Photoexcitation and ionization in molecular oxygen: Theoretical studies of electronic transitions in the discrete and continuous spectral intervals

Theoretical studies of valence-electron (1πg, 1πu, 3σg) photoexcitation and ionization cross sections in molecular oxygen are reported employing separated-channel static-exchange calculations and the Stieltjes–Tchebycheff moment-theory technique. As in previously reported investigations of photoexcitation and ionization in small molecules following this approach, canonical Hartree–Fock orbitals, large Gaussian basis sets, and many-electron eigenstates of correct symmetry are used in defining appropriate noncentral static-exchange potentials and in computations of the appropriate discrete and continuum transition strengths. It is particularly important in molecular oxygen to incorporate the appropriate ionic parentages of the various photoionization multiplet states in order to obtain the correct partial-channel cross sections. The calculated discrete series associated with 1πg excitation are found to be in good agreement with available experimental assignments and previously reported theoretical studies, and the predicted states associated with 1πu and 3σg excitations are in general accord with assignments for the higher series based on spectral and quantum-defect analysis. Although the observed photoelectron spectra and photoionization cross sections are relatively complex, the calculated total vertical electronic photoabsorption cross section and the partial-channel photoionization cross sections for production of X 2πg, a 4πu, A 2πu, 2 2πu, 3 3IIu, b 4∑g-, and B 2∑g-, ionic states are found to be in good accord with recent synchrotron radiation, line-source, electron-impact, and (e,2e) dipole oscillator-strength measurements when proper account is taken of the parentages of the various multiplet states. The partial-channel cross sections exhibit resonancelike structures that can be attributed to contributions from diabatic valencelike virtual states that appear in the appropriate photoionization continua, rather that in the corresponding discrete spectral intervals. These features in the dipole spectrum of molecular oxygen are discussed and are contrasted and compared with the results of previously reported related studies in molecular nitrogen and carbon monoxide

Possible world-wide middle miocene iridium anomaly and its relationship to periodicity of impacts and extinctions

In a study of one million years of Middle Miocene sediment deposition in ODP Hole 689B in the Weddell Sea near Antarctica, a single iridium (Ir) anomaly of 44 (+ or - 10) x 10 to the 12th gram Ir per gram rock (ppt) was observed in core 6H, section 3, 50 to 60 cm, after background contributions associated with manganese precipitates and clay are subtracted. The ODP Hole 689B is 10,000 km away from another site, DSDP Hole 588B in the Tasman Sea north of New Zealand, where a single Ir anomaly of 144 + or - 7 ppt over a background of 11 ppt was found in an earlier study of 3 million years of deposition. From chemical measurements the latter deposition was thought to be impact-related. Ir measurements were made, following neutron activation, with the Iridium Coincidence Spectrometer. The age vs depth calibration curves given in the DSDP and ODP preliminary reports indicate the ages of the Iranomalies are identical, 11.7 million years, but the absolute and relative uncertainties in the curves are not known. Based on the newest age data the age estimate is 10 million years. As the Ir was deposited at the two sites at about the same time and they are one quarter of the way around the world from each other it seems likely that the deposition was world-wide. The impact of a large asteroid or comet could produce the wide distribution, and this data is supportive of the impact relationship deduced for Deep Sea Drilling Project (DSDP) 588B from the chemical evidence. If the surface densities of Ir at the two sites are representative of the world-wide average, the diameter of a Cl type asteroid containing the necessary Ir would be 3 + or - 1 km, which is large enough to cause world-wide darkness and hence extinctions although the latter point is disputed

Wetting layer thickness and early evolution of epitaxially strained thin films

We propose a physical model which explains the existence of finite thickness wetting layers in epitaxially strained films. The finite wetting layer is shown to be stable due to the variation of the non-linear elastic free energy with film thickness. We show that anisotropic surface tension gives rise to a metastable enlarged wetting layer. The perturbation amplitude needed to destabilize this wetting layer decreases with increasing lattice mismatch. We observe the development of faceted islands in unstable films.Comment: 4 pages, 3 eps figure

Giacomo Serpotta e il "pareggiamento delle arti": la decorazione degli oratori fra manipolazione vitalistica e vocazione classicista

