The advancement in extraterrestrial exploration has highlighted the crucial need for studying how the human cardiovascular system adapts to space conditions.Human development occurs under the influence of gravity,shie...The advancement in extraterrestrial exploration has highlighted the crucial need for studying how the human cardiovascular system adapts to space conditions.Human development occurs under the influence of gravity,shielded from space radiation by Earth’s magnetic field,and within an environment characterized by 24-hour day-night cycles resulting from Earth’s rotation,thus deviating from these conditions necessitates adaptive responses for survival.With upcoming manned lunar and Martian missions approaching rapidly,it is essential to understand the impact of various stressors induced by outer-space environments on cardiovascular health.This comprehensive review integrates insights from both actual space missions and simulated experiments on Earth,to analyze how microgravity,space radiation,and disrupted circadian affect cardiovascular well-being.Prolonged exposure to microgravity induces myocardial atrophy and endothelial dysfunction,which may be exacerbated by space radiation.Mitochondrial dysfunction and oxidative stress emerge as key underlying mechanisms along with disturbances in ion channel perturbations,cytoskeletal damage,and myofibril changes.Disruptions in circadian rhythms caused by factors such as microgravity,light exposure,and irregular work schedules,could further exacerbate cardiovascular issues.However,current research tends to predominantly focus on disruptions in the core clock gene,overlooking the multifactorial nature of circadian rhythm disturbances in space.Future space missions should prioritize targeted prevention strategies and early detection methods for identifying cardiovascular risks,to preserve astronaut health and ensure mission success.展开更多
Spaceflight and ground-based microgravity analog experiments have suggested that microgravity can affect microbial growth and metabolism. Although the effects of microgravity and its analogs on microorganisms have bee...Spaceflight and ground-based microgravity analog experiments have suggested that microgravity can affect microbial growth and metabolism. Although the effects of microgravity and its analogs on microorganisms have been studied for more than 50 years, plausible conflicting and diverse results have frequently been reported in different experiments, especially regarding microbial growth and secondary metabolism. Until now, only the responses of a few typical microbes to microgravity have been investigated; systematic studies of the genetic and phenotypic responses of these microorganisms to microgravity in space are still insufficient due to technological and logistical hurdles. The use of different test strains and secondary metabolites in these studies appears to have caused diverse and conflicting results. Moreover, subtle changes in the extracellular microenvironments around microbial cells play a key role in the diverse responses of microbial growth and secondary metabolisms. Therefore, "indirect" effects represent a reasonable pathway to explain the occurrence of these phenomena in microorganisms. This review summarizes current knowledge on the changes in microbial growth and secondary metabolism in response to spaceflight and its analogs and discusses the diverse and conflicting results. In addition, recommendations are given for future studies on the effects of microgravity in space on microbial growth and secondary metabolism.展开更多
When analyze the uncertainty of the cost and the schedule of the spaceflight project, it is needed to know the value of the schedule-cost correlation coefficient. This paper deduces the schedule distribution, consider...When analyze the uncertainty of the cost and the schedule of the spaceflight project, it is needed to know the value of the schedule-cost correlation coefficient. This paper deduces the schedule distribution, considering the effect of the cost, and proposes the estimation formula of the correlation coefficient between the in（schedule） and the cost. On the basis of the fact and Taylor expansion, the relation expression between the schedule-cost correlation coefficient and the in-schedule-cost correlation coefficient is put forward. By analyzing the value features of the estimation formula of the in-schedule-cost correlation coefficient, the general rules are proposed to ascertain the value of the schedule-cost correlation coefficient. An example is given to demonstrate how to approximately amend the schedule-cost correlation coefficient based on the historical statistics, which reveals the traditional assigned value is inaccurate. The universality of this estimation method is analyzed.展开更多
[ Objective] To explore the effects of spaceflight on the second-generation seeds of alfalfa and provide a theoretical basis for mutation breeding. [Method] The seeds of Medicago stavia L. lines no. 1, no. 2 and no. 4...[ Objective] To explore the effects of spaceflight on the second-generation seeds of alfalfa and provide a theoretical basis for mutation breeding. [Method] The seeds of Medicago stavia L. lines no. 1, no. 2 and no. 4 were carried into space by the Shijian-8 seed breeding satellite for a 15-d spaceflight treatment. After returning to the ground, seedlings were transplanted to field. Traits of the second-generation seeds of alfalfa were evaluated. [Result] The 1 000-grain weight of the second-generation seeds were 5% -9% significantly higher than that the control （P 〈 0.05）. The germination rate, seedling weight, shoot length and root length were significantly increased （P 〈 0.05）. The hard seed rate and the rate of moldy seeds were significantly decreased （ P 〈 0.05）. However, the rate of dead seeds was increased. [ Conclusion] Spaceflight treatment has positive mutagenic effects on the second-generation seeds of alfalfa.展开更多
