App-Free Method for Visualization of Polymers in 3D and Augmented Reality.

The rise of virtual and online education in recent years has led to the development and popularization of many online tools, notably three-dimensional (3D) models and augmented reality (AR), for visualizing various structures in chemical sciences. The majority of the developed tools focus on either small molecules or biological systems, as information regarding their structure can be easily accessed from online databases or obtained through relatively quick calculations. As such, due to a lack of crystallographic and theoretical data available for nonbiological macromolecules, there is a noticeable lack of accessible online tools for the visualization of polymers in 3D. Herein, using a few sample polymers, we showcase a workflow for the generation of 3D models using molecular dynamics and Blender. The 3D structures can then be hosted on p3d.in, where AR models can be generated automatically. Furthermore, the hosted 3D models can then be shared via quick response (QR) codes and used in various settings without the need to download any applications.

Catechol Moiety Integrated Tri-Aryl Type AIEgen for Visual and Quantitative Boronic Acid Detection.

Novel functional AIEgen based on three compact bound aryl skeletons is designed and synthesized. This tri-aryl type luminogen (TA-Catechol) embedded with catechol moiety responds rapidly to series of boronic acids. Real-time visual and quantitative dual-mode detection method is established for the first time with modest precision and low detection limit (8.0 µM). Detailed mechanistic discussion identifies tetra-coordinated boronic species as the key intermediate within sensing procedure. Wide range of organic boronic acids compatible with this strategy is displayed which is promising in high throughput screening technology. Furthermore, solid-state sensing capability of TA-Catechol is also demonstrated.

MTIF2 impairs 5 fluorouracil-mediated immunogenic cell death in hepatocellular carcinoma in vivo: Molecular mechanisms and therapeutic significance.

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related morbidity and mortality; it has been reported that immune cell infiltration is a prognosis factor. Here we identified genes that associated with tumor immune cell infiltrate; the underlying mechanism was verified by in vivo and in vitro experiment. In this study, Weighted correlation network analysis (WGCNA) and CIBERSORT tool were used to identify MTIF2 as the hub tumor immune infiltrating gene in HCC. To investigate the underlying role played by MTIF2, MTIF2 was knocked down by transfection of shRNA targeting MTIF2, CCK8, and EdU incorporation assay was used to evaluate the effect of MTIF2 on proliferation, wound heal assay and transwell assay was used to confirm its effect on cell migration. Ecto-calreticulin on the cell surface was evaluated by flow cytometry, ATP, and HMGB1 secretion were tested to the investigated effect of MTIF2 on the immunogenic cell death (ICD) process. We found that down-regulation of MTIF2 impaired proliferation and migration capacity of HCC cells, chemoresistance to 5-Fluorouracil (5-FU) weakened after MTIF2 was knocked down. Reduced release of damage-associated molecular patterns (DAMP) was observed after MTIF2 was overexpressed, which subsequently impaired dendritic cell (DC) maturation and proliferation of CD8 + T cells. Mechanically, the co-IP experiment confirmed that MTIF2 could interact with AIFM1, prevents AIFM1 induced transcription of caspase3, and finally suppress apoptosis. In vivo experiment also used to confirm our previously conclusion, our result indicated that MTIF2 overexpression suppresses tumor apoptosis and immune cell activity in the 5-FU therapy in vivo model, by suppression maturation of tumor-infiltrated DC. Collectively, our study confirmed that MTIF2 impair drug-induced immunogenic cell death in hepatocellular carcinoma cells.

Thermally activated delayed fluorescence materials with aggregation-induced emission properties: a QM/MM study.

Organic molecules with thermally activated delayed fluorescence (TADF) and aggregation induced emission (AIE) properties have attracted increasing research interest due to their great potential applications in organic light emitting diodes (OLEDs), especially for those with multicolor mechanochromic luminescence (MCL) features. Theoretical research on the luminescence characteristics of organic TADF emitters based on the aggregation states is highly desired to quantify the relationship between the TADF properties and aggregation states. In this work, we study the 4,4'-(6-(9,9-dimethylacridine-10(9H)-yl)quinoline-2,3-dibenzonitrile (DMAC-CNQ) emitter with TADF and AIE properties, and calculate the photophysical properties in gas, solid and amorphous states by using the quantum mechanics and molecular mechanics (QM/MM) method. Our simulations demonstrate that the aggregation states enhance obviously the reverse intersystem crossing rates and transition dipole moments of the DMAC-CNQ emitter, and suppress the non-radiative rates from the lowest excited singlet state (S1) to ground state (S0). Specifically, the molecular stacking of DMAC-CNQ in solid phases can mainly restrict the geometric torsion of the DMAC moiety for decreasing non-radiative decay rates, and the torsion of the CNQ moiety for increasing the reverse intersystem crossing rates. As a result, the calculated fluorescence efficiencies of the DMAC-CNQ emitter in the crystal and amorphous states are 67% and 26% respectively, and in good agreement with the experimental results.

Graph analysis of proton conduction pathways in scandium-doped barium zirconate.

Understanding the relationship between the acceptor dopant size and proton conductivity in barium zirconate, BaZrO3, is important for maximizing efficiency in this promising fuel cell material. While proton conduction pathways with larger YZr ' and smaller AlZr ' defects have been explored, proton pathways with ScZr ', a defect of comparable size to the replaced ion, have not been investigated using centrality measures, periodic pathway searches, and kinetic Monte Carlo (KMC). Centrality measures in BaSc0.125Zr0.875O3 highlight a trapping region by ScZr ' and scattered high centrality regions on undoped planes. Connected long-range high centrality regions are found mainly in undoped planes for BaAl0.125Zr0.875O3 and in the dopant planes for BaY0.125Zr0.875O3. The best long-range proton conduction periodic pathways in AlZr ' and ScZr ' systems travel between dopant planes, while those for yttrium-doped BaZrO3 remained on dopant planes. KMC trajectories at 1000 K show long-range proton conduction barriers of 0.86 eV, 0.52 eV, and 0.25 eV for AlZr ', ScZr ', and YZr ' systems, respectively. Long-range periodic conduction highway limiting barrier averages correlate well with the connectivity of the most central regions in each system but ignore diffusion around the dopant and through other high centrality regions. BaSc0.125Zr0.875O3 shows an intermediate overall conduction barrier limited by trapping, which earlier experiments and simulations suggest that it can be mitigated with increased oxygen vacancy concentration.

Strong Solid-State Fluorescence Induced by Restriction of the Coordinate Bond Bending in Two-Coordinate Copper(I)-Carbene Complexes.

The photophysical properties of two-coordinate copper(I) complexes have become a new research hotspot due to their nearly perfect luminescent properties and low price and promising applications in organic light-emitting diodes (OLEDs). In this work, we employ the hybrid quantum mechanics and molecular mechanics (QM/MM) approach, coupled with our early developed thermal vibration correlation function (TVCF) rate formalism, to study the aggregation effect on the luminescent properties of the cyclic (alkyl)(amino)carbene-copper(I)-Cl complex. Our calculations reveal that the transition properties changes from metal-ligand-charge-transfer (MLCT) in solution to hybrid halogen ligand charge-transfer (XLCT) and MLCT in solid state, which induces the blue-shifted emission spectra from solution to solid phase. Upon aggregation, the restriction of the bending vibrations of the C-Cu-Cl and Cu-C-N bonds largely slow down the nonradiative decay, which induces strong fluorescence. This study provides a clear rationalization for the highly efficient fluorescence character of two-coordinate Cu(I) complexes.

Effects of Shape and Orientation of Pore Canals on Mechanical Behaviors of Lobster Cuticles.

