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Zheng A, Kira M, Adam RD, Papageorgiou P, Shambrook J, Abbas A, Vedwan K, Long J, Walkden M, Harden S, Peebles C, Flett AS. Characteristics and long-term outcomes of patients with reduced ejection fraction referred for adenosine stress perfusion cardiac magnetic resonance imaging. Eur Heart J Cardiovasc Imaging 2021. [DOI: 10.1093/ehjci/jeab090.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Funding Acknowledgements
Type of funding sources: None.
Background
Adenosine stress perfusion has been shown to be of minimal incremental benefit in distinguishing between ischaemic and non-ischaemic aetiology of severe left ventricular systolic dysfunction (LVSD) over and above that obtained from Cardiac Magnetic Resonance (CMR) with Late Gadolinium Enhancement (LGE). Stress CMR has, however, been shown to be effective in risk-stratifying LVSD patients, with ischaemia being an independent predictor of cardiovascular death or myocardial infarction (MI) and associated with higher rates of further intervention.
Purpose
Evaluate real world data from a single tertiary UK cardiac MRI centre to determine the characteristics and long-term clinical outcomes of patients with LVSD referred for stress CMR.
Methods
As part of an ongoing registry, all consenting patients with Ejection Fraction (EF) ≤40% and a completed adenosine stress perfusion CMR between January 2015 and December 2019 were included with prospective baseline data collection. All-cause mortality and cardiac hospitalisation, coronary angiography/revascularisation was determined from electronic hospital records. Outcomes were compared between the inducible ischaemia vs. no ischaemia groups, and LGE present vs. no LGE groups using chi square.
Results
The sample included 86 patients. The mean EF was 32 ± 6%. Median follow up was 3.8 years (range 41-2222 days). The indications for CMR were: 30 (35%) assess ischaemia, 35 (41%) assess LVSD aetiology and 21 (24%) LVSD assess viability.
Inducible ischemia was present in 30 (35%) patients and absent in 56 (65%). Patient characteristics and outcomes are shown in Table 1. Baseline characteristics were similar between the groups but there was a higher rate of hypertension and ischaemic heart disease in the ischaemia group. There was a non-significant difference in combined mortality and cardiac hospitalisation rates between the groups (40% vs. 27% p = 0.20).
LGE was present in 69 (80%) patients (28 with ischaemia; 41 without) and absent in 17 (20%, 2 with ischaemia, 15 without). The event rate was 23 (33%) vs. 4 (24%) between LGE vs. No LGE groups (p = 0.44). Of the 15 patients (17%) with no LGE or ischaemia; 2 died and 1 was hospitalised, there were no MI"s and no Percutaneous Coronary Intervention (PCI).
The lack of statistical difference in event rates between ischaemia and no ischaemia groups may be due to our relatively small sample size or could reflect the effectiveness of contemporary disease modifying treatment for Heart Failure with reduced EF.
Conclusion
This real-world data supports published findings that in patients with LVSD and no LGE on CMR, ischaemia is very uncommon and stress CMR is unlikely to increase diagnostic yield. Conversely, if stress CMR is performed and ischaemia is absent, incidence of subsequent angiography and revascularisation is very low, which is reassuring in clinical practice. In those patients without ischaemia and LGE, likelihood of MI is low.
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Affiliation(s)
- A Zheng
- University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom of Great Britain & Northern Ireland
| | - M Kira
- University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom of Great Britain & Northern Ireland
| | - RD Adam
- University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom of Great Britain & Northern Ireland
| | - P Papageorgiou
- University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom of Great Britain & Northern Ireland
| | - J Shambrook
- University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom of Great Britain & Northern Ireland
| | - A Abbas
- University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom of Great Britain & Northern Ireland
| | - K Vedwan
- University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom of Great Britain & Northern Ireland
| | - J Long
- University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom of Great Britain & Northern Ireland
| | - M Walkden
- University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom of Great Britain & Northern Ireland
| | - S Harden
- University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom of Great Britain & Northern Ireland
| | - C Peebles
- University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom of Great Britain & Northern Ireland
| | - AS Flett
- University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom of Great Britain & Northern Ireland
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2
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Borsch M, Schmid CP, Weigl L, Schlauderer S, Hofmann N, Lange C, Steiner JT, Koch SW, Huber R, Kira M. Super-resolution lightwave tomography of electronic bands in quantum materials. Science 2021; 370:1204-1207. [PMID: 33273100 DOI: 10.1126/science.abe2112] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 10/28/2020] [Indexed: 11/02/2022]
Abstract
Searching for quantum functionalities requires access to the electronic structure, constituting the foundation of exquisite spin-valley-electronic, topological, and many-body effects. All-optical band-structure reconstruction could directly connect electronic structure with the coveted quantum phenomena if strong lightwaves transported localized electrons within preselected bands. Here, we demonstrate that harmonic sideband (HSB) generation in monolayer tungsten diselenide creates distinct electronic interference combs in momentum space. Locating these momentum combs in spectroscopy enables super-resolution tomography of key band-structure details in situ. We experimentally tuned the optical-driver frequency by a full octave and show that the predicted super-resolution manifests in a critical intensity and frequency dependence of HSBs. Our concept offers a practical, all-optical, fully three-dimensional tomography of electronic structure even in microscopically small quantum materials, band by band.
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Affiliation(s)
- M Borsch
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, USA
| | - C P Schmid
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - L Weigl
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - S Schlauderer
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - N Hofmann
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - C Lange
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - J T Steiner
- Department of Physics, University of Marburg, Marburg, Germany
| | - S W Koch
- Department of Physics, University of Marburg, Marburg, Germany
| | - R Huber
- Department of Physics, University of Regensburg, Regensburg, Germany.
| | - M Kira
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, USA.
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3
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Adhikari S, Bhattarai K, Abe Y, Kira M, Fujitani M, Miyada T, Kishida T. Dietary daidzein decreases food intake accompanied with delayed gastric emptying in ovariectomized rats. Biosci Biotechnol Biochem 2020; 84:1232-1238. [PMID: 32067573 DOI: 10.1080/09168451.2020.1723404] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
We previously found that equol, a metabolite of intestinal bacterial conversion from soy isoflavone daidzein, has female-specific anorectic effects. In the present study, we used seven-week-old female ovariectomized (OVX) Sprague Dawley rats to test the hypothesis that the anorectic effect of dietary daidzein may be attributed to delayed gastric emptying. Results suggest that dietary daidzein delays gastric emptying and that it has an anorectic effect with residual gastric contents, but not without gastric contents. Dietary equol significantly decreased daily food intake in the OVX rats without sleeve gastrectomy, but not in those with sleeve gastrectomy, suggesting that the accumulation of food in the stomach is required for the anorectic effect of equol to occur. These results support the hypothesis that the anorectic effect of dietary daidzein is attributed to delayed gastric emptying.
