The flux of an evolving wavepacket is the definite time integral of its probability current density. A new method for calculating the flux, based on a Chebychev polynomial expansion of the quantum evolution operator is presented. The central point of the development is that the time integration of the current density is performed analytically, resulting in a scheme which eliminates additional numerical errors. Using this method, one benefits from both the time-dependent and time-independent frameworks of the dynamics. Furthermore, the method requires only a small modification to the existing Chebychev polynomial evolution code. Examples of performance and accuracy and an application to the calculation of recombinative desorption probabilities of N2 on Re are shown and discussed.
This contribution describes the synthesis and properties of NLO-active self-assembled chromophoric multilayers. The stilbazolium self-assembled multilayers were prepared by new topotactic approaches based on siloxane self-assembly technology. X-ray photoelectron spectroscopy (XPS), advancing aqueous contact angle (θa) measurements, transmission optical spectroscopy, polarized second harmonic generation (SHG), and specular X-ray rellectivity (XRR) show that the resulting self-assembled chromophoric superlattices have very high structural regularity and very large second-order nonlinear optical susceptibility.
The long-lasting effect of reading experience in Hebrew and English on phonemic segmentation was examined in skilled readers. Hebrew and English orthographies differ in the way they represent phonological information. Whereas each phoneme in English is represented by a discrete letter, in unpointed Hebrew most of the vowel information is not conveyed by the print, and, therefore, a letter often corresponds to a CV utterance (i.e., a consonant plus a vowel). Adult native speakers of Hebrew or English, presented with words consisting of a consonant, a vowel, and then another consonant, were required to delete the first "sound" of each word and to pronounce the remaining utterance as fast as possible. Hebrew speakers deleted the initial CV segment instead of the initial consonant more often than English speakers, for both Hebrew and English words. Moreover, Hebrew speakers were significantly slower than English speakers in correctly deleting the initial phoneme, and faster in deleting th
The subject of antisemitism was discussed in an interdisciplinary context, within a historical framework ranging from the Hellenistic-Roman period and the emergence of Christianity to the present times. The major part of the proceedings focused on the Modern Era and contemporary aspects.
Antisemitism was not dealt with as a phenomenon per se, but within the conceptual framework of the "other" as a threat and the "demonization" of social groups. In making this choice we were guided by the need to examine what is common, different, and unique in various forms of hostility.
By the "other" as a threat we had in mind primarily the perception of the "other" as an existential threat to the very continuation of the physical, spiritual, cultural, religious or social existence. This is often presented paradoxically as a threat of a minority or underprivileged group to the dominant majority.
In dealing with "demonization", our intention was to examine the gap between genuine factors which lead to antagonism, such as social, economic or political conditions, religious differences or ethnic origin and the demonic perceptions of "danger" (e.g. the threat of domination or destruction). We also explored the origins and development of images and accusations leading to the demonization of specific groups.
The proceedings of the conference are being prepared for publication.
Unimolecular processes can be described as the decay of an ensemble of N excited resonances coupled to K decay channels. Resonances are metastable states characterized by a complex energy whose real part is the position of the state along the energy axis while the imaginary part gives the individual decay rate of the state. Resonances usually overlap in the RRKM regime. The degree of overlap is measured by the parameter R = /dE where is the average of the individual decay rates of the excited resonances and dE is the average spacing between their position. In the exact degeneracy limit, that is, for an infinite value of R, (N-K) resonances have a zero width, so that a fraction of the initial excitation remains permanently trapped in the bound subspace. This trapping effect subsists in the non degenerate case but is not complete. We use a random coupling effective Hamiltonian model to discuss the effect of the degree of overlapping R, and of the number of resonances N and decay channels K, on the temporal evolution laws of the bound subspace and of the fragments. The decay law of the bound subspace and the temporal evolution of the yields in fragments exhibit several time regimes. This is due to the fact that after the diagonalization of the effective Hamiltonian, the decay widths of the resonances cluster into one group of K large widths and one group of(N-K) small ones. The trapping effect is due to the (N-K) small widths. The amount of trapping depends on the value of the degree of overlapping R, and for a given value of R, on the ratio N/K: large values of R and of N/K correspond to a large amount of trapping in the bound subspace for times long when compared to h/. The temporal evolution laws of the yields in fragment are also strongly affected by the degree of overlapping and the value of the ratio N/K. Due to the reorganization of the partial widths which follows the diagonalization of the effective Hamiltonian, we show that the nature of the dominant product can change while increasing the value of R and N/K. We also discuss the time evolution of the sampling of phase space for a specific preparation in terms of these two parameters. The volume sampled is computed using an entropic measure. When the resonances overlap, there is not enough time to completely sample phase space prior to dissociation. The fraction sampled decreases as the amount of trapping in the bound phase space increases.
