V-shaped Geometry Research Articles

Early Miocene sand wedge deposits in Southwestern Tarim Basin and Implications for the Uplift of the Northern Tibetan Plateau

The uplift of the Tibet Plateau and its climatic effects have long been a hot topic in academic research. However, there is still significant controversy regarding the uplift history and related climate changes along the northern margin of the plateau. In this paper, we present sand wedge deposits from the base of the Wuqia Group (∼20 Ma) on the southwestern Tarim Basin, representing the oldest reported sand wedges in the Tibetan Plateau. A comprehensive study was conducted on lithostratigraphy, sedimentary environment, and macroscopic–microscopic features of the sand wedge deposits. The results indicate that the lithostratigraphic succession preserving the sand wedge deposits consists mainly of lenticular conglomerates and cross-bedded gravelly sandstone interbedded with medium–thin-bedded mudstone, consistent with the braided fluvial environment. The sand wedge deposits commonly exhibit a V-shape geometry and are filled with gravelly sandstone, with the gravels arranged parallel to the walls of the wedge. The clasts of the wedge-filled sandstone are well-rounded and show a unimodal grain size distribution. The quartz surfaces commonly display dish-shaped and crescent-shaped impact features, indicating an eolian origin and an arid climate. Based on the relationship between the formation temperature of modern sand wedges, the atmospheric temperature gradient, and altitude, the reconstructed paleo-elevation of the sand wedge deposits at the base of the Wuqia Group in the southwestern Tarim Basin is approximately ∼ 1000 m. These results indicate that the northern margin of the Tibet Plateau had already reached an elevation of ∼ 1000 m during the Early Miocene, forming a seasonal arid and cold climate.

Air Interactions of Magnetically Driven Plasma Discharges in Crossflow

Motivated by the use of magnetohydrodynamic devices in fluid dynamic flow control research, the current work experimentally studied the actuation mechanism and the resulting aerodynamic interactions of magnetically driven low-current arc-plasma discharges. The investigation was conducted in the context of boundary-layer interactions in low-speed crossflow conditions through the use of coaxial and v-shaped geometries. Time-averaged velocity field measurements showed that the toroidal region of vorticity induced by the coaxial geometry in quiescent air resulted in the formation of a horseshoe vortex in crossflow. Similarly, the v-shaped actuator resulted in the formation of streamwise vortices. The resulting boundary layers had s-shaped streamwise velocity profiles as measured in the wall-normal direction characteristic for the flow downstream of a conventional vortex generator pair, due to the three-dimensional mixing induced by coherent vortex structures. A simplified model based on intermolecular momentum transfer through collisions is proposed to explain the fundamental discharge–air interactions and the induced flowfields. These results inform the applications of various magnetically driven discharges in the field of aerodynamic flow control.

Computational prediction of surface-tension flow mechanism of molten filler in a V-shaped groove geometry in the brazing process of a heat exchanger

When the temperature rises during the brazing process, only the brazing material melts because of its low melting point. Several analytical approaches have been used to describe filler flow in channels and the progression of erosion grooves. However, only a few studies have examined filler-flow behavior in microgrooves during brazing. In this study, a computational model was constructed to examine the flow in microgrooves on an extruded material’s surface. The capillary flow of the aluminum brazing material was numerically analyzed to investigate the physical properties and surface behavior. Specifically, the surface-tension flow behavior was analyzed by simulating various cross-sectional shapes of the channel grooves and various contact angles of the filler. The effects of various parameters, such as viscosity and boundary conditions, on the filler flow were also analyzed. When the cross-sectional area of the channel groove increases, the filler-flow velocity increases, and the rate of unsteady fluctuation increases with the increasing filler tip velocity. The driving force of the filler flow in the channel groove is considered to be (1) the surface tension, which is based on the filler free-surface curvature, or (2) the dynamic change in the shape of the meniscus, which can be unsteady and induced by Rayleigh–Taylor instability. As the cross-sectional area of the channel groove increases, the capillary force based on the dynamic change in meniscus shape dominates the unsteady change in filler tip velocity, rather than the surface tension based on the filler free-surface curvature formed in the groove.

Crack mechanism and experimental verification on straightening of AZ31B magnesium alloy plate

When plates with edge cracks in the rolling process is straightened by cyclic tensile and compressive stress, the tip of edge crack always accompanied by stress concentration, which leads to crack propagation. In this paper, damage parameters are imported into the plate straightening model based on determining the GTN damage parameters of magnesium alloy materials by inverse finite element calibration method, the influence of different straightening process schemes and prefabricated V-shaped crack geometry on crack growth is analyzed through the way of the combination of simulation and straightening experiment. The results show that the peak values of equivalent stress and equivalent strain under each straightening roll appear at the crack tip. The value of longitudinal stress and equivalent stain decrease with the distance to crack tip becomes larger. The peak value of longitudinal stress appears when the crack circumferential angle is about 100°, and the crack tip is easy to form crack propagation; when the plate passes roll 2 and roll 4, the equivalent stress and strain concentration at the crack tip are most obvious; when the reduction reaches a certain degree, the void volume fraction (VVF) reaches the VVF of the material breaking; with the increase of the entrance reduction, the number of VVF at the crack tip which reaches the material fracture increases, and the length of crack propagation increases; the stress concentration at the tip of V-shaped crack with large length–width ratio is obvious, and the VVF is more likely to reach the VVF at the time of material fracture, crack initiates and propagates easily.

Highly sensitive V-shaped SPR PCF biosensor for cancer detection

In this paper, a novel design of photonic crystal fiber (PCF) biosensor based on surface plasmon resonance (SPR) is introduced and analyzed for cancer cell detection. The full vectorial finite element method (FVFEM) is used throughout the numerical analysis of the suggested biosensor. The reported PCF has a V-shaped surface that is coated with ZrN as a plasmonic material. A coupling occurs between the core guided mode and surface plasmon mode SPM which depends on the studied analyte. Such a coupling is improved by using the suggested V-shape geometry which increases the sensor sensitivity.The geometrical parameters are optimized to achieve high sensor sensitivity. The proposed biosensor has high optical sensitivity of 6214.28, 3800, and 5008.33 nm/RIU, for quasi-transverse magnetic (TM), and 6000 nm/RIU, 4400 nm/RIU, and 5333.3 nm/RIU, for quasi-transverse magnetic (TE), for breast, basal, and cervical cancer cells, respectively. The reported optical sensor can pave the way for efficient and simple technique for cancer detection with low cost and high sensitivity instead of surgical and chemical techniques.

V-shaped chiral hosts based on π-extended hematoxylin.

Hematoxylin has a V-shaped chiral geometry, but its potential in chiroptical self-assembled materials is underdeveloped. Herein, three novel V-shaped chiral hematoxylin derivatives were synthesized, and they showed extended skeletons as well as photophysical and chiroptical behaviors. Moreover, their host-guest interactions with C60 were investigated. Our findings could aid in the design and synthesis of novel chiral host molecules from natural products.

BN-Embedded V-Shaped Polycyclic Aromatic Hydrocarbons Exhibiting Tunable Molecular Packing and Supramolecular Interactions.

Three novel BN-embedded V-shaped polycyclic aromatic hydrocarbons with different π-conjugation lengths were designed and successfully synthesized. Their single-crystal structures were confirmed by X-ray crystallographic analysis, and it is found that the molecular stacking structure can be effectively tuned by extending the length of π conjugation. Meanwhile, owing to the unique V-shaped molecular geometry, they exhibit moderate host-guest supramolecular interactions with both fullerenes C60 and C70.

Analytical Model for the Depth Progress during Laser Micromachining of V-Shaped Grooves.

An analytical model is presented that allows predicting the progress and the final depth obtained by laser micromachining of grooves in metals with ultrashort laser pulses. The model assumes that micromachined grooves feature a V-shaped geometry and that the fluence absorbed along the walls is distributed with a linear increase from the edge to the tip of the groove. The depth progress of the processed groove is recursively calculated based on the depth increments induced by successive scans of the laser beam along the groove. The experimental validation confirms the model and its assumptions for micromachining of grooves in a Ti-alloy with femtosecond pulses and different pulse energies, repetition rates, scanning speeds and number of scans.

