Computational synthesis,structure, and glass transition of (1,4) Cis‐polyisoprene‐based nanocomposite by multiscale modeling

The main goal of the present study was to produce insights from the atomistic modeling into the structural changes in elastomer‐based polymer nanocomposites caused by the surface modifications of the filler particles, and by the crosslinking of the participating polymer matrix. The fully atomistic molecular‐dynamics computer simulations of crosslinked (1,4) cis‐polyisoprene (PI) films capped by amorphous silica substrates was set‐up, in the presence of realistic coupling and covering agents. The PI film stratified structure has been studied in the proximity of the corresponding glass transition, by varying the degree of crosslinking and the PI film thickness. Some monomer ordering induced by the pristine (bare) silica disappeared almost completely in films with modified surfaces. The average monomer density increased with degree of crosslinking. As compared with PI bulk, the glass‐transition temperature was slightly larger for highly crosslinked PI films with bare silica and surfaces with coupling agents, and increased with increasing confinement. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 473–485     

Carbon Monoxide Dehydrogenase Reduces Cyanate to Cyanide

The biocatalytic function of carbon monoxide dehydrogenase (CODH) has a high environmental relevance owing to its ability to reduce CO₂. Despite numerous studies on CODH over the past decades, its catalytic mechanism is not yet fully understood. In the present combined spectroscopic and theoretical study, we report first evidences for a cyanate (NCO⁻) to cyanide (CN⁻) reduction at the C-cluster. The adduct remains bound to the catalytic center to form the so-called CN⁻-inhibited state. Notably, this conversion does not occur in crystals of the Carboxydothermus hydrogenoformans CODH enzyme (CODHII_Ch), as indicated by the lack of the corresponding CN⁻ stretching mode. The transformation of NCO⁻, which also acts as an inhibitor of the two-electron-reduced C_red2 state of CODH, could thus mimic CO₂ turnover and open new perspectives for elucidation of the detailed catalytic mechanism of CODH.     

Optimal complex field holographic projection

We describe a technique that uses complex field holograms to project three-dimensional light patterns. Holographic projection commonly uses phase-only encoding since accurately representing complex holograms using both amplitude and phase spatial light modulators reduces the optical throughput significantly. Here, we use a lossless projection via the generalized phase contrast method to produce the necessary amplitude pattern required for complex field holographic projection. We numerically evaluate the technique and demonstrate high optical throughput with reduced undesired high diffraction orders.     

Isolation of mineralizing Nestin+ Nkx6.1+ vascular muscular cells from the adult human spinal cord

Background

Evidence suggests that rheumatoid arthritis (RA) may enhance or reduce the progression of Alzheimer's disease (AD). The present study was performed to directly explore the effects of collagen-induced rheumatoid arthritis (CIA) on amyloid plaque formation, microglial activation, and microvascular pathology in the cortex and hippocampus of the double transgenic APP/PS1 mouse model for AD. Wild-type or APP/PS1 mice that received type II collagen (CII) in complete Freund's adjuvant (CFA) at 2 months of age revealed characteristics of RA, such as joint swelling, synovitis, and cartilage and bone degradation 4 months later. Joint pathology was accompanied by sustained induction of IL-1β and TNF-α in plasma over 4 weeks after administration of CII in CFA.

Results

CIA reduced levels of soluble and insoluble amyloid beta (Aβ) peptides and amyloid plaque formation in the cortex and hippocampus of APP/PS1 mice, which correlated with increased blood brain barrier disruption, Iba-1-positive microglia, and CD45-positive microglia/macrophages. In contrast, CIA reduced vessel density and length with features of microvascular pathology, including vascular segments, thinner vessels, and atrophic string vessels.

Conclusions

The present findings suggest that RA may exert beneficial effects against Aβ burden and harmful effects on microvascular pathology in AD.     

Aroma-Active Compounds in Robusta Coffee Pulp Puree—Evaluation of Physicochemical and Sensory Properties

Wet coffee processing generates a large amount of coffee pulp waste that is mostly disposed of in the processing units. To reduce this waste and the associated environmental burden, an alternative strategy would be to exploit the coffee pulp to produce a durable and stable consumable product. Accordingly, a puree produced from Robusta coffee pulp was investigated in relation to its physicochemical and sensory properties. After thermal and chemical stabilization, the obtained puree (pH 3.6) was found to exhibit a multimodal particle size distribution, shear-thinning behavior, and lower discoloration, as well as an antioxidant capacity of 87.9 µmol_TE/g_DM. The flavor of the puree was examined by sensory evaluation and the corresponding analyses of aroma-active volatile compounds, as determined using aroma extract dilution analyses (AEDA) and gas chromatography-mass spectrometry/olfactometry (GC-MS/O). The puree was characterized by dominant fruity (4.4), floral (3.4), citrusy (3.3) and hay-like (3.3) odor impressions. The aroma-active compounds were predominantly aldehydes, acids, and lactones, whereby (E)-β-damascenone, geraniol, 4-methylphenol, 3-hydroxy-4,5-dimethylfuran-2(5H)-one, and 4-hydroxy-3-methoxybenzaldehyde exhibited the highest flavor dilution (FD) factor (1024), thereby indicating their high impact on the overall aroma of the puree. This study demonstrates an approach to stabilize coffee pulp to produce a sweet, fruity puree with comparable physical properties to other fruit purees and that can be used as a new and versatile flavoring ingredient for various food applications.     

