ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (74,135)
  • Elsevier  (58,570)
  • American Institute of Physics (AIP)  (8,513)
  • Blackwell Publishing Ltd  (7,052)
  • 2020-2023  (27)
  • 2000-2004  (2)
  • 1990-1994  (74,108)
  • 1935-1939
  • 2020  (29)
  • 1990  (74,106)
Collection
Years
Year
Journal
  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters B 294 (1992), S. 466-478 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters B 317 (1993), S. 474-484 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2022-05-25
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Jacox, M. G., Alexander, M. A., Siedlecki, S., Chen, K., Kwon, Y., Brodie, S., Ortiz, I., Tommasi, D., Widlansky, M. J., Barrie, D., Capotondi, A., Cheng, W., Di Lorenzo, E., Edwards, C., Fiechter, J., Fratantoni, P., Hazen, E. L., Hermann, A. J., Kumar, A., Miller, A. J., Pirhalla, D., Buil, M. P., Ray, S., Sheridan, S. C., Subramanian, A., Thompson, P., Thorne, L., Annamalai, H., Aydin, K., Bograd, S. J., Griffis, R. B., Kearney, K., Kim, H., Mariotti, A., Merrifield, M., & Rykaczewski, R. Seasonal-to-interannual prediction of North American coastal marine ecosystems: forecast methods, mechanisms of predictability, and priority developments. Progress in Oceanography, 183, (2020): 102307, doi:10.1016/j.pocean.2020.102307.
    Description: Marine ecosystem forecasting is an area of active research and rapid development. Promise has been shown for skillful prediction of physical, biogeochemical, and ecological variables on a range of timescales, suggesting potential for forecasts to aid in the management of living marine resources and coastal communities. However, the mechanisms underlying forecast skill in marine ecosystems are often poorly understood, and many forecasts, especially for biological variables, rely on empirical statistical relationships developed from historical observations. Here, we review statistical and dynamical marine ecosystem forecasting methods and highlight examples of their application along U.S. coastlines for seasonal-to-interannual (1–24 month) prediction of properties ranging from coastal sea level to marine top predator distributions. We then describe known mechanisms governing marine ecosystem predictability and how they have been used in forecasts to date. These mechanisms include physical atmospheric and oceanic processes, biogeochemical and ecological responses to physical forcing, and intrinsic characteristics of species themselves. In reviewing the state of the knowledge on forecasting techniques and mechanisms underlying marine ecosystem predictability, we aim to facilitate forecast development and uptake by (i) identifying methods and processes that can be exploited for development of skillful regional forecasts, (ii) informing priorities for forecast development and verification, and (iii) improving understanding of conditional forecast skill (i.e., a priori knowledge of whether a forecast is likely to be skillful). While we focus primarily on coastal marine ecosystems surrounding North America (and the U.S. in particular), we detail forecast methods, physical and biological mechanisms, and priority developments that are globally relevant.
    Description: This study was supported by the NOAA Climate Program Office’s Modeling, Analysis, Predictions, and Projections (MAPP) program through grants NA17OAR4310108, NA17OAR4310112, NA17OAR4310111, NA17OAR4310110, NA17OAR4310109, NA17OAR4310104, NA17OAR4310106, and NA17OAR4310113. This paper is a product of the NOAA/MAPP Marine Prediction Task Force.
    Keywords: Prediction ; Predictability ; Forecast ; Ecological forecast ; Mechanism ; Seasonal ; Interannual ; Large marine ecosystem
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 2022-02-16
    Description: On September 6, 2017, the solar active region AR 2673 emitted two solar flares: the first at 08:57 UT (X2.2) and the second at 11:53 UT (X9.3); both were powerful enough to black-out high and low frequency radio waves (where UT is universal time). The X9.3 was the strongest solar flare event in the past decade. In this study, we took the advantage of these two extreme flare events to investigate corresponding effects on the ionosphere using multi-instrument observations from magnetometers, Global Positioning System – Total Electron content (GPS-TEC) receivers, ionosondes and Swarm satellites over a large geographical extent covering South American, African and European sectors. During the X2.2 flare, European and African sectors were sunlit and during X9.3 European, African, and South American sectors were sunlit and exposed to the solar flare radiation. During the X2.2 flare, there was an ionosonde blackout for a duration of about 45 min, while during the X9.3 flare this blackout lasted for 1 h and 30 min. The blackout are seen over a large global extent which demonstrates the severity of solar flare events in disrupting the radio communication. The horizontal component of Earth’s geomagnetic field has shown ripples and enhancements during these flare events. The ionospheric Vertical Total Electron Content (VTEC) showed a positive phase along with an intensification of the Equatorial Ionization Anomaly (EIA) over the South American and African sectors. The dynamical and physical processes associated with the TEC and EIA variabilities due to solar flare are discussed.
    Description: Published
    Description: 1775-1791
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2022-01-07
    Description: Palaeoenvironmental reconstructions with temporal coverages extending beyond Marine Isotope Stage (MIS) three are scarce within the data sparse region of Chukotka, Far East Russia. The objective of this paper is to infer palaeoenvironmental variability from a 10.76 m long, OSL- and 14C- dated sediment core from Lake Ilirney, Chukotka (67°21′N, 168°19′E). We analysed high-resolution sediment-geochemistry (XRF), sedimentology (TC, TN, TOC, grain-size), mineralogy (XRD) and preliminary micropalaeontological data (diatoms and pollen) from the core as well as acoustic sub-bottom profiling data from the lake basin. Our results affirm the application of XRF-based sediment-geochemical proxies as effective tracers of palaeoenvironmental variability within arctic lake systems. Our study reveals that a lake formed during MIS3 from 51.8 (±4.1) ka BP, following extensive MIS4 glaciation. Catchment palaeoenvironmental conditions during this time remained harsh associated with the continued presence of a catchment glacier until 36.2 (±2.6) ka BP. Partial amelioration reflected by increased diatom, catchment vegetation and lake organic productivity and clastic sediment input from mixed sources from 36.2 (±2.6) ka BP resulted in a lake high-stand ∼15 m above present and is interpreted as evidence of a more productive palaeoenvironment coincident with the MIS3 interstadial optimum. A transitional period of deteriorating palaeoenvironmental conditions occurred ∼30–27.9 ka BP and was superseded by periglacial-glacial conditions from 27.9 (±0.8) ka BP, during the last glacial maximum. Deglaciation as marked by sediment-geochemical proxies commenced at 20.2 (±0.8) ka BP. Our findings are compared with lacustrine, Yedoma and river-bluff records from across Beringia and potentially yield limited support for a marked Younger Dryas cooling in the study area.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Publication Date: 2022-06-10
    Description: In fold and thrust belts developing at convergent margins, the migration of the advancing wedge is accompanied by bulging of the downgoing plate, followed by the development of a foredeep basin filled by a thick succession of syn-orogenic sediments. The transition from forebulge to foredeep marks a key moment in the evolution of the orogenic system. In deep water environments, the record of this transition is typically complete and progressive. Conversely, in the shallow-water/continental environment of many collisional systems, the uplift of the forebulge area can imply emersion and erosion, obliterating the stratigraphic record of key steps of the evolution of the orogenic system. The southern Apennines constitute one of these collisional fold and thrust belts where the development of the forebulge has implied emersion and erosion, with the development of a Miocene forebulge erosional unconformity, accompanied by extensional deformation associated with the bending of the lithosphere during the forebulge stage. In this paper, we use strontium isotope stratigraphy to constrain with unprecedented time-resolution the age of the forebulge unconformity in areas presently incorporated in the northern sector of the southern Apennines fold and thrust belt. Integration of our results and those of previous studies indicates, at the regional scale, a younging toward the foreland of the forebulge unconformity across the belt. Our highresolution ages also reveal a diachronous onset of the flexural subsidence over short distances, associated with the occurrence of horst and graben structures, possibly resulting from inherited paleotopography along with forebulge extension. This work highlights how high-resolution dating is critical to unravel the evolution of foreland basin systems at different scales.
    Description: Published
    Description: 105634
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: 2TR. Ricostruzione e modellazione della struttura crostale
    Description: 2IT. Laboratori analitici e sperimentali
    Description: JCR Journal
    Keywords: Foreland basin system ; Forebulge unconformity ; Strontium isotope stratigraphy ; Forebulge extension ; Miocene ; Southern Apennines (Italy)
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Du, J., Park, K., Yu, X., Zhang, Y. J., & Ye, F. Massive pollutants released to Galveston Bay during Hurricane Harvey: Understanding their retention and pathway using Lagrangian numerical simulations. Science of the Total Environment, 704, (2019): 135364, doi: 10.1016/j.scitotenv.2019.135364.
    Description: Increasing frequency of extreme precipitation events under the future warming climate makes the storm-related pollutant release more and more threatening to coastal ecosystems. Hurricane Harvey, a 1000-year extreme precipitation event, caused massive pollutant release from the Houston metropolitan area to the adjacent Galveston Bay. 0.57 × 106 tons of raw sewage and 22,000 barrels of oil, refined fuels and chemicals were reportly released during Harvey, which would likely deteriorate the water quality and damage the coastal ecosystem. Using a Lagrangian particle-tracking method coupled with a validated 3D hydrodynamic model, we examined the retention, pathway, and fate of the released pollutants. A new timescale, local exposure time (LET), is introduced to quantitatively evaluate the spatially varying susceptibility inside the bay and over the shelf, with a larger LET indicating the region is more susceptible to the released pollutants. We found LET inside the bay is at least one order of magnitude larger for post-storm release than storm release due to a quick recovery in the system's flushing. More than 90% of pollutants released during the storm exited the bay within two days, while those released after the storm could stay inside the bay for up to three months. This implies that post-storm release is potentially more damaging to water quality and ecosystem health. Our results suggest that not only the amount of total pollutant load but also the release timing should be considered when assessing a storm's environmental and ecological influence, because there could be large amounts of pollutants steadily and slowly discharged after storm through groundwater, sewage systems, and reservoirs.
    Description: We like to acknowledge the Texas Coastal Management Program, the Texas General Land Office and NOAA for partial funding of this project through CMP Contract #19-040-000-B074. This work was performed using computing facilities at the College of William and Mary, which were provided by contributions from the National Science Foundation, the Commonwealth of Virginia Equipment Trust Fund and the Office of Naval Research.
    Keywords: Storm discharge ; Retention ; Local exposure time ; Particle tracking ; SCHISM
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Mundl-Petermeier, A., Walker, R. J., Jackson, M. G., Blichert-Toft, J., Kurz, M. D., & Halldorsson, S. A. Temporal evolution of primordial tungsten-182 and he-3/He-4 signatures in the Iceland mantle plume. Chemical Geology, 525, (2019): 245-259. doi: 10.1016/j.chemgeo.2019.07.026.
    Description: Studies of short-lived radiogenic isotope systems and noble gas isotopic compositions of plume-derived rocks suggest the existence of primordial domains in Earth's present-day mantle. Tungsten-182 anomalies together with high 3He/4He in Phanerozoic rocks from large igneous provinces and ocean island basalts demonstrate the preservation of early-formed (within the first 60 Ma of solar system history) mantle domains tapped by modern mantle plumes. It has proven difficult to link the evidence for primordial domains with geochemical evidence for more recent processes, such as recycling. The Greenland-Iceland plume system, starting with eruptions of the Paleocene North Atlantic Igneous Province, is later manifested in the mid-Miocene to modern volcanic products of Iceland. Here, we report Pb isotopic compositions, μ182W (deviations in 182W/184W of a sample from a laboratory reference standard in parts per million), and 3He/4He, as well as highly siderophile element concentrations and Re-Os isotopic systematics of basaltic samples erupted at different times during the ~60 Ma history of the Greenland-Iceland plume. Paleocene samples from Greenland, representing the early stage of the mantle plume, are characterized by variable 3He/4He ranging from 7 to 48 R/RA (measured 3He/4He normalized to the atmospheric ratio) and an average μ182W of −4.0 ± 3.6 (2SD), within modern upper mantle-like values of 0 ± 4.5. The basalts from Iceland can be divided into two groups based on their Pb isotope compositions. One group, consisting mostly of Miocene basalts, is characterized by 206Pb/204Pb ranging from ~18.4 to 18.5, 3He/4He ranging from 17.8 to 40.2 R/RA, and μ182W values ranging from +1.7 to −9.1 ± 4.5. The other group, consisting mainly of Pleistocene and Holocene basalts, is characterized by higher 206Pb/204Pb, ranging from ~18.7 to 19.2, 3He/4He ranging from 7.9 to 25.7 R/RA, and μ182W values ranging from −0.6 to −11.7 ± 4.5. Collectively, the Greenland-Iceland suite examined requires mixing between a minimum of three mantle source domains characterized by distinct Pb-He-W isotopic compositions, in order to account for this range of isotopic data. The temporal changes in the isotopic data for these rocks appear to track the dominant contributing plume components as the system evolved. One of the domains is indistinguishable from the ambient upper oceanic mantle and contributed substantial material throughout the time progression. The other two domains are most likely primordial reservoirs that underwent limited de-gassing. Given the negative μ182W values in some rocks, one of these domains likely formed within the first 60 Ma of solar system history and is a major contributor to the youngest basalts. The isotopic characteristics of Greenland-Iceland plume-derived rocks reveal episodic changes in the source component proportions.
    Description: This study was supported by NSF grant EAR-1624587 (to RJW and AMP). AMP acknowledges FWF grant V659-N29. MJ acknowledges NSF grant EAR-1624840, and MK acknowledges OCE-1259218. We would like to thank Lotte M. Larsen and Asger K. Pedersen for providing the West Greenland samples, and Bernard Marty for the samples from East Greenland. We thank Catherine Chauvel for the editorial handling and Rita Parai, Dominique Weis, David Graham and an anonymous reviewer for the helpful and constructive comments on this and an earlier version of the manuscript.
