51 research outputs found
Size selective spectroscopy of Se microclusters
The electronic structure and photofragmentation in outer and inner valence regions of Se-n (n <= 8) clusters produced by direct vacuum evaporation have been studied with size-selective photoelectron-photoion coincidence technique by using vacuum-ultraviolet synchrotron radiation. The experimental ionization potentials of these clusters were extracted from the partial ion yield measurements. The calculations for the possible geometrical structures of the Se-n microclusters have been executed. The ionization energies of the clusters have been calculated and compared with the experimental results. In addition, theoretical fragment ion appearance energies were estimated. The dissociation energies of Se-n clusters were derived from the recurrent relation between the gas phase enthalpies of the formation of corresponding cationic clusters and experimental ionization energies. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737633
Role of the Renner-Teller effect after core hole excitation in the dissociation dynamics of carbon dioxide dication
The fragmentation of the doubly-charged carbon dioxide molecule is studied
after photoexcitation to the C 1s 12Ï u and O 1s 12Ï u states using a
multicoincidence ion-imaging technique. The bent component of the Renner-
Teller split states populated in the 1sâ Ï* resonant excitation at both the
carbon and oxygen 1sionization edges opens pathways to potential surfaces in
highly bent geometries in the dication. Evidence for a complete deformation of
the molecule is found in the coincident detection of C+ and O+2 ions. The
distinct alignment of this fragmentation channel indicates rapid deformation
and subsequent fragmentation. Investigation of the complete atomization
dynamics in the dication leading to asymmetric charge separation shows that
the primary dissociation mechanisms, sequential, concerted, and asynchronous
concerted, are correlated to specific fragment kinetic energies. The study
shows that the bond angle in fragmentation can extend below 20°
Commissioning of a photoelectron spectrometer for soft X ray photon diagnostics at the European XFEL
Commissioning and first operation of an angle-resolved photoelectron spectrometer for non-invasive shot-to-shot diagnostics at the European XFEL soft X-ray beamline are described. The objective with the instrument is to provide the users and operators with reliable pulse-resolved information regarding photon energy and polarization that opens up a variety of applications for novel experiments but also hardware optimization
Role of the Renner-Teller effect after core hole excitation in the dissociation dynamics of carbon dioxide dication
Drug Screening Platform Using Human Induced Pluripotent Stem Cell-Derived Atrial Cardiomyocytes and Optical Mapping
Current drug development efforts for the treatment of atrial fibrillation are hampered by the fact that many preclinical models have been unsuccessful in reproducing human cardiac physiology and its response to medications. In this study, we demonstrated an approach using human induced pluripotent stem cellâderived atrial and ventricular cardiomyocytes (hiPSCâaCMs and hiPSCâvCMs, respectively) coupled with a sophisticated optical mapping system for drug screening of atrialâselective compounds in vitro. We optimized differentiation of hiPSCâaCMs by modulating the WNT and retinoid signaling pathways. Characterization of the transcriptome and proteome revealed that retinoic acid pushes the differentiation process into the atrial lineage and generated hiPSCâaCMs. Functional characterization using optical mapping showed that hiPSCâaCMs have shorter action potential durations and faster Ca2+ handling dynamics compared with hiPSCâvCMs. Furthermore, pharmacological investigation of hiPSCâaCMs captured atrialâselective effects by displaying greater sensitivity to atrialâselective compounds 4âaminopyridine, AVE0118, UCL1684, and vernakalant when compared with hiPSCâvCMs. These results established that a model system incorporating hiPSCâaCMs combined with optical mapping is wellâsuited for preclinical drug screening of novel and targeted atrial selective compounds
Angular asymmetry and attosecond time delay from the giant plasmon resonance in C-60 photoionization
This combined experimental and theoretical study demonstrates that the surface plasmon resonance in C-60 alters the valence photoemission quantum phase, resulting in strong effects in the photoelectron angular distribution and emission time delay. Electron momentum imaging spectroscopy is used to measure the photoelectron angular distribution asymmetry parameter that agrees well with our calculations from the time-dependent local density approximation (TDLDA). Significant structure in the valence photoemission time delay is simultaneously calculated by TDLDA over the plasmon active energies. Results reveal a unified spatial and temporal asymmetry pattern driven by the plasmon resonance and offer a sensitive probe of electron correlation. A semiclassical approach facilitates further insights into this link that can be generalized and applied to other molecular systems and nanometer-sized metallic materials exhibiting plasmon resonances
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Comparison of Ajmaline and Procainamide Provocation Tests in the Diagnosis of Brugada Syndrome.
OBJECTIVES: The authors studied the response rates and relative sensitivity of the most common agents used in the sodium-channel blocker (SCB) challenge. BACKGROUND: A type 1 Brugada electrocardiographic pattern precipitated by an SCB challenge confers a diagnosis of Brugada syndrome. METHODS: Patients undergoing an SCB challenge were prospectively enrolled across Canada and the United Kingdom. Patients with no prior cardiac arrest and family histories of sudden cardiac death or Brugada syndrome were included. RESULTS: Four hundred twenty-five subjects underwent SCB challenge (ajmaline, n = 331 [78%]; procainamide, n = 94 [22%]), with a mean age of 39 ± 15 years (54% men). Baseline non-type 1 Brugada ST-segment elevation was present in 10%. A total of 154 patients (36%) underwent signal-averaged electrocardiography, with 41% having late potentials. Positive results were seen more often with ajmaline than procainamide infusion (26% vs. 4%, p < 0.001). On multivariate analysis, baseline non-type 1 Brugada ST-segment elevation (odds ratio [OR]: 6.92; 95% confidence interval [CI]: 3.15 to 15.2; p < 0.001) and ajmaline use (OR: 8.76; 95% CI: 2.62 to 29.2; p < 0.001) were independent predictors of positive results to SCB challenge. In the subgroup undergoing signal-averaged electrocardiography, non-type 1 Brugada ST-segment elevation (OR: 9.28; 95% CI: 2.22 to 38.8; p = 0.002), late potentials on signal-averaged electrocardiography (OR: 4.32; 95% CI: 1.50 to 12.5; p = 0.007), and ajmaline use (OR: 12.0; 95% CI: 2.45 to 59.1; p = 0.002) were strong predictors of SCB outcome. CONCLUSIONS: The outcome of SCB challenge was significantly affected by the drug used, with ajmaline more likely to provoke a type 1 Brugada electrocardiographic pattern compared with procainamide. Patients undergoing SCB challenge may have contrasting results depending on the drug used, with potential clinical, psychosocial, and socioeconomic implications
Introduction
"In the spring of 1995 a call for research proposals was published by the Royal Netherlands Academy of Arts and Sciences (KNAW), soliciting projects submitted jointly by Indonesian and Dutch research groups. A collaborative research proposal was then formulated by a small group of linguistic phoneticians at the University of Indonesia and at Leiden University, asking for a subsidy of around MÆ 1.5 (now approximately k⏠680). The grant money covered five PhD projects, each of which was to result in a doctoral thesis, the appointment of two half-time postdoc for four years, and the transfer of equipment (computers, recorders, microphones) and speech processing software to a phonetics laboratory to be founded by the University of Indonesia
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