Publications by authors named "Annan Li"

Polymerization shrinkage is a major side effect of resin composite materials that affects the success and longevity of caries restorations. This study was to analyze the effect of the internal angle and shape of the lining on the shrinkage residual stress of dental restorations in Class II mesio-occlusal-distal (MOD) cavities through finite element analysis (FEA). A 3D reconstructed model of a human mandibular first molar was created from micro-CT images, and then the tooth was prepared as a Class II MOD cavity.

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Mastication displays much importance in people's lives. The masticatory mandibular motion associated with dental kinematics also impacts temporomandibular joint (TMJ) kinematics and even TMJ health status. How food properties impact kinematical parameters of TMJs is a meaningful question for the conservative treatment of temporomandibular disorders (TMD) and evidence for the diet recommendation of TMD patients.

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Article Synopsis
  • The study focused on the cyclization of farnesyl diphosphate (FPP) into polycyclic sesquiterpenes and analyzed the crystal structures of three specific sesquiterpene synthases (BcBOT2, DbPROS, and CLM1) involved in this process.
  • These synthesizing enzymes were examined using quantum mechanics/molecular mechanics (QM/MM) simulations, revealing crucial details about their catalytic mechanisms and the roles of important active site residues in stabilizing reactive intermediates.
  • Findings from site-directed mutagenesis and isotopic labeling experiments enhanced understanding of the enzymes' functions and highlighted potential applications in enhancing synthetic biology, particularly for pharmaceutical and fragrance production.
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Background And Objective: The incisal biting was one of the most regular jaw activities. The direction of bite force on the incisor tip and the mandible position were relevant to the incisor angle as biting. This study was carried out to explore the influence on the temporomandibular joint (TMJ) caused by the incisor angle.

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Finite element (FE) analysis has become a popular method of exploring the biomechanical characteristics of temporomandibular joint (TMJ). However, the FE model should be improved and its reliability should be verified further. This study developed a complete maxillofacial model by cone-beam computed tomography (CBCT) and magnetic resonance imaging (MRI).

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Background: Clinical diagnosis and treatment depended heavily on the motion analysis of the human joints. Although the dynamic joint space (DJS) of other organs was widely used in academic investigations, they were not universally used in the temporomandibular joint (TMJ) field, which was also important for the motion evaluation of the TMJ. The objectives of this study are to introduce the DJS of the TMJ and characterize the DJS regulars of mandibular movements.

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Background: Temporomandibular disorder (TMD) symptoms were found to be common in the patients with maxillofacial deformities. The mandibular structure was in relation with the stress within temporomandibular joint (TMJ). However, the current studies on the TMJ stresses in the patients with different maxillofacial deformities are not comprehensive enough.

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The crystal structures of cattleyene synthase (apo-CyS), and CyS complexed with geranylgeranyl pyrophosphate (GGPP) were solved. The CyS variant exhibited an increased production of cattleyene and other diterpenes with diverse skeletons. Its structure showed a widened active site cavity explaining the relaxed selectivity.

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Article Synopsis
  • Orthognathic surgery is commonly used to fix facial deformities, but it also alters the positions of the condyles (the rounded ends of the lower jaw that connect to the skull).
  • This study focuses on how these surgeries affect the shape and function of temporomandibular joints (TMJs) and explores the relationship between TMJ changes and temporomandibular disorders (TMDs).
  • Results indicate that while the surgeries improve facial structure, they maintain pre-surgery stress levels in TMJs and highlight that specific joint spaces are linked to TMD symptoms.
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Pimarane-type diterpenoids are widely distributed in all domains of life, but no structures or catalytic mechanisms of pimarane-type diterpene synthases (DTSs) have been characterized. Here, we report that two class I DTSs, Sat1646 and Stt4548, each accept copalyl diphosphate (CPP) as the substrate to produce isopimara-8,15-diene (1). Sat1646 can also accept syn-CPP and produce syn-isopimaradiene/pimaradiene analogues (2-7), among which 2 possesses a previously unreported "6/6/7" ring skeleton.

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Temporomandibular joint (TMJ) is an important and complex joint in the human body. It is necessary to explore the biomechanical influence on the TMJs caused by different mandibular deformities. The maxillofacial models from 34 subjects were built to analyze the maximum and minimum principal stresses of the TMJs in the control group and three test groups.

