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Schwarz C, Fitschek F, Primavesi F, Stättner S, Margonis GA, Weiss MA, Stavrou GA, Oldhafer KJ, Kornprat P, Wundsam H, Fischer I, Längle F, Függer R, Hauer A, Klug R, Kieler M, Prager G, Schindl M, Stremitzer S, Bodingbauer M, Sahora K, Kaczirek K. Metachronous hepatic resection for liver only pancreatic metastases. Surg Oncol 2020; 35:169-173. [PMID: 32889249 DOI: 10.1016/j.suronc.2020.08.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 07/22/2020] [Accepted: 08/02/2020] [Indexed: 12/22/2022]
Abstract
BACKGROUND The value of liver resection (LR) for metachronous pancreatic ductal adenocarcinoma (PDAC) metastases remains controversial. However, in light of increasing safety of liver resections, surgery might be a valuable option for metastasized PDAC in selected patients. METHODS We performed a retrospective, multicenter study including patients undergoing hepatectomy for metachronous PDAC liver metastases between 2004 and 2015 to analyze postoperative outcome and overall survival. All patients were operated with curative intent. Patients with oligometastatic metachronous liver metastasis with definitive chemotherapy (n = 8) served as controls. RESULTS Overall 25 patients in seven centers were included in this study. The median age at the time of LR was 63.8 years (56.9-69.9) and the median number of metastases in the liver was 1 (IQR 1-2). There were eight non-anatomical resections (32%), 15 anatomical minor (60%) and 2 major LR (8%). Postoperative complications occurred in eleven patients (eight Clavien-Dindo grade I complications (32%) and three grade IIIa complications (12%), respectively). The 30-day mortality was 0%. The median length of stay was 8.6 days (IQR 5-11). Median overall survival following LR was 36.8 months compared to 9.2 months in patients with metachronous liver metastasis with chemotherapy (p = 0007). DISCUSSION Liver resection for metachronous PDAC metastasis is safe and feasible in selected patients. To address general applicability and to find factors for patient selection, larger trials are urgently warranted.
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Mukhopadhyay DP, Schleier D, Wirsing S, Ramler J, Kaiser D, Reusch E, Hemberger P, Preitschopf T, Krummenacher I, Engels B, Fischer I, Lichtenberg C. Methylbismuth: an organometallic bismuthinidene biradical. Chem Sci 2020; 11:7562-7568. [PMID: 32874526 PMCID: PMC7450715 DOI: 10.1039/d0sc02410d] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 06/02/2020] [Indexed: 12/04/2022] Open
Abstract
We report the generation, spectroscopic characterization, and computational analysis of the first free (non-stabilized) organometallic bismuthinidene, BiMe. The title compound was generated in situ from BiMe3 by controlled homolytic Bi-C bond cleavage in the gas phase. Its electronic structure was characterized by a combination of photoion mass-selected threshold photoelectron spectroscopy and DFT as well as multi-reference computations. A triplet ground state was identified and an ionization energy (IE) of 7.88 eV was experimentally determined. Methyl abstraction from BiMe3 to give [BiMe2]• is a key step in the generation of BiMe. We reaveal a bond dissociation energy of 210 ± 7 kJ mol-1, which is substantially higher than the previously accepted value. Nevertheless, the homolytic cleavage of Me-BiMe2 bonds could be achieved at moderate temperatures (60-120 °C) in the condensed phase, suggesting that [BiMe2]• and BiMe are accessible as reactive intermediates under these conditions.
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Hirsch F, Pachner K, Fischer I, Issler K, Petersen J, Mitric R, Bakels S, Rijs AM. Do Xylylenes Isomerize in Pyrolysis? Chemphyschem 2020; 21:1515-1518. [PMID: 32501625 PMCID: PMC7496364 DOI: 10.1002/cphc.202000317] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 06/05/2020] [Indexed: 01/06/2023]
Abstract
We report infrared spectra of xylylene isomers in the gas phase, using free electron laser (FEL) radiation. All xylylenes were generated by flash pyrolysis. The IR spectra were obtained by monitoring the ion dip signal, using a IR/UV double resonance scheme. A gas phase IR spectrum of para-xylylene was recorded, whereas ortho- and meta-xylylene were found to partially rearrange to benzocyclobutene and styrene. Computations of the UV oscillator strength for all molecules were carried out and provde an explanation for the observation of the isomerization products.
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Jocher B, Nakajima T, Tanaka Y, Fischer I, Schilling J, Ewald G, Itoh A. Incidence and Risk Factors for Acute Kidney Injury Post-Heart Transplant: An Analysis of Peri-Operative Hemodynamics. J Heart Lung Transplant 2020. [DOI: 10.1016/j.healun.2020.01.643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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Skroch L, Fischer I, Meisgeier A, Kozolka F, Apitzsch J, Neff A. Condylar remodeling after osteosynthesis of fractures of the condylar head or close to the temporomandibular joint. J Craniomaxillofac Surg 2020; 48:413-420. [DOI: 10.1016/j.jcms.2020.02.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 01/20/2020] [Accepted: 02/10/2020] [Indexed: 10/25/2022] Open
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Tanaka Y, Vu V, Fischer I, Nakajima T, Soyama Y, Jocker B, May-Newman K, Itoh A. Significance of Aortic Valve Insufficiency with Left Ventricular Assist Device: Duration and Regurgitant Flow in a Mock Loop Study. J Heart Lung Transplant 2020. [DOI: 10.1016/j.healun.2020.01.154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Mukhopadhyay DP, Schleier D, Fischer I, Loison JC, Alcaraz C, Garcia GA. Photoelectron spectroscopy of boron-containing reactive intermediates using synchrotron radiation: BH 2, BH, and BF. Phys Chem Chem Phys 2020; 22:1027-1034. [PMID: 31854408 DOI: 10.1039/c9cp06010c] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mass selected slow photoelectron spectra (SPES) of three boron-containing reactive species, BH2, BH, and BF were recorded by double imaging photoion-photoelectron coincidence spectroscopy (i2PEPICO) using synchrotron radiation. All species were generated in a flow reactor from the H-abstraction of B2H6 by F atoms created in a F2 microwave discharge. The spectrum of BH2+ exhibits a long bending mode progression with a 970 cm-1 spacing due to the large geometry change from bent to linear upon ionization. Its ionization energy was determined as 8.12 ± 0.02 eV. For BH, photoionisation from both X1Σ+ singlet and a3Π triplet state was observed, permitting the experimental determination of the singlet/triplet gap (ΔEST) from the observed IE's of 9.82 eV and 8.48 eV. In addition, a threshold photoelectron spectrum of BF was recorded, which leads to an IE of 11.11 eV and an improved value for νBF+ of 1690 cm-1. All spectra were simulated by calculating Franck-Condon factors from optimised structures based on quantum chemical calculations.
