Kenichi Karatsu
Publications
- Optimisation-based alignment of wide-band integrated superconducting spectrometers for submillimeter astronomy
Moerman, A.; Karatsu, K.; Yates, S. J. C.; Huiting, R.; Steenvoorde, F.; Dabironezare, S. O.; Takekoshi, T.; Baselmans, J. J. A.; Brandl, B. R.; Endo, A.;
Astronomy & Astrophysics,
Volume 684, pp. A161, Apr. 2024. - Origin of the mm-submm loss in deposited dielectrics
B.T. Buijtendorp; A. Endo; W. Jellema; K. Karatsu; K. Kouwenhoven; D. Lamers; A. J. van der Linden; K. Rostem; M. Veen; E. J. Wollack; J. J. A. Baselmans; S. Vollebregt;
arXiv:2405.13688,
2024.
document - Origin of mm-submm loss in deposited dielectrics for superconducting astronomical instrumentation
Bruno T. Buijtendorp; Akira Endo; Willem Jellema; Kenichi Karatsu; Ton van der Linden; Dimitry Lamers; Karwan Rostem; Edward J. Wollack; Jochem J. A. Baselmans; Sten Vollebregt; Robert Huisman; Martijn Veen;
In Proceedings Volume PC13102, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XII,
2024. DOI: 10.1117/12.3020071 - DESHIMA 2.0 on ASTE: commissioning and science verification of an ultra-wideband integrated superconducting spectrometer
Akira Endo; Kenichi Karatsu; Tatsuya Takekoshi; Yoichi Tamura; Akio Taniguchi; Matus Rybak; Kotaro Kohno; Hiroki Akamatsu; Javier Aguilera; Tom J. L. C. Bakx; Bruno T. Buijtendorp; Scott Cray; Shahab Dabironezare; Yasunori Fujii; Kazuyuki Fujita; Masato Hagimoto; Shaul Hanany; Shuji Hotta; Robert Huiting; Takahiro Iino; Chihiro Imamura; Shun Ishii; Kotaro Iwakami; Tetsu Kitayama; Kuniaki Konishi; Ryohei Kawabe; Micah Klettke; ;
In Proceedings Volume PC13102, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XII,
2024. DOI: 10.1117/12.3015295 - Improvement of on-chip terahertz spectroscopy by nanometer-scale control of electron-beam lithography
Leon Olde Scholtenhuis; Kenichi Karatsu; David J. Thoen; Louis H. Marting; Jochem J. A. Baselmans; Sten Vollebregt; Akira Endo;
In Proceedings Volume 13092, Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave,
2024. DOI: 10.1117/12.3017946 - PyPO: a Python package for Physical Optics
Arend Moerman; Maikel H. Gafaji; Kenichi Karatsu; Akira Endo;
Journal of Open Source Software,
Volume 8, Issue 88, pp. 5247, 2023. DOI: 10.21105/joss.05478 - Hydrogenated amorphous silicon carbide: A low-loss deposited dielectric for microwave to submillimeter-wave superconducting circuits
B. T. Buijtendorp; S. Vollebregt; K. Karatsu; D. J. Thoen; V. Murugesan; K. Kouwenhoven; S. Hähnle; J. J. A. Baselmans; A. Endo;
Physical Review Applied,
Volume 18, pp. 064003, 2022. DOI: 10.1103/PhysRevApplied.18.064003 - Hydrogenated Amorphous Silicon Carbide: A Low-loss Deposited Dielectric for Microwave to Submillimeter Wave Superconducting Circuits
Buijtendorp, B. T.; Vollebregt, S. ; Karatsu, K.; Thoen, D. J.; Murugesan, V.; Kouwenhoven, K.; Hähnle, S.; Baselmans, J. J. A.; Endo, A.;
Physical Review Applied,
Volume 18, Issue 6, pp. 064003, 2022. DOI: https://doi.org/10.1103/PhysRevApplied.18.064003 - DESHIMA 2.0: Development of an Integrated Superconducting Spectrometer for Science Grade Astronomical Observations
