The main goal of this paper is to examine the economic relations of the Republic of Congo in its bilateral cooperation with China and to see its real implications in the Congolese economy. In other words, this paper i...The main goal of this paper is to examine the economic relations of the Republic of Congo in its bilateral cooperation with China and to see its real implications in the Congolese economy. In other words, this paper is going to highlight the real status of the Republic of Congo in the recent intensification of cooperation with the Middle Kingdom. Indeed, China has always been criticized as a predator of African raw materials by its opponents (traditional partners of Africa). Thus, in the Congolese context, the authors try to analyze and see whether this cooperation has corroborated that anti-thesis or not. After examining various facets of Chinese interventions in Congo, the authors conclude that: The cooperation between these two countries is a kind of cooperation for the modernization and industrialization of the Congo, which is now developing in a satisfactory way. It brings real benefits to people of both countries, and it is also welcomed by both of them. Congo and China are bound by a traditional friendship, they have cooperated with each other since 1964, and both countries must be determined to further strengthen this cooperation to achieve a common development. It should also be noted that China is first and foremost a strategic partner of development for the Congo because of the positive results recorded by its actions in different areas of its operations in that country. The authors have also noted some pitfalls and have made some suggestions accordingly, in order to enhance the performance of cooperation between the two countries. It is particularly in terms of the transfer of technology, compliance with the regulations in force in Congo by Chinese enterprises, the adjustments made by China concerning the training of Congolese students who receive scholarships from the Chinese government for their training in China and on Chinese language, and finally the area of diversification of production, it is worth pointing out that the Congo only exports its main raw materials to China, such as oil and wood, and moreover, those materials are exported in the raw state, thus reducing the incentives of diversification of its domestic production. The data used in this article cover the periods from 1995 to 2005, which are inadequate for this work, given the momentum taken by the development of cooperation between the two countries. Then, for future researchers, they have to refine the work concerning the next state of Sino-African cooperation.展开更多
A numerical study based on direct thermal to electric energy conversion was performed in a reciprocal flow porous media burner embedded with two layers of thermoelements. The burner lean combustibility limit was sough...A numerical study based on direct thermal to electric energy conversion was performed in a reciprocal flow porous media burner embedded with two layers of thermoelements. The burner lean combustibility limit was sought in order to maximize global efficiency of thermal to electrical energy conversion by minimizing fuel consumption. Once the pairs of operational variables, composition and filtrational velocity of gas inlet mixture were found, the optimal length and placement of thermoelectric elements within the reactor high thermal gradients were sought to maximize the electric current, thermoelements and system overall efficiency. A two temperature-resistance model for finite time thermodynamics was developed for the thermoelectric elements energy fluxes. Results indicate a distribution of current and efficiencies that presents a maximum at different themoelements length. Maximum values for current and system efficiency obtained were 44.3 m A and 2.5%, respectively.展开更多
The goal of education is to cultivate learner autonomy. Studies in metacognition suggest that the ideal way to accomplish this is through metacognitive strategy training. Research also indicates that effective trainin...The goal of education is to cultivate learner autonomy. Studies in metacognition suggest that the ideal way to accomplish this is through metacognitive strategy training. Research also indicates that effective training programs depend on monitoring. To cultivate self-regulation or learner autonomy, it is necessary to exert external monitoring at the beginning, and gradually reduce external supervision as the students become more autonomous. The present study argues for cooperative group learning and regular evaluation as the main monitoring strategies. A semester long study indicates that cooperative group learning, besides being valuable in cultivating social relationship, and fostering cooperation and learner autonomy, can also serve as a good monitoring strategy in metacognitive strategy training. Regular evaluation, when it is progress- oriented and learner-centered, and conducted at proper times, will also provide valuable information for students to check, evaluate and adjust their learning. Self-questioning sheets and learner portfolios are also useful techniques in monitoring students' learning.展开更多
In this paper,the authors primarily explore a delayed competitor-competitor-mutualist Lotka-Volterra model,which is a system of differential equation with infinite integral.The authors first study the existence of pos...In this paper,the authors primarily explore a delayed competitor-competitor-mutualist Lotka-Volterra model,which is a system of differential equation with infinite integral.The authors first study the existence of positive periodic solutions of the model by using the Krasnoselskii's fixed point theorem,and then present an example to illustrate the main results.展开更多
