386 research outputs found
When do generalized entropies apply? How phase space volume determines entropy
We show how the dependence of phase space volume of a classical
system on its size uniquely determines its extensive entropy. We give a
concise criterion when this entropy is not of Boltzmann-Gibbs type but has to
assume a {\em generalized} (non-additive) form. We show that generalized
entropies can only exist when the dynamically (statistically) relevant fraction
of degrees of freedom in the system vanishes in the thermodynamic limit. These
are systems where the bulk of the degrees of freedom is frozen and is
practically statistically inactive. Systems governed by generalized entropies
are therefore systems whose phase space volume effectively collapses to a
lower-dimensional 'surface'. We explicitly illustrate the situation for
binomial processes and argue that generalized entropies could be relevant for
self organized critical systems such as sand piles, for spin systems which form
meta-structures such as vortices, domains, instantons, etc., and for problems
associated with anomalous diffusion.Comment: 5 pages, 2 figure
The effect of social balance on social fragmentation
With the availability of cell phones, internet, social media etc. the interconnectedness of people within most societies has increased drastically over the past three decades. Across the same timespan, we are observing the phenomenon of increasing levels of fragmentation in society into relatively small and isolated groups that have been termed filter bubbles, or echo chambers. These pose a number of threats to open societies, in particular, a radicalisation in political, social or cultural issues, and a limited access to facts. In this paper we show that these two phenomena might be tightly related. We study a simple stochastic co-evolutionary model of a society of interacting people. People are not only able to update their opinions within their social context, but can also update their social links from collaborative to hostile, and vice versa. The latter is implemented such that social balance is realised. We find that there exists a critical level of interconnectedness, above which society fragments into small sub-communities that are positively linked within and hostile towards other groups. We argue that the existence of a critical communication density is a universal phenomenon in all societies that exhibit social balance. The necessity arises from the underlying mathematical structure of a phase transition phenomenon that is known from the theory of a kind of disordered magnets called spin glasses. We discuss the consequences of this phase transition for social fragmentation in society
The Nimbus 4 Infrared Spectroscopy Experiment, IRIS-D. Part 1: Calibrated Thermal Emission Spectra
Calibrated infrared emission spectra of earth and atmosphere using high resolution interferometer spectrophotometer on Nimbus 4 satellit
The effect of social balance on social fragmentation
With the availability of internet, social media, etc., the interconnectedness of people within most societies has increased tremendously over the past decades. Across the same timespan, an increasing level of fragmentation of society into small isolated groups has been observed. With a simple model of a society, in which the dynamics of individual opinion formation is integrated with social balance, we show that these two phenomena might be tightly related. We identify a critical level of interconnectedness, above which society fragments into sub-communities that are internally cohesive and hostile towards other groups. This critical communication density necessarily exists in the presence of social balance, and arises from the underlying mathematical structure of a phase transition known from the theory of disordered magnets called spin glasses. We discuss the consequences of this phase transition for social fragmentation in society
Scaling-violation phenomena and fractality in the human posture control systems
By analyzing the movements of quiet standing persons by means of wavelet
statistics, we observe multiple scaling regions in the underlying body
dynamics. The use of the wavelet-variance function opens the possibility to
relate scaling violations to different modes of posture control. We show that
scaling behavior becomes close to perfect, when correctional movements are
dominated by the vestibular system.Comment: 12 pages, 4 figures, to appear in Phys. Rev.
