Unique Arc Research Articles

“Yes, I Use Sunscreen,” and Other Takeaways from a Black Girl at Sleepaway Camp

Summary Have you ever been curious about what it is like to be a speck of pepper in a sea of salt, or the only Black or brown body in a sea of white bodies? Speaking from experience, there are times when your body will experience a sudden shock of recognition or understanding. Things you had not fully grasped before become clear–you feel your differences in your body even before it registers in your mind. My story is about the unique arc of trauma my body experienced at predominately white summer camps simply because it was different from the other bodies. One goal of this piece is to impress upon you, the need to create a sense of belonging for bodies of non-dominate campers. To achieve this, it is critical to seek to understand and gain knowledge about the trauma Black and brown bodies experience because they are different and to create emotionally safe environments for all bodies. Information © CAB International 2024

Telltale signs of metal recycling in the circumgalactic medium of a z ∼ 0.77 galaxy

ABSTRACT We present gravitational-arc tomography of the cool-warm enriched circumgalactic medium (CGM) of an isolated galaxy (‘G1’) at z ≈ 0.77. Combining VLT/MUSE adaptive-optics and Magellan/MagE echelle spectroscopy, we obtain partially resolved kinematics of Mg ii in absorption and [O ii] in emission. The unique arc configuration allows us to probe 42 spatially independent arc positions transverse to G1, plus four positions in front of it. The transverse positions cover G1’s minor and major axes at impact parameters of ≈10–30 and ≈60 kpc, respectively. We observe a direct kinematic connection between the cool-warm enriched CGM (traced by Mg ii) and the interstellar medium (traced by [O ii]). This provides strong evidence for the existence of an extended disc that co-rotates with the galaxy out to tens of kiloparsecs. The Mg ii velocity dispersion (σ ≈ 30–100 km s−1, depending on position) is of the same order as the modelled galaxy rotational velocity (vrot ≈ 80 km s−1), providing evidence for the presence of a turbulent and pressure-supported CGM component. We regard the absorption to be modulated by a galactic-scale outflow, as it offers a natural scenario for the observed line-of-sight dispersion and asymmetric profiles observed against both the arcs and the galaxy. An extended enriched co-rotating disc together with the signatures of a galactic outflow, are telltale signs of metal recycling in the z ∼ 1 CGM.

Numerical simulation on the nonaxisymmetry arc characteristics in narrow gap TIG welding: responses to welding parameters

Narrow gap TIG welding is a high efficiency and low-cost welding technique for heavy structures building. Due to the narrow groove’s constriction, the TIG arc characteristics are different from butt welding. Understanding the unique arc characteristics of narrow gap TIG welding is the foundation for investigating the heat and mass transfer, metallurgic process, as well as process design. This research conducted numerical simulation on the TIG arc plasma in the narrow groove. The effects of welding current and arc length on the arc characteristics are investigated. Results show that, with the welding current increasing, the global velocity magnitude of plasma rises. The evolution of axial velocity and radial velocity has different responses to the current changes. The arc pressure increases drastically, and the global temperature of arc plasma also goes up. With the arc length increasing, global axial velocity rises, but the axial velocity and its gradients decrease near the anode surface. Centripetal radial velocity near the cathode increases, while centrifugal radial velocity rises at the outside of arc plasma and drops near the central axis. The maximum arc pressure on the anode surface decreases. At the lower part of the arc, arc temperature decreases near the central axis and increases at the outside of the arc.

Prediction of Dirac semimetals and hourglass surface states in stacked hydrogenated Xenes ( X=Sn and Pb)

