Adaptive decision threshold for an optical multipath-interference-impaired short-reach 50-Gbps PAM4 transmission.

The short-reach optical transmission systems based on intensity modulation and direct detection (IM/DD) are gradually evolving into the networks with complex link topologies and connections, especially inside the data center. Multipath interference (MPI) introduces irregular fluctuations in the 4-level pulse amplitude modulation (PAM4) signals and therefore affects the transmission performance. This Letter proposes an adaptive decision threshold (ADT) scheme to dynamically update the decision threshold, which can track the signal fluctuations in real time and mitigate the impact of MPI noise on the transmitted PAM4 signals. Numerical simulation results present that the proposed ADT scheme can significantly improve the bit error rate (BER) performance of the MPI-impaired PAM4 transmission system considering different MPI levels and laser linewidths. In a 50-Gbps PAM4 transmission system, the ADT can improve the MPI tolerance by more than beyond 6 dB when the BER reaches the KP4-forward error correction (FEC) criterion (2.4 × 10-4), presenting a better denoising performance than the existing MPI-mitigation algorithms A1 and A2. Moreover, the ADT scheme offers a lower computation complexity compared with A1 and A2, making it more practical for implementation.

Efficient capacity enhancement using OFDM with interleaved subcarrier number modulation in bandlimited UOWC systems.

We propose and demonstrate an efficient capacity enhancement scheme for bandlimited underwater optical wireless communication (UOWC) systems by utilizing orthogonal frequency division multiplexing with interleaved subcarrier number modulation (OFDM-ISNM). In the proposed OFDM-ISNM, joint number and constellation mapping/de-mapping is utilized to avoid error propagation and subblock interleaving is further applied to address the low-pass effect of the bandlimited UOWC system. The feasibility and superiority of the proposed OFDM-ISNM scheme for practical bandlimited UOWC systems have been verified through both simulations and experiments. The obtained results demonstrate that the proposed OFDM-ISNM scheme is capable of efficiently improving the achievable data rate of the bandlimited UOWC system. Specifically, the experimental results show a significant 28.6% capacity enhancement by OFDM-ISNM over other benchmark schemes, achieving a data rate of 3.6 Gbps through a 2-m water channel.

Phytosterols Protect against Osteoporosis by Regulating Gut Microbiota.

Osteoporosis is increasingly prevalent worldwide, representing a major health burden. However, there is a lack of nutritional strategies for osteoporotic therapy. Phytosterols, as natural bioactive compounds, have the potential to alleviate osteoporosis. In this study, a glucocorticoid-induced osteoporosis mouse model and treatment with low and high concentrations of phytosterols for 4 weeks were established. The results demonstrated that compared to the control group, low-concentration phytosterols (LP) (0.3 mg/mL) increased bone mass, improved trabecular microstructure, reduced serum levels of cross-linked C-telopeptide of type I collagen (CTX-1), and elevated serum levels of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3). Conversely, high-concentration phytosterols (0.5 mg/mL) showed no effect. Additionally, we validated the effect of LP in ameliorating osteoporosis using an ovariectomized (OVX)-induced osteoporosis mouse model. Mechanistically, phytosterols altered the microbial composition to counteract glucocorticoid-induced gut microbiota disorder and improve the length and morphology of the small intestine. Particularly, based on selection strategy and correlation analysis, phytosterols increased the relative abundance of Ruminococcus and decreased the relative abundance of Bilophila, which were significantly associated with glucocorticoid-induced osteoporosis indications. Overall, these findings suggest that phytosterols regulate gut microbiota to increase bone mass, thereby exerting an antiosteoporotic effect.

Polyolefin-Based Separator with Interfacial Chemistry Regulation for Robust Potassium Metal Batteries.

Potassium metal batteries (KMBs) are ideal choices for high energy density storage system owing to the low electrochemical potential and low cost of K. However, the practical KMB applications suffer from intrinsically active K anode, which would bring serious safety concerns due to easier generation of dendrites. Herein, to explore a facile approach to tackle this issue, we propose to regulate K plating/stripping via interfacial chemistry engineering of commercial polyolefin-based separator using multiple functional units integrated in tailored metal organic framework. As a case study, the functional units of MIL-101(Cr) offer high elastic modulus, facilitate the dissociation of potassium salt, improve the K+ transfer number and homogenize the K+ flux at the electrode/electrolyte interface. Benefiting from these favorable features, uniform and stable K plating/stripping is realized with the regulated separator. Full battery assembled with the regulated separator showed ∼19.9 % higher discharge capacity than that with glass fiber separator at 20 mA g-1 and much better cycling stability at high rates. The generality of our approach is validated with KMBs using different cathodes and electrolytes. We envision that the strategy to suppress dendrite formation by commercial separator surface engineering using tailor-designed functional units can be extended to other metal/metal ion batteries.

