1,447 research outputs found
Vector mesons in systems
A new selection rule is described for the vector mesons in the decuplet
representations of flavor SU(3)Comment: 7 pages and 1 figur
Ramsey's Method of Separated Oscillating Fields and its Application to Gravitationally Induced Quantum Phaseshifts
We propose to apply Ramsey's method of separated oscillating fields to the
spectroscopy of the quantum states in the gravity potential above a vertical
mirror. This method allows a precise measurement of quantum mechanical
phaseshifts of a Schr\"odinger wave packet bouncing off a hard surface in the
gravitational field of the earth. Measurements with ultra-cold neutrons will
offer a sensitivity to Newton's law or hypothetical short-ranged interactions,
which is about 21 orders of magnitude below the energy scale of
electromagnetism.Comment: 7 pages, 6 figure
Micro Laser Melting: Analyses of Current Potentials and Restrictions for the Additive Manufacturing of Micro Structures
Although there is a significant requirement for complex micro parts, current metal processing
additive manufacturing techniques are limited in achievable part accuracy and geometric
resolution. Due to the recently developed process of Micro Laser Melting (MLM) new
potentials in micro manufacturing are realizable.
This paper gives an overview of the present potentials of MLM using 316L steel powder.
While using powder material with a grain size of ≤ 5 µm this technique enables layer
thicknesses from 5 to 7 µm. Due to the use of different exposure strategies and laser modes
(pulsed and continuous radiation) high aspect ratios up to 260 could be realized with thin wall
structures. Furthermore, the influence of laser mode and exposure sequence on the part
density, surface quality and accuracy of lattice structures with a minimum wall thickness
lower than 40 µm is analyzed.Mechanical Engineerin
Light Hadron Spectroscopy: Theory and Experiment
Rapporteur talk at the Lepton-Photon Conference, Rome, July 2001: reviewing
the evidence and strategies for understanding scalar mesons, glueballs and
hybrids, the gluonic Pomeron and the interplay of heavy flavours and light
hadron dynamics. Dedicated to the memory of Nathan Isgur, long-time
collaborator and friend, whose original ideas in hadron spectroscopy formed the
basis for much of the talk.Comment: to be published in "Lepton Photon 2001 Conference Proceedings" (World
Scientific Publishing), 19 pages with 6 figure
Communication and Surveillance for Ground Transportation
For high speed intercity or low speed intracity operation, communications and surveillance are important aspects in the design of control systems for advanced ground transportation. New technological approaches in communications and surveillance can provide improvements in system capacity, operational economy, safety and passenger convenience.
A dielectric waveguide for communications and surveillance of vehicle characteristics (position and velocity) has been under experimental and analytical investigation for use along fixed guideways for ground transportation. This communication concept is nonradiating, has a broad bandwidth and provides a high rate of information transfer. Another important aspect of guideway surveillance is the detection of foreign obstacles that may cause vehicle damage or compromise passenger safety. For this application, an optical concept using a set of laser beams along the wayside is under investigation. The operating characteristics and method of deployment along TACV and railway guideways are presented
Molecular Evidence for Inclusion on the Phylum Pentastomida in the Crustacea
The phylogenetic status of the phylum Pentastomida (tongue worms) was considered on the basis of comparison of nucleotide sequences of 18S ribosomal RNA from the pentastome Porocephalus crotali, the branchiuran crustacean fish louse Argulus nobilis, other crustaceans, and representatives of the Annelida, Chelicerata, Myriapoda, and Insecta. Maximum parsimony and invariants (at P \u3c 0.04) analyses support an Argulus/Porocephalus clade, providing strong support for the proposal that tongue worms are highly modified crustaceans closely related to fish lice
Selective Laser Melting of Porous Structures
Within the Center of Smart Interfaces “Understanding and Designing Fluid Boundaries”,
a German Excellence Initiative, the Institute of Production Management, Technology and
Machine Tools examines the manufacturing of porous structures by using selective laser melting
(SLM). In this paper two different strategies are presented in order to obtain porosity: One
strategy is to manufacture geometrically defined lattice structures. SLM allows here complex
geometries that cannot be manufactured by conventional technologies to be built. The second
approach is to manufacture geometrically undefined porosity by a specific modification of
exposure parameters. The SLM generated porous structures are investigated with respect to the
heat and mass transfer. The research focus is to increase the efficiency of spraycooling effects
and the manipulation of the Leidenfrost point.Mechanical Engineerin
Physiological ageing in a polar and a temperate swimming scallop
We compared physiological ageing parameters in 2 scallops, the temperate Aequipecten opercularis and the Antarctic Adamussium colbecki. These 2 species are phylogenetically closely related and display a similar lifestyle but have distinctly different maximum lifespans (MLSP). A. opercularis does not live longer than 8 to 10 yr, whereas A. colbecki lives over 18 yr. The development of several physiological ageing parameters over time, chosen according to the ‘free radical theory of ageing‘, was compared in the 2 species to identify differences in the ageing process. In the shorter-lived A. opercularis, activities of the mitochondrial enzymes citrate synthase and cytochrome c oxidase and of the antioxidant enzyme catalase showed a more pronounced decrease with increasing age than in the longer-lived A. colbecki. In line with this finding, lipofuscin accumulation increased more distinctly in A. opercularis than in A. colbecki, while tissue protein content decreased in A. opercularis but increased in A. colbecki. Its better preservation of mitochondrial and antioxidant enzyme activities and the avoidance of waste accumulation may enable A. colbecki to live longer than A. opercularis. Mitochondrial function investigated in A. opercularis showed only minor changes with age, and mitochondrial H2O2 generation rates were low at all ages. We relate our findings to the ‘free radical–rate of living’ theory, to the ‘uncoupling to survive‘ hypothesis, and to the particular lifestyle of these scallops
- …