The Influence of Weaving Technologies on the Integral Characteristics of Synthetic Vascular Prostheses.

The aim of the study is to determine physical and structural properties of woven synthetic prostheses depending on the type of the weave. Materials and Methods: Ten vascular prostheses manufactured at the Science and Technology Park of the BNTU "Polytechnic" (Minsk, Republic of Belarus) have been analyzed. The prostheses differed in the type of weaving, duration and temperature of thermal fixation during crimping. Three samples had a single-layer structure and 7 samples had a double-layer structure. Tests for water permeability, resistance to radial bending, and porosity of the prostheses have been performed. Results: The single-layer woven prostheses have demonstrated a low level of water permeability: the best result was shown by sample No.1: 80 [77.1; 80.5] ml/min/cm2. A strong direct correlation was revealed for these prostheses: the larger the pore diameter, the greater permeability (r=0.778; p=0.05). The single-layer woven prostheses appeared to be most resistant to radial bending, samples No.1 and 3 had no deformations at the minimum radius of the cylinder (r<4 mm), sample No.2 showed deformation on the cylinder with r=5 mm. For the single-layer prostheses, a strong negative correlation was noted (r=‒0.97; p=0.04) between the density of the warp threads and the kinking radius.All double-layer prostheses have demonstrated higher water permeability and weak resistance to deformation during radial bending. Samples No.4 and 8 were found to have minimum and maximum water permeability of 276.5 [258.3; 288.4] and 538.8 [533.3; 564.3] ml/min/cm2, respectively. The minimum kinking radius (7 mm) was shown by samples No.9 and 10. The worst results were demonstrated by sample No.6, which was deformed with minimal bending. Conclusion: Samples with ordinary plain weave have a low level of water permeability and high resistance to radial deformation, which makes them look most promising for the application in vascular surgery.

Imaging spin filter for electrons based on specular reflection from iridium (001).

As Stern-Gerlach type spin filters do not work with electrons, spin analysis of electron beams is accomplished by spin-dependent scattering processes based on spin-orbit or exchange interaction. Existing polarimeters are single-channel devices characterized by an inherently low figure of merit (FoM) of typically 10⁻4-10⁻³. This single-channel approach is not compatible with parallel imaging microscopes and also not with modern electron spectrometers that acquire a certain energy and angular interval simultaneously. We present a novel type of polarimeter that can transport a full image by making use of k-parallel conservation in low-energy electron diffraction. We studied specular reflection from Ir (001) because this spin-filter crystal provides a high analyzing power combined with a "lifetime" in UHV of a full day. One good working point is centered at 39 eV scattering energy with a broad maximum of 5 eV usable width. A second one at about 10 eV shows a narrower profile but much higher FoM. A relativistic layer-KKR SPLEED calculation shows good agreement with measurements.

Highly efficient multichannel spin-polarization detection.

Since the original work by Mott, the low efficiency of electron spin polarimeters, remaining orders of magnitude behind optical polarimeters, has prohibited many fundamental experiments. Here we report a solution to this problem using a novel concept of multichannel spin-polarization analysis that provides a stunning increase in efficiency by 4 orders of magnitude. This improvement was demonstrated in a setup using a hemispherical electron energy analyzer. An imaging setup proved the principal capability of resolving more than 10(5) data points in parallel.