245 research outputs found
Purification of the chloroplast-membrane dicyclohexylcarbodi-imide-binding proteolipid by ion-exchange chromatography
Analysis of normalized point source sensitivity as a performance metric for large telescopes
We investigate a new metric, the normalized point source sensitivity (PSSN), for characterizing the seeing-limited performance of large telescopes. As the PSSN metric is directly related to the photometric error of background limited observations, it represents the efficiency loss in telescope observing time. The PSSN metric properly accounts for the optical consequences of wave front spatial frequency distributions due to different error sources, which differentiates from traditional metrics such as the 80% encircled energy diameter and the central intensity ratio. We analytically show that multiplication of individual PSSN values due to individual errors is a good approximation for the total PSSN when various errors are considered simultaneously. We also numerically confirm this feature for Zernike aberrations as well as for the numerous error sources considered in the error budget of the Thirty Meter Telescope (TMT) using a ray optics simulator. Additionally, we discuss other pertinent features of the PSSN, including its relations to Zernike aberration, RMS wave front error, and central intensity ratio
Probing the order parameter symmetry in the cuprate high temperature superconductors by SQUID microscopy
The orbital component of the order parameter in the cuprate high-Tc cuprate
superconductors is now well established, in large part because of phase
sensitive tests. Although it would be desirable to use such tests on other
unconventional superconductors, there are a number of favorable factors
associated with the properties of the cuprates, and a number of technical
advances, that were required for these tests to be successful. In this review I
will describe the development of phase sensitive pairing symmetry tests using
SQUID microscopy, underlining the factors favoring these experiments in the
cuprates and the technical advances that had to be made.Comment: 12 pages, 7 figure, invited review to be published in Comptes Rendus
de l'Academie des Sciences (Comptes Rendus Physique
Observation of Vortex Coalescence, Vortex Chains and Crossing Vortices in the Anisotropic Spin-Triplet Superconductor
Scanning SQUID force microscopy is used to study magnetic flux
structures in single crystals of the layered spin triplet superconductor
SrRuO. Images of the magnetic flux configuration above the
-face of the cleaved crystal are acquired, mostly after
field-cooling the sample. For low applied magnetic fields, individual vortices
are observed, each carrying a single quantum of flux. Above 1 gauss,
coalescence of vortices is discovered. The coalescing vortices may indicate the
presence of domains of a chiral order parameter. When the applied field is
tilted from the -axis, we observe a gradual transition from vortex
domains to vortex chains. The in-plane component of the applied magnetic field
transforms the vortex domains to vortex chains by aligning them along the field
direction.This behavior and the inter-chain distance varies in qualitative
agreement with the Ginzburg Landau theory of anisotropic 3D superconductors.
The effective mass anisotropy of SrRuO, =20, is the
highest observed in three dimensional superconductors. When the applied field
is closely in plane, the vortex form flux channels confined between the
crystal-layers. Residual Abrikosov vortices are pinned preferentially on these
channels. Thus the in-plane vortices are decorated by crossing Abrikosov
vortices: two vortex orientations are apparent simultaneously, one along the
layers and the other perpendicular to the layers.Comment: to appear in Physica C M2S conference Dresde
Analysis of Normalized Point Source Sensitivity as a performance metric for the Thirty Meter Telescope
We investigate a new metric, Normalized Point Source Sensitivity (PSSN), for characterizing the seeing limited performance of the Thirty Meter Telescope. As the PSSN metric is directly related to the photometric error of background limited observations, it truly represents the efficiency loss in telescope observing time. The PSSN metric properly accounts for the optical consequences of wavefront spatial frequency distributions due to different error sources, which makes it superior to traditional metrics such as the 80% encircled energy diameter. We analytically show that multiplication of individual PSSN values due to individual errors is a good approximation for the total PSSN when various errors are considered simultaneously. We also numerically confirm this feature for Zernike aberrations, as well as for the numerous error sources considered in the TMT error budget using a ray optics simulator, Modeling and Analysis for Controlled Optical Systems. We also discuss other pertinent features of the PSSN including its relations to Zernike aberration and RMS wavefront error
Dislocations and the enhancement of superconductivity in odd-parity superconductor SrRuO
We report observation of the enhancement of superconductivity near lattice
dislocations and the absence of the strengthening of vortex pinning in
odd-parity superconductor SrRuO, both surprising results in direct
contrast to the well known sensitivity of superconductivity in SrRuO to
disorder. The enhanced superconductivity appears to be related fundamentally to
the two-component nature of the superconducting order parameter, as revealed in
our phenomenological theory taking into account the effect of symmetry
reduction near a dislocation.Comment: 5 pages, 4 figures, submitted to Physical Review Letter
Magnetic skyrmions and their lattices in triplet superconductors
Complete topological classification of solutions in SO(3) symmetric
Ginzburg-Landau free energy has been performed and a new class of solutions in
weak external magnetic field carrying two units of magnetic flux has been
identified. These solutions, magnetic skyrmions, do not have singular core like
Abrikosov vortices and at low magnetic field become lighter for strongly type
II superconductors. As a consequence, the lower critical magnetic field Hc1 is
reduced by a factor of log(kappa). Magnetic skyrmions repel each other as 1/r
at distances much larger then magnetic penetration depth forming relatively
robust triangular lattice. Magnetic induction near Hc1 increases gradually as
(H-Hc1)^2. This agrees very well with experiments on heavy fermion
superconductor UPt3. Newly discovered Ru based compounds Sr2RuO4 and
Sr2YRu(1-x)Cu(x)O6 are other possible candidates to possess skyrmion lattices.
Deviations from exact SO(3) symmetry are also studied.Comment: 23 pages, 10 eps figure
Ginzburg-Landau theory of superconductors with short coherence length
We consider Fermions in two dimensions with an attractive interaction in the
singlet d-wave channel of arbitrary strength. By means of a
Hubbard-Stratonovich transformation a statistical Ginzburg-Landau theory is
derived, which describes the smooth crossover from a weak-coupling BCS
superconductor to a condensate of composite Bosons. Adjusting the interaction
strength to the observed slope of H_c2 at T_c in the optimally doped high-T_c
compounds YBCO and BSCCO, we determine the associated values of the
Ginzburg-Landau correlation length xi and the London penetration depth lambda.
The resulting dimensionless ratio k_F xi(0) approx 5-8 and the Ginzburg-Landau
parameter kappa=lambda xi approx 90-100 agree well with the experimentally
observed values. These parameters indicate that the optimally doped materials
are still on the weak coupling side of the crossover to a Bose regime.Comment: 12 pages, RevTeX, 6 postscript figures, resubmitted with minor
changes in section III, to appear in Physical Review
DFB Lasers Between 760 nm and 16 μm for Sensing Applications
Recent years have shown the importance of tunable semiconductor lasers in optical sensing. We describe the status quo concerning DFB laser diodes between 760 nm and 3,000 nm as well as new developments aiming for up to 80 nm tuning range in this spectral region. Furthermore we report on QCL between 3 μm and 16 μm and present new developments. An overview of the most interesting applications using such devices is given at the end of this paper
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