On the prediction of particle collision behavior in coarse-grained and resolved systems

The discrete element method (DEM) simulates granular processes and detects inter-particle collisions during the simulation. Detection of collision helps researchers to study the occurrence of particulate mechanisms such as aggregation, breakage, etc. DEM demands high computational costs in simulating industrial-level systems, as it involves an enormous number of particles. DEM coarse-grained model can help to overcome this high computational cost issue. However, the frequency and probability of collisions for different particle size classes may change when coarser particles are introduced. This study introduces a new mathematical formulation, namely the collision dependency function (CDF), which predicts the probability of collisions between different particle classes for systems containing resolved and coarse-grained particles. The CDF is extracted by executing one DEM simulation consisting of number-based uniformly distributed particles. Furthermore, a new optimized scheme is used inside the DEM to store the collision data efficiently. Finally, the collision probabilities between size classes obtained from DEM simulations are compared successfully against their counterparts calculated from the developed model for verification.</p

Structure-Based Peptide Design to Modulate Amyloid Beta Aggregation and Reduce Cytotoxicity

<div><p>The deposition of Aβ peptide in the brain is the key event in Alzheimer disease progression. Therefore, the prevention of Aβ self assembly into disease-associated oligomers is a logical strategy for treatment. π stacking is known to provide structural stability to many amyloids; two phenylalanine residues within the Aβ 14–23 self recognition element are in such an arrangement in many solved structures. Therefore, we targeted this structural stacking by substituting these two phenylalanine residues with their D-enantiomers. The resulting peptides were able to modulate Aβ aggregation <i>in vitro</i> and reduce Aβ cytotoxicity in primary neuronal cultures. Using kinetic analysis of fibril formation, electron microscopy and dynamic light scattering characterization of oligomer size distributions, we demonstrate that, in addition to altering fibril structural characteristics, these peptides can induce the formation of larger amorphous aggregates which are protective against toxic oligomers, possibly because they are able to sequester the toxic oligomers during co-incubation. Alternatively, they may alter the surface structure of the oligomers such that they can no longer interact with cells to induce toxic pathways.</p></div

Mesoporous Nitrogen-Doped Carbon-Glass Ceramic Cathodes for Solid-State Lithium–Oxygen Batteries

The composite of nitrogen-doped carbon (N–C) blend with lithium aluminum germanium phosphate (LAGP) was studied as cathode material in a solid-state lithium–oxygen cell. Composite electrodes exhibit high electrochemical activity toward oxygen reduction. Compared to the cell capacity of N–C blend cathode, N–C/LAGP composite cathode exhibits six times higher discharge cell capacity. A significant enhancement in cell capacity is attributed to higher electrocatalytic activity and fast lithium ion conduction ability of LAGP in the cathode

Electron microscopy and dynamic light scattering analysis of end-products of 24 hour oligomer (4°C) preparations in the presence or absence of peptides.

<p>(A) Aβ 1–42, (B) D19, (C) D20, (D) D19/20, (E) Aβ 1–42 + D19, (F) Aβ 1–42 + D20 and (G) Aβ 1–42 + D19/20. Scale bars are 100 nm. The size (Rh) distribution by mass has been plotted. Averages of ten readings are shown with error bars representing standard deviation.</p

Aβ 1–42 toxicity correlated with hydrodynamic radii of oligomers.

<p>A bubble plot correlates the size and toxicity observed for Aβ 1–42 oligomers with or without peptide co-incubation at 4°C. The size of each bubble represents the percentage of mass with that particular radius.</p

10 μM Aβ 1–42 fibril aggregation in the presence of 20 μM peptides over 40 hours.

<p>(A-B) Data from eight experiments (total n = 22 for Aβ 1–42) is shown. Error bars = SD. * p < 0.05, ** P < 0.01, *** p < 0.001, **** p < 0.0001. (A) Average changes in lag time relative to Aβ 1–42 alone (normalized to 1). (B) Average changes in ThT fluorescence relative to Aβ 1–42 alone (normalized to 1). (C-F) A representative kinetic experiment showing the inherent variability of Aβ 1–42 aggregation in the absence (C) or presence of D19 (D), D20 (E) or D19/20 (F) in replicate wells (n = 3). Despite this variability, the lag phases are always prolonged in the presence of D-peptide.</p

Morphology of D19/20 large spherical aggregates.

<p>(A-B) Electron micrographs of occasionally observed large aggregates from D19/20 oligomer incubation reactions. Scale bar 1000 nm. (C) Rh distribution of aggregates. Average of twelve readings shown. Error bars represent standard deviation.</p

Structure of Aβ peptides 1-40/42 showing the position of residues 14–23 in the fibril formed.

<p>(A) Aβ 1–40, two fold symmetry; (B) Aβ 1–40, three fold symmetry; and (C) Aβ 1–42, two fold symmetry. (D) The position of the Phe19 and Phe20 within the PDB:2BEG structure. (E) Amino acid sequence of Aβ 14–23, the substrate for peptide substitution in this study.</p

Rescue of cell viability after treatment with Aβ 1–42 oligomers co-incubated with D19, D20 or D19/20, as measured by MTS assay in primary cortical neurons.

<p>Cell toxicity was partially rescued when cells were treated with oligomer reactions of Aβ 1–42 co-incubated with peptide (Aβ42+peptide). No rescue was observed if cells were treated sequentially with Aβ 1–42 oligomers and then peptide oligomers (Aβ 1-42(+peptide)), without prior co-incubation. Values shown are normalized to Aβ 1–42 toxicity levels. n ≥ 6. ** p < 0.01.</p

Green Color Purification in Tb³⁺ Ions through Silica Inverse Opal Heterostructure

The ordered SiO₂:Tb³⁺ inverse opal heterostructure films are fabricated through polystyrene spheres hetero-opal template using the convective self-assembly method to examine their potential for color purification. Their optical properties and photoluminescence have been investigated and compared with individual single inverse opals and reference (SiO₂:Tb³⁺ powder). The heterostructures are shown to possess two broad photonic stop bands separated by an effective pass band, causing suppression of blue, orange, and red emission bands corresponding to ⁵D₄ → ⁷F_<i>j</i>; <i>j</i> = 6, 4, 3 transitions, respectively and an enhancement of green emission (i.e., ⁵D₄ → ⁷F₅). Although the suppression of various emission occurs because of its overlap with the photonic band gaps (PSBs), the enhancement of green radiation is observed because of its location matching with the pass band region. The Commission International de l’Eclairage (CIE) chromaticity coordinates of the emission spectrum of the heterostructure based on polystyrene sphere of 390 and 500 nm diameter are <i>x</i> = 0.2936, <i>y</i> = 0.6512 and lie closest to those of standard green color (wavelength 545 nm). In addition, a significant increase observed in luminescence lifetime for ⁵D₄ level of terbium in inverse opal heterostructures vis-à-vis reference (SiO₂:Tb³⁺ powder) is attributed to the change in the effective refractive index