Akio Taniguchi; Tom J. L. C. Bakx; Jochem J. A. Baselmans and Robert Huiting; Kenichi Karatsu; Nuria Llombart; et al.;
Journal of Low Temperature Physics,
Volume 209, pp. 278-286, Nov. 2022. DOI: 10.1007/s10909-022-02888-5 - TiEMPO: open-source time-dependent end-to-end model for simulating ground-based submillimeter astronomical observations
Huijten, E.; Roelvink, Y.; Brackenhoff, S. A.; Taniguchi, A.; Bakx, T. J. L. C.; Marthi, K. B.; Zaalberg, S.; Doing A.-K.; Baselmans, J. J. A.; Chin, K. W.; Huiting, R.; Karatsu, K.; Pascual Laguna, A.; Tamura, Y.; Takekoshi, T.; Yates, S. J. C.; van Hoven, M.; Endo, A.;
J. of Astronomical Telescopes, Instruments and systems,
Volume 8, Issue 2, 2022. DOI: http://dx.doi.org/10.1117/1.JATIS.8.2.028005 - Low-loss a-SiC:H for superconducting microstrip lines for (sub-)millimeter astronomy
Bruno T. Buijtendorp; Akira Endo; Kenichi Karatsu; David Thoen; Vignesh Murugesan; Kevin Kouwenhoven; Sebastian Hähnle; Jochem J. A. Baselmans; Sten Vollebregt;
In Proc. SPIE PC12190, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XI,
pp. PC121900W, 2022. DOI: 10.1117/12.2630107 - Simulating the radiation loss of superconducting submillimeter wave filters and transmission lines using Sonnet EM
Endo, A.; Pascual Laguna, A.; Haehnle, S.; Karatsu, K.; Thoen, D. J.; Murugesan, V.; Baselmans, J. J. A;
In Proc. SPIE 11453, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X,
2022. DOI: https://doi.org/10.1117/12.2560458 - Terahertz band-pass filters for wideband superconducting on-chip filter-bank spectrometers
Pascual Laguna, A.; K. Karatsu; D.J. Thoen; V. Murugesan; B. T. Buijtendorp and A. Endo; J.J.A. Baselmans;
IEEE Transactions on Terahertz Science and Technology,
Volume 11, Issue 6, pp. 635-646, Nov. 2021. DOI: 10.1109/TTHZ.2021.3095429 - Superconducting Microstrip Losses at Microwave and Submillimeter Wavelengths
Hähnle, S.; Kouwenhoven, K.; Buijtendorp, B.; Endo, A.; Karatsu, K.; Thoen, D.J.; Murugesan, V.; Baselmans, J.J.A.;
Physical Review Applied,
Volume 16, Issue 1, pp. 014019, Jul. 2021. DOI: 10.1103/PhysRevApplied.16.014019
document - Hydrogenated Amorphous Silicon Carbide: A Low-loss Deposited Dielectric for Microwave to Submillimeter Wave Superconducting Circuits
B. T. Buijtendorp; S. Vollebregt; K. Karatsu; D. J. Thoen; V. Murugesan; K. Kouwenhoven; S. Hähnle; J. J. A. Baselmans, A. Endo;
arXiv,
2021.
document - DESHIMA 2.0: Rapid redshift surveys and multi-line spectroscopy of dusty galaxies
Rybak, M.; Bakx, T.; Baselmans, J.; Karatsu, K.; Kohno, K.; Takekoshi, T.; Tamura, Y.; Taniguchi, A.; van der Werf, P.; Endo, A.;
Journal of Low Temperature Physics,
2021. DOI: https://doi.org/10.1007/s10909-022-02730-y - DESHIMA on ASTE: On-Sky Responsivity Calibration of the Integrated Superconducting Spectrometer
T. Takekoshi; K. Karatsu; J. Suzuki; Y. Tamura; T. Oshima; A. Taniguchi; S. Asayama; T.J.L.C. Bakx; J.J.A. Baselmans; S. Bosma; J. Bueno; K.W. Chin; Y. Fujii; K. Fujita; R. Huiting; S. Ikarashi; T. Ishida; S. Ishii; R. Kawabe; T.M. Klapwijk; K. Kohno; A. Kouchi; N. Llombart; J. Maekawa; V. Murugesan; S. Nakatsubo; M. Naruse; K. Ohtawara; Pascual Laguna, A.; K. Suzuki; D.J. Thoen; T. Tsukagoshi; T. Ueda; P.J. ;
J. Low Temp. Phys.,
2020.