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Affiliation(s)
- Sudhashree Adhikari
- The United Graduate School of Agricultural Sciences, Ehime University, Matsuyama, Japan
| | - Keshab Bhattarai
- The United Graduate School of Agricultural Sciences, Ehime University, Matsuyama, Japan
| | - Yasuhiro Abe
- Graduate School of Agriculture, Ehime University, Matsuyama, Japan
| | - Mayu Kira
- Graduate School of Agriculture, Ehime University, Matsuyama, Japan
| | - Mina Fujitani
- Graduate School of Agriculture, Ehime University, Matsuyama, Japan
| | - Tomihiro Miyada
- Department of Clinical Nutrition, Faculty of Health Science and Technology, Kawasaki University of Medical Welfare, Kurashiki, Japan
| | - Taro Kishida
- The United Graduate School of Agricultural Sciences, Ehime University, Matsuyama, Japan.,Graduate School of Agriculture, Ehime University, Matsuyama, Japan
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4
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Matteo D, Pigeon J, Tochitsky SY, Huttner U, Kira M, Koch SW, Moloney JV, Joshi C. Control of the nonlinear response of bulk GaAs induced by long-wavelength infrared pulses. Opt Express 2019; 27:30462-30472. [PMID: 31684294 DOI: 10.1364/oe.27.030462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 09/15/2019] [Indexed: 06/10/2023]
Abstract
The nonlinear optical response of GaAs is studied using extremely nonresonant 10 μm laser pulses with peak intensities greater than 2 GW/cm 2. We observe over an order of magnitude enhancement in the four-wave mixing efficiency by decreasing the CO 2 laser beat-wave frequency. This enhancement is attributed to currents of photoexcited unbound carriers modulated at the beat frequency, confirmed by measurements of nonlinear absorption at this long wavelength as well as a fully microscopic analysis of the excitation dynamics. Modeling of such nonperturbative semiconductor-laser interactions predicts that further decreasing the beat frequency can increase the nonlinear response and allow for its control over two orders of magnitude.
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5
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Langer F, Schmid CP, Schlauderer S, Gmitra M, Fabian J, Nagler P, Schüller C, Korn T, Hawkins PG, Steiner JT, Huttner U, Koch SW, Kira M, Huber R. Lightwave valleytronics in a monolayer of tungsten diselenide. Nature 2018; 557:76-80. [PMID: 29720633 PMCID: PMC6205603 DOI: 10.1038/s41586-018-0013-6] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 02/16/2018] [Indexed: 11/09/2022]
Abstract
As conventional electronics is approaching its ultimate limits1, nanoscience has urgently sought for novel fast control concepts of electrons at the fundamental quantum level2. Lightwave electronics3 – the foundation of attosecond science4 – utilizes the oscillating carrier wave of intense light pulses to control the translational motion of the electron’s charge faster than a single cycle of light5–15. Despite being particularly promising information carriers, the internal quantum attributes of spin16 and valley pseudospin17–19 have not been switchable on the subcycle scale20–21. Here we demonstrate lightwave-driven changes of the valley pseudospin and introduce distinct signatures in the optical read out. Photogenerated electron–hole pairs in a monolayer of tungsten diselenide are accelerated and collided by a strong lightwave. The emergence of high odd-order sidebands and anomalous changes in their polarization direction directly attest to the ultrafast pseudospin dynamics. Quantitative computations combining density-functional theory with a non-perturbative quantum many-body approach assign the polarization of the sidebands to a lightwave-induced change of the valley pseudospin and confirm that the process is coherent and adiabatic. Our work opens the door to systematic valleytronic logic at optical clock rates.
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Affiliation(s)
- F Langer
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - C P Schmid
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - S Schlauderer
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - M Gmitra
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - J Fabian
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - P Nagler
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - C Schüller
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - T Korn
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - P G Hawkins
- Department of Physics, University of Marburg, Marburg, Germany
| | - J T Steiner
- Department of Physics, University of Marburg, Marburg, Germany
| | - U Huttner
- Department of Physics, University of Marburg, Marburg, Germany
| | - S W Koch
- Department of Physics, University of Marburg, Marburg, Germany
| | - M Kira
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, USA.
| | - R Huber
- Department of Physics, University of Regensburg, Regensburg, Germany
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6
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Langer F, Hohenleutner M, Huttner U, Koch SW, Kira M, Huber R. Symmetry-controlled time structure of high-harmonic carrier fields from a solid. Nat Photonics 2017; 11:227-231. [PMID: 28572835 PMCID: PMC5447365 DOI: 10.1038/nphoton.2017.29] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 02/08/2017] [Indexed: 05/31/2023]
Abstract
High-harmonic (HH) generation in crystalline solids1-6 marks an exciting development, with potential applications in high-efficiency attosecond sources7, all-optical bandstructure reconstruction8,9, and quasiparticle collisions10,11. Although the spectral1-4 and temporal shape5 of the HH intensity has been described microscopically1-6,12, the properties of the underlying HH carrier wave have remained elusive. Here we analyse the train of HH waveforms generated in a crystalline solid by consecutive half cycles of the same driving pulse. Extending the concept of frequency combs13-15 to optical clock rates, we show how the polarization and carrier-envelope phase (CEP) of HH pulses can be controlled by crystal symmetry. For some crystal directions, we can separate two orthogonally polarized HH combs mutually offset by the driving frequency to form a comb of even and odd harmonic orders. The corresponding CEP of successive pulses is constant or offset by π, depending on the polarization. In the context of a quantum description of solids, we identify novel capabilities for polarization- and phase-shaping of HH waveforms that cannot be accessed with gaseous sources.
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Affiliation(s)
- F. Langer
- Department of Physics, University of Regensburg, 93040 Regensburg, Germany
| | - M. Hohenleutner
- Department of Physics, University of Regensburg, 93040 Regensburg, Germany
| | - U. Huttner
- Department of Physics, University of Marburg, 35032 Marburg, Germany
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - S. W. Koch
- Department of Physics, University of Marburg, 35032 Marburg, Germany
| | - M. Kira
- Department of Physics, University of Marburg, 35032 Marburg, Germany
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - R. Huber
- Department of Physics, University of Regensburg, 93040 Regensburg, Germany
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7
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Langer F, Hohenleutner M, Schmid CP, Poellmann C, Nagler P, Korn T, Schüller C, Sherwin MS, Huttner U, Steiner JT, Koch SW, Kira M, Huber R. Lightwave-driven quasiparticle collisions on a subcycle timescale. Nature 2016; 533:225-9. [PMID: 27172045 PMCID: PMC5034899 DOI: 10.1038/nature17958] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 03/18/2016] [Indexed: 12/24/2022]
Abstract
Ever since Ernest Rutherford scattered α-particles from gold foils, collision experiments have revealed insights into atoms, nuclei and elementary particles. In solids, many-body correlations lead to characteristic resonances--called quasiparticles--such as excitons, dropletons, polarons and Cooper pairs. The structure and dynamics of quasiparticles are important because they define macroscopic phenomena such as Mott insulating states, spontaneous spin- and charge-order, and high-temperature superconductivity. However, the extremely short lifetimes of these entities make practical implementations of a suitable collider challenging. Here we exploit lightwave-driven charge transport, the foundation of attosecond science, to explore ultrafast quasiparticle collisions directly in the time domain: a femtosecond optical pulse creates excitonic electron-hole pairs in the layered dichalcogenide tungsten diselenide while a strong terahertz field accelerates and collides the electrons with the holes. The underlying dynamics of the wave packets, including collision, pair annihilation, quantum interference and dephasing, are detected as light emission in high-order spectral sidebands of the optical excitation. A full quantum theory explains our observations microscopically. This approach enables collision experiments with various complex quasiparticles and suggests a promising new way of generating sub-femtosecond pulses.
