Nonadiabatic generation of coherent phonons

The time-dependent density functional theory (TDDFT) is the leading computationally feasible theory to treat excitations by strong electromagnetic fields. Here the theory is applied to coherent optical phonon generation produced by intense laser pulses. We examine the process in the crystalline semimetal antimony (Sb), where nonadiabatic coupling is very important. This material is of particular interest because it exhibits strong phonon coupling and optical phonons of different symmetries can be observed. The TDDFT is able to account for a number of qualitative features of the observed coherent phonons, despite its unsatisfactory performance on reproducing the observed dielectric functions of Sb. A simple dielectric model for nonadiabatic coherent phonon generation is also examined and compared with the TDDFT calculations.Comment: 19 pages, 11 figures. This is prepared for a special issue of Journal of Chemical Physics on the topic of nonadiabatic processe

Time-dependent density functional theory for strong electromagnetic fields in crystalline solids

We apply the coupled dynamics of time-dependent density functional theory and Maxwell equations to the interaction of intense laser pulses with crystalline silicon. As a function of electromagnetic field intensity, we see several regions in the response. At the lowest intensities, the pulse is reflected and transmitted in accord with the dielectric response, and the characteristics of the energy deposition is consistent with two-photon absorption. The absorption process begins to deviate from that at laser intensities ~ 10^13 W/cm^2, where the energy deposited is of the order of 1 eV per atom. Changes in the reflectivity are seen as a function of intensity. When it passes a threshold of about 3 \times 1012 W/cm2, there is a small decrease. At higher intensities, above 2 \times 10^13 W/cm^2, the reflectivity increases strongly. This behavior can be understood qualitatively in a model treating the excited electron-hole pairs as a plasma.Comment: 27 pages; 11 figure

Glueball mass from quantized knot solitons and gauge-invariant gluon mass

We propose an approach which enables one to obtain simultaneously the glueball mass and the gluon mass in the gauge-invariant way to shed new light on the mass gap problem in Yang-Mills theory. First, we point out that the Faddeev (Skyrme--Faddeev-Niemi) model can be induced through the gauge-invariant vacuum condensate of mass dimension two from SU(2) Yang-Mills theory. Second, we obtain the glueball mass spectrum by performing the collective coordinate quantization of the topological knot soliton in the Faddeev model. Third, we demonstrate that a relationship between the glueball mass and the gluon mass is obtained, since the gauge-invariant gluon mass is also induced from the relevant vacuum condensate. Finally, we determine physical values of two parameters in the Faddeev model and give an estimate of the relevant vacuum condensation in Yang-Mills theory. Our results indicate that the Faddeev model can play the role of a low-energy effective theory of the quantum SU(2) Yang-Mills theory.Comment: 17 pages, 2 figures, 3 tables; a version accepted for publication in J. Phys. A: Math. Gen.; Sect. 2 and sect. 5 (old sect. 4) are modified. Sect. 4, Tables 1 and Table 3 are adde

Phase transitions of a tethered surface model with a deficit angle term

Nambu-Goto model is investigated by using the canonical Monte Carlo simulations on fixed connectivity surfaces of spherical topology. Three distinct phases are found: crumpled, tubular, and smooth. The crumpled and the tubular phases are smoothly connected, and the tubular and the smooth phases are connected by a discontinuous transition. The surface in the tubular phase forms an oblong and one-dimensional object similar to a one-dimensional linear subspace in the Euclidean three-dimensional space R^3. This indicates that the rotational symmetry inherent in the model is spontaneously broken in the tubular phase, and it is restored in the smooth and the crumpled phases.Comment: 6 pages with 6 figure

Ductile rupture of prestrained X100 pipeline steel sheets

International audienceThe mechanical and damage behavior of a X100 steel after prestrain is studied in thiswork. Experimental results show both a plastic and rupture anisotropy: the T direction exhibits ahigher ultimate stress but the lowest ductility and toughness. Prestrain reduces ductility and crackgrowth resistance. A model able to represent the plastic and damage behaviour of the material beforeand after prestrain is proposed. The model incorporates plastic anisotropy, kinematic hardening, voidgrowth of the primary cavities, nucleation of secondary voids on carbides. Using the model afterimplementation in a FE software, allows to reproduce experimental trends

Mercury emissions and stable isotopic compositions at Vulcano Island (Italy)