Enhancing underwater VLC with spatial division transmission and pairwise coding.

In this paper, we propose and evaluate two spatial division transmission (SDT) schemes, including spatial division diversity (SDD) and spatial division multiplexing (SDM), for underwater visible light communication (UVLC) systems. Moreover, three pairwise coding (PWC) schemes, including two one-dimensional PWC (1D-PWC) schemes, i.e., subcarrier PWC (SC-PWC) and spatial channel PWC (SCH-PWC), and one two-dimensional PWC (2D-PWC) scheme are further applied for signal-to-noise ratio (SNR) imbalance mitigation in the UVLC systems using SDD and SDM with orthogonal frequency division multiplexing (OFDM) modulation. The feasibility and superiority of applying SDD and SDM with various PWC schemes in a practical bandlimited two-channel OFDM-based UVLC system have been verified through both numerical simulations and hardware experiments. The obtained results show that the performance of SDD and SDM schemes are largely determined by both the overall SNR imbalance and the system spectral efficiency. Moreover, the experimental results demonstrate the robustness of SDM with 2D-PWC against bubble turbulence. Specifically, SDM with 2D-PWC can obtain bit error rates (BERs) under the 7% forward error correction (FEC) coding limit of 3.8 × 10-3 with a probability higher than 96% for a signal bandwidth of 70 MHz and a spectral efficiency of 8 bits/s/Hz, achieving an overall data rate of 560 Mbits/s.

Convolutional-neural-network-based versus vision-transformer-based SNR estimation for visible light communication networks.

Visible light communication (VLC) has emerged as a promising technology for future sixth-generation (6 G) communications. Estimating and predicting the impairments, such as turbulence and free space signal scattering, can help to construct flexible and adaptive VLC networks. However, the monitoring of impairments of VLC is still in its infancy. In this Letter, we experimentally demonstrate a deep-neural-network-based signal-to-noise ratio (SNR) estimation scheme for VLC networks. A vision transformer (ViT) is first utilized and compared with the conventional scheme based on a convolutional neural network (CNN). Experimental results show that the ViT-based scheme exhibits robust performance in SNR estimation for VLC networks compared to the CNN-based scheme. Specifically, the ViT-based scheme can achieve accuracies of 76%, 63.33%, 45.33%, and 37.67% for 2-quadrature amplitude modulation (2QAM), 4QAM, 8QAM, and 16QAM, respectively, against 65%, 57.67%, 41.67%, and 34.33% for the CNN-based scheme. Additionally, data augmentation has been employed for achieving enhanced SNR estimation accuracies of 95%, 79.67%, 58.33%, and 50.33% for 2QAM, 4QAM, 8QAM, and 16QAM, respectively. The effect of the SNR step size of a contour stellar image dataset on the SNR estimation accuracy is also studied.

Effects of Dietary Phytosterol Supplementation on the Productive Performance, Egg Quality, Length of Small Intestine, and Tibia Quality in Aged Laying Hens.

This study aimed at investigating the effects of phytosterols on the productive performance, egg quality, length of small intestine, and tibia quality in aged laying hens. A total of 960 Dawu Jinfeng commercial laying hens (75 weeks of age) were randomly assigned to three groups. Each group had 16 replicates and every replicate contained four cages (five birds/cage). The control group hens received the basal diet without phytosterols. The hens in the experimental groups received a diet containing phytosterols at concentrations of 20 mg/kg and 40 mg/kg for 7 weeks. The results showed that phytosterols had a linearly increasing effect on egg weight, eggshell surface area, albumen height, and haugh unit at week 5 of experiment (p < 0.05). Supplemental phytosterols linearly and quadratically increased eggshell thickness (p < 0.05). At week 7 of the experiment, dietary supplementation of phytosterols linearly increased egg weight and eggshell weight (p < 0.05). Supplementation of 20 mg/kg, but not 40 mg/kg, phytosterols increased the length of the small intestine. However, dietary phytosterols had no effect on the laying rate, mortality, or liver index (p > 0.1). The results of tibia quality detected by micro-CT also showed no difference in the treatment of phytosterols. Therefore, supplementation with 20 mg/kg phytosterols in the diet improves egg quality and increases the length of small intestine, but has no effects on the quality of the tibia.

