249 research outputs found
An isotropic antenna based on Rydberg atoms
Governed by the hairy ball theorem, classical antennas with isotropic
responses to linearly polarized radio waves are unrealizable. This work shows
that the antenna based on Rydberg atoms can theoretically achieve an ideal
isotropic response to linearly polarized radio waves; that is, it has zero
isotropic deviation. Experimental results of isotropic deviation within 5 dB,
and 0.3 dB achievable after optimization, in microwave and terahertz wave
measurements support the theory and are at least 15 dB improvement than the
classical omnidirectional antenna. Combined with the SI traceable and
ultrawideband property, the ideal isotropic response will make radio wave
measurement based on atomic antenna much more accurate and reliable than the
traditional method. This isotropic atomic antenna is an excellent example of
what a tailored quantum sensor can realize, but a classical sensor cannot. It
has crucial applications in fields such as radio wave electrometry
High bandwidth laser-frequency-locking for wideband noise suppression
Ultra-low frequency noise lasers have been widely used in laser-based
experiments. Most narrow-linewidth lasers are implemented by actively
suppressing their frequency noise through a frequency noise servo loop (FNSL).
The loop bandwidths (LBW) of FNSLs are currently below megahertz, which is
gradually tricky to meet application requirements, especially for wideband
quantum sensing experiments. This article has experimentally implemented an
FNSL with loop-delay-limited 3.5 MHz LBW, which is an order higher than the
usual FNSLs. Using this FNSL, we achieved 70 dB laser frequency noise
suppression over 100 kHz Fourier frequency range. This technology has broad
applications in vast fields where wideband laser frequency noise suppression is
inevitable
Noise analysis of the atomic superheterodyne receiver based on flat-top laser beams
Since its theoretical sensitivity is limited by quantum noise, radio wave
sensing based on Rydberg atoms has the potential to replace its traditional
counterparts with higher sensitivity and has developed rapidly in recent years.
However, as the most sensitive atomic radio wave sensor, the atomic
superheterodyne receiver lacks a detailed noise analysis to pave its way to
achieve theoretical sensitivity. In this work, we quantitatively study the
noise power spectrum of the atomic receiver versus the number of atoms, where
the number of atoms is precisely controlled by changing the diameters of
flat-top excitation laser beams. The results show that under the experimental
conditions that the diameters of excitation beams are less than or equal to 2
mm and the read-out frequency is larger than 70 kHz, the sensitivity of the
atomic receiver is limited only by the quantum noise and, in the other
conditions, limited by classical noises. However, the experimental
quantum-projection-noise-limited sensitivity this atomic receiver reaches is
far from the theoretical sensitivity. This is because all atoms involved in
light-atom interaction will contribute to noise, but only a fraction of them
participating in the radio wave transition can provide valuable signals. At the
same time, the calculation of the theoretical sensitivity considers both the
noise and signal are contributed by the same amount of atoms. This work is
essential in making the sensitivity of the atomic receiver reach its ultimate
limit and is significant in quantum precision measurement
Quantum scaling atomic superheterodyne receiver
Measurement sensitivity is one of the critical indicators for Rydberg atomic
radio receivers. This work quantitatively studies the relationship between the
atomic superheterodyne receiver's sensitivity and the number of atoms involved
in the measurement. The atom number is changed by adjusting the length of the
interaction area. The results show that for the ideal case, the sensitivity of
the atomic superheterodyne receiver exhibits a quantum scaling: the amplitude
of its output signal is proportional to the atom number, and the amplitude of
its read-out noise is proportional to the square root of the atom number.
Hence, its sensitivity is inversely proportional to the square root of the atom
number. This work also gives a detailed discussion of the properties of transit
noise in atomic receivers and the influence of some non-ideal factors on
sensitivity scaling. This work is significant in the field of atom-based
quantum precision measurements
Knock-Down of a Tonoplast Localized Low-Affinity Nitrate Transporter OsNPF7.2 Affects Rice Growth under High Nitrate Supply
The large nitrate transporter 1/peptide transporter family (NPF) has been shown to transport diverse substrates, including nitrate, amino acids, peptides, phytohormones, and glucosinolates. However, the rice (Oryza sativa) root-specific expressed member OsNPF7.2 has not been characterized. Here, our data show that OsNPF7.2 is a tonoplast localized low-affinity nitrate transporter, and affects rice growth under high nitrate supply. The expression analysis showed that OsNPF7.2 was mainly expressed in the elongation and maturation zones of roots, especially in the root sclerenchyma, cortex and stele. It was also induced by high concentrations of nitrate. Subcellular localization analysis showed that OsNPF7.2 was localized on the tonoplast of large and small vacuoles. Heterogenous expression in Xenopus laevis oocytes suggested that OsNPF7.2 was a low-affinity nitrate transporter. Knock-down of OsNPF7.2 retarded rice growth under high concentrations of nitrate. Therefore, we deduce that OsNPF7.2 plays a role in intracellular allocation of nitrate in roots, and thus influences rice growth under high nitrate supply
Up-regulation of CNDP2 facilitates the proliferation of colon cancer
BACKGROUND: Cytosolic nonspecific dipetidase (CN2) belongs to the family of M20 metallopeptidases. It was stated in previous articles that higher expression levels of CN2 were observed in renal cell carcinoma and breast cancer. Our study explored the correlation between CN2 and colon carcinogenesis. METHODS: We analysed the relationship between 183 patients clinicopathological characteristics and its CN2 expression. To detect the levels of CN2 in colon cancer cell lines and colon cancer tissues by western blot. To verify cell proliferation in colon cancer cells with knockdown of CNDP2 and explore the causes of these phenomena. RESULTS: The expression levels of CN2 in clinical colon tumors and colon cancer cell lines were significantly higher than that in normal colon mucosa and colon cell lines. The difference in CN2 levels was associated with tumor location (right- and left-sided colon cancer), but there was no significant association with age, gender, tumor size, tumor grade, tumor stage or serum carcinoembryonic antigen (CEA). Knockdown of CNDP2 inhibited cell proliferation, blocked cell cycle progression and retarded carcinogenesis in an animal model. The signaling pathway through which knockdown of CNDP2 inhibited cell proliferation and tumorigenesis involved in EGFR, cyclin B1 and cyclin E. CONCLUSIONS: Knockdown of CNDP2 can inhibit the proliferation of colon cancer in vitro and retarded carcinogenesis in vivo
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