Steep Sides Research Articles

The vertical structure and kinematics of grand design spirals

Abstract We use an N-body simulation to study the 3D density distribution of spirals and the resulting stellar vertical velocities. Relative to the disc's rotation, the phase of the spiral's peak density away from the mid-plane trails that at the mid-plane. In addition, at fixed radius the density distribution is azimuthally skewed, having a shallower slope on the trailing side inside corotation and switching to shallower on the leading side beyond corotation. The spirals induce non-zero average vertical velocities, 〈Vz〉, as large as 〈Vz〉 ∼ 10–20 km s−1, consistent with recent observations in the Milky Way. The vertical motions are compressive (towards the mid-plane) as stars enter the spiral, and expanding (away from the mid-plane) as they leave it. Since stars enter the spiral on the leading side outside corotation and on the trailing side within corotation, the relative phase of the expanding and compressive motions switches sides at corotation. Moreover, because stars always enter the spiral on the shallow density gradient side and exit on the steeper side, the expanding motions are larger than the compressing motions.

Terahertz metal bi-grating fabrication using ultra-thick photoresist process

As a key part of terahertz vacuum electronic device, metal grating cant be fabricated using traditional methods due to its tiny dimension. The photoetching process of metal bi-grating for radiation source at some terahertz band was presented. The influence of the procedure (including substrate preparation, spin-coating, pre-bake, exposure, post-bake and developing) on photoetching was analyzed experimentally. The problems such as film drop and crack, films combination and the photoresist remaining at gaps which were caused by thick film and high aspect ratio, were solved by the optimizing the process parameters. Finally, a good film microstructure with steep side wall and smooth surface was achieved, with a thickness of 700 m and an aspect ratio of 14. The work presented in this paper provides a technological guide to the similarly related project.

Flow separation and shear stress over angle-of-repose bed forms: A numerical investigation

Large asymmetric bed forms commonly develop in rivers. The turbulence associated with flow separation that develops over their steep lee side is responsible for the form shear stress which can represent a substantial part of total shear stress in rivers. This paper uses the Delft3D modeling system to investigate the effects of bed form geometry and forcing conditions on flow separation length and associated turbulence, and bed form shear stress over angle-of-repose (30° lee side angle) bed forms. The model was validated with lab measurements that showed sufficient agreement to be used for a systematic analysis. The influence of flow velocity, bed roughness, relative height (bed form height/water depth), and aspect ratio (bed form height/length) on the variations of the normalized length of the flow separation zone, the extent of the wake region (where the turbulent kinetic energy (TKE) was more than 70% of the maximum TKE), the average TKE within the wake region and the form shear stress were investigated. Form shear stress was found not to scale with the size of the flow separation zone but to be related to the product of the normalized extent of the wake region (extent of the wake region/extent of water body above the bed form) and the average TKE within the wake region. The results add to understanding of the hydrodynamics of bed forms and may be used for the development of better parameterizations of small-scale processes for application in large-scale studies.

