Laser synthesis of nanocomposite hydrocarbon fuel and CARS diagnostics of its combustion flame

We report an analysis of diffusive combustion in oxygen of a composite fuel formed by the addition of aluminium nanoparticles (NPs) to isopropanol. The process of obtaining Al NPs consisted in laser fragmentation of initially large industrial NPs using radiation of a pulsed nanosecond neodymium laser. The size distribution of Al NPs was determined using a measuring disk centrifuge. The average nanoparticle size was 20 nm, which is confirmed by transmission electron microscopy data. A diagnostic system based on coherent anti-Stokes Raman scattering (CARS) was used to experimentally study the diffusive combustion of composite fuel. The temperature distributions were measured in two mutually orthogonal directions (along the flame and in the transverse direction) in pure isopropanol and in isopropanol with the addition of 0.15 wt % of Al nanoparticles.

Initial Dynamic Susceptibility of Maghemite Nanoparticles Dispersed in Surface-Treated Polymeric Template

Magnetic nanocomposites based on maghemite nanoparticles supported (ex situ route) on styrene- divinilbenzene (Sty-DVB) copolymer templates were produced and characterized for their structure and morphology. The as-produced nanocomposites were further chemically-treated with different oxidant agents and surface-coated with stearic acid. X-ray diffraction and transmission electron microscopy data show that the incorporated nanoparticles are preserved despite the aggressive chemical treatments employed. From the dynamical susceptibility measurements performed on the nanocomposites, the values of the saturation magnetization (76 emu/g) and the effective magnetic anisotropy (1.7 × 104 J/m3) were obtained, in excellent agreement with the values reported in the literature for maghemite. This finding strongly supports the preservation of the magnetic properties of the supported nanosized maghemite throughout the entire samples’ processing.

Studying the influence of the energy parameters of the plasma dynamic synthesis process on the dispersed products of the W–C system

Tungsten carbide and its different crystalline phases are widely used for production of metalworking tools due to their excellent physical and mechanical characteristics. However, there is still a problem of synthesizing the cubic modification of tungsten carbide. This paper demonstrates the results on studying the influence of the energy parameters of the plasma dynamic synthesis process on the dispersed products of the W–C system. It was revealed that the initial energy parameters directly influence the phase composition of synthesized products. There were found the optimal conditions for synthesizing the dispersed products from the standpoint of the high output of cubic tungsten carbide phase (more than 85 wt.%). According to transmission electron microscopy data, all the products are characterized by the presence of particles with a core-shell structure embedded into the amorphous carbon matrix.

Theaflavins as a novel cross-linker quickly stabilize demineralized dentin collagen against degradation

To investigate the ability of theaflavins (TF) from black tea to protect dentin collagen against enzymatic degradation via cross-linking effect under clinically relevant conditions. 10-µm-thick dentin films were microtomed from dentin slabs of human molars. Following demineralization, films or slabs were treated with TF at two concentrations (0.4% and 2%) for 30 s. A well-known collagen cross-linker grape seed proanthocyanidins (PA) was used as control. Collagen cross-linking interactions and stabilization against enzymatic degradation were investigated by Fourier transform infrared spectroscopy, weight loss, hydroxyproline release, and scanning/transmission electron microscopy. Data were analyzed by ANOVA, Tukey’s and Student’s T test (α = 0.05%). The results showed collagen cross-linking and stabilization efficacy was dependent on TF/PA concentrations. At 2.0%, TF and PA offered nearly full protection to collagen; at 0.4%, TF exhibited a significantly better collagen stabilization effect than PA (P < 0.05), while untreated collagen was completely digested. It’s concluded that TF cross-links dentin collagen within a clinically relevant time (30 s) and offers excellent collagen protection against enzymatic degradation, with efficacy comparable to or better than PA. The study supports the potential use of TF as a novel, promising collagen cross-linker for degradation resistant, long-lasting dentin bonding in composite restorations.