document - Suppression of radiation loss in high kinetic inductance superconducting co-planar waveguides Suppression of radiation loss in high kinetic inductance superconducting co-planar waveguides
S. Haenle; N. v. Marrewijk; A. Endo; K. Karatsu; D.J. Thoen; V. Murugesan; J.J.A. Baselmans;
Applied Physics Letters,
Volume 116, Issue 18, 2020. DOI: 10.1063/5.0005047
document - Experimental Validation of the Beam Pattern of a Wide Band Quasi-Optical System for DESHIMA Spectrometer
Shahab Oddin Dabironezare; Kenichi Karatsu; Stephen Yates; Vignesh Murugesan; David Thoen; Jochem Baselmans; Nuria Llombart;
In 14th European Conference on Antennas and Propagation (EuCAP),
Copenhagen, Denmark, March 2020. - Wideband Superconducting Integrated Filter-bank for THz Astronomy
Pascual Laguna, A.; Karatsu, K.; Thoen, D.J.; Murugesan, V.; Endo, A.; Baselmans, J.J.A.;
In 14th European Conference on Antennas and Propagation (EuCAP),
Copenhagen, Denmark, March 2020. - Filter-bank for Broadband Sub-mm Wave Superconducting On-chip Spectrometers
Pascual Laguna, A.; Karatsu, K.; Thoen, D. J.; Murugesan, V.; Endo, A.; Baselmans, J. J. A.;
In Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X,
Yokohama, Japan, SPIE, International Society for Optics and Photonics, 2020. DOI: 10.1117/12.2560483 - Combining UV-and Electron beam lithography for superconducting bandpass filters in mm/sub-mm astronomy
Thoen, D.J.; Murugesan, V.; Karatsu, K.; Pascual Laguna, A.; Endo, A.; Baselmans,J.J.A.;
In Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X,
Yokohama, Japan, SPIE, International Society for Optics and Photonics, 2020. DOI: 10.1117/12.2561452 - Broadband Quasi-Optical System for On-chip Filter-bank Spectrometer Operating at Sub-mm Wavelengths
Dabironezare, S.O.; Karatsu, K.; Yates, S.J.C.; Pascual Laguna, A.; Murugesan, V.; Thoen, D.J.; Endo, A.; Baselmans, J.J.A.; Llombart, N.;
In Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X,
Yokohama, Japan, SPIE, International Society for Optics and Photonics, 2020. DOI: 10.1117/12.2562383 - DESHIMA on ASTE: on-sky performance and upgrade to ultra wideband
Akira Endo; Kenichi Karatsu; Yoichi Tamura; Tai Oshima; Akio Taniguchi; Tatsuya Takekoshi; Shin'ichiro Asayama; Tom J. L. C. Bakx; Sjoerd Bosma; Juan Bueno; Bruno Buijtendorp; Kah Wuy Chin; Yasunori Fujii; Kazuyuki Fujita; Esmee Huijten; Robert Huiting; Soh Ikarashi; Tsuyoshi Ishida; Shun Ishii; Ryohei Kawabe; Teun M. Klapwijk; Kotaro Kohno; Akira Kouchi; Nuria Llombart; Jun Maekawa; Vignesh Murugesan; Shunichi Nakatsubo; Masa;
In Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X,
SPIE, International Society for Optics and Photonics, 2020. DOI: 10.1117/12.2560669 - Development of an absolute frequency calibration system for a superconducting integrated spectrometer
Kenichi Karatsu; Zhongyue Zhang; Pascual Laguna A.; Shahab O. Dabironezare; Akira Endo; David J. Thoen; Vignesh Murugesan; Jochem J. A. Baselmans;
In Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X,
