American Institute of Mathematical Sciences

Advanced
June  2018, 23(4): 1559-1579. doi: 10.3934/dcdsb.2018059

Dynamics of a Lotka-Volterra competition-diffusion model with stage structure and spatial heterogeneity

Shuling Yan 1,2, and  Shangjiang Guo 1,,

1. 

College of Mathematics and Econometrics, Hunan University, Changsha, Hunan 410082, China
2. 

Department of Mathematics and Statistics, Jiangsu Normal University, Xuzhou, Jiangsu 221116, China

* Corresponding author: S. Guo

Received  April 2017 Revised  August 2017 Published  February 2018

Fund Project: The second author is supported by NSF of China (Grants No. 11671123).

This paper is concerned with a Lotka-Volterra competition-diffusion model with stage structure and spatial heterogeneity. By analyzing the sign of the principal eigenvalue corresponding to each semi-trivial solution, we obtain the linear stability and global attractivity of the semi-trivial solution. In addition, an attracting region was obtained by means of the method of upper and lower solutions.

Keywords: Spatial heterogeneity, stage structure, Lotka-Volterra competition, steady state solution.
Mathematics Subject Classification: Primary: 92D25, 92D40; Secondary: 35K57.
Citation: Shuling Yan, Shangjiang Guo. Dynamics of a Lotka-Volterra competition-diffusion model with stage structure and spatial heterogeneity. Discrete & Continuous Dynamical Systems - B, 2018, 23 (4) : 1559-1579. doi: 10.3934/dcdsb.2018059
References:
[1]

W.G. Aiello and H. I. Freedman, A time-delay model of single-species growth with stage structure, Mathematical Biosciences, 101 (1990), 139-153.  doi: 10.1016/0025-5564(90)90019-U.  Google Scholar

[2]

S. Busenberg and W. Huang, Stability and Hopf bifurcation for a population delay model with diffusion effects, Journal of Differential Equations, 124 (1996), 80-107.  doi: 10.1006/jdeq.1996.0003.  Google Scholar

[3]

R. S. Cantrell and C. Cosner, Spatial Ecology Via Reaction-Diffusion Equations, John Wiley & Sons, 2003.  Google Scholar

[4]

S. Chen and J. Shi, Stability and hopf bifurcation in a diffusive logistic population model with nonlocal delay effect, Journal of Differential Equations, 253 (2012), 3440-3470.  doi: 10.1016/j.jde.2012.08.031.  Google Scholar

[5]

T. Faria, Stability and bifurcation for a delayed predator-prey model and the effect of diffusion, Journal of Mathematical Analysis and Applications, 254 (2001), 433-463.  doi: 10.1006/jmaa.2000.7182.  Google Scholar

[6]

H. I. Freedman and X. Zhao, Global asymptotics in some quasimonotone reaction-diffusion systems with delays, Journal of Differential Equations, 137 (1997), 340-362.  doi: 10.1006/jdeq.1997.3264.  Google Scholar

[7]

P. Georgescu and Y.-H. Hsieh, Global dynamics of a predator-prey model with stage structure for the predator, SIAM Journal on Applied Mathematics, 67 (2007), 1379-1395.  doi: 10.1137/060670377.  Google Scholar

[8]

S.A. Gourley and Y. Kuang, A delay reaction-diffusion model of the spread of bacteriophage infection, SIAM Journal on Applied Mathematics, 65 (2004), 550-566.  doi: 10.1137/S0036139903436613.  Google Scholar

[9]

S. Guo, Stability and bifurcation in a reaction-diffusion model with nonlocal delay effect, Journal of Differential Equations, 259 (2015), 1409-1448.  doi: 10.1016/j.jde.2015.03.006.  Google Scholar

[10]

S. Guo, Spatio-temporal patterns in a diffusive model with non-local delay effect, IMA Journal of Applied Mathematics, 82 (2017), 864-908.  doi: 10.1093/imamat/hxx018.  Google Scholar

[11]

S. Guo, Y. Chen and J. Wu, Two-parameter bifurcations in a network of two neurons with multiple delays, Journal of Differential Equations, 244 (2008), 444-486.  doi: 10.1016/j.jde.2007.09.008.  Google Scholar

[12]

