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Trenches
Selected AbstractsGeoarchaeology of Tonga: Geotectonic and geomorphic controlsGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 2 2007William R. Dickinson Ancient settlement patterns in central Tonga, at the southeastern limit of Lapita expansion into Remote Oceania ,3 ka, were conditioned by island geomorphology as controlled by spatial geotectonic features and temporal changes in relative sea level on island coasts. Volcanic islands provided lithic resources, but human populations were concentrated on nonvolcanic forearc islands underlain by limestone covered by airfall tephra blankets that weathered to form rich agricultural soils and eroded to provide terrigenous sand for ceramic temper. The forearc islands lie along the Tonga platform, a linear tract of shoals uplifted diachronously by subduction of the buoyant Louisville Ridge at the Tonga Trench. Multiple transverse structural discontinuities break the forearc into discrete structural blocks, some tectonically stable during late Holocene time but others undergoing postuplift subsidence. Understanding the paleoenvironmental settings of Tongan archaeological sites requires reconstructing the contrasting geologic histories of different forearc island clusters. © 2007 Wiley Periodicals, Inc. [source] Strike-slip earthquakes in the oceanic lithosphere: observations of exceptionally high apparent stressGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2002George L. Choy Summary The radiated energies, ES, and seismic moments, M0, for 942 globally distributed earthquakes that occurred between 1987 to 1998 are examined to find the earthquakes with the highest apparent stresses (,a=,ES/M0, where , is the modulus of rigidity). The globally averaged ,a for shallow earthquakes in all tectonic environments and seismic regions is 0.3 MPa. However, the subset of 49 earthquakes with the highest apparent stresses (,a greater than about 5.0 MPa) is dominated almost exclusively by strike-slip earthquakes that occur in oceanic environments. These earthquakes are all located in the depth range 7,29 km in the upper mantle of the young oceanic lithosphere. Many of these events occur near plate-boundary triple junctions where there appear to be high rates of intraplate deformation. Indeed, the small rapidly deforming Gorda Plate accounts for 10 of the 49 high- ,a events. The depth distribution of ,a, which shows peak values somewhat greater than 25 MPa in the depth range 20,25 km, suggests that upper bounds on this parameter are a result of the strength of the oceanic lithosphere. A recently proposed envelope for apparent stress, derived by taking 6 per cent of the strength inferred from laboratory experiments for young (less than 30 Ma) deforming oceanic lithosphere, agrees well with the upper-bound envelope of apparent stresses over the depth range 5,30 km. The corresponding depth-dependent shear strength for young oceanic lithosphere attains a peak value of about 575 MPa at a depth of 21 km and then diminishes rapidly as the depth increases. In addition to their high apparent stresses, which suggest that the strength of the young oceanic lithosphere is highest in the depth range 10,30 km, our set of high- ,a earthquakes show other features that constrain the nature of the forces that cause interplate motion. First, our set of events is divided roughly equally between intraplate and transform faulting with similar depth distributions of ,a for the two types. Secondly, many of the intraplate events have focal mechanisms with the T -axes that are normal to the nearest ridge crest or subduction zone and P -axes that are normal to the proximate transform fault. These observations suggest that forces associated with the reorganization of plate boundaries play an important role in causing high- ,a earthquakes inside oceanic plates. Extant transform boundaries may be misaligned with current plate motion. To accommodate current plate motion, the pre-existing plate boundaries would have to be subjected to large horizontal transform push forces. A notable example of this is the triple junction near which the second large aftershock of the 1992 April Cape Mendocino, California, sequence occurred. Alternatively, subduction zone resistance may be enhanced by the collision of a buoyant lithosphere, a process that also markedly increases the horizontal stress. A notable example of this is the Aleutian Trench near which large events occurred in the Gulf of Alaska in late 1987 and the 1998 March Balleny Sea M= 8.2 earthquake within the Antarctic Plate. [source] Baguio Mineral District: An oceanic arc witness to the geological evolution of northern Luzon, PhilippinesISLAND ARC, Issue 4 2008Graciano P. Yumul Jr Abstract The Baguio Mineral District exposes rock formations that evince the geological and tectonic evolution of this district from a subduction-related marginal basin to an island arc setting. Available onshore and offshore data are consistent with an Early (onset phase) to Middle (developed phase) Miocene arc polarity reversal from the east (termination of subduction along the proto-East Luzon Trough) to the west (initiation of subduction along the Manila Trench). Geophysical modeling and geochemical data calculation showed a 30 ± 5 km crustal thickness for the mineral district. Subduction-related multiple arc