Sex-Specific Alterations in Placental Proteomics Induced by Intrauterine Hyperglycemia.

Gestational diabetes mellitus (GDM) with intrauterine hyperglycemia induces a series of changes in the placenta, which have adverse effects on both the mother and the fetus. The aim of this study was to investigate the changes in the placenta in GDM and its gender differences. In this study, we established an intrauterine hyperglycemia model using ICR mice. We collected placental specimens from mice before birth for histological observation, along with tandem mass tag (TMT)-labeled proteomic analysis, which was stratified by sex. When the analysis was not segregated by sex, the GDM group showed 208 upregulated and 225 downregulated proteins in the placenta, primarily within the extracellular matrix and mitochondria. Altered biological processes included cholesterol metabolism and oxidative stress responses. After stratification by sex, the male subgroup showed a heightened tendency for immune-related pathway alterations, whereas the female subgroup manifested changes in branched-chain amino acid metabolism. Our study suggests that the observed sex differences in placental protein expression may explain the differential impact of GDM on offspring.

Revealing the Denoising Principle of Zero-Shot N2N-Based Algorithm from 1D Spectrum to 2D Image.

Denoising is a necessary step in image analysis to extract weak signals, especially those hardly identified by the naked eye. Unlike the data-driven deep-learning denoising algorithms relying on a clean image as the reference, Noise2Noise (N2N) was able to denoise the noise image, providing sufficiently noise images with the same subject but randomly distributed noise. Further, by introducing data augmentation to create a big data set and regularization to prevent model overfitting, zero-shot N2N-based denoising was proposed in which only a single noisy image was needed. Although various N2N-based denoising algorithms have been developed with high performance, their complicated black box operation prevented the lightweight. Therefore, to reveal the working function of the zero-shot N2N-based algorithm, we proposed a lightweight Peak2Peak algorithm (P2P) and qualitatively and quantitatively analyzed its denoising behavior on the 1D spectrum and 2D image. We found that the high-performance denoising originates from the trade-off balance between the loss function and regularization in the denoising module, where regularization is the switch of denoising. Meanwhile, the signal extraction is mainly from the self-supervised characteristic learning in the data augmentation module. Further, the lightweight P2P improved the denoising speed by at least ten times but with little performance loss, compared with that of the current N2N-based algorithms. In general, the visualization of P2P provides a reference for revealing the working function of zero-shot N2N-based algorithms, which would pave the way for the application of these algorithms toward real-time (in situ, in vivo, and operando) research improving both temporal and spatial resolutions. The P2P is open-source at https://github.com/3331822w/Peak2Peakand will be accessible online access at https://ramancloud.xmu.edu.cn/tutorial.

Rapid Sample Pretreatment Facilitating SERS Detection of Trace Weak Organic Acids/Bases in Complex Matrices.

Fast and efficient sample pretreatment is the prerequisite for realizing surface-enhanced Raman spectroscopy (SERS) detection of trace targets in complex matrices, which is still a big issue for the practical application of SERS. Recently, we have proposed a highly performed liquid-liquid extraction (LLE)-back extraction (BE) for weak acids/bases extraction in drinking water and beverage samples. However, the performance efficiency decreased drastically on facing matrices like food and biological blood. Based on the total interaction energies among target, interferent, and extractant molecules, solid-phase extraction (SPE) with a higher selectivity was introduced in advance of LLE-BE, which enabled the sensitive (µg L-1 level) and rapid (within 10 min) SERS detection of both koumine (a weak base) and celastrol (a weak acid) in different food and biological samples. Further, the high SERS sensitivity was determined unmanned by Vis-CAD (a machine learning algorithm), instead of the highly demanded expert recognition. The generality of SPE-LLE-BE for various weak acids/bases (2 < pKa < 12), accompanied by the high efficiency, easy operation, and low cost, offers SERS as a powerful on-site and efficient inspection tool in food safety and forensics.

Signal2signal: Pushing the Spatiotemporal Resolution to the Limit by Single Chemical Hyperspectral Imaging.