Based on density-functional theory calculations and symmetry analysis, topological Dirac semimetals (DSMs) and exotic hourglass surface states are predicted in stacked hydrogenated stanene and plumbene [Xenes ($X$ = Sn and Pb)]. Two types of topologically nontrivial DSMs are predicted in the hydrogenated Xene crystals, with the two most stable stacking patterns, respectively. The Dirac points in SnH are found occurring along the three- or sixfold (screw) rotation axes due to the inversion of the Sn $5s$ ($5{p}_{z}$) and Sn $5{p}_{x,y}$ bands. The unique Fermi arcs are observed on the surfaces parallel to the rotation axes in the crystals. Very specially, the nonsymmorphic symmetry of a glide-mirror plane in the hydrogenated Xene crystals gives rise to exotic hourglass surface states which can lead to a giant value of spin-Hall conductivity and make the crystals be ideal systems applied in prospective dissipationless spintronics. The topological nature of the both types of the DSMs is identified by the calculations of the ${\mathrm{Z}}_{2}$ indexes. Phase transitions from topologically nontrivial DSM states to normal insulators (NIs) or to other types of DSMs are also investigated. Our work provides an ideal material platform for carrying out DSMs and a comprehensive study for understanding how DSMs evolve from two-dimensional NIs or quantum spin Hall materials.

Knotting probability of an arc diagram

The knotting probability of an arc diagram is defined as the quadruplet of four kinds of finner knotting probabilities which are invariant under a reasonable deformation containing an isomorphism on an arc diagram. In a separated paper, it is shown that every oriented spatial arc admits four kinds of unique arc diagrams up to isomorphisms determined from the spatial arc and the projection, so that the knotting probability of a spatial arc is defined. The definition of the knotting probability of an arc diagram uses the fact that every arc diagram induces a unique chord diagram representing a ribbon 2-knot. Then the knotting probability of an arc diagram is set to measure how many nontrivial ribbon genus 2 surface-knots occur from the chord diagram induced from the arc diagram. The conditions for an arc diagram with the knotting probability 0 and for an arc diagram with the knotting probability 1 are given together with some other properties and some examples.

Multiple fermions in MoP

Based on the first-principles calculation, we report that the WC-type MoP is a new type of topological semimetal. It can host Weyl semimetal phase with six pairs of Weyl points (WPs) in the first whole Brillouin zone (BZ). In the absence of spin-orbit coupling (SOC), band inversion forms a gapless nodal ring protected by horizontal mirror symmetry [Formula: see text]. The strong SOC in MoP makes the nodal ring fully gapped in the mirror plane, and generates multiple WPs away from the plane. As one hallmark of Weyl semimetals, the unique Fermi arcs are also observed by calculating the projected surface states and Fermi surfaces. Besides the above prodigious features, it also possess an additional four pairs of massless fermions with triply degenerate points (TDPs) in the vicinity of the Fermi level. Each TDP is a band crossing between degenerate and non-degenerate bands along the high-symmetry line in the Brillouin zone, and is protected by crystalline symmetries. Such new type of topological semimetal realizes multiple fermions states and further provides a fancy platform to study emergent physical phenomena.

Prediction of DC flashover voltage of cap‐and‐pin polluted insulator

The aim of this work is to estimate the flashover voltage of cap-and-pin insulator using a novel improvement of the pollution resistance evaluation. In cap-and-pin suspension insulators, local arcing starts around the pin where the dry bands first appear due to the evaporation of the conductive layer. In appropriate conditions, a unique dominant arc starting from the pin propagates toward the cap resulting in a complete flashover. Since the highest current density is concentrated around the arc root during propagation, the pollution layer residual resistance variation, with respect to the arc position, is non-linear. Thus an original three-dimensional model, which depicts a real insulator using COMSOL Multiphysics TM to evaluate the residual resistance, is developed. This model takes into consideration the actual geometry of the insulator and the current restriction at the arc root for a specific arc radius. A novel mathematical model for calculating the residual resistance of this polluted insulator was elaborated for all possible arc radii. The mathematical model and the 3D simulation results are in satisfactory agreement. To evaluate the flashover voltage, a new approach based on Saddle Point Finding Method is proposed. The new approach and model have been validated using experimental results of previous studies.