magmatism and ophiolite accretion contributed to crustal thickening. Recent information on the Oligo,Miocene Zigzag and Klondyke formations in the mineral district reveal that the marginal basin, where these rocks were deposited, has received eroded materials from adjacent terrains characterized by siliceous lithologies. Furthermore, adakitic rocks, high permeable zones and extensional zones which are exploration markers applied to identify possible mineralization targets, are prevalent in the mineral district. The geological evolution that the district had undergone mimics the evolution of island arcs worldwide in general and northern Luzon in particular. [source] Evolution of an accretionary complex along the north arm of the Island of Sulawesi, IndonesiaISLAND ARC, Issue 1 2004Yusuf Surachman Djajadihardja Abstract Seismic reflections across the accretionary prism of the North Sulawesi provide excellent images of the various structural domains landward of the frontal thrust. The structural domain in the accretionary prism area of the North Sulawesi Trench can be divided into four zones: (i) trench area; (ii) Zone A; (iii) Zone B; and (iv) Zone C. Zone A is an active imbrication zone where a decollement is well imaged. Zone B is dominated by out-of-sequence thrusts and small slope basins. Zone C is structurally high in the forearc basin, overlain by a thick sedimentary sequence. The subducted and accreted sedimentary packages are separated by the decollement. Topography of the oceanic basement is rough, both in the basin and beneath the wedge. The accretionary prism along the North Sulawesi Trench grew because of the collision between eastern Sulawesi and the Bangai,Sula microcontinent along the Sorong Fault in the middle Miocene. This collision produced a large rotation of the north arm of Sulawesi Island. Rotation and northward movement of the north arm of Sulawesi may have resulted in southward subduction and development of the accretionary wedge along North Sulawesi. Lateral variations are wider in the western areas relative to the eastern areas. This is due to greater convergence rates in the western area: 5 km/My for the west and 1.5 km/My for the east. An accretionary prism model indicates that the initiation of growth of the accretionary prism in the North Sulawesi Trench occurred approximately 5 Ma. A comparison between the North Sulawesi accretionary prism and the Nankai accretionary prism of Japan reveals similar internal structures, suggesting similar mechanical processes and structural evolution. [source] Rock magnetism and paleomagnetic stratigraphy of forearc sediments of the Japan Trench, ODP Sites 1150 and 1151ISLAND ARC, Issue 1 2004Toshiya Kanamatsu Abstract Magnetic measurements were carried out to investigate rock magnetic properties and paleomagnetic directions of late and middle Miocene sediments recovered from the land side of the Japan Trench during the Ocean Drilling Program Leg 186. Because the low coercive component in natural remanent magnetization (NRM) normalized by anhysteretic remanent magnetization shows that the drilling-induced magnetization is severe in the sections obtained by the advanced hydraulic piston coring method, careful analyses of demagnetization of NRM using the ,demagnetization plane' were carried out to decompose the direction and intensity. Magnetostratigraphic correlation down to the upper Miocene, supplemented by biostratigraphic data, revealed that the sedimentation rates are characterized by drastic changes, with the early Pliocene having the highest rate. This high sedimentation rate is related to the subsidence of the southern deep-sea terrace of the Japan Trench. [source] The Poetry of Melesina Trench: A Growing Skill at SorrowJOURNAL FOR EIGHTEENTH-CENTURY STUDIES, Issue 2 2005KATHARINE KITTREDGE First page of article [source] Devolution and Power in the United Kingdom , Edited by Alan TrenchPARLIAMENTARY HISTORY, Issue 2 2009JAMES L. NEWELL No abstract is available for this article. [source] Pieces On Our Craft: Short Attention Spans and Glazed Eyes: Teaching World Politics in the University TrenchesINTERNATIONAL STUDIES PERSPECTIVES, Issue 4 2001Steven Majstorovic No abstract is available for this article. [source] Shattered Windows, German Spies, and Zigzag Trenches: World War I through the Eyes of Richard Harding DavisTHE HISTORIAN, Issue 1 2002Rodney Stephens [source] Seed plants of Fiji: an ecological analysisBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2006MICHAEL HEADS An annotated list of indigenous Fijian seed plant genera is presented and comprises 484 genera and 1315 species in 137 families. The relative diversity of the largest families and genera in Fiji is indicated and compared with floras in New Caledonia and the Upper Watut Valley, Papua New Guinea. Differences and similarities appear to be due to biogeographical/phylogenetic factors rather than ecological differences or means of dispersal. Generic diversity for the seed plants as a whole is greatest between 0,100 m and decreases monotonically with altitude. However, in the largest family, Orchidaceae, maximum diversity occurs between 200,400 m. Fifty percent of the families are recorded from shore habitat. Twenty-seven percent of the families and 80 species occur in or around mangrove, where the most diverse families are Orchidaceae, Rubiaceae, and the legumes. Some of the