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Reusch E, Holzmeier F, Gerlach M, Fischer I, Hemberger P. Decomposition of Picolyl Radicals at High Temperature: A Mass Selective Threshold Photoelectron Spectroscopy Study. Chemistry 2019; 25:16652-16659. [PMID: 31637775 PMCID: PMC6972682 DOI: 10.1002/chem.201903937] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 10/16/2019] [Indexed: 01/24/2023]
Abstract
The reaction products of the picolyl radicals at high temperature were characterized by mass-selective threshold photoelectron spectroscopy in the gas phase. Aminomethylpyridines were pyrolyzed to initially produce picolyl radicals (m/z=92). At higher temperatures further thermal reaction products are generated in the pyrolysis reactor. All compounds were identified by mass-selected threshold photoelectron spectroscopy and several hitherto unexplored reactive molecules were characterized. The mechanism for several dissociation pathways was outlined in computations. The spectrum of m/z=91, resulting from hydrogen loss of picolyl, shows four isomers, two ethynyl pyrroles with adiabatic ionization energies (IEad ) of 7.99 eV (2-ethynyl-1H-pyrrole) and 8.12 eV (3-ethynyl-1H-pyrrole), and two cyclopentadiene carbonitriles with IE's of 9.14 eV (cyclopenta-1,3-diene-1-carbonitrile) and 9.25 eV (cyclopenta-1,4-diene-1-carbonitrile). A second consecutive hydrogen loss forms the cyanocyclopentadienyl radical with IE's of 9.07 eV (T0 ) and 9.21 eV (S1 ). This compound dissociates further to acetylene and the cyanopropynyl radical (IE=9.35 eV). Furthermore, the cyclopentadienyl radical, penta-1,3-diyne, cyclopentadiene and propargyl were identified in the spectra. Computations indicate that dissociation of picolyl proceeds initially via a resonance-stabilized seven-membered ring.
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Hirsch F, Flock M, Fischer I, Bakels S, Rijs AM. The Gas-Phase Infrared Spectra of Xylyl Radicals. J Phys Chem A 2019; 123:9573-9578. [PMID: 31593463 DOI: 10.1021/acs.jpca.9b09153] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The three isomers of the xylyl radical, C8H9, are possible intermediates in the formation of soot and polycyclic aromatic hydrocarbons (PAH). Their infrared spectra have been recorded by IR/UV ion dip spectroscopy using free electron laser radiation. The radicals were generated by flash pyrolysis from the corresponding nitrites and resonantly ionized via the D3 ← D0 transition around 310 nm. Mid-infrared spectra of the three xylyl isomers were recorded between 550 and 1700 cm-1 and are in excellent agreement with computations, provided that overtones and combination bands are included in the simulation. The results show that the three xylyl isomers can be distinguished by their infrared spectra and that no isomerization occurs in the pyrolysis reactor. The IR spectra obtained at m/z = 208 indicate that dimerization of xylyl radicals leads to substituted stilbenes, which has not been observed for benzyl.
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Cunillera A, Soriano MC, Fischer I. Cross-predicting the dynamics of an optically injected single-mode semiconductor laser using reservoir computing. CHAOS (WOODBURY, N.Y.) 2019; 29:113113. [PMID: 31779359 DOI: 10.1063/1.5120822] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Accepted: 10/23/2019] [Indexed: 06/10/2023]
Abstract
In real-world dynamical systems, technical limitations may prevent complete access to their dynamical variables. Such a lack of information may cause significant problems, especially when monitoring or controlling the dynamics of the system is required or when decisions need to be taken based on the dynamical state of the system. Cross-predicting the missing data is, therefore, of considerable interest. Here, we use a machine learning algorithm based on reservoir computing to perform cross-prediction of unknown variables of a chaotic dynamical laser system. In particular, we chose a realistic model of an optically injected single-mode semiconductor laser. While the intensity of the laser can often be acquired easily, measuring the phase of the electric field and the carriers in real time, although possible, requires a more demanding experimental scheme. We demonstrate that the dynamics of two of the three dynamical variables describing the state of the laser can be reconstructed accurately from the knowledge of only one variable, if our algorithm has been trained beforehand with all three variables for a limited period of time. We analyze the accuracy of the method depending on the parameters of the laser system and the reservoir. Finally, we test the robustness of the cross-prediction method when adding noise to the time series. The suggested reservoir computing state observer might be used in many applications, including reconstructing time series, recovering lost time series data and testing data encryption security in cryptography based on chaotic synchronization of lasers.
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Schleier D, Reusch E, Lummel L, Hemberger P, Fischer I. Threshold Photoelectron Spectroscopy of IO and HOI. Chemphyschem 2019; 20:2413-2416. [PMID: 31508875 PMCID: PMC6790590 DOI: 10.1002/cphc.201900813] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Indexed: 11/08/2022]
Abstract
Iodine oxides appear as reactive intermediates in atmospheric chemistry. Here, we investigate IO and HOI by mass-selective threshold photoelectron spectroscopy (ms-TPES), using synchrotron radiation. IO and HOI are generated by photolyzing iodine in the presence of ozone. For both molecules, accurate ionization energies are determined, 9.71±0.02 eV for IO and 9.79±0.02 eV for HOI. The strong spin-spin interaction in the 3 Σ- ground state of IO+ leads to an energy splitting into the Ω=0 and Ω=±1 sublevels. Upon ionization, the I-O bond shortens significantly in both molecules; thus, a vibrational progression, assigned to the I-O stretch, is apparent in both spectra.