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Affiliation(s)
- F Langer
- Department of Physics, University of Regensburg, 93040 Regensburg, Germany
| | - M Hohenleutner
- Department of Physics, University of Regensburg, 93040 Regensburg, Germany
| | - C P Schmid
- Department of Physics, University of Regensburg, 93040 Regensburg, Germany
| | - C Poellmann
- Department of Physics, University of Regensburg, 93040 Regensburg, Germany
| | - P Nagler
- Department of Physics, University of Regensburg, 93040 Regensburg, Germany
| | - T Korn
- Department of Physics, University of Regensburg, 93040 Regensburg, Germany
| | - C Schüller
- Department of Physics, University of Regensburg, 93040 Regensburg, Germany
| | - M S Sherwin
- Department of Physics and the Institute for Terahertz Science and Technology, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| | - U Huttner
- Department of Physics, University of Marburg, 35032 Marburg, Germany
| | - J T Steiner
- Department of Physics, University of Marburg, 35032 Marburg, Germany
| | - S W Koch
- Department of Physics, University of Marburg, 35032 Marburg, Germany
| | - M Kira
- Department of Physics, University of Marburg, 35032 Marburg, Germany
| | - R Huber
- Department of Physics, University of Regensburg, 93040 Regensburg, Germany
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8
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Vänskä O, Tittonen I, Koch SW, Kira M. Coherent terahertz control of vertical transport in semiconductor heterostructures. Phys Rev Lett 2015; 114:116802. [PMID: 25839300 DOI: 10.1103/physrevlett.114.116802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Indexed: 06/04/2023]
Abstract
Coherent-control protocols are introduced to selectively transport electrons, excitons, or pure two-particle correlations through semiconductor interfaces. The scheme is tested in a double-quantum-well structure where a sequence of terahertz pulses is applied to induce the vertical excitation transfer between the wells. Using a microscopic theory, it is shown that efficient and highly selective transfer can be realized even in the presence of the unavoidable scattering and dephasing processes.
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Affiliation(s)
- O Vänskä
- Department of Micro- and Nanosciences, Aalto University, P.O. Box 13500, FI-00076 Aalto, Finland
- Department of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, 35032 Marburg, Germany
| | - I Tittonen
- Department of Micro- and Nanosciences, Aalto University, P.O. Box 13500, FI-00076 Aalto, Finland
| | - S W Koch
- Department of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, 35032 Marburg, Germany
| | - M Kira
- Department of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, 35032 Marburg, Germany
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9
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Abstract
Sufficiently strong interactions promote coherent quantum transitions in spite of thermalization and losses, which are the adversaries of delicate effects such as reversibility and correlations. In atomic Bose–Einstein condensates (BECs), strong atom–atom interactions can eject atoms from the BEC to the normal component, yielding quantum depletion instead of temperature depletion. A recent experiment has already been verified to overcome losses. Here I show that it also achieves coherent quantum-depletion dynamics in a BEC swept fast enough from weak to strong atom–atom interactions. The elementary coherent process first excites the normal component into a liquid state that evolves into a spherical shell state, where the atom occupation peaks at a finite momentum to shield 50% of the BEC atoms from annihilation. The identified coherent processes resemble ultrafast semiconductor excitations expanding the scope of BEC explorations to many-body non-equilibrium studies. To overcome losses and thermalization, a quantum system requires strong interactions. Following recent experiments, Mackillo Kira shows that a BEC swept fast enough from weak to strong interactions exhibits coherent quantum-depletion dynamics dominated by particle clusters, resembling semiconductor excitations.
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Affiliation(s)
- M Kira
- Department of Physics, Philipps-University Marburg, Renthof 5, D-35032 Marburg, Germany
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10
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Berger C, Huttner U, Mootz M, Kira M, Koch SW, Tempel JS, Aßmann M, Bayer M, Mintairov AM, Merz JL. Quantum-memory effects in the emission of quantum-dot microcavities. Phys Rev Lett 2014; 113:093902. [PMID: 25215985 DOI: 10.1103/physrevlett.113.093902] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Indexed: 06/03/2023]
Abstract
The experimentally measured input-output characteristics of optically pumped semiconductor microcavities exhibits unexpected oscillations modifying the fundamentally linear slope in the excitation power regime below lasing. A systematic microscopic analysis reproduces these oscillations, identifying them as a genuine quantum-memory effect, i.e., a photon-density correlation accumulated during the excitation. With the use of projected quantum measurements, it is shown that the input-output oscillations can be controlled and enhanced by an order of magnitude when the quantum fluctuations of the pump are adjusted.
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Affiliation(s)
- C Berger
- Department of Physics, Philipps-Universität Marburg, Renthof 5, D-35032 Marburg, Germany
| | - U Huttner
- Department of Physics, Philipps-Universität Marburg, Renthof 5, D-35032 Marburg, Germany
| | - M Mootz
- Department of Physics, Philipps-Universität Marburg, Renthof 5, D-35032 Marburg, Germany
| | - M Kira
- Department of Physics, Philipps-Universität Marburg, Renthof 5, D-35032 Marburg, Germany
| | - S W Koch
- Department of Physics, Philipps-Universität Marburg, Renthof 5, D-35032 Marburg, Germany
| | - J-S Tempel
- Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund, Germany
| | - M Aßmann
- Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund, Germany
| | - M Bayer
- Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund, Germany and Ioffe Physical-Technical Institute of the Russian Academy of Sciences, Saint Petersburg, 194021, Russia
| | - A M Mintairov
- Ioffe Physical-Technical Institute of the Russian Academy of Sciences, Saint Petersburg, 194021, Russia and Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - J L Merz
- Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA
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11
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Almand-Hunter AE, Li H, Cundiff ST, Mootz M, Kira M, Koch SW. Quantum droplets of electrons and holes. Nature 2014; 506:471-5. [DOI: 10.1038/nature12994] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 12/12/2013] [Indexed: 11/09/2022]
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12
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Jahnke F, Kira M, Koch S. Linear and nonlinear optical properties of excitons in semiconductor quantum wells and microcavities. ACTA ACUST UNITED AC 2014. [DOI: 10.1007/s002570050490] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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13
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Rice WD, Kono J, Zybell S, Winnerl S, Bhattacharyya J, Schneider H, Helm M, Ewers B, Chernikov A, Koch M, Chatterjee S, Khitrova G, Gibbs HM, Schneebeli L, Breddermann B, Kira M, Koch SW. Observation of forbidden exciton transitions mediated by Coulomb interactions in photoexcited semiconductor quantum wells. Phys Rev Lett 2013; 110:137404. [PMID: 23581371 DOI: 10.1103/physrevlett.110.137404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2012] [Revised: 11/27/2012] [Indexed: 06/02/2023]
Abstract
We use terahertz pulses to induce resonant transitions between the eigenstates of optically generated exciton populations in a high-quality semiconductor quantum well sample. Monitoring the excitonic photoluminescence, we observe transient quenching of the 1s exciton emission, which we attribute to the terahertz-induced 1s-to-2p excitation. Simultaneously, a pronounced enhancement of the 2s exciton emission is observed, despite the 1s-to-2s transition being dipole forbidden. A microscopic many-body theory explains the experimental observations as a Coulomb-scattering mixing of the 2s and 2p states, yielding an effective terahertz transition between the 1s and 2s populations.
