71 research outputs found

    Analyzing the two-dimensional plot of the interannual climate variability for detection of the climate change in the Large Karoun River Basin, Iran

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    In most studies on climate change, the first problem often faced by the researcher is detecting the climate change of the study area during the past periods and attributing it to the greenhouse gases. In this study, an attempt has been made to introduce a method for detecting the climate change during the past periods in regional scale and attributing it to greenhouse gases with regard to climate processes in a region. For this purpose, at first it is necessary to calculate the interannual variability range of the region climatic variables, resulting from the interaction between the climate systems of the ‘earth’ (atmosphere, biosphere, etc.). Hence, long-term statistics (1000 years) of the temperature and precipitation, resulting from control run (fix greenhouse gases) of AOGCM models (HadCM3 and CGCM3), were used for Large Karoun River Basin. Then, based on the two-variant normal distribution, the interannual climate variability range of the study area was plotted as two-dimensional temperatureprecipitation graphs. Next, the annual temperature and precipitation anomaly values of the observation stations in different regions of Large Karoun River Basin were compared with the region interannual variability range for detecting the climate change of the study area during the past and attributing it to greenhouse gases. The results show increase in temperature and decrease in precipitation trends, denoting the fact that the temperature variable has been influenced by the climate change. So, in all regions of the Large Karoun River Basin, the final years of the period (1971 to 2009) have almost been located outside the interannual climate variability range, indicating the effect of climate change on the climatic variables of the said years.Key words: Interannual climate variability, detecting the climate change, AOGCM models, Large Karoun River Basin

    Correlation of reconstructed scaphoid morphology with clinical outcomes

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    Background: Scaphoid malunion alters the carpal kinematics and impairs clinical outcome because of pain, weakness, restricted range of motion and predisposing the wrist joint to early osteoarthritis. The aim of this study was to evaluate the influence of the scaphoid morphological angles on clinical outcomes in patients with reconstructed scaphoid by non-vascularized bone graft. Methods: Seventeen male patients with the mean age of 31.7±3.7 years and mean non-union time of 31.5±14.7 months were enrolled in this retrospective study. Average follow up was 48.8±9.4 months. At the last follow-up, the patients were evaluated clinically for pain, wrist range of motion, grip strength, and wrist functional status. They were also evaluated radiologically by wrist radiographs and computerized tomography (CT). The overall clinical outcomes were evaluated by the Cooney wrist function score. The morphology of the reconstructed scaphoids was evaluated by the lateral intrascaphoid angle, antroposterior intrascaphoid angle, dorsal cortical angle, measuring the length (mm), and height-to-length ratio on CT scan. The radiological measurements were compared against the overall clinical outcomes. Results: There were 7 excellent, 7 good, 3 fair clinical results. The mean Cooney wrist function score was 83±4. The mean lateral intrascaphoid angle was 34.8±1.4 degrees, mean antroposterior intrascaphoid angle was 33.4±2.2 degrees, mean dorsal cortical angle was 158.3±4.8 degrees, mean scaphoid length was 22.1± 0.7 mm, and mean scaphoid height-to-length ratio was 0.74±0.04. There were no significant statistical correlations between the lateral intrascaphoid angles, antroposterior intrascaphoid angles, dorsal cortical angles, scaphoid lengths and scaphoid height-to-length ratios and Cooney wrist scores in the patients. Conclusion: In the current study, all the patients had some degree of scaphoid malunion; however, the radiological measurements of the reconstructed scaphoids did not correlate with the clinical outcomes. © 2015 BY THE ARCHIVES OF BONE AND JOINT SURGERY

    Auger decay and subsequent fragmentation pathways of ethylene following K-shell ionization

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    Citation: Gaire, B., Haxton, D. J., Sturm, F. P., Williams, J., Gatton, A., Bocharova, I., . . . Weber, T. (2015). Auger decay and subsequent fragmentation pathways of ethylene following K-shell ionization. Physical Review A, 92(1), 13. doi:10.1103/PhysRevA.92.013408The fragmentation pathways and dynamics of ethylene molecules after core ionization are explored using coincident measurements of the Auger electron and fragment ions by employing the cold target recoil-ion momentum spectroscopy method. The influence of several factors on the dynamics and kinematics of the dissociation is studied. These include propensity rules, ionization mechanisms, symmetry of the orbitals from which the Auger electrons originate, multiple scattering, conical intersections, interference, and possible core-hole localization for the double ionization of this polyatomic molecule. Energy correlation maps allow probing the multidimensional potential energy surfaces and, in combination with our multiconfiguration self-consistent field calculations, identifying the populated electronic states of the dissociating dication. The measured angular distributions of the Auger electrons in the molecular frame further support and augment these assignments. The deprotonation and molecular hydrogen ion elimination channels show a nearly isotropic Auger electron angular distribution with a small elongation along the direction perpendicular to the molecular axis. For the symmetric breakup the angular distributions show a clear influence of multiple scattering on the outgoing electrons. The lowest kinetic energy release feature of the symmetric breakup channel displays a fingerprint of entangled Auger and photoelectron motion in the angular emission pattern identifying this transition as an excellent candidate to probe core-hole localization at a conical intersection of a polyatomic molecule.Additional Authors: Landers, A. L.;Belkacem, A.;Dorner, R.;Weber, T

