Flat Segment Research Articles

A novel algorithm to solve for an underwater line source sound field based on coupled modes and a spectral method

A high-precision numerical sound field is the basis of underwater target detection, positioning and communication. A line source in a plane is a common type of sound source in computational ocean acoustics. The exciting waveguide in a range-dependent ocean environment is often structurally complicated; however, traditional algorithms often assume that the waveguide has a simple seabed boundary and that the line source is located at a horizontal range of 0 m, although this ideal situation is rarely encountered in the actual ocean. In this paper, a novel algorithm is designed that can solve for the sound field excited by a line source at any position in a range-dependent ocean environment. The proposed algorithm uses the classic stepwise approximation approach to address the range dependence of the environment and uses the Chebyshev–Tau spectral method to solve for the horizontal wavenumbers and modes of approximately range-independent segments. Once the modal information of these flat segments has been obtained, a global matrix is constructed to solve for the coupling coefficients of all segments, and finally, the complete sound field is synthesized. Numerical experiments using a robust numerical program developed based on this algorithm verify the correctness and usability of our novel algorithm and software. Furthermore, a detailed analysis and test of the computational cost of this algorithm show that it is efficient.

Clay mineral assemblages as indicators of paleoenvironmental and diagenetic dynamics in the Neogene Fiambalá Basin, NW Argentina

Clay mineral characterization is a valuable tool for unraveling the evolution of continental sedimentary basins. The Fiambalá basin is a foreland Andean basin located in the Southwest of the province of Catamarca (Argentina), on the flat subduction segment. In order to characterize its paleoenvironment and post-depositional evolution, petrographic, X-ray diffraction (XRD), and scanning microscopy (SEM-EDS) studies were carried out in detrital and volcaniclastic samples from the Tambería, Guanchín, and Rodados de la Puna Fms. Petrographic and XRD analyses show a predominance of phyllosilicates, quartz, plagioclase, and low proportions of feldspar and anhydrite, sporadic calcite, analcime, heulandite, and hematite. In the XRD fraction <2 μm, minerals from the smectite and illite groups dominate, with lower proportions of chlorite and kaolinite. An analyzed tuff level presents smectite solely in this fraction. The textural-compositional analyses of SEM-EDS show that illite and chlorite have a detrital origin. Their preservation would be consistent with the dominance of an arid climate in the region during the erosion and deposition of material from the source areas. The smectites are of the magnesium-rich beidellite-montmorillonite type and, together with the zeolites would be authigenic as a product of the alteration of both the volcanic material and magnesian detrital phases (chlorite and biotite), possibly under the influence of an alkaline environment related to the arid climate. From a thermal point of view, the presence of smectite throughout all stratigraphic succession allows interpreting maximum temperatures that, even in the deepest levels of the basin, inhibit the development of prograde phases (such as smectite/illite and smectite/chlorite mixed-layered) and allow the preservation of smectite. Based on the authigenic clays present in the basin, paleogeothermal gradients of between 13 and 18 °C/km (considered a fill of 4000 m thick) and between 8 and 11 °C/km (considered a fill of 6000 m thick) could be estimated.

Automated detection and removal of flat line segments and large amplitude fluctuations in neonatal electroencephalography.

BackgroundArtefact removal in neonatal electroencephalography (EEG) by visual inspection generally depends on the expertise of the operator, is time consuming and is not a consistent pre-processing step to the pipeline for the automated EEG analysis. Therefore, there is the need for the automated detection and removal of artefacts in neonatal EEG, especially of distinct and predominant artefacts such as flat line segments (mainly caused by instrumental error where contact between electrodes and head box is lost) and large amplitude fluctuations (related to neonatal movements).MethodA threshold-based algorithm for the automated detection and removal of flat line segments and large amplitude fluctuations in neonatal EEG of infants at term-equivalent age is developed. The algorithm applies thresholds to the absolute second difference, absolute amplitude, absolute first difference and the ratio between the frequency content above 50 Hz and the frequency content across all frequencies.ResultsThe algorithm reaches a median accuracy of 0.91, a median hit rate of 0.91 and a median false discovery rate of 0.37. Also, a significant improvement (≈10%) in the performance of a four-stage sleep classifier is observed after artefact removal with the proposed algorithm as compared to before its application.SignificanceAn automated artefact removal method contributes to the pipeline of automated EEG analysis. The proposed algorithm has shown to have good performance and to be effective in neonatal EEG applications.

