Observation of chiral phonons Zhu, Hanyu; Yi, Jun; Li, Ming-Yang ...
Science (American Association for the Advancement of Science),
02/2018, Letnik:
359, Številka:
6375
Journal Article
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Chirality reveals symmetry breaking of the fundamental interaction of elementary particles. In condensed matter, for example, the chirality of electrons governs many unconventional transport ...phenomena such as the quantum Hall effect. Here we show that phonons can exhibit intrinsic chirality in monolayer tungsten diselenide. The broken inversion symmetry of the lattice lifts the degeneracy of clockwise and counterclockwise phonon modes at the corners of the Brillouin zone. We identified the phonons by the intervalley transfer of holes through hole-phonon interactions during the indirect infrared absorption, and we confirmed their chirality by the infrared circular dichroism arising from pseudoangular momentum conservation. The chiral phonons are important for electron-phonon coupling in solids, phonon-driven topological states, and energy-efficient information processing.
Rearrangement reactions have attracted considerable interest over the past decades due to their high bond-forming efficiency and atom economy in the construction of complex organic architectures. In ...contrast to the well-established 3,3-rearrangement, 1,3 O-to-C rearrangement has been far less vigorously investigated, and stereospecific 1,3-rearrangement is extremely rare. Here, we report a metal-free intramolecular hydroalkoxylation/1,3-rearrangement, leading to the practical and atom-economical assembly of various valuable medium-sized lactams with wide substrate scope and excellent diastereoselectivity. Moreover, such an asymmetric cascade cyclization has also been realized by chiral Brønsted acid-catalyzed kinetic resolution. In addition, biological tests reveal that some of these medium-sized lactams displayed their bioactivity as antitumor agents against melanoma cells, esophageal cancer cells and breast cancer cells. A mechanistic rationale for the reaction is further supported by control experiments and theoretical calculations.
As hot topics in the chemical conversion of CO2, the photo‐/electrocatalytic reduction of CO2 and use of CO2 as a supporter for energy storage have shown great potential for the utilization of CO2. ...However, many obstacles still exist on the road to realizing highly efficient chemical CO2 conversion, such as inefficient uptake/activation of CO2 and mass transport in catalysts. Covalent organic frameworks (COFs), as a kind of porous material, have been widely explored as catalysts for the chemical conversion of CO2 owing to their unique features. In particular, COF‐based functional materials containing diverse active sites (such as single metal sites, metal nanoparticles, and metal oxides) offer great potential for realizing CO2 conversion and energy storage. This Minireview discusses recent breakthroughs in the basic knowledge, mechanisms, and pathways of chemical CO2 conversion strategies that use COF‐based functional catalysts. In addition, the challenges and prospects of COF‐based functional catalysts for the efficient utilization of CO2 are also introduced.
This Minireview discusses recent developments in the basic knowledge, mechanisms, and CO2 utilization strategies regarding the use of functional materials based on covalent‐organic frameworks (COFs) with diverse active sites as catalysts. Insight is provided into the challenges and prospects of COF‐based catalysts for the design of the next‐generation photo‐/electrocatalysts for the utilization of CO2.
Studies of gene rearrangements and the consequent oncogenic fusion proteins have laid the foundation for targeted cancer therapy. To identify oncogenic fusions associated with glioma progression, we ...catalogued fusion transcripts by RNA-seq of 272 gliomas. Fusion transcripts were more frequently found in high-grade gliomas, in the classical subtype of gliomas, and in gliomas treated with radiation/temozolomide. Sixty-seven in-frame fusion transcripts were identified, including three recurrent fusion transcripts: FGFR3-TACC3, RNF213-SLC26A11, and PTPRZ1-MET (ZM). Interestingly, the ZM fusion was found only in grade III astrocytomas (1/13; 7.7%) or secondary GBMs (sGBMs, 3/20; 15.0%). In an independent cohort of sGBMs, the ZM fusion was found in three of 20 (15%) specimens. Genomic analysis revealed that the fusion arose from translocation events involving introns 3 or 8 of PTPRZ and intron 1 of MET. ZM fusion transcripts were found in GBMs irrespective of isocitrate dehydrogenase 1 (IDH1) mutation status. sGBMs harboring ZM fusion showed higher expression of genes required for PIK3CA signaling and lowered expression of genes that suppressed RB1 or TP53 function. Expression of the ZM fusion was mutually exclusive with EGFR overexpression in sGBMs. Exogenous expression of the ZM fusion in the U87MG glioblastoma line enhanced cell migration and invasion. Clinically, patients afflicted with ZM fusion harboring glioblastomas survived poorly relative to those afflicted with non-ZM-harboring sGBMs (P < 0.001). Our study profiles the shifting RNA landscape of gliomas during progression and reveled ZM as a novel, recurrent fusion transcript in sGBMs.
