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The role of lipids in periodontitis has not been well studied. Thus, this study aimed to explore periodontitis-associated lipid profile changes and identify differentially expressed lipid metabolites in gingival tissues.Gingival tissues from 38 patients with periodontitis (periodontitis group) and 38 periodontally healthy individuals (control group) were collected. A ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry-based non-targeted metabolomics platform was used to identify and compare the lipid profiles of the two groups. The distribution and expression of related proteins were subsequently analysed via immunohistochemistry to further validate the identified lipids.Lipid profiles significantly differed between the two groups, and 20 differentially expressed lipid species were identified. Lysophosphatidylcholines (lysoPCs), diacylglycerols (DGs), and phosphatidylethanolamines (PEs) were significantly up-regulated, while triacylglycerols (TGs) were downregulated in the periodontitis group. Moreover, the staining intensity of ABHD5/CGI-58, secretory phospholipase A2 (sPLA2), and sPLA2-IIA was significantly stronger in the gingival tissues of patients with periodontitis than in those of healthy controls.LysoPCs, DGs, and PEs were significantly up-regulated, whereas TGs were down-regulated in gingival tissues of patients with periodontitis. Correspondingly, the immunohistochemical staining of ABHD5/CGI-58, sPLA2, and sPLA2-IIA in gingival tissues was consistent with the downstream production of lipid classes (lysoPCs, TGs, and DGs).

This study investigated and tested a novel cone-beam computed tomography (CBCT) scanning technique capable of obtaining clear contours of soft tissues in the esthetic area.Twenty-three periodontally healthy participants underwent this novel CBCT scanning technique. Soft tissue morphological parameters were measured on the CBCT images obtained. Intraoral clinical data were also collected at the same locations, and the accuracy of the CBCT method was tested.The median (interquartile range [IQR]) of the supracrestal gingival tissue thickness as 0.91 (0.73-1.13) mm, and the thickness of the central incisors was significantly greater than that of the canines (P0.05). The median (IQR) of keratinized tissue thickness was 0.73 (0.55-0.91) mm, which also showed a significantly greater thickness in the central incisors than in the canines (P0.05). Bland-Altman analysis suggested that CBCT could be accurate for measuring soft tissues in the esthetic area.The novel CBCT technique described yields clear contours of soft tissues in the esthetic area without the need for auxiliary tools. Moreover, measurements of soft tissue morphological parameters on CBCT appear to be accurate.

Item does not contain fulltext Periodontal ligament (PDL) cells are regarded as the cell type with the highest potential for periodontal regeneration. Biophysical cues of the culture substrate are increasingly identified as vital parameters to affect cell behavior. Compared to traditional tissue culture polystyrene (TCPS), polydimethylsiloxane (PDMS) substrates corroborate more closely the elastic modulus values of the physiological environment. Consequently, the aim of this study was to evaluate the effect of PDMS-based substrates with different stiffness on cellular responses of human PDL cells. PDMS substrates with different stiffness were fabricated by varying the ratio of base to curing component. The influence of PDMS substrates on PDL cell spreading and cytoskeletal morphologies, motility, proliferation, stemness gene expression, and osteogenic differentiation was evaluated and compared to that on conventional TCPS. PDL cells cultured on PDMS substrates exhibited a smaller cell size and more elongated morphology, with less spreading area, fewer focal adhesions, and faster migration than cells on TCPS. Compared to TCPS, PDMS substrates promoted the rapid in vitro expansion of PDL cells without interfering with their self-renewal ability. In contrast, the osteogenic differentiation ability of PDL cells cultured on PDMS was lower in comparison to cells on TCPS. PDL cells on PDMS exhibited similar cell morphology, motility, proliferation, and self-renewal gene expression. The stiffer PDMS substrate increased the osteogenic gene expression of PDL cells compared to the soft PDMS group in one donor. These data indicate that PDMS-based substrates have the potential for the efficient PDL cell expansion. 01 december 2019

