Sharp Bend Research Articles

Геохимическая зональность рудной залежи Ново-Учалинского колчеданного месторождения (Южный Урал, Россия)

Novo-Uchaly essentially zinc (CZn>>CCu) VMS deposit is one of the largest in the Urals. Currently, it is under additional exploration by fans of underground drilling wells and mine workings. The paper describes a novel geochemical zonation of the sulphide deposit (the example of Cu, Zn, Au and In), discusses conditions of formation and factors that caused its complication. We carried geostatistical calculations in addition to the analysis of the zonation of the deposit. The ore deposit is represented by a large subvertical ribbon of a whimsical structure, inclined southward, which is confined to the wing of an inverted large anticlinal fold, cut by mafic dikes and characterized by a complex, combined geochemical zonality. The distribution of Cu and Zn is generally asymmetric. Copper-rich ores tend to the northern wedge of the deposit, and to the south, along its declination, the concentration of Zn increases, while Cu decreases, and the middle part of the deposit is represented by zinc-rich ores. In the section, copper maxima are more often noted in the footwall side of the deposit, and zinc — in the hanging side. The intrusion of a thick gabbro-diorite dyke and subsequent dynamometamorphism, including hydrothermal solutions, caused the redeposition of more mobile Cu in the near-contact zones of the dyke and areas of swell of the ore body thickness. Within the swell of the thickness of the deposit, in the hinge of the fold of the 2nd order, rich copper-zinc ores occur, which are enriched by Zn, Pb, Au, Ag, In, Ba and some other rare elements. The similarity of their behavior in ores is confirmed by their high positive pair correlation. In the ore body, the distribution patterns of gold and indium are rather symmetrical. High concentrations of gold and indium are confined to a sharp bend in the ore body, and small indium maxima occur in the footwall of the ore lode. As a result of dynamometamorphism, the deposit acquired a whimsical structure with the formation of thick swells; ores were significantly recrystallized, and locally enriched by non-ferrous and precious metals.

Flow Pattern and Erosion in a 90-Degrees Sharp Bend around a W−Weir

Different flow-altering methods, such as W−Weirs, have been developed to reduce erosion. For this study, we performed two experiments: (1) installing a W−Weir in various positions to determine the best angle for placement, and (2) investigating the variation of flow patterns and bed shear stress distribution in a 90-degree sharp bend by measuring the 3D components of flow velocities, with and without W−Weirs, where the greatest scour depth occurs. The results from the three installation angles indicate that less scour depth and volume of sediment removal occur when the weir is located close to the end of a bend. In addition, the value of the secondary circular power without a weir was higher than the position with a weir; however, this value significantly increased at 70 degrees due to turbulence flow near the W−Weir. This secondary flow power reduction at 45 degrees with a W−Weir increased by 65.8 percent for a Froude number value of 0.17, and by 29.8 percent for a Froude number value of 0.28, compared to values without the W−Weir, respectively.

Characterization of trajectories and drag coefficients of large wood in sharp river bends from flume experiments

AbstractThe transport of large wood (LW) has been a focus of research in the last decades because of its importance for river ecosystems, fluvial dynamics and flood protection. Riverine processes connected with the presence of LW have largely been based on laboratory experiments carried out in straight or weakly bended channels. The dynamics of LW in sharp river bends has received less attention, so there exist many open questions regarding how LW is transported through such channel parts. For this reason, this paper presents results of unique laboratory experiments designed to study the trajectories of single wooden dowels in sharp bends. Dowel trajectories were determined for four dowel sizes, two initial dowel orientations with respect to the main channel axis and three inlet positions. Information about the 3D velocity field in the bend were obtained from a previous study that used the same channel with identical hydraulic boundary conditions. Furthermore, a force‐balance analysis was developed for interpreting the dowel trajectory and drag coefficient of LW in sharp river bends. The experimental results show that the dowel length is the main parameter controlling dowel trajectory in a sharp bend, and indicate the role of inertial effects that drive the dowel drift along the bend. The obtained drag coefficients ranged between 0.35 and 1, which is in agreement with previous values for submerged, or semi‐submerged, fixed pieces of wood in straight river reaches.

