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Abstract In this paper, a direction of arrival (DOA) estimation algorithm for non-circular signal by a large-spacing uniform array with an auxiliary element has been presented. The auxiliary element is placed away from the last element of the large-spacing uniform array. The spacing between arbitrary two elements of the whole array is not limited by the half-wavelength of the signal. Firstly, two initial signal subspaces corresponding to the large-spacing uniform array and two row vectors corresponding to the auxiliary element are obtained by eigenvalue decomposition (EVD) of the correlation matrix. The two row vectors are expanded into two virtual signal subspaces by using the two initial signal subspaces. Then, the relationship between the virtual signal subspaces and the initial signal subspaces are used to form a high-dimensional signal subspace corresponding to a uniform linear array with half-wavelength spacing. Finally, DOA estimation can be got by using the estimation of signal parameters via the rotational invariance techniques (ESPRIT) algorithm. Compared with the traditional ESPRIT algorithm and non-circular ESPRIT (NC-ESPRIT) algorithm based on a conventional uniform linear array, the proposed algorithm has higher accuracy for DOA estimation and stronger robustness to the mutual coupling.

Oxidative stress and aging lead to progressive senescence of nucleus pulposus (NP) cells, resulting in intervertebral disc (IVD) degeneration (IVDD). In some cases, degenerative IVD can further cause low back pain (LBP). Several studies have confirmed that delaying and rejuvenating the senescence of NP cells can attenuate IVDD. However, the relatively closed tissue structure of IVDs presents challenges for the local application of anti-senescence drugs. Here, we prepared an anti-senescence hydrogel by conjugating phenylboronic acid-modified gelatin methacryloyl (GP) with quercetin to alleviate IVDD by removing senescent NP cells. The hydrogel exhibited injectability, biodegradability, prominent biocompatibility and responsive release of quercetin under pathological conditions. In vitro experiments demonstrated that the hydrogel could reduce the expression of senescence markers and restore the metabolic balance in senescent NP cells. In vivo studies validated that a single injection of the hydrogel in situ could maintain IVD tissue structure and alleviate sensitivity to noxious mechanical force in the rat models, indicating a potential therapeutic approach for ameliorating IVDD and LBP. This approach helps prevent potential systemic toxicity associated with systemic administration and reduces the morbidity resulting from repeated injections of free drugs into the IVD, providing a new strategy for IVDD treatment.

Effective control of post-extraction hemorrhage and alveolar bone resorption is critical for successful extraction socket treatment, which remains an unmet clinical challenge. Herein, an injectable Tetra-PEG hydrogel that possesses rapid gelation, firm tissue adhesion, high mechanical strength, suitable degradability, and excellent biocompatibility is developed as a sutureless and coagulation-independent bioadhesive for the management of extraction sockets. Our results demonstrate that the rapid and robust adhesive sealing of the extraction socket by the Tetra-PEG hydrogel can provide reliable protection for the underlying wound and stabilize blood clots to facilitate tissue healing. In vivo experiments using an anticoagulated rat tooth extraction model show that the hydrogel significantly outperformed clinically used cotton and gelatin sponge in hemostatic efficacy, wound closure, alveolar ridge preservation, and in situ alveolar bone regeneration. Histomorphological evaluations reveal the mechanisms for accelerated bone repair through suppressed long-term inflammation, elevated collagen deposition, higher osteoblast activity, and enhanced angiogenesis. Together, our study highlights the clinical potential of the developed injectable Tetra-PEG hydrogel for treating anticoagulant-related post-extraction hemorrhage and improving socket healing.