Item does not contain fulltext AIM: The implantation of bone marrow-derived mesenchymal stem cells (MSCs) has previously been shown successful to achieve periodontal regeneration. However, the preferred pre-implantation differentiation strategy (e.g. maintenance of stemness, osteogenic or chondrogenic induction) to obtain optimal periodontal regeneration is still unknown. This in vivo study explored which differentiation approach is most suitable for periodontal regeneration. MATERIALS AND METHODS: Mesenchymal stem cells were obtained from Fischer rats and seeded onto poly(lactic-co-glycolic acid)/poly(varepsilon-caprolactone) electrospun scaffolds, and then pre-cultured under different in vitro conditions: (i) retention of multilineage differentiation potential; (ii) osteogenic differentiation approach; and (iii) chondrogenic differentiation approach. Subsequently, the cell-scaffold constructs were implanted into experimental periodontal defects of Fischer rats, with empty scaffolds as controls. After 6 weeks of implantation, histomorphometrical analyses were applied to evaluate the regenerated periodontal tissues. RESULTS: The chondrogenic differentiation approach showed regeneration of alveolar bone and ligament tissues. The retention of multilineage differentiation potential supported only ligament regeneration, while the osteogenic differentiation approach boosted alveolar bone regeneration. CONCLUSION: Chondrogenic differentiation of MSCs before implantation is a useful strategy for regeneration of alveolar bone and periodontal ligament, in the currently used rat model. 01 april 2015

Item does not contain fulltext Various cell types have been assessed for experimental periodontal tissue regeneration in a variety of animal models. Nonetheless, the efficacy of cell-based approaches for periodontal regeneration is still controversial. Therefore, the purpose of this study was to systematically review cell-based approaches for periodontal regeneration in animal studies including a meta-analysis to obtain more clarity on their efficacy. The results of this systematic review and meta-analysis revealed that cell-based approaches have a favorable effect on periodontal tissue regeneration, as displayed by the positive effect of cell-based approaches on new bone, cementum, and periodontal ligament (PDL) formation in periodontal defects. Moreover, subgroup analysis showed a favorable effect on PDL formation by PDL-derived cells, but not by bone marrow mesenchymal stem cells (BMSCs). However, meta-analysis did not show any statistically significant differences in effect between PDL-derived cells and BMSCs. These results provide important information for the implementation of cell-based approaches in clinical practice as a routine treatment for periodontal regeneration in the future.

Item does not contain fulltext Periodontitis is the most common human infectious disease. Regeneration of bone and soft tissue defects after periodontitis remains challenging, although the transplantation of periodontal ligament (PDL) cells seems a liable strategy. However, little is known about the function of PDL cells after transplantation. In the current study, a combination of in vitro coculture systems and in vivo immunohistochemistry (IHC) was used to investigate the role of PDL cells in the regenerative process. First, a coculture method was used, in which mesenchymal cells (representing the host tissue) were brought into direct contact with PDL cells (representing the transplanted cell population). It was found that PDL cells significantly increased mineralized matrix formation and osteocalcin expression, whereas control cells did not. Similar results were obtained when a noncontact coculture system was applied separating PDL and mesenchymal cells. In an in vivo rat model, regeneration of alveolar bone and ligament was seen after PDL cell transplantation. Implanted PDL cells were found clustered along the newly formed tissues. IHC showed enhanced osteopontin expression and gap junction staining in areas neighboring implanted PDL cells. In conclusion, PDL cells enhance periodontal regeneration through a trophic factor stimulating the osteogenic activity of the surrounding host cells.

The optimization design method of geometric parameters of skid shoe which is used to subject weight of marine structures is proposed. Considering skid shoe as steel frame structure, total weight and the bearing capacity of the skid shoe are selected as optimal objectives, and geometric parameters of the skid shoe are taken as design variables. Taking the strength, stiffness, local stability of the skid shoe as the constraint conditions, multi-objectives constraints optimization model of geometric parameters is established, and solved based on complex method. According to research results, a computer program has been developed using VC language. Then geometric optimum parameters of skid shoe in service of CNOOC are analyzed by the program. The results show that optimized design decreases steel volume, steel plate thickness by 28.7%, 18.4%, respectively, compared with original design. The optimization method has a series of advantages, such as simple model, fast calculating speed, high calculation accuracy.