Connectivity in the Deep: Phylogeography of the Velvet Belly Lanternshark
PublishedThe velvet belly lanternshark, Etmopterus spinax, is a deep-sea bioluminescent squaloid shark, found predominantly in the northeast Atlantic and Mediterranean Sea. It has been exposed to relatively high levels of mortality associated with by-catch in some regions. Its late maturity and low fecundity potentially renders it vulnerable to over-exploitation, although little remains known about processes of connectivity between key habitats/regions. This study utilised DNA sequencing of partial regions of the mitochondrial control region and nuclear ribosomal internal transcribed spacer 2 to investigate population structure and phylogeography of this species across the northeast Atlantic and Mediterranean Basin. Despite the inclusion of samples from the range edges or remote locations, no evidence of significant population structure was detected. An important exception was identified using the control region sequence, with much greater (and statistically significant) levels of genetic differentiation between the Mediterranean and Atlantic. This suggests that the Strait of Gibraltar may represent an important bathymetric barrier, separating regions with very low levels of female dispersal. Bayesian estimation of divergence time also places the separation between the Mediterranean and Atlantic lineages within the last 100,000 years, presumably connected with perturbations during the last Glacial Period. These results demonstrate population subdivision at a much smaller geographic distance than has generally been identified in previous work on deep-sea sharks. This highlights a very significant role for shallow bathymetry in promoting genetic differentiation in deepwater taxa. It acts as an important exception to a general paradigm of marine species being connected by high levels of gene-flow, representing single stocks over large scales. It may also have significant implications for the fisheries management of this species.We would like to thank Trude Thangstad, Merete Kvalsund (Institute of Marine Research, Norway), Cecilia Pinto, Eleonora de Sabata and the scientists and crew of the RV Celtic Explorer for assistance in the collection of samples. Funding for this project was provided by the University of Salford and the University of Bristol. We are grateful to all those who helped with sample collection, including the MEDITS survey programme, the Department of Fisheries and Marine Research (DFMR) of Cyprus, the Annual Demersal and Deep Water Fish Monitoring Surveys financed by the Azores Government and the CONDOR project (supported by a grant from Iceland, Liechtenstein, Norway through the EEA Financial Mechanism (PT0040/2008)
Mapping the Structure of Human Values through Conceptual Representations
The present research provides the first direct examination of human values through concept categorization tasks that entail judging the meaning of values. Seven studies containing data from nine samples (N = 1086) in two countries (the UK and Brazil) asked participants to compare the meaning of different values found within influential quasi-circumplex model of values. Different methods were used across experiments, including direct similarity judgment tasks, pile sorting, and spatial arrangement. The results of these diverse conceptual assessments corresponded to spatial configurations that are broadly convergent with Schwartz's model, both between and within participants
A self-organized model for cell-differentiation based on variations of molecular decay rates
Systemic properties of living cells are the result of molecular dynamics
governed by so-called genetic regulatory networks (GRN). These networks capture
all possible features of cells and are responsible for the immense levels of
adaptation characteristic to living systems. At any point in time only small
subsets of these networks are active. Any active subset of the GRN leads to the
expression of particular sets of molecules (expression modes). The subsets of
active networks change over time, leading to the observed complex dynamics of
expression patterns. Understanding of this dynamics becomes increasingly
important in systems biology and medicine. While the importance of
transcription rates and catalytic interactions has been widely recognized in
modeling genetic regulatory systems, the understanding of the role of
degradation of biochemical agents (mRNA, protein) in regulatory dynamics
remains limited. Recent experimental data suggests that there exists a
functional relation between mRNA and protein decay rates and expression modes.
In this paper we propose a model for the dynamics of successions of sequences
of active subnetworks of the GRN. The model is able to reproduce key
characteristics of molecular dynamics, including homeostasis, multi-stability,
periodic dynamics, alternating activity, differentiability, and self-organized
critical dynamics. Moreover the model allows to naturally understand the
mechanism behind the relation between decay rates and expression modes. The
model explains recent experimental observations that decay-rates (or turnovers)
vary between differentiated tissue-classes at a general systemic level and
highlights the role of intracellular decay rate control mechanisms in cell
differentiation.Comment: 16 pages, 5 figure
Evolution of the Greater Caucasus Basement and Formation of the Main Caucasus Thrust, Georgia