The work is to investigate the relationships between the microstructures and mechanical behaviors of lobster cuticles and reveal the inner mechanisms of the anisotropic mechanical properties of the cuticles and give the helpful guidance for the design of high-performance man-made composites. First, the tensile mechanical properties of the longitudinal and transverse specimens of the cuticles of American lobsters were tested with a mechanical-testing instrument. It is was found that the fracture strength and elastic modulus of the longitudinal specimens are distinctly larger than those of the transverse specimens. Then, the microstructural characteristics of the fracture surfaces of the specimens were observed with scanning electron microscope. It was observed that the pore canals in the cuticles are elliptic and their orientations are along the longitudinal orientation of the cuticles. Furthermore, the stresses and micro-damage of the longitudinal and transverse specimens were calculated with the rule of progressive damage by finite element method. It was revealed that the shape and orientation of the pore canals in the cuticles give rise to the anisotropic mechanical property of the cuticles and ensure that the cuticles possess the largest fracture strength and elastic modulus along their largest main-stress orientation.

Error-free operation of a polarization-insensitive 4λ x 25 Gbps silicon photonic WDM receiver with closed-loop thermal stabilization of Si microrings.

We report the first closed-loop operation of a 100 Gbps polarization-insensitive, 4-channel wavelength-tracking WDM receiver in silicon photonics platform. Error-free operation is achieved with input polarization scrambling over input wavelength change of 4.5 nm using efficient thermal tuning of Si microring demux, corresponding to greater than 60°C fluctuation in temperature.

Efficient, tunable flip-chip-integrated III-V/Si hybrid external-cavity laser array.

We demonstrate a surface-normal coupled tunable hybrid silicon laser array for the first time using passively-aligned, high-accuracy flip chip bonding. A 2x6 III-V reflective semiconductor optical amplifier (RSOA) array with integrated total internal reflection mirrors is bonded to a CMOS SOI chip with grating couplers and silicon ring reflectors to form a tunable hybrid external-cavity laser array. Waveguide-coupled wall plug efficiency (wcWPE) of 2% and output power of 3 mW has been achieved for all 12 lasers. We further improved the performance by reducing the thickness of metal/dielectric stacks and achieved 10mW output power and 5% wcWPE with the same integration techniques. This non-invasive, one-step back end of the line (BEOL) integration approach provides a promising solution to high density laser sources for future large-scale photonic integrated circuits.

QM/MM Study on Mechanistic Photophysics of Alloxazine Chromophore in Aqueous Solution.

Compared with isoalloxazine, the core chromophore of biologically important flavins, alloxazine exhibits much lower fluorescence quantum yield and larger intersystem-crossing quantum yield. However, its efficient radiationless relaxation pathways are still elusive. In this work, we have used the QM(MS-CASPT2//CASSCF)/MM method to explore the mechanistic photophysics of alloxazine chromophore in aqueous solution. On the basis of the optimized minima, conical intersections, and crossing points in the lowest (1)ππ*, (1)nπ*, (3)ππ*, and (3)nπ* states, we have proposed three energetically possible nonadiabatic relaxation pathways populating the lowest (3)ππ* triplet state from the initially populated excited (1)ππ* singlet state. The first is the direct (1)ππ*→ (3)ππ* intersystem crossing via the (1)ππ*/(3)ππ* crossing point. The second is an indirect (1)ππ* → (3)ππ* intersystem crossing relayed by the dark (1)nπ* singlet state. In this route, the (1)ππ* system first decays to the (1)nπ* state via the (1)ππ*/(1)nπ* conical intersection, followed by an (1)nπ*→ (3)ππ* intersystem crossing at the (1)nπ*/(3)ππ* crossing point to arrive at the final (3)ππ* state. The third is similar to the second one; but its intersystem crossing is relayed by the (3)nπ* triplet state. The (1)ππ* system first decays to the (3)nπ* state via the (1)ππ*/(3)nπ* crossing point; the generated (3)nπ* state is then de-excited to the (3)ππ* state through the (3)nπ*→ (3)ππ* internal conversion at the (3)nπ*/(3)ππ* conical intersection. According to the classical El-Sayed rule, we suggest the second and third paths play a much more important role than the first one in the formation of the lowest (3)ππ* state.

Demonstration of 12.2% wall plug efficiency in uncooled single mode external-cavity tunable Si/III-V hybrid laser.

