BACKGROUND Management of chronic refractory wounds is one of the toughest clinical challenges for surgeons.Because of poor blood supply,less tissue coverage,and easy exposure,the lower leg is a common site for chronic...BACKGROUND Management of chronic refractory wounds is one of the toughest clinical challenges for surgeons.Because of poor blood supply,less tissue coverage,and easy exposure,the lower leg is a common site for chronic refractory wounds.The current therapeutic regimens often lead to prolonged hospital stay and higher healthcare costs.Concentrated growth factor(CGF)is a novel blood extract that contains various growth factors,platelets,and fibrins to promote wound healing process.However,there has been little research reported on the treatment of lower extremity wounds with CGF.CASE SUMMARY A 37-year-old man,without any past medical history,presented an ulcerated chronic wound on his right lower leg.The skin defect exhibited clear boundaries,with a size of 2.0 cm×3.5 cm.The depth of wound was up to the layer of deep fascia.Staphylococcus aureus was detected by bacterial culture.The final diagnosis was right lower extremity ulcers with infection.Cefathiamidine,silver sulfadiazine,and mupirocin cream were applied to control the infection.CGF gel was prepared from the patient’s blood sample,and was used to cover the wound after thorough debridement.The skin wound was successfully healed after three times of CGF treatment.CONCLUSION CGF displays an excellent wound healing promoting effect in patients with lowerextremity chronic refractory wounds.展开更多
A pilot study by Reyes [1] previously showed that ingestion of single dose of whole coffee fruit concentrate (WCFC) powder increased blood levels of brain derived neurotrophic factor (BDNF) during the first 60 minutes...A pilot study by Reyes [1] previously showed that ingestion of single dose of whole coffee fruit concentrate (WCFC) powder increased blood levels of brain derived neurotrophic factor (BDNF) during the first 60 minutes after ingestion. In the present report, we performed a single dose, placebo-controlled, within-subject study to confirm and further investigate this effect. Twenty healthy subjects with ages ranging from 25 to 35 participated in this study. All fasted and resting subjects received placebo on Day 1, WCFC on Day 2, and a cup of freshly brewed coffee on Day 3. Treatment with WCFC resulted in a statistically significant increase in plasma BDNF compared to placebo (p = 0.0073) or coffee (p = 0.0219) during first 60 minutes. In addition, e isolated exosomes from serum and found that they contained BDNF. Furthermore, oral WCFC consumption acutely increased BDNF levels in serum exosomes. In summary, all presented results justify further clinical investigation of WCFC as a tool to manage BDNF-dependent health conditions.展开更多
Objective To explore the effect of concentrated growth factor(CGF)combined with autologous fat transplantation in augmentation mammoplasty.Methods Clinical data of 28 female patients who underwent autologous fat by CG...Objective To explore the effect of concentrated growth factor(CGF)combined with autologous fat transplantation in augmentation mammoplasty.Methods Clinical data of 28 female patients who underwent autologous fat by CGF mixed with purified fat between May 2015 and June 2018 were retrospectively analyzed.Clinical evaluation was performed to observe and measure the shape of the breast after breast augmentation,the increase in the value of the nipple plane measurement,and complications.Results All of 28 patients,after 12 months of follow-up,all patients no fat infection,hematoma,breast nodules and other complications.It showed that the contouring of breast were improved and more chubbiness than that before operation.The results were satisfied from patients.Conclusion Concentrated growth factor combined with autologous fat transplantation has a stable breast augmentation effect,beautiful breast shape,simple operation and small damage,which achieves breast rejuvenation.展开更多
Studies have shown that platelet concentrates can induce the proliferation of the dermal papilla and the vascularization of the perifollicular tissue, as well as accelerate the telogen-to-anagen transition, thereby pr...Studies have shown that platelet concentrates can induce the proliferation of the dermal papilla and the vascularization of the perifollicular tissue, as well as accelerate the telogen-to-anagen transition, thereby promoting the regrowth of hair improving the appearance of hair loss. Herein, we report on the application of a new, modified form of platelet concentrates, namely, concentrated growth factors (CGFs), in 15 cases of androgenetic alopecia (AGA). 