Tenuous transcriptional threshold of human sex determination. II. SRY exploits water-mediated clamp at the edge of ambiguity.

Y-encoded transcription factor SRY initiates male differentiation in therian mammals. This factor contains a high-mobility-group (HMG) box, which mediates sequence-specific DNA binding with sharp DNA bending. A companion article in this issue described sex-reversal mutations at box position 72 (residue 127 in human SRY), invariant as Tyr among mammalian orthologs. Although not contacting DNA, the aromatic ring seals the domain's minor wing at a solvent-exposed junction with a basic tail. A seeming paradox was posed by the native-like biochemical properties of inherited Swyer variant Y72F: its near-native gene-regulatory activity is consistent with the father's male development, but at odds with the daughter's XY female somatic phenotype. Surprisingly, aromatic rings (Y72, F72 or W72) confer higher transcriptional activity than do basic or polar side chains generally observed at solvated DNA interfaces (Arg, Lys, His or Gln). Whereas biophysical studies (time-resolved fluorescence resonance energy transfer and heteronuclear NMR spectroscopy) uncovered only subtle perturbations, dissociation of the Y72F complex was markedly accelerated relative to wild-type. Studies of protein-DNA solvation by molecular-dynamics (MD) simulations of an homologous high-resolution crystal structure (SOX18) suggest that Y72 para-OH anchors a network of water molecules at the tail-DNA interface, perturbed in the variant in association with nonlocal conformational fluctuations. Loss of the Y72 anchor among SRY variants presumably "unclamps" its basic tail, leading to (a) rapid DNA dissociation despite native affinity and (b) attenuated transcriptional activity at the edge of sexual ambiguity. Conservation of Y72 suggests that this water-mediated clamp operates generally among SRY and metazoan SOX domains.

Leipothrix argutae (Acari: Eriophyidae) infesting kiwi fruit trees in Jilin province, Northeastern China

Eriophyoid mites are herbivorous mites of a worldwide distribution. The genus Leipothrix (Eriophyidae) was established by Keifer (1966) and currently consisted of 53 species (including two species unpublished). This genus is characterized by (1) the absence of femoral setae bv from both legs and (2) the distinctive form of dorsal palp genual setae d, which is moderately long and bifurcate, with its branch being minute or very minute (sometimes seen as a sharp bend in the seta). Most Leipothrix spp. cause no damage and are vagrant on the leaf surface. However, some of them caused russeting and drying of the leaves when the mites were in high density. During field surveys in Zuojia Experimental Plot in Jilin Province, China, we collected two sympatric morphs of Leipothrix species from the hardy kiwi, Actinidia arguta (Siebold & Zucc.) Planch. ex Miq. (Actinidiaceae), a cultivated vine. The mites were later described as L. argutae Han, Wang & Ai, 2020, which is a deuterogynous species (Han et al. 2020). These mites were found with large rust on the surfaces of leaves and fruits of the host plant. Local people wrongly attributed these symptoms to a kind of plant disease. Sometimes L. argutae is also confused with Phyllocoptruta oleivora (Ashmead), which also causes rust in Citrus sp. and other related plant species. This is the first record of Leipothrix species on a species of Actinidiaceae, and also a new record of an eriophyoid mite causing serious symptoms and affecting fruit quality in kiwi fruits. 

Geomorphic Analysis of Baghain River, Yamuna Basin, and its Implication for Drainage Characteristic and Tectonics using Remote Sensing and GIS Techniques

Abstract The present study aims to access the geomorphic analysis of the Baghain river basin and its implication on landscape evolution. Baghain river originates from the Panna hill, and flows through marginal and central Ganga plain. It empties itself in to Yamuna river near Chilla village, Banda district, Uttar Pradesh. The river basin comprises of three major geological units associated with this basin: Bundelkhand gneissic complex, Vindhyan Supergroup (hard rock terrain known as Panna hill) and Alluvial deposit (marginal Ganga plain and central Ganga plain). The current work focuses on study of morphometric parameters and geomorphic indices of Baghain river basin using digital elevation model (DEM) and topographic maps (1:50,000 scale). This basin exhibits four types of drainage patterns: dendritic, parallel, trellis and rectangular. Bifurcations ratio (4.82) of river basin suggest that the most part of the basin is not influenced by any geological structures. The elongation ratio (0.50) suggests that the basin is moderately elongated. The drainage density (0.62) and stream frequency (0.22) also suggest that the basin has moderate to high permeable and easily erodible alluvium terrain. The escarpment height is low in the proximal part (Panna Hill) and high in the middle and distal parts of the basin (marginal Ganga plain and central Ganga plain, respectively. Asymmetric factor (52) shows a leftward tilt of the basin. The region lies under marginal Ganga plain, and Bundelkhand plateau. The sharp bend present is probably due to the lithological variation. It reflects moderate gradient in the upper part (Panna hill), steep gradient in the lower part (Panna hill), and low gradient in the marginal to central Ganga plain.

A simple elastic phononic crystal plate with adjustable topological valley transmission paths

The study of topological insulator devices has now been extended from electromagnetic and acoustic waves to the field of elastic waves. Topology-protected wave transmission has stimulated great interest due to its strong robustness. In this paper, we design an elastic phononic crystal plate (EPCP) with tunable topological valley transmission. The inversion of the topological energy band is attained just by adjusting the relative height of the bolts. Moreover, by calculating the topological invariants, the topological property of this EPCP is further demonstrated. The topological boundary transport immunity to defect, sharp bend, and disturbance is verified using the finite element method and experiments. By simply regulating the relative heights of the bolts in the unit cell, topological valley transmission for different shaped paths is achieved, which is important for the practical application of tunable topology elastic wave transmission devices.

Geomagnetic field behaviour during the early Cretaceous Normal Superchron from palaeomagnetic analysis of the Ramon Volcanics, Israel

SUMMARY Unravelling the long-term behaviour of the geomagnetic field is crucial for understanding the dynamics of the deep Earth. Yet, obtaining an accurate measure of geomagnetic palaeosecular variations (PSV) is difficult, partly because of tectonically induced rotations that overprint the original palaeomagnetic signal. We present a detailed palaeomagnetic investigation based on 99 sampling sites collected from the 119 to 112.6 Ma Ramon Volcanics exposed near the dormant Ramon Fault, southern Israel. These basaltic rocks were emplaced at equatorial palaeolatitudes during the beginning of the Cretaceous Normal Superchron (CNS; 123.4–83.6 Ma), during which there were no polarity reversals. Structurally corrected remanence directions consistently vary across the investigated area, whereby the sites found near a sharp bend of the Ramon Fault are clockwise rotated, whereas the other sites show no obvious rotational pattern. Elasto-plastic modelling suggests that the rotations were induced by up to 1.5 km of dextral horizontal slip accommodated by the fault, consistent with previous geological and geophysical estimations. Considering the remanence directions obtained from sites that were not influenced by the fault, we calculated an SB value of $13.3_{ - 1.3}^{ + 1.9 \circ }$ (95 percent confidence, 46 sites), which corresponds to previous SB estimations from pre- and early-CNS volcanic bodies emplaced at low palaeolatitudes (λ < 20°). This observation suggests that the emergence of the superchron was not accompanied by a change in the behaviour of the geomagnetic PSV. Finally, our results, together with previous palaeo-equatorial observations, show that the middle part of the superchron had lower angular dispersion (i.e. lower SB) compared to the scatter that prevailed during the beginning of the superchron. This observation suggests that the geomagnetic field transitioned into a more axial dipole dominance state towards the middle part of the superchron. Altogether, our analysis indicates that the superchron cannot be treated as a period characterized by a steady-state field behaviour.