There is growing interest in developing a high-performance self-supervised denoising algorithm for real-time chemical hyperspectral imaging. With a good understanding of the working function of the zero-shot Noise2Noise-based denoising algorithm, we developed a self-supervised Signal2Signal (S2S) algorithm for real-time denoising with a single chemical hyperspectral image. Owing to the accurate distinction and capture of the weak signal from the random fluctuating noise, S2S displays excellent denoising performance, even for the hyperspectral image with a spectral signal-to-noise ratio (SNR) as low as 1.12. Under this condition, both the image clarity and the spatial resolution could be significantly improved and present an almost identical pattern with a spectral SNR of 7.87. The feasibility of real-time denoising during imaging was well demonstrated, and S2S was applied to monitor the photoinduced exfoliation of transition metal dichalcogenide, which is hard to accomplish by confocal Raman spectroscopy. In general, the real-time denoising capability of S2S offers an easy way toward in situ/in vivo/operando research with much improved spatial and temporal resolution. S2S is open-source at https://github.com/3331822w/Signal2signal and will be accessible online at https://ramancloud.xmu.edu.cn/tutorial.

How do probiotics alleviate constipation? A narrative review of mechanisms.

Constipation is a common gastrointestinal condition, which may occur at any age and affects countless people. The search for new treatments for constipation is ongoing as current drug treatments fail to provide fully satisfactory results. In recent years, probiotics have attracted much attention because of their demonstrated therapeutic efficacy and fewer side effects than pharmaceutical products. Many studies attempted to answer the question of how probiotics can alleviate constipation. It has been shown that different probiotic strains can alleviate constipation by different mechanisms. The mechanisms on probiotics in relieving constipation were associated with various aspects, including regulation of the gut microbiota composition, the level of short-chain fatty acids, aquaporin expression levels, neurotransmitters and hormone levels, inflammation, the intestinal environmental metabolic status, neurotrophic factor levels and the body's antioxidant levels. This paper summarizes the perception of the mechanisms on probiotics in relieving constipation and provides some suggestions on new research directions.

Comprehensive 3-dimensional Positional and Morphological Analyses of Condyle and Glenoid Fossa in Patients with Skeletal Class II Malocclusion following Bimaxillary Orthognathic Surgery.

This study aimed to comprehensively and quantitatively characterize 3-dimensional (3D) positional and morphological changes of the condyle and glenoid fossa in patients with skeletal Class II malocclusion treated with bimaxillary orthognathic surgery. Twenty eligible patients treated at our institution from January 2016 to December 2021 with more than 12 months of postoperative follow-up were retrospectively enrolled. Radiographic data of cone-beam computed tomography (CBCT) for each patient were collected at 3 stages: 1 week preoperatively (T0), immediately after surgery (T1), and at least 12 months postoperatively (T2). Positional changes, surface and volumetric alterations of condyle, and bone remodeling in glenoid fossa were measured and compared based on voxel- and surface registrations in visual 3D methods. Most patients exhibited a tendency for condyles to shift posteriorly, laterally, superiorly, and rotated outward, downward, and forward immediately after surgery. Posterior, medial, superior movement and outward, upward, and backward rotation of condyles were observed during follow-up (T1-T2). Bone resorption frequently occurred in the posterior area of condylar surfaces, while bone remodeling was more common in the anterior region of the glenoid fossa. Reduced volume of the condyle was found in most cases, which was not associated with the amount of mandibular advancement. Overall, the condyle and its corresponding glenoid fossa remained relatively stable during the follow-up. Our results reveal positional and morphological alterations in the condyle and the glenoid fossa after bimaxillary orthognathic surgery in patients with skeletal class II malocclusion. These changes predominantly fall within the spectrum of physical adaption.

1D Gradient-Weighted Class Activation Mapping, Visualizing Decision Process of Convolutional Neural Network-Based Models in Spectroscopy Analysis.

