Figure 12. The discrepancy of d-aggregate GM and s-aggregate GM from the empirical data. This chapter explores gravity, its impact on life when gravity changes, necessity of gravity for life, and the role of gravity in the evolution of life on the Earth. However, some regions and their nearby regions include water-surface cells, potentially biasing the estimation of ρ¯(d). First, rapid population growth tends to increase income disparities between UDCs and developed countries because the per capita incomes decline with growth in numbers in the former. We set α=0.8, β=0.4 and γ=1.0. We set dag=1, with which we aggregated three cells to calculate the population density at the source or destination of the immigration in the two extensions of the GM. See, Somu-sho Tokei-kyoku ni okeru Chiiki Mesh Tokei no sakusei. The rapid growth diagram narrows to a point, indicating that the number of individuals decreases rapidly with age. Life from the cellular level through adult humans exposed to spaceflight is briefly examined and examples from spaceflight and ground-based experiments are discussed in the chapter. Much of this ability is related to human intelligence, society, and communication. All life on Earth evolved to live with the Earth's gravity, and humans are no exception. (a) d-aggregate GM, dag=1 km. 2004). This result reflects the observation that highly populated cells tend to grow and vice versa [35–37] (but see ). Gravity is thus a limiting factor in the growth of individual cells. Data are available from http://e-stat.go.jp/SG2/eStatGIS/page/download.html. Figure 1. The results were qualitatively the same as those based on the Pearson correlation coefficient (appendix D). A very massive body can compress matter ( hence increasing its density). (a) GM. This result suggests that cells surrounded by cells with a large (small) population density within ≈20 km are more … • The effect of density is not simple —it probably depends on many other factors in the situation. Countries with rapid growth have a pyramidal shape in their age structure diagrams, showing a preponderance of younger individuals, many of whom are of reproductive age or will be soon. A thin line represents ρk′(d) for aregion. (d) (t1,t2)= (2000,2005), dag=5 km. The thick lines represent ρ¯′(d), which is the average of ρk′(d) over all the regions. What type of population change do you think stage 4 represents? Dependence of the population growth rate in a cell on the population density at distance d, ρ¯(d), calculated for the population change between2000 and 2005. Growth hormone at high doses may decrease body fat in these patients, but the effects of growth hormone at more physiologic doses on bone density and body composition have not been convincingly shown. (b) (t1,t2)=(2000,2005). The diagonal in (a) is blank because the inflow and outflow are equal when α=β in the GM, resulting in no population change. (a) d-aggregate GM. The biggest problem about low gravity and development is reproduction. (a) Net flow for the GM. Figure 14. The depletion of the ozone layer, erosion due to acid rain, and damage from global climate change are caused by human activities. Many countries have attempted to reduce the human impact on climate change by reducing their emission of the greenhouse gas carbon dioxide. The present study has limitations. Figure 6. We set α=0.4, β=1.6 and γ=1.0. Data were obtained from refs. The net flow, inflow and outflow for the GM, d-aggregate GM and s-aggregate GM in the one-dimensional model with 21 cells. We set α=0.4, β=1.2 and γ=1.0.Download figureOpen in new tabDownload powerPointFigure 13. The two lines almost overlap with each other. The ρk(d) for each region k is plotted as a function of d in figure 14. We also confirmed that the discrepancy increased as dag increased (figures 20 and 21). (f) s-aggregate GM, dag=25 km.Download figureOpen in new tabDownload powerPoint. Table 2.The number of births, deaths, incoming inhabitants and outgoing inhabitants in the 47 prefectures in Japan between 2005 and 2009. The lack of data also prohibited us from looking into the effect of the age of inhabitants. The actual growth rates in different countries are shown in Figure 4, with the highest rates tending to be in the less economically developed countries of Africa and Asia. We set α=0.4, β=0.4 and γ=1.0.Download figureOpen in new tabDownload powerPointFigure 21. The ranges indicated by the dashed lines represent 95% confidence intervals (CIs) generated by spatially random distributions of the number of inhabitants on the inhabited cells. (c) s-aggregate GM. (c) s-aggregate GM. Dependence of the population growth rate in a cell on the population density at distance d, ρ¯(d). Because precise optimization is computationally too costly, we set γ=1 and set α, β∈{0.4,0.8,1.2,1.6} to search for the optimal pair of α and β. Efforts to control population growth led to the one-child policy in China, which used to include more severe consequences, but now imposes fines on urban couples who have more than one child. (b) d-aggregate GM. It’s difficult to tell what the gravity on another world is for sure without going there, as density can vary between worlds, but it doesn’t take much to begin adding the pounds. By examining the effects that microgravity can have on a human being, we can assume these effects will be the same but slightly less severe for humans on Mar’s surface. Cells which were naturally larger than the size that gravity alone would allow for had to develop means to protect against internal sedimentation. The age structure of a population is an important factor in population dynamics. For example, a recently proposed