4,191 research outputs found
Momentum Regularity and Stability of the Relativistic Vlasov-Maxwell-Boltzmann System
In the study of solutions to the relativistic Boltzmann equation, their
regularity with respect to the momentum variables has been an outstanding
question, even local in time, due to the initially unexpected growth in the
post-collisional momentum variables which was discovered in 1991 by Glassey &
Strauss \cite{MR1105532}. We establish momentum regularity within energy spaces
via a new splitting technique and interplay between the Glassey-Strauss frame
and the center of mass frame of the relativistic collision operator. In a
periodic box, these new momentum regularity estimates lead to a proof of global
existence of classical solutions to the two-species relativistic
Vlasov-Boltzmann-Maxwell system for charged particles near Maxwellian with hard
ball interaction.Comment: 23 pages; made revisions which were suggested by the referee; to
appear in Comm. Math. Phy
Spacecraft redesign to reduce microphonic response of a VCO component
Reaction wheel vibration was found to induce out of specification sidebands on the carrier frequencies of some spacecraft components containing mechanical voltage control oscillators (VCOs). Concurrent investigations were performed to redesign the VCOs to reduce their response to the wheel vibration, and to design a reaction wheel isolation system to reduce the vibration input to the affected components. Component level tests indicated that both efforts provided viable solutions. The redesigned VCO will be incorporated into future spacecraft in the series, while affected spacecraft already in production will be retrofitted with the reaction wheel isolation system
Passive mode-locking in semiconductor lasers with saturable absorbers bandgap shifted through quantum well intermixing
Passive mode-locking in semiconductor lasers in a Fabry–Perot configuration with a bandgap blueshift applied to the saturable absorber (SA) section has been experimentally characterized. For the first time a fully post-growth technique, quantum well intermixing, was adopted to modify the material bandgap in the SA section. The measurements showed not only an expected narrowing of the pulse width but also a significant expansion of the range of bias conditions generating a stable train of optical pulses. Moreover, the pulses from lasers with bandgap shifted absorbers presented reduced chirp and increased peak power with respect to the nonshifted case
Comparative chromatography of chloroplast pigment
Methods for isolation of low concentration pigments of the cocklebur species are described. The methods entail two step chromatography so that the different sorption properties of the various pigments in varying column parameters can be utilized. Columnar and thin layer methods are compared. Many conditions influence separability of the chloroplasts
Ultrashort Q-switched pulses from a passively mode-locked distributed Bragg reflector semiconductor laser
A compact semiconductor mode-locked laser (MLL) is presented that demonstrates strong passive Q-switched mode-locking over a wide range of drive conditions. The Q-switched frequency is tunable between 1 and 4Â GHz for mode-locked pulses widths around 3.5Â ps. The maximum ratio of peak to average power of the pulse-train is >120, greatly exceeding that of similarly sized passively MLLs
High-extinction-ratio TE/TM selective Bragg grating filters on silicon-on-insulator
We report on the design and fabrication of TE and TM polarization selective Bragg grating filters in the form of sinusoidal perturbations on the waveguide sidewall and etched holes on the top of the waveguide, respectively. Combining the two geometries on a silicon-on-insulator waveguide resulted in Bragg grating filters with high extinction ratios of approximately 60 dB
High Extinction Ratio Polarization Selective TE/TM Bragg Gratings Filters on Silicon-on-insulator
No abstract available
High-extinction-ratio TE/TM selective Bragg grating filters on silicon-on-insulator
We report on the design and fabrication of TE and TM polarization selective Bragg grating filters in the form of sinusoidal perturbations on the waveguide sidewall and etched holes on the top of the waveguide, respectively. Combining the two geometries on a silicon-on-insulator waveguide resulted in Bragg grating filters with high extinction ratios of approximately 60 dB
The preparation, identification and properties of chlorophyll derivatives
In the investigation of 10-hydroxy chlorophylls a and b novel techniques included modification of chromatography and the use of fully-deuterated compounds isolated from fully-deuterated autotropic algae to determine the molecular structure of the chlorophylls
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