Results 21 to 30 of about 12,552,614 (315)
One Time, Two Times, or No Time? [PDF]
, 2021 Contemporary research programs in fundamental physics appear to suggest that there could be two (physical) times---or none at all. This essay articulates these possibilities in the context of quantum gravity, and in particular of cosmological models developed in an approach called `loop quantum gravity', and explains how they could nevertheless ...
openaire +2 more sources
382 mW External-Cavity Frequency Doubling 461 nm Laser Based on Quasi-Phase Matching
Photonics, 2023 To rapidly improve strontium optical clocks, a high-power, high-efficiency, and high-beam-quality 461 nm laser is required. In blue lasers based on periodically poled KTiOPO4 crystals, the optical absorption in the crystals can induce thermal effects ...
Yingxin Chen +3 more
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A Quantum-Based Microwave Magnetic Field Sensor
Sensors, 2018 In this paper, a quantum-based method for measuring the microwave magnetic field in free space is presented by exploring atomic Rabi resonance in the clock transition of 133Cs.
Hao Shi +5 more
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Recent Advances Concerning the 87Sr Optical Lattice Clock at the National Time Service Center
Applied Sciences, 2018 We review recent experimental progress concerning the 87Sr optical lattice clock at the National Time Service Center in China. Hertz-level spectroscopy of the 87Sr clock transition for the optical lattice clock was performed, and closed-loop operation of
Yebing Wang +4 more
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Photonics, 2021 A polarization-insensitive recirculating delayed self-heterodyne method (PI-RDSHM) is proposed and demonstrated for the precise measurement of sub-kilohertz laser linewidths. By a unique combination of Faraday rotator mirrors (FRMs) in an interferometer,
Jing Gao +8 more
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Primitive TiderThis paper has provided an overview over the Viking Age burials containing textile- and cooking equipment, such as spindlewhorls, woolcombs, weaver`s baton, frying pans and loom weights in combination with weapons.
Lillian Time
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Experimental Evaluation of the Blackbody Radiation Shift in the Cesium Atomic Fountain Clock
Applied Sciences, 2022 The cesium atomic fountain clock is the world’s most accurate microwave atomic clock. The uncertainty of blackbody radiation (BBR) shift accounts for an increasingly large percentage of the uncertainty associated with fountain clocks and has become a key
Fan Yang +10 more
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Pediatric Blood &Cancer, EarlyView.ABSTRACT Background Pediatric patients with extracranial solid tumors (ST) receiving chemotherapy are at an increased risk for Pneumocystis jirovecii pneumonia (PJP). However, evidence guiding prophylaxis practices in this population is limited. A PJP‐related fatality at our institution highlighted inconsistent prescribing approaches and concerns about
Kriti Kumar +8 more
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Sickle Cell Disease Is an Inherent Risk for Asthma in a Sibling Comparison Study
Pediatric Blood &Cancer, EarlyView.ABSTRACT Introduction Sickle cell disease (SCD) and asthma share a complex relationship. Although estimates vary, asthma prevalence in children with SCD is believed to be comparable to or higher than the general population. Determining whether SCD confers an increased risk for asthma remains challenging due to overlapping symptoms and the ...
Suhei C. Zuleta De Bernardis +9 more
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Precision measurement of transverse velocity distribution of a strontium atomic beam
AIP Advances, 2014 We measure the transverse velocity distribution in a thermal Sr atomic beam precisely by velocity-selective saturated fluorescence spectroscopy. The use of an ultrastable laser system and the narrow intercombination transition line of Sr atoms mean that ...
F. Gao +7 more
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