Association of Quantitative ST- Segment Depression with Early Mortality among Naive Patients of Non- ST- Segment Elevation Acute Coronary Syndrome

Objective: To determine the association of quantitative ST– segment depression with early mortality within 30 day in patients with first non-ST – segment elevation acute coronary syndrome (NSTE-ACS). Methodology: This descriptive case series study was conducted at the cardiology department of LUMHS, from October 2016 to March 2017. Patients with NSTE-ACS and positive cardiac biomarkers, patients older than 25 years and both genders admitted to CCU were included. The ST-Segment depression was assessed on 12 lead electrocardiography. The ST segment is the line that starts from the end of the QRS complex (J wave) to the beginning of the T wave. Normally ST segment is straight line and, isoelectric to base line, ST segment depressed below isoelectric line is said ST depression, down sloping or flat depressed ST segments indicate coronary ischemia, more than 0.5 mm ST depression significant for ischemia. All patients were followed for 30-days for early mortality. All information obtained was recorded on the study Performa. Results: A total of 148 cases with acute myocardial infarction were integrated; the patient's average age was achieved as, 42.5±5.43 years, and males were in the majority 96(64%). On electrocardiography, ST-Segment depression was found in 60.13%, which is further divided into 0.5mm, &gt;0.5-0.9 mm, &gt;1-1.9 mm, and &gt;2 mm with percentages of 12.83%, 22.29%, 16.89%, and 8.12%, respectively. Short term mortality was significantly associated with the severity of ST segment depression score (p-value 0.001). Conclusions: In the study conclusion, the severity of ST-Segment depression score was observed to be significantly correlated with short term mortality (30-day) in cases with early NSTE-ACS.

Low-Noise Optical Accelerometers: Bridging the Gaps among Geophones, Accelerometers, and Broadbands in a Deep Borehole

Abstract Earthquakes and other seismic sources produce waves with frequency content spanning many orders of magnitude. Recording a broader frequency band of interest has historically required deploying multiple instruments designed to work the best within limited, overlapping frequency ranges. Here, we detail a 300 m deep borehole deployment of a sensor package, including three new optical accelerometers that can potentially replace many dedicated instruments with a single, low-noise sensor. These instruments are designed with a flat frequency response from 0.005 to 1500 Hz, spanning the flat response segments of broadband sensors and geophones, as well as a low-noise floor and high sensitivity. The sensors have been functioning normally for over four years, fully grouted at depths of &amp;gt;100 m. Year-long power spectral density (PSD) profiles show that the optical accelerometers have a lower noise floor than a colocated geophone for all frequencies, with 20 dB noise reduction at 250 Hz. PSD comparisons to a broadband sensor installed at the surface show a 5–30 dB noise reduction for the optical accelerometer above 1 Hz, although this is likely due, in part, to the broadband sensor being subjected to much higher surface noise. At periods &amp;gt;5 s, the broadband sensor shows up to 20 dB lower noise than the optical accelerometer, which in turn has up to 50 dB lower noise floor than the colocated geophone. Finally, modeling the Brune displacement spectrum for theoretical seismicity within 1 km of the borehole shows that the optical accelerometers could potentially deliver a detection threshold improvement of one magnitude unit relative to the colocated geophone.