Enabling Resist Processing Technologies for Advanced Packaging

The increasing adoption of advanced wafer-level packaging (WLP) technologies and high density interposer concepts clearly reflect the permanent need for form factor reduction, smaller process geometries and higher-count I/O on ICs. Currently, several strategies are being pursued to achieve these goals. The most promising approaches are summarized under the concept of three-dimensional integrated circuits (3D-IC) and three-dimensional wafer level packaging (3D-WLP) technology. A key component for 3D device integration schemes is the requirement of vertical through-silicon-via (TSV) interconnections that enables electrical through-chip communication through stacks of vertically integrated layers on the wafer scale. Ultimately, the use of TSVs also enables higher performance and smaller package sizes. In order to realize TSV connections, a series of process steps is required such as the thinning and bonding of the wafer to a carrier prior to the formation of through-wafer vias, followed by the passivation and metallization of the vias. Despite the potential benefits associated with the integration of TSVs also significant challenges have to be overcome. One of the greatest challenges for present and even more for upcoming TSV design strategies still remains the processing of photoresist and other functional polymers at and within TSV geometries. To this day, it is still very difficult to achieve a conformal polymer coating in deep cavities, along steep side walls and especially within the extreme aspect ratios of TSV. Mainly this is due to the fact that standard surface coating methods such as spin coating were just not developed to meet the requirements posed by these high aspect ratio microstructures. New and innovative approaches are needed to meet these new challenges. Spray coating is one of the most promising technologies to overcome current barriers. However, even most of the available spray deposition equipment is facing its limits with steadily decreasing via diameters and increasing aspect ratios on the other hand. Successively, the multitude of these challenging technological developments in the 3D-IC and wafer-level packaging area has created the demand for innovative manufacturing approaches, new equipment and related tools. Herein we present our new EVG ®NanoSprayTM coating technology with unique capabilities to overcome the present limits of conformal resist coating over extreme topography. We demonstrate one particularly promising application for conformal polymer coatings; as an annular lining at the interface between the conducting metal filling in the TSV and the silicon wafer. The intrinsic properties of the polymer allow a TSV design solution that is more forgiving on coefficient of thermal expansion (CTE) mismatch-induced stress between the silicon substrate and the interfacing metal. Consequently, this new type of polymer buffered TSV interconnect design promises to significantly reduce thermal stress-induced TSV delamination as one of the dominant failure modes for 3-D interconnects. We further demonstrate the application of EVG ®NanoSprayTM as enabling coating technology for llithographic processing of conformal coated TSVs. The patterning of thin photoresist layers at the bottom of vias and along the steep sidewalls of deep cavities allows for more degrees of freedom in electrical contact formation. The presented EVG ®NanoSprayTM coating technology opens new dimensions in advanced wafer level packaging and provokes reconsidering prevailing limitations in interconnect design.

Excerpt from Brothers Under a Same Sky

Excerpt from Brothers Under a Same Sky Gary Pak (bio) Around 1422 the North Koreans attacked, running over several small hills. George Company was forced to retreat into a narrow valley. There was no other place to go. George Company was trapped. Fierce fighting ensued, with American losses mounting. The company was pushed against a cliff. Here they dug in, hoping for a miracle. The North Koreans were persistent in their unflinching assault. Air power was radioed in, and for a short while the friendly forces were successful in stopping the advance of the North Korean front. Then the North Korean army sent another attack, this time cutting off George Company from the rest of the U.S. forces. By 2000 hours, the main brunt of the attacks ceased, and though sporadic shelling and gunfire continued through the night, nightfall became a savior for George Company, letting the men recuperate temporarily until the break of dawn. They had climbed a narrow trail up a steep side of the valley to where the trail widened but was covered with a large boulder and other rubble, loosened from above by the heavy bombardment. Thoreau was killed below while trying to retreat with the Browning. The only other survivors of the attack that Han knew were Jenkins and Pirelli, but he had lost track of Jenkins. Perhaps he was dead, too. [End Page 27] Pirelli was leaning against the boulder, his eyes wide and surprisingly, Han thought, scared. Han wanted to get away from him, but it would be stupid, he told himself, to move from a relatively safe place. And they were still on the same side. So he stayed next to Pirelli, crouching, with his back too against the granite boulder, the coldness of the rock seeping into his spine as he listened to the bombardments and their echoes off the valley walls. Perhaps the others in the squad were scattered on the hillside nearby, but he did not know. Most of them, he was sure, were dead. He decided to pray. Halfway through the prayer he was interrupted by Pirelli. “Han . . . hey, you there?” “Yes? What is it?” “You know, I don’t think we’re going to make it out of here. This is it. This is my last night. Yours.” “You have to have faith.” “Don’t give me that Jesus talk. I had enough of that bullcrap.” “God will help those who help himself.” “I said shut the crap up! You’re preaching to the Pope. I had enough of that religious talk. I had that ever since I was born. Don’t talk to me about this.” “But if you pray, you will have faith.” “That’s bullshit, man. Bullshit. God listens to people who have money, not the poor guy who has nothing. He’s not looking down at me and feeling sorry for me. If he was, I wouldn’t be here in the first place. I’m here in this God-forsaken place because I don’t have a father and a mama, and anyway if I did they would be too poor to make a political contribution.” “Why are you full of hate?” “What? What you fucking talking about, Chink?” “I’m not Chinese. I’m Korean.” “Then mind your own business, gook.” “That’s not my name.” “Fuck you.” He pointed his rifle at Han’s head, his eyes bloodshot and his hands shaking. “I’ll blow your head off in a [End Page 28] second, you gook fuck! Fuck off! I should do it. You’re not worth the shit you shit. You’re a fucking gook. That’s what you are. A fucking gook. You’re no American. Damn, of all people to be stuck with at the end of my life. Don’t bother me with your Jesus talk.” Pirelli lowered his rifle. Han crawled to the other side of the boulder, away from Pirelli’s wild eyes, his heart beating hard and steady. Now he was exposed to any incoming fire, but he had no other choice. He quieted himself, closing his eyes and praying, but he saw the faceless child searching for him. Gripping his rifle...