ABSTRACT GIACOMO SERPOTTA AND THE “EQUALIZATION OF THE ARTS”: DECORATION OF THE ORATORIES BETWEEN VITALISTIC MANIPULATION AND CLASSICIST VOCATION Ettore Sessa The value of the whole of Giacomo Serpotta's artistic vision in the orchestration of the figu¬rative apparatuses of his oratories was certainly one of the principal primers of his historical-critical raising in the modernist period. In 1901 Mauceri and in 1911 Ricci and Basile heighten a profile of it, however synthetic, of angling and above all of different breath from the rediscovery realized in positivist age. Classifiable, in fact, among the eighteenth century precedents of Gesamtkunstwerk aesthetical plant (according to a rather diffused custom within the artistic historiography of modernist culturaI area or of decadentist origin, as in different formalistic demonstrations of the wealthiest society Belle Époque) the progress of Serpottas artistic way towards tangible expressions of the idea of «the whole work of art» has a unmistakable im¬print of his and, at the same time, a feasibility thanks to the plasticism of gestures and to the uni¬tary multiplicity of his modeled. In his oratories arrangements the "realist" component, not exempted from hedonistic sensual witty remarks, acts on a foundation of Hellenic taste (also in the use of profiles and architectural elements). With wise modulation and with dosing diversified for intensity, according the nature of the subjects, combines history (see the «teatrini» with perspective sceneries, among which the Lepanto battle), micro history (from feminine allegorical subjects, to attractive dames modernly adorned with ends and brocades, to "picciotti" proudly ragged and to the anecdotal of the daily life), mysticism (from the devotional subjects to the allegories of the virtues), obscurity (from numerological components to philosophical attributes) and, finally, mythology (from the allegorical correspondences between Christianity and paganism to classical simbology). Despite the actual halving of this group of oratories (was destroyed by traumatic events as earthquakes and war actions, or by villainous demolitions big part of Serpottas works, among which the SS. Sacrament oratories to Kalsa and those of Saint Maria del Ponticello), the comparison among the palermitan examples reached us entire allows the individualization of the characters of originality typical of the generaI composition, over that of those figurative unanimously accredited among the most valid of the late- Baroque European sculpture. The typical scheme of these oratories, places with a strong secular imprint (predisposed as for cultural reunions how as for the preclusive congregational assemblies, to which the only ones not admitted affiliate were the artists), has as constants: the hall with a rectangular plant; the skiff or pavilion vault with plaster decorations dissimulating the constructive geometry; the sculptural wall register above of a high plinth; windows on the greatest sides (in number of three); two doors in the counterfacade, originally with desk for the assemblies in central position, below the principal devotional allegorical composition. The first oratory to which Giacomo Serpotta imposes an unitary imprint, except the cappellone only defined between 1717 and the following year) is that of SS. Rosary in S. Cita; he has worked since 1685 to 1688 on behalf of SS. Rosary Company. Serpotta is twenty nine, but already since almost ten years, after the apprenticeship with subordinate roles, he showed himself almost beginning in mute with the decorations of Madonna of the Pity church in Monreale, where he operated like Procopio De' Ferrari's collaborator, and perhaps with his interventions in 1678 in the lateral walls of S. Mercurio oratory, to which follow the 1679 decoration works in the Charity oratory in St. Bartholomeo of the Incurable people (no more existing), perhaps S. Pietro and S. Paolo statues dating back to 1680 for the greatest altar in Gancia church, the marble model for Charles H's equestrian monument for Messina (then realized in 1684) and during the two years 1683-1684 the scenic decorations for the transept altars of Carmine Maggiore church (where he collaborates with his brother Giuseppe and realizes the couples of twisted columns gilded and commented by a theory of plaster miniature scenes disposed according to a spiral development). Immediately after S. Cita oratory he realized, between 1688 and 1691, the decorative apparatuses of the Sacrament oratory in S. Nicolò to Kalsa (destroyed because of 1823 earthquake). Only eight years after the completion of this work (about which it was hypothesized that it were an advancement in comparison to the intervention in S. Cita) Giacomo Serpotta is entrusted by S. Francesco from Assisi and S. Lorenzo Companies to realize the complex allegorical and explanatory cycle of the plasters of S. Lorenzo orato¬ry. He worked partly on Giacomo Amato's sketches (to which are probably owed the reform interventions that confer to this oratory a great architectural "squaring" in comparison to others), completing the presbytery within 1706, while already from 1701 he is busy in the definition of the walls. In 1703 he began the counter facade with the monumental wall framework and high-relief representation of St. Lorenzo Martyrdom

