Publications by authors named "Qun Lei"

Background: Overerupted maxillary molars is common in adults, which can lead to insufficient intermaxillary vertical space ,great difficulty in prosthetic reconstruction ,and cause occlusal interference in movements.To reconstruct occlusal function, it is necessary to prepare enough space for prostheses. The aim of the present study was to evaluate the effect of space-adjustment occlusal splint on overerupted maxillary molars by clinical and electromyographic signals analysis.

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Objective: This study aims to determine the variations in myocardial work among patients with essential hypertension at varying risk levels by analyzing the left ventricular pressure-strain loop. Additionally, this research aims to investigate the potential diagnostic significance of myocardial work parameters in identifying myocardial dysfunction in patients with essential hypertension.

Methods: We conducted a study with 79 patients who have essential hypertension and 30 healthy adults.

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Objective: Occlusal splints are always applied on individuals with bruxism to reduce tooth wear and relieve orofacial symptoms such as myofascial pain. The stomatognathic system is mainly composed of tooth, occlusion, masticatory muscles, and temporomandibular joint. The occlusion and masticatory muscles function are regarded as the important parameters for evaluating the stomatognathic system state objectively.

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In order to study the matching relationship between polymer(HPAM) molecular weight and reservoir permeability, in this paper, the injection performance of polymers with different molecular weights in rock cores with different permeability is studied. Using nuclear magnetic resonance technology combined with conventional core displacement equipment, the change law of the displacement process was analyzed from three aspects of nuclear magnetic resonance spectrum, core layering, and imaging. Finally, the fluidity of the polymer solution in the core was analyzed by injection pressure control features.

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Natural fractures (NFs) and bedding planes (BPs) are well developed in shale reservoirs. The propagation of hydraulic fractures (HFs) and the opening of NFs and BPs can produce induced stress fields (ISFs) within the fracturing process, causing interference to the in situ stress field. Aiming at the "stress shadow" effect among HFs in horizontal wells, the calculation models of HFs, BPs, and NFs for induced stress distributions are established based on displacement discontinuity theory, which can quantitatively characterize the composite ISF of the three under different connecting states.

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The existence of two structural forms in liquid water has been a point of discussion for a long time. A phase transition between these two forms of liquid water has been proposed based on evidence from molecular simulations, and experiments have also been very recently able to track the proposed transition of the low-density liquid form to the high-density liquid form. We propose to use the average angle an oxygen atom makes with its neighbors to describe the structural environment of a water molecule.

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The preparation and classification of nanocellulose are briefly introduced, and the modification of nanocellulose and the application of modified nanocellulose in oilfield chemistry are reviewed. The principles and methods of surface modification, including surface adsorption, oxidation, acetylation, silanization, etherification, and polymer grafting, are summarized. Meanwhile, this paper focuses on the application of nanocellulose research progress in drilling fluid, enhanced oil recovery, and oilfield sewage treatment.

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In recent years, visualization technology based on magnetic resonance imaging has been widely used in core flooding experiments and mechanism research. In this research, the visualization of produced oil is realized by subtracting from image signals collected in different displacement stages. The distribution images of the produced oil can be used to clearly analyze the oil displacement characteristics of cores with different permeabilities and chemical agents with different functions.

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Background: Phosphate is the major ingredient of bone tissue, and is also an important component of commercial bone substitute materials, bone scaffolds, and implant surface coatings. With the dissolution of the bone substitute materials and the degradation by cells, local ion concentrations will change and affect bone tissue reconstruction. Bone marrow -derived mesenchymal stem cells (BM-MSCs) are main autologous cells to repair injured bone.

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Triblock copolymers poly(methyl methacrylate)--poly(ethylene oxide)--poly(methyl methacrylate) (PMMA--PEO--PMMA) with designed molecular weight of PMMA and PEO blocks were synthesized via the activator regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP) of MMA. The Br-terminated Br-PEO-Br with the molecular weights of 20k and 100k were used as  macroinitiators. ARGET ATRP was performed with ppm level amount CuBr as the catalyst and ascorbic acid as the reducing agent to overcome the sensitivity to oxygen in a traditional ATRP.

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Hydraulic fracturing has become a key technology to economically extract oil and gas from unconventional reservoirs. During hydraulic fracturing, fluid loss and water invasion into formation can cause serious permeability reduction near fracture face. At the same time, field practice also showed that well shut-ins after hydraulic fracturing could significantly increase hydrocarbon outputs, whereas the inner mechanism still remains unknown.

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Janus colloidal surfactants with opposing wettabilities are receiving attention for their practical application in industry. Combining the advantages of molecular surfactants and particle-stabilized Pickering emulsions, Janus colloidal surfactants generate remarkably stable emulsions. Here we report a straightforward and cost-efficient strategy to develop Janus nanoplate surfactants (JNPS) from an aluminosilicate nanoclay, halloysite, by stepwise surface modification, including an innovative selective surface modification step.

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Objective: This study aimed to investigate the effect of calcium ion (Ca²⁺) on the migration and osteogenic differentiation of human osteoblasts and explore the proper concentration and correlation mechanism.

Methods: A series of Ca²⁺ solutions with different concentrations was prepared. Osteoblast migration was assessed by Transwell assay, and proliferation was studied via the CCK-8 colorimetric assay.

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Recovery of crude oil in rock nanopores plays an important role in the petroleum industry. In this work, we carried out molecular dynamics (MD) simulations to study the process of ionic surfactant solution driven oil-detachment in model silica (SiO) nanochannels. Our MD simulation results revealed that the oil-detachment induced by the ionic surfactant flooding can be described by a three-stage process including the formation and delivery of surfactant micelles, the surfactant micelle disintegration-spread and migration on the oil-aggregate surface, and oil molecular aggregate deformation-to-detachment.

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Human mesenchymal stem cells-bone marrow (BM-hMSCs) are considered as the most suitable seed cells for bone tissue engineering. Calcium ions (Ca(2+)) forms an important component of a number of commercial bone substitutes and support materials. For efficient bone tissue engineering, it is crucial to explore the effect of extracellular Ca(2+) on the growth and differentiation of BM-hMSCs, and to understand their molecular mechanisms.

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Objective: The objective of this study was to compare soft tissue healing after implant placement in flap and flapless surgery in the dog model.

Study Design: Mandibular premolars were extracted from 10 beagle dogs. The extraction sockets were allowed to heal for 8 weeks.

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To investigate the effects of ovariectomy (OVX) on rat mandibular bone, the physicochemical compositions of mandibular cortical bone of ovariectomy and sham operated rats 2, 4, and 8 months after surgery were compared using Raman spectroscopy. With principal component analysis and linear discriminant analysis based on the Raman spectra, the mandibular cortical bone of the OVX group was clearly distinguished from that of the sham-operated group 8 months after surgery with no overlap. Specifically, significant reductions in the mineral-to-matrix ratio and full width at half-maximum as well as a significant increase in the carbonate-to-phosphate ratio were observed in the mandibular cortical bone of the OVX group.

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