490 research outputs found
Stormwater Runoff Control: A Model Ordinance for Meeting Local Water Quality Management Needs
Axions and saxions from the primordial supersymmetric plasma and extra radiation signatures
We calculate the rate for thermal production of axions and saxions via
scattering of quarks, gluons, squarks, and gluinos in the primordial
supersymmetric plasma. Systematic field theoretical methods such as hard
thermal loop resummation are applied to obtain a finite result in a
gauge-invariant way that is consistent to leading order in the strong gauge
coupling. We calculate the thermally produced yield and the decoupling
temperature for both axions and saxions. For the generic case in which saxion
decays into axions are possible, the emitted axions can constitute extra
radiation already prior to big bang nucleosynthesis and well thereafter. We
update associated limits imposed by recent studies of the primordial helium-4
abundance and by precision cosmology of the cosmic microwave background and
large scale structure. We show that the trend towards extra radiation seen in
those studies can be explained by late decays of thermal saxions into axions
and that upcoming Planck results will probe supersymmetric axion models with
unprecedented sensitivity.Comment: 16 pages, 7 figures; v2: references added, minor clarifying
additions, matches published versio
Flora robotica -- An Architectural System Combining Living Natural Plants and Distributed Robots
Key to our project flora robotica is the idea of creating a bio-hybrid system
of tightly coupled natural plants and distributed robots to grow architectural
artifacts and spaces. Our motivation with this ground research project is to
lay a principled foundation towards the design and implementation of living
architectural systems that provide functionalities beyond those of orthodox
building practice, such as self-repair, material accumulation and
self-organization. Plants and robots work together to create a living organism
that is inhabited by human beings. User-defined design objectives help to steer
the directional growth of the plants, but also the system's interactions with
its inhabitants determine locations where growth is prohibited or desired
(e.g., partitions, windows, occupiable space). We report our plant species
selection process and aspects of living architecture. A leitmotif of our
project is the rich concept of braiding: braids are produced by robots from
continuous material and serve as both scaffolds and initial architectural
artifacts before plants take over and grow the desired architecture. We use
light and hormones as attraction stimuli and far-red light as repelling
stimulus to influence the plants. Applied sensors range from simple proximity
sensing to detect the presence of plants to sophisticated sensing technology,
such as electrophysiology and measurements of sap flow. We conclude by
discussing our anticipated final demonstrator that integrates key features of
flora robotica, such as the continuous growth process of architectural
artifacts and self-repair of living architecture.Comment: 16 pages, 12 figure
Hybrid Societies : Challenges and Perspectives in the Design of Collective Behavior in Self-organizing Systems
Hybrid societies are self-organizing, collective systems, which are composed of different components, for example, natural and artificial parts (bio-hybrid) or human beings interacting with and through technical systems (socio-technical). Many different disciplines investigate methods and systems closely related to the design of hybrid societies. A stronger collaboration between these disciplines could allow for re-use of methods and create significant synergies. We identify three main areas of challenges in the design of self-organizing hybrid societies. First, we identify the formalization challenge. There is an urgent need for a generic model that allows a description and comparison of collective hybrid societies. Second, we identify the system design challenge. Starting from the formal specification of the system, we need to develop an integrated design process. Third, we identify the challenge of interdisciplinarity. Current research on self-organizing hybrid societies stretches over many different fields and hence requires the re-use and synthesis of methods at intersections between disciplines. We then conclude by presenting our perspective for future approaches with high potential in this area
Flora Robotica – Mixed Societies of Symbiotic Robot-Plant Bio-Hybrids
Besides the life-as-it-could-be driver of artificial life research there is also the concept of extending natural life by creating hybrids or mixed societies that are built from both natural and artificial components. In this paper, we motivate and present the research program of the project flora robotica. We present our concepts of control, hardware de-sign, modeling, and human interaction along with preliminary experiments. Our objective is to develop and to investigate closely linked symbiotic relationships between robots and natural plants and to explore the potentials of a plant-robot society able to produce archi-tectural artifacts and living spaces. These robot-plant bio-hybrids create synergies that allow for new functions of plants and robots. They also create novel design opportunities for an architecture that fuses the design and construction phase. The bio-hybrid is an example of mixed societies between ‘hard artificial and ‘wet natural life, which enables an interaction between natural and artificial ecologies. They form an embodied, self-organizing, and distributed cognitive system which is supposed to grow and develop over long periods of time resulting in the creation of meaningful architectural structures. A key idea is to assign equal roles to robots and plants in order to create a highly integrated, symbiotic system. Besides the gain of knowledge, this project has the objective to cre-ate a bio-hybrid system with a defined function and application – growing architectural artifacts
Discovery of a parsec-scale bipolar nebula around MWC 349A
We report the discovery of a bipolar nebula around the peculiar emission-line
star MWC 349A using archival Spitzer Space Telescope 24 um data. The nebula
extends over several arcminutes (up to 5 pc) and has the same orientation and
geometry as the well-known subarcsecond-scale (~400 times smaller) bipolar
radio nebula associated with this star. We discuss the physical relationship
between MWC 349A and the nearby B0 III star MWC 349B and propose that both
stars were members of a hierarchical triple system, which was ejected from the
core of the Cyg OB2 association several Myr ago and recently was dissolved into
a binary system (now MWC 349A) and a single unbound star (MWC 349B). Our
proposal implies that MWC 349A is an evolved massive star (likely a luminous
blue variable) in a binary system with a low-mass star. A possible origin of
the bipolar nebula around MWC 349A is discussed.Comment: 9 pages, 6 figures, accepted for publication in A&
Constraints on the Reheating Temperature in Gravitino Dark Matter Scenarios
Considering gravitino dark matter scenarios, we study constraints on the
reheating temperature of inflation. We present the gauge-invariant result for
the thermally produced gravitino yield to leading order in the Standard Model
gauge couplings. Within the framework of the constrained minimal supersymmetric
Standard Model (CMSSM), we find a maximum reheating temperature of about 10^7
GeV taking into account bound-state effects on the primordial Li abundance.
We show that late-time entropy production can relax this constraint
significantly. Only with a substantial entropy release after the decoupling of
the lightest Standard Model superpartner, thermal leptogenesis remains a viable
explanation of the cosmic baryon asymmetry within the CMSSM.Comment: 13 pages, 15 figures, revised version accepted for publication
(reheating phase considered, improved treatment of entropy production,
revised last section, references added
The formation of planetary disks and winds: an ultraviolet view
Planetary systems are angular momentum reservoirs generated during star
formation. This accretion process produces very powerful engines able to drive
the optical jets and the molecular outflows. A fraction of the engine energy is
released into heating thus the temperature of the engine ranges from the 3000K
of the inner disk material to the 10MK in the areas where magnetic reconnection
occurs. There are important unsolved problems concerning the nature of the
engine, its evolution and the impact of the engine in the chemical evolution of
the inner disk. Of special relevance is the understanding of the shear layer
between the stellar photosphere and the disk; this layer controls a significant
fraction of the magnetic field building up and the subsequent dissipative
processes ougth to be studied in the UV.
This contribution focus on describing the connections between 1 Myr old suns
and the Sun and the requirements for new UV instrumentation to address their
evolution during this period. Two types of observations are shown to be needed:
monitoring programmes and high resolution imaging down to, at least,
milliarsecond scales.Comment: Accepted for publication in Astrophysics and Space Science 9 figure
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