    Keywords: μ182W ; Iceland ; Mantle plume ; 3He/4He ; Primordial reservoir
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wheat, C. G., Seewald, J. S., & Takai, K. Fluid transport and reaction processes within a serpentinite mud volcano: South Chamorro Seamount. Geochimica Et Cosmochimica Acta, 269, (2020): 413-428, doi: 10.1016/j.gca.2019.10.037
    Description: Natural fluids with a pH (25 °C) up to 12.3 were collected from a sub-seafloor borehole observatory (Ocean Drilling Program (ODP) Hole 1200C) on South Chamorro Seamount, a serpentinite mud volcano in the Mariana forearc. We used systematic differences in the chemical compositions of pore waters from drilling operations during ODP Leg 195 and borehole fluids collected subsequently from Hole 1200C to define two endmember solutions, one of which was a sulfate-rich fluid with a methane concentration of 50 mM that ascends from the subduction channel and the other was a low-sulfate fluid. The sequence of sample collection and fluid compositions constrain subsurface hydrologic conditions. Deep-sourced, sulfate- and methane-rich, sterile fluids from the subduction channel can reach the seafloor unchanged within the central conduit, whereas other fluid pathways likely intersect the pelagic sediment that underlies the serpentinite mud volcano, providing potentially suitable conditions and inoculum for microbial anaerobic oxidation of methane (AOM). These AOM-affected, low-sulfate fluids also make it to the seafloor where they discharge. The source of the sulfate- and methane-rich fluid in the subduction channel is attributed to abiotic methane production fueled by hydrogen production from serpentinization and carbonate dissolution. This methane production includes a mechanism to raise the pH above values from serpentinization alone. Results from South Chamorro Seamount represent an end member along a transect defined by the distance from the trench. Results from this site are applied to other serpentinite mud volcanoes along this transect to speculate on likely chemical conditions within shallower and cooler portions of the subduction channel.
    Description: The authors thank the entire shipboard parties of cruises NT09-01 and NT09-07 on the R/V Nastushima and the crews and pilots of the ROV HyperDolphin. We also thank Tom Pettigrew for removing the dummy plug and designing the insert for the borehole. This research was supported by the National Science Foundation (OCE-0727120 and 1439564 (CGW) and OCE--0725204 (JS)) and the Japan Agency for Marine-Earth Science and Technology. This is C-DEBI contribution 497.
    Keywords: Serpentinization ; Mud volcano ; Subduction ; Mariana forearc ; Dissolved gases ; Anaerobic methane oxidation
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Horowitz, E. J., Cochran, J. K., Bacon, M. P., & Hirschberg, D. J. 210Po and 210Pb distributions during a phytoplankton bloom in the North Atlantic: implications for POC export. Deep-Sea Research Part I: Oceanographic Research Papers, 164, (2020): 103339, doi:10.1016/j.dsr.2020.103339.
    Description: During the North Atlantic Bloom Experiment (NABE) of the Joint Global Ocean Flux Study (JGOFS), water column sampling for particulate and dissolved 210Po and 210Pb was performed four times (26 April and 4, 20, 30 May 1989) during a month-long Lagrangian time-series occupation of the NABE site, as well as one-time samplings at stations during transit to and from the site. There are few prior studies documenting short-term changes in 210Po and 210Pb profiles over the course of a phytoplankton bloom, and we interpret the profiles in terms of the classical “steady-state” (SS) approach used in most studies, as well as by using a non-steady state approach suggested by the temporal evolution of the profiles. Changes in 210Po profiles during a bloom are expectable as this radionuclide is scavenged and exported. During NABE, 210Pb profiles also displayed non-steady state, with significant increases in upper water column inventory occurring midway through the experiment. Export of 210Po from the upper 150 m using the classic “steady-state” model shows increases from 0.5 ± 8.5 dpm m−2 d−1 to 68.2 ± 4.2 dpm m−2 d−1 over the ~one-month occupation. Application of a non-steady state model, including changes in both 210Pb and 210Po profiles, gives higher 210Po export fluxes. Detailed depth profiles of particulate organic carbon (〉0.8 μm) and particulate 210Po (〉0.4 μm) are available from the 20 and 30 May samplings and show maxima in POC/Po at ~37 m. Applying the POC/210Po ratios at 150 m to the “steady state” 210Po fluxes yields POC export from the upper 150 m of 8.2 ± 1.5 mmol C m− 2 d−1 on 20 May and 6.0 ± 1.6 mmol C m−2 d−1 on 30 May. The non-steady state model applied to the interval 20 to 30 May yields POC export of 24.3 mmol C m−2 d−1. The non-steady state (NSS) 210Po-derived POC fluxes are comparable to, but somewhat less than, those estimated previously from 234Th/238U disequilibrium for the same time interval (37.3 and 45.0 mmol m−2 d−1, depending on the POC/Th ratio used). In comparison, POC fluxes measured with a floating sediment trap deployed at 150 m from 20 to 30 May were 11.6 mmol m−2 d−1. These results suggest that non-steady state Po-derived POC fluxes during the NABE agree well with those derived from 234Th/238U disequilibrium and agree with sediment trap fluxes within a factor of ~2. However, unlike the 234Th-POC flux proxy, non-steady stage changes in profiles of 210Pb, the precursor of 210Po, must be considered.
    Description: We are grateful to T. Hammar and A. Fleer (WHOI) for assistance at sea and in the laboratory. This work was supported originally by National Science Foundation (United States) grant OCE-8819544 to JKC and more recently by OCE-1736591. We thank Stephen Thurston (American Museum of Natural History) for graphics assistance Robert Aller, Steven Beaupre, and two anonymous reviewers for helpful comments.
    Keywords: Polonium-210 ; Lead-210 ; 210Po ; 210Pb ; North Atlantic ; Spring bloom ; POC flux
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 11
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lin, P., Pickart, R. S., Fissel, D., Ross, E., Kasper, J., Bahr, F., Torres, D. J., O'Brien, J., Borg, K., Melling, H., & Wiese, F. K. Circulation in the vicinity of Mackenzie Canyon from a year-long mooring array. Progress in Oceanography, 187, (2020): 102396, doi:10.1016/j.pocean.2020.102396.
    Description: Data from a five-mooring array extending from the inner shelf to the continental slope in the vicinity of Mackenzie Canyon, Beaufort Sea are analyzed to elucidate the components of the boundary current system and their variability. The array, part of the Marine Arctic Ecosystem Study (MARES), was deployed from October 2016 to September 2017. Four distinct currents were identified: an eastward-directed flow adjacent to the coast; a westward-flowing, surface-intensified current centered on the outer-shelf; a bottom-intensified shelfbreak jet flowing to the east; and a recirculation at the base of the continental slope within the canyon. The shelf current transports −0.120.03 Sv in the mean and is primarily wind-driven. The response is modulated by the presence of ice, with little-to-no signal during periods of nearly-immobile ice cover and maximum response when there is partial ice cover. The shelfbreak jet transports 0.030.02 Sv in the mean, compared to 0.080.02 Sv measured upstream in the Alaskan Beaufort Sea over the same time period. The loss of transport is consistent with a previous energetics analysis and the lack of Pacific-origin summer water downstream. The recirculation in the canyon appears to be the result of local dynamics whereby a portion of the westward-flowing southern limb of the Beaufort Gyre is diverted up the canyon across isobaths. This interpretation is supported by the fact that the low-frequency variability of the recirculation is correlated with the wind-stress curl in the Canada Basin, which drives the Beaufort gyre.
    Description: The authors are indebted to Fisheries and Oceans Canada for building the logistics for MARES into the at-sea missions of the Integrated Beaufort Observatory. We are grateful to the captain and crew of the CCGS Sir Wilfred Laurier for ably deploying and recovering the MARES array. Marshall Swartz assisted with the cruise preparation logistics. We thank the two anonymous reviewers for their input which helped improve the paper. This project was funded by the US Bureau of Ocean Energy Management (BOEM), on behalf of the National Ocean Partnership Program. The Canadian contribution was supported by the Environmental Studies Research Fund (ESRF Project 2014-02N). MARES publication 003.
    Keywords: Canadian Beaufort Sea ; Mackenzie Canyon ; Boundary currents ; Canyon circulation ; Ice-ocean interaction
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    Publication Date: 2022-10-27
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hirst, W. G., Biswas, A., Mahalingan, K. K., & Reber, S. Differences in intrinsic tubulin dynamic properties contribute to spindle length control in Xenopus species. Current Biology, 30(11), (2020): 2184-2190.e5, doi: 10.1016/j.cub.2020.03.067.
    Description: The function of cellular organelles relates not only to their molecular composition but also to their size. However, how the size of dynamic mesoscale structures is established and maintained remains poorly understood [1, 2, 3]. Mitotic spindle length, for example, varies several-fold among cell types and among different organisms [4]. Although most studies on spindle size control focus on changes in proteins that regulate microtubule dynamics [5, 6, 7, 8], the contribution of the spindle’s main building block, the αβ-tubulin heterodimer, has yet to be studied. Apart from microtubule-associated proteins and motors, two factors have been shown to contribute to the heterogeneity of microtubule dynamics: tubulin isoform composition [9, 10] and post-translational modifications [11]. In the past, studying the contribution of tubulin and microtubules to spindle assembly has been limited by the fact that physiologically relevant tubulins were not available. Here, we show that tubulins purified from two closely related frogs, Xenopus laevis and Xenopus tropicalis, have surprisingly different microtubule dynamics in vitro. X. laevis microtubules combine very fast growth and infrequent catastrophes. In contrast, X. tropicalis microtubules grow slower and catastrophe more frequently. We show that spindle length and microtubule mass can be controlled by titrating the ratios of the tubulins from the two frog species. Furthermore, we combine our in vitro reconstitution assay and egg extract experiments with computational modeling to show that differences in intrinsic properties of different tubulins contribute to the control of microtubule mass and therefore set steady-state spindle length.
    Description: This article was prompted by our stay at the Marine Biological Laboratory (MBL), Woods Hole, MA in the summer of 2016 funded by the Princeton-Humboldt Strategic Partnership Grant together with the lab of Sabine Petry (Princeton University). We thank Jeff Woodruff (UT Southwestern), David Drechsel (IMP), and Marcus J. Taylor (MPI IB) for constructive criticism and comments on the manuscript and Helena Jambor for constructive comments on figure design. We thank the AMBIO imaging facility (Charité, Berlin) and Nikon at MBL for imaging support, Aliona Bogdanova and Barbara Borgonovo (MPI CBG) for their help with protein purification, and Francois Nedelec (University of Cambridge) for help with Cytosim. We are grateful to the Görlich lab (MPI BPC), in particular Bastian Hülsmann and Jens Krull, and the NXR for supply with X. tropicalis frogs. We thank Antonina Roll-Mecak (National Institute of Neurological Disorders and Stroke) for help with mass spectrometry analysis and discussions and Duck-Yeon Lee in the Biochemistry Core (National Heart, Lung and Blood Institute) for access to mass spectrometers. For mass spectrometry, we would like to acknowledge the assistance of Benno Kuropka and Chris Weise from the Core Facility BioSupraMol supported by the Deutsche Forschungsgemeinschaft (DFG). We thank all former and current members of the Reber lab for discussion and helpful advice, in particular, Christoph Hentschel and Soma Zsoter for technical assistance and Sebastian Reusch for help with tubulin purification. S.R. acknowledges funding from the IRI Life Sciences (Humboldt-Universität zu Berlin, Excellence Initiative/DFG). W.G.H. was supported by the Alliance Berlin Canberra co-funded by a grant from the Deutsche Forschungsgemeinschaft (DFG) for the International Research Training Group (IRTG) 2290 and the Australian National University. K.K.M. was supported by funds in the Roll-Mecak lab, intramural program of the National Institute of Neurological Disorders and Stroke.
    Keywords: Spindle scaling ; Tubulin ; Microtubule dynamics ; Xenopus ; Spindle length
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marty, B., Almayrac, M., Barry, P. H., Bekaert, D., V., Broadley, M. W., Byrne, D. J., Ballentine, C. J., & Caracausi, A. An evaluation of the C/N ratio of the mantle from natural CO2-rich gas analysis: Geochemical and cosmochemical implications. Earth and Planetary Science Letters, 551, (2020): 116574, doi:10.1016/j.epsl.2020.116574.
    Description: The terrestrial carbon to nitrogen ratio is a key geochemical parameter that can provide information on the nature of Earth's precursors, accretion/differentiation processes of our planet, as well as on the volatile budget of Earth. In principle, this ratio can be determined from the analysis of volatile elements trapped in mantle-derived rocks like mid-ocean ridge basalts (MORB), corrected for fractional degassing during eruption. However, this correction is critical and previous attempts have adopted different approaches which led to contrasting C/N estimates for the bulk silicate Earth (BSE) (Marty and Zimmermann, 1999; Bergin et al., 2015). Here we consider the analysis of CO2-rich gases worldwide for which a mantle origin has been determined using noble gas isotopes in order to evaluate the C/N ratio of the mantle source regions. These gases experienced little fractionation due to degassing, as indicated by radiogenic 4He / 40Ar* values (where 4He and 40Ar* are produced by the decay of U+Th, and 40K isotopes, respectively) close to the mantle production/accumulation values. The C/N and C/3 He ratios of gases investigated here are within the range of values previously observed in oceanic basalts. They point to an elevated mantle C/N ratio (∼350-470, molar) higher than those of potential cosmochemical accretionary endmembers. For example, the BSE C/N and 36 Ar / N ratios (160-220 and 75 x 10-7, respectively) are higher than those of CM-CI chondrites but within the range of CV-CO groups. This similarity suggests that the Earth accreted from evolved planetary precursors depleted in volatile and moderately volatile elements. Hence the high C / N composition of the BSE may be an inherited feature rather than the result of terrestrial differentiation. The C / N and 36 Ar / N ratios of the surface (atmosphere plus crust) and of the mantle cannot be easily linked to any known chondritic composition. However, these compositions are consistent with early sequestration of carbon into the mantle (but not N and noble gases), permitting the establishment of clement temperatures at the surface of our planet.
    Description: M.A, D.V.B, M.W.B, D.J.B and B.M were supported by the European Research Council (PHOTONIS project, grant agreement No. 695618 to B.M.). Samples were collected as part of Study # YELL-08056 - Xenon anomalies in the Yellowstone Hotspot. We would like to thank Annie Carlson and all of the rangers at the Yellowstone National Park for providing invaluable advice and help when collecting the samples. This work was partially supported by a grant (G-2016-7206) from the Alfred P. Sloan Foundation and the Deep Carbon Observatory to P.H.B as well as NSF award 2015789 to P.H.B.. Sampling at Mt. Etna and gas analysis was supported by Instituto Nazionale di Geofisica e Vulcanologia Palermo. Fruitful discussions with Marc Hirschmann helped us to shape the ideas presented in this work. We acknowledge detailed and insightful reviews by Sami Mikhail and an anonymous reviewer, and efficient editing by Frederic Moynier. This is CRPG contribution 2741.