SPIE, International Society for Optics and Photonics, pp. 436 - 447, 2020. DOI: 10.1117/12.2561473 - Simulating the Radiation Loss of Superconducting Submillimeter Wave Filters and Transmission Lines Using Sonnet EM
A. Endo; Pascual Laguna, A.; S. Hähnle; K. Karatsu; D. J. Thoen; V. Murugesan; and J.J.A. Baselmans;
In Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X,
SPIE, International Society for Optics and Photonics, pp. 436 - 447, 2020. DOI: 10.1117/12.2560458 - TiEMPO: Open-Source Time-Dependent End-to-End Model for Simulating Ground-Based Submillimeter Astronomical Observations
E. Huijten; Y. Roelvink; S.A. Brackenhoff; A. Taniguchi; T.J.L.C. Bakx; K.B. Marthi; S. Zaalberg; J.J.A. Baselmans; K.W. Chin; R. Huiting; K. Karatsu; Pascual Laguna, A. ; Y. Tamura; T. Takekoshi; S.J.C. Yates; M. van Hoven; A. Endo;
In Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X,
SPIE, International Society for Optics and Photonics, pp. 562 - 581, Dec. 13 2020. DOI: 10.1117/12.2561014 - Large format imaging spectrograph for the Large Submillimeter Telescope (LST)
Kotaro Kohno; Ryohei Kawabe; Yoichi Tamura; Akira Endo; Jochem J. A. Baselmans; Kenichi Karatsu; Akio K. Inoue; Kana Moriwaki; Natsuki H. Hayatsu; Naoki Yoshida; Yuki Yoshimura; Bunyo Hatsukade; Hideki Umehata; Tai Oshima; Tatsuya Takekoshi; Akio Taniguchi; Pamela D. Klaassen; Tony Mroczkowski; Claudia Cicone; Frank Bertoldi; Helmut Dannerbauer; Tomoka Tosaki;
In Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X,
SPIE, International Society for Optics and Photonics, pp. 128 - 138, 2020. DOI: 10.1117/12.2561238 - Sky noise removal for submillimeter spectroscopy based on statistical methods
Akio Taniguchi; Yoichi Tamura; Kotaro Kohno; Shigeru Takahashi; Osamu Horigome; Jun Maekawa; Takeshi Sakai; Nario Kuno; Tetsuhiro Minamidani; Tom Bakx; Koyo Suzuki; Tatsuya Takekoshi; Takashi Tsukagoshi; Tai Oshima; Akira Endo; Kenichi Karatsu;
In Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X,
SPIE, International Society for Optics and Photonics, 2020. DOI: 10.1117/12.2560908 - Wideband on-chip terahertz spectrometer based on a superconducting filterbank
A.Endo; K. Karatsu; Pascual Laguna, A.; B. Mirzaei; R. Huiting; D.J. Thoen; V. Murugesan; S.J.C. Yates; J. Bueno; N. van Marrewijk; S. Bosma; O. Yurduseven; N. Llombart; J. Suzuki; M. Naruse; P.J. de Visser; P.P. van der Werf; T.M. Klapwijk; and J.J.A. Baselmans;
J. Astron. Telesc. Instrum. Syst.,
Volume 5, Issue 3, pp. 35004-(1-12), 2019.
document - First light demonstration of the integrated superconducting spectrometer
A. Endo; K. Karatsu; Y. Tamura; T. Oshima; A. Taniguchi; T. Takekoshi; S. Asayama; T.J.L. C. Bakx; S. Bosma; J. Bueno; K. W. Chin; Y. Fujii; K. Fujita; R. Huiting; S. Ikarashi; T. Ishida; S. Ishii; R. Kawabe; T. M. Klapwijk; K. Kohno; A. Kouchi; N. Llombart; J. Maekawa; V. Murugesan; S. Nakatsubo; M. Naruse; K. Ohtawara; Pascual Laguna, A.; J. Suzuki; K. Suzuki; D.J. Thoen; T. Tsukagoshi; T. Ueda; P.J. de Vis;
Nat. Astron.,
Volume 3, pp. 989-996, 2019.