Coal principal stresses with reservoir plane is analyzed, consequently coal seam crushed classification method is presented based on Hoek-Brown criterion. According to the coefficient of coal crushing, coal seam crushed coefficient size, four grades of A,B,C,D are divided for coal crushed degree along wellbore direction, and coal crushed classification standard is determined. Using the classification method and standard, the distribution regularity of coal crushing is studied for ZP-05 Well in QinShui basin. The research results show that coal crushing of ZP-05 is considered as grade B. The prediction results agree well with the measured values.

The aim of this study is to optimize enzymatic control over gelation of chitosan-based hydrogels for the delivery of periodontal ligament cells (PDLCs). The results reveal that the gelation time, strength, and degradation rate of the chitosan hydrogels can be controlled precisely by variation of the urea and urease concentrations. PDLCs remain viable inside these hydrogels for up to 30 days. Cells released from the hydrogel upon degradation and collected after 3, 15, and 30 days are able to form colonies and osteogenically differentiate. In conclusion, the enzymatic control over the gelation of chitosan hydrogels offers options for the delivery of PDLCs.

Item does not contain fulltext The murine-derived MC3T3-E1 cell line provided by the American Type Culture Collection (ATCC) is a well-known osteogenic cell culture model system to test materials in vitro. However, the effect of passaging on its mineralization capacity has never been described and their culture supplements can be further optimized. Therefore, we evaluated the influence of the passage number and different osteogenic culture supplements, including ascorbic acid (AsAP) and dexamethasone (Dex) on the osteogenic capacity of MC3T3-E1 cells. This capacity was measured by the deposited calcium, the alkaline phosphatase activity, and the expression of osteogenic-related genes, including bone sialoprotein (BSP), osteocalcin (OC), and osteopontin (OPN). The results indicated that the mineralization capacity of MC3T3-E1 cells significantly decreased during passaging and got exhausted at passage 34, as assessed by measuring calcium deposition after 28 days of osteogenic induction. Moreover, the combination of AsAP and Dex triggered significantly more mineralization in MC3T3-E1 cells than the ATCC recommended addition of AsAP alone, as indicated by increased calcium deposition and higher expression of BSP and OPN. However, Dex alone could not trigger this effect, but only in combination with the AsAP, which indicates that Dex has no direct effect on mineralization. In conclusion, the passage number of MC3T3-E1 cells is of great importance and the use of cells above 30 passages should be avoided. In addition, the favored osteogenic supplements providing an improved osteogenic differentiation of MC3T3-E1 cells are the combination of AsAP and Dex.

Item does not contain fulltext Stem cells, having the potential for self-renewal and multilineage differentiation, are the building blocks for tissue/organ regeneration. Stem cells can be isolated from various sources but are, in general, available in too small numbers to be used directly for clinical purpose without intermediate expansion procedures in vitro. Although this in vitro expansion of undifferentiated stem cells is necessary, stem cells typically diminish their ability to self-renew and proliferate during passaging. Consequently, maintaining the stemness of stem cells has been recognized as a major challenge in stem cell-based research. This review focuses on the latest developments in maintaining the self-renewal ability of stem cells during in vitro expansion by biomaterial strategies. Further, this review highlights what should be the focus for future studies using stem cells for regenerative applications.

The differential GPS navigation and positioning technique, multi-channel shallow seismic exploration and high resolution single channel seismic technique were used for the geophysical exploration of the shallow stratum in Jiangshidi nuclear power plant site and its surrounding areas. Based on seismic data post processing results, the seismic section interpretation was performed, combined with regional geological background, borehole data and shallow anatomy data. Five main seismic reflection surfaces were recognized by using seismic stratigraphic method, and eight breakpoints were found according to the active fault discrimination criteria. Then the distribution and activity characteristics of main faults were obtained. The results show that any fault and marked deformation in the quaternary sediments has not been observed in the range of 5 km away from Jiangshidi nuclear power plant site. So the stability analysis results of shallow stratum in target area can meet the requirement of nuclear power plant site selection code.

