scholarly journals Microstructures in a shear margin: Jarvis Glacier, Alaska

2021 ◽  
pp. 1-14
Author(s):  
Christopher Gerbi ◽  
Stephanie Mills ◽  
Renée Clavette ◽  
Seth Campbell ◽  
Steven Bernsen ◽  
...  
Keyword(s):  
Flow Dynamics ◽  
Mechanical Anisotropy ◽  
Lateral Margin ◽  
Natural Setting ◽  
Alaska Range ◽  
The Core ◽  
Grain Sizes ◽  
Strong Control ◽  
Crystallographic Orientations

Abstract Microstructures, including crystallographic fabric, within the margin of streaming ice can exert strong control on flow dynamics. To characterize a natural setting, we retrieved three cores, two of which reached bed, from the flank of Jarvis Glacier, eastern Alaska Range, Alaska. The core sites lie ~1 km downstream of the source, with abundant water present in the extracted cores and at the base of the glacier. All cores exhibit dipping layers, a combination of debris bands and bubble-free domains. Grain sizes coarsen on average approaching the lateral margin. Crystallographic orientations are more clustered and with c-axes closer to horizontal nearer the lateral margin. The measured fabric is sufficiently weak to induce little mechanical anisotropy, but the data suggest that despite the challenging conditions of warm ice, abundant water and a short flow distance, many aspects of the microstructure, including measurable crystallographic fabric, evolved in systematic ways.

Rapid environmental changes of the Late-glacial and Holocene in a sediment record from the Yagour Plateau, High Atlas, Morocco

2021 ◽  
Author(s):  
Henk Cornelissen ◽  
William Fletcher ◽  
Philip Hughes ◽  
Benjamin Bell ◽  
Ali Rhoujjati ◽  
...  
Keyword(s):  
Environmental Change ◽  
North Atlantic ◽  
Climate Changes ◽  
Late Glacial ◽  
Sediment Supply ◽  
Climate Forcing ◽  
High Atlas ◽  
The Core ◽  
Grain Sizes ◽  
Late Glacial And Holocene

<p>The High Atlas mountains of Morocco represent a climatological frontier between the Atlantic and Saharan realms as well as a site of major Pleistocene glacier expansion. However, Late-glacial and Holocene environmental change is weakly constrained, leaving open questions about the influence of high- and low-latitude climate forcing and the expression of North Atlantic rapid climate changes. High elevation lakes on the sandstone plateaux of the High Atlas have been recognised as archives of Late Quaternary environmental change but remain little explored. Here, we present findings from new sedimentological, palaeoecological and geochronological investigation of a lake marginal sediment core recovered in June 2019 from the <em>Ifard </em>Lake located on the Yagour Plateau. The plateau is a distinctive sandstone upland located to the southeast of Marrakech in the High Atlas (31.31°N, 7.60°W, 2460 m.a.s.l.). The lake is located within a small, perched catchment area, offering an opportunity to isolate catchment effects and investigate atmospheric deposition of organic and inorganic tracers of past environmental change. The core stratigraphy reveals shifts between inorganic sands and lake muds with fluctuations in grain sizes and sediment reddening. The differences in these stratigraphic layers are most likely linked to hydrological changes associated with changing snowpack conditions and local catchment erosion dynamics. The core chronology is well-constrained by AMS radiocarbon dating of pollen concentrates, with the core sequence spanning the last ca. 14,000 years. The driving agents of environmental change on the plateau are inferred using a multiproxy approach, combining sedimentological analyses (particle-size by laser granulometry, elemental analysis by core-scanning XRF, C/H/N/S analysis), palynology (pollen, spores, non-pollen palynomorphs) and contiguous macrocharcoal analysis. High-resolution, well-constrained proxies therefore permit novel regional insights into past environmental and climatic changes at centennial timescales. A prime working hypothesis is that the imprint of wider palaeoclimatic changes of both the North Atlantic region and Saharan realm (African Humid Period, AHP) is detected at this site. Key climatic periods such as the Younger Dryas and multi-centennial cooling episodes around 8000 and 4200 years ago are distinctly characterised in the record by finer grain sizes and the accumulation of pollen-rich material and charcoal. These responses are thought to be governed by regional climate forcing and local snowmelt moisture supply to the Yagour Plateau. An increase in fine sediment supply, magnetic susceptibility and Fe content in the upper part of the core may be related to enhanced atmospheric dust deposition following the end of the AHP. Whilst taking anthropological influences on the local environment into account, this study will contribute to the detection of long-term and rapid climate changes in a sensitive mountain region at the rim of the Atlantic and Saharan climate systems.</p>

