Co-Doped Porous Carbon/Carbon Nanotube Heterostructures Derived from ZIF-L@ZIF-67 for Efficient Microwave Absorption.

Carbon-based magnetic metal composites derived from metal-organic frameworks (MOFs) are promising materials for the preparation of broadband microwave absorbers. In this work, the leaf-like co-doped porous carbon/carbon nanotube heterostructure was obtained using ZIF-L@ZIF-67 as precursor. The number of carbon nanotubes can be controlled by varying the amount of ZIF-67, thus regulating the dielectric constant of the sample. An optimum reflection loss of -42.2 dB is attained when ZIF-67 is added at 2 mmol. An effective absorption bandwidth (EAB) of 4.8 GHz is achieved with a thickness of 2.2 mm and a filler weight of 12%. The excellent microwave absorption (MA) ability is generated from the mesopore structure, uniform heterogeneous interfaces, and high conduction loss. The work offers useful guidelines to devise and prepare such nanostructured materials for MA materials.

Hydrophilic modification of PVDF-based SERS imprinted membrane for the selective detection of L-tyrosine.

The polyvinylidene difluoride (PVDF) membrane has received considerable attention as a flexible surface enhanced Raman scattering (SERS) substrate due to its excellent mechanical and physicochemical properties. However, the poor fouling resistance of PVDF membrane due to its intrinsic hydrophobic property limits its practical application. To address this, in this investigation, a SERS imprinted membrane is synthesized based on W18O49/Ag composites. Firstly, to promote hydrophilicity, N-vinyl-2-pyrrolidone (NVP) and triethoxyvinylsilane (VTES) are copolymerized by hydrolysis condensation and linked with engineered polyvinypyrrolidone (PVP) chains exposed on the surface of membrane. Furthermore, W18O49/Ag composites are dispersed on the membrane under the assistance of polydopamine (pDA) to promote the pollution resistance. Subsequently, in order to demonstrate the practical detection property, W18O49/Ag/PVDF membrane is selected as the SERS substrate to synthesize SERS imprinted membrane by precipitation polymerization for the selective detection of L-tyrosine. The characteristic results reveal that the SERS-imprinted membrane exhibits satisfactory hydrophilicity, and it can effectively degrade the pollutant molecules absorbed on its surface under ultraviolet light illumination. It is proved from the detection results that the LOD of WADP-MIMs for L-tyrosine reached 10-9 mol L-1 when the concentration of L-tyrosine changed between 10-3-10-9 mol L-1. The correlation coefficient (R2) is 0.994 and the limit of detection is 10-9 mol L-1. Meanwhile, it can be applied for the selective detection of L-tyrosine in mixture samples. Overall, this study presents a novel approach for the hydrophilic modification and pollution resistance enhancement of PVDF-based SERS imprinted membrane, which can be effectively utilized for the selective detection of practical samples.

Real-Time Pedestrian Tracking Terminal Based on Adaptive Zero Velocity Update.

In the field of pedestrian dead reckoning (PDR), the zero velocity update (ZUPT) method with an inertial measurement unit (IMU) is a mature technology to calibrate dead reckoning. However, due to the complex walking modes of different individuals, it is essential and challenging to determine the ZUPT conditions, which has a direct and significant influence on the tracking accuracy. In this research, we adopted an adaptive zero velocity update (AZUPT) method based on convolution neural networks to classify the ZUPT conditions. The AZUPT model was robust regardless of the different motion types of various individuals. AZUPT was then implemented on the Zynq-7000 SoC platform to work in real time to validate its computational efficiency and performance superiority. Extensive real-world experiments were conducted by 60 different individuals in three different scenarios. It was demonstrated that the proposed system could work equally well in different environments, making it portable for PDR to be widely performed in various real-world situations.

Graphene oxide supported gold nanoclusters for the sensitive and selective detection of nitrite ions.

The research progress on the selective and sensitive fluorescent detection of nitrite anions has greatly relied on the development of new fluorescent materials. Herein, a novel nanohybrid exhibiting dual emissions in blue and red wavelength ranges is fabricated for the rapid, on-site, and sensitive detection of nitrite anions. Such a nanohybrid system consists of graphene oxide (GO-C6NH2) and gold nanoclusters (HSA-Au NCs), which have been hybridized by electrostatic attraction and hydrogen bonding interaction. The nanohybrid has been completely characterized with respect to its fluorescence properties, photostability, and morphology. It has been found that red fluorescence of gold nanoclusters selectively responds to nitrite, whereas the blue fluorescence of graphene oxide remains constant, resulting in a distinct fluorescence color evolution from red to blue. Therefore, we apply the nanohybrid for the detection of nitrite anions by a fluorescence ratiometric method and estimate a detection limit of 46 nM, lower than the allowable level (∼21 µM) in drinking water set by U.S. Environmental Protection Agency. The method has been further validated by applying it for the determination of nitrite anions in real samples, including tap water, lake water, and cured meat.

Fluorescence signaling of hydrogen sulfide in broad pH range using a copper complex based on BINOL-benzimidazole ligands.