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Affiliation(s)
- W D Rice
- Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005, USA
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14
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Cundiff S, Hunter A, Smith R, Mootz M, Kira M, Koch S. Quantum-Optical Spectroscopy of Semiconductors. EPJ Web of Conferences 2013. [DOI: 10.1051/epjconf/20134104001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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15
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Tomaino JL, Jameson AD, Lee YS, Khitrova G, Gibbs HM, Klettke AC, Kira M, Koch SW. Terahertz excitation of a coherent λ-type three-level system of exciton-polariton modes in a quantum-well microcavity. Phys Rev Lett 2012; 108:267402. [PMID: 23005012 DOI: 10.1103/physrevlett.108.267402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Indexed: 06/01/2023]
Abstract
Interactions of few-cycle terahertz pulses with the induced optical polarization in a quantum-well microcavity reveal that the lower and higher exciton-polariton modes together with the optically forbidden 2p-exciton state form a unique Λ-type three-level system. Pronounced nonlinearities are observed via time-resolved strong-terahertz and weak-optical excitation spectroscopy and explained with a fully microscopic theory. The results show that the terahertz pulses strongly couple the exciton-polariton states to the 2p-exciton state while no resonant transition between the two polariton levels is observed.
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Affiliation(s)
- J L Tomaino
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
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Blanchard F, Golde D, Su FH, Razzari L, Sharma G, Morandotti R, Ozaki T, Reid M, Kira M, Koch SW, Hegmann FA. Effective mass anisotropy of hot electrons in nonparabolic conduction bands of n-doped InGaAs films using ultrafast terahertz pump-probe techniques. Phys Rev Lett 2011; 107:107401. [PMID: 21981526 DOI: 10.1103/physrevlett.107.107401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Revised: 04/20/2011] [Indexed: 05/31/2023]
Abstract
The anisotropic effective mass of energetic electrons in an isotropic, nonparabolic conduction band is revealed using ultrafast THz-pump-THz-probe techniques in a n-doped InGaAs semiconductor thin film. A microscopic theory is applied to identify the origin of the observed anisotropy and to show that the self-consistent light-matter coupling contributes significantly to the THz response.
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Affiliation(s)
- F Blanchard
- INRS-EMT, Advanced Laser Light Source, Université du Québec, Varennes, Québec J3X 1S2, Canada
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17
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Smith RP, Wahlstrand JK, Funk AC, Mirin RP, Cundiff ST, Steiner JT, Schafer M, Kira M, Koch SW. Extraction of many-body configurations from nonlinear absorption in semiconductor quantum wells. Phys Rev Lett 2010; 104:247401. [PMID: 20867334 DOI: 10.1103/physrevlett.104.247401] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Indexed: 05/29/2023]
Abstract
Detailed electronic many-body configurations are extracted from quantitatively measured time-resolved nonlinear absorption spectra of resonantly excited GaAs quantum wells. The microscopic theory assigns the observed spectral changes to a unique mixture of electron-hole plasma, exciton, and polarization effects. Strong transient gain is observed only under cocircular pump-probe conditions and is attributed to the transfer of pump-induced coherences to the probe.
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Affiliation(s)
- R P Smith
- JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309-0440, USA
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18
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Okazaki K, Kira M, Yamai H, Nakagawa Y, Nagao T, Kenzaki K, Bando Y, Morimoto T, Kondo K, Tangoku A. Phase II trial report of the new neoadjuvant chemotherapy with S-1 and docetaxel for advanced breast cancer. J Clin Oncol 2009. [DOI: 10.1200/jco.2009.27.15_suppl.1121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
1121 Background: Primary chemotherapy with anthracycline and taxanes is a gold standard regimen which realize pathologically complete response in 20% of patients with advanced breast cancer. However, sequential administration of anthracycline and taxanes induces serious side effects. This regimen is therefore difficult to use for higj-risk patients. S-1 is a new oral anti-tumor drug, which is composed of 5-fluoro-1-(tetrahydro -2- furanyl)-2, 4(1H, 3H)-pyrimidinedione (Tegafur, FT), 5-chloro-2, 4- dihydroxypyridine (Gimeracil, CDHP) and potassium 1, 2, 3, 4-tetrahydro-2, 4-dioxo-1, 3, 5-triazine-6-carboxylate (potassium Oteracil, Oxo). Combined treatment with docetaxel and S-1 yielded significant response in patients with gastric cancer with minimal side effects due to biochemical modulation of both CDHP and Oxo. The purpose of this study was to evaluate the efficacy and toxicity of docetaxel in combination with S-1 for advanced breast cancer. Methods: Patients with advanced breast cancer (Stage IIA to IV) were treated with i.v. docetaxel (40mg/m2) on day 1 and oral S-1(80mg as FT/m2/day) on days 1 to 14 every 3 weeks for 8 courses. The clinical response was evaluated every 3 months with MMG, MRI, ultrasonography and CT scan based on RECIST criteria. The patients underwent surgery after completion of chemotherapy. Pathologic examination was performed with thin-sliced specimens. The specimens were also reserved for genetic analysis. Written informed consent was obtained from all patients or family members after the Ethics Committee of Tokushima University Hospital approved the study protocol. Results: Twenty-two patients completed the therapy and underwent surgery. Four cases (18.2%) of pathologic complete response (pCR) were recognized on pathologic examination. The response rate was 90.9% and 95.5% of the patients could preserved their breast. Bone marrow suppression was substantial, and low-grade anorexia, nausea, and peripheral neuropathy were observed. Conclusions: The new regimen of S-1 combined with docetaxel is expected to exhibit satisfactory efficacy in treating advanced breast cancer as primary chemotherapy. Genetic analysis will be performed to examine and to find biomarkers for measurement of the efficacy of this therapy. No significant financial relationships to disclose.