    Keywords: Carbon ; Nitrogen ; Earth ; Mantle ; Gases
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    Publication Date: 2022-06-09
    Description: Joint analysis of high-penetration multi-channel and high-resolution single-channel seismic reflection profiles, calibrated by deep well boreholes, allowed a detailed reconstruction of the Late Miocene to Recent tectonic history of the Capo Granitola and Sciacca fault systems offshore southwestern Sicily. These two fault arrays are part of a regional system of transcurrent faults that dissect the foreland block in front of the Neogene Sicilian fold and thrust belt. The Capo Granitola and Sciacca faults are thought to reactivate inherited Mesozoic to Miocene normal faults developed on the northern continental margin of Africa. During Latest Miocene-Pliocene, the two ~NNE-SSW striking faults were active in left transpression, which inverted Late Miocene extensional half-grabens and created push-up ridges along both systems. Tectonic activity decreased during the Pleistocene, but transpressional folds deform Middle-Late Pleistocene sediments as well, suggesting that the two fault systems are active. The ~40 km long longitudinal amplitude profile of 1st order folds (Capo Granitola and Sciacca anticlines) shows ~15–20 km bell-shaped undulations that represents 2nd order folds. The length of these undulations together with the map pattern of faults allowed to divide the CGFS and SFS into two segments, northern and southern, respectively. Total uplift of the Sciacca Anticline is twice than the uplift of the Capo Granitola Anticline. Incremental fold growth rates decreased during time from 0.22 mm/yr (Capo Granitola Anticline) and 0.44 mm/yr (Sciacca Anticline) in the Pliocene, to 0.07 and 0.22 mm/yr, respectively, during the last ~1.8 Ma.
    Description: Published
    Description: 187-204
    Description: 2T. Deformazione crostale attiva
    Description: 3A. Geofisica marina e osservazioni multiparametriche a fondo mare
    Description: JCR Journal
    Keywords: Multiscale analysis ; Basin inversion ; Strike-slip faults ; Fold growth rates ; Pelagian foreland ; SW Sicily offshore ; 04.07. Tectonophysics ; 04.04. Geology ; 04.02. Exploration geophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    Publication Date: 2022-06-14
    Description: Observations from satellites provide high-resolution images of ground deformation allowing to infer deformation sources by developing advanced modeling of magma ascent and intrusion processes. Nevertheless, such models can be strongly biased without a precise model of the internal structure of the volcano. In this study, we jointly exploited two interferometric techniques to interpret the 2011–2013 unrest at Campi Flegrei caldera (CFc). The first is the Interferometric Synthetic Aperture Radar (InSAR) technique, which provides highly-resolved spatial and temporal images of ground deformation. The second is the Ambient Noise Tomography (ANT), which images subsurface structures, providing the constraints necessary to infer the depth of the shallow source at CFc (between 0.8 and 1.2 km). We applied for the first time a tool to delineate the deformation source boundaries from the observed deformation maps: the Total Horizontal Derivative (THD) technique. The THD processes the vertical component of the ground deformation field detected through InSAR applied to COSMO-SkyMed data. The patterns retrieved by applying the THD technique show consistent spatial correlations with (1) the seismic group-velocity maps achieved through the ANT and (2) the distribution of the earthquakes nucleated during the unrest at ~1 km. High-velocity anomalies, the retrieved geometrical features of the deformation field, and the spatial distribution of seismicity coincide with extinct volcanic vents in the eastern part of the caldera (Solfatara/ Pisciarelli and Astroni). Such a coincidence hints at a significant role of the extinct plumbing system in either constraining or channeling the eastward propagation of magmatic fluids. Here, we demonstrated that a joint analysis of the InSAR patterns, seismic structures, and seismicity allows us to model in space and time the characteristics and nature of the shallow deformation source at CFc. Using published literature, we show that the effects of structural heterogeneities at shallow depths may have a more significant early-stage impact on the evolution of the surface displacement signals than deeper magmatic sources: these secondary structural effects may produce local amplification in the deformation records which can be mistakenly interpreted as early signals of impending eruptions. The achieved results are particularly relevant for the understanding of the origin of deformation signal at volcanoes where magma propagation within sills is expected, as at CFc.
    Description: Published
    Description: 111440
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: JCR Journal
    Keywords: InSAR ; Ambient noise tomography ; Total horizontal derivative ; Campi Flegrei caldera ; Natural seismicity
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    Publication Date: 2022-06-10
    Description: Active lava lakes represent a variety of open-vent volcanism in which a sizable body of lava accumulates at the top of the magma column, constrained by the vent and/or crater geometry. The longevity of lava lakes reflects a balancing of cooling and outgassing occurring at the surface and input of hot and gas-rich magma from below. Due to their longevity and relative accessibility, lava lakes provide a natural laboratory for studying fundamental volcanic processes such as degassing, convection and cooling. This article examines all seven lakes that existed at the time of writing in 2018, located in the Pacific, Antarctica, Africa, and South and Central America. These lakes span all tectonic environments, and a range of magma compositions. We focus on analysis of the lake surface motion using image velocimetry, which reveals both similarities and contrasts in outgassing and lake dynamics when comparing the different lakes. We identify two categories of lake behavior: Organized (Erta’Ale, Nyiragongo, Kīlauea after 2011, and Erebus) and Chaotic (Villarrica, Masaya, Marum). This division does not map directly to lake size, viscosity, gas emission rate, or temperature. Instead, when examined together, we find that the lakes follow a linear relationship between average surface speed and the ratio of total gas flux to lake surface area. This relationship points to the combined importance of both flux and lake size in addition to the total volume of gas emission, and suggests that a shared deep mechanism controls the supply of heat and gas to all lakes. On the other hand, the differences between Chaotic and Organized lakes highlight the important role of the geometry of the conduit-lake transition, which superimposes a shallow signal on that of the deep circulation. The spatial patterns of surface motion we document suggest that the release of gas bubbles at Chaotic lakes is more efficient (i.e., bubbles are less likely to be retained and recycled) compared with Organized lakes. In addition, the data presented here indicate that the solidified crust of Organized lakes plays a role in regulating convection and outgassing in lava lakes.
    Description: Published
    Description: 16-31
    Description: 5V. Processi eruttivi e post-eruttivi
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    Publication Date: 2022-06-09
    Description: A 3D crustal density model for Egypt was compiled. It is constrained by available deep seismic refraction, receiver functions analysis, borehole, and geological data. In Egypt, seismic data are sparsely and irregularly distributed. Consequently, we developed the crustal thickness model by integrating seismic and gravity data. Satellite gravity data was inverted to build an initial model, which was followed by a detailed 3D forward gravity modelling. The initial crustal thickness is determined by applying seismically constrained non-linear inversion, based on the modified Bott's method and Tikhonov regularization assuming spherical Earth approximation. Moreover, the gravity inversion-based Moho depth estimates are in good agreement with results of seismic studies and are exploited for the 3D forward modelling. Crustal thicknesses range from 25 to 30 km along the rifted margins of the Red Sea, which thin toward the Mediterranean Sea. Thicknesses in southern Egypt reach values between 35 and 40 km. A maximum crustal thickness of 45 km is found in the southwestern part of Egypt. Within the Sinai Peninsula, the thickness varies from the shallow southern edge (∼ 31 km) and increases toward the North (∼ 36 km). Our model revealed a thick lower crust beneath the southern part of Egypt, which can be associated with crustal modification that occurred during the collision of East Gondwana and the Saharan Metacraton along the Keraf suture zone during the final assembly of Gondwana in the Neoproterozoic. Finally, the isostatic implications of the differences between the seismic and gravity-derived Mohos are thoroughly discussed. In conclusion, the developed 3D crustal thickness model provides high-resolution Moho depth estimates that closely resembles the major geological and tectonic features. Also, the existing correlation between the topography, Bouguer anomalies, and Moho depths indicates that the investigated area is close to its isostatic equilibrium.
    Description: Published
    Description: 52-67
    Description: 2TR. Ricostruzione e modellazione della struttura crostale
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rastetter, E. B., & Kwiatkowski, B. L. An approach to modeling resource optimization for substitutable and interdependent resources. Ecological Modelling, 425, (2020): 109033, doi:10.1016/j.ecolmodel.2020.109033.
    Description: We develop a hierarchical approach to modeling organism acclimation to changing availability of and requirements for substitutable and interdependent resources. Substitutable resources are resources that fill the same metabolic or stoichiometric need of the organism. Interdependent resources are resources whose acquisition or expenditure are tightly linked (e.g., light, CO2, and water in photosynthesis and associated transpiration). We illustrate the approach by simulating the development of vegetation with four substitutable sources of N that differ only in the cost of their uptake and assimilation. As the vegetation develops, it uses the least expensive N source first then uses progressively more expensive N sources as the less expensive sources are depleted. Transition among N sources is based on the marginal yield of N per unit effort expended, including effort expended to acquire C to cover the progressively higher uptake costs. We illustrate the approach to interdependent resources by simulating the expenditure of effort to acquire light energy, CO2, and water to drive photosynthesis in vegetation acclimated to different conditions of soil water, atmospheric vapor pressure deficit, CO2 concentration, and light levels. The approach is an improvement on the resource optimization used in the earlier Multiple Element Limitation (MEL) model.
    Description: This work was supported in part by the National Science Foundation under NSF grants 1651722, 1637459, 1603560, 1556772, 1841608. Any Opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect those of the National Science Foundation.
    Keywords: Resource optimization ; Acclimation ; Substitutable resources ; Interdependent resources ; Resource limitation ; Multiple resource limitation
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Trathan, P. N., Wienecke, B., Barbraud, C., Jenouvrier, S., Kooyman, G., Le Bohec, C., Ainley, D. G., Ancel, A., Zitterbart, D. P., Chown, S. L., LaRue, M., Cristofari, R., Younger, J., Clucas, G., Bost, C., Brown, J. A., Gillett, H. J., & Fretwell, P. T. The emperor penguin - vulnerable to projected rates of warming and sea ice loss. Biological Conservation, 241, (2020): 108216, doi:10.1016/j.biocon.2019.108216.
    Description: We argue the need to improve climate change forecasting for ecology, and importantly, how to relate long-term projections to conservation. As an example, we discuss the need for effective management of one species, the emperor penguin, Aptenodytes forsteri. This species is unique amongst birds in that its breeding habit is critically dependent upon seasonal fast ice. Here, we review its vulnerability to ongoing and projected climate change, given that sea ice is susceptible to changes in winds and temperatures. We consider published projections of future emperor penguin population status in response to changing environments. Furthermore, we evaluate the current IUCN Red List status for the species, and recommend that its status be changed to Vulnerable, based on different modelling projections of population decrease of ≥50% over the current century, and the specific traits of the species. We conclude that current conservation measures are inadequate to protect the species under future projected scenarios. Only a reduction in anthropogenic greenhouse gas emissions will reduce threats to the emperor penguin from altered wind regimes, rising temperatures and melting sea ice; until such time, other conservation actions are necessary, including increased spatial protection at breeding sites and foraging locations. The designation of large-scale marine spatial protection across its range would benefit the species, particularly in areas that have a high probability of becoming future climate change refugia. We also recommend that the emperor penguin is listed by the Antarctic Treaty as an Antarctic Specially Protected Species, with development of a species Action Plan.
    Description: We thank Thomas J. Bracegirdle, Tony Phillips and Kevin Hughes for helpful comments on earlier drafts of this manuscript. PNT acknowledges the support of WWF-UK under GB095701 and SJ the support of NSF OPP1744794 and 1643901.
    Keywords: Antarctic ; Climate change ; Aptenodytes forsteri ; IUCN Red List threat status ; Protection ; Conservation
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Jin, D., Hoagland, P., & Buesseler, K. O. The value of scientific research on the ocean's biological carbon pump. Science of the Total Environment, 749, (2020): 141357, doi:10.1016/j.scitotenv.2020.141357.
    Description: The ocean's biological carbon pump (BCP) sequesters carbon from the surface to the deep ocean and seabed, constituting one of Earth's most valuable ecosystem services. Significant uncertainty exists surrounding the amounts and rates of organic carbon sequestered in the oceans, however. With improved understanding of BCP sequestration, especially its scale, world policymakers would be positioned to make more informed decisions regarding the mitigation of carbon emissions. Here, an analytical model of the economic effects of global carbon emissions—including scientific uncertainty about BCP sequestration—was developed to estimate the value of marine scientific research concerning sequestration. The discounted net economic benefit of a putative 20-year scientific research program to narrow the range of uncertainty around the amount of carbon sequestered in the ocean is on the order of $0.5 trillion (USD), depending upon the accuracy of predictions, the convexities of climate damage and economic output functions, and the initial range of uncertainty.
    Description: This research is supported by WHOI's Ocean Twilight Zone program which is part of the Audacious Project, a collaborative endeavor, housed at TED. DJ was also funded by National Oceanic and Atmospheric Administration (NOAA) Cooperative Institutes (CINAR) award NA14OAR4320158. KB was also funded by National Aeronautics and Space Administration (NASA) as part of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) program award 80NSSC17K0555. We thank Ankur Shah for research assistance and three anonymous reviewers for their constructive suggestions.
    Keywords: Economic value of scientific research ; Value of information ; Biological carbon pump ; Carbon sequestration ; Ecosystem service ; Ocean twilight zone
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 21
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Brothers, L. L., Foster, D. S., Pendleton, E. A., & Baldwin, W. E. Seismic stratigraphic framework of the continental shelf offshore Delmarva, USA: implications for Mid-Atlantic Bight evolution since the Pliocene. Marine Geology, 428, : (2020)106287, doi:10.1016/j.margeo.2020.106287.