The Calc-Alkaline Hidden Bay and Kagalaska Plutons and the Construction of the Central Aleutian Oceanic Arc Crust

Abstract Calc-alkaline plutons are the major crustal building blocks of continental margins, but are rarely exposed in oceanic island arcs. Two of the best examples are the ∼10 km wide Hidden Bay and Kagalaska plutons that intrude Eocene mafic volcanic–sedimentary rocks on Adak and Kagalaska islands in the central Aleutian arc. Twenty new Ar/Ar and U/Pb ages, coupled with published ages, show that the Hidden Bay pluton was intruded in multiple stages from ∼34·6 to 30·9 Ma, whereas the Kagalaska pluton was intruded at ∼14 Ma. The plutons largely consist of medium- to high-K2O hornblende-bearing cumulate diorite (53–55 wt % SiO2) and hornblende–biotite granodiorite (57–64 wt %), with lesser amounts of gabbro (50–52 wt % SiO2), leucogranodiorite (67–69 wt % SiO2) and aplite (76–77 wt % SiO2) that can generally be linked to each other by crystal fractionation. The compositions of these plutons are generally similar to those of continental plutons, except for more oceanic-like large ion lithophile element and isotopic signatures (87Sr/86Sr = 0·703–0·7033; ɛNd = 9·4–7·7) that reflect oceanic- rather than continental-type crustal contaminants. Chemical similarities between the Hidden Bay homogeneous gabbros and high-Al basalts in Adak Pleistocene-Holocene volcanoes indicate little temporal evolution in the general character of the mantle-derived basalts. Rather than a unique arc setting and distinctive magmas, formation of the Aleutian calc-alkaline plutons seems to require a sufficient crustal thickness (∼37 km) and a high enough water content to stabilize pargasitic hornblende amphibole in a relatively closed magma system that favors increasing K, Ti and H2O at the end of a magmatic cycle. This termination of magmatism coincides with a northward migration of the magmatic front that is inferred to be associated with fore-arc subduction erosion. In accord with Adak region crustal architecture based on seismic data, crystallization models for the plutons suggest that mantle-generated hydrous arc basalts fractionated olivine and clinopyroxene in the lower crust to form high-Al basaltic composition magmas that rose into the mid-crust, where gabbro and diorite crystallized to form the magmas that buoyantly rose into the upper crust and crystallized to form the volumetrically dominant granodiorite (58–63 wt % SiO2). The most important temporal changes in chemistry can be explained by fore-arc crust incorporated into the mantle wedge by fore-arc subduction erosion creating ‘adakitic’ signatures at times of northward arc migration and a change to a more continental subducted sediment component at the time of Plio-Pleistocene glaciation.

A Novel Comprehensive Evaluation Method of Forest State Based on Unit Circle

Comprehensive evaluation of forest state is the precondition and critical step for forest management. To solve the problem that the radar plot and unit circle only focus on the value of each the evaluation index, this paper proposes a novel method for comprehensively and simultaneously evaluating the functionality and inhomogeneity of forest state based on the modified unit circle method. We evaluated the forest state of the Quercus aliena BL. var. acuteserrata Maxim. ex Wenz. broad-leaved mixed forest in the Xiaolong Mountains Forest Area of Gansu Province and the Pinus koraiensis Sieb. et Zucc. broad-leaved mixed forest in Jilin Province in China. According to the principle of comprehensive, scientific and operability, 10 evaluation indices on forest structure and vitality were selected to construct the evaluation indicator system. Each index was normalized based on the assignment method and ensured to be strictly positive based on reciprocal transformation method. The areas and arc length of the closed graph, formed by connecting every two adjacent indicators, in the radar plot and unit circle were extracted. Based on the isoperimetric theorem (isoperimetric inequality), a comprehensive evaluation model was constructed. Compared with radar chart and unit circle method, each index in the newly proposed unit circle method is represented by an independent sector region, reflecting the contribution of the index to the overall evaluation result. Each index has the same relative importance weight, contributing to the estimation the relative sizes of each aspect of forest state. The unique area and arc length of the closed graph help summarize the overall performance with a global score. The expression effect of improved unit circle has been enhanced, and as an English proverb put it, “A picture is worth a thousand words.” The new proposed method simultaneously evaluates the functionality and inhomogeneity of the forest state and it is a powerful tool for the diagnosis of forest state problems and the decision-making of forest management.

