Microstructure and biodegradation behavior of as-cast and hot extruded Mg-5Zn-1Y alloy containing different amountsof calcium （0.0%, 0.1%, 0.5%, and 1.0%, mass fraction） were explored. The extrusion process was cond...Microstructure and biodegradation behavior of as-cast and hot extruded Mg-5Zn-1Y alloy containing different amountsof calcium （0.0%, 0.1%, 0.5%, and 1.0%, mass fraction） were explored. The extrusion process was conducted at three differenttemperatures of 300, 330, and 370 ℃. Chemical composition, phase constitution, microstructure, and biodegradation behavior of thealloys were investigated. The macro- and micro-scopic examination revealed that the addition of Ca refines the grain structure andforms an intermetallic phase, Ca2Mg6Zn3. The hot extrusion process resulted in breaking the intermetallic phases into fine particlesrouted to the extrusion direction. Moreover, dynamic recrystallization happened in almost all alloys, and more bimodalmicrostructure was formed in the alloys when the alloys were extruded at 370 ℃. Polarization curves showed no passive region,which indicated that active polarization dominated in the alloys; therefore, grain refining through Ca addition and dynamicrecrystallization over hot extrusion operation increased biodegradation rate. The results show that the as-cast Mg-5Zn-1Y-0.1Caalloy provides the highest corrosion resistance, and the extruded Mg-5Zn-1Y-0.5Ca alloy at 300 ℃ shows the lowestbiodegradation rate among the extruded alloys. Therefore, hot extrusion does not always improve the biodegradation behavior ofmagnesium alloys.展开更多
Biodiesel （fatty acid methyl ester） has been identified as a non-toxic biodegradable alternative fuel that is obtained from renewable sources. Over the last decade, there has been increasing interest in producing bi...Biodiesel （fatty acid methyl ester） has been identified as a non-toxic biodegradable alternative fuel that is obtained from renewable sources. Over the last decade, there has been increasing interest in producing biodiesel from conventional sources such as soybean, canola, sunflower, and coconut oils. Current efforts are directed towards the development of new non-edible resources. Among these Jatropha Curcas comes at the forefront. In Egypt, Jatropha Curcas has grown successfully using primary treated wastewater. Also, extensive R＆D efforts identified the optimum conditions for the various processing stages namely crushing, extraction, transesterification and purification. Based on the research findings, the techno-economic appraisal of biodiesel production from Jatropha Curcas is conducted. Two nominal capacities namely 8,000 and 50,000 metric tons/yr have been proposed. Several scenarios have been formulated to take into consideration varying productivity （3.4 to 5.8 ton fruits per 4,000 m^2 （acre）） and varying recovery rates of oil from seeds. Economic indicators including capital and production costs for the various processing stages and revenues according to current prices of oil and cake have been obtained. The price of biodiesel that provides a simple rate of return （SRR） on investments of 10% was in the range of $0.3-0.7/liter for the different assumed scenarios which is lower than the prevailing price of biodiesel （about $1/liter） in the US. Thus, in view of experimental results and economic assumptions, there are positive prospects for the production of biodiesel from Jatropha Curcas under Egyptian conditions.展开更多
Guided bone regeneration(GBR)is a therapeutic procedure used to enhance alveolar bone volume before dental implants.Commercial non-absorbable membranes(i.e.,titanium membranes)typically require a second surgery to rem...Guided bone regeneration(GBR)is a therapeutic procedure used to enhance alveolar bone volume before dental implants.Commercial non-absorbable membranes(i.e.,titanium membranes)typically require a second surgery to remove,whereas absorbable membranes(i.e.,collagen membranes)will fail when put over extensive bone lesions due to their low mechanical strength.The GBR membrane that has been sought is still being developed.Biodegradable metals(BMs),particularly Mg and Zn,have recently been postulated as promising barrier membrane candidates.Herein,the goal of this research is to evaluate the mechanical and biological feasibility of using BMs as GBR membranes.It shows that BMs have a wide range of potential applications as GBR membranes,owing to their benign biocompatibility,sufficient mechanical support,tunable degradation rate,good osteogenic capabilities,broad-spectrum antibacterial behavior,and improved wound healing ability.The rapid degradation rate,hydrogen evolution impact,and stress corrosion cracking behavior all pose obstacles to the use of Mg-based membranes,which can be improved by surface modifications,heat treatment,alloying,etc.Due to its acceptable degradation rate and lack of gas production,Zn appears to be a better candidate for usage as a GBR membrane.In general,advances in the development of BMs have paved the door for BMs to be used as GBR membranes in oral clinical trials.展开更多