    Description: Understanding how past coastal systems have evolved is critical to predicting future coastal change. Using over 12,000 trackline kilometers of recently collected, co-located multi-channel boomer, sparker and chirp seismic reflection profile data integrated with previously collected borehole and vibracore data, we define the upper (〈 115 m below mean lower low water) seismic stratigraphic framework offshore of the Delmarva Peninsula, USA. Twelve seismic units and 11 regionally extensive unconformities (U1-U11) were mapped over 5900 km2 of North America's Mid-Atlantic continental shelf. We interpret U3, U7, U9, U11 as transgressive ravinement surfaces, while U1,2,4,5,6,8,10 are subaerial unconformities illustrating distinct periods of lower sea-level. Based on areal distribution, stratigraphic relationships and dating results (Carbon 14 and amino acid racemization estimates) from earlier vibracore and borehole studies, we interpret the infilled channels as late Neogene and Quaternary courses of the Susquehanna, Potomac, Rappahannock, York, James rivers and tributaries, and a broad flood plain. These findings indicate that the region's geologic framework is more complex than previously thought and that Pleistocene paleochannels are abundant in the Mid-Atlantic. This study synthesizes and correlates the findings of other Atlantic Margin studies and establishes a large-scale Quaternary framework that enables more detailed stratigraphic analysis in the future. Such work has implications for inner continental shelf systems tract evolution, the relationship between antecedent geology and modern coastal systems, assessments of eustacy, glacial isostatic adjustment, and other processes and forcings that play a role in passive margin evolution.
    Description: This work was supported by the U.S. Department of the Interior's Response to Hurricane Sandy.
    Keywords: N Atlantic ; Shelf (morphology and stratigraphy) ; Quaternary stratigraphy ; Paleochannels ; Geophysics (seismic)
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 22
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lin, H. T., Hsieh, C. C., Repeta, D. J., & Rappé, M. S. Sampling of basement fluids via circulation obviation retrofit kits (CORKs) for dissolved gases, fluid fixation at the seafloor, and the characterization of organic carbon. Methodsx, 7, (2020): 101033, doi:10.1016/j.mex.2020.101033.
    Description: The advanced instrumented GeoMICROBE sleds (Cowen et al., 2012) facilitate the collection of hydrothermal fluids and suspended particles in the subseafloor (basaltic) basement through Circulation Obviation Retrofit Kits (CORKs) installed within boreholes of the Integrated Ocean Drilling Program. The main components of the GeoMICROBE can be converted into a mobile pumping system (MPS) that is installed on the front basket of a submersible or remotely-operated-vehicle (ROV). Here, we provide details of a hydrothermal fluid-trap used on the MPS, through which a gastight sampler can withdraw fluids. We also applied the MPS to demonstrate the value of fixing samples at the seafloor in order to determine redox-sensitive dissolved iron concentrations and speciation measurements. To make the best use of the GeoMICROBE sleds, we describe a miniature and mobile version of the GeoMICROBE sled, which permits rapid turn-over and is relatively easy for preparation and operation. Similar to GeoMICROBE sleds, the Mobile GeoMICROBE (MGM) is capable of collecting fluid samples, filtration of suspended particles, and extraction of organics. We validate this approach by demonstrating the seafloor extraction of hydrophobic organics from a large volume (247L) of hydrothermal fluids. • We describe the design of a hydrothermal fluid-trap for use with a gastight sampler, as well as the use of seafloor fixation, through ROV- or submersible assisted mobile pumping systems. • We describe the design of a Mobile GeoMICROBE (MGM) that enhances large volume hydrothermal fluid sampling, suspended particle filtration, and organic matter extraction on the seafloor. • We provide an example of organic matter extracted and characterized from hydrothermal fluids via a MGM.
    Description: We dedicate this work to Dr. James P. Cowen, who had envisioned and constructed the integrated instrumentation, GeoMICROBE, to monitor the sub-basement biosphere. We thank the chief scientists, captains, crews, and science teams on board R/V Atlantis cruises AT15-35, AT15-51, AT15-66, AT18-07, MSM20-5, AT26-03, and AT26-18, and the pilots and crews of ROV Jason II and HOV Alvin. We thank our student assistants, Natalie Hamada, Kathryn Hu, Ryan Matzumoto, Everette Omori, and Fan-Chieh Chuang. This work was supported by the National Science Foundation-Microbial Observatory Project (NSF-MCB06-04014 to J. P. Cowen), Center for Dark Energy Biosphere Investigations (C-DEBI; NSF award OCE-0939564 to M. S. Rappé), NSF award OCE-1260723 (to M. S. Rappé), and the Ministry of Science and Technology of Taiwan award (MOST 105-2119-M-002-034, MOST 107-2611-M-002-002, MOST 108-2611-M-002-006, and MOST109-2611-M-002-008 to H.-T. Lin). Ministry of Education (MOE) Republic of China (Taiwan) 109L892601 to H.-T. Lin. NSF award OCE-1634080 (to D. J. Repeta), the Simons Foundation-Simons Collaboration on Ocean Processes and Ecology (SCOPE) award 329108 (to D. J. Repeta), the Gordon and Betty Moore Foundation award 6000 (to D. J. Repeta). This paper is SOEST contribution number 11121, HIMB contribution 1804 and C-DEBI contribution number 543.
    Keywords: GeoMICROBE ; Hydrothermal fluid ; Crustal fluid ; Mobile pumping system ; Helium ; Methane ; Dissolved organic matter ; Extraction and preconcentration ; Deep subseafloor
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 23
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Arenas Gomez, C. M., Woodcock, M. R., Smith, J. J., Voss, S. R., & Delgado, J. P. A de novo reference transcriptome for Bolitoglossa vallecula, an Andean mountain salamander in Colombia. Data in Brief, 29, (2020): 105256, doi:10.1016/j.dib.2020.105256.
    Description: The amphibian order Caudata, contains several important model species for biological research. However, there is need to generate transcriptome data from representative species of the primary salamander families. Here we describe a de novo reference transcriptome for a terrestrial salamander, Bolitoglossa vallecula (Caudata: Plethodontidae). We employed paired-end (PE) illumina RNA sequencing to assemble a de novo reference transcriptome for B. vallecula. Assembled transcripts were compared against sequences from other vertebrate taxa to identify orthologous genes, and compared to the transcriptome of a close plethodontid relative (Bolitoglossa ramosi) to identify commonly expressed genes in the skin. This dataset should be useful to future comparative studies aimed at understanding important biological process, such as immunity, wound healing, and the production of antimicrobial compounds.
    Description: This work was funded by a research grant from COLCIENCIAS 569 (GRANT 027-2103) and CODI (Programa Sostenibilidad) 2013–2014 of the University of Antioquia. A PhD fellowship to the first author, Claudia Arenas was funded by the COLCIENCIAS 567 Grant. We thank the lab of Juan Fernando Alzate from the University of Antioquia for their help in developing our bioinformatic methodological approach. We thank Andrea Gómez and Melisa Hincapie for their help in animal collection and husbandry.
    Keywords: Bolitoglossa ; Plethodontid ; Salamanders ; Skin ; Transcriptomics
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 24
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Li, Y., Stumpf, R. P., McGillicuddy, D. J.,Jr, & He, R. Dynamics of an intense Alexandrium catenella red tide in the Gulf of Maine: satellite observations and numerical modeling. Harmful Algae, 99, (2020): 101927, doi:10.1016/j.hal.2020.101927.
    Description: In July 2009, an unusually intense bloom of the toxic dinoflagellate Alexandrium catenella occurred in the Gulf of Maine. The bloom reached high concentrations (from hundreds of thousands to one million cells L−1) that discolored the water and exceeded normal bloom concentrations by a factor of 1000. Using Medium Resolution Imaging Spectrometer (MERIS) imagery processed to target chlorophyll concentrations (〉2 µg L−1), patches of intense A. catenella concentration were identified that were consistent with the highly localized cell concentrations observed from ship surveys. The bloom patches were generally aligned with the edge of coastal waters with high-absorption. Dense bloom patches moved onshore in response to a downwelling event, persisted for approximately one week, then dispersed rapidly over a few days and did not reappear. Coupled physical-biological model simulations showed that wind forcing was an important factor in transporting cells onshore. Upward swimming behavior facilitated the horizontal cell aggregation, increasing the simulated maximum depth-integrated cell concentration by up to a factor of 40. Vertical convergence of cells, due to active swimming of A. catenella from the subsurface to the top layer, could explain the additional 25-fold intensification (25 × 40=1000-fold) needed to reach the bloom concentrations that discolored the water. A model simulation that considered upward swimming overestimated cell concentrations downstream of the intense aggregation. This discrepancy between model and observed concentrations suggested a loss of cells from the water column at a time that corresponded to the start of encystment. These results indicated that the joint effect of upward swimming, horizontal convergence, and wind-driven flow contributed to the red water event, which might have promoted the sexual reproduction event that preceded the encystment process.
    Description: DJM gratefully acknowledges support of the Woods Hole Center for Oceans and Human Health, funded jointly by the National Science Foundation (OCE-1314642 and OCE-1840381) the National Institute of Environmental Health Sciences (P01ES021923–01 and P01 ES028938–01). RH acknowledges support made possible by NOAA grant NA15NOS4780196 and NA16NOS0120028.
    Keywords: Red water ; Bloom patches ; Cell accumulation ; Coastal upwelling ; Upward swimming
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 25
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kantha, L., Weller, R. A., Farrar, J. T., Rahaman, H., & Jampana, V. A note on modeling mixing in the upper layers of the Bay of Bengal: importance of water type, water column structure and precipitation. Deep-Sea Research Part II-Topical Studies in Oceanography, 168, (2019): 104643. doi: 10.1016/j.dsr2.2019.104643.
    Description: Turbulent mixing in the upper layers of the northern Bay of Bengal is affected by a shallow layer overlying the saline waters of the Bay, which results from the huge influx of freshwater from major rivers draining the Indian subcontinent and from rainfall over the Bay during the summer monsoon. The resulting halocline inhibits wind-driven mixing in the upper layers. The brackish layer also alters the optical properties of the water column. Air-sea interaction in the Bay is expected to play a significant role in the intraseasonal variability of summer monsoons over the Indian subcontinent, and as such the sea surface temperature (SST) changes during the summer monsoon are of considerable scientific and societal importance. In this study, data from the heavily instrumented Woods Hole Oceanographic Institution (WHOI) mooring, deployed at 18oN, 89.5oE in the northern Bay from December 2014 to January 2016, are used to drive a one-dimensional mixing model, based on second moment closure model of turbulence, to explore the intra-annual variability in the upper layers. The model results highlight the importance of the optical properties of the upper layers (and hence the penetration of solar insolation in the water column), as well as the temperature and salinity in the upper layers prescribed at the start of the model simulation, in determining the SST in the Bay during the summer monsoon. The heavy rainfall during the summer monsoon also plays an important role. The interseasonal and intraseasonal variability in the upper layers of the Bay are contrasted with those in the Arabian Sea, by the use of the same model but driven by data from an earlier deployment of a WHOI mooring in the Arabian Sea at 15.5 oN, 61.5 oE from December 1994 to December 1995.
    Description: LK was supported by U.S. Office of Naval Research (ONR) MISO/BoB DRI under grant number N00014-17-1-2716. RW and JTF were supported by ONR Grants N00014-13-1-0453 and N00014-17-1-2880, and the WHOI mooring was funded by Grant N00014-13-1-0453. RW was supported by ONR for the 1994–1995 deployment of the surface mooring in the Arabian Sea. HR and VJ wish to thank Dr. SSC Shenoi, the Director of INCOIS and Dr. M Ravichandran, Director, NCPOR for the encouragement and support to carry out this study. This work was supported by the Ministry of Earth Sciences (MoES), Govt. of India. This is also INCOIS Contribution number 349.
    Keywords: Bay of Bengal ; Arabian sea ; Mixing in the upper layers ; Second moment closure ; Turbulence ; WHOI mooring ; OMNI mooring ; Water type ; Solar insolation ; Precipitation
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 26
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Schwing, F. B., Sissenwine, M. J., Batchelder, H., Dam, H. G., Gomez-Gutierrez, J., Keister, J. E., Liu, H., & Peterson, J. O. William (Bill) Peterson's contributions to ocean science, management, and policy. Progress in Oceanography, 182, (2020): 102241, doi:10.1016/j.pocean.2019.102241.
    Description: In addition to being an esteemed marine ecologist and oceanographer, William T. (Bill) Peterson was a dedicated public servant, a leader in the ocean science community, and a mentor to a generation of scientists. Bill recognized the importance of applied science and the need for integrated “big science” programs to advance our understanding of ecosystems and to guide their management. As the first US GLOBEC program manager, he was pivotal in transitioning the concept of understanding how climate change impacts marine ecosystems to an operational national research program. The scientific insight and knowledge generated by US GLOBEC informed and advanced the ecosystem-based management approaches now being implemented for fishery management in the US. Bill held significant leadership roles in numerous international efforts to understand global and regional ecological processes, and organized and chaired a number of influential scientific conferences and their proceedings. He was passionate about working with and training young researchers. Bill’s academic affiliations, notably at Stony Brook and Oregon State Universities, enabled him to advise, train, and mentor a host of students, post-doctoral researchers, and laboratory technicians. Under his collegial guidance they became critical independent thinkers and diligent investigators. His former students and colleagues carry on Bill Peterson’s legacy of research that helps us understand marine ecosystems and informs more effective resource stewardship and conservation.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 27
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in McCollom, T. M., Klein, F., Moskowitz, B., Berquo, T. S., Bach, W., & Templeton, A. S. Hydrogen generation and iron partitioning during experimental serpentinization of an olivine-pyroxene mixture. Geochimica Et Cosmochimica Acta, 282, (2020): 55-75, doi:10.1016/j.gca.2020.05.016.
    Description: A series of laboratory experiments was conducted to investigate serpentinization of olivine–pyroxene mixtures at 230 °C, with the objective of evaluating the effect of mixed compositions on Fe partitioning among product minerals, H2 generation, and reaction rates. An initial experiment reacted a mixture of 86 wt.% olivine and 14 wt.% orthopyroxene (Opx) with the same initial grain size for 387 days. The experiment resulted in extensive reaction (∼53% conversion), and solids recovered at termination of the experiment were dominated by Fe-bearing chrysotile and relict olivine along with minor brucite and magnetite. Only limited amounts of H2 were generated during the first ∼100 days of the experiment, but the rate of H2 generation then increased sharply coincident with an increase in pH from mildly alkaline to strongly alkaline conditions. Two shorter term experiments with the same reactants (26 and 113 days) produced a mixture of lizardite and talc that formed a thin coating on relict olivine and Opx grains, with virtually no generation of H2. Comparison of the results with reaction path models indicates that the Opx reacted about two times faster than olivine, which contrasts with some previous studies that suggested olivine should react more rapidly than Opx at the experimental conditions. The models also indicate that the long-term experiment transitioned from producing serpentine ± talc early in the early stages to precipitation of serpentine plus magnetite, with brucite beginning to precipitate only late in the experiment as Opx was depleted. The results indicate that overall reaction of olivine and Opx was initially relatively slow, but reaction rates accelerated substantially when the pH transitioned to strongly alkaline conditions. Serpentine and brucite precipitated from the olivine-Opx mixture had higher Fe contents than observed in olivine-only experiments at mildly alkaline pH, but had comparable Fe contents to reaction of olivine at strongly alkaline pH implying that higher pH may favor greater partitioning of Fe into serpentine and brucite and less into magnetite. Despite the presence of brucite, dissolved silica activities during the long-term olivine-Opx experiment maintained levels well above serpentine-brucite equilibrium. Instead, silica activities converged on levels close to metastable equilibrium between brucite and olivine. It is proposed that silica levels during the experiment may have been regulated by exchange of SiO2 between the fluid and a silica-depleted, brucite-like surface layer on dissolving olivine.
    Description: This research was supported by the U. S. National Science Foundation Marine Geology and Geophysics program through grant NSF-OCE 0927744 and by the NASA Astrobiology Institute through Cooperative Agreement NNA15BB02A. Additional support to TMM from the Hanse Wissenschaftskolleg (Delmenhorst, Germany) at an early stage of this project is gratefully acknowledged. FK acknowledges support through Grant NSF-OCE 1427274. The IRM is supported by the Instruments and Facilities Program of the NSF Division of Earth Science. This is IRM contribution 1711. We very much appreciate the comments of Fabrice Brunet, Gleb Pokrovski and an anonymous reviewer that helped us refine our interpretations and improve communication of the results.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 28
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Babbin, A. R., Buchwald, C., Morel, F. M. M., Wankel, S. D., & Ward, B. B. Nitrite oxidation exceeds reduction and fixed nitrogen loss in anoxic Pacific waters. Marine Chemistry, 224, (2020): 103814, doi:10.1016/j.marchem.2020.103814.
    Description: The diversity of nitrogen-based dissimilatory metabolisms in anoxic waters continues to increase with additional studies to the marine oxygen deficient zones (ODZs). Although the microbial oxidation of nitrite (NO2–) has been known for over a century, studies of the pathways and microbes involved have generally proceeded under the assumption that nitrite oxidation to nitrate requires dioxygen (O2). Anaerobic NO2– oxidation until now has been conclusively shown only for anammox bacteria, albeit only as a limited sink for NO2– in their metabolism compared to the NO2– reduced to N2. Here, using direct experimental techniques optimized for replicating in situ anoxic conditions, we show that NO2– oxidation is substantial, widespread, and consistent across the ODZs of the eastern tropical Pacific Ocean. Regardless of the specific oxidant, NO2– oxidation rates are up to an order of magnitude larger than simultaneous N2 production rates for which these zones are known, and cannot be explained by anammox rates alone. Higher rates of NO2– oxidation over reduction in anoxic waters are paradoxical but help to explain how anammox rates can be enhanced over denitrification in shallow anoxic waters (σθ 〈 26.4) at the edge of the ODZs but not within the ODZ core. Furthermore, nitrite oxidation may be the key to reconciliation of the perceived imbalance of the global fixed nitrogen loss budget.
    Description: This work was funded by National Science Foundation grants OCE–1029951 to B.B.W, BIO–1402109 to A.R.B., and OCE-1260373 to S.D.W. Additional financial support to A.R.B. was provided by Simons Foundation grant 622065 and the generous contributions of Dr. Bruce L. Heflinger.
    Keywords: Nitrogen cycling ; Oxygen deficient zones ; Nitrite oxidation ; Denitrification ; Anammox
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 29
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Gu, S., Liu, Z., Oppo, D. W., Lynch-Stieglitz, J., Jahn, A., Zhang, J., & Wu, L. Assessing the potential capability of reconstructing glacial Atlantic water masses and AMOC using multiple proxies in CESM. Earth and Planetary Science Letters, 541, (2020): 11629, doi:10.1016/j.epsl.2020.116294.
    Description: Reconstructing the Atlantic Meridional Overturning Circulation (AMOC) during the Last Glacial Maximum (LGM) is essential for understanding glacial-interglacial climate change and the carbon cycle. However, despite many previous studies, uncertainties remain regarding the glacial water mass distributions in the Atlantic and the AMOC intensity. Here we use an isotope enabled ocean model with multiple geotracers (δ 13 C,E Νd,231 Pa/ 230Th,δ 18 Ο and Δ 14 C) and idealized water tracers to study the potential constraints on LGM ocean circulation from multiple proxies. Our model suggests that the glacial Atlantic water mass distribution can be accurately constrained by the air-sea gas exchange signature of water masses (δ13 C AS), but E Nd might overestimate the North Atlantic Deep Water (NADW) percentage in the deep Atlantic probably because of the boundary source of Nd. A sensitivity experiment with an AMOC of similar geometry but much weaker strength suggests that the correct AMOC geometry is more important than the AMOC strength for simulating the observed glacial δ13 C AS and E Nd and distributions. The kinematic tracer 231Pa/230Th is sensitive to AMOC intensity, but the interpretation might be complicated by the AMOC geometry and AABW transport changes during the LGM. δ 18 Ο in the benthic foraminifera (δ 18 Οc) from the Florida Straits provides a consistent measure of the upper ocean boundary current in the model, which potentially provides an unambiguous method to reconstruct glacial AMOC intensity. Finally, we propose that the moderate difference between AMOC intensity at LGM and PD, if any, is caused by the competition of the responses to CO2 forcing and continental ice sheet forcing.
    Description: We thank two anonymous reviewers for their useful and constructive comments. We also thank Editor Dr Laura F. Robinson for handling the manuscript. This work is supported by National Science Foundation of China No. 41630527, US National Science Foundation (NSF) P2C2 projects (1401778, 1401802, and 1566432). We would like to acknowledge the high-performance computing support from Yellowstone (ark:/85065/d7wd3xhc) and Cheyenne (doi:10.5065/D6RX99HX) provided by NCAR's Computational and Information Systems Laboratory, sponsored by the National Science Foundation and from Center for High Performance Computing and System Simulation, Pilot National Laboratory for Marine Science and Technology (Qingdao). Data used to produce the results in this study can be obtained from HPSS at CISL: /home/sgu28/CTRACE_decadal or by contacting the authors.
    Keywords: Last Glacial Maximum ; AMOC ; Water mass ; Multi-proxy
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 30
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4438-4445 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Studies of nonlinear acoustic interactions in superfluid helium at temperatures below 0.2 K have culminated in the construction of an all-acoustic parametric amplifier at gigahertz frequencies. This device represents the shortest wavelength parametric amplifier ever made, with signal wavelengths shorter than 1000 A(ring) and pump wavelengths shorter than 600 A(ring). In the experiment, plane waves are mixed at a predefined angle in the superfluid helium. Two gain regimes are observed. The first regime is a noncollinear phase-matched process, in which the signal phonon stimulates decay of the pump phonon to create gain at the signal frequency. The second regime is a four-phonon collinear process, in which gain on the signal is created by the second harmonic of the pump. This four-phonon process is unusual and is shown to be a combination of three-phonon processes wherein the lack of conservation of energy and momentum in one process is mostly compensated by the other.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 31
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ferromagnetic Heusler alloy Pd2MnSn shows large reduction in magnetization by cold working, without any appreciable change in the Curie temperature. In order to clarify the relationship between the reduction and the defect structure in Pd2MnSn, transmission electron microscopic observation, high-resolution neutron powder diffraction, and magnetization studies have been performed. In the deformed Pd2MnSn sample, dislocations are distributed inhomogeneously and form a cell structure. In the cell walls, a large amount of antiphase domain boundaries exist. A method of Rietveld refinement has been proposed for analyzing the powder neutron diffraction patterns of the cold-worked sample, where all the contributions of defects (size, strain, and antiphase domain boundary) and the instrumental resolution to each reflection line are expressed in terms of Fourier coefficients, and inverse Fourier transforms of those product represent the calculated profile which is used for least-squares refinement. Analyzing the experimental data with the method proposed, it is concluded that the reduction in magnetization in the deformed Pd2MnSn is due to an increase in the number of small antiphase domains which couple antiferromagnetically to each other.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 32
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4777-4781 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A Raman study has been performed, under resonant conditions, on a GaAs bevelled-edge layer grown on a Si substrate to characterize the optical and crystalline properties of the epilayer near the interface. According to the geometrical characteristics of the sample, a theoretical expression for the Raman intensities profile has been established and compared to the experimental data. This fitting procedure enables us to investigate the absorption coefficient of the GaAs layer due to the disorder-induced softening of the E1 edge. A quantitative analysis of the lattice disorder has been carried out on both longitudinal and transverse optical modes by studying the Raman line-shape evolution versus the laser spot position on the bevel edge. From this study, we have followed the recovery of the crystalline quality of the epilayer while going away from the interface, and evaluated the "Raman thickness'' of the dislocated layer. Using the spatial correlation model as a relationship between the disorder amount and the outcoming effects on the Raman line peaks, we have estimated the dislocation density at the heterostructure interface.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 33
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4811-4815 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Examination with x-ray photoelectron spectroscopy (XPS) of CF4 plasma etched GaAs(100) wafers unveils a residual surface reaction layer composed of Ga-fluoride and Ga-oxide. Efficient removal of this contamination layer by a brief immersion in a dilute NH4OH wet etch is demonstrated. The formation of a thin native oxide upon exposure to atmosphere of the clean substrate surface cannot be avoided, however. Prospective replacement of this wet etch processing by in situ thermal annealing in hydrogen was investigated. The recorded XPS spectra show almost complete desorption of fluorine after annealing at 200 °C, whereas a temperature of ∼600 °C is required for entire removal of residual surface Ga-oxide. Heat treatment in H2 also compares favorably with vacuum annealing, for which a noticeable reduction of the surface contamination layer was found only after annealing at 600 °C. The cleaning efficiency of hydrogen processing may be attributed to the reactive nature of this ambient.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 34
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4375-4384 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time-dependent production of higher-silane gases and a-Si:H film are measured relative to decomposed silane in rf and dc, hot and cold cathode, static-gas discharges. From the absence of higher-silane production in very low silane partial-pressure discharges, it is inferred that most higher silanes are produced by gas-phase SiH2-initiated reactions. The higher silanes are thus tracers of SiH2, while the film production traces the fraction of H, SiH, and SiH3 in the initial decomposition. From the measured stable product yields, we deduce that SiH4→SiH2+2H is the dominant electron-collisional dissociation channel.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 35
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4426-4437 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Three methods of evaluating the second-order contributions to the mechanical velocity shift and reflection coefficient for isotropic groove gratings are presented. The second-order terms contain the effect of evanescent and bulk modes generated through the interaction of a surface acoustic wave with a periodic overlay. All three methods will be shown to be numerically equivalent when calculated self-consistently, verifying the validity of all three within their respective limitations. The extension of these methods to arbitrary anisotropic substrates and overlays is discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 36
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4474-4480 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Characteristics of phototriggered discharges in pure argon and neon have been experimentally and theoretically investigated at pressures between 0.5 and 5 bars and reduced electric fields E/N in the range 5 to 50 Td. Emphasis is laid on the breakdown delay time, defined as the time lag between the application of a very short preionization pulse and the occurrence of the discharge. The model, developed in the frame of the local field approximation, gives breakdown delay time values in excellent agreement with the experimental results. However, in pure neon, the experiments have revealed a large influence of very small amounts of easily ionizable impurities. The calculations point out that the discharge behavior is mainly determined by the electron multiplication rate due to direct ionization of ground state atoms. Other ionizing processes, such as two-step ionization or Penning effects, or the electrical parameters of the circuit (inductance, capacitance, and intensity of the preionization) have only a secondary effect on the breakdown delay time.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 37
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fully developed, viscous liquid-metal velocity profiles and induced magnetic field contours were studied for Hartmann numbers of M=2 and 10 and for different load currents for a particular rectangular channel configuration (two-dimensional Couette flow). The rectangular channel was assumed to have a homogeneous external (axial) magnetic field parallel to the moving, perfectly conducting top wall and the stationary, perfectly conducting bottom wall. The two stationary side walls were also perfect conductors. The small gap between the moving wall and each side wall was an insulating, free surface. The method of weighted residuals was used to obtain truncated series solutions for the variables of interest. The heavy load currents across the channel were obtained by simulating an external potential to the conducting moving wall. The load currents in each case were opposed by the induced electric field. Since there is no pressure gradient, the flow along the channel is driven by the viscous effects of the moving wall and the Lorentz body force and is retarded by the stationary walls. In the case where no load current is applied across the channel, the current circulates in the channel.The circulation is driven by the generator that is due to the axial variation of velocity in an axial magnetic field. The numerical results presented show that the radial gap and the free surface region represent electrical resistances in parallel between the perfectly conducting stationary wall and the perfectly conducting moving wall. The numerical results also show that the resistance of the radial gap increases as M2 while that of the free surface increases by M or M1/2. Thus, as M increases, the division of current shifts to the free surface region and the current density in the radial gap decreases as M−1. The theoretical magnetohydrodynamic model presented here was developed to provide numerical parameters to help in the design of liquid-metal current collectors. Numerical results were computed for one-dimensional Couette flow with no pressure gradient in an external, homogeneous axial magnetic field. One-dimensional Couette flow has no end effects, and thus the numerical results were compared with corresponding numerical results for the two-dimensional Couette flow case to determine end effects.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 38
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4494-4502 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The heat capacities of liquid and crystalline Au-Pb-Sb alloys in the glass-forming composition range were measured with droplet emulsion and bulk samples. Based on the measured Cp data, the entropy, enthalpy, and Gibbs free-energy differences between the eutectic solid mixture and undercooled liquid were determined as a function of temperature over ∼60% of the undercooling range below the liquidus temperature and compared with theoretical predictions. The results indicate an isentropic temperature at 313 (±5) K, which agrees well with experimental data for the glass transition. The thermodynamic evaluation was applied further to develop a kinetics analysis of the nucleation undercooling response during cooling. Use of different approximations for the Gibbs free energy leads to a variation of the prefactor terms of six orders of magnitude for classical nucleation theory and, consequently, large variation in calculated transformation diagrams which is more pronounced with increasing undercooling. Extrapolations into the glass-forming temperature range and the effects of viscosity, transient nucleation, and estimated Kauzmann temperatures on the crystallization kinetics at high undercooling have been evaluated. This analysis reveals the importance of using measured values of thermophysical properties, even if they represent a limited temperature range at modest undercooling, rather than model approximations in order to obtain reliable evaluations of crystallization kinetics at high undercooling in the glass-forming temperature range.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 39
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4531-4534 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Shock waves of order 100 kbar were launched into 50-μm-thick single crystals of silicon (111) by irradiation with nanosecond pulses of 1.05-μm laser light at irradiances in the region of 2×1010 W cm−2. A separate laser beam, synchronous but delayed with respect to the shock-driving beam, and containing approximately 25 J of 0.53-μm laser light in a pulse of 1 ns (FWHM), was focused to a tight (〈100 μm) spot on a separate titanium target to produce a plasma which was a prolific source of He-like Ti x rays. The x rays were Bragg diffracted from the rear surface of the shocked crystal and the spectrum recorded on an x-ray streak camera. Changes in interatomic spacings in a region within several microns of the surface were thus deduced from the resultant shift in Bragg angle with a temporal resolution of 50 ps. Shock waves with compressions of order 6% were observed. We observed the crystal in a state of dynamic tension as the two rarefaction waves met. The results are in good agreement with hydrocode simulations in conjunction with x-ray diffraction calculations.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 40
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4556-4560 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Amorphous Si/Ge artificial multilayers with a repeat length around 60 A(ring) have been partially mixed with 1.5-MeV Ar+ ions at temperatures in the range 77–673 K. The diffusive component of the square of the mixing length, obtained by subtracting out the ballistic contribution, does not depend on the dose rate at a given dose, and shows an Arrhenius-type temperature dependence with activation enthalpies between 0.13 and 0.22 eV. Possible mechanisms for migration and annihilation processes of defects are discussed to understand these low activation enthalpies.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 41
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4581-4585 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ZnTe-ZnS short period (∼30 A(ring)) strained layer superlattices were grown by molecular beam epitaxy and the growth process was observed in situ by using reflection high energy electron diffraction (RHEED). Surface lattice constant (a(parallel)) behavior shows a transition from one state in which a(parallel) is equal to that of the substrate to the other in which a(parallel) depends on the depositing constituents. RHEED patterns show the same streaks for both states except the difference in streak separation. Transmission electron micrograph reveals that the resultant multilayer structures of the two states have the same quality. The experimental data may suggest a possible assumption that there exists multiple states for two-dimensional growth of a strained system with substantial lattice mismatch.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 42
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4604-4609 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed optical study of the metastable III/V semiconductor alloy InP1−xSbx is presented. InP1−xSbx layers are grown throughout the entire compositional range by atmospheric pressure organometallic vapor phase epitaxy on InP, InAs, and InSb substrates. Composition and strain are measured by combined electron microprobe analysis and x-ray diffractometry. The dependence of band gap on composition is experimentally established for the first time from absorption spectra measured at 10 and 300 K. The resultant value of the band-gap bowing parameter is 1.52±0.08 eV, independent of temperature. The absorption spectra show the InP1−xSbx layers to have long band tails, which extend further into the gap as the Sb concentration is increased. The band tails are induced by compositional clustering. Photoluminescence (PL) spectra are measured between 10 and 300 K. The PL peaks are assigned to recombination between carriers occupying band-tail states or to recombination via deep centers in the gap.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 43
