Two-gap and paramagnetic pair-breaking effects on upper critical field of SmFeAsO0.85_{0.85} and SmFeAsO0.8_{0.8}F0.2_{0.2} single crystals

We investigated the temperature dependence of the upper critical field [$H_{c2}(T)$] of fluorine-free SmFeAsO$_{0.85}$ and fluorine-doped SmFeAsO$_{0.8}$F$_{0.2}$ single crystals by measuring the resistive transition in low static magnetic fields and in pulsed fields up to 60 T. Both crystals show that $H_{c2}(T)$'s along the c axis [$H_{c2}^c(T)$] and in an $ab$-planar direction [$H_{c2}^{ab}(T)$] exhibit a linear and a sublinear increase, respectively, with decreasing temperature below the superconducting transition. $H_{c2}(T)$'s in both directions deviate from the conventional one-gap Werthamer-Helfand-Hohenberg theoretical prediction at low temperatures. A two-gap nature and the paramagnetic pair-breaking effect are shown to be responsible for the temperature-dependent behavior of $H_{c2}^c$ and $H_{c2}^{ab}$, respectively.Comment: 21 pages, 8 figure

Contrast enhancement behavior of hydrogen silsesquioxane in a salty developer

The authors investigated a contrast enhancement behavior of hydrogen silsesquioxane (HSQ) in a salty development system (NaOH/NaCl). Time-resolved analysis of contrast curves and line-grating patterns were carried out to investigate the unique properties of a salty development process. In NaOH developer without salt, the development process was saturated beyond a certain development time. On the other hand, the addition of salt enabled a continuous development, which was not observed in the pure NaOH development. The continuous thinning process enhances the contrast of HSQ in the salty developer, which allows a fast collapsing behavior in HSQ line-grating patterns. During development process, salt seems to have the role of modifying HSQ by breaking network bonds preferentially, leading to a continuous development rate

Fenolni sastav i antioksidativna svojstva esencijalnog ulja dobivenog iz piljevine pačempresa mikrovalnom ekstrakcijom i hidrodestilacijom

Reactive oxygen species and free radicals play a major role in food deterioration. Current research is directed towards finding naturally occurring antioxidants of plant origin. In the present study, the chemical composition analysis of the essential oil obtained from sawdust of Chamaecyparis obtusa (COEO) was conducted by gas chromatography coupled with mass spectroscopy (GC-MS). Further, the phenolic content and antioxidant capacity of the COEO were investigated using different radical scavenging assays. The COEO obtained from the dried sawdust material using a microwave-assisted hydrodistillation technique resulted in the determination of 46 different compounds by GC-MS analysis, representing 98.94 % of total oil content. The COEO was characterised by the presence of mono- and sesquiterpene hydrocarbons, oxygenated mono- and sesquiterpenes, steroids, diterpenes and indole derivatives. At the highest tested concentration range, the COEO showed antioxidant capacity, i.e. the inhibition of DPPH, nitric oxide, superoxide and hydroxyl radicals of 80.16, 82.93, 72.99 and 71.62 %, respectively. Moreover, the COEO displayed concentration-dependent reducing power ability and remarkable inhibitory effect on ferric ion-induced lipid peroxidation in bovine brain extract. In addition, the COEO yielded (6.13±0.05) mg of gallic acid per g of dry mass. The present study confirms that the C. obtusa essential oil has potent antioxidant, lipid peroxidation inhibition and radical scavenging abilities; therefore, it might be used as a natural antioxidant to prevent food deterioration.Reaktivni spojevi kisika i slobodni radikali glavni su uzrok propadanja hrane, pa su najnovija istraživanja usmjerena na pronalazak prirodnih antioksidanasa biljnoga podrijetla. U ovom je radu plinskom kromatografijom i masenom spektrometrijom analiziran kemijski sastav esencijalnog ulja dobivenog iz piljevine pačempresa (Chamaecyparis obtusa). Udjel fenolnih spojeva i antioksidativna svojstva dobivenog ulja ispitani su pomoću različitih mehanizama uklanjanja slobodnih radikala. U esencijalnom je ulju pačempresa dobivenom mikrovalnom ekstrakcijom i hidrodestilacijom sušene piljevine pomoću plinske kromatografije i masene spektrometrije određeno 46 spojeva koji čine 98,94 % ukupnog sastava ulja. Ulje sadržava mono- i seskviterpene, oksigenizirane mono- i seskviterpene, steroide, diterpene i derivate indola. Pri najvećoj je koncentraciji esencijalno ulje pačempresa inhibiralo 80,16 % DPPH radikala, 82,93 % dušikovog monoksida, 72,99 % superoksida i 71,62 % hidroksilnih radikala. Osim toga, utvrđeno je da je reducirajuća snaga ulja ovisila o njegovoj koncentraciji, te da je ulje znatno inhibiralo peroksidaciju lipida kataliziranu ionima željeza(II) u goveđem ekstraktu. Ulje je sadržavalo (6,13±0,05) mg galne kiseline po gramu suhe tvari. Ovo istraživanje potvrđuje da esencijalno ulje pačempresa ima jaka antioksidativna svojstva, te dobru sposobnost inhibicije peroksidacije lipida i uklanjanja slobodnih radikala, pa se može upotrijebiti kao prirodni antioksidans u svrhu očuvanja svježine hrane