COMPOSITE GEOMETRICALLY SMOOTH CUBIC HERMITE CURVES IN SPACE AND ON THE PLANE

The article considers constructive algorithms for creating compound curves using parametric cubic equations. The possibilities of modern computer technology and systems of computer mathematics make it possible to implement algorithms of graph analytics using fractional rational parametric equations of the fifth, seventh and higher orders. The article considers a constructive algorithm for creating a compound cubic curve passing through given points with direction vectors specified in these points. Direction vectors can be used for monitoring the shape of a constructed curve. At the junction points of the cubic curve segments, second order geometric flatness is ensured, due to the equicontinuity of the camber and curvature. The required curve is made sequentially by attaching a new segment to the previous segment. Each segment must comply with the same group of geometric conditions: frequency at boundary points, contact with direction vectors, fixed curvature at one or both boundary points. The article proposes a constructive algorithm for constructing a three-dimensional or flat cubic Hermite segment that satisfies this group of conditions. The problem of constructing a compound geometrically smooth curve boils down to sequential construction of cubic segments using the proposed algorithm. The method proposed in the article for constructing a smooth compound curve allows: to shape a spatial curve with a given curvature at the starting point; to construct a plane curve with given radii of curvature at the nodes (in particular, with zero curvature at the nodal points); insert a cubic segment into a break in a curved line; find a smooth (without a break in a curve) conjugation of curvilinear and rectilinear sections of the constructed line. A distinctive feature of the algorithm is the significant use of reference tools and design capabilities of three-dimensional computer graphics. All necessary actions are performed using a desktop calculator and any software product that supports three-dimensional graphics (Compass-3D, AutoCAD, etc.). Five transparent examples of constructing flat and spatial composite cubic curves of the second order of smoothness are considered.

The topographic signature of temperature-controlled rheological transitions in an accretionary prism

Abstract. The local topographic slope of the accretionary prism is often used together with the critical taper theory to determine the effective friction on subduction megathrust. In this context, extremely small topographic slopes associated with extremely low effective basal friction (μ≤0.05) can be interpreted either as seismically locked portions of megathrust, which deforms episodically at dynamic slip rates or as a viscously creeping décollement. Existing mechanical models of the long-term evolution of accretionary prism, sandbox models, and numerical simulations alike, generally do not account for heat conservation nor for temperature-dependent rheological transitions. Here, we solve for advection–diffusion of heat with imposed constant heat flow at the base of the model domain. This allows the temperature to increase with burial and therefore to capture how the brittle–ductile transition and dehydration reactions within the décollement affect the dynamic of the accretionary prism and its topography. We investigate the effect of basal heat flow, shear heating, thermal blanketing by sediments, and the thickness of the incoming sediments. We find that while reduction of the friction during dewatering reactions results as expected in a flat segment often in the forearc, the brittle–ductile transition results unexpectedly in a local increase of topographic slope by decreasing internal friction. We show that this counterintuitive backproduct of the numerical simulation can be explained by the onset of internal ductile deformation in between the active thrusts. Our models, therefore, imply significant viscous deformation of sediments above a brittle décollement, at geological rates, and we discuss its consequences in terms of interpretation of coupling ratios at subduction megathrust. We also find that, with increasing burial and ductile deformation, the internal brittle deformation tends to be accommodated by backthrusts until the basal temperature becomes sufficient to form a viscous channel, parallel to the décollement, which serves as the root to a major splay fault and its backthrust and delimits a region with a small topographic slope. Morphologic resemblances of the brittle–ductile and ductile segments with forearc high and forearc basins of accretionary active margins, respectively, allow us to propose an alternative metamorphic origin of the forearc crust in this context.

Dispersionless transport in washboard potentials revisited

We reassess the ‘dispersionless transport regime’ of Brownian particles in tilted periodic potentials. We show that the particles exhibit normal diffusive motion right after transitioning into the running state dragged by the constant bias force. No special transient dynamics appears, contrary to conjectures in the previous studies. The observed flat segment in the dispersion evolution curve is solely due to the broad spatial distribution of particles formed in the early superdiffusion stage. We quantitatively describe the whole evolution of the distribution function during superdiffusion and the transition to the normal diffusion that follows, in the framework of the two-well potential in the velocity space model. We show that the superdiffusion exponent is α = 3. The duration of the ostensible ‘dispersionless regime’ is derived analytically. It is shown to diverge exponentially as the temperature decreases to zero.

