Tunable THz metamaterials based on an array of paraelectric SrTiO<Subscript>3</Subscript> rods

This work presents theoretical and experimental investigations of a tunable metamaterial which exhibits negative permeability in the THz frequency range. The tunability is obtained by temperature changes, and the sample consists of an array of high-permittivity SrTiO₃ (STO) rods micromachined by a femtosecond laser. Structures exhibiting a negative permeability on multiple frequency bands are also investigated and a proper choice of the dimensions of the pattern allows us to achieve a substantial broadening of the frequency band with negative μ.     

Microorganisms baroinactivation of germinated mung bean (green gram) seeds

It is possible to describe the pressure degradation of microorganisms as being analogous to thermal inactivation. Equation for baroinactivation is derived from thermal death time (TDT) model D _p = D _pref 10^{(pref-p)/z _p} , where D _pref is decimal reduction time at the reference pressure (min), p _ref is the reference pressure (MPa), z _p is the pressure increase (MPa) required to reduce the D _p value by a factor of 10. This method was used for the calculation of baroinactivation model parameters of the total number of microorganisms of pressurized germinated mung bean (green gram) seeds (Vigna radiata (L.) Wilczek). Microbial contamination of germinated mung bean (green gram) seeds can be effectively decreased by treatment at a high pressure of 400 MPa, time of pressurization 5 min.     

Thin SiC<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> layers prepared by hybrid laser–magnetron deposition

Thin SiC _x films were fabricated by hybrid laser–magnetron deposition system. KrF excimer laser was used for deposition of carbon and magnetron at the same time for sputtering of Si species. Films were fabricated in argon/hydrogen ambient with and without additional RF discharge. The substrate temperature was changed up to 700°C. Films topology, crystallinity, composition, chemical bonds and optical emission spectra were studied. Films were smooth and amorphous. Films of thickness 400–1000 nm were fabricated. Adhesion moved from 8 to 14 N, depending on deposition conditions.     

Biocompatible hydrogels based on chitosan,cellulose/starch,PVA and PEDOT:PSS with high flexibility and high mechanical strength

Fabricating mechanically strong hydrogels that can withstand the conditions in internal tissues is a challenging task. We have designed hydrogels based on multicomponent systems by combining chitosan, starch/cellulose, PVA, and PEDOT:PSS via one-pot synthesis. The starch-based hydrogels were homogeneous, while the cellulose-based hydrogels showed the presence of cellulose micro- and nanofibers. The cellulose-based hydrogels demonstrated a swelling ratio between 121 and 156%, while the starch-based hydrogels showed higher values, from 234 to 280%. Tensile tests indicated that the presence of starch in the hydrogels provided high flexibility (strain at break?>?300%), while combination with cellulose led to the formation of stiffer hydrogels (elastic moduli 3.9–6.6 MPa). The ultimate tensile strength for both types of hydrogels was similar (2.8–3.9 MPa). The adhesion and growth of human osteoblast-like SAOS-2 cells was higher on hydrogels with cellulose than on hydrogels with starch, and was higher on hydrogels with PEDOT:PSS than on hydrogels without this polymer. The metabolic activity of cells cultivated for 3 days in the hydrogel infusions indicated that no acutely toxic compounds were released. This is promising for further possible applications of these hydrogels in tissue engineering or in wound dressings.

Graphical abstract

     

Resistively shunted Josephson tunnel junctions

SIS tunnel junctions have externally been shunted by a thin metallic film. It is shown that such devices exhibit radiation induced steps as point contacts or microbridges. This result agrees qualitatively with the commonly used lumped circuit model of Josephson junctions.     

Current-versus voltage source model in Josephson effect

The height of the calculated radiation-induced constant-voltage steps in the characteristic of a Josephson junction with linear-periodic current-phase relation is compared with the magnitude of the current spikes obtained from the voltage-source model.     

Active optical control of the terahertz reflectivity of high-resistivity semiconductors

We study theoretically and demonstrate experimentally light-controllable terahertz reflectivity of high-resistivity semiconductor wafers. Photocarriers created by interband light absorption form a thin conducting layer at the semiconductor surface, which allows the terahertz reflectivity of the element to be tuned between antireflective (R <3%) and highly reflective (R >85%) limits by means of the intensity and wavelength of the optical illumination.