S. Guo and L. Ma, Stability and bifurcation in a delayed reaction-diffusion equation with dirichlet boundary condition, Journal of Nonlinear Science, 26 (2016), 545-580.  doi: 10.1007/s00332-016-9285-x.  Google Scholar

[13]

S. Guo and J. Wu, Bifurcation Theory of Functional Differential Equations, Springer, 2013.  Google Scholar

[14]

S. Guo and S. Yan, Hopf bifurcation in a diffusive Lotka-Volterra type system with nonlocal delay effect, Journal of Differential Equations, 260 (2016), 781-817.  doi: 10.1016/j.jde.2015.09.031.  Google Scholar

[15]

X. He and W. Ni, The effects of diffusion and spatial variation in Lotka-Volterra competition--diffusion system I: Heterogeneity vs. homogeneity, Journal of Differential Equations, 254 (2013), 528-546.  doi: 10.1016/j.jde.2012.08.032.  Google Scholar

[16]

X. He and W. Ni, Global dynamics of the Lotka-Volterra competition-diffusion system: Diffusion and spatial heterogeneity I, Communications on Pure and Applied Mathematics, 69 (2016), 981-1014.  doi: 10.1002/cpa.21596.  Google Scholar

[17]

W. Huang, Global dynamics for a reaction--diffusion equation with time delay, Journal of Differential Equations, 143 (1998), 293-326.  doi: 10.1006/jdeq.1997.3374.  Google Scholar

[18]

K.-Y. Lam and W. Ni, Uniqueness and complete dynamics in heterogeneous competition-diffusion systems, SIAM Journal on Applied Mathematics, 72 (2012), 1695-1712.  doi: 10.1137/120869481.  Google Scholar

[19]

D. Li and S. Guo, Bifurcation and stability of a Mimura-Tsujikawa model with nonlocal delay effect, Mathematical Methods in the Applied Sciences, 40 (2017), 2219-2247.   Google Scholar

[20]

J. Li and Z. Ma, Stability switches in a class of characteristic equations with delay-dependent parameters, Nonlinear Analysis: Real World Applications, 5 (2004), 389-408.  doi: 10.1016/j.nonrwa.2003.06.001.  Google Scholar

[21]

Z. Li, M. Han and F. Chen, Global stability of a predator-prey system with stage structure and mutual interference, Discrete & Continuous Dynamical Systems-Series B, 19 (2014), 173-187.   Google Scholar

[22]

Y. Lin, X. Xie, F. Chen and T. Li, Convergences of a stage-structured predator-prey model with modified Leslie-Gower and Holling-type II schemes, Advances in Difference Equations, 2016 (2016), 19pp.  Google Scholar

[23]

S. Liu, L. Chen, G. Luo and Y. Jiang, Asymptotic behaviors of competitive Lotka-Volterra system with stage structure, Journal of Mathematical Analysis and Applications, 271 (2002), 124-138.  doi: 10.1016/S0022-247X(02)00103-8.  Google Scholar

[24]

R. H. Martin and H. L. Smith, Abstract functional-differential equations and reaction-diffusion systems, Transactions of the American Mathematical Society, 321 (1990), 1-44.   Google Scholar

[25]

C. V. Pao, Coupled nonlinear parabolic systems with time delays, Journal of Mathematical Analysis and Applications, 196 (1995), 237-265.  doi: 10.1006/jmaa.1995.1408.  Google Scholar

[26]

C. V. Pao, Dynamics of nonlinear parabolic systems with time delays, Journal of Mathematical Analysis and Applications, 198 (1996), 751-779.  doi: 10.1006/jmaa.1996.0111.  Google Scholar

[27]

M. H. Protter and H. F. Weinberger, Maximum Principles in Differential Equations, Springer-Verlag, New York, 1984.  Google Scholar

[28]

Y. Qu and J. Wei, Bifurcation analysis in a predator--prey system with stage-structure and harvesting, Journal of the Franklin Institute, 347 (2010), 1097-1113.  doi: 10.1016/j.jfranklin.2010.03.017.  Google Scholar

[29]

H. L. Smith, Monotone Dynamical Systems: An Introduction to the Theory of Competitive and Cooperative Systems, Mathematical Surveys and Monographs, 41. American Mathematical Society, Providence, RI, 1995.  Google Scholar

[30]