mangrove-associate species are pantropical or Indo-Pacific but most are locally or regionally endemic. Fifty-six percent of the Fijian families are recorded on limestone. Twenty-nine species are restricted to limestone and 12 species usually occur on limestone. The importance of calcium in reducing the effects of salinity is emphasized and 39 species are recorded from both mangrove and limestone. A plagiotropic habit occurs in 38 species which occur on limestone or around beaches, and 20 of these are Pacific endemics. Genera restricted to higher altitudes include many present elsewhere in Melanesia but absent from Australia despite suitable habitat there, again indicating the importance of biogeographical and historical factors. Altitudinal anomalies in Fiji taxa are cited and include 7 anomalously high records from northern Viti Levu, a site of major uplift, and 22 anomalously low altitudinal records in the Lau Group, a site of subsidence. It is suggested that the Fijian flora has not been derived from immigrants from Asia, but has evolved more or less in situ. Taxa would have survived as metapopulations on the individually ephemeral volcanic islands always found at oceanic subduction zones and hot spots, and the atolls which characterize areas of subsidence. The complex geology of Fiji is determined by its position between two subduction zones of opposite polarity, the Vanuatu and Tonga Trenches, in what is currently a region of transform faulting. The large islands comprise fragments of island arcs that have amalgamated and welded together. There has been considerable uplift as well as subsidence in the islands and it is suggested that both these processes have had drastic effects on the altitudinal range of the taxa. Limestone and mangrove floras could have provided a widespread, diverse ancestral species pool from which freshwater swamp forest, lowland rainforest, dry forest, secondary forest, thickets, and montane forest have been derived during phases of uplift. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 89, 407,431. [source] Dating floodplain sediments using tree-ring response to burial,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2005Jonathan M. Friedman Abstract Floodplain sediments can be dated precisely based on the change in anatomy of tree rings upon burial. When a stem of tamarisk (Tamarix ramosissima) or sandbar willow (Salix exigua) is buried, subsequent annual rings in the buried section resemble the rings of roots: rings become narrower, vessels within the rings become larger, and transitions between rings become less distinct. We combined observations of these changes with tree-ring counts to determine the year of deposition of sedimentary beds exposed in a 150-m-long trench across the floodplain of the Rio Puerco, a rapidly filling arroyo in New Mexico. This method reliably dated most beds thicker than about 30 cm to within a year of deposition. Floodplain aggradation rates varied dramatically through time and space. Sediment deposition was mostly limited to brief overbank flows occurring every few years. The most rapid deposition occurred on channel-margin levees, which migrated laterally during channel narrowing. At the decadal timescale, the cross-section-average sediment deposition rate was steady, but there was a shift in the spatial pattern of deposition in the 1980s. From 1936 to 1986, sediment deposition occurred by channel narrowing, with little change in elevation of the thalweg. After 1986 sediment deposition occurred by vertical aggradation. From 1936 to 2000 about 27 per cent of the arroyo cross-section filled with sediment. The rate of filling from 1962 to 2000 was 0·8 vertical m/decade or 85 m2/decade. Published in 2005 by John Wiley & Sons, Ltd. [source] Detection of a low-relief 18th-century British siege trench using LiDAR vegetation penetration capabilities at Fort Beauséjour,Fort Cumberland National Historic Site, CanadaGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 5 2009Koreen Millard Airborne Light Detection and Ranging (LiDAR), a remote sensing data collection technique, has many applications in the field of archaeology, including aiding in the planning of field campaigns, mapping features beneath forest canopy, and providing an overview of broad, continuous features that may be indistinguishable on the ground. LiDAR was used to create a high-resolution digital elevation model (DEM) in a heavily vegetated area at Fort Beauséjour,Fort Cumberland National Historic Site, Canada. Previously undiscovered archaeological features were mapped that were related to the siege of the fort in 1755. Features that could not be distinguished on the ground or through aerial photography were identified by overlaying hillshades of the DEM created with artificial illumination from various angles. LiDAR provides accurate digital topographic models with the additional benefit of mapping vertical surfaces in accurate detail below the forest canopy. © 2009 Wiley Periodicals, Inc. [source] Transient deformation of a poroelastic channel bedINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2002P.C. Hsieh Abstract The coupled transient response of a poroelastic bed form due to stream flow and non-linear water waves is investigated numerically. The theory of potential flow is applied to channel flow while Biot's theory of poroelasticity (J. Appl. Phys. 1962; 