15 cases of androgenetic alopecia were treated with the use of monthly, subcutaneous injections of autologous CGF in the scalp. A total of 3 injections were administered 4 weeks apart, and the patients were followed up for 6 months. Assessments were performed before the treatments and at 4, 8, 12 and 24 weeks after the first treatment. The treatment outcomes were assessed by taking macroscopic photographs and trichoscopic photomicrographs, as well as by using the Global Aesthetic Improvement Scale (GAIS) and the patient satisfaction survey. In order to determine the safety of the treatment, the injection area was observed for signs of infection or mass evaluation. The photographs showed significant improvement in hair appearance after injections of CGF. The hair photomicrographs showed that CGF promoted the regrowth of hair in balding areas, with an increased hair density and an increased ratio of terminal to vellus hair. The GAIS suggested that CGF treatments were effective in treating AGA, and the majority of patients were satisfied with their improvement. In addition, treatments resulted in a faster rate of hair growth and a decrease in the greasy and unpleasant sensation of the hair of the patients. At the last visit, none of the 15 patients reported experiencing side-effects during the follow-up period. To conclude, the application of CGF can be an effective method in the treatment of androgenetic alopecia.展开更多
Objective: To study the effect of concentrated growth factor (CGF) combined with guided bone regeneration on cell proliferation and bone resorption in patients with severe periodontitis. Methods: Patients with severe ...Objective: To study the effect of concentrated growth factor (CGF) combined with guided bone regeneration on cell proliferation and bone resorption in patients with severe periodontitis. Methods: Patients with severe periodontitis who were treated in Stomatology Department of Shenmu Hospital between May 2014 and February 2017 were selected as the research subjects and randomly divided into two groups, surgery + CGF group received concentrated growth factor combined with guided bone regeneration, and pure surgery group received guided bone regeneration. The contents of inflammatory response, cell proliferation and bone resorption markers in gingival crevicular fluid were determined 1 week after treatment. Results: 1 week after treatment, HMGB1, ICAM1, E-selectin, Smac, FasL, Caspase-8, Caspase-9, Caspase-3, RANKL and NTX contents in gingival crevicular fluid of surgery + CGF group were significantly lower than those of pure surgery group while PD-L1, hBD-3, Wnt3a, BGP and OPG contents were significantly higher than those of pure surgery group. Conclusion:Concentrated growth factor combined with guided bone regeneration for severe periodontitis can inhibit inflammatory response, apoptosis and bone resorption, which is beneficial to the reconstruction of periodontal tissue.展开更多
Platelet concentrates(PC) [platelet-rich plasma(PRP) and platelet-rich fibrin(PRF)] are frequently used for surgical procedures in medical and dental fields,particularly in oral and maxillofacial surgery,plastic surge...Platelet concentrates(PC) [platelet-rich plasma(PRP) and platelet-rich fibrin(PRF)] are frequently used for surgical procedures in medical and dental fields,particularly in oral and maxillofacial surgery,plastic surgery and sports medicine.The objective of all these technologies is to extract all the elements from a blood sample that could be used to improve healing and promote tissue regeneration.Although leukocyte rich and leukocyte poor PRP's have their own place in literature,the importance of non-platelet components in a platelet concentrate remains a mystery.PC have come a long way since its first appearance in 1954 to the T-PRF,A-PRF and i-PRF introduced recently.These PC find varied applications successfully in periodontics and implant dentistry as well.However,the technique of preparation,standing time,transfer process,temperature of centrifuge,vibration,etc.,are the various factors for the mixed results reported in the literature.Until the introduction of a proper classification of terminologies,the PC were known by different names in different countries and by different commercial companies which also created a lot of confusion.This review intends to clarify all these confusion by briefing the exact evolution of PC,their preparation techniques,recent advances and their various clinical and technical aspects and applications.展开更多
Atmospheric particulate matter(PM2.5) seriously influences air quality. It is considered one of the main environmental triggers for lung and heart diseases. Air pollutants can be adsorbed by forest. In this study we i...Atmospheric particulate matter(PM2.5) seriously influences air quality. It is considered one of the main environmental triggers for lung and heart diseases. Air pollutants can be adsorbed by forest. In this study we investigated the effect of forest cover on urban PM2.5 concentrations in 12 cities in Heilongjiang Province,China. The forest cover in each city was constant throughout the study period. The average daily concentration of PM2.5 in 12 cities was below 75 lg/m^3 during the non-heating period but exceeded this level during heating period. Furthermore, there were more moderate pollution days in six cities. This indicated that forests had the ability to reduce the concentration of PM2.5 but the main cause of air pollution was excessive human interference and artificial heating in winter. We classified the 12 cities according to the average PM2.5 concentrations. The relationship between PM2.5 concentrations and forest cover was obtained by integrating forest cover, land area,heated areas and number of vehicles in cities. Finally,considering the complexity of PM2.5 formation and based on the theory of random forestry, we selected six cities and analyzed their meteorological and air pollutant data. The main factors affecting PM2.5 concentrations were PM10,NO_2, CO and SO_2 in air pollutants while meteorological factors were secondary.展开更多
