Nonsequential Double Recombination in Intense Laser Fields

A second plateau in the harmonic spectra of laser-driven two-electron atoms is observed both in the numerical solution of a low-dimensional model helium atom and using an extended strong field approximation. It is shown that the harmonics well beyond the usual cut-off are due to the simultaneous recombination of the two electrons, which were emitted during different, previous half-cycles. The new cut-off is explained in terms of classical trajectories. Classical predictions and the time-frequency analysis of the ab initio quantum results are in excellent agreement. The mechanism corresponds to the inverse single photon double ionization process in the presence of a (low frequency) laser field.Comment: 4 pages, RevTeX, v2 with an extended strong field approximation treatment of the process; instead, v1 describes an attosecond control scheme to enhance the proces

Momentum distributions in time-dependent density functional theory: Product phase approximation for non-sequential double ionization in strong laser fields

We investigate the possibility to deduce momentum space properties from time-dependent density functional calculations. Electron and ion momentum distributions after double ionization of a model Helium atom in a strong few-cycle laser pulse are studied. We show that, in this case, the choice of suitable functionals for the observables is considerably more important than the choice of the correlation potential in the time-dependent Kohn-Sham equations. By comparison with the solution of the time-dependent Schroedinger equation, the insufficiency of functionals neglecting electron correlation is demonstrated. We construct a functional of the Kohn-Sham orbitals, which in principle yields the exact momentum distributions of the electrons and the ion. The product-phase approximation is introduced, which reduces the problem of approximating this functional significantly.Comment: 8 pages, 5 figures, RevTeX

Wissenschaftliche Auswertung der Hamburger Dioxin Kohorte: Abschlussbericht

Das Forschungsprojekt ist ein Follow-up einer Studienkohorte von rd. 1.600 ehemaligen Mitarbeitern der Firma Boehringer in Hamburg, die 1952 bis 1984 bei der Produktion von Pflanzenschutzmitteln hohen Konzentrationen von Dioxin sowie weiteren Substanzen wie Furanen und Benzol ausgesetzt waren. Ziel des Projekts war die Untersuchung von Langzeitwirkungen im Hinblick auf die Mortalität der Betroffenen. Im Ergebnis zeigten sich geschlechtsspezifisch differenziert statistisch erhöhte Risiken der Gesamtmortalität sowie für bestimmte Tumorerkrankungen. Allerdings bestehen für die Studie verschiedene Limitationen wie der nicht bekannte Raucherstatus, die z. T. geringe Fallzahl bei einzelnen Tumorerkrankungen sowie fehlende Messungen am Arbeitsplatz. Insgesamt erbrachte die Studie neue Hinweise auf Ursachenzusammenhänge zwischen Dioxin und bestimmten Erkrankungen

Observation and modeling of energetic particles at synchronous orbit on July 29, 1977

In the twelve hours following a worldwide storm, there was a series of at least four magnetospheric substorms, the last and largest of which exhibited an expansion phase onset at approximately 1200 UT. Data from six spacecraft in three general local time groupings (0300, 0700, and 1300 LT) were examined and vector magnetic field data and energetic electron and ion data from approximately 15 keV to 2 MeV were employed

Gradual diffusion and punctuated phase space density enhancements of highly relativistic electrons: Van Allen Probes observations

Abstract The dual-spacecraft Van Allen Probes mission has provided a new window into mega electron volt (MeV) particle dynamics in the Earth\u27s radiation belts. Observations (up to E ~10 MeV) show clearly the behavior of the outer electron radiation belt at different timescales: months-long periods of gradual inward radial diffusive transport and weak loss being punctuated by dramatic flux changes driven by strong solar wind transient events. We present analysis of multi-MeV electron flux and phase space density (PSD) changes during March 2013 in the context of the first year of Van Allen Probes operation. This March period demonstrates the classic signatures both of inward radial diffusive energization and abrupt localized acceleration deep within the outer Van Allen zone (L ~4.0 ± 0.5). This reveals graphically that both competing mechanisms of multi-MeV electron energization are at play in the radiation belts, often acting almost concurrently or at least in rapid succession. Key Points Clear observations to higher energy than ever before Precise detection of where and how acceleration takes place Provides new eyes on megaelectron Volt

