In purple reaction centers, primary charge separation may lead to radical pair states which differ in the orientation of their dipole moments by {approx equal}31{degree} as revealed in the crystal ...structure analysis. Depending on the mechanism, two-step sequential or unistep superexchange, the primary radical pair states are either P{sup +}B{sup {minus}}H or P{sup +}BH{sup {minus}} (P, B, and H denoting the bacteriochlorphyll dimer, bacteriochlorophyll monomer, and bacteriopheophytin, respectively). Since this fact is reflected in the angular dependence of the primary charge separation rate in an external electric field, it also shows up in the excitation anisotropy of electric field induced changes of the fluorescence yield from the primary donor {sup 1}P{sup *}. This method has been applied to the fluorescence from reaction centers of Rb. sphaeroides, R-26, and an angle larger than 52{degree} between the dipole of the primary radical pair and the photoselected transition moment of the Q{sub x} transition of H{sub B} at the inactive pigment branch B has been determined at low temperatures. Allowing for considerable uncertainties in the directions of dipole and transition moments, this angle is only compatible with H{sub A} at the active branch A being the primary acceptor and excludes kinetic participation of B{sub A} located between P and H{sub A} in reaction centers embedded in a polymer membrane at temperatures below 180 K.
The Ny-Alesund Ozone Measurements Intercomparison (NAOMI) campaign for measurements of stratospheric ozone and temperature was conducted at the Primary Station of the NDSC in Ny-Alesund/Spitsbergen ...during January-February 1998. Local instrumentation (ozone and aerosol lidar, microwave radiometer RAM, ECC-type ozone sondes) was complemented with the NDSC mobile ozone lidar from NASA/GSFC. The aim was the validation of stratospheric ozone and temperature profiles according to NDSC guidelines. The blind intercomparison of ozone profiles revealed good agreement (< plus or minus 5%) up to 31 km. At higher altitudes the different altitude ranges and resolutions of the instruments, as well as effects of retrieval algorithms have to be considered. Temperature data of the two lidar systems agreed well and revealed the stratospheric warming, which occurred in early February 1998. NCEP temperature analyses for Spitsbergen agreed very well with lidar data before, but not during this warming event.
Two-step sequential and unistep, superexchange primary electron transfer form primary radical pair states which differ in the direction and magnitude of their dipole moments as revealed in the X-ray ...structure analysis. The direction can be measured by the excitation anisotropy of electric field induced changes of the fluorescence yield. This method determines angles between the dipole of the primary radical pair and photoselected transition moments (in absorption and emission) of cofactors in the reaction centers. Transitions particularly favourable for discrimination between the two models of primary electron transfer are discussed.
A major application of the CHAMP occultation data is the preparation of processing systems for future occultation missions. The University of Graz (IGAM) uses data and analysis results to prepare for ...the ACE+ multi-satellite occultation mission, which is currently foreseen to be launched in 2008. We compare vertical profiles of refractivity, derived by GFZ and IGAM, with ECMWF data (European Centre for Medium-Range Weather Forecasts) and discuss the deviations. Good agreement is observed in the upper troposphere and stratosphere. The magnitude of the observed refractivity bias in the lower troposphere depends significantly on the quality control criterion. The bias can be nearly eliminated by the application of the Full Spectrum Inversion analysis method down to ∼1 km above the Earth's surface.
Friedrich Robert Helmert (1843-1917) defined geodesy as the science “of measurements and mappings of the Earth’s surface”. Over time, this definition of geodesy has been extended, mainly as a ...consequence of technological developments allowing geodesy to observe the Earth on global scales with high accuracy. Today, geodesy is the science of determining the geometry, gravity field, and rotation of the Earth and their evolution in time. This understanding of modern geodesy has led to the definition of the “three pillars of geodesy”, namely (1) Geokinematics, (2) Earth Rotation and (3) the Gravity Field (see Figure 1.1 on page 4). These three pillars are intrinsically linked to each other, and they jointly change as a consequence of dynamical processes in the Earth system as a whole.
The temperatures retrieved from MIPAS/ENVISAT limb mid-infrared emission and CHAMP GPS radio occultation measurements are compared at altitudes between 8 – 30 km during the stratospheric major sudden ...warming in the southern hemisphere winter of 2002. The mean differences between the correlative measurements of the two instruments are less than ∼1 K with rms deviations of ∼3–5 K. The MIPAS temperatures are slightly higher than those of GPS-RO around 30 km. Possible explanation is discussed.
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