Tenuous Transcriptional Threshold of Human Sex Determination. I. SRY and Swyer Syndrome at the Edge of Ambiguity.

Male sex determination in mammals is initiated by SRY, a Y-encoded transcription factor. The protein contains a high-mobility-group (HMG) box mediating sequence-specific DNA bending. Mutations causing XY gonadal dysgenesis (Swyer syndrome) cluster in the box and ordinarily arise de novo. Rare inherited variants lead to male development in one genetic background (the father) but not another (his sterile XY daughter). De novo and inherited mutations occur at an invariant Tyr adjoining the motif’s basic tail (box position 72; Y127 in SRY). In SRY-responsive cell lines CH34 and LNCaP, de novo mutations Y127H and Y127C reduced SRY activity (as assessed by transcriptional activation of principal target gene Sox9) by 5- and 8-fold, respectively. Whereas Y127H impaired testis-specific enhancer assembly, Y127C caused accelerated proteasomal proteolysis; activity was in part rescued by proteasome inhibition. Inherited variant Y127F was better tolerated: its expression was unperturbed, and activity was reduced by only twofold, a threshold similar to other inherited variants. Biochemical studies of wild-type (WT) and variant HMG boxes demonstrated similar specific DNA affinities (within a twofold range), with only subtle differences in sharp DNA bending as probed by permutation gel electrophoresis and fluorescence resonance-energy transfer (FRET); thermodynamic stabilities of the free boxes were essentially identical. Such modest perturbations are within the range of species variation. Whereas our cell-based findings rationalize the de novo genotype-phenotype relationships, a molecular understanding of inherited mutation Y127F remains elusive. Our companion study uncovers cryptic biophysical perturbations suggesting that the para-OH group of Y127 anchors a novel water-mediated DNA clamp.

Topological coupling and decoupling of photonic crystal waveguides: Application to topological wavelength demultiplexing

Photonic crystal waveguides (PCWs) coupling has broad applications in the realm of optical communications and optical integration. However, conventional PCWs couplers suffer inevitable backscattering that leads to energy loss and signal distortion due to local perturbation and sharp bends. This paper investigates topological coupling and decoupling of PCWs based on valley photonic crystals by the coupled-mode theory. The topological power transfer between the neighbouring PCWs can be existed or eliminated due to the coupling or decoupling. As a potential application of our work, a topological wavelength demultiplexer is designed and numerically demonstrated. The proposed device not only exhibits high transmission at three communication wavelengths but also is robust against sharp bend, structural disorder and defects due to the topological properties of structure. This method can be extended to novel designs of topological coupling devices of PCWs.

A superior approach for production of protein isolates from de‐oiled soy meal and its comparison with conventional method

SummaryProtein isolates were prepared from de‐oiled soy meal by a superior approach, i.e. biological precipitation using two lactic acid bacterial strains and a conventional acid precipitation method. The isolates were characterised for physico‐chemical, functional, anti‐nutritional and structural properties and compared with isolates prepared using the conventional method. The purity, yield, lightness, whiteness index and degree of hydrolysis were higher (P ≤ 0.05) for biologically precipitated soy protein isolates (BPSPIs). The functional properties of BPSPI samples were also superior. BPSPIs showed 1.85 mg g−1 and 1.44 TIU mL−1, whereas acid‐precipitated soy protein isolates (APSPIs) showed 3.65 mg g−1 and 3.16 TIU mL−1 of phytic acid and trypsin inhibition activity respectively. A sharp bend in the wavelength ranges from 3700 to 3900 cm−1 was observed in BPSPI samples, which depicts structural changes owing to fermentation by lactic acid bacteria. Two characteristic peaks at 2Ɵ = 20° and 2Ɵ = 15° were observed in both the samples; however, intensity and crystallinity were higher in BPSPIs. Hexagonal‐shaped particles of different sizes were displayed by field emission scanning electron microscopy images. The results thus confirm that the soy protein samples prepared through the biological precipitation process had better properties over conventionally prepared soy protein samples, which can be further used as novel ingredients in protein‐based functional products.