Insight into crush performance comparison of composite profiles and flat plates

This study investigates the correlation between the specific energy absorption (SEA) behavior of various right-angled profiles, e.g., those with angle-, channel-, and square geometries. The behavior is also compared with that of flat plates and circular tubes. The study proposes an approach, which allows for utilizing the results obtained from a small number of profile crush tests to predict the crush properties of other profiles. The proposed approach is to separate the effect of the resistance at the profile corners from the crushing force of the profile flat segments. A generic crush property of a corner and that of a flat segment, calculated from crush-testing a few profile specimens, has been utilized to predict the crush properties of right-angled profiles with different shapes and dimensions. The predicted crush properties of numerous profiles of different shapes and sizes proved to be practically identical to those obtained experimentally. The calculated crushing SEA of the profile flat segments has also proved to be identical to that of flat plates. • Predicting the crush properties of right-angled composite profiles with different shapes from testing other profiles. • Separating the corner's resistance to tearing from the crushing force of profile flat segments. • Predicting profile properties from corner tearing resistance and crushing properties of flat segments. • Specific energy absorption of profile flat segments proved to be identical to those of flat plates. • Circular tubes show different tearing mechanisms and geometry-dependent occurrences.

Monte Carlo simulations of the self-assembly of hierarchically organized metal-organic networks on solid surfaces

The coordination-driven self-assembly of two-dimensional (2D) supramolecular architectures is a convenient method of rational construction of one-atom-thick nanomaterials with desired topology, intriguing physicochemical properties and high cognitive value. In this work, we use coarse-grained Monte Carlo (MC) computer simulations to study the self-assembly of functional bridging ligands with mononuclear metal centers on a triangular lattice. Particularly, we focus on the role of anisotropic, reversible ligand → metal coordinate bonds in the bottom-up formation of hierarchically organized metal-organic networks composed of star-shaped and rod-like linkers (representing real organic molecules) and trivalent metal atoms. In our model π aromatic ligands were modeled in a simplified way as a collection of flat, rigid, and interconnected segments with properly encoded short-ranged interactions. Depending on the composition of the investigated overlayers, we observed the spontaneous formation a cascade of openwork (co)crystals with a hierarchical structure, controllable chirality and scalable morphological properties like porosity, connectivity, density, etc. Our theoretical findings can pave the way for the experimental fabrication of the novel surface-confined metal-organic networks (SMONs) in which anisotropic coordinate bonds play a decisive role.

Three‐Dimensional Variation of the Slab Geometry Within the South American Subduction System

AbstractSubduction of the Nazca plate results in the uneven distributions of earthquakes and arc volcanoes along the South America's western margin. Here, we construct a high‐resolution shear‐wave velocity model from immediately offshore to the backarc in South America, using advanced full‐wave ambient noise tomography. Our new model confirms and provides further constraints on three major features, including (a) extensive low‐velocity anomalies within the continental crust, (b) two high‐velocity flat slab segments located beneath southern Peru and central Chile, and (c) complex slab geometry at flat‐to‐normal transitional subduction. The flat slab segments roughly correlate with the volcanic gaps but not with the seismicity gaps. We suggest that variations of slab geometry along strike and down dip have significantly modified the flow patterns within the mantle wedge. Subduction of oceanic ridges has altered the slab dehydration processes, which can influence the distribution of arc volcanism and the occurrence of intermediate‐depth earthquakes.

