Structural Position Research Articles

Experimental study and refined numerical simulation of ultimate pressure-bearing performance of rope-reinforced airship envelope structures

Stratospheric airships require a lightweight envelope to contain lighter-than-air buoyancy gas, making the lightweight design and pressure-bearing performance of the envelope structure a key research issue. The stress state at different cross-sectional positions of the airship envelope structure is different, resulting in a low utilization rate of the overall material performance of the envelope structure. This paper proposes a design scheme for reinforcing envelope structures with sliding reinforcing cable to improve the bearing capacity of the composite fabric structure while reducing its weight, ultimately achieving the optimal strength-to-weight ratio. Two types of composite fabric structures (A-airship and B-airship) were subjected to inflatable burst tests, and the strain changes in the envelope gores were analyzed by digital image correlation. Through re-assembly of the broken composite fabric pieces and analysis of their tear textures, crack origination positions, failure causes, and the stress behavior and state at the failure position were identified. An envelope structural model with consideration of the cutting pattern effect was established, allowing the stress distribution of the envelope to be analyzed and the damage positions to be more accurately predicted. Based on the analysis of the ultimate pressure-bearing performance of an airship envelope structure, a novel idea of incorporating coupled tensile-shear stress into the strength criterion was proposed. Through the data in the study and existing references, it is verified that the strength criterion can accurately predict the ultimate pressure-bearing performance of the envelope structure.

The current state of relic rocky grasslands with <i>Sesleria tatrae</i> and <i>Calamagrostis varia</i> in the Eastern Sudetes (Śnieżnik Massif, SW Poland)

The unique, basophilic rocky grasslands on the Pulinka rock near Kletno in the Śnieżnik Massif (Eastern Sudetes) have been known since the 1960s. The aim of the study was to, re-analyze the status of this plant community with reference to species composition, functional structure, habitat conditions and syntaxonomic position 50 years afer its discovery, and first description. For this purpose, we used archival and contemporary data. The obtained results revealed close compositional similarity between the vegetation plots collected in 1968 and 2022. The abundance of relic species documented in phytosociological relevès has remained constant (<i>Sesleria tatrae</i>, <i>Galium anisophyllon</i>) or increased (<i>Scabiosa lucida</i>). Additionally, the first locality of <i>Calamagrostis varia</i> was found on the Pulinka – a species not yet recorded in the Sudetes. On the other hand, some regular fluctuations in the abundance of sporadic species were observed. However, these were not reflected in changes in community-weighted means for environmental variables (temperature, light, nutrients, soil reaction, and moisture) and functional traits (specific leaf area, seed mass, and leaf dry matter content). We also found no differences in the functional diversity index (FD Rao) between the first and last surveys. Therefore, the lack of temporal changes in the main ecological features may indicate a high stability of the studied grasslands despite the pressure of external factors (progressive climate warming and nitrogen deposition). The phytosociological analysis carried out suggests that the studied community belongs to the class <i>Elyno-Seslerietea</i> and the order <i>Seslerietalia caeruleae</i>. However, due to the unusually poor species composition of the studied rocky grasslands, we did not find it currently possible to classify them at the alliance and association level. This requires further studies and classification based on broader data, including Western Carpathian calcicolous swards.

Socioeconomic Dynamics in Kathmandu Valley: A World-System Perspective

The socioeconomic dynamics of the Kathmandu Valley, Nepal, are analyzed through the lens of World-System Theory, providing insights into its position within the global economic hierarchy. This theoretical framework, pioneered by Immanuel Wallenstein, categorizes nations into core, semi-peripheral, and peripheral regions based on their economic and structural positions in the global system. The Kathmandu Valley's spatial distribution of economic resources illustrates core-periphery dynamics, with urban centers like Kathmandu emerging as core areas boasting robust economic activities, while peripheral regions face marginalization and limited access to economic opportunities. Disparities in infrastructure development further highlight these dynamics, as core areas benefit from superior infrastructure, while peripheral regions contend with limited development, exacerbating urban-rural inequalities. Migration patterns within the Kathmandu Valley reflect responses to economic imbalances perpetuated by the global capitalist system, with rural residents migrating to urban centers in search of opportunities, straining urban infrastructure and widening disparities. Additionally, globalization's impact on cultural dynamics contributes to the homogenization of cultures, eroding traditional practices and identities in favor of Western consumer culture. Social stratification within Nepali society is reinforced by the hierarchical structure of the world-system, perpetuating cycles of privilege and disadvantage. Understanding these dynamics through World-System Theory highlights the interconnectedness of global and local processes, emphasizing the need for systemic change to address disparities and foster equitable development in the Kathmandu Valley.