33(4):1482) is adopted to deal with the deformable porous bed. A boundary-fitted co-ordinate system is used to calculate the variation in the bed form. The result of a simple periodic wave form over a soft poroelastic bed agrees well with the analytical solution of Hsieh et al. (J. Eng. Mech., ASCE 2000; 126(10):1064). However, due to the rapidly damping second dilatational wave inside the soft poroelastic bed, the solution for transient bed form near the interface is not easy to compute accurately. In order to overcome this difficulty, a simplified numerical model based on the boundary layer correction concept proposed by Hsieh et al. (2000) is established, which neglects Darcy's terms. The transient deformation of an irregular poroelastic bed that includes a trench and a downward step at the channel bed is simulated successfully. Copyright © 2002 John Wiley & Sons, Ltd. [source] Finite element modelling of free-surface flows with non-hydrostatic pressure and k,, turbulence modelINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2005C. Leupi Abstract Validation of 3D finite element model for free-surface flow is conducted using a high quality and high spatial resolution data set. The commonly numerical models with the conventional hydrostatic pressure still remain the most widely used approach for the solution of practical engineering problems. However, when a 3D description of the velocity field is required, it is useful to resort to a more accurate model in which the hydrostatic assumption is removed. The present research finds its motivation in the increasing need for efficient management of geophysical flows such as estuaries (multiphase fluid flow) or natural rivers with the presence of short waves and/or strong bathymetry gradient, and/or strong channel curvature. A numerical solution is based on the unsteady Reynolds-averaged Navier,Stokes equations on the unstructured grid. The eddy viscosity is calculated from the efficient k,, turbulence model. The model uses implicit fractional step time stepping, and the characteristics method is used to compute the convection terms in the multi-layers system (suitable for the vertical stratified fluid flow), in which the vertical grid is located at predefined heights and the number of elements in the water column depends on water depth. The bottommost and topmost elements of variable height allow a faithful representation of the bed and the time-varying free-surface, respectively. The model is applied to the 3D open channel flows of various complexity, for which experimental data are available for comparison. Computations with and without non-hydrostatic are compared for the same trench to test the validity of the conventional hydrostatic pressure assumption. Good agreement is found between numerical computations and experiments. Copyright © 2005 John Wiley & Sons, Ltd. [source] Transpressional tectonics of the Mineoka Ophiolite Belt in a trench,trench,trench-type triple junction, Boso Peninsula, JapanISLAND ARC, Issue 4 2005Ryota Mori Abstract Structures developed in metamorphic and plutonic blocks that occur as knockers in the Mineoka Ophiolite Belt in the Boso Peninsula, central Japan, were analyzed. The aim was to understand the incorporation processes of blocks of metamorphic and plutonic rocks with an arc signature into the serpentinite mélange of the Mineoka Ophiolite Belt in relation to changes in metamorphic conditions during emplacement. Several stages of deformation during retrogressive metamorphism were identified: the first faulting stage had two substage shearing events (mylonitization) under ductile conditions inside the crystalline blocks in relatively deeper levels; and the second stage had brittle faulting and brecciation along the boundaries between the host serpentinite bodies in relatively shallower levels (zeolite facies). The first deformation occurred during uplift before emplacement. The blocks were intensively sheared by the first deformation event, and developed numerous shear planes with spacing of a few centimeters. The displacement and width of each shear plane were a few centimeters and a few millimeters, respectively, at most. In contrast, the fault zone of the second shearing stage reached a few meters in width and developed during emplacement of the Mineoka Ophiolite. Both stages occurred under a right-lateral transpressional regime, in which thrust-faulting was associated with strike-slip faulting. Such displacement on an outcrop scale is consistent with the present tectonics of the Mineoka Belt. This implies that the same tectonic stress has been operating in the Boso trench,trench,trench-type triple junction area in the northwest corner of the Pacific since the emplacement of the Mineoka Ophiolite. The Mineoka Ophiolite Belt must have worked as a forearc sliver fault during the formation of a Neogene accretionary prism further south. [source] Interdevice isolation characteristics for design and fabrication of 60-GHz WPAN SoCsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2008Sungil Kim Abstract The high interdevice isolation levels is one of the key technologies in the design and fabrication of 60-GHz WPAN SoC. To obtain proper interdevice isolation levels, we have analyzed and measured substrate coupling effects with various isolation techniques like a trench and implant structure. From the analyzed and measured results, the feasibility of the implant has confirmed to be applicable to the mm-wave SoC, and also derived an equivalent circuit form these results, which can be helpful to the design and fabrication of the 60-GHz WPAN SoC. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1699,1702, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23470 [source] Phylogeographic analysis of the red seaweed Palmaria palmata reveals a Pleistocene marine glacial refugium in the English ChannelMOLECULAR ECOLOGY, Issue 3 2005JIM PROVAN Abstract Phylogeography has provided a new approach to the analysis of the postglacial history of a wide range of taxa but, to date, little is known about the effect of glacial periods on the marine biota of Europe. We have utilized a combination of nuclear, plastid and mitochondrial genetic markers to study the biogeographic history of the red seaweed Palmaria palmata in the North Atlantic. Analysis of the nuclear rDNA operon (ITS1-5.8S-ITS2), the plastid 16S- trnI- trnA-23S-5S, rbcL- rbcS and rpl12- rps31- rpl9 regions and the mitochondrial cox2,3 spacer has revealed the existence of a previously unidentified marine refugium in the English Channel, along with possible secondary refugia off the southwest coast of Ireland and in northeast North America and/or Iceland. Coalescent and mismatch analyses date the expansion of European populations from approximately 128 000 bp and suggest a continued period of exponential growth since then. Consequently, we postulate that the penultimate (Saale) glacial maximum was the main event in shaping the biogeographic history of European P. palmata populations which persisted throughout the last (Weichselian) glacial maximum (c. 20 000 bp) in the Hurd Deep, an enigmatic trench in the English Channel. [source] The changing faces of Streptococcus antigen I/II polypeptide family adhesinsMOLECULAR MICROBIOLOGY, Issue 2 2010L. Jeannine Brady Summary Streptococcus mutans antigen I/II (AgI/II) protein was one of the first cell wall-anchored adhesins identified in Gram-positive bacteria. It mediates attachment of S. mutans to tooth surfaces and has been a focus for immunization studies against dental caries. The AgI/II family polypeptides recognize salivary glycoproteins, and are also involved in biofilm formation, platelet aggregation, tissue invasion and immune modulation. The genes encoding AgI/II family polypeptides are found among Streptococcus species indigenous to the human mouth, as well as in Streptococcus pyogenes, S. agalactiae and S. suis. Evidence of functionalities for different regions of the AgI/II proteins has emerged. A sequence motif within the C-terminal portion of Streptococcus gordonii SspB (AgI/II) is bound by Porphyromonas gingivalis, thus promoting oral colonization by this anaerobic pathogen. The significance of other epitopes is now clearer following resolution of regional crystal structures. A new picture emerges of the central V (variable) region, predicted to contain a carbohydrate-binding trench, being projected from the cell surface by a stalk formed by an unusual association between an N-terminal ,-helix and a C-terminal polyproline helix. This presentation mode might be important in determining functional conformations of other Gram-positive surface proteins that have adhesin domains flanked by ,-helical and proline-rich regions. [source] Frost heave and thaw consolidation of ploughing boulders in a mid-alpine environment, Finse, Southern NorwayPERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2001Ivar Berthling Abstract The frost heave and thaw consolidation of five large ploughing boulders were studied at Finse (UTM32VMN185198), southern Norway, by optical levelling from a bedrock benchmark. The boulders heave 3,7 cm, mainly during the early winter. Thaw consolidation starts while the boulders are still completely snow-covered in spring, but accelerates considerably when a trench in the snow is melted down to the ground surface around the boulders. During four years of measurements, the vertical position of the boulders lowered by a total mean of 5 mm. Boulder heave was well correlated to the square root of the freezing index, although differences in snow cover between subsequent years had marked effects on the heave of some of the boulders. The overburden pressure of the boulders also influenced total heave. An equation was obtained, relating boulder heave to the square root of the freezing index and the average height of the boulder. Copyright © 2001 John Wiley & Sons, Ltd. RÉSUMÉ Le soulèvement par le gel et la retombée au dégel de 5 grands blocs labourant ont été observés à Finse (UTM MN185198), au sud de la Norvège, par nivellement optique à partir d'un repère fixé sur la roche en place. Le soulèvement est de 3-7 cm et se réalise principalement pendant le début de l'hiver. L'affaissement au dégel débute au printemps alors que les blocs sont encore complètement couverts de neige, mais s'accélère beaucoup quand la neige a fondu autour des blocs. Pendant les quatre années de mesures, les blocs se sont affaissés au dégel d'une moyenne totale de 5 mm. Le soulèvement des blocs est bien corrélé avec la racine carrée de l'index de gel, quoique des différences dans la couverture de neige suivant les années ont des effets marqués sur le soulèvement de quelques blocs. La pression des blocs influence aussi le soulèvement total. Une équation a