2,637 research outputs found
4-Dimensional Tracking with Ultra-Fast Silicon Detectors
The evolution of particle detectors has always pushed the technological limit
in order to provide enabling technologies to researchers in all fields of
science. One archetypal example is the evolution of silicon detectors, from a
system with a few channels 30 years ago, to the tens of millions of independent
pixels currently used to track charged particles in all major particle physics
experiments. Nowadays, silicon detectors are ubiquitous not only in research
laboratories but in almost every high-tech apparatus, from portable phones to
hospitals. In this contribution, we present a new direction in the evolution of
silicon detectors for charge particle tracking, namely the inclusion of very
accurate timing information. This enhancement of the present silicon detector
paradigm is enabled by the inclusion of controlled low gain in the detector
response, therefore increasing the detector output signal sufficiently to make
timing measurement possible. After providing a short overview of the advantage
of this new technology, we present the necessary conditions that need to be met
for both sensor and readout electronics in order to achieve 4-dimensional
tracking. In the last section we present the experimental results,
demonstrating the validity of our research path.Comment: 72 pages, 3 tables, 55 figure
Relation between TMAOase activity and content of formaldehyde in fillet minces and bellyflap minces from gadoid fishes
Minced fish is a significant component of a number of frozen fishery products like fish fingers, cakes and patties. Predominately minced fish is produced from gadoid species (Alaska pollack, cod, saithe, hake and others) possessing the enzyme trimethylamine oxide demethylase (TMAOase, E.C. 4.1.2.32) (Rehbein and Schreiber 1984). TMAOase catalyses the degradation of trimethylamine oxide (TMAO) to formaldehyde (FA) and dimethylamine (DMA), preferentially during frozen storage of products (Hultin 1992). In most gadoid species light muscle contains only low
activity of TMAOase, the activity of red muscle and bellyflaps being somewhat higher. In contrast, the TMAOase
activity in blood, kidney and other tissues, residues of which may contaminate minced fish flesh, may be higher for
several orders of magnitude (Rehbein and Schreiber 1984)
4D tracking with ultra-fast silicon detectors
The evolution of particle detectors has always pushed the technological limit in order to provide enabling technologies to researchers in all fields of science. One archetypal example is the evolution of silicon detectors, from a system with a few channels 30 years ago, to the tens of millions of independent pixels currently used to track charged particles in all major particle physics experiments. Nowadays, silicon detectors are ubiquitous not only in research laboratories but in almost every high-tech apparatus, from portable phones to hospitals. In this contribution, we present a new direction in the evolution of silicon detectors for charge particle tracking, namely the inclusion of very accurate timing information. This enhancement of the present silicon detector paradigm is enabled by the inclusion of controlled low gain in the detector response, therefore increasing the detector output signal sufficiently to make timing measurement possible. After providing a short overview of the advantage of this new technology, we present the necessary conditions that need to be met for both sensor and readout electronics in order to achieve 4D tracking. In the last section, we present the experimental results, demonstrating the validity of our research path
Experimental measurement of stress at a four-domain junction in lead zirconate titanate
A junction between two lamellar bands of ferroelectric domains in a lead zirconate titanate (PZT) ceramic is analysed using Kikuchi diffraction patterns in the transmission electron microscope. Indexing of the diffraction patterns allowed the determination of the 3D relative orientation of the 4 different domains at the junction and thus the characterisation of the domain boundaries. The local c/a ratio could also be determined from the misorientations at the domain boundaries. Analysis of the data showed that large stresses were concentrated at the junction, and that this is inevitable at such band junctions. Such stress concentrations could act as nuclei for cracking of the ceramic under additional loading in service, perhaps particularly as a consequence of extended electromechanical cycling. Moreover, the stresses would increase with increasing c/a making the issues all the more serious for Ti-rich compositions having larger c/a ratios
Coinitial sets and fixed points in partially ordered sets
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45432/1/12_2005_Article_BF01191777.pd
DNA condensation and redissolution: Interaction between overcharged DNA molecules
The effective DNA-DNA interaction force is calculated by computer simulations
with explicit tetravalent counterions and monovalent salt. For overcharged DNA
molecules, the interaction force shows a double-minimum structure. The
positions and depths of these minima are regulated by the counterion density in
the bulk. Using two-dimensional lattice sum and free energy perturbation
theories, the coexisting phases for DNA bundles are calculated. A
DNA-condensation and redissolution transition and a stable mesocrystal with an
intermediate lattice constant for high counterion concentration are obtained.Comment: 26 pages, 10 figure
Trapped ions in optical lattices for probing oscillator chain models
We show that a chain of trapped ions embedded in microtraps generated by an
optical lattice can be used to study oscillator models related to dry friction
and energy transport. Numerical calculations with realistic experimental
parameters demonstrate that both static and dynamic properties of the ion chain
change significantly as the optical lattice power is varied. Finally, we lay
out an experimental scheme to use the spin degree of freedom to probe the phase
space structure and quantum critical behavior of the ion chain
Spatially Resolved Study of Backscattering in the Quantum Spin Hall State
The discovery of the quantum spin Hall (QSH) state, and topological insulators in general, has sparked strong experimental efforts. Transport studies of the quantum spin Hall state have confirmed the presence of edge states, showed ballistic edge transport in micron-sized samples, and demonstrated the spin polarization of the helical edge states. While these experiments have confirmed the broad theoretical model, the properties of the QSH edge states have not yet been investigated on a local scale. Using scanning gate microscopy to perturb the QSH edge states on a submicron scale, we identify well-localized scattering sites which likely limit the expected nondissipative transport in the helical edge channels. In the micron-sized regions between the scattering sites, the edge states appear to propagate unperturbed, as expected for an ideal QSH system, and are found to be robust against weak induced potential fluctuations
Deconfinement Transition and Bound States in Frustrated Heisenberg Chains: Regimes of Forced and Spontaneous Dimerization
We use recently developed strong-coupling expansion methods to study the
two-particle spectra for the frustrated alternating Heisenberg model,
consisting of an alternating nearest neighbor antiferromagnetic exchange and a
uniform second neighbor antiferromagnetic exchange. Starting from the limit of
weakly coupled dimers, we develop high order series expansions for the
effective Hamiltonian in the two-particle subspace. In the limit of a strong
applied dimerization, we calculate accurately various properties of singlet and
triplet bound states and quintet antibound states. We also develop series
expansions for bound state energies in various sectors, which can be
extrapolated using standard methods to cases where the external
bond-alternation goes to zero. We study the properties of singlet and triplet
bound states in the latter limit and suggest a crucial role for the bound
states in the unbinding of triplets and deconfinement of spin-half excitations.Comment: 17 figures, revte
Heterogeneities in Supercooled liquids: A Density Functional Study
A metastable state, characterized by a low degree of mass localization is
identified using Density Functional Theory. This free energy minimum, located
through the proper evaluation of the competing terms in the free energy
functional, is independent of the specific form of the DFT used. Computer
simulation results on particle motion indicate that this heterogeneous state
corresponds to the supercooled state.Comment: 10 pages, 6 figure
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