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Röder A, Petersen J, Issler K, Fischer I, Mitrić R, Poisson L. Exploring the Excited-State Dynamics of Hydrocarbon Radicals, Biradicals, and Carbenes Using Time-Resolved Photoelectron Spectroscopy and Field-Induced Surface Hopping Simulations. J Phys Chem A 2019; 123:10643-10662. [DOI: 10.1021/acs.jpca.9b06346] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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63
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Flock M, Bosse L, Kaiser D, Engels B, Fischer I. A time-resolved photoelectron imaging study on isolated tolane: observation of the biradicalic 1A u state. Phys Chem Chem Phys 2019; 21:13157-13164. [PMID: 31173002 DOI: 10.1039/c9cp02222h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Tolane (diphenylacetylene, C14H10) was studied by picosecond time-resolved photoionisation and photoelectron imaging in a supersonic jet. The low-energy part of the 1B1u← S0 REMPI spectrum is very similar to an earlier LIF spectrum, however additional bands were observed at higher energies above the fluorescence cut-off. For a number of bands the dynamics were investigated via pump-probe photoionisation and photoelectron spectroscopy. Around the 1B1u origin the lifetimes are in the ns range, but they drop to some 10 ps at higher excitation energies. For the short-lived bands at higher energies a sequential two-step relaxation to a long-lived electronic state was observed proceeding via an intermediately populated state with a lifetime of 100-200 ps. By comparison with previous quantum chemical calculations we assign this state as the biradicalic trans-bent1Au state that is ionised in a two-photon process.
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Reusch E, Kaiser D, Schleier D, Buschmann R, Krueger A, Hermann T, Engels B, Fischer I, Hemberger P. Pentadiynylidene and Its Methyl-Substituted Derivates: Threshold Photoelectron Spectroscopy of R 1-C 5-R 2 Triplet Carbon Chains. J Phys Chem A 2019; 123:2008-2017. [PMID: 30776230 DOI: 10.1021/acs.jpca.8b12244] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mass-selective threshold photoelectron spectroscopy in the gas phase was employed to characterize the dialkynyl triplet carbenes pentadiynylidene (HC5H), methylpentadiynylidene (MeC5H), and dimethylpentadiynylidene (MeC5Me). Diazo compounds were employed as precursors to generate the carbenes by flash pyrolysis. The R1-C5-R2 carbon chains were photoionized by vacuum ultraviolet (VUV) synchrotron radiation in photoelectron photoion coincidence (PEPICO) experiments. High-level ab initio computations were carried out to support the interpretation of the experiments. For the unsubstituted pentadiynylidene (R1 = R2 = H) the recorded spectrum yields an adiabatic ionization energy (IEad) of 8.36 ± 0.03 eV. In addition, a second carbene isomer, 3-(didehydrovinylidene)cyclopropene, with a singlet electronic ground state, was identified in the spectrum based on the IEad of 8.60 ± 0.03 eV and Franck-Condon simulations. We found that multireference computations are required to reliably calculate the IEad for this molecule. CASPT2 computations predicted an IEad = 8.55 eV, while coupled-cluster computations significantly overestimate the IE. The cyclic isomer is most likely formed from another isomer of the precursor present in the sample. Stepwise methyl-substitution of the carbene leads to a reduction of the IE to 7.77 ± 0.04 eV for methylpentadiynylidene and 7.27 ± 0.06 eV for dimethylpentadiynylidene. The photoionization and dissociative photoionization of the precursors is investigated as well.
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Ramler J, Poater J, Hirsch F, Ritschel B, Fischer I, Bickelhaupt FM, Lichtenberg C. Carbon monoxide insertion at a heavy p-block element: unprecedented formation of a cationic bismuth carbamoyl. Chem Sci 2019; 10:4169-4176. [PMID: 31057745 PMCID: PMC6471928 DOI: 10.1039/c9sc00278b] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 02/27/2019] [Indexed: 12/20/2022] Open
Abstract
The first insertion reaction of CO with a molecular complex of the heavy p-block elements is reported (principal quantum number > 4).
Major advances in the chemistry of 5th and 6th row heavy p-block element compounds have recently uncovered intriguing reactivity patterns towards small molecules such as H2, CO2, and ethylene. However, well-defined, homogeneous insertion reactions with carbon monoxide, one of the benchmark substrates in this field, have not been reported to date. We demonstrate here, that a cationic bismuth amide undergoes facile insertion of CO into the Bi–N bond under mild conditions. This approach grants direct access to the first cationic bismuth carbamoyl species. Its characterization by NMR, IR, and UV/vis spectroscopy, elemental analysis, single-crystal X-ray analysis, cyclic voltammetry, and DFT calculations revealed intriguing properties, such as a reversible electron transfer at the bismuth center and an absorption feature at 353 nm ascribed to a transition involving σ- and π-type orbitals of the bismuth-carbamoyl functionality. A combined experimental and theoretical approach provided insight into the mechanism of CO insertion. The substrate scope could be extended to isonitriles.