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4620-4633 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hole trapping phenomena in SiO2 were examined using an optically assisted hot carrier injection technique on p-channel insulated gate field effect transistors. It was found that only a single, field-dependent, capture-cross-section hole trap is present. The capture cross section of these hole traps at a field of 4 mV/cm across the gate insulator, corresponding to a gate voltage just above the threshold voltage, was found to be 8.5×10−14 cm2. Injected holes were found to trap with an initial efficiency of approximately 60% at this gate field. Depopulation of trapped holes at room temperature was also examined, and found to be significant. The neutral hole trap density in unirradiated device gate insulators after post-metal annealing was found to be approximately 7.0×1012 cm−2. Based on a study of the threshold voltage shift as a function of gate insulator thickness, coupled with the model recently proposed by Walters and Reisman for determining charge centroid, it appears that for oxides with thicknesses greater than 10 nm, the hole traps lie in a band of finite thickness with a charge centroid 5 nm from the substrate-SiO2 interface. In addition, there exists a layer approximately 3.7 nm thick at each interface that appears void of trapped charge. Therefore, oxides less than 7.4 nm thick should not trap charge, which was found to be the case experimentally. This implies that as devices are scaled down, hole trapping will disappear, which is of particular significance in oxides subjected to ionizing irradiation, either during processing or during use.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 44
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4667-4673 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The problem of calculating the valence-band structure of strained-layer quantum wells in the effective-mass approximation is reviewed. Using the spherical approximation and exploiting the simplicity of the infinitely deep well model we show that the in-plane effective mass is determined by two factors—a splitting contribution which is dominant at large strains, and a quantum confinement contribution. A model for finite-depth wells is presented which gives analytic expressions for the zone-center in-plane mass and associated nonparabolicity factor, and it is applied to the system InxGa1−xAs/GaAs. The model allows the computation of valence-band structure using no more than a pocket calculator. It is shown to give results in reasonable agreement with experiment.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 45
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4662-4666 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Silicon dioxide layers of 250 A(ring) thick were grown on Si at 1000 °C in a dry O2/TCA ambient. Thermal nitridation of the samples was performed in a pure ammonia ambient at temperatures from 900 to 1100 °C with one hour time intervals up to a maximum of 4 h. The fixed charge state densities at the interface of the samples were determined from high frequency C-V measurements, and the breakdown fields from I-V curves. Secondary ion mass spectroscopy depth profiles show low levels of contaminants, and high levels of nitrogen at the interface for samples annealed at temperature greater than or equal to 1000 °C and for periods longer than 2 h. Post metal annealing of the nitrided samples appears to help in reducing the trapped charges. Better quality films with lower Qf and VFB shifts, and higher breakdown fields were achieved for samples annealed at 1100 °C. Metal-oxide-semiconductor device quality nitrided films with a Qf of 1010/cm2 were achieved by optimizing the process conditions at 1100 °C. The fixed charge build up for lower nitridation temperatures (〈1000 °C) and times (〈2 h)is due to the dissociation of Si—O bonds in the presence of hydrogen, and is in accordance with the earlier results in the literature. However, the reduction in the fixed charge buildup at 1100 °C, we believe, is due to the increased levels of nitrogen.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 46
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4700-4702 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Josephson voltage standards utilize microwave-induced constant voltage steps in the dc characteristic of Josephson tunnel junctions. This paper describes the design and operation of array circuits with 108 and 2000 junctions connected in series. In contrast with similar realizations, simple Q-band equipment is used for the microwave supply. The microwave attenuation of 1000 junctions was about 1 dB. The version with 2000 junctions generated Josephson voltages up to 1.2 V when operated at 35 GHz. The stability times of the quantized levels were, under normal laboratory conditions (unshielded room), better than 10 min.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 47
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4724-4727 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results obtained in part I are interpreted in terms of the viscosity field arising from independent processes of directional ordering for magnetic defects dispersed in the amorphous structure and interacting with the magnetization vector. A specific model is developed in order to take into account the changes in the ordering kinetics induced by the periodic magnetization rotations described in part I. This model, however, requires that the magnetic induction remain constant during the whole measurement; as a consequence, the model's predictions cannot be directly compared with the experimental results, obtained instead at constant applied field. This difficulty is overcome by deriving a general relationship between the magnetic-induction decay and the viscosity field kinetics for an arbitrary number of half-periods of the square-wave field. The agreement of our theory with the experimental results turns out to be quite satisfactory. As consequence, the ordering processes responsible for the magnetic aftereffect in amorphous ferromagnets may be described as essentially uncorrelated.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 48
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4772-4776 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed a very interesting feature in the mid-infrared region of copper-doped semi-insulating liquid encapsulated Czochralski grown GaAs at liquid helium temperature. After gettering copper using backside mechanical damage, the transmittance of this particular feature became much weaker. The first absorption feature occurs at 1182 cm−1 (0.147 eV), the second at 1460 cm−1 (0.181 eV), and the third at 1750 cm−1 (0.217 eV), which is a transition of an electron from the valence of three copper levels. This electronic mode absorption allows us to obtain information about the activation energies of deep-level impurities like Cu and their relative concentration after each process. This electronic mode absorption at multilevels of Cu in GaAs is proposed for the first time using the Fourier transform infrared technique to detect deep-level metal impurities in GaAs.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 49
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4795-4801 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The authors report time-resolved measurements of the emission of positive and negative charge from Si and Ge surfaces irradiated with 248-nm KrF excimer laser pulses. With pulse energies both below and above the melting threshold, the time evolution of the emission currents is complex and strikingly different for Si and Ge. The positive ion emission signal from Ge persists only for the duration of the laser pulse (〈60 ns), but in sharp contrast, the signal from Si continues for several microseconds. A tentative suggestion is made that the positive ions encounter a Knudsen layer created just above the surface of the Si target. More refined experiments, coupled with a theoretical effort, are proposed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 50
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4802-4810 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultraviolet laser irradiation of surfaces, in the course of photoemission or surface photochemical studies, often produce copious electron emission, up to 1000's of A/cm2. The time-dependent fields produced by these electrons accelerate some of the electrons up to 5.4 times their initial energies. The steady-state fields return most of the emitted electrons to the surface. We discuss and illustrate both phenomena with theoretical simulations and experiment, and discuss possible implications.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 51
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4825-4829 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The composition of the reaction gases in a hot-filament reactor for chemical vapor deposition of diamond films was analyzed using a gas chromatograph coupled with a quartz microprobe. Concentrations of several hydrocarbons were determined as functions of filament temperature (FT) and the position of the probe relative to the filament for two feed gases, methane/hydrogen and acetylene/hydrogen. The diamond growth rate was measured as a function of FT in both feed gases. The major chemical process in these reaction systems is found to be conversion between methane and acetylene with ethane and ethylene as reaction intermediates. For FT≤1800 °C, the chemical reactivity is low, and no diamond deposition is observed. For FT≥1900 °C, nearly identical chemical composition near the filament is obtained from both feed gases (indicating possible attainment of thermodynamic equilibrium in the gas mixtures), and the measured diamond growth rates are similar. A substantial depletion of carbon in the reaction gases near the filament is observed and is shown to be due to thermal diffusion. Downstream of the filament, a nonequilibrium state is observed, possibly caused by slow methane/acetylene conversion and/or fast diffusion. The trend of the diamond growth rate, which increases with increasing FT from 1900 to 2200 °C, correlates well with the concentration profile of acetylene but not that of methane.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 52
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4873-4875 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using (100) Cu(1000 A(ring)) /Ni/Cu(1000 A(ring)) structures with a different Ni thickness, a complete reversal in magnetic anisotropy is observed between the structures with 1000 and 50 A(ring) Ni, respectively. The structures were deposited on (100) Si, with the first Cu layer in the (100) orientation as the seed, followed by epitaxial Ni and another Cu layer. Comparing the magnetization for the field applied parallel to the film plane, M(parallel), with that perpendicular to it, M⊥, M⊥ is found to increase and M(parallel), to decrease with decreasing Ni thickness. At a Ni thickness of 50 A(ring), a squared hysteresis loop is observed for M⊥. The M(parallel) curve, on the other hand, changes from a normal one at 1000 A(ring) Ni to one with little hysteresis at 50 A(ring) Ni. These are accompanied by an increasing deformation of the (100)Ni cubic lattice into a tetragonal one with decreasing Ni thickness, due to its mismatch with Cu. The deformation is discussed to assess the roles of stress in the observed reversal in magnetic anisotropy.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 53
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4879-4881 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The emission spectra resulting from ion beam sputtering a Y-Ba-Cu-O target were observed as a function of beam voltage and beam current. The spectra were relatively clean with several peaks readily attributed to each of Y, Ba, and Ar. Monitoring of copper and oxygen was more difficult with a single CuO peak and one O peak evident. The intensities of the cation peaks were linear with respect to beam voltage above 400 V. Since target current was found not to be directly proportional to beam current, target power was defined as the product of beam voltage and target current. The response of cation peak height to changes in target power was linear and similar for variations of either beam voltage or target current.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 54
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4876-4878 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optically transparent, free-standing single crystals of the high-temperature superconductor Bi2Sr2CaCu2O8 have been prepared with a typical size of a×b×c=1 mm×1 mm×1500 A(ring). The thickness of the samples has been determined by x-ray transmission measurements and was found to be uniform to within a lattice spacing. Transmission electron microscopy and diffraction revealed a pseudotetragonal lattice with a twinning free, incommensurate superstructure. X-ray microanalysis shows that the composition of the sample is homogeneous. Electrical resistivity and magnetic susceptibility measurements indicate that the crystals are good quality superconductors.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 55
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4882-4884 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spatially resolved measurements of the change in resistance with temperature of bulk high-temperature superconductors are generated by heating a localized region of a sample with a modulated laser beam. The amplitude of the thermally induced resistance change is related to the heat capacity and derivative of resistance with temperature whereas the phase of the signal is related to the thermal diffusivity of the sample. By moving the sample with respect to the focused laser beam, spatially resolved measurements may be made. Images with ∼50-μm resolution have been used to locate defects in polycrystalline Bi-Sr-Ca-Cu-O sample and to estimate the thermal diffusivity of the bulk material.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 56
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4888-4890 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An efficient numerical algorithm was developed to solve the continuity equations describing charged particle transport and potential distribution in a low-pressure glow discharge in an argonlike gas. A parametric investigation of the effect of gas pressure and electrode spacing on the discharge properties was conducted.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 57
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4885-4887 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the epitaxial growth rate of Si in the disilane/hydrogen system for different experimental conditions in a rapid thermal processing–low-pressure chemical vapor deposition reactor. The measured activation energy is about 43 kcal/mol for temperatures below 700 °C. The growth rate dependence on disilane or hydrogen partial pressures is measured in order to verify the reliability of a proposed model for the decomposition of the disilane molecule in the torr pressure regime. The obtained crystal quality is comparable to that obtained with silane gas except for higher growth rate in the disilane system.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 58
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4894-4896 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature photoluminescence was used to study the Si+- and Si++P+-implanted InP. A broadband at ∼ 1.26 eV appears in photoluminescence spectra for Si+-implanted InP after annealing. The intensity of this broadband decreases with increasing the coimplanted P+ dose and increases with increasing the implanted Si+ dose. The temperature dependence of the photoluminescence data shows that the change in the half-width of the broadband can fit the configuration coordinate model. This band is believed to be due to VP-SiP complex. The results indicate that silicon is an amphoteric species in InP.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 59
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4891-4893 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stable and highly reproducible current-limiting characteristics are observed for polycrystalline ceramics prepared by sintering mixtures of coarse-grained, donor-doped BaTiO3 (tetragonal) as the major phase and ultrafine, undoped cubic perovskite such as BaSnO3, BaZrO 3, SrTiO3, or BaTiO3 (cubic). The linear current-voltage (I-V) relation changes over to current limiting as the field strength increases, when thermal equilibrium is attained. The grain-boundary layers with low donor and high Sn, Zr, or Sr have depleted charge carrier density as compared to that in the grain bulk. The voltage drop at the grain-boundary layers diminishes the temperature gradient between the interior and surface regions.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 60
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4900-4902 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new self-aligned subtractive gate process is proposed by alternating several masking and polycrystalline silicon gate etching steps from a conventional process to build high-voltage (up to 100 V) and complementary thin-film transistors (TFT) on insulating substrates. The new process is compatible with conventional TFT mask sets and standard processing techniques. The advantage of using this new process is to eliminate the difficulty in stripping photoresist on insulating substrates after high-dose phosphorus implant and to improve the off-state breakdown voltage in high-voltage transistors. Complementary metal-oxide-semiconductor and high-voltage TFT devices were successfully fabricated by this new process.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 61
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4897-4899 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonlinear refractive index changes for the wavelengths near the fundamental edge in an ultrapure epitaxial layer of GaAs were obtained directly by the photoreflectance method. The nonlinearities are due to the electric field effect for pump intensities lower than 0.06 W/cm2 and the plasma screening and the band filling effect for pump intensities higher than 0.06 W/cm2.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 62
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4906-4906 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 63
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4903-4905 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An improved version of a prior model is given for specific resistance of ohmic contacts to n-GaAs. Instead of the two-band model used in the prior work for the transmission coefficient, a more rigorous three-band model due to E. O. Kane [J. Phys. Chem. Solids 1, 249 (1957)] is used in the improved version. In the doping range of interest, the theoretical contact resistance can differ by more than an order of magnitude, particularly at high intrinsic barrier heights. The contact resistance is given as a function of doping and the intrinsic barrier height. An ultimate limit to the contact resistance is also given.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 64
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3809-3813 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time-dependent intensities of the spectral lines emitted by laser-induced plasmas generated in several gases are presented. The time-resolved and spatially varying intensities of two once-ionized nitrogen lines were used to calculate radial temperature distribution of temperature within the plasma. A modified blast wave theory, in which ionization was included through the Saha equation and the equation of conservation of charge, was used to calculate time-dependent intensities of several spectral lines of C, N, He, and Ar. The temporal profiles of the spectral lines appear to be dependent on the ionization potentials of the species in the plasma.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 65
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3818-3821 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The general approach to cylindrically symmetric force-free magnetic fields first introduced by Lüst and Schlüter [Z. Astrophys. 34, 263 (1954)], is restricted to fields of the form H=[0,Hφ(r),Hz(r)], and subsequently used to determine a set of solutions to the force-free field equations with nonconstant α. The first element of the set is the well-known constant α solution of Lundquist [Ark. Fys. 2, 361 (1951)]. These solutions may have practical applications with respect to high-temperature superconductors.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 66
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3822-3825 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The performance characteristics of ridge waveguide In0.2Ga0.8As/GaAs multiquantum-well lasers are reported. The lasers emit more than 50 mW/facet in the temperature range 20–100 °C in the fundamental transverse mode. The external differential quantum efficiency of 250-μm-long lasers is 0.4 mW/mA/facet. The internal optical loss is 14 cm−1. The optical gain is found to vary linearly with current. The increase in threshold current with increasing temperature in these lasers is primarily due to decreasing carrier lifetime (increased carrier loss) at high temperature. Increasing the heterobarrier height may further improve the high-temperature performance of these devices.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 67
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3814-3817 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Third-harmonic generation (THG) was used to monitor ground-state atomic hydrogen H(1s 2S1/2) in a dc plasma system. A 364.6 nm laser beam focused through H2 or CH4/H2 plasmas induced THG at 121.5 nm, near the atomic hydrogen 2p 2PoJ→1s 2S1/2 Lyman-α transition. Both the intensity and frequency shift of the excitation spectra exhibited dependence on the plasma power. Absolute H atom concentration was estimated by comparing the frequency shift to that obtained in a calibrated microwave discharge flow system. The sensitivity was ∼4×1013 cm−3 (100 ppm). The measured atomic hydrogen densities were substantially less than in other diamond chemical vapor deposition methods and may explain the lower diamond deposition rates obtained with dc plasma systems of this type.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 68
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3826-3831 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A low-loss, high-intensity color modulator based on the dichroic-mirror-induced separation of the light into three color channels, modulated by polymer dispersed liquid-crystal shutters, is described. The maximum contrast obtained with the light-scattering-based shutter is estimated and compared with experimental values. The quality of color reproduction of the modulator is presented in a standard 2D CIE diagram while the luminance is included in the 3D version with an incandescent lamp used as the light source. The white color is reconstructed by the modulator with an efficiency of 50%.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 69
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3832-3837 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tin-diffused GaAs layer samples, with mean concentrations larger than 1019 cm−3, were obtained by irradiating with a ruby laser GaAs substrates covered with thin tin layers. Mobilities between 100 and 200 cm2/V s were obtained. Both carrier concentration and mobility decrease with increasing energy density. Strong segregation effects were observed in the samples processed with large energy densities.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 70
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3844-3848 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of an experimental investigation to improve the performance of a discharge-pumped iodine monofluoride laser are reported. Lasing was observed at 478.7, 484.7, 490.7, and 496.5 nm. Electrical measurements of the discharge characteristics permitted the energy flow in the circuit to be followed and laser efficiencies to be calculated. Parametric studies of gas mixtures were carried out. By optimizing several parameters, single-pulse lasing energies greater than 50 mJ were obtained.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 71
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3838-3843 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temporal variation of the electron and current densities as well as the discharge voltage in a XeCl excimer laser discharge is studied as function of gas pressure and HCl+Xe concentration. The results show that independent of pressure and gas mix composition the electron drift velocity is a constant of vd=(1.2±0.2)×106 cm s−1. While in discharges containing only helium the current and electron density are independent of pressure P, both quantities vary as P0.6 once Xe and HCl have been added. The results are examined considering the most important atomic reaction rates.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 72
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3849-3855 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical and magneto-optical properties of weakly guiding single-mode buried channel waveguides in substituted yttrium iron garnet have been investigated experimentally. The propagation constant difference Δβ of the two coupled TE and TM modes, which is of particular interest for waveguide isolator application, is found to be strongly dependent on waveguide geometry. Measured results can be explained by the specific growth of the top cladding layer, which occurs into different crystallographic directions around the etched waveguide core. This leads to a local variation of the refractive index, which effects the guidance of light, and to a local variation of birefringence, which effects Δβ. The measured variation of Δβ is shown to be primarily caused by growth induced birefringence. It is demonstrated that Δβ can be controlled to small values at selectable waveguide widths as required for waveguide isolator application simply by an appropriate setting of fabrication parameters.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 73
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3856-3860 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Be ions are implanted into Te-doped Ga0.96Al0.04Sb layers grown by liquid-phase epitaxy. Be distribution is analyzed from secondary-ion mass spectrometry profiles and is found to be in good agreement with a computed simulation one. Hall-effect measurements show a complete electrical activity of the Be-implanted ions. Mesa devices are realized on the Ga0.96Al0.04Sb p+/Ga0.96Al0.04Sb n−/GaSb+ system: Be implantation leads to good quality junctions exhibiting homogeneous multiplication.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 74
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3861-3864 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ionization coefficients of holes and electrons (kp and kn) in Ga0.96Al0.04Sb have been derived from the variations of the photocurrent multiplication as a function of the reverse bias in Be-implanted p+Ga0.96Al0.04Sb/n Ga0.96Al0.04Sb/n+ GaSb mesa diodes. Three wavelength values have been used for the illumination in order to obtain pure hole injection, nearly pure electron injection, and mixed injection. The kp and kn values thus determined for electric fields varying from 18 to 32 V/μm exhibit a high ratio value showing the interest of this material for avalanche photodiodes devices.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 75
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3865-3871 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear piezoelectric photoacoustic (PA) effect of silicon wafers in the applied dc electric field is studied experimentally and theoretically. The apparent nonlinear dependencies of PA amplitude and phase on the laser power are observed in experiments with different dc electric fields. The nonlinearity is explained theoretically by considering the nonlinear surface and bulk Auger recombinations. We present a "subsurface approximation'' method to solve the nonlinear transport equation for photogenerated carriers in semi-infinite samples. A good agreement between the experimental results and theoretical predictions is obtained as the incident laser beam with and/or less than medium power.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 76
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3872-3883 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Laplace equation can be solved in any two- and three-dimensional porous medium by means of a vectorized numerical code. It is applied to several structures such as random media derived from site percolation; close to the percolation threshold, the critical exponents are found to be very close to the ones corresponding to networks; the results are usefully compared to previous variational upper bounds and to the prediction of an approximate space renormalization. Media with double porosity such as catalyst pellets are also addressed. Finally the conductivity of most fractals is shown to follow an Archie's law in the limit of large generation numbers; the exponents of the power laws can be retrieved by various renormalization arguments.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 77
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3884-3891 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A two-dimensional model is developed for material damage caused by melting and vaporization during pulsed laser irradiation. The problem is formulated by using the energy conservation equation (the Stefan condition) at various points on the solid-liquid and liquid-vapor interfaces. The effect of curvature of the solid-liquid and liquid-vapor interfaces are taken into account and the problem is solved numerically by using the Runge–Kutta method. For determining the maximum damage that can occur during laser irradiation, the laser energy is considered to be utilized only to melt and vaporize the material. The effect of various laser parameters, such as the laser power, laser beam diameter, pulse-on time, and the number of pulses per second on the depth and the radius of the crater is presented. Also, the tapering angle of the crater and the formation of recast layer in the crater during laser irradiation are examined in this study. Finally, a linear relationship between the maximum crater depth and the "gross'' laser intensity is derived phenomenologically and verified by using the numerical results of this study.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 78
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3892-3903 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new Brownian motion simulation technique developed by Torquato and Kim [Appl. Phys. Lett. 55, 1847 (1989)] is applied and further developed to compute "exactly'' the effective conductivity σe of n-phase heterogeneous media having phase conductivities σ1, σ2, ..., σn and volume fractions φ1, φ2, ..., φn. The appropriate first passage time equations are derived for the first time to treat d-dimensional media (d=1, 2, or 3) having arbitrary microgeometries. For purposes of illustration, the simulation procedure is employed to compute the transverse effective conductivity σe of a two-phase composite composed of a random distribution of infinitely long, oriented, hard cylinders of conductivity σ2 in a matrix of conductivity σ1 for virtually all volume fractions and for several values of the conductivity ratio α=σ2/σ1, including perfectly conducting cylinders (α=∞). The method is shown to yield σe accurately with a comparatively fast execution time.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 79
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3904-3915 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A continuum model was used to analyze charged particle transport and potential distribution in low-pressure radio frequency (rf) glow discharges. The method of lines with orthogonal collocation on finite elements for the spatial discretization was found to be an effective numerical technique for solving the model equations. An argonlike (electropositive) discharge was compared to a pure chlorine (electronegative) discharge. The electronegative discharge was found to have much thinner sheaths, much greater potential drop and electric field strength in the bulk plasma, and severe modulation by the applied rf (10 MHz frequency) of the electron temperature, ionization, and excitation rate, even in the bulk. The effect of varying excitation frequency was also examined. The results showed that continuum models can capture the essential features of both kinds of discharges. Integration of these models with neutral species transport and reaction can result in powerful tools for the modeling and design of plasma reactors.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 80
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3916-3934 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion bombardment energy and angle distributions have been measured in an argon plasma. The measured ion angle distribution at 10 mTorr shows that 30% of the ions have incident angles greater than 10° from the surface normal. However, ions with large incident angles have much lower energies than those incident perpendicular to the surface. At 500 mTorr a very large fraction of the ions have large incident angles, and the average energies of these ions are relatively independent of incident angle. Monte Carlo simulations of the sheath kinetics predict the trends shown in the experimental data for ion energy and angle distributions. Fine structure in the ion energy distribution was observed below 50 mTorr and is shown to be caused by charge-exchange collisions in the sheath. The average ion energy in a symmetric parallel plate system is linearly related to the voltage applied across the electrodes for measured plasma pressures up to 500 mTorr.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 81
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3935-3946 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The energy density of the electron flux in magnetized 30-Torr He and He:N2:CO2 dc glow discharges was obtained by Monte Carlo simulation of the cathode region. The application of transverse magnetic fields to the cathode region caused an increase in collisions. This effect became increasingly important in the second half of the cathode region, where magnetic trapping of high-energy electrons occurred. Ionization was enhanced in the cathode region as well as the negative glow, with maximal electron multiplication observed for magnetic field strengths of approximately 0.1 T. This suggests both that a lower cathode fall may be possible in a magnetized discharge and that the electric field reversal in the negative glow will be accentuated. Thus, magnetization of the cathode region may improve the electrical efficiency of CO2 lasers.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 82
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3947-3952 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We discuss extreme ultraviolet and x-ray spectral lines emitted by ions of the Cu i and Na i isoelectronic sequences and show that certain intensity ratios of these lines are sensitive to electron density in the range from about 1018 to 1022 cm−3. These lines therefore provide density diagnostics for high-temperature plasmas. We illustrate the density dependence for four ions of the Cu i sequence (Z=60, 71, 82, 92) and seven ions of the Na i sequence (Z=32, 42, 52, 62, 72, 82, 92). We also show that the dependence of the ratios on electron temperature is not strong, and demonstrate that opacity can be kept small by employing the spot spectroscopy technique.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 83
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3957-3963 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a calculation of the characteristic curves of the silver/chalcogenide glass inorganic photoresists which is based on a theory of photoinduced diffusion of silver into the chalcogenide glasses. The silver concentration profiles in the glasses are calculated for the cases of semi-infinite as well as finite slabs. We also consider the effect on the silver concentration profiles of the intrinsic absorption of photons, which results when illumination by photons whose energies are above the band-gap energies of the glass is employed. It is found that very high values of the contrast parameter are attainable for prolonged development.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 84
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3953-3956 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of group-V donor impurities on the behavior of indium atoms implanted into silicon single crystals has been studied by Rutherford backscattering spectrometry/channeling spectrometry, and differential Hall-effect/resistivity measurements. Flat arsenic or phosphorus profiles of concentrations between ∼1.4×1020 cm−3 and 3×1020 cm−3 were produced by As+ or P+ implantation followed by rapid thermal annealing (RTA) (20 s, 1100 °C). Subsequently In was implanted to peak concentrations of 1.7×1020 cm−3 or 3.5×1020 cm−3 and annealed by RTA (15 s, 700–1050 °C).Compared to single indium implants, the presence of the preimplanted group-V impurities is found to reduce the redistribution of the implanted indium atoms during RTA and to increase the concentration of indium atoms incorporated on (or close to) lattice sites (up to ∼2×1020 cm−3). The value of the indium substitutional fraction is found to be dependent on anneal temperature and type of donor impurity. A reduction in the free-electron concentration is observed in both the phosphorus and arsenic predoped samples at the same depths as that of the indium atoms.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 85
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3964-3969 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Double crystal x-ray analysis has been carried out on GaAs wafers implanted with 1.15 MeV sulfur ions at a dose of 5×1014/cm2, followed by rapid thermal anneal for 10 s at temperatures between 300 and 1100 °C. A systematic reduction of strain with increased annealing temperature has been observed, as measured from the separation between the peak of the unimplanted substrate and the major peak of the strained region. Calculations of strain distribution based on existing numerical models are correlated with implantation parameters using Pearson's type-VI distribution functions. Strain reduction after a silicon nitride encapsulation process is found to be equivalent to that after a 300 °C, 10 s rapid thermal anneal (RTA). It is also found that strain relaxation by RTA is strongly dependent on both sample size and the annealing geometry.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 86
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3970-3974 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the effect of CF4/O2 plasma treatment before ion implantation on the activation efficiency for Si-implanted GaAs by rapid thermal annealing. WSiN-capped, SiO2-capped, and capless rapid thermal annealings at 900 °C for 10 s in an Ar atmosphere were compared. The annealed samples were characterized by Hall-effect, capacitance-voltage, secondary-ion mass spectrometry, and 77-K photoluminescence measurements. The large decrease in activation efficiency by CF4/O2 plasma treatment was observed in SiO2-capped rapid thermal annealing. On the other hand, the decrease in activation efficiency by this plasma treatment was small in both WSiN-capped and capless rapid thermal annealings.〈squeeze1.6p〉
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 87
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3975-3978 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mercury ions were implanted in amorphized potassium titanyl phosphate (KTiOPO4) in the range of 50–400 keV. The implanted depth distribution was measured by Rutherford backscattering of 2.1 MeV He ions. The mean projected ranges and range stragglings obtained are compared with our calculation based on Biersack's angular diffusion model and Monte Carlo simulation. The results show that the experimental mean projected range is in good agreement with the calculated value within the experimental errors but the range straggling is systematically higher than the calculated value. However, significant deviations from the transport of ions in matter (TRIM'89) prediction for mean projected range and range straggling are found.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 88
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3979-3982 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Development of solid-state laser drivers of higher operating fluence is dependent upon the damage resistance of the frequency conversion crystals. We have demonstrated the correlation between the purity of the crystal growth solution and the laser damage threshold of single-crystal potassium dihydrogen phosphate (KDP). Impurities introduced in the growth process can be atomic species, inorganic or organic compounds (dissolved or particulate), or bacteria. We have developed a purification process for KDP that minimizes contamination: initial recrystallization of bulk KDP followed by ozonation to remove oxidizable material, ultrafiltration to remove nonoxidized particles, and UV-light exposure to suppress bacterial growth. We have also developed a crystal growth method that excludes load-bearing surfaces, which are a potential source of particulate contamination, from the growth environment. The method, which incorporates continuous filtration and continuous flow of the growth solution has yielded crystals with damage thresholds of 28.6 J/cm2 at 355 nm and greater than 64 J/cm2 at 1064 nm (10-ns pulse length).