Study of the mandibular canal and its surrounding canals by multi-view cone-beam computed tomography

ObjectivesTo determine the mandibular anatomical structures by observing cone-beam computed tomography (CBCT) from multiple angles.Materials and methodsThis retrospective study analyzed 1593 consecutive CBCT images. Ultimately, 95 CBCTs met the inclusion criteria. The mandibular, inferior lingual, and bony canals at the tooth apex were studied by multi-angle observation CBCT. Descriptive statistics were used for statistical analysis.ResultsIt is beneficial to further observe the anastomosis of the mandibular, lingual, and mandibular canals when the course of the mandibular lingual canal is observed on CBCT cross-section. The frequency of the inferior lingual canal anastomosis with the mandibular canal was 43.2% (95% confidence interval (CI) 33, 53.3) in the sample. The mental foramen was located below the long axis of the tooth in a few samples, with an occurrence rate of 29.5% (95% CI 20.1, 38.8). The occurrence rate of various types of the bony canal at the apex of the tooth in canines, first premolars, second premolars, first molars, and second molars under the root apex was recorded through the multi-angle observation of the dental volume reformat (DVR) and three-dimensional (3D) levels in CBCT.ConclusionThis study demonstrates the utility of CBCT imaging in examining mandibular anatomy from multiple angles, providing valuable insights into anatomical variations, and enhancing our understanding of mandibular structures. This research emphasizes the crucial role of meticulous CBCT examination in precisely identifying and understanding key anatomical structures, ultimately reducing the risk of surgical complications.Critical relevance statementBy examining cone-beam computed tomography scans from various perspectives, it is possible to determine the precise position of anatomical structures within the jaw. This allows for a more accurate assessment, reducing the risk of harm to these structures during treatment.Key points• It is crucial to utilize image data effectively to enhance the comprehension of human anatomy.• We captured detailed images of the mandible from different angles and orientations utilizing cone-beam computed tomography (CBCT).• This study provides essential anatomical information for procedural planning to ensure optimal outcomes and patient safety.Graphical

Purge–Mainstream Interactions in a Turbine Stage With Rotor Endwall Contouring

Abstract Purge flows are prevalent in modern gas turbine design, allowing for increased turbine entry temperatures. The purge flow passes through a rim seal and interacts with the mainstream flow, modifying the blade secondary flow structures and reducing stage efficiency. These structures may be controlled using end wall contouring (EWC), though experimental demonstration of their benefit is seldom reported in the literature. The optically accessible turbine at the University of Bath was designed to directly measure and visualize the flow field within the blade passage for a rotor with EWC. The single-stage turbine enables phase-locked flow field measurements with volumetric particle image velocimetry (PIV). Purge flow was supplied to investigate a range of operating conditions in which the secondary flow structures were modified. The modular turbine rotor allowed for expedient change of a bladed ring, or bling, featuring non-axisymmetric EWC. The identified secondary flow structures were the pressure-side leg of the horse shoe vortex (PS-HSV) and an egress vortex (EV) of concurrent rotational direction. An increase in purge flowrate monotonically shifted the EV toward the suction-side (SS) of the adjacent blade. The migration of the PS-HSV toward the SS caused the two aforementioned vortices to merge. The EWC rotor design included a leading-edge (LE) feature to alter the PS-HSV and a trough to guide the EV low spanwise in the passage and maintain displacement from the adjacent suction-side. The EWC rotor was found to be effective at altering the formation and positioning of the secondary flow structures at a range of purge flow conditions.