Flexural behavior of hybrid FRP-concrete-steel double-skin tubular beams with PBL shear connectors

Hybrid fiber-reinforced polymer (FRP)-concrete-steel double-skin tubular beams (DSTBs) have a very ductile load–deflection response but may experience a relatively large slip between the concrete and the inner steel tube. Perfobond (PBL) shear connectors, which have a perforated steel plate with transverse reinforcing bars passing through the perforations, are widely used to enhance the bond performance between the concrete and the steel section for composite beams. In this study, for the first time, PBLs are employed in hybrid DSTBs to tackle the excessive slip problem. Four-point bending tests are performed on eight hybrid DSTBs with two cross-sectional shapes of inner steel tubes, two types of PBL plates, and four different PBL arrangements. Results identify that a typical load–deflection curve consists of three segments: an initial linear segment up to the yielding of steel tube bottom surface, a hardening segment, and an almost flat load plateau segment. The slips between concrete and steel tubes increase in a faster rate when yielding occurs at steel tube bottom surface. Overall, specimens with PBLs placed along the full span have the smallest slips (around 0.2 mm), whereas maximum slips occur for specimens with foams inserted at the spacings between PBLs (i.e., 2.33 and 0.59 mm for specimens with a circular and a square steel inner tube respectively). PBL shear connectors have efficiently reduced the slip, when comparing with the results of some hybrid DSTBs in previous studies.

Variscan granitic magmatism in the Western Carpathians with linkage to slab break-off

The Variscan basement within the Western Carpathian Alpine architecture generally consists of metaluminous/peraluminous tonalite/granodiorite massifs and high-grade metamorphic complexes of metapelites, metaultramafites, and metabasites with relics of eclogites. Unfortunately, the Variscan crystalline basement of the Western Carpathians is only fragmentally exposed. Therefore, the proposed geodynamic evolutionary model for the Variscan granites of the Western Carpathians is primarily based on granite data from the Malá Fatra Mts. with additional dating from the High Tatra Mts. The oldest magmatic age of 362 ± 4 Ma in the Malá Fatra horst was recorded in diatexites from a high-grade metamorphic complex, which is related to crustal anatexis during Variscan subduction. Subsequent collisional event and break-off of the subducted slab promoted exhumation of the diatexites within the high grade metamorphic complex and intrusion of 353 ± 3 Ma old Tournaisian tonalite. Intensive heat input after slab break-off from the rising asthenosphere generated melting of the lower crust and extensive calc-alkaline, Mg-rich granitic magmatism in a short time span from 347 ± 4 to 342 ± 3 Ma. These Visean granitic rocks caused thermal overprint on the roof metamorphic rocks, including diatexites and Tournaisian tonalites at ca. 348 ± 5.6 to 342 ± 3 Ma. The Visean granite formation was controlled by the mixing of hot magmas, which is indicated by the presence of composite oligoclase/andesine plagioclase with preserved labradorite cores, alkali feldspars with Na2O ≥ 2 wt%, zoned apatite, the presence of antiperthite, and quartz ocelli. Elevated contents of mantle-derived elements like V, Ni, Cr, Ba, high Sr/Y ratio of ~44, steep LREE and flat HREE segments of chondrite-normalised patterns document adakite-like feature of the investigated granitic rocks which resulted from melting of a mixed lower-crustal and mantle sources and crystallisation in the presence of garnet. Unusual abundance of Fe–Ti oxides in granodiorites with magmatic cooling temperatures of 735–756 °C supports high-T input from mantle. In the High Tatra Mts., diorite xenolith shows the age of 359.2 ± 3 Ma, and its host granodiorite the age of 350.1 ± 2.6 Ma. The diorite contains acicular zircons, which points to rapid exhumation. Stubby zircon of the host granodiorite shows regular, oscillatory zoning controlled by a gradual temperature decrease. The non-comagmatic relationships between diorite and host granodiorite are indicated also by a difference in zircon Th/U ratio, which is 0.2 for the host granodiorite, but 1.0 for the diorite on average. The presented data show that slab break-off could have been a mechanism that promoted Variscan granitic magmatism in the Western Carpathians.