scholarly journals Melt regimes, stratigraphy, flow dynamics and glaciochemistry of three glaciers in the Alaska Range

2012 ◽  
Vol 58 (207) ◽  
pp. 99-109 ◽  
Author(s):  
Seth Campbell ◽  
Karl Kreutz ◽  
Erich Osterberg ◽  
Steven Arcone ◽  
Cameron Wake ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Ice Core ◽  
Chemical Diffusion ◽  
Flow Dynamics ◽  
Alaska Range ◽  
Ice Volume ◽  
Glacier Ice ◽  
Age Model ◽  
Ground Penetrating ◽  
Climate Studies

AbstractWe used ground-penetrating radar (GPR), GPS and glaciochemistry to evaluate melt regimes and ice depths, important variables for mass-balance and ice-volume studies, of Upper Yentna Glacier, Upper Kahiltna Glacier and the Mount Hunter ice divide, Alaska. We show the wet, percolation and dry snow zones located below ~2700ma.s.l., at ~2700 to 3900ma.s.l. and above 3900ma.s.l., respectively. We successfully imaged glacier ice depths upwards of 480 m using 40-100 MHz GPR frequencies. This depth is nearly double previous depth measurements reached using mid-frequency GPR systems on temperate glaciers. Few Holocene-length climate records are available in Alaska, hence we also assess stratigraphy and flow dynamics at each study site as a potential ice-core location. Ice layers in shallow firn cores and attenuated glaciochemical signals or lacking strata in GPR profiles collected on Upper Yentna Glacier suggest that regions below 2800ma.s.l. are inappropriate for paleoclimate studies because of chemical diffusion, through melt. Flow complexities on Kahiltna Glacier preclude ice-core climate studies. Minimal signs of melt or deformation, and depth-age model estimates suggesting ~4815 years of ice on the Mount Hunter ice divide (3912ma.s.l.) make it a suitable Holocene-age ice-core location.

A Home Away from Home: Bellefontaine Cemetery, St. Louis, and the Rural Cemetery Movement

Prospects ◽  
1988 ◽  
Vol 13 ◽  
pp. 135-179 ◽  
Author(s):  
Ruth L. Bohan
Keyword(s):  
Urban Parks ◽  
Flowering Plants ◽  
Natural Setting ◽  
American City ◽  
American Family ◽  
The Core ◽  
The Family ◽  
Physical Setting ◽  
Family Home ◽  
Burial Grounds

Much has been written in recent years about 19th-century rural cemeteries. Beginning with the establishment of Boston's Mount Auburn Cemetery in 1831, these rural retreats rapidly replaced existing church burial grounds and by the 1850s had led to the development of urban parks and garden suburbs as well. Like urban parks and garden suburbs, rural cemeteries were meant to provide relief from the crowding, grid-iron regularity, and grittiness of the country's rapidly expanding industrial centers by embracing the openness, spontaneity, and verdant freshness of nature. Trees, shrubs, and flowering plants punctuated and enhanced the gentle contours of the land; lakes and roadways reflected and extended nature's beauties; manmade structures, too, nestled into the undulating rhythms of the land, exhibiting a oneness with the varied and carefully orchestrated richness of the natural setting. The garden suburb and the rural cemetery shared a further distinction of being located on the periphery of existing cities and were frequently entered through imposing gates that effectively announced their separateness from the surrounding terrain. Even more fundamental, however, but not fully understood, is the fact that at the core of the creation of both the rural cemetery and the garden suburb was a desire to emphasize and consolidate the American family by providing it with a new physical setting and a new set of symbols. By the Civil War, virtually every large American city had a rural cemetery, where its dead were buried in ample family lots that were adorned with imposing family monuments, and set off from other family lots by elaborate iron fences or stone copings similar to those that edged the family home.