Catalysts and ligands possessing the great ability to tolerate over a wide range of mechanistically unrelated reactions are remarked as "privileged", which are rather scarce but extremely meaningful ...in asymmetric catalysis. Feng and co‐workers have developed a library of conformationally flexible, C2‐symmetric N,N'‐dioxide amide compounds with original design and featured structure (named as Feng ligand now). They were initially reported as chiral organocatalysts in 2005 and have been further developed as a new class of privileged chiral ligands since 2006. Tremendous success, including versatile coordination chemistry with plenty of metal sources (main‐group metals, transition metals, and rare‐earth metals), a truly broad scope of asymmetric reactions (more than 50 types), diverse areas of catalysis (organocatalysis, Lewis‐acid catalysis, bimetallic relay catalysis, and photocatalysis), numerous synthetic applications of bioactive compounds, has been achieved using Feng N,N'‐dioxide. Besides, they demonstrate that chiral ligands with conformationally flexible property can offer excellent chiral environment as well, which challenges the conventional idea preferring rigid structures in the design of chiral ligands. Herein, we briefly introduced the discovery of Feng ligand and the millstones during the development. We also covered the successful applications of Feng ligand by other scientists as well as novel chiral ligands inspired by them.
Background and aimsLiver fibrosis is a wound-healing response that disrupts the liver architecture and function by replacing functional parenchyma with scar tissue. Recent progress has advanced our ...knowledge of this scarring process, but the detailed mechanism of liver fibrosis is far from clear.MethodsThe fibrotic specimens of patients and HLF (hepatic leukemia factor)PB/PB mice were used to assess the expression and role of HLF in liver fibrosis. Primary murine hepatic stellate cells (HSCs) and human HSC line Lx2 were used to investigate the impact of HLF on HSC activation and the underlying mechanism.ResultsExpression of HLF was detected in fibrotic livers of patients, but it was absent in the livers of healthy individuals. Intriguingly, HLF expression was confined to activated HSCs rather than other cell types in the liver. The loss of HLF impaired primary HSC activation and attenuated liver fibrosis in HLFPB/PB mice. Consistently, ectopic HLF expression significantly facilitated the activation of human HSCs. Mechanistic studies revealed that upregulated HLF transcriptionally enhanced interleukin 6 (IL-6) expression and intensified signal transducer and activator of transcription 3 (STAT3) phosphorylation, thus promoting HSC activation. Coincidentally, IL-6/STAT3 signalling in turn activated HLF expression in HSCs, thus completing a feedforward regulatory circuit in HSC activation. Moreover, correlation between HLF expression and alpha-smooth muscle actin, IL-6 and p-STAT3 levels was observed in patient fibrotic livers, supporting the role of HLF/IL-6/STAT3 cascade in liver fibrosis.ConclusionsIn aggregate, we delineate a paradigm of HLF/IL-6/STAT3 regulatory circuit in liver fibrosis and propose that HLF is a novel biomarker for activated HSCs and a potential target for antifibrotic therapy.
Since early December 2019, the 2019 novel coronavirus disease (COVID-19) has caused pneumonia epidemic in Wuhan, Hubei province of China. This study aimed to investigate the factors affecting the ...progression of pneumonia in COVID-19 patients. Associated results will be used to evaluate the prognosis and to find the optimal treatment regimens for COVID-19 pneumonia.
Patients tested positive for the COVID-19 based on nucleic acid detection were included in this study. Patients were admitted to 3 tertiary hospitals in Wuhan between December 30, 2019, and January 15, 2020. Individual data, laboratory indices, imaging characteristics, and clinical data were collected, and statistical analysis was performed. Based on clinical typing results, the patients were divided into a progression group or an improvement/stabilization group. Continuous variables were analyzed using independent samples t-test or Mann-Whitney U test. Categorical variables were analyzed using Chi-squared test or Fisher's exact test. Logistic regression analysis was performed to explore the risk factors for disease progression.
Seventy-eight patients with COVID-19-induced pneumonia met the inclusion criteria and were included in this study. Efficacy evaluation at 2 weeks after hospitalization indicated that 11 patients (14.1%) had deteriorated, and 67 patients (85.9%) had improved/stabilized. The patients in the progression group were significantly older than those in the disease improvement/stabilization group (66 51, 70 vs. 37 32, 41 years, U = 4.932, P = 0.001). The progression group had a significantly higher proportion of patients with a history of smoking than the improvement/stabilization group (27.3% vs. 3.0%, χ = 9.291, P = 0.018). For all the 78 patients, fever was the most common initial symptom, and the maximum body temperature at admission was significantly higher in the progression group than in the improvement/stabilization group (38.2 37.8, 38.6 vs. 37.5 37.0, 38.4°C, U = 2.057, P = 0.027). Moreover, the proportion of patients with respiratory failure (54.5% vs. 20.9%, χ = 5.611, P = 0.028) and respiratory rate (34 18, 48 vs. 24 16, 60 breaths/min, U = 4.030, P = 0.004) were significantly higher in the progression group than in the improvement/stabilization group. C-reactive protein was significantly elevated in the progression group compared to the improvement/stabilization group (38.9 14.3, 64.8 vs. 10.6 1.9, 33.1 mg/L, U = 1.315, P = 0.024). Albumin was significantly lower in the progression group than in the improvement/stabilization group (36.62 ± 6.60 vs. 41.27 ± 4.55 g/L, U = 2.843, P = 0.006). Patients in the progression group were more likely to receive high-level respiratory support than in the improvement/stabilization group (χ = 16.01, P = 0.001). Multivariate logistic analysis indicated that age (odds ratio OR, 8.546; 95% confidence interval CI: 1.628-44.864; P = 0.011), history of smoking (OR, 14.285; 95% CI: 1.577-25.000; P = 0.018), maximum body temperature at admission (OR, 8.999; 95% CI: 1.036-78.147, P = 0.046), respiratory failure (OR, 8.772, 95% CI: 1.942-40.000; P = 0.016), albumin (OR, 7.353, 95% CI: 1.098-50.000; P = 0.003), and C-reactive protein (OR, 10.530; 95% CI: 1.224-34.701, P = 0.028) were risk factors for disease progression.