X. Song and L. Chen, Optimal harvesting and stability for a predator-prey system with stage structure, Acta Mathematicae Applicatae Sinica, 18 (2002), 423-430.  doi: 10.1007/s102550200042.  Google Scholar

[31]

H.R. Thieme and X. Zhao, A non-local delayed and diffusive predator--prey model, Nonlinear Analysis: Real World Applications, 2 (2001), 145-160.  doi: 10.1016/S0362-546X(00)00112-7.  Google Scholar

[32]

C. C. Travis and G. F. Webb, Existence and stability for partial functional differential equations, Transactions of the American Mathematical Society, 200 (1974), 395-418.  doi: 10.1090/S0002-9947-1974-0382808-3.  Google Scholar

[33]

J. Wu, Theory and Applications of Partial Functional Differential Equations, volume 119. Springer Science & Business Media, 1996.  Google Scholar

[34]

M. Xiao and J. Cao, Stability and Hopf bifurcation in a delayed competitive web sites model, Physics Letters A, 353 (2006), 138-150.   Google Scholar

[35]

S. Yan and S. Guo, Bifurcation phenomena in a {L}otka-{V}olterra model with cross-diffusion and delay effect, International Journal of Bifurcation and Chaos, 27 (2017), 1750105, 24pp.  Google Scholar

[36]

S. Yan and S. Guo, Stability analysis of a stage structure model with spatiotemporal delay effect, Computers & Mathematics with Applications, 73 (2017), 310-326.  doi: 10.1016/j.camwa.2016.11.029.  Google Scholar

[37]

T. Yi and X. Zou, Global attractivity of the diffusive Nicholson blowflies equation with Neumann boundary condition: a non-monotone case, Journal of Differential Equations, 245 (2008), 3376-3388.  doi: 10.1016/j.jde.2008.03.007.  Google Scholar

show all references

References:
[1]

W.G. Aiello and H. I. Freedman, A time-delay model of single-species growth with stage structure, Mathematical Biosciences, 101 (1990), 139-153.  doi: 10.1016/0025-5564(90)90019-U.  Google Scholar

[2]

S. Busenberg and W. Huang, Stability and Hopf bifurcation for a population delay model with diffusion effects, Journal of Differential Equations, 124 (1996), 80-107.  doi: 10.1006/jdeq.1996.0003.  Google Scholar

[3]

R. S. Cantrell and C. Cosner, Spatial Ecology Via Reaction-Diffusion Equations, John Wiley & Sons, 2003.  Google Scholar

[4]

S. Chen and J. Shi, Stability and hopf bifurcation in a diffusive logistic population model with nonlocal delay effect, Journal of Differential Equations, 253 (2012), 3440-3470.  doi: 10.1016/j.jde.2012.08.031.  Google Scholar

[5]

T. Faria, Stability and bifurcation for a delayed predator-prey model and the effect of diffusion, Journal of Mathematical Analysis and Applications, 254 (2001), 433-463.  doi: 10.1006/jmaa.2000.7182.  Google Scholar

[6]

H. I. Freedman and X. Zhao, Global asymptotics in some quasimonotone reaction-diffusion systems with delays, Journal of Differential Equations, 137 (1997), 340-362.  doi: 10.1006/jdeq.1997.3264.  Google Scholar

[7]

P. Georgescu and Y.-H. Hsieh, Global dynamics of a predator-prey model with stage structure for the predator, SIAM Journal on Applied Mathematics, 67 (2007), 1379-1395.  doi: 10.1137/060670377.  Google Scholar

[8]

S.A. Gourley and Y. Kuang, A delay reaction-diffusion model of the spread of bacteriophage infection, SIAM Journal on Applied Mathematics, 65 (2004), 550-566.  doi: 10.1137/S0036139903436613.  Google Scholar

[9]

S. Guo, Stability and bifurcation in a reaction-diffusion model with nonlocal delay effect, Journal of Differential Equations, 259 (2015), 1409-1448.  doi: 10.1016/j.jde.2015.03.006.  Google Scholar

[10]

S. Guo, Spatio-temporal patterns in a diffusive model with non-local delay effect, IMA Journal of Applied Mathematics, 82 (2017), 864-908.  doi: 10.1093/imamat/hxx018.  Google Scholar

[11]

S. Guo, Y. Chen and J. Wu, Two-parameter bifurcations in a network of two neurons with multiple delays, Journal of Differential Equations, 244 (2008), 444-486.  doi: 10.1016/j.jde.2007.09.008.  Google Scholar

