7,734 research outputs found
Acoustic waves: should they be propagated forward in time, or forward in space?
The evolution of acoustic waves can be evaluated in two ways: either as a
temporal, or a spatial propagation. Propagating in space provides the
considerable advantage of being able to handle dispersion and propagation
across interfaces with remarkable efficiency; but propagating in time is more
physical and gives correctly behaved reflections and scattering without effort.
Which should be chosen in a given situation, and what compromises might have to
be made? Here the natural behaviors of each choice of propagation are compared
and contrasted for an ordinary second order wave equation, the time-dependent
diffusion wave equation, an elastic rod wave equation, and the Stokes'/ van
Wijngaarden's equations, each case illuminating a characteristic feature of the
technique. Either choice of propagation axis enables a partitioning the wave
equation that gives rise to a directional factorization based on a natural
"reference" dispersion relation. The resulting exact coupled bidirectional
equations then reduce to a single unidirectional first-order wave equation
using a simple "slow evolution" assumption that minimizes effect of subsequent
approximations, while allowing a direct term-to-term comparison between exact
and approximate theories.Comment: 12 pages, v2 correcte
Order parameters in the Verwey phase transition
The Verwey phase transition in magnetite is analyzed on the basis of the
Landau theory. The free energy functional is expanded in a series of components
belonging to the primary and secondary order parameters. A low-temperature
phase with the monoclinic P2/c symmetry is a result of condensation of two
order parameters X_3 and \Delta_5 . The temperature dependence of the shear
elastic constant C_44 is derived and the mechanism of its softening is
discussed.Comment: 4 pages, 1 figur
Ocular attention-sensing interface system
The purpose of the research was to develop an innovative human-computer interface based on eye movement and voice control. By eliminating a manual interface (keyboard, joystick, etc.), OASIS provides a control mechanism that is natural, efficient, accurate, and low in workload
The structure of an LIM-only protein 4 (LMO4) and deformed epidermal autoregulatory factor-1 (DEAF1) complex reveals a common mode of binding to LMO4
LIM-domain only protein 4 (LMO4) is a widely expressed protein with important roles in embryonic development and breast cancer. It has been reported to bind many partners, including the transcription factor Deformed epidermal autoregulatory factor-1 (DEAF1), with which LMO4 shares many biological parallels. We used yeast two-hybrid assays to show that DEAF1 binds both LIM domains of LMO4 and that DEAF1 binds the same face on LMO4 as two other LMO4-binding partners, namely LIM domain binding protein 1 (LDB1) and C-terminal binding protein interacting protein (CtIP/RBBP8). Mutagenic screening analysed by the same method, indicates that the key residues in the interaction lie in LMO4LIM2 and the N-terminal half of the LMO4-binding domain in DEAF1. We generated a stable LMO4LIM2-DEAF1 complex and determined the solution structure of that complex. Although the LMO4-binding domain from DEAF1 is intrinsically disordered, it becomes structured on binding. The structure confirms that LDB1, CtIP and DEAF1 all bind to the same face on LMO4. LMO4 appears to form a hub in protein-protein interaction networks, linking numerous pathways within cells. Competitive binding for LMO4 therefore most likely provides a level of regulation between those different pathways.SJ was funded by an Australian Postgraduate Award (education.gov.au/australian-postgraduate-awards). JPM and JMM were awarded Senior Research
Fellowships from the Australian National and Medical Research Council (www.nhmrc.gov.au). This project was funded by an Australian Research Council (www.
arc.gov.au) Discovery Project Grant (DP110104332) to JMM and LC
Noncovariant gauge fixing in the quantum Dirac field theory of atoms and molecules
Starting from the Weyl gauge formulation of quantum electrodynamics (QED),
the formalism of quantum-mechanical gauge fixing is extended using techniques
from nonrelativistic QED. This involves expressing the redundant gauge degrees
of freedom through an arbitrary functional of the gauge-invariant transverse
degrees of freedom. Particular choices of functional can be made to yield the
Coulomb gauge and Poincar\'{e} gauge representations. The Hamiltonian we derive
therefore serves as a good starting point for the description of atoms and
molecules by means of a relativistic Dirac field. We discuss important
implications for the ontology of noncovariant canonical QED due to the gauge
freedom that remains present in our formulation.Comment: 8 pages, 0 figure
New Approach to Nonlinear Dynamics of Fullerenes and Fullerites
New type of nonlinear (anharmonic) excitations -- bushes of vibrational modes
-- in physical systems with point or space symmetry are discussed. All infrared
active and Raman active bushes for C60 fulerene are found by means of special
group-theoretical methods.Comment: LaTeX, 8 pages, to be published in Fizika Tverdogo Tela, 200
A Comparison Of Perceptions: Students And Bankruptcy Filers On Causes Of Financial Distress
This study compares opinions about the causes of bankruptcy held by students at Texas A&M University –Corpus Christi with those of individuals who have filed for Chapter 13 bankruptcy. Personal bankruptcy affects many Americans and is the source of much controversy. This study should be helpful to creditors, who need to avoid losses from unpaid debts, educators who must be aware of students’ perceptions and misperceptions to effectively teach financial management, and legislators who pass laws on bankruptcy and related topics. Attorneys, accountants, and other financial advisors also need to be aware of signals of financial trouble in their clients
Polarization Squeezing of Continuous Variable Stokes Parameters
We report the first direct experimental characterization of continuous
variable quantum Stokes parameters. We generate a continuous wave light beam
with more than 3 dB of simultaneous squeezing in three of the four Stokes
parameters. The polarization squeezed beam is produced by mixing two quadrature
squeezed beams on a polarizing beam splitter. Depending on the squeezed
quadrature of these two beams the quantum uncertainty volume on the
Poincar\'{e} sphere became a `cigar' or `pancake'-like ellipsoid.Comment: 4 pages, 5 figure
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