19,466 research outputs found
Analytical and experimental investigation of sidelobe suppression techniques for reflector type spacecraft antenna Final technical report
Near axis sidelobe suppression techniques for circularly polarized reflector type spacecraft antenna
Cuntz-Pimsner C*-algebras associated with subshifts
By using C*-correspondences and Cuntz-Pimsner algebras, we associate to every
subshift (also called a shift space) a C*-algebra , which is a
generalization of the Cuntz-Krieger algebras. We show that is the
universal C*-algebra generated by partial isometries satisfying relations given
by . We also show that is a one-sided conjugacy invariant of .Comment: 28 pages. This is a slightly updated version of a preprint from 2004.
Submitted for publication. In version 2 the Introduction has been changed,
two remarks (Remark 7.6 and 7.7) have been added and the list of references
has been update
The VLQ Calorimeter of H1 at HERA: A Highly Compact Device for Measurements of Electrons and Photons under Very Small Scattering Angles
In 1998, the detector H1 at HERA has been equipped with a small backward
spectrometer, the Very Low Q^2 (VLQ) spectrometer comprising a silicon tracker,
a tungsten - scintillator sandwich calorimeter, and a Time-of-Flight system.
The spectrometer was designed to measure electrons scattered under very low
angles, equivalent to very low squared four - momentum transfers Q^2, and high
energy photons with good energy and spatial resolution. The VLQ was in
operation during the 1999 and 2000 run periods. This paper describes the design
and construction of the VLQ calorimeter, a compact device with a fourfold
projective energy read-out, and its performance during test runs and in the
experiment.Comment: 32 pages, 25 figures, 2 tables (To be submitted to Nucl. Instrum.
Meth. A
Structure of a Complete ATP Synthase Dimer Reveals the Molecular Basis of Inner Mitochondrial Membrane Morphology
We determined the structure of a complete, dimeric F1Fo-ATP synthase from yeast Yarrowia lipolytica mitochondria by a combination of cryo-EM and X-ray crystallography. The final structure resolves 58 of the 60 dimer subunits. Horizontal helices of subunit a in Fo wrap around the c-ring rotor, and a total of six vertical helices assigned to subunits a, b, f, i, and 8 span the membrane. Subunit 8 (A6L in human) is an evolutionary derivative of the bacterial b subunit. On the lumenal membrane surface, subunit f establishes direct contact between the two monomers. Comparison with a cryo-EM map of the F1Fo monomer identifies subunits e and g at the lateral dimer interface. They do not form dimer contacts but enable dimer formation by inducing a strong membrane curvature of âŒ100°. Our structure explains the structural basis of cristae formation in mitochondria, a landmark signature of eukaryotic cell morphology
Off-diagonal disorder in the Anderson model of localization
We examine the localization properties of the Anderson Hamiltonian with
additional off-diagonal disorder using the transfer-matrix method and
finite-size scaling. We compute the localization lengths and study the
metal-insulator transition (MIT) as a function of diagonal disorder, as well as
its energy dependence. Furthermore we investigate the different influence of
odd and even system sizes on the localization properties in quasi
one-dimensional systems. Applying the finite-size scaling approach in
conjunction with a nonlinear fitting procedure yields the critical parameters
of the MIT. In three dimensions, we find that the resulting critical exponent
of the localization length agrees with the exponent for the Anderson model with
pure diagonal disorder.Comment: 12 pages including 4 EPS figures, accepted for publication in phys.
stat. sol. (b
Uniaxial pressure dependencies of the phase transitions in GdMnO
GdMnO shows an incommensurate antiferromagnetic order below
K, transforms into a canted A-type antiferromagnet below K, and for
finite magnetic fields along the b axis ferroelectric order occurs below
K. From high-resolution thermal expansion measurements along all
three principal axes, we determine the uniaxial pressure dependencies of the
various transition temperatures and discuss their correlation to changes of the
magnetic exchange couplings in MnO ().Comment: 2 pages, 3 figures, submitted to JMMM (Proceedings of ICM'06, Kyoto
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