Highly relativistic speeds are desirable for interstellar travel. Relativistic time dilation would reduce the subjective duration of the trip for the travelers, so that they can cover galaxy-scale distances in a reaso...Highly relativistic speeds are desirable for interstellar travel. Relativistic time dilation would reduce the subjective duration of the trip for the travelers, so that they can cover galaxy-scale distances in a reasonable amount of personal time. Unfortunately, as spaceship velocities approach the speed of light, interstellar hydrogen H, although only present at a density of approximately 1.8 atoms/cm3, turns into intense radiation that would quickly kill passengers and destroy electronic instrumentation. In addition, the energy loss of ionizing radiation passing through the ship’s hull represents an increasing heat load that necessitates large expenditures of energy to cool the ship. Stopping or diverting this flux, either with material or electromagnetic shields, is a daunting problem. Going slow to avoid severe H irradiation sets an upper speed limit of v ~ 0.5 c. This velocity only gives a time dilation factor of about 15%, which would not substantially assist galaxy-scale voyages. Diffuse interstellar H atoms are the ultimate cosmic space mines and represent a formidable obstacle to interstellar travel.展开更多
To evaluate the cost risk and the schedule risk of the spaceflight project,the schedule-cost(S-C)correlation coefficient is directly appointed according to the experts'experience usually.This paper deduces SDMCU(t...To evaluate the cost risk and the schedule risk of the spaceflight project,the schedule-cost(S-C)correlation coefficient is directly appointed according to the experts'experience usually.This paper deduces SDMCU(the schedule distribution model considering the effect of the cost uncertainty),and then proposes the approximate formula to estimate the ln(S)-C correlation coefficient based on the models of SDMCU and CDMSU(the cost distribution model considering the effect of the schedule uncertainty).Furthermore,an approximate relationship expression of the S-C and the ln(S)-C correlation coefficients is put forward according to general facts and the Taylor expansion,and advanced by means of mass numerical validation is the general rule of obtaining the estimation value of the schedule-cost correlation coefficient based on the historical data.展开更多
On September 21,1992, the feasibility report on implementing China's Manned Spaceflight Project was approved and a three-step development strategy was also determined. From then on, China's Manned Spaceflight ...On September 21,1992, the feasibility report on implementing China's Manned Spaceflight Project was approved and a three-step development strategy was also determined. From then on, China's Manned Spaceflight Project has developed rapidly.展开更多
The LM-2F launch vehicle is China's first launch carrier developed for China's Manned Space Program,which is one of the most important parts of the Program.It is developed from the LM-2E launch vehicle,with ad...The LM-2F launch vehicle is China's first launch carrier developed for China's Manned Space Program,which is one of the most important parts of the Program.It is developed from the LM-2E launch vehicle,with addition of two new systems,an escape system and a fault detection system.展开更多
Dear Editor,As space exploration transitions from short orbital missions to extended stays on the International Space Station(ISS)and,ultimately,interplanetary travel,astronaut health has emerged as a critical focus.I...Dear Editor,As space exploration transitions from short orbital missions to extended stays on the International Space Station(ISS)and,ultimately,interplanetary travel,astronaut health has emerged as a critical focus.In particular,safeguarding cardiovascular function has become an operational imperative.Yet beyond safeguarding those in orbit,the physiological adaptations observed in microgravity offer a compelling lens through which to examine persistent challenges in terrestrial medicine,from orthostatic intolerance in the elderly to deconditioning in critical care survivors.By studying how the human cardiovascular system functions in the absence of gravity.展开更多
The Chinese space station will be built around 2020. As a national space laboratory, it will offer unique opportunities for studying the physiological effects of weightlessness and the efficacy of the countermeasures ...The Chinese space station will be built around 2020. As a national space laboratory, it will offer unique opportunities for studying the physiological effects of weightlessness and the efficacy of the countermeasures against such effects. In this paper, we described the development of countermeasure systems in the Chinese space program. To emphasize the need of the Chinese space program to implement its own program for developing countermeasures, we reviewed the literature on the negative physiological effects of weightlessness, the challenges of completing missions, the development of countermeasure devices, the establishment of countermeasure programs, and the efficacy of the countermeasure techniques in American and Russian manned spaceflights. In addition, a brief overview was provided on the Chinese research and development on countermeasures to discuss the current status and goals of the development of countermeasures against physiological problems associated with weightlessness.展开更多
