Spatial Stability of Incompressible Attachment-Line Flow

Linear stability analysis of incompressible attachment-line flow is presented within the spatial framework. The system of perturbation equations is solved using spectral collocation. This system has been solved in the past using the temporal approach and the current results are shown to be in excellent agreement with neutral temporal calculations. Results amenable to direct comparison with experiments are then presented for the case of zero suction. The global solution method utilized for solving the eigenproblem yields, aside from the well-understood primary mode, the full spectrum of least-damped waves. Of those, a new mode, well separated from the continuous spectrum is singled out and discussed. Further, relaxation of the condition of decaying perturbations in the far-field results in the appearance of sinusoidal modes akin to those found in the classical Orr-Sommerfeld problem. Finally, the continuous spectrum is demonstrated to be amenable to asymptotic analysis. Expressions are derived for the location, in parameter space, of the continuous spectrum, as well as for the limiting cases of practical interest. In the large Reynolds number limit the continuous spectrum is demonstrated to be identical to that of the Orr-Sommerfeld equation

Realization of phase grating comb reflectors and their application to widely tunable DBR lasers

Widely tunable InP lasers often require comb reflectors as an integral part of their design. It is desirable to achieve comb reflectors with as "top-hat" like a response as possible. There are several ways to do this, but one simple and practical way is by utilizing a phase grating. Previously these have been discussed theoretically, but here we will describe the fabrication of such gratings and how they can find application as the reflectors in widely tunable InP lasers. The example devices which we will discuss show that phase-grating-based distributed Bragg reflector lasers can have tuning ranges of around 35 nm combined with excellent sidemode suppression ratio of better than 45 dB at the mode centers

What Have You Done for Me Lately? Friendship-Selection in the Shadow of the Dark Triad Traits

The current studies examined how the Dark Triad personality traits (i.e., Machiavellianism, narcissism, and psychopathy) facilitate the strategic structuring of an individual's social environment in terms of same- and opposite-sex friends. In one study using normative questions ( N = 267) and another using a budget-allocation task ( N = 114), we found that the Dark Triad traits were associated with choosing friends for strategic purposes and to create a volatile environment. Narcissistic individuals reported relatively more reasons to form friendships, such as shared interests, makes me feel good, and intelligence. Women high in narcissism chose same-sex friends who were attractive and women high on Machiavellianism chose same-sex friends who have social status. Men high on psychopathy devalued traits associated with good social relationships in favor of friends who could facilitate their mating efforts and to offset risks incurred in their life history strategy. Results are discussed using the selection-manipulation-evocation framework for explaining how personality traits interact with social environments and integrated with findings from evolutionary biology