Закономерности образования карбидов титана и вольфрама из продуктов электровзрывного разрушения проводников

A series of electrical explosions in propane-butane of single and strand-connected Ti and W conductors with various diameters was carried out. Electrophysical characteristics of the explosion revealed that resistive heating of conductors is characterized by two monotonically ascending sections on the voltage – current curves separated by a flat segment (plateau), which corresponds to relatively stable electrical resistivity of refractory metals in the liquid state. The energy deposited by changing the power input into the conductor during its resistive heating, which can be higher or lower than its sublimation energy and can be regulated by changing the external adjustable parameters of the discharge circuit, is a key indicator determining the structural-phase state of destructed and chemically synthesized products after the explosion. The conditions are achieved under which micro- and nano-sized powder products do not contain residual metals and consist of carbide phases completely (TiC with an average microhardness of 29580 MPa as a result of the titanium explosion and a mixture of W2C+WC1-х, in which stabilized high-temperature non-stoichiometric cubic carbide WC1-x dominates, with an average microhardness of 16770 MPa as a result of tungsten explosion).

Unraveling the petrogenesis of the Miocene La Peña alkaline intrusive complex, Mendoza, Argentina: Insights from the study of the disregarded late dykes

The La Peña Complex (LPC) is a silica-undersaturated alkaline potassic intrusive system, with a subduction-related signature, linked to the early Miocene retroarc magmatism of the Southern Central Andes, in the flat slab segment. The LPC is composed of several intrusions, predominantly plutonic (clinopyroxenite, malignite and syenite), cross cut by a voluminous swarm of radial and annular dikes with mostly volcanic-subvolcanic textures and variable compositions (foid-bearing alkali feldspar trachyte, trachyte, benmoreite, ledmorite, syenite, tephrite, tephriphonolite and alkaline lamprophyre). In the TAS classification these rocks plot in the alkaline series covering a wide spectrum of compositions following two different trends: 1) alkaline (potassic) strongly silica-undersaturated series, from tephrite, phonotephrite to tephra-phonolite, and 2) mid-alkaline, less silica-undersaturated series, ranging from basaltic trachyandesite to trachyandesite (benmoreite), and trachyte. Dikes from the alkaline series show higher K2O/Na2O ratios and Sr, La, Ce, contents compared to those from the mid-alkaline series. Rocks of the alkaline series are richer in K-feldspar, sodalite, leucite (pseudoleucite), biotite, potassic-ferro-pargasite and garnet than the less silica-undersaturated (trachytic) rocks, reflecting a stronger alkaline potassic affinity. A review of geochemical, isotopic and mineralogical data, and a new geochemical modeling performed on the LPC dikes, suggests that both trends represent separated magmatic series that evolved from two different parental magmas lodged ∼30 km deep in the crust. Our results suggest that the compositional variations observed in LPC dikes, cannot be explained by a simple magmatic evolution via fractional crystallization from a unique parental magma, and that an assimilation and fractional crystallization (AFC) process is required to explain some compositional differences. Our results suggest an upper crustal contaminant (evolved rocks) with a Grenvillian isotope signature. On the other hand, analyses of feldspar crystals from the tephriphonolitic dikes indicate local mixing effects, between an evolved tephriphonolitic melt and a less evolved and hotter mafic magma.The origin of both parental magmas could be explained by different melting degrees of the same mantle source, a phlogopite-bearing spinel lherzolite metasomatized by subduction derived fluids. We consider as a possible explanation that alkaline and coeval calc-alkaline magmatism in this part of the Andes, is due to local heterogeneities in the mantle source, and different degrees of partial melting Similar isotopic compositions of the LPC dikes, with those from other Miocene magmatic occurrences with arc-signature and similar age (e.g., Paramillos de Uspallata, Las Máquinas basalt, Abanico Fm and Farellones Fm) suggest an analogous mantle source for these rocks, from arc and retroarc in the Pampean flat slab regions. However, our results suggest that the isotopic trend contamination of LCP is different from that of Paramillos de Uspallata and other arc rocks of the Southern Volcanic Zone. The crustal contaminant of LPC possibly has another composition that those of Precordillera and Principal Cordillera Miocene rocks. The age of LPC rocks (∼19 Ma) and their arc-related signature agree with the eastward broadening of the arc magmatism between 17 and 19 Ma in this part of the flat slab. According to our interpretations, the LPC is a singular occurrence of two alkaline magmatic series on destructive plate margins, associated with calc-alkaline magmatism, occurring closely in time and space.

