19,941 research outputs found
Solution of the dispersionless Hirota equations
The dispersionless differential Fay identity is shown to be equivalent to a
kernel expansion providing a universal algebraic characterization and solution
of the dispersionless Hirota equations. Some calculations based on D-bar data
of the action are also indicated.Comment: Late
Writing in your own voice: An intervention that reduces plagiarism and common writing problems in students' scientific writing.
In many of our courses, particularly laboratory courses, students are expected to engage in scientific writing. Despite various efforts by other courses and library resources, as instructors we are often faced with the frustration of student plagiarism and related writing problems. Here, we describe a simple Writing in Your Own Voice intervention designed to help students become more aware of different types of plagiarism and writing problems, avoid those problems, and practice writing in their own voice. In this article, we will introduce the types of plagiarism and writing problems commonly encountered in our molecular biology laboratory course, the intervention, and the results of our study. From the evaluation of 365 student reports, we found the intervention resulted in nearly 50% fewer instances of plagiarism and common writing problems. We also observed significantly fewer instances of severe plagiarism (e.g. several sentences copied from an external source). In addition, we find that the effects last for several weeks after the students complete the intervention assignment. This assignment is particularly easy to implement and can be a very useful tool for teaching students how to write in their own voices. © 2019 International Union of Biochemistry and Molecular Biology, 47(5):589-598, 2019
On the Miura map between the dispersionless KP and dispersionless modified KP hierarchies
We investigate the Miura map between the dispersionless KP and dispersionless
modified KP hierarchies. We show that the Miura map is canonical with respect
to their bi-Hamiltonian structures. Moreover, inspired by the works of Takasaki
and Takebe, the twistor construction of solution structure for the
dispersionless modified KP hierarchy is given.Comment: 19 pages, Latex, no figure
A study of the application of singular perturbation theory
A hierarchical real time algorithm for optimal three dimensional control of aircraft is described. Systematic methods are developed for real time computation of nonlinear feedback controls by means of singular perturbation theory. The results are applied to a six state, three control variable, point mass model of an F-4 aircraft. Nonlinear feedback laws are presented for computing the optimal control of throttle, bank angle, and angle of attack. Real Time capability is assessed on a TI 9900 microcomputer. The breakdown of the singular perturbation approximation near the terminal point is examined Continuation methods are examined to obtain exact optimal trajectories starting from the singular perturbation solutions
Hands-on Gravitational Wave Astronomy: Extracting astrophysical information from simulated signals
In this paper we introduce a hands-on activity in which introductory
astronomy students act as gravitational wave astronomers by extracting
information from simulated gravitational wave signals. The process mimics the
way true gravitational wave analysis will be handled by using plots of a pure
gravitational wave signal. The students directly measure the properties of the
simulated signal, and use these measurements to evaluate standard formulae for
astrophysical source parameters. An exercise based on the discussion in this
paper has been written and made publicly available online for use in
introductory laboratory courses.Comment: 5 pages, 4 figures; submitted to Am. J. Phy
Non-linear enhancement of laser generated ultrasonic Rayleigh waves by cracks
Laser generated ultrasound has been widely used for detecting cracks, surface and sub-surface defects in
many different materials. It provides a non-contact wideband excitation source which can be focused into
different geometries. Previous workers have reported enhancement of the laser generated Rayleigh wave
when a crack is illuminated by pulsed laser beam irradiation. We demonstrate that the enhancement
observed is due to a combination of source truncation, the free boundary condition at the edge of the crack
and interference effects. Generating a Rayleigh wave over a crack can lead to enhancement of the
amplitude of the Rayleigh wave signal, a shift in the dominant frequency of the wideband Rayleigh wave
and strong enhancement of the high frequency components of the Rayleigh wave
Memory B cells and CD8âș lymphocytes do not control seasonal influenza A virus replication after homologous re-challenge of rhesus macaques.
This study sought to define the role of memory lymphocytes in the protection from homologous influenza A virus re-challenge in rhesus macaques. Depleting monoclonal antibodies (mAb) were administered to the animals prior to their second experimental inoculation with a human seasonal influenza A virus strain. Treatment with either anti-CD8α or anti-CD20 mAbs prior to re-challenge had minimal effect on influenza A virus replication. Thus, in non-human primates with pre-existing anti-influenza A antibodies, memory B cells and CD8αâș T cells do not contribute to the control of virus replication after re-challenge with a homologous strain of influenza A virus
Entropy of gravitationally collapsing matter in FRW universe models
We look at a gas of dust and investigate how its entropy evolves with time
under a spherically symmetric gravitational collapse. We treat the problem
perturbatively and find that the classical thermodynamic entropy does actually
increase to first order when one allows for gravitational potential energy to
be transferred to thermal energy during the collapse. Thus, in this situation
there is no need to resort to the introduction of an intrinsic gravitational
entropy in order to satisfy the second law of thermodynamics.Comment: 9 pages, 4 figures. Major changes from previous version. We consider
only thermodynamic entropy in this version. Published in PR
Determination of cosmological parameters: an introduction for non-specialists
I start by defining the cosmological parameters and
. Then I show how the age of the universe depends on them,
followed by the evolution of the scale parameter of the universe for various
values of the density parameters. Then I define strategies for measuring them,
and show the results for the recent determination of these parameters from
measurements on supernovas of type 1a. Implications for particle physics is
briefly discussed at the end.Comment: 12 pages, Latex with epsf.sty. Invited talk at the ``Discussion
meeting on Recent Developments in Neutrino Physics'', held at the Physical
Research Laboratory, Ahmedabad, February 2--4, 199
Matrix elements of atomic interaction operators for d sup n configurations
Tabulation of matrix elements of atomic interaction operators for various configuration
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