A weakly fluorescent complex derived from a binaphthol-benzimidazole ligand was designed and synthesized for hydrogen sulfide at different pH conditions. It was demonstrated that the probe showed the same reactivity to various hydrogen sulfide species in a broad range of pH values to generate highly fluorescent product through a displacement reaction mechanism, whereas the product's fluorescence spectrum exhibited a hypsochromic shift of ∼73 nm (2393 cm(-1)) as pH increased from neutral to basic, which can be used for distinguishing the various species of hydrogen sulfide. This turn-on fluorescence probe was highly selective and sensitive to hydrogen sulfide with a detection limit of 0.11 µM. It was then applied for evaluating the total content of sulfide (including hydrogen sulfide, hydrosulfide, and sulfide) as well as for the visual detection of gaseous H2S in air using a simple test paper strip.

[Vertebral in vivo motion of adjacent segments in patients with degenerative spondylolisthesis].

OBJECTIVE: To observe the in vivo vertebral motion of adjacent segments in patients with degenerative spondylolisthesis (DS) during functional weight-bearing activities. METHODS: A total of 15 symptomatic L4 DS patients (mean age 54.4 years) and 15 asymptomatic volunteers (mean age 53.4 years) were recruited. The vertebral segment motion of each subject was reconstructed with three-dimensional computed tomography and solid modeling software. In vivo lumbar vertebral motion during functional postures (flexion-extension, left-right twisting and left-right bending) was observed with dual fluoroscopic imaging. Coordinate systems were established at the vertebral center of L3-S1 to obtain the intervertebral range of motion (ROM) at L3/4, L4/5 and L5/S1 in DS and normal groups. RESULTS: The motion pattern at L3/4 with DS was altered. During left-right bending, the rotation along sagittal axis was significantly larger than normal group (4.4° ± 2.8° vs 2.1° ± 1.7°, P < 0.05). During left-right twisting, the rotation along vertical axis was significantly larger than normal group (4.3° ± 2.8° vs 2.1° ± 1.3°, P < 0.05). During flexion to extension, the rotation along frontal axis was larger than DS group (3.9° ± 3.3° vs 3.2° ± 2.5°). However the difference was insignificant. The motion pattern at L4/5 and L5/S1 with DS had no significant difference with normal group. CONCLUSION: The slipped segments of degenerative spondylolisthesis are stable. However, the ROM of cranial segment increases.

[Application of digital orthopedic technology for observing degenerative lumbar segmental instability of three-dimensional kinematic characteristics in vivo].

OBJECTIVE: To explore the characteristics of three-dimensional motion of lumbar instability segmental in vivo under physiological weight bearing so as to establish three-dimensional diagnostic criteria for degenerative lumbar segmental instability (DLSI). METHODS: Eight patients aged 29-65 years with DLSI at L3/4 were studied as instability group (L3/4), 9 patients aged 51-60 years with DLSI at L4/5 as instability group (L4/5) and 10 healthy volunteers aged 26-51 years as normal group. Three-dimension (3D) reproductions by matching lumbar spine models were reconstructed from thin-section computed tomography scans. Spine motions were then reproduced by matching lumber spine models and images from dual fluoroscopic imaging system (DFIS). The models were matched to the osseous outlines of images from two orthogonal views to determine the SD position of vertebrae for each pose. From local coordinate systems at end plates, the motion of cephalad vertebrae relative to cauddal vertebrae was calculated for vertebrae levels. RESULTS: The motion pattern at L3/4 was altered . During flexion-extension, migration was significantly larger than normal group along sagittal axis (P < 0.05); rotation was significantly larger than normal group along vertical axis; migration was significantly smaller than normal group along vertical axis; during left-right twisting, rotation was significantly larger than normal group along vertical axis (P < 0.05). The motion pattern at L4/5 was also altered . During flexion-extension, migrations was significantly larger than normal group along sagittal axis (P < 0.05). During left-right twisting, migration and rotation were significantly smaller than normal group along vertical axis (P < 0.05). Rotation was significantly larger than normal group along sagittal axis. During left-right bending, rotation was significantly larger than normal group along sagittal axis (P < 0.05). CONCLUSION: Lumbar instability segments were significantly different compared with normal lumbar segments. And lumbar instability segments (at L3/4) were also different from lumbar instability segments (at L4/5). Different three-dimensional diagnostic criteria should be formulated for different lumbar instability segments.

Development of practical techniques for simultaneous detection and distinction of current and emerging SARS-CoV-2 variants.

Countless individuals have fallen victim to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and have generated antibodies, reducing the risk of secondary infection in the short term. However, with the emergence of mutated strains, the probability of subsequent infections remains high. Consequently, the demand for simple and accessible methods for distinguishing between different variants is soaring. Although monitoring viral gene sequencing is an effective approach for differentiating between various types of SARS-CoV-2 variants, it may not be easily accessible to the general public. In this article, we provide an overview of the reported techniques that use combined approaches and adaptable testing methods that use editable recognition receptors for simultaneous detection and distinction of current and emerging SARS-CoV-2 variants. These techniques employ straightforward detection strategies, including tests capable of simultaneously identifying and differentiating between different variants. Furthermore, we recommend advancing the development of uncomplicated protocols for distinguishing between current and emerging variants. Additionally, we propose further development of facile protocols for the differentiation of existing and emerging variants.