Immunohistochemically detectable levels of p53 may be seen early in the malignant transformation of some neoplasms. To determine if p53 is immunocytochemically detectable, and therefore presumptively abnormal, in oral dysplasias and in situ carcinomas, and to explore the natural history of p53 protein expression in these lesions, sequential biopsies from patients with lesions occurring in the same anatomic site were examined. Formalin-fixed, paraffin-embedded sections from 19 patients were evaluated immunohistochemically for p53 protein using antibody clones Pab1801 and BP53-12. With two exceptions, comparable results were observed with these antibodies. p53 protein was detected immunocytochemically in 6 of 13 patients with dysplasias; 3 of these progressed to p53-positive invasive carcinoma, one advanced to a more severe grade of p53-positive dysplasia, one developed into a p53-negative verrucous carcinoma, and one represented a p53-positive dysplasia developing five years after treatment of a p53-positive carcinoma. The p53-positive dysplasias, which were found in all subtypes (mild, moderate, severe), preceded histologic malignant change by months to years. p53 detection was evident in 4 of 6 patients with in situ lesions. Sequential biopsies of three of these lesions showed no change in lesion histology or p53 staining, and one lesion advanced to a p53-positive carcinoma. It is concluded that p53 protein may be detected early in the development of a subset of p53-positive oral squamous cell carcinomas. This phenomenon may be seen in dysplasias and in situ lesions, and it may have prognostic implications.
BACKGROUND:
Oxygen-derived radicals are implicated in the pathogenesis of tissue damage and ulcerogenesis. This study aimed to examine the effect of manganese, glycine, and carotene, oxygen radical scavengers, on ethanol-induced gastric lesions in the rat and on ethanol cytotoxicity in epithelial cell culture.
METHODS:
MnCl2 + glycine (12.5-50 mg/rat) were injected subcutaneously up to 6 h before oral administration of 1 ml of 96% ethanol, and 0.5 ml carrot juice or beta-carotene was given orally 30 min before the ethanol. Mucosal injury was evaluated 1 h later by gross and microscopic scoring. The effect of Mn2+ and carrot juice was also tested in monolayers of radiolabeled epithelial cells exposed to H2O2 + ethanol injury as expressed by the extent of the isotope leakage.
RESULTS:
Mn2+ and glycine pretreatment dose-dependently reduced ethanol-induced gastric lesion formation. Protection was maximal when treatment was applied 4 h before the insult. Gross damage was also markedly prevented by pretreatment with carotenes and dimethylthiourea (DMTU, 75 mg/kg intraperitoneally) but not by allopurinol. Mixtures of subtoxic concentrations of ethanol and H2O2 were highly lethal for epithelial cell monolayers. In this model, cell death was markedly attenuated by catalase, DMTU, Mn2+, and carrot juice.
CONCLUSIONS:
Ethanol-induced gastric mucosal damage may involve generation of oxygen-derived radicals, independent of the xanthine oxidase system. By acting as oxygen radical scavengers, Mn2+, glycine, and carotenes, like catalase and DMTU, provide significant gastroprotection.
Cell-impermeable inhibitors of phospholipase A2 were prepared by linking inhibiting molecules to macromolecular carriers which prevent the inhibitor's internalization. These preparations inhibit the release of oxygen reactive species from neutrophils and cell death induced by inflammatory agents, as well as bleomycin-induced lung injury.
The role of assembled versus addressed phonology in reading was investigated by examining the size of the minimal phonological unit that is recovered in the reading process. Readers named words in unpointed Hebrew that had many or few missing vowels in their printed forms. Naming latencies were monotonically related to the number of missing vowels. Missing vowels had no effects on lexical decision latencies. These results support a strong phonological model of naming and suggest that even in deep orthographies, phonology is not retrieved from the mental lexicon as a holistic lexical unit but is initially computed by applying letter-to-phoneme computation rules. The partial phonological representation is shaped and completed through top-down activation.
The effect on differential and integral cross sections of varying the potential energy of the entrance channel to a polyatomic reaction is investigated theoretically. The rotating bond approximation (RBA) is used for the CH4 + OH –> CH3 + H2O reaction. The reaction exhibits peripheral dynamics, with a higher reactivity at higher impact parameters. Due to the significant potential barrier the scattering of the products is however sideways and not forward. It is found that varying the long-range isotropic terms in the potential has almost no effect on the opacity function or the cross sections. The addition of long range anisotropic terms induces rotational transitions of the OH reactant and thereby reduces the reactivity at higher impact parameters, resulting in backward scattering.
