Cone Field Research Articles

On the creation of high energy bremsstrahlung and intensity by a multitarget and repeated focusing of the scattered electrons by small-angle backscatter at the wall of a cone and magnetic fields—A possible way to improve linear accelerators in radiotherapy and to verify Heisenberg–Euler scatter

The yield of bremsstrahlung from collisions of fast electrons (energy at least 6MeV) with a Tungsten target can be significantly improved by exploitation of Tungsten wall scatter in a multi-layered target. The Tungsten wall can serve to refocuse small angle scattered electrons. It is necessary that the thickness of one Tungsten layer does not exceed 0.02mm. Further repeated focusing of electrons results from suitable magnetic fields with field strength between 0.5T and 6T (if the cone with multi-layered targets is rather narrow). Linear accelerators in radiation therapy only need repeated focusing by wall scatter without further magnetic fields (standard case: ca. 100–000 plates with 0.01mm thickness and 1mm distance between the plates). The construction of a very narrow bremsstrahlung beam with extremely high photon intensity requires an additional strong magnetic field (order 1–6T), which provides the possibility to check Heisenberg–Euler scatter of high energy photons.

A unique volcanic field in Tharsis, Mars: Pyroclastic cones as evidence for explosive eruptions

Based on theoretical grounds, explosive basaltic volcanism should be common on Mars, yet the available morphological evidence is sparse. We test this hypothesis by investigating a unique unnamed volcanic field north of the shield volcanoes Biblis Patera and Ulysses Patera on Mars, where we observe several small conical edifices and associated lava flows. Twenty-nine volcanic cones are identified and the morphometry of many of these edifices is determined using established morphometric parameters such as basal width, crater width, height, slope, and their respective ratios. Their morphology, morphometry, and a comparison to terrestrial analogues suggest that they are martian equivalents of terrestrial pyroclastic cones, the most common volcanoes on Earth. The cones are tentatively interpreted as monogenetic volcanoes. According to absolute model age determinations, they formed in the Amazonian period. Our results indicate that these pyroclastic cones were formed by explosive activity. The cone field is superposed on an old, elevated window of fractured crust which survived flooding by younger lava flows. It seems possible that a more explosive eruption style was common in the past, and that wide-spread effusive plain-style volcanism in the Late Amazonian has buried much of its morphological evidence in Tharsis.

On smooth time functions

AbstractWe are concerned with the existence of smooth time functions on connected time-oriented Lorentzian manifolds. The problem is tackled in a more general abstract setting, namely in a manifold M where is just defined a field of tangent convex cones (Cx)x ∈ M enjoying mild continuity properties. Under some conditions on its integral curves, we will construct a time function.Our approach is based on the definition of an intrinsic length for curves indicating how a curve is far from being an integral trajectory of Cx. We find connections with topics pertaining to Hamilton–Jacobi equations, and make use of tools and results issued from weak KAM theory.

Hyperbolic dynamics in graph-directed IFS

A cone space is a complete metric space ( X , d ) with a pair of functions c s , c u : X × X → R , such that there exists K > 0 satisfying 1 K d ( x , x ′ ) ⩽ max ( c s ( x , x ′ ) , c u ( x , x ′ ) ) ⩽ K d ( x , x ′ ) for x , x ′ ∈ X . For a partial map f between cone spaces X and Y we introduce | f | s which measures the stable contraction rate and 〈 f 〉 u which measures the unstable expansion rate. We say that f is cone-hyperbolic if | f | s < 1 < 〈 f 〉 u . Using cone field and graph-directed IFS we build an abstract metric model which describes the dynamics of the hyperbolic-like systems. This allows to obtain estimations from below and above of the fractal dimension of the hyperbolic invariant set.