CO2 concentrations in different plant communities (larch, birch, lilac, and grassland) were measured during the growing season in the Heilongjiang Forest Botanical Garden to study diurnal variation, seasonal and ann...CO2 concentrations in different plant communities (larch, birch, lilac, and grassland) were measured during the growing season in the Heilongjiang Forest Botanical Garden to study diurnal variation, seasonal and annual dynamics and factors that impact CO2 concentration in different spaces. CO2 concentration in different communities in green lands had an obvious diurnal variation, chronically decreasing, and temperature influenced the lilac area and the grassland. Seasonally, CO2 was lowest in the larch green land (344.03 ±23.03 μmol/mol) and highest in the grassland (360.13 ± 22.43 μmol/mol). The overall trend in CO2 concentration was autumn 〉 spring 〉 summer; temperature is the main factor controlling variation in CO2 concentrations during the growing season; the CO2 concentration at the larch, birch, lilac, and grassland types of sites was negatively correlated with land surface temperature and air temperature, and the CO2 concentration at the larch and birch sites was positively correlated with atmospheric pressure. Without any obvious annual change law, further study and observation are needed.展开更多
Finite element models were established to analyze the influence of soft filler on stress concentration for a rectangular plate with an elliptic hole in the center. The influence was quantified by means of stress conce...Finite element models were established to analyze the influence of soft filler on stress concentration for a rectangular plate with an elliptic hole in the center. The influence was quantified by means of stress concentration factor (SCF). Seven shape factors of the elliptic hole and three levels of elasticity modulus of the soft filler were considered. The reduction coefficient and sensitivity index of SCF are the two indicators in evaluating the influence of soft filler. It was found that the reduction coefficient of SCF increases significantly as the shape factor and the elasticity modulus of the filler increase, indicating that soft filler can reduce the concentrated stress effectively, especially when the shape factor is great. Analysis for the sensitivity index of SCF indicates that SCF is more sensitive to materials with small elasticity modulus than to materials with large one.展开更多
Neuber rule and Arola-Ramulu model are widely used to predict the stress concentration factor of rough specimens. However, the height parameters and effective valley radius used in these two models depend strongly on ...Neuber rule and Arola-Ramulu model are widely used to predict the stress concentration factor of rough specimens. However, the height parameters and effective valley radius used in these two models depend strongly on the resolution of the roughness-measuring instruments and are easily introduce measuring errors. Besides, it is difficult to find a suitable parameter to characterize surface topography to quantitatively describe its effect on stress concentration factor. In order to overcome these disadvantages, profile moments are carried out to characterize surface topography, surface topography is simulated by superposing series of cosine components, the stress concentration factors of different micro cosine-shaped surface topographies are investigated by finite element analysis. In terms of micro cosine-shaped surface topography, an equation using the second profile moment to estimate the stress concentration factor is proposed, predictions for the stress concentration factor using the proposed expression are within 10% error compared with the results of finite element analysis, which are more accurate than other models. Moreover, the proposed equation is applied to the real surface topography machined by turning. Predictions for the stress concentration factor using the proposed expression are within 10% of the maximum stress concentration factors and about 5% of the effective stress concentration factors estimated from the finite element analysis for three levels of turning surface topographies under different simulated scales. The proposed model is feasible in predicting the stress concentration factors of real machined surface topographies.展开更多
In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stre...In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stress concentration factor distribution along the weld toe in the hot spot stress region for tubular X-joints subject to axial loads have been analyzed by use of finite element method. Through numerical analysis, it has been found that the peak stress concentration factor is located at the saddle position. Thereafter, 80 models have been analyzed, and the effect of the geometric parameters of a tubular X-joint on the stress concentration factor has been investigated. Based on the experimental values of the numerical stress concentration factor, a parametric equation to calculate the stress concentration factor of tubular X-joints has been proposed. The accuracy of this equation has been verified against the requirement of the Fatigue Guidance Review Panel, and the proposed equation is found capable of producing reasonably accurate stress concentration factor values for tubular X-joints subject to axial loads.展开更多