Solvent-induced electronic predissociation (X –> B –> al(g)((3) Pi) state) of molecular iodine is discussed using a classical ensemble representation of Heisenberg's equations of motion. Excitation of the intermediate B state by an ultrafast pulse creates a coherent vibrational motion in this bound state. The localized solvent-induced coupling to the a state results in the spawning of dissociation products which occurs in bursts, twice per vibrational period. Equations of motion for both the electronic and nuclear degrees of freedom in each electronic state are derived from a quantum mechanical Hamiltonian. These equations are coupled whenever two electronic states are interacting. The formalism includes coupling to the surrounding classical solvent. Comparison with a pump-probe experiment is provided.
The assumption that cellular injury induced in infectious and in inflammatory sites might be the result of a well-orchestrated, synergistic "cross-talk" among oxidants, membrane-damaging agents, proteinases, and xenobiotics was further investigated in a tissue culture model employing monkey kidney epithelial cells (BGM) labeled either with 51 chromium or [3H]arachidonate. The cells could be killed in a synergistic manner following exposure to combinations among H2O2 and the following membrane-damaging agents: streptolysins S (SLS) and O (SLO), poly-D-lysine, arachidonic acid, eicosapentanoic acid, arachidic acid, lysophosphatidylcholine, lysophosphatidylinositol, lysophosphatidylglycerol, ethanol, and sodium taurocholate. Peroxyl radical (ROO) generated by azobisdiamidinopropane dihydrochloride (AAPH) further enhanced cell killing induced by SLS, SLO, and nitroprusside when combined with H2O2 and trypsin. BGM cells labeled either with chromium or with tritiated arachidonate, which had been treated with increasing concentrations of sodium nitroprusside (a donor of NO) and with subtoxic amounts of SLS and H2O2, were also killed in a synergistic manner and also lost a substantial amounts of their arachidonate label. Both cell killing and the release of membrane lipids were totally inhibited by hemoglobin (an NO scavenger) but not by methylene blue, an antagonist of NO2-BGM cells that had been treated with increasing concentrations of taurocholic acid were killed in a synergistic manner by a mixture of subtoxic amounts of ethanol, H2O2, and crystalline trypsin (quadruple synergism). Normal human serum possessing IgM complement-dependent cytotoxic antibodies against Ehrlich ascites tumor cells were killed in a dose-dependent fashion. Cell killing was doubled by the addition of H2O2. Cell killing and the release of membrane lipids by all the mixture of agonists tested were both strongly inhibited by the antioxidants catalase, Mn2+, vitamin A, and by fresh carrot juice. It appears that in order to overcome the antioxidant capacities of the epithelial cells, a variety of membrane-damaging agents had to be present in the reaction mixtures. Taken together, it might be speculated that the killing of mammalian cells in infectious and in inflammatory sites is a synergistic phenomenon that might be inhibited by antagonizing the cross-talk among the various proinflammatory agonists generated by microorganisms by activated phagocytes or by combinations among these agents. Our studies might also open up new approaches to the assessment of the toxicity of xenobiotics and of safe drugs to mammalian cells by employing tissue culture techniques.
An iterated map which mimics the dynamics of a high Rydberg electron revolving around an anisotropic ionic core is described. The map specifies the change in the quantum numbers of the electron due to its passage near to the rotating core. Attention is centered on the limiting case of physical interest where the rotation of the core is faster than the orbital motion of the electron. While the map does provide for a very efficient way to numerically simulate the motion, its main advantage is in that it delineates the various dimensionless coupling parameters that govern the dynamics. To make contact with many experiments, external electrical and magnetic fields are included in the Hamiltonian. The stretch of the kinetic time axis due to the presence of external fields is discussed. The full map can be further approximated by a one-dimensional map which captures the essence of the dynamics. The primary aspects having to do with the three-dimensional character of the actual motion are incorporated in the magnitude of the dimensionless coupling parameters. A simple but realistic limit of the one-dimensional map is discussed which can be considered as the electron undergoing diffusion in its energy. The mean first passage time out of the detection window and the branching fractions for ionization vs. stabilization of the electron are computed in the diffusion approximation. As is experimentally observed, the lifetime of the high Rydberg states exhibits a maximal value when plotted vs. the energy.