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Primavesi F, Klieser E, Cardini B, Marsoner K, Fröschl U, Thalhammer S, Fischer I, Hauer A, Urbas R, Kiesslich T, Neureiter D, Zitt M, Klug R, Wundsam H, Sellner F, Függer R, Cakar-Beck F, Kornprat P, Öfner D, Stättner S. Prognostic Value of C-Reactive Protein in a New Preoperative Clinical Risk Score for Survival after Surgery for Sporadic, Non-Functioning Pancreatic Neuroendocrine Neoplasia. Eur J Surg Oncol 2019. [DOI: 10.1016/j.ejso.2018.10.263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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Babikov D, Benoit D, Bowman J, Burd T, Clary D, Donovan R, Fischer I, Gianturco F, Hochlaf M, Kar S, Kirrander A, Leone S, Malcomson T, Manthe U, McCoy AB, Petersen J, Richardson J, Slavíček P, Stoecklin T, Szalewicz K, van der Avoird A, Wester R, Worth G, Zehnacker-Rentien A. Quantum dynamics of isolated molecules: general discussion. Faraday Discuss 2018; 212:281-306. [PMID: 30511069 DOI: 10.1039/c8fd90052c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Bacic Z, Benoit D, Biczysko M, Bowman J, Bradforth S, Burd T, Chambaud G, Clary D, Crépin C, Dracinsky M, Felker P, Fischer I, Gianturco F, Hochlaf M, Kouril K, Kratochvilova I, Liu C, McCoy A, Miyazaki J, Mouhib H, Richardson J, Slaviček P, Stoecklin T, Szalewicz K, van der Avoird A, Zehnacker-Rentien A. Molecules in confinement in clusters, quantum solvents and matrices: general discussion. Faraday Discuss 2018; 212:569-601. [PMID: 30520925 DOI: 10.1039/c8fd90053a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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69
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Issler K, Röder A, Hirsch F, Poisson L, Fischer I, Mitrić R, Petersen J. Excited state dynamics and time-resolved photoelectron spectroscopy of para-xylylene. Faraday Discuss 2018; 212:83-100. [PMID: 30238117 DOI: 10.1039/c8fd00083b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We investigated the excited-state dynamics of para-xylylene using a combination of field-induced surface hopping (FISH) simulations and time-resolved ionisation experiments. Our simulations predict an ultrafast decay of the initially excited bright state (S2/S3) to the S1 state on a sub-100 fs time scale, followed by return to the ground state within ∼1 ps. This is accompanied by a transient change of the biradical character of the molecule, as monitored by calculating natural orbital occupation numbers. Specifically, the initially low biradicality is increased by electronic excitation as well as by vibrational activation. Experimentally, para-xylylene was generated by pyrolysis from [2,2]paracyclophane and excited with 266 nm radiation into the S2/S3 bright state. The subsequent dynamics were followed using ionisation as the probe step, with both mass spectra and photoelectron spectra recorded as a function of pump-probe delay. The observed decay of photoelectron and photoion intensities closely matches the theoretical predictions and is consistent with the sequential mechanism found in the simulations. This mechanism exhibits characteristic signatures in both time-resolved mass and photoelectron spectra, in particular in the appearance of fragment ions that are exclusively generated from the S1 state. This allows for a separation of the S2 and S1 dynamics in the photoelectron and mass spectra. An excellent agreement between the observed and the simulated ion signal is observed.
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Bacic Z, Benoit D, Besemer M, Bowman J, Bradforth S, Clary D, Donovan R, Fischer I, Gianturco F, Hochlaf M, Houston P, Knowles P, Leone S, Linguerri R, Manthe U, McCoy AB, Petersen J, Richardson J, Shan X, Slavíček P, Stoecklin T, Szalewicz K, van der Avoird A, Wester R, Worth G, Zehnacker-Rentien A. Precise characterisation of isolated molecules: general discussion. Faraday Discuss 2018; 212:137-155. [PMID: 30507986 DOI: 10.1039/c8fd90050g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Hirsch F, Reusch E, Constantinidis P, Fischer I, Bakels S, Rijs AM, Hemberger P. Self-Reaction of ortho-Benzyne at High Temperatures Investigated by Infrared and Photoelectron Spectroscopy. J Phys Chem A 2018; 122:9563-9571. [PMID: 30444617 DOI: 10.1021/acs.jpca.8b09640] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
ortho-Benzyne, a Kekulé-type biradical is considered to be a key intermediate in the formation of polycyclic aromatic hydrocarbons (PAH) and soot. In the present work we study the ortho-benzyne self-reactions in a hot microreactor and identify the high-temperature products by IR/UV spectroscopy and by photoion mass-selected threshold photoelectron spectroscopy (ms-TPES) in a free jet. Ms-TPES confirms formation of ortho-benzyne as generated from benzocyclobutenedione, as well as benzene, biphenylene, diacetylene, and acetylene, originating from the reaction o-C6H4 → HCC-CCH + C2H2, and CH3. PAH molecules like naphthalene, 2-ethynylnaphthalene, fluorene, phenanthrene, and triphenylene are identified based on their IR/UV spectra. By comparison with recent computations their formation starting from o-benzyne can be readily understood and supports the importance of the biradical addition (1,4-cycloaddition followed by fragmentation) pathway to PAH molecules, recently proposed by Comandini et al.
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Flock M, Herbert MP, Fischer I. The excited-state structure and photophysics of isolated acenaphthylene. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.05.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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73
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Schleier D, Humeniuk A, Reusch E, Holzmeier F, Nunez-Reyes D, Alcaraz C, Garcia GA, Loison JC, Fischer I, Mitric R. Diborene: Generation and Photoelectron Spectroscopy of an Inorganic Biradical. J Phys Chem Lett 2018; 9:5921-5925. [PMID: 30234995 DOI: 10.1021/acs.jpclett.8b02338] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Diborenes, R-BB-R', are of current interest in inorganic chemistry because they offer the opportunity to tune the properties of a biradical by modifying the substituents of the diborene parent, HBBH. Here we synthesize the elusive diborene by H atom abstraction from diborane, B2H6, using fluorine atoms and report a vibrationally resolved photoelectron spectrum of the HBBH biradical. The spectrum is interpreted by comparison with high-level ab initio computations, taking into account the Renner-Teller splitting in the X+ 2Π ionic ground state, which show an excellent agreement with the experimental spectrum. An adiabatic ionization energy of 9.080 ± 0.015 eV was determined, and a vibrational progression in the boron-boron stretching vibration of 0.14 eV is visible. This is due to the reduction of bond order upon ionization, accompanied by an increase of the computed boron-boron bond length, RBB, from 1.514 to 1.606 Å.
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Hupp B, Nitsch J, Schmitt T, Bertermann R, Edkins K, Hirsch F, Fischer I, Auth M, Sperlich A, Steffen A. Stimulus-induzierte Anion-Kation-Exciplexbildung in Kupfer(I)-Komplexen als Mechanismus für mechanochrome Phosphoreszenz. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201807768] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Hupp B, Nitsch J, Schmitt T, Bertermann R, Edkins K, Hirsch F, Fischer I, Auth M, Sperlich A, Steffen A. Stimulus-Triggered Formation of an Anion-Cation Exciplex in Copper(I) Complexes as a Mechanism for Mechanochromic Phosphorescence. Angew Chem Int Ed Engl 2018; 57:13671-13675. [PMID: 30048568 DOI: 10.1002/anie.201807768] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Indexed: 12/12/2022]
Abstract
The investigation of the mechanisms of mechanochromic luminescence is of fundamental importance for the development of materials for photonic sensors, data storage, and luminescence switches. The structural origin of this phenomenon in phosphorescent molecular systems is rarely known and thus the formulation of structure-property relationships remains challenging. Changes in the M-M interactions have been proposed as the main mechanism with d10 coinage metal compounds. Herein, we describe a new mechanism-a mechanically induced reversible formation of a cation-anion exciplex based on Cu-F interactions-that leads to highly efficient mechanochromic phosphorescence and unusual large emission shifts from UV-blue to yellow for CuI complexes. The low-energy luminescence is thermo- and vaporesponsive, thus allowing the generation of white light as well as for recovering the original UV-blue emission.
