Abstract
A quantum spin Hall (QSH) insulator hosts topological states at the one-dimensional (1D) edge, along which backscattering by nonmagnetic impurities is strictly prohibited. Its 3D analogue, a ...weak topological insulator (WTI), possesses similar quasi-1D topological states confined at side surfaces. The enhanced confinement could provide a route for dissipationless current and better advantages for applications relative to strong topological insulators (STIs). However, the topological side surface is usually not cleavable and is thus hard to observe. Here, we visualize the topological states of the WTI candidate ZrTe
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by spin and angle-resolved photoemission spectroscopy (ARPES): a quasi-1D band with spin-momentum locking was revealed on the side surface. We further demonstrate that the bulk band gap is controlled by external strain, realizing a more stable WTI state or an ideal Dirac semimetal (DS) state. The highly directional spin-current and the tunable band gap in ZrTe
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will provide an excellent platform for applications.
The major breakthroughs in understanding of topological materials over the past decade were all triggered by the discovery of the Z
-type topological insulator-a type of material that is insulating ...in its interior but allows electron flow on its surface. In three dimensions, a topological insulator is classified as either 'strong' or 'weak'
, and experimental confirmations of the strong topological insulator rapidly followed theoretical predictions
. By contrast, the weak topological insulator (WTI) has so far eluded experimental verification, because the topological surface states emerge only on particular side surfaces, which are typically undetectable in real three-dimensional crystals
. Here we provide experimental evidence for the WTI state in a bismuth iodide, β-Bi
I
. Notably, the crystal has naturally cleavable top and side planes-stacked via van der Waals forces-which have long been desirable for the experimental realization of the WTI state
. As a definitive signature of this state, we find a quasi-one-dimensional Dirac topological surface state at the side surface (the (100) plane), while the top surface (the (001) plane) is topologically dark with an absence of topological surface states. We also find that a crystal transition from the β-phase to the α-phase drives a topological phase transition from a nontrivial WTI to a normal insulator at roughly room temperature. The weak topological phase-viewed as quantum spin Hall insulators stacked three-dimensionally
-will lay a foundation for technology that benefits from highly directional, dense spin currents that are protected against backscattering.
The article considers the discovery of a complex of Early Paleolithic sites with a bifacial industry in the central part of Vietnam. Vietnam is one of the unique regions of Southeast Asia, in terms ...of the settlement of ancient populations of people, the evolution of their culture and the development of man himself, due to its geographical proximity to South China in the north, and during the existence of Sundaland, could serve as one of the transit territories migrations of ancient hominins. In the Gia Lai province in the area of the city of An Khe, the Russian-Vietnamese expedition discovered more than thirty Early Paleolithic sites with pebble-flake industry and bifacially worked tools such as hand axes. According to the tektites found in the cultural layer together with bifaces and pebble tools, two dates were obtained using the 40K/38Ar method: 806 22 thousand years ago and 782 20 thousand years ago These dates indicate that the Early Paleolithic industry discovered in Vietnam existed simultaneously with the industry in the Baise Basin in southern China. Also on the territory of Southeast Asia, several sites with bifacially processed objects and stratified objects with similar technological characteristics of primary splitting dating back to this period were found.
This article describes the successful endovascular treatment of a dural arteriovenous fistula of a rare localization (the area of sphenoid bone lesser region). We examine one report of an unusually ...located dural arteriovenous fistula successfully treated with Onyx (ev3, Irvine, USA) using a combination of endovascular adjuvant techniques: pressure cooker and remodeling balloon protection of cerebral artery. The article includes previously published observations of such fistulas and discusses anatomic features and venous drainage of dural arteriovenous fistulas in the given location.
North Vietnam is situated on a major route of Pleistocene hominin dispersal in East Asia, and the area's karstic caves preserve many prehistoric shell middens. Fossil and genomic evidence suggest a ...complex human history in this region and more widely across Southeast Asia and southern China, but related archaeological investigations are hampered by challenging site stratigraphies. Recent investigations of shell middens in other geographical settings have revealed the microstratigraphic complexity of these anthropogenic deposits. But caves promote distinctive site formation processes, while tropical climates may catalyse geomorphic and diagenetic changes. These environmental factors complicate the interpretation of North Vietnam's shell middens and constraining their effects upon the formation, preservation and destruction of these sites is critical to understanding the archaeology of this region. We examine two archaeological cave sites, dated to the Late Pleistocene and located in the limestone uplands surrounding the Hanoi Basin. Each contains multiple shell midden layers associated with prehistoric occupation and burials. Using thin-section micromorphology (microstratigraphy), we reconstruct the depositional and post-depositional histories of these sites, presenting a geoarchaeological framework of interpretation that is applicable to shell middens in mainland Southeast Asia and tropical zones more widely. This work represents a further step towards improving our understanding of prehistoric human dispersals and adaptations in this region. This article is part of the theme issue 'Tropical forests in the deep human past'.