Experimental investigation of flow pattern at 180° bend with rigid bed in effect of twin convergent bridge piers

The generation of vortices in sharp bends of rivers is a well-known phenomenon. However, their influence on the bridge pier has not been investigated deeply. This study studies the flow pattern around the twin convergent bridge pier in a sharp bend by an experimental approach. The test facility includes a channel located at Advanced Hydraulic Laboratory, Persian Gulf University, with a 1 m width and 2 m central radius. The flow 3D velocity is measured along the bend by an ADV velocimeter. It is realized that the most important vortex from a sediment transport point of view is located adjacent to a pier in a plane just parallel to the flow direction. Furthermore, it could be concluded that the pier influencing range has an approximate dimension of 10 times pier diameter in a plane parallel to flow and 3 timer pier diameters in the vertical plane. Results and discussions are presented throughout the paper.

Detailed experimental and numerical analysis of hydrodynamics in the outflow measurement channel of a sewage treatment plant

Abstract The ‘Bajo Grande’ Wastewater Treatment Plant has a design capacity of 2.78 m3/s, and discharges into the Suquia River (Córdoba, Argentina). The river has an average flow rate of 10 m3/s, with lower values during the summer. Currently, the treatment plant does not have an accurate discharge-measurement system prior to the discharge into the river, which makes it difficult to evaluate the dosing of the disinfection treatment. The outflow rate is measured in a straight flume. However, at the inlet section of the flume, a 180° sharp bend induces a complex turbulent flow with instabilities and low-frequency velocity fluctuations which are not appropriate for flow quantification. In this type of flow, most of the in situ flow discharge-measurement systems have great uncertainty. Therefore, in situ flow measurements with an Acoustic Doppler Current Profiler, Large-Scale Particle-Tracking Velocimetry techniques and a prototype-scale Detached Eddy Simulation model were combined to obtain a detailed characterization of the turbulent flow. The results provide flow rates, fields of mean flow velocity, temporal evolution, and characteristic parameters of the turbulence. This allowed a better understanding of the effects of turbulence and flow instabilities. The results provide a basis to validate numerical models used in the hydraulics design of contact chambers to improve the disinfection process.

Morphological Changes of Sharp Bends in Response to Three Gorges Project Operation at Different Discharges

Dam construction often changes downstream fluvial processes by reducing sediment supply. Taking Tiaoguan reach and Laijiapu reach of the lower Jingjiang Reach downstream of the Three Gorges Project as examples, three-dimensional flow velocity, sediment, and bed elevation were observed in the two bends for investigating the impact of flow structure and sediment transport of different discharges on sharp bend morphology. Results indicated that the flow structure and sediment transport process in curved channels depended upon the flow stages, which affected the patterns of erosion and deposition along the point bars and concave banks. Flow separation and development of secondary flow were depended on the shapes of point bars and flow depths nearby, and the strength of secondary flow increased with flow discharge. The high flow discharges, which had high sediment carrying capacity and stream power, provided the main driving force for erosion on upstream point bar, thus the type and duration of floods were crucial factors in the morphological evolution of meandering bends. The reduction of sediment supply should be responsible for erosion on the point bars, causing the flow to migrate toward the convex banks. In meandering rivers with reduced sediment supply, retreats (push inward) of inner (convex) banks dominated advances (pull inward) of outer (concave) banks. In addition, the formation and development of concave-bank bars might relate particularly to meander curvature. This study is expected to constitute a reference for bank protection and river management in meandering bends downstream of reservoirs.