Series Arc Fault Identification for Photovoltaic System Based on Time-Domain and Time-Frequency-Domain Analysis

This paper aims at providing a reliable algorithm to identify photovoltaic (PV) series arc faults regardless of complex fault-like interferences. Through conducting various arc fault experiments with different PV current levels, arc gap lengths, and load types, PV series arc fault features have been understood comprehensively. To avoid unwanted nuisance tripping, fault-like conditions are analyzed to confirm the unique arc fault features. Based on the loop current signature, a greater unstable fluctuation in the time domain and extra arc noises in the time-frequency domain are chosen as identification features. By quantificational evaluations, optimal detection variables with the Hamming window and the proper time resolution have been established to achieve the best identification results. By building fusion coefficients, two variables are arithmetically fused to achieve the arc fault discovery. The algorithm could also classify fault-like into normal and adjust the threshold value dynamically to fit different normal current levels. Its validity has been verified by experimental results on the simulated platform.

Validation Of The Cybex Arc Trainer Estimation Of Energy Expenditure

PURPOSE: Elliptical machine exercise has grown in popularity in the fitness community. Despite the popularity of the Cybex Arc Trainer, (AT) which utilizes a unique arc motion unlike other elliptical machines, little is known about the validity of the AT console display of energy expenditure (EE). The purpose of this study was to examine the accuracy of the AT estimation of EE during a 30-minute moderate intensity workout. METHODS: Thirteen participants (5 normal-weight, 8 overweight) were fitted with the Oxycon Mobile (OXY), a portable indirect calorimeter system. Resting heart rate was used to calculate heart rate reserve, (HRR) an individual characterization of workout intensity. To maintain a moderate intensity throughout the 30-minute bout, participants were instructed to change the resistance level to yield a rating of perceived exertion of 12-13, while maintaining stride rate at 114 ± 5 strides per min.Criterion EE measured via the OXY was compared to EE values on the AT console display at the end of the workout. Linear mixed effects models and correlations were used to examine differences in EE between the AT and OXY and the relationship between EE OXY and EE AT. RESULTS: The AT significantly overestimated EE compared to the OXY (NW: 12.4%; OW: 18.0%). Correlations between OXY and AT EE ranged from r = 0.96 to 0.97 for NW and OW groups, respectively. No differences were observed in % HRR between groups. CONCLUSIONS: Although correlations between OXY and AT EE were high, AT consistently overestimated EE. Additionally, the EE overestimation was larger for the overweight group. These results indicate that the AT EE display is inaccurate. Therefore, users do not receive correct EE feedback. This will affect user ability to achieve desired EE goals, and over-time this discrepancy may have a substantial impact on weight-loss management. Fitness professionals should consider these results when prescribing AT exercise in physical activity interventions.

A function space from a compact metrizable space to a dendrite with the hypo-graph topology

Abstract Let X be an infinite compact metrizable space having only a finite number of isolated points and Y be a non-degenerate dendrite with a distinguished end point v. For each continuous map ƒ : X → Y , we define the hypo-graph ↓vƒ = ∪ x∈X {x} × [v, ƒ (x)], where [v, ƒ (x)] is the unique arc from v to ƒ (x) in Y . Then we can regard ↓v C(X, Y ) = {↓vƒ | ƒ : X → Y is continuous} as the subspace of the hyperspace Cld(X × Y ) of nonempty closed sets in X × Y endowed with the Vietoris topology. Let be the closure of ↓v C(X, Y ) in Cld(X ×Y ). In this paper, we shall prove that the pair , ↓v C(X, Y )) is homeomorphic to (Q, c0), where Q = Iℕ is the Hilbert cube and c0 = {(xi )i∈ℕ ∈ Q | limi→∞xi = 0}.

Fixed points and best approximation in arcwise connected spaces

It is shown that several theorems known to hold in complete geodesically bounded R-trees extend to arcwise connected Hausdorff topological spaces which have the property that every monotone increasing sequence of arcs is contained in an arc. Let X be such a space and let [u,v] denote the unique arc joining u,v∈X. Among other things, it is shown and if Y is a closed connected subset of X and if f:Y→X is continuous, then f has a ‘best approximation’ in Y in the sense that there exists a point z∈Y such that [z,f(z)]∩Y={z}. A set-valued analog of this result is also discussed.