Two explicit expressions of the stress concentration factor for a tension finite-width strip with a central elliptical hole and an eccentric elliptical hole, respectively, are formulated by using a semi-analytical and...Two explicit expressions of the stress concentration factor for a tension finite-width strip with a central elliptical hole and an eccentric elliptical hole, respectively, are formulated by using a semi-analytical and semi-empiricai method. Accuracy of the results obtained from these expressions is better, and application scope is wider, than the results of Durelli's photo-elastic experiment and Isida's formula. When eccentricity of the elliptical hole is within a certain range, the error is less than 8%. Based on the relation between the stress concentration factor and the stress intensity factor, a stress intensity factor expression for tension strips with a center or an eccentric crack is derived with the obtained stress concentration factor expressions. Compared with the existing formulae and the finite element analysis, this stress intensity factor expression also has sufficient accuracy.展开更多
During the course of a major sandstorm from April 17 to April 23, 2008 in the Taklimakan Desert, data pertaining to the mass concentrations of different-sized atmospheric particulate matter were observed continuously ...During the course of a major sandstorm from April 17 to April 23, 2008 in the Taklimakan Desert, data pertaining to the mass concentrations of different-sized atmospheric particulate matter were observed continuously with Grimm 1.108, Thermo RP 1400a, TSP, and CAWS-600 instruments. The results showed that: (1) during the entire sandstorm process there were some dif- ferences between the daily mean particle concentration peaks and the hourly mean particle concentration peaks because the actual sandstorm lasted for only about 4 hr, whereas more particles were accumulated in the floating dust days before and after the actual sandstorm; (2) the intensity of the sandstorm was enhanced with the increase of wind speed, and this was related to the peak mass concentrations of atmospheric particulate matter; the wind speed directly affected the concentration of atmospheric particulate matter: the higher the wind speed, the higher the mass concentration (〉0.23 μm was 39,496.5 μg/m^3, and 〉20.0 μm was 5,390.7μg/m^3); (3) the concentration changes of PM10 and TSP were also related to the course and intensity of the sandstorm; and (4) the mass concentration of atmospheric particulate matter had the following sequence during the dust weather: clear day 〈 floating dust 〈 floating and blowing dust 〈 sandstorm. Temperature, relative humidity, and barometric pressure are important factors affecting the strength of storms, which could also indirectly affect the concentration change of atmospheric particulate matter.展开更多
In order to improve the bending load-carrying capacity (BLCC) of undermatched butt joint under three-point bending load, the influence of joint geometric parameters on stress concentration factors (SCF) at the wel...In order to improve the bending load-carrying capacity (BLCC) of undermatched butt joint under three-point bending load, the influence of joint geometric parameters on stress concentration factors (SCF) at the weld bottom center and the weld toe of uudermatched butt joint with single V-groove are studied respectively based on the finite element method in this paper. Results show that the reinforcement height and the cover pass width play decisive role in the BLCC for undermatched butt joint. BLCC of undermatched butt joint can be improved by choosing the appropriate joint geometric parameters.展开更多
In this paper,the influence of geometric parameters on the stress concentration factors due to three different types of axial loading on 81 TY tubular structures is studied.Our results reveal that,geometric parameters...In this paper,the influence of geometric parameters on the stress concentration factors due to three different types of axial loading on 81 TY tubular structures is studied.Our results reveal that,geometric parameters have a considerable impact on the variation of stress concentration factors on tubular TY-joints under axial loads.Thus,the highest stress concentration factor values are observed on the vertical brace than on the inclined one.The finite element results of the tubular structures were verified by parametric equations and experimental data.A parametric study was carried out by analyses using the nonlinear regression method to obtain parametric equations.These equations are used to calculate stress concentration factors and to analyse the fatigue resistance of TY-joints due to axial loads.展开更多