It used to be held that fracturing sand control construction would severely affect the strength and duration of casing in deep well. Based on 5 inch and 7inch casings, the article intends to conduct modeling and analysis, by means of the finite element method, of a multi-tube model of casing of different steel grades and a combination of different perforation parameters, under different environmental conditions (different internal and external pressure). The results show that under the same perforation parameters, the equivalent stress within the casing increases with the external pressure and the changes linearly. Equivalent stress within the casing decreases drastically with the increase of internal pressure. When the internal pressure is greater than the external pressure, the equivalent stress of the casing tends to slow down. Stress condition in the casing perforation improves when internal pressure is applied in the casing. The result shows that fracturing sand control construction improves the stress condition of the casing rather than affect the strength and duration of casing.

Based on the orthotropic physical properties of coal cleats, the fluid-solid coupling model for stress sensibility coal seams is established. The equations of the coupling model are solved by using the finite element method. The history matching for JS-3 well in Ordos basin is carried on by using the coupling model. The comparison between calculated results based on the coupling model and the measured values indicates their good agreement, which verifies the accuracy and rationality of the model. The effect of the permeability orthotropic coefficient of coal cleats on the pressure distribution in coal seams is analyzed. The results show that the pressure along the butt cleats direction increases with permeability orthotropic coefficient increasing; The pressure along the face cleats decreases with permeability orthotropic coefficient increasing between 0m~30m and 170m~200m, whereas both increases from 30m to 170m.

According to Mohr-Coulomb criterion, the yield approach index (YAI) of Hoek-Brown criterion is derived. The rock-mass intact coefficient KV is introduced, and coal failure approach index is defined by combining failure degree. On the basis of logging data and stratified in-site stress model, the failure approach index and yield approach index are calculated in wellbore direction. Based on FAI values, coal fracture degree is divided four grades of A, B, C, D, and coal fracture classification method is proposed. Taking ZP-1 Well in QinShui basin as an example, the distribution regularity of coal fracture degree is predicted by the method. The results indicate that failure approach index of ZP-01 well is between 0.8-1.2; the section of 551-552.7m of coal seam is fractured (grade A), and the rest section of coal seam is regarded as grade B. Through electron microscope to scan coal sample structure, the results agree well with the prediction results, therefore the classification method is reliable. Depending on theory results, computer program is corresponding developed.

Stable evaluation of coal strength is needed in coal well-bore stability analysis. The regular analysis method of wellbore stability adopts Mohr-Coulomb strength criteria to judge the collapse pressure. Coal is dual porosity structure and contains joint fissures richly. Hoek-Brown criterion is much more reasonable to estimate the strength of jointed and fractured rock. So Hoek-Brown criterion is used to analyze the stability of multi-lateral horizontal coal bed methane well. Considering the GSI (geological strength index), structural and surface conditions of coal, the coal and rock mass strength parameters are converted into the underground coal mechanical parameters based on the triaxial test of intact coal. According to the stress state of multi-lateral horizontal well, the borehole collapse formulas are established based on Hoek-Brown Criterion. The effects on the wellbore stability, due to the joint fissures of coal, borehole size, drilling disturbance, are also discussed in this paper.

The mathematical model of Two-Phase flow of water and gas in aquifer is established based on the Darcy linear percolation law and law of conservation of mass of fluid mechanics. According to the fully implicit difference method, time and spatial discretization of the model lead to a set of nonlinear equations, which can be transferred into a group of linear equations. The linear equations can be solved using the Jacobi-iteration pretreatment because of its high stability and fast convergence speed of the solution positively. The distribution of the saturation and formation pressure with time in the process of gas injection is analyzed by using the mathematical model. The results show that the gas saturation increases with the gas injection rate, the permeability and reservoir thickness increasing whereas the formation pressure increases slowly under same cumulative gas injection rate. The formation pressure increases at first and then decreases to reach a steady value.

In this paper, a creep test was carried out for simulating the creeping of the core of the mudstone under condition of deep formation subsurface conditions by MTS-810 test system, the creep rule and the characteristic parameters of the mudstone formation were obtained from the experiments. According to the test results, the finite element model for casings load calculation was established, and the calculation program was also written. With the program, the casing load of one western oil well was calculated in mudstone formation. The numerical simulation results show that the casing load has a relationship with phase angle θ and creep time, and the casing load is 10% greater than the stress in situ.