Being characterized by the self-adaption and high accuracy, the deep learning-based models have been widely applied in the 1D spectroscopy-related field. However, the "black-box" operation and "end-to-end" working style of the deep learning normally bring the low interpretability, where a reliable visualization is highly demanded. Although there are some well-developed visualization methods, such as Class Activation Mapping (CAM) and Gradient-weighted Class Activation Mapping (Grad-CAM), for the 2D image data, they cannot correctly reflect the weights of the model when being applied to the 1D spectral data, where the importance of position information is not considered. Here, aiming at the visualization of Convolutional Neural Network-based models toward the qualitative and quantitative analysis of 1D spectroscopy, we developed a novel visualization algorithm (1D Grad-CAM) to more accurately display the decision-making process of the CNN-based models. Different from the classical Grad-CAM, with the removal of the gradient averaging (GAP) and the ReLU operations, a significantly improved correlation between the gradient and the spectral location and a more comprehensive spectral feature capture were realized for 1D Grad-CAM. Furthermore, the introduction of difference (purity or linearity) and feature contribute in the CNN output in 1D Grad-CAM achieved a reliable evaluation of the qualitative accuracy and quantitative precision of CNN-based models. Facing the qualitative and adulteration quantitative analysis of vegetable oils by the combination of Raman spectroscopy and ResNet, the visualization by 1D Grad-CAM well reflected the origin of the high accuracy and precision brought by ResNet. In general, 1D Grad-CAM provides a clear vision about the judgment criterion of CNN and paves the way for CNN to a broad application in the field of 1D spectroscopy.

Gut microbiota-derived succinate aggravates acute lung injury after intestinal ischaemia/reperfusion in mice.

INTRODUCTION: Acute lung injury (ALI) is a major cause of morbidity and mortality after intestinal ischaemia/reperfusion (I/R). The gut microbiota and its metabolic byproducts act as important modulators of the gut-lung axis. This study aimed to define the role of succinate, a key microbiota metabolite, in intestinal I/R-induced ALI progression. METHODS: Gut and lung microbiota of mice subjected to intestinal I/R were analysed using 16S rRNA gene sequencing. Succinate level alterations were measured in germ-free mice or conventional mice treated with antibiotics. Succinate-induced alveolar macrophage polarisation and its effects on alveolar epithelial apoptosis were evaluated in succinate receptor 1 (Sucnr1)-deficient mice and in murine alveolar macrophages transfected with Sucnr1-short interfering RNA. Succinate levels were measured in patients undergoing cardiopulmonary bypass, including intestinal I/R. RESULTS: Succinate accumulated in lungs after intestinal I/R, and this was associated with an imbalance of succinate-producing and succinate-consuming bacteria in the gut, but not the lungs. Succinate accumulation was absent in germ-free mice and was reversed by gut microbiota depletion with antibiotics, indicating that the gut microbiota is a source of lung succinate. Moreover, succinate promoted alveolar macrophage polarisation, alveolar epithelial apoptosis and lung injury during intestinal I/R. Conversely, knockdown of Sucnr1 or blockage of SUCNR1 in vitro and in vivo reversed the effects of succinate by modulating the phosphoinositide 3-kinase-AKT/hypoxia-inducible factor-1α pathway. Plasma succinate levels significantly correlated with intestinal I/R-related lung injury after cardiopulmonary bypass. CONCLUSION: Gut microbiota-derived succinate exacerbates intestinal I/R-induced ALI through SUCNR1-dependent alveolar macrophage polarisation, identifying succinate as a novel target for gut-derived ALI in critically ill patients.

Fe3+-cysteine enhanced persulfate fenton-like process for quinclorac degradation: A wide pH tolerance and reaction mechanism.

A green, high-efficiency, and wide pH tolerance water remediation process has been urgently acquired for the increasingly exacerbating contaminated water. In this study, a Fe3+/persulfate (Fe3+/PS) system was employed and enhanced with a green natural ligand cysteine (Cys) for the degradation of quinclorac (QNC). The introduction of Cys into the Fe3+/PS system widened the effective pH range to 9 with a superior removal rate for QNC. The mechanism revealed that the Fe3+/Cys/PS system can enhance the ability of degrading QNC by accelerating the Fe3+/Fe2+ redox cycle, maintaining Fe2+ concentration and thereby generating more HO• and SO4•-. The impact factors (i.e., pH, concentrations of PS, Fe3+ and Cys) were optimized as well. This work provides a promising strategy with high catalytic activity and wide pH tolerance for organic contaminated water remediation.