Drag reduction of Clark-Y hydrofoil by biomimetic fish scale structure under the condition of biomimetic jet

Hydrofoil, as the basic shape of the fluid blade, is widely used in fluid transport and energy conversion. However, friction resistance and pressure differential resistance are generated in the hydrofoil flow process, resulting in substantial energy consumption and negatively affecting the economy. On this basis, we propose two drag-reducing structures based on Clark-Y hydrofoil. In the design process of the jet structure, we considered the bionic jet velocity, jet angle and jet structure position as the design parameters and obtained the optimal jet structure by using Taguchi method. Finally, the two schemes (Clark-Yori and Clark-Yopt) are numerically simulated using large eddy simulation. Results show that when Ujet = 1.44 m/s, θ = 3° and x = 18.6 mm, the jet structure can play a significant drag reduction effect. Compared with Clark-Yori, the drag coefficient of Clark-Yopt is reduced by 26.5%, and the lift drag ratio is increased by 16.4%. Compared with Clark-Yori, Clark-Yopt can reduce the wall shear stress of the leading edge of the hydrofoil, thereby diminishing the frictional resistance. Meanwhile, the jet structure can effectively balance the area of the low-pressure region on the suction side of the hydrofoil, significantly reducing the pressure differential resistance. Clark-Yopt can accelerate the vortex collapse that decreases turbulence intensity and turbulence resistance. Moreover, it can effectively block the near-wall reflux of hydrofoil and reduce the internal friction between the reflux and the main flow.

Effect of structural support size and position on depressed tibial plateau fractures: A finite element analysis

ObjectiveStructural support for depressed tibial plateau fractures is receiving increasing attention. Currently, there has been little biomechanical evaluation of structural support. This work aimed to investigate the effect of structural support size and position on fracture fixation stability. MethodsA split-depressed tibial plateau fracture model was created according to the fracture map. Cortical screws combined with structural filler were used for fracture fixation. The filler diameter was set to small, medium and large, and the filler position was set to the center and offset by 1, 2 and 3 mm to study the effect of position and size on stability. ResultsThe maximum stress on the implant in all scenarios occurs at the lower contact surface between the anterior screw and the filler. Increased support size resulted in increased mean maximum screw stress, depressed fragment axial displacement and separated fragment transverse displacement (screw stress: 266.6 ± 37.7 MPa vs. 266.7 ± 51.0 MPa vs. 273.8 ± 41.5 MPa; depressed displacement: 0.123 ± 0.036 mm vs. 0.133 ± 0.049 mm vs. 0.158 ± 0.050 mm; separated displacement: 0.402 ± 0.031 mm VS 0.412 ± 0.047 mm VS 0.437 ± 0.049 mm). The larger the offset of the support position was, the larger the peak screw stress and the larger the reduction loss of depressed and separated fragment reduction, regardless of the support size. The medium support combined with the central position presented the minimum of peak stress and reduction loss. Cortical bone was below 2 % and trabecular strain was below 10 % for all scenarios. ConclusionCentral placement of structural support provides superior stability for the treatment of depressed tibial plateau fractures compared to the eccentric placement. When a support is placed centrally, optimal stability is achieved when the diameter matches the diameter of the depressed region. Thus, the utilization of equal-diameter fillers to provide central support appears to be an ideal selection for depressed tibial plateau fractures.

Depth estimation of buried targets using integrated geophysical methods: comparative studies at Ahmadu bello university geophysics test site

