19,697 research outputs found
Hertz-level Measurement of the 40Ca+ 4s 2S1/2-3d 2D5/2 Clock Transition Frequency With Respect to the SI Second through GPS
We report a frequency measurement of the clock transition of a single ^40Ca^+
ion trapped and laser cooled in a miniature ring Paul trap with 10^-15 level
uncertainty. In the measurement, we used an optical frequency comb referenced
to a Hydrogen maser, which was calibrated to the SI second through the Global
Positioning System (GPS). Two rounds of measurements were taken in May and June
2011, respectively. The frequency was measured to be 411 042 129 776 393.0(1.6)
Hz with a fractional uncertainty of 3.9{\times}10^-15 in a total averaging time
of > 2{\times}10^6 s within 32 days
Privatization, Public R&D Policy, and Private R&D Investment in China's Agriculture
Private R&D is a major source of innovation and productivity growth in agriculture worldwide. This paper examines trends and determinants of agricultural R&D in China. Results show that while the public sector monopolized agricultural research until recently, private agricultural R&D has grown rapidly since 2000, driven largely by agribusiness privatization. Public-sector R&D investments in basic research also encouraged private R&D research, but public investments in technology development crowded out private R&D investment. China’s private R&D investment would grow more rapidly if the government shifted public resources from technology development to basic research.Agriculture, China, Private R&D, Privatization, Public R&D, Research and Development/Tech Change/Emerging Technologies,
Scheme for sharing classical information via tripartite entangled states
We investigate schemes for quantum secret sharing and quantum dense coding
via tripartite entangled states. We present a scheme for sharing classical
information via entanglement swapping using two tripartite entangled GHZ
states. In order to throw light upon the security affairs of the quantum dense
coding protocol, we also suggest a secure quantum dense coding scheme via W
state in analogy with the theory of sharing information among involved users.Comment: 4 pages, no figure. A complete rewrritten vession, accepted for
publication in Chinese Physic
From insulator to quantum Hall liquid at low magnetic fields
We have performed low-temperature transport measurements on a GaAs
two-dimensional electron system at low magnetic fields. Multiple
temperature-independent points and accompanying oscillations are observed in
the longitudinal resistivity between the low-field insulator and the quantum
Hall (QH) liquid. Our results support the existence of an intermediate regime,
where the amplitudes of magneto-oscillations can be well described by
conventional Shubnikov-de Haas theory, between the low-field insulator and QH
liquid.Comment: Magneto-oscillations governed by Shubnikov-de Haas theory are
observed between the low-field insulator and quantum Hall liqui
LinearCoFold and LinearCoPartition: Linear-Time Algorithms for Secondary Structure Prediction of Interacting RNA molecules
Many ncRNAs function through RNA-RNA interactions. Fast and reliable RNA
structure prediction with consideration of RNA-RNA interaction is useful. Some
existing tools are less accurate due to omitting the competing of
intermolecular and intramolecular base pairs, or focus more on predicting the
binding region rather than predicting the complete secondary structure of two
interacting strands. Vienna RNAcofold, which reduces the problem into the
classical single sequence folding by concatenating two strands, scales in cubic
time against the combined sequence length, and is slow for long sequences. To
address these issues, we present LinearCoFold, which predicts the complete
minimum free energy structure of two strands in linear runtime, and
LinearCoPartition, which calculates the cofolding partition function and base
pairing probabilities in linear runtime. LinearCoFold and LinearCoPartition
follows the concatenation strategy of RNAcofold, but are orders of magnitude
faster than RNAcofold. For example, on a sequence pair with combined length of
26,190 nt, LinearCoFold is 86.8x faster than RNAcofold MFE mode (0.6 minutes
vs. 52.1 minutes), and LinearCoPartition is 642.3x faster than RNAcofold
partition function mode (1.8 minutes vs. 1156.2 minutes). Different from the
local algorithms, LinearCoFold and LinearCoPartition are global cofolding
algorithms without restriction on base pair length. Surprisingly, LinearCoFold
and LinearCoPartition's predictions have higher PPV and sensitivity of
intermolecular base pairs. Furthermore, we apply LinearCoFold to predict the
RNA-RNA interaction between SARS-CoV-2 gRNA and human U4 snRNA, which has been
experimentally studied, and observe that LinearCoFold's prediction correlates
better to the wet lab results
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