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Fsa2 and Phm7 are a unique pair of pericyclases catalyzing [4 + 2] cycloaddition reactions with reverse stereoselectivities in the biosynthesis of equisetin and phomasetin, both of which are potent HIV-1 integrase inhibitors. We here solve the crystal structures of Fsa2 and Phm7, both of which possess unusual "two-β barrel" folds. Different residues are evident between the active sites of Fsa2 and Phm7, and modeling experiments provide key structural information determining the reverse stereoselectivities.

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Computerized pupillary light reflex assessment devices (CPLRADs) may serve as an effective screening tool for glaucomatous optic neuropathy, since they can dynamically detect abnormal pupillary responses from a novel sequence of light stimuli and functionally-shaped stimuli. The aim of this study was to systematically evaluate the current state of advanced CPLRADs and accuracy of application in detecting glaucoma. An electronic literature search of PubMed, MEDLINE, and Embase from database inception to December 2019 was performed.

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Seven new 4-acyl-2-aminoimidazoles, designated strepimidazoles A-G (-), were discovered from the endophytic sp. PKU-EA00015 isolated from Bunge, whose dry root "Danshen" is one of the most widely used traditional Chinese medicines. The resonance signals of the 2-aminoimidazole moiety in - were absent in the NMR spectra due to tautomerization, and the structures of - were identified after preparation of their acetylation products -, respectively.

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Predictive scene parsing is a task of assigning pixellevel semantic labels to a future frame of a video. It has many applications in vision-based artificial intelligent systems, e.g.

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The skin is the largest organ of our body. Skin disease abnormalities which occur within the skin layers are difficult to examine visually and often require biopsies to make a confirmation on a suspected condition. Such invasive methods are not well-accepted by children and women due to the possibility of scarring.

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A search for bioactive natural products as anticancer lead compounds resulted in the isolation of one previously undescribed and three known clerodane diterpenoids (1-4) from Casearia kurzii. The structures of these compounds were established by analysis of their NMR, MS, and electronic circular dichroism data. The cytotoxic activities of four compounds against three human cancer cell lines were evaluated.

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Identifying vulnerable plaque is important in coronary heart disease diagnosis. Recent emerged imaging modality, Intravascular Optical Coherence Tomography (IVOCT), has been proved to be able to characterize the appearance of vulnerable plaques. Comparing with the manual method, automated fibroatheroma identification would be more efficient and objective.

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The quality of input images significantly affects the outcome of automated diabetic retinopathy (DR) screening systems. Unlike the previous methods that only consider simple low-level features such as hand-crafted geometric and structural features, in this paper we propose a novel method for retinal image quality classification (IQC) that performs computational algorithms imitating the working of the human visual system. The proposed algorithm combines unsupervised features from saliency map and supervised features coming from convolutional neural networks (CNN), which are fed to an SVM to automatically detect high quality vs poor quality retinal fundus images.

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The in vivo assessment and visualization of skin structures can be performed through the use of high resolution optical coherence tomography imaging, also known as HD-OCT. However, the manual assessment of such images can be exhaustive and time consuming. In this paper, we present an analysis system to automatically identify and quantify the skin characteristics such as the topography of the surface of the skin and thickness of the epidermis in HD-OCT images.

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Basal cell carcinoma (BCC) is the most common non-melanoma skin cancer. Conventional diagnosis of BCC requires invasive biopsies. Recently, a high-definition optical coherence tomography (HD-OCT) technique has been developed, which provides a non-invasive in vivo imaging method of skin.

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Automated glaucoma detection is an important application of retinal image analysis. Compared with segmentation based approaches, image classification based approaches have a potential of better performance. However, it still remains a challenging problem for two reasons.

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Numerous approaches on object tracking have been proposed during the past decade with demonstrated success. However, most tracking algorithms are evaluated on limited video sequences and annotations. For thorough performance evaluation, we propose a large-scale database which contains 365 challenging image sequences of pedestrians and rigid objects.

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Epidermis segmentation is a crucial step in many dermatological applications. Recently, high-definition optical coherence tomography (HD-OCT) has been developed and applied to imaging subsurface skin tissues. In this paper, a novel epidermis segmentation method using HD-OCT is proposed in which the epidermis is segmented by 3 steps: the weighted least square-based pre-processing, the graph-based skin surface detection and the local integral projection-based dermal-epidermal junction detection respectively.

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Subspace-based face representation can be looked as a regression problem. From this viewpoint, we first revisited the problem of recognizing faces across pose differences, which is a bottleneck in face recognition. Then, we propose a new approach for cross-pose face recognition using a regressor with a coupled bias-variance tradeoff.

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