Accurate prediction of depth and position of underground structures is a critical step in structural foundation surveys such as civil engineering excavations to adequately maintain the existing underground utilities. The study presents the results of comparative studies conducted to evaluate the performance of electrical resistivity tomography (ERT) alongside the VLF-EM method regarding depth estimation and location of buried targets of known materials, properties and dimensions. A laboratory test was carried out on the buried targets to determine the electrical properties of the buried targets before burial. The pre-burial geophysical investigation indicates no major anomaly within the site that could influence the geophysical response of the buried objects significantly. The results of the post-burial geophysical investigation indicate high variations in electrical resistivity values varying from 47 Ωm – 1081 Ωm (before) and 0.113 Ωm – 19,879 Ωm (after) the buried targets, while the VLF-EM data indicates that the current density values within the site were significantly influenced due to the presence of buried materials, confirming major influence or distortion of geophysical signature of the site. In post-burial ERT investigation, the Wenner and dipole-dipole (DD) arrays registered 67 % and 80 % degrees of alignment with the actual depth of the buried targets, respectively. Both Wenner and DD arrays show strength in depth estimation. However, the DD array indicates higher strength in terms of depth estimation and it is potentially suitable for near-surface utilities investigation due to its high precision in depth estimation. In comparison, VLF-EM captured six (6) out of eight (8) buried targets with a 47 % degree of alignment with the actual depth of the buried targets, which is far lower than the ER method, and may not be considered the most preferable method for geophysical prospecting where depth estimation of targets is of prime interest. However, the depth of targets varies from one method to another and one array to another.

Anatomical Prior and Inter-slice Consistency for Semi-supervised Vertebral Structure Detection in 3D Ultrasound Volume.

Three-dimensional (3D) ultrasound imaging technique has been applied for scoliosis assessment, but the current assessment method only uses coronal projection images and cannot illustrate the 3D deformity and vertebra rotation. The vertebra detection is essential to reveal 3D spine information, but the detection task is challenging due to complex data and limited annotations. We propose VertMatch to detect vertebral structures in 3D ultrasound volume containing a detector and classifier. The detector network finds the potential positions of structures on transverse slice globally, and then the local patches are cropped based on detected positions. The classifier is used to distinguish whether the patches contain real vertebral structures and screen the predicted positions from the detector. VertMatch utilizes unlabeled data in a semi-supervised manner, and we develop two novel techniques for semi-supervised learning: (1) anatomical prior is used to acquire high-quality pseudo labels; (2) inter-slice consistency is used to utilize more unlabeled data by inputting multiple adjacent slices. Experimental results demonstrate that VertMatch can detect vertebra accurately in ultrasound volume and outperforms state-of-the-art methods. Moreover, VertMatch is also validated in automatic spinous process angle measurement on forty subjects with scoliosis, and the results illustrate that it can be a promising approach for the 3D assessment of scoliosis.

Placing African Cities in Chinese Lives: A Comparative Study of Migrant Geographies

Based on ethnographic research on Chinese migrants in Nigeria, Botswana, and Namibia from 2011 to 2015, this article has three lines of argumentation and contribution. First, it proposes a framing of migrant geographies from a humanistic comparative perspective in order to complement the political economy approaches in geographies of migration. Second, lying in the intersection of urban studies and migration studies, it illustrates the different positionalities of cities in three aspects of migrant geographies – migrant space, network, and belonging – echoing the multiscalar analysis of city-making in migration processes. Third, specifically in the context of Chinese migrant geographies, three African cities, Lagos, Gaborone, and Windhoek, are placed in three migrants’ geographic worlds, not always according to their positions in multiscalar power structures, but partly through migrant experiences in which top-down power horizontally works.

HydraProt: A New Deep Learning Tool for Fast and Accurate Prediction of Water Molecule Positions for Protein Structures.

Water molecules are integral to the structural stability of proteins and vital for facilitating molecular interactions. However, accurately predicting their precise position around protein structures remains a significant challenge, making it a vibrant research area. In this paper, we introduce HydraProt (deep Hydration of Proteins), a novel methodology for predicting precise positions of water molecule oxygen atoms around protein structures, leveraging two interconnected deep learning architectures: a 3D U-net and a Multi-Layer Perceptron (MLP). Our approach starts by introducing a coarse voxel-based representation of the protein, which allows for rapid sampling of candidate water positions via the 3D U-net. These water positions are then assessed by embedding the water-protein relationship in the Euclidean space by means of an MLP. Finally, a postprocessing step is applied to further refine the MLP predictions. HydraProt surpasses existing state-of-the-art approaches in terms of precision and recall and has been validated on large data sets of protein structures. Notably, our method offers rapid inference runtime and should constitute the method of choice for protein structure studies and drug discovery applications. Our pretrained models, data, and the source code required to reproduce these results are accessible at https://github.com/azamanos/HydraProt.