Abstract Background Hypothermia is a promising therapy for traumatic brain injury (TBI) in the clinic. However, the neuroprotective outcomes of hypothermia-treated TBI patients in clinical studies are inconsistent due to several severe side effects. Here, an injectable refrigerated hydrogel was designed to deliver 3-iodothyronamine (T1AM) to achieve a longer period of local hypothermia for TBI treatment. Hydrogel has four advantages: (1) It can be injected into injured sites after TBI, where it forms a hydrogel and avoids the side effects of whole-body cooling. (2) Hydrogels can biodegrade and be used for controlled drug release. (3) Released T1AM can induce hypothermia. (4) This hydrogel has increased medical value given its simple operation and ability to achieve timely treatment. Methods Pol/T hydrogels were prepared by a low-temperature mixing method and characterized. The effect of the Pol/T hydrogel on traumatic brain injury in mice was studied. The degradation of the hydrogel at the body level was observed with a small animal imager. Brain temperature and body temperature were measured by brain thermometer and body thermometer, respectively. The apoptosis of peripheral nerve cells was detected by immunohistochemical staining. The protective effect of the hydrogels on the blood–brain barrier (BBB) after TBI was evaluated by the Evans blue penetration test. The protective effect of hydrogel on brain edema after injury in mice was detected by Magnetic resonance (MR) in small animals. The enzyme linked immunosorbent assay (ELISA) method was used to measure the levels of inflammatory factors. The effects of behavioral tests on the learning ability and exercise ability of mice after injury were evaluated. Results This hydrogel was able to cool the brain to hypothermia for 12 h while maintaining body temperature within the normal range after TBI in mice. More importantly, hypothermia induced by this hydrogel leads to the maintenance of BBB integrity, the prevention of cell death, the reduction of the inflammatory response and brain edema, and the promotion of functional recovery after TBI in mice. This cooling method could be developed as a new approach for hypothermia treatment in TBI patients. Conclusion Our study showed that injectable and biodegradable frozen Pol/T hydrogels to induce local hypothermia in TBI mice can be used for the treatment of traumatic brain injury. Graphical Abstract

Annulus fibrosus (AF) plays a crucial role in the biomechanical loading of intervertebral disc (IVD). AF is difficult to self-heal when the annulus tears develop, because AF has a unique intricate structure and biologic milieu in vivo. Tissue engineering is promising for repairing AF rupture, but construction of suitable mechanical matching devices or scaffolds is still a grand challenge. To deeply know the varied forces involved in the movement of the native annulus is highly beneficial for designing biomimetic scaffolds to recreate the AF function. In this review, we overview six freedom degrees of forces and adhesion strength on AF tissue. Then, we summarize the mechanical modalities to simulate related forces on AF and to assess the characteristics of biomaterials. We finally outline some current advanced techniques to develop mechanically adaptable biomaterials for AF rupture repair.

Abstract Background Hydrogels show great potential to be used for intraocular applications due to their high-water content and similarity to the native vitreous. Injectable thermosensitive hydrogels through a small-bore needle can be used as a delivery system for drugs or a tamponading substitute to treat posterior eye diseases with clear clinical potential. However, none of the currently available thermosensitive hydrogels can provide intraocular support for up to 3 months or more. Method In this study, an injectable polytetrahydrofuran (PTHF)-based thermosensitive hydrogel was synthesized by polyurethane reaction. We examined the injectability, rheological properties, microstructure, cytotoxicity, and in vivo compatibility and stability of the hydrogels in rabbit eyes. Results We found that the PTHF block type and PTHF component ratio could modulate thermogelation properties of the polyurethane polymers. The PTHF-based hydrogel implants retained normal retinal structure and function. Incorporating bioinert PTHF generated highly biocompatible and more stable thermogels in the vitreous cavity, with gel networks and the presence of polymer still observed after 3 months when other thermogels would have been completely cleared. Moreover, despite lacking hydrolytically cleavable linkages, the polymers could be most naturally removed from the native vitreous by bio-erosion without additional surgical interventions. Conclusion Our findings suggest the potential of incorporating hydrophobic bioinert blocks to enhance the in vivo stability of supramolecularly associated hydrogels for long-term intraocular applications. Graphical Abstract

