Volume Interactions Research Articles

Brain volumes and cortical thickness on MRI in the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER)

BackgroundThe Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) was a multicenter randomized controlled trial that reported beneficial effects on cognition for a 2-year multimodal intervention (diet, exercise, cognitive training, vascular risk monitoring) versus control (general health advice). This study reports exploratory analyses of brain MRI measures.MethodsFINGER targeted 1260 older individuals from the general Finnish population. Participants were 60–77 years old, at increased risk for dementia but without dementia/substantial cognitive impairment. Brain MRI scans were available for 132 participants (68 intervention, 64 control) at baseline and 112 participants (59 intervention, 53 control) at 2 years. MRI measures included regional brain volumes, cortical thickness, and white matter lesion (WML) volume. Cognition was assessed at baseline and 1- and 2-year visits using a comprehensive neuropsychological test battery. We investigated the (1) differences between the intervention and control groups in change in MRI outcomes (FreeSurfer 5.3) and (2) post hoc sub-group analyses of intervention effects on cognition in participants with more versus less pronounced structural brain changes at baseline (mixed-effects regression models, Stata 12).ResultsNo significant differences between the intervention and control groups were found on the changes in MRI measures. Beneficial intervention effects on processing speed were more pronounced in individuals with higher baseline cortical thickness in Alzheimer’s disease signature areas (composite measure of entorhinal, inferior and middle temporal, and fusiform regions). The randomization group × time × cortical thickness interaction coefficient was 0.198 (p = 0.021). A similar trend was observed for higher hippocampal volume (group × time × hippocampus volume interaction coefficient 0.1149, p = 0.085).ConclusionsThe FINGER MRI exploratory sub-study did not show significant differences between the intervention and control groups on changes in regional brain volumes, regional cortical thicknesses, or WML volume after 2 years in at-risk elderly without substantial impairment. The cognitive benefits on processing speed of the FINGER intervention may be more pronounced in individuals with fewer structural brain changes on MRI at baseline. This suggests that preventive strategies may be more effective if started early, before the occurrence of more pronounced structural brain changes.Trial registrationClinicalTrials.gov, NCT01041989. Registered January 5, 2010.

Effective Temperature in Active Brownian Particles

In this paper, we perform a numerical analysis of the effective temperature extracted from the deviations from the fluctuation dissipation theorem in a system of active Brownian spherical particles with excluded volume interactions. We show that, in the low density homogeneous phase at fixed Péclet number, the effective temperature decreases when the density of the system is increased. We compare this trend to the one found in the literature with simulations of other active models.

Molecular Interaction Studies in Ternary Liquid Mixtures Containing 2-Nitroanisole and 1- Pentanol in n- Hexane at Different Temperatures using Ultrasonic Techniques

The experimental values of ultrasonic velocity, density and viscosity have been measured for the ternary liquid mixtures containing 2-Nitroanisole and 1-Pentanol in n-Hexane at 303,308 and 313K. To calculate various acoustical parameters like adiabatic compressibility, free volume, internal pressure, acoustical impedance, adsorption co-efficient and molecular interaction parameters have been computed using the experimental data. The linearity of variation in ultrasonic velocity and other parameters are due to the molecular interaction between donor acceptor molecules in liquid-liquid mixture. The various molecular interactions like dipole-dipole, dipole-induced dipole, induced-induced dipole have been discussed for the liquid mixture containing 2-Nitroanisone, 1-Pentanol in n-Hexane at different temperatures and concentration.

Multifunctional UV and Gas Sensors Based on Vertically Nanostructured Zinc Oxide: Volume Versus Surface Effect.

This article reports that it is possible to make multifunctional sensing devices with ZnO infiltrated polymers while the sensing interactions could occur throughout the polymer. As such, we find that infiltrated devices with SU-8 polymer can result in highly sensitive UV sensors. Mesh dielectric core devices were found to make sensitive gas sensors with a better than 5 ppm sensitivity for formaldehyde and NO2. A new type of p-n junction device is further demonstrated that is sensitive to UV illumination, thus making it an enhanced UV sensor. Sensing devices relying on volume interactions, such as light absorption, can significantly benefit from the infiltrated polymer. In contrast, devices that rely on surface interactions, such as gas sensors, do not gain performance in any significant way with or without the infiltrated polymer.