scholarly journals In-Situ Synchrotron SAXS and WAXS Investigation on the Deformation of Single and Coaxial Electrospun P(VDF-TrFE)-Based Nanofibers

2021 ◽  
Vol 22 (23) ◽  
pp. 12669
Author(s):  
Yi-Jen Huang ◽  
Yi-Fan Chen ◽  
Po-Han Hsiao ◽  
Tu-Ngoc Lam ◽  
Wen-Ching Ko ◽  
...  
Keyword(s):  
Hierarchical Structures ◽  
Electrospun Nanofibers ◽  
Mechanical Anisotropy ◽  
Core Shell ◽  
Length Scale ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Core ◽  
Nanofiber Alignment

Coaxial core/shell electrospun nanofibers consisting of ferroelectric P(VDF-TrFE) and relaxor ferroelectric P(VDF-TrFE-CTFE) are tailor-made with hierarchical structures to modulate their mechanical properties with respect to their constituents. Compared with two single and the other coaxial membranes prepared in the research, the core/shell-TrFE/CTFE membrane shows a more prominent mechanical anisotropy between revolving direction (RD) and cross direction (CD) associated with improved resistance to tensile stress for the crystallite phase stability and good strength-ductility balance. This is due to the better degree of core/shell-TrFE-CTFE nanofiber alignment and the crystalline/amorphous ratio. The coupling between terpolymer P(VDF-TrFE-CTFE) and copolymer P(VDF-TrFE) is responsible for phase stabilization, comparing the core/shell-TrFE/CTFE with the pristine terpolymer. Moreover, an impressive collective deformation mechanism of a two-length scale in the core/shell composite structure is found. We apply in-situ synchrotron X-ray to resolve the two-length scale simultaneously by using the small-angle X-ray scattering to characterize the nanofibers and the wide-angle X-ray diffraction to identify the phase transformations. Our findings may serve as guidelines for the fabrication of the electrospun nanofibers used as membranes-based electroactive polymers.

Tectonic control over exhumation in the Arunachal Himalaya: new constraints from Apatite Fission Track Analysis

2018 ◽  
Vol 481 (1) ◽  
pp. 65-79 ◽  
Author(s):  
Vikas Adlakha ◽  
R. C. Patel ◽  
Akhil Kumar ◽  
Nand Lal
Keyword(s):  
Fission Track ◽  
Eastern Himalaya ◽  
Tectonic Deformation ◽  
Apatite Fission Track ◽  
The Core ◽  
Exhumation Rates ◽  
Crustal Exhumation ◽  
Arunachal Himalaya ◽  
Strong Control ◽  
Track Analysis

AbstractNew apatite fission track (AFT) ages have been obtained from a synformal nappe of the Higher Himalayan Crystallines emplaced over the Lesser Himalayan metasedimentary zone of the Arunachal Himalaya, India. The AFT cooling ages within the nappe range between 5.0 ± 0.8 and 14.4 ± 1.3 Ma. Modelled exhumation rates calculated from these cooling ages vary from 0.25 ± 0.12 to 0.69 ± 0.25 mm a−1, which indicates slow exhumation since the Middle to Late Miocene. The AFT cooling ages are younging on both the northern and southern flanks of the synform and the oldest ages are confined to the core. The close mimicking of a shallow crustal exhumation pattern with the synformal structure suggests a strong control of the development of the synform on the exhumation path of the rocks and hence a tectonics–exhumation linkage in the central Arunachal Himalaya. Comparison of these AFT ages with the regional thermochronological record of the Eastern Himalaya reflects a variation in exhumation rates with strike. The AFT age pattern in the central Arunachal Himalaya does not match the pattern of precipitation, which suggests an absence of climate-driven tectonic deformation via focused erosion.

