439 research outputs found
The compatible conversion system
Compatible conversion system centralizes the solution of general problems arising from the use of direct access mass storage. It also provides a simple stable interface for the conversion of production programs to process on third generation computer system
recent techniques and applications using soft X-ray spectroscopy
The aim of a more precise knowledge about molecular structures and the nature
of chemical bonds is the driving force behind the development of numerous
experimental methods and theories. Recent soft X-ray based techniques provide
novel opportunities for tackling the structure and the dynamics of chemical
and biochemical systems in solution. In our research group we are developing
experimental methods for mapping the electronic structure and dynamics of
molecular systems in solution during bond-building and breaking using soft
X-ray absorption and emission spectroscopy. The combination of such recent
developments with conventional spectroscopy as well as theoretical modeling
allows us to address open questions about hydrogen bonds, thermodynamics and
active centers of biological systems. Based on the core-hole clock and
pump–probe spectroscopy dynamics on the time scale from sub-femtoseconds up to
picoseconds can be revealed
Apresentação
Apresentação do Dossiê BRASIL-ALEMANHA: IMIGRAÇÃO, CIDADANIA E COOPERAÇÃ
Charge transfer to solvent dynamics in iodide aqueous solution studied at ionization threshold
We explore the early-time electronic relaxation in NaI aqueous solution
exposed to a short UV laser pulse. Rather than initiating the charge transfer
reaction by resonant photoexcitation of iodide, in the present time-resolved
photoelectron spectroscopy study the charge-transfer-to-solvent (CTTS) states
are populated via electronic excitation above the vacuum level. By analyzing
the temporal evolution of electron yields from ionization of two transient
species, assigned to CTTS and its first excited state, we determine both their
ultrafast population and relaxation dynamics. Comparison with resonant-
excitation studies shows that the highly excited initial states exhibit
similar relaxation characteristics as found for resonant excitation.
Implications for structure and dynamical response of the hydration cage are
discussed
Computational protein profile similarity screening for quantitative mass spectrometry experiments
Motivation: The qualitative and quantitative characterization of protein abundance profiles over a series of time points or a set of environmental conditions is becoming increasingly important. Using isobaric mass tagging experiments, mass spectrometry-based quantitative proteomics deliver accurate peptide abundance profiles for relative quantitation. Associated data analysis workflows need to provide tailored statistical treatment that (i) takes the correlation structure of the normalized peptide abundance profiles into account and (ii) allows inference of protein-level similarity. We introduce a suitable distance measure for relative abundance profiles, derive a statistical test for equality and propose a protein-level representation of peptide-level measurements. This yields a workflow that delivers a similarity ranking of protein abundance profiles with respect to a defined reference. All procedures have in common that they operate based on the true correlation structure that underlies the measurements. This optimizes power and delivers more intuitive and efficient results than existing methods that do not take these circumstances into account. Results: We use protein profile similarity screening to identify candidate proteins whose abundances are post-transcriptionally controlled by the Anaphase Promoting Complex/Cyclosome (APC/C), a specific E3 ubiquitin ligase that is a master regulator of the cell cycle. Results are compared with an established protein correlation profiling method. The proposed procedure yields a 50.9-fold enrichment of co-regulated protein candidates and a 2.5-fold improvement over the previous method
Experimental entanglement verification and quantification via uncertainty relations
We report on experimental studies on entanglement quantification and
verification based on uncertainty relations for systems consisting of two
qubits. The new proposed measure is shown to be invariant under local unitary
transformations, by which entanglement quantification is implemented for
two-qubit pure states. The nonlocal uncertainty relations for two-qubit pure
states are also used for entanglement verification which serves as a basic
proposition and promise to be a good choice for verification of multipartite
entanglement.Comment: 5 pages, 3 figures and 2 table
Realtime calibration of the A4 electromagnetic lead fluoride calorimeter
Sufficient energy resolution is the key issue for the calorimetry in particle
and nuclear physics. The calorimeter of the A4 parity violation experiment at
MAMI is a segmented calorimeter where the energy of an event is determined by
summing the signals of neighbouring channels. In this case the precise matching
of the individual modules is crucial to obtain a good energy resolution. We
have developped a calibration procedure for our total absorbing electromagnetic
calorimeter which consists of 1022 lead fluoride (PbF_2) crystals. This
procedure reconstructs the the single-module contributions to the events by
solving a linear system of equations, involving the inversion of a 1022 x
1022-matrix. The system has shown its functionality at beam energies between
300 and 1500 MeV and represents a new and fast method to keep the calorimeter
permanently in a well-calibrated state
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