continuous-space GM assumes that the unit of analysis is an infinitesimally small spatial segment [12]. Humans are unique in their ability to alter their environment with the conscious purpose of increasing its carrying capacity. Figure 7 confirms that the results shown in figure 6 remain qualitatively the same in a wide range of α and β. (c) d-aggregate GM, dag=5 km. We tested an intermittent short-arm centrifuge of 1.4 G with 60-W ergometric exercise with a step-up increase of 0.2 G and 15 W, respectively, for 30 min every day for 21 days during −6° head-down bedrest . We set α=0.8, β=0.4 and γ=1.0. Studies of migration, such as those using the GM [8,17] and other migration models [11,22], are often based on subdivisions of the space that define the unit of analysis such as administrative units (e.g. The relative contribution of migration to demographic dynamics, denoted by RC in the table, is defined by (inflow + outflow)/(the number of births + the number of deaths + inflow + outflow). This correlation length was shorter than that observed in previous studies of data recorded in the USA [31] (≈1000 km) and spatial correlation in the population growth rate in Spain [33] (≈500 km) and the USA [34] (over 5000 km). In spite of this fact, human population is still growing exponentially. The results for the three models are shown in figure 5. Both authors wrote the manuscript. In astronomy there are many examples. We set G=(13)α+β−1, α=0.4, β=0.6 and γ=1.0.Download figureOpen in new tabDownload powerPoint. Rapid population growth also affects UDCs in relation to the world economy in a number of ways. To examine the statistical significance of ρ¯(d), we carried out bootstrap tests by shuffling the number of inhabitants in the populated cells at t2 without shuffling that at t1 and calculating ρ¯(d). (h) Inflow for the s-aggregate GM. The results for the different regions are superposed on top of each other.The thick lines represent ρ¯(d), which is the average of ρk(d) over all the regions. Figure 17. We varied the values of dag. the value of ρ¯(d) decayed faster than the empirical values. Therefore, migration rather than births and deaths seems to be a main driver of spatially untangled population changes in Japan during the observation period. s-aggregate GM with dag=25 km shown in figure 6b). To compare to some of the epidemics of the past, the percentage of the world’s population killed between 1993 and 2002 decreased from 0.30 percent of the world’s population to 0.24 percent. (a) (t1,t2)=(2005,2010). In NZ many farms have seen there soils bulk densities increase over time decreasing soil productivity The data on 2000 are also publicly available although they are less accurate than those in 2005 and 2010 [30]. This issue is related to the modifiable areal unit problem in geography, which stipulates that different units of analysis may provide different results [23]. Dependence of the population growth rate in a cell on the population density at distance d, ρk(d), calculated from the empirical data. The model has attained reasonably accurate description of human migration in some cases [8,16,17], as well as other phenomena such as international trades [18,19] and the volume of phone calls between cities [20,21]. (b) (t1,t2)=(2000,2005). We set α=0.4, β=0.4, γ=1 and dag=0.65 km. In the main text, we refer to the two time points 2005 and 2010 as t1 and t2, respectively. If this is the case, individuals may make decisions by taking into account the environment in a neighbourhood of the current residence and/or the destination of the migration up to a certain distance. The distribution of inhabitants at time t2 (i.e. (b) d-aggregate GM. Portal Site of Official Statistics of Japan. Di(d), is therefore underestimated when cell i is located near water (e.g. Therefore, we examined the ρk(d) values for region k such that all cells within region k and those within 30 km from any cell in region k are not in the sea. (a) (t1,t2)=(2005,2010). Although humans have increased the carrying capacity of their environment, the technologies used to achieve this transformation have caused unprecedented changes to Earth’s environment, altering ecosystems to the point where some may be in danger of collapse. As shown in the following, the results were qualitatively the same as those shown in the main text for (t1,t2)=(2005,2010) (figures 4–7), except for the behaviour of the GM. The ranges indicated by the dashed lines represent 95% confidence intervals (CIs) generated by spatially random distributions of the number of inhabitants on the inhabited cells.Download figureOpen in new tabDownload powerPoint. A consequence of exponential human population growth is the time that it takes to add a particular number of humans to the Earth is becoming shorter. Figure 15. We investigated spatial patterns of demographic dynamics through the analysis of the population census data in Japan in 2005 and 2010. For example, particular partitions of geographical areas can affect parameter estimates of gravity models [24]. Dependence of the population growth rate in a cell on the population density at distance d, ρ¯(d), calculated for the population change between2000 and 2005. And it would be an immediate physiological adjustment, not a long-term genetic one. The inflow for the d-aggregate GM was similar to that for the GM (figure 9h) and the outflow decreased as x′ increased for the d-aggregate GM (figure 9i). We set γ=1 and dag=0.65 km.Download figureOpen in new tabDownload powerPoint. Mass is independent of gravity, unlike weight, which is the force exerted by mass due to the acceleration of gravity (F = ma). In space, without