Nonmonotonic quantum phase gathering in curved spintronic circuits

Spin carriers propagating along quantum circuits gather quantum spin phases depending on the circuit's size, shape, and spin-orbit coupling (SOC) strength. These phases typically grow monotonically with the SOC strength, as found in Rashba quantum wires and rings. In this work we show that the spin-phase gathering can be engineered by geometric means, viz. by the geometric curvature of the circuits, to be non-monotonic. We demonstrate this peculiar property by using one-dimensional polygonal models where flat segments alternate with highly curved vertices. The complex interplay between dynamic and geometric spin-phase components -- triggered by a series of emergent spin degeneracy points -- leads to bounded, global spin phases. Moreover, we show that the particulars of the spin-phase gathering have observable consequences in the Aharonov-Casher conductance of Rashba loops, a connection that passed unnoticed in previous works.

Rapid Assembly and Eruption of a Shallow Silicic Magma Reservoir, Reyðarártindur Pluton, Southeast Iceland

AbstractAlthough it is widely accepted that shallow silicic magma reservoirs exist, and can feed eruptions, their dynamics and longevity are a topic of debate. Here, we use field mapping, geochemistry, 3D pluton reconstruction and a thermal model to investigate the assembly and eruptive history of the shallow Reyðarártindur Pluton, southeast Iceland. Primarily, the exposed pluton is constructed of a single rock unit, the Main Granite (69.9–77.7 wt.% SiO2). Two further units are locally exposed as enclaves at the base of the exposure, the Granite Enclaves (67.4–70.2 wt.% SiO2), and the Quartz Monzonite Enclaves (61.8–67.3 wt.% SiO2). Geochemically, the units are related and were likely derived from the same source reservoir. In 3D, the pluton has a shape characterized by flat roof segments that are vertically offset and a volume of &gt;2.5 km3. The pluton roof is intruded by dikes from the pluton, and in two locations displays depressions associated with large dikes. Within these particular dikes the rock is partially to wholly tuffisitic, and rock compositions range from quartz monzonite to granite. We interpret these zones as eruption‐feeding conduits from the pluton. A lack of cooling contacts throughout the pluton indicates rapid magma emplacement and a thermal model calculates the top 75 m would have rheologically locked up within 1,000 years. Hence, we argue that the Reyðarártindur Pluton was an ephemeral part of the wider plumbing system that feeds a volcano, and that timeframes from emplacement to eruption were rapid.

Design strategy for optimizing the bandwidth of the hardening vibration generator with customized response

For popular nonlinear vibration energy harvesting systems, such as the Duffing type or the piecewise type, the stiffness profile generally follows a specific explicit expression. The response is thus determined by the coefficients of the stiffness expression and the performance trade-off between high- and low- frequency ranges always exists. To break the restriction, the non-typical nonlinear system whose stiffness profile is arbitrarily variable without an explicit expression is a promising approach. This paper proposes a novel design strategy for the hardening system to optimize the bandwidth. A customized response composed of the starting segment and the flat transition segment is firstly sketched for a target frequency range. The first segment is adopted from a linear oscillator with the rapidly increasing response while the second segment is a straight line connecting the response peak at the high cut-off frequency to the starting segment at the low-end frequency. By finding out the flattest straight line for the transition segment, the high-frequency response is ensured and the low-frequency response is maximized at the same time. Experimental tests on an elaborated prototype show that the designed generator can achieve the optimized response as desired. The superior performance due to the performance enhancement in the low-frequency range is confirmed by comparison with literature generators.