A Si/III-V hybrid laser has been a highly sought after device for energy-efficient and cost-effective high-speed silicon photonics communication. We present a high wall-plug efficiency external-cavity hybrid laser created by integrating an independently optimized SOI ring reflector and a III-V gain chip. In our demonstration, the uncooled integrated laser achieved a waveguide-coupled wall-plug efficiency of 12.2% at room temperature with an optical output power of ~10 mW. The laser operated single-mode near 1550 nm with a linewidth of 0.22 pm. This is a tunable light source with 8 nm wavelength tuning range. A proof-of-concept laser wavelength stabilization technique has also been demonstrated. Using a simple feedback loop, we achieved mode-hop-free operation in a packaged external-cavity hybrid laser as bias current was varied by 60mA.

Microring-based multi-chip WDM photonic module.

We report on a packaged prototype of a WDM photonic transceiver. It is an all-solid state hybrid assembly based on 130nm SOI photonic circuitry integrated with a 40nm CMOS VLSI driver. Our prototype supports eight tunable WDM channels operating at 10Gb/s, each capable of both transmitting and receiving data on the same chip. We discuss two options to close the link using the optical fiber or a waveguide bridge chip. We provide integration details and supporting link measurement data to describe packaged photonic module and its power efficient functionality with its on-chip power per channel averaging 1.3pJ/bit, excluding off-chip laser electrical power.

An all-solid-state, WDM silicon photonic digital link for chip-to-chip communications.

We describe a multiwavelength hybrid-integrated solid-state link on a 3 µm silicon-on-insulator (SOI) nanophotonic platform. The link spans three chips and employs germanium-silicon electroabsorption waveguide modulators, silicon transport waveguides, echelle gratings for multiplexing and demultiplexing, and pure germanium waveguide photo-detectors. The 8λ WDM Tx and Rx components are interconnected via a routing "bridge" chip using edge-coupled optical proximity communication. The packaged, retimed digital WDM link is demonstrated at 10 Gb/s and 10(-12) BER, with three wavelength channels consuming an on-chip power below 1.5 pJ/bit, excluding the external laser power.

A high-speed, tunable silicon photonic ring modulator integrated with ultra-efficient active wavelength control.

We report the first complete 10G silicon photonic ring modulator with integrated ultra-efficient CMOS driver and closed-loop wavelength control. A selective substrate removal technique was used to improve the ring tuning efficiency. Limited by the thermal tuner driver output power, a maximum open-loop tuning range of about 4.5nm was measured with about 14mW of total tuning power including the heater driver circuit power consumption. Stable wavelength locking was achieved with a low-power mixed-signal closed-loop wavelength controller. An active wavelength tracking range of > 500GHz was demonstrated with controller energy cost of only 20fJ/bit.

High power and widely tunable Si hybrid external-cavity laser for power efficient Si photonics WDM links.

A highly efficient silicon (Si) hybrid external cavity laser with a wavelength tunable ring reflector is fabricated on a complementary metal-oxide semiconductor (CMOS)-compatible Si-on-insulator (SOI) platform and experimental results with high output power are demonstrated. A III-V semiconductor gain chip is edge-coupled into a SOI cavity chip through a SiN(x) spot size converter and Si grating couplers are incorporated to enable wafer-scale characterization. The laser output power reaches 20 mW and the highest wall-plug efficiency of 7.8% is measured at 17.3 mW in un-cooled condition. The laser wavelength tuning ranges are 8 nm for the single ring reflector cavity and 35 nm for the vernier ring reflector cavity, respectively. The Si hybrid laser is a promising light source for energy-efficient Si CMOS photonic links.

Surface-enhanced Raman scattering with Ag nanoparticles optically trapped by a photonic crystal cavity.

We demonstrate a reusable and reconfigurable surface enhanced Raman scattering (SERS) platform by optically trapping Ag nanoparticles with a photonic crystal cavity integrated with a microfluidic chip. High-performance SERS is performed in a very reproducible manner, owing to the fact that Ag aggregates are produced by optical trapping in a controllable process that is monitored in real-time by the cavity resonance shift that occurs with the trapping of each additional nanoparticle.

Vertical-coupled high-efficiency tunable III-V- CMOS SOI hybrid external-cavity laser.

