PREF: Phasorial Embedding Fields for Compact Neural Representations

We present an efficient frequency-based neural representation termed PREF: a shallow MLP augmented with a phasor volume that covers significant border spectra than previous Fourier feature mapping or Positional Encoding. At the core is our compact 3D phasor volume where frequencies distribute uniformly along a 2D plane and dilate along a 1D axis. To this end, we develop a tailored and efficient Fourier transform that combines both Fast Fourier transform and local interpolation to accelerate na\"ive Fourier mapping. We also introduce a Parsvel regularizer that stables frequency-based learning. In these ways, Our PREF reduces the costly MLP in the frequency-based representation, thereby significantly closing the efficiency gap between it and other hybrid representations, and improving its interpretability. Comprehensive experiments demonstrate that our PREF is able to capture high-frequency details while remaining compact and robust, including 2D image generalization, 3D signed distance function regression and 5D neural radiance field reconstruction

A Bioinspired and Biocompatible ortho-sulfiliminyl phenol Synthesis

Synthetic methods inspired by Nature often offer unique advantages including mild conditions and biocompatibility with aqueous media. Inspired by an ergothioneine biosynthesis protein EgtB, a mononuclear non-haem iron enzyme capable of catalysing the C–S bond formation and sulfoxidation, herein, we discovered a mild and metal-free C–H sulfenylation/intramolecular rearrangement cascade reaction employing an internally oxidizing O–N bond as a directing group. Our strategy accommodates a variety of oxyamines with good site selectivity and intrinsic oxidative properties. Combining an O–N bond with an X–S bond generates a C–S bond and an S¼N bond rapidly. The newly discovered cascade reaction showed excellent chemoselectivity and a wide substrate scope for both oxyamines and sulfenylation reagents. We demonstrated the biocompatibility of the C–S bond coupling reaction by applying a coumarin-based fluorogenic probe in bacterial lysates. Finally, the C–S bond coupling reaction enabled the first fluorogenic formation of phospholipids, which self-assembled to fluorescent vesicles in situ

Dielectric barrier discharge-based defect engineering method to assist flash sintering

Oxygen vacancy OV plays an important role in a flash sintering (FS) process. In defect engineering, the methods of creating oxygen vacancy defects include doping, heating, and etching, and all of them often have complex processes or equipment. In this study, we used dielectric barrier discharge (DBD) as a new defect engineering technology to increase oxygen vacancy concentrations of green billets with different ceramics (ZnO, TiO2, and 3 mol% yttria-stabilized zirconia (3YSZ)). With an alternating current (AC) power supply of 10 kHz, low-temperature plasma was generated, and a specimen could be treated in different atmospheres. The effect of the DBD treatment was influenced by atmosphere, treatment time, and voltage amplitude of the power supply. After the DBD treatment, the oxygen vacancy defect concentration in ZnO samples increased significantly, and a resistance test showed that conductivity of the samples increased by 2–3 orders of magnitude. Moreover, the onset electric field (E) of ZnO FS decreased from 5.17 to 0.86 kV/cm at room temperature (RT); while in the whole FS, the max power dissipation decreased from 563.17 to 27.94 W. The defect concentration and conductivity of the green billets for TiO2 and 3YSZ were also changed by the DBD, and then the FS process was modified. It is a new technology to treat the green billet of ceramics in very short time, applicable to other ceramics, and beneficial to regulate the FS process

Chinese Higher Education at the Turn of the Century : Observations from Field Trips at South-East Provinces in 2004

Since the initiation of Socialist Market policies, Chinese higher education steadily expanded its enrollment. The growth was accelerated at the end of the 1990s under a shift of governmental policy geared for achievement of mass higher education in the early years of the 21st Century. The radical shift was corresponded with dramatic changes at the institutional level with ambitious investments in infrastructure and new course designs. What are the causes of the changes? How higher education institutions have changed around the turn of the century? What are the main problems behind the changes? This report examine these questions based on the data and interviews collected through field trips at Fujian, Zhejiang and Anhui Provinces of Southeast China in early summer of 2004

Label-free analysis of protein biomarkers using pattern-optimized graphene-nanopyramid SERS for rapid diagnosis of Alzheimer’s disease

The quantitative and highly sensitive detection of biomarkers such as Tau proteins and Aβ polypeptides is considered one of the most effective methods for the early diagnosis of Alzheimer’s disease (AD). Surface-enhanced Raman spectroscopy (SERS) detection is a promising method that faces, however, challenges like insufficient sensitivity due to the non-optimized nanostructures for specialized analyte sizes and insufficient control of the location of SERS hot spots. Thus, the SERS detection of AD biomarkers is restricted. We reported here an in-depth study of the analytical Raman enhancement factor (EF) of the wafer-scale graphene-Au nanopyramid hybrid SERS substrates using a combination of both theoretical calculation and experimental measurements. Experimental results show that larger nanopyramids and smaller gap spacing lead to a larger SERS EF, with an optimized analytical EF up to 1.1 × 1010. The hybrid SERS substrate exhibited detection limits of 10–15 M for Tau and phospho-Tau (P-Tau) proteins and 10–14 M for Aβ polypeptides, respectively. Principal component analysis correctly categorized the SERS spectra of different biomarkers at ultralow concentrations (10–13 M) using the optimized substrate. Amide III bands at 1200–1300 cm–1 reflect different structural conformations of proteins or polypeptides. Tau and P-Tau proteins are inherently disordered with a few α-helix residuals. The structure of Aβ42 polypeptides transitioned from the α-helix to the β-sheet as the concentration increased. These results demonstrate that the hybrid SERS method could be a simple and effective way for the label-free detection of protein biomarkers to enable the rapid early diagnosis of AD and other diseases

