Experimental ionization of atomic hydrogen with few-cycle pulses

We present the first experimental data on strong-field ionization of atomic hydrogen by few-cycle laser pulses. We obtain quantitative agreement at the 10% level between the data and an {\it ab initio} simulation over a wide range of laser intensities and electron energies

Site-directed mutagenesis of the glycine-rich loop of death associated protein kinase (DAPK) identifies it as a key structure for catalytic activity

AbstractDeath associated protein kinase (DAPK) is a calmodulin (CaM)-regulated protein kinase that is a therapeutic target for central nervous system (CNS) disorders. We report here the results of studies that test the hypothesis of McNamara et al. (2009) that conformational selection in DAPK's glycine-rich region is key for catalytic activity. The hypothesis was tested by site-directed mutagenesis of glutamine-23 (Q23) in the middle of this loop. The glycine-rich loop exhibits localized differences in structure among DAPK conformations that correlate with different stages of the catalytic cycle. Changing the Q23 to a Valine (V23), found at the corresponding position in another CaM regulated protein kinase, results in a reduced catalytic efficiency. High resolution X-ray crystal structures of various conformations of the Q23V mutant DAPK and their superimposition with the corresponding conformations from wild type catalytic domain reveal localized changes in the glycine-rich region. The effect of the mutation on DAPK catalytic activity and the finding of only localized changes in the DAPK structure provide experimental evidence implicating conformational selection in this domain with activity. This article is part of a Special Issue entitled: 11th European Symposium on Calcium

Unimolecular Reactions of Peroxy Radicals Formed in the Oxidation of α-pinene and β-pinene by Hydroxyl Radicals

Atmospheric oxidation of monoterpenes (emitted primarily by evergreen trees) is known to contribute to the formation and growth of aerosol particles. While recent research has tied the formation of organic aerosol to unimolecular chemistry of the organic peroxy radicals (RO_2) formed in the oxidation of monoterpenes, the fundamental physical chemistry of these RO_2 remains obscure. Here we use isomer-specific measurements and ab initio calculations to determine the unimolecular reaction rates and products of RO_2 derived from the hydroxyl radical (OH) oxidation of α-pinene and β-pinene. Among all of the structural isomers of the first-generation RO_2 from both monoterpenes, we find that the first-generation RO_2 produced following opening of the four-membered ring undergo fast unimolecular reactions (4 ± 2 and 16 ± 5 s^(–1) for α-pinene and β-pinene, respectively) at 296 K, in agreement with high-level ab initio calculations. The presence of the hydroxy group and carbon–carbon double bond in the ring-opened RO_2 enhances the rates of these unimolecular reactions, including endo-cyclization and H-shift via transition states involving six- and seven-membered rings. These reaction rate coefficients are sufficiently large that unimolecular chemistry is the dominant fate of these monoterpene-derived RO_2 in the atmosphere. In addition, the overall yields of first-generation α-pinene and β-pinene hydroxy nitrates, C_(10)H_(17)NO_4, at 296 K and 745 Torr are measured to be 3.3 ± 1.5% and 6.4 ± 2.1%, respectively, for conditions where all RO_2 are expected to react with NO ([NO] > 1000 ppbv). These yields are lower than anticipated

Electron-Impact Excitation from the (4p⁵5s) Metastable States of Krypton

Theoretical results from multistate semirelativistic Breit-Pauli R-matrix calculations and two first-order distorted-wave calculations are presented for electron-impact excitation of krypton from the (4p55s) J = 0,2 metastable states to the (4p55s) and (4p55p) manifolds. Except for a few cases, in which the method to account for relativistic effects becomes surprisingly critical, fair overall agreement between the predictions from the various theoretical models is achieved for intermediate and high energies. However, significant discrepancies remain with the few available experimental data