Coarse‐Grained Dendrimers in a Good Solvent: Comparison of Monte Carlo Simulations, Self‐Consistent Field Theory, and a Hybrid Modeling Strategy

AbstractRecently, a hybrid method has been developed, wherein the positions of some polymer segments are constrained to a small volume. The volume's position is sampled with a Monte Carlo algorithm. The distribution of the remaining segments is determined with Scheutjens–Fleer self‐consistent field theory (SF‐SCF). This incorporates thermal fluctuations into the model. Here it is investigated whether this also leads to an improved treatment of the excluded volume interactions. Dendrimers, with f = 1⋅⋅⋅7 generations, g = 2⋅⋅⋅5 spacers per branch point, and spacers of 20 or 50 segments, are used as a model system. The focus is on the radius of gyration, the asphericity, the radial density, and the end point and first branch point distribution. As expected, both SCF methods underestimate the radius of gyration due to underestimating the short range excluded volume. The SF‐SCF model, however, also gives a slightly different scaling and, in contrast to the other models, also predicts a bimodal distribution for first generation branch points for large f and g. This difference is attributed to overestimating the excluded volume at long ranges. As the hybrid method does not show this, localizing just a few segments largely compensates this shortcoming in the SF‐SCF theory.

Performance evaluation of activated carbon with different pore sizes and functional groups for VOC adsorption by molecular simulation

Volatile organic compounds (VOCs) are growing pollutants now that cause air pollution and threaten human health. In this paper, the Grand Canonical Monte Carlo was used to simulate the adsorption performance of activated carbon on VOCs (benzene, toluene, acetone and methanol). After simulating different pore sizes (0.902 nm,1.997 nm,3 nm and 4 nm) adsorption performances of activated carbon, activated carbon with a pore size of 1.997 nm was selected to further study the influence of functional groups (carboxyl, amino, hydroxyl and hydrogen), and the capillary condensation was explained by the Kelvin equation. Furthermore, effects of functional groups under saturated vapor pressure (P0) of VOCs that range from 0 to 0.1 P0 were explained by the accessible volume and intermolecular interaction potential, respectively. Under pressure range of 0–0.1 P0, at the beginning of adsorption of acetone and methanol, carboxyl and amino groups could reduce the threshold pressure while hydroxyl and hydrogen have the opposite effect. For benzene and toluene, all functional groups have little effect on the threshold pressure, and they reduce the adsorption capacity instead. It could be concluded that the activated carbon could achieve the best adsorption effect on acetone and methanol, on the contrary, the addition of functional groups on benzene and toluene will weaken their adsorption performance.

Dose-Response Relative Risk of Injury From Acute Alcohol Consumption in 22 Countries: Are Women at Higher Risk Than Men?

The risk of injury from alcohol consumption was analyzed by gender, controlling for frequency of heavy drinking occasions, and by cause of injury (traffic, violence, fall, other). Case-crossover analysis was conducted on 18,627 injured patients arriving at the emergency department (ED) within six hours of the event. Risk of injury was similar for females and males at ≤3 drinks prior to injury (OR = 2.74 vs. 2.76, respectively). At higher volume levels females were at greater risk than males, and significantly so at 3.1-6 drinks and 6.1-10 drinks (gender by volume interaction: OR = 0.60, CI = 0.39-0.93 and OR = 0.50, CI = 0.27-0.93, respectively). For those reporting 5+ ≥ monthly, females were at higher risk than males at all volume levels, and the gender by volume interaction was stronger than for those consuming 5+ <monthly at ≤3 drinks (OR = 0.51, CI = 0.28-0.92) and 6.1-10 drinks (OR = 0.39, CI = 0.18-0.82). Females were at higher risk of injury than males for all causes of injury except those related to traffic at lower levels of consumption (<6 drinks), although the gender by volume interaction was significant only for injury from other causes at 3.1-6 drinks (OR = 0.23, CI = 0.09-0.87). Females are at higher risk of injury than males, regardless of frequency of heavy drinking and for all causes other than those related to traffic.

Coarse-Grained Simulations of Nanogel Composites: Electrostatic and Steric Effects

Monte Carlo coarse-grained simulations of nanogels loaded with nanoparticles are presented, paying special attention to two phenomena revealed by experiments with real composites: the deswelling and charge inversion observed after the absorption of nanoparticles. Both can be justified here exclusively in terms of electrostatic and excluded volume interactions. According to our results, charge inversion in composites presents its own peculiarities. For instance, it only takes place if the charge of the nanoparticle exceeds a threshold value that increases with the nanoparticle size. Simulations also show that the distribution of nanoparticles inside the polyelectrolyte network varies with the nanoparticle charge. In addition, the location of nanoparticles inside the nanogel strongly depends on whether charge inversion occurs.

Pairing Effects on Bubble Nuclei**Supported by the National Natural Science Foundation of China under Grant Nos U1832120 and 11675265, the State Scholarship Fund of China Scholarship Council under Grant No 201708130035, and the Natural Science Foundation for Outstanding Young Scholars of Hebei Province of China under Grant No A2018210146.

