21,920 research outputs found
Numerical investigation of novel microwave applicators based on zero-order mode resonance for hyperthermia treatment of cancer
This paper characterizes three novel microwave applicators based on zero-order mode resonators for use in hyperthermia treatment of cancer. The radiation patterns are studied with numerical simulations in muscle tissue-equivalent model at 434 MHz. The relative performance of the applicators is compared in terms of reflection coefficient, current distribution, power deposition (SAR) pattern, effective field size in 2D and 3D tissue volumes, and penetration depth. One particular configuration generated the most uniform SAR pattern, with 25% SAR covering 84 % of the treatment volume extending to 1 cm depth under the aperture, while remaining above 58% coverage as deep as 3 cm under the aperture. Recommendations are made to further optimize this structure
How was the Hubble sequence 6 Gyrs ago?
The way galaxies assemble their mass to form the well-defined Hubble sequence
is amongst the most debated topic in modern cosmology. One difficulty is to
link distant galaxies to those at present epoch. We aim at establishing how
were the galaxies of the Hubble sequence, 6 Gyrs ago. We intend to derive a
past Hubble sequence that can be causally linked to the present-day one. We
selected samples of nearby galaxies from the SDSS and of distant galaxies from
the GOODS survey. We verified that each sample is representative of galaxies.
We further showed that the observational conditions necessary to retrieve their
morphological classification are similar in an unbiased way. Morphological
analysis has been done in an identical way for all galaxies in the two samples.
We found an absence of number evolution for elliptical and lenticular galaxies,
which strikingly contrasts with the strong evolution of spiral and peculiar
galaxies. Spiral galaxies were 2.3 times less abundant in the past, that is
exactly compensated by the strong decrease by a factor 5 of peculiar galaxies.
It strongly suggests that more than half of the present-day spirals had
peculiar morphologies, 6 Gyrs ago, and this has to be accounted by any scenario
of galactic disk evolution and formation. The past Hubble sequence can be used
to test these scenarios as well as to test evolution of fundamental planes for
spirals and bulges.Comment: Version accepted by Astronomy and Astrophysics, October 21 2009.
Including low resolution images. 11 pages, 8 figure
Superconducting charge qubits from a microscopic many-body perspective
The quantised Josephson junction equation that underpins the behaviour of
charge qubits and other tunnel devices is usually derived through cannonical
quantisation of the classical macroscopic Josephson relations. However, this
approach may neglect effects due to the fact that the charge qubit consists of
a superconducting island of finite size connected to a large superconductor.
We show that the well known quantised Josephson equation can be derived
directly and simply from a microscopic many-body Hamiltonian. By choosing the
appropriate strong coupling limit we produce a highly simplified Hamiltonian
that nevertheless allows us to go beyond the mean field limit and predict
further finite-size terms in addition to the basic equation.Comment: Accepted for J Phys Condensed Matte
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