1
|
Braun E, Marom S. Universality, complexity and the praxis of biology: Two case studies. STUDIES IN HISTORY AND PHILOSOPHY OF BIOLOGICAL AND BIOMEDICAL SCIENCES 2015; 53:68-72. [PMID: 25903120 DOI: 10.1016/j.shpsc.2015.03.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 03/30/2015] [Indexed: 06/04/2023]
Abstract
The phenomenon of biology provides a prime example for a naturally occurring complex system. The approach to this complexity reflects the tension between a reductionist, reverse-engineering stance, and more abstract, systemic ones. Both of us are reductionists, but our observations challenge reductionism, at least the naive version of it. Here we describe the challenge, focusing on two universal characteristics of biological complexity: two-way microscopic-macroscopic degeneracy, and lack of time scale separation within and between levels of organization. These two features and their consequences for the praxis of experimental biology, reflect inherent difficulties in separating the dynamics of any given level of organization from the coupled dynamics of all other levels, including the environment within which the system is embedded. Where these difficulties are not deeply acknowledged, the impacts of fallacies that are inherent to naive reductionism are significant. In an era where technology enables experimental high-resolution access to numerous observables, the challenge faced by the mature reductionist-identification of relevant microscopic variables-becomes more demanding than ever. The demonstrations provided here are taken from two very different biological realizations: populations of microorganisms and populations of neurons, thus making the lesson potentially general.
Collapse
Affiliation(s)
- Erez Braun
- Technion-Israel Institute of Technology, Israel
| | - Shimon Marom
- Technion-Israel Institute of Technology, Israel.
| |
Collapse
|
2
|
Tkačik G, Ghosh A, Schneidman E, Segev R. Adaptation to changes in higher-order stimulus statistics in the salamander retina. PLoS One 2014; 9:e85841. [PMID: 24465742 PMCID: PMC3897542 DOI: 10.1371/journal.pone.0085841] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 12/02/2013] [Indexed: 11/30/2022] Open
Abstract
Adaptation in the retina is thought to optimize the encoding of natural light signals into sequences of spikes sent to the brain. While adaptive changes in retinal processing to the variations of the mean luminance level and second-order stimulus statistics have been documented before, no such measurements have been performed when higher-order moments of the light distribution change. We therefore measured the ganglion cell responses in the tiger salamander retina to controlled changes in the second (contrast), third (skew) and fourth (kurtosis) moments of the light intensity distribution of spatially uniform temporally independent stimuli. The skew and kurtosis of the stimuli were chosen to cover the range observed in natural scenes. We quantified adaptation in ganglion cells by studying linear-nonlinear models that capture well the retinal encoding properties across all stimuli. We found that the encoding properties of retinal ganglion cells change only marginally when higher-order statistics change, compared to the changes observed in response to the variation in contrast. By analyzing optimal coding in LN-type models, we showed that neurons can maintain a high information rate without large dynamic adaptation to changes in skew or kurtosis. This is because, for uncorrelated stimuli, spatio-temporal summation within the receptive field averages away non-gaussian aspects of the light intensity distribution.
Collapse
Affiliation(s)
- Gašper Tkačik
- Institute of Science and Technology Austria, Klosterneuburg, Austria
- * E-mail:
| | - Anandamohan Ghosh
- Indian Institute of Science Education and Research-Kolkata, Mohanpur (Nadia), India
| | - Elad Schneidman
- Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel
| | - Ronen Segev
- Faculty of Natural Sciences, Department of Life Sciences and Zlotowski Center for Neuroscience, Ben Gurion University of the Negev, Be'er Sheva, Israel
| |
Collapse
|
3
|
Escera C, Malmierca MS. The auditory novelty system: An attempt to integrate human and animal research. Psychophysiology 2013; 51:111-23. [DOI: 10.1111/psyp.12156] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 08/06/2013] [Indexed: 11/30/2022]
Affiliation(s)
- Carles Escera
- Institute for Brain; Cognition and Behavior (IR3C); University of Barcelona; Catalonia Spain
- Cognitive Neuroscience Research Group; Department of Psychiatry and Clinical Psychobiology; University of Barcelona; Catalonia Spain
| | - Manuel S. Malmierca
- Auditory Neurophysiology Laboratory; The Institute of Neuroscience of Castilla y Leon (INCyL); University of Salamanca; Salamanca Spain
- Department of Cell Biology and Pathology; The Medical School; University of Salamanca; Salamanca Spain
| |
Collapse
|
4
|
The systems biology of mitochondrial fission and fusion and implications for disease and aging. Biogerontology 2013; 15:1-12. [DOI: 10.1007/s10522-013-9474-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 09/28/2013] [Indexed: 12/21/2022]
|
5
|
Fox-Rabinovich GS, Yamamoto K, Beake BD, Gershman IS, Kovalev AI, Veldhuis SC, Aguirre MH, Dosbaeva G, Endrino JL. Hierarchical adaptive nanostructured PVD coatings for extreme tribological applications: the quest for nonequilibrium states and emergent behavior. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2012; 13:043001. [PMID: 27877499 PMCID: PMC5090555 DOI: 10.1088/1468-6996/13/4/043001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 06/21/2012] [Indexed: 05/04/2023]
