PhysNet

Insufficient exploration of the dependence between diseases of degenerative bones and the range of motion (ROM) during torsion, flexion and lateral bending limits further understanding about the lumbar biomechanics and treating of the lumbar related dysfunction. The objective of this study was to determine the effect of vertebral degradation on the instability of spine 2 motion L2–L4 segments during torsion, flexion and lateral bending by the finite element method (FEM). Three different 3D FE models comprising the healthy state and the degradation of trabecular bone and cortical bone were developed. Nonlinear numerical analyses of lumbar spine stability discovered that osteoporotic degradation can lead to critical segmental ROM and intervertebral shearing values, which results in the loss of spine stability for the case of flexion loading. Instability is caused by microscopic changes in the thickness of cortical shell. This analysis of the intervertebral shearing and ROM may be further used to diagnose such translation abnormalities like hypomobility or hypermobility.

The Co2MnSi (CMS) Heusler alloy films with thickness d = 90 ÷ 110 nm were grown by DC magnetron sputtering on both nonheated and heated Si(100) and MgO(100) substrates. The films grown (annealed) at T ≥ 400°C demonstrated a nanocrystalline structure with a partially ordered B2 phase and traces of a highly ordered L21 phase as found from XRD measurements. The films deposited onto the nonheated substrates followed by annealing at Tann = 300 ÷ 500°C demonstrated a gradual increase of the saturation magnetisation, Msat, up to about 4.0 μB/f.u. (at 295 K) while the coercity field, Hc, of the films increased from about 10 to 12 kA/m with Tann increasing from 400 to 500°C. Unusually low Hc values of about 0.1 and 0.3 kA/m have been indicated for the films grown in situ at 400°C on MgO and Si, respectively. A significant increase of the Hc values found for the films grown in situ at Ts = 450°C and reduced Msat values for similar films grown at 500°C have been associated with the instability of the ordered L21 structure at high temperatures.

This paper presents a study of the photoluminescence properties of hybrid perovskite films deposited on titanium and magnesium zinc oxide films, as electron transport layers, using the spin-coating technique. The subject of the investigation was continuous wave photoluminescence versus temperature, excitation power and transient photoluminescence. Moreover, the paper discusses possible carrier recombination mechanisms. Complex temporal decay was approximated through the use of several models, but only the four-exponent model and the model using the sum of two hyperbolic functions provided a good agreement with the experimental data. The first attempt to replace titanium dioxide with magnesium zinc oxide in conjunction with the perovskite layer showed improved optical properties such as a weaker non-radiative recombination process and a longer decay time constant.

Dependences of the contrast ratio on the angular deviation of the optical axis with a step of 2 arcmin 28 arcsec have been obtained for Pockels cells based on beta barium borate crystals in the 49 arcmin 34 arcsec range. The investigation was conducted for a single Pockels cell and for a double cell based on optically aligned crystals. The results of investigations can be applied for the calculation of the laser beam focus in order to use a high contrast ratio in high-power laser systems when the light is modulated using Q-switching.

The design of a simple cost-effective planar semiconductor microwave diode is proposed. The operation is based on hot carrier phenomena and rectification of microwave currents flowing through the structure composed of two diodes connected in series and having different active region areas. A simplified technological process and the use of simplex semiconductor material result in the reduction of both the time and the cost of fabrication of a dual microwave diode. By choosing an appropriate GaAs substrate, two types of microwave diodes were produced simultaneously: one almost demonstrating the ohmic behaviour and the other two having the asymmetrical Schottky-like I–V characteristic. The Schottky-like planar diodes exhibited a higher responsivity to millimetre range microwave radiation and a faster response to pulsed (down to a nanosecond scale) excitation, but the ohmic ones demonstrated better noise properties.

We report electrical and magnetoresistive properties of Ag point-probe contacts formed by attaching the bent Ag wire (∅ = 0.25 mm) to the top of the La2/3Sr1/3MnO3 (LSMO) thin film magnetron sputtered at 800 °C on MgO(100) single crystal substrates. Significant contact magnetoresistance values (up to 13% at T = 295 K and μ0H = 0.73 T) have been measured for the Ag/LSMO junctions by applying a 3 point-probe method. The origin of both temperature-dependent resistance and magnetoresistance of the Ag/LSMO contacts has been explained taking into account the dominating role of spreading resistance. It was found that keeping of the films in air for 1 month as well as ultrathin overlayers (d ~ 3–5 nm) of the highly resistive multiferroic BiFeO3 magnetron sputtered onto the manganite film resulted in a significant increase of contact resistance and reduced magnetoresistance values.

La0.67Sr0.33MnO3 thin films exhibiting a highly (001)-plane oriented and polycrystalline structure with a variable amount of (011)-textured crystallites have been grown in situ by RF magnetron sputtering on crystalline MgO(001) substrates by changing deposition temperature from 550 to 800 °C. Competing contribution of grains and grain boundaries to resistivity and magnetoresistance of the films has been investigated at T = (78–330) K. A model based on two parallel channels of current flow across grain boundaries has been applied to explain coexistence of low (LFMR) and high field (HFMR) magnetoresistance effects in the polycrystalline films at low temperatures. The LFMR effect has been understood assuming tunnelling of spin-polarized carriers via magnetic field-driven tunnelling barriers formed naturally between neighbouring misoriented grains. Meanwhile, the HFMR phenomenon has been associated with magnetic field-dependent hopping of carriers via the intergrain regions with reduced carrier density. Importance of the phase separation phenomenon on possible inhomogeneity of the material at grain boundaries has been discussed.

The results of colossal magnetoresistance (MR) relaxation investigations in nanostructured and epitaxial La-Sr-Mn-O films grown by the MOCVD technique are presented. The films were studied in a pulsed magnetic field ranged from 2 to 10 T at the temperature of 80 K. The slow relaxation of resistance which takes place during milliseconds when the magnetic field is switched off is analysed using the Kohlrausch-Williams-Watts model. It was found that this relaxation is typical of spin-glass materials and is related with properties of disordered grain boundaries of nanostructured films. The MR relaxation of epitaxial films was not observed. The influence of film preparation conditions on MR relaxation was analysed in order to develop high pulsed magnetic field sensors exhibiting small dynamic “memory” effect and operating at low temperatures.

This paper presents the study of variation in ozone concentration and volumetric activities of radon decay products as well as their relationship at the ground level of the atmosphere on the Curonian Spit. The simultaneous measurements of the ground-level ozone concentration and volumetric activity of radon progeny gave a possibility to identify the presence of a breeze phenomenon on the Curonian Spit during an extreme weather event in summer when ozone concentration exceeded the target value of 120 μg m-3 that can have a negative impact on human health. The evident influence of wind direction on ozone concentration and volumetric activity of radon progeny was estimated.

The long-term stability of electrical resistance and magnetoresistance in nanostructured La1-xSrxMnO3 (x = 0.17) manganite thin films grown on lucalox (Al2O3 + MgO) substrate by the MOCVD method was investigated. It was found that the storage of up to 3 months of the free surfaces of these films in normal atmosphere (air) conditions increases their resistivity by almost two times, while the annealing of the films in an Ar atmosphere at 450 °C decreases their resistivity only by 15%. It was concluded that the final increase of resistivity is determined by a long-term relaxation of the grain boundaries in the nanostructured films. The magnetoresistance of the films does not change significantly, which produces an advantage for magnetic field sensor applications. The passive protective coating of the free surfaces of the films stabilizes their electrical and magnetic properties. The results were analysed using various electron scattering mechanisms when the films were in a ferromagnetic state, and the Mott’s variable range hopping model when they were in a paramagnetic insulating state.