Reciprocity has core significance for understanding basic human living conditions:our social nature is founded on reciprocal relations,and reciprocity strengthens the ties between people.Reciprocity-based anthropology...Reciprocity has core significance for understanding basic human living conditions:our social nature is founded on reciprocal relations,and reciprocity strengthens the ties between people.Reciprocity-based anthropology is a kind of cultural logic,one that stresses the interaction between different groups.Fundamentally,it involves studying forms of the mutually beneficial relations involved in complementary differences.This perspective reconciles differences,creating a communicative space for diverse cultures’coexistence,symbiosis and sharing.The various channels formed through human activity include ways in and ways out,constant incomings and outgoings,the coexistence of different cultures,ways of life and ideas,and complementarity.The launching of the Belt and Road Initiative includes channels with multiple characteristics and functions,so research on this topic involves the analysis of society and culture based on roadways rather than locations.展开更多
Aims Intensive land management practices can compromise soil biodiversity,thus jeopardizing long-term soil productivity.Arbuscular mycorrhizal fungi(AMF)play a pivotal role in promoting soil productivity through oblig...Aims Intensive land management practices can compromise soil biodiversity,thus jeopardizing long-term soil productivity.Arbuscular mycorrhizal fungi(AMF)play a pivotal role in promoting soil productivity through obligate symbiotic associations with plants.However,it is not clear how properties of plant communities,especially species richness and composition influence the viability of AMF populations in soils.Methods Here we test whether monocultures of eight plant species from different plant functional groups,or a diverse mixture of plant species,maintain more viable AMF propagules.To address this question,we extracted AMF spores from 12-year old plant monocultures and mixtures and paired single AMF spores with single plants in a factorial design crossing AMF spore origin with plant species identity.Important Findings AMF spores from diverse plant mixtures were more successful at colonizing multiple plant species and plant individuals than AMF spores from plant monocultures.Furthermore,we found evidence that AMF spores originating from diverse mixtures more strongly increased biomass than AMF from monocultures in the legume Trifolium repens L.AMF viability and ability to interact with many plant species were greater when AMF spores originated from 12-year old mixtures than monocultures.Our results show for the first time that diverse plant communities can sustain AMF viability in soils and demonstrate the potential of diverse plant communities to maintain viable AMF propagules that are a key component to soil health and productivity.展开更多
Aims Seed dispersal by endozoochory is an important process in plant regeneration and the establishment of new populations.Seeds with dormancy may especially benefit after disperser gut passage.However,the ways in whi...Aims Seed dispersal by endozoochory is an important process in plant regeneration and the establishment of new populations.Seeds with dormancy may especially benefit after disperser gut passage.However,the ways in which gut passage affect the germination of plant species with physiological dormancy remain unclear.Here,we experimentally assessed the mutualistic interaction between the Austral parakeet(Enicognathus ferrugineus)as a disperser of calafate(Berberis microphylla),a thorny bush inhabiting the understory of the Austral temperate forests of South America with seeds that are characterized by deep physiological dormancy.Methods Germination success and viability of calafate seeds obtained from faeces and from intact fruits were tested under four treatments:(i)digested seeds,(ii)digested seeds with faecal extract,(iii)intact seeds from fruit and(iv)intact seeds from fruit with pulp.Important Findings About 65%of the Austral parakeet droppings contained calafate seeds.Viability of seeds did not differ between treatments.However,germination was significantly higher in digested seeds than in intact seeds from fruits,while no difference was found between faecal and pulp extracts.Neither faecal matter nor fruit pulp provided seeds with any ecological advantages derived from enhancing germinability,but did confer some disadvantage in germination time.Faecal matter is expected to be completely lacking around seeds after several months under snow before germinating in the following spring,given intense washing due to persistent rain and the spring thaw in the Patagonian Andes.The higher germinability along with faster germination of digested seeds supports the hypothesis of a legitimate mutualistic interaction between Austral parakeets and calafate.We hypothesized that the passage through the disperser digestive tract might break physiological dormancy as differences in germinability between ingested and non-ingested seeds.Our results highlight the relevant role of endozoochory in plant species with physiological dormancy living in highly seasonal environments.展开更多
