On the role of softness in ionic microgel interactions.

Thermoresponsive microgels are a popular model system to study phase transitions in soft matter, because temperature directly controls their volume fraction. Ionic microgels are additionally pH-responsive and possess a rich phase diagram. Although effective interaction potentials between microgel particles have been proposed, these have never been fully tested, leading to a gap in our understanding of the link between single-particle and collective properties.

Controlling the morphology of microgels by ionic stimuli.

Stimuli-responsive microgels have attracted much interest for their use as vehicles for drug delivery or as the building blocks of adaptive materials. Ionic microgel particles, including popular poly(NIPAM-co-acrylic acid), show strong mechanical responsiveness to many external stimuli, including changes in ionic strength or acidity. In this work, we demonstrate that combining multiple ionic stimuli can enable detailed control over the morphology of microgels.

Efficient configurational-bias Monte-Carlo simulations of chain molecules with "swarms" of trial configurations.

The pruned-enriched Rosenbluth method (PERM) is a popular and powerful Monte-Carlo technique for sampling flexible chain polymers of substantial length. In its original form, however, the method cannot be applied in Markov-chain Monte-Carlo schemes, which has rendered PERM unsuited for systems that consist of many chains. The current work builds on the configurational-bias Monte-Carlo (CBMC) method.

Deswelling behaviour of ionic microgel particles from low to ultra-high densities.

The swelling of ionic microgel particles is investigated at a wide range of concentrations using a combination of light, X-ray and neutron scattering techniques. We employ a zero-average contrast approach for small-angle neutron scattering experiments, which enables a direct determination of the form factor at high concentrations. The observed particle size initially decreases strongly with the particle concentration in the dilute regime but approaches a constant value at intermediate concentrations.

Swelling of micro-hydrogels with a crosslinker gradient.

A heterogeneous distribution of crosslinker in micro-hydrogels (microgels) results in a non-uniform polymer density inside the particles. Identifying the morphology of the hydrogel backbone enables a bottom-up approach towards the structural and rheological properties of microgel systems. On a local level we use a Flory-Rehner inspired model that focuses on highly swollen networks, characterized by a Poisson's ratio of 1/4.

Liquid Crystal Phase Transition in Epitaxial Monolayers of DNA-Functionalized Nanoparticle Superlattices.

Epitaxial growth of DNA-functionalized nanoparticles is used to grow extended superlattices with a preferred orientation for optimizing the physical properties of metamaterials for real applications. Like any solid in nature, superlattices can contain different kinds of structural defects, which significantly alter their physical properties. Further development of these materials requires a deeper understanding of, as well as precise control over, structural defect formation.

Anomalous system-size dependence of electrolytic cells with an electrified oil-water interface.

Manipulation of the charge of the dielectric interface between two bulk liquids not only enables the adjustment of the interfacial tension but also controls the storage capacity of ions in the ionic double layers adjacent to each side of the interface. However, adjusting this interfacial charge by static external electric fields is difficult since the external electric fields are readily screened by ionic double layers that form in the vicinity of the external electrodes. This leaves the liquid-liquid interface, which is at a macroscopic distance from the electrodes, unaffected.

Effective charges and virial pressure of concentrated macroion solutions.

The stability of colloidal suspensions is crucial in a wide variety of processes, including the fabrication of photonic materials and scaffolds for biological assemblies. The ionic strength of the electrolyte that suspends charged colloids is widely used to control the physical properties of colloidal suspensions. The extensively used two-body Derjaguin-Landau-Verwey-Overbeek (DLVO) approach allows for a quantitative analysis of the effective electrostatic forces between colloidal particles.

'Soft' amplifier circuits based on field-effect ionic transistors.

Soft materials can be used as the building blocks for electronic devices with extraordinary properties. We introduce a theoretical model for a field-effect transistor in which ions are the gated species instead of electrons. Our model incorporates readily-available soft materials, such as conductive porous membranes and polymer-electrolytes to represent a device that regulates ion currents and can be integrated as a component in larger circuits.

Crystallization and reentrant melting of charged colloids in nonpolar solvents.

We explore the crystallization of charged colloidal particles in a nonpolar solvent mixture. We simultaneously charge the particles and add counterions to the solution with aerosol-OT (AOT) reverse micelles. At low AOT concentrations, the charged particles crystallize into body-centered-cubic (bcc) or face-centered-cubic (fcc) Wigner crystals; at high AOT concentrations, the increased screening drives a thus far unobserved reentrant melting transition.

No effect of 1 or 7 d of green tea extract ingestion on fat oxidation during exercise.

