Smart worm-like micelles responsive to CO₂/N₂ and light dual stimuli

CO₂/N₂ and light dual stimuli-reponsive worm-like micelles (WLMs) were obtained by addition of a relatively small amount of a switchable surfactant, 4-butyl-4´-(4-N,N-dimethylhexyloxy-amine) azobenzene bicarbonate (AZO-B6-CO₂), sensitive to the same triggers into a binary aqueous solution of cetyltrimethyl ammonium bromide (CTAB) and sodium salycilate (NaSal)

Phase correction at millimeter wavelengths using observations of water vapor at 22 GHz

We present results from phase correction efforts at the Owens Valley Radio Observatory millimeter array (OVRO). A brief description of the theory of phase correction is followed by a description of the water line monitors (WLMs) constructed and placed on each of the six antennas of the array. A summary of the current software in place is also included. We present examples of data corrected using this technique and the first image created using radiometric phase correction at OVRO. The phase correction system is undergoing further development and will soon be made available for general observing at the array. A brief discussion of application of the technique for future arrays (e.g. MMA, LSA, etc.) is included as a conclusion to this contribution

STRUCTURE, DYNAMICS AND RHEOLOGY OF SURFACTANT MICELLES AND MICELLE-NANOPARTICLE SOLUTIONS: A MOLECULAR DYNAMICS STUDY

Surfactant micelles are widely used in a number of industrial, commercial and household products and processes. Understanding flow-microstructure coupling in micellar systems can benefit applications ranging from targeted drug delivery and detergency to enhanced oil recovery and hydrofracking. Amongst micellar fluids, wormlike micelles (WLMs) are extremely interesting due to their structural similarity to polymers and their ability to constantly undergo scission and recombination at equilibrium. More recently, much has been generated in studying the effect of adding colloidal particles to WLMs. Colloidal particles can not only add functionality to the fluid but also act as viscosity modifiers. Such solutions can be used to design active nanomaterials for applications in energy harvesting and sensing. While several theories and continuum-level computational models have been developed to study the dynamics and rheology of WLMs, molecular-level explorations of the flow-structure coupling in such solutions is lacking. Further, in the case of mixtures of colloidal particles and WLMs, there are only a handful of attempts to develop theoretical/computational frameworks capable of describing their thermodynamics, self-assembly and phase behavior. The goals of this thesis are to uncover mechanisms by which WLMs interact with colloidal particles and to determine how these interactions affect the macroscopic properties of mixtures of model WLMs and colloidal nanoparticles (NPs) using molecular dynamics (MD) simulations. Coarse-grained (CG) molecular models and corresponding force-fields are employed to describe the NP, cationic cetyltrimethylammonium chloride (CTAC) surfactant, hydrotropic sodium salicylate (NaSal) salt, solvent and the underlying physico-chemical interactions. Results are first presented for the dynamics of a single self-assembled rodlike micellar aggregate under shear flow. The effect of shear rate on the configurational dynamics, e.g. orientation distribution of the end-to-end vector and tumbling frequency are presented and compared to experimental observations as well as predictions from stochastic simulations and mesoscopic theories. Further, a relationship between micelle length and stretching force is presented and compared with experimental estimates of similar forces in biological systems. Finally, a shear rate-independent energy barrier for micelle scission is identified for relatively large shear rates. We also show that the addition of NPs to surfactant solutions can result in the formation of NP-surfactant complexes (NPSCs). The effect of NP charge and surface chemistry on the nature of the self-assembly is discussed. Further, such NPSCs can further interact with WLMs, in the presence of NaSal salt, to form electrostatically stabilized micelle-NP junctions via an end cap attachment mechanism. The dynamics, energetics and stability of such junction formation is also described in detail. These junctions can give rise to unique rheological modifications of WLMs such as significant buildup in viscosity and viscoelasticity. Large-scale equilibrium and non-equilibrium MD simulations consisting of several NPs and WLMs are performed to study the flow-microstructure coupling in such systems. The relationship between the zero-shear viscosity, NP volume fraction and salt concentration at a fixed surfactant concentration is presented. Shear thinning behavior is observed for all of the systems studied. Shear thinning is accompanied by flow-alignment and shear-induced isotropic-to-nematic transitions in micellar systems. Further, the evolution of the first normal stress difference, N1, is presented as a function of time and shear rate, and compared with experimental observations for similar systems. The results of this work provides insight into the mechanisms of self-assembly in WLMs and colloidal NPs and demonstrate that rheological properties of WLMs can be uniquely controlled by the addition of NPs

