Lithium niobate (LiNbO 3 ) is an excellent electrooptic material due to its low loss, large electrooptic coefficient, linear modulation response, and large modulation bandwidth. In this letter, we ...present the first LiNbO 3 thin-film Mach-Zehnder optical modulator that employs silicon nitride surface ridge optical waveguides. The modulator contains a 1.2-cm-long push-pull phase modulation section and a pair of multimode interferometric 3-dB couplers. It demonstrated V π · L of ~3 V · cm and a 3-dB bandwidth of ~8 GHz.
A polydimethylsiloxane cylindrical‐hole‐template‐confined solution‐growth method is developed to fabricate densely packed CsPbCl3−
x
Br
x
microdisk laser arrays. Furthermore, a strategy to integrate ...multicolored microdisk laser (MDL) arrays is demonstrated that simultaneously lase in the deep blue, blue, cyan, and green by means of gas‐phase replacement of Cl by Br from initial CsPbCl3 MDLs in HBr vapor.
3D organic–inorganic hybrid perovskites have featured high gain coefficients through the electron–hole plasma stimulated emission mechanism, while their 2D counterparts of Ruddlesden–Popper ...perovskites (RPPs) exhibit strongly bound electron–hole pairs (excitons) at room temperature. High‐performance solar cells and light‐emitting diodes (LEDs) are reported based on 2D RPPs, whereas light‐amplification devices remain largely unexplored. Here, it is demonstrated that ultrafast energy transfer along cascade quantum well (QW) structures in 2D RPPs concentrates photogenerated carriers on the lowest‐bandgap QW state, at which population inversion can be readily established enabling room‐temperature amplified spontaneous emission and lasing. Gain coefficients measured for 2D RPP thin‐films (≈100 nm in thickness) are found about at least four times larger than those for their 3D counterparts. High‐density large‐area microring arrays of 2D RPPs are fabricated as whispering‐gallery‐mode lasers, which exhibit high quality factor (Q ≈ 2600), identical optical modes, and similarly low lasing thresholds, allowing them to be ignited simultaneously as a laser array. The findings reveal that 2D RPPs are excellent solution‐processed gain materials potentially for achieving electrically driven lasers and ideally for on‐chip integration of nanophotonics.
Room‐temperature 2D Ruddlesden–Popper perovskite (RPP) amplified spontaneous emission and lasing are achieved by ultrafast energy transfer along the cascade quantum well to concentrate on the lowest‐bandgap quantum well for population inversion. High‐density large‐area microring arrays of 2D‐RPPs are fabricated as whispering‐gallery‐mode lasers with high quality factor, identical optical modes, and similarly low lasing threshold.
Combination of natural ventilation approaches is a new trend for free space cooling/heating in buildings. A critical review was then undertaken to provide an overview of the combined technologies ...that hope to initialize new ideas and promote future endeavors. The advantages of the integrated natural ventilation systems can be summarized into several principles, including achieving beyond the existing performance by single system, maintaining indoor temperature stability, realizing heat energy recovery, overcoming the inadequacy of a single system, and providing a more comprehensive and useful energy-saving scheme. Most of the existing studies on combined systems are found based on thermal buoyancy, while only a small amount dealt with the combination of wind-driven and buoyancy-induce due to the complexity. Parametric studies in most previous studies focused on several major ones, so a systematic analysis is critically needed to address the performance of the overall combination to achieve stable and durable performance. A thoughtful investigation is also required to avert unpredictable delivery of air flow, such as through the manipulation of external wind forces. The related research focuses should also be shifted following the trend of multi-storey buildings under the rapidly growing population. No guideline was found that arranges these natural ventilation systems in terms of performance and applicability for their practical selections and usages. Also, the thermal bridge breaking in cold winter and condensation in summer may compromise the natural ventilation performance and durability, and longevity of buildings. The studies on the coupling between different natural ventilation systems are still insufficient, requiring quite a bit of effort in future works.
•Combined natural ventilation systems in single building were reviewed.•Advantages of combined natural ventilation systems were summarized.•Existing systems much reply on thermal buoyancy but not combined buoyancy and wind.•Research focuses should be shifted following the trend of multi-storey buildings.•Studies on coupling different natural ventilation systems are still insufficient.
•Effect of EGCG on the gelatinisation and retrogradation of wheat starch was studied.•EGCG retarded the retrogradation of wheat starch.•EGCG and wheat starch had hydrogen bond interactions during ...retrogradation.•EGCG may be a useful additive in wheat products and nutrition-related applications.
The effects of epigallocatechin gallate (EGCG) on the gelatinisation and retrogradation characteristics of wheat starch (WS) were investigated using rapid viscosity analysis (RVA), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), and Raman spectroscopy. The addition of EGCG resulted in decreased peak viscosity, trough viscosity, final viscosity and setback value of WS, as shown by RVA tests. After storage at 4 °C, observations by XRD and TGA revealed that the EGCG-WS complex had lower crystallinity and thermal stability than the control, indicating that EGCG retarded the retrogradation of WS. FT-IR and Raman spectroscopy results showed that EGCG formed hydrogen bonds with WS, through which EGCG could interfere with the reassociation of starch chains during storage, thereby delaying retrogradation. EGCG may therefore prove to be a useful additive in wheat products and in nutrition-related applications.
