A New Hybrid Algorithm to Image Lightning Channels Combining the Time Difference of Arrival Technique and Electromagnetic Time Reversal Technique

Very-high-frequency (VHF) electromagnetic signals have been well used to image lightning channels with high temporal and spatial resolution due to their capability to penetrate clouds. A lightning broadband VHF interferometer with three VHF antennas configured in a scalene-triangle shape has been installed in Lhasa since 2019, to detect the lightning VHF signals. Using the signals from the VHF interferometer, a new hybrid algorithm, called the TDOA-EMTR technique, combining the time difference of arrival (TDOA) and the electromagnetic time reversal (EMTR) technique is introduced to the image the two-dimensional lightning channels. The TDOA technique is firstly applied to calculate the initial solutions for the whole lightning flash. According to the results by the TDOA method, the domain used for the EMTR technique is predetermined, and then the EMTR technique is operated to obtain the final positioning result. Unlike the original EMTR technique, the low-power frequency points for each time window are removed based on the FFT spectrum. Metrics used to filter noise events are adjusted. Detailed imaging results of a negative cloud-to-ground (CG) lightning flash and an intra-cloud (IC) lightning flash by the TDOA method and the TDOA-EMTR are presented. Compared with the original EMTR method, the positioning efficiency can be improved by more than a factor of 3 to 4, depending on the scope of the pre-determined domain. Results show that the new algorithm can obtain much weaker radiation sources and simultaneously occurring sources, compared with the TDOA method.

Examination of 4th Grade Students' Definitions for Square, Rectangle and Triangle Geometric Shapes

The aim of this study is to obtain information about students' definitions, mistakes, misconceptions, and van Hiele geometry thinking levels by using the definitions of 4th grade students for geometric shapes of rectangle, square, isosceles triangle, equilateral triangle, and scalene triangle. The study was carried out with 156 primary school 4th grade students. In the study, the case design, one of the qualitative methods, was used. Students were asked to describe geometric shapes. It was observed that most of the 4th grade students participating in the study were in the visualization stage of van Hiele. There are very few definitions of the hierarchical structure in the study. Most correct definitions are in the partitional form. In the study, misconceptions were detected in some of the students.

Examination of 4th Grade Students' Definitions for Square, Rectangle and Triangle Geometric Shapes

The aim of this study is to obtain information about students' definitions, mistakes, misconceptions, and van Hiele geometry thinking levels by using the definitions of 4th grade students for geometric shapes of rectangle, square, isosceles triangle, equilateral triangle, and scalene triangle. The study was carried out with 156 primary school 4th grade students. In the study, the case design, one of the qualitative methods, was used. Students were asked to describe geometric shapes. It was observed that most of the 4th grade students participating in the study were in the visualization stage of van Hiele. There are very few definitions of the hierarchical structure in the study. Most correct definitions are in the partitional form. In the study, misconceptions were detected in some of the students.

On Polyhedral Realization with Isosceles Triangles

Answering a question posed by Joseph Malkevitch, we prove that there exists a polyhedral graph, with triangular faces, such that every realization of it as the graph of a convex polyhedron includes at least one face that is a scalene triangle. Our construction is based on Kleetopes, and shows that there exists an integer i such that all convex i-iterated Kleetopes have a scalene face. However, we also show that all Kleetopes of triangulated polyhedral graphs have non-convex non-self-crossing realizations in which all faces are isosceles. We answer another question of Malkevitch by observing that a spherical tiling of Dawson (Renaissance Banff, Bridges Conference, pp. 489–496, 2005) leads to a fourth infinite family of convex polyhedra in which all faces are congruent isosceles triangles, adding one to the three families previously known to Malkevitch. We prove that the graphs of convex polyhedra with congruent isosceles faces have bounded diameter and have dominating sets of bounded size.

An overview of the findings of dynamic upper limbs’ arterial and venous duplex in cases of vascular thoracic outlet syndrome

Background To describe the findings of the dynamic upper limb arterial and venous duplex in the assessment of vascular compression in cases of VTOS. This study was conducted on 58 patients with VTOS; they were evaluated by dynamic duplex examination. Results Vascular compression was subdivided into a venous compression that was detected in (84.4%, n = 49), arterial compression that was seen in (1.7%, n = 1), and combined arterial and venous compression that was present in (13.7%, n = 8); bilateral compression was existing in (94.4%, n = 55), compression at the scalene triangle was seen in (1.7%, n = 1), at the costo-clavicular space was seen in (91.3%, n = 53), and at the retro-pectoral space was depicted in (8.6%, n = 5). Complicated arterial compression was detected in (1.7%, n = 1), whereas venous complications were seen in (6.8%, n = 4). Conclusion Dynamic duplex ultrasound offered a simple, noninvasive, and quick technique that can help in the evaluation of the vascular thoracic outlet syndrome without exposure to ionizing radiation or contrast media administration like that in CT; nevertheless, it is done with the patient in the upright position, thus avoiding the high false-negative results associated with the supine position that is used in the CT and MRI studies.

YAKIV ORENSTEIN: AN EXPATRIATED UKRAINOPHIL FROM GALICIA

Ukrainian-Jewish relations in Galicia between the two World Wars were the reflection of the difference in the status of the two nations. The sides failed to come to mutual understanding, the basis for which was provided by the policy of the West Ukrainian People’s Republic / the Western Oblast of the Ukrainian People’s Republic. Taking into account the involvement of the third party, the Polish state, the situation can be described as an interethnic scalene triangle. One of the active figures in this complicated interaction was Yakiv Orenstein (1875–1942), Jewish publisher from Kolomyia, symbolic ‘Ukrainian’, follower of the faith of Moses. His life and work in Galicia in the interwar years is a personalized example of publicly declared pro-Polishness and actual Ukrainophilia.

Arterial Thoracic Outlet Syndrome

Arterial thoracic outlet syndrome (TOS) is the least common form of TOS in adults. It is an entity that is associated with bony anomalies resulting in chronic subclavian artery compression. Most patients with arterial TOS are young adults presenting either with limb-threatening upper extremity ischemia or chronic symptoms suggestive of arterial insufficiency involving the extremity. Initial diagnostic evaluation involves chest radiography, which may reveal cervical or anomalous first rib. Catheter-based arteriography has a diagnostic as well as therapeutic role. Magnetic resonance angiography and computed tomographic angiography, which are readily available, can be used in surgical planning. Treatment involves revascularization of the extremity, subsequent first rib resection, and possible reconstruction of the subclavian artery. This review contains 4 figures, 1 table and 45 references Key Words: arterial complication, brachial thromboembolectomy, cervical rib, costoclavicular space, first rib resection, pectoralis minor space, scalene triangle, subclavian artery stenosis, thoracic outlet syndrome