π-hole bonding: A new retention mechanism for the solid phase extraction of polycyclic aromatic hydrocarbons from the hexane extracts of soil samples.

In this work, the perfluorobenzene-bonded silica sorbent was tested to adsorb polycyclic aromatic hydrocarbons in hexane. In the comparison experiments, the perfluorobenzene-bonded sorbent's performance was better than octadecyl silica sorbent and phenyl-bonded silica sorbents, which indicated that the π-hole···π bonds between perfluorobenzene and the polycyclic aromatic hydrocarbons were stronger than π···π interactions and hydrophobic interactions in hexane. Then the perfluorobenzene-bonded silica sorbent was applied to solid-phase extraction of 15 polycyclic aromatic hydrocarbons from the hexane extracts of soil samples directly without the solvent replacement, which simplified the soil pretreatment process. And the results showed that under the optimal conditions, the proposed method for the determination of polycyclic aromatic hydrocarbons in the environment soil presented good recoveries and stabilities for the 10 heavier polycyclic aromatic hydrocarbons with the recoveries ranging from 75.1% to 104.6% and the relative standard deviations being in the range of 1.4%-5.8%. The limits of detection of the method varied from 0.1 to 2 ng/g. This work reveals the great application potential of the π-hole bond as a new retention mechanism in the field of solid-phase extraction.

Preliminary study of short-term outcomes and learning curves of robotic-assisted THA: comparison between closed platform robotic system and open platform robotic system.

BACKGROUND: Both closed platform and open platform robotic-assisted total hip arthroplasty (THA) have recently been recommended as a viable treatment option for achieving accurate positioning of components. Yet, limited studies paid attention to the differences between the closed platform robotic system and the open platform robotic system. Hence, this study aimed to investigate clinical outcomes, radiographic outcomes, complication rates and learning curve of two systems. MATERIALS AND METHODS: We retrospectively included 62 patients (31 closed robotic system and 31 open robotic system) who underwent THA between February 2021 and January 2023. The demographics, operating time, cup positioning, complications and hip Harris score were evaluated. Learning curves of operation time was conducted using cumulative sum (CUSUM) analysis. RESULTS: There were no differences in surgical time (76.7 ± 12.1 min vs. 72.3 ± 14.8 min), estimated blood loss (223.2 ± 13.2 ml vs. 216.9 ± 17 ml) and Harris Hip score (HHS) between closed platform robotic system and the open platform robotic system. The closed robotic system and the open robotic system were associated with a learning curve of 9 cases and 7 cases for surgical time respectively, based on the satisfying rate of Lewinnek's safe zone outliers (1/31, 96.8%) and no occurrence of complication. Both robotic systems had significant reduction in overall surgical time, the duration of acetabulum registration, and estimated blood loss between learning phase and proficiency phase. CONCLUSION: The authors suggest that the surgical outcomes and safe zone outlier rate of the open robotic-assisted THA were similar to those of the closed robotic-assisted THA. These two robotic-assisted are associated with comparable learning curves and both have the precise positioning of acetabular component. From learning phase to proficiency phase, the rate of positions within the safe zone differed only marginally (88.9-100% vs. 85.7-100%) based on a rather low number of patients. This is not a statistically significant difference. Therefore, we suggest that THA undergoing with the robotic-assisted system is the relatively useful way to achieve planned acetabular cup position so far.

Using an Expanded Cervical Flap With an Overlapping Tissue Expansion Technique to Resurface Middle and Lower Facial Defects.