The influence of back-arc extension direction on the strain partitioning associated with continental indentation: Analogue modelling and implications for the Circum-Moesian Fault System of South-Eastern Europe

Continental indentation is associated with deformation transfer from shortening to strike-slip faulting and is often affected by subduction related processes such as slab roll-back driven back-arc extension. We use crustal-scale analogue modelling to investigate the effects of extension direction on the strain partitioning and deformation transfer during indentation. The modelling results show that extension parallel to the strike-slip margin of the indenter creates subsidence distributed in several areas which may connect to form a large sedimentary basin behind the indenter. This transtensional basin with v-shape geometry narrows gradually towards the strike-slip margin of the indenter. In contrast, models with extension perpendicular to the strike-slip margin distributes transtensional deformation away from the indenter. Our results are in good correlation with the evolution of the Carpatho-Balkanides orocline of South-Eastern Europe, where the Circum-Moesian Fault System accommodates oroclinal bending during indentation against the Moesian Platform. In this area, the modelling explains the coeval and contrasting extensional features observed along the strike-slip margin and behind the indenter (i.e. the Getic Depression and the Morava Valley Corridor), driven by the roll-back of the Carpathian embayment and Adriatic slabs.

Organic dyes with multi-branched structures for highly efficient photocatalytic hydrogen evolution under visible-light irradiation

Direct photocatalytic water splitting is an attractive strategy for clean energy, in which, organic photocatalytic systems with broad light-harvesting region and efficient charge separation are highly desired and still challenging. In this paper, three multi-branched organic dyes were designed and synthesized with dipolar, V-shaped, and octupolar geometries, respectively. The multiple intramolecular charge transfer processes by electronic pull-push effect along the branches can provide more channels for light-harvesting and carrier transporting. Also, the interactions with polymeric carbon nitride (PCN) can be optimized by multiple anchoring units and defect filling effect, resulting in the gradually enhanced photocatalytic hydrogen evolution performance with the increased number of branches. Accordingly, the highest one of 996.9 μmol h−1 was achieved, which is over 40-folders that of PCN/Pt (24.8 μmol h−1) under the same conditions. It provides an efficient strategy for molecular design of organic dyes as photocatalyst, promoting development of PHE system from the molecular level.

Determination of Current Flow Induced by Transcutaneous Electrical Nerve Stimulation for the Treatment of Migraine: Potential for Optimization.

Introduction: Transcutaneous electrical nerve stimulation (TENS) for migraine involves the application of pulsatile stimulation through electrodes placed on the forehead to target the underlying trigeminal nerves. It is a simple, safe modality and has secured clinical approval in several markets including the European Union and the United States. Despite nearing almost 7 years of use (postclinical approval), the exact mechanism of action is not fully known. Guided by the need to stimulate the trigeminal nerves bilaterally, electrode dimensions are simply required to extend enough to cover the underlying nerves. The goal of this study is to examine induced current flow [magnitude and spatial distribution of electric field (EF)] and another driver of stimulation [activating function (AF)] due to TENS therapy for migraine for the first time. We further consider the effect of changing the electrode dimension and shape and propose a design modification to deliver optimal flow.Methods: We developed the first ultra-high-resolution finite element (FE) model of TENS for migraine incorporating the target supratrochlear (ST) and the supraorbital (SO) nerves. We first simulated the clinically approved V-shaped geometry. We then considered three additional designs: extended V-shaped, idealized pill-shaped, and finally an extended V-shaped but with greater contact spacing (extended V-shaped +CS).Results: Our findings revealed that the clinically approved electrode design delivered substantially higher mean current flow to the ST nerve in comparison with the SO nerves (Medial: 53% and Lateral: 194%). Consideration of an extended design (~10 mm longer and ~ 4 mm shorter) and a pill-like design had negligible impact on the induced current flow pattern. The extended V-shaped +CS montage delivered relatively comparable current flow to each of the three target nerves. The EF induced in the ST nerve was 49 and 141% higher in the Medial and Lateral SO nerve, respectively. When considering maximum induced values, the delivery of comparable stimulation was further apparent. Given the existing electrode design's established efficacy, our results imply that preferential targeting of the ST nerve is related to the mechanism of action. Additionally, if comparable targeting of all three nerves continues to hold promise, the extended V-shaped +CS montage presents an optimized configuration to explore in clinical studies.

Characteristics of continental rifting in rotational systems: New findings from spatiotemporal high resolution quantified crustal scale analogue models

Continental rifts are the expression of regional horizontal stretching and are in modelling studies often assumed to be the result of orthogonal or oblique extension. However, naturally occurring V-shaped rift geometries infer an underlying rotational component, resulting in a divergence velocity gradient. Here we use such analogue models of rifting in rotational settings to investigate and quantify the effect of such a divergence velocity gradient on normal fault growth and rift propagation towards a rotation pole. Particularly, we apply different divergence velocities and use different brittle-ductile ratios to simulate different crustal configurations and analyse its effect on rift propagation and surface deformation. Surface deformation is captured using stereoscopic 3D Digital Image Correlation, which allows for quantifying topographic evolution and surface displacement including vertical displacement. In combination with X-Ray computed tomography, we gain insights into the three-dimensional structures in our two-layer models. Based on our models, we present a novel characterisation of normal fault growth under rotational extension which is described by 1) an early stage of bidirectional stepwise growth in length by fault linkage with pulses of high growth rates followed by a longer and continuous stage of unidirectional linear fault growth; 2) segmented rifting activity which promotes strain partitioning among competing conjugate faults and 3) along-strike segmented migration of active faulting from boundary faults inwards to intra-rift faults allowing different fault generations to be simultaneously active over the entire rift length. For models with higher divergence velocities, inward migration is delayed but other first-order observations are similar to models with lower divergence velocities. Our quantitative analysis provides insights on spatiotemporal fault growth and rift propagation in analogue models of rotational rifting. Although natural rifts present complex systems, our models may contribute to a better understanding of natural rift evolution with a rotational component.

(NHC)Si═C═N-R: A Two-Coordinated Si0-Isocyanide Compound as Si(NHC) Transfer Reagent.

Experimental and theoretical studies are reported of the first two-coordinated Si0-isocyanide compound (SIDipp)Si═C═N-ArMes (1: SIDipp (NHC) = C[N(Dipp)CH2]2, ArMes = 2,6-dimesitylphenyl), supported by an N-heterocyclic carbene (NHC). A Si atom economic two-step synthesis of 1 involves a 2e reduction of the isocyanide-stabilized silyliumylidene salt [SiBr(CNArMes)(SIDipp)][B(ArF)4] (2[B(ArF)4], ArF = B(C6H3-3,5-(CF3)2)4) with KC8. 2[B(ArF)4] was obtained from SiBr2(SIDipp) after bromide abstraction with an equimolar mixture of Na[B(ArF)4] and ArMesNC. Exact adherence to the stoichiometry is crucial in the latter reaction, since 2[B(ArF)4] reacts with SiBr2(SIDipp) via isocyanide exchange to afford the disilicon(II) salt [Si2Br3(SIDipp)2)][B(ArF)4] (3[B(ArF)4]), the reaction leading to an equilibrium that favors 3[B(ArF)4] (Keq(298 K) = 10.6, ΔH° = -10.6 kJ mol-1; ΔS° = -16.0 J mol-1 K-1). 3[B(ArF)4] was obtained selectively from the 2:1 reaction of SiBr2(SIDipp) with Na[B(ArF)4] and fully characterized. Detailed studies of 1 reveal an intriguing structure featuring a planar CNHC-Si-C-N skeleton with a V-shaped geometry at the dicoordinated Si0 center, a slightly bent Si═C═N core, a CNHC-Si-CCNR 3c-2e out of plane π-bond (HOMO), and an anticlinal conformation of the SIDipp and ArMes substituents leading to axial chirality and the presence of two enantiomers, (Ra)-1 and (Sa)-1. Compound 1 displays structural dynamics in solution, rapidly interconverting the enantiomers. The silacumulene 1 is a potent Si(SIDipp) transfer agent as demonstrated by the synthesis and full characterization of the NHC-supported germasilyne (Z)-(SIDipp)(Cl)Si═GeArMes (4) from 1 and Ge(ArMes)Cl.

Determination of calibration parameters of cantilevers of arbitrary shape by finite element analysis

The use of atomic force microscopy in nanomechanical measurements requires accurate calibration of the cantilever's spring constant (kc) and the optical lever sensitivity (OLS). The thermal method, based on the cantilever's thermal fluctuations in fluids, allows estimation of kc in a fast, non-invasive mode. However, differences in the cantilever geometry and mounting angle require the knowledge of three correction factors to get a good estimation of kc: the contribution of the oscillation mode to the total amplitude, the shape difference between the free and end-loaded configurations, and the tilt of the cantilever with respect to the measured surface. While the correction factors for traditional rectangular and V-shaped cantilever geometries have been reported, they must be determined for cantilevers with non-traditional geometries and large tips. Here, we develop a method based on finite element analysis to estimate the correction factors of cantilevers with arbitrary geometry and tip dimensions. The method relies on the numerical computation of the effective cantilever mass. The use of the correction factor for rectangular geometries in our model cantilever (PFQNM-LC) will lead to values underestimated by 16%. In contrast, experiments using pre-calibrated cantilevers revealed a maximum uncertainty below 5% in the estimation of the OLS, verifying our approach.

Two Cu(II) and Co(II) Coordination Polymers: Important Values on Colon Cancer Patients by Reducing Insulin Resistance.

In the current study, via utilizing H5L (H5L = 2,4-di(3',5'-dicarboxylphenyl)benzoic acid), the symmetrical rigid polycarboxylic acid ligand with V-shape geometry, two new coordination polymers containing Cu(II) and Co(II) have been produced, and their chemical formulae respectively are {[Co5(L)2(H2O)12]·6H2O} n (1) and {[H2N(Me)2][Cu2(L)(H2O)]·DMF·H2O} n (2), leading to a variety kinds of coordination patterns of H5L and multifunctional skeletons. Their inhibitory activity on the insulin resistance of colon cancer patients was assessed. In addition, the detailed mechanism of the compound was also investigated. Firstly, the detection of enzyme-linked immunosorbent assay was carried out and the Tumor Necrosis Factor-α (TNF-α) level and the Interleukin-1β (IL-1β) level was detected. Then, the glucose concentration was determined with blood glucose meter. Next, the insulin receptor expression levels of β cells were determined with the real time reverse transcription-polymerase chain reaction assay. Ultimately, the cytotoxicity of compounds 1 and 2 was determined with Cell Counting Kit-8 assay.

Giant negative Poisson's ratio in two-dimensional V-shaped materials.

Two-dimensional (2D) auxetic materials with exceptional negative Poisson's ratios (NPR) are drawing increasing interest due to their potential use in medicine, fasteners, tougher composites and many other applications. Improving the auxetic performance of 2D materials is currently crucial. Here, using first-principles calculations, we demonstrated giant in-plane NPRs in MX monolayers (M = Al, Ga, In, Zn, Cd; X = P, As, Sb, S, Se, Te) with a unique V-shaped configuration. Our calculations showed that GaP, GaAs, GaSb, ZnS and ZnTe monolayers exhibit exceptional all-angle in-plane NPRs. Remarkably, the AlP monolayer possesses a giant NPR of −1.779, by far the largest NPR in 2D materials. The NPRs of these MX monolayers are correlated to the highly anisotropic features of the V-shaped geometry. The exotic mechanical properties of the V-shaped MX monolayers provide a new family of 2D auxetic materials, as well as a useful guidance for tuning the NPR of 2D materials.