Intervertebral disc (IVD) degeneration occurred with the increasing age or accidents has puzzled peoples in daily life. To seal IVD defect by injectable hydrogels is a promising method for slowing down IVD degeneration. Herein, we reported a rapidly in situ forming injectable chitosan/PEG hydrogel (CSMA-PEGDA-L) through integrating photo-crosslink of methacrylate chitosan (CSMA) with Schiff base reaction between CSMA and aldehyde polyethylene glycol (PEGDA). The CSMA-PEGDA-L possessed a stronger compressive strength than the photo-crosslinked CSMA-L hydrogel and Schiff-base-crosslinked CSMA-PEGDA hydrogel. This chitosan/PEG hydrogel showed low cytotoxicity from incubation experiments of nucleus pulpous cells. When implanted on the punctured IVD of rat's tail, the CSMA-PEGDA-L hydrogel could well retard the progression of IVD degeneration through physical plugging, powerfully proven by radiological and histological evaluations. This work demonstrated the strategy of in situ injectable glue may be a potential solution for prevention of IVD degeneration.

During 14–16 March 2021, a large-scale dust storm event occurred in the northern region of China, and it was considered the most intense event in the past decade. This study employs observation data for PM2.5 and PM10 from the air quality monitoring station, the HYSPLIT model, ground-based polarized Lidar networks, AGRI payload data from Fengyun satellites and CALIPSO satellite Lidar data to jointly explore and scrutinize the three-dimensional spatial and temporal characteristics of aerosol transport. Firstly, by integrating meteorological data for PM2.5 and PM10, the air quality is assessed across six stations within the Lidar network during the dust storm. Secondly, employing a backward trajectory tracking model, the study elucidates sources of dust at the Lidar network sites. Thirdly, deploying a newly devised portable infrared 1064 nm Lidar and a pulsed 532 nm Lidar, a ground-based Lidar observation network is established for vertical probing of transboundary dust transport within the observed region. Finally, by incorporating cloud imagery from Fengyun satellites and CALIPSO satellite Lidar data, this study revealed the classification of dust and the height distribution of dust layers at pertinent sites within the Lidar observation network. The findings affirm that the eastward movement and southward compression of the intensifying Mongolian cyclone led to severe dust storm weather in western and southern Mongolia, as well as Inner Mongolia, further transporting dust into northern, northwestern, and northeastern parts of China. This dust event wielded a substantial impact on a broad expanse in northern China, manifesting in localized dust storms in Inner Mongolia, Beijing, Gansu, and surrounding areas. In essence, the dust emanated from the deserts in Mongolia and northwest China, encompassing both deserts and the Gobi region. The amalgamation of ground-based and spaceborne Lidar observations conclusively establishes that the distribution height of dust in the source region ranged from 3 to 5 km. Influenced by high-pressure systems, the protracted transport of dust over extensive distances prompted a gradual reduction in its distribution height owing to sedimentation. The comprehensive analysis of pertinent research data and information collectively affirms the precision and efficacy of the three-dimensional aerosol monitoring conducted by the ground-based Lidar network within the region.

Multi-channel SMLM imaging is powerful. Here the authors report globLoc, a GPU-based global fitting algorithm, to extract maximum information from multichannel single molecule data; this gives improved localisation precision for biplane and 4Pi-SMLM and colour assignment in multi-colour astigmatic SMLM.

Hydrogels are extracellular-matrix-like biomimetic materials that have wide biomedical applications in tissue engineering and drug delivery. However, most hydrogels cannot simultaneously fulfill the mechanical and cell compatibility requirements. In the present study, we prepared a semi-interpenetrating network composite gel (CG) by incorporating short chain chitosan (CS) into a covalent tetra-armed poly(ethylene glycol) network. In addition to satisfying physicochemical, mechanics, biocompatibility, and cell affinity requirements, this CG easily encapsulated acetylsalicylic acid (ASA) via electrostatic interactions and chain entanglement, achieving sustained release for over 14 days and thus promoting periodontal ligament stem cell (PDLSC) proliferation and osteogenic differentiation. In vivo studies corroborated the capacity of PDLSCs and ASA-laden CG to enhance new bone regeneration in situ using a mouse calvarial bone defect model. This might be attributed to PDLSCs and host mesenchymal stem cells expressing monocyte chemoattractant protein-1, which upregulated M2 macrophage recruitment and polarization in situ, indicating its appealing potential in bone tissue engineering.