Depending on the mechanical characteristics of casing located at the bending part of sidetrack horizontal well, the calculation model of casing collapsing strength under the effect of bending load is established, and corresponding theoretical formulae is derived. During the process of deducing formulas, the influence of bending load on the casing section out of roundness is ignored, which made the calculation formula benefits intuition and practicality comparing to the T.Tamano formula. The result of this paper is verified through the simulation value and laboratory test of casing used in the Jilin oilfield. It shows that the formula of this paper can meet the engineering commands; the axial load is significant to affect casing collapsing strength, and in the actual production process should be strictly controlled.

In the process of drilling well, the kinematics of drill string is quite complicated. The drill string not only vibrates in longitudinal, transverse and torsional direction, but also random impacts and contacts well wall. Considering the random load of drill bit and rock, contact impact of drill string and well wall, a model is proposed to simulate the contact-impact of drill string and formation. The results show that: in the condition of this article the first principal stress of the drill string can reach to 130 MPa, for the random impacts, the strength of drill collar will reduced under cyclic loading; contact-impact is the principal source of drill premature failure. In this paper, an explicit integration and nonlinear finite element was adopted to simulate the collision between the drill string and formation, the process of the collision between the drill string and formation can be revealed compressively and delicately. Through an example, we can obtain the foundation for nonlinear dynamic theory of drill string system collision in the actual work condition, and has important theory significance and academic value.

With the application of ANSYS finite element analysis software and environmental data in ChengDao oil field, a nonlinear finite element model of suspended submarine pipeline coupled with sea-floor soil is developed. Discarding the traditional and imprecise pipeline model with double clamped or simply supported ends, the model is founded on the theory of elastic foundation beam, in which the nonlinear effect between pipeline and sea-floor soil is considered. Base on the model we developed, the influences of span length and shear strength of soil at the ends of span on the span’s natural frequency are discussed. And the effects of span length, shear strength of soil and current velocity on the dynamic response of span are also analyzed in this paper. The model we developed in this paper fits the actual structure better, and the analysis is instructive for preventing and controlling the suspending of submarine pipeline.

In order to complete the numerical simulation on internal flow and operating characteristics of down hole multiphase pump compress unit, establishing perfect finite element model, the three-dimensional turbulent current fields inside the impellers of compression unit for down hole multiphase pumps were simulated by using ANSYS. The calculation of multiphase flow is based on the standard k-ε turbulent current model. Reference information for the improvement of the pump can be obtained by the analysis of the flow of gas-oil in the channel of pump. Based on the finite method, we analyzed several situations in a pumping period. The velocity and liquid pressure distributing of sucker rod pump is studied in this paper, which may offer some evidences for the engineering design of sucker rod pump.

Local thinning of submarine pipeline always exists due to the complexity and dynamic of marine environment loads. However, the location and extent of thinning areas are random. Mechanical research on the randomness of local thinning of submarine pipelines is significant for pipeline’s stress analysis and failure evaluation. In this paper, finite element model of locally thinned submarine pipeline is established and based on the Monte-Carlo method, the effect of input random variables on the submarine pipeline’s reliability is analyzed. Probability distribution ranges of equivalent stresses are got and further, relationship equation between confidence level and stress limit has been obtained. The result more accurately reveals the relationships of locally thinned pipeline and its elastic modulus with equivalent stress, which can provide foundation for safety analysis of locally thinned submarine pipeline with internal pressure.

The deep drill string is subjected to many kinds of loading under the condition of vibration and precession, such as tension, compression, bending and torsion, while the temperature and press are very high. Under this circumstance, the shallow drill string is more likely to failure. Based on the force analysis of the drill string, the drilling process of the deep drill string is simulated using finite element software. The stress distribution and displacement of the drill string is obtained under the interaction of drilling pressure, torque and temperature. At the same time, the effect of transverse vibration, longitudinal vibration and torsional vibration, on the stress and displacement of the drill string, is compared. The change law of the natural frequency of transverse vibration varying with the length of drill string, rotational speed and the hole size is discussed. Connected with concrete examples, the reliability and sensitivity of some influencing factors such as external diameter, wall thickness, the minimum yield strength, temperature, elastic modulus, Poisson’s ratio, axial loading and torque is obtained. The main factors that influence the reliability of the drill string are the yield strength and torque. The reliability of the drill string increases as the increase of yield strength, and decreases as the increase of the torque.

