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Ecological and functional optimization of the pretreatment process for plasma based coatings of cutting tools
Increasing demands in machining of high-tech materials and dry machining lead to higher thermal and mechanical loads on cutting tools. In response to these challenges, enhanced coating solutions are applied to increase performance and life of cutting tools. However, during the production process the cemented carbide substrates are contaminated with grinding oils and residues of organic material. For the subsequent physical vapor deposition (PVD) coating process an intensive and high-quality cleaning process is necessary. In this contribution, plasma electrolytic polishing (PEP) is used as a novel alternative to conventional ecologically harmful cleaning baths. Apart from the ecological advantage, the surface of the substrate can be optimized with regard to the coating adhesion. To examine the performance of the different cleaning processes, machining tests were performed at the IWF to evaluate the layer adhesion and tool life of the tools
Spin Foams and Noncommutative Geometry
We extend the formalism of embedded spin networks and spin foams to include
topological data that encode the underlying three-manifold or four-manifold as
a branched cover. These data are expressed as monodromies, in a way similar to
the encoding of the gravitational field via holonomies. We then describe
convolution algebras of spin networks and spin foams, based on the different
ways in which the same topology can be realized as a branched covering via
covering moves, and on possible composition operations on spin foams. We
illustrate the case of the groupoid algebra of the equivalence relation
determined by covering moves and a 2-semigroupoid algebra arising from a
2-category of spin foams with composition operations corresponding to a fibered
product of the branched coverings and the gluing of cobordisms. The spin foam
amplitudes then give rise to dynamical flows on these algebras, and the
existence of low temperature equilibrium states of Gibbs form is related to
questions on the existence of topological invariants of embedded graphs and
embedded two-complexes with given properties. We end by sketching a possible
approach to combining the spin network and spin foam formalism with matter
within the framework of spectral triples in noncommutative geometry.Comment: 48 pages LaTeX, 30 PDF figure
Seesaw and noncommutative geometry
The 1-loop corrections to the seesaw mechanism in the noncommutative standard
model are computed. Other consequences of the Lorentzian signature in the inner
space are summarised.Comment: Dedicated to Alain Connes on the occasion of his 60th birthda
'Schwinger Model' on the Fuzzy Sphere
In this paper, we construct a model of spinor fields interacting with
specific gauge fields on fuzzy sphere and analyze the chiral symmetry of this
'Schwinger model'. In constructing the theory of gauge fields interacting with
spinors on fuzzy sphere, we take the approach that the Dirac operator on
q-deformed fuzzy sphere is the gauged Dirac operator on fuzzy
sphere. This introduces interaction between spinors and specific one parameter
family of gauge fields. We also show how to express the field strength for this
gauge field in terms of the Dirac operators and alone. Using the path
integral method, we have calculated the point functions of this model and
show that, in general, they do not vanish, reflecting the chiral non-invariance
of the partition function.Comment: Minor changes, typos corrected, 18 pages, to appear in Mod. Phys.
Lett.
Versatile control of Be ions using a spectrally tailored UV frequency comb
We demonstrate quantum control of Be ions directly implemented by an
optical frequency comb. Based on numerical simulations of the relevant
processes in Be for different magnetic field regimes, we demonstrate a
wide applicability when controlling the comb's spectral properties. We
introduce a novel technique for the selective and efficient generation of a
spectrally tailored narrow-bandwidth optical frequency comb near 313 nm. We
experimentally demonstrate internal state control and internal-motional state
coupling of Be ions implemented by stimulated-Raman manipulation using
a spectrally optimized optical frequency comb. Our pulsed laser approach is a
key enabling step for the implementation of quantum logic and quantum
information experiments in Penning traps.Comment: Includes supplementary materia
Algebraic approach to quantum field theory on a class of noncommutative curved spacetimes
In this article we study the quantization of a free real scalar field on a
class of noncommutative manifolds, obtained via formal deformation quantization
using triangular Drinfel'd twists. We construct deformed quadratic action
functionals and compute the corresponding equation of motion operators. The
Green's operators and the fundamental solution of the deformed equation of
motion are obtained in terms of formal power series. It is shown that, using
the deformed fundamental solution, we can define deformed *-algebras of field
observables, which in general depend on the spacetime deformation parameter.
This dependence is absent in the special case of Killing deformations, which
include in particular the Moyal-Weyl deformation of the Minkowski spacetime.Comment: LaTeX 14 pages, no figures, svjour3.cls style; v2: clarifications and
references added, compatible with published versio
AKT and SGK kinases regulate cell migration by altering Scar/WAVE complex activation and Arp2/3 complex recruitment
Cell polarity and cell migration both depend on pseudopodia and lamellipodia formation. These are regulated by coordinated signaling acting through G-protein coupled receptors and kinases such as PKB/AKT and SGK, as well as the actin cytoskeletal machinery. Here we show that both Dictyostelium PKB and SGK kinases (encoded by pkbA and pkgB) are dispensable for chemotaxis towards folate. However, both are involved in the regulation of pseudopod formation and thus cell motility. Cells lacking pkbA and pkgB showed a substantial drop in cell speed. Actin polymerization is perturbed in pkbA- and reduced in pkgB- and pkbA-/pkgB- mutants. The Scar/WAVE complex, key catalyst of pseudopod formation, is recruited normally to the fronts of all mutant cells (pkbA-, pkgB- and pkbA-/pkgB-), but is unexpectedly unable to recruit the Arp2/3 complex in cells lacking SGK. Consequently, loss of SGK causes a near-complete loss of normal actin pseudopodia, though this can be rescued by overexpression of PKB. Hence both PKB and SGK are required for correct assembly of F-actin and recruitment of the Arp2/3 complex by the Scar/WAVE complex during pseudopodia formation
Strange quarks and lattice QCD
The last few years have seen a dramatic improvement in our knowledge of the
strange form factors of the nucleon. With regard to the vector from factors the
level of agreement between theory and experiment gives us considerable
confidence in our ability to calculate with non-perturbative QCD. The
calculation of the strange scalar form factor has moved significantly in the
last two years, with the application of new techniques which yield values
considerably smaller than believed for the past 20 years. These new values turn
out to have important consequences for the detection of neutralinos, a
favourite dark matter candidate. Finally, very recent lattice studies have
resurrected interest in the famed H-dibaryon, with modern chiral extrapolation
of lattice data suggesting that it may be only slightly unbound. We review some
of the major sources of uncertainty in that chiral extrapolation.Comment: Invited talk at the Asia-Pacific few Body Conference, Seoul Kore
Neue Lerntechnologien für Umweltwissenschaften
Umweltwissenschaften/Ökologie sind durch ihren hohen Grad an Vernetzung, Inter- und Transdisziplinarität dazu prädestiniert, um umweltrelevantes Wissen mit "neuen Lerntechnologien" (E-Learning; internet-based learning; Multimedia-Unterricht) zu vermitteln. Dieser Beitrag stellt eine Auswahl von solchen Aktivitäten an den Universitäten Basel, Bern und Zürich sowie der ETH Zürich vor
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