document - Mitigation of cosmic ray effect on microwave kinetic inductance detector arrays
K. Karatsu; A. Endo; J. Bueno; P.J. de Visser; R. Barends; D.J. Thoen; V. Murugesan; N. Tomita; J.J.A. Baselmans;
Appl. Phys. Lett.,
Volume 114, Issue 3, 2019.
document - Wideband Sub-mm Wave Superconducting Integrated Filter-bank Spectrometer
Pascual Laguna, A.; K. Karatsu; A. Neto; A. Endo; J. J. A. Baselmans;
In 44th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW THz-2019),
Paris, France, Sep. 2019. - Designing a Gas Cell Experiment for the Calibration of DESHIMA
Z. Zhang; K. Karatsu; S. O. Dabironezare; D. Thoen; B. Brandl; J. Baselmans;
In 18th International Workshop on Low Temperature Detectors (LTD-18),
Milan, Italy, July 2019. - On the Design of Wideband Sub-mm Wave Superconducting Integrated Filter-bank Spectrometers
Pascual Laguna, A.; Karatsu, K.; Neto, A.; Endo, A.; Baselmans, J. J. A.;
In 18th International Workshop on Low Temperature Detectors,
Milan, Italy, 2019. - DESHIMA on ASTE: First astronomical light captured with an integrated superconducting spectrometer
A. Endo; K. Karatsu; Y. Tamura; T. Oshima; A. Taniguchi; T. Takekoshi; S. Asayama; T.J.L.C. Bakx; S. Bosma; J. Bueno; K.W. Chin; Y. Fujii; K. Fujita; R. Huiting; S. Ikarashi; T. Ishida; S. Ishii; R. Kawabe; T.M. Klapwijk; K. Kohno; A. Kouchi; N. Llombart; J. Maekawa; V. Murugesan; S. Nakatsubo; M. Naruse; K. Ohtawara; Pascual Laguna, A.; J. Suzuki; K. Suzuki; D.J. Thoen; T. Tsukagoshi; T. Ueda; P.J. de Visser;
In 18th International Workshop on Low Temperature Detectors,
Milan, Italy, 2019. - DESHIMA on ASTE: On-Sky Responsivity Calibration of the Integrated Superconducting Spectrometer
T. Takekoshi; K. Karatsu; J. Suzuki; Y. Tamura; T. Oshima; A. Taniguchi; S. Asayama; T.J.L.C. Bakx; J.J.A. Baselmans; S. Bosma; J. Bueno; K.W. Chin; Y. Fujii; K. Fujita; R. Huiting; S. Ikarashi; T. Ishida; S. Ishii; R. Kawabe; T.M. Klapwijk; K. Kohno; A. Kouchi; N. Llombart; J. Maekawa; V. Murugesan; S. Nakatsubo; M. Naruse; K. Ohtawara; Pascual Laguna, A.; K. Suzuki; D.J. Thoen; T. Tsukagoshi; T. Ueda; P.J. ;
In 18th International Workshop on Low Temperature Detectors,
Milan, Italy, 2019. - Ultrasensitive Kilo-Pixel Imaging Array of Photon Noise-Limited Kinetic Inductance Detectors Over an Octave of Bandwidth for THz Astronomy
J. Bueno; V. Murugesan; K. Karatsu; D.J. Thoen; J.J.A. Baselmans;
Journal of Low Temperature Physics,
2018. DOI: 10.1007/S10909-018-1962-8 - Superconducting submicron-CPW resonators for on-chip THz filterbank
Naruse, M.; Karatsu, K.; Pascual Laguna, A.; Yurduseven, O.; Thoen, D. J.; Murugesan, V.; Baselmans, J. J. A.;
In 31st International Symposium on Superconductivity (ISS 2018),
Tsukuba, Japan, 2018. - First light of DESHIMA on ASTE: on-chip filterbank spectrometer for submillimeter wave astronomy