    Hydrogen and fluorine migration in photo-double-ionization of 1,1-difluoroethylene (1,1-C2H2F2) near and above threshold

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    We have studied the nondissociative and dissociative photo-double-ionization of 1,1-difluoroethylene using single photons of energies ranging from 40 to 70 eV. Applying a coincident electron-ion three-dimensional momentum imaging technique, kinematically complete measurements have been achieved. We present the branching ratios of the six reaction channels identified in the experiment. Electron-ion energy maps and relative electron emission angles are used to distinguish between direct and indirect photo-double-ionization mechanisms at a few different photon energies. The influence of selection and propensity rules is discussed. Threshold energies of double ionization are extracted from the sum of the kinetic energies of the electrons, which hint to the involvement of different manifolds of states. The dissociative ionization channels with two ionic fragments are explored in detail by measuring the kinetic energy release of the fragment ions, sum of the kinetic energies, as well as the energy sharing of the two emitted electrons. We investigate the migration of hydrogen and fluorine atoms and compare the experimental results to the photo-double-ionization of centrosymmetric linear and planar hydrocarbons (C[subscript 2]H[subscript 2] and C[subscript 2]H[subscript 4]) whenever possible

    Incorporating real time velocity map image reconstruction into closed-loop coherent control

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    We report techniques developed to utilize three-dimensional momentum information as feedback in adaptive femtosecond control of molecular dynamics. Velocity map imaging is used to obtain the three-dimensional momentum map of the dissociating ions following interaction with a shaped intense ultrafast laser pulse. In order to recover robust feedback information, however, the two-dimensional momentum projection from the detector must be inverted to reconstruct the full three-dimensional momentum of the photofragments. These methods are typically slow or require manual inputs and are therefore accomplished offline after the images have been obtained. Using an algorithm based upon an “onion-peeling” (also known as “back projection”) method, we are able to invert 1040 × 1054 pixel images in under 1 s. This rapid inversion allows the full photofragment momentum to be used as feedback in a closed-loop adaptive control scheme, in which a genetic algorithm tailors an ultrafast laser pulse to optimize a specific outcome. Examples of three-dimensional velocity map image based control applied to strong-field dissociation of CO and O2 are presented

    Carrier-envelope phase control over fragmentation of H2 + and D2

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    Citation: Zohrabi, M., Berry, B., Kling, N. G., Jochim, B., Severt, T., Ablikim, U., . . . Ben-Itzhak, I. (2015). Carrier-envelope phase control over fragmentation of H2 + and D2. 635(11). doi:10.1088/1742-6596/635/11/112045We demonstrate control over fragmentation of H2 + and D2 molecules via the carrier-envelope phase of sub-5 fs laser pulses. Moreover, we attribute our findings to interferences between different pathways involving different net numbers of photons, revealing "high-order" pathways and the importance of the bandwidth. © Published under licence by IOP Publishing Ltd

    The importance of Rydberg orbitals in dissociative ionization of small hydrocarbon molecules in intense few-cycle laser pulses

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    Citation: Jochim, B., Siemering, R., Zohrabi, M., Voznyuk, A., Mahowald, J. B., Schmitz, D. G., . . . De Vivie-Riedle, R. (2015). The importance of Rydberg orbitals in dissociative ionization of small hydrocarbon molecules in intense few-cycle laser pulses. 635(11). doi:10.1088/1742-6596/635/11/112043We demonstrate the importance of ionization from Rydberg orbitals via experimental and theoretical work focusing on the strong-field dissociative single ionization of small hydrocarbons. Our findings suggest that Rydberg states should be routinely considered when studying polyatomic molecules in intense laser fields. © Published under licence by IOP Publishing Ltd.Additional Authors: Wells, E.;De Vivie-Riedle, R

    The Magellan-TESS Survey I: Survey Description and Mid-Survey Results

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    One of the most significant revelations from Kepler is that roughly one-third of Sun-like stars host planets which orbit their stars within 100 days and are between the size of Earth and Neptune. How do these super-Earth and sub-Neptune planets form, what are they made of, and do they represent a continuous population or naturally divide into separate groups? Measuring their masses and thus bulk densities can help address these questions of their origin and composition. To that end, we began the Magellan-TESS Survey (MTS), which uses Magellan II/PFS to obtain radial velocity (RV) masses of 30 transiting exoplanets discovered by TESS and develops an analysis framework that connects observed planet distributions to underlying populations. In the past, RV measurements of small planets have been challenging to obtain due to the faintness and low RV semi-amplitudes of most Kepler systems, and challenging to interpret due to the potential biases in the existing ensemble of small planet masses from non-algorithmic decisions for target selection and observation plans. The MTS attempts to minimize these biases by focusing on bright TESS targets and employing a quantitative selection function and multi-year observing strategy. In this paper, we (1) describe the motivation and survey strategy behind the MTS, (2) present our first catalog of planet mass and density constraints for 25 TESS Objects of Interest (TOIs; 20 in our population analysis sample, five that are members of the same systems), and (3) employ a hierarchical Bayesian model to produce preliminary constraints on the mass-radius (M-R) relation. We find qualitative agreement with prior mass-radius relations but some quantitative differences (abridged). The the results of this work can inform more detailed studies of individual systems and offer a framework that can be applied to future RV surveys with the goal of population inferences.Comment: 101 pages (39 of main text and references, the rest an appendix of figures and tables). Submitted to AAS Journal
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