In the framework of the Skyrme–Hartree–Fock–Bogoliubov approach with the SkT interaction, the pairing effects on the proton bubble structures of 46Ar and 206Hg are discussed. In calculations, three kinds of pairing forces (volume, surface and mixed pairing interactions) are used. For 46Ar, it is shown that the bubble structure with the volume pairing is almost the same as that with the mixed pairing. The bubble with the surface pairing is less pronounced than those with the volume and mixed pairings. Analyzing the density distributions and occupation probabilities of the proton s states and the quasi-degeneracy between the proton 2s1/2 and 1d3/2 orbitals, we explain the difference between the bubble structure with the surface pairing and those with the volume and mixed pairings. For 206Hg, it is seen that the proton density distribution with the surface pairing is different from those with the volume and mixed pairings in the whole region of the radial distance. In addition, it is found that the bubbles with the three pairing forces are different from each other and the least pronounced bubble is obtained with the surface pairing. Thus the selection of the pairing force is important for the study of the nuclear bubble structure.

Solution and Melts of Barbwire Bottlebrushes: Hierarchical Structure and Scale-Dependent Elasticity

We present a scaling theory describing hierarchical structural organization of semidilute solutions and melts of ”barbwire” bottlebrushes. Such macromolecules consist of a long flexible main chain (backbone) and several side chains emanating from each branching point of a backbone in a starlike manner. We investigate local and large scale conformational properties as well as extensional elasticity of barbwire bottlebrushes in a melt and solutions within a broad concentration range. On small length scale depending on the architectural parameters bottlebrushes exhibit either cylindrical or spherical symmetry imposed by excluded volume interactions between side chains. On a larger scale bottlebrushes behave in solution as self-avoiding chains. Upon increasing the solution concentration the excluded volume interactions get screened on progressively decreasing length scales. We identify semidilute solution regimes that differ with respect to power-law dependences of large scale and local conformational propert...

Measuring Ionic Strength Changes using Fluorescence Lifetime and Time-Resolved Anisotropy

Intracellular ionic strength affects many factors such as cell volume, catalytic activities, and molecular interactions. A family of hetero-FRET sensors has been designed to detect changes in ionic strength in vivo and in vitro. These proteins consist of a donor (mCerulean) and an acceptor (mCitrine) that are connected via a single flexible polypeptide hinge with a basic helix and an acidic helix. The basic helices are enriched with either arginine or lysine, and the acidic helices are enriched with either glutamate or aspartate. The FRET sensors (RE, RD, and KE) are designed to have maximal energy transfer at low ionic strength and to decrease monotonically as electrostatic screening of the charged helices occurs with increasing ionic strength. In this study, we investigate the effects that different linker structures have on the energy transfer efficiencies as measured using fluorescence lifetime and time-resolved anisotropy. We find that RE consistently has the greatest energy transfer across all salt concentrations and RD has the lowest, with KE having intermediate sensitivity. This family of proteins has been characterized as a function of potassium chloride and other ions in the Hofmeister series. Our solution studies indicate that these proteins are useful sensors of biologically relevant ionic strengths. Importantly they have potential for dynamically mapping ionic strength changes in response to biological stimuli.

A Molecular Mechanism for Membrane Geometry-Specific Protein Localization

Biological membranes have distinct geometries that confer specific functions. However, the molecular mechanisms underlying the phenomenological structure/function correlations remain elusive. We studied the effect of membrane geometry on membrane-bound protein localization. Quantitative experiments with controlled spherical and cylindrical membrane geometries revealed that geometry regulates the spatial segregation of proteins. The measured geometry-driven segregation efficiency reached 50-fold, for membranes of the same mean curvature. Combining experiments with molecular-field theory calculations surprisingly demonstrated a crucial contribution from Gaussian curvature to geometry discrimination. Our calculations reveal that the underlying physical and molecular mechanisms are dominated by the exclusion volume and hydrophobic interactions. Our results propose a new biological function to membrane polymorphism and suggest why and how distinct membrane geometries can have a specific effect on cellular membrane biology.

