Digital Holographic Microscopy of Phase Separation in Multicomponent Lipid Membranes

Lateral in-homogeneities in lipid compositions cause microdomains formation and change in the physical properties of biological membranes. With the presence of cholesterol and mixed species of lipids, phospholipid membranes segregate into lateral domains of liquid-ordered and liquid-disordered phases. Coupling of two-dimensional intralayer phase separations and interlayer liquid-crystalline ordering in multicomponent membranes has been previously demonstrated. By the use of digital holographic microscopy (DHMicroscopy), we quantitatively analyzed the volumetric dynamical behavior of such membranes. The specimens are lipid mixtures composed of sphingomyelin, cholesterol, and unsaturated phospholipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine. DHMicroscopy in a transmission mode is an effective tool for quantitative visualization of phase objects. By deriving the associated phase changes, three-dimensional information on the morphology variation of lipid stacks at arbitrary time scales is obtained. Moreover, the thickness distribution of the object at demanded axial planes can be obtained by numerical focusing. Our results show that the volume evolution of lipid domains follows approximately the same universal growth law of previously reported area evolution. However, the thickness of the domains does not alter significantly by time; therefore, the volume evolution is mostly attributed to the changes in area dynamics. These results might be useful in the field of membrane-based functional materials

Renewable Support, Intermittency and Market Power: An Equilibrium Investment Approach

Renewable energy sources (RES) play an increasing role in many electricity systems thanks to climate and support policies and subsequent cost reductions in recent years. Compared to conventional generation technologies, RES has two main important distinctive features: First, their cost pattern is characterized by high investment and negligible variable costs and second, their operational decision is governed by weather conditions limiting their availability. In this paper, we aim to analyze the role of RES in electricity markets focusing on the interplay of investment and dispatch decisions under different levels of market competitiveness and different support schemes; namely, feed-in tariff, feed-in premium, and investment subsidies. To this end, we develop a two-stage model of endogenous investment and operation with both intermittent and conventional technologies to obtain analytical solutions for investment and operation decisions. We show that there are feedback effects between the investments of different firms, and between the different technologies of the same firm. Exercise of market power results in underinvestment in the conventional technology; but the effect on renewables is ambiguous due to the interplay of opposing investment incentives. The results furthermore highlight that for the optimal design of a support policy the underlying competiveness of the market needs to be considered

Accurate testing of aspheric surfaces using the transport of intensity equation by properly selecting the defocusing distance

In the last decade, the transport of intensity has been increasingly used in microscopy, wavefront sensing, and metrology. In this study, we verify by simulation and experiment the use of the transport of intensity equation (TIE) in the accurate testing of optical aspheric surfaces. Guided by simulation results and assuming that the experimental setup parameters and the conic constants are known, one can estimate an appropriate defocusing distance Äz that leads to an accurate solution of the TIE. In this paper, this method is verified through the construction of a nonnulled experiment for testing the 2D profile of an aspheric surface. The theoretical method and experimental results are compared to validate the results. Finally, to validate the TIE methodology, the phase distribution obtained by TIE is compared with the phase distribution obtained by a Shack-Hartmann sensor. © 2016 Optical Society of America

Digital holographic microscopy of phase separation in multicomponent lipid membranes

Lateral in-homogeneities in lipid compositions cause microdomains formation and change in the physical properties of biological membranes. With the presence of cholesterol and mixed species of lipids, phospholipid membranes segregate into lateral domains of liquid-ordered and liquid-disordered phases. Coupling of two-dimensional intralayer phase separations and interlayer liquid-crystalline ordering in multicomponent membranes has been previously demonstrated. By the use of digital holographic microscopy (DHMicroscopy), we quantitatively analyzed the volumetric dynamical behavior of such membranes. The specimens are lipid mixtures composed of sphingomyelin, cholesterol, and unsaturated phospholipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine. DHMicroscopy in a transmission mode is an effective tool for quantitative visualization of phase objects. By deriving the associated phase changes, three-dimensional information on the morphology variation of lipid stacks at arbitrary time scales is obtained. Moreover, the thickness distribution of the object at demanded axial planes can be obtained by numerical focusing. Our results show that the volume evolution of lipid domains follows approximately the same universal growth law of previously reported area evolution. However, the thickness of the domains does not alter significantly by time; therefore, the volume evolution is mostly attributed to the changes in area dynamics. These results might be useful in the field of membrane-based functional materials. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

A guide to properly select the defocusing distance for accurate solution of transport of intensity equation while testing aspheric surfaces

In this paper, the Transport of Intensity Equation (TIE) for testing of an aspheric surface is verified experimentally. Using simulation, a proper defocus distance Δo that leads to an accurate solution of TIE is estimated whenever the conic constant and configuration of the experiment are known. To verify this procedure a non-nulled experiment for testing an aspheric is used. For verification of the solution, the results are compared with the Shack-Hartmann sensor. The theoretical method and experimental results are compared to validate the results. © 2016 SPIE