BACKGROUND: Extensive facial burn scars are a tragedy for patients and often pose a great challenge to surgeons because of the high esthetic and functional demands. For patients with healthy skin in the neck region, a cervical flap is highly recommended for facial resurfacing; however, the skin on the midline of the neck often needs more expansion than that on either side, especially for the treatment of large facial defects. The sufficient longitudinal soft tissue in the anterior neck ensures a normal neck shape as well as a normal range of cervical extension, rotation, and lateral flexion. To overcome this, we developed an expanded cervical flap with an overlapping tissue expansion technique to gain more length centrally. METHODS: First, 2 tissue expanders were embedded in the anterior neck region overlapping each other at the midline of the neck. After adequate inflation of the expander, the expanded flap was dissected and rotated to repair defects in the middle and lower face. The anchor position of the flap was placed on the horizontal line of the thyroid cartilage to restore the cervicomental angle. RESULTS: Sixteen patients were treated with this method in this single-center study. All defects affected the middle and lower face, with an area ranging from 135 to 185 cm 2 , and were caused by a massive facial burn. Among them, 12 patients suffered ectropion of the lower lip, 3 suffered limited mouth opening due to scar contraction, and one patient had a cervicomental adhesion. The area of the expanded flap was approximately 163 to 266 cm 2 . The average period of expansion was 89.5 days. Patients were followed up after the operation, with the follow-up period ranging from 6 to 12 months. In all cases, good defect coverage was achieved, with primary closure of the donor sites and a good postoperative cervical configuration. CONCLUSION: We conclude that the expanded cervical flap with the overlapping tissue expansion technique proved to be a reliable method for facial skin reconstruction with functional and aesthetic improvement.

Blood Supply of the Temporal Flap Pedicled With Orbicularis Oculi Muscle: Anatomy and Its Clinical Implications.

BACKGROUND: Traumatic injury or tumor resection can lead to eyelid defects, nasal defects, and cheek defects. The temporal flap pedicled with orbicularis oculi muscle (OOM) can be used to repair these defects. This cadaver-based anatomic study aimed to evaluate the blood supply of this flap and investigate its clinical implications. METHODS: Twenty hemifaces from 10 cadavers were used in this study. The number of arteries supplying OOM of the flap, the diameter of the artery entering OOM, and the maximum width of OOM were recorded. All data were presented as mean±SD values and analyzed using Student t -test. A P value<0.05 was considered statistically significant. RESULTS: Of these 10 specimens, 7 were males and 3 were females. The average age was 67.7 years (range, 53-78 y). The number of arteries supplying OOM was 8.5±1.4 in the male and 7.8±1.2 in the female. The diameter of the zygomatico-orbital artery was detected as 0.53±0.06 mm in the male and 0.40±0.11 mm in the female. The maximum width of OOM was detected as 2.5±0.1 cm in the male and 2.2±0.1 cm in the female. Males had significantly larger average values than females in the diameter of zygomatico-orbital artery and maximum width of OOM ( P =0.012, P <0.001, respectively). However, the number of arteries supplying OOM did not differ significantly between sex ( P =0.322). CONCLUSIONS: We conclude that the blood supply of the temporal flap pedicled with OOM is abundant and reliable. The findings provide surgeons with valuable anatomic knowledge for repairing facial defects with this flap.

A 20-Year Experience with Tissue Expansion for Large Cervical Fascial Defects: An Algorithm Based on Different Clinical Flap Designs.

Over the past 20 years, we have designed various types of expanded cervical flaps for large facial defects and achieved excellent tissue matching. This study was performed to propose a treatment strategy for flap selection for the reconstruction of different facial units. The authors retrospectively reviewed the application of cervical expanded flaps for facial rehabilitation in our department between January 2003 and January 2023. The study included 122 patients with unilateral (62.3%) and bilateral (37.7%) facial deformities ranging from the zygomatic arch to the chin. The median area of the tissue defect was 15.2 × 8.5 cm2 (ranging from 6 × 4 cm2 to 27 × 12 cm2). The expansion period ranged from 61 to 175 days (mean: 86.5 days). Maximum and minimum sizes of pre-expanded cervical flaps were 30 × 13 cm2 to 7 × 5 cm2. All the flaps could be summarized into type 1, an advanced expanded cervical flap; type 2, a wing-shaped expanded cervical flap with overlapping tissue expansion; and type 3, an expanded single-lobed transposition flap rotated based on the anterior neck. Cervical flaps reliably meet the reconstructive requirements for different facial units, especially for large cutaneous defects in the clinic. The selection of these flaps can be planned preoperatively according to the location and size of the defect or lesion.