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Affiliation(s)
- K. Okazaki
- The University of Tokushima Graduate School, Tokushima, Japan; Department of Pathology, Tokushima University Hospital, Tokushima, Japan
| | - M. Kira
- The University of Tokushima Graduate School, Tokushima, Japan; Department of Pathology, Tokushima University Hospital, Tokushima, Japan
| | - H. Yamai
- The University of Tokushima Graduate School, Tokushima, Japan; Department of Pathology, Tokushima University Hospital, Tokushima, Japan
| | - Y. Nakagawa
- The University of Tokushima Graduate School, Tokushima, Japan; Department of Pathology, Tokushima University Hospital, Tokushima, Japan
| | - T. Nagao
- The University of Tokushima Graduate School, Tokushima, Japan; Department of Pathology, Tokushima University Hospital, Tokushima, Japan
| | - K. Kenzaki
- The University of Tokushima Graduate School, Tokushima, Japan; Department of Pathology, Tokushima University Hospital, Tokushima, Japan
| | - Y. Bando
- The University of Tokushima Graduate School, Tokushima, Japan; Department of Pathology, Tokushima University Hospital, Tokushima, Japan
| | - T. Morimoto
- The University of Tokushima Graduate School, Tokushima, Japan; Department of Pathology, Tokushima University Hospital, Tokushima, Japan
| | - K. Kondo
- The University of Tokushima Graduate School, Tokushima, Japan; Department of Pathology, Tokushima University Hospital, Tokushima, Japan
| | - A. Tangoku
- The University of Tokushima Graduate School, Tokushima, Japan; Department of Pathology, Tokushima University Hospital, Tokushima, Japan
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19
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Werchner M, Schafer M, Kira M, Koch SW, Sweet J, Olitzky JD, Hendrickson J, Richards BC, Khitrova G, Gibbs HM, Poddubny AN, Ivchenko EL, Voronov M, Wegener M. One dimensional resonant Fibonacci quasicrystals: noncanonical linear and canonical nonlinear effects. Opt Express 2009; 17:6813-6828. [PMID: 19365510 DOI: 10.1364/oe.17.006813] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A detailed experimental and theoretical study of the linear and nonlinear optical properties of different Fibonacci-spaced multiple-quantum-well structures is presented. Systematic numerical studies are performed for different average spacing and geometrical arrangement of the quantum wells. Measurements of the linear and nonlinear (carrier density dependent) reflectivity are shown to be in good agreement with the computational results. As the pump pulse energy increases, the excitation-induced dephasing broadens the exciton resonances resulting in a disappearance of sharp features and reduction in peak reflectivity.
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Affiliation(s)
- M Werchner
- Department of Physics and Material Sciences Centre, Philipps-Universität, Renthof 5, D-35032 Marburg, Germany.
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20
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Golde D, Wagner M, Stehr D, Schneider H, Helm M, Andrews AM, Roch T, Strasser G, Kira M, Koch SW. Fano signatures in the intersubband terahertz response of optically excited semiconductor quantum wells. Phys Rev Lett 2009; 102:127403. [PMID: 19392323 DOI: 10.1103/physrevlett.102.127403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Indexed: 05/27/2023]
Abstract
Absorption and transmission spectra of broadband terahertz pulses are measured to probe the intersubband response of an optically excited quantum-well heterostructure. While the terahertz absorption shows the single peak of the resonant intersubband transition, the transmission spectra display strong Fano signatures due to the phase sensitive superposition of ponderomotive and terahertz currents as predicted by our microscopic theory.
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Affiliation(s)
- D Golde
- Department of Physics and Materials Sciences Center, Philipps-University, Renthof 5, 35032 Marburg, Germany.
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21
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Chatterjee S, Grunwald T, Köhler D, Pierz K, Golde D, Kira M, Koch S. THz measurements of the optical response in a two-dimensional electron gas. ACTA ACUST UNITED AC 2009. [DOI: 10.1002/pssc.200880337] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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22
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Leinb S, Kampfrath T, Volkmann K, Wolf M, Steiner JT, Kira M, Koch SW, Leitenstorfer A, Huber R. Terahertz coherent control of optically dark paraexcitons in Cu2O. Phys Rev Lett 2008; 101:246401. [PMID: 19113639 DOI: 10.1103/physrevlett.101.246401] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2008] [Indexed: 05/27/2023]
Abstract
Intense multiterahertz fields of order megavolts per centimeter are used to coherently promote optically dark and dense paraexcitons in Cu2O from the 1s into the 2p state. The nonlinear field response of the intraexcitonic degrees of freedom is directly monitored in the time domain via ultrabroadband electro-optic sampling. The experimental results are analyzed with a microscopic many-body theory, identifying up to two internal Rabi cycles. The effects of population inversion and ponderomotive contributions are disentangled.
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Affiliation(s)
- S Leinb
- Fachbereich Physik, Universität Konstanz, Fach M 696, 78457 Konstanz, Germany
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23
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Schneebeli L, Kira M, Koch SW. Characterization of strong light-matter coupling in semiconductor quantum-dot microcavities via photon-statistics spectroscopy. Phys Rev Lett 2008; 101:097401. [PMID: 18851657 DOI: 10.1103/physrevlett.101.097401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Indexed: 05/26/2023]
Abstract
It is shown that spectrally resolved photon-statistics measurements of the resonance fluorescence from realistic semiconductor quantum-dot systems allow for high contrast identification of the two-photon strong-coupling states. Using a microscopic theory, the second-rung resonance of Jaynes-Cummings ladder is analyzed and optimum excitation conditions are determined. The computed photon-statistics spectrum displays gigantic, experimentally robust resonances at the energetic positions of the second-rung emission.
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Affiliation(s)
- L Schneebeli
- Department of Physics and Material Sciences Center, Philipps-University, 35032 Marburg, Germany.
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24
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Danielson JR, Lee YS, Prineas JP, Steiner JT, Kira M, Koch SW. Interaction of strong single-cycle terahertz pulses with semiconductor quantum wells. Phys Rev Lett 2007; 99:237401. [PMID: 18233409 DOI: 10.1103/physrevlett.99.237401] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Indexed: 05/25/2023]
Abstract
An experiment-theory comparison is presented to demonstrate terahertz-induced extreme-nonlinear transients in a GaAs/AlGaAs quantum-well system. The terahertz-pump and optical-probe experiments show pronounced spectral modulations of the light- and heavy-hole excitonic resonances. Excellent agreement with the results of microscopic many-body calculations is obtained, identifying clear ponderomotive contributions and the generation of terahertz harmonics.
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Affiliation(s)
- J R Danielson
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
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25
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Bozsoki P, Thomas P, Kira M, Hoyer W, Meier T, Koch SW, Maschke K, Varga I, Stolz H. Characterization of disorder in semiconductors via single-photon interferometry. Phys Rev Lett 2006; 97:227402. [PMID: 17155841 DOI: 10.1103/physrevlett.97.227402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Indexed: 05/12/2023]
Abstract
The method of angular photonic correlations of spontaneous emission is introduced as an experimental, purely optical scheme to characterize disorder in semiconductor nanostructures. The theoretical expression for the angular correlations is derived and numerically evaluated for a model system. The results demonstrate how the proposed experimental method yields direct information about the spatial distribution of the relevant states and thus on the disorder present in the system.