Several factors that led to the progression of COVID-19 pneumonia were identified, including age, history of smoking, maximum body temperature at admission, respiratory failure, albumin, and C-reactive protein. These results can be used to further enhance the ability of management of COVID-19 pneumonia.
Abstract We present detailed and comprehensive data reduction and point-spread-function (PSF) model construction for all public JWST NIRCam imaging data from the COSMOS-Web treasury program (up to ...2023 June, totaling 0.28 deg 2 ). We show that the NIRCam PSF has significant short-timescale temporal variations and random spatial variations in all four filters (F115W, F150W, F277W, and F444W). Combining NIRCam with archival Hubble Space Telescope imaging, we perform multiwavelength active galactic nucleus (AGN)+host image decomposition to study the properties of 143 X-ray-selected ( L bol = 10 43.6–47.2 erg s −1 ) broad-line AGNs at 0.35 ≲ z ≲ 3.5. Leveraging the superb resolution, wavelength coverage, and sensitivity of NIRCam, we successfully detect host stellar emission after decomposing the central AGN point source in 142 objects. ∼2/3 AGNs are in star-forming galaxies based on the UVJ diagram, suggesting that there is no instantaneous negative AGN feedback. X-ray-selected broad-line AGN hosts follow a similar stellar mass–size relation as inactive galaxies, albeit with slightly smaller galaxy sizes. We find that although major mergers are rare (∼7%–22%) among the sample, more subtle nonaxisymmetric features from stellar bars, spiral arms, and minor mergers are ubiquitous, highlighting the importance of secular processes and minor mergers in triggering AGN activity. For a subsample of 30 AGNs at 1 < z < 2.5 with black hole mass measurements from single epoch spectra, they follow a similar black hole mass-stellar mass relation as local inactive early-type galaxies but reside preferentially near the upper envelope of nearby AGNs. We caution that selection biases and the intrinsic differences of AGN populations at different redshifts may significantly affect their location on the black hole mass-stellar mass plane.
The recent development of 2D monolayer lateral semiconductor has created new paradigm to develop p‐n heterojunctions. Albeit, the growth methods of these heterostructures typically result in alloy ...structures at the interface, limiting the development for high‐efficiency photovoltaic (PV) devices. Here, the PV properties of sequentially grown alloy‐free 2D monolayer WSe2‐MoS2 lateral p‐n heterojunction are explores. The PV devices show an extraordinary power conversion efficiency of 2.56% under AM 1.5G illumination. The large surface active area enables the full exposure of the depletion region, leading to excellent omnidirectional light harvesting characteristic with only 5% reduction of efficiency at incident angles up to 75°. Modeling studies demonstrate the PV devices comply with typical principles, increasing the feasibility for further development. Furthermore, the appropriate electrode‐spacing design can lead to environment‐independent PV properties. These robust PV properties deriving from the atomically sharp lateral p‐n interface can help develop the next‐generation photovoltaics.
By sequential growth of alloy‐free 2D monolayer WSe2‐MoS2 lateral p‐n heterojunction, photovoltaic devices show extraordinary power conversion efficiencies of 2.56%. The large surface active area of the devices enables the full exposure of the depletion region, leading to excellent omnidirectional light harvesting characteristic. Modeling studies demonstrate the devices comply with typical principles. The appropriate electrode‐spacing design leads to environment‐independent properties.
Monolayer transition metal dichalcogenide heterojunctions, including vertical and lateral p–n junctions, have attracted considerable attention due to their potential applications in electronics and ...optoelectronics. Lattice-misfit strain in atomically abrupt lateral heterojunctions, such as WSe2–MoS2, offers a new band-engineering strategy for tailoring their electronic properties. However, this approach requires an understanding of the strain distribution and its effect on band alignment. Here, we study a WSe2–MoS2 lateral heterojunction using scanning tunnelling microscopy and image its moiré pattern to map the full two-dimensional strain tensor with high spatial resolution. Using scanning tunnelling spectroscopy, we measure both the strain and the band alignment of the WSe2–MoS2 lateral heterojunction. We find that the misfit strain induces type II to type I band alignment transformation. Scanning transmission electron microscopy reveals the dislocations at the interface that partially relieve the strain. Finally, we observe a distinctive electronic structure at the interface due to hetero-bonding.
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