Termination of the 2018 Florida red tide event: A tracer model perspective

The 2018 Karenia brevis harmful algal bloom experienced along the west coast of Florida was the worst red tide occurrence there since 2005. Cell concentrations peaked in early fall of 2018, lessened in winter, and disappeared early in 2019. Here we examine the termination of this red tide event by using hindcast simulations of the West Florida Coastal Ocean Model, a numerical ocean circulation model that downscales from the deep Gulf of Mexico, across the continental shelf and into the estuaries. The underlying hypothesis is that without an offshore source of K. brevis cells, a nearshore bloom may quickly dissipate under the influence of a persistent upwelling circulation. To test this hypothesis, we used a passive tracer (without consideration of biological growth or decay) in the model to virtually indicate K. brevis cells. The tracer, inputted along the central West Florida coast where highest bloom concentrations were observed, was subsequently transported southward along the coast and offshore, significantly reducing the tracer concentrations over the three-month-long experimental duration, as was observed for the actual K. brevis cell concentrations. Whereas modeled tracer concentrations decreased over most of the West Florida coast, relatively higher concentrations remained just south of Sanibel Island, trapped there by the sharp bend in the coastline. Longer residence time for this area has important K. brevis implications. Lake Okeechobee nutrient flux through the Caloosahatchee River was thought to contribute to red tide in this region, and while these inputs may be a factor, a persistent upwelling circulation may also play a contributing role.

Ultracompact Photonic Circuits without Cladding Layers

Cladding layers of waveguides prevent interchannel interference yet are unfavorable for the integration of photonic circuits. Here, we report the realization of ultracompact waveguide arrays, bends, and circuits with essentially zero interchannel separation. This supercompactness is achieved via arrays of waveguides with shifted spatial dispersions, where each waveguide functions as both the transmission channel and an effective “cladding layer” of its neighboring waveguides, and has been experimentally realized in low-loss all-dielectric photonic crystals. We show that the zero-spacing transmission array possesses the remarkable features of negligible crosstalk, high-efficiency sharp bending, and ultracompact photonic routing where the light can traverse the entire physical space. This finding opens a new avenue for extreme space utilization efficiency in waveguide physics and integrated photonics.6 MoreReceived 26 June 2021Revised 3 January 2022Accepted 8 February 2022DOI:https://doi.org/10.1103/PhysRevX.12.011053Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasIntegrated opticsMetamaterialsNanophotonicsPhotonic crystalsWaveguide arraysCondensed Matter, Materials & Applied Physics

Topological boundary states of two-dimensional restricted isosceles triangular photonic crystals.

We propose an all-media photonic crystal (PC) composed of isosceles triangle dielectric cylinders that realizes the topological phase transition by simply rotating the isosceles triangular dielectric cylinders. Additionally, the topological phase transition is closely linked with the size parameters and rotation angle of the isosceles triangle. The topological boundary states with lossless transmission are constructed on the interface of two different topological structures, and the optical quantum spin Hall effect is simulated. Further, we verified that the boundary state is unidirectional and immune to disorder, cavity, and sharp bend defects. By rotating the angle of the triangle to control the transmission path of the pseudo-spin state, we realize diverse transport pathways of light, such as the "straight line" shape, "Z" shape, "U" shape, and "Y" shape. This topological system shows a higher degree of freedom, which can promote the research on topological boundary states and the development of topological insulators in practical applications.

Three-dimensional magnetohydrodynamic flow around a 180° sharp bend under transverse magnetic field

