Dielectric response of a polar fluid trapped in a spherical nanocavity

We present extensive Molecular Dynamics simulation results for the structure, static and dynamical response of a droplet of 1000 soft spheres carrying extended dipoles and confined to spherical cavities of radii $R=2.5$, 3, and 4 nm embedded in a dielectric continuum of permittivity $\epsilon' \geq 1$. The polarisation of the external medium by the charge distribution inside the cavity is accounted for by appropriate image charges. We focus on the influence of the external permittivity $\epsilon'$ on the static and dynamic properties of the confined fluid. The density profile and local orientational order parameter of the dipoles turn out to be remarkably insensitive to $\epsilon'$. Permittivity profiles $\epsilon(r)$ inside the spherical cavity are calculated from a generalised Kirkwood formula. These profiles oscillate in phase with the density profiles and go to a ``bulk'' value $\epsilon_b$ away from the confining surface; $\epsilon_b$ is only weakly dependent on $\epsilon'$, except for $\epsilon' = 1$ (vacuum), and is strongly reduced compared to the permittivity of a uniform (bulk) fluid under comparable thermodynamic conditions. The dynamic relaxation of the total dipole moment of the sample is found to be strongly dependent on $\epsilon'$, and to exhibit oscillatory behaviour when $\epsilon'=1$; the relaxation is an order of magnitude faster than in the bulk. The complex frequency-dependent permittivity $\epsilon(\omega)$ is sensitive to $\epsilon'$ at low frequencies, and the zero frequency limit $\epsilon(\omega=0)$ is systematically lower than the ``bulk'' value $\epsilon_b$ of the static primitivity.Comment: 12 pages including 17 figure

Hormone-Sensitive Lipase Serine Phosphorylation and Glycerol Exchange Across Skeletal Muscle in Lean and Obese Subjects : Effect of β-Adrenergic Stimulation

OBJECTIVE—Increased intramuscular triacylglycerol (IMTG) storage is a characteristic of the obese insulin-resistant state. We aimed to investigate whether a blunted fasting or β-adrenergically mediated lipolysis contributes to this increased IMTG storage in obesity

Effect of polydextrose and soluble maize fibre on energy metabolism, metabolic profile and appetite control in overweight men and women.

High-fibre diets offer several beneficial health effects. The objective of the present study was to investigate whether replacement of 30% of the available carbohydrates with polydextrose (PDX) or soluble maize fibre (SCF) at breakfast and lunch would result in an increased fat oxidation rate and satiety, which may be of relevance for body weight control and diabetes prevention. In a single-blind, randomised cross-over study, eighteen overweight men and women underwent four different dietary interventions, which consisted of a PDX diet, a SCF diet and two control diets (full energetic and isoenergetic, comparable with PDX with respect to g or energy percentage of macronutrients, respectively). Glycaemic profile, energy expenditure and substrate oxidation were measured for 24h in a respiration chamber. Circulating insulin, NEFA and TAG concentrations were determined over a 14h period during daytime. Appetite ratings were assessed using visual analogue scales. The replacement of available carbohydrates with PDX or SCF reduced the peak glucose response, which was accompanied by reduced postprandial insulin responses. Moreover, higher concentrations of circulating NEFA were observed after consumption of both fibre diets, which were accompanied by an increased fat oxidation over 24h. This effect was mainly attributed to the lower energetic value of the fibre diets and not to the fibres per se. Besides increasing fat oxidation, PDX exerted a pronounced suppressive effect on appetite ratings. The replacement of available carbohydrates with PDX may be of special interest because of its beneficial effects on metabolic profile and it may affect body weight control in the long term

An anisotropic effective model for the simulation of semiflexible ring polymers

This is an open access article published under a Creative Commons Attribution (CC-BY) License.We derive and introduce anisotropic effective pair potentials to coarse-grain solutions of semiflexible ring polymers of various lengths. The system has been recently investigated by means of full monomer-resolved computer simulations, revealing a host of unusual features and structure formation, which, however, cannot be captured by a rotationally averaged effective pair potential between the rings' centers of mass [ Bernabei, M.; Soft Matter 2013, 9, 1287 ]. Our new coarse-graining strategy is to picture each ring as a soft, penetrable disk. We demonstrate that for the short- and intermediate-length rings the new model is quite capable of capturing the physics in a quantitative fashion, whereas for the largest rings, which resemble flexible ones, it fails at high densities. Our work opens the way for the physical justification of general, anisotropic penetrable interaction potentials.This work has been supported by the Austrian Science Fund (FWF), Grant 23400-N16.Peer Reviewe

What do emulsification failure and Bose-Einstein condensation have in common?

Ideal bosons and classical ring polymers formed via self-assembly, are known to have the same partition function, and so analogous phase transitions. In ring polymers, the analogue of Bose-Einstein condensation occurs when a ring polymer of macroscopic size appears. We show that a transition of the same general form occurs within a whole class of systems with self-assembly, and illustrate it with the emulsification failure of a microemulsion phase of water, oil and surfactant. As with Bose-Einstein condensation, the transition occurs even in the absence of interactions.Comment: 7 pages, 1 figure, typeset with EUROTeX, uses epsfi

Nutritional strategies to attenuate postprandial glycemic response

Maintaining good glycemic control to prevent complications is crucial in people with type 2 diabetes and in people with prediabetes and in the general population. Different strategies to improve glycemic control involve the prescription of blood glucose-lowering drugs and the modulation of physical activity and diet. Interestingly, lifestyle intervention may be more effective in lowering hyperglycemia than pharmaceutical intervention. Regulation of postprandial glycemia is complex, but specific nutritional strategies can be applied to attenuate postprandial hyperglycemia. These strategies include reducing total carbohydrate intake, consuming carbohydrates with a lower glycemic index, the addition of or substitution by sweeteners and fibers, using food compounds which delay or inhibit gastric emptying or carbohydrate digestion, and using food compounds which inhibit intestinal glucose absorption. Nevertheless, it must be noted that every individual may respond differently to certain nutritional interventions. Therefore, a personalized approach is of importance to choose the optimal nutritional strategy to improve postprandial glycemia for each individual, but this requires a better understanding of the mechanisms explaining the differential responses between individuals

Incontinence-associated dermatitis: reducing adverse events

Incontinence-associated dermatitis (IAD) is a common problem in patients with faecal and/or urinary incontinence. Urine alters the normal skin flora and increases permeability of the stratum corneum and faecal enzymes on the skin contribute to skin damage. Faecal bacteria can then penetrate the skin, increasing the risk of secondary infection. However, IAD can be prevented and healed with timely and appropriate skin cleansing and skin protection. This includes appropriate use of containment devices. This article also looks at HARTMANN incontinence pads that have been developed to absorb the fluids that cause IAD and maintain the skin's acidic pH. The acidic pH of the skin contributes to its barrier function and defence against infection. Therefore, maintaining an acidic pH will help protect the skin from damage