Morphological and electrical characteristics of amino acid–AuNP nanostructured two-dimensional ensembles

The interaction between amino acids (l-cysteine, l-lysine) and gold nanoparticle layers deposited on ITO glasses was investigated. The citrate capped gold nanoparticles (AuNP) were first deposited as a thin layer onto silanized ITO and subsequently linked with an amino acid, due to strong affinity of thiol and amine groups to gold. The gold nanoparticles had an elliptical shape, with size varying between 7 and 14 nm, as indicated by TEM analysis. After deposition on ITO substrate, the nanoparticles self-assembled into large aggregates with poor contact between, as revealed by AFM. After linking l-cysteine or l-lysine to the surface of nanoparticles layer, a change in morphology occured. A better contact between the gold aggregates boundary developed, which improved the conducting properties of the nanostructured layer. The electrical resistance of the AuNPs layer, obtained from I–V measurements, was very high (2.8 × 10¹³ Ω) and slightly decreased after linking the NPs with amino acids.     

Conductance oscillations in a mesoscopic ring threaded by a harmonically time-dependent magnetic flux

We consider a microscopic model for a one-dimensional ring of non-interacting electrons threaded by a magnetic flux of the form Φ(t)=Φ₀+Φ₁cos(Ω₀t)$\Phi (t)={\Phi }_0+{\Phi }_1\cos ({\Omega }_{0}t)$. The ring is attached to two reservoirs at which a bias voltage is applied. We focus on small amplitudes of Φ₁${\Phi }_1$, and we analyze the behavior of the conductance as a function of Φ₀${\Phi }_0$. We solve the problem by means of non-equilibrium Green function techniques.     

Liquefying Flavonoids with Terpenoids through Deep Eutectic Solvent Formation

The formation of deep eutectic solvents (DES) is tied to negative deviations to ideality caused by the establishment of stronger interactions in the mixture than in the pure DES precursors. This work tested thymol and menthol as hydrogen bond donors when combined with different flavonoids. Negative deviations from ideality were observed upon mixing thymol with either flavone or flavanone, two parent flavonoids that only have hydrogen bond acceptor (HBA) groups, thus forming non-ionic DES (Type V). On the other hand, the menthol systems with the same compounds generally showed positive deviations from ideality. That was also the case with the mixtures containing the more complex hydroxylated flavonoid, hesperetin, which resulted in positive deviations when mixed with either thymol or menthol. COSMO-RS successfully predicted the behavior of the solid-liquid phase diagram of the studied systems, allowing for evaluation of the impact of the different contributions to the intermolecular interactions, and proving to be a good tool for the design of DES.     

The influence of the melt cooling rate on the properties of YIG single crystal grown by the flux method form sintered polycrystalline maeteral

A method for the single crystal growth of Yttrium Iron Garnet (YIG) in a PbO/PbF₂/B₂O₃ flux mixture with a melt cooling rate of 1–2.5 °C/h is described. In order to keep constant the crystal stoichiometry as well as its specific structural and magnetic properties at such high rates of the cooling process, a previously sintered polycrystalline garnet has been used as raw material. The YIG single crystal quality was checked-up by metallographic analysis, X-ray diffraction, SEM, and magnetic susceptibility measurements.     

Mapping the Distribution of Melanin Concentration in Different Fitzpatrick Skin Types Using Hyperspectral Imaging Technique

Measuring skin melanin concentration in order to assess skin phototype according to Fitzpatrick's classification is a constant research goal. In this study, a new approach for assessing skin melanin concentration based on hyperspectral imaging combined with an appropriate analytical model that exploits specific spectral bands to generate maps of melanin content distribution on different Fitzpatrick skin phototypes is presented. Hyperspectral images from the proximal inner side of the forearms of 51 young volunteers covering the first four classes of Fitzpatrick's phototypes were acquired using a hyperspectral imaging system. The images were analyzed using a modified Beer–Lambert law that segregates the contribution of melanin from the other constituents to the skin absorption spectrum. The performance of the model was evaluated using the coefficient of determination (r-squared). The results revealed that the approach proposed in this study generated accurate melanin concentration distribution maps that allowed a correct classification of skin phototype. In conclusion, the proposed approach for assessing skin melanin concentration proved to be very reliable for classifying skin phototypes, and, as it provides maps that are easily read, it has the advantage of a possible extension of its applications to other research concerning skin pigmentation.     

New Hydrogels Based on Agarose/Phytagel and Peptides

Short aromatic peptide derivatives, i.e., peptides or amino acids modified with aromatic groups, such as 9-fluorenylmethoxycarbonyl (Fmoc), can self-assemble into extracellular matrix-like hydrogels due to their nanofibrillar architecture. Among different types of amino acids, lysine (Lys) and glycine (Gly) are involved in multiple physiological processes, being key factors in the proper growth of cells, carnitine production, and collagen formation. The authors have previously successfully presented the possibility of obtaining supramolecular gels based on Fmoc-Lys-Fmoc and short peptides such as Fmoc-Gly-Gly-Gly in order to use them as a substrate for cell cultures. This paper investigates how the introduction of a gelling polymer can influence the properties of the network as well as the compatibility of the resulting materials with different cell types. A series of hydrogel compositions consisting of combinations of Fmoc-Lys-Fmoc and Fmoc-Gly-Gly-Gly with Agarose and Phytagel are thus obtained. All compositions form structured gels as shown by rheological studies and scanning electron microscopy. Fourier transform infrared spectroscopy analysis evidences the formation of H-bonds between the polysaccharides and amino acids or short peptides. Moreover, all gels exhibit good cell viability on fibroblasts as demonstrated by a live-dead staining test and good in vivo biocompatibility, which highlights the great potential of these biomaterials for biomedical applications.