Abstract Double‐network (DN) hydrogels consisting of noncovalent interacting networks are highly desired due to their well‐controlled compositions and environmental friendliness, but the low water resistance always impairs their mechanical strength. Here, an anti‐swelling hydrogel possessing the core/shell architecture through rational regulation of multiple weak noncovalent interactions is prepared. A composite hydrogel consists of chitosan (CS) and poly(N‐acryloyl 2‐glycine) (PACG), readily forming the shell‐structured DN hydrogel after soaking in a FeCl3 solution because of in situ formation of chain entanglements, hydrogen bonds, and ionic coordination. The produced DN hydrogels exhibit excellent anti‐swelling behaviors and mechanical durability for over half a year, even in some strict situations. Taking the merits of noncovalent bonds in adjustability and reversibility, the swelling property of these hydrogels can be easily customized through control of the ion species and concentrations. A dynamically reversible transition from super‐swelling to anti‐swelling is realized by breaking up and rebuilding the metal‐coordination complexes. This facile but efficient strategy of turning the noncovalent interactions and consequently the mechanics and anti‐swelling properties is imperative to achieve the rational design of high‐performance hydrogels with specific usage requirements and expand their applicability to a higher stage.

Development of versatile theranostic agents that simultaneously integrate therapeutic and diagnostic features remains a clinical urgent. Herein, we aimed to prepare uniform PEGylated (lactic-co-glycolic acid) (PLGA) microcapsules (PB@(Fe3O4@PEG-PLGA) MCs) with superparamagnetic Fe3O4 nanoparticles embedded in the shell and Prussian blue (PB) NPs inbuilt in the cavity via a premix membrane emulsification (PME) method. On account of the eligible geometry and multiple load capacity, these MCs could be used as efficient multi-modality contrast agents to simultaneously enhance the contrasts of US, MR and PAT imaging. In-built PB NPs furnished the MCs with excellent photothermal conversion property and embedded Fe3O4 NPs endowed the magnetic location for fabrication of targeted drug delivery system. Notably, after further in-situ encapsulation of antitumor drug of DOX, (PB+DOX)@(Fe3O4@PEG-PLGA) MCs possessed more unique advantages on achieving near infrared (NIR)-responsive drug delivery and magnetic-guided chemo-photothermal synergistic osteosarcoma therapy. In vitro and in vivo studies revealed these biocompatible (PB+DOX)@(Fe3O4@PEG-PLGA) MCs could effectively target to the tumor tissue with superior therapeutic effect against the invasion of osteosarcoma and alleviation of osteolytic lesions, which will be developed as a smart platform integrating multi-modality imaging capabilities and synergistic effect with high therapy efficacy.

In order to conduct more thorough research on the structural characteristics of the atmosphere and the distribution and transmission of atmospheric pollution, the use of remote sensing technology for multi-dimensional detection of the atmosphere is needed. A light-weight, low-volume, low-cost, easy-to-use and low-maintenance mini Infrared Lidar (mIRLidar) sensor is developed for the first time. The model of lidar is established, and the key optical parameters of the mIRLidar are optimized through simulation, in which wavelength of laser, energy of pulse laser, diameter of telescope, field of view (FOV), and bandwidth of filter are included. The volume and weight of the lidar system are effectively reduced through optimizing the structural design and designing a temperature control system to ensure the stable operation of the core components. The mIRLidar system involved a 1064 nm laser (the pulse laser energy 15 μJ, the repetition frequency 5 kHz), a 100 mm aperture telescope (the FOV 1.5 mrad), a 0.5 nm bandwidth of filter and an APD, where the lidar has a volume of 200 mm × 200 mm × 420 mm and weighs about 13.5 kg. It is shown that the lidar can effectively detect three-dimensional distribution and transmission of aerosol and atmospheric pollution within a 5 km detection range, from Horizontal, scanning and navigational atmospheric measurements. It has great potential in the field of meteorological research and environmental monitoring.