Geomorphometric variability of “monogenetic” volcanic cones: Evidence from Mauna Kea, Lanzarote and experimental cones

Volcanic cones are the most common volcanic constructs on Earth. Their shape can be quantified using two morphometric ratios: the crater/cone base ratio (W cr/W co) and the cone height/width ratio (H co/W co). The average values for these ratios obtained over entire cone fields have been explained by the repose angle of loose granular material (i.e. scoria) controlling cone slopes. The observed variability in these ratios between individual cones has been attributed to the effect of erosional processes or contrasting eruptive conditions on cone morphometry. Using a GIS-based approach, high spatial resolution Digital Elevation Models and airphotos, two new geomorphometry datasets for cone fields at Mauna Kea (Hawaii, USA) and Lanzarote (Canary Islands, Spain) are extracted and analyzed here. The key observation in these datasets is the great variability in morphometric ratios, even for simple-shape and well-preserved cones. Simple analog experiments are presented to analyze factors influencing the morphometric ratios. The formation of a crater is simulated within an analog cone (i.e. a sand pile) by opening a drainage conduit at the cone base. Results from experiments show that variability in the morphometric ratios can be attributed to variations in the width, height and horizontal offset of the drainage point relative to the cone symmetry axis, to the dip of the underlying slope or to the influence of a small proportion of fine cohesive material. GIS analysis and analog experiments, together with specific examples of cones documented in the field, suggest that the morphometric ratios for well-preserved volcanic cones are controlled by a combination of 1) the intrinsic cone material properties, 2) time-dependent eruption conditions, 3) the local setting, and 4) the method used to estimate the cone height. Implications for interpreting cone morphometry solely as either an age or as an eruption condition indicator are highlighted.

Rift zone volcanism and associated cinder cone field in Utopia Planitia, Mars

We analyzed a small cone field in SW Utopia Planitia that shows striking similarities to volcanic rift zones on Earth. This is of particular interest as the study area lies off any of the volcanic centers of Mars in the northern hemisphere lowlands and is surrounded by material of the Amazonian aged Vastitas Borealis Formation (VBF). We believe that the study area could be the first direct evidence for volcanic activity in Utopia Planitia prior to the resurfacing by VBF material. The most striking characteristics that we observed are (1) a set of broad eruptive fissures showing signs of ongoing extension during cone formation, (2) parallel dike swarms, (3) magmatic intrusions, and (4) a number of lava flows that have erupted from the fissures and pitted cones that surround a larger cone in the center of the study area and that are often associated with, or aligned along, the fissures and dikes. Cratering model ages indicate that the study area is of Late Noachian to Early Hesperian age and is thus distinctly older than the surrounding VBF, falling into the time frame of the main phases of activity in the volcanic centers of Syrtis Major, Elysium Planitia, and the southern highlands.

Bernoulli linked-twist maps in the plane

We prove that certain area-preserving linked-twist maps defined in the plane are metrically isomorphic to a Bernoulli shift. This is the first such result for explicitly defined linked-twist maps on a manifold other than the two-torus. Our work builds on that of Wojtkowski [Linked twist mappings have the K-property, Nonlinear dynamics; Proceedings of the International Conference, New York, NY, December 17–21, 1979] who established an ergodic partition for the maps in question, using an invariant cone field in the tangent space.