3-mol% Y2O3 and 0.3 to 3-mol % Cr2O3 co-doped ZrO2 nanopowders were synthesized using co-precipitation technique and investigated by terms of X-ray diffraction, transmission electron microscopy and ...X-ray photoelectron spectroscopy. Structural analysis shows no significant impact of chromium on powders structure except of presence of small amount of m-phase. Surface analysis reveals segregation of yttrium and chromium atoms to the surface along with surface enrichment by oxygen that can be attributed to residual water. Chromium surface atoms present in three oxidation states with catalytically active Cr2+ sites possibly controlling m-phase appearance through lattice distortion.
Background. Urgent osteosynthesis requires number of organizational, material, technical and staff resources.
Aim of the study to determine advantages and disadvantages of existing strategies for ...osteosynthesis basing on literature data and comparative analysis of organization of osteosynthesis on the first day after injury and at a later time.
Methods. Data were collected through review of medical records from first half of 2021 calendar year and consist of the patients have been treated by different types of osteosynthesis on the first day after admission to the hospital and later. Average length of hospital stay (LOS) for surgical procedures and duration of the operative time were compared.
Results. In total 266 osteosynthesis of the extremities immediately after admission to the hospital were performed in the first half of 2021 in 260 patients. The most frequently performed ankle fractures fixation (20.7%) and clavicle fractures surgical repairment (13.9%). Cases of early infections complications and no revision surgeries required due to unstable fixation after urgent osteosynthesis were excluded. In the same period 659 delayed osteosynthesis were performed. Mean value of inpatient day in patients, who underwent urgent surgery, was 8.4016.67 days, while patients, who underwent delayed surgery, spent significantly greater (p0.05) amount of time in the hospital 12.986.28 days in average.
Discussion. Three strategies of osteosynthesis exist: urgent surgeries, delayed surgeries in daytime in operating rooms for planned surgeries and combination of these approaches. Urgent osteosynthesis surgeries do not lead to infectious complications or unstable fixation, what makes them viable option while choosing treatment tactics in case of some injuries. Precise determination of patient groups according to fracture pattern and its localization, that can be operated on in urgent manner, is necessary. Moreover, introduction of urgent osteosynthesis requires serious organizational measures. It is also necessary to perform economical assessment of described approach. Only after solving these questions, it will be possible to make final conclusions about optimal strategy for performing osteosynthesis.
The
Objective
was to assess and improve the treatment results of victims with spleen injury in blunt abdominal trauma by using high-tech minimally invasive methods of diagnosis and treatment.
...Methods and materials.
The article analyzed the results of treatment of 86 patients with isolated and combined blunt spleen injuries who received conventional surgery, and 52 similar patients who were treated in accordance with the new algorithm. This algorithm included conventional splenectomy for unstable hemodynamics and non-operative and minimally invasive management for stable hemodynamics after MSCT. In the absence of CT signs of ongoing bleeding, non-operative management was performed, if ongoing bleeding signs were detected, angiography with selective angioembolization was performed.
Results
. In both groups, most of the victims with blunt spleen injury were admitted to the trauma center after traffic accidents and catatraumas. There were no statistically significant differences in the injury severity (ISS, Tsibin scales), and the condition severity (VPH-SP). The tactics of non-operative and minimally invasive management was applied in 31 patients of the prospective group with stable hemodynamics. Non-operative management was performed on 16 patients of the prospective group. Four patients of this group underwent angiography and selective embolization of the branches of the splenic artery. In the retrospective group, there was a greater number of local complications compared to the prospective group (p=0.006). The decrease in the number of visceral and generalized complications was statistically insignificant (p>0.05). In the retrospective group, 21 victims died. Of these, 12 patients died from severe combined trauma and massive blood loss during the first 24 hours. In the prospective group, the total number of deaths was 10 patients. Of these, 6 died from polytrauma with acute massive blood loss, 1 – from severe traumatic brain injury, 1 – from PE, 2 – from sepsis. In the prospective group, among the patients with stable hemodynamics who had conservative treatment of abdominal trauma, 2 deaths were observed in the long-term period due to severe traumatic brain injury and PE.
Conclusion
. Organ-preserving management was carried out in 26 of 52 (50 %) patients, the number of performed diagnostic laparocenteses was reduced by 50.6 %, laparoscopies – by 16.5 %, laparotomies – by 60.7 %, the duration of inpatient treatment of surviving patients was more than for 7 days, mortality – by 5.2 %.
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