Conductor galloping seriously threatens the safe operation of power systems and may lead to various damages such as wire fractures or tower collapses and large-scale grid breakdowns. Real-time galloping data are important in the mechanism and effect analysis of conductor dancing prevention; moreover, they are critical for verifying anti-galloping designs and developing galloping prevention plans. However, owing to the limitations of using sensors on cables, obtaining complete galloping data is an ill-posed and challenging problem. In this study, a novel curve reconstruction method using a conditional generative adversarial network (GAN), CR-CGAN, is proposed for fully synthesizing transmission line galloping curves. We use the modeling capabilities of the recently introduced GAN by imposing additional constraints to achieve full reconstruction of the galloping curves. Moreover, we introduce a novel design in the generator-discriminator pair for improved results and a new refined loss function to enhance details. The generator uses an autoencoder with skip connections, and the inception module is used to capture different scales of spatiotemporal correlation. The discriminator is designed to use global information to determine the reliability and smoothness of the reconstructed curve. The refined loss function is aimed at reducing artifacts introduced by the GAN and ensures better reconstruction quality. A single-degree-of-freedom model is constructed to verify the effectiveness and feasibility of the proposed method. Simulation results demonstrate that the proposed method can accurately reconstruct galloping curves with limited use of sensors, thus meeting the energy efficiency demands of the monitoring system.

Severe hemorrhage is a leading cause of high mortality in critical situations like disaster, accidents, and warfare. The resulting wounds could induce severe physical and psychological trauma to patients and also bring an immense socio-economic burden. Hence, rapid hemostasis and wound healing techniques have become critical initiatives for life-saving treatment. Although traditional methods relying on bandages and gauzes are effective in controlling hemorrhage, they suffer from several limitations: nonbiodegradability, being susceptible to infection, being unsuitable for the irregular wound, secondary tissue damage, and being almost ineffective for wound healing. Owing to the merits of high porosity, good biocompatibility, tunable physicochemical properties, and being beneficial for wound healing, hydrogels with excellent performance have drawn intensive attention and numerous novel effective hydrogel dressings have been widely developed. In this Review, after introducing some commonly used strategies for the synthesis of hydrogels, the most recent progress on polymer-based hydrogels as wound dressings is discussed. Particularly, their hemostasis, antibacterial, and biodegradation properties are introduced. Finally, challenges and future perspectives about the development of hydrogels for wound dressings are outlined.

Controlling shape-shift and size-growth in nanostructures are important developments in nanoscience but controlling morphology change with an instant on/off function remains challenging. Here the authors demonstrate control over morphology and size transformation of POSS molecules based on living thiol-disulfide exchange reactions.

We present a highly adaptable design platform for multi-responsive, multilayered composite nanoparticles (MC-NPs) with fine-tunable functional layers. A flexible disulfide-linked nanogel template is obtained by a controlled in-situ gelation method, enabling a high degree of control over each successive layer. From this template, we optimize “smart” biomaterials with biofunctional surfaces, tunable drug release kinetics, and magnetic or pH-responsive functionality, fabricated into MC-NPs for targeted drug release and periosteum-mimetic structures for controlled rhBMP-2 release towards bone tissue formation in-vivo. Such a versatile platform for the design of MC-NPs is a powerful tool that shows considerable therapeutic potential in clinical fields such as oncology and orthopedics.

With continuous technological development, the future development trend of LiDAR in the field of remote sensing and mapping is to obtain the elevation and spectral information of ground targets simultaneously. Airborne hyperspectral imaging LiDAR inherits the advantages of active and passive remote sensing detection. This paper presents a simulation method to determine the design parameters of an airborne hyperspectral imaging LiDAR system. In accordance with the hyperspectral imaging LiDAR equation and optical design principles, the atmospheric transmission model and the reflectance spectrum of specific ground targets are utilized. The design parameters and laser emission spectrum of the hyperspectral LiDAR system are considered, and the signal-to-noise ratio of the system is obtained through simulation. Without considering the effect of detector gain and electronic amplification on the signal-to-noise ratio, three optical fibers are coupled into a detection channel, and the power spectral density emitted by the supercontinuum laser is simulated by assuming that the signal-to-noise ratio is equal to 1. The power spectral density emitted by the laser must not be less than 15 mW/nm in the shortwave direction. During the simulation process, the design parameters of the hyperspectral LiDAR system are preliminarily demonstrated, and the feasibility of the hyperspectral imaging LiDAR system design is theoretically guaranteed in combination with the design requirements of the supercontinuum laser. The spectral resolution of a single optical fiber of the hyperspectral LiDAR system is set to 2.5 nm. In the actual prototype system, multiple optical fibers can be coupled into a detection channel in accordance with application needs to further improve the signal-to-noise ratio of hyperspectral LiDAR system detection.