Strain-induced vertical self-organization of semiconductor quantum dots: A computational study

Atomistic strain simulations based on the valence force field method are employed to study the vertical arrangements of semiconductor quantum dot (QD) multilayers. The effects of the QD shape, dimensions, and materials parameters are systematically investigated, varying independently the following parameters: spacer width H, QD lateral spacing D, base b, and height h, slope of the side facets, elastic properties of the dot and the substrate materials, and lattice mismatch between the dot and the substrate. The transition between vertically aligned and anti-aligned structures is found to be determined mainly by the ratios H/D and b/D, as well as by the strain anisotropy of the substrate and to a lesser extent of the QD. The dependence on the QD height h is significant only for steep side facets and large aspect ratios h/b, and the effects of the lattice mismatch strain and the bulk elastic moduli are found to be negligible. The comparison with experimental data shows an excellent agreement with the results from the simulations, demonstrating that the presented analysis results in precise theoretical predictions for the vertical self-organization regime in a wide range of QD materials systems.

Evolution and coarsening of Si-rich SiGe islands epitaxially grown at high temperatures on Si(0 0 1)

In this work we investigate by means of atomic force microscopy in combination with selective wet etching experiments coalescence and coarsening effects on the morphology evolution of Si-rich SiGe quantum dots and islands grown epitaxially at high temperatures on Si(001) substrates. We demonstrate that under certain growth conditions remarkably uniform island size distributions can be achieved for dome and cupola islands, while the morphological transition is dominated by coarsening and coalescence effects similar to Ostwald ripening. Under further deposition the uniformly sized cupola islands transform into larger islands with even steeper side facets (>80°). The footprints obtained from selective wet etching experiments performed on the merging islands reveal that basically all atoms of the two islands are involved in the coarsening process.

The Interacting Effects of Ungulate Hoofprints and Predatory Native Ants on Metamorph Cane Toads in Tropical Australia

Many invasive species exploit the disturbed habitats created by human activities. Understanding the effects of habitat disturbance on invasion success, and how disturbance interacts with other factors (such as biotic resistance to the invaders from the native fauna) may suggest new ways to reduce invader viability. In tropical Australia, commercial livestock production can facilitate invasion by the cane toad (Rhinella marina), because hoofprints left by cattle and horses around waterbody margins provide distinctive (cool, moist) microhabitats; nevertheless the same microhabitat can inhibit the success of cane toads by increasing the risks of predation or drowning. Metamorph cane toads actively select hoofprints as retreat-sites to escape dangerous thermal and hydric conditions in the surrounding landscape. However, hoofprint geometry is important: in hoofprints with steep sides the young toads are more likely to be attacked by predatory ants (Iridomyrmex reburrus) and are more likely to drown following heavy rain. Thus, anthropogenic changes to the landscape interact with predation by native taxa to affect the ability of cane toads in this vulnerable life-history stage to thrive in the harsh abiotic conditions of tropical Australia.

Pyroclastic density currents (PDC) of the 16–17 August 2006 eruptions of Tungurahua volcano, Ecuador: Geophysical registry and characteristics

Tungurahua, located in the Eastern Cordillera of the Ecuadorian Andes, is a 5023m-high active volcano, notable for its extreme relief (3200m), steep sides, and frequent eruptive cycles. From 1999 until 2006 Tungurahua experienced short periods of low to moderate strombolian activity, characterized by fire fountaining, explosions, frequent ash falls and debris flows, and no PDC events. Without warning, Tungurahua initiated PDC activity on 15–16 July 2006, which became more intense on the night of 16–17 August 2006, which is the focus of this study.Continuous monitoring of Tungurahua has employed seismic (both short period and broadband (BB) instruments), SO2 gas emission (COSPEC and DOAS), and geodetic methods (EDM, tilt meters, and GPS), in addition to thermal imagery (airborne and ground-based). Acoustic flow monitors (AFM) installed to monitor lahar activity were important for detecting PDC events. Acoustic signals were monitored at Riobamba, 40km to the SW, as well as by infrasound sensors at Tungurahua's BB seismic stations.Based on geophysical parameters, visual observations, and PDC deposit characteristics, four phases of distinct eruptive activity are recognized during the 16–17 August episode. Phase I (08H37 to 21H13 of 16 Aug.) (local time) experienced low to moderate strombolian activity with occasional high energy impulsive bursts and small PDC. Phase II (21H13-16 Aug. to 00H12-17 Aug.) was characterized by a number of discrete events with high amplitude seismo-acoustic signals, followed by the generation of larger PDC that overran monitoring stations and had velocities of 30–33m/s. After midnight, Phase III (00H12 to 01H14) saw an intense period of unrelenting eruptive activity corresponding to the episode's greatest energy release. It was characterized by subplinian activity accompanied by a series of high energy outbursts and constant low frequency jetting that together formed a continuous plume. It was during this phase that the largest PDC were produced, reaching the surrounding river valleys. Phase IV (after 01H14) followed the cessation of the paroxysmal eruption, but witnessed many granular PDC generated by degassed lava spill outs from the crater that developed lobe and channel morphology on the cone's lower flanks. Hours later a blocky lava flow issued from the crater.During these episodes, more than 30 PDC events were detected, the majority being small flows that remained high on the cone. The two largest PDC occurred after midnight, probably generated by fountain collapse. Their descent down the cone's upper steep flanks (~28°) and 2.4km in length favored air entrainment, resulting in PDC with greater fluidity. These flows had volumes of 9 to 17×106m3 and produced widespread, but relatively thin (1–2m thick) normally-graded deposits at their distal ends. The character and evolution of the PDC activity apparently reflect decreasing volatile contents of the magma and a diminishing magma supply.

Distribution and inferred age of exfoliation joints in the Aar Granite of the central Swiss Alps and relationship to Quaternary landscape evolution

Exfoliation joints are well-known natural fractures limited to near the ground surface. Relatively few details, however, are known about their distribution and age in the Swiss Alps. Exfoliation joints follow the landscape surface at the time of their formation; the age of the associated landscape feature then provides a maximum age of exfoliation joints. While landscape forms can change through time, exfoliation joints preserve elements of former landscape morphologies by their undisturbed orientations. The Grimsel region of the Central Alps is well-suited for analyzing the impact of erosional episodes, and accompanying stress changes, on exfoliation joint formation in granitic rocks. Mapping above and below ground revealed that exfoliation joints are widespread and occur between valley bottoms and mountain crests within glacial (inner and hanging U-shaped trough valleys, glacial cirques, and steep mountain crests) and predominantly fluvial landforms (gently inclined linear slopes above the inner trough valleys, narrow inner-valley gorges, and steep V-shaped side gullies). Based primarily on their geometric properties at the ground surface, three exfoliation joint types were distinguished in our study area: (1) closely spaced (<1m) joints oriented distinctly parallel to the present-day ground surface, (2) intermediately spaced (0.6–2m) joints that are nearly parallel (<10° difference) to today's mean ground surface at a 10-m scale, and (3) widely spaced (≫2m) joints not parallel to the ground surface. Relating the mapped distribution of exfoliation joint types to identified erosional episodes and landscape features of known and inferred ages, respectively, enables us to distinguish four exfoliation joint generations in the Grimsel area, which most likely formed during the lower Pleistocene (~1.5–1Ma), middle Pleistocene (~0.7–0.4Ma), upper Pleistocene (0.1–0.02Ma), and Late Glacial/Holocene (<0.02Ma). We demonstrate that the most prominent and deepest exfoliation joint generation is associated with erosion of the inner glacial troughs of the upper Aar valley, which likely occurred during the mid-Pleistocene Revolution. Our study shows how exfoliation joint episodes can be dated, and, conversely, that better knowledge of the distribution of exfoliation joint sets can reveal unique information about the morphological evolution of an Alpine valley.

Characteristics of abrasive slurry jet micro-machining: A comparison with abrasive air jet micro-machining

Abrasive slurry jet micro-machining (ASJM) uses a well-defined jet of abrasive slurry to erode features in a solid target. Compared with abrasive water jet machining (AWJM), the present ASJM system operates at pressures that are roughly two orders of magnitude lower and uses a premixed slurry of relatively low concentration. The objective of the present study was to gain a better understanding of the mechanics of erosion in ASJM by comparing its performance in the micro-machining of holes and channels in borosilicate glass with that of abrasive air jet micro-machining (AJM), a process that is simpler and relatively well understood. A new ASJM system was developed and used to machine blind holes and smooth channels of relatively uniform depth that did not suffer from the significant waviness previously reported in the literature. The effect of particle velocity, particle concentration, jet traverse speed and jet impact angle were examined. A direct comparison of ASJM and AJM results was possible since novel measurements of the crushing strength of the aluminum oxide abrasive particles used in both experiments proved to be unaffected by water. Brittle erosion was shown to be the dominant material removal mechanism in both ASJM and AJM in spite of the significant flow-induced decrease in the local impact angles of many of the particles in ASJM. A new model of the rapid particle deceleration near the target surface helped explain the much smaller erosion rates of ASJM compared with those in AJM. The modeling of the erosion process during the micro-machining of channels showed that the effect of the local impact angle at the leading edge of the advancing jet was much more significant in ASJM than in AJM, primarily due to the narrower focus of the jet impact zone in ASJM. The differences in the water and air flow fields and associated particle trajectories were used to explain the steeper side walls and flatter bottoms of the holes and channels machined with unmasked ASJM compared to those with masked AJM. The respective structures of the water and air jets also explained the much sharper definition of the edges of these features using ASJM compared with maskless AJM. The results of the study show that ASJM can be used to accurately micro-machine channels and holes with a width of 350–500μm and an aspect ratio of 0.5–1.3 without the use of masks.

Wet Prairie: People, Land, and Water in Agricultural Manitoba by Shannon S. Bower

Reviewed by: Wet Prairie: People, Land, and Water in Agricultural Manitoba by Shannon S. Bower Jennifer Bonnell Bower, Shannon S. – Wet Prairie: People, Land, and Water in Agricultural Manitoba. Vancouver: University of British Columbia Press, 2011. Pp. 238. In this elegantly written book, Shannon Stunden Bower brings meaning and clarity to the complex topic of drainage and agricultural settlement in southern Manitoba’s “wet prairie” in the late-nineteenth and twentieth century. Occupying the southeastern quadrant of the province, the wet prairie formed what has been described as a “soup bowl,” with “slopes seemingly designed to collect precipitation and relatively impermeable soils that ensured the water pooled” (p. 2). A rich agricultural landscape, its topography meant that in many years it was too wet to farm. Stunden Bower tells the story of Manitobans’ efforts to alter this landscape for permanent agricultural settlement, from early drainage efforts by municipalities to the provincial government’s establishment of a district system of drainage in the 1890s, and the extensive and often problematic drainage projects that resulted in the 1910s and 1920s. This is an unusual prairie history. While most scholars of prairie environments have concentrated on the issue of drought, Stunden Bower turns her attention to the subject of surface water and its effects both on the experiences of residents and the nature of governance in southern Manitoba’s distinctly wet, flood-prone landscape. Settlers faced not only inconvenience from lands that were sometimes wet, sometimes dry, but very tangible threats of starvation when conditions were too wet to grow crops. Efforts to address these problems, Stunden Bower argues, “bore on the ultimate shape of the government itself” (p. 9). The expense of drainage, and the considerable coordination it required across municipalities and regions, directly influenced the size and character of the Manitoba government. The environmental circumstances of the wet prairie also affected relations between the province and the Dominion government, whose limited understanding of the particular challenges of the region made the process of renegotiating Manitoba’s terms in Confederation even more problematic. Here, maps and illustrations are used effectively to clarify what is at times a complicated story. In exploring the role of the state in the provision of drainage, Stunden Bower engages a growing scholarly literature on the expression and effects of liberal ideology in the Canadian context. With its core tenets of individualism, property ownership, self-determination, and capitalism, liberalism defined the logic of Canadian institutions and elites as they rose to power between 1870 and 1930. Applied to the circumstances of [End Page 223] southern Manitoba farmers and their struggles with a wet and dynamic terrain, the liberal state facilitated the generation of wealth on privately owned farms. Drainage, in this context, became “part of the infrastructure of settlement” (p.12). Surface water, however, did not affect all farmers equally. The topographical conditions of the “soup bowl,” with its steep sides and flat bottom, meant that “surface water ran from the lands of some (those on the sides) and pooled on the lands of others (those on the bottom)” (p.12). The result was a conflict between “highlanders” and “lowlanders”: those on higher ground were unwilling to contribute to the costs of draining the water that flowed off their lands, while those on low ground felt wrongfully burdened with the task of disposing water that flowed from elsewhere. These divergent interpretations of property rights and responsibilities exemplify what Stunden Bower calls “colloquial liberalism,” the ways that non-experts understood and applied abstract liberal principles based on their daily experience and the position and character of the land they worked (p.13). The second half of the book explores the history of transboundary water management. In her study of agreements between Canada and the United States in the 1920s and 30s over transboundary flooding, and the novel approaches pursued by the American conservation organization Ducks Unlimited to restore waterfowl habitat in Canada, she shows how Manitoba’s wet prairie was significant to those outside Canadian borders. Especially interesting here is the narrative of opportunities lost. Although international influences and conservationist ideas contributed to a gradual shift among Manitobans from an “ideal of permanence” to recognition of the need for...

Numerical modelling of landfill lining system–waste interaction: implications of parameter variability

ABSTRACT: Numerical modelling techniques can be used to examine the serviceability limit states of landfill side-slope lining systems in response to waste placement. A study has been conducted in which the variability of significant model input parameters have been investigated within a probabilistic framework using Monte Carlo simulation. Key model parameters are treated as random variables, and the statistical information required to describe their distributions has been derived from a laboratory repeatability testing programme, a literature survey and an expert consultation process. Model outputs include relative shear displacements between lining components, and tensile strains in the geosynthetic layers that occur in response to staged placement of waste against the side slope. It was found that analyses including input parameter variability were able to identify mechanisms influencing liner performance and their probability of occurrence. These mechanisms include large (i.e. ≫100 mm) relative displacements at interfaces that can generate post-peak strengths, and mobilised tensile strains in the geomembrane and geotextile layers. Additionally, it was found that relative displacements at the controlling (i.e. weakest) liner interface are greater for landfills with a steep side slope, for stiffer waste and thicker waste lifts, while tensile strains in the geosynthetic elements are greater for steep side slopes, more compressible waste and thinner waste lifts. Outputs from probabilistic analyses such as that used in this study can guide engineers regarding geometries and materials that could produce waste-settlement-generated serviceability limit state failures, and hence can be used to support more reliable designs.

Genesis and morphology of cold-water coral ridges in a unidirectional current regime

Cold-water coral ridges with waveform morphology are commonly observed in mound surfaces in the Northeast Atlantic Ocean and interpreted as sediment waves overgrown by corals. This work documents the first cold-water coral ridges that are waveform but lack sand dune cores. These coral ridges are situated at the base of the Miami Terrace in the Straits of Florida (depths of 630 to 870m). They are entirely biogenic in origin and are unrelated to antecedent topography. Five lines of evidence, based on 27km2 of high-resolution geophysical, oceanographic, and ground-truthing data, support this interpretation. First, the waveform coral ridges are aligned perpendicular to a southward flowing bottom current and juxtaposed to an active sand dune field devoid of corals. Both the coral ridges and sand dunes are asymmetric in profile with respect to the current. However, the ridges have their steep sides facing the current, whereas the dunes exhibit a steep leeside. Second, the coral ridge matrix consists of very fine sand to mud particles with no bedload sand transport on the ridge flanks or troughs. In contrast, active sand ripples superimpose the juxtaposed sand dunes indicating that coarse sand is transported via traction in this domain. Third, bedload sand transport occurs in linear streaks at the shallowest part of the surveyed area. These streaks orthogonally crosscut some coral ridges, but coral colonies are not aligned along these streaks. Instead, the bedload sand smothers the coral colonies and thereby segments the ridges. Fourth, the sand dune and coral ridge acoustic responses are different. Below the dunes, there is no sub-bottom reflection due to energy attenuation. In contrast, a continuous reflection below the coral ridges proves the absence of attenuating sand cores. Fifth, this continuous sub-bottom reflection is not correlated with the coral ridge topography, indicating that antecedent topography does not control the waveform morphology and spatial distribution of the ridges. The differences in depositional profiles, sediment dynamics and features, as well as acoustic facies between the coral ridges and the juxtaposed dunes show that the coral ridges are entirely bioconstructional and not a veneer of corals covering paleo-sand dunes. This field of biogenic ridges at the Miami Terrace and the distribution of sand streaks as well as active sand dunes provide new insights how the lateral variability of current velocities and sediment transport conditions control the morphology, distribution and genesis of cold-water coral features.

A mechanism to explain the spectrum of Hessdalen Lights phenomenon

In this work, we present a model to explain the apparently contradictory spectrum observed in Hessdalen Lights (HL) phenomenon. According to our model, its nearly flat spectrum on the top with steep sides is due to the effect of optical thickness on the bremsstrahlung spectrum. At low frequencies self-absorption modifies the spectrum to follow the Rayleigh–Jeans part of the blackbody curve. This spectrum is typical of dense ionized gas. Additionally, spectrum produced in the thermal bremsstrahlung process is flat up to a cutoff frequency, ν cut, and falls off exponentially at higher frequencies. This sequence of events forms the typical spectrum of HL phenomenon when the atmosphere is clear, with no fog.

Ultra thick epoxy-based dry-film resist for high aspect ratios

This work presents a new type of high-resolution dry-film resist laminates for the fabrication of extremely thick epoxy based polymer structures. Via a lamination process a resist thickness of up to d=360@mm can be applied by one single process step. Afterwards, the dry-film resist is patterned by standard UV-lithography. An epoxy based resist mixture which contains epoxy resins, reactive diluents, additives, and a photo acid generator is deposited onto a PET supporting film by doctor blading for fabrication of the resist film. The films can be cut defect-free into favoured sheet sizes. Currently, dry-film resists with a layer thickness of up to 400@mm can be produced reproducible. With the tested d=360@mm thick dry-film resist an aspect ratio of 15:1 (height:width) has been achieved. By lamination and UV-patterning of two layers resist a master for 700@mm thick electroplated Nickel structures was fabricated. Thereby, steep side walls with an angle deviation of @a<1^o have been generated.

The influence of environmental changes on local and regional vegetation patterns at Rieme (NW Belgium): implications for Final Palaeolithic habitation

Late-glacial vegetation changes were studied at Rieme, NW Belgium. Human occupation of this cover sand area occurred from the Final Palaeolithic onwards. The research area is situated on the northern side of a large cover sand ridge in an undulating landscape with small ridges and depressions. The past landscape was reconstructed using a multi-disciplinary approach, including geomorphological, sedimentological, loss-on-ignition, botanical (micro- and macrofossil) and zoological analyses. AMS 14C dating provided an accurate chronology for the sediments. Analyses were performed on three sequences located ~200–300 m apart. Our study shows that during the Bolling (GI-1e) wet meadows developed on the sandy soils and groundwater levels increased probably as result of permafrost melting. Shallow pools formed in depressions. During the Older Dryas (GI-1d) shrubs with juniper, sea-buckthorn and willow developed. Many shallow depressions were overblown with sand and deposition of organic material almost ceased. In the early Allerod (GI-1c) open birch woodlands developed. Due to the final melting of permafrost, groundwater levels rose further and ponds with floating-leaved open water vegetation developed. Large water level fluctuations occurred in one of the ponds. Accumulation of organic deposits ceased during the mid-Allerod. Indirect evidence for human occupation during the Allerod (GI-1c) was found in indications of burning of the reed-swamps in combination with the presence of large herbivores. Final Palaeolithic people probably used the northern side of the cover sand ridge as hunting area, while they settled their temporary (base) camps on the steep southern side along the extensive and deeper Moervaart lake.

