413 research outputs found
Optical-parametric-oscillator solitons driven by the third harmonic
We introduce a model of a lossy second-harmonic-generating (chi^2) cavity
externally pumped at the third harmonic, which gives rise to driving terms of a
new type, corresponding to a cross-parametric gain. The equation for the
fundamental-frequency (FF) wave may also contain a quadratic self-driving term,
which is generated by the cubic nonlinearity of the medium. Unlike previously
studied phase-matched models of chi^2 cavities driven at the second harmonic
(SH) or at FF, the present one admits an exact analytical solution for the
soliton, at a special value of the gain parameter. Two families of solitons are
found in a numerical form, and their stability area is identified through
numerical computation of the perturbation eigenvalues (stability of the zero
solution, which is a necessary condition for the soliton's stability, is
investigated in an analytical form). One family is a continuation of the
special analytical solution. At given values of parameters, one soliton is
stable and the other one is not; they swap their stability at a critical value
of the mismatch parameter. The stability of the solitons is also verified in
direct simulations, which demonstrate that the unstable pulse rearranges itself
into the stable one, or into a delocalized state, or decays to zero. A soliton
which was given an initial boost C starts to move but quickly comes to a halt,
if the boost is smaller than a critical value C_cr. If C>C_cr, the boost
destroys the soliton (sometimes, through splitting into two secondary pulses).
Interactions between initially separated solitons are investigated too. It is
concluded that stable solitons always merge into a single one. In the system
with weak loss, it appears in a vibrating form, slowly relaxing to the static
shape. With stronger loss, the final soliton emerges in the stationary form.Comment: Latex file, 22 pages, 18 figures (33 figures files
Multi-soliton states under triangular spatial modulation of the quadratic nonlinearity
We introduce multi-soliton sets in the two-dimensional medium with the
second-harmonic-generating nonlinearity subject to spatial modulation in the
form of a triangle of singular peaks. Various families of symmetric and
asymmetric sets are constructed, and their stability is investigated. Stable
symmetric patterns may be built of 1, 4, or 7 individual solitons, while stable
asymmetric ones contain 1, 2, or 3 solitons. Symmetric and asymmetric patterns
may demonstrate mutual bistability. The shift of the asymmetric single-soliton
state from the central position is accurately predicted analytically. Vortex
rings composed of three solitons are produced too.Comment: to be published in Eur. Phys. J. Special Topics (special issue
"Nonlinear Dynamics in Physics: New Techniques and Applications"
Pneumonia Due to Mycoplasma in Gnotobiotic Mice I. Pathogenicity of \u3cem\u3eMycoplasma pneumoniae\u3c/em\u3e, \u3cem\u3eMycoplasma salivarium\u3c/em\u3e, and \u3cem\u3eMycoplasma pulmonis\u3c/em\u3e for the Lungs of Conventional and Gnotobiotic Mice
Pneumonia due to mycoplasma in gnotobiotic mice. I. Pathogenicity of Mycoplasma pneumoniae, Mycoplasma salivarium, and Mycoplasma pulmonis for the lungs of conventional and gnotobiotic mice. J. Bacteriol. 92:1154–1163. 1966.—Two species of mycoplasma of human origin, Mycoplasma pneumoniae and M. salivarium, were tested for their ability to produce respiratory disease in the Ha/ICR mouse when inoculated by the intranasal route. The mouse pathogen M. pulmonis was studied as a positive control. Conventional and gnotobiotic Ha/ICR mice were employed, the latter to provide a system free from indigenous mycoplasma and bacteria. Pneumonia from which mycoplasma were isolated was produced in all groups of the conventional Ha/ICR mice, including those inoculated with sterile broth. Only M. pulmonis produced disease when inoculated intranasally into the gnotobiotic mice, and the gross and microscopic lesions resembled those described in conventional mice. The gnotobiotic mouse provided a tool to study the pathogenicity of different mycoplasma species, and indicated marked differences in host specificity that could not be clearly seen when conventional mice were used
Radio astronomy Explorer-B in-flight mission control system development effort
A description is given of the development for the Mission Analysis Evaluation and Space Trajectory Operations (MAESTRO) program to be used for the in-flight decision making process during the translunar and lunar orbit adjustment phases of the flight of the Radio Astronomy Explorer-B. THe program serves two functions: performance and evaluation of preflight mission analysis, and in-flight support for the midcourse and lunar insertion command decisions that must be made by the flight director. The topics discussed include: analysis of program and midcourse guidance capabilities; methods for on-line control; printed displays of the MAESTRO program; and in-flight operational logistics and testing
Using Learning Goals to Promote Self-Directedness: How Problems in Research led to Solutions in Teaching
In promoting self-directedness, our process at MCNY’s Learning Enhancement Center begins by having the student construct learning goals. A qualitative analysis of these student learning goals was conducted based on the premise that a student’s ability to articulate a goal in a clear, specific, complex, and measurable manner will improve over time. Although our findings did not support our hypothesis, the complex exercise of creating a customized rubric to measure the goals helped us arrive at a standardized evaluation method and build a transparent self-assessment tool to foster independent learning. This attempt to quantify student learning goals created successful iterative loops, which married research discussion with the refinement of pedagogical practices aimed at raising the quality of student learning goals
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