Integration of Reaction-Diffusion Master Equation and Brownian Dynamics Methodologies to Simulate a Minimal Cell

Simulating whole-cells at the genome scale involves the integration of models which operate at incompatible length, time, and concentration scales. Hybrid simulation schemes are necessary to bridge these scales. Progress is presented on a method combining the reaction-diffusion master equation (RDME) with Brownian dynamics (BD) into Lattice Microbes, a GPU-based RDME simulation code. RDME is used for protein diffusion, while BD is used for diffusion of particles larger than the subvolume size (ribosomes). The BD integration is performed on the GPU, allowing both simulations to progress in lockstep. Owing to the dense molecular crowding observed in living cells, accounting for excluded volume interactions is necessary to predict the spatial distribution and diffusion time scale of chemical species. Particles interact through a shared excluded volume field which influences the spatial transition rate of RDME particles as well as the friction coefficient of BD particles. Integration of the methods shows little impact on the time-to-solution compared to a pure RDME simulation. A proof of principle is presented using the particle densities and geometry of a 500-nm diameter minimal cell. This minimal cell, named JCVI-syn3A, with a 543-kbp genome and 493 genes, provides a versatile platform to study the basics of life. This computational methodology will become a major component of the goal to simulate JCVI-syn3A at a spatially resolved, stochastic level.

Role of particles in the rheology of solid-stabilized high internal phase emulsions

HypothesisThe presence of colloidal particles on fluid interfaces can have a significant impact on the rheology of solid-stabilized high internal phase emulsions (HIPEs). ExperimentsUsing dynamic oscillatory rheometry and confocal microscopy, we investigate a broad array of solid-stabilized HIPEs formulated along four different compositional trajectories in their ternary state diagram, using particles of three different sizes and two different surface chemistries. FindingsWe unveil three important consequences of the use of particles, in lieu of surfactants, on the rheology of HIPEs. First, particle excluded volume interactions take a pronounced role in the transition to solid-like rheology due to crowding. An effective dispersed phase volume fraction, taking into account the particle three-phase contact angle, must be defined to account for the dependence of the mixture’s rheology on its composition. Second, weak, chemistry-dependent attractive colloidal interactions through the continuous phase result in a finite elastic modulus at low effective dispersed phase volume fractions. Third, we observe a secondary rise in the mixture’s elastic modulus at increasingly high dispersed-to-continuous-phase volumetric ratios. We postulate these interactions stem from attractive lateral capillary interactions between the particles, due to thinning of the continuous fluid film between faceted droplets.

The effects of conductive nano fillers alignment on the dielectric properties of copolymer matrix

This research focuses on the improvement of the dielectric and energy harvesting properties of piezoelectric P(VDF-TrFE) copolymer matrix by the alignment of conductive reduced graphene oxide nano fillers. The dispersion and the morphology of the conductive nano fillers on the co-polymer matrix were characterized by scanning electron microscopy which showed a configurational phase transition due to highly conductive nano channel formation, steric hindrance, excluded volume interaction van-der-walls forces between adjacent reduced graphene oxide sheets. Five different piezoelectric nanocomposites were prepared by varying the reduced graphene oxide contents in P(VDF-TrFE) matrix to realize its optimum concentration in the matrix. From our analysis, we observed that, an optimized morphological structure plays a vital role in the formation of polar electroactive β phase on the co-polymer matrix through the good dispersion, filler alignment and interfacial interaction of reduced graphene oxide nano fillers. The as prepared nanocomposite film showed an enhanced crystallinity (50 ∼ 52%), dielectric constant (72 at 1 kHz), piezoelectric charge constant (−23 pC/N) with an output power of 3.2 µW at 1.8 MΩ load for 2 N mechanical force. All the outputs were observed without applying poling process. We expect that our synthesized self-poled nanocomposite can be a useful candidate for energy harvesting applications.

Revisiting the strong stretching theory for pH-responsive polyelectrolyte brushes: effects of consideration of excluded volume interactions and an expanded form of the mass action law.

In this paper, we develop a theory to account for the effect of excluded volume (EV) interactions in the strong stretching theory (SST) based description of pH-responsive polyelectrolyte (PE) brushes. The existing studies have considered the PE brushes to be present in a θ-solvent and hence have neglected the EV interactions; however, such a consideration cannot describe the situations where the pH-responsive brushes are in a "good" solvent. Secondly, we consider a more expanded form of the mass action law, governing the pH-dependent ionization of the PE molecules, in the SST description of the PE brushes. This expanded form of the mass action law considers different values of γa3 (γ is the density of chargeable sites on the PE molecule and a is the PE Kuhn length) and therefore is an improvement over the existing SST models of PE brushes as well as other theories involving pH-responsive PE molecules that always consider γa3 = 1. Our results demonstrate that the EV effects enhance the brush height by inducing additional PE inter-segmental repulsion. Similarly, the consideration of the expanded form of the mass action law would lead to a reduced (enhanced) brush height for γa3 < 1 (γa3 > 1). We also quantify variables such as the monomer density distribution, the distribution of the ends of the PE brush, and the EDL electrostatic potential and explain their differences with respect to those obtained with no EV interactions or γa3 = 1.

