988 research outputs found
A combined research agenda towards integrated conservation and development for Madagascar
Better integration of social and natural science activities seems to be the key to improve the efficiency of conservation and development. While there is no recipe for success, this paper argues that conservation has to pay for itself if it wants to be anchored in present day societies. In systems where humans depend largely on subsistence activities, economic benefits from conservation must outweigh the benefits from increasing these activities. Coming from a natural science perspective, this paper proposes some activities that could improve the basis for decision making and contribute to the long term integration of sustainable conservation and development. It is argued that experiences from various projects must be evaluated and be accessible; data should be stored in a central database that can be used to develop future programs; restoration of various sorts providing direct income for the local human populations (including gardens, native and exotic tree plantations with valuable species) should be a priority; and natural science projects should add analyses of processes to the present preponderance of describing patterns. All these activities should result in integrated action to maintain natural biodiversity as a key component to maintain and improve local livelihoods.
KEYWORDS: Restoration, database management, ecosystem function, ecosystem process
Dynamics and Dissipation induced by Single-Electron Tunneling in Carbon Nanotube Nanoelectromechanical Systems
We demonstrate the effect of single-electron tunneling (SET) through a carbon
nanotube quantum dot on its nanomechanical motion. We find that the frequency
response and the dissipation of the nanoelectromechanical system (NEMS) to SET
strongly depends on the electronic environment of the quantum dot, in
particular on the total dot capacitance and the tunnel coupling to the metal
contacts. Our findings suggest that one could achieve quality factors of
10 or higher by choosing appropriate gate dielectrics and/or by improving
the tunnel coupling to the leads
Adiabatic quantum simulations with driven superconducting qubits
We propose a quantum simulator based on driven superconducting qubits where
the interactions are generated parametrically by a polychromatic magnetic flux
modulation of a tunable bus element. Using a time-dependent Schrieffer-Wolff
transformation, we analytically derive a multi-qubit Hamiltonian which features
independently tunable and -type interactions as well as local bias
fields over a large parameter range. We demonstrate the adiabatic simulation of
the ground state of a hydrogen molecule using two superconducting qubits and
one tunable bus element. The time required to reach chemical accuracy lies in
the few microsecond range and therefore could be implemented on currently
available superconducting circuits. Further applications of this technique may
also be found in the simulation of interacting spin systems.Comment: 11 pages, 6 figure
A low-loss, broadband antenna for efficient photon collection from a coherent spin in diamond
We report the creation of a low-loss, broadband optical antenna giving highly
directed output from a coherent single spin in the solid-state. The device, the
first solid-state realization of a dielectric antenna, is engineered for
individual nitrogen vacancy (NV) electronic spins in diamond. We demonstrate a
directionality close to 10. The photonic structure preserves the high spin
coherence of single crystal diamond (T2>100us). The single photon count rate
approaches a MHz facilitating efficient spin readout. We thus demonstrate a key
enabling technology for quantum applications such as high-sensitivity
magnetometry and long-distance spin entanglement.Comment: 5 pages, 4 figures and supplementary information (5 pages, 8
figures). Comments welcome. Further information under
http://www.quantum-sensing.physik.unibas.c
Continental exhumation triggered by partial melting at ultrahigh pressure
International audiencePartial melting textures, observed in most continental crust buried in ultrahigh-pressure (UHP) conditions, have mostly been related to their retrograde evolution during exhumation in collisional orogens. Analysis of leucosomes from the Western Gneiss Region (WGR, Norway) UHP and HP domains in the Caledonides show a wide scatter of their chemistries, from early ones close to trondhjemites restricted to UHP domains, to granites in late occurrences or associated with HP domains. Nearly trondhjemitic compositions compare with hydrous melts produced in felsic systems at high pressure (>2 GPa) and moderate temperature (<900 °C). Partial melting experiments at higher temperatures or in dry conditions produce granitic glasses similar to late leucosomes from the WGR. Comparison of pressure-temperature paths for Caledonian eclogites with melting and dehydration reactions for the surrounding gneiss suggest that (1) the continental crust remained partially hydrated during its subduction to ultrahigh pressure, and (2) partial melting reactions producing the trondhjemitic melts started as soon as the WGR rocks reached their hydrated solidus, at the peak pressure recorded by the eclogites. The limited partial melting degree at the peak conditions induced weakening of the continental crust, decoupling from the lithospheric root, and initiation of exhumation
Analysis of kinematics and dynamics of modular robot assemblies
The development of self-reconfigurable modular robots has experienced significant progress. Continuous improvement during the past twenty years produced flexible and easy maintainable robot mechanisms. Self reconfiguring modular robots consist of various similar robotic modules and are designed to establish manifold connections between each of these link modules. Moreover these modules are able to perform movements to change the shape or the position of the robotic chain. In this thesis the main focus lies on the analysis of kinematics and dynamics of small modular robot organisms and their movement pattern. Although diverse linkage mechanisms do exist, practically no motion of one module can be accomplished without interacting with a second one. Therefore furthermore fundamental is the study and examination of dyad kinematics which represent the pattern of movement between solely two modules. However generation and simulation of models of modular robot kinematics and dynamics are complex and manual derivation needs tremendous efforts as every configuration and alternation of shape induce new changes of parametersÂŽ values. Besides machinedriven computation requires a great deal of energy and increased storage capacity if every module constellation and applicable movements are predefined in a database. To avoid this squandering of resources a framework is implemented in Matlab based on ChenÂŽs theory to design an accurate dynamic model. In the end, this thesis shall provide a farther step towards a robust and flexible modular robot organism which is able to perform reliable interaction with the environment to constitute to an optimized and effective realization of tasks assigned to it in industry or in the future private households
Photonic nano-structures on (111) oriented diamond
We demonstrate the fabrication of single-crystalline diamond nanopillars on a
(111)-oriented chemical vapor deposited diamond substrate. This crystal
orientation offers optimal coupling of nitrogen-vacancy (NV) center emission to
the nanopillar mode and is thus advantageous over previous approaches. We
characterize single native NV centers in these nanopillars and find one of the
highest reported saturated fluorescence count rates in single crystalline
diamond in excess of 10 counts per second. We show that our
nano-fabrication procedure conserves the preferential alignment as well as the
spin coherence of the NVs in our structures. Our results will enable a new
generation of highly sensitive probes for NV magnetometry and pave the way
toward photonic crystals with optimal orientation of the NV center's emission
dipole.Comment: 4 pages original manuscript, 3 pages supplementary materia
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