A Home Away from Home: Bellefontaine Cemetery, St. Louis, and the Rural Cemetery Movement

Prospects ◽  
1988 ◽  
Vol 13 ◽  
pp. 135-179 ◽  
Author(s):  
Ruth L. Bohan
Keyword(s):  
Urban Parks ◽  
Flowering Plants ◽  
Natural Setting ◽  
American City ◽  
American Family ◽  
The Core ◽  
The Family ◽  
Physical Setting ◽  
Family Home ◽  
Burial Grounds

Much has been written in recent years about 19th-century rural cemeteries. Beginning with the establishment of Boston's Mount Auburn Cemetery in 1831, these rural retreats rapidly replaced existing church burial grounds and by the 1850s had led to the development of urban parks and garden suburbs as well. Like urban parks and garden suburbs, rural cemeteries were meant to provide relief from the crowding, grid-iron regularity, and grittiness of the country's rapidly expanding industrial centers by embracing the openness, spontaneity, and verdant freshness of nature. Trees, shrubs, and flowering plants punctuated and enhanced the gentle contours of the land; lakes and roadways reflected and extended nature's beauties; manmade structures, too, nestled into the undulating rhythms of the land, exhibiting a oneness with the varied and carefully orchestrated richness of the natural setting. The garden suburb and the rural cemetery shared a further distinction of being located on the periphery of existing cities and were frequently entered through imposing gates that effectively announced their separateness from the surrounding terrain. Even more fundamental, however, but not fully understood, is the fact that at the core of the creation of both the rural cemetery and the garden suburb was a desire to emphasize and consolidate the American family by providing it with a new physical setting and a new set of symbols. By the Civil War, virtually every large American city had a rural cemetery, where its dead were buried in ample family lots that were adorned with imposing family monuments, and set off from other family lots by elaborate iron fences or stone copings similar to those that edged the family home.

Aluminum CVD for Interconnect Thin Films

1992 ◽  
Vol 282 ◽  
Author(s):  
Donna M. Speckman
Keyword(s):  
Thin Films ◽  
Chemical Vapor Deposition ◽  
Titanium Oxide ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Flow Dynamics ◽  
Aluminum Films ◽  
Grain Sizes ◽  
Sensitive Function ◽  
Trimethylamine Alane

ABSTRACTAluminum thin films were deposited by chemical vapor deposition on SiO2 substrates using trimethylamine alane (TMAA) in a standard low pressure CVD reactor system, with argon as a carrier gas. Film quality and morphology were found to be a sensitive function of reactor flow dynamics. High purity films were obtained with resistivities of ∼5.0 μΩ-cm and grain sizes of 1–2 μm in diameter, but many of these films also exhibited aluminum whiskers, which caused VLSI processing problems. The CVD aluminum films exhibited conformal deposition over 0.5μm topographies, and also demonstrated electromigration lifetimes comparable to those of sputtered aluminum films. Aluminum films deposited using TMAA were also found to be selective at 90°C for titanium oxide.

scholarly journals PENDIDIKAN INKLUSI DI SEKOLAH DASAR NEGERI LEBAK BULUS 06 PAGI DKI JAKARTA

2018 ◽  
Vol 1 (01) ◽  
Author(s):  
Rossi Iskandar ◽  
Febrianti Yuli Satriyani ◽  
Robiatul Munajah
Keyword(s):  
Special Needs ◽  
School Health ◽  
Qualitative Approach ◽  
Natural Setting ◽  
Health Unit ◽  
The Core ◽  
Inclusion Education ◽  
Child Friendly ◽  
The Impact ◽  
Study Inclusion

