39,519 research outputs found
In situ analysis for intelligent control
We report a pilot study on in situ analysis of backscatter data for intelligent control of a scientific instrument on an Autonomous Underwater Vehicle (AUV) carried out at the Monterey Bay Aquarium Research Institute (MBARI). The objective of the study is to investigate techniques which use machine intelligence to enable event-response scenarios. Specifically we analyse a set of techniques for automated sample acquisition in the water-column using an electro-mechanical "Gulper", designed at MBARI. This is a syringe-like sampling device, carried onboard an AUV. The techniques we use in this study are clustering algorithms, intended to identify the important distinguishing characteristics of bodies of points within a data sample. We demonstrate that the complementary features of two clustering approaches can offer robust identification of interesting features in the water-column, which, in turn, can support automatic event-response control in the use of the Gulper
A study of aseptic maintenance by pressurization
Pressure differential for spacecraft sterilization against microbe contaminatio
Mechanical fluidity of fully suspended biological cells
Mechanical characteristics of single biological cells are used to identify
and possibly leverage interesting differences among cells or cell populations.
Fluidity---hysteresivity normalized to the extremes of an elastic solid or a
viscous liquid---can be extracted from, and compared among, multiple
rheological measurements of cells: creep compliance vs. time, complex modulus
vs. frequency, and phase lag vs. frequency. With multiple strategies available
for acquisition of this nondimensional property, fluidity may serve as a useful
and robust parameter for distinguishing cell populations, and for understanding
the physical origins of deformability in soft matter. Here, for three disparate
eukaryotic cell types deformed in the suspended state via optical stretching,
we examine the dependence of fluidity on chemical and environmental influences
around a time scale of 1 s. We find that fluidity estimates are consistent in
the time and the frequency domains under a structural damping (power-law or
fractional derivative)model, but not under an equivalent-complexity
lumpedcomponent (spring-dashpot) model; the latter predicts spurious time
constants. Although fluidity is suppressed by chemical crosslinking, we find
that adenosine triphosphate (ATP) depletion in the cell does not measurably
alter the parameter, and thus conclude that active ATP-driven events are not a
crucial enabler of fluidity during linear viscoelastic deformation of a
suspended cell. Finally, by using the capacity of optical stretching to produce
near-instantaneous increases in cell temperature, we establish that fluidity
increases with temperature---now measured in a fully suspended, sortable cell
without the complicating factor of cell-substratum adhesion
Quantum speed limit for relativistic spin-0 and spin-1 bosons on commutative and noncommutative planes
Quantum speed limits of relativistic charged spin-0 and spin-1 bosons in the
background of a homogeneous magnetic field are studied on both commutative and
oncommutative planes. We show that, on the commutative plane, the average
speeds of wave packets along the radial direction during the interval in which
a quantum state evolving from an initial state to the orthogonal final one can
not exceed the speed of light, regardless of the intensities of the magnetic
field. However, due to the noncommutativity, the average speeds of the wave
packets on noncommutative plane will exceed the speed of light in vacuum
provided the intensity of the magnetic field is strong enough. It is a clear
signature of violating Lorentz invariance in quantum mechanics region.Comment: 8 pages, no figures. arXiv admin note: text overlap with
arXiv:1702.0316
Numerical solution of the Navier-Stokes equations for arbitrary two-dimensional multi-element airfoils
The development of a numerical simulation of time dependent, turbulent, compressible flow about two dimensional multi-element airfoils of arbitrary shape is described. The basis of this simulation is a technique of automatic numerical generation of coordinate systems fitted to the multiple bodies regardless of their number or shape. Procedures developed whereby the coordinate lines are automatically concentrated in the boundary layer at any Reynolds number are discussed. The compressible turbulent solution involves an algebraic eddy viscosity turbulence model. The laminar version was run for transonic flow at free stream Mach numbers up to 0.9
Single and Many Particle Correlation Functions and Uniform Phase Bases for Strongly Correlated Systems
The need for suitable many or infinite fermion correlation functions to
describe some low dimensional strongly correlated systems is discussed. This is
linked to the need for a correlated basis, in which the ground state may be
postive definite, and in which single particle correlations may suffice. A
particular trial basis is proposed, and applied to a certain quasi-1D model.
The model is a strip of the 2D square lattice wrapped around a cylinder, and is
related to the ladder geometries, but with periodic instead of open boundary
conditions along the edges. Analysis involves a novel mean-field approach and
exact diagonalisation. The model has a paramagnetic region and a Nagaoka
ferromagnetic region. The proposed basis is well suited to the model, and
single particle correlations in it have power law decay for the paramagnet,
where the charge motion is qualitatively hard core bosonic. The mean field also
leads to a BCS-type model with single particle long range order.Comment: 23 pages, in plain tex, 12 Postscript figures included. Accepted for
publication in J.Physics : Condensed Matte
Self-consistent relativistic quasiparticle random-phase approximation and its applications to charge-exchange excitations and -decay half-lives
The self-consistent quasiparticle random-phase approximation (QRPA) approach
is formulated in the canonical single-nucleon basis of the relativistic
Hatree-Fock-Bogoliubov (RHFB) theory. This approach is applied to study the
isobaric analog states (IAS) and Gamov-Teller resonances (GTR) by taking Sn
isotopes as examples. It is found that self-consistent treatment of the
particle-particle residual interaction is essential to concentrate the IAS in a
single peak for open-shell nuclei and the Coulomb exchange term is very
important to predict the IAS energies. For the GTR, the isovector pairing can
increase the calculated GTR energy, while the isoscalar pairing has an
important influence on the low-lying tail of the GT transition. Furthermore,
the QRPA approach is employed to predict nuclear -decay half-lives. With
an isospin-dependent pairing interaction in the isoscalar channel, the
RHFB+QRPA approach almost completely reproduces the experimental -decay
half-lives for nuclei up to the Sn isotopes with half-lives smaller than one
second. Large discrepancies are found for the Ni, Zn, and Ge isotopes with
neutron number smaller than , as well as the Sn isotopes with neutron
number smaller than . The potential reasons for these discrepancies are
discussed in detail.Comment: 34 pages, 14 figure
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