Free energy and stacking of eumelanin nanoaggregates

Eumelanin, a member of the melanin family, is a black-brown insoluble pigment. It possesses a broad range of properties such as antioxidation, free radical scavenging, photo-protection, and charge carrier transportation. Surprisingly, the exact molecular structure of eumelanin remains undefined. It is, however, generally considered to consist of two main building blocks, 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole carboxylic acid (DHICA). We focus on DHI and report, for the first time, a computational investigation of structural properties of DHI eumelanin aggregates in aqueous solutions. First, multi-microsecond molecular dynamics (MD) simulations at different concentrations were performed to investigate aggregation and ordering of tetrameric DHI-eumelanin protomolecules. This was followed by umbrella sampling (US) and density functional theory (DFT) calculations to study the physical mechanisms of stacking. Aggregation occurs through formation of nanoscale stacks and was observed in all systems. Further analyses showed that aggregation and coarsening of the domains is due to decrease in hydrogen bonds between the eumelanins and water; while domains exist, there is no long-range order. The results show non-covalent stacks with and interlayer distance between eumelanin protomolecules being less than 3.5 Å. This is in good agreement with transmission electron microscopy data. Both free energy calculations and DFT revealed strong stacking interactions. The electrostatic potential map provides an explanation and a rationale for the slightly sheared relative orientations and, consequently, for the curved shapes of the nanoscale domains.

Reduction of Pericyte Coverage Leads to Blood-Brain Barrier Dysfunction Via Endothelial Transcytosis Following Chronic Cerebral Hypoperfusion

Background: Chronic cerebral hypoperfusion (CCH) is the leading cause for cerebral small vessel disease (CSVD). CCH is strongly associated with blood–brain barrier (BBB) dysfunction and white matter lesions (WML) in CSVD. But the effects of CCH on BBB integrity and constituents as well as the cellular and molecular mechanisms about the consequences of BBB dysfunction remain elusive. Whether maintaining BBB integrity can reverse CCH induced brain damage has also not been explored. Methods: In this study, we used a rat model of CSVD, established via permanent bilateral common carotid artery occlusion (2VO) to mimic the chronic hypoperfusive state of CSVD. The progression of BBB dysfunction and components of the BBB was assessed using immunostaining, western blotting and transmission electron microscopy. Data were analyzed using the one-way ANOVA test or two-tailed unpaired Student’s t tests.Results: We noted a transient yet severe breakdown of the BBB in the CC following CCH. The BBB was severely impaired as early as 1 day post operation and most severely impaired 3 days post operation. BBB breakdown preceded WML and neuroinflammatory responses. Moreover, pericyte loss was associated with BBB impairment and accumulation of serum proteins was mediated by increased endothelial transcytosis in the CC. BBB dysfunction led to brain damage by regulating TGF-β/Smad2 signaling. Further, protection of the BBB via inhibition of endothelial transcytosis ameliorated serum proteins leakage, microglial activation, oligodendrocyte progenitor cells (OPCs) activation and inappropriate TGF-β/Smad2 signaling activation. Conclusions: Our results indicate that reduced pericyte coverage leads to increased BBB permeability via endothelial transcytosis and protection of the BBB integrity ameliorates brain damage by regulating TGF-β/Smad2 signaling following CCH, therefore reversal of BBB dysfunction may be a promising strategy to treat CSVD.

Influence of nanoscale-modified apatite-type calcium phosphates on the biofilm formation by pathogenic microorganisms

Nanoparticles (25–50 nm) of chemically modified calcium phosphates Ca10−x−y M ii x Na y (PO4)6−z (CO3) z (OH)2 (M ii – Cu2+, Zn2+) were synthesized via a wet precipitation method at room temperature. The Fourier-transform infrared spectroscopy data confirmed the partial substitution of PO 4 3 − {\text{PO}}_{4}^{3-} → CO 3 2 − {\text{CO}}_{3}^{2-} (B-type) in apatite-type structure. The influence of prepared phosphates on biofilm formation by pathogenic microorganisms was investigated. It was found that the samples Na+, CO 3 2 − {\text{CO}}_{3}^{2-} -hydroxyapatite (HAP) and Na+, Zn2+, CO 3 2 − {\text{CO}}_{3}^{2-} -HAP (5–20 mM) had the highest inhibitory effect on biofilm formation by Staphylococcus aureus strains. The sample Na+, CO 3 2 − {\text{CO}}_{3}^{2-} -HAP had the slight influence on the formation of the biofilm by Pseudomonas aeruginosa, while for the samples Na+, Cu2+, CO 3 2 − {\text{CO}}_{3}^{2-} -HAP and Na+, Zn2+, CO 3 2 − {\text{CO}}_{3}^{2-} -HAP such an effect was not detected. According to transmission electron microscopy data, a correlation between the activity of synthesized apatite-related modified calcium phosphates in the processes of biofilm formation and their ability to adhere to the surface of bacterial cells was established. The prepared samples can be used for the design of effective materials with antibacterial activity for medicine.