While early investigations into the physiological effects of spaceflight suggest the body’s ability to reversibly adapt,the corresponding effects of long-term spaceflight(>6months)aremuch less conclusive.Prolonged...While early investigations into the physiological effects of spaceflight suggest the body’s ability to reversibly adapt,the corresponding effects of long-term spaceflight(>6months)aremuch less conclusive.Prolonged exposure to microgravity and radiation yields profound effects on the cardiovascular system,including a massive cephalad fluid translocation and altered arterial pressure,which attenuate blood pressure regulatory mechanisms and increase cardiac output.Also,central venous pressure decreases as a result of the loss of venous compression.The stimulation of baroreceptors by the cephalad shift results in an approximately 10%–15%reduction in plasma volume,with fluid translocating from the vascular lumen to the interstitium.Despite possible increases in cardiac workload,myocyte atrophy and notable,yet unexplained,alterations in hematocrit have been observed.Atrophy is postulated to result from shunting of protein synthesis from the endoplasmic reticulum to the mitochondria via mortalin-mediated action.While data are scarce regarding their causative agents,arrhythmias have been frequently reported,albeit sublethal,during both Russian and American expeditions,with QT interval prolongation observed in long,but not short duration,spaceflight.Exposure of the heart to the proton and heavy ion radiation of deep space has also been shown to result in coronary artery degeneration,aortic stiffness,carotid intima thickening via collagen-mediated action,accelerated atherosclerosis,and induction of a pro-inflammatory state.Upon return,long-term spaceflight frequently results in orthostatic intolerance and altered sympathetic responses,which can prove hazardous should any rapidmobilization or evacuation be required,and indicates that these cardiac risks should be especially monitored for future missions.展开更多
Controlled ecological life support systems provide food, air, water, and other basic living resources for crew members on long-duration spaceflight missions. Plants are an important basic requirement of these systems ...Controlled ecological life support systems provide food, air, water, and other basic living resources for crew members on long-duration spaceflight missions. Plants are an important basic requirement of these systems and their biological characteristics in space have very high research value. Based on experiments of spaceflight in Shenzhou 8 spacecraft and simulating microgravity effects on three-dimensional （3-D） clinostat, the biological characteristics of tomato＇s leaf cell sub-microstructure and antioxidant enzyme activities were studied and compared in this work. Results showed that leaf cell sub-microstructure of the tomato samples experiencing spaceflight had more changes than effects, and both peroxidase （POD） and superoxide dismutase （SOD） that of the samples processed by simulated microgravity activities increase obviously in both the environments.展开更多
Objective: Spaceflight has long been perceived as an effective way to improve the quantity and quality of plants with wide applications. In order to obtain stable and inheritable descendants of spaceflightinduced Salv...Objective: Spaceflight has long been perceived as an effective way to improve the quantity and quality of plants with wide applications. In order to obtain stable and inheritable descendants of spaceflightinduced Salvia miltiorrhiza lines, we investigated and analyzed four lines m16, m50, m51, m57(three individuals of each line) and the ground control(three individuals) of the third generation of spaceflight-induced S. miltiorrhiza from primary/secondary metabolism and antioxidative abilities.Methods: A portable photosynthesis system(Li-6400) with red/blue LED light source was used to perform the photosynthetic characteristics to evaluate their primary productivity. The secondary metabolites(phenolic acids, tanshinones, total phenolics and flavonoids) and antioxidant activity of roots were analyzed to assess their quality.Results: Compared with control, line m16 presented weak photosynthetic ability, but high apparent quantum yield(AQY), higher contents of secondary metabolites, and stronger antioxidative abilities.Line m57 had a strong gas exchange ability, relatively higher secondary metabolites contents, and ascending antioxidative abilities. Lines m50 and m51 were in the middle level of lines m16 and m57.The principal component analysis for all the original data revealed three components including a rootrelated index, a leaf-related index, and a CO_(2) response parameter could be used to distinguish spaceflight-induced S. miltiorrhiza lines.Conclusion: Line m57 could be an appropriate material for the investigation of targeted breeding towards high production, and line m16 could be used to identify essential genes and unravel sophisticated pathways underlying the secondary metabolisms.展开更多
基金supported by the National Natural Science Fund for Distinguished Young Scholars of China(82125004).
