Quantum cascade ~QC! lasers, based on intersubband transitions in semiconductor quantum wells, are characterized by ultrafast ~picosecond! carrier lifetimes. An important consequence of this unique property is the expected absence of relaxation oscillations in the transient response of these devices. Here, we discuss and experimentally verify this prediction by measuring the modulation response...

We describe gravitational stirring models of planetary debris disks using a new multi-annulus planetesimal evolution code. The current code includes gravitational stirring and dynamical friction; future studies will include coagulation, fragmentation, Poynting-Robertson drag, and other physical processes. We use the results of our calculations to investigate the physical conditions required for...

An integrated mathematical model, which incorporates scaffold proteins into a mitogen-activated protein kinases cascade, is constructed. By employing Monte Carlo simulation, regulatory property of scaffold protein on signaling ability for the mitogen-activated protein kinases cascade is investigated theoretically. It is found that (i) scaffold binding increases signal amplification if dephospho...

The simplest high gain free electron laser (FEL) amplifier concept is proposed. A klystron amplifier has the useful property that the various electronic processes take place in separate portions of the amplifier, rather than overlapping as in FEL amplifier with an uniform undulator. The klystron consists of two fundamental parts: succession of 2-3 cascades (modulator), and an output undulator (...

By modeling the transition paths of nuclear $\ensuremath{\gamma}$-decay cascade using a scale-free random network, we uncover universal power-law distribution $\ensuremath{\gamma}$-ray intensity ${\ensuremath{\rho}}_{I}(I)\ensuremath{\propto}{I}^{\ensuremath{-}2}$, with $I$ each transition. This property is consistently observed for all datasets sufficient number entries in National Nuclear Dat...

a simple semi-phenomenological model, which accurately predicts the dependence of thresholdcurrent for temperature of resonant-phonon three well quantum cascade laser based on verticaltransitions is offered. we found that, the longitude optical phonon scattering of thermally excitedelectrons is the most important limiting factor for thermal performance of high frequency thz qcls.in low frequenc...

In this paper, we introduce cascade normal forms for underactuated mechanical systems that are convenient for control design. These normal forms are partially linear which results from a well-known fact that un-deractuated systems can be partially linearized using a change of control 12]. The diiculty arises when the new control appears both in the linear and nonlin-ear subsystems. We introduce...