Milk fat globule epithelial growth factor VIII(MFG-E8) is a novel adhesion protein mainly produced by macrophages and dendritic cells; it is expressed in most of the human tissues and functions to prompt cancer progre...Milk fat globule epithelial growth factor VIII(MFG-E8) is a novel adhesion protein mainly produced by macrophages and dendritic cells; it is expressed in most of the human tissues and functions to prompt cancer progression and survival. MFG-E8 contains a signal sequence for secretion, two epidermal growth factor(EGF)-like domains at the NH2 terminus and two discoidin domains with blood-clotting factor V/factor Ⅷ(C1 and C2) at the COOH terminus. The second EGF domain contains an arginine-glycine-aspartic(RGD) integrin-binding motif that engages α_vβ_5 integrins to facilitate cell adhesion and induce integrinmediated signal transduction. Integrin α_vβ_3 associates with VEGF receptor 2, engagement of integrins can promote angiogenesis, which plays key roles in growth, proliferation, and survival of cancer cells. VEGF stimulates the expression of α_vβ_3 and α_vβ_5 integrins on angiogenic vasculature, thereby potentiating effects of VEGF receptor engagement. Mice expressing a mutant form of α_vβ_3 integrin are unable to undergo tyrosine phosphorylation, confirming the important role that this integrin plays in pathological angiogenesis and providing important mechanistic insights. The C-terminus discoidin-like domains promote binding to membrane phospholipids, functioning close to VEGF like angiogenesis. MFG-E8 is an opsonin for apoptotic cells, and it acts as a bridging protein between apoptotic cells and phagocytes. It also influences cell immunities by altering CD4^+ and/or CD8^+ cells. Antibody or small peptide works with MFG-E8 at different functional sites or interacts with EGF-like domains and/or discoidin-like domains may play an important role in anti-angiogenesis or immune restoration. Altering the structures and/or functions of MFG-E8 and/or its domains is promising for development of novel anti-cancer strategies.展开更多
基金Supported by Shenzhen Longhua District Science and Innovation Bureau for Key Laboratory Construction,No.20160919A0410022Shenzhen Longhua District Science and Innovation Bureau Fund for Medical Institutions,No.2020038 and No.2017136。
文摘BACKGROUND Management of chronic refractory wounds is one of the toughest clinical challenges for surgeons.Because of poor blood supply,less tissue coverage,and easy exposure,the lower leg is a common site for chronic refractory wounds.The current therapeutic regimens often lead to prolonged hospital stay and higher healthcare costs.Concentrated growth factor(CGF)is a novel blood extract that contains various growth factors,platelets,and fibrins to promote wound healing process.However,there has been little research reported on the treatment of lower extremity wounds with CGF.CASE SUMMARY A 37-year-old man,without any past medical history,presented an ulcerated chronic wound on his right lower leg.The skin defect exhibited clear boundaries,with a size of 2.0 cm×3.5 cm.The depth of wound was up to the layer of deep fascia.Staphylococcus aureus was detected by bacterial culture.The final diagnosis was right lower extremity ulcers with infection.Cefathiamidine,silver sulfadiazine,and mupirocin cream were applied to control the infection.CGF gel was prepared from the patient’s blood sample,and was used to cover the wound after thorough debridement.The skin wound was successfully healed after three times of CGF treatment.CONCLUSION CGF displays an excellent wound healing promoting effect in patients with lowerextremity chronic refractory wounds.
文摘A pilot study by Reyes [1] previously showed that ingestion of single dose of whole coffee fruit concentrate (WCFC) powder increased blood levels of brain derived neurotrophic factor (BDNF) during the first 60 minutes after ingestion. In the present report, we performed a single dose, placebo-controlled, within-subject study to confirm and further investigate this effect. Twenty healthy subjects with ages ranging from 25 to 35 participated in this study. All fasted and resting subjects received placebo on Day 1, WCFC on Day 2, and a cup of freshly brewed coffee on Day 3. Treatment with WCFC resulted in a statistically significant increase in plasma BDNF compared to placebo (p = 0.0073) or coffee (p = 0.0219) during first 60 minutes. In addition, e isolated exosomes from serum and found that they contained BDNF. Furthermore, oral WCFC consumption acutely increased BDNF levels in serum exosomes. In summary, all presented results justify further clinical investigation of WCFC as a tool to manage BDNF-dependent health conditions.
文摘Objective To explore the effect of concentrated growth factor(CGF)combined with autologous fat transplantation in augmentation mammoplasty.Methods Clinical data of 28 female patients who underwent autologous fat by CGF mixed with purified fat between May 2015 and June 2018 were retrospectively analyzed.Clinical evaluation was performed to observe and measure the shape of the breast after breast augmentation,the increase in the value of the nipple plane measurement,and complications.Results All of 28 patients,after 12 months of follow-up,all patients no fat infection,hematoma,breast nodules and other complications.It showed that the contouring of breast were improved and more chubbiness than that before operation.The results were satisfied from patients.Conclusion Concentrated growth factor combined with autologous fat transplantation has a stable breast augmentation effect,beautiful breast shape,simple operation and small damage,which achieves breast rejuvenation.