文摘The advancement in extraterrestrial exploration has highlighted the crucial need for studying how the human cardiovascular system adapts to space conditions.Human development occurs under the influence of gravity,shielded from space radiation by Earth’s magnetic field,and within an environment characterized by 24-hour day-night cycles resulting from Earth’s rotation,thus deviating from these conditions necessitates adaptive responses for survival.With upcoming manned lunar and Martian missions approaching rapidly,it is essential to understand the impact of various stressors induced by outer-space environments on cardiovascular health.This comprehensive review integrates insights from both actual space missions and simulated experiments on Earth,to analyze how microgravity,space radiation,and disrupted circadian affect cardiovascular well-being.Prolonged exposure to microgravity induces myocardial atrophy and endothelial dysfunction,which may be exacerbated by space radiation.Mitochondrial dysfunction and oxidative stress emerge as key underlying mechanisms along with disturbances in ion channel perturbations,cytoskeletal damage,and myofibril changes.Disruptions in circadian rhythms caused by factors such as microgravity,light exposure,and irregular work schedules,could further exacerbate cardiovascular issues.However,current research tends to predominantly focus on disruptions in the core clock gene,overlooking the multifactorial nature of circadian rhythm disturbances in space.Future space missions should prioritize targeted prevention strategies and early detection methods for identifying cardiovascular risks,to preserve astronaut health and ensure mission success.
基金supported by the China Manned Space Engineering Program(CMSE,921–2)the National Program on Key Basic Research Project(973 Program,No.2014CB744400)the General Financial Grant from the China Postdoctoral Science Foundation(No.2016 M602971)
文摘Spaceflight and ground-based microgravity analog experiments have suggested that microgravity can affect microbial growth and metabolism. Although the effects of microgravity and its analogs on microorganisms have been studied for more than 50 years, plausible conflicting and diverse results have frequently been reported in different experiments, especially regarding microbial growth and secondary metabolism. Until now, only the responses of a few typical microbes to microgravity have been investigated; systematic studies of the genetic and phenotypic responses of these microorganisms to microgravity in space are still insufficient due to technological and logistical hurdles. The use of different test strains and secondary metabolites in these studies appears to have caused diverse and conflicting results. Moreover, subtle changes in the extracellular microenvironments around microbial cells play a key role in the diverse responses of microbial growth and secondary metabolisms. Therefore, "indirect" effects represent a reasonable pathway to explain the occurrence of these phenomena in microorganisms. This review summarizes current knowledge on the changes in microbial growth and secondary metabolism in response to spaceflight and its analogs and discusses the diverse and conflicting results. In addition, recommendations are given for future studies on the effects of microgravity in space on microbial growth and secondary metabolism.
基金This project was supported by Weapon System Advanced Research Foundation(51419010204KG01) and National ScienceFoundation of China(70272002).
文摘When analyze the uncertainty of the cost and the schedule of the spaceflight project, it is needed to know the value of the schedule-cost correlation coefficient. This paper deduces the schedule distribution, considering the effect of the cost, and proposes the estimation formula of the correlation coefficient between the in（schedule） and the cost. On the basis of the fact and Taylor expansion, the relation expression between the schedule-cost correlation coefficient and the in-schedule-cost correlation coefficient is put forward. By analyzing the value features of the estimation formula of the in-schedule-cost correlation coefficient, the general rules are proposed to ascertain the value of the schedule-cost correlation coefficient. An example is given to demonstrate how to approximately amend the schedule-cost correlation coefficient based on the historical statistics, which reveals the traditional assigned value is inaccurate. The universality of this estimation method is analyzed.