The measurement of rock joint surfaces is essential for the estimation of the shear strength of the rock discontinuities in rock engineering. Commonly used techniques for the acquisition of the ...morphology of the surfaces, such as profilometers and laser scanners, either have low accuracy or high cost. Therefore, a high-speed, low-cost, and high-accuracy method for obtaining the topography of the joint surfaces is necessary. In this paper, a smartphone structure from motion (SfM) photogrammetric solution for measuring rock joint surfaces is presented and evaluated. Image datasets of two rock joint specimens were taken under two different modes by using an iPhone 6s, a Pixel 2, and a T329t and subsequently processed through SfM-based software to obtain 3D models. The technique for measuring rock joint surfaces was evaluated using the root mean square error (RMSE) of the cloud-to-cloud distance and the mean error of the joint roughness coefficient (JRC). The results show that the RMSEs by using the iPhone 6s and Pixel 2 are both less than 0.08 mm. The mean errors of the JRC are -7.54 and -5.27% with point intervals of 0.25 and 1.0 mm, respectively. The smartphone SfM photogrammetric method has comparable accuracy to a 3D laser scanner approach for reconstructing laboratory-sized rock joint surfaces, and it has the potential to become a popular method for measuring rock joint surfaces.
2D Ruddlesden–Popper perovskites (RPPs) are a class of quantum‐well (QW) materials, composed of layered perovskite QWs encapsulated between two hydrophobic organic layers. Different from widely ...investigated 3D‐perovskites with free carriers at room temperature, 2D‐RPPs exhibit strongly bound electron–hole pairs (excitons) for high‐performance solar cells and light emitting diodes (LEDs). Herein, it is reported that self‐organized multiple QWs in 2D‐RPP thin films naturally form an energy cascade, which enables an ultrafast energy transfer process from higher energy‐bandgap QWs to lower energy‐bandgap QWs. Therefore, photoexcitations are concentrated on lower‐bandgap QWs, facilitating the build‐up of population inversion. Room‐temperature amplified spontaneous emission (ASE) from 2D‐RPP thin films is achieved at dramatically low thresholds, with gain coefficients as high as >300 cm−1, and stoichiometrically tunable ASE wavelengths from visible to near‐infrared spectral range (530–810 nm). In view of the high efficiency reported for LEDs, these solution‐processed 2D‐RPP thin films may hold the key to realize electrically driven lasers.
Room‐temperature amplified spontaneous emission (ASE) from thin films of 2D Ruddlesden–Popper perovskites is achieved at dramatically low thresholds, with gain coefficients as high as >300 cm−1 comparable to that reported for 3D‐perovskites, and stoichiometrically tunable ASE wavelengths from visible to near‐infrared spectral range.
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•The effect of PUL and PEC on digestibility of PS during frying was investigated.•The long-range and short-range structures of fried PS-PUL/PEC samples were evaluated.•Both PUL and ...PEC significantly reduced the digestibility of fried PS.•Intact granular morphology of starch granules was preserved upon addition of PUL/PEC.•PUL/PEC protected both the short- and long-range structures of starch during frying.
The granular morphology, long-range and short-range ordered structures of fried potato starch were measured in the absence and presence of the dietary fibers. The in vitro digestibility of the fried starchy samples was also quantified using the Englyst method with logarithm-of-slope (LOS) analysis. After frying, the starch granules disintegrated, their internal crystalline structure disappeared, and the quantity of double helices present decreased. As a result of these changes, the fried starch was digested rapidly. Addition of pullulan or pectin to the samples prior to frying, reduced the structural changes observed in the starch granules during frying. Consequently, the fractions of slowly digestible and resistant starch (SDS and RS) increased significantly in the presence of the dietary fibers. These effects were attributed to the ability of the dietary fibers to sequester some of the water, thereby reducing starch granule structural changes, as well as due to their ability to coat the starch granules and interfere with the starch digestion process.
Segmentectomy and wedge resection have been recommended as appropriate surgical treatments for patients with poor pulmonary function or major comorbidities. However, for stage I non–small cell lung ...cancer (NSCLC), it is still undecided whether survival is better with segmentectomy or with wedge resection.
A meta-analysis was performed of studies examining survival outcomes after sublobar resection in patients with stage I NSCLC. Three electronic databases were searched to identify studies that investigated overall survival, cancer-specific survival, and disease-free survival between patients receiving segmentectomy versus wedge resection. A total of 19 relevant studies published before 31 April 2018 that satisfied the inclusion criteria were included in this meta-analysis.
The 19 studies involved a total of 14,197 patients with stage I NSCLC. Overall survival was significantly better after segmentectomy than after wedge resection (hazard ratio HR = 0.82; 95% confidence interval CI, 0.77-0.88; P < 0.00001). This was also true of cancer-specific survival (HR = 0.71; 95% CI, 0.64-0.79; P < 0.00001) and disease-free survival (HR = 0.73, 95% CI, 0.54-0.98; P = 0.04). A fixed-model was applied for the analysis as there was no significant heterogeneity between the studies.
Survival after lobar resection for stage I NSCLC is significantly better with segmentectomy than with wedge resection.
Organic gain materials (OGMs) currently used in organic lasers and optical amplifiers are focused on singlet-fluorescence materials, while triplet-phosphorescence-based OGMs have hardly been ...developed yet. Herein, we report a novel pure organic phosphorescence gain molecule (SBP) for optical amplification by stimulated emission from triplet states. The introduction of the benzophenone carbonyl group and sulfur atoms increases the spin orbit coupling constant of SBP, which accelerates the intersystem crossing (ISC) and phosphorescence processes. Experimental and theoretical results verify that the formation of the H-type dimer aggregate decreases the fluorescence radiation rate while accelerating the ISC rate, also enhancing the phosphorescence emission of SBP. Doping SBP molecules into a PMMA matrix can stabilize triplet excitons, yielding the maximum phosphorescence quantum yield of 18.9%. We realized triplet phosphorescent amplified spontaneous emission (ASE) at 557 nm from 30.0 wt % SBP@PMMA samples. Our results provide a novel strategy to develop triplet phosphor OGMs.
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