453 research outputs found
Nature in Robert Browning’s Poems
Different from Romantic understanding of nature, in Browning’s poems, when nature is mentioned, there are two kinds of depictions. One type is to describe nature itself only, and there is nothing symbolic one can infer from the descriptions of nature or the descriptions have little relationship with its subject, that is, nature for nature’s sake. Though some depictions are related to the subject, they present the negative aspects of nature. As illustrated in “Childe Roland to the Dark Tower Came”, the natural settings are forlorn and bleak, like in a wasteland
The N-terminal domain of Lhcb proteins is critical for recognition of the LHCII kinase
AbstractThe light-harvesting chlorophyll (Chl) a/b complex of photosystem (PS) II (LHCII) plays important roles in the distribution of the excitation energy between the two PSs in the thylakoid membrane during state transitions. In this process, LHCII, homo- or heterotrimers composed of Lhcb1–3, migrate between PSII and PSI depending on the phosphorylation status of Lhcb1 and Lhcb2. We have studied the mechanisms of the substrate recognition of a thylakoid threonine kinase using reconstituted site-directed trimeric Lhcb protein–pigment complex mutants. Mutants lacking the positively charged residues R/K upstream of phosphorylation site (Thr) in the N-terminal domain of Lhcb1 were no longer phosphorylated. Besides, the length of the peptide upstream of the phosphorylated site (Thr) is also crucial for Lhcb phosphorylation in vitro. Furthermore, the two N-terminal residues of Lhcb appear to play a key role in the phosphorylation kinetics because Lhcb with N-terminal RR was phosphorylated much faster than with RK. Therefore, we conclude that the substrate recognition of the LHCII kinase is determined to a large extent by the N-terminal sequence of the Lhcb proteins. The study provides new insights into the interactions of the Lhcb proteins with the LHCII kinase
Multi-Factors Aware Dual-Attentional Knowledge Tracing
With the increasing demands of personalized learning, knowledge tracing has
become important which traces students' knowledge states based on their
historical practices. Factor analysis methods mainly use two kinds of factors
which are separately related to students and questions to model students'
knowledge states. These methods use the total number of attempts of students to
model students' learning progress and hardly highlight the impact of the most
recent relevant practices. Besides, current factor analysis methods ignore rich
information contained in questions. In this paper, we propose Multi-Factors
Aware Dual-Attentional model (MF-DAKT) which enriches question representations
and utilizes multiple factors to model students' learning progress based on a
dual-attentional mechanism. More specifically, we propose a novel
student-related factor which records the most recent attempts on relevant
concepts of students to highlight the impact of recent exercises. To enrich
questions representations, we use a pre-training method to incorporate two
kinds of question information including questions' relation and difficulty
level. We also add a regularization term about questions' difficulty level to
restrict pre-trained question representations to fine-tuning during the process
of predicting students' performance. Moreover, we apply a dual-attentional
mechanism to differentiate contributions of factors and factor interactions to
final prediction in different practice records. At last, we conduct experiments
on several real-world datasets and results show that MF-DAKT can outperform
existing knowledge tracing methods. We also conduct several studies to validate
the effects of each component of MF-DAKT.Comment: Accepted by CIKM 2021, 10 pages, 10 figures, 6 table
High-resolution Resonance Bragg-scattering spectroscopy of an atomic transition from a population difference grating in a vapor cell
The laser spectroscopy with a narrow linewidth and high signal to noise ratio
(S/N) is very important in the precise measurement of optical frequencies.
Here, we present a novel high-resolution backward resonance Bragg-scattering
(RBS) spectroscopy from a population difference grating (PDG). The PDG is
formed by a standing-wave (SW) pump field in thermal 87Rb vapor, which
periodically modulates the space population distribution of two levels in the
87Rb D1 line. A probe beam, having the identical frequency and the orthogonal
polarization with the SW pump field, is Bragg-scattered by the PDG. Such
Bragg-scattered light becomes stronger at an atomic resonance transition, which
forms the RBS spectrum with a high S/N and sub-natural linewidth. Using the
scheme of the coherent superposition of the individual Rayleigh-scattered light
emitted from the atomic dipole oscillators on the PDG, the experimentally
observed RBS spectroscopy is theoretically explained.Comment: 18 pages, 4 figure
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