Personality Traits in Miners with Past Occupational Elemental Mercury Exposure

In this study, we evaluated the impact of long-term occupational exposure to elemental mercury vapor (Hg(0)) on the personality traits of ex-mercury miners. Study groups included 53 ex-miners previously exposed to Hg(0) and 53 age-matched controls. Miners and controls completed the self-reporting Eysenck Personality Questionnaire and the Emotional States Questionnaire. The relationship between the indices of past occupational exposure and the observed personality traits was evaluated using Pearson’s correlation coefficient and on a subgroup level by machine learning methods (regression trees). The ex-mercury miners were intermittently exposed to Hg(0) for a period of 7–31 years. The means of exposure-cycle urine mercury (U-Hg) concentrations ranged from 20 to 120 μg/L. The results obtained indicate that ex-miners tend to be more introverted and sincere, more depressive, more rigid in expressing their emotions and are likely to have more negative self-concepts than controls, but no correlations were found with the indices of past occupational exposure. Despite certain limitations, results obtained by the regression tree suggest that higher alcohol consumption per se and long-term intermittent, moderate exposure to Hg(0) (exposure cycle mean U-Hg concentrations > 38.7 < 53.5 μg/L) in interaction with alcohol remain a plausible explanation for the depression associated with negative self-concept found in subgroups of ex-mercury miners. This could be one of the reason for the higher risk of suicide among miners of the Idrija Mercury Mine in the last 45 years

Electron-Impact Excitation to the 4p⁵5s and 4p⁵5p Levels of Kr | Using Different Distorted-Wave and Close-Coupling Methods

Electron-impact excitation of the 4p55s and 4p55p levels of Kr I has been investigated in detail by calculating cross sections using distorted-wave and close-coupling approaches. The results are presented from the excitation thresholds up to 50 eV incident energy. They are contrasted among the different calculations and compared with other theoretical predictions and experimental data. Significant disagreement is found with many of the recent experimental data of Chilton et al. [Phys. Rev. A 62, 032714 (2000)]

Diffuse versus square-well confining potentials in modelling AA@C60_{60} atoms

Attention: this version-$2$ of the manuscript differs from its previously uploaded version-$1$ (arXiv:1112.6158v1) and subsequently published in 2012 J. Phys. B \textbf{45} 105102 only by a removed typo in Eq.(2) of version-$1$; there was the erroneous factor "2" in both terms in the right-hand-side of the Eq.(2) of version-$1$. Now that the typo is removed, Eq.(2) is correct. A perceived advantage for the replacement of a discontinuous square-well pseudo-potential, which is often used by various researchers as an approximation to the actual C$_{60}$ cage potential in calculations of endohedral atoms $A$@C$_{60}$, by a more realistic diffuse potential is explored. The photoionization of endohedral H@C$_{60}$ and Xe@C$_{60}$ is chosen as the case study. The diffuse potential is modelled by a combination of two Woods-Saxon potentials. It is demonstrated that photoionization spectra of $A$@C$_{60}$ atoms are largely insensitive to the degree $\eta$ of diffuseness of the potential borders, in a reasonably broad range of $\eta$'s. Alternatively, these spectra are found to be insensitive to discontinuity of the square-well potential either. Both potentials result in practically identical calculated spectra. New numerical values for the set of square-well parameters, which lead to a better agreement between experimental and theoretical data for $A$@C$_{60}$ spectra, are recommended for future studies.Comment: 11 pages, 4 figure

Ready or Not, Here They Come: Acting Interns’ Experience and Perceived Competency Performing Basic Medical Procedures

OBJECTIVE: To assess acting interns’ (AI’s) experience with and perceived level of competency performing 6 basic medical procedures. DESIGN: Fourth-year medical students at the University of Cincinnati (UCCOM) are required to complete 2 AI rotations in Internal Medicine. All AIs in 2003–2004 (n = 150) and 2004–2005 (n = 151) were asked to complete a survey about whether during each of their rotations they had performed and felt competent performing the following procedures: phlebotomy, intravenous (IV) catheter insertion, arterial blood gas (ABG), nasogastric (NG) tube insertion, lumbar puncture (LP), and Foley catheter insertion. RESULTS: Four hundred sixty-seven of 601 possible surveys (across both years and both rotations) were completed (78% response rate). During both rotations, relatively few students performed the procedures, ranging from 9% for Foley catheter insertion (24/208) to 50% for both ABG and NG tube insertion (130/259). The two procedures most often performed were ABG (range 46–50%) and NG tube insertion (range 42–50%). Feelings of competency varied from 12% (LP) to 82% (Foley catheter). Except for LP, if students performed a procedure at least once, they reported feeling more competent (range 85% for ABG to 96% for Foley catheter insertion). Among the students who performed LP during a rotation, many still did not feel competent performing LPs: 23 (74%) in rotation 1 and 20 (40%) in rotation 2. CONCLUSION: Many fourth-year students at UCCOM do not perform basic procedures during their acting internship rotations. Procedural performance correlates with feelings of competency. Lumbar puncture competency may be too ambitious a goal for medical students