Stability of Solid State Reaction Fronts

We analyze the stability of a planar solid-solid interface at which a chemical reaction occurs. Examples include oxidation, nitridation, or silicide formation. Using a continuum model, including a general formula for the stress-dependence of the reaction rate, we show that stress effects can render a planar interface dynamically unstable with respect to perturbations of intermediate wavelength

Stress-driven instability in growing multilayer films

We investigate the stress-driven morphological instability of epitaxially growing multilayer films, which are coherent and dislocation-free. We construct a direct elastic analysis, from which we determine the elastic state of the system recursively in terms of that of the old states of the buried layers. In turn, we use the result for the elastic state to derive the morphological evolution equation of surface profile to first order of perturbations, with the solution explicitly expressed by the growth conditions and material parameters of all the deposited layers. We apply these results to two kinds of multilayer structures. One is the alternating tensile/compressive multilayer structure, for which we determine the effective stability properties, including the effect of varying surface mobility in different layers, its interplay with the global misfit of the multilayer film, and the influence of asymmetric structure of compressive and tensile layers on the system stability. The nature of the asymmetry properties found in stability diagrams is in agreement with experimental observations. The other multilayer structure that we study is one composed of stacked strained/spacer layers. We also calculate the kinetic critical thickness for the onset of morphological instability and obtain its reduction and saturation as number of deposited layers increases, which is consistent with recent experimental results. Compared to the single-layer film growth, the behavior of kinetic critical thickness shows deviations for upper strained layers.Comment: 27 pages, 11 figures; Phys. Rev. B, in pres

Morphology of epitaxial core-shell nanowires

We analyze the morphological stability against azimuthal, axial, and general helical perturbations for epitaxial core-shell nanowires in the growth regimes limited by either surface diffusion or evaporation-condensation surface kinetics. For both regimes, we find that geometric parameters (i.e., core radius and shell thickness) play a central role in determining whether the nanowire remains cylindrical or its shell breaks up into epitaxial islands similar to those observed during Stranski-Krastanow growth in thin epilayers. The combination of small cores and rapid growth of the shell emerge as key ingredients for stable shell growth. Our results provide an explanation for the different core-shell morphologies reported in the Si-Ge system experimentally, and also identify a growth-induced intrinsic mechanism for the formation of helical nanowires.Comment: In press, Nano Letters (7 pages, 4 figures

The Impact of Inpatient Boarding on ED Efficiency: A Discrete-Event Simulation Study

In this study, a discrete-event simulation approach was used to model Emergency Department’s (ED) patient flow to investigate the effect of inpatient boarding on the ED efficiency in terms of the National Emergency Department Crowding Scale (NEDOCS) score and the rate of patients who leave without being seen (LWBS). The decision variable in this model was the boarder-released-ratio defined as the ratio of admitted patients whose boarding time is zero to all admitted patients. Our analysis shows that the Overcrowded+ (a NEDOCS score over 100) ratio decreased from 88.4% to 50.4%, and the rate of LWBS patients decreased from 10.8% to 8.4% when the boarder-released-ratio changed from 0% to 100%. These results show that inpatient boarding significantly impacts both the NEDOCS score and the rate of LWBS patient and this analysis provides a quantification of the impact of boarding on emergency department patient crowding

Towards an Embodied Sociology of War

While sociology has historically not been a good interlocutor of war, this paper argues that the body has always known war, and that it is to the corporeal that we can turn in an attempt to develop a language to better speak of its myriad violences and its socially generative force. It argues that war is a crucible of social change that is prosecuted, lived and reproduced via the occupation and transformation of myriad bodies in numerous ways from exhilaration to mutilation. War and militarism need to be traced and analysed in terms of their fundamental, diverse and often brutal modes of embodied experience and apprehension. This paper thus invites sociology to extend its imaginative horizon to rethink the crucial and enduring social institution of war as a broad array of fundamentally embodied experiences, practices and regimes