: Learning, Memory, and Cognition, 1997[Jul], Vol 23[4], 829-856). On page 854, two Hebrew words are missing from Appendix F. The corrected Appendix appears with the erratum. (The following abstract of the original article appeared in record [rid]1997-05320-003[/rid].) All Hebrew words are composed of 2 interwoven morphemes: a triconsonantal root and a phonological word pattern. The lexical representations of these morphemic units were examined using masked priming. When primes and targets shared an identical word pattern, neither lexical decision nor naming of targets was facilitated. In contrast, root primes facilitated both lexical decisions and naming of target words that were derived from these roots. This priming effect proved to be independent of meaning simila
The modification of glucose oxidase by palmitic acid ester of N-hydroxysuccinimide leads to the formation of a new hydrophobized enzyme with five covalently bound C16 groups. Such a modification was shown not to alter noticeably the native structure of the enzyme. The modified glucose oxidase displays enhanced surface activity at the water/air interface in comparison with the native enzyme. The max. redn. of surface tension at all concns. studied was higher for the modified glucose oxidase than for the native one. The modified enzyme also displayed a much steeper rise of the surface potential with time and a much more rapid attainment of the satn. plateau than the unmodified enzyme. [on SciFinder(R)]
Marie Anne Schneeweiss, Dieter M Kolb, DeZhong Liu, and Daniel. Mandler. 1997. “Anodic oxidation of Au(111)..” Can. J. Chem.Canadian Journal of Chemistry, 75, 11, Pp. 1703 - 1709. Abstract
The initial stages of the anodic oxidn. of Au(111) were studied by cyclic voltammetry as well as in situ scanning tunneling microscopy (STM). Probably the place exchange process, which initiates the oxide formation, starts at step edges. The oxide phase was imaged in situ by scanning tunneling and at. force microscopy (AFM). The topog. information acquired by the two techniques is compared. [on SciFinder(R)]
We report here measurements of the orientational and frequency dependence of the anomalously large second-order nonlinear optical (NLO) susceptibilities observed in guest−host DANS [4-(N,N-dimethylamino)-4‘-nitrostilbene]/PMMA [poly(methyl methacrylate)] films poled in an “in-plane” electrode configuration. The resonant response is sharply peaked (fwhm decreases by a factor of 4) in comparison to identical samples poled by standard corona field techniques. Additionally, these anomalous susceptibilities, which are oriented normal to the electric poling field, exhibit unusually strong features at long wavelengths where the linear absorption is low. We also report the first direct experimental EPR evidence for nitrogen-centered cation radicals, hence the creation of charged chromophores trapped in the polymeric matrix by charge injection from the poling electrodes. These observations are in qualitative agreement with the very large NLO response magnitudes and distinct spectral features predicted by sum-over-states perturbative calculations performed for positively charged centrosymmetric chromophore dimers and provide strong computational evidence that the observed anomalous NLO response is due to charged chromophore aggregates.
Evidence is given for the structure of aryl-substituted trimethylenemethane dianions from NMR data, and the importance of p-pi conjugation is discussed.
Self-assembled monolayers (SAMs) of ω-mercaptoalkanesulfonic acid on Au surfaces were studied by electrochem. and other surface techniques. In spite of the fact that these monolayers are disorganized, i.e., of brush type, they are impermeable to inorg. anions due to their high neg. charge. Also, an ω-mercaptodecanesulfonic acid (MDS) monolayer is also impermeable to org. species, regardless of their charge, because of its high hydrophilicity. The combination of these properties made it possible to apply Au electrodes modified with MDS for the detn. of Fe(III) ions in the presence of org. species that are either electroactive throughout the same potential window or form strong complexes with Fe(III). [on SciFinder(R)]
This contribution presents a quantum chemical investigation of the nonlinear optical response of charged centrosymmetric aggregates of the archetypical chromophore p-nitroaniline using an ab initio supermolecular approach. Localized hole states, responsible for aggregate nonlinearity, are predicted to be more stable than delocalized states. The calculated aggregate hyperpolarizabilities are consistently larger than in the isolated chromophore, and the mechanism giving rise to the nonlinearity is essentially “intramolecular” in nature. The aggregate formation is predicted to stabilize the positive charge and to enhance the nonlinearity. Moreover, the calculations reveal that a (formally) centrosymmetric charged aggregate can possess a substantial dipole moment the principal axis of which is oriented perpendicular to the principal hyperpolarizability tensor; the dipole moment arises because electron localization breaks the charge distribution symmetry. These results explain a number curious features of chromophoric polymer films which are electric field poled with an “in-plane” electrode geometry.
The original paper presents an efficient algorithm for routing an Omega-1 × Omega nonblocking network. This comment presents an extra step required to route an Omega+Omega network.