QSAR modelling for predicting adsorption of neutral, cationic, and anionic pharmaceuticals and other neutral compounds to microalgae Chlorella vulgaris in aquatic environment

Environmental fate or transport of pharmaceutical waste depends on the adsorptive interactions of pharmaceuticals with various environmental phases e.g. soil, sediment, microalgae, and bacteria etc. Therefore, it is important to understand these adsorptive interactions. As part of the study, we studied the adsorptive interaction of 30 chemicals with microalgae, i.e. Chlorella vulgaris, because it is ubiquitous and its surface area occupies a high proportion in aquatic environments. For this study, isotherms between C. vulgaris and 30 micropollutants in neutral and ionic forms (i.e. 15 cations, 5 anions, and 10 neutrals) were experimentally measured, and their adsorptive affinities were then theoretically predicted based on the concept of the linear free energy relationship. For modeling, the dataset was divided into a training set and a test set, where the training set was used for model development and the test set was performed for model validation. This process was repeated ten times. Finally, we suggested one model which has high predictability in R2 of 0.96 and standard error (SE) of 0.17 log unit for the training set, R2 of 0.818 and SE = 0.217 log unit for the test set, and R2 of 0.926 and SE of 0.169 log unit for the total dataset. Moreover, it was found that dispersive force, H-bond basicity, molecular volume, and electrostatic interaction of anion significantly contribute to the model developed based on the entire dataset. Here, dispersive and hydrophobic interactions (proportional to the magnitude of molecular size) are main attractive forces, while the rest cases are repulsive. In addition, it was found that the adsorption property of the surface of C. vulgaris differs from those of Gram negative bacteria Escherichia coli and dissolved organic matters in an aquatic environment.

Formation of spiral coils among self-propelled chains

We study the dynamics of self-propelled chains with the excluded volume interaction via the Brownian dynamics simulation, in which the bending elasticity of chains is varied. The changes of the bending elasticity lead to various characteristics of the clustering behavior in the short-chain-only system. When a long self-propelled chain is mixed with these short chains, it can fold into the spiral-coil, a steadily rotating spiral conformation, either at a high density of short chains or at a low density if the long chain itself is sufficiently flexible. Our results qualitatively support the speculation on that the formation of the spiral-coil in the swarm of Vibrio alginolyticus is triggered by collisions from the clusters of the shorter bacteria.

Mechanical, nanomorphological and biological reconstruction of early‑stage apoptosis in HeLa cells induced by cytochalasinB.

There is a growing interest in the fact that mechanical signals may be as important as biological signals in evaluating cell viability. To investigate the alterations in biomechanics, nanomorphology and biological apoptotic signals during early apoptosis, an apoptosis model was established for cervical cancer HeLa cells induced by cytochalasin B (CB). The cellular mechanical properties, geometry, morphology and expression of key apoptotic proteins were systematically analyzed. The findings indicated a marked decline in cellular elastic modulus and volume and a considerable increase in surface roughness occurring prior to the activation of biological apoptosis signals (such as phosphatidylserine exposure or activation of CD95/Fas). Moreover, the depolymerization of filamentous actin aggravated the intracellular crowding degree, which induced the redistribution of different-sized protein molecules and protrusions across the cell membrane arising from excluded volume interactions. Statistical analysis revealed that the disassembly of the actin cytoskeleton was negatively correlated with the cellular elastic modulus and volume, but was positively correlated with surface roughness and CD95/Fas activation. The results of the present study suggest that compared with biological signals, mechanical and geometrical reconstruction is more sensitive during apoptosis and the increase in cell surface roughness arises from the redistribution of biophysical molecules. These results contribute to our in-depth understanding of the apoptosis mechanisms of cancer cells mediated by cytochalasin B.

Rubber elasticity of realizable ideal networks

The rubber elasticity of four types of defectless crystalline-like networks has been investigated by coarse-grained molecular dynamics simulations to test the validity of Kuhn’s affine network theory of rubber elasticity. The shear moduli of the realizable ideal networks are obtained through their uniaxial deformation. The relation between the shear modulus and the partial chain density reveals that the elasticity of the phantom ideal networks with no excluded volume interactions can be explained by a generalized Kuhn’s theory. In addition, the shear moduli of the real networks with excluded volume interactions are usually lower than those of the corresponding phantom networks, which is because of a decrease in the conformational entropy of each partial chain. Coarse-grained molecular dynamics simulations of phantom networks is a promising approach to deeply understand cross-linked rubbers.