The dynamic mechanics model was built up to analyze the contact-impact between drill string and wellbore according to the characteristics of contact-impact, based on non-linear finite element method and Lagrange method. The dynamic mechanics equations were deduced by the dynamic mechanics model. The stress and deformation field of drill string with different parameters of bottom hole were obtained and tested by experiments and numerical simulation respectively. And also, the propagation laws of stress wave generated by contact-impact in drill pipe were studied. The comprehensive results indicate that the numerical results agree well with the actual dynamic process of contact-impact. The stress waves generated by contact-impact cause the change of stress. The contact-impact between drill string and wellbore under air drilling is the main reason for early drill string failure.

The first excursion failure criterion was introduced to calculate the dynamic reliability of drill string elements. Considering the random of geometry size and mechanical property parameters of drill string in deep & ultra-deep wells, the drill string system was dispersed into several basic elements according to the structure, strength and differences in the nature of formation rock in the well depth direction. And the overall dynamic reliability was quantitatively calculated through the serial theory. Through an example, the results show that the dynamic reliability of the drill string elements appeared fluctuation near the depth of 4500 meters for the inside worn of the drill string and casing, and uneven loading of drill string. The dynamic reliability of drill string in deep and complicated formation was less than any other drill strings. The drilling pressure, rotation speed and drilling depth were the main influencing factors on the dynamic reliability of drill string.

An optimization design method is developed for the beam pumping unit, which is based on the API-RP-11L design criteria. The Response Surface Method is used to calculate the structural reliability of the beam pumping unit. The optimization design method not only provides an efficient and fast optimization tool for the modular design of the beam pumping unit, but also offers an integral design calculation in accordance with the API design code. The function and theory of this optimization design method are given by this paper, as well as some concrete calculation examples.

Based on analysis of different guidelines and standards for material selection of casing which belong to six companies in four countries, the main factors that influence the material selection of casing have been generalized. Through comparing the safety and corrosion resistance properties of materials recommended by different guidelines in specific conditions, a synthetic guideline has been developed, which can provide a more appropriate suggestion. The environmental conditions and materials adopted in East Sichuan region have been taken for example. By comparing the proposed results with adopted materials of field well completion, it demonstrates that the result provided by the synthetic guideline is accurate and reliable.

Considering the various influencing factors of enrichment of coal bed methane, the evaluation indexes of enrichment for coal bed methane are determined. The weight values of all factors indexes are given and the fuzzy mathematics model is established on the basis of the fuzzy mathematics. As a case study, the fuzzy mathematics model is applied to the assessment of enrichment of coal bed methane. The results show that the No.5 coal seam of Shan 2 of Shanxi formation in Daning-Jixian is a better enrichment area. The evaluation result performed on the basis of the fuzzy mathematics model is in good agreement with the measured result. The example indicates that the method is credible and has high precise. The assessment system established in the paper can be regarded as a reference model in coal bed methane exploitation potential assessment.

In order to know something about the structure reliability of beam pumping unit, the methods of Monte-Carlo and response surface method are used to analyze the pumping unit. According to the analysis and calculation, the approach of how to calculate and analyze the reliability of complex structure is obtained. The results show that using the method of reliability can make the pumping unit more reliable and reveal the components of pumping unit more clearly which can make the design of pumping unit more reasonable.

Sand inflow is one of the problems in unconsolidated sandstone oil reservoir recovery. The most frequently applied sandcontrol method is high-pressure gravel squeeze packing sand control technology. But incorrect knowledge of stratum shapes under high-pressure squeeze packing leads to unreasonable technology and implement parameters. This thesis, based on the discrete element theory and by means of two-dimension grain flow simulation software PFC2D, considers three oil wells with unconsolidated sandstone in terms of their cementing strengths . The simulation result shows that strata with diverse cementing strengths vary remarkably when high-pressure squeeze pack is asserted. Established calculation pattern might lead to sizable deviation.