Aims Ecosystem engineers substantially modify the environment via their impact on abiotic conditions and the biota,resulting in facilitation of associated species that would not otherwise grow.Yet,reciprocal effects a...Aims Ecosystem engineers substantially modify the environment via their impact on abiotic conditions and the biota,resulting in facilitation of associated species that would not otherwise grow.Yet,reciprocal effects are poorly understood as studies of plant–plant interactions usually estimate only benefits for associated species,while how another trophic level may mediate direct and indirect feedback effects for ecosystem engineers is hardly considered.Methods We ran a field experiment with two ecosystem engineers(Arenaria tetraquetra and Hormathophylla spinosa)blooming either alone or with associated plants to decompose net effects and to test the hypothesis that pollinator-mediated interactions provide benefits that balance costs of facilitation by ecosystem engineers.Important Findings We found that net costs of facilitation are accompanied by pollinator-mediated benefits.Despite ecosystem engineers producing fewer flowers per plant,they were visited by more and more diverse pollinators per flower when blooming with associated plants than when blooming alone.Although seed production per plant was higher when ecosystem engineers bloomed alone,fruit set and seed set varied between species.In one case(A.tetraquetra),fruit and seed sets were negatively affected by the presence of associated plants,whereas,in another case(H.spinosa),fruit set and seed set were higher and unaffected when ecosystem engineers bloomed with associated plants,respectively.Our findings suggest that besides experiencing direct costs,ecosystem engineers can also benefit from facilitating other species via increasing their own visibility to pollinators.Thus,we highlight that pollination interactions can compensate for costs of facilitation depending on ecosystem engineer species.This study illuminates how the outcome of direct plant–plant interactions might be mediated by indirect interactions including third players.展开更多
This paper is concerned with a system of semilinear parabolic equations with two free boundaries describing the spreading fronts of the invasive species in a mutualistic eco- logical model. The local existence and uni...This paper is concerned with a system of semilinear parabolic equations with two free boundaries describing the spreading fronts of the invasive species in a mutualistic eco- logical model. The local existence and uniqueness of a classical solution are obtained and the asymptotic behavior of the free boundary problem is studied. Our results indi- cate that two free boundaries tend monotonically to finite or infinite limits at the same time, and the free boundary problem admits a global slow solution with unbounded free boundaries if the intra-specific competitions are strong, while if the intra-specific competitions are weak, there exist the blowup solution and global fast solution.展开更多
We propose two models of one hyper-connected mutualistic-species described by delay differential equations of Lotka-Volterra type. An hyper-connected model comprises a central species interacting with a number of peri...We propose two models of one hyper-connected mutualistic-species described by delay differential equations of Lotka-Volterra type. An hyper-connected model comprises a central species interacting with a number of peripheral species around it, that is to say, one animal species (pollinators or dispersers) that interacts with several plant species (flowering plants or fruit trees), or several animal species that interact with one plant species. We derive a necessary and sufficient condition for the global asymptotic stability of the unique coexisting steady state of hyper-connected systems by means of novel Lyapunov functionals.展开更多
文摘The main goal of this paper is to examine the economic relations of the Republic of Congo in its bilateral cooperation with China and to see its real implications in the Congolese economy. In other words, this paper is going to highlight the real status of the Republic of Congo in the recent intensification of cooperation with the Middle Kingdom. Indeed, China has always been criticized as a predator of African raw materials by its opponents (traditional partners of Africa). Thus, in the Congolese context, the authors try to analyze and see whether this cooperation has corroborated that anti-thesis or not. After examining various facets of Chinese interventions in Congo, the authors conclude that: The cooperation between these two countries is a kind of cooperation for the modernization and industrialization of the Congo, which is now developing in a satisfactory way. It brings real benefits to people of both countries, and it is also welcomed by both of them. Congo and China are bound by a traditional friendship, they have cooperated with each other since 1964, and both countries must be determined to further strengthen this cooperation to achieve a common development. It should also be noted that China is first and foremost a strategic partner of development for the Congo because of the positive results recorded by its actions in different areas of its operations in that country. The authors have also noted some pitfalls and have made some suggestions accordingly, in order to enhance the performance of cooperation between the two countries. It is particularly in terms of the transfer of technology, compliance with the regulations in force in Congo by Chinese enterprises, the adjustments made by China concerning the training of Congolese students who receive scholarships from the Chinese government for their training in China and on Chinese language, and finally the area of diversification of production, it is worth pointing out that the Congo only exports its main raw materials to China, such as oil and wood, and moreover, those materials are exported in the raw state, thus reducing the incentives of diversification of its domestic production. The data used in this article cover the periods from 1995 to 2005, which are inadequate for this work, given the momentum taken by the development of cooperation between the two countries. Then, for future researchers, they have to refine the work concerning the next state of Sino-African cooperation.
