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Soft and Hard Implant Fabrication Using 3D-Bioplotting TM
At the Freiburger Materialforschungszentrum we have developed a new process (3DBioplotting
TM) that permits most kind of polymers and biopolymers to be used in 3D scaffold
design, including hydrogels (e.g. collagen, agar), polymer melts (e.g. PLLA, PGA, PCl) and twocomponent systems (e.g. chitosan, fibrin). Cells can be incorporated within the construction
process, making this an ideal Rapid Prototyping technique for Organ Printing. Tailor-made
biodegradable soft or hard scaffolds can so be fabricated in a short time using individual
computer-tomography data from the patient. In-vitro tests showed promising results and in-vivo
experiments are now under observation.Mechanical Engineerin
Robustness of the O() universality class
We calculate the critical exponents for Lorentz-violating O()
scalar field theories by using two independent methods. In
the first situation we renormalize a massless theory by utilizing normalization
conditions. An identical task is fulfilled in the second case in a massive
version of the same theory, previously renormalized in the BPHZ method in four
dimensions. We show that although the renormalization constants, the
and anomalous dimensions acquire Lorentz-violating quantum corrections, the
outcome for the critical exponents in both methods are identical and
furthermore they are equal to their Lorentz-invariant counterparts. Finally we
generalize the last two results for all loop levels and we provide symmetry
arguments for justifying the latter
Cosmic homogeneity: a spectroscopic and model-independent measurement
Cosmology relies on the Cosmological Principle, i.e., the hypothesis that the
Universe is homogeneous and isotropic on large scales. This implies in
particular that the counts of galaxies should approach a homogeneous scaling
with volume at sufficiently large scales. Testing homogeneity is crucial to
obtain a correct interpretation of the physical assumptions underlying the
current cosmic acceleration and structure formation of the Universe. In this
Letter, we use the Baryon Oscillation Spectroscopic Survey to make the first
spectroscopic and model-independent measurements of the angular homogeneity
scale . Applying four statistical estimators, we show that the
angular distribution of galaxies in the range 0.46 < z < 0.62 is consistent
with homogeneity at large scales, and that varies with
redshift, indicating a smoother Universe in the past. These results are in
agreement with the foundations of the standard cosmological paradigm.Comment: 5 pages, 2 figures, Version accepted by MNRA
Semiclassical Series from Path Integrals
We derive the semiclassical series for the partition function in Quantum
Statistical Mechanics (QSM) from its path integral representation. Each term of
the series is obtained explicitly from the (real) minima of the classical
action. The method yields a simple derivation of the exact result for the
harmonic oscillator, and an accurate estimate of ground-state energy and
specific heat for a single-well quartic anharmonic oscillator. As QSM can be
regarded as finite temperature field theory at a point, we make use of Feynman
diagrams to illustrate the non-perturbative character of the series: it
contains all powers of and graphs with any number of loops; the usual
perturbative series corresponds to a subset of the diagrams of the
semiclassical series. We comment on the application of our results to other
potentials, to correlation functions and to field theories in higher
dimensions.Comment: 18 pages, 4 figures. References update
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