[12]

S. Guo and L. Ma, Stability and bifurcation in a delayed reaction-diffusion equation with dirichlet boundary condition, Journal of Nonlinear Science, 26 (2016), 545-580.  doi: 10.1007/s00332-016-9285-x.  Google Scholar

[13]

S. Guo and J. Wu, Bifurcation Theory of Functional Differential Equations, Springer, 2013.  Google Scholar

[14]

S. Guo and S. Yan, Hopf bifurcation in a diffusive Lotka-Volterra type system with nonlocal delay effect, Journal of Differential Equations, 260 (2016), 781-817.  doi: 10.1016/j.jde.2015.09.031.  Google Scholar

[15]

X. He and W. Ni, The effects of diffusion and spatial variation in Lotka-Volterra competition--diffusion system I: Heterogeneity vs. homogeneity, Journal of Differential Equations, 254 (2013), 528-546.  doi: 10.1016/j.jde.2012.08.032.  Google Scholar

[16]

X. He and W. Ni, Global dynamics of the Lotka-Volterra competition-diffusion system: Diffusion and spatial heterogeneity I, Communications on Pure and Applied Mathematics, 69 (2016), 981-1014.  doi: 10.1002/cpa.21596.  Google Scholar

[17]

W. Huang, Global dynamics for a reaction--diffusion equation with time delay, Journal of Differential Equations, 143 (1998), 293-326.  doi: 10.1006/jdeq.1997.3374.  Google Scholar

[18]

K.-Y. Lam and W. Ni, Uniqueness and complete dynamics in heterogeneous competition-diffusion systems, SIAM Journal on Applied Mathematics, 72 (2012), 1695-1712.  doi: 10.1137/120869481.  Google Scholar

[19]

D. Li and S. Guo, Bifurcation and stability of a Mimura-Tsujikawa model with nonlocal delay effect, Mathematical Methods in the Applied Sciences, 40 (2017), 2219-2247.   Google Scholar

[20]

J. Li and Z. Ma, Stability switches in a class of characteristic equations with delay-dependent parameters, Nonlinear Analysis: Real World Applications, 5 (2004), 389-408.  doi: 10.1016/j.nonrwa.2003.06.001.  Google Scholar

[21]

Z. Li, M. Han and F. Chen, Global stability of a predator-prey system with stage structure and mutual interference, Discrete & Continuous Dynamical Systems-Series B, 19 (2014), 173-187.   Google Scholar

[22]

Y. Lin, X. Xie, F. Chen and T. Li, Convergences of a stage-structured predator-prey model with modified Leslie-Gower and Holling-type II schemes, Advances in Difference Equations, 2016 (2016), 19pp.  Google Scholar

[23]

S. Liu, L. Chen, G. Luo and Y. Jiang, Asymptotic behaviors of competitive Lotka-Volterra system with stage structure, Journal of Mathematical Analysis and Applications, 271 (2002), 124-138.  doi: 10.1016/S0022-247X(02)00103-8.  Google Scholar

[24]

R. H. Martin and H. L. Smith, Abstract functional-differential equations and reaction-diffusion systems, Transactions of the American Mathematical Society, 321 (1990), 1-44.   Google Scholar

[25]

C. V. Pao, Coupled nonlinear parabolic systems with time delays, Journal of Mathematical Analysis and Applications, 196 (1995), 237-265.  doi: 10.1006/jmaa.1995.1408.  Google Scholar

[26]

C. V. Pao, Dynamics of nonlinear parabolic systems with time delays, Journal of Mathematical Analysis and Applications, 198 (1996), 751-779.  doi: 10.1006/jmaa.1996.0111.  Google Scholar

[27]

M. H. Protter and H. F. Weinberger, Maximum Principles in Differential Equations, Springer-Verlag, New York, 1984.  Google Scholar

[28]

Y. Qu and J. Wei, Bifurcation analysis in a predator--prey system with stage-structure and harvesting, Journal of the Franklin Institute, 347 (2010), 1097-1113.  doi: 10.1016/j.jfranklin.2010.03.017.  Google Scholar

[29]