This study attempts to characterize the variation of pressure loss and the evolution of vortex structures in the steady three-dimensional flow around a 180° sharp bend under a transverse magnetic field. This study is conducted with the Reynolds number, 100≤Re≤400, and Hartmann number, 0≤Ha≤2000. This range of Re and Ha captures both complex three-dimensional structures and the inception of quasi-two-dimensional flows. Numerical simulations display how the pressure loss across the bend region (Δp0) and the vortex structures undergo four regimes by increasing Ha for fixed Re. These regimes are referred to as regimes I–IV. N1c, N2c, and N3c, the critical values of interaction number Nc for the first appearance of regimes II–IV, are recognized at values 0.8, 3.2, and 40, respectively. In regime I (N≤0.8), Δp0 increases slightly and the magnetohydrodynamic flow promotes the recirculating bubble. In regime II (0.8<N≤3.2), as Δp0 decreases, the scope of the recirculating bubble reaches its peak. In regime III (3.2<N≤40), Δp0 grows, while the shrinkage of the recirculating bubble is triggered. Simultaneously, the flow tends to be two-dimensional [J. Sommeria and R. Moreau, “Why, how, and when, MHD turbulence becomes two-dimensional,” J. Fluid Mech. 118, 507 (1982)]. In regime IV (40<N), Δp0 is linearly dependent on Ha/Re. The non-monotonic behavior of the recirculating bubble length is caused by the redistribution of momentum at low Ha and by the predominant effect of the Lorentz force at large Ha. The law of how to distinguish the three-dimensional (3D) flow and quasi-two-dimensional (Q2D) flow is discovered by assessing the recirculating bubble length in the center plane.

Location of the Lhasa terrane in the Late Cretaceous and its implications for crustal deformation

The Cenozoic crustal deformation of the Asian continent is constrained by the location of its southern margin in the Late Cretaceous, which is, however, affected by potential remagnetization and inclination shallowing of redbeds in the Linzhou Basin. Our paleomagnetic results from the Shexing Formation redbeds in the Late Cretaceous yield a mean paleo-inclination of ~21.5°, consistent with the recalculation of previous data. Rock-magnetic, paleomagnetic and petrographic analyses indicate that the redbeds have recorded the original paleomagnetic field and have not suffered from significant inclination shallowing. The paleopole from 70 redbeds sites is at 71.8°N, 281.5°E with A 95 = 2.6°, yielding a paleolatitude of ~12.0 ± 2.6°N at ~70–91 Ma for the Linzhou Basin. This result indicates a latitudinal convergence of 1264 ± 477 km north of the sampling area within Asia since the Late Cretaceous. Combined with previous data, our results show that the southern margin of Asia was at ~11–15°N in the Late Cretaceous, aligning in a WNW-ESE direction, which is similar to its present-day orientation. A review of available data shows that the sharp bending of the southern margin of Asia around the eastern Himalayan syntaxis (EHS) is probably due to different crustal movement patterns around the EHS. The shape of the southern margin of Asia determines the arc-shaped orientation of Himalayan orogen. • The Shexing Formation redbeds have recorded the prefold magnetizatioin. • The southern margin of Asia was oriented in a WNW-ESE direction at ~12°N. • Different movement around the eastern Himalayan syntaxis make a sharp turn. • The southern margin of Asian plays a primary role in shaping the Himalayan orogen.

Molecular mechanism of UV damage modulation in nucleosomes

Exposure to ultraviolet (UV) light causes the formation of mutagenic cyclobutane pyrimidine dimers (CPDs) in cellular DNA. Previous studies have revealed that CPD formation in nucleosomes, the building blocks of chromatin, shows a striking ∼10 base pair (bp) periodic pattern. CPD formation is suppressed at positions where the DNA minor groove faces toward the histone octamer (minor-in) and elevated CPD formation at positions where the minor groove faces away from the histone octamer (minor-out). However, the molecular mechanism underlying this nucleosome photofootprint is unclear. Here, we analyzed ∼180 high-resolution nucleosome structures to characterize whether differences in DNA mobility or conformation are responsible for the CPD modulation in nucleosomes. Our results indicate that differences in DNA mobility cannot explain CPD modulation in nucleosome. Instead, we find that the sharp DNA bending around the histone octamer results in DNA conformations with structural parameters more susceptible to UV damage formation at minor-out positions and more resistant to CPD formation at minor-in positions. This analysis reveals the molecular mechanism responsible for periodic modulation of CPD formation and UV mutagenesis in nucleosomal DNA.