Purpose: The aim of this study was to investigate the effects of 1 and 7 d of green tea extract (GTE) ingestion on whole body fat oxidation during moderate-intensity exercise.

Methods: Thirty-one men completed two exercise trials (60-min cycle, 50% Wmax). After the baseline trial (day 0), subjects were randomly assigned to one of three conditions involving a week supplementation of the following: 1) 7 d of placebo, 2) 6 d of placebo followed by 1 d of GTE (GTE1), and 3) 7 d of GTE ingestion (GTE7).

Electrostatic interactions between Janus particles.

In this paper we study the electrostatic properties of "Janus" spheres with unequal charge densities on both hemispheres. We introduce a method to compare primitive-model Monte Carlo simulations of the ionic double layer with predictions of (mean-field) nonlinear Poisson-Boltzmann theory. We also derive practical Derjaguin Landau Verwey Overbeek (DLVO)-like expressions that describe the Janus-particle pair interactions by mean-field theory.

Metabolic response to green tea extract during rest and moderate-intensity exercise.

Background: Green tea catechins have been hypothesized to increase energy expenditure and fat oxidation by inhibiting catechol-O-methyltransferase (COMT) and thus promoting more sustained adrenergic stimulation. Metabolomics may help to clarify the mechanisms underlying their putative physiological effects.

Objective: The study investigated the effects of 7-day ingestion of green tea extract (GTE) on the plasma metabolite profile at rest and during exercise.

Charge reversal of moisturous porous silica colloids by take-up of protons.

The net charge of porous Stöber silica colloids is studied using a modified Poisson-Boltzmann theory in a spherical cell, with a focus on the case of water-filled porous silica particles suspended in a non-aqueous solvent. We show that the silica's usual negative surface charge, due to deprotonisation of the Si-OH group, is counteracted by an excess uptake of protons in the water-filled pores of the particle at low enough pH. A small volume fraction of pores suffices to induce a point of zero charge at pH≈4.

Phase diagrams of colloidal spheres with a constant zeta-potential.

We study suspensions of colloidal spheres with a constant zeta-potential within Poisson-Boltzmann theory, quantifying the discharging of the spheres with increasing colloid density and decreasing salt concentration. We use the calculated renormalized charge of the colloids to determine their pairwise effective screened-Coulomb repulsions. Bulk phase diagrams in the colloid concentration-salt concentration representation follow, for various zeta-potentials, by a mapping onto published fits of phase boundaries of point-Yukawa systems.

Health potential for functional green teas?

Obesity is a major health problem in the developed and developing world. Many "functional" foods and ingredients are advocated for their effects on body composition but few have consistent scientific support for their efficacy. However, an increasing amount of mechanistic and clinical evidence is building for green tea.

Effects of catechin enriched green tea on body composition.

Obesity is a major health problem in the developed and developing world. Many "functional" foods and ingredients are advocated for their effects on body composition but few have consistent scientific support for their efficacy. However, an increasing amount of mechanistic and clinical evidence is building for green tea (GT).

Macronutrient distribution over a period of 23 years in relation to energy intake and body fatness.

The distribution of the four macronutrients is associated with energy intake and body fatness according to short-term interventions. The present study involves macronutrient distribution in relation to energy intake and body fatness over a period of 23 years in individuals who have ad libitum access to food. Eight follow-up measurements have been performed in 168 men and 182 women who participate in the Amsterdam Growth and Health Longitudinal Study.

The effects of hydralazine on lipolysis in subcutaneous adipose tissue in humans.

Recent evidence from animal research and in vitro experiments indicates that changes in dietary calcium intake could cause changes in lipolysis through alterations of the intracellular calcium concentration in adipocytes. The objective of the study was to examine whether the calcium antagonist hydralazine affects blood flow and lipolysis in subcutaneous abdominal adipose tissue in vivo in humans. Three different concentrations of hydralazine (12.

Effects of 3 diets with various calcium contents on 24-h energy expenditure, fat oxidation, and adipose tissue message RNA expression of lipid metabolism-related proteins.

Background: Evidence from molecular and animal research and epidemiologic investigations indicates that calcium intake may be inversely related to body weight, possibly through alterations in 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] metabolism.

Objective: We tested whether energy and substrate metabolism and adipose tissue enzyme messenger RNA (mRNA) expression can be altered by dietary calcium intake in healthy, nonobese, human volunteers consuming an isocaloric diet.

Design: Twelve healthy men [age: 28 +/- 2 y; body mass index (BMI; in kg/m(2)): 25.