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Affiliation(s)
- P Bozsoki
- Department of Physics and Material Sciences Center, Philipps-Universität Marburg, D-35032, Marburg, Germany
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26
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Affiliation(s)
- K. Ebihara
- a Dept. of Appl. Physics , Tokyo Institute of Technology , Tokyo , 152 , Japan
| | - S. Koshihara
- a Dept. of Appl. Physics , Tokyo Institute of Technology , Tokyo , 152 , Japan
- b Photodynamics Res. Center, Inst. Phys. 4 Chem. Res. (RIKEN) , Sendai , 980 , Japan
| | - T. Miyazawa
- b Photodynamics Res. Center, Inst. Phys. 4 Chem. Res. (RIKEN) , Sendai , 980 , Japan
| | - M. Kira
- b Photodynamics Res. Center, Inst. Phys. 4 Chem. Res. (RIKEN) , Sendai , 980 , Japan
- c Dept. Chemistry, Graduate School of Science , Tohoku University , Sendai , 980-77 , Japan
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27
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Koch SW, Kira M, Khitrova G, Gibbs HM. Semiconductor excitons in new light. Nat Mater 2006; 5:523-31. [PMID: 16819475 DOI: 10.1038/nmat1658] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2006] [Accepted: 04/18/2006] [Indexed: 05/10/2023]
Abstract
Excitons are quasi-particles that form when Coulomb-interacting electrons and holes in semiconductors are bound into pair states. They have many features analogous to those of atomic hydrogen. Because of this, researchers are interested in exploring excitonic phenomena, from optical, quantum-optical and thermodynamic transitions to the possible condensation of excitons into a quantum-degenerate state. Excitonic signatures commonly appear in the optical absorption and emission of direct-gap semiconductor systems. However, the precise properties of incoherent exciton populations in such systems are difficult to determine and are the subject of intense debate. We review recent contributions to this discussion, and argue that to obtain detailed information about exciton populations, conventional experimental techniques should be supplemented by direct quasi-particle spectroscopy using the relatively newly available terahertz light sources. Finally, we propose a scheme of quantum-optical excitation to generate quantum-degenerate exciton states directly.
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Affiliation(s)
- S W Koch
- Department of Physics and Material Sciences Centre, Philipps-Universität, Renthof 5, D-35032 Marburg, Germany.
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28
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Hoyer W, Knorr A, Moloney JV, Wright EM, Kira M, Koch SW. Photoluminescence and terahertz emission from femtosecond laser-induced plasma channels. Phys Rev Lett 2005; 94:115004. [PMID: 15903868 DOI: 10.1103/physrevlett.94.115004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2004] [Indexed: 05/02/2023]
Abstract
Luminescence as a mechanism for terahertz emission from femtosecond laser-induced plasmas is studied. By using a fully microscopic theory, Coulomb scattering between electrons and ions is shown to lead to luminescence even for a spatially homogeneous plasma. The spectral features introduced by the rod geometry of laser-induced plasma channels in air are discussed on the basis of a generalized mode-function analysis.
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Affiliation(s)
- W Hoyer
- Arizona Center for Mathematical Sciences and Optical Sciences Center, University of Arizona, Tucson, AZ 85721, USA.
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29
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Peyghambarian N, Qiu T, Polynkin P, Schulzgen A, Li L, Temyanko V, Mansuripur M, Moloney JV, Chatterjee S, Ell C, Mosor S, Khitrova G, Gibbs HM, Hoyer W, Kira M, Koch SW, Prineas JP, Stolz H. Semiconductor Optics. ACTA ACUST UNITED AC 2004. [DOI: 10.1364/opn.15.12.000041] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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30
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Kira M, Koch SW. Exciton-population inversion and terahertz gain in semiconductors excited to resonance. Phys Rev Lett 2004; 93:076402. [PMID: 15324255 DOI: 10.1103/physrevlett.93.076402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2004] [Indexed: 05/24/2023]
Abstract
The buildup of exciton populations in resonantly laser excited semiconductors is studied microscopically. For excitation around the 2s-exciton resonance, it is shown that polarization with a strict s-type radial symmetry can be efficiently converted into an incoherent p-type population. As a consequence, inversion between the 2p and 1s exciton states can be obtained leading to the appearance of significant terahertz gain.
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Affiliation(s)
- M Kira
- Fachbereich Physik and Material Sciences Center, Philipps Universität, Renthof 5, 35032 Marburg, Germany
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31
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Hoyer W, Kira M, Koch SW, Stolz H, Mosor S, Sweet J, Ell C, Khitrova G, Gibbs HM. Entanglement between a photon and a quantum well. Phys Rev Lett 2004; 93:067401. [PMID: 15323660 DOI: 10.1103/physrevlett.93.067401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2003] [Indexed: 05/24/2023]
Abstract
The lack of translational invariance perpendicular to the plane of a single quantum well causes equal probability for spontaneous emission to the left or right. Combining one emission path from the left and one from the right into a common detector leads to interference fringes for fundamentally indistinguishable paths corresponding to geometries where the same in-plane momentum is transferred to the quantum well. For all other paths, no interference is observed because of the entanglement between the photon and extended Bloch states of the many-body system. In multiple-quantum-well structures the interference can be controlled via the spacing between the wells.
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Affiliation(s)
- W Hoyer
- Department of Physics, Philipps-University, Renthof 5, D-35032 Marburg, Germany.
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Chatterjee S, Ell C, Mosor S, Khitrova G, Gibbs HM, Hoyer W, Kira M, Koch SW, Prineas JP, Stolz H. Excitonic photoluminescence in semiconductor quantum wells: plasma versus excitons. Phys Rev Lett 2004; 92:067402. [PMID: 14995274 DOI: 10.1103/physrevlett.92.067402] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2003] [Indexed: 05/24/2023]
Abstract
Time-resolved photoluminescence spectra after nonresonant excitation show a distinct 1s resonance, independent of the existence of bound excitons. A microscopic analysis identifies exciton and electron-hole plasma contributions. For low temperatures and low densities, the excitonic emission is extremely sensitive to details of the electron-hole-pair population making it possible to identify even minute fractions of optically active excitons.
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Affiliation(s)
- S Chatterjee
- Optical Sciences Center, The University of Arizona, Tucson, Arizona 85721-0094, USA
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Abstract
By the reduction of an isolable dialkylsilylene, 2,2,5,5-[tetrakis(trimethylsilyl)]-1-silacyclopentane-1,1-diyl (1), with cesium, rubidium, potassium, sodium, and lithium 4,4'-di(tert-butyl)biphenylide in DME at low temperatures, the corresponding silylene radical anion 2 was generated as the first persistent silylene radical anion in solution and characterized by ESR spectroscopy. Radical anion 2 is rather stable at -70 degrees C in DME but decomposes rapidly at room temperature with a half-life time of ca. 20 min. The g-factor and 29Si hyperfine splitting constants (hfs's) of 2 are almost independent of the countercations, indicating that 2 exists as a free ion or a solvent-separated ion pair in a polar DME solution. A very small hfs due to the 29Si nucleus of the divalent silicon (3.0 mT) as well as a very large g-factor (2.0077) indicates that an unpaired electron is accommodated in the vacant 3ppi orbital of silylene 1.