Along the northern margin of the ArabiaâEurasia collision zone in the western Greater Caucasus, the Main Caucasus Thrust (MCT) juxtaposes Paleozoic crystalline basement to the north against Mesozoic metasedimentary and volcaniclastic rocks to the south. The MCT is commonly assumed to be the trace of an active plateâboundary scale structure that accommodates ArabiaâEurasia convergence, but field data supporting this interpretation are equivocal. Here we investigate the deformation history of the rocks juxtaposed across the MCT in Georgia using field observations, microstructural analysis, UâPb and 40Ar/39Ar geochronology, and 40Ar/39Ar and (UâTh)/He thermochronology. Zircon UâPb analyses show that Greater Caucasus crystalline rocks formed in the Early Paleozoic on the margin of Gondwana. Lowâpressure/temperature amphiboliteâfacies metamorphism of these metasedimentary rocks and associated plutonism likely took place during Carboniferous accretion onto the Laurussian margin, as indicated by igneous and metamorphic zircon UâPb ages of ~330â310Â Ma. 40Ar/39Ar ages of ~190â135Â Ma from muscovite in a greenschistâfacies shear zone indicate that the MCT likely developed during Mesozoic inversion and/or rifting of the Caucasus Basin. A Mesozoic 40Ar/39Ar biotite age with release spectra indicating partial resetting and Cenozoic (<40Â Ma) apatite and zircon (UâTh)/He ages imply at least ~5â8Â km of Greater Caucasus basement exhumation since ~10Â Ma in response to ArabiaâEurasia collision. Cenozoic reactivation of the MCT may have accommodated a fraction of this exhumation. However, Cenozoic zircon (UâTh)/He ages in both the hanging wall and footwall of the MCT require partitioning a substantial component of this deformation onto structures to the south.Plain Language SummaryCollisions between continents cause deformation of the Earthâs crust and the uplift of large mountain ranges like the Himalayas. Large faults often form to accommodate this deformation and may help bring rocks once buried at great depths up to the surface of the Earth. The Greater Caucasus Mountains form the northernmost part of a zone of deformation due to the ongoing collision between the Arabian and Eurasian continents. The Main Caucasus Thrust (MCT) is a fault juxtaposing old igneous and metamorphic (crystalline) rocks against younger rocks that has often been assumed to be a major means of accommodating ArabiaâEurasia collision. This study examines the history of rocks along the MCT with a combination of field work, study of microscopic deformation in rocks, and dating of rock formation and cooling. The crystalline rocks were added to the margins of presentâday Eurasia about 330â310 million years ago, and the MCT first formed about 190â135 million years ago. The MCT is likely at most one of many structures accommodating presentâday ArabiaâEurasia collision.Key PointsAmphiboliteâfacies metamorphism and plutonism in the Greater Caucasus basement took place ~330â310Â MaThe Main Caucasus Thrust formed as a greenschistâfacies shear zone during Caucasus Basin inversion and/or rifting (~190â135Â Ma)The Main Caucasus Thrust may have helped facilitate a portion of at least 5â8Â km of basement exhumation during ArabiaâEurasia collisionPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/1/tect21292-sup-0002-2019TC005828-ts01.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/2/tect21292-sup-0006-2019TC005828-ts05.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/3/tect21292_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/4/tect21292-sup-0003-2019TC005828-ts02.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/5/tect21292-sup-0005-2019TC005828-ts04.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/6/tect21292.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154626/7/tect21292-sup-0004-2019TC005828-ts03.pd
The Deep Water Abundance on Jupiter: New Constraints from Thermochemical Kinetics and Diffusion Modeling
We have developed a one-dimensional thermochemical kinetics and diffusion
model for Jupiter's atmosphere that accurately describes the transition from
the thermochemical regime in the deep troposphere (where chemical equilibrium
is established) to the quenched regime in the upper troposphere (where chemical
equilibrium is disrupted). The model is used to calculate chemical abundances
of tropospheric constituents and to identify important chemical pathways for
CO-CH4 interconversion in hydrogen-dominated atmospheres. In particular, the
observed mole fraction and chemical behavior of CO is used to indirectly
constrain the Jovian water inventory. Our model can reproduce the observed
tropospheric CO abundance provided that the water mole fraction lies in the
range (0.25-6.0) x 10^-3 in Jupiter's deep troposphere, corresponding to an
enrichment of 0.3 to 7.3 times the protosolar abundance (assumed to be H2O/H2 =
9.61 x 10^-4). Our results suggest that Jupiter's oxygen enrichment is roughly
similar to that for carbon, nitrogen, and other heavy elements, and we conclude
that formation scenarios that require very large (>8 times solar) enrichments
in water can be ruled out. We also evaluate and refine the simple time-constant
arguments currently used to predict the quenched CO abundance on Jupiter, other
giant planets, and brown dwarfs.Comment: 42 pages, 7 figures, 4 tables, with note added in proof. Accepted for
publication in Icarus [in press
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