gravity, bones lose … Figure 3: Typical age structure diagrams are shown. This inconsistency was due to an increase in the outflow at the central cell as x′ increased (figure 9c), whereas the inflow at the central cell was not sensitive to x′ (figure 9b). We can think of gravity as the invisible force that pulls two masses together. (a) GM. The distribution of inhabitants at time t2 (i.e. Figure 9. In addition, the minimum discrepancy for the GM (=1.469) was larger than that for the d-aggregate GM and s-aggregate GM (=1.163 and 1.161, respectively). As d increased, ρ¯(d) decreased and reached ≈0 for d≥20 km. Thus, we enter the future with considerable uncertainty about our ability to curb human population growth and protect our environment. The patterns of migration flows for the d-aggregate and s-aggregate GMs were qualitatively different from those for the GM (figure 9d–i). The diagonals in (a) are blank because the inflow and outflow are the same when α=β in the GM, resulting in a zero population growth rate in all cells. (b) s-aggregate GM, dag=1 km. Gravity can and does affect density. When dag=5 and 25 km, the behaviour of ρ¯(d) was qualitatively different, with ρ¯(d) first increasing and then decreasing as d increased, or even more complicated behaviour (i.e. However, there is no a priori reason to assume that any one of these units is an appropriate choice. The policy itself, its social impacts, and the effectiveness of limiting overall population growth are controversial. We set α=0.4, β=1.6, γ=1 and dag=0.65 km. That's why astronauts can look odd: their faces, filled with fluid, puff up, and their legs, which can lose about a liter of fluid each, thin out. A dark hue represents a large discrepancy value. This ability is a major factor responsible for human population growth and a way of overcoming density-dependent growth regulation. The number of inhabitants in cell i (1≤i≤K) at time t is denoted by ni(t). The ordinary gravity model does not capture this empirical observation. (i) Outflow for the s-aggregate GM.Download figureOpen in new tabDownload powerPoint. Humans are unique in their ability to alter their environment with the conscious purpose of increasing its carrying capacity. (g) Net flow for the s-aggregate GM. N.M. acknowledges the support provided through JST, ERATO, Kawarabayashi Large Graph Project. Many Sci fi books and films have artificial gravity for example in Enders Game the school had an artificial gravity field and zero gravity in the battle room. Figure 16. Basic statistics of the data at the three time points are presented in table 1. At some point the food supply may run out because of the subsequent need to produce more and more food to feed our population. To reach its biotic potential, all females would have to become pregnant every nine months or so during their reproductive years. A region included 9600 cells at most. Dependence of the population growth rate in a cell on the population density at distance d, ρk(d), calculated from the empirical data. We set x=2.8 and x′=2.2 for illustration. (b) (t1,t2)=(2000,2005), dag=1 km. The schematic of the GM models on a chain. We found that the population growth rate in a cell was positively correlated with the population density in cells nearby, in addition to that in the focal cell. In spite of population control policies, the human population continues to grow. Figure 15. We thus divided the range of the latitude into 45 windows, i.e. Many dire predictions have been made about the world’s population leading to a major crisis called the “population explosion.” In the 1968 book The Population Bomb, biologist Dr. Paul R. Ehrlich wrote, “The battle to feed all of humanity is over. Combined with the simplifying assumption of the one-dimensional landscape, we aimed at revealing a minimal set of conditions under which the empirically observed patterns were produced. Figure 18. (b) d-aggregate GM. We set γ=1 and dag= 0.65 km.Download figureOpen in new tabDownload powerPointFigure 20. The world’s human population is currently experiencing exponential growth even though human reproduction is far below its biotic potential (Figure 1). In the d-aggregate GM, this change was mainly owing to changes in the inflow, which increased as x′ increased (figure 9e). We deemed the value of ρ¯(d) for the original data to be significant if it was not included in the 95% confidential interval (CI) calculated on the basis of the 100 randomized samples. (d) (t1,t2)= (2000,2005), dag=5 km. In the analysis of the growth rate of cells described in this section, we only used focal cells i whose population size was between 10 and 100 at t1. The relative contribution of migration to demographic dynamics, denoted by RC in the table, is defined by (inflow + outflow)/(the number of births + the number of deaths + inflow + outflow). (g) Net flow for the s-aggregate GM. Furthermore, the role of human activity in causing climate change has become a hotly debated socio-political issue in some developed countries, including the United States. This result was inconsistent with the empirically observed pattern (figure 4). The discrepancy of the GM, d-aggregate GM and s-aggregate GM from the empirical data, calculated for the population change between 2000 and 2005. We generated 100 randomized samples and calculated the distribution of ρ¯(d) for each sample. Blood pressure equalizes and becomes about 100 mmHg throughout the body. Human population growth since 1000 AD is exponential (dark blue line). The thicklines represent the average of ρk(d) over all the regions satisfying the aforementioned criterion. (c) d-aggregate GM, dag=5 km. We then show that the empirical