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Affiliation(s)
- S Ishida
- Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
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Ishida S, Iwamoto T, Kabuto C, Kira M. A stable silicon-based allene analogue with a formally sp-hybridized silicon atom. Nature 2003; 421:725-7. [PMID: 12610620 DOI: 10.1038/nature01380] [Citation(s) in RCA: 218] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2002] [Accepted: 12/17/2002] [Indexed: 11/09/2022]
Abstract
Carbon chemistry exhibits a rich variety in bonding patterns, with homo- or heteronuclear multiple bonds involving sp-hybridized carbon atoms as found in molecules such as acetylenes, nitriles, allenes and carbon dioxide. Carbon's heavier homologues in group 14 of the periodic table--including silicon, germanium and tin--were long thought incapable of forming multiple bonds because of the less effective p(pi)-p(pi) orbital overlap involved in the multiple bonds. However, bulky substituents can protect unsaturated bonds and stabilize compounds with formally sp-hybridized heavy group-14 atoms: stable germanium, tin and lead analogues of acetylene derivatives and a marginally stable tristannaallene have now been reported. However, no stable silicon compounds with formal sp-silicon atoms have been isolated. Evidence for the existence of a persistent disilaacetylene and trapping of transient 2-silaallenes and other X = Si = X' type compounds (X, X' = O, CR2, NR, and so on) are also known, but stable silicon compounds with formally sp-hybridized silicon atoms have not yet been isolated. Here we report the synthesis of a thermally stable, crystalline trisilaallene derivative containing a formally sp-hybridized silicon atom. We find that, in contrast to linear carbon allenes, the trisilaallene is significantly bent. The central silicon in the molecule is dynamically disordered, which we ascribe to ready rotation of the central silicon atom around the molecular axis.
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Affiliation(s)
- S Ishida
- Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
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36
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37
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Affiliation(s)
- T Iwamoto
- Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai, 980-8578, Japan
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38
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Kira M, Hoyer W, Stroucken T, Koch SW. Exciton formation in semiconductors and the influence of a photonic environment. Phys Rev Lett 2001; 87:176401. [PMID: 11690287 DOI: 10.1103/physrevlett.87.176401] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2001] [Indexed: 05/23/2023]
Abstract
A fully microscopic theory is presented for interacting electrons, holes, photons, and phonons in semiconductor heterostructures. The formation dynamics and statistics of incoherent excitons are analyzed for different densities, lattice temperatures, and photonic environments. Luminescence experiments are shown to depend strongly on the photonic environment in contrast to suggested terahertz absorption measurements. Whereas luminescence in free space is dominated by plasma contributions, terahertz absorption should be able to directly measure excitonic populations.
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Affiliation(s)
- M Kira
- Laser Physics and Quantum Optics, Royal Institute of Technology, Lindstedsvägen 24, S-10044 Stockholm, Sweden
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Veszprémi T, Takahashi M, Hajgató B, Kira M. The mechanism of 1,2-addition of disilene and silene. 1. Water and alcohol addition. J Am Chem Soc 2001; 123:6629-38. [PMID: 11439050 DOI: 10.1021/ja0040823] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mechanism of 1,2-addition reactions of water, methanol, and trifluoromethanol to Si=Si, Si=C, and C=C bonds has been investigated by ab initio quantum chemical methods. Geometries and relative energies of the stationary points and all the transition states were determined using the MP2/6-311++G(d,p), B3LYP/6-311++G(d,p), and CBS-Q levels of theory. The investigated reactions can be characterized by two main thermodynamical profiles. The type in which the reagent molecule attacks a carbon atom is moderately exothermic, with a high activation barrier. The second type, in which water or alcohol attacks a silicon, is strongly exothermic, with a small activation energy. At the early stage of all the reactions, a weakly bonded initial complex is found which determines the further mechanism of the reaction. On the basis of the HOMO, LUMO, and Laplacian of electron distribution of disilene and silene, several mechanisms have been assumed, depending on the substrate (disilene, substituted disilene, silene, or ethene) and the reagent (water, methanol, or trifluoromethanol). The reaction diagrams and proposed mechanisms explain the experimentally found regioselectivity and diastereoselectivity well.
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Affiliation(s)
- T Veszprémi
- Department of Inorganic Chemistry, Technical University of Budapest, 1521 Budapest, Hungary
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Abstract
Mechanisms of the reactions of three tetrakis(trialkylsilyl)disilenes and a tetraaryldisilene with various haloalkanes such as carbon tetrachloride, chloroform, dichloromethane, which gave the corresponding 1-alkyl-2-chlorodisilanes and/or 1,2-dichlorodisilanes, were investigated in detail. As evidenced by an ESR observation of an intermediate radical, these reactions were quite unusual, forming neutral radical pairs from two closed shell molecules at the first step; no similar reactions have been observed between alkenes and haloalkanes. Low oxidation potentials of these disilenes, large negative activation entropies, and solvent effects for the rates are in good accord with the direct halogen abstraction of disilenes from haloalkanes instead of single-electron transfer at the rate-determining first step. The structure--reactivity relationship of the reactions and the Hammond postulate suggest that the transition state structures for the first step are similar to those for the halogen abstraction by silyl radicals, but more product-like.
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Affiliation(s)
- M Kira
- Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
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Ohyama Y, Tomiguchi S, Kira T, Kira M, Tsuji A, Koi A, Matsumoto M, Takahashi M, Inobe Y, Yasue H. Diagnostic accuracy of simultaneous acquisition of transmission and emission data with technetium-99m transmission source on thallium-201 myocardial SPECT. Ann Nucl Med 2001; 15:21-6. [PMID: 11355777 DOI: 10.1007/bf03012126] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
PURPOSE This study evaluates not only the clinical usefulness but also the problems in attenuation correction for thallium-201 (Tl-201) myocardial SPECT by means of simultaneous transmission and emission data acquisition in the detection of coronary artery disease (CAD). METHODS A three-detector SPECT system equipped with a Tc-99m line source and fan-beam collimators was used for simultaneous transmission and emission data acquisition for Tl-201 myocardial SPECT in 73 patients (18 patients for normal database and 55 patients for the evaluation of diagnostic accuracy). Attenuation-corrected (AC) images and non-attenuation-corrected (NC) images were reconstructed with an iterative maximum-likelihood estimation-corrected (ML-EM) algorithm. Both sets of images were reoriented into the short axis. Normal database polar maps were constructed from the AC and NC images for quantitative analysis. RESULTS There was a significant difference in specificity between NC and AC images in the RCA territory and those in specificity and accuracy in the LCX territory. There was no significant difference in sensitivity found between NC and AC images in either territory, but sensitivity in both territories tended to decrease with attenuation correction. In the LAD territory, there were various changes in sensitivity and specificity observed with attenuation correction in cases with each quantitative criterion. CONCLUSIONS Diagnostic performance of significant stenosis in the RCA and LCX territories quantitatively improved with attenuation correction because of an increase in specificity, but no significant improvement in diagnostic performance was obtained in the LAD territory with attenuation correction. We recommend combined interpretation of AC and NC images and careful evaluation of any SPECT image by means of transmission computed tomography.