été obtenue mettant en relation le soulèvement des blocs avec la racine carrée de l'index de gel et la hauteur moyenne des blocs. Copyright © 2001 John Wiley & Sons, Ltd. [source] Lithographically patterned nanowire electrodepositionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2008Chengxiang Xiang Abstract Lithographically Patterned Nanowire Electrodeposition (LPNE) is a new nanofabrication technique in which photolithography is used to define the position of electrodeposited nanowires on the surface of a dielectric such as glass or oxidized silicon. In LPNE, a resist-covered nickel film with a thickness of beween 6 and 100 nm is photopatterned. After development of the resist, the exposed nickel is dissolved in nitric acid under conditions that produce an "undercut" at the resist edges. This undercut functions as a horizontal trench into which metals (e.g., Au, Pt, Pd) can be electrodeposited using the exposed nickel edge present within this trench. As this trench is filled during electrodeposition, a nanowire with a precisely defined height and width is formed along the entire perimeter of the photoresist. LPNE nanowires can have minimum dimensions of 6 nm (h) x 20 nm (w) and lengths of more than 1 cm. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] 3D Monte Carlo simulation of transport in electro-statically confined silicon nanochannelsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008Mohamed Mohamed Abstract This study investigates transport and electrostatic behavior of quasi 1D nanowires adopting a relatively simple planar fabrication technique. The confined conduction channel is created by etching an oxide trench, realizing a T-gate structure. Since multiple channels are normally needed to realize sufficient current drive in practical applications, the behavior of single and coupled adjacent silicon nanowires is characterized using a 3D quantum corrected Monte Carlo approach. Results indicate that a single T-gate structure provides over 27% increase in current drive compared to conventional MOSFET at a drain voltage of 1V. In addition, design consideration and recommendation is presented. Cross section of a T-gate MOSFET. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mid,Cretaceous Episodic Magmatism and Tin Mineralization in Khingan-Okhotsk Volcano,Plutonic Belt, Far East RussiaRESOURCE GEOLOGY, Issue 1 2002Kohei SATO Abstract: Age of magmatism and tin mineralization in the Khingan-Okhotsk volcano,plutonic belt, including the Khingan, Badzhal and Komsomolsk tin fields, were reviewed in terms of tectonic history of the continental margin of East Asia. This belt consists mainly of felsic volcanic rocks and granitoids of the reduced type, being free of remarkable geomagnetic anomaly, in contrast with the northern Sikhote-Alin volcano,plutonic belt dominated by oxidized-type rocks and gold mineralization. The northern end of the Khingan-Okhotsk belt near the Sea of Okhotsk, accompanied by positive geomagnetic anomalies, may have been overprinted by magmatism of the Sikhote-Alin belt. Tin,associated magmatism in the Khingan-Okhotsk belt extending over 400 km occurred episodically in a short period (9510 Ma) in the middle Cretaceous time, which is coeval with the accretion of the Kiselevka-Manoma complex, the youngest accretionary wedge in the eastern margin of the Khingan-Okhotsk accretionary terranes. The episodic magmatism is in contrast with the Cretaceous-Paleogene long,lasted magmatism in Sikhote,Alin, indicating the two belts are essentially different arcs, rather than juxtaposed arcs derived from a single arc. The tin-associated magmatism may have been caused by the subduction of a young and hot back-arc basin, which is inferred from oceanic plate stratigraphy of the coeval accre-tionary complex and its heavy mineral assemblage of immature volcanic arc provenance. The subduction of the young basin may have resulted in dominance of the reduced-type felsic magmas due to incorporation of carbonaceous sediments within the accretionary complex near the trench. Subsequently, the back-arc basin may have been closed by the oblique collision of the accretionary terranes in Sikhote,Alin, which was subjected to the Late Cretaceous to Paleogene magmatism related to another younger subduction system. These processes could have proceeded under transpressional tectonic regime due to oblique subduction of the paleo-Pacific plates under Eurasian continent. [source] War, Politics, and Voice: The Vocal Fold Paralysis of George Orwell,THE LARYNGOSCOPE, Issue 2 2007Lucian Sulica MD Abstract Background: In 1936, like many individuals who felt the menace of fascism, George Orwell traveled to Spain to lend his support to the cause of the Republic, battling a right-wing coup. Spain, during its Civil War, was an eye-opening experience for him, yielding insights that allowed, and even compelled him to write Animal Farm and 1984. Spain was also a close brush with death. In May of 1937, in a trench on a windswept ridge near Huesca, Orwell was shot through the neck by a sniper, leaving him with a paralyzed vocal fold. Design: A thorough review of firsthand accounts of Orwell's injury and subsequent care was made. These are presented in the context of current knowledge of ballistics, penetrating neck trauma, and vocal fold paralysis. Results and Conclusion: Orwell survived largely because of the nature