[Vertebral three-dimensional motion characteristics of adjacent segments in patients with isthmic spondylolisthesis in vivo].

Objective: To observe vertebral three-dimensional motion characteristics of adjacent segments in patients with symptomatic L 4 isthmic spondylolisthesis (IS). Methods: Fourteen symptomatic L 4 IS patients who underwent surgery treatment (trial group) and 15 asymptomatic volunteers without back pain and other lesions of spine (control group) were recruited. There was no significant difference in gender, age, body mass index, and bone mineral density between the two groups ( P>0.05). The three-dimensional reconstruction model of lumbar spine was acquired from the thin slice CT of the lumbar spine of the subjects by combining dual-X-ray fluoroscopy imaging system with spiral CT examination. The model was matched to the double oblique X-ray fluoroscopy images captured by dual-X-ray fluoroscopy imaging system at different active positions of the lumbar spine to reproduce the three-dimensional instantaneous of lumbar spondylolisthesis at different state of motion. The motion and relative displacement of adjacent segments (L 3, 4 and L 5, S 1) of spondylolisthesis were measured quantitatively by establishing a three-dimensional coordinate system at the geometric center of the vertebral body. The results were compared with those of the control group. Results: When L 3, 4 in the control group were flexed flexion-extension, left-right twisting, and left-right bending, and when L 5, S 1 in the control group were flexed left-right twisting and left-right bending, the activity along the main axis of motion (main axis of motion) tended to increase compared with that along the corresponding coupled axis of motion (secondary axis of motion); however, this trend disappeared in the trial group, and the main and secondary movements were disordered. Because of the coronal orientation of the facet joints of L 5, S 1, the degree of motion along the main axis of motion decreased during flexion and extension, but this trend disappeared in the trial group. Compared with the control group, L 3, 4 in the trial group exhibited displacement instability in flexion-extension, left-right twisting, and left-right bending ( P<0.05); there was no significant difference in the relative displacement of L 5, S 1 intervertebral bodies along x, y, and z axes between the trial group and the control group in flexion-extension, left-right twisting, and left-right bending curvature ( P>0.05). Conclusion: Patients with symptomatic L 4 IS have disorders of primary and secondary movement patterns in adjacent segments, while IS showed significantly displacement instability in L 3, 4 and significantly decreased motion in L 5, S 1.

[Development research of in vivo kinematics in lumbar degenerative spondylolisthesis].

OBJECTIVE: To review the researches of in vivo kinematics in lumbar degenerative spondylolisthesis (DS). METHODS: Related literature concerning the in vivo kinematics in patients with lumbar DS was extensively reviewed and comprehensively analyzed in 4 terms of the instability of lumbar DS, vertebral motion pattern, the morphological changes of spinal canal, and intraoperative biomechanical measurement. RESULTS: Whether there is lumbar segmental instability in lumbar DS patients is still controversial, which should be based on degenerative stage of lumbar spine and grade of slip. The hypomobility of the lumbar spinous processes and the facet joint is seen in DS. The diameter, cross-sectional area, and volume of spinal canal in lumbar DS patients are significantly smaller than those of the normal control. Because of its invasive procedure and medical ethics, the use of the intraoperative measurement device is limited. These reported researches of in vivo kinematics in DS are almost on the sagittal plane. However, few data have been reported on the 6-degree-of-freedom (6DOF) kinematics of the diseased levels under physiological loading conditions. CONCLUSION: The 6DOF kinematics data can accurately reflect the segmental motion characteristics in lumbar DS patients, recent studies have been reported, further studies are still needed.

Fluorescent nanohybrid of gold nanoclusters and quantum dots for visual determination of lead ions.

Highly green emissive gold nanoclusters (Au NCs) are synthesized using glutathione as a stabilizing agent and mercaptopropionic acid as a ligand, and the intensity of fluorescence is specifically sensitive to lead ions. We then fabricated a ratiometric fluorescence nanohybrid by covalently linking the green Au NCs to the surface of silica nanoparticles embedded with red quantum dots (QDs) for on-site visual determination of lead ions. The green fluorescence can be selectively quenched by lead ions, whereas the red fluorescence is inert to lead ions as internal reference. The different response of the two emissions results in a continuous fluorescence color change from green to yellow that can be clearly observed by the naked eyes. The nanohybrid sensor exhibits high sensitivity to lead ions with a detection limit of 3.5 nM and has been demonstrated for determination of lead ions in real water samples including tap water, mineral water, groundwater, and seawater. For practical application, we dope the Au NCs in poly(vinyl alcohol) (PVA) film and fabricate fluorescence test strips to directly detect lead ions in water. The PVA-film method has a visual detection limit of 0.1 µM, showing its promising application for on-site identification of lead ions without the need for elaborate equipment.