Temporally and spectrally resolved subpicosecond energy transfer within the peripheral antenna complex (LH2) and from LH2 to the core antenna complex in photosynthetic purple bacteria.

We report studies of energy transfer from the 800-nm absorbing pigment (B800) to the 850-nm absorbing pigment (B850) of the LH2 peripheral antenna complex and from LH2 to the core antenna complex (LH1) in Rhodobacter (Rb.) sphaeroides. The B800 to B850 process was studied in membranes from a LH2-reaction center (no LH1) mutant of Rb. sphaeroides and the LH2 to LH1 transfer was studied in both the wild-type species and in LH2 mutants with blue-shifted B850. The measurements were performed by using approximately 100-fs pulses to probe the formation of acceptor excitations in a two-color pump-probe measurement. Our experiments reveal a B800 to B850 transfer time of approximately 0.7 ps at 296 K and energy transfer from LH2 to LH1 is characterized by a time constant of approximately 3 ps at 296 K and approximately 5 ps at 77 K. In the blue-shifted B850 mutants, the transfer time from B850 to LH1 becomes gradually longer with increasing blue-shift of the B850 band as a result of the decreasing spectral overlap between the antennae. The results have been used to produce a model for the association between the ring-like structures that are characteristic of both the LH2 and LH1 antennae.

Estimation of satellite antenna phase center offsets for Galileo

Satellite antenna phase center offsets for the GalileoInOrbitValidation(IOV) and FullOperationalCapability (FOC) satellites are estimated by two different analysiscenters based on tracking data of a global GNSS network. The mean x- and y-offsets could be determined with a precision of a few centimeters. However, daily estimates of thex-offsets of the IOV satellites show pronounced systematic effects with a peak-to-peak amplitude of up to 70 cm that depend on the orbit model and the elevation of the Sun above the orbital plane. For the IOV y-offsets, no dependence on the orbit model exists but the scatter strongly depends on the elevation of the Sun above the orbital plane. In general, these systematic effects are significantly smaller for the FOC satellites. The z-offsets of the two analysis centers agree within the 10–15 cm level, and the time series do not show systematic effects. The application of an averaged Galileo satellite antenna model obtained from the two solutions results in a reduction of orbit day boundary discontinuities by up to one third—even if an independent software package is used.

A synthesis method for broad-band antenna impedance matching networks /

Vita.

Analysis and design of the log-periodic dipole antenna.

At head of title: Antenna Laboratory.

The equiangular spiral antenna /

"Contract AF33(616)-3220 Project No. 6(7-4600), Task No. 40572, Wright Air Development Center."

The characteristic impedance of the fin antenna of infinite length /

"Contract No. AF33(616)-3220 Project No. 6(7-4600) Task 40572 Wright Air Development Center"

Directional characteristics of a u-shaped slot antenna /

"Contract AF33(616)-3220 Project No. 6(7-4600) Task 40572 Wright Air Development Center"

An analytical study of spaced loop ADF antenna systems /

"Contract No. AF33(616)-3220 Project No. 6(7-4600) Task 40572 Wright Air Development Center."

Input impedance of a spherical ferrite antenna with a latitudinal current /

"Contract No. AF33(616)-310 RDO No. R-112-110 SR-6f2"

A unidirectional equiangular spiral antenna /

"Contract AF33(616)-3220 Project No. 6(7-4600) Task 40572 Wright Air Development Center"

The asymmetrically excited spherical antenna /

"Contract No. AF33(616)-310 RDO No. R-112-110 SR-6f2"

Coupling of antenna elements to a circular surface waveguide /

"Contract No. AF33(616)-310 RDO No. R-112-110 SR-6f2"

Evaluation of cross-correlation methods in the utilization of antenna systems /

Contract AF33(616)-6079 Project No. 9-(13-6278) Task 40572. Sponsored by: Wright Air Development Center"

Non-planar logarithmically periodic antenna structures /

"Contract AF33(616)-3220 Project No. 6(7-4600) Task 40572 Wright Air Development"