Catalytic conversion of sustainable cellulose to the value-added chemicals and high quality biofuel has been recognized as a perfect approach for the alleviation of the dependence on the non-renewable fossil resources...Catalytic conversion of sustainable cellulose to the value-added chemicals and high quality biofuel has been recognized as a perfect approach for the alleviation of the dependence on the non-renewable fossil resources. Previously, we successfully de- signed and explored novel and efficient cooperative ionic liquid pairs for this renewable material, which has advantages of high reactor efficiency than current technologies because of the dissolution and in situ catalytic decomposition mechanism. Here, the determinant of this process is further studied by the intensive investigation on the relationship between the cellulose conversion and the properties of ionic liquid catalyst and solvent. Scanning electron microscope （SEM）, thermogravimetric analysis （TG） and elemental analysis were used for the comparative characterization of raw cellulose and the residues. The re- suits demonstrate that this consecutive dissolution and in situ catalysis process is much more dependent on the dissolution ca- pability of ionic liquid solvent, while comparatively, the effect of in situ acid catalysis is relatively insignificant.展开更多
The adoption of grammatical modifier for im- plants or other kinds of biomaterials eventually absorbed by the body has been a long-standing confusing issue, and there are diverse terms in the large fields of research,...The adoption of grammatical modifier for im- plants or other kinds of biomaterials eventually absorbed by the body has been a long-standing confusing issue, and there are diverse terms in the large fields of research, which not only causes the difficulties when searching on the Internet, but also blurs the meaning and boundaries for researchers. Prior unification attempts at laws/standards set the basis for such research fields towards researching, labeling, marketing and instructions for use. Considering this, the typical gram- matical modifiers ＂biodegradable＂, ＂resorbable＂ ＂absorbable＂, along with their noun forms used in the decades of scien- tific research have been reviewed and explained, interdiscipli- nary in chemistry, ecology, materials science, biology, micro- biology, medicine, and based on usage customs, laws, stan- dards and markets. The term ＂biodegradable＂ has been not only used in biomaterials but also in ecology waste manage- ment, biomedicine and even natural environment. Mean- while, the term ＂resorbable＂ has long been used in biological reaction （osteoclast driven bone resorption）, but is inappro- priate for implants that do not carry the potential to grow back into their original form. The term ＂absorbable＂ focuses more on the host metabolism to the foreign biodegradation products of the implanted material/device compared with the term ＂degradable/biodegradable＂. Meanwhile the coherence and normalization of the term ＂absorbable＂ carried by its own in laws and standards contributes as well. In general, the au- thors consider the term ＂absorbable＂ to be the best grammat- ical modifier with respect to other adjectives which share the same inherence. A further internationally unified usage is proposed by us.展开更多
基金Shahid Rajaee Teacher Training University for the financial support (Vote No. 26234)
文摘Microstructure and biodegradation behavior of as-cast and hot extruded Mg-5Zn-1Y alloy containing different amountsof calcium （0.0%, 0.1%, 0.5%, and 1.0%, mass fraction） were explored. The extrusion process was conducted at three differenttemperatures of 300, 330, and 370 ℃. Chemical composition, phase constitution, microstructure, and biodegradation behavior of thealloys were investigated. The macro- and micro-scopic examination revealed that the addition of Ca refines the grain structure andforms an intermetallic phase, Ca2Mg6Zn3. The hot extrusion process resulted in breaking the intermetallic phases into fine particlesrouted to the extrusion direction. Moreover, dynamic recrystallization happened in almost all alloys, and more bimodalmicrostructure was formed in the alloys when the alloys were extruded at 370 ℃. Polarization curves showed no passive region,which indicated that active polarization dominated in the alloys; therefore, grain refining through Ca addition and dynamicrecrystallization over hot extrusion operation increased biodegradation rate. The results show that the as-cast Mg-5Zn-1Y-0.1Caalloy provides the highest corrosion resistance, and the extruded Mg-5Zn-1Y-0.5Ca alloy at 300 ℃ shows the lowestbiodegradation rate among the extruded alloys. Therefore, hot extrusion does not always improve the biodegradation behavior ofmagnesium alloys.
文摘Biodiesel （fatty acid methyl ester） has been identified as a non-toxic biodegradable alternative fuel that is obtained from renewable sources. Over the last decade, there has been increasing interest in producing biodiesel from conventional sources such as soybean, canola, sunflower, and coconut oils. Current efforts are directed towards the development of new non-edible resources. Among these Jatropha Curcas comes at the forefront. In Egypt, Jatropha Curcas has grown successfully using primary treated wastewater. Also, extensive R＆D efforts identified the optimum conditions for the various processing stages namely crushing, extraction, transesterification and purification. Based on the research findings, the techno-economic appraisal of biodiesel production from Jatropha Curcas is conducted. Two nominal capacities namely 8,000 and 50,000 metric tons/yr have been proposed. Several scenarios have been formulated to take into consideration varying productivity （3.4 to 5.8 ton fruits per 4,000 m^2 （acre）） and varying recovery rates of oil from seeds. Economic indicators including capital and production costs for the various processing stages and revenues according to current prices of oil and cake have been obtained. The price of biodiesel that provides a simple rate of return （SRR） on investments of 10% was in the range of $0.3-0.7/liter for the different assumed scenarios which is lower than the prevailing price of biodiesel （about $1/liter） in the US. Thus, in view of experimental results and economic assumptions, there are positive prospects for the production of biodiesel from Jatropha Curcas under Egyptian conditions.
