47 research outputs found
Testrun results from prototype fiber detectors for high rate particle tracking
A fiber detector concept has been realized allowing to registrate particles
within less than 100 nsec with a space point precision of about 0.1 mm at low
occupancy. Three full size prototypes have been build by different producers
and tested at a 3 GeV electron beam at DESY. After 3 m of light guides 8-10
photoelectrons were registrated by multichannel photomultipliers providing an
efficiency of more than 99%. Using all available data a resolution of 0.086 mm
was measured.Comment: 18 pages, 17 figure
Mastitis diagnostics and performance monitoring: a practical approach
In this paper a review is given of frequently used mastitis diagnostic methods in modern dairy practice. Methods used at the quarter, cow, herd and regional or national level are discussed, including their usability for performance monitoring in udder health. Future developments, such as systems in which milk-derived parameters are combined with modern analytical techniques, are discussed. It is concluded that, although much knowledge is available and science is still developing and much knowledge is available, it is not always fully exploited in practice
μ‑Oxo Dimerization Effects on Ground- and Excited-State Properties of a Water-Soluble Iron Porphyrin CO<sub>2</sub> Reduction Catalyst
Iron 5,10,15,20-tetra(para-N,N,N-trimethylanilinium)porphyrin
(Fe-p-TMA) is a water-soluble catalyst capable of
electrochemical
and photochemical CO2 reduction. Although its catalytic
ability has been thoroughly investigated, the mechanism and associated
intermediates are largely unknown. Previous studies proposed that
Fe-p-TMA enters catalytic cycles as a monomeric species.
However, we demonstrate herein that, in aqueous solutions, Fe-p-TMA undergoes formation of a μ-oxo porphyrin dimer
that exists in equilibrium with its monomeric form. The propensity
for μ-oxo formation is highly dependent on the solution pH and
ionic strength. Indeed, the μ-oxo form is stabilized in the
presence of electrolytes that are key components of catalytically
relevant conditions. By leveraging the ability to chemically control
and spectrally address both species, we characterize their ground-state
electronic structures and excited-state photodynamics. Global fitting
of ultrafast transient absorption data reveals two distinct excited-state
relaxation pathways: a three-component sequential model consistent
with monomeric relaxation and a two-component sequential model for
the μ-oxo species. Relaxation of the monomeric species is best
described as a ligand-to-metal charge transfer (τ1 = ∼500 fs), an ionic strength-dependent metal-to-ligand charge
transfer (τ2 = 2–4 ps), and finally relaxation
of a ligand field excited state to the ground state (τ3 = 5 ps). Conversely, excited-state relaxation of the μ-oxo
species proceeds via cleavage of an FeIII–O bond
to generate transient FeIVO and FeII porphyrin species (Ï„1 = 2 ps) that recombine to
the ground-state μ-oxo species (τ2 = ∼1
ns). This latter lifetime extends to timescales relevant for chemical
reactivity. It is therefore emphasized that further consideration
of catalyst speciation and chemical microenvironments is necessary
for elucidating the mechanisms of catalytic CO2 reduction
reactions
Test of a position-sensitive photomultiplier for fast scintillating fiber detector read-out
SIGLEAvailable from TIB Hannover: RA2999(92-176) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman