Slow acoustic surface modes through the use of hidden geometry

The acoustic surface modes supported by a partly covered periodic meander groove structure formed in an assumed perfectly rigid plate are investigated. This allows one to create a slower acoustic surface wave than can be achieved with the same uncovered meander structure. By changing the size of the uncovered section the phase and group speeds can be tuned. When the uncovered section of the meander structure is centred along the grooves then the distance along the grooves between neighbouring holes is the same on both sides of the structure so no band gap is observed at the first Brillouin zone boundary due to glide symmetry. This then gives quite linear dispersion. As the uncovered section’s position is moved away from the centre of the meander structure a band gap opens at the Brillouin zone boundary.

Transtensional Flanking Structures

<p><span><span>Flanking structures are deflections of an existing planar fabric (e.g., foliation) alongside a cross-cutting element (e.g., a vein) that can develop in a wide range of rock types, ranging from eclogites to unconsolidated sediments, and also glacier ice, which deforms in temperate glaciers dominantly by dislocation creep and can be considered as a monomineralic metamorphic rock analogue. The finite geometry of flanking structures depends on several factors, such as initial orientation of the cross-cutting element (CE) relative to the shear zone boundary and the kinematic vorticity of the shear zone flow. However, nearly all published examples of flanking structures are interpreted to have formed either under simple shear or transpressional general shear, although in theory flanking structures should also form under transtensional general shear. Here we describe the geometry and development of transtensional flanking structures in glacial ice of the Pasterze, Austria’s largest alpine valley glacier. Mapping was carried out with the aid of high-resolution drone photography and the structures’ attitudes were determined using traditional field techniques. The studied flanking structures develop in an area situated on the orographic right side of the glacier tongue and downstream of a transverse crevasse field. The CEs are closed crevasses containing granular ice and rotate clockwise (when viewed from above), consistent with the large-scale flow field of the glacier. The penetrative foliation, which is regionally parallel to the glacier’s flow direction, is locally deflected alongside the CEs, forming a- (antithetic) and s-type (synthetic) flanking structures. The variability of the cross-cutting elements’ orientation systematically decreases downstream as they rotate into a stable position. We compare the mapped flanking structures with model results of a semi-analytical modified Eshelby solutions for a frictionless CE embedded in an isotropic linear viscous matrix. The model results demonstrate that a variety of a- and s-type flanking structures form under transtensional shear flow for a broad range</span></span><span><span> of </span></span><span><span>kinematic vorticity numbers and initial orientations of the CE but also show that shear bands do not form a stable structure. On the other hand, s-type flanking folds may be diagnostic for transtension because they form stable structures (but still accumulate displacement) when the CE has been rotated parallel to the fabric attractor, which is oblique to the shear zone boundary under transtension. Because of the abundance of shear bands and the lack of s-type flanking structures in natural rocks we speculate that transtensional ductile shear zones rarely occur in nature.</span></span></p><p> </p>

Effect of Distance to Orthogonal Buffer Zone Boundary on Contaminant Detection Well Layout at Solid Waste Impoundment

A modeling investigation examined the effect of nearby buffer zone (property) boundaries on passive groundwater monitoring networks at a hypothetical landfill. Network designs considered the unknown location of a small point source in the landfill's liner, contaminant concentrations simulated in groundwater, and the need to detect a contaminant before its concentration at a buffer zone boundary reached a certain threshold. Several buffer zone boundaries were considered, ranging from 6 m to 51 m downgradient of the landfill's downgradient corner. Monitoring wells in each network were located 5 m downgradient of the landfill's downgradient boundaries. Both the minimum number of wells, and the rate of increase in number of wells, increased with proximity of the landfill's downgradient corner to the buffer zone boundary. Based on out-comes of this study, landfill designers should consider a possible need for many closely-spaced detection wells for small potential point sources and close buffer zone boundaries.

Tectono-Metamorphic Evolution of Serpentinites from Lanzo Valleys Subduction Complex (Piemonte—Sesia-Lanzo Zone Boundary, Western Italian Alps)

In the upper Tesso Valley the folded contact between Piemonte Zone ophiolites and Sesia-Lanzo Zone continental crust is exposed. Here serpentinites, metabasites, calcschists and fine-grained gneisses are deformed by four ductile superposed groups of structures, associated with different mineral assemblages. Different serpentinite lithologies have been recognized and studied in detail. Mylonitic D2 structures are pervasive and mineral assemblages point to re-equilibration at T of 450 ± 50 ∘C and P of 0.8 ± 0.3 GPa, under blueschist/epidote amphibolite-facies conditions. Pre-D2 structures and mineral assemblages are relics within S2 and indicate a re-equilibration under eclogite-facies conditions, at T of 570 ± 50 ∘C and P > 1.8 GPa. Post-D2 occurs under greenschist-facies conditions. Numerical modeling of a subduction zone allows exploration of the geodynamic context in which such PT path could have developed, and to make hypotheses about the possible timing of such a scenario, in agreement with the timing generally proposed for the Alpine subduction and collision. Model predictions indicate that pre-D2 mineral assemblages may have developed during Paleocene at 60–90 km depth and 115–145 km from the trench, or, alternatively, during lower Eocene at ca. 70–90 km depth, and 135–160 km from the trench.