Biomechanical Analysis of Cadaveric Thoracic Aorta Zones: The Isthmus is the Weakest Region

The thoracic aorta is a site of multiple pathological processes, such as aneurysms and dissections. When considering the development of endovascular devices, this vessel has been extensively manipulated because of aortic diseases, as well as to serve as a route for procedures involving the head and neck vessels. Therefore, the aim of the present study was to obtain biomechanical experimental information about the strength and deformability of this vessel. Thirty-one thoracic aorta specimens were harvested during the autopsy procedure. They were carefully dissected and transversally sectioned according to Criado's aortic arch map landing zones (0 to 4). The supra-aortic trunks were removed, and the aortic rings were opened in their convexity, which resulted in flat tissue segments. Four millimeter-wide strips were prepared from each zone after which they were attached to a clip system connected to the INSTRON SPEC 2200 device, which was responsible for pulling the fragment up to its rupture during the uniaxial tension test. The INSPEC software was used to coordinate the test, and data management was conducted via the SERIES IX software. The biomechanical variables that were measured included failure stress, failure tension, and failure strain. When comparing the five segments from all 31 aortas, three different strength levels were observed. Zones 0 and 1 exhibited the highest failure stress and failure tension values, followed by Zones 2 and 4. Zone 3 (aortic isthmus) was the weakest segment that was tested when compared to the stress and tension of Zones 0 and 1 (P < 0.001), the stress and tension of Zone 2 (P=0.005 and P=0.002, respectively) and the stress and tension of Zone 4 (P=0.023 and P=0.006, respectively). Among donors > 65 years-old, women presented significantly weaker descending aortas than men in regards to stress (P=0.049) and tension (P=0.014). Among male donors, the elderly donors presented significantly stiffer aortic walls and weaker ascending (P=0.029 for stress) and descending (P=0.004 for stress; P=0.031 for tension) aortas than younger men. Uniaxial tensile strength tests revealed that the thoracic aorta is a very heterogeneous vessel. Isthmus frailty may add to the understanding of the pathophysiology of some aortic diseases that commonly compromise this region. The lower strength that was verifiedin some aortic segments from elderly donors may contribute to the genesis of some thoracic aorta diseases among that group of donors. These data can contribute to the development of new endovascular devices that are specifically designed for this vessel.

Paleoseismological Findings at a New Trench Indicate the 1714 M8.1 Earthquake Ruptured the Main Frontal Thrust Over all the Bhutan Himalaya

The 1714 Bhutan earthquake was one of the largest in the Himalaya in the last millennium. We show that the surface rupture caused by this earthquake extended further to the east than previously known, it was at least 175 km long, with slip exceeding 11 m at our study site. The age of the surface rupture was constrained by a combination of radiocarbon and traditional optically stimulated luminescence dating of affected river sediments. Computations using empirical scaling relationships, fitting historical observations and paleoseismic data, yielded a plausible magnitude of Mw 8.1 ± 0.4 and placed the hypocentre of the 1714 Bhutan earthquake on the flat segment of the Main Himalayan Thrust (MHT), the basal décollement of the Himalayan orogen. Calculations of Coulomb stress transfer indicate that great earthquakes along the leading part of the MHT would cause surface rupture. In contrast, distal earthquakes may not immediately trigger surface rupture, although they would increase the stresses in the leading part of the MHT, facilitating future surface-rupturing earthquakes. Frontal earthquakes would also transfer stress into the modern foreland basin facilitating southward propagation of the MHT as a blind basal décollement. In conclusion, studies of surface-rupturing events alone likely underestimate the seismic slip along the Himalayan megathrust.