文摘A numerical study based on direct thermal to electric energy conversion was performed in a reciprocal flow porous media burner embedded with two layers of thermoelements. The burner lean combustibility limit was sought in order to maximize global efficiency of thermal to electrical energy conversion by minimizing fuel consumption. Once the pairs of operational variables, composition and filtrational velocity of gas inlet mixture were found, the optimal length and placement of thermoelectric elements within the reactor high thermal gradients were sought to maximize the electric current, thermoelements and system overall efficiency. A two temperature-resistance model for finite time thermodynamics was developed for the thermoelectric elements energy fluxes. Results indicate a distribution of current and efficiencies that presents a maximum at different themoelements length. Maximum values for current and system efficiency obtained were 44.3 m A and 2.5%, respectively.
文摘The goal of education is to cultivate learner autonomy. Studies in metacognition suggest that the ideal way to accomplish this is through metacognitive strategy training. Research also indicates that effective training programs depend on monitoring. To cultivate self-regulation or learner autonomy, it is necessary to exert external monitoring at the beginning, and gradually reduce external supervision as the students become more autonomous. The present study argues for cooperative group learning and regular evaluation as the main monitoring strategies. A semester long study indicates that cooperative group learning, besides being valuable in cultivating social relationship, and fostering cooperation and learner autonomy, can also serve as a good monitoring strategy in metacognitive strategy training. Regular evaluation, when it is progress- oriented and learner-centered, and conducted at proper times, will also provide valuable information for students to check, evaluate and adjust their learning. Self-questioning sheets and learner portfolios are also useful techniques in monitoring students' learning.
基金supported by the National Natural Science Foundation of China under Grant No.11302002the Foundation of Outstanding Young Talent in University of Anhui Province of China under Grant No.2011SQRL022ZD
文摘In this paper,the authors primarily explore a delayed competitor-competitor-mutualist Lotka-Volterra model,which is a system of differential equation with infinite integral.The authors first study the existence of positive periodic solutions of the model by using the Krasnoselskii's fixed point theorem,and then present an example to illustrate the main results.
基金supported by the the Major Project of the Humanities and Social Sciences Key Research Base of the Ministry of Education,"Research on Rural Social Reconstruction and Governance Innovation"(16JJD840015)
文摘Reciprocity has core significance for understanding basic human living conditions:our social nature is founded on reciprocal relations,and reciprocity strengthens the ties between people.Reciprocity-based anthropology is a kind of cultural logic,one that stresses the interaction between different groups.Fundamentally,it involves studying forms of the mutually beneficial relations involved in complementary differences.This perspective reconciles differences,creating a communicative space for diverse cultures’coexistence,symbiosis and sharing.The various channels formed through human activity include ways in and ways out,constant incomings and outgoings,the coexistence of different cultures,ways of life and ideas,and complementarity.The launching of the Belt and Road Initiative includes channels with multiple characteristics and functions,so research on this topic involves the analysis of society and culture based on roadways rather than locations.
基金supported by the German Research Foundation(RO2397/7)conducted in the framework of the Jena Experiment(FOR 456/1451)+1 种基金with additional support from the Friedrich Schiller University of JenaFurther support was provided by the German Centre for Integrative Biodiversity Research(iDiv)Halle-Jena-Leipzig,funded by the German Research Foundation(FZT 118).
文摘Aims Intensive land management practices can compromise soil biodiversity,thus jeopardizing long-term soil productivity.Arbuscular mycorrhizal fungi(AMF)play a pivotal role in promoting soil productivity through obligate symbiotic associations with plants.However,it is not clear how properties of plant communities,especially species richness and composition influence the viability of AMF populations in soils.Methods Here we test whether monocultures of eight plant species from different plant functional groups,or a diverse mixture of plant species,maintain more viable AMF propagules.To address this question,we extracted AMF spores from 12-year old plant monocultures and mixtures and paired single AMF spores with single plants in a factorial design crossing AMF spore origin with plant species identity.Important Findings AMF spores from diverse plant mixtures were more successful at colonizing multiple plant species and plant individuals than AMF spores from plant monocultures.Furthermore,we found evidence that AMF spores originating from diverse mixtures more strongly increased biomass than AMF from monocultures in the legume Trifolium repens L.AMF viability and ability to interact with many plant species were greater when AMF spores originated from 12-year old mixtures than monocultures.Our results show for the first time that diverse plant communities can sustain AMF viability in soils and demonstrate the potential of diverse plant communities to maintain viable AMF propagules that are a key component to soil health and productivity.