Low‐productivity Hawaiian volcanism between Kaua‘i and O‘ahu

The longest distance between subaerial shield volcanoes in the Hawaiian Islands is between the islands of Kaua‘i and O‘ahu, where a field of submarine volcanic cones formed astride the axis of the Hawaiian chain during a period of low magma productivity. The submarine volcanoes lie ∼25–30 km west of Ka‘ena Ridge that extends ∼80 km from western O‘ahu. These volcanoes were sampled by three Jason2 dives. The cones are flat topped, &lt;400 m high and 0.4–2 km in diameter at water depths between ∼2700 and 4300 m, and consist predominantly of pillowed flows. Ar‐Ar and K‐Ar ages of 11 tholeiitic lavas are between 4.9 and 3.6 Ma. These ages overlap with shield volcanism on Kaua‘i (5.1–4.0 Ma) and Wai‘anae shield basalts (3.9–3.1 Ma) on O‘ahu. Young alkalic lavas (circa 0.37 Ma) sampled southwest of Ka‘ena Ridge are a form of offshore secondary volcanism. Half of the volcanic cones contain high‐SiO2 basalts (51.0–53.5 wt % SiO2). The trends of isotopic compositions of West Ka‘ena tholeiitic lavas diverge from the main Ko‘olau‐Kea shield binary mixing trend in isotope diagrams and extend to lower 208Pb/204Pb and 206Pb/204Pb than any Hawaiian tholeiitic lava. West Ka‘ena tholeiitic lavas have geochemical and isotopic characteristics similar to volcanoes of the Loa trend. Hence, our results show that the Loa‐type volcanism has persisted for at least 4.9 Myr, beginning prior to the development of the dual, subparallel chain of volcanoes. Several West Ka‘ena samples are similar to higher SiO2, Loa trend lavas of Ko‘olau Makapu‘u stage, Lāna‘i, and Kaho‘olawe; these lavas may have been derived from a pyroxenite source in the mantle. The high Ni contents of olivines in West Ka‘ena lavas also indicate contribution from pyroxenite‐derived melting. Average compositions of Hawaiian shield volcanoes show a clear relation between 206Pb/204Pb and SiO2 within Loa trend volcanoes, which supports a prominent but variable influence of pyroxenite in the Hawaiian plume source. In addition, both Pb isotopes and volcano volume show a steady increase with time starting from a minimum west of Ka‘ena Ridge. The entrained mafic component in the Hawaiian plume is probably not controlling the increasing magma productivity in the Hawaiian Islands.

Homotopy shadowing

Michael Shub proved in 1969 that the topological conjugacy class of an expanding endomorphism on a compact manifold is determined by its homotopy type. In this article we generalize this result in two directions. In one direction we consider certain expanding maps on metric spaces. In a second direction we consider maps which are hyperbolic with respect to product cone fields on a product manifold. A key step in the proof is to establish a shadowing theorem for pseudo-orbits with some additional homotopy information.

Morphometric and morphological development of Holocene cinder cones: A field and remote sensing study in the Tolbachik volcanic field, Kamchatka

The evolution of landscape over time is a central aspect of geological, paleogeographical and geomorphological studies. Volcanic features like cinder cones offer the opportunity to monitor the processes and development of the landscape. Cinder cones are perhaps the simplest and most common volcanic landforms in the world. Morphological and morphometric study of cinder cones has proven an efficient tool for determining their relative dates, and the erosional processes affecting them. The extensive Kamchatka volcanic province (Russian Far East), with its large Tolbachik cinder cone field, is an excellent case study for spatial and temporal classification and calibration of changes in morphometric values with time. We show how the morphological and morphometric values of the monogenetic cinder cones, measured in the field and by digital elevation models, can be used to validate their age and erosional processes. Field data were GPS measurements of cinder cones formed at the Tolbachik 1975–1976 eruption and of Holocene cinder cones; erosion processes on the cinder cones and lava flows were identified and evaluated. For every studied cinder cone morphometric parameters were assessed on the basis of remotely sensed data and digital elevation model. Morphometric measurements were taken of cone height and slope and average axis diameter and the height–width ratio was obtained. The comparison of morphometric parameters calculated from ASTER DEM and topographic map clearly supports the concept of relative morphometric dating as the most recent cinder cones are always associated with the highest slopes and h/W ratio. The measured morphometric values of the recent Tolbachik cinder cones are valuable benchmark data for determining erosion rates, such as the measured values for the Paricutin cone in Mexico after the 1943 eruption. The variability of the morphometric values of the recent cinder cones is due to their lithological coarse composition. A comparison with the older cinder cones in the area shows that the climatic conditions of the Kamchatka peninsula and the slow development of vegetation cover determine a high rate of erosion and rapid change in the morphometric values, as compared to published values for other volcanic fields.

