Time lag and co-operativity in the transient growth dynamics of microalgae

The spontaneous pairing of rolled-up vortices in a laminar jet is investigated as a global secondary instability of a time-periodic spatially developing vortex street. The growth of subharmonic perturbations, associated with vortex pairing, is analysed both in terms of modal Floquet instability and in terms of transient growth dynamics. The article has the double objective to outline a toolset for the global analysis of time-periodic flows, and to leverage such an analysis for a fresh view on the vortex pairing phenomenon. Axisymmetric direct numerical simulations (DNS) of jets with single-frequency inflow forcing are performed, in order to identify combinations of the Reynolds and Strouhal numbers for which vortex pairing is naturally observed. The same DNS calculations are then repeated with an added time-delay control term, which artificially suppresses pairing, so as to obtain time-periodic unpaired base flows for linear stability analysis. It is demonstrated that the natural occurrence of vortex pairing in nonlinear DNS coincides with a linear subharmonic Floquet instability of the underlying unpaired vortex street. However, DNS results suggest that the onset of pairing involves much stronger temporal growth of subharmonic perturbations than that predicted by modal Floquet analysis, as well as a spatial distribution of these fast-growing perturbation structures that is inconsistent with the unstable Floquet mode. Singular value decomposition of the phase-shift operator (the operator that maps a given perturbation field to its state one flow period later) is performed for an analysis of optimal transient growth in the vortex street. Non-modal mechanisms near the jet inlet are thus found to provide a fast route towards the limit-cycle regime of established vortex pairing, in good agreement with DNS observations. It is concluded that modal Floquet analysis accurately predicts the parameter regime where sustained vortex pairing occurs, but that the bifurcation scenario under typical conditions is dominated by transient growth phenomena.

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Cristal-growth dynamics of n-doped gaAs

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100132352 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1544-1545

Author(s):

Pham V. Huong ◽

Stéphanie Bouchet ◽

Jean-Claude Launay

Keyword(s):

Crystal Growth ◽

Spatial Resolution ◽

Epitaxial Layer ◽

Outer Surface ◽

Gaas Substrate ◽

Structural Modification ◽

Growth Dynamics ◽

Argon Laser ◽

High Anisotropy ◽

Crystal Gaas

Microstructure of epitaxial layers of doped GaAs and its crystal growth dynamics on single crystal GaAs substrate were studied by Raman microspectroscopy with a Dilor OMARS instrument equipped with a 1024 photodiode multichannel detector and a ion-argon laser Spectra-Physics emitting at 514.5 nm.The spatial resolution of this technique, less than 1 μm2, allows the recording of Raman spectra at several spots in function of thickness, from the substrate to the outer deposit, including areas around the interface (Fig.l).The high anisotropy of the LO and TO Raman bands is indicative of the orientation of the epitaxial layer as well as of the structural modification in the deposit and in the substrate at the interface.With Sn doped, the epitaxial layer also presents plasmon in Raman scattering. This fact is already very well known, but we additionally observed that its frequency increases with the thickness of the deposit. For a sample with electron density 1020 cm-3, the plasmon L+ appears at 930 and 790 cm-1 near the outer surface.

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Cross-Lagged Relationships Between Self-Esteem, Self-Construal, and Happiness in a Three-Wave Longitudinal Study

Journal of Individual Differences ◽

10.1027/1614-0001/a000290 ◽

2019 ◽

Vol 40 (3) ◽

pp. 177-185

Author(s):

Daniela Moza ◽

Laurențiu Maricuțoiu ◽

Alin Gavreliuc

Keyword(s):

Structural Equation ◽

Time Lag ◽

Self Esteem ◽

Equation Modeling ◽

Future Research ◽

Cross Sectional ◽

Self Construal ◽

Self Worth ◽

Practical Implications ◽

Independent Person

Abstract. Previous research established that an independent construal of the self is associated with higher self-esteem, which, in turn, is associated with increased happiness. Regarding the directionality of these relationships, theoretical arguments have suggested that self-construal precedes self-esteem and that self-esteem precedes happiness. However, most research in this area is cross-sectional, thus limiting any conclusions about directionality. The present study tested these relationships in 101 Romanian undergraduates using a 3-wave cross-lagged design with a 6-month time lag between every two waves. Structural equation modeling analyses revealed that self-esteem is an antecedent of both happiness and dimensions of independent self-construal (i.e., consistency vs. variability and self-expression vs. harmony). In other words, one’s positive evaluation of self-worth precedes one’s self-perception as being a happy and independent person. The findings are discussed with respect to the theoretical and practical implications, along with limitations and suggestions for future research.

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Relationships Between Bidirectional Work-Family Interactions and Psychological Well-Being

Journal of Personnel Psychology ◽

10.1027/1866-5888/a000107 ◽

2014 ◽

Vol 13 (2) ◽

pp. 87-96 ◽

Cited By ~ 4

Author(s):

Xi-Chao Zhang ◽

Oi Ling Siu ◽

Jing Hu ◽

Weiwei Zhang

Keyword(s):

Family Conflict ◽

Structural Equation ◽

Time Lag ◽

Well Being ◽

Equation Modeling ◽

Family Interactions ◽

Work Family Conflict ◽

Psychological Well Being ◽

Direct Model ◽

Work Family

This study investigated the direct, reversed, and reciprocal relationships between bidirectional work-family conflict/work-family facilitation and psychological well-being (PWB). We administered a three-wave questionnaire survey to 260 married Chinese employees using a time lag of one month. Cross-lagged structural equation modeling analysis was conducted and demonstrated that the direct model was better than the reversed causal or the reciprocal model. Specifically, work-to-family conflict at Time 1 negatively predicted PWB at Time 2, and work-to-family conflict at Time 2 negatively predicted PWB at Time 3; further, work-to-family facilitation at Time 1 positively predicted PWB at Time 2. In addition, family-to-work facilitation at Time 1 positively predicted PWB at Time 2, and family-to-work conflict at Time 2 negatively predicted PWB at Time 3.

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