In this paper, a quantitative analysis for the micro geometrical characteristic of rough surface profile is researched with the fractal theory. Firstly, the fractal dimensions of profile curves under different surface roughness are obtained by using the vertical section method, and then the theoretical relationship between the surface roughness and the fractal dimension is built. Secondly, according to the surface profile curve composed of many triangle peaks, the angles and heights of them are calculated to study the micro geometrical size. Through their variation laws changing with the fractal parameters, the calculation formulas of their average values related to fractal dimension are obtained by using mathematics regression tools. Finally, combing three theoretical relationships built above, the geometrical characteristic of the rough surface profile can be calculated with the surface roughness and accuracy requirement known.

In this paper, the calculation formulas of the asperity’s deformation related with the surface contact pressure are deduced by using the simplified contact model. Firstly, we assume that the rough surface is composed of a set of cones as asperities, and the cones are arranged in different ways along two directions. Secondly, according to the mechanical analysis of a rigid conical punch on a half-space, the theoretical relationship between the average pressure of the micro contact area and the property parameters of a conical punch is obtained. Meanwhile, the calculation formula of the average pressure is given under the reasonable assumptions, which is related with the asperity’s deformation and the contact pressure. Finally, combining two theoretical relationships above, the quantitative analysis method for micro asperity’s deformation of two rough surfaces in contact is provided by using the average pressure as a connection bridge.

In this paper, the main design parameters of seal structure for non-API pipe connection are studied. First, as the total contact pressure consists of the radial preload generated by interference fit and the radial pressure caused by gas pressure in pipe, the variation laws of their values changing with the sealing diameter are analyzed. The sealing diameter value which maximizes the total contact pressure can be obtained from the derivation formula for calculating the total contact pressure. Second, considering the yield condition of pipe connection under the internal and the external pressures, the minimum wall thickness of the seal structure is derived. Then the cone angle is calculated by the sealing length and the minimum wall thickness known. Finally, take the 7in casing connection for example, the main design parameters are calculated by the above analysis.

Item does not contain fulltext This study is aimed to evaluate the in vivo biocompatibility and periodontal regenerative potential of enzymatically solidified chitosan hydrogels with or without incorporated periodontal ligament cells (PDLCs). To this end, chitosan hydrogels, with (n=8; CHIT+CELL) or without (n=8; CHIT) fluorescently labeled PDLCs, were prepared and transplanted into rat intrabony periodontal defects; untreated defects were used as empty controls (n=8; EMPTY). After 4 weeks, maxillae were harvested, decalcified, and used for histological, histomorphometrical, and immunohistochemical assessments. The results showed that PDLCs remained viable upon encapsulation within chitosan hydrogels before transplantation. Histological analysis demonstrated that the chitosan hydrogels were largely degraded after 4 weeks of implantation, without any adverse reaction in the surrounding tissue. In terms of periodontal regeneration, alveolar bone height, alveolar bone area, and epithelial downgrowth were comparable for CHIT, CHIT+CELL, as well as EMPTY groups. In contrast, both CHIT and CHIT+CELL showed a significant increase in functional ligament length compared with EMPTY. From a cellular perspective, the contribution of chitosan hydrogel-incorporated cells to the periodontal regeneration could not be ascertained, as no signal from transplanted PDLCs could be detected at 4 weeks posttransplantation. The results demonstrated that enzymatically solidified chitosan hydrogels are highly biocompatible and biodegradable. Moreover, chitosan hydrogels without cell loading can improve periodontal regeneration in terms of functional ligament length, indicating the great potential of this hydrogel in clinical applications. Further work on the use of chitosan hydrogels as cell carriers is required.

The aim of this study is to optimize enzymatic control over gelation of chitosan-based hydrogels for the delivery of periodontal ligament cells (PDLCs). The results reveal that the gelation time, strength, and degradation rate of the chitosan hydrogels can be controlled precisely by variation of the urea and urease concentrations. PDLCs remain viable inside these hydrogels for up to 30 days. Cells released from the hydrogel upon degradation and collected after 3, 15, and 30 days are able to form colonies and osteogenically differentiate. In conclusion, the enzymatic control over the gelation of chitosan hydrogels offers options for the delivery of PDLCs.

