24,908 research outputs found
Dynamic model for failures in biological systems
A dynamic model for failures in biological organisms is proposed and studied
both analytically and numerically. Each cell in the organism becomes dead under
sufficiently strong stress, and is then allowed to be healed with some
probability. It is found that unlike the case of no healing, the organism in
general does not completely break down even in the presence of noise. Revealed
is the characteristic time evolution that the system tends to resist the stress
longer than the system without healing, followed by sudden breakdown with some
fraction of cells surviving. When the noise is weak, the critical stress beyond
which the system breaks down increases rapidly as the healing parameter is
raised from zero, indicative of the importance of healing in biological
systems.Comment: To appear in Europhys. Let
Study of Resistive Micromegas in a Mixed Neutron and Photon Radiation Field
The Muon ATLAS Micromegas Activity (MAMMA) focuses on the development and
testing of large-area muon detectors based on the bulk-Micromegas technology.
These detectors are candidates for the upgrade of the ATLAS Muon System in view
of the luminosity upgrade of Large Hadron Collider at CERN (sLHC). They will
combine trigger and precision measurement capability in a single device. A
novel protection scheme using resistive strips above the readout electrode has
been developed. The response and sparking properties of resistive Micromegas
detectors were successfully tested in a mixed (neutron and gamma) high
radiation field supplied by the Tandem accelerator, at the N.C.S.R. Demokritos
in Athens. Monte-Carlo studies have been employed to study the effect of 5.5
MeV neutrons impinging on Micromegas detectors. The response of the Micromegas
detectors on the photons originating from the inevitable neutron inelastic
scattering on the surrounding materials of the experimental facility was also
studied
Magnetoelectric Effects on Composite Nano Granular Films
Employing a new experimental technique to measure magnetoelectric response
functions, we have measured the magnetoelectric effect in composite films of
nano granular metallic iron in anatase titanium dioxide at temperatures below
50 K. A magnetoelectric resistance is defined as the ratio of a transverse
voltage to bias current as a function of the magnetic field. In contrast to the
anomalous Hall resistance measured above 50 K, the magnetoelectic resistance
below 50 K is significantly larger and exhibits an even symmetry with respect
to magnetic field reversal . The measurement technique required
attached electrodes in the plane of the film composite in order to measure
voltage as a function of bias current and external magnetic field. To our
knowledge, the composite films are unique in terms of showing magnetoelectric
effects at low temperatures, 50 K, and anomalous Hall effects at high
temperatures, 50 K.Comment: ReVTeX, 2 figures, 3 page
Giant Flexoelectric Effect in Ferroelectric Epitaxial Thin Films
We report on nanoscale strain gradients in ferroelectric HoMnO3 epitaxial
thin films, resulting in a giant flexoelectric effect. Using grazing-incidence
in-plane X-ray diffraction, we measured strain gradients in the films, which
were 6 or 7 orders of magnitude larger than typical values reported for bulk
oxides. The combination of transmission electron microscopy, electrical
measurements, and electrostatic calculations showed that flexoelectricity
provides a means of tuning the physical properties of ferroelectric epitaxial
thin films, such as domain configurations and hysteresis curves.Comment: Accepted by Phys. Rev. Let
New Measurements of Ge Decay: Impact on the Gallium Anomaly
A dedicated high-statistics measurement of the Ge half-life is found
to be in accurate agreement with an accepted value of 11.430.03 d,
eliminating a recently proposed route to bypass the "gallium anomaly" affecting
several neutrino experiments. Our data also severely constrain the possibility
of Ge decay to low-energy excited levels of the Ga daughter
nucleus as a solution to this puzzle. Additional unpublished measurements of
this decay are discussed. Following the incorporation of this new information,
the gallium anomaly survives with high statistical significance.Comment: 3 pages, 2 figure
Electronic Transport in the Oxygen Deficient Ferromagnetic Semiconducting TiO
TiO films were deposited on (100) Lanthanum aluminates
LaAlO substrates at a very low oxygen chamber pressure
mtorr employing a pulsed laser ablation deposition technique. In previous work,
it was established that the oxygen deficiency in these films induced
ferromagnetism. In this work it is demonstrated that this same oxygen
deficiency also gives rise to semiconductor titanium ion impurity donor energy
levels. Transport resistivity measurements in thin films of TiO
are presented as a function of temperature and magnetic field. Magneto- and
Hall- resistivity is explained in terms of electronic excitations from the
titanium ion donor levels into the conduction band.Comment: RevTeX4, Four pages, Four Figures in ^.eps forma
Simple Scheme for Efficient Linear Optics Quantum Gates
We describe the construction of a conditional quantum control-not (CNOT) gate
from linear optical elements following the program of Knill, Laflamme and
Milburn [Nature {\bf 409}, 46 (2001)]. We show that the basic operation of this
gate can be tested using current technology. We then simplify the scheme
significantly.Comment: Problems with PDF figures correcte
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