of his wounding with a high-velocity jacketed military round. His recovery followed a course in many ways typical for patients with vocal fold paralysis. His writings leave us a unique and extraordinary account of the experience of being shot, of the medical care of the day, of the handicap of paralytic dysphonia, and of survival and heroism under extraordinary circumstances. [source] Scanning Electron Microscopic Study of the Lingual Papillae in the Arctic Fox (Alopex lagopus L., 1758)ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 5 2009H. Jackowiak Summary This study aims to show the distribution and the three-dimensional structure of the lingual papillae in the arctic fox. The macro- and microscopic structure of the tongue and its lingual papillae was studied in 11 adult arctic foxes. Two types of mechanical papillae were distinguished on the dorsal surface of the tongue , filiform papillae and conical papillae. The gustatory papillae in the arctic fox are represented by fungiform, vallate and foliate papillae. The keratinized filiform papillae on the anterior part of tongue are composed of one big posterior process accompanied by 10,12 secondary anterior processes. The number of anterior processes of filiform papillae undergo a complete reduction within the area between the posterior part of the body of the tongue and area of the vallate papillae. The conical papillae cover the whole dorsal surface of the root of the tongue, including the lateral parts surrounding the area of the vallate papillae and the posterior part of the root. The size of the conical papillae increases towards the root of the tongue but their density decreases. In the arctic fox, there are three pairs of vallate papillae distributed on the plan of a triangle. The diameter of vallate papillae in each successive pair is bigger. The wall surrounding the body of the vallate papilla and its gustatory trench is composed of six to eight conical papillae joined at various degree. The foliate papillae on both margins of the tongue consist of seven to nine laminae. [source] Geophysical investigation of the Environs of Rattin Castle Tower House, County Westmeath, IrelandARCHAEOLOGICAL PROSPECTION, Issue 1 2009T. O'Rourke Abstract No visible archaeological features are today associated with Rattin Castle Tower House in County Westmeath, Ireland located near the boundary of the Pale, the area around Dublin and adjoining counties where English control prevailed. However, both magnetic and resistance data show that Rattin Castle was surrounded by a substantial bawn wall, which has since been removed. Interpretation of two-dimensional resistivity shows a deep trench at the site of the bawn wall. A small (12 by 16,m) rectangular low-resistance anomaly located outside the northern section of the bawn wall but connected to it, is interpreted as a possible gatehouse providing access to the castle. Less than 20,m from this anomaly, the course of an old military road is delineated by magnetic data but is seen most clearly on the resistance data where it is represented by two parallel low-resistance anomalies 230,m long. This road is possibly older than the castle. Rattin is associated with an extensive network of subrectangular field boundaries and enclosures, most noticeably west of the castle. The presence of the military road, potential gatehouse, substantial bawn wall and geographical location all suggest that Rattin Castle was an important strategic fortification in Ireland. Copyright © 2009 John Wiley & Sons, Ltd. [source] Trench-forearc interactions reflected in the sedimentary fill of Talara basin, northwest PeruBASIN RESEARCH, Issue 3 2008Andrea Fildani ABSTRACT Exceptional exposure of the forearc region of NW Peru offers insight into evolving convergent margins. The sedimentary fill of the Talara basin spans the Cretaceous to the Eocene for an overall thickness of 9000 m and records within its stratigraphy the complicated history of plate interactions, subduction tectonics, terrane accretion, and Andean orogeny. By the early Tertiary, extensional tectonism was forming a complex horst and graben system that partitioned the basin into a series of localized depocentres. Eocene strata record temporal transitions from deltaic and fluvial to deep-water depositional environments as a response to abrupt, tectonically controlled relative sea-level changes across those depocentres. Stratigraphic and provenance data suggest a direct relationship between sedimentary packaging and regional tectonics, marked by changes in source terranes at major unconformities. A sharp shift is recognized at the onset of deepwater (bathyal) sedimentation of the Talara Formation, whose sediments reflect an increased influx of mafic material to the basin, likely related to the arc region. Although the modern topography of the Amotape Mountains partially isolates the Talara basin from the Lancones basin and the Andean Cordillera to the east, provenance data suggest that the Amotape Mountains were not always an obstacle for Cordilleran sediment dispersal. The mountain belt intermittently isolated the Talara basin from Andean-related sediment throughout the early Tertiary, allowing arc-related sediment to reach the basin only during periods of subsidence in the forearc region, probably related to plate rearrangement and/or seamounts colliding with the trench. Intraplate