-heterocyclic carbene (NHC) has been widely used as an organocatalyst for both umpolung and non-umpolung chemistry. Previous works mainly focus on species including Breslow intermediate, azolium ...enolate intermediate, homoenolate intermediate, alkenyl acyl azolium intermediate, etc. Notably, the NHC-bound alkynyl acyl azolium has emerged as an effective intermediate to access functionalized cyclic molecular skeleton until very recently. In this review, we summarized the generation and reactivity of the NHC-bound alkynyl acyl azolium intermediates, which covers the efforts and advances in the synthesis of achiral and axially chiral cyclic scaffolds via the NHC-bound alkynyl acyl azolium intermediates. In particular, the mechanism related to this intermediate is discussed in detail.
Planar-chiral cyclophanes have gained considerable concerns for drug discovery due to their unique conformational strain and 3D structure. However, the enantioselective synthesis of planar-chiral ...cyclophanes is a long-standing challenge for the synthetic community. We herein describe an N-heterocyclic carbene (NHC)-catalyzed asymmetric construction of planar-chiral cyclophanes. This transformation occurs through a dynamic kinetic resolution (DKR) process to convert racemic substrates into planar-chiral macrocycle scaffolds in good to high yields with high to excellent enantioselectivities. The ansa chain length and aromatic ring substituent size is crucial to achieve the DKR approach. Controlled experiments and DFT calculations were performed to clarify the DKR process.
Tourniquet is currently widely used in total knee arthroplasty to reduce intraoperative blood loss. The academic view of tourniquet application in TKA is now in dispute. Some scholars argue that ...tourniquet may cause quadriceps injury and bring extra side effects, so they oppose the application of tourniquet. Others find that tourniquet application has no significant adverse impact on TKA patients. Regarding its advantages in reducing intraoperative blood loss, they advocate the regular application of tourniquet in TKA. Quadriceps injury is considered the main cause of tourniquet side effects. There are now many high-quality trials about tourniquet application in TKA but few of them concentrate on quadriceps morphology and function.
A prospective, single-blind, randomized controlled trial will be adopted. The target sample is 130. Patients who meet the eligibility criteria will be randomly allocated to the tourniquet group and non-tourniquet group. The primary outcome is quadriceps thickness evaluated by ultrasound test. Secondary outcomes include quadriceps stiffness, rehabilitation outcomes, operation time, intraoperative and postoperative blood loss, blood transfusion rate, thigh circumference, VAS score, opioid consumption, D-dimer and C-reactive protein level in the serum, knee function score, postoperative satisfaction score, and complications.
This proposed study will contribute to improve evidence of tourniquet application in total knee arthroplasty. This will be a high-quality single-blind randomized controlled trial with a sufficient sample size and strict study design. It will investigate the effects of tourniquet application especially on the morphology and function of quadriceps in patients undergoing total knee arthroplasty and offer advice for tourniquet application in clinical practice.
Chinese Clinical Trial Registry ChiCTR2000035097 . Registered on 31 July 2020.
The main task of remote sensing change detection (CD) is to identify object differences in bitemporal remote sensing images. In recent years, methods based on deep convolutional neural networks have ...made great progress in remote sensing CD. However, due to illumination changes and seasonal changes in the images acquired by the same sensor, the problem of “pseudo change” in the change map is still difficult to solve. In this article, in order to reduce “pseudo changes,” we propose a multiscale difference feature enhancement network (MDFENet) to extract the most discriminative features from bitemporal remote sensing images. MDFENet contains three procedures: first, multiscale bitemporal features are generated by a shared weighted Siamese encoder. Then features of each scale are fed into a difference enhancement module to generate refined difference features. Finally, they are combined and reconstructed by a decoder to generate change map. The difference enhancement module includes multiple layers of difference enhancement encoder and transformer decoder. They are applied to features of different scales to establish long-range relationships of pixels semantic changes, while high-level difference features participate in the generation of low-level difference features to enhance information transmission among features of different scales, reducing “pseudo changes.” Compared with state-of-the-art methods, the proposed method achieved the best performance on two datasets, with F1 of 81.15% on the SYSU-CD dataset and 90.85% on the LEVIR-CD dataset.
