638 research outputs found
Thermoplastic deformation of silicon surfaces induced by ultrashort pulsed lasers in submelting conditions
A hybrid 2D theoretical model is presented to describe thermoplastic
deformation effects on silicon surfaces induced by single and multiple
ultrashort pulsed laser irradiation in submelting conditions. An approximation
of the Boltzmann transport equation is adopted to describe the laser
irradiation process. The evolution of the induced deformation field is
described initially by adopting the differential equations of dynamic
thermoelasticity while the onset of plastic yielding is described by the von
Mise's stress. Details of the resulting picometre sized crater, produced by
irradiation with a single pulse, are then discussed as a function of the
imposed conditions and thresholds for the onset of plasticity are computed.
Irradiation with multiple pulses leads to ripple formation of nanometre size
that originates from the interference of the incident and a surface scattered
wave. It is suggested that ultrafast laser induced surface modification in
semiconductors is feasible in submelting conditions, and it may act as a
precursor of the incubation effects observed at multiple pulse irradiation of
materials surfaces.Comment: To appear in the Journal of Applied Physic
Controlling the morphology and outgrowth of nerve and neuroglial cells: The effect of surface topography
Unlike other tissue types, like epithelial tissue, which consist of cells
with a much more homogeneous structure and function, the nervous tissue spans
in a complex multilayer environment whose topographical features display a
large spectrum of morphologies and size scales. Traditional cell cultures,
which are based on two-dimensional cell-adhesive culture dishes or coverslips,
are lacking topographical cues and mainly simulate the biochemical
microenvironment of the cells. With the emergence of micro- and
nano-fabrication techniques new types of cell culture platforms are developed,
where the effect of various topographical cues on cellular morphology,
proliferation and differentiation, can be studied. Different approaches
(regarding the material, fabrication technique, topographical charactertistics,
etc.) have been implemented. The present review paper aims at reviewing the
existing body of literature on the use of artificial micro- and
nano-topographical features to control neuronal morphology, outgrowth and
neural network topology. The cell responses from phenomenology to investigation
of the underlying mechanisms- on the different topographies, including both
deterministic and random ones, are summarized
Accelerator performance analysis of the Fermilab Muon Campus
Fermilab is dedicated to hosting world-class experiments in search of new
physics that will operate in the coming years. The Muon g-2 Experiment is one
such experiment that will determine with unprecedented precision the muon
anomalous magnetic moment, which offers an important test of the Standard
Model. We describe in this study the accelerator facility that will deliver a
muon beam to this experiment. We first present the lattice design that allows
for efficient capture, transport, and delivery of polarized muon beams. We then
numerically examine its performance by simulating pion production in the
target, muon collection by the downstream beam line optics, as well as
transport of muon polarization. We finally establish the conditions required
for the safe removal of unwanted secondary particles that minimizes
contamination of the final beam.Comment: 10 p
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