New criteria for systematic mapping and reliability assessment of monogenetic volcanic vent alignments and elongate volcanic vents for crustal stress analyses

Linear arrays of monogenetic volcanic vent alignments represent an important source of stress/strain data from volcanic regions of the Earth and other planets. Currently, however, there is no standard methodology for mapping vent alignments or for assessing alignment reliability, which are essential to defining a robust stress datum from vent alignments. Here we define a systematic method for defining monogenetic vent alignments by mapping the locations and shapes of vents. Elongation of vents into elliptical shapes is directly related to the trend of subsurface fissures that control alignments. Elongated vents therefore are critical for defining reliable regional vent alignments, and also provide an independent means for assessing stress directions. Our reliability assessment system (A > B > C > D) for vent alignments is based on the number of vents, the standard deviation of vent center points from a best-fit line, the numbers and types of elongate vents, the standard deviation of long axes of elliptical vents from a best-fit line, and, in cases where alignments lack elongate vents, by vent spacing distances. We quantified morphometric parameters of well-defined fissure-fed vent alignments from polygenetic volcanoes and platform volcanic fields to establish appropriate threshold values for reliability assessments. In this new method, the combined analysis of vent locations and shapes optimizes the process of alignment mapping and the assessment of the reliability of alignments to be incorporated in stress analyses. We provide quality-ranking schemes for stress data derived from reliability-assessed vent alignments and from elongate vents. We demonstrate the utility of this new mapping and assessment methodology by analyzing monogenetic cinder cone fields within a platform volcanic field (the San Francisco volcanic field in Arizona) and within a volcanic field on the flank of a polygenetic volcano (Mount Morning in Antarctica).

Preparation and characterization of the amorphous tungsten cone field emitter arrays by Ar + etching

Uniform amorphous tungsten cone arrays in high density were fabricated by Ar + reduction etching of WO 3 nanowire film. The etching process was performed in the analysis chamber of an X-ray photoelectron spectroscopy (XPS) system. SEM and TEM results revealed that the tip radius of the etched cones was 10 nm, and the cones were amorphous with a high aspect ratio of over 250. XPS analysis proved the cones to be metallic tungsten. In the aspect of field-emission property, the tungsten cone arrays had a lower turn-on field of 3 MV m −1 compared with 5 MV m −1 of the as-grown original WO 3 nanowire film.

Cone fields in SW Elysium Planitia: Hydrothermal venting on Mars?

We have studied a large cone field in SW Elysium Planitia that shows unique characteristics that have, as yet, not been described elsewhere on Mars. Pitted cones and cone fields are quite common on Mars and the Elysium Planitia region where they have been mainly interpreted as pseudocraters. The cones in the study area differ from cones elsewhere on Mars in morphology, geologic setting, and their assemblage with pitted ridges as well as their close association to Aeolis Planum–Medusae Fossae Formation (MFF) material. The cones appear almost exclusively along an extensive contact zone, several hundred kilometers long, where lava flows that emanated from the Cerberus Fossae flooded fine‐grained MFF material of the Aeolis Planum complex. Particularly striking is the observation that several cones in the study area have developed on top of mesas and terraces of Aeolis Planum material that were embayed but not overflowed by lava and can thus not be explained as pseudocraters. We propose that the striking assemblage of these structures was formed by a combination of pseudocrater formation and hydrothermal venting through mesas of Aeolis Planum‐MFF material by a process similar to hydrothermal vent complexes on Earth. The voluminous Cerberus Fossae lava flows that flooded the study area covered large parts of Aeolis Planum material, initiating the mobilization of volatiles and leading to hydrothermal activity along the lava‐MFF contact. Furthermore, our observations strongly support the hypothesis that the volatile content of the MFF is (or was) high, at least in that part of the MFF constituting the Aeolis Planum complex.