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76
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Ahmed B, Kumar S, Ojha AK, Hirsch F, Riese S, Fischer I. Facile synthesis and photophysics of graphene quantum dots. J Photochem Photobiol A Chem 2018. [DOI: 10.1016/j.jphotochem.2018.07.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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77
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Holzmeier F, Wolf TJA, Gienger C, Wagner I, Bozek J, Nandi S, Nicolas C, Fischer I, Gühr M, Fink RF. Normal and resonant Auger spectroscopy of isocyanic acid, HNCO. J Chem Phys 2018; 149:034308. [DOI: 10.1063/1.5030621] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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78
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Köhler G, Fischer I, Kaltenböck R, Mitteregger M, Seitinger G, Szyszkowitz A. Critical evaluation of an innovative mesh for bilateral transabdominal preperitoneal (TAPP) repair of inguinal hernias. Hernia 2018; 22:857-862. [PMID: 29869074 DOI: 10.1007/s10029-018-1786-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2018] [Accepted: 05/31/2018] [Indexed: 11/27/2022]
Abstract
PURPOSE Transabdominal preperitoneal hernia mesh plasty (TAPP) offers significant benefits to patients undergoing bilateral inguinal hernia repair. We evaluated a novel pre-shaped, large-pored, titanium-coated, lightweight polypropylene mesh for bilateral placement as an alternative to two separate meshes. METHODS Thirty-six patients underwent elective surgical repair of bilateral inguinal hernias with the new mesh at three departments of surgery in Linz and Graz, Austria, between May 1, 2015 and June 30, 2017. RESULTS All operations were completed without intraoperative complications or conversion to open procedures. The mean operation time was 74 min. There were no postoperative procedure-related complications with the exception of one hematoseroma of the spermatic cord. Two symptomatic medial recurrences (2/36 patients = 5.6%, 2/72 hernia repairs = 2.8%, respectively) after supravesical and medial hernia repair with the bilateral mesh were seen at structured follow-up examinations 6 and 12 months postoperatively. CONCLUSION Treatment of bilateral inguinal hernias with the newly designed bilateral mesh for TAPP theoretically brings benefits in terms of resistance to forces acting on the mesh. The larger area may decrease the risk for mesh bulging and recurrence, and one large mesh might provide more stable support than two separate meshes overlapping at the midline. The results of our study do not confirm these theoretical benefits regarding a high recurrence rate (2.8%) after treatment of medial hernia defects. We recommend re-designing the mesh with only a small central slit, which would provide a broader mesh bridge with sufficient overlap for all types of inguinal and femoral hernias, including medial and supravesical defects. After the mesh has been re-designed, a new study should evaluate its real benefits before it is marketed.
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79
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Ma X, Wenzel M, Schmitt HC, Flock M, Reusch E, Mitrić R, Fischer I, Brixner T. Disentangling the photochemistry of benzocyclobutenedione. Phys Chem Chem Phys 2018; 20:15434-15444. [PMID: 29799041 DOI: 10.1039/c8cp01937a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The ultrafast photophysics and photochemistry of benzocyclobutenedione (BCBD) dissolved in dichloromethane is investigated by transient absorption spectroscopy in both the IR and the UV/Vis regime. The molecule is excited at 300 nm to the S3 (ππ*) state and a time scale from roughly 100 fs to several nanoseconds is covered. The initially excited S3 deactivates quickly to the lower-lying S1 (nπ*) state. Three parallel photochemical reaction pathways starting in the S1 state that compete with deactivation to S0 are identified in the transient IR spectra, two of them consisting of a sequence of steps. DFT/TDDFT calculations of the normal modes of the reactant and various photoproducts support the analysis of the transient spectra. The rapid internal conversion (IC) to the S1 state of BCBD is followed by a sub-picosecond vibrational relaxation (VR) to S1 (ν = 0). In parallel BCBD loses one carbonyl group and forms benzocyclopropenone, which subsequently rearranges to cyclopentadienylidene ketene. Ring opening in the S1 (ν = 0) state produces vibrationally hot bisketene, which cools within 22 ps. This reaction competes with the intramolecular rearrangement to singlet oxacarbene, which subsequently converts into the triplet carbene via intersystem crossing (ISC). The late-time product identified in the transient UV/Vis spectra is probably due to dimerization of the carbene. Molecular dynamics (MD) simulations of the early-time photochemistry of BCBD successfully reproduce the formation of the three main photoproducts.
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80
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Argyris A, Bueno J, Fischer I. Photonic machine learning implementation for signal recovery in optical communications. Sci Rep 2018; 8:8487. [PMID: 29855549 PMCID: PMC5981473 DOI: 10.1038/s41598-018-26927-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 05/21/2018] [Indexed: 11/30/2022] Open
Abstract
Machine learning techniques have proven very efficient in assorted classification tasks. Nevertheless, processing time-dependent high-speed signals can turn into an extremely challenging task, especially when these signals have been nonlinearly distorted. Recently, analogue hardware concepts using nonlinear transient responses have been gaining significant interest for fast information processing. Here, we introduce a simplified photonic reservoir computing scheme for data classification of severely distorted optical communication signals after extended fibre transmission. To this end, we convert the direct bit detection process into a pattern recognition problem. Using an experimental implementation of our photonic reservoir computer, we demonstrate an improvement in bit-error-rate by two orders of magnitude, compared to directly classifying the transmitted signal. This improvement corresponds to an extension of the communication range by over 75%. While we do not yet reach full real-time post-processing at telecom rates, we discuss how future designs might close the gap.
