KBe2BO3F2 (KBBF) is the sole nonlinear optical (NLO) crystal that can practically generate deep-ultraviolet (UV) coherent light by a direct second-harmonic generation (SHG) process. However, the ...toxic BeO and crystal layer habit limit its application. With this background, a new beryllium-free borate, K5Mg2La3(BO3)6 (KMLBO), has been designed and synthesized through a high-temperature solution method. KMLBO crystallizes into the noncentrosymmetric space group P31m (No. 157) and features a three-dimensional framework structure consisting of alveolate LaBO3∞ layers further tightly bound via interlayer BO33– groups. KMLBO not only exhibits desirable performances including deep-UV transparency, large SHG (∼3.1 × KH2PO4), and phase-matchability but also overcomes the crystal layer habit of KBBF, demonstrating that it is a potential deep-UV NLO crystal.
Intrinsic isotropic near‐zero thermal expansion is discovered in borate crystal Zn4B6O13 with high transparency in the ultraviolet region. First‐principles calculations demonstrate that the very low ...thermal expansion originates mainly from the invariability of the solid B24O48 truncated octahedra that are fixed by the Zn4O13 clusters in the ZBO structure.
Injuries to the central nervous system (CNS) are inefficiently repaired. Resident neural stem cells manifest a limited contribution to cell replacement. We have uncovered a latent potential in neural ...stem cells to replace large numbers of lost oligodendrocytes in the injured mouse spinal cord. Integrating multimodal single-cell analysis, we found that neural stem cells are in a permissive chromatin state that enables the unfolding of a normally latent gene expression program for oligodendrogenesis after injury. Ectopic expression of the transcription factor OLIG2 unveiled abundant stem cell-derived oligodendrogenesis, which followed the natural progression of oligodendrocyte differentiation, contributed to axon remyelination, and stimulated functional recovery of axon conduction. Recruitment of resident stem cells may thus serve as an alternative to cell transplantation after CNS injury.
Abstract This article addresses the phenomenon of Netspeak reductions with special reference to Mandarin computer-mediated communication. A tentative classification of Chinese Netspeak reductions is ...first provided, namely, two-, three-, or four-character reductions occurring at both the lexical and the syntactic levels and other atypical reductions. It is then proposed that Zipf’s Principle of Least Effort, which usually works at the lexical level, can work as well at the utterance level and can account for the increasing number of Netspeak reductions in daily communication, that is, the frequency of using Netspeak reduction determines its vitality and distribution.
Abstract Divalent lanthanide inorganic compounds can exhibit unique electronic configurations and physicochemical properties, yet their synthesis remains a great challenge because of the weak ...chemical stability. To the best of our knowledge, although several lanthanide monoxides epitaxial thin films have been reported, there is no chemically stable crystalline divalent lanthanide chalcogenide synthesized up to now. Herein, by using octahedra coupling tetrahedra single/double chains to construct an octahedral crystal field, we synthesized the stable crystalline La(II)-chalcogenide, LaMg 6 Ga 6 S 16 . The nature of the divalent La 2+ cations can be identified by X-ray photoelectron spectroscopy, X-ray absorption near-edge structure and electron paramagnetic resonance, while the stability is confirmed by the differential thermal scanning, in-situ variable-temperature powder X-ray diffraction and a series of solid-state reactions. Owing to the particular electronic characteristics of La 2+ (5 d 1 ), LaMg 6 Ga 6 S 16 displays an ultrabroad-band green emission at 500 nm, which is the inaugural instance of La(II)-based compounds demonstrating luminescent properties. Furthermore, as LaMg 6 Ga 6 S 16 crystallizes in the non-centrosymmetric space group, P −6, it is the second-harmonic generation (SHG) active, possessing a comparable SHG response with classical AgGaS 2 . In consideration of its wider band gap ( E g = 3.0 eV) and higher laser-induced damage threshold (5×AgGaS 2 ), LaMg 6 Ga 6 S 16 is also a promising nonlinear optical material.
This paper investigates a particular type of non-canonical construction in Mandarin Chinese displaying an apparent semantics-syntax mismatch. We conducted an acceptability judgment experiment on ...native Mandarin speakers to evaluate whether such sequences could stand out of context as acceptable fragments. Analyses on experimental results revealed that: both semantic and syntactic acceptability of these sequences were significantly lower than those of canonical nominal classifier phrases; whereas if contextualized, the syntactic acceptability of those sequences became similar to that of canonical nominal phrases. This suggests that the non-canonical sequences are grammatically not on the same footing as canonical expressions; and it is the sentential context that makes these sequences appear structurally well-formed. These findings contribute to general discussions on relationship between constituency and grammaticality by demonstrating the gradient nature of grammaticality, and advocate a dynamic perspective in linguistic analysis that looks at a sequence of words in interaction with other elements in a sentence.