Dynamic X-Ray Imaging of Additively Manufactured Reactive Components in Solid Propellants

A variety of methods have been developed to enhance solid propellant burning rates, including adjusting oxidizer particle size, changing the formulation, modifying the propellant core geometry, and adding catalysts or wires. Fully consumable reactive wires embedded in propellant have been demonstrated to increase the burning rate by increasing the surface area; however, the observation of this effect has been limited to viewing via an intrusive window next to the wire. Here, dynamic X-ray radiography is employed to analyze the evolution of the internal burning profile of propellant embedded with additively manufactured reactive components. This avoids heat loss at the window and allows analysis of the three-dimensional volumetric consumption of strands with internal branching geometries. Printable reactive wires made of aluminum/polyvinylidene fluoride were embedded as single wires, pitchforks, and U- and V-shaped geometries. The nano-aluminum-based formulation produced cone-shaped burning surfaces at 1 atm without the ejection of unburned propellant, even for multiple wires burning in close proximity. The results demonstrate a route to preferentially tailor the internal burning profile of propellants with embedded printable reactive wires and a dynamic X-ray imaging technique to qualitatively and quantitatively characterize the complex internal perforation development.

Phase-Incoherent Photonic Molecules in V-Shaped Mode-Locked Vertical-External-Cavity Surface-Emitting Semiconductor Lasers

Passively mode-locked vertical external-cavity surface-emitting semiconductor lasers (VECSELs) composed of a gain chip and a semiconductor saturable absorber have been drawing much attention due to their excellent performance figures. In this work we investigate how localized structures and incoherent, non-locally bound, pulse molecules emerge in a long cavity VECSELs using a V-shaped cavity geometry. We show that these states are bistable with the laser off state and that they are individually addressable. Using a model based upon delay differential equations, we demonstrate that pulse clusters result from the cavity geometry and from the non-local coupling with the gain medium; this leads to locally independent, yet globally bound phase, incoherent photonic molecules. Using a multiple time-scale analysis, we derive an amplitude equation for the field that allows us to predict analytically the distance between the elements of a cluster.

Phenyl-Linked Anthracene-Based Macrocycles with Geometrically Tunable Optical Properties

Anthracene has been widely explored because of its intrinsic photophysical and photochemical properties. Here, two novel anthracene-based macrocycles (1 and 2) were designed and synthesized with para- and meta-phenylene spacers. X-ray crystallographic analysis demonstrates that compound 1 with para-phenylene spacers adopts a nearly planar structure, while compound 2 with meta-phenylene spacers displays a V-shaped geometry. The photophysical properties of the resultant macrocycles, which are structural isomers, are well studied using photoluminescence spectra and time-resolved absorption spectra, which are further corroborated by density functional theory calculations. The optical properties of these two novel macrocycles can be finely tuned via their geometries.

Chair- and V-Shaped of H-bonded Supramolecular Complexes of Azophenyl Nicotinate Derivatives; Mesomorphic and DFT Molecular Geometry Aspects.

New geometrical architectures of chair- and V-shaped supramolecular liquid crystalline complexes were molded through 1:1 intermolecular hydrogen bonding interactions between 4-(4-(hexyloxy)phenylazo)methyl)phenyl nicotinate and 4-alkoxybenzoic acids. The length of terminal alkoxy acid chains varied, n = 6 to 16 carbons. The mesomorphic behaviour of these complexes was examined through differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fourier-transform infrared spectroscopy (FT-IR) was carried out to confirm the presence of Fermi bands that appeared for the hydrogen bonding formation. Enantiotropic nematic phases were observed and covered all lengths of alkoxy chains. The geometrical structures of the prepared supramolecular complexes geometries were estimated by Density functional theory (DFT) calculations. The supramolecular complexes I/An are projected to exhibit a nonlinear geometry with V-shaped and chair-shaped geometry. The chair-shaped conformers of I/An were found to be more stable than V-shaped isomeric complexes. Moreover, the effect of the change of the mesogenic core on the mesophase thermal stability (TC) has been investigated by a comparative study of the present azo supramolecular H-bonding LCs (SMHBCs) I/An and our previously reported their Schiff base analogue complexes, II/An. The findings of the DFT illustrated the high impact of CH=N as a mesogenic core on the mesomorphic behavior in terms of the competitive lateral and terminal intermolecular interactions as well as the molecular electrostatic potential (MEP).