基金supported by the grants of the National Key Technology R&D Program (2008BADB3B04 )Basic Science and Research Special Fund for the State Level and Public Scientific Research Institute (Grassland Research Institute,Chinese Academy of Agricultural Sciences) (2007-1-02)
文摘[ Objective] To explore the effects of spaceflight on the second-generation seeds of alfalfa and provide a theoretical basis for mutation breeding. [Method] The seeds of Medicago stavia L. lines no. 1, no. 2 and no. 4 were carried into space by the Shijian-8 seed breeding satellite for a 15-d spaceflight treatment. After returning to the ground, seedlings were transplanted to field. Traits of the second-generation seeds of alfalfa were evaluated. [Result] The 1 000-grain weight of the second-generation seeds were 5% -9% significantly higher than that the control （P 〈 0.05）. The germination rate, seedling weight, shoot length and root length were significantly increased （P 〈 0.05）. The hard seed rate and the rate of moldy seeds were significantly decreased （ P 〈 0.05）. However, the rate of dead seeds was increased. [ Conclusion] Spaceflight treatment has positive mutagenic effects on the second-generation seeds of alfalfa.
文摘Highly relativistic speeds are desirable for interstellar travel. Relativistic time dilation would reduce the subjective duration of the trip for the travelers, so that they can cover galaxy-scale distances in a reasonable amount of personal time. Unfortunately, as spaceship velocities approach the speed of light, interstellar hydrogen H, although only present at a density of approximately 1.8 atoms/cm3, turns into intense radiation that would quickly kill passengers and destroy electronic instrumentation. In addition, the energy loss of ionizing radiation passing through the ship’s hull represents an increasing heat load that necessitates large expenditures of energy to cool the ship. Stopping or diverting this flux, either with material or electromagnetic shields, is a daunting problem. Going slow to avoid severe H irradiation sets an upper speed limit of v ~ 0.5 c. This velocity only gives a time dilation factor of about 15%, which would not substantially assist galaxy-scale voyages. Diffuse interstellar H atoms are the ultimate cosmic space mines and represent a formidable obstacle to interstellar travel.
文摘To evaluate the cost risk and the schedule risk of the spaceflight project,the schedule-cost(S-C)correlation coefficient is directly appointed according to the experts'experience usually.This paper deduces SDMCU(the schedule distribution model considering the effect of the cost uncertainty),and then proposes the approximate formula to estimate the ln(S)-C correlation coefficient based on the models of SDMCU and CDMSU(the cost distribution model considering the effect of the schedule uncertainty).Furthermore,an approximate relationship expression of the S-C and the ln(S)-C correlation coefficients is put forward according to general facts and the Taylor expansion,and advanced by means of mass numerical validation is the general rule of obtaining the estimation value of the schedule-cost correlation coefficient based on the historical data.
文摘On September 21,1992, the feasibility report on implementing China's Manned Spaceflight Project was approved and a three-step development strategy was also determined. From then on, China's Manned Spaceflight Project has developed rapidly.
文摘The LM-2F launch vehicle is China's first launch carrier developed for China's Manned Space Program,which is one of the most important parts of the Program.It is developed from the LM-2E launch vehicle,with addition of two new systems,an escape system and a fault detection system.
文摘Dear Editor,As space exploration transitions from short orbital missions to extended stays on the International Space Station(ISS)and,ultimately,interplanetary travel,astronaut health has emerged as a critical focus.In particular,safeguarding cardiovascular function has become an operational imperative.Yet beyond safeguarding those in orbit,the physiological adaptations observed in microgravity offer a compelling lens through which to examine persistent challenges in terrestrial medicine,from orthostatic intolerance in the elderly to deconditioning in critical care survivors.By studying how the human cardiovascular system functions in the absence of gravity.
基金the Chinese Manned Space Flight Projectthe National Natural Science Foundation of China (No.81571845)the Key Project of Logistics Research (No.BWS14C024).
文摘The Chinese space station will be built around 2020. As a national space laboratory, it will offer unique opportunities for studying the physiological effects of weightlessness and the efficacy of the countermeasures against such effects. In this paper, we described the development of countermeasure systems in the Chinese space program. To emphasize the need of the Chinese space program to implement its own program for developing countermeasures, we reviewed the literature on the negative physiological effects of weightlessness, the challenges of completing missions, the development of countermeasure devices, the establishment of countermeasure programs, and the efficacy of the countermeasure techniques in American and Russian manned spaceflights. In addition, a brief overview was provided on the Chinese research and development on countermeasures to discuss the current status and goals of the development of countermeasures against physiological problems associated with weightlessness.