Oxychalcogenides capable of exhibiting excellent balance among large second‐harmonic generation (SHG) response, wide band gap (Eg), and suitable birefringence (Δn) are ideal materials class for ...infrared nonlinear optical (IR NLO) crystals. However, rationally designing a new high‐performance oxychalcogenide IR NLO crystal still faces a huge challenge because it requires the optimal orientations of the heteroanionic groups in oxychalcogenide. Herein, a series of antiperovskite‐type oxychalcogenides, Ae3QGeOQ3 (Ae = Ba, Sr; Q = S, Se), which were synthesized by employing the antiperovskite‐type Ba3SGeS4 as the structure template. Their structures feature novel three‐dimensinoal frameworks constructed by distorted QAe6 octahedra, which are further filled by GeOQ3 tetrahedra to form antiperovskite‐type structures. Based on the unique antiperovskite‐type structures, the favorable alignment of the polarizable GeOQ3 tetrahedra and distorted QAe6 octahedra have been achieved. These contribute the ideal combination of large SHG response (0.7–1.5 times that of AgGaS2), wide Eg (3.52–4.10 eV), and appropriate Δn (0.017–0.035) in Ae3QGeOQ3. Theoretical calculations and crystal structure analyses revealed that the strong SHG and wide Eg could be attributed to the polarizable GeOQ3 tetrahedra and distorted QAe6 octahedra. This research provides a new exemplification for the design of high‐performance IR NLO materials.
The heteroanionic antiperovskite‐type infrared nonlinear optical materials, Ae3QGeOQ3 (Ae = Ba, Sr; Q = S, Se), have been synthesized. Their structures consist of the heteroanionic GeOQ3 tetrahedra and the Q‐centered octahedral QAe6 groups linked together through vertices to form the antiperovskite framework. They exhibit promising properties including high SHG responses, large Eg as well as appropriate birefringence.
Terahertz (THz) technology is an emerging field that is promising for future applications. Nonlinear optical (NLO) materials can effectively convert incident light into the THz frequency range using ...optics methods. Ionic-type organic π-conjugated NLO crystals containing electron donor-π-acceptor motifs have long attracted attention for their possibility to achieve large nonlinear optical coefficients. In this paper, an overview of the recent progress in ionic-type organic NLO crystals for highly efficient THz wave generation is presented. The substitution design strategies of cations and anions, for increasing optical nonlinearities and reducing absorptions in different structure series, are summarized. In addition, the progress in crystal growth and their THz output performance are also discussed.
Reading comprehension is never considered a simple task in linguists' views as it requires a full set of linguistic knowledge, such as word decoding, understanding syntactic and morphological ...structures, and deriving proper meanings from these structures in a given context. Bearing the simple view of reading, the primary goal of this study is to explore whether the split presentation of Chinese splittable compounds influences the recognition of the compounds in second language (L2) Chinese reading comprehension, and how the reading skills, i.e., word decoding and linguistic comprehension, cooperate to complete this reading comprehension task. Splittable compounds (SCs) in Chinese are typically verbs composed of two constituents with limited separability. The separable property of SCs and their vague morpho-syntactic status are supposed to cause difficulties for L2 Chinese learners in recognizing the compounds. Especially for those whose native language manifests lexical integrity, the split presentation of the compounds may invite the L2 Chinese readers to process them with a mechanism different from that for their non-split forms. To the best of our knowledge, the efforts on investigating this issue are insufficient. In this study, 27 Spanish speaking L2 Chinese learners were invited to complete tasks including reading and interpreting 6 selected SCs in the split and non-split forms, rating their familiarities with each SC and reporting the syntactic category of the SCs based on their existing linguistic knowledge. The results, showed that the split presentation of SCs did cause challenges for L2 Chinese learners in recognizing the compounds in the reading process, regardless of their Chinese proficiencies. The L2 Chinese participants performed significantly worse in recognizing split SCs in salient Verb-Object structures than recognizing those in unsalient Verb-Object structures. These findings underscore the importance of linguistic comprehension in L2 Chinese in-text word reading comprehension and suggest words as the basic processing units.
Background/Aims: Transplantation of bone-marrow derived stem/progenitor cells has an established therapeutic effect on cardiac muscle repair after injury. However, the exact mechanism that underlies ...this phenomenon is not completely understood. Methods: Here we transplanted mesenchymal stem cells (MSCs), a major population from the bone-marrow derived stem/progenitor cells, and studied its effects on cardiac muscle repair after injury. Results: MSCs transplantation significantly improved cardiac muscle repair after injury. The grafted MSCs did not significantly differentiate into cardiac muscle cells themselves, but appeared to induce neovascularization in the injured heart. In a loss-of-function experiment, we further show that production and secretion of placental growth factor, but not vascular endothelial growth factor A in MSCs, were essential for the MSCs-induced neovasularization after cardiac muscle injury to facilitate cardiac muscle repair. Conclusion: Our study thus sheds light on an undescribed role of placental growth factor in cardiac muscle regeneration.
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