Site investigation for disaster reconstruction in Aceh, Sumatra

The tsunami that struck and devastated large sections of the coastline of Aceh in northern Sumatra, on 26 December 2004 was generated by a massive offshore earthquake of magnitude 9·3. As part of the reconstruction programme, UNICEF is engaged in the replacement of old schools and health clinics at over 580 locations throughout the province of Aceh and the island of Nias. The programme is urgent and tight, compounded frequently by difficult access. An approach to the examination of the ground conditions at the sites had to be established that would allow the use of light equipment and tools and a relatively unskilled workforce. In situ tests were conducted using a locally manufactured equivalent light Dutch cone apparatus, a dynamic cone penetrometer (DCP) and field vane equipment. Laboratory testing, apart from normal identification and classification tests, included undrained shear strength determinations. This paper sets out the modus operandi developed to suit the site conditions, and describes the types of soil and conditions encountered. The paper also presents a tentative correlation between the results of the in situ (DCP) testing and the undrained shear strength of the samples recovered for laboratory testing. The approach should have merit when responding to future disasters.

Petrological inferences on the evolution of magmas erupted in the Andagua Valley, Peru (Central Volcanic Zone)

Major and trace element and Sr and Nd isotope data is presented from the Andagua valley scoria cone and lava field (15°32′ S 72°19′ W), Southern Peru in the northernmost part of the Central Volcanic Zone (CVZ). The rocks are all quite evolved in composition (SiO 2 = 55–64 wt.%) and classify as benmoreites, latites and few mugearites and trachytes. Samples are characterized by high Na 2O (4.2–5.2 wt.%), Sr (600–1300 ppm), Ba (800–1600 ppm). The main difference between the benmoreites and latites is in the Na 2O content that reach the highest so far reported from CVZ for these SiO 2 concentrations. The rocks are generally nearly aphyric but latites and trachytes are more porphyritic. Amphibole microphenocrysts generally are only present in latites and trachytes. The difference between benmoreite and latite samples is reflected in lower P 2O 5 and Zr content of the latite samples documenting the existence of two compositional different parental magma types. The investigated volcanic activity spans the Pleistocene to Recent with the historic activity concentrated in the area just south of Andagua. Combined relative stratigraphy, petrography and geochemistry define volcanic units and demonstrate that rocks from Chilcayoc Grande, Chilcayoc Chico 2, Jenchana, Sucna 1 and Chilcayoc Chico 1 represent the most recent volcanic activity. The main trend samples, each form a co-magmatic group resulting in sub-parallel trends in many variations diagrams. It is furthermore shown that these trends point towards calculated mixing lines relating the individual units through a binary mixing process, thus indicating a two stage evolution. In the case of Jenchana, Sucna 1 and Chilcayoc Chico 1, the samples define positive correlation trends in the Sr vs. Rb diagram that can be extrapolated back towards origo indicating nearly perfect incompatibility of Sr and Rb. This together with generally high Sr/Y (50–105) and low Y content (< 16 ppm) suggest lack of plagioclase fractionation and residual garnet in the source and is taken as evidence for relatively high pressure (lower crustal) origin of the mixing event. The amphibole bearing samples form individual co-magmatic groups that cannot be related to each other. This means that the amphibole bearing samples originates from different magmas. The lavas of the Ninamama group are comparable in age to the main trend samples but different in petrography and composition, why the two compositional different magmas must have existed within a small confined area within a limited time span.

Higher-order neighbor analysis of the Tartarus Colles cone groups, Mars: The application of geographical indices to the understanding of cone pattern evolution

Cone fields of ambivalent origin exist in the Elysium, Amazonis, Cerberus, Isidis, Acidalia and Cydonia regions of Mars. Considerable interest exists in regard to their location and origin as their occurrence in many instances, is most likely associated with near surface ground ice; the presence of which has consequences for past and present climate, astrobiological activity, and future exploration. This research has outlined an understanding of both spatial and geomorphic processes of cone development for a region within the Tartarus Colles, Mars, as well as the manner in which spatial statistical indices can be affected by modification to the areal unit of study. This study found that cone groups for the region of the Tartarus Colles, are completely spatially random (CSR) across all distances extending to their sixth-order neighbor. However, significant statistical indices of aggregation were found for groups where post-emplacement erosional modification may have occurred by solifluction-like mechanisms or magmatic incursion into or over frozen ground. Such circumstances imply that R-indices reflect both the underlying spatial and geologic processes of cone formation, and also, an overprint of erosional modification of the cone-field within a glacial or periglacial setting, in this instance. The comparison of spatial indices can therefore offer a viewpoint from which geomorphic change can be recognized and quantitatively evaluated for cone fields.