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81
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Hirsch F, Constantinidis P, Fischer I, Bakels S, Rijs AM. Front Cover: Dimerization of the Benzyl Radical in a High-Temperature Pyrolysis Reactor Investigated by IR/UV Ion Dip Spectroscopy (Chem. Eur. J. 30/2018). Chemistry 2018. [DOI: 10.1002/chem.201802179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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82
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Hirsch F, Constantinidis P, Fischer I, Bakels S, Rijs AM. Dimerization of the Benzyl Radical in a High-Temperature Pyrolysis Reactor Investigated by IR/UV Ion Dip Spectroscopy. Chemistry 2018. [DOI: 10.1002/chem.201802180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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83
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Hirsch F, Constantinidis P, Fischer I, Bakels S, Rijs AM. Dimerization of the Benzyl Radical in a High-Temperature Pyrolysis Reactor Investigated by IR/UV Ion Dip Spectroscopy. Chemistry 2018. [PMID: 29528193 DOI: 10.1002/chem.201800852] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
We investigate the self-reaction of benzyl, C7 H7 , in a high-temperature pyrolysis reactor. The work is motivated by the observation that resonance-stabilized benzyl radicals can accumulate in reactive environments and contribute to the formation of polycyclic aromatic hydrocarbons (PAHs) and soot. Reaction products are detected by IR/UV ion dip spectroscopy, using infrared radiation from the free electron laser FELIX, and are identified by comparison with computed spectra. Among the reaction products identified by their IR absorption are several PAHs linked to toluene combustion such as bibenzyl, phenanthrene, diphenylmethane, and fluorene. The identification of 9,10-dihydrophenanthrene provides evidence for a mechanism of phenanthrene formation from bibenzyl that proceeds by initial cyclization rather than an initial hydrogen loss to stilbene.
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84
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Schleier D, Constantinidis P, Faßheber N, Fischer I, Friedrichs G, Hemberger P, Reusch E, Sztáray B, Voronova K. Kinetics of the a-C 3H 5 + O 2 reaction, investigated by photoionization using synchrotron radiation. Phys Chem Chem Phys 2018; 20:10721-10731. [PMID: 29340384 DOI: 10.1039/c7cp07893e] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The kinetics of the combustion-relevant reaction of the allyl radical, a-C3H5, with molecular oxygen has been studied in a flow tube reactor at the vacuum ultraviolet (VUV) beamline of the Swiss Light Source storage ring, using the CRF-PEPICO (Combustion Reactions Followed by Photoelectron Photoion Coincidence Spectroscopy) setup. The ability to measure threshold photoelectron spectra enables a background-free detection of reactive species as well as an isomer-specific analysis of reaction products. Allyl was generated by direct photodissociation of allyl iodide at 266 nm and 213 nm and indirectly by the reaction of propene with Cl atoms, which were generated by photolysis from oxalyl chloride at 266 nm. Experiments were conducted at room temperature at low pressures between 0.8 and 3 mbar using Ar as the buffer gas and with excess O2 to maintain nearly pseudo-first-order reaction conditions. Whereas allyl was detected by photoionisation using synchrotron radiation, the main reaction product allyl peroxy was not observed due to dissociative ionisation of this weakly bound species. From the concentration-time profiles of the allyl signal, second-order rate constants between 1.35 × 1011 cm3 mol-1 s-1 at 0.8 mbar and 1.75 × 1011 cm3 mol-1 s-1 at 3 mbar were determined. The rates obtained for the different allyl radical generation schemes agree well with each other, but are about a factor of 2 higher than the ones reported previously using He as a buffer gas. The discrepancy is partly attributed to the higher collision efficiency of Ar causing a varying fall-off behavior. When allyl is produced by the reaction of propene with Cl atom, an unexpected product is observed at m/z = 68, which was identified as 1,3-butadienal in the threshold photoelectron spectrum. It is formed in a secondary reaction of allyl with the OCCl radical, which is generated in the 266 nm photolysis of oxalyl chloride.
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85
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Ahmed B, Ojha AK, Singh A, Hirsch F, Fischer I, Patrice D, Materny A. Well-controlled in-situ growth of 2D WO 3 rectangular sheets on reduced graphene oxide with strong photocatalytic and antibacterial properties. JOURNAL OF HAZARDOUS MATERIALS 2018; 347:266-278. [PMID: 29329009 DOI: 10.1016/j.jhazmat.2017.12.069] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 11/29/2017] [Accepted: 12/28/2017] [Indexed: 06/07/2023]
Abstract
Finding the materials, which help to control the water pollution caused by organic and bacterial pollutants is one of the challenging tasks for the scientific community. 2D sheets of WO3 and composite of WO3 and reduced graphene oxide (rGO) have been synthesized in a well-controlled way using a hydrothermal method. The as synthesized 2D sheet of WO3 and rGO-WO3 composite were characterized by various techniques. The 2D sheets of WO3 and rGO-WO3 composite are efficiently utilized for the photocatalytic degradation of methylene blue (MB) and Rhodamine B (RhB) dyes under sunlight. The rGO-WO3 composite reveals excellent photocatalytic degradation of RhB dye by degrading it upto 85% under sunlight. However, the MB dye was degraded by 32%. The greater degradation of RhB dye was explained in terms of the molecular electrostatic potential. We found that RhB has a more positive potential compared to MB dye where O2- and OH̊ radicals interact more strongly, resulting in a greater degradation of the RhB dye. The antibacterial activity of the 2D sheets of WO3 and rGO-WO3composite was also investigated on gram positive (B. subtilis) and gram negative (P. aeroginosa) microbes for the first time.