Sampling and analyses methods for determining the stable isotopic compositions of Hg in an active volcanic system were tested and optimized at the volcanic complex of Vulcano (Aeolian Islands, Italy). Condensed gaseous fumarole Hg(fum) T , plume gaseous elemental Hg(g) 0 and plume particulate Hg(p) II were obtained at fumaroles F0, F5, F11, and FA. The average total Hg emissions, based on HgT/SO2 in condensed fumarolic gases and plumes, range from 2.5 to 10.1 kg y−1, in agreement with published values [Ferrara, R., Mazzolai, B., Lanzillotta, E., Nucaro, E., Pirrone, N., 2000. Volcanoes as emission sources of atmospheric mercury in the Mediterranean Basin. Sci. Total Environ. 259(1–3), 115–121; Aiuppa, A., Bagnato, E., Witt, M.L.I., Mather, T.A., Parello, F., Pyle, D.M., Martin, R.S., 2007. Real-time simultaneous detection of volcanic Hg and SO2 at La Fossa Crater, Vulcano (Aeolian Islands, Sicily). Geophys. Res. Lett. 34(L21307).]. Plume Hg(p) II increases with distance from the fumarole vent, at the expense of Hg(g) 0 and indicates significant in-plume oxidation and condensation of fumarole Hg(fum) T . Relative to the NIST SRM3133 Hg standard, the stable isotopic compositions of Hg are δ202Hg(fum) T =−0.74‰±0.18 (2SD, n=4) for condensed gaseous fumarole Hg(fum) T , δ202Hg(g) 0 =−1.74‰±0.36 (2SD, n=1) for plume gaseous elemental Hg(g) 0 at the F0 fumarole, and δ202Hg(p) II =−0.11‰±0.18 (2SD, n=4) for plume particulate Hg(p) II . The enrichment of Hg(p) II in the heavy isotopes and Hg(g) 0 in the light isotopes relative to the total condensed fumarolic Hg(fum) T gas complements the speciation data and demonstrates a gas-particle fractionation occurring after the gas expulsion inambient T° atmosphere. A first order Rayleigh equilibriumcondensation isotope fractionation model yields a fractionation factor αcond-gas of 1.00135±0.00058

Osteopontin Expression during Early Cerebral Ischemia-Reperfusion in Rats: Enhanced Expression in the Right Cortex Is Suppressed by Acetaminophen

Osteopontin (OPN) is a pleiotropic protein implicated in various inflammatory responses including ischemia-reperfusion (I-R) injury. Two distinct forms of the protein have been identified: an extensively studied secreted form (sOPN) and a less-well-known intracellular form (iOPN). Studies have shown that increased OPN expression parallels the time course of macrophage infiltration into injured tissue, a late event in the development of cerebral infarcts. sOPN has been suggested to promote remodeling of the extracellular matrix in the brain; the function of iOPN may be to facilitate certain signal transduction processes. Here, we studied OPN expression in adult male Sprague-Dawley rats subjected to global forebrain I-R injury. We found iOPN in the cytoplasm of both cortices and the hippocampus, but unexpectedly only the right cortex exhibited a marked increase in the iOPN level after 45 min of reperfusion. Acetaminophen, a drug recently shown to decrease apoptotic incidence, caspase-9 activation, and mitochondrial dysfunction during global I-R, significantly inhibited the increase in iOPN protein in the right cortex, suggesting a role for iOPN in the response to I-R injury in the right cortex

Solid State Neutral Particle Analyzer Array on NSTX

A Solid State Neutral Particle Analyzer (SSNPA) array has been installed on the National Spherical Torus Experiment (NSTX). The array consists of four chords viewing through a common vacuum flange. The tangency radii of the viewing chords are 60, 90, 100, and 120 cm. They view across the three co-injection neutral beam lines (deuterium, 80 keV (typ.) with tangency radii 48.7, 59.2, and 69.4 cm) on NSTX and detect co-going energetic ions. A silicon photodiode used was calibrated by using a mono-energetic deuteron beam source. Deuterons with energy above 40 keV can be detected with the present setup. The degradation of the performance was also investigated. Lead shots and epoxy are used for neutron shielding to reduce handling any hazardous heavy metal. This method also enables us to make an arbitrary shape to be fit into the complex flight tube