文摘Studies have shown that platelet concentrates can induce the proliferation of the dermal papilla and the vascularization of the perifollicular tissue, as well as accelerate the telogen-to-anagen transition, thereby promoting the regrowth of hair improving the appearance of hair loss. Herein, we report on the application of a new, modified form of platelet concentrates, namely, concentrated growth factors (CGFs), in 15 cases of androgenetic alopecia (AGA). 15 cases of androgenetic alopecia were treated with the use of monthly, subcutaneous injections of autologous CGF in the scalp. A total of 3 injections were administered 4 weeks apart, and the patients were followed up for 6 months. Assessments were performed before the treatments and at 4, 8, 12 and 24 weeks after the first treatment. The treatment outcomes were assessed by taking macroscopic photographs and trichoscopic photomicrographs, as well as by using the Global Aesthetic Improvement Scale (GAIS) and the patient satisfaction survey. In order to determine the safety of the treatment, the injection area was observed for signs of infection or mass evaluation. The photographs showed significant improvement in hair appearance after injections of CGF. The hair photomicrographs showed that CGF promoted the regrowth of hair in balding areas, with an increased hair density and an increased ratio of terminal to vellus hair. The GAIS suggested that CGF treatments were effective in treating AGA, and the majority of patients were satisfied with their improvement. In addition, treatments resulted in a faster rate of hair growth and a decrease in the greasy and unpleasant sensation of the hair of the patients. At the last visit, none of the 15 patients reported experiencing side-effects during the follow-up period. To conclude, the application of CGF can be an effective method in the treatment of androgenetic alopecia.
文摘Objective: To study the effect of concentrated growth factor (CGF) combined with guided bone regeneration on cell proliferation and bone resorption in patients with severe periodontitis. Methods: Patients with severe periodontitis who were treated in Stomatology Department of Shenmu Hospital between May 2014 and February 2017 were selected as the research subjects and randomly divided into two groups, surgery + CGF group received concentrated growth factor combined with guided bone regeneration, and pure surgery group received guided bone regeneration. The contents of inflammatory response, cell proliferation and bone resorption markers in gingival crevicular fluid were determined 1 week after treatment. Results: 1 week after treatment, HMGB1, ICAM1, E-selectin, Smac, FasL, Caspase-8, Caspase-9, Caspase-3, RANKL and NTX contents in gingival crevicular fluid of surgery + CGF group were significantly lower than those of pure surgery group while PD-L1, hBD-3, Wnt3a, BGP and OPG contents were significantly higher than those of pure surgery group. Conclusion:Concentrated growth factor combined with guided bone regeneration for severe periodontitis can inhibit inflammatory response, apoptosis and bone resorption, which is beneficial to the reconstruction of periodontal tissue.
文摘Platelet concentrates(PC) [platelet-rich plasma(PRP) and platelet-rich fibrin(PRF)] are frequently used for surgical procedures in medical and dental fields,particularly in oral and maxillofacial surgery,plastic surgery and sports medicine.The objective of all these technologies is to extract all the elements from a blood sample that could be used to improve healing and promote tissue regeneration.Although leukocyte rich and leukocyte poor PRP's have their own place in literature,the importance of non-platelet components in a platelet concentrate remains a mystery.PC have come a long way since its first appearance in 1954 to the T-PRF,A-PRF and i-PRF introduced recently.These PC find varied applications successfully in periodontics and implant dentistry as well.However,the technique of preparation,standing time,transfer process,temperature of centrifuge,vibration,etc.,are the various factors for the mixed results reported in the literature.Until the introduction of a proper classification of terminologies,the PC were known by different names in different countries and by different commercial companies which also created a lot of confusion.This review intends to clarify all these confusion by briefing the exact evolution of PC,their preparation techniques,recent advances and their various clinical and technical aspects and applications.
基金supported by the Natural Science Foundation of Heilongjiang Province,China(Grant No.G2016001)
文摘Atmospheric particulate matter(PM2.5) seriously influences air quality. It is considered one of the main environmental triggers for lung and heart diseases. Air pollutants can be adsorbed by forest. In this study we investigated the effect of forest cover on urban PM2.5 concentrations in 12 cities in Heilongjiang Province,China. The forest cover in each city was constant throughout the study period. The average daily concentration of PM2.5 in 12 cities was below 75 lg/m^3 during the non-heating period but exceeded this level during heating period. Furthermore, there were more moderate pollution days in six cities. This indicated that forests had the ability to reduce the concentration of PM2.5 but the main cause of air pollution was excessive human interference and artificial heating in winter. We classified the 12 cities according to the average PM2.5 concentrations. The relationship between PM2.5 concentrations and forest cover was obtained by integrating forest cover, land area,heated areas and number of vehicles in cities. Finally,considering the complexity of PM2.5 formation and based on the theory of random forestry, we selected six cities and analyzed their meteorological and air pollutant data. The main factors affecting PM2.5 concentrations were PM10,NO_2, CO and SO_2 in air pollutants while meteorological factors were secondary.