A Weyl-geodesic field of cones in a three-dimensional Riemannian space II. First integrals of geodesics

We study three-dimensional Riemannian spaces and Weyl spaces such that the geodesic equations admit a first integral of second order. With respect to a special coordinate system, we find objects which completely determine connection of these spaces as well as the integrals.

A combined DJM-PVD method for soft ground improvement

Dry jet mixing (DJM) and prefabricated vertical drains (PVDs) have been successfully used for soft ground improvement worldwide. They both have advantages and limitations, and have been used independently so far. In this study, DJM and PVDs were used in combination to enhance the performance of soft ground improvement. In the combined method, PVDs are first installed and then DJM columns are installed between the PVDs at larger spacing. This combined method improves the effectiveness of ground improvement and creates a more economical solution. This paper presents the concept, mechanisms, construction procedures, and field validation of this new method. In situ standard penetration tests were performed in dry mixed columns and cone penetration tests and field vane shear tests were performed in soils between the columns. Plate load tests were subsequently conducted on the treated ground. Excess porewater pressures were monitored during and after the installation of DJM columns with and without PVDs. Field validation was conducted through a pilot highway embankment on very soft clay in Jiangsu, China. Long-term settlement monitoring was carried out for the construction of this highway embankment. Field tests and monitoring clearly showed that the DJM-PVD method performed well in enlarged spacing as compared with the conventional DJM method with close spacing.

Nearest‐neighbor analysis of small features on Mars: Applications to tumuli and rootless cones

Fields of low relief cones, domes, and mounds on Mars have been interpreted as tumuli, rootless cones, and pingos. The spatial distribution of such features can be characterized by their nearest‐neighbor (NN) distances. The NN distributions can provide insight into the physical processes that affected field formation and can possibly provide a future diagnostic of the feature type present on Mars. The conventional approach for analyzing the observed NN distribution is based on the Poisson probability distribution and uses one statistic, c. Our simulations of spatial randomness show that there is an unrecognized bias in c that often leads to erroneous conclusions. Three alternative extensions of the Poisson distribution are proposed here. The first accounts for a minimum threshold on the size of features discerned, the second considers the scavenging of the resources necessary to form neighboring features (e.g., inflation pressurization and subsurface volatiles), and the third models self‐limiting growth of the feature population. Three statistical tests are proposed to improve the conventional NN analysis. We provide the critical regions needed to perform these tests for common sample sizes of these geologic features. Our methodology is applied to tumuli at Mauna Ulu, Hawaii, and conjectured tumuli and rootless cones on Mars. Each example exhibits a different aspect of spatial randomness. These applications suggest avenues for further field and theoretical studies to develop this approach as a remote‐sensing diagnostic.

Fields in Planar Anisotropic Transmission-Line Metamaterials

An electromagnetic analysis of wave propagation in planar anisotropic transmission-line metamaterials is presented. It is shown that a planar square-celled grid, series-loaded with orthogonal inductors and capacitors and positioned over a ground plane, is magnetically anisotropic and may be described in terms of a diagonal permeability tensor. Resonance cone field concentrations form when two of the three diagonal elements of the permeability tensor are opposite in sign and the dispersion surface becomes hyperbolic. A theoretical treatment of an electric line current source excitation shows that the formation of resonance cones is a consequence of the singularity associated with the characteristic surface of a hyperbolic equation. The resonance cone angle, which also describes the direction of local power flow in the region between the grid and the ground plane, can be predicted to a good degree of accuracy. To the authors' best knowledge, the present work also verifies experimentally for the first time that current flow reverses direction across the resonance cone. Experiments, simulations, and analytical calculations of the cone angle are in good agreement