基金K.S.and S.A.L.were funded by the projects PICT 2015-2072 and PICT 2018-1623.
文摘Aims Seed dispersal by endozoochory is an important process in plant regeneration and the establishment of new populations.Seeds with dormancy may especially benefit after disperser gut passage.However,the ways in which gut passage affect the germination of plant species with physiological dormancy remain unclear.Here,we experimentally assessed the mutualistic interaction between the Austral parakeet(Enicognathus ferrugineus)as a disperser of calafate(Berberis microphylla),a thorny bush inhabiting the understory of the Austral temperate forests of South America with seeds that are characterized by deep physiological dormancy.Methods Germination success and viability of calafate seeds obtained from faeces and from intact fruits were tested under four treatments:(i)digested seeds,(ii)digested seeds with faecal extract,(iii)intact seeds from fruit and(iv)intact seeds from fruit with pulp.Important Findings About 65%of the Austral parakeet droppings contained calafate seeds.Viability of seeds did not differ between treatments.However,germination was significantly higher in digested seeds than in intact seeds from fruits,while no difference was found between faecal and pulp extracts.Neither faecal matter nor fruit pulp provided seeds with any ecological advantages derived from enhancing germinability,but did confer some disadvantage in germination time.Faecal matter is expected to be completely lacking around seeds after several months under snow before germinating in the following spring,given intense washing due to persistent rain and the spring thaw in the Patagonian Andes.The higher germinability along with faster germination of digested seeds supports the hypothesis of a legitimate mutualistic interaction between Austral parakeets and calafate.We hypothesized that the passage through the disperser digestive tract might break physiological dormancy as differences in germinability between ingested and non-ingested seeds.Our results highlight the relevant role of endozoochory in plant species with physiological dormancy living in highly seasonal environments.
基金supported by the Swiss National Science Foundation[grant numbers 148261,170645 and 180195]by the ETH Biocommunication group.
文摘Aims Ecosystem engineers substantially modify the environment via their impact on abiotic conditions and the biota,resulting in facilitation of associated species that would not otherwise grow.Yet,reciprocal effects are poorly understood as studies of plant–plant interactions usually estimate only benefits for associated species,while how another trophic level may mediate direct and indirect feedback effects for ecosystem engineers is hardly considered.Methods We ran a field experiment with two ecosystem engineers(Arenaria tetraquetra and Hormathophylla spinosa)blooming either alone or with associated plants to decompose net effects and to test the hypothesis that pollinator-mediated interactions provide benefits that balance costs of facilitation by ecosystem engineers.Important Findings We found that net costs of facilitation are accompanied by pollinator-mediated benefits.Despite ecosystem engineers producing fewer flowers per plant,they were visited by more and more diverse pollinators per flower when blooming with associated plants than when blooming alone.Although seed production per plant was higher when ecosystem engineers bloomed alone,fruit set and seed set varied between species.In one case(A.tetraquetra),fruit and seed sets were negatively affected by the presence of associated plants,whereas,in another case(H.spinosa),fruit set and seed set were higher and unaffected when ecosystem engineers bloomed with associated plants,respectively.Our findings suggest that besides experiencing direct costs,ecosystem engineers can also benefit from facilitating other species via increasing their own visibility to pollinators.Thus,we highlight that pollination interactions can compensate for costs of facilitation depending on ecosystem engineer species.This study illuminates how the outcome of direct plant–plant interactions might be mediated by indirect interactions including third players.
文摘This paper is concerned with a system of semilinear parabolic equations with two free boundaries describing the spreading fronts of the invasive species in a mutualistic eco- logical model. The local existence and uniqueness of a classical solution are obtained and the asymptotic behavior of the free boundary problem is studied. Our results indi- cate that two free boundaries tend monotonically to finite or infinite limits at the same time, and the free boundary problem admits a global slow solution with unbounded free boundaries if the intra-specific competitions are strong, while if the intra-specific competitions are weak, there exist the blowup solution and global fast solution.
文摘We propose two models of one hyper-connected mutualistic-species described by delay differential equations of Lotka-Volterra type. An hyper-connected model comprises a central species interacting with a number of peripheral species around it, that is to say, one animal species (pollinators or dispersers) that interacts with several plant species (flowering plants or fruit trees), or several animal species that interact with one plant species. We derive a necessary and sufficient condition for the global asymptotic stability of the unique coexisting steady state of hyper-connected systems by means of novel Lyapunov functionals.