基金supported by the National Key R&D Program of China(2018YFC1106600)the National Natural Science Foundation of China(52071008,and U20A20390)Beijing Natural Science Foundation(2192027)。
文摘Guided bone regeneration(GBR)is a therapeutic procedure used to enhance alveolar bone volume before dental implants.Commercial non-absorbable membranes(i.e.,titanium membranes)typically require a second surgery to remove,whereas absorbable membranes(i.e.,collagen membranes)will fail when put over extensive bone lesions due to their low mechanical strength.The GBR membrane that has been sought is still being developed.Biodegradable metals(BMs),particularly Mg and Zn,have recently been postulated as promising barrier membrane candidates.Herein,the goal of this research is to evaluate the mechanical and biological feasibility of using BMs as GBR membranes.It shows that BMs have a wide range of potential applications as GBR membranes,owing to their benign biocompatibility,sufficient mechanical support,tunable degradation rate,good osteogenic capabilities,broad-spectrum antibacterial behavior,and improved wound healing ability.The rapid degradation rate,hydrogen evolution impact,and stress corrosion cracking behavior all pose obstacles to the use of Mg-based membranes,which can be improved by surface modifications,heat treatment,alloying,etc.Due to its acceptable degradation rate and lack of gas production,Zn appears to be a better candidate for usage as a GBR membrane.In general,advances in the development of BMs have paved the door for BMs to be used as GBR membranes in oral clinical trials.
基金supported by the National Natural Science Foundation of China (N21336002, 51306191, 21276094)the Natural Science Foundation of Guangdong Province, China (2015A030311048)
文摘Catalytic conversion of sustainable cellulose to the value-added chemicals and high quality biofuel has been recognized as a perfect approach for the alleviation of the dependence on the non-renewable fossil resources. Previously, we successfully de- signed and explored novel and efficient cooperative ionic liquid pairs for this renewable material, which has advantages of high reactor efficiency than current technologies because of the dissolution and in situ catalytic decomposition mechanism. Here, the determinant of this process is further studied by the intensive investigation on the relationship between the cellulose conversion and the properties of ionic liquid catalyst and solvent. Scanning electron microscope （SEM）, thermogravimetric analysis （TG） and elemental analysis were used for the comparative characterization of raw cellulose and the residues. The re- suits demonstrate that this consecutive dissolution and in situ catalysis process is much more dependent on the dissolution ca- pability of ionic liquid solvent, while comparatively, the effect of in situ acid catalysis is relatively insignificant.
基金supported by the National Key Research and Development Program of China (2016YFC1102402)National Natural Science Foundation of China (NSFC, 51431002)the NSFC and the Research Grants Council (RGC) of Hong Kong Joint Research Scheme (51361165101 and 5161101031)
文摘The adoption of grammatical modifier for im- plants or other kinds of biomaterials eventually absorbed by the body has been a long-standing confusing issue, and there are diverse terms in the large fields of research, which not only causes the difficulties when searching on the Internet, but also blurs the meaning and boundaries for researchers. Prior unification attempts at laws/standards set the basis for such research fields towards researching, labeling, marketing and instructions for use. Considering this, the typical gram- matical modifiers ＂biodegradable＂, ＂resorbable＂ ＂absorbable＂, along with their noun forms used in the decades of scien- tific research have been reviewed and explained, interdiscipli- nary in chemistry, ecology, materials science, biology, micro- biology, medicine, and based on usage customs, laws, stan- dards and markets. The term ＂biodegradable＂ has been not only used in biomaterials but also in ecology waste manage- ment, biomedicine and even natural environment. Mean- while, the term ＂resorbable＂ has long been used in biological reaction （osteoclast driven bone resorption）, but is inappro- priate for implants that do not carry the potential to grow back into their original form. The term ＂absorbable＂ focuses more on the host metabolism to the foreign biodegradation products of the implanted material/device compared with the term ＂degradable/biodegradable＂. Meanwhile the coherence and normalization of the term ＂absorbable＂ carried by its own in laws and standards contributes as well. In general, the au- thors consider the term ＂absorbable＂ to be the best grammat- ical modifier with respect to other adjectives which share the same inherence. A further internationally unified usage is proposed by us.