A terrestrial Devonian-Carboniferous boundary section in East Greenland

Terrestrial Devonian-Carboniferous boundary sections are present in the East Greenland Devonian Basin. The boundary section on Stensiö Bjerg developed in deep, distal lake sediments with a pair of lakes representing the boundary. A diverse spore assemblage developed as the lake flooded the basin. Previously abundant spores, notably Retispora lepidophyta, Diducites spp., Rugospora radiata and all forms with bifurcate tips (Ancyrospora and Hystricosporites), then became extinct through just over a metre of section. The spore assemblage is then lost into AOM rich very high TOC% lake sediments. There is a negative δ13CTOC excursion in the Stensiö Bjerg section interpreted to represent the upper part of the positive excursion known from marine sections. The upper lake contains the simple VI spore assemblage of the earliest Carboniferous age. The correlative section on Rebild Bakker was developed in shallow proximal facies without AOM and shows that a Devonian-Carboniferous LN* to VI spore zone boundary can be picked in the lower lake based on the last occurrence of Retispora lepidophyta in an assemblage otherwise dominated by simple spores and Grandispora cornuta. Spores in this VI spore assemblage, particularly Grandispora cornuta, show sculpture malformation that is entirely characteristic of UV-B radiation damage to their DNA prior to deposition of its protective wall layer. This palynological record showing the rapid extinction of major elements within the Late Devonian microflora can be reconciled with accounts claiming there was no mass extinction of plants and spores across the boundary. The palaeobiology of the major spore groups that became extinct is reviewed.

Sill intrusion into pyroxenitic mush and the development of the Lower-Upper Critical Zone boundary of the Bushveld Complex: Implications for the origin of stratiform anorthosites and chromitites in layered intrusions

Layered mafic-ultramafic intrusions are the fossilized remnants of magmatic plumbing systems and provide excellent natural laboratories to investigate the processes of magma differentiation and solidification. The Rustenburg Layered Suite is the plutonic mafic-ultramafic part of the Bushveld Complex of South Africa and it has traditionally been assumed to have formed from an upwardly-aggrading (and in-sequence) crystal pile in a melt-dominated chamber. In this study, we present field and petrological observations, complemented with detailed plagioclase mineral chemistry (molar An, LREE and strontium isotopes) for the first stratiform anorthosite layer (MG3F anorthosite) at the Lower-Upper Critical Zone boundary (LCZ-UCZ) in the eastern limb of the Bushveld Complex. We use these data to test the overarching paradigm of a melt-dominated chamber for the magmatic evolution of the Rustenburg Layered Suite. The MG3F anorthosite is immediately overlain by the MG3 chromitite and both are surrounded by pyroxenite. A distinctive ‘egg-box’ structure, consisting of round pyroxenite blocks mantled by chromitite, marks the LCZ-UCZ boundary, and represents an erosional disconformity at the base of the MG3F anorthosite. The MG3F anorthosite is laterally continuous for 100s km in the eastern limb. In the northern-central sector of the eastern limb, the 1.5 m thick MG3F anorthosite is characterized by non-cotectic proportions of foliated plagioclase and chromite chains that lie parallel to the foliation. The MG3F anorthosite is divisible into two sub-layers on the basis of (i) a compositional break in plagioclase molar An, LREE and strontium isotope composition and, (ii) a peak in chromite mode (up to 12 vol%). In the lower half of the layer plagioclase LREE concentrations increase upward, molar An shows a marginal decrease upward and strontium isotopes are relatively homogeneous (87Sr/86Sr2.06Ga 0.7056-0.7057). In the upper half of the layer, plagioclase LREE concentrations decrease upward, molar An shows a marginal increase upward and strontium isotopes show strong inter- and intra-grain variability (87Sr/86Sr2.06Ga 0.7053-0.7064). Strontium isotopes in interstitial plagioclase in the immediate footwall and hangingwall pyroxenites show similar 87Sr/86Sr2.06Ga values to the MG3F anorthosite and decrease with distance from the MG3F anorthosite. In the southern sector of the eastern limb, the 4 m thick MG3F anorthosite exhibits identical stratigraphic compositional trends in terms of molar An in plagioclase. We infer that the MG3F anorthosite formed by two successive sill-like injections of magma into a resident viscoplastic pyroxenitic crystal mush. An initial pulse of plagioclase-saturated melt underwent in situ fractional crystallization, manifested as upwardly decreasing molar An and upwardly increasing LREE in plagioclase in the lower half of the MG3F anorthosite. Sill intrusion caused deformation of the viscoplastic pyroxenite mush and vortices of superheated liquid generated by frictional viscous heating caused disaggregation of the footwall pyroxenitic mush. Disaggregated blocks of pyroxenitic mush reacted with the superheated liquid (a hybrid chromite-saturated melt) to produce chromite-rich rims at the base of the MG3F anorthosite (egg-box structure). A second sill-like injection of magma then entered the chamber that halted in situ crystallization. This sill was a plagioclase slurry that contained isotopically distinct plagioclase laths compared to those present in the previous sill. The upward increase in molar An of plagioclase, and decreasing LREE, may be explained by the slurry becoming more primitive in melt composition with time. The second sill also caused mush disaggregation and renewed the production of a hybrid chromite-saturated melt. Chromite crystals were then mobilized and injected as slurries at the interface between the sill and resident mush towards the back of the flow, culminating in the development of the MG3 chromitite. Our model for the development of the Lower-Upper Critical Zone boundary questions the existence of a melt-dominated chamber and it has implications for the origin of stratiform anorthosites (and chromitites) in crustal magma chambers.

KONFLIK SOSIAL ANTARA OJEK PANGKALAN DAN GOJEK DI KOTA SURAKARTA

<p>In this research try to raise the theme of conflict research between traditional ojek drivers and GoJek in the city of Surakarta. GoJek is present with various services needed and influential for the community in all activities quickly and efficiently. But on the other hand Gojek is a rival for traditional ojek drivers and the exsistence of GoJek triggers conflict. The purpose of this research is to find out how conflicts occur between traditional ojek drivers and GoJek, what are the forms of conflict, factors that affect conflict and how conflict prevention efforts. The theory used is social conflict theory from Lewis L. Coser. Types of research used in this phenomenon is descriptive qualitative, with data collection techniques through observation, interviews and from secondary data and documentation. The sample uses a purposive sampling technique. With the stipulation of the informants of the traditional ojek drivers,GoJek drivers and traditional ojek and GoJek consumers. The data validity technique uses source triangulation. While the data analysis uses 3 channels namely data reduction, data presentation and drawing conclusions.<strong></strong></p><p>The results showed that the conflict that occurred between traditional ojek driver and GoJek occurred due to the reduced income of ojek, because people preferred to use GoJek. The form of conflict that occurs between conventional ojek and GoJek is divided into two, namely the form of manifest conflict (open) and latent conflict (closed). Forms of manifest conflicts include beatings, quarrels and struggles for attributes. While latent forms of conflict include jealousy and envy and disappointment. Conflict between conventional ojek and GoJek is caused by several factors including land limitations, system differences, and tariff differences. So that the conflict does not continue, several efforts have been made to overcome the conflict, namely the determination of the red zone boundary, warning or warning, and reporting to the authorities.<strong></strong></p>

Spatial Scope of the Regional Hazard Mitigation Plan

This study suggests the spatial scope of the regional hazard mitigation plan, reflecting the feature of natural hazards occurring beyond the administrative zone boundary. The damage caused by natural hazards is not randomly distributed across a space but has interdependent characteristics with the nearby area; therefore, the spatial influence of an adjacent area should be considered. In particular, as damage due to natural disasters is increasing in Korea, it is necessary to establish a regional hazard mitigation plan considering the spatial characteristics of hazards. However, the current hazard mitigation plan sets the scope of the plan based on administrative boundaries. In this study, we measured the vulnerability index of each area using data spanning 10 years from 2008 to 2017 and verified spatial correlations through LISA (Local Indicator of Spatial Autocorrelation). According to LISA analysis, we found that a link exists between si/gun/gu and we identified the spatial characteristics of natural disaster damage. The results confirmed that natural hazard characteristics occur beyond the boundaries of administrative areas.

Fluid wetting infiltration mechanism at the micro-contact zone boundary of rubber–glass interfaces

Purpose This paper aims to clarify the fluid infiltration mechanism at the micro-contact zone boundary of rubber-glass interfaces. Design/methodology/approach An in situ observation instrument was putted up; then the fluid infiltration process was recorded. Experimental results indicated that the fluid infiltration was more likely to occur in a high-contact-area-ratio zone, and the path order of fluid infiltration was first inner normal to the boundary of micro-contact area, and then along the boundary, at last external normal to the direction of boundary. Findings By analysis, capillary pressure is the driven force of fluid at interfaces. The micro-channel size at higher-contact-area-ratio zone is smaller, and the capillary pressure is bigger. Moreover, along different section directions of wedge-shaped region, the horizontal driving force of fluid is different due to difference of conical angle. Originality/value The main contribution of this study is proposing a new wedge-shaped model for better understanding the phenomena of fluid infiltration at rubber contact interfaces. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-10-2019-0453