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Affiliation(s)
- Y Ohyama
- Department of Radiology, Kumamoto University School of Medicine, Japan
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Takahashi M, Tsutsui S, Sakamoto K, Kira M, Müller T, Apeloig Y. Dimers of diaminosilylenes: doubly bonded or bridged? The dimers of (i-Pr(2)N)(2)Si:. J Am Chem Soc 2001; 123:347-8. [PMID: 11456528 DOI: 10.1021/ja003463d] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- M Takahashi
- Photodynamics Research Center The Institute of Physical and Chemical Research (RIKEN) 519-1399, Aoba, Aramaki, Aoba-ku, Sendai 980-0845, Japan
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Ell C, Brick P, Hübner M, Lee ES, Lyngnes O, Prineas JP, Khitrova G, Gibbs HM, Kira M, Jahnke F, Koch SW, Deppe DG, Huffaker DL. Quantum correlations in the nonperturbative regime of semiconductor microcavities. Phys Rev Lett 2000; 85:5392-5395. [PMID: 11136004 DOI: 10.1103/physrevlett.85.5392] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2000] [Indexed: 05/23/2023]
Abstract
The nonlinear optical response of semiconductor microcavities in the nonpertubative regime is studied in resonant single-beam-transmission and pump-probe experiments. In both cases a pronounced third transmission peak lying spectrally between the two normal modes is observed. A fully quantized theory is essential for the agreement with the experimental observations, demonstrating that quantum fluctuations leading to intraband polarizations are responsible for this effect.
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Affiliation(s)
- C Ell
- Optical Sciences Center, University of Arizona, Tucson, Arizona 85721, USA
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Sano S, Kira M, Takagi S, Yoshikawa K, Takeda J, Itami S. Two distinct signaling pathways in hair cycle induction: Stat3-dependent and -independent pathways. Proc Natl Acad Sci U S A 2000; 97:13824-9. [PMID: 11087819 PMCID: PMC17660 DOI: 10.1073/pnas.240303097] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The hair follicle is an epidermal derivative that undergoes cycles of growth, involution, and rest. The hair cycle has well-orchestrated kinetics regulated by interactions between mesenchymal and epithelial cells, although the intracellular signals remain unclear. We previously established keratinocyte-specific Stat3-disrupted mice, by which we demonstrated that signal transducer and activator of transcription 3 (Stat3) is required for wound healing and anagen progression in the hair cycle. Growth factor-dependent migration of Stat3-disrupted keratinocytes was severely impaired, suggesting that not only wound healing but also telogen-to-anagen progression required organized keratinocyte migration in response to mesenchymal stimuli. In the present study, to examine whether Stat3 activation in keratinocytes is a prerequisite for hair cycle progression, we applied methods for experimental anagen induction to Stat3-disrupted mice. It was demonstrated that anagen was successfully induced in Stat3-disrupted as well as wild-type mice by chemical or mechanical stimulation, i.e. , by topical application of phorbol 12-myristate 13-acetate (PMA) or by hair plucking, respectively. This result indicated that anagen in these methods occurred in the absence of Stat3. Furthermore, PMA stimulated the migration of Stat3-disrupted keratinocytes in vitro, supporting a hypothesis that the protein kinase C (PKC) and Stat3 pathways occur independently in the postnatal anagen induction. Both Stat3-dependent and -independent migration of keratinocytes was inhibited by a phosphoinositide 3-kinase (PI3K) inhibitor, wortmannin. Therefore, we infer that entry into anagen is mediated by at least two distinct signaling pathways: Stat3-dependent pathway for spontaneous hair cycling and Stat3-independent (probably PKC-dependent) pathway for exogenously induced hair cycling, whereas both pathways require PI3K activation.
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Affiliation(s)
- S Sano
- Departments of Dermatology and Social and Environmental Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
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Abstract
In contrast to carbon, silicon does not readily form double bonds, and compounds containing silicon-silicon double bonds can usually be stabilized only by protection with bulky substituents. We have isolated a silicon analog of spiropentadiene 1, a carbon double-ring compound that has not been isolated to date. In the crystal structure of tetrakis[tri(t-butyldimethylsilyl)silyl]spiropentasiladiene 2, a substantial deviation from the perpendicular arrangement of the two rings is observed, and the silicon-silicon double bonds are shown to be distorted. Spectroscopic data indicate pronounced interaction between two remote silicon-silicon double bonds in the molecule. Silicon-silicon bonds may be more accessible to synthesis than previously assumed.
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Affiliation(s)
- T Iwamoto
- Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
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Kojima A, Ohyama Y, Tomiguchi S, Kira M, Matsumoto M, Takahashi M, Motomura N, Ichihara T. Quantitative planar imaging method for measurement of renal activity by using a conjugate-emission image and transmission data. Med Phys 2000; 27:608-15. [PMID: 10757612 DOI: 10.1118/1.598900] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
We are proposing a method to accurately measure renal activity in renography using Tc-99m labeled tracers. This method uses a conjugate-view image and transmission data for attenuation correction, the triple energy window (TEW) method for scatter correction, and background correction techniques that consider the source volume for accurate background activity correction. To examine this method in planar imaging, we performed two renal phantom studies with various uniform background activity concentrations. One study used two ideal box-shaped kidney phantoms with a thickness of 2 or 4 cm in a water tank and the other study employed two real kidney-shaped phantoms in a fillable abdominal cavity. For these studies the kidney phantom-to-background activity concentration ratio (S) was changed from 5 to infinity. The transmission data were obtained with an external Tc-99m line array source. The anterior- and posterior-view emission images were acquired with a dual-headed gamma camera simultaneously and the TEW method was used to correct scatter for the emission and transmission images. The results showed that this method with both the accurate background correction and scatter correction could give depth-independent count rates and could estimate the true count rate with errors of less than 5% for all S values. However, if either accurate background correction or scatter correction was performed alone, the absolute error increased to about 50% for the smaller S values. Our proposed method allows one to accurately and simply measure the renal radioactivity by planar imaging using the conjugate-emission image and transmission data.
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Affiliation(s)
- A Kojima
- Radioisotope Research Center, Kumamoto University, Japan.
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Manaka T, Hoshi H, Ishikawa K, Takezoe H, Koshihara S, Kira M, Miyazawa T. Large order–disorder transition in polydihexylsilane films as studied by second-harmonic generation spectroscopy. Chem Phys Lett 2000. [DOI: 10.1016/s0009-2614(99)01382-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Park S, Zapasskii V, Wick D, Nelson T, Ell C, Gibbs H, Khitrova G, Schulzgen A, Kira M, Jahnke F, Koch S. Spontaneous emission lifetime of carriers in a semiconductor microcavity measured by photoluminescence without distortion by reabsorption. Opt Express 1999; 4:512-524. [PMID: 19396309 DOI: 10.1364/oe.4.000512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A theory for carrier decay rates and a technique for measuring them are reported. Modification of the spontaneous emission rate of carriers by a semiconductor microcavity is investigated with 100-nm-thick bulk GaAs. Reabsorption makes the cavity-mode photoluminescence (PL) decay much faster than the square of the carrier density. Here reabsorption distortion is avoided by collecting PL that escapes the microcavity directly without multiple reflections: a ZnSe prism glued to the top mirror allows PL to escape at angles beyond the cutoff angle for total internal reflection without the prism. At these steep angles, the stop band of the top mirror has shifted to higher energy, so that it does not impede PL emission. Removal of most of the bottom mirror decreases the true carrier decay rate by only 25%, showing that the large enhancements deduced from cavity-mode PL are incorrect. Fully quantum mechanical computation including guided modes corroborates this conclusion. The prism technique could be used to study carrier dynamics and competition between guided and cavity modes in microcavities below and near threshold.
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