Clinical Application of an Augmented Reality Navigation System for Transforaminal Epidural Injection: A Randomized Controlled Trial.

Objectives: Augmented reality (AR) navigation systems are emerging to simplify and enhance the precision of medical procedures. Lumbosacral transforaminal epidural injection is a commonly performed procedure for the treatment and diagnosis of radiculopathy. Accurate needle placement while avoiding critical structures remains a challenge. For this purpose, we conducted a randomized controlled trial for our augmented reality navigation system. Methods: This randomized controlled study involved 28 patients, split between a traditional C-arm guided group (control) and an AR navigation guided group (AR-NAVI), to compare procedure efficiency and radiation exposure. The AR-NAVI group used a real-time tracking system displaying spinal structure and needle position on an AR head-mounted display. The procedural time and C-arm usage (radiation exposure) were measured. Results: All patients underwent successful procedures without complications. The AR-NAVI group demonstrated significantly reduced times and C-arm usage for needle entry to the target point (58.57 ± 33.31 vs. 124.91 ± 41.14, p < 0.001 and 3.79 ± 1.97 vs. 8.86 ± 3.94, p < 0.001). Conclusions: The use of the AR navigation system significantly improved procedure efficiency and safety by reducing time and radiation exposure, suggesting a promising direction for future enhancements and validation.

Slimmable transformer with hybrid axial-attention for medical image segmentation

The transformer architecture has achieved remarkable success in medical image analysis owing to its powerful capability for capturing long-range dependencies. However, due to the lack of intrinsic inductive bias in modeling visual structural information, the transformer generally requires a large-scale pre-training schedule, limiting the clinical applications over expensive small-scale medical data. To this end, we propose a slimmable transformer to explore intrinsic inductive bias via position information for medical image segmentation. Specifically, we empirically investigate how different position encoding strategies affect the prediction quality of the region of interest (ROI) and observe that ROIs are sensitive to different position encoding strategies. Motivated by this, we present a novel Hybrid Axial-Attention (HAA) that can be equipped with pixel-level spatial structure and relative position information as inductive bias. Moreover, we introduce a gating mechanism to achieve efficient feature selection and further improve the representation quality over small-scale datasets. Experiments on LGG and COVID-19 datasets prove the superiority of our method over the baseline and previous works. Internal workflow visualization with interpretability is conducted to validate our success better; the proposed slimmable transformer has the potential to be further developed into a visual software tool for improving computer-aided lesion diagnosis and treatment planning.

Noncovalent hybridization of Fe single-atom with biochar for highly efficient peroxymonosulfate activation: Built-in electric field-driven radical and non-radical processes

A non-covalent hybridisation method was used to manipulate the electron transfer from BC to an iron monoatomic catalyst (SA Fe-N-C) using biochar (BC) as a dopant. By optimizing the mass proportion of BC to SA Fe-N-C during co-pyrolysis, the stack structure of two componants was successfully fabricated. The built-in electric field (BIEF) is induced by the defect position of graphite carbon structure in BC and the electron-withdrawing nitrogen atom in SA Fe-N-C. The electron transport road from BC to SA Fe-N-C was established by using the BIEF between the interfaces. As a result, the non-covalent stack of BC/SA Fe-N-C rendered a promising way in activating peroxymonosulfate (PMS), and meanwhile exhibited superior stability concerning their robust geometric skeleton. The degradation experiments showed that the degradation efficiency of the composite was increased to 91% compared with that of the pristine SA Fe-N-C (69%) at a extremely higher concentration of TC (20 mg/L). Based on theoretical calculations and in-situ detections, it was found that the PMS activation follows the route of generating radicals (SO4•–,•OH) and non-radical (1O2, Fe(V)=O). The presence of the BIEF accelerated the electron delocalization, driving the electrons transfer for Fe(III)/Fe(II) and Fe(V)=O/Fe(III) recycle. The present study offer a new pathway for the synergistic PMS activation by combing single atom catalysts and biochar.