Akira Endo; Kenichi Karatsu; Yoichi Tamura; Shun Ishii; Tatsuya Takekoshi; Tai Oshima; Akio Taniguchi; Tsuyoshi Ishida; Koyo Suzuki; David Thoen; Robert Huiting; Toshihiko Kobiki; Tom Bakx; Kaui Chin; Kazuyuki Fujita; Vignesh Murugesan; Sjoerd Bosma; Ozan Yurduseven; Tetsutaro Ueda; Masato Naruse; Shunichi Nakatsubo; Akira Kouchi; Jun Maekawa; Stephen Yates; Nuria Llombart; Teun Klapwijk; Ryohei Kawabe; Shin'ichiro Asayama and;
In SPIE Astronomical Telescopes + Instrumentation,
Austin, Texas, USA, July 2018. - DESHIMA: 新技術「超伝導オンチップ・フィルターバンク」による初の天体スペクトル検出
A. Endo; D.J. Thoen; O. Yurduseven; S. Bosma; N. Llombart; T.M. Klapwijk; K. Karatsu; R. Huiting; V. Murugesan; S.J.C. Yates; J.J.A. Baselmans; P.P. van der Werf; T. Ishida; A. Taniguchi; T. Takekoshi; K. Kohno; T. Oshima; S. Ishii; C. Kah Wuy; J. Maekawa; R. Kawabe; T. Kobiki; S. Asayama; K. Suzuki; T. Ueda; Y. Tamura; M. Naruse; K. Fujita; A. Kouchi; S. Nakatsubo; T.J.L.C. Bakx;
In Annual Meeting of the Astronomical Society of Japan,
Chiba, Japan, Chiba University, Mar. 14-17 2018. - Astronomical First Light of DESHIMA: On-chip Filterbank Spectrometer for Submillimeter Astronomy
A. Endo; D.J. Thoen; K. Karatsu; S. Bosma; O. Yurduseven; N. Llombart; M. Naruse; N. Tomita; J. Suzuki; A. Taniguchi; K. Kohno; S. Ishii; J. Maekawa; R. Kawabe; T. Oshima; K. Chin; Y. Tamura; T. Takekoshi; K. Fujita; A. Kouchi; S. Nakatsubo; T.M. Klapwijk; P.P. van der Werf; S.J.C. Yates; A.M. Baryshev; V. Murugesan; R. Huiting; J.J.A. Baselmans;
In A workshop to discuss science/technical aspects of the Atacama Large-Aperture Submm/mm Telescope (AtLAST),
ESO-HQ, Garching, München, Germany, Jan. 17-19 2018.
document - A kilo-pixel imaging system for future space based far-infrared observatories using microwave kinetic inductance detectors
J.J.A. Baselmans; J. Bueno; S.J.C. Yates; O. Yurduseven N. Llombart K. Karatsu; A.M. Baryshev L. Ferrari; A. Endo; D.J. Thoen; et al;
arXiv preprint,
2017. DOI: 10.1051/0004-6361/201629653
document - Development of ’DESHIMA’ on ASTE: towards a
field test of a submillimeter wave superconducting on-chip filterbank spectrometer based on kinetic
inductance detectors
A. Endo; D. Thoen; K. Karatsu; N. van Marrewijk; S. Bosma; O. Yurduseven; N. Llombart; M. Naruse; N. Tomita; J. Suzuki; A. Taniguchi; K. Kohno; S. Ishii; J. Maekawa; R. Kawabe; T. Oshima; K. Chin; Y. Tamu;
In 17th International Workshop on Low Temperature Detectors (LTD),
Kurumu, Japan, July 2017. - Development of Microwave Kinetic Inductance Detector for Cosmological Observations
K. Karatsu; S. Mima; S. Oguri; et al;
IEICE Transactions on Electronics,
Volume E98-C, Issue 3, pp. 207-218, March 2015.
document - Development of Frequency Sweeping Readout System for Microwave Kinetic Inductance Detectors
K. Karatsu; et al;
In The International Workshop on Low Temperature Detectors (LTD),
Grenoble, France, July 2015. - Radiation Tolerance of Al Microwave Kinetic Inductance Detector
K. Karatsu; et al;
In The International Workshop on Low Temperature Detectors (LTD),
Grenoble, France, July 2015.