Mapping the boundaries of soil horizons using ground-penetrating radar

The article considers the role of GPR in solving problems of soil science, as well as the accuracy of tracking soil horizons using the example of field data. The study of the current state of the issue has shown that there is significant variability in the electrophysical properties of different types of soil. In this case, the dielectric constant of the soil horizons can both increase and decrease with depth. This fact determines the need for parameterization of the soil profile in GPR studies to prevent errors. Based on a generalizing analysis of practical examples, it has been established that the error in determining individual soil horizons by a GPR is on average 2–10 cm, depending on the frequency of the GPR antenna and the structural features of the soil. Experimental and methodological work to substantiate the main conclusions was carried out to trace the soil horizons by the GPR method using the example of typical entic podzol located on the Zaonezhsky Peninsula (Republic of Karelia), the structure and composition of which were described in detail earlier. The survey was carried out by a georadar OKO-2 (Logis-Geotech, Russia) with an antenna unit with a central frequency of 400 MHz. Fieldwork on the study site was carried out along separate transects, according to the reference soil profile. A detailed analysis of the radargrams provided, first of all, tracking the base of the BC horizon. The results obtained showed that the thickness of the soil within the profile varies from 23 to 32 cm, and the average observation error was ± 3 cm. Besides, the influence on the recording of shungite shale fragments and the differentiation of moisture content in the soil horizons was revealed. The presence of shungite shale leads to the formation of diffracted waves and an increase in the amplitudes of the reflected signal, while an increase in humidity is characterized by a decrease in the velocities of the electromagnetic wave

COMBINED FEMORAL FIXATION TECNIQUE IN HAMSTRING TENDON ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION: ASESSMENT OF TUNNEL WIDENING

Purpose – to assess the influence of combined femoral fixation technique during arthroscopic ACL reconstruction on the femoral tunnel widening at long term follow-up.Material and methods. 99 patients with primary hamstring tendon (HT) ACL reconstruction performed in 2007-2008 were analyzed. In the study group (42 patients) on the femoral side a combined cortical suspension (Endobutton CL, Smith & Nephew) and transverse (Rigid Fix, Depuy Mitek) fixation of graft was used. In control group, isolated cortical suspension fixation (Endobutton CL, Smith & Nephew) was used. On the tibial side for graft fixation a biodegradable screw (Biointrafix, DePuy Mitek) was used in all cases. Tunnel widening was calculated in percentage against primary tunnel diameter created during the surgery. MRI data were exported to eFilm (Merge Healthcare software), measurement of femoral tunnel diameters was performed on T1 sequences in coronal and sagittal planes on three different levels.Results. The mean age at the last follow up in the study group was 38.9±1.4, in control group – 38,6±1,08. The median time from surgery to follow up was 9 years and 4 months in the study group and 8 years 7 months in the controls. The incidence of graft failure in the study group was reported as 14.3%, while in the control group as 17,5%. The median femoral tunnel widening was larger in the control group at the joint aperture and midsection levels both in coronal and sagittal plane, although there was no statistically significant differences (p>0,05).Conclusion. The combination of cortical suspension and transverse HT femoral graft fixation technique is likely to reduce tunnel enlargement at the long term follow-up. However further research and larger sample groups are required