STRUCTURAL POSITION AND DISTRIBUTION OF THE LOWER CRETACEOUS BLACK SHALE DEPOSITS WITHIN THE SILESIAN NAPPE OF THE UKRAINIAN CARPATHIANS

The article presents the results of studying the structural position and distribution of potentially oil-generating, organic-enriched Lower Cretaceous black shale deposits of the Shypot Formation, developed within the Silesian Nappe, using the methods of geological mapping and structural analysis. We concluded, that these deposits, which are exposed in the Vicha River basin near the town of Volovets among a continuous field of Oligocene flysch, are the part of the stratigraphic succession of the Silesian Nappe, and they are not a large olistolith or an allochthonous tectonic remnant of another, more internal nappe. Shypot Formation fills a large (1 × 3 km) subvertical tectonic lens. The rocks of the Shypot Formation are represented here by medium-rhythmic flysch: sandstone beds alternating with dark gray and black foliated mudstone (black shale) layers. They are lithified products of both medium-density turbidite flows and hemipelagic deposition of clayey material with a significant amount of organic matter. In the contact zone of the tectonic lens with the surrounding rocks, the deposits are intensively deformed, almost isoclinal folds with subvetrical hinges are observed, which suggest the strike-slip movements. A tectonic mélange is recorded here, which is represented by small blocks (clastolites) of brittle sandstones, sometimes similar to Shypot sandstones, placed in a silt-pelitic ductile matrix. Foliation of the mélange matrix is also subvertical and close to the meridional and/or subcarpathian direction. The structural studies carried out show that in the zone of this contact there were compressive stresses perpendicular to the Carpathian orogen, and stress fields that caused strike-slip movements, most likely right-lateral along the Carpathian thrusts. The tectonic lens is located within the broad Latorytsa-Stryi shear zone, and probably extruded out from deep horizons by transpressive movements (compression and strike-slip) and forms a “positive flower structure”. The vertical foliation in the mélange suggests that small blocks of Shypot sandstones were extruded up together with the ductile mélange matrix during diapirism. Similar processes probably led to the rise of a large lens of Shypot sandstones as the positive flower structure. The studies suggests that the black shale deposits of the Shypot Formation, enriched with organic matter, are widespread at some depth within the Silesian Nappe, and in some places are pushed up to the level of the Oligocene flysch. As a result, the Shypot Formation and Oligocene flysch are now in direct contact along faults/mélange zones. The presence of Lower Cretaceous potentially oil- and gas-generating black shale deposits within the Silesian Nappe significantly increases the prospects for oil and gas exploration in this area.

Compact HD Map Construction via Douglas-Peucker Point Transformer

High-definition (HD) map construction requires a comprehensive understanding of traffic environments, encompassing centimeter-level localization and rich semantic information. Previous works face challenges in redundant point representation or high-complexity curve modeling. In this paper, we present a flexible yet effective map element detector that synthesizes hierarchical information with a compact Douglas-Peucker (DP) point representation in a transformer architecture for robust and reliable predictions. Specifically, our proposed representation approximates class-agnostic map elements with DP points, which are sparsely located in crucial positions of structures and can get rid of redundancy and complexity. Besides, we design a position constraint with uncertainty to avoid potential ambiguities. Moreover, pairwise-point shape matching constraints are proposed to balance local structural information of different scales. Experiments on the public nuScenes dataset demonstrate that our method overwhelms current SOTAs. Extensive ablation studies validate each component of our methods. Codes will be released at https://github.com/sweety121/DPFormer.

More or complex actions? Effects of supply networks on firms' competitive aggressiveness

PurposeThis study investigates the extent to which a firm’s centrality and autonomy in its supply network are associated with the intensity and complexity of its competitive actions.Design/methodology/approachUtilizing social network analysis and dynamic panel data models, this study analyzes a comprehensive panel dataset with 10,802 firm-year observations across various industries between 2011 and 2018 to test the hypotheses.FindingsOur findings show that a firm’s level of centrality in its supply network has an inverted U-shaped relationship with both competitive intensity and competitive complexity. In addition, the turning points of these two inverted U-shaped relationships differ in that firms with a lower level of centrality tend to compete aggressively by launching more actions within fewer categories, while firms with a higher level of centrality tend to compete aggressively by launching fewer actions that cover a larger range of categories. Finally, we find that a firm’s structural autonomy has a positive relationship with competitive complexity.Originality/valueThis study bridges the gap between the supply chain management literature and strategic management literature and investigates how supply networks shape competitive aggressiveness. In particular, this research investigates how a firm’s structural position in its supply network affects its competitive actions, an important intermediate mechanism for competitive advantage that has been overlooked in the supply chain management literature.