文摘CO2 concentrations in different plant communities (larch, birch, lilac, and grassland) were measured during the growing season in the Heilongjiang Forest Botanical Garden to study diurnal variation, seasonal and annual dynamics and factors that impact CO2 concentration in different spaces. CO2 concentration in different communities in green lands had an obvious diurnal variation, chronically decreasing, and temperature influenced the lilac area and the grassland. Seasonally, CO2 was lowest in the larch green land (344.03 ±23.03 μmol/mol) and highest in the grassland (360.13 ± 22.43 μmol/mol). The overall trend in CO2 concentration was autumn 〉 spring 〉 summer; temperature is the main factor controlling variation in CO2 concentrations during the growing season; the CO2 concentration at the larch, birch, lilac, and grassland types of sites was negatively correlated with land surface temperature and air temperature, and the CO2 concentration at the larch and birch sites was positively correlated with atmospheric pressure. Without any obvious annual change law, further study and observation are needed.
基金Supported by National Natural Science Foundation of China (No. 50878142)
文摘Finite element models were established to analyze the influence of soft filler on stress concentration for a rectangular plate with an elliptic hole in the center. The influence was quantified by means of stress concentration factor (SCF). Seven shape factors of the elliptic hole and three levels of elasticity modulus of the soft filler were considered. The reduction coefficient and sensitivity index of SCF are the two indicators in evaluating the influence of soft filler. It was found that the reduction coefficient of SCF increases significantly as the shape factor and the elasticity modulus of the filler increase, indicating that soft filler can reduce the concentrated stress effectively, especially when the shape factor is great. Analysis for the sensitivity index of SCF indicates that SCF is more sensitive to materials with small elasticity modulus than to materials with large one.
基金Supported by National Defense Preliminary Research Project of China(Grant No.104010205)
文摘Neuber rule and Arola-Ramulu model are widely used to predict the stress concentration factor of rough specimens. However, the height parameters and effective valley radius used in these two models depend strongly on the resolution of the roughness-measuring instruments and are easily introduce measuring errors. Besides, it is difficult to find a suitable parameter to characterize surface topography to quantitatively describe its effect on stress concentration factor. In order to overcome these disadvantages, profile moments are carried out to characterize surface topography, surface topography is simulated by superposing series of cosine components, the stress concentration factors of different micro cosine-shaped surface topographies are investigated by finite element analysis. In terms of micro cosine-shaped surface topography, an equation using the second profile moment to estimate the stress concentration factor is proposed, predictions for the stress concentration factor using the proposed expression are within 10% error compared with the results of finite element analysis, which are more accurate than other models. Moreover, the proposed equation is applied to the real surface topography machined by turning. Predictions for the stress concentration factor using the proposed expression are within 10% of the maximum stress concentration factors and about 5% of the effective stress concentration factors estimated from the finite element analysis for three levels of turning surface topographies under different simulated scales. The proposed model is feasible in predicting the stress concentration factors of real machined surface topographies.
基金The research work was financially supported by the National Natural Scientice Foundation of China(Grant No.10142001)by the Shandong Provincial Natural Scientice Foundation(Grant No.Y2006F46)
文摘In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stress concentration factor distribution along the weld toe in the hot spot stress region for tubular X-joints subject to axial loads have been analyzed by use of finite element method. Through numerical analysis, it has been found that the peak stress concentration factor is located at the saddle position. Thereafter, 80 models have been analyzed, and the effect of the geometric parameters of a tubular X-joint on the stress concentration factor has been investigated. Based on the experimental values of the numerical stress concentration factor, a parametric equation to calculate the stress concentration factor of tubular X-joints has been proposed. The accuracy of this equation has been verified against the requirement of the Fatigue Guidance Review Panel, and the proposed equation is found capable of producing reasonably accurate stress concentration factor values for tubular X-joints subject to axial loads.
基金supported by the National Natural Science Foundation of China (No. 51179115)
文摘Two explicit expressions of the stress concentration factor for a tension finite-width strip with a central elliptical hole and an eccentric elliptical hole, respectively, are formulated by using a semi-analytical and semi-empiricai method. Accuracy of the results obtained from these expressions is better, and application scope is wider, than the results of Durelli's photo-elastic experiment and Isida's formula. When eccentricity of the elliptical hole is within a certain range, the error is less than 8%. Based on the relation between the stress concentration factor and the stress intensity factor, a stress intensity factor expression for tension strips with a center or an eccentric crack is derived with the obtained stress concentration factor expressions. Compared with the existing formulae and the finite element analysis, this stress intensity factor expression also has sufficient accuracy.
