2,887 research outputs found
Exhumation history of eastern Ladakh revealed by Ar-40/Ar-39 and fission-track ages: the Indus River-Tso Morari transect, NW Himalaya
Fission-track and Ar-40/Ar-39 ages place time constraints on the exhumation of the North Himalayan nappe stack, the Indus Suture Zone and Molasse, and the Transhimalayan Batholith in eastern Ladakh (NW India). Results from this and previous studies on a north-south transect passing near Tso Morari Lake suggest that the SW-directed North Himalayan nappe stack (comprising the Mata, Tetraogal and Tso Morari nappes) was emplaced and metamorphosed by c. 50-45 Ma, and exhumed to moderately shallow depths (c. 10 km) by c. 45-40 Ma. From the mid-Eocene to the present, exhumation continued at a steady and slow rate except for the root zone of the Tso Morari nappe, which cooled faster than the rest of the nappe stack. Rapid cooling occurred at c. 20 Ma and is linked to brittle deformation along the normal Ribil-Zildat Fault concomitant with extrusion of the Crystalline nappe in the south. Data from the Indus Molasse suggest that sediments were still being deposited during the Miocene
Nonlinear metrology with a quantum interface
We describe nonlinear quantum atom-light interfaces and nonlinear quantum
metrology in the collective continuous variable formalism. We develop a
nonlinear effective Hamiltonian in terms of spin and polarization collective
variables and show that model Hamiltonians of interest for nonlinear quantum
metrology can be produced in Rb ensembles. With these Hamiltonians,
metrologically relevant atomic properties, e.g. the collective spin, can be
measured better than the "Heisenberg limit" . In contrast to other
proposed nonlinear metrology systems, the atom-light interface allows both
linear and non-linear estimation of the same atomic quantities.Comment: 8 pages, 1 figure
A diode laser stabilization scheme for 40Ca+ single ion spectroscopy
We present a scheme for stabilizing multiple lasers at wavelengths between
795 and 866 nm to the same atomic reference line. A reference laser at 852 nm
is stabilized to the Cs D2 line using a Doppler-free frequency modulation
technique. Through transfer cavities, four lasers are stabilized to the
relevant atomic transitions in 40Ca+. The rms linewidth of a transfer-locked
laser is measured to be 123 kHz with respect to an independent atomic
reference, the Rb D1 line. This stability is confirmed by the comparison of an
excitation spectrum of a single 40Ca+ ion to an eight-level Bloch equation
model. The measured Allan variance of 10^(-22) at 10 s demonstrates a high
degree of stability for time scales up to 100 s.Comment: 8 pages, 11 figure
Conceptual design of elliptical cavities for intensity and position sensitive beam measurements in storage rings
Position sensitive beam monitors are indispensable for the beam diagnostics
in storage rings. Apart from their applications in the measurements of beam
parameters, they can be used in non-destructive in-ring decay studies of
radioactive ion beams as well as enhancing precision in the isochronous mass
measurement technique. In this work, we introduce a novel approach based on
cavities with elliptical cross-section, in order to compensate for existing
limitations in ion storage rings. The design is aimed primarily for future
heavy ion storage rings of the FAIR project. The conceptual design is discussed
together with simulation results.Comment: Added definition of Uv and Pdiss in the introduction section. Added
Mode numbering in table 1 and figure 1 for more clarity. Corrected one wrong
figure reference. Other minor typo correction
Engineering Quantum States, Nonlinear Measurements, and Anomalous Diffusion by Imaging
We show that well-separated quantum superposition states, measurements of
strongly nonlinear observables, and quantum dynamics driven by anomalous
diffusion can all be achieved for single atoms or molecules by imaging
spontaneous photons that they emit via resonance florescence. To generate
anomalous diffusion we introduce continuous measurements driven by L\'evy
processes, and prove a number of results regarding their properties. In
particular we present strong evidence that the only stable L\'evy density that
can realize a strictly continuous measurement is the Gaussian.Comment: revtex4-1, 17 pages, 7 eps figure
Transition from sea to land: olfactory function and constraints in the terrestrial hermit crab Coenobita clypeatus
The ability to identify chemical cues in the environment is essential to most animals. Apart from marine larval stages, anomuran land hermit crabs (Coenobita) have evolved different degrees of terrestriality, and thus represent an excellent opportunity to investigate adaptations of the olfactory system needed for a successful transition from aquatic to terrestrial life. Although superb processing capacities of the central olfactory system have been indicated in Coenobita and their olfactory system evidently is functional on land, virtually nothing was known about what type of odourants are detected. Here, we used electroantennogram (EAG) recordings in Coenobita clypeatus and established the olfactory response spectrum. Interestingly, different chemical groups elicited EAG responses of opposite polarity, which also appeared for Coenobita compressus and the closely related marine hermit crab Pagurus bernhardus. Furthermore, in a two-choice bioassay with C. clypeatus, we found that water vapour was critical for natural and synthetic odourants to induce attraction or repulsion. Strikingly, also the physiological response was found much greater at higher humidity in C. clypeatus, whereas no such effect appeared in the terrestrial vinegar fly Drosophila melanogaster. In conclusion, our results reveal that the Coenobita olfactory system is restricted to a limited number of water-soluble odourants, and that high humidity is most critical for its function
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