Demonstration of chronometric leveling using transportable optical clocks beyond laser coherence limit

Optical clock network requires the establishment of optical frequency transmission link between multiple optical clocks, utilizing narrow linewidth lasers. Despite achieving link noise levels of 10${^{-20}}$, the final accuracy is limited by the phase noise of the clock laser. Correlation spectroscopy is developed to transmit frequency information between two optical clocks directly, enabling optical clock comparison beyond the phase noise limit of clock lasers, and significantly enhancing the measurement accuracy or shorten the measurement time. In this letter, two compact transportable ${^{40}}$Ca${^+}$ clocks are employed to accomplish the correlation spectroscopy comparison, demonstrating an 10 cm level measurement accuracy of chronometric leveling using a mediocre clock laser with linewidth of 200 Hz. The relative frequency instability reaches $6.0\times10{^{-15}}/\sqrt{\tau/s}$, which is about 20 times better than the result with Rabi spectroscopy using the same clock laser. This research greatly reduces the harsh requirements on the performance of the clock laser, so that an ordinary stable-laser can also be employed in the construction of optical clock network, which is essential for the field applications, especially for the chronometric leveling

Characterization of <i>Colletotrichum</i> Species Infecting Litchi in Hainan, China

Litchi (Litchi chinensis) is an evergreen fruit tree grown in subtropical and tropical countries. China accounts for 71.5% of the total litchi cultivated area in the world. Anthracnose disease caused by Colletotrichum species is one of the most important diseases of litchi in China. In this study, the causal pathogens of litchi anthracnose in Hainan, China, were determined using phylogenetic and morphological analyses. The results identified eight Colletotrichum species from four species complexes, including a proposed new species. These were C. karsti from the C. boninense species complex; C. gigasporum and the proposed new species C. danzhouense from the C. gigasporum species complex; C. arecicola, C. fructicola species complex; C. arecicola, C. fructicola and C. siamense from the C. gloeosporioides species complex; and C. musicola and C. plurivorum from the C. orchidearum species complex. Pathogenicity tests showed that all eight species could infect litchi leaves using a wound inoculation method, although the pathogenicity was different in different species. To the best of our knowledge, the present study is the first report that identifies C. arecicola, C. danzhouense, C. gigasporum and C. musicola as etiological agents of litchi anthracnose

Evaluation of the systematic shifts of a

Quantum-logic-based $${}^{27}\text {Al}^{+}$$ optical clock has been demonstrated in several schemes as there are different choices of the auxiliary ion species. In this paper, we present the first detailed evaluation of the systematic shift and the total uncertainty of an $${}^{27}\text {Al}^{+}$$ optical clock sympathetically cooled by a $${}^{40}\text {Ca}^{+}$$ ion. The total systematic uncertainty of the $${}^{40}\text {Ca}^{+}- {}^{27}\text {Al}^{+}$$ quantum logic clock has been estimated to be $$7.9\times 10^{-18}$$, which was mainly limited by the uncertainty of the quadratic Zeeman shift. By comparing the frequency of two counter-propagating clock beams on the same ion, we measured the frequency stability to be $$3.7 \times 10^{-14} /\sqrt{\tau }$$

Vegetation indices used in this study and their method of calculation.

<p>R_R = Reflectance of red band with the range from 650–680 nm</p><p>R_NIR = Reflectance of near-infrared band with the range from 780–890 nm</p><p>R_G = Reflectance of green band with the range from 560–600 nm.</p><p>Vegetation indices used in this study and their method of calculation.</p

Linear correlation between spectral reflectance and disease indexes of wheat powdery mildew at GS 10.5.3, 10.5.4 and 11.1 in 2009–2010 and 2010–2011 seasons for the plant density 1 (60 kg seed ha^-1) (A) and density 2 (120 kg seed ha^-1) (B).

<p>Linear correlation between spectral reflectance and disease indexes of wheat powdery mildew at GS 10.5.3, 10.5.4 and 11.1 in 2009–2010 and 2010–2011 seasons for the plant density 1 (60 kg seed ha^-1) (A) and density 2 (120 kg seed ha^-1) (B).</p

Progress curves of wheat powdery mildew epidemics on plant density 1 (60 kg seed/ha) (A) and density 2 (120 kg seed/ha) (B) with different concentrations of fungicide applications in Langfang City in 2009–2010 and 2010–2011 seasons.

<p>Disease severity was assessed (0–9 scale) at GS 10.5.3, 10.5.4 and 11.1.</p