基金supported by Natural Science Foundation of China (Nos. 41175017,41175140)Public Service sectors (meteorology) research and special funds by the Ministry of Science and Technology (Nos.GYHY201006012,GYHY201106025)
文摘During the course of a major sandstorm from April 17 to April 23, 2008 in the Taklimakan Desert, data pertaining to the mass concentrations of different-sized atmospheric particulate matter were observed continuously with Grimm 1.108, Thermo RP 1400a, TSP, and CAWS-600 instruments. The results showed that: (1) during the entire sandstorm process there were some dif- ferences between the daily mean particle concentration peaks and the hourly mean particle concentration peaks because the actual sandstorm lasted for only about 4 hr, whereas more particles were accumulated in the floating dust days before and after the actual sandstorm; (2) the intensity of the sandstorm was enhanced with the increase of wind speed, and this was related to the peak mass concentrations of atmospheric particulate matter; the wind speed directly affected the concentration of atmospheric particulate matter: the higher the wind speed, the higher the mass concentration (〉0.23 μm was 39,496.5 μg/m^3, and 〉20.0 μm was 5,390.7μg/m^3); (3) the concentration changes of PM10 and TSP were also related to the course and intensity of the sandstorm; and (4) the mass concentration of atmospheric particulate matter had the following sequence during the dust weather: clear day 〈 floating dust 〈 floating and blowing dust 〈 sandstorm. Temperature, relative humidity, and barometric pressure are important factors affecting the strength of storms, which could also indirectly affect the concentration change of atmospheric particulate matter.
基金The authors are grateful to be financially supported by Projects of Natural Science Foundation of Heilongjiang Province (No. E201458) , State Key Lab of Advanced Welding and Joining, Har- bin Institute of Technology (AWJ-M13-14) and Hei longjiang Prov- ince Department of Education (12541679).
文摘In order to improve the bending load-carrying capacity (BLCC) of undermatched butt joint under three-point bending load, the influence of joint geometric parameters on stress concentration factors (SCF) at the weld bottom center and the weld toe of uudermatched butt joint with single V-groove are studied respectively based on the finite element method in this paper. Results show that the reinforcement height and the cover pass width play decisive role in the BLCC for undermatched butt joint. BLCC of undermatched butt joint can be improved by choosing the appropriate joint geometric parameters.
文摘In this paper,the influence of geometric parameters on the stress concentration factors due to three different types of axial loading on 81 TY tubular structures is studied.Our results reveal that,geometric parameters have a considerable impact on the variation of stress concentration factors on tubular TY-joints under axial loads.Thus,the highest stress concentration factor values are observed on the vertical brace than on the inclined one.The finite element results of the tubular structures were verified by parametric equations and experimental data.A parametric study was carried out by analyses using the nonlinear regression method to obtain parametric equations.These equations are used to calculate stress concentration factors and to analyse the fatigue resistance of TY-joints due to axial loads.
基金Supported by a grant from Medical Technology Research Center for Health Development of China National Health and Family Planning Commission(No.W2012FZ007)
文摘Milk fat globule epithelial growth factor VIII(MFG-E8) is a novel adhesion protein mainly produced by macrophages and dendritic cells; it is expressed in most of the human tissues and functions to prompt cancer progression and survival. MFG-E8 contains a signal sequence for secretion, two epidermal growth factor(EGF)-like domains at the NH2 terminus and two discoidin domains with blood-clotting factor V/factor Ⅷ(C1 and C2) at the COOH terminus. The second EGF domain contains an arginine-glycine-aspartic(RGD) integrin-binding motif that engages α_vβ_5 integrins to facilitate cell adhesion and induce integrinmediated signal transduction. Integrin α_vβ_3 associates with VEGF receptor 2, engagement of integrins can promote angiogenesis, which plays key roles in growth, proliferation, and survival of cancer cells. VEGF stimulates the expression of α_vβ_3 and α_vβ_5 integrins on angiogenic vasculature, thereby potentiating effects of VEGF receptor engagement. Mice expressing a mutant form of α_vβ_3 integrin are unable to undergo tyrosine phosphorylation, confirming the important role that this integrin plays in pathological angiogenesis and providing important mechanistic insights. The C-terminus discoidin-like domains promote binding to membrane phospholipids, functioning close to VEGF like angiogenesis. MFG-E8 is an opsonin for apoptotic cells, and it acts as a bridging protein between apoptotic cells and phagocytes. It also influences cell immunities by altering CD4^+ and/or CD8^+ cells. Antibody or small peptide works with MFG-E8 at different functional sites or interacts with EGF-like domains and/or discoidin-like domains may play an important role in anti-angiogenesis or immune restoration. Altering the structures and/or functions of MFG-E8 and/or its domains is promising for development of novel anti-cancer strategies.