Background
Primary hyperparathyroidism (PHPT) is an endocrine disorder with high serum calcium and parathyroid hormone (PTH) levels. Excessive secretion of PTH can cause bone loss and may have ...potential damage to implant fixation after total knee arthroplasty (TKA). However, there is currently no research or literature reporting prosthesis loosening after TKA associated with PHPT.
Case presentation
This case report describes a TKA failure of tibial prothesis loosening associated with PHPT. The patient faced aggravated pain and difficulty in walking 6 months after the primary TKA. Further examinations showed high serum calcium and PTH levels indicating the presence of PHPT. After the surgery of parathyroidectomy, the patient received revision TKA with 3D‐printed metaphyseal cone. Knee symptoms and function were finally improved.
Conclusion
PHPT is a risk factor for prosthesis loosening after TKA. Preoperative screening test of serum calcium and PTH levels is important to diagnose PHPT. For patients with PHPT undergoing TKA, preoperative endocrinotherapy and parathyroidectomy are recommended to improve the survival of prosthesis.
Deep network models rely on sufficient training samples to perform reasonably well, which has inevitably constrained their application in classification of hyperspectral images (HSIs) due to the ...limited availability of labeled data. To tackle this particular challenge, we propose a hybrid relation network, H-RNet, by combining three-dimensional (3-D) convolution neural networks (CNN) and two-dimensional (2-D) CNN to extract the spectral–spatial features whilst reducing the complexity of the network. In an end-to-end relation learning module, the sample pairing approach can effectively alleviate the problem of few labeled samples and learn correlations between samples more accurately for more effective classification. Experimental results on three publicly available datasets have fully demonstrated the superior performance of the proposed model in comparison to a few state-of-the-art methods.
Introduction:
Alkaline pectin lyase is an important enzyme with a wide range of applications in industrial production, It has been widely used in many important fields such as fruit juice processing ...and extraction, the dyeing and processing of cotton and linen textiles, degumming plant fibers, environmental industrial wastewater treatment, and pulp and paper production. PGLA-rep4 was previously generated as a modified alkaline pectin lyase with high specific activity at pH 11.0°C and 70°C. However, the pre-constructed high-activity pectin lyase expression strains are still difficult to apply in industrial production due to their limited enzymatic activity. We hope to solve these problems by combining modern breeding techniques with high-throughput equipment to rapidly screen alkaline pectin lyase with higher enzymatic activity and lower cost.
Methods:
We fused the genes encoding PGLA-rep4 and fluorescent protein
egfp
using a flexible linker peptide and ligated them into a temperature
-
sensitive plasmid, pKD46. The constructed screening plasmid pKD46-PGLA-rep4-
egfp
was then transformed into an expression host and screened via flow-cytometric cell sorting coupled with UV mutagenesis.
Results:
Following mutagenesis, primary screening, and secondary screening, the high-expression strain, named
Escherichia coli
BL21/1G3, was obtained. The screening plasmid pKD46-PGLA-rep4-
egfp
was eliminated, and the original expression plasmid pET28a-PGLA-rep4 was then retransformed into the mutant strains. After induction and fermentation, pectin lyase activity in
E. coli
BL21/1G3 was significantly increased (1.37-fold relative to that in the parental
E. coli
BL21/PGLA-rep4 strain,
p
< 0.001), and the highest activity was 230, 240 U/mL at 144 h. Genome sequencing revealed that genes encoding ribonuclease E (RNase E) and diadenosine tetraphosphatase (ApaH) of
E. coli
BL21/1G3 were mutated compared to the sequence in the original
E. coli
BL21 (DE3) strain, which could be associated with increased enzyme expression.