Penetration Pathways Induced by Low-Frequency Sonophoresis with Physical and Chemical Enhancers: Iron Oxide Nanoparticles versus Lanthanum Nitrates

Low-frequency sonophoresis (LFS) has been shown to disrupt the structure of stratum corneum (SC) lipid bilayers and enhance SC permeability. In this study, we examined the penetration pathway of lanthanum nitrate (LaNO3) tracer in viable epidermis after combined treatment of LFS and tape stripping (TS), as a physical enhancer, or oleic acid (OA) application, as a chemical enhancer, using transmission electron microscopy (TEM). As a positive control, we visualized the passive diffusion pathway of LaNO3 and iron oxide (Fe3O4) nanoparticles after the incision of hairless mouse skin. Next, we applied LFS immediately after TS or OA application and visualized the penetration pathway of LaNO3. Each treatment showed restricted penetration to the SC–stratum granulosum (SG) interface or upper SG layer. However, the additional application of LFS induced diffuse intracellular distribution of LaNO3 throughout the viable epidermis. Quantitative analysis also revealed that combined treatment significantly increases LaNO3 penetration into viable epidermis when compared with each treatment. Our ultrastructural findings show the synergistic effect of LFS and TS or OA application on transdermal drug delivery. We also found that this combined treatment enhances the penetration of LaNO3 through the viable epidermis through an intracellular pathway

Correlation of Fe-Based Superconductivity and Electron-Phonon Coupling in an FeAs/Oxide Heterostructure

Interfacial phonons between iron-based superconductors (FeSCs) and perovskite substrates have received considerable attention due to the possibility of enhancing preexisting superconductivity. Using scanning tunneling spectroscopy, we studied the correlation between superconductivity and e−ph interaction with interfacial phonons in an iron-based superconductor Sr2VO3FeAs (Tc≈33  K) made of alternating FeSC and oxide layers. The quasiparticle interference measurement over regions with systematically different average superconducting gaps due to the e−ph coupling locally modulated by O vacancies in the VO2 layer, and supporting self-consistent momentum-dependent Eliashberg calculations provide a unique real-space evidence of the forward-scattering interfacial phonon contribution to the total superconducting pairing. © 2017 American Physical Society6

Low-temperature formation of epitaxial graphene on 6H-SiC induced by continuous electron beam irradiation

It is observed that epitaxial graphene forms on the surface of a 6H-SiC substrate by irradiating electron beam directly on the sample surface in high vacuum at relatively low temperature (similar to 670 degrees C). The symmetric shape and full width at half maximum of 2D peak in the Raman spectra indicate that the formed epitaxial graphene is turbostratic. The gradual change of the Raman spectra with electron beam irradiation time increasing suggests that randomly distributed small grains of epitaxial graphene form first and grow laterally to cover the entire irradiated area. The sheet resistance of epitaxial graphene film is measured to be similar to 6.7 k Omega/sq.open4

Phonon structure in I-V characteristic of MgB2_{2} point-contacts

The search of the phonon structure at the above-gap energies was carried out for $d^{2}V/dI^{2}(V)$ spectra of MgB$_{2}$ point contacts with a normal metal. The two-band model is assumed not only for the gap structure in $dV/dI(V)$-characteristics, but also for phonons in $d^{2}V/dI^{2}(V)$ point-contact spectra, with up to the maximum lattice vibration energy. Since the current is carried mostly by charges of 3D-band, whereas the strong electron-phonon interaction occurs in 2D-band, we observe the phonon peculiarities due to ''proximity'' effect in {\it k}-space, which depends on the variation of interband coupling through the elastic scattering.Comment: 6 pages, 4 figures, revtex4, reported in International Conference "Modern Problems in Superconductivity", 9-13 September, Yalta, Ukrain