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86
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Osmanagic-Myers S, Kiss A, Hamza O, Sedlmayer F, Fischer I, Fichtinger P, Grillari J, Eriksson M, Podesser BK, Foisner R. 37Progerin expression in endothelial tissue leads to endothelial dysfunction and impaired diastolic cardiac function. Cardiovasc Res 2018. [DOI: 10.1093/cvr/cvy060.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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87
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Kotkar K, Anand S, Fischer I, Ewald G, Balsara K, Masood M, Itoh A. Surgical Debridement of Driveline Infection with Uninterrupted Warfarin Anticoagulation is Associated with Reduced Postoperative Bleeding Events, Blood Transfusion and Shorter Hospital Stay. J Heart Lung Transplant 2018. [DOI: 10.1016/j.healun.2018.01.934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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88
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Jüngling T, Soriano MC, Oliver N, Porte X, Fischer I. Consistency properties of chaotic systems driven by time-delayed feedback. Phys Rev E 2018; 97:042202. [PMID: 29758606 DOI: 10.1103/physreve.97.042202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Indexed: 06/08/2023]
Abstract
Consistency refers to the property of an externally driven dynamical system to respond in similar ways to similar inputs. In a delay system, the delayed feedback can be considered as an external drive to the undelayed subsystem. We analyze the degree of consistency in a generic chaotic system with delayed feedback by means of the auxiliary system approach. In this scheme an identical copy of the nonlinear node is driven by exactly the same signal as the original, allowing us to verify complete consistency via complete synchronization. In the past, the phenomenon of synchronization in delay-coupled chaotic systems has been widely studied using correlation functions. Here, we analytically derive relationships between characteristic signatures of the correlation functions in such systems and unequivocally relate them to the degree of consistency. The analytical framework is illustrated and supported by numerical calculations of the logistic map with delayed feedback for different replica configurations. We further apply the formalism to time series from an experiment based on a semiconductor laser with a double fiber-optical feedback loop. The experiment constitutes a high-quality replica scheme for studying consistency of the delay-driven laser and confirms the general theoretical results.
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89
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Kaiser D, Reusch E, Hemberger P, Bodi A, Welz E, Engels B, Fischer I. The ortho-benzyne cation is not planar. Phys Chem Chem Phys 2018; 20:3988-3996. [PMID: 29350226 DOI: 10.1039/c7cp08055g] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A recent review on the photoionisation of the C6H4 isomer ortho-benzyne suggests that bands reported in earlier photoelectron spectra might be due to side products or contaminations, while computations raise doubts, whether the cation has a planar geometry. We therefore reinvestigate the photoionisation of ortho-benzyne, generated by pyrolysis from benzocyclobutenedione, by photoion mass-selected threshold photoelectron (ms-TPE) spectroscopy using synchrotron radiation. The experiments are accompanied by a theoretical study that investigates the structure of the ortho-benzyne cation systematically as a function of the computational method, up to CASPT2(11,14) ab initio computations. Our study leads to a re-evaluation of the ionisation energy of ortho-benzyne. It reveals that the ortho-benzyne cation has indeed a twisted C2 geometry rather than a C2v structure. A vertical ionisation energy IEvert of 9.77 eV and an adiabatic ionisation energy of IEad = 9.56 eV are computed for ortho-benzyne. A Franck-Condon simulation of the photoelectron spectrum based on the CASPT2 results and including three electronic states of the cation is in agreement with the experiment and yields IEad = 9.51 eV (+50 meV/-100 meV). Since this value is in contrast with previous work, the ionisation energy has to be revised based on our study. Computational methods based on density functional theory give a reasonable description of the cationic ground state, but fail for the corresponding excited electronic states that are indispensible for a proper assignment of the photoelectron spectrum.
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90
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Hoche J, Schmitt HC, Humeniuk A, Fischer I, Mitrić R, Röhr MIS. The mechanism of excimer formation: an experimental and theoretical study on the pyrene dimer. Phys Chem Chem Phys 2018; 19:25002-25015. [PMID: 28876005 DOI: 10.1039/c7cp03990e] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The understanding of excimer formation in organic materials is of fundamental importance, since excimers profoundly influence their functional performance in applications such as light-harvesting, photovoltaics or organic electronics. We present a joint experimental and theoretical study of the ultrafast dynamics of excimer formation in the pyrene dimer in a supersonic jet, which is the archetype of an excimer forming system. We perform simulations of the nonadiabatic photodynamics in the frame of TDDFT that reveal two distinct excimer formation pathways in the gas-phase dimer. The first pathway involves local excited state relaxation close to the initial Franck-Condon geometry that is characterized by a strong excitation of the stacking coordinate exhibiting damped oscillations with a period of 350 fs that persist for several picoseconds. The second excimer forming pathway involves large amplitude oscillations along the parallel shift coordinate with a period of ≈900 fs that after intramolecular vibrational energy redistribution leads to the formation of a perfectly stacked dimer. The electronic relaxation within the excitonic manifold is mediated by the presence of intermolecular conical intersections formed between fully delocalized excitonic states. Such conical intersections may generally arise in stacked π-conjugated aggregates due to the interplay between the long-range and short-range electronic coupling. The simulations are supported by picosecond photoionization experiments in a supersonic jet that provide a time-constant for the excimer formation of around 6-7 ps, in good agreement with theory. Finally, in order to explore how the crystal environment influences the excimer formation dynamics we perform large scale QM/MM nonadiabatic dynamics simulations on a pyrene crystal in the framework of the long-range corrected tight-binding TDDFT. In contrast to the isolated dimer, the excimer formation in the crystal follows a single reaction pathway in which the initially excited parallel slip motion is strongly damped by the interaction with the surrounding molecules leading to the slow excimer stabilization on a picosecond time scale.
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91
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Ban L, Bowman J, Bradforth S, Chambaud G, Dracinsky M, Fischer I, Góra R, Hochlaf M, Janicki M, Kirrander A, McCoy AB, Petersen J, Richardson J, Slavicek P, Szalewicz K, Zehnacker-Rentien A. Molecules in confinement in liquid solvents: general discussion. Faraday Discuss 2018; 212:383-397. [DOI: 10.1039/c8fd90051e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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92
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Fischer A, Fischer I. Behandlung einer akuten Achillessehnenruptur mit Methoden des Fasziendistorsionsmodells. MANUELLE MEDIZIN 2017. [DOI: 10.1007/s00337-017-0338-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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93
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Hicke K, Brunner D, Soriano MC, Fischer I. Role of dynamical injection locking and characteristic pulse events for low frequency fluctuations in semiconductor lasers. CHAOS (WOODBURY, N.Y.) 2017; 27:114307. [PMID: 29195304 DOI: 10.1063/1.5006945] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We investigate the dynamics of semiconductor lasers subject to time-delayed optical feedback from the perspective of dynamical self-injection locking. Based on the Lang-Kobayashi model, we perform an analysis of the well-known Low Frequency Fluctuations (LFFs) in the frequency-intensity plane. Moreover, we investigate a recently found dynamical regime of fragmented LFFs by means of a locking-range analysis, spectral comparison and precursor pulse identification. We show that LFF dynamics can be explained by dynamical optical injection locking due to the delayed optical feedback. Moreover, the fragmented LFFs occur due to a re-injection locking induced by a particular optical pulse structure in the chaotic feedback dynamics. This is corroborated by experiments with a semiconductor laser experiencing delayed feedback from an optical fiber loop. The dynamical nature of the feedback injection results in an eventual loss, but also possible regaining, of the locking, explaining the recently observed phenomenon of fragmented LFFs.