Abstrak: Tujuan  penelitian ini adalah untuk mengetahui dan mengkaji pendidikan inklusi di SDN Lebak Bulus 06 Pagi, Penelitian ini menggunakan pendekatan kualitatif dalam mengkaji fenomena dan aktivitas yang terjadi dalam latar alamiah. Metode utama yang digunakan adalah pengamatan dan wawancara. Hasil analisis dan pembahasan dari penelitian di SDN Lebak Bulus 06 Pagi mengenai kerja sama antara pihak sekolah dan orang tua, ditemukan data bahwa kerjasama sudah terjalin dengan baik antara orang tua/wali siswa dan pemerintah karena disitu sudah ada partisipasi kepada pihak sekolah, seperti penyumbangan sarana dan prasarana. Salah satu kekurangan yang menjadi temuan yaitu kurangnya jumlah toilet jika dibandingkan dengan jumlah siswa, dan masih belum ada toilet untuk anak berkebutuhan khusus. Kekurangan lain yang ditemukan yaitu, dijadikannya satu ruangan guru dengan ruang kepala sekolah yang menimbulkan kurang efektifnya proses kegiatan kependidikan. Sarana prasarana lain yang tersedia yaitu Unit Kesehatan Sekolah (UKS). Sekolah ramah anak juga berjalan cukup kondusif sehingga sekolah tersebut dinamakan sebagai sekolah sample project. SDN Lebak Bulus 06 Pagi adalah sekolah inti, dan sekolah imbasnya adalah SDN Lebak Bulus 02,03 & 04 Pagi. Sekolah ramah anak atau yang biasa disebut sebagai sekolah sample project belum ditanamkan sebagai sekolah ramah anak. Seharusnya sekolah tersebut harus mejalankan sekolah ramah anak agar siswa-siswinya bisa meniru hal-hal baik untuk diaplikasikan dalam kegiatan sehari-hari.Kata Kunci: pendidikan, inklusiAbstract: The purpose of this research is to know and study inclusion education at SDN Lebak Bulus 06 Pagi. This research uses a qualitative approach in studying phenomenon and activities that occur in a natural setting. The main methods used are observations and interviews. The Result of analysis and discussion from research at SDN Lebak Bulus 06 Pagi regarding cooperation between school and parents, found data that cooperation has been well established between parent/guardian of student and government because there is already participating to school party, like the contribution of means and infrastructure. One of the drawbacks of the findings is the lack of toilet numbers compared to the number of students, and there is still no toilet for children with special needs. Another deficiency that is found is, made one room teacher with the headroom of the school causes less effective process of education activities. Another available infrastructure is the School Health Unit (UKS). Child-friendly schools are also running quite conducive so that the school is named as a sample project school. SDN Lebak Bulus 06 Pagi is the core school, and the impact school is SDN Lebak Bulus 02,03 & 04 Pagi. Child-friendly schools or commonly referred to as sample project schools have not been instilled as child-friendly schools. The school should run a child-friendly school so that students can imitate the good things to be applied in daily activities.Keywords: education, inclusion

Microindentation of Coarse-Grained Polycrystalline α-Brass

2002 ◽  
Vol 750 ◽  
Author(s):  
Nian Zhang ◽  
Changjin Xie ◽  
Wei Tong
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Indentation Depth ◽  
Strong Dependence ◽  
Weak Dependence ◽  
Coarse Grained ◽  
Grain Sizes ◽  
Vickers Indenter ◽  
Indent Depth ◽  
Crystallographic Orientations

ABSTRACTEffects of the indent depth, the distance between the indent and the grain boundary, grain sizes, and crystallographic orientations on the microhardness of annealed coarse-grained polycrystalline α-brass were investigated using a Vickers indenter with indents much smaller than the α-brass grains (ranging from 80 μm to 550 μm). It is found that the microhardness of α-brass crystals shows a strong dependence on the indentation depth when it is smaller than 5 μm and a very weak dependence on both the distance between the indent and the grain boundary and the grain size when the indentation depth is about 5 μm and more. No significant dependence of the microhardness on the crystallographic orientations was observed in the fourteen grains of different orientations studied in this investigation.

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