171 research outputs found
Thermodynamics of MHD flows with axial symmetry
We present strategies based upon extremization principles, in the case of the
axisymmetric equations of magnetohydrodynamics (MHD). We study the equilibrium
shape by using a minimum energy principle under the constraints of the MHD
axisymmetric equations. We also propose a numerical algorithm based on a
maximum energy dissipation principle to compute in a consistent way the
equilibrium states. Then, we develop the statistical mechanics of such flows
and recover the same equilibrium states giving a justification of the minimum
energy principle. We find that fluctuations obey a Gaussian shape and we make
the link between the conservation of the Casimirs on the coarse-grained scale
and the process of energy dissipation
Relativistic Klein-Gordon charge effects by information-theoretic measures
The charge spreading of ground and excited states of Klein-Gordon particles
moving in a Coulomb potential is quantitatively analyzed by means of the
ordinary moments and the Heisenberg measure as well as by use of the most
relevant information-theoretic measures of global (Shannon entropic power) and
local (Fisher's information) types. The dependence of these complementary
quantities on the nuclear charge Z and the quantum numbers characterizing the
physical states is carefully discussed. The comparison of the relativistic
Klein-Gordon and non-relativistic Schrodinger values is made. The
non-relativistic limits at large principal quantum number n and for small
values of Z are also reached.Comment: Accepted in New Journal of Physic
Transport and Magnetic Studies on the Spin State Transition of Pr1-xCaxCoO3 up to High Pressure
Transport and magnetic measurements and structural and NMR studies have been
carried out on (Pr1-yR'y)1-xAxCoO3 {R'=(rare earth elements and Y); A=(Ca, Ba
and Sr)} at ambient pressure or under high pressure. The system exhibits a
phase transition from a nearly metallic to an insulating state with decreasing
temperature T, where the low spin (LS) state of Co3+ is suddenly stabilized.
For y=0, we have constructed a T-x phase diagram at various values of the
external pressure p. It shows that the (T, x) region of the low temperature
phase, which is confined to a very narrow region around x=0.5 at ambient
pressure, expands as p increases, suggesting that the transition is not due to
an order-disorder type one. For the occurrence of the transition, both the Pr
and Ca atoms seem to be necessary. The intimate relationship between the local
structure around the Co ions and the electronic (or spin) state of Co3+ ions is
discussed: For the smaller unit cell volume or the smaller volume of the CoO6
octahedra and for the larger tilting angle of the octahedra, the temperature of
the transition becomes higher. The role of the carriers introduced by the
doping of the A atoms, is also discussed. By analyzing the data of 59Co-NMR
spectra and magnetic susceptibilities of Pr1-xCaxCoO3 the energy separations
among the different spin states of Co3+ and Co4+ are roughly estimated.Comment: 15 pages, 15 figures, 2 tables, submitted to J. Phys. Soc. Jp
Organization, Evolution, Cognition and Dynamic Capabilities
Using insights from âembodied cognitionâ and a resulting âcognitive theory of the firmâ, I aim to contribute to the further development of evolutionary theory of organizations, in the specification of organizations as âinteractorsâ that carry organizational competencies as âreplicatorsâ, within industries as âpopulationsâ. Especially, I analyze how, if at all, âdynamic capabilitiesâ can be fitted into evolutionary theory. I propose that the prime purpose of an organization is to serve as a cognitive âfocusing deviceâ. Here, cognition has a wide meaning, including perception, interpretation, sense making, and value judgements. I analyse how this yields organizations as cohesive wholes, and differences within and between industries. I propose the following sources of variation: replication in communication, novel combinations of existing knowledge, and a path of discovery by which exploitation leads to exploration. These yield a proposal for dynamic capabilities. I discuss in what sense, and to what extent these sources of variation are âblindâ, as postulated in evolutionary theory.
The enchanted snake and the forbidden fruit: the ayahuasca âfairy taleâ tourist
This ethnographic study increases our understanding of Westerners seeking genuine fairy tale experiences of magic, transformation and enchantment within South American psychedelic ayahuasca tourism. Examining 63 tourists, this study shows how vision-based spirit sensegivers facilitate individuals in exorcising demons, to make sense of themselves as spiritual beings within an enchanted universe. However, and with this potion quickly wearing off upon returning to the West, tourists feel abandoned by their spirits, and disconnected from the fairy lands. Coupled with not wanting to re-experience intense inner tensions from stepping in and out of a fairy tale, further tourism is rejected. As such, ayahuasca tourism becomes a âforgottenâ fairy tale, rarely told
Is my memory an extended notebook?
