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Measurement of magnetic field stability using 40Ca+ ion
Pham, Minh Tuan ; Lešundák, Adam ; Čížek, Martin ; Podhora, L. ; Řeřucha, Šimon ; Jedlička, Petr ; Slodička, L. ; Lazar, Josef ; Číp, Ondřej
One of the main limitations in the long-term measurement of the clock transition's absolute frequency is the magnetic field's fluctuation. The time-varying fluctuation of the external magnetic field leads to frequency shifts of the Zeeman components, thereby reducing the optical clock's frequency stability over time. Currently, optical atomic references are usually implemented with the help of a single ion. However, scaling the number of ions to higher values brings an indisputable benefit in the form of a high signal-to-noise ratio and, thus to the efficiency of the entire measurement process. In this case, the ions are spread over a large area, forming so-called ionic Coulomb crystals. In addition to the spatial stability of the magnetic field, the homogeneity of the magnetic field is also significant when working with Coulomb crystals. Excessive magnetic perturbation can be greatly reduced by covering the assembly with a magnetic shield or by using permanent magnets instead of conventionally used magnetic coils. Another method is averaging over multiple-level transitions. This contribution presents a simple method for measuring the stability of the magnetic field at the ion position.
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SMV-2022-31: He-Ne-I2 cells
Hrabina, Jan ; Holá, Miroslava ; Lazar, Josef ; Šarlejová, Tatiana ; Šlechtický, Stanislav
The contractual research was oriented towards the development of optical frequency references intended for the frequency stabilisation of ultra-compact laser sources. These optical references were based on absorption cells filled with ultra-pure absorption gases and they allow precise locking of the lasers with the methods of laser spectroscopy. The cells will serve as the references of optical frequencies in systems of primary length standards (633 nm wavelength).
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Studies of cell signaling triggered by the TRH receptor
Trubačová, Radka ; Novotný, Jiří (advisor) ; Brejchová, Jana (referee) ; Lazar, Josef (referee)
Activation of thyrotropin-releasing hormone receptor (TRH-R) signaling has an irreplaceable role in a number of cellular processes. Thyroliberin (TRH) plays an important role in the regulation of secretion of other hormones and there are also mentions of its possible antiapoptotic and neuroprotective effects. On the other hand, TRH is quickly degraded and also its other properties, such as cardiac and endocrine side effects and low lipophilicity, disadvantage the therapeutic applications of this hormone compared to its various analogues. Due to their effects on the central nervous systém, TRH and its analogues represent a potential possibility for the treatment of various neurological diseasses, including neurodegenerative disorders. The molecular mechanisms responsible for the beneficial effects of TRH and its analogues have not yet been fully elucidated. So far, little is known about the involvement of TRH, or its analogues, in the regulation of energy metabolism or impact on the cellular phosphoproteome. In the first part of the thesis, we focused on the study of the effect of TRH and interacting partners of TRH-R on the lateral mobility of this receptor in the membrane of the TRY-1 cell line stably expressing TRH-R labeled with yellow fluorescent protein (YFP) at the C-terminus. The results of...
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Fragmentation-free ultrastable transfers through shared optical fibers
Vojtěch, J. ; Smotlacha, V. ; Havliš, O. ; Šlapák, M. ; Altmannová, L. ; Kundrát, J. ; Vohnout, R. ; Velc, R. ; Čížek, Martin ; Hrabina, Jan ; Řeřucha, Šimon ; Pravdová, Lenka ; Lazar, Josef ; Číp, Ondřej ; Kuna, Alexander ; Roztočil, J.
Fibre optics transfers of precise time and ultra-stable optical frequency are gradually becoming part of portfolio of network services of research and educational networks. These national infrastructures very often share fibres with regular data transmission, because of significant share of fibre cost rental on the Total Cost of Ownership (TCO). Situation is very similar in the Czech Republic, where there was more than 3000 km of ultra-stable transmissions within Czech e-Infrastructure, which itself runs over about 5800 km of dark fibre lines.
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Highly-coherent laser for precise optical frequencies dissemination
Pravdová, Lenka ; Čížek, Martin ; Hrabina, Jan ; Jelínek, Michal ; Řeřucha, Šimon ; Mikel, Břetislav ; Lazar, Josef ; Havliš, O. ; Altmannová, L. ; Smotlacha, V. ; Vojtěch, J. ; Velc, R. ; Číp, Ondřej
The paper presents a multipurpose laser with a very narrow spectral line, operating at a wavelength of 1540 nm and designed for cooled ions spectroscopy and the dissemination of precise optical frequencies over optical fibre links. The optical frequency of a commercial single-mode laser (NKT Photonics Koheras Basik) is spectrally narrowed to the level of several Hz using a high-quality optical resonator as an optical reference and an acousto-optic modulator as an active control element. The optical resonator is made of a low length thermal expansion coefficient material and is placed in a multi-shell vacuum chamber providing a stable operating environment. Optical frequency stabilisation uses PDH (Pound-Drewer-Hall) modulation and detection technique.
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