Frost peat mounds on Hermansenøya (Oscar II Land, NW Svalbard) – their genesis, age and terminology

Here we present research on previously uninvestigated frost peat mounds occurring on a peat bog in the southern part of Hermansenøya, NW Svalbard. Detailed characteristics are given of the environmental conditions of the peat bog and of the morphological features and surface structure of the frost peat mounds, as well as an analysis of the internal structure of one mound. Three types of frost peat mounds have been distinguished: disc‐shaped mounds (low), mid‐sized mounds with gentle sides, and high mounds with steep sides. Radiocarbon dating of the peat within the frost peat mound performed for the first time on Svalbard and a detailed analysis of the deposits demonstrated that in the high mound (1.3 m) there is an ice‐peat core and peat cover without ice. There are three layers of peat of different ages separated by at least two hiatuses. A generalized history of the development of the peat bog from about 8 ka BP is established. The studied mound displays two development cycles unknown elsewhere. The older relict part of the peat mound was formed during a climatic cooling about 3.0–2.5 ka BP, while the younger part originated during the Little Ice Age (c. AD 1550–1850). Despite certain similarities of these mounds to some palsas, this term should not be applied to the mounds because they are smaller and their cores consist mostly of layers of massive injection ice, the presence of which indicates a pressurized system in their genesis.

Spatial relationship between topography and rock uplift patterns in asymmetric mountain ranges based on a stream erosion model

The spatial relationship between topography and rock uplift patterns in asymmetric mountain ranges was investigated using a stream erosion model in which the asymmetric rock uplift was given and erosion rates were proportional to the m-th power of the drainage area and the n-th power of the channel gradient. The model conditions were simple, and thus the effects of horizontal rock movement, diffusional processes, and erosion thresholds were neglected, and spatially uniform precipitation, lithology, and vegetation were assumed. In asymmetric mountain ranges, under realistic exponent conditions ( m < n) and the above assumptions, the surface erosion rate is faster on the steeper side and slower on the gentler side. The topographic axis migrates away from the rock uplift axis toward the center of the mountain range owing to the contrast in erosion rates. This migration continues until the erosion is balanced with rock uplift. In a dynamic steady state, the topographic pattern is independent of the rock uplift rate as indicated by an analytical solution, and is prescribed by the rock uplift pattern and the exponents m and n. As the asymmetry of the rock uplift pattern increases, the topographic axis migrates a greater distance. The location of the topographic axis is related to the location of the rock uplift axis by a simple logarithmic function, for a wide range of m and n. The fit of the numerical results and the logarithmic function is particularly good when m = 0.5 and n = 1.0. If the rock uplift pattern in asymmetric mountain ranges is known, the value of n − 5 m/4 can be constrained based on the logarithmic relation, assuming a dynamic steady state. On the other hand, if the value of n − 5 m/4 is known in an asymmetric mountain range, the rock uplift pattern can be estimated directly from the topography. This relation was applied to the Suzuka Range in central Japan, and the value of n − 5 m/4 was estimated for an assumed reverse fault motion.

Analysis of growth directions of columnar stromatolites from Walker Lake, western Nevada

Samples of digitate, branching, columnar stromatolites were collected from the steep sides and near horizontal top of four in situ boulders located on the southwestern side of Walker Lake, Nevada, to test the widely held assumption that stromatolite column formation represents a phototropic response. We would predict that the columns on the steeply dipping sides of the boulder would bend upwards toward the light during growth if phototropism was significant during stromatolite morphogenesis. Angle of growth measurements on >300 stromatolites demonstrate that the stromatolites grew nearly normal to their growth surface, regardless of the inclination of their growth surface. No significant differences in the distribution of growth angles between north-, south-, east-, or west-facing samples were observed, and stromatolite lamina thickness did not systematically vary with position on the boulder. The lack of a strong phototropic response does not rule out a biological origin for the Walker Lake structures, but it does suggest that phototropic growth was not a dominant factor controlling stromatolite morphogenesis in these stromatolites and that column formation cannot be uniquely attributed as a phototropic response in stromatolites. It is interesting to note that the morphology of the stromatolites on the top of the boulder is identical to stromatolites on the steep sides. Stromatolite morphogenetic models that predict branching typically require a vertically directed sedimentary component, a feature that would have likely affected the stromatolites on the tops of the boulders, but not the sides, suggesting that other factors may be important in stromatolite morphogenesis.