Clark and Chalmers' conception of spatially extended memory is under- pinned by an objectified conception of biological memory. To the extent that this can be identified with a âstorageâ approach to memory, criticisms of it are well known and an alternative approach, perhaps more suited to an enactive account of cognition, might be one which focuses on remembering as a type of action. In the Otto story the objectification of memory is apparent not only in C&Câs characterization of the notebook but also in the notion that Ingaâs memory is notebook-like. Insofar as Ingaâs practices, or conceptions, of remembering might be notebook-like this should not be taken as evidence of the existence of an internal store, but could instead be the result of prior interaction with notebook-like artifacts
Health and climate related ecosystem services provided by street trees in the urban environment
At the Crossroads of Sustainability: The Natural Recompositioning of Architecture
It is widely acknowledged that the mantra of sustainability has triggered a fundamental reversal in the core of design practice: If the original purpose of architecture was to protect humans from the destructive actions of nature,today it should protect nature from the damaging actions of humans. But sustainable design is far from being a coherent body of fully totalized ideas:it has a broad spectrum of disputing interpretations that oscillate between the
deterministic models of energy control and technological efficiencies, and the moralistic and romantic approaches that attempt to see in nature and natural processes a fundamental way to de-escalate the global urban footprint and its associated patterns of consumption.
However, mainstream green design has been evolving by progressively absorbing the narrative of deep ecology. Nature has been being integrated into architecture literally, by inserting vegetation onto buildings; digitally, by bringing environmental data into the design process (climate records, wind streams, sun rotation and air flows are computed, modelled and effectually shape architectures), and transcendentally, by claiming that sustainable architecture nurtures âthe existing and evolving connections between spiritual and
material consciousness.â The acknowledgement of the inexorable affiliation between architecture and the environment is, of course, not exactly new. What
is distinctive today is the reification of the role of nature in architecture as an ideological stance, now totally intertwined with state-of-art data processing
and the market-driven tools brought by Natural Capitalism.
This paper will examine emblematic âgreenâ buildings produced by leading architects such as Pelli Clarke Pelli, William McDonough, Stefano Boeri,
Norman Foster and BIG in the light of Tim Mortonâs, Slavoj Zizek and Bruno Latourâs critique of nature. It will illustrate how, despite being able to successfully
forge new creative freedoms by exploring hybridizations between the domains of design and science, sustainabilityâs self-righteous ânaturalisticâ narrative is enabling a vision of the architect as an âexpert managerâ
focused on producing projects of ecologic âbeautificationâ while assumed to be âsaving the world,â effectively depoliticizing the architectural practice.
Nevertheless, these examples attest that there is a vast and fertile field of ideas to be explored and in this regard it is important to underline that we are still
in the embryonic outset of the engagement of architecture with sustainability
Context dependency in risky decision making: Is there a description-experience gap?
When making decisions involving risk, people may learn about the risk from descriptions or from experience. The description-experience gap refers to the difference in decision patterns driven by this discrepancy in learning format. Across two experiments, we investigated whether learning from description versus experience differentially affects the direction and the magnitude of a context effect in risky decision making. In Study 1 and 2, a computerized game called the Decisions about Risk Task (DART) was used to measure people's risk-taking tendencies toward hazard stimuli that exploded probabilistically. The rate at which a context hazard caused harm was manipulated, while the rate at which a focal hazard caused harm was held constant. The format by which this information was learned was also manipulated; it was learned primarily by experience or by description. The results revealed that participants' behavior toward the focal hazard varied depending on what they had learned about the context hazard. Specifically, there were contrast effects in which participants were more likely to choose a risky behavior toward the focal hazard when the harm rate posed by the context hazard was high rather than low. Critically, these contrast effects were of similar strength irrespective of whether the risk information was learned from experience or description. Participants' verbal assessments of risk likelihood also showed contrast effects, irrespective of learning format. Although risk information about a context hazard in DART does nothing to affect the objective expected value of risky versus safe behaviors toward focal hazards, it did affect participants' perceptions and behaviors-regardless of whether the information was learned from description or experience. Our findings suggest that context has a broad-based role in how people assess and make decisions about hazards
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