A semianalytic model for the computation of imbibition through polygonal cross sections

We develop a semianalytic method for the computation of arc‐menisci motion in an imbibition process through any irregular polygonal cross section for any arbitrary wetting angle from 0° to 90°. The method produces the sequence of unique arc meniscus configurations that develop as the capillary pressure decreases throughout the imbibition process. To test for robustness of the algorithm, we apply the method to the analysis of arc meniscus motion for imbibition processes in a sample of 23,639 throat cross sections obtained from analysis of X‐ray computed tomographic images of 22% porosity Fontainebleau sandstone. Extending the work of Glantz and Hilpert (2011), we define the chord axis, which captures the motion of stable arc menisci in a polygonal cross section. Unlike the one‐parameter family of drainage axes introduced by Lindquist (2006), the chord axis is independent of the wetting angle. We demonstrate that the semianalytic method can be used to construct the chord axis for any polygonal cross section.

Curves of infinite length in labyrinth fractals

AbstractWe define an infinite class of fractals, called horizontally and vertically blocked labyrinth fractals, which are dendrites and special Sierpiński carpets. Between any two points in the fractal there is a unique arc α; the length of α is infinite and the set of points where no tangent to α exists is dense in α.

Possible early Neoproterozoic magmatism associated with slab window in the Pingshui segment of the Jiangshan-Shaoxing suture zone: Evidence from zircon LA-ICP-MS U-Pb geochronology and geochemistry

We report here geochemical data, U-Pb zircon ages, and Hf isotopes for the high-Mg diorites (HMDs), Nb-enriched basaltic porphyrys (NEBPs) and plagiogranites (PLAGs) in the Pingshui segment of the Jiangshan-Shaoxing suture zone. The HMDs are characterized by high Mg# (>60), high Na and LREE contents, depletion of HREE and HFSE, and pronounced positive eNd(t) values of 7.0 to 7.7, similar to some adakitic high-Mg andesites. The NEBPs are relatively Na-rich (Na2O/K2O>6) and display high abundances of P2O5 (∼1.00%), TiO2 (∼3.08%) and HFSE (e.g., Nb=9.53–10.27 ppm). Their Nd isotopic compositions (eNd(t)=6.8–8.0) are comparable to those of the HMDs. The PLAGs are metaluminous (A/CNK=0.84–0.89) and sodic (Na2O/K2O>10). Their depletion in HFSE (e.g., Nb, Ta) is consistent with “SSZ-type” plagiogranite. Zircon LA-ICP-MS U-Pb dating yields an age of 932±7 Ma for the HMD, 916±6 Ma for the NEBP, and 902±5 Ma for the PLAG, respectively, indicating that they were products of early Neoproterozoic magmatism. The PLAGs exhibit relatively high zircon Hf isotopes and positive eHf(t) values of 11.0 to 16.2, consistent with their Nd isotopic data (eNd(t)=7.5–8.4). Such features are similar to those of oceanic plagiogranites in ophiolites and distinct from those of crust-derived granites. The PLAGs were most likely derived from partial melting of subducted oceanic crust in an active continental margin. Considering these results in the context of the regional geology, we suggest that a slab window in the subducting oceanic crust between the Yangtze Block and Cathaysia Block was possibly the principal cause for the unique arc magmatism in the area. The upwelling asthenosphere below the slab window may have provided significant thermodynamic conditions.

Remarks on best approximation in R-trees

An R-tree is a geodesic space for which there is a unique arc joining any two of its points, and this arc is a metric segment. If X is a closed convex subset of an R-tree Y; and if T : X ! 2 Y is a multivalued mapping, then a point z for which 0 < dist(z;T (z)) = inf x2X dist(x;T (z)) is called a point of best approximation. It is shown here that if T is an - semicontinuous mapping whose values are nonempty closed convex subsets of Y; and if T has at least two distinct points of best approximation, then T must have a fixed point. We also obtain a common best approximation theorem for a commuting pair of mappings t : X ! Y and T : X ! 2 Y where t is single-valued continuous and T is -semicontinuous.

Curves of infinite length in 4 × 4-labyrinth fractals

We study 4 × 4-labyrinth fractals, which are self similar dendrites. For all 4 × 4-labyrinth fractals we answer the question, whether there is a curve of finite length in the fractal from one point to another point in the fractal. In the first case, between any two points in the fractal there is a unique arc a, the length of a is infinite, and the set of points, where no tangent exists to a, is dense in a. In the second case, there are also pairs of points between that there is a unique arc of finite length.

