1,535 research outputs found
Polariton lasing in high-quality Selenide-based micropillars in the strong coupling regime
We have designed and fabricated all-epitaxial ZnSe-based optical micropillars
exhibiting the strong coupling regime between the excitonic transition and the
confined optical cavity modes. At cryogenic temperatures, under non-resonant
pulsed optical excitation, we demonstrate single transverse mode polariton
lasing operation in the micropillars. Owing to the high quality factors of
these microstructures, the lasing threshold remains low even in micropillars of
the smallest diameter. We show that this feature can be traced back to a
sidewall roughness grain size below 3 nm, and to suppressed in-plane polariton
escape.Comment: 5 pages, 3 figure
Flow instabilities in circular Couette flow of wormlike micelle solutions with a reentrant flow curve
In this work, we numerically investigate flow instabilities of inertialess
circular Couette flow of dilute wormlike micelle solutions. Using the
reformulated reactive rod model (RRM-R) [Hommel and Graham, JNNFM 295 (2021)
104606], which treats micelles as rigid Brownian rods undergoing reversible
scission and fusion in flow, we study the development and behavior of both
vorticity banding and finger-like instabilities. In particular, we focus on
solutions that exhibit reentrant constitutive curves, in which there exists
some region where the shear stress, , has a multivalued relation to shear
rate, . We find that the radial dependence of the shear stress in
circular Couette flow allows for solutions in which parts of the domain lie in
the region of the flow curve where ,
while others lie in the region where ; this mixed behavior can lead to complex flow instabilities that manifest as
finger-like structures of elongated and anisotropically-oriented micelles. In
3D simulations we find that the initial instability is 2D in origin, and 3D
finger-like structures arise through the axial instability of 2D sheets.
Finally, we show that the RRM-R can capture vorticity banding in narrow-gap
circular Couette flow and that vorticity bands are linearly stable to
perturbations.Comment: 42 pages, 27 figures, 5 supplemental movie
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Venture capital contracting in theory and practice: Implications for entrepreneurship research
This article provides a comprehensive theoretical and empirical literature review of venture capital contracts. This outlines the differences between theoretical and practical uses of contract designs; that is, (1) how does the choice of securities give rise to different adverse selection problems in terms of attracting different types of entrepreneurial companies; how does the choice of securities in conjunction with cash flow and control rights provisions affect (2) the effort levels by the entrepreneur and the investor; and (3) ultimately affect entrepreneurial outcomes. This article highlights the major discrepancies between theory and practice and points out potential avenues for further research
Actions travel with their objects: evidence for dynamic event files
Moving a visual object is known to lead to an update of its cognitive representation. Given that object representations have also been shown to include codes describing the actions they were accompanied by, we investigated whether these action codes “move” along with their object. We replicated earlier findings that repeating stimulus and action features enhances performance if other features are repeated, but attenuates performance if they alternate. However, moving the objects in which the stimuli appeared in between two stimulus presentations had a strong impact on the feature bindings that involved location. Taken together, our findings provide evidence that changing the location of an object leaves two memory traces, one referring to its original location (an episodic record) and another referring to the new location (a working-memory trace)
Social Cognition 2.0: Toward Mechanistic Theorizing
Social cognition emerged in the 1970s and 80s as an attempt to answer social-psychological questions by adopting experimental techniques and theoretical concepts from cognitive psychology. Recently, cognitive psychologists began to build complementary bridges between cognitive and social psychology by showing increasing interest in the cognitive implications of social situations. Here, we take a closer look at the remaining obstacles to join cognitive and social perspectives on human behavior. Using conformity as an example, we attempt to demonstrate that the social-cognition approach has been successful in adopting cognitive concepts and experimental methods, but is still lagging behind with respect to (1) mechanistic theorizing, as it often engages in merely describing phenomena in terms of reasons rather than explaining it in terms of causes and (2) reflecting the sociohistorical context of the phenomenon under investigation. As we try to show, developing mechanistic theories for social phenomena, including the effects of individual differences and their sociohistorical dependencies, is not only possible but necessary to eliminate the boundaries between cognitive and social accounts of human behavior.Action Contro
Action comprehension: deriving spatial and functional relations.
A perceived action can be understood only when information about the action carried out and the objects used are taken into account. It was investigated how spatial and functional information contributes to establishing these relations. Participants observed static frames showing a hand wielding an instrument and a potential target object of the action. The 2 elements could either match or mismatch, spatially or functionally. Participants were required to judge only 1 of the 2 relations while ignoring the other. Both irrelevant spatial and functional mismatches affected judgments of the relevant relation. Moreover, the functional relation provided a context for the judgment of the spatial relation but not vice versa. The results are discussed in respect to recent accounts of action understanding
Coherent Propagation of Polaritons in Semiconductor Heterostructures: Nonlinear Pulse Transmission in Theory and Experiment
The influence of coherent optical nonlinearities on polariton propagation
effects is studied within a theory-experiment comparison. A novel approach that
combines a microscopic treatment of the boundary problem in a sample of finite
thickness with excitonic and biexcitonic nonlinearities is introduced.
Light-polarization dependent spectral changes are analyzed for single-pulse
transmission and pump-probe excitation
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