H. L. Smith, Monotone Dynamical Systems: An Introduction to the Theory of Competitive and Cooperative Systems, Mathematical Surveys and Monographs, 41. American Mathematical Society, Providence, RI, 1995.  Google Scholar

[30]

X. Song and L. Chen, Optimal harvesting and stability for a predator-prey system with stage structure, Acta Mathematicae Applicatae Sinica, 18 (2002), 423-430.  doi: 10.1007/s102550200042.  Google Scholar

[31]

H.R. Thieme and X. Zhao, A non-local delayed and diffusive predator--prey model, Nonlinear Analysis: Real World Applications, 2 (2001), 145-160.  doi: 10.1016/S0362-546X(00)00112-7.  Google Scholar

[32]

C. C. Travis and G. F. Webb, Existence and stability for partial functional differential equations, Transactions of the American Mathematical Society, 200 (1974), 395-418.  doi: 10.1090/S0002-9947-1974-0382808-3.  Google Scholar

[33]

J. Wu, Theory and Applications of Partial Functional Differential Equations, volume 119. Springer Science & Business Media, 1996.  Google Scholar

[34]

M. Xiao and J. Cao, Stability and Hopf bifurcation in a delayed competitive web sites model, Physics Letters A, 353 (2006), 138-150.   Google Scholar

[35]

S. Yan and S. Guo, Bifurcation phenomena in a {L}otka-{V}olterra model with cross-diffusion and delay effect, International Journal of Bifurcation and Chaos, 27 (2017), 1750105, 24pp.  Google Scholar

[36]

S. Yan and S. Guo, Stability analysis of a stage structure model with spatiotemporal delay effect, Computers & Mathematics with Applications, 73 (2017), 310-326.  doi: 10.1016/j.camwa.2016.11.029.  Google Scholar

[37]

T. Yi and X. Zou, Global attractivity of the diffusive Nicholson blowflies equation with Neumann boundary condition: a non-monotone case, Journal of Differential Equations, 245 (2008), 3376-3388.  doi: 10.1016/j.jde.2008.03.007.  Google Scholar

Figure 1.  Solutions of model (7) with $\tau = 0.3<\tau_*$ tend to the semi-trivial steady state solution $(\theta_{d_1,\alpha,0},0)$.
Figure Options

Download full-size image

Download as PowerPoint slide

Figure 2.  Solutions of model (7) with $\tau = 3>\tau^*$ tend to the semi-trivial steady state solution $(0, \theta_{d_2,r})$.
Figure Options

Download full-size image

Download as PowerPoint slide

Figure 3.  Solutions of model (7) with $\tau = 1.485\in(\ln\dfrac{c\bar{\alpha}}{\bar{r}}, \ln\dfrac{\bar{\alpha}}{a\bar{r}})$ tend to a positive steady state.
Figure Options

Download full-size image

Download as PowerPoint slide

[1]

Qi Wang. On steady state of some Lotka-Volterra competition-diffusion-advection model. Discrete & Continuous Dynamical Systems - B, 2020, 25 (3) : 859-875. doi: 10.3934/dcdsb.2019193
[2]

Yukio Kan-On. Global bifurcation structure of stationary solutions for a Lotka-Volterra competition model. Discrete & Continuous Dynamical Systems, 2002, 8 (1) : 147-162. doi: 10.3934/dcds.2002.8.147
[3]

Hélène Leman, Sylvie Méléard, Sepideh Mirrahimi. Influence of a spatial structure on the long time behavior of a competitive Lotka-Volterra type system. Discrete & Continuous Dynamical Systems - B, 2015, 20 (2) : 469-493. doi: 10.3934/dcdsb.2015.20.469
[4]

Yukio Kan-On. Bifurcation structures of positive stationary solutions for a Lotka-Volterra competition model with diffusion II: Global structure. Discrete & Continuous Dynamical Systems, 2006, 14 (1) : 135-148. doi: 10.3934/dcds.2006.14.135
[5]

Fang Li, Liping Wang, Yang Wang. On the effects of migration and inter-specific competitions in steady state of some Lotka-Volterra model. Discrete & Continuous Dynamical Systems - B, 2011, 15 (3) : 669-686. doi: 10.3934/dcdsb.2011.15.669
[6]

Yueding Yuan, Yang Wang, Xingfu Zou. Spatial dynamics of a Lotka-Volterra model with a shifting habitat. Discrete & Continuous Dynamical Systems - B, 2019, 24 (10) : 5633-5671. doi: 10.3934/dcdsb.2019076
[7]