MO-D-351-02: An Efficient Approach To Volumetric Modulated Arc Therapy Optimization and Sequencing

Purpose: To develop and evaluate an efficient algorithm for inverse treatment planning of volumetric arc therapy (VMAT). Method and Materials: VMAT plans were generated by first applying a direct machine parameter optimization algorithm from a research version of a commercial treatment planning system (Pinnacle 8.1v) to 18 beams spaced equidistantly at 20 degrees. At each beam angle, the number of segments was variable (typically 3 to 8) to match the intensity modulation fluence map. Low weight or small area segments were eliminated during optimization. The resulting segments were redistributed around the arc such that each individual segment was at a unique arc angle. Segments were sorted according to shape similarity in order to reduce leaf travel in between arc angle positions. To ensure accuracy of the final dose calculation, additional interpolated segments were generated, followed by a segment weight optimization to identify beam‐off segments that would otherwise conflict with plan objectives. The approach was evaluated for six cases (three head‐and‐necks, two prostate, and one brain) with respect to treatment delivery time, and overall plan quality in comparison to step‐and‐shoot IMRT using a conventional number of static beams and identical objectives and constraints as in the VMAT case. Results: The dynamic arc plans consistently demonstrated target coverage and critical structure sparing comparable to step‐and‐shoot plans. For the head‐and‐neck cases, sparing of the brainstem and the spinal cord could be improved substantially. Treatment parameter optimization and dose calculation required 15 to 20 minutes on standard hardware. Estimated delivery times were between 1.5 and 4 minutes, which is mainly determined by the leaf trajectories, gantry speed and dose rate. Conclusion: A method for inverse planning for VMAT delivery was developed. The method produces treatment plans with high dosimetric quality and efficient delivery time with clinically feasible user time and effort.

The operad of finite labeled lattices

This paper is a continuation of the series of papers [1–5]. We study various classes of finite labeled graphs (nonoriented or oriented) which form operads with respect to the composition operations introduced in [1]. The partially ordered sets and, in particular, lattices, form important classes of oriented graphs. The families of finite labeled partially ordered sets and lattices also possess operad structures. In this paper, we study elements of the operad of lattices that admit no nontrivial decomposition into operad composition. It turns out that the question on such lattices is closely related to the question on the structure of the congruence Θ(a, b) from [6]. Namely, an element of the operad of finite labeled lattices (i.e., a finite lattice) is operad indecomposable if and only if, on this lattice, there exist no congruences of the following form. Elements a ≤ b are fixed (where either a = 0 or b = 1), and x ∼ y if (and only if) either a ≤ x, y ≤ b or x = y. We succeeded in finding many examples of lattices with this property. Note that the operad composition on the family of finite partially ordered sets bears similarities to Plonka’s Agassiz sums (see the definition in [7], P. 46; [8], P. 314–315). It should be also noted that in the literature on the graph theory (independently of the literature on the universal algebra) one can find constructions similar to the operad composition from [1] (see, e.g., [9, 10]). The operad language, however, is not used. In this paper, we construct the operad of finite labeled lattices and its generalization, the operad of finite labeled partially ordered sets. We establish a criterion of operad decomposability for lattices. Using this criterion, we prove operad indecomposability of a series of families of lattices. In particular, the following classes of lattice turn out to be indecomposable: simple lattices, lattices decomposable into product, lattices with relative complements, modular lattices with complements, many of finite distributive lattices, and all finite geometric lattices. We use definitions, results, and notation from [1] with changes appeared later in [11]. Some preliminary versions of results of this paper were announced in [3–5]. Denote by Lat(n) the set of finite lattices with n elements enumerated by the numbers from 1 to n. We consider the same lattice with different enumerations of elements as different elements of Lat(n). The groupΣn of permutations of degree n acts on Lat(n) by permutation of numbers of elements. From the aforesaid it follows that the orbits of the action of Σn correspond to different lattices. We introduce an operad structure on the family Lat = {Lat(n) | n ≥ 1} regarding lattices as a partial case of oriented graphs: x ≤ y means that there is a unique arc from a vertex x to a vertex y. Then the definition of the composition for oriented graphs (with regard to the structure of partially ordered sets) takes the form