Straw removal or non-removal affects cadmium (Cd) accumulation in soil-rice (Oryza sativa L.) system at different ambient air Cd levels.

Despite the potential importance of the removal of contaminated straw for heavy metal output from agricultural soils, previous studies have primarily focused on the variation in the metal concentration without considering the impact input of heavy metals from atmospheric deposition. Here, rice was grown under field conditions, and, as a reference, in a deposition-free environment, and exposed to different ambient air Cd levels. Two consecutive years of pot experiments were conducted in two study areas (ZZ and LY) to examine the changes in soil physicochemical properties as well as Cd accumulation in the soil-rice (Oryza sativa L.) system in response to straw return or removal. The results showed that rice straw return enhanced the soil pH and organic matter (OM) content, but reduced the soil redox potential (Eh); and the variation in amplitude increased with number of cultivation years. After two years of cultivation, the concentrations of soil total Cd and extractable Cd in the straw-removal treatments reduced by 9.89-29.49% and 4.88-37.74%, respectively, whereas those in the straw-return treatments exhibited a slight decrease, or even an increase. This indicated that straw removal could effectively reduce the concentration and bioavailability of Cd in contaminated farmland, which was further confirmed by the results for accumulation of Cd in rice tissues. In addition, the contribution from atmospheric deposition was confirmed by the greater variation in Cd concentration in soils and rice tissues under deposition-free conditions. A major implication of our findings is that the adoption of reasonable straw-treatment measures and proper control over ambient air heavy metals can promote the remediation efficiency of Cd-contaminated fields.

Recycling Valuable Metals from Spent Lithium-Ion Batteries Using Carbothermal Shock Method.

Pyrometallurgy technique is usually applied as a pretreatment to enhance the leaching efficiencies in the hydrometallurgy process for recovering valuable metals from spent lithium-ion batteries. However, traditional pyrometallurgy processes are energy and time consuming. Here, we report a carbothermal shock (CTS) method for reducing LiNi0.3 Co0.2 Mn0.5 O2 (NCM325) cathode materials with uniform temperature distribution, high heating and cooling rates, high temperatures, and ultrafast reaction times. Li can be selectively leached through water leaching after CTS process with an efficiency of >90 %. Ni, Co, and Mn are recovered by dilute acid leaching with efficiencies >98 %. The CTS reduction strategy is feasible for various spent cathode materials, including NCM111, NCM523, NCM622, NCM811, LiCoO2 , and LiMn2 O4 . The CTS process, with its low energy consumption and potential scale application, provides an efficient and environmentally friendly way for recovering spent lithium-ion batteries.

Visualization of a Machine Learning Framework toward Highly Sensitive Qualitative Analysis by SERS.

Surface-enhanced Raman spectroscopy (SERS), providing near-single-molecule-level fingerprint information, is a powerful tool for the trace analysis of a target in a complicated matrix and is especially facilitated by the development of modern machine learning algorithms. However, both the high demand of mass data and the low interpretability of the mysterious black-box operation significantly limit the well-trained model to real systems in practical applications. Aiming at these two issues, we constructed a novel machine learning algorithm-based framework (Vis-CAD), integrating visual random forest, characteristic amplifier, and data augmentation. The introduction of data augmentation significantly reduced the requirement of mass data, and the visualization of the random forest clearly presented the captured features, by which one was able to determine the reliability of the algorithm. Taking the trace analysis of individual polycyclic aromatic hydrocarbons in a mixture as an example, a trustworthy accuracy no less than 99% was realized under the optimized condition. The visualization of the algorithm framework distinctly demonstrated that the captured feature was well correlated to the characteristic Raman peaks of each individual. Furthermore, the sensitivity toward the trace individual could be improved by least 1 order of magnitude as compared to that with the naked eye. The proposed algorithm distinguished by the lesser demand of mass data and the visualization of the operation process offers a new way for the indestructible application of machine learning algorithms, which would bring push-to-the-limit sensitivity toward the qualitative and quantitative analysis of trace targets, not only in the field of SERS, but also in the much wider spectroscopy world. It is implemented in the Python programming language and is open-source at https://github.com/3331822w/Vis-CAD.