Discussion:
Our work provides an effective method for the construction of strains expressing pectin lyase at high levels.
Objectives
The reconstruction of bone defects in tibial revision knee arthroplasty is challenging. In this study, we evaluated the primary stability of a novel three‐dimensional (3D)‐printed ...custom‐made metaphyseal cone for Anderson Orthopedic Research Institute (AORI) IIb or III bone defect reconstruction in tibial revision knee arthroplasty using the combination of finite‐element analysis and biomechanical experiments.
Methods
In the finite‐element analysis, AORI II b and III medial tibial bone defects were designed at varying depths. A novel 3D‐printed custom‐made metaphyseal cone was designed and used to reconstruct the bone defect with or without a stem in simulated revision total knee arthroplasty (RTKA). A no‐stem group and a stem group were established (based on whether a stem was used or not). Von Mises stress and micromotion were calculated with varying depths of bone defects, ranging from 5 mm to 35 mm, and then micromotions at the bone–implant interface were calculated and compared with the critical value of 150 μm. In the biomechanical experiment, the no‐stem group was used, and the same bone defects were made in four synthetic tibias using patient‐specific instruments. Micromotions at the bone–implant interface were investigated using a non‐contact optical digital image correlation system and compared with the critical value of 150 μm.
Results
When the bone defect was <30 mm, micromotions at the bone–implant interface in the finite‐element analysis were all below 150 μm both in the stem groups and no‐stem groups, whereas those in the biomechanical experiment were also below 150 μm in the no‐stem group.
Conclusions
The 3D‐printed custom‐made metaphyseal cone in RTKA has excellent primary stability and does not require stems in reconstructing tibial AORI type IIb or III bone defects with a depth of <30 mm.
In this letter, we present an intraoperative magnetic resonance imaging (MRI)-guided robot for bilateral stereotactic procedures. Its compact design enables robot's operation within the constrained ...space of standard imaging head coil. magnetic resonance (MR) safe and high-performance hydraulic transmissions are incorporated. A maximum stiffness coefficient of 24.35 N/mm can be achieved with transmission fluid preloaded at 2 bar. Sufficient targeting accuracy (average within ≤1.73 mm) has been demonstrated in a simulated needle insertion task of deep brain stimulation. A novel MR-based wireless tracking technique is adopted. It is capable of offering real-time and continuous (30-40 Hz) three-dimensional (3-D) localization of robotic instrument under the proper MR tracking sequence. It outperforms the conventional method of using low-contrast passive fiducials that can only be revealed in the MR image domain. Two wireless tracking units/markers are integrated with the robot, which are two miniaturized coil circuits in size of 1.5 × 5 × 0.2 mm 3 , fabricated on flexible thin films. A navigation test was performed under the standard MRI settings in order to visualize the 3-D localization of the robotic instrument. MRI compatibility test was also carried out to prove the minimal interference to MR images of the presented hydraulic robotic platform.
Eight-membered ring skeletons are widely present in a variety of natural products and bioactive molecules. In particular, eight-membered nitrogen-heterocycles are compelling privileged structures for ...drug discovery, especially for challenging targets that are difficult to modulate using conventional small molecule screening libraries. However, the construction of eight-membered N-heterocycles is a formidable challenge in chemistry owing to unfavorable entropic and enthalpic effects. Thus, the development of novel strategies to access these scaffolds is highly desirable. In this review, we summarize the progress in the synthesis of eight-membered N-heterocycles in the past 20 years (1995-2023), with a focus on reaction mechanisms associated with typical reactions. We aim to inspire synthetic chemists to develop efficient strategies for the construction of eight-membered N-heterocycles.
This review summarized the progress in synthesizing eight-membered N-heterocycles over the past two decades (1995-2023), inspiring synthetic chemists to develop more efficient strategies for the construction of these skeletons.
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