Settlement of Macoma balthica larvae in response to benthic diatom films

The role of multi-species benthic diatom films (BDF) in the settlement of late pediveliger larvae of the bivalve Macoma balthica was investigated in still-water bioassays and multiple choice flume experiments. Axenic diatom cultures that were isolated from a tidal mudflat inhabited by M. balthica were selected to develop BDF sediment treatments characterized by a different community structure, biomass, and amount of extracellular polymeric substances (EPS). Control sediments had no added diatoms. Although all larvae settled and initiated burrowing within the first minute after their addition in still water, regardless of treatment, only 48-52% had completely penetrated the high diatom biomass treatments after 5 min, while on average 80 and 69% of the larvae had settled and burrowed into the control sediments and BDF with a low diatom biomass (<3.5 mu g Chl a g(-1) dry sediment), respectively. The percentage of larvae settling and burrowing into the sediment was negatively correlated with the concentration of Chl a and EPS of the BDF. This suggests higher physical resistance to bivalve penetration by the BDF with higher diatom biomass and more associated sugar and protein compounds. The larval settlement rate in annular flume experiments at flow velocities of 5 and 15 cm s(-1) was distinctly lower compared to the still-water assays. Only 4.6-5.8% of the larvae were recovered from BDF and control sediments after 3 h. Nonetheless, a clear settlement preference was observed for BDF in the flume experiments; i.e., larvae settled significantly more in BDF compared to control sediments irrespective of flow speed. Comparison with the settlement of polystyrene mimics and freeze-killed larvae led to the conclusion that active selection, active secondary dispersal and, at low flow velocities (5 cm s(-1)), passive adhesion to the sediment are important mechanisms determining the settlement of M. balthica larvae in estuarine biofilms

Plasmonic Nanogel: Structure, Rheology, and Optical Properties

The invention of plasmonic nanogels (PNG) opens up the field of nanotechnology to a wide variety of applications such as, enhanced light trapping in solar cells, design of smart glasses, chemical detection, and optofluidic devices. In this work, it was determined that, the synthesis of a nanoparticle-micelle network in a fluid state is performed with the ability to suspend metal nanoparticles in a gel-like solution in a stable fashion. Furthermore, the stable suspension of the nanoparticles in the fluidic system allows the user to easily tune the PNG’s optical and rheological properties by controlling the concentration of the nanoparticles and salts within the PNGs. Ultimately, the control of such properties enables the PNG to be used for many desirable applications

Component analysis of nutritionally rich chloroplasts: recovery from conventional and unconventional green plant species

A study of the literature indicates that chloroplasts synthesise a range of molecules, many of which have nutritional value for humans, but as yet no one has established the nutritional credentials of chloroplasts recovered from plant cells. Chloroplast-rich-fractions (CRFs) were prepared from green plant species and the macro- and micronutrient composition compared with the whole leaf materials (WLMs). The results indicated that, on a dry weight basis, CRF material from a range of green biomass was enriched in lipids and proteins, and in a range of micronutrients compared with the WLM. Vitamins E, pro-vitamin A, and lutein were all greater in CRF preparations. Of the minerals, iron was most notably concentrated in CRF. Spinach CRFs possessed the highest α-tocopherol (62 mg 100 g-1 , dry weight (DW)), β-carotene (336 mg 100 g- 1 DW) and lutein (341 mg 100 g-1 DW) contents, whilst grass CRFs had the highest concentration of alpha-linolenic acid (ALA) (69.5 mg g-1). The higher concentrations of α-tocopherol, β-carotene, lutein, ALA and trace minerals (Fe and Mn) in CRFs suggest their potential use as concentrated ingredients in food formulations deficient in these nutrients