Effect of Photoinitiator Concentration and Film Thickness on the Properties of UV-Curable Self-Matting Coating for Wood-Based Panels

Matte coatings have found wide-ranging applications across diverse industries. In this study, self-matting films with surface wrinkles were produced by exposing UV-curable polyurethane acrylate (UV-WPUA) resin to 172 nm Xe2* excimer and medium-pressure mercury lamps. The gloss values, micromorphologies, water contact angles (WCAs), roughness values, and friction behaviors of UV-WPUA films with different photoinitiator (PI) concentrations and thickness were investigated for the first time. The results indicate that the gloss values of the films at the same thickness enhance with the increase of PI concentration, while the amplitude of wrinkles, roughness, and WCAs decrease; however, the friction coefficient shows insignificant variations. While the PI concentration is unchanged, an increase in film thickness results in a decrease in gloss value and an increase in roughness and friction coefficient. Nevertheless, the WCA is relatively constant. The PI concentration of 0.5 wt% (lowest gloss value of cured film) was utilized to prepare the UV-WPUA wood coating. The cured coating film exhibited low gloss (4.9 GU at 60° and 5.2 GU at 85°) and outstanding mechanical properties, including 3H pencil hardness, grade 0 adhesion, excellent wear resistance, and tensile property. These findings can be utilized to guide the development of self-matting wood coatings and the production of wood-based panels used in industrial finishing

Conjugate Addition vs Heck Reaction: A Theoretical Study on Competitive Coupling Catalyzed by Isoelectronic Metal (Pd(II) and Rh(I))

Density functional theory studies have been carried out to investigate the mechanism of the Pd(II(bpy)-and Rh(I)(bpy)-catalyzed conjugate additions and their competitive Heck reactions involving alpha,beta-unsaturated carbonyl compounds. The critical steps of the mechanism are insertion and termination. The insertion step favors 1,2-addition of the vinyl-coordinated species to generate a stable C-bound enolate intermediate, which then may isomerize to either an oxa-pi-allyl species or an O-bound enolate. The termination step involves a competition between beta-hydride elimination, leading to a Heck reaction product, and protonolysis reaction that gives a conjugate addition product. These two pathways are competitive in the Pd(II)-catalyzed reaction, while a preference for protonolysis has been found in the Rh(I)-catalyzed reaction. The calculations are in good agreement with the experimental observations. The potential energy surface and the rate-determining step of the beta-hydride elimination are similar for bcth Pd(II)- and Rh(I)-catalyzed processes. The rate-determining steps of the Pd(II)- and Rh(I)-catalyzed protonolysis are different. Introduction of an N- or P-ligand significantly stabilizes the protonolysis transition state via the O-bound enolate or oxa-pi-allyl complex intermediate, resulting in a reduced free energy of activation. However, the barrier of the beta-hydride elimination is less sensitive to ligands. For the Rh(I)-catalyzed reaction, protonolysis is calculated to be more favorable than the beta-hydride elimination for all investigated N and P ligands due to the significant ligand stabilization to the protonolysis transition state. For the Pd(II)-catalyzed reaction, the complex with monodentate pyridine ligands prefers the Heck-type product through beta-hydride elimination, while the complex with bidentate N and P ligands favors the protonolysis. The theoretical finding suggests the possibility to control the selectivity between the conjugate addition and the Heck reaction by using proper ligands

Research progress of alloy materials' application in lithium metal anode

Lithiumis are considered as an ideal anode material for the next generation high energy density secondary batteries owing to its extremely low reduction potential and high specific capacity. However, its commercial application in lithium metal batteries is hindered by the problems of lithium dendritic growth, volume expansion effect and interface instability. To solve this problems, effective strategies including alloy anode, interface protection, structured anode design and solid electrolyte have been developed. Alloy materials play an important role in above strategies with its superior specific capacity, high Li+ conductivity and good lithium affinity. The electrochemical properties of alloy were reviewed and the recent research development of alloy materials' application in lithium metal anode was futher discussed. Last, the main existing problems of alloy materials' application in lithium metal anode were summarized and it was pointed out that the basic theoretical research should be strengthened

Effect of Thermal Modification on the Nano-Mechanical Properties of the Wood Cell Wall and Waterborne Polyacrylic Coating

Masson pine (Pinus massoniana Lamb.) samples were heat-treated at different treatment temperatures (150, 170, and 190 °C), and the nano-mechanical properties of the wood cell wall, which was coated with a waterborne polyacrylic (WPA) lacquer product, were compared. The elastic modulus (Er) and hardness (H) of wood cell wall and the coating were measured and characterized by nanoindentation, and the influencing factors of mechanical properties during thermal modification were investigated by chemical composition analysis, contact angle analysis, and colorimetric analysis. The results showed that with the increase in the heat treatment temperature, the contact angle of the water on the wood’s surface and the colorimetric difference increased, while the content of the cellulose and hemicelluloses decreased. After thermal modification of 190 °C, the Er and H of the wood cell wall increased by 13.9% and 17.6%, respectively, and the Er and H of the WPA coating applied to the wood decreased by 12.1% and 22.2%. The Er and H of the interface between the coating and wood were lower than those near the coating’s surface. The Er and H of the cell wall at the interface between the coating and wood were lower than those far away from the coating. This study was of great significance for understanding the binding mechanism between coating and wood cell walls and improving the finishing technology of the wood materials after thermal modification