MeV magnetosheath ions energized at the bow shock

A causal relationship between midlatitude magnetosheath energetic ions and bow shock magnetic geometry was previously established for ion energy up to 200 keV e−1 for the May 4, 1998, storm event. This study demonstrates that magnetosheath ions with energies above 200 keV up to 1 MeV simply extend the ion spectrum to form a power law tail. Results of cross-correlation analysis suggest that these ions also come directly from the quasi-parallel bow shock, not the magnetosphere. This is confirmed by a comparison of energetic ion fluxes simultaneously measured in the magnetosheath and at the quasi-parallel bow shock when both regions are likely connected by the magnetic field lines. We suggest that ions are accelerated at the quasi-parallel bow shock to energies as high as 1 MeV and subsequently transported into the magnetosheath during this event

Evaluating the Productive Energy Content of High-Protein Distillers Dried Grains in Swine Diets

A total of 300 pigs (DNA 400 × 200), initially 24.5 lb, were used in a study to evaluate the effects of increasing amounts of high-protein distillers dried grains (HP DDG) on growth performance, and to estimate the productive energy of HP DDG. Pens were allocated with 5 pigs each and fed a common diet for 21 d after weaning. Then, pens were assigned to treatments in a randomized complete block design. There were 5 treatments with 12 pen replicates per treatment. Treatments consisted of 0, 10, 20, 30, or 40% HP DDG. Pigs were weighed weekly for 21 d to evaluate average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (F/G). Caloric efficiency was obtained by multiplying ADFI by kcal of net energy (NE) per lb of diet and dividing by ADG. Productive energy was estimated based on caloric efficiency relative to the diet without HP DDG. Data were analyzed with the GLIMMIX procedure of SAS with block as a random effect and pen as the experimental unit. From d 0 to 7 and 7 to 14, increasing amounts of HP DDG linearly decreased (P \u3c 0.01) ADG, which was mainly driven by lower (linear, P \u3c 0.01) ADFI. The inclusion of HP DDG negatively impacted (linear; P \u3c 0.01) F/G from d 0 to 7 with no evidence for differences from d 7 to 14 (P ≥ 0.321). From d 14 to 21, there was a decrease (linear, P \u3c 0.01) in ADFI and improvement (linear, P = 0.029) in F/G as HP DDG inclusion increased. Overall (d 0 to 21), pigs fed diets with increasing HP DDG had a linear decrease (P \u3c 0.01) in ADG, ADFI, and final body weight. There was a tendency for a quadratic response (P = 0.051) in F/G, with the best F/G observed for pigs fed diets with 40% HP DDG. There was a linear reduction (P \u3c 0.01) in caloric efficiency with increasing amounts of HP DDG, indicating an underestimation of HP DDG NE. The productive energy of HP DDG was estimated as 1,218 kcal/lb or 97.3% of corn NE

In Vivo Biotransformation of 3,3′,4,4′-Tetrachlorobiphenyl by Whole Plants−Poplars and Switchgrass

Polychlorinated biphenyls (PCBs) are widely distributed persistent organic pollutants. In vitro research has shown that plant cell cultures might transform lower chlorinated congeners to hydroxylated PCBs, but there are few studies on in vivo metabolism of PCBs by intact whole plants. In this research, poplar plants (Populus deltoides × nigra, DN34) and switchgrass (Panicum vigratum, Alamo) were hydroponically exposed to 3,3′,4,4′-tetrachlorobiphenyl (CB77). Metabolism in plants occurred rapidly, and metabolites were detected after only a 24 h exposure. Rearrangement of chlorine atoms and dechlorination of CB77 by plants was unexpectedly observed. In addition, poplars were able to hydroxylate CB77 and the metabolite 6-hydroxy-3,3′,4,4′-tetrachlorobiphenyl (6-OH-CB77) was identified and quantified. Hybrid poplar was able to hydroxylate CB77, but switchgrass was not, suggesting that enzymatic transformations are plant specific. Sulfur-containing metabolites (from the action of sulfotransferases) were investigated in this study, but they were not detected in either poplar or switchgrass

"We can remember it for you": location, memory, and commodification in social networking sites

This article explores the spatial self through the performative aspects of location sharing and geotagging in the process of self-representation on social networking sites (SNSs). Based on the legacy of early experimentations with location-based technologies for social interaction, the article asserts that the representation of location in SNSs has more temporal than spatial attributes. The article explores the immediacy of networks and the different kinds of temporality encountered in SNSs to address the commodification of geotagged content uploaded on SNSs. Location-based data are valuable commodities bought and sold in the market. Therefore, the act of archiving memories on SNSs is commodified and performed within the predetermined functions and actions set within the SNSs’ interfaces. SNSs devise ways to keep users constantly interacting with the present moment in time and simultaneously create memories of the recent past while disclosing personal data that companies use for profit