Guo-Bao Zhang, Ruyun Ma, Xue-Shi Li. Traveling waves of a Lotka-Volterra strong competition system with nonlocal dispersal. Discrete & Continuous Dynamical Systems - B, 2018, 23 (2) : 587-608. doi: 10.3934/dcdsb.2018035
[8]

Lih-Ing W. Roeger, Razvan Gelca. Dynamically consistent discrete-time Lotka-Volterra competition models. Conference Publications, 2009, 2009 (Special) : 650-658. doi: 10.3934/proc.2009.2009.650
[9]

Qi Wang, Yang Song, Lingjie Shao. Boundedness and persistence of populations in advective Lotka-Volterra competition system. Discrete & Continuous Dynamical Systems - B, 2018, 23 (6) : 2245-2263. doi: 10.3934/dcdsb.2018195
[10]

Yuan Lou, Dongmei Xiao, Peng Zhou. Qualitative analysis for a Lotka-Volterra competition system in advective homogeneous environment. Discrete & Continuous Dynamical Systems, 2016, 36 (2) : 953-969. doi: 10.3934/dcds.2016.36.953
[11]

Bang-Sheng Han, Zhi-Cheng Wang, Zengji Du. Traveling waves for nonlocal Lotka-Volterra competition systems. Discrete & Continuous Dynamical Systems - B, 2020, 25 (5) : 1959-1983. doi: 10.3934/dcdsb.2020011
[12]

Dan Wei, Shangjiang Guo. Qualitative analysis of a Lotka-Volterra competition-diffusion-advection system. Discrete & Continuous Dynamical Systems - B, 2021, 26 (5) : 2599-2623. doi: 10.3934/dcdsb.2020197
[13]

Lin Niu, Yi Wang, Xizhuang Xie. Carrying simplex in the Lotka-Volterra competition model with seasonal succession with applications. Discrete & Continuous Dynamical Systems - B, 2021, 26 (4) : 2161-2172. doi: 10.3934/dcdsb.2021014
[14]

Jian Fang, Jianhong Wu. Monotone traveling waves for delayed Lotka-Volterra competition systems. Discrete & Continuous Dynamical Systems, 2012, 32 (9) : 3043-3058. doi: 10.3934/dcds.2012.32.3043
[15]

Jong-Shenq Guo, Ying-Chih Lin. The sign of the wave speed for the Lotka-Volterra competition-diffusion system. Communications on Pure & Applied Analysis, 2013, 12 (5) : 2083-2090. doi: 10.3934/cpaa.2013.12.2083
[16]

Qi Wang, Chunyi Gai, Jingda Yan. Qualitative analysis of a Lotka-Volterra competition system with advection. Discrete & Continuous Dynamical Systems, 2015, 35 (3) : 1239-1284. doi: 10.3934/dcds.2015.35.1239
[17]

Juan Luis García Guirao, Marek Lampart. Transitivity of a Lotka-Volterra map. Discrete & Continuous Dynamical Systems - B, 2008, 9 (1) : 75-82. doi: 10.3934/dcdsb.2008.9.75
[18]

Qihuai Liu, Dingbian Qian, Zhiguo Wang. Quasi-periodic solutions of the Lotka-Volterra competition systems with quasi-periodic perturbations. Discrete & Continuous Dynamical Systems - B, 2012, 17 (5) : 1537-1550. doi: 10.3934/dcdsb.2012.17.1537
[19]

Qi Wang. Some global dynamics of a Lotka-Volterra competition-diffusion-advection system. Communications on Pure & Applied Analysis, 2020, 19 (6) : 3245-3255. doi: 10.3934/cpaa.2020142
[20]

Li-Jun Du, Wan-Tong Li, Jia-Bing Wang. Invasion entire solutions in a time periodic Lotka-Volterra competition system with diffusion. Mathematical Biosciences & Engineering, 2017, 14 (5&6) : 1187-1213. doi: 10.3934/mbe.2017061

2019 Impact Factor: 1.27

Tools

Metrics

  • PDF downloads (295)
  • HTML views (393)
  • Cited by (2)

Other articles
by authors

[Back to Top]

Copyright © 2021 American Institute of Mathematical Sciences