Objectives.STRO-1 positive periodontal ligament cells (PDLCs) and unsorted PDLCs have demonstrated potential for periodontal regeneration, but the comparison between unsorted cells and the expanded STRO-1 sorted cells has never been reported. Additionally, Wnt3a is involved in cell proliferation thus may benefitin vitroPDLC expansion. The aim was to evaluate the effect of STRO-1 cell sorting and Wnt3a treatment on cell behavior of human PDLCs (hPDLCs).Materials and Methods.STRO-1 positive hPDLCs were sorted and the sorted cells were expanded and compared with their unsorted parental cells. Thereafter, hPDLCs were treated with or without Wnt3a and the cell proliferation, self-renewal, and osteogenic differentiation were evaluated.Results.No differences were measured between the expanded STRO-1-sorted cells and unsorted parental cells in terms of proliferation, CFU, and mineralization capacity. Wnt3a enhanced the proliferation and self-renewal ability of hPDLCs significantly as displayed by higher DNA content values, a shorter cell population doubling time, and higher expression of the self-renewal geneOct4. Moreover, Wnt3a promoted the expansion of hPDLCs for 5 passages without affecting cell proliferation, CFU, and osteogenic capacity.Conclusions.Expanded STRO-1-sorted hPDLCs showed no superiority compared to their unsorted parental cells. On the other hand, Wnt3a promotes the efficient hPDLC expansion and retains the self-renewal and osteogenic differentiation capacity.

To construct and confirm a recombinant lentiviral vector containing human bone morphogenetic protein 2 (hBMP2) and human nerve growth factor (hNGF).The Neomycin gene was digested from pLentiTrident1-EGFP-Neo and then was subcloned into lentiviral vector. The hBMP2 and hNGF genes were amplified by polymerase chain reaction (PCR), and then the PCR product was inserted to proper sites of the vector. Finally, the recombinant vector pLentiTrident1-hBMP2-Neo-hNGF was confirmed by agarose gel electrophoresis and DNA sequence analysis.The construction of recombinant lentiviral vector pLentiTrident-hBMP2 -Neo-hNGF was confirmed through restriction enzyme maping analysis and DNA sequencing.The recombinant lentiviral vector which can coexpress hBMP2 and hNGF is successfully constructed,which lays a solid foundation of studying the effect of neuro factors on bone regeneration.

The quantity of regenerated bone induced by recombinant human bone morphogenetic protein-2 (rhBMP2) is encouraging, but sometimes the quality is inferior. Recombinant human beta-nerve growth factor (rh beta-NGF) plays a major role in bone remodeling. This study evaluates the quality and quantity of regenerated bone in periodontal regeneration following topical application of the two growth factors to Class III furcation defects.Thirty-six inflamed Class III furcation defects were created in six beagle dogs at sites of mandibular premolars 2, 3, and 4, and then biodegradable hydrogel incorporating rhBMP2 and rh beta-NGF was topically applied to the defects. The groupings were as follows: G1, untreated (control group A); G2, carrier alone (control group B); G3, 0.4% rhBMP2 + carrier; G4, 2% rh beta-NGF + carrier; G5, 0.4% rhBMP2 + 2% rh beta-NGF + carrier; and G6, 0.2% rhBMP2 + 1% rh beta-NGF + carrier. Eight weeks after application, the quality and quantity of regenerated tissue were evaluated by scanning electron microscopy observation, calcium/phosphorus ratio analysis, and histologic evaluation.The regenerated bone in G5 exhibited the highest calcium/phosphorus ratio among all groups and showed a denser structure with more calcified substances on the collagen fiber surface than that in the other groups. Histomorphometric analysis revealed that 0.4% rhBMP2 + 2% rh beta-NGF promoted the highest percentage of periodontal regeneration among all groups.The results of this pilot study suggest that a topical application of rhBMP2 and rh beta-NGF may improve the quality and quantity of regenerated bone in artificially created Class III furcation defects of beagle dogs.