A hyperspectral lidar system with focal plane splitting unit is proposed, including an off-axis receiving telescope, a grating spectrometer, and a single-tube detector array. The spectrum of the system covers 380-930nm, and is separated by grating spectrometer. The microlens-fiber coupling system guides the echo signal of 50 channels into each detector. The system solves the data processing problem of the bandwidth and gain the line array and area array detector in traditional hyperspectral lidar. And it also meets the requirement of the high efficiency splitting coupling and weak signal acquisition and detection.

Cloud is an important factor that affects weather and climate, and the vertical distribution of cloud determines its role in the atmospheric radiation transfer process. In this paper, the characteristics of different cloud types and their vertical cloud base height distributions over Eastern China are investigated with a four-year 2B-CLDCLASS-LIDAR product. The intercomparison of cloud base height distribution from ground-based lidar, CloudSat and CALIPSO measurements was studied with observations over the Hefei and Jinhua areas. The 2B-CLDCLASS-LIDAR product has the potential to uncover geographical and seasonal changes in cloud base height distribution over the Hefei area and Jinhua area, which may be beneficial for local climate models, although the CPR on CloudSat suffers from surface clutter or blind-zones. The results show that for non-precipitation cloud over the defined region (Eastern China), the occurrence frequencies of altocumulus, stratocumulus, and cirrus clouds are 29.4%, 21.0%, and 18.9%, respectively. The vertical occurrence frequencies of their cloud base heights are 0.5−8.5 km, below 3.5 km, and 5.5−17.0 km. The precipitation clouds are dominated by nimbostratus (48.4%), cumulus (17.9%), and deep convective clouds (24.2%), and their cloud base heights are all below 3.0 km. The cloud base height distributions have large differences below 3 km between the satellite measurement and ground-based measurement over Hefei site. Between the Hefei site and Jinhua site, the difference in cloud base height distribution measured by ground-based lidar is in good agreement with that measured by satellite over their matched grid boxes. Over the Hefei site, the vertical occurrence frequencies of cloud base height measured by ground-based lidar are higher than the satellite measurement within 0−0.5 km during all the seasons. It is suggested that more cloudy days may result from the sufficient water vapor environment in Hefei. In summer, the occurrence frequency of the cloud base height distribution at a height of 0−2.0 km is lower than other seasons over Jinhua city, which may be associated with the local weather system. Over the Jinhua site, the difference in seasonal cloud base height distribution based on satellite is in good agreement with that based on ground-based lidar. However, it does not appear over Hefei site. Thus, a multi-platform observation of cloud base height seems to be one of the essential ways for improvement in the observation of cloud macroscopic properties.

This paper proposes a sparse array consisting of two separate generalized nested arrays. The unit element-spacing of each generalized nested array can be adjusted to multiple half-wavelengths of the incident signal. By adjusting the element-spacing, the mutual coupling effect can be greatly reduced. For this array, a direction of arrival (DOA) estimation method of quasi-stationary signals has also been proposed. By using the received signals of the separated generalized nested array, a signal subspace is obtained. Then, this subspace is filled into a higher-order signal subspace to avoid angle ambiguity. Using the higher-order signal subspace, DOAs of all signals can be estimated by spectral peak search. Simulation results show that the proposed separated generalized nested array has better performance than the conventional nested array in DOA estimation. [ABSTRACT FROM AUTHOR]