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94
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Pachner K, Steglich M, Hemberger P, Fischer I. Photodissociation dynamics of the ortho- and para-xylyl radicals. J Chem Phys 2017; 147:084303. [DOI: 10.1063/1.4999906] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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95
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Röder A, Issler K, Poisson L, Humeniuk A, Wohlgemuth M, Comte M, Lepetit F, Fischer I, Mitric R, Petersen J. Femtosecond dynamics of the 2-methylallyl radical: A computational and experimental study. J Chem Phys 2017; 147:013902. [PMID: 28688397 DOI: 10.1063/1.4974150] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate the photodynamics of the 2-methylallyl radical by femtosecond time-resolved photoelectron imaging. The experiments are accompanied by field-induced surface hopping dynamics calculations and the simulation of time-resolved photoelectron intensities and anisotropies, giving insight into the photochemistry and nonradiative relaxation of the radical. 2-methylallyl is excited at 236 nm, 238 nm, and 240.6 nm into a 3p Rydberg state, and the subsequent dynamics is probed by multiphoton ionization using photons of 800 nm. The photoelectron image exhibits a prominent band with considerable anisotropy, which is compatible with the result of theory. The simulations show that the initially excited 3p state is rapidly depopulated to a 3s Rydberg state, from which photoelectrons of high anisotropy are produced. The 3s state then decays within several 100 fs to the D1 (nπ) state, followed by the deactivation of the D1 to the electronic ground state on the ps time scale.
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96
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Reusch E, Holzmeier F, Constantinidis P, Hemberger P, Fischer I. Isomer-Selective Generation and Spectroscopic Characterization of Picolyl Radicals. Angew Chem Int Ed Engl 2017; 56:8000-8003. [DOI: 10.1002/anie.201703433] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2017] [Indexed: 11/10/2022]
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97
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Reusch E, Holzmeier F, Constantinidis P, Hemberger P, Fischer I. Isomerenselektive Erzeugung und spektroskopische Charakterisierung der Picolyl-Radikale. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201703433] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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98
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Röder A, Humeniuk A, Giegerich J, Fischer I, Poisson L, Mitrić R. Femtosecond time-resolved photoelectron spectroscopy of the benzyl radical. Phys Chem Chem Phys 2017; 19:12365-12374. [PMID: 28453017 DOI: 10.1039/c7cp01437f] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present a joint experimental and computational study of the nonradiative deactivation of the benzyl radical, C7H7, after UV excitation. Femtosecond time-resolved photoelectron imaging was applied to investigate the photodynamics of the radical. The experiments were accompanied by excited state dynamics simulations using surface hopping. Benzyl has been excited at 265 nm into the D-band (ππ*) and the dynamics was probed using probe wavelengths of 398 nm or 798 nm. At a probe wavelength of 398 nm a single time constant of around 70-80 fs was observed. When the dynamics was probed at 798 nm, a second time constant τ2 = 1.5 ps was visible, which can be attributed to further non-radiative deactivation to the lower-lying D1/D2 states.
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99
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Keuninckx L, Soriano MC, Fischer I, Mirasso CR, Nguimdo RM, Van der Sande G. Encryption key distribution via chaos synchronization. Sci Rep 2017; 7:43428. [PMID: 28233876 PMCID: PMC5324067 DOI: 10.1038/srep43428] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 01/18/2017] [Indexed: 11/09/2022] Open
Abstract
We present a novel encryption scheme, wherein an encryption key is generated by two distant complex nonlinear units, forced into synchronization by a chaotic driver. The concept is sufficiently generic to be implemented on either photonic, optoelectronic or electronic platforms. The method for generating the key bitstream from the chaotic signals is reconfigurable. Although derived from a deterministic process, the obtained bit series fulfill the randomness conditions as defined by the National Institute of Standards test suite. We demonstrate the feasibility of our concept on an electronic delay oscillator circuit and test the robustness against attacks using a state-of-the-art system identification method.
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100
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Schmitt HC, Flock M, Welz E, Engels B, Schneider H, Radius U, Fischer I. Electronic Structure and Excited-State Dynamics of an Arduengo-Type Carbene and its Imidazolone Oxidation Product. Chemistry 2017; 23:3084-3090. [PMID: 28071828 DOI: 10.1002/chem.201605027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Indexed: 11/06/2022]
Abstract
We describe an investigation of the excited-state dynamics of isolated 1,3-di-tert-butyl-imidazoline-2-ylidene (tBu2 Im, C11 H20 N2 , m/z=180), an Arduengo-type carbene, by time- and frequency-resolved photoionization using a picosecond laser system. The energies of several singlet and triplet excited states were calculated by time-dependent density functional theory (TD-DFT). The S1 state of the carbene deactivates on a 100 ps time scale possibly by intersystem crossing. In the experiments we observed an additional signal at m/z=196, that was assigned to the oxidation product 1,3-di-tert-butyl-imidazolone, tBu2 ImO. It shows a well-resolved resonance-enhanced multiphoton ionization (REMPI) spectrum with an origin located at 36951 cm-1 . Several low-lying vibrational bands could be assigned, with a lifetime that depends strongly on the excitation energy. At the origin the lifetime is longer than 3 ns, but drops to 49 ps at higher excess energies. To confirm formation of the imidazolone we also performed experiments on benzimidazolone (BzImO) for comparison. Apart from a redshift for BzImO the spectra of the two compounds are very similar. The TD-DFT values display a very good agreement with the experimental data.
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