基金Thisworkwas funded byNASA(GrantNos.NNX14AH50G and NNX17AB26G)the National Institutes of Health(Grant No.R25EB020393).
文摘While early investigations into the physiological effects of spaceflight suggest the body’s ability to reversibly adapt,the corresponding effects of long-term spaceflight(>6months)aremuch less conclusive.Prolonged exposure to microgravity and radiation yields profound effects on the cardiovascular system,including a massive cephalad fluid translocation and altered arterial pressure,which attenuate blood pressure regulatory mechanisms and increase cardiac output.Also,central venous pressure decreases as a result of the loss of venous compression.The stimulation of baroreceptors by the cephalad shift results in an approximately 10%–15%reduction in plasma volume,with fluid translocating from the vascular lumen to the interstitium.Despite possible increases in cardiac workload,myocyte atrophy and notable,yet unexplained,alterations in hematocrit have been observed.Atrophy is postulated to result from shunting of protein synthesis from the endoplasmic reticulum to the mitochondria via mortalin-mediated action.While data are scarce regarding their causative agents,arrhythmias have been frequently reported,albeit sublethal,during both Russian and American expeditions,with QT interval prolongation observed in long,but not short duration,spaceflight.Exposure of the heart to the proton and heavy ion radiation of deep space has also been shown to result in coronary artery degeneration,aortic stiffness,carotid intima thickening via collagen-mediated action,accelerated atherosclerosis,and induction of a pro-inflammatory state.Upon return,long-term spaceflight frequently results in orthostatic intolerance and altered sympathetic responses,which can prove hazardous should any rapidmobilization or evacuation be required,and indicates that these cardiac risks should be especially monitored for future missions.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2011CB710902)the National Manned Spaceflight Project of China
文摘Controlled ecological life support systems provide food, air, water, and other basic living resources for crew members on long-duration spaceflight missions. Plants are an important basic requirement of these systems and their biological characteristics in space have very high research value. Based on experiments of spaceflight in Shenzhou 8 spacecraft and simulating microgravity effects on three-dimensional （3-D） clinostat, the biological characteristics of tomato＇s leaf cell sub-microstructure and antioxidant enzyme activities were studied and compared in this work. Results showed that leaf cell sub-microstructure of the tomato samples experiencing spaceflight had more changes than effects, and both peroxidase （POD） and superoxide dismutase （SOD） that of the samples processed by simulated microgravity activities increase obviously in both the environments.
基金supported by grants from the Twelfth Five-Year Plan for Science&Technology Support of China(No.2015BAC01B03)the National Natural Science Foundation of China(No.81373908)。
文摘Objective: Spaceflight has long been perceived as an effective way to improve the quantity and quality of plants with wide applications. In order to obtain stable and inheritable descendants of spaceflightinduced Salvia miltiorrhiza lines, we investigated and analyzed four lines m16, m50, m51, m57(three individuals of each line) and the ground control(three individuals) of the third generation of spaceflight-induced S. miltiorrhiza from primary/secondary metabolism and antioxidative abilities.Methods: A portable photosynthesis system(Li-6400) with red/blue LED light source was used to perform the photosynthetic characteristics to evaluate their primary productivity. The secondary metabolites(phenolic acids, tanshinones, total phenolics and flavonoids) and antioxidant activity of roots were analyzed to assess their quality.Results: Compared with control, line m16 presented weak photosynthetic ability, but high apparent quantum yield(AQY), higher contents of secondary metabolites, and stronger antioxidative abilities.Line m57 had a strong gas exchange ability, relatively higher secondary metabolites contents, and ascending antioxidative abilities. Lines m50 and m51 were in the middle level of lines m16 and m57.The principal component analysis for all the original data revealed three components including a rootrelated index, a leaf-related index, and a CO_(2) response parameter could be used to distinguish spaceflight-induced S. miltiorrhiza lines.Conclusion: Line m57 could be an appropriate material for the investigation of targeted breeding towards high production, and line m16 could be used to identify essential genes and unravel sophisticated pathways underlying the secondary metabolisms.