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 89
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3983-3989 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A computational method is developed for analyzing interactions between near-surface lateral cracks and residual stresses due to localized plastic zones. The latter are approximated as either prismatic or shear dislocation dipole pairs. Two-dimensional plane-strain conditions are assumed. A complete linear elastic solution is obtained using half-space dislocations for the dipole pairs and for the dislocation distribution function that accounts for the stress-free crack surface boundary condition. The crack-tip stress intensity factors show that mode-II driving forces are important for both prismatic and shear zones. The tendency for crack deflection to the free surface derived from energy release rates is complex. The dipole representation results do not provide a simple rationalization for lateral crack chipping.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 90
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3990-3997 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Crystals formed upon crystallization of amorphous solids are often plate shaped and contain a high density of twins. The objective of the present work was to further the understanding of the microstructure of such crystals. It is suggested that the elastic energy associated with the crystallization-induced dilatational strains can be reduced significantly by the formation of a macroscopically invariant plane, lying parallel to the basal plane of plate-shaped crystals. The invariant plane is obtained by means of a double-twinning mechanism. The model accounts for continuity being maintained across the crystal-amorphous matrix interface in spite of the volume change involved in the crystallization. The situation bears close resemblance to that dealt with by the crystallographic theory of the martensitic transformation.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 91
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3998-4001 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The internal friction of YBa2Cu3O7−δ is measured at 7.8, 40, and 144 kHz as a function of temperature (from 300 to 1100 K) and oxygen partial pressure. At 40 kHz a marked damping peak occurs at ∼800 K which is attributable to oxygen hopping in the basal plane. The oxygen diffusion coefficient calculated from the hopping relaxation time is in good agreement with other estimates yielding an activation enthalpy, hm=1.07±0.05 eV and D0=1.8×10−4 cm2/s. At a critical value of δ∼0.25 the diffusion coefficient begins to rise rapidly similar to the occurrence of a fast-ion transition.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 92
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4002-4007 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth kinetics of an amorphous (a-)interlayer in polycrystalline Zr and Hf thin films on (111)Si have been investigated by cross-sectional transmission electron microscopy. The growth of the a-interlayer in group-IVb metals and silicon systems was found to exhibit similar behaviors. The growth was found to follow a linear growth law initially. The growth rate then slows down and deviates from a linear growth law as a critical thickness of the a-interlayer was reached. Crystalline silicide (ZrSi or HfSi) was found to nucleate at the a-interlayer/Si interface in samples after prolonged and/or high-temperature annealing. Silicon atoms were found to be the dominant diffusing species during the formation of amorphous alloys. The activation energy of the linear growth and maximum thickness of the a-interlayer were measured to be 1.4 eV, 17 nm and 1.2 eV, 27 nm in Zr/Si and Hf/Si systems, respectively. The correlations among the differences in atomic size between metal and Si atoms, growth rate and activation energy of the linear growth, critical and maximum a-interlayer thickness, the largest heat of formation energy for crystalline silicides, the calculated free-energy difference in forming amorphous phase, as well as the atomic mobility in Ti/Si, Zr/Si, and Hf/Si systems are discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 93
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4008-4013 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The diffusion of Si in GaAs was investigated using diffusion sources from different tie triangle regions on the Si-Ga-As ternary phase diagram which provide constant chemical potentials for the three components under isothermal conditions. The Si profiles are measured with secondary ion mass spectrometry and differ significantly for the different sources. The Ga-Si-GaAs tie triangle source produces p-type Si doping with concentration independent diffusion coefficients, and a neutral As or Ga vacancy is proposed as the dominant mobile defect for these conditions. Arsenic-rich sources from two tie triangle regions and also a Si-GaAs tie line source produce Si donor diffusion with concentration-dependent diffusion behavior. The concentration-dependent diffusion coefficients of donor Si for As-rich source diffusion are related to the net ionized donor concentration showing three different regimes: intrinsic regime, intermediate regime, and saturation regime. Ga vacancies are proposed to be responsible for donor Si diffusion in GaAs: a V0Ga and/or V−Ga mechanism for the intrinsic regime; and a V−Ga related mechanism for the extrinsic and saturation regimes. The Si-GaAs tie line source resulted in two branch type profiles, intermediate between the As-rich and the Ga-rich source diffusion cases.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 94
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4014-4019 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microlithographic patterning has been used to elucidate the mechanisms controlling diamond film nucleation and grain growth. The approach is capable of establishing a degree of control over diamond nucleation on the substrate, which can be used to improve film uniformity and enhance fine grained microstructure. The observed microstructures in the patterned films are consistent with an intrinsic growth mechanism based upon defect-initiated renucleation.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 95
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper compares Hall-effect measurements combined with rapid thermal annealing (RTA) and low-temperature photoluminescence (4-K PL) as characterization techniques for the optimization of the growth of pseudomorphic InGaAs channel modulation-doped field-effect-transistor structures. The Hall-effect measurements with the RTA were used to determine the optimized growth temperature. 4-K PL was used to determine the quality of the InGaAs quantum well and the In mole fraction.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 96
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3598-3608 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The first-order Raman spectra of individual 8-μm-diam PAN-derived carbon fibers which had been annealed at five temperatures from 1700 to 2800 °C are measured as a function of incident laser power from 1 to 140 mW. In all fibers studied, the Raman frequencies of the graphite G band at ca. 1580 cm−1 and the disordered-induced D band at ca. 1360 cm−1 shift to lower frequency with increasing laser power. The largest shifts observed before the fiber is physically damaged are about 13 cm−1 at a laser power of 30 mW. The band positions decrease further at higher laser power, up to a maximum of about 20 cm−1 at 40 mW, and at powers above 30 mW the linewidths and the ID/IG intensity ratio change irreversibly as the fiber begins to erode. The irreversible changes extend several hundred μm away from the 2-μm spot illuminated by the laser. The effects are attributed to laser heating. To quantify the degree of laser heating the temperature dependence of the Raman shift (G band) in pure bulk, highly oriented pyrolytic graphite (HOPG) is measured. To study the heating effect in more detail, a Raman imaging experiment is carried out in which a 0.1-mm spot on a fiber is heated by a focused laser while the fiber is illuminated for Raman characterization along a 1.6 mm length by a low power probe laser. The spatially resolved Raman shifts obtained in this way are combined with the HOPG frequency-temperature calibration to obtain the in situ temperature profile of the laser heated fiber. The measured temperature profile along the fiber is in excellent agreement with a simple convective heat-transfer model. Assuming that the temperature dependence of the G-band position is the same in the fibers as in bulk graphite, the present experiments show that a laser power of 30 mW heats an 8 μm fiber to 330 °C and that above 330 °C irreversible changes are produced by erosion of the fiber. Unperturbed room-temperature Raman frequencies for the five groups of fibers are obtained by extrapolating to zero laser power.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 97
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3630-3634 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron-beam (EB)-induced pattern etching of AlxGa1−xAs (0≤x≤0.7) is described. An ultra-thin GaAs oxide at the surface of a GaAs/AlGaAs heterostructure wafer is used as a resist film. The GaAs oxide resist can be selectively removed by EB irradiation in a Cl2 ambient, which results in pattern etching of GaAs/AlGaAs. The etch rate of AlGaAs is examined as functions of substrate temperature, AlAs mole fraction, and EB flux. The results indicate that pattern etching is realized in the AlAs mole fraction range of 0≤x≤0.7
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 98
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3653-3660 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Buried oxynitride layers were formed in silica glass by N+ only or both N+- and Si+-ion implantation. These samples were characterized by secondary-ion mass spectroscopy, Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, and scanning electron microscope. The depth profile of implanted N without Si implantation is a trapezoidal shape at a high-dose condition (more than about 3 × 1016 ions/cm2). In the N+ implantation only, a part of implanted N reacts with Si, and forms a SiON layer which is thermally unstable. In both Si+ (100 keV, 1 × 1017 ions/cm2) and N+ (50 keV, 11× 1017 cm2) implantation, the depth profile of N is a Gaussian distribution, and the thermal stability of a SiON layer is dramatically improved. However, bubbles were generated near the projected range of Si and N at a high-dose condition (the total dose was 4 × 1017 ion/cm2 and the dose ratio Si/N=3/4). The generation of bubbles was suppressed by two-step N+ implantation (40 and 60 keV).
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 99
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3669-3678 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The adsorption and decomposition of PH3 on Si(111)-(7×7) was investigated in ultrahigh vacuum by means of temperature programmed desorption, low-energy electron diffraction, Auger electron spectroscopy (AES), and electron stimulated desorption (ESD) methods. Phosphine adsorbs on Si(111)-(7×7) at T=120 K with an initial sticking coefficient of S0(approximately-equal-to)1 through a mobile (extrinsic) precursor state. Some PH3 dissociative adsorption at 120 K is observed. Thermal activation of the adsorbed species results in desorption of a molecular PH3 species up to 550 K. Further heating produces H2(g) desorption at T(approximately-equal-to)740 K and P2(g) desorption at T(approximately-equal-to)1010 K, thus indicating that PH3 decomposition has occurred. AES and ESD studies of the adsorbed species reveal that decomposition takes place by the breaking of PH bonds in PHx(a) to form SiH species on the surface for 120 K〈T〈700 K.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 100
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3701-3706 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The high-performance AuCr/SiO2/InSb metal-oxide-semiconductor capacitor was fabricated successfully using photoenhanced chemical vapor deposition. The 1200-A(ring)-thick SiO2 layer was deposited on the InSb substrate at a temperature below 200 °C. Their electrical and structural properties were analyzed by capacitance-voltage and Auger electron spectroscopy, respectively. The capacitance-voltage results show that the optimal growth temperature of SiO2 is 150 °C at which the flat-band voltage of the capacitor is close to ideal and the slow interface state density is less than 5 × 1010 cm−2. For SiO2 deposited at a lower temperature, although the flat-band voltage and interface state are poorer, the subsequent thermal annealing at 150 °C for 12 h improves both quantities to the level as the optimal condition. However, for SiO2 deposited at a higher temperature (190 °C), the flat-band voltage shifts to −4 V and the slow state density increases to 1.1 × 1011 cm−2. It is found from the Auger depth profile that whatever the deposition temperature was a Si-rich region followed by an oxygen-rich region was formed at the SiO2/InSb interface. These observations are shown to be consistent with the electrical characteristics of the capacitor.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...