coupling and/or partial locking of subduction plates could be among the major causes behind shifts from contraction to extension (and enhanced subduction erosion) in the forearc region. Eventually, collisional tectonic and terrane accretion along the Ecuadorian margin forced a major late-Eocene change in sediment dispersal. [source] Controlling factors of gullying in the Maracujá Catchment, southeastern BrazilEARTH SURFACE PROCESSES AND LANDFORMS, Issue 11 2005L. de A. P. Bacellar Abstract Hundreds of gullies (,voçorocas') of huge dimensions (up to 400,500 m long, 150 m wide and 50 m deep) are very common in the small Maracujá Catchment in southeastern Brazil. These erosional features, which occur with an uneven intensity throughout the area, started due to bad soil management practices at the beginning of European settlement, at the end of the 17th century, and nowadays are still evolving, but at a slower rate. As surface soils are usually very resistant to erosion, the outcrop of the more erodible basement saprolites seems to be an essential condition for their beginning. An analysis of well known erosion controlling factors was performed, aiming to explain the beginning and evolution of these gullies and to understand the reasons for their spatial distribution. Data shows that geology and, mainly, geomorphology are the main controlling factors, since gullies tend to be concentrated in basement rock areas with lower relief (domain 2) of Maracujá Catchment, mainly at the fringes of broad and flat interfluves. At the detailed scale (1:10 000), gullies are more common in amphitheatre-like headwater hollows that frequently represent upper Quaternary gullies (paleogullies), which demonstrate the recurrence of channel erosion. So, gullies occur in areas of thicker saprolites (domain 2), in places with a natural concentration of surface and underground water (hollows). Saprolites of the preserved, non-eroded hollows are usually pressurized (confined aquifer) due to a thick seal of Quaternary clay layer, in a similar configuration to the ones found in hollows of mass movement (mudflow) sites in southeastern Brazil. Therefore, the erosion of the resistant soils by human activities, such as road cuts and trenches (,valos'), or their mobilization by mudflow movements, seem to be likely mechanisms of gullying initiation. Afterwards, gullies evolve by a combination of surface and underground processes, such as wash and tunnel erosion and falls and slumps of gully walls. Copyright © 2005 John Wiley & Sons, Ltd. [source] Somatic war syndromes: no man's land between the trenches?EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 7 2000De Loos First page of article [source] Synthesis of Poly(4-vinylpyridine) Thin Films by Initiated Chemical Vapor Deposition (iCVD) for Selective Nanotrench-Based Sensing of NitroaromaticsADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Wyatt E. Tenhaeff Abstract A new nanoscale sensing concept for the detection of nitroaromatic explosives is described. The design consists of nitroaromatic-selective polymeric layers deposited inside microfabricated trenches. As the layers are exposed to nitroaromatic vapors, they swell and contact each other to close an electrical circuit. The nitroaromatic selective polymer, poly(4-vinylpyridine) (P4VP), is deposited in the trenches using initiated chemical vapor deposition (iCVD). P4VP is characterized for the first time as a selective layer for the absorption of nitroaromatic vapors. The Flory,Huggins equation is used to model the swelling response to nitroaromatic vapors. The Flory,Huggins interaction parameter for the P4VP,nitrobenzene system at 40,°C is 0.71 and 0.25 for P4VP,4-nitrotoluene at 60,°C. Sensing of nitrobenzene vapors is demonstrated in a prototype device, while techniques to improve the performance of the design in terms of response time and sensitivities are described. Modeling shows that concentration and mass limits of detection of 0.95,ppb and 3 fg, respectively, can be achieved. [source] Densely Packed Arrays of Ultra-High-Aspect-Ratio Silicon Nanowires Fabricated using Block-Copolymer Lithography and Metal-Assisted EtchingADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Shih-Wei Chang Abstract Metal-assisted etching is used in conjunction with block-copolymer lithography to create ordered and densely-packed arrays of high-aspect-ratio single-crystal silicon nanowires with uniform crystallographic orientations. Nanowires with diameters and spacings down to 19,nm and 10,nm, respectively, are created as either continuous carpets or as carpets within trenches. Wires with aspect ratios up to 220 are fabricated, and capillary-induced clustering of wires is eliminated through post-etching critical point drying. The wires are single crystals with ,100, axis directions. The distribution of wire diameters is narrow and closely follows the size distribution of the block copolymer, with a standard deviation of 3.12,nm for wires of mean diameters 22.06,nm. Wire arrays formed in carpets and in channels have hexagonal order with good fidelity to the block copolymer pattern. Fabrication of wires in topographic features demonstrates the ability to accurately control wire placement. Wire arrays made using this new process will have applications in the creation of arrays of photonic and sensing devices. [source] | ||||||||||||||||||||||||||||