Abstract
Adaptive wear-resistant coatings produced by physical vapor deposition (PVD) are a relatively new generation of coatings which are attracting attention in the development of nanostructured materials for extreme tribological applications. An excellent example of such extreme operating conditions is high performance machining of hard-to-cut materials. The adaptive characteristics of such coatings develop fully during interaction with the severe environment. Modern adaptive coatings could be regarded as hierarchical surface-engineered nanostructural materials. They exhibit dynamic hierarchy on two major structural scales: (a) nanoscale surface layers of protective tribofilms generated during friction and (b) an underlying nano/microscaled layer. The tribofilms are responsible for some critical nanoscale effects that strongly impact the wear resistance of adaptive coatings. A new direction in nanomaterial research is discussed: compositional and microstructural optimization of the dynamically regenerating nanoscaled tribofilms on the surface of the adaptive coatings during friction. In this review we demonstrate the correlation between the microstructure, physical, chemical and micromechanical properties of hard coatings in their dynamic interaction (adaptation) with environment and the involvement of complex natural processes associated with self-organization during friction. Major physical, chemical and mechanical characteristics of the adaptive coating, which play a significant role in its operating properties, such as enhanced mass transfer, and the ability of the layer to provide dissipation and accumulation of frictional energy during operation are presented as well. Strategies for adaptive nanostructural coating design that enhance beneficial natural processes are outlined. The coatings exhibit emergent behavior during operation when their improved features work as a whole. In this way, as higher-ordered systems, they achieve multifunctionality and high wear resistance under extreme tribological conditions.
Collapse
Affiliation(s)
- German S Fox-Rabinovich
- Department of Mechanical Engineering, McMaster University, 1280 Main St. W. Hamilton, Ontario L8S 4L7, Canada
| | - Kenji Yamamoto
- Materials Research Laboratory, Kobe Steel Ltd, 1-5-5 Takatsuda-dai, Nishi-ku, Kobe, Hyogo, 651-2271, Japan
| | - Ben D Beake
- Micro Materials Limited, Willow House, Yale Business Village, Ellice Way, Wrexham LL13 7YL, UK
| | - Iosif S Gershman
- All-Russian Railway Research Institute, 10 Third Mytishchinskaya Street, Moscow, 29851, Russia
| | - Anatoly I Kovalev
- Surface Phenomena Research Group, CNIICHERMET, 9/23, 2-nd Baumanskaya Street, Moscow, 105005, Russia
| | - Stephen C Veldhuis
- Department of Mechanical Engineering, McMaster University, 1280 Main St. W. Hamilton, Ontario L8S 4L7, Canada
| | - Myriam H. Aguirre
- EMPA, Solid State Chemistry and Catalysis, CH-8600 Dübendorf, Switzerland
| | - Goulnara Dosbaeva
- Department of Mechanical Engineering, McMaster University, 1280 Main St. W. Hamilton, Ontario L8S 4L7, Canada
| | - Jose L Endrino
- Albengoa Research, Energía Solar 1, Palmas Altas, Seville, 41014, Spain
| |
Collapse
|
6
|
Christopoulos VN, Boeff DV, Evans CD, Crowe DA, Amirikian B, Georgopoulos A, Georgopoulos AP. A network analysis of developing brain cultures. J Neural Eng 2012; 9:046008. [PMID: 22750729 DOI: 10.1088/1741-2560/9/4/046008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We recorded electrical activity from four developing embryonic brain cultures (4-40 days in vitro) using multielectrode arrays (MEAs) with 60 embedded electrodes. Data were filtered for local field potentials (LFPs) and downsampled to 1 ms to yield a matrix of time series consisting of 60 electrode × 60 000 time samples per electrode per day per MEA. Each electrode time series was rendered stationary and nonautocorrelated by applying an ARIMA (25, 1, 1) model and taking the residuals (i.e. innovations). Two kinds of analyses were then performed. First, a pairwise crosscorrelation (CC) analysis (±25 1 ms lags) revealed systematic changes in CC with lag, day in vitro (DIV), and inter-electrode distance. Specifically, (i) positive CCs were 1.76× more prevalent and 1.44× stronger (absolute value) than negative ones, and (ii) the strength of CC increased with DIV and decreased with lag and inter-electrode distance. Second, a network equilibrium analysis was based on the instantaneous (1 ms resolution) logratio of the number of electrodes that were above or below their mean, called simultaneous departure from equilibrium, SDE. This measure possesses a major computational advantage over the pairwise crosscorrelation approach because it is very simple and fast to calculate, an important factor for the analysis of large networks. The results obtained with SDE covaried highly with CC over DIV, which further validates the usefulness of this measure as a computationally effective tool for large scale network analysis.
Collapse
Affiliation(s)
- V N Christopoulos
- Department of Computer Science and Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | | | | | | | | | | | | |
Collapse
|
7
|
Acimovic J, Teppola H, Selinummi J, Linne ML. Computational tools for assessing the properties of 2D neural cell cultures. BMC Neurosci 2009. [DOI: 10.1186/1471-2202-10-s1-p170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
|