Carbon-coated TiNb2O7 nanosheet arrays as self-supported high mass-loading anodes for flexible Li-ion batteries.

A TiNb2O7 anode constructed with carbon-coated nanosheet arrays on carbon cloth is prepared by a facile solvothermal process and post carbon-coating for the first time. With nanosized diffusion-length and reduced polarization resistance, this anode exhibits superior high-rate capability based on relatively high mass-loading. Meanwhile, it demonstrates excellent cycling stability and mechanical flexibility as expected from flexible Li-ion batteries.

The effects of structural properties on the lithium storage behavior of mesoporous TiO2.

Understanding the effects of structural properties on the lithium storage behavior of mesoporous TiO2 is crucial for further optimizing its performance through rational structure design. To achieve this, herein, the surface area and the grain size of the prepared mesoporous TiO2 are intentionally adjusted by controlling the calcination temperatures. It is found that the capacities of the mesoporous TiO2 contain both the lithium-ion insertion into the bulk phase (Q in) and the additional surface lithium storage (Q as). The Q in gradually increases with grain sizes to a steady level and then slightly drops. By contrast, the Q as is directly proportional to the specific surface area of the mesoporous TiO2 and is ascribed to the capacity originated from the lithium-ion insertion into the surface layer. The experimental comparison and analysis demonstrate that the fast kinetics of the Q as ensure both the better rate performance and capacity retention of mesoporous TiO2 than bulk ones. Specially, the mesoporous TiO2 calcinated at 350 °C shows the highest reversible specific capacity of 250.2 mA h g-1, the best rate capability (132.5 mA h g-1 at 2C) and good cycling stability. Our findings shed great light on the design of high-performance nanostructured TiO2 with surface lithium storage.

High-Capacity and Self-Stabilized Manganese Carbonate Microspheres as Anode Material for Lithium-Ion Batteries.

Manganese carbonate (MnCO3) is an attractive anode material with high capacity based on conversion reaction for lithium-ion batteries (LIBs), but its application is mainly hindered by poor cycling performance. Building nanostructures/porous structures and nanocomposites has been demonstrated as an effective strategy to buffer the volume changes and maintain the electrode integrity for long-term cycling. It is widely believed that microsized MnCO3 is not suitable for use as anode material for LIBs because of its poor conductivity and the absence of nanostructure. Herein, different from previous reports, spherical MnCO3 with the mean diameters of 6.9 µm (MnCO3-B), 4.0 µm (MnCO3-M), and 2.6 µm (MnCO3-S) were prepared via controllable precipitation and utilized as anode materials for LIBs. It is interesting that the as-prepared MnCO3 microspheres demonstrate both high capacity and excellent cycling performance comparable to their reported nanosized counterparts. MnCO3-B, MnCO3-M, and MnCO3-S deliver reversible specific capacities of 487.3, 573.9, and 656.8 mA h g(-1) after 100 cycles, respectively. All the MnCO3 microspheres show capacity retention more than 90% after the initial stage. The advantages of MnCO3 microspheres were investigated via constant-current charge/discharge, cyclic voltammetry and electrochemical impedance spectroscopy. The results indicate that there should be substantial structure transformation from microsized particle to self-stabilized nanostructured matrix for MnCO3 at the initial charge/discharge stage. The evolution of EIS during charge/discharge clearly indicates the formation and stabilization of the nanostructured matrix. The self-stabilized porous matrix maintains the electrode structure to deliver excellent cycling performance, and contributes extra capacity beyond conversion reaction.

Direct synthesis of high-quality water-soluble CdTe:Zn2+ quantum dots.

The synthesis of water-soluble and low-cytotoxicity quantum dots (QDs) in aqueous solution has received much attention recently. A one-step and convenient method has been developed for synthesis of water-soluble glutathione (GSH)-capped and Zn(2+)-doped CdTe QDs via a refluxing route. Because of the addition of Zn ions and the epitaxial growth of a CdS layer, the prepared QDs exhibit superior properties, including strong fluorescence, minimal cytotoxicity, and enhanced biocompatibility. The optical properties of QDs are characterized by UV-vis and fluorescence (FL) spectra. The structure of QDs was verified by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectrometry (XPS), energy dispersive spectroscopy (EDS), atomic absorption spectrometry (AAS), and Fourier transform infrared spectroscopy (FTIR). Furthermore, the low cytotoxicity of the prepared QDs was proved by the microcalorimetric technique and inductively coupled plasma-atomic emission spectrometry (ICP-AES).