observation is better accounted for by extensions of the gravity model such that individuals are assumed to perceive the attractiveness, approximated by the population density, of the source or destination cell of migration as the spatial average over a circle of radius ≈1 km. When a baby forms, its cells differentiate often. Dependence of the population growth rate in a cell on the population density at distance d, ρk(d), calculated from the empirical data. Dependence of the population growth rate in a cell on the population density at distance d, ρ¯(d), calculated from the empirical data and the numerical datagenerated from the sd-aggregate GM. Due to the fact that some couples wish to have a male heir, many Chinese couples continue to have more than one child. We set dag, the width for spatial smoothing of the population density at the source or destination cell in the extended GM models, to 0.65 km in the previous sections. This work is supported by JST, CREST (grant no. In fact, individuals at a certain life stage are more likely to migrate in general [4,5]. The correlation measure C(d) is defined by equation (2.1), and d is the distance between the two cells. A thin line represents ρk(d) for such a 50×50 km region. http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited. The initial condition is a symmetric distribution of the density of inhabitants that is uniform except in the central three cells. It should be noted that cell i may be partially water-surfaced. After more than 50 years of human spaceflight, NASA is an expert in what happens to the human body when it’s in zero gravity. Figure 4. The discrepancy between the model and empirical data (equation (2.8)) was small in a wide parameter region (figure 19). The net flow, inflow and outflow in the three models are shown in figure 9. The d-aggregate GM yielded a good agreement with the data in a wide parameter region (figure 11b). The data obtained from the GM were inaccurate except when α or β was small. Figure 11. Reduced gravity also altered angeogenesis and vasculogenesis and promoted genes involved in rheumatoid arthritis, tumor growth and wound … Aggregation of cells near the destination cell models behaviour of individuals that perceive the population of the destination cell as a sum (or average) of the population over the cells neighbouring the destination cell. Volcanic eruptions represent an example of density-dependent limits on population growth False Which of the following examples of population growth in nonhuman organisms show a pattern similar to that of the humans on Easter Island? year 2010). Other significant effects include fluid redistribution (causing the "moon-face" appearance typical of pictures of astronauts in weightlessness), a slowing of the cardiovascular system as blood flow decreases in response to a lack of gravity, a decreased production of red blood cells, balance disorders, and a weakening of the immune system. The results for the different regions are superposed on top of each other.The thick lines represent ρ¯(d), which is the average of ρk(d) over all the regions. Therefore, we measured the spatial correlation coefficient in the population size between a pair of cells, C(d), where d was the distance between a pair of cells. In the main text, we showed the values of ρk(d) averaged over all regions of size 50×50 km, denoted by ρ¯(d) (figure 4). (c) Outflow for the GM. See, Effects of the distant population density on spatial patterns of demographic dynamics, The number of births, deaths, incoming inhabitants and outgoing inhabitants in the 47 prefectures in Japan between 2005 and 2009. And it would be an immediate physiological adjustment, not a long-term genetic one. (b) (t1,t2)=(2000,2005). Data on migration flows between cells, births, deaths and the age distribution, which are not included in the present dataset, are expected to enable further investigations of the spatial patterns of population changes examined in the present study. The average of RC over the 47 prefectures is 0.801. The Effects of Hypergravity. Figure 13. The thicklines represent the average of ρk(d) over all the regions satisfying the aforementioned criterion. Notice that the highest growth is occurring in less economically developed countries in Africa and Asia. The authors declare that they have no competing interests. http://cnx.org/contents/185cbf87-c72e-48f5-b51e-f14f21b5eabd@9.44:1/Biology. You are basically looking at all the same physiological effects as weightlessness, just to a lesser degree. (f) Outflow for the d-aggregate GM. If the address matches an existing account you will receive an email with instructions to reset your password. We simulated migration dynamics using the gravity model [8,10,15] and its variants and compared the projection obtained from the models with the empirical data. (c) Outflow for the GM. In the main text, we used the data on the population census in Japan in 2005 and 2010. We measured the spatial correlation in the number of inhabitants between a pair of cells at distance d by [31]. Global death from infectious disease declined from 16.4 million in 1993 to 14.7 million 1993. The objects toward the Earth, and humans are no exception affected various! Life stage are more dramatic in young, developing mice may run out because the. And select “ Launch movie ” for an animation discussing the global impacts human! Two cells figure 6b ) old age because of less-than-optimal living conditions spatial average on scale! Less economically developed countries in Africa and Asia attempted to reduce the human body there is no a priori to! 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