Probing dipole-forbidden autoionizing states by isolated attosecond pulses

We propose a general technique to retrieve the information of dipole-forbidden resonances in the autoionizing region. In the simulation, a helium atom is pumped by an isolated attosecond pulse in the extreme ultraviolet (EUV) combined with a few-femtosecond laser pulse. The excited wave packet consists of the $^1S$, $^1P$, and $^1D$ states, including the background continua, near the $2s2p(^1P)$ doubly excited state. The resultant electron spectra with various laser intensities and time delays between the EUV and laser pulses are obtained by a multilevel model and an ab initio time-dependent Schr\"odinger equation calculation. By taking the ab initio calculation as a "virtual measurement", the dipole-forbidden resonances are characterized by the multilevel model. We found that in contrast to the common assumption, the nonresonant coupling between the continua plays a significant role in the time-delayed electron spectra, which shows the correlation effect between photoelectrons before they leave the core. This technique takes the advantages of ultrashort pulses uniquely and would be a timely test for the current attosecond technology.Comment: 10 pages, 6 figure

DEVELOPMENT AND CHARACTERIZATION OF NOVEL MONOCLONAL ANTIBODIES FOR STUDYING PRION PATHOGENESIS

Monoclonal antibodies (mAbs) recognizing different regions of PrP are potential tools in the study of prion diseases and immunotherapy. We used shuffled recombinant prion protein containing elk and mouse PrP as antigen to produce monoclonal antibodies in mice. We found that mAb 5C6 mapped to a discontinuous epitope comprised of amino acid 132 and 158 (mouse numbering). Monoclonal anibody 9E9 which maps to a unique N-terminal epitope at amino acid preferentially recognized cervid PrP. In contrast, the epitope of mAb 9H9 is located in the C-terminus and only reacted with mouse and hamster. The epitope for mAb 7H11 appears to be affected by the glycosylation of PrP and by the presence or absence of the disulfide bond. To confirm the epitopes of these mAbs, we constructed elk and mouse mutants both with and without reactivity to 5C6 and 9E9. We then used these mutants to investigate the effect of each epitope on the conversion of PrPC to PrPsc. In one approach to map the epitopes of newly-generated monoclonal antibodies (mAbs), we generated a series of contiguous ten amino acids deletion constructs spanning amino acids 107 to 230 and expressed these recombinant proteins in mammalian cells (RK13) or bacteria. Using Western blotting, all deletion constructs could be recognized with antibodies to the extreme C-terminus of PrP, or the N-terminal region upstream of the structured globular domain of PrP. However, mAb 5C6 failed to react with all internally deleted PrP constructs expressed in mammalian cells, and to a lesser extent bacterially produced mutant recombinant proteins. We confirmed the surprising result using the well-defined antibodies 6H4 and D18, which recognize epitopes in the same internal region as 5C6. Our results suggest the formation of an ultra-stable, SDS-resistant conformation in PrP harboring deletions mutations in the globular domain of PrP. We hypothesize that epitope burying within this stable conformation(s) precludes mAb recognition by 5C6, 6H4 and D18. It will be of extreme interest to determine the relationship of this previously undefined PrP conformation to the pathogenic process of PrP conformational change

Photoionization of the Be Isoelectronic Sequence: Relativistic and Nonrelativistic R-Matrix Calculations

The photoionization of the beryllium-like isoelectronic series has been studied. The bound state wave functions of the target ions were built with CIV3 program. The relativistic Breit-Pauli R-matrix method was used to calculate the cross sections in the photon energy range between the ionization threshold and 1s24f7/2 threshold for each ion. For the total cross sections of Be, B+, C+2, N+3, and O+4, our results match experiment well. The comparison between the present work and other theoretical works are also discussed. We show the comparison with our LS results as it indicates the importance of relativistic effects on different ions. In the analysis, the resonances converging to 1s22lj and 1s23lj were identified and characterized with quantum defects, energies and widths using the eigenphase sum methodology. We summarize the general appearance of resonances along the resonance series and along the isoelectronic sequence. Partial cross sections are also reported systematically along the sequence. All calculations were performed on the NERSC system

Assessing the Stress-relief Benefit of Outdoor Travel Using Physiological and Psychological Measures

Tourism, which can be defined as leisure travels outside an individual’s usual environment, has been widely recognized as a necessity of human life (Richards 1999). Thus, scholars from different disciplines have paid increasing attention to the topic of travel benefits (Chen, Petrick, and Shahvali 2016a). For example, several studies have found that leisure travels can help relieve stress and anxiety (Frtiz and Sonnentag 2006; Strauss-Blasche et al. 2005; Westman and Etzion 2001), which is arguably an important finding because chronic stress can lead to poor health conditions (Matousek, Dobkin, and Pruessner 2010). However, most studies examining the stress relief benefit of travel only used psychological measures by asking respondents to self-report their perceived levels of stress (Chen and Petrick 2013). As it is well-documented that there are often discrepancies between physiological measures and psychological perceptions of the same affective state (Matousek et al. 2010), the goal of this study is to assess how the stress level fluctuates during an outdoor travel using the physiological measure of salivary cortisol as well as the psychological perceptions of stress

Near-ionization-threshold emission in atomic gases driven by intense sub-cycle pulses

We study theoretically the dipole radiation of a hydrogen atom driven by an intense sub-cycle pulse. The time-dependent Schr\"odinger equation for the system is solved by ab initio calculation to obtain the dipole response. Remarkably, a narrowband emission lasting longer than the driving pulse appears at a frequency just above the ionization threshold. An additional calculation using the strong field approximation also recovers this emission, which suggests that it corresponds to the oscillation of nearly-bound electrons that behave similarly to Rydberg electrons. The predicted phenomenon is unique to ultrashort driving pulses but not specific to any particular atomic structure.Comment: 8 pages, 2 figure