Od zapominania do (u)pamięt(ni)ania? Wrocławskie elity o niemieckim dziedzictwie stolicy Dolnego Śląska

The status of German heritage in Wrocław is rather specific, and has been changing over the past seven decades under the influence of not only state and local politics, but also the biographical experiences of successive generations of residents. Calling German heritage troublesome is a frequently used rhetorical figure as well as — or perhaps primarily as — an epithet describing a social fact. This article aims to provide answers concerning the troublesome nature of German heritage for contemporary Wrocław elites. The empirical material comprises unstructured interviews conducted in 2011 and 2022, on the basis of which the relationship between the German heritage and persons occupying specific privileged positions in the social structure of the capital of Lower Silesia was determined. As the study proceeded, three types of approach to this relationship emerged. The first considers the relationship with German heritage unproblematic — either due to it being made “ours,” or because of it being treated superficially. The second approach recognizes the troublesome nature of this relationship, resulting from the tensions between local and national memory policy, including the state’s historical policy offering an antagonistic vision of Polish-German relations. The third type points to the relationship being troublesome due to the attitude to German heritage during the communist era; the memory of this difficult relationship with the heritage back then, and contemporary efforts to restore memory of Wrocław’s pre-1945 history. The approaches thus identified are present in the stories, regardless of the time — they can be found both when the city’s multicultural identity and local memory were intensively discussed a decade ago, and today, when the city is addressing new urban challenges.

Beyond the Anticodon: tRNA Core Modifications and Their Impact on Structure, Translation and Stress Adaptation.

Transfer RNAs (tRNAs) are heavily decorated with post-transcriptional chemical modifications. Approximately 100 different modifications have been identified in tRNAs, and each tRNA typically contains 5-15 modifications that are incorporated at specific sites along the tRNA sequence. These modifications may be classified into two groups according to their position in the three-dimensional tRNA structure, i.e., modifications in the tRNA core and modifications in the anticodon-loop (ACL) region. Since many modified nucleotides in the tRNA core are involved in the formation of tertiary interactions implicated in tRNA folding, these modifications are key to tRNA stability and resistance to RNA decay pathways. In comparison to the extensively studied ACL modifications, tRNA core modifications have generally received less attention, although they have been shown to play important roles beyond tRNA stability. Here, we review and place in perspective selected data on tRNA core modifications. We present their impact on tRNA structure and stability and report how these changes manifest themselves at the functional level in translation, fitness and stress adaptation.

Dynamic 1D search and processive nucleosome translocations by RSC and ISW2 chromatin remodelers.

Eukaryotic gene expression is linked to chromatin structure and nucleosome positioning by ATP-dependent chromatin remodelers that establish and maintain nucleosome-depleted regions (NDRs) near transcription start sites. Conserved yeast RSC and ISW2 remodelers exert antagonistic effects on nucleosomes flanking NDRs, but the temporal dynamics of remodeler search, engagement, and directional nucleosome mobilization for promoter accessibility are unknown. Using optical tweezers and two-color single-particle imaging, we investigated the Brownian diffusion of RSC and ISW2 on free DNA and sparse nucleosome arrays. RSC and ISW2 rapidly scan DNA by one-dimensional hopping and sliding, respectively, with dynamic collisions between remodelers followed by recoil or apparent co-diffusion. Static nucleosomes block remodeler diffusion resulting in remodeler recoil or sequestration. Remarkably, both RSC and ISW2 use ATP hydrolysis to translocate mono-nucleosomes processively at ~30 bp/s on extended linear DNA under tension. Processivity and opposing push-pull directionalities of nucleosome translocation shown by RSC and ISW2 shape the distinctive landscape of promoter chromatin.