We demonstrate a hybrid III-V/SOI laser by vertically coupling a III-V RSOA chip with a SOI-CMOS chip containing a tunable wavelength selective reflector. We report a waveguide-coupled wall-plug-efficiency of 5.5% and output power of 10 mW. A silicon resistor-based microheater was integrated to thermally tune a ring resonator for precise lasing wavelength control. A high tuning efficiency of 2.2 nm/mW over a range of 18 nm was achieved by locally removing the SOI handler substrate. C-band single mode lasing was confirmed with a side mode suppression ratio of 35 dB. This grating coupler based vertical integration approach can be scaled up in two dimensions for efficient multi-wavelength sources in silicon photonics.

Research on biomimetic design and impact characteristics of periodic multilayer helical structures.

Osteons are composed of concentric lamellar structure, the concentric lamellae are composed of periodic thin and thick sub-lamellae, and every 5 sub-lamellae is a cycle, the periodic helix angle of mineralized collagen fibers in two adjacent sub-lamellae is 30°. Four biomimetic models with different fiber helix angles were established and fabricated according to the micro-nano structure of osteon. The effects of the fiber periodic helical structure on impact characteristic and energy dissipation of multi-layer biomimetic composite were investigated. The calculation results indicated that the stress distribution, contact characteristics and fiber failur during impact, and energy dissipation of the composite are affected by the fiber helix angle. The stress concentration of composite materials under external impact can be effectively improved by adjusting the fiber helix angle when the material composition and material performance parameters are same. Compared with the sample30, the maximum stress of sample60 and sample90 increases by 38.1% and 69.8%, respectively. And the fiber failure analysis results shown that the model with a fiber helix angle of 30° has a better resist impact damage. The drop-weight test results shown that the impact damage area of the specimen with 30° helix angle is smallest among the four types of biomimetic specimens. The periodic helical structure of mineralized collagen fibers in osteon can effectively improve the impact resistance of cortical bone. The research results can provide useful guidance for the design and manufacture of high-performance, impact-resistant biomimetic composite materials.

Data-driven analysis of the simulations of the spread of COVID-19 under different interventions of China.

Since February 2020, COVID-19 has spread rapidly to more than 200 countries in the world. During the pandemic, local governments in China have implemented different interventions to efficiently control the spread of the epidemic. Characterizing transmission of COVID-19 under some typical interventions is essential to help countries develop appropriate interventions. Based on the pre-symptomatic transmission patterns of COVID-19, we established a novel compartmental model: Susceptible-Infectious-Confirmed-Removed (SICR) model, which allowed the effective reproduction number to change over time, thus the effects of policies could be reasonably estimated. Using the epidemic data of Wuhan, Wenzhou, and Shenzhen, we migrated the corresponding estimated policy modes to South Korea, Italy, and the United States and simulated the potential outcomes for these countries when they adopted similar policy strategies to China. We found that the mild interventions implemented in Shenzhen were effective in controlling the epidemic in the early stage, while more stringent policies which were implemented in Wuhan and Wenzhou were necessary if the epidemic became severe and needed to be controlled in a short time.

An integrated microparticle sorting system based on near-field optical forces and a structural perturbation.

We demonstrate an integrated microparticle passive sorting system based on the near-field optical forces exerted by a 3-dB optical splitter that consists of a slot waveguide and a conventional channel waveguide. We show that 320 nm and 2 µm polystyrene particles brought into the splitter are sorted so that they exit along the slot waveguide and channel waveguide, respectively. Electromagnetic simulations and precise position tracking experiments are carried out to investigate the sorting mechanism. As the waveguides are separated by 200 nm, they provide two potential wells for the smaller particles, but only one broad potential well for the larger particles, since their diameters exceed the distance between the two field maxima. A structural perturbation consisting of a stuck bead transfers the smaller particles to the second well associated with the slot waveguide, while the larger particles are brought to the region between the two waveguides and eventually follow the channel waveguide, as it is associated with a deeper potential well. This label-free passive particle sorting system requires low guided power (20 mW in these experiments), and provides a new technique for sorting sub-micron particles.