Touch-Programmable Metasurface for Various Electromagnetic Manipulations and Encryptions.

Previous programmable metasurfaces integrated with diodes or varactors require external instructions for field programmable gate arrays (FPGAs), which usually rely on computer-inputs or pre-loaded algorithms. But the complicated external devices make the coding regulation process of the programmable metasurfaces cumbersome and difficult to use. To simplify the process and provide a new interaction manner, a touch-programmable metasurface (TPM) based on touch sensing modules is proposed to realize various electromagnetic (EM) manipulations and encryptions. By simply touching the meta-units of the TPM, the state of the diodes can be changed. Through the touch controls, the TPM can achieve independent and direct manipulations of meta-units and efficient inputs of coding patterns without using a FPGA or other control modules. Various coding patterns are demonstrated to achieve diverse scattering-field control and flexible near-field EM information encryptions, which verifies the feasibility of the TPM design. The presented TPM will have wide application prospects in imaging displays, wireless communications, and EM information encryptions.

Highly birefringent hollow-core anti-resonant terahertz fiber with a thin strut microstructure.

A novel highly birefringent and low transmission loss hollow-core anti-resonant (HC-AR) fiber with a central strut is proposed for terahertz waveguiding. To the best of our knowledge, it is the first time that a design of a highly birefringent terahertz fiber based on the hybrid guidance mechanism of the anti-resonant mechanism and the total internal reflection mechanism is provided. Several HC-AR fibers with both ultra-low transmission loss and ultra-low birefringence have been achieved in the near-infrared optical communication band. We propose a HC-AR fiber design in terahertz band by introducing a microstructure in the fiber core which leads to tremendous improvement in birefringence. Calculated results indicate that the proposed HC-AR fiber achieves a birefringence higher than 10-2 in a wide wavelength range. In addition, low relative absorption loss of 0.8% (8.6%) and negligible confinement loss of 1.69×10-4 dB/cm (9.14×10-3 dB/cm) for x-polarization (y-polarization) mode at 1THz are obtained. Furthermore, the main parameters of the fiber structure are evaluated and discussed, proving that the HC-AR fiber possesses great design and fabrication tolerance. Further investigation of the proposed HC-AR fiber also suggests a good balance between birefringence and transmission loss which can be achieved by changing strut thickness to cater numerous applications ideally.

Low bending loss few-mode hollow-core anti-resonant fiber with glass-sheet conjoined nested tubes.

A novel hollow-core anti-resonant fiber (HC-ARF) with glass-sheet conjoined nested tubes that supports five core modes of LP01-LP31 with low mode couplings, large differential group delays (DGDs), and low bending losses (BLs) is proposed. A novel cladding structure with glass-sheet conjoined nested tubes (CNT) is induced for the proposed HC-ARF which can suppress mode couplings between the LP01-LP31 modes and the cladding modes. The higher-order modes (HOMs) which are LP11-LP31 modes also have very low loss by optimizing the radius of the nested tube and the core radius. Moreover, the large effective refractive index differences Δneff between HOMs are all larger than 1 × 10-4 which contributes to a large DGD in the wavelength range from 1.3 to 1.7 µm. The bending loss of the HC-ARF is analyzed and optimized emphatically. Our calculation results show that bending losses of LP01-LP31 modes are all lower than 3.0 × 10-4 dB/m in the wavelength range from 1.4 to 1.61 µm even when the fiber bending radius of the HC-ARF is 6 cm.