Complexation Properties of a Carbon-Bridged Cryptand with Metal Ions in Aqueous Solution at 25°C

Abstract

Thermodynamic quantities (log K, ΔH, and ΔS) for the interactions of a carbon-bridged cryptand with Li⁺, Na⁺, K⁺, Ca²⁺, Sr²⁺, Ba²⁺, and Pb²⁺ were determined at 25° C by calorimetric titration in aqueous solution. The cryptand forms complexes with Na⁺, Sr²⁺, Ba²⁺, and Pb²⁺ with log K ≤ 2. Complexation was not detected for Li⁺, K⁺, and Ca²⁺. Weak interactions with Li⁺ and K⁺ and a log K value of 2.4 for Na⁺ suggest that the cavity size of the cryptand is close to that of Na⁺ but too small for K⁺ and too large for Li⁺. The carbon-bridged cryptand selectively binds Sr²⁺ (log K = 3.2) over Ca²⁺ and Ba²⁺ by more than one order of magnitude.     

Divergent synthesis and self‐assembly of amphiphilic polymeric dendrons with selective degradable linkages

Enhancing the structural complexity and functionality of the building blocks allows the construction of supramolecular assemblies. In this work, we demonstrate a strategy for the design and synthesis of complex macromolecular architectures. We use atom transfer radical polymerization to produce well‐defined polymers with telechelic end‐group functionality, and “click” them together to form functional 3rd generation dendrons, and incorporated degradable linkages and certain functionality at the polymer chain‐ends of each generation. The 3rd generation polymeric dendrons consisted of homopolymer polystyrene (PSTY) with either four solketals or eight alcohols, diblock PSTY and poly(t‐butyl acrylate), and amphiphilic diblock. The peripheral ends consisting of alcohols create functionalization points for further chemical modification or chemical coupling and the cleavable linkages between the 2nd and 3rd generations all provide the first steps toward smart nanostructures. Importantly, we can synthesize these dendrons in pure form. The self‐assembly of the amphiphilic dendrons (the inner and outer generations consisting of PSTY and polyacrylic acid, respectively) in water produced micelles of uniform size with an aggregation number of 43 dendrons per micelle. The size of the micelles was small (D_H =20.7 nm) and comparable to the size found by transmission electron microscopy (14–18 nm). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1533–1547, 2008     

A proof of Coleman's conjecture

Almost thirty years ago Coleman made a conjecture that for any convex lattice polygon with v vertices, g (g?1) interior lattice points and b boundary lattice points we have b?2g-v+10. In this note we give a proof of the conjecture. We also aim to describe all convex lattice polygons for which the bound b=2g-v+10 is attained.     

Trends in adsorption of open-shell atoms and small molecular fragments on the Ag(1 1 1) surface

The chemisorption of various atoms (C, N, O, Cl) and molecular fragments (OH, NH, CH, NH₂, CH₂) on the Ag(1 1 1) surface has been studied by employing the embedded cluster and multireference single- and double-excitation configuration interaction (MRD-CI) methods. Ground and excited states of the cluster-adsorbate systems have been computed and molecular orbitals (MOs) as well as electronic charge density distributions and Mulliken populations have been analyzed in order to extract general trends in chemisorption properties for different adsorbates. It has been found that the adsorbate-surface bond is energetically most favorable when a maximum of two electrons of the metal are shared with a given adsorbate. As a result atomic/molecular fragments with less than six valence electrons (N, CH, C) retain some open shells upon adsorption, whereas oxygen as well as chlorine isovalent species form a singlet ground state on the surface. All species considered except for Cl have mainly covalent bonding character to the surface, with an electronic charge of up to 1.0 transferred to the adsorbate from the silver cluster. It has been shown that the ionicity of the bond is strongly correlated with the electron affinity of the adsorbed species. Binding energies, equilibrium geometry and adsorbate location on the cluster have been computed and compared with available experimental data. In addition, the characteristic properties of chemisorption on Ag(1 1 1) and Pt(1 1 1) surfaces have been compared.