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result(s) for
"Ren, Xi"
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Metasurface-assisted phase-matching-free second harmonic generation in lithium niobate waveguides
The phase-matching condition is a key aspect in nonlinear wavelength conversion processes, which requires the momenta of the photons involved in the processes to be conserved. Conventionally, nonlinear phase matching is achieved using either birefringent or periodically poled nonlinear crystals, which requires careful dispersion engineering and is usually narrowband. In recent years, metasurfaces consisting of densely packed arrays of optical antennas have been demonstrated to provide an effective optical momentum to bend light in arbitrary ways. Here, we demonstrate that gradient metasurface structures consisting of phased array antennas are able to circumvent the phase-matching requirement in on-chip nonlinear wavelength conversion. We experimentally demonstrate phase-matching-free second harmonic generation over many coherent lengths in thin film lithium niobate waveguides patterned with the gradient metasurfaces. Efficient second harmonic generation in the metasurface-based devices is observed over a wide range of pump wavelengths (
λ
= 1580–1650 nm).
Phase matching is a crucial condition for nonlinear optical processes. Here, Wang et al. demonstrate that a gradient metasurface composed of phased array antennas allows phase-matching-free frequency conversion over a pump wavelength range of almost 100 nm.
Journal Article
Extracellular matrix dynamics: tracking in biological systems and their implications
The extracellular matrix (ECM) constitutes the main acellular microenvironment of cells in almost all tissues and organs. The ECM not only provides mechanical support, but also mediates numerous biochemical interactions to guide cell survival, proliferation, differentiation, and migration. Thus, better understanding the everchanging temporal and spatial shifts in ECM composition and structure – the ECM dynamics – will provide fundamental insight regarding extracellular regulation of tissue homeostasis and how tissue states transition from one to another during diverse pathophysiological processes. This review outlines the mechanisms mediating ECM-cell interactions and highlights how changes in the ECM modulate tissue development and disease progression, using the lung as the primary model organ. We then discuss existing methodologies for revealing ECM compositional dynamics, with a particular focus on tracking newly synthesized ECM proteins. Finally, we discuss the ramifications ECM dynamics have on tissue engineering and how to implement spatial and temporal specific extracellular microenvironments into bioengineered tissues. Overall, this review communicates the current capabilities for studying native ECM dynamics and delineates new research directions in discovering and implementing ECM dynamics to push the frontier forward.
Journal Article
Electrochromic windows with fast response and wide dynamic range for visible-light modulation without traditional electrodes
Electrochromic (EC) devices represent an emerging energy-saving technology, exhibiting the capability to dynamically modulate light and heat transmittance. Despite their promising potential, the commercialization of EC devices faces substantial impediments such as high cost, intricate fabrication process, and low optical contrast inherent in conventional EC materials relying on the ion insertion/extraction mechanism. In this study, we introduce an innovative “electrode-free” electrochromic (EC) device, termed the EECD, which lacks an EC-layer on the electrodes during device assembling and in the bleached state. This device features a simplified fabrication process and delivers superior optical modulation. It achieves a high optical contrast ranging from 68-85% across the visible spectrum and boasts a rapid response time, reaching 90% coloring in just 17 seconds. In addition, EECD exhibits stable cycling for over 10,000 cycles without noticeable degradation and maintains functionality across a broad temperature range (0 °C to 50 °C). Furthermore, the fabricated large-area devices (40 cm × 40 cm) demonstrate excellent tinting uniformity, suggesting excellent scalability of this approach. Our study establishes a paradigmatic breakthrough for EC smart windows.
Cheng Yang and co-workers develop an “electrode-free” electrochromic window, featuring a simplified fabrication process and delivering superior optical modulation capability.
Journal Article
Polarization entanglement enabled by orthogonally stacked van der Waals NbOCl2 crystals
Polarization entanglement holds significant importance for photonic quantum technologies. Recently emerging subwavelength nonlinear quantum light sources, e.g., GaP and LiNbO
3
thin films, benefiting from the relaxed phase-matching constraints and volume confinement, have shown intriguing properties, such as high-dimensional hyperentanglement and robust entanglement anti-degradation. Van der Waals (vdW) NbOCl
2
crystal, with strong optical nonlinearities, has emerged as a potential candidate for ultrathin quantum light sources. However, polarization entanglement is inaccessible in the NbOCl
2
crystal due to its unfavorable nonlinear susceptibility tensor. Here, by leveraging the twist-stacking degree of freedom inherently in vdW systems, we showcase the preparation of polarization entanglement and quantum Bell states.
Van der Waals NbOCl2 crystal is a candidate platform for subwavelength thin film photon-pair sources. Here, the authors demonstrate generation of polarization entangled states from a two-layer stack of orthogonally oriented van der Waals crystal.
Journal Article
Ultrathin quantum light source with van der Waals NbOCl2 crystal
Interlayer electronic coupling in two-dimensional materials enables tunable and emergent properties by stacking engineering. However, it also results in significant evolution of electronic structures and attenuation of excitonic effects in two-dimensional semiconductors as exemplified by quickly degrading excitonic photoluminescence and optical nonlinearities in transition metal dichalcogenides when monolayers are stacked into van der Waals structures. Here we report a van der Waals crystal, niobium oxide dichloride (NbOCl
2
), featuring vanishing interlayer electronic coupling and monolayer-like excitonic behaviour in the bulk form, along with a scalable second-harmonic generation intensity of up to three orders higher than that in monolayer WS
2
. Notably, the strong second-order nonlinearity enables correlated parametric photon pair generation, through a spontaneous parametric down-conversion (SPDC) process, in flakes as thin as about 46 nm. To our knowledge, this is the first SPDC source unambiguously demonstrated in two-dimensional layered materials, and the thinnest SPDC source ever reported. Our work opens an avenue towards developing van der Waals material-based ultracompact on-chip SPDC sources as well as high-performance photon modulators in both classical and quantum optical technologies
1
–
4
.
A van der Waals crystal, niobium oxide dichloride, with vanishing interlayer electronic coupling and considerable monolayer-like excitonic behaviour in the bulk, as well as strong and scalable second-order optical nonlinearity, is discovered, which enables a high-performance quantum light source.
Journal Article
ADARs act as potent regulators of circular transcriptome in cancer
Circular RNAs (circRNAs) are produced by head-to-tail back-splicing which is mainly facilitated by base-pairing of reverse complementary matches (RCMs) in circRNA flanking introns. Adenosine deaminases acting on RNA (ADARs) are known to bind double-stranded RNAs for adenosine to inosine (A-to-I) RNA editing. Here we characterize ADARs as potent regulators of circular transcriptome by identifying over a thousand of circRNAs regulated by ADARs in a bidirectional manner through and beyond their editing function. We find that editing can stabilize or destabilize secondary structures formed between RCMs via correcting A:C mismatches to I(G)-C pairs or creating I(G).U wobble pairs, respectively. We provide experimental evidence that editing also favors the binding of RNA-binding proteins such as PTBP1 to regulate back-splicing. These ADARs-regulated circRNAs which are ubiquitously expressed in multiple types of cancers, demonstrate high functional relevance to cancer. Our findings support a hitherto unappreciated bidirectional regulation of circular transcriptome by ADARs and highlight the complexity of cross-talk in RNA processing and its contributions to tumorigenesis.
RNA editing and circRNAs are involved in tumorigenesis. Here the authors report that ADARs regulate the circular transcriptome in a bidirectional manner through and beyond their editing function in multiple cancer cells.
Journal Article
Anionic redox reaction in layered NaCr2/3Ti1/3S2 through electron holes formation and dimerization of S–S
The use of anion redox reactions is gaining interest for increasing rechargeable capacities in alkaline ion batteries. Although anion redox coupling of S
2−
and (S
2
)
2−
through dimerization of S–S in sulfides have been studied and reported, an anion redox process through electron hole formation has not been investigated to the best of our knowledge. Here, we report an O3-NaCr
2/3
Ti
1/3
S
2
cathode that delivers a high reversible capacity of ~186 mAh g
−1
(0.95 Na) based on the cation and anion redox process. Various charge compensation mechanisms of the sulfur anionic redox process in layered NaCr
2/3
Ti
1/3
S
2
, which occur through the formation of disulfide-like species, the precipitation of elemental sulfur, S–S dimerization, and especially through the formation of electron holes, are investigated. Direct structural evidence for formation of electron holes and (S
2
)
n−
species with shortened S–S distances is obtained. These results provide valuable information for the development of materials based on the anionic redox reaction.
Anionic redox reactions are gaining interest as a means to optimize capacities of alkaline ion batteries. Here, the authors investigate various charge compensation mechanisms and report S–S dimerization and the formation of electron holes on sulfur in a model sulfide cathode.
Journal Article
Label-Free Single-Molecule Conalbumin Analysis
Nanoaperture optical tweezers (NOTs) were used to analyze conalbumin in various forms. By analyzing the power spectrum of the NOT-transmitted laser signal, differences between iron and iron-free conalbumin were observed; the corner frequency extrapolated to zero-laser power was significantly larger in magnitude for conalbumin with iron, which was interpreted as coming from the enhanced electrostatic interactions close to the surface of the nanoaperture. Conalbumin in a diluted, but otherwise unprocessed, egg white sample showed the same behavior as purified iron-free conalbumin. Dynamic two-state transitions in the NOT signal were observed for iron-free conalbumin and conalbumin in egg white samples. We used this to determine the dominant state as a function of temperature, with one state showing a maximum occupancy around 30.4 °C. Deconvolution of the probability distribution function was used to find the energy landscape associated with this two-state transition. This work shows the potential of NOTs to see variations with metal ion binding, including conformational dynamics related to the binding at timescales not accessible to other methods.
Journal Article
Probiotic characteristics of Lactobacillus plantarum E680 and its effect on Hypercholesterolemic mice
Background
Probiotics have been reported to reduce total cholesterol levels in vitro, but more evidence is needed to determine the clinical relevance of this activity. Chinese traditional fermented pickles are a good source of lactic acid bacteria. Therefore, pickle samples were collected for screening lactic acid bacteria based on their ability to survive stresses encountered during gastrointestinal passage and cholesterol reducing potency.
Results
Seventy five lactic acid bacteria strains were isolated from 22 fermented pickles. From these bacteria,
Lactobacillus plantarum
E680, showed the highest acid (85.25%) and bile tolerance (80.79%). It was sensitive to five of the eight antibiotics tested, inhibited the growth of four pathogenic bacteria, and reduced the total cholesterol level by 66.84% in broth culture. In vivo testing using hypercholesterolemic mice fed high-fat emulsion, independent of food intake, found that
L. plantarum
E680 suppressed body weight gain and reduced total cholesterol and low-density lipoprotein cholesterol levels, with no effect on high-density lipoprotein cholesterol.
Conclusions
Chinese traditional fermented pickles are a good source for probiotics.
L. plantarum
E680, isolated from pickles, was acid and bile tolerant, sensitive to antibiotics